| 摘要 |
PURPOSE:To eliminate any error of a stop position, and miniaturize the positioning device for a load by providing on a piston, a groove seal member, which is formed of a raw material having a small friction coefficient, for sealing the screw groove of a feed screw. CONSTITUTION:When a pressure medium is supplied from a pressure control valve to one of cylinder chambers 21 which are partitioned by a piston 17, the piston 17 and a table 18 on which a load is installed are moved in a prescribed direction. When the piston 17 is moved to the vicinity of a target stop position, the piston 17 and the table 18 are stopped. When a fluid pressure in a cylinder chamber 21 is reduced by the pressure control valve, acting force of a load which is applied to the table 18 is balanced with the thrust of the piston 17 by supply fluid pressure, and a feed screw 12 is rotted by an electrically driven motor 13 in this condition, the piston 17 and the table 18 are moved in the direction opposite to their moving direction, so that the load can be correctly stopped in the target stop position by the electrically driven motor 13. |
