Pump

Claim 1

IN A CONSTANT DISPLACEMENT PUMP OPERATED AT VARYING SPEEDS, SAID PUMP COMPRISING AN INTAKE CHAMBER, A DISCHARGE CHAMBER AND INTAKE AND EXHAUST PORTS, THE COMBINATION OF MEANS PROVIDING A DISCHARGE PASSAGE HAVING A RESTRICTED POSITION CONNECTED TO SAID DISCHARGE CHAMBER, A BRANCH DISCHARGE PASSAGE OF RELATIVELY SMALL DIAMETER EXTENDING FROM SAID RESTRICTED PORTION AND OPENING TO SAID EXHAUST PORT, MEANS PROVIDING A BYPASS PASSAGE INTERCONNECTING SAID DISCHARGE PASSAGE AND SAID INTAKE CHAMBER, SAID BYPASS PASSAGE INCLUDING A RESTRICTED PORTION CONNECTING SAID INTAKE PORT TO SAID INTAKE CHAMBER, AND A VALVE IN SAID BYPASS PASSAGE UPSTREAM OF SAID SECOND-MENTIONED RESTRICTED PORTION AND DOWNSTREAM OF SAID FIRST-MENTIONED RESTRICTED PORTION RESPONSIVE TO THE PRESSURE IN SAID DISCHARGE PASSAGE, SAID VALVE BEING DISPLACED TO PLACE SAID DISCHARGE PASSAGE IN COMMUNICATION WITH SAID BYPASS PASASGE WHEN SUCH PRESSURE REACHES A PREDETERMINED VALUE DETERMINED BY THE DIAMETER OF SAID BRANCH DISCHARGE PASSAGE, SAID PUMP BEING FURTHER CHARACTERIZED IN OPERATION IN THAT FLOW OF FLUID IN SAID BYPASS PASSAGE THROUGH SAID SECOND MENTIONED RESTRICTED PORTION PAST SAID INTAKE PORT HAS A SUPERCHARGING ACTION WITH RESPECT TO SAID INTAKE CHAMBER AND IN THAT WITH SAID VALVE DISPLACED AND WITH THE PUMP OPERATING AT A PREDETERMINED SPEED HIGHER THAN ITS MINIMUM SPEED THE VELOCITY OF THE FLUID FLOWING IN SAID FIRST-MENTIONED RESTRICTED PORTION PAST SAID BRANCH DISCHARGE PASSAGE OPERATES TO LIMIT THE FLOW RATE FROM SAID EXHAUST PORT.