Liquid fuel pumping apparatus

Claim 1

A liquid fuel pumping apparatus for supplying fuel to internal combustions and comprising an injection pump, a member adjustable to control the timing of injection of fuel to the engine, a fluid pressure operable piston contained within a cylinder, means connecting said piston to said member so that movement of the piston will effect adjustment of said member, an end closure for the cylinder, a coiled compression spring acting between the piston and said end closure, said spring acting to urge the piston towards one end of the cylinder, a bore formed in said piston, a servovalve slidable in said bore for controlling the fluid pressure applied to the piston at its end remote from its spring, a further spring acting on the servovalve, passage means through which a first fluid pressure can be admitted to the bore so as to act on the servovalve in opposition to its spring, the magnitude of said first fluid pressure being dependent upon the speed at which the apparatus is driven, a part slidable in the open end at the bore and which is loaded against said end closure by the action of the further spring, and further passage means for admitting a second fluid pressure to the bore so as to act on the servovalve to assist the acTion of its spring, the magnitude of said second fluid pressure being dependent upon the load applied to the engine and the part serving to prevent said second fluid pressure from acting on the piston.