CA1050400A - Sawmill log-handling system - Google Patents

Abstract

SAWMILL LOG-HANDLING SYSTEM
Abstract of the Disclosure Logs are advanced through a saw while they are engaged between driven pusher dogs and retarded hold-back dogs. The pusher dogs are mounted on a lower endless roller chain below the logs, and the hold-back dogs are on an upper endless roller chain above the logs.
The upper chain and its hold-back dogs are vertically movable to elevations dependent on the elevation of a log, thus assuring proper engagement. When the sawed portion of a log is retained laterally on a support, the hold-back dogs are moved forwardly away from the log so that a hold-back dog will be in the path of the next log to be handled by the system.

Description

10~040g This inventlon relates to sawmill apparatus and methods, and particularly to a loK handling system which engages and advances logs accurately through a saw;
even in instances where the logs are of irregul~r sizes and ~hape~.
In one prior art system, known as a skrag ~aw, a log i~ balanced on a narrow chain carrier provided with pu~her dogs which push the log~ through circular saws or opposed band ~aws. On the outfeed side of the saws, upright guides called ~Isplitters~ are positioned ln the cut made by the saw blade. The inaccuracies inherent in ~uch systems restrict their practical use, where accuracy i~ important, to the ~awing o~ small short logs of e~sentially cylindrlcal characteristics.
It has b~en recogn~zed heretofore that logs of varying lengths may be accurately sawed by engaging their opposite ends by member~ which apply a gripping force thereto. U.S. patents 3,503~428 and 3,731,578 to Bo Ingemar Ackerfeldt disclose thi~ general concept in highly com-plicated systems which are far more complex and expensive than the present invention. Ackerfeldt ~uspend~ his forward and rear log-engaging means from a common overhead track; both log-en~aging means are coupled to and disengagable from a ~ommon drive cable; and, a spring is used to apply a gripping force between the log-engaging mean~.
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i 105(~400 The present invention represents a significant advance over the prior art systems described above. Unlike ,. ,.:, the prior skrag saws, logs of irregular shapes may ~e sawed accurately, and the necessity for the often-troublesome splitters is avoided. It is superior to the Ackerfeldt system due to its relative simplicity which makes the apparatus more compact, simpler to operate, less expensive to manufacture and sell, and thus more accessible to the small or medium sized sawmill operator.
One ob~ect of the invention is to hold logs under positive control during sawing, thus providing a degree of safety and accuracy which cannot be attained in systems where logs are held precariously.
Another object of the invention is to provide a system capable of handling rough, mis-shapen logs which cannot be fed through many existing systems due to their limb or knot projections, crooks, sweep~ swell, rotten hearts, angled or splintered ends and other flaws.
Still another object of the invention is to produce completely accurate products, usually flitches, to provide a maximum recovery of lumber even from poor quality logs.
A further object of the invention is to provide a system which may handle a random mix and sequence of logs of varying lengths and diameters.
Another object is to provide a system which is relatively uncomplicated so that it may be manufactured :`: :

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and sold at moderate prices, thus making it available to a large variety of sawmill operators. -An~ther object is to provide a system which is extremely compact and does not required an eXcessive amount , of mill space. ', Other objects of the invention are to provide a ,.
system which is extremely fast due to its avoidance of the necessity of troublesome components such as splitters ' ~;~
or chipper heads; to provide a system capable of handling hard wood, soft wood or frozen stock; and, to provide a system which is due to its relative simplicity and - , automatic features does not require an experienced ,, operator. '~ ~ ' ~ .
Various ones of the preceding objects of the invention are attributable to one or more of the inventive concepts utilized in the preferred embodiment of the inv-ntion disolosed in~this specification. , ' One~of~the inventive concepts r~ates~ the,U
of~a~driven~,log-engaging~means operable on the rear or énd of~a~log,~together with a forward log-engaging ,,~' ch~engages~ithe;~forward or~leading end of a log 'is ,suppo~ted OD à chain~or other'endless~carrier , ~ ~ 'n ~above~the~path of~the~log.~ Another inventive "
ve8~the~use,0f~a~ ~iven~rear log-engaging means, t~ A~

retarded as a log is advanced through a saw, whereby the log is grasped during sawing between the driven rear log-engaging means and the retarded forward log-engaging means. ~ :
Still another inventive concept pertains to the arrangement which advances the forward log-engaging means away from the log after the sawed log is held on its support by a stablilizer means. A further inventive concept is directed to a vertically adjustable forward log-engaging ~ -means which i8 moved vertically in response to signals from a sensor for detecting the elevation of the forward end of a log. .. :. :
In accordance with one broad aspect, the invention relates to a sawmill log handling system for advancing logs longitudinally along a given path from an infeed side of a saw, through the saw and to an o~tfeed side of the saw, said system ~:
~mprising, rear log engaging means for engaging a rearward end of a log, first carrier means attached to and supporting said rear log engaging means, rear drive means for moving said first :. . .
carrier means to advance the rear log engaging means along said given path to carry said log from said infeed side, through the saw and to said outfeed side, forward log engaging means for:
engaging a forward end of said log while said log is being moved by said rear drive means, ~econd carrier means for supporting .
one or more said forward log engaging means for movement from ::.
an initial position at the infeed side of the saw to the outfeed ~;~ side of the saw as said log is cut by the saw, and forward - drive means for moving said second carrier means to bring a s~aid~ forward log engaging means to said in~tial posit~on after : a log i8 cut~by the saw.

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~ typical preferred system embodying all of the inventive concepts is disclosed in the accompanY~i`ng drawings wherein:
Fi~g. 1 is a perspecti~e view, diagrammatic in some respects, of the log handling system of the invention;
Fig. 2 is a side elevation of the system of ~ig. 1;
Fig. 3 is a plan view of the log handling system of Fig. l;
Fi.g. 4 is a sectional View thereof as seen along the line 4-4 in Fig. 2; and Fig. 5 is a perspective view of a modified log handling system.
Throughout the drawings, a twin bandsaw assembly is shown in diagrammatic form having a pair of saw-~ands 2 and 4 supported on their respective wheels or pulleys 6, 8, 10 and 12. Means are provided for rotating the wheels in a conventional manner to cause the bandsaws to cut a .

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10504~)0 log which is advanced longitudinally therethrough, the sides of the log being cut by the adjacent vertical portions of the saw bands 2 and 4. This normally produces two slabs and a centari heart piece which is known in the art as a flitch or cant. The saws are preferably shifting saws for producing a heart piece of a thickness ranging from about four inches to any larger size which may be accommodated by secondary reduction resaws available at the mill. Of `
course, any number of saw blades of the band or rotary type may be used within the context of this invention.
A pair of known driven jump turning rolls 14 and 16 are provided at the infeed side of the saw blades 2 and 4. These rolls 14 and 16 are used to support and orient a log prior to sawing. They have spaced full length guide bars to promote engagement with a log and they are rotatable about their longitudinal axes by a hydraulic motor so as to position a log preliminarily at a desired ori~ntation.
The rolls 14 and 16 are vertically ~ovable which permits them to be elevated to raise a log above the path of the pusher ;; dogs~desoribed below.
As seen in Fig. 3, the log turning roll~ 14 and ~16 are spaced apart to accommodate therebetween an endless roller chain 18 which is positioned below the path followed by logs in the apparatus. This ~hain 18 serves as a lo*er carrier for supporting a series of rear log engaging means sùch as the pusher dogs illustrated at 20. The upper horizontal run of the chain 18 rides on a guide rail 22 ~ ~ : , . .
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:lOS0400 and the chain is engaged on a series of sprockets 24, 26, 28 and 30, the ~tteP being shown only in Fig. 2. The lower horizontal run of the chain extends between the pulleys 26 and 30 and the chain is moved in a continuous path on its sprockets and guide rail 22 by a drive means including the hydraulic fluid motor 32. The sprocket 34 of hydraulic motor 32 is engaged with the chain 18 by a reduction system illustrated in F~g. 1 and including the chain 36, enlarged sprocket 38, shaft 40, re~uced sprocket 42, chain 44 and the sprocket 46 which is coupled directly to the sprocket 28 for the chain 18. Operation of the hydraulic motor 32 drives the chain 18 and its pusher dogs 20 in a counter-clockwise direction as seen in Figs. 1 and 2, thus causing the pusher dogs 20 to engage the rear end of a log and propel the log along a given path in the direction indicated by the arrow 48. This carries the log through the saw and to the outfeed side of the saw.
Prior to movement of a log into the saw bands 2 and 4, its forward end is engaged by a hold-back dog 50 which serves as the forward log-engaging means of the apparatus. Dogs 50 are supported on an upper roller chain 52 which is continuous and moves in an endless path on the guide rail 54 and sprockets 56 and 58. These sprockets 56 and 58 are rotatably supported on an upper frame 59 formed of a pair of elongated parallel plates 60 and 62 which are spaced apart to support the guide rail 54 as shown in Fig. 4.

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~ ~ 7 ~,f, ~050400 The upper frame 59 is vertically movable to permit the dogs 50 to engage the upper part of the forward end of a log at an appropriate elevation. This vertical movement is produced by a hydraulic cylinder 64 which has its plunger rod 66 connected at 67 to the frame 59 and to a horizontal : -leg of a bellcrank lever 68 which is pivotally mounted on the rotatable stationary pivot axle 70. The vertical arm of ~ :
the bellcrank lever 68 is pivotally connected to an elongated -~hk 72, the opposite end of which is connected to the upper end of a similar leg of a bellcrank lever 74, the latter using :
supported on a stationary pivot axle 76 and being connected ~: .
to the frame at 78, thus causing the portion of the frame in the vicinity of the saws to move vertically the same ; .
distance as the frame in the vicinity of the hydraulic cylinder 64. It will be observed that an identical arrange- :
ment including an hydraulic cylinder and bellcrank linkages :
is provided on both sides of the frame 59 which supports ~::
the chain 52 and its hold-back dogs 50. ~ .
: The operation of the hydraulic cylinders 64 may be ~;:
performed by a mchine operator who observes the elevation ~ . :
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; of the forward end of a log being fed toward the saw by the rear pusher dogs 20. However, this change in elevation may .
be performed automatically by providing a limit switch 80 ::
at a location prior to a point where the forward end of a : ::
~: log comes into contact with ~hold-back dog 50. The actuator of limit switch 80 will be contacted by a log of large ~ - 8 ,,~::~:: :

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lOS04~0 diameter, thus sensing the elevation of a forward end of a log prior to engagement of the log with the hold-back dogs 50. Actuation of the limit switch 80 will automatically operate hydraulic cylinder 64 to elevate the frame 59, thus moving the chain 52 and dogs 50 to an appropriate height.
During the sawing operation, firm engagement of the hold-back dogs 50 with the log is assured by retarding the movement of the dogs 50 as the lo~ is advanced through the saw by the drive means for the pusher dogs, thus causing the log to be grasped between the pusher dog 20 and the hold-back dogs 50. The retardation of the hold-back dogs 50 is achieved by resistance means which includes the friction of the means for supporting and engaging the chain 52, and also the deactivated hydraulic fluid motor 82 which i8 coupled to the sprocket 58. Actually, the motor 82 will be connected to the spro~ket 58 by a reduction means similar to that used for driving the lower chain 18 with the motor 32, ~ut this construction has been eliminated from the drawings for purposes of clarity. Retardation of the ~hold-back dogs may also be produced by a brake on one of .
the sprocket shafts for chain 52. Initial engagement of the hold-back dog 50 with the log may be achieved by momentarily ;~ reversing the motor 82.
The motor 82 also serves as a drive means for moving the hold-back dog 50 forwardly at or toward the nclusion of the saw operation. At this point, the log will be supported on a rail 84 shown best in Fig. 4. Upon ~ _ g ~ ~ :
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105~4~0 completion of sawing, the slabs will fall onto the con-ventional screw rolls 86 which are provided with helical ribs (not shown) and are rotated about their axes to move -~
the slabs in the directions indicated by the arrows 87.
The flitch or cant is held or retained on the upper edge of the rail 84 by the rolls 88 and 90 which are stabilizer means for retaining the log on the ~og support rail 84 -to prevent lateral displacement of the lo,gs after sawing. The rolls 88 and 90 are supported by vertical shafts 92 and 93, the upper ends of which are pivotally mounted for lateral swinging movement. -Of course, once the log is engaged by the stab~lizer rolls 88 and 90, the hold-back dogs 50 are no longer required.
As these dogs SO arrive at and engage the limit switch 94, a circuit i8 actuated to energize the hydraulic motor 82 for the upper chain 52. The hydraulic motor 82 drives the chain 52, moving the dogs 50 forwardly away from the log when the log is retained by the stabilizer rolls 88 and 90.
The hydraulic motor 82 is deactivated when one of the hold-back dogs 50 arrives at and trips the limi-t switch 96 positioned at the rear end of the upper frame 59. This deactivates the hydraulic motor 82, and stops movement of the upper carrier chain 52 at a point when one of the hold-back dogs 50 is positioned in the path for engaging the forward end of the next ~og to be moved through the apparatus.
~ he operation of this ~p~ratus~-will be~ev~ident from the preceding description. A log is fed to the turning '-' ' . ':
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" ~, , lOS~)400 rolls 14 and 16 by a conventional log deck which has a log stop and loader. The rolls 14 and 16 are rotated by an hydraulic motor (not shown) to place the log at an appropriate orientation. The rolls 14 and 16 are elevated during rotation to hold the log above the path of the pusher dogs 20. When rotation is completed, the rolls are lowered to place the log in the path of pusher dog 20, Motor 32 drives chain 18 to carry one of the pusher dogs 20 into engagement with a lower part of the rear end of a log, thus moving the log toward the saw. At this stage, one of the forward hold-back dogs 50 is positioned in the path of the advancing log. Before a large log engages the dog 50, it will actuate the limit switch 80 to actuate the hydraulic cylinder 64 and raisè the frame 59, chain 52 and the hold-back dog 50. The upper part of the forward end of the log then comes into engagement with the hold-back dog 50 which is preposi*ioned in the path of the log. The dog 50 resists movement due to the fr~ction in itSsupport ing and driving m~ans and the presence of the deactivated motor 82, thus imposing on the log a rearward force which places the log under longitudinal compression and tends to clamp the log firmly between a hold-back dog 50 and a pusher dog 20. Be~ng positively clamped in this manner, the log acts as a rigid torsional resist~ng~be,am as it is advanced through the bands 2 and 4 of the saw. As one of the two hol~d_back dogs 50 moves with the log, the other dog 50 ~i~ ' '' . . . .

carried by chain 52 in a direction toward its log-receiving position. The sawed log is supported on the rail 84 and the slabs fall onto the screw rolls 86, to be carried under the bridge section of the outfeed system by cross -transfer chains, and to a slab resaw. If a reverse even index of slabs passing to the slab resaw is desired, the screw rolls may be replaced by slab-receiving short driven belts or slat bed sections which carry the slabs to camel back chains passing under the bridge section of the outfeed system.
I The stabilizer rolls 88 and 90 reta~n the log on the rail 84, and the forward lug 50 actuates the limit switch 94. This energizes the hydraulic motor 82 and drives the chain 52 to move the hold-back dog 50 forwardly away from the log. When one of the dogs 50 on chain 52 comes to the limit switch 96, the switch 96 is actuated to deactivate the hydraulic motor 82, thus leaving a dog 50 in a position ~ where it may engage the next log to be handled by the 1 system.
! Those skilled in the ar-t will realize that I many of the advantageous concepts of the invention may be ¦: utilized by apparatus other than the specific embodiment I disclosed herein. Various types of means may be used to ~; support the log before and after sawing, and some aspects 1~ of the invention may be utilized without the endless chains - 18 and 52 for supporting and transmitting the driving forces 1~ to the dogs 20 and 50. V~rtical adjustability of the upper .~: .

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1.~.. . . .. , ~ . - -105~4(10 chain is desirable but not essential in all systems. In view of the vast possibilities of modifying the system without departing from its important inventive concepts, it is emphasized that the invention is not limited to the disclosed embodiment but encompasses other modifications and variations thereof which fall within the spirit of the following claims.

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,~ ~o ~1 1050400 The modiflcatlon ~llus~rated in Flg. 5 includes a reversal of elements shown in the embodiment o~ F~gs. 1-4, in that the pusher dogs 102 are located on an upper endles~ carrier chain 104 and the hold-back dogs 106 are located on a lower endless carrler chain 108. The chaln 104 ls supported on sprockets 110 and is positlvely driven by a motor so that the pusher dog~ 102 will engage the rear end Or a log and drlve lt rorwardly from the lnfeed slde to the outfeed side of the twln band saws 112. As the log i8 belng driven, lts forward end ls engaged with one of the hold-back dogs 106 on the lower ~orward carrler 108, the latter belng retarded by a drag means such as brake or a deactlvated hydraullc motor so that the log will be flrmly engaged between the dogs 102 and 106. After a log has completed its pas~ through the saws 112, the slabs or other slde ple¢es fall onto the takeo~r rolls 114 and the cant remains on the center support member 116, belng prevented from ~alling therefrom by the ~lange wheel rollers 118 on the plvoted arms 120. A drive motor ls then actlvated to drive one f the sprockets 122 and carrler chaln 108, movlng the forward hold-back dog 106 away ~rom the log, brlnglng another one Or the ~ hold-back dogs 106 or chaln 108 lnto a posltlon in the path of I ~ the rorward end of the next lo~ to be passed through the apparatus.
, The embodiment Or Flg. 5 is constructed to receive logs l ~r dir~erent dlameters. The pusher dogs 102 and their carrler 104 are vertically ad~ustable, such ad~ustment being made by ~ lctuatlon o~ the hydraulic cylinders 124 which vertically move i~ the sllde blocks 126 which are arfixed to the support beam 128 ror sprockets 110. The sllde blocks 126 are supported on a track 130 ~hlch 18 looat-d on the statlonary vertical pedestals 132.

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Another feature of the Fig. 5 embodiment ls that the longitudlnal axis of the lnfeed log support such as turning rolls 134 may be slewed so that the axl~ of a supported log is not coincldent with the line o~ movement of the dogs 102 and 106. Thls permlts taper sawlng 1~ deslred to maxlmize the lumber yield from a glven log. Such slewing movement is provlded by the hydraulic cylinders 136 whose rods are connected by members 138 to the support platform 140 of the turning rolls 134. The upper surface of a stationary support plate 142 slidingly supports the members 138.
As an aid to the operator of the cyllnders 136, the apparatus Or Fig~ 5 18 provided wlth light beam pro~ectors 144 whlch create spots Or llght on the leading and trailing ends of :
a lo~ posltloned on the rolls 134. The pro~ected beams Or light are parallel to the path establlshed by the dogs 102 and 106, and they preferably are ln dlrect allgnment with the cuttlng portlons of the saw blades. An operator may observe the locatlon o~ the spots of llght on a log and ad~u~t the posltion of the rolls 134 to ~udge the approprlate positlon Or the log~ 0~ course, the proJectors 144 between the turning rolls 134 and the saw blade~ must be provlded wlth a retractlng means which removes them from the path of the log as lt approaches the saw.
In some sltuatlons, it may be deslrable to provlde a means for lowerlng the plate 140 and turning rolls 134 arter a log has been engaged between the dogs 102 and 106. This may become partlcularly lmportant when the axes of the turnlng rolls 134 and the longitudinal axi~ of a log thereon are slewed slgnl~1cantly wlth respect to the path o~ the dag~ 102 and 104.
Such downward retractlon would remove the rorward portlons of the turnlng roll~ 134 ~rom the path Or the tralllng portlon of a log ving toward the ~aw.

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~ -15-, , " ; , ~ - , , ~ " - : : - ~ " ", ~ , " ,, ,,, , " ,~;, The term "logs" as used in thls speclfication refers to large longitudlnally elongated bodles o~ wood, lncluding unsawn logs and cants.

Claims (12)

CLAIMS:

1. A sawmill log handling system for advancing logs longitudinally along a given path from an infeed side of a saw, through the saw and to an outfeed side of the saw, said system comprising, rear log engaging means for engaging a rearward end of a log, first carrier means attached to and supporting said rear log engaging means, rear drive means for moving said first carrier means to advance the rear log engaging means along said given path to carry said log from said infeed side, through the saw and to said outfeed side, forward log engaging means for engaging a forward end of said log while said log is being moved by said rear drive means, second carrier means for supporting one or more said forward log engaging means for movement from an in-itial position at the infeed side of the saw to the outfeed side of the saw as said log is cut by the saw, and forward drive means for moving said second carrier means to bring a said forward log engaging means to said initial position after a log is cut by the saw.

2. The sawmill log handling system of claim 1 wherein each of said carrier means is an endless member movable in a continuous path.

3. The sawmill log handling system of claim 2 wherein both of said carrier means are endless chains.

4. The sawmill log handling system of claim 1 including a resistance means for retarding movement of the forward log engaging means as the log is advanced through the saw by the rear drive means, whereby said log is grasped between the driven said rear log engaging means and the retarded said forward log engaging means.

5. The sawmill log handling system of claim 4 wherein said forward drive means is a hydraulic motor, and said resistance means is said hydraulic motor in a deactivated condition.

6. The sawmill log handling system of claim 1 having a log support means for underlying and supporting a log on the outfeed side of the saw, stabilizing means for retaining said log on the log support means to prevent lateral displacement of the log after sawing.

7. The sawmill log handling system of claim 1 having sensor means for sensing the elevation of the forward end of a log prior to its engagement with said forward log-engaging means, and means for moving the forward log-engaging means vertically in response to the elevation sensed by said sensor means.

8. The sawmill log handling system of claim 7 having a vertically movable upper frame supporting the forward log engaging means, and having bellcrank lever means for moving the upper frame vertically.

9. The sawmill log handling system of claim 1 wherein the first carrier means is an endless member located above the given path of the logs, and the second carrier means is an endless member located below the given path of the logs.

10. The sawmill log handling system of claim 1 wherein said forward drive means drives said forward log engaging means forwardly away from the log after the log has passed through the saw.

11. The sawmill log handling system of claim 1 having on the infeed side of the saw a log support means for supporting a log for lateral movement with respect to the axis of said given path prior to its engagement by said log engaging means.

12. The sawmill log handling system of claim 11 wherein said log support means is operable to move a log thereon to a position where the axis of the log is not coincident with the axis of said given path.