surfaces 5 and 6 and there automatically self adjusts in its horizontal position the transmission of force takes place between the surface of the support element and the two support surfaces 5 and 6 in this connection the forces act symmetrically on the cable so that they intersect at the vertical axis of symmetry formed by the cable a uniform and selective transmission of force from the drive pulley to the support element is thus guaranteed fig2 shows an exemplary construction of the support element in which the support element has a polygonal shape in cross section the support element thereby has on the surface planar or flat regions 3 which extend over the entire length of the support element the support on the drive pulley is thereby improved because the drive pulley and support element co operate over a larger region however this is guaranteed only when the surface of the support element is formed parallel to the surface of the drive pulley a defined and uniform transmission of force is also made possible by the defined support surface in that case the height h is substantially equal to the width b of the support element fig3 similarly shows a support element which is polygonal in cross section and which lies on a drive pulley the support element has at the upper.