The present invention relates to a thermally insulating packaging, and more particularly but not necessarily exclusively to a thermally insulating panel to form at least in part such packaging. More particularly, but again not necessarily exclusively, the invention relates to a method of forming a thermally insulating panel. The invention further relates to an apparatus for forming a thermally insulating panel, preferably using said method, and to a thermally insulating packaging container which again preferably utilises one or more of the said panels.

Temperature sensitive goods which are required to be transported, such as certain foods or pharmaceuticals, are typically thermally insulated with thermally insulated packaging during transportation.

For example, the temperature sensitive goods may be stored in boxes formed from expanded plastics such as expanded polystyrene, polypropylene or polyethylene. Such materials have good insulative properties; however, they are not conventionally biodegradable and may be difficult to recycle.

In view of consumer environmental concerns, governments are increasingly discouraging or restricting the use of plastic based packaging. Thus, it is desirable to find a non-plastic, compostable or biodegradable alternative to plastic-based thermally insulating packaging. Containers are sometimes loosely filled with biodegradable starch foam particles to protect goods from impact during transportation. Starch foam can have good insulative properties; however, in loose-fill particulate form this can be limited. Additionally, removing goods from containers loosely filled with starch foam particles can be inconvenient and time-consuming, especially due to the surrounding particles obstructing visibility of the goods. Furthermore, such particles may begin to degrade when wet and can attract vermin. As such, individual starch foam particles are unsuitable for transporting temperature sensitive goods.

The present invention seeks to provide a solution to these problems.

In accordance with the first aspect of the invention, there is provided a method of forming a thermally insulating panel for thermally insulating a temperature-sensitive item from an exterior environment during transportation, the panel having two opposing major surfaces and at least one minor surface which extends therebetween, the method comprising the steps of: a) at least part-filling a flexible container with a plurality of biodegradable foam members; b) abutting the flexible container with a former; and c) compressing the flexible container whilst constrained by the former so that the former imparts flatness or substantial flatness to the or each minor surface of the panel so as to in use improve abutment with an adjacent panel to prevent or limit heat flow between the exterior environment and the temperature-sensitive item.

Biodegradable may be herein defined as being able to be broken down by micro organisms within a relatively short period of time, for example a year. The term biodegradable is intended to cover compostable materials which are not only broken down but break down into non-toxic components. Biodegradable does not include conventional plastics, but preferably would include bio-degradable plastics.

Forming individual foam members into a panel allows for the beneficial properties of the foam members, such as thermal insulation and biodegradability, to be utilised without having loose fill foam members filling the packaging container. As such, the temperature sensitive item may be more conveniently removed from the packaging container. Forming the minor surface with the former so that at least one of the minor surfaces has flatness allows for adjacent panels to closely abut each other, and thereby prevent or limit gaps between adjacent panels. Preventing, limiting or minimizing gaps whilst maximising an abutment surface limits, inhibits or reduces the movement of air or convection between the temperature sensitive item and the exterior environment and therefore may close or substantially close a heat transfer path.

Using a container for the foam members can protect the foam members from exposure to moisture, which may assist in preventing their degradation.

Preferably, during step c), the compressing may be done via a vacuum or partial vacuum being applied to the flexible container and foam members. A vacuum allows for the foam members to be rapidly and conveniently compressed by the flexible container. Additionally, using a vacuum does not require the use of specialised materials for the flexible container, for example shrink-wrap material. This may enable the use of a flexible container formed from biodegradable material. Advantageously, during step c), the flexible container may be sealed. Sealing the flexible container maintains the vacuum within the flexible container and/or prevents foam members from being lost from the panel.

Beneficially, the flexible container may comprise material which is shrinkable on application of heat. In other words, the flexible container may comprise shrink wrap. Shrink wrap allows for the flexible container and/or foam members to be compressed without applying a vacuum, and therefore may increase a rate and reduce a cost of manufacture.

Optionally, the panel may have a rectangular major surface. As such, the panel conforms to a shape of a wall of a typical packaging container.

Preferably, the former imparts flatness or substantial flatness to at least one of the major surfaces. As such, a flat minor surface of an adjacent panel may closely abut the major surface of the initial panel.

Additionally, the or each minor surface may be planar or substantially planar. The minor surface being planar or substantially planar ensures that a larger contact area is made between adjacent panels which may assist with reducing gapping therebetween.

In a preferable embodiment, the panel has a plurality of minor surfaces and the former imparts flatness or substantial flatness to each minor surface. As such each minor surface may be able to closely abut an adjacent tile.

Preferably, during step b) or c) the foam members may be compacted via a compaction pressure. Compacting the foam members can improve the mechanical properties of the panel, for example the rigidity of the panel. Compaction may additionally improve the thermally insulative properties.

Advantageously, said compaction pressure may be applied via the former. The former applying compaction pressure, for example via moving inwards towards the foam member, may apply a greater compaction pressure than may be achieved only by applying a vacuum.

Beneficially, said compaction pressure may be applied at a plurality of surfaces. This ensures a more uniformly compacted panel or a panel with more uniform properties, such as density. Optionally, the foam members may comprise a polysaccharide. Polysaccharides are components which are typically readily biodegradable, and can usually be obtained without the use of petrochemicals for manufacture which may be advantageous for environmental reasons.

Additionally, the foam members may comprise starch. Starch foam is a cost effective and readily available biodegradable foam which has good thermally insulating properties. Starch is also a renewable resource.

In a preferable embodiment, the flexible container may comprise a biodegradable material. In this way more of or the whole panel would be biodegradable.

Preferably, the flexible container may comprise a polysaccharide.

Additionally, the, each or at least one of the minor surfaces may be perpendicular to at least one of the major surfaces. As such, the panel may abut the major surface of a perpendicularly arranged adjacent panel.

Alternatively, the, each or at least one of the minor surfaces is non-perpendicular to at least one of the major surfaces. As such, the panel may abut a similarly angled minor surface of a perpendicularly arranged adjacent panel.

Preferably, the former may comprise at least four contiguous sides and a base, said at least four contiguous sides for defining four of said minor surfaces of the panel and the base for defining one of said major surfaces of the panel and, the flexible container comprising a bag, and during step c), the bag is compressed via a vacuum or partial vacuum which removes air from inside the bag. The use of a bag permits for the vacuum to be applied inside of the bag so as to compress the walls of the bag around the foam members. The side walls and base permit for the bag to be held during formation of the panel, and impart an efficient shape to the panel. The base may be contiguous with the sides. A top of the former, if also included, for defining one of said major surfaces of the panel could also be contiguous with the sides.

According to a second aspect of the invention there is provided an apparatus preferably for a method according to the first aspect of the invention, the apparatus comprising: compression means for compressing the flexible container; and a former for constraining the flexible container whilst the flexible container is compressed by the compression means so as to impart flatness or substantial flatness to the or each minor surface. The compression means may otherwise be referred to as any one of a compressing device, a suction device, and a combination of a heating device and the flexible container comprising shrink-wrap.

Preferably the former may have a base and at least one side wall for imparting flatness to at least one of the minor surfaces. The base may provide a surface for positioning the flexible container on and may assist with constraining the flexible container. The side wall imparts flatness to the flexible container.

Advantageously, the former may have four side walls. In this way a resulting panel would have four flat minor surfaces.

Beneficially, at least one side wall may project perpendicularly from the base. This allows for the panel to have a minor surface which is perpendicular to a major surface. As such, such the panel may abut the major surface of a perpendicularly arranged adjacent panel.

Preferably, said at least one side wall projects non-perpendicularly from the base. This allows for the panel to have a minor surface which is at a non-perpendicular angle to a major surface. As such, the panel may abut a similarly angled minor surface of a perpendicularly arranged adjacent panel.

Beneficially, the former may have a top for constraining the flexible container during compression. This may assist with the flexible container maintaining contact with the or each side wall, particularly if the foam members are compacted during compression. The top may be moveable towards the flexible container to ensure contact is maintained, for example being moveable under gravity or using an actuator.

According to a third aspect of the invention there is provided a thermally insulating packaging container for receiving a temperature-sensitive item in a temperature- sensitive-item receiving volume, the packaging container comprising: a packaging- container body; and at least one thermally insulating panel preferably formed by the method according to the first aspect of the invention positioned between the packaging- container body and the temperature-sensitive-item receiving volume of the container body.

Preferably, there are a plurality said of thermally insulating panels, at least one minor surface of at least one thermally insulating panel abutting an adjacent thermally insulating element. A plurality of panels allows for the temperature sensitive item to be insulated in multiple directions. Advantageously, the packaging-container body may comprise paperboard or cardboard. Paperboard and cardboard are commonly available and lightweight packaging materials.

According to a fourth aspect of the invention there is provided a thermally insulating panel for insulating a temperature-sensitive item from an exterior environment during transportation, the thermally insulating panel comprising: a plurality of biodegradable foam members; and a container which compresses the biodegradable foam members.

The thermally insulating packaging container according to the third aspect of the invention may use the thermally insulating panel according to the fourth aspect of the invention. Preferably, the panel has two opposing major surfaces and at least one flat or substantially flat minor surface which extends therebetween.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows an apparatus according to a second aspect of the invention forming a thermally insulating panel according to fourth and fifth aspects of the invention via a method according to a first aspect of the invention.

Figure 2 shows a perspective top view of the thermally insulating panel of Figure

1 ;

Figure 3 shows a perspective side view of the thermally insulating panel of Figure 1 ;

Figure 4 shows a representation of an arrangement of a plurality of thermally insulating panels according to third and fourth aspects of the invention; and

Figure 5 shows a thermally insulating packaging container according to a third aspect of the invention having the arrangement of thermally insulating panels of Figure 4.

Referring to Figure 1 , there is shown a flexible container 10 which is at least part-filled with insulation members 12. The insulation members 12 are preferably biodegradable or compostable foam members, are more preferably polysaccharide foam members, and are most preferably starch foam members. The outline of the foam members 12 is shown in Figure 2 in a thermally insulating panel 100, tile or element formed from the flexible container 10 and foam members 12.

The starch foam members 12 are preferably formed by extruding a mixture of starch and a blowing agent to create starch foam strands in an extrusion foaming process. The starch is preferably obtained from plants or vegetables, for example corn, wheat, tapioca, mung bean or potatoes. As such the foam members may be plant-based foam members. The blowing agent is preferably water and may also act as a plasticiser. The amount of water typically amounts to approximately 25% to 50% by weight of starch and other additives may also be used to improve the extrusion or foaming process, such as polyvinyl alcohol or talc. The mixture is heated through an extruder, for example to temperatures of around 150 °C, under high pressure. This gelatinises the starch and causes the water to dissolve. On exiting the extruder, the lower pressure causes the water to precipitate and nucleate in the starch gel as a gas and thereby create starch foam strands which solidify. The starch foam strands are then cut into segments to form foam members 12.

The foam members 12 are preferably of a closed cell type, although it will be appreciated that open cell foams may also be considered. The foam members here comprise air holes dispersed in a solid phase, the solid phase being flexible so that the foam members are compactible or compressible. However, it will be appreciated that the solid phase may be rigid. A cross-section of the extruded strand is typically circular or approximately circular, and thus the foam members 12 preferably also have a circular cross-section. The foam members 12 may therefore be cylindrical in shape, although other geometries may be considered such as square or triangular cross-sections. The foam members 12 are here not-elongate and as such the length is approximately equal to the width. However, it will be appreciated that elongate foam members 12 may also be considered. The foam members 12 may have a length of greatest dimension of between 1 mm and 100 mm and more preferably between 5 mm and 20 mm.

Although starch is suggested, it will be appreciated that other polysaccharides may also be used, for example cellulose. Whilst extrusion is suggested, it will be appreciated that other manufacturing techniques may be considered, such as cutting the foam members 12 from sheets or blocks, or individual formation of foam members 12 for example via casting. It will also be appreciated that spherical foam members 12 may be considered. Although foam is used as the insulating material, it will be appreciated that non-foam biodegradable insulation members 12 may be considered.

The flexible container 10 is here a bag. As such the flexible container 10 preferably comprises two flexible sheets which are joined along three edges. A fourth edge is left open to allow insertion of the foam members 12. The sheets or walls of the flexible container 10 are thin. Whilst such a configuration of a bag is described, it will be appreciated that other bag configurations may be considered. The flexible container 10 is preferably formed from a biodegradable or compostable material, such as a polysaccharide, for example starch or cellulose. However, it will be appreciated that other materials may be considered, such as polystyrene. Additionally, the flexible container 10 may be formed from a shrink-wrap material, such as polyolefin. Shrink-wrap material is a material which contracts on application of heat.

To form the thermally insulating panel 100, the flexible container 10 is filled or at least part-filled with foam members 12. Referring to Figure 1 , the flexible container 10 is then positioned at, adjacent to, or in a former 14. Here the former 14 has four side walls 16 and thus has a rectangular or square cross-section. Each of the side walls 16 preferably has a flat, substantially flat, planar or substantially planar flexible-container-facing surface 18. The side walls 16 preferably interengage so as to be contiguous, although it will be appreciated that this may not be the case. The former 14 may preferably also have a base 20. Whilst four side walls 16 are suggested other numbers of side walls may be considered, for example only a singular side wall.

The flexible container 10 is positioned between the side walls 16 and here on top of the base 20. The flexible container 10 preferably engages the flexible-container-facing surface 18 of each of the side walls 16. At least one side wall 16 is preferably formed from two separable parts 22 and/or has an aperture therein to allow excess material 10a of the flexible container 10 to extend beyond the boundary of the former 14. The former 14 may additionally comprise a removable top or openable lid, not shown, which may extend between the side walls 16.

The flexible container 10 is then compressed against the foam members 12. This may result in the foam members 12 being compacted. The flexible container 10 is compressed via a compressing device 24 or a compression means. In Figure 1 , the compression means is a vacuum sealing device 24. As such, the flexible container 10 is compressed via a vacuum or a partial vacuum. The former 14 and the flexible container 10 are positioned in the vacuum chamber 26 of the vacuum sealing device 24. The vacuum chamber 26 is then evacuated of air, or at least partially evacuated of air. The evacuation of air removes air from the flexible container 10 via the opening and such evacuation may result in the compaction of the foam members 12 and/or the compression of the flexible container 10 onto the foam members 12. The opening is then sealed shut, for example via a heat seal formed via a sealing bar 28 on the vacuum sealing device 24. Other sealing means may be considered, such as an adhesive. The vacuum chamber 26 is then re-filled with air. The pressure difference between the interior of the flexible container 10 and the exterior environment at atmospheric pressure maintains compression on the flexible container 10 and/or compaction of the foam members 12. This forms the thermally insulating panel 100. The flexible container 10 constrains the movement of the foam members 12 and thus the thermally insulating panel 100 is rigid, at least partly rigid, and/or more rigid than the material of the flexible container 10 alone.

During this compression the former 14 preferably abuts and constrains the flexible container 10 and the foam members 12. The side walls 16 of the former 14 laterally engage the flexible container 10 and the foam members 12. In the instance that the foam members 12 compact or reduce in volume, it will be appreciated that a top of the former 14 may be used to constrain, urge or push the foam members 12 inwardly during compression to prevent or limit the foam members 12 and flexible container 10 from moving away from the side walls 16 during compression, compaction or contraction. The top may be moveably downwards, for example via an actuator such as a piston, to ensure this, or may be weighted. The top of the former may also apply a compaction pressure. However, it will also be appreciated that a former top may not be necessary, and that gravity may ensure that the foam members 12 fill the space between the side walls 16, even during compaction.

Additionally or alternatively, at least one of the side walls 16 of the former 14 may be moveable inwards towards an opposing side wall 16 to apply a compaction pressure or force on the foam members 12 and/or the flexible container 10. This may result in a greater compaction of the foam members 12 than may be achieved only by the application of the vacuum and/or the compression of the flexible container 10. At least one side wall 16 moving inwards may also assist with maintaining contact between the side walls 16 and the flexible container 10. Referring to Figures 2 and 3, via the laterally constraining action of the side walls 16 of the former 14, the flexible container 10 and foam members 12 conform to the shape of the former 14. Given the that the former 14 has four flat or planar side walls 16, the resulting thermally insulating panel 100 has at least four flat, substantially flat, planar or substantially planar surfaces. Here said flat surfaces are minor surfaces 30 which extend between two opposing major surfaces 32. The minor surfaces 30 may be considered to be side surfaces whilst the major surfaces 32 may be considered to be top and bottom surfaces or front and back surfaces. The two major surfaces 32 are also flat or planar, and such a configuration may be assisted by the presence of a flat top and/or flat base 20 of the former 14. The minor surfaces 30 are so-called due to each having a smaller area, length or width than each major surface 32.

Although a rounded or angular profile of individual foam members 12 may protrude through the flexible container 10, the overall shape of each minor surface 30 is substantially flat, planar or level. Whilst the minor surfaces 30 are here planar, it will be appreciated that each minor surface 30 may in fact be rounded or curved. The presence of at least one flat, straight or substantially flat or straight line extending at least part way longitudinally along each minor surface 30 allows for the adjacent panels 100 to be closely abutted together.

The width or height of each minor surface 30 preferably comprises a plurality of individual foam members 12, for example between two and ten foam members 12, and more preferably approximately three foam members 12.

Although four minor surfaces are described, other numbers of minor surfaces may be considered, for example three minor surfaces for a triangular shaped panel, or one minor surface for a circular shaped panel.

The side walls 16 of the former 14 are upstanding from the base 20 and extend or project perpendicularly, normally, or at right angles, therefrom. As such, the panel 100 which is formed has minor surfaces 30 which are perpendicular or at right angles to the major surface 32. Therefore, the minor surfaces 30 of a first panel are able to engage a major surface 32 of a second panel which is positioned at right angles or perpendicularly to the first panel. However, it will be appreciated that the side walls of the former may extend at an angle inwardly to the base or outwardly from the base. Such an angle may be between 30 ⁰ and 60 °, and would more preferably be 45 °. This would result in minor surfaces 30 which are at a non-perpendicular angle to the major surface 32. Therefore, the minor surfaces 30 of perpendicular or laterally arranged adjacent panels 100 may conveniently engage each other. Alternatively, the side walls of the former may be stepped to form stepped minor surfaces which may engage a correspondingly stepped minor surface of an adjacent perpendicular panel. The steps may be formed via a former having a corresponding step shape. Such stepped minor surfaces may have multiple flat surfaces, and thus the former would still impart flatness to the minor surface. Alternatively, the minor surface may, for example be formed by the former so as to have a projecting or protruding element, which may be received in a corresponding recess formed in the major surface. The area around the protruding element is preferably flat or substantially flat. The former imparts a profile to the minor surface.

Whilst the compression means is described as being a vacuum sealing device 24, it will be appreciated that other compression means may be considered. For example, shrink- wrapping may be used. In the instance that the flexible container 10 is formed from a shrink-wrap material, the foam members 12 are positioned inside the flexible container 10. The flexible container 10 may be closed or sealed, although it will be appreciated that this may not be necessary. Such closure may be achieved via an adhesive. The flexible container 10 is then positioned in the former 14 as previously described and heat is applied to the flexible container 10. This causes the flexible container 10 to shrink around and against the foam members 12. This provides a compression force on the foam members 12 to restrict or prevent their movement. Said compression force may additionally compact the foam members 12. The flexible container 10 may be sealed around the foam members 12, although it will be appreciated that this may not be necessary.

Referring to Figures 4 and 5 a plurality of thermally insulating panels 100 can be used to thermally insulate a temperature-sensitive item during transportation. The panels 100 may be arranged as shown in Figure 4 within a packaging-container body 34 or shell, as shown in Figure 5. The packaging-container body 34 is typically a box, for example a cardboard or paperboard box. The packaging container body 34 may usually have limited thermally insulation properties, and thus the thermally insulating panels 100 used with the packaging container body 34 forms an enhanced packaging container. Whilst a packaging-container shell is described, it will be appreciated that this may not be necessary and the panels may be attached to each other, for example via an adhesive. A base thermally insulating panel 100a may be positioned on a base of the packaging- container body 34. Next, side thermally insulating panels 100b are positioned at side walls 16 of the packaging-container body 34. One of the minor surfaces 30 of each side panel 100b engages the major surface 32, and preferably an edge thereof, of the base thermally insulating panel 100a. Given the planarity or flatness of the minor surfaces 30 and the major surface 32, close or tight abutment is achieved therebetween which prevents or limits a heat transfer path therebetween, or an edge heat loss. Additionally, given the flatness of the panel, a contact area between panels is increased which prevents or limits heat loss. One minor surface 30 of each side panel 100b engages or abuts one major surface 32 of one of the adjacent side panels 100b. Similarly, given the planarity or flatness of the minor surface 30 and the major surface 32, close or tight abutment is achieved therebetween which prevents or limits a heat transfer path therebetween. Once the temperature sensitive item is positioned between the side panels 100b and overlying the base panel 100a, a top panel 100c may then be positioned on top of the side panels 100b so that one of the major surfaces 32 of the top panel 100c engages each of the minor surfaces 30 of the side panels 100b. The flatness of the major and minor surfaces 30 prevents or limits a heat transfer path therebetween. The box, which here has closing flaps, may then be closed around the thermally insulating panels 100 and secured.

The panels 100 and the walls of the packaging-container body 34 are preferably sized so as to correspond to each other. For example, the dimensions of the major surface 32 of the base 20 panel 100 may match those of the base 20 of the packaging-container body 34. Additionally, the width of the side walls 16 of the packaging-container body 34 may each match the width of a side panel 100 major surface 32 together with the width of a side panel 100 minor surface 30. The height of the side walls 16 may each match the height of the side panel 100 major surface 32 together with the width of two side panel 100 minor surfaces 30. However, it will be appreciated that panels 100 may be shaped with different dimensions, using differently shaped or arranged formers, to correspond to different containers. For example, a wall of the packaging-container body 34 may have a width double that of a panel, and therefore two panels may be used for each wall.

Whilst the flexible container 10 is described as being a bag, it will be appreciated that the flexible container may in fact initially comprise two disjoined sheets between which the foam members may be positioned, with the sheets being joined and sealed to each other after compression.

A first part of the flexible container may comprise a first sheet, wall or film and is preferably flexible at room temperature. The first sheet may comprise any of the materials previously described for the flexible container. The first sheet is formed into an open container via a former, pocket or mould. For example, the first sheet may be extended across the former and then may be drawn into the former via a vacuum or may be pressed into the former via a die. To allow for the first sheet to more easily conform to the shape of the former, the first sheet may be heated to increase its flexibility or pliability. Thus, the first sheet may be thermoformed. The former in this example is preferably similarly shaped to the precedingly described former so that the resulting first part has flat, substantially flat, planar, or substantially planar minor surfaces or sides.

Whilst in the former, the first part of the flexible container is then filled with insulation members such as foam members as previously described. A second part of the flexible container, which is here a second sheet, wall or film, is then laid across the first part of the container, although the second part is not yet sealed or joined to the first part. A vacuum is then applied which evacuates the first part of the container of air and may contract the foam members. The second sheet is then sealed to the edge or edge portions of first sheet, for example via a heat-sealing element. The panel is thereby formed having a lower interior pressure than atmospheric pressure. As such, walls of the flexible container compress onto the foam members.

Such a method may be utilised to produce multiple panels simultaneously. For example, a first sheet is laid across and conformed to a plurality of formers to form a plurality of open containers. Said plurality of open containers may then each be at least part-filled with foam members. A second sheet may be large enough to be laid across said plurality of open containers. A vacuum may then be applied as previously described and the second sheet may be sealed to the first sheet around each open container to form a plurality of panels. The first and second sheets may then be cut or broken between the panels so as to separate the panels from each other.

A thermoforming or rollstock vacuum packaging machine may be utilised for this purpose. Whilst the foam members are described as being biodegradable, it will be appreciated that they may in fact not be biodegradable and may comprise plastic, for example expanded polystyrene.

Although the panel is described as being formed with the use of a former, it will be appreciated that the panel may not be formed using a former.

It is therefore possible to provide an at least in part biodegradable thermally insulating panel for a packaging container. The panel has flat minor surfaces, or sides, via the use of a former during manufacture. Flat minor surfaces allow for adjacent panels to be closely abutted with each other, and/or increase a contact surface area, to prevent or reduce gaps therebetween. This increases an insulative effect when utilising multiple panels in a packaging container. The panel is formed from a bag which is compressed around foam members which allows the formation of a rigid panel from multiple individual foam members.

The words ‘comprises/comprising’ and the words ‘having/including’ when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined herein.