EXTENSION LADDER

Abstract: An extension ladder comprising at least two separate single ladders (10, 20, 30, 40) which in their starting position lie upon one another and are slidable in relation to one another is shown. One of the two adjacent ladders comprises guide means for the other. Between each adjacent single ladder there is arranged a line pull system comprising line guides (1, 1'; 2, 2'; 3, 3'; 4) over which the line (7) runs and changes direction. Such a line pull system is independently arranged between two adjacent single ladders, so that a four-part extension ladder has three independent line pull systems.

Description: EXTENSION LADDEK. The present invention relates to an extension ladder, comprising at least two separate single ladders which in their starting position lie upon and are slidable in relation to one another, and where one of the two adjacent ladders includes guide means for the other. By extension ladder is meant a ladder that consists of at least two single ladders and where there are employed auxiliary means, such as a line, to hoist the slidable single ladder. In addition, the extension ladder must have locking hooks, or drop hooks, which lock the ladder both during hoisting and in its extended position. An extension ladder when completely extended would be capable of reaching a length of up to 15 m. Particularly with respect to rescue ladders, continuous developmental work has been carried out to meet the constant¬ ly increasing requirements for safety and functional efficiency. Thus, there is a need for rescue ladders that can both rapidly and easily be brought to their extended position without the need to use great force and without any notable inconvenience with respect to the lines. There has long been a need for extension ladders that provide for handling of the free end of the line so as to prevent it from merely gathering into a tangled mass on the ground. In the presently described extension ladder, as the single ladders are being hoisted, the lines will be gathered up continuously by the ladder itself, so that the line does not collect on the ground. The present extension ladder will also provide for more rapid extension, for example, against a wall, which could be a critical factor in a rescue situation. In order to make the ex-tension ladder as self-contained as possible, it is an advantage to equip it with support legs affording it a four-point contact with the ground, such that it can be totally free-standing in extended position. For rescue purposes, it is advantageous to have rapidly engage- able support legs of the type, for example, described in the simultaneously filed Norwegian application no. 891965. The above mentioned objectives are achieved with an extension ladder of the type mentioned in the introduction, charac¬ terized in that between each pair of adjacent single ladders there is arranged a line pull system, comprising line guides over which the line runs and changes direction, that a first ladder at one end thereof is provided with first line guides, one on each side or two on the same side, and at the opposite end with a pair of third line guides on one side, that a second ladder is provided with second line guides, one on each side or two on the same side, and in addition a fourth line guide on the one side and at the same end as the third line guides, the line at a first end thereof being secured to the second ladder in the same end region as the second line guide and running to the first line guide and further to the second line guide, to the secondary second line guide, to the secondary first line guide, to the third line guide, to the fourth line guide, to the secondary third line guide and further to a drop hook device attached to the second ladder, which drop hook device engages with sections of the first ladder for locking thereto. The line can advantageously pass from the second line guide to the secondary line guide through a ladder rung. Thus, the stepping path on the ladder will be totally free of crossing and longitudinal lines. The line guides may be of any suitable type, such as funnel shaped holders, movable pulleys, castors or a combination thereof. The single ladder that is to be hoisted first can advantage¬ ously be equipped with a top wheel to rest against a wall or similar base. As previously mentioned, the extension ladder may also include support legs that afford four-point contact with the ground or floor so as to render it self-supporting and freestanding even when the entire ladder is fully extended. The line guides, pulleys or castors may be disposed in respective fittings which in turn are attached to the respective side members. Although the ladder may be manufactured from any suitable mater-ial, a practical and light-weight embodiment may presently be constructed of aluminum. If the extension ladder consists of more than two single ladders, the respective lines can be marked, for example with the aid of coloring, so that the ladder sections may be hoisted in an appropriate sequence. Other additional objectives, features and advantages will be apparent from the following description of the presently preferred embodiment of the invention, provided for the purpose of description only and without thereby being limiting, and given in connection with the enclosed drawings, where: Figure 1 shows an extension ladder in accordance with the invention, with partially hoisted single ladders, and seen from the front, Figure 2 shows the ladder in accordance with Figure 1 seen from the end, Figure 3 shows the ladder in accordance with Figure 1 seen from the side, and Figure 4 shows the principle for the line pull and the line guides. Referring to Figure 1, an extension ladder is shown consist¬ ing of four single ladders 10, 20, 30, 40. Although the extension ladder may consist of fewer or more single ladders, the embodiment that is shown with four single ladders is particularly favorable with respect to compactness in collapsed position and the extent of its reach In hoisted position. As is apparent from the figure, the bottom ladder 10 is widest and the top ladder 40 is narrowest. Each single ladder comprises respective side members or stringers 5, 5'; 15, 15'; 25, 25'; 30, 30* and rungs 6, 16, 26, 36. The top ladder 40 may be provided with a top wheel 9 adapted to rest against a wall or the like during the hoisting operation. As mentioned earlier, the ladder can advantageou¬ sly be manufactured of aluminum, which combines in an excellent manner the requisite rigidity, strength and light weight. As is clearly apparent from Figure 2, the single ladders 10, 20, 30, 40 lie within one another, with the width for each single ladder decreasing by about two rail widths, which amounts roughly to a total of between 80 mm and 120mm. The side members are equipped with guide means (not shown) which allow each of the two adjacent single ladders to guide and support the other. Figure 3 shows the single ladders 10, 20, 30, 40 seen from the side and indicates how the single ladders lie within and guide one another. On the side rail that is being displaced, there is provided a locking device or drop hook (not shown), which is described in more detail in Norwegian patent no. 151.755. The drop hook has the capability of engaging with the rungs on the adjacent ladder so that the ladders may be locked in relation to one another for each step increment. Figure 1 also shows a rope pull or line pull for hoisting of the respective ladders. The line pull consists of a line 7 and respective line guides (1, 1'; 2, 2'; 3, 3';4) where the line guides in the embodiment shown are in the form of pulleys or castors. These may of course have other forms, such as an elbow tube with outwardly bent or flared holder openings in each end. It is important to keep clearly in view that there is an independent line pull between each pair of adjacent single ladders, so that in the four-part extension ladder shown there are three independent line pull systems, namely one between the single ladders 10 and 20, one between the single ladders 20 and 30 and one between the single ladders 30 and 40. Accordingly, only one line pull system between two single ladders will be described. Normally, the hoisting of the extension ladder will be done by first pulling up the narrowest ladder or the top ladder 40. Then the single ladder 30 is drawn up, taking with it the single ladder 40. Finally, the single ladder 20 is hoisted, in turn taking with it each of the extended single ladders 30 and 40. The line pull is schematically shown in further detail in Figure 4. From the figure it is apparent that the line pulls have the capability of changing the direction of the line 7 about an angle of either 90° or 180° As is apparent from Figures 1 and 4, the line 7 is fastened at one end to the bottom end of a side member 15 and runs up to a first pulley 1 and turns 180° down to a second pulley 2, then 90° and through a ladder rung 16 and to a secondary second pulley 2', then 90° up to a secondary first pulley 1' and 180° back down to a third pulley 3 and 180° up to a fourth pulley 4 and 180° back down to a secondary third pulley 3' and 180° back up to a drop hook (not shown), which is attached to the side member 15' of the ladder 20. Accordingly, the drop hook follows upwards with the side member 15' and is capable of lock-ing to a ladder rung 6 on the adjacent ladder 10. As the ladder 20 is displaced in relation to ladder 10, the part of the line 7 lying between the attachment to the side member 15 and the first pulley 1 becomes progressively shorter. At the other end of the line 7 where the drop hook is attached, the portion of line 7 lying between the secondary third pulley 3' and the drop hook is extended accordingly. The section of the line 7 lying between the first pulley 1 and the second pulley 2 and, respectively, the secondary pulley 2' and the secondary first pulley 1' becomes shorter, and this line is again taken up between the third pulley 3 and the fourth pulley 4 and the secondary third pulley 3'. In this way all of the line is accommodated and remains in the system without any of the line collecting on the ground. It should be noted that the extension ladder would also function satisfactorily if all the line guides were placed on one side of the ladder. This embodiment form thus would also reside within the scope of the present invention. However, the embodiment form with line guides placed on both sides is presently a preferred embodiment form, since it affords a good distribution of force to both sides of the ladder during the extension thereof. As mentioned earlier, the ladder may be equipped with support legs for four-point contact with the ground such that it forms a freestanding extension ladder unit. If the ladder consists of more than two single ladders, it may be advantageous to mark the lines, for example by coloring, so that the single ladders are hoisted in a given sequence, preferably the top ladder 40 first, followed by ladder 30, and finally ladder 20. The respective line guides in the embodiment shown are disposed in fittings that are attached to the respective side members by, for example, riveting or welding.

Claims: P a t e n t C l a i m s 1. An extension ladder, comprising at least two separate single ladders (10,20,30,40) which in their starting position lie upon and are slidable in relation to one another, and where one of the two adjacent ladders includes guide means for the other, c h a r a c t e r i z e d i n that between each pair of adjacent ladders (10 and 20, 20 and 30, 30 and 40), there Is provided a manually operated line pull system, comprising line guides over which a line (7) runs and changes direction, that a first ladder (10) at its upper end is provided with first line guides (1,1'), one on each side or two on the same side, and at its lower end with a pair of third line guides (3,3') on one side, that an adjacent ladder (20) at the lower end thereof is provided with second line guides (2,2'), one on each side or two on the same side, and in addition a fourth line guide (4) on the one side and at the same end as the third line guides (3,3'), the line (7) at a first end (8) thereof being secured to the second ladder (20) in the same end region as the second line guide (2,2') and running to the first line guide (1) and further to the second line guide (2), to the secondary second line guide (2'), to the secondary first line guide (1'), to the third line guide (3), to the fourth line guide (4), to the secondary third line guide (3') and further to a drop hook device attached to the second ladder (20), which drop hook device engages with sections of the first ladder (20) for locking thereto. 2. An extension ladder in accordance with claim 1, c h a r a c t e r i z e d i n that the line passes from the second line guide (2) to the secondary line guide (2') through a ladder rung (16). 3. An extension ladder In accordance with claim 1 or 2, c h a r a c t e r i z e d i n that the line guides constitute holder devices, pulleys, castors or a combination thereof. 4. An extension ladder in accordance with claim 1, 2 or 3, c h a r a c t e r i z e d i n that the ladder (40) that is to be hoisted first comprises a top wheel (9). 5. An extension ladder in accordance with claims 1 - 4, c h a r a c t e r i z e d i n that it comprises support legs of the type affording four-point contact with a base surface, for the purpose of being self-supporting. 6. An extension ladder in accordance with claim 3, c h a r a c t e r i z e d i n that the pulleys or castors are disposed in respective fittings attached to the respec¬ tive side members or stringers (5,5'; 15,15'; 25,25'; 35,35' ). 7. An extension ladder in accordance with claims 1 - 6, c h a r a c t e r i z e d i n that it is manufactured from aluminum. 8. An extension ladder in accordance with claims 1 - 7, c h a r a c t e r i z e d i n that the lines (7) are marked to indicate the hoisting sequence.

Inventors: HEGGEN HANS, HEGGEN, HANS
Applicants: RAUFOSS AS, RAUFOSS A/S
Application year: 1990
Main classification: E06C1
IPC codes: E06C1, E06C7