| 摘要 |
A mechanism for effecting both coarse and fine adjustment or positioning of an element includes a fine resolution positioner comprising a longitudinally extending shaft having two threaded sections of different pitch. Threadably received on one of the threaded sections is a coarse range selector which is mounted for free rotative motion on a seat in a support plate. An adjusting member is threadably received on the other threaded section of the fine resolution positioner. Coarse adjustment or positioning is accomplished by turning the coarse range selector, resulting in longitudinal movement of either the selector or the adjusting member along the fine resolution positioner. Fine adjustment or positioning is accomplished by turning the fine resolution positioner which results in its turning in both the coarse range selector and adjusting member to effect displacement of both along the fine resolution positioner. The relative displacement between the two is a function of the difference in the pitches of the two threaded sections of the fine resolution positioner on which they are respectively received.
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