| 摘要 |
PROBLEM TO BE SOLVED: To easily and accurately elevate/lower an upper surface plate and stop the upper surface plate at a fixed location by a small elevating/lowering mechanism, even if the gross weight is large, by normally energizing a surface plate supporting frame supporting the upper surface plate upward by air cylinders for receiving load. SOLUTION: A surface plate supporting frame 5 supports on a base member 12 which is freely rotatably mounted at one end of a machine body 1 by a bearing 11 so that the frame 5 may freely elevate/lower by an elevating/lowering mechanism 10. The elevating/lowering mechanism 10 is provided with a plurality of air cylinders 15 for receiving load which normally energize the surface plate supporting frame 5 upward and partially support a part of load of an upper surface plate assembly 3A including the surface plate supporting frame 5 and the upper surface plate. The plurality of air cylinders 15 normally support about 1/3 to 2/3 of load of the upper surface plate assembly 3A, for instance, and the remaining load is supported by a servo motor 16. As a result, the elevating/lowering mechanism 10 can be miniaturized, and the elevating/lowering and stopping at a fixed location of the upper plate assembly 3A can be easily and accurately performed. |
