Abstract: A self-levelling seat suspension system for vehicles wherein the seat is reciprocally supported by a cushion of pressurized air interposed between the seat and its supporting base unit. Pressurized air is supplied to or vented from the air cushion by a level control valve bodily movable with the seat and relative to an actuating cam. By way of example, the level control valve is fixed to one of a pair of links hingedly connecting the seat and its base and serving additionally to restrain the seat from rotation about its axis of reciprocation.The control valve is actuated by a cam which is manually adjustable to support the seat in any one of several different neutral levels while the occupant is seated.

Abstract: A motor vehicle security system for trucks, trailers and the like equipped with conventional fluid operated braking assemblies. The security system comprises a manually operable valve for controlling the application of fluid under pressure to the braking assemblies to manually set the vehicle brakes. The valve is arranged with a mechanical, key-operated lock for controlling and locking the valve in a selected position. When the valve is in a "locked" position it allows the brakes to be set and the vehicle maintained in situ to prevent the unauthorized movement thereof. The brake assemblies are also secured and locked to prevent the manual operation thereof by use of a conventional lockout tool.