GB2319120A

GB2319120A - Ladder

Info

Publication number: GB2319120A
Application number: GB9623263A
Authority: GB
Inventors: Anthony George Hassall
Original assignee: RICH MULLER Ltd
Current assignee: RICH MULLER Ltd
Priority date: 1996-11-07
Filing date: 1996-11-07
Publication date: 1998-05-13
Also published as: GB9623263D0

Abstract

A ladder, eg a cable ladder (2), includes a pair of elongate side walls (6,8) and a plurality of spaced apart elongate rungs (10,12,14) extending between the two side walls, each end of each rung having at least one ear (20,22) passing through a respective aperture in one of the side walls and being attached to the opposite side of the side wall to the rung. In this way, the separate components (i.e. rungs and side walls) of a ladder may be fabricated and galvanised separately and the complete ladder then assembled. Thus the galvanised process may be easier to do and the ladders cheaper to make. Furthermore, there may be a saving on storage space when stocking separate piece parts.

Description

CABLES BLADDER This invention relates to cable ladders and to a method for constructing cable ladders.

The term "cable ladder" includes ladder-like structures for supporting electric cables and/or service pipes and the like. Such ladder-like structures may also include coupling components such as bends (for changing the direction in which the cable ladder extends), Tconnectors and cross-connectors. For convenience, all such structures will be hereinafter referred to as "cable ladders".

A conventional cable ladder consists of a pair of substantially parallel elongate side walls between which extend a plurality of spaced apart elongate rungs. Each rung extends substantially perpendicularly between the two side walls.

Conventionally such cable ladders are produced by welding the rungs to the side walls. The completed cable ladder is then galvanised by a hot dip galvanising process.

Conventional ladders are fabricated in this way since it is not usually practical to galvanise the individual components and then weld them together to form a ladder as the welding operation has the disadvantage that the zinc galvanisation coating in the vicinity of the weld is likely to be damaged or destroyed. Thus, over the course of time, corrosion of the parts in the vicinity of the weld may occur and the corroded welded joint may eventually become an area of weakness.

However the process has the disadvantage that it is difficult to galvanise a prefabricated ladder as it requires a hot dip galvanising apparatus big enough to receive the entire ladder and furthermore it is difficult to physically manipulate such a completed ladder. The volume to mass ratio of a completed ladder is relatively large and so it is less economically viable to galvanise the ladder in this form.

The present invention aims to provide a cable ladder and a method of making a cable ladder which reduces some or all of the above problems.

Accordingly, in a first aspect, the present invention provides a cable ladder including a pair of elongate side walls and a plurality of spaced apart elongate rungs, each rung extending between the two side walls, wherein there is provided at each end of each rung at least one ear, each ear passing through a respective aperture in one of the side walls and being attached to the opposite side of the side wall to the rung.

In this way, the separate components (i.e. rungs and side walls) of a ladder may be fabricated and galvanised separately and the complete ladder then assembled. Thus the galvinisation process may be easier to do and the ladders cheaper to make.

Furthermore there may be a saving on storage space when stocking separate piece parts.

Preferably the side walls of the cable ladder are substantially parallel and the rungs may extend substantially perpendicularly between the two side walls. Preferably the ladder i.e. the walls, rungs and ears, are all made from metal or metal alloy.

Preferably the ear of each rung is perpendicular to the rung and parallel to the side wall through which it extends.

The ear is fixed to the metal structure surrounding the aperture by a suitable fixing technique. Suitable techniques may be tension welding or rivetting, although post galvinisation welding may be disadvantageous for the reason described above.

One preferable technique for fixing the ears (and therefore the rungs) to the side walls is a "tox" method. This involves punching a portion of the ear through into the adjacent metal of the side wall so as to form a protrusion on the opposite side of the side wall to the ear. The metal of the ear is not broken but merely stretched so as to extend through the side wall, thereby gripping the ear to the side wall. This method is particularly advantageous as it does not require any tension welding and is therefore suitable for using after the parts of the ladder have been galvanised.

Preferably each end of each rung is provided with a pair of ears. Each one of the pair of ears may be bent in an opposite direction to the other ear. Preferably each pair of ears is bent such that the distance between the ends of the two ears which are farthest from the rung is greater than the distance between the ends of the two ears which are nearest to the rung. In other words, the ears are bent "outwards" away from each other. The pair of ears may pass through a single aperture in the side wall.

In one embodiment the aperture and its respective ear are mutually dimensioned such that during fabrication of the ladder the ear extends away from the rung in a parallel direction to the longitudinal axis of the rung and is insertable through the aperture. Once the ear has passed through the aperture it is then bent over so as to lie against a part of the side wall and in the bent over position is not removable from the aperture.

This embodiment has the advantage that the apertures may be of a simple (e.g. square or rectangular) shape and therefore easy to manufacture. However this method has the possible disadvantage that the bending of the ears after galvinisation may result in partial removal of the galvanised layer in the area of the bend.

In order to overcome this disadvantage, in a further embodiment of the invention each aperture and its associated ear are mutually dimensioned such that the ear may be inserted through a portion of the aperture in its bent condition and subsequently moved to a further portion of the aperture at which location at least part of the ear lies against part of the side wall. In this position the rung is not movable away from the side wall.

With this embodiment, the ears may be bent prior to galvinisation and then the ladder assembled using e.g.

the above described tox method to join the ears to the side walls. This enables the ladder to be constructed without affecting the galvinisation.

In one embodiment, the apertures may be substantially "L" shaped i.e. comprising a first wide portion through which the ear may be passed whilst the ear lies in a plane substantially parallel to the plane of the side wall, and a second narrow portion into which the base of the ear adjacent the rung may be slid after the ear has passed through the first wide portion. This construction gives mechanical strength to the cable ladder structure and permits the use of metals e.g.

stainless steel and/or aluminium, which are difficult to weld, so that such metals can be used in addition to or instead of steel.

In a second aspect, the present invention provides a kit of parts for a cable ladder which kit when assembled forms a cable ladder according to any embodiment as described above.

In a third aspect, the present invention provides a method of constructing a cable ladder including fabricating rungs having at least one ear as described above and side walls having apertures as described above, followed by assembling the ladder by passing the ears through the respective apertures and fixing the ears to the side walls using any fixing method as described above.

Preferably the rungs and side walls are galvanised prior to assembly into a complete cable ladder. In one embodiment, the ears may be bent into place after being passed through the apertures as described above.

In a broader sense, the invention may be applicable not only to cable ladders but also to ladders and similar structures in general.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a cable ladder according to a first embodiment of the present invention.

Figure 2 is a cross sectional view of two pieces of metal joined together using a tox join.

Figure 3 is a side view of a portion of a side wall of a cable ladder incorporating rungs according to a first and second embodiment of the present invention.

Figure 4 is a cross sectional view on the line 4-4 of figure 3.

Figure 5 is a side view of a portion of a side wall of a cable ladder according to a third embodiment of the present invention.

Figure 1 shows a cable ladder (2) comprising a pair of side walls (6, 8) and, in this example, three rungs (10, 12, 14). Each side wall has a pair of flanges (16, 18) for added strength, both of which may be provided with a "safe edge" (not shown).

Each end of each rung (10, 12, 14) is provided with a pair of ears (20, 22) which are fastened to a respective one of the side walls (6, 8). The ears, (20, 22) pass through respective apertures in the side walls which will be shown in more detail in figures 35.

The ears may be fastened to the side walls using any suitable fastening method e.g. welding or rivetting.

However one preferable method of fastening is a "tox" join and this is illustrated in figure 2. Figure 2 is a cross sectional view through a join between an ear (20) and a portion of a side wall (8). Part (24) of the ear (20) is "stamped" through the side wall (8) so as to protrude through the opposite side of the side wall to the main part of the ear (20). The ear (20) however remains unbroken and a portion (26) of the stamped out portion (24) lies on the opposite side of the side wall (8) and fixes the ear (20) in position.

Figure 3 shows a portion of a side wall (8) to which two rungs (not shown) have been fixed. The locations of the two rungs are shown by reference numerals (30 and 32).

In a first embodiment, both of the pair of ears (20, 22) have been passed through a single aperture (34) and subsequently bent over so that they lie against portions (36, 38) respectively of the side wall (8) each ear (20, 22) has been fixed to its respective portion (36, 38) of the side wall (8) using a fixing method as described above.

In a second embodiment, each ear (20, 22) of the rung (32) has been passed through a separate respective aperture (40, 42) in the side wall (8). As with rung (30), the ears have then been bent over away from each other and fixed to the side wall (8).

Figure 4 is a cross sectional view taken along the line 4-4 shown in figure 3. This figure shows more clearly the way in which the ears (20, 22) pass through respective apertures (40, 42) and are then bent over to lie against respective portions (36, 38) of the side wall member (8).

Figure 5 shows a third embodiment of the present invention in which a rung (not shown, but designated generally 50) is fixed to a side wall member (8). The ears (20, 22) of the rung (50) pass through apertures (52, 54) in the side wall (8) and are fixed as before to portions of the side wall (8).

In this embodiment the apertures (52, 54) are generally "L" shaped and consist of respective first wide portions (56, 58) and second narrow portions (60, 62).

When assembling the cable ladder the ears (20, 22) are pre-bent and then passed through the respective wide portions (56, 58). Following this the rung (50) is then moved so that the ears (20, 22) lie adjacent respective portions (64, 66) of the side wall (8) i.e.

the portions of the ears (20, 22) which are nearest to the rung (50) lie in respective narrow portions (60, 62) of the apertures (52, 54). In this position the rung (50) cannot then be pulled away from the side wall (8).

The above embodiments of the present invention have been described by way of example only and various alternative features or modifications from what has been specifically described and illustrated can be made within the scope of the invention, as will be readily apparent to the person skilled in the art.

Claims

CLAIMS:

1. A cable ladder including a pair of elongate side walls and a plurality of spaced apart elongate rungs, each rung extending between the two side walls, wherein there is provided at each end of each rung at least one ear, each ear passing through a respective aperture in one of the side walls and being attached to the opposite side of the side wall to the rung.

2. A claim according to claim 1 wherein the side walls of the cable ladder are substantially parallel and the rungs extend substantially perpendicularly between the two side walls.

3. A claim according to claim 1 or claim 2 wherein the ear of each rung is perpendicular to the rung and parallel to the side wall through which it extends.

4. A claim according to any one of claims 1 to 3 wherein the ear is fixed to the metal structure surrounding the aperture by tension welding or rivetting.

5. A claim according to any one of the above claims wherein each ear is fixed to the side walls by punching a portion of the ear through into the adjacent metal of the side wall so as to form a protrusion on the opposite side of the side wall to the ear.

6. A claim according to any one of the above claims wherein each end of each rung is provided with a pair of ears.

7. A claim according to claim 6 wherein each one of the pair of ears is bent in an opposite direction to the other ear.

8. A claim according to any one of the above claims wherein the aperture and its respective ear are mutually dimensioned such that during fabrication of the ladder the ear extends away from the rung in a parallel direction to the longitudinal axis of the rung and is insertable through the aperture; once the ear has passed through the aperture it is then bendable over so as to lie against a part of the side wall and in the bent over position is not removable from the aperture.

9. A claim according to any one of claims 1 to 7 wherein each aperture and its associated ear are mutually dimensioned such that during manufacture the ear may be inserted through a portion of the aperture in its bent condition and subsequently moved to a further portion of the aperture at which location at least part of the ear lies against part of the side wall.

10. A claim according to claim 9 wherein the apertures are substantially "L" shaped i.e. comprising a first wide portion through which the ear may be passed whilst the ear lies in a plane substantially parallel to the plane of the side wall, and a second narrow portion into which the base of the ear adjacent the rung may be slid after the ear has passed through the first wide portion.

11. A kit of parts for a cable ladder which kit when assembled forms a cable ladder according to any embodiment as described above.

12. A method of constructing a cable ladder including the steps of: fabricating rungs having at least one ear, fabricating side walls having apertures as described above, followed by assembling the ladder by passing the ears through the respective apertures and fixing the ears to the side walls.

13. A method according to claim 12 wherein the rungs and side walls are galvanised prior to assembly into a complete cable ladder.

14. A method according to claim 12 or claim 13 wherein in the finished ladder the side walls of the cable ladder are substantially parallel and the rungs extend substantially perpendicularly between the two side walls.

15. A method according to any one of claims 12 to 14 wherein in the finished ladder the ear of each rung is perpendicular to the rung and parallel to the side wall through which it extends.

16. A method according to any one of claims 12 to 15 wherein the ear is fixed to the metal structure surrounding the aperture by tension welding or rivetting.

17. A method according to any one of claims 12 to 16 wherein each ear is fixed to the side walls by punching a portion of the ear through into the adjacent metal of the side wall so as to form a protrusion on the opposite side of the side wall to the ear.

18. A method according to any one of claims 12 to 17 wherein each end of each rung is provided with a pair of ears.

19. A method according to claim 18 wherein each one of the pair of ears is bent in an opposite direction to the other ear.

20. A method according to any one of claims 12 to 19 wherein the aperture and its respective ear are mutually dimensioned such that during fabrication of the ladder the ear extends away from the rung in a parallel direction to the longitudinal axis of the rung and is insertable through the aperture; once the ear has passed through the aperture it is then bendable over so as to lie against a part of the side wall and in the bent over position is not removable from the aperture.

21. A method according to any one of claims 12 to 20 wherein each aperture and its associated ear are mutually dimensioned such that during manufacture the ear may be inserted through a portion of the aperture in its bent condition and subsequently moved to a further portion of the aperture at which location at least part of the ear lies against part of the side wall.

22. A method claim according to claim 21 wherein the apertures are substantially "L" shaped i.e. comprising a first wide portion through which the ear may be passed whilst the ear lies in a plane substantially parallel to the plane of the side wall, and a second narrow portion into which the base of the ear adjacent the rung may be slid after the ear has passed through the first wide portion.