Signal valve for pressure compensated system

In a hydraulic system (10) having a tank (12), a pump (11), a supply conduit (16) connected to the pump, a control valve (14) connected to the supply conduit (16) and to a hydraulic jack (17), said control valve (14) being movable between a neutral position at which the hydraulic jack (17) is isolated from the supply conduit (16) and an operating position at which fluid from the supply conduit (16) is directed to the hydraulic jack, fluid repsonsive means (27) having a signal chamber (34) therein and being effective to control the fluid flow through the supply conduit (16) in response to the pressure level of a load pressure signal directed to the signal chamber (34), and a signal line (23) connected to the control valve and to the signal chamber (34) of the fluid responsive means for directing a load pressure signal to the signal chamber at the operating position of the control valve, the improvement comprising:

• valve means (37) repsonsive to the fluid pressure in the supply conduit (16) for directing an artificial load signal to the signal chamber (34) of the fluid responsive means (27) when the control valve (14) is at the operating position and the fluid pressure in the supply conduit (16) is below a preselected level.