CA1233729A - Saw chain - Google Patents
Saw chainInfo
- Publication number
- CA1233729A CA1233729A CA000468863A CA468863A CA1233729A CA 1233729 A CA1233729 A CA 1233729A CA 000468863 A CA000468863 A CA 000468863A CA 468863 A CA468863 A CA 468863A CA 1233729 A CA1233729 A CA 1233729A
- Authority
- CA
- Canada
- Prior art keywords
- link
- depth gauge
- cutting
- tooth
- chain
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Sawing (AREA)
Abstract
Abstract of the Disclosure An anti-kickback saw chain having a drop-away articulated depth gauge link preceding each cutting or fibre removing link.
The depth gauge surface of the depth gauge link is spaced for-wardly of the cutting tooth and the trailing edge thereof is located aft of the pivotal connection with the cutting tooth link when the pivot points of the links are aligned. In one form of the invention, the link sequence utilize a V-shaped cutter tooth link followed by a generally L-shaped raker tooth link, each being preceded by a depth gauge link. In a second form, each sequence includes a half-V side mounted slitter tooth and a transversely inclined raker tooth for removing wedge shaped chips. Each said slitter and raker tooth being provided with a break-away articulated depth gauge link connected therewith. The position of the slitter tooth and the orientation of the next adjacent raker tooth is reversed in each successive link sequence such that the score formed by each slitter is operated on by two succeeding raker teeth. Both the slitter teeth and raker teeth are provided with knife edge cutting surfaces.
The depth gauge surface of the depth gauge link is spaced for-wardly of the cutting tooth and the trailing edge thereof is located aft of the pivotal connection with the cutting tooth link when the pivot points of the links are aligned. In one form of the invention, the link sequence utilize a V-shaped cutter tooth link followed by a generally L-shaped raker tooth link, each being preceded by a depth gauge link. In a second form, each sequence includes a half-V side mounted slitter tooth and a transversely inclined raker tooth for removing wedge shaped chips. Each said slitter and raker tooth being provided with a break-away articulated depth gauge link connected therewith. The position of the slitter tooth and the orientation of the next adjacent raker tooth is reversed in each successive link sequence such that the score formed by each slitter is operated on by two succeeding raker teeth. Both the slitter teeth and raker teeth are provided with knife edge cutting surfaces.
Description
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SAFETY SAW CHAIN
ield_of the Invention The present invention relates to the field of chain saws and in particular to anti-kickback cutting chains and to an im-proved cutter tooth, raker tooth and depth gauge sequence for improving the chip flow and non-binding properties of the saw chain which results in faster cutting speeds and smoother cu~ting action. The cutter tooth comprises a half-V slitter element followed by a plural raker tooth action.
_scription of the Prior Art Chain saws are provided with a guide bar on which the cutting chain is mounted. In operation, the chain moves away from the operator across the top of the guide bar in a substantially straight or linear run, is drawn around the radius or nose on the outboard end of the bar and returns toward the operator along the underslde of the bar in a second linear run. Drive for the chain is provided by a drive sprocket about which the chain is tralned and which is powered by a prime mover, such as an internal combus-tion engine, electric motor or other motor means such as com-pressed air for example. Various ones of the links of the cutting chain include cutting elements which extend outwardly from the chain when it is mounted on the guide bar.
Increasing attention has focused on chain saw safety owing to the number and severity of injuries to chain saw opera-tors, both amateur and professional. ~his concern is heightened ,,.. ,~, , :.. .. ~, .
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by the fact that chain saw sales to non-professional users have increased dramatically in the past several years. A major cause o~ serious chain saw injuries relates to the phenomenon known as "kickback". Kickback occurs when the chain traversing the upper portion of the nose of the guide bar digs excessively into the wood or "snags" as may occurr for example, on encountering a split or knot in the wood or when limbing with the nose of the bar.
Kickback of varying degrees may also be experienced when initiat-ing a "boring" cut into the wood surface with the nose of the guide bar. under these conditions the relationship between the cutting tooth, depth gauge and wood surface may cause the tooth to dig excessively into the uncut surface. When this occurs, the chain is momentarily stopped and the energy of the moving chain is transferred so as to propel the guide bar and moving chain upward toward the head and shoulders of the operatorO During kickback, the operator can lose his grip on the forward handle allowing his hand or arm to engage the rotating cutter chain. The kickback may also operate to propel the saw bar in the opposike direction. A
severe kickback or kickback coupled with loss of grip can result in the operating chain saw being thrown back into contact with the operator causing extremely serious injury.
The primary cause of chain jamming and locking and the resulting "kickback" is the fact that the present day depth gauges used to limit the cutting depth of a cutter tooth or a raker tooth either become ineffective, or are caused themselves to dig into the wood. If the depth gauge becomes ineffective when a knot or , ~33729 other obstacle is encountered, a crack or split occurs in the wood or for some other reason, the associated cutter or raker tooth is allowed to ;'dlg in" and halt rotation of the chain. It is well appreciated in the art that, although a depth gauge setting on conventional saw chains may be designed for safe and efficient removal of chips over the top or bottom linear runs of the saw bar, the chain looses its cutting efficiency in the area of the nose because the effective difference between the height of the depth gauge and the cutter or raker tooth is severely lessened due to the curvature of the kerf. As a result, the chain will not "bore", i.e., cut with the nose or radius of the chain bar, with-out substantial increased pressure being applied by the operator.
The use of the nose of the chain is also important for specialty - .:
work such as "limbing", an essential operation for the profes-sional loggerO The problem created for the professional is especially acute since his production level may depend on the "boring" and "limbing" efficiency of the saw as well as straight cutting. In the past, the solution for the dilemma of the profes-sional has been to simply file down the depth gauge to obtain the desired efficiency for boring or limbing, leaving the chain ex-tremely "hungry" when straight cutting. The term "hungry'l indicates that the cutting depth of the cutter and raker teeth is far beyond the safety design range for the chain, enhancing the chances of kickback on straight cutting. Operating a hungry chain also results in a rough cutting action which significantly in-creases chain saw vibration. One well recognized hazard to the 37;2~
professional operator is the development of a condition commonly known in the trade as "white fingers" and technically described as chronic occupational occlusive arterial disease of the hands and fingers, Peripheral Vascular Diseases, Allen Barker & Hines, third edition, published by Wu B. Saunders & Co. Persistent pain, coldness and discoloration of the fingers may develop after a period of years and in some cases the disease may produce permanent physical impairment requiring the patient to discontinue his occupation. Since the present chain need not be made to run hungry, the chain maintains its smoothness and the problem may be alleviated. Other mechanical problems resulting from chain vibration include saw bar overheating and wear as well as engine deterioration.
~, One approach to overcoming this safety hazard has been~
the use of a chain brake which stops rotation of the chain around the guide bar when kickback occurs. Many types of guards and ~
external attachments such as nose guards to prevent the use of the chain for "boring" have been introduced for increased safety. The common approach of both professional and amateur is to immediately remove these devices to regain operating efficiency. Another approach to prevention of kickback-related injuries is the provi-sion of a chain which has a reduced tendancy to dig in and jam.
Such chains may include additional guard links or the like preced-ing a cutting linkO In addition, the cutting link may include an integral depth gauge extending from the cutting link at a position ahead of the cutter. One of the problems with this solution is 33~;~9 that the additional materlal or bulk of the chain tends to block chip flow res~lting in clogging and again, efficiency is lost.
Although such chains have helped reduce kickback-related injuries, such injuries with prior art chains remain unacceptably common and the number of injuries increases with the increased number of chain saws in use today. Productivity is the essence of profes~
sional chain saw use. Although all professional loggers endorse safety and opt for reduced workman's insurance premiums, if loss of productive revenue equals or exceeds the cost of insurance the use of safety devices will never be willingly accepted. The sought after solution to this dilemma is, of course, a chain which can be designed to eliminate the problems of kickback and vibration and yet display cutting speeds and efficiencies which are acceptable for the production requirements of professional c u t t i n g .
Other drawbacks or problems with prior art cutting chains include such phenomena as binding of the chain in the kerf whlch is being cut due to the fact that once wood fibers under stress are c~t or severed a slight expansion occurs rendering the width of the kerf actually less than the mechanical width of the chain ~itself. Also, need arises for a cutting chain that can actually be caused to cut a slightly curved kerf so as to allow the user to match up with a previous cut as for instance when "undercutting".
In fact, with conventional chain, especially of the V-tooth type, unless the chain bar is maintained at right angles with the direction of wood grain it will tend to pull to one side or the , .
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other in an effect to cut "level" with the fibers, thus increasing the tendency to bind even more. In both instances, the user of the saw must continually "push" or pressure the sawbar to maintain the cutting action. During professional high production use the fatigue factor can be substantial.
~_mmary of the Invention The cutting chain o~ the present invention dramatically reduces the kickback tendency of chain saws. This saw chain includes two kinds of cutting links for optimum cutting effi-ciency; either V-shaped or half-V cutter tooth links and generally L-shaped raker tooth links. The preferred embodiments, cutter and raker tooth links are each immediately preceded by a combined guard and depth gauge link. The saw chain may thus be formed of a combined guard-depth gauge link followed by a cutter link, a spacer link, another combined guard-depth gauge link, and a raker tooth link. The direction of the L-shaped raker tooth and the side link mounting of the associated depth gauge is reversed in successive cutting sequences to achieve lateral balance to the rotating chain. One or more spacer links may be interposed between such successive cutting segments as desired to obtain the desired chip flow capacity.
The combined guard-depth gauge link which precedes each cutter and raker link is so formed and connected to cooperate with the associated cutting link as to reduce chain saw kickback. This dual function depth gauge link is so designed that its upper portion, which limits the depth of penetration of the cutting , 3L~33~
chain into the wood, actually 'Idrops" or breaks away when an obstruction is encountered instead of digging in as conventional depth gauges do. Because of its articulated connection with the adjacent cutter or raker link an upsettin~ moment is applied to the cutter or raker link which results in pivoting it in a manner that forces the depth gauge to return to its original position to prevent the cutting tooth from digging in, thus avoiding jamming of the chain.
The geometry of the break away-articulated depth gauge link and connected cutter or raker link, set at a nominal clear-ance of seventeen thousands of an inch, is such that the cutting ability of the chain is retained at the nose or radius of the bar thus eliminating the need to file the depth gauges below safe levels in order to "bore" or "limb". Because it is not necessary to file down the depth gauges, the chain does not run "hungry" on the straight run and hence excessive vibration and the problem attendant thereto are alleviated.
In one form the cutting chain of the present invention provldes a depth gauge, a cutter tooth and raker tooth sequence which, in addition to the antikick-back feature provided by the particular depth gauge configuration, results in the formation of a kerf which is slightly wider than the mechanical width of the chain. The particular mounting of the depth gauge and cutter and raker links enable the formation of a chain of the semi-skip type which utilizes only five links in each sequence. In addition, the cutter tooth comprises a half-V slitter element of novel configu-ration which is utilized in cornbination with two succeeding raker ~2~3~
teeth, also of novel construction, and a succeeding reverse position half-V slitter for irnproved chip flow. Each half~V
slitter thus coopera-tes with the succeeding raker links for chip removal. The fact that the kerf is wider than the mechanical width of the chain, along with the feature of alternating half-V
slitters, avoids the problem of prior art V-s'naped cutter teeth.
The combination of cutter and raker teeth sequence and cooperation with the particular articulated depth gauge links results in a superior performance cutting chain with excellent antikick--back safety features.
Brief De~ E_ion of the Draw _gs - Fig. 1 is a perspective view of a section of the saw ~ chain according to the present invention;
Fig. 2 is a side elevational view of a sectisn of saw chain according to the present invention illustrating the links along a linear run of the chain;
Fig. 3 is a side elevational view of a section of saw chain according to the present invention illustrating the configu-ration of the links as they pass around the nose of the chain guide bar;
Fig. 4 is a side elevational view of a section of a prior art saw chain illustrating the configuration of the links ~as they pass around the nose of the chain guide bar.
Fig. S is a perspective view of a section of saw chain according to a secon~ embodirnent of the present lnvention;
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Fig~ 6 is a side elevational view of a section of the Fig. 5 embodiment, illustrating the configuration of the links as they pass around the nose of the chain guide bar; and Fig. 7 is a side elevational view of a section of the Fig. 5 embodiment, illustrating the configuration of the links at the initiation of a bore cut into a planar wood face.
Fig. 8 is a perspective view of a section of the saw chain according to the present invention;
Fig. 9 is a side elevational view of a section of saw chain according the present invention illustrating the links along a linear run of the chain;
Fig. 10 is a perspective view of a half-V slitter tooth according to the present invention;
.,: . .
Fig. 11 is an end elevational view of the novel ~raker tooth configuration taken in a plane normal to the plane of the tooth surface; and Figs. 12-15 are cross sectional diagrams taken substan-tially along lines 12-12 to 15-15 of Fig. 9, illustrating the sequence of removal of alternately directed wedge shaped chips.
Description of Preferred Embodiments Fig. 1 illustrates a full sequence of links forming a segment of one preferred embodiment of the saw chain of the present lnvention. It will be understood that such sequence is repeated in the order and arrangement shown throughout the length of the chain. The saw chain includes center mounted spacer links 11, center mounted depth gauge links 12, side mounted depth gauge :' _g_ ~33~9 links 13, side mounted cutter links 14, center mounted raker links 16, and side connector links 17. Each of the center links 11, 12 and 16 comprises a single link element which is pivotally con-nected adjacent its ends to pairs of side link elements which form the adjacent side links. The center and side links are fastened together by rivets 18 which extend through both the side link elements and center link. Each center link, regardless of its f~nction includes a conventional depending sprocket engaging drive tooth 19 which extends into a slot in the guide bar 21 as shown in Fig. 3 and engages the drive sprocket of the chain saw.
The center mounted spacer links 11 serve to increase the distance between successive cutter and raker links 14, 1~ and to space successive segments containing cutter and raker links 14, 16 . ~ :.. .
~ from one another. The number of spacer links between segments may - ~~
.. = .. ;~ .. . ..
be varied within well known limits to attain the desired chip flow for any given chain.
The depth gauge links determine the depth of penetration of the chain into the wood. A depth gauge link 12 or 13 is posi-tioned immediately ahead oE each cutter and raker link 14, 16 respectively to prevent such link from taking an excessively deep cut and binding in the wood. Although the links 12 are center links and the links 13 are side links, their general configuration and ~unctions as depth gauges are identical and herein reference will be made to the link 12 for the sake of clarity with the understanding that the description applies equally well to both types of links. As illustrated in Figs. 1-3, the upper surface of 372~
the depth gauge links 12 which contacts the bottom of the saw kerf is provided with an elongated and substantially flat top surface 22. In the embodi~ent o~ the chain illustrated in Figs 1-3, the extent of the flattened top surface 22 may be approximately 1/10"
in length. This distance, however, may be varied without depart-ing from the scope of the invention. As viewed most clearly in Fig. 2, when the chain is in a linear configuration with the centers of the rivets 18 aligned, the line L passing through the associated rivet center and normal to the line passing through the rivet centers of the chain preferably bisects the surface 22. As seen in Fig. 2, the direction of travel of the chain is to the left and, in this position the trailing edge 23 of the depth gauge link is behind the line L and spaced forward of the assoclated--cutter or raker link 14, 16. The top sur~ace 22 thus engages and_-~rides along the bottom of the saw kerf and limits the depth of cut of the associated cutter or raker tooth to a predetermined cutting or raking depth as is well known in the art. It will also be noted that, with this configuration, the forward edge 24 of the depth gauge link and the trailing edge 23 are the same radial distance from the center of the rivet which connects the link to the adjacent cutter or raker link. A leading inclined surface 26 extends downwardly and forwardly ~rom the forward edge 24 and a trailing surface 27 extends downwardly away from the trailing edge 23.
As best shown in Fig. 1, the cutter link includes two cutter teeth 28r 2g which extend upwardly and outwardly from two side link elements. The two teeth 28, 29 are mirror images of one : ,.
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another and generally define a V which is wider at its top than the rest of the chain. As seen in Figs. 1 and 2 the cutter teeth 28, 29 may be formed with a top rake or taper such that the lead-ing edge of each tooth is higher than the trailing edge thereof.
The teeth may also be provided with a side taper such that the leading edge of tne teeth are spaced farther apart than their trailing edges. The lower portions 31, 32 of the cutter teeth 28, 29 respectively extend forwardly of the associated cutter teeth and form the side connector links which are pivotally connected to the preceding center mounted depth gauge link 12.
Still referring to Figs. 1 and 2, each raker link 16 has a single tooth or bit 33 which extends vertically from its center mounted sprocket engaging base and is offset laterally from the centerline of the-chain.- The upper surface of the~raker tooth 33 is generally planar and extends essentially the full width between the inside of teeth 28, 29 of the cutter link 14. The general configuration of the raker tooth is well known in the art and it will be appreciated that the leading edge of the raker tooth 33 may be raked at an angle from the center line of the chain and the upper surface of the tooth may be inclined at an angle such that the leading edge is higher than the trailing edge. The rake angle and the angle of inclination of the top surface may also be varied as discussed in connection with the rake angles of the cutter teeth. As shown in Fig. 1, succeeding raker teeth are formed as mirror images of one another such that the free side edge of the upper surface of the teeth 33 is alternately positioned adjacent ~Z3~37;2~
the left and right sides of the chain. The lower portion 34 of each raker link extends forwardly of the tooth and forms a center pivotal connection to the preceding side mounted depth gauge link on one side and an opposed side connector link on the other.
Figs. 5-7 illustrate a second embodiment of the invention utilizing a modified depth gauge configuration for enhanced anti-kickback performance under special cutting conditions. The previously described depth gauge configuration of Figs. 1-3 dra-matically reduces the kickback tendency as compared to prior art saw chains under all operating conditions, however, some amount of "kick" may still result under specialized use. Although not a common occurrence, the occasion does arise when it is necessary to initiate a bore cut into a flat or planar sur~ace such as a saw-cut butt end of a log as illustrated in Fig. 7. When this is attempted there is of course, initially no kerf for the depth gauge to ride in and hence, as the depth gauge and cutter or raker tooth pass around the radius of the bar nose, where the cutting is to occur, the depth gauge which precedes this cutting tooth drops away leaving the cutting tooth unprotected. The result of course is that the tooth may instantaneously dig excessively into the wood fibre and kick the saw bar upwardly. The harder the particular wood, the more severe this problem becomes~ It has been discovered that, b~ extending the length of the depth gauge surface rearwardly in the direction of the cutting tooth, addi-tional depth gauge protection may be obtained in order to allevi-ate this condition~ It has been found also that the added depth ~2,;3~372~
gauge protection may be obtained without appreciably affecting the cutting abili~y during the normal "bore" cutting once the kerf is formed. Figs. 5-7 also illustrate a modified arrangement of side link depth gauge mounting which facilitates saw filing when using this extended depth gauge surface.
Referring to Figs. 5 and 6 the length of the depth gauge surface 22a on both center and side mounted links 12a and 13a respectively, has been extended rearwardly toward the associated cutting tooth. This rearward extension of the depth gauge surface contrasts with the Figs. 1-3 embodiment wherein the surface 22 is ideally bisected by the line L as previously explained. In practice the depth gauge surface 22a has been extended .072 inches with good results. The actual limit to which the depth gauge~
surface may be extended is dictated by the proximity of the-a-d~a---cent cutting tooth 14 or 16. It is necessary, of course to provide adequate space between the depth gauge trailing surface 27a and the cutting tooth to permit filing of the cutting tooth.
Although not the case with the center mounted depth gauge link 12a, additional space to allow filing of the side mounted depth gauge links 13a must be gained by reversing the position of these teeth relative to the associated raker teeth 16. As seen most clearly in Fig. 5, the side mounted depth gauge links are mounted on the side of the chain adjacent the free or extended side edge of the associated raker tooth or bi~ 33. Because of the angle at which these teeth are filed, additional clearance is obtained for filing by this arrangement. It will be understood that the re-maining construction of the chain remains identical to that de-scribed in connection with Figs. 1-3.
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Fig. 6 illustrates the relationship between the ~arious links as the chain operates in a kerf and passes around the radius of the bar nose~ As wîll presently be described with relation to Fig. 6, the break-away or drop-away action of the depth gauge surface and its interaction with the cutting tooth to prevent "kick back" remains identical to that described for the Figs. 1-3 embodiment. The ability of the depth gauge to avoid digging into the wood surface depends on the initial clockwise rotation of the depth gauge link in its break-away action, hence the rearwardly extended depth gauge surface 22a does not interfere. Further, since the surface is extended in a rearward direction it does not appreciably reduce normal cutting ability on the bar nose.
,~ Fig. 8 illustrates a double 5 link semi-skip sequence of- -, , : _ ~ links forming a segment of a further~embodiment of the:saw chain,~ -. ~ ~
of the present invention. It will be understood that the link sequence in this embodiment is repeated in the order,and arrange- -ment shown throughout the length of the chain. The -saw chain,, includes center mounted spacer links 111, center mounted depth gauge links 112, side mounted depth gauge links 113, side mounted cutter links 114, center mounted raker links 116, and side connec-tor links 117. Each of the center links 111, 112 and 116 comprises a single link element which is pivotally connected adjacent its ends to pairs of side link elements. The center and side links are fastened together by rivets 118 which e~tend through holes the side and center link elements in a conventional manner. Each center link, regardless of its function includes a ::
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conventional depending sprocket engaging drive tooth 119 which extends into a longitudinal slot in the guide bar of the saw so as to engage the drive sprocket in a well known manner.
The center mounted spacer links 111 serve to maintain a predetermined spacing between successive cutter and raker links 1]4, 116 and to space successive cutter and raker link sequences.
In the prior art the number of center links (i.e. drive tooth links) normally in a repetitive sequence is four. This usually includes either a cutter and raker combination or pairs of oppo-sitely directed chisel bit cutters with one spacer between the cutter/raker or chisel bit cutters and one spacer between the sequence, making the total of four regularly spaced drive links.
The term "full skip" is used to describe an eight successive drive link sequence wherein the number of-normal drive teeth is doubled ~ ~ . -- . .
by adding four spacers. A "semi-skip" sequence thus refers to a six link sequence wherein the normal four link sequence is sepa-rated by only two additional spacer drive links. With the present arrangement of links it is possible to attain the conventional semi-skip configuration, i.e. two additional spacer links between link sequences with he use of only five drive links. The use of side link mounted articulated depth gauges preceding alternately directed raker teeth in successive sequences makes this possible.
The advantage, of course, is a more compact cutting chain with ample room for chip flow.
The depth gauge links determine the depth of penetration of the associate cutting link into the wood. A depth gauge link 112 or 113 is thus positioned immediately ahead of each cutter and 37;Z~
raker link 114, 116 respectively to control the depth below the bottom of the kerf to which the associated cutting tooth may penetrate. According to the present invention both types of depth gauge links 112 and 113 are pivotally connected to the associated cutting tooth at one end and to the preceding link at the other end or leading end. Although the links 112 are center drive linkst including the drive tooth portion 119, and the links 113 are side links, their general configuration and function as depth gauges are identical and herein reference will be made to link 112 ror the sake of clarity with the understanding that the descrip-tion applies equally well to both types of links. Referring to Figs. 8 and 9, it will be understood that the description and function of the top surface 121, trailing edge 122, forward edge 123. material surface 124 and trailing surface 126 of this depth gauges 112 and 113 are identical to that described for the embodi-ment of Figs. 1 and 2. The cutter tooth of the link 114 is best characterized as a half-V slitter tooth the details of which are illustrated most clearly in Fig. 10. As shown in Figs. 8 and 9 the links 114 comprise side links pivotally connected at their forward ends to an associated depth gauge link and at their rear-ward end to center mounted spacer drive link 111. It is also to be noted that the links 114 in successive link sequences are mirror images of each other and that their positions are reversed in successive link sequences, i.e. from right hand to left hand, although the preceding articulated depth gauge links are center mounted. Referring in detail to Fig. 9 the link 114 comprises a lower or base portion 127 which extends forwardly from the slitter tooth in the direction of travel of the chain to form the side connector links between the associated depth gauge link 112 and spacer link 111. Referring to Fig. 10, each slitter includes a tooth body 128 which extends upwardly and outwardly away from the centerline of the saw chain and terminates in an upper edge 129 of reduced thickness designed to score the bottom wall of the kerf as will be presently described. As used hereinafter in this specification, the term "score" will be understood to mean an actual cutting or severing of the wood fibers so as to form a groove in the kerf wall. The slitter teeth 128 may be formed with a top rake or taper such that the leading edge of each tooth lS
higher than the trailing edge thereof. The slitter teeth may also be provided with a`si~de` taper``such that the leading edgë is spaced .. ..
farther from the centerline of the chain than the trailing edge.
Each slitter tooth is also provided ith a side cuttlng surface 131 which may be formed by conventional filing and is so oriented that-the cutting or knife edge 132 thereof is on the outboard side of the tooth body 128 and the cutting surface tapers rearwardly and inwardly relative to the direction of travel of the chain and the center]ine thereof. The function of the surface and edge 131, 132 is to cause tne slitter tooth to tend to lead into the side wall of the kerf so as to slightly widen the kerf walls beyond the mechanical width of the chain and remove any uncut fibers or loose fiber ends which extend into the kerf by a "cutting" action. This feature is contrasted with conventional V-tooth cutter construc-tion which typically requires filing or grinding straight across, ~L~33~251 i.e. normal to the direction of chain travel. With conventional V-cutters the wood fibers are thus severed by a "shearing" action rather than by a knife edge "cutting" action and the straight filed cutter is ineffective to remove loose fiber ends which extend into and tend to clog the kerf. According to the present e~lbodiment, the half-V slitter is sharpened at an angle which produces the knife edge and may be filed or ground at the same angle as the raker teeth. This is of importance when sharpening maintenance is accomplished with a chain grinder since the need for setting the wheel in a position normal to the chain is eliminated. Since the successive slitter teeth are a]ternated on the right and left hand sides of the chain, the result is to enlarge the kerf walls to allow for free` and smooth non-binding running of the chain.` It also gives~enough ~lateral freedom -to enable a slightly curved kerf to be formed when a`ttempting to align with a previously cut kerf.
The raker links ll6 of-the present invention are also of novel configuration. Referring to Figs 8 and 9, each raker link 116 has a single tooth or bit 133 which extends vertically from its center mounted sprocket engaging base and is ofset laterally from the centerline of the chain. The upper surace I34 of each raker tooth 133 is generally planar and extends essentially the full width between the inside of slitter teeth 128 of the links 11~. The leading edge 136 of each raker tooth may be raked at an an~le from the centerline of the chain and the upper surface 134 may be inclined longitudinally at an angle such that the leading ~ 3~7~
edge is higher than the trailing edge. The rake angle and the longitudinal angle oE inclination of the top surface 134 may be varied as will be understood by those skilled in the art. As shown in Fig. 8, succeeding raker teeth are formed as mirror images of one another such that the free side edge of the upper surface 134 is alternately positioned adjacent the left and right sides of the chain. The lower portion 137 of each raker link extends forwardly of the tooth and forms a center pivotal connec-~ion to the preceding side mounted depth gauge link on one side and an opposed si~e connector on the other.
Fig, 11 is an end elevation of the raker tooth 116 taken in a plane normal to the plane of the surface 134 and illustrating a novel feature according to the present-invention, As~ will be~-,,, .. ,, ~ . _, .
noted, the upper surface 134 of the raker--tooth or bit is inclined transversely at an angle of approximately 6 degrees with the center line of the lower body portion 137. This angle may, of course, be varied depending on certain limitations as will be presently understood. The free or outside edge of the surface 134 is the "high" side of the surface and is located on the same lateral side of the chain as the side link depth gauge which immediately precedes the raker. This relationship is also main-tained with respect to the raker tooth in the preceding link sequence on the opposite side of the chain. The raker tooth is provided with a cutting surface 38 on its leading edge as is conventional with chisel bit teeth. Since the raker tooth is filed at a transverse angle, a cutting edge extends along the edge ~3372~
138 and downwardly along the side at 13~. It will also be noted that the "high" side of the raker tooth surface i5 disposed on the same side of the chain as the immediately preceding side link mounted slitter tooth 128.
Referring now to ~ig. 9, the relationship between the depth gauges, slitter teeth and raker teeth is illustrated which gives optimum cutting results. The depth gauge surfaces 121, whether center mounted or side link mounted are ideally kept at the same level. It will be understood however that the relative depth gauge settings between the half-~ slitter and associate depth gauges as well as the depth gauge settings for the raker teeth are by way of e~ample or illustration and may be varied. In the embodiment of Fig. 9, the slitter tooth tip or forward end of the edge 129 is set .050 inches above the preceding depth gauge.
The high side of each raker tooth is set at approximately .025 inches or only half of the slitter tooth depth gauge setting. The low side of the raker tooth surface 134 is in the neighborhood of .025 below the high side. This relationship holds with each suc-cessive link sequence. As a result of these depth gauge settings and the transverse inclination of the raker tooth surface, the score made by each slitter tooth is operated on by the two suc-ceeding raker teeth. A first bite is made by the high side of the first succeeding raker tooth to the depth of .025 inches and a second bite is made by the low side of the second succeeding raker tooth for the remaining .025 inches of the original .050 inch score. Because of the transverse slant of the raker, the chip 33t7~9 removed is wedge shaped. It ls also to be noted that since the radius and edge 138 of the rakers are cutting edges the low side of the chip will be smoothly removed even though the slitter tooth becomes worn or the score is of insufficient depth for any reason.
QPERATIO'~
As previously mentioned, Fig. 2 depicts the orientation of one embodiment of the cutting chain of the present invention along a linear run of the chain with the centers of the rivets in substantial alignment. This cutting mode is encountered when using the chain for a straight cut by applying the rail side (upper or lower) of the chain bar to the work piece. As seen in Fig. 2 the depth gauge links ride in the saw kerf with the flat portions 22 contacting the kerf bottom to apply a predetermined limit to the depth of cut and rake. Fig. 3 on the other hand illustrates the positions of the various links as the chain passes around the radius of the bar nose and the action of the depth gauge of the present invention when an obstacle is encountered. To better understand the problem of the pxior art, Fig. 4 is used to contrast the action of one well known prior art integral depth gauge cutter tooth configuration under the same circumstances.
Considering first the saw chain of the present invention as illustrated in Fig. 3, it will be noted that, because of the articulated connection between the depth gauge links and the associated cutter or raker tooth link, a substantial portion of the depth of cut of the cutters and raker 1~, 16 is maintained.
Stated another way, the difference between the height of the depth 37~
gauges and the cutter and raker -teeth about the curved path of the kerf is not severely diminished thereby maintaining cutting efficiency about the har nose such as in "boring". This occurs because the depth gauge links pivot about a different axis than the associated cutter or raker. Fig. 4 illustrates what occurs with the conventional depth gauge and cutter link. In Fig. 4 it may be seen that/ due to the curvature of the kerf about the nose of the bar the effective cutting depth, iOe., difference between the height of the depth gauge 36 and the cutter tooth 37 is se-verely diminished, destroying the cutting efficiency of the chain.
This is because the cutting depth is fixed on a straight line such as in straight cutting and, being integral, the depth gauge and cutter tooth pivot about the same axis as the chain traverses the ---radius of the nose. _ _ Fig. 3 also illustrates the action of the depth gauge of the present invention in the event an obstacle is encountered by the moving depth gauge link. Such an encounter directs a force against the leading inclined surface 26 in the direction of the arrow a causing the depth gauge link to pivot about the axis of the rivet connecting it to the cutter link in the direction of the arrow b. This pivoting moves the depth gauge to the dotted line position illustrated as the chain continues to move. Since the trailing edge 23 of the depth gauge/ which is in contact with the kerf bottom, is only slightly forward of the line at right angles to a line pass ng through the centers of the rivets of the cutter link 14, the trailing edge drops away from the kerf bottom bring-ing the leading edge 24 into contact with the kerf bottom. Since:' ~;~33~
these two points are the same radial distance from the axis about which the link pivots the depth gauge does not dig in but instead maintains its cutting depth. In the event the obstruction is severe enough to move the depth gauge away from the kerf bottom, pressure will be applied against the forward end of the cutter link in the direction of the arrow c. This ~orce will tend to rock the cutter tooth toward the kerf bottom in the direction o~
the arrow d causing a momentary digging in of the cutter tooth.
Because of the configuration of the cutter link, however, any digging in of the cutter tooth will tend to rotate the cutter link about the axis of its rear pivot in the direction of the arrow e.
This will in turn create a counter force in the direction of arrow f to restore the depth gauge link to its operative positionr-thus , avoiding any jamming or lock~ng of the chain and attendant "kickback". The same action, of course, occurs with the raker tooth 16 and its associated depth gauge. Further, the anti kick-back action ]ust described wil-l occur on the straight cut as well as with boring or limbing with the bar nose.
The severe problem of kickback experienced with at least one type of prior art depth gauge is illustrated in ~ig. 4. The solid line position of the integral depth-gauge cutter-link is that normally maintained about the curvature of the bar nose. The link 38 immediately preceding the depth gauge 36 and pivotally connected thereto is something termed a "guard" link and is intended to prevent any excess digging in of the depth gauge and cutter tooth. At least on the nose radius, however, an obstacle encountered by the protruding depth gauge 3~ will tend to ~'33729 rotate the entire integral cutter link about the axis of the rear rivet and because of the radial distance oE the depth gauge from this axis, severe digging in will occur as illustrated by the dotted line position before the guard link 38 encounters the curved bottom of the kerf. In addition, as the depth gauge digs in, the cutter tooth itself is raised to an extremely sharp angle with further forward movement of the chain only tending to dig the depth gauge and cutter tooth into the wood. Both the guard link and the depth gauge have been rendered inoperative, there being no counter balancing forces to dislodge the cutter link. At this point the chain is halted and the entire momentum of the moving chain is transformed into a force which kicks the bar back away from the work piece. It may also be appreciated at this point that the same action occurs on the straight cut and that filing the`depth gauge 36 down to increase the depth of ~utting about the nose radius enhances the chance of causing the cutter tooth to initiate the action and to solidly dig into the wood fibre.
Referring to the embodiment of Figs. 5-7, it will be understood that the break-away action of the depth gauge links 12a and 13a and the resultant rotational and counter rotational forces applied to the depth gauge and cutting links when an obstacle is encountered are identical to that described relative to the Figs.
1-3 embodiment. Although the surface 22a is extended rearwardly, it merely drops away when this link 12a or 13a is rotated clockwise. In practice it has been found that with .072 inch extension of the depth gauge surface, with the chain configuration ~3'33~729i illustrated, no appreciable loss of cutting ability at the bar nose is experienced. On the straight cut along the linear run of the chainr oE course, the extension has no effect in cutting ability.
Fig. 7 illustrates the situation wherein boring is initiated into the flat or subs'cantially planar face of a log surface 39 such as a saw-cut butt end. Since there is initially no kerf, the depth gauge link 13a and cutting link 16 are in the dotted line positions shown. At the moment the cutting tooth starts to enter the wood surface the depth gauge link is com pletely out of contact with the wood surface leaving the cutting tooth unprotected and free to dig excessively into the wood fibre.
In order to prevent a mild '7kick" at this point, the extended depth gauge surface 22a comes into play. As the cutting tooth-enters the wood fibre it is "upset" or rotated in the clockwise ~:
direction about its rear pivot as indicated by the arrow f in Fig.
7. This rotation serves to lift the rear end of the depth gauge link 13a upwardly as the link is rotated about is forward pivot as indicated by the arrow g. Because of the rearwardly extended surface 22a, the trailing edge of this depth gauge surface is caused to momentarily contact the wood surface and limit the depth of penetration of the cutting tooth. Any tendency for the chain saw to "kick" is thus avoided. The greater the rearward extension of the depth gauge surface, the less chance there will be for "kick" but, as the bore progresses, cutting ability will be pro-gressively affected the more the depth gauge surface is extended.
iL~33~
Figs. 12-15 illustrate diagrammatlcally the removal of alternate wedge shaped chips according to the half-V cutter and raker tooth con~iguration of Figs. 8-11. The sequence of steps assumes that a saw kerf has been initiated and the chain is run-ning in a direction away from the observer. The work piece 138 may be a log or other iibrous wood material with the kerf walls shown at 139. As viewed in Fig. 5, approximately one half o~ the score from a previously passing slitter remains on one side as illustrated at 141. At this assumed cross sectional point a slitter tooth 128 is producing a .050 score on the opposite side of the kerf bottom under the control of the center mounted depth gauge 112. The kerf bottom at this point is, of course slightly inclined due to previous wedge shape chip removal. The next step, illustrated in Fig 6, involves the removal of a chip 142 by~he~~ -. ~ , ,,. . ~ . .~
first succeeding raker tooth, the "high" side of which cuts ap-proximately .025 inches into the .050 inch score 143 made by the slitter tooth and the "low " side of which cuts substantially to the bottom of the score 141 under control of the depth gauge 113, resulting in the wedge shape of the chip 142. Fig. 7 illustrates the next step wherein the next succeeding slitter 128 on the opposite side of the chain makes a second score 144 under control of its associated depth gauge 112. Fig. 8 shows the completed cycle of chip removal wherein the "high" side of the next raker tooth, inclined in the opposite direction from that depicted in Fig. 6, removes approximately .025 inches o~ the score 144 and the "low" side cuts substantially to the bottom of the score 143 under :
~ ~3 3~ 9 ..
control of the associated side mounted depth gauge 113. The resulting chip 146 is also wedge shaped and, of course, oppositely inclined from chip 142. As afore mentioned but not illustrated the sharpened side edge 132 on the slitter 128 tend to "lead" into the side wall of the kerf as the scores are formed so as to actually widen the kerf beyond the mechanical width of the chain.
The result is a free running chain with no tendency to bind or pull the chain away from the bar as with prior art V-tooth cutter chains. Also, as a result of the alternate right and left hand positioning of the slitter teeth, the chain does not seek to run "level" with the wood grain structure and the cut may be made at any angle without the binding effect.
Although the invention has been described with respect to a specific preferred embodiments, further modifications are_con-sidered to be within the scope of the inventions.
SAFETY SAW CHAIN
ield_of the Invention The present invention relates to the field of chain saws and in particular to anti-kickback cutting chains and to an im-proved cutter tooth, raker tooth and depth gauge sequence for improving the chip flow and non-binding properties of the saw chain which results in faster cutting speeds and smoother cu~ting action. The cutter tooth comprises a half-V slitter element followed by a plural raker tooth action.
_scription of the Prior Art Chain saws are provided with a guide bar on which the cutting chain is mounted. In operation, the chain moves away from the operator across the top of the guide bar in a substantially straight or linear run, is drawn around the radius or nose on the outboard end of the bar and returns toward the operator along the underslde of the bar in a second linear run. Drive for the chain is provided by a drive sprocket about which the chain is tralned and which is powered by a prime mover, such as an internal combus-tion engine, electric motor or other motor means such as com-pressed air for example. Various ones of the links of the cutting chain include cutting elements which extend outwardly from the chain when it is mounted on the guide bar.
Increasing attention has focused on chain saw safety owing to the number and severity of injuries to chain saw opera-tors, both amateur and professional. ~his concern is heightened ,,.. ,~, , :.. .. ~, .
9~2337;~
by the fact that chain saw sales to non-professional users have increased dramatically in the past several years. A major cause o~ serious chain saw injuries relates to the phenomenon known as "kickback". Kickback occurs when the chain traversing the upper portion of the nose of the guide bar digs excessively into the wood or "snags" as may occurr for example, on encountering a split or knot in the wood or when limbing with the nose of the bar.
Kickback of varying degrees may also be experienced when initiat-ing a "boring" cut into the wood surface with the nose of the guide bar. under these conditions the relationship between the cutting tooth, depth gauge and wood surface may cause the tooth to dig excessively into the uncut surface. When this occurs, the chain is momentarily stopped and the energy of the moving chain is transferred so as to propel the guide bar and moving chain upward toward the head and shoulders of the operatorO During kickback, the operator can lose his grip on the forward handle allowing his hand or arm to engage the rotating cutter chain. The kickback may also operate to propel the saw bar in the opposike direction. A
severe kickback or kickback coupled with loss of grip can result in the operating chain saw being thrown back into contact with the operator causing extremely serious injury.
The primary cause of chain jamming and locking and the resulting "kickback" is the fact that the present day depth gauges used to limit the cutting depth of a cutter tooth or a raker tooth either become ineffective, or are caused themselves to dig into the wood. If the depth gauge becomes ineffective when a knot or , ~33729 other obstacle is encountered, a crack or split occurs in the wood or for some other reason, the associated cutter or raker tooth is allowed to ;'dlg in" and halt rotation of the chain. It is well appreciated in the art that, although a depth gauge setting on conventional saw chains may be designed for safe and efficient removal of chips over the top or bottom linear runs of the saw bar, the chain looses its cutting efficiency in the area of the nose because the effective difference between the height of the depth gauge and the cutter or raker tooth is severely lessened due to the curvature of the kerf. As a result, the chain will not "bore", i.e., cut with the nose or radius of the chain bar, with-out substantial increased pressure being applied by the operator.
The use of the nose of the chain is also important for specialty - .:
work such as "limbing", an essential operation for the profes-sional loggerO The problem created for the professional is especially acute since his production level may depend on the "boring" and "limbing" efficiency of the saw as well as straight cutting. In the past, the solution for the dilemma of the profes-sional has been to simply file down the depth gauge to obtain the desired efficiency for boring or limbing, leaving the chain ex-tremely "hungry" when straight cutting. The term "hungry'l indicates that the cutting depth of the cutter and raker teeth is far beyond the safety design range for the chain, enhancing the chances of kickback on straight cutting. Operating a hungry chain also results in a rough cutting action which significantly in-creases chain saw vibration. One well recognized hazard to the 37;2~
professional operator is the development of a condition commonly known in the trade as "white fingers" and technically described as chronic occupational occlusive arterial disease of the hands and fingers, Peripheral Vascular Diseases, Allen Barker & Hines, third edition, published by Wu B. Saunders & Co. Persistent pain, coldness and discoloration of the fingers may develop after a period of years and in some cases the disease may produce permanent physical impairment requiring the patient to discontinue his occupation. Since the present chain need not be made to run hungry, the chain maintains its smoothness and the problem may be alleviated. Other mechanical problems resulting from chain vibration include saw bar overheating and wear as well as engine deterioration.
~, One approach to overcoming this safety hazard has been~
the use of a chain brake which stops rotation of the chain around the guide bar when kickback occurs. Many types of guards and ~
external attachments such as nose guards to prevent the use of the chain for "boring" have been introduced for increased safety. The common approach of both professional and amateur is to immediately remove these devices to regain operating efficiency. Another approach to prevention of kickback-related injuries is the provi-sion of a chain which has a reduced tendancy to dig in and jam.
Such chains may include additional guard links or the like preced-ing a cutting linkO In addition, the cutting link may include an integral depth gauge extending from the cutting link at a position ahead of the cutter. One of the problems with this solution is 33~;~9 that the additional materlal or bulk of the chain tends to block chip flow res~lting in clogging and again, efficiency is lost.
Although such chains have helped reduce kickback-related injuries, such injuries with prior art chains remain unacceptably common and the number of injuries increases with the increased number of chain saws in use today. Productivity is the essence of profes~
sional chain saw use. Although all professional loggers endorse safety and opt for reduced workman's insurance premiums, if loss of productive revenue equals or exceeds the cost of insurance the use of safety devices will never be willingly accepted. The sought after solution to this dilemma is, of course, a chain which can be designed to eliminate the problems of kickback and vibration and yet display cutting speeds and efficiencies which are acceptable for the production requirements of professional c u t t i n g .
Other drawbacks or problems with prior art cutting chains include such phenomena as binding of the chain in the kerf whlch is being cut due to the fact that once wood fibers under stress are c~t or severed a slight expansion occurs rendering the width of the kerf actually less than the mechanical width of the chain ~itself. Also, need arises for a cutting chain that can actually be caused to cut a slightly curved kerf so as to allow the user to match up with a previous cut as for instance when "undercutting".
In fact, with conventional chain, especially of the V-tooth type, unless the chain bar is maintained at right angles with the direction of wood grain it will tend to pull to one side or the , .
~3~37~
other in an effect to cut "level" with the fibers, thus increasing the tendency to bind even more. In both instances, the user of the saw must continually "push" or pressure the sawbar to maintain the cutting action. During professional high production use the fatigue factor can be substantial.
~_mmary of the Invention The cutting chain o~ the present invention dramatically reduces the kickback tendency of chain saws. This saw chain includes two kinds of cutting links for optimum cutting effi-ciency; either V-shaped or half-V cutter tooth links and generally L-shaped raker tooth links. The preferred embodiments, cutter and raker tooth links are each immediately preceded by a combined guard and depth gauge link. The saw chain may thus be formed of a combined guard-depth gauge link followed by a cutter link, a spacer link, another combined guard-depth gauge link, and a raker tooth link. The direction of the L-shaped raker tooth and the side link mounting of the associated depth gauge is reversed in successive cutting sequences to achieve lateral balance to the rotating chain. One or more spacer links may be interposed between such successive cutting segments as desired to obtain the desired chip flow capacity.
The combined guard-depth gauge link which precedes each cutter and raker link is so formed and connected to cooperate with the associated cutting link as to reduce chain saw kickback. This dual function depth gauge link is so designed that its upper portion, which limits the depth of penetration of the cutting , 3L~33~
chain into the wood, actually 'Idrops" or breaks away when an obstruction is encountered instead of digging in as conventional depth gauges do. Because of its articulated connection with the adjacent cutter or raker link an upsettin~ moment is applied to the cutter or raker link which results in pivoting it in a manner that forces the depth gauge to return to its original position to prevent the cutting tooth from digging in, thus avoiding jamming of the chain.
The geometry of the break away-articulated depth gauge link and connected cutter or raker link, set at a nominal clear-ance of seventeen thousands of an inch, is such that the cutting ability of the chain is retained at the nose or radius of the bar thus eliminating the need to file the depth gauges below safe levels in order to "bore" or "limb". Because it is not necessary to file down the depth gauges, the chain does not run "hungry" on the straight run and hence excessive vibration and the problem attendant thereto are alleviated.
In one form the cutting chain of the present invention provldes a depth gauge, a cutter tooth and raker tooth sequence which, in addition to the antikick-back feature provided by the particular depth gauge configuration, results in the formation of a kerf which is slightly wider than the mechanical width of the chain. The particular mounting of the depth gauge and cutter and raker links enable the formation of a chain of the semi-skip type which utilizes only five links in each sequence. In addition, the cutter tooth comprises a half-V slitter element of novel configu-ration which is utilized in cornbination with two succeeding raker ~2~3~
teeth, also of novel construction, and a succeeding reverse position half-V slitter for irnproved chip flow. Each half~V
slitter thus coopera-tes with the succeeding raker links for chip removal. The fact that the kerf is wider than the mechanical width of the chain, along with the feature of alternating half-V
slitters, avoids the problem of prior art V-s'naped cutter teeth.
The combination of cutter and raker teeth sequence and cooperation with the particular articulated depth gauge links results in a superior performance cutting chain with excellent antikick--back safety features.
Brief De~ E_ion of the Draw _gs - Fig. 1 is a perspective view of a section of the saw ~ chain according to the present invention;
Fig. 2 is a side elevational view of a sectisn of saw chain according to the present invention illustrating the links along a linear run of the chain;
Fig. 3 is a side elevational view of a section of saw chain according to the present invention illustrating the configu-ration of the links as they pass around the nose of the chain guide bar;
Fig. 4 is a side elevational view of a section of a prior art saw chain illustrating the configuration of the links ~as they pass around the nose of the chain guide bar.
Fig. S is a perspective view of a section of saw chain according to a secon~ embodirnent of the present lnvention;
37;2~
Fig~ 6 is a side elevational view of a section of the Fig. 5 embodiment, illustrating the configuration of the links as they pass around the nose of the chain guide bar; and Fig. 7 is a side elevational view of a section of the Fig. 5 embodiment, illustrating the configuration of the links at the initiation of a bore cut into a planar wood face.
Fig. 8 is a perspective view of a section of the saw chain according to the present invention;
Fig. 9 is a side elevational view of a section of saw chain according the present invention illustrating the links along a linear run of the chain;
Fig. 10 is a perspective view of a half-V slitter tooth according to the present invention;
.,: . .
Fig. 11 is an end elevational view of the novel ~raker tooth configuration taken in a plane normal to the plane of the tooth surface; and Figs. 12-15 are cross sectional diagrams taken substan-tially along lines 12-12 to 15-15 of Fig. 9, illustrating the sequence of removal of alternately directed wedge shaped chips.
Description of Preferred Embodiments Fig. 1 illustrates a full sequence of links forming a segment of one preferred embodiment of the saw chain of the present lnvention. It will be understood that such sequence is repeated in the order and arrangement shown throughout the length of the chain. The saw chain includes center mounted spacer links 11, center mounted depth gauge links 12, side mounted depth gauge :' _g_ ~33~9 links 13, side mounted cutter links 14, center mounted raker links 16, and side connector links 17. Each of the center links 11, 12 and 16 comprises a single link element which is pivotally con-nected adjacent its ends to pairs of side link elements which form the adjacent side links. The center and side links are fastened together by rivets 18 which extend through both the side link elements and center link. Each center link, regardless of its f~nction includes a conventional depending sprocket engaging drive tooth 19 which extends into a slot in the guide bar 21 as shown in Fig. 3 and engages the drive sprocket of the chain saw.
The center mounted spacer links 11 serve to increase the distance between successive cutter and raker links 14, 1~ and to space successive segments containing cutter and raker links 14, 16 . ~ :.. .
~ from one another. The number of spacer links between segments may - ~~
.. = .. ;~ .. . ..
be varied within well known limits to attain the desired chip flow for any given chain.
The depth gauge links determine the depth of penetration of the chain into the wood. A depth gauge link 12 or 13 is posi-tioned immediately ahead oE each cutter and raker link 14, 16 respectively to prevent such link from taking an excessively deep cut and binding in the wood. Although the links 12 are center links and the links 13 are side links, their general configuration and ~unctions as depth gauges are identical and herein reference will be made to the link 12 for the sake of clarity with the understanding that the description applies equally well to both types of links. As illustrated in Figs. 1-3, the upper surface of 372~
the depth gauge links 12 which contacts the bottom of the saw kerf is provided with an elongated and substantially flat top surface 22. In the embodi~ent o~ the chain illustrated in Figs 1-3, the extent of the flattened top surface 22 may be approximately 1/10"
in length. This distance, however, may be varied without depart-ing from the scope of the invention. As viewed most clearly in Fig. 2, when the chain is in a linear configuration with the centers of the rivets 18 aligned, the line L passing through the associated rivet center and normal to the line passing through the rivet centers of the chain preferably bisects the surface 22. As seen in Fig. 2, the direction of travel of the chain is to the left and, in this position the trailing edge 23 of the depth gauge link is behind the line L and spaced forward of the assoclated--cutter or raker link 14, 16. The top sur~ace 22 thus engages and_-~rides along the bottom of the saw kerf and limits the depth of cut of the associated cutter or raker tooth to a predetermined cutting or raking depth as is well known in the art. It will also be noted that, with this configuration, the forward edge 24 of the depth gauge link and the trailing edge 23 are the same radial distance from the center of the rivet which connects the link to the adjacent cutter or raker link. A leading inclined surface 26 extends downwardly and forwardly ~rom the forward edge 24 and a trailing surface 27 extends downwardly away from the trailing edge 23.
As best shown in Fig. 1, the cutter link includes two cutter teeth 28r 2g which extend upwardly and outwardly from two side link elements. The two teeth 28, 29 are mirror images of one : ,.
~2337;~
another and generally define a V which is wider at its top than the rest of the chain. As seen in Figs. 1 and 2 the cutter teeth 28, 29 may be formed with a top rake or taper such that the lead-ing edge of each tooth is higher than the trailing edge thereof.
The teeth may also be provided with a side taper such that the leading edge of tne teeth are spaced farther apart than their trailing edges. The lower portions 31, 32 of the cutter teeth 28, 29 respectively extend forwardly of the associated cutter teeth and form the side connector links which are pivotally connected to the preceding center mounted depth gauge link 12.
Still referring to Figs. 1 and 2, each raker link 16 has a single tooth or bit 33 which extends vertically from its center mounted sprocket engaging base and is offset laterally from the centerline of the-chain.- The upper surface of the~raker tooth 33 is generally planar and extends essentially the full width between the inside of teeth 28, 29 of the cutter link 14. The general configuration of the raker tooth is well known in the art and it will be appreciated that the leading edge of the raker tooth 33 may be raked at an angle from the center line of the chain and the upper surface of the tooth may be inclined at an angle such that the leading edge is higher than the trailing edge. The rake angle and the angle of inclination of the top surface may also be varied as discussed in connection with the rake angles of the cutter teeth. As shown in Fig. 1, succeeding raker teeth are formed as mirror images of one another such that the free side edge of the upper surface of the teeth 33 is alternately positioned adjacent ~Z3~37;2~
the left and right sides of the chain. The lower portion 34 of each raker link extends forwardly of the tooth and forms a center pivotal connection to the preceding side mounted depth gauge link on one side and an opposed side connector link on the other.
Figs. 5-7 illustrate a second embodiment of the invention utilizing a modified depth gauge configuration for enhanced anti-kickback performance under special cutting conditions. The previously described depth gauge configuration of Figs. 1-3 dra-matically reduces the kickback tendency as compared to prior art saw chains under all operating conditions, however, some amount of "kick" may still result under specialized use. Although not a common occurrence, the occasion does arise when it is necessary to initiate a bore cut into a flat or planar sur~ace such as a saw-cut butt end of a log as illustrated in Fig. 7. When this is attempted there is of course, initially no kerf for the depth gauge to ride in and hence, as the depth gauge and cutter or raker tooth pass around the radius of the bar nose, where the cutting is to occur, the depth gauge which precedes this cutting tooth drops away leaving the cutting tooth unprotected. The result of course is that the tooth may instantaneously dig excessively into the wood fibre and kick the saw bar upwardly. The harder the particular wood, the more severe this problem becomes~ It has been discovered that, b~ extending the length of the depth gauge surface rearwardly in the direction of the cutting tooth, addi-tional depth gauge protection may be obtained in order to allevi-ate this condition~ It has been found also that the added depth ~2,;3~372~
gauge protection may be obtained without appreciably affecting the cutting abili~y during the normal "bore" cutting once the kerf is formed. Figs. 5-7 also illustrate a modified arrangement of side link depth gauge mounting which facilitates saw filing when using this extended depth gauge surface.
Referring to Figs. 5 and 6 the length of the depth gauge surface 22a on both center and side mounted links 12a and 13a respectively, has been extended rearwardly toward the associated cutting tooth. This rearward extension of the depth gauge surface contrasts with the Figs. 1-3 embodiment wherein the surface 22 is ideally bisected by the line L as previously explained. In practice the depth gauge surface 22a has been extended .072 inches with good results. The actual limit to which the depth gauge~
surface may be extended is dictated by the proximity of the-a-d~a---cent cutting tooth 14 or 16. It is necessary, of course to provide adequate space between the depth gauge trailing surface 27a and the cutting tooth to permit filing of the cutting tooth.
Although not the case with the center mounted depth gauge link 12a, additional space to allow filing of the side mounted depth gauge links 13a must be gained by reversing the position of these teeth relative to the associated raker teeth 16. As seen most clearly in Fig. 5, the side mounted depth gauge links are mounted on the side of the chain adjacent the free or extended side edge of the associated raker tooth or bi~ 33. Because of the angle at which these teeth are filed, additional clearance is obtained for filing by this arrangement. It will be understood that the re-maining construction of the chain remains identical to that de-scribed in connection with Figs. 1-3.
~,, ~%3372~
Fig. 6 illustrates the relationship between the ~arious links as the chain operates in a kerf and passes around the radius of the bar nose~ As wîll presently be described with relation to Fig. 6, the break-away or drop-away action of the depth gauge surface and its interaction with the cutting tooth to prevent "kick back" remains identical to that described for the Figs. 1-3 embodiment. The ability of the depth gauge to avoid digging into the wood surface depends on the initial clockwise rotation of the depth gauge link in its break-away action, hence the rearwardly extended depth gauge surface 22a does not interfere. Further, since the surface is extended in a rearward direction it does not appreciably reduce normal cutting ability on the bar nose.
,~ Fig. 8 illustrates a double 5 link semi-skip sequence of- -, , : _ ~ links forming a segment of a further~embodiment of the:saw chain,~ -. ~ ~
of the present invention. It will be understood that the link sequence in this embodiment is repeated in the order,and arrange- -ment shown throughout the length of the chain. The -saw chain,, includes center mounted spacer links 111, center mounted depth gauge links 112, side mounted depth gauge links 113, side mounted cutter links 114, center mounted raker links 116, and side connec-tor links 117. Each of the center links 111, 112 and 116 comprises a single link element which is pivotally connected adjacent its ends to pairs of side link elements. The center and side links are fastened together by rivets 118 which e~tend through holes the side and center link elements in a conventional manner. Each center link, regardless of its function includes a ::
~3~72~
conventional depending sprocket engaging drive tooth 119 which extends into a longitudinal slot in the guide bar of the saw so as to engage the drive sprocket in a well known manner.
The center mounted spacer links 111 serve to maintain a predetermined spacing between successive cutter and raker links 1]4, 116 and to space successive cutter and raker link sequences.
In the prior art the number of center links (i.e. drive tooth links) normally in a repetitive sequence is four. This usually includes either a cutter and raker combination or pairs of oppo-sitely directed chisel bit cutters with one spacer between the cutter/raker or chisel bit cutters and one spacer between the sequence, making the total of four regularly spaced drive links.
The term "full skip" is used to describe an eight successive drive link sequence wherein the number of-normal drive teeth is doubled ~ ~ . -- . .
by adding four spacers. A "semi-skip" sequence thus refers to a six link sequence wherein the normal four link sequence is sepa-rated by only two additional spacer drive links. With the present arrangement of links it is possible to attain the conventional semi-skip configuration, i.e. two additional spacer links between link sequences with he use of only five drive links. The use of side link mounted articulated depth gauges preceding alternately directed raker teeth in successive sequences makes this possible.
The advantage, of course, is a more compact cutting chain with ample room for chip flow.
The depth gauge links determine the depth of penetration of the associate cutting link into the wood. A depth gauge link 112 or 113 is thus positioned immediately ahead of each cutter and 37;Z~
raker link 114, 116 respectively to control the depth below the bottom of the kerf to which the associated cutting tooth may penetrate. According to the present invention both types of depth gauge links 112 and 113 are pivotally connected to the associated cutting tooth at one end and to the preceding link at the other end or leading end. Although the links 112 are center drive linkst including the drive tooth portion 119, and the links 113 are side links, their general configuration and function as depth gauges are identical and herein reference will be made to link 112 ror the sake of clarity with the understanding that the descrip-tion applies equally well to both types of links. Referring to Figs. 8 and 9, it will be understood that the description and function of the top surface 121, trailing edge 122, forward edge 123. material surface 124 and trailing surface 126 of this depth gauges 112 and 113 are identical to that described for the embodi-ment of Figs. 1 and 2. The cutter tooth of the link 114 is best characterized as a half-V slitter tooth the details of which are illustrated most clearly in Fig. 10. As shown in Figs. 8 and 9 the links 114 comprise side links pivotally connected at their forward ends to an associated depth gauge link and at their rear-ward end to center mounted spacer drive link 111. It is also to be noted that the links 114 in successive link sequences are mirror images of each other and that their positions are reversed in successive link sequences, i.e. from right hand to left hand, although the preceding articulated depth gauge links are center mounted. Referring in detail to Fig. 9 the link 114 comprises a lower or base portion 127 which extends forwardly from the slitter tooth in the direction of travel of the chain to form the side connector links between the associated depth gauge link 112 and spacer link 111. Referring to Fig. 10, each slitter includes a tooth body 128 which extends upwardly and outwardly away from the centerline of the saw chain and terminates in an upper edge 129 of reduced thickness designed to score the bottom wall of the kerf as will be presently described. As used hereinafter in this specification, the term "score" will be understood to mean an actual cutting or severing of the wood fibers so as to form a groove in the kerf wall. The slitter teeth 128 may be formed with a top rake or taper such that the leading edge of each tooth lS
higher than the trailing edge thereof. The slitter teeth may also be provided with a`si~de` taper``such that the leading edgë is spaced .. ..
farther from the centerline of the chain than the trailing edge.
Each slitter tooth is also provided ith a side cuttlng surface 131 which may be formed by conventional filing and is so oriented that-the cutting or knife edge 132 thereof is on the outboard side of the tooth body 128 and the cutting surface tapers rearwardly and inwardly relative to the direction of travel of the chain and the center]ine thereof. The function of the surface and edge 131, 132 is to cause tne slitter tooth to tend to lead into the side wall of the kerf so as to slightly widen the kerf walls beyond the mechanical width of the chain and remove any uncut fibers or loose fiber ends which extend into the kerf by a "cutting" action. This feature is contrasted with conventional V-tooth cutter construc-tion which typically requires filing or grinding straight across, ~L~33~251 i.e. normal to the direction of chain travel. With conventional V-cutters the wood fibers are thus severed by a "shearing" action rather than by a knife edge "cutting" action and the straight filed cutter is ineffective to remove loose fiber ends which extend into and tend to clog the kerf. According to the present e~lbodiment, the half-V slitter is sharpened at an angle which produces the knife edge and may be filed or ground at the same angle as the raker teeth. This is of importance when sharpening maintenance is accomplished with a chain grinder since the need for setting the wheel in a position normal to the chain is eliminated. Since the successive slitter teeth are a]ternated on the right and left hand sides of the chain, the result is to enlarge the kerf walls to allow for free` and smooth non-binding running of the chain.` It also gives~enough ~lateral freedom -to enable a slightly curved kerf to be formed when a`ttempting to align with a previously cut kerf.
The raker links ll6 of-the present invention are also of novel configuration. Referring to Figs 8 and 9, each raker link 116 has a single tooth or bit 133 which extends vertically from its center mounted sprocket engaging base and is ofset laterally from the centerline of the chain. The upper surace I34 of each raker tooth 133 is generally planar and extends essentially the full width between the inside of slitter teeth 128 of the links 11~. The leading edge 136 of each raker tooth may be raked at an an~le from the centerline of the chain and the upper surface 134 may be inclined longitudinally at an angle such that the leading ~ 3~7~
edge is higher than the trailing edge. The rake angle and the longitudinal angle oE inclination of the top surface 134 may be varied as will be understood by those skilled in the art. As shown in Fig. 8, succeeding raker teeth are formed as mirror images of one another such that the free side edge of the upper surface 134 is alternately positioned adjacent the left and right sides of the chain. The lower portion 137 of each raker link extends forwardly of the tooth and forms a center pivotal connec-~ion to the preceding side mounted depth gauge link on one side and an opposed si~e connector on the other.
Fig, 11 is an end elevation of the raker tooth 116 taken in a plane normal to the plane of the surface 134 and illustrating a novel feature according to the present-invention, As~ will be~-,,, .. ,, ~ . _, .
noted, the upper surface 134 of the raker--tooth or bit is inclined transversely at an angle of approximately 6 degrees with the center line of the lower body portion 137. This angle may, of course, be varied depending on certain limitations as will be presently understood. The free or outside edge of the surface 134 is the "high" side of the surface and is located on the same lateral side of the chain as the side link depth gauge which immediately precedes the raker. This relationship is also main-tained with respect to the raker tooth in the preceding link sequence on the opposite side of the chain. The raker tooth is provided with a cutting surface 38 on its leading edge as is conventional with chisel bit teeth. Since the raker tooth is filed at a transverse angle, a cutting edge extends along the edge ~3372~
138 and downwardly along the side at 13~. It will also be noted that the "high" side of the raker tooth surface i5 disposed on the same side of the chain as the immediately preceding side link mounted slitter tooth 128.
Referring now to ~ig. 9, the relationship between the depth gauges, slitter teeth and raker teeth is illustrated which gives optimum cutting results. The depth gauge surfaces 121, whether center mounted or side link mounted are ideally kept at the same level. It will be understood however that the relative depth gauge settings between the half-~ slitter and associate depth gauges as well as the depth gauge settings for the raker teeth are by way of e~ample or illustration and may be varied. In the embodiment of Fig. 9, the slitter tooth tip or forward end of the edge 129 is set .050 inches above the preceding depth gauge.
The high side of each raker tooth is set at approximately .025 inches or only half of the slitter tooth depth gauge setting. The low side of the raker tooth surface 134 is in the neighborhood of .025 below the high side. This relationship holds with each suc-cessive link sequence. As a result of these depth gauge settings and the transverse inclination of the raker tooth surface, the score made by each slitter tooth is operated on by the two suc-ceeding raker teeth. A first bite is made by the high side of the first succeeding raker tooth to the depth of .025 inches and a second bite is made by the low side of the second succeeding raker tooth for the remaining .025 inches of the original .050 inch score. Because of the transverse slant of the raker, the chip 33t7~9 removed is wedge shaped. It ls also to be noted that since the radius and edge 138 of the rakers are cutting edges the low side of the chip will be smoothly removed even though the slitter tooth becomes worn or the score is of insufficient depth for any reason.
QPERATIO'~
As previously mentioned, Fig. 2 depicts the orientation of one embodiment of the cutting chain of the present invention along a linear run of the chain with the centers of the rivets in substantial alignment. This cutting mode is encountered when using the chain for a straight cut by applying the rail side (upper or lower) of the chain bar to the work piece. As seen in Fig. 2 the depth gauge links ride in the saw kerf with the flat portions 22 contacting the kerf bottom to apply a predetermined limit to the depth of cut and rake. Fig. 3 on the other hand illustrates the positions of the various links as the chain passes around the radius of the bar nose and the action of the depth gauge of the present invention when an obstacle is encountered. To better understand the problem of the pxior art, Fig. 4 is used to contrast the action of one well known prior art integral depth gauge cutter tooth configuration under the same circumstances.
Considering first the saw chain of the present invention as illustrated in Fig. 3, it will be noted that, because of the articulated connection between the depth gauge links and the associated cutter or raker tooth link, a substantial portion of the depth of cut of the cutters and raker 1~, 16 is maintained.
Stated another way, the difference between the height of the depth 37~
gauges and the cutter and raker -teeth about the curved path of the kerf is not severely diminished thereby maintaining cutting efficiency about the har nose such as in "boring". This occurs because the depth gauge links pivot about a different axis than the associated cutter or raker. Fig. 4 illustrates what occurs with the conventional depth gauge and cutter link. In Fig. 4 it may be seen that/ due to the curvature of the kerf about the nose of the bar the effective cutting depth, iOe., difference between the height of the depth gauge 36 and the cutter tooth 37 is se-verely diminished, destroying the cutting efficiency of the chain.
This is because the cutting depth is fixed on a straight line such as in straight cutting and, being integral, the depth gauge and cutter tooth pivot about the same axis as the chain traverses the ---radius of the nose. _ _ Fig. 3 also illustrates the action of the depth gauge of the present invention in the event an obstacle is encountered by the moving depth gauge link. Such an encounter directs a force against the leading inclined surface 26 in the direction of the arrow a causing the depth gauge link to pivot about the axis of the rivet connecting it to the cutter link in the direction of the arrow b. This pivoting moves the depth gauge to the dotted line position illustrated as the chain continues to move. Since the trailing edge 23 of the depth gauge/ which is in contact with the kerf bottom, is only slightly forward of the line at right angles to a line pass ng through the centers of the rivets of the cutter link 14, the trailing edge drops away from the kerf bottom bring-ing the leading edge 24 into contact with the kerf bottom. Since:' ~;~33~
these two points are the same radial distance from the axis about which the link pivots the depth gauge does not dig in but instead maintains its cutting depth. In the event the obstruction is severe enough to move the depth gauge away from the kerf bottom, pressure will be applied against the forward end of the cutter link in the direction of the arrow c. This ~orce will tend to rock the cutter tooth toward the kerf bottom in the direction o~
the arrow d causing a momentary digging in of the cutter tooth.
Because of the configuration of the cutter link, however, any digging in of the cutter tooth will tend to rotate the cutter link about the axis of its rear pivot in the direction of the arrow e.
This will in turn create a counter force in the direction of arrow f to restore the depth gauge link to its operative positionr-thus , avoiding any jamming or lock~ng of the chain and attendant "kickback". The same action, of course, occurs with the raker tooth 16 and its associated depth gauge. Further, the anti kick-back action ]ust described wil-l occur on the straight cut as well as with boring or limbing with the bar nose.
The severe problem of kickback experienced with at least one type of prior art depth gauge is illustrated in ~ig. 4. The solid line position of the integral depth-gauge cutter-link is that normally maintained about the curvature of the bar nose. The link 38 immediately preceding the depth gauge 36 and pivotally connected thereto is something termed a "guard" link and is intended to prevent any excess digging in of the depth gauge and cutter tooth. At least on the nose radius, however, an obstacle encountered by the protruding depth gauge 3~ will tend to ~'33729 rotate the entire integral cutter link about the axis of the rear rivet and because of the radial distance oE the depth gauge from this axis, severe digging in will occur as illustrated by the dotted line position before the guard link 38 encounters the curved bottom of the kerf. In addition, as the depth gauge digs in, the cutter tooth itself is raised to an extremely sharp angle with further forward movement of the chain only tending to dig the depth gauge and cutter tooth into the wood. Both the guard link and the depth gauge have been rendered inoperative, there being no counter balancing forces to dislodge the cutter link. At this point the chain is halted and the entire momentum of the moving chain is transformed into a force which kicks the bar back away from the work piece. It may also be appreciated at this point that the same action occurs on the straight cut and that filing the`depth gauge 36 down to increase the depth of ~utting about the nose radius enhances the chance of causing the cutter tooth to initiate the action and to solidly dig into the wood fibre.
Referring to the embodiment of Figs. 5-7, it will be understood that the break-away action of the depth gauge links 12a and 13a and the resultant rotational and counter rotational forces applied to the depth gauge and cutting links when an obstacle is encountered are identical to that described relative to the Figs.
1-3 embodiment. Although the surface 22a is extended rearwardly, it merely drops away when this link 12a or 13a is rotated clockwise. In practice it has been found that with .072 inch extension of the depth gauge surface, with the chain configuration ~3'33~729i illustrated, no appreciable loss of cutting ability at the bar nose is experienced. On the straight cut along the linear run of the chainr oE course, the extension has no effect in cutting ability.
Fig. 7 illustrates the situation wherein boring is initiated into the flat or subs'cantially planar face of a log surface 39 such as a saw-cut butt end. Since there is initially no kerf, the depth gauge link 13a and cutting link 16 are in the dotted line positions shown. At the moment the cutting tooth starts to enter the wood surface the depth gauge link is com pletely out of contact with the wood surface leaving the cutting tooth unprotected and free to dig excessively into the wood fibre.
In order to prevent a mild '7kick" at this point, the extended depth gauge surface 22a comes into play. As the cutting tooth-enters the wood fibre it is "upset" or rotated in the clockwise ~:
direction about its rear pivot as indicated by the arrow f in Fig.
7. This rotation serves to lift the rear end of the depth gauge link 13a upwardly as the link is rotated about is forward pivot as indicated by the arrow g. Because of the rearwardly extended surface 22a, the trailing edge of this depth gauge surface is caused to momentarily contact the wood surface and limit the depth of penetration of the cutting tooth. Any tendency for the chain saw to "kick" is thus avoided. The greater the rearward extension of the depth gauge surface, the less chance there will be for "kick" but, as the bore progresses, cutting ability will be pro-gressively affected the more the depth gauge surface is extended.
iL~33~
Figs. 12-15 illustrate diagrammatlcally the removal of alternate wedge shaped chips according to the half-V cutter and raker tooth con~iguration of Figs. 8-11. The sequence of steps assumes that a saw kerf has been initiated and the chain is run-ning in a direction away from the observer. The work piece 138 may be a log or other iibrous wood material with the kerf walls shown at 139. As viewed in Fig. 5, approximately one half o~ the score from a previously passing slitter remains on one side as illustrated at 141. At this assumed cross sectional point a slitter tooth 128 is producing a .050 score on the opposite side of the kerf bottom under the control of the center mounted depth gauge 112. The kerf bottom at this point is, of course slightly inclined due to previous wedge shape chip removal. The next step, illustrated in Fig 6, involves the removal of a chip 142 by~he~~ -. ~ , ,,. . ~ . .~
first succeeding raker tooth, the "high" side of which cuts ap-proximately .025 inches into the .050 inch score 143 made by the slitter tooth and the "low " side of which cuts substantially to the bottom of the score 141 under control of the depth gauge 113, resulting in the wedge shape of the chip 142. Fig. 7 illustrates the next step wherein the next succeeding slitter 128 on the opposite side of the chain makes a second score 144 under control of its associated depth gauge 112. Fig. 8 shows the completed cycle of chip removal wherein the "high" side of the next raker tooth, inclined in the opposite direction from that depicted in Fig. 6, removes approximately .025 inches o~ the score 144 and the "low" side cuts substantially to the bottom of the score 143 under :
~ ~3 3~ 9 ..
control of the associated side mounted depth gauge 113. The resulting chip 146 is also wedge shaped and, of course, oppositely inclined from chip 142. As afore mentioned but not illustrated the sharpened side edge 132 on the slitter 128 tend to "lead" into the side wall of the kerf as the scores are formed so as to actually widen the kerf beyond the mechanical width of the chain.
The result is a free running chain with no tendency to bind or pull the chain away from the bar as with prior art V-tooth cutter chains. Also, as a result of the alternate right and left hand positioning of the slitter teeth, the chain does not seek to run "level" with the wood grain structure and the cut may be made at any angle without the binding effect.
Although the invention has been described with respect to a specific preferred embodiments, further modifications are_con-sidered to be within the scope of the inventions.
Claims (22)
1. In a saw chain, the combination comprising;
a cutting link pivotally connected to succeeding chain links at a first pivot point, a depth gauge link pivotally connected to said cutting link at a second pivot point and to a preceding chain link at a third pivot point, said depth gauge link including a kerf engaging depth gauge surface on the top side thereof for limiting the depth of cut of said cutting link to a predetermined depth, said depth gauge surface extending a distance less than the distance between said second and third pivot points and located such that a straight line passing through said second pivot point and normal to a straight line passing through said second and third pivot points passes through the depth gauge surface.
a cutting link pivotally connected to succeeding chain links at a first pivot point, a depth gauge link pivotally connected to said cutting link at a second pivot point and to a preceding chain link at a third pivot point, said depth gauge link including a kerf engaging depth gauge surface on the top side thereof for limiting the depth of cut of said cutting link to a predetermined depth, said depth gauge surface extending a distance less than the distance between said second and third pivot points and located such that a straight line passing through said second pivot point and normal to a straight line passing through said second and third pivot points passes through the depth gauge surface.
2. The combination according to claim 1 wherein, said normal line passes through the approximate mid point of said depth gauge surface and said depth gauge surface includes a trailing edge, relative to the cutting direction of the chain, and said cutting link includes a cutting tooth, said trailing edge being located forward of said cutting tooth.
3. The combination according to claim 1 wherein, said normal line passes through said depth gauge surface at a point where the major: portion of said surface is located rearwardly thereof in the direction of travel of the chain and said depth gauge surface includes a trailing edge, and said cutting link Page -29-includes a cutting tooth, said trailing edge being located for-ward of said cutting tooth.
4. The combination according to claim 2 wherein, said trailing edge is located rearward of a second line passing through said second pivot point and normal to a straight line passing through said first and second pivot points when the pivot points of the chain links are aligned for straight cutting and being located forward of said second normal line when the chain is passed about the radius of a saw bar.
5. The combination according to claim 3 wherein, said trailing edge is located rearwardly of a second line passing through said second pivot point and normal to a straight line passing through said first and second pivot points when the pivot points of the chain links are aligned for straight cutting and when the chain is passed about the radius of a saw bar.
6. The combination of claim 4 wherein, said depth gauge surface is substantially flat and further includes a leading edge, said trailing edge and said leading edge being the same approximate radial distances from the center of said second pivot point.
7. The combination of claim 6 wherein, said depth gauge link includes an inclined surface extending downwardly and for-wardly from said leading edge, whereby an obstacle engaging said inclined surface will cause said depth gauge link to pivot clockwise about said second pivot point so as to drop said depth gauge surface away from the kerf bottom.
Page -30-
Page -30-
8. The combination according to claim 3 wherein, said depth gauge link includes an inclined surface extending downwardly and forwardly from said leading edge, whereby an obstacle engaging said inclined surface will cause said depth gauge link to pivot clockwise about said second pivot point so as to drop said depth gauge surface away from the kerf bottom.
9. The combination according to claim 7 wherein, said cut-ting tooth is located rearward of said second pivot point, whereby a force tending to move said depth gauge link away from the kerf bottom forces said cutting tooth into engagement with the kerf bottom resulting in a counter moment tending to rotate said cut-ting link in a clockwise direction about said first pivot point to restore said depth gauge against the kerf bottom.
10. The combination according to claim 8 wherein, said cut-ting tooth is located rearwardly of said second pivot point, whereby a force tending to move said depth gauge link away from the kerf bottom forces said cutting tooth into engagement with the kerf bottom resulting in a counter moment tending to rotate said cutting link in a clockwise direction about said first pivot point to restore said depth gauge against the kerf bottom.
11. The combination according to claim 2 wherein, said depth gauge link is a center mounted link and said cutting link com-prises first and second side link elements pivotally connected to said depth gauge link.
12. The combination according to claim 3 wherein, said depth gauge link is a center mounted link and said cutting link com-prises first and second side link elements pivotally connected to said depth gauge link.
Page -31-
Page -31-
13. The combination according to claim 2 wherein, said depth gauge link is a side mounted link and said cutting link comprises a center mounted link pivotally connected to said depth gauge link.
14. The combination according to claim 3 wherein, said depth gauge link is a side mounted link and said cutting link comprises a center mounted link pivotally connected to said depth gauge link.
15. In a saw chain, the combination comprising;
a depth gauge link adapted for pivotal connection to a succeeding cutting link having a cutting tooth carried thereby, said depth gauge including a kerf engaging depth gauge surface spaced forwardly of an adjacent cutting tooth for limiting the depth of cut thereof, and means pivotally connecting said depth gauge link to said cutting link with said kerf engaging depth gauge surface so lo-cated as to be dropped away from the bottom of a kerf when said depth gauge link encounters an obstacle tending to rotate said link in a clockwise direction.
a depth gauge link adapted for pivotal connection to a succeeding cutting link having a cutting tooth carried thereby, said depth gauge including a kerf engaging depth gauge surface spaced forwardly of an adjacent cutting tooth for limiting the depth of cut thereof, and means pivotally connecting said depth gauge link to said cutting link with said kerf engaging depth gauge surface so lo-cated as to be dropped away from the bottom of a kerf when said depth gauge link encounters an obstacle tending to rotate said link in a clockwise direction.
16. The combination according to claim 15 wherein:
at least the major portion of said depth gauge surface is located rearwardly of the pivotal connection between said depth gauge link and said cutting link in the direction of travel of the chain when said saw chain is in a straight line configuration.
Page -32-
at least the major portion of said depth gauge surface is located rearwardly of the pivotal connection between said depth gauge link and said cutting link in the direction of travel of the chain when said saw chain is in a straight line configuration.
Page -32-
17. the combination according to claim 16 wherein;
said cutting link is pivotally connected to succeeding links at a first pivot point, said pivotal connection between said cutting link and said depth gauge link comprises a second pivot point, said depth gauge link is pivotally connected to a preced-ing link at a third pivot point, and said at least a major portion of said depth gauge surface is located rearwardly of a straight line passing through said second pivot point and normal to a straight line passing through said second and third pivot points, whereby said at least a major portion of said depth gauge link is so related to said cutting tooth and said second pivot as to be dropped away form the bottom of a kerf when said depth gauge link encounters an obstacle tending to rotate said link in a clockwise direction.
said cutting link is pivotally connected to succeeding links at a first pivot point, said pivotal connection between said cutting link and said depth gauge link comprises a second pivot point, said depth gauge link is pivotally connected to a preced-ing link at a third pivot point, and said at least a major portion of said depth gauge surface is located rearwardly of a straight line passing through said second pivot point and normal to a straight line passing through said second and third pivot points, whereby said at least a major portion of said depth gauge link is so related to said cutting tooth and said second pivot as to be dropped away form the bottom of a kerf when said depth gauge link encounters an obstacle tending to rotate said link in a clockwise direction.
18. The combination according to claim 17 wherein;
said depth gauge surface includes a trailing edge, said trailing edge being located forward of said cutting tooth.
said depth gauge surface includes a trailing edge, said trailing edge being located forward of said cutting tooth.
19. The combination according to claim 18 wherein;
said depth gauge surface is substantially flat and in-cludes a leading edge thereon, and an inclined surface extending downwardly and forwardly from said leading edge, whereby an obstacle engaging said inclined surface will cause said depth gauge link to pivot clockwise about said second pivot point so as to drop said depth gauge surface away from the kerf bottom.
Page -33-
said depth gauge surface is substantially flat and in-cludes a leading edge thereon, and an inclined surface extending downwardly and forwardly from said leading edge, whereby an obstacle engaging said inclined surface will cause said depth gauge link to pivot clockwise about said second pivot point so as to drop said depth gauge surface away from the kerf bottom.
Page -33-
20. The combination according to claim 19 wherein;
said cutting tooth is located rearwardly of said second pivot point, whereby a force tending to move said depth gauge link away form the kerf bottom forces said cutting tooth into engage-ment with the kerf bottom resulting in a counter moment tending to rotate said cutting link in a clockwise direction about said first pivot point to restore said depth gauge against the kerf bottom.
said cutting tooth is located rearwardly of said second pivot point, whereby a force tending to move said depth gauge link away form the kerf bottom forces said cutting tooth into engage-ment with the kerf bottom resulting in a counter moment tending to rotate said cutting link in a clockwise direction about said first pivot point to restore said depth gauge against the kerf bottom.
21. The combination according to claim 20 wherein;
said depth gauge link is a center mounted link and said cutting link includes a side link element pivotally connected to said depth gauge link.
said depth gauge link is a center mounted link and said cutting link includes a side link element pivotally connected to said depth gauge link.
22. The combination according to claim 20 wherein;
said depth gauge link is a side mounted link and said cutting link comprises a center mounted link pivotally connected to said depth gauge link.
Page -34-
said depth gauge link is a side mounted link and said cutting link comprises a center mounted link pivotally connected to said depth gauge link.
Page -34-
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/555,604 US4567803A (en) | 1983-07-20 | 1983-11-28 | Safety saw chain |
| US555,604 | 1983-11-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1233729A true CA1233729A (en) | 1988-03-08 |
Family
ID=24217916
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000468863A Expired CA1233729A (en) | 1983-11-28 | 1984-11-28 | Saw chain |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1233729A (en) |
-
1984
- 1984-11-28 CA CA000468863A patent/CA1233729A/en not_active Expired
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