Abstract: A compound disc brake comprises a pair of pressure plates with a ball and ramp camming mechanism, one of the plates comprises a driven plate keyed to a rotating axle shaft to be braked, and the other plate comprises a servo plate carried from the driven plate by the camming mechanism. The servo plate has a torque-transmitting structure in the form of a separate annular disc keyed to the outer peripheral edge of the servo plate. The torque-transmitting structure transmits torque applied to that region by a primary braking apparatus to the central region of the servo plate. Retardation of the servo plate by the primary braking apparatus causes the pressure plates to separate axially and move into engagement with relatively stationary braking surfaces in the brake housing whereafter servo braking occurs.

Abstract: In a power assistance system for a vehicle steering mechanism fluid pressure providing the assistance is supplied from a pump driven intermittently by an infinitely-variable electric motor. For a rack and pinion mechanism fluid pressure chambers are formed by sealing boots at each end of the rack, and are connected through the pump, which is operative to create a pressure differential between the chambers, and thus across the rack to provide power assistance. The electric motor is energized as required to drive the pump in the appropriate direction, and when the motor and pump are inoperative fluid is allowed to flow freely between the chambers to accommodate fluid displacement as a result of unassisted operation of the steering. The pump is preferably a turbine pump, which allows fluid flow when inoperative. The system provides power assistance efficiently, and relatively cheaply.