US3788412A — Snowmobile suspension system

Claim 1

Independent Claim 377 words

In combination with a snowmobile having an elongated body chassis with a rearward portion Of inverted U cross-section providing a tunnel opening for receiving a suspension, surface engaging runners disposed to support substantially the forward portion of said body chassis, a motor mechanism mounted on said forward chassis portion, and a tread driving mechanism mounted on said chassis adjacent the forward end of said tunnel opening, said driving mechanism including sprocket wheel means, a suspension system for said tread providing limited degrees of movement in all directions, said systems including an elongated tead supporting frame within said tunnel and providing a pair of rigid slide bars extending substantially from the front to rear of said suspension along the bottom thereof, an endless flexible tread moving within said tunnel and enclosing said frame, said sprocket means being in driving engagement with said tread, said slide bars bearing against and urging the bottom run of said tread into traction engagement with the ground beneath said snowmobile as said tread is driven, pivot arms means connecting the forward portion of said frame to said chassis and being inclined downwardly and rearwardly, spring means yieldably pressing said pivot arms in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, means for guiding said tread onto the forward portions of said slide bars, and idle wheel means mounted on the rearward end portions of said slide bars for guiding said tread to return to said sprocket means, said idle wheels being fixed against forward shifting with respect to said slide bars, wherein the improvement comprises: a pair of combination coil spring and shock absorber means mounted at the rear of said chassis along each side thereof outside of said tunnel, said combination means having their lower ends pivotally connected to the rear portion of said frame adjacent said idle wheels and their upper ends pivotally connected to said chassis, said combination means being disposed with their axes extending upwardly and rearwardly, said idle wheels being movable upwardly by contracting said combination means and movable downwardly by extending said combination means, and said coil springs of said combination means urging said idle wheels and the rear end portions of said slide bars downwardly and forwardly.

Claim 2

Dependent Claim 377 words

In combination with a snowmobile having an elongated body chassis with a rearward portion Of inverted U cross-section providing a tunnel opening for receiving a suspension, surface engaging runners disposed to support substantially the forward portion of said body chassis, a motor mechanism mounted on said forward chassis portion, and a tread driving mechanism mounted on said chassis adjacent the forward end of said tunnel opening, said driving mechanism including sprocket wheel means, a suspension system for said tread providing limited degrees of movement in all directions, said systems including an elongated tead supporting frame within said tunnel and providing a pair of rigid slide bars extending substantially from the front to rear of said suspension along the bottom thereof, an endless flexible tread moving within said tunnel and enclosing said frame, said sprocket means being in driving engagement with said tread, said slide bars bearing against and urging the bottom run of said tread into traction engagement with the ground beneath said snowmobile as said tread is driven, pivot arms means connecting the forward portion of said frame to said chassis and being inclined downwardly and rearwardly, spring means yieldably pressing said pivot arms in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, means for guiding said tread onto the forward portions of said slide bars, and idle wheel means mounted on the rearward end portions of said slide bars for guiding said tread to return to said sprocket means, said idle wheels being fixed against forward shifting with respect to said slide bars, wherein the improvement comprises: a pair of combination coil spring and shock absorber means mounted at the rear of said chassis along each side thereof outside of said tunnel, said combination means having their lower ends pivotally connected to the rear portion of said frame adjacent said idle wheels and their upper ends pivotally connected to said chassis, said combination means being disposed with their axes extending upwardly and rearwardly, said idle wheels being movable upwardly by contracting said combination means and movable downwardly by extending said combination means, and said coil springs of said combination means urging said idle wheels and the rear end portions of said slide bars downwardly and forwardly.

Claim 3

Dependent Claim 62 words

The combination of claim 1 wherein said improvement is further characterized by the fact that said combination coil spring and shock absorber means are disposed to incline upwardly and rearwardly from said slide bars to said chassis at an angle within the range of 5 to 45* to the vertical when said slide bars are horizontal and said combination means are uncompressed.

Claim 4

Dependent Claim 23 words

The combination of claim 1 wherein means is provided to permit selective adjustment of the rearward and upward inclination of said combination means.

Claim 5

Dependent Claim 21 words

The combination of claim 1 wherein means is provided to permit selective adjustment of a pre-set compression for said coil springs.

Claim 6

Dependent Claim 353 words

In combination with a snowmobile having an elongated body chassis with a rearward portion of inverted U cross-section providing a tunnel opening for receiving a suspension, surface engaging runners disposed to support substantially the forward portion of said body chassis, a motor mechanism mounted on said forward chassis portion, and a tread driving mechanism mounted on said chassis adjacent the forward end of said tunnel opening, said driving mechanism including sprocket wheel means, a suspension system for said tread providing limited degrees of movement in all directions, said system including an elongated tread supporting frame within said tunnel and providing a pair of rigid slide bars extending substantially from the front to rear of said suspension along the bottom thereof, an endless flexible tread moving within said tunnel and enclosing said frame, said sprocket means being in turning engagement with said thread, said slide bars bearing against and urging the bottom run of said tread into traction engagement with thE ground beneath said snowmobile as said thread is driven, pivot arm means connecting the forward portion of said frame to said chassis and being inclined downwardly and rearwardly, spring means yieldably pressing said pivot arms in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, means for guiding said tread onto the forward portions of said slide bars, and idle wheel means mounted on the rearward end portions of said slide bars for guiding said tread to return to said sprocket means, said idle wheel means being fixed against forward shifting with respect to said slide bars, wherein the improvement comprises: combination coil spring and shock absorber means having a common axis mounted at the rear of said chassis along the sides thereof outside of said tunnel, said combination means having their lower end pivotally connected to the rear portion of said frame, said combination spring means being disposed to incline upwardly and rearwardly from said slide bars to said chassis at an angle of 15* to 35* with respect to the vertical when said slide bars are horizontal and said combination means are uncompressed.

Claim 7

Dependent Claim 353 words

In combination with a snowmobile having an elongated body chassis with a rearward portion of inverted U cross-section providing a tunnel opening for receiving a suspension, surface engaging runners disposed to support substantially the forward portion of said body chassis, a motor mechanism mounted on said forward chassis portion, and a tread driving mechanism mounted on said chassis adjacent the forward end of said tunnel opening, said driving mechanism including sprocket wheel means, a suspension system for said tread providing limited degrees of movement in all directions, said system including an elongated tread supporting frame within said tunnel and providing a pair of rigid slide bars extending substantially from the front to rear of said suspension along the bottom thereof, an endless flexible tread moving within said tunnel and enclosing said frame, said sprocket means being in turning engagement with said thread, said slide bars bearing against and urging the bottom run of said tread into traction engagement with thE ground beneath said snowmobile as said thread is driven, pivot arm means connecting the forward portion of said frame to said chassis and being inclined downwardly and rearwardly, spring means yieldably pressing said pivot arms in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, means for guiding said tread onto the forward portions of said slide bars, and idle wheel means mounted on the rearward end portions of said slide bars for guiding said tread to return to said sprocket means, said idle wheel means being fixed against forward shifting with respect to said slide bars, wherein the improvement comprises: combination coil spring and shock absorber means having a common axis mounted at the rear of said chassis along the sides thereof outside of said tunnel, said combination means having their lower end pivotally connected to the rear portion of said frame, said combination spring means being disposed to incline upwardly and rearwardly from said slide bars to said chassis at an angle of 15* to 35* with respect to the vertical when said slide bars are horizontal and said combination means are uncompressed.

Claim 8

Dependent Claim 43 words

The combination of claim 5 in which said rear idle wheels are mounted on a common shaft, said shaft extending outwardly beyond said wheels, and said combination means have their lower ends pivotally connected to the said outward extensions of said common shaft.

Claim 9

Dependent Claim 46 words

The combination of claim 5 in which means are provided permitting selective adjustment of the rearward and upward inclination of said combination means within said range of 15* to 35*, and means are also provided permitting selective adjustment of a pre-set compression for said coil springs.

Claim 10

Dependent Claim 311 words

A suspension system for a tracked vehicle having an elongated chassis and an endless track forming an elongated loop with a top run from rear to front and a ground-engaging bottom run from front to rear, said track being disposed underneath and longitudinally of said chassis, elongated rigid slide bar members extending within said track and serving to press said ground-engaging run against the ground, driving sprocket wheel means mounted on the front portion of said chassis for driving said track, idle wheel means disposed within said track loop for engaging the rear end portion of said track loop and carried by said rigid members, said idle wheels being mounted on said rigid members by means rigidly holding said wheels against forward movement with respect to said rigid members, spring-loaded pivot arm movably connecting to said chassis the front portion of said rigid members, said pivot arms being inclined downwardly and rearwardly and being yieldably spring-biased in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, and means for guiding said tread onto the forward portions of said slide bars, wherein the improvement comprises: axially compressible coil spring means mounted between said chassis and the rear portions of said slide bar members externally of said track, said coil spring means having axes inclining rearwardly from points adjacent said idle wheels upwardly to said chassis and being mounted by pivot means permitting the said rearward inclination to increase or decrease, said slide bar rear portions being movable both upwardly and downwardly from their normal substantially horizontal alignment with resulting change in the said rearward inclination of said spring means and said upward movement compressing said coil spring means, whereby the spring compression resistance to the upward movement of said slide bar rear portions increases as the said rearward inclination of said spring means decreases.

Claim 11

Dependent Claim 311 words

A suspension system for a tracked vehicle having an elongated chassis and an endless track forming an elongated loop with a top run from rear to front and a ground-engaging bottom run from front to rear, said track being disposed underneath and longitudinally of said chassis, elongated rigid slide bar members extending within said track and serving to press said ground-engaging run against the ground, driving sprocket wheel means mounted on the front portion of said chassis for driving said track, idle wheel means disposed within said track loop for engaging the rear end portion of said track loop and carried by said rigid members, said idle wheels being mounted on said rigid members by means rigidly holding said wheels against forward movement with respect to said rigid members, spring-loaded pivot arm movably connecting to said chassis the front portion of said rigid members, said pivot arms being inclined downwardly and rearwardly and being yieldably spring-biased in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, and means for guiding said tread onto the forward portions of said slide bars, wherein the improvement comprises: axially compressible coil spring means mounted between said chassis and the rear portions of said slide bar members externally of said track, said coil spring means having axes inclining rearwardly from points adjacent said idle wheels upwardly to said chassis and being mounted by pivot means permitting the said rearward inclination to increase or decrease, said slide bar rear portions being movable both upwardly and downwardly from their normal substantially horizontal alignment with resulting change in the said rearward inclination of said spring means and said upward movement compressing said coil spring means, whereby the spring compression resistance to the upward movement of said slide bar rear portions increases as the said rearward inclination of said spring means decreases.

Claim 12

Dependent Claim 46 words

The suspension system of claim 8 in which said axes of said coil spring means are disposed to incline upwardly and rearwardly from said slide bars to said chassis at an angle of from 5* to 45* to the vertical when said slide barS are horizontal.

Claim 13

Dependent Claim 52 words

The suspension system as claimed in claim 8 further including elongated shock absorber means having one end acting on said slide bar members adjacent said rear idle wheels and the other end acting on said chassis above the top run of said track, said shock absorbers also extending externally of said track.

Claim 14

Dependent Claim 24 words

The suspension system as claimed in claim 10, wherein the piston rods of said shock absorber means are surrounded by said coil spring means.

Claim 15

Dependent Claim 55 words

The suspension as claimed in claim 11, wherein the upper ends of said shock absorber means are pivotally connected to brackets secured to, and upstanding from, the top of the chassis, and wherein the lower ends of said shock absorber means are pivotally connected to a shaft on which said rear idle wheels are mounted.

Claim 16

Dependent Claim 54 words

The suspension system as claimed in claim 12 wherein said brackets have at least two similar connecting means spaced longitudinally of said chassis for selective pivotal connection of the upper end of said shock absorbers in angular relation to the vertical, said connecting means being arranged to permit said angular relation to be varied.

Claim 17

Dependent Claim 51 words

The suspension system as claimed in claim 8 wherein said spring means provide a preload compression resistance to the upward movement of said slide bar rear portions from their normal horizontal positions and wherein an adjustment means is provided for adjusting the said preload compression resistance of said coil spring means.

Claim 18

Dependent Claim 154 words

The suspension system as claimed in claim 8, wherein there are at least two transversely spaced rigid members disposed adjacent the respective sides of said track, and there are two of said rear idler wheels, each associated with, and carried by, one rigid member, said wheels being arranged on a common transverse shaft and further including torsion bar means pivotally connected to said chassis and to said common shaft at spaced points therealong and resiliently resisting transverse inclination movement of said common shaft with respect to said chassis, while allowing free up-and-down movement of said common shaft relative to said chassis, said torsion bar means including a U-shaped member providing legs connected by a cross portion and having its cross portion pivitally connected to said chassis about a transverse axis, and sleeves telescopically receiving the respective legs of said U-shaped member, said sleeves being rotatably mounted on said common shaft of said idler wheels.

Claim 19

Dependent Claim 354 words

A suspension system for a tracked vehicle having an elongated chassis and an endless track forming an elongated loop with a top run from rear to front and a ground-engaging bottom run from front to rear, said track being disposed underneath and longitudinally of said chassis, elongated rigid slide bar members extending within said track and serving to press said ground-engaging run against the ground, driving sprocket wheel means mounted on the front portion of said chassis for driving said track, idle wheel means disposed within said track loop for engaging the rear end portion of said track loop and carried by said rigid members, said idle wheels being mounted on said rigid members by means rigidly holding said wheels against forward movement with respect to said rigid members, spring-loaded pivot arm means movably connecting to said chassis the front portion of said rigid members, said pivot arms being inclined downwardly and rearwardly and being yieldably spring-biased in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, and means for guiding said tread onto the forward portions of said slide bars, wherein the improvement comprises: axially compressible coil spring means mounted between said chassis and the rear portions of said slide bar members externally of said track, said coil spring means having axes inclining rearwardly from points adjacent said idle wheels upwardly to said chassis and being mounted by pivot means permitting the said rearward inclinAtion to increase or decrease, said coil spring means having an axial inclination of from 5* to 45* to the vertical when said slide bar is horizontal and means associated therewith permitting selective adjustment of the degree of rearward and upward inclination of said coil spring means, said slide bar rear portions being movabe both upwardly and downwardly from their normal substantially horizontal alignment with resulting change in the said rearward inclination of said spring means and said upward movement compressing said coil spring means, whereby the spring compression resistance to the upward movement of said slide bar rear portions increases as the said rearward inclination of said spring means decreases.

Claim 20

Dependent Claim 354 words

A suspension system for a tracked vehicle having an elongated chassis and an endless track forming an elongated loop with a top run from rear to front and a ground-engaging bottom run from front to rear, said track being disposed underneath and longitudinally of said chassis, elongated rigid slide bar members extending within said track and serving to press said ground-engaging run against the ground, driving sprocket wheel means mounted on the front portion of said chassis for driving said track, idle wheel means disposed within said track loop for engaging the rear end portion of said track loop and carried by said rigid members, said idle wheels being mounted on said rigid members by means rigidly holding said wheels against forward movement with respect to said rigid members, spring-loaded pivot arm means movably connecting to said chassis the front portion of said rigid members, said pivot arms being inclined downwardly and rearwardly and being yieldably spring-biased in a downward direction, means for positively limiting the extent to which said pivot arms can swing downwardly, and means for guiding said tread onto the forward portions of said slide bars, wherein the improvement comprises: axially compressible coil spring means mounted between said chassis and the rear portions of said slide bar members externally of said track, said coil spring means having axes inclining rearwardly from points adjacent said idle wheels upwardly to said chassis and being mounted by pivot means permitting the said rearward inclinAtion to increase or decrease, said coil spring means having an axial inclination of from 5* to 45* to the vertical when said slide bar is horizontal and means associated therewith permitting selective adjustment of the degree of rearward and upward inclination of said coil spring means, said slide bar rear portions being movabe both upwardly and downwardly from their normal substantially horizontal alignment with resulting change in the said rearward inclination of said spring means and said upward movement compressing said coil spring means, whereby the spring compression resistance to the upward movement of said slide bar rear portions increases as the said rearward inclination of said spring means decreases.

Claim 21

Dependent Claim 48 words

The suspension system of claim 16 in which said selective adjustment means confines the adjustment of said upward and rearward inclination of said coil spring means to angles of from 15* to 35* with respect to the vertical when said slide bars are in their normal horizontal alignment.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1977-01-28	1977-07-30	1978-01-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1981-01-28	1981-07-30	1982-01-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1985-01-28	1985-07-30	1986-01-29	$7700.00	Window Closed / Lapsed

Snowmobile suspension system

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