The present invention relates to an extendable, load-bearing structure that includes a main structure and a driving element. The extent of the extendable, load-bearing structure is arranged to be changeable in both directions between a first position, in which the extendable, load-bearing structure has a smallest extent, and a second position, in which the extendable, load-bearing structure has a largest extent. The main structure includes at least one driving arm. The driving element is placed in connection with the at least one driving arm to drive the extendable, load-bearing structure between said positions. The invention further includes a method for erecting an extendable, load-bearing structure.

Extendable structures are known from before, for example for use in lifts and so-called "scissor tables".

A lift typically has a driving arm, which may drive a platform between a first position and a second position. The driving arm may comprise one or more elements connected to each other by joints.

A scissor table usually has several driving arms. In a typical embodiment, a scissor table may include four driving arms, wherein pairs of driving arms form X's, and wherein the driving arms are connected at the centres of the X's. The two X's, formed by the driving arms, are arranged to carry a platform. The platform can be driven between a first position and a second position by the angle of the driving arms being changed relative to a base.

The load-bearing capacities of extendable, load-bearing structures are dependent on the designs of the structures. A lift with only one driving arm must have a far stronger driving arm to carry the same weight as a scissor table with four driving arms. However, the scissor table, too, needs a robust structure. Such a robust structure may be heavy and therefore, in some situations, not very suitable.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features that are specified in the description below and in the claims that follow.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect of the present invention, an extendable, load-bearing structure has been provided, the extendable, load-bearing structure comprising a main structure, a driving element, a lock mechanism and a supporting structure. The extent of the extendable, load-bearing structure is arranged to be changeable in both directions between a first position, in which the extendable, load-bearing structure has a smallest extent, and a second position, in which the extendable, load-bearing structure has a largest extent. The main structure includes at least one driving arm. The driving element is placed in connection with the at least one driving arm to drive the extendable, load-bearing structure between said positions. The supporting structure comprises at least one supporting arm. The at least one supporting arm of the supporting structure is shorter than the at least one driving arm of the main structure. The supporting arm includes at least two supporting-arm elements which are connected to each other by a joint. When the extendable, load-bearing structure is in its second position, the supporting-arm elements are substantially in line. The lock mechanism is arranged to re- leasably lock the supporting-arm elements of the supporting structure in position when these are in line.

The lock mechanism may be arranged to releasably lock the supporting-arm elements of the supporting structure in position when these are in line, by each joint, connecting two supporting-arm elements belonging to a supporting arm, being arranged to lockingly engage in a releasable manner with the main structure when the load- bearing structure is in its second position, so that, in its second position, the load- bearing structure forms a lattice.

The extendable, load-bearing structure will normally include four supporting arms, but it may also include fewer than four supporting arms, such as three, two or one, or it may include more than four, such as five, six or more than six supporting arms.

The at least one supporting arm may comprise more than two supporting-arm ele- merits. Normally, the supporting arm will comprise two supporting-arm elements, but it may also comprise three, four five or more than five supporting-arm elements.

The extendable, load-bearing structure will normally include four driving arms, but may also include fewer than four driving arms, such as three, two or one, or it may include more than four, such as five, six or more than six driving arms.

Like the at least one supporting arm, the at least one driving arm may comprise several arm elements. Normally, the driving arm will comprise two driving-arm elements, but it may also comprise just one driving-arm element, or it may comprise more than two driving-arm elements, such as three, four, five or more than five driving-arm elements. In cases in which there are more than one driving-arm element, the driving- arm elements will be connected to each other by a joint.

The main structure of the extendable, load-bearing structure may work and look like a scissor table, but the extra supporting structure gives an obvious advantage in relation to a typical scissor table. With the supporting structure, the extendable, load-bearing structure will have a considerably better load-bearing capacity in the longitudinal direction of the supporting structure. This allows the main structure not to be as strong, and thereby not as heavy, as the structure of a scissor table in order to carry the same load.

A scissor table, as described earlier, may consist of an X-section, in which the arms that form the X are movable and in which the arms, when being moved, can lift or lower a platform. A scissor table may also consist of several X-sections, arranged in series. In that way, such a scissor table may have a larger maximum extent compared with a scissor table consisting of only one X-section. The same principle applies to the extendable, load-bearing structure according to the present invention. The extendable, load-bearing structure may consist of a single extendable section, or two or more extendable sections.

Each extendable section may have a main structure shaped like an X, or a double X, as in the case of the scissor table. It may also have other shapes. For example, it may be formed from two opposite Vs. Each such V consists of a driving arm, each driving arm comprising two driving-arm elements that are connected to each other by a joint. Such a V-structure will give a larger maximum extent than an X-structure in relation to the size of the area covered by the structure on a base from which it is erected; that is to say in relation to a so-called "footprint".

The extendable, load-bearing structure may be used as an extendable structure in the vertical direction, in the horizontal direction, or in any direction between the vertical and horizontal directions.

The supporting structure may include end portions. One or more of these end portions may be placed in engagement with the main structure. With such a solution, the extendable, load-bearing structure may form a lattice in its second position and thereby form a very solid structure of great load-bearing capacity.

The lock mechanism may comprise a lock bail as part of the main structure and a receiving bail as part of the supporting structure. The lock bail may comprise a cylinder and a piston, and the receiving bail may include a receiving device for a piston, called a piston receiver in what follows. The lock mechanism may be arranged to place the supporting structure into releasable locking engagement with the main structure by the piston of the lock bail being driven into the piston receiver of the receiving bail when the extendable, load-bearing structure is in its second position. A lockable engagement will further increase the load-bearing capacity and the stability of the structure.

The lock bail may be provided with a spring to prevent the bail from rotating in a manner which may lead to problems in locking. For the same reason, the receiving bail may be provided with a spring. The purpose of the springs is thus to ensure that the lock bail and the receiving bail have the correct orientations relative to each other.

The lock mechanism that ensures the lockable engagement may be hydraulically operated in a manner known per se, or it may be electrically operated.

The extendable, load-bearing structure may include a guiding device for the transport of equipment. The guiding device may be formed of the supporting arms of the supporting structure. The guiding device may include a rail with a track adapted for a motorized means of conveyance to be moved between the end portions of the extendable, load-bearing structure when the extendable, load-bearing structure is in its second position; that is to say when the supporting-arm elements of each supporting arm are in line. This guiding device may be advantageous as it may facilitate the conveyance of, for example, tools to and/or from a user of the extendable, load-bearing structure.

The extendable, load-bearing structure may include a plurality of guiding devices. It may include two, three, four or more than four guiding devices. Two or more guiding devices may be arranged to be parallel to each other when the extendable, load- bearing structure is in its second position. The extendable, load-bearing structure may further be provided with a biasing element for the supporting arms of the supporting structure to be pushed out from the main structure when the lock mechanism releases a lockable engagement between the supporting structure and the main structure. Such a biasing element has the effect of enabling the joints of the supporting structures to be displaced so that the supporting- arm elements of each supporting arm will no longer be in line when the supporting- arm elements are no longer in the locked position. This property may be advantageous when the extendable, load-bearing structure is to be driven from its most extended position.

In a second aspect, the invention relates to a method for erecting an extendable, load- bearing structure in accordance with the first aspect of the invention, the extendable, load-bearing structure having a supporting structure which, in the second position of the extendable, load-bearing structure, is brought into engagement with the main structure.

The method may further include the step of the supporting structure being locked in releasable locking engagement with the main structure when the extendable, load- bearing structure takes its second position.

In what follows, examples of preferred embodiments will be described, which are illustrated in the accompanying drawings, in which :

Figure 1 shows a section of an extendable, load-bearing structure;

Figure 2 shows a schematic illustration of an extendable, load-bearing structure consisting of four sections, in a position between a first position and a second position;

Figure 3 shows a schematic illustration of an extendable, load-bearing structure consisting of four sections, in the extended positon;

Figure 4 shows an extendable, load-bearing structure consisting of two sections, the sections of the extendable, load-bearing structure each being provided with a driving element, and a driving element being connected to the lowermost part of the extendable, load-bearing structure; and

Figure 5 shows an embodiment of the main structure of the extendable, load- bearing structure of figure 1, seen from above, the main structure further including a spring for holding a lock bail in position. Figure 1 shows an embodiment of a section 10 of an extendable, load-bearing structure 1. The extendable, load-bearing structure 1 may comprise one such section 10, or two or more such sections 10 connected in series. The figure shows how the extendable, load-bearing structure 1 is constructed from a main structure 2 including four inner V's 25a, 25b, 26a, 26b of opposite orientations in pairs. These V's 25a, 25b, 26a, 26b are each formed of a driving arm 21, each driving arm 21 being formed of two driving-arm elements 22 which are connected to each other by a joint 23. Further, the figure shows how a supporting structure 3 of the load-bearing structure 1 includes four outer V's 35a, 35b, 36a, 36b of opposite orientations in pairs, each V 35a, 35b, 36a, 36b being formed of a supporting arm 31, and each supporting arm 31 consisting of two supporting-arm elements 32 which are connected to each other by a joint 33. The supporting arms 31 are shorter than the driving arms 21 so that the supporting arms 31 will reach the extended position before the driving arms 21. In their extended positions, the supporting arms 31 will form I's as the supporting-arm elements 32 of the supporting arms 31 will be in line in their extended positions.

In the embodiment shown in figure 1, the extendable, load-bearing structure 1 is of such a design that the main structure 2 and the supporting structure 3 will engage with each other when the supporting-arm elements 32 of the supporting arms 31 are in line. The extendable, load-bearing structure 1 further includes a lock mechanism 4 which can be used to place the supporting structure 3 into releasable locking engagement with the main structure 2. The lock mechanism 4 includes two lock bails 28a, 28b and two receiving bails 38a, 38b. The lock bails 28a, 28b each include two cylinders 41 and two pistons 42, and the receiving bails 38a, 38b each include two piston receivers 44. When the extendable, load-bearing structure 1 is in its most extended position and the supporting structure 3 is in engagement with the main structure 2, the lock mechanism 4 places the supporting structure 3 in releasable locked engagement with the main structure 2 by the pistons 42 of the lock mechanism 4 being pushed into the piston receivers 44.

The driving arms 21 of the main structure 2 are parallel in pairs. The locking bails 28a, 28b form connections between the joints 23 of each pair of drive arms 21 of the main structure 2, which are parallel to each other. In the same way, the supporting arms 31 of the supporting structure 3 are parallel in pairs, with the receiving bail 38a, 38b arranged in connection between the joints 33 of each pair of supporting arms 31 of the supporting structure 31 that are parallel to each other.

Further, the supporting structure 3 of the extendable, load-bearing structure 1 in- eludes a rail 36 with a guiding device 37, indicated here as toothings. In the figure, two such rails 36 with guiding devices 37 are shown, but it will be understood that the extendable, load-bearing structure 1 may include more than two such rails 36 with guiding devices 37, or it may include fewer than two.

Figure 2 shows a schematic illustration of the extendable, load-bearing structure 1 with four sections 11, 12, 13, 14 corresponding to the section 10 shown in figure 1. The extendable, load-bearing structure 1 is in a position between its smallest extent and its largest extent.

Figure 3 shows the same as figure 2, but in figure 3 the extendable, load-bearing structure 1 is in its second position, in which the extendable, load-bearing structure has its largest extent. In figure 3, the supporting-arm elements 32 of the supporting arms 31 are in line in pairs, and the supporting structure 3 is in releasable locking engagement with the main structure 2. In this embodiment and in this position the extendable, load-bearing structure 1 forms a lattice.

Figure 3 shows further that each joint 33 connecting two supporting-arm elements 32 belonging to a supporting arm 31 is arranged to lockingly engage in a releasable manner with the main structure 2 when the supporting structure 1 is in its second position.

It should be noted that even though the extendable, load-bearing structure 1 is shown as a structure erected in height, "standing" that is, it will be understood that the extendable, load-bearing structure 1 may equally well be used "lying", or in any position between the standing position shown and said lying position.

In figure 4, the extendable, load-bearing structure 1 is illustrated with driving elements 6a, 6b, 6c. The extendable, load-bearing structure 1 is placed on a base 7 and consists of two sections 11, 12. Each section is provided with a driving element 6b, 6c. In addition, the extendable, load-bearing structure 1 is provided with a driving element 6a standing on the base 7 and being connected to the lowermost part of the extendable, load-bearing structure 1. The driving elements 6a, 6b, 6c may be one of or a combination of: electric motors, hydraulic motors, or mechanical driving elements 6a, 6b, 6c, for example a threaded rod.

It should be noted that even though it is indicated in simple lines, the main structure 2 shown in figure 4 is in principle identical to the main structure 2 shown in the preceding figures.

Figure 5 shows only the main structure 2 of figure 1 seen from above, but the main structure 2 further includes a spring 27. The spring 27 connects a lock bail 28 to a driving-arm element 22. The purpose of the spring 27 is to provide for the lock bail 28 to be biased into a correct position relative to the piston receiver 44 shown in figure 1.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.