An upholstered furniture member comprising a base part with wadding welded thereon, a method for forming such a furniture, as well as an apparatus for forming such a furniture

Technical Field

The present invention relates to upholstered seating furniture and especially to a furniture member of such seating furniture, such as an armrest of a sofa. The present invention also relates to a method for providing a furniture member and an apparatus for forming such a furniture member.

Prior Art

In upholstered seating furniture, wadding or batting is used for providing a comfortable layer outside the inner, often rigid, structure of the seating furniture. An exterior layer, usually made of fabric, is thereafter attached covering the wadding. The exterior layer forms the outside of the seating furniture being visible to the consumer or user.

Usually, seating furniture such as sofas or armchairs are manufactured by assembling pre-manufactured pieces of wood-based materials which form for instance armrests, seating areas, or backrests of the furniture. The wadding is thereafter applied on the outside of the wooden structure, for example by gluing, nailing, and/or using metal clips or staples. The wadding material may in some cases comprise several layers, such as a comfort or cushioning layer as well as a lining layer. The layers may be glued or sewn together to ensure their respective position relative to each other.

The current methods of attaching the wadding to the pre-manufactured furniture pieces, especially armrests, are all extremely time consuming. In view of the above, an improved furniture member to form part of an upholstered seating furniture is therefore desired.

Summary

It is therefore an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to provide an upholstered furniture member which is far less difficult to manufacture than prior art.

According to a first aspect, an upholstered furniture member, such as an armrest for a seating furniture, is provided. The furniture member comprises at least one base part and a wadding. The base part may e.g. define an exterior side of the furniture member. The wadding is welded to the base part, optionally to the exterior side. At least one of the wadding and the base part is at least partly made from a plastic material. Although the welding technique requires the wadding and the base part to be compatible with such joining process, it will greatly reduce the manufacturing time for pre- manufactured upholstered furniture members.

Preferably, the plastic material is a thermoplastic material. A thermoplastic material suitable for the embodiments of the present disclosure is, under the conditions of the step of establishing a weld joint, solid. 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.

Examples of the thermoplastic material applicable in the embodiments of the present disclosure are thermoplastic polymers, co-polymers or filled polymers, wherein the basic polymer or co-polymer is e.g. polyethylene, polypropylene, polyamides (in particular Polyamide 12, Polyamide 11 , Polyamide 6, or Polyamide 6.6),

Polyoxymethylene, polycarbonateurethane, polycarbonates or polyester carbonates, acrylonitrile butadiene styrene (ABS), Acrylester-Styrol-Acrylnitril (ASA), Styrene- acrylonitrile, polyvinyl chloride, polystyrene, Polyetherimide (PEI), Polysulfon (PSET), Poly(p-phenylene sulfide) (PPS), Liquid crystall polymers (LCP) etc. Further polymers that could be applicable include polyester (PET), polylactic acid (PLA), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), and polyethylene 2,5-furandicarboxylate (PEF).

Welding is preferably performed by transferring energy suitable for liquefaction of the plastic material in an amount and for a time sufficient for

liquefaction of the plastic material. The transferred energy may be mechanical vibration energy.

For welding, the plastic material is solid (at ambient temperature) and preferably comprises thermoplastic properties (i.e. it is liquefiable with the aid of thermal energy, and the material of the other part (the base part or the wadding) is also solid (at ambient temperature).

During welding, the energy necessary for liquefying the plastic material is supplied to either one of the base part or the wadding, preferably in the form of mechanical vibration, in particular ultrasonic vibration, to be transformed into friction heat at the interface between the wadding and the base part. Other sorts of energy such as e.g. irradiation with electromagnetic energy for which suitable absorbing means are to be provided at the locations where the welding is performed, or corresponding heating (e.g. inductive or resistive heating) are applicable also.

The base part may be a rigid part, forming part of a support structure, and being at least partly formed by a plastic material, preferably a thermoplastic material. It is preferably formed at least partly by injection molding. Injection molding is not only a very fast and accurate manufacturing method, but it also allows the use of plastic materials which are possible to use in welding processes.

The wadding may at least partly be formed by a plastic material, preferably a thermoplastic material. Preferably the wadding comprises fibers comprising

thermoplastic material.

The wadding may comprise a liner part, preferably the liner part comprises fibers, such as fibers of polyester, or co-polymers thereof. Preferably the liner part being a layered material comprising at least two layers, preferably the at least two layers being bonded to each other.

The base part may comprise a planar portion, and the wadding may comprise a planar part which is welded to the planar portion of the base part along at least a part of its periphery. Efficient manufacturing and design of the furniture member is thereby achieved; in particular for an armrest such embodiment is particularly advantageous.

The base part may further comprise a curved portion, and the wadding may comprise a folded part which is arranged onto the curved portion. The furniture member may thereby exhibit complex and aesthetically appealing designs, still allowing for a simple manufacturing. The folded part of the wadding is preferably shaped to correspond to the curved portion of the base part; shaping may either be done by actual folding, or the folded part may be pre-formed to a desired shape. The term“folded” should thereby only be interpreted as a reference to the traditional way of arranging originally planar wadding to a curved rigid part.

The folded part may be welded to the base part along at least a part of its periphery. Optionally, the wadding further comprises a liner part which is arranged onto the folded part. The liner part may in such embodiment be welded to the base part and/or to the folded part and/or the planar part along at least a part of its periphery. This also allows for a simple, yet extremely versatile manufacturing of the furniture member, since not every wadding piece must be welded to the base part.

The liner part may be made of a fire retardant material.

According to a second aspect, a seating furniture is provided. The seating furniture, which may e.g. be a chair, sofa, etc. comprises at least one furniture member according to the first aspect.

The at least one furniture member may be a backrest, a planar seating area, a curved seating area, or an armrest.

According to a third aspect, a method for forming an upholstered furniture member of a seating furniture is provided. The method comprises a first step of providing at least one base part, and a second step of arranging a wadding on the base part, where at least one of the wadding and the base part is at least partly made from a plastic material. The method comprises a third step of welding the wadding to the base part to form the upholstered furniture member.

The method may further comprise a step of welding a planar part of the wadding to a planar portion of the base part along at least a part of its periphery.

The method may further comprise a step of arranging a folded part of the wadding onto a curved portion of the base part.

The method may further comprise a step of welding the folded part of the wadding to the base part and/or to a further part of the wadding along at least a part of its periphery.

The method may further comprise a step of arranging a liner part of the wadding onto the base part, preferably the liner part being at least partly arranged on a folded part of the wadding.

The method may further comprise a step of welding the liner part to the base part and/or to a further part of the wadding, such as to the folded part of the wadding along at least a part of its periphery.

The step of welding may be performed by ultrasonic welding, preferably by line welding.

According to a fourth aspect, an apparatus for forming an upholstered furniture member of a seating furniture is provided. The apparatus comprises a structure configured to receive and hold a base part having a wadding arranged thereon, and a welding unit being configured to weld the wadding to the base part to form the upholstered furniture member.

The apparatus may further comprise a driving unit configured to move the welding unit to a position where it contacts the wadding prior to activation to perform welding. Alternatively, the position of the welding unit is fixed while the driving unit is connected to the base part for moving the base part towards the welding unit.

Preferably, the welding unit is mechanical vibration welding unit, in particular an ultrasonic welding unit.

The welding unit may, in itself, have a temperature close to room temperature. Thereby the welding unit will function as a heat sink that cools the welded area, such that liquefied polymer in the area of the weld will very rapidly cool down and solidify. A very speedy process is thereby possible, as the weld will, immediately after stopping the ultrasonic energy supply, solidify and have full strength, by being cooled by the welding unit.

The ultrasonic welding unit may comprise a plurality of spaced-apart welding heads, each welding head being configured to provide a point-like weld joint.

In another embodiment the ultrasonic welding unit comprises at least one elongated welding head configured to provide a line weld joint.

The apparatus may comprise a plurality of welding units.

The plurality of welding units may be distributed in accordance with an intended welding path, such that simultaneous activation of the plurality of welding units will provide welding along said welding path.

Brief Description of the Drawings

The present invention will be described further below by way of example and with reference to the enclosed drawings. In the drawings:

Figs la-c are isometric views of seating furniture according to different embodiments,

Fig. 2 is an exploded view of an armrest, forming a furniture member for a seating furniture according to an embodiment,

Fig. 3 is an isometric view of the armrest shown in Fig. 2,

Fig. 4 is a schematic view of a method for providing a furniture member according to an embodiment,

Fig. 5a is an isometric view of a welding apparatus according to an

embodiment, Fig. 5b is a detailed view of the welding head of the apparatus shown in Fig.

5 a,

Fig. 6a is an isometric view of a welding apparatus according to another embodiment,

Fig. 6b is a detailed view of a resulting weld joint when the apparatus shown in

Fig. 6a has been activated,

Fig. 7 is an isometric view of a welding apparatus according to a yet further embodiment,

Fig. 8 is an isometric view of a welding apparatus according to another embodiment, and

Figs. 9a-c are cross-sectional views of a welding process according to embodiments.

Detailed Description of Embodiments

The term“upholstered furniture member” as used in the present application relates to any furniture member having upholstery. Hence, in this term is included various parts, such as armrests, seating areas, back rests and frames, of seating furniture, such as sofas, armchairs, dining chairs, office chairs etc. Furthermore,“upholstered furniture member” also includes other furniture members having upholstery, such as bed frames and headboards of beds. Initially reference is made to Figs la-c, in which different examples of seating furniture 10 are shown. In Fig. la an example of a sofa 10 is provided, having a planar backrest 12 attached to a planar seating area 14.

In Fig. lb an example of a chair 10 is provided, having a curved seating area 16 also extending upwards to an integrally formed backrest.

Fig. lc shows another example of a sofa 10, having a rigid seating area 18 and a rigid backrest 19. Two armrests 20 are provided on each side of the sofa 10, connecting preferably to the seating area 18 as well as to the backrest 19. Each armrest 20 defines an exterior side 24, and the armrests 20 are provided with wadding 30. As used in the current application“wadding” means a soft material intended to provide a soft feeling to a piece of furniture by being applied to a structural body of the piece of furniture. The wadding may comprise liners, such as non-woven polyester liners having one or more layers, and/or comfort layers, such as polyurethane foam layers.

As will be described in the following, improved furniture members will be described as well as a method for providing such furniture members. From Figs la-c, such furniture member will include pre-manufactured pieces for upholstered seating furniture; i.e. the backrests 12, 19, the seating area 14, 16, 18, or the armrests 20 may all be such furniture members within the context of this specification.

With respect to Figs. 2-3 details on embodiments of armrests 20 will be given, however the technical concept of welding the wadding 30 to a base part comprising plastic material is equally applicable to other upholstered furniture members.

Again with reference to Fig. lc, the sofa 10 has two armrests 20 on each lateral side thereof. Although identical armrests could be used, for this sofa 10 one armrest 20 is a mirror version of the opposite armrest 20.

Each armrest 20 has an exterior side 24, facing outwards. The exterior side 24 is not necessarily limited to the lateral surface 24a indicated in Fig. lc, but may also include the upper curved portion 24b, and/or the inner portion 24c.

In Fig. 2 an exploded view of an armrest 20 is shown. The armrest 20 comprises a support structure 21 which is formed by at least one base part 22. However, in the shown example the support structure 21 is formed by two base parts 22 being manufactured separately and connected to each other. Each base part 22 preferably comprises a polymer material, such as a plastic material, such as a thermoplastic material, and the exact shape of each base part 22 is obtained by injection molding the base part 22 from a polymer material.

The base part 22, either made as a single piece or as several pieces connected to each other, may have different portions of different shape. For example, as is shown in Fig. 2, the support structure 21 formed by the base parts 22 has a planar portion 22a and a curved portion 22b. The planar portion 22a is intended to be oriented outwardly, furthest away from the seating area of the associated sofa 10, while the curved portion 22b preferably forms the upper and front surface of the armrest 20.

The base part 22, to which the wadding 30 will be attached by means of welding, is in some embodiments a rather thick body, thereby providing a robust structure for the furniture. The base part 22 is in some embodiments a hollow body, however in other embodiments the base part 22 is solid. In yet further embodiments, the base part 22 is a combination of a solid base part and a hollow base part. Such configuration may e.g. be provided by forming the base part 22 by connecting two or more portions 22a-b, which form at least one cavity therebetween.

The structural parts of the armrest 20 will not be discussed in great detail, reference is instead made to SE1850347-4 by the same applicant in which an armrest 20 is described with which the teachings herein are especially beneficially combined. The wadding 30 is at least partly made of a material being possible to use in a welding process. Although several such materials exist, it is preferred to use a non-toxic and environmentally friendly material, for example a liner of the type described in WO2015/177267 could be used at least as a part of the wadding 30. The wadding material may comprise a layered material comprising at least two layers that may be thermally bonded to each other. In a preferred embodiment, one or more of the layers comprises fibres of polyester, or co-polymers thereof.

The wadding 30 comprises a number of separate parts 32, 34, 36, of which at least one is configured to be welded to the base part(s) 22. Welding provides a secure bond between the wadding 30 and the base part 22 of the armrest 20 without the need to provide any additional materials, or complex and time consuming procedures, where staples, adhesives, nails, or clips etc. are used. Welding also reduces the risk for crease forming of the wadding 30, which otherwise may be a highly undesired and common issue when using for instance staples. The wadding 30 is preferably welded to the exterior side 24 of the base part 22 on a laterally outer side thereof to avoid that the user is able to feel the actual weld when resting or leaning against an inner side 24c of the armrest 20.

In Fig. 2, a planar part 32 of the wadding 30 is shown. The planar part 32 is configured to cover the outside 24a of the armrest 20, as shown in Fig. lc. The shape of the planar part 32 therefore essentially conforms to the shape of the outside 24a of the armrest 20. The planar part 32 may be manufactured from a material exhibiting fire retardant properties.

Also, in an alternative embodiment, the planar part 32 may be attached to the base part 22 by a conventional method such as gluing, stapling etc. to form an outer surface base part to which further wadding parts 34, 36 can be welded onto. Such embodiment is especially beneficial in cases where the outer side 24a of the armrest 20 is made from a material which is unsuitable for welding, in which case the planar part 32 may form a surface which provides more beneficial properties for welding the other parts 34, 36 of the wadding 30 to this planar part 32.

In a preferred embodiment, the planar part 32 is prepared, prior to welding, to fit with the dimensions of the base part 22 to which it is supposed to be welded to. This is beneficial in that post-processing of the upholstered furniture member is avoided, which otherwise would add time and cost to the manufacturing process. It also allows for more simple welding apparatus, as there is a distinct fit of the wadding 30 to the base part 22 thereby improving correct positioning of the different parts. Yet further, waste is reduced as no cutting of the wadding 30 after welding is required.

The planar part 32 is configured to form a cushioning layer or comfort layer together with a folded part 34, constituting the majority of the thickness of the wadding 30. The folded part 34 is configured to be arranged onto the curved portion 22b of the base part 22, preferably to form the upper and front portion 24b of the armrest 20. The folded part 34 is configured to enclose the curved portion 22b. The folded part 34 does not necessarily need to be welded to the base part 22, but it may instead be held in place by a liner part 36 arranged outside the folded part 34, as will be explained further below.

In other embodiments, the folded part 34 is in fact welded to the base part 22.

The folded part 34 may be manufactured from the same layered material as described above, or e.g. from a vertically lapped nonwoven material which is to be considered a material known to a person skilled in the art. Such a material could comprise several different types of fibres, where at least some are plastic materials or another material which is suitable for welding. Polyester fibres are beneficially used to some extent in such material. The folded part 34 is typically folded around the curved portion 22b, however it may also be manufactured such that it is has the approximate shape that is shown in Fig. 2 whereby it can be placed onto the curved portion 22b without having to fold it.

For the embodiment where the folded part 34 is not welded, more traditional wadding materials may be considered such as polyurethane foam materials.

Fig. 2 also shows the liner part 36. The liner part 36 is preferably manufactured by a material having fire retardant properties and which is possible to use in a welding process, as has been described above. Another example of such a material, to be used for part of or in the entire wadding 30 (i.e. the planar part 32, the folded part 34, and the liner part 36) is the liner material described in WO2015/177267. For example, the planar part 32 and the liner part 36 could be made, for example, from a material of the type described in WO2015/177267, and the folded part 34 could be made of a foam material.

The liner part 36 is configured to cover the entire folded part 34, and to be welded to the base part 22 of the armrest 20, or to be welded to the planar part 32. To facilitate the welding, the liner part 36 may be provided with an edge 37 thus forming a flat area of material which can be more easily welded onto the base part 22 or to the planar part 32. The planar part 32 may be configured to be arranged such that it to some extent overlaps the folded part 34 and/or the lining part 36. More specifically the planar part 32 may be arranged to overlap the edge 37 of the liner part 36. The planar part 32 could also be configured to overlap a portion of the folded part 34.

In Fig. 3 an assembled armrest 20 is shown. In the embodiment of Fig. 3, all wadding parts 32, 34, 36 have been secured to the base part 22 by means of welding, either directly or indirectly. A first weld 40 is formed along the periphery of the planar part 32, along the welding paths 4la-b indicated by dashed lines in Fig. 2. This first weld 40 secures the planar part 32 to the base part 22. Preferably, the first weld 40 is provided at a certain distance inside the outer periphery of the planar part 40. Such positioning of the first weld 40 improves the robustness of the first weld 40, as the risk for welding outside the periphery of the planar part 32 is eliminated. A second weld 42 is formed along the edge 37 of the liner part 36, along the welding path 43 indicated by dashed lines in Fig. 2. Preferably, the second weld 42 is provided at a certain distance from the outer periphery of the liner part 36. In the illustrated embodiment the second weld 42 connects the edge 37 directly to the base part 22. However, in alternative embodiments the second weld 42 could connect the edge 37 to the planar part 32, thereby indirectly, via the planar part 32, connecting the edge 37 to the base part 22. In such embodiment the weld 42 could be made to also include the weld 4la shown in Fig. 2

The distance between the weld 40, 42 and the periphery of the wadding 30, 32, 34, 36 is preferably in the range of 0,1-5 cm, such as between 0,1 and 2,5 cm.

It will be appreciated that the folded part 34 is in the illustrated embodiment, Fig. 3, in itself not welded to the base part 22, but the liner part 36 encloses the folded part 34 and holds it to the base part 22. As is seen, the wadding 30 encapsulates the base part 22, apart from minor portions of the base part 22 which are preferably configured to be connected to other parts of the seating furniture 10. The wadding 30 is securely held in place with the welds 40, 42.

To ensure a strong bond between the liner part 36, the folded part 34, the planar part 32, and the base part 22, each weld 40, 42 is beneficially positioned on a portion of the base part 22 which is formed by a plastic material, which to some degree is allowed to form a melt bond with the wadding material during the welding process. Preferably, such portion of the base part 22 is formed by a thermoplastic material.

In Fig. 4, a schematic outline of a method 100 for providing an upholstered furniture member is shown. The method 100 comprises a first step 102 of providing at least one base part 22, defining an exterior side 24 of the furniture member 20. A subsequent step 104 is thereafter performed by arranging a wadding 30 on the exterior side 24 of the base part 22. As explained earlier, in some embodiments the wadding 30 is pre-cut to fit with the dimensions of the base part 22, such that no post-cutting of the wadding 30 is required. The wadding 30 is, in a step 106, welded to the exterior side 24 of the base part 22 to form the upholstered furniture member 20.

The step 106 of welding may further comprise a sub-step 108 of welding a planar part 32 of the wadding 30 to a planar portion 22a of the base part 22 along at least a part of its periphery (preferably at a distance from the periphery), a sub-step 110 of arranging a folded part 34 of the wadding 30 onto a curved portion 22b of the base part 22, and/or a sub-step 112 of welding a liner part 36 to the base part 22 and/or to the planar part 32 along at least a part of its periphery (preferably at a distance from the periphery).

Optionally, the folded part 34 of the wadding 30 may also be welded to the base part 22 and/or to the planar part 32 and/or to a further part 32 of the wadding 30 along at least a part of its periphery, preferably at a distance from the periphery. Further, as has been explained above, the liner part 36 of the wadding 30 is preferably arranged onto the base part 22, preferably at least partly on the folded part 34 prior to welding of the liner part 36 to the base part 22. The liner part 36 may optionally be welded to the folded part 34.

Welding of the wadding 30 to the base part 22 may be performed in various ways of which some will be described in the following with reference to Figs. 5-8. It should be pointed out that welding at a distance from the periphery of the wadding 30 does not only reduces the risk for a misalignment of the welding apparatus, but it also allows for welding of the wadding at specific locations, thereby forming a welding pattern across the wadding. Such welding pattern could e.g. be used to improve the attachment of the wadding 30 to the base part 22, but it also allows for improving the design of the upholstered furniture member, as these welding areas will appear as topographic variations. It is also possible to weld points, lines or any patterns to compress the wading 30 locally. This can be performed in order to flatten out wadding at edges to avoid excess wadding 30 thickness.

In one embodiment, ultrasonic welding is performed by operating a sonotrode, or ultrasonic transducer.

Mechanical vibration or oscillation suitable for ultrasonic welding has preferably a frequency between 2 and 200 kHz (even more preferably between 10 and 100 kHz, or between 15 and 40 kHz) and a vibration energy of 0.2 to 20 W per square millimeter of active surface. The vibrating tool (e.g. the sonotrode) is e.g. designed such that its contact face oscillates predominantly in the direction of the tool axis

(longitudinal vibration) and with an amplitude of between 1 and lOOpm, preferably around 30 to 60 pm.

In Fig. 5a an apparatus 200 is shown. The apparatus 200 comprises a table 210 or other suitable structure to hold and receive the base part 22 having a piece of wadding 30 arranged thereon. The apparatus 200 further comprises a welding unit 220. The welding unit 220 is configured to weld the wadding 30 to the base part 22 to form the upholstered armrest.

The apparatus further comprises a driving unit 230 configured to move the welding unit 220 to a position where it contacts the wadding 30 prior to activation to perform welding. The driving unit may e.g. be realized as one or more linear motors, preferably configured to move the welding unit 220 in three dimensions (x-y-z).

The welding unit 220 is preferably an ultrasonic welding unit, and as can be seen in Fig. 5b it comprises a plurality of spaced-apart point-shaped welding heads 222. Each welding head 222 is configured to provide a point-like weld joint upon activation, as can be seen in Fig. 5a. The welding heads 222 are preferably connected to a common sonotrode, which transfers mechanical energy to each welding head 222.

By moving the welding unit 220 along the intended welding path 4la point-like welds 240 will be provided to ensure a fixation of the wadding 30 to the base part 22. Welding can thus be performed step-wise, as indicated in Fig. 5a. The welding unit 220 is first positioned in contact with the wadding 30, whereby the sonotrode is activated to perform welding at positions corresponding to the current position of the welding heads 222. The welding unit 220 is thereafter moved along the intended welding path, so that another welding can be performed adjacent to the position of the previous welding operation.

The welding unit 220 has in itself a temperature close to room temperature. Thereby the welding unit 220 will function as a heat sink that cools the welded area, such that liquefied polymer in the area of the weld will very rapidly cool down and solidify. Thereby a very speedy process is possible, as the weld will, immediately after stopping the ultrasonic energy supply, solidify and have full strength, by being cooled by the welding unit 220, meaning the welding unit 220 can quickly be moved further along the path 41. In Fig. 6a another embodiment of a welding apparatus 200 is shown. The welding apparatus 200 is a modification of the apparatus 200 shown in Fig. 5a, as the present apparatus 200 of Fig. 6a comprises a plurality of welding units 220 arranged in accordance with the intended welding path 4 la. In this embodiment, five welding units 220 are provided. The welding units 220 have a fixed position relative each other, and they are connected to a common driving unit (not shown). Hence, for welding all welding units 220 will be positioned at the wadding 30, and they will be activated simultaneously. Each welding unit 220 has an elongated welding head 224. The result is shown in Fig. 6b, where a number of welds 240 are provided along the welding path. The plurality of individual welds 240 together represent a common weld 40, as illustrated in Fig. 3.

The welding units 220 may either be of the type described with reference to Fig. 5a, with each welding unit 220 having multiple welding heads 222, or of the type described in Fig. 6a having an elongated welding head 224, or the welding units 220 may be in accordance with the welding unit 220 described below with reference to Figs.

7 or 8.

In Fig. 7 the welding unit 220 has an elongated welding head 224, configured to provide a line weld joint upon actuation. Hence, once positioned in contact with the wadding 30 the welding unit 220 can be moved along the intended welding path 4 la; as the welding unit 220 is continuously activated, the weld joint 240 will also be continuous as indicated in Fig. 7.

In Fig. 8 the welding unit 220 has a plurality of individual point-like welding heads 222 arranged along the periphery of a rotary body 226. The rotary body 226 is configured to rotate around an axis R as the welding unit 220 moves along the wadding 30. Upon operation, the welding unit 220 will provide a series of welds 240 along the welding path 4 la, wherein the distance between two adjacent welds 240 is set by the circumferential distance between two adjacent welding heads 222. In the shown example the rotary body 226 is provided with eight welding heads 222; of course the exact number of welding heads 222 could be varied depending on the particular application.

An example of the welding process is schematically shown in Figs. 9a-c. The welding unit 220 is provided with a welding head, either a point-like welding head 222 or a line-shaped welding head 224. The parts to be welded show a similar appearance as described with reference to Fig. 2; a base part 22, a planar wadding part 32, a folded wadding part 34, and a liner wadding part 36. As can be seen in Fig. 9b, before activation of the welding unit 220 the welding unit 220 is positioned in contact with the outermost part of the wadding 30, i.e. the liner part 36, preferably at a distance from the outer edge, or periphery, of the wadding 30. The welding unit 220 is further pressed downwards and is then activated to cause liquefying of the wadding 30 and/or the base part 22. After activation has stopped, and the weld has solidified, the welding unit 220 may be removed as indicated in Fig. 9c; and the final weld joint 240 is established.

An advantage of ultrasonic welding is that it does not add heat in a large scale to the objects to be welded, heat is added only just at the contact between the objects to be welded.

An additional advantage of ultrasonic welding is that it requires a single device only. This is contrary to welding apparatuses using electrical current, and two electrodes. Such two-device systems can only be used for very thin base parts, and for very thin waddings. Normally, the plastic material of the base part and/or the wadding will be insulating, thereby further reducing the practical applicability of electrode welding systems.

Returning to the advantages of ultrasonic welding, another benefit is that it can provide high quality welds also for thick base parts 22 of plastic material, either rigid or hollow. With reference to Figs. 9a-c, the ultrasonic welding unit 220 operates perfectly independently of the thickness of the base part 22, or the rigid/hollow configuration of the base part 22. In some embodiments, the weld is provided at a position at which the base part 22 is hollow.

Optionally, ultrasonic welding may be performed in a controlled manner, such that the ultrasonic transducer is digitally controlled to move along the welding paths thus further improving automation and manufacturing speed. A further advantage of ultrasonic welding is that it is easy to measure and control the amount of energy put into the welding, and the input energy goes, to a very high degree, to the welding process itself and not into heating surrounding structures.

Welding may also be performed using other techniques in which the wadding 30 is melt-bonded to the base part 22 without the need for external fastening means.

Hence bonding of the wadding 30 to the base part 22 may be achieved by applying heat, friction, or mechanical vibration to mention only a few possible variants. Examples of such other welding techniques include HF (high frequency) welding, hot air welding, hot contact welding, etc. It is sufficient that one of the wadding 30 and the base part 22 is made from a material that can melt and re-solidify, such as a thermoplastic material.

Hence, in one embodiment the wadding 30 could comprise a thermoplastic material while the base part 22 does not comprise a thermoplastic material, or comprises a thermoplastic material that does not reach its melting temperature during the welding process. This means that in the welding process the wadding 30 becomes partly melted such that wadding material can penetrate into porosities in the base part 22, meaning that after re-solidification of the wadding 30 it becomes bonded to the base part.

In another embodiment the wadding 30 does not comprise a thermoplastic material, or comprises a thermoplastic material that does not reach its melting temperature during the welding process, while the base part 22 comprises a

thermoplastic material. This means that in the welding process the base part 22 becomes partly melted such that base part material can penetrate into porosities in the wadding 30, meaning that after re-solidification of the base part 22 it becomes bonded to the wadding.

Still further, both the wadding 30 and the base part 22 may comprise thermoplastic material, meaning both wadding 30 and base part 22 will melt during the welding and bond to each other after re-solidification.

Using a thermoplastic material, it is possible to achieve a connection by melting part of either the base part 22 or the wadding 30 at or close to the interphase of these materials. Hence, it is not required to essentially melt the edge of the wadding 30, in order to form the connection with the base part 22.

In a yet further embodiment only a portion of the base part 22 and/or wadding 30 is made from a plastic material. For example. A strip of plastic material may be adhered to a wooden base part, whereby welding is performed at the area of the plastic strip. The plastic strip may thus have the shape of the intended welding path 4 la.

The welding method referred to in all embodiments herein is preferably ultrasonic welding. A specific advantage of ultrasonic welding is that it provides localized melting only at the interfaces, for example only in the interface between wadding 30 and base part 22, without any significant global heating of surrounding structures. However, other plastic welding techniques are also possible such as friction welding, laser welding etc.

It should be mentioned that the inventive concept is by no means limited to the embodiments described herein, and several modifications are feasible without departing from the scope of the appended claims. In the claims, the term“comprises/comprising” does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly

advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. The terms“a”,“an”,“first”,“second” etc do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.