Patent GB-1164604-A (GB)
Title: Track-Mounted devices for Influencing the Speed of Railway Vehicles
Inventor: ESCOTT JOHN CHARLES
IPC: B61K7/00
Filed: 1966-06-15
Abstract: 1,164,604. Track propulsion systems. DOWTY MINING EQUIPMENT Ltd. 18 May, 1967 [15 June, 1966], No.26647/66. Heading B7L. [Also in Division F2] A device for exerting an accelerating or retarding force on a railway vehicle wheel, comprises two fluid-operated telescopic members 11, 24, Figs. 1 and 3, of which the member 11 is arranged to be fixed, by bolts 14, adjacent to a track rail 13 so that the member 24 is movable in a generally vertical direction, guide surfaces 17, 18 formed on the fixed member 11 parallel to the direction of movement of the movable member 24, and a head member 19 guided by the surfaces 17, 18 the head member 19 having abutting engagement with the upper end of the member 24 and being engageable by the flange 20 of a wheel rolling along the rail 13 so as to transmit the downward component of wheel force to the member 24 but to transmit the horizontal component of wheel force in a direction parallel to the rail, substantially to the surfaces 17, 18. The member 11 is an hydraulic cylinder having an upper mounting bracket 12 for the bolts 14. The bracket includes a pair of plate members 15, 16 which with the surfaces 17, 18 form a pair of rectangular-sectioned channels to receive the sides 21, 22 of an inverted U-shaped resilient head-member 19 having a base 23 to engage the top of the member 24 in the form of a hollow piston. Upward movement of the piston 24 is limited by outturned ends 26, 27 of the member 19 engaging stops 28, 29 secured by bolts 31 to the plates 15, 16. The device can operate as a speed retarder and/or speed booster by functioning in known manner by fluid-pressure, and includes a connector 32 for a low hydraulic pressure supply and a connector 33 for a high hydraulic pressure supply. In the preferred form of the invention Fig. 3, the device serves as a speed retarder only. The cylinder 11 has a bore 41 sealed at 43 from the piston 24 and has a variable volume chamber 44 from which hydraulic fluid is discharged during downward piston movement into a reservoir 45 in the piston 24 and vice versa. The reservoir 45 has a bore 46 for a separator piston 47 above which is a gas filled chamber 48 chargeable through a valve 49. The chambers 44, 45 are connected by radial holes 51 in the piston and radial holes 52 in a flow-sensitive valve 53 normally held open by a spring 54 but which closes when a predetermined pressure difference across the holes 52 is exceeded. The chamber 44 is also connected to the reservoir via holes 55 in the piston and a valve seat 56 normally closed by a valve member 57 loaded by a spring 58. A spring-loaded pilot relief valve 59 normally rests against a valve seat 61 in the valve 57 to close a flow path through a restricting orifice 62 in the lower end of the piston 24 and through the valve 57 to the reservoir. When the piston 24 is rapidly moved there is substantial fluid pressure resistance built-up, the piston being finally extended again by the pressure of the gas in the chamber 48 without exerting any substantial force on the wheel flange 20. If the piston 24 is moved slowly downwardly, its movement is then only resisted by gas pressure in the chamber 48 without exerting any substantial retarding force on the wheel flange.