| 摘要 |
A spindle device providing a hydraulic system for moving a drawbar in a tool holding direction. The drawbar extends through a spindle shaft and is slidably provided therein. A piston is fixedly connected to the drawbar, and a pressure chamber is defined by the spindle shaft, the drawbar and the piston. Upon application of hydraulic pressure in the pressure chamber, the piston as well as the draw bar are moved in the tool holding direction. In one embodiment, at least one free piston is provided in the pressure chamber for dividing the same into first and second pressure chambers. The hydraulic pressure is applied to the first chamber to urge the free piston toward the second pressure chamber in which a liquid is hermetically accumulated. The liquid pressure within the second pressure chamber is increasable higher than the hydraulic pressure for urging the piston toward the tool holding direction with an increased force.
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