CN220898535U

CN220898535U - Food cooking device and heating component

Info

Publication number: CN220898535U
Application number: CN202322657256.7U
Authority: CN
Inventors: 黄战彬; 任卓; 陈旭潮
Original assignee: Shenzhen Huyi Technology Co Ltd
Current assignee: Shenzhen Huyi Technology Co Ltd
Priority date: 2023-09-28
Filing date: 2023-09-28
Publication date: 2024-05-07
Anticipated expiration: 2033-09-28

Abstract

A food cooking device and a heating component thereof are provided, wherein the food cooking device comprises a food support frame and the heating component. The food material support frame is used for supporting food materials, and the heating component comprises a ceramic heat conductor and a heating piece. The ceramic heat conductor is positioned below the food material supporting frame, the heating element and the ceramic heat conductor form a heat transfer structure, and the ceramic heat conductor can absorb heat of the heating element and heat food materials positioned above the ceramic heat conductor. The ceramic heat conductor is provided with at least one oil leakage hole which is vertically communicated, and oil dripped in the high-temperature heating process of the food material can drop downwards from the oil leakage hole, so that the condition that the oil drops onto the ceramic heat conductor is reduced, and the burning of the oil on the ceramic heat conductor is reduced.

Description

Food cooking device and heating component

Technical Field

The application relates to the field of food cooking, in particular to a heating component of a food cooking device.

Background

In a general food cooking apparatus (for example, a high-temperature heating cooking apparatus such as an electric oven or an electric fumigating oven), a stainless steel heating tube or a quartz glass heating tube is generally used for heating. However, most stainless steel heating pipes have their surfaces not specially treated, and have emissivity of about 0.5-0.6, and have weak heat radiation performance; the quartz glass heating tube is easy to break and lose efficacy in the environment of high temperature and grease for a long time due to the material of the glass shell, and has poor long-term reliability in products of electric ovens and electric smoking ovens.

In addition, there are food cooking devices on the market that use a ceramic heating plate as a heat source, but the heat conducting structure easily generates a large amount of black smoke in the process of heating the food, and affects the cooking flavor and effect.

Disclosure of Invention

The application provides a food cooking device which is used for reducing the phenomenon that dripping grease is not completely burnt in high-temperature cooking of food.

The application also provides a heating component which can be applied to the food material cooking device to reduce the phenomenon that dripping grease is not completely burnt in high-temperature cooking of the food material.

According to an aspect of the present application, there is provided a food cooking apparatus including:

The food material support frame is used for supporting food materials;

The heating component comprises a ceramic heat conductor and a heating element, and the heating element and the ceramic heat conductor form a heat transfer structure; the ceramic heat conductor is positioned below the food material supporting frame, and can absorb heat of the heating element and heat food materials positioned above the ceramic heat conductor;

The ceramic heat conductor is provided with at least one oil leakage hole which is vertically communicated, the oil leakage hole is used for communicating the lower space and the upper space of the ceramic heat conductor, and grease dropped by the food can drop downwards from the oil leakage hole.

In one embodiment, the ceramic heat conductor has a top surface facing the food material, and a ratio a of an area of the top surface to a sum of open areas of all oil leakage holes is: a is more than or equal to 0.8 and less than or equal to 1.4.

In one embodiment, the ceramic heat conductor has a top surface facing the food material, and a turning surface between the top end of the wall of the oil leakage hole and the top surface is a smooth transition surface.

In one embodiment, the ceramic heat conductor comprises a ceramic body and a glaze layer, wherein at least the top surface of the ceramic body is provided with the glaze layer, and the surface emissivity of the glaze layer is more than or equal to 0.8.

In one embodiment, the ceramic body surface is entirely covered with a glaze layer.

In one embodiment, the heating element is embedded in the ceramic heat conductor, and the ceramic heat conductor forms an insulating package for the heating element.

In one embodiment, the ceramic heat conductor has a grid-like structure, the grid-like structure has a plurality of ribs arranged side by side or in a staggered manner, the oil leakage holes are located between the ribs, and the heating elements are respectively embedded in the ribs.

In one embodiment, the food material supporting frame is provided with a plurality of gaps, and the gaps of the food material supporting frame are at least partially overlapped with the oil leakage holes of the ceramic heat conductor on the vertical orthographic projection surface.

In one embodiment, the heating assembly includes a protective mesh disposed over the ceramic thermal conductor.

In one embodiment, the device further comprises a base, wherein one end of the heating component is rotatably connected with the base and used for rotatably opening the heating component.

According to a second aspect of the present application, in one embodiment, there is provided a heating component of a food cooking device, including a ceramic heat conductor and a heating element, wherein the heating element and the ceramic heat conductor form a heat transfer structure; the ceramic heat conductor can absorb heat of the heating element and heat food materials;

In one embodiment, the ceramic heat conductor has a top surface facing the food material, and a transition surface between an upper end of a wall of the oil leakage hole and the top surface is a smooth transition surface.

According to the embodiment, the food cooking device comprises a food support frame and a heating component. The food material support frame is used for supporting food materials, and the heating component comprises a ceramic heat conductor and a heating piece. The ceramic heat conductor is positioned below the food material supporting frame, the heating element and the ceramic heat conductor form a heat transfer structure, and the ceramic heat conductor can absorb heat of the heating element and heat food materials positioned above the ceramic heat conductor. The ceramic heat conductor is provided with at least one oil leakage hole which is vertically communicated, and oil dripped in the high-temperature heating process of the food material can drop downwards from the oil leakage hole, so that the condition that the oil drops onto the ceramic heat conductor is reduced, and the burning of the oil on the ceramic heat conductor is reduced.

Drawings

FIG. 1 is a schematic diagram showing the positional relationship between a ceramic heat conductor and a food supporting rack in an embodiment of the application;

FIG. 2 is a schematic view of a ceramic heat conductor and a food support frame in a longitudinal section according to an embodiment of the application;

FIG. 3 is a schematic view of a ceramic thermal conductor according to an embodiment of the present application;

FIG. 4 is a longitudinal cross-sectional view of a ceramic thermal conductor in one embodiment of the application;

Fig. 5 (a), (b), (c), and (d) are schematic diagrams of oil leakage holes of ceramic heat conductors according to an embodiment of the present application;

Fig. 6 is a schematic structural view of a cooking device for food materials according to an embodiment of the present application;

FIG. 7 is an exploded view of a food cooking device in accordance with one embodiment of the present application;

fig. 8 is a longitudinal sectional view of a cooking apparatus for food materials according to an embodiment of the present application;

Fig. 9 is a schematic view showing vertical widths of oil leakage holes and ribs in a ceramic heat conductor according to an embodiment of the present application.

Detailed Description

The application will be described in further detail below with reference to the drawings by means of specific embodiments. Wherein like elements in different embodiments are numbered alike in association. In the following embodiments, numerous specific details are set forth in order to provide a better understanding of the present application. However, one skilled in the art will readily recognize that some of the features may be omitted, or replaced by other elements, materials, or methods in different situations. In some instances, related operations of the present application have not been shown or described in the specification in order to avoid obscuring the core portions of the present application, and may be unnecessary to persons skilled in the art from a detailed description of the related operations, which may be presented in the description and general knowledge of one skilled in the art.

Furthermore, the described features, operations, or characteristics of the description may be combined in any suitable manner in various embodiments. Also, various steps or acts in the method descriptions may be interchanged or modified in a manner apparent to those of ordinary skill in the art. Thus, the various orders in the description and drawings are for clarity of description of only certain embodiments, and are not meant to be required orders unless otherwise indicated.

The numbering of the components itself, e.g. "first", "second", etc., is used herein merely to distinguish between the described objects and does not have any sequential or technical meaning. The term "coupled" as used herein includes both direct and indirect coupling (coupling), unless otherwise indicated.

The application provides a food cooking device which can convert electric energy into heat energy and heat food at high temperature. In particular, the food cooking device may be a device that easily causes the food to drip, and may be, but is not limited to, an electric oven, an electric stove, etc.

Referring to fig. 1 and 2, in some embodiments, the food cooking apparatus 11 includes a food support 100, a heating assembly 200, and other related components. The food material supporter 100 is for supporting the food material 2. The food material supporting rack 100 can be used for hanging, holding or other ways of fixing the food material 2 to support the food material 2. For example, in the embodiment shown in fig. 1, 2, 6 and 7, the food item support stand 100 is a grill with a void 101. When the food material 2 is placed on the grill, the grease overflowed by the heating of the food material 2 falls down through the gap 101. In other embodiments, the food material holder 100 may be replaced by a hanging bar, and the food material 2 (e.g., whole chicken) may be hung on the hanging bar for baking or smoking.

The heat generating component 200 includes a ceramic thermal conductor 210 and a heat generating element 220. The heating element 220 may have any structure capable of generating heat, and in particular, an electrothermal conversion structure such as an electrothermal wire. Of course, in some embodiments, the heat generating component 220 may be an electric heating tube or other structures.

The heat generating element 220 and the ceramic heat conductor 210 form a heat transfer structure, so that the heat generated by the heat generating element 220 can be transferred to the ceramic heat conductor 210, and the ceramic heat conductor 210 toasts or smokes the food material 2 by heat radiation or other heating methods to cook the food material 2. The ceramic thermal conductor 210 has the characteristics of high emissivity and high temperature. Meanwhile, the ceramic heat conductor 210 has high hardness, is not easy to scratch in the use process, is resistant to high temperature, and the use temperature of the sintered ceramic can be more than 1000 ℃ generally. Ceramic thermal conductor 210 is also corrosion resistant and reliable for use in a cooking environment.

Referring to fig. 1, 2, 7 and 8, in some embodiments, the ceramic heat conductor 210 is located below the food material supporting frame 100, and the ceramic heat conductor 210 is located below the food material supporting frame 100, so that the hot air rises to heat the food material 2 better than when the ceramic heat conductor 210 is disposed above or beside the food material 2.

In some embodiments, the whole plate of ceramic heat conductor 210 is used to heat the food material 2, but a lot of black smoke often appears in the heating process, so that the flavor of the food is poor and the use experience is poor. Through repeated experiments and comparison, the inventor finally finds that when the ceramic heat conductor 210 of the whole plate is adopted to heat the food 2, grease precipitated from food can drop on the surface of the ceramic heat conductor 210, the surface temperature of the ceramic heat conductor 210 is higher than the ignition point of the grease, but the internal space of the food cooking device 1 is limited, and the ceramic heat conductor 210 of the whole plate has a blocking effect on air flow, so that the oxygen content of the air around the surface of the ceramic heat conductor 210 is low, the dropped grease can be incompletely combusted, and a large amount of black smoke can appear under the condition of hypoxia.

1-4, In some embodiments, the ceramic thermal conductor 210 has at least one oil leakage hole 211 disposed vertically through, and the oil leakage hole 211 communicates the lower space with the upper space of the ceramic thermal conductor 210. Because the ceramic heat conductor 210 is located below the food material 2, the grease dropped from the food material 2 in the high-temperature heating process can drop downwards from the oil leakage hole 211, at least a part of the grease cannot drop on the ceramic heat conductor 210, and further the burning of the grease on the ceramic heat conductor 210 is reduced.

In addition, the oil leakage holes 211 can also communicate the lower space with the upper space of the ceramic heat conductor 210, so that the air flow rate of the surface of the ceramic heat conductor 210 is increased, the oxygen amount of the surface space of the ceramic heat conductor 210 is increased, the grease dropped on the ceramic heat conductor 210 can be completely combusted to generate open fire, and the grill temperature can be increased while black smoke is eliminated.

Taking high-temperature grilling cooking of steak as an example, the ceramic heat conductor 210 with the oil leakage holes 211 can enable a part of grease to drop on the surface of the ceramic heat conductor 210, and the oil leakage holes 211 can also provide enough air for complete combustion. The other part of grease directly passes through the ceramic heat conductor 210 through the oil leakage hole 211 and flows to other oil receiving devices, so that combustion does not occur.

The ceramic heat conductor 210 may be connected to the heat generating element 220 by any heat transfer structure, for example, heat conduction may be achieved by direct contact or indirect contact, where the indirect contact is that the ceramic heat conductor 210 is not in direct contact with the heat generating element 220, but performs heat conduction through other intermediate components capable of conducting heat, such as a heat conducting pad, a heat conducting glue, and the like. Preferably, to achieve higher heat transfer efficiency, ceramic thermal conductor 210 may be in direct thermally conductive contact with heat-generating component 220.

Referring to fig. 4, in some embodiments, the heat generating element 220 is embedded in the ceramic heat conductor 210, so as to increase the contact area between the ceramic heat conductor 210 and the heat generating element 220, and improve the heat conduction efficiency.

Further, in some embodiments, the heat generating element 220 may be embedded in each physical portion of the ceramic thermal conductor 210, so as to facilitate rapid heat transfer to each portion of the ceramic thermal conductor 210. In other embodiments, the heat generating element 220 may be embedded in only a portion of the solid portion of the ceramic heat conductor 210.

In some embodiments, the ceramic heat conductor 210 forms an insulating package for the heat-generating element 220, so that not only the contact area between the ceramic heat conductor 210 and the heat-generating element 220 can be increased, but also the insulation effect of the ceramic material itself can be utilized to prevent the heat-generating element 220 from being conducted with other conductive materials, and no additional insulation structure is required for the heat-generating element 220, thereby simplifying the structure.

In some embodiments, the heating element 220 employs a heating wire, which is energized to generate heat by utilizing its resistance characteristic, and the heating wire has a small diameter, so that the overall size and volume of the ceramic thermal conductor 210 are not excessively increased when the heating wire is filled into the ceramic thermal conductor 210.

Of course, in addition to disposing the heat generating component 220 inside the ceramic thermal conductor 210, in some embodiments, the heat generating component 220 may be disposed outside the ceramic thermal conductor 210, such as semi-embedded on the ceramic thermal conductor 210, or affixed to a surface of the ceramic thermal conductor 210.

Further, referring to fig. 1-3, in some embodiments, the larger the solid portion of the ceramic thermal conductor 210, the larger the heat radiation area of the food material 2, and the higher the heating temperature. However, with respect to the oil leakage hole 211, the larger the number of oil leakage holes 211 and the single hole area is, the greater the possibility of leaking out the grease overflowed from the food material 2 is. However, the larger the open area, the more power distribution of the ceramic heat conductor 210 is dispersed, which results in low cooking efficiency of the food cooking device 1. Therefore, there is a contradictory and mutually restricted relationship between the size of the solid portion of the ceramic heat conductor 210 and the open area of the oil holes 211, and the inventor finally obtains a scheme by numerous repeated experiments and demonstration analyses, in which, please refer to fig. 1-3, the ceramic heat conductor 210 has a top surface 213 disposed toward the food material 2, and the ratio a of the area of the top surface 213 of the ceramic heat conductor 210 to the sum of the open areas of all the oil holes 211 is: a is more than or equal to 0.8 and less than or equal to 1.4. At this ratio, not only the heating power of the ceramic heat conductor 210 can be ensured, but also a suitable opening area of the oil leakage hole 211 can be formed, so that part of grease can leak from the oil leakage hole 211, part of grease drops on the ceramic heat conductor 210 to be fully combusted, and the formation of black smoke in the heating process is reduced.

Further, the oil leakage holes 211 on the ceramic heat conductor 210 may exist in various shapes and arrangements. As shown in fig. 5 (a), in some embodiments, the oil leakage hole 211 may be a plurality of rectangular holes formed on the ceramic heat conductor 210 and arranged in a column vertically (up-down direction in the drawing). As shown in fig. 5 (b), in some embodiments, the oil leakage holes 211 may be a plurality of rectangular holes formed on the ceramic heat conductor 210 and arranged in a row in a lateral direction (left-right direction in the drawing). As shown in fig. 5 (c), in some embodiments, the oil leakage hole 211 may be a plurality of rectangular holes formed on the ceramic heat conductor 210 and arranged in two vertical rows. As shown in fig. 5 (d), in some embodiments, the oil leakage hole 211 may have a different vertical width or lateral width. Of course, in other embodiments, the oil leakage hole 211 may be square, circular, oval, triangular, polygonal (more than four sides), or other irregular shapes besides rectangle.

In some embodiments, the oil leakage holes 211 are arranged in a regular manner in addition to the lateral or vertical direction, as shown in fig. 5. In addition, the random distribution may be not limited to the one shown in fig. 5.

Referring to fig. 9, in some embodiments, the oil leakage holes 211 may be a plurality of rectangular holes formed on the ceramic heat conductor 210 and arranged in a column vertically (up-down direction in the drawing). Wherein, too large openings can lead to a dispersion of the power distribution of the ceramic heat conductor 210, which in turn leads to a low cooking temperature of the food material 2. Therefore, in some embodiments, the ratio of the vertical width b of the oil drain hole 211 to the vertical width c of the rib portion is controlled to be between 0.8 and 1.5 (including 0.8 and 1.5).

In some embodiments, referring to fig. 1-4, the solid portion between the oil leakage holes 211 is a rib 212, and each rib 212 is embedded or otherwise provided with a heat generating element 220, so as to ensure the heating efficiency of the ceramic heat conductor 210.

Further, referring to fig. 1-4, in some embodiments, the ceramic heat conductor 210 has a grid-like structure, the grid-like structure has a plurality of ribs 212 arranged side by side or alternatively, the oil leakage holes 211 are located between the ribs 212, and the heat generating elements 220 are respectively embedded or otherwise disposed in the ribs 212.

Referring to fig. 3, in some embodiments, the ceramic heat conductor 210 has a top surface 213 disposed towards the food material 2, a turning surface between an upper end of a wall of the oil leakage hole 211 and the top surface 213 is a smooth transition surface 214, and the smooth transition surface 214 is also beneficial for the oil on the ceramic heat conductor 210 to slide down. Further, the rounded transition surface 214 increases the contact surface area with the grease dripping on the food material 2, and the dripping grease is more easily ignited. At the same time, the smooth surface of the smooth transition surface 214 is more convenient for guiding the air flow to the surface of the ceramic heat conductor 210, so as to improve the probability of complete combustion of the grease on the ceramic heat conductor 210.

Further, in order to increase the surface emissivity of the ceramic thermal conductor 210 and further increase the heating efficiency of the ceramic thermal conductor 210, in some embodiments, the ceramic thermal conductor 210 includes a ceramic body and a glaze layer, wherein at least the top surface 213 of the ceramic body is provided with the glaze layer, and the surface emissivity of the glaze layer is greater than or equal to 0.8.

The ceramic body may have a glazed layer on only the top surface 213, or may have a glazed layer covering other or all surfaces to enhance the external heat radiation of the ceramic heat conductor 210. Meanwhile, the glaze layer can further enhance the scratch resistance of the surface of the ceramic heat conductor 210 besides improving the surface emissivity.

In some embodiments, the glaze layer is a dark-colored glaze-burning process, which enhances the external heat radiation of the ceramic thermal conductor 210, thereby increasing the cooking temperature. In some embodiments, the dark color is dark brown or pure black, preferably pure black, with a higher emissivity effect.

Further, referring to fig. 2, in some embodiments, the food material supporting rack 100 has a plurality of voids 101, and the voids 101 of the food material supporting rack 100 at least partially overlap with the oil leakage holes 211 of the ceramic heat conductor 210 on a vertical orthographic plane (a projection along a direction indicated by an arrow in fig. 2). The gap 101 of the food material supporting frame 100 is staggered with the opening of the oil leakage hole 211 of the ceramic heat conductor 210, so that the heating speed and the radiant heat effect can be improved, and correspondingly, the dropped grease can be ignited better.

Further, referring to fig. 7 and 8, in some embodiments, the heat generating component 200 includes a protective mesh 300, and the protective mesh 300 is disposed above the ceramic heat conductor 210. Specifically, the protection net 300 can protect the ceramic heat conductor 210 from above, so as to prevent the food 2 or other sundries from falling onto the ceramic heat conductor 210 and damaging the ceramic heat conductor 210.

Referring to fig. 7 and 8, in some embodiments, the heat-generating component 220 assembly may further include a lower support mesh 400, and the ceramic thermal conductor 210 is located above the lower support mesh 400. The ceramic heat conductor 210 may be directly mounted on the lower support net 400, or may be unconnected to the lower support net 400. The lower support mesh 400 may protect the ceramic thermal conductor 210 from below. The lower support net 400 may also function to support the ceramic thermal conductor 210 when the ceramic thermal conductor 210 is mounted on the lower support net 400.

Referring to fig. 7 and 8, in some embodiments, the heat generating component 200 further includes a base 500, and one end of the heat generating component 200 is rotatably connected to the base 500 to rotatably open the heat generating component 200, so as to facilitate the assembly and disassembly of the ceramic heat conductor 210. The base 500 may be used as a housing of the food cooking device 1 (as shown in fig. 7 and 8), or may be provided in the food cooking device 1.

Specifically, referring to fig. 7 and 8, in some embodiments, the ceramic heat conductor 210 is fixedly mounted on a support joint 700, and a rotation joint 510 is provided on the base 500, and the support joint 700 is rotatably connected to the rotation joint 510, so as to facilitate rotation of the ceramic heat conductor 210. In some embodiments, the two support joints 700 are disposed on opposite sides of the ceramic thermal conductor 210, thereby forming a rotating structure that rotates about the two support joints 700.

Referring to fig. 7 and 8, in some embodiments, an insulating housing 600 is further included, the insulating housing 600 having an insulating cavity within which the heat generating component 200 is disposed. The heat shield 600 is installed in the base 500 together with the heat generating component 200. The heat shield 600 is provided with an opening 610, and the rotary joint 510 of the base 500 is rotatably connected with the support joint 700 through the opening 610. Of course, the support joint 700 may be rotatably coupled to the rotary joint 510 through the opening 610.

Referring to fig. 6 and 7, in some embodiments, the food cooking apparatus 1 may have an upper cover 800, and the upper cover 800 and the base 500 enclose a cooking cavity for cooking the food 2. The upper cover 800 may be opened and closed to access the food material 2 and to mount and dismount other components, such as the heating assembly 200, disposed within the base 500. In the embodiment shown in fig. 6 to 8, the upper cover 800 is opened and closed by rotating, and the rotation direction of the upper cover 800 coincides with the rotation direction of the ceramic heat conductor 210.

Of course, in other embodiments, the upper cover 800 may be omitted from the food cooking device 1 to form a semi-closed or fully open structure.

The above describes the various configurations of the food cooking device 1, and in other embodiments, the heat generating assembly 200 may be used alone in other food cooking devices.

The foregoing description of the invention has been presented for purposes of illustration and description, and is not intended to be limiting. Several simple deductions, modifications or substitutions may also be made by a person skilled in the art to which the invention pertains, based on the idea of the invention.

Claims

1. A food cooking device, comprising:

The food material support frame is used for supporting food materials;

2. A food cooking device according to claim 1, wherein the ceramic heat conductor has a top surface disposed toward the food, and wherein a ratio a of an area of the top surface to a sum of open areas of all oil leakage holes is: a is more than or equal to 0.8 and less than or equal to 1.4.

3. The food cooking apparatus of claim 1, wherein the ceramic heat conductor has a top surface facing the food, and a turning surface between an upper end of a wall of the oil leakage hole and the top surface is a smooth transition surface.

4. The food cooking device of claim 1, wherein the ceramic heat conductor comprises a ceramic body and a glaze layer, wherein at least a top surface of the ceramic body is provided with the glaze layer, and wherein a surface emissivity of the glaze layer is greater than or equal to 0.8.

5. The food cooking apparatus according to claim 1, wherein the ceramic heat conductor has a grid-like structure having a plurality of ribs arranged side by side or alternately, the oil leakage holes are located between the ribs, and the heat generating members are buried in the ribs respectively;

The food material support frame is provided with a plurality of gaps, and the gaps of the food material support frame are at least partially overlapped with oil leakage holes of the ceramic heat conductor on the vertical orthographic projection plane.

6. The heating component of the food cooking device is characterized by comprising a ceramic heat conductor and a heating element, wherein the heating element and the ceramic heat conductor form a heat transfer structure; the ceramic heat conductor can absorb heat of the heating element and heat food materials;

7. The heat-generating component as set forth in claim 6, wherein said ceramic heat conductor has a top surface disposed toward said food material, and wherein a ratio a of an area of said top surface to a sum of open areas of all oil leakage holes is: a is more than or equal to 0.8 and less than or equal to 1.4.

8. The heating assembly of claim 6, wherein the ceramic heat conductor has a top surface facing the food material, and a transition surface between an upper end of a wall of the oil leakage hole and the top surface is a smooth transition surface.

9. The heat-generating component of claim 6, wherein the ceramic heat conductor comprises a ceramic body and a glaze layer, wherein at least a top surface of the ceramic body is provided with the glaze layer, and wherein a surface emissivity of the glaze layer is greater than or equal to 0.8.

10. The heating assembly of claim 6, wherein the ceramic heat conductor has a grid-like structure having a plurality of ribs arranged side by side or alternately, the oil leakage holes are located between the ribs, and the heating elements are embedded in the ribs respectively.