Abstract:
Hard anodized aluminum cookware has either a copper or stainless steel mesh embedded in the base. Copper mesh can be embedded in the bottom or base of the cookware prior to the anodizing process to enhance thermal conductivity and improved cookware&#39;s capacity to vertically spread heat. In contrast, stainless steel mesh is embedded in hard anodized aluminum cookware after anodizing, making the cookware suitable for use with the induction ranges or burner&#39;s.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of priority to the US Provisional Patent Application of the same title that was filed on Mar. 20, 2012, having application Ser. No. 61/613,337, which is incorporated herein by reference. 
         [0002]    The present application also claims the benefit of priority to the US Provisional Patent Application of the same title that was filed on Sep. 24, 2012, having application Ser. No. 61/705,036, which is incorporated herein by reference. 
         [0003]    The present application also claims the benefit of priority to the International (PCT) patent application that was filed on 12 Mar. 2013, having application serial no. PCT/US13/30537 and is incorporated herein by reference. 
     
    
     BACKGROUND OF INVENTION 
       [0004]    The present invention relates to a cookware article, and in particular to pots and pans that are warned substantially of anodized aluminum. 
         [0005]    While many forms of cookware vessels utilize a combination of metals, anodized aluminum cookware is generally formed entirely of aluminum. Additional metals, such as magnetic ferrous materials, enable the use of the anodized cookware with induction heating sources, which rather than providing a hot surface or flame to transfer heat to the vessel, directly heat the vessel by the transfer of energy in the electromagnetic radiation. The electromagnetic radiation is generated by conductive coils in the induction heating source, which upon entering the skin layer of metal induce eddy currents that cause resistive heating in the cookware vessels bottom. 
         [0006]    While copper is much more thermally conductive than aluminum, it&#39;s incorporation into aluminum requires sophisticated fabrication of the sheet stock used to form the cookware vessel. 
         [0007]    Anodized aluminum cookware, although it generally requires a bonded base of magnetic metal for induction cooking, has the benefit of very hard aluminum oxide exterior surfaces formed during anodizing to provide non marring finishes. Although other metals can be used in such cookware to provide induction capability, the aggressiveness of the acidic anodizing solution used to create the aluminum oxide coating usually necessitates additional steps of masking the additional metals layers that would be bonded to the base. 
         [0008]    It is therefore a first object of the present invention to provide anodized cookware, which benefit substantially from the harness and durability of the aluminum oxide on the interior and exterior surfaces that incorporates additional metals that provide other benefits. 
         [0009]    It is a further objective of the invention to provide such benefits with a minimum additional manufacturing steps and costs. 
       SUMMARY OF INVENTION 
       [0010]    In the present invention, the first object is achieved by providing an article of cookware, comprising a substantially horizontal bottom, having an interior bottom surface and an exterior bottom surface on the side opposing the interior bottom surface, substantially upright sidewall extending upward from and encircling said bottom to form a fluid retaining interior region, wherein a metal mesh is embedded in the exterior bottom surface, and the vessel other than the metal mesh is formed substantially of aluminum or an alloy of aluminum and has one or more interior and exterior surface portions covered by an aluminum oxide layer. 
         [0011]    A second aspect of the invention is characterized in that the metal mesh is copper and is partially exposed on the exterior bottom surface. 
         [0012]    Another aspect of the invention is characterized in that the metal mesh is stainless steel and is partially exposed on the exterior bottom surface. 
         [0013]    Another aspect of the invention is characterized by providing a process for forming such cookware vessels, the process comprising the steps of providing an aluminum disk, providing a stainless steel mesh, deep drawing the aluminum disk to form a vessel capable of retaining fluid, the vessel having an interior bottom surface and an exterior bottom surface, anodizing the aluminum vessel, providing a compression mold having a male interior member and a female exterior member, wherein the male interior member number substantially conforms to the shape of the interior bottom of the anodized aluminum vessel and has a textured surface, placing the stainless steel mesh and the anodized aluminum vessel  400  in the compression mold with the stainless steel mesh disposed between the female exterior member and the exterior bottom of the anodized aluminum vessel bottom, and compressing the anodized aluminum vessel between the male and female members of the compression mold so as to impart the textured surface of the male member to the interior surface of the anodized aluminum vessel and embed the stainless steel mesh into the exterior bottom portion of the anodized aluminum vessel. 
         [0014]    Another aspect of the invention is characterized by providing another process for forming such cookware vessels, the process for forming a cookware vessel, the process comprising the steps of providing an aluminum disk, providing a copper mesh, deep drawing the aluminum disk to form a vessel capable of retaining fluid, the vessel having an interior autumn surface and an exterior bottom surface, providing a compression mold having a male interior member and a female exterior member, wherein the male interior member substantially conforms to the shape of the interior bottom surface of the vessel and the female exterior member substantially conforms to the shape of the exterior bottom surface of the vessel, placing the copper mesh on the aluminum vessel in the compression mold with the copper mesh disposed between the female exterior member and the exterior bottom of the aluminum vessel bottom, compressing the aluminum vessel between the male and female members of the compression mold so as to embed the copper mesh into the exterior bottom of the aluminum vessel, anodizing the aluminum vessel and polishing the bottom of the anodized aluminum vessel to remove oxide formed on the copper mesh. 
         [0015]    The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a perspective view of an inverted cookware article showing the embedding of a metal mesh into the exterior bottom cooking surface. 
           [0017]      FIG. 2A through 2F  are combination of plan and side elevation views in the steps of forming a metal mesh that can be embedded into the exterior bottom cooking surface of a cookware article. 
           [0018]      FIG. 3  illustrates via a cross-sectional elevation a first step in forming the cookware article shown in  FIG. 1  from a metal sheet. 
           [0019]      FIG. 4  illustrates via a cross-sectional elevation a step in embedding a metal mesh into the bottom exterior surface of the cookware, whereas  FIG. 4B  is an expanded view of a portion of  FIG. 4A . 
           [0020]      FIG. 5A  is a cross-sectional elevation of the resulting cookware from the embedding step in  FIG. 4 , whereas  FIG. 5B  is an expanded view of a portion of  FIG. 5A . 
           [0021]      FIG. 6  illustrates via a cross-sectional elevation an alternative embodiment of the step of embedding the metal mesh into the bottom exterior surface of the cookware. 
           [0022]      FIG. 7A  is a cross-sectional elevation of the resulting cookware from the embedding step in  FIG. 6 , whereas  FIG. 7B  is an expanded view of a portion of  FIG. 7A . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring to  FIGS. 1 through 7  wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved anodized cookware vessel having embedded metal mesh, generally denominated  100  herein. 
         [0024]    In accordance with the present invention, as illustrated in  FIGS. 1 ,  5  and  7 , a cookware article  100  has a bottom portion with the exterior surface  101  facing downward and the opposing bottom interior surface  102  facing upward. Surrounding walls extend substantially upright from the bottom portion to provide a vessel capable of holding a fluid, the walls terminating at a rim  105 . The interior surface of the surrounding wall is designated  102  while the exterior surface of the surrounding wall is designated  103 . A metal mesh  110  is embedded in the exterior bottom surface  101 . The cookware article  100  is formed substantially of aluminum, including alloys of aluminum, and has an anodized exterior surface  109  (see  FIGS. 5   b  and  7 B), consisting substantially of aluminum oxide. 
         [0025]    In another embodiment of the invention illustrated in  FIGS. 2  A through F, the metal mesh  110  is optionally formed by starting with a planar metal sheet  20 . As shown in  FIG. 2A , an overlapping array of rows of substantially vertical slits  21  are formed in the metal sheet. In the next step,  FIG. 2B , the thus perforated metal mesh  20  is expanded vertically in the direction of arrow  201 , which is perpendicular to the slit axis, wherein the slits open up forming rhombohedra with holes  111  shown in plan view in  FIGS. 2B &amp; 2E .  FIG. 2C-D  are orthogonal cross-sectional elevations of the mesh  110  shown in  FIG. 2B , whereas  FIG. 2F  is a cross-sectional elevation of the expanded mesh shown in  FIG. 2E  in plan view. 
         [0026]      FIGS. 3 through 5  illustrate another embodiment of the invention as a process for forming the cookware article  100  illustrated in  FIG. 1  in which the cookware vessel is initially formed in  FIG. 3  from a planar sheet of aluminum metal  10  forming pre-form  400 , which can then be anodized on substantially all the surfaces, including the exterior bottom  401  and the interior bottom surface  402 . Metal sheet  10  is deep drawn between male  310  and female  320  generally mated forming dies, with the perimeter of sheet  10  clamped at arrows  320 . The lower forming die  302  has a central portion that moves downward in coordination with the upper male forming die  301 . The forming dies  301  and  302  can also provide a slight convex shape to the interior bottom  402  of the vessel pre-form  401 , as well as optionally shape the rim  105 . As shown in  FIG. 4 , another pair of mated male  410  and female  420  compression forming dies are then used to force the mesh  110  placed on the upper surface  421  of the lower female forming die  420  into the exterior bottom surface  401  of the pre-form vessel  400  as they assert pressure or compression force of the mesh  110 , which then deforms the portion of surface  401  in contact therewith admitting the mesh into the deformed portions, with the pressure from the compression molds  410  and  420  closing the deformed region around the mesh  110  via openings  111 . Hence, as shown in  FIG. 5 , the metal mesh  110  is embedded in the exterior bottom surface  101  of the finished vessel  100 . It should be appreciated that the forming dies  410  and  420  can also be used to shape or further shape the bottom surface  401  and  402 , as well as the resulting rim region  105  of the finished vessel  100 . it was surprising discovered that the vessel pre-form  400  could be anodized before the embedding step shown in  FIG. 4 , when the mesh  110  was stainless steel, without destroying, delaminating or de-bonding the surfaces thereof that came in contact with the mesh  110  or forming dies  410  and  420 . The embedded stainless steel survived multiple shock heating and cooling cycles without de-bonding or distortion of either the stainless steel or the vessel. Typically the vessel pre-form  400  has side and bottom thickness of about 3 mm. To the extent the embedding is done after anodizing, it is preferred that substantially all the shaping of the vessel  100 , occurs to the pre-form  400  before anodizing. 
         [0027]      FIGS. 3 ,  6  and  7  illustrate another embodiment of the process for forming the cookware vessel article  100  illustrated in  FIG. 1  in which a cookware vessel pre-form  400  vessel is initially formed as shown and described above with respect to  FIG. 3  from a planar sheet  10  of aluminum metal or aluminum metal alloy. In this instance, the metal mesh  110  is copper, or an alloy thereof, and is embedded in the bottom exterior surface  101  of the vessel prior to the anodizing step. As shown in  FIG. 7 , the pair of mated male  410  and female  420  compression forming dies are used to force the mesh  110  placed on the upper surface  421  of the lower female compression forming die  420  into the exterior bottom surface  401  of the pre-form vessel  400 . Hence, as shown in  FIG. 7 , the metal mesh  110  is embedded in the exterior bottom surface  101  of the finished vessel  100 . It should be appreciated that the forming dies  410  and  420  can also be used to shape or further shape the bottom surface  401  and  402 , as well as the resulting rim region  105  of the finished vessel  100 . 
         [0028]    It is also preferred that the male metal forming die  410  has a textured lower surface  411  and this textured pattern is imparted to the interior bottom  102  of the cookware vessel  130  during the embedding process. It should be appreciated that the lower or female compression forming die  420  can also be used to shape or further shape the bottom surface  401 , and the upper portion of forming dies  410  and  402 , to shape or reshape the resulting rim region  105  of the finished vessel  100 . The texture thus imparted to surface  102  can be decorative or functional, such as for enhancing the adhesion or durability of inorganic, organic and non-stick coatings, as well as imparting texture or sear marks to food, and can be linear, circular, random, repeating or fractal, as well as a 2-dimensional. This texture can be light or heavy, that is deep between peeks and alleys, and need not cover the entire interior surface. Likewise, the mesh  110 , need not cover the entire exterior bottom surface  110 , and can be deployed to cover pre-selected portions thereof. 
         [0029]    As shown in  FIG. 2A-F , the metal mesh  110  is preferably formed by slitting metal sheet  20 , shown in  FIG. 2A , with rows of overlapping slits  21  and expanding the sheet  20  perpendicular to the slip direction (vertical double arrow  201  in  FIG. 2B ). It should be noted that in this process, the resulting mesh holes in  FIG. 2E , being in the shape of rhombohedra (diamond), which have opposing corners with equal angle, with adjacent corners having angles of about 60 and 30 degree. It should be appreciated that in alternative embodiments of the invention, such mesh  110  can be formed by punching holes in the planar sheet  20 , with such holes  111  having any shape, and are optionally square. 
         [0030]    Independent of the method of forming the mesh  110 , and the shapes of the holes  111  in the mesh  110 , it is desirable that the mesh have a particular thickness range and spacing between holes. 
         [0031]    Both stainless steel and copper meshes with the thickness of about 0.5 to 1 mm have been successfully embedded in plain aluminum when the mesh openings  111  were from about 3 mm to about 4 mm wide, and the width of the metal between these openings was from about 0.5 mm to about 1 mm, and preferably about 0.75 mm. 
         [0032]    To the extent that the mesh  110  is embedded after anodizing process, it is important that the portions of the grid material  112  between the mesh openings  111  are relatively thin and spaced apart and that the mesh material  110  is considerably hard when compared to anodized aluminum. 
         [0033]    Stainless steel mesh with a thickness of about 0.5 to 1 mm have been successfully embedded in anodized aluminum when the mesh openings  111  were from about 3 mm to about 4 mm wide, and the width of the metal between these openings was from about 0.5 mm to about 1 mm, and preferably about 0.75 mm. While it has been discovered that it is not possible to embed copper mesh in flat anodized aluminum, stainless steel mesh can be embedded by this process as described above. 
         [0034]    It should also be appreciated that the forming step shown in  FIG. 3 , or another step prior to the embedding process shown in  FIGS. 4 and 6  may be used to place mesh shaped depression in the lower surface  401  of the pre-form  400 , hence enabling of a thicker or softer metal into the exterior bottom surface  401  that might be possible with a generally planar surface. This assume registry of the mesh  110  with these depressions. However, the registry in any case may be accomplished even before inserting the pre-form  400  between compression forming dies  410  and  420 . This step of forming these depressions can be accomplished by molding, pressing, impacting, machining or electric discharge and like processes. Further, it may be desirable to at least lightly bond the mesh  110  in the depressions, such as by exterior tape, foil or spot welding, as well as inverting the dies  410  and  420  so that the pre-form  400  is inverted and the mesh  110  rests on the surface  401 . 
         [0035]    Copper mesh  110  can be embedded in the plain aluminum or aluminum alloys exterior base or bottom  101  of the cooking vessel after the drawing to form the basic vessel shape  400 . The vessel  400  can then be anodized by conventional methods of applying high current in an acidic bath, thus converting the outer aluminum skin of the surface to a hard and durable aluminum oxide layer. While the exposed portions of the copper mesh will be degraded to at least partially soluble oxides of copper during this anodizing process, the rate of degradation is relatively small compared to the time required to convert the aluminum to aluminum oxide during the anodizing process. Hence, if the copper mesh originally has a thickness of at least about 0.5 mm, and more preferably at least about 1 mm, only a small portion of the copper is oxidizing. The porous or soft copper oxides that remain after the anodizing step are readily removed by a subsequent polishing step. The step of polishing however does not remove a substantial amount of the aluminum oxide from the aluminum vessel. 
         [0036]    While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be within the spirit and scope of the invention as defined by the appended claims.