WO2011008154A1

WO2011008154A1 - Fastening device and use of fastening device

Info

Publication number: WO2011008154A1
Application number: PCT/SE2010/050606
Authority: WO
Inventors: Anders Carlsson; Johan Iraeus
Original assignee: Modul-System Hh Ab
Priority date: 2009-07-16
Filing date: 2010-06-02
Publication date: 2011-01-20
Also published as: SE0900992A1; EP2454127A1

Abstract

The present invention relates to a fastening device (1) for energy absorption, comprising two fastening portions (2) and an expansion part (3), in which the expansion part (3) has a direction of extension between said fastening portions (2) arranged on an opposite side each of the expansion part (3). The expansion part (3) comprises at least one reticular pattern (5) of connected link portions (8) which meet at nodal points (6, 6'), wherein at least a first imaginary straight line (L1) along a link portion (8) extends between two nodal points (6, 6') connected by said link portion (8) and said line (L1) being arranged at an angle (α) to the direction of extension of the expansion part.

Description

FASTENING DEVICE AND USE OF SAID FASTENING DEVICE

Technical field

The present invention relates to a fastening device for energy absorption, comprising two fastening portions and an expansion part, in which the expansion part has a direction of extension between said fastening portions arranged on an opposite side each of the expansion part. The present invention also relates to the use of such a fastening device. Background art

It is customary in service vehicles to equip a loading space or a rear space of a vehicle with, for example, cabinets, tool holders, shelves or modular systems which can be made up of modular units. This is usually done in a separate stage after the vehicle has been produced, i.e. equipping of the vehicle in question is carried out separately from the production. Before the vehicle is equipped with special equipment, the loading space in the vehicle is usually provided with an inner floor, usually of wood. This floor acts as a good support for working, standing and walking on and can also be used as an anchor for the modular system.

The modular system is often also at least partially fitted to the wall and the aim is to prevent the unit from tilting, for example in a turn. It is customary to fix the modular unit(s) in the wall with angle irons and fixing elements, for example screws or the like in the wall of the vehicle. The modular system is generally fixed at at least two points. One angle bar is placed on one side of the modular system, and another on the other side of the same modular system. There is a risk, however, during severe retardation of the vehicle, that the modular system or a modular unit may break loose and cause damage inside the vehicle. The modular system/units are usually quite heavy, especially when equipped with tools and materials, and they may in this case pose a safety risk. During severe retardation or collision of the vehicle, the modular unit can in a "worst case scenario", if not securely fastened to the vehicle, break through to the driver's cab and thus also cause personal injury.

As already stated, common angle brackets are often used, together with, for example, screws, bolts or other suitable fixing elements, to fasten the modules to the wall. These angle brackets and fixing elements are subjected to extremely large forces in the event of a severe deceleration. The weakest link is often the interface to the vehicle or the fixing element, where, for example, the screw is broken off before the energy in the severe deceleration is at an end and the module can thus break loose and cause damage. In order to reduce the risk, a more secure system for fixing modular

systems/units in vehicles is therefore required.

It is previously known to make use of energy-absorbing fastening elements to fasten, for example, a safety barrier/net in a loading space in which, in the event of a severe declaration, load goes forward and hits the barrier/net. The fastening element can then absorb parts of the force. WO96/06756 and US20070035158 have energy-absorbing fastening elements of this kind.

Such fastening elements can be complicated to produce so as to obtain the desired energy absorption and can require a certain space between the wall and fitting to be mounted. This space can possibly cause a further fitting not to be accommodated, since there is only a limited space available in the loading space.

There is therefore still a need for an alternative fastening device which can absorb energy. Summary of the invention

The object of the present invention is to meet the above requirements. This object is achieved according to the invention by virtue of the fact that the device of the type specified in the introduction comprises a fastening device for energy absorption, comprising two fastening portions and an expansion part, in which the expansion part has a direction of extension between said fastening portions arranged on an opposite side each of the expansion part. The expansion part comprises at least one reticular pattern of connected link portions which meet at nodal points, wherein at least a first imaginary straight line along a link portion extends between two nodal points connected by said link portion and said line being arranged at an angle to the direction of extension of the expansion part. As a result of this reticular pattern, a fastening device is obtained which can effectively absorb the energy which is generated in, for example, a severe retardation. A stable energy absorption can also be obtained. The reticular pattern means that effective use can be made of the material and it also means that the weight of the fastening device can be less than with a common angle bar.

Expediently, the angle between the first line and the direction of extension of the expansion part is greater than 45° and expediently greater than 60°.

By having a greater angle in the direction of extension of the expansion part, a longer link portion can be obtained (depends, inter alia, also on the relative positioning of the nodal points), and with a large angle the nodal points can be displaced by a longer distance in the direction of extension of the expansion part than if the link portion had been short and/or the angle had been small already in the starting position. The whole of the fastening device can thus be extended further.

Expediently, the expansion part, when the fastening device is subjected to and exceeds a predefined force, expands, whereupon the nodal points are displaced relative to one another. By predefining a force which the fastening device must be capable of absorbing, it is possible to adapt the design of the expansion part, i.e. inter alia the reticular check pattern, so that the expansion part expands in the direction of extension of the expansion part when this force is exceeded. This force should, however, be less than the maximum capacity of the fastening device.

Expediently, said imaginary line moves from its first angle to a second angle, which second angle is less than said first angle measured from the direction of extension of the expansion part.

Expediently, the reticular pattern of connected link portions which meet at nodal points is delimited by limiting portions, preferably in the form of cutouts, wherein two closest together limiting portions, which are arranged at a distance apart transversely to the direction of extension of the expansion part, being arranged at a distance from at least one further limiting portion in the direction of extension of the expansion part, which limiting portions are evenly displaced in relation to one another transversely to the direction of extension of the expansion part. By arranging at least some of the limiting portions as described above, an at least partially homogeneous region is obtained in which the force is absorbed. This homogeneous region means that forces are evenly distributed within this region. If all limiting portions are arranged like this over the whole of the surface of the expansion part in the direction of extension of the expansion part, a homogeneous expansion part is obtained in which the force is distributed evenly over the whole of the expansion part. The force equilibrium means that the force is equally large along the whole of the extension.

Expediently, the reticular pattern of connected link portions which meet at nodal points is delimited by at least one cutout. The advantage with cutouts is that they are easy to produce. They can, for example, be punched or cut out if a flat material is used, or else they can be formed directly in the production process if the expansion part, for example, is cast.

The cutouts can have an oval shape. Expediently, the oval cutout has a greatest extent which extends transversely to the direction of extension of the expansion part. At least one of the cutouts can have a substantially rectangular shape. Expediently, the rectangular cutout has a greatest extent which extends transversely to the direction of extension of the expansion part. At least one of the cutouts can be a slot. Expediently, the slot-shaped cutout has an extent which extends transversely to the direction of extension of the expansion part. By virtue of the fact that the cutouts have a greatest extent transversely to the direction of extension of the expansion part, the imaginary straight line can have a greater angle in the direction of extension of the expansion part than if the cutouts had been arranged in the extension of the expansion part. The link portion, too, can be longer. This gives the

advantages which have been stated earlier.

Expediently, the cutouts have rounded corners. By having rounded corners, fractures are prevented from occurring as a result of cracking in the corners of the cutouts when the expansion element expands, i.e. is

elongated.

Expediently, the expansion part is flat. A flat expansion part means that the production of the expansion part is simple. The cutouts can then be punched/cut out etc. in the same production stage as when the expansion part itself is made.

Expediently, at least one of said two fastening portions is flat. Flat fastening portions are easy to produce. If, moreover, the expansion part is flat, the fastening device can be produced as one part from one and the same material. This saves production time and costs.

At least one of the fastening portions can be arranged at an angle to the expansion part. By angling of the fastening portions, the fastening device can easily be adapted to the environment on which it shall be mounted.

Expediently, the expansion part and/or at least one of the fastening portions is/are made of a hardening metallic material. The advantage with such a material is that if a point/region in the material is subjected to load and deformed, then this point/region will harden, and since the material directly adjoining is weaker, it means that the deformation is transferred there.

Gradually "all" material is engaged and thus deformed, which means that it takes a long time before there is a localization of deformation which leads to fractures. More energy can thus be absorbed than if a material without hardened effect is used. For example, the stainless steel material EN1.4301 , AISI 304 or EN 1.4307, AISI 304L from the supplier Outo Kumpu, or Domex 220 from the company SSAB, can be used.

Expediently, at least one fastening device as described according to the above is used to fasten a fitting to a wall in a service vehicle.

Various other distinguishing features emerge from the following description which is given with reference to the appended drawings, which show embodiments and realizations of the invention as non-limiting

examples. Brief description of the drawings

The invention will be described in greater detail below with reference to appended schematic drawings which, for illustrative purposes, show presently preferred embodiments of the invention.

Fig. 1 shows an open perspective view of a service vehicle comprising a modular system having fastening devices according to the invention.

Fig. 2 shows a perspective view of the fastening device according to the invention fastened to a wall and to a part of a modular system.

Fig. 3a shows a fastening device according to the invention in a first embodiment with the expansion part shown in front view.

Fig. 3a' and fig. 3a" show a part of the fastening device in fig. 3a.

Fig. 3b shows the fastening device in fig. 3a viewed in perspective.

Fig. 3c shows the fastening device in fig. 3a in an expanded state in perspective.

Fig. 3d shows a part of the expanded fastening device in fig. 3c with the expansion part shown in front view.

Fig. 4a shows a fastening device according to the invention in a second embodiment in a front view.

Fig. 4b shows the fastening device in fig. 4a viewed in perspective. Fig. 5a shows a fastening device according to the invention in a third embodiment in a front view.

Fig. 5b shows the fastening device in fig. 5a viewed in perspective.

Al the figures are extremely schematic and are not necessarily to scale. They show only parts which are necessary in order to illustrate the invention, other parts are omitted or merely proposed.

Description of preferred embodiments

The above, as well as further parts, distinguishing features and advantages of the present invention will be better understood as a result of the following illustrative and non-limiting detailed description of preferred embodiments of the present invention with reference to the appended drawings, in which the same reference number will be used for like elements. Fig. 1 shows a motor vehicle, for example a service vehicle 10, having a modular system 11 arranged in the loading space 20 in the service vehicle 10. The modular system 11 has a frame construction made up of rails 15 in which cabinets 12 are arranged. Shelves or other modules can also be arranged therein. The modular system 11 is not, however, limited to this structure. It can have any design whatsoever. The modular system 11 is placed on the floor 13 and can be fixed thereto. The modular system 11 is fastened to the wall 14 with a plurality of fastening devices 1. Fig. 2 shows more clearly how the modular system is coupled to the wall. In fig. 1 , two fastening devices 1 are shown. Both are arranged on one side of the modular system 11 toward the rear part of the loading space 20, but more can be arranged on the other side of the modular system 11 or somewhere therebetween. One fastening device 1 is arranged on the upper part of the modular system 11 , and the other one between the upper and the lower part of the modular system 11. Fig. 2 shows the fastening device 1 fitted to a rail 15 which is part of the modular system 11 shown in fig. 1. The fastening device 1 is fitted to the rail 15 with a bolt 16 with the aid of, for example, a nut (not shown). The nut is here arranged in the rail 15 in an undercut groove 17. All conceivable ways of fitting a fastening device to a fitting or to a wall are possible, without being confined to a rail having an undercut groove in which a nut is arranged. The fastening device 1 is then fastened to the wall 14 with a further bolt 16. The fastening device is not limited to being fastened either to the wall or in the modular system in this way. For example, screws, rivets, rapid fasteners can be used. That end of the fastening device which is shown here as mounted on a wall can also be mounted on parts other than a wall, for example on an intermediate part such as an inner wall or at a distance from the wall or on another modular system. All possible suitable alternatives are possible. The fastening device 1 can also be used to fasten fittings other than modular systems, such as cabinets, drawers, etc.

Figs. 3a and 3b show the fastening device 1 in a front view and a perspective view respectively. Fig. 3 a^' and fig. 3a" show a part of fig. 3a. The fastening device 1 consists of two fastening portions 2 and an

intermediate part 3. The intermediate part is an expansion part 3, i.e. when the fastening device 1 is subjected to a force arising from, for example, severe deceleration of the vehicle in the event of a crash, the force/energy will be absorbed by the expansion part 3 through an extension of the expansion part 3 when the force exceeds a certain value for which the expansion part 3 is optimized. The expansion part 3 has a direction of extension between said fastening portions 2, which are arranged on an opposite side each of the expansion part 3. The direction of extension is shown in fig. 3a" as the line L. The fastening device 1 is expediently designed such that, when it is arranged in the vehicle, the direction of extension of the expansion part is substantially in the direction of travel of the vehicle. Which is the same direction in which the force will come in the event of a severe deceleration. In the coordinate system in fig. 3a, the direction of extension of the expansion part is in the x- direction, and the direction transversely to the direction of extension of the expansion part is in the y-direction. The fastening portions 2 each have a fastening point 21. Here the fastening point 21 is a continuous hole, in which a fixing element can be led through. Such a fixing element can be, for example, a screw, bolt, rivet or a rapid fastener. The fastening point 21 is not, however, limited to being a hole. It can be any sort of device which is suited to fixing the fastening device to the wall or alternatively to the fitting, and they can be different on the two fastening portions.

The expansion part 3 and the fastening portions 2 are flat and made together from one and the same material in order to obtain a fastening device which is as simple as possible in production terms. The expansion part 3 and the fastening portions 2 are not, however, limited to being flat and/or of one and the same material, and they can be made separately so as then to be fitted together. The fastening portions 2 are arranged on an opposite side each of the expansion part 3 and each at an angle to the expansion part 3. These angles are determined by where on the wall 14 in the vehicle 10 or where on the modular system 11 the fastening device 1 shall be fastened (fig.1 ). By virtue of this structure, different variants of the fastening device, which can be adapted to individual vehicles and/or fittings, can be made in an easy and cost-effective manner. The expansion part 3 has a reticular pattern 5 of connected link portions 8 which meet at nodal points 6, 6^'. The reticular pattern 5 is delimited by limiting portions 7, 7^', preferably in the form of cutouts. The limiting portions 7, T can also be non-continuous recesses (not shown) from one or both sides of the expansion part 3. The reticular pattern is henceforth described from a perspective in which cutouts 7, 7^' limit the look of the reticular pattern. The cutouts 7, T thus acquire the same reference number as the limiting portion 7, 7^'. The cutouts 7, 7' are arranged in various rows R1-R11 transversely to the direction of extension of the expansion part. The direction of extension of the expansion part is, as stated, the direction in which the expansion part 3 will extend when subjected to a force. Every alternate row has the same configuration as row one R1 and every alternate row has the same configuration as row two R2. i.e. R1 , R3, R5 etc. have one configuration and R2, R4, R6 etc. have another configuration. Hereinafter, reference will be made only to row one R1 and row two R2, but the

distinguishing features apply also to the other rows. The expansion part 3 is not limited to this; however, each row can have its own configuration or only certain rows can have the same configuration. All the cutouts 7, 7' have a rounded shape, such as, for example, an oval shape (illustrated here). Each row has two cutouts. The cutouts on each row are distributed evenly over the expansion part, i.e. the distance between the cutouts is equally large. The expansion part 3 is not, however, limited to two cutouts or to the oval shape, or to all having the same shape, but rather just one or more cutouts can be provided on each row and they can have different distances between them. The cutout can have the shape of a slot, can be round, rectangular, or can assume any other shape suitable for the embodiment. The oval cutout 7, 7' has a greatest extent which extends transversely to the direction of extension of the expansion part. Row two R2 differs from row one R1 in that row two R2 has a wholly oval cutout 7' and two half cutouts 7^' on either side of the wholly oval cutout, i.e. the rows are arranged in the expansion part such that the cutouts 7 in row one R1 are displaced in relation to the cutouts T in row two R2. Here the cutouts 7 are displaced, see fig. 3a^', such that a line 18, which is substantially parallel with the direction of extension of the expansion part, extends through the center of one of the cutouts T in row two R2, which line 18 intersects a point 19 located substantially midway between two cutouts 7 in row one R1. This placement of the cutouts 7, 7^' provides that between each cutout 7, 7^' on each row a nodal point 6, 6^' is formed, see fig. 3a. By nodal point is meant not only a point, but it can also be a region. Point 19 in fig. 3a' is the same point as the nodal point 6. It can also be regarded like this: the reticular pattern 5 of connected link portions 8 which meet at the nodal points 6, 6^' is delimited by cutouts 7, 7^', wherein two closest together cutouts 7, 7^' which are arranged at a distance apart transversely to the direction of extension of the expansion part being arranged at a distance from at least one further cutout 7, T in the direction of extension of the expansion part, which cutouts are evenly displaced in relation to one another

transversely to the direction of extension of the expansion part. The rows do not need to be displaced as described above, but rather they can be displaced more irregularly to one another. By virtue of the above-described placement of the cutouts, row one R1 acquires three nodal points 6 and row two R2 two nodal points 6'.

Fig. 3a^" shows how the nodal points 6, 6^' in the two rows are connected by link portions 8 made of material, which together enclose the cutouts 7, 7'. A link portion 8 (the dashed region) thus extends from nodal point 6 in row one R1 to nodal point 6' in row two R2. The nodal points 6, 6'are arranged one to another such that a first imaginary straight line L1 along the link portion 8 extends between the two nodal points 6, 6^' connected by said link portion 8. The first line L1 is arranged at an angle αi to the direction of extension of the expansion part, which is here shown as the line L. This angle CH is expediently as large as possible in order to obtain the longest possible link portion 8. Expediently, the angle αi is greater than 45°, preferably greater than 60°. As shown in the figures, the same nodal point 6 in row one R1 is also coupled to a further nodal point 6' in row two by a link portion 8 (not shown, with the dashed region which is described above is equivalent between the nodal point 6 and the other nodal point 6^'). The nodal points 6, 6^' are here too arranged one to another such that an imaginary straight line L2 along the link portion 8 extends between the two nodal points 6, 6^' connected by said link portion 8. The second line L2 too is arranged at an angle α_∑ to the direction of extension L of the expansion part. This angle az too is expediently as large as possible in order to obtain as long a portion δ as possible. Expediently, the angle αi is greater than 45°, preferably greater than 60°. The angles CH and α₂ are here equally large. They can, however, be of different sizes. The nodal points 6' in row two R2 are then coupled in the same way to the nodal points 6 in row three R3, which gives both a third and a fourth imaginary straight line L3, L4 and further imaginary lines which are not shown. The couplings continue in the same way over the whole of the expansion part 3, which gives the expansion part 3 its reticular pattern. Here only that nodal point 6 in row one R1 which is arranged between the two cutouts 7 is described, yet the other two nodal points 6 are arranged in a similar manner to the nodal points 6' in row two R2. The cutouts 7, 7' are, as stated, oval in shape, in which the oval shape has its greatest extent transversely to the direction of extension of the expansion part. The placement, shape and extent of the cutout 7, 7 transversely to the direction of extension L of the expansion part, and the angles CH , α₂ of the first line L1 and the second line L2 and all the other lines which are formed over the whole of the expansion part, which lines each intersect two nodal points 6, 6' linked together by a link portion 8, determine the look of the expansion part 3. If all rows R1-R11 are considered, then all cutouts 7, T and angles α are of the same shape and size and with the same distance between the cutouts 7, 7', and the cutouts 7, 7 ^' on one row are evenly displaced toward the nearest situated other row. The configuration of the expansion part 3 and its reticular pattern are not, however, limited to this, but can vary over the surface of the expansion part 1 in the direction of extension of the expansion part.

The possible force/energy absorption of the expansion part 3 is determined, apart from by the configuration of the expansion part 3, also by the material of which the expansion part 3 is made. Expediently, it is made of a ductile metal material, also termed a hardening material. This means that when a point in the structure is subjected to load and deformed, then this will harden and, since the material directly adjoining is weaker, it means that the deformation is transferred there. Gradually "all" material is engaged and thus deformed, which means that it takes a long time before there is a localization of deformation which can lead to fractures. For example, the stainless steel material EN 1.4301 , AISI 304 or EN 1.4307, AISI 304L from the supplier Outo Kumpu, or Domex 220 from the company SSAB₁ can be used.

The possible force/energy absorption of the expansion part 3 is also affected by the combination material thickness, width of the expansion part 3 and length of the expansion part 3 in the direction of extension of the expansion part and in combination with the number of cutouts and the shape of the cutouts, the width of the material between the cutouts (dimension of the link portion) and the angles of the imaginary lines which extend between two nodal points along a link portion 8 in relation to the direction of extension of the expansion part. The expansion part 3 here has a width of about 45 mm and a length of about 70 mm and a thickness of about 3mm. The oval cutouts 7, 7^' here have a width of about 15mm and a height of about 4 mm. The fastening device is not, however, limited to this.

Figs. 3c and 3d show how the fastening device 1 and its expansion part 3 look after it has been subjected to a certain force and has hence absorbed the generated energy. In the coordinate system in fig. 3d, the direction of extension of the expansion part is in the x-direction and the direction transversely to the direction of extension of the expansion part is in the y-direction. When the expansion part 3 in figs. 3a and 3b is subjected to a force which substantially comes in the x-direction, and if this force exceeds a predefined value to which the expansion part 3 is tailored, the expansion part will be extended in the direction of extension of the expansion part (x- direction). This force should, however, be less than the maximum capacity of the fastening device.

In equipped service vehicles, the fastening device 1 must desirably be capable of expanding by about 150 mm before it reaches a force of about 7kN. The fastening device is not, however, limited to this. The fastening device 1 can be dimensioned to cope with higher or lower forces by varying the abovementioned factors. When the expansion part 3 is subjected to the force which substantially comes in the direction of extension of the expansion part, the link portions 8, which extend between two nodal points 6, 6^", will rotate about the nodal points 6, 6^' and move in the direction of extension of the expansion part. If the link portion 8 described in fig 3a^" is looked at, then the nodal point 6^' in row two R2 and the nodal point 6 in row one R1 will move away from one another in the direction of extension of the expansion part. Both nodal points are displaced each in their respective direction, i.e. the nodal points 6, 6^' are displaced relative to one another. In order to

understand what is happening, it is possible to explore the occurrence by stating that nodal point 6 in row one R1 does not move, i.e. it stays in its starting position. If the link portion 8 is then subjected to a force, the nodal point 6' in row two R2 will be displaced upward (in the x-direction) in the direction of extension L of the expansion part, i.e. the imaginary line L1 described earlier, which has an angle αi in fig 3a", will acquire a smaller angle (a second angle, angle αi in fig. 3d) after the expansion of the

expansion part.

The nodal point 6' in row two R2 in fig. 3d is farther away from the nodal point 6 in row 1 R1 in the X-direction than it is in fig. 3a" and nearer to the nodal point 6 in the Y-direction. By having long link portions 8 in the expansion element 3, the link portions can move a longer distance in the direction of extension of the expansion part than if one had had short portions. It means that the whole of the expansion part can be extended by a longer distance in the direction of extension of the expansion part. However, the link portions should be adapted such that the expansion element 3 is sufficiently stable and does not have any weak points already prior to the load. The above-described expansion part 3 from figs. 3a, 3b has been elongated by almost 100 %, as is shown in fig. 3c.

What happens during the extension is that the material in the link portion 8 is deformed when it is bent (when the angle is changed) and hardens. It works such that when a point/region in the material is bent, it deformes and hardens, and the adjoining soft material is engaged, i.e. the deformation is transferred there and the point/region hardens. Gradually, all material in the link portion is engaged, and by virtue of the fact that the whole of the reticular pattern hangs together, then the whole of the expansion element will gradually harden. In this way, the expansion element 3 absorbs the energy which is generated in, for example, a crash. Apart from being bent, the link portions will also be stretched later in the process. The oval cutout which extended transversely to the direction of extension of the expansion part in fig. 3a (prior to expansion) will now also extend in the direction of extension of the expansion part. The total displacement of the nodal point 6' is also limited by the fact that the same nodal point 6' in row two R2 sits together with a further nodal point 6 in row one R1. Hence the cutouts 7 now acquire the shape of a rectangle, in which two opposite corners each point in that direction of extension of the expansion part which is shown in fig. 3d. The width of the expansion part 3 is also affected by the force and the look of the reticular pattern. The width of the expansion part also narrows the greater the force to which it is subjected, i.e. the further it is extended.

Figs. 4a and 4b show a fastening device 1 having cutouts 7 in the expansion part 3, in which the cutouts are shaped as slots in which the slots extend transversely to the direction of extension of the expansion part. The corners of the slots are expediently rounded in order to avoid obvious ultimate stress limits which can be formed in pointed corners. The slots 7 are arranged one to another as described above.

Figs. 5a and 5b show a fastening device 1 having cutouts 7 in the expansion part 3, in which the cutouts are shaped as rectangles in which two opposite corners are directed in the direction of extension of the expansion part and in which the greatest extent of the rectangle, i.e. between the tips, extends transversely to the direction of extension of the expansion part. The corners of the rectangles are expediently rounded in order to prevent obvious ultimate stress limits which can be formed in pointed corners. The rectangles 7 are arranged one to another as described above.

Even though individual embodiments of the invention have been described herein, it will be evident to the person skilled in the art that variations can be made in the design and the relationship between parts without deviating from the scope of the invention as defined in the appended claims.

Claims

1. A fastening device (1) for energy absorption, comprising two fastening portions (2) and an expansion part (3), in which the expansion part (3) has a direction of extension between said fastening portions (2) arranged on an opposite side each of the expansion part (3), wherein the fastening device (1) being characterized in that the expansion part (3) comprises at least one reticular pattern (5) of connected link portions (8) which meet at nodal points (6, 6^'), wherein at least a first imaginary straight line (L1) along a link portion (8) extends between two nodal points (6, 6^') connected by said link portion (8) and said line (L1) being arranged at an angle (α1) to the direction of extension of the expansion part.

2. The fastening device (1) as claimed in claim 1 , wherein the angle (α1) between the first line (Li) and the direction of extension of the expansion part is greater than 45° and expediently greater than 60°.

3. The fastening device (1) as claimed in any one of the above claims, wherein the expansion part (3), when the fastening device (1) is subjected to and exceeds a predefined force, expands, whereupon the nodal points (6, 6^') are displaced relative to one another.

4. The fastening device (1) as claimed in claim 3, wherein said line (L1) moves from its first angle (α1) to a second angle, which second angle is less than said first angle (α1) measured from the direction of extension of the expansion part.

5. The fastening device (1) as claimed in any one of the above claims, wherein the reticular pattern (5) of connected link portions (8) which meet at nodal points (6, 6') is delimited by limiting portions (7, 7^'), preferably in the form of cutouts, wherein two closest together limiting portions (7, 7'), which are arranged at a distance apart transversely to the direction of extension of the expansion part, being arranged at a distance from at least one further limiting portion (7, 7') in the direction of extension of the expansion part, which limiting portions are evenly displaced in relation to one another transversely to the direction of extension of the expansion part.

6. The fastening device (1) as claimed in any one of the above claims, wherein the reticular pattern (5) of connected link portions (8) which meet at nodal points (6, 6^') is delimited by at least one cutout (7, 7^').

7. The fastening device (1) as claimed in claim 6, wherein at least one of the cutouts (7, 7^') has an oval shape.

8. The fastening device (1) as claimed in claim 7, wherein the oval cutout (7, T) has a greatest extent which extends transversely to the direction of extension of the expansion part.

9. The fastening device (1) as claimed in any of claims 6-8, wherein at least one of the cutouts (7) has a substantially rectangular shape.

10. The fastening device (1) as claimed in claim 9, wherein the rectangular cutout (7, 7') has a greatest extent which extends transversely to the direction of extension of the expansion part.

11. The fastening device (1 ) as claimed in any one of claims 6-10, wherein at least one of the cutouts (7, 7^') is a slot.

12. The fastening device (1) as claimed in claim 11 , wherein the slot- shaped cutout (7, 7') has an extent which extends transversely to the direction of extension of the expansion part.

13. The fastening device (1) as claimed in any one of claims 9-12, wherein the cutouts (7, T) have rounded corners.

14. The fastening device (1) as claimed in any one of the above claims, wherein the expansion part (3) is flat.

15. The fastening device (1) as claimed in any one of the above claims, wherein at least one of said two fastening portions (2) are flat.

16. The fastening device (1) as claimed in any one of the above claims, wherein at least one of the fastening portions (2) is arranged at an angle to the expansion part (3).

17. The fastening device (1) as claimed in any one of the above claims, wherein the expansion part (3) and/or at least one of the fastening portions (2) is/are made of a hardening metallic material.

18. The use of at least one fastening device (1) as claimed in any one of the above claims to fasten a fitting (11) to a wall (14) in a service vehicle (10).