Patent GB-882906-A (GB)
Title: Apparatus for automatically identifying objects from numerically representative marks carried thereby
IPC: B61L25/04
Filed: 1958-03-17
Abstract: 882,906. Identifying railway vehicles. LKBPRODUKTER - FABRIKSAKTIEBOLAG. March 17, 1958 [March 18, 1957], No. 8460/58. Class 105. Marks which are representative of the identifying numbers assigned to railway vehicles moving past an identification post on the track or stations past which an identification post moves, are ascertained independently of the relative speed between the vehicle and identification post by a reading member having a plurality of sensing coils which, at least, at the instant of sensing are excited by a magnetic flux and are so arranged that their magnetic fluxes at such instant are affected by indicating cores of ferromagnetic or electrically conducting metallic or other material such as iron, copper, aluminium or sintered " Ferraxcube " (Registered Trade Mark), whose disposition denotes in an arbitary code system the identifying number and a device is provided for establishing which coils have had their fluxes affected by the indicating cores during the sensing period. As described, the indicating cores are carried on a number plate affixed to a vehicle and the sensing device and appurtenances associated therewith are located stationarily at an identification post on the track. The indicating ferromagnetic cores 2, Fig. 1, are disposed on the number plate 1 in a line in the direction of movement indicated by the arrow according to a combined binary and decimal code. The sensing member comprises a plurality of differential transformers 7 whose secondary windings are each formed of two coils 21, 22, Figs. 2-4, wound in opposite directions on associated cores 28, 29 energized by a primary winding 9 common to all the transformers, there being one transformer for each indicating core position on the number plate 1. In the presence of the indicating cores, the balance of the transformer is upset by the proximity of an indicating core being nearer to one of the cores 28, 29 than the other, resulting in a secondary voltage which is applied to a storage device, shown in the form of a magnetic core recorder 13, Fig. 4, but may take other forms, e.g. relays, cold cathode tubes, relaxation circuits, through a rectifier 18 and coil 14 and may be used immediately or later to operate an indicating device such as a punched card system or visual indicator. The indicating rods 2 are so disposed on the number plate 1 that they will be directly opposite the corresponding sensing coils at the same moment. The primary coil 9 is excited by current pulses of short duration from a thyratron unit 8, Fig. 1, and in order to transmit a current pulse at the exact instant when the cores 2 are directly opposite the sensing coils two starting rods or cores 3, 4 on the number plate 1 interact with respective starting differential transformers 5, 6 on the sensing device when at the instant of sensing the indicating cores are directly opposite their respective sensing coils. The transformer 5 is a differential transformer similar to the sensing members 22, the transformer 6 is a double differential transformer having a plane of symmetry perpendicular to the direction of movement of the plate 1 so as to produce a secondary voltage whose amplitude and phase is dependent upon the position of the rod 4 in relation to the plane of symmetry. The primary windings of the transformers 5, 6 are excited by current from an oscillator 10 and secondary voltages generated in the transformers 5, 6 are amplified in amplifiers 23, 24 respectively and shaped in squarewave forming devices 25, 26 before application to open electronic gates 19, 20 to enable pulses from a pulse-forming network 11 fed from the oscillator 10 to pass through to fire the thyratron 8, to excite the primary windings of the sensing coils 22 and generate secondary voltages in the transformers corresponding to the indicating cores present, these secondary voltages being recorded on the magnetic core recorder 13. To maintain the distance between the number plate 1 on a railway vehicle and the sensing device as constant as possible, the plate 1 is mounted on an unsprung wheel bearing box. The balanced transformers, two alternatives of which are shown in Figs. 2 and 3, may be replaced by a balanced impedance bridge, Fig. 4, fed from an oscillator 38. Repeated application of storage pulses to the storage device in the event that the number plate 1 should remain stationary opposite the identification post sensing device is avoided by a further gate (Fig. 6, not shown), series connected with gates 19, 20 and controlled by a relaxation circuit reset from the thyratron 8. In the event of a train moving backwards, out of range of the sensing device and then passing the device again, to prevent a second recording by the sensing device, restoration of the relaxation circuit for opening the further gate must either be performed manually or by a device which e.g. closes a contact only after a car interspace has passed. To enable the device shown in Fig. 1 to be used for movement in both directions, the two coils of the starting transformer 6 are made reversible or the phase of the amplifier 24 and of the wave generator 26 may be reversed. To increase the output voltages from the sensing coils, the ferromagnetic indicating cores or rods 2 are arranged in a shallow tray 50, Fig. 8, and the space between the rods is filled with non-magnetic material 52 of high electrical conductivity, e.g. aluminium, copper or magnesium. The presence of the non- magnetic electrical-conducting filling reverses the phase of the output of the sensing coil which phase is not affected by the presence of an indicating core and a gate is employed to eliminate the transmission of the positive part of that output to the storage apparatus.