PURPOSE: To obviate the necessity of the mounting/demounting work by using a hydraulic hose and improve the working efficiency by constituting a closed circuit between a chuck cylinder and a revolution side cylinder, and installing a check valve, relief valve, and an auxiliary tank, in order to maintain the oil pressure balance in the closed circuit.
CONSTITUTION: When a fixed side cylinder 3 is extended, the rod of a revolution side cylinder 2 extends through a bearing, and the oil on the rod side flows into the rod side of a chuck cylinder 1, passing through the pipes (a) and (b). When the fixed side cylinder 3 is extended, in order to produce the cylinder internal pressure, the revolution side cylinder 2 extends, and the oil in the rod side is compressed, and an internal pressure is produced, and a chuck force is allowed to act on the casing tube by the internal pressure. When the fixed side cylinder 3 contracts, the revolution side cylinder 2 contracts through a bearing, and the oil on the head side of the revolution side cylinder 2 flows into the head side of the chuck cylinder 1, passing through a pipe (c). When the chuck cylinder 1 operates and a band is separated from the casing tube, the chuck is opened.