Electrical cables form a crucial part of many types of outdoor installation, in particular transportation infrastructures. For example, in railway infrastructures, electrical cables are commonly used to convey telecommunications signals and power for railway signal systems. The cables are typically arranged alongside railway tracks on a track bed, and cable management systems are frequently employed to manage the cables.

These cable management systems perform several functions. They guide the cables alongside the track, clearly mark their position, and guard against movement of the cables on soft ground or loose ballast. Cable management systems may be used to separate and organise different types of cables. Some arrangements also shield the cables from view, improve the aesthetic of the railway line, and some offer a degree of protection against the weather and against unauthorised access to the cables. Installing the cables in a cable management system also reduces the trip hazard that could otherwise be presented by loose cables.

It will be appreciated that substantial lengths of cable are present in railway infrastructure, and hence cable management systems that can be used over long distances are required. It is therefore important that such cable management systems are inexpensive to produce and simple to install. The cable management system is usually arranged on track ballast that forms the upper layer of the track bed, and it must therefore be capable of sitting stably on the uneven surface of the track ballast without movement, and must also allow for access to the cables for maintenance. The most common cable management system is a cable trough or ducting system that is made up of a plurality of pre-cast concrete cable troughs, such as that illustrated in Figure 1. Each cable trough 1 takes the form of an elongate open-ended pre-cast concrete unit 2 having a base 3 and a pair of upstanding side walls 4. The base 3 and walls 4 are arranged so that the unit is 'U'-shaped in cross-section and defines a channel 5 for receiving cables (not shown). The channel 5 is closed by a removable lid 6. The cable troughs 1 may typically be between approximately 10 cm and 35 cm deep, between 9 cm and 30 cm wide, and approximately 50 cm to 1 m long.

In use, the cable troughs 1 are placed end-to-end alongside a railway track to form a continuous channel. The cables are laid inside the channel, and, if lids are used, the lids are placed on the cable troughs 1. The lids are removable, so as to provide easy access points to the cable.

The simple design of the cable troughs, and the use of concrete, which is a relatively low-cost material, means that the cable troughs are inexpensive to produce, durable and weather-resistant. The cable troughs can be installed quickly and easily, which is particularly advantageous in view of the large number of cable troughs that must be installed along a stretch of railway track. The weight of the cable troughs means that they sit stably on the track ballast and are relatively difficult to move once arranged in place. Cables installed in the troughs are also easily accessible for maintenance. The simple construction and arrangement of the cable troughs described above therefore provides a cheap and effective cable management system. However, the relatively easy access to the cables is readily exploited by thieves, who steal copper cables from such cable troughs to sell them for scrap at a high price. To steal a cable, a thief will typically use a 'cut-and-puH' method, in which a cable is cut at two locations spaced some distance apart to create a severed section of cable having two free ends, and the severed section of cable is pulled out of the cable troughs in a longitudinal direction from one of the ends. When employing this method, little time is required to remove a relatively long length of cable, allowing thieves to steal the cable quickly and easily. Cable theft is a significant and increasing problem. A report entitled "Cable theft on the railway" issued in 2012 by the UK's House of Commons transport committee estimated that, in the UK, cable theft cost Network Rail £43 million between 2009 and 201 1 , and lead to an estimated 3.8 million passenger journeys being delayed or cancelled in 2011 alone.

Strategies for preventing the theft of cables, which include, for example, burying cables, encasing cables in concrete, and gluing trough lids closed, have been suggested. However, these strategies add significant complexity to the otherwise simple cable trough system, negating many of its benefits, and such strategies are prohibitively costly and cumbersome to implement. Furthermore, these strategies would hinder access to the cables for legitimate purposes such as maintenance.

Instead, it would be desirable to provide a simple means for releasably securing a lid on a cable trough of the type shown in Figure 1 that is low-cost and easy to install, so that unauthorised removal of the lid is made significantly more difficult. It is against this background that the present invention has been devised.

Summary of the invention

From a first aspect, the invention resides in a device for securing a lid on a cable trough. The cable trough comprises an upstanding wall for supporting the lid. The device comprises a trough grip configured to embrace and grip the upstanding wall of the trough, and a retainer configured to extend from the trough grip over the lid.

In this way, the invention provides a simple and inexpensive means for securing a lid on a cable trough. Because the trough grip is configured to embrace and grip the upstanding wall of the trough, the trough grip is easily fitted over the upstanding wall. No special features are required on the upstanding wall or the lid and no special tools are required, so the device can be easily retro-fitted to existing cable troughs.

The trough grip may comprise inner and outer arms arranged to embrace the upstanding wall of the trough therebetween. The inner and outer arms of the trough grip may be sprung to grip the upstanding wall of the trough. The inner and outer arms therefore provide a simple embracing and gripping means. So that the trough grip may be easily fitted to the upstanding wall of the trough, the trough grip may be configured to engage with the upstanding wall of the trough by push- fitting. The inner and outer arms may be connected by a top member so that the trough grip is of substantially U-shaped cross-section. The device may be configured such that the top member lies atop the upstanding wall of the trough when installed. In this way, the trough grip may be contoured to match the shape of the top of the upstanding wall that it embraces, so that the trough grip is relatively compact.

The top member may comprise a striking plate. The striking plate provides a surface that may be struck, for example with a hammer, to fit the trough grip to the upstanding wall. In this way, the trough grip may be fitted to the upstanding wall using only simple tools. To increase a gripping force on the upstanding wall, at least one arm preferably comprises gripping means for gripping the trough wall. The gripping means comprises one or more barbs.

The retainer may be releasably engageable with the trough grip. In this way, the retainer may be engaged with the trough grip to secure the lid in place and prevent unauthorised access, and released from the trough grip by authorised personnel to permit removal of the retainer and allow access to the trough for legitimate purposes such as maintenance.

To facilitate engagement of the trough grip and the retainer, the device may comprise a ramp to guide the retainer into engagement with the trough grip.

The retainer may comprise engagement means for releasably engaging the trough grip. The trough grip may comprise a stop, and the engagement means of the retainer may be configured to cooperate with the stop to guard against disengagement of the retainer from the trough grip.

Preferably, the engagement means of the retainer comprises one or more teeth.

The trough grip may comprise an aperture or recess for receiving a part of the retainer. To allow easy insertion of the retainer into the aperture or recess, the aperture or recess may be upwardly-facing when the trough grip embraces the wall. For example, the trough grip may comprise a ledge that extends away from the trough wall, and the aperture or recess may be provided in the ledge. Preferably, the trough grip comprises at least two apertures or recesses for receiving respective parts of the retainer. The retainer may comprise at least two legs for engaging with the trough grip. In this case the device may be configured such that, upon engagement of the retainer with the trough grip, the legs splay apart to accommodate a part of the retainer therebetween.

In embodiments where the retainer is releasably engagable with the trough grip, the retainer may be deformable to release the retainer from engagement with the trough grip. This provides a simple means for releasing the engagement between the trough grip and the retainer.

The retainer may comprise means for engaging with a tool to facilitate deformation of the retainer, thereby to release the retainer from engagement with the trough grip. Preferably, the tool-engaging means are apertures for engaging with circlip pliers. By virtue of the tool-engaging means, the retainer can be deformed relatively easily, so long as the correct tool is used. The device may comprise first and second trough grips, and the retainer may be configured to extend between the trough grips to bridge over the lid. The retainer may be releasably engagable with both the first trough grip and the second trough grip. In this way, the retainer may be engaged with a trough grip at two ends, making deformation of the retainer particularly difficult, and keeping the lid particularly well-secured.

For a compact design, the first and second trough grips may be separate pieces. The retainer and the or each trough grip may be formed as separate pieces. This allows particular flexibility in the process of fitting the device to the cable trough. For example, the trough grips may be fitted to the cable trough off site, and the retainer may be attached on site, once the lid is in place. Alternatively, all the pieces may be fitted on site.

Preferably, the retainer is a single piece. However, embodiments are also envisaged in which the retainer comprises a plurality of engagable pieces that may be configured to extend over the lid. For ease of manufacture, the retainer and/or the or each trough grip may be a stamped and/or folded sheet.

From another aspect, the invention resides in a method of securing a lid on a cable trough. The cable trough comprises an upstanding wall for supporting the lid. The method comprises fitting a trough grip over the upstanding wall of the cable trough, placing the lid on the upstanding wall of the cable trough, and engaging a retainer with the trough grip to secure the lid. In this way, the invention provides a method of securing a cable trough that is quick and easy to carry out, and that requires no special tools. The method may be used to secure a lid on a cable trough as it is newly installed, or the method may be used to secure a lid on a pre-installed cable trough. The method may comprise striking the trough grip to fit it over the upstanding wall. In this way, the trough grip can be securely fitted to the cable trough with relative ease, and without the need for special tools.

The method may comprise fitting first and second grips over two parallel upstanding walls of the cable trough. In this case, the method may comprise engaging the retainer with both the first trough grip and the second trough grip, such that the retainer bridges over the lid.

The method may comprise fitting the or each trough grip over the upstanding wall of the cable trough before placing the lid on the upstanding wall. Alternative embodiments are envisaged in which the trough grip is fitted over the upstanding wall at the same time as the lid.

The method may comprise fitting the or each trough grip over the upstanding wall before engaging the retainer with the or each trough grip. Alternative embodiments are envisaged in which the retainer is engaged with the or each trough grip before the or each trough grip is fitted over the upstanding wall.

The invention also extends to a method of installing a cable. The method comprises laying a plurality of cable troughs in end-to-end abutment, placing a cable in the plurality of cable troughs and securing a lid to one or more of the plurality of cable troughs using the method described above. The invention extends further to a retainer for use in the device described above, and to a trough grip for use in the device described above. The invention extends still further to a combination of the retainer described above and the trough grip described above.

Preferred and optional features of each aspect may be used, alone or in appropriate combination, in the other aspects also.

Brief description of the drawings

Reference has already been made to Figure 1 of the accompanying drawings, which is a perspective view of a known cable trough. Preferred embodiments of the present invention will now be described with reference to the remaining drawings, in which:

Figure 2 is a perspective view of a device according to an embodiment of the invention in use in securing a lid on a cable trough; Figure 3 is a perspective view of a trough grip forming part of the device of Figure 2;

Figure 4 is a front view of the trough grip of Figure 3;

Figure 5 is a side view of the trough grip of Figure 3;

Figure 6 is a perspective view of the trough grip of Figures 3 to 5 installed on a cable trough;

Figure 7 is a perspective view of a retainer forming part of the device of Figure 2;

Figure 8 is a side view of the retainer of Figure 7; and

Figure 9 is a detailed view of the device of Figure 2, with the retainer engaged with the trough grip. Terms such as 'horizontal', 'vertical', 'upper', 'lower', and so on refer to the orientation of the device as illustrated in the accompanying drawings. It will be appreciated, however, that the device need not be used in the orientation illustrated, but may be used in any suitable orientation.

Detailed description of embodiments of the invention

Figure 2 shows a cable trough 10 of the type shown in Figure 1 , having a trough body 12 that defines a channel 14 for receiving cables (not shown), and a lid 16 that closes the channel 14. The lid 16 is secured on the trough body 12 by means of a device 30 according to a first embodiment of the invention.

The trough body 12 comprises a base 18 and a pair of upstanding side walls 20. The base 18 and walls 20 are arranged so that the trough body 12 is 'U'-shaped in cross- section. The lid 16 rests on the tops 22 of the upstanding walls 20, so that an undersurface of the lid 16 is in contact with the tops 22 of the walls 20.

The device 30 generally comprises two trough grip parts 40, only one of which is visible in Figure 2, and a retainer part 80. As will be explained in more detail later, the trough grip parts 40 are fitted over the upstanding walls 20 and grippingly engage the walls 20. The retainer part 80 is releasably engageable with the trough grip parts 40 at each of its ends. When engaged with the trough grip parts 40, the retainer part 80 extends over the lid 16 to secure the lid 16 on the trough body 12. Referring to Figures 3 to 5, each trough grip part 40 comprises two plate-like arms 42, 44 that extend downwardly from a bridge piece 46. In this way, the trough grip part 40 is 'U'- shaped in cross section (as best illustrated in Figure 5), so that the arms 42, 44 are arranged to embrace the respective upstanding wall 20 of the trough body 12. The bridge piece 46 is contoured to follow the shape of the top 22 of the respective upstanding wall 20 of the trough body 12. Accordingly, the bridge piece 46 includes a planar major portion 48, a curved portion 50 which connects an outer one 42 of the arms to the planar major portion 48, and an inclined portion 52 which connects an inner one 44 of the arms to the planar major portion 48 on the opposite side of the bridge piece 46 to the outer arm 42. Each of the arms 42, 44 includes a pair of inwardly-directed barbs 54, 56. The barbs 54, 56 take the form of triangular prongs that are formed by cutting and bending the arms 42, 44. When the grip part 40 is fitted, the arms 42, 44 splay apart to accommodate the upstanding wall 20 therebetween. In this way, the grip part 40 acts as a spring clip to grip the upstanding wall 20 of the trough body 12, with the barbs 54, 56 pressed into the surfaces of the upstanding wall 20 by the spring force.

A middle portion of the outer arm 42 is bent outwardly to define a C-shaped rail 58 that extends horizontally across the outer arm 42 to separate an upper part 42a of the arm 42 from a lower part 42b of the arm 42. The rail 58 comprises a central plate section 60 bounded by an upper side 62 and a lower side 64. The upper side 62 of the rail 58 presents a generally horizontal, upward facing surface that defines a ledge.

The upper and lower sides 62, 64 of the rail 58 each comprise a pair of apertures 66, 68. The apertures 66 in the upper side 62 of the rail 58 also extend into the upper part 42a of the outer arm 42, and are arranged to receive a portion of the retainer part 80 from above, as will be described later. The apertures 66 are separated by a spacer 70, which forms a part of the upper side 62 of the rail 58. The apertures 68 in the lower side 64 of the rail 58 also extend into the lower part 42b of the outer arm 42. The apertures 68 in the lower side 64 of the rail 58 are larger than the apertures 66 in the upper side 62 of the rail 58.

Figure 6 shows the trough grip parts 40 fitted to a cable trough 10. The trough grip parts 40 are fitted over the respective upstanding walls 20 on opposite sides of the trough body 12. Each trough grip part 40 embraces and grips the respective upstanding wall 20. The inwardly-directed barbs 54, 56 are pressed against the inner and outer surfaces of the upstanding wall 20, and tend to engage with surface pores or roughness in the wall 20 to hinder removal of the trough grip part 40 from the upstanding wall 20. The trough grip parts 40 are fitted so that the outer arm 42 of each trough grip part 40, and hence the rail 58, is disposed outside the trough body 12, and the inner arm 44 is disposed inside the channel 14. The shape of the bridge piece 46 aids the correct orientation of the trough grip parts 40 during installation. When installed, the major portion 48 of the bridge piece 46 of each trough grip part 40 rests on the top 22 of the upstanding wall 20. The bridge piece 46 therefore acts as a stop for the trough grip part 40 during installation, to ensure that the apertures 66, 68 in the rail 58 are positioned at the appropriate distance from the top 22 of the upstanding wall 20. The major portion 48 of the bridge piece 46 can be used as a striking plate during installation, to allow each trough grip part 40 to be tapped into place with a hammer or other tool. Referring now to Figures 7 and 8, the retainer part 80 comprises a strap with fixing members 82 at each end. As will be explained in more detail below, the fixing members 82 are configured to engage with the respective trough grip parts 40 once they are fitted to the trough 10. Accordingly, the fixing members 82 extend downwardly from a central strip 84 so that the retainer part 80 is 'U'-shaped in cross-section, and the retainer part 80 is dimensioned to bridge over the lid 16 when in use.

Each fixing member 82 comprises two generally parallel, downwardly-extending legs 86. Upper portions 86a of the legs 86 are substantially rectangular, and are separated by a thin slot 88 to allow the legs 86 to splay apart during installation.

Lower portions 86b of the legs 86, which engage with the trough grip parts 40 in use, are of smaller width than the upper portions 86a. Part of each lower leg portion 86b is provided with a set of teeth 90 that act as engagement means for engaging with the trough grip part 40, as will be described in detail later. As best seen in Figure 8, the sets of teeth 90 are provided on opposed faces of the legs 86, so that the teeth 90 face towards one another across the gap between the legs 86. The teeth 90 are of saw-tooth design, so that each tooth 90 comprises a generally horizontal upper surface 96, and a lower surface 98 that is ramped at an angle of approximately 45° to the horizontal. Each leg 86 has a pointed tip portion 86c at its lowermost end. The pointed tip portion 86c helps to guide the legs 86 into the apertures 66 in the ledge 62 of the trough grip part 40 during installation.

Installation of the device 30 will now be described. First, the trough grip parts 40 are fitted over the tops 22 of the upstanding walls 20 of the cable trough 10. To fit the trough grip parts 40, each trough grip part 40 is placed on top of an upstanding wall 20, and the planar major portion 48 of the bridge piece 46 is struck with a hammer or other suitable tool to drive the trough grip part 40 into position, as shown in Figure 6. Once the trough grip parts 40 have been fitted, the lid 16 is placed on the upstanding wall 20. The lid 16 rests on the tops 22 of the upstanding walls 20 and the bridge pieces 46 of the trough grip parts 40. Referring back to Figure 2 and additionally to Figure 9, the retainer part 80 is then fitted over the lid 16 and engaged with the trough grip parts 40. The pair of legs 86 of each fixing member 82 is inserted into the corresponding pair of apertures 66 in the top side 62 of the rail 58 of the respective trough grip part 40. The retainer part 80 is then pushed downwardly, such that the lower part 86b of each leg 86 extends through the respective rail 58 by way of the corresponding upper and lower apertures 66, 68, as is best seen in Figure 9. In this way, each leg 86 is retained behind the central plate section 60 of the respective rail 58. As each pair of legs 86 is inserted into the respective pair of upper apertures 66, the ramped surfaces 98 of the opposing teeth 90 bear against respective edges of the spacer 70 between the apertures 66. This causes the legs 86 to splay apart as successive teeth 90 pass into the apertures 66. Insertion of the legs 86 continues until the strip 84 of the retainer part 80 meets the lid 16, as shown in Figure 2.

Referring again to Figure 9, when the retainer part 80 is engaged with the trough grip part 40, each side of the spacer 70 is arranged between two neighbouring teeth 90 of each leg 86. The horizontal upper surfaces 96 of the teeth 90 engage with the undersurface of the spacer 70 to guard against the fixing members 82 being pulled out of engagement with the trough grip parts 40. The splaying apart of the legs 86 gives rise to an elastic spring force that keeps the teeth 90 in engagement with the spacer 70.

In this way, the spacer 70 acts as a stop that cooperates with the fixing members 82 of the retainer 80 to guard against disengagement of the retainer part 80 from the trough grip part 40. In turn, the trough grip parts 40 are anchored to the upstanding walls 20 of the trough body 12, in particular by the gripping action of the barbs 54, 56. The device 30 therefore securely fixes the lid 16 to the trough body 12, discouraging unauthorised access to the trough 10. To remove the lid 16 to access the trough 10, it is necessary to release the retainer part 80 from the trough grip parts 40. This can be achieved by using a suitable tool to prise apart the legs 86 of each fixing member 82, so as to disengage the teeth 90 from the spacer 70 and allow the legs 86 to be withdrawn from the trough grip parts 40 to free the retainer part 80. To this end, in the illustrated embodiment, the lower portion 86b of one leg 86 of each member 82 is provided with a pair of holes 100 that are configured to engage with circlip pliers, which can then be used to prise the legs 86 apart. It will be appreciated that other tool-engagement features could be provided in place of, or in addition to, the holes 100. For high-security applications, the tool-engagement features can be configured to engage only with a specialised tool. The trough grip parts 40 and the retainer part 80 are made from spring steel or another suitably stiff material. The material must be sufficiently stiff to provide the spring force necessary for the trough grip parts 40 to grip the upstanding wall 20 of the cable trough 10, and to resist deformation if a moderate force is applied, for example by pulling the lid 16 upwardly.

To make the trough grip parts 40 and the retainer part 80, a sheet of spring steel is stamped or cut as required, and then bent into shape. The material must therefore be sufficiently flexible to allow manufacture of the trough grip parts 40 and the retainer part 80 in this way.

Many variations and modifications of the invention are possible. For example, the trough grip parts and the retainer part may be made of any suitable material, and by any suitable process. The retainer part need not be a single piece but may be formed as a plurality of pieces that can be engaged, for example by hooking together, to form the retainer part. The device may comprise a single trough grip part, and the retainer part may engage only with the single trough grip part to secure the lid. The retainer part need not bridge over the lid entirely, but may extend only partially over the lid.

If two or more trough grip parts are provided, the trough grip parts need not be formed from separate pieces, but may be formed as a single piece. For example, the trough grip parts may be joined by a bridging element that extends across the channel. Embodiments are also envisaged in which the retainer part and one or more trough grip parts are formed as a single piece. The device may be fitted to the lid and the lid and device may be lowered together onto the upstanding walls of the cable trough to fit the device and secure the lid on the trough body.

In the illustrated embodiment, to increase the gripping effect of the teeth 90 on the spacer 70, the spacing between each pair of legs 86 is narrower than the width of the spacer 70 between the apertures 66 in the ledge 62, so that the legs 86 splay apart upon insertion of their tips 86c into the apertures 66. However, in other embodiments, particularly when the retainer part is relatively stiff, the legs may be spaced such that only the ramped undersurface of the teeth causes the legs to splay apart.

The stop on the trough grip part need not be a rail, but may be of any suitable form, and may be arranged in any suitable location on the trough grip. The legs need not be received in apertures, but may instead be received in recesses, or the legs may be accommodated outside the trough grip part and engage with an external surface thereof.

The engagement means on the retainer part need not be teeth, but may be any suitable means. The ramped surfaces that guide insertion of the retainer part into the apertures need not be provided on the teeth but may be provided elsewhere on the retainer part, or on the trough grip part.

It will be appreciated that many other variations of the cable trough assembly are envisaged that fall within the scope of the following claims.