BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to multi-ply, bonded cookware, and in particular to multi-ply, bonded cookware having a core layer of perforated graphite between at least two metal layers metallurgically bonded together. A method for making the cookware using a solid state bonding technique is also disclosed.

Description of Related Art

It has long been known to manufacture multi-layer bonded composite cookware in which various materials are joined together to combine the desired physical properties of each of the materials into a composite. For example, the corrosion resistance of stainless steel is ideal for the cooking surface as well as for the exterior surface of cookware; however, the thermal conductivity of stainless steel is relatively low. On the other hand, aluminum and/or copper offer much higher thermal conductivities and have been bonded to stainless steel to provide well-known composite cookware items such as pots, pans, and the like. Multi-layer bonded cookware is known in the art, as shown in a number of patents, such as, for example: U.S. Pat. Nos. 4,246,045 and 4,167,606 to Ulam; and U.S. Pat. Nos. 8,133,596 and 6,267,830 to Groll. These patents demonstrate the manufacture of multi-layer bonded cookware having stainless steel outer layers bonded to central layer(s) of a higher conductivity aluminum and/or copper. The bonding between layers of these different materials is commonly achieved by conventional roll-bonding techniques using strips of aluminum and/or copper, roll-bonded to outer strips of stainless steel.

A solid state bonding technique using high static pressure and heat applied over time to make a plurality of composite blanks of, for example, a combination of stainless steel—aluminum—stainless steel in manufactured cookware, is disclosed in U.S. Pat. No. 9,078,539 to Groll et al. There is a continued need in the art for producing cookware made using solid state bonding techniques for reducing the weight and improving thermal characteristics of the cookware.

SUMMARY OF THE INVENTION

In view of the existing need in the art, it would be desirable to develop new methods of producing cookware using solid state bonding techniques. It would be further desirable to provide cookware made by such methods, wherein the cookware has reduced weight and improved thermal characteristics over existing cookware made by solid state bonding techniques.

In accordance with some embodiments or aspects of the present disclosure, cookware may be made from a bonded multi-layer composite. The cookware may have at least one upper metal layer, a lower metal layer having a plurality of spaced-apart upwardly protruding dimples formed thereon, and a graphite core layer disposed between the at least one upper metal layer and the lower metal layer. The graphite core layer may have a plurality of spaced-apart holes extending therethrough. The plurality of dimples may extend through the plurality of holes, and the plurality of dimples may be metallurgically bonded to the at least one upper metal layer.

In accordance with some embodiments or aspects of the present disclosure, the at least one upper metal layer may have a layer of stainless steel or titanium bonded to a sub-layer of aluminum. The at least one upper metal layer may be made from an aluminum alloy of 1000 series, such as an 1100 alloy, or an Alclad material. The lower metal layer may be made from stainless steel or titanium and the plurality of dimples may be bonded to the aluminum alloy of the at least one upper layer. The stainless steel of the lower metal layer may be a ferro-magnetic grade of stainless steel or other corrosion-resistant grade of stainless steel. The graphite core layer may be made from pyrolytic graphite.

In accordance with some embodiments or aspects of the present disclosure, the lower metal layer may have a central portion and an outer portion surrounding the central portion, with the plurality of dimples being formed in the central portion. The central portion may be recessed relative to the outer portion to receive the graphite core layer. The outer portion may be directly bonded to the at least one upper metal layer to form a fully bonded sidewall of the cookware.

In accordance with some embodiments or aspects of the present disclosure, cookware made from a bonded multi-layer composite may have an upper layer of stainless steel or titanium pre-bonded to a sub-layer of aluminum. The cookware may further have a graphite core layer having a plurality of spaced-apart holes formed therethrough. The cookware may further have a lower layer of stainless steel or titanium having a central portion including a plurality of upwardly protruding, spaced-apart dimples extending through the plurality of holes in the graphite core disc, and an outer portion surrounding the central portion. The central portion may be recessed relative to the outer portion. The outer portion may be bonded to the sub-layer of aluminum, and the plurality of dimples may be bonded to the sub-layer of aluminum.

In accordance with some embodiments or aspects of the present disclosure, the sub-layer of aluminum is made from an aluminum alloy of 1000 series, such as an 1100 alloy, or an Alclad material. The lower layer may be made from a ferro-magnetic grade of stainless steel or other corrosion-resistant grade of stainless steel. The graphite core disc may be made from pyrolytic graphite.

In accordance with some embodiments or aspects of the present disclosure, a method of making cookware may include (a) providing an upper metal disc comprising aluminum; (b) providing a graphite core disc having a plurality of spaced-apart holes therethrough; (c) providing a lower metal disc of stainless steel or titanium having a plurality of upwardly protruding, spaced-apart dimples in a central portion of the lower metal disc with an outer portion surrounding the central portion, wherein the central portion is recessed relative to the outer portion; (d) stacking the discs provided in steps (a)-(c) in a blank assembly such that the graphite core disc is received within the central portion whereby the plurality of dimples in the lower metal disc are aligned with and pass through the plurality of holes in the graphite core disc, with the plurality of dimples having upper end portions extending above an upper surface of the graphite core disc such that a lower surface of the upper metal disc contacts an upper surface of the outer portion of the lower metal disc and the upper end portions of the plurality of dimples; and (e) pressing the blank assembly by applying a force in a direction perpendicular to a plane of the discs in the blank assembly and concurrently heating the blank assembly to achieve a metallurgical bond between metal materials of the discs in the blank assembly to provide a bonded blank assembly. The method may further include (f) cooling the bonded blank assembly; and (g) forming the bonded blank assembly into the cookware.

In accordance with some embodiments or aspects of the present disclosure, cookware having a multi-layer bonded composite wall structure may have an upper pre-bonded layer having a stainless steel or titanium layer defining an inside surface of the cookware and a first layer of aluminum bonded thereto. The cookware may further have a core layer with a central graphite disc having a plurality of spaced-apart holes formed in a patterned array. The core layer further may have a second ring-shaped outer core layer of aluminum surrounding the graphite disc. The core layer may face the first layer of aluminum. The cookware may further have a lower layer of stainless steel or titanium facing the core layer and defining an outside surface of the cookware. The lower layer of stainless steel or titanium may have a plurality of dimples formed therein in a patterned array to match the patterned array of holes formed in the graphite disc such that whereby the dimples of the lower layer of stainless steel or titanium may form a bond with the first layer of aluminum in a central area of the cookware occupied by the graphite disc. A peripheral area of the cookware defining the sidewall including the upper and lower layers of stainless steel or titanium may be continuously bonded together by way of the first and second layers of aluminum.

In accordance with some embodiments or aspects of the present disclosure, cookware made from a bonded multi-layer composite may have a core construction including a central core disc of graphite having a plurality of spaced-apart holes formed therethrough and a ring-shaped outer core layer of aluminum surrounding the central core disc of graphite. The cookware may further have an upper pre-bonded layer having an upper disc of stainless steel or titanium bonded to a lower disc of aluminum. The lower disc of aluminum may be bonded to the ring-shaped outer core layer of aluminum having a lower layer of stainless steel or titanium with a central portion having a plurality of upwardly protruding, spaced-apart dimples formed therein. The dimples may extend through the holes in the graphite central core disc and may be bonded to the lower disc of aluminum of the upper pre-bonded layer. The lower stainless steel or titanium layer further may have an outer portion surrounding the dimples and bonded to the ring-shaped outer core layer of aluminum.

These and other features and characteristics of the cookware described herein, as well as methods of making such cookware, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting. Further, it is to be understood that the disclosure may assume various alternative variations and step sequences, except where expressly specified to the contrary.

