GB2416420A - Adjustment system for railway points according to input received from a position detection device - Google Patents

Abstract

A railway points control system has a stretcher bar lock rod and a lock blade connected to the lock rod. The lock blade has first 19 and second 15 components. A first adjustable coupling 16 is provided between the first component of the lock blade and the stretcher bar lock rod; and a second adjustable coupling 20 is provided between the first and second components of the lock blade. The first and second components of the lock blade are each provided with a position detection recess (17, 21 Fig.5), each for the detection of one points position, and the system further comprises a position detector 18 for engagement with the position detection recesses. The invention allows essential checks and adjustments to be carried out on railway point machines from a position of safety separated from trains. It also allows adjustments to be made more easily, more accurately and more often without creating delays to the railway.

Description

24 1 6420 Adiustment System for Railway Points This invention relates to

the monitoring and control of railway points.

A train is typically directed from one track to another using a set of points, commonly called a 'switch' in railway parlance, which comprises a pair of movable switch blades held apart by stretcher bars. Usually each switch has its own point machine, set to drive its blades from the 'Nonnal Position' to the 'Reverse Position' or vice versa as demanded by the signalman.

it is an absolute safety requirement that, at the end of each operation, the switch is proven to have moved sufficiently to bring the appropriate switch blade to within a controlled clearance of the stock rail and to have locked it against movement before the train is allowed to pass. This clearance can change over time due to movement of the stock rail, possibly as a result of wear, track disturbance and temperature changes, and the point machine is so designed that if the clearance moves outside the allowable limits, the machine dock wild jam and cause the switch to operate in a fail-safe mode. Consequently, the clearance needs to be regularly checked by railway maintenance crew to maintain the r pliability of the switch and avoid excessive train delays.

At present, maintaining correct lock clearances is a manual process that can delay trains itself. It also exposes personnel to risk from trains.

According to the invention, there is provided a railway points control system comprising: a stretcher bar lock rod; a lock blade connected to the lock rod, the lock blade comprising first and second components; a first adjustable coupling between the first component of the lock blade and the stretcher bar lock rod; and a second adjustable coupling between the first and second components of the lock blade, wherein the first and second components of the lock blade are each provided with a position detection recess, each for the detection of one points position, and wherein the system further comprises a position detector for engagement with the position detection recesses.

The invention can be described as an 'Active Lock Detection and Adjustment System'. Its purpose is to allow essential checks and adjustments to be carried out on railway point machines from a position of safety separated from trains. It also allows adjustments to be made more easily, more accurately and more often without creating delays to the railway.

Finally it offers a means of making the machine itself carry out a selfcheck and carry out any adjustments automatically.

The first adjustable coupling may comprise a drivable drop lug and the second adjustable coupling may comprise a drivable blade nut. A drive unit is preferably provided for adjusting the first and second adjustable couplings, and they may be electrically, hydraulically or pneumatically actuated. They may additionally be manually mechanically actuated. The first and second adjustable couplings may each comprise a threaded sleeve, restrained from rotation and engaged by a nut driven via a worm and gearwheel from a source of power.

A backside control unit may receive the position detector information. The position detector may comprise, for each component of the lock blade, a pair of microswitches for detecting the position of the respective position detector recess.

A third adjustable coupling may be provided at one end of the stretcher bar for adjustment of the position of the point machine drive with respect to the stretcher bar.

An example of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure l shows a known points arrangement; Figure 2 shows a system of the invention; Figure 3 shows in more detail one drive coupling used in the system of Figure 2; Figure 4 shows in more detail another drive coupling used in the system of Figure 2; and Figure 5 shows in more detail the detection arrangement used in the system of Figure 2.

On a standard railway the trains are directed from one track to another using a set of points, whose general arrangement is as shown in Figure 1. Such points typically comprise a pair of movable rails 1, located within the stock rails 2 on which the trains nonnally run. The movable rails are typically located and held apart by a set of meta] ties and brackets called stretcher bars 3. Normally each of the movable rails is machined to gradually taper down to a narrow end tip 4 to provide flexibility of movement and ensure that there is no lateral step for the wheels to negotiate as the train is guided into its new path. Because of this, the movable rails I are commonly called 'switch blades' and an individual set of points is commonly referred to as a 'switch'.

Typically each switch is driven by its own 'point machine' 5, whose primary function is to move the switch blades from the 'Normal Position' (Figure la) to the 'Reverse Position' (Figure 1 b) or vice versa on demand from the signalman. There are different types of point machine in use, but in most cases they are designed to be located next to the track on extended sleepers, called 'bearers' 6 and they drive, lock and confirm the correct position of the switch via metal rods that run under the nearest stock rail and connect to stretcher bars at or near the switch tips.

Two of the rods running between the point machine and the switch are electrical detection rods 7. These are connected between the point machine and each of the switch tips and they operate switches within each point machine that confirm that both switch tips have travelled the correct distance. The third rod is of heavier section and is called the lock rod 8. The lock rod is connected between the switch tip stretcher bar and the lock slide assembly 9 of the point machine. As the switch moves from one position to the other the lock rod pushes and pulls the lock slide through the machine. The lock slide comprises two separate rectangular section bars called 'lock blades' 10a, lob, laid parallel to one another. Each lock blade has two rectangular cut-outs 11. The positional relationship between each of the lock blades, as well as the position of the whole lock slide assembly with respect to the switch blades is normally adjusted using the nuts at 12 and 13 respectively. In this way, the position of each of the lock slide cut-outs is arranged to correspond with the machine stopping in its correct 'Normal' and 'Reverse' positions. At each of these positions the machine automatically drives a rectangular locking pin, called a lock dog' 14 through the corresponding cut-out to ensure that the switch cannot move under the wheels of the train. s

It is an absolute requirement for railway safety that the point machine is proven to have driven the steering switch tip into close proximity with its stock rail and to have locked the switch against movement before the train is allowed to pass over the switch. The gap between the switch tip and its adjacent stock rail after point machine movement normally needs to be maintained between 1.5mm and 3mm at all times. This gap can change with time due to stock raid movement as a result of wear, track disturbance and temperature change. The point machine mechanical lock clearances are especially chosen so that if tip clearances move outside the allowable limits the machine will jam by virtue of it not being able to drive the dock dog through the dock slide cut-out. In such cases the machine will fad] to detect full movement, the route will not be set and the signals will remain at red, causing a delay to the train. This is a fail-safe design. Consequently, to maintain the reliability of the switch and avoid excessive train delays the tip gap needs to be checked periodically by railway maintenance personnel. Cunrently, checks must to be performed manually by inserting shims between the switch tips and the stock rails and, it necessary, the lock slide has to be adjusted by turning nuts with large spanners. The current necessity for maintenance personnel to actually visit the switch for checking and carrying out adjustments is undesirable because it demands that a temporary possession be taken out on the line concerned and exposes personnel to risk from trains on open lines when crossing tracks and walking to the machine.

The invention provides a means of carrying out essential switch dock checks and adjustments more easily, more accurately and more often without causing train delays and from a position of safety adjacent to the railway. Ultimately, it would provide the means whereby the point machine itself could canry out any checks and adj ustments automatically and immediately they are needed, merely informing the maintenance team when the process had been completed.

The invention in its generic form is a 'Active Lock Detection and Adjustment System', which comprises replacement components that wild allow a standard point machine, i.e. One needing manua] checking and adjustment, to be changed into a machine that diagnoses its own state of lock clearance and can actively initiate its own adjustment. In its basic form the system would allow the machine to automatically raise an alarm to the maintenance team if it needs adjusting and would provide motorised drives and adjusting devices that allow adjustment to be carried out under manual control but remotely and without spanners, using a Trackside Control Unit. Ultimately the system could be configured to allow the machine to adjust itself automatically within specified limits, only raising an alarm if these limits would otherwise be exceeded.

Although the concept of active dock detection and adjustment could pertain to all types of point machine, the general arrangement described below pertains to devices such as the GEC/Alstom Type HW point machine and the Westinghouse Type 63 point machine, ] 5 which are installed on extended bearers.

Figure 2 shows a system of the invention, described specifically for the GEC/Alstom Type HW machine. For such machines, the system of the invention comprises the following basic elements: a) An Actively Adjustable Fixed Blade, fitted with a Drivable Drop Lug b) An Actively Adjustable Movable Blade, fitted with a Drivable Blade Nut c) Optionally, an Actively Adjustable Drive Lug d) A dock blade True Position Detector (TPD) e) A Remote Drive Unit (RDU) f) Flexible mechanical drives g) A Trackside Contro] Unit (TCU) h) A RDU to TCU umbilical cable The Actively Adjustable Fixed Blade 15 is a straightforward replacement for a standard fixed blade lob of Figure 1. It differs frown the standard item in that it is fitted with a Drivable Drop Lug 16 and has an additional shadow groove 21 machined across its upper surface positioned an accurate distance from its narrower cut out 11. The Drivable Drop Lug 16 is a direct replacement for the standard drop lug and serves the same purpose, in that it firmly locates the lock rod. However, it houses an apparatus which, when driven via a flexible rotary drive of known design, causes an adjustment of the relationship between the lock rod and the lock slide assembly in the longitudinal direction. A preferred design of Drivable Drop Lug is described subsequently.

The additional detent groove 21 is the means by which True Position Detector (or TPD) 18 can detect whether the machine is in need of adjustment. The TPD is a device for sensing whether the point machine is moving the correct distance to allow the lock dog to pass easily through the appropriate lock slide cut-out. It would be preferable that the TPD functions according to simple and familiar mechanical logic, reflecting the current method used for detecting correct machine operation, which employs roller limit switches of known design activated by strategically placed detent grooves in the detector slides. In the first instance the TPD needs to be capable of retrofitting to a standard point machine without disrupting its safe operation. A preferred design of TPD is described subsequently.

In a similar way to the Actively Adjustable Fixed Blade, the Actively Adjustable Movable Blade 19 is a straightforward replacement for the standard movable blade lOa of Figure 1 but has been modified in design to fit the Drivable Blade Nut 20. The Drivable Blade Nut replaces the forged 'crook' in the end of the standard movable blade and serves the same purpose, in that it firmly locates the Actively Adjustable Movable Blade with respect to the Actively Adjustable Fixed Blade. In common with the Drivable Drop Lug, the Drivable Blade Nut houses an apparatus which, when driven via a flexible rotary drive causes an adjustment of the relationship between the Actively Adjustable Movable Blade and the Actively Adjustable Fixed Blade in the longitudinal direction. A preferred detailed design of Drivable Blade Nut is also described subsequently.

For the same reason as for the Actively Adjustable Fixed Blade it also has an additional groove machined across its upper surface for use by the TPD.

Optionally, it may be desirable in some cases to be able to adjust the relationship between tle forces imparted by the point machine to the switch blades when in the Normal arid Reverse positions, to make them more equal. This could be achieved by fitting an Actively Adjustable Drive Lug 22 between the machine drive rod and the switch drive stretcher bar.

This functions by making small adjustments of the start and end positions of the switch drive. The mechanical construction of the Actively Adjustable Drive Lug is essentially identical to that of the Drivable Drop Lug described below.

The Remote Drive Unit, or RDU is mounted near to or directly on the point machine. It comprises a robust, weatherproof housing within which are located separate drive motors, power supplies and position sensors for the Drivable Drop Lug, the Drivable Blade Nut and, if fitted, the Adjustable Drive Lug. A mechanical flexible drives connects each of the individual adjusting devices to its motor located in the RDU. Power and control signals are fed to and from the RDU and the Trackside Control Unit via an umbilical cable of known design.

The Trackside Control Unit, or TCU is located in a place a safety (having the means of access sufficiently remote from trains to minimise risk to railway maintenance personnel) and consists of a robust lockable cabinet within which is an electrical control panel that can be used for carrying out a 'normal' adjustment of the point machine. A normal adjustment is one that is capable of being carried out within the mechanical stroke limitation of the Adjusting Devices. Any adjustments outside these limits would still need to be done manually as before.

The TCU senses and records the signals from the TPD at the end of each machine operation and if appropriate sends a warning or an alarms signal to the maintenance team to indicate that an adjustment is required. The signals can be sent using any standard method of telecommunications. After unlocking the TCU the maintainer can initiate an auto-adjust program or, if required, use electrical buttons to 'inch' the machine back into a state of correct adjustment.

The essential requirements for all the Adjusting Devices, i.e. the Drivable Drop Lug, the Drivable Blade Nut and the Actively Adjustable Drive Lug are as follows: a) it must not be capable of being back-driven by forces imposed via the lock rod b) it must be fail-safe and continue to allow manual adjustment as an alternative c) it must be capable of functioning in the railway environment of shock and vibration, dust and contamination and extremes of ambient conditions d) it must be at least as robust and reliable as the other components of the switch e) it must require little or no maintenance f) it should not contain electrical equipment, whose failure could create a track circuit safety hazard.

One preferred method of constructing a Drivable Drop Lug 16 is as shown in Figure 3.

l0 The device essentially consists of a Sleeve 27 fashioned with an external, square-section acme thread through which the lock rod 8 can be passed and fixed with ordinary nuts 28 in the normal fashion. Onto the sleeve is threaded a Nut 29 which has been manufactured to have Axial Thrust Faces 30 and an External Wheel Gear 31. The wheel gear is driven by a Worrn Gear 32 of known design; arranged in a standard worm and wheel configuration.

The sleeve is fitted with a Fork 33 at one end, which in turn is located by a Pin 34. The purpose of the fork is to stop the sleeve from rotating about its axis when the nut is rotated by the worm, thereby forcing the sleeve to move axially by an amount dictated by the pitch of the acme thread and carrying the lock rod with it. The worth 32 and nut 29 are located and protected within a Split Housing 35, the larger part 35a of which is formed to fit the end of the fixed blade 15 in a manner similar to that of a standard drop lug. The worth is rotated by a flexible mechanical drive 23 of known design that is threaded into the Housing Cap 35b. The flexible drive 23 is driven remotely from the RDU 24, which contains an appropriate electric motor and gearbox, also of known design.

One prefcn ed method of constructing a Drivable Blade Nut 20 is as shown in Figure 4. It can be seen that, apart from slightly smaller components, the basic construction and the principle of operation of the Drivable Blade Nut is essentially identical to those of the Drivable Drop Lug. In this case the larger part of the split housing 36 is conned into an Extension Arm 36a for the adjustable slide and the Drivable Blade Nut is driven through the housing cap 36b.

As previously stated, the optional Actively Adjustable Drive Lug would be essentially identical to the Drivable Drop Lug.

Figure 5 shows the principle of operation of the True Position Detector in its simplest fonm. Four micro-switches 37 of generally known design are located within a rugged, weather-proof housing 38 mounted above the lock slide and rigidly fixed with respect to the point machine chassis. Of the four micro-switches 37, one pair of facing switches is used to sense the 'Normal' position using the adjustable blade and the other pair of switches is used to sense the 'Reverse' position using the fixed blade. Specifically, micro- switches 37a and 37b are operated by detent groove 17, which has been accurately machined and precisely positioned a distance 'L' from the narrow cut-out in the fixed blade. Similarly, micro-switches 37c and 37d are operated by detent groove 21, which is the equivalent for the adjustable blade. . Figure 5b shows the lock slide assembly after the switch has moved to the 'Reverse' position and found its true central position, so that the fixed slide cut-out 11 is equispaced about the lock dog 14. In this state both micro-switches 37a and 37b are activated and no fault is detected by the TCU. In Figure 5a the lock slide assembly has come to rest a certain distance 'X' to the left, causing the roller of micro-switch 37b to remain lifted so that the switch contacts are not made. This combination of micro-switch states indicates that the switch tip cannot travel far enough and consequently there is an increased danger of the dock dog failing to engage in the cut-out. On the other hand, in Figure 5c the lock slide assembly has come to rest a distance 'X' to the right, this time causing micro-switch 37a to fail to activate. This combination indicates that the switch tip is tending to travel too far. Again there is a danger that the lock dog will fail to engage.

The TCU would provisionally record either or both of these conditions as impending alarm conditions. If either or both are found to persist sufficiently to indicate a trend, the TCU automatically sends an alarm signal to the maintenance team control room. The maintainer can then visit the backside TCU and fine-adjust the machine back to a correct operational state using the Drivable Drop Lug and Drivable Blade Nut and the positions of the micro switches as shown by lamps situated within the TPD.

It can be seen that the invention provides an Active Lock Detection and Adjustment System that can be attached to a railway point machine in order to detect and adjust the lock position from a remote place of safety using a mechanical or electromechanical contrivance which can fitted either on the basis of a retrofit, or as a in-life manufacturing design modification or as an integral part of a new design of point machine.

The invention allows a point machine lock to be fine-adjusted by indirect and non-manual means, that is, without the necessity to approach the machine and use spanners, whilst at the same time retaining the option to do so.

A mechanism for fine adjustment of linear position of the adjustable couplings is designed to be incapable of being back-driven by external forces imparted through the stretchers and rods of the railway switch.

The Trackside Control Unit that can interpret the status of the True Position Detector after each machine operation and on a regular periodic basis, make logical decisions and where appropriate can raise both advisory and urgent alarms via any known telecommunications method. The system can display its operational and alarm status both externally and internally to provide the maintenance technician with the controls to readjust the point machine lock from a remote position. This could be from a position of safety backside, from the local maintenance depot, from the loca] signal box or from a remote control room.

The device can be programmed to run an auto-adjust algorithm that carries out an optimised, automatic adjustment of the point machine on the instigation of the maintenance technician and confirm that this has been competed.

Claims (10)

1. A railway points control system comprising: a stretcher bar lock rod; a lock blade connected to the lock rod, the lock blade comprising first and second components; a first adjustable coupling between the first component of the lock blade and the stretcher bar lock rod; and a second adjustable coupling between the first and second components of the lock blade, wherein the first and second components of the lock blade are each provided with a position detection recess, each for the detection of one points position, and wherein the system further comprises a position detector for engagement with the position detection recesses.

2. A system as claimed in claim 1, wherein the first adjustable coupling comprises a drivable drop lug.

3. A system as claimed in claim 1 or 2, wherein the second adjustable coupling comprises a drivable blade nut.

4. A system as claimed in any preceding claim, further comprising a drive unit for adjusting the first and second adjustable couplings.

5. A system as claimed in any preceding claim, wherein the first and second adjustable couplings are electrically actuated.

6. A system as claimed in any one of claims I to 4, wherein the first and second adjustable couplings are hydraulically actuated.

7. A system as claimed in claim 5 or 6, wherein the first and second adjustable couplings can additionally be manually mechanically actuated.

8. A system as claimed in any preceding claim, further comprising a backside control unit which receives the position detector information.

9. A system as claimed in any preceding claim, wherein the first and second adjustable couplings each comprise a threaded sleeve, restrained from rotation and engaged by a nut driven via a womb and gearwheel from a source of power.

10. A system as claimed in any preceding claim, wherein the position detector comprises, for each component of the lock blade, a pair of microswitches for detecting the position of the respective position detector recess.

] 1. A device as claimed in any preceding claim, further comprising a third adjustable coupling provided at one end of the stretcher bar for adjustment of the position of the point machine drive with respect to the stretcher bar.