Patent GB-1335449-A (GB)
Title: Brake units for example for rail vehicles
IPC: B61H1/00
Filed: 1971-04-19
Abstract: 1335449 External shoe brakes; transmitting mechanism; load-regulation of brakes; components KNORR-BREMSE GmbH 19 April 1971 [4 March 1970] 23132/71 Headings F2E and F2F  A brake unit 1 comprises a brake cylinder 3 controlling a piston member 15, the piston member being coupled to the first lever arm 34 of an automatic brake linkage adjuster 35 pivoted at 38, the second lever arm 36 being coupled to one end of a longitudinally-displaceable thrust rod 37 extending transversely of axis 38 through guide means 39 fixed relative to the unit to apply a brake block 40 to a wheel 41; the angular spacing about pivot 38 of lever arms 34 and 36 is adjustable to maintain constant brake release play. As shown, the unit is fitted to a rail vehicle and has features which are a function of the load. Thus, piston 15 is a " no-load " piston and a balance beam 26 on which piston-rod 25 acts is fulcrummed on a pivot bearing 27 whose horizontal position is determined by a piston 32 subject to a pressure at 30 dependent on vehicle loading and to a return spring 31. Also, a " load " piston 10 having a rod 16 ending in a plate 18 is provided to assist piston 15. In operation, with the loading of the vehicle in the range from zero to half, compressed air is admitted at 22 to chamber 21, forcing diaphragm 14 and thus piston 15 downwards, whereby levers 34 and 36 are rotated clockwise and brake block 40 is applied to tread 41 of wheel 42. The position of pivot bearing 27 is governed by loadcontrolled pressure admitted at 33 (see below). 35 is a linkage adjuster of known type whereby lever 36 is automatically adjusted in a clockwise direction relative to lever 34 when the block-tread clearance is excessive, the original angle between levers 34, 36 may be restored for the purpose of replacing block 40. With loading of the vehicle from half to full, compressed air is admitted to both chambers 21 and 19 at 22 and 20 respectively. Plate 18 thereupon transmits to diaphragm 14 and to " no load " piston 15 the force exerted by the " load " piston 10 so the brake is applied by both pistons. If brake cylinder pressures already controlled according to load are available for admission to chambers 19 and 21, pivot bearing 27 and its appurtenances may be omitted. Lever 34 is then arranged to point the other way and rod 25 acts directly on it. For light vehicles needing only small braking forces, pivot bearing 27 &c. is retained but the " load " brake piston, cylinder &c., may be omitted, and air pressure independent of load is admitted to chamber 21. For particularly large braking force ratios between the vehicle empty and the vehicle loaded, the load-dependent pivot bearing 27 may be retained and in addition load-dependent pressure may be admitted to chamber 21. The line 33 communicating with chamber 30 is connected to a load-sensitive valve (not illustrated) to control the pressure. The loadsensitive valve admits pressure at a value which increases with vehicle loading until the pressure is a maximum at average loading. As the load increases beyond this, the load sensitive valve may interconnect the connections 20, 22 in a known manner, and reduce the pressure at 30 to the " no load " pressure. As the load increases further, the valve may increase the pressure at 30 until at maximum load it is a maximum once more.