Control system for a pump

Claim 1

THE COMBINATION OF A VARIABLE DISPLACEMENT PUMP AND A CONTROL SYSTEM THEREFOR, A COMPRISING: FLUID OPERATED CONTROL MEANS FOR VARYING THE OUTPUT OF SAID PUMP; SAID PUMP HAVING SAID OUTLET PORT; FIRST PASSAGE MEANS COMMUNICATING WITH SAID OUTLET PORT; A FLOW RESTRICTION IN SAID FIRST PASSAGE MEANS SEPARATING SAID FIRST PASSAGE MEANS INTO TWO PORTIONS; FIRST VALVE MEANS COMMUNICATED WITH BOTH PORTIONS OF SAID FIRST PASSAGE MEANS; SECOND PASSAGE MEANS COMMUNICATING SAID FIRST VALVE MEANS WITH SAID FLUID OPERATED CONTROL MEANS; SECOND VALVE MEANS LOCATED IN SAID SECOND PASSAGE MEANS AND COMMUNICATED WITH SAID FIRST PASSAGE MEANS; THIRD PASSAGE MEANS COMMUNICATING A LOW PRESSURE SOURCE TO SAID FIRST VALVE MEANS; SAID FIRST VALVE MEANS BEING SO ARRANGED AND CONSTRUCTED THAT IT COMMUNICATES WITH SAID THIRD PASSAGE MEANS WITH SAID SECOND PASSAGE MEANS IN ONE OPERATING POSITION, COMMUNICATES SAID FIRST PASSAGE MEANS WITH SAID SECOND PASSAGE MEANS IN A SECOND OPERATING POSITION, AND CUTS OFF SAID SECOND PASSAGE MEANS FROM SAID FIRST PASSAGE MEANS AND SAID THIRD PASSAGE MEANS IN A THIRD OPERATING POSITION; SAID SECOND VALVE MEANS BEING SO ARRANGED AND CONSTRUCTED THAT IT COMMUNICATES SAID FIRST VALVE MEANS WITH SAID FLUID OPERATED CONTROL MEANS IN A NORMAL POSITION AND CUTS OFF COMMUNICATION BETWEEN SAID FIRST VALVE MEANS AND SAID FLUID OPERATED CONTROL MEANS WHILE COMMUNICATING SAID FIRST PASSAGE MEANS TO SAID FLUID OPERATED CONTROL MEANS IN AN OVERRIDE POSITION, SAID FIRST VALVE MEANS BEING RESPONSIVE TO THE PRESSURE DIFFERENTIAL ACROSS SAID FLOW RESTRICTION; SAID SECOND VALVE MEANS BEING RESPONSIVE TO PRESSURE BEYOND A PREDETERMINED LIMIT IN ONE OF SAID PORTIONS OF SAID FIRST PASSAGE MEANS; WHEREBY SAID FLUID OPERATED CONTROL MEANS WILL BE CONTROLLED BY SAID FIRST VALVE MEANS WHEN THE PRESSURE IN SAID ONE PORTION OF SAID FIRST PASSAGE MEANS IS BELOW SAID PREDETERMINED LIMIT AND SAID FLUID ACTUATED CONTROL MEANS WILL BE CONTROLLED BY SAID SECOND VALVE MEANS WHEN THE PRESSURE IN SAID ONE PORTION OF SAID FIRST PASSAGE MEANS IS BEYOND SAID PREDETERMINED LIMIT.