Cable trays are conventionally used for supporting long runs of cable within buildings such as factories, warehouses, and offices where, often, a number of different cables, some of which might be heavy duty cables, are installed along the same path. Cable tray systems conventionally comprise a series of interconnected straight or curved lengths of cable tray supported from the ceiling of the building or other overhead support structure. In most conventional cable tray systems, the lengths of cable tray are suspended from the ceiling or other overhead support structure by a series of depending support rods extending along each of the two longitudinal sides of the tray. A separate mounting is required for each support rod from the ceiling whereby mounting of the cable tray system can be relatively time- consuming. Also, the positioning of the support rods at the sides of the tray requires the cables to be inserted into the tray by being pulled through the tray.

In US patent specification 3363048 there is disclosed a cable tray system utilising a cable tray comprising a central longitudinal spine and cable-receiving portions at opposite sides of the spine. The cable tray is supported from the ceiling by a row of support rods spaced along the length of the spine. Installation of this type of cable tray is faster than installation of conventional cable trays as it is only necessary to provide mounting points in the ceiling for a single row of support rods and, also, the centrally mounted support rods have the advantage that the cable- receiving portions are not obstructed by the rods from the sides of the tray whereby runs of cable can be located in the respective cable-receiving portions of the tray by passing over the sides of the tray rather than by drawing the cables through the entire length of the tray as is necessary when the support rods are at each side of the tray.

Although a system such as this can provide substantial advantages in reduction of installation time and costs, due to the mounting of the tray using centrally positioned support rods, difficulties can sometimes arise if the tray is subject to significant asymmetric loading,

particularly during cable installation, when the loading on the cable-receiving portion of the tray at one side of the spine is significantly greater than that on the other side. Under certain circumstances the tray can tilt and also displace laterally in a pendulum-type displacement about the points at which the support rods are anchored to the ceiling, the deflection causing the support rods to bow. Attempts have been proposed to address this problem by installing support brackets from the ceiling, but this has not proved very satisfactory.

According to one aspect of the present invention, there is provided a support device for a cable tray having a central spine and cable-receiving portions at opposite sides of the spine, said support device including a coupling engageable with the central spine and adapted to carry support rods laterally spaced at opposite sides of the spine for supporting the spine from overlying support structure.

In use of the device, the two support rods are firmly clamped relative to the spine in order to resist lateral tipping of the tray under substantial asymmetric loading. To provide additional resistance, particularly in the case of relatively long drops between the overlying support structure and the cable tray, the support rods may be braced one relative to the other by bracing means extending between the two rods.

Advantageously, the upper ends of the support rods are mounted to a common mounting attachable to the overlying support structure preferably by means of a single point fixing.

The support device can be used both to connect two adjacent lengths of cable tray and also to support the two connected trays at their adjacent ends. Alternatively the support device can be used as an intermediate support for the cable tray.

In one particularly preferred embodiment, a single form of coupling can be used to provide support by means of a dual support rod system as specified above or alternatively by means of a single support rod. Preferably, the coupling, or at least certain components of the

coupling, can also be used as a corner connector between lengths of cable tray inclined at a variable angle. In this case, the coupling can also mount an infill assembly which acts as a bridge between the two adjacent cable trays.

Advantageously, the parts of the support rods within the cable tray are covered by shielding means to prevent contact between the cables within the tray and the support rods.

The shielding means may also act as spacers to maintain the cables spaced from the spine.

Further according to the invention, there is provided a coupling device for coupling two lengths of cable tray, each length of cable tray comprising a central spine and cable- receiving portions at opposite sides of the spine, said coupling device enabling the two lengths of cable tray to be positioned with the spines of the two lengths relatively inclined at a variable angle, said coupling device having means engageable with the spines of the two lengths of cable tray, and means permitting one of said lengths to be swivelled to a selected angle relative to the other of said lengths.

Still further according to the invention, there is provided a cable support system including a cable tray having a spine and cable-receiving portions at opposite sides of the spine, and means for supporting the tray from overlying support structure, said support means including parallel support rods extending downwardly from the overlying support structure and firmly fixed relative to the cable tray at opposite sides of the spine, whereby to resist tilting of the tray under asymmetric loading conditions of the cable-receiving portions.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:- Figure 1 is a schematic perspective view of a length of cable tray of a type with which support devices in accordance with preferred embodiments of the invention are used; Figure 2 is a perspective view of one form of support device in accordance with a preferred embodiment of the invention, the support device acting as a coupling to connect two lengths of cable tray of the type shown in Figure 1;

Figure 3 is an exploded view of the coupling shown in Figure 2; Figure 4 is a schematic perspective view showing the manner in which lateral support rods of the coupling are attached by a single-point fixing to the ceiling; Figure 5 shows the coupling of Figures 2 and 3 modified for use as a corner connector between two adjacent lengths of cable tray; Figure 6 is an exploded view showing components of an infill assembly used with the corner connector, the infill assembly having two infill ribs; Figure 6a illustrates a modified form of infill assembly having only a single infill rib; Figure 7 illustrates the coupling of Figures 2 and 3 modified for use as a connector between adjacent lengths of cable tray of different size; Figure 8 is a perspective view illustrating a form of support device for use as an intermediate support for the cable tray; Figure 9 is a perspective view showing a transition module connected to different types of cable tray using couplings as shown in Figures 2 and 3; Figure 10 is an exploded view of an alternative form of coupling; Figure 11 is a perspective view of a hinge connector for connecting two adjacent lengths of cable tray at a variable inclination; and As shown in Figure 1 a cable tray comprises a longitudinal central spine 2 which forms the main structural component of the tray. In the form shown, the spine 2 is of tubular form of rectangular cross-section. Cable-receiving portions 4 are formed at each side of the spine 2 by a series of transverse ribs 6 attached to the spine 2. Adjacent lengths of the cable tray are interconnected by a coupling 10 (Figure 2) which mates with the central spines 2 of the two adjacent cable trays and also forms a mounting by which the tray is attached to the ceiling or other overlying support structure at that point. As will be described, the coupling 10 is constructed for use with a pair of parallel support rods 12 lying at opposite sides of the central spines 2 and this has been found to provide very firm support for the cable trays which is sufficient to prevent tilting of the tray and pendulum-like lateral movement under the effects of substantial asymmetric loading.

The coupling 10 comprises upper and lower clamping plates 14 of identical construction. The adjacent ends of the spines 2 of the two cable trays are clamped between the upper and lower plates 14 by bolts (not shown) passing through vertically-aligned apertures 16 in the upper and lower clamping plates 14 and also through corresponding apertures 18 formed through the spines 2. To facilitate a rigid connection between the plates 14 and the spines 2, each of the plates 14 has on its inner surface a conical boss 20 (see Figure 3) in alignment with the aperture 16 to engage within the aperture 18 formed within the spine 2. When the clamping bolts are tightened, the conical bosses 20 are drawn tightly into the apertures 18 in the spines 2 and provide a connection which acts in cantilever fashion to prevent any vertical deflection of the spines 2 within the coupling 10. The two clamping plates 14 also formed with lateral apertures 22 for receiving the pair of laterally-spaced vertical support rods 12 which extend from a common mounting plate 30 (Figure 4) attached to the ceiling. The support rods 12 are threaded at least at their upper and lower ends and in practice will be threaded along their entire length. At their lower ends the support rods 12 extend through the apertures 22 in the two clamping plates 14 and are clamped thereto by nuts 32 on the support rods 12.

The two support rods 12 lie laterally outside of the two adjacent spines 2. To prevent contact between the cables within the cable-receiving portions 4 and the rods 12, particularly if the cables are being drawn through the tray, the coupling 10 preferably includes infill panels 34 between the two clamping plates 14 in order to shield the rods 12 against contact with the cables and also to provide a smooth surface which will facilitate drawing the cables through the tray. It will be appreciated that the infill panels 34 project laterally from the sides of the spines 2 and the presence of these infill panels 34 at regularly-spaced intervals along the length of the interconnected trays constitutes a series of longitudinally-spaced ramp-like projections which will maintain the cables spaced from the spine and hence reduce frictional contact between the cables and the spine whereby to reduce the force required to draw the cables through the tray.

Advantageously, the two infill panels 34 of each coupling 10 are integrally formed as

part of a seating element 36 of channel section moulded from a plastics material (see Figure 3). The ends of the two adjacent spines 2 are seated within the interior of the element 36 and to facilitate assembly, the lower of the two clamping plates 14 is clipped to the underside of the seating element 36. The lower end portions of the two lateral support rods 12 pass through vertical passages 38 in the seating element 36; to facilitate assembly, the passages 38 preferably include an array of flexible tags 38a to engage with the threads in the support rods 12 and thereby retain the seating element 36 and lower clamping plate 14 on the support rods 12 prior to application of the lower nuts.

In a modified arrangement (not shown), the seating element 36 may also act as a spacer for the adjacent ends of the two spines 2, for which purpose the element includes a central transverse wall and the ends of the two spines 2 abut onto the opposite surfaces of the central wall.

At their upper ends, the support rods 12 engage in the common mounting plate 30 (Figure 4) which has a single point fixing to the ceiling or other overlying support structure.

The fixing to the ceiling is effected through a slotted aperture 30a which permits adjustment in the position of the mounting plate 30. The threaded upper ends of the two support rods 12 engage in threaded through-bores within the mounting plate 30 and this enables the support rods 12 to be screwed through the mounting plate 30 into tight engagement with the ceiling whereby to provide a very stable mounting for the mounting plate 30 which will prevent rocking of the plate even if the underlying surface of the ceiling is uneven. The screwing of the support rods 12 into tight engagement with the underside of the ceiling may also act to provide a degree of pre-tensioning in the mounting plate 30 which will further enhance the rigidity of the mounting.

The use of the two laterally-spaced support rods 12 passing either side of the central spines 2 provides a mounting for the cable tray which is able to provide substantial stability for the tray even when subject to significant asymmetric loading between the opposed cable- receiving portions 4 of the tray. However, the two support rods are coupled to a common

mounting plate 30 having a single-point fixing from the ceiling whereby the time required for installation is not significantly greater than that of existing systems of this type involving a single row of support rods.

It will be noted from Figure 2 that the opposed clamping plates 14 may also include a central aperture 42. This central aperture is able to receive a single central support rod in situations where increased stability against movement arising from substantial asymmetric loading is not required. It also enables the upper and lower clamping plates 14 to be used as part of a corner connection between two adjacent cable trays arranged at an angle one to the other, for example 900 or any other angle as shown in Figures 7 and 8. In this case the two clamping plates are used without the seating insert 36 previously described. The two clamping plates 14 are bolted to the adjacent ends of the two spines 2 in the manner previously described and the coupling uses a single support rod 12' passing through the central apertures of the clamping plates 14. The laterally outermost apertures 16 of the clamping plates 14 carry a bolt 50 which supports an infill assembly comprising one or two ribs 52 which act as a bridge between the ribs 6 of the two relatively inclined cable trays.

The infill assembly can be pivoted about the axis of the bolt 50 and the bolt 50 carries above the infill assembly a roller 54 which facilitates feeding of the cable around the corner.

Preferably, the infill rib assembly comprises a pair of universal clamping plates 56 which, as illustrated, can be assembled either with two ribs 52 or with a single rib 52 (Figure 6a) depending on requirements.

Figure 7 illustrates how the coupling 10 can be used to couple cable trays of different size wherein the cable tray of smaller size will have a central spine 2 of reduced depth in comparison with that of the larger sized tray. In this case, the coupling 10 connects to the larger spine in the manner previously described and connects to the smaller spine 2 via an intermediate spacer 60 interposed between the upper clamping plate 14 and the smaller spine 21.

Although for many applications the loading on the cable tray system will be such that

the cable trays can be supported from the ceiling or other overlying support structure at each connection between adjacent trays using only the couplings 10 as previously described, for systems where the loading is such that intermediate support is also required, an intermediate support coupling 70 as shown in Figure 8 may be used. This intermediate support coupling 70 comprises opposed clamping plates 72 which are clamped to the spine 2 by nuts 32 on the lower end of the two support rods 12. Sleeves or covers 74 acting as cable shields are mounted on the part of the support rods 12 between the two clamping plates 72 in order to prevent contact with the cables.

It will be noted that in each of the couplings 10,70 described, the lower ends of the support rods 12 extend beneath the lower clamping plate 14,72. It will be appreciated that by extending the lower ends of the support rods 12 significantly beneath the lower clamping plate 14,72, the same support rods can also be used to mount a lower tier of cable tray beneath the first.

Although for many applications, the use of the two laterally-spaced support rods 12 will be sufficient to prevent tilting and lateral movement of the tray under substantial asymmetric loading, in systems where there is a relatively long drop from the ceiling, added stability can be obtained by laterally "tying" the two lateral support rods 12 together by means of one or more lateral bracing clips along the length of the two rods. Suitable clips may be of two-part form clamped onto the two rods 12, or in the form of a single component snap- fitted onto the two rods 12. These bracing clips have the effect of reducing the bending deflection of the two rods 12 and hence act to rigidify the structure.

Figure 9 illustrates a transition module 90 between a cable tray having a single spine 2 and a cable tray having two parallel spines 2a. This figure illustrates how couplings 10 of the type previously described can be used to connect the transition module 90 to the two cable trays.

An alternative form of coupling for use with the two lateral support rods 12 is shown

in Figure 10. This coupling comprises a tubular section 100 of a size to fit into the interior of the two adjacent spines 2, the coupling tube 100 being secured to the two spines 2 by bolts passing through aligned apertures in the coupling tube 100 and spines 2. The coupling tube 100 comprises upper and lower lateral pairs of lugs 102 for receiving the lower ends of the support rods. Cover plates 104 are mounted on the parts of the rods 12 between the lugs 102 to prevent contact with the cables.

In cable tray systems it is sometimes required to connect two lengths of cable tray with one length inclined upwardly or downwardly relative to the adjacent length. Figure 11 illustrates a hinge connector 110 for this purpose. The hinge connector 110 comprises two identical components 112 each connected to a respective one of the two spines 2 by engagement of a connector portion 114 within the interior of the spine 2 and bolted thereto.

Head portions 116 of the two components are coupled by a bolt 118 which permits the two components to swivel one relative to the other about a horizontal axis defined by axis of the bolt 118 so as to set the two cable trays at the required angle.

The embodiments have been described by way of example and modifications are possible within the scope of the invention.