Fuel injection pumping apparatus

Claim 1

A fuel injection pumping apparatus comprising in combination a displacement piston located within a cylinder, an outlet from one end of the cylinder, a fluid pressure operable member mounted within a further cylinder for actuating said piston and causing fuel to be delivered through said outlet, means operable upon movement of the piston to a predetermined position in said cylinder during delivery of fuel through said outlet by the piston, to terminate flow of fuel through the outlet and valve means operable to place an end of said further cylinder in communication with a source of fluid under pressure to effect movement of the displacement piston in a direction to deliver fuel through said outlet, or with a drain to permit return motion of the piston, an adjustable orifice disposed intermediate said valve means and said one end of said further cylinder, said adjustable orifice acting to control at least the initial flow of fluid to said one end of said further cylinder thereby to control the rate of fuel supply through said outlet, and a non-return valve disposed in parallel with said orifice, said non-return valve being arranged to permit substantially unrestricted flow of liquid out of said end of the further cylinder, and in which said adjustable orifice is defined by a port formed in the wall of an additional cylinder, said port communicating with said one end of said further cylinder, an inlet to one end of said additional cylinder, and through which liquid can flow to said further cylinder by way of the port when said valve means is operated to cause delivery of fuel, a piston in said additional cylinder said piston being subjected at one end to the pressure of liquid at the inlet of the additional cylinder, said piston determining the effective size of said port and means for limiting the rate of movement of the piston in the direction to increase the effective size of said port.