Patent GB-893253-A (GB)
Title: Control system for railway car classification yard
IPC: B61L17/00
Filed: 1959-08-07
Abstract: 893,253. Hump yard railway retarder control systems. GENERAL RAILWAY SIGNAL CO. Aug. 7, 1959 [Aug. 28,1958], No. 27079/59. Class 105. A railway retarder control system ensures that the total retarding force required to reduce a vehicle speed to a desired value is applied incrementally over substantially the whole length of the retarder. A voltage analogue is established representing the permissible speed of the vehicle at each point of its travel through the retarder, and is a function of the vehicle's position in the retarder, the desired leaving speed and the characteristics of the retarder; if a voltage representing the actual vehicle speed exceeds this analogue voltage a braking pressure is applied according to the vehicle weight. The vehicles are classified by weighing means WR and WD, and directional antenna and transmitter-receivers 10, 21 obtain a beat-frequency representing the vehicle speed by the Doppler principle. The beat frequency is applied to No. 1 and No. 2 discriminators controlling speed and to anticipation relays S1, S2, A1, A2. The desired exit velocity from the group retarders is derived as a D.C. voltage by computor 12 from track characteristics, rollability, weight, vehicle length, distance to coupling and other factors, and is applied via wires 13, 15 to circuits 14, 16 of the discriminators, controlling relays S1, S2 which are released when the vehicle speed drops to the desired level. A voltage, which is a function of, but greater than, that in wire 13 is applied via potentiometer 17, 60 to circuits 19, 27 controlling relays A1, A2 which are released when the vehicle speed has been reduced to a value somewhat greater than the desired exit speed, to produce a partial release of the retarder. The beat frequency from the transmitterreceiver 21 (Fig. 1B gives details of the discriminators) is applied via cathode follower 22 to circuits 23, 24, 25. The circuit 25 picks up or releases exit relay 2EX whenever the beatfrequency amplitude is above or below, respectively, a minimum value, indicating the car is approaching or has passed the antenna. Circuit 24 also operating according to amplitude picks up relay 2CK when the weight detector is initially actuated provided the amplitude is above a minimum value and maintains relay 2CK up whilst the vehicle is in the retarder. The same applies for relays 1CK, 1EX in Fig. 1A. Negative-going pulses, produced from circuit 23 and amplifier-inverter 26 are applied to speed relay control circuits 14, 16 which compare the voltage appearing in wire 13 with the frequency of the pulses from the inverter, and for actual vehicle speeds above the release speed, a triode 35 is cut off and triode 37 is conductive to pick-up relay S2, and for actual speeds below this speed triode 35 is conductive and relay S2 is released. A capaitor 47, Fig. 1B, is charged with the voltage analogue representing the permissible speed at each point of travel in the retarder, a different voltage for different weights, and being obtained from a potentiometer 49 via back contacts 50, 51 of relays 2CK, 1CK. When the vehicle actuates detector WD, the relays 1CK, 2CK are picked up to open the charging circuit. The charge on capacitor 47 is then applied to triode 52 whose output is applied via rectifier 54 to wire 13 and is initially greater than the output of computer 12; and only appears in wire 13 when it is greater than the output of computor 12. As the vehicle proceeds through the retarder, the capacitor 47 is continually discharging via triode 55, the grid of which is connected to pulse forming circuits 23. The resistor 56 of tube 55 is such that the known number of pulses that should be produced whilst the vehicle travels through the retarders will discharge capacitor 47 to a value less than the expected output of computor 12 when the vehicle leaves the No. 2 retarder. For a vehicle near the maximum of its weight class, the speed is reduced gradually throughout the retarders but for a vehicle near the minimum of its weight class, the retarder No. 1 tends to reduce its speed quickly but capacitor 47 is being continuously discharged. When the vehicle speed produces a voltage slightly above the existing capacitor voltage, the relay A1 releases to provide a partial opening of the retarder No. 1. The vehicle then decelerates at a less rapid rate, if the speed-voltage equals or is less than the voltage on capacitor 47, then relay S1 is released and retarder No. 1 opened. If, however, the speed remains constant, capacitor 47 is discharged until S1 may again pick up and cause the retarder to again brake the vehicle. No. 2 retarder has the same mode of operation in respect of relays A2, S2. When the capacitor is discharged to equal the output of computor 12, the rectifier 54 is effective to prevent the output of triode 52 being impressed on wire 13, the control of relay A2, S2 being then in accordance with the output of computor 12. The retarder control mechanism, Fig. 3, 1RCM or 2RCM, is such that when no vehicle approaches the retarder, relays 1CK, 1CKP are released and the operating mechanism energized via 39, 40 and input No. 4 to fully close the retarder. When a vehicle approaches, relays 1CK and 1CKP are picked up connecting energy supply (+) to wire 41 via contact 39. If S1 is picked up (due to speed exceeding the desired value), the wire 41 is connected to wire 47 via contact 42. For a heavy vehicle, for example, relay 1H is picked up and since the approach speed is normally above that at which relay A1 is released, the energy is supplied to input No. 4 for fully applying the retarder. As the speed decreases, firstly A1 is released to close the back contact, and open the front contact, of contact 46 to energize input No. 3 resulting in a partial opening of the retarder; the speed again drops until relay S1 releases and input No. 0 is energized to open the retarder. The No. 2 retarder then operates. For medium and light vehicles, input No. 3 is initially energized and then No. 2. Reference has been directed by the Comptroller to Specifications 781,904 and 811,821.