Patent GB-1170036-A (GB)
Title: Improvements relating to methods and apparatus for adjusting rail track aligning equipment
IPC: B61K9/08
Filed: 1968-04-01
Abstract: 1,170,036. Track position correcting machine. MATISA MATERIEL INDUSTRIEL S.A. 1 April, 1968 [31 March, 1967], No. 15496/68. Heading B7N. In a track aligning or levelling machine in which the deviation of a measuring point X from a line or curve defined by points A, B and C is used to control track shifting or lifting means, apparatus is provided for initially setting the zero deviation of the machine in the absence of a perfect straight or curved section of track. In normal operation the deviation of the point X is transmitted to a movable core 6 positioned between the primary 7 and two secondaries 8 of a transformer 5. The output voltages from the two secondaries which differ in dependence on the deviation of X are amplified 9 and applied via transformers 10, bridge rectifiers 12 and polarity reversing switch 13b, 13c, 13d, 13e, to a pair of potentiometers 15, 16 having fixed centre taps and variable taps driven by motors 17, 18 respectively. The fixed centre tap of 16 is earthed via switch 30d in normal operation and the voltage at the fixed tap of 15 is applied via switch 30a to an amplifier 21 and thence via switches 30b and 23 to an hydraulic device 24, 20 which shifts the rails and the point X until the difference voltage drops to zero. The apparatus is adjusted for zero setting on a straight portion of track having allowable errors in position by adjusting the apparatus to the mean value of a number of error readings. In this mode switch 30 is switched to the I position and the process is controlled by a pulse generator 33 which provides an output each time a measuring device 32 indicates that the machine has travelled a set distance. The pulses drive a motor 34 which steps a tap along a potentiometer 31 each step being equal in value to resistor 37 connected in series with the potentiometer and also via a cam 35 opens and closes a switch 36; each step and switch operation occurring in synchronism with an issued pulse. With switch 39 in its I position and the tap on potentiometer 31 in its first position the voltage at fixed centre tap of potentiometer 15 is applied to amplifier 21 and thence to motor 18 which drives the tap on potentiometer 16. Potentiometer 11 is now adjusted to unbalance the circuit and bring the driven tap on potentiometer 16 to its centre position as indicated by meter 19. Switch 39 is now moved to its II position so that the voltage at the variable tap of 15 is applied to the amplifier and on pickup of relay 14 the amplifier output is applied to motor 17 to drive tap 15. The machine is now moved along the track and the tap is moved to reduce the deviation voltage to zero. When the machine has moved the set distance a pulse is issued which causes potentiometer 34 to move one step and also to open switch 36 whereby relay 14 is released so that the amplifier drive is connected to motor 18 and the polarity of the supply to the potentiometers 15, 16 is changed over. The motor 18 drives tap 16 to the position occupied by tap 15 on change over, i.e. to a position which was a function of the deviation at the change over point. The tap 16 is now driven about this new position in response to the deviation of point X until the next pulse is generated when the position of tap 16 at this instant is transferred back to tap 15 by operating relay 14. In this way the deviations of the point X at the instants of pulse issue are summed and represented by the distance of the tap being driven from the centre point of the potentiometer. The machine is stopped after say 30 values are added and switch 39 is moved to position III in which relay 14 is released to apply the amplifier output to drive motor 18 and the input to the amplifier is obtained from the fixed centre tap of potentiometer 15 and this is adjusted to zero. With the switch in position IV the voltage between the fixed centre tap of potentiometer 15 and the driven tap, being a function of the sum of the deviations, is applied across resistor 37 and potentiometer 38 (now driven to its 30th position) and the voltage at the junction, being a 30th of the sum is applied to the amplifier 21. The potentiometer 11 is now adjusted until this voltage drops to zero and the circuit is balanced about the mean value of the rail deviations taking into account the deviation existing at the position at which the machine is stopped.