Patent ID: 8079310

Claim:
A compensating device for controlling a vertical position of a body mounted on a chassis of a vehicle relative to a datum line, said vehicle having a source of pressurized fluid, a plurality of wheels mounted on said chassis, a primary suspension positioned between said wheels and said chassis, and a fluid pressurized secondary suspension positioned between said chassis and said body, said compensating device comprising: a chamber in fluid communication with said secondary suspension; a piston positioned within said chamber, said piston and said chamber being movable relatively to one another; a biasing element positioned between said piston and said chamber; a first and a second valve mounted on one of said piston and said chamber, the other of said piston and said chamber being mountable on said body, said first valve having an inlet in fluid communication with said source of pressurized fluid, and an outlet in fluid communication with said secondary suspension and said chamber, said second valve having an inlet in fluid communication with said secondary suspension and said chamber, said second valve also having an outlet; an actuating mechanism extending between said first and second valves and said chassis, said actuating mechanism opening said first valve in response to motion of said body toward said chassis, said actuating mechanism closing said first valve when said body is at a predetermined vertical position relative to said datum line, said actuating mechanism opening said second valve in response to motion of said body away from said chassis and closing said second valve when said body is at said predetermined vertical position relative to said datum line.