by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column with a liquid chamber between a piston actuated by a cam and a piston acting on a valve stem
by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column with a liquid chamber between a piston actuated by a cam and a piston acting on a valve stem