Power steering system and control valve therefor

Claim 1

A CONTROL VALVE COMPRISING (A) INLET AND EXHAUST PASSAGES, FIRST AND SECOND CONTROL PASSAGES, AND FIRST AND SECOND MOTOR PASSAGES; (B) METERING VALVE MEANS INCLUDING FIRST AND SECOND DELIVERY PASSAGES AND HAVING A NEUTRAL POSITION IN WHICH IT ESTABLISHED A PAIR OF UNLOADED PATHS BETWEEN THE INLET AND EXHAUST PASSAGES, EACH OF WHICH INCLUDES ONE OF SAID MOVABLE IN A FIRST DIRECTION FROM VALVE MEANS BEING MOVABLE IN A FIRST DIRECTION FROM THE NEUTRAL POSITION TO PROGRESSIVELY RESTRICT COMMUNICATION BETWEEN THE INLET PASSAGE AND THE FIRST DELIVERY PASSAGE AND BETWEEN THE SECOND DELIVERY PASSAGE AND THE EXHAUST PASSAGE, AND BEING MOVABLE IN A SECOND, OPPOSITE DIRECTION FROM THE NEUTRAL POSITION TO PROGRESSIVELY RESTRICT COMMUNICATION BETWEEN THE INLET PASSAGE AND THE SECOND DELIVERY PASSAGE AND BETWEEN THE FIRST DELIVERY PASSAGE AND THE EXHAUST PASSAGE; (C) LOCK VALVE MEANS RESPONSIVE TO MOVEMENT OF THE METERING VALVE MEANS AND SERVING TO ISOLATE EACH MOTOR PASSAGE FROM THE OTHER PASSAGES WHEN THE METERING VALVE MEANS IS IN NEUTRAL POSITION AND TO CONNECT THE FIRST AND SECOND MOTOR PASSAGES WITH THE FIRST AND SECOND DELIVERY PASSAGES, RESPECTIVELY, WHEN THE METERING VALVE MEANS MOVES AWAY FROM NEUTRAL POSITION IN EITHER DIRECTION; (D) SWITCH VALVE MEANS FOR SELECTIVELY CONNECTING THE INLET PASSAGES WITH THE FIRST AND SECOND CONTROL PASSAGES WHEN THE METERING VALVE MEANS MOVES IN SAID FIRST AND SECOND DIRECTIONS, RESPECTIVELY; (E) FIRST AND SECOND PILOT PASSAGES CONNECTING THE FIRST AND SECOND CONTROL PASSAGES, RESPECTIVELY, WITH THE FIRST AND SECOND DELIVERY PASSAGES; (F) FIRST AND SECOND VARIABLE AREA CONTROL ORFICES IN SAID FIRST AND SECOND PILOT PASSAGES, RESPECTIVELY, AND CONTROLLED BY THE POSITION OF THE METERING VALVE MEANS, THE ORIFICES BEING ARRANGED SO THAT EACH IS CLOSED WHEN THE METERING VALVE MEANS IS IN NEUTRAL POSITION, THE FIRST IS OPENED PROGRESSIVELY AS THE METERING VALVE MEANS MOVE SAID SECOND DIRECTION, AND THE SECOND IS OPENED PROGRESSIVELY AS THE METERING VALVE MEANS MOVES IN SAID FIRST DIRECTION; (G) SPRING MEANS BIASING THE METERING VALVE MEANS TO ITS NEUTRAL POSITION; AND (H) ACTUATING MEANS RESPONSIVE TO THE PRESSURES IN THE TWO CONTROL PASSAGES FOR SHIFTING THE METERING VALVE MEANS IN SAID FIRST DIRECTION AS THE PRESSURE IN THE SECOND CONTROL PASSAGE RISES ABOVE THE PRESSURE IN THE FIRST CONTROL PASSAGE, AND FOR SHIFTING THE METERING VALVE MEANS IN THE OPPOSITE DIRECTION AS THE PRESSURE IN THE FIRST CONTROL PASSAGE RISES ABOVE THE PRESSURE IN THE SECOND CONTROL PASSAGE.