Protruding from the movable support element (7), the main portion 16 of the edge portions (9), the support element (7) fixed with a contact surface (12) with at least one mandrel (13) having a main portion (16) generated by the pin head (8) and is pin connected to the head 8 of the contact surface 12 of the pin has a peak (14), it is arranged in a movable enemy within the recess 16 a pressure spring 21 which is in contact with the axial elasticity that is exerted pin, and the pin and the support element (7) comprises at least one centering device 18, and the central magazine (18) has at least one elastically deformable ring (19) between the includes, and ring 19, while proceeds to the having an outside diameter of the pin head (8), recess (16) in a side pressure spring 21 from the pin head (8) direction and located in a recess 16 At the same time located at a convex surface (23) portion formed by reducing the diameter of the pin is located between the pressure spring 21 and the pin head (8), Is arranged to be movable in the unit, it forms a in a direction away from the pressure spring (21) ring (19) concave surface (22) it loses the thickness of the wall, the recessed surface 22 has a convex surface 23 the contact surface in the complementary relationship.