System and method for coating a surface

Abstract

The present invention relates to a system (1) and a method for coating a surface (3a) of an object (3) with a spray coating tool (2) spraying atomised coating particles (10) onto. A conditioning hood (20) is applied defining a spray chamber. In operation the spray coating tool (2) is mounted at a coating tool mounting end (21), and an output end (22) is positioned in proximity of the surface (3a) of the object (3) to be coated. The spray coating tool (2) is operated to spray atomised coating particles (10) which travel from the coating tool (2), through the spray chamber and the output end (22) to the surface (3a) of the object (3). A carrier gas is injected that in operation carries the atomised coating particles (10) to the surface (3a) of the object (3).

Claims

1. A system for coating a surface of an object with a spray coating tool spraying atomised coating particles, comprising: a conditioning hood defining a spray chamber and having: a coating tool mounting end; and an output end opposite the coating tool mounting end, the output end is configured to be positioned in proximity of the surface of the object to be coated, wherein: the spray coating tool is mounted at the coating tool mounting end; and the output end is positioned in proximity of the surface of the object to be coated; and the spray coating tool is operated to spray atomised coating particles which travel from the coating tool, through the spray chamber and the output end to the surface of the object, a carrier gas installation in communication with the coating tool mounting end of the conditioning hood or with the spray coating tool, configured to provide a carrier gas to carry residual atomised coating particles from the spray chamber to the output end of the conditioning hood towards an inner annular duct; wherein the conditioning hood has three concentric walls, namely outer wall, intermediate wall and inner wall, the inner wall defining the spray chamber, the outer wall and the intermediate wall defining an annular outer duct and the intermediate wall and the inner wall defining the inner annular duct, wherein the inner annular duct is separated from the spray chamber, wherein the inner annular duct has an outer end which extends fully separate from the spray chamber; a gas extraction installation in communication with the outer end of the inner annular duct, configured to extract the carrier gas with the residual atomised coating particles adjacent the output end of the conditioning hood; and a shielding fluid injection installation in communication with the annular outer duct, configured to inject shielding fluid to the annular outer duct which leaves the annular outer duct at the output end thereof, thereby shielding the spray chamber from the environment.

2. The system according to claim 1, wherein the conditioning hood has a conical shape with the coating tool mounting end of the conditioning hood has a smaller opening than the output end of the conditioning hood.

3. The system according to claim 1, wherein the three concentric walls of the conditioning hood are provided are parallel to each other.

4. The system according to claim 1, wherein a spray chamber adjustment mechanism is provided for adjusting the distance d.sub.i between the surface of the object and the inner wall defining the spray chamber at the output end of the conditioning hood.

5. The system according to claim 1, wherein an outer wall adjustment mechanism is provided for adjusting the distance d.sub.o between the surface of the object and at least the outer wall at the output end of the conditioning hood.

6. The system according to claim 1, further comprising a particle sensor provided in the spray chamber detecting the particle size and/or particle density, and a central control system communicatively connected to the particle sensor and to the coating material supply and/or the carrier gas installation, for controlling the coating process based on input data from the particle sensor, such as a coating material flow rate and/or a carrier gas flow rate.

7. The system according to claim 1, further comprising a carrier gas injection installation, configured to inject a carrier gas.

Description

(1) The invention is furthermore elucidated in relation to the drawings, in which:

(2) FIG. 1 schematically depicts a system for coating according to the prior art;

(3) FIG. 2 schematically depicts a system for coating according to the second aspect of the invention;

(4) FIG. 3 schematically depicts a system for coating according to the first aspect of the invention;

(5) FIG. 4 schematically depicts an alternative system for coating according to the first aspect of the invention.

(6) In FIG. 1 a prior art system 1 for coating with a spray coating tool 2 spraying atomised coating particles 10, for example paint, onto a surface 3a of an object 3 is shown. Visible is that an external factor, such as wind 8, causes overspray 11.

(7) Generally, when the distance between the spray coating tool 2 and the surface is 5-10 cm, the least effect from external factors is experienced. With larger distances, the transfer efficiency of coating particles adhering onto the surface reduces significantly.

(8) The optimum particle size of atomised coating particles to effectively adhere onto the surface and form a coating may deviate up to 10-15%, depending on the type of coating material.

(9) In general, the type of coating material determines an associated spray coating tool and nozzle.

(10) In FIG. 2 a system 1 is shown according to the invention. The shown system 1 coats a surface 3a of an object 3 with a spray coating tool 2 spraying atomised coating particles 10, for example paint. The system comprises a conditioning hood 20 defining a spray chamber 5.

(11) In the inventive system, the distance between the spray coating tool 2 and the surface is 10 cm for smaller surfaces, and can be increased up to 30 cm for larger objects to be coated.

(12) The conditioning hood has: a coating tool mounting end 21, possibly closing off the spray chamber at this coating tool mounting end, an output end 22 opposite the coating tool mounting end, which output end is adapted to be positioned in proximity of the surface of the object to be coated.

(13) In operation: the spray coating tool is mounted at the coating tool mounting end, and the output end is positioned in proximity of the surface of the object to be coated, and the spray coating tool is operated to spray atomised coating particles which travel from the coating tool, through the spray chamber and the output end to the surface of the object.

(14) The system further comprises a carrier gas installation 30, which in operation is in communication with the coating tool mounting end 21 of the conditioning hood or with the coating tool, adapted to provide a carrier gas that in operation carries the atomised coating.

(15) The shown conditioning hood 20 according to the second aspect of the invention has three concentric walls, namely outer wall 25, intermediate wall 26 and inner wall 27, the inner wall defining the spray chamber 5, the outer wall and the intermediate wall defining an annular outer duct 28 and the intermediate wall and the inner wall defining an and inner annular duct 29.

(16) The system of the invention further comprises a gas extraction installation 35, schematically shown, in communication with the inner annular duct 29, adapted to extract gas with residual atomised coating particles adjacent the output end of the conditioning hood.

(17) Furthermore, the system comprises a shielding fluid injection installation 40 in communication with the outer annular duct 28, adapted to inject shielding fluid to the outer annular duct which leaves the annular duct at the output end thereof, thereby shielding the spray chamber from the environment.

(18) FIGS. 3 and 4 depicts a system 1 for coating according to a first aspect of the invention. The system 1 is a system for coating a surface 3a of an object 3 with a spray coating tool 2 spraying atomised coating particles 10, for example paint. The system comprises a coating material supply 6 in communication with the coating tool 2. The coating material supply 6 comprises a coating material pump (not shown in detail) setting a coating material flow rate.

(19) The system further comprises a conditioning hood, not shown, e.g. the hood as shown in FIG. 2, or a conditioning hood as known from the prior art, defining a spray chamber 5.

(20) The conditioning hood has a coating tool mounting end and an output end opposite the coating tool mounting end, which output end is adapted to be positioned in proximity of the surface of the object to be coated. In operation: the spray coating tool 2 is mounted at the coating tool mounting end, and the output end is positioned in proximity of the surface of the object to be coated, and the spray coating tool is operated to spray atomised coating particles which travel from the coating tool, through the spray chamber and the output end to the surface of the object.

(21) Possibly, the step of providing the coating material supply 6 into communication with the coating tool 2 is a separate step.

(22) The system further comprises a carrier gas installation 30. In operation, the carrier gas installation is in communication with the coating tool mounting end of the conditioning hood or with the coating tool 2, and is adapted to provide a carrier gas that in operation carries the atomised coating particles

(23) In the embodiment shown in FIG. 4, a gas extraction installation 35 is schematically shown, comprising a pump 38 setting the extraction rate, a filter 37 and a particle sensor 36 provided in an annular duct 29 defined by two concentric walls (not visible) of the conditioning hood, as shown in detail in FIG. 2.

(24) In the system according to the first aspect of the invention, a particle sensor is provided in the conditioning hood, detecting the particle size distribution and/or the particle density. In FIG. 3, the particle sensor 23 is provided in the spray chamber. In the embodiment of FIG. 4, the particle sensor 36 is provided in the annular duct 29.

(25) According to the first aspect of the invention, a central control system 45 is provided which is communicatively connected to the particle sensor 23, 36 and to the coating material supply 6 and/or the carrier gas installation 30, for controlling the coating process based on input data from the particle sensor, such as the coating material flow rate.

(26) Examples of parameters that can be controlled based on input data from the particle sensor are: a distance ds between the spray coating tool 2 and the object surface 3a; a distance d.sub.i between the inner wall defining the spray chamber 27 and the surface of the object 3a; a distance d.sub.m between the intermediate wall 26 and the surface of the object 3a; a distance d.sub.o between the outer wall 25 and the surface of the object 3a; the coating material flow rate; the carrier gas flow rate, e.g. by controlling a carrier gas injection pump and/or by controlling a gas extraction pump; the ratio between coating material and carrier gas; the viscosity of the coating material, e.g. by adding water or solvent, or by controlling the temperature of the coating material; the temperature in the spray chamber 5; the humidity in the spray chamber 5.

(27) In the embodiment of FIG. 4, it is also conceivable that the central control system 45 is communicatively connected to the pump 38 of the extraction installation.