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. Similarly, if pressurized air in the trailer reservoir tanks is lost, sufficient pressure is maintained in the system to keep the spring brakes released for safe parking of the tractor-trailer combination.
An pneumatic system (10) for a tractor trailer truck (6) which increases compressed air flow to the trailer reservoir (52) whenever the tractor (7) is parked. This decreases the time it takes to charge the trailer reservoir (52) to a sufficient pressure to release the trailer brakes allowing the truck (6) to move. In normal over the road operation the trailer reservoir (52) is charged through a tractor protection control valve (14) which is mounted on the tractor dash. However when the tractor (7) is parked and a tractor park valve (12) which is mounted on the tractor dash is pulled out compressed air from the tractor secondary reservoir (42) is delivered with an increased flow rate to the trailer supply line (50). When the tractor park control valve (12) is pushed in releasing the tractor parking brake the trailer charging reverts back to charging through the dash mounted tractor protection control valve (14). Pulling the tractor protection control valve (14) out vents the trailer supply line (50) in both the fast and normal charge mode.
A simplified integrated full-function valve for heavy duty brake systems comprising a valve body having individual ports for fluid communication with spring brake chambers, service brake chambers, pressurized-air reservoir and exhaust and for receiving pressurized control and supply air from respective sources thereof; internal passageways within the valve body providing selected fluid communication with the various ports; a plurality of valve modules within the valve body comprising a spring brake valve module, a relay valve module and a biased one-way pressure protection valve module, and disposed to selectively determine the fluid communications within the internal passageways and ports responsive to the respective positions of the valve modules; the port and related internal passageways for the spring brake chambers being fluid-communicatively-isolated from the reservoir, the service brake chambers and the control air, whereby the number of the internal passageways within the valve body is minimized; the simplified design lending itself to functional flexibility.
A full-function brake valve for a tandem trailer is contained within a single housing and provides a boost to the control air signal arriving at the full-function valve so that the control air signal can be delivered to a second trailer full-function valve without degradation of the control air signal. The signal boost function is provided by an aperture in the piston of the relay valve that connects the control air inlet to the supply air, to cause the supply air pressure to boost the control air signal.
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.
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.
