PURPOSE: To enable it to clamp a bolt or the like so efficiently by forming both first and second thread grooves installed in the same direction each on the outer circumferential surface of a piston end and the inner circumferential surface of an attachment body, and installing each of ball bodies being fitted in these thread grooves.
CONSTITUTION: When a piston 1 of a cylinder part 2 is moved forward by hydraulic pressure, a piston end 3 advances forward in the inner part of an attachment body 4. At this time, a ball screw mechanism is composed of a first thread groove 3a formed on an outer circumferential surface of the piston end 3, a second thread groove 4a formed on an inner circumferential surface of the attachment body 4 and a ball body 3b fitted in both these grooves 3a, 4a. Accordingly, a forward movement of the piston end 3 can be converted into rotation of the attachment body 4 at high transmission efficiency. With rotation of this attachment body 4, a bolt, a nut or the like are clampable.
NAGASUMI MASAO
MURAKAMI TOSHIRO
