Patent GB-1016001-A (GB)
Title: Improvements in apparatus for controlling the velocity of wheeled vehicles
Inventor: BICK DAVID EWART
IPC: B61K7/00
Filed: 1961-03-06
Abstract: 1,016,001. Track brakes. DOWTY MINING EQUIPMENT Ltd. March 7, 1962 [March 6, 1961], No. 8109/61. Heading B8E. [Also in Division F2] Speed control apparatus for free-running railway vehicles comprises a cylinder arranged for mounting adjacent a track rail, a piston 13 mounted in the cylinder to enclose a variable volume chamber 29, a reciprocable head 14 connected to the piston and mounted for engagement by the periphery of a vehicle wheel and a valve in the cylinder including high and low pressure ports 21, 22 arranged for connection to external high and low pressure liquid sources and a valve element 23 which is axially movable to connect the chamber 29 with either port 21 or 22. The piston 13 is provided with a downwardly extending tapered needle 33 which co-operates with the opening 28 in the valve element 23 to provide a restricted orifice. The tapered needle 33 is provided with a cap 34 which has a diameter larger than the opening 28 and constitutes a lost motion connection between the piston and valve element. Liquid is expelled from chamber 29 through the opening 28 and ports 25 to the low pressure port 22 on downward movement of the piston due to a vehicle moving over the head 14 at a speed less than a critical speed. Towards the end of its downstroke the piston 13 moves the valve element 23 downwards to admit high pressure liquid into chamber 31 thereby exerting an upward force on the piston 13 which is transmitted by the head 14 to the vehicle wheel after it has passed over the central position whereby the vehicle is accelerated. The valve element is returned by the cap 34 to its upper position. On downward movement of the piston due to a vehicle moving over the head 14 at a speed greater than the critical speed the pressure developed across the orifice formed between the tapered needle 33 and the opening 28 and acting over the annular area of the flange 27 of the valve element is sufficient to move the latter downwardly against the action of friction ring 35 to connect the chamber 31 to the high pressure source. Downward piston movement is thus resisted. On upward movement of the piston the pressure developed across the orifice is sufficient to move the element 23 upwards to connect the chamber 31 with the low pressure source for most of the upward piston movement. The vehicle is thus retarded. To prevent low speed vehicles which are travelling backwards over the apparatus from being accelerated a supplementary valve mechanism is provided. The vehicle first turns a lever 36 so that cam 38 depresses push rod 41, downward movement of which acts resiliently through spring 46 upon the spring box 43 and push rod 47 causing a central ball 51 to spread outer balls 52 apart so as to project beyond the upper edge of opening 28. Upon downward piston movement the balls 52 displace the valve element 23 downwardly at the beginning of the stroke and when the element 23 is stopped by the base plug 15 the balls 52 collapse inwardly to overcome the compression of the spring 46, the piston continuing its downward stroke. Thus the chamber 31 is connected to the high pressure source for the downward piston movement which is consequently resisted. The element 23 will not be displaced upwardly until near the end of the upward piston stroke during which the high pressure liquid acts on the piston. The net assistance given to the vehicle in its movement up the track is zero. Reference has been directed by the Comptroller to Specification 909,181.