| 摘要 |
PURPOSE:To prevent the dispersion of the stopping accuracy of a stage being due to the change of the quantity of screw backlash by making the engaging faces of internal and external threads for driving the stage noncontact to prevent the wear of the thread being due to its direct contact. CONSTITUTION:In the case of pushing out a stage 2, an external screw 3 is right-handedly rotated by an external thread driving motor 1. In this case, a thread engaging face 5 narrows to bring the thread into mutual contact, and hence high pressure air compressed by a compressor 6 is fed to the thread engaging faces 5 through the high pressure air piping 7 of a line A at the same time when a thread rotating signal gets into CPU to enlarge a space between the thread engaging faces 5 for making the threads noncontact, and the stage 2 can be therefore moved under noncontacting condition. Thus, the change of backlash quantity caused by the wear of a stage driving thread engaging face can be prevented to keep the stopping accuracy of the stage constant. |
