A pneumatic brake system employing dual-diaphragm, spring-actuated, air-released brake actuators is provided with an inversion valve which, in the event of a brake system failure, prevents the brakes from being automatically applied while permitting controlled brake application by releasing compressed air from each actuator's spring chamber in an inverse ratio to that normally supplied from the system by the operator applied brake valve thus permitting a controlled spring brake application. The valve employs first and second pressure responsive pistons with associated valve seats to maintain the actuator springs compressed with air at supply pressure when the vehicle is normally operated. The air at supply pressure in each actuator's spring chamber is automatically ported to a lower pressure through the valve when a system failure occurs and prior to brake application to insure fast response time of the spring actuated brake.
The invention relates to a pneumatic operating unit for compressed air brakes including a housing having at least one exterior compressed air connection device and at least one air-carrying connection. The operating unit further includes at least one piston, at least one piston rod, at least one valve body, at least one valve seat and at least one cylinder body fitted into the housing. The at least one cylinder body has at least one transverse connection and includes one or more of the at least one piston, valve seat and body. The at least one cylinder body also includes a seal in an axial direction between two transverse connections with respect to the housing so that the transverse connections are sealed off with respect to one another.
A braking system for a towing vehicle having a trailer brake valve (24) and hydraulically operated brakes (12) and a trailer having hydraulically operated brakes (14). A novel pilot operated control valve (34) directs the output of the trailer brake valve (24) to both the vehicle brakes (12) and the trailer brakes (14). If the line (46) to the trailer brakes (14) should burst, flow to the trailer brakes is substantially throttled off due to the valve spool (62) shifting to substantially block the flow of fluid through port (40) thereby permitting continued operation of the vehicle brakes. The operating pressure ranges of the brakes may be different. Thus, the operating pressure range of the vehicle brakes (12) is the same as pilot line (74) pressure, which is the output pressure of the brake master cylinder (16), while the operating pressure range of the trailer brakes (14) is the same as output pressure of the trailer brake valve (24) in line (44). The trailer brake valve (24) may have an output proportionately different than pilot line pressure (30).
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.
Pneumatic valve construction comprising a valve chamber having opposing inlet ports with opposing axially located valve seats, and a ball therebetween constructed and arranged to move off of one valve seat into engagement with the other valve seat upon an unbalance in pressure. The construction includes a bottom outlet port that extends to the top of another larger cylindrical chamber having an elastomeric piston therein with fluid flow clearance between the piston and the side walls of the chamber. A tubular exhaust port extends axially inwardly from the bottom side of the chamber to abut the bottom side of the rubber piston. An annular fluid flow chamber exists between the tubular exhaust seat and the side walls of the cylindrical chamber to allow flow past the piston through the space to a delivery port. The rubber piston includes a conically shaped lip which extends out into engagement with the side walls of the cylindrical chamber to help center the piston in the cylinder and to prevent reverse flow from the outlet port back to the inlet ports.
A brake system for an air braked trailer includes a first control line for transmitting air from a source, a second control line for transmitting air, a relay valve allowing air to flow therethrough, and a pneumatic control module (PCM) having structure for reducing pressure from an inlet port of the PCM to an outlet port of the PCM. The PCM is connected to the first control line and is solely connected to the relay valve by the second control line. The first and second control lines are capable of being decoupled from the PCM and being coupled to each other to remove the PCM from the system so that a technician can check the system. An exhaust valve is integrally connected with the PCM and is capable of exhausting air to atmosphere. When the system is used on trailer, the PCM is mounted away from the relay valve, and preferably forwardly of a forward axle of the trailer.
