US Patent 7882815 Hydraulic cam follower

A hydraulic cam follower for simultaneous actuation of several equal-acting gas-exchange valves, especially for a tappet pushrod valve train of an engine, includes an outer part, whose base forms a cam contacting surface, and from whose head hollow-cylindrical guides extend in the same number as the valves in a direction towards the base. A housing of a hydraulic play compensation element is provided in each guide and sits with its bottom side on an inside of the bottom of the outer part. A concentric pressure piston is guided in a borehole starting from a head end of each housing so it can move axially. A non-return valve is located at a bottom-side base of the piston and a high-pressure space is formed axially between the base and the bottom side of the housing. A reservoir for hydraulic medium is formed between the base and a head end of the piston.