A fluid pressure control system engages the power take-off of a tractor-trailer combination vehicle equipped with air brakes while simultaneously applying the parking brakes of both the tractor and the trailer. However, when the vehicle is to be moved and the power take-off disengaged, the vehicle operator must, in addition to moving the power take-off control to the position disengaging the power take-off, must also operate the parking control valves which release the parking brakes on both the...

In a brake valve for the operation of the service brake and spring-loaded brake installation of a utility vehicle trailer, a service brake valve (3) and a spring-loaded valve (1) are provided in a common housing (5) in mirror image arrangement. The two valves, operating in a manner known per se, are constructed of identical components and a common ventilation in the form of a ventilation insert (47) in the center of the housing (5). The two valves are fed either from a common reservoir (55) or f...

Conventional fluid control circuits for brakes, including separate parking and retarding valves, include high volume lines and/or complex mechanical linkages to selectively effect the braking functions. This invention provides a relatively non-complex fluid control circuit (10) for closely controlling engagement of brakes (15), including a first valve (25) for controlling engagement of the brakes (15), a pilot line (20), a second valve (47) connected to the pilot line (20), and movable between a...

A simplified brake control system comprises a source of pressurized fluid, a spring-set brake with a hydraulic release mechanism and a control valve connected between the brake and the source. The control valve has a valve body and a flow control mechanism in the body and mounted for movement between a first (solenoid-energized) position and a second (solenoid-de-energized) position. A one-way check valve is built into the valve body. How the system operates depends upon two factors, namely, (a)...

A brake release mechanism for a spring-loaded, normally applied vehicle brake releasable by system hydraulic pressure when the system is disabled includes a pilot-operated brake release valve for isolating the brake from the disabled system, a brake control valve disposed between the system and the brake, and a manual hydraulic pump communicating with the brake for supplying fluid pressure thereto. A pilot-operated shunt valve is provided for shunting a hydraulic motor associated with the brake ...

Separate inputs for air pressure supply and parking brake control are provided to a parking brake control valve for a towed vehicle to enable manual release of the parking brakes using air pressure stored in either one of two mutually protected reservoirs on the towed vehicle without bleeding one source of stored air pressure into another.

A fluid pressure braking system for a tractor-trailer vehicle in which the braking system of the tractor is connected to the braking system of the trailer through trailer control and trailer supply lines includes a relay valve which controls communication between service reservoirs on the tractor and the trailer control line in response to operation of the vehicle brake valve. Use of the relay valve to control the communication to the trailer control line permits greater volumes of air to be sup...

This invention relates to a rail vehicle brake system comprising an air brake cylinder (10, 11) with a piston (12) which is spring-biased for brake application on one side thereof, and a control system for selectively supplying pressurized air to said cylinder. On both sides of the piston (12) the air brake cylinder spaces (10, 11) are connected to a common control system (28, 31) for the supply of pressurized air thereto. The control system--by controlling the supply and discharge to and from t...

A unitary full-function valve is used to control the operation of a service brake system and a spring brake system. The valve includes a valve body that has multiple ports, including separate ports for providing fluid communication to a spring brake chamber, a service brake chamber, a fluid reservoir and an exhaust port. The valve body also has ports for receiving pressurized supply fluid and control fluid. The supply fluid inhibits the activation of the spring brakes so that the spring brakes a...

A full function valve incorporating a proportioning valve module that initially directs supply air pressure during initial system charging to the spring brake chambers to prepare the spring brakes for prompt release when there is sufficient system supply air pressure to operate the service brakes. The proportioning valve module then opens to increase supply air pressure to the reservoir, while charging of the spring brake chambers continues, until the service brakes become operable and the sprin...