Patent ID: 7455141

Claim:
A track drive system comprising: a chassis frame; a drive wheel rotatably coupled to the chassis frame; an upper idler rotatably coupled to the chassis frame rearwardly of the drive wheel; a forward idler rotatably coupled to the chassis frame below the drive wheel; a suspended frame; a rear idler rotatably coupled to a rear portion of the suspended frame; a lower idler rotatably coupled to a forward portion of the suspended frame; an upper swing arm having forward and rearward ends, the upper swing arm pivotally coupled at the forward end thereof to the chassis frame, and pivotally coupled at the rearward end thereof to the suspended frame at a location displaced generally upwardly from an axis of the rear idler by a rear idler offset distance; a lower swing arm having forward and rearward ends, the lower swing arm pivotally coupled at the forward end thereof to the chassis frame and pivotally coupled at the rearward end thereof to the suspended frame; and a biasing means for biasing the suspended frame away from the chassis frame, wherein the suspended frame is moveable between an extended position and a compressed position, and a perimeter defined around the drive wheel, upper idler, rear idler, lower idler and forward idler remains substantially constant as the suspended frame moves between the extended position and the compressed position.