Liquid fuel injection pumping apparatus

Claim 1

A liquid fuel injection pumping apparatus for supplying fuel to an internal combustion engine comprising an injection pump adapted to be driven in timed relationship with an associated engine, a fluid pressure operable member for controlling the timing of delivery of fuel to the associated engine, means for generating a fluid pressure responsive to an operating characteristic of the associated engine, conduit means through which said pressure is applied to said member, resilient means loading said member against the action of the fluid pressure, a pressure responsive piston forming an abutment for said resilient means, said piston being movable from a first to a second position when pressure is applied thereto as to vary the force exerted by said resilient means on said member, a pressure responsive valve for controlling the application of pressure to said piston, said valve comprising a valve cylinder, a valve element movable in said cylinder, a port in the wall of said valve cylinder, further conduit means for communicating the pressure at said port to said pressure responsive piston, resilient means biasing said valve element to one end of said cylinder, a pair of axially spaced grooves on said valve element, a pair of passages through which said grooves communicate with the opposite ends of the valve cylinder respectively, passage means communicating the other end of said valve cylinder with the means generating said fluid pressure so that the valve element moves in response to variations in said fluid pressure, and further passage means through which said one end of the cylinder communicates with a drain, said valve element acting depending on its position, to place said port in communication with one or the other end of said valve cylinder.