US Patent 7493935 Cylinder device for screw core removal

In a cylinder device of the present invention, based on a screwing relationship between a screw rod 30 and a ball screw mechanism 35 and through oil supply port control, the piston and sleeve 15 is made to advance or retract while being rotated. A rear end side of a rod 12 is fitted into a sleeve portion 34 of the piston and sleeve 15. Then, a fitting and coupling mechanism that uses an engagement key 41 and a key groove 42 causes only a rotation torque of the piston and sleeve 15 to act on the rod 12. The rod 12 with a screw core 22 coupled thereto operates at a pitch defined by a screwing relationship between the rod 12 and a rod cover 13. The pitch defined by the screwing relationship is the same as a pitch of the screw core 22.