Main spindle apparatus of machine tool

Abstract

A tool holder is detachably secured to the lower end of a main spindle by means of a clamping nut having a female screw cooperating with a male screw of the main spindle such that keys are inserted into corresponding key recesses formed in an upper end face of the tool holder. Within the main spindle, there is arranged a driving shaft movably in an axial direction. Within the tool holder, a piston member is arranged movably in the axial direction. To a lower end of the driving shaft is provided a projection having a circular recess formed in an outer surface thereof. To an upper end portion of the piston member are secured a plurality of steel balls movably in a radial direction. A lower end of the piston member is formed as an inclined surface which is engaged with a cam surface of a tool fitting plate arranged movably in the radial direction. When the driving shaft is moved downward, the balls are inserted into the circular recess formed in the projection of the driving shaft so that the driving shaft is coupled with the piston member. Therefore, by moving the driving shaft up and down, the piston member is also moved up and down and this movement of the piston member is converted into the radial movement of the tool fitting plate. By moving the driving shaft upward, the tool holder may be exchanged automatically.

Dependencies are inferred from the claim text.