Fuel injection nozzles

Claim 1

A fuel injection nozzle comprising a fluid pressure operable valve member slidable within a bore, a seating located at one end of the bore, the valve member being shaped for cooperation with said seating to prevent fuel flow from an inlet to an outlet, resilient means biasing the valve member into contact with the seating, a chamber, a valve means through which fuel under pressure can flow to said chamber, a surface in said chamber, the fuel pressure in said chamber acting on said surface to create a force which assists the action of said resilient means, said surface being defined upon a piston member which engages said valve member, said valve means including a bore formed in the piston member, one end of the bore being open to said chamber and the other end of the bore communicating with a drain, a valve element slidable in the bore, a spring biasing the valve element towards said one end of the bore whereby the position of the valve element within the bore will be dependent upon the pressure in said chamber, passage means defined by the piston and valve element, said passage means connecting said inlet with said chamber, the flow of fuel through said passage means into said chamber being prevented when the pressure of fuel in the chamber attains a predetermined value, and a non-return valve in said passage means, said non-return valve acting to prevent fuel flow through said passage means from the chamber.