Draw tube drive mechanism, spindle unit, and machine tool

A spindle unit comprising:

• a rotation shaft configured to hold a holding target;
• a support supporting the rotation shaft rotatably about a first axis;
• a rotary driver configured to rotate the rotation shaft about the first axis;
• a draw tube movable in the first axis relative to the support;
• a driver configured to move a moving member in a moving direction substantially perpendicular to the first axis;
• a first link connected to the moving member via a first pin rotatable around the first pin;
• a third link connected to the first link via a third pin rotatable around the third pin and configured to receive a force from the moving member via the first link and to transmit the force to the draw tube;
• a second link connected to the first link via a second pin rotatable around the second pin and connected to the support via the fourth pin rotatable around the fourth pin, the second pin being provided between the first pin and the third pin;
• each of the first pin, the second pin, the third pin, and the fourth pin extending along a pin direction substantially perpendicular to both of the first axis and the moving direction;
• the first pin, the second pin, and the third pin being arranged substantially on a straight line when viewed from a direction along the pin direction;
• and
• each of a distance between the first pin and the second pin and a distance between the second pin and the third pin being substantially equal to a distance between the second pin and the fourth pin.

A machine tool comprising:

• a machining head configured to hold a tool;
• a machining head driver configured to move the machining head;
• and
• a workpiece holding device comprising:
• a rotation shaft configured to hold a workpiece;
• a support supporting the rotation shaft rotatably about a first axis;
• a rotary driver configured to rotate the rotation shaft about the first axis;
• a draw tube movable along the first axis relative to the support;
• a driver configured to move a moving member in a moving direction substantially perpendicular to the first axis;
• a first link connected to the moving member via a first pin rotatable around the first pin;
• a third link connected to the first link via a third pin rotatable around the third pin and configured to receive a force from the moving member via the first link and to transmit the force to the draw tube;
• a second link connected to the first link via a second pin rotatable around the second pin and connected to the support via the fourth pin rotatable around the fourth pin, the second pin being provided between the first pin and the third pin;
• each of the first pin, the second pin, the third pin, and the fourth pin extending along a pin direction substantially perpendicular to both of the first axis and the moving direction;
• the first pin, the second pin, and the third pin being arranged substantially on a straight line when viewed from a direction along the pin direction;
• and
• each of a distance between the first pin and the second pin and a distance between the second pin and the third pin being substantially equal to a distance between the second pin and the fourth pin.