brake elements 7 8 are now disposed in a first braking position s they are pressed against the guide rails by a pressing force determined by the compression springs 18 as illustrated in fig4 one of the two brake elements 7 8 is further pivoted through the contact between guide rail 4 and two brake elements 7 8 by means of friction couple by way of the relative movement of the guide rail 4 in the example depending on the direction of the relative movement the second brake element 8 is further pivoted in that case due to the shape of the brake elements similar to eccentrics the first brake element 7 loses contact with the guide rail 4 and it is drawn back by its spring not illustrated towards the control plate due to the shape and arrangement of the second brake element 8 and the surface 19 of the control plate 6 the control plate 6 is simultaneously moved back in direction u into the rest position e in fig5 the pivotation of the second brake element into a second braking position z is concluded whereby the second braking area 11 has been brought into contact with the guide rail 4 the brake element 8 has during the clamping in the second braking position z drawn the support 22 together with the counter braking lining 13 towards the guide rail and stressed the plate springs 14 so that a desired braking force could be built up the brake elements 7 8 are preferably provided with end abutments relative to the support 22 so that further rotation of the brake elements 7.