Patent GB-813150-A (GB)
Title: Control valve mechanism for railway vehicle air springs
IPC: F16K31/524
Filed: 1957-02-27
Abstract: 813,150. Railway vehicle undercarriages; pneumatic springs. WESTINGHOUSE AIR BRAKE CO. Feb. 27, 1957 [Feb. 27, 1956], No. 6555/57. Classes 103(6) and 108(3) In a railway vehicle having a body 24 Fig. 3, supported upon on unsprung axle 25 by means of an air spring 23, a control valve mechanism 10, 68 is provided to control the admission of air to and the release of air from the spring 23 so as to maintain the height of the body 24 above the axle at a predetermined value independent of the load on the body. As shown in Fig. 1 the mechanism 10, 68 carried by the body 24 comprises a valve element 11, waisted at 14 and slidable in a bushing 13 provided with ports 18, 19, 20 communicating with chambers 26, 21, 27 connected by conduits a, b, Fig. 3, and 28 to a compressed air reservoir R, to the spring 23 and to atmosphere, respectively. The valve 11 is connected at 29, 30 to a piston slidable in a bushing 33. Above the piston 31 is a chamber 37 filled with oil and connected through a choke (not shown) with a chamber 37 connected to atmosphere. Slidable in the piston 31 is a follower 42, 43 which engages through a rocker 76 carried on a pivotal arm, with a cam 66 having two circular cam surfaces 85, 86 of different radii connected by a short ramp 87. The follower 42, 43 is urged downwardly by a spring 73 and is provided with slidable collars 45, 46 between which acts a spring 44, the follower, collars and spring being retained in the piston by a stop ring 50. The cam 66 is rotatable by a shaft 78 interconnected through a link 82 with the axle 25. In the neutral position of the mechanism shown in Fig. 1, the ports 19 and thus the air spring 23 are sealed-off. When load is reduced on the body 24 the cam is caused to rotate anti-clockwise so that the follower 42, 43 is pushed upwardly. Since the piston is restrained by the oil dashpot the follower moves relative thereto, the spring 44 being compressed and thereafter urges the piston upwardly under control of the dashpot so that the valve 11 causes the ports 19, 20 to be connected and thus air to be released from the spring 23 to the conduit 28. Consequently the body falls and the cam rotates clockwise to the position shown, the spring 73 moving the follower downwardly whilst the piston 31 lags behind because of the partial vacuum formed in the chamber 37. Finally the piston 31 returns the valve 11 to the position shown. Similarly when the load on the body 24 increases, the cam rotates clockwise from the position shown and the follower is moved downwardly by the spring 73 with the piston following-up owing to the dashpot under the urge of the spring 44, until the valve 11 connects the ports 19, 18 to supply air to the spring. Thereafter the body rises to move the cam back to the position shown, the piston subsequently moving the valve 11 back to the position shown. A check valve 84, Fig. 3, prevents the pressure in the air spring from falling below a predetermined minimum value. The control valve mechanism may be mounted on the axle and the operating link coupled to the vehicle body.