GB2394773A - Reflector for use with an optical monitoring system - Google Patents

Abstract

A device for use with a monitoring system, such as a system for monitoring the level, cant and distance apart of adjacent railway tracks, comprises a housing 50, which in use, is attached to a structure to be monitored (eg. a rail) and a reflector 8 located within the housing. The reflector may comprise a retro-reflective material provided on a support such as a cylinder (figure 14) or a triangular prism (figure 15), and may include two adjacent strips of differently coloured reflective material. The support may be rotatable about a longitudinal axis A-A with respect to the housing, and a cover (62, figure 11) may be provided so as to protect the reflective material from debris. Also disclosed is the use of said device with a position monitoring system whereby said device provides data as to its position which may be measured and stored, and compared with subsequent data to check for position deviation of the device.

Description

A DEVICE FOR USE WITH A MONITORING SYSTEM

The present invention relates to a device for use with a monitoring system for monitoring a structure. Such a structure which may be section of railway track and 5 ancillary works that may be subject to deformation or disturbance.

When engineering works are being undertaken on or near a section of railway track it is important that all position data, such as the levels, cant and gauge of the track, is carefully monitored to check for deviations. At present this is carried out largely by 10 means of an engineering team on the tracks with measuring tools and levelling instruments. The teams usually operate in "red zone" conditions under the authority of a Controller of Site Safety (or COSS) accompanied by a number of certified advance train lookout personnel. The Pack measurements are obtained at least once per working day and can be read to indicate the level, cant and distance apart of adjacent tracks. This 15 routine proceeds throughout the length of a contract which is usually several months.

This is a very expensive and labour intensive process and requires personnel to work in potentially dangerous conditions.

An alternative to this method of obtaining track data is to use on-track machinery to 20 record measurements. This is even more expensive and more intrusive to normal railway operational use.

A further option is to use a remote monitoring system which utilises optoelectronic measuring instruments to sight retro-reflective targets which are stuck to the rail or 25 mounted on brackets attached at, or near, the rail. A remote monitoring system such as this offers benefits over the present methods. In particular, it allows measurements to be obtained more regularly during the day and even at night. However, there are still a number of limitations with the system. The retro-reflective targets are flat and are stuck, usually using glue, to the rail. In order to effectively sight the target the angle of 30 incidence between the monitoring apparatus and the target must not be greater than approximately 45 . This greatly limits the range and effectiveness of the remote monitoring system using flat targets stack to the rail.

-2 The present invention seeks to alleviate or reduce many of the limitations of traditional track monitoring systems.

S According to the present invention there is provided a device for use with a monitoring system, comprising a housing which, in use, may be attached to a structure to be monitored and a reflector located within the housing.

Preferably the reflector is provided on a support mounted within the housing. The 10 support may suitably be cylindrical or in the shape of a triangular prism with the reflector provided on an outer surface. The reflector preferably completely covers the outer surface of the support. When this is the case, the device presents a reflective surface which may be measured from any position.

15 It is preferred that the support is moveable with respect to the housing. More preferably, the support is rotatable within the housing, preferably about its longitudinal axis. When the device is mounted on a structure which is subjected to regular vibration, for example a rail forming a section of a railway track, the support may be free to rotate about its axis as the structure vibrates, for example as a result of vibrations caused by the passage of 20 trains. This action facilitates the shedding of dirt and debris from the from the reflector and also provides a clean face for observing the reflector.

Advantageously, the housing comprises two generallyparallel surfaces connected by an intermediate section with the support being longitudinally disposed between the two 25 parallel surfaces. The housing may suitably be in the form of a generally C-shaped member. The outer surface of the intermediate section is preferably provided with means for attaching tile device to the structure to be monitored. The outer surface of the 30 intermediate section may be provided with one half of a hook and loop fastening and the other half of the hook and loop fastening may be provided on the structure to be monitored. This enables the device to be releasably attached to the structure. The hook

and loop fastening is preferably"industrial strength". Other suitable methods of attaching the device to the structure may be used, for example, epoxy resin.

The housing may suitably further comprise a shield to shield at least a portion of the 5 reflector. The shield is preferablymoveable with respect to the remainder ofthe housing.

The shield is provided to protect the reflector from the environment, specifically debris which may otherwise obscure the reflector.

The reflectormay suitablybe in the form oftwo adjacent sections of differently coloured 10 reflective material. The adj acent coloured sections preferably extend around the support.

In use, when the device is attached to a structure, the join between the adjacent sections preferably defines a horizontal sight line.

The reflector is preferably provided as a retro-reflective material.

Preferably, the structure to be monitored comprises a rail forming a section of a railway track. The consistent positioning ofthe reflector, and consequently the device, on therail is important. In order to ensure that the device is accurately positioned the housing may suitably be profiled such that it conforms to the underside of the rail head. When the 20 device is to be used to monitor a rail it is preferred that the vertical axis of the support is designed to align with the running edge of the rail. This facilitates more accurate measurement of track geometry.

It is preferred that the monitoring system is a remote monitoring system.

According to a second aspect of the present invention there is provided a remote monitoring system for monitoring a structure comprising: one or more devices, each device comprising a housing and a reflector located within 30 the housing, the or each device being positioned at a location on the structure; a position measuring apparatus located at a fixed point remote from said devices; and

-4 position storing means, wherein, for the or each device, the position measuring apparatus is arranged to produce data corresponding to the position of the device and this data is stored in the position 5 storing means and compared with subsequent such data to check for position deviation of the device.

For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example, to the 10 accompanying drawings in which: Fig. I shows a plan view of a section of railway track; Fig. 2 shows a known device for mounting a reflector; Fig. 3 shows another known device for mounting a reflector; 15 Fig. 4 shows a sectional view of a known device and reflector mounted on a section of railway track; Fig. 5 shows a sectional view of a known bracket and reflector mounted on a section of railway track; Fig. 6 shows a sectional view of another known bracket and reflector mounted on 20 a section of railway track; Fig. 7 shows side view of the bracket of Fig. 6; Fig. 8 shows a sectional view of a known device and reflector mounted on a section of railway track; Fig. 9 shows a template for fixing a known device and reflector to a section of track; 25 Fig. 10 shows a first embodiment of a device for use with a monitoring system; Fig. 11 shows a second embodiment of a device for use with a monitoring system; Fig. I shows a plan view of a monitoring system set up to monitor a structure. The structure being monitored is a section of railway track 2. Position measuring apparatus 30 4 such as those supplied by Total Station Instruments is set up in a safe location away from the track 2. The position measuring apparatus 4 may be set up outside the railway "red zone" boundary providing it has an unobstructed view of the section of track to be

-5 monitored. Alternatively, the apparatus 4 could be set up on an over track bridge. The position should be carefully selected to ensure that no extraneous light emissions from the apparatus 4 could adversely effect the health and safety of train drivers or other railway personnel. In order to obtain accurate readings it is preferred that the position 5 measuring apparatus 4 is an electronic distance meter (EDM).

When maintenance or investigative work is being carried out on railway embankments 6 or other structures subject to de-stabilised formations it is essential that frequent engineering checks are performed before, during and after the work to ensure that the 10 level, cant and distance apart of adjacent tracks remains within the safety tolerances prescribed according to line speed.

Reflectors 8 are positioned at locations along the section oftrack 2 to be monitored. The reflectors 8 must all be visible from the position measuring apparatus 4. The reflectors 15 8 are fixed to each side of the rail 10 just below the rail head. The reflectors 8 are located at fixed intervals along the section oftrack. The reflectors 8 may be spaced apart by up to 5 metres. Preferably the reflectors 8 are spaced apart by a minimum of 3.3 metros. 20 The position measuring apparatus 4 is set up and its initial position is logged by means of triangulation with markers at fixed locations. This enables the system to be packed away at night and then set up again the following day without the loss of data. The initial position of each of the reflectors 8 is determined by the position measuring apparatus 4 and is stored in the position storing means. The position measuring 25 apparatus 4 will record all position data in its memory. The position of the reflectors 8 is then monitored periodically and the newly measured position data is compared with the initial position data to check for deviation. The position measuring apparatus 4 enables data comparison to be done in the field which allows prompt action to be taken.

Data can also be downloaded serially to a PC for entry into an Excel spreadsheet. The 30 system also allows for an alarm to be raised if excessive deviation is detected. This is a particular advantage over traditional track monitoring systems since it allows

-6 immediate action to be taken as opposed to the traditional system in which it is common for measurements to be taken only once a day.

Referring now to Figs. 2 and 3. These show two embodiments of known devices 12 5 used for mounting reflectors 8 to the rail 10 or other structure which may be the subject of deformation or disturbance.

A basic device 12 is shown in Fig. 2. It is a triangular prism made of a light-weight, durable plastics material. A variety of different triangular shaped prisms may be used 10 to obtain the required angle of incidence between the reflector 8 and the position measuring apparatus 4. The devices 12 are designed to be fixed indefinitely to the rail 10 or to be removable and used as a detachable, re-useable product. One face of the prism is provided with one half of an industrial hook and loop fastening (not shown).

The respective other half of the hook and loop fastening is attached to the rail 10 15 enabling the device 12 to be fixed in place. In order for the device 12 to remain in place the contact point on the rail 10 must be prepared by means of emery cloth, power tool or some other suitable method. Other suitable means may be used for fixing the device 12 in place, for example epoxy resin. A reflector (not shown) is attached to another one of the faces of the prism.

An alternative known device 12 Is shown in Fig. 3. The device 12 has the same basic triangular prism shape as the device 12 of Fig. 2 but is attached along one edge 14 to a planar rectangular member 16. The planar rectangular member 16 is made of the same resilient plastics material and the edge 14 along which the join acts as a resilient hinge.

25 The planar rectangular member 16 is provided with one half of the industrial hook and loop fastening 18 (both halves shown) and the reflector (not shown) is provided on a face 20 of the triangular prism adjacent the hinged edge 14 and opposite the hook and loop fastening 18. Adjusting means in the form of a screw headed bolt 22 engages with an opening in the face 23 of the triangular prism opposite the hinged edge 14. One 30 preferred screw headed bolt 22 is a 25mm long No. 6 stove bolt or a screw of similar size. The adjusting means enables the angle between the face 20 of the triangular prism bearing the reflector and the adjacent face of the rectangular member 16 to be

adjusted when the device 12 is fixed in place on the rail 10. The natural bias of the resilient hinge can be overcome by engaging the screw threaded bolt 22 with the triangular prism such that it projects out of a corresponding opening on the opposite face. When the device 12 is fixed the rail 10 this face will lie against the rail 10. When 5 the screw threaded bolt 22 projects out of this face it will bear against the rail 10 and force the body of the prism to pivot about the hinge thus decreasing the angle between the reflector bearing face 20 and the planar rectangular member 16. This adjustment can be used to alter the angle of incidence between the reflector and the beam from the position measuring apparatus 4. The angle of incidence is the angle 10 measured between the beam from the position measuring apparatus 4 and the surface normal to the reflector and for best results this angle should be 0 . However, this is not always possible and it is acceptable to have the angle of incidence between 0 and 45 but preferably not more than 30 .

15 Referring now to Figs. 4-8, these show four embodiments of known devices 12 for mounting reflectors 8 on a rail 10. Fig. 4 shows a device 12 such as is shown in Figs. 2 and 3 carrying a reflector 8, attached by industrial hook and loop tape] 8 to the underside of the rail head 24. In order to obtain accurate position data the device 12 needs to be attached at a fixed distance from the rail head 24 and this can be done by 20 means of the template shown in Fig. 9. For best results the angle of incidence between the reflector 8 and the beam from the position measuring apparatus 4 is preferably 0 and in most cases this can be achieved by adjustment of the screw threaded bolt 22 in the device 12 of Fig. 3 25 In Fig. 5 the device 12 carrying the reflector 8 is attached to a plastic or metal bracket 26 and fixed to the outside 28 of the rail head 24. The reflector is located level with the rail top 30 and is aligned as before to achieve the optimum angle of incidence. The device 12 used is of the type shown in Fig.2 since the adjusting means of the mounting in Fig.3 would not work. The bracket 26 is an L-shaped bracket attached to the outside 30 28 of the running rail 10 and must give the mounting 12 at least 30mm clearance to allow for power car wheel projection.

-8 Fgs.6 and 7 show a third embodiment of a reflector and device 12. In thi s embodiment the reflector 8 and device 12 are attached to the top of a frame bracket 32. This bracket 32 is secured by being entrapped between the spandrel clips 34 of the rail and sleeper 36. Holes 38 are provided in the bracket 32 which enable a user to insert a tommy bar 5 and twist the bracket 32 in order to accurately align the reflector 8 to the line of sight of the position measuring apparatus 4. This embodiment is only used when visibility to the embodiments of Figs. 6 and 7 is limited. It is used only for height monitoring in subsequent calculation as it has no consistent offset measurement from the running edge oftherail]O. In Fig. 8 the device 12 carrying the reflector 8 is mounted horizontally on the bottom flange 48 of the rail 10. As before, adjustment can be made to the device 12 in order to facilitate overhead observation by the position measuring apparatus 4. Such a configuration may be useful where an over track bridge provides the most suitable 15 observation point. The consistency ofthepositioningrelative to the running edge ofthe rail 10 can be controlled by simple measurement in each case.

Fig. 9 shows a template 40 which can be used to align the device 12 when it is fixed below the rail head 24 as shown in Fig.4. In order to obtain accurate position data it is 20 important that the device 12, and therefore the retro-reflective prism, is positioned at a known distance from the rail head 24. The template 40 is generally "C" shaped and has a first portion 42 which, in use, lies along the top surface ofthe rail head 24. A second portion 44 of the template 40 is perpendicular to the first portion 42 and, in use, lies along the outside 28 of the rail head 24 and extends below the rail head 24. A third 25 portion 46 of the template 40 is parallel to the first portion 42 and extends under the rail head 24. The bottom of the device 12 is lined up with the third portion 46 of the template 40 and fixed to the underside of the rail head 24.

Fig. 10 shows a first embodiment of a device 12 comprising a reflector 8 according to 30 the present invention for use with a monitoring system. The devicel2 is made of a suitable plastics material and may conveniently be formed by vacuum moulding.

Alternatively, the device 12 may made of metal. The reflector 8 is in the form of a

suitable retro-reflective matenal. The Reflexite TM material is particularly recommended as the retro-reflective material. In an alternative embodiment the reflectors are not retro-reflective material, rather they are plastic markers of a colour lighter than "Kodak grey" which reflect the laser light and enable the position to be 5 determined. In this case the invention the position measuring apparatus 4 is a pulse laser or DR technology such as the type produced by Trimble. The range and accuracy is slightly less than that achieved when using retro- reflective material but in some situations it can prove to be more effective.

10 The device 12 is a two piece construction comprising a housing 50 and a rotatable portion 52 mounted within the housing 50. The housing 50 is generally C-shaped having top and bottom parallel sections 54, 56 connected by an intermediate section 58. The intermediate section 58 is provided with one half of a hook and loop fastening (not shown) and the corresponding half of the hook and loop fastening is attached to the rail.

15 In this manner the device 12 can be releasably attached to the rail. The rotatable portion 52 of the device 12 is generally cylindrical in shape. The rotatable portion 52 has a general ly cylindrical body from which a section has been cut away. The cut away section is in the form of a planar surface 60 which lies along the centre line of the cylinder and is perpendicular to the top and bottom sections 54, 56 of the cylinder. The retro 20 reflective material 8 is fixed in place on the planar surface 60 such that the centre of the retro-reflective material 8 is at the centre of the planar surface 60. This ensures that the position of the centre of the retro- reflective material 8 is always the same even when the r otatable portion 52 is rotated.

25 One end of the rotatable portion 52 is attached to the top parallel section 54 of the housing 50 such that the cylinder is able to rotate about its longitudinal axis (A-A). The rotatable portion 52 may be attached to the housing 50 by means of a rivet (not shown) or any other suitable anchoring means which will allow the rotatable portion 52 to freely rotate. Alternatively, the rotatable portion 52 may be attached to the housing 50 at the 30 top and bottom sections 54,56. Since the position ofthe retro-reflective material 8 must remain constant whilst the measurements are being taken, the torque required to rotate the rotatable portion 52 about its axis is sufficient to ensure that once the position has

-lo- been set it should not be accidentally moved, for example by wind or debris. However, the required torque should be set at a level such that the rotatable portion 52 can be adjusted by hand. In an alternative embodiment, the required torque may be set at a higher level such that a specialist tool is required for adjustment.

In a further embodiment of the device 12 shown in Fig. 10, rather than being freely rotatable, the rotatable portion 52 maybe fullyremovable from the housing 50. This will allow the position to be adjusted and then rotatable portion 52 may then be re-attached.

This may be done by any suitable means such as a snap fit attachment between the 10 rotatable portion 52 and the housing 50.

Fig. l l shows a second embodiment of a device 12 according to the present invention.

The general construction of the device 12 is the same as the mount shown in Fig. 10 with the addition of a shield portion 62. The shield portion 62 is provided to protect the 15 retro-reflective material 8 from dirt and debris. The shield 62 is in the form of a rectangular member of approximately equal size to the intermediate section 58 of the housing 50. The shield 62 may suitably be made of a clear plastics material such that the retro-reflective material 8 can be viewed at all times. The shield 62 fits into rebates (not shown) in the top and bottom sections 54, 56 of the housing 50 and its position may be 20 adjusted by sliding it in the rebates. Although the shield 62 is provided to protect the retroreflective material 8 it is important that it does not obscure the view of the position measuring apparatus 4. The shield 62 mayconvenientlybe removed from the mount and cleaned. Alternative forms of shield will be readily apparent.

25 Fig.12 shows a view of a further embodiment of a housing 50 for a device 12 according to the present invention. The housing 50 is generally similar in shape to the housing 50 in Fig. 11, having top and bottom generally parallel sections 54, 56 connected by an intermediate section 58. The top section 54 of the housing 50 is contoured to conform to the profile of the underside of the rail head. This ensures that the device will be 30 accurately positioned in use.

-I 1 A ferrule 64 is provided extending upwardly from the bottom section 56 of the housing 50. The ferrule 64 is cylindrical and has a diameter slightly smaller than that of the cylindrical support 66 which is mounted on it in use (See Fig. 14). The ferrule 64 is positioned in the housing 50 such that when the device] 2 is mounted on the underside 5 ofthe rail head the vertical axis ofthe ferrule 64, and consequently/hat ofthe cylindrical support 66, is aligned with the running edge of the rail.

A lip 68 is provided on the top and bottom sections 54,56 for engagement with a shield as described in relation to Fig. 11.

Fig. 13 shows a view of a cylindrical support 66 which is used in conjunction with the housing 50 of Fig. 12. The outer surface of the cylinder 66 is covered with retro reflective material 8. The top half 66a of the cylinder 66 is covered with a differently coloured retroreflective material to the bottom half 66b, for example, the top half 66a 15 may be a silver coloured retro-reflective material and the bottom half 66b may be a gold coloured retro-reflective material. This produces a distinct line around the centre of the cylinder 66, mid-way between the top and bottom, which can be used as a horizontal sight line for the monitoring apparatus 4. On sighting the device the surveyor must optically bisect the cylindrical support 66 both horizontally and vertically. This enables 20 the axial coordinates of the device to be obtained. Alternatively, a black band may be provided around the mid- point of the cylinder 66 which will serve a similar purpose.

Figs. 14 shows the housing 50 of Fig. 12 in conjunction with the support 66 of Fig. 13.

The cylindrical support 66 is located on the ferrule 64 and, unlike the device 12 of Figs. 25 10 and 11, is free to rotate about its vertical axis. This rotation may be caused by vibrations created by the passage of trains on the track. This action facilitates the shedding of any dirt and debris which may have accumulated on the retro-reflective material 8 and presents a clean face for observing the reflector.

30 Fig. 15 shows a further embodiment of the device 12 in which the support 66 is in the form of a triangular prism which is free to rotate within the housing 50 about its vertical axis B-B.

-12 Although the remote monitoring system has been described with reference to the monitoring of a section of railway track 2 it may suitably be used to monitor a variety of structures. It is particularly suitable for monitoring structures in which obstruction of the observation angle of the target makes it difficult or impossible to sight with single 5 aspect targets. The 360 degree aspect of the cylinder enables three dimensional coordinates of its centre to be obtained from any instrument position around the target.

It is also advantageous where safety is important since it enables results to be obtained by a single operator from a safe distance.

10 One example of a further use for the remote monitoring system according to the present invention is in emergency crane operations. Structures which have been involved in accidents can sometimes be in a precarious state and it is quite common for police and the emergency services to restrict access to such structures. However, it is also necessary to obtain the precise positions of the wreckage for the purposes of lifting, rescue 15 operations and crash investigations. Traditionally a surveyor would have to wait to obtain clearance and then clamber over wreckage recording measurements. With the present invention all that is required is for someone to place the reflectors on the structure in question and the surveyor can obtain accurate position data from a safe distance. The remote monitoring apparatus may also be used in other surveying and monitoring applications. For example, the present invention may have applications in hydrographical surveying, flood defence monitoring, subsidence and seismic activity monitoring and as a tool for monitoring erosion. Upon reading the description of the

25 remote monitoring system in relation to the monitoring of a section of railway track it will be understood by someone of reasonable skill how the system may be used for the remote monitoring of other suitable structures.

Claims (18)

-13 CLAIMS

1. A device for use with a monitoring system, comprising a housing which, in use, may be attached to a structure to be monitored and a reflector located within the housing.

2. A device according to claim 1, wherein the reflector is provided on a support mounted within the housing.

3. A device according to claim 2, wherein the support is a cylinder with the reflector 10 provided on an outer surface thereof.

4. A device according to claim 2, wherein the support is a triangular prism with the reflector provided on an outer surface.

15

5. A device according to any one of claims 2 - 4, wherein the support is moveable with respect to the housing.

6. A device according to claim 5, wherein the support is rotatable within the housing.

20

7. A device according to claim 6, wherein the support is rotatable about a longitudinal axis.

8. A device according to any one of claims 2 7, wherein the housing comprises two generally parallel surfaces connected by an intermediate section with the support being 25 longitudinally disposed between the two parallel surfaces.

9. A device according to claim 8, wherein the outer surface of the intermediate section is provided with means for attaching the device to the structure to be monitored.

30

10. A device according to claim 9, wherein the outer surface ofthe intennedate section is provided with one half of a hook and loop fastening and the other half of the hook and loop fastening is provided on the structure to be monitored.

-14

1 1. A device according to any one of claims 8 - 10, wherein the housing further comprises a shield to shield at least a portion of the reflector.

12. A device according to claim 11, wherein the shield is moveable with respect 5 to the remainder of the housing.

13. A device according to any one of claims 2 - 12, wherein the reflector is in the form of two adjacent strips of differently coloured reflective material.

10

14. A device according to any preceding claim, wherein the reflector is provided as a retro-reflective material.

15. A device according to any preceding claim, wherein the structure to be monitored comprises a rail forming a section of a railway track.

16. A device according to claim 14, wherein the housing is profiled such that it conforms the underside of the rail head.

17. A device according to any preceding claim, wherein the monitoring system 20 is a remote monitoring system.

18. A remote monitoring system for monitoring a structure comprising: one or more devices, each device comprising a housing and a reflector located within 25 the housing, the or each device being positioned at a location on the structure; a position measuring apparatus located at a fixed point remote from said devices; and position storing means, wherein, for the or each device, the position measuring apparatus is arranged to produce data corresponding to the position of the device and this data is stored in the position

-15 storing means and compared with subsequent such data to check for position deviation of the device.