| 摘要 |
PROBLEM TO BE SOLVED: To apply a mechanical feedback control and to return a spool valve to a neutral position when a machine or the like is stopped, in a cylinder with an electric servo. SOLUTION: The spool valve 4 is provided at the bottom 14 of a hydraulic cylinder 11. A nut 6 of a ball screw is placed on a cylinder rod 7 of the hydraulic cylinder 11. A neutral spring is provided to feed back a cylinder stroke by rotating it, through a rod 5 of the ball screw to the spool valve of the bottom 14, and to return the spool valve to the neutral position. In the mechanism of the cylinder in which the spool valve is moved and the cylinder stroke is feed back, the cylinder has a structure in which the spool valve is returned to the neutral position only by spring force of the neutral spring.
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