The present invention relates to a repair method, in particular to a method of repairing a wall panel for a caravan that has been printed with a design.

Typically, the shell of a caravan is produced by assembling two side panels, two end panels, a floor and a roof (although one or both of the end panels may be integral with the roof). The floor, side panels and end panels are mounted onto a chassis, and the roof is then fitted.

The term "wall panel" will be used herein to cover both side panels and end panels. Figure 1 is a cross-section through a conventional wall panel (which may be either a side panel or an end panel) for a caravan. The wall panel has an inner skin 2 and an outer skin 3 which are mounted on a supporting matrix 1 . The matrix 1 typically comprises a wooden frame, with openings in the frame being filled with polystyrene to provide thermal insulation. The outer skin (which forms the exterior of the caravan) is typically powder-coated aluminium, and the inner skin 2 is typically formed of 3mm plywood. The aluminium outer skin 3 and the plywood inner skin 2 are each glued to the matrix by a respective glue layer 6. Wallpaper 4 or some other decorative covering is provided on the inner surface of the inner skin 2. The outer skin 3 is usually decorated with printed self-adhesive vinyl elements 5 and possibly badges (not shown) that are stuck onto the outer skin 3 during or after assembly of the wall panel.

Depending on the size of the caravan and on the material used for the inner skin, the inner skin may be continuous over a side panel or may be made up of a number of portions as indicated by joint 8 in figure 1 . The outer skin is preferably continuous over a side panel, to maximise weather resistance.

UK patent application GB 2476808 and PCT published application WO 201 1/083341 , the contents of which are hereby incorporated by reference, describe a method of manufacturing a wall panel for a caravan (or mobile home, motor home etc). In this method a first design is printed onto a first skin of a wall panel, which may be either the inner skin or the outer skin when the wall panel is assembled into a caravan. Optionally a second design is printed onto a second skin of the wall panel. The design(s) is/are printed on to the skin(s) of the wall panel using a direct-to-substrate printer, for example an inkjet printer using UV-based or conventional inks. Printing the designs allow the wallpaper 4 and vinyl elements 5 of figure 1 to be eliminated.

Figure 2 is a schematic cross-section through a wall panel manufactured according to a method of GB 2476808 or WO 201 1/083341 . In the wall panel shown in figure 2 the wall panel has thickness of approximately 1 inch (25.4mm), which is a typical thickness for a caravan wall panel. The matrix 1 has a width of approximately 22mm, the inner skin 2 in figure 2 is a GRP (glass-reinforced plastic) skin (although other materials such as foam PVC may alternatively be used) with a width of approximately 3mm and the powder-coated aluminium outer skin 3 has a width of approximately 0.5mm. The inner and outer skins 2, 3 are glued to the matrix 1 by glue layers 6. Skins of this composition and thickness provide sufficient structural thickness and so the matrix may be formed of a sheet of expanded polystyrene (preferably with mounting members (for example wood) being provided in the matrix at locations where it is desired to join the wall panel to another wall panel or to the chassis, floor or roof of the caravan, or where it is desired to mount a component onto the wall panel). The wall panel of GB 2476808 or WO 201 1/083341 is not however limited to these particular dimensions or to these materials. A desired first design 9 is printed onto one side of the wall panel using a direct-to-substrate printer, and a desired second design 10 is printed onto the other side of the wall panel using a direct-to-substrate printer

In GB 2476808 or WO 201 1/083341 , after the design has been printed, a transparent, and preferably glossy, protective coating is usually applied over the design to protect the printed design against damage, spillage and weathering. This transparent protective coating is generally referred to as a "clearcoat" or "clear coat". The clear coat may be any transparent coating that is durable enough to resist abrasion and chemically stable enough to withstand UV light, and may for example be a urethane coating or a UV-curable coating. The clear coat may be applied by the direct-to- substrate printer that prints the design on the skin, or it may be applied in a separate process, for example by spraying or by use of a roller-coating machine.

In GB 2476808 or WO 201 1/083341 a design printed onto the inner skin of a side or end panel may include decoration (as would be provided by wallpaper in a conventional wall panel), and may also include text such as one or more safety notices and/or operating instructions, and/or may include positions where components, such as interior furniture and/or fittings, are subsequently to be mounted on the wall panel. A design printed onto the outer skin may include one or more of decoration, the manufacturer's name and/or the model of the caravan, and text such as one or more safety notices, a weight plate label and/or operating instructions. (When a design is printed onto the outer skin, the outer skin will usually have a desired background colour so that the design need be printed only where additional decoration and/or information text is desired.)

The present invention provides a method of repairing a wall panel for a caravan comprises flattening a damaged portion of the first skin of the wall panel, and applying an image to the flattened portion of the first skin of the wall panel, using a transfer or a thin film self-adhesive decal. A transparent protective coating may then be applied over the transfer or decal. The term "self-adhesive decal" as used herein denotes a self-adhesive graphic element, having a support film that is provided with an adhesive layer on one surface and having a design printed on the other surface. The decal is adhered on a desired substrate, by the adhesive layer. A "thin film" self-adhesive decal" as used herein denotes a self-adhesive decal having an overall thickness of 25μΐη or less. (The overall thickness of a self-adhesive decal is defined primarily by the support film and the adhesive layer, since the printed image adds only negligibly to the overall thickness.) A "transfer" is used herein to denote a graphics element in which an adhesive is combined within the ink or other substance that provides a desired design. There is no integral support film - the adhesive/ink are initially provided on a suitable carrier, and are transferred from the carrier to the desired substrate. The thickness of the adhesive/ink, after transfer to the desired substrate, is very low (and less than 25 μΐη) since the carrier is discarded.

Road-going vehicles such as caravans and motorhomes are inevitably involved in road traffic accidents, leading to damage to one or more of the wall panels of the vehicle - and such damage will also damage any design printed onto the damaged wall panel(s). If a wall panel suffers serious damage it will generally be necessary to remove the damaged wall panel and fit a replacement wall panel, but where a wall panel suffers only minor damage it is however preferable to repair the wall panel rather than replace it. Hitherto, when a wall panel is repaired after damage, if a design applied to the wall panel is damaged, the design is generally repaired or replaced in the same way that the design was originally provided on the wall panel (so, for example, where a design is applied to a wall panel using self-adhesive graphics, after repairs to the panel new self- adhesive graphics would be applied), so as to minimise any difference in appearance between a repaired part of the wall panel and an original, undamaged part of the wall panel (or between a repaired part of the wall panel and another, undamaged wall panel of the vehicle). However, where the design is printed onto the wall panel using a direct-to-substrate printer as described in GB 2476808 or WO 201 1/083341 , it is not practical to replace a design in the same way that the design was originally provided.

A method of the invention is particularly suited for providing a replacement design on a wall panel where the original design was printed on the wall panel using a direct-to- substrate printer, since use of a transfer or thin-film self-adhesive decal means that the replacement design will be similar in appearance to any undamaged portions of the original design, so making the design less conspicuous. A method of the invention is particularly suited for providing a replacement design on a wall panel manufactured according to a method of GB 2476808 or WO 201 1/083341 , when the wall panel is repaired after having been damaged.

Other features of the invention are set out in the dependent claims. Preferred embodiments of the invention will be described by way of illustrative example with reference to the accompanying drawings in which:

Figure 1 shows a typical wall panel for a caravan;

Figure 2 shows a wall panel for a caravan according to GB 2476808 or WO 201 1/083341 ;

Figure 3 is a block flow diagram showing the principle steps of a method according to one embodiment of the invention; and

Figure 4 is a schematic sectional view through a wall panel repaired according a method of the present invention. The starting point for the method of figure 3 is a wall panel which has had a design printed on at least one skin using a direct-to-substrate printer according to a method as described in GB 2476808 or WO 2011/083341 (for example a wall panel as shown in figure 2), and that has suffered damage. For simplicity the method will be described below with reference to damage to the outer skin of the wall panel since the outer skin is more likely to be damaged in, for example, a road traffic accident, although a method of the invention may be used to repair damage to the inner skin as well as, or in addition to, damage to the outer skin. It will be assumed that the damage to the wall panel is not so severe to require replacement of the wall panel - for example the damage may be relatively minor dents, scratches and/or gouging in the outer skin of the wall panel.

Initially, at block 1 of figure 3, the damaged area of the outer skin of the wall panel is made smooth. This will be referred to as "flattening" the outer skin, but it should be noted that the term "flattening" does not imply that the invention is limited to a wall panel having a planar ("flat") surface. The invention may be applied to a wall panel having a curved surface as well as to a wall panel having a planar surface, and the term "flattening" refers generally to the process of restoring the outer skin to its desired profile.

In block 1 of figure 3 any regions of the wall panel that, following the damage, are recessed beyond the desired surface of the wall panel (for example where dents or gouges have occurred) are filled and flattened off using any suitable repair technique for the specific material of which the out skin of the wall panel is made. Also, if the damage has caused any material to protrude beyond the desired surface of the wall panel this protruding material is removed to flatten the surface of the wall panel. Typical materials for the outer skin of a wall panel are aluminium, in particular powder- coated aluminium, plastics material, and composite materials such as glass-reinforced plastics, and suitable filling/repair techniques for these materials are well-known and will not be described.

Once the outer skin has been restored to its desired outer profile, the repaired area(s) of the wall panel is/are then coloured, for example painted, at block 2 of figure 3. Usually, the repaired area of the outer skin of the wall panel is painted in the body colour of the vehicle, for example by spray painting. There may be cases where painting the repaired area is not necessary (for example where the damaged areas are only within an area of printed decoration), and in such cases block 2 of figure 3 can be omitted. In general, however, it will be desirable to paint or otherwise colour the repaired area in order to make the repaired area as inconspicuous as possible.

If the area of damage to the outer skin of the wall panel happens to run over an element of the design printed onto the wall panel, this element of the design inevitably will be partly or completely obscured in the repair process of smoothing and re-painting the damaged area of the wall panel. At block 3 of figure 3, therefore, the design provided on the outer skin of the wall panel is repaired. This is done using a thin film self-adhesive decal or transfer. The thin film decal or transfer has been printed with a desired image, and is optionally opaque to allow better colour matching of the printed image with the original design on the wall panel. The thin film decal or transfer may have the same background colour as the original wall panel. If the outer skin had been printed with a decorative design, the image applied using the transfer or thin-film self-adhesive decal would match the original printed design, and would be applied at the exact same location on the sidewall so as to replicate, to the greatest extent possible, the original design and so minimise the visual effect of the repair. (In a case where the original printed design contained text such as a warning notice, instructions or a weight plate label, it would not be necessary for the image applied using the thin- film decal to exactly match the original printed design, provided that the applied image included all relevant information that was present in the original printed design.) Finally, at block 4 of figure 3 a protective clearcoat is applied to the repaired area, for example is sprayed on to the repaired area. Once dry, the clearcoat may be polished so that the repaired area has the same gloss finish as the original wall panel. Any suitable clear coat material may be used, for example a urethane coating or a UV- curable coating.

Where a thin-film self-adhesive decal is used, the thin-film decal may have a film thickness of 25μιη or less, for example may have a film thickness of 10-20μιη, for example may have a film thickness of 15μιη. Use of such a thin-film decal, or use of a transfer, means that, when over-sprayed with the clearcoat, the decal or transfer would become embedded in the clearcoat, giving the exact same appearance as other graphics on the wall panel that were printed directly on the substrate. (In principle a self-adhesive decal having a thickness of under ^" Ι Ομιη could be used, but a self- adhesive decal with a thickness of under ^" Ι Ομιη is likely to be fragile and its use may be difficult or impractical, particularly for larger designs.)

Figure 4 is a schematic sectional view through a wall panel 12 that has been repaired using a method of the invention. The wall panel 12 has the construction described with reference to figure 2, and has a matrix 1 sandwiched between an inner skin 2 and an outer skin 3. Graphics elements 10a, 10b, 10c are printed on the outer surface of the outer skin 3, and a protective clearcoat 1 1 is applied over the outer skin 3 and the graphics elements 10a, 10b, 10c (the thickness of the graphics elements 10a, 10b, 10c is exaggerated in figure 4, for clarity).

A region of the outer skin 3 of the wall panel has been damaged, in the example of figure 4 dented, and one of the graphics elements 10b is within the damaged region. (The matrix 2 of the wall panel has also been damaged, although this is of less importance since the process of filling the damaged area will restore the wall panel to its original thickness.) The damaged area of the wall panel has been filled using a suitable filler 13. The surface of the filler has been flattened so that it is level with the surface of the undamaged areas of the wall panel 12 - since the outer layer of the wall panel in figure 4 is the original clearcoat 1 1 , the surface of the filler 13 is flattened so that it is level with the surface of the clearcoat 1 1 . The filler is then coloured to match the background colour of the wall panel, for example by spray painting (the paint layer is omitted from figure 4, as its thickness is small).

A new graphics element 10b' is applied on the newly re-painted background colour, applied to the filler 13, to replace the graphics elements 10b that is within the damaged region and that is now covered by the filler 13 and painted background colour. In general, the replacement graphics element 10b' will be the same design as, and will be applied in the same position on the surface of the wall panel as, the graphics elements 10b that is within the damaged region. As explained above, according to the invention the replacement graphics element 10b' is a transfer or a thin-film self-adhesive decal. (The thickness of the new graphics elements 10b' is also exaggerated in figure 4.) A protective clearcoat 1 1 ' is then applied over the repaired area of the wall panel. As is indicated in figure 4, the new clearcoat 1 1 ' preferably also partially extends over the undamaged region(s) of the wall panel, to minimise the risk of water penetrating into the interface between the filler 13 and the damaged area of the wall panel. The new clearcoat 1 1 ' is then "polished in", to smooth the edges 14a, 14b of the new clearcoat 1 1 ' and so make the edges less perceptible to a user, and minimise any difference in appearance between the repaired area and undamaged region(s) of the wall panel. The new clearcoat 1 1 ' is applied on the surface of the filler 13 which, as described above, is flattened to be level with the original clearcoat 1 1 . In consequence, as figure 4 indicates, the new clearcoat 1 1 ' is slightly proud of the original clearcoat 1 1 . The use of a thin-film self-adhesive decal for the new graphics element 10b' however means that the thickness of the new clearcoat 11 ' can be kept low, thereby minimising the additional thickness of the repaired portion of the wall panel and so making the edges 14a, 14b of the new clearcoat 1 1 ' virtually imperceptible to a user. Alternatively a transfer is inherently thin and will embed naturally within a clearcoat, and use of a transfer to provide the new graphics element 10b' again means that the thickness of the new clearcoat 1 1 ' can be kept low.

In contrast, if the replacement graphics element 10b' were applied using a conventional self-adhesive decal with a typical overall thickness of 80-1 ΟΟμιη (as used for the self- adhesive graphics 5 in the conventional wall panel of figure 1 ), the new clearcoat 1 1 ' would be required to have a thickness of more than 80-100μιη, since the thickness of the new clearcoat 1 1 ' has to be greater than the thickness of the replacement graphics element 10b'. This would lead to a perceptible change in thickness at the edges 14a, 14b of the new clearcoat 1 1 '.

As noted, the invention may also be applied to the repair of damage to an inner skin. plastics material, and composite materials. Typical materials for the inner skin of a wall panel are plywood, plastics material, and composite materials such as glass-reinforced plastics, and suitable filling/repair techniques for use on these materials at block 1 of figure 3 are known. When the invention is applied to repair of an inner skin, at block 2 of figure 3 the repaired area of the inner skin is painted, if necessary, in a colour that matches the interior or the vehicle, rather than in the body colour of the vehicle.