CHAIN SAW

SCIE A CHAINE

English Abstract

ABSTRACT
The specification discloses a chain saw having a guide bar which is
fastened to the frame of the chain saw so that most of the guide bar is out-
ward of the chain saw frame (referred to as the forward portion), which portion
is exposed for effective cutting, but with a mounting portion rearward of the
frame and the drive sprocket of the chain saw for improved mounting and adjust-
ment. The guide bar forms a part of a cassette which also includes a drive
sprocket trapped in the bar and a saw chain extending around the sprocket ant
the forward portion of the bar. A cover has clamping bosses clamping the bar
to the frame, and an adjustment screw engaging the rearward end of the bar is
mounted on the frame at the rear thereof so that it is readily accessible.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An assembly including a saw chain, guide bar, and drive
sprocket and further including means for mounting the assembly as
a unit to a chain saw housing,
the guide bar including a guide portion having guide
slots along the side edges adapted to entrain therein the guide
tangs of a saw chain, end guide means at one end of the guide
portion for guiding the saw chain around said end from one side
edge guide slot to the other side edge guide slot, a drive
sprocket receiving portion extending from the guide bar portion
on the end opposite the end guide means, a drive sprocket mounted
in said drive sprocket receiving portion, the drive sprocket
including sprocket teeth and a spindle provided with means for
interengaging the drive sprocket to the drive shaft of a chain
saw so that the sprocket can engage a loop of a saw chain entrained
in the guide slots and end guide means of the guide bar portion
and passing over the drive sprocket, the saw bar having a mounting
portion extending past the drive sprocket portion and adapted to
be fastened to the chain saw housing.
2. An assembly according to claim 1 wherein said guide bar
comprises a pair of plates that in said guide portion of the guide
bar are so spaced apart as to form said guide slots and end guide
means,
wherein in the drive sprocket receiving portion said
plates are spaced farther apart so as to receive the drive
sprocket, and one of the plates has a slot therein through which
a boss portion of the sprocket can extend.

3. An assembly according to claim 2 wherein the plates
are in abutment with each other in the mounting portion of the
guide bar.
4. An assembly according to claim 1, 2 or 3 including
releasable means for clamping the mounting portion of
the guide bar to the chain saw housing in a position in which the
guide bar extends forwardly from the sprocket,
and adjustment screw means mounted on the housing at the
rear of the sprocket and engaging the mounting portion of the
guide bar to hold the guide bar against rearward movement.
5. An assembly according to claim 1, wherein said drive
sprocket receiving portion of the guide bar has sides spread apart
for adjustably receiving said drive sprocket therebetween, said
guide bar carrying said drive sprocket, and including means for
releasably fastening said mounting portion rearwardly of said
drive sprocket to said chain saw housing for disposing said drive
sprocket in position for engaging the drive shaft while disposing
said guide bar and chain longitudinally forward of said sprocket.
6. An assembly according to claim 1 wherein
said guide bar includes a pair of side plates comprising
said guide portion spaced a predetermined distance apart so as to
form said guide slots and end guide means for said saw chain, said
predetermined distance being less than the width of said saw chain,
said guide plates having intermediate sprocket entrapping portions
defining said drive sprocket receiving portion, said drive sprocket
being carried by said intermediate portions, said intermediate

portions being spaced apart sufficiently farther than said pre-
determined distance and farther apart than the width of said saw
chain for adjustably receiving said drive sprocket therebetween,
the chain being entrained on the sprocket between said
intermediate portions and around said forward guiding portions,
said mounting portion of the guide bar located behind
said intermediate portions from said guiding portions being con-
structed for releasable mounting rearwardly of said drive sprocket
on said chain saw housing for disposing said drive sprocket in
engaging relation with the drive shaft while disposing said guide
bar and chain longitudinally forward of said sprocket substantial-
ly past said drive shaft.
7. An assembly according to claim 1 wherein the guide bar
mounting portion is constructed for releasable mounting rearwardly
of said drive sprocket on said chain saw housing for disposing
said drive sprocket in engaging relation with the drive shaft while
disposing said guide bar and chain longitudinally forward of said
sprocket substantially past said housing,
said mounting portion being provided with a longitudinal-
ly elongated slot for receiving a fastener and said housing includ-
ing a clamping cover for securing said guide bar to said housing
by means of said fastener.
8. An assembly according to claim 7 further including
adjustment screw means for mounting on said housing and adjustably
engaging the mounting portion of said guide bar for urging said
chain forwardly with respect to said sprocket.

Description

~3~
This is a division of our co-pending Canadian Patent Application No.
345,648 filed on February 14th, 1980.
This invention relates to an improved chain saw.
The invention provides an assembly including a saw chain, guide bar,
and drive sprocket and further including means for mounting the assembly as
a unit to a chain saw housing, the guide bar including a guide portion having
guide slots along the sidc cdgos adapted to entrain therein the guide tangs of
a saw chain, end guide means at one cnd of the guide portion for guiding the
saw chain around said end from one side edge guide slot to the other side edge
guide slot, a drive sprocket receiving portion extending from the guide bar
portion on the end opposite the end guide means, a drive sprocket mounted in
said drive sprocket receiving portion, the drive sprocket including sprocket
teeth and a spindle provided with means for interengaging the drive sprocket to
the drive shaft of a chain saw so that the sprocket can engage a loop of a saw
chain entrained in the guide slots and end guide means of the guide bar portion
and passing over the drive sprocket, the saw bar having a mounting portion
extending past the drive sprocket portion and adapted to be fastened to the
chain saw housing.
In the disclosed embodiment the guide bar includes two plates having
first portions secured to a spacer plate to form a forwardly extended saw chain
guiding portion and also has sprocket clearance portions extending around the
drive sprocket. The mounting portion of the saw bar extends past the drive
sprocket and rearward of the drive sprocket where it is clamped against the
frame of the chain saw by a boss on a cover to form a cantilever mounting.
The invention will further be described by way of example only, with
reference to the accompanying drawings, wherein:
Figure 1 is a perspective view of an improved chain saw forming one
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embodiment of the invention;
Figure 2 is a fragmentary, vertical, sectional view of the chain saw
of Figure l;
Figure 3 is a horizontal, sectional view taken along line 3-3 of
Figure 2;
Figurc 4 is an enlarged, vertical, sectional, view taken along line
4-4 of Figure 2;
Figure 5 is an cnlarged, vertical, sectional view taken along
line 5-5 of Figure 3, and,
Figure 6 is an enlarged, vertical, sectional view taken along line
6-6 of Figure 5.
A chain saw 10 forming one embodiment of the invention includes
a chain saw housing 12 having a motor housing 14, a handle 16, a head end frame
or casting 18 secured by long screws to the motor housing and a cover 20. A
cassette 22 has a saw bar 24 guiding a saw chain 26 driven by a drive sprocket
28 mounted on a motor shaft 30. The cassette includes the saw chain and the
sprocket, and is attachable to and detachable from the saw as a unit.
The saw bar 24 is clamped to the head end casting 18 both at the
front and at the rear of the sprocket by boss portions 40 and 42 of the cover
20 and lands 44 and 46 of the casting 18. A wing nut 48 screwed onto a stud 52
clamps the cover to the casting. An ad~ustment screw 56 screwed into a nut 58
welded to the casting 18 engages the end of the saw bar 24 and adjusts it to a
chain tightening position while the wing nuts are loosened. This adjustment
mechanism gives a strong, positive tightening of the saw chain, and is conven-
iently located at the rear of the chain saw. Also such adjustment is achieved
at a remote point from the saw chain and thus offers the advantage of increased
safety.
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113t~962
The saw bar 24 includes outer plates 60 and 62 welded to a center
plate 64 by spotwelds 66 and trap a nose sprocket 68 having an axle member 70
projecting through holes 72 in nose portion 74 of the plates 60 and 62. The
saw chain is guided by guide edges 76 of the forward or chain guiding portions
of plates 60 and 62, outcr edgo portions of the plates 60 and 62 forming a
groove for the chain with the edge of thc centerplate. The rearward end
portion of the saw bar is formed by tho two plates 60 and 62 welded together
by spotwelds 78. The saw bar has a longitudinal guidc slot 80, which could be
off-center to insurc that the cassotte cannot be rcversed. Also, a pair of
lands 84 forms a guideway for longitudinal adjustment of the saw, the pair of
lands 84 being rearward or to the left of the sprocket, as viewed in Figure 2.
The sprocket 28 is screwed onto an adapter 90 having a keying socket
92 receiving the shaft 30 of an electric motor of the saw. A capscrew 94
screwed into tapped bore 96 of the shaft locks the adapter to the shaft. Inter-
mediate entrapping portions 98 and 100 of the plates 60 and 62 are spaced apart
by bent portions 102, 104, 106 and 108 from each other to accommodate the drive
sprocket and provide clearance for the portion of the saw chain passing around
the sprocket. The portions 98 and 100 have longitudinal slots 110 and 112 in
which boss portions 114 and 116 of the sprocket fit.
The saw bar 24 being clamped both rearwardly and forwardly at points
spaced apart almost half the length o the saw bar is very securely held. Also
since the saw bar is securedly held rearwardly thereof, the casting 18 and
cover 20 need and do extend in the forward direction only slightly beyond the
sprocket 28 so that a very long portion of the saw bar and saw chain are exposed
and effective for sawing.
The saw bar 24, the saw chain 26 and the sprocket 28 are a unit and
installed, removed and handled as such. The unit may be easily assembled in
the saw and disassembled therefrom.