Fuel injector pump with hydraulically controlled injection valve

Claim 1

IN A UNIT FUEL INJECTOR-PUMP, A PUMP CYLINDER OPEN AT ONE END, A PLUNGER RECIPROCABLE IN SAID CYLINDER FOR DISPLACING FUEL THEREFROM VIA SAID OPEN END, A FUEL INJECTOR HAVING A VALVE BODY SECURED TO SAID END OF THE CYLINDER, SAID VALVE BODY HAVING A CAVITY FACING THE CYLINDER, A SPRING CHAMBER, A PASSAGE CONNECTING SAID CAVITY AND CHAMBER, A FUEL DELIVERY PASSAGE CONNECTED AT ONE END TO SAID CAVITY AND TERMINATING AT ITS OTHER END WITH A FUEL OUTLET, A NEEDLE VALVE NORMALLY CLOSING SAID OUTLET, A BORE SLIDABLY GUIDING SAID NEEDLE VALVE FOR MOVEMENT TOWARD AND AWAY FROM SAID OUTLET, A SPRING IN SAID CHAMBER BIASING THE NEEDLE VALVE CLOSED, SAID NEEDLE VALVE HAVING A PISTON PORTION EXPOSED TO FUEL PRESSURE IN SAID DELIVERY PASSAGE TENDING TO OPEN THE NEEDLE VALVE AND EXPOSED TO FUEL PRESSURE IN THE SPRING CHAMBER TENDING TO CLOSE THE NEEDLE VALVE, AND A CHECK VALVE MOVABLE IN SAID CAVITY BETWEEN A POSITION INTERCONNECTING SAID PASSAGES AND A POSITION INTERCONNECTING SAID CYLINDER AND SAID FUEL DELIVERY PASSAGE.