Clamp device

A clamp device for removably mounting a tool holder with a

• tool to a spindle of a rotary spindle device, which device includes:
• a hollow spindle body constituting the spindle;
• a cylindrical clamp sleeve axially slidably disposed in an interior space of the spindle body;
• and a forward small diameter portion conformable to an outside diameter of the clamp sleeve and a forward large diameter portion diametrally expanded from the above diameter portion, the forward small diameter portion and forward large diameter portion defined in a forward bore region of the spindle body, and which is equipped with a clamp mechanism which establishes a clamp state to clamp down a pull-stud bolt connected to a tip of the tool holder by moving a distal end of the clamp sleeve in the bore region of the spindle body from the forward large diameter portion to the forward small diameter portion, and which establishes an unclamp state to release the pull-stud bolt from clamping by moving the distal end of the clamp sleeve from the forward small diameter portion to the forward large diameter portion,
• the clamp device further comprising:
• a draw-in bolt having an end connected to a rear end of the clamp sleeve opposite from the tool holder;
• a cylindrical draw-in sleeve axially slidably disposed in the interior space of the spindle body on the opposite side from the clamp sleeve;
• and
• a clamp jig slidably inserted in the draw-in sleeve from a rear end thereof and axially reciprocated in the spindle body as connected to a reciprocation drive mechanism on a side opposite from the tool holder of the spindle, wherein
• the draw-in bolt has the other end engaged with a front end of the draw-in sleeve via an elastic member,
• the draw-in sleeve includes:
• a plurality of through-holes formed on a circumference of a rear end thereof at equal angular spaces;
• and steel balls fitted in the respective through-holes as allowed to move outward from and inward of the through-holes and having a diameter greater than the thickness of the draw-in sleeve,
• the spindle body includes on a rear side of the bore region thereof opposite from the tool holder:
• a rearward small diameter portion conformable to an outside diameter of the draw-in sleeve;
• a diametrally expanding portion progressively increasing in diameter from the rearward small diameter portion toward the rear side in a tapered fashion;
• and a rearward large diameter portion constant in diameter and continuous to the diametrally expanding portion,
• the clamp jig includes:
• a jig large diameter portion conformable to an inside diameter of the draw-in sleeve;
• a jig diametrally reducing portion progressively decreasing in diameter from a rear end of the jig large diameter portion in a tapered fashion;
• and a jig small diameter portion constant in diameter and continuous to the jig diametrally reducing portion, and
• clamp jig places the clamp mechanism in the unclamp state by way of forward movement produced by the reciprocation drive mechanism in which movement the draw-in bolt, the other end of which is engaged in the draw-in sleeve, is pushed forward against a biasing force of the elastic member, thus moving forward the clamp sleeve, or
• places the clamp mechanism in the clamp state by way of rearward movement produced by the reciprocation drive mechanism in which movement the draw-in sleeve engaged with the clamp jig via the steel balls is moved rearward to bring the through-holes thereof to the rearward large diameter portion in the bore region of the spindle body and further rearward to a position where the steel balls are retained between the rearward large diameter portion and the jig large diameter portion, while the retreated draw-in sleeve moves rearward the draw-in bolt and the clamp sleeve by way of the biasing force of the elastic member.