COOKING UTENSIL

Abstract: A cooking utensil has an outer shell (11), an inner shell (12) disposed inside the outer shell forming a cylindrical wall space (16) between the outer and inner shells. The wall apace (16) is formed betwen the outer and inner shells substantially along the highest of the inner shell (12). The cooking utensil also has a first heat conductive plate (14) being in contact with an inner bottom surface of the outer shell (11) and an outer bottom surface of the inner shell (12) to allow even distribution of heat throughout the bottom surface of the inner shell. A second heat conduction plate (15) is affixed to and in contact with an outer bottom surface of the outer shell. The wall space (16) between the outer and inner shells contains ambiant air. Alternatively, the wall space defined by the outer and inner shells contains a heat conduction medium (206), such as silicon oil. A support cover (13) is configured to fit in surrounding relation to the second heat conduction plate. The cooking utensil is equipped with an inner lid (20) that fits over a flange of the inner shell and covers an opening defined by the inner shell. A cover (30) that fits over a flange of the inner shell and the lid substantially covers an opening defined by the inner shell. The cover and the lid define an air gap space therebetween for trapping heat.

Description: COOKING UTENSIL The present invention relates to a cooking utensil, and particularly, to a cooking utensil having a double-layered wall structure which preserves heat entrapped during cooking. Various types of cooking utensil are known and used in a kitchen. Such a cooking utensil is made of one or more layers of stainless steel and has a single- layered bottom. The single-layered bottom is good for directly transmitting heat to the food contained in the utensil, but also causes burning of the food when not attended to carefully. To solve the above problems, a cooking utensil having a double-layered structure has been proposed for preventing burnt food and to improve food flavour. One of such ideas is published in Korean Utility Laid-Open Publication No. 85-7307 which teaches that paraffin is injected between a space provided by a double-layered structure and an air-hole is established thereon. Moreover, a pot of a double-layered structure and a pot having a double- layered structure into which a working fluid is injected are taught by Japanese Laid-Open Publication No. 56-169825. Instead of charging the space with paraffin, a structure into which a fluid of heat-medium is injected and sealed is disclosed in Korean Laid-Open Publication No. 97-4035. In such pots having the above-mentioned structures of the related arts, the gaps between the double-layered structure are filled with heat media to provide even-heat distribution and to save heat energy. Unfortunately, the structures of the related arts are filled with the heat medium substances and have to be sealed to prevent the substances from leaking out, resulting in the difficulties in manufacturing the cookware. According to the present invention, there is provided a cooking utensil having sides, a bottom and an upper opening, formed by an inner shell disposed inside an outer shell to provide a space between the inner and outer shells, wherein the utensil has a wall space between side walls of the inner and outer shells filled at least partially with air, and the utensil has a heat conductive body positioned in contact with both an inner bottom surface of the outer shell and an outer bottom surface of the inner shell. There will now be described a number of preferred and optional features and combinations of features of the invention. It is particularly to be appreciated that the following statements relate to preferred or optional or exemplary features and do not necessarily set out essential features of the invention. In some cases these features may provide independent inventive concepts which may be utilised independently of other features. The present invention may be directed to a cooking utensil that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. An object of the present invention is to provide a cooking utensil having a double-layered structure which provide even heat distribution and preserves heat for a longer period of time. Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realised and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. To achieve these and other advantages and in accordance with a purpose of the present invention, as embodied and broadly described, the present invention provides a cooking utensil comprising an outer shell having an opening; an inner shell disposed inside the outer shell forming a cylindrical wall space between the outer and inner shells, wherein the wall space is formed substantially along the height of the inner shell; and a first heat conductive plate being in contact with an inner bottom surface of the outer shell and an outer bottom surface of the inner shell to allow even distribution of heat throughout the bottom surface of the inner shell. According to one aspect of the present invention, the wall space between the outer and inner shells contains ambient air. Alternatively, the wall space defined by the outer and inner shells contains a heat conduction medium, such as silicon oil. According to another aspect of the present invention, a second heat conduction plate is affixed to and in contact with an outer bottom surface of the outer shell. In addition, a support cover is configured to fit in surrounding relation to the second heat conduction plate. An inner lid that fits over a flange of the inner shell covers an opening defined by the inner shell. The inner lid comprises a disk having a diameter sufficiently large to cover the opening of the inner shell; and a ring coupled to the disk and circumferentially covering outer edges of the disk. The disk is made of one selected from the group of tempered glass, stainless steel, aluminium and aluminium alloy. A cover that fits over a flange of the inner shell and the lid substantially covers an opening defined by the inner shell. The cover and the lid define an air gap space therebetween for trapping heat. According to another aspect of the present invention, the outer and inner shells are each made of a plurality of layer of materials comprising at least one of stainless steel, aluminium, aluminium alloy and copper. When heat conducting medium, such as silicon oil is contained in the wall space defined by vertical cylindrical walls of the outer and inner shells, the amount of silicon oil stored in the wall space is approximately 55 to 75% and more preferably about 65% by volume. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Embodiments of the invention will now be described by way of example with reference to the accompanying drawing in which:- Figure 1 is a perspective view of the cooking utensil embodying the present invention; Figure 2 is a cross-sectional view of a first embodiment of cooking utensil according to the present invention; and Figure 3 is a cross-sectional view of a second embodiment of cooking utensil according to the present invention. Figure 1 is a perspective view of a cooking utensil 100 according to an embodiment of the present invention. The cooking utensil 100 generally comprises a body 10 for receiving and cooking food contained therein, an inner lid 20 for substantially covering the body 10 and a thermal insulating cover 30 disposed above the inner lid 20 and covering the opening of the body 10. Figure 2 is a cross-sectional view of the cooking utensil 100 having at least a double-layered structure according to the present invention. According to the preferred embodiment, the inner lid 20 is constructed with a dome-shaped disk 21 of which edge is surrounded by a safety ring 22 preferably made of stainless steel or other suitable materials. The safety ring 22 is attached to the edges of the disk 21 , thereby preventing damage to the disk 21. However, the inner lid 20 may be used without the ring 22. Preferably, the disk 21 is made to form a slight convexed surface with respect to the body 10 of the cookware. The disk 21 of the inner lid 20 is preferably made of tempered glass of approximately 4 mm thick. Alternatively, the disk 21 may be made of stainless steel, aluminium, aluminium alloy or other suitable materials known to one of ordinary skill in the art. A handle 23 is attached to the centre of the dome-shaped disk 21 by, for example, piercing the central portion of the disk 21. Alternatively, the handle 23 may be affixed to the disk 21 by using adhesives or other fasteners. The thermal insulating cover 30 is preferably made of a stainless steel plate 31 being about 0.5 to 0.7 mm thick, and preferably about 0.6 mm thick, and has a dome like shape. The insulating cover 30 and the inner lid 20 form a horizontal air gap 26 which acts as an insulating layer to trap and hold heated air therein. Alternative to a single sheet structure, the cover 30 may comprise a plurality of layers of stainless steel and/or aluminium for increased durability and preservation of heat. In the thermal insulating cover 30, a knob 32 is attached to the centre of the thermal insulating cover 30. In the present embodiment, the knob 32 may include a built-in temperature gauge for measuring the inside temperature of the cookware. The temperature gauge allows the user to remove the cooking utensil 100 from the heat source once a desired temperature has been reached. The body 10 of the cooking utensil 100 according to the present embodiment includes an outer shell 11 and an inner shell 12 disposed adjacent the outer shell. Edges of the outer and inner shells 11 and 12 are preferably rolled together to form a rolled joint 17. As a result, a vertical space 16 filled with an air pocket is provided between the outer and inner shells 11 and 12. The air pockets are sealed and are not in fluid communication with outside air. The vertical space 16 filled with air is preferably filled with ambient air during the manufacturing process. In the preferred embodiment, the distance between the outer and inner shells 11 and 12 is approximately 15 to 25 mm, and preferably about 20 mm. Preferably, the outer and inner shells 11 and 12 are made of such materials as AISI304 stainless steel that has a thickness of about 0.6 mm. Alternatively, instead of using a single-layered stainless steel, a multiple-layered composite material may be used. Typically, three or more layers of stainless steel or a combination of stainless copper and steel are preferred. In the preferred embodiment of the present invention, both the outer and inner shells 11 and 12 are jointly rolled about five to eight times, and preferably seven times, to form the rolled joint 17. The tightly rolled joint 17 prevents the air contained in the vertical space 16 from escaping even when the cooking utensil 100 is subjected to intense heat. The unique structure of the rolled joint 17 and the thickness of the walls of the outer and inner shells 11 and 12 allow the cooking utensil 100 to be used without any air escape valves built into the wall of the body 10 to prevent the utensil against possible explosion. As a result of the construction, once the heat source is removed from underneath the cooking utensil 100, the air gap 26 and the vertical space 16 filled with ambient air insulate the inner shell 12 from outside and reduce heat loss, thus keeping the food contained in the inner shell 12 warmer for a longer period of time. More importantly, the structure of the utensil embodying the present invention allows the food to be cooked even after removing heat from the cooking utensil. Referring to Figure 2, there is provided a first heat conduction plate 14 placed between the outer and inner shells 11 and 12. The first heat conduction plate 14 is preferably made of an aluminium disk, copper or other suitable material known to one or ordinary skill in the art. The first heat conduction plate 14 is preferably flushly affixed to the bottom of the outer shell 11. The first heat conduction plate 14 is about 1.5 to 2.5 mm thick, and preferably about 2 mm thick. To provide speedy transmission of heat to the food contained in the cooking utensil 100, the first heat conduction plate 14 also abuts against the bottom of the inner shell 12. Due to the presence of the first conduction plate 14, there is no space or air gap 16 between the bottom of the inner shell 12 and that of the outer shell 11. In the preferred embodiment, a second heat conduction plate 15 is disposed below the bottom surface of the outer shell 11 preferably below the first heat conduction plate 14. Similar to the first heat conduction plate, the second heat conduction plate 15 is preferably made of an aluminium disk or other suitable materials known to one of ordinary skill in the art. The second heat conduction plate 15 is about 2 to 4 mm thick, and preferably about 3 mm thick. The second heat conduction plate 15 is securely affixed to the bottom of the outer shell 11 by brazing or other suitable method known to one of ordinary skill in the art. The second heat conduction plate 15 is covered by a support cover 13. The support cover 13 is attached to an outer bottom surface of the outer shell 11 fully surrounding and in contact with the second heat conduction plate 15. The support cover 13 is preferably made of the same material as that of the body 10 of the cooking utensil 100. In particular, the support cover 13 is made of AISI304 stainless steel that has a thickness of about 0.5 mm. In the body, the first heat conduction plate 14, the bottom wall of the outer shell 11 , the second heat conduction plate 15 and the support cover 13 are in thermal communication with each other. Figure 3 illustrates a second embodiment of the present invention. A cooking utensil 200 according to the second embodiment is substantially the same as that of the first embodiment except that a vertical space 205 formed between the outer and inner shells 11 and 12 is at least partially filled with a heat conduction medium 206, such as silicon oil or other suitable materials known to one of ordinary skill in the art. In the cooking utensil 200, the vertical space 205 is partially filled with silicon oil up to about 55 to 90% by volume. Preferably, the silicon oil is filled up to about 65% of the vertical space 205 to accommodate for increased pressure in the vertical space 205. For example, while cooking, the pressure of the vertical space 205 varies from 200 mmAG to 600 mmAG due to expansion of the silicon oil. The operation of the preferred embodiment of the present invention is described in accordance with the first embodiment of the present invention for the purpose of illustration. The operation of the second embodiment is identical to the first embodiment, and therefore, will not be repeated for the sake of brevity. Once the bottom of the cooking utensil 100 is in contact with a heat source, the contents contained in the inner shell 12 are heated by the heat transmitted through the support cover 13, second heat conduction plate 15, outer shell 11 , first heat conduction plate 14 and finally the inner shell 12, successively. Because the heat source generally provides for uneven distribution of heat to a bottom surface, the bottom of the cooking utensil 100 is unevenly heated. However, due to the presence of the support cover 13, second heat conduction plate 15 and first heat conduction plate 14, the heat from the heat source is more evenly distributed to the bottom of the inner shell 12 allowing even distribution of heat to the food contained therein. The first and second conduction plates 14 and 15 also serve to heat the vertical cylindrical walls of the cooking utensil 100. Although the most of the heat transmitted tot he bottom of the outer shell 11 is conducted to the first heat conduction plate 14, the rest of the heat from the first and second conduction plates 14 and 15 is transferred to the side walls of the outer and inner shells 11 and 12, respectively. Then, the temperature of the air in the space 16 is gradually increased and the heat energy of the air is transmitted to the inner shell 12 and spread out throughout the entire wall of the inner shell 12. Therefore, the temperature along the inner shell 12 is substantially constant at any region thereof. In other words, the temperature of the bottom of the inner shell 12 is about the same as that of the cylindrical wall. The presence of air in the vertical space 16 delays heat transfer between the sides of the outer and inner shells 11 and 12 as well as providing even heat distribution, as the heat conducted through the outer shell 11 of the cooking utensil 100 primarily is not transferred to the inner shell 12 of the pot but is partially conveyed through the air. The heat distributed uniformly in the inner shell 12 heats up the contents in the cooking utensil 100. Once heated, the double-layered structure of the cooking utensil 100 according to the present embodiment maintains the trapped heat, even after the heat source is removed, for a prolonged period. The heat losses through the sidewalls of the inner and outer shells 11 and 12 are slowed due to the presence of the air pockets 16. Moreover, it is easy to preserve the heat inside the cooking utensil 100 as the lid 20 and the thermal insulating cover stop the heat dissipating upward. The third air-pocket 26 formed between the lid 20 and the insulating cover 30 traps heat therein and holds the temperature for an extended period of time. Accordingly, the present embodiment prevents the food from being burnt or being partially heated, since the flame of heating source is not directed to the inner shell 12 and heat is not focused in any one region. In addition, the air stored in the vertical cylindrical space 16 acts as an insulator. Therefore, the food stays hotter for a longer period of time. Moreover, heat efficiency of the cooking utensil is improved.

Claims: CLAIMS 1. A cooking utensil having sides, a bottom and an upper opening, formed by an inner shell (12) disposed inside an outer shell (11) to provide a space between the inner and outer shells (12, 11), wherein the utensil has a wall space (16) between side walls of the inner and outer shells (12, 11) filled at least partially with air, and the utensil has a heat conductive body (14) positioned in contact with both an inner bottom surface of the outer shell (11) and an outer bottom surface of the inner shell (12). 2. A cooking utensil according to Claim 1 , wherein said wall space (16) extends substantially throughout the height of the inner shell (12). 3. A cooking utensil according to Claim 1 , in which the heat conductive body (14) comprises a heat conductive plate. 4. A cooking utensil according to Claim 1 , wherein the wall space (16) between the outer and inner shells (11 , 12) contains ambient air. 5. A cooking utensil according to Claim 1 , further comprising a second heat conductive body comprising a heat conductive plate (15), affixed to and in contact with an outer bottom surface of the outer shell (11). 6. A cooking utensil according to Claim 5, further comprising a support cover (13) configured to fit in surrounding relation to the second heat conduction body (15). 7. A cooking utensil according to Claim 1 , further comprising an inner lid (20) that fits over a flange of the inner shell (12) to substantially cover said opening of the utensil which is defined by the inner shell (12). 8. A cooking utensil according to Claim 7, wherein the inner lid (20) comprises a disk (21) having a diameter sufficiently large to cover the opening of the inner shell (12), and a ring (22) coupled to the disk (21) and circumferentially covering outer edges of the disk (21). 9. A cooking utensil according to Claim 8, wherein the disk is made of tempered glass, stainless steel, aluminium or aluminium alloy. 10. A cooking utensil according to Claim 1 , further comprising a cover (30) which fits over a flange of the inner shell (12) to substantially cover said opening of the utensil, which is defined by the inner shell (12). 11. A cooking utensil according to Claim 10, further comprising an inner lid (20) that fits over a flange of the inner shell (12) to substantially cover said opening of the utensil which is defined by the inner shell (12), wherein the cover (30) and the lid (20) define an air gap space therebetween for trapping heat. 12. A cooking utensil according to Claim 1 , wherein the outer shell (11) includes stainless steel. 13. A cooking utensil according to Claim 1 , wherein the outer and inner shells (11 , 12) are joined by a rolled joint of at least three rotations to prevent air in the wall space from escaping. 14. A cooking utensil according to Claim 1 , wherein the wall space (16) between the outer and inner shells (11 , 12) contains a heat conduction medium (16, 206). 15. A cooking utensil according to Claim 14, wherein the heat conduction medium is a non-gaseous material. 16. A cooking utensil according to Claim 15, wherein the heat conduction medium is silicon oil. 17. A cooking utensil according to Claim 15, wherein the amount of heat conduction medium stored in the wall space defined by the outer and inner shells is approximately 55% to 75% by volume. 18. A cooking utensil according to Claim 17, wherein the amount of heat conduction medium stored in the wall space is approximately 65% by volume. 19. A cooking utensil comprising: an outer shell (11) having an opening; an inner shell (12) disposed inside the outer shell (11) through the opening, forming a wall space (16) between the outer and inner shells, wherein the wall space is formed substantially along the height of the inner shell (12) and at least partially contains air; and a first heat conductive plate (14) being in contact with both an inner bottom surface of the outer shell (11) and an outer bottom surface of the inner shell (12) to allow even distribution of heat throughout the bottom surface of the inner shell (12).

Inventors: PARK JONG DO PETER, PARK, JONG, DO, PETER
Applicants: PARK JONG DO PETER, PARK, JONG, DO, PETER
Application year: 2000
Main classification: A47J27
IPC codes: A47J27, A47J36