GB2130023A

GB2130023A - Cable ladder

Info

Publication number: GB2130023A
Application number: GB08314239A
Authority: GB
Inventors: Ronald Leslie Albert White; Geoffrey Owers
Original assignee: BICC PLC
Current assignee: Balfour Beatty PLC
Priority date: 1979-12-20
Filing date: 1983-05-23
Publication date: 1984-05-23
Also published as: GB8314239D0; GB2130023B

Abstract

Each stringer 1 and rung 2 are permanently connected by at least two parts of the rung or stringer. At each connection, a tongue 8 at an end of the rung engages in a slot 3 in the stringer so that the wall of the stringer is engaged between the tongue and flanges 11 at the end of the rung. Lugs 12 at the ends of the flanges 11 pass through an aperture 6 in the stringer 2 and an aligned aperture 9 in the tongue 8 and are folded over the tongue to clamp it against the outwardly facing surface of the stringer. <IMAGE>

Description

SPECIFICATION An improved cable ladder This invention relates to ladder-like structures for supporting electric cables and/or service pipes, which structures comprise a pair of elongate side members (generally and hereinafter referred to as "stringers") and, extending transversely between and secured to the stringers at spaced positions along their lengths, a plurality of elongate support members (generally and hereinafter referred to as "rungs"). Such ladder-like structures may also include coupling components such as bends for supporting electric cables and/or service pipes as the direction and/or plane in which they extend gradually changes, tee-connectors and crossconnectors, all such coupling components having, as common features, at least one pair of stringers interconnected by mutually spaced transversely extending rungs.For convenience, all such ladderlike structures and coupling components therefor will hereinafter be included in the generic expression "cable ladder".

In cable ladders of metal or metal alloy it is the general practice to secure the rungs to the stringers by a welding operation. In addition to being a time-consuming and hence expensive operation, where the stringers and rungs are zinccoated, a welding operation has the disadvantage that zinc coating in the vicinity of a weld is likely to be so damaged or destroyed that, unless the welded joint is subsequently coated with zinc, in the course of time, corrosion of a stringer and/or rung in the vicinity of a weld may occur and a corroded welded joint may eventually become an area of weakness.

It is an object of the present invention to provide an improved cable ladder which can be readily and inexpensively assembled and, when the cable ladder is of metal or metal alloy, in which risk of corrosion at the positions at which the stringers and rungs are secured together is substantially reduced.

According to the invention, in the improved cable ladder, at at least one of said spaced positions along a stringer at which a rung is secured to the stringer, a part of the rung or stringer is engaged between and permanently locked by at least two parts of the stringer or rung.

Preferably, the inter-engaging parts of the rung and stringer are clamped together by at least one overlying lug or ear integral with the rung or stringer.

Each stringer preferably has, at each of a plurality of positions spaced along its length, at least one slot in which engages a tongue formed at an end of a rung, the tongue being folded against and clamped to a surface of the stringer by at least one over-lying lug or ear cut from and integral with the rung or stringer.

In a preferred embodiment, the stringer also has an aperture adjacent to but spaced from the or each slot; the tongue engaging in the slot has an aperture which registers with the aperture in the stringer; and at least one lug or ear integral with the rung passes through the apertures and is folded over to overlie the tongue and clamp it to a surface of the stringer.

At each of a plurality of mutually spaced positions along each stringer, a single slot may extend lengthwise of the stringer and may be formed by punching or otherwise forming a substantially rectangular depression in the outwardly facing surface of the stringer to form on the inwardly facing surface of the stringer a similarly shaped protuberance having a longitudinally extending slot along its upper edge.

Where, as is preferred, each rung is of substantially channel-shaped cross-section, at each end of the rung, the side walls of the channel are folded inwardly to form flanges which, when a tongue integral with the base of the channel engages in a lengthwise-extending slot in one of the stringers, bear against the inwardly facing surface of the stringer, each flange having an intregal lug which passes through the aligned apertures in the stringer and rung and is folded back to overlie the tongue and clamp it against the outwardly facing surface of the stringer.

Preferably, the end faces of the rungs abut surfaces of the stringers.

The invention also includes a kit of parts for assembling a cable ladder substantially as hereinbefore described.

The invention is further illustrated by a description, by way of example, of a preferred cable ladder with reference to the accompanying drawings, in which: Figure 1 is a fragmentai pictorial view of the cable ladder; Figures 2 and 3, respectively, are fragmental perspective views of the stringer and one of the rungs of the cable ladder, and Figure 4(a) to (c) illustrate the stages of the method of inter-engaging and interlocking an end of a rung with one of the stringers of the cable ladder.

Referring to the drawings, the cable ladder comprises two steel stringers 1 of channel-shaped cross-section arranged substantially parallel to one another with the flanges of the stringers pointing outwardly and, extending transversely between and secured to the stringers at spaced positions along their lengths, a plurality of steel rungs 2 each of channel-shaped cross-section.

Each stringer 1 has, at each of a plurality of positions along its length, a single lengthwiseextending slot 3 formed by punching a substantially rectangular depression 4 in the outwardly facing surface of the stringer to form on the inwardly facing surface of the stringer, a similarly shaped protuberance 5 with the slot 3 running along its upper marginal edge. Below the slot 3 is a rectangular aperture 6. At each end of each rung 2, the base 7 is folded through 900 to form a tongue 8 having a rectangular aperture 9 of the same shape and size as the apertures 6 in the stringers 1. Each end of the side walls 10 of the rung 2 are folded inwardly through 900 to form flanges 11 having integral lugs 12 extending from their end edges.

In assembling a stringer 1 and rung 2, the tongue 8 at one end of the rung is inserted into a slot 3 in the stringer so that the wall of the stringer is engaged between the tongue 8 and the flanges 11 and the rectangular apertures 6 and 9 are in alignment. The lugs 12 are folded outwardly through the aligned apertures 6 and 9 and over the tongue 8 to clamp it against the outwardly facing surface of the stringer.

Claims

1. A cable ladder comprising a pair of stringers and, extending transversely between and secured to the stringers at spaced positions along their lengths, a plurality of rungs, wherein, at at least one of said spaced positions along a stringer at which a rung is secured to the stringer, a part of the rung or stringer is engaged between and permanently locked by at least two parts of the stringer or rung.

2. A cable ladder as claimed in Claim 1, wherein the inter-engaging parts of the rung and stringer are clamped together by at least one overlying lug or ear integral with the rung or stringer.

3. A cable ladder as claimed in Claim 2, wherein each stringer has at each of a plurality of positions spaced along its length at least one slot in which engages a tongue formed at an end of a rung, the tongue being folded against and clamped to a surface of the stringer by at least one overlying lug or ear cut from and integral with the rung or stringer.

4. A cable ladder as claimed in Claim 3, wherein the stringer also has an aperture adjacent to but spaced from the or each slot; the tongue engaging in the slot has an aperture which registers with the aperture in the stringer; and at least one lug or ear integral with the rung passes through the apertures and is folded over to overlie the tongue and clamp it to a surface of the stringer.

5. A cable ladder as claimed in claim 4, wherein, at each of the plurality of mutually spaced positions along each stringer, a single slot extends lengthwise of the stringer and is formed by punching or otherwise forming a substantially rectangular depression in the outwardly facing surface of the stringer to form on the inwardly facing surface of the stringer a similarly shaped protuberance having a longitudinally extending slot along its upper edge.

6. A cable ladder as claimed in Claim 5 in which each rung is of substantially channel-shaped cross-section, wherein at each end of the rung, the side walls of the channel are folded inwardly to form flanges which, when a tongue integral with the base of the channel engages in a lengthwise extending slot in one of the stringers, bear against the inwardly facing surface of the stringer, each flange having an integral lug which passes through the aligned apertures in the stringer and rung and is folded back to overlie the tongue and clamp it against the outwardly facing surface of the stringer.

7. A cable ladder as claimed in any one of the preceding Claims, wherein the end faces of thze rungs abut surfaces of the stringers.

8. A kit of parts for assembling a cable ladder as claimed in any one of the preceding Claims.

8. A cable ladder substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

9. A kit of parts for assembling a cable ladder as claimed in any one of the preceding Claims.

New claims or amendments to claims filed on 21 November 1983.

Superseded claims 1 to

9.

New or amended claims: CLAIMS

1. A cable ladder comprising a pair of stringers and, extending transversely between and secured to the stringers at spaced positions along their lengths, a plurality of rungs, wherein, at at least one of said spaced positions along a stringer at which a rung is secured to the stringer, a part of the rung or stringer is engaged and permanently locked between at least two parts of the stringer or rung by at least one lug or ear which is integral with one of said parts of the stringer or rung and which is folded over against the other of said parts of the stringer or rung.

2. A cable ladder as claimed in Claim 1, wherein each stringer has at each of a plurality of positions spaced along its length at least one slot in which engages a tongue formed at an end of a rung, the tongue being folded against and clamped to a surface of the stringer by at least one lug or ear cut from and integral with the rung and folded over against the tongue.

3. A cable ladder as claimed in Claim 2, wherein the stringer also has an aperture adjacent to but spaced from the or each slot; the tongue engaging in the slot has an aperture which registers with the aperture in the stringer; and at least one lug or ear integral with the rung passes through the apertures and is folded over to overlie the tongue and clamp it to a surface of the stringer.

4. A cable ladder as claimed in Claim 3, wherein, at each of the plurality of mutually spaced positions along each stringer, a single slot extends lengthwise of the stringer and is formed by punching or otherwise forming a substantially rectangular depression in the outwardly facing surface of the stringer to form on the inwardly facing surface of the stringer a similarly shaped protuberance having a longitudinally extending slot along its upper edge.

5. A cable ladder as claimed in Claim 4 in which each rung is of substantially channel-shaped cross-section, wherein at each end of the rung, the side walls of the channel are folded inwardly to form flanges which, when a tongue integral with the base of the channel engages in a lengthwiseextending slot in one of the stringers, bear against the inwardly facing surface of the stringer, each flange having an integral lug which passes through the aligned apertures in the stringer and rung and is folded back to overlie the tongue and clamp it against the outwardly facing surface of the stringer.

6. A cable ladder as claimed in any one of the preceding Claims, wherein the end faces of the rungs abut surfaces of the stringers.

7. A cable ladder substantially as hereinbefore described with reference to and as shown in the accompanying drawings.