Fuel injection nozzles

Claim 1

A fuel injection nozzle for supplying fuel to an internal combustion engine, comprising a valve member slidable within a bore, a seating defined at one end of the bore, the valve member being shaped at one end for cooperation with said seating, a walled chamber into which the other end of said valve member extends, a spring abutment carried on said other end of the valve member, a coiled compression spring located in said chamber and engaging said spring abutment to bias the valve member into contact with the seating, an outlet from said one end of the bore, a step defined on the valve member, passage means extending from a nozzle inlet and through which the pressure of fuel supplied to said inlet can act on said step to lift the valve member from the seating to allow fuel flow through said outlet, a periphery of said spring abutment having a working clearance with the wall of the chamber, a port communicating with a first portion of the chamber located on one side of the spring abutment which is remote from the valve member, passage means communicating with a second portion of the chamber located on another side of the spring abutment, a cylinder, a plunger slidable in said cylinder, said port being connected to one end of the cylinder and the passage means to the other end thereof, a spring biasing the plunger to said one end of the cylinder, said plunger being subjected to the pressure difference between said portions of the chamber when the valve member is lifted from its seating and being moved against the action of its spring, said plunger forming part of an electric switch means from which a signal can be obtained indicative of lifting of the valve member from its seating, and a drain extending from said chamber.