WO2001056859A1

WO2001056859A1 - Attachment means for a signalling device and method of identification

Info

Publication number: WO2001056859A1
Application number: PCT/GB2001/000432
Authority: WO
Inventors: Susan Jane Kirby; Alan Lindsay; Darrie Jon Windeatt
Original assignee: Site Access Services Limited
Priority date: 2000-02-04
Filing date: 2001-02-02
Publication date: 2001-08-09
Also published as: AU2001230398A1

Abstract

The present invention provides a fog signal device comprising a fog signal body (2) containing explosive and magnetic attachment means (6) for holding the body (2) onto a railway rail (3). A device (1) for attaching a disc shaped fog signal body (2) to a railway rail (3) comprises a first layer (6) and a second layer (8). The first layer (6) is an annular shape and is made from an anisotropic magnetic material. The second layer (8) is a circular disc shape and is also made from an anisotropic magnetic material. The first layer (6) is placed on top of the second layer (8). The first layer (6) and second layer (8) are naturally attracted towards each other due to the magnetic properties of the respective layers. An additional adhesive may be placed between the contacting surfaces to provide a better bond between the layers. When the two layers (6, 8) are placed together a circular recess is formed. The fog signal body (2) is placed on the first layer (6) of the device (1). The fog signal body (2) comprises a metal casing that contains explosive material. The fog signal body (2) is naturally attracted to the magnetic device (1).

Description

ATTACHMENT MEANS FOR A SIGNALLING DEVICE AND METHOD OF IDENTIFICATION

The present invention relates to magnetic means for attaching a signalling device to a railway rail, and a method of identification thereof and is concerned particularly with a magnetic lamina for attaching a signalling device to a railway rail and a method for attaching a signalling device to a railway rail.

A known signalling device used on railway tracks is called a fog signal. The fog signal device comprises a tablet shaped metal body that contains explosive material and two fixing straps attached to the underside of the body. The straps are made of lead. In order to secure the metal body onto the top of a rail the fog signal is placed on top of the rail and the two lead straps are folded around the edges of the rail. When a train runs over the fog signal the explosive is detonated.

We have discovered that the lead straps easily break off from the body rendering the fog signal unusable.

The term 'fog signal' is used hereinafter to include any suitable audible signalling device.

At present fog signal devices are used by maintenance crews working on a particular length of track. The fog signal devices warn of an approaching train. Where there is extensive work being carried out many different crews may be employed and it can be difficult identifying the ownership of particular fog signal devices. This can lead to a dangerous situation where fog signal devices are removed in error. Also, the present fog signal devices are particularly difficult to see especially as they are used in conditions of poor visibility due to fog or heavy rain. According to a first aspect of the present invention there is provided a fog signal device comprising a fog signal body containing explosive material and magnetic attachment means for holding the fog signal body onto a railway rail.

Preferably, the magnetic means comprises a layer of magnetic material, the arrangement being such that, in use, the layer of magnetic material holds the fog signal body onto a surface of a railway rail.

A portion of the layer of magnetic material may be positioned in direct contact with a surface of the fog signal body. The fog signal body may be made out of a ferrous metal that is attracted to the layer of magnetic material.

In use a portion of the magnetic layer is preferably disposed between the fog signal body and the rail.

The magnetic means preferably comprises a flexible magnetic sheet material.

The flexible magnetic material preferably has been so magnetised as to comprise a series of magnetic poles.

The series of magnetic poles are preferably arranged in an identifiable pattern, which may be a regular or an irregular pattern.

According to a first embodiment of the present invention the magnetic means comprises a first layer of magnetic material in contact with a second layer of magnetic material, the arrangement being such that, in use, the first layer is in contact with the fog signal body and the second layer is in contact with the railway rail. The first layer of magnetic material is preferably an annular shape.

The second layer of magnetic material is preferably an elongate shape. The second layer of magnetic material is preferably a rectangular shape. The elongate shape of the second layer of magnetic material provides additional magnetic attracting force for attaching the fog signal body onto the rail.

Preferably in use the second layer of magnetic material extends along the longitudinal length of the rail and is in contact with the uppermost surface of the railway rail.

Alternatively, in use, two ends of the elongate layer of magnetic material are in contact with the two respective sides of the railway rail.

The second layer is preferably formed with a pair of straps, each strap extending from the respective sides of the second layer.

In use the straps are preferably folded over the top of the fog signal body. The straps folded over the top of the signal provide additional means for securing the fog signal body and the magnetic material together.

Alternatively the straps extend downwardly along the respective sides of the railway rail. In this arrangement the straps provide additional means for security the fog signal body onto the rail.

The magnetic material preferably has been so magnetised as to comprise a series of magnetic pole strips. According to a second embodiment of the present invention the magnetic means comprises an elongate layer of magnetic material, the arrangement being such that, in use, the uppermost surface of the elongate layer is in contact the fog signal body and the lowermost surface of the elongate layer is in contact with the railway rail.

The elongate layer is preferably formed with a pair of straps, each strap extending from the respective sides of the second layer.

The layer of magnetic material has preferably been so magnetised as to comprise a series of magnetic poles.

According to a third aspect of the present invention there is provided a method for attaching a fog signal body to a railway rail, the method comprising using magnetic means to hold the fog signal onto the rail.

Preferably the method comprises first placing a magnetic material onto the fog signal body and then placing the magnetic material and fog signal body onto a railway rail.

The fog signal body may be a non-ferrous material such that the magnetic means is not attracted to the fog signal body. It would be advantageous to provide means for attaching the magnetic attachment means to the fog signal body that is not dependent on the material of the fog signal body.

According to a fourth aspect of the present invention there is provided a fog signal device comprising a fog signal body containing an explosive, a first intermediate layer bonded to the fog signal body and magnetic attachment means for holding the fog signal body and the first intermediate layer onto a railway rail. The first intermediate layer is preferably an annular shape. The annular shape provides a recess feature that may be utilised when using the magnetic attachment means with fog signal bodies comprising broken fixing straps.

Preferably, the first intermediate layer is a non-magnetic material.

The first intermediate layer is preferably a foam material comprising a bonding agent.

The fog signal device preferably comprises a second intermediate layer bonded to the first intermediate layer, the second intermediate layer being disposed between the first intermediate layer and the magnetic means.

The second intermediate layer is preferably a metallic material.

Preferably the second intermediate layer is bonded to the magnetic means.

The magnetic means is preferably a magnetic sheet.

The magnetic sheet is preferably so magnetised as to comprise a series of magnetic poles arranged in an identifiable pattern.

The magnetic pole configuration is preferably in the form of pole strips.

Preferably, adjacent pole strips have an alternate polarity.

The pole strips preferably do not all have the same pitch width. According to a fifth aspect of the present invention there is provided a method of identifying a fog signal device comprising a fog signal body containing explosive material and magnetic attachment means for holding the body onto a railway rail, the method comprising placing a flux sensitive film over the magnetic means in order to reveal a magnetic field signature of the magnetic means.

Preferably the magnetic attachment means comprise a sheet material formed with a series of magnetic poles arranged in an identifiable magnetic field signature.

According to a sixth aspect of the present invention there is provided a fog signal device for attachment to a railway rail, the fog signal device comprising a fog signal body containing an explosive material, a magnetic element for attachment to the railway rail, and a reflector element, the arrangement being such that in use a portion of the reflector element extends substantially upwardly.

The reflector element preferably comprises a first portion being disposed between the magnetic element and the fog signal body, a second portion comprising a light reflective surface, and hinge means connecting the first portion to the second portion.

The hinge means preferably allows the second portion of the reflector element to be placed onto the upper surface of the fog signal body in a closed condition. In the closed condition the fog signal device may be placed in a stack arrangement of similar devices and placed in a tubular container. The hinge means preferably comprises resilient properties such that the hinge means urge the second portion of the reflector element into an upright position.

The second portion of the reflector element is preferably a disc shape.

The disc shaped second portion preferably has a diameter substantially the same as a diameter of the fog signal body.

The second portion preferably comprises a first light reflective surface of a first colour and a second light reflective surface of a second colour.

The fog signal device preferably comprises an intermediate metal layer disposed between the magnetic element and the first portion of the reflector element.

The fog signal device preferably comprises means to attach the intermediate metal layer to the first portion of the reflective element.

The means to attach the intermediate metal layer to the first portion preferably comprises a bonding layer. Preferably the bonding layer comprises a foam sheet comprising two adhesive surface.

The fog signal device preferably comprises means to attach the first portion of the reflector element to the fog signal body.

The means to attach the first portion to the fog signal body preferably comprises a bonding layer.

The bonding layer preferably comprises a foam sheet comprising two adhesive surfaces. There are particular advantages to combining the features of the various aspects of the present invention and the invention may include any combination of the features or limitations referred to herein.

The present invention may be carried into practice in various ways and some embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure la is a plan view of part of a first embodiment of the present invention and shows an annular magnetic layer;

Figure lb is a plan view of part of a first embodiment and shows a magnetic disc;

Figure lc is a side view of a fog signal body attached to a rail by the annular magnetic layer shown in Figure la and the magnetic disc shown in Figure lb;

Figure 2a is a plan view of a second embodiment of the present invention and a fog signal body;

Figure 2b is a side view of the second embodiment and the fog signal body and the fog signal body placed on a rail;

Figure 3a is a plan view of a third embodiment of the present invention;

Figure 3b is a side view of the third embodiment and the fog signal body placed on a rail; Figure 4a is a plan view of a fourth embodiment of the present invention;

Figure 4b is a side view of the fourth embodiment and a fog signal body placed on a rail;

Figure 5a is a plan view of a fifth embodiment of the present invention;

Figure 5b is a side view of the fifth embodiment and a fog signal placed on a rail;

Figure 6a is a plan view of first magnetic layer of a sixth embodiment of the present invention;

Figure 6b is a plan view of a second layer of the sixth embodiment;

Figure 6c is a side view of the sixth embodiment and a fog signal body placed on a rail;

Figure 7a is a plan view of a fog signal body;

Figure 7b is a side view of a fog signal body showing one attached lead strap and one broken lead strap;

Figure 8a is a plan view of a seventh embodiment of the present invention showing a pair of straps in an open arrangement;

Figure 8b is a plan view of the seventh embodiment shown in

Figure 8a placed on a rail and including a fog signal body, the straps being in a closed arrangement; Figure 8c is a side view of the fog signal body shown in Figure 8b placed on a rail;

Figure 9a is a side view of an eighth embodiment of the present invention placed on a rail;

Figure 9b is a base view of the fog signal device shown in

Figure 9a;

Figure 9c is a cross-section through X-X of the fog signal device shown in Figure 9b;

Figure 10 is a plan view of a sheet of flux sensitive film;

Figure 11 is a plan view of the sheet shown in Figure 10 placed over the magnetic layer of the fog signal device shown in Figure 9a; and

Figures 12 and 13 are views corresponding to Figure 9b showing modified configurations of the magnetic poles;

Figure 14 is a side view of a fog signal device placed on a railway rail, the body comprising a light reflective element;

Figure 15 is a front view of the fog signal device shown in Figure 14;

Figure 16 is a plan view of the fog signal device shown in Figures 14 and 15;

Figure 17 is an isometric view of the light reflective element shown in Figures 14 to 16; and Figure 18 is a side view of a stack of fog signal devices each comprising a light reflective element in a closed condition.

With reference to Figures la, lb, lc, a device 1 for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises a first layer 6 and a second layer 8. The first layer 6 is an annular shape and is made from an anisotropic magnetic material. The second layer 8 is a circular disc shape and is also made from an anisotropic magnetic material. The first layer 6 is placed on top of the second layer 8. The first layer 6 and second layer 8 are naturally attracted towards each other due to the magnetic properties of the respective layers. An additional adhesive may be placed between the contacting surfaces to provide a better bond between the layers. When the two layers 6,8 are placed together a circular recess is formed.

The fog signal body 2 is placed on the first layer 6 of the device 1. The fog signal body 2 comprises a metal casing that contains explosive material. The fog signal body 2 is naturally attracted to the magnetic device 1. Additional adhesive can be used to provide a stronger bond between the device 1 and the fog signal body 2. A number of units comprising the device 1 and the fog single body 2 can be assembled. It is normal practice in the railway industry to carry packs of ten fog signal devices. In use the fog signal body 1 and the device 1 are placed on the uppermost surface 20 of the rail 3. The magnetic property of the device 1 holds the device 1 against the rail 3 and the fog signal body 2 in place.

Figure 7a and 7b show a known type of fog signal device 10 comprising a disc shaped body 12 and two lead straps 14, 15. The lead straps 14, 15 are originally attached to the underneath surface of the body 12. A common problem with these types of fog signal 10 is that the lead straps brake off. In Figure 7b strap 14 has broken off and there is a short portion 18 left extending from the underneath surface of the body 12. The brake of the strap tends to be near the signal body 12. Once one or more of the straps have broken off the fog signal is unusable.

With the present invention either a new fog signal body having no straps or an old fog signal body with broken straps can be placed on the uppermost surface of the first layer 6. The circular recess that is formed by the first and second layers 6,8 receives the short portions 18 of the broken straps.

With reference to Figures 2a and 2b, a device for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises a rectangular lamina strap 22 formed with two tongues 24,25 that extend from the respective longitudinal edges 26,27 of the strap 22. The strap 22 is made from a flexible anisotropic magnetic sheet material. When the device 22 is place placed along the railway rail 3 (see Figure 2b) the two tongues 24, 25 fold downwardly against the respective sides of the rail 3. The tongues 24, 25 are magnetically attracted to the metal rail 3. The tongues 24, 25 help to hold the device 22 and the fog signal body 2 onto the rail 3.

With reference to Figures 3a and 3b, a device for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises a rectangular lamina strap 32 formed with two longitudinal slits 34, 35 that extend through the strap 32. The strap 32 is made from a flexible anisotropic magnetic sheet material. The slits 34, 35 form a central rectangular portion 36. The body 2 is slid under the central portion 36 and is held between the two slits 34, 35.

With reference to Figures 4a and 4b, a device for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises an upper rectangular lamina strip 42 attached to a lower rectangular strip 44. The upper strip 42 is formed with a pair of arcuate upstanding collars 46, 48. The collars 46, 48 define a central region 50. The fog signal body 2 is placed onto the central region 50. The collars 46, 48 abut the radially outermost circular surface of the body 2 and help hold the body 2 onto the central region 50.

With reference to Figures 5a and 5b, a device for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises a central annular portion 50 and two straps 52, 53 extending radially therefrom. The annular portion 50 is formed with a central circular hole 54 that extends through the portion 50. The device is made from a flexible anisotropic magnetic sheet material. In use the fog signal body 2 is placed over the hole 54 and onto the uppermost surface of the annular portion 50. The annular portion 50 is then placed onto the uppermost surface of the rail 3. The two straps 52, 53 extend downwardly against the respective sides of the rail 3.

With reference to Figures 6a, 6b and 6c, a device for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises an upper oval lamina strip 62 attached to a lower oval strip 64. The upper strip 62 is formed with a circular hole 66 extending there through. The fog signal body 2 is placed onto the uppermost surface of the upper oval strip 62. When the fog signal body 2 comprises a short portion 18 of broken lead strap the portion 18 is received within the hole 66.

With reference to Figures 8a, 8b and 8c, a device 70 for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises a rectangular strip 71 formed with two rectangular straps 72, 74 extending perpendicularly from the respective longitudinal edges 76, 78 of the strip 71. Disposed on the uppermost surface of the strip 71 is an annular portion 80. The device 1 is made from a flexible anisotropic magnetic sheet material. In use the fog signal body 2 is placed on the uppermost surface of the annular portion 80 and the straps 72, 74 are folded over the top of the body 2. The straps 72, 74 are magnetically attracted to the metal body 2 and help hold the body 2 onto the annular portion 80. The combined device and body 2 are placed on the rail 3. The strip 71 extends along the longitudinal length of the rail 3.

When the device 70 and the fog signal body 2 are transported the two halves of the strip 71 can be folded over on top of each other, one of the halves will be in contact with the straps 72, 74 and the body 2. The two folded halves of the strip 71 are held in the closed arrangement due to the magnetic property of the material.

With reference to Figures 9a, 9b, 9c, a device 80 for attaching a disc shaped fog signal body 2 to a railway rail 3 comprises a first intermediate layer 82, a second intermediate layer 84, and a magnetic layer 86.

The first intermediate layer 82 is an annular shape and is made from an acrylic foam material. The second intermediate layer 84 is a circular disc shape which has a thickness of 0.5mm and is made from a metallic material such as zinc plated mild steel. The second intermediate layer 84 is bonded to the magnetic layer 86 and helps to retain the magnetic field of the magnetic layer 86. The first intermediate layer 82 is bonded to the base of the fog signal body 2 by a suitable adhesive, and is also bonded to the second intermediate layer 84 by a suitable adhesive.

The magnetic layer 86 is a circular disc shape of hi-energy flexible bonded magnetic sheet. The magnetic sheet is so magnetised as to comprise a series of parallel strips of alternate north and south poles. The pattern of the strips preferably provides a magnetic pull of about 2.5Kg on a mild steel surface. Preferably, the pitch widths of each strip are not the same. The combination of different widths can be provided for a particular batch of devices 80. The arrangement of the different widths of the strips can be a signature of a particular batch.

With reference to Figures 10 and 11 , a flux film 90 (the film being known to the skilled person in the field of magnets) is used to provide an image of the strips of the magnetic layer 86. When the film 90 is placed over the magnetic layer 86 a dark image 91 of the magnetic flux of the respective strips appears on the film 90. The combination of the different widths 90 and 92 can be seen and the particular batch identified using the flux film. The different widths of the magnetic layer act as a kind of 'barcode' to enable the particular batch to be identified.

In an alternative arrangement of the strips of the magnetic layer 86 one or more of the strips is/are formed with a bulge or kink. This feature would be common to a particular batch of devices. Once again the flux film would be used to reveal the identifying feature of the device and so identify the particular batch.

Figure 13 shows an alternative pattern of wavy pole strips that can be created by suitably magnetising the magnetic sheet material of layer 86, and Figure 12 shows a radial pattern of pole strips. In both cases the non-uniform pattern can provide identification of the device.

The overall thickness of the body, the first intermediate layer 82, the second intermediate layer 84 and a magnetic layer 86 substantially equals the thickness of the existing fog signal device 10 (shown in Figures 7a and 7b) . This fact means that a batch of the inventive devices can be carried in existing transport containers without any excessive rattling. The skilled person should appreciate that the elements of the present invention may be adapted for fog signal bodies that are not an enclosed container. The fog signal body may comprise housing formed with a cup-like portion containing the explosive material and being enclosed by one of the layers described herein.

With reference to Figures 14 to 17, a fog signal device 100 comprises a plurality of layers including a disc-shaped layer of magnetic material 102, a disc-shaped metal layer 104, a first bonding layer 106, a light reflection element 108, a second bonding layer 1 10 and a fog signal body 112 containing explosive material. The fog signal device 100 is placed on railway rail 3 and is held there by the layer of magnetic material 102.

The first bonding layer 106 and second bonding layer 110 each comprise suitable bonding agents and are used to attach the respective neighbouring layers together. The bonding layers 106 and 110 may comprise any type of suitable bonding agent but preferably they each comprise a layer of foam material having contact adhesive surfaces. The second bonding layer 110 may be an annular shape in order to provide a recess for the short portion 18 as hereinbefore described.

The reflective element 108 comprises a first circular disc-shaped portion 114, a second circular disc-shaped portion 116 and a spring hinge 118 that connects the first portion 114 to the second portion 116. The first portion 114 is disposed between the first bonding layer 106 and the second bonding layer 110. The second portion 116 comprises a layer of light reflective material 120 bonded to a front surface of the second portion 116 and a layer of light reflective material 122 bonded to a rear surface of the second portion 116. The colours of the reflective materials 120 and 122 may be chosen to suit any particular operating system on the railways, for example the reflective material 120 may be white and the reflective material 122 may be red. The colours may be used to identify a particular direction of approach to the signal. The colour of the reflective material may signify a particular batch of fog signal devices or the ownership of a batch of devices.

The spring hinge 118 urges the second portion 116 up to a substantially vertical upright position, as shown in the Figures 14 to 16. The second portion 116 may be folded towards the uppermost surface of the fog signal body 112 in a direction 125. In a closed condition of the reflective element 108 the fog signal device 100 is readily stackable and may form a stack 130 as shown in Figure 18. When a fog signal device 100 is taken from the stack 130 the hinge 118 urges the second portion 116 into an upright open position. The spring hinge 118 may be made of any suitable resilient material but preferably the spring hinge 118 is a metal material.

In a preferred embodiment, the reflective element 108 is made from a single sheet of metal. The reflective element 108 is punched from the sheet metal and formed into the shape shown in Figure 17.

Claims

1. A fog signal device comprising a fog signal body containing explosive material and magnetic attachment means for holding the fog signal body onto a railway rail.

2. A fog signal device as claimed in claim 1 , wherein the magnetic means comprises a layer of magnetic material, the arrangement being such that, in use, the layer of magnetic material holds the fog signal body onto a surface of a railway rail.

3. A fog signal device as claimed in claim 2, wherein a portion of the layer of magnetic material may be positioned in direct contact with a surface of the fog signal body.

4. A fog signal device as claimed in claim 2 or claim 3, wherein in use a portion of the magnetic layer is disposed between the fog signal body and the rail.

5. A fog signal device as claimed in any one of claims 1 to 4, wherein the magnetic means comprises a flexible magnetic sheet material.

6. A fog signal device as claimed in any one of claims 2 to 4, wherein the flexible magnetic material has been so magnetised as to comprise a series of magnetic poles.

7. A fog signal device as claimed in claim 6, wherein the series of magnetic poles are arranged in an identifiable pattern, which may be a regular or an irregular pattern.

8. A fog signal device as claimed in claim 1 , wherein the magnetic means comprises a first layer of magnetic material in contact with a second layer of magnetic material, the arrangement being such that, in use, the first layer is in contact with the fog signal body and the second layer is in contact with the railway rail.

9. A fog signal device as claimed in claim 8, wherein the first layer of magnetic material is an annular shape.

10. A fog signal device as claimed in claim 8 or claim 9, wherein the second layer of magnetic material is an elongate shape.

11. A fog signal device as claimed in claim 10, wherein the second layer of magnetic material is a rectangular shape.

12. A fog signal device as claimed in any one of claims 8 to 11 , wherein in use the second layer of magnetic material extends along the longitudinal length of the rail and is in contact with the uppermost surface of the railway rail.

13. A fog signal device as claimed in claim 10, wherein in use, two ends of the elongate layer of magnetic material are in contact with the two respective sides of the railway rail.

14. A fog signal device as claimed in any one of claims 8 to 13, wherein the second layer is formed with a pair of straps, each strap extending from the respective sides of the second layer.

15. A fog signal device as claimed in claim 14, wherein in use the straps are folded over the top of the fog signal body.

16. A fog signal device as claimed in claim 14, wherein the straps extend downwardly along the respective sides of the railway rail.

17. A fog signal device as claimed in any one of claims 2 to 16, wherein the magnetic material has been so magnetised as to comprise a series of magnetic pole strips.

18. A fog signal device as claimed in claim 17, wherein adjacent pole strips have an alternate polarity.

19. A fog signal device as claimed in claim 18, wherein the pole strips are straight parallel strips.

20. A fog signal device as claimed in claim 1 , wherein the magnetic means comprises an elongate layer of magnetic material, the arrangement being such that, in use, the uppermost surface of the elongate layer is in contact the fog signal body and the lowermost surface of the elongate layer is in contact with the railway rail.

21. A fog signal device as claimed in claim 20, wherein the elongate layer is formed with a pair of straps, each strap extending from the respective sides of the second layer.

22. A fog signal device as claimed in claim 21 , wherein the layer of magnetic material has been so magnetised as to comprise a series of magnetic poles.

23. A method for attaching a fog signal body to a railway rail, the method comprising using magnetic means to hold the fog signal body onto the rail.

24. A method as claimed in claim 23, wherein the method comprises first placing a magnetic material onto the fog signal body and then placing the magnetic material and fog signal body onto a railway rail.

25. A fog signal device comprising a fog signal body containing an explosive material, a first intermediate layer bonded to the fog signal body and magnetic attachment means for holding the fog signal body and the first intermediate layer onto a railway rail.

26. A fog signal device as claimed in claim 25, wherein the first intermediate layer is an annular shape.

27. A fog signal device as claimed in claim 26, wherein the first intermediate layer is a non-magnetic material.

28. A fog signal device as claimed in claim 27, wherein the first intermediate layer is a foam material comprising a bonding agent.

29. A fog signal device as claimed in any one of claims 25 to 28, wherein the fog signal device comprises a second intermediate layer bonded to the first intermediate layer, the second intermediate layer being disposed between the first intermediate layer and the magnetic means.

30. A fog signal device as claimed in claim 29, wherein the second intermediate layer is a metallic material.

31. A fog signal device as claimed in claim 30, wherein the second intermediate layer is bonded to the magnetic means.

32. A fog signal device as claimed in claim 31 , wherein the magnetic means is a magnetic sheet.

33. A fog signal device as claimed in claim 32, wherein the magnetic sheet is so magnetised as to comprise a series of magnetic poles arranged in an identifiable pattern.

34. A fog signal device as claimed in claim 33, wherein the magnetic pole configuration is preferably in the form of pole strips.

35. A fog signal device as claimed in claim 34, wherein adjacent pole strips have an alternate polarity.

36. A fog signal device as claimed in claim 35, wherein the pole strips do not all have the same pitch width.

37. A method of identifying a fog signal device comprises a fog signal body containing explosive material and magnetic attachment means for holding the body onto a railway rail, the method comprising placing a flux sensitive film over the magnetic means in order to reveal a magnetic field signature of the magnetic means.

38. A method as claimed in claim 37, wherein the magnetic attachment means comprise a sheet material formed with a series of magnetic poles arranged in an identifiable magnetic field signature.

39. A fog signal device for attachment to a railway rail, the fog signal device comprising a fog signal body containing an explosive material, a magnetic element for attachment to the railway rail, and a reflector element, the arrangement being such that in use a portion of the reflector element extends substantially upwardly.

40. A fog signal device as claimed in claim 39, wherein the reflector element comprises a first portion being disposed between the magnetic element and the fog signal body, a second portion comprising a light reflective surface, and hinge means connecting the first portion to the second portion.

41. A fog signal device as claimed in claim 40, wherein the hinge means allows the second portion of the reflector element to be placed onto the upper surface of the fog signal body in a closed condition.

42. A fog signal device as claimed in claim 41 , wherein the hinge means comprises resilient properties such that the hinge means urge the second portion of the reflector element into an upright position.

43. A fog signal device as claimed in any one of claims 40 to 42, wherein the second portion of the reflector element is a disc shape.

44. A fog signal device as claimed in claim 43, wherein the disc-shaped second portion has a diameter substantially the same as a diameter of the fog signal body.

45. A fog signal device as claimed in any one of claims 40 to 44, wherein the second portion comprises a first light reflective surface of a first colour and a second light reflective surface of a second colour.

46. A fog signal device as claimed in any one claims 40 to 45, wherein the fog signal device comprises an intermediate metal layer disposed between the magnetic element and the first portion of the reflector element.

47. A fog signal device as claimed in claim 46, wherein the fog signal device comprises means to attach the intermediate metal layer to the first portion of the reflective element.

48. A fog signal device as claimed in claim 47, wherein the means to attach the intermediate metal layer to the first portion comprises a bonding layer.

49. A fog signal device as claimed in claim 48, wherein the bonding layer comprises a foam sheet comprising two adhesive surface.

50. A fog signal device as claimed in any one of claims 40 to 49, wherein the fog signal device comprises means to attach the first portion of the reflector element to the fog signal body.

51. A fog signal device as claimed in claim 50, wherein the means to attach the first portion to the fog signal body comprises a bonding layer.

52. A fog signal device as claimed in claim 51 , wherein the bonding layer comprises a foam sheet comprising two adhesive surfaces.