Patent GB-567460-A (GB)
Title: Improvements in the braking system for vehicles with a short wheel base, especially railway bogies
IPC: B61H13/24
Filed: 1943-03-26
Abstract: 567,460. Regulating brake pressure. SVENSKA AKTIEBOLAGET BROMSREGULATOR, and BROWALL, B. H. March 26, 1943, No. 4957. [Class 103 (i)] In a brake system for vehicles, particularly railway vehicles, means for distributing unequally the pressure applied to the brakes on the wheels at the two ends of the vehicle are shifted from one position to another by means operated by rotation of a wheel axle whereby the pressure applied to the front wheel brakes may be greater than that applied to the rear wheel brakes irrespective of the direction of travel of the vehicle. In one arrangement, Fig. 1, brake blocks 3, 4 and 10, 11 for the axles 1, 2 of a railway bogie are applied respectively by brake cylinders 9, 16 supplied by pipes 17, 18 connected to a slide-valve 19 to which also are connected a pipe 22 leading from the pressure source and a pipe 25 connected to the pipe 22 through a reducing valve 24. The suspension link 6 of the block 4 is connected to the slide 26 of the valve 19 and has a lost-motion connection with the suspension bolt 29. When the brake is applied with the vehicle travelling towards the right the frictional drag of the brake block 4 moves the slide 26 to the position shown if it is not already in that position so that compressed air at the full pressure is supplied to the cylinder 16 whereas the supply to the cylinder 9 is at the reduced pressure determined by the valve 24. When the vehicle is travelling in the reverse direction, the slide 26 is moved to the upper position by the brake block so that air at the full pressure is supplied to cylinder 9 and at the reduced pressure to cylinder 16. In another construction, Figs. 3, 5, the brakes of the bogie are applied by a single cylinder through a pull-rod 36 and an equalizing bar 35 connected by links 38, 39 to the two sets of brake blocks associated with the respective axles. To determine which set of brake blocks receives the greater pressure, the pivot 40 by which the rod 36 is connected to the bar 35 is shiftable along the bar. For this purpose it is carried by a block 35a slidable in a slot 35b in the bar 35 and the forked end of the rod 36 engages upper and lower pins 42 projecting from a member 43 freely mounted on a nut 44 engaging a threaded spindle 45 mounted on the bar 35 and rotated by the wheel axle 2 through a flexible shaft 48 and worm-gearing 56. The nut has a projection 52 arranged to engage a projection 53 and a pair of pawls 54, 55 each of which permits rotation of the nut in one direction only, the directions being opposite. Assuming the vehicle to be travelling in one direction, the nut 44 will remain in the end position shown corresponding to such direction because the pawl 54 permits it to rotate with the screw 45. If the direction of travel of the vehicle is reversed, rotation of the nut in the corresponding direction being prevented at first by the pawl 54 and then by the projection 53 it travels along the screw until the projection 52 engages the pawl 55 which again permits it to rotate so that its axial movement ceases. To prevent undue stress in the driving mechanism of the nut should the brakes be applied before the nut has time to reach its new position after a change of direction of the vehicle a slipping friction clutch 49, 50 is disposed between the worm-wheel 47 and the spindle 45. In a further construction, Fig. 8, the pivot 40 is shifted by the piston rod 68 of a pair of hydraulic cylinders 66, 67 carried by the bar 35 connected to a pump 70 driven by the wheel axle, a reservoir 71 being also provided.