Piston 3, subject to the working pressure developed by variable-displacement pump 1, which delivers fluid to power cylinder 2, overcomes the resistance of spring 4 and actuates the mechanism for increasing the pump output. By selecting spring 4 with the proper load characteristics, it is possible to compensate automatically for leakage occurring in the hydraulic system at increased pressures by increasing the output of pump 1. Surplus fluid in the system drains back to the tank through relief valve 5. Relief valve 6 maintains a definite back pressure in the system.
$4141$CHP,Dr$