Patent GB-1158673-A (GB)
Title: Improvements in Vehicle Brake Systems
IPC: B60T13/26
Filed: 1967-01-12
Abstract: 1,158,673. Tractor/trailer braking system. ROBERT BOSCH G.m.b.H. 12 Jan., 1967 [14 Jan., 1966], No. 1711/67. Addition to 1,134,032. Heading F2F. A pneumatic two line brake system for the tractor vehicle of a lorry train whose trailer has its own reservoir and trailer brake valve, comprises a first brake circuit 11, 15 for applying the tractor vehicle brakes, a second circuit 23, 25 including a trailer brake line 25 leading to a trailer brake coupling head 30, a trailer reservoir feed line 26 leading to a trailer reservoir coupling head 37, a multi-circuit main brake valve 9 with a common actuator operating the first and second brake circuits simultaneously, an auxiliary brake valve 29 for causing application of tractor brakes by a storage spring actuator 18, 19 having a releasing cylinder therefore, and a valve assembly 20 having a stop valve 33 in the trailer brake line, a relay valve 34 controlling a line to the storage spring cylinder responsively to operation of the auxiliary brake valve and having a control element 55 provided with means 68 normally subjected at opposite sides to the pressure in the trailer brake line 25 and in the first brake circuit respectively, and an emergency brake valve 35 connecting the trailer reservoir feed line 26 to the trailer brake line 25 when the stop valve is closed, and a lever 36 interconnecting the control element of the relay valve and the actuating element of the emergency brake valve to render operation of these valves interdependent. Operation.-When the brake system is without pressure compressed air passes from reservoirs 4, 5, through line 22 to reserve air chamber 65 to raise relay valve 34, and through chamber 63, line 76, 75, 82 to trailer reservoir feed line 26. Air flows past the opened relay valve to line 21 to release the storage spring brakes and also acts in piston 64, the differential pressure due to the shoulder 57 causing the element 55 to move down when the required trailer reservoir pressure is reached and thus seat valve 61. On application of foot valve 9 pressure in line 11 actuates the tractor brakes and through line 23 and chambers 43, 41 to the trailer brake line 25 to brake the trailer. Pressure below piston 68 of the relay valve, supplied through conduit 24 from line 11, is balanced by the trailer brake line pressure reaching the top of the piston 68 by passages 84, 83, 86, 79, 70. If the hand brake 29 is operated, without foot brake actuation, air flows from line 28 to move piston 46 and its stop valve downwards, the lever 39 lifting the valve 35 to raise valve disc 77 off its seat 80. Relay valve 34 is moved downwards allowing air in line 21 to escape to atmosphere and actuates the storage spring brakes. The lowered valve 38 cuts off communication between lines 25 and 23 and air flows from line 22 (tractor reservoir) past partly open seats 80, 81 to space 83 and passage 84 to the trailer brake line 25 to brake the trailer, the valve disc 77 then engaging the seat 80 to shut off line 22 from the trailer. If feed line 22, 26 is fractured the trailer is automatically braked by the trailer brake valve. If trailer brake relay line 23 leaks then chamber 69 does not receive pressure on braking. Tractor brake pressure from line 24 acts in chamber 71 to raise, via lever 36, the rod 39 and tube 85 of the stop and emergency valves 33, 35, the latter shutting off the trailer reservoir feed line by seat 81 and connecting lines 26, 25 to apply the trailer brakes. If line 25 breaks, on application of the foot-brake pressure fails to build up in chamber 69 and air pressure in chamber 71 of valve 34 raises the element 55 together, by lever 36, with element 85 of the valve 35. Valve disc 77 then abuts seat 81, connecting the trailer feed line with the fractured line 25 and the trailer brake valve operates as before to apply the trailer brakes. The lever also raises the stop valve 33 to cut off connection between lines 23 and 25 to protect the tractor braking circuit. The throttle 78 in the emergency brake valve 35 prevents build up of pressure above piston 87.