Patent GB-931205-A (GB)
Title: Improvements in or relating to brake installations for railway trains
IPC: B60T15/18
Filed: 1961-03-16
Abstract: 931,205. Fluid-pressure brakes. KNORRBREMSE G.m.b.H. March 16, 1961 [March 26, 1960], No. 9730/61. Class 103 (1). In a brake installation for railway trains, of the type in which the driving vehicle of the train has a compressed air brake system and the trailer vehicles have a vacuum brake system, or vice versa, and wherein the brakes of each system are actuated indirectly by relay valves according to the pressure in a control pipe arranged to give maximum braking when open to atmospheric pressure, a relay valve is provided on the driving vehicle which is adapted to be actuated only when atmospheric pressure resides in one control pipe and a pressure corresponding to released brakes occurs in the other control pipe, to cause the other control pipe also to be opened to atmospheric pressure, so that when emergency braking of the trailer vehicles occurs, as when a coupling breaks, the brakes of the driving vehicle are immediately applied also. In one embodiment, Fig. 1, a driver's valve 1 controls the pressure in a vacuum control pipe 5 serving the trailer vehicles, and another driver's valve 3 controls the pressure in a line 13 controlling, via a relay valve 11, the pressure in the control pipe 17 supplying the individual relay valves 31 for the driving vehicle brake cylinder 35, line 9 being connected to a main source of compressed air, and a reservoir 33 of compressed air maintained charged in the usual way being provided for each cylinder 35. A relay valve 37 has four pistons 41, 43, 45, 47, 41 being acted on on their undersides respectively by pressure in the pipe 5, pressure in the pipe 17, pressure in a pipe 61 and pressure in the line 9. Pipe 61 is normally connected via a port 69 to chamber 67 which is open to atmosphere. A spring 49 is arranged to maintain the piston assembly of the valve 37 in its lower position shown under all conditions except that of full or emergency braking of the trailer vehicles in conjunction with released brakes on the driving vehicle, e.g. the condition caused by parting of a coupling in the pipe 5. When this condition occurs the piston assembly is raised, causing piston 47 to pass over port 69, whereupon the main source of compressed air is connected via the chamber 63 to line 61, causing operation of change-over valves 15, 21 which respectively shut off the pipe 17 from the relay valve 11 and open that line to atmosphere, causing relay valve 31 to supply full pressure from the reservoir 33 to the brake cylinder 35. The increase of pressure in line 61 operates on the underside of piston 45 to maintain valve 37 operated regardless of subsequent variations of pressure in the pipe 5 and pipe 17. The valve 37 is restored to its normal condition by operation of a pushbutton valve 51 which applies the pressure in line 9 to the space above the piston 41. A non- return valve 57 and restriction 55 cause slow return of pressure the underside of piston 43. A " dead man's handle " may be incorporated in the system, being connected via a double check valve 25 with the line 61 to the changeover valves 15, 21. In an alternative embodiment, Fig. 3, the brakes of the driving vehicle are vacuum brakes each operated by a relay valve 77 from the pipe 5, while the pipe 17 is the control pipe for the trailer vehicle brakes which are operated by compressed air. The emergency application of the driving vehicle brakes upon operation of valve 37 is effected via a changeover valve 75 which opens pipe 5 to atmosphere when pipe 61 is connected with the line 9. The valve 37 is modified in that an extra piston 71 is provided for resetting the valve 37 upon operation of the push-button valve 51, the spring 49 is omitted, and the pressures in the pipes 5 and 17 act on the upper sides of the pistons 41, 43, respectively, instead of on the undersides, so that the opening of the pipe 17 to atmosphere again results in the piston assembly moving upwards from a normally lowered position.