GB2065211A - Ladder - Google Patents

Abstract

A ladder comprises side pieces 11 and rungs 13 all of glass-fibre reinforced plastics material. The ends of each rung 13 are turned so as to be located axially as well as transversely within associated holes 15 within the side pieces 11, 12. Locking members in the form of headed plugs 18 pass from outside each side piece and locate within apertures in each end of each rung 13. The rungs 13 are affixed to their respective side pieces 11, 12 and plugs 18 by means of an epoxy adhesive. <IMAGE>

Description

SPECIFICATION All-fibreglass ladder The invention relates to ladders.

Traditional ladders have their side pieces and rungs made from hard wood. They are very strong, but at the present time they are relatively expensive. They are also, and always have been, heavy in relation to their size, because wood has a relatively high specific gravity.

In recent years, ladders have been designed and marketed with aluminium side pieces and rungs, in an attempt to overcome the drawbacks of traditional wooden ladders. These aluminium ladders are very much lighter than the traditional wooden ones. They can also be quite strong. They are however not as strong as the traditional wooden ladder. They suffer also from the disadvantage that they are prone to corrosion for example, when they are immersed in river water or sewage effluent for anything other than a very short time.

There are many instances in which ladders are needed, and in which neither the traditional wooden ladder nor the more recent aluminium ladder is wholly suitable. For example, ladders which have to be immersed in water or in effluent must be able to withstand corrosion and, if they are to be readily removed and replaced, must also be reasonably light and easily handled.

According to the invention, a ladder has side pieces and rungs all of which are formed of glassfibre reinforced plastics material; the ends of the rungs are a sliding fit in respective associated holes which are formed in the side pieces; each hole, or the end of the rung which is received in it, has a portion which is reduced in diameter so that the rung is located axially as well as transversely within the hole; the ends of the rungs are glued into their locating holes so that each rung projects from the inside of each side piece; locking members are located on the outside of each side piece; each such locking member fits around or inside the end of an associated rung; and each such locking member is glued to the outside of its side piece and is also glued around or within the end of the rung.

In one possible embodiment of the invention, when the rung is located in its holes in the side pieces, the ends of the rung may project beyond their respective side pieces; and the locking members may comprise collars which are a sliding fit over the projecting ends of the rungs and which are glued to the side pieces and glued around the projecting rung ends.

In another embodiment, the ends of the rungs may be received in their locating holes without projecting from the outside of the each side piece; apertures are formed in the ends of the rungs; and a headed plug is inserted into each such aperture from the outside of the side piece. In such a case, the plug would be glued within the aperture, and the underside of the head of the plug (which would be larger than the locating holes) would be glued against the outside of the side piece of the ladder.

An embodiment having this last mentioned feature is illustrated in the accompanying drawings, and will now be described by way of example only.

In the drawings: Figure 1 shown in "exploded" perspective the component parts of a ladder embodying the invention; Figure 2, drawn to an enlarged scale, shows in cross-section how the ladder is assembled; and Figure 3, drawn larger again, than Figure 2, shows the parts of Figure 2 after assembly and in side elevation.

There is shown in Figure 1 a ladder which is made up from two side pieces 11, 12 which are held parallel to, and spaced apart from, one another by a series of rungs 13. Only one of the rungs 13 is shown in Figure 1, but it will be understood that all the rungs 13 will project at right angles from the inside faces 14 of the two side pieces 11,12.

Each side piece 11, 12 is made of glassfibre reinforced plastics material. The particular side pieces illustrated are of U-section elongate form.

Alternatively L-section or I-section forms could be used. Any form which consists basically of a flanged section is preferred, because the flanges give to the section considerable strength whilst at the same time not adding unduly to its overall weight. Box section side pieces could be used, but they are heavier than a flanged section. In addition, the holes in which the ends of the rungs 13 locate are more liable to be formed inaccurately in a box section side piece, since each side piece has two holes one in each of its side faces and there is more chance of the two holes defining an axis which is not precisely at right angles to the side piece as a whole.

A hole 1 5 is drilled in the web of each flanged side piece 11, 12. This hole receives and locates one end of one of the rungs 13. As Figure 2 shows, each rung 13 is a hollow tubular component, and as Figure 1 shows the outside of each rung 13 is longitudinally fluted. The rungs, like the side pieces, of the ladder are made of fibreglass plastics reinforced material.

Each opposite end of each rung 1 3 is turned down so that a reduced diameter portion 16 projects from each end of the rung 13. The reduced diameter portion 1 6 is a sliding fit in the hole 1 5 formed in the ladder side piece. The hole 1 5 thus locates the rung axially as well as transversely in the side piece 11, 1 2. As Figure 2 is intended to show, when the rung 13 is fully located in the side piece 12, the reduced diameter portion 16 does not project beyond the outside face 1 7 of the ladder side piece.

A plastics plug 18, which need not necessarily be fibreglass reinforced, is cylindrical and is so sized that it is a sliding fit within the rung 13. As Figure 2 shows, the plug 18 is headed and the head on the plug will not pass through the hole 1 5 formed in the ladder side piece. The leading end of each plug 1 8 is chamferred as indicated at 1 9.

To assemble the ladder, respective layers G of Glue are applied around the reduced diameter portion 16 at each end of each rung and around the body of each plug 18. The rung end 16 is slid into its hole 1 5 from the inside face 14 of the side piece 11, 12; and the plug 18 is slid into the rung from the outside face 17 of the ladder side piece.

As Figure 3 shows, part of each layer of glue is squeezed out around the components as they are brought together. When the glue sets, the rung 13 is secured firmly inside the hole 1 5 and against the inside face 14 of the side piece 11, 12; and the plug 18 is secured firmly inside the rung 13 and against the outside face 17 of the side piece 11,12.

As the ladder is assembled, the chamferred leading edge 19 of each plug 18 guides the plug into the rung 13; and wastage of glue due to inaccurate location is minimized.

The "shoulders" of hardened glue surrounding the rung 13 and the head of the plug 1 8 can if desired cleaned off without affecting the strength of the bond between the components.

Because the ladder is all-plastics in its construction, it is light in weight and is also extremely resistant to corrosion. At the same time, the way in which each rung is firmly bonded both to the inside face and - via the plugs 18 - to the outside face of each side piece makes the ladder extremely resistant to bending stresses. Also, because the thickness of the plug 18 is added to the wall thickness of the tubular rungs 13 in the region where the rungs pass through the hole 15, the resistance of the rung to shear failure is greatly increased.

The glue used to assemble the ladder described above is a two-part adhesive marketed by Ciba Geigy (U.K.) Limited under the Trade Mark "Araldite" AV1 38/HV998. Other glues could be used, provided they had the necessary resistance to chemical attack and were compatible with the materials of the ladder.

Claims (9)

1. A ladder which comprises side pieces and rungs formed of glass-fibre reinforced plastics material, the rungs being located both axially and transversely within associated holes in the side pieces and affixed thereto with adhesive, and locking members outside the side pieces fixed to the ends of each rung with adhesive.

2. A ladder as claimed in claim 1 in which the ends of each rung project beyond their respective side pieces and the locking members comprise collars which are a sliding fit over the projecting ends of the rungs and which are affixed to the projecting ends and side pieces by means of adhesive.

3. A ladder as claimed in claim 1 in which the ends of the rungs are received in their locating holes without projecting from the outside of each side piece, apertures are located in the ends of each rung, and a headed plug is inserted into each such aperture from the outside of each respective side piece.

4. A ladder as claimed in claim 3 in which the plug is fixed within the aperture with adhesive and the underside of the head of the plug, which is larger than the locating holes, is fixed against the outside of the side piece of the ladder with adhesive.

5. A ladder as claimed in either of claims 3 or 4 in which the plug projects sufficiently far into the aperture to increase the strength of the rung in this area.

6. A ladder as claimed in any one of claims 1 to 5 in which the adhesive is an epoxy resin.

7. A ladder as claimed in any one of claims 1 to 6 in which the side pieces are of U-section elongate form.

8. A ladder as claimed in any one of claims 1 to 7 in which the rungs are longitudinally fluted hollow tubular members.

9. A ladder substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.