EP1669538A1

EP1669538A1 - Ladder with structure to prevent slipping

Info

Publication number: EP1669538A1
Application number: EP05111745A
Authority: EP
Inventors: Antoon Teel
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-12-08
Filing date: 2005-12-06
Publication date: 2006-06-14
Anticipated expiration: 2025-12-06
Also published as: DE602005007685D1; ATE399249T1; NL1027692C2; EP1669538B1

Abstract

Ladder consisting of two stiles with rungs fitted between them. Close to the bottom end a structure is fitted that prevents slipping out thereof. This structure consists of a supplementary bar that is braced against the ground essentially parallel to the rungs. The supplementary bar is fastened to the stiles via supplementary arms at 80 - 160 cm from the bottom of the ladder. A reaction bar acts between the bottom end of the supplementary arm and the stiles. The supplementary arm consists of two resiliently connected parts for positioning the supplementary bar and thus provides stable positioning of the ladder.

Description

The present invention relates to a ladder according to the precharacterising clause of Claim 1.
Such a ladder is disclosed in US 4 130 181 and is described in more detail with reference to Fig. 5.
In this publication a strut is proposed that extends centrally between the stiles and is braced against the ladder between the ninth and tenth rung with a spring. In the description it is claimed that slipping of the ladder is prevented by this measure.
Although such a structure is satisfactory at relatively firm ground, there are many situations in which safety still cannot be guaranteed as yet.
The aim of the present invention is to provide a ladder with which slipping is prevented in an effective manner under all circumstances.
This aim is achieved with a ladder as described above having the features of Claim 1.
According to the present invention the supplementary bar is fitted such that it can be moved relative to the lower end of the ladder. This supplementary bar is braced against the ground concerned. One (or more) supplementary arm(s) extends/extend from the supplementary bar towards the ladder, which arm functions as a strut and provides stability to the structure. By having a variable length, the supplementary arm can provide adjustment in the event of possible sinking and/or repositioning. It has been found that in this way slipping of the bottom of the stiles is effectively prevented. By fitting a supplementary arm of variable length on both sides, differences in height left and right of the centrally positioned ladder are compensated, as a result of which unsafe situations are prevented.
In order to optimise the stability of this structure as far as possible, according to a preferred embodiment of the invention the width of the supplementary bar is at least the same as the width of the ladder close to the lower end thereof.
The reaction bar can extend at an angle to the horizontal, but is preferably arranged essentially approximately horizontally in the use position.
In order to optimise strutting as far as possible the supplementary arm is fastened to the ladder at a distance of between 80 and 160 cm from the bottom of the ladder. This fastening is preferably effected on the outside of the stile.
Preferably both the supplementary arm and the supplementary bar are of adjustable length and width, respectively, in order to provide optimum adjustment to the prevailing conditions.
The variable length of the supplementary arm that alters during use can be achieved by making this supplementary arm in two parts that can slide relative to one another and fitting a spring between them. This spring is preferably made such that it drives the two parts apart, that is to say drives the supplementary arm away from the lower end of the ladder. According to the present invention when the ladder is placed in position the supplementary bar is positioned flat against the ground concerned. In addition, the length of the supplementary arm is adjusted by sliding the two parts relative to one another such that there is no tension or only slight tension. Thereafter locking of the parts relative to one another is established in such a way that these two parts can only telescope against the resistance of the spring. In the event that shifting occurs after the ladder has been placed, this spring is automatically tensioned and continually presses the supplementary bar against the ground in an optimum manner, as a result of which a particularly stable entity is obtained.
It has been found that an optimum effect is obtained if the spring has a spring constant of approximately 2 - 3 N/mm. Assuming a tension of 300 N in the spring when the ladder is placed, optimum adjustment to the prevailing conditions is provided. Slightly different values can optionally be chosen if the weight of the user differs substantially from the average weight of a user.
The invention also relates to means for preventing shifting of a ladder, comprising a supplementary bar to which a supplementary arm and a reaction bar are fastened, wherein the free ends of both the supplementary arm and the reaction bar are made for fastening to a ladder in a pivoting manner, wherein the supplementary arm consists of two parts that can move relative to one another under the influence of spring force. The fastening in a pivoting manner can in principle be any fastening known in the state of the art, but preferably comprises a ball joint at the fastening to the ladder, so that the arms can diverge sideways.
According to a further advantageous embodiment the supplementary arms engage on the second or third rung from the bottom. If the supplementary arm engages on a higher rung the stability of the structure will be reduced.
It will be understood that the spring concerned can be a helical spring, gas spring or the like.
The invention will be explained below in more detail with reference to an illustrative embodiment shown in the drawing. In the drawing:

Fig. 1 shows, diagrammatically, the placing of the ladder according to the invention against an exterior wall;
Fig. 2 shows the detail II from Fig. 1; and
Fig. 3 shows the detail III from Fig. 2 in the state immediately before placing.

In Fig. 1 the ladder according to the present invention is indicated by 1. This is placed against an exterior wall 2. In this example shown the ladder has a length of approximately 7 m, but it will be understood that this length can vary depending on the structure of the ladder (extendable or non-extendable). Ladder 1 consists of two opposing stiles 4, between which rungs extend.
The ladder has been placed on ground 6. If the ground is insufficiently stable or the ladder has been inexpertly placed, there is the risk that the ladder slips out in the direction of arrow 7. As a result of this there are a substantial number of accidents every year so that the authorities no longer permit the use of ladders in this manner by professionals.
The risk of slipping is prevented according to the present invention by the structure located at the bottom of the ladder at the back thereof. Details of this can be seen in Fig. 2.
There is a supplementary bar 10 consisting of two adjustable parts 11 and 12 that can slide relative to one another. These parts are secured in a specific position relative to one another and locked with bolt 13. A supplementary arm 14 is connected to supplementary bar 10 via pivot joints 19. Supplementary arm 14 also consists of two telescopic parts 15, 16. There is a spring 23 (Fig. 3) that drives part 15 and part 16 apart. Spring 23 is braced, on the one hand, against pin 17 in part 15 and is braced, on the other hand, against the end of part 16. Reaction bar 20 consists of parts 21 and 22, which can be secured in a position relative to one another with a pin 25. That is to say, after setting, the position of the parts 21 and 22 relative to one another no longer changes. Part 21 is connected to the stile 4 via a ball joint. Supplementary arm 14 is connected to the stile 4 and 3, respectively, via pivot joints 18. The distance between pivot point 18 and the lower end of the ladder is between 80 and 160 cm. Opposing pivot joints, such as pivot joints 18 can be connected using a threaded rod 35, shown diagrammatically. Ball joints can also be used instead of simple pivot joints.
A reaction bar 20 is fastened at a low level via pivot joint 27 to either side of each stile 3 and 4, respectively. The reaction bar 20 consists of two telescopic parts 21, 22 that can slide relative to one another. Part 22 is connected to the supplementary arm 14 in a pivoting manner at 26.
The spring 23 has a spring constant between 2 and 3 N/mm. The spring can be moved from a relaxed state to a tensioned state. The relaxed state is shown in Fig. 3b, a bolt 17 being in contact with the free end of spring 23 without any substantial pressure. The tensioned state is shown in Fig. 3a. Both supplementary arms can have the same type of spring, but it is also possible to fit different springs.
The structure described above is used as follows:
When the ladder is placed the width of the supplementary bar 10 is set. Preferably this is as wide as possible. The maximum width (B) can be 2 m or more. The position of the parts relative to one another can optionally be fixed using pin 13. The rearwards position of the supplementary bar 10 can also be set by mutual adjustment of the parts 21 and 22 of the reaction bar 20. This position of the parts relative to one another is then fixed by inserting pin 25. During all these operations pin 17 does not have to be in part 15. That is to say, part 16 can move freely relative to part 15 and when the ladder is placed the supplementary bar will drop to the ground under its own weight. Pin 17 is then put into part 15 in this position, in which the free end of spring 23 is in contact with pin 17 or is situated a very small distance therefrom. The correct position can be assured by, for example, colouring the appropriate end of spring 23, by which means the position of that end can be seen through the openings in part 15.
When the ladder is then used and "settling" occurs, the parts 15 and 16 will be pushed in with respect to one another. This movement will be counteracted by the tension in spring 23. As a result both the bottom 9 and the supplementary bar 10 will be made to grip the ground firmly. Shifting is then no longer possible. If, through use of the ladder, a small displacement of the bottom of the ladder is caused, this will be compensated later by the variable length of the supplementary arm 14.
By correctly sizing the different lengths of the supplementary arm 14, reaction bar 20 and supplementary bar 10, only a limited relative movement between part 16 and part 15 is needed. According to an advantageous embodiment the relative movement is a few centimetres, with a maximum of approximately 11 cm.
It has been found that even on very slippery surfaces the risk of slipping is completely eliminated. The weight of the ladder and the persons positioned thereon is not important.
Optionally the structure that is intended to prevent slipping can be so made that the reaction bar 20 can easily be detached, either at pivot joint 26 or at pivot joint 27, as a result of which the supplementary arm 14 can be folded down alongside the stiles 3, 4 and thus can be provided as a compact entity for transport.
Optionally the height of pivot point 18 can be made adjustable. To this end there can be a special clamp structure that engages in a clamping manner inside the hollow rungs.
After use the structure according to the invention can simply be removed from the ladder to enable space-saving storage. The pin part of the pivot joints can remain on the ladder, whilst the eye part can be removed in a simple manner. Obviously the same applies if ball joint connections are used.
After reading the above variants will be immediately obvious to those skilled in the art. In the light of the above these are obvious and fall within the scope of the appended claims.

Claims

Ladder (1) comprising two spaced stiles (4) and rungs (5) fitted between them and means in the position of use close to the lower end for preventing shifting of that lower end, said means comprising a supplementary bar (10) extending substantially parallel to said rungs (5), said supplementary bar being fastened to a supplementary arm (14) of variable length, said supplementary arm being fastened at the other end to said ladder at a distance from said lower end, and a reaction bar (20) connected to said supplementary bar, said reaction bar (in the position of use) being fastened to said ladder at a position below the fastening position of said supplementary arm to said ladder, characterised in that a supplementary arm (14) of variable length is fitted to each stile.
Ladder according to Claim 1, wherein the width (B) of said supplementary bar is at least the same as the width (b) of the ladder close to the lower end thereof.
Ladder according to one of the previous claims, wherein the reaction bar extends essentially horizontally.
Ladder according to one of the previous claims, wherein said supplementary arm (14) is fastened to said ladder at a distance of 80 - 160 cm from the bottom end of said ladder.
Ladder according to one of the previous claims, wherein said reaction bar has an adjustable length.
Ladder according to one of the previous claims, wherein said supplementary arm is provided with a spring structure (23) for achieving said variable length.
Ladder according to Claim 6, wherein said spring has a spring constant of 2 - 3 N/mm and said spring can be moved from a maximally tensioned state to a maximally relaxed state.
Ladder according to Claim 7, wherein said force of said spring in tensioned state is at least 300 N.
Ladder according to one of Claims 7 or 8 comprising locking means (17) for limiting the maximum variation in the length of the supplementary arm.
Ladder according to one of the previous claims, wherein said supplementary arm and the reaction bar are fastened to said stile (4) on the outside away from the rungs.
Ladder according to Claim 10, wherein said supplementary arm is fastened to said ladder at the second or third rung from the bottom.
Means for preventing shifting of a ladder, comprising a supplementary bar (10) to which two supplementary arms (14) some distance apart and associated reaction bars are fastened, wherein the free ends of both each supplementary arm and each reaction bar are made for fastening to a ladder in a pivoting manner, wherein each supplementary arm comprises of two parts that can move relative to one another under the influence of spring force.