GB1462543A - Motor vehicle trailer over-run braking mechanism - Google Patents

Abstract

1462543 Over-run brakes HAHN FAHRZEUGBAU GmbH 13 March 1975 [4 April 1974] 10441/75 Heading F2E In an over-run braking arrangement, the hand-brake lever can move the brake linkage by a greater amount than the service brake lever. As shown in Fig. 2, the latter lever 5 is actuated by draw-bar 4 on over-run, is freely pivoted on spindle 13 and engages a first stop 17 on the end connection 21 of a brake linkage 7. The hand brake lever (not shown) and two operating members 12 (one on each side of lever 5) are fixed to spindle 13 members 12 having slots 25 which can engage further stops 18 on connection 21; the stops 18 are further from spindle 13 than is stop 17. The above arrangement is used in association with a drum brake of the sort in which operation of the service brake while reversing produces no braking action but the greater force applied by the hand brake ensures braking irrespective of the direction of vehicular movement. As shown in Fig. 5 the primary and secondary shoes 26, 27 of the brake are supported on piston 40 and pivoted cam plate 32 respectively. The forces imposed on primary shoe 26 during braking of forward movement are transmitted through piston 40, spring assembly 42 and piston 41 to cam plate 38 which pivots into contact with abutment 39 so that secondary shoe 27 has a fixed support. During reversing, application of the service brake merely causes shoe 27 to pivot cam plate 32 anticlockwise and no effective braking results. Application of the handbrake however causes this rotation to continue to the point at which shoe 27 is in two point contact with the plate, as shown, and the abutment is once again fixed.