Fuel injector pump with hydraulically controlled injection valve

Claim 1

IN A UNIT FUEL INJECTOR-PUMP, A RELATIVELY LOW PRESSURE FUEL SUPPLY CONNECTION, A PUMPING CYLINDER, A PUMP PLUNGER RECIPROCABLE IN THE CYLINDER, SAID CYLINDER HAVING TWO SIDE PORTS EACH SEQUENTIALLY CLOSABLE AND OPENABLE BY THE PLUNGER DURING ITS PUMPING STROKE AND AN OPENING FOR FUEL DISPLACEABLE BY THE PLUNGER DURING THE PORTION OF SAID STROKE WHEN BOTH SAID PORTS ARE CLOSED, A FUEL DELIVERY PASSAGE CONNECTED TO SAID OPENING AND TERMINATING WITH AN OUTLET, AN INJECTION VALUE NORMALLY CLOSING SAID OUTLET BUT MOVABLE TO OPEN THE SAME IN RESPONSE TO A PREDETERMINED RELATIVELY HIGH FUEL PRESSURE DEVELOPED IN THE CYLINDER BY THE PLUNGER DURING SAID PORTION OF ITS PUMPING STROKE, A CHAMBER SEPARATE FROM SAID PASSAGE, SAID VALVE BEING EXPOSED TO PRESSURE IN SAID CHAMBER ACTING THEREON IN THE DIRECTION TOWARD CLOSURE OF SAID OUTLET, SAID PLUNGER HAVING BYPASS MEANS CONNECTED TO SAID OPENING AND CONNECTABLE TO SAID PORTS IN RESPONSE TO OPENING OF SAID PORTS BY THE PLUNGER, ONE OF SAID PORTS BEING CONNECTED TO SAID SUPPLY CONNECTION FOR VENTING SAID RELATIVELY HIGH FUEL PRESSURE DEVELOPED IN THE CYLINDER TO THE SUPPLY CONNECTION IN RESPONSE TO CONNECTING SAID BYPASS MEANS TO SAID ONE PORT, THE OTHER OF SAID PORTS BEING CONNECTED TO SAID CHAMBER FOR APPLYING SAID RELATIVELY HIGH FUEL PRESSURE THERETO FROM THE CYLINDER TO BIAS THE VALVE CLOSED IN ADVANCE OF SAID VENTING OF THE CYLINDER TO THE SUPPLY CONNECTION, SAID CHAMBER BEING IN DIRECT FLUID COMMUNICATION SOLEY WITH SAID OTHER PORT.