The present invention relates to cable channelling.

Cable channelling is channelling which is laid generally flush with the ground surface and primarily intended to receive cabling of various kinds (although it can be used for other purposes, such as carrying pipes for fluids). Such channelling is in wi despread use in railway systems, for carrying cables alongside railway tracks (although its use is not confined to railways).

Such channelling is conventionally formed of concrete sections of two major types; troughs and covers. A trough has a U-shaped section (but with squared corners), and a cover is a simple slab the width of which is the same as the outer width of a trough. In use, a shallow trench is dug, troughs are laid end to end along it, the cables are laid in the resulting channel, and covers are laid over the troughs to close the channel and so protect the cables.

If it should be necessary to change the cabling, eg by adding another cable, the covers are removed from the troughs, the new cable is laid in the channel, and the covers are replaced.

This known system is simple and effective. However, it has a number of disadvantages. The components have to be robust, as they are liable to receive fairly rough treatment; for example, they may well be thrown off a railway wagon when they are first being laid out in position. To achieve this, the concrete is thick - typically in the region of 50 mm. This makes the components very heavy, and hence considerable effort is required to handle them. A trough weighs typically about 100 kg, and although a cover weighs considerable less, it is nevertheless physically demanding to remove and replace the covers over a distance which may be of the order of 1 km or more. Despite this, however, they still have an appreciable fragility, because the substantial thickness of say a trough is counteracted by its equally substantial weight if it is dropped.

The continuing development of plastics materials has now made it technically feasible to construct such cable channelling components out of suitable plastics material at a competitive cost. Materials known as structural foams, which are

basically high-density polyethylene, are suitable for this purpose, though other materials can of course be used as well.

The substitution ot such plastics materials for concrete can be done without changing the basic design of the components. We have realized, however, that this change of material provides opportunities for certain changes of design and for the provision of additional features not present in concrete components. Further, some of these changes and additional features have undesirable side- effects, and further features are desirable to alleviate these side-effects.

According to its main aspect, the present invention provides a cable chan¬ nelling trough ana cover, the trough comprising a generally U-shaped section with open ends and the cover being generally rectangular and fitting over the open top of the trough, characterized m that the trough is formed of plastics material in the form of a web which has a first pair of set-backs forming a pair of rabbets and a second pair of set-backs forming the upper edges of the trough, the web also having a pattern of intersecting ribs on its outer surface, and the cover is formed of plastics material in the form of a web with a pattern of intersecting ribs underneath the web and fitting over the trough with its web substantially level with the upper edges of the trough and being supported by outer longitudinal ribs resting on the rabbets of the trough.

Conventional concrete components normally have a simple solid block con¬ struction, the shape of the trough is a roughly square rectangular block with a rectangular channel running along one side and that of the cover is a (relatively thin) rectangular block. The present components are preferably formed of rela¬ tively thin webs with a network of external ribs. This construction combines strength and lightness. The present components are also preferably formed with substantially the same overall dimensions as conventional concrete components, so that they can be used in conjunction with existing concrete components. (One standard concrete trough is approximately 1 m long, 0.25 m wide, and 0.27 m deep.)

With conventional concrete channelling, there is a need, in addition to the standard troughs and covers, for special troughs with outlets to the side to allow cables to leave the channelling. With the present components of plastics mater¬ ials, the need for such special components is reduced, as it is relatively easy to cut holes in the sides ot standard troughs. The present troughs can conveni-

ently be grooved to define panels of a suitable size which are readily removable, eg by cutting out. Similarly, the present trough and cover can be cut to shorten them, if necessary, to fit the end of the channelling snugly against some fixed installation

The covers are preferably formed with a suitable ridged pattern on their upper face to provide a non-slip surface. This is important for safety, as workers will often walk on the channelling in preference to the railway track itself or the ballast beside tht. track. The upper face of the covers can also have a logo and/or message (eg a warning or information about the type of cabling) formed on it.

With conventional concrete components, the troughs and covers have the same width, with the covers being laid flat on top of the troughs The present covers are preferably formed slightly narrower than the troughs, with the troughs being rabbeted to receive the covers. This locates the covers more positively on the troughs.

To install cable channelling, a small trench must be dug alongside the railway track, the troughs laid in the trench, the cabling paid in the troughs, and the covers placed over the troughs

With conventional concrete components, the troughs are simply laid end to end in the trench. As a result, there is likely to be a certain amount of misalignment between the troughs. A modest degree of misalignment is of no great significance, but if the misalignment should increase, eg as a result of earth movement either during installation or later, the capacity of the channelling may be reduced and, in extreme cases, the cabling may be damageα.

The present troughs are therefore preferably provided with interlocking means which maintain them in alignment. The interlocking means are preferably releasable, and preferably also allow limited longitudinal movement between interlocked troughs, so that seasonal expansion and contraction of the troughs can be accommodated. The interlocking means extends the length of the trough beyond that of the concrete trough, but can easily be cut of f if it has to be fitted against an existing concrete trough.

The trench dug during installation must be made somewhat wider than the troughs, so that gaps will be left along the sides of the troughs, and part of the spoil from the digging of the trench will often be pushed back into these gaps, both to reduce the amount of spoil and to help to hold the troughs in position. This is obviously liable to result in some spillage of soil into the troughs. Similar spillage may occur if additional cabling is being placed in the troughs, with the covers being removed and then replaced again.

A small amount of spillage into the troughs is generally of no importance, but it is undesirable for any spillage to remain on the edges of the troughs, as such spillage can prevent the covers from seating properly. With conventional concrete components, the edges of the troughs can be wi ped clear fairly easily. With the present troughs, the rabbets (shoulders) cannot easily be wiped clean. The rabbets are therefore preferably formed with a sloping profile, so that spil¬ lage on them will tend to slide off and down into the bottom of the trough. (If some should stay on the rabbet, a kick on the side of the trough will usually dislodge it.)

It is also desirable to provide the present covers and troughs with releas¬ able snap-action engagement means so that the covers can be positively engaged with the troughs but removed again from the troughs if desired. This prevents casual removal of the covers, and also prevents them from possible sliding (side¬ ways or lengthways) if they are stepped on.

The engagement means preferably produce an audible sound (a "click" or "pop") when the cover is engaged with the trough. This means that a worker who is fitting a row of covers onto their troughs, eg by kicking the covers roughly into position and then walking along on the covers, can readily hear each cover in turn engaging.

Locking means may also be provided to allow the covers to be locked in engagement with the troughs. Such locking means may conveniently consist of a shaft mounted vertically in the cover, having an upper end which can be engaged by a suitable key and a cranked lower end which can be turned to engage under a suitable portion of the trough. The shaft may conveniently be of rust-proof material such as stai nless steel.

As noted above, it is not uncommon that additional cabling has to be installed in an existing run of channelling, with the covers being removed and then replaced after the additional cabling has been laid in the troughs. It may be convenient to take the covers off the channelling some little time before the additional cabling in put in place. Although the lightness of the present components has many advantages, we have realized that it has a potential draw¬ back in this situation, because if a train (particularly a high-speed one) should pass while the covers are off and free, it can produce sufficient wind in passing to blow the covers about.

To overcome this, the present covers are therefore preferably provided with releasable interlocking means whereby they can be attached to each other. The loose covers can therefore be locked together in stacks of convenient size (say some 5 or 6 covers to a stack), such that the stacks are heavy enough to withstand the passage of trains nearby. The stacks can of course be separated when the covers are to be replaced on their troughs.

Further features of the invention will become apparent from the following detailed description of a trough and cover embodying the invention, given by way of example and with reference to the drawings, in which:

Fig. 1 is a partial side view of the trough and cover;

Fig. 2 is an end view of the trough and cover;

Fig. 3 is a partial top view of the trough.

Fig 4 is a partial top view of the cover; and

Fig. 5 is a section through the cover and part of the trough.

Figs. 1 and 2 show a trough 10 with a cover 30 above it ready to be low¬ ered onto the trough. The trough 10 has an inner web 1 1 forming a U-shaped channel with a rectangular network of strengthening ribs 12. Towards the top of the channel, the web 1 1 is set back to form a pair of rabbets 13. The cover 30 has a top web 31 and a rectangular network of strengthening ribs 32, of which the outer longitudinal two 32A and 32B on each side rest on the rabbets 1 3 when the cover is placed on the trough.

It is desirable for the cover to fit snugly into the trough. As described aDove, the trough is intended to be set in a trench so that its top edges are roughly flush with the ground surface. As a result, small quantities of dirt may fall into the trough. Because of the slope of the rabbets 13, such dirt is likely to fall further down into the bottom of the trougn, and if some dirt should remain on the rabbets, a sideways blow (such as a kick) to the top edge of the trough should normally be sufficient to dislodge it. Further, if the dirt is soft, any dirt which does remain on the rabbets will readily be displaced and squeezed up between the two ribs 32A and 32B. Thus snug fitting of the cover to the trough wi ll almost always be readily achieved, and the need to clean off the rabbets will arise only very rarely.

The cover 30 has a pai r of lugs 34 located one halfway along each side.

As shown i n Fig. 1 , each lug is slightly widened towards its lower end. The trough 10 has a corresponding pair of slots 14 halfway along the top of each side, each slot being slightl y pinched or narrowed at its top (open) end.

When the cover 30 is placed on the trough 10, the lugs 34 wi ll rest in the openi ngs of the slots 1 4. Firm pressure on the cover will result in the wide ends of the lugs being forced through the pinches at the top of the slots. Each slot 14 is flanked by a pair of auxiliary slots 1 5 which reduce the force required for this. The lugs will thus snap into the slots, with the sudden downward movement of the cover which results producing an audible "snap" or click". The cover can be disengaged from the trough by a firm u pward pull at either end.

The trough 10 has a recess 20 (Fig. 3) at the bottom of its channel at one end, with a tongue 2 1 attached to the i nner end of this recess by a narrowed neck 22. At the other end of the trough, a pair of projections 23 with inwardly turned ends 24 define a recess 25 (which extends slightly into the main body of the trough, as shown). If two troughs are placed end to end, the tongue 21 of one will engage in the recess 25 of the other, so locki ng the two troughs together. The recess 25 is slightly longer than the wide part of the tongue 21 , to allow a small amount of relative movement between the two troughs. Sl ight angular misal i gnments and slight longitudinal movements (eg due to expan¬ sion or contraction can thus be accommodated.

The trough 10 has a groove 28 formed as shown in Fig. 1 , extending across the side of the trough in the form of a squared U\'; this groove is formed in the outer side of the main body of the trough and in the webs 12. The groove acts as a line of weakness, enabling a panel to be readily cut out if it is desired to pass a cable into or out of the channelling. These panels may be formed at any convenient positions; there are preferably two such panels, one as shown and the other in a corresponding position diagonally opposite on the other side of the trough.

Fig. 4 is a partial top view of the cover 30. The top surface has a patterning 35 of raised ridges, as shown at the left-hand end, which gives the upper surface a non-slip characteristic. A legend (not shown) may be moulded into this top surface if desired. Alternatively, the top surface may have a recess (not shown) into which a removable legend may be inserted. The legend may be used to indicate the manufacturer, the nature of the contents of the channelling, and/or a safety warning.

The cover has a releasable interlocking arrangement 40 at the centre of each end. As shown in Fig. 5, which is a sectional view along the line V-V, the arrangement 40 comprises two portions. The first portion consists of a recess 4 1 with a pin 42 across it as shown. (The pin may be of the same plastics material as the rest of the cover, but in view of its small diameter is preferably of metal, for strength.) The second portion consists of a dependent lug or tab 43 with a slot 44 having an enlarged inner end.

If two covers are placed one above another, the tab 43 of the upper cover will rest over the recess 41 of the lower cover, with the lower end of the slot 44 resting on the pin 42. Firm pressure on the upper cover will result in the pin 42 of the lower cover being forced into slot 44 of the tab of the upper cover and into its enlarged inner end, so locking the covers together. A stack of covers can be built up in the same way. The covers can be disengaged by firmly pulling them apart.

The pin 42 can also be engaged by a hook (not shown) to pull the cover off a trough with which it is engaged (by the slots 14 and lugs 44).

The cover also has a locking arrangement 45 at each end. As shown in

Fi g 5, the locking arrangement 45 consists of a shaf t 46 held in a downward

extension 47 of the cover forming a bushing for the shaft. The shaft has a head 48 which is located in a recess 49 in the surface of the cover 30, and has its lower end bent to form a crank 50. The head 48 is formed so that it can be turned by a suitable key (.not shown . The cover is free if the crank 50 is aligned parallel with the sides of the cover. If the crank is turned to point outwards, it engages with a slot 27 (Fig. 1 ) in the trough 10, as shown in Fig. 5, so locking the cover and trough together. The slots 27 may be either open as shown or. closed (blind).

The pin 42 and the shaft 46 are conveniently made of rust-proof material such as stainless steel.