US20070151434A1

US20070151434A1 - Power miter saw with hinge linkage linear guides

Info

Publication number: US20070151434A1
Application number: US11/714,981
Authority: US
Inventors: Stephen Oberheim
Original assignee: Individual
Current assignee: Robert Bosch GmbH; Robert Bosch Tool Corp
Priority date: 2005-11-22
Filing date: 2007-03-07
Publication date: 2007-07-05
Also published as: EP1787773B1; EP1787773A1; TWI462816B; CN1974092B; US8499672B2; TW200914225A; CN1974092A; TW200726556A; TWI396598B; US20070113718A1

Abstract

A power miter saw comprises a saw base having a fence for positioning a work piece, a table rotatably connected to the saw base; a miter arm assembly for angularly positioning the table relative to the saw base, a saw blade and motor assembly operatively connected to the table, a linear guide mechanism attached to the table and being configured to support the saw blade and motor assembly and enable movement of the assembly along a predetermined linear path in either forward or rearward directions, the mechanism having a horizontal shaft about which the assembly is pivotable to move a saw blade vertically into and out of cutting position, the mechanism also having a multiple link hinge pivotally interconnecting the motor assembly and the table with generally horizontal shafts that are parallel to one another.

Description

This is a continuation-in-part of Ser. No. 11/284,931 filed Nov. 22, 2005.

BACKGROUND OF THE INVENTION

The present invention generally relates to power miter and abrasive cut off saws.
Miter saws have been the subject of continued research and development efforts in the power tool arena for decades, and many improvements have been made that has resulted in increased ease of use and productivity. Artisans who install trim carpentry have used power miter saws for some time and it is well known that wide stock such as crown molding and the like often requires a miter saw with either a bigger saw blade or a configuration that enables the blade to be moved along a horizontal path away and toward the fence of the miter saw. Such blade moving configurations are generally marketed as sliding compound miter saws, principally because most if not all commercially available saws of this type have a sliding guide assembly comprised of elongated rods that slide in respective bushings to move the saw blade and motor assembly relative to the fence of the saw.
Such sliding guide assemblies are an expensive component of such miter saws. The current state of the art for such sliding miter saws includes a linear guide that typically consists of two of such bushings and rod combinations. These relatively expensive linear bearings consist of recirculating ball bearings that operate together with turned, ground, polished and hardened steel rods that are approximately 40 cm long and 30 mm in diameter. To have minimum play and deflection of the saw blade and motor assembly, precise fits are required between the rods and the linear recirculating ball bearings over the entire linear travel of the rods. The rod must be made of a high hardness steel to prevent indentation by the hard steel balls. Such construction is relatively expensive.
Additionally, an undesirable feature of such bushing and rod linear guides is that space must be provided behind the saw for the rods to extend when the saw blade is positioned near the fence. Because of this space requirement, such a sliding saw cannot be put next to a wall which results in a larger footprint being occupied by such a saw. Additionally, these bushings and rod linear guide mechanisms are susceptible to damage from dirt and grit, particularly if the saw is a sliding abrasive cut off saw where an abrasive wheel is used to cut steel and other materials. The abrasive wheel grinds its way through the steel and produces a considerable volume of abrasive particles that generally come out of the back of the saw. These abrasive particles can penetrate into the ball bushings and damage the bearing. While it is possible to cover the rods with a bellows or similar cover, the hostile environment generally leads to degradation of the fabric and penetration of the ball bushing by the abrasive particles.
There is a continuing need for improvement in the design and development of miter and cut-off saws that have linear guide assemblies.

SUMMARY OF THE INVENTION

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a right side perspective view of a first preferred embodiment of the present invention, particularly illustrating the saw blade being located in the extended position away from the fence;
FIG. 2 is a right side perspective view of the embodiment shown in FIG. 1, but illustrating the saw blade in a position near the fence;
FIG. 3 is a side elevation of the embodiment shown in FIG. 1 with the saw blade in the extended position away from the fence;
FIG. 4 is a rear view of the embodiment shown in FIG. 1, with the saw blade away from the fence;
FIG. 5 is a right front perspective view of a second preferred embodiment of the present invention, particularly illustrating the saw blade being located in the extended position away from the fence;
FIG. 6 is a right front perspective view of the embodiment shown in FIG. 5, but illustrating the saw blade in a position near the fence;
FIG. 7 is a side elevation of the embodiment shown in FIG. 5 but illustrating the saw blade in a position near the fence;
FIG. 8 is a rear view of the embodiment shown in FIG. 5, with the saw blade in a position away from the fence;
FIG. 9 is a third preferred embodiment of the present invention, particularly illustrating the saw blade being located in the extended position away from the fence;
FIG. 10 is a side elevation of the embodiment shown in FIG. 9 with the saw blade in the extended position away from the fence.
FIG. 11 is another side elevation of the embodiment shown in FIG. 9, with the saw blade near the fence; and
FIG. 12 is a rear view of the embodiment shown in FIG. 9, with the saw blade located away the fence;
FIG. 13 is a perspective view of the right side of a fourth preferred embodiment, with the blade and motor assembly in an extended and lowered position;
FIG. 14 is a perspective view of the left side of the fourth preferred embodiment, with the blade and motor assembly in a retracted and lowered position;
FIG. 15 is a right side view of the fourth preferred embodiment, with the blade and motor assembly in an extended position;
FIG. 16 is a right side view of the fourth preferred embodiment, with the blade and motor assembly in the retracted and lowered position;
FIG. 17 is a left side view of the fourth preferred embodiment, with the blade and motor assembly in the extended and lowered position;
FIG. 18 is a top view of the fourth preferred embodiment, with portions removed to illustrate the vertically oriented hinge linkage; and
FIG. 19 is a detailed plan view, partially in section, illustrating the construction of one of the pivot connections that are utilized in the fourth preferred embodiment.

DETAILED DESCRIPTION

Four embodiments of the present invention are shown and described herein, with the each of the embodiments having a multiple hinge linkage that is designated herein as a horizontal hinge linkage that interconnects the saw blade and motor assembly to the table of the miter saw. It should be understood that while it is referred to herein as a generally horizontal hinge linkage, the several shafts of the linkage may not always be exactly horizontal, and may have a pivot axis that can vary up to about 30 degrees in either direction from exact horizontal. However, it is preferred that the axes be in a substantially horizontal orientation when the saw is set at a zero degree bevel position. Regardless of the bevel angle or the orientation of the surface on which the saw is supported, the shafts are preferably substantially parallel to the arbor shaft in which the blade is mounted and therefore substantially perpendicular to the plane of the saw blade.
The horizontal hinge linkage is utilized rather than an elongated rod and bushing configuration and provides increased stiffness to undesired movement of the saw blade arising from structural deflections during cutting operations. Two of the three embodiments also have a vertical hinge linkage for maintaining the elevation of the saw pivot head (to which the saw blade and motor assembly is attached) constant during movement of the saw blade and motor assembly away and toward the fence during a cutting operation. A third preferred embodiment utilizes the horizontal hinge linkage together with a single rod and bushing arrangement whereby the rod and bushing arrangement also maintains a constant elevation of the saw pivot head as the saw blade and motor assembly is moved toward and away from the fence during a cutting operation. It should be understood that the saw blade and motor assembly 22 is pivotable about a saw pivot that is part of the saw pivot head, which is attached to the horizontal hinge linkage. The saw blade and motor assembly can be pivoted up out of contact with a work piece or moved down into contact with a work piece during a cutting operation as is conventional for miter saws.
Such hinge linkages have a cost advantage compared to conventional bushing and rod guides because they have a simpler construction, which may comprise as few as two generally planar shaped linkages that are connected together by shafts that may preferably incorporate rotary bushings or low cost ball bearings and which are also linked to the support frame of the rotatable table as well as to the saw pivot head. Tight tolerance fits between hinge components are relatively easier to achieve using low cost ball bearings that are preloaded in the axial direction so that nearly all axial and radial play is removed. In contrast, conventional bushings and sliding rod systems require expensive manufacturing processes to ensure that the outside surface of the rod is precise over its entire length. Another advantage of the use of hinge linkages is that their stiffness characteristics are determined primarily from the width of the hinge linkages as measured along the pivot, i.e., shaft axis. Thus, increased system stiffness can be achieved by making the hinge larger and this is generally less expensive than using larger rods and bushings.
As previously mentioned, the horizontal hinge linkage pivots around axes that are parallel to the cutting plane of the blade and therefore provides increased stiffness along the axis of rotation of the saw blade and because of this desirable characteristic, the length of the hinge shafts is greater than other shaft lengths such as those used in the vertical hinge linkage. The structural stiffness is very important to the quality of cuts made by the saw. Without the requisite structural stiffness, it is common for the saw blade to deflect out of the desired cutting plane on an intermittent basis which can result in one or more cut discontinuities or jagged cut portions, rather than a continuous smooth cut at the desired angle.
Another advantage of the hinge linkage is that it has greatly reduced sensitivity to dirt and grit because the bearing surfaces of a hinge linkage are not exposed but are contained within a ball bearing or short rotary bushing. Such ball bearing or rotary bushings can be relatively easily sealed compared to a rod and bushing system where the entire rod is a critical bearing surface and therefore has to be sealed with a large accordion or bellow shaped fabric or other type of cover which is often easily damaged.
Turning now to the first preferred embodiment shown in FIGS. 1-4, the miter saw, indicated generally at 10, has a generally circular base 12 with an attached fence 14, which base supports a rotatable table 16 that has a miter arm control assembly, indicated generally at 18, for adjusting the rotational position of the table for setting the miter angle of work piece that would be placed on the table 16. A saw blade and motor assembly, indicated generally at 20, is operatively connected to the table 16 by a linear guide mechanism, indicated generally at 22. The saw blade and motor assembly 20 has an electric motor 24 that is operatively connected through a gear mechanism, not shown but located within housing portion 26 that drives a saw blade 28. A handle 30 enables an operator to move the blade and motor assembly 20 into and out of engagement with a work piece that may be placed on the table 16 adjacent the fence 14. The blade and motor assembly 20 is pivotable about a saw pivot shaft 32 that is connected to a saw pivot head 34 to which the linear guide mechanism 22 is attached. The blade and motor assembly 20 is shown in FIG. 1 to be in a position where the blade is moved to its extended position away from the fence 14 and lowered into cutting position were a work piece placed on the table 16. During operation, an operator places a work piece on the table 16, brings the handle 30 down into cutting position either before or after activating the motor 24 and then pushes the handle 30 toward the fence 14 to have the blade 28 cut the work piece. At the end of the cut, the blade and motor assembly 20 would be essentially in the position shown in FIG. 2 where the bottom reach of the blade 28 is generally coextensive with the fence 14.
The linear guide mechanism 22 of the first preferred embodiment shown in FIGS. 1-4 is designed so that the miter saw has a dual bevel operation, rather than a single bevel operation, meaning that the bevel angle can be adjusted either right or left from the normal zero angle or position wherein the plane of the blade 28 is perpendicular to the plane of the top surface of the table 16. The blade and motor assembly 20 as well as the linear guide mechanism and rotate about a bevel pivot shaft 36, with the linear guide mechanism having a support frame 38 with a generally cylindrical end portion 40 to which the bevel pivot shaft 36 is connected to. The shaft 36 extends through an opening in an enlarged extension 42 of the table 16. Thus, the end portion 40 can rotate relative to the extension 42 and be supported by the shaft 36. The support frame 38 is preferably a casting that has a lower flange 44, an upper flange 46 as well as vertically oriented flanges 48 and 50.
A horizontal hinge linkage is comprised of links 52 and 54 which have adjacent ends connected together by a shaft 56. The saw pivot head 34 has a pair of spaced flanges 58 as well as a single flange 60 located below the flanges 58. The link 54 has its opposite end connected to the flanges 58 by a shaft 62. Similarly, the opposite end of the link 52 is connected to the vertical flanges 48 and 50 by a shaft 64. As previously mentioned and while not specifically illustrated, the shafts 32, 62, 56, 64, 78 and 82 are preferably of the type which utilize rotary bushings or low cost ball bearings so that they are freely rotatable and will have an extended useful life.
As is best shown in FIGS. 1 and 2, the link 52 has a generally L-shaped side configuration with the transverse extension 66 having the aperture in which the shaft 56 is located. This permits the two links 52 and 54 to be folded together in a generally parallel arrangement as shown in FIG. 2 when the blade and motor assembly 20 is moved into its final cutting position where the blade is adjacent to the fence 14. As is best shown in FIG. 4, the width of the links 52 and 54 is relatively large and therefore the shafts 56, 62 and 64 that interconnect the links 52 and 54 with one another and with the saw pivot head 34 and support frame 38 are relatively long. This contributes to the desirable stiffness of the linear guide mechanism which substantially reduces, if not eliminates, any movement by the blade out of the cutting plane which can result in poor quality cutting. Stated in other words, the extremely wide links and their coupling to the saw pivot head and support frame 38 results in high rigidity reducing torsional and linear deflection of the saw blade away from its intended cutting plane which is very desirable from a cut quality standpoint.
As best shown in FIG. 4, the link 52 is not a solid construction, but has side walls 68 and end walls 70 with cross braces 72 provided to provide increased overall strength for the link. The link 54 is similarly constructed as is shown in FIG. 1, it also having similarly configured side walls, end walls and cross braces. The hinge links 52 and 54 are preferably die cast aluminum but can be steel stamping if desired.
The vertical hinge linkage is located below the horizontal hinge linkage and it comprises links 74 and 76 which have adjacent ends connected together by a vertical shaft 78. The links 74 and 76 are not as wide as the horizontal hinge links 52 and 54 for the reason that their functionality is to maintain the elevation of the saw pivot head 34 constant during movement of the blade and motor assembly 20 toward and away from the fence 14. Elevational deflections are not as critical for a miter saw cut quality for the reason that the work piece is generally being completely cut through.
The narrower links 74 and 76 are vertically displaced from one another which requires the elongated vertical shaft 78 to extend to interconnect them. The link 74 is located between the horizontal flanges 44 and 46 and is pivotally connected to these flanges by a shaft 80. Similarly, the link 76 has spaced flange portions that are connected to the flange 60 by a shaft 82. As is shown in FIG. 1, the flange 60 is located beneath the near flange 58 and the flanges 44 and 46 are also located beneath the vertical flanges 48 and 50, and the shaft 78 that interconnects the links 74 and 76 extends away or to the left side of the saw (as viewed from the handle 30) so that when the vertical and horizontal linkages are folded together as shown in FIG. 2, little if any portion of the links extend outside of the width of the flanges 48 and 50. This is significant in that changing of the bevel angle of the blade and motor assembly 20 can be accomplished in either the left or right direction and the hinge linkages will not interfere with the dual bevel adjusting capability.
It should also be apparent from FIG. 2 that when the blade and motor assembly 20 are moved as far toward the fence 14 as is possible, the linkages do not extend in any rearward direction beyond the original position end of the support frame 38. This enables the miter saw to be placed near a wall, for example, and be fully operational, unlike many conventional sliding rod and bushing configurations of compound miter saws.
A second preferred embodiment is shown in FIGS. 5-8 and have many similar components as the embodiment shown in FIGS. 1-4. In the following description, components that are labeled with the same numbers as those shown and described with regard to the first preferred embodiment are substantially similar in their design, configuration and operation and therefore will not be described in detail. Components with reference numbers having a prime or double prime designation are similar to those that are identified with regard to the embodiment shown in FIGS. 1-4, but may have some structural differences which are apparent or which will be generally described. or which will be given different numbers than those illustrated in FIGS. 1-4.
The second preferred embodiment is indicated generally at 100 in FIGS. 5-8 and has many similarities to the first preferred embodiment, but while the first embodiment is a dual bevel configuration saw, the second embodiment saw 100 is a single bevel configuration. The links 74′ and 76′ are connected together by a shaft 78′ that is not as long as the shaft 78 of the first preferred embodiment, because the links 74′ and 76′ are vertically adjacent one another rather than being spaced apart. Also, the link 76′ is at an elevation that is substantially similar to the elevation of the link 54′ and therefore unable to fold toward the link 52″ and 54′. Thus, the connection between link 74′ and 76′ extends outwardly away from the links 52′ and 54′. Because of the outward extension, particularly when it is folded as shown in FIGS. 6 and 8, the links interfere with other portions of the saw 100 when the saw would be pivoted in the counterclockwise direction as shown in FIG. 8. Therefore, the single bevel operation of this second preferred embodiment is in the clockwise direction as shown in FIG. 8.
A third preferred embodiment of the invention is the saw 110 that is shown in FIGS. 9-12 is less detail than the embodiments of FIGS. 1-8. Saw 110 has a horizontal hinge linkage comprising links 52″ and 54″ that are interconnected and operate substantially similar to those described in the embodiments of FIGS. 1-8. The saw pivot head 34″ has a slightly different configuration and the end of the link 54″ is connected to the saw pivot shaft 32 which is also journaled in the saw pivot head 34″. An elongated rod 112 is journaled in a bushing (not shown but located in the upper end of support frame 38) and maintains the saw pivot head 34″ at a constant elevation as the blade and motor assembly 22 moves the blade 28 toward the fence 14. Only one rod 112 is provided for the reason that control of the saw blade cutting plane is provided by the horizontal hinge linkage, as is the case with the other embodiments shown in FIGS. 1-8, and the only function that is performed by the rod 112 is to keep the pivot head 34″ at a constant elevation during operation. In this regard, the blade and motor assembly 20 is shown in its retracted position in FIGS. 9 and 10 and in the cutting position in FIG. 11 where the blade 28 is adjacent the fence 14. In the position shown in FIG. 11, it is apparent that the rod 112 will extend beyond the rear surface of the support frame 38″ which requires a larger footprint in that it would not be possible to place the saw 110 with the support frame 38″ located close to a wall or other similar surface. Thus, while this embodiment does not have the space advantages of the first and second preferred embodiments, this embodiment has the advantage of controlling the saw blade cutting plane by a generally horizontal hinge as is achieved in all embodiments and only one rod and bushing combination is required which provides a cost benefit compared to conventional arrangements which have a pair of rod and bushing configurations.
A fourth preferred embodiment is shown in FIGS. 13-19 and is indicated generally at 200. Many of the components are similar to the embodiment 10 so that where reference numbers are the same as the description of the FIG. 1 embodiment, such components and their functionality are very similar if not identical. Components with reference numbers above 200 are sufficiently different from analogous components of the other embodiments to warrant separate numbers or are new in the fourth preferred embodiment.
This embodiment also has a generally circular base 12 with an attached fence 14, which base supports a rotatable table 16 that has a miter arm control assembly, indicated generally at 18, for adjusting the rotational position of the table for setting the miter angle of a workpiece that would be placed on the table 16. A saw blade and motor assembly, is also indicated generally at 20, is operatively connected to the table by a linear guide mechanism, indicated generally at 202. The saw blade and motor assembly 20 has an electric motor 24 that is operably connected through a gear mechanism (not shown), but located within the housing portion 26 that drives a saw blade 28. A handle 30 enables the operator to move the blade and motor assembly 20 into and out of engagement with a workpiece that is placed on the table 16 adjacent the fence 14. The blade and motor assembly is pivotable about a saw pivot shaft 32 that is connected to saw pivot head 204. When the handle 30 is lowered by an operator, the blade 28 will be lowered into its cutting position and as shown in FIG. 13, it slightly penetrates a slot 206. The pivot head 204 has a pair of spaced flanges 208 that extend upwardly and which are attached to a first horizontal link 210 by pivot connection shaft 212. The first horizontal link 212 is connected to a longer link 214 by pivot connection shaft 216. The link 214 has its lower end portion connected to a vertical support 18 by pivot connection shaft 220. The link 214 has a generally transverse extension 222 at its upper end portion which facilitates articulation of the links 212 and 214 relative to one another. In this regard, the width of the link 212 is narrower than the width of the extension 222 so that the link 212 can nest within the extension 222. As is best shown in FIG. 16, when the blade and motor assembly 20 is in its retracted position, the link 214 is in a generally vertical orientation. It should be appreciated that the shaft 212, 216 and 220 are oriented parallel to one another and substantially perpendicular to the plane of the blade 28. The links 212 and 214 are relatively wide and the thickness of them is substantial so that they resist bending which would detrimentally affect the quality of the cut by the blade 28.
The vertical support 218 is integrally formed with a support frame 224 that is generally cylindrically shaped. A bevel pivot shaft 226 supported by an extension 228 of the table 16 enables the support frame 224 and vertical support 218 to pivot for the purpose of providing bevel cuts. The vertical support 218 also has a side mounting structure 230 with a tongue portion 232 for supporting an angled link 234 that is connected to the tongue portion by a pivot connection shaft 236. The upper end of the link 234 is connected to another link 238 by pivot connection shaft 240. The link 238 has its other end connected to a tongue portion 242 that is part of the pivot head 204 by a pivot connection shaft 244.
As with the embodiment shown in FIG. 1, the vertical shafts 236, 240 and 244 maintain the elevation of the pivot head 240 substantially constant relative to the table 16. The width and thickness of the links 234 and 238 are comparable to the links 212 and 214. However, the amount of possible bending of the links 234 and 238 is not as critical as bending that could occur with the links 212 and 214 inasmuch as the quality of a cut is generally not affected by vertical movement of the blade during extension and retraction because the blade penetrates the slot 206 during most cutting operations. As is evident from the drawings, and particularly FIGS. 13 and 15, the links 234 and 238 are not solid but are preferably cast of aluminum and have reinforcing ribs 246 that extend across the interior of the links to impart additional strength. While not as clearly shown, the construction of the links 210 and 214 are similar in that they have reinforcing ribs that are also cast with the links.
Additional structural strength is provided with the fourth preferred embodiment for the reason that the link 234 has spaced flanges 248 that fit around the tongue 232 and the shaft 236 is thereby supported at both ends rather than an overhung load connection. The double-ended support provides a stronger connection that imparts an increased strength to the linkage. Similarly, the upper end of the link 234 has a tongue 250 and the link 238 has a pair of spaced flanges 252 in which shaft 240 is secured. The shaft 240 is therefore also supported at opposite ends which is a stronger connection. The other end of the link 238 also has a pair of flanges 254 that support both ends of the shaft 244.
It should be understood that the angle of the link 234 relative to the vertical shaft 236 is such that the link 234 does not interfere with or contact the extension 228. If the tongue portion 232 is located higher than as shown, the angle of the link 234 would necessarily be less, i.e., more toward horizontal. It should be understood that the length of the vertical support 218 may be increased so that the location of the tongue 232 may be changed so that it may be at the same height above the table 16 as the shafts 240 and 244. In other words, the link 234 may be horizontally oriented just as is the link 238. However, if this is done, there is an issue of the saw being undesirably top heavy. Another consideration is that the angle between the links 210 and 214 as determined by the line of action between a line extending through shafts 212 and 216 relative to the line of action through shafts 216 and 220 identified as angle θ in FIG. 17 as well as the angle through the vertically oriented shafts 236, 240 and 244 marked as angle θ in FIG. 18 should be less than 130° to prevent a toggle action of the links. The toggle action is defined herein to mean an increased necessary force to push the blade and motor assembly 20 from its extended position as shown in FIGS. 13, 15 and 18 toward the retracted position. If a toggle action is experienced, a greater noticeable and appreciable force is required to start the movement. If the angles of the links are less than 130°, such toggle action is not experienced.
It is desirable that the linear guide mechanism 202 very little unnecessary movement or play in the pivot connections that would or could result in decreased cut quality by the saw. While this is more important with the pivot connections of the links 210 and 214 relative to the pivot head 204 and vertical support 218, it is also important with regard to the pivot connections of the links 234 and 238. For this reason, it is preferred that the pivot connections utilize ball bearings on both ends of the shafts. Referring to FIG. 19 which is exemplary and diagrammatic, a link 214 is shown with the shaft 216. It passes through an aperture 256 and has one end portion 258 that bears against an inner race 260 of a ball bearing, indicated generally at 262 that also has an outer race 264 and a plurality of balls 266. The other ball bearing 268 also has an inner race 270, an outer race 272 and a plurality of balls 274. A nut 276 is threaded on the end of the shaft 216 and is tightened so as to pull the inner races 260 and 270 toward one another which offsets the inner and outer races of each ball bearing relative to one another and takes any play or looseness out of the ball bearing which prevents the ball bearings from contributing to looseness that would create a deterioration of the quality of the cut. Also, a pair of cap screws 278 is provided in apertures 280 in the link 210 and are tightened to bear against the shaft 216 and lock it from rotation or other movement relative to the link 210. Therefore, with the immobilization of the shaft 216 as well as the removal of any play in the ball bearings 262 and 268.
Because of the design of the linear guide mechanism 202, there is a natural tendency for the blade and motor assembly 20 to gravitate toward the extended position. To counteract this tendency, it is therefore preferred to have at least one spring or other biasing mechanism provided to neutralize this tendency. In this regard, a torsion spring in one of the pivot connections may be provided or a tension spring interconnecting the link 214 with the pivot head 208 may be used, for example.
Also during transport, the blade and motor assembly 20 may undesirably move from one position to another which can be somewhat hazardous to a carrier and it is desirable to have a locking mechanism that prevents unwanted movement while it is being carried. In this regard and referring to FIG. 17, an elongated slotted member 280 having a pivot connection 282 to the link 214 and a handle 284 associated with the pivot head 204 may be provided. If the blade and motor assembly 20 is placed in its extended position such as shown in FIG. 17, the knob 284 can be tightened to hold the saw in this position during transport.
A desirable attribute of the fourth preferred embodiment is particularly illustrated in FIG. 16 wherein the blade and motor assembly 20 is in its retracted position and the link 214 is substantially vertical. Since the link 214 does not extend rearwardly beyond the vertical support 218, it can be appreciated that the saw 200 can be placed very close to a rear wall or the like without impairing the normal operation of the saw.
While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.
Various features of the invention are set forth in the following claims.

Claims

1. A power miter saw comprising:

a saw base having a fence for positioning a work piece;

a table rotatably connected to said saw base;

a miter arm assembly for angularly positioning said table relative to said saw base;

a saw blade and motor assembly operatively connected to said table;

a linear guide mechanism attached to said table configured to support said saw blade and motor assembly and enable movement of said assembly along a predetermined linear path between forward and rearward positions and having a first pivot axis perpendicular to the plane of said saw blade about which said saw blade and motor assembly is pivotable to move a saw blade into and out of cutting position;

said mechanism comprising a saw pivot head in which said first pivot axis is provided, a first multiple link hinge comprising two hinge links that are pivotally connected together and to said pivot head and said table with pivot axes that are parallel to one another and to said first pivot axis;

at least one of said pivot axes comprises an elongated shaft that is supported at opposite end portions, each end portion having a ball bearing with an inner race mounted in one of said links, said pivot head and said table, an outer race mounted in another of said links, said pivot head and said table and balls positioned between said inner race and said outer race.

2. A power miter saw as defined in claim 1 wherein said links have a predetermined width and thickness that substantially inhibits bending and twisting of said hinge, at least one of said links having a predetermined width that approximates the length thereof.

3. A power miter saw as defined in claim 1 wherein said elongated shaft has a first end portion bearing against the outside of said inner race and a nut threaded on the opposite end of said shaft bearing against the outside of said inner race of the other ball bearing, whereby tightening of said nut causes said inner races of both ball bearings to be moved toward one another to reduce play in said ball bearings.

4. A power miter saw as defined in claim 1 wherein said elongated shaft is located in an aperture in a tongue portion of one of said links, said pivot head and said table, said saw further comprising at least one member secured in said tongue portion for contacting said shaft to prevent any movement of said shaft relative to said tongue portion.

5. A power miter saw as defined in claim 1 wherein said mechanism further comprises a second multiple link hinge pivotally interconnecting said assembly and said table with pivot axes that are generally parallel to one another and perpendicular to said first pivot axis.

6. A power miter saw as defined in claim 5 wherein said second multiple link hinge comprises two hinge links that are pivotally connected together and to said pivot head and said table by said pivot axes, a first hinge link having a first end connected to said table and a second end connected to a second hinge link, said second hinge link having a first end connected to said pivot head and a second end connected to said second end of said first hinge link

7. A power miter saw as defined in claim 6 wherein said first end of said first hinge link is closer to the plane of the top surface of said table than said second end, said first and second ends of said second hinge link being substantially the same distance from the plane of the top surface of said table.

8. A power miter saw as defined in claim 6 wherein said pivot axes of said second multiple link hinge comprises an elongated shaft that is supported at opposite end portions, each end portion having a ball bearing with an inner race mounted in one of said links, said pivot head and said table, an outer race mounted in another of said links, said pivot head and said table and balls positioned between said inner race and said outer race.

9. A power miter saw as defined in claim 8 wherein said elongated shaft has a first end portion bearing against the outside of said inner race and a nut threaded on the opposite end of said shaft bearing against the outside of said inner race of the other ball bearing, whereby tightening of said nut causes said inner races of both ball bearings to be moved toward one another to reduce play in said ball bearings.

10. A power miter saw as defined in claim 1 wherein the angle between said two interconnected hinge links of at least said first multiple link hinge is less than a threshold angle of approximately 130 degrees to substantially remove toggling.

11. A power miter saw as defined in claim 10 wherein said angle between said two interconnected hinge links comprises the angle between said pivot axis interconnecting said hinge links and the pivot axis on the opposite end of each link.

12. A power miter saw as defined in claim 11 wherein toggling requires an appreciable additional force to initiate movement of said saw blade and motor assembly from said extended position to said retracted position.

13. A power miter saw comprising:

a saw base having a fence for positioning a work piece;

a table rotatably connected to said saw base;

a saw blade and motor assembly operatively connected to said table;

wherein the angle between said two interconnected hinge links of at least said first multiple link hinge is less than a threshold angle of approximately 130 degrees to substantially remove toggling.

14. A power miter saw comprising:

a saw base having a fence for positioning a work piece;

a table rotatably connected to said saw base;

a saw blade and motor assembly operatively connected to said table;

said mechanism comprising a saw pivot head in which said first pivot axis is provided, a first multiple link hinge comprising two hinge links that are pivotally connected together and to said pivot head and said table with pivot axes that are parallel to one another and to said first pivot axis, and a second multiple link hinge comprising two hinge links that are pivotally connected together and to said pivot head and said table with pivot axes that are generally parallel to one another and perpendicular to said first pivot axis;

wherein said pivot axes of said first and second multiple link hinges comprise an elongated shaft that is supported on opposite ends.

15. A power miter saw as defined in claim 14 wherein said two hinge links comprise a first hinge link having a first end connected to said table and a second end connected to a second hinge link, said second hinge link having a first end connected to said pivot head and a second end connected to said second end of said first hinge link

16. A power miter saw as defined in claim 15 wherein said first end of said first hinge link is closer to the plane of the top surface of said table than said second end, said first and second ends of said second hinge link being substantially the same distance from the plane of the top surface of said table.

17. A power miter saw comprising:

a saw base having a fence for positioning a work piece;

a table rotatably connected to said saw base;

a saw blade and motor assembly operatively connected to said table;

wherein said second multiple link hinge comprises a first link oriented at an angle and having a lower first end connected to said table with a vertical pivot axis having a first elongated shaft and a second higher end connected to a first end of a second link with a vertical pivot axis having a second elongated shaft, said second link being connected to said pivot head with a vertical pivot axis having a third elongated shaft;

at least said first and second elongated shafts being supported on opposite end portions.

18. A power miter saw as defined in claim 17 wherein said second link is generally parallel to the plane of the top of said table.

19. A power miter saw as defined in claim 17 wherein said two hinge links of at least said first multiple link hinge are pivotally interconnected by said pivot axis and said hinge is movable when said saw blade and motor assembly is moved along said predetermined path between an extended position and a retracted position, the angle between lines of action through said pivot axes of said interconnected hinge links being less than a predetermined angle to prevent toggle action of said hinge.

20. A power miter saw as defined in claim 19 wherein said predetermined angle is approximately 130 degrees.