Note: Descriptions are shown in the official language in which they were submitted.
lZ~2~i
Saw chains having chisel-type cutter links, that is cutter links
in which the top plate portion and the 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 clS 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 being less adapted to
slitting than Ihe sharp corner of the chisel-type teeth but being sharpen-
able without the great skill required by the chisel teeth. In each of
Silvon United States patents 3,263,717 and 3,469,610, Oehrli United States
patent 3,260,287 and Frederickson United States patent 3,1~9,064, there is
disclosed a tooth adapted to have its top cutting edge sha~pened uniformly
with little skill required but the side slitter edge must be hand filed and
this tooth does not present an easily maintained sharp corner. Neumeier
United States patent 3,581,785 also shows top cutting teeth which can be
sharpened easily but which have no side slitter portions. Dolata et al
United States patents 3,921,490 and 4,023,453 disclose a saw chain having
a twisted tooth which can be top sharpened and a side slitter which can be
sharpened at the outside edge. However, both the top edge and the side
slitting edge must include such large angles that they are not good cutters
and a sharp corner is not provided. Also, such teeth break off easily.
Most top cutting edges can be sharpened employing an abrasive
stone mounted adjacent the drive sprocket of a chain saw and movable radial-
ly inwardly against the chain, one example being illustrated in the afore-
mentioned Oehrli United States patent 3,260,287. A grinding stone or the
like can also be made elongated and arcuate whereby plural top cutting edges
are sharpened as the chain passes around the sprocket, for example as
illustrated in the aforementioned Dolata patents, in Carter United States
patent 3,457,969, Silvon United States patents 3,435,860, 3,487,591 and
3,516,459, Condon et al United States patent 3,526,156 and Van Ourkerk
-- 2 --
~ :'
lZ~286
United States patent 3,534,638. These devices are rather com-
plex and expensive, and furthermore the sharpening stone is sub-
ject to wear and damage. Graversen United States patent
3,529,495 and Stihl et al United ~tates patent 3,603,179 disclose
curved backing plates or the like which support abrasive strip
material adjacent the path of the cutter teeth. However, these
devices tend to produce rapid wear or damage in the strip mater-
ial when the same is urged toward the moving saw chain.
Also, the prior art does not disclose a satisfactory
device for automa-tically sharpening cutter teeth with outer side
sharpenable surfaces. Although Dolata United States patent
4,023,453 discloses sharpening a rounded corner, no means is
disclosed for sharpening an outer side cutting edge of a chisel-
type tooth having a sharp corner at the juncture of the side
cutting edge and a top cutting edge.
An object of the present invention is to provide an
improved method and means for outside sharpening a chisel-type
saw tooth.
Summary of the Invention
The invention provides a sharpener for a saw device
having a plurality of cutter teeth provided with top sharpenable
surfaces and movable along a predetermined curved path, said
sharpener comprising: a flexible abrasive member, and locating
means mounted relative to said predetermined path for positioning
said flexible abrasive member adjacent said path, said member
having an abrasive surface disposed thereby generally along said
path and facing the top sharpenable surfaces of said cutter
teeth, support means on said locating means engaging said flex-
ible abrasive member at spaced apart points and restraining said
abrasive member such that it intercepts said path with said
abrasive surface engaging the said top sharpenable surface of
said cutter teeth, said flexible abrasive member being free of
12~'~Z8~
external support between said support means and being self-
suppor-ting therebetween whereby it is free to move toward and
away from said path in the area of contact of said abrasive
member with the cutter teeth top surfaces so that said member
can assume the contour of the path of the cutter teeth top sur-
faces in said area of contact.
The invention also provides a sharpener for a chain
saw, said chain saw including a saw bar with a curved end, a saw
chain entrained around the edge of said saw bar, and driving
means for driving said chain around said bar, said sharpener
comprising: an attachment removably engageable with said saw
bar for receiving a strip of flexible abrasive material having an
abrasive surface disposed by said attachment in generally
parallel relation to the path of said chain and facing the top
surfaces of cutters forming part of said saw chain, said attach-
ment including strip supporting means for flexing said strip for
causing the abrasive surface thereof to be urged radially inward-
ly of said saw bar in contacting relation with the top surfaces
of said cutters of said chain, said strip being longitudinally
restrained and supported upstream along said strip from an area
of chain contact by said strip, said strip being unrestrained
longitudinally forwardly along the path of chain travel from
said contact area, the strip immediately adjacent the top sur-
faces of said cutters being free to flex radially toward the top
surfaces of said cutters.
From another aspect, the invention provides the method
of sharpening cutter teeth having top sharpenable surfaces, said
method comprising: moving said cutter teeth along a predeter-
mined arcuate path, disposing a Elexible strip of abrasive mater-
ial adjacent sald path with an abrasive surface thereof facingthe path of -the top surfaces of said cutter teeth, longitudinally
restraining said strip at a given point adjacent said path, and
C - 4 -
)42~6
at a second point spaced from said given point applying a force
to said strip to cause said strip to be urged toward said path
thereby to engage the top surfaces of said teeth over an area of
contact with said strip, and while applying said force applying
no ex-ternal restraint to said strip in said area of contact
whereby said strip is free to flex toward and away from said top
surfaces.
The invention also provides the method of sharpening
cutter teeth having top sharpenable surfaces and outer side
sharpenable surfaces, said method comprising: moving said cutter
teeth along a predetermined path, disposing a flexible strip of
abrasive material adjacent said path with an abrasive surface
thereof generally parallel to the top surfaces of said cutter
teeth, longitudinally restraining said strip at a given point,
f].exing said strip relative to said cutter teeth to engage the
top surfaces thereof along the direction of teeth travel from
said given point, and simultaneously sharpening outer side
sharpenable surfaces of said cutter teeth by disposing substan-
tially planar abrasive surfaces against the outer sides of said
cutter teeth moving along said path.
The strip of abrasive material is longitudinally
restrained at a given point out of contact with the cutter teeth
and is flexed toward the cutter teeth to engage the top sharpen-
able surfaces thereof at a point downstream or along the direc-
tion of teeth travel from such given point. However, the strip
of abrasive material is longitudinally unrestrained along said
path farther downstream from the cutter teeth contact area and
moreover the strip immediately adjacent the top surfaces of the
cutter teeth is free to flex radially toward or away from said
top surfaces. That is, the strip is not provided with a pre-
formed backing device forcing the same into the teeth but rather
the strip is urged toward the teeth in response to flexural
12~ 86
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
cutter teeth immediately adjacent the area of contact with a
backing member.
Substantially planar abrasive surfaces are movable
against the outer side sharpenable surfaces of said cutter teeth
moving along the path, these abrasive surfaces being canted
inwardly toward the bottom of said side sharpenable surfaces to
provide said cutter teeth with vertical and horizontal side
plate clearance angles. Ordinarily the cutter teeth top surfaces
and side surfaces are sharpened simultaneously with an attachment
embodying aspects of the present invention, said attachment suit-
ably being removably securable to the nose end of a chain saw
bar.
The subject matter which we regard as our invention is
particularly pointed out and distinctly claimed in the concluding
portion of this specification. The invention, however, both as
to organization and method of operation, together with further
advantages and objects
- 5a -
2~i6
thereof, may best be understood by reference to the follow-
ing description taken in connection with the accompanying
drawings wherein like reference characters refer to like
elements.
Brief Description of the Drawings
Figs. 1 and la are perspective views of an improved
chisel-type cutter link;
Fig. 2 is a side elevation view oE the cutter
link of Fig. l;
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, vertic,al, sectional view
taken along line 4-4 of Fig. 2;
Fig. 5 is a top plan view taken a:Long line 5-5
of Fig. 2;
Fig. 6 is a side elevation view taken along
line 6-6 of Fig. 5;
Fig. 7 is a fragmentary, side elevation view of
an improved 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, top plan view of the
saw chain of Fig. 7;
Figs. g-12 are perspective views of the several
stages of making a cutter link like 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 attach-
ment mounted on a saw bar thereof;
Fig. 14 is a fragmentary, side elevation view of
the chain saw and sharpe~ing attachment of Fig. 13;
JPD/lm 231~ 10~'27/80 B-l ~
1~S?~ 6
Fig. 15 is a bottom plan view taken along line
15-15 of Fig. 14;
Fig. 16 is a perspective view of the chain saw
with the saw chain of Fig. 7 and a second embodiment of
a sharpening attachment mounted on the saw bar thereof;
Fig. 17 is a more detailed cross-sectional view
illustrating the attachment of the embodiment of Fig. 16,
said cross-sectional view being taken at 17-17 in Fig. 18;
Fig. 18 is a transverse cross-sectional view of
the latter attachment, being taken at 18-18 in Fig. 17;
Fig. 19 is an exploded view of the sharpening
attachment according to the second embodiment;
Fig. 20 is a side view, partially broken away and
partially in cross section, illustrating in greater detail
a saw bar with the attachment according to the second em-
bodiment mounted thereon;
Fig. 21 is a perspective view, partially broken away,
illustrating a third embodiment of a sharpening attachment
and the saw bar upon which it is mountable;
Fig. 22 is a side view of the Fig 21 attachment;
Fig. 23 is a top view of the attachment according
to the third embodiment;
Fig. 24 is a transverse cross-sectional view of
the attachment according to the third embodiment;
Fig. 25 is a side view, partially broken away and
partially in cross section, illustrating in greater detail
a sharpening attachment according to the third embodiment
mounted on a saw bar, the cross-sectional portion being
taken at 25-25 in Fig. 24;
Fig. 26 is a partial cross-sectional view illustrating
a variation of the sharpening attachment according to the
U/ 111~ , l U / ~ / / O U L~
3 2~?~2~36
third embodiment;
Fig. 27 is an enlarged explanatory view illus-
trating the canting of abrasive surf`aces in the third
embodiment to produce a side plate clearance angle on a
saw tooth; and
Fig. 28 is a top view of a link which has been
sharpened employing the third embodiment and further
illustrating a side plate clearance angle.
Description
A completely outside sharpenable saw chain 10
(Figs. 7 and 8) has novel top and side sharpenable chisel-type
cutter links or teeth 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, i.e. 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 downwardly 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. Throughout this description
and the claims, for purposes of clarity in describing the
cutter links 11 and 12, it will be assumed that the body
portions are in upright positio~s with the top plates
uppermost. "Forwardly" means in the direction of chain
travel, e.g. to the right in Fig. 2, while "rearwardly"
~2~2~16
refers to the opposite direction. Also, "inwardly" means
toward the longitudinal center plane of the chain and
"outwardly" means laterally away from the plane.
Each link 11 (and 12) has a sharp point 40 formed
at the junction of a top sharpenable surface ~2, an outer,
planar side sharpena~le surface 46 and an inner surface 4~
preferably chrome, 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 rear-
wardly 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 are preferably sharpened by
power, and may be sharpened by an arcuate abrasive member
60 (Figs. 13-15) of a sharpening attachment 63 on a chain saw
62, when the member 60 is pressed toward a nose portion 64
~0 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. Arcuate abrasive member
60 is somewhat flexible, including a backing comprising a tnin
strip of spring metal or the like, and is placed in contact
with the saw chain top surfaces by depressing bail 120 which
raises crank 122 and draws member 60 to the left in Fig. 14.
Simultaneously, the member 60 also abrades top surfaces 57
of the depth gauge portions to reduce their height pro-
portionately to the reduction of the height of the cutters
by the sharpening. Rear end 68 (Fig. 2) of each depth
gauge portion is the gauging portion thereof and is positioned
_ g
~2(~ 6
substantially farther forwardly of the midpoint of an
imaginary line 70 ~oining the centers of 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 of the top plate
portion 24 relative to the horizontal (angle B~) is from about
30 to about 40 such that the included angle of the cutting
edge is from about 30 to about 40. 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 22 with a line 79 (Fig. 5) normal to the
plane of the body portion.
The kerf side cutting edges 54 of the side plate
portions 20 of the links 11 and 12 are sharpened by press-
ing planar abrasive members 80 and 81 (Figs. 13-15) against
the sides of the saw chain 10 as the chain is driven by
the chain saw to abrade the side sharpening surfaces 46
(Figs. 1-6). It will be noted that planar abrasive members
80 and 81 are pivotally carried by sharpening attachment
63 and are spring biased against the side sharpening sur-
faces 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
pGrtionS 14 of the cutter links 11 and 12 during sharpening,
-- 10 --
36
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 ~, 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 eclges 54 is be-
tween 30 and 40. This slope also perr,lits many sharpen-
ings of the side cutting edges without weakening the side
:lo 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 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 and it is then heat treated to
harden it to a Rockwell hardness of from about 50 to about
65 on the Rockwell Scale C, it being feasible to ma]ce the
teeth even as hard as the 65, since filing is not required
to sharpen the cutting edges 50 and 5~.
After the hardening of the links 11 and 12, 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
~ood being cut against the top plate portion 24 and the
side plate portion 20 so that there is no tendency to peel
~JrL)~ lU/ ~ SU 1~--L g~
off the chromium plating.
The top plate portion, proceeding from the bent
portion 26 at its outer edge, is ~ilted 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 5û to extend
somewhat rearwardly proceeding from the corner or point
4û. This gives the cutting edge a slicing as well as a
chiseling action.
lû To provide the hook shape of the side cutting
edge 54, the side plate portion 2û tllts 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 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 lû 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 centerline of
the chain so that the top plate portions 24 of the links
11 and 12 overlap one anotherO
The bent edge portion 26 at the juncture of the
side plate portion 2û and the top plate portion 24 so
extends inwardly and downwardly' that, as the to~ sharpening
surface 42 and the side sharpening surface 46 are sharpened
substantially equally, the point 40 is maintained substantially
- 12 -
. JPD~lm 23-~ 1 12/10/80
8~;
at the center 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 while shown as substantially p:Lanar may instead
be 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 30. The side plate portion 20 tilts
inwardly proceeding upwardly at an angle of about 10 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 111~.
The shank portion 18 is sloped at an angle of about 45 to
the body portion 14. The angle C of the side cutting
edge 54 relative to the vertical is about 22. The thick-
ness of the chromium plating on the lower face 44 of the topplate portion 24 and the inner face 52 of the side plate
portion 20 is about 0.0004 inches. The l:ink 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 porti'on 24, the side plate portion 20
and tne shank portion 18, in transverse cross-section, are
co~bined, concave and roughly in the form of a "C" having
~ ~ ~ 4 b
a combined concave inner surface which may vary from a
substantially uniform curvature to being highly angled
at the bent portions.
A method and apparatus for sharpening the cutter
edges by power is further il:Lustrated in Figs. 16 through
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 saw 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 form-
ing 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 alignr.lent with apextures 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 attach-
ment 124 in sharpening position on the saw bar. The attach-
ment is thus installed or released by moving handle 136
temporarily outwardly against the spring bias of the mechanism.
The attachment 124 comprises locating means for
- 14 -
:~S~'86
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 flexin~
or bending into an arcuate shape. The attachment 124
positions the strip 154 adjacent the saw bar with the
stri~'s abrasive surface 175 in generally parallel re-
lation to the path of saw chain 130 as the saw chain
traverses 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 the abrasive surface
facing the top sharpenable 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 bending of
the strip around the curve~ path of the teeth without sub-
stantially 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 in
some instances be somewhat limited in extent.
The strip 154 is longitudinally restrained and
supported upstream of the direction of cutter teeth travel
from the area of tan~ential contact with the cutter teeth
for the purpose of restraining longitudinal movement of the
strip. In the case of the embodiment being described, a
narrow strip 154 is folded over and secured, and/or providedwith a tab at one end as illustrated at 15~, and is received
4~8~i
into the case throuyh a slot 158 which is somewhat slanted
and orients the strip with a tangential attitude relative
to the path of the saw chain. The edges of the slot 158
act to engaye the tab 156 and restrain the strip longitudin-
S ally, i.e. so the same will retain its position despitefrictional movement of the saw chain therea~ainst tendiny
to urge the strip farther along the saw chain path.
The attachment 124 includes further supporting
means for said strip in the form of a flat spring member 160
positioned rearwardly of 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 from 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 lower post 164 to
a second position or location 158 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 sharpeniny the same. The stiff~
ness of the strip 154 and the rearward support thereof at
locations 166 and 168 is such that strip 154 is stressed
- 16 -
~ JPD/lm 23~ 12/10/80
~?~
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 interrnediate the positions 166 and 16$, i.eA in the
area where the strip contacts the chain, whereby the strip
is free to fle~ and adjust to the contour of the saw chain
surfaces. It is noted no stationary bacl~ing member or
pressure plate is applied against the back of the strip in
the area of chain contact as would force the strip between
such plate and the sharpenable surface, and hence no tearing
or breaking of the strip is produced.
The strip 154 is longitudinally unrestrained ad-
jacent the path of the saw chain cutter.teeth in a direction
downstream of the direction of teeth travel from the con-
tact area. Thus, in the present embodiment, 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 160
in the region 170 aids in preventing a negative slope at
the cutting edge since a convéntional abrasive backing
member can produce a negative slope or the li~e unless
contact between the cutter and the abrasive surface is
286
very accurately controlled.
An abrasive strip track is provided on the
inside walls of the attachment, said track comprising
upraised ridges 177 and 178 on side memhers 127 and 128
respectively. These ridges are located adjacently along
the strip ~54, 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 somewhat short-radius
curved region 180 adapted to contact 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 center of the
strip 154 a'to the right (in 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
is 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 ridges 177 and 178
are positioned at locations corresponding to the lowest
- sharpenable profile of a chain resulting after customary
~ear and sharpening over the lifetime of the chain.
The strip 154 suitably comprises a fabric backed
;~5 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. However,
a me~er other than a completely fabric backed abrasive
strip can be similarly employed. For example, abrasive
- 18 -
JPD/lm 2~ 1 12/10/80 C-l ~
~Z~ Z8~;
member 60 in the embodiment of Fig. 14 includes a thin
strip of spring metal or the like as a backing layer
which is sufficiently flexible to follow the contour of
the sharpenable surfaces without imposing the rigidness
or predetermined path of a conventional, stationary
backing member. However, even in the case of the embodi--
ment of Fig. 14, 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
L0 material. Consequently, the embodiment of Figs. 16-20
and su~sequent embodiments are preferred. Moreover, the
construction of Figs. 16-20 is quite economical and utilizes
an economical and easily replaceable abrasive strip.
In use of the device of Figs. 16-20, an abrasive
:L5 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 1~8
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.
Referring to Figs. 21-25, another embodiment
of the present invention is illustrated comprising an
attachment 182 mountable on the nose of saw bar 184,
the latter being provided with a top shrapenable and
side sharpenable chain 186. This embodiment is similar
in many respects to the embodiment of Figs. 16-20, for
-- 19 --
~2Q~:86
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 displaced inwardly 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 hale 206. With holes 208 and
212 aligned, screw 210 is inserted therethrough and
secured with wing nut 214.
- 2~ -
Y I I 1 ' / l V / ~ U
12~42136
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 Fiys. 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 there-
from. The rear or terminal ends of the platen are secured
to the inside of end 195 of member 190 as illustrated
]5 in Fig. 25.
The mechanism 218 draws the platen 216 rearwardly
away from the contact area 226, whereby the strip is
free to flex and adjust to the contour of the saw chain
surfaces. The mechanism 21~ 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 ha~ing 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. ~djustment of screw 228 by
turning knurled head 230 can be employed to change support
locations 220 and 222 slightly and thereby adjust the
- 21 -
J L~ m ~ L ~
lZ~42~6
tension and position of strip 188.
The flexible strip 188 is secured to the platen
by means ~f the knurled head 230 of screw 228, the shank
of which passes through a hole near end 224 of strip 18~.
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 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, for thereby causing the strip to flex to-
ward the cutter teeth in the contact areaO 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 ~f 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
- 22 -
JPD/lm 23~ 1 12/11/8~ C-l ~
2~36
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 em-
bodiment. Again, this material is comparatively stiff
but can u~dergo 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 detachable
metal plates mounted on the insides of legs 192 and 194
of U-shaped ~etal mernber 190 and disposed adjacent saw
chain 186. The plates are generally circular and sub-
stantially flat and each is provided with a peripheral
area of abrasive ~aterial 238 on the inward side of the
plate disposed in facing relation toward the side sharpen-
able surfaces of the cutter teeth for bearing thereagainst.
Each abrasive surface extends along the curved path of
the saw cllain adjacent the curved end of the saw bar and
contacts the cutter side sharpenable surfaces before and
after the top sharpenable surface of the sa~e 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
- 23 -
;~2(?4~
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
maximurll 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 sharpen-
able surfaces. The springs yieldably urge the abrasive
surfaces of the plates into contacting relation with the
side sharpenable surfaces and are sufficiently compliant
to provide just sufficient force for sharpening the side
surfaces at the same time the top surfaces are sharpened ~y
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 the plates can be detached if it is desired
that the device be used only for sharpening the top surfaces
of the hain.
Although generally planar, the plates 196 and 198
are desirably contoured somewhat in the peripheral area-
of abrasive material 238 whereby the abrasive surfacemakes an acute angle with tne top sharpenable surfaces of
the cutter teeth along the path of the saw chain to provide
a desired c:Learance angle. The abrasive surfaces bow back-
wardly or are canted toward the spring mounting means 244
and 246 respectively to present a somewihat convex surface
- 24 -
JPD/lm 23~ ` 12~11/80 C~1 ~
toward the chain. Figs. 27 and 28 illustrate the reason
for this configuration. It will be seen that side sharpen-
able surface 46 of link 11 makes an angle D of less than
90 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 4 is produced, said vertical side plate clearance
angle equaling 90-D. Since the top plate portion 24
slopes rearwardly and downardly, 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 pro-
vided 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 part of a cylindrical sur-
face of revoluation having as its center the center of
curvature at the nose end of the saw bar. Although sharpen-
ing 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 sproc~et end.
A variation of the third embodiment i5 illustrated
in Fiy. 26. According to this variation, strip 188 com-
prises a full, loosely formed belt loop provided therealong
Witil an aperture for receiving the shank of screw 228.
Sharpening contact between the strip 188 and the saw
~0 chain will automatically position the strip in the correct
location for sharpening. The large free loop 249 which
- 25 -
42~
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 the third embodiment is sub-
stantially the same as in the case of the embodimentshereinbefore 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 for a short time at low speed, as here-
inbefore described, to accomplish sharpening.
While we have shown and described several em-
bodiments of our invention, it will be apparent to those
skilled in the art that many changes and modifications
may be made without departing from our invention in its
broader aspects. We therefore intend the appended claims
to cover all such changes and modifications as fall within
the true spirit and scope of our invention.
- 26 ~
