Patent GB-724844-A (GB)
Title: Improvements relating to railway car speed determining and control apparatus
IPC: B61L17/02
Filed: 1953-04-21
Abstract: 724,844. Brake control systems. WESTINGHOUSE AIR BRAKE CO. April 21, 1953 [April 23, 1952], No. 10885/53. Class 103 (1). The invention relates to speed determining and control apparatus for car retarders used particularly in railway hump shunting yards, and is similar to that described in Specification 576,132. The control gear is adapted to be used with brake rail operating mechanism of the kind shown in part 1b of the drawings. In this mechanism, the brake rails are adapted to be applied by fluid pressure from a source at approximately 100 lbs. per square inch acting in cylinder 10 upon an actuating piston 12. Pressure is admitted to, or exhausted from, the cylinder 10 according to the operation of valves 13 and 18 controlled by magnets R and X. Pressure responsive devices 1P, 2P and 3P, operate to de-energize the magnet R to maintain the pressure in cylinder 10 within the ranges 25-35, 50-60, and 75-85 lbs. per square inch. In Figure 1a, the car retarder is represented diagrammatically by the part CR. The track la within the retarder is made electrically continuous while the track 1b is formed of a series of short insulated sections 1s to 11s of substantially the same length. As a wheel and axle unit runs through the car retarder unit direct current from a battery TB1 causes energization of the respective track relays IT to 10T as a result of the wheels providing an electrical connection between the rail 1a and the appropriate section of rail 1b, the last relay 11T being however energized by a battery TB2. The track relays by operation of series of front and back contacts 35-44 and 54-63 respectively energize holding circuits which control time measuring means by which the speed at which a pair of wheels moves through an individual track section is determined. The time measuring means comprise an alternating current cycle repeater CP, a unit cycle counter VC and a multiple cyclometer MS. These units are similar to those described in Specification 576,132. The alternating current is preferably 60 cycle commercial supply at the terminals BX and NX. The cycle repeater supplies current impulses to a chain of six relays (of which only one 4U is shown) in the unit cycle counter. These, in combination with six counting relays (of which only one 6M is shown) in the multiple cycled counter MC, measure the time occupied by a wheel in passing through any track section. The cycle repeater unit is controlled by relays 1SU and 2SU which are operated alternately as the consecutive tract sections 1S to 11S are occupied. To prevent a false measurement of speed through the retarder as a result of one pair of wheels being part of the way through before the first pair has left the section 11S even and odd cancellation relays EC and OC are provided which cancel the first speed measurement after occupancy of the leaving track circuit. They also function to hold the retarder in its non- braking or open position for stalled or very slow cars. A normal reset relay, NR and emergency reset relay ER operate to reset the track relays IT to 11T when the leading pair of car wheels has .passed the last section 11S. To provide automatic control which so adjusts the pressure on the brake bars to cause a vehicle to leave the retarder at any of a number of selective speeds, the time measuring means is linked to the retarder pressure control unit PV through a speed-pressure selective control unit SP having a series of push buttons 1PB ... 6PB corresponding to different leaving speeds such as 4, 5, 6 ... 9 miles per hour. This unit is the subject of Specification 724,845. Each push button PB operates a corresponding repeater relay in the series 1PR to 6PR which through relays 1PPR, 1SPR, 2PPR and 2SPR, control circuits including the terminals 133-141 wherebythe pressure responsive devices 1P, 2P and 3P are made effective to cause pressure to be applied to the brake bars to cause the car to leave the retarder at the required speed.