Apparatus and method for valve control

A method for controlling a valve, the method comprising the following steps:

• providing an apparatus comprising
• a housing comprising a hydraulic chamber, the hydraulic chamber being disposed between a first bore and a second bore so that the first bore and the second bore discharge into the hydraulic chamber,
• the first bore at least partially accommodating a primary drive, the primary drive being axially displaceable within the first bore, the primary drive comprising a piston bore disposed therein, the second bore at least partially accommodating a secondary-side lifter element that extends through the hydraulic chamber and at least partially extends into the piston bore, the lifter element being axially displaceable within the second bore, hydraulic chamber and piston bore,
• the lifter element and the piston bore defining a piston chamber within the piston bore,
• the housing further comprising a piston conduit in communication with the piston chamber, the piston chamber being in communication with the hydraulic chamber,
• the second bore being connected to a connecting conduit with a distal end of the lifter element disposed therebetween, the second bore also being connected to a discharge conduit;
• during at least a portion of the operation of the valve, maintaining the valve in a quiescent position wherein the primary drive is displaced away from the hydraulic chamber, the lifter element is displaced away from the piston bore and into the second bore and the distal end of the lifter element isolates the connecting conduit from the discharge conduit;
• during at least a portion of the operation of the valve, moving the lifter element into the piston bore by reducing the volume of the hydraulic chamber with the primary drive so that the pressure the hydraulic chamber is increased resulting in the lifter element being moved into the piston bore and the distal end of the lifter element away from the connecting conduit thereby establishing communication between the connecting conduit and the discharge conduit thereby reducing pressure in the connecting conduit;
• returning the valve to the quiescent position by pushing the primary drive away from the hydraulic chamber so that the pressure therein decreases and resulting in movement of the lifter element away from the piston bore to the distal end of the lifter element engages the connecting conduit and isolates the connecting conduit from the discharge conduit;
• leaking fluid between the piston chamber and the hydraulic chamber;
• replenishing fluid leaked from the piston chamber with fluid supplied from the piston conduit.