TRAILER LIFTING AND LOWERING SYSTEM

摘要

A lifting and lowering system for a trailer or the like includes one or more extendible and retractable legs, with the legs being provided with springs or the like urging the legs toward their retracted position. The system is a pressurized air/hydraulic system, and includes an air-operated booster valve for extending the legs when loaded. A master valve assembly is provided for controlling supply of air to the system and for allowing retraction of the legs. The master valve and air valve include a common actuator shaft so that the system is selectively connected to pressurized air or vented, as appropriate, when leg extension or retraction occurs. The master valve includes a cam actuator/cam follower piston operated system for selectively providing fluid pressure to a lock valve associated with each leg. The lock valve is biased toward a normally closed position, and is selectively movable to an open position for allowing extension or retraction of the legs.