GB2431034A - Track circuit apparatus for taking possession of a section of track by altering the circuit as an indication of an intention to take possession - Google Patents

Abstract

Electrical track circuit apparatus for taking possession of a signalling section of track is disclosed. The apparatus is securely located near the track circuit and consists of a switch to be incorporated into the track circuit. The switch alters the operation of the track circuit to give an indication of a intention to take possession of the section of railway track. The apparatus may have actuating means which may be identification means such as a keyed interlock. The switch may consist of several switches, each of which are fitted in series along the track circuit. The apparatus may also include signalling means to indicate that the track circuit has been altered. The signal may a light, a placard and/or an aural warning. The signal may be detachable from the apparatus, with a actuating means enabling the connection between the apparatus and the signal to be released. Also disclosed is a train signalling apparatus for taking passion of a section of railway track comprising signalling means operable to indicate that possession of the section of track is in force.

Description

I

APPARATUS AND SYSTEM FOR TAKING POSSESSION OF A RAILWAY TRACK

SIGNALLING SECTION

The present invention relates to a system for taking possession of a signalling section of a railway track, and apparatus for use therein.

In order to control the movement of trains within a railway network, lengths of railway track are typically divided up into logical sections called signalling sections or blocks.

Such sections typically range from one or two miles to under one hundred metres in length.

Figure 1 is a schematic diagram for explaining the layout and operation of such signalling sections. In Figure 1, a length of railway track 1 has been divided up into a plurality of signalling sections 2, 4, 6, 8, and 10. A train may pass along railway track 1 and pass successively through the signalling sections. For example, a train may pass from signalling section 2 to signalling section 10, or from signalling section 10 to signalling section 2.

For the sake of safety, only one train is generally permitted into a section at any one time. The train is considered to have taken "possession" of that section. In order to control the passage of trains through the sections, signals are typically located at or in the vicinity of the boundary between adjacent signalling sections. Those signals may then be controlled based on the location of the train to indicate which section(s) are blocked due to a possession. In Figure 1, signals 12, 14, 16, and 18, are provided at the boundaries between adjacent sections 2, 4, 6, 8, and 10.

An example of how such sections and signals may be used will now be explained with reference to Figure 1. For the following explanation, it is assumed that railway track I is a one-way section of railway track, and that trains may pass along railway track 1 from section 2 towards section 10.

A first train is considered to be travelling along railway track 1 and to have slowed down within section 8 such that it remains therein for a considerable period of time. As aforementioned, when a train is in a particular section, in this case in section 8, the train is considered to have taken "possession" of that section and signals are controlled to indicate that the possession has been taken.

Typically, rail signals show double amber to indicate that the next two sections are clear and that possession of the following section has been taken. Similarly, a single amber signal is typically used to indicate that the next section is clear and that possession of the following section has been taken. A red signal is typically used to indicate that a possession of the immediately following section has been taken. In this case, therefore, signal 12 would be set to double amber, signal 14 to amber, and signal 16 to red.

In the present example, a second train approaching the aforementioned first train will therefore encounter a double amber signal (signal 12) as it passes from section 2 to section 4, and will typically be required to reduce its speed. The second train will then encounter a single amber signal (signal 14) as it passes from section 4 to section 6, and will typically be required to reduce its speed still further. Finally, the second train will encounter a red signal (signal 16) immediately preceding section 8, and will typically be required to come to a halt. That is, a train encountering a red signal will not typically be permitted into the next section, in this case into section 8. In this way, the safety of the first train still within section 8 is maintained.

Additional equipment not shown in Figure 1, partly provided onboard trains and partly distributed across the railway network, may be used in conjunction with signals 12, 14, 16, and 18, in order to automatically cause the second train to reduce its speed as above-mentioned and to eventually come to a halt without entering section 8, in which the possession has been taken.

In order for a train to take possession of a section of railway track, it is necessary to know in which section the train is. One system used to detect whether a train is in a particular section is the electrical track circuit. Typically, each section is provided with its own track circuit capable of detecting the presence of a train in that section.

Many different designs of track circuit exist. Most types of track circuit operate by taking advantage of the electrically conductive path provided between the two running rails of a section of railway track via the metallic wheels and axle of a train.

Figures 2A to 2C are schematic diagrams of three different types of track circuit, the operation of which will now be explained.

In Figure 2A, rails 21 and 22 represent the two running rails of a section of railway track. A power source 24 is provided at one end of rail 21, and connected thereto via a resistance 26 and cabling 28. The other end of rail 21 is connected to ground.

Accordingly, electrical current may flow through rail 21 to ground.

Rail 22 is also connected to ground. A train present somewhere within the section will create a conductive path between rails 21 and 22. Accordingly, when a train is present somewhere within the section, electrical current will also flow from the power source 24 to ground via rail 22. This change in configuration of the track circuit may be measured in different ways, for example by measuring current flows, or voltage drops within the circuit to identify that a train is in the section.

The track circuit of Figure 2B is a simple loop circuit in which rails 21 and 22 form outbound and return paths for a current to flow to and from power source 24 via resistance 26 and cabling 28. In order to form the loop, rails 21 and 22 are connected together at the opposite end to the end at which power source 24 is connected.

Typically, a relay 27 is provided along the circuit to monitor the operation thereof. A train present somewhere within the section will create a conductive path between rails 21 and 22. The conductive path provided by the train wheels and axles typically has a lower resistance than a path through the relay 27. Accordingly, more current flows from the power source 24, causing a larger voltage drop over resistance 26, which may for example be an internal resistance of power source 26. The resulting drop in voltage across rails 21 and 22 causes the relay 27 to open, thereby indicating the presence of a train within the section.

The track circuit of Figure 2C uses two separate loop circuits, one provided for each of rails 21 and 22. Each loop circuit has its own power source 24, resistance 26, and cabling 28. Cabling 28 runs along the length of rails 21 and 22 in order to complete the two loop circuits. Optionally, duplicate cabling 29 may be provided as an alternative current path in the event of a failure in cabling 28. As for the previously discussed track circuits, a train present somewhere within the section will create a conductive path between rails 21 and 22. This change in configuration of the track circuit may be measured in different ways, depending for example on the voltage output and polarity of the two power sources 24. Current flows, or voltage drops within the circuit could be measured to identify that a train is in the section.

The track circuits in Figures 2A to 2C utilise the rails 21 and 22 to make up part of the respective track circuits. Therefore, in order to retain the independence of one track circuit from adjacent track circuits, it is necessary to install insulators along the rails at the boundaries between one track circuit and the next. Such insulators are typically known as insulated block joints (IBJ5).

The operation of the track circuits of Figures 2A to 2C has been described in relation to DC techniques, utilising a DC power supply and measuring direct currents or voltages.

However, track circuits may also operate using AC techniques, utilising an AC power supply. This operation is particularly useful when one or both of the running rails are used as a return path for the current supply used to power trains. In that case, the alternating current of the track circuit can be identified by its frequency of transmission using conventional filtering techniques.

Track circuits using AC techniques may also be used on continuous rails. Such track circuits are known as jointless track circuits, and utilise signals at high frequencies for which attenuation in the rails is not insignificant.

There are a number of problems with the existing track circuit systems. In certain situations, it is necessary to take possession of a section of railway track even when a train is not in that section. For example, during maintenance activities personnel may be working in a section and it may therefore be necessary to take possession of that section so as to prevent a train from entering it inadvertently. Conventionally, such possessions are normally taken using one of the two following methods. Each of these methods has associated disadvantages.

Firstly, a possession may be pre-arranged with a signalman and caused to come into affect by the signalman himself. That is, the signalman may operate the signals from a central station so as to take possession of a designated section for a designated period of time. There are a number of disadvantages associated with this method. Errors in communication between personnel engaged in such maintenance activities and the signalman may result in a possession being taken at a different section, thereby leaving maintenance personnel exposed in an unprotected section. As a direct result, fatalities have occurred in such mistakenly un- protected sections. Another related disadvantage is that such pre- arrangement can be burdensome and bureaucratic thereby making it difficult to rearrange a scheduled possession, or terminate it early.

The result has been that possessions are often taken for longer periods than necessary. Accordingly, unnecessary and costly interruptions to rail services have occurred.

Secondly, a possession may be caused to come into affect by personnel in location at the section at which the possession is intended. Such possessions may or may not be pre-arranged with a signalman. Typically, such possessions are taken by simulating the effect of a train in the section concerned, i.e. by creating a conductive path between the two running rails. Such a conductive path may be, for example, a metal bar or chain, such as a track circuit operating device (TCOD), placed across the tracks, and optionally clipped into place. There are a number of disadvantages associated with this method. Vandals may be able to either place an imitation metal conductor over the rails themselves so as to create an unwanted possession, or to remove a genuine TCOD from the rails so as to re-open a section of track when it is supposed to be possessed. Further, when the running rails are used to carry return currents from operating trains, transient voltage differences in the region of about 1500 to 2000 Volts may be set up between the two running rails. Such a transient voltage may cause a surge of current across the conducting bar or chain causing it to be damaged or fully blown away from the rails, thereby possibly damaging the running surface of the running rails, and/or inadvertently re-opening the section.

It is desirable to solve the above-mentioned problems. It is desirable to provide a safe and reliable system, and apparatus for use therein, for taking possession of a section of railway track. It is further desirable for such a system to utilise existing electrical track circuitry.

According to an embodiment of a first aspect of the present invention, there is provided electrical-track-circuit apparatus for use in a system for taking possession of a signalling section of a railway track, the apparatus being adapted to be securely located in the vicinity of an electrical track circuit of said railway track, the apparatus comprising switching means adapted to be incorporated into the electrical track circuit and being operable, after having been so incorporated, to controllably alter an operation of said track circuit as an indication of an intention to take possession of said signalling section of the railway track.

Advantageously, by such switching means being incorporable into the track circuit, and being controllable, a stable means is provided with which to alter an operation of the track circuit. Further, by altering an operation of the track circuit, the intention to take possession of the signalling section can be detected by monitoring the track circuit.

Accordingly, such apparatus may advantageously be compatible with existing track circuitry and track circuitry monitoring means.

Such apparatus may advantageously enable protection within a section of railway track to be afforded through a physical disconnection of a track circuit when the apparatus is activated. Such apparatus may additionally comprise interlocking between a unique key for operating the apparatus, and indicating means (for example, a "Stop" board) which may display a danger aspect when the track circuit has been disconnected.

Such apparatus may enable: rapid protection of locations where cyclical engineering activity requires frequent access; protection of engineering sites by signals and associated signal interlocking through the disconnection of the track circuit; standardisation of the point of protection at a particular location thereby reducing the potential for human error when protection at that point is required; and a level of sophistication that may enable possessions to be taken both of the "T2" type (in which no train access to the possessed section is permitted) and the "T3" type ( in which controlled access of engineering trains is permitted).

Advantageously, said switching means may be adapted to be permanently incorporated into said track circuit. Such permanent incorporation may allow the apparatus to be permanently on site, so that maintenance personnel do not need to carry around the apparatus or install it themselves. The apparatus may, for example, be permanently installable in the ufour foot" between the running rails. Such permanent incorporation may allow the switching means to be electrically bonded to the track circuit by following a predetermined installation procedure, without incurring any detrimental effect on track or electrification circuits.

Preferably, said track circuit is an existing operational track circuit, and the switching means is adapted to be retro-fitted into the track circuit. That is, preferably the existing track circuitry may be utilised without the need to replace the track circuitry itself.

Advantageously, this may allow interfacing with existing signalling technology, and further allow for both T2 and T3 type possessions.

Preferably, the apparatus further comprises actuating means operable, when the apparatus is in use, to actuate the switching means so as to cause the switching means to bring about said alteration in operation of the track circuit. Advantageously, the actuating means may be operable to mechanically actuate the switching means.

Mechanical actuating means may be advantageous as it is likely to be robust and be relatively low in complexity as compared to electronic actuating means for example.

Thereby, such mechanical actuating means may advantageously require little maintenance, if any. The apparatus may therefore be simple to operate but provide enough mechanical integrity to ensure the protection afforded by it.

Preferably, the actuating means comprises identification means operable to positively identify a predetermined symbol of authorisation to use the apparatus. That is, preferably, the actuating means may be operable to identify an authorised user. For example, the identification means is preferably operable: to receive a candidate symbol of authorisation from a prospective user of the apparatus; if the received candidate symbol is the predetermined symbol, to positively identify the received candidate symbol as being the predetermined symbol; and following such positive identification, to allow the prospective user to operate said actuating means. Further, the identification means is preferably operable, if the received candidate symbol is a symbol other than the predetermined symbol, to hinder or prevent the prospective user from operating said actuating means. The identification means may, for example, comprise a keyed interlock, and the predetermined symbol of authorisation may, for example, comprise a key capable of operating the keyed interlock. Preferably, in the case of a key and keyed interlock, the apparatus is capable of temporarily retaining the key in an inserted position within a keyway of the keyed interlock. This may, for example, ensure that a user of the apparatus performs a required task before the key may be removed therefrom. It may be possible, therefore, to ensure that the apparatus cannot be disabled whilst in use by any person other than the individual who enabled it (or another authorised person). Other combinations of identification means and predetermined symbols of authorisation may be utilised, for example: a keypad and password; or a combination lock and numerical code.

Preferably, the switching means comprises a switch. Optionally, the switching means may comprise a plurality of switches. In the case of a plurality of switches, the actuating means is preferably capable of operating the plurality of switches simultaneously. The use of one or more switches enables a configuration of the track circuit to be changed. For example, a current path may be switched to be either open circuited, or switched to follow a different path.

Preferably, the or each of said switches has a closed and an open setting, and preferably the or each of said switches is adapted to be fitted in series along a current path of the track circuit such that, when one or more of said switches are operated such that they change setting from the closed setting to the open setting, one or more open circuits are created in said track circuit as the indication of the intention to take possession of said signalling section of the railway track. That is, the apparatus is preferably capable of disconnecting the track circuit, or a part thereof, rather than "shunting" it.

Advantageously, the one or more open circuits may serve, when the apparatus is in use, to prevent any current from flowing through said track circuit. Typical monitoring means monitoring the track circuit would normally deduce thereby that either the track circuit is faulty, or, more seriously, that at least one of the running rails is broken. Such a deduction would normally raise an alarm as well as bringing the intended possession into force. Thereby, such apparatus would advantageously bring any unplanned possession to the attention of a signalman. Furthermore, in the case of a pre-planned possession, such an alarm could advantageously enable a signalman to easily identify the possession as it comes into force, and confirm its occurrence.

Preferably, the apparatus further comprises signalling means operable to indicate that the operation of said track circuit has been so altered. Such an indication may serve as a warning to approaching trains and maintenance personnel that a possession is intended and/or already in force. Preferably, the actuating means may be operable, when the apparatus is in use, to control the operation of said signalling means. That is, a user of the apparatus may be able to control both the switching means and the signalling means via the actuating means. Optionally, the actuating means may be operable to control the switching means and the indicating means simultaneously.

Alternatively, the actuating means may be operable to control the switching means and the indicating means separately.

The signalling means is preferably operable to visually indicate that the operation of said track circuit has been so altered. A visual indication could be readily recognised by railway personnel. Optionally, the signalling means may comprise a light operable to illuminate so as to indicate that the operation of said track circuit has been so altered. Such a visual indication may, for example, have a high visibility at night. The signalling means may additionally or alternatively comprise a placard having a surface decoration thereon. Such a surface decoration may be for example a warning sign, for example a "STOP" sign. The surface decoration may comprise fluorescent colours, and/or may glow in the dark.

The signalling means is preferably operable to aurally indicate that the operation of said track circuit has been so altered. An aural indication could be detected in poor visual conditions, and possibly at some distance from the apparatus. For example, the signalling means may comprise a loudspeaker operable to generate a sound so as to indicate that the operation of said track circuit has been so altered. The loudspeaker could be, for example, a siren.

Preferably, the signalling means is capable of being located on the apparatus in first and second different orientations relative to the apparatus. The first orientation may be for indicating that the operation of said track circuit has been so altered, and the second orientation may be for indicating that the operation of said track circuit has not been so altered. This may advantageously enable personnel to quickly and easily identify, possibly at some distance from the apparatus, whether or not the track circuit has been so altered. Preferably, the actuating means may be operable to move the signalling means between said first and second orientations. This may enable ease of movement of the signalling means by a user of the apparatus.

Preferably, the signalling means is detachable from the apparatus. For example, when the apparatus is not in use, the signalling means may be detached therefrom and stored away, or used with other such apparatus. Further, by detaching the signalling means from the apparatus, it may be possible to clearly indicate to personnel that the apparatus is not in use. The actuating means may, for example, be operable to enable a connection between said signalling means and the apparatus to be released so as to enable said signalling means to be detached therefrom. Similarly, the actuating means may, for example, be operable to enable said connection to be closed so as to attach said signalling means to the apparatus. Such a connection may provide a secure mount for such signalling means. The signalling means may be, for example, a standard stop board, or Possession Limit Board (PLB).

Advantageously, the apparatus may be configurable into a plurality of modes of operation. Such a plurality of modes may enable a user of the apparatus to configure the apparatus into a number of different configurations, for example when setting up the apparatus for operation, or when securing the apparatus after operation. Further, the plurality of modes may enable the apparatus to be capable of providing protection for both 12 and T3 possessions. In the case of the latter method of protection (T3), the signalling means (e.g. a PLB) is preferably removable to permit the entry and exit of engineer's trains into and out of the possessed section, whilst maintaining the disconnection of the track circuit. The protection provided by the apparatus may advantageously be provided by mechanical interlocking between the operation of the signalling means (e.g. a PLB) and the key (e.g. an operator's key). For example, the modes of operation may be configured such that the apparatus can only be operated by using both the signalling means and the key (or other symbol of authorisation).

The plurality of modes may comprise: a first mode in which said switching means is in an inactive state in which, when the apparatus is in use, the alteration in configuration of the track circuit has not been made; and a second mode in which said switching means is in an active state in which, when the apparatus is in use, said alteration in configuration of the track circuit has been made. Preferably, in said first mode, the signalling means may be detached from, or positioned for attachment to, the apparatus. The first mode may be, for example, an "inactive" mode, for use when the apparatus is not use and not being called upon to provide protection for personnel in a section (in the form of a possession). The second mode may be, for example, an "active" mode in which the apparatus is affording full protection for such personnel by altering the operation of the track circuit and thereby enabling a possession to be brought into force. In said second mode, said signalling means may be attached to the apparatus and, when the apparatus is in use, configured to indicate that the operation of said track circuit has been so altered.

The plurality of modes of operation further may comprise a third mode in which said switching means is in said inactive state, and in which said connection means has been closed such that said signalling means has been attached to the apparatus. The third mode may be, for example, an "install" mode, which may initialise a protection sequence. The third mode may, for example, therefore be used between the first and second modes. The third mode may, also or alternatively, be a "remove" mode, which may be used when transitioning from the second mode back to the first mode, to terminate a possession and prepare the apparatus for the first mode. In this case, said signalling means may be positioned on the apparatus ready to be removed therefrom.

The plurality of modes of operation may further comprise a fourth mode in which said switching means is in said active state, and in which said signalling means may be detached from the apparatus. The fourth mode may be, for example, a "controlled access" mode in which maintenance equipment carried on trains may be brought into a section in which a possession is in force. In the case that the signalling means may be positioned in the path of such trains when in use, it may therefore be desirable to be able to detach the signalling means from the apparatus when the apparatus is in the fourth mode.

Preferably, the actuating means is operable to configure the apparatus into any of said modes. This may enable ease of use of the apparatus by the user.

The apparatus may comprise a housing portion having said switching means located therein. The housing portion may afford a degree of protection for the switching means. For example, if the switching means is permanently incorporated in a track circuit, the housing may protect the switching means from corrosion over time due to the surrounding weather conditions, or from tampering by unauthorised personnel or vandals. . Preferably, the housing portion also has said actuating means located therein. The housing portion may be constructed in such a way that its internal mechanism (actuating means) is protected from accidental damage and to deter vandalism. The housing portion may enable the apparatus to be capable of operating in the railway environment such that track detritus will not impact upon its mechanical integrity and such that it is able to withstand full submersion. That is, preferably no points of ingress for detritus exist. The nature of the components in the housing portion is preferably such as to allow them to be fully submersed without any deterioration in their operation. The housing portion may enable the apparatus to resist being undermined by malicious acts.

The housing portion may advantageously be suitable for being mounted between running rails of the railway track such that a train may pass along the running rails over the housing portion without making contact therewith. That is, the housing portion (and the switching and/or actuating means therein) may be small enough so as not to be hit by a train when so located. The housing portion may, for example, be mounted such that by design it is automatically situated at a predetermined height and position relative to the adjacent running rails. Such a location for the apparatus is advantageous as it does not require

any land adjacent to the running rails, which land may in some cases be occupied by other running rails.

According to an embodiment of a second aspect of the present invention, there is provided a system for taking possession of a signalling section of a railway track, the system comprising: switching means adapted to be incorporated into an electrical track circuit of said railway track and being operable to alter an operation of said track circuit as an indication of an intention to take possession of said signalling section of the railway track; track-circuit monitoring means operable to detect said alteration in operation of the track circuit; and signallingequipment controlling means operable, in dependence on an output of said track-circuit monitoring means, to control an operation of signalling equipment so as to indicate that said possession has been taken.

According to an embodiment of a third aspect of the present invention, there is provided train-signalling apparatus for use in a system for taking possession of a signalling section of a railway track, the apparatus being adapted to be securely located in the vicinity of said railway track, the apparatus comprising: signalling means operable to indicate that a possession of said signalling section is currently in force; and actuating means operable, when the apparatus is in use, to mechanically actuate the signalling means so as to cause the signalling means to change state from a first state, for indicating that said possession is not currently in force, to a second state, for indicating that said possession is currently in force. Advantageously, the indication so made may be stable and durable due to the secure location of the apparatus, and also due to the mechanical operation of the actuating means.

The signalling means is preferably operable to visually indicate that the operation of said track circuit has been so altered. A visual indication could be readily recognised by railway personnel. Optionally, the signalling means may comprise a light operable to illuminate so as to indicate that the operation of said track circuit has been so altered. Such a visual indication may, for example, have a high visibility at night. The signalling means may additionally or alternatively comprise a placard having a surface decoration thereon. Such a surface decoration may be for example a warning sign, for example a "STOP" sign. The surface decoration may comprise fluorescent colours, and/or may glow in the dark.

The signalling means is preferably operable to aurally indicate that the operation of said track circuit has been so altered. An aural indication could be detected in poor visual conditions, and possibly at some distance from the apparatus. For example, the signalling means may comprise a loudspeaker operable to generate a sound so as to indicate that the operation of said track circuit has been so altered. The loudspeaker could be, for example, a siren.

In said first state, the signalling means of apparatus according to an embodiment of the third aspect of the present invention may be located on the apparatus in a first orientation relative thereto, and in said second state, the signalling means may be located on the apparatus in a second orientation relative thereto different to said first orientation. This may advantageously enable personnel to quickly and easily identify, possibly at some distance from the apparatus, whether or not the track circuit has been so altered.

Preferably, the signalling means is detachable from the apparatus. For example, when the apparatus is not in use, the signalling means may be detached therefrom and stored away, or used with other such apparatus. Further, by detaching the signalling means from the apparatus, it may be possible to clearly indicate to personnel that the apparatus is not in use. The actuating means may, for example, be operable to enable a connection between said signalling means and the apparatus to be released so as to enable said signalling means to be detached therefrom. Similarly, the actuating means may, for example, be operable to enable said connection to be closed so as to attach said signalling means to the apparatus.

Preferably, apparatus according to an embodiment of the third aspect of the present invention further comprises switching means adapted to be incorporated into the electrical track circuit and being operable, after having been so incorporated, to controllably alter a configuration of said track circuit as an indication of an intention to take possession of said signalling section of the railway track. Advantageously, by such switching means being incorporable into the track circuit, and being controllable, a stable means is provided with which to alter an operation of the track circuit. Further, by altering an operation of the track circuit, the intention to take possession of the signalling section can be detected by monitoring the track circuit. Accordingly, such apparatus may advantageously be compatible with existing track circuitry and track circuitry monitoring means. Preferably, the actuating means is operable, when the apparatus is in use, to actuate the switching means so as to cause the switching means to bring about said alteration in operation of the track circuit.

According to an embodiment of the fourth aspect of the present invention, there is provided an electrical track circuit comprising apparatus according to the aforementioned first or third aspects of the present invention.

Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1, as described above, is a schematic diagram of signalling sections.

Figures 2A to 2C, as described above, are track circuit schematic diagrams.

Figure 3 is a perspective view of apparatus 1000 embodying the present invention.

Figure 4 is a schematic diagram showing a plan view of part of apparatus 1000.

Figure 5 is close-up plan view of cabling connections into and out of junction box 300.

Figure 6 is a perspective view of apparatus 1000.

Figure 7 is a perspective view of main housing 100.

Figure 8 is a perspective view of protective cover 102.

Figure 9A is a perspective view of upper casing 104.

Figures 9B and 9C are perspective views of part 107.

Figure 10 is a perspective view of main housing 100 with the protective cover 102 and upper casing 104 removed therefrom.

Figure 11 is a perspective view of shaft assembly 130.

Figure 12 is a perspective view of detent assembly 150.

Figure 13 is a perspective view of rocker assembly 163.

Figure 14 is a perspective view of turntable assembly 160, which comprises the rocker assembly 163.

Figure 15 is a cross-section view of turntable assembly 160.

Figure 16 is a perspective view of switching apparatus 180.

Figures 1 7A to 1 7D are close-up views of a portion of main housing 100.

Figure 18 is a block diagram detailing modes of operation of apparatus 1000.

Figures 19 and 20 are photographs of an example prototype of part or all of apparatus 1000.

Figure 3 is a perspective view of apparatus 1000 embodying the present invention.

Apparatus 1000 is shown in use, and is installed on a signalling-section of railway track. The section of railway track comprises two running rails 32 and 34, supported by a plurality of sleepers 36. Cables 38 of the track circuit of the present section of railway track are shown attached to the apparatus 1000.

Apparatus 1000 comprises a main housing 100, signalling means 200, a junction box 300, a supporting beam 400, and an operating key 500.

Supporting beam 400 is supported by one of the sleepers 36 and is connected to running rails 32 and 34 at either end by means of a suitable rail fastening system.

Supporting beam 400 may be as disclosed in GB 2347456, for example. Junction box 300 and the main housing 100 are affixed to the supporting beam 400. Preferably, and as shown in Figure 3, junction box 300 and the main housing 100 are affixed to the supporting beam 400 such that they are adjacent to one another.

Signalling means 200 is shown installed in the top of the main housing 100. Operating key 500 is shown inserted into a keyhole in the side of the main housing 100. In use, the operating key 500 may be rotated to a number of discrete positions, each said position configuring apparatus 1000 into one of a plurality of different operating modes.

In at least one of the different operating modes, switching apparatus (not shown) within the main housing 100 is caused to change state from a closed state to an open state.

In the signalling section of Figure 3, the track circuit is similar to the track circuit of Figure 2C, in the case when there is duplicate cabling 28 and 29. Duplicate cabling 38 is therefore shown emerging from alongside running rail 32, passing along (or under or through) supporting beam 400 and into junction box 300. Further, the duplicate cabling 38 is shown emerging from junction box 300 and passing under running rail 34 towards a line-side cabinet (not shown) which powers the track circuit.

Figure 4 is a schematic diagram showing a plan view of part of apparatus 1000, for explaining the layout of track circuit cabling. Running rails 32 and 34 of a particular signalling-section of railway track are shown supported by a number of sleepers 36, as in Figure 3. Also, the main housing 100 and junction box 300 are shown affixed to the supporting beam 400.

The track circuit used in the signalling-section of Figure 4, as in Figure 3, is similar to the track circuit of Figure 2C, in the case when there is duplicate cabling 28 and 29.

The cabling is shown both before the parts of apparatus have been installed, and after the installation.

Before the installation, duplicate cables 38 running alongside running rail 32 pass along paths 44 (shown dashed) across the gap between running rails 32 and 34, such that they run under running rail 34 and into lineside cabinet 42, which powers the track circuit.

After installation, the duplicate cables pass instead along paths 46, such that they run, from alongside running rail 32, along or adjacent to supporting beam 400 and terminate at junction box 300. The circuit is then completed from the junction box along the remaining part of paths 46. That is, the duplicate cabling continues from junction box 300 and runs under running rail 34 and into line-side cabinet 42.

The effect of the installation is to place switching means (not shown) within the main housing 100 and connected to the junction box 300 in series into each of the duplicate cables. As aforementioned, apparatus 1000 may thus be used to create an open circuit in the track circuit so as to indicate that a possession is intended. The indication may cause track circuit monitoring means (not shown) to operate railway signals (not shown) accordingly, as explained previously with reference to Figure 1. Accordingly, in this way, the possession may be brought into force. As the open circuit is made with switching apparatus, the circuit may be reclosed to indicate that the possession is no longer required.

In the present embodiment, as the track circuit comprises duplicate cabling, an open circuit is created in each of the duplicate cables, such that no current may flow through the track circuit. This provides an easily detectable change in operation of the track circuit.

Figure 5 is close-up plan view of cabling connections into and out of junction box 300.

Accordingly only part of main housing 100, supporting beam 400 and the cabling 38 is shown.

Duplicate cabling 38 is shown emerging from under main housing 100 and terminating at junction box 300. Further duplicate cabling 38 is shown emerging from junction box 300. A connection 37 is shown between the main housing 100 and the junction box 300, through which circuitry may pass to connect switching means (not shown) within the main housing 100 in series into the track circuit. In this case, as there is duplicate cabling, the switching means is connected such that an open circuit may be made in each of the current paths of the two duplicate cables 38. Terminals 39 within the junction box may connect the cabling 38 with internal cabling of apparatus 1000.

Figure 6 is a perspective view of apparatus 1000 configured differently to that of Figure 3. As in Figure 3, apparatus 1000 is shown in use, and is installed on the signalling- section of railway track comprising running rails 32 and 34. Cables 38 of the track circuit of the present section of railway track are shown attached to the apparatus 1000. Supporting beam 400 is supported by one of the sleepers 36 and is connected to running rails 32 and 34 at either end by means of a suitable rail fastening system.

Junction box 300 and the main housing 100 are affixed to the supporting beam 400.

Junction box 300 and the main housing 100 are affixed to the supporting beam 400 such that they are not immediately adjacent to one another. Accordingly, connection 37 of Figure 5 is made via the supporting beam 400 in Figure 6, and therefore cannot be seen.

Figure 7 is a perspective view of main housing 100. Main housing 100 comprises protective cover 102 and upper casing 104. Protective cover 102 and upper casing 104 may be made of, for example, sheet metal. A slot 106 in the top face of upper casing 104 enables one end of a supporting shaft of the signalling means 200 (not shown) to be inserted into the main housing. A slot 108 in a side face of upper casing 104 enables the operating key 500 to be inserted therethrough into a keyway within the main housing 100. Protective cover 102 is shown in a released position, in which slots 106 and 108 are not covered thereby. Protective cover 102 may be repositioned on the upper casing 104 into a secured position, in which slots 106 and 108 are covered thereby. Protective cover 102 may be locked into the secured position.

Figure 8 is a perspective view of the protective cover 102. When the protective cover 102 is positioned on the upper casing 104 in the secured position, part 110 covers slot 106. At that time, a side face of the protective cover 102 covers slot 108. Runners 112 are affixed to the inner sides of protective cover 102 with screws or rivets 114. Screws 116 are provided on the lower portions of protective cover 102 and serve to guide the protective cover between the released and secured positions by sliding alongside parallel runners (not shown) affixed to a lowermost surface of main housing 100.

Figure 9A is a perspective view of upper casing 104. Parallel runners 112 are affixed to the upper face of upper casing 104 with screws or rivets 114. Parrallel runners 112 may assist in the smooth running of the protective cover 102 thereover. A further part is affixed to the upper face of upper casing 104 with screws or rivets 114 in order to form slot 106.

Figures 9B and 9C are two perspective views of an alternative version 107 of the further part which may be affixed to the upper surface of upper casing 104 with screws or rivets 114 in order to form slot 106. Part 107 has a helical surface 109 formed around slot 106 so as to guide a supporting shaft (having a peg fitted therethrough) of signalling means 200 into a predetermined angle of rotation as supporting shaft is inserted into slot 106. The supporting shaft may be so inserted under the action of gravity, for example if the shaft has been rested over slot 106, or by the deliberate act of a user of apparatus 1000. The predetermined angle of rotation may be such that a signal of the signalling means 200 faces parallel to the running rails when apparatus 1000 is installed. One reason for this, is to prevent a user of apparatus 1000 from inadvertently installing signalling means 200 into slot 106 in a different angle of rotation, for example such that a signal of the signalling means 200 faces in the direction of oncoming rail traffic. This may help to ensure that the signalling means 200 faces in the direction of oncoming rail traffic only when apparatus has been specifically so configured. Such configuration will be described later.

Figure 10 is a perspective view of main housing 100 with the protective cover 102 and upper casing 104 removed therefrom. As can be seen from Figure 10, main housing further comprises a lower casing 120, a keyway plate 122, a shaft assembly 130, a turntable assembly 160, and a switch assembly 180.

Keyway plate 122 serves as a rigid passageway via which the operator's key 500 may be inserted into a keyway itself (not shown), which keyway is part of the shaft assembly 130. Keyway plate 122 also serves to retain the operator's key 500 in the keyway (not shown) except in the rotational position shown in Figure 10 (and in a similar rotational position 180 degrees therefrom) in which the key may be removed from the keyway via keyway plate 122. Shaft assembly 130 is affixed to the lower casing 120 such that the keyway is aligned with the slot 108 in the upper casing 104 when it is affixed to the lower casing 120, and the corresponding slots in the keyway plate 122.

Turntable assembly 160 is affixed to the lower casing 120 such that it is centred under slot 106 when the upper casing 104 is affixed to the lower casing 120. Further, turntable assembly 160 and shaft assembly 130 are positioned such that they mechanically interact with one another, which mechanical interaction will be described later.

Switch assembly 180 is affixed to lower casing 120 such that it may be operated by a locking cam of the shaft assembly 130. The operation of shaft assembly 130 will be described later. Cabling from the junction box 300 passes through the switch assembly so as to place the switch(es) of the switch assembly in series in the track circuit as aforementioned.

Figure 11 is a perspective view of shaft assembly 130. Shaft assembly 130 comprises a keyway 132 comprising a slot 133 and a key locator 134, a shaft 135, a detent assembly 150, a plurality of shaft supports 138, a shaft retaining collar 139, a locking cam 140, and a switch cam 141. Figure 12 is a perspective view of detent assembly 150, which comprises a detent shaft 151, a locking nut 152, a split pin 153, a detent arm 154, a spring 155, and a spring anchor 156.

Shaft 135 is supported by the plurality of shaft supports 138 such that it may be rotated about its axis. Shaft retaining collar 139 retains the shaft 135 in a predetermined axial position. Keyway 132 is affixed to one end of shaft 135 such that the operator's key 500 may (when inserted into the keyway 132 and rotated about its axis) rotate the shaft. Slot 133 aligns with slot 108 in the upper casing 104 when the main housing is has been fully assembled. Key locator 134 may engage with a complementary feature of the operator's key 500 so as to assure proper insertion of the operator's key into the keyway 132.

The detent assembly 150 is attached to the shaft assembly 130 in two places. The detent shaft 151 is partly located within a hole in one of the mount assemblies 138, and is retained therein by locking nut 152. Detent arm 154 is located at one end on the detent shaft 151 and retained thereon by split pin 153. Detent arm 154 is operable to rotate in a plane perpendicular to the axis of shaft 135 about its connection to detent shaft 151.

Spring anchor 156 is connected to the top of one of the mount assemblies 138. Spring 155 is connected between the spring anchor 156 and the free end of detent arm 154.

Accordingly, spring 155 applies a force to the free end of detent arm 154 such that it is spring-biased against a portion 136 of shaft 135.

Portion 136 of shaft 135 has a square cross-section. Accordingly, the effect of detent arm 154 being spring-biased there against is that four discrete positions of rotation of shaft 135 are provided at which detent arm 154 rests against the four flat sides of shaft portion 136, respectively. As shaft 135 is rotated from one of those four positions to the next (by rotation of the operator's key 500), detent arm 154 is forced to move temporarily further away from the axis of shaft 135 (as it is spring-biased against portion 136), and then back towards the axis of shaft 135 until is rests once more against the next one of the four flat sides thereof. That is, the spring-bias of detent arm 154 acting against portion 136 serves to bias the shaft 135 into any one of the four positions of rotation, Of course, in another embodiment of the invention, portion 136 could have a different cross-section, such that a different number of discrete positions of rotation is provided.

Locking cam 140 is attached to shaft 135 at a predetermined position, such that it may mechanically interact with the turntable assembly 160 when the main housing is fully assembled. Locking cam 140 comprises four different outer profiles 144, 146, 148 and 149, and is affixed to shaft 135 such that, at each of the aforementioned four positions of shaft 135, one of those outer profiles will be aligned with the turntable assembly 160 such that it may mechanically interact therewith. Outer profile 144 is that of a sector of a disc having a uniform radius and thickness. Outer profile 146 is similar to that of outer profile 144, except that two notches have been removed therefrom to form a tooth shape. Outer profile 148 is similar to that of outer profile 144, but has a larger thickness. Outer profile 149 is similar to that of outer profile 146, except that only one notch has been removed therefrom, that single notch occupying a substantial proportion of outer profile 149. Of course, the outer profiles may be structured differently in another embodiment of the present invention.

Two recesses 142 are formed in shaft 135, one on each side of locking cam 140. Each of those recesses serve to mechanically interact with the turntable assembly 160 when the main housing 100 is fully assembled.

Switch cam 141 is affixed towards one end of shaft 135 such that it may mechanically interact with switch assembly 180 when the main housing 100 is fully assembled.

Switch cam 141 has a variable radius and serves to activate a switch(es) within switch assembly 180 at one or more of the positions of rotation of shaft 135.

Figure 13 is a perspective view of a rocker assembly 163 alone. Figure 14 is a perspective view of turntable assembly 160, which comprises the rocker assembly 163.

Figure 15 is a cross-section view of turntable assembly 160.

Rocker assembly 163 comprises a rocker unlocker 167, a pivot 168, and a compression spring 169. Rocker unlocker 167 serves as a lever and may rotate about pivot 168. Pivot 168 is mounted within turntable assembly 160, as can be seen in Figure 15. Compression spring 169 is connected under one end of rocker unlocker 167 and serves to spring-bias rocker unlocker 167 into a locked position.

When main housing 100 is fully assembled, rocker unlocker 167 is positioned such that shaft 135 passes through two holes 164 formed in one end thereof. When the rocker unlocker is in the aforementioned locked position, two fingers 165 and 166 (which protrude towards one another from rims that surround holes 164) may fit within the recesses 142 within shaft 135 to prevent it from rotating. That is, rocker unlocker 167 serves, in its locked position, to lock shaft 135 in position.

Turntable assembly 160 comprises a central shaftway 161 having an inner profile similar to the shape of slot 106. That is, shaftway 161 has a cylindrical core with two channels 174 formed on opposite sides thereof. Accordingly, when main housing 100 is fully assembled, a supporting shaft of signalling means 200, having a guiding peg fitted therethrough, may be passed through slot 106 and into shaftway 161. The guiding peg of the supporting shaft is fitted therein such that its ends may pass along channels 174. Such location of the supporting shaft of the signalling means 200 into the central shaftway 161 causes the rocker unlocker 167 to be rotated about pivot 168 against the spring-bias of compression spring 169. In this way, rocker unlocker 167 is caused to change position from the locked position to an unlocked position, in which fingers 165 and 166 no longer fit within recesses 142 within shaft 135. That is, in its unlocked position, rocker unlocker 167 no longer prevents shaft 135 from rotating.

Turntable assembly 160 further comprises an outer collar 162. Turntable assembly 160 is mountable to lower casing 120 such that outer collar 162 and central shaftway 161 may be rotated about the central axis of central shaftway 161. When the supporting shaft of signalling means 200 is inserted into the shaftway 161, a user of the apparatus may try to rotate it. Due to the location of the guiding peg of the supporting shaft within the channels 174, such rotation of the supporting shaft (for example, by rotating the signalling means 200 itself) would cause the central shaftway 161 and the outer collar 162 to rotate therewith. Once the signalling means has been rotated such that the central shaftway 161 has been rotated, the guiding peg will ensure that the supporting shaft (and therefore the signalling means 200 itself) is held within the central shaftway 161, until the channels 174 are re-aligned with slot 106 once more.

The outer collar 162 has a number of different outer profiles, of which two are profiles and 172. The outer profiles of the outer collar 162 mechanically interact with outer profiles 144, 146, 148 and 149 of locking cam 140 when the main housing 100 is in use. That is, the angle and direction of rotation of the signalling means within the shaftway 161 available to the user depends on which outer profile of the locking cam is aligned with which outer profile of the outer collar 162 of the turntable assembly 160. Further, the angle and direction of rotation of the shaft 135 (of the shaft assembly 130) available to the user (through rotation of the operator's key 500) depends also on which outer profile of the locking cam 140 is aligned with which outer profile of the outer collar 162 of the turntable assembly 160. In this way, the mechanical interaction between the turntable assembly 160 and the shaft assembly 130 describes four operationally different modes of operation of the apparatus 1000, in which the position of the signalling means and the operation of the switching apparatus may be different.

The modes of operation of apparatus 1000 will be described later.

Turntable assembly 160 may optionally employ a detent feature to provide positive feedback as to its position or angle of rotation. Such a detent feature may generate a resistance to rotation of the outer collar 162 at specific angles of rotation. This may enable a user causing such rotation to occur to be aware when the outer collar 162 is at the specific angles of rotation. Such a detent feature may comprise a ball and spring configured to mechanically interact with the outer profile of collar 162, or another part of turntable assembly 160. Such a detent feature, or detent means, may assist a user when configuring the apparatus 1000 into one of the four possible modes of operation by positively confirming that the central shaftway 161, and therefore the signalling means 200, has been correctly rotated, for example through an angle of 90 degrees.

As above-mentioned, the modes of operation of apparatus 1000 will be described later.

Figure 16 is a perspective view of switching apparatus 180. Switching apparatus 180 comprises a switch(es) 181, a cam follower 182, cabling 184, anti-vibration mounts 186, and a switch cage 188.

Switching apparatus 180 is mountable within main housing 100 such that cam follower 182 may mechanically interact with switch cam 141. When main housing 100 is in use, the position of cam follower 182 within switch 181 is determined by the rotational position of shaft 135, and therefore of switch cam 141. The position of cam follower 182 within switch 181 determines whether switch 181 is in an open state (in which an opencircuit is generated within circuitry passing through switch 181 via cabling 184), or a closed state (in which current may flow through circuitry of cabling 184 via the switch(es)).

Switch 181 is mounted to switch cage 188 via anti-vibration mounts 186. In the main housing 100, switch cage 188 is mounted to the lower casing 120. Switch cage 188 is designed to support switch 181 in the event that anti-vibration mounts 186 fail.

Figures 17A to 17D are close-up views of a portion of main housing 100 with the operator's key 500 inserted into the keyway 132. Each of Figures 17A to 17D shows the position of the operator's key 500 in one of the aforementioned modes of operation of apparatus 1000. Operation of apparatus 1000 into each of the modes of operation will now be explained. However, it is understood that the following explanation details operation of the present embodiment only, and that other embodiments could be designed within the scope of the present invention and therefore operate differently.

Figure 1 7A shows the position of the operator's key 500 in an "inactive" mode of operation of apparatus 1000. In the inactive mode, apparatus 1000 is not in use, and is not being called upon to indicate that a possession is intended. The operator's key may have been inserted into the keyway 132, as shown in Figure 17A, or may have been withdrawn therefrom. Similarly, the signalling means 200 may have been detached from the main housing 100. The switch 181 is in the closed state, and accordingly the track circuit to which apparatus 1000 is connected may operate normally.

Figure 1 7B shows the position of the operator's key 500 in an "install" mode of operation of apparatus 1000. In the install mode, the supporting shaft of signalling means 200 must, in the present embodiment, have been inserted into the central shaft 161 via slot 106, such that the "STOP" sign and warning light of signalling means 200 (not shown) are parallel to the running rails (not shown). Such insertion has unlocked the shaft 135 and allowed it to be rotated. Further, in rotating the operator's key to the "install" mode position, it has become mechanically held within the keyway 132, as aforementioned in reference to the keyplate 122. The switch 181 is still in the closed state, and accordingly the track circuit to which apparatus 1000 is connected may still operate normally.

Figure 1 7C shows the position of the operator's key 500 in an "active" mode of operation of apparatus 1000. In the active mode, the supporting shaft of signalling means 200 will have been rotated in the central shaft 161 such that the "STOP" sign and warning light of signalling means 200 (not shown) are perpendicular to the running rails (not shown) and facing potential oncoming rail traffic. The warning light will be on or flashing to indicate that a possession is intended, or that the possession may already be in force. As a result of this rotation, the signalling means will now be mechanically held attached to the main housing 100. The switch 181 is now in the open state, and accordingly an open circuit has been created in the track circuit to which apparatus 1000 is connected. Associated track circuit monitoring means may sense the open circuit and bring the intended possession into force.

In rotating the operator's key to the "active" mode position, it will no longer be mechanically held within the keyway 132 and may be removed by the user.

Accordingly, once the operator's key 500 has been so removed, only a user possessing the operator's key 500 may take apparatus 1000 out of the active mode and end the possession. This offers a degree of safety to personnel working in the possessed section.

Figure 1 7D shows the position of the operator's key 500 in a "controlled access" mode of operation of apparatus 1000. In the controlled access mode, the supporting shaft of signalling means 200 will have been rotated in the central shaft 161 such that the "STOP" sign and warning light of signalling means 200 (not shown) are once more parallel to the running rails (not shown). As a result of this rotation, the signalling means will now no longer be mechanically held attached to the main housing 100 and may be detached therefrom. However, the switch 181 is still in the open state, and accordingly the open circuit in the track circuit to which apparatus 1000 is connected remains. Associated track circuit monitoring means therefore may still sense the open circuit and leave the possession in force. In the controlled access mode, engineer's trains having special permission may enter the possessed section to carry out associated maintenance work. In rotating the operator's key to the "controlled access" mode position, it will once more be mechanically held within the keyway 132 and may not be removed by the user. Once the engineer's train has gained access to the possessed section, apparatus 1000 may be returned to the "active" mode once more and the operator's key then removed.

Once the possessed section is ready to be re-opened to normal rail traffic, apparatus 1000 may be placed back in the "install" mode of Figure 17B, which in this case would normally be referred to as a "remove" mode. The "remove" mode is operationally equivalent to the "install" mode, and accordingly, the signalling means may be rotated and removed from the central shaftway 161, and the operator's key will be mechanically retained within the keyway 132. In this mode, the switch 181 will return to the closed state such that the track circuit to which apparatus 1000 is connected may once more operate normally. Associated track circuit monitoring means may sense the closing of the circuit and bring the intended possession out of force. The apparatus may then be returned to the "inactive" mode, and the operator's key removed.

Figure 18 is a block diagram detailing the operation of apparatus 1000 in a system for taking possession of a section of railway track. Figure 18 considers a particular example of apparatus 1000 called "GATEKEEPER". The acronym PICOP stands for "Person In Charge of a Possession", and the acronym COSS stands for "Controller of Site Safety".

In relation to Figure 18, an overview of the way in which apparatus embodying the present invention could be operated and the relationships and interfaces between personnel that may exist to allow that operation will now be provided. The following overview assumes use of apparatus 1000, but could of course be adapted for use with other apparatus embodying the invention.

Firstly, a process for taking a possession will be discussed, assuming that an Operator (being an authorised user of apparatus 1000) is already in location at apparatus 1000, and assuming that the apparatus is installed in a track circuit.

The Operator may begin the process by contacting a Signaller (being a signalman responsible for the section in which the possession is intended) to obtain permission to block the line by bringing the possession into force, and to confirm the identity of the apparatus 1000 and therefore which track circuit it is installed into. Then, the Operator may insert signalling means 200 (in this case, a PLB) into the main housing 100 of apparatus 1000 as aforementioned, such that the warning "STOP" sign is parallel to the running rails, and therefore to oncoming rail traffic. Next, the Operator may insert the operator's key 500 into the keyway 132 (as in Figure 1 7A) and rotate it through 90 degrees (clockwise in this case) to the install position (as in Figure 17B). In the install position, the operator's key 500 is retained within the keyway 132. Then the PLB should then be rotated through 90 degrees to face oncoming rail traffic. Next, the operator's key is turned through a further 90 degrees (clockwise) to the active position (as in Figure 1 7C). This operation disconnects the track circuit. The operator's key 500 is then removed leaving the PLB locked in position. At this point, the Operator may contact the Signaller to confirm that the track circuit is giving an occupied (or possessed) indication, and that the signal in rear (the PLB and/or a normal track signal) is displaying a danger aspect. In response, the Signaller may: confirm that the track circuit has been disconnected; confirm that the signal in rear is displaying a danger aspect; grant the blockage of the line; and make an entry in a Train Register Book or Occurrence Log accordingly.

Secondly, a process for providing access for an engineer's train into the possession (the possessed section) will be discussed, assuming that a blockage of the line (a possession) has already been granted and is in force, and that appropriate authority has been given by the Signaller and PICOP/COSS to proceed in this way.

The Operator may begin the process by inserting the operator's key 500 into the keyway 132 in the active position (as in Figure 17C) and then turning it through 90 degrees (in this case, clockwise) to the controlled access position (as in Figure 1 7D).

The PLB 200 may then be turned through 90 degrees and removed from the device.

At this point the track circuit remains disconnected and the operator's key 500 is retained in the device. The driver of the engineer's train seeking access may then be given permission to enter the possession (the possessed section), and thereafter the engineer's train may pass over main housing 100 and into the possessed section.

Once the engineer's train has passed beyond apparatus 1000, the Operator may continue the process by inserting the PLB back into the main housing 100 and turning it degrees counter clockwise such that it is reattached thereto. Further, the operator may then turn the operator's key 500 (in this case, counter clockwise) through 90 degrees from the controlled access position (as in Figure 1 7D) to the active position (as in Figure 1 7C). The operator's key 500 may then be removed.

Thirdly, a process for providing egress for an engineer's train out of the possession (the possessed section) will be discussed, assuming that an engineer's train is currently within the possessed section, and that appropriate authority has been given for the engineer's train to leave the possession.

The Operator may begin the process by inserting the operator's key 500 into the keyway 132 in the active position (as in Figure 1 7C) and then turning it through 90 degrees (in this case, clockwise) to the controlled access position (as in Figure 17D).

The PLB 200 may then be turned through 90 degrees and removed from the device.

At this point the track circuit remains disconnected and the operator's key 500 is retained in the device. The driver of the engineer's train seeking egress may then be given permission to leave the possession (the possessed section), and thereafter the engineer's train may pass over main housing 100 and out of the possessed section.

Once the engineer's train has passed beyond apparatus 1000, the Operator may continue the process by inserting the PLB back into the main housing 100 and turning it degrees counter clockwise such that it is reattached thereto. Further, the operator may then turn the operator's key 500 (in this case, counter clockwise) through 90 degrees from the controlled access position (as in Figure 1 7D) to the active position (as in Figure 1 7C). The operator's key 500 may then be removed.

Fourthly, and finally, a process for removing the "block" (bringing the possession out of force) will be discussed, assuming that all work within the possessed section (for example, maintenance work) is complete and appropriate authorisations have been received to permit the line to be unblocked and to give up the protection provided by the possession.

The Operator may begin the process by inserting operator's key 500 into the keyway 132 in the active position (as in Figure 17C) and then turning it through 90 degrees (in this case, anticlockwise) to the install position (as in Figure 17B). This operation reconnects the track circuit so that it may operate normally. In the install position, the operator's key 500 is retained within the keyway 132. The PLB may then be turned through 90 degrees and removed from the device. The Operator may then rotate the operator's key 500 through another 90 degrees (anticlockwise) from the install position (as in Figure 1 7B) to the inactive position (as in Figure 1 7A). The operator's key 500 may then be removed from the keyway 132. At this point, the Operator may contact the Signaller to confirm that the track circuit has been re-energised. In response, the Signaller may confirm that the track circuit has been re-energised and is operating normally, and make an entry in the Train Register Book or Occurrence Log accordingly.

Figures 19 and 20 are photographs of part or all of apparatus 1000 installed on a section of railway track. Those parts previously mentioned have been numbered the same. Signalling means 200 comprises a "STOP" sign 240, and a warning light 220.

A number of benefits and advantages of apparatus 1000, and of other embodiments of the present invention, may be summarised as follows: a. the apparatus may be permanently installed making it always available to appropriately trained personnel holding the correct operator's key; b. track workers (and other personnel) and worksites may be protected with the same level of integrity as trains and passengers, i.e. by making use of the track signalling system; c. the permanent fixed location of the apparatus may ensure protection is correctly afforded to work groups of personnel at such a location(s); d. the protection afforded by the embodiments may be taken, and given up, speedily; e. the apparatus may support both "T2" and "T3" possessions; f. the embodiments may contribute to reducing the number of "possession irregularities" attributable to possessions being deployed at the wrong location and/or or time.

Claims (53)

1. CLAIMS: 1. Electrical-track-circuit apparatus for use in a system for

   taking possession of a signalling section of a railway track, the apparatus being adapted to be securely located in the vicinity of an electrical track circuit of said railway track, the apparatus comprising: switching means adapted to be incorporated into the electrical track circuit and being operable, after having been so incorporated, to controllably alter an operation of said track circuit as an indication of an intention to take possession of said signalling section of the railway track.
2. 2. Apparatus according to claim 1, wherein said switching means is adapted to be permanently incorporated into said track circuit.
3. 3. Apparatus according to claim 1 or 2, wherein said track circuit is an existing operational track circuit, and wherein the switching means is adapted to be retro-fitted into the track circuit.
4. 4. Apparatus according to any preceding claim, further comprising: actuating means operable, when the apparatus is in use, to actuate the switching means so as to cause the switching means to bring about said alteration in operation of the track circuit.
5. 5. Apparatus according to claim 4, wherein said actuating means is operable to mechanically actuate said switching means.
6. 6. Apparatus according to claim 4 or 5, wherein the actuating means comprises identification means operable to positively identify a predetermined symbol of authorisation to use the apparatus.
7. 7. Apparatus according to claim 6, wherein said identification means is operable: to receive a candidate symbol of authorisation from a prospective user of the apparatus; if the received candidate symbol is the predetermined symbol, to positively identify the received candidate symbol as being the predetermined symbol; and following such positive identification, to allow the prospective user to operate said actuating means.
8. 8. Apparatus according to claim 7, wherein the identification means is further operable: if the received candidate symbol is a symbol other than the predetermined symbol, to hinder or prevent the prospective user from operating said actuating means.
9. 9. Apparatus according to any one of claims 6 to 8, wherein said identification means comprises a keyed interlock, and wherein said predetermined symbol of authorisation comprises a key capable of operating the keyed interlock.
10. 10. Apparatus according to claim 9, wherein said key may be inserted into a keyway of the keyed interlock, and wherein the apparatus is capable of temporarily retaining the key in such an inserted position.
11. 11. Apparatus according to any preceding claim, wherein said switching means comprises a switch.
12. 12. Apparatus according to any preceding claim, wherein said switching means comprises a plurality of switches.
13. 13. Apparatus according to claim 12 when read as appended to claim 4, wherein said actuating means is capable of operating said plurality of switches simultaneously.
14. 14. Apparatus according to claim 11, 12, or 13, wherein the or each of said switches has a closed and an open setting, and wherein the or each of said switches is adapted to be fitted in series along a current path of the track circuit such that, when one or more of said switches are operated such that they change setting from the closed setting to the open setting, one or more open circuits are created in said track circuit as the indication of the intention to take possession of said signalling section of the railway track.
15. 15. Apparatus according to claim 14, wherein said one or more open circuits serve, when the apparatus is in use, to prevent any current from flowing through said track circuit.
16. 16. Apparatus according to any preceding claim, further comprising: signalling means operable to indicate that the operation of said track circuit has been so altered.
17. 17. Apparatus according to claim 16 when read as appended to claim 4, wherein said actuating means is operable, when the apparatus is in use, to control the operation of said signalling means.
18. 18. Apparatus according to claim 16 or 17, wherein said signalling means is operable to visually indicate that the operation of said track circuit has been so altered.
19. 19. Apparatus according to any one of claims 16 to 18, wherein said signalling means comprises a light operable to illuminate so as to indicate that the operation of said track circuit has been so altered.
20. 20. Apparatus according to any one of claims 16 to 19, wherein said signalling means comprises a placard having a surface decoration thereon.
21. 21. Apparatus according to any one of claims 16 to 20, wherein said signalling means is operable to aurally indicate that the operation of said track circuit has been so altered.
22. 22. Apparatus according to any one of claims 16 to 21, wherein said signalling means comprises a loudspeaker operable to generate a sound so as to indicate that the operation of said track circuit has been so altered.
23. 23. Apparatus according to any one of claims 16 to 22, wherein said signalling means is capable of being located on the apparatus in first and second different orientations relative to the apparatus.
24. 24. Apparatus according to claim 23, wherein said first orientation is for indicating that the operation of said track circuit has been so altered, and wherein said second orientation is for indicating that the operation of said track circuit has not been so altered.
25. 25. Apparatus according to claim 23 or 24 when read as appended to claim 17, wherein said actuating means is operable to move said signalling means between said first and second orientations.
26. 26. Apparatus according to any one of claims 16 to 24, wherein said signalling means is detachable from the apparatus.
27. 27. Apparatus according to claim 26 when read as appended to claim 17, wherein said actuating means is operable to enable a connection between said signalling means and the apparatus to be released so as to enable said signalling means to be detached therefrom.
28. 28. Apparatus according to claim 27, wherein said actuating means is operable to enable said connection to be closed so as to attach said signalling means to the apparatus.
29. 29. Apparatus according to any preceding claim, being configurable into a plurality of modes of operation comprising: a first mode in which said switching means is in an inactive state in which, when the apparatus is in use, said alteration in configuration of the track circuit has not been made; and a second mode in which said switching means is in an active state in which, when the apparatus is in use, said alteration in configuration of the track circuit has been made.
30. 30. Apparatus according to claim 29 when read as appended to claim 28, wherein, in said first mode, said signalling means may be detached from, or positioned for attachment to, the apparatus, and wherein said plurality of modes of operation further comprises: a third mode in which said switching means is in said inactive state, and in which said connection means has been closed such that said signalling means has been attached to the apparatus.
31. 31. Apparatus according to claim 29 or 30 when read as appended to claim 28, wherein, in said second mode, said signalling means is attached to the apparatus and, when the apparatus is in use, configured to indicate that the operation of said track circuit has been so altered.
32. 32. Apparatus according to any one of claims 29 to 31 when read as appended to claim 28, wherein said plurality of modes of operation further comprises: a fourth mode in which said switching means is in said active state, and in which said signalling means may be detached from the apparatus.
33. 33. Apparatus according to any one of claims 29 to 32 when read as appended to claim 4, wherein the actuating means is operable to configure the apparatus into any of said modes.
34. 34. Apparatus according to any preceding claim, further comprising: a housing portion having said switching means located therein.
35. 35. Apparatus according to claim 34, wherein said housing portion also has said actuating means located therein.
36. 36. Apparatus according to claim 34 or 35, wherein said housing portion is suitable for being mounted between running rails of said railway track such that a train may pass along said running rails over the housing portion without making contact therewith.
37. 37. A system for taking possession of a signalling section of a railway track, the system comprising: switching means adapted to be incorporated into an electrical track circuit of said railway track and being operable to alter an operation of said track circuit as an indication of an intention to take possession of said signalling section of the railway track; track-circuit monitoring means operable to detect said alteration in operation of the track circuit; and signalling-equipment controlling means operable, in dependence on an output of said track-circuit monitoring means, to control an operation of signalling equipment so as to indicate that said possession has been taken.
38. 38. Train-signalling apparatus for use in a system for taking possession of a signalling section of a railway track, the apparatus being adapted to be securely located in the vicinity of said railway track, the apparatus comprising: signalling means operable to indicate that a possession of said signalling section is currently in force; and actuating means operable, when the apparatus is in use, to mechanically actuate the signalling means so as to cause the signalling means to change state from a first state, for indicating that said possession is not currently in force, to a second state, for indicating that said possession is currently in force.
39. 39. Apparatus according to claim 38, wherein said signalling means is operable to visually indicate that said possession is currently in force.
40. 40. Apparatus according to claim 38 or 39, wherein said signalling means comprises a light operable to illuminate so as to indicate that said possession is currently in force.
41. 41. Apparatus according to any one of claims 38 to 40, wherein said signalling means comprises a placard having a surface decoration thereon.
42. 42. Apparatus according to any one of claims 38 to 41, wherein said signalling means is operable to aurally indicate that said possession is currently in force.
43. 43. Apparatus according to any one of claims 38 to 42, wherein, in said first state, the signalling means is located on the apparatus in a first orientation relative thereto, and wherein, in said second state, the signalling means is located on the apparatus in a second orientation relative thereto different to said first orientation.
44. 44. Apparatus according to any one of claims 38 to 43, wherein said signalling means is detachable from the apparatus.
45. 45. Apparatus according to claim 44, wherein said actuating means is operable to enable a connection between said signalling means and the apparatus to be released so as to enable said signalling means to be detached therefrom.
46. 46. Apparatus according to claim 45, wherein said actuating means is operable to enable connection to be closed so as to attach said signalling means to the apparatus.
47. 47. Apparatus according to any one of claims 38 to 46, being adapted to be securely located in the vicinity of an electrical track circuit of said railway track, the apparatus further comprising: switching means adapted to be incorporated into the electrical track circuit and being operable, after having been so incorporated, to controllably alter a configuration of said track circuit as an indication of an intention to take possession of said signalling section of the railway track.
48. 48. Apparatus according claim 47, wherein said actuating means is operable, when the apparatus is in use, to actuate the switching means so as to cause the switching means to bring about said alteration in operation of the track circuit.
49. 49. An electrical track circuit comprising the apparatus according to any one of claims 1 to 36, 47, and 48.
50. 50. Electrical-track-circuit apparatus as hereinbefore described with reference to the accompanying Figures 3 to 20.
51. 51. A system as hereinbefore described with reference to the accompanying figures 3to20.
52. 52. Train-signalling apparatus as hereinbefore described with reference to the accompanying figures 3 to 20.
53. 53. An electrical track circuit comprising electrical-track-circuit apparatus and/or train- signalling apparatus as hereinbefore described with reference to the accompanying figures 3 to 20.