Patent GB-230105-A (GB)
Title: Continuous one-chamber compressed air-brake for railway cars
IPC: B60T15/18
Filed: 1925-03-02
Abstract: 230,105. Jordan, F. Feb. 28, 1924, [Convention date]. Fluid-pressure. - The distributing-valves of an automatic compressed-air brake are arranged for control either by variations in train pipe pressure, or by electromotors, the current through which is varied to secure different braking pressures. The pressure in the train pipe, or that exerted by the electromotors, acts on the distributing-valves in conjunction with brake cylinder pressure and in opposition to auxiliary reservoir pressure in such a way that brake cylinder pressure is strictly proportional to the fall in train pipe pressure or the fall in the prassure exerted by the electromotors. The time required for filling the brake cylinders is made independent of the stroke of the piston; and manually-operated means is provided, in the case of goods trains, to vary the maximum pressure in the auxiliary reservoir, and the brake cylinder pressure corresponding to a given fall in train pipe pressure, so that all the vehicles of a train suffer the same retardation when the brakes are applied. The apparatus shown, which is suitable for goods trains, comprises an auxiliary reservoir 3, a brake cylinder 4, and a distributor 30, containing a piston 2, controlling a slide valve 1 and subject to auxiliary reservoir pressure in the chamber 31, and a piston 8 subject to brake cylinder pressure through the pipes 9, 5. A slotted link 10 mounted on a. sliding pivot 12 connects the piston rod 7 to a piston 33, subject to the pressure in the train pipe 35 through a pipe 34, or when electric control is operative, to the pressure of a rod 40 to which the torque of an electromotor 42 is transmitted by gears 41. Extending from the pivot 12 is a link 11, connected to a lever 20, pivoted at 36 and bearing at one end upon a spring 16, so that when the setting of the spring is varied by means of a spindle 21, the pivot 12 is moved to vary the lengths of the arms of the lever 10. The spring 16 bears also against the piston rod of a piston 17 controlling a slide valve 15. With the distributor in the release position shown, the auxiliary reservoir is charged from the train pipe through the pipes 37, 18, 32 past the slide valve 15 to a pressure determined by the setting of the spring 16. Auxiliary reservoir pressure is thus less than train pipe pressure, and as the arrangement is such that train pipe pressure never falls below the maximum auxiliary reservoir pressure, the latter pressure can be maintained during a brake application. In the release position, the brake cylinder exhausts through the pipe 5 and a port 6. When the brakes are applied by a reduction in train pipe pressure, the movement of the piston 33 to the left moves the slide valve 1 to the right to cut off the brake cylinder from the exhaust and open it to the auxiliary reservoir. The brake cylinder pressure then rises until the pressure on the piston 8 returns the slide valve to lap position, the areas of the pistons 2, 8, 33 being so determined that the brake cylinder pressure is proportional to the fall in train pipe pressure. The port leading from the chamber 31 to the pipe 5 is made large, and since the brake pressure rises slowly when the stroke of the brake piston is long, and rapidly when the stroke is short, the movement of the slide valve is greater in the first instance because the counter pressure of the piston 8 rises more slowly, so that the time for filling the brake cylinders throughout a train is the same. By varying the setting of the spring 16, the maximum auxiliary reservoir pressure may be varied to suit the weight of the vehicle, the lengths of the arms of the lever 10 being simultaneously varied, so that an increase in auxiliary reservoir pressure corresponds to an increased brake cylinder pressure for a given fall in train pipe pressure. When the piston 33 is to be controlled electrically by the rod 40, a cock 43 is turned to isolate the train pipe from the chamber 13, and a cock 44 is provided, whereby the braking-apparatus of any vehicle can be cut out of action, a further cock 45 being provided in the pipe 32 two isolate the auxiliary reservoir from the brake cylinder and connect the chamber 31 to atmosphere during shunting operations. In the application of the invention to passenger trains, where the weight of each vehicle is substantially constant, the levers 10, 20 and the piston 33 may be dispensed with, train pipe pressure then being arranged to act between the pistons 2, 8, the rod 40 on the outer side of the piston 8, and the spring 16 being adjusted by a set screw.