Abstract: A combination quick release and service relay brake valve assembly is used to consolidate multiple valve functions within a common valve assembly, which reduces cost and overall complexity in an associated vehicle brake system. The combination quick release and service relay brake valve assembly includes a valve body with a quick release portion that has a parking brake port and a service brake control port, which is in fluid communication with an anti-compounding passage. The valve body also includes a service relay portion that has a supply port fluidly connected to a service brake air reservoir and a delivery port fluidly connected to a brake actuator that generates service brake requests.

Abstract: A brake system for a tractor-trailer vehicle includes a service brake system and a park brake system. The service and park brake systems are used to brake both a tractor and a trailer towed by the tractor. A trailer hand control valve is actuated by a vehicle operator to brake the trailer. The park brake system includes a park brake control valve that receives input commands from the vehicle operator to apply and release park brakes on the tractor and the trailer. An interlock valve assembly fluidly connects the park brake control valve to primary and secondary air supplies. The trailer hand control valve is also fluidly connected to the interlock valve assembly. The interlock valve assembly includes an outlet port that supplies an air signal to the trailer from one of the primary air source, secondary air source, or trailer hand control valve via a single connection line.

Abstract: A brake system for a heavy-duty vehicle includes a service brake system and a park brake system. The park brake system includes a park brake control valve that receives input commands from a vehicle operator and a park brake interlock valve that is in fluid communication with an air supply and the park brake control valve. After the park brakes are moved to an applied position, the park brakes can only be released if a park brake release command is communicated to the park brake control valve and the service brake system is in an applied position. The park brake interlock valve includes an inlet port in fluid communication with a vehicle air supply, an outlet port in fluid communication with the park brake control valve, and a valve assembly for controlling fluid flow between the inlet and outlet ports. When service brakes are applied, the valve assembly allows fluid communication from the inlet port to the outlet port, which pressurizes the park brakes to move the park brakes to the released position.