FIELD OF THE INVENTION

This invention relates to a method of applying a graphic to vehicles and vehicle accessories, particularly motorcycles and motorcycle accessories.

BACKGROUND TO THE INVENTION

Graphics are applied to motorcycles and other vehicles as an essential element of a brand strategy. Attractive graphics appeal to the customer and assist sales of vehicles, such as motorcycles and motorcycle accessories. However, the current process for application of graphics to motorcycles and motorcycle accessories is difficult and expensive.

In a first stage of a conventional process, decals or stickers are prepared and printed with desired markings or graphics. The preparation and printing processes make decals expensive and, accordingly, maintaining an inventory of decals for a high production capacity for motorcycles is also expensive. If poor quality materials are available, defects are likely within the product decals. The decals are then separated from a backing material and pasted or adhered to motorcycle accessories with an adhesive. A lacquer* coat is then applied over the decal to provide a shiny attractive appearance. The process is labour and time intensive and therefore expensive. As the process also requires precision to be done well, a further problem arises as defects are likely to arise during the application process even if performed by highly skilled operators, errors are particularly common in the adhesion step of applying decal to motorcycle Part and the required skill and error levels make productivity improvements difficult.

An alternative to a decal graphic application method is painting. However, quality of manual painting is variable, not suited to mass production and - with vehicle accessories of complex three dimensional geometry - paint dripping along steep contours of vehicle parts causes undesirable blemishes.

It is an object of the present invention to provide a method of applying graphics to a vehicle or vehicle accessory which has reduced cost and high potential for productivity improvements over current technology.

It is a further object of the method of the invention to provide an opportunity to automate the graphic application process.

With these objects in view, the present invention provides a method of applying a graphic to a vehicle or vehicle accessory comprising the steps of locating a vehicle accessory of three dimensional geometry in a position for application of the graphic; applying a marking agent to the vehicle accessory to form the graphic through a predetermined number of marking agent streams directed from marking means located within a controlled distance range from a surface of the vehicle accessory to be provided with a graphic; and finishing the graphic in a finishing step.

A vehicle accessory may have complex geometry not being cylindrical, elliptical or otherwise regular in shape. An important example of such a vehicle accessory is a petrol tank for a motorcycle. Petrol tanks and other vehicle accessories may require the graphic to be applied over a complex curved surface or curved topography which extends in three dimensions with varying contour or high gradient topography at least in certain regions of the vehicle accessory. Such a varying contour may require either that head(s) of the marking means, or the vehicle accessory, be moved during the graphic application operation in order to provide a graphic of the required quality. That is, best results are achieved when a stream of marking agent is directed at the accessory from a point within a controlled distance range in accordance with a preset marking algorithm.
Advantageously, one or more marking agent streams may be directed at the vehicle accessory at controlled angle of incidence relative to the surface of the vehicle accessory.

Streams of marking agents may be directed at different portions of the vehicle accessory. One or more marking streams, having different colours or shades, may be directed at the vehicle accessory either simultaneously or sequentially.

The vehicle accessory may be marked as the accessory is held in one orientation. The vehicle accessory may have its orientation varied, for example by rotation, during the graphic application process. The orientation of the vehicle accessory may be varied so as to maintain an angle of incidence between the marking stream(s) and the surface of the vehicle accessory within a predetermined range. For example, the angle of incidence may be maintained approximately perpendicular to the surface of the vehicle accessory. The change in orientation may conveniently be achieved by use of a robotic apparatus. A change in orientation or position of the vehicle accessory is preferred to a change in position of the marking heads, which are advantageously kept stationary, though the repositioning or re-orientation of the vehicle accessory should still meet the criterion that the delivery point of a marking stream should be within a controlled distance of the surface of the vehicle accessory.

Marking is advantageously by printing, particularly direct ink jet printing on to the accessory. Suitable inks or paints are specially formulated for the duty. Advantageously, the inks or paints employed have a rapid or instantaneous curing time because, where accessories have a complex geometry, with high gradient topography in certain regions, dripping of paint could blemish the final product so a rapid or instantaneous curing time is needed to avoid or minimise such dripping. Acrylic paints have been formulated for the duty, such paints being instantaneously or near instantaneously cured by ultra-violet radiation. Such curing may be selective being only achievable through application of ultra-violet radiation. This improves the print quality preventing over wetting, sagging and inter-colour bleed as well as running on three dimensional accessories. Suitable UV pinning units can be advantageously used here to partially cure the inks, avoiding any drip and yet allowing deposition of another coat of same or compatible ink. Final UV curing can follow after completion of printing. The paints may be printed on. to a wide variety of substrates including directly on to metal and painted substrates. In this embodiment of invention, the inks after printing need to comply with cross cut adhesion test ASTM D3359 specification of 4B to 5B (less than 5% area removed). Chemical composition of paints / inks and UV curing parameters are formulated to meet this requirement. In case of subsequent lacquer coat this test is performed after the lacquer coat and its baking.

Flow and jetting properties of the paints are suitable for mass production capability with marking or ink jet heads. The paints may include metallic or dense or heavy pigments. The paints employed are advantageously sufficiently opaque to give true colors after printing on painted substrates as the method does not use a white base coat under the graphics. However, for silver color, to achieve sparkle effect, a white undercoat/ basecoat is used. This is required because silver color has aluminum particles which are restricted to small size to allow jetting without nozzle clogging. For sparkle effect, coarse size aluminum particles are needed. White undercoat helps to achieve the sparkle effect. A wide range of colors can also be produced by mixing of colors for example using C, M, Y and K as base colors.

Finishing may involve applying a lacquer coat over the graphics and then baking the marked vehicle accessory for a predetermined time at a predetermined temperature. The paints employed are resistant to such lacquer coating and also to the baking treatment.
The baking conditions may involve baking at a temperature between 70° and 90° C for a period of between 40 and 50 minutes, preferably between 75° and 85° C for a period of between 42 and 48 minutes.

The method of applying a graphic of the present invention has a number of advantages over the prior art. First, the waste and error rates encountered using decals is eliminated. Automation also allows for the graphic to be applied using less skill than previously required and this lowers expenses for operator training, application and monitoring of the graphic application process. Further, this invention allows customization of graphics to suit requirements of product variants and / or customer needs.

The method of applying a graphic of the present invention may be more fully understood from the following description of a preferred embodiment of the invention made with reference to the accompanying drawings in which:

Figure 1 is a flowchart showing the steps of a method of applying a graphic to a vehicle accessory in accordance with one embodiment of the present invention;

Figure 2 shows a petrol tank to have a graphic applied to it in accordance with the method shown in flowchart in Figure 1; and

Figure 3 shows a schematic of a robotic arm for locating a petrol tank for application with the graphic.

Referring now to Figure 1, the steps in applying a graphic to the petrol tank 10 ("P.T. 10") of a motorcycle, using a robotic marking or printing station, are shown in schematic form in the flowchart. The petrol tank 10 is not a two dimensional surface. Rather the petrol tank 10, as shown in Figure 2, has a three dimensional shape of complex curved geometry or topography characterized in certain regions by high or steep gradients (see certain regions 12 and 14 of petrol tank 10) which would encourage dripping of paint if misapplied to these regions 12 and 14.

The petrol tank 10 is first painted with its background color and this is cured by baking in high temperature ovens. It is then ready for application of a graphic such as a device or logo, or brand name such as "Bajaj". Following this step, the petrol tank 10 is directed to a robotic marking or printing station, suitable for handling mass production of petrol tanks for use in motorcycles, where the petrol tank 10 is located in a position for application of the graphic. Petrol tanks 10 are fed through the printing station at a constant speed as controlled by control unit for the printing station. The printing station is provided with a number of marking means in the form of stationary ink jet heads 11!, available under the trade mark Xaar HSS 1001, which are arranged to direct streams of marking agent at the petrol tank 10 to produce the required graphic in accordance with an algorithm, specific to the graphic to be applied to the accessory, programmed into the control unit. One or a library of algorithms may be programmed into the control unit. Algaorithms and applied graphics may be edited or programmed for the first time at the printing station allowing customization of graphics for particular customers.

Each ink jet head is Capable of printing at 0.42 m/s at 1018 dpi (dots per inch) grey scale resolution with up to 8 levels of grey scale using drop volumes from 6 Pico litre to 8 Pico litre enabling high quality printing to be achieved at production line speeds.

The graphic extends over a curved surface and, as it is desired to apply the paint or ink at a consistent thickness, the petrol tank 10 is re-positioned or reoriented so as to keep the ink jet head and the delivery point of the ink jet within a controlled distance range. The controlled distance range is 2 to 6mm in the illustrated embodiment and noting the particular printing equipment used. Failure to comply with a controlled distance range will result in a graphic of less than optimum quality.

The petrol tank 10 may require re-orientation, that is its orientation to be varied, for example by rotation (see Figure 3), during the painting operation to enable proper application of a graphic and the robotic painting station has provision (such as robotic arm 13) to implement this change in orientation.

The paints, or inks, delivered by the ink jet heads have a viscosity suitable for delivery through ink jet heads. The paints may contain metallic, heavy or dense pigments and are advantageously acrylic paints selectively curable by ultra-violet radiation and available under |the trade mark Vivide. The paints are also sufficiently opaque to give true colors after printing on to the painted substrate of the petrol tank. This allows for instantaneous or near instantaneous curing, resulting in paint solidification, by ultra-violet radiation from a UV lamp mounted proximate the printing station. Such instantaneous curing avoids the problem of paint dripping which would cause blemishing of the finished petrol tank 10.

Following ink jet printing, the petrol tank 10 is ready for a finishing treatment. First, the graphic and petrol tank 10 is coated with lacquer to give a shiny or lustrous appearance attractive to the customer. The petrol tank 10 is then baked at 80° C for 45 minutes in a suitable curing oven. Petrol tanks 10 are then ready for use in a motorcycle production line.

The ink jet printing Method for applying the graphic to petrol tank 10 has a number of advantages over the prior art. First, the waste and error rates encountered using decals is eliminated as the processes are distinct. Automation of the graphic application process also allows for the graphic to be applied using less skill than previously require and this lowers expenses for operator training, graphic application and monitoring of the graphic application process.

Modifications and variations to the method of applying a graphic of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are deemed within the scope of the present invention

WE CLAIM:

1. A method of applying a graphic to a vehicle or vehicle accessory (10) comprising the steps of locating a vehicle accessory (10) of three dimensional geometry in a position for application of the graphic; applying a marking agent to the vehicle accessory (10) to form the graphic through a predetermined number of marking agent streams directed from marking means (11,13) located within a controlled distance range from a surface of the vehicle accessory (10) to be provided with a graphic; and finishing the graphic in a finishing step.

2. A method of claim 1 wherein said vehicle accessory (10) has complex geometry not being cylindrical, elliptical or otherwise regular in shape.

3. A method of claim 2 wherein said vehicle accessory (10) requires a graphic to be applied over a complex curved surface or curved topography which extends in three dimensions with varying contour or high gradient topography at least in certain regions (12,14) of said vehicle accessory.

4. A method of claim 3 wherein said vehicle accessory is a petrol tank (10) for a motorcycle.

5. A method of claim 3 or 4 wherein said varying contour or high gradient topography requires either marking head(s) (11) of the marking means (11,13), or said vehicle accessory (10) be moved during the graphic application operation in order to provide a graphic of the required quality.

6. A method as claimed in any one of the preceding claims wherein a stream of marking agent is directed at the vehicle accessory (10) from a delivery point within a controlled distance range in accordance with a preset marking algorithm.

7. A method as claimed in any one of the preceding claims wherein stream(s) of marking agent are directed at said vehicle accessory (10) at controlled angles of incidence relative to said surface of said vehicle accessory (10).

8. A method as claimed in claim 6 or 7 wherein stream(s) of marking agents are directed at different portions of the vehicle accessory (10).

9. A method as claimed in claim 8 wherein one or more marking streams, having different colours or shades, are directed at the vehicle accessory (10) either simultaneously or sequentially.

10. A method as claimed in any one of the preceding claims wherein said vehicle accessory (10) is held in one orientation.

11. A method as claimed in any one of the preceding claims wherein said vehicle accessory (10) has its orientation varied during the graphic application process.

12. A method as claimed in claim 11 wherein said orientation of said vehicle accessory (10) is varied so as to maintain an angle of incidence between said marking agent stream(s) and said surface of said vehicle accessory (10).

13. A method as claimed in claim 12 wherein said angle of incidence is maintained approximately perpendicular to said surface of said vehicle accessory (10).

14. A method as claimed in any one of claims 11 to 13 wherein variation in orientation is achieved by use of a robotic apparatus (13).

15. A method as claimed in any one of claims 1 to 4 wherein marking head(s) (11) of said marking means are kept stationary.

16. A method as claimed in any one of claims 11 to 15 wherein, during repositioning or re-orientation of said vehicle accessory (10), a delivery point of a marking stream remains within a controlled distance of said surface of said vehicle accessory (10).

17. A method as claimed in any one of the preceding claims wherein marking is by printing, particularly direct ink jet printing, on to said vehicle accessory (10).

18. A method as claimed in claim 14 wherein inks or paints are used as marking agents, said marking agents having a rapid or instantaneous curing time.

19. A method as claimed in claim 18 wherein said marking agent is an acrylic paint, said paint being instantaneously or near instantaneously curable by ultra-violet radiation.

20. A method as claimed in claim 19 wherein curing is selective, only being achievable through application of ultra-violet radiation to said marking agent.

21. A method as claimed in any one of the preceding claims wherein said finishing step involves applying a lacquer coating over said graphic and then baking the marked vehicle accessory (10) for a predetermined time at a predetermined temperature.

22. A method as claimed in claim 21 wherein said marking agent, preferably an acrylic paint, is resistant to said lacquer coating and also to the baking treatment.

23. A method as claimed in claim 22 wherein baking conditions involve baking at a temperature between 70° and 90° C for a period of between 40 and 50 minutes.

24. A method as claimed in claim 21 wherein baking conditions involve baking at a temperature between 75° and 85° C for a period of between 42 and 48 minutes.

25. A vehicle accessory (10) having a graphic applied by the method of any one of the preceding claims.

26. A vehicle including a vehicle accessory as claimed in claim 25.

27. A method of applying a graphic to a vehicle or vehicle accessory substantially as hereinbefore described with reference to the drawings.