IES83490Y1 - A ladder - Google Patents

Abstract

ABSTRACT An extendable ladder having a lower ladder section with two opposing side—rails and a series of rungs running between the side—rails so as to define foot spaces between adjacent rungs and side—rails; and upper ladder section of the same general construction which is nestable and slidable on the lower section so that the ladder is extendable by sliding of the upper section relative to the lower section. The upper ladder section has two opposing rung engaging members arranged to engage a selected one of the rungs of the lower section and at least one stop arranged on at least one side—rail of the upper section , and so as not to interfere with normal relative sliding motion of the ladder sections, but arranged to prevent the rung engaging members of the upper section being engaged with a rung on the lower section when the upper section is inserted or attempted to be inserted through a foot space on the lower section.

Description

Title of the Invention A Ladder Field of the Invention The present invention relates to the field of ladders. The invention in particular relates to the field of extendable ladders.

Background to the Invention Ladders have been known for quite some time and they are used for many different tasks. Accordingly specific ladders have been made for specific end user applications for example extension or extendable ladders comprise multiple sections (usually 2 or 3), which can be extended or retracted relative to one another so as to increase or decrease the reach of the ladder as desired. Normally an upper section of the ladder is slidable relative to a lower section and can be locked in position relative to the lower section.

Step ladders are designed for climbing relatively low heights and conventionally comprise of four legs, two of which are provided by the side-rails of the climbing section of the step ladder, and two support legs pivotally connected to the top of the side-rails for propping the climbing section in a given position. The ladder is normally foldable between a stowed position where the four legs are close to each other and an operating position where the stabilising legs and the support legs are splayed apart.

Over the years extendable ladders have been disassembled and employed as a step ladder. This occurs by taking apart a lower and upper section of the ladder. The upper section of the ladder is then engaged with the lower section of the ladder in an arrangement where the two parts of the ladder are inclined to each other. While in the past this was an accepted use of the ladder this use is now considered dangerous on health and safety grounds.

Object of the Invention It is an object of the present invention to provide an extendable ladder which cannot have sections thereof employed in the assembly of a step ladder type arrangement.

Summary of the Invention The present invention provides an extendable ladder comprising: (i) a lower ladder section having two opposing side—rails with a series of rungs running between the side—rails so as to define foot spaces between adjacent rungs and the side-rails; (ii) an upper ladder section having two opposing side—rails with a series of rungs running between the side—rails so as to define foot spaces between adjacent rungs and the side—rails, the upper section being nestable and slidable on the lower section so that the ladder is extendable by sliding of the upper section relative to the lower section, the upper ladder section further comprising two opposing rung engaging members arranged to engage a selected one of the rungs of the lower section; the ladder further comprising at least one stop arranged on at least one side-rail of the upper section, and so as not to interfere with normal relative sliding motion of the ladder sections, but arranged to prevent the rung engaging members of the upper section being engaged with a rung on the lower section when the upper section is inserted or attempted to be inserted through a foot space on the lower section.

Generally the upper section will be inverted for such insertion so that one could equally define the function of the stop(s) as preventing the rung engaging members of the upper section being engaged with a rung on the lower section when the lower section is inverted.

It will be appreciated by those skilled in the art that the ladder in question may comprise 2/3 or more sections. In any event it is desirable that the base section of the ladder (ie. that part of the ladder which rests on the ground) and the next section up of the ladder are arranged as described above. Where there are three or more sections it is desirable that all of the upper sections (i.e. the middle and top sections) of the ladder are provided with a stop in accordance with the present invention. In cases where there are 3 ladder sections provided it is also desirable that a stop is provided which does not allow the top section of the ladder to be engaged with the middle section or bottom section of the ladder in such a way so as to form a step ladder type arrangement.

In each case it will be appreciated that the stop is arranged so as not to interfere with the normal extension and retraction movements of the ladder. These sections of the ladder may be extended and retracted as usual.

It will be appreciated that each side—rail has an exterior face opposing an interior face.

The interior face of each side—rail faces towards the rungs of the ladder while the exterior face (is on an opposing side of the rail and) faces away from the rungs of the ladder. In one arrangement the stop is provided on an exterior face of the side-rail of the upper ladder section.

In one arrangement it is desirable that two stops are provided one on each of the side- rails of the upper section. Providing two stops in this way makes it even more difficult for the ladder to be disassembled and reassembled in a step ladder type configuration.

Desirably both stops are on exterior faces of the side—rails.

The stop or stops may be of any desired shape.

The nesting of the upper ladder section in the lower ladder section may be achieved in the conventional fashion i.e. by having the distance between the exterior face of the side-rails of the upper ladder section shorter than the distance between the interior faces of the side-rails of the lower ladder section. Generally the two sections of the ladder will be a close fit so that the separation between the exterior faces of the side-rails of the upper section and the interior faces of the side—rail of the lower section is small.

Typically the distance between the exterior face of the side-rails of the upper ladder section is shorter than the distance between the interior faces of the side-rails of the lower ladder section by less than about 5 cm, usually less than about 4 cm, typically less than about 3 cm usually about 2 cm.

It will be appreciated therefore that the stops should extend sufficiently far from the exterior face of the side-rails of the upper section to prevent the side-rails of the upper section being inserted through a foot space in the lower section. In this respect the term "foot space") includes the space above the top rung, below the bottom rung of a ladder or ladder section. This prevents the assembly of the upper and lower sections in a step ladder arrangement.

It is desirable that the stops are provided on the side-rails at a position proximate the rung engaging members. It is the rung engaging members which can be utilised to grip a rung of the lower section of the ladder so as to form a step ladder type arrangement. In particular the upper section of the ladder is inverted and the side—rails of the upper section are inserted into a foot space in the lower section (proximate the upper end of the lower section) so as to engage the rung engaging members with a rung in the lower section. In such a configuration the ladder sections are inclined with respect to each other typically at an angle of greater than 10 O , such as greater than about 15°. This is prevented by the stop(s) of the present invention.

Typically the distance between the stop(s) and the rung engaging members (measured in a direction parallel to the side-rails) of the upper section is less than about 30 cm, more particularly less than about 25 cm. Typically the distance is less than about 15 cm for example less than about 10 cm. Conveniently the stop(s) and the rung engaging members are arranged to be substantially coincident (though usually on different faces of the side-rails). This ensures that any attempt to engage the rung engaging members of the upper section with a rung of the lower section will not be successful.

In particular it is desirable that the stop(s) are positioned on the side rail(s) at a position below the bottom rung of the upper section.

On the other hand it is desired that the stop(s) do not project beyond the outside face of the side rails of the lower section of the ladder.

The stop(s) is at least lcm long by 1cm in width.

The present invention extends to a ladder substantially as described herein with reference to figures 2 and 3 the accompanying drawings.

Brief Description of the Drawings The invention will now be described in greater detail with reference to the accompanying drawings in which: Figure 1A shows a perspective view of a known prior art ladder in its operational position; Figure 1B shows a perspective view of a known prior art lower ladder section of Figure 1A; Figure 1C shows an inverted perspective view of a known prior art upper ladder section of Figure 1A; Figure 1D shows a perspective view of a known prior art step ladder constructed from the ladder depicted in Figures 1A, 1B and 1C; Figure 2 shows a perspective view of a ladder of the invention in its operational position; Figure 3 is a side elevation of the upper ladder section of Figure 2.

Detailed Description of the Drawings Figure 1 shows a prior art extendable ladder. In particular Figure 1A shows an extendable ladder in normal assembled mode with an upper section of the ladder mounted on a lower section thereof, Figure 1B and Figure 1C show the lower and upper ladder sections respectively and Figure 1D shows the upper ladder portion inverted and inserted through a foot space on the lower ladder section to form a step ladder.

As shown in Figures 2 and 3, the (extendable) ladder comprises a lower ladder section 1 and an upper ladder section 2, the upper section 2 being nestable and slidable on the lower ladder section 1 so as to extend/retract the ladder as desired. The lower ladder section 1 has two opposing side—rails 3 with a plurality of rungs 4 running between the side-rails 3 so as to define foot spaces 5 between adjacent rungs 4 (and the side-rails 3).

The upper ladder section 2 has two opposing side-rails 6 with a plurality of rungs 7 running between the side-rails 6 so as to define foot spaces 5 between adjacent rungs 7 (and the side-rails 6). The upper ladder section 2 is nestable and slidable relative to the lower ladder section 1 parallel to the line 1-1 which provides the means for extending and retracting the ladder. Generally the upper section is guided in its sliding motion by guides 8 on the side-rails 3 of the lower section 1 of the ladder.

As shown in the drawings, the upper ladder section 2 further comprises two opposing rung engaging members (shown in the embodiment as hooks 9) and at least one stop (in the embodiment, two stops 10) arranged on at least one side-rail (in the embodiment one stop 10 on each of side rails 6) of the upper ladder section 2 in close proximity to the opposing rung engaging members 9.

In use, the ladder can be extended or retracted by slidably moving the upper ladder section 2 relative to the lower ladder section 1. To secure the upper ladder section 2 in the desired position, the opposing rung engaging members 9 engage a selected rung 4 on the lower ladder section 1 thereby adjustably locking the upper ladder section 2 in position. To further adjust the extension or retraction of the ladder, the upper section 2 is slidably moved to the desired position relative to the lower ladder section 1 and the opposing rung engaging members 9 are engaged on a further selected rung 4 on the lower ladder section 1.

The stop 10 is arranged on the side rail 6 of the upper ladder section 2 to provide a local widening of the upper ladder section 2 in this region to prevent the rung engaging members 6 of the upper ladder section 2 being engaged with a rung 4 on the lower ladder section 1 when the upper ladder section 2 is inserted or attempted to be inserted through a foot space 5 on the lower ladder section 1. The stop 10 is arranged on the side—rail 6 of the upper ladder section 2 so as not to interfere with the normal extension and retraction movements of the ladder.

In general for ladders having more than two sections the principle will be that each of the upper sections is provided with at least one stop in accordance with the present invention so that any given section of the ladder will have a stop provided so that the rung engaging members of that ladder will not engage with any lower section of that ladder.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

The words "comprises/comprising" and the words "having/including" when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof,

Claims (5)

1. An extendable ladder comprising: (i) a lower ladder section having two opposing side-rails with a series of rungs running between the side—rails so as to define 3 foot spaces between adjacent rungs and the side-rails; (ii) an upper ladder section having two opposing side—rails with a series of rungs running between the side-rails so as to define foot spaces between adjacent rungs and the side-rails, the upper section being nestable and slidable on the lower section so that 10 the ladder is extendable by sliding of the upper section relative to the lower section, the upper ladder section further comprising two opposing rung engaging members arranged to engage a selected one of the rungs of the lower section; the ladder further comprising at least one stop arranged on at least one side-rail of 15 the upper section, and so as not to interfere with normal relative sliding motion of the ladder sections, but arranged to prevent the rung engaging members of the upper section being engaged with a rung on the lower section when the upper section is inserted or attempted to be inserted through a footspace on the lower section. 20

2. A ladder according to claim 1 wherein; (i) the upper section is inverted for said insertion and/or; (ii) two stops are provided, one on each side of the side—rails of the upper section and/or; (iii) the stop(s) is(are) on exterior faces of the side—rails. 25

3. A ladder according to claim 1 or claim 2 wherein; (i) the stop(s) extend(s) sufficiently far from the exterior face of the side—rails of the upper section to prevent the side—rails of the upper section being inserted through a foot space in the lower section and/or; 30 (ii) the stop(s) is (are) provided on the side—rails at a position proximate the rung engaging members and/or; (iii) the distance between the stop(s) and the rung engaging members of the upper section is less than about 30cm.

4. A ladder according to any preceding claim wherein; (i) the stop(s) and the rung engaging members are arranged to be 5 substantially coincident and/or; (ii) the stop(s) are positioned below the bottom rung of the upper section and/or; (iii) the stop(s) are positioned below the rung engaging members of the upper section and/or; 10 (iv) the stop(s) are arranged so as not to project beyond the outside face of the side-rails of the lower section of the ladder.

5. A ladder substantially as described herein with reference to and as illustrated in