Cooking vessel with flat bottom structure and method for manufacturing same

Abstract

To provide a cooking container having a flat bottom structure and a manufacturing method thereof.SOLUTION: A cooking container includes: a dome-shaped plate having a bottom face and a top face, which is formed curved like a dome swollen downward so as to store food; a cup-shaped base for supporting the periphery of the central part of the bottom face of the dome-shaped plate; and an aluminum core material interposed between the dome-shaped plate and the cup-shaped base for connecting them. The dome-shaped plate can include a concave part caved upward in a thickness direction from the central part of the bottom face. The invention can include a manufacturing method of the cooking container having a flat bottom structure.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cooking vessel having a flat bottom structure, and more particularly to a cooking vessel providing a domed plate with a flat bottom structure. The present invention also includes a method of making the cooking vessel described above. [Background technology]

[0002] As is well known, hot pot is a dish in which various ingredients such as beef, pork, and vegetables are placed in a pot, soup is poured over, and the pot is boiled. Hot pot dishes have a wide, shallow, dome-shaped bottom to allow for quick heating, and as shown in Figure 6a, the pot has a structure suitable for heating on a gas range R1. Such conventional pots have a streamlined, curved bottom surface that makes them prone to inadvertent tipping. Furthermore, only the center of the bottom surface of the container body is heated locally, limiting the ability to cook at a uniform temperature due to the temperature difference between the center and periphery of the container body.

[0003] Recently, induction lenses have been gaining attention in homes and restaurants due to their advantages of providing a comfortable indoor environment without the risk of burns or fires caused by sparks, generating less harmful gases such as carbon monoxide, and consuming less oxygen indoors. As shown in Figure 6b, when a conventional pot is placed on the top plate of an induction range R2, which generally has a flat structure, and heated, the contact area with the cooking zone is reduced, resulting in a significant decrease in heating efficiency and making it impossible to ensure stable placement of the pot. For this reason, cooking vessels with a flat bottom structure have been proposed that can be used with kitchen heating appliances that have flat tops, such as induction ranges, high-light ranges, hot plates, etc. Such cooking vessels with a flat bottom structure are manufactured by impact bonding a dome-shaped vessel body and a stainless steel bottom plate, as disclosed in Patent Document 1, which has already been registered and has the same applicant as the present invention, Lee Un-hak.

[0004] In Patent Document 1, the container body and the stainless steel bottom plate are joined via an aluminum plate using an impact bonding method, but there is a limit to maintaining the alignment between the container body and the stainless steel bottom plate during the instantaneous pressure bonding process using a press. In addition, there is a problem in that molten or semi-molten aluminum often escapes from between the container body and the stainless steel bottom plate and may leak to the outside. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Registration No. 10-2175889 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is intended to solve such problems, and its purpose is to provide a cooking container consisting of a dome-shaped container body like a pot, with a flat bottom structure so that it can be seated stably on a flat cooking utensil. The present invention also includes a method of making a cooking vessel that provides a flat bottom configuration to a domed plate as described above. [Means for solving the problem]

[0007] To achieve the above object, the cooking vessel according to the present invention includes a dome-shaped plate having a bottom surface and a top surface, and curved in a downwardly bulging dome shape so that food can be accommodated therein; a cup-shaped base that supports the center of the bottom surface of the dome-shaped plate; and an aluminum core material interposed and joined between the dome-shaped plate and the cup-shaped base, wherein the dome-shaped plate may have a recess that is recessed upward in the thickness direction from the center of the bottom surface.

[0008] In an embodiment of the present invention, the cup-shaped base may include a flat bottom surface and a side surface extending upward along the periphery of the bottom surface. The present invention allows a recess to be disposed within the upper opening of the cup-shaped base. The recessed portion may have an inclined surface that is inclined upward in the circumferential direction. In an embodiment of the present invention, the dome-shaped plate may be made of a stainless steel plate material, and the cup-shaped base may be made of a stainless steel material.

[0009] In another embodiment of the present invention, the dome-shaped plate may be made of a clad plate material in which a lower stainless steel plate material, an aluminum plate material, and an upper stainless steel plate material are stacked in this order, and the cup-shaped base may be made of stainless steel material.

[0010] In another embodiment of the present invention, the recess may be recessed upward to expose the aluminum plate material.

[0011] In the cooking vessel of the present invention, the dome-shaped plate, the aluminum core, and the cup-shaped base can be joined by impact bonding.

[0012] The present invention may also include a method of making a cooking vessel having a flat bottom configuration.

[0013] The present invention includes the steps of providing a press consisting of an upper punch and a lower die, preparing and arranging a dome-shaped plate, a cup-shaped base, and an aluminum core, and pressing the press to join the dome-shaped plate, the aluminum core, and the cup-shaped base by impact bonding, wherein the dome-shaped plate has a bottom surface and a top surface with recesses formed therein and is curved into a dome shape that bulges downward to accommodate food, the cup-shaped base supports the periphery of the center of the bottom surface of the dome-shaped plate, and the aluminum core can be interposed between the dome-shaped plate and the cup-shaped base to be joined.

[0014] Incidentally, the upper punch can have a pressure surface having a shape corresponding to the upper surface of the dome-shaped plate, and the lower die can have an upper accommodating portion formed in a shape corresponding to the bottom surface of the dome-shaped plate, and a lower seating portion formed in the internal region of the upper accommodating portion so as to be recessed downward and to accommodate a cup-shaped base.

[0015] Preferably, the upper punch can have a first electromagnet disposed on the lower surface of the pressing surface, and the lower die can have a second electromagnet disposed on the upper surface of the lower seat portion opposite to the first electromagnet. According to the present invention, the first electromagnet and the second electromagnet can be configured to exert attractive forces with polarities different from each other during the pressing step of the press.

[0016] Furthermore, the recessed portion can be recessed upward in the thickness direction from the center of the bottom surface of the dome-shaped plate, forming an inclined surface that is inclined upward in the circumferential direction.

[0017] In an embodiment of the present invention, the dome-shaped plate may be made of a stainless steel plate material, and the cup-shaped base may be made of a stainless steel material.

[0018] In another embodiment of the present invention, the dome-shaped plate may be made of a clad plate material in which a lower stainless steel plate material, an aluminum plate material, and an upper stainless steel plate material are stacked in this order, and the cup-shaped base may be made of stainless steel material.

[0019] In another embodiment of the present invention, the recess may be recessed upward to expose the aluminum plate material.

[0020] The features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Prior to this, the terms or words used in this specification and claims should not be interpreted in their ordinary and dictionary sense, but should be interpreted in a meaning and concept that corresponds to the technical idea of ​​the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best explain his / her invention. [Effects of the Invention]

[0021] As described above, the present invention provides a cooking vessel having a flat bottom structure that allows a downwardly bulging dome-shaped plate, such as a pot, to be stably seated on a flat cooking utensil, such as an induction range. The present invention uses an aluminum core that becomes thicker from the center to the edges to stably support the dome-shaped plate, increase the bonding strength between the dome-shaped plate and the base, and improve the thermal conductivity and heat retention of the cooking vessel. The present invention is also designed to gather food in the center of the top surface of the dome-shaped plate for easy food intake. The present invention has the advantage of significantly reducing the product defect rate by applying impact bonding technology, which uses a powerful press to instantly bond the base to the center of the bottom surface of the dome-shaped plate, ensuring alignment between the dome-shaped plate and the base and preventing external exposure of aluminum during the process. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a perspective view of a cooking vessel having a flat bottom configuration according to one embodiment of the present invention; FIG. [Figure 2]2 is a longitudinal cross-sectional view schematically illustrating the cooking vessel having the flat bottom structure shown in FIG. 1. FIG. [Figure 3] 1 is a diagram showing a state in which a cooking vessel having a flat bottom structure according to the present invention is used; [Figure 4] FIG. 10 is a longitudinal cross-sectional view schematically illustrating a cooking vessel having a flat bottom structure according to another embodiment of the present invention. [Figure 5a] 1A-1C are diagrams showing the steps of a method for manufacturing a cooking vessel having a flat bottom structure according to the present invention. [Figure 5b] 1A-1C are diagrams showing the steps of a method for manufacturing a cooking vessel having a flat bottom structure according to the present invention. [Figure 5c] 1A-1C are diagrams showing the steps of a method for manufacturing a cooking vessel having a flat bottom structure according to the present invention. [Figure 6a] 1 is a diagram showing a state in which a conventional cooking vessel is placed on a gas range and heated; [Figure 6b] 1 is a diagram showing a schematic view of a conventional cooking vessel placed on the cooking zone of an induction range for heating; DETAILED DESCRIPTION OF THE INVENTION

[0023] The objectives, particular advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments taken in conjunction with the accompanying drawings. In this specification, when assigning reference numerals to components in each drawing, it should be noted that identical components will be assigned the same numerals as much as possible, even if they appear in different drawings. Furthermore, when describing the present invention, if it is determined that a detailed description of related known technology may unnecessarily obscure the gist of the present invention, such a detailed description will be omitted. In this specification, terms such as "first" and "second" are used to distinguish one component from another, and the components are not limited by these terms. In the accompanying drawings, some components are exaggerated, omitted, or illustrated schematically, and the size of each component does not accurately reflect its actual size.

[0024] The present invention relates to a kitchen heating appliance including a flat top plate made of tempered glass, ceramic, heat-resistant plastic, etc., such as a cooking container with a flat bottom structure configured to stably seat cooking containers such as pots even in the cooking zone of an induction range. For this purpose, the present invention employs a multi-layered bottom structure having a thickness that gradually increases from the center to the edge of the flat bottom surface so that the dome-shaped plate can be supported from below.

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0026] 1 to 3, a cooking vessel having a flat bottom structure according to one embodiment of the present invention (hereinafter referred to as the cooking vessel) comprises a dome-shaped plate 10 for accommodating food to be cooked, a cup-shaped base 20 that covers and supports the bottom surface 11 of the dome-shaped plate 10 around the center, and an aluminum core 30 that is interposed and joined between the dome-shaped plate 10 and the base 20. In the present specification, the term "center" refers to the central portion of the dome-shaped plate that overlaps the cup-shaped base and / or the aluminum core, and hereinafter the term "periphery" refers to the edge portion of the dome-shaped plate that does not overlap the cup-shaped base and / or the aluminum core.

[0027] The cooking vessel according to one embodiment of the present invention has a bottom structure formed by impact bonding a dome-shaped plate 10, which has a curved shape like a pot, an aluminum core 30, and a cup-shaped base 20 in a triple-layered structure. However, the present invention is not limited to this, and the bottom structure of the cooking vessel can be manufactured in a triple-layered structure using various methods such as high-frequency brazing and friction pressing.

[0028] Preferably, the dome-shaped plate 10 and the cup-shaped base 20 are made of stainless steel, which is durable, rust-resistant, and has a beautiful appearance.

[0029] In one embodiment of the present invention, dome-shaped plate 10 is a component that provides a space capable of accommodating food to be cooked. Dome-shaped plate 10 is a container formed by curving a stainless steel plate having a predetermined thickness between bottom surface 11 and top surface 12 into a downwardly bulging dome shape. As shown in the figure, top surface 12 is concave, curving upward from the center toward the edge, providing an open top and a storage space that is concave toward the center for accommodating food. Similarly, bottom surface 11 of dome-shaped plate 10 is also formed in a convex shape with a predetermined curvature, curving upward.

[0030] The dome-shaped plate 10 has an upper surface 12 that is concave toward the center, which allows the food to be cooked to gather in the center of the upper surface of the dome-shaped plate, providing the advantage of making it easy to scoop and eat soup from hot pot dishes, etc. The dome-shaped plate also increases the heat transfer area with the food, allowing it to boil quickly and be eaten.

[0031] Specifically, the dome-shaped plate 10 has a recess 111 recessed upward in the thickness direction at the center of the bottom surface 11. In other words, the dome-shaped plate 10 has a recess 111 recessed in the thickness direction from the bottom surface 11 to the top surface 12 at its center. As described above, the dome-shaped plate 10 is made of a stainless steel plate having a predetermined thickness, specifically, a second thickness T2, between the bottom surface 11 and the top surface 12. However, the center of the dome-shaped plate overlapping the cup-shaped base 20 and / or the aluminum core 30 has a first thickness T1 due to the recess. The first thickness T1 at the center is thinner than the second thickness T2 at the periphery of the dome-shaped plate 10. The recess 111 may be formed in the stainless steel plate by etching, roll forming, or the like, but is not limited thereto and may be formed by various methods.

[0032] As shown in the figure, the recess 111 is formed to a size and shape that allows it to be placed within the upper opening of the cup-shaped base 20, but the diameter of the recess is smaller than the inner diameter of the upper opening of the base. In addition, the recess 111 forms an inclined surface 111a that slopes upward along its circumference. In other words, the cross-sectional shape of the recess can be formed to have a narrow top and wide bottom structure. Additionally, the dome-shaped plate 10 may be provided with one or more handles (not shown) around its periphery.

[0033] As described above, the base 20 is formed to have a size and shape that allows the recess 111 to be positioned in the upper opening of the base and to cover the center of the bottom surface 11 of the dome-shaped plate 10, and may be provided in a cup or saucer shape so as to be able to sufficiently support the center of the bottom surface of the dome-shaped plate 10. To this end, the cup-shaped base 20 is composed of a flat bottom surface 21 and side surfaces 22 that extend upward along the periphery of the bottom surface 21. When the dome-shaped plate 10 is seated and supported on the side surfaces 22 of the cup-shaped base 20, the side surfaces 22 can be set to a predetermined height so that the center of the bottom surface of the dome-shaped plate 10 does not come into contact with the bottom surface 21.

[0034] Alternatively, the cup-shaped base 20 may have a tapered truncated cone shape with a wide top and narrow bottom structure on the side 22, thereby increasing the contact area between the aluminum core 30 and the bottom of the dome-shaped plate 10 and improving heat transfer efficiency. In addition, the present invention not only ensures stable positioning of the dome-shaped plate when joining the dome-shaped plate 10 and base 20 through the wide top and narrow bottom structure on the side, but also ensures smooth joining without excessive bending at the contact boundary with the bottom of the dome-shaped plate.

[0035] As shown in FIG. 3, in the present invention, magnetic field lines generated by an induction coil installed under the cooking zone on the top plate of induction range R2 pass through cup-shaped base 20 seated in the cooking zone, generating eddy currents that heat the cup-shaped base and pass through aluminum core 30 to heat dome-shaped plate 10. Here, base 20 can be made of a magnetic material, such as stainless steel containing iron (F2).

[0036] Furthermore, the present invention uses the bottom surface 21 of the cup-shaped base 20 to achieve a flat bottom structure, allowing the cooking vessel to be stably seated on the flat top plate of the induction lens R2. The cooking vessel according to one embodiment of the present invention can be used to cook food using a gas range, a high-heat range, a hot plate, etc. in addition to an induction range.

[0037] In the cooking vessel of the present invention, an aluminum core 30 is interposed between the bottom surface 11 of the dome-shaped plate 111 and the cup-shaped base 20 so that the stainless steel dome-shaped plate and cup-shaped base can be joined via the aluminum core 30. Of course, the present invention ensures uniform heating throughout the dome-shaped plate through the aluminum core, which has thermal conductivity and heat retention properties. Here, the aluminum core can be made of aluminum or an aluminum alloy.

[0038] As shown in the figure, the thickness of the aluminum core 30 of the present invention increases from the center to the periphery of the bottom of the dome-shaped plate 10 to correspond to the space between the center of the bottom of the dome-shaped plate 10 and the bottom of the cup-shaped base 20. When the induction range R2 is operated, heat generated from the cup-shaped base 20, which provides the flat bottom structure of the cooking vessel, is transferred to the dome-shaped plate 10 through the aluminum core 30, cooking the food. The cooking vessel of the present invention incorporates the aluminum core 30, which has excellent thermal conductivity, into the bottom structure. This allows the center of the aluminum core 30, which is relatively thinner than the edges of the aluminum core 30, to heat more quickly during heating. This creates upward convection in the center of the dome-shaped plate and spreads to the edges of the dome-shaped plate, quickly cooking the food placed on the top surface of the dome-shaped plate. Furthermore, the thicker edges of the aluminum core 30 of the present invention, compared to commercially available cooking vessels with a triple-bottom structure, offer the advantage of maintaining heat uniformly and for a long period of time in the dome-shaped plate.

[0039] As described above, the present invention uses impact bonding to stack and bond dissimilar metal plates. While applying pressure using a press, the aluminum core 30 can be softened so that it can spread widely and uniformly fill the internal space defined by the bottom surface of the dome-shaped plate 10 and the cup-shaped base 20 without creating voids. As is well known to those skilled in the art, the softened aluminum core 30 can be instantaneously compressed, for example, using a press, to melt the surfaces that contact the dome-shaped plate 10 and the cup-shaped base 20, thereby metallurgically bonding the contact interfaces between the stainless steel plate (e.g., the dome-shaped plate and base) and the aluminum plate (e.g., the aluminum core). Such bonding methods between dissimilar metals are well known, and a detailed description thereof will not be provided herein.

[0040] A portion of the molten aluminum in the aluminum core 30 enters the recess 111 of the dome-shaped plate 10, firmly bonding the dome-shaped plate 10 and the aluminum core 20 together. In other words, the increased surface area of ​​the center of the bottom surface 11 of the dome-shaped plate 10 due to the recess 111 not only increases the bonding strength of the dissimilar metal materials, but is also expected to improve thermal conductivity. Furthermore, the recess 111 of the dome-shaped plate 10 serves as an escape space for the molten aluminum generated during crimping, preventing it from escaping between the dome-shaped plate 10 and the cup-shaped base 20 and leaking to the outside.

[0041] Furthermore, recess 111 ensures smooth inflow of molten aluminum by means of inclined surface 111a that is narrow at the top and wide at the bottom, and can increase the surface area of ​​the inclined surface to increase the contact area with the aluminum core material.

[0042] Fig. 4 is a longitudinal cross-sectional view schematically illustrating another embodiment of a cooking vessel having a flat bottom structure according to the present invention. The cooking vessel shown in Fig. 4 is a modified example of the cooking vessel according to the present invention shown in Figs. 1 to 3, and has a very similar structure except for the material of the dome-shaped plate. Therefore, to facilitate a clear understanding of the present invention, a description of the similar or identical structure will be omitted here.

[0043] A cooking vessel according to another embodiment of the present invention comprises a dome-shaped plate 10 made of clad plate material, a cup-shaped base 20 that covers the bottom surface 11 of the dome-shaped plate 10 around the center to support it, and an aluminum core material 30 that is interposed between the dome-shaped plate 10 and the base 20 to join them together.

[0044] As described above, the dome-shaped plate 10 is a clad plate made of stainless steel and aluminum. As shown in the figure, the dome-shaped plate 10 is fabricated by laminating stainless steel plates 10a and 10c on both sides of an aluminum plate 10b, resulting in a triple laminate of stainless steel / aluminum / stainless steel.

[0045] As is well known to those skilled in the art, the clad plate material constituting the dome-shaped plate 10 is manufactured by heating and rolling a stainless steel plate material and an aluminum plate material to bond them together. Of course, the dome-shaped plate 10 may also be a container manufactured by bending a clad plate material into a dome shape.

[0046] In the present invention, the dome-shaped plate 10 may be a triple-clad plate material in which stainless steel plates 10a and 10c are laminated on both sides of an aluminum plate material 10b, as shown in the figure, or alternatively, it may be a double-clad plate material in which stainless steel plate material 10a is laminated on one side, i.e., one side, of an aluminum plate material 10b.

[0047] Preferably, the present invention provides a recess 111 recessed upward in the thickness direction from the center of the bottom surface 10a of the dome-shaped plate 10. More preferably, the present invention forms the recess 111 in the lower stainless steel plate 10a that constitutes the bottom surface 11 of the dome-shaped plate 10. The recess 111 can be formed by drilling the lower stainless steel plate 10a in the thickness direction to expose a portion of the aluminum plate 10b. Such a recess 111 can be provided by etching and punching a portion of the lower stainless steel plate, but is not limited to this, and recesses can be formed in the clad plate that constitutes the dome-shaped plate in various ways.

[0048] As shown, the recess 111 is formed in a size and shape that allows it to be placed within the upper opening of the cup-shaped base 30, and can include upwardly sloping inclined surfaces 111a that define the sides of the recess.

[0049] The present invention can integrally bond the clad plate and cup-shaped base 20 using an aluminum core 30 interposed between the center of the bottom surface of the dome-shaped plate 10 and the cup-shaped base 20. The aluminum core 30 melts the lower stainless steel plate 10a constituting the dome-shaped plate 10 and the surface that faces the cup-shaped base 20, metallurgically bonding their contact interface. In particular, a cooking vessel according to another embodiment of the present invention bonds the aluminum plate 10b exposed by the recess 111 to the aluminum core 30. Generally, when bonding similar materials, an advantage is that the bond strength can be increased in proportion to the amount of energy input.

[0050] As a result, the cooking vessel according to another embodiment of the present invention can increase heat conservation efficiency and heat transfer efficiency by arranging the aluminum core 30 adjacent to the heat source of the kitchen heating mechanism and incorporating the aluminum plate material 10b throughout the dome-shaped plate 10. In addition, the cooking vessel according to another embodiment of the present invention can achieve a lightweight product through the use of aluminum.

[0051] As described above, the present invention is characterized by providing a flat bottom structure to a downwardly bulging dome-shaped plate. The following describes a manufacturing method for joining a cup-shaped base to the center of the bottom surface of the dome-shaped plate. Here, the present invention will step by step explain the manufacturing process of a cooking vessel based on a dome-shaped plate made of triple clad board material.

[0052] [Press provision step (S100)] FIG. 5 a shows the step of providing a press (S 100 ) consisting of an upper punch 1000 and a lower die 2000 .

[0053] The upper punch 1000 is configured to be able to move relative to the lower die 2000, for example, up and down, and can join the respective components by descending toward the lower die 2000 and instantly crimping the different metal plate materials with ultra-high pressure. The pressing surface of the upper punch 110 is formed to be curved in a shape corresponding to the concave upper surface 12 of the dome-shaped plate 10 (see FIG. 2). This allows the pressing surface of the upper punch to be aligned with the upper surface of the dome-shaped plate in the crimping step using the upper punch and the lower die, which will be described later.

[0054] Additionally, the upper punch 1000 has a first electromagnet 1100 installed on the underside of its pressing surface. As is well known to those skilled in the art, the first electromagnet is a component that generates magnetic force by being magnetized when an electric current is applied, and is positioned at the center of the underside of the pressing surface as shown. In the present invention, the dome-shaped plate 10 can be attached to and detached from the upper punch 1000 by the magnetic force of the first electromagnet 1100. The dome-shaped plate 10, more specifically, the upper stainless steel plate material 10c of the dome-shaped plate, may be made of a ferromagnetic material that is sensitive to magnetic force.

[0055] The lower die 2000 is configured to assist in seating the cup-shaped base 20 and the aluminum core 30, as shown.

[0056] As shown in the figure, the lower die 2000 includes an upper receiving portion 2000a and a lower seating portion 2000b recessed downward from the interior of the upper receiving portion 2000a. The upper receiving portion 2000a is formed to have a shape corresponding to the peripheral portion of the bottom surface 11 of the dome-shaped plate 10 and a size large enough to accommodate the bottom surface so that it can support the peripheral edge, i.e., the peripheral portion of the bottom surface. The lower seating portion 2000b is recessed into the lower die 2000 so that the cup-shaped base 20, which corresponds to the bottom surface of the cooking vessel, can be aligned with the center of the bottom surface of the dome-shaped plate 10 and the central axis of the upper punch 1000. The lower seating portion 2000b has an inner diameter smaller than that of the upper receiving portion 2000a, so that it is aligned coaxially with the center of the upper receiving portion 2000a.

[0057] In addition, the lower seating portion 2000b is formed to have a shape corresponding to the outer shape of the cup-shaped base 20 and a size capable of accommodating the cup-shaped base 20, thereby helping to ensure that the cup-shaped base is securely placed.

[0058] Preferably, the lower die 2000 has a second electromagnet 2100 installed on the upper surface of the lower seat 2000b facing the first electromagnet 1100. The second electromagnet 2100 is also magnetized when a current is applied to it, generating a magnetic force, which can attach and detach the cup-shaped base 20 to and from the lower seat 2000b of the lower die 200. Of course, the cup-shaped base can be made of a ferromagnetic material that is sensitive to magnetic force.

[0059] The second electromagnet 2100 is magnetized by the application of current, but is magnetized with a polarity different from that of the first electromagnet 1100, and the attractive force generated between the first and second electromagnets more securely adheres the upper punch 1000, which is descending vertically, to the lower die 2000. Due to the attractive force between the electromagnets, the present invention can maintain the alignment between the upper punch 1000 and the lower die 2000 as well as the adhesion between the dome-shaped plate 10 and the cup-shaped base 20 during the crimping step described below.

[0060] [Preparation / arrangement step of each component of the cooking vessel (S200)] The cooking vessel according to the present invention includes a dome-shaped plate 10, a cup-shaped base 20, and an aluminum core 30 as its constituent members.

[0061] As shown in Fig. 5b, the worker places the dome-shaped plate 10 under the pressure surface of the upper punch 1000. The worker also places the cup-shaped base 20 in the lower seating portion 2000b of the lower die 2000, and seats the aluminum core 30 on the cup-shaped base 20, which is limited by the bottom surface 21 and the side surface 22. At this time, current is applied to the first electromagnet 1100 of the upper punch 1000 and the second electromagnet 2100 of the lower die 2000, causing the first and second electromagnets to be magnetized, thereby fixing the dome-shaped plate 10 below the pressing surface of the upper punch 1000 and fixing the cup-shaped base 20 on the lower seat 2000b of the lower die 2000. The magnetization of the first and second electromagnets in the present invention allows the dome-shaped plate 10 and the cup-shaped base 20 to be reliably aligned with each other, which prevents the upper punch 1000, dome-shaped plate 10, cup-shaped base 20, and lower die 2000 from moving apart from their coaxial lines when the upper punch descends or when pressure is applied through the upper punch.

[0062] Furthermore, the cooking vessel of the present invention can achieve more reliable bonding by inserting a powder or a solvent such as flux into the upper and lower surfaces of the aluminum core 30 and using impact bonding. After stacking and arranging the dissimilar metal plates, i.e., the cup-shaped base 20 and the aluminum core 30, on the lower die, the present invention may further include a step of heating the aluminum core 30. To heat the aluminum core 30 seated on the cup-shaped base 20, the lower die 120 may have a separate heating unit 2200 (see FIG. 5a) disposed around the lower seating portion 2000b. Optionally, the heating unit 2200 preheats and softens the aluminum core 30 to a temperature below 660°C, the melting point of aluminum, preferably in the range of 400°C to 500°C. The softened aluminum core 30 can be deformed in the subsequent pressing step to reliably fill the space between the center of the bottom surface 11 of the dome-shaped plate 10 and the cup-shaped base 20, while also improving the bonding strength between the dome-shaped plate and the cup-shaped base.

[0063] [Press bonding step (S300)] FIG. 5c shows a schematic diagram of the pressing step (S300) of the press. The upper punch 1000 applies a pressure of 1000 to 1600 tons downward toward the lower die 2000, and this instantaneous pressure allows the aluminum core 30 and the cup-shaped base 20 to be bonded to the bottom surface of the dome-shaped plate 10. The present invention allows for instantaneous application of ultra-high pressure to crimp and bond a dome-shaped plate, a (softened) aluminum core, and a cup-shaped base. The bottom structure of a cooking vessel, in which dome-shaped plate 10, aluminum core 30, and cup-shaped base 20 are stacked, reliably fills the center of the bottom surface of the dome-shaped plate, including recess 111, up to the contact boundary between the cup-shaped base and the center, due to the good fluidity of the softened aluminum, expanding the contact area of ​​the aluminum core and joining each component into an integral unit. The present invention can promote interfacial bonding between the aluminum sheet material 10b exposed by the recesses 111 (see FIG. 5b) of the dome-shaped plate 10 and the aluminum core material 30. The recesses 111 of the dome-shaped plate 10 can induce an increase in surface area and can be used as an escape space for molten aluminum generated during compression bonding.

[0064] As a result, the present invention can provide a cooking vessel having a bottom structure in which the thickness gradually increases from the center to the edge of the flat bottom surface 21 so as to compensate for the gap between the top plate of the induction range and the dome-shaped plate 10 through the crimping step (S300). In addition, the present invention prevents the aluminum from being exposed to the outside because the aluminum core material 30 is inserted into the space defined by the bottom surface 11 of the dome-shaped plate 10 and the cup-shaped base 20. As is well known, aluminum and aluminum alloys react with water to form aluminum hydroxide, which causes the surface color to blacken and is known to induce Alzheimer's disease.

[0065] The present invention activates the first electromagnet 1100 and the second electromagnet 2100 during the pressing step (S300) to help align the dome-shaped plate 10 and the cup-shaped base 20 in a fixed position without any play, while the attractive force acting between the upper punch 1000 and the lower die 2000 ensures that the upper punch moves downward in a straight line toward the lower die. After the joining and molding is completed, the upper punch moves upward, allowing the cooking vessel to be removed. The present invention helps to enable the upper punch to move upward and the cooking vessel to be removed by deactivating the current in the first electromagnet 1100 and the second electromagnet 2100. The formed cooking vessel undergoes a slow cooling step to minimize changes in its structure. Finally, the present invention can be produced as a commercially available product by cutting and / or grinding away any burrs or the like that may have been undesirably formed on the cooking vessel during the compression step.

[0066] For reference, although Figures 5a-5c are described as a series of steps, the order of these steps may be changed in other examples, and some of the steps shown and / or described may be omitted in whole or in part. Furthermore, the cooking vessel according to the present invention is not limited to the above steps and can be manufactured in various ways.

[0067] The present invention has been described in detail above using embodiments, but these are merely for the purpose of specifically explaining the present invention. The cooking vessel having a flat bottom structure and the method for manufacturing the same according to the present invention are not limited to these embodiments, and it should be understood that modifications and improvements can be made by those skilled in the art within the technical spirit of the present invention. Any mere modification or change of the present invention should fall within the scope of the present invention, and the specific protection scope of the present invention will be made clear by the appended claims. [Explanation of symbols]

[0068] 10 Domed Plate 11 Bottom 111 recess 20 Cup-shaped base 21 Bottom 22 Side 30 Aluminum core material 1000 Upper Punch 1100 First electromagnet 2000 Lower Die 2100 Second electromagnet R1 Gas Range R2 Induction Range

Claims

1. a dome-shaped plate having a bottom surface and a top surface, curved in a downwardly bulging dome shape so that food can be accommodated therein, and made of clad plate material in which a lower stainless steel plate material, an aluminum plate material, and an upper stainless steel plate material are laminated in this order; a cup-shaped base that supports the periphery of the center of the bottom surface of the dome-shaped plate; an aluminum core material interposed between and joined to the dome-shaped plate and the cup-shaped base, the dome-shaped plate has a recess recessed upward in a thickness direction from the center of the bottom surface, The cooking vessel has a flat bottom structure, and the recess is recessed upward to expose the aluminum plate material.

2. The cooking vessel having a flat bottom structure according to claim 1 , wherein the cup-shaped base includes a flat bottom surface and a side surface extending upward along the periphery of the bottom surface.

3. The cooking vessel having a flat bottom structure according to claim 1 , wherein the recess is disposed within an upper opening of the cup-shaped base.

4. The cooking vessel having a flat bottom structure according to claim 1 , wherein the recess forms an inclined surface that slopes upward in the circumferential direction.

5. A cooking container having a flat bottom structure as described in claim 1, wherein the cup-shaped base is made of stainless steel material.

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