Patent GB-855466-A (GB)
Title: Improvements relating to compressed fluid braking apparatus
IPC: B60T15/30
Filed: 1959-02-26
Abstract: 855,466. Fluid-pressure brakes. WESTING- HOUSE AIR BRAKE CO. Feb. 26, 1959 [Feb: 28, 1958], No. 6690/59. Class 103 (1). In a compressed fluid braking system, a valve device controlled by brake pipe pressure acting in opposition to auxiliary reservoir pressure, supplies pressure from the reservoir to the brake cylinders on reduction of brake pipe pressure, until when the auxiliary reservoir pressure is reduced to the brake pipe pressure, a lap position is assumed in which fluid is trapped in the brake cylinders and a communication is established between the brake pipe and the auxiliary reservoir to maintain the reservoir pressure against leakage. The device 2 includes a quick-service valve 11 having a diaphragm 55 subjected to spring 56 and atmosphere in chamber 57 and brake cylinder pressure in chamber 58, and carrying a follower 63 controlling valve 64; a release ensuring valve 12; and a diaphragm 13 subjected to brake pipe pressure in chamber 15 and auxiliary reservoir pressure in chamber 19, and carrying in a follower 21 an auxiliary valve slide 26 and between shoulders 24, 25 a main valve slide 23 with a lost-motion connection. Initially, reservoir 5 is charged from brake pipe 4 via passages &c. 18, 35-38, 19 and 20. Air from chamber 19 also passes to emergency reservoir 6 via restricted port 39, port 40 and passage 41. The brake cylinder 7 is vented to atmosphere via passages &c. 42-49, 50, 51 and 8. On braking, brake pipe pressure is reduced and when the auxiliary reservoir pressure exceeds it by 0.5 p.s.i., the diaphragm 13 rises to move auxiliary slide 26 relative to slide 23 to lap ports 37 and 40 to cut off reservoir 5 from brake pipe and emergency reservoir 6, a plunger 32 carried by follower 21 abutting the main slide 23. On further reduction, of about 0.5 p.s.i., the diaphragm 13 rises to move auxiliary slide 26 further relative to slide 23, the plunger 32 compressing spring 30, until shoulders 25, 74 abut, the lost-motion having been taken up and a passage 75 in slide 26 connects ports 76, 77 to permit flow of air from brake pipe 4 via passages &c. 16, 76, 75, 77, 78 to quick-service volume 79, open to atmosphere via choke 80, to create a reduction wave in pipe 4. The pressure in volume 79 and pipe 4 reduces via choke 80, until pressure in chamber 15 is such that diaphragm 13 rises with slides 23 and 26 to the brake applied position in which follower 14 abuts the wall of chamber 15. Port 76 is disconnected from passage 16 to terminate quick-service venting; compressed-air flows from reservoir 5 to brake cylinder 7 via passages &c. 20, 19, 81, 48, 47, 46, 45, 44, 43 and 42. The air also passes from brake pipe 4 to brake cylinder 7, via 16, 82, 83, 84, 85, 86, 44, 43 and 42, to augment braking as well as further reduce the brake pipe pressure. Some air from passage 48 flows via choke 61 and passages &c. 61, 60, 64, 87, 44 to the brake cylinders at a rapid rate to take up slack in the brake rigging, until brake pipe pressure in chamber 58 exceeds 10 p.s.i., when stem 63 is moved up to disconnect passages 85, 84 and close valve 64. Lap position.-When auxiliary reservoir pressure in chamber 19 drops just below brake pipe pressure, diaphragm 13 moves follower 21 to a lap position in which shoulder 24 engages the main slide 23, Fig. 2. The air supply to cylinders 7 being stopped by blocking port 75, and the auxiliary reservoir pressure being maintained against leakage, from brake pipe 4 via passages &c. 18, 36, 53, 54, 40, 39 and 20. Brake release.-Increase in pressure in brake pipe and chamber 15 moves slides 23, 26 to the release position, Fig. 1. In the braking and lap positions, a port 88 connects passage 73 to passage 78 and volume 79, so that should the slide 23 stick, then when brake pipe pressure exceeds auxiliary reservoir pressure by 1.5 p.s.i. the brake pipe pressure in chamber 66 of valve 12 moves abutment 65 to connect chamber 68 to passage 73 and volume 79 to sharply reduce auxiliary reservoir pressure, to move slide 23 and diaphragm 13. In a modification in Fig. 3, not shown, the port 53 of slide 23 is connected to port 37 via a restriction instead of to port 40.