Abstract: 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 tractor and the trailer. Accordingly, the parking brakes cannot be inadvertently released by merely disengaging the power take-off control, although engagement of the power take-off control automatically sets or applies the parking brakes on both the tractor and the trailer.

Abstract: 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 supplied to the trailer control line, thereby appreciably reducing transmission times of brake application signals.

Abstract: A vehicle air brake system includes a conventional automotive air compressor operated by the vehicle engine for charging a storage reservoir with compressed air. Air is communicated through an air dryer which cleans and dries the air before it is communicated to the storage reservoir. A governor is responsive to the pressure level in the storage reservoir to generate a pressure control signal in response to the pressure level in the reservoir reaching a predetermined level. The compressor is unloaded by the signal from the governor so that, while it may continue to be operated by the vehicle engine, it does not compress air. The unloading signal also opens the purge valve on the air dryer, which backflows a quantity of air through the air dryer to regenerate the desiccant.

Abstract: Fluid pressure braking system (10) for supplying fluid pressure to actuate the service brake actuators (26) and to supply hold-off pressure to release the spring brake actuators (22) of the trailer portion of a tractor-trailer combination vehicle includes a spring brake relay valve (32) having a delivery port (38) communicated with the spring brake actuators (26), a control port (34) communicated with the trailer supply line or conduit (12), and a supply port (36) communicated with the supply line (12) through a bypass passage (40). Accordingly, hold-off pressure can be supplied directly to the spring brake actuator (26) before the reservoir (44) is fully charged. The reservoir (44) is charged through the supply line (12) and a pressure protection valve (54) which opens to permit charging of the reservoir (44) only when the pressure in the system exceeds a predetermined level.

Abstract: A fluid pressure braking system for the trailer portion of a tractor-trailer combination vehicle includes valving mechanism which permits the vehicle spring applied, fluid pressure released parking brakes to be released after a single brake system failure. The system requires a pair of fluid pressure reservoirs, and includes the necessary interlock to permit both of the reservoirs to be charged while protecting the reservoirs in case of a leak in the system. The system also permits the vehicle parking brakes to be charged with the fluid pressure stored in either of the reservoirs. Both of the reservoirs normally provide the fluid pressure to actuate the vehicle service brakes.

Abstract: A vehicle fluid pressure braking system is disclosed which includes brake-applying devices having separate service and parking actuators. Separate service and parking actuation circuits are provided to control actuation of the service and parking actuators, respectively. An interlocking valve is provided which prevents release of the parking actuator until a predetermined fluid pressure level is communicated to the service actuator. This interlocking valve prevents inadvertent release of the parking actuators, and also prevents release of the parking actuators in a situation in which a malfunction of the service braking circuit would render operation of the vehicle dangerous.

Abstract: A fluid pressure braking system for a vehicle having brake actuators which may be mechanically held in the brake-applied position when the vehicle is parked and which may be actuated from either service or emergency actuating systems, is provided with a fluid communication limiting valve which limits fluid communication through the service actuating system to the brake actuators when the actuators have been actuated by the emergency system, thereby providing an "anti-compounding" capability so that the brake actuators cannot be actuated by the combined full capacities of both actuating systems. The system further includes a standby valve which is responsive to a normal brake application to communicate fluid pressure to the actuators through the emergency system when the failure of the primary fluid pressure system prevents communication to the actuators through the service system.

Abstract: A fluid pressure braking system for an articulated vehicle. The system includes valving which senses a failure in the brake service line connection between the tractor and trailer portions of the vehicle. If a failure in the service line connection is detected, the valving closes communication between the tractor and trailer portions of the vehicle and causes actuation of the trailer emergency brakes. When the brakes of the vehicle are released, the valving automatically resets itself to release the trailer emergency brakes.