Fuel pumping apparatus

Claim 1

A fuel pumping apparatus for supplying fuel to an internal combustion engine comprising: a pumping plunger reciprocable within a bore; an outlet from one end of the bore for connection in use to an injection nozzle of an associated engine; an engine driven cam for imparting inward movement to the pumping plunger to effect displacement of fuel from said one end of the bore; a spill valve operable to allow fuel displaced by the pumping plunger to flow to a drain thereby to control the quantity of fuel supplied by the apparatus; a restricted flow path from said one end of the bore and cooperating valving edges formed on the pumping plunger and the wall of the bore; said restricted flow path having a passage in said plunger, a circumferential groove in the plunger, and restricted drillings through which the passage is in communication with said groove; said valving edges being defined by an end wall of said groove and by an end wall of a recess in said wall of said bore; said groove being disposed with respect to said recess such that said groove is adjacent to and in communication with said recess during an initial period of the pumping plunger stroke, and is not adjacent to and is not in communication with said recess for the remainder of the pumping plunger stroke, whereby said flow path is open during a predetermined initial portion of the pumping plunger stroke during the inward movement of the pumping plunger and is closed for the remaining portion of the stroke.