HYDRAULIC TYPE PUMP CONTROLLER

摘要

A fluid pressure supply system incorporates two pumping units P1 and P2 for supplying fluid under pressure to a load 13. Pump P1 supplies the load continuously. Pump P2 is also connected to the load 13 through a load valve 15 when pressure in the load is low but is connected to drain through the load valve when load pressure is high. A pressure relief valve 14 controls the load valve 15 by a connection from port 22 to port 28 which applies system pressure to the load valve at low pressure and drain pressure via port 23 at higher pressures in response to relief valve spool movement. The high control pressure moves load valve spool 25 to connect its inlet port 29 to load 13 through port 33. When system pressure is high and control pressure is low, inlet 29 is connected to drain port 31 so that pump P2 is off-load in that it is pumping direct to drain.