Patent ID: 7451938

Claim:
A fuel injector comprising: a nozzle body forming a blind bore with a valve seating at a blind end of the blind bore: a valve member that is moveable within the blind bore and that is engageable with the valve seating to control fuel delivery from the injector, the valve member being provided with an annular recess; an amplifier arrangement having a piston member and a control chamber, the amplifier arrangement being hydraulically coupled to the valve member via the piston member and the control chamber, the piston member having a piston bore in which a further recess is provided; an actuator arrangement coupled to the piston member; and a mechanical coupler that is disposed between the piston member and the valve member, the mechanical coupler comprising C-shaped spring that is received within the annular recess and that is arranged to cooperate with the further recess so as to mechanically couple the piston member to the valve member during an initial retraction of the actuator arrangement and to mechanically de-couple the piston member from the valve member after completion of the initial retraction of the actuator; whereby the actuator arrangement applies an initial retracting force to the piston member during the initial retraction of the actuator arrangement while the valve member is mechanically coupled to, and, thus, constrained to move with, the piston member away from the valve seating; and whereby the actuator arrangement subsequently applies a second retracting force to the piston member, while the valve member and the piston member are mechanically decoupled from, and may thus move relative to, one another.