Cookware, multi-layer blank assembly for making the cookware, and method for making the cookware

Abstract

To provide cookware made from a joined multi-layer blank assembly.SOLUTION: The cookware has: a first metal layer 102; a second metal layer 110 having a cavity 112 with a plurality of spaced apart posts projecting from a bottom surface of the cavity; and a perforated graphite layer 108 having a thickness of at least 0.010 inches (0.254 mm) and having a plurality of spaced apart holes 114 formed therethrough. The perforated graphite layer is positioned within the cavity of the second metal layer such that the plurality of spaced apart posts extends through the plurality of spaced apart holes. The second metal layer is metallurgically bonded to the first metal layer at least through the plurality of spaced apart posts. Methods of making bonded multi-layer composite cookware are also disclosed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - reference to Related Applications This application is a divisional application of Japanese Patent Application No. 2022 - 535616, which claims priority to U.S. Patent Application No. 16 / 714,120, filed on December 13, 2019, and the entire disclosure of the document immediately prior to the division is incorporated herein by reference.

[0002] The present disclosure generally relates to a multi - ply joined cooking utensil, specifically, a multi - ply joined cooking utensil in which a perforated graphite core layer is disposed between at least two metal layers joined to each other by metal bonding. A method of manufacturing the cooking utensil using a solid - state bonding technique is also disclosed.

Background Art

[0003] It has been previously known to manufacture a composite cooking utensil in which multiple layers are joined. In such a cooking utensil, various materials are joined to each other to form a composite material that combines the desired physical properties of each material. For example, the corrosion resistance of stainless steel is desirable for the cooking surface and the outer surface of the cooking utensil, but the thermal conductivity of stainless steel is relatively low. On the other hand, aluminum and / or copper provide a relatively high thermal conductivity and have been joined to stainless steel to provide well - known composite cooking utensils such as pots and frying pans. Multi - ply joined cooking utensils are known in the art as shown in several patents such as Patent Documents 1 and 2 of Ulam, and Patent Documents 3 and 4 of Groll. These documents illustrate the manufacture of multi - ply joined cooking utensils in which an outer layer of stainless steel is joined to a central layer of more conductive aluminum and / or copper. The joining between such layers of dissimilar materials is usually achieved by conventional roll - bonding techniques using strips of aluminum and / or copper roll - bonded to an outer strip of stainless steel.

[0004] For example, in order to manufacture cooking utensils from a plurality of composite material blanks of a stainless steel-aluminum-stainless steel combination, a solid-state bonding technique that applies high static pressure and heat over a certain period of time is disclosed in Patent Document 5 of Groll et al. There is still a need in the art to produce cooking utensils using an improved solid-state bonding technique in order to reduce the weight of the cooking utensils and improve their thermal properties.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the conventional needs in the art, it is desirable to develop a new method for producing cooking utensils using an improved solid-state bonding technique. It is further desirable to provide a cooking utensil produced by such a method, which has a reduced weight and improved thermal properties compared to the current cooking utensils produced by the solid-state bonding technique.

Means for Solving the Problems

[0007] According to some embodiments or aspects of the present disclosure, a cooking appliance made from a plurality of joined layers of blank assemblies may include a first metal layer, a second metal layer having a cavity with a plurality of posts protruding from the bottom surface of the cavity and spaced apart, and a perforated graphite layer having a thickness of at least 0.010 inches (0.254 mm) and formed with a plurality of spaced-apart holes therethrough. The perforated graphite layer may be positioned within the cavity of the second metal layer such that the plurality of spaced-apart posts extend through the plurality of spaced-apart holes. The second metal layer may be metallurgically joined to the first metal layer via at least the plurality of spaced-apart posts.

[0008] According to some embodiments or aspects of the present disclosure, the surface of the second metal layer that surrounds the cavity is metallurgically joined to the first metal layer. Preferably, the surface is flat. The depth of the cavity may be less than, equal to, or greater than the thickness of the perforated graphite layer. The plurality of spaced-apart posts may have a circular cross-section or a polygonal cross-section.

[0009] According to some embodiments or aspects of the present disclosure, the perforated graphite layer may be made from anisotropic graphite. The first metal layer may be made of aluminum, stainless steel, or titanium. The second metal layer may be made of aluminum.

[0010] According to some embodiments or aspects of the present disclosure, a third metal layer may be metallurgically joined to the flat side of the second metal layer opposite the cavity. The third metal layer may be made of stainless steel.

[0011] According to some embodiments or aspects of the present disclosure, the second metal layer may include an outer metal layer and a central metal layer received within a central opening of the outer metal layer. The cavity may be provided on the central metal layer. The outer metal layer may be thinner than the central metal layer.

[0012] According to some embodiments or aspects of the present disclosure, the first metal layer may have a first sublayer made of aluminum joined to spaced posts and a second sublayer made of stainless steel. The second metal layer may be metallurgically joined to the first sublayer of the first metal layer. The surface of the second metal layer that surrounds the void may be metallurgically joined to the first sublayer of the first metal layer. Preferably, the surface is flat.

[0013] According to some embodiments or aspects of the present disclosure, a method of fabricating a cooking appliance includes: (a) providing a first metal layer; (b) providing a perforated graphite layer having a thickness of at least 0.010 inches (0.254 mm) and formed with a plurality of spaced-apart holes therethrough; (c) providing a second metal layer having a void with a plurality of spaced-apart posts protruding from a bottom surface of the void; (d) stacking the layers provided in (a)-(c) to form a blank assembly such that the perforated graphite layer is received within the void of the second metal layer, whereby the plurality of spaced-apart posts of the second metal layer are aligned with and extend through the plurality of spaced-apart holes of the perforated graphite layer such that a lower surface of the first metal layer contacts at least an upper surface of upper end portions of the plurality of spaced-apart posts; and (e) crimping the blank assembly by applying a force in a direction perpendicular to a plane of the layers of the blank assembly and simultaneously heating the blank assembly to effect a metallurgical bond between the first and second metal layers through at least the plurality of spaced-apart posts to provide a joined blank assembly.

[0014] According to some embodiments or aspects of the present disclosure, the method may further include: (f) cooling the joined blank assembly; and (g) forming a cooking appliance from the joined blank assembly. The first metal layer may be made of aluminum, stainless steel, or titanium, and the second metal layer may be made of aluminum.

[0015] According to some embodiments or aspects of the present disclosure, the method may further include (h) providing a third metal layer and laminating the third metal layer with the layers of the blank assembly before pressing the blank assembly so that the third metal layer faces the flat side of the second metal layer on the opposite side of the cavity.

[0016] According to some embodiments or aspects of the present disclosure, the method may further include (i) providing a fourth metal layer and laminating the fourth metal layer on the first metal layer of the blank assembly before pressing the blank assembly. The third metal layer and the fourth metal layer may be made of stainless steel.

Advantages of the Invention

[0017] These and other characteristics and features of the cooking appliance described herein and the method of making such a cooking appliance will become more apparent by considering the following description and the appended claims with reference to the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments and, together with the description, serve to explain the principles of the disclosure. It should be clearly understood that the drawings are for the purpose of illustration and description only. Therefore, specific dimensions and other physical characteristics related to the embodiments disclosed herein should not be considered limiting. Further, it should be understood that the present disclosure contemplates various alternative variations and orders of steps unless otherwise indicated.

Brief Description of the Drawings

[0018]

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Best Mode for Carrying Out the Invention

[0019] In FIGS. 1 to 22, unless otherwise specified, the same reference numerals represent the same components.

[0020] As used in the specification and claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

[0021] For the following description of this specification, the terms "end", "upper", "lower", "right", "left", "vertical", "horizontal", "top", "bottom", "lateral", "longitudinal", and their derivatives are used with reference to the orientation of the present disclosure in the drawings. However, it should be understood that the present disclosure can assume various alternative modifications and orders of steps, unless there is a clear contrary specification.

[0022] It should be understood that all numbers and ranges used in the specification and claims are modified by the term "about" in all examples. By "about", plus or minus 25 percent of the presented value, such as plus or minus 10 percent of the presented value, is intended. However, this should not be considered as limiting the analysis of values under the doctrine of equivalents.

[0023] Unless otherwise specified, it should be understood that all ranges or ratios disclosed in this specification include the first and last values and any sub-ranges or sub-ratios contained therein. For example, the presented range or ratio "from 1 to 10" should be considered to include any sub-ranges or sub-ratios between the minimum value of 1 and the maximum value of 10 (including those numbers), i.e., all sub-ranges or sub-ratios that start with a minimum value of 1 or more and end with a maximum value of 10 or less. The ranges and / or ratios disclosed in this specification represent the average value for the specified range and / or ratio.

[0024] Without limitation, all documents such as issued patents and patent applications referred to in this specification should be considered to be "incorporated by reference" in their entirety, unless otherwise specified.

[0025] The terms "first", "second", etc. do not refer to a particular order or sequence, but rather to different states, characteristics, or elements.

[0026] The term "at least" is synonymous with "greater than or equal to".

[0027] As used herein, "at least one of" is synonymous with "one or more of". For example, the phrase "at least one of A, B, and C" means any one of A, B, or C, or any combination of any two or more of A, B, or C. For example, "at least one of A, B, and C" includes one or more of only A, or one or more of only B, or one or more of only C, or one or more of A and one or more of B, or one or more of A and one or more of C, or one or more of B and one or more of C, or one or more of all of A, B, and C.

[0028] The term "includes" is synonymous with "comprises".

[0029] As used herein, the term "parallel" or "substantially parallel" means that the relative angle (when extended to the theoretical intersection point) between two objects, such as an elongated object including a reference line, is from 0° to 5°, or from 0° to 3°, or from 0° to 2°, or from 0° to 1°, or from 0° to 0.5°, or from 0° to 0.25°, or from 0° to 0.1°, including the recited values.

[0030] As used herein, the term "perpendicular" or "substantially perpendicular" means that the relative angle between two objects at the actual or theoretical intersection point is from 85° to 90°, or from 87° to 90°, or from 88° to 90°, or from 89° to 90°, or from 89.5° to 90°, or from 89.75° to 90°, or from 89.9° to 90°, including the recited values.

[0031] As used herein, the term "solid state bonding" means a method of joining two or more stacked metal layers or metal alloy layers to each other using high pressure (typically greater than 5,000 psi (34.5 MPa)) and high temperature (typically greater than 600°F (315°C)), where the high pressure is applied at a right angle or perpendicular to the plane of the stacked layers, i.e., at 90°.

[0032] As used herein, the term "metallurgical bonding" or "metallurgically bonded" refers to a bond formed between like or dissimilar metal materials where there are no voids or discontinuities at the bond interface.

[0033] Referring to the drawings, FIGS. 1 - 3 show various views of a blank assembly 100 used in fabricating some embodiments of the cooking appliance described in the present disclosure. In some embodiments or aspects, each blank assembly 100 can be used to form a cooking appliance such as a pan or a frying pan shown in FIGS. 5 - 7. As discussed herein, the blank assembly 100 is formed from a plurality of stacked disks or layers, and those disks or layers are metallurgically bonded to each other to form an integral blank assembly 100. In some embodiments or aspects, the plurality of stacked disks or layers may be stacked such that the individual disks are substantially parallel to each other. The stacked assembly of disks or layers may then be joined to each other using solid state bonding techniques, and the stacked disks or layers are joined using high pressure (typically greater than 5,000 psi (34.5 MPa)) and high temperature (typically greater than 600°F (315°C)). Desirably, the high pressure is applied at a right angle, i.e., 90°, to the plane of the stacked disks or layers. The joined disks or layers constitute the joined multi - layer blank assembly 100. The joined multi - layer blank assembly 100 is shown in FIGS. 2 - 3.

[0034] Continuing to refer to FIGS. 1-3, the blank assembly 100 has at least one upper (first) metal disk or metal layer 102 (hereinafter referred to as the "first metal layer 102" in this specification) and at least one lower (third) metal disk or metal layer 104 (hereinafter referred to as the "third metal layer 104" in this specification). A second disk or layer 106 (hereinafter referred to as the "second layer 106" in this specification) is disposed between the first metal layer 102 and the third metal layer 104. The upper surface or top surface of the first metal layer 102 forms the inner surface of the cooking appliance, and the lower surface or bottom surface of the third metal layer 104 forms the outer surface of the cooking appliance. In some embodiments or aspects, the arrangement of the layers of the blank assembly 100 can be reversed 180° such that the lower surface or bottom surface of the first metal layer 102 forms the outer surface of the cooking appliance and the upper surface or top surface of the third metal layer 104 forms the inner surface of the cooking appliance.

[0035] Continuing to refer to FIGS. 1-3, the material from which the first metal layer 102 is made is selected to have the desirable scratch resistance, wear, and heat properties required for the cooking surface of the cooking appliance. In some embodiments or aspects, the first metal layer 102 may be formed from food-grade stainless steel. The stainless steel of the first metal layer 102 may be, for example, a 400-series stainless steel such as 436 stainless steel or a 300-series stainless steel such as 304 stainless steel. In some embodiments or aspects, the stainless steel of the first metal layer 102 may be any corrosion-resistant stainless steel alloy suitable for use as a food preparation surface. In further embodiments or aspects, the first metal layer 102 may be made from a titanium alloy suitable for use as a food preparation surface. In further embodiments or aspects, the material of the first metal layer 102 may include aluminum. In some embodiments or aspects, the material of the first metal layer 102 may be, for example, high-purity aluminum or an alloy aluminum material with one or both sides coated with a thin layer of pure aluminum to be compatible with metal bonding. In some embodiments or aspects, the material of the first metal layer 102 may be a 1000-series aluminum alloy such as 1100 aluminum alloy.

[0036] In some embodiments or aspects, the first metal layer 102 may be a disk having a diameter of about 14 inches (355.6 mm) to form a blank of a size close to the finished product for manufacturing cooking utensils such as a frying pan with a diameter of 10 inches (254 mm). In other embodiments or aspects, the first metal layer 102 may be a disk having a diameter of about 5 inches to about 20 inches (127 mm to 508 mm) for forming cooking utensils of various sizes. The diameter of the first metal layer 102 is selected to be large enough to form the bottom, side wall, and rim of the finished cooking utensil. The diameter of the first metal layer 102 is selected to match the diameter of at least one of the second layer 106 and the third metal layer 104. In some embodiments or aspects, the thickness of the first metal layer 102 may be from about 0.010 inches (0.25 mm) to about 0.025 inches (0.65 mm), such as about 0.015 inches (0.40 mm). Those skilled in the art will readily understand that the diameter and thickness of the first metal layer 102 can be increased or decreased, respectively, to manufacture cooking utensils with larger or smaller diameters and thicknesses.

[0037] In some embodiments or aspects as shown in FIGS. 20-22, the blank assembly 100 may include a fourth metal layer 140 laminated on a first metal layer 102. As discussed herein, the first metal layer 102 may be made of a material having a bonding affinity to the metal materials of the fourth metal layer 140 and the second layer 106. In further embodiments or aspects, the blank assemblies 200, 300 (shown in FIGS. 8-10 and FIGS. 14-16) may include a fourth metal layer (not shown) laminated on the first metal layers 202, 302. The material of the first metal layers 102, 202, 302 may be aluminum. In some embodiments or aspects, the material of the first metal layers 102, 202, 302 may be, for example, high-purity aluminum, or an aluminum alloy material with any surface coated with a pure aluminum thin layer to be compatible with metal bonding. In some embodiments or aspects, the material of the first metal layers 102, 202, 302 may be a 1000 series aluminum alloy such as 1100 aluminum alloy. In some embodiments or aspects, the thickness of the first metal layers 102, 202, 302 may be from about 0.020 inches (0.5 mm) to about 0.100 inches (2.5 mm), such as about 0.040 inches (1.0 mm).

[0038] Continuing to refer to FIGS. 20-22, the material of the fourth metal layer 140 is selected to have the desirable scratch resistance, wear, and thermal properties required for the cooking surface of the cooking appliance. In some embodiments or aspects, the material of the fourth metal layer 140 may be food-grade stainless steel. The stainless steel of the fourth metal layer 140 may be, for example, a 400 series stainless steel such as 436 stainless steel or a 300 series stainless steel such as 304 stainless steel. In some embodiments or aspects, the stainless steel of the fourth metal layer 140 may be any corrosion-resistant stainless steel alloy suitable for use as a food preparation surface. In further embodiments or aspects, the fourth metal layer 140 may be made of a titanium alloy suitable for use as a food preparation surface. In some embodiments or aspects, the thickness of the fourth metal layer 140 may be from about 0.010 inches (0.25 mm) to about 0.025 inches (0.65 mm), such as about 0.015 inches (0.4 mm).

[0039] In some embodiments or aspects, the third metal layer 104 may be made of a material having desirable scratch resistance, wear, and heat properties required for the outer surface of the cooking appliance. The material of the third metal layer 104 is selected to have a bonding affinity to the metal material of at least a portion of the second layer 106, as discussed herein. In some embodiments or aspects, the third metal layer 104 may be made of ferromagnetic stainless steel such as 400 grade stainless steel to fabricate a finished cooking appliance suitable for use in an electromagnetic induction cooking device. The stainless steel of the third metal layer 104 may be a magnetic grade of stainless steel, such as 430 stainless steel, for example. In some embodiments or aspects, the stainless steel of the third metal layer 104 may be any stainless steel alloy suitable for use as a food preparation surface. In further embodiments or aspects, the third metal layer 104 may be made of a titanium alloy suitable for use as a food preparation surface. The material of the third metal layer 104 may be selected to have similar or identical material properties as the first metal layer 102.

[0040] In some embodiments or aspects, the third metal layer 104 may be a disk having a diameter of about 14 inches (355.6 mm) to form a blank of a size close to the finished product for fabricating a cooking appliance such as a frying pan with a diameter of 10 inches (254 mm). In other embodiments or aspects, the third metal layer 104 may be a disk having a diameter of about 5 inches to about 20 inches (127 mm to 508 mm) to form cooking appliances of various sizes. The diameter of the third metal layer 104 is selected to be large enough to form the bottom, sidewall, and rim of the finished cooking appliance. In some embodiments or aspects, the thickness of the third metal layer 104 may be from about 0.010 inches (0.25 mm) to about 0.025 inches (0.6 mm), such as about 0.015 inches (0.4 mm). Those skilled in the art will readily understand that the diameter and thickness of the third metal layer 104 can be increased or decreased respectively to fabricate cooking appliances with larger or smaller diameters and thicknesses. The bottom surface 124 of the third metal layer 104 may be substantially flat and may have no protrusions or recesses.

[0041] Continuing with reference to FIGS. 1 - 3, the second layer 106 is disposed between the first metal layer 102 and the third metal layer 104. The second layer 106 has a perforated graphite disk or layer 108 (hereinafter referred to as the "perforated graphite layer 108" in this specification) formed such that a plurality of spaced - apart holes 114 penetrate therethrough. The second layer 106 further has a second metal disk or metal layer 110 (hereinafter referred to as the "second metal layer 110" in this specification) having a cavity 112 configured to receive the perforated graphite layer 108.

[0042] In some embodiments or aspects, as discussed herein, the second metal layer 110 may be made of a material having a bonding affinity to the metal materials of the first metal layer 102 and the third metal layer 104. The material of the second metal layer 110 may be aluminum. In some examples or aspects, the second metal layer 110 may be made of high - purity aluminum or an aluminum alloy material having any surface coated with a pure aluminum thin layer so as to be compatible with metal bonding. In some embodiments or aspects, the second metal layer 110 may be made of a 1000 - series aluminum alloy such as, for example, 1100 aluminum alloy.

[0043] In some embodiments or aspects, the second metal layer 110 may be a disk having a diameter of about 14 inches (355.6 mm) to form a blank of a size close to the finished product for manufacturing cooking utensils such as a frying pan with a diameter of 10 inches (254 mm). In other embodiments or aspects, the second metal layer 110 may be a disk having a diameter of about 5 inches to about 20 inches (127 mm to 508 mm) for forming cooking utensils of various sizes. The diameter of the second metal layer 110 is selected to be large enough to form the bottom, sidewall, and rim of the finished cooking utensil. In some embodiments or aspects, the thickness of the second metal layer 110 may be from about 0.020 inches (0.5 mm) to about 0.200 inches (5.0 mm), such as about 0.040 inches (1.0 mm). Those skilled in the art will readily understand that the diameter and thickness of the second metal layer 110 can be increased or decreased respectively to manufacture cooking utensils with larger or smaller diameters and thicknesses. The bottom surface 126 of the second metal layer 110 may be substantially flat and may have no protrusions or recesses.

[0044] In some embodiments or aspects, the void 112 may have a circular shape having a diameter that is the same as or slightly larger than the diameter of the circular perforated graphite layer 108. For example, the void 112 may have a diameter of from about 3 inches (76.2 mm) to about 12 inches (305 mm), such as about 7 inches (178 mm). The perforated graphite layer 108 may have a diameter corresponding to about 90 - 99.9% of the diameter of the void 112. In other embodiments or aspects, the void 112 may have any desired geometric shape corresponding to any desired geometric shape of the perforated graphite layer 108. The void 112 may have a depth (i.e., the distance by which the void 112 is recessed with respect to the upper surface 120 of the second metal layer 110) of from about 0.010 inches (0.25 mm) to about 0.100 inches (2.5 mm), such as about 0.020 inches (0.5 mm). The void may have a uniform depth, or may have different non-uniform depths in at least a portion of the void 112. In some embodiments or aspects, the void 112 may be centered on the second metal layer 110 such that the void 112 and the second metal layer 110 have a common axis. One of ordinary skill in the art will readily understand that the diameter and depth of the void 112 can be increased or decreased, respectively, to accommodate a larger and thicker perforated graphite layer 108.

[0045] The second metal layer 110 has a plurality of spaced-apart posts 116 (hereinafter referred to as "posts 116" in this specification) projecting upwardly within a cavity 112. The posts 116 extend upwardly from the bottom surface 118 of the cavity 112, and the cavity 112 is recessed with respect to the upper surface 120 of the second metal layer 110. As shown in FIG. 4, the posts 116 may be arranged in a regular array or randomly distributed within the cavity 112. For example, the posts 116 may be arranged in a circular array with equal or unequal spacing between adjacent posts 116. In various embodiments or aspects, the density of the posts 116 (i.e., the number of posts 116 per unit area) may be uniform throughout the cavity 112 or may vary between different portions of the cavity. For example, the density of the posts 116 may be higher or lower in the radial direction of the cavity 112. In some embodiments or aspects, the posts 116 may be provided in one or more groups. The posts 116 may have the same size (i.e., diameter) or different sizes relative to each other.

[0046] Referring to FIG. 4, the cavity 112 and the posts 116 may be formed by removing material from the upper surface 120 of the second metal layer 110, such as by machining. In some embodiments or aspects, the cavity 112 and the posts 116 may be cast using a mold. The posts 116 may have a cross-sectional shape that is circular, polygonal (such as hexagonal), or any other geometric shape.

[0047] In some embodiments or aspects, the post 116 may have a height of from about 0.010 inch (0.254 mm) to about 0.100 inch (2.54 mm), such as about 0.020 inch (0.508 mm), above the bottom surface 118 of the cavity 112. In some embodiments or aspects, the height of the post 116 is selected to be slightly higher than the thickness of the perforated graphite layer 108 such that the topmost portion of the post 116 projects through the holes of the perforated graphite layer 108, as described herein. In embodiments or aspects where the post 116 has a circular shape, the post 116 may have a diameter of from about 0.050 inch (1.27 mm) to about 0.250 inch (6.35 mm), such as about 0.125 inch (3.175 mm). In other embodiments or aspects where the post 116 has a non-circular shape, the post 116 is about 0.12in 2 (7.9mm 2 ) and may have a surface area of from about 0.002in 2 (1.3mm 2 ) to about 0.050in 2 (32mm 2 ). In some embodiments or aspects, the post 116 may have a constant width or diameter along its longitudinal length measured in a direction from the bottom surface 118 of the cavity 112 towards the upper surface 120. In other embodiments or aspects, the width or diameter of the post may narrow or widen in a direction from the bottom surface 118 of the cavity 112 towards the upper surface 120.

[0048] In some embodiments or aspects, the perforated graphite layer 108 may be made of anisotropic graphite configured to transfer thermal energy primarily in the radial direction (rather than the axial direction). In this way, the cooking surface can be heated uniformly while avoiding hot spots. Graphite is preferably selected because of its high thermal conductivity coefficient (about 500 - 1500 W / mK compared to about 220 W / mK for aluminum and 340 W / mK for copper). The anisotropic graphite can have a thermal conductivity about 2 - 6 times that of copper in the direction of the XY plane defining the cooking surface. The anisotropic graphite also weighs about 1 / 6 that of copper and acts as a thermal insulator in the Z direction (i.e., the direction substantially perpendicular to the cooking surface) compared to copper. The low conductivity in the Z direction (about 1 / 100 of the XY plane) acts as a thermal dam that temporarily impedes the direct flow of heat from the heat source to the food preparation surface, and thus additional time is given to the thermal energy to spread uniformly along the cooking surface. The perforated graphite layer 108 is effective in spreading heat uniformly across the cooking surface while impeding the flow of heat in the direction perpendicular to the cooking surface. Without being bound by theory, it has been found that the presence of the perforated graphite layer 108 increases the resistance to electric current, thereby enhancing the efficiency of induction heating compared to a cooking appliance without the perforated graphite layer 108.

[0049] In some embodiments or aspects, the perforated graphite layer 108 may have a circular shape with a diameter of from about 3 inches (76.2 mm) to about 12 inches (305 mm), such as about 7 inches (178 mm). As referred to herein, the perforated graphite layer 108 may have a diameter corresponding to about 90 - 99.9% of the diameter of the cavity 112. In other embodiments or aspects, the perforated graphite layer 108 may have any desired geometry corresponding to any desired geometry of the cavity 112. The perforated graphite layer 108 may have a thickness of from about 0.010 inches (0.25 mm) to about 0.100 inches (2.5 mm), such as about 0.020 inches (0.5 mm). The perforated graphite layer 108 may have a minimum thickness of about 0.010 inches (0.25 mm). Without being bound by theory, it has been found that a perforated graphite layer 108 having a thickness less than the minimum thickness may be damaged during the solid state bonding process, and in that case, the ability to uniformly distribute heat along the cooking surface of the cooking appliance is impaired. Further, a perforated graphite layer 108 having at least the minimum thickness is easier to handle and less expensive to manufacture than a perforated graphite layer having a thickness less than the minimum thickness, and as such, the overall cost of the cooking appliance is reduced. Further, a perforated graphite layer 108 having at least the minimum thickness is configured to transfer more energy in the plane defining the cooking surface than a perforated graphite layer having a thickness less than the minimum thickness. In some embodiments or aspects, the thickness of the perforated graphite layer 108 is selected to be less than the height of the posts 116 of the second metal layer 110. Thus, the upper surface of the perforated graphite layer 108 may be recessed within the cavity 112 relative to the upper surface 120 of the second metal layer 110 and the uppermost portions of the posts 116.

[0050] In some embodiments or aspects, the thickness of the perforated graphite layer 108 is selected to be less than the height of the posts 116 / depth of the cavities 112 of the second metal layer 110. Thus, the upper surface of the perforated graphite layer 108 may be recessed within the cavity 112 relative to the upper surface 120 of the second metal layer 110 and the top of the posts 116. In other embodiments or aspects, the thickness of the perforated graphite layer 108 is selected to be the same as the height of the posts 116 / depth of the cavities 112. In further embodiments or aspects, the thickness of the perforated graphite layer 108 may be selected to be slightly greater than the height of the posts 116 / depth of the cavities 112 of the second metal layer 110. Thus, the upper surface of the perforated graphite layer 108 may protrude slightly from the cavity 112 relative to the upper surface 120 of the second metal layer 110 and the top of the posts 116. Since the perforated graphite layer 108 is more compressible than the first and second metal layers 102, 110, it is compressed into the cavity 112 during the solid-state bonding process.

[0051] Continuing to refer to FIGS. 1-3, each of the holes 114 penetrates the material of the perforated graphite layer 108 between its upper and lower surfaces. The size and arrangement of the holes 114 in the perforated graphite layer 108 are selected to correspond to the size and arrangement of the posts 116 on the second metal layer 110. Thus, the posts 116 can be arranged such that all of the posts 116 are associated with (i.e., aligned with) all of the holes 114 and each post 116 is received within a respective hole 114. For example, in an embodiment where the posts 116 are arranged in a circular array and the spacing between the posts 116 is uniform across the entire cavity 112 of the second metal layer 110, the holes 114 have a corresponding circular array arrangement such that the posts 116 can be received within the holes 114. The holes 114 are shaped such that a single post 116 can be received within a single hole 114. In some embodiments or aspects, multiple posts 116 may be received within a single hole 114. In further embodiments or aspects, the number of holes 114 may be greater than the number of posts 116, such that some of the holes 114 do not have a post 116 therein.

[0052] The hole 114 may have the same shape as or a different shape from the post 116. For example, the hole 114 may have a circular shape to receive a circular or non-circular post 116. In embodiments or aspects where the hole 114 has a circular shape, the hole 114 may have a diameter of from about 0.050 inches (1.27 mm) to about 0.250 inches (6.35 mm), such as about 0.125 inches (3.175 mm). The holes 114 may have the same size and shape or different sizes and shapes.

[0053] Referring to FIGS. 8-10, a blank assembly 200 according to another embodiment or aspect of the present disclosure is shown. The components of the blank assembly 200 shown in FIGS. 8-10 are substantially similar to the components of the blank assembly 100 described herein with reference to FIGS. 1-3. The reference numerals in FIGS. 8-10 are used to indicate the same components as the corresponding reference numerals in FIGS. 1-3, except that the most significant digit of each reference numeral is replaced with the digit 2. For example, the first metal layer shown in FIGS. 1-3 is identified by reference numeral 102, while the same first metal layer shown in FIGS. 8-10 is identified by reference numeral 202. Since the previous description regarding the components of the blank assembly 100 schematically shown in FIGS. 1-3 applies to the blank assembly 200 shown in FIGS. 8-10, only the relative differences between the two blank assemblies are discussed herein below. The joined multi-layer blank assembly 200 is shown in FIGS. 9-10.

[0054] Referring to FIGS. 8-10, the blank assembly 200 has at least one upper (first) metal disk or metal layer 202 (hereinafter referred to as the "first metal layer 202" in this specification) and at least one lower (second) metal disk or metal layer 210 (hereinafter referred to as the "second metal layer 210" in this specification). A core disk or core layer 206 (hereinafter referred to as the "core layer 206" in this specification) is disposed between the first metal layer 202 and the second metal layer 210. The upper surface or top surface of the first metal layer 202 forms the inner surface of the cooking appliance, and the lower surface or bottom surface of the second metal layer 210 forms the outer surface of the cooking appliance.

[0055] The first metal layer 202 may be formed from a food-grade stainless steel such as 400 series stainless steel like 436 stainless steel or 300 series stainless steel like 304 stainless steel, or from a titanium alloy suitable for use as a food preparation surface. The material of the first metal layer 202 may be aluminum. In some embodiments or aspects, the first metal layer 202 may be formed from high-purity aluminum or an alloy aluminum material with any surface coated with a pure aluminum thin layer to be compatible with metal bonding. In some embodiments or aspects, the first metal layer 202 may be made of a 1000 series aluminum alloy such as, for example, 1100 aluminum alloy. The material of the second metal layer 210 is selected to have a bonding affinity with the metal material of the first metal layer 202. The material of the second metal layer 210 may include aluminum. In some embodiments or aspects, the second metal layer 210 may be made of, for example, high-purity aluminum or an alloy aluminum material with any surface coated with a pure aluminum thin layer to be compatible with metal bonding. In some embodiments or aspects, the second metal layer 210 may be made of a 1000 series aluminum alloy such as, for example, 1100 aluminum alloy. The bottom surface 224 of the second metal layer 210 may be substantially flat, without protrusions or recesses.

[0056] Continuing with reference to FIGS. 8 - 10, a core layer 206 is disposed between the first metal layer 202 and the second metal layer 210. The core layer 206 is a perforated graphite disk or layer 208 (hereinafter referred to as the "perforated graphite layer 208" in this specification) formed such that a plurality of spaced - apart holes 214 penetrate therethrough. The second layer 106 of FIGS. 1 - 3 has a second metal layer 110 and a perforated graphite layer 108 received within a cavity 112 of the second metal layer 110, while the core layer 206 of FIGS. 8 - 10 has only the perforated graphite layer 208. The perforated graphite layer 208 is configured to be received within a cavity 212 that is recessed with respect to the upper surface 220 of the second metal layer 210.

[0057] In some embodiments or aspects, the cavity 212 may have a circular shape with a diameter that is the same as or slightly larger than the diameter of the circular perforated graphite layer 208. In other embodiments or aspects, the cavity 212 may have any desired geometric shape corresponding to any desired geometric shape of the perforated graphite layer 208. In some embodiments or aspects, the cavity 212 may be centered on the second metal layer 210 such that the cavity 212 and the second metal layer 210 have a common axis.

[0058] Continuing with reference to FIGS. 8 - 10, a plurality of spaced - apart posts 216 (hereinafter referred to as the "posts 216" in this specification) project upward from the bottom surface 218 of the cavity 212. Similar to the posts 116 shown in FIG. 4, the posts 216 may be arranged in a regular array or randomly distributed within the cavity 212. The posts 216 may have a cross - sectional shape that is circular, polygonal (such as hexagonal), or any other geometric shape.

[0059] In some embodiments or aspects, the perforated graphite layer 208 may be made of anisotropic graphite configured to transfer thermal energy primarily in the radial direction (rather than the axial direction). In this way, the cooking surface can be heated uniformly while avoiding hot spots. As described herein using the embodiments shown in FIGS. 1-4, the perforated graphite layer 208 may have a minimum thickness of about 0.010 inches (0.25 mm). Without being bound by theory, it has been found that a perforated graphite layer 208 with a thickness less than the minimum thickness may be damaged during the solid-state bonding process, and in that case, the ability to distribute heat uniformly along the cooking surface of the cooking appliance is impaired. Further, a perforated graphite layer 208 having at least the minimum thickness is easier to handle and less expensive to manufacture than a perforated graphite layer having a thickness smaller than the minimum thickness, and thus the overall cost of the cooking appliance is reduced. Further, a perforated graphite layer 208 having at least the minimum thickness is configured to transfer more energy in the plane defining the cooking surface than a perforated graphite layer having a thickness smaller than the minimum thickness. In some embodiments or aspects, the thickness of the perforated graphite layer 208 is selected to be less than the height of the posts 216 / depth of the cavities 212 of the second metal layer 210. In this way, the upper surface of the perforated graphite layer 208 may be recessed within the cavity 212 relative to the upper surface 220 of the second metal layer 210 and the top of the posts 216. In other embodiments or aspects, the thickness of the perforated graphite layer 208 is selected to be the same as the height of the posts 216 / depth of the cavities 212. In further embodiments or aspects, the thickness of the perforated graphite layer 208 may be selected to be slightly greater than the height of the posts 216 / depth of the cavities 212 of the second metal layer 210. In this way, the upper surface of the perforated graphite layer 208 may protrude slightly from the cavity 212 relative to the upper surface 220 of the second metal layer 210 and the top of the posts 216. Since the perforated graphite layer 208 is more compressible than the first and second metal layers 202, 210, it is compressed into the cavity 212 during the solid-state bonding process.

[0060] Continuing with reference to FIGS. 8 - 10, each of the holes 214 penetrates through the material of the perforated graphite layer 208 between its upper and lower surfaces. The size and arrangement of the holes 214 in the perforated graphite layer 208 are selected to correspond to the size and arrangement of the posts 216 on the second metal layer 210. In this way, the posts 216 can be arranged such that all of the posts 216 are associated with (i.e., aligned with) all of the holes 214 and each post 216 is received within a respective hole 214. In some embodiments or aspects, a plurality of posts 216 may be received within a single hole 214. In further embodiments or aspects, the number of holes 214 may be greater than the number of posts 216, such that some of the holes 214 do not have a post 216 therein. The holes 214 may have the same shape as the posts 216 or a different shape.

[0061] Referring to FIGS. 14 - 16, a blank assembly 300 according to another embodiment or aspect of the present disclosure is shown. The components of the blank assembly 300 shown in FIGS. 14 - 16 are substantially similar to the components of the blank assembly 100 described herein with reference to FIGS. 1 - 3. The reference numerals in FIGS. 14 - 16 are used to indicate the same components as the corresponding reference numerals in FIGS. 1 - 3, except that the leading digit of each reference numeral is replaced by the number 3. For example, the first metal layer shown in FIGS. 1 - 3 is identified by reference numeral 102, while the same first metal layer shown in FIGS. 14 - 16 is identified by reference numeral 302. Since the previous description regarding the components of the blank assembly 100 schematically shown in FIGS. 1 - 3 applies to the blank assembly 300 shown in FIGS. 14 - 16, only the relative differences between the two blank assemblies are discussed herein below. The joined multi - layer blank assembly 300 is shown in FIGS. 15 - 16.

[0062] Referring to FIGS. 14 to 16, the blank assembly 300 has at least one upper (first) metal disk or metal layer 302 (hereinafter referred to as "the first metal layer 302" in this specification) and at least one lower (third) metal disk or metal layer 304 (hereinafter referred to as "the third metal layer 304" in this specification). A second disk or layer 306 (hereinafter referred to as "the second layer 306" in this specification) is disposed between the first metal layer 302 and the third metal layer 304. The upper surface or top surface of the first metal layer 302 forms the inner surface of the cooking appliance, and the lower surface or bottom surface of the third metal layer 304 forms the outer surface of the cooking appliance.

[0063] The first metal layer 302 may be formed from a food-grade stainless steel such as 400 series or 436 series stainless steel, or from a titanium alloy suitable for use as a food preparation surface. The material of the third metal layer 304 is selected to have a bonding affinity to at least a portion of the metal material of the second layer 306, as discussed herein. In some embodiments or aspects, the third metal layer 304 may be made from a food-grade stainless steel such as 400 series or 436 series stainless steel, or from a titanium alloy. The material of the third metal layer 304 may include aluminum. In some embodiments or aspects, the material of the third metal layer 304 may be, for example, high-purity aluminum, or an alloy aluminum material with any surface coated with a pure aluminum thin layer to be compatible with metal bonding. In some embodiments or aspects, the material of the third metal layer 304 may be a 1000 series aluminum alloy such as 1100 aluminum alloy. The bottom surface 324 of the third metal layer 304 may be substantially flat and may have no protrusions or recesses.

[0064] Continuing with reference to FIGS. 14 to 16, a second layer 306 is disposed between the first metal layer 302 and the third metal layer 304. The second layer 106 of FIGS. 1 to 3 has a second metal layer 110 and a perforated graphite layer 108 received within a cavity 112 of the second metal layer 110, while the second layer 306 of FIGS. 14 to 16 includes a second metal layer 310 and a perforated graphite disk or layer 308 (hereinafter referred to as the "perforated graphite layer 308" in this specification). The second metal layer 310 has a central metal core disk or layer 310a (hereinafter referred to as the "central metal layer 310a" in this specification) and a ring-shaped outer core metal disk or metal layer 310b (hereinafter referred to as the "outer metal layer 310b" in this specification) surrounding the central metal layer 310a. The perforated graphite layer 308 is received within a cavity 312 of the second metal layer 310. The cavity 312 is formed on the central metal layer 310a. The material of the outer metal layer 310b and / or the central metal layer 310a may be aluminum. In some embodiments or aspects, the material of the outer metal layer 310b and / or the central metal layer 310a may be, for example, high-purity aluminum or an aluminum alloy material with any surface coated with a thin layer of pure aluminum to be suitable for metal bonding. In some embodiments or aspects, the material of the outer metal layer 310b and / or the central metal layer 310a may be a 1000 series aluminum alloy such as 1100 aluminum alloy. Thus, the material of the second metal layer 310 may be aluminum.

[0065] The outer metal layer 310b has a central opening 322 shaped to receive the central metal layer 310a therein. In some embodiments or aspects, the central opening 322 may have a circular shape with a diameter that is the same as or slightly larger than the diameter of the circular central metal layer 310a. For example, the central opening 322 may have a diameter from about 3 inches (76.2 mm) to about 12 inches (305 mm), such as about 7 inches (178 mm). The thickness of the central metal layer 310a may be the same as or different from the thickness of the outer metal layer 310b. For example, the central metal layer 310a may be thinner or thicker than the outer metal layer 310b. In some embodiments or aspects, the central metal layer 310a may be thicker (such as by 0.004 inches (0.1 mm)) than the outer metal layer 310b. Thus, the additional material of the central metal layer 310a may be compressed during solid state bonding so that the upper and lower surfaces of the central metal layer 310a and the outer metal layer 310b are substantially flat. Compression of the additional material of the central metal layer 310a contributes to a stronger bond with the perforated graphite layer 308 during solid state bonding. The bottom surfaces 326a, 326b of the central metal layer 310a and the outer metal layer 310b may be substantially flat and may have no protrusions or recesses.

[0066] Continuing with reference to FIGS. 14 - 16, the void 312 may have a circular shape with a diameter that is the same as or slightly larger than the diameter of the circular perforated graphite layer 308. In other embodiments or aspects, the void 312 may have any desired geometry corresponding to any desired geometry of the perforated graphite layer 308. In some embodiments or aspects, the void 312 may be centered on the central metal layer 310a such that the void 312 and the central metal layer 310a have a common axis.

[0067] Continuing with reference to FIGS. 14 - 16, a plurality of spaced - apart posts 316 (hereinafter referred to as "posts 316" in this specification) protrude upward from the bottom surface 318 of the cavity 312. Similar to the posts 116 shown in FIG. 4, the posts 316 may be arranged in a regular array or randomly distributed within the cavity 312. The posts 316 may have a cross - sectional shape that is circular, polygonal (such as hexagonal), or any other geometric shape.

[0068] In some embodiments or aspects, the perforated graphite layer 308 is formed such that a plurality of spaced - apart holes 314 penetrate therethrough. Each of the holes 314 penetrates the material of the perforated graphite layer 308 between its upper surface and its lower surface. The size and arrangement of the holes 314 in the perforated graphite layer 308 are selected to correspond to the size and arrangement of the posts 316 on the central metal layer 310a. In this way, the posts 316 can be arranged such that all the posts 316 are associated (i.e., aligned) with all the holes 314 and each post 316 can be received within its respective hole 314. In some embodiments or aspects, a plurality of posts 316 may be received within a single hole 314. In further embodiments or aspects, the number of holes 314 may be greater than the number of posts 316, such that some of the holes 314 do not have a post 316 therein. The holes 314 may have the same shape as or a different shape from the posts 316.

[0069] The perforated graphite layer 308 may be made of anisotropic graphite configured to transfer thermal energy primarily (more so in the radial direction than the axial direction). In this way, the cooking surface can be heated evenly while avoiding hot spots. As described herein, the perforated graphite layer 308 may have a minimum thickness of about 0.010 inches (0.25 mm). Without being bound by theory, it has been found that a perforated graphite layer 308 with a thickness less than the minimum thickness may be damaged during the solid-state bonding process, and if so, the ability to distribute heat evenly along the cooking surface of the cooking appliance is impaired. Furthermore, a perforated graphite layer 308 having at least the minimum thickness is easier to handle and less expensive to manufacture than a perforated graphite layer having a smaller thickness, and as a result, the overall cost of the cooking appliance is reduced. Additionally, the perforated graphite layer 308 having the minimum thickness is configured to transfer more energy in the plane defining the cooking surface than a perforated graphite layer having a smaller thickness. In some embodiments or aspects, the thickness of the perforated graphite layer 308 is selected to be less than the height of the posts 316 of the central metal layer 310a. In this way, the upper surface of the perforated graphite layer 308 may be recessed within the cavity 312 relative to the upper surface 320 of the central metal layer 310a and the top of the posts 316. In other embodiments or aspects, the thickness of the perforated graphite layer 308 is selected to be the same as the height of the posts 316 / depth of the cavity 312. In further embodiments or aspects, the thickness of the perforated graphite layer 308 may be selected to be slightly greater than the height of the posts 316 / depth of the cavity 312 of the second metal layer 310. In this way, the upper surface of the perforated graphite layer 308 may protrude slightly from the cavity 312 relative to the upper surface 320 of the second metal layer 310 and the top of the posts 316. Since the perforated graphite layer 308 is more compressible than the first and second metal layers 302, 310, it is compressed into the cavity 312 during the solid-state bonding process.

[0070] Although the structures of the blank assemblies 100, 200, 300 according to various embodiments or aspects of the present disclosure have been described, a method of manufacturing a cooking appliance using the joined multiple-layer blank assemblies 100, 200, 300 will be described here. Before joining, the layers of the blank assemblies 100, 200, 300 are subjected to appropriate surface treatment steps such as degreasing, surface ablation by chemical or mechanical methods. After appropriate surface treatment, the unjoined blank assemblies 100, 200, 300 are formed by laminating the various layers on top of each other. Desirably, the layers are aligned such that the centers of each layer have a common axis. In some embodiments or aspects, the layers may be laminated such that their centers are offset from each other. For manufacturing efficiency, a plurality of unjoined blank assemblies 100, 200, 300 may be laminated on top of each other with or without a spacer layer between adjacent blank assemblies 100, 200, 300.

[0071] In the case of the blank assembly 100 shown in FIGS. 1 to 3, the second layer 106 is laminated on the upper surface of the third metal layer 104. The perforated graphite layer 108 of the second layer 106 is disposed within the cavity 112 of the second metal layer 110 such that the holes 114 of the perforated graphite layer 108 are aligned with the posts 116 of the cavity 112. The top of the post 116 is configured to be at the same height as or extend above the upper surface of the perforated graphite layer 108 when the post 116 is received within the hole 114 of the perforated graphite layer 108. The first metal layer 102 is laminated on the second layer 106 such that the lower surface of the first metal layer 102 faces the upper surfaces of the second metal layer 110 and the perforated graphite layer 108. When laminated, the first metal layer 102, the second layer 106, and the third metal layer 104 are substantially parallel to each other. For manufacturing efficiency, a plurality of unjoined blank assemblies 100 may be laminated on top of each other with or without a spacer layer between adjacent blank assemblies 100.

[0072] In the case of the blank assembly 200 shown in FIGS. 8 to 10, the core layer 206 (i.e., the perforated graphite layer 208) is disposed within the cavity 212 of the second metal layer 210 such that the holes 214 of the perforated graphite layer 208 are aligned with the posts 216 of the cavity 212. The top of the post 216 is configured to be at the same height as or extend above the upper surface of the perforated graphite layer 208 when the post 216 is received within the hole 214 of the perforated graphite layer 208. The first metal layer 202 is laminated over the core layer 206 and the second metal layer 210 such that the lower surface of the first metal layer 202 is positioned to face the upper surfaces 220 of the second metal layer 210 and the perforated graphite layer 208. When laminated, the upper metal layer 22, the perforated graphite layer 208, and the second metal layer 210 are substantially parallel to each other.

[0073] In the case of the blank assembly 300 shown in FIGS. 14 to 16, the central metal layer 310a and the outer metal layer 310b are positioned on the upper surface of the third metal layer 304 such that the central metal layer 310a is received within the central opening 322 of the outer metal layer 310b. The perforated graphite layer 308 is disposed within the cavity 312 of the central metal layer 310a such that the holes 314 of the perforated graphite layer 308 are aligned with the posts 316 of the cavity 312. The top of the post 316 is configured to be at the same height as or extend above the upper surface of the perforated graphite layer 308 when the post 316 is received within the hole 314 of the graphite layer 308. The first metal layer 302 is laminated over the second layer 306 (i.e., the central metal layer 310a, the outer metal layer 310b, and the perforated graphite layer 308) such that the lower surface of the first metal layer 302 is positioned to face the upper surfaces of the central metal layer 310a, the outer metal layer 310b, and the perforated graphite layer 108. When laminated, the first metal layer 302, the second layer 306, and the third metal layer 304 are substantially parallel to each other.

[0074] Next, the blank assemblies 100, 200, 300 or a plurality of stacked blank assemblies 100, 200, 300 are placed on a press device (not shown) for applying a load or pressure in a direction perpendicular or vertical to the plane of the layers of the blank assemblies 100, 200, 300 by a solid-state bonding technique. The solid-state bonding technique for joining pre-cut near-net shape plate blanks not only reduces the scrap loss that used to occur in the manufacture of composite cooking utensils by conventional roll bonding, but also enables the use of other materials in the production of a plurality of composite materials that have been considered difficult, impossible and / or expensive with roll bonding. For example, solid-state bonding allows the use of different grades of stainless steel that are not normally possible with conventional roll bonding to reduce the cost of materials. Furthermore, solid-state bonding further enables the encapsulation of materials such as graphite that cannot be joined to stainless steel by alternative methods.

[0075] While applying a pressure between 5,000 psi and 20,000 psi (34.5 - 137.9 MPa), heat between approximately 500°F and 1,000°F (260 - 538°C) is applied to one or more of the blank assemblies 100, 200, 300 for a sufficient time (about 1 - 4 hours) to achieve solid-state bonding (i.e., metal bonding) between the metal layers of one or more of the blank assemblies 100, 200, 300. During the solid-state bonding process, air that may exist between the post of the core metal layer and the perforated graphite layer due to the dimensional difference between the core metal layer and the perforated graphite layer is extruded from the blank assemblies 100, 200, 300.

[0076] In the case of the blank assembly 100 shown in FIGS. 1 to 3, during the solid-phase bonding process, the lower surface of the second metal layer 110 is metal-bonded to the upper surface of the third metal layer 104. The upper surfaces of the second metal layer 110 and the post 116 are metal-bonded to the lower surface of the first metal layer 102. The perforated graphite layer 108 is completely encapsulated between the second metal layer 110 and the first metal layer 102 by the cavity 112 of the second metal layer 110 completely surrounding the perforated graphite layer 108 on its lower and side surfaces and the first metal layer 102 sealing its upper surface.

[0077] Next, each of the blank assemblies 100, 200, 300 is removed from the pressing apparatus and cooling becomes possible. In some embodiments or aspects, the cooling may be achieved by exposure to the outside air or by using a coolant such as forced air or liquid.

[0078] After solid-state joining, the joined blank assemblies 100, 200, 300 are formed into the desired shape of the cooking utensil 400, such as the frying pan shape shown in FIGS. 5-7, FIGS. 11-13, and FIGS. 17-19, using a draw press, a spinning machine, or a hydroforming machine (not shown). The joined blank assemblies 100, 200, 300 may be oriented such that the first metal layers 102, 202, 302 form the inner surface of the cooking utensil 400 and the second metal layer 210 or the third metal layers 104, 304 form the outer surface of the cooking utensil 400, but may be turned 180° so that the first metal layers 102, 202, 302 form the outer surface of the cooking utensil 400 and the second metal layer 210 or the third metal layers 104, 304 form the inner surface of the cooking utensil 400. The cooking utensil 400 has a substantially flat cooking surface 402 and an upstanding side wall 404 that surrounds the cooking surface 402 and projects vertically above the cooking surface 402. The side wall 404 has a curved portion 406 connected to the cooking surface 402 and a rim 408 at its free end. One or more handles (not shown) may be attached to the cooking utensil by known techniques. In further embodiments or aspects, a non-stick coating may be applied to the cooking surface 402 of the cooking utensil 400. The cooking utensil 400 formed using the blank assemblies 100, 200, 300 described herein is lightweight, being approximately 30% lighter than conventional cooking utensils due to the use of lightweight graphite and aluminum materials. Further, the cooking utensil 400 has improved performance compared to conventional cooking utensils because the perforated graphite layer promotes a high heating rate and uniform heat distribution across the entire cooking surface.

[0079] In various examples, the present disclosure may further be characterized by one or more of the following items.

[0080] Item 1. A cooking appliance 400 made from a plurality of joined blank assemblies 100; 200; 300, the cooking appliance 400 comprising a first metal layer 102; 202; 302, a second metal layer 110; 210; 310 having cavities 112; 212; 312 from the bottom surfaces 118; 218; 318 of which a plurality of spaced-apart posts 116; 216; 316 protrude, and a perforated graphite layer 108; 208; 308 having a thickness of at least 0.010 inches (0.254 mm) and formed with a plurality of spaced-apart holes 114; 214; 314 therethrough, the perforated graphite layer 108; 208; 308 being positioned within the cavities 112; 212; 312 of the second metal layer such that a plurality of spaced-apart posts 116; 216; 316 extend through a plurality of spaced-apart holes 114; 214; 314, and the second metal layer 110; 210; 310 being metallurgically joined to the first metal layer 102; 202; 302 via at least a plurality of spaced-apart posts 116; 216; 316.

[0081] Item 2. The cooking appliance 400 according to item 1, wherein the surface of the second metal layer 110; 210; 310 that surrounds the cavities 112; 212; 312 is metallurgically joined to the first metal layer 102; 202; 302, and the surface is preferably flat.

[0082] Item 3. The cooking appliance 400 according to item 1 or 2, wherein the depth of the cavities 112; 212; 312 is the same as or greater than the thickness of the perforated graphite layer 108; 208; 308.

[0083] Item 4. The cooking appliance 400 according to any one of items 1 to 3, wherein the plurality of spaced-apart posts 116; 216; 316 have a circular cross-section or a polygonal cross-section.

[0084] Item 5. The cooking appliance 400 according to any one of items 1 to 4, wherein the perforated graphite layer 108; 208; 308 is made from anisotropic graphite.

[0085] Item 6. The cooking appliance 400 according to any one of Items 1 to 5, wherein the perforated graphite layers 108; 208; 308 have a thickness between 0.010 inches (0.25 mm) and 0.100 inches (2.5 mm).

[0086] Item 7. The cooking appliance 400 according to any one of Items 1 to 6, wherein the first metal layers 102; 202; 302 are made of aluminum.

[0087] Item 8. The cooking appliance 400 according to Item 7, wherein the aluminum is 1100 alloy.

[0088] Item 9. The cooking appliance 400 according to any one of Items 1 to 6, wherein the first metal layers 102; 202; 302 are made of stainless steel.

[0089] Item 10. The cooking appliance 400 according to any one of Items 1 to 6, wherein the first metal layers 102; 202; 302 are made of titanium.

[0090] Item 11. The cooking appliance 400 according to any one of Items 1 to 10, wherein the second metal layers 110; 210; 310 are made of aluminum.

[0091] Item 12. The cooking appliance 400 according to any one of Items 1 to 11, further comprising a third metal layer 104; 304 that is metallically joined to the flat side of the second metal layers 110; 310 opposite to the voids 112; 312.

[0092] Item 13. The cooking appliance 400 according to Item 12, wherein the third metal layer 104; 304 is made of aluminum.

[0093] Item 14. The cooking appliance 400 according to Item 13, wherein the aluminum is 1100 alloy.

[0094] Item 15. The cooking appliance 400 according to Item 12, wherein the third metal layer 104; 304 is made of stainless steel.

[0095] Item 16. The cooking appliance 400 according to item 15, wherein the stainless steel is a ferromagnetic grade stainless steel.

[0096] Item 17. The cooking appliance 400 according to item 12, wherein the third metal layer 104; 304 is made of titanium.

[0097] Item 18. The cooking appliance 400 according to any one of items 9 to 17, wherein the second metal layer 310 includes an outer metal layer 310b and a central metal layer 310a provided in a central opening 322 of the outer metal layer 310b, and the cavity 312 is provided on the central metal layer 310a.

[0098] Item 19. The cooking appliance 400 according to item 18, wherein the outer metal layer 310b is thinner than the central metal layer 310a.

[0099] Item 20. The cooking appliance 400 according to any one of items 1 to 19, wherein the first metal layer 102 includes a first sub-layer 102a made of aluminum and a second sub-layer 102b made of stainless steel, and the first sub-layer 102a is metallurgically bonded to spaced posts 116.

[0100] Item 21. The cooking appliance according to claim 20, wherein the second metal layer 110 is metallurgically bonded to the first sub-layer 102a of the first metal layer 102.

[0101] Item 22. In the cooking appliance 400 according to item 20, the surface of the second metal layer 110 surrounding the cavity 112 is metallurgically bonded to the first sub-layer 102a of the first metal layer 102, and the surface is preferably flat.

[0102] Item 23. The cooking appliance 400 according to any one of items 1 to 22, wherein the second metal layer 112; 212; 312 is metallurgically bonded to the flat lower surface of the first metal layer 102; 202; 302.

[0103] Item 24. The cooking appliance 400 according to any one of items 1 to 23, wherein the bottom surface of the second metal layer 110; 210; 310 is flat.

[0104] Item 25. A method of fabricating a cooking appliance 400, comprising: (a) providing a first metal layer 102; 202; 302; (b) providing a perforated graphite layer 108; 208; 308 having a thickness of at least 0.010 inches (0.254 mm) and formed such that a plurality of spaced-apart holes 114; 214; 314 penetrate therethrough; (c) providing a second metal layer 110; 210; 310 having cavities 112; 212; 312 and from the bottom surfaces 118; 218; 318 of the cavities 112; 212; 312, a plurality of spaced-apart posts project; (d) stacking the layers provided in (a)-(c) to form a blank assembly 100; 200; 300 such that the perforated graphite layer 108; 208; 308 is received within the cavities 112; 212; 312 of the second metal layer 110; 210; 310, whereby a plurality of spaced-apart posts 116; 216; 316 of the second metal layer 110; 210; 310 are aligned with and extend through the plurality of spaced-apart holes 114; 214; 314 of the perforated graphite layer 108; 208; 308, such that the lower surface of the first metal layer 102; 202; 302 contacts at least the upper surfaces of the upper end portions of the plurality of spaced-apart posts 116; 216; 316; and (e) applying a force in a direction perpendicular to the plane of the layers of the blank assembly 100; 200; 300 to crimp the blank assembly 100; 200; 300 while heating the blank assembly 100; 200; 300 to effect a metal bond between the first metal layer 102; 202; 302 and the second metal layer 110; 210; 310 through at least the plurality of spaced-apart posts 116; 216; 316, thereby providing a joined multi-layer blank assembly 100; 200; 300.

[0105] Item 26. The method according to item 25, further comprising: (f) cooling the joined multi-layer blank assembly 100; 200; 300; and (g) forming a cooking appliance 400 from the joined multi-layer blank 100; 200; 300 assembly.

[0106] Item 27. The method according to item 25 or 26, wherein the first metal layer 102; 202; 302 is made of aluminum or stainless steel or titanium, and the second metal layer 110; 210; 310 is made of aluminum.

[0107] Item 28. (h) Further comprising laminating a third metal layer 104; 304 with other layers of the blank assembly 100; 300 before crimping the blank assembly 100; 300 so that the third metal layer 104; 304 faces the flat side on the opposite side of the voids 114; 314 in the second metal layer 110; 310. The method according to any one of items 25 to 27.

[0108] Item 29. (i) Further comprising laminating a fourth metal layer on the first metal layer of the blank assembly before crimping the blank assembly. The method according to item 28.

[0109] Item 30. The method according to item 29, wherein the third metal layer and the fourth metal layer are made of stainless steel.

[0110] Item 31. A cooking appliance made from a plurality of laminated blank assemblies, the cooking appliance comprising: a first metal layer; a lower metal layer; and a core disposed between the first metal layer and the lower metal layer, the core having a void, from the bottom surface of the void, a plurality of spaced posts projecting, an aluminum core metal layer, and a perforated graphite layer formed such that a plurality of spaced holes penetrate therethrough, the graphite layer being positioned in the void of the core metal layer such that the plurality of posts extend through the plurality of holes, the core metal layer being metallurgically joined to the first metal layer through at least the plurality of posts and to the second metal layer through the bottom surface of the core metal layer.

[0111] Item 32. The cooking appliance according to item 31, wherein the upper surface surrounding the void in the core metal layer is metallurgically joined to the first metal layer.

[0112] Item 33. The cooking appliance according to item 31 or 32, wherein the depth of the cavity is smaller than, equal to, or greater than the thickness of the graphite layer.

[0113] Item 34. The cooking appliance according to any one of items 31 to 33, wherein the core metal layer is metallurgically joined to the flat lower surface of the first metal layer.

[0114] Item 35. The cooking appliance according to any one of items 31 to 34, wherein the plurality of posts have a circular cross-section.

[0115] Item 36. The cooking appliance according to any one of items 31 to 35, wherein the plurality of posts have a polygonal cross-section.

[0116] Item 37. The cooking appliance according to any one of items 31 to 36, wherein the bottom surface of the core metal layer is flat.

[0117] Item 38. The cooking appliance according to any one of items 31 to 37, wherein the core metal layer includes an outer core metal layer and a central core metal layer received within a central opening of the outer core metal layer.

[0118] Item 39. The cooking appliance according to item 38, wherein the outer core metal layer has the same thickness as the central core metal layer.

[0119] Item 40. The cooking appliance according to item 39, wherein the outer core metal layer has a thickness smaller than that of the central core metal layer.

[0120] Item 41. The cooking appliance according to any one of items 31 to 40, wherein the first metal layer is made of stainless steel or titanium.

[0121] Item 42. The cooking appliance according to item 41, wherein the stainless steel is a ferromagnetic grade of stainless steel.

[0122] Item 43. The cooking appliance according to any one of items 31 to 42, wherein the lower metal layer is made of stainless steel or titanium.

[0123] Item 44. The cooking appliance according to item 43, wherein the stainless steel is a ferromagnetic grade stainless steel.

[0124] Item 45. The cooking appliance according to any one of items 31 to 44, wherein the core metal layer is made of aluminum.

[0125] Item 46. The cooking appliance according to item 45, wherein the aluminum is alloy 1100.

[0126] Item 47. The cooking appliance according to any one of items 31 to 46, wherein the graphite layer is made of anisotropic graphite.

[0127] Item 48. The cooking appliance according to any one of items 31 to 47, wherein the first metal layer includes a first sub-layer made of aluminum and a second sub-layer made of stainless steel.

[0128] Item 49. The cooking appliance according to item 48, wherein the core metal layer is metallurgically joined to the first sub-layer of the first metal layer.

[0129] Item 50. The cooking appliance according to any one of items 31 to 51, wherein the graphite layer has a thickness between 0.010 inches (0.25 mm) and 0.100 inches (2.5 mm).

[0130] Item 51. A method of manufacturing a cooking appliance, comprising: (a) providing an upper metal disk of stainless steel; (b) providing a perforated graphite disk formed such that a plurality of spaced-apart holes penetrate therethrough; (c) providing an aluminum core metal disk having a cavity, and a plurality of posts projecting from the bottom surface of the cavity and spaced apart from each other; (d) providing a lower metal disk of stainless steel; (e) positioning the graphite disk within the cavity of the core metal disk such that the upper end portions of the plurality of posts extend above the upper surface of the graphite disk, aligning the plurality of posts of the core metal disk with the plurality of holes of the graphite disk and extending them therethrough, so that the lower surface of the upper metal disk contacts the upper surface of the upper portion of the core metal disk and the upper end portions of the plurality of posts; stacking the disks provided in (a) to (d) to form a blank assembly; and (f) applying a force in a direction perpendicular to the plane of the disks of the blank assembly to crimp the blank assembly, and simultaneously heating the blank assembly to effect metal bonding between the metal materials of the disks of the blank assembly to provide a bonded blank assembly.

[0131] Item 52. The method according to Item 51, further comprising: (g) cooling the bonded blank assembly; and (h) forming a cooking appliance from the bonded blank assembly.

[0132] Item 53. A cooking appliance manufactured from a bonded multi-layer blank assembly, the cooking appliance comprising: a first metal layer; a lower metal layer having a cavity, and a plurality of posts projecting from the bottom surface of the cavity and spaced apart from each other; and a perforated graphite layer formed such that a plurality of spaced-apart holes penetrate therethrough, wherein the graphite layer is positioned within the cavity of the core metal layer such that the plurality of posts extend through the plurality of holes, and the lower metal layer is metallurgically bonded to the first metal layer at least via the plurality of posts.

[0133] Item 54. The cooking appliance according to item 53, wherein an upper surface of the lower metal layer that surrounds the cavity is metallically joined to the first metal layer.

[0134] Item 55. The cooking appliance according to item 53 or 54, wherein a depth of the cavity is smaller than, equal to, or greater than a thickness of the graphite layer.

[0135] Item 56. The cooking appliance according to any one of items 53 to 55, wherein the second metal layer is metallically joined to a flat lower surface of the first metal layer.

[0136] Item 57. The cooking appliance according to any one of items 53 to 56, wherein the plurality of posts have a circular cross section.

[0137] Item 58. The cooking appliance according to any one of items 53 to 57, wherein the plurality of posts have a polygonal cross section.

[0138] Item 59. The cooking appliance according to any one of items 53 to 58, wherein a bottom surface of the core metal layer is flat.

[0139] Item 60. The cooking appliance according to any one of items 53 to 59, wherein the first metal layer is made of stainless steel or titanium.

[0140] Item 61. The cooking appliance according to item 60, wherein the stainless steel is a ferromagnetic grade of stainless steel.

[0141] Item 62. The cooking appliance according to any one of items 51 to 61, wherein the lower metal layer is made of aluminum.

[0142] Item 63. The cooking appliance according to item 62, wherein the aluminum is 1100 alloy.

[0143] Item 64. The cooking appliance according to any one of items 53 to 63, wherein the graphite layer is made of anisotropic graphite.

[0144] Item 65. A method of manufacturing a cooking appliance, comprising: (a) providing an upper metal disk of stainless steel; (b) providing a perforated graphite disk formed such that a plurality of spaced-apart holes penetrate therethrough; (c) providing a lower metal disk of aluminum having a cavity and having a plurality of posts projecting from the bottom surface of the cavity; (d) aligning and extending the plurality of posts of the lower metal disk through the plurality of holes of the graphite disk such that the graphite disk is received within the cavity of the lower metal disk and, thereby, the upper end portions of the plurality of posts extend above the upper surface of the graphite disk, whereby the lower surface of the upper metal disk contacts the upper surface of the outer portion of the lower metal disk and the upper end portions of the plurality of posts; stacking the disks provided in (a) to (c) to form a blank assembly; and (e) applying a force in a direction perpendicular to the plane of the disks of the blank assembly to crimp the blank assembly while heating the blank assembly to effect a metal bond between the metal materials of the disks of the blank assembly and provide a joined blank assembly.

[0145] Item 66. The method according to item 65, further comprising: (f) cooling the joined blank assembly; and (g) forming a cooking appliance from the joined blank assembly.

[0146] The disclosure has been described with reference to specific details of particular examples. Such details are not to be regarded as limitations on the scope of the disclosure as long as they are included within the scope of the appended claims.

Claims

1. Manufactured from a plurality of joined blank assemblies, a first metal layer, a second metal layer having voids and a plurality of posts protruding therefrom spaced apart from the bottom surface of the voids, a perforated graphite layer having a thickness of at least 0.010 inches (0.254 mm) and formed with a plurality of spaced-apart holes therethrough and comprising, the perforated graphite layer is positioned within the void of the second metal layer such that the plurality of spaced-apart posts extend through the plurality of spaced-apart holes, the second metal layer is metallurgically joined to the first metal layer through at least the plurality of spaced-apart posts, a cooking appliance.

2. The cooking appliance according to claim 1, further comprising a third metal layer metallurgically joined to a flat side of the second metal layer opposite the void.

3. The cooking appliance according to claim 2, wherein the third metal layer is made of stainless steel.

4. The cooking appliance according to claim 1, wherein a surface of the second metal layer surrounding the void is metallurgically joined to the first metal layer.

5. The cooking appliance according to claim 1, wherein a surface of the second metal layer surrounding the void is flat.

6. The cooking appliance according to claim 1, wherein the depth of the void is less than, equal to, or greater than the thickness of the perforated graphite layer.

7. The cooking appliance according to claim 1, wherein the plurality of spaced-apart posts have a circular cross-section or a polygonal cross-section.

8. The cooking appliance according to claim 1, wherein the first metal layer is made of aluminum or stainless steel, the perforated graphite layer is made of anisotropic graphite, and the second metal layer is made of aluminum.

9. The first metal layer comprises a first sublayer made of aluminum and a second sublayer made of stainless steel, the second metal layer is metallurgically joined to the first sublayer of the first metal layer, the cooking appliance according to claim 1.

10. The cooking appliance according to claim 1, wherein the second metal layer is an alloy aluminum material coated with a pure aluminum thin layer on any surface to be compatible with metallurgical joining.

11. A plurality of blank assemblies for making a cooking appliance, comprising a first metal layer, a second metal layer having voids and a plurality of posts protruding therefrom spaced apart from the bottom surface of the voids, A perforated graphite layer having a thickness of at least 0.010 inches (0.254 mm) and formed with a plurality of spaced-apart holes therethrough, and comprising wherein the perforated graphite layer is positioned within the cavity of the second metal layer such that the plurality of spaced-apart posts extend through the plurality of spaced-apart holes, A multi-layer blank assembly in which the second metal layer is configured to be metallurgically joined to the first metal layer through at least the plurality of spaced-apart posts. **Claim 12** The multi-layer blank assembly according to claim 11, further comprising a third metal layer configured to be metallurgically joined to a flat side of the second metal layer opposite the cavity. **Claim 13** The multi-layer blank assembly according to claim 12, wherein the third metal layer is made of stainless steel. **Claim 14** The multi-layer blank assembly according to claim 11, wherein a surface of the second metal layer surrounding the cavity is metallurgically joined to the first metal layer. **Claim 15** The multi-layer blank assembly according to claim 11, wherein the plurality of spaced-apart posts have a circular cross-section or a polygonal cross-section. **Claim 16** The multi-layer blank assembly according to claim 11, wherein the perforated graphite layer is made of anisotropic graphite, the first metal layer is made of stainless steel, and the second metal layer is made of aluminum. **Claim 17** A method of manufacturing a cooking appliance, comprising: (a) providing a first metal layer; (b) providing a perforated graphite layer having a thickness of at least 0.010 inches (0.254 mm) and formed with a plurality of spaced-apart holes therethrough; (c) providing a second metal layer having a cavity and having a plurality of spaced-apart posts protruding from a bottom surface of the cavity; (d) stacking the layers provided in (a) - (c) to form a blank assembly such that the perforated graphite layer is received within the cavity of the second metal layer, whereby the plurality of posts of the second metal layer are aligned with and extend through the plurality of holes of the perforated graphite layer, such that a lower surface of the first metal layer contacts at least an upper surface of upper end portions of the plurality of posts. A method comprising: (e) crimping the blank assembly by applying a force in a direction perpendicular to the plane of the layer of the blank assembly, and simultaneously heating the blank assembly to achieve a metal bond between the first metal layer and the second metal layer, thereby providing a blank assembly of a plurality of joined layers.

18.

19. The method according to claim 17, further comprising: (f) preparing a third metal layer and laminating the third metal layer with the layer of the blank assembly before crimping the blank assembly such that the third metal layer faces a flat side of the second metal layer opposite the void.

19.

20. The method according to claim 18, further comprising: (g) cooling the joined blank assembly; and (h) forming the cooking appliance from the joined blank assembly.

20.

20. The method according to claim 17, wherein the first metal layer is made of aluminum or stainless steel. The method according to claim 17, wherein the perforated graphite layer is made of anisotropic graphite. The method according to claim 17, wherein the second metal layer is made of aluminum.

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