| 摘要 |
A two-pressure brake control valve for a single stage releasing indirectly acting airbrake particularly for railway vehicles has a service brake portion in which is a main control element to control a valve so as to subject a brake cylinder to the action of air from an auxiliary air reservoir in response to a decrease in pressure in the brake line per unit time below a predetermined value. An emergency brake portion has a main piston as a main control element and an auxiliary piston is mounted on this main piston. The main piston controls a second valve to further subject the brake cylinder to the action of air from an emergency brake reservoir in response to a decrease in pressure in the brake line per unit time exceeding the predetermined value. A service brake accelerator valve is actuated by the auxiliary piston in response to a variation of pressure in the brake line during a service braking operation when the main piston is in an inactive position.
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