two cylindrical sections 9 a 9 b with a larger and a smaller diameter connected to one another by a conical section 9 c the diameter of the section 9 a corresponds to the diameter of the bore 5 d of the extension piece 5 a in the position illustrated the traction cable anchor 9 with its cylindrical section 9 a blocks any inward movement of the ball 7 with the result that the clutch 6 is closed the first clutch component 4 and the second clutch component 5 are locked relative to one another in the axial direction fig4 shows the clutch 6 of fig3 when it is open i e uncoupled released so that the two clutch components 4 5 can move axially relative to one another by actuating the traction cable 10 in the direction of the arrow e see fig2 the traction cable anchor 9 is moved so that the cylindrical section 9 b with the smaller diameter is in the area of the radial bore 12 this enables the ball 7 to move radially inward and the block is released disengaged for subsequent closing i e coupling locking of the clutch 6 the two clutch components 4 5 are once more moved into the other and together whereby the ball 7 is pressed by the conical.