Lost motion actuator

A lost motion hydraulic actuator for use in a bore in the cylinder head of an internal combustion engines having a tubular housing member, a shoulder intermediate the ends of the housing dividing the housing into an upper chamber and a lower chamber, a lower piston mounted for reciprocal motion in the lower chamber and biased outward by a first bias spring from the shoulder to the piston, an upper piston mounted for reciprocal motion in the upper chamber and biased outward by means of a second bias spring, a second shoulder in the upper chamber for locating the upper piston in its normal position, at least one inlet means through the housing for receiving hydraulic fluid into the lower chamber, the actuator characterized in that

• a fluid communication way means intermediate the ends of the housing member between the walls of the bore and the outside periphery of the housing member, said communication way intersecting the inlet and controlling the flow of hydraulic fluid between the chambers,
• a communication port connecting said fluid communication way with the upper chamber, said port being opened and closed by the reciprocal motion of the upper piston, and
• an orifice disk member mounted on the first shoulder in the upper chamber and biased against the first shoulder by the second bias spring,
• said disk having a plurality of flow ring passages around the periphery of said disk for allowing flow of hydraulic fluid from the lower chamber to the upper chamber, and
• a thin orifice centrally located in said orifice disk member for controlling the flow of hydraulic fluid from the upper chamber to the lower chamber when the upper piston closes said communication port providing damping of the upper piston during the reciprocal movement of the upper piston toward its normal position.