Note: Descriptions are shown in the official language in which they were submitted.
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Backqround of the In_ention:
The present invention relates to a chain saw bar
tightener. More particularly, the invention relates to a
chain saw bar tightener for a chain saw having a chain bar of
substantially elongated plate-like configuration having
elongated top and bottom edges with a groove formed therein
for guiding a chain. The chain bar has front and back edges
with a groove for guiding the chain and a slot extending sub-
stantially parallel to the top and bottom edges from the back
edge into the chain bar to an end intermediate the front and
back edges of the chain bar. The chain saw also has a housing.
Chain saw bar tighteners are disclosed in United
States patents Nos. 2,109,702; 2,718,908; 2,728,566;
2,767,746; 2,910,099; 3,194,284; 3,267,973; 3,636,995
and 3,866,320.
The principal object of the invention is to provide
a chain saw bar tightener which is installed with facility,
convenience and rapidity in chain saws of all ages and which
tightens, and applies increased tension on, the chain of a
chain saw.
An object of the invention is to provide a chain saw
bar tightener of simple structure, which is inexpensive in
manufacture and functions to tighten, and apply increased
tension on, the chain of a chain saw.
Another object of the invention is to provide a
chain saw bar tightener which functions efficiently,
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effectively and reliably to selectively tighten and loosen
the chain of a chain saw without the need for dismantling
the saw.
Still another object of the invention is to provide
a chain saw bar tightener of simple structure, w~ich is in-
expensive in manufacture, installed with facility, safety,
convenience and rapidity in chain saws of all types and ages,
and functions efficiently, effectively and reliably to
selectively tighten and loosen the chain of a saw chain, and
thereby apply increased tension on the chain of a chain saw,
as desired, without the need for dismantling the saw.
.
Brief Summarv of the Invention:
In accordance with the invention, a chain saw bar
tightener for a chain saw having a chain bar of substantially
elongated plate-like configuration having elongated top and
bottom edges with a groove formed therein for guiding a
chain, front and back edges with a groove for guiding the
chain and a slot extending substantially parallel to the top
and bottom edges from the back edge into the chain bar to an
end intermediate the front and back edges of the chain bar,
and a housing, comprises a bar pin passing into the chain
bar slot and secured in position relative to said housing.
A bar extension plug is removably positioned in the chain bar
slot between the bar pin and the intermediate end of the
chain bar slot thereby being interposed between the bar pin
and the intermediate end of the chain bar slot and
positioning the front edge of the chain bar farther from the
housing and resulting in tightening the chain on the chain
bar and applying increased tension on the chain. The inter-
mediate end of the chain bar slot is substantially semicircular
and has a predetermined diameter, the bar pin has a predeterm-
ined diameter, and the bar extension plug has spaced substanti-
ally parallel top and bottom edges, a convex substantially
semicircular front edge having substantially the same diameter
as the intermediate end and a concave substantially semicircu- -
lar back edge having substantially the same diameter as the barpin. The bar extension plug has a pair of spaced substantially
parallel substantially planar faces, a bore formed through the
plug at a point intermediate the front and back edges of the
plug, substantially equidistant from the top and bottom edges
of the plug, substantially perpendicular to the faces of the
plug and opening at the faces, and a slot extending substanti-
ally parallel to the top and bottom edges from the back edge
into the plug to the bore for permitting the top and bottom
edges of the plug to be moved toward each other at the back
edge thereof for positioning the plug in the chain bar slot and
for removing the plug from the chain bar slot. The slot of the
bar extension plug tapers downward from the back edge of the
plug to the bore.
In accordance with the invention, a chain saw bar
tightener for a chain saw having a chain bar of substantially
elongated plate-like configuration having elongated top and
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bottom edges with a groove formed therein for guiding a
chain, front and back edges with a groove for guiding the
chain and a slot extending substantially parallel to the top
and bottom edges from the back edge into the chain bar to an
end intermediate the front and back edges of the chain bar,
and a housing, comprises a bar pin passing into the chain
bar slot and secured in position relative to the housing.
A chain tightening device is affixed to the housing and in
cooperative relation with the bar pin for applying selected
forward and backward thrusts to the bar pin in a manner where-
by when the bar pin is given a forward thrust, the bar pin is
moved forward thereby moving the chain bar to tighten the
chain of the saw and when the bar pin is given a backward
thrust, the bar pin is moved backward thereby permitting the
chain bar to loosen the chain of the saw. A bar extension
plug is removably positioned in the chain bar slot between the
bar pin and the intermediate end of the chain bar slot there-
by being interposed between the bar pin and the intermediate
end of the chain bar slot and positioning the front edge of
the chain bar farther from the housing and resulting in
tightening the chain on the chain bar and applying increased
tension on the chain. The intermediate end of the chain bar ;~
slot is substantially semicircular and has a predetermined
diameter, the bar pin has a predetermined diameter, and the
bar extension plug has spaced substantially parallel top and
bottom edges, a convex substantially semicircular front edge
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having substantially the same diameter as the intermediate
end and a conca~ve substantially semicircular back edge having
substantially -the same diameter as the bar pin. The bar extens-
ion plug has a pair of spaced substantially parallel sub-
stantially planar faces, a bore formed through the plug at a
point intermediate the front and back edges of the plug, sub-
stantially equidistant from the top and bottom edges of the
plug, substantially perpendicular to the faces of the plug
and opening at the faces, and a slot extending substantially
parallel to the top and bottom edges from the back edge into
the plug to the bore for permitting the top and bottom edges
of the plug to be moved toward each other at the back edge
thereof for positioning the plug in the chain bar slot and for
removing the plug from the chain bar slot. The slot of the
bar extension plug tapers downward from the back edge of the
plug to the bore.
In accordance with the invention, a chain saw bar
tightener for a chain saw having a chain bar of substantially
elongated plate-like configuration having elongated top and
bottom edges with a groove formed therein for guiding a chain,
front and back edges with a groove for guiding the chain and
a slot extending substantially parallel to the top and bottom
edges from the back edge into the chain bar to an end inter-
mediate the front and back edges of the chain bar, and a
housing, comprises a disc having an axial bore therethrough.
A substantially semiannular slot having a diameter smaller
.
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than that of the disc is formed through the disc with its
ends substantially on a diameter of the disc. The semi-
annular slot has one end adjacent the circumference of the
disc and the other end adjacent the axial bore between the
bore and a point diametrically opposite that adjacent the one
end of the slot. A plurality of spaced accommodation slots
extend radially in mutually spaced relation in the area of
approximately half the circumference of the disc. A disc
mounting device rotatably mounts the disc for rotation via a
stud passing through the slot of the chain bar and affixed to
the housing. A bar pin passes through the semiannular slot
of the disc and into the chain bar slot in a manner whereby
when the disc is rotated by a tool in the accommodation slots
of the disc, when the bar pin is given a forward thrust, the
bar pin is moved forward thereby moving the chain bar to
tighten the c~ain of the saw and when the Ibar pin is given a
backward thrust, the bar pin is moved backward thereby
permitting the chain bar to loosen the chain of the saw. A
bar extension plug is removably positioned in the chain bar
slot between the bar pin and the intermediate end of the chain
bar slot thereby being interposed between the bar pin and the
intermediate end of the chain bar slot and positioning the
front edge of the chain bar farther from the housing and
resulting in tightening of the chain on the chain bar and
applying increased tension on the chain. The intermediate
end of the chain bar slot is substantially semicircular and
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has a predetermined diameter, the bar pin has a predetermined
diameter, and the bar extension plug has spaced substantially
parallel top and bottom edges, a convex substantially semi-
circular front edge having substantially the same diameter as
the intermediate end and a concave substantially semicircular
back edge having substantially the same diameter as the bar
pin. The bar extension plug has a pair of spaced substanti-
ally parallel substantially planar faces, a bore formed through
the plug at a point intermediate the front and back edges of
the plug, substantially equidistant from the top and bottom
edges of the plug, substantially perpendicular to the faces
of the plug and opening at the faces, and a slot extending sub-
stantially parallel to the top and bottom edges from the back
edge into the plug to the bore for permitting said top and
bottom edges of the plug to be moved toward each other at the
back edge thereof for positioning the plug in the chain bar
; slot and for removing the plug from the chain bar slot. The
slot of the bar extension plug tapers downward from the back
edge of the plug to the bore.
Brief Description of the Drawinqs:
In order that the invention may be readily carried
into effect, it will now be described with reference to the . .
accompanying drawings, wherein:
FIGo 1 is an exploded perspective view of an embodi-
ment of the chain saw bar tightener of my United States
patent No. 4,129,943, issued December 19, 1978;
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FIG~ 2 is a view, partly in section, of the
embodiment of FIG~ l;
FIG~ 3 is a view, partly in section, taken along
the lines III-III, of FIG~ 2;
FIG~ 4 is a view of the embodiment of FIG~ 3
adjusted to tighten the chain of the saw;
FIG~ 5 is a view of the embodiment of FIG~ 3
adjusted to tighten the chain of the saw to a greater extent
than in FIG. 4;
FIG~ 6 is a partly cutaway, partly sectional view,
taken along the lines VI-VI, of FIG~ 2;
FIG~ 7 is a view, taken along the lines VII-VII,
of FIG~ 6;
FIG~ 8 is a view, on an enlarged scale, of an em-
bodiment of the bar extension plug of the present invention,
installed in the chain bar of the chain saw of FIGS~ 1 to 7;
FIG~ 9 is a view, on an enlarged scale, of the em-
bodiment of FIG~ 8 of the bar extension plug of the invention;
FIGo 10 is a back end view, taken along the lines
X~X~ of FIG~ 9; and
FIG~ 11 iS a cross-sectional view, taken along the
lines XI-XI, of FIG~ 9
Detailed Description of the Invention:
The chain saw bar tightener of the invention is
described with reference to the chain saw disclosed in my
United States patent No. 4,129,943. The chain saw of my
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U. S. patent has a chain bar 1 (FIGS. 1 to 5 and 8) of sub-
stantially elongated plate-like configuration having elongat-
ed top and bottom edges 2 and 3, respectively (FIGS. 1, 3 to
5 and 8), with a groove formed therein for guiding a chain
(not shown in the FIGS.). The groove 4 formed in the top
edge 2 is shown in FIG. 2. The chain bar 1 has a front edge
(not shown in the FIGS.) and a back edge 5 (FIGS. 1 to 5)
with a groove for guiding the chain. The groove 6 formed
in the back edge 5 is shown in FIG. 2. A slot 7 (FIGS. 1,
3 to 5 and 8) extends substantially parallel to the top and
bottom edges 2 and 3 from the bac~ edge 5 into the chain bar
1 to an end 31 (FIG. 8) intermediate the front and back edges
of said chain bar. The chain saw also has a housing or
housing casting 8 (FIGS. 1, 2 and 5).
The chain bar tightener of the invention comprises
a disc 9 (FIGS. 1 to 6) having an axial bore 10 (FIG. 1)
formed therethrough. A substantially semiannular slot 11
having a diameter smaller than that of the disc 9 is formed
through said disc with its ends 12 and 13 substantially on a
diameter of the disc, as shown in FIGSl and 3 to 6. The semi-
annular slot 11 has one end 12 adjacent the circumference 14
(FIG. 1) of the disc and the other end 13 adjacent the axial
. .
bore 10 between said bore and a point diametrically opposite
that adjacent the end 12 of the slot, as shown in FIGS. 1 and
3 to 6.
A plurality of spaced accommodation slots 15, 16,
17, and so on, extend radially in mutually spaced relation in
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the area of approximately half the circumference 14 of the
disc 9 (FIGS. 1 and 3 to 5).
A disc mounting device comprising a stud 18 (FIGS.
1 to 6) passes through the axial bore 10 of the disc 9 and
through the slot 7 of the chain bar 1 and is affixed to the
housing 8 for rotatably mounting the disc for rotation about
its axis. The stud 18 and a second stud 19 (FIGSo 1 to 6)
and corresponding nuts 20 and 21 threadedly coupled to the
studs 18 and 19, respectively (FIGS. 1 and 2), fasten a cover
plate 22 (FIGS. 1, 2, 6 and 7) to the housing 8 with the chain
bar 1 sandwiched between said housing and said cover plate,
thereby securing said chain bar in positi~n. The chain bar
1 is secured in position in an adjustable manner, since both
studs 18 and 19 pass through the slot 7 thereof.
A bar pin 23 (FIGS. 1 to 6) passes through the semi-
annular slot 11 of the disc 9 and fits into the slot 7. The
bar pin 23 is secured in position relative to the housing 8.
When the disc 9 is rotated clockwise by a screwdriver 24
(FIG. 2) which is passed with an up and down motion through
an access slot 25 formed through the cover plate 22 (FIGS. 1
and 2) into an accommodation slot 15, 16, 17, and so on, of
the disc in a manner whereby the bar pin 23 is given a forward
thrust, in the direction of an arrow 26 of FIG. 2, the bar pin
is moved forward and thereby moves the chain bar 1 in the same
direction of the arrow 26 to tighten the chain of the saw.
When the screwdriver 24 is inserted into an accommodation
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11
slot 15, 16, 17 and so on, of the disc 9 and rotates the
disc counterclockwise in the opposite direction, the bar pin
23 is given a backward thrust, in the direction of an arrow
27 of FIG. 2, and said bar pin is moved backward, thereby
permitting the chain bar l to be moved in the direction of the
arrow 27 to loosen the chain of the saw.
The disc slot ll controls the movement of the bar
pin 23.
A bar pin holder 28 is sui~ably mounted in the
cover plate 22, as shown in FIGS. l, 2, 5, 6 and 7.
The groove 6 is approximately l/4 inch deep to
accommodate the saw chain. There is no clearance between the
saw bar, the disc and the cover, since these parts must be
solid and tight to prevent the disc from moving when the
nuts 20 and 21 are tight. Since the disc cannot turn when
the nuts 20 and 21 are tight, it is not necessary to tighten
such nuts as much as other saws thereby preventing possible
stripping of threads in engine castings, as the nuts are -
threaded. When the nuts are loosened, all the components
move easily. The components cannot move, however, when the
nuts are tightened.
The bar pin 23 is clear at its head end. mis is ::
necessary, since the cover does not tighten properly if the
bar pin is too long. However, there must be no clearance
where the bar pin 23 fits into the disc slot 11, since this
causes looseness of the chain bar l. The bar pin 23 is ~-
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12
securely fixed in the disc slot 11. It is impossible for
the chain bar 1 to loosen, since the disc 9 cannot rotate
when the nuts 20 and 21 are tight.
The bar pin holder 28 functions only to keep the
bar pin 23 from being lost when the cover 22 is removed.
The bar pin holder 28 maintains the bar pin 23 on the cover
22. The notches on the head of the bar pin holder 28 keep
said bar pin holder in place, and said holder retains the
bar pin 23, in turn. When the cover 22 is removed, the bar
pin 23 is easily removed by prying the bar pin holder 28 out
of said cover with a screwdriver via an opening 30 (FIGS.
6 and 7).
The bar pin holder 28 may easily be pried out for
cleaning, yet will prevent the bar pin 23 from belng lost,
even with rough usage. The studs for tightening the cover 22
are very easy to reach. The access slot 25 is readily access-
ible, as shown in FIG. 1, and permits the tightening adjust-
ment of the chain.
The chain saw bar tightener of my U. S. Patent
No. 4,129,943 has many advantages and is practical. The chain
will not loosen in, or after,use, since the disc 9 cannot
turn when the nuts 20 and 21 are tight. The accommodation or
adjustment slots in the disc 9 of the chain saw bar tightener ~ ~
are easily accessible and positive in adjusting chain tension. ~ -
The bar pin 23 of the chain saw bar tightener is readily and
rapidly removable by the slipping out of the bar pin holder 28
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13
for cleaning the bar pin head groove. The nuts 20 and 21 do
not have to be overly tight to hold the chain adjustment,
thus preventing thread stripping.
The chain saw bar tightener of my U.S. patent
No. 4,129,943 functions very well with chain bars two feet
in length and less. However, with a chain bar considerably
longer than two feet, when the chain is worn to a certain
extent, it has a tendency to stretch and a link or more has
to be eliminated from the chain in order to adjust its
tension. The bar extension plug of the invention overcomes
this problem by placing the proper tension on the chain due
to its advancing of the length of the chain bar relative to
the housing of the chain saw.
The bar extension plug 32 of the invention is
shown in FIGS. 8 to 11. As shown in FIG. 8, the bar
extension plug 32 is removably positioned in the chain bar
slot 7 between the bar pin 23 and the intermediate end 31
of said chain bar slot. The bar extension plug 32 is there-
by interposed, between the bar pin 23 and the intermediate
end 31 of the chain bar slot 7, and positions the front edge
tnot shown in the FIGS.) of the chain bar 1 farther from the
housing 8 (FIG. l)o This results in the tightening of the
chain bar and the application of increased tension on the
chain. The disc 9 is placed in its slack position when the
bar extension plug 32 is inserted. The disc 9 may be placed
in its slack position to start again in adjusting the chain.
:
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14
The bar extension plug 32 eliminates the nead for removal
of chain links in order to readjust the tension on the
chain.
As shown in FIG. 8, the intermediate end 31 of the
chain bar slot 7 is substantially semicircular and has a
predetermined diameter DS. The bar pin 23 has a predetermined
diameter DB, as shown in FIG. 8. The bar extension plug 32
has spaced substantially parallel top and bottom edges 33
and 34, respectively, as shown in FIGS. 9 to 11. The bar
extension plug 32 also has a convex substantially semicircu-
lar front edge 3-5 (FIG. 9) having a diameter DP, asshown in
FIG. 9, which is substantially the same as the diameter DS
of the intermediate end 31 of the slot 7, as shown in FIG. 8.
The bar extension plug 32 also has a concave substantially
semicircular back edge 36 (FIGS. 9 and 10) having a diameter
DE (FIG. 9) which is substantially the same as the diameter
DB of the bar pin 23, as shown in FIG. 8.
As shown in FIGS. 10 and 11, the bar extension
plug 32 has a pair of spaced, substantially parallel, sub-
stantially planar faces 37 and 38! respectively. A bore 39
(FIGS. 8 and 9) is formed through the bar extension plug 32
at a point 40 intermediate the front and back edges 35 and
36, respectively, of said plug, as shown in FIG. 9. The bore
39 is substantially equidistant from the top and bottom
edges 33 and 34, respectively, of the bar extension plug 32
and substantially perpendicular to the faces 37 and 38 of
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6~
said plug and opens at said faces. A slot 41 (FIGS. 9 to 11)
extends substantially parallel to the top and bottom edges
33 and 34, respectively, from the back edge 36 into the bar ~-
extension plug 32 to the bore 39 thereof. The slot 41 permits
the top and bottom edges 33 and 34, respectively, of the
plug 32 to be moved toward each other at the back edge 36
thereof in order to position said plug in the chain bar slot
7 and to permit removal of said plug from said chain bar slot.
As shown in FIGS. 9 to 11, the slot 41 of the bar
extension plug 32 tapers downward ~rom the back edge 36 of
said plug to the bore 39 thereof. The taper is a slight one
and is evident when the bar extension plug 32 is free from
the chain saw. When the bar extension plug 32 is inserted
in the slot 7 of the chain bar l of a chain saw, the slot 41
of said bar extension plug loses its taper since it is
squeezed in said slot, as shown in FIG. 8.
The bar extension plug 32 of the invention is
preferably approximately 5~8 inch in length and is preferably
steel having sufficient flexibility to permit its top and
bottom edges 33 and 34 to be compressed toward each other
and to permit said plug to remain in a compressed condition
in the slot 7 of the chain bar 1 as long as desired.
The purpose of the bore 39 through the bar extens-
ion plug 32 is to prevent the breaking of said plug and to
permit said plug to remain tightly in position in the slot
of the chain bar 1. The bar extension plug 32 is readily ;-
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16
installed in, and removed from, the slot 7 of the chain bar
1 by a pair of slip joint pliers with the jaws contacting
the top and bottom edges 33 and 34, respectively, thereof in
proximity with the back edge 36 thereof. The plug 32 is
partially positioned in the slot 7 and is then gently tapped
into its position shown in FIG. 8. When the plug 32 is to
be removed from the chain bar 1, it is gently tapped so that
the area of its back edge 36 is moved out of the slot 7 of
said chain bar and the pliers are then again used to compress
said bar applying pressure to the top and bottom edges 33
and 34, respectively, thereof, in proximity with said back
edge.
The bar extension plug 32 may comprise any suitable
material suc~ as, for example, metal, plastic, or the like,
Since there is no wear on the plug 32, it may be made of any
suitable plastic material such as, for example, Nylon.
The bar extension plug 32 has a thickness slightly
. . . ~ ., .
less than that of the chain bar l to permit a tight fit of
all the parts when the stud nuts are tight. As hereinbefore
stated, the disc 9 must be in its slack position when the
bar extension plug 32 is installed. This gives the disc a
new start in adjusting the chain. The chain bar 1 and the
disc 9 are preferably of approximately the same thickness
in order to provide a good bearing surface for the bar pin
23 in the disc slot 11.
1 ~S 6Z6~ ~
: 17
While the invention has been described by means
` of a specific example and in a specific embodiment, I
do not wish to be limited thereto, for obvious modifica-
, tions will occur to those skilled in the art without ~.
departing from the spirit and scope of the inventionO
