Patent Application
20130017410
1. Field of the Invention
The present invention relates to multi-ply bonded metal composites of aluminum cookware articles such as pots and pans and methods for making them.
2. Description of the Related Art
Cookware, such as pots and pans, has been manufactured from aluminum alloy for a considerable time. Aluminum alloy has been a popular metal for the construction of cookware because of its physical properties. Aluminum alloy has a high degree of thermal conductivity, is relatively strong, formable, and is suitable for the application of numerous decorative and functional coatings. The conventional aluminum cookware is usually made from a single layer of aluminum alloy which may be anodized on the outside surface and given a non-stick surface on the inside, cooking surface. Oftentimes such cookware is made from 3003 aluminum alloy or a like aluminum alloy which offers higher strength than purer aluminum such as 1100 aluminum.
It is also well known to manufacture cookware, such as pots and pans, made from composite bonded metal layers of stainless steel with an aluminum core layer or with a copper core layer to improve the thermal conductivity of the composite, as evidenced by U.S. Pat. No. 4,004,892 to Ulam and U.S. Pat. No. 6,267,830 to Groll. It is also known to provide a composite bonded metal construction with a core layer of stainless steel or titanium to provide a heat diffusion layer or “heat dam” to provide a more even heating distribution to the cooking surface as evidenced by U.S. Pat. No. 6,926,971 to Groll.
It is also known to use an “Alclad” layer or layers of pre-bonded aluminum layers in the manufacture of cookware. The Alclad product may consist of a three-layer composite of inner and outer layers of a relatively pure layer of aluminum such as 1100, 1130, 1145 aluminum bonded to a core layer of a stronger aluminum alloy such as 3003, 3004, or 5005 aluminum alloy. The purer aluminum layers offer superior bonding properties for bonding to other dissimilar metal layers such as stainless steel or copper, for example, as disclosed in U.S. Pat. No. 4,246,045 to Ulam. It is also known that Alclad pre-bonded material is produced as a two-layer product consisting of a relatively pure aluminum layer of the 1XXX series, roll-bonded to an aluminum alloy of 3003 or 3004 aluminum alloy for use in cookware, where the aluminum alloy forms the outer layer of the cookware and the pure aluminum is bonded to a layer of stainless steel or copper, for example.
Briefly stated, the present invention, in its basic form, is a lightweight, three-layer bonded composite comprising two layers of a higher strength aluminum alloy, such as 3003 (or similar aluminum alloy), bonded to two sides of a central core layer of a higher purity aluminum of the 1XXX series, such as 1050, 1100, 1145 or the like to make a three-layer bonded aluminum composite which is then formed, as by drawing, hydroforming, or spinning, or the like, into a desired shape for cookware, such as a pot or pan. The aluminum alloy outer layers are well suited for strength and formability, as well as suitable for the application of surface treatments, such as non-stick coating or anodizing. The central core layer of higher purity aluminum has a higher coefficient of thermal conductivity than the outer aluminum alloy layers to provide improved uniform heating characteristics for the cookware by minimizing hot spots on the cooking surface, strength and light weight. The present invention further contemplates the use of additional combinations of the above-described three-layer bonded composite in the manufacture of five-layer or seven-layer all aluminum cookware products, for example. These, as well as other attributes and advantages of the present invention, will become more apparent when reference is made to the following drawings when taken with the detailed description thereafter.
With reference now to the drawings,
The use of the higher purity aluminum core 10 provides higher thermal conductivity in the core of the composite so as to improve the performance of the cookware by yielding more uniform heat distribution at the cooking surface. This uniform heating feature prevents hot spots from developing on the cooking surface to permit more even cooking and to provide a longer life for the non-stick coating 2. A non-stick coating will tend to thermally degrade more rapidly in the area of high temperature hot spots. Hence, the life of the non-stick coating 2 is enhanced in the present invention as well as cooking performance. Uniform temperature across the cooking surface also reduces the probability of burning food and makes clean-up easier.
The aluminum alloy layers 5, 15, and core 10 of higher purity aluminum are bonded by any of the well-known commercial methods such as roll-bonding, for example. The relative thickness ratios of the outer layer 5/core layer 10/outer layer 15 may vary from about 10%/80%/10% (100% total thickness) to about 45%/10%/45%. A presently-preferred thickness ratio is about 16%/68%/16%. The thickness ratios of the outer layers 5 and 15 may also be an asymmetric arrangement, such as, for example, 20%/70%/10%. Also, the two aluminum alloy layers 5 and 15 do not need to be comprised of the same alloy. For example, one of the aluminum alloy layers could be 3003 aluminum alloy while the other could be 3002 or 3004 aluminum alloy or the like. A typical overall thickness for the composite layers 5, 15, and 10 is on the order of about 0.130″ to about 0.180″. Preferably, the overall thickness is about 0.160″.
As mentioned previously, the aluminum alloy layers 5 and 15 are well suited for strength, formability, and for the application of surface treatments. The small amounts of alloy additions, such as iron, copper, manganese, magnesium, or silicon, to mention a few, which bring about these desirable characteristics, also give the outer layers 5 and 15 a lower coefficient of thermal conductivity than a higher purity aluminum, such as in core layer 10. Higher purity core layer 10 is, by its nature, not as strong as an aluminum alloy or as suitable for forming or coating as the alloyed exterior layers 5 and 15 but, as mentioned, it has a desirable higher coefficient of thermal conductivity which makes it suitable for use as the core layer 10 in the bonded composite. By way of example, the coefficient of thermal conductivity of 3003 aluminum alloy is 162 W/m-K at 25° C., while the coefficient of thermal conductivity of higher purity 1145 aluminum is 227 W/m-K at 25° C. Hence, the higher purity aluminum has a coefficient of thermal conductivity about 40% greater than the aluminum alloy which makes it ideally suited for a core material in the composite cookware.
In order to further enhance the cooking characteristics and physical properties, such as strength, weight, durability, and thermal properties of the cookware, additional layers of aluminum alloy and higher purity aluminum may be bonded to the basic three-ply composite 1 shown in
These further embodiments are depicted in
A still further embodiment of the present invention is a seven-ply bonded composite 40 depicted in
The various embodiments described herein, namely, three-ply, five-ply, and seven-ply bonded composites, as well as others, such as nine-ply composite or more, may occur to those skilled in the art, without departing from the spirit of the invention, and provide cookware with enhanced cooking performance and strength while preserving the light weight of aluminum compared with conventional cookware containing heavier copper or stainless steel layers.
This application claims priority to U.S. Provisional Application No. 61/507,167 filed Jul. 13, 2011, which is incorporated herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61507167 | Jul 2011 | US |
