Gripper for tools of a machine tool

A machine tool comprising:

• (a) a working spindle;
• (b) a stationary stopper element;
• (c) a tool holder magazine;
• and
• (d) transfer means for transferring tool holders between said tool holder magazine and said working spindle, said transfer means having a movable gripper for gripping said tool holders and having
• a hand with two jaws being each arranged pivotally about an axis and being each provided with two cams, respectively, for pivoting said jaws into a first operating position with said jaws closed for gripping one of said tool holders in a form-locking relationship or into a second operating position, respectively, with said jaws spread apart for introducing one of said tool holders between said jaws or for removing said tool holder therefrom, respectively,
• an axially displaceable, spring-loaded bolt being provided with four guiding surfaces extending at an angle relative to a longitudinal bolt axis, said guiding surfaces being distributed over a bolt periphery in oppositely directed pairs,
• four bolts being arranged one each between one of said guiding surfaces and one each of said cams to pivot said jaws between said first operating position with said spring released and said second operating position with said spring compressed by alternately urging a first and a second of said bolts against a first and a second of said cams on one each of said jaws by means of a first and a second of said guiding surfaces or urging a third and a fourth of said bolts against a third and a fourth of said cams on one each of said jaws by means of a third and a fourth of said guiding surfaces, and
• displacement means for displacing said movable gripper to bring said spring-loaded bolt into mechanical contact with said stationary stopper element thereby axially displacing said bolt.