Variable-displacement rotary piston pump 1 delivers fluid to the head (working) end of cylinder 2. Outlet from the exhaust end of the cylinder is blocked off by valve member 3, subject to the action of spring 4 and opened by piston 5. Spring 4 can be adjusted so that valve member 3 is opened when piston 5 is subject to a definite working pressure. Surplus fluid is discharged from the system through relief valve 6.
$4140$CHP,Dr$