Hydraulic system

Claim 1

A HYDRAULIC SYSTEM COMPRISING (A) A CONTROL MEANS FOR CONTROLLING THE MOVEMENT OF A WORK LOAD, (B) A SOURCE OF WORKING FLUID, (C) A CONTROL VALVE FOR ACTUATING SAID CONTROL MEANS, (D) SAID CONTROL VALVE INCLUDING (1) FIRST INLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR RECEIVING SAID FLUID FROM SAID SOURCE, (2) FIRST OUTLET MEANS OPERATIVELY CONNECTED TO SAID CONTROL MEANS FOR FEEDING SAID FLUID BETWEEN SAID FIRST OUTLET MEANS AND SAID CONTROL MEANS (3) SECOND OUTLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR FEEDING SAID FLUID FROM SAID CONTROL VALVE TO SAID SOURCE, AND (4) A CONTROL MEMBER MOVABLE INTO (A'') ONE POSITION EFFECTIVE TO OERATIVELY CONNECT SAID FIRST INLET MEANS TO SAID SECOND OUTLET MEANS, AND TO CLOSE SAID FIRST OUTLET MEANS, AND (B'') TWO OTHER POSITIONS EFFECTIVE TO OPERATIVELY CONNECT RESPECTIVE ONES OF TWO SIDES OF SAID CONTROL MEANS TO SAID FIRST INLET MEANS AND THE RESPECTIVE OTHER OF SAID TWO SIDES TO SAID SECOND OUTLET MEANS, (E) MEANS OPERATIVELY CONNECTED TO SAID SECOND OUTLET MEANS, FOR MAINTAINING A PREDETERMINED MINIMUM BACK PRESSURE AT SAID SECOND OUTLET MEANS, (F) ACTUATING MEANS OPERATIVELY CONNECTED TO SAID CONTROL MEMBER FOR MOVING THE LATTER INTO SAID POSITIONS, (G) A PILOT VALVE FOR CONTROLLING SAID ACTUATING MEMBER, (H) SAID PILOT VALVE INCLUDING (1) SECOND INLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR RECEIVING SAID FLUID FROM SAID SOURCE, (2) THIRD OUTLET MEANS FOR FEEDING SAID FLUID BETWEEN SAID ACTUATING MEANS AND SAID PILOT VALVE, (3) FOURTH OUTLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR FEEDING SAID FLUID FROM SAID PILOT VALVE TO SAID SOURCE, AND (4) ANOTHER CONTROL MEMBER MOVABLE INTO (A'') ONE POSITION EFFECTIVE TO CLOSE SAID SECOND INLET MEANS AND TO OPERATIVELY CONNECT SAID THIRD OUTLET MEANS TO SAID FOURTH OUTLET MEANS, AND (B'') TWO OTHER POSITIONS EFFECTIVE TO OPERATIVELIY CONNECT RESPECTIVE ONES OF TWO SIDES OF SAID ACTUATING MEANS TO BOTH SAID SECOND INLET MEANS AND SAID FOURTH OUTLET MEANS, AND TO OPERATIVELY CONNECT THE RESPECTIVE OTHER OF SAID TWO SIDES OF SAID ACTUATING MEANS TO SAID FOURTH OUTLET MEANS, AND (I) MEANS, INCLUDING SAID SECOND INLET MEANS, FOR FEEDING SAID FLUID AT A SUBSTANTIALLY CONSTANT RATE OF FLOW FROM SAID SOURCE TO SAID PILOT VALVE WHEN SAID OTHER CONTROL MEMBER IS DISPOSED IN EITHER OF SAID TWO OTHER POSITIONS THEREOF, (J) WHEREIN (1) SAID OTHER CONTROL MEMBER (A'') IS A SUBSTANTIALLY STRAIGHT ELONGATED MEMBER, AND (B'') HAS THREE LANDS AXIALLY SPACED THEREON TO AFFORD A RECESS BETWEEN EACH ADJACENT PAIR OF LANDS, (2) EACH OF SAID RECESSES IS CONNECTED TO A RESPECTIVE ONE OF SAID TWO SIDES OF SAID ACTUATING MEANS IN BOTH SAID TWO OTHER POSITIONS OF SAID OTHER CONTROL MEMBER, (3) ONE OF SAID RECESSES IS CONNECTED TO SAID FOURTH OUTLET MEANS, AND THE OTHER OF SAID RECESSES IS CONNECTED TO SAID FOURTH OUTLET MEANS AND SAID SECOND INLET MEANS WHEN SAID OTHER CONTROL MEMBER IS DISPOSED IN ONE OF SAID TWO OTHER POSITIONS THEREOF, AND (4) SAID ONE RECESS IS CONNECTED TO SAID FOURTH OUTLET MEANS AND SAID SECOND INLET MEANS AND SAID OTHER RECESS IS CONNECTED TO SAID FOURTH OUTLET MEANS, WHEN SAID OTHER CONTROL MEMBER IS DISPOSED IN THE OTHER OF SAID TWO OTHER POSITIONS THEREOF, (K) SAID LANDS BEING TAPERED IN SUCH POSITION AS TO PROGRESSIVELY OPEN SAID SECOND INLET MEANS AND PROGRESSIVELY CLOSE SAID FOURTH OUTLET MEANS AS SAID OTHER CONTROL MEMBER MOVES INTO EITHER ONE OF SAID TWO OTHER POSITIONS.