Hydraulic-mechanical valve operating mechanism

A hydraulic-mechanical operating mechanism for a breathing valve of an internal combustion engine, comprising two compression springs engaging said valve in opposing directions, one in valve opening and the other in valve closing direction, said valve being movable between open and closed end positions and being provided with first and second cam areas, a first hydraulic cylinder and a first piston structure arranged so as to engage said first cam area for retaining said valve in its closed position, said first hydraulic cylinder and piston structure including first spring means biasing said first piston into engagement with said first cam area, and a second hydraulic cylinder and a second piston structure including a second spring means biasing said second piston away from said second cam area, and means for supplying fluid under pressure to said first hydraulic cylinder and piston structure for releasing said valve from its closed position and to said second hydraulic cylinder and piston structure for engaging said valve in its open position.