US Patent 7603767 Workpiece picking and placing method

A workpiece holding method and holding system able to shorten the workpiece attachment/detachment time, wherein pressurized air is circulated through a nozzle of an ejector unit of a chuck at all times to make the inside of a suction chamber a negative pressure before chucking a workpiece, completion of chucking is detected based on a pressure value detected by a pressure sensor after chucking the workpiece, and the workpiece is unchucked by having a valve close an exhaust port to raise the pressure inside an exhaust chamber and introducing pressurized air from the ejector unit to the suction chamber.