A graphite heating tube for a baking apparatus

Abstract

The application discloses a graphite heating tube for a baking device, which comprises an outer tube, graphite heating sheets arranged in the outer tube, and conductive pieces connected to the ends of the graphite heating sheets and partially penetrating the outer tube. The inner part of the outer tube is filled with inert gas, and the absolute pressure in the inner part of the outer tube is controlled to be 0.005-0.068 MPa. In the application, the inert gas in the inner part of the outer tube forms a heat buffering and equalizing layer, which blocks the heat generated by the graphite heating sheets and diffuses the heat, so that the heat transferred to the outer tube is relatively equalized, the temperature of the wall of the graphite heating tube is more uniform, the baking effect on food is improved, and the problem of cracks or even breakage caused by the non-uniform temperature of the tube wall is avoided, thereby prolonging the service life of the graphite heating tube.

Description

Technical Field

[0001] This invention relates to the field of heating tube technology, and more specifically to a graphite heating tube for baking apparatus. Background Technology

[0002] Graphite heating elements are thin films made of carbon-based materials. They have two-dimensional isotropic thermal conductivity in the planar direction and can heat up quickly and efficiently when energized. As a result, graphite heating elements are increasingly being used in baking equipment to improve the cooking efficiency of baking equipment.

[0003] However, due to the influence of the graphite heating element manufacturing process, graphite sheets with the same structure inside the graphite heating tube may exhibit different heating temperatures, i.e., temperature anomalies. This results in uneven heating of the outer tube wall corresponding to the graphite sheet. In particular, when the amount of inert gas sealed inside the graphite heating tube is inappropriate, the temperature of the graphite heating tube wall becomes even more uneven, leading to poor baking results for food. Furthermore, with prolonged use, the uneven temperature of the graphite heating tube wall can easily cause cracks or even breakage, affecting the service life of the graphite heating tube. Summary of the Invention

[0004] The purpose of this invention is to provide a graphite heating tube for baking equipment, which solves the problem of uneven surface temperature of existing graphite heating elements due to abnormal heating temperature points, thereby improving the baking effect of food and extending the service life of the graphite heating tube.

[0005] To achieve the above objectives, the present invention provides a graphite heating tube for a baking apparatus, comprising an outer tube, a graphite heating element disposed inside the outer tube, and a conductive element connected to the end of the graphite heating element, wherein the conductive element extends out of the outer tube, and the interior of the outer tube is sealed with an inert gas, and the absolute pressure inside the outer tube is controlled at 0.005-0.068 MPa.

[0006] In this invention, an inert gas is sealed inside the outer tube while maintaining the absolute pressure inside the outer tube at 0.005-0.068 MPa. This allows the inert gas to form a heat buffer layer, which blocks the heat generated by the graphite heating element and allows the heat to diffuse, resulting in a more even distribution of heat to the outer tube. This leads to a more uniform temperature on the graphite heating tube wall, improving the baking effect and preventing cracks or even breakage caused by uneven temperature distribution, thus extending the lifespan of the graphite heating tube. If the absolute pressure inside the outer tube is below 0.005 MPa, the insufficient gas volume will not effectively block the heat, failing to form a heat buffer layer and achieve a uniform temperature. Conversely, if the absolute pressure inside the outer tube is above 0.068 MPa, excessive gas volume will hinder heat diffusion, again failing to achieve a uniform temperature.

[0007] In a preferred embodiment of a graphite heating tube for a baking apparatus, the absolute pressure inside the outer tube is controlled at 0.035-0.058 MPa.

[0008] This allows the temperature and pressure of the outer tube to be kept within a more reasonable range, enabling more effective control of the surface temperature of the outer tube, preventing uneven surface temperature, ensuring the baking effect of food, and extending the service life of the graphite heating tube.

[0009] In a preferred embodiment of a graphite heating tube for a baking apparatus, the power distributed per unit resistance of the graphite heating element is less than 50W, so that the heating temperature of the outer tube surface is less than 600°C.

[0010] The power distributed per unit resistance of the graphite heating element is less than 50W. When the heat generation, heat storage, radiation, and heat exchange with the outside environment per unit resistance reach equilibrium, the surface temperature of the outer tube is less than 600℃. This prevents heat from being transferred to the temperature controller too quickly, avoiding premature power-off during the heating process and preventing a drop in heating temperature. It also prevents frequent circuit switching that could cause a decrease in the internal temperature of the baking device. Furthermore, the surface temperature of the outer tube being less than 600℃ ensures that the food is cooked through while preventing the surface temperature from becoming too high, thus preventing the food from burning.

[0011] In a preferred embodiment of a graphite heating tube for a baking apparatus, the graphite heating tube further includes a coil-shaped support ring disposed inside an outer tube. The support ring includes a central portion and an outer peripheral portion. The central portion of the support ring is fixedly connected to a conductive element, and the outer peripheral portion of the support ring is configured close to the inner peripheral surface of the outer tube. The diameter D1 of the outer peripheral portion and the inner diameter D2 of the outer tube satisfy 0.90≤D1 / D2≤0.94.

[0012] The central part of the support ring is fixedly connected to the conductive component, which is connected to the end of the graphite heating element, thus achieving the purpose of supporting the graphite heating element. Furthermore, the outer circumference of the support ring is positioned close to the inner circumference of the outer tube, and the diameter D1 of the outer circumference and the inner diameter D2 of the outer tube satisfy 0.90≤D1 / D2≤0.94. This design allows for a gap between the support ring and the outer tube, facilitating installation. Additionally, the support ring is positioned as close as possible to the inner wall of the outer tube, improving its support for the graphite heating element and limiting the distance between the graphite heating element and the outer tube wall. This prevents the graphite heating element from directly contacting the outer tube wall, which could lead to excessively high surface temperatures, eliminating abnormal temperature points, improving the uniformity of the outer tube surface temperature, and reducing safety hazards.

[0013] In a preferred embodiment of a graphite heating tube for a baking apparatus, the distance d between the end of the support ring and the end of the graphite heating element along the axial direction of the outer tube satisfies 0 ≤ d ≤ 8 mm.

[0014] Since the smaller the distance d between the support ring and the end of the graphite heating element along the axial direction of the outer tube, the better the support effect of the support ring on the graphite heating element, when 0≤d≤8mm, the support effect of the support ring on the graphite heating element can be improved, and the graphite heating element can be prevented from directly contacting the tube wall of the outer tube to cause abnormal temperature points, so that the temperature of each part of the outer tube wall is uniform.

[0015] In a preferred embodiment of a graphite heating tube for a baking apparatus, a conductive element is located on the central axis of the graphite heating element and at the center of a support ring, so that the graphite heating element is centrally located inside the outer tube.

[0016] The conductive element is located on the central axis of the graphite heating element and at the center of the support ring. This means that the support ring can support the graphite heating element through the conductive element and ensure that the graphite heating element is centered inside the outer tube. This prevents excessive differences in distance between different parts of the graphite heating element and the wall of the outer tube, avoids excessively high local temperature on the wall of the outer tube, eliminates abnormal temperature points, and improves the uniformity of the surface temperature of the outer tube.

[0017] In a preferred embodiment of a graphite heating tube for a baking apparatus, the inert gas is argon, nitrogen, or a mixture of nitrogen and halogen.

[0018] The aforementioned inert gas is non-toxic and odorless, and does not readily react chemically with the graphite heating element, thus preventing its oxidation. Furthermore, even if the gas leaks, it will not harm the user, thereby enhancing safety.

[0019] In a preferred embodiment of a graphite heating tube for a baking apparatus, a wire sleeve is fitted over the portion of the conductive element that extends out of the outer tube, and an elastic connection is provided between the end of the outer tube and the wire sleeve to completely enclose the portion of the conductive element located between the end of the outer tube and the wire sleeve.

[0020] A sleeve is fitted over the portion of the conductive component that protrudes from the outer tube. This sleeve protects the conductive component, preventing it from being exposed and protecting it from damage or failure in oily fumes and high-temperature environments. This ensures the strength and conductivity of the conductive component and extends its service life. Furthermore, an elastic connection is provided between the end of the outer tube and the sleeve to completely enclose the portion of the conductive component between the end of the outer tube and the sleeve. This isolates the conductive component from the outside environment, preventing oxidation caused by contact with air. The elastic connection also creates a good seal, preventing gas inside the outer tube from diffusing outwards through the gap between the conductive component and the outer tube, maintaining the air pressure inside the outer tube, and ensuring the normal operation of the graphite heating tube.

[0021] In a preferred embodiment of a graphite heating tube for a baking apparatus, the conductive element is provided with an elastic portion for absorbing the expansion and contraction of the graphite heating element.

[0022] When the graphite heating element expands and contracts due to heat, the elastic part can absorb the expansion and contraction of the graphite heating element, thereby buffering the compressive or tensile force between the conductive component and the graphite heating element, preventing damage to the graphite heating element and the conductive component, and extending the service life.

[0023] In a preferred embodiment of a graphite heating element for a baking apparatus, the graphite heating element includes a planar portion and a linear side portion. The distance L1 between the planar portion and the inner wall of the outer tube satisfies: 0.15cm < L1 < 0.5cm, and the distance L2 between the side portion and the inner wall of the outer tube satisfies: 0.05cm < L2 < 0.25cm.

[0024] The values ​​of 0.15cm < L1 < 0.5cm and 0.05cm < L2 < 0.25cm can prevent the graphite heating element from getting close to or sticking tightly to the inner wall of the outer tube, thereby avoiding excessively high temperatures on the outer tube wall, preventing the graphite heating tube from reaching abnormal temperature points, and reducing safety hazards. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 This is a schematic diagram of the baking apparatus according to one embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the structure of a graphite heating tube according to one embodiment of the present invention.

[0028] Figure 3 for Figure 2 Enlarged schematic diagram of part A in the middle.

[0029] Figure 4 for Figure 2 Enlarged schematic diagram of section B.

[0030] Figure 5 This is a schematic diagram of the structure of a graphite heating element according to one embodiment of the present invention.

[0031] Figure 6 This is a partial structural schematic diagram of a graphite heating tube according to one embodiment of the present invention.

[0032] Explanation of reference numerals in the attached drawings: 1-Outer tube; 2-Graphite heating element; 21-Unit resistor; 3-Conductive component; 4-Support ring; 5-Wire sleeve; 6-Elastic connection part. Detailed Implementation

[0033] To more clearly illustrate the overall concept of the present invention, a detailed description will be provided below with reference to the accompanying drawings and examples.

[0034] It should be noted that many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0035] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the present invention provides a graphite heating tube for a baking apparatus, comprising an outer tube 1, a graphite heating element 2 disposed inside the outer tube 1, and a conductive element 3 connected to the end of the graphite heating element 2. The conductive element 3 extends out of the outer tube 1, and the interior of the outer tube 1 is sealed with an inert gas, and the absolute pressure inside the outer tube 1 is controlled at 0.005-0.068 MPa.

[0036] In a preferred embodiment of the present invention, the absolute air pressure inside the outer tube 1 is controlled at 0.035-0.058 MPa.

[0037] Specifically, this invention conducts tests on the heating uniformity of the graphite heating tube under different gas pressures. Taking a power distribution of 46.5W per unit resistance of the graphite heating element as an example, the positions of the five temperature measuring points (a, b, c, o, e) of the graphite heating tube are referenced. Figure 4 As shown in the table below, the graphite heating elements corresponding to the five temperature measurement points have the same structure. The experimental results are shown in the table below:

[0038]

[0039] As can be seen from the table above:

[0040] In Examples 1-6, the internal air pressure of the outer tube was controlled between 0.005-0.068 MPa, and the maximum temperature difference between each temperature measuring point was 2°C.

[0041] In Examples 3-5, the internal air pressure of the outer tube was controlled between 0.035-0.058 MPa, and the maximum temperature difference between each temperature measuring point was 1℃.

[0042] In Comparative Examples 1-3, the internal air pressure of the outer tube was not controlled between 0.005-0.068 MPa, and the temperature difference between the various temperature measuring points ranged from a maximum of 50℃ to a minimum of 36.1℃.

[0043] Therefore, the temperature difference between each temperature measuring point of the graphite heating tube provided by the present invention is small, and the temperature is more uniform.

[0044] In summary, this invention, by sealing an inert gas inside the outer tube and maintaining the absolute pressure inside the outer tube at 0.005-0.068 MPa, allows the inert gas to form a heat buffer layer. This heat buffer layer blocks the heat generated by the graphite heating element and allows the heat to diffuse, resulting in a relatively even distribution of heat to the outer tube. This leads to a more uniform temperature on the graphite heating tube wall, improving the baking effect on food and preventing cracks or even breakage caused by uneven temperature distribution on the tube wall, thus extending the service life of the graphite heating tube. If the absolute pressure inside the outer tube is below 0.005 MPa, the insufficient gas volume will not effectively block the heat, thus failing to form a heat buffer layer and achieve a uniform temperature. Conversely, if the absolute pressure inside the outer tube is above 0.068 MPa, the excessive gas volume will hinder heat diffusion, again failing to achieve a uniform temperature.

[0045] The absolute air pressure inside the outer tube 1 is controlled at 0.035-0.058MPa, which allows the temperature and pressure of the outer tube to be within a more reasonable range. This enables more effective control of the surface temperature of the outer tube, prevents uneven surface temperature, ensures the baking effect of food, and extends the service life of the graphite heating tube.

[0046] It should be noted that the material of the outer tube 1 is not specifically limited in this invention. The outer tube 1 can be made of stainless steel, quartz, etc.

[0047] In a preferred embodiment of the present invention, the power distributed per unit resistance of the graphite heating element 2 is less than 50W, so that the heating temperature on the surface of the outer tube 1 is less than 600°C.

[0048] like Figure 5 As shown, the graphite heating element 2 has multiple unit resistors 21 connected in series. Current flows through the graphite resistors to generate heat. Experiments have verified that the hot resistance of a single unit resistor is approximately 0.16Ω, meaning the power allocated to each unit resistor should be within 8W. Matching the oven's test temperature field, graphite heating elements with a power allocated to each unit resistor of less than 8W are more suitable for ovens. Therefore, under normal operating conditions, the power allocated to each unit resistor of the graphite heating element is within 50W.

[0049] The power distributed per unit resistance of the graphite heating element 2 is less than 50W. When the heat generation, heat storage, radiation, and heat exchange with the outside environment per unit resistance reach a state of equilibrium, the surface temperature of the outer tube 1 is less than 600℃. This prevents heat from being transferred to the temperature controller more quickly, avoiding premature power-off of the temperature controller during the heating process, thus preventing a drop in the heating temperature and avoiding frequent circuit switching that could cause a decrease in the internal temperature of the baking device. In addition, the surface temperature of the outer tube 1 is less than 600℃, ensuring that the food is cooked through while preventing the surface temperature of the outer tube 1 from becoming too high, thereby preventing the food from burning.

[0050] As a preferred embodiment of the present invention, such as Figure 6 As shown, the graphite heating tube also includes a coil-shaped support ring 4 disposed inside the outer tube 1. The support ring 4 includes a central part and an outer peripheral part. The central part of the support ring 4 is fixedly connected to the conductive element 3. The outer peripheral part of the support ring 4 is configured close to the inner peripheral surface of the outer tube 1, and the diameter D1 of the outer peripheral part and the inner diameter D2 of the outer tube 1 satisfy 0.90≤D1 / D2≤0.94.

[0051] The central part of the support ring 4 is fixedly connected to the conductive element 3, which is connected to the end of the graphite heating element 2, thereby achieving the purpose of the support ring 4 supporting the graphite heating element 2. In addition, the outer peripheral part of the support ring 4 is configured close to the inner peripheral surface of the outer tube 1, and the diameter D1 of the outer peripheral part and the inner diameter D2 of the outer tube 1 satisfy 0.90≤D1 / D2≤0.94. On the one hand, there is a gap between the support ring 4 and the outer tube 1, which facilitates the installation of the support ring 4; on the other hand, the support ring 4 can be as close as possible to the inner wall of the outer tube 1, thereby improving the support effect of the support ring 4 on the graphite heating element 2, and limiting the distance between the graphite heating element 2 and the tube wall of the outer tube 1, avoiding direct contact between the graphite heating element 2 and the tube wall of the outer tube 1, which would cause the surface temperature of the outer tube 1 to be too high, eliminating abnormal temperature points, improving the uniformity of the surface temperature of the outer tube 1, and reducing safety hazards.

[0052] Furthermore, such as Figure 6 As shown, the distance d between the end of the support ring 4 and the graphite heating element 2 along the axial direction of the outer tube 1 satisfies 0≤d≤8mm.

[0053] Since the smaller the distance d between the support ring 4 and the end of the graphite heating element 2 along the axial direction of the outer tube 1, the better the support effect of the support ring 4 on the graphite heating element 2, when 0≤d≤8mm, the support effect of the support ring 4 on the graphite heating element 2 can be improved, and the graphite heating element 2 can be prevented from directly contacting the tube wall of the outer tube 1 to cause abnormal temperature points, so that the temperature of each part of the tube wall of the outer tube 1 is uniform.

[0054] Preferably, the distance d between the end of the support ring 4 and the graphite heating element 2 along the axial direction of the outer tube 1 satisfies 3≤d≤5mm. On the one hand, this can further improve the support effect of the support ring 4 on the graphite heating element 2, and on the other hand, it can prevent the distance d between the end of the support ring 4 and the end of the graphite heating element 2 along the axial direction of the outer tube 1 from being too small, which would affect the installation of the graphite heating element 2.

[0055] Furthermore, such as Figure 6 As shown, the conductive element 3 is located on the central axis of the graphite heating element 2, and the conductive element 3 is located at the center of the support ring 4, so that the graphite heating element 2 is centrally located inside the outer tube 1.

[0056] The conductive element 3 is located on the central axis of the graphite heating element 2 and is located at the center of the support ring 4. That is, the support ring 4 can support the graphite heating element 2 through the conductive element 3 and ensure that the graphite heating element 2 is centrally located inside the outer tube 1. This can prevent the distance difference between various parts of the graphite heating element 2 and the tube wall of the outer tube 1 from being too large, avoid the local temperature of the tube wall of the outer tube 1 from being too high, eliminate abnormal temperature points, and improve the uniformity of the surface temperature of the outer tube 1.

[0057] In a preferred embodiment of the present invention, the inert gas is argon, nitrogen, or a mixture of nitrogen and halogen.

[0058] The aforementioned inert gas is non-toxic and odorless, and does not readily react chemically with the graphite heating element 2, thus preventing the graphite heating element 2 from oxidizing. Moreover, even if the aforementioned gas leaks, it will not cause harm to the user, thereby improving safety.

[0059] As a preferred embodiment of the present invention, such as Figure 3 As shown, the portion of the conductive element 3 that extends out of the outer tube 1 is fitted with a wire sleeve 5, and an elastic connection portion 6 is provided between the end of the outer tube 1 and the wire sleeve 5 to completely wrap the portion of the conductive element 3 located between the end of the outer tube 1 and the wire sleeve 5.

[0060] A sleeve 5 is fitted over the portion of the conductive element 3 that extends out of the outer tube 1. This sleeve protects the conductive element 3, preventing it from being exposed and thus protecting it from damage or failure in environments with oil fumes and high temperatures. This ensures the strength and conductivity of the conductive element 3 and extends its service life. Furthermore, an elastic connection portion 6 is provided between the end of the outer tube 1 and the sleeve 5 to completely enclose the portion of the conductive element 3 located between the end of the outer tube 1 and the sleeve 5. This isolates the conductive element 3 from the outside environment, preventing oxidation caused by contact with air. The elastic connection portion 6 also provides a good seal, preventing gas inside the outer tube 1 from diffusing outwards through the gap between the conductive element 3 and the outer tube 1, maintaining the air pressure inside the outer tube 1, and ensuring the normal operation of the graphite heating tube.

[0061] It should be noted that the present invention does not specifically limit the structure of the elastic connecting part 6. It can be directly fixed between the outer tube 1 and the wire sleeve 5 by applying glue (room temperature curing silicone rubber) between the end of the outer tube 1 and the wire sleeve 5. Alternatively, an elastic connecting part 6 can be provided separately and then connected between the end of the outer tube 1 and the wire sleeve 5 by means of bonding, riveting, etc., which will not be elaborated here.

[0062] In a preferred embodiment of the present invention, the conductive element 3 is provided with an elastic portion (not shown in the figure) for absorbing the expansion and contraction of the graphite heating element 2.

[0063] When the graphite heating element 2 expands and contracts due to heat, the elastic part can absorb the expansion and contraction of the graphite heating element 2, thereby buffering the squeezing or stretching force between the conductive element 3 and the graphite heating element 2, avoiding damage to the graphite heating element 2 and the conductive element 3, and extending the service life.

[0064] As a preferred embodiment of the present invention, such as Figure 3 and Figure 6 As shown, the graphite heating element 2 includes a planar portion and a linear side portion. The distance L1 between the planar portion and the inner wall of the outer tube 1 satisfies: 0.15cm < L1 < 0.5cm, and the distance L2 between the side portion and the inner wall of the outer tube 1 satisfies: 0.05cm < L2 < 0.25cm.

[0065] The values ​​of 0.15cm < L1 < 0.5cm and 0.05cm < L2 < 0.25cm can prevent the graphite heating element 2 from getting close to or sticking tightly to the inner wall of the outer tube 1, thereby avoiding excessively high temperatures on the outer tube 1, preventing the graphite heating tube from reaching abnormal temperature points, and reducing safety hazards.

[0066] The technical solutions protected by this invention are not limited to the above embodiments. It should be noted that any combination of the technical solutions of any embodiment with one or more other embodiments is within the protection scope of this invention. Although the invention has been described in detail above with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of this invention are within the scope of protection claimed by this invention.

Claims

1. A graphite heating tube for a baking apparatus, comprising an outer tube, a graphite heating element disposed within the outer tube, and a conductive element connected to the end of the graphite heating element, wherein the conductive element partially extends out of the outer tube, characterized in that, The power distributed per unit resistance of the graphite heating element is less than 50W, so that the heating temperature on the surface of the outer tube is less than 600℃. The interior of the outer tube is sealed with inert gas, and the absolute pressure inside the outer tube is controlled at 0.005-0.035MPa or 0.046-0.058MPa. The graphite heating tube also includes a coil-shaped support ring disposed inside the outer tube. The support ring includes a central portion and an outer peripheral portion. The central portion of the support ring is fixedly connected to the conductive element, and the outer peripheral portion of the support ring is configured close to the inner peripheral surface of the outer tube.

2. A graphite heating tube for a baking apparatus according to claim 1, characterized in that, The diameter D1 of the outer circumference and the inner diameter D2 of the outer tube satisfy 0.90≤D1 / D2≤0.

94.

3. A graphite heating tube for a baking apparatus according to claim 2, characterized in that, The distance d between the end of the support ring and the graphite heating element along the axial direction of the outer tube satisfies 0 ≤ d ≤ 8 mm.

4. A graphite heating tube for a baking apparatus according to claim 3, characterized in that, The conductive element is located on the central axis of the graphite heating element and at the center of the support ring, so that the graphite heating element is centrally located inside the outer tube.

5. A graphite heating tube for a baking apparatus according to claim 1, characterized in that, The inert gas is argon, nitrogen, or a mixture of nitrogen and halogen.

6. A graphite heating tube for a baking apparatus according to claim 1, characterized in that, The portion of the conductive element that extends out of the outer tube is fitted with a wire sleeve, and an elastic connection portion is provided between the end of the outer tube and the wire sleeve to completely enclose the portion of the conductive element located between the end of the outer tube and the wire sleeve.

7. A graphite heating tube for a baking apparatus according to claim 1, characterized in that, The conductive element is provided with an elastic portion for absorbing the expansion and contraction of the graphite heating element.

8. A graphite heating tube for a baking apparatus according to claim 1, characterized in that, The graphite heating element includes a planar portion and a linear side portion. The distance L1 between the planar portion and the inner wall of the outer tube satisfies: 0.15cm < L1 < 0.5cm, and the distance L2 between the side portion and the inner wall of the outer tube satisfies: 0.05cm < L2 < 0.25cm.

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