Patent Application
20230058504
The invention is in the fields of mechanical engineering and construction, especially mechanical construction, for example automotive engineering, aircraft construction, railway industry, shipbuilding, machine construction, toy construction, building industries, etc. In particular, it relates to a method of - mechanically - securing a second object to a first object.
In the automotive, aviation and other industries, there has been a tendency to move away from steel-only constructions and to use lightweight material such as aluminum or magnesium metal sheets or polymers, such as carbon fiber reinforced polymers or glass fiber reinforced polymers or polymers without reinforcement, for example polyesters, polycarbonates, etc. instead.
The new materials cause new challenges in bonding elements of these materials.
To meet these challenges, the automotive, aviation and other industries have started heavily using adhesive bonds. Adhesive bonds can be light and strong. However, adhesive bonds may lead to a rise in manufacturing cost, both, because of material cost and especially because of delays caused in manufacturing processes due to slow hardening processes. The manufacturing process for a certain part essentially has to be interrupted until the adhesive connection has sufficiently hardened before a next process step can begin. Therefore, in a manufacturing line, an intermediate store has to be provided for hardening parts.
For example in WO 2018/130 524 it has been proposed to combine an adhesive connection between two objects having thermoplastic material with a connection via a profile body. For fastening, both, the profile body and an adhesive are placed between the objects. The objects then are pressed against each other while mechanical energy impinges on at least one of the objects, until the thermoplastic material becomes flowable and the profile body is embedded in both objects. This embedding of the profile body in both objects secures, after re-solidification of the thermoplastic material, the objects to each other at the position of the profile body. The adhesive that will be present at other positions between the objects may then harden subsequently while the assembly of the two objects is subject to further processing steps.
For making sure that there is an adhesive gap for the adhesive, WO 2018/130 524 firstly proposes to provide indentations in the surface of the first object and/or the second object and to dispense the adhesive in these indentations. This ensures that the adhesive gap has well-defined dimensions but may require additional manufacturing steps for providing the indentations. Alternatively, WO 2018/130 524 suggests to shape the portions that are to be embedded in the object material in a manner that the mechanical resistance rises during the process so that the embedding will stop while there is still a considerable distance between the object surfaces thereby yielding an adhesive gap. This, however, has the disadvantage that the exact distance, i.e. the exact width of the adhesive gap may be poorly defined.
The necessity of there being a gap with a well-defined width between two objects bonded to each other may also arise in situations other than the situation in which the gap is used for an adhesive. Examples include the placement of sealing means, the compensation of variations due to inaccuracies in manufacturing processes, compensation of different thermal expansion between different parts, or the requirement of there being such gap of other constructional reasons.
It is an object of the present invention to provide a bonding method that overcomes drawbacks of prior art bonding methods, especially in terms of reliability and/or manufacturing cost. It is also an object to provide a connector to be used in such method.
In accordance with an aspect of the invention, a method of bonding a first object and a second object together is provided.
The method firstly comprises the step of providing a connector, the connector having a first sheet portion and a second sheet portion. The first sheet portion has a first outer (large) surface and a first inner (large) surface and the second sheet portion has a second outer (large) surface end a second inner (large) surface, the first and second inner surfaces facing each other. The first sheet portion has at least one outwardly protruding first attachment portion, with the sheet portion being locally bent towards outwardly and forming an edge that especially may face towards outwardly. In analogy, the second sheet portion has at least one outwardly protruding second attachment portion where the sheet portion is locally bent towards outwardly and forms an edge that especially may face towards outwardly. The respective attachment portions may be formed around openings (perforations) in the first/second sheet portion, respectively.
The connector further has a spacer between the first and second sheet portions. Such spacer comprises a spacer portion of the first and/or second sheet portion, i.e. a part of the first/second sheet portion that is bent to lie inwardly of a first/second sheet plane. More in concrete, the first sheet portion and the second sheet portion define parallel sheet planes, and the first sheet portion and/or the second sheet portion has/have a part that is bent inwardly to protrude into a space between the first and second sheet portion planes and to abut material of the respective other sheet portion. The part that defines the spacer portion may abut against the plane part of the other sheet portion, or it may abut against a spacer portion of the other sheet portion so that the abutting spacer portions together define the spacer..
In a group of embodiments, the spacer portion is bent to have an angle of about 90° with respect to the sheet portions.
In another group of embodiments, the spacer portion comprises an embossed (stamped) portion of the sheet portion.
In embodiments, the spacer portions are embossed indentations having a for example round shape (in section parallel to the sheet planes) or an other shape with rounded features, such as a polygon with rounded corners. Two such indentations of the first and second sheet portions, respectively, at corresponding positions may together define a pot spacer.
Embodiments that combine embossed spacer portions with folding the connector of a metal sheet into a spacer having the first and second sheet portions feature the substantial advantage that the punching/deformation step for the (outwardly) protruding attachment portion on the one hand and the embossing step for the inwardly protruding embossed spacer portions on the other hand each have to be made from one side only prior to folding. This is in contrast to embodiments of the prior art with one single sheet having attachment portions protruding to both sides, where punching has to be carried out from two sides.
The connector may in addition or possibly as a first alternative comprise a spacer sheet portion connected to the first and/or second sheet portion, such spacer sheet portion being bent to lie parallel to the first and second sheet portions. It may in addition or possibly as a further alternative comprise a separate spacer object.
If the spacer comprises a spacer portion of the first and/or second sheet portion, such spacer portion may be arranged at an in-plane position that is central. Then, the first/second sheet portion may be locally disrupted, for example by the spacer portion being cut out of the first/second sheet portion. In addition or as an alternative a spacer portion may be formed by bending a peripheral feature of the first/second sheet portion in a manner that it lies between the first and second sheet portions.
In accordance with a further aspect of the invention, the connector has a self-stabilizing configuration. This means that the connector has a structure in which after the bonding process the presence of the bonded first and/or second object attached to the connector prevents unfolding of the connector. Especially, the for example essentially planar inner object surface of at least one of the objects may form an abutment surface preventing disassembling by unfolding of the connector.
In embodiments, the connector is folded from a sheet, such as a metal sheet. The configuration of the connector may be such that a first and/or second object when extending along one of the large surfaces of the connector and being bonded thereto prevents unfolding of the sheet.
In a group of embodiments, the sheet portions of the connector are stabilized by a foldover portion, i.e. a portion extending from one of the sheet portions (for example the second sheet portion) and being folded over the outer surface of the other sheet portion (for example first sheet portion). In a sub-group of embodiments, the other (for example first) sheet portion is provided with a receiving indentation receiving the foldover portion so that the foldover portion does not add to the thickness of the connector or does so to a lesser extent than if no such receiving indentation was present. Such foldover portion may especially be folded over the respective (for example first) sheet portion from an edge different from the edge along which it is connected to the other sheet portion, whereby the foldover portion ensures a self-stabilizing configuration in the above sense.
In another group of embodiments, one of the sheet portions has a plurality of sections extending from different edges, whereby the configuration is self-stabilizing also without any (optionally nevertheless present) foldover portions.
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 is formed from different portions folded from the sheet portion constituting the other large surface, namely from portions folded 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.
The self-stabilizing configuration especially ensures an out-of-plane rigidity and a stability against tilting movements between the first and second objects even if the shape of the first/second movements would allow such tilting movement.
A self-stabilizing configuration as described herein may also be an option for a connector with at least one first attachment portion and at least one second attachment portion, which connector does not comprise a spacer.
Depending on the application, it may be desired that the stability against relative movements in in-plane (x-y-) directions are not maximized but adapted to specific requirements. For example, some elasticity with respect to in-plane movements may be desired to compensate for different coefficients of thermal expansion or to absorb kinetic energy by allowing for a plastic and/or elastic deformation of the sheet material for example in the event of a crash situation. Such absorption of kinetic energy will lead to a temporary and/or permanent deformation without the first and second objects being entirely disconnected, whereby the connection in the herein described manner may be a security feature, for example in vehicles or airplanes.
In accordance with a group of embodiments, therefore, a section that connects the first and second sheet portions, therefore, may be provided with at least one cutout. Such connecting section may comprise a fold that connects the first and second sheet portions, or may comprise a foldover bridge that connects a foldover portion with the sheet portion from which it extends. A cutout makes the connection between the first and second sheet portions more pliant in a targeted manner. The location and extension of the fold(s) and foldover portions as well as, if applicable, the shape, size and distribution of such cutout(s) may be adapted to specific requirements. The connector may be configured to have a greater stiffness with respect to shear in one in-plane dimension compared to the other in-plane dimension. With cutouts that are elongate and at an angle to the z-direction (the direction perpendicular to the sheet planes), it is even possible to produce asymmetry between opposing in-plane directions.
The method comprises the further step of providing the first and second objects, wherein both, the first object and the second object comprise thermoplastic material.
The first and second objects and the connector are positioned relative to each other so that the connector is placed between the first and second objects. Then, the first and second objects 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 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.
In addition to comprising a spacer, the connector may comprise a material connection, such as a spot weld connection or solder (for example spot solder) connection or glue (for example spot glue) connection, and/or a positive fit and/or interference fit connection, such as a clinching or clipping connection, between the first and second sheet portions. Comprising such a spot weld or solder or glue connection etc. between first and second sheet portions may also be an option for a connector with at least one first attachment portion and at least one second attachment portion, which connector does not comprise a spacer.
Such spot weld and/or solder, glue connection may for example be located at an in-plane position opposite a fold that connects the first and second sheet portions together.
The at least one spot weld and/or solder glue a connection may be an indirect connection via the spacer. However, the connection may also be a direct connection.
In embodiments, the connector may comprise a shape that is not-rectangular, especially adapted to specific requirements. For example, the connector may be instead of being rectangular form at least one arc to follow a contour of the objects to be fastened to each other, or of a part thereof.
The following options may apply:
Especially, if two objects are fastened to each other by an adhesive, often the waiting time until the adhesive connection is sufficiently strong and the lack of stability of the connection therebefore is an issue. This issue is even more severe if the adhesive connection and hence the thickness of an applied adhesive portion have to be comparably thick, for example so that the connection exhibits a residual flexibility necessary for compensating different thermal expansion behaviors if necessary. Similarly, thick layers of adhesive are in many situations necessary if the adhesive has the additional function of sealing. Often one- or two-component Polyurethane adhesives are used for such purposes.
Embodiments of the present invention, therefore make a combination of the securing approach according to the invention with applying an adhesive having a predetermined thickness possible. Due to the connection via the connector, the assembly of the first and second objects with the connector and the adhesive between them may be subject to further processing steps without any waiting time for the adhesive to cure.
In addition or as an alternative, the adhesive or a portion thereof may be used as a sealant around the connector, for example to prevent any corrosion.
The connector, if it does not comprise a separate spacer object of the above-discussed kind, may be one-piece and formed by a contiguous sheet material for example a metal sheet. Especially, in any embodiment, the first and second sheet portions may be portions of a contiguous sheet of folded sheet material.
Especially if the spacer is a separate spacer object, the method may comprise the onsite adjustment of a connector width w. Then, the method may comprise providing a connector part comprising the first and second sheet portions and having an initial width, provisionally arranging the first and second object and the connector relative to one another, determining a desired connector width based on a dimension of this resulting arrangement, choosing a spacer object out of a plurality of available spacer objects, inserting this chosen spacer between the sheet portions and carrying out the subsequent pressing and vibration energy coupling step that, depending on a width of the chosen spacer object, may comprise deforming, by the pressing force, the connector part to have a final width that is smaller than the initial width.
Pressing and coupling the vibration energy into the first and/or second object may take place simultaneously, meaning that at least for some time both, the pressing force and the mechanical vibrations act. This does not, however, imply that the pressing force and the vibrations start and end at the same time.
Rather, especially the pressing force may optionally set in prior to the vibrations or possibly also after onset of the vibrations.
In embodiments, the pressing force may be maintained until the flow portions have re-solidified at least to some extent to prevent a spring-back effect. This may for example be advantageous in situations in which a spring-back-effect would be caused by an elastic deformation of the first object and/or the second object or by an elastic compression behavior of an adhesive between the first and second objects.
In other embodiments, especially embodiments without any adhesive, it may be advantageous to stop the pressing force when the vibrations stop, so that the system may relax prior to re-solidification. Thereby, internal stress in the first and second objects may be minimized, so that object deformation is prevented.
For applying a counter force to the pressing force, the respective other object may be placed against a support, for example a non-vibrating support. In embodiments, this other (for example second) object is placed against a support with no elastic or yielding elements between the support and the second object, so that the support rigidly supports the second object. Alternatively, vibrations are coupled into the assembly from both sides, i.e. sonotrodes act on both, the first and the second objects.
The present invention also concerns a connector adapted for carrying out the method according to any embodiment of the invention. The connector features described in this text when describing the method generally are possible features of the connector according to the present invention, and features of the connector according to the present invention described in this text are possible features of connectors used in the method according to the invention.
The invention even more concerns an apparatus comprising a source of mechanical vibration and being configured and/or programmed to carry out the method according to any embodiment of the present invention. Moreover, the invention concerns a set that comprises such apparatus and at least one connector.
Optionally, in addition to the mechanical vibration energy, further energy may be coupled into the assembly. In an example, the first and/or second object and/or the connector may be pre-heated by IR irradiation, induction (as far as having an electrically conducting component), a hot air stream, etc. In addition or as an alternative, the thermoplastic material of the first and/or second object may be pre-heated locally near the interface to the edge, for example by electromagnetic heating as described WO 2017/015 769, by irradiation, etc. For example, for electromagnetic heating as described in WO 2017/015 769, the thermoplastic material in the attachment zone may be provided with a magnetic dopant. In embodiments in which the connector is metallic, such magnetic dopant may be not necessary, since impinging electromagnetic energy may be absorbed directly by the connector, whereby the connector is pre-heated.
The first/second flow portion of the thermoplastic material is the portion of the thermoplastic material that during the process and due to the effect of the mechanical vibration is caused to be liquefied and to flow. The respective flow portion does not have to be one-piece but may comprise parts separate from each other.
In this text, the term “sheet plane” denotes the plane/surface defined by the shape of the generally planar (first, second) sheet portion, especially in a region around the edge, for example around the perforation (if any). The sheet plane may be planar in the sense of extending straight into two dimensions. Alternatively, the sheet plane may be curved and thereby follow a more complex 3D shape, for example if the first and second objects have complex surface shapes adapted to each other, for example as belonging to a body of a vehicle or aircraft.
In a group of embodiments, the first object and/or the second object comprises a structured contact side that comprises the thermoplastic material. The contact side is the side of the first object that is brought into contact with connector for the connecting. The fact that the contact side is structured means that it is different from just being flat and even and that it comprises protrusions/indentations. For example, it may comprise a pattern of ridges and grooves, for example a regular pattern.
Generally, the first and second objects are construction components (construction elements) in a broad sense of the word, i.e. elements that are used in any field of mechanical engineering and construction, for example automotive engineering, aircraft construction, shipbuilding, building construction, machine construction, toy construction etc. Generally, the first and second objects as well as a connector piece (if applicable) will all be artificial, man-made objects. The use of natural material such as wood-based material in the first and/or second object is thereby not excluded.
Turning back to the thermoplastic material(s) of the first object and of the second object, in this text the expression “thermoplastic material being capable of being made flowable e.g. by mechanical vibration” or in short “liquefiable thermoplastic material” or “liquefiable material” or “thermoplastic” is used for describing a material comprising at least one thermoplastic component, which material becomes liquid (flowable) when heated, in particular when heated through friction i.e. when arranged at one of a pair of surfaces (contact faces) being in contact with each other and vibrationally moved relative to each other, wherein the frequency of the vibration has the properties discussed hereinbefore. In some situations, for example if the first object itself has to carry substantial loads, it may be advantageous if the material has an elasticity coefficient of more than 0.5 GPa. In other embodiments, the elasticity coefficient may be below this value, as the vibration conducting properties of the first object thermoplastic material do not play a role in the process. In special embodiments, the thermoplastic material therefore may even comprise a thermoplastic elastomer.
Thermoplastic materials are well-known in the automotive and aviation industry. For the purpose of the method according to the present invention, especially thermoplastic materials known for applications in these industries may be used.
The thermoplastic materials of the first and second objects may be identical or may be different. They may be capable of being welded together or not.
A thermoplastic material suitable for the method according to the invention is solid at room temperature (or at a temperature at which the method is carried out). It preferably comprises a polymeric phase (especially C, P, S or Si chain based) that transforms from solid into liquid or flowable above a critical temperature range, for example by melting, and re-transforms into a solid material when again cooled below the critical temperature range, for example by crystallization, whereby the viscosity of the solid phase is several orders of magnitude (at least three orders of magnitude) higher than of the liquid phase. The thermoplastic material will generally comprise a polymeric component that is not cross-linked covalently or cross-linked in a manner that the cross-linking bonds open reversibly upon heating to or above a melting temperature range. The polymer material may further comprise a filler, e.g. fibres or particles of material which has no thermoplastic properties or has thermoplastic properties including a melting temperature range which is considerably higher than the melting temperature range of the basic polymer.
In this text, generally a “non-liquefiable” or “not liquefiable” material is a material that does not liquefy at temperatures reached during the process, thus especially at temperatures at which the thermoplastic material is liquefied. This does not exclude the possibility that the material would be capable of liquefying at temperatures that are not reached during the process, generally far (for example by at least 80° C.) above a liquefaction temperature (melting temperature for crystalline polymers for amorphous thermoplastics a temperature above the glass transition temperature at which the becomes sufficiently flowable, sometimes referred to as the ‘flow temperature’ (sometimes defined as the lowest temperature at which extrusion is possible), for example the temperature at which the viscosity drops to below 104 Pa*s (in embodiments, especially with polymers substantially without fiber reinforcement, to below 103 Pa*s)), of the thermoplastic material. For example, the non-liquefiable material may be a metal, such as aluminum or steel, or wood, or a hard plastic, for example a reinforced or not reinforced thermosetting polymer or a reinforced or not reinforced thermoplastic with a melting temperature (and/or glass transition temperature) considerably higher than the melting temperature/glass transition temperature of the liquefiable part, for example with a melting temperature and/or glass transition temperature higher by at least 50° C. or 80° C. or 100° C.
In this text, “melting temperature” is sometimes used to refer to the named liquefaction temperature at which the thermoplastic material becomes sufficiently flowable, i.e. the conventionally defined melting temperature for crystalline polymers and the temperature above the glass transition temperature at which the thermoplastic material becomes flowable sufficiently for extrusion.
Specific embodiments of thermoplastic materials are: Polyetherketone (PEEK), polyesters, such as polybutylene terephthalate (PBT) or Polyethylenterephthalat (PET), Polyetherimide, a polyamide, for example Polyamide 12, Polyamide 11, Polyamide 6, or Polyamide 66, Polymethylmethacrylate (PMMA), Polyoxymethylene, or polycarbonateurethane, a polycarbonate or a polyester carbonate, or also an acrylonitrile butadiene styrene (ABS), an Acrylester-Styrol-Acrylnitril (ASA), Styrene-acrylonitrile, polyvinyl chloride, polyethylene, polypropylene, and polystyrene, or copolymers or mixtures of these.
In addition to the thermoplastic polymer, the thermoplastic material may also comprise a suitable filler, for example reinforcing fibers, such as glass and/or carbon fibers. The fibers may be short fibers. Long fibers or continuous fibers may be used also, especially, but not only, for portions of the first and/or of the second object that are not liquefied during the process. In case long fibers or continuous fibers are used for portions that become liquefied, fibers may be cut through during the process, which however is not necessarily a problem.
The fiber material (if any) may be any material known for fiber reinforcement, especially carbon, glass, Kevlar, ceramic, e.g. mullite, silicon carbide or silicon nitride, high-strength polyethylene (Dyneema), etc..
Other fillers, not having the shapes of fibers, are also possible, for example powder particles.
Mechanical vibration or oscillation suitable for embodiments of the method according to the invention has preferably a frequency between 2 and 200 kHz (even more preferably between 10 and 100 kHz, or between 20 and 40 kHz) and a vibration energy of 0.2 to 20 W per square millimeter of active surface.
In many embodiments, especially embodiments that comprise coupling the vibration into the first object, the vibrating tool (e.g. sonotrode) is e.g. designed such that its contact face oscillates predominantly in the direction of the tool axis (longitudinal vibration), the tool axis corresponding to the axis along which the first object and second objects are moved relative to one another by the effect of the energy input and pressing force when the attachment portions are forced into material of the first object and second object, respectively) and with an amplitude of between 1 and 100 µm, preferably around 30 to 60 µm. Such preferred vibration is e.g. produced by ultrasonic devices as e.g. known from ultrasonic welding.
Depending on the application, a vibration power (more specifically: the electrical power by which an ultrasonic transducer is powered) may be at least 100 W, at least 200 W, at least 300 W, at least 500 W, at least 1000 W or at least 2000 W.
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:
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.
The thermoplastic materials of the first and second objects 1, 2 may be identical or may be different.
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.
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.
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.
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.
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 (
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.
In addition to embodiments in which a small gap as illustrated with respect to
In the embodiment of
In the embodiment of
In connectors of the kind depicted in
The connectors of
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.
The spacer portions 61, 62 of the first and second sheet portions 31, 32 are aligned with each other and abut against each other.
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.
Also the embodiment of
Like the embodiment of
The embodiments of
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.
In the concept of
Like the embodiments described hereinafter referring to
The connector 3 of
In the embodiment of
The embodiment of
The embodiment of
In the embodiment of
Embodiments with foldover portions or embodiments of the kind shown in
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.
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
In
In
In
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
Parameters that may be used to influence the stiffness with respect to in-plane forces include:
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 00047/20 | Jan 2020 | CH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/050690 | 1/14/2021 | WO |
