Cookware and a method of forming same

Abstract: A method of forming a cooking surface on a cooking utensil having an aluminium substrate is disclosed which comprises the steps of hard anodizing substrate, spraying a particular layer of material which is preferably ceramic, aluminium oxide or stainless steel on the anodized layer and applying a non-stick coating. The presence of the particular layer provides a half spherical layer of particles which creates high peaks/deep valleys to provide an increased anchoring effect for the subsequently deposited non-stick layer.

Description: This invention relates to cookware having a non-stick cooking surface. It has been proposed, for example in the applicants' European Patent Applications 259056 entitled "Frying Pans" and 424072 entitled "Cookware" to provide various non-stick cooking surfaces for cookware. By far and away the most widely used and best known non-stick surface is that provided by a PTFE coating. Such coatings are applied to the interior surfaces of cookware and the cookware may, for example be made of a number of materials including aluminium. There are, however, problems in the abrasion resistance of such a PTFE coating since it is a relatively soft material and easily scratched. Furthermore, problems are encountered in attaching the PTFE coating to the aluminium substrate. The two European Patent applications mentioned above, the contents of which are incorporated herein by reference, disclose means for increasing the abrasion resistance and adhesion of a PTFE coating . It is an object of the invention to provide a cooking surface and a method of forming same which provides a more durable non-stick layer. According to the invention in a first aspect there is provided a method of forming a cooking surface on an aluminium cooking utensil having an aluminium substrate comprising the steps of hard anodizing the substrate and applying a non-stick coating thereto, characterised in that a particulate layer of material is sprayed on the anodised layer prior to applying the non-stick coating. Preferably, the layer of material is sprayed by arc spraying, plasma spraying or flame spraying and the material used is selected from ceramics, aluminium oxide or stainless steel. In particular, arc spraying is used for stainless steel, while plasma spraying or flame spraying is used for either ceramics,aluminium oxide or stainless steel. The presence of the sprayed layer provides a half spherical layer of particles on a hard anodized layer which creates high peaks/deep valleys to provide an increased anchoring effect for the subsequently deposited non-stick layer. Preferably the non-stick layer is formed by conventional means, for example with the use of a primer coat followed by PTFE intermediate and top coats. Preferably the substrate is roughened or etched. According to the invention in a further aspect there is provided a cooking utensil having a cooking surface formed in accordance with the method recited above. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic cross sectional view of a cooking surface of a cooking utensil formed in accordance with a first embodiment of the invention. Figure 2 is a view similar to figure 1 of a cooking utensil formed in accordance with a second embodiment of the invention. Figure 3 is a view similar to figure 1 of a cooking utensil formed in accordance with a third embodiment of the invention. Figure 4 is a view similar to figure 1 of a cooking utensil formed in accordance with a fourth embodiment of the invention. The method of the invention is substantially the same as that disclosed in European Patent Application 424072 in which the surface layer 12 of an aluminium substrate 10 is hard anodized. However, at this stage, an additional method step is added in accordance with the present invention, namely that a layer of material 14 is sprayed onto the hard anodized layer 12. The spraying method may be of any suitable form, for example arc spraying, plasma spraying or flame spraying and the material may be ceramic, aluminium oxide or stainless steel. In particular, arc spraying is used for stainless steel, while plasma spraying and flame spraying is used for either ceramics, aluminium oxide or stainless steel. Spraying does not provide a flat layer on the hard anodized material but, rather, provides a distributed array of half-spherical particles which provide a highly undulating structure with high peaks being formed by the particles and deep valleys therebetween. Following the application of the sprayed layer, a PTFE coating is applied in the usual way, namely by the application of a primer layer 16, for example polyphenylene sulphide (PPF) or PES resin and following this, two layers of PTFE, an intermediate coat 18 and top coat 20. Thereafter, the whole is cured in a conventional manner by heating to approximately 427°C which cures the primer and the PTFE to provide the non-stick surface. The particle layer by providing such an uneven surface increases the ability of the non-stick layer to anchor itself to the aluminium substrate thus improving the durability of the coating. In both figures 1 and 2, the aluminium substrate 10 is roughened, for example by grit blasting, chemical etching or electro chemical etching, in accordance with the method disclosed in European Patent Application 424072. Because of the high peak/deep valley effect, however, we can eliminate the previous roughening process of an aluminium substrate , for example see figures 3 and 4. Figure 2 is the same as figure 1 whilst figure 3 is the same as figure 4, save that figures 2 and 4 show the invention applied to an aluminium substrate having a saw-tooth pattern of similar form to that disclosed in European Patent application 259056 which provides both the advantages of increased durability of the present invention together with increased wear resistance of the PTFE layer as a whole.

Claims: A method of forming a cooking surface of a cooking utensil having a aluminium substrate (10) comprising the steps of hard anodizing the substrate (10) and applying a non-stick coating (16,18,20) thereto, characterized in that a particulate layer of material (14) is sprayed on the anodized layer (12) prior to applying the non-stick coating (16,18,20). A method as claimed in claim 1 wherein the layer of material is sprayed by arc spraying, plasma spraying or flame spraying. A method as claimed in claim 1 or claim 2 wherein the sprayed material is selected from ceramics, aluminium oxide, or stainless steel. A method as claimed in anyone of the preceding claims wherein the non-stick layer is formed from PTFE. A method as claimed in claim 4 wherein the PTFE layer is formed from a primer coat followed by intermediate and top coats. A method as claimed in anyone of the preceding claims wherein the substrate is roughened or etched prior to hard anodizing. A method as claimed in anyone of the preceding claims wherein the substrate is formed with a plurality of peaks and troughs. A method as claimed in claim 7 wherein the peaks and troughs give the substrate a surface having a saw-tooth pattern. A cooking utensil having a cooking surface formed in accordance with the method of any one of the preceding claims. A cooking utensil having a cooking surface formed from hard-anodized aluminum (12) and having a particular layer of material (14) sprayed thereon and a non-stick coating (16,18,20) applied to the sprayed layer. A cooking utensil as claimed in claim 10 wherein the particulate material is ceramics, aluminium oxide or stainless steel. A cooking utensil as claimed in claim 10 or claim 11 wherein the substrate is provided with a pattern of peaks and troughs.

Inventors: CHENG STANLEY KIN-SUI, CHENG, STANLEY KIN-SUI
Applicants: MEYER MANUF CO LTD, MEYER MANUFACTURING CO., LTD
Application year: 1993
Main classification: A47J37
IPC codes: A47J27, C25D11, B05D5