Abstract: In a hydraulic brake system the fluid slack is maintained at a predetermined volume by a flow control valve that is positioned between a fluid reservoir and a slack adjusting cylinder. The flow control valve closes the fluid path to the reservoir after a chamber in the cylinder fills with a predetermined amount of slack fluid. The flow control valve can be held open with a detent mechanism to permit servicing of the brake system. The detent is automatically released when the brakes are applied.

Abstract: An electro-pneumatic pilot valve device is operably connected to a relay valve device for governing fluid pressure control of friction brakes of a vehicle in accordance with at least one variable analog signal input to the pilot valve device. The electro-pneumatic pilot valve device has a differential piston assembly comprising a valve plunger having ball valves disposed coaxially thereon and input, vent, and pilot chambers associated with the valves wherein one of the valves selectively connects the input chamber to the pilot chamber, and another valve selectively connects the pilot chamber to the vent chamber. A linear torque motor is governed by a variable input electrical signal for selectively applying a force axially to the plunger to vent fluid from the pilot chamber to atmosphere through the vent chamber. A balance of forces acting on the plunger permits operation of the valves to a lap position.

Abstract: An electro-pneumatic brake valve includes counteracting torque motors which rotate a cam in response to friction brake pressure, dynamic braking effort and/or an electrical control signal. The cam actuates switching elements to apply or release the friction brakes via a pair of solenoid actuated valves which control fluid flow from the valve inlet to the friction brake actuators and from the friction brake actuators to vent.