Fuel pumping apparatus

Claim 1

A fuel pumping apparatus for supplying fuel to an internal combustion engine comprising a reciprocable plunger pump operable in use to deliver fuel in timed relationship with the associated engine, a chamber communicating with a pumping chamber of the pump, a bore opening into said chamber and a piston member slidable in the bore, an outlet through which fuel displaced from the pumping chamber can flow to the associated engine, resilient biasing means biasing the piston towards an end wall of the chamber, a recess defined between said end wall and the end of said piston when the latter is in contact with the end wall, first electrically operable means operable to place said recess in communication with said chamber thereby to allow the pressure of fuel in said chamber to drive the piston out of said chamber, a valve member having a head for co-operation with a seating defined about a bore extending from the chamber for controlling the escape of fuel from said chamber, said head being located in the chamber so that it will be pressure actuated into contact with the seating and being tapered to narrow towards the seating and being located so that pressure from said pumping chamber acts on said head to maintain said head in contact against the seating when the valve member is closed, and an electromagnetic device which when energized maintains the head of the valve member away from the seating for controlling the operation of said valve member, the arrangement being such that at the start of a delivery stroke of said pumping plunger, said piston will be in contact with said end wall and said valve member will be open, closure of said valve member will cause delivery of fuel through the outlet and later operation of said first electrically operated means will allow outward movement of the piston, the piston movement absorbing further fuel displaced by the plunger.