Abstract: A hydraulic pressure control valve uses a stepped valve spool having a differential area exposed to supply pressure to provide a small resultant force on the spool. A linear electric solenoid provides a linearly variable force on the valve spool to variably position the spool. In a basic embodiment, the linear solenoid force opposes the resultant supply pressure force to position the spool and control hydraulic outlet pressure. Other embodiments are employed to control brake pressure in a transit car. In a second embodiment, the resultant hydraulic pressure force is opposed by the linear solenoid force to position the spool during normal service braking. Brake pressure is proportioned to car weight by varying current to the linear solenoid. When the transit car emergency brake pipe is dumped, load weigh air pressure and spring forces position the spool in an emergency brake pressure position proportional to car weight.

Abstract: A railway brake actuator which provides both service and parking braking comprises a cylinder having an operating cavity. A piston assembly in the operating cavity has a stepped bore forming second and third cavities and is extended by hydraulic pressure and retracted by a spring to apply and release the service brake. Hydraulic pressure extends a hollow parking brake piston from the second cavity to extend the piston assembly and apply the parking brake. A one-way clutch comprising ramps and rollers locks the piston in parking brake applied position. Hydraulic pressure disables the clutch to enable spring retraction of the parking brake piston and the piston assembly to release the parking brake. A gripper ring on the piston assembly operates between cylinder abutments to limit piston assembly retraction to provide slack, and enables slippage on the piston assembly on extension to adjust for brake wear.

Abstract: A brake actuator for a railway brake which provides both service and parking braking comprises a cylinder having an operating cavity. A piston assembly extends into the operating cavity and has a stepped bore including second and smaller third cavities. A first hydraulic supply admits pressurized hydraulic fluid into the operating cavity to extend the piston assembly to apply the service brake. A spring applies a retracting force on the piston smaller than the hydraulic force. A hollow parking brake piston carried in the second cavity extends to react against the cylinder and extend the piston assembly in response to the supply of pressurized fluid to the second cavity from a second hydraulic supply to apply the parking brake. A mechanical lock, comprising a one-way clutch utilizing ramps and rollers, locks the piston extended from the piston assembly cylinder to maintain the parking brake applied upon removal of the second hydraulic supply force.

Abstract: Three embodiments of a hydraulic braking system are shown and described. Each embodiment provides a precisely controlled hydraulic braking system for a railway vehicle, which features a pilot pressure controlled brake control valve. The pilot pressure is selectively varied by operation of pressure control and flow control valves so that the power requirements for the hydraulic braking system are minimized. The braking system can be used with either spring-apply, pressure-release or pressure-apply, spring-release braking actuators. An auxiliary hydraulic system is provided to operate the brakes if the primary hydraulic system should fail. The pilot pressure fluid which operates the brake control valve can be either hydraulic or pneumatic. The brake control valve can be provided with a pneumatic emergency brake override control.

Abstract: A mechanism for mounting a brake disc on a rotatable member using a plurality of mounting bolts, which mechanism includes a mounting ring secured against radial movement and interposed between the bolts and the disc which permits radial expansion of the disc without transmitting the disc movement to the mounting bolts.

Abstract: A vehicle friction brake control system applicable in both brake and power modes for controlling slip and slide of the vehicle wheels utilizes a speed signal for each vehicle axle whose amplitude is dependent upon axle angular speed. There is a front axle speed comparison circuit and a rear axle speed comparison circuit. Each of the speed comparison circuits utilize speed signals from their respective axles, as well as electrically isolated speed signals from the other axles. The speed comparison circuits each compare the highest or lowest axle speed from their respective axles with the highest or lowest of all four axle speeds to provide a slip/brake system signal.