Hydraulic circuits

Claim 1

IN A HYDRAULIC PRESSURE SYSTEM COMPRISING A DELIVERY CIRCUIT, A PRESSURE SOURCE AND A RESERVOIR, SAID SYSTEM INCLUDING A BY-PASS VALVE CONNECTED BETWEEN THE PRESSURE SOURCE AND THE RESERVOIR AND IN COMMUNICATION THEREWITH, SAID BY-PASS VALVE BEING RESPONSIVE TO PRESSURE IN THE DELIVERY CIRCUIT AND TO BIAS MEANS, A RETURN CIRCUIT, A REVERSIBLE MOTOR CONNECTED IN SERIES BETWEEN SAID DELIVERY CIRCUIT AND SAID RETURN CIRCUIT, A DISTRIBUTOR VALVE IN THE PATH OF FLOW OF FLUID FROM SAID REVERSIBLE MOTOR, A VALVE IN SAID DISTRIBUTOR VALVE HAVING A NEUTRAL POSITION IN WHICH THE PATH OF FLOW IS OBSTRUCTED AND MOVABLE SELECTIVELY TO ONE OF TWO OPERATING POSITIONS IN WHICH THE LECTIVELY TO ONE OF TWO OPERATING POSITIONS IN WHICH THE PATH OF FLOW IS UNOBSTRUCTED, ONE OPERATING POSITION OF SAID VALVE IN SAID DISTRIBUTOR VALVE BEING ON EACH SIDE OF SAID NEUTRAL POSITION THEREOF, A SUPPLEMENTARY BY-PASS MEANS TO BY-PASS MONENTARILY SAID DISTRIBUTOR VALVE IN RESPONSE TO DISPLACEMENT OF THE VALVE OF SAID DISTRIBUTOR VALVE TO A POSITION INTERMEDIATE SAID NEUTRAL POSITION AND ONE OF THE OPERATING POSITIONS WHEREBY A MOMENTARY DROP OF PRESSURE IS CAUSED IN THE DELIVERY CIRCUIT WHICH PERMITS SAID BIAS MEANS TO ACTUATE SAID FIRST-NAMED BY-PASS VALVE AND DISPLACE THE SAME TOWARDS A CLOSED POSITION.