Patent Application
20220110475
The present invention relates to cookware and surfaces thereof, such as food preparation surfaces and induction heating features of pots, pans, platens, griddles and grills.
Some foods tend to stick to cookware surfaces. This tendency is particularly common with heated cookware surfaces when preparing such foods. To combat this tendency, cookware articles may be outfitted with what is often referred to as “nonstick” or “easy release” cooking surfaces. These surfaces typically include coated metal surfaces including fluorocarbons, such as PTFE (polytetrafluoroethylene); vitreous enamel; silicones; and ceramics.
According to a first embodiment, a cookware article includes a base material layer, at least a first mesh layer, and a nonstick coating layer. The base material layer may have at least a first base surface along a first side. The first mesh layer may be disposed on the first base surface, and may include a plurality of first network segments embedded in the first base surface and that extend outward therefrom to a planar outer first mesh surface. The first network segments may define a plurality of first interior regions between adjacent first network segments. The nonstick coating layer may be disposed on the first base surface, within the first interior regions between the adjacent first network segments, and extend outward therefrom to an outer nonstick coating surface adjacent to the outer first mesh surface. The outer first mesh surface may be disposed outward at least as far as the adjacent outer nonstick coating surface. At least a portion of the first base surface of the base material layer under the nonstick coating layer may have an arithmetic average roughness (Ra) of greater than 160 microinches and less than 289 microinches.
In some embodiments, the portion of the first base surface of the base material layer under the nonstick coating layer may have the arithmetic average roughness (Ra) of greater than or equal to 180 microinches and less than approximately 200 microinches. In other embodiments, the portion of the first base surface of the base material layer under the nonstick coating layer may have the arithmetic average roughness (Ra) of greater than or equal to 180 microinches and less than 200 microinches. Also, the portion of the first base surface of the base material layer under the nonstick coating layer may be the entire first base surface.
The first base surface and layers thereon may employ a variety of configurations. For example, in various embodiments, the portion of the first base surface of the base material layer under the nonstick coating layer may be planar. In some embodiments, the outer nonstick coating surface may include a plurality of discrete surfaces interspersed between the first network segments. The first network segments may be interconnected and surround the plurality of first interior regions. In one embodiment, the base material layer is (or includes) aluminum and the first mesh layer is (or includes) stainless steel first network segments. Adjacent first network segments may define one of parallelogram, hexagonal, or rhomboidal first interior regions. For example, adjacent first network segments may define hexagonal interior regions.
Various cookware articles employing the inventive surface features may include a pot, pan, tray, platter, platen, grill, griddle surface, baking tray, or pizza pan.
According to a second embodiment, a method of making a surface of a cookware article may include providing a base material including a metal or metal alloy, increasing an arithmetic average roughness (Ra) of at least one planar surface of the metal or alloy to greater than 160 microinches and less than 289 microinches, and coating the planar surface of the metal or alloy with an organic nonstick material. The method may further include compressing a mesh including a plurality of network segments that include a metal or metal alloy onto the coated surface to embed the network segments into the base material. The network segments may define a plurality of interior regions between adjacent network segments. The network segments may also extend outward of the base material at least as far as the nonstick material.
In various embodiments, the method may further include increasing the arithmetic average roughness (Ra) of that at least one planar surface of the metal or alloy to greater than or equal to 180 microinches and less than approximately 200 microinches. The method may further include increasing the arithmetic average roughness (Ra) of that at least one planar surface of the metal or alloy to greater than or equal to 180 microinches and less than 200 microinches.
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.
Novel features of the present invention are set forth with particularity in the appended claims. However, the various embodiments of the present invention described herein, both as to organization and manner of operation, may be best understood by reference to the following description, taken in conjunction with the accompanying drawings in which:
Nonstick or easy release cooking surfaces are typically deployed as coatings. The durability of these coatings may be enhanced through chemistry, particulate reinforcement, and layers. However, even when enhanced, nonstick or easy release coatings may still be easily scratched or cut by hard tools or other cookware, such as cookware utensils including sharp tools like knives and circular pizza cutters, or with similar sharp instruments. Thus, this lack of durability also limits cross-use of cookware articles that may damage a coating of either article.
According to various embodiments, the present disclosure describes reinforced nonstick cookware article surfaces, generally denominated article surface 100 in
With reference to
The cookware article surface 100 may also include a mesh layer 120 disposed over at least a portion of a surface 111 of the base material layer 110. The portion of the surface 111 onto which the mesh layer 120 is disposed will typically be planar. Thus, the mesh layer 120 may be disposed over a planar surface portion of the surface 111. The mesh layer 120 includes a plurality of network segments 121 arranged along the surface 111 of the base material layer 110 that extend outward therefrom to together define a generally planar outer mesh surface 122 above the base material surface 111. Adjacent network segments 121 along the mesh layer 120 may define a plurality interior regions 123. The interior regions 123 may have various shapes and sizes as described in more detail below. The interior regions 123 may be patterned to include consistent sizes, shapes, and alignments. The network segments 121 may be interconnected to surround interior regions 123 or may be partially or entirely disconnected to partially surround interior regions 123. The mesh layer 120 may embed within the surface 111 of the base material layer 110. For example, as shown, inwardly positioned portions of the network segments 121 that interface with the surface 111 may embed in the base material layer 110.
The cookware article surface 100 may also include a nonstick coating layer 130 that coats a portion of the surface 111 of the base material layer 110 between the adjacent network segments 121 within the interior regions 123. The nonstick coating layer 130 may extend outward of the base material layer 110 to an outer nonstick coating surface 132 adjacent to the planar outer mesh surface 122. Thus, the nonstick coating layer 130 may be interspersed among the network segments 121 to, together with the mesh layer 120, provide an outer surface comprising a plurality of outer nonstick coating surface 132 regions disposed between outer mesh surface 122 regions. In various embodiments, the outer nonstick coating surface 132 may include discrete or interconnected regions. In the embodiment illustrated in
Interior regions 123 may preferably have a spacing or diameters between about 0.8 mm and about 2 mm. Smaller dimensions or larger dimensions may also be used. The width of the network segments 121 between the interior regions 123 may preferably be between about 0.3 mm and about 0.5 mm, although smaller or larger width dimensions may also be used. The thickness of the network segments 121 may also preferably be between about 0.5 mm to about 1 mm normal to the cookware article surface 100; however, smaller or larger thicknesses may be used. In various embodiments, the base material layer 110 may preferably be between 3 mm and 4 mm thick, although smaller or larger thicknesses may be used.
The base material layer 110 may be coated with the nonstick coating layer 130 according to any suitable method. For example, various U.S. patents teach compositions of matter and methods of applying organic based and nonstick coatings to cookware vessels. These include U.S. Pat. No. 3,986,993 to Vassiliou (issued Oct. 19, 1976); U.S. Pat. No. 4,118,537 to Vary, et al. (issued Oct. 3, 1978); U.S. Pat. No. 4,321,177 to Wilkinson (issued Mar. 23, 1982); U.S. Pat. No. 5,691,067 to Patel (issued Oct. 25, 1997) and U.S. Pat. No. 6,133,359 to Bate, et al. (issued Oct. 17, 2000), all of which are incorporated herein by reference. The nonstick coating layer 130 may typically contain one or more low surface energy polymers of resin, particularly fluorinated resins or fluorinated silicone resins, and silicone resins, including, PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene), PFA (Perfluoroalkoxy) and combinations thereof, along with reinforcing fillers such as glass, aluminum oxide titanium oxide, silicon carbide, and the like, and may preferably be deposited as multilayer coatings with varying compositions so the exposed outer surface, though softer, is more chemically inert and water and oil repellent. The nonstick coating layer 130 may also include one or more binder resins such as polyamide-imide (PAI), polyphenylene sulphide (PPS), polyether sulphone (PES), or a silicone and possibly also pigments.
In various embodiments, the mesh layer 120 may be embedded into the base material layer 110 by force. For example, surface 111 of the base material layer 110 may be coated with the nonstick coating layer 130 and the mesh layer 120 may be forced against the exposed nonstick coating layer 130. As the mesh layer 120 is embedded by force into the base material layer 110, it penetrates the nonstick coating layer 130 which is then exposed within the interior regions 123 between the network segments 121 of the mesh layer 120. The embedding process may result in the planar outer mesh surface 122 being positioned no lower than the outer nonstick coating surface 132 positioned within the interior regions 123 along the outer surface. In some embodiments, the outer mesh surface 122 is approximately level with the outer nonstick coating surface 132. In other embodiments, the outer mesh surface 122 extends beyond the outer nonstick coating surface 132, such as between 0 mm and about 0.01 mm, or between about 0.01 mm and about 0.1 mm.
The mesh layer 120 preferably comprises a metal material, including alloys thereof, harder than the organic nonstick coating material of the nonstick coating layer 130 and the base material of the base material layer 110. For example, a mesh layer 120 formed of stainless steel network segments 121 may be readily embedded into an aluminum base material after a nonstick coating layer 130, as stainless steel network segments 121 are harder than both the aluminum base material and the nonstick coating material. The planar outer mesh surface 122 extending beyond or level with the nonstick coating outer surface 132 provides a network of protective shields that prevent hard surfaces, such as sharp steel tool surfaces, from digging into the nonstick coating 130 within the interior regions 123. In some embodiments, the mesh layer 120 may be any other material (such as any other metal) that is harder than the base material (such as metal) of the base material layer 110
The mesh layer 120 may be formed by casting, forming, assembly, material removal techniques such as excising material from sheets, or other suitable fabrication techniques to form the network segments 121. In one example, the arrangement of the network segments 121 of the mesh layer 120 illustrated in
In various embodiments, a cookware article comprises the cookware article surface 100. The cookware article surface 100 may optionally be any portion of a pot, pan, tray, platter, platen, grill, or griddle surface, for example. In one embodiment, the cookware article surface 100 is a portion of a nonstick surface of a baking tray, or pizza pan wherein the mesh layer 120 protects the outer nonstick surface 132 from a knife blade, such as a mezzaluna, or circular pizza cutting wheel.
With reference to
In the illustrated embodiment, the cookware article surface 100 comprises a base material layer 110, first and second mesh layers 120, 120′, and a nonstick coating layer 130 wherein the first mesh layer 120 and the nonstick coating layer 130 are disposed on a first surface 111 of the base material layer 110 and the second mesh layer 120′ is disposed on a second surface 111′ of the base material layer 110, generally opposite the first surface 111. The first mesh layer 120 includes a plurality of first network segments 121 embedded in the first surface 111 and extending to a first outer mesh surface 122. The nonstick coating layer 130 is disposed within interior regions 123 defined by the first network segments 121 and extends outward from the first surface 111 to a plurality of outer nonstick coating surfaces 132 in an arrangement similar to that described with respect to
The second mesh layer 120′ includes a plurality of second network segments 121′ embedded in the second surface 111′ and extending to a generally planar second outer mesh surface 122′. The second network segments 121′ are arranged to define interior regions 123′ between adjacent segments 121′ within which the second surface 111′ of the base material layer 110 is exposed to form an outer base material surface 112. In various embodiments, the base material layer 110 may preferably be between 3 mm and 4 mm thick, although smaller or larger thicknesses may be used. While the base material layer 110 is illustrated as the same across and through the thickness of the expanse of the cookware article surface 100, in various embodiments a same base material layer may not form both the first and second surfaces 111, 111′. For example, the base material layer 110 may comprise multiple base materials layers 110.
The second network segments 121′ of the second mesh layer 120′ are illustrated as being embedded deeper in the base material layer 110 than the first network segments 121 of the first mesh layer 120. In other embodiments the first network segments 121 may be embedded the same depth or deeper than the second network segments 121′. The second outer mesh surface 122′ is disposed no lower than the outer base material surface 112. Thus, the second outer mesh surface 122′ may extend outward beyond the outer base material surface 112 along the second surface 111′. The outer base material surface 112 may also be level with second outer mesh surface 122. The thickness of the second network segments 121′ may be similar to the thickness of the first network segments 121. For example, in some embodiments, the thickness of the second network segments 121′ may be between about 0.5 mm to about 1 mm normal to the cookware article surface 100; however, smaller or larger thicknesses may be used. For example, first or second network segments 121, 121′ having larger thicknesses may be used to increase strength and durability.
The second network segments 121′ may be interconnected to surround interior regions 123′ or may be partially or entirely disconnected to partially surround interior regions 123′. Similarly, the outer base material surface 112 may be interconnected or comprise discrete regions. For example, the outer base material surface 112 may include a discrete surface region within each interior region 123′ between interconnected second network segments 121′.
The second network segments 121′ of the second mesh layer 120′ are illustrated as having a width similar to the first network segments 121 of the first mesh layer 120. For example, the width of the second network segments 121′ between the interior regions 123′ may preferably be between about 0.3 mm and about 0.5 mm. In other embodiments, the first network segments 121 may have larger or smaller widths than the second network segments 121′. For example, the second network segments 121′ may include thicknesses larger than 0.5 mm to increase induction capacity, when applicable, or the structural strength and durability therealong.
The second network segments 121′ may define interior regions 123′ having any shape, such as parallelogram, rhomboidal, hexagonal, arcuate, geometric, nongeometric, regular, or irregular shapes. The second network segments 121′ may also define interior regions having shapes, sizes, or in arrangements similar to or different than the shapes, sizes, or arrangements defined by the first network segments 121. In some embodiments, the second network segments 121′ are illustrated as defining interior regions 123′ having similar diameters as the interior regions 123 defined by the first network segments 121. For example, the interior regions 123 may have a spacing or diameter between about 0.8 mm and about 2 mm. However, in other embodiments, second network segments 121′ define interior regions 123′ having smaller or larger diameters than the interior regions 123 defined by the first network segments 121.
The outer base material surface 112 may correspond to the outer nonstick coating surface 132 in size, shape, or location. However, in other embodiments, outer base material surface 112 may not correspond to the outer nonstick coating surface 132 with respect to one or more of size, shapes, or location.
The second mesh layer 120′ and second network segments 121′ thereof may comprise materials and be fabricated in a manner similar to that described with respect to the first mesh layer 120. In various embodiments, the second network segments 121′ comprise a material harder than the base material along the second surface 111′, such as a hard metal or alloy. In some embodiments, the second network segments 121′ comprise stainless steel. In some embodiments, the second mesh layer 120′ may be configured to provide induction heating features. For example, the second network segments 121′ may comprise a ferromagnetic material. In one embodiment, the second mesh layer 120′ comprises magnetic stainless steel for induction heating of the first outer surfaces 122/132.
The second network segments 121′ disposed along the underside of the pan are preferably magnetic stainless steel for induction heating of the outer surfaces 122/132. The first and second network segments 121, 121′ may define interior regions 123, 123′ of any shape. In one embodiment, the first network segments 121, the second network segments 121′, or both define hexagonal, parallelogram, rectangular, or rhomboidal shaped interior regions 123, 123′ with a spacing or diameter between about 0.8 mm and about 2 mm. The width of the network segments 121, 121′ between the interior regions 123, 123′ may preferably be between about 0.3 mm and about 0.5 mm. The thickness of the network segments 121, 121′ may also preferably be between about 0.5 mm to about 1 mm normal to the cookware article surface 100. The base material layer 110 may preferably be between 3 mm and 4 mm thick. The base material layer 110 along the second surface 111′ may comprise similar base materials as described above with respect to
The dish shape of the cookware article 10 may be formed before or after embedding the first mesh layer 120, second mesh layer 120, or both. For example, the network segments 121, 121′ may be embedded when a pot or pan is formed. Side surfaces 104, 104′ surround the planar cooking article surface 100. In various embodiments, interior or exterior side surfaces 104, 104′ may also include a mesh layer 120, 120′, nonstick layer 130, or both. For example, in the illustrated embodiment, the interior side surface 104 includes a nonstick layer. The cookware article 10 is preferably made by embedding network segments 121, 121′ in a respective surface 111, 111′ of the base material layer 110 after an organic nonstick material is coated onto the at least one surface 111, 111′. The network segments 121, 121′ will first penetrate through the nonstick coating layer 130, but thereafter form a protective barrier from cutting tools, such as knives, mezzalunas, cutting wheels, spatulas and the like.
It will be appreciated that the embodiments illustrated in
Another aspect of the invention is an improved process for attaching the first mesh layer 120 to the cookware article 100 by embedding it in the nonstick coating layer 130. As is discussed below, the process includes a roughening step where the surface 111 of the base material layer 110 is roughened to an arithmetic average roughness (Ra) of greater than 160 microinches and less than 289 microinches, and more specifically an Ra of greater than or equal to 180 microinches and less than approximately 200 microinches (i.e., 200 microinches+/−5 microinches). These Ra ranges have been unexpectedly found to cause greater adhesion between the surface 111 and the non-stick coating layer 130. Further details regarding this surprising find are discussed below with regard to
The next step 520 is to roughen the interior surface 111 of the cookware body before the deposition of the non-stick coating thereon in step 530. Any portion of the interior surface 111 of the cookware body may be roughened. For example, the entire interior surface 111 of the cookware body may be roughened. As another example, only the portion of the interior surface 111 that will be in contact with the non-stick coating may be roughened.
The roughness may be achieved by various means, such as abrasion of the original surface 111, or addition of further layers that inherently form a rough layer (such as the addition of metals, like stainless steel, or arc spray ceramic particles). However, since the subsequent step 550 is to embed the mesh 120 in the non-stick coating layers 130 to penetrate the interior surface 111 of the cookware body, the roughening step is preferably by abrasion methods such as abrasive blasting with grit particles. This may avoid increasing the interior surface 111 hardness to a degree that would impede such penetration of the mesh 120. Further details regarding this roughening step are discussed below.
After the step of roughening, the non-stick coating is first deposited in step 530 and then cured in step 540. As non-stick coatings frequently deploy 2 to 3 sub-layers of different composition(s), the curing may be carried out after each sub-layer is deposited as a solution and/or slurry, after which the liquid vehicle or solvent may be removed by evaporation, such as by heating. Curing may refer to such heating steps, which also promote sintering and/or chemical bonding and adhesion of organic and inorganic components in layer or sub-layers of the non-stick coating.
In step 550, a sufficient level of force is applied to the mesh 120 (e.g., to the top surface of the mesh 120), so as to cause the mesh 120 to penetrate through the nonstick coating layer 130 and further penetrate into the surface 111. This may cause the mesh 120 to become bonded to the surface 111. In a preferable example, the upper surface of the mesh 120 should be level with (or slightly above) the upper surface of the non-stick coating layer 130.
With regard to the roughening step 520 of
Ra may be measured using a profilometer, in some embodiments. In other embodiments, Ra may be measured using any of the devices and/or methods discussed in ASME B46.1 (2020).
For aluminum surfaces, it has been traditionally understood that the minimum arithmetic average roughness (Ra) for sufficient adhesion and durability is at least about 150-160 microinches. It has also been traditionally understood that further increasing the minimum arithmetic average roughness (i.e., increasing it above 150-160 microinches) would cause improved adhesion (between the non-stick coating layer 130 and the surface 111), without any changes in observable performance. Furthermore it has also been traditionally understood that the best way for achieving this minimum arithmetic average roughness (Ra) for aluminum surfaces is to grit blast the aluminum surface with a 60 #grit for a time sufficient to reach the Ra.
To test this traditional thinking, testing was performed on a surface 111 that was roughened to an Ra of at least about 150-160 microinches. Initial observations of the cookware noted that the nonstick coating 130 appeared to properly adhere to the surface 111. Specifically, the initial observations indicated no cosmetic defects or functional defects (e.g., where the non-stick coating 130 is delaminated or de-bonded from the mesh 120 or the surface 111) had occurred.
However, additional testing of the cookware with extended cycles of cooking and cleaning was conducted to further test that this traditional thinking regarding an Ra of at least about 150-160 microinches was sufficient to cause the adhesion and integrity of the product mesh 120 and non-stick coating 130 to remain over extended use. This testing involved repeating cycles of (1) cooking a series of foodstuffs in a regular sequence, and (2) cleaning of the cookware surface before the next cooking cycle. After every fifth cooking cycle, the cookware was cleaned in a dishwasher with detergent. Between every other cooking cycle, other than dishwasher cleaning, the cookware was cleaned by hand.
A complete test constituted 80 cooking cycles, as follows:
Cycles 1-20: Eggs were cooked without olive oil at 250° C., flipping the egg after each side is cooked (using 20 eggs for a total of 20 cooking cycles).
Cycle 21-40: Eggs were cooked with a tablespoon of olive oil at 250° C., flipping the eggs after each side is cooked (using 20 eggs for total of 20 additional cycles).
Cycles 41-60: A first side of the steaks were cooked with a tablespoon of olive oil at 250° C., and then the second side of the steaks were cooked without additional olive oil (using 20 steaks for a total of 20 additional cycles).
Cycles 61-80: Chicken wings were cooked with soy sauce and without olive oil at 250° C. (using 20 chicken wings for 20 additional cycles, in which a cycle consisted of cooking both sides of each chicken wing).
As illustrated in the flow chart of
However, it was surprisingly discovered that roughening the surface 111 to an arithmetic average roughness (Ra) of greater than 160 microinches and less than 289 microinches, and more specifically an Ra of greater than or equal to 180 microinches and less than approximately 200 microinches (i.e., 200 microinches+/−5 microinches) unexpectedly caused greater adhesion between the surface 111 and the non-stick coating layer 130. For example, it was discovered that the cooking and cleaning protocol of
Further, it was also discovered that this range of roughness level was achievable by using a more coarse blasting grit, that is #30 or #35, as opposed to a #60 grit. A preferred embodiment of the process of
This specification has been written with reference to various non-limiting and non-exhaustive embodiments and/or examples. However, it will be recognized by persons having ordinary skill in the art that various substitutions, modifications, or combinations of any of the disclosed embodiments and/or examples (or portions thereof) may be made within the scope of this specification. Thus, it is contemplated and understood that this specification supports additional embodiments and/or examples not expressly set forth in this specification. Such embodiments and/or examples may be obtained, for example, by combining, modifying, or reorganizing any of the disclosed steps, components, elements, features, aspects, characteristics, limitations, and the like, of the various non-limiting and non-exhaustive embodiments and/or examples described in this specification. In this manner, Applicant reserves the right to amend the claims during prosecution to add features as variously described in this specification.
