| 摘要 |
The present invention relates to an actuator for turning a shaft to a limited degree, e.g. the shaft of a butterfly valve or the like, the actuator comprising a housing having a cylindrical chamber inlets and outlets for a pressure fluid to the cylindrical chamber, a piston in the cylindrical chamber, which can be displaced in the cylindrical chamber by means of a pressure fluid and is provided with a rack with a toothed segment cooperating with a gear ring segment fixedly mounted on the shaft which extends right through the cylindrical chamber and through the wall of the housing The characteristic feature of the invention is that the toothed segment is disposed at the bottom of a groove in the rack that the gear ring segment has a breadth in the axial direction, which corresponds to the breadth of the groove, and that the gear ring segment is provided in the groove to mesh with the toothed segment, the shaft in this way being fixed in the axial direction in the housing
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