To control a pressing force by adjusting the opening of a valve by the deviation of the rotation angle through a process of applying pressing force to an object through a rod of a piston.
A three-way valve 26 can take three states of forward side opening (CW opening), backward side opening (CCW opening), and closing (neutral) by the deviation of rotation angle of a sleeve 5 facing a spool 4. A head side 24 is communicated with an oil supplying line 25 in CW opening, and operating oil is allowed to flow from a rod side 23 to the head side 24. A piston 22 is moved to the rod side 23, and a piston rod 6 is moved left. The head side 24 is communicated with a discharging line 27 in CCW opening, operating oil is supplied from the oil supplying line 25 to the rod side 23 and also discharged from the head side 24 to the discharaing line 27. Therefore, a piston 22 is moved to the head side 24, and the piston rod 6 is moved right. In neutral, the piston 22 is not moved. Accordingly, a pressing force can be controlled by adjustment of the opening of the valve.
ITAGAKI TOSHIHIRO
MURAKAMI SHIRO
