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US 4,053,980 AGranted
Chain saw including an overtorque releasing clutch
AssigneeOutboard Marine Corporation
InventorArthur G. Poehlman
Life of this patent
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AssigneeOutboard Marine Corporation
InventorArthur G. Poehlman
Estimating the term…
Disclosed herein is a chain saw including a drive shaft, a chain sprocket and a clutch including a drive member driven by the drive shaft and a driven member for rotating the chain sprocket in response to rotation of the drive shaft. One of the members is axially movable relative to the other between an engaged or driving position and a released position wherein they are disengaged from each other. The drive and driven members have intermeshing clutch teeth which coact to produce an axial force in a direction tending to separate the axially movable one of the members from the other. The members are releasably held in the driving position by a resilient element which is movable between a first position wherein it yieldably resists axial displacement of the axially movable one of the members and a second position which is spaced from the first position so as to permit movement of the axially movable one of the members to the released position. The resilient element is moved from the first position to the second position when the axially directed separating force exceeds a predetermined level and remains in the second position in absence of a reset force being applied thereto in an axial direction opposite to the separating force.
A chain saw comprising a frame, an engine mounted on said frame, a drive shaft rotatably mounted on said frame and driven by said engine, a chain sprocket mounted for rotation coaxially with said drive shaft, a cutter bar supported by said frame, a saw chain trained around said sprocket and said cutter bar, a clutch including a drive member mounted for common rotation with said drive shaft and having one or more clutch teeth, a driven member having one or more clutch teeth adapted to be drivingly engaged by said drive member clutch teeth and being mounted for rotation coaxially with said drive member, one of said drive and driven members being mounted for axial movement relative to the other between a released position wherein said drive and driven members are disengaged and a driving position wherein said drive and driven members are in driving engagement to afford transmission of torque therebetween with said clutch teeth coacting to produce a separating force directed axially in one direction and tending to axially displace said one of said drive and driven members toward said released position, means for drivingly connecting said driven member to said sprocket in response to rotation of said drive shaft, and a resilient element interacting with said one of said drive and driven members and being movable between a first position wherein said resilient element yieldably resists axial displacement of said one of said drive and driven members toward said released position and a second position which is spaced from said first position so as to permit movement of said one of said drive and driven members to said released position, said resilient element moving from said first position to said second position when the axially directed separating force exceeds a predetermined level, said resilient element remaining in said second position in the absence of a reset force applied thereto in the direction opposite from said one direction.
A centrifugal clutch comprising a drive member adapted to be mounted on a driving shaft for common rotation therewith and having one or more clutch teeth, a clutch drum supported for rotation coaxially with and independently of said driving shaft, a driven member having one or more clutch teeth adapted to drivingly engage said drive member clutch teeth and being mounted for rotation coaxially with said drive member, one of said drive and driven members being mounted for axial movement relative to the other between a released position wherein said drive and driven members are disengaged and a driving position wherein said drive and driven members are in driving engagement to afford transmission of torque therebetween with said clutch teeth coacting to produce a separating force directed axially in one direction and tending to axially displace said one of said drive and driven members toward said released position, a plurality of clutch shoes, means on said clutch shoes and on said driven member for rotatably driving said clutch shoes in response to rotation of said driven member and for guiding said clutch shoes for outward movement radially relative to said driven member, in response to rotation of said driven member, from a retracted position spaced from said clutch drum to an extended position in driving engagement with such clutch drum, and a resilient element interacting with said one of said drive and driven members and being movable between a first position wherein said resilient element yieldably resists axial displacement of said one of said drive and driven members toward said release position and a second position which is spaced from said first position so as to permit movement of said one of said drive and driven members to said released position, said resilient element moving from said first position to said second position when the axially directed separating force exceeds a predetermined level, said resilient element remaining in said second position in the absence of a reset force applied thereto in the direction opposite from said one direction.
Dependencies are inferred from the claim text.
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Chain saws; Equipment therefor: drives or gearings; Devices for swivelling or tilting the chain saw
With at least one part moving axially between engagement and disengagement: the axially moving part being coaxial with the rotation, e.g. a gear…
Saws for wood or similar material
Couplings for transmitting rotation
Term ended 18 Oct 1994 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The invention relates to chain saws and more particularly to clutches for chain saws.
It is common practice to drive the saw chain of a chain saw by an engine through a centrifugal clutch which operates in response to rotation above a predetermined speed to drivingly connect a chain drive sprocket to the engine. Such clutches are often arranged to permit some slippage in the event the saw chain becomes squeezed in the kerf or otherwise is restrained from movement. This restraining force on the chain frequently can be greater than the force transmitted from the engine to the chain and can result in damage to the chain, the engine or intervening components. Such forces develop so rapidly that conventional centrifugal clutches often cannot react or disengage rapidly enough to avoid damage to the chain saw.
Representative examples of prior chain saw centrifugal clutch constructions are disclosed in the following U.S. Pat. Nos.:
FIG. 1 is a perspective view of a chain saw incorporating various of the features of the invention.
FIG. 2 is an enlarged, fragmentary, end elevational view, partially in section, of the clutch employed in the chain saw shown in FIG. 1 illustrating the position of the components when the clutch is in a driving position of the components when the clutch is in a released position.
FIG. 2A is an enlarged, fragmentary, and elevational view partially in section, of the clutch employed in the chain saw shown in FIG. 1, illustrating the position of the components when the clutch is in a released position.
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawing. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purposes of description and should not be regarded as limiting.
Illustrated in the drawings is a chain saw 10 including a frame 12 supporting an engine 14 drivingly connected to a rotatable drive shaft 16, together with a cutter bar 18 around which a saw chain 20 is guided for travel. The drive shaft 16 can either be the engine output shaft or another shaft driven by the engine output shaft. Power is transmitted from the engine 14 to the chain saw 20 through a centrifugal clutch 22 and a chain sprocket 24 (FIG. 2) driven by the clutch 22 and rotatably mounted on the drive shaft 16.
In the construction illustrated in FIGS. 1-6, the clutch 22 includes a drive element or member 26 which is suitably mounted on the drive shaft 16 for common rotation therewith and a clutch drum 28 which is drivingly connected to the chain sprocket 24. The clutch drum 28 has a cylindrical inner surface 30, and is suitably mounted on the drive shaft 16 for rotation coaxially with and independently of the drive member 26. The clutch 22 also includes a driven element or member 32 which is suitably mounted for rotation coaxially with the drive shaft 16 and for axial movement relative to the drive member 26.