Chain tensioning device for snowmobile type transmission

Claim 1

A snowmobile, comprising: a chain case assembly including means for transmitting power from the engine to the endless track of the snowmobile, said assembly including a housing, a pair of spaced-apart parallel shafts, each having one end extending inside said housing at a fixed distance therebetween, means for applying the engine power to one of said shafts for applying torque to said one shaft in a first direction and means for decelerating the said one shaft by applying torque to said one shaft in a second direction opposite to the first direction, the other of said shafts being connected to said endless track by drive sprocket wheel means; sprocket means mounted on each end of said shafts; endless chain means entrained around said sprocket means; said chain means defining opposite first and second intermediate strands extending between said sprocket means; the first intermediate strand being under tension and the second intermediate strand being slack when the engine power is applied to the first shaft in said first direction, and the second intermediate strand being under tension and the first intermediate strand being slack when the decelerating means is applying torque to the first shaft in said second direction, a pair of separate tensioners pivotally mounted to said housing; each said tensioner disposed adjacent an associated intermediate strand and including a shoe element having a wear-resistant surface made of hard material in contact with said associated strand; said tensioners further including spring means for causing each said surface to be maintained in contact engagement with said associated intermediate strand and to exert thereon a force sufficient to take up substantially all slack in said associated strand to maintain said chain means under constant tension independently of the direction of the direction of the torque applied to said one shaft by said applying means and by said declerating means.