Patent ID: 7862131

Claim:
An undercarriage for providing traction to a working vehicle on the ground, the working vehicle having a center of gravity that shifts between a first position and a second position spaced apart from the first position along a longitudinal direction of the undercarriage during operation of the working vehicle, the center of gravity of the working vehicle being located at the first position when the working vehicle carries a first load and being located at the second position when the working vehicle carries a second load greater than the first load, the undercarriage comprising: a frame; a drive wheel; a plurality of roller wheels distributed along the longitudinal direction of the undercarriage; and an endless track disposed around the drive wheel and the roller wheels for engaging the ground, the drive wheel being rotatable to move the endless track, the roller wheels contacting a lower run of the endless track, the endless track having a working surface in contact with the ground to provide traction during operation of the working vehicle; the undercarriage being operable in a first mode when the center of gravity of the working vehicle is located at the first position and in a second mode when the center of gravity of the working vehicle is located at the second position, the undercarriage being responsive to a shift of the center of gravity of the working vehicle from the first position to the second position to pass from the first mode to the second mode, the working surface of the endless track being longer in the second mode than in the first mode.