Fuel pumping apparatus

Claim 1

A fuel pumping apparatus for supplying fuel under pressure to a fuel injection nozzle of an internal combustion engine comprising a plunger reciprocable within a bore, a piston connected to the plunger and of larger diameter than the plunger, valve means operable to apply a fluid under pressure to one surface of the piston to effect movement of the piston and the plunger thereby to cause fuel contained within the bore to be delivered to the injection nozzle, and electrically controlled actuating means for the valve means characterised in that the piston is constructed as a double acting piston and the valve means is movable from an intermediate position in which the supply of fluid under pressure to the opposite ends of the cylinder containing the piston is prevented, towards one or other operating positions in which fluid under pressure is supplied to one end of the cylinder and allowed to escape from the other end of the cylinder and vice versa, the apparatus further comprising resilient means acting between the piston and an output member of the actuating means, the arrangement being such that the extent of the return movement of the piston and plunger following delivery of fuel, is determined by the force generated by the actuating means and which is at least in part, opposed by the force exerted by the resilient means.