Chain saw

Information

  • Patent Grant
  • 6564459
  • Patent Number
    6,564,459
  • Date Filed
    Monday, March 5, 2001
    23 years ago
  • Date Issued
    Tuesday, May 20, 2003
    21 years ago
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)
Number Name Date Kind
3636995 Newman Jan 1972 A
3839795 Dooley Oct 1974 A
3866320 Progl Feb 1975 A
3962929 Silvon Jun 1976 A
4129943 Bricker Dec 1978 A
4316327 Scott et al. Feb 1982 A
4355551 Kolleas Oct 1982 A
4382334 Reynolds May 1983 A
4567658 Wissmann et al. Feb 1986 A
4615117 Flath Oct 1986 A
4835868 Nagashima Jun 1989 A
5070618 Edlund Dec 1991 A
5144751 Weber Sep 1992 A
5174029 Talberg Dec 1992 A
5184403 Schliemann Feb 1993 A
5345686 Zimmermann Sep 1994 A
5491899 Schliemann et al. Feb 1996 A
5896670 Gibson et al. Apr 1999 A
5938508 Canella et al. Aug 1999 A
Foreign Referenced Citations (3)
Number Date Country
21 32 747 Feb 1972 DE
93 11 081 Nov 1994 DE
9833631 Aug 1998 WO