GB2131728A

GB2131728A - Saw cutter sharpening method and apparatus

Info

Publication number: GB2131728A
Application number: GB08328537A
Authority: GB
Inventors: Duane M Gibson; Lewis A Scott
Original assignee: Omark Industries Inc
Current assignee: Omark Industries Inc
Priority date: 1981-02-23
Filing date: 1983-10-26
Publication date: 1984-06-27
Also published as: JPS57168826A; GB2093743A; CA1204286A; GB2093743B; JPH0416291B2; GB2131728B; IT1154293B; GB8328537D0; IT8247828A0; SE8201095L; SE8603025L; SE8603025D0; SE450628B

Abstract

A completely outside sharpenable saw chain 10 of the chisel type is sharpened by an attachment 63 securable to the nose end 64 of a saw bar around which the saw chain passes, the attachment carrying a pair of side elements 81 having abrasive surfaces spring biased against the saw chain side cutter portions to sharpen these. The attachment also includes a flexible strip 60 of abrasive material held against the saw chain top plate portions by flexure of the strip. <IMAGE>

Description

1 GB 2 131 728 A 1

SPECIFICATION

Saw cutter sharpening method and apparatus The invention relates to a method of and an apparatus for sharpening the cutters or cutter 5 teeth of a saw.

Saw chains having chisel-type cutter links, that is, cutter links in which a top plate portion and a side slitter portion form a sharp angle, and therefore a sharp corner at the juncture of the top cutting edge and the side cutting edge, are very effective. However, they require expertise in sharpening and are not nearly so widely used as saw chains of the chipper-type which have a rounded corner formed by the top cutting edge and the side cutting edge. The rounded corner is less adapted to slitting than the sharp corner of the chisel-type teeth but is sharpenable without the great skill required in sharpening chisel teeth.

The present invention is concerned with the 85 provision of an improved method and means for outside sharpening a chisel-type saw tooth.

The invention accordingly provides a sharpener for a saw having a plurality of cutters movable along a predetermined path, the sharpener 90 comprising one or both of means locating adjacent to the path top sharpening means for sharpening sharpenable top surfaces of the cutters, and means locating side sharpening means on opposite sides of the path, the side sharpening 95 means being yieldably urged towards the path to sharpen sharpenable side surfaces of the cutters.

The invention also provides a method of sharpening the cutters of a saw, the method comprising the steps of moving the cutters along a 100 path and disposing adjacent the path both of cutter top sharpening means arranged to sharpen sharpenable top surfaces of cutters moving on the path, and cutter side sharpening means yieldably urged to engage and sharpen sharpenable side surfaces of cutters moving on the path.

The top sharpenable means can comprise a flexible strip or web of abrasive material which has some stiffness, the abrasive surface of the material being disposed in substantially parallel relation to the top sharpenable surfaces of the cutter teeth. The strip of abrasive material can be longitudinally restrained at a given point out of contact with the cutters or cutter teeth and flexed toward them to engage the top sharpenable surfaces thereof at a point downstream or along the direction of travel from the given point. However, the strip of abrasive material can be longitudinally unrestrained ilong the path farther downstream from the cutter teeth contact area and moreover the strip immediately adjacent the top surfaces of the cutter teeth can be free to flex radially toward or away from said top surfaces. That is, the strip is not provided with a preformed backing device forcing it into the teeth but rather the strip is urged toward the teeth in response to flexural resistance or restoring force of the strip itself. The strip may be flexed toward the cutter teeth by bending the same around an upstream support which also longitudinally restrains the strip, and/or by providing a downstream support which tends to curve or bend the strip of abrasive material around or against the path of the cutter teeth without forcing the strip into the teeth immediately adjacent the area of contact with a backing member.

The sharpenable side cutter teeth surfaces can be sharpened by employing a pair of abrasive elements, located on respective sides of the longitudinal path or centre line of the cutter teeth. The planar surfaces may be angled or canted somewhat to provide the cutter teeth with a side plate clearance angle. Conveniently, the cutter top and side surfaces are sharpened simultaneously with an attachment embodying both aspects of the invention, the attachment suitably being removably securable to the nose end of a chain saw bar. The invention can be employed for sharpening a completely outside sharpenable cutter tooth having a side plate portion sloping inwardly and rearwardly with its forward and side surface portion comprising a sharpenable surface forming a side slitting edge at the forward end of the inside face of the side plate portion. Such a tooth also has a top plate portion sloping rearwardly and downwardly and joined to the upper edge of the said plate portion by a small radius corner, the forward and top surface portion of the top plate portion comprising a sharpenable surface and forming, with the bottom surface of the top plate portion, a top cutting edge providing a sharp point with the side slitting edge. For a better understanding of the invention reference may be made to the following illustrative description and the accompanying drawings, in which: Figs. 1 and 1 a are perspective views of a chiseltype cutter link; 105 Fig. 2 is a side view of the cutter link of Fig. 1 Fig. 3 is a rear view of the cutter link of Fig. 1 taken along line 3-3 of Fig. 2; Fig. 4 is an enlarged, vertical, sectional view taken along line 4-4 of Fig. 2; 110 Fig. 5 is a top plan view taken along line 5-5 of Fig. 2; Fig. 6 is a side view taken along line 6-6 of Fig. 5; Fig. 7 is a fragmentary side view of a chisel- type saw chain including the link of Fig. 1 and showing a sequence and a half of the saw chain; Fig. 8 is a fragmentary plan view of the saw chain of Fig. 7; 120 Figs. 9-12 are perspective views of stages of making a cutter link similar to that of Fig. 1 but of the opposite hand; Fig. 13 is a perspective view of a chain saw with the saw chain of Fig. 7 and with a sharpening attachment embodying the invention mounted on the saw bar thereof; Fig. 14 is a fragmentary, side view of the chain saw and sharpening attachment of Fig. 13 on a larger scale; 2 GB 2 131 728 A 2 Fig. 15 is an underneath view taken along line 15-15 of Fig. 14 on a smaller scale.

Fig. 16 is a perspective view of the chain saw with the saw chain of Fig. 7 and a second sharpening attachment embodying the invention mounted on the saw bar thereof; Fig. 17 is a more detailed cross-sectional view of the attachment of Fig. 16, the view being taken on line 17-17 of Fig. 18.

Fig. 18 is a transverse cross-sectional view of the attachment of Fig. 16 taken on line 18-18 of Fig. 17; Fig. 19 is an exploded view of the sharpening attachment of Fig. 16; Fig. 20 is a view similar to that of Fig. 17 but showing the saw bar in place in the attachment; Fig. 21 is a perspective view, partially broken away, of a third sharpening attachment embodying the invention and a saw bar upon which the attachment can be mounted; Fig. 22 is a side view of the attachment of Fig. 21; Fig. 23 is a top view of the attachment of Fig. 21; Fig. 24 is a transverse cross-sectional view of the attachment of Fig. 21; Fig. 25 is a side view, partially broken away and partially in cross-section, of the attachment of Fig.

21 mounted on a saw bar, the cross-sectional portion being taken on line 25-25 of Fig. 24; Fig. 26 is a partial cross-sectional view illustrating a modification of the attachment of Fig. 21; Fig. 27 is an enlarged explanatory view illustrating the -canting of abrasive surfaces in the 100 attachment of Fig. 21 to produce a side plate clearance angle on a saw tooth; and Fig. 28 is a top view of a chain saw link which has been sharpened by means of the sharpening attachment of Fig. 21, illustrating a side plate clearance angle.

A completely outside sharpenable saw chain 10 (Fies. 7 and 8) has top and side sharpenable chisel-type cutter links 11 and 12. The links 11 are identical to the links 12 except that the links 11 are righthand and the links 12 are lefthand, that is, the links are allochiral, and hence only the links 11 will be described in detail.

Each link 11 (Figs. 1-6) has a flat body portion 14, a depth gauge portion 16, an offsetting shank portion 18, a rearwardly, inwardly and somewhat downwardly sloping, generally flat or slightly rounded side plate portion 20 joined to the shank or offset portion 18 by a rounded, bent portion 22, and a rearwardly and dowardly sloping, flat, top plate portion 24 joined along one side edge thereof to the top edge of the side plate portion 20 by an angular or rounded, bent portion 26. The shank portion is joined to the body portion 14 by a rounded, bent portion 30. The body portion has holes 32 and 34 for rivets.

For purposes of clarity in describing the cutter links 11 and 12, it will be assumed that the body portions are in upright positions with the top plates uppermost. "Forwardly" means in the direction of 130 chain travel, e.g. to the right in Fig. 2, while.1 rearwardly" refers to the opposite direction. Also, Inwardly" means toward the longitudinal centre plate of the chain and "outwardly- means laterally away from this plane.

Each link 11 (and 12) has a sharp point 40 formed at the junction of a top sharpenable surface 42, an outer, planar side sharpenable surface 46 and an inner surface 48 preferably chromium plated, of the angular portion 26. An inner or bottom surface 44 of the top plate portion 24 is chromium plated and forms a sharp, rearwardly and inwardly extending top cutting edge 50 extending inwardly and somewhat rearwardly from the point 40. An inner surface or side 52 of the side plate portion 20 also preferably is chromium plated and forms a kerf side cutting edge 54, which extends somewhat downwardly, and preferably inwardly and somewhat rearwardly from the point 40 so that it is hook-like.

The cutting edges 50 may be sharpened by power, as by an arcuate abrasive member 60 (Figs. 13-15) of a sharpening attachment 63 on a chain saw 62, in which the member 60 is pressed toward a nose portion 64 of a saw bar 65 of the chain saw to always engage at least two of the top surfaces 42 as the chain is driven by a sprocket (not shown) of the saw. The arcuate abrasive member 60 is somewhat flexible and includes a backing comprising a thin strip of spring metal or the like; it is placed in contact with the saw chain top surfaces by depressing a bail 120 which raises a crank 122 and draws the member 60 to the left in Fig. 14. Simultaneously, the member 60 also abrades the top surfaces 67 of the depth gauge portions to reduce their height proportionately to the reduction of the height of the cutting edges by the sharpening. The rear end 68 (Fig. 2) of each depth gauge portion is the gauging portion thereof and is positioned substantially farther forwardly of the midpoint of an imaginary line 70 joining the centres of the rivet holes 32 and 34 in the body portion than is the top cutting edge 50 to the rear of that midpoint. As a result, the rear end 68 of each depth gauge portion is always a selected distance lower than the cutting edge 50. The forward slope of rear edge 76 of the depth gauge portion 16 and the rearward slope of the bottom surface 44 of the top plate portion are such that the height differential between the rear end 68 and the cutting edge 50 is kept constant even after repeated sharpenings. Preferably, the downward slope represented by angle B, Fig. 1, of the top plate portion 24 relative to the horizontal is from about 301 to about 401. The top plate portion 24 slopes somewhat upwardly, proceeding inwardly from the bent portion 26, to an extent such that the edge 50 forms an angle of about 220 with a line 79 (Fig. 5) normal to the plane of the body portion.

The kerf side cutting edges 54 of the side plate portion 20 of the links 11 and 12 are sharpened by pressing planar abrasive members 80 and 81 (Figs. 13-15) against the sides of the saw chain W Z 3 GB 2 131 728 A 3 as the chain is driven by the chain saw to abrade the side sharpening surfaces 46 (Figs. 1-6). The planar abrasive members 80 and 81 are pivotally carried by sharpening attachment 63 and are spring biased against the side sharpening surfaces of the chain during sharpening operation. Members 80 and 81 can alternatively be latched out of sharpening position as shown by dashed lines in Fig. 15. The sharpening faces of the members 80 and 81 may be parallel to the body portions 14 of the cutter links 11 and 12 during sharpening, or, to increase the hooking configuration of the side cutting edges 54 and to provide some kerf side wall clearance, may be tilted preferably about 4', somewhat inwardly proceeding upwardly as viewed in Figs. 13 and 14. The surfaces 46 are, of course, planar. The inward slope of the side plate portions 20 is preferably such that the acuteness of the side cutting edges 54 is between 301 and 401. This slope also permits many sharpenings of the side cutting edges without weakening the side plate portions.

A preferred method of making the links 11 and 12 is to cut a blank 90 (Fig. 9) of sheet steel in soft condition, saw chain steel of about 0.043 inches thickness being one very satisfactory material, and to then stretch form an upper portion 91 (Fig. 10) about a vertical axis 92 at back edge portion 93 to provide the offset shank portion 18. Then, with a wiping and slight coining action, the upper portion 91 is bent at rounded portion 26. This completes the shaping of the link which is then heat treated to harden it to a Rockwell hardness of from about 50to about 65 on the Rockwell Scale 100 C, it being feasible to make the teeth even as hard as 65 on this Scale, since filing is not required to sharpen the cutting edges 50 and 54.

After the hardening of the links 11 and 12, the bottom face 48 of the top plate portion 24 and the inside face 52 of the side plate portion 20 are preferably plated with chromium, to provide very hard, wear resistant material for the cutting edges 50 and 54. Also, during use of these cutter links, the hard chromium surface is pressed by the wood being cut against the top plate portion 24 and the side plate portion 20 so that there is no tendency to peel off the chromium plating.

The top plate portion, proceeding from the bent portion 26 at its outer edge, is tilted up somewhat so that the abrasion of the sharpening surface 42, which lies in a portion of a cylinder centered on an axis normal to the body portion 14, causes the cutting edge 50 to extend somewhat rearwardly proceeding from the corner or point 40. This gives the cutting edge a slicing as well as a chiseling action.

To provide the hook shape of the side cutting edge 54, the side plate portion 20 tilts out of a vertical plane proceeding downwardly from the upper bent portion 26 to the lower bent portion 22. Then, when the side sharpening surface 46 is ground in a substantially vertical plane, the side cutting edge 54 slopes somewhat rearwardly, proceeding downwardly therealong. This slope or 130 hook is increased if the sharpening member is tilted inwardly at its lower end.

It will be understood that the chain 10 is endless and that only a segment, one and one-half sequences, is shown in Fig. 7. The chain 10 includes driving links 110 connected by rivets 111 to the body portions 14 of the cutter links 11 and 12 and side links 112, and also connected to bumper links 113 positioned between the cutter links. Each top plate portion 24 extends over the centreline of the chain so that the top plate portions 24 of the links 11 and 12 overlap one another.

The bent edge portion 26 at the juncture of the side plate portion 20 and the top plate portion 24 so extends inwardly and downwardly that, as the top sharpening surface 42 and the side sharpening surface 46 are sharpened substantially equally, the point 40 is maintained substantially at the centre of the bent edge portion 48. The bent edge portions 22 and 26 extend in somewhat converging directions, proceeding rearwardly therealong, so that the side plate portion narrows somewhat from front to rear. The side plate portion 20 which show as substantially planar may instead by somewhat rounded.

The cutter link 11 of a constructed saw chain which operated very successfully is shown with its geometry in Figs. 1-6. The angle A of the side plate portion 20 to the plane of the body portion 14 proceeding rearwardly, or the angle of the side plate portion to the sharpenable surface, is about 301. The side plate portion 20 tilts inwardly proceeding upwardly at an angle of about 101 to the vertical. The angle of the top cutting edge 50 relative to a line 79 normal to the body portion is 22'. The angle of the top plate portion 24 to the body portion 14 is 1111. The shank portion 18 is sloped at an angle of about 450 to the body portion 14. The angle C of the side cutting edge 54 relative to the vertical is about 22 0. The thickness of the chromium plating on the lower face 44 of the top plate portion 24 and the inner face 52 of the side plate portion 20 is about 0.0004 inches. The link was hardened to a hardness of about 56 on the Rockwell C Scale. The side sharpenable surface 46 is disposed in a substantially vertical plane parallel to line 70 and body portion 14. A sloping forward corner portion 99 was provided on the depth gauge 16 to lessen the abrupt interference with wood being cut, particularly in boring.

The top plate portion 24, the side plate portion 20 and the shank portion 18, in transverse cross- section, are combined, concave and roughly in the form of a "C" having a combined concave inner surface which may vary from a substantially uniform curvature to being highly angled at the bent portions.

A second sharpener for sharpening the cutter edges by power is illustrated in Figs. 16-20. A sharpening attachment 124 is mountable on the nose end of a saw bar 126 located at the forward end of chain saw 129, the chain saw being provided with an appropriate motor for driving 4 said chain 130 around the periphery of the bar. The saw chain 130 is suitably of the type illustrated in Figs. 7 and 8 having cutter teeth with top sharpenable surfaces and outer side sharpenable surfaces as further illustrated at 42 and 46 in Fig. 20. The attachment 124 is generally U-shaped taking the form of a slotted case which slides over the end of the saw bar and comprises a pair of mating plastic side members 127 and 128 joined at their wider ends to provide an enclosure therebetween, while forming a saw bar receiving slot 131 between their narrower forward ends for fitting over the nose end of the saw bar. A spring detent mechanism 132, secured to member 127 by screw 134, extends longitudinally of member 127, terminating in an outwardly curved handle portion 136 adjacent the narrow end of the case. The detent mechanism carries pins 138 and 140 adapted to extend through apertures 142 and 144 in member 127 in alignment with apertures 146 and 148 in member 128. The pins are also receivable through holes 150 and 152 in saw bar 126 so as to removably secure the attachment 124 in sharpening position on the saw bar. The attachment is thus installed or released by moving 90 handle 136 temporarily outwardly against the spring bias of the mechanism.

The attachment 124 comprises locating means for receiving and positioning a flexible abrasive member preferably in the form of a flexible strip or web 154 which is comparatively stiff but which can undergo flexing or bending into an arcuate shape. The attachment 124 positions the strip 154 adjacent the saw bar with the strip's abrasive surface 175 in generally parallel relation to the path of saw chain 130 as the saw chain transverses the saw bar 126, and, since the attachment 124 is preferably located at the nose end of the saw bar, the strip 154 is positioned adjacent a curved portion of the path of the saw chain. In particular, the strip is disposed in substantially normal relation to the long axis of the saw bar 126 but is curved somewhat around the saw chain path as illustrated in Fig. 20 with abrasive surface facing the top sharpenable 110 surfaces of the cutter teeth on the cutter links, as well as, of course, the depth gauges. The flexible strip 154 is flexed so as to bear against the top surfaces of the cutter teeth to sharpen the same, and in particular the attachment causes flexing or 11 bending of the strip around the curved path of the teeth without substantially exceeding the elastic limit of the material. Therefore, the strip 154 follows around the curved path of the cutter teeth over a tangential contact area which may be 120 somewhat limited in extent.

The strip 154 is longitudinally restrained and supported upstream of the direction of cutter teeth travel from the area of tangential contact with the cutter teeth for the purpose of restraining longitudinal movement of the strip. As shown, the narrow strip 154 is folded over and secured, and/or provided with a tab at one end as illustrated at 156, and is received into the case through a slot 158 which is somewhat slanted GB 2 131 728 A 4 and orients the strip with a tangential attitude relative to the path of the saw chain. The edges of the slot 158 act to engage the tab 156 and restrain the strip longitudinally, i.e. so the same will retain its position despite frictional movement of the saw chain thereagainst tending to urge the strip further along the saw chain path.

The attachment 124 includes a further supporting means for the strip 154 in the form of a flat spring member 160 positioned rearwardly of the strip 154, that is on the opposite side of the strip from the saw chain. The spring 160 is secured around posts 162 and 164 which are upstanding from side member 127 and received in matching sockets in opposite side member 128. Spring 160 extends frorn post 162 to a position 166 immediately to the rear of strip 154 and upstream from the contact area 172. At position 166 the spring is bent rearwardly where it provides support for the strip in conjunction with the edges of slot 158, for example when the attachment is located in place over a saw chain. Spring 160 also extends from the lower post 164 to a second position or location 168 where the spring is bent rearwardly to support the strip 154 downstream from the area 172 of chain contact. A straight line between the first and second positions of support would intersect the path of the cutter top surfaces traversing around the saw bar. Consequently the strip 154 is flexed radially of the saw bar and exerts force radially inwardly against the cutter top surfaces for sharpening the same. The stiffness of the strip 154 and the rearward support thereof at locations 166 and 168 is such that strip 154 is stressed whereby the strip tends to restore itself to a non-bent or straight configuration and presses inwardly against the chain top sharpenable surfaces.

The spring 160 is bent away from said strip at 170 intermediate the positions 166 and 168, i.e. in the area where the strip contacts the chain, whereby the strip is free to flex and adjust to the contour of the saw chain surfaces. No stationary backing or pressure plate is applied against the back of the strip 154 in the area of chain contact, such as would force the strip between such a plate and the sharpenable surface, and hence no tearing or breaking of the strip is produced.

The strip 154 is longitudinally unrestrained adjacent the path of the saw chain cutter teeth in a direction downstream of the direction of teeth travel from the contact area. Thus, leading end 174 of the strip is unrestrained longitudinally although being backed laterally by spring 160 at position 168. It has been found that longitudinal restraint of the web at a downstream point immediately adjacent the path of the cutter teeth can cause a bunching in the strip and the buildup of a frontal wave in the strip as a cutter tooth travels therealong in contact therewith. Such a wave tends to generate a negative slope at the cutting edge of a cutter tooth, tending to dull rather than sharpen the cutter. The longitudinal freedom of end 174 insures sharpening with a positive relief angle. Also, the clearance of spring c, GB 2 131 728 A 5 in the region 170 aids in preventing a negative slope at the cutting edge since a conventional abrasive backing member can produce a negative slope of the like unless contact between the cutter and the abrasive surface is 70 very accurately controlled.

An abrasive strips track is provided on the inside walls of the attachment, in the form of upraised ridges 177 and 178 on the side members 127 and 128 respectively. These ridges are located adjacently to and extend along the strip 154, and along the path of the cutter teeth when the attachment is in place at the nose end of a saw bar. The ridges, however, have a relatively short-radius curved region 180 adapted to dontact the forward or abrasive side of strip 154, with the ridges flaring back from the strip 154 in more or less linear fashion at either side of region 180.

These ridges urge the centre of the strip 154 to the right (Fig. 17) prior to the time the strip engages the saw chain, and prevent movement of the abrasive surface to an undesired extent toward the saw chain between cutter links. That is, the strip 154 it held out of the way of the saw chain except for the sharpenable surface and depth gauge portions thereof to prevent incorrect sharpening of the cutter edges as well as damage to the strip. The apices of the ridges 117 and 178 are positioned at locations corresponding to the lowest sharpenable profile of a chain resulting after customary wear and sharpening over the lifetime of the chain.

The strip 154 suitably comprises a fabric backed abrasive web suitable for the removal of metal. The strip may be cut from conventional abrasive cloth material usually employed for abrasive disks and belts, metal polishing, cleaning, etc., and is fairly stiff, as hereinbefore mentioned, so that it tends to retain a flat orientation but can undergo flexing or bending without folding. 105 However, a member other than a completely fabric backed abrasive strip can be similarly employed.

For example, abrasive member 60 in the embodiment of Figs. 13-15 includes a thin strip of spring metal or the like as a backing layer which 110 is sufficiently flexible to follow the contour of the sharpenable surfaces without imposing the rigidness of predetermined path of a conventional, stationary backing member. However, even in the case of the embodiment of Figs. 13-15, appreciable care needs to be taken in moving member 60 against the saw chain so as to prevent improper pressure and damage to the chain or the abrasive material, and the embodiment of Figs.1 6-20, and embodiments subsequently described are preferred. The embodiment of Figs. 16-20 is economical and uses an economical and easily replaceable abrasive strip.

In use of the sharpener of Figs. 16-20, an abrasive strip 154 is inserted through slot 158 and the device is mounted on a saw bar by upraising handle 136 and sliding the device onto the end of the bar. The holes 146 and 148 are conveniently lined up visually with the matching holes 150 and 152 in the bar and the detent mechanism 132 is allowed to lock pins 138 and 140 into apertures 150 and 152. The saw motor is then operated at approximately one-third to one- half speed for approximately fifteen to twenty seconds for moving the top sharpenable surfaces against the abrasive surface for sharpening the cutting edge.

The embodiment of the invention shown in Figs. 21-25 comprises an attachment 182 mountable on the nose of saw bar 184, the latter being provided with a top sharpenable and side sharpenable chain 186. This embodiment is similar in many respect to the embodiment of Figs. 16-20, for example in that the attachment 182 is substantially U-shaped and slides over the nose end of the saw bar where it can be secured in place. A chain saw motor (not shown) drives saw chain 186 against a flexible strip or web 188 of abrasive material disposed in generally parallel relation to the path of the saw chain. The strip 188 is preferably positioned adjacent the curved portion of the path of the saw chain, and, in particular, in substantially normal relation to the long axis of the saw bar 184.

The attachment 182 in this instance includes a U-shaped metal member 190 having parallel sides or legs 192 and 194 defining a slot therebetween for reception of the saw bar. Immediately adjacent the abrasive member 188, and therefore immediately adjacent the end of the saw bar, the attachment carries a pair of side elements 196 and 198 respectively adapted for sharpening the outer side sharpenable surfaces of saw chain 186. Farther from the flexible strip 188, the sides or legs 192 and 194 are displacedinwardly at 200 and 202, ending in inwardly directed tabs 204 which register with a hole 206 in the saw bar. The sides further include apertures 208 in the inwardly directed parts which receive a screw 210. Screw 210 is also receivable through a hole 212 in the saw bar and is secured with a wing nut 214. Thus, the attachment 182 can be installed at the nose end of the saw bar by spreading the sides thereof slightly and sliding the attachment along the saw bar until the tabs 204 engage hole 206. With holes 208 and 212 aligned, scew 210 is inserted therethrough and secured with wing nut 214.

The attachment 182 includes supporting means for strip 188 in the form of a curved metal platen 216, suitably comprising a flat spring member configured into a loop shape. The platen is curved at each end and drawn together centrally by mechanism 218 so as to provide a first or upstream location of support 220 and a second or downstream location of support 222 for flexible strip 188, the latter being curved around the upper end of the platen as illustrated in Figs. 21, 22 and 25. Location 220 is upstream with reference to chain travel from the area 226 of contact between strip 188 and the chain, while location 222 is downstream therefrom. The rear or terminal ends of the platen area secured to the inside of end 195 of the member 190 as illustrated in Fig. 25.

The mechanism 218 draws the platen 216 rearwardly away from the contact area 226, 6 GB 2 131 728 A 6 whereby the strip is free to flex and adjust to the contour of the saw chain surfaces. The mechanism 218 comprises a screw 228 having a knurled head 230 bearing against the curved end 195 of member 190, the screw being threadably received in a block 232 having tabs 234 which engage the forward side of the platen. Consequently, rotation of screw 228 is adapted to bow the platen and draw central portion 236 thereof rearwardly into a concave configuration. It is noted that no stationary backing member or pressure plate is applied against the back of the strip in the area of chain contact and consequently no tearing or breaking of the strip is produced. Adjustment of screw 228 by turning knurled head 230 can be employed to change support locations 220 and 222 slightly and thereby adjust the tension and position of strip 188.

The flexible strip 188 is secured to the platen by means of a knurled head 230 of screw 228, the shank of which passes through a hole near end 224 of strip 183. The strip 188 is curved around the upper end of the platen and then extends downwardly toward chain contact area 226, thus being longitudinally restrained by the platen upstream of the direction of chain travel from contact area 226 to prevent movement of the strip along the chain path. Moreover, the upper part of the platen 216 restrains the plane of the strip with an attitude curving the strip away from the path of the cutter teeth, upstream of the contact area, so as to cause the strip to flex toward the cutter teeth in the contact area. The flexural resistance or restoring force of the strip applies pressure against the saw chain top sharpenable surfaces without employing a conventional stationary backing member and without causing undesired damage to the strip. The lower end of the strip is unrestrained longitudinally along the path of the cutters, e.g. toward location 222, such that buildup of a frontal wave in the strip, as might generate a negative slope at the cutting edge of a cutter tooth is avoided. Furthermore, the clearance of the platen in area 236 adjacent contact area 226 aids in presenting a negative slope at the cutting edge as could result from an improperly positioned backing member. Although flexural restoring force in the strip is produced in large part by the bending of the strip around the upper curved end of the platen and can be attained without the lateral constraint of the strip at location 222, the general shape of the platen prevents undesired movement of the strip away from the saw bar and adjustment of position 222 toward the strip can add tension as desired.

The flexible strip 188 suitably comprises the same type of material as strip 154 in the previous embodiment. Again, this material is comparatively stiff but can undergo flexing without folding or substantially exceeding the elastic limit thereof whereby the material itself is able to supply a restoring force which exerts sufficient pressure against the chain cutter teeth to sharpen the same.

Side elements 196 and 198 comprise 130 detachable metal plates mounted on the insides of legs 192 and 194 of Ushaped metal member 190 and disposed adjacent saw chain 186. The plates are generally circular and substantially flat and each is provided with a peripheral area of abrasive material 2338 on the inward side of the plate disposed in facing relation toward the side sharpenable surfaces of the cutter teeth for bearing thereagainst. Each abrasive surface extends along the curved path of the saw chain adjacent the curved end of the saw bar and contacts the cutter side sharpenable surfaces before and after the top sharpenable surface of the same tooth engages flexible strip 188.

The plates 196 and 198 have a radius slightly larger than the radius of the nose end of the saw bar but are positioned in generally concentric relation thereto. The plates are not completely round but are cut off along straight rear edges 240 which are perpendicular to the long axis of the saw bar, and along forward straight edges 242, also perpendicular to the long axis of the saw bar. Edges 242 are disposed adjacent strip 188 to accomplish the same function provided by the track 177, 178 in the prior embodiment, i.e., to restrain movement of the strip 188 farther than a predetermined distance in the direction of the cutter teeth so the strip will not become inserted between cutter teeth along the saw chain. The positioning of edge 242 is such as to allow for the maximum sharpening of the cutter teeth during the life of the chain.

Plates 196 and 198 are mounted on spider springs 244 and 246 which dispose the plates at each side of the device in inwardly facing relation toward the side sharpenable surfaces. The springs yieldably urge the abrasive surfaces of the plates into contacting relation with the side sharpenable surfaces are are sufficiently compliant to provide just sufficient force for sharpening the side surfaces at the same time the top surfaces are sharpened by strip 188. The springs 244, 246 are provided with tabs 248 and 250 adapted to be received in mating slots in legs 192 and 194 so that the plates can be detached if it is desired that the device be used only for sharpening the top surfaces of the chain.

Although generally planar, the plates 196 and 198 are desirably contoured somewhat in the peripheral area of abrasive material 238 whereby the abrasive surface makes an acute angle with the top sharpenable surfaces of the cutter teeth along the path of the saw chain to provide a desired clearance angle. The abrasive surfaces bow backwardly or are canted toward the spring mounting means 244 and 246 respectively to present a somewhat convex surface toward the chain. Figs. 27 and 28 illustrate the reason for this configuration. It will be seen that side sharpenable surface 46 of link 11 makes an angle D of less than 900 with top sharpenable surface 42 as a result of the contour or canting of the left- hand abrasive surface 238. Consequently, a vertical side plate clearance angle of about 41 is produced, said vertical side plate clearance angle - Z q 7 GB 2 131 728 A 7 equalling 90'-D. Since the top plate portion 24 slopes rearwardly and downwardly, the formation of a vertical side plate clearance angle also produces a horizontal side plate clearance angle indicated at E in Fig. 28. Thus, a desired horizontal relief angle is provided relative to point 40 by canting the abrasive surface 238 as illustrated.

The desired relief behind cutting edge 50 is provided in any of the embodiments because sharpening is carried out at the curved end of the saw bar with top sharpenable surface 42 forming 75 part of a cylindrical surface of revolution having as its centre the centre of curvature at the nose end of the saw bar. Although sharpening at the curved nose end of the saw bar is preferred, an attachment according to the present invention may alternatively be employed at the opposite curved end of the saw bar, i.e. at the sprocket end.

A modification of the third sharpener embodying the invention is illustrated in Fig. 26.

According to this variation, strip 188 comprises a 85 full, loosely formed belt loop provided therealong with an aperture for receiving the shank of screw 228. Sharpening contact between the strip 188 and the saw chain will automatically position the strip in the correct location for sharpening. The large free loop 249 which forms at the end in the direction of chain travel functions in the same manner as the non-constrained end of the strip in the embodiment of Figs. 21-25.

The operation of a third embodiment is 95 substantially the same as in the case of the embodiments hereinbefore described. That is, the attachment is placed on the nose end of the saw bar, with or without the side elements, and secured in place. The chain saw is then operated 100 for a short time at low speed, as described above, to accomplish sharpening.

Claims

1. A sharpener for a saw having a plurality of cutters movable along a predetermined path, the sharpener comprising one or both of means locating adjacent to the path top sharpening means for sharpening sharpenable top surfaces of the cutters, and means locating side sharpening means on opposite sides of the path, the side sharpening means being yieldably urged towards the path to sharpen sharpenable side surfaces of the cutters.

2. A sharpener for a saw having a plurality of cutters provided with top sharpenable surfaces and movable along a predetermined path, the sharpener comprising locating means mounted relative to the path for positioning a flexible abrasive member adjacent the path, the member having an abrasive surface disposed thereby generally along the path and facing the top sharpenable surfaces of the cutters, the member being flexed to bear against the cutter top surfaces while being otherwise restrained in an area of contact with the top surfaces.

3. A sharpener as claimed in claim 2 wherein the flexible abrasive member comprises a flexible strip of abrasive material adjacent said path having an area of contact with the top surfaces of the cutter teeth moving along the path, the strip of abrasive material being supported by said locating means to impart the flexure to said strip relative to the top surfaces of the cutter teeth.

4. A sharpener as claimed in claim 2 or 3 wherein the locating means includes means upstream of the direction of cutter travel from the area of contact for restraining movement of the member longitudinally thereof.

5. A sharpener as claimed in claim 4 wherein the upstream means includes means for restraining the plane of the member with an attitude causing the member to curve away from the path for causing the member in the region of contact to flex toward the cutters.

6. A sharpener as claimed in claim 4 or 5 wherein the locating means includes means downstream of the direction of cutter travel from the area of contact for co-operating with the upstream means to urge the member against the cutter teeth and provide the flexure, the path of the cutters being curved between the downstream means and the upstream means.

7. A sharpener as claimed in claim 2, 3, 4 or 5 wherein the member is longitudinally unrestrained adjacent the member in a direction downstream of the direction of cutter travel from the area of contact.

8. A sharpener for cutters movable in one direction in an arcuate path on a saw, the sharpener comprising means for mounting an elongate flexible abrasive strip member adjacent the arcuate path of the cutters to engage and sharpen top radially outwardly facing surfaces of the cutters at a contact region, the mounting means including means upstream from the contact region for restraining the strip against longitudinal movement in the direction of movement of the cutters, a pair of strip support members spaced apart along the path upstream and downstream, respectively, of the contact region and so positioned that a straight line connecting the support members defines a chord of the arcuate path to cause a portion of the strip member extending therebetween and supported thereby to be urged into contact with the cutters at the contact region, the strip member being otherwise unrestrained in the region of contact.

9. A sharpener as claimed in claim 8 wherein the strip member is free of longitudinal restraint in said path downstream from the contact region.

10. A sharpener as claimed in any preceding claim for a saw comprising a chain saw having a saw bar around which a saw chain is driven defining the path, the chain including links provided with the cutters, wherein the sharpener comprising an attachment for application to a curved end of the saw bar adjacent a curved portion of the saw chain path, with the flexible member being flexed to curve around at least part of the curved portion of the path.

11. A sharpener for a chain saw, the chain saw including a saw bar with a curved end, a saw chain entrained around the edge of the saw bar, and 8 GB 2 131 728 A 8 driving means for driving the chain around the bar, the sharpener comprising an attachment removably engageable with the saw bar for receiving a strip of flexible abrasive material having an abrasive surface disposed by the attachment in generally parallel relation to the path of the chain and facing the top surfaces of cutters forming part of the chain, the attachment including strip supporting means for flexing the strip for causing the abrasive surface thereof to be urged radially inwardly of the saw bar in contacting relation with the top surfaces of the cutters, the strip being longitudinally restrained and supported upstream along the strip from an area over which the chain contacts the strip, and being unrestrained longitudinally forwardly along the path of chain travel from the contact area, the strip immediately adjacent the top surfaces of the cutters being free to flex radially toward these top surfaces.

12. A sharpener as claimed in claim 11 wherein the strip supporting means secures the strip so as to flex the strip against the saw chain.

13. A sharpener as claimed in claim 11 or 12 wherein the strip supporting means comprises a platen around which the portion of the strip located opposite the direction of chain travel from the contact area is curved away from the saw bar for causing the strip to flex toward the saw chain in the region of contact of the strip with the top surfaces of the cutters.

14. A method of sharpening a saw as claimed in claim 11, 12, or 13 including simultaneously sharpening top surfaces of the cutters.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1984. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

1 I@ Z:1

14. A sharpener as claimed in claim 13 wherein the platen comprises a spring member forming a loop around which the strip is curved and secured, the spring member being curved at one end thereof to define a first location of support, and being curved at the opposite end thereof to define a position of support for the strip spaced therealong in the direction of chain travel from the area of chain contact, the spring member being bent away from the strip adjacent the area of chain contact so that the strip is free to flex radially toward and away from the cutter top surfaces. 45

15. A sharpener as claimed in claim 14 having 110 means for adjustably shifting the spring member away from the strip between said positions.

16. A sharpener as claimed in claim 11 wherein the strip supporting means further supports the strip rearwardly at a position spaced along the 115 strip in the direction of chain travel from the area of chain contact.

17. A sharpener as claimed in claim 16 wherein the strip supporting means comprises spring means located on the rearward side of the strip from the saw chain for contacting the strip upstream and downstream of the area of chain contact.

18. A sharpener as claimed in claim 17 wherein the spring means comprises a spring bent away from the strip adjacent the area of contact so that the strip is free to flex radially toward and away from the top surfaces of the cutters.

19. A sharpener as claimed in claim 16, 17 or 18 wherein a straight line extending from the position to the location of support upstream along the strip from the area of chain contact intersects the path of the cutter top surfaces on the saw bar, whereby the strip is flexed to exert pressure against the cutter top surfaces.

20. A sharpener as claimed in claim 19 further including means for restraining said strip from flexing toward said saw chain to points intermediate cutter links on said saw chain by more than a predetermined amount.

2 1. A sharpener as claimed in any one of claims to 20 wherein the said attachment is removably mountable on a said curved end of said saw bar.

22. A sharpener as claimed in claim 18 wherein the attachment comprises a slotted case slidable onto the saw bar and having means for attaching the spring means therewithin, the case having an aperture for receiving the strip into a position between the spring means and the saw bar, the edges of the aperture in the case acting to restrain the strip longitudinally.

23. A sharpener as claimed in claim 22 including a track on inside walls of the case for restraining the strip from flexing toward the saw chain to points intermediate cutter links on the said chain by more than a predetermined amount.

24. A sharpener as claimed in claim 22 or 23 wherein the case is provided with a spring detent mechanism for removably attaching the case to the saw bar.

25. A sharpener as claimed in any one of claims 2 to 24 having side sharpening elements disposed adjacent sides of the saw to sharpen side sharpenable surfaces of the cutters.

26. A sharpener for a saw having a plurality of cutters with side sharpenable surfaces which are movable along a predetermined path, the sharpener comprising side sharpening elements for sharpening the side sharpenable surfaces, means for mounting the side sharpening elements at each side of the path and facing toward the side sharpenable surfaces moving along the path, the side sharpening elements having abrasive surfaces for contacting the side sharpenable surfaces, and means for yieldably urging the side sharpening elements toward the cutter side sharpenable surfaces.

27. A sharpener as claimed in claim 26 wherein each side sharpener element is contoured to provide a side sharpenable surface with a side plate clearance angle.

28. A sharpener as claimed in claim 26 or 27 wherein the abrasive surfaces are substantially planar.

29. A sharpener as claimed in claim 26,27 or 28 wherein each element abrasive surface makes an acute angle with the top surfaces of cutters along the path.

30. A sharpener as claimed in claim 26, 27,28 or 29 wherein the side sharpening elements comprise plates and the means for yieldably urging the elements comprise springs on which the plates are mounted.

3 1. A sharpener as claimed in any one of claims a 9 GB 2 131 728 A 9 26 to 30 wherein the side sharpening elements are detachably mounted.

32. A sharpener as claimed in any one of claims 26 to 31 for a chain saw including a saw bar with a curved end, a saw chain having the cutters and entrained around the edge of the saw bar, and driving means for driving the chain around the bar, the sharpener comprising an attachment removably engageable with the saw bar and carrying the sharpening elements.

33. A sharpener as claimed in claim 32 wherein the attachment includes a pair of legs extending over the sides of the saw bar for supporting the side elements against the saw chain.

34. A sharpener as claimed in clairn 311 wherein 80 the attachment is substantially U-shaped having opposed legs for positioning on respective sides of the saw bar and is provided with side sharpening elements at the legs.

35. A sharpener as claimed in claim 32, 33 or 85 34 including end means for sharpening top surfaces of the cutters.

36. A sharpener as claimed in claim 35 wherein the end means comprises a flexible strip of abrasive material flexed toward the top surfaces.

37. A sharpener as claimed in claim 36 wherein the side sharpening elements act to restrain the strip from moving toward the saw chain to points intermediate cutter links on said saw chain by more than a predetermined amount.

38. A sharpener for a saw, substantially as herein described with reference to Figures 13-15, Figures 16-20, and Figures 21-25, 27 and 28, or Figure 26 of the accompanying drawings.

39. A method of sharpening the cutters of a saw, the method comprising the steps of moving the cutters along a path and disposing adjacent the path both of cutter top sharpening means arranged to sharpen sharpenable top surfaces of 105 cutters moving on the path, and cutter side sharpening means yieldably urged to engage and sharpen sharpenable side surfaces of cutters moving on the path.

40. A method of sharpening cutters having top 110 sharpenable surfaces, the method comprising moving the cutters along a predetermined path, disposing a flexible strip of abrasive material adjacent the path with an abrasive surface thereof generally parallel to the top surfaces of the cutters, 115 longitudinally restraining the strip at a given point, and flexing the strip relative to the cutters to engage the top surfaces thereof along the direction of cutter travel from a given point.

41. A method as claimed in claim 40 including 1. A sharpener for a saw having a plurality of simultaneously sharpening outer side sharpenable cutters with side sharpenable surfaces which are surfaces on the cutters by disposing substantially 120 movable along a predetermined path, the planar abrasive surfaces against the outer sides of the cutters moving along the path.

42. A method of sharpening cutters having outer side sharpenable surfaces on side plates, the 43. A method as claimed in claim 42 wherein the cutters have top sharpenable surfaces, the method including the step of disposing a flexible strip of abrasive material adjacent the path longitudinally restraining the strip at a given point, and flexing the strip so as to engage the top sharpenable surfaces with an abrasive surface thereof.

44. A method as claimed in claim 40,41 or 43 wherein the strip is flexed toward the cutters by curving the strip away from the cutters teeth proximate the given point.

45. A method as claimed in claim 40,41 or 43 including flexing the strip by curving the strip toward the path of the cutters downstream of the direction of teeth travel from where the strip engages the top surfaces of the cutters, the path of the cutters curving away from the otherwise extended position of the strip downstream from where the strip engages the cutters.

46. A method as claimed in claim 40,41,43, 44 or 45 including limiting flexure of the strip toward the cutters to prevent substantial movement of the strip between cutters along the path.

47. A method as claimed in claim 40,41 or any one of claims 43 to 46, including moving the cutter teeth along a curved path to provide relief back of the forward cutting edges of the top sharpenable surfaces.

48. A method as claimed in claim 41, 42 or 43 including canting the substantially planar abrasive surfaces inwardly toward the bottom of the side sharpenable surfaces to provide the cutter's teeth 100 with a side plate clearance angle.

49. A method as claimed in claim 41, 42 or 43 wherein the cutters have rearwardly and downwardly sloping surfaces on top plates, the method comprising the step of canting the abrasive surfaces inwardly toward the bottom of the side sharpenable surfaces to provide the cutters with vertical and horizontal side plate clearance angles.

50. A method of sharpening a saw, substantially as herein described with reference to Figures 13-15, Figures 16-20, Figures 21-25, 27 and 28, or Figure 26 of the accompanying drawings.

1. A saw sharpened by the method of any one of claims 39 to 49.

Superseded claims 1-51. New or amended claims:- sharpener comprising side sharpening elements for sharpening the side sharpenable surfaces, means for mounting the side sharpening elements at each side of the path and facing toward the side method comprising moving the cutters along a 125 sharpenable surfaces moving along the path, the side predetermined path, and disposing substantially planar abrasive surfaces against the outer side sharpenable surfaces of the cutters.

sharpening elements having abrasive surfaces for contacting the side sharpenable surfaces, and means for yielclably urging the side sharpening GB 2 131 728 A 10 elements toward the cutter side sharpenable surfaces.

2. A sharpener as claimed in claim 4 wherein each side sharpening element is contoured to 35 provide a side sharpenable surface with a side plate clearance angle.

3. A sharpener as claimed in claim 1 or 2 wherein the abrasive surfaces are substantially planar.

4. A sharpener as claimed in claim 1, 2 or 3 wherein each element abrasive surface makes an acute angle with the top surfaces of cutters along the path.

5. A sharpener as claimed in claim 1, 2, 3 or 4 wherein the side sharpening elements comprise plates and the means for yieldably urging the elements comprise springs on which the plates are mounted.

6. A sharpener as claimed in any preceding claim for a chain saw including a saw bar with a curved end, a saw chain having the cutters and entrained around the edge of the saw bar, and driving means for driving the chain around the bar, the sharpener comprising an attachment removably engageable with the saw bar and carrying the sharpening elements.

7. A sharpener as claimed in claim 6 wherein the attachment includes a pair of legs extending over the sides of the saw bar for supporting the side elements against the saw chain.

8. A sharpener as claimed in claim 7 wherein the attachment is substantially U-shaped having opposed legs for positioning on respective sides of the saw bar and is provided with side sharpening elements at the legs.

9. A sharpener as claimed in any preceding claim wherein the side sharpening elements are detachably mounted.

10. A sharpener as claimed in any preceding claim including means for sharpening top surfaces of the cutters.

11. A method of sharpening cutters having outer side sharpenable surfaces on side plates, the method comprising moving the cutters along a predetermined path, and disposing substantially planar abrasive surfaces against the outer side sharpenable surfaces of the cutter.

12. A method as claimed in claim 10 wherein the cutters have rearwardly and downwardly sloping surfaces on top plates, the method comprising the step of canting the abrasive surfaces inwardly toward the bottom of the side sharpenable surfaces to provide the cutters with vertical and horizontal side plate clearance angles.

13. A method as claimed in Claim 10 including canting the substantially planar abrasive surfaces inwardly toward the bottom of the side sharpenable surfaces to provide the cutter's teeth with a side plate clearance angle.