A release mechanism for indirectly acting air brakes of a railway vehicle has a valve device which is actuated by the pressure in the main air line and upon actuation lowers the pressure in the control chamber of the brake control valve which connects the brake cylinder to the atmosphere. The valve device is connected to an air tank. A manually operated release valve is provided to actuate the pressure releasing function of the valve device. The valve device has a valve member which is subjected to the pressure of the air tank when in the closed position and opens and closes a connection between the control chamber of the brake control valve and the air tank. The valve member is slidably mounted in the hollow shaft of the piston and brings about the connection of the control chamber to a vent by means of a shut-off member coupled to the shaft. The piston acting in conjunction with the valve member in the opening direction of the shut-off member as well as in the closing direction of the valve member of the control chamber connection is subjected to the pressure of an air tank through the release valve and, in the closing direction of the shut-off member, is subjected to the pressure in the main air line.
An air brake system for a railway vehicle has a brake control valve connected to a main air line which is maintained at a certain pressure when the brakes are released. Connected to the brake control valve is an air reservoir and a brake cylinder which is connected through suitable linkage to operate a friction brake. A valve device is provided which is actuated in response to the operating state of the friction brake and pressure in the main air line and includes a venting valve connected to the main air line so that the venting valve is opened during a simultaneous occurrence of the brake being in the braking state and the regular pressure level is maintained in the air line. Under other conditions the venting valve is closed.
A control system for a press having a clutch and a brake includes a clutch control valve and a brake control valve. The clutch control valve operates the clutch by supplying pressurized air to the clutch. The brake control valve operates the brake by supplying pressurized hydraulic fluid to the brake. The brake control valve is activated by pressurized fluid from the clutch control valve in order to insure simultaneous release of the brake with engagement of the clutch as well as simultaneous application of the brake with disengagement of the clutch.
