Railway switches and signals – Block-signal systems – Automatic
Patent
1981-11-16
1984-04-17
Groody, James J.
Railway switches and signals
Block-signal systems
Automatic
246 34R, 246121, 246167R, B61L 2100, B61L 300
Patent
active
044429886
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to apparatus for transmission of information through the rails between a railway track and a set of vehicles circulating in the same direction on that track, along which there are a number of successive zones of information transmission.
More specifically, the present invention concerns an improvement brought about in such a device which has been described notably in the European patent application publication No. 0007 271 and PCT publication No. WO81/02714, October, 1981.
As is known, such a device comprises:
1. On the track, for each information transmission zone:
a signal generator oscillating at a determined frequency which constitutes the carrier frequency of the information to be transmitted, this frequency to be selected outside the band of frequencies utilized in the block-section system;
a modulator of the said signals;
a unit for control of the modulator in such a way that the signals will be modulated as a function of the information to be transmitted;
an insulated winding of a conductor placed in the form of a loop between the two rails of the track, near the downstream end of the said information transmission zone;
an impedance-adapting and circuit-separation transformer whose primary receives the modulated signals, and whose secondary is connected to the terminals of the loop winding;
two resonant circuits tuned to the carrier frequency, connected between the two rails of the track, one at the downstream end and the other at the upstream end of the information transmission zone.
2. On board each vehicle:
reception mechanisms, tuned to the respective carrier frequencies of the information transmission zones.
With a view to ensuring the intrinsic security of the device, in the railroading sense of the term, it is necessary to limit greatly the crosstalk within a given zone. Thus, the user must know at any instant if the resonant circuits forming each information transmission zone may be open, or may present a resonant frequency different from that emitted by the signal generator, because from augmentation of the impedance of one of these resonant circuits there would result an inopportune propagation of the signals emitted in one zone to an adjacent zone, and thus a crosstalk which could be substantial.
To this end, an object of the present invention is to provide a new and improved information transmission device and apparatus, particularly useful in railroading and similar applications and constructed to obviate the above and other difficulties and disadvantages.
Other and further objects are hereinafter presented and are more fully delineated in the appended claims.
In summary, according to the present invention, a series resonant circuit tuned to the carrier frequency connected between the two rails of the track at each of the ends of a transmission zone is formed of two identical series resonant circuits arranged in parallel, and each comprising a capacitor in series with the primary winding of a transformer, the secondary windings of the two transformers being connected in series and in opposition, in such a way that a signal oscillating at the carrier frequency appears at the terminals of the circuit thus formed when the two series resonant circuits present differing characteristics.
According to a second mode of realization of the invention, the circuits constituted by the secondary windings connected in series and in opposition of the two transformers of each of the two resonant circuits, tuned to two different frequencies, and connected respectively at the downstream end of one, and the upstream end of the immediately adjacent zone, are connected in series through the intermediary of the secondary winding of a fifth transformer, to the terminals of the primary winding of which is applied an oscillating signal, so that in case of modification of the characteristics of one of the resonant circuits, the frequency of the alternating signal appearing at the terminals of the circuit thus formed enables determination of the failed resonant circuit. With a view t
REFERENCES:
patent: 4026505 (1977-05-01), Geiger et al.
patent: 4074879 (1978-02-01), Clark et al.
Laurent Daniel M.
Theze Claude
Groody James J.
Jeumont-Schneider Corporation
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