SECURING A SECOND OBJECT TO A FIRST OBJECT

Abstract

The method of bonding a first object (1) to a second object (2) uses a connector, the connector having a first sheet portion and a second sheet portion (32). The first sheet portion has at least one outwardly protruding first attachment portion (33), and the second sheet portion has at least one outwardly protruding second attachment portion (34). The connector (3) further has a spacer between the first and second sheet portions. For bonding, the first and second objects (1, 2) and the connector (3) are positioned relative to each other so that the connector is placed between the first and second objects. Then the first and second objects (1, 2) are pressed against each other while mechanical vibration energy impinges on the first and/or second object until a first flow portion of thermoplastic material of the first object in contact with the first attachment portion(s) and a second flow portion of thermoplastic material in contact with the second attachment portion(s) become flowable allowing the respective attachment portions (33, 34) to be pressed into material of the first and second object, respectively. After re-solidification of the flow portions, a positive-fit connection between the first and second objects via the connector results. The spacer defines a width (w) of a gap between the first and second objects (1, 2) after bonding.

Claims

1-29. (canceled)

30. A method of mechanically securing a first object to a second object, the method comprising: providing the first object comprising a thermoplastic material in a solid state and providing the second object comprising a thermoplastic material in a solid state; providing a connector, the connector having a first sheet portion and a second sheet portion, wherein the first and second sheet portions have inner surfaces facing each other, wherein the first sheet portion has at least one outwardly protruding first attachment portion and the second sheet portion has at least one outwardly protruding second attachment portion, and wherein the connector has a spacer between the first and second sheet portions, wherein the spacer comprises a spacer portion of the first sheet portion being a part of the first sheet portion bent away from a sheet plane and/or a spacer portion of the second sheet portion being a part of the second sheet portion bent away from a sheet plane, the spacer defining a distance between the inner surfaces; positioning the first object, the second object and the connector relative to one another so that the connector is placed between the first and second objects; pressing the first and second objects against each other while the connector is between the first and second objects and while mechanical vibration energy is coupled into the first object or the second object or both, the first and second objects, until a first flow portion of thermoplastic material of the first object in contact with the first attachment portion and a second flow portion of thermoplastic material in contact with the second attachment portion become flowable, thereby allowing the first and second attachment portions to be pressed into material of the first and second object, respectively; and causing the first and second flow portions to re-solidify, to create a positive-fit connection between the first object and the connector and a positive-fit connection between the second object and the connector.

31. The method according to claim 30, wherein the first attachment portion and/or the second attachment portion is an outwardly protruding portion of sheet material of the first and/or second sheet portion respectively, the outwardly protruding portion extending around an opening and ending in an edge.

32. The method according to claim 30, wherein the first sheet portion and the second sheet portion are portions of a contiguous sheet folded to comprise the first and second sheet portions, wherein the sheet preferably is a metal sheet.

33. The method according to claim 30, wherein the connector comprises a plurality of first attachment portions and a plurality of second attachment portions.

34. The method according to claim 30, wherein pressing the first and second objects against each other is carried out until inner surfaces of the first and second objects abut against a flat part of the first sheet portion and the second portion, respectively.

35. The method according to claim 30, further comprising applying an adhesive to the first object and/or to the second object prior to positioning the first object, the second object and the connector relative to one another, the adhesive being applied at a position that, after positioning the first object, the second object and the connector relative to one another, is different from the position at which the connector is located and is between the first and second objects.

36. The method according to claim 30, wherein the spacer portion or at least one of the spacer portions is a portion bent to have an angle of about 90° with respect to sheet planes of the first and second sheet portions and/or is an embossed portion of the first and/or second sheet portion.

37. The method according to claim 30, wherein the connector has a self-stabilizing configuration, whereby after creating the positive-fit connection with the first and second objects, an inner object surface of at least one of the first and second objects forms an abutment surface preventing unfolding of the connector, and wherein the connector is a folded metal sheet, and the shape of the connector is such that the first and/or second object when extending along one of the large surfaces of the connector and being bonded thereto prevents unfolding of the metal sheet.

38. The method according to claim 37, wherein a large surface of the connector that comes into contact with the inner surface of one of the first and second objects comprises different portions folded from the sheet portion constituting the other large surface, namely from portions folded into different folding directions, wherein the different portions folded are folded along non-parallel folding axes and/or into opposite directions.

39. The method according to claim 30, wherein the first and second sheet portions of the connector are stabilized by a foldover portion, the foldover portion extending from one of the sheet portions and being folded over an outer surface of the other sheet portion, wherein the other sheet portion has a receiving indentation in the outer surface, the receiving indentation receiving the foldover portion.

40. The method according to claim 30, wherein the first sheet portion has a plurality of first sheet portion sections, each first sheet portion section connected to the second sheet portion by a fold, the folds running into different directions.

41. The method according to claim 30, wherein a section that connects the first and second sheet portions has at least one cutout.

42. A connector for carrying out a method according to claim 30, the connector having a first sheet portion and a second sheet portion, wherein the first and second sheet portions have inner surfaces facing each other, wherein the first sheet portion has at least one outwardly protruding first attachment portion and the second sheet portion has at least one outwardly protruding second attachment portion, and wherein the connector has a spacer between the first and second sheet portions, wherein the spacer comprises a spacer portion of the first sheet portion being a part of the first sheet portionbent away from a sheet plane and/or a spacer portion of the second sheet portion being a part of the second sheet portion bent away from a sheet plane, the spacer defining a distance between the inner surfaces.

43. The connector according to claim 42, wherein the first and second sheet portions each have a plurality of attachment portions, each attachment portion comprising an outwardly protruding portion of sheet material of the first and/or second sheet portion respectively, the outwardly protruding portion extending around an opening.

44. The connector according to claim 42, where the connector is constituted by a metal sheet folded to yield the first and second sheet portions, wherein the shape of the connector is such that an object abutment surface lying against a large surface of the connector and parallel thereto acts to prevent unfolding of the sheet.

45. The connector according to claim 44, further comprising at least one foldover portion being a portion extending from one of the sheet portions and being folded over an outer surface of the other sheet portion, wherein the other sheet portion preferably has a receiving indentation in the outer surface, the receiving indentation receiving the foldover portion.

46. The connector according to claim 44, wherein an outer large surface of the connector comprises different portions folded from the sheet portion constituting another, opposing large surface, namely from portions folded into different folding directions, wherein the different portions are folded along non-parallel folding axes and/or into opposite directions.

47. The connector according to claim 42, wherein the spacer portion or at least one of the spacer portions is a portion bent to have an angle of about 90° with respect to sheet planes of the first and second sheet portions, and/or is an embossed portion of the first and/or second sheet portion.

48. The connector according to claim 42, wherein the first sheet portions has a plurality of first sheet portion sections, each section connected to the second sheet portion by a fold, the folds running into different directions.

49. The connector according to claim 42, wherein a section that connects the first and second sheet portions has at least one cutout.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In the following, ways to carry out the invention and embodiments are described referring to drawings. The drawings are all schematical and not to scale. In the drawings, same reference numerals refer to same or analogous elements. The drawings show:

[0067] FIG. 1 In section, an arrangement of a first object, a second object, a connector and an adhesive, pressed together between a sonotrode and a counter element;

[0068] FIG. 2 the arrangement of FIG. 1 after the process;

[0069] FIGS. 3, 4 views of a connector (not according to the claimed invention);

[0070] FIGS. 5, 6 views of another connector (not according to the claimed invention);

[0071] FIGS. 7, 8 views of a sheet piece for forming a connector during a folding process (not according to the claimed invention);;

[0072] FIG. 9 a further arrangement of a first object, a second object, a connector and an adhesive;

[0073] FIGS. 10-11 views of further connectors shown in section (not according to the claimed invention);;

[0074] FIGS. 12, 13 views of connectors;

[0075] FIGS. 14-16 views of an even further connector during different stages of its manufacturing;

[0076] FIGS. 17-22 views of yet further connectors; and

[0077] FIG. 23 in section, an arrangement of a first object, a second object and a connector after the process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] FIG. 1 illustrates the principle of bonding a first object and a second object together by means of a connector that has outwardly protruding attachment portions forming edges. The figure shows an arrangement of a first object 1 comprising a thermoplastic material, a second object 2 also comprising a thermoplastic material, and a connector 3, the connector arranged between the inner object surfaces 11, 21 of the first and second object. Also an adhesive 5 is arranged between the inner object surface 11 of the first object 1 and the inner object surface 21 of the second object. The adhesive 5 is in an uncured state.

[0079] In the depicted embodiment, the first and second objects 1, 2 are shown as plates of the thermoplastic material. Generally, it is sufficient if the first and second objects each have a section comprising the thermoplastic material, the section comprising the respective inner object surfaces 11, 21. The first objects may consist of such section or may comprise further sections of other materials, depending on their function.

[0080] The thermoplastic materials of the first and second objects 1, 2 may be identical or may be different.

[0081] The first and second objects 1, 2 each form an outer object surface 12, 22 that is approximately opposite the respective inner object surface 11, 21 and serves for applying the force for pressing the first and second objects against each other. At least one of the outer object surfaces 12, 22 further serves for coupling the mechanical vibration energy into the assembly. The respective outer object surface may be approximately parallel to the inner object surface. It is, however, also possible that the outer object surfaces have different and/or more complex shapes.

[0082] The connector 3 has a first sheet portion 31 having a plurality of first attachment portions 33 and a second sheet portion 32 having a plurality of second attachment portions 34. The attachment portions 33, 34 are formed by outwardly bent portions of the sheet material, these outwardly bent portions extending around an opening 36 and ending in an edge 35.

[0083] Generally, (this pertains to all embodiments), the connector may be formed of a metal sheet. A particularly suitable material is steel. Steel has a high modulus of elasticity, so that the sheet can be thin and light. It allows large deformation and maintains its rigidity after large deformation. For embodiments with a direct connection between portions or parts (such as a spot weld connection), it has a high weldability.

[0084] In the depicted configuration, a sonotrode 6 is used for coupling the vibration energy and a pressing force into the assembly, wherein the assembly is pressed against a counter element 7, i.e. the pressing force is applied between the sonotrode 6 and the counter element 7. In alternative embodiments, the counter element 7 is replaced by a second sonotrode, whereby the mechanical vibration energy is coupled into the assembly from both sides.

[0085] As an effect of the mechanical vibration energy input and the pressing force, with the edges 35 of the attachment portions 33, 34 being pressed against the thermoplastic material of the first/second object, energy absorption at the locations where the thermoplastic materials is in physical contact with the connector causes local heating and softening/making flowable of the thermoplastic material, so that as a consequence of this softening and the pressing force the respective attachment portions are pressed into the material of the first/second object, respectively. After re-solidification, a fixation between the first and second objects via the connector 3 results in that both, the first and second objects are secured to the connector 3 by a positive fit connection (FIG. 2). The principle of a positive fit connection between a sheet-like object (such as the present connector 3) having suitable attachment portions and am object having a thermoplastic material (such as the present first/second objects) is described in WO 2017/055 548.

[0086] The process including the re-solidification of the flow portion of the thermoplastic material may be relatively quick (for example a few seconds). It ensures a fixation of the first and second objects with respect to each other, with a gap between them, a width w of the gap being defined by properties of the connector, as explained in more detail hereinafter. The adhesive 5 that at least partially fills the gap may take more time to cure. Because of the fixation via the connector, during this curing time the assembly may be subject to further processing steps, including for example assembly with further objects. Thus, the approach according to embodiments of the present invention ensures that processing/assembly is not delayed by the time it takes the adhesive to cure, so that the approach may bring about substantial advantages in a manufacturing line.

[0087] FIGS. 3 and 4 show a connector 3 of which the first sheet portion 31 and a second sheet portion 32 lie immediately against each other, i.e. the inner surfaces of the respective sheet portions are in physical contact. The width w of the gap between the first and second objects thus may especially be the cumulated thickness of the first and second sheet portions. The sheet portions both belong to a common folded metal sheet (fold 37). Opposite the fold 37, the sheet portions are connected by a spot weld or glue or solder connection 38.

[0088] In addition to embodiments in which a small gap as illustrated with respect to FIGS. 1-4 is sufficient, it is also proposed to configure the connector to define a wider gap. A first possibility to do so is to increase the thickness of the sheet portion material. However, often this is not advantageous. According to an alternative option, the connector may comprise a spacer. FIGS. 5-8 illustrate the possibility of a spacer being constituted by a spacer sheet portion 40. The connector in this is folded (folds 37) from a sheet into three sections of approximately same areas, the outer two sections forming the first sheet portion 31 and the second sheet portion 32, and the middle section forming the spacer sheet portions. Other configurations, for example with the spacer sheet portion formed by an outer section and the first and second sheet portions being folded over the spacer sheet portion are possible also.

[0089] In the embodiment of FIGS. 5-7, the spacer sheet portion 40 has spacer sheet openings 47 at the positions of the (aligned) openings 36 in the first and second sheet portions 31, 32, respectively, around which the attachment portions 33, 34 are present so that there is more volume for the flow portions of the thermoplastic material to evade. If the flow portions of material of the first and second objects are sufficiently large, this will allow a weld between the flow portions that causes an additional fastening effect between the first and second objects.

[0090] In the embodiment of FIG. 8, the spacer sheet portion 40 does not have such spacer sheet openings.

[0091] FIG. 9 shows an arrangement with the first and second object 1, 2 secured to each other by a connector similar to the one of FIGS. 5-8 (but with the folds 37 at narrow side edges). The width w of the gap is approximately three times the thickness of the sheet material from which the connector is manufactured. This width w in the case of essentially flat inner surfaces 11, 21 (attachment surfaces) of the first and second objects is also the width of the adhesive gap (adhesive 5).

[0092] In connectors of the kind depicted in FIGS. 5-9, the width of the gap is approximately three times the thickness of the sheet material from which the connector is manufactured. This concept may readily be extended to a larger number by providing a plurality of spacer sheet portions 40. In the embodiment of FIG. 10, the connector is depicted to have a total of six spacer sheet portions 40 by having a total of seven folds 37.

[0093] The connectors of FIGS. 3 and 4 on the one hand and of FIGS. 5-10 on the other hand have in common that the thickness of the metal sheet determines the width of the gap. The metal sheet thickness, however, is determined by requirements upon the connector, such as formability, sufficient stiffness, etc. The embodiments of FIGS. 5-10 also lead to connectors that are comparably heavyweight. It is therefore advantageous if the width of the gap can be designed independently of the thickness of the metal sheet. This is achieved by the spacers of the above-discussed kind. According to a first option (FIG. 11), therefore, the spacer is constituted by an initially separate spacer object. This has the advantage that the width of the gap can be chosen independently of the thickness of the sheet material. However, depending on the spacer material, the weight of the construction may still be an issue; also the spacer manufacturing process requires additional step and an additional part. The embodiments of FIGS. 12-23 having spacer portions formed from the sheet portions themselves solve also this issue.

[0094] FIG. 11 shows the concept of the connector having an initially separate spacer object 50 as an alternative - or in addition - to the spacer sheet portion(s). Such separate spacer object may be essentially plate shaped or have an other shape and may be of any suitable material, including the possibility of the spacer object being of a polymer material that is weldable to material of the first and/or second object.

[0095] It is especially possible that the spacer object 50 is inserted only after the first and second object and the connector are placed relative to one another, and that its dimensions may be chosen based on a desired width of a gap between the first and second object. The method may then comprise deforming, depending on a width of the chosen spacer object 50, the connector part to have a final width that is smaller than the initial width. This may comprise deforming a peripheral part 55 of the first and/or second sheet portion 31, 32.

[0096] FIG. 12 depicts a first example of a connector with a spacer portion of the first and/or second sheet portion being a part of the respective sheet portion that is bent inwardly for the other sheet portion or a spacer portion thereof to abut thereagainst. In the embodiment of FIG. 12, the first sheet portion 31 forms a first spacer portion 61 and the second sheet portion 32 forms a second spacer portion 62. The spacer portions 61, 62 are formed from the sheet material of the respective sheet portions 31, 32 by punching, the punch used forming an elongate indentation 64. In accordance with a first possibility, the used punch forms the indentation 64 may be an impression, i.e. an embossment. As an alternative the spacer could be formed by punching in a manner that a punching through hole is formed (i.e., in a piercing manner), with the spacer portion 61, 62 being a bead around the respective hole.,.

[0097] The spacer portions 61, 62 of the first and second sheet portions 31, 32 are aligned with each other and abut against each other.

[0098] To act against unfolding, the first and second sheet portions may be connected by a rigid bond, such as a material connection. For example, a spot weld in the pots formed by the spacer portions 61, 62 of the sheet portions, or a spot solder connection or spot glue connection between the abutting spacer portions may form such a rigid bond. In this, the rigid bond is indirect, i.e. via the spacer portions.

[0099] Also the embodiment of FIG. 13 comprises aligned spacer portions 61, 62 of the first and second sheet portion 31, 32 abutting against each other. Also in the embodiments of FIG. 13, the spacer portions 61, 62 may be or impressions, i.e. embossements or possibly, as an alternative, beads around a punched hole. In contrast to FIG. 12, the spacer portions have a shape and arrangement corresponding to the shape and arrangement of the attachment portions 33, 34 and in FIG. 13 are interleaved with them.

[0100] Like the embodiment of FIG. 12, the embodiment of FIG. 13 may comprise a rigid bond, for example between corresponding spacer portions 61, 62 of the first and second sheet portions.

[0101] The embodiments of FIGS. 12 and 13 are examples of connectors the spacer portions of which are arranged centrally in the first and/or second sheet portions and thereby require a disruption (punched hole; alternatively a cut or the like could serve as disruption) of the respective sheet portion. The embodiment of FIGS. 14-16 described hereinafter, in contrast, is an example of a connector with a peripheral spacer portion.

[0102] FIGS. 14-16 thus show a further embodiment with spacer portions formed from the sheet material of the sheet portions 62. The spacer portions are initially (blank shown in FIG. 16) arranged peripherally and are folded into the positions shown in FIG. 14. The connector also comprises a bridge portion 37 that after folding forms the fold, has a width corresponding to the width of the spacers and connects the first and second sheet portions 31, 32 together, as well as a foldover portion 72 (in the shown embodiment, there are three foldover portions 72) that is folded over a receiving indentation 71 for stabilizing the connector in the folded state. The foldover portion 72 is connected to the second sheet portion 32 via a foldover bridge 74 that also has a width approximately corresponding to the width of the spacers.

[0103] The connection between the foldover portion 72 and the first sheet portion may optionally be a latching connection, wherein the first sheet portion may be latched down onto into the configuration where it abuts against the spacer portions. Compared to the embodiments with a foldover portion described hereinafter, such latching connection may be relatively stiff.

[0104] In the concept of FIGS. 14-16, the entire blank defining all dimensions may be manufactured in one manufacturing step, for example by laser cutting or waterjet cutting. The freely choosable width w.sub.s of thus manufactured structures 62 defines the spacer z extension and thus ultimately the width w of the gap. Further advantages are that the spacer structures may be configured arranged independently of the attachment portions 33, 34, so that the design degrees of freedom are maximized. Also, no embossing step is required. A disadvantage is the relatively sophisticated folding process, compared to the embodiments of FIGS. 13 and 13.

[0105] Like the embodiments described hereinafter referring to FIGS. 18-23, the connector of Figs, 14-16 does not require a rigid bond between the sheet portions and may therefore have some elasticity with respect to deformations in in-plane directions.

[0106] FIG. 17 illustrates – for an example of a connector based on the principle described referring to FIGS. 12 and 13, especially with a rigid bond for acting against unfolding – the possibility of shaping the connector in a manner that deviates from a simply rectangular shape. The connector of FIG. 17 is essentially arc shape, with a comparably short (in in-plane dimensions) fold 37 allowing some flexibility with respect to in-plane displacements of the relative positions of the first and second sheet portions 31, 32. More in general, the shape of the connector may be adapted in view of dimensions of the objects to be connected as well as in view of flexibility requirements.

[0107] The connector 3 of FIG. 18 in contrast to the embodiment of FIGS. 14-16 has the following features that are independent of each other: [0108] The connector has spacers formed by pairs of spacer portions 61, 62 formed by indentations in the first and second sheet portions 31, 32. [0109] The fold 37 as arranged along a long edge (broad side edge) of the connector being essentially rectangular. This leads to enhanced stability with respect to certain in-plane relative movements (see also the discussion hereinafter). [0110] The foldover portions 72 are folded over parts of the first sheet portion 31 that are not indented, i.e. the foldover portions protrude above the outer surface of the first sheet portion 31.

[0111] In the embodiment of FIG. 19, the foldover portion 72 extends along a long edge of the essentially rectangular connector. Also, the fold 37 has slit-shaped first cutouts 39. Similarly the foldover bridge 74 has slit-shaped second cutouts 75.

[0112] The embodiment of FIG. 20 is distinct from the embodiment of FIG. 19 by the following two independent features: [0113] The foldover portion 72 is folded over an indented portion of the first sheet portion so that the outer surface of the foldover portion is approximately flush with the outer surface of the first sheet portion. [0114] The second cutouts 75 (and/or the first cutouts 39) are inclined with respect to directions perpendicular to the sheet planes.

[0115] The embodiment of FIG. 21 has two foldover portions 72 that are relatively narrow and extend from the narrow side edges of the second sheet portion 32.

[0116] In the embodiment of FIG. 22, the first sheet portion 31 is constituted by two sections, each extending from a broad side edge. Thus, instead of being connected by one fold 37 and stabilized by a foldover portion, the first and second sheet portions are connected by two folds 37 extending along opposing edges.

[0117] Embodiments with foldover portions or embodiments of the kind shown in FIG. 22 apply the principle of self-stabilization. This principle is illustrated, for the example of a connector having two foldover portions extending from opposing edges of the second sheet portion 32, like embodiments of FIGS. 14-16 and 21, in FIG. 23. FIG. 23 shows the assembly of the first object 1, the second object 2 and the connector 3 after the bonding process. The connector has at least one spacer formed by two spacer portions 61, 62 and defines a gap with a width w between the inner surfaces of the objects. As illustrated by the block arrows 81, the first object 1 after the bonding process defines an abutment for the foldover portions 72 preventing them from flexing back. Therefore, the assembly is stable also with respect to forces pulling the first and second objects 1, 2, apart, i.e. forces in z direction, just due to the folding configuration and the bond of the first and second object to the first and second sheet plane, respectively.

[0118] More specifically, in a self-stabilizing configuration the resistance against pulling forces pulling the first and second objects apart from each other is higher than just the resistance of the sheet portions and possible foldover portions against bending. A self-stabilizing configuration uses the – usually very high – stability of a sheet material against in-plane deformations to prevent unfolding/out-of-plane deformations from occurring.

[0119] FIG. 23 also illustrates re-solidified flow portions 91, 92 of the first object and second -object-respectively, whereby the inner surfaces 11, 12 of the first and second objects in a vicinity of the attachment portions 33, 34 may be less smooth than originally.

[0120] A condition for such a self-stabilizing configuration to be possible may be that a large surface of the connector that comes into contact with the inner surface of one of the objects (the upper surface in a the embodiments of FIGS. 14-16 and 18-23) is formed from portions folded from the sheet portion constituting the other large surface into different folding directions. Different folding directions are especially present if the respective folding is done along non-parallel folding axes or, in case of parallel folding axes, into opposite directions. This is illustrated in FIGS. 14, 21 and 22 where the folding axes 100 are illustrated.

[0121] In FIG. 14, the folding axis of the first sheet portion (the upper folding axis 100 in FIG. 14) and of the foldover portion 72 are parallel along opposite edges of the connector but with the folding being in opposite directions, as schematically illustrated by the arrows.

[0122] In FIG. 21, the folding axes 100 of the foldover portions 72 are parallel to each other, with opposite folding directions, and the folding axis 100 of the first sheet portion 31 with respect to the second sheet portion 32 is at an angle of 90° to the folding axes of the foldover portions. For the self-stabilizing effect, in this configuration, it would be sufficient if just one of the foldover portions 72 was present.

[0123] In FIG. 22, the folding axes 100 of the two sections of the first sheet portion are parallel, namely along the broad side edges, with opposite folding directions. In such a configuration, the self-stabilizing effect arises even without any foldover portion.

[0124] The connector 3 may be designed to have tailor-made properties with respect to shear forces, i.e. translational and/or rotational in-plane forces of the two objects relative to one another. In-plane forces in the present context are forces parallel to the sheet planes, i.e. parallel to the x-y-plane in the coordinate system used (see for example FIGS. 20-23).

[0125] Parameters that may be used to influence the stiffness with respect to in-plane forces include: [0126] The location of the fold (for example along the broad side or narrow side). [0127] The extension (length) of the fold; compare for example FIGS. 15 and 18 with each other, showing embodiments with a short fold and a long fold, respectively. [0128] The number of folds (the embodiment of FIG. 22 has two folds, the other shown embodiments have one fold). The configuration of FIG. 22 is an example of a configuration having large stiffness with respect to shear forces y-directions and a much smaller stiffness with respect to shear forces in x-directions. This is because of the location of the folds (along the broad side, parallel to the y-diretion), the length of the folds (long) and because of the two-fold configuration characteristic for the embodiment of FIG. 22. [0129] The number, location and size of foldover portions [0130] The use of receiving indentations (receiving indentations enhance the stiffness) [0131] The number, size and distribution of first and/or second cutouts. For example, the embodiment of FIG. 19 has, compared to the embodiment of FIG. 22, a reduced y-stiffness because of the cutouts 39, 75 as well as because it has just one fold and the foldover portion is not received in a receiving indentation. [0132] Further measures (not shown in the figures) influencing the stiffness of the sheet portions themselves. [0133] Finally, the rigid bonds, for example by welding/gluing/soldering or clinching, for example of embossed spacer portions, as described referring to FIGS. 12, 13, and 17 are structures influencing the stiffness with respect to in-plane forces. Especially, such rigid bonds make the connector relatively stiff by not allowing any relative in-plane movements between the sheet portions.

[0134] In all cases, the respective structure can be manufactured from a simple deformable sheet part, for example a metal sheet part. Thus an important advantage of embodiments of the invention – namely the possibility to manufacture the connector in a cost-efficient manner – is not impaired by measures for securing a tailor-made shear stiffness.