Patent GB-845460-A (GB)
Title: Improvements in or relating to railway axle counting systems
IPC: B61L1/16
Filed: 1958-02-03
Abstract: 845,460. Counting-apparatus. HEUBERGER, R. Feb. 3, 1958, No. 3496/58. Class 106 (1). [Also in Group XXX] A railway axle counting-system comprises a pair of monitors disposed to be passed in turn by an axle and connected in respective oscillatory circuits, each of said monitors, on an axle passing thereby, suffering an impulsive change in an electrical characteristic so as to vary the outputs of said oscillatory circuits and are also connected in circuit with a counting-register and a mono-stable signal-operating circuit, the latter being connected to be held in the unstable condition only under predetermined conditions of the register and both monitor circuits and is returned to the stable condition when there is a variation of either monitor circuit relative to the other such as a variation of either relative to a reference frequency circuit. In the embodiment described a binary counting register is connected to the monitors through a system of gates which prevent transmission to the register, e.g. of spurious pulses unless there is a predetermined sequence of variations of both monitor circuits relative to the reference frequency circuit. The oscillator outputs are used to generate pulses of the oscillator frequency and the phase of the pulses is compared with the phase of the reference pulses and any phase differences are employed to change the monostable signal operating circuit from its unstable position in which the signals are held at " green " to its stable position in which the signals are changed to " red " and the resetting of this signal operating circuit to its unstable condition is dependent on the correct transmission of a response pulse from the register at the completion of a count. In the case of failure of any of the circuits, the signal operating circuit reverts to its stable condition, causing the signals to indicate "red." As shown, monitors A, B, each consisting of a coil on a ferro-magnetic core are connected in respective oscillatory circuits A24, B24 fed to respective pulse generators A25, B25 synchronized by oscillator 32 to produce co-phasal positive pulses A26, B26 and smaller co-phasal negative pulses A27, B27 approximately in phase opposition to the positive pulses. The negative pulses A27, B27 trigger monostable flip-flop circuits A23, B23, e.g. comprising transistor elements to produce square waveform pulses A28, B28 of longer duration than pulses A26, B26 and which occur just behind the flanks of the latter pulses as indicated at 29, 30, so that when pulses A26, and B28 are fed to the normally-closed AND gate B22, since there is no coincidence of the pulses, the gate B22 is not opened, and likewise pulses B26 and A28 fed to AND gate A22, do not open this normally closed gate. The presence of a wheel closer to monitor A than monitor B with consequent relative inductance variation of monitor A causes a relative change in the phase of pulse A28 so that it coincides with pulse B26 and opens the AND gate A22 and causes a pulse to be passed to a bistable multivibrator circuit selector A4. Likewise when the wheel is nearer monitor B the AND gate B22 is opened and a pulse is transmitted to a bistable multi-vibrator circuit selector B4. When the wheel is midway between monitors A and B, the gates A22, B22 remain closed, but the reference AND gate 6 which is normally open by the co-phasal pulses A26, B26 and pulse 31 from the generator 32, is now closed, pulses A26 and B26 being out-ofphase with pulse 31, and results in a lowering of the potential applied to the monostable signal operating circuit or evaluator 1, Fig. 3, over the line 18 and the evaluator returns to its stable condition switching the signal " S " to red. At the same time the AND gate A22 opens, allowing pulses to selector A4 throwing this selector and resulting in the emission of a pulse which is blocked, however, by a closed gate B8, Fig. 1, but causing gate A8 to open. When the wheel is nearer monitor B, opening of gate B22 throws selector B4 and the resulting emitted pulse passes through the gate A8, Fig. 1, to the register 5, Fig. 2, over line 15. The binary counting register utilizes bi-stable multi-vibrator stages connected in series, the first and last stages only being shown. The first stage is non-directional and all other stages are operated by the gates A8 and B8, Fig. 2, controlled by the selector in such a way that transfer pulses derived from selector A4, Fig. 1, are passed to the individual stages in the zero position of each stage and transfer pulses derived from the selector B4 are only passed in the 180 degrees position of each counter stage. With the registration of the count in the register 5, a response pulse is emitted and passes through gate A8, Fig. 2, to selector A4 throwing it back to normal, thus closing gate A8, Fig. 1. The return-to-normal pulse emitted from the selector A4 has no effect on evaluator 1, as there is still a low potential thereon. When the wheel ceases to influence the monitors the different circuits except circuit 1 revert to normal, the monitor gate 3 and reference gate 6 open and pulses transmitted from the latter pass through the open alignment gate A9 (Fig. 1) comprising two gates in series, throwing the selector B4 back to normal with consequent emission of a pulse which does not affect the evaluator 1 and closes the gates A9 and B8, Fig. 1. As the wheel travels over the other end of the railway block or returns back over the monitors B, A, the above-described sequence of operations occurs in reverse. Selector B4 being thrown first, opening gate B8, Fig. 1, then selector A4 is thrown, causing a pulse to be transmitted to the register 5 through the open gate B8 and acting to eliminate the count in the register. The resulting response pulse from the register throws back selector B4 to normal via the open gate B8, followed by selector A4 being thrown back to normal by a pulse from the reference pulse gate 6 via the gate B9, Fig. 1. Selectors A4 and B4 in their normal positions throw the evaluator 1 to its unstable position and hold it there, the circuits being then in the normal atrest positions.