Title of Invention

"A PROCESS FOR THE MANUFACTURE OF DECORATIVE-STAINLESS STEEL ARTICLES"

Abstract

A process for the manufacture of a decorative steel srticle which comprises washing stainless steel preform of desired size and shape with a conventional washing agent, subjecting the washed preform to a deoxidizing temperature to remove impurities therefrom, applying a conventional base coat to said preform, if desired, applying in any conventional manner, lacquer on said base coat to impart thereto a smooth finish, applying on said coated preform a transfer foil of the kind as described in the specification or an image to be imprinted on the said preform, removing any air bubbles present therein, heating the transfer foil pasted preform, allowing the preform to cool and removing the transfer foil to obtain the decorative stainless steel article having printed thereon the desired design or image.

Full Text

BACKGROUND OF THE INVENTION The present invention relates to a novel process for the manufacture of decorative stainless steel articles. More particularly, the present invention relates to a process for the manufacture of stainless steel articles having imprinted or laminated thereon colourful images and designs. Stainless steel articles of particular interest manufactured in accordance with the process of the present invention are table and kitchenware such as dishes, casseroles and utensils. The designs and images imprinted on the stainless steel articles by the process of the present invention are cf permanent nature and resistant to erasure, fading or peeling under normal conditions. Prior art discloses several processes for imprinting designs and. images on materials other than stainless steel. Attempts to imprint permanent images and designs on smooth metallic surfaces such as stainless steel have always failed to meet with success. Apart from the fact that imprinting designs on stainless steel articles is highly expensive and therefore, not commercially viable, the designs imprinted tend to crack, peel and fade even under a normal careful usage. It is therefore, an object of the present invention to provide a process for the manufacture of decorative stainless steal articles which is simple to carry out and is commercially and economically viable. It is a further object of the present invention to provide a process for the manufacture of decorative stainless steel articles, which are highly aesthetic. It is a further object, of the present invention to provide a process, which successfully imprints aesthetic designs and images on stainless steel articles with a uniform and smooth or matt finish. It yet another object of the present invention to provide permanent and aesthetic designs on stainless steel articles which are resistant to peeling, fading, discolouring arid erasure under normal conditions of usage and wear and tear. These and other objects of the present invention are achieved by the process of the present invention which is carried out under a combination of novel and carefully selected and controlled process parameters and conventional art of employing transfer foils to transfer images and designs to the articles. SUMMARY OF THE INVENTION The present invention provides a process for the manufacture of decorative stainless steel articles which comprises washing a stainless steel preform with a conventional washing agent, subjecting the washed preform to a temperature in the region of from 120 to 140 C to remove impurities therefrom, applying, if desired, a conventional base coat to said preform, affixing a transfer foil containing the design to be imprinted on to said base coated preform, removing any air bubbles present therein, and heating the preform to a temperature between 140 to 160 C, allowing the preform to cool and removing said transfer foil to obtain said decorative stainless steel article having the desired design imprinted thereon. The process of the present invention has several industrial applications. It can be applied to any stainless article of industrial use where a permanent aesthetic appeal is an important factor. It can also be applied to various household and commercial items such as dishes, utensils, casseroles, wall ornaments, artificial jewelleries and the like. Compared to ceramic and porcelain, stainless steel per se has a very wide industrial application by virtue of it being unbreakable and rust proof. The process of beautifying it with permanent images and designs, which are extremely appealing to the naked eye further adds considerable value to the alloy the aesthetics of which hitherto was restricted to mirror finish. DETAILED DESCRIPTION OF THE PREFFERRED EMBODIMENT The present invention provides a process for manufacturing decorative stainless steel articles. It utilizes a step of imprinting colourful designs, pictures, images and ornamentations on to stainless steel in a permanent fashion by a unique and novel step of transferring images from a transfer foil under carefully controlled heat treatment. The invention will now be described in a greater detail with reference to a non-limitative preferred embodiment for manufacturing a decorative dish, which is for the purpose of illustration only. It will be readily apparent to a person skilled in the art that various other embodiments of the process can be carried out for the manufacture of articles other than that described in the preferred embodiment without deviating from the spirit and scope of the invention. From a non magnetic stainless steel sheet, circles, hereinafter referred to as preforms, are cut. The size and gauge are not critical and are purely dictated by the size and thickness of the finished article. required. The preforms are thereafter, pressed on conventional moulds and dies to obtain a dish. Preferably, double action presses are used. The dish is then thoroughly polished to make the surface smooth since a rough and uneven surface can adversely affect the application of the base coat paint and can also leave undesirable gaps in the finish of the final product. The polished dish is then washed with a conventional cleaning agent, preferably, a conventional thinner and thereafter subjected to a heat treatment in furnace. Most preferably, industrial thinner such as nitre cellulose is employed. Care is taken to ensure that that the temperature of the furnace is maintained between 120 to 140 C so that any impurity present on the surface of the dish is removed. The temperature itself is not critical but merely a matter of convenience to ensure that the possibility of any impurity present on the dish surface after the washing step is eliminated. Also, at this temperature, the surface of the dish gets deoxidised which improves the surface bonding between the paint and steel surface and also ensures better and durable printing. After heat treatment, the surface of the dish is painted with a conventional industrial paint to form a base coat. Good results are obtained by painting with a spray gun using a stoving paint, which is a mixture of pigment, and enamel oil., The base coated dish is baked at a conventional baking temperature, the actual temperature and the duration depending upon the industrial paint employed. Best results are obtained if the baking temperature is in the region of 160 to 180 C for about 45 minutes, preferably for 15 to 25 minutes, most preferably for about 20 minutes. Baking ensures that the paint remains permanent and does not. peel off from the smooth metallic surface. Once the base coat is firmly baked on the dish,, the dish is removed from the furnace and air cooled. To obtain an excellent smooth finish, the painted dish is sprayed with a special TSA lacquer and passed through a furnace at 160 to 180 C for about 20 minutes and thereafter air cooled. Transfer foil containing the desired images or designs is then affixed to the lacquered dish with a conventional glue, preferably, glue diluted with water. Transfer foil employed is preferably a very thin type cf foil made of release paper on which oil-based inks are used. These inks have the property of leaving their impressions on select surfaces such as porcelain, china, plastic etc. However,, for the first time, the applicants have been successful in transferring images on a stainless steel surface by employing carefully selected temperature range, washing steps and diluted glues. Optimum results are obtained if the glue: water ratio is maintained at 1:20. Once the transfer foil is affixed to the dish, air is vacuumed out to eliminate all air bubbles. Thereafter the dish is subjected to a temperature of 140 to 160 C and air cooled. Using a 3 D Converter foil transfer machine with a conveyor belt ensures uniform heating of the machine from all directions. Ideally, the dish is heated for about 15 to 45 minutes, preferably for about 20 minutes. The temperature and duration are of critical importance to ensure complete and uniform transfer of images on the dish surface. Thereafter, the dish is removed from the machine followed by the removal of the foil from the dish. The dish has the desired image or design transferred thereon. We claim: 1. A process for the manufacture of a decorative steel article which comprises washing stainless steel preform of desired size and shape with a conventional washing agent, subjecting the washed preform to a deoxidising temperature to remove impurities therefrom, applying a conventional base coat to said preform, if desired, applying in any conventional manner, lacquer on said base coat to impart thereto a smooth finish, applying on said coated preform a transfer foil of the kind such as herein described containing the desired design or image to be imprinted on said preform, removing any air bubbles present therein, heating the transfer foil pasted preform to a temperature between 140 to 160°C, allowing the preform to cool and removing the transfer foil to obtain said finished decorative stainless steel article having printed thereon the desired design or image. 2. A process as claimed in claim 1 wherein said preform is a shaped article. 3. A process as claimed in claim 2 wherein said shaped article is a dish, utensil or a casserole. 4. A process as claimed in any preceding claim wherein said deoxidizing temperature is preferably between 120 to 140°C. 5. A process as claimed in any preceding claim wherein said preform is polished prior to washing it. 6. A process as claimed in any preceding claim wherein said washing agent is a conventional thinner, such as nitrocellulose. 7. A process as claimed in any preceding claim wherein said conventional base coat is an industrial paint. 8. A process as claimed in claim 7, wherein said paint is a stoving paint comprising pigment and enamel oil. 9. A process as claimed in claim 7 or 8 wherein the painted preform is subjected to baking. 10. A process as claimed in claim 9, wherein the baking temperature is between 160 to 180°C. 11. A process as claimed in claim 9 or 10 wherein the baking is carried out for a period of 45 minutes, preferably, 15 to 25 minutes and most preferably, for about 20 minutes. 12. A process as claimed in claim 11, wherein said baked preform is coated with a special TSA lacquer. 13. A process as claimed in claim 12 wherein said lacquered preform is heated at a temperature between 160 to 180°C for about 20 minutes and thereafter, air cooled. 14. A process as claimed in any preceding claim wherein said transfer foil comprises a very thin foil of release paper with oil based ink. 15. A process as claimed in any preceding claim wherein said transfer foil is affixed on said preform with a diluted colourless glue. 16. A process as claimed in claim 15 wherein said colourless glue has a glue : water ratio of 1 : 20. 17. A process for the manufacture of a decorative stainless steel article substantially as hereinbefore described.

Documents:

2229-del-1998-abstract.pdf

2229-del-1998-claims.pdf

2229-del-1998-correspondence-others.pdf

2229-del-1998-correspondence-po.pdf

2229-del-1998-description (complete).pdf

2229-del-1998-form-1.pdf

2229-del-1998-form-13.pdf

2229-del-1998-form-19.pdf

2229-del-1998-form-2.pdf

2229-del-1998-form-3.pdf

2229-del-1998-form-4.pdf

2229-del-1998-petition-138.pdf