| 摘要 |
A braking system for a vehicle includes a pressure relief valve which rids the -system of moisture and liquid therein. The braking system includes a controller which is in fluid communication with the vehicle brakes, an air source, and an air signal that is supplied by the application of the vehicle's brakes. The controller includes piston structure therein which can be moved relative thereto to selectively allow the air from the source to be supplied to the vehicle brakes when a preset air pressure acts against the piston. The piston has a sump therein for collecting any moisture or liquid present in the structure. In an embodiment, the valve includes a vent hole through the piston and a band or ring which overlies the vent hole. The band or ring is preferably positioned around a necked-down portion of the piston. In another embodiment, the sump is effectively eliminated by a plug which overlays the sump and the valve includes a vent hole through an upper portion of the piston and a spring-biased plunger. The band, ring or plunger is moved away from its engagement with the piston when the pressure acting against the piston becomes greater than a preset pressure to vent the moisture and liquid to the vehicle brakes. An upper portion of the piston may be concave to funnel any liquid or moisture present therein into the sump.
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