GB1595202A

GB1595202A - Ladders

Info

Publication number: GB1595202A
Application number: GB28283/77A
Authority: GB
Original assignee: Abru Aluminium Ltd
Current assignee: Abru Aluminium Ltd
Priority date: 1977-07-06
Filing date: 1977-07-06
Publication date: 1981-08-12
Also published as: IT7853480V0; DE2860615D1; CA1094028A; ES471508A1; AR219759A1; IT7868578A0; BR7804218A; AU3774078A; EP0000344B1; ZA783722B; DK305678A; NO782223L; IT1172892B; FI782172A7; JPS5418362A; EP0000344A1

Description

PATENT SPECIFICATION

( 11) 1 595 202 ( 21) ( 23) ( 44) Application No 28283/77 ( 22) Filed 6 July 1977

Complete Specification filed 24 May 1978

Complete Specification published 12 Aug 1981 ( 51) INT CL 3 E 06 C 7/08 ( 52) Index at acceptance E 15 L 57 ( 72) Inventor EDWIN JOHN BRUTON ( 54) IMPROVEMENTS IN OR RELATING TO LADDERS ( 71) We, ABRU ALUMINIUM LIMITED, a British Company, of Pennygillam Industrial Estate, Launceston, Cornwall PL 15 7 ED, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:The present invention relates to stiles and other components of ladders, as well as to ladders, especially extension ladders.

As is well known, aluminium has become very expensive and alternative materials, particularly for extension ladders, are urgently being sought Plastics material has been suggested as an alternative in DE-A 24 15441.

According to a first aspect of the present invention there is provided a stile for a ladder (as hereinbefore defined), which stile comprises a hollow box section, the hollow section comprising two interlocking elongate sections of thin steel and the hollow eing filled with a synthetic plastics material foam, such as polyurethane foam.

According to a second aspect of the present invention, there is provided a ladder (as hereinbefore defined) which comprises one or more stile(s) in accordance with the first aspect of the present invention.

According to a third aspect of the present invention, there is provided an extension ladder component which comprises two stiles, each stile comprising a hollow box section, the hollow section comprising two interlocked elongate sections of thin steel and the hollow being filled with a synthetic plastics material foam.

According to a fourth aspect of the present invention, there is provided an extension ladder which comprises two components, each component comprising two stiles and a multiplicity of rungs, each of which stiles comprises a hollow section filled with polyurethane foam, the hollow section comprising two interlocked elongate sections of thin steel coated with polyvinyl chloride.

The term "ladder" as used herein is a generic term that includes extension ladders, ladders, steps and the like.

Whilst there are obviously many ways of forming a hollow section, the hollow section is preferably formed from two separate sections which, when slid together, form the 55 hollow section The two separate sections are made of thin steel (generally having a wall thickness in the range of from 0 5 to 0 8 mm when using the steel).

The formed hollow section will have good 60 strength in pure bending about either the X-X or Y-Y axes, the strength naturally being dependent on the size of section, wall thickness of the material and the material itself However, such a hollow section will 65 have little or no "torsional rigidity" because both sections are "open" sections.

To obtain good torsional rigidity, it has been found possible to restrain each face of the section from moving relative to the 70 other face by filling the section with a synthetic plastics material foam, especially a low density polyurethane foam Whilst one could use a foam other than a low density foam, this is not advantageous from a cost or 75 weight point of view The filling of the section serves not only the purpose of giving good torsional rigidity to the section but it also stiffens the thin walls of the section.

Normally, the sections of steel will be 80 made of strip steel coated with P V C Of course, the steel will normally be treated against rusting prior to coating with P V C.

The forming of the hollow by using two sections is preferred for two basic reasons, 85 namely to allow the use of P V C coated steel or similar material that cannot be welded into a hollow section and to allow the rungs of the ladder to be fitted with no external protrusions 90 The basic advantages of a ladder, particularly applicable to extension ladders, with stiles made of foam filled steel is that, especially when a low density polyurethane foam is used, the ladder is considerably lighter 95 than an equivalent wooden ladder, it is very little heavier than an equivalent aluminium ladder, it is very much cheaper, at least at the present time, than an equivalent aluminium ladder and the price is compar 100 tr 0 rti 1 595 202 able, at least at the present time, with an equivalent wooden ladder.

The preferred low density polyurethane foam has a density of about 3 lb per cubic foot.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:Figure 1 shows a perspective view of part of an assembled extension ladder, and Figure 2 shows a series of plan/sectional views showing how a tread is fastened to stiles.

Figure 1 of the drawings shows stiles 1 made up of sections 2 and 3, connected by treads 4, with the stiles being filled with foam 5.

Referring now to Figure 2 of the drawings, an aluminium section of ribbed tube 6, preferably of generally circular crosssection, has two ribs 7 formed thereabout, in the aluminium, spaced at the distance apart that the stiles are to be positioned, which strengthened tube is to form a rung or tread for the extension ladder Two inner hollow section members 2 with appropriately dimensioned holes therein have the ends of the requisite number of treads inserted therein and then an additional rib 8 is formed at each end of each tread, so that each tread is securely fastened to each inner hollow section member 2 Caps (not shown) of steel for example are then generally fitted to the ends of the tube 6 to prevent ingress of foam thereinto in the later stages of manufacture (for economy of foam) A second hollow section member 3 is then slid onto each of the hollow section members 2 having treads 6 fastened thereto and the formed hollow section is then filled with low density polyurethane foam which is allowed to cure therein The end product is an extension ladder section The hollow section members 2 and 3 are advantageously made of P V C.

coated steel of thickness in the range of from 0 5 to 0 8 mm.

The tube 6 forming the tread can of course be any convenient shape, for example of "D" shape or be rectangular in cross section.

Of course, the present invention could be used in the manufacture of ladders other than extension ladders, if so desired.

Claims

WHAT WE CLAIM IS:

1 A stile for a ladder (as hereinbefore defined), which stile comprises a hollow box section, the hollow section comprising two interlocked elongate sections of thin steel and the hollow being filled with a synthetic plastics material foam.

2 A stile according to Claim 1, wherein the two elongate sections are interlocked by having been longitudinally slid one inside 65 the other.

3 A stile according to Claim I or 2, wherein the steel is plastics material coated.

4 A stile according to Claim 1, 2 or 3, wherein the elongate sections are made of 70 steel of a thickness in the range of from 0 5 to 0 8 mm.

A ladder (as hereinbefore defined) which comprises one or more stile(s) in accordance with any one ot the preceding 75 claims.

6 An extension ladder component which comprises two stiles, each stile comprising a hollow box section, the hollow section comprising two interlocked elongate 80 sections of thin steel and the hollow being filled with a synthetic plastics material foam.

7 An extension ladder which comprises two components, each component comprising two stiles and a multiplicity of rungs, 85 each of which stiles comprises a hollow section filled with polyurethane foam, the hollow section comprising two interlocked elongate sections of thin steel coated with polyvinyl chloride 90 8 An extension ladder according to Claim 7, wherein the rungs are locked to a respective one section of each hollow section, so that the end of each rung is within the respective stile and capped prior to the 95 infill of foam into the stiles.

9 An extension ladder according to Claim 7 or 8, wherein the elongate sections are made of steel of a thickness in the range of from 0 5 to 0 8 mm 100 A component for a ladder, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

11 An extension ladder, substantially 105 as hereinbefore described with reference to, and as shown in, the accompanying drawings.

FORRESTER, KETLEY & CO, Chartered Patent Agents Forrester House, 52 Bounds Green Road, London N 11 2 EY and also at Rutland House, 148 Edmund St.

Birmingham B 3 2 LD and Scottish Provident Building, 29 St Vincent Place, Glasgow G 1 2 DT.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd, Berwick-upon-Tweed, 1981 Published at the Patent Office, 25 Southampton Buildings, London, WC 2 A I AY, from which copies may be obtained.