Patent GB-207163-A (GB)
Title: Improvements in automatic brake applying mechanism for trailer vehicles
IPC: B60T7/20
Filed: 1923-10-16
Abstract: 207,163. Clark, J. H. Nov. 17, 1922, [Convention date]. Actuated by backward pressure of tractor or relaxation of pull; hand-actuation; compensating for wear; force-transmitting mechanism.-The brakes of a trailer vehicle are adapted to be applied by the relative longitudinal movement of the draw-bar when this vehicle tends to overrun the tractor vehicle, a spring being interposed in the brake actuating mechanism. A single manually operated member is provided for preventing the operation of the brakes as iust described and for operating them by hand. The draw-bar frame comprises a pair of bars 10 of channel section arranged to form a box-like structure at the forward ends, provided with spacing blocks 13 through which passes the sliding pull-rod 14. The rear end of the pull-rod has a nut 18 abutting against a sleeve 17 between which and the front block 13 is interposed a spring 16 through which the pull of the tractor is transmitted, the arrangement being such that the pull rod 14 may be moved freely backwards. Supported by a plate 20 secured to the bars 10 is a housing comprising a cylindrical guide 22, a chamber 24 and a guide 23. The rear end of the rod 14 abuts against a rod 32 which slides in the guide 23 and carries a head 31 between which and a head 34 on a rod 35 a spring 30 is interposed. The spring 30 and heads 31, 34 are disposed in a hollow plunger 28 sliding in the guide 22. The rod 35 is connected by a lever 36 and link 38 to an equalizing bar 40 pivoted at its ends to sectors 41 on a pair of shafts 42 carrying cams 44 for applying brake shoes 46 to drums 45 on the front wheels of the trailer. The sectors 41 are provided with a number of holes to receive the ends of the bar 40 to permit adjustment for wear of the brake shoes. A spring surrounding the link 38 and abutting against a fixed bracket 39 and the rear end of the link holds the parts normally in the position shown with the brakes released. If the trailer vehicle tends to overrun the tractor however, the rods 14 and 32 are pressed backward relatively to the trailer, the plunger 28 and rod 35 are also moved rearwardly by the pressure transmitted through the spring 30 and the brakes are applied. The spring 30 takes up excess of rearward movement of the rod 32 and prevents injury to the brake mechanism. To prevent this automatic application of the brakes and also to permit of the brakes being applied by hand, there is provided a cam member having upper and lower parts 52 pivoted at 53, 54 and formed with recesses 55 adapted to receive rollers 51 on an arm 50 secured to the plunger 28. When the lever 57 of the cam and consequently also the recesses 55 are parallel to the rods 32, 35, the rollers 51 are free to travel along the recesses and the automatic operation of the brakes is permitted. If the lever 57 is turned to the position shown in Fig. 5, the member 50 is forced to the left, the spring 30 is compressed and the brakes are applied. If the lever 57 is turned to a position transversely to the rods 32, 35 but on the other side thereof to that shown in Fig. 5 the member 50 and rod 32 are locked in position with the brakes released. The lever 57 may be locked in its several positions by turning it over about the pivot 58 on to the part 56 so as to engage a lug 59 on the lever with projections 60, 61, 62.