AU660788B2 - Railway signalling system - Google Patents

Description

6 6 0 7. ooil gu ation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: RAILWAY SIGNALLING SYSTEM r The following statement is a full description of this invention, including the best method of performing it known to us: e GH&CO REF: P20988-F:COS:RK GS/4415 Railway Signalling System This invention relates to railway signalling systems and particularly, although not exclusively, to such systems for detecting the passage of a complete train.

Railway signalling systems on some lightly-used railways are not equipped with continuous track circuiting to prove sections of the track clear before signalling a train to enter the section.

Railways in which stations and passing loops are not fully signalled, sometimes use "Last Vehicle Detector" equipment to prove that trains arrive complete at the end of long single line sections.

Such systems use a variety of technology, but a system which has been used quite widely is one in which a large permanent magnet is hung from the rear coupling of each train before it begins its journey. On arrival in each passing loop, the bypassed section of line is proved clear by inference, from proof that the tail magnet is still in place. A divided train would leave its tail magnet behind in the section. At each passing loop, a magnetic Field sensitive switch a dry reed switch) is placed in the track. Contacts of this switch close momentarily as the tail magnet passes over it, and energise a relay circuit which is used to release the route behind the train.

1A Such a system has the disadvantage that it clearly requires an electrical power supply at each passing loop, both to operate the signalling, and to power a relay via the reed switch contacts.

In recent years, the availability of voice and data radio systems, passive transponders and safe computers have led to the development of a new type of signalling system for such lightly used lines.

In these radio signalling systems, passive transponders are placed in the track at intervals, and authority is given to trains from a control centre, via data messages over radio, to pass over certain transponders (which each have a unique code). Transponder interrogator equipment on each locomotive energises the track transponders inductively, and receives a message containing the identity of each transponder passed. These identities can be relayed by radio back to the computer at the control centre, enabling it to ;update its record of train positions, and therefore to release routes after the passage of trains.

This tyF.e of system does not, of course, prove the completeness of each train arriving at a passing loop, and accidents are known to have occurred due to wagons being left in sections in error after shunting by trains). There is, in general, no power supply available at passing loops on such railways, and therefore •m !traditional last vehicle detector systems are inappropriate.

Alternative solutions have been proposed that described in our Patent Application Serial No.2225887), but these still need a trackside power supply..

It is an advantage that in an embodiment the present invention may therefore provide a railway signalling system for detecting the passage of predetermined train lengths. It is a further advantage that in an embodiment the present invention may provide a system for confirming the return to normal of a switching arrangement which is activated by the passage of a train.

In an aspect of the present invention there is provided a railw" V signalling system comprising first and second transponders positioned at relatively up-line and down-line locations on a line section, first and second Aswitch operating means positioned relatively forward and -2rearward on a train, a switching arrangement mounted on the track so as to cooperate with the switch operating means during passage of the train and effect switching of the transponders between first and second conditions, the passage of the first switch operating means leaving the first transponder in its first condition and the second transponder in its second condition and the passage of the second switch operating means leaving t:he first transponder in its second condition and the second transponder in its first condition, each transponder being adapted to transmit, in its first condition, and in response to interrogation from radio means on the train, a signal characteristic of the passage of the respective switch operating means that caused the first condition, and the arrangement being such that each transponder is within range of the radio means during the time in which that transponder is in its first condition.

The switching arrangement may comprise single switch means adapted to maintain opposite conditions of the transponders. The switch operating means are preferably permanent magnets which may be oppositely directed, the switch means comprising a bistable magnetic S• switch adapted to be switched to its two switch conditions by the passage of the permanent magnets respectively.

S 20 The permanent magnets or other switch operating means may be positioned on the forward and rear vehicles of the train respectively.

The radio means is preferably mounted on the forward vehicle of the

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oU* train. There may be an associated central radio transmitter/receiver means at a remote control centre adapted to record the position of trains from 25 information derived from the train radio means.

U. U, According to a preferred feature of the invention, the first condition of at least one transponder may cause a signal to be returned to the train radio means indicative of correct operation and the second condition of this transponder cause a signal to be returned to the train radio means indicative cG incorrect operation. In this preferred case the switching arrangement may be adapted to switch each transponder between two unique response signal codes.

Alternatively, the first condition of at least one said transponder may cause a signal to be returned to the train radio means -3indicative of correct operation and the second condition of this transponder cause no signal to be returned to the train radio means.

In this case, the switching arrangement may be adapted to switch power to the two transponders alternatively so that each transponder is inactive in its second condition.

One embodiment of a railway signalling system in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, of which: Figure 1 is a diagram of a train entering a passing loop; Figure 2 is a diagram of part of the system in an enable/disable embodiment; and Figure 3 is a similar diagram in an alternative signal embodiment.

Referring to Figure 1 of the drawings, a train 1 is shown having only a.locomotive 3 and a last carriage 5, for simplicity. The train is shown entering a passing loop which extends from point A to point B. Outside this passing loop AB, the track 7 is single line.

The leading or forward vehicle of the train, ie the locomotive 3, is fitted with a permanent magnet 9, which is suspended close to the t track and in a position such that its field can control a dry reed relay 11 mounted in the track just inside the passing loop. At the rear of the train, in the rear vehicle 5, a similar permanent magnet t.oo 13 is suspended. The reed relay is of a bistable kind and adopts a i condition determined by the direction of the last magnetic field which influenced it. The two magnets 9 and 13 are mounted with oppositely to 0: directed fields so as to switch the reed relay 11 to opposite conditions as they pass over or close to it.

The locomotive additionally has a radio transponder interrogator and radio transceiver for communicating with a remote control centre (not shown). These are shown collectively as 15. A transmitting antenna 17 provides information to the control centre and an interrogating antenna 39 cooperates with transponders to be described.

Two passive transponders, 21 and 23 are positioned along the track (within the passing loop) the transponder 21 being 'up-line' of that, 23, but fairly close to the reed relay 11. The latter relay -4consists of a pair of fixed contacts and a magnetised armature which is driven to one or other of the two contacts according to the ambient magnetic field. The two magnets 9 and 13 are suspended with a north pole downward and a south pole downward respectively. The switching arrangement shown in Figure 1 embraces two alternative embodiments shown in more detail in Figures 2 and 3. Assuming first the arrangement of Figure 2, the reed relay 11 closes the 'power' supply path to one transponder and opens it to the other.

Before the arrival of the train, the "eed relay 11 will be in the condition shown., ie the terminals 31 of the first transponder 21 will be open circuit and hence the transponder 21 is disabled, while the terminals 33 of transponder 23 will be connected and consequently transponder 23 will be enabled.

Referring to Figure 2, this shows transponder21 in its disabled condition, which is referred to as its second condition, the enabled or active condition being referred to as its first condition.

The same terminology applies to the second transponder 23.

S, Being passive transponders, bearing in mind that we are catering for a situation in which there is no local power supply, the ~transponders have to derive their energy from the train interrogator transmission. On interrogation, a series of radio frequency pulses *are received by a loop aerial 25, rectified and stored on a capacitor arrangement 27. This provides a 'power' supply, in which there is a pair of contacts 31, ie those shown in Figure 1.

The transmitter 29, in response to energisation from the supply 27, transmits a pulse train coded uniquely by an EPROM This unique signal is transmitted back to the locomotive by way 3f transponder antenna 37 and locomotive antenna 39. The transponder, and thus the location, is uniquely identified.

Transponder 23 is similar to that shown in Figure 2 but its contacts 33 are in the opposite condition to that shown, ie closed.

Thus transponder 23 is in its enabled or first condition prior to arrival of a train.

The spacing of the transponders 21 and 23 is such that the locomotive interrogator must not have passed beyond range of the transponder 23 as the rear magnet 13 on the train engages the reed relay 11. This is achieved with some tolerance by making the distance from the reed relay 11 to the down-line transponder 23 greater than the length of any train to be expected.

Since the most common application of the invention is confirmation of passage of the last carriage (or other last train unit) the rear magnet must be positioned on the last carriage. To ensure that it is then in fact on the last carriage the magnet is fitted to the rear coupling in such a way as to block the introduction of the next hook.

In operation, a train with magnets fitted approaches the passing loop AB. As the front magnet 9 passes adjacent to the reed relay the latter changes over to enable the transponder 21 and disable the transponder 23. The locomotive interrogator, making periodic interrogations, energises the transponder 21 which responds with a unique code identifying the transponder location and indicating the passage of a front end. It could not be a rear end ragnet for that would have disabled the transponder. The unique cude is stored in the locomotive's computer.

As the train proceeds into the passing loop the rear end magnet 13 'engages' the reed relay 11 so returning the transponder 21 to its disabled ('second') condition and switching transponder 23 to its enabled ('first') condition, and before the locomotive interrogator reaches it. Transponder 23 therefore responds to the Ointerrogation only when the rear magnet 13, and consequently the last carriage of the train, is within the line section, ie the passing .ii. loop. A second unique signal code is transmitted to the locomotive o which again stores it. This information may then be used on the train to confirm that the single line section prior to the passing loop is clear, or may be transmitted to the control centre.

If the train had become divided the rear magrqt 13 would not have passed the reed relay 11 and the 'front end' coded signal (from transponder 21) would not be followed, within some time-out period by the 'rear-end' coded signal (from now disabled transponder 23). An alarm would then be raised.

-6- It will be apparent that the position of the 'switching arrangement', the reed relay 11, relative to the transponder 21 depends upon the relative positions of the front magnet 9 and the interrogator 15 on the locomotive. The requirement is that the interrogator 1, must not be forward of the transponder 21 when the magnet 9 is adjacent the relay 11. The transponder 21 could therefore be up-line of the relay 11 as long as the interrogator 15 were further back from the magnet 9.

In the alternative embodiment of Figure 3, the first and second conditions of the transponders 21 and 23 are both enabled but the coding is switched so that one or other of two unique codes is transmitted according to the condition of the transponder and the Scondition of the relay 11. Referring to Figure 3, it may be seen that the power supply path is permanently closed but the switch contacts 31 switch the EPROM between two stored unique codes.

In this case, it will be seen that unique signals are received from both transponders bt the nature of the signals will indicate a fault conditiorn (if one exists). It is also possible to combine the two systems, in which case the first transponder 21 would have its power supply switched and the second transponder 23 would have its codes switched. In this way a positive indication of an incomplete train is obtained.

While the invention finds most imnediate application in the detection of last carriages, the signals generated by the transponders are equally indicative of the correct or faulty operation of different "switching arrangements". Thus, the same system may be used to monitor any other form of steady contact at the trackside, for example, to prove that hand operated, or spring, points have been I returned to the normal position after the passage of a train.

In the above scheme, for the detection of the passage of complete trains or, from another point of view, the detection of the last carriage, it is essential that the permanent magnets be located on the first and last vehicles, In other circumstances it might be desirable merely to record the passage of carriages other than the end ones. Clearly the same principles apply when the permanent magnets are fitted to intermediate carriages.

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Claims (13)

1. A railway signalling system comprising first and second transponders positioned at relatively up-line and down-line locations onr a line section, first and second switch operating means positioned relatively forward and rearward on a train, a switching arrangement mounted on the track so as to cooperate with the switch operating means during passage of the train and effect switching of the transponders between first and second conditions, the passage of the first switch operating means leaving the first transponder in its first condition and the second transponder in its second condition and the passag, of the second switch operating means leaving the first transponder in its second condition and the second transponder in its first condition, each transponder being adapted to transmit, in its said first condition, and in response to interrogation from radio means on the train, a signal characteristic of the passage of the respective switch operating means that caused the said first condition, and the arrangement being such that each transponder is within range of the radio means during the time in which that transponder is in its first condition.

2. A signalling system according to claim 1, wherein said S 20 switching arrangement comprises single switch means adapted to maintain opposite conditions of said transponders.

3. A signalling system according to claim 2, wherein said switch operating means are permanent magnets.

4. A signalling system according to claim 3, wherein said permanent magnets are oppositely directed and said switch means comprises a bistable magnetic switch adapted to be switched to its two switch conditions by the passage of said permanent magnets respectively.

A signalling system according to any one of claims 1 to 4, wherein said switch operating means are positionod on, the forward and rear vehicles of the train respectively.

6. A signalling system according to any preceding claim, wherein said radio means is mounted on the forward vehicle of the train.

7. A signalling system according to claim 6, including central radio transmitter/receiver means at a remote control centre adapted to record the position of trains from information derived from the train radio means. -8-

8. A signalling system according to any preceding claim, wherein the first condition of at least one said transponder causes a signal to be returned to the train radio means indicative of correct operation and the second condition of said at least one transponder causes a signal to be returned to the train radio means indicative of incorrect operation.

9. A signalling system according to any one of claims 1 to 7, wherein the first condition of at least one said transponder causes a signal to be returncd to the train radio means indicative of correct operation and the second condition of said at least one transponder causes no signal to be returned to the train radio means.

A sign':iing system according to claim 8, wherein said switching arrangement is adapted to switch each transponder between two unique response signal codes.

11. A signalling system according to claim 9, wherein said switching arrangement is adapted to switch power to the two transponders o alternatively so that each transponder is inactive in its second condition.

12. A signalling system according to claim 5, or any one of claims 6 to 11 as appendent to claim 5, adapted to provide an indication of the :completeness of a train in a line section. 20

13. A railway signalling system for confirming the completeness of a train in a line section, substantially as herein before described with reference to Figure 1 and Figure 2 or to Figure 1 and Figure 3, of the accompanying drawings. 25 DATED this 10th day of April 1995 6. GEC ALSTHOM LIMITED 9 By their Patent Attorneys GRIFFITH HACK CO. S:20988F -9- ABSTRACT RAILWAY SIGNALLING SYSTEM A railway signal system for detection of the passage of a complete train in regions where there is no provision of continuous track circuits. Each train is fitted at front and rear with a permanent magnet switching member The track section which has to be known to be clear of the train has a transponder (21,23) at each end which, when energised, transmits to a receiver (15) on *6*G the train its own address and condition. The front end magnet on passing the first transponder (TI) enables it and disables the I second transponder When the rear magnet (13) passes the first transponder the second transponder (23) is enabled to transmit a signal to the train saying the complete train is in the section. Figure 1 C Figure 1 C