Diesel fuel injector with double dump configuration

Claim 1

A fuel injector for an internal combustion engine comprising: a body having an axially extending bore; a primary pumping plunger and a secondary plunger positioned within said body for at least partial axial movement therein; a nozzle situated at an end of said bore remote from said second plunger; a timing chamber defined in said body between said primary pumping plunger and said secondary plunger; a metering chamber defined in said body between said secondary plunger and said nozzle; first passages in said injector for receiving pressurized fuel and transmitting said fuel into said timing chamber and said metering chamber; and an electromagnetic control element for controlling the timing of the discharge of fuel from the metering chamber through the nozzle and the quantity of fuel stored in said metering chamber subsequent to said discharge of fuel; fuel dump means for dumping the fuel in the timing and metering chambers as a function of the motion of the secondary plunger including fuel dumping ports located on said bore and uncovered by the motion of said secondary plunger including a timing chamber dump port and a metering chamber dump port; a spring cage, in communication with said timing chamber dump port and adapted to receive a portion of a needle valve, containing biasing means for urging said needle valve to prohibit the discharge of fuel therefrom; second passages means for communicating said spring cage to a drain including, in series, an orifice and a check valve; and third passage means for communicating said metering chamber dump port to said drain.