GB256732A - Improvements in and relating to brake systems and apparatus for railway, tramway andlike vehicles - Google Patents

Abstract

256,732. Peters & Co., Ltd., G. D., Porter, A. S., and Palmer, B. W. May 27, 1925. Fluid-pressure. - In "dead-man" valve mechanism for effecting the application of the brakes of a vehicle in the event of release of the brake valve handle by the driver, the dead-man valve is a pilot valve held in the inoperative position against fluid pressure by a lever on the driver's valve handle and controlling a relay valve which controls an emergency valve adapted to connect the main reservoir to the brake cylinder. The relay valve may also control a switch for cutting off the power current of the vehicle. Serviceapplications of the brakes by the driver may beeffected by "straight air," the "dead-man" valve device becoming operative, however, even when the handle is grasped, in the emergency position of the driver's valve. The system shown comprises a main reservoir 41 normally connected by way of the emergency valve 43 and pipes 47, 48 to the driver's valves 5 at both ends of the vehicle. Compressed air can thus be supplied to the brake cylinder 40 by the valves 5 for service applications of the brakes by way of the pipes 54, 55 the cavity 60 of the valve 43 and pipe 56. The valve 43 is maintained normally in the position shown by main reservoir pressure supplied through pipe, 44, 14 a relay valve R and a pipe 51. The relay valves each comprise a pair of poppet valves controlled by a piston 28 and adapted to connect the pipe 51 leading from the emergency valve 43 either to the main reservoir pipe 14 or to the exhaust pipe 59 either the exhaust or the supply being effected through both of the relay valves by way of the pipe 58 according as to whether operation is being effected from the left hand end of the car, as shown, or the other end. The relay valves R, R<1> are controlled by pilot valves 4 which constitute the " dead-man " valves proper. These valves each comprise a pair of poppet alves 2, 3 the stem 24, Fig. 2 of the lower one abutting on a lever 20 pivoted at 21 on a casing 4 secured to the driver's valve casing and engaged by a lever 1 pivoted at 16 to the handle 18 of this valve. At the non-operating end the valves 2, 3 will be constantly in the lower position, whereby main reservoir pressure is supplied to both sides of the piston 28 of the relay valve R' at that end so that it assumes the position shown. At the operating end when the handle 1, 18 is grasped and in all positions of the handle other than emergency, the valves 2, 3 will be raised whereby one side of the piston 28 of the relay valve connects the piston chamber of the emergency valve 43 to the main reservoir. If the driver releases his grasp on the handle 1, 18 the valves 2, 3 at the operating end drop and main reservoir pressure being thus admitted to both sides of the piston of the relay valve R it connects the piston chamber of the emergency valve 43 to exhaust by the pipes 14, relay valve R<1> and pipes 59. The valve 43 then cuts off the supply pipe 47 leading to the driver's valves 5 and connects the reservoir 41 to the brake cylinder 40 directly by the pipe 56. In the emergency position of the driver's valve handle the lever 1 becomes disengaged from the lever 20 so that the " deadman " valve 2, 3 is operated to effect an application of the brakes as just described. The pipe 51 leading to the emergency valve 43 may also connect with the cylinder 33 of a cut-out device for the power current comprising contacts 37 normally engaging a conducting part of the piston rod but engaging a non-conducting part when the pressure in the cylinder 33 is relieved simultaneously with the emergency application of the brakes. The usual pressure gauges G connected to the brake cylinder and main reservoir are shown.