US Patent 7146951 Switchable cam follower

A switchable cam follower, comprising two relatively movable, e.g., telescopable, units which can be connected via a coupling which engages over a dividing face between the units such that there is a large valve stroke. It is possible to generate no valve stroke or a small valve stroke if the coupling does not engage. At least one spring, which can be loaded compressively or torsionally, acts as a lost motion spring between the units. A compression limiting device impedes movement of the lost motion spring to the blocked position. In an incorrect switching operation in which the coupled units move undesirably toward each other and in a sudden manner under the influence of a valve spring force, movement of the spring into the “blocked” position to become seated is prevented by the limiting device.