Switchable Tappet

A tappet cam follower having grooves on its head, cooperates with high lift and low lift or no lift cams. The lash adjustment is either mechanical or hydraulic.
At a mode of operation the grooves are at a direction providing space to the high lift cams to rotate without displacing the tappet which, in this mode, is actuated by the low lift or the no lift cams.
At another mode of operation the grooves are at a direction that cancels the disengagement of the high lift cams which, in this mode, actuate the tappet.
Despite the discontinuity of the head  tappet surface, due to the grooves, there is smooth and continuous touch between the camshaft and the tappet at all modes.
The tappet is simple, short, light and space effective: no oil passages, no locking pins, no additional springs, no idle parts.
The pure mechanical control is adequate, the hydraulic control is just an option. The task of the control is just to rotate and keep the tappet at specific angles.
More than two modes of operation are possible.
Applicable on overhead cam and side cam engines.
Easy to install as retrofit on existing engines.

Switchable
Roller Finger Follower (RFF)

A "single piece" RFF cooperates with high lift cam and low lift or no lift cams.
The lash adjustment is either mechanical or hydraulic.
At a first position of an external control member, the camming action from the high lift cam is transferred, via a roller, to the RFF providing a high valve lift profile. At a second position of the external control member the high lift cam is disengaged from the RFF which is actuated by the low lift (or the no lift) cams to provide a low valve lift profile (or valve deactivation).
The RFF is strong, simple, light and space effective: no oil passages, no locking pins carried by the RFF, no additional springs, no idle parts.
The cylinder head remains untouched.
The transition from mode to mode involves no impact: it could last a few cycles, if desirable.
More than two modes of operation are possible.
Easy to install as retrofit on existing engines.