LOAD HOLDING FOR METERLESS CONTROL OF ACTUATORS

摘要

First and second mechanical hydraulic valves (342, 340) are disposed between a pump (180) and the cap side chamber (170) of an actuator (132) and the pump (180) and the rod chamber (168) of the pump (180). The first and second valves (340, 342) are actuated as a result of respective pressure differentials applied across the valves (340, 342). A controller (320) controls flow from a pump (180) in response to a commanded motion to control movement of the actuator (132), and cause the valves (340, 342) to open. The valves (340, 342) are disposed in their no-flow positions when the pump (180) is not operative, and when the hydraulic system (104) of off or locked out to hold a load.