IMPROVEMENTS RELATING TO CABLE LADDERS

Abstract: A cabble ladder system comprises a plurality of parts comprising cable ladder sections and accessories. Each part is made up of spaced side rails connected by support rungs. Adjacent pairs of rail ends form coupling ends so that ladder sections may be connected end to end or to accessories. The rail ends have male and female integral and complementary coupling formations so that the ladder sections and accessories may be coupled without the use, as in conventional or separate connector pieces.

Description: Improvements Relating to Cable Ladders This invention relates to cable ladders, that is to say structures which serve to support in particular electrical cables but which can also be used to support othor--ooavice means such as conduit for water, gas or the like in the roof or floor voids of building, and also for providing a means for containing such cables or pipes as they travel between different floor levels in buildings. Cable ladders comprise essentially side rails connected by transverse support means. The transverse support means may be in the form of bars to resemble the rungs of conventional ladders, hence the name "cable ladders" but the support means need not be rungs but could be plates, channels or tubes and the rails may also be plates integral with the support means. When such supporting structures are formed from plate sections, they are often referred to as "cable trays". The present invention is concerned mainly with cable ladders comprising clearly defined side rails connected by support means. The support means will normally be transverse spaced bars, but could be plates. The invention could be adapted for use with cable trays, in which case the sides would comprise the side rails and the base would comprise the support means, and the expression "cable ladders" should be construed accordingly. It is usual furthermore for cable ladders and indeed cable trays to be constructed from metallic components, ' but this is not essential to the present invention, even although reference may be made hereinafter mainly to the use of metallic components. In the erection of a system for the support of electrical cables and/or service pipes, it is usual to provide a plurality of cable ladders and various accessories enabling different ladder sections to be interconnected. For example it may be required to connect ladder sections which are in alignment, and at which there is a T-junction, or it may be required to connect cable ladder sections which lie at an angle to each other and so on. In making, the connections using conventional systems, it is usual to provide connector pieces at least when cable ladders and cable ladder accessories are being connected, and the provision of accessories of course increases the cost of the system, and increases the time required to install the system. The present invention seeks to provide a cable ladder system wherein: the use of connectors may be avoided. The system according to the invention comprises cable ladder sections which may be straight or curved, and cable ladder accessories enabling sections to be interconnected. Additionally, as will become clear hereinafter, a plurality of parts must be provided to form the system, but the inventive aspect can be identified in a single piece, and therefore the invention also extends to a single cable ladder section or accessory. In accordance with the present invention there is provided a cable ladder system comprising a cable ladder section or a cable ladder accessory comprising side rails connected by cable support means, said side rails defining at least two pairs of ends forming coupling means for coupling the cable ladder section as necessary to another part of the system being a cable ladder section or accessory, and " wherein, of the rail ends of each pair, the ends have integral complimentary male and female coupling formations, and of each rail the respective ends have said integral male and female coupling formations. Thus, when similarly constructed cable ladder sections or cable ladder accessories are juxtaposed, the respective pairs of rail ends can be made to interfit in overlapping relationship, and can be directly secured together by bolts or other means. It will be understood that, in an entire system involving a number of cable ladder sections and accessories, of each cable ladder section, and of the side rails thereof, each rail has an end formation type A (female) at one end, and an end formation type B (male) at the other end, and at each end of the cable ladder section the rails have respectively type A and type B formations. This construction means that the rails of respective cable ladder sections and accessories can be plugged into each other whereby the construction of a cable ladder system can be effected quickly and accurately. Preferably, each of said rails of each cable ladder section or accessory is of constant cross section and is channel shaped, except that to provide the rail end formations type A, the end is joggled so as to become of reduced cross section so that the reduced cross section portion can fit into the channel section at end B which is of said constant cross section. Complicated cable ladder systems enabling the ladder system to extend in any of a large number of directions can be constructed. As to the accessories, the system can be made effective for all types of combinations of accessories and cable tray sections and no separate coupling devices are required. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, wherein:- Fig. 1 shows a portion of a cable tray system according to the embo iment of the invention; and Fig. 2 is a plan view illustrating how the system according to the invention can be used for constructing a wide variety of cable tray system patterns. Referring to the drawings, and firstly to Fig. 1, several elements of a cable ladder system according to the invention are shown and comprise a straight cable ladder section 10, a cable ladder accessory 12 for forming a T-junction, and a second straight cable ladder section 14. The ladder tray section 14 has been truncated for the purposes of illustration and the remote end is not shown and also in relation to the cable ladder section 10, the detail of the remote end of the section is not shown and a number of the cross bars have been omitted. Each of the straight cable ladder sections 10 and 14 comprises a pair of rails 16 and 20 which are channel sections of U-shaped cross section. The rails are turned edge on so that the bases of the rails face each other and the flanges of the sections face outwards. The bases are connected as shown by cross bars or rungs 22 suitably connected to the rails 16 and 20 to form straight ladder sections as shown. The rails 16 and 20 are of constant cross section except that of each rail 16 and 20 one end is formed as indicated by reference A to have a reduced cross section whilst at the same end of the ladder section the rail 20 at end B is not of reduced cross section. The ends A and B are complimentary and form integral female and male couplings in that end A is adapted to fit inside a corresponding end B and at the other end of each section as indicated by section 10 complementary ends A and B are again provided but each rail 16 and 20 has an A end and a B end. In the region of said ends the bases of the rails have apertures 24 to enable complementary interfitting sections and accessories to be bolted together for example as indicated by bolts and nuts 26, 28. The accessory 12 defining the T-junction has three rails 30, 32 and 34 each of which has an A end and a B end as shown, so that the accessory has three coupling ends and where the T- junction accessory 12 is adapted for example to be connected to straight section 10 or 14, it presents a complementary pair of ends A and B so that interfitting is quick and simple. The rungs 22 of the cable ladder straight sections and accessories serve to support cables or service pipes or the like, and to this end the rungs 22 are provided with apertures 36 and 38 which respectively lie longitudinally of the bars 22 and transverse thereto. An extremely flexible cable ladder system is provided by so arranging the section and accessory rail ends into integral end types A and B which are capable of being interfitted as will be apparent from Fig. 1. Fig. 2 indicates to some extent the flexibility of the system in schematic illustration and shows how the A and B type ends interfit to connect straight cable ladder sections 40, 45° bend sections 42, 90° bend sections 44, four way accessory sections 46, and it will be appreciated that combinations of cable tray layouts which may be constructed using sections and accessories according to the invention is limitless. In Fig. 2, the A ends are represented by the offset joggles as will be clearly understood. The cable ladder system according to the invention as will be appreciated requires no separate coupling parts between cable ladder sections and accessories. Although not shown in Fig. 2, it will be appreciated that straight cable ladder sections can be connected end to end.

Claims: CLAIMS 1. A cable ladder system comprising a cable ladder section or a cable ladder accessory comprising side rails connected by cable support means, said side rails defining at least two pairs of ends forming coupling means for coupling the cable ladder section as necessary to another par;t of the system being a cable ladder section or accessory, and wherein, of the rail ends of each pair, the ends have integral complimentary male and female coupling formations, and of each rail the respective ends have said integral male and female coupling formations. 2. A cable ladder system according to Claim 1, wherein a cable ladder section is provided and comprises parallel, straight rails connected by support rungs forming said support means. 3. A cable ladder system according to Claim 1 or 2, wherein a cable ladder accessory is provided and comprises three or more coupling means. 4. A cable ladder system according to any one of the preceding claims, wherein each rail of the cable ladder section or the cable ladder accessory comprises a U-sectioned channel of which the open side faces outwardly and the support means is connected to the inwardly facing base. 5. A cable ladder system according to claim 4, wherein the female coupling formation comprises a reduced cross section portion at the end of the rail. 6. A cable ladder system according to any preceding claim, comprising a plurality of cable ladder sections and a plurality of cable ladder accessories.

Inventors: DAVIES GARETH JOHN, DAVIES, GARETH, JOHN
Applicants: SWIFTS OF SCARBOROUGH LTD, SWIFTS OF SCARBOROUGH LIMITED
Application year: 1990
Main classification: H02G3
IPC codes: H02G3