elements 7 8 9 are essentially arranged so that they are parallel and vertical to the insertion direction 17 in which direction part 3 can be inserted into part 2 the contact elements 7 8 9 are formed so that they are essentially claw or latch shaped and on their inner surface that radially faces inwards to the longitudinal bore hole 20 present a concave curvature which essentially corresponds to a corresponding curvature of the snap ring groove 49 furthermore the contact elements 7 8 9 run wedge shaped in the direction radially inward whereby this wedge shape is essentially complementary to the shape of the snap ring groove 49 see fig1 in level 14 the contact elements 7 8 9 adjustably run on bearings in levels 14 15 and 16 between their contact position 11 and their withdrawal position 10 in different supporting rings 25 26 27 at the same time the contact elements are force and in particular spring pressurized in the direction of the withdrawal position 10 because of this pressurization the contact elements 7 8 9 make contact on the usually rotatable locating elements 29 with an inner surface of the ring 24 see fig2 of the cam rings 22 whereby the corresponding sliding cams 23 or the.