Chain saw safety method and apparatus

Claim 2

In a chain saw operable to be hand held by an operator having: a housing including, a frame handle, and a control handle; a guide rail connected to said housing; a cutting chain operably carried by said guide rail; power means mounted within said housing including, a drive shaft operably connectable with said cutting chain; sprocket means meshed in driving engagement with said cutting chain; clutch means, at least in part connected to said drive shaft, operable for selectively connecting said drive shaft and said sprocket means for driving said cutting chain; the improvement comprising: disc means fixedly connected to said sprocket means and operably engageable with said clutch means in a driving relationship; means for biasing at least a portion of said disc means into said operable engagement with said clutch means; cam means connected to said housing and operably engageable with said disc means; and actuation means connected to said housing for actuating said cam means against said disc means in response to at least one of an abrupt upward pivot of said guide rail generally about the center of gravity of the chain saw and physical engagement of at least a portion of said actuation means by an operator''s hand slipping from said frame handle in order to overcome said bias on said disc and disengage said disc from driving engagement with said clutch means to thus remove driving torque from said cutting chain.

Claim 3

A chain saw as defined in claim 1 wherein: said disc means comprises, a hub connected to said sprocket; a plurality of resilient spokes radiating from said hub, and a peripheral outer rim connecting the outer ends of said spokes, and said clutch means comprises, a driving member connected to said drive shaft, a cylindrical driven member surrounding said driving member and being selectively connectable with said driving member, said cylindrical driven member having a radial face and a plurality of axially projecting driving studs connected to said radial face, wherein said plurality of resilient spokes being operable to bias said peripheral outer rim toward said clutch means and to engage said driving studs between adjacent ones of said plurality of resilient spokes for operably connecting said disc and said clutch means in a driving relationship.

Claim 4

A chain saw as defined in claim 1 wherein said cam means comprises: a cylindrical sleeve rotatably mounted within said chain saw housing and being coaxially disposed about said clutch means, including at least one sloping cam surface; and at least one cam ramp fashioned within said housing for engagement with said at least one sloping cam surface to axially translate said cylindrical sleeve upon rotation of said cam means wherein, said axial translation of said cylindrical sleeve serves to engage an outer rim of said disc means and disengage said disc means from driving engagement with said clutch means.

Claim 5

A chain saw as defined in claim 3 wherein: said cylindrical sleeve being fashioned with a pair of sloping cam surfaces each extending approximately 180* about the periphery of one end of said cylindrical sleeve; said housing being fashioned with a pair of cam ramps for engagement with said pair of sloping cam surfaces; and a tab longitudinally extending upon said cylindrical sleeve at a junction of the pair of sloping cam surfaces for connecting said cam means with said actuation means.

Claim 6

A chain saw as defined in claim 1 wherein said actuation means comprises: a lever pivotally connected to said housing including an integral dog; a cowl pivotally connected to said housing and coaxially positioned with respect to said cam means, including a detent operable to engage with said dog; means connected Between said lever and said cowl for pivotally biasing said cowl toward said lever upon engagement of said dog with said detent; and means connecting said cowl with said cam means whereby rotation of said cowl will serve to rotate said cam means and operably disengage said drive shaft from said cutting chain.

Claim 7

A chain saw as defined in claim 5 wherein said lever comrpsies: a bell crank with said dog being fashioned upon a short arm thereof and an inertia mass connected to the long arm thereof.

Claim 8

A chain saw as defined in claim 5 wherein said lever comprises: a bell crank with said dog being fashioned upon a short arm thereof and a guard bar normally extending from the free end of a long arm thereof generally parallel to said frame handle and between said frame handle and said cutting chain.

Claim 9

In a chain saw operable to be hand held by an operator having: a housing including, a frame handle, and a control handle; a guide rail connected to said housing; a cutting chain operably carried by said guide rail; power means mounted within said housing including, a drive shaft operably connectable with said cutting chain; sprocket means meshed in driving engagement with said cutting chain; clutch means, at least in part connected to said drive shaft, operable for selectively connecting said drive shaft and said sprocket means for driving said cutting chain; the improvement comprising: first spring disc means fixedly connected to said sprocket means and being self biased against and operably engageable with said clutch means in a driving relationship; second spring disc means positioned between a thrust bearing and said sprocket means for biasing said sprocket toward said clutch means; cam means connected to said housing and operably engageable with said disc means; and actuation means connected to said housing for actuating said cam means against said first disc means in response to at least one of an abrupt upward pivot of said guide rail generally about the center of gravity of the chain saw and physical engagement of at least a portion of said actuation means by an operator''s hand slipping from said frame handle in order to overcome the serially combined bias of said first and second disc means and disengage said first disc from driving engagement with said clutch means to thus remove driving torque from said cutting chain.

Claim 10

In a chain saw operable to be hand held by an operator having: a housing including, a frame handle, and a control handle; a guide rail connected to said housing; a cutting chain operably carried by said guide rail; power means mounted within said housing including, a drive shaft operably connectable with said cutting chain; sprocket means meshed in driving engagement with said cutting chain; clutch means, at least in part connected to said drive shaft, operable for selectively connecting said drive shaft and said sprocket means for driving said cutting chain; the improvement comprising: first spring disc means fixedly connected to said sprocket means and being self biased against and operably engageable with said clutch means in a driving relationship; second spring disc means positioned between a thrust bearing and said sprocket means for biasing said sprocket toward said clutch means; cam means connected to said housing and operably engageable with said disc means; and actuation means connected to said housing for actuating said cam means against said first disc means in response to at least one of an abrupt upward pivot of said guide rail generally about the center of gravity of the chain saw and physical engagement of at least a portion of said actuation means by an operator''s hand slipping from said frame handle in order to overcome the serially combined bias of said first and second disc means and disengage said first disc from driving engagement with said clutch means to thus remove driving torque from said cutting chain.

Claim 11

A chain saw as defined in claim 8 wherein: the spring strength of said second disc is generally similar to the spring strength of said first disc whereby upon actuation of said cam against said first disc said first and second spring disc means will flex in series to disengage said first disc from said clutch means.

Claim 12

A chain saw as defined in claim 8 wherein: the spring strength of said second disc is substantially greater than the spring strength of said first disc whereby disengagement of said first disc from said clutch means is achieved without substantially flexing said second spring disc.

Claim 13

A chain saw as defined in claim 8 wherein the spring strength of said first disc is substantially greater than the spring strength of said second disc whereby disengagement of said first disc from said clutch means is achieved without substantially flexing said first spring disc.

Claim 14

In a chain saw operable to be hand held by an operator having: a housing including, a frame handle, and a control handle; a guide rail connected to said housing; a cutting chain operably carried by said guide rail; power means mounted within said housing including, a drive shaft operably connectable with said cutting chain; sprocket means meshed in driving engagement with said cutting chain; clutch means including a driving hub connected to said drive shaft, a driven drum freely pivotally mounted upon said drive shaft, and clutch shoe means carried by said driving hub and being operable to selectively conneCt said driving hub with said driven drum; the improvement comprising: spring disc means connected to said sprocket means including, a hub portion connected to said sprocket, a plurality of resilient spokes radiating from said hub and being normally inclined toward said clutch drum, and a peripheral outer rim connecting the outer ends of said spokes; a plurality of driving lugs mounted about the periphery of said clutch drum and generally axially projecting therefrom; said resilient spokes of said spring disc means being operable to self bias said spring disc means against said clutch drum with adjacent ones of said plurality of resilient spokes extending on opposite sides of respective ones of said plurality of driving lugs whereby driving torque is operably transmitted to said disc means through said driving lugs; at least one arcuate cam ramp coaxially fashioned within said chain saw housing adjacent said clutch drum; a cylindrical sleeve cam rotatably mounted within said chain saw housing between said spring disc and said at least one arcuate cam ramp and coaxially about said clutch drum including a first end edge cut by a plane extending normal to the axis of said cylindrical sleeve, said first end edge extending contiguous to but spaced from said peripheral outer rim of said spring disc, and a second end edge fashioned with at least one sloping surface operably compatible with said at least one arcuate cam and extending contiguous thereto whereby rotation of said cylindrical sleeve cam will cause said at least one sloping cam surface to ride up said at least one arcuate cam ramp and axially translate said sleeve cam against said peripheral outer rim of said spring disc to disengage said plurality of radially extending spokes from driving engagement with said plurality of driving lugs; a generally cylindrical cowl pivotally mounted upon said chain saw housing coaxially with said clutch drum and being connected to said cylindrical sleeve cam whereby rotation of said cowl effectuates corresponding rotation of said cylindrical sleeve cam, said cowl being provided with a detent in the outer periphery thereof; a bell crank having a short leg and a long leg and being pivotally mounted upon said chain saw housing adjacent said cowl and including a dog fashioned upon the short leg of said bell crank and being operable to engage with said detent in said cowl to prevent rotation of said cowl; biasing means connected between said bell crank and said cowl to bias said cowl to rotate toward said bell crank when said dog is in engagement with said detent; and means connected to the long arm of said bell crank for inducing said bell crank to pivot and remove said dog from said detent in response to at least one of an abrupt upward pivot of said guide rail generally about the center of gravity of the chain saw and physical engagement of at least a portion of said actuation means by an operator''s hand slipping from said frame handle whereby said cowl will rotate said cam and disengage said spring disc from driving engagement with said clutch drum to remove driving torque from said sprocket and cutting chain.

Claim 15

In a chain saw operable to be hand held by an operator having: a housing including, a frame handle, and a control handle; a guide rail connected to said housing; a cutting chain operably carried by said guide rail; power means mounted within said housing including, a drive shaft operably connectable with said cutting chain; sprocket means meshed in driving engagement with said cutting chain; clutch means including a driving hub connected to said drive shaft, a driven drum freely pivotally mounted upon said drive shaft, and clutch shoe means carried by said driving hub and being operable to selectively conneCt said driving hub with said driven drum; the improvement comprising: spring disc means connected to said sprocket means including, a hub portion connected to said sprocket, a plurality of resilient spokes radiating from said hub and being normally inclined toward said clutch drum, and a peripheral outer rim connecting the outer ends of said spokes; a plurality of driving lugs mounted about the periphery of said clutch drum and generally axially projecting therefrom; said resilient spokes of said spring disc means being operable to self bias said spring disc means against said clutch drum with adjacent ones of said plurality of resilient spokes extending on opposite sides of respective ones of said plurality of driving lugs whereby driving torque is operably transmitted to said disc means through said driving lugs; at least one arcuate cam ramp coaxially fashioned within said chain saw housing adjacent said clutch drum; a cylindrical sleeve cam rotatably mounted within said chain saw housing between said spring disc and said at least one arcuate cam ramp and coaxially about said clutch drum including a first end edge cut by a plane extending normal to the axis of said cylindrical sleeve, said first end edge extending contiguous to but spaced from said peripheral outer rim of said spring disc, and a second end edge fashioned with at least one sloping surface operably compatible with said at least one arcuate cam and extending contiguous thereto whereby rotation of said cylindrical sleeve cam will cause said at least one sloping cam surface to ride up said at least one arcuate cam ramp and axially translate said sleeve cam against said peripheral outer rim of said spring disc to disengage said plurality of radially extending spokes from driving engagement with said plurality of driving lugs; a generally cylindrical cowl pivotally mounted upon said chain saw housing coaxially with said clutch drum and being connected to said cylindrical sleeve cam whereby rotation of said cowl effectuates corresponding rotation of said cylindrical sleeve cam, said cowl being provided with a detent in the outer periphery thereof; a bell crank having a short leg and a long leg and being pivotally mounted upon said chain saw housing adjacent said cowl and including a dog fashioned upon the short leg of said bell crank and being operable to engage with said detent in said cowl to prevent rotation of said cowl; biasing means connected between said bell crank and said cowl to bias said cowl to rotate toward said bell crank when said dog is in engagement with said detent; and means connected to the long arm of said bell crank for inducing said bell crank to pivot and remove said dog from said detent in response to at least one of an abrupt upward pivot of said guide rail generally about the center of gravity of the chain saw and physical engagement of at least a portion of said actuation means by an operator''s hand slipping from said frame handle whereby said cowl will rotate said cam and disengage said spring disc from driving engagement with said clutch drum to remove driving torque from said sprocket and cutting chain.

Claim 16

A chain saw as defined in claim 12 and further comprising: another spring disc means coaxially positioned upon said drive shaft and between a thrust bearing and said sprocket means for biasing said sprocket means toward said clutch drum.

Claim 17

A chain saw as defined in claim 13 wherein: the spring strength of said another spring disc is generally similar to although less than the spring strength of said spring disc means whereby upon actuation of said cam against said spring disc means said spring disc means and said another spring disc means will both flex in series to disengage the spokes of said spring disc means from engagement with said driving lugs.

Claim 18

A chain saw as defined in claim 12 and further comprising: land means normally projecting upon opposite sides of each of saiD plurality of resilient spoke for contacting said driving lugs upon opposite sides of said driving lugs.

Claim 19

A chain saw as defined in claim 12 and further comprising: a tab longitudinally extending upon said cylindrical sleeve cam, said tab projecting through an arcuate slot fashioned through said housing; and a tab well fashioned within said cowl to intimately receive the free end of said tab whereby rotation of said cowl will carry said tab about said arcuate slot to effectuate rotation of said cylindrical sleeve cam.

Claim 20

A chain saw as defined in claim 12 wherein said biasing means connected between said bell crank and said cowl comprises: a helicial tension spring having one end at least partially wrapped around the outer periphery of said cowl and being fixed thereto by a pin extending within said cowl and having the other end connected by a pin to the short leg of said bell cranes.

Claim 21

A chain saw as defined in claim 17 and further comprising: a slot fashioned within the short leg of said bell crank and being sloped away from the point of connection of the other end of said tension spring; and means for adjustably fixing the location of the pin connected to the other end of said tension spring within said slot whereby the tension on said spring may be selectively adjusted.

Claim 22

A chain saw as defined in claim 18 and further comprising: an arm radially projecting beyond the outer periphery of said cowl to serve as a lever for counter rotation of said cowl to engage the dog of said short leg with the detent in the cowl and store energy within said helical tension spring.

Claim 23

A chain saw as defined in claim 12 wherein said means connected to the long leg of said bell crank comprises: an inertia mass.

Claim 24

A chain saw as defined in claim 20 wherein said inertia mass comprises: a generally U-shaped bar normally projecting from the free and of the long leg of said bell crams and extending generally parallel with said frame handle between said frame handle and said guide bar for blocking movement of an operator hand toward said guide bar.

Claim 27

A metHod for operating a chain saw as defined in claim 22 wherein the disc means is self biasing toward the clutch means and further comprising the steps of: providing another self biasing disc means between a thrust bearing and the sprocket means to bias the sprocket means toward the clutch means; and flexing both disc means in series in response to actuation of the cam to remove driving torque from the sprocket and cutting chain.

Claim 28

A method for operating a chain saw as defined in claim 22 wherein the cam means includes at least one arcuate sloping cam surface and the chain saw housing includes a compatibly dimensioned cam ramp and further comprising the steps of: rotating the cam in response to actuation of the actuating means; and thereby axially translating the cam into abutting engagement with the disc means to disengage the disc means from driving engagement with the clutch means.

Claim 29

A method for operating a chain saw as defined in claim 24 wherein the actuating means includes a cowl mounted upon the chain saw housing coaxially with the clutch means and having a detent fashioned in the periphery thereof and a bell crank pivotally mounted upon the chain saw housing including a protruding dog compatibly dimensioned with the detent in the cowl and further comprising the steps of: biasing the cowl to rotate toward the bell crank upon engaging the dog within the detent; connecting the cam means to the cowl; and releasing the dog from the detent upon actuation of the actuation means to rotate the cowl and cam and thus disengage the spring disc from driving engagement with the clutch means.

Claim 30

In a chain saw operable to be hand held by an operator having: a housing including, a frame handle, and a control handle; a guide rail connected to said housing; a cutting chain operably carried by said guide rail; power means mounted within said housing including, a drive shaft operably connectable with said cutting chain; sprocket means meshed in driving engagement with said cutting chain; clutch means, at least in part connected to said drive shaft, operable for selectively connecting said drive shaft and said sprocket means for driving said cutting chain; the improvement comprising: means for operably engaging and disengaging said drive shaft from said cutting chain; and a bell crank pivotally mounted upon said chain saw housing and having a short arm thereof operably connected to said means for engaging and disengaging and a long arm thereof fitted with an inertia mass at the remote end thereof for actuating said means for engaging and disengaging to operably disengage said drive shaft from said cutting chain in response to an abrupt upward pivot of said guide rail generally about the center of gravity of the chain saw.

Claim 31

In a chain saw operable to be hand held by an operator having: a housing including, a frame handle, and a control handle; a guide rail connected to said housing; a cutting chain operably carried by said guide rail; power means mounted within said housing including, a drive shaft operably connectable with said cutting chain; sprocket means meshed in driving engagement with said cutting chain; clutch means, at least in part connected to said drive shaft, operable for selectively connecting said drive shaft and said sprocket means for driving said cutting chain; the improvement comprising: means for operably engaging and disengaging said drive shaft from said cutting chain; and a bell crank pivotally mounted upon said chain saw housing and having a short arm thereof operably connected to said means for engaging and disengaging and a long arm thereof fitted with an inertia mass at the remote end thereof for actuating said means for engaging and disengaging to operably disengage said drive shaft from said cutting chain in response to an abrupt upward pivot of said guide rail generally about the center of gravity of the chain saw.