Description:FIELD OF INVENTION

The present invention relates to a process for painting the roof of an automobile such as a passenger car. In particular, the present invention relates to a process for painting the roof of an automobile in a colour different from the body color thereof. More particularly, the present invention relates to a process for finish (topcoat) painting the roof of an automobile when the other body parts are applied with a primer/surfacer.

BACKGROUND OF THE INVENTION

Normally, the automobile manufacturers producing passenger cars under mass-production are using a triple-coat, three-bake process. This time and energy consuming process has a significant impact on the overall product cost.

The conventional painting process adopted by all car manufacturers involves a first step of pretreatment followed by a step of cathodic electro deposition (CED) coating and the final step of baking of the vehicle body.

This CED coated vehicle is forwarded for applying a primer surfacer. This primer surfacer applied vehicle is then forwarded for baking. After baking is over, the vehicle is applied with a solid/ metallic topcoat and a flash-off of 08-10-minutes is provided thereafter, which is followed by applying a clear coat, and finally the baking is carried out at a temperature of 140°C of Effective Metal Temperature (EMT) for 20 minutes to ensure complete curing of paint.

Nowadays, the demand for vehicles painted in two-tone is continuously increasing in the market for all automobile variants. To fulfill this increasing market-demand, two-tone painting of vehicles has become a necessity for the passenger car manufacturers.
However, there are some issues with the existing painting process used for two-tone painting by the automobile manufacturers, as summarized below:

Existing Two-Tone Painting Process:

Current process for two-tone painting of vehicles involves applying CED coated vehicle with primer surfacer [(Vertically: 35±5 micron (μm); Horizontally: 40±5 micron (μm)]. Followed by this, primer surfacer applied vehicle is forwarded for baking at a temperature of about 140°C (EMT) for 20 minutes to ensure a complete curing of paint. Thereafter, the baked vehicle is forwarded for carrying out Body masking other than roof and then it is forwarded for Roof painting with a base coat application (Matt/Glossy : 20±2 μm) and then a clear coat application is carried out (Vertically: 35± 5 μm; Horizontally : 40±5 μm), and finally the baking is carried out at a temperature of about 140°C (EMT) for 20 minutes.

After baking is accomplished, the vehicle is forwarded for Body De-masking and Roof Masking for carrying out Body painting with a base coat application of solid/ metallic paint (20± 2μm) followed by a clear coat application (Vertically: 35±5 μm; Horizontally: 40±5 μm), and finally the baking is carried out at a temperature of about 140°C (EMT) for 20 minutes. Thereafter, the baking inspection is conducted, and the vehicle is sent for assembly.

However, the disadvantages of painting of vehicles in two-tone paint by the above process is an increase in the overall process time and painting costs involved therein. Ultimately, the painting vehicle in two-tone colour shade by conventional process reduces the overall productivity of car manufacturers.

Therefore, there is an existing need for increasing the productivity of the conventional two-tone painted vehicle manufacturing by adopting a single-pass two-tone painting process.
The present invention proposes and provides a sandwich-process for painting two-tone painting of passenger cars, in which the vehicle roof is finish-painted along with the car-body (body-in-white or BIW) and the primer surfacer is simultaneously applied on the car body except for the roof thereof.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a two-tone painting process involving a single-pass, two-tone painting system for applying roof finish paint in a single-process cycle.

Another object of the present invention is to provide a single-pass, two-tone painting process eliminating one baking cycle, reducing the requirement of painting and masking materials.

Still another object of the present invention is to provide a single-pass, two-tone painting process which reduces the overall painting process time.

Yet further object of the present invention is to provide a single-pass, two-tone painting process which increases the productivity of car manufacture.

Still further object of the present invention is to provide a single-pass, two-tone painting process which requires less material such as the masking paper.

Yet further object of the present invention is to provide a single-pass, two-tone painting process which improves the sustainability thereof.

A still object of the present invention is to provide a single-pass, two-tone painting process which reduces the overall cost of the painting process.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.

DESCRIPTION OF THE INVENTION

In accordance with the single-pass, two-tone process of the present invention, the cathodic electro deposition (CED) coated car body (BIW) is received in the primer booth, where the car roof is applied with W/W Primer (15 ± 3 μm) and the rest of the car body is applied with B/B primer (Vertically: 35 ± 5 μm and Horizontally: 40 ± 5 μm), i.e. a wet-on-wet painting process.

Thereafter, the car body (BIW) is applied with a W/W Base coat (15 ± 3 μm) and W/W Clear Coat (40 ± 5 μm) only on the roof thereof. Then, this car body (BIW) is sent to a baking station for baking @ 140°C (EFT) for 20 minutes to ensure a complete curing of the paint.

Thereafter, the roof masking of the only roof-baked car body is done and the car body is forwarded for a base coat application with base coat paint (20±2μm) followed by a clear coat application (Vertically: 35±5 μm and Horizontally: 40 ± 5 μm), and finally, the car body is baked @140°C (EMT) for 20 minutes. Thereafter, the baking inspection of this car body is carried out and it is sent for assembly of components thereon.

This single-pass, two-tone painting process offers a significant productivity enhancement over the conventional two-pass painting process, because the production achieved by the conventional painting process was at 10 cars per hour and if 02 cars out of these 10 are painted in two-tones, the actual productivity reduces to 08 cars per hour.
In contrast with the conventional two-tone car painting process, the single-pass, two-tone car painting process configured in accordance with the present invention reduces the process time with no loss in productivity, which achieves a production of 10 two-tone painted cars per hour.

This is higher by 20% per hour over the conventional two-tone painting process discussed above due to the elimination of the body-masking activity and carrying out only roof-masking does not pose any bottleneck at the masking stage.

SUMMARY OF INVENTION

In accordance with the present invention, there is provided a single-pass, two-tone painting process of a car body (BIW) coated by cathodic electro deposition (CED), the single-pass, two-tone painting process comprises:

• applying a sealer on the car body in the primer booth;

• applying B/B primer on the interior thereof;

• applying W/W primer of 15±3 μm thickness on the roof thereof;

• applying B/B primer on the rest of the exterior (except roof) thereof, followed by a flash-off of 150 seconds;

• applying W/W base coat on the roof thereof;

• applying W/W clear coat on the roof thereof, followed by a flash-off of 180 seconds;

• first baking at 140°C Effective Metal Temperature (EMT) in a baking oven for 20 minutes;

• roof masking for conducting base coat application thereafter;
• applying base coat of matt/glossy paint on the car body;

• applying a clear coat on the car body; and

• second baking at 140°C (EMT) in a baking oven for 20 minutes;

wherein the car body (BIW) painted in two-tone by above process is finally inspected and sent for assembly of components/subassemblies thereon.

Typically, the car body exterior (except roof) is applied with a coat of B/B primer of vertical thickness 35±5 μm and horizontal thickness 40±5 μm.

Typically, the roof is applied with a W/W base coat of thickness 15±3 μm of matt/glossy paint.

Typically, the roof is applied with a W/W clear coat of thickness 40±5 μm of paint, followed by a flash-off for 180 seconds.

Typically, the first baking of the car body is carried out at 140°C (EMT) in a baking oven for 20 minutes to ensure complete curing of the car body paint.

Typically, after roof-masking, the car body is applied with a base coat of matt/glossy paint of thickness 20±2 μm.

Typically, the car body exterior is applied with a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm.

Typically, the second baking is carried out at 140°C (EMT) in a baking oven for 20 minutes to ensure complete curing of the car body paint.

Typically, the B/B primer coat is applied manually on the interior of the car body.

Typically, the application of the B/B primer, W/W primer, base coat and clear coat are carried out by a robot.

Typically, the roof-masking of car body is carried out manually.

Typically, the application of base coat of matt/glossy paint on the car body comprises:

(i) manually applying a 20±2 μm thick base coat of matt/glossy paint on the car body;

(ii) applying a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on the car body exterior by a robot; and

(iii) applying a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on the car body interior by a robot.

Typically, the application of a clear coat on the car body comprises:

(a) manually applying a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on the car body;

(b) applying a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on the car body exterior by a robot; and

(c) applying a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on the car body interior by a robot.

Typically, the roof-masking is manually removed (roof de-masking) before carrying out the final inspection of the painted car body and sending the same for assembly of components/subassemblies thereon.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described in the following with reference to the accompanying drawings.

Figure 1 shows a schematic flow-diagram of the conventional double-pass, two-tone process for painting of car bodies or automobiles.

Figure 2 shows a schematic flow-diagram of the improved single-pass, two-tone process for painting of car bodies or automobiles configured in accordance with the present invention.

Figure 3 shows process-flow of the conventional double-pass, two-tone process for painting of car bodies or automobiles.

Figure 4 shows an improved process-flow of the single-pass, two-tone process for painting of car bodies or automobiles configured in accordance with the present invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, a two-tone painting process involving a single-pass, two-tone painting system configured in accordance with the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention.

Figure 1 shows a schematic flow-diagram of the conventional double-pass, two-tone process for painting of car bodies or automobiles. According to this painting process, there are two process paths, i.e., a first process path, FPP (PA6-PA9) and a second process path, SPP (PA10-PA14). This process starts at step PA1 in which a sealer is applied on the car body C, followed by a manual application of B/B primer [Vertically: 35 ± 5 micron (μm); Horizontally: 40 ± 5 micron (μm)] thereon at step PA2. At step PA3, this car body is subjected to flash-off for 150 seconds to step PA4, whereafter it is sent at step PA5 for a first baking @140°C (EMT) in a baking oven for 20 minutes. Here, the car body is subjected to flash-off for 150 seconds. The first process path FPP starts at point S1 and body masking (except the roof) is carried out at step PA6. At the next step PA7, a base coat of matt/glossy paint is applied on the roof (Vert. 20 ± 2 μm) and at step PA8, a clear coat (Vert. 35 ± 5 μm; Hori. 40 ± 5 μm) is applied thereon. Thereafter, this car body is sent to a second baking @140°C (EMT) in a baking oven for 20 minutes, at step PA9. The second process path SP starts at point S2 and at step PA10, body demasking is carried out, followed by roof masking at step PA11. Then at step PA12, a base coat of matt/glossy paint is applied on the car body (Vert. 20 ± 2 μm), followed by the step PA13 of clear coat (Vert. 35 ± 5 μm; Hori. 40 ± 5 μm) application thereon. Finally at step PA14, the roof and body painted car body is sent for baking @140°C (EMT) in a third baking oven for 20 minutes, whereafter the roof and body painted car body is sent for further processing such as the assembly of components thereon.

Figure 2 shows a schematic flow-diagram of the improved single-pass, two-tone process for painting of car bodies or automobiles configured in accordance with the present invention. According to this improved painting process, the car body C coated by Cathodic Electro Deposition (CED) is received in the primer booth and a sealer is applied thereon at step P1, followed by a step P2 of manual application of B/B primer on the interior thereof. At step P3, the roof is applied with W/W primer (15 ± 3 μm) and at step P4, rest of the car body exterior is applied with B/B primer (Vertically: 35 ± 5 μm; Horizontally: 40 ± 5 μm). Here, the car body is also subjected to flash-off for 150 seconds. Now, only roof is applied with W/W base (15 ± 3 μm) at step P5, followed by W/W clear coat application (40 ± 5 μm) thereon at step P6. At step P7, the car body is subjected to flash-off for 180 seconds. Then, it is sent at step B1 for first baking @140°C (EMT) in a baking oven for 20 minutes. Thereafter, the roof is masked at step P8, and at step P9, car body is forwarded for base coat application with matt/glossy paint (20 ± 2 μm) followed by a step P10 of clear coat application (Vert. 35±5 μm; Hori. 40±5 μm) on the exterior thereof. Then at step B2, this roof and body painted car body is sent to second baking @140°C (EMT) in a baking oven for 20 minutes.

Figure 3 shows a detailed process-flow of the conventional double-pass, two-tone process for painting of car bodies or automobiles. According to this existing painting process, car body C coated by cathodic electro deposition (CED) is received in the primer booth and a sealer is applied on the car body shell at step PA1, followed by the step PA2 of manual application of B/B (surface) primer (Vert. 35 ± 5 μm; Hori. 40 ± 5 μm) on the interior thereof. At steps PA31-PA32, this car body is externally applied with surface primer by a robot, whereafter it is sent at step PA4 to an inspection zone (including a flash-off for 150 seconds), followed by the first baking step PA5 for baking @140°C (EMT) in a baking oven for 20 minutes (including a flash-off lasting for 180 seconds). At step PA6, the first pass path FPP is started at point S1, and the body masking BM1 (except the roof) is carried out to facilitate the subsequent roof painting. At the next step PA71, a base coat of matt/glossy paint is manually applied (Vert. 20 ± 2 μm) on the interior thereof, which is followed by step PA72 of base coat application on the roof by a robot. At the next step PA81, a clear coat (Vert. 35 ± 5 μm; Hori. 40 ± 5 μm) is manually applied on the interior thereof, followed by a step PA82 of clear coat application by a robot on the exterior roof thereof. Then, this roof-painted car body is sent at step PA9 for a second baking @140°C (EMT) in a baking oven for 20 minutes and followed by the car body demasking BDM at step PA10, whereupon the roof masking RM1 is started at point S2. The roof masking is carried out manually at step PA111, followed by the step PA112 of base coat of matt/glossy paint applied on the car body (Vert. 20 ± 2 μm) by a robot. Now, a clear coat (Vert. 35 ± 5 μm; Hori. 40 ± 5 μm) is manually applied on the car body interior at step PA121, followed by a step PA122 of clear coat application on the exterior of the car body by a robot. Finally at step PA13, both roof and body painted car body is sent for third baking @140°C (EMT) in a baking oven for 20 minutes, whereafter at step PA14 roof is demasked from this car body and it is subjected to final inspection and sent for assembly of components thereon.

Figure 4 shows a detailed improved process-flow of the single-pass, two-tone process for painting of car bodies or automobiles configured in accordance with the present invention. According to this improved painting process, the car body C coated by Cathodic Electro Deposition (CED) is received in the primer booth and a sealer is applied thereon at step P1, followed by a step P2 of manual application of B/B primer thereon on the interior thereof. Now, at step P3, the roof is applied with W/W primer (15 ± 3 μm) and at step P4, the rest of car body exterior (except roof) is applied with B/B primer (Vertically: 35 ± 5 μm; Horizontally: 40 ± 5 μm). Now at step P5, a robot applies the roof with W/W base coat (15 ± 3 μm) of matt/glossy paint, followed by a step P6 of W/W clear coat (40 ± 5 μm) paint applied thereon. The car body is subjected to flash-off P7 for 150 seconds, whereafter at step B1, the car body is baked @140°C (EMT) in a first baking oven for 20 minutes. Then, the roof is masked at step P8, and at step P91, this car body is manually applied with a base coat of matt/glossy paint (20 ± 2 μm) thereon, followed by steps P92-P93 of clear coat application (Vert. 35 ± 5 μm; Hori. 40 ± 5 μm) respectively on the exterior and interior thereof. At step P101, the car body interior is manually applied with clear coat paint (Vert. 35 ± 5 μm; Hori. 40 ± 5 μm), followed by steps P102-P103 respectively of a clear coat application (Vertically: 35±5 μm; Horizontally: 40±5 μm) by a robot on the exterior and interior thereof. Then at step B2, this roof and body painted car body is sent for baking @140°C (EMT) in second baking oven for 20 minutes and this is followed at step P11, by roof demasking. Finally, the roof demasking is carried out at step P11 and followed by the step P12 of final inspection and subsequently, the car body with internally and externally painted roof and body thereof is forwarded for further processing, e.g. assembly of different components thereon.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The single-pass, two-tone painting process configured in accordance with the present invention offers the following advantages:

• Eliminates one baking cycle from the two-tone painting process.

• Significantly reduces the requirement of painting materials.

• Substantially reduces the requirement of masking materials.

• Enhances the productivity of the painting process.

• Promotes sustainability of the painting process.

• Reduces energy consumption and manpower requirement.

• Reduces the overall cost of painting process.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.
Although, the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to imply including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.

The description of the exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top”, and “bottom” as well as derivatives thereof (e.g. “horizontally”, “inwardly”, “outwardly”; “downwardly”, “upwardly” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion.

These relative terms are for convenience of description and do not require that the corresponding apparatus or device be constructed or operated in a particular orientation.

Terms concerning attachments, coupling and the like, such as “connected” and “interconnected”, refer to a relationship, wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. , Claims:We claim:

1. A single-pass, two-tone painting process of a car body (BIW) coated by cathodic electro deposition (CED), said single-pass, two-tone painting process comprises:

• applying (P1) a sealer on said car body (BIW) in the primer booth;

• applying (P2) B/B primer on the interior thereof;

• applying (P3) W/W primer of 15±3 μm thickness on the roof thereof;

• applying (P4) B/B primer on the rest of the exterior (except roof) thereof, followed by a flash-off for 150 seconds;

• applying (P5) W/W base coat on the roof thereof;

• applying (P6) W/W clear coat on the roof thereof, followed by a flash-off (P7) for 180 seconds;

• first baking (B1) at 140°C (EMT) in a baking oven for 20 minutes;

• roof masking (P8) for conducting base coat application thereafter;

• applying (P9) base coat of matt/glossy paint on said car body;

• applying (P10) a clear coat on said car body; and

• second baking (B2) at 140°C (EMT) in a baking oven for 20 minutes;

wherein said car body (BIW) painted in two-tone by above process is finally inspected and sent for assembly of components/subassemblies thereon.

2. The single-pass, two-tone painting process as claimed in claim 1, wherein said car body exterior (except roof) is applied with a coat of B/B primer of vertical thickness 35±5 μm and horizontal thickness 40±5 μm, at step (P4).

3. The single-pass, two-tone painting process as claimed in claim 1, wherein said roof is applied with a W/W base coat of thickness 15±3 μm of matt/glossy paint, at step (P5).

4. The single-pass, two-tone painting process as claimed in claim 1, wherein said roof is applied with a W/W clear coat of thickness 40±5 μm of paint, at step (P6) followed by a flash-off for 180 seconds.

5. The single-pass, two-tone painting process as claimed in claim 1, wherein at step (B1), the first baking of said car body is carried out at 140°C Effective Metal Temperature (EMT) in a baking oven for 20 minutes to ensure complete curing of said car body paint.

6. The single-pass, two-tone painting process as claimed in claim 1, wherein after roof-masking at step (P8), said car body is applied with a base coat of matt/glossy paint of thickness 20±2 μm, at step (P9).

7. The single-pass, two-tone painting process as claimed in claim 1, wherein said car body exterior is applied with a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm, at step (P10).

8. The single-pass, two-tone painting process as claimed in claim 1, wherein said second baking is carried out at 140°C of Effective Metal Temperature (EMT) in a baking over for 20 minutes to ensure complete curing of said car body paint, at step (B2).

9. The single-pass, two-tone painting process as claimed in claim 2, wherein said B/B primer coat is applied (P2) manually on car body interior.

10. The single-pass, two-tone painting process as claimed in claim 2, wherein said steps (P3) to (P6) are carried out by a robot.
11. The single-pass, two-tone painting process as claimed in claim 1, wherein said roof-masking at step (P8) is carried out manually.

12. The single-pass, two-tone painting process as claimed in claim 1, wherein applying (P9) base coat of matt/glossy paint on said car body comprises:

(i) manually applying (P91) 20±2 μm thick base coat of matt/glossy paint on said car body;

(ii) applying (P92) a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on said car body exterior by a robot; and

(iii) applying (P93) a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on said car body interior by a robot.

13. The single-pass, two-tone painting process as claimed in claim 1, wherein applying (P10) clear coat on said car body comprises:

(a) manually applying (P101) a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on said car body;

(b) applying (P102) a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on said car body exterior by a robot; and

(c) applying (P103) a clear coat of vertical thickness 35±5 μm and horizontal thickness 40±5 μm on said car body interior by a robot.

14. The single-pass, two-tone painting process as claimed in claim 8, wherein said roof-masking at step (P8) is manually removed (roof de-masking) before carrying out the final inspection of said painted car body and sending the same for assembly of components/subassemblies thereon.

Dated this 21st day of June 2023.

Digitally / e-Signed by:

(SANJAY KESHARWANI)
APPLICANT’S PATENT AGENT
REGN. NO. IN/PA-2043.