Patent GB-1146837-A (GB)
Title: Wagon speed-control system
Inventor: LAMBETH DENNIS ERNEST
IPC: B61K7/00
Filed: 1965-09-16
Abstract: 1,146,837. Railway systems. DOWTY TECHNICAL DEVELOPMENTS Ltd. 5 Sept., 1966 [16 Sept., 1965], No. 39546/65. Heading B7L. [Also in Division F2] A system controlling the speeds of wagons moving along a railway track comprises hydraulic displacement devices fixed to the track to execute contraction and expansion movement as the wagon wheels move over the devices, and control valve mechanism including a speed sensing valve responsive to the flow rate of liquid discharged by a first one of the devices to act when the flow rate is less than or greater than a predetermined value to cause the devices to discharge to a low or a high pressure source respectively, a further valve acting on the completion of discharge to the low or the high pressure source to connect both devices to the high pressure or the low pressure source respectively. The system thus accelerates slow moving wagons and brakes fast moving wagons. A particular embodiment of the invention comprises a pair of hydraulic piston and cylinder devices 11, 13 and a further pair 12, 14 secured to respective rails 6, 7 so that the pistons may be depressed by the flanges of passing wheels, the spacing of devices 11, 14 from the respective devices 12, 13 being about 4 inches in the direction of wagon travel. The pairs of devices are respectively connected by conduits 15, 16 to the valve device 17 which is connected to a highpressure main 8 and a low pressure main 9 by branch pipes 18, 19, respectively. Operation. (a) By a slow wagonÀ-Liquid is first expelled from device 11 through pipe 15 and orifices 21 of the speed sensing valve 22 to the low pressure pipe 19, the pressure drop across the orifices 21 being insufficient to raise the valve 22 against spring 28. After a short interval the second device 12 begins to contract, fluid flowing through conduit 16 to move the dummy piston 23 downwards, liquid beneath this piston passing through orifice 48 in the speed sensing valve 22 to low pressure pipe 19. Near the end of the contraction stroke of device 12 piston 23 abuts sleeve valve 25 and moves it to connect the high pressure fluid in pipe 18 to the underside of piston 23 (Fig. 4, not shown), the liquid flowing through port 30 and passage 27 to pipe 15, raising and closing valve 22 and causing the device 11, which is now fully contracted, to expand under pressure in contact with the passing wheel flange thus accelerating the wagon. High fluid pressure is also transmitted to dummy piston 23 to pipe 16 to expand device 12. Near the end of the expansion of device 12 the rising piston 23 raises sleeve valve 25 to cut off the H.P. supply. (b) By a wagon travelling at a speed above a critical value.-As device 11 is more rapidly contracted the pressure drop across the orifices 21 cause the speed sensing valve 22 to rise, fluid from conduit 15 passing past non-return valve 29 to the H.P. line 18 and, at high flow rates, through orifices 42 of relief valve 31. When after a short interval device 12 begins to contract dummy piston 23 cannot descend because the passage 47 is closed by valve 22, the fluid from conduit 16 passing N.R. valve 32 and relief valve 33. When device 11 starts to expand, pressure falls in line 15, valve 22 re-opens to connect line 15 to L.P. conduit 19. Valve housing 52 of valve then lifts to allow low pressure fluid to pass to conduit 16. In this case the devices retard the wagon as they are contracted against high pressure and exert no appreciable acceleration force as they expand. The piston 23 is fitted with a friction ring 40 and a spring detent may act between the ported spigot 49 and the ported sleeve 25, the tappet 50 on the piston being formed as a spring device to result in rapid movement of the sleeve 25 when the spring force overcomes the detent.