Device for lacquer transfer

Abstract

A device for lacquer transfer includes a frame, a transfer roller with a circumferential lateral wall, a drive unit and a lacquer application unit. The lacquer application unit is mounted on the frame and applies lacquer to a work surface of a work piece while the device is moved in an application direction across the work surface. The drive unit drives the transfer roller in a rotation direction about an axis of rotation. An outside contact surface of the lateral wall comprises a plurality of depressions forming a predetermined structure. The transfer roller rolls with the outside contact surface on the work surface of the work piece for transferring the predetermined structure defined by the depressions in the outside contact surface to lacquer previously applied to the work surface by the lacquer application unit.

Claims

1. A device for lacquer transfer, the device comprising: a frame; a transfer roller with a circumferential lateral wall, which has an outside contact surface that comprises a plurality of depressions forming a predetermined structure; a drive unit configured to drive the transfer roller in a rotation direction about an axis of rotation relative to the frame; a lacquer application unit, which is mounted on the frame and is configured for applying lacquer to a work surface of a work piece while the device is moved in an application direction across the work surface; and a light source, which is configured for emitting radiation for hardening the lacquer applied to the work surface, wherein the light source is arranged inside the transfer roller, such that radiation emitted by the light source impinges on the lacquer previously applied to the work surface by the lacquer application unit at least in a region where the outside contact surface is in contact with the lacquer; wherein the transfer roller is mounted rotatably about the axis of rotation on the frame and is configured to roll with the outside contact surface on the work surface of the work piece for transferring the predetermined structure defined by the depressions in the outside contact surface to the lacquer previously applied to the work surface by the lacquer application unit; and wherein the circumferential lateral wall of the transfer roller is formed from a material which is at least partly transparent to the radiation emitted by the light source.

2. The device of claim 1, wherein the radiation emitted from the light source is in an ultraviolet spectrum.

3. The device of claim 2, comprising a shielding, which is not transparent to radiation emitted from the light source and is arranged between the transfer roller and the lacquer application unit in order to reduce an amount of radiation that impinges on the lacquer applied to the work surface before the lacquer is contacted by the transfer roller.

4. The device of claim 3, wherein the shielding comprises a housing of the transfer roller.

5. The device of claim 1, wherein the lacquer application unit comprises at least one slit nozzle for dispensing lacquer.

6. The device of claim 5, wherein the lacquer is dispensed by the slit nozzle directly onto the work surface.

7. The device of claim 5, wherein the lacquer is dispensed by the slit nozzle onto a lacquer application roller for transferring the lacquer from the slit nozzle to the work surface.

8. The device of claim 1, comprising a lacquer thickness control device, which is configured to control a thickness of the lacquer applied to the work surface and is arranged between the lacquer application unit and the transfer roller in order to provide a homogenous distribution of lacquer with a constant thickness on the work surface.

9. The device of claim 8, wherein the lacquer thickness control device is a doctor blade, a doctor roller, or a soft lip scraper.

10. The device of claim 1, comprising a shielding, which is not transparent to radiation emitted from the light source and is arranged between the transfer roller and the lacquer application unit to reduce an amount of radiation that impinges on the lacquer applied to the work surface before the lacquer is contacted by the transfer roller.

11. The device of claim 10, wherein the shielding comprises a housing of the transfer roller.

12. The device of claim 10, wherein the radiation emitted from the light source is in an ultraviolet spectrum.

13. The device of claim 10, wherein the lacquer application unit comprises at least one slit nozzle for dispensing lacquer.

14. The device of claim 13, wherein the lacquer is dispensed by the slit nozzle directly onto the work surface.

15. The device of claim 13, wherein the lacquer is dispensed by the slit nozzle onto a lacquer application roller for transferring the lacquer from the slit nozzle to the work surface.

16. The device of claim 13, comprising a lacquer thickness control device, which is configured to control a thickness of the lacquer applied to the work surface and is between the lacquer application unit and the transfer roller in order to provide a homogenous distribution of lacquer with a constant thickness on the work surface.

17. The device of claim 16, wherein the lacquer thickness control device is a doctor blade, a doctor roller, or a soft lip scraper.

18. The device of claim 10, comprising a lacquer thickness control device, which is configured to control a thickness of the lacquer applied to the work surface and is between the lacquer application unit and the transfer roller to provide a homogenous distribution of lacquer with a constant thickness on the work surface.

19. The device of claim 18, wherein the lacquer thickness control device is a doctor blade, a doctor roller, or a soft lip scraper.

20. The device of claim 19, wherein the radiation emitted from the light source is in an ultraviolet spectrum.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the following the disclosure herein will be described in more details with reference to an exemplary embodiment of a device shown in the drawing, wherein:

(2) FIG. 1 shows a sectional view of an embodiment of a device for lacquer transfer.

DETAILED DESCRIPTION

(3) The device 1 for lacquer transfer shown in FIG. 1 comprises a frame 3, a transfer roller 5 and a lacquer application unit 7. Both the transfer roller 5 and the lacquer application unit 7 are mounted to the frame 3 although the connection between the frame 3 and the other elements 5, 7 is not shown in the sectional drawing of FIG. 1.

(4) The frame 3 can be releasably connected to a handling device (not shown), for example, in form of a robot with a robot arm 11. The latter is shown partially in FIG. 1 and is used to move the device 1 in an application direction 13 across a work surface 15 of a work piece 17. The work piece 17 may, for example, be a wing or a control surface of an aircraft and the work surface 15 is an outer surface of the wing or the control surface that is subjected to air flow when the aircraft is flying.

(5) While the handling device 11 moves the device 1 in the application direction 13, lacquer 19 is dispensed directly onto the work surface 15 by the lacquer application unit 7. To this end the lacquer application unit 7 comprises an extended slit nozzle 21 having a muzzle 22 that points in a direction extending perpendicularly to a plane of the work surface 15. Preferably, the angle of the muzzle 22 relative to the frame 3 can be adjusted to accommodate uneven or other complex shaped surfaces. It is possible to form the slit nozzle from multiple separate elements such that the width over which lacquer 19 is dispensed by the device 1 can be modified by turning individual elements on and off. Instead of a slit nozzle it may, for example, also possible to use a spray nozzle.

(6) Applying the lacquer 19 directly onto the work surface 15 has the advantage that even complex work surfaces 15 with changing curvatures or steps can be covered homogeneously with wet or liquid lacquer 19. This stands in contrast to systems were lacquer is first applied to a transfer roller and may already be partly cured or hardened before it comes into contact with the work surface 15. Compared to these systems, the interface between the lacquer 19 and the work surface 15 is improved as there are fewer bubbles and a more homogeneous lacquer distribution can be achieved.

(7) The lacquer application unit 7 further comprises a device 23 for controlling the thickness of the lacquer 19 in form of a doctor roller 23. As indicated by an arrow 25 pointing perpendicular to the work surface 15, the doctor roller 23 is biased by a spring 27 towards the work surface 15 and exerts a constant force onto the lacquer 19 such that the lacquer 19 is distributed homogenously on the work surface 15. The spring 27 is mounted on the frame 3 which is, however, not shown in FIG. 1.

(8) It should be noted that the use of a device 23 for controlling the thickness of the lacquer 19 is optional and may not be necessary if a homogenous distribution of lacquer 19 can already be achieved by the lacquer application unit 7.

(9) The transfer roller 5 comprises a lateral wall 27 which is formed by an inflated tire 27. The pressure in the inflated tire 27 can be modified to control the pressure that is exerted by the transfer roller 5 onto the work surface 15 and the lacquer 19.

(10) The entire transfer roller 5 is rotatably mounted to the frame 3. It can be rotated about an axis of rotation 29 and rotates in operation in a direction of rotation 31. In order to set the transfer roller 5 into rotation, a drive unit 33 is provided inside the transfer roller 5 and directly or indirectly attached to the frame 3. The drive unit 33 is used to control the speed of rotation of the transfer roller 5 so that it matches the velocity or speed with which the device 1 is moved in the application direction 13. If the speed of rotation and the speed in the application direction 13 match, an outer contact surface 35 remains essentially stationary in the application direction 13 while in contact with the lacquer 19. This improves the quality of a structure embossed by the transfer roller 5 into the lacquer 19 as there are no stick-and-slip effects that could smear out the structure.

(11) The outer contact surface 35 of the lateral wall 27 comprises a plurality of depressions which define a negative structure to be embossed into the lacquer 19. In other words, the arrangement of the depressions or the outer shape or contour of the outer contact surface 35 defines the structure to be applied to the work surface 15 using the device 1 for lacquer transfer. The depressions may also be referred to as a microstructure.

(12) In order to harden or cure the lacquer 19 as soon as the structure has been embossed, an ultraviolet (UV) light source 37 is arranged inside the transfer roller 5. The UV light source 37 emits radiation in the UV spectrum as indicated by the dotted arrows 39. Since the lateral wall 27 is made from a material that is at least partially and preferably fully transparent to UV radiation, the UV radiation is transmitted through the lateral wall 27 and the outer contact surface 35 and impinges on the lacquer 19 which has previously been applied to the work surface 15 by the lacquer application unit 7. When the UV radiation impinges on the lacquer 19, a chemical reaction is triggered and the lacquer 19 begins to harden.

(13) The UV light source 37 is arranged in a housing 41 with a shutter 43 which are both nontransparent to UV radiation and form a first shielding 41, 43 that limits the area of the lacquer that is irradiated or illuminated by the UV radiation. The area that is illuminated is further restricted by providing a housing 45 for the transfer roller 3 which is also nontransparent for UV radiation. The housing forms a second shielding 45 that reduces in particular the amount of scattered UV radiation 47 that could be scattered back onto the lacquer 19.

(14) As can be seen in FIG. 1 by the first and second shielding 41, 43, 45 the area in which UV radiation impinges onto the lacquer 19 is confined to an area shortly before and after the area in which the transfer roller 5 is in contact with the lacquer 19. Hence, the lacquer is only hardened shortly before, while and after the structure has been embossed into the lacquer 19 which improves the quality of the embossed structure. Also, as compared to previous device where lacquer is applied to the transfer roller 5, hardening of the lacquer before it is applied to the work surface 15 is avoided. This improves the adherence between the lacquer 19 and the work surface 15 and therefore the robustness of the structure.

(15) Finally, it should be noted that also the lacquer application unit 7 is provided with a housing 49 that prevents environmental UV radiation from interacting with lacquer 19 after it has been applied to the work surface 15.

(16) In operation, the device 1 is moved across the work surface 15 in the application direction 13 by the robot arm 11. First, lacquer 19 is dispensed onto the work surface 15 by the lacquer application unit 7 and, in particular, the slit nozzle 21. The recently applied lacquer 19 is then evenly distributed and limited to a predefined thickness by a doctor roller 23, though this step may be omitted. Afterwards, the transfer roller 5 is rolled over the lacquer 19 such that depressions formed in the outer contact surface 35 of the lateral wall 27 of the transfer roller 5 emboss a predefined structure into the lacquer 19. In this way, the structure is transferred from the transfer roller 5 to the work surface 15. At the same time UV radiation 39 emitted by the UV light source 37 at least partially cures the lacquer 19 to preserve the recently embossed structure. The device 1 therefore provides an efficient way of applying lacquer 19 with a predefined structure onto a work surface 15 that may be of complex shape.

(17) For the sake of completeness it is pointed out that the depression in the outer contact surface 35 and the microstructure embossed into the lacquer 19 are not shown in the drawing.

(18) While at least one example embodiment of the invention(s) herein is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the example embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.