PNEUMATIC TIMER FOR DELAYING THE APPLICATION OF AN EMERGENCY BRAKING PRESSURE

摘要

A pneumatic emergency brake release timer comprises a high capacity transfer valve, a timing reservoir in communication with the pilot port of the high capacity transfer valve (50), the check valve (64) and choke circuit (62) providing parallel connections between the main source of pressure and the reservoir through a check valve and opposite flow through a dissipating choke. A pneumatic relay valve controls the pressure to the brake cylinders. The high capacity transfer valve (50) can select a pilot pressure (48) to the pneumatic relay valve from two different pressure sources : a controlled pressure and an emergency pressure. Normally a controlled pressure is selected, e.g. a modulated pressure for wheel slip control. In the case of emergency braking, the timing reservoir (54) maintains the high capacity transfer valve (50) during a present time in a position wherein the controlled pressure is still selected. Thereafter, the emergency pressure is selected, thereby bypassing the pressure controller (44). The advantage is that wheel slip control is still possible during emergency braking for a present time, using pneumatic elements only.