Abstract: A full function brake valve for a semi-trailer is contained within a single housing and provides ports for receiving supply air and control air, and for delivering and receiving air from reservoirs, service brakes and spring brakes, and delivering air to an exhaust. The internal valves include a reservoir check valve and a relay valve to respectively pressurize a reservoir and to deliver supply air to service brakes. A secondary reservoir is supplied via a secondary reservoir check valve and a secondary reservoir outlet in the full function valve, or in a secondary relay valve, and is controlled by a secondary relay valve module to provide a redundant braking system for additional safety.

Abstract: A simplified and less-costly quick-release valve with controlled hysteresis for a vehicle spring-set air-release parking brake system lengthens the operating life of the valve, reduces energy consumption, extends compressor life and alleviates noise problems. The valve comprises a valve body and a plurality of internal passageways each of which is selectively connectable to at least another of the passageways. The selective connection is controlled by an integrally-formed flexural spring-brake-control release diaphragm within the valve body and disposed to either isolate or selectively connect the passageways depending on the relative pressure conditions within the passageways and respective areas of the diaphragm exposed to the pressures. The components are designed so that the normal variations or cycling of the supply or intake pressurized air does not cause cycling of the pressure in the spring-brake chambers.

Abstract: A full function brake valve for a semi-trailer is contained within a single housing and provides ports for receiving supply air and control air, and for delivering and receiving air from reservoirs, service brakes and spring brakes, and delivering air to an exhaust. The internal valves include a pressure protection valve which communicates with a first check valve and a quick release valve to pressurize spring brake chambers, and a reservoir check valve and a relay valve to respectively pressurize a reservoir and to deliver supply air to service brakes. An orifice preferably provided in a second check valve permits partial air flow to the spring brakes to release the spring brakes for towing the vehicle.

Abstract: A full function skid control valve assembly for use in an air brake system which provides for brake control utilizing a compact single assembly. The system provides for the maintenance of certain minimum operating pressures so that, when the air pressure within the vehicle brake system falls below predetermined levels, the valve assembly automatically partially or entirely exhausts the air pressure sometimes causing the spring parking brakes to engage. Once the air pressure within the brake system returns to predetermined levels, the valve assembly will allow a reservoir to be charged and the spring brakes to be deactuated. During operation, the assembly provides control of the service brakes while preventing undesired skid conditions.

Abstract: A proportioning module for automatically changing the ratio of delivery pressure to control pressure according to whether a mode control pressure is present or absent. When the mode control pressure is present, the proportioning module is deactivated, causing the delivery pressure to be substantially equivalent to control pressure. When the mode control pressure is absent, the proportioning module functions to provide control pressure to delivery pressure ratios which are dependant upon the control pressure and the resultant delivery pressure.

Abstract: A valve assembly for use with spring-set air-release vehicle parking brakes comprises a particular arrangement of conventional components providing desired spring brake operational characteristics heretofore requiring costly, complex specially-designed units. The valve assembly typically employs a plurality of interconnected check valves in combination with pressure protection and quick release valves to provide the desired characteristics. These include a system whereby at startup pressurized air from the tractor fills the trailer reservoir tanks and the spring brake chambers simultaneously. The valve assembly also assures that if during tractor-trailer operation the supply air from the tractor is severed or otherwise lost, service brake air in the trailer reservoir tanks is retained at a sufficient pressure to provide adequate service brake operation.