Information
-
Patent Grant
-
6564459
-
Patent Number
6,564,459
-
Date Filed
Monday, March 5, 200123 years ago
-
Date Issued
Tuesday, May 20, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Shoap; Allan N.
- Nguyen; Phong
Agents
-
CPC
-
US Classifications
Field of Search
US
- 083 375
- 083 378
- 083 386
- 083 385
- 083 830
- 083 816
- 083 817
- 292 333
-
International Classifications
-
Abstract
In a chain saw having a sprocket (11), which is supported in rotary fashion in a housing (10) and is for a saw chain (12) guided on a guide (13), and having a chain tension device (14) for longitudinally moving the blade (13), which device has a cam (15) that moves the guide (13) and a rotating member (17) for rotating the cam (15), in order to preset a chain tension that is optimal for operation and is independent of the user, the rotary connection between the rotating member (17) and cam (15) is embodied as a detent overload clutch (18), whose detent overload force is set in accordance with the required chain tension (FIG. 2).
Description
BACKGROUND OF THE INVENTION
The invention relates to a chain saw.
In a known chain saw of this type (DE 21 32 747 A1), a torsion spring is disposed between the rotating member and the cam, and this torsion spring drives the cam resting against the stop in a rotation direction such that the guide is constantly subjected to a longitudinal displacing force which strives to increase the guide's distance from the sprocket so that the saw chain is subjected to a constant tension force which compensates for a progressive lengthening of the saw chain due to abrasion and temperature increase during operation. During assembly, the torsion spring is stretched by means of the rotating member embodied as a turning knob until the cam rests against the stop with a sufficient degree of initial stress.
In a likewise known chain saw with a chain tension device (WO 98/33631 A1), the guide that guides the saw chain is fastened between two securing plates and is secured together with them to the housing so that it can be moved in the longitudinal direction of the blade. A bolt that passes through a bore in a cam and an oblong hole in the housing is screwed into the one securing plate, which is guided in a longitudinally movable fashion on the housing, and fixes the cam to the housing by means of its bolt head. In order to stretch the chain tight, the bolt is loosened slightly and the cam, which is supported with its circumference against a housing stop, is rotated so that the bolt moves with the securing plates in the direction of the free end of the blade. The rotation of the cam is stopped when it is evident by feel that the saw chain has reached a sufficiently high tension. The bolt is then tightened again so that the cam and the securing plates are fixed to the housing, with the guide in the adjusted position.
SUMMARY OF THE INVENTION
The chain saw according to the invention has the advantage that the detent overload clutch always sets a chain tension that is present at the factory and is independent of the user, and consequently, the user is not presented with the problem of whether the chain tension that he adjusts by feel is also the correct chain tension for an optimal operation of the chain saw. The chain tension device can thus be operated manually without tools which is why it requires only a rotating movement and no other axial movements of the blade whatsoever. An automatic loosening of the chain tension device resulting in decreasing chain tension during operation of the chain saw can be reliably prevented by means of a simple additional measure.
According to an advantageous embodiment of the invention, the cam is supported on the rotating member in a rotating, but axially fixed manner and the detent overload clutch has a first clutch disk provided with detent elements and non-rotatably fixed to the cam and a second clutch disk provided with detent elements and non-rotatably fixed to the rotating member as well as a prestressed clutch spring which presses the two clutch disks axially against each other, with their detent elements engaging one another. With this structural embodiment, the detent coupling is realized in a technically very simple manner and the detent overload force and thus the chain tension can be set by means of the clutch spring that is embodied as a compression spring.
According to a preferred embodiment of the invention, the rotating member is embodied as a clamping sleeve which is screwed with an internally threaded section onto an externally threaded section of a stay rod secured in the housing. In order to actuate the clamping sleeve, a turning knob is slid onto it in a nonrotating, preferably form-fitting manner. This structural embodiment achieves a simple operation of the chain tension device by means of a turning knob.
According to an advantageous embodiment of the invention, the stay rod protrudes through an oblong hole embodied in the guide, while the clamping sleeve overlaps the oblong hole and by being screwed onto the stay rod, pressed against the guide so that it is immovably fixed to the housing after the chain saw is stretched tight. As a result, the set chain tension is reliably maintained during operation of the chain saw.
According to an advantageous embodiment of the invention, the sprocket and the chain tension device are covered by a protective hood which is attached to the housing and permits the damping sleeve to protrude through it, and the turning knob non-rotatably slid onto the clamping sleeve is guided in rotary fashion in the protective hood. Between the turning knob and the protective hood, there is a manually detachable detent mechanism whose form-fitting engagement prevents the turning knob from turning back counter to the rotation direction for screwing the clamping sleeve onto the stay rod. This detent mechanism reliably prevents a loosening of the chain tension device through vibrations during operation of the chain saw.
According to an advantageous embodiment of the invention, the stop on the guide for supporting the cam is embodied as a tensioning piece, which at the one end is slid with a pin in form-fitting manner into a bore in the guide and at the other end, rests with a shaped element in a lateral, form-fitting manner in the oblong hole of the guide and preferably rests against the end of the oblong hole remove from the sprocket.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained in detail in the description below in conjunction with an exemplary embodiment shown in the drawings.
FIG. 1
shows a side-view detail on a chain saw in the vicinity of a chain tension device with the protective hood removed,
FIG. 2
is a section along the line
11
—
11
in FIG.
1
through the chain saw with the protective hood in place,
FIG. 2
a
is an exploded view of the section of
FIG. 2
,
FIG. 3
is a top view of a cam with the first clutch disk of the chain tension device in
FIGS. 1 and 2
,
FIG. 4
is a section along the line IV—IV in
FIG. 3
,
FIG. 5
is a top view of a second clutch disk of the chain tension device in
FIGS. 1 and 2
,
FIG. 6
is a side view of a clamping sleeve of the chain tension device in
FIGS. 1 and 2
,
FIG. 7
is a longitudinal section through the clamping sleeve in FIG.
6
.
FIG. 8
is a top view of the clamping sleeve in the direction of arrow VIII in
FIG. 6
,
FIG. 9
is a top view of a turning knob of the chain tension device in
FIGS. 1 and 2
,
FIG. 10
is a partially sectional view of the turning knob in the direction of arrow X in
FIG. 9
,
FIG. 11
is a section along the line XI—XI in
FIG. 9
,
FIG. 12
is a top view of a tensioning piece of the chain tension device in
FIGS. 1 and 2
,
FIG. 13
is a side view of the tensioning spring in the direction of arrow XIII of FIG.
12
.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1
schematically depicts a detail of a chain saw which has a housing
10
in which a sprocket
11
for driving a saw chain
12
is supported in rotary fashion. The sprocket
11
is driven by a transmission, not shown here, of an internal combustion or electric motor and its teeth engage in the saw chain
12
. The saw chain
12
is guided along the edge of a guide
13
protruding from the housing
10
. In order to produce a saw chain tension, the guide
13
is secured to the housing
10
in a longitudinally movable fashion so that the distance between the guide
13
and sprocket
11
can be changed and as a result, the saw [blade] chain
12
can be stretched more or less tight.
In order to stretch the saw chain
12
fight and to fix the guide
13
in a position on the housing
10
that maintains the set chain tension, a chain tension device
14
is provided which is fastened in a protective hood
40
(
FIG. 2
) attached to the housing
10
. The chain tension device
14
has a cam
15
, which is rotatably fixed to the side of the housing and supported against a stop
16
fixed to the [blade] guide
13
, and has a rotating member
17
for rotating the cam
15
. The rotary connection between the rotating member
17
and the cam
15
Is embodied as an detent overload clutch
18
whose detent overload force is adjusted in accordance with the required chain tension. With this chain tension device
14
, by rotating the cam
15
by means of the rotating member
17
and the detent overload clutch
18
, the guide
13
is slid forward in a direction that increases the distance from the sprocket
11
and this action stretches the saw chain
12
tight. If the saw chain
12
has now come completely into contact in the guide groove in the longitudinal edge of the guide
13
and is therefore stretched tight, the resistance to the movement of the guide
13
increases. If the rotating member
17
is then turned further in the clockwise direction in
FIG. 1
, a detent overload of the detent overload clutch
18
occurs as soon as the force for moving the guide
13
exceeds the detent overload force that is set in the detent overload clutch
18
. The detent overload clutch
18
therefore assures that after actuation of the chain tension device
14
, the saw chain
123
always has the same chain tension which is determined by the detent overload force of the detent overload clutch
18
that is set at the factory. As a result, the chain tension is predetermined independent of the individual feel of the user and is designed for an optimal operation.
In the exemplary embodiment of the chain tension device
14
described, the rotating member
17
is embodied as a clamping sleeve
19
(
FIGS. 6
to
8
) which is screwed with an internally threaded section
20
onto an externally threaded section
21
of a stay rod
22
(FIG.
2
). The stay rod
22
is fastened with its end in the housing
10
and protrudes at right angles from a housing projection
101
of the housing
10
to which the guide
13
is secured in a longitudinally movable fashion. In order to guide the guide
13
on the housing projection
101
, the latter has two guide bumps
23
which, in order to guide the guide
13
, engage in a form-fitting manner with movement play in an oblong hole
24
in the guide
13
, which extends in the longitudinal direction of the guide. The stay rod
22
protrudes through the oblong hole
24
in the guide
13
, while the clamping sleeve
19
screwed onto the stay rod
22
overlaps the oblong hole
24
and by being screwed onto the stay rod
22
, is able to press the guide
13
against the housing projection
101
and to thereby immovably fix the guide
13
to the housing
10
. In order to rotate the clamping sleeve
19
, a turning knob
25
is non-rotatably slid onto its free end. For this purpose, on its end remote from the guide
3
, the clamping sleeve
19
has a radially protruding flange
26
which is contained in a form-fitting manner in the turning knob
25
and is supported with its top against a collar
27
formed inside the turning knob
25
and snap hooks
28
that are of one piece with the turning knob
25
engage behind the bottom of the flange
25
(FIG.
2
). The cam
15
is supported in rotatary fashion on the clamping sleeve
19
and is prevented from moving axially toward the guide
13
by means of a securing ring
29
affixed in the clamping sleeve
19
.
The detent overload clutch
18
disposed between the cam
15
and clamping sleeve
19
has a first clutch disk
30
non-rotatably connected to the cam
15
with detent elements
31
disposed equidistantly over the disk circumference (FIG.
3
), a second clutch disk
32
non-rotatably fixed to the clamping sleeve
19
provided with detent elements
33
disposed equidistantly over the disk circumference (FIG.
5
), and a clutch spring
33
. The two clutch disks
30
,
32
rest with their detent elements
31
,
33
against each other, wherein the detent elements
31
of the clutch disk
30
are formed onto the cam
15
and are of one piece with it, and the detent elements
31
,
33
are pressed against each other in the axial direction by the clutch spring
34
. As
FIG. 2
shows, the clutch spring
34
is embodied as a helical compression spring, which is supported at one end against the back side of the second clutch disk
32
remote from the cam
15
and is supported at the other end against the underside of the flange
26
on the clamping sleeve
19
, oriented toward this second clutch disk
32
. The detent overload force of the detent overload clutch
18
is set through greater or lesser prestressing of the clutch spring
34
. As can be inferred from
FIGS. 2
,
5
,
6
, and
7
, and rotationally fixed connection between the second clutch disk
32
and the clamping sleeve
19
is achieved by means of form fitting engagement by virtue of the fact that a flattening
35
is respectively provided on diametrically opposite sides of the clamping sleeve
19
, onto which the second clutch disk
32
is slid with corresponding, parallel flat edges
36
of a central slide-mount opening
37
. The annular groove
38
in
FIGS. 6 and 7
, which is disposed on the circumference of the clamping sleeve
19
, serves to contain the previously mentioned securing ring
29
for axially fixing the cam
15
.
As can be seen in
FIG. 2
, the turning knob
25
, which is slid in a form-fitting manner onto the flange
26
of the clamping sleeve
19
and engages the flanges
26
in detent fashion, is guided in rotary fashion in the protective hood
40
that covers the sprocket
11
and the chain tension device
14
, to which end the protective hood
40
has a circular, cuplike recess
41
coaxial to the clamping sleeve
19
, and the turning knob
25
is inserted into this recess
41
. The turning knob
25
is depicted by means of a grip strip
43
embodied on it in a top view in
FIG. 9
, in a partially sectional side
3
view in
FIG. 10
, and in a longitudinal section in FIG.
2
. It has a flat knob plate
42
, with the diametrically extending grip strip
43
protruding at right angles from it, and a continuous, radially protruding annular rib
44
on the knob plates
42
. The turning knob
25
rests with its knob plate
42
against the cup bottom of the recess
41
and leaving a rotary play, engages with its annular rib
44
behind a number of detent hooks
45
disposed in the annular wall of the recess
41
in the protective hood
40
.
As shown in
FIGS. 9 and 11
, a manually detachable detent mechanism
46
is provided between the turning knob
25
—and its knob plate
42
in fact—and the protective hood
40
—and the cup bottom of the recess
41
in fact—which prevents the turning knob
25
from turning back counter to the rotation direction for screwing the clamping sleeve
19
onto the stay rod
22
, i.e. a counterclockwise rotation in FIG.
9
. This detent mechanism
46
prevents the clamp connection between the clamping sleeve
19
, the guide
13
, and the housing projection
101
from loosening during operation of the chain saw and consequently prevents the chain tension from changing. The detent mechanism
46
has an annular saw-toothed strip
47
(
FIG. 11
) formed onto the cup bottom of the recess
41
, coaxial to the clamping sleeve
19
, as well as two diametrically disposed detent projections
48
elastically protruding from the underside of the turning knob
25
oriented toward the protective hood
40
, which engage in a frictional and form-fitting manner in the saw-toothed strip
47
. Each detent projection
48
is disposed on the underside of a flexible tongue
49
that is cut out from the knob plate
42
on three sides. At the base of the flexible tongue
49
, a tab
50
that is of one piece with the flexible tongue
49
protrudes at right angles and extends parallel to the grip strip
43
spaced slightly apart from it. If the tabs
50
are pressed toward the grip strip
43
with the thumb and finger, then the flexible tongues
49
lift up slightly, as shown with dashed lines in
FIG. 11
, and the detent projections
48
disengage from the saw-toothed grip
47
as a result of which, the detent mechanism
46
is released and the turning knob
25
can then be also turned in the opposite direction, i.e. counter to arrow
51
in
FIG. 9
, in order to release the clamped connection between the clamping sleeve
19
and the blade
13
.
FIGS. 12 and 13
show another exemplary embodiment for the stop
16
on the guide
13
, which stop cooperates with the cam
15
. For a simplified manufacture of the blade
13
, the stop
16
is embodied on a separate tensioning piece
52
manufactured using zinc diecasting, which is attached to the guide
13
during assembly. To this end, the tensioning piece
52
, which is shown in a top view in FIG.
12
and in a side view in
FIG. 13
, has a pin
53
protruding at right angles from it and a shaped element
54
protruding from the same side. During assembly of the chain saw, the tensioning piece
52
is inserted in a form-fitting manner into a corresponding bore in the guide
13
so that the shaped element
54
rests in a lateral, form fitting manner in the oblong hole
24
of the blade
13
and preferably rests against the end of the oblong hole
24
remote from the sprocket
11
. The stop
16
protrudes from the top of the tensioning piece
52
remote from the pin
53
and the shaped element
54
and after assembly, is flush with the cam.
The chain tension device
14
described above functions as follows:
In order to stretch the saw chain tight by rotating the turning knob
25
in the arrow direction
51
in
FIG. 9
, the clamping sleeve
19
is rotated and thus the cam
15
is rotated by means of the detent overload clutch
18
. As a result of this rotating movement of the cam
15
clockwise in
FIGS. 2 and 9
, the outer curved track
151
of the cam
15
(
FIG. 3
) comes into contact with the stop
16
on the tensioning piece
52
of the blade
13
. Because of the outer curved track
151
of the cam
15
, the guide
13
is then slid forward away from the sprocket
11
. As a result, the saw chain
12
, which is guided in the groove of the guide
13
, is stretched increasingly tight. It the saw chain
12
has come into complete contact in the groove of the guide
13
and is thereby stretched tight, the resistance at the tensioning piece
52
to the movement of the guide
13
increases. If the turning knob
25
is then rotated further in the clockwise direction and the resistance of the tensioning piece
52
is then greater than the detent elements
31
and
33
on the clutch disk
30
and
32
disengage and the detent overload clutch
18
experiences a detent overload. A further rotation of the turning knob
25
causes the clamping sleeve
19
, which is being screwed further onto the externally threaded section
21
of the stay rod
22
, to the clamp guide
13
to the housing projection
101
of the housing
10
. Because of the presence of the detent mechanism
46
between the turning knob
25
and the protective hood
40
, tightening the clamping sleeve
19
causes a form-fitting connection to be produced so that an automatic loosening of the turning knob
25
and thereby a loosening of the chain tension cannot occur during operation of the chain saw.
Claims
- 1. A chain saw having a housing (10) having a sprocket (11) supported in the housing (10) for the motor-powered driving of a saw chain (12), having a guide (13) protruding from the housing (10), which continuously guides the saw chain (12) engaging the sprocket (11) along its blade edge and which, in order to stretch the saw chain (12) tight, is secured to the housing (10) so that it can be moved longitudinally in a direction that increases the distance to the sprocket (11), and having a chain tension device (14) that has a cam (15), which is supported against a stop (16) fixed to the guide (13) and produces a longitudinal movement of the guide (13), and has a rotating member (17) for rotating the cam (15), characterized in that the rotary connection between the rotating member (17) and cam (15) is embodied as a detent overload clutch (18), whose detent overload force is set in accordance with the required chain tension of the saw chain (12).
- 2. The chain saw according to claim 1, characterized in that the cam (15) is supported on the rotating member (17) in a rotating, but axially fixed manner and that the detent overload clutch (18) has a first clutch disk (30) provided with detent elements (31) and non-rotatably fixed to the cam (15) and a second clutch disk (32) provided with detent elements (33) and non-rotatably fixed to-the rotating member (17) as well as a prestressed clutch spring (34) which presses the two clutch disks (30, 32) axially against each other, with their detent elements (31, 33) resting against one another.
- 3. The chain saw according to claim 2, characterized in that the first clutch disk (30) is embodied as being of one piece with the cam (15).
- 4. The chain saw according to claim 2 or 3, characterized in that the rotating member (17) is embodied as a clamping sleeve (19) which is screwed with an internally threaded section (20) onto an externally threaded section (21) of a stay rod (22) secured in the housing (10) and that in order to actuate the clamping sleeve (19), a turning knob (25) is slid onto this clamping sleeve in a non-rotating fashion.
- 5. The chain saw according to claim 4, characterized in that the stay rod (22) protrudes through an oblong hole (24) embodied in the guide (13) and that the clamping sleeve (19) overlaps the oblong hole (24) and by being screwed onto the stay rod (22), can be pressed against the guide (13) in order to fix the guide (13) to the housing (10).
- 6. The chain saw according to claim 5, characterized in that the sprocket (11) and the chain tension device (14) are covered by a protective hood (40) which is attached to the housing (10) and permits the clamping sleeve (19) to protrude through it, that the turning knob (25) non-rotatably slid onto the clamping sleeve (19) is guided in rotary fashion in the protective hood (40), and that between the turning knob (25) and the protective hood (40), a manually detachable detent mechanism (46) is provided which, through form-fitting engagement, prevents the turning knob (25) from turning back counter to the rotation direction for screwing the clamping sleeve (19) onto the stay rod (22).
- 7. The chain saw according to claim 6, characterized in that the detent mechanism (46) has an annular saw-toothed strip (47) disposed on the protective hood (40) coaxial to the clamping sleeve (19) and at least one detent projection (48) elastically protruding from the underside of the turning knob (25) oriented toward the protective hood (40) and this detent projection (48) engages in a frictional and form-fitting manner in the saw-toothed strip (47).
- 8. The chain saw according to claim 6 or 7, characterized in that the turning knob (25) has a flat knob plate (42), with a diametrically extending grip strip (43) protruding at right angles from it, that the knob plate (42) rests against the bottom of a circular, cup-like recess (41) in the protective hood (40) and has a continuous, radially protruding annular rib (44) which a number of detent hooks (45) disposed in the annular wall of the recess (40) engage behind with rotary play.
- 9. The chain saw according to claim 4, characterized in that on its end remote from the guide (13), the clamping sleeve (19) has a radially protruding flange (26) which is contained in a form-fitting manner in the turning knob (25) and that the clutch spring (34) is a helical compression spring that is slid onto the clamping sleeve (19) and is supported between the flange (26) and the second clutch disk (32).
- 10. The chain saw according to claim 9, characterized in that the flange (26) is supported with its top against a collar (27) formed inside the turning knob (25) and snap hooks (28) that are of one piece with the turning knob (25) engage behind the bottom of the flange (26).
Priority Claims (1)
Number |
Date |
Country |
Kind |
198 31 250 |
Jul 1999 |
DE |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/DE00/01924 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO01/03896 |
1/18/2001 |
WO |
A |
US Referenced Citations (19)
Foreign Referenced Citations (3)
Number |
Date |
Country |
21 32 747 |
Feb 1972 |
DE |
93 11 081 |
Nov 1994 |
DE |
9833631 |
Aug 1998 |
WO |