Patent Description:
Various welding techniques are being developed for aircraft structures. These welding techniques include resistance welding, induction welding, ultrasonic welding and laser welding. These welding techniques, however, may require a relatively high capital investment and relatively long welding times in minutes to tens of minutes to achieve each weld. In addition, thermoplastic materials are increasingly being used in various aerospace applications. Forming fibre-reinforced thermoplastic structures, however, may be time consuming and costly using known formation processes.

One possibility is to use vibration welding for forming thermoplastic structures and structures made from other materials such as some metals. This can be particularly advantageous when forming hollow structures where access to the interior of the structure to form welds is limited and where forming the structure in a single operation is complex and expensive. Forming such structures by welding nonhollow components together can simplify the manufacturing process. There is a need in the art therefore for improved processes for forming hollow structures such as hollow fibre-reinforced thermoplastic structures which may decrease formation time, complexity and/or expense.

<CIT> discloses methods and apparatus for the bonding together of two similarly shaped articles made of dissimilar thermoplastic materials, utilizing oscillatory motion between the two articles combined with an external heat source to generate sufficient heat to form a hermetic seal therebetween.

<CIT> discloses a thermoplastic container end spinwelded to a container body. The spin welding apparatus includes heating means, which preheat the friction welding zone of the component with the higher melt temperature. A first mandrel is inserted into the container body part, the mandrel having radially expandable portions to cause the body part to be expanded to a cylindrical configuration of predetermined diameter. A second mandrel holds and can rotate the end closure, the mandrels being axially movable towards each other. Heat is also applied while the second mandrel is being rotated.

According to an example of the disclosure, there is provided a method of forming a hollow structure as recited in claim <NUM>.

In this example, or any of the following examples of the disclosure, the load may be a bending load.

It will be appreciated by those skilled in the art that, the disclosed method may require fewer components to form a weld joint than may be required by the prior art methods.

It will further be appreciated, that at least in some examples, when forming hollow structures by the disclosed method, there is no need for internal devices such as hard blocks or bladders to be used. The prior art requires use of such devices in the hollow space during the formation process to provide the required weld load. Eliminating the need for supporting means reduces tooling costs and reduces the welding cycle time by removing the step of inserting and removing these internal devices.

It will further be appreciated, that with certain component designs it is not possible to remove such internal devices after the forming process is complete. As such, the disclosed method may expand the variety of hollow structures than can be manufactured by vibration welding.

In any example of the disclosure, the first component may comprise a thermoplastic material.

In any example of the disclosure, the first component may comprise a first fibre-reinforced thermoplastic composite.

In any example of the disclosure, the first fibre-reinforced thermoplastic composite may comprise fibres, wherein the fibres may be: either continuous or discontinuous; and/or unidirectional; and/or arranged to resist the load; and/or arranged to stiffen the flange against the load.

In any example of the disclosure, the second component may comprise a thermoplastic material.

In any example of the disclosure, the second component may comprise a second fibre-reinforced thermoplastic composite.

In any example of the disclosure, the second fibre-reinforced thermoplastic composite may comprise fibres, wherein the fibres may be: either continuous or discontinuous; and/or unidirectional; and/or arranged to resist a load.

In any example of the disclosure, the flange or the first component may be formed to be resilient.

In any example of the disclosure, the first component may be formed such that the flange extends from the base portion at a first angle and wherein applying the load may change the first angle to a second, different angle.

In any example of the disclosure, the second angle may be smaller than the first angle.

In any example of the disclosure, the first component may be fixed in position and the second component may be moved relative to or pushed against the first component to apply the load to the flange.

In any example of the disclosure, the second component may be fixed in position and the first component may be moved relative to or pushed against the second component to apply the load to the flange.

In any example of the disclosure, the second weld joint may be formed by pushing the first and second components together during the vibrating one of the first and the second components to form the first weld joint.

In any example of the disclosure, the second component may be configured to fit over the first component.

In any example of the disclosure, the second component may comprise a base wall, a first side wall and a second side wall.

In some examples, at least part of the first side wall may be arranged to be welded to a flange of the first component.

In some examples, the second side wall may extend from the base wall and may be spaced from the first side wall.

In some examples, the second side wall may extend at an angle to the base wall.

In some examples, a mounting portion may be provided on the second side wall. The mounting portion may comprise a flange configured to be in engagement with the first component when the first and second components are assembled together.

In other examples, an end of the second side wall may be arranged to be vibration welded to the first component.

According to any example of the disclosure, the flange of the first component may be a first flange extending from the base portion at a first end thereof and the first component may further comprise a second flange extending from the base portion at a second end thereof. The second end may be opposite to the first end.

In some examples, two second components may be provided and arranged so as to form a weld joint with the first flange and the second flange respectively.

At least in some examples, each of the two second components may be arranged so as to also form a weld joint with the base portion.

At least in some examples, the method may comprise bringing each of the two second components and the respective first and second flanges into abutment and applying a respective load to the respective first and second flanges via the respective second components.

At least in some examples, a first load may be applied to the first flange and a second load may be applied to the second flange.

At least in some examples, the second load may act in a direction opposite to the first load.

At least in some examples, the second load may be substantially the same strength as the first load.

At least in some examples of the disclosure, the second component may comprise a base portion and a flange extending from the base portion, the method further comprising: bringing the first component and the flange of the second component into abutment and applying a second load to the flange of the second component via the first component, wherein the flange of the second component is biased against the first component by a reaction of the second component to the second load; and vibrating one of the first and the second components to form a weld joint between at least a part of the first component and at least a part of the flange of the second component.

According to another aspect, there is provided a welding system as recited in claim <NUM>.

In any example of the disclosure, the first fibre-reinforced thermoplastic composite may comprise fibres, wherein the fibres may be: either continuous discontinuous; and/or unidirectional; and/or arranged to resist the load; and/or arranged to stiffen the flange against the load.

In any example of the disclosure, the second fibre-reinforced thermoplastic composite may comprise fibres, wherein the fibres may be: either continuous discontinuous; and/or unidirectional; and/or arranged to resist the load.

In any example of the disclosure, the first component may be formed such that the flange extends from the base portion at a first angle and wherein applying the load changes the first angle to a second, different angle.

The second weld joint may be formed by pushing the first and second components together during the vibrating one of the first and the second components to form the first weld joint.

At least in some examples, the system may be configured to bring each of the two second components and the respective first and second flanges into abutment and to apply a respective load to the respective first and second flanges via the respective second components, wherein the first component forms a spring to bias the first and second flanges to the respective second components.

At least in some examples, the system may be configured to apply a first load to the first flange and to apply a second load to the second flange.

Certain examples of the disclosure will now be described by way of example only and with reference to the accompanying drawings in which:.

In any example, the disclosure may provide a method of vibration welding two components together. In vibration welding, the two components are brought into contact under pressure and one of the two components is vibrated relative to and against the other of the two components in order to generate heat at a welding interface between the two components. The heat from the generated friction between the components may melt a material of the components locally at the welding interface. The two components are fused or, in other words, welded together as the melted material re-solidifies once vibration has stopped. The pressure necessary to weld the components together is herein referred to as a weld load.

In any example of the disclosure, each of the two components may be constructed from a common or a unique material. The material may be any suitable material including a malleable metal such as aluminium or a thermoplastic. The material may also be a thermoplastic composite. Fibre reinforcements, for example, may be embedded within a thermoplastic material or, in other words, matrix to form a fibre-reinforced thermoplastic composite. Examples of the fibre reinforcements include but are not limited to metal fibres (e.g., aluminium fibres, brass fibres, and stainless steel fibres), carbon fibres (including graphite fibres such as polyacrylonitrile (PAN)-based carbon fibres, rayon-based carbon fibres, lignin-based carbon fibres, and pitch-based carbon fibres, insulating fibres (e.g., glass fibres), organic fibres (e.g., aramid fibres, polyparaphenylene benzoxazole (PBO) fibres, polyphenylene sulfide fibres, polyester fibres, acrylic fibres, nylon fibres, and polyethylene fibres), and inorganic fibres (e.g. silicon carbide fibres and silicon nitride fibres). Some or all of these fibres may be continuous fibres. Some or all of the fibres may also or alternatively be discontinuous, for example some or all of the fibres may be chopped fibres.

Examples of the thermoplastic material include, but are not limited to, a semicrystalline thermoplastic resin and an amorphous thermoplastic resin. Examples of the semicrystalline thermoplastic resin include, but are not limited to, polyester, polyolefin, polyoxymethylene (POM), polyamide (PA), polyarylene sulfide, polyketone (PK), polyetherketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyaryletherketone (PAEK), polyether nitrile (PEN), fluororesin, and liquid crystal polymer (LCP). Examples of the polyester include, but are not limited to, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terphthalate (PTT), polyethylene naphthalate (PEN), and liquid crystal polyester. Examples of the polyolefin include, but are not limited to, polyethylene (PE), polypropylene (PP), and polybutylene. An example of the polyarylene sulfide includes, but is not limited to, polyphenylene sulfide (PPS). An example of the fluororesin includes, but is not limited to, polytetrafluoroethylene. Examples of the amorphous thermoplastic resin include, but are not limited to, polystyrene, polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyphenylene ether (PPE), polyimide (PI), polyamide imide (PAI), polyetherimide (PEI), polysulfone (PSU), polyether sulfone (PES), and polyarylate (PAR).

In any example of the disclosure, each of the two components may be constructed from one or more layers. Each or some of these component layers may include fibre reinforcements within a thermoplastic material. Within each component layer, the fibre reinforcements may be unidirectional. The fibre reinforcements may alternatively be multi-directional (e.g., in a woven sheet, a mat of chopped fibres, etc.) in one or more of the component layers.

In any example of the disclosure, each of the two components may include between twenty percent (<NUM>%) and eighty percent (<NUM>%) of the fibre reinforcement (e.g., fibres) per unit of volume and between twenty percent (<NUM>%) and eighty percent (<NUM>%) of the thermoplastic material per unit of volume. In any example, one or more component layer in a respective component may include between thirty-five percent (<NUM>%) and eighty percent (<NUM>%) of the fibre reinforcement (e.g., fibres) per unit of volume and between twenty percent (<NUM>%) and sixty-five percent (<NUM>%) of the thermoplastic material per unit of volume.

<FIG> illustrates a flow diagram of a method <NUM> of forming a weld joint according to an example of the disclosure. <FIG> illustrate a schematic sectional view of part of an example first component <NUM> and part of an example second component <NUM> at various stages in a welding method according to the disclosure.

In the method <NUM>, a first component is provided (step <NUM>). The first component comprises a base portion and a flange extending from the base portion. The first component may be made of any suitable material as discussed above. In any example of the disclosure, the first component may be made of a thermoplastic composite, such as a fibre-reinforced thermoplastic. The first component may be formed using one or more formation processes such as, for example laminating, molding, pressing, injection molding, stamp forming, continuous compression molding and overmolding. The first component may comprise a first fibre-reinforced thermoplastic composite.

A second component is also provided (step <NUM>). The second component may again be made of any suitable material as discussed above. In any example of the disclosure, the second component may be made of a thermoplastic composite, such as a fibre-reinforced thermoplastic. The second component may be formed using one or more formation processes such as, for example laminating, molding, pressing, injection molding, stamp forming, continuous compression molding and overmolding. The second component may be formed of a different material and/or may be formed by a different formation process from the first component. The second component may comprise a second fibre-reinforced thermoplastic composite. The second fibre-reinforced thermoplastic composite may differ from the first fibre-reinforced thermoplastic composite in at least one of length, direction, volume-fraction and material of the fibre reinforcements. The second fibre-reinforced thermoplastic composite may differ in thermoplastic material from the first fibre-reinforced thermoplastic composite. In some examples, the second component may not comprise fibre-reinforcements at all.

In the method <NUM>, the flange of the first component and the second component are then brought into abutment with one another (step <NUM>) and a load is applied to the flange (step <NUM>). This causes the flange to be biased against the second component as will be described in further detail below. It will be understood that the steps of bringing the first and second components into abutment and of applying a load to the flange may be carried out in a single step, for example by pushing the second component against the first component when the first component is fixed.

After the load has been applied to the flange, one of the first and second components is vibrated relative to the other to form a weld joint between at least a part of the flange and at least a part of the second component (step <NUM>).

It will be understood that the first and second components may take various different forms. <FIG> illustrates a schematic sectional view of part of a first component <NUM> and part of a second component <NUM> according to an example of the disclosure and prior to vibration welding, for example at steps <NUM> and <NUM> of the method <NUM>. The first component <NUM> comprises a base portion <NUM> and a flange <NUM>. The flange <NUM> is arranged to be vibration welded to the second component <NUM>. The base portion <NUM> may comprise a generally flat first planar surface <NUM> and a generally flat second planar surface <NUM> which may extend parallel to and opposite the first planar surface <NUM> to define a thickness tb of the base portion <NUM>.

The flange <NUM> may comprise a generally flat first planar surface <NUM> and a generally flat second planar surface <NUM> which may extend parallel to and opposite the first planar surface <NUM> to define a thickness tf of the flange <NUM>. The flange <NUM> extends from the base portion <NUM> of the first component <NUM> at an angle α, where the angle α is defined as the angle between the first planar surface <NUM> of the base portion <NUM> and the first planar surface <NUM> of the flange <NUM>. Although illustrated as an obtuse angle, the angle α may instead comprise a right angle or an acute angle. The flange <NUM> and the base portion <NUM> may form a unitary structure. A juncture <NUM> is formed between the flange <NUM> and the base portion <NUM>. The juncture <NUM> may comprise a bend or a corner. The first planar surface <NUM> of the base portion <NUM> and the first planar surface <NUM> of the flange <NUM> may therefore form a continuous surface. Further, they may form a first outer surface <NUM> of the first component <NUM>. The second planar surface <NUM> of the base portion <NUM> and the second planar surface <NUM> of the flange <NUM> may form a continuous surface. Further, they may form a second outer surface <NUM> of the first component <NUM>. The second component <NUM> may also comprise a first generally flat, planar surface <NUM> and a second generally flat, planar surface <NUM>, which may extend parallel to and opposite the first planar surface <NUM> to define a thickness tc of the second component <NUM>. The second component <NUM> may be generally flat.

It will be understood that in any example of the disclosure any of the thicknesses of the base portion <NUM>, the flange <NUM> and the second component <NUM> may be constant along a length thereof or may vary depending on the required shape of the first and second components. In any example of the disclosure, any of the thicknesses of the base portion <NUM>, the flange <NUM> and the second component <NUM> may be selected with consideration to the material properties of the respective component. It will further be understood that the magnitude of the load applied to the flange in step <NUM> may be selected with consideration to any of the above thicknesses and/or respective material properties (for example the stiffness module).

<FIG> illustrates a schematic view of the first component <NUM> and the second component <NUM> of <FIG> after the first and second components <NUM>, <NUM> have been brought into abutment (in step <NUM>) so as to apply a load F1 to the flange <NUM> of the first component <NUM> (step <NUM>). As seen in <FIG>, after the bending load F1 has been applied, the flange <NUM> is bent to an angle α' relative to the base portion <NUM>. The angle α' is less than the angle α. When the flange is at the angle α' from the base portion <NUM>, a welding interface <NUM> is formed between at least a part of the second surface <NUM> of the flange <NUM> and at least a part of the first planar surface <NUM> of the second component <NUM>.

The welding interface <NUM> may be provided on a portion of the first planar surface <NUM> of the second component <NUM> and/or on a portion of the flange <NUM>. The first planar surface <NUM> of the second component <NUM> and the second planar surface <NUM> of the flange <NUM> may lie in the same plane when the flange <NUM> is bent to the angle α'. The first surface <NUM> of the second component <NUM> and the flange <NUM> are in contact with one another. The welding interface <NUM> lies in a first plane. In the example of <FIG>, the first plane is the z-y plane but it will be appreciated that this is only one possible example.

The flange <NUM> of the first component <NUM> and the second component <NUM> may be brought into abutment with one another (step <NUM>) and a load may be applied to the flange <NUM> (step <NUM>) in various different ways. In a first set of examples, the first component <NUM> is fixed in position and the second component <NUM> is moved relative to the first component <NUM> or pushed against the first component <NUM>. The second component <NUM> is configured to move towards the first component <NUM> to bring the components into abutment. The second component <NUM> is pushed against the flange <NUM> of the first component <NUM> so as to apply a load F1 thereto (step <NUM>). Movement of the base portion <NUM> of the first component <NUM> is restricted in the direction of movement of the second component <NUM>. The base portion <NUM> thus acts as a fixed end with regards to the flange <NUM>. The load F1 may be a bending load. The second component <NUM> is moved towards the first component in a direction normal to the first plane (for example normal to the welding interface). The flange <NUM> is compressed due to the second component <NUM> being pushed towards the first component <NUM>. The compression of the flange <NUM> is resisted by a reaction force F2 generated by the flange <NUM> or the first component <NUM>. The reaction force F2 generated by the first component <NUM> under the load F1 biases the flange <NUM> against the second component <NUM>. In this regard, the first component <NUM> may form a spring to bias the flange <NUM> to the second component <NUM>. Contact between the second surface <NUM> of the flange <NUM> and the first planar surface <NUM> of the second component <NUM> is maintained as a result of the reaction force F2. The first and second component <NUM>, <NUM> are thus held into contact at the welding surface <NUM> under pressure. The reaction force F2 may be a spring back force. The pressure exerted on the second component <NUM> by the first component <NUM> may act to generate a spring back force on the welding interface <NUM> between the flange <NUM> and the second component <NUM>, The force may be great enough to allow the flange <NUM> to be welded to the second component <NUM> during the vibration welding process. In examples, the pressure across the welding surface <NUM> may vary. The pressure may be strongest towards the juncture <NUM> between the flange <NUM> and the base portion <NUM>.

In a second set of examples, the second component <NUM> is fixed in position and the first component <NUM> is moved relative to the second component <NUM> or pushed against the second component <NUM>. The first component <NUM> is configured to move towards the second component <NUM> to bring the components into abutment. The flange <NUM> of the first component <NUM> is pushed against the first planar surface <NUM> of the second component <NUM> so as to apply a load to the flange <NUM> of the first component <NUM> (step <NUM>). Movement of the second component <NUM> is restricted in the direction of movement of the first component <NUM>. The load applied to the flange <NUM> may be a bending load. The base portion <NUM> thus acts as a fixed end with regards to the flange <NUM>. The first component <NUM> is moved in a direction normal to the first plane (i.e. normal to the welding interface). The flange <NUM> is compressed due to the first component <NUM> being pushed towards the second component <NUM>. The compression of the flange <NUM> is resisted by a reaction force F2. The reaction generated by the first component <NUM> under the load F1 biases the flange <NUM> against the second component <NUM>. In this regard, the first component <NUM> may form a spring to bias the flange <NUM> to the second component <NUM>. Contact between the between the second surface <NUM> of the flange <NUM> and the first planar surface <NUM> of the second component <NUM> is maintained as a result of the reaction force F2. The first and second component <NUM>, <NUM> are thus held into contact at the welding surface <NUM> under pressure. The reaction force F2 may be a spring back force. The pressure exerted on the second component <NUM> by the first component <NUM> may be sufficient to weld the flange <NUM> to the second component <NUM> during the vibration welding process. In examples, the pressure across the welding surface <NUM> may vary. The pressure may be strongest towards the juncture <NUM> between the flange <NUM> and the base portion <NUM>.

It will be understood that in any example of the disclosure, the first component may comprise fibres that are arranged so as to stiffen the flange against the load. In examples, the fibres may be unidirectional or aligned in substantially the same direction so that the fibres are loaded under compression when the load is applied to the flange.

In step <NUM> of the method <NUM> of <FIG>, one of the first and the second components is vibrated relative to the other one of the first and the second components to weld the first and second components together. In some examples therefore, the first component <NUM> is vibrated and the second component <NUM> is held stationary. In other examples, the second component <NUM> is vibrated and the first component <NUM> is held stationary. The vibration may occur within the first plane (or in other words, in the plane of the welding interface <NUM>). With reference to the example of <FIG>, the vibration may occur in any direction within the z-y plane. At least in some examples of the disclosure, the vibration is linear. In other examples, the vibration may be orbital.

<FIG> illustrates a schematic view of the first component <NUM> and the second component <NUM> of <FIG> after vibration welding has occurred. A weld joint <NUM> is formed between the first and second components <NUM>, <NUM>. The weld joint <NUM> is formed at the welding interface <NUM>. The first and the second components <NUM>, <NUM> are therefore welded together to form a welded component <NUM>.

There are a number of parameters that may be varied in the execution of the method <NUM>. For example, it may be necessary to vary the thickness, the material properties and the structural features of the first and/or the second component depending on the desired application of the welded component formed. It may further be necessary to select appropriate load and welding frequency.

In one example of carrying out the method <NUM>, the first component is a carbon fibre reinforced polyphenylene sulfide (Toray TC1105). The first component has varied thickness of <NUM> - <NUM> along the welding interface. The second component includes a glass fibre reinforced polyphenylene sulfide (Toray TC1100) plus carbon fibre reinforced polyphenylene sulfide (Toray TC1105). The second component has a thickness of <NUM>. The load applied to the flange is configured to apply a weld pressure of <NUM> MPa. The first component is vibrated relative to the second component at a weld frequency of <NUM>.

The method described above can be used to form a number of different structures and components. These may have various configurations and may be used in a number of applications including but not limited to aeronautical, aerospace and automotive applications. In some examples, the method may be used to form a plurality of weld joints simultaneously. The plurality of weld joints may lie in the same plane or within different planes. It will be appreciated that the welding load necessary to form one or more weld joints according to any example of the disclosure is generated by the reaction force pushing the flange of the first component against a load. As such, there may be no need to provide supporting means, such as tooling, hard blocks and/or bladders, to generate a reaction force at the flange and to push the two components to be vibration welded together. As a result, tooling costs may be reduced, the vibration welding process may be simplified, and/or a high weld strength between the flange and the second component may be maintained.

<FIG> illustrates a cross-section of an example hollow structure <NUM>, which can be manufactured using the method of forming a weld joint described above. <FIG> illustrates a cross-section of another example hollow structure <NUM>, which can be manufactured by the method of forming a weld joint described above. It will be understood that the method of the disclosure may be advantageous at least in some such hollow structures where access to the interior of the structure in order to apply a welding load is limited. The term hollow structure is used herein to refer to a structure comprising an internal cavity. In at least some examples, the hollow structures may comprise a closed cross-section.

The structures <NUM>, <NUM> of the examples shown are fibre-reinforced thermoplastic structures although other materials as described elsewhere in the specification could be used. Each of the structures <NUM>, <NUM> may for example comprise or may be part of an aircraft component, such as an aircraft seat. The structures <NUM> and <NUM> may alternatively be configured as a part of a fuselage or a wing of the aircraft. The structures <NUM>, <NUM> may still alternatively be configured as a part of a propulsion system or interior parts for the aircraft; e.g. a component of a nacelle, etc. The present disclosure, however, is not limited to the forgoing exemplary aircraft structures. Furthermore, it is contemplated that the structures <NUM>, <NUM> of the present disclosure may also be configured for non-aircraft applications.

In some examples such as that of <FIG>, the structure <NUM> is generally tubular. The structure <NUM> extends along a longitudinal axis <NUM> from a first end <NUM> to a second end <NUM>. A channel <NUM> extends longitudinally through the structure <NUM>. The channel <NUM> extends along the longitudinal axis <NUM> between the first end <NUM> and the second end <NUM>. The channel <NUM> is formed by an internal surface <NUM> of the structure <NUM>. The channel <NUM> forms a cavity.

The structure <NUM> is formed by a first component <NUM> and a second component <NUM>. The first and the second components <NUM>, <NUM> are configured to be welded together to form the structure <NUM> in which the cavity formed by the channel <NUM> is internal to the closed cross-section formed by the first component <NUM> and the second component <NUM> when welded together.

In the example shown, the first component <NUM> comprises a base portion <NUM> and a flange <NUM> extending from the base portion at an angle β. It will be appreciated that the flange <NUM> is configured to be biased against the second component <NUM> when the first and second components are assembled together for welding. Thus, when the first and second components are not assembled together, the flange <NUM> may extend from the base portion at an angle greater than the angle β at which it extends when the first and second components are assembled together. The flange <NUM> is arranged to be vibration welded to the second component <NUM>. The base portion <NUM> comprises a generally flat first planar surface <NUM> and a generally flat second planar surface <NUM> which may extend parallel to and opposite the first planar surface <NUM> to define a thickness of the base portion <NUM>. The flange <NUM> comprises a generally flat first planar surface <NUM> and a generally flat second planar surface <NUM> which may extend parallel to and opposite the second planar surface <NUM> to define a thickness of the flange <NUM>. The angle β is defined as the angle between the first planar surface <NUM> of the base portion <NUM> and the first planar surface <NUM> of the flange <NUM>.

The flange <NUM> and the base component <NUM> may form a unitary structure. The first planar surface <NUM> of the base portion <NUM> and the first planar surface <NUM> of the flange <NUM> may therefore form a first inner surface <NUM> of the first component <NUM>. The second planar surface of <NUM> the base portion <NUM> and the second planar surface <NUM> of the flange <NUM> may form a first outer <NUM> surface of the first component <NUM>.

The first component <NUM> extends between a first end <NUM> and a second end <NUM> thereof. The first component <NUM> extends along the longitudinal axis <NUM>. The first component <NUM> may have a uniform cross-section along its length. The first component <NUM> comprises a generally L-shaped cross-section.

In the example shown, the second component <NUM> forms an inverted U shape and is configured so as to fit over the first component. The second component comprises a base wall <NUM>, a first side wall <NUM> and a second side wall <NUM>. The base wall <NUM> is substantially planar. The base wall <NUM> comprises a first base surface <NUM> and a second base surface <NUM>. The first base surface <NUM> is generally flat and planar. The second base surface <NUM> is parallel to and opposite the first base surface <NUM>. The first side wall <NUM> extends from the base wall <NUM>. The first side wall <NUM> may extend from the second base surface <NUM>. The first side wall <NUM> may be perpendicular to the base wall <NUM>. The first side wall <NUM> may comprise a first generally flat, planar surface <NUM> and a second generally flat, planar surface <NUM>, which may extend parallel to and opposite to the first planar surface <NUM>. At least part of the first side wall <NUM> is arranged to be welded to the flange <NUM>. The second side wall <NUM> extends from the base wall <NUM> and is spaced from the first side wall <NUM>. The second side wall <NUM> may extend from the second base surface <NUM>. The second side wall <NUM> extends at an angle to the base wall <NUM>. The second side wall <NUM> comprises a first generally flat, planar surface <NUM> and a second generally flat, planar surface <NUM>, which may extend parallel to and opposite to the first planar surface <NUM>. A mounting portion <NUM> may be provided on the second side wall <NUM>. The mounting portion <NUM> may comprise a flange configured to be in engagement with the first component <NUM> when the first and second components are assembled together. The mounting portion <NUM> may be arranged to be vibration welded to the first component <NUM>. In other examples, the second side wall <NUM> may not comprise the mounting portion <NUM> and an end of the second side wall <NUM> may instead be arranged to be vibration welded to the first component <NUM>.

The base wall <NUM>, the first side wall <NUM> and the second side wall <NUM> may form a unitary structure. The second base surface <NUM> of the base wall <NUM>, the second planar surface <NUM> of the first side wall <NUM> and the second planar surface <NUM> of the second side wall <NUM> may therefore form an inner surface <NUM> of the second component <NUM>. The first base surface <NUM> of the base wall <NUM>, the first planar surface <NUM> of the first side wall <NUM> and the first planar surface <NUM> of the second side wall <NUM> may therefore form an outer <NUM> surface of the first component <NUM>.

The second component <NUM> extends between a first end <NUM> and a second end <NUM> thereof. The second component <NUM> extends along the longitudinal axis <NUM>. The second component <NUM> may have a uniform cross-section along its length. The second component <NUM> may comprise a generally U-shaped cross section as described above.

The internal surface <NUM> of the structure <NUM> is formed by the first inner surface <NUM> of the first component <NUM> and by a second surface <NUM> of the second component <NUM>.

The first and second components <NUM>, <NUM> when assembled as shown in <FIG> are joined together at a first welding interface <NUM> and at a second welding interface <NUM>. The first and second component <NUM>, <NUM> are joined by a first weld joint <NUM> at the first welding interface <NUM> and by a second weld joint <NUM> at the second weld interface <NUM>. The first weld interface <NUM> lies within a first plane and the second weld interface <NUM> lies along a second, different plane. The first welding interface <NUM> is formed between the flange <NUM> and the first side wall <NUM>. The first welding interface <NUM> is formed between the flange of the first component <NUM> and the second surface of the second component <NUM>. The second welding interface may be formed between the base portion <NUM> and a mounting portion <NUM> of the second side wall <NUM>. The second welding interface <NUM> may be formed between the second surface of the first component <NUM> and the second surface <NUM> of the second component <NUM>.

During formation of the structure <NUM>, one of the first and the second components <NUM>, <NUM> is vibrated relative to the other one of the first and the second components <NUM>, <NUM> whilst the first side wall <NUM> of the second component <NUM> is pushed against the flange <NUM> and the mounting portion <NUM> is pushed against the base portion <NUM> so as to weld the first and second components together. The first and second weld joints <NUM>, <NUM> may be formed simultaneously. The first weld joint <NUM> may be formed by a method such as that described in relation to <FIG>. The vibration is a linear vibration. The vibration occurs within the first plane (i.e. in the plane of the first welding interface <NUM>) and within a second plane (i.e. a plane of the second welding interface <NUM>). With reference to <FIG>, the vibration may occur in the y-direction.

<FIG> shows a structure <NUM> according to another example of the disclosure which is formed by a first component <NUM> and a second component <NUM>. The first and the second components <NUM>, <NUM> are both substantially U-shaped in cross section and are configured to be welded together to form the structure <NUM>.

In some examples, the structure <NUM> is generally tubular. The structure <NUM> extends along a longitudinal axis <NUM> between a first end <NUM> and a second end <NUM>. A channel <NUM> extends longitudinally through the structure <NUM>. The channel <NUM> extends along the longitudinal axis <NUM> between the first end <NUM> and the second end <NUM>. The channel <NUM> is formed by an internal surface <NUM> of the structure <NUM>.

In the example shown, the first component <NUM> comprises a base portion <NUM>, a flange <NUM> extending from the base portion at an angle γ to form a first side portion and a further, opposite side portion <NUM>. It will be appreciated that the flange <NUM> is configured to be biased against the second component <NUM> when the first and second components are assembled together for welding. Thus, when the first and second components are not assembled together, the flange <NUM> may extend from the base portion at an angle greater than the angle γ at which it extends when the first and second components are assembled together.

The flange <NUM> is arranged to be vibration welded to the second component <NUM>. The further side portion <NUM> is also arranged to be vibration welded to the second component <NUM> as will be described further below. The base portion <NUM> comprises a generally flat first planar surface <NUM> and a generally flat second planar surface <NUM> which may extend parallel to and opposite the first planar surface <NUM> to define a thickness of the base portion <NUM>. The flange <NUM> comprises a generally flat first planar surface <NUM> and a generally flat second planar surface <NUM> which may extend parallel to and opposite the second planar surface <NUM> to define a thickness of the flange <NUM>. The angle γ is defined as the angle between the first planar surface <NUM> of the base portion <NUM> and the first planar surface <NUM> of the flange <NUM>. The further side portion <NUM> comprises a generally flat first planar surface <NUM> and a generally flat second planar surface <NUM> which may extend parallel to and opposite the second planar surface <NUM> to define a thickness of the side portion <NUM>.

The flange <NUM>, the base component <NUM> and the side portion <NUM> may form a unitary structure. The first planar surface <NUM> of the base portion <NUM>, the first planar surface <NUM> of the flange <NUM> and the first planar surface <NUM> of the side portion <NUM> may therefore form a first inner surface <NUM> of the first component <NUM>. The second planar surface of <NUM> the base portion <NUM>, the second planar surface <NUM> of the flange <NUM> and the second planar surface <NUM> of the side portion <NUM> may form a first outer <NUM> surface of the first component <NUM>.

The first component <NUM> extends between a first end <NUM> and a second end <NUM>. The first component <NUM> extends along the longitudinal axis <NUM>. The first component <NUM> may have a uniform cross-section along its length. The first component <NUM> comprises a generally U-shaped cross-section.

In the example shown, the second component <NUM> comprises a base wall <NUM>, a first side wall <NUM> and a second side wall or flange <NUM>. The base wall <NUM> is substantially planar. The base wall <NUM> comprises a first base surface <NUM> and a second base surface <NUM>. The first base surface <NUM> is generally flat and planar. The second base surface <NUM> is parallel to and opposite the <NUM>. The first side wall <NUM> extends from the base wall <NUM>. The first side wall <NUM> may extend from the second base surface <NUM>. The first wall <NUM> may be perpendicular to the base wall <NUM>. The first wall <NUM> comprises a first generally flat, planar surface <NUM> and a second generally flat, planar surface <NUM>, which may extend parallel to and opposite to the first planar surface <NUM>. At least part of the first side wall <NUM> is arranged to be welded to the flange <NUM>. The second side wall <NUM> extends from the base wall <NUM>. The second side wall <NUM> may extend from the second base surface <NUM>. The second side wall <NUM> extends at an angle to the base wall <NUM>. The second side wall <NUM> comprises a first generally flat, planar surface <NUM> and a second generally flat, planar surface <NUM>, which may extend parallel to and opposite to the first planar surface <NUM>. The second side wall <NUM> is a flange. The second side wall <NUM> extends from the base wall <NUM> at an angle δ. The angle δ is defined as the angle between the first planar surface <NUM> of the base portion <NUM> and the first planar surface <NUM> of second side wall <NUM>. It will be appreciated that the second side wall <NUM> is configured to be biased against the first component <NUM> when the first and second components are assembled together for welding. Thus, when the first and second components are not assembled together, the second side wall <NUM> may extend from the base portion <NUM> at an angle greater than the angle δ at which it extends when the first and second components are assembled together.

The second component <NUM> extends between a first end <NUM> and a second end <NUM>. The second component <NUM> extends along the longitudinal axis <NUM>. The second component <NUM> may have a uniform cross-section along its length. The second component <NUM> may comprise a generally U-shaped cross section. The first component <NUM> and second component <NUM> may comprise a substantially identical cross-section and may be assembled together by inserting the open end of the second component <NUM> into the open end of the first component <NUM>.

The internal surface <NUM> of the structure <NUM> when assembled is formed by the first inner surface <NUM> of the first component <NUM> and by a second surface <NUM> of the second component <NUM>.

The first and second components <NUM>, <NUM> are joined together at a first welding interface <NUM> and at a second welding interface <NUM>. The first and second component <NUM>, <NUM> are joined by a first weld joint <NUM> at the first welding interface <NUM> and by a second weld joint <NUM> at the second weld interface <NUM>. The first weld interface <NUM> lies within a first plane and the second weld interface <NUM> lies along a second, different plane. The second plane is parallel to the first plane. The first welding interface <NUM> is formed between the flange <NUM> and the first side wall <NUM>. The first welding interface <NUM> is formed between the first surface of the first component <NUM> and the second surface of the second component <NUM>. The second welding interface <NUM> is formed between the base portion <NUM> and the second side wall <NUM>. The second welding interface <NUM> is formed between the second surface of the first component <NUM> and the first surface of the second component <NUM>.

During formation of the structure <NUM>, one of the first and the second components <NUM>, <NUM> is vibrated relative to the other one of the first and the second components <NUM>, <NUM> to weld the components together. The first and second weld joints <NUM>, <NUM> may be formed simultaneously. The first and second weld joints <NUM>, <NUM> may be formed by a method <NUM> such as that described in relation to <FIG>. Thus, force may be applied to push the first side wall <NUM> inwardly against the flange <NUM> of the first component <NUM> and to push the further, opposite side portion <NUM> of the first component <NUM> inwardly against the second side wall <NUM>. As described above, a reaction force will act to push the flange <NUM> back against the first side wall <NUM> and to push the second side wall <NUM> back against the further, opposite side portion <NUM>, thus providing the required weld load. The vibration is a linear vibration. The vibration occurs within the first plane (i.e. in the plane of the first welding interface <NUM>) and within a second plane (i.e. a plane of the second welding interface <NUM>). With reference to <FIG>, the vibration may occur in the y-direction.

Hollow structures, such as the structures <NUM>, <NUM> of <FIG>, manufactured by the method disclosed herein may be difficult or even impossible to manufacture by other traditional methods. It will be appreciated that internal devices such as tooling, hard blocks and/or bladders have been inserted inside the hollow space defined by a hollow structure during manufacture. Such internal devices may provide a reaction force to bias a first component against another component to aid in providing a weld force for vibration welding. However, hollow structures comprising complex geometries or completely enclosed internal cavities may not allow for such internal devices to be recovered after the welding process has been completed. In addition, the welding interface may not be accessible in some hollow structures and in such circumstances, manufacture of the hollow component would not be possible without providing a means of providing a weld force to push the first and second components together at the weld interface as an internal device cannot be provided. The hollow structures formed by the method of the current invention can be formed without the need for any internal devices.

<FIG> illustrates a welding system <NUM> which may be used in the method of <FIG>. The system <NUM> may be used for forming at least one weld joint to form a structure <NUM>. The structure <NUM> of this example is similar to the hollow structure <NUM> shown in <FIG>, and thus a detailed description is omitted for conciseness. The structure <NUM> differs from the structure <NUM> in that it is formed of a first component <NUM> and two second components 630A and 630B. Each of the two second-components 630A and 630B is identical to the other but mirrored in construction.

The first component <NUM> comprises a first flange 612A extending from the base portion <NUM> at a first end thereof and a second flange 612B extending from the base portion <NUM> at a second, opposite end thereof.

When the structure <NUM> is assembled and/or completed, the first one of the second components 630A is arranged such that it is welded to the first flange 612A and the base portion <NUM>, while the second one of the second components 630B is arranged such that it is welded to the second flange 612B and the base portion <NUM>.

The welding system <NUM> comprises the first component <NUM>, the two second components 630A, 630B and a welding machine <NUM>. The welding machine <NUM> is adapted to vibrate one component with respect to another, and may also comprise a set of tooling to locate and hold components in contact with one another and/or means for applying force to a welding interface formed between components. The welding machine may comprise means for vibrating one or more of the components. The means for vibrating may comprise an oscillating platform. The oscillating platform may be actuated by an electromagnetic motor or by hydraulics. The set of tooling may include any number of fixtures, jigs or fasteners for securing and locating components to the welding machining <NUM>. The means for applying force may comprise a lifting platform configured to bring the first and second components in contact with one another. The means for applying force may alternatively or additionally include any number of actuators <NUM>. The welding process may be carried out at a frequency range between <NUM> and <NUM>, and at amplitudes between <NUM> and <NUM>.

The first component <NUM> may be arranged on the welding machine <NUM> with a first group of tooling (not shown). The first group of tooling may secure the first component to the oscillating platform <NUM>. The first group of tooling may be configured to restrict motion of the first component <NUM> relative to the means of vibrating. In this regard, the first component <NUM> vibrates with the oscillating platform <NUM>. The second components 630A, 630B may be arranged with a second group of tooling <NUM>. The second group of tooling <NUM> may be configured to locate the second components 630A and 630B in relation to one another and to the first component <NUM>. The second group of tooling <NUM> may comprise a base tool <NUM>, a first side tool <NUM> and a second side tool <NUM>.

The side tools <NUM>, <NUM> are configured to apply a load to the flanges 612A, 612B of the first component <NUM>. The side tools <NUM>, <NUM> may be actuated to push inwardly, in some examples towards each other. The side tools <NUM>, <NUM> may act to push each of the second components 630A, 630B against the respective flanges 612A, 612B of the first component <NUM>. In other examples, the side tools <NUM>, <NUM> may comprise a fixture configured to clamp the second components 630A, 630B against the respective flanges 612A, 612B of the first component <NUM>.

The second group of tooling <NUM> may further comprise a tool <NUM> for applying a weld load by pushing the mounting portion 640A, 640B of each respective second component 630A, 630B against the base portion <NUM> of the first component <NUM>.

During vibration welding, the first component <NUM> is vibrated by the oscillating platform <NUM> in relation to the second component 630A and 630B. After the step of vibrating the first component <NUM> is complete, the tooling may hold the first component <NUM> and the second components 630A, 630B in position until the thermoplastic material at each welding interface cools under pressure, re-solidifying and thereby providing the respective weld joint. Thereafter, the structure <NUM> formed by the welded first and second components is released from the tooling.

Claim 1:
A method of forming a hollow structure (<NUM>; <NUM>), the method comprising:
forming a first weld joint (<NUM>; <NUM>) internal to the hollow structure (<NUM>; <NUM>) by:
providing a first component (<NUM>; <NUM>) having a base portion (<NUM>; <NUM>) and a flange (<NUM>; <NUM>) extending from the base portion (<NUM>; <NUM>);
providing a second component (<NUM>; <NUM>);
bringing the second component (<NUM>; <NUM>) and the flange (<NUM>; <NUM>) into abutment and applying a load to the flange (<NUM>; <NUM>) via the second component (<NUM>; <NUM>),
wherein the flange (<NUM>; <NUM>) is biased against the second component (<NUM>; <NUM>) by a reaction of the first component (<NUM>; <NUM>) to the load; and
vibrating one of the first and the second components to form the first weld joint (<NUM>; <NUM>) between at least a part of the second component (<NUM>; <NUM>) and at least a part of the flange (<NUM>; <NUM>), and
characterised in that the method further comprises:
forming a second weld joint (<NUM>; <NUM>) between the second component (<NUM>; <NUM>) and the first component (<NUM>; <NUM>) to form the hollow structure (<NUM>; <NUM>).