| 摘要 |
A railroad truck having at least four wheels comprising brakes for braking the wheels; a single enclosed air cylinder mounted on the truck; the air cylinder having first and second chambers; a conduit to supply service air pressure to the first chamber; the first chamber containing a piston pneumatically operated by service air pressure to apply controlled service braking pressure, emergency braking pressure and, when the truck is stopped, parking braking pressure, to the brakes; the second chamber containing a spring which applies automatic parking pressure to the brakes when the truck is stopped, and applies emergency fail-safe pressure to the brakes when there is a pneumatic system failure to supply air to the first chamber; apparatus to supply pressurized air to the second chamber to keep the spring from applying pressure to the brakes so long as adequate air pressure is maintained in the second chamber; a handbrake assembly mounted on the truck in a position readily accessible for manual operation when the railroad truck is joined to a vehicle or separated therefrom; and the handbrake assembly including a longitudinally reciprocal rod operative to compress the spring so that the brakes can be fully released and maintained released for an indefinite time so long as pneumatic braking pressure is not applied to the first chamber and upon reverse movement of the said longitudinally reciprocal rod compression of the spring is released so that the spring can apply pressure to the brakes unless pneumatic pressure supplied to the first and second chambers prevents application of braking pressure by the spring.
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