Fuel injection pump with pneumatic damper

Claim 1

IN A FUEL INJECTION PUMP HAVING A FUEL PUMP CHAMBER, MEANS INCLUDING A FUEL RESERVOIR CHAMBER AND A PUMP CHAMBER INLET CONNECTED TO SAID RESERVOIR CHAMBER FOR INTRODUCING FUEL AT RELATIVELY LOW PRESSURE TO SAID PUMP CHAMBER, A PUMP CHAMBER OUTLET, A PLUNGER RECIPROCABLE IN SAID PUMP CHAMBER AND OPERATIVE DURING ITS PUMPING STROKE THEREIN TO SEQUENTIALLY BLOCK AND RE-ESTABLISH COMMUNICATING BETWEEN SAID INLET AND OUTLET, WHEREBY FUEL IS DISCHARGED FROM THE PUMP CHAMBER VIA SAID OUTLET WHILE SAID COMMUNICATION IS BLOCKED AND THENCE FUEL IS BYPASSED TO SAID RESERVOIR CHAMBER VIS SAID INLET WHEN SAID COMMUNICATION IS RE-ESTABLISHED, AND MEANS INCLUDING RETURN SPRING MEANS FOR RECIPROCATING SAID PLUNGER, THE IMPROVEMENT WHEREIN SAID SPRING MEANS COMPRISES A GUIDE PART AND AN AIR CYLINDER OF LARGER DIAMETER THAN SAID GUIDE PART LOCATED IN TANDEM RELATION AT ONE END OF SAID PUMP CHAMBER AND FORMING AN AIR CHAMBER COAXIAL WITH THE PLUNGER, A PISTON SLIDABLY FITTING SAID AIR CHAMBER HAVING AN AXIALLY EXTENDING GUIDE PLUNGER SLIDABLY FITTING IN SAID GUIDE PART, SAID AIR CHAMBER HAVING AN END WALL BETWEEN SAID CYLINDER AND SAID GUIDE PART FACING SAID PISTON, MEANS CONNECTING SAID GUIDE PLUNGER AND SAID PISTON TO SAID PUMP PLUNGER FOR MOVEMENT THEREWITH TOWARD AND AWAY FROM SAID END WALL DURING RECIPROCATION OF SAID PLUNGER, AND MEANS CONNECTED TO SAID AIR CHAMBER FOR INTRODUCING AIR UNDER PRESSURE TO SAID AIR CHAMBER BETWEEN SAID END WALL AND PISTON AND MEANS IN SAID GUIDE PART FOR RETAINING SAID AIR UNDER PRESSURE DEVELOPED IN SAID AIR CHAMBER BY SAID PISTON DURING THE PUMPING STROKE OF THE PLUNGER.