Kitagawa Energy Saving Cylinder - How it works 

The open-centre cylinder achieves its massive, 24-fold efficiency advantage by allowing the electrically driven pump to cut the hydraulic oil supply once the chuck is clamped. Clamping pressure is maintained using a internal locking mechanism which is only released during the chuck unclamp process. This is in contrast to conventional cylinders, which deliver the hydraulic supply constantly to maintain holding force.