Chuck for polygonal shank ends of tools

A chuck for a polygonal shank end of a tool comprising

• a bushing for transmission of a driving force, the bushing having a cavity corresponding in shape to the polygon cross section of the shank end;
• a ball, the bushing having a window-shaped opening in which the ball is disposed to serve as pressure member acting on the shank upon insertion of the shank into the cavity;
• a spring supported by the bushing, and an actuating sleeve encircling the bushing and enclosing the window-shaped opening and being displaceable against action of the spring;
• wherein the diameter of the ball is greater than the thickness of a wall of the bushing;
• the actuating sleeve which presses against the ball upon activation of the sleeve;
• the window-shaped opening has a first set and a second set of support shoulders for engagement with the ball, all of said support shoulders being located at an edge of said window-shaped opening facing said cavity, the window-shaped opening communicating with the chamber at one polygonal edge thereof;
• the shank end has a recess for receiving the ball, the recess being located at a polygonal edge of the shank end, the recess having a V-shape with two triangular sidewalls, each sidewall having a vertex opposite a groove of the recess for engaging the ball;
• the ball has a diameter which is less than half of a diameter of the shaft end, and extends partially into the cavity;
• the ball lies in two-point application against the vertices of the sidewalls of the recess;
• the diameter of the ball is more than twice as great as a spacing between the vertices of the sidewalls of the recess, the groove of the recess extending in a transverse plane of the shank end;
• and
• the clamping surface of the sleeve is inclined in wedge shape manner in a direction of action of the spring, and is angled relative to a longitudinal axis of the chuck, angulation of the clamping surface being within a self-locking region.