# US 4,374,591 A · Strut-type steering ski suspension for snowmobiles

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- Number: US 4,374,591 A
- Document ID: US4374591A
- Status: Granted
- Kind: A
- Application number: 06/160,471
- Filed: 1980-06-18
- Granted: 1983-02-22
- Earliest claimed: 1979-06-27
- Assignees: Yamaha Hatsudoki Kabushiki Kaisha
- Inventors: Takashi Kobayashi
- Web page: https://patentgrep.com/patent/US4374591A

## CPC

- B62B 17/04: resiliently suspended
- B62M 27/02: power driven
- B62M 2027/026: {Snow mobiles characterised by the suspension means}
- B62B: HAND-PROPELLED VEHICLES, e.g. HAND CARTS OR PERAMBULATORS; SLEDGES (characterised by animal propulsion B62C; propulsion of sledges by driver or engine B62M)
- B62M: RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR {SINGLE-TRACK} CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES (arrangements or mounting of transmissions in vehicles in general B60K; transmission elements per se F16)

## Abstract

A strut-type steering ski suspension having minimal height for a given stroke. The suspension includes shock-absorber means with a movable cylinder and a fixed rod, the rod being fixed relative to the frame of the snowmobile. A ski is mounted to the lower end of the movable cylinder. A bias spring is incorporated in the suspension, which bears in compressive opposition between the lower portion of the movable cylinder and the rod or some other structure which is fixed to the frame, thereby utilizing otherwise "dead" space for the spring, and shortening the length of suspension needed for a given stroke length.

## Claims

### Claim 1

In a steering ski suspension for a snowmobile, said snowmobile having a frame, said suspension including a stationary cylinder fixed to said frame a movable cylinder slidably mounted in said stationary cylinder, and a ski mounted to the lower end of said movable cylinder so as to turn therewith, the improvement comprising: a cap member fixed to the upper end of said stationary cylinder; and coil spring bias means entirely confined within one of said cylinders and compressively opposed between a lower portion of said movable cylinder and said cap member or structure rigidly attached to said cap member, said movable cylinder being rotatably and axially movable in said stationary cylinder whereby to make the ski steerable and to provide an elastic suspension for said frame.

### Claim 2 (depends on 1)

Apparatus according to claim 1 in which said spring bias means bears against said cap member, and comprises a coil spring which surrounds said movable cylinder.

### Claim 3 (depends on 2)

Apparatus according to claim 2 in which a flange is provided on each of said cylinders, said flanges facing one another, and in which stopper means is interposed between said flanges to limit the extension excursion of said movable cylinder by simultaneous abutment of both of said flanges against said stopper.

### Claim 4 (depends on 1)

Apparatus according to claim 1 in which said structure comprises a rigid rod projecting from said cap member into said movable cylinder, said spring bias means comprising a coil spring contained inside said movable cylinder, and an apertured cap fixed to the upper end of said movable cylinder which passes said rod.

### Claim 5 (depends on 4)

Apparatus according to claim 4 in which said rod also functions as a portion of a fluid transfer shock absorber to impede shocks by limiting the rate of flow of fluid across it.

### Claim 6 (depends on 4)

Apparatus according to claim 4 in which said bias spring means is rotationally free where it opposes said movable cylinder.

### Claim 7 (depends on 4)

Apparatus according to claim 4 in which a flange is provided on said rod, and in which stopper means is interposed between said cap and said flange to limit the extension excursion of said movable cylinder by simultaneous abutment of said cap and said flange against said stopper.

### Claim 8 (depends on 1)

Apparatus according to claim 1 in which stopper means is placed inside said fixed cylinder, against said cap member to limit the compressive excursion of said movable cylinder by abutment with said stopper means.