AU773579B2 - Improvements in forming metallic laminates - Google Patents

Description

Our Ref:7618710 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): Address for Service: Breville Pty Ltd Building 2, Port Air Industrial Estate 1A Hale Street Botany New South Wales 2019 Australia DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Improvements in forming metallic laminates Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 P:\WPDOCSCAB\SPECI\751380.doc-O&M0WI -1- IMPROVEMENTS IN FORMING METALLIC LAMINATES The present invention relates to methods of forming metallic composites incorporating laminates and more particularly, composites having laminates of aluminium and stainless steel.

Modem cooking appliances such as saucepans, frypans and the like are preferably formed with a stainless steel cooking surface or a "non-stick" covering of an aluminium utensil. Stainless steel cooking surfaces are extremely durable and easier to maintain in good condition by use of abrasive cleaners while providing an inert cooking surface.

Additionally, non-stick coatings have a temperature limit of around 265°C before being degraded while a stainless steel surface can operate at 400 0 C without difficulty. Such *benefits compare more than favourably with temperature sensitive "non-stick" coating materials that can be rapidly damaged by incorrect abrasive cleaning procedures or overheating.

A drawback with stainless steel has been its cost when compared with aluminium while its heat transmission properties also suffer in comparison. These disadvantages have been addressed by forming aluminium and stainless steel laminates under high pressure or, more expensively, copper-cored stainless steel cooking appliances.

The stainless steel and aluminium laminates when used for electric frypans and the like have required the heating element(s) to be adhered to the underside aluminium surface by such as brazing. This adds a production cost to the formation of such appliances when compared with imbedding of an electrical heating element into an element groove on the underside of an entirely aluminium appliance formed by, say, die-casting.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated integer or step or group P:\WPOOCSCCAB\SPECI7513t00.doc-8O& M1 -2of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The present invention in one form proposes a method of forming an aluminium and stainless steel composite material comprising placing a sheet of aluminium and stainless steel laminate in an aluminium die-casting mould with the exposed stainless steel surface against a wall of the mould and adding aluminium to the mould such that the added aluminium bonds with the exposed aluminium surface of said laminate to form said composite material.

By means of the present invention it becomes possible to form aluminium posts having element grooves onto a sheet of stainless steel and aluminium laminate; whereafter an electrical heating element can be fitted in the element groove in the conventional manner of producing an aluminium appliance.

An embodiment of the present invention provides a dished or wok like aluminium and stainless steel composite laminate which is mounted in an aluminium die-casting mould having locations in the mould for forming one continuous element groove post onto the aluminium backing sheet to the stainless steel surface, wherein the element groove post is located around the base of the dish shape as well as up the walls of the dish toward an upper perimeter of the dish. By this embodiment it becomes readily possible to locate the electrical heating element at virtually any position between the base and the upper perimeter of the dish shaped aluminium undersurface of an aluminium and stainless steel composite wok. Temperature control of not only the bottom of the wok but also up its wall toward the perimeter provides a substantial advantage in more closely approaching the rapid cooking characteristics of a conventional wok when used over an intense gasfired burner.

The present invention will now be described by way of example with reference to the accompanying drawings, in which P:\WPDOCS\CAB\SPECI\75138O0.dooM)AIl -3- Figure 1 is a cross-sectional view through a mould adapted to form a composite in accord with an embodiment of the present invention; Figure 2 is a view similar to Figure 1 but showing an embodiment for the formation of a wok or similar cooking appliance; Figure 3 is a cross-sectional view similar to Figure 1 but showing an embodiment for the formation of a ribbed grilling surface; and Figure 4 is a cross-sectional view similar to Figure 1 but showing an embodiment for the formation of an open pored or slotted grilling plate formed with spaced apart grill bars.

As shown in Figure 1, aluminium 10 and stainless steel 11 sheets are laminated in a 15 known way then fitted into aluminium die-casting mould 12. Typically, the stainless steel sheet 11 is 0.5 mm thick while aluminium sheet 10 is 4 mm thick. Appropriate laminates are readily commercially available and currently employed in the production of cookware items as will be understood by the addressee. Laminate thicknesses can be varied as desired within the requirements for the end use of the final form of composite material.

With the laminate, composed of sheets 10 and 11, fitted into mould 12, aluminium is injected or poured into the mould cavity 13 to bond with the exposed surface of aluminium sheet 10 and form posts 14 in cavity 13. The mould 12 can then be separated to release the composite of stainless steel and aluminium which includes aluminium post 14 defining an element groove In one embodiment molten aluminium at about 750 C is gravity fed into the mould containing the shaped laminate.

P:\WPDOCS\CABSPECI\751300o.dto4 MOI -4- The embodiment of Figure 2 shows a mould for forming an electrical wok in accordance with the method of the present invention. In this embodiment like parts are similarly numbered to those shown in Figure 1.

Post 14 is continuous as between lower level 14' and upper level 14" nearer to the perimeter of the bowl or wok-shaped cooker 16. An example of the path for post 14 can be seen from our United States Patent No. 5778768.

Figures 3 and 4 show further mould embodiments for the formation of different forms of grilling surfaces employing the method of formation of a composite material in accordance with the present invention. In those drawings like parts are numbered as per the numbering used for those parts in Figure 1.

Finally, it is to be understood that the inventive concept in any of its aspects can be incorporated in many different constructions so that the generality of the preceding description is not to be superseded by the particularity of the attached drawings.

Various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.

Claims (7)

1. A method of forming an aluminium and stainless steel composite material comprising placing a sheet of aluminium and stainless steel laminate in an aluminium die- casting mould with the exposed stainless steel surface against a wall of the mould and adding aluminium to the mould such that the added aluminium bonds with the exposed aluminium surface of said laminate to form said composite material.

2. A method as claimed in claim 1, wherein the added aluminium is injected or extruded into the mould.

3. A method as claimed in claim 1, wherein the added aluminium is gravity fed in molten form into the mould.

4. A method as claimed in claim 3, wherein the molten aluminium is at approximately 750°C. An electrically powered cooking appliance when made according to the method of any one of the preceding claims.

6. A cooking appliance as claimed in claim 5 wherein the added aluminium is moulded to form posts for supporting an electrically powered heating element.

7. An appliance as claimed in claim 5 or 6, wherein the appliance is a wok.

8. A method of forming an aluminium and stainless steel composite material substantially as hereinbefore described with reference to the accompanying drawings. 20 9. An electrically powered cooking appliance when made according to claim 8. DATED this 3 0 th day of March, 2004. BREVILLE PTY LTD 25 By Its Patent Attorneys DAVIES COLLISON CAVE