Pneumatic spring for a vehicle seat

Abstract

A pneumatic spring for damping the relative motion between a vehicle seat and a base upon which the seat is mounted utilizes a rolling lobe sleeve, a plug secured within one end of the sleeve and a piston secured within the other end of the sleeve for movement toward and away from the plug as the sleeve rolls along the outside surface of the piston. The piston, sleeve and plug provide the surfaces of a variable-volume chamber, and the piston includes an internal piston cavity of a fixed size and shape. The variable-volume chamber and piston cavity contain a pneumatic fluid, and an orifice is provided within the piston which permits flow communication between the variable-volume chamber and the piston cavity. When the internal pressure of the variable-volume cavity is increased as the piston is moved toward the plug in response to relative motion between the seat and base, the orifice controls the rate at which pneumatic fluid contained within the variable-volume chamber is permitted to flow into the piston cavity so that the spring is provided with desirable rate characteristics when exposed to either low frequency input or high frequency input. In addition, the permitted flow of pneumatic fluid between the variable-volume chamber and the piston cavity returns the spring to rest in a condition of equilibrium relatively quickly and with few cyclic movements.