Patent ID: 6238152
Filing Date: 2001-05-29
Classification: B23B,B23Q,Y10T

Abstract:
A tool clamping mechanism of the ball-chuck type, in which a draw bar is moved with respect to a main spindle in the axial direction thereof, whereby a ball chuck portion is moved to pull in or release a tool or tool holder,said draw bar having, in the outer peripheral portion thereof, a first recess in a shape such that a rolling element can submerge therein,said tool clamping mechanism comprising:a first sleeve fixed to the inner peripheral surface of the main spindle between the draw bar and the ball chuck portion, the inner peripheral surface being formed having a second recess in a shape such that the rolling element can submerge therein;a second sleeve located between the first sleeve and the draw bar for movement in the axial direction with respect to the first sleeve and the draw bar, the second sleeve being formed having a hole penetrating the second sleeve in the radial direction thereof; andthe, rolling element stored in the hole of the second sleeve, the first recess in the inner peripheral portion of the draw bar and the second recess in the inner peripheral portion of the first sleeve constituting a pulling force amplifying mechanism for amplifying a force along the axial direction of the draw bar, thereby amplifying a pulling force to be transmitted to the ball chuck portion.