Sur la distribution des longueurs des geodesiques fermees d''''une surface compacte a bord totalemen

A variable control mechanism for regulating the opening of an engine valve during each cycle of operation is disclosed. The control mechanism essentially includes hydraulic restraint means which control the relationship between camshaft movement and valve opening in an operating train wherein rotary motion of the camshaft is translated into linear movement of the valve. One form of the invention includes a pivotable rocker arm, one end of which is operatively connected to the cam shaft by a cam follower and push rod and the other end of which is operatively connected to the valve. Effective movement of the rocker arm to actuate the valve is controlled by a hydraulic system, including a movable sleeve the operation of which is controlled by varying hydraulic pressures so that by increasing or decreasing the hydraulic pressure the opening of the cylinder valve can be controlled. Another form of the invention eliminates the rocker arm and controls opening of the valve by hydraulically varying the timing between camshaft movement and the transfer of hydraulic pressure to the valve.