Method and apparatus for preparing a surface for bonding a glass pane to a window aperture of a vehicle passenger compartment

TECHNICAL FIELD

The present invention relates to a method according to claim 1 and also to an apparatus in accordance with claim 5. BACKGROUND ART

In the automotive industry, window panes are often attached to vehicle frameworks by strong resilient bonding, so that crash structures of vehicle compartments are reinforced by the window panes. Usually, the vehicle structure comprises a sheet metal framework which has been coated with a plurality of coatings for corrosion prevention and for appearance.

It is a problem that each additional layer of coatings may reduce the strength of bonding between glass pane and sheet metal framework. Structural strength and light weight are important features when designing vehicle compartments. The requirement for bonding glass to the frame of a vehicle compartment is a clean substrate that guarantees the best adhesion of the bonding adhesive to the compartment frame. Therefore, the current solution consists of masking the areas where the adhesive will be applied, on top of a first coating. The application of masking material can be performed with robots in the paint shop.

The masking material must be applied before applying base and top coats. For example, a truck compartment is painted in different steps with three layers of coatings. A first layer is applied by electrolytic dip coating. Then said masking material is applied onto said coating, to the areas which will be used for bonding. A base coat is applied on top of the first layer. Then a final layer of paint of the desired colour is added on top of the base coat for appearance. When the paint coatings have cured, the masking material can be removed to enable attachment of glass panes to the compartment by bonding. Thus, the masking material is an extra material that requires two extra operations (application and removal) and a special handling of waste material afterwards. Therefore there is a need for a solution that would lead to improvements from time, cost and environment perspectives. DISCLOSURE OF INVENTION

Thus, one object of the present invention is to provide an alternative method to masking that enables improvements in terms of cost, time and for the environment. Another object of the invention is to provide an apparatus for performing the method according to the invention efficiently.

A method for preparing a surface for bonding a glass pane to a window aperture of a vehicle body in accordance with the invention is characterized in the steps of applying surface coatings to the vehicle body, curing said coatings, and removing one or more of the cured coatings from the areas of the body to which the glass pane will be bonded, by means of contactless energy transfer. The method ensures that both surplus layers of paint and pollution like dust particles and/or other debris are removed before bondning.

The invention also provides an apparatus for preparing a surface for bonding a glass pane to a window aperture of a vehicle passenger compartment, characterized in a means for contactless energy transfer to the surface area to be used for said bonding.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be described in a few embodiments with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a robotic manipulator in the process of preparing glass pane surfaces of a vehicle compartment for bonding in accordance with the invention,

Fig. 2 shows a robotic manipulator workhead with tools for perfoming the invention, and

Fig. 3 schematically shows one embodiment of the invention comprising a laser apparatus for contactless energy transfer.

MODES FOR CARRYING OUT THE INVENTION

In Fig. 1 a robotic manipulator 10 for assembling glass panes to a vehicle compartment 11 is shown, comprising a foot base 12, an upright leg 13, a horizontal arm 14 and a tool workhead 15. Preferably, the manipulator 10 is articulated with multiple axles for providing freedom of motion in all directions. The workhead 15 carries one or more tools for performing the invention. The manipulator 10 is controlled by a computer 16 programmed to deploy the tools in sequence to prepare surfaces of the compartment for assembling, to apply adhesive to said surfaces and to transfer a glass pane, for example a truck cab windshield, to a correct position for bonding. For this object, the workhead 15 is connected to a laser head 17 for contactless energy transfer to the surfaces to be bonded and for removal of fumes generated by said energy transfer. The workhead 15 is also provided with a means for supply of a bonding adhesive to the surfaces. Preferably, the workhead is also provided with a means for transferring a glass pane to a correct position for bondning.

Fig. 2 shows a workhead configuration diagrammatically in larger scale, in the process of removing paint 18 from a paint coated sheet metal panel 19, and also in the process of applying bonding adhesive 20 to the metal panel 19 in the area of removed paint. In the embodiment of the invention according to Fig. 2, the workhead 15 comprises a laser head 21 including a laser tube 22 and a suction nozzle 23 for evacuation of smoke and debris from the treated surface area 24. A control unit 25 is connected to the laser head 21 via lines 26 for supply of energy to the laser tube and for supply of vacuum pressure to the suction nozzle 23. The workhead 15 also comprises an applicator 27 connected via lines 28 to a controller 29 for supply of a suitable bonding adhesive 20. A third tool is schematically depicted to illustrate a suction cup manipulator 30, which is connected via a line 31 to a controller 32 for lifting and positioning a glass pane with its edges in full contact with the bonding adhesive.

Fig. 3 shows in larger scale an example of a conventional laser head 21 , which can be adapted for preparing a painted surface 34 before bonding, in accordance with the invention. The laser head 21 is provided with a first set of sensors 33 for detecting that the laser head is within the working distance range from an opaque work surface 34, for example between 30-250 mm. If the sensors 33 are out of range from the surface 34, the laser head 21 will not be able to start, or will immediately shut down if it is moved away from the surface 34.

A second set of sensors 35 are arranged inside the laser head 21 to detect if laser light escapes past an internal baffle 36. A lens 37 together with a diffractive means reduce the spatial coherence of the laser beam 38. The laser head is shielded with an opaque, light absorbing shroud 39 which is connected to the internal baffle 36. The laser effect can be approximately 500 W, the laser pulse duration is preferably less than 15 ns, and the repetition speed of the laser head is preferably around 100 kHz. The wave length is preferably approximately 1000 nm and the maximum energy consumption of the laser head can be in the range of circa 1000 W.

The invention is not limited to the above described embodiments. Instead, several modifications are possible within the scope of the following claims.