A pressure control valve having a pressure fluid inlet chamber connected to a pressure fluid source via a brake valve. A pressure fluid outlet chamber of the pressure control valve communicates with a brake cylinder. The pressure fluid inlet chamber and the pressure fluid outlet chamber can be connected to a control chamber via an inlet valve. The pressure fluid outlet chamber can be connected to the atmosphere via a controllable outlet valve. From the pressure fluid outlet chamber, a first connecting conduit leads to the control chamber of the inlet valve. The first connecting conduit can be monitored by a control valve embodied as a 2/2-way valve. A second connecting conduit, which is always open, is also provided between the control chamber of the inlet valve and the pressure fluid inlet chamber. This conduit exerts a delaying action upon pressure fluid flowing at high speed through it. The pressure control valve is usable in compressed-air-actuated vehicle brake systems, in particular those having an anti-skid system.
The electropneumatic control system for the pressure in the main air pipe (37) of compressed air brakes of rail cars is provided with one inlet and one outlet solenoid valve (3 and 4) to control the pressure in a control chamber (26) of a relay valve (19). The inlet solenoid valve (3) and the relay valve (19) are supplied with compressed air from a main reservoir pipe (34). The relay valve controlled by the pressure in the control chamber (26) against the pressure in the main air pipe (37) controls the compressed air lead-in and lead-out for the main air pipe (37). To avoid the undesired response of the relay valve (19) to pressure changes elsewhere in the main air pipe (37), the two sides of the piston (20) of the relay valve (19) are closed without any throttling by way of the secondary valve parts (13 or 14) of the two solenoid valves (3 and 4) in the unactuated state of the control system (2).
This invention achieves a complete dissipation of a residual pressure in a brake cylinder. The air brake system has a pressure control valve arranged between a brake valve and the brake cylinder. This pressure control valve has an outlet valve which controls the connection between an outlet chamber to which the brake cylinder is connected, and a venting space and has a control chamber. A connection between the control chamber and the venting space can be controlled by way of a control valve. There is furthermore a connecting conduit between the outlet chamber and the control chamber of the outlet valve. In the case of a braking operation, the control valve is switched briefly into its open position after the actuation of the brake valve ceases, allowing the residual pressure in the brake cylinder to be dissipated to the venting space via the connecting conduit. The method can be employed in commercial-vehicle air brake systems.
In a brake control device with a traction control function, there is provided a traction control valve for connecting a first conduit extending from a first pressure source to a brake valve to a second conduit extending from a second pressure source for arbitrarily switching the route of the pressure of air supplied from the traction valve to the modulator. With this construction, it is possible to obtain the compact brake control device capable of reducing the number of parts and enhancing the brake responsiveness with a low cost.
A modulator comprising an inlet, an exhaust and an outlet, the modulator comprising a piston moveable in response to a control pressure in a control chamber to vary to supply of fluid under pressure to the outlet, wherein the modulator comprises a first end face and a second end face wherein the exhaust and the inlet are provided in the first end face and the outlet is provided in the second end face. The modulator further comprising a hold solenoid connected between the inlet and the control chamber, and a dump solenoid connected between the control chamber and the exhaust, wherein the connections between the hold solenoid, the exhaust and the control chamber and the connections between the dump solenoid, the control chamber and the inlet do not cross the plane of the piston.
A contaminant-ejecting relay valve for a pneumatic brake system is disclosed. Two embodiments of the valve are disclosed: in one embodiment, the valve is actuated by pilot air pressure, which is either supply air pressure or control air pressure; in another embodiment, the valve is solenoid-actuated. In both embodiments, the valve comprises a housing enclosing a chamber; a control port in the housing in fluid communication with the chamber; an exhaust port in the housing permitting removal of contaminants from the chamber; a main piston mounted within the chamber and movable between a first position and a second position; an exhaust passage through the main piston connecting the chamber and the exhaust port in fluid communication; and a blocking member movable between an open and closed position for opening and closing the exhaust passage, such that when the blocking member is in the open position it permits pressurized air from the control port to eject contaminants from the chamber. Preferably, the main piston includes a hollow stem, and the blocking member comprises an exhaust piston slidably mounted within the hollow stem and movable between an exhaust passage open and an exhaust passage closed position. The main piston may include an inverted conical face adjacent the chamber to direct contaminants toward the exhaust passage and away from valve seals and lubricants.
