GB2479203A

GB2479203A - Stile with telescopic sections having spacer studs

Info

Publication number: GB2479203A
Application number: GB1005583A
Authority: GB
Inventors: Richard Weston
Original assignee: JAMES LAWRENCE WESTON
Current assignee: JAMES LAWRENCE WESTON
Priority date: 2010-04-01
Filing date: 2010-04-01
Publication date: 2011-10-05
Also published as: GB201005583D0

Abstract

A stile is disclosed for a telescopically collapsible ladder structure or scaffold. The stile comprises a plurality of sections 10, 12 of progressively reducing diameter telescopically received within each other. Within each adjacent pair of sections, the inner section 12 has a smaller outer diameter than the inner diameter of the outer section 10 to leave a gap 18 between the two sections and spacing means are fitted around the lower end of the inner section 12 to take up the gap and maintain the two sections coaxial. The spacing means comprises three or more studs 120 which serve to take up the gap only at locations that are spaced around the circumference of the inner section. This prevents dirt from being trapped in the gap 18 between the sections 10, 12 and also allows the sections to distort to prevent them from jamming on account of differential thermal contraction.

Description

STILE FOR A TELESCOPICALLY COLLAPSIDE LADDER STRUCTURE

Field of the invention

The present invention relates to a stile for a telescopically collapsible ladder structure, such as a freestanding ladder or a side of collapsible scaffolding tower.

Background of the invention

Telescopically collapsible ladders are known and one that can be collapsed rapidly is disclosed in EP 0527766. A collapsible scaffold tower has also been proposed in EP 1392940 in which in which the two sides of the tower are ladder-like structures constructed on the same principle.

The above prior art references describe in detail how the sections o the stiles are locked in their extended position and how they can be released to allow the ladder or tower to be collapsed.

The present invention is concerned with the manner in which the sections of the telescopically collapsible stiles are guided relative to one another and the description herein will be confined to the internal construction of the stiles. The manner in which the stile sections are connected to the rungs and the design of the locking mechanism will not be described as they may be generally conventional.

The stile sections are required to extend and collapse easily and to slide smoothly but at the same time they must allow minimal bending of the stiles when they are extended.

Because of the need for the sections to move easily, the sections cannot be an accurate fit within one another. An accurate fit would result in the sections locking up if the stiles are bent slightly or if dirt enters between the sections.

Instead, the sections of the stiles are designed to leave a clearance gap between adjacent sections and spacing means in the form of a collar are placed around the lower

end of each inner stile section. Such a prior art

construction is shown in Figures 1 to 4 of the accompanying drawings, in which:-Figure 1 is a section through two tube sections of a stile of a ladder attached to two rungs, Figure 2 is a perspective view of one of the tubular sections of the stile shown in Figure 1, Figure 3 is a perspective view of a spacer collar, and Figure 4 is a section along the line A-A in Figure 1.

Figure 1 shows just two sections 10 and 12 of one of the two stiles of a ladder and rungs 14 and 16. The opposite ends of each rung 14,16 are each connected to a section of a respective one of the two stiles, so that the spacing between the rungs increases and decreases as the stiles are extended and contracted telescopically.

In each stile, each inner or upper section 12 has an outer diameter that is less than the inner diameter of the next lower section 10 leaving a gap 18 between them. At the lower end only of the inner section 12, this gap is closed by a spacer collar 20. The spacer collar 20 is connected to move with the inner section 12 by inwardly projecting spigots 22 that engage in holes 24 formed near the lower end of the inner section 12.

The spacer collar 20 acts a bearing to permit the sections 10 and 12 to slide freely relative to one another while at the same time maintaining their axes parallel to one another so that the stile resists bending even when the sections are extended.

The present invention recognises certain disadvantages

in the prior art construction described above.

A first disadvantage is that any dirt that succeeds in passing between the inner section 12 and the rung 14 connected to the upper section 10 becomes permanently trapped in the gap 18 between the two sections. Such dirt can cause the tube sections to wear and can also cause them jam relative to one another.

A second disadvantage is that at certain ambient temperatures the ladder can be difficult to extend and contract on account of the fact that the tubular sections 10 and 12 are commonly made of aluminium while the spacer collar 20 is made of a plastics material. As these material have different coefficients of thermal expansion, the thickness of the collar 20 can at times exceed the width of the gap 18, causing the sections to jam.

Summary of the invention

With a view to mitigating the foregoing problems, the present invention provides a stile for a telescopically collapsible ladder structure, comprising a plurality of sections of progressively reducing diameter telescopically received within each other, wherein, within each adjacent pair of sections, the inner section has a smaller outer diameter than the inner diameter of the outer section to leave a gap between the two sections and wherein spacing means are fitted around the lower end of the inner section to take up the gap and maintain the two sections coaxial, characterised in that the spacing means comprise three or more studs which serve to take up the gap only at locations that are spaced around the circumference of the inner section.

Preferably, each inner section in a pair is formed with a plurality of holes near its lower end and each of the studs has a shank received in a hole in the inner section and a head of larger cross sectional area than the shank received in the gap between the inner and outer sections.

Because individual studs are provided in the present invention to act as spacers instead of one continuous collar, the gap between the two sections is not occupied around the entire circumference. For this reason, any dirt that enters into the gap can escape by falling between the individual studs. Furthermore, in the event of differential thermal expansion, it is possible for the walls of the tubular sections to distort, which prevents them from jamming inside one another.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which Figures 1 to 4, as earlier described, show the construction adopted in the prior art to maintain the sections of a telescopically collapsible ladder stile coaxial, Figure 5 shows an inner section having holes near its lower end with a spacer stud fitted in only one of the holes, Figure 6 shows a cross section of a spacer stud, Figure 7 is a section similar to that of Figure 4 showing an embodiment of the invention, and Figure 8 is a section similar to that of Figure 7 showing how the spaced studs allow distortion of the tubular sections of the stile in the event of differential thermal expansion.

Detailed description of the preferred embodiment

The difference between the embodiment of the invention shown in Figures 5 to 8 and the prior art construction shown in Figures 1 to 4 resides in the fact that the single spacer collar 20 has been replaced by four separate studs 120.

Three studs would suffice to prevent the stile from bending in all axial planes but it is preferred to provide four studs.

As shown in Figure 6 each stud 120 has a shank 122 dimensioned to fit in one of the holes 24 in the inner section 12 (as shown in Figure 5) and an enlarged head 126 to fit in the gap 18 between the sections 10 and 12 to act as a spacer and a bearing.

As is clear from Figure 7, because the studs 122 are spaced apart around the circumference of the gap 18, any dirt or rubble that enters the gap 18 can fall out through the unoccupied space between the studs 120.

Figure 8 shows in an exaggerated manner the effect of contraction of the sections 10 and 12 under low temperature conditions. It can be seen in the regions between the studs 120 the walls of the sections 10 and 12 can distort to prevent the sections from jamming against one another. Hence the radius of curvature of the regions of the outer section between the studs 120 can increase and the radius of curvature of the regions of the inner section 12 between the studs 120 can decrease to take up the effects of differential thermal contraction.

Claims

CLAIMS1. A stile for a telescopically collapsible ladder structure, comprising a plurality of sections of progressively reducing diameter telescopically received within each other, wherein within each adjacent pair of sections, the inner section has a smaller outer diameter than the inner diameter of the outer section to leave a gap between the two sections and wherein spacing means are fitted around the lower end of the inner section to take up the gap and maintain the two sections coaxial, characterised in that the spacing means comprise three or more studs which serve to take up the gap only at locations that are spaced around the circumference of the inner section.
2. A stile as claimed in claim 1, wherein each inner section in a pair is formed with a plurality of holes near its lower end and each of the studs has a shank received in a hole in the inner section and a head of larger cross sectional area than the shank received in the gap between the inner and outer sections.
3. A stile constructed substantially as hereinbefore described with reference to and as illustrated in Figures 5 to 8 of the accompanying drawings.