FIELD OF TECHNOLOGY The present invention relates to a bed, more specifically a rigid or articulated bed comprising modules.

BACKGROUND

At present there are several function to obtain an adjustable firmness in beds, normally this is done by utilizing a motor applying a force on one, or several, compression planes in the bed in order to create a variable tension in springs arranged on or above the compression plane. If the motor presses the compression plane in an upward direction, the springs will, as a consequence, be compressed, which leads to one type of firmness in the mattress, while an adjustment of the compression plane in the downward direction yields less compressed springs leading to another type of firmness in the mattress. These actions are usually applied on a particular part of the bed, referred to as a compressing zone. In the case that the bed is articulated, that is, if the bed comprises a number of modules that can be angled relative a horizontal plane a number of motors can used to obtain an adjustable firmness in the different modules, as described above. This is however fairly expensive since it necessitates a large number of motors, and it is moreover complicated to synchronize the partitioned zone with several motors. It is therefore a need to provide alternative mechanisms for rigid or articulated beds. SUMMARY

The present invention aims to provide technology that at least partially overcomes some of the above mentioned drawbacks. The invention aims in particular to provide technology that makes it possible to extend the impact from a single compressing zone of a base module to adjacent modules. In this way it will only necessitate the use of a single motor, or alike, that is adapted to control the height in a base module. The invention displays a number of embodiments that makes it possible to translate the height adjustment caused by the motor to the side modules. According to a first aspect of the present invention it is provided a bed comprising at least two modules, a base module and a side module, the base module comprises two planes, a base plane and a compression plane whose relative positions may be altered to obtain an alteration of the compression level of the compression plane. The side module 4 of the bed comprises two planes, a side module base plane and a tail plane. The tail plane comprises two end sections, a first end section and a second end section, the first end section of the tail plane is attached to the compression plane of the base module 1 by means of a fixation means. The fixation means allows a rotation of the tail plane relative the compression plane 3 of the base module, and is further adapted to fixate the first end section of the tail plane to the compression plane of the base module in such a way that a motion of the compression plane induces the same motion of the first end section, whereby an alteration of the compression level of the compression plane, caused by a change in the relative position between the base plane and compression plane, causes an alteration of the compression level of the side module.

According to a second aspect of the present invention there is provided a side module to be combined with an existing base module in order to create an articulated and compressible bed. Such a side module comprises a tail plane and a side module base plane, the tail plane comprises a first end section and a second end section. The first end section comprises fixation means adapted to attach to a compression plane of the base module. The fixation means are arranged to attach the tail plane to the compression plane in such a way that a rotation of the tail plane relative the compression plane is enabled. The fixation means are also adapted to fixate the first end section of the tail plane to the compression plane of the base module in such a way that a motion of the compression plane induces the corresponding motion of the first end section whereby an alteration of the compression level of the base module, cause by a change in the relative position between a base plane in the base module and the compression plane, causes an alteration of the compression level of the side module. Embodiments of the present invention take advantage of the height adjustment of the base module and translates it to the tail plane of the side module. The connection between the modules locates the tail plane of the side modules to the same height as the compression plane of the base module. The remaining position and angle of the tail plane are controlled by additional actions. The embodiments enables alternative constructions of articulated beds that requires a smaller number of compressing motors and, as a consequence, also provides economic advantages.

BRIEF DESCRIPTION OF DRAWINGS

Below follows a short description of the drawings that will be referred to. The reference numerals of the drawings relates to similar or identical elements.

Fig. 1 a shows a side view in cross-section illustrating the mutual arrangements of the base module and side module in a possible embodiment. The base plane of the side module is in the raised position and the tail plane in its upper position.

Fig. 1 b shows, in cross-section, the vital parts of a possible embodiment of the two modules.

Fig. 2a shows a possible embodiment where one end of the tail plane of the side module is resting against the compression plane of the base module. The base plane of the side module is either rigid or lowered and the compression plane is in its upper position.

Fig. 2b shows a possible embodiment where one end of the tail plane of the side module is resting against the compression plane of the base module. The base plane of the side module is in an angled position and the compression plane is in its lower position.

Fig. 3a shows a possible embodiment where the compression planes of the base- and side modules are connected to each other. The base plane of the side module is in the down position and the compression plane in its upper position. Fig. 3b shows a possible embodiment where the compression planes of the base- and side module are connected to each other. The base plane of the side module is in an angled position and the compression plane in its upper position. Fig. 4a shows a possible embodiment where the planes of the side module is locked into a parallel mutual position. The base plane of the side module is in its down position and the compression plane in its upper position.

Fig. 4b shows a possible embodiment where the planes of the side module are locked into a parallel mutual position. The base plane of the side module is in an angled position and the compression plane in its lower position.

Fig. 4c shows a possible embodiment corresponding to Fig.4a but where the abutment comprises a wheel.

Fig. 4d shows a possible embodiment corresponding to Fig.4b but where the abutment comprises a wheel.

Fig. 5a shows a possible embodiment where the height of the end of the tail plain that is opposite the base module is adjusted by means of a link. The base plane of the side module is in an angled position and the compression plane is in its upper position.

Fig. 5b shows a possible embodiment where the height of the end of the tail plain that is opposite the base module is adjusted by means of a link. The base plane of the side module is in its down position and the compression plane is in its lower position.

Fig. 6a shows a possible embodiment comprising a wire function. The base plane of the side module is in the down position and the compression plane in its upper position.

Fig. 6b shows a possible embodiment comprising a wire function. The base plane of the side module is in an angled position and the compression plane in its upper position. Fig. 7a shows a possible embodiment where the height of the tail plane is adjusted by means of a link from the motor of the base plane. The base plane of the side module is in an angled position and the compression plane is in its upper position. Fig. 7b shows a possible embodiment where the height of the tail plane may be adjusted by the motor of the base plane through a chain, a sprocket, a lifting arrangement or some other imparting means. The base plane of the side module is in an angled position and the compression plane is in its upper position. Fig. 8 shows possible embodiments of a fixation means according to the present invention.

8a illustrates a hinge having hinges in a compressed state.

8b illustrates a hinge having hinges in an extended state.

8c illustrates a hinge having a constrained rotary motion due to a stop.

8d illustrates a fixation means on which an applied surface may slide

In order to facilitate reading, below is provided a reference designation list.

1 Base module

2 Base plane

3 Compression plane

4 Side module

5 Side module base plane

6 Tail plane

7 First end section opposing base module

8 Second end section

9 Distance between 2 and 3

10 Distance between 5 and 6

1 1 Fixation means

13 Motor for tilting of the side module

14 Motor for compression

15 Lifting means

16 Hinge

17 Compressible element 18 The horizontal plane of the compression plane

19 Link

20 Chain

21 Abutment

5 22 First sprocket

24 Rigid element or guiding rod

25 Lifting arrangement

26 Adjustment sprocket

27 End sprocket

10 28 Link rod

29 Wheel

30 Wire

31 Sleeve

33 Stop

15 35 Lower roll

36 Upper roll

DETAILED DESCRIPTION

20 The present invention is based on existing beds comprising zones having the feature that the bed springs tension may be adjusted. These zones comprises a compression plane whose height may be controlled by a motor. A bed may have several compressible planes with separate motors. The springs of the bed is compressed between the compression plane and an abutment. The components of the bed may

25 vary and may be combined in various ways. One particular construction may be a frame bed comprising a frame having a set of springs. On the frame bed a mattress may be placed on top of which a bed mattress in turn may be placed.

Another possible construction relates to so called motor beds, these comprises bed 30 sections that are connected by means of leads. Usually a motor bed comprises a back section that can be tilted, a rigid horizontal middle section and two sections for legs and feet's, respectively. A motor bed has a separate motor that adjusts the angle of the different sections. These two existing solutions may together create user scenarios with four extremes:

- maximal compression with rigid or lowered side module,

- maximal compression with raised side module,

- minimal compression with rigid or lowered side module,

- minimal compression with raised side module.

The present invention aims to provide mechanisms that enable one:

- to extend a compressible zone over a lead between two bed sections,

- to be able to connect two independent compressible zones with a middle section with gradually changed compression level along the zone.

Fig. 1 a shows a cross-section of a possible embodiment of a bed with a base module 1 , the purpose of which is to enable a varied bias on the springs in an overhead layer. The present technology aims to translate this functionality to side module 4 without having to provide an additional motor 14.

According to one aspect of the present technology, illustrated in Figs. 1 a-b, there is provided a bed comprising at least two modules, a base module 1 and a side module 4, the base module comprises two planes, a base plane 2 and a compression plane 3, whose relative positions may change to achieve a change in the compression level of the base module. The side module of the bed comprises two planes, a side module base plane 5 and a tail plane 6. Tail plane 6 comprises two end sections, a first end section 7 and a second end section 8, the first end section 7 of the tail plane 6 is connected to compression plane 3 of the base module 1 through a fixation means 1 1. The fixation means 1 allows a rotation of the tail plane 6 relative the compression plane of the base module, and is also adapted to fixate the first end section 7 of the tail plane 6 to the compression plane 3 of the base module in such a way that a movement of the compression plane 3 imparts the corresponding movement of the first end section 7, whereby a change of the compression level of the base plane 1 , caused by a change in the relative position between base plane 2 and compression plane 3, causes a change in the compression level of the side module 4.

An advantage with this embodiment is that a smoothly varying firmness of the bed is achieved. It should be noted that the side module 4 may be attached to the base module 1 in such way that the side module 4 can be angled relative the base module. In this way an articulate bed is obtained. The various mechanisms that are described herein are therefore equally suitable for a regular bed, i.e. a bed where the side module 4 and the base module 1 are horizontally attached, and an articulated bed. As is clear from Fig. 1 a, the base module 1 comprises a compression plane 3 and a base plane 2. These planes are arranged in the base module 1 in such a way that they can move relative each other in a vertical direction, directly or indirectly affected by a motor 14. With compression plane is also intended devices that moves in a vertical fashion from the base plane during compression of element 17, e.g. a lifting device. One or several side modules 4 can be attached to the base module 1 . These also comprises two planes, a plane 5 that can be tilted, also referred to as a side module base plane 5, which can be tilted in respect to the base module 1 , and a tail plane 6. In Fig. 1 a is the left side module 4 raised by means of a separate motor 13 that is adapted to tilt the side module 4 relative the base module 1 .

Fig. 1 b illustrates a detailed cross-section of possible embodiment of the side module 4 and the base module 1 . The drawing shows that the side module base plane 5 is in its lowered, or fixed, position and that the compression plane 3 is in its upper position. One purpose with the design illustrated in Fig.1 a andFig.l b is that the compression plane 3 of the base module 1 shall control the height of the end section 7, closest to the base plane 1 , of the tail plane 6 of the side module 4

The end section 7 of the tail plane 6 is attached to the compression plane 3 through a fixation means 1 1 that allows that the tail plane 6 is tilted relative the compression plane 3. The tail plane 6 is placed in the side module 4 but are connected to, and affected by, the base module 1.

The fixation means 1 1 may, beyond providing a support in the vertical plane, also be adapted to provide a firm, a free or a constrained horizontal motion by e.g. utilizing hinges or articulated hinges, springs or mechanical stops. Since the distance between the base module 1 and the side module 4 may be altered bases on their mutual tilt, one or more flex zones may be necessary. The fixation means 1 1 may provide such a flex zone. Fig. 2a-b, shows a cross-section of a possible embodiment of the base module 1 and side module 4, in which the end section 7 of the tail plane connects to the compression plane 3 through fixation means 1 1 which may provide a vertical support from the compression plane 3 and enable a rotation around the fixation means 1 1 , which in turn makes it possible to control the height of the second end section 8 of the tail plane 6 based on the position where it was attached or leans towards.

Fig. 2a provides an illustration where the side module base plane 5 is fixed or lowered and the first end section 7 of the tail plane of the side module is in an upper position corresponding to the compression plane 3 in the base module 1 due to the fixation means 1 1 , it also illustrates how the second end section 8 is leaning down towards the side module base plane 5. The end section 8 may be affected by a separate motor or another module.

Fig. 2b illustrates a tilted side module base plane 5 affecting the tail plane 6 in such a way that the end section is raised above the fixation means. The purpose of this embodiment is that the tail plane 6 may mirror the height of the compression plane 3 by a gradual lowering in the direction from the base module 1 .

According to a particular embodiment of the proposed technology there is provided a be comprising means 33 that limits the vertical motion of the second end section 8 of the tail plane in such a way that the end section 8 is always parallel with, or located above, the horizontal position of the compression plane 3 in order to ensure that the tail plane 6 only is allowed to rotate in a direction that renders the end section 8 to be located above the compression plane 3.

Fig. 3a shows a cross-section of such an embodiment where the ability to tilt the tail plane 6 of the side module is limited relative the compression plane 3 of the base module 1 . The purpose of this limitation is to ensure that the height of the whole tail plane of the side module is not lower than the fixation means 1 1 , that is, it may only be tilted in a direction upwards from a lowest horizontal position. This means that the tail plane 6 of the side module is always more or less horizontal with the compression plane 3 of the base module 1 when the side module base plane is lowered to a horizontal position.

In this particular embodiment is the tail plane 6 of the side module 4 allowed to rotate around the fixation means 1 1 in such a way that the opposite section 8 of the tail plane, as seen from the fixation means 1 1 , is only allowed to have a height that is equal to or above the height of the fixation means 1 1. This particular limitation of the rotation may, according to a particular embodiment, be obtained by means of a stop 33 that consists of an extension of the tail plane 6 through the fixation means 1 1 which, together with the compression plane of the base module, prohibits a rotation under the horizontal plane. Another embodiment may be the reverse, in which an extension of the compression plane 4 prohibits the tail plane to rotate under the horizontal plane.

Fig. 3b illustrates the embodiment of Fig. 3a when the side module base plane 5 is in the raised state and the compression plane 3 is in its lower position. The fixation means 1 1 allows the side module base plane 5 to affect the tail plane 6 so that the latter obtains a raised tilted position. The purpose of this is to make sure that the whole tail plane 6 of the side module takes a horizontal height that corresponds to the height of the compression plane 3 of the base module.

Yet another embodiment of the proposed technology provides a bed where the side module 4 comprises, or can be connected to, means adapted to tilt the side module 4 relative the base module 1 , whereby also the side module base plane 5 is tilted relative the base module. Examples of such a means may be motors, but also a manually affected tilting is possible.

A possible embodiment of an articulated bed comprises lifting means 19, 24 adapted to raise the second end section 8 of the tail plane 6 in order to ensure that the distance between the tail plane 6 and the side module base plane 4 are tilted relative the base module.

Fig. 4a provides an illustration of a possible embodiment where the planes of the side module are locked into a mutual parallel position. The side module base plane is lowered and the compression plane is in its upper position. The purpose is to control the motion of the tail plane 6 in such a way that it is essentially forced to move in parallel with the side module base 5 with a mutual distance 10 that more or less corresponds to the distance 9 between the base plane 2 and the compression plane3 of the base module.

According to a particular version of this embodiment of a bed the lifting means 19, 24 consists of a rigid element 24 that is fixed to the side of the tail plane 6 that is opposite the side module base plane 5, said rigid element extends from the tail plane 6, through an aperture in the side module base plane 5 and ends in a holder 21 that is fixed to the side of the side module base plane that is not opposed the tail plane 6, said holder having a width dimension that is slightly larger than the width dimension of the rigid element, whereby the rigid element 24 and the holder 21 , upon a tilt of the side module 4, cooperates to raise the tail plane 6 and ensure that the distance between the tail plane 6 and the side module base plane is essentially constant. One particular example of a rigid element comprises a rod, also referred to as a guiding rod. It is however also possible to use a spring or alike.

The guiding rod 24 is, according to one possible embodiment, a fixed and angled protrusion that protrudes from the tail plane 6, the motion of the guiding rod is constrained by an abutment 21 that is fixed against the side module base plane 5. The abutment 21 only allows the guiding rod 24 to move vertically towards the side module base plane, with the result that the tail plane 6 only may take a position that is parallel to the side module plane 5. Examples of an abutment may e.g. be wheels 29, bearings, a roll or some other element that may withstand pressure in one direction while allowing motion with reduced friction in another direction. This embodiment is schematically illustrated in Figs. 4a and 4b.

According to a possible embodiment of the above bed the holder 21 comprises at least one wheel 29 so arranged that said rigid element 24 runs along said wheel 29 on the side of said wheel that is farthest from the end section 8 of the tail plane 6. Fig. 4b illustrates a possible embodiment where the planes of the side module are locked into mutual parallel positions. The side module base plane is in its raised position and the compression plane in its lower position.

The implementation illustrates how the side module plane 5 steers the tail plane 6 by utilizing a guiding rod 24 and an abutment 21 .

Fig. 4c illustrates a possible embodiment where the planes of the side module are locked into a mutual parallel position. The side module base plane is lowered and the compression plane is in its upper position. The abutment 21 is, in this particular implementation, a wheel provided below the side module base plane and between the guiding rod 24 and the base module 1 .

Fig. 4d illustrates the embodiment of Fig. 4c but when the side module base plane is in its raised position and the compression plane is in its lower position.

According to yet another embodiment of a bed the lifting means 19, 24 comprises an arrangement comprising a link, said link having one end fixed to the base plane 2 and another end fixed to the tail plane at a position in the vicinity of the end section 8 of the tail plane 6, said link extends through an aperture in the compression plane whereby a relative change of the compression planes 3 position relative the base plane 2 results in a relative stretch of the link relative its anchor point which in turn results in a relative change of the position of the tail plane 6 relative the side module base plane 5. According to a version of this embodiment of a bed, said link also comprises a wire 30 and a supporting sleeve 31 , said wire having one end attached to the base plane 2 and the second end attached to the tail plane 6 at a position in the vicinity of the end section 8 of the tail plane, said supporting sleeve 31 has a first end attached to the compression plane 3 and a second end fixed to the side module 4 at a position above the highest point of the tail plane. This embodiment is schematically illustrated in Figs. 5a and 5b. Figs. 5a-b provides illustrations of cross-sections of a possible embodiment whose purpose is to control the motion of the tail plane 6 in such way that it moves in parallel against the side module base plane 5 with a mutual distance 10 that corresponds to the distance 9 between the planes in the base module 1 irrespective of whether the side module 4 is tilted or not. The first end section of the tail plane 6 is anchored to the compression plane 3 by means of fixation means 1 1 , the second end section 8 of the tail plane 6 is attached to a link 19 that raises the end section 8 a height that corresponds to the height of the compression plane 3 plus the height of the side module 5 at the end section 8.

A possible embodiment of the link 19 comprises a wire 30, which in one end attaches to the end section 8 and in the other end attaches to the base plane 2 or the compression plane 3. The wire may partially be enclosed by a supporting and flexible sleeve 31 having one end is fixed against the side module 4 at a height above the side module base plane that at least corresponds to the maximum distance between the planes in the base module 1 , the second end of the sleeve 31 is fixed against the plane in the base module 1 that does not fixate the wire. The drawings illustrate the situation where the wire is attached to the base plane 2 and the sleeve is fixed against the second plane, i.e. the compression plane 3. The link 19 may comprise a wire with supporting sleeve, a chain, link rods or some other functional means that is adapted to transfer a pulling force or pressure.

Fig. 5a illustrates a possible embodiment where the height of the end of the tail plane that is opposite the base module is controlled by a link. The side module base plane is raised and the compression planes are in their upper positions.

Fig. 5b illustrates a possible embodiment where the end of the tail plane that is opposite the base module is controlled by a link. The side module base plane is lowered and the compression planes are in their lower positions. The height of the second end section 8 corresponds to the sum of the height of the side module base plane, under the end section 8, and the distance between the planes of the base module 1. According to yet another embodiment of a bed, the lifting means 19, 24 comprises an arrangement having a wire and at least one roll, said wire having one end fixed to the compression plane and one end arranged on the tail plane 6, preferably adjacent to the end section 8 of the tail plane, the wire is adapted to run from the compression plane 3, through the roll 35, arranged at a position underneath the fixation means 1 1 , to the trail plane 6, whereby a change in the position of the compression plane, relative the base plane 2, leads to a relative stretch of the wire leading in turn to a change in the position of the tail plane 6 relative the side module base plane 5.

A version of this embodiment provides a bed where the wire is attached to the tail plane through yet another roll 36, said roll being fixed in the side module, at a position above the highest position of the tail plane 6. This embodiment is schematically illustrated in Fig. 6a and Fig. 6b.

Fig. 6a-b illustrates a possible embodiment where the purpose is to ensure that the planes of the side module 4 moves in parallel to each other, corresponding to the planes of the base module 1 , irrespective of whether the side module 4 is tilted or horizontal.

The first end section 7 of the trail plane 6 of the side module is fixed against the compression plane 3 through fixation means 1 1 , the height of the second end section 8 is affected by a wire 30 that runs over an upper roll 36 and a lower roll 35 to finally attach to the compression plane 3 in the base plane 1 .

The wire may in an alternative embodiment be replaced by a chain and sprocket or by a corresponding means that is able to transfer a pulling force

Fig. 6a illustrates a possible embodiment having a wire function. The side module base plane is lowered and the compression plane is in its lower position. Fig. 6b also illustrates a possible embodiment with a wire function. The side module base plane is in its upwardly angled state and compression plane is in its upper position. Fig. 7a illustrates a cross-section of a possible embodiment where the motion of a motor 14, or a lifting device 15 in the base module 1 , is used directly or indirectly via link 28 to a steered lifting device 25 in the side module 4. Fig. 7b illustrates a cross-section of a possible embodiment where a torque from the motor 14, or the motion of the lifting device 15, or the motion of the compression plane is transferred, via sprocket 22 and chain 20, possibly through an optional middle sprocket 26 to an end sprocket 27 with a lifting device 25 arranged on the side module 4. The lifting device 25 may comprise one or several arms, or some other function that aims to press the tail plane 6 upwards. The chain 20 and socket may in another embodiment be replace by wires and rolls. The attachment points for the various part may be adjusted to obtain correct gearing as well as controlling the height changes during tilting of the module. Fig. 8 illustrates possible embodiments of the fixation means 1 1. The purpose is to show that the fixation means 1 1 , the attachment points and anchoring points may have a flex zone to control varying mutual distances between the functions that they connect. One embodiment of such a flexible fixation means may comprise one or several interconnected hinges which are folded during compression and stretched in the extended state. Another embodiment may be an encapsulated spring that is allowed to expand but that withstands pressure.

Fig. 8 shows in particular an articulated hinge with a flex function in the compressed state.

Fig 8b illustrates an articulated hinge with a flex function in the extended state.

Fig. 8c illustrates hinges having rotatory motion constrained by an abutment.

Fig. 8d illustrates fixation means along which an applied surface may slide.

According to another aspect of the proposed technology there is also provided a side module 4 to be combined with an existing base module 1 in order to create an articulated and compressible bed.

Such a side module 4 comprises a tail plane 6 and a side module base plane 5, the tail plane 6 comprises a firs end section 7 and a second end section 8. The first end section 7 comprises fixation means 1 adapted to be attached to the compression plane 3 of said base module 1 . The fixation means 1 1 are adapted to attach the tail plane 6 to the compression plane 3 to allow a rotation of the tail plane 6 relative the compression plane 3 of the base module. The fixation means 1 1 is further adapted to fix the first end section 7 of the tail plane 6 to the compression plane 3 of the base module in such a way that a motion of the compression plane 3 yields the corresponding motion of the first end section 7, whereby a change of the compression level of the base module 1 , caused by the change in the relative position of a base plane 2 in the base module and the compression plane 3, induces a change in the compression level of the side module 4.

A particular embodiment of such a side module 4 comprises organs 33 adapted to constrain the vertical motion of the second end section 8 of the tail plane 6 in such a way that the end section 8 is always essentially parallel with, or lies above, the compression plane 3 in order to ensure that the tail plane 6 is only allowed to rotate in a direction that makes the end section 8 lie above the compression plane 3.

Yet another embodiment of such a side module comprises, or can be attached to, organs that are adapted to tilt the side module 4 relative the base module 1 , whereby the side module base plane 5 is tilted relative base module 1. An example of such an organ may be a motor.

Still another embodiment of such a side module 4 comprises lifting means 19, 24 that are adapted to lift the second end section 8 of the tail plane 6 during tilting of the side module 4 relative the base module to ensure that the distance between the tail plane 6 and the side module base plane 5 is essentially constant even when the side module 4 is tilted relative the base module.

A particular version of a side module 4 provides a side module where the lifting means 19, 24 comprises a rigid element 24 attached to the side of the plane that is opposite the side module base plane 5. The rigid element 24 runs from the tail plane 6 through an aperture in the side module base plane 5 and ends in a holder 21 that is fixed on the side of the side module base plane 5 that is not opposite the tail plane 6. The holder 21 has width dimension that are slightly larger than the width dimension of the rigid element, whereby the rigid element 24 and the holder 21 , during tilting, cooperates to lift the tail plane 6 and ensure that the distance between the tail plane 6 and the side module base plane 5 is essentially constant. The holder 21 may in one embodiment comprise at least one wheel 29 so arranged that said rigid element 24 runs along said wheel 29 on the side of the wheel that is farthest from the end section 8 of the tail plane 6. Other embodiments comprises one or several opposite wheel pairs 29. The region between the wheel pairs are traversed by the rigid element 24. The present invention has been described using a number of specific embodiments. These embodiments are merely intended to facilitate an understanding of the main concept of the invention and should not constitute limitations to the scope of the invention which is defined by the appended claims. A person skilled in the art will upon studying the application realize that it is possible to combine technically compatible embodiments and that these embodiments allows for combinations that are not explicitly described.