Title of Invention

"A METHOD FOR MAKING POWDER COATED PANELS OR CABINETS FOR HOME APPLIANCES AND AN APPARATUS THEREFOR"

Abstract The present invention relates to a process and appartus for the preparation of the powder coated panel for home appliances especially for the refrigerators wherein the coating of the refrigerator panel and door are of incosistent dry film thickness and apparatuds thereof.
Full Text Field of the invention:
The present invention relates to a process and the apparatus for the preparation of powder coated panel for home appliances.
More specifically, it relates to a process and the apparatus used for powder coating the substrate prepared galvanised steel sheet to be used in the home appliances.
Prior Art
The powder coated conventional panels have bare CRCA (cold rolled cold annealed) sheet resulting in the rusting of sheets during monsoon. The process also produces lots of effluent and the pollution level also is high. The paint quality specification in terms of corrosion resistance and paint adhesion was not good. The adhesion of the paint to the substrate applied panel and powder coated panel did not show satisfactory results. The said sheet was susceptible to scratching giving a a worn out look to the appliance after some time in turn decreasing the market value of the product.
Thus there is a need to develop a process which overcomes all the above mentioned drawbacks of the conventional process.
It is an object of the current invention to develop an improved process of powder coating to produce better quality paint having corrosion resistance properties.
It is an object of the present invention to develop a process of powder coating which reduces the effluent produced in the process decreasing the pollution.
It is also an object of the present invention to develop a process of powder coating to produce the paint of quality specification (physical and chemical
both) having good adhesion, flexibility, resistance to scratch and water and fast colour.
Summary of the invention:-
The present invention relates to a process and apparatus used for powder coating the substrate prepared galvanised steel sheet The substrate preparation is done prior to powder coating of the galvanised steel sheet to be used in home appliances. The substrate preparation is a 2-step novel process which involves degreasing and rinsing of the galvanised steel sheet.
The novel process of substrate preparation producing better quality substrate is explained in our co-pending Indian Patent Application No. 533/D EL/2002.
The substrate prepared galvanised steel sheet is taken to the water drying oven. The degreased, rinsed and dried galvanised steel sheet is then taken and placed in the cleaned class-l chamber provided with the overhead conveyor belt system for holding the said sheet for powder coating.
The process for powder coating involves the spray drying the Epoxy polyester hybrid powder having a particular particle size distribution. The powder is filled in the main feed hopper having the pneumatically operated transfer pumps. The powder is sprayed on the galvanised steel sheet by means of plurality of automatic guns having a corresponding said transfer pump and a control unit. The transfer pumps are connected to the automatic spray guns by means of powder hoses. The number of automatic guns depends on the size of the appliance and accordingly the number of transfer pumps. Each automatic gun has different powder flow having a uniform air pressure, diameter and current. The different powder flow of the guns depends on the pneumatic pressure applied on the corresponding transfer pump of each automatic gun. Each automatic gun has a corresponding control unit which supplies current to the gun and thereby charges the
powder. The said powder is sprayed by means of the said automatic guns on the substrate. The manual gun is also used during the process having a particular air pressure and a current to ensure proper powder coating on the appliance. The said powder coated galvanised steel sheet moves to the curing oven for baking oven at a particular baking temperature for melting of the powder.
Accordingly the present invention relates to a process for the preparation of powder coated panel for home appliances comprises the following steps :
- taking the dried , rinsed and degreased substrate prepared galvanised steel
sheet.
- placing the said sheet in different positions in a cleaned class I chamber by
means of the overhead conveyor belt system.
- spraying the said powder through automatic guns provided at the further end
of the said chamber at different powder flow.
-maintaining the powder flow coming out of the main feed hopper at different powder flow by means of pneumatically operated transfer pumps and current supplied to the electrode of the automatic spray guns. 1. baking the powder coated galvanised steel sheet
Accordingly the present invention relates to an apparatus used for the preparation of powder coated panel for home appliances comprises:
- a cleaned class I chamber having a conveyor belt for holding the substrate
prepared galvanised steel sheet at the top end with a plurality of automatic
spray guns provided at the other end of the said chamber.
- means for energising the automatic spray guns
-means for controlling the flow and different pressure of powder coming out of
the automatic spray guns
-means for connecting the pneumatic transfer pumps with the automatic spray
guns.
- means for controlling the speed and duration of the conveyor belt system
- means for baking the powder coated galvanised steel sheet.The ultimate requirement of the of the subject invention is to meet all the quality specifications, the physical and chemical paint properties and to pass the tests like cross-hatch, coating hardness, conical mandrill, impact test, salt spray, humidity and warm water resistance.
The subject invention may better be understood with reference to accompanying drawings of the apparatus. However, the same should not be construed to restrict the scope of the application as they are for illustrative purposes only.
BRIEF DESCRIPTION OF THE DRAWINGS:-

1. Fig. 1 shows the apparatus used in the powder coating process. Detailed Description of the Invention:-
The present invention describes a process and apparatus used for powder coating the substrate prepared galvanised steel sheet to be used in home appliances.
The subject invention relates to a process for powder coating the galvanised steel sheet to meet all the paint quality specifications like no corrosion, high flexibilit
The degreased , rinsed substrate prepared galvanised steel sheet moving on the conveyor belt system is taken to the water drying oven and dried which is further taken and placed in a cleaned class I chamber provided with the overhead conveyor belt system for holding the said sheet for powder coating to be used for home appliance.
The said conveyor belt system moves at a speed of 3.3 meters/minute. The speed is verified by means of the stop watch and frequency of verification is once per month.
The said process involves the spray drying of epoxy polyester hybrid powder on the said sheet. The powder has the particle size distribution of The cleaned class I chamber is cleaned by vacuum cleaner and automatic spray guns , powder hoses are cleaned properly by means of compressed air
before starting the process. The actual charge at the gun tip is checked with the help of KV meter for all the automatic spray guns.
After spraying of powder on the cabinet of the appliance, the powder is taken to the curing oven for baking and melting of the opowder at a temperature of 220 +/- deg C. the temperature is verified by means of the temperature gauge and frequency of verification is once per shift.
The above process is not intended to limit the scope of the invention. While the particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications within the scope of the invention.
In the above process the powder is supplied to the guns from the main feed hopper by means of transfer pumps provided in the said main feed hopper wherein the powder flow is maintained between 0.8 to 2.4 bars.
In thesaid process for the preparation of powder coated panel for home appliance the control unit energises the electrode of the automatic guns provided in the said chamber wherein the current is maintained in the range of 40-45 micro ampere and the air pressure is maintained at a pressure 3.0-3.8 bars.
The above process is carried out in a device comprising :
- a cleaned class-1 chamber, having a conveyor belt for holding the substrate
at the top and a plurality of automatic spray gun provided at the other end of
the chamber;
- means for energising the spray guns;
- means for controlling the flow and different pressure of powder coming out
of the spray guns;
- means guns;
- means for connecting the pneumatic transfer pumps with automatic spray 'i ans for controlling the speed and duration of the conveyor belt system.
The said device of preparing a powdered coated panel for home appliance wherein the said chamber is maintained at class I cleaniness and the means for energising the automatic spray guns is a control unit.
The device for preparing a powdered coated panel for home appliance has the means for controlling the flow at different pressure of powder coming out of the spray guns are pneumatically operated transfer pumps wherein the said means for connecting the pneumatic transfer pumps with the automatic spray guns is a powder hose.
While particular embodiments of the present invention have been illustrated and described , it would be obvious to those skilled in the art that the various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intented to cover in appended claims all such changes and modifications within the scope of this invention.




WE CLAIM:-
1. A process for the preparation of powder coated panel for home appliance
comprises the following steps:-
- taking the dried rinsed and degreased substrate of galvanised steel sheet;
- placing the said sheet in different position in air cleaned chamber by means
of overhead conveyor belt system;

- spraying the said powder through automatic guns provided at the further
end of the said chamber having different powder flow;
- maintaining the powder flow coming out of main feed hopper at different
powder flow by means of penumatically operated transfer pumps, and
current- supplied to the electrode of the automatic guns.

2. A process for the preparation of powder coated panel for home appliance
as claimed in claim 1, wherein the powder is supplied to the guns from the
main feed hopper by means of transfer pumps provided in the said main feed
hopper.
3. A process for the preparation of powder coated panel for home appliance
as claimed in claim 1, wherein the powder flow is maintained between 0.8 to
2.4 bars.
4. A process for the preparation of powder coated panel for home appliance
as claimed in claim 1, wherein the control unit energises the electrode of the
automatic guns provided in the said chamber.
5. A process for the preparation of powder coated panel for home appliance
as claimed in claim 1, wherein the said current is maintained in the range of
40-45 micro ampere.
6. A process for the preparation of powder coated panel for home appliance
as claimed in claim 1, wherein the air pressure is maintained at a pressure
3.0-3.8 bars.
7. A device for preparing a powdered coated panel for home appliance as
claimed in claim 1, comprises:

- a cleaned class-1 chamber, having a conveyor belt for holding the substrate
at the top and a plurality of automatic spray gun provided at the other end of
the chamber;
- means for energising the spray guns;
- means for controlling the flow and different pressure of powder coming out
of the spray guns;
- means for connecting the pneumatic transfer pumps with automatic spray
guns;
- means for controlling the speed and duration of the conveyor belt system.

8. A device for preparing a powdered coated panel for home appliance as
claimed in claim 7, wherein the said chamber is maintained at class one
cleaniness.
9. A device for preparing a powdered coated panel for home appliance as
claimed in claim 7, wherein the said means for energising the automatic spray
guns is a control unit.

10. A device for preparing a powdered coated panel for home appliance as
claimed in claim 7, wherein the said means for controlling the flow at different
pressure of powder coming out of the spray guns are pneumatically operated
transfer pumps.
11. A device for preparing a powdered coated panel for home appliance as
claimed in claim 7, wherein the said means for connecting the pneumatic
transfer pumps with the automatic spray guns is a powder hose.
12. A process for the preparation of powder coated panel for home appliance,
substantially as hereinbefore described with reference to the accompanying
drawings.
13. A device for preparing a powdered coated panel for home appliances,
substantially as hereinbefore described with reference to the accompanying
drawings.

Documents:

539-del-2002-abstract.pdf

539-del-2002-claims.pdf

539-del-2002-correspondence-others.pdf

539-del-2002-correspondence-po.pdf

539-del-2002-description (complete).pdf

539-del-2002-drawings.pdf

539-del-2002-form-1.pdf

539-del-2002-form-19.pdf

539-del-2002-form-2.pdf

539-del-2002-form-26.pdf

539-del-2002-form-3.pdf


Patent Number 197401
Indian Patent Application Number 539/DEL/2002
PG Journal Number 51/2007
Publication Date 21-Dec-2007
Grant Date 27-Sep-2007
Date of Filing 08-May-2002
Name of Patentee WHIRLPOOL OF INDIA LIMITED, an Indian Company
Applicant Address 7TH FLOOR, ATMA RAM HOUSE, 1, TOLSTOY MARG, NEW DELHI-110001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 RITESH BHATIA WHIRLPOOL OF INDIA LIMITED, 28, N.I.T. FARIDABAD -121001, HARYANA, INDIA.
2 VIJAY SABHARWAL WHIRLPOOL OF INDIA LIMITED, 28, N.I.T. FARIDABAD-121001, HARYANA, INDIA.
PCT International Classification Number B05B 15/12
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA