Liquid heating cooker

Abstract

An objective of the present invention is to provide a liquid heating cooker in which electric discharge is not generated as a result of metal components used in a cooking unit during microwave cooking. In the liquid heating cooker of the present invention, an electrically non-conductive member such as a ceramic material is disposed at the position of a hole in a top plate where sparks are most likely to fly, and all or at least a part of a hanging member is made of an electrically non-conductive material. By using electrically non-conductive members, no electric discharge occurs due to the formation of incomplete contacting portions between metal components, even when microwaves are radiated, thereby making it possible to avoid damage to the liquid heating cooker. When at least a part of the hanging member is made of an electrically non-conductive material, the position of the electrically non-conductive part of the hanging member is controlled taking into account the size of a liquid tank and a food basket so that the electrically non-conductive part coincides with the hole in the top plate when the food basket is lowered into the liquid tank to cook food.

Description

liquid heating cooker

[0001] The present invention relates to an improvement to commercial liquid heating cookers (e.g., fryers and noodle boilers) used in convenience stores, fast food restaurants, etc. to heat ingredients such as fried chicken, fried foods, and noodles, and in particular to a liquid heating cooker that uses microwaves as a heat source.

[0002] Convenience stores and other establishments require fast and efficient service, and commercial cooking appliances used to prepare frozen foods and other foods in-store are desirably equipped with a heating means capable of rapidly heating ingredients. To this end, a heating method is employed in which microwaves are irradiated to vibrate the molecules of a substance, raising the temperature of the object through the resulting frictional heat. Microwave heating allows for rapid heating, resulting in an immediate temperature rise after heating begins, enabling heating in a short time. Because microwaves can heat the inside of a substance by heating the moisture contained within it, they are suitable for quickly heating frozen foods and other deep-fried foods (see, for example, Patent Document 1 below).

[0003] Unlike microwave ovens, cooking appliances that immerse food in liquid in a heating tank and then irradiate it with microwaves require that the food be placed together in a designated food basket, which is then placed in the liquid tank for cooking, requiring a lifting device to move the food basket up and down.

[0004] International Publication No. 2018 / 225859

[0005] In liquid cooking appliances, where microwaves heat ingredients to high temperatures and also heat the liquid in the heating tank, the food basket and lifting device, including the hanging member, are typically made of metal to withstand high temperatures and long-term operation. Furthermore, as evidenced by the phenomenon of sparks flying when aluminum foil is placed inside a microwave oven and turned on, if there is a metal object inside the cooking unit of a microwave-based cooking appliance, microwaves can be concentrated, causing sparks and damaging the liquid cooking appliance. While metals have the property of reflecting radio waves, they also contain freely mobile electrons on their surfaces. When these electrons move violently due to microwave vibrations, they are released into the air and jump to other objects, causing a discharge. Electricity is particularly likely to gather on protruding parts, and it is said that uneven metal edges are more likely to cause discharge.

[0006] The lifting device for a liquid cooking appliance uses a hanging member that hooks onto and supports the food basket. A lift motor moves the hanging member up and down to immerse and lift the food basket into the liquid bath. To prevent microwaves from leaking outside, a cooking unit must be equipped with a top plate to create an enclosed space. Metal top plates are typically used for ease of processing and cost reasons. However, when metal hanging members are passed through holes drilled in the top plate, imperfect contact occurs between the metal parts. As a result, microwaves are concentrated all at once, causing sparks due to the aforementioned discharge phenomenon, which could damage the magnetron. Heat from the discharge could also create holes in the waveguide, resulting in microwave energy leaking outside.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid heating cooker that does not generate discharge due to metal parts used in the cooking unit during microwave cooking.

[0008] To solve the above problems, the liquid cooking device of the present invention has a structure in which a hanging member that passes through a hole in the top plate of the cooking unit engages with a food container where food is placed, and a lift mechanism raises and lowers the food container by moving the hanging member up and down, and all or at least a portion of the hanging member is made of a non-conductive material. When at least a portion of the hanging member is made of a non-conductive material, the position of the non-conductive portion is controlled taking into account the size of the liquid vat and the food basket so that the non-conductive portion of the hanging member aligns with the hole in the top plate when the food basket is lowered into the liquid vat to cook the ingredients. The above problems can also be solved by placing a non-conductive material such as a ceramic material in the position of the hole in the top plate where sparks are likely to fly.

[0009] The liquid heating cooker of the present invention uses non-conductive materials, so even if microwaves are radiated, no discharge occurs due to the formation of incomplete contact between metal parts, thereby preventing damage to the liquid heating cooker.

[0010] Fig. 1 is an external view of a liquid heating cooker according to an embodiment of the present invention, and a diagram showing the state of opening the door and removing a food basket. Fig. 2 is a perspective view of a lifting device for the liquid heating cooker. Fig. 3 is a cross-sectional view of the liquid heating cooker. Fig. 4 is a diagram showing the position of a hanging rod when the food basket is lifted and lowered. Fig. 5 is a diagram showing an example of covering holes in a top plate with a non-conductive material.

[0011] A preferred embodiment of the present invention will be described in detail below with reference to the drawings. In this embodiment, a fryer is used as an example of a liquid heating cooker, but the present invention is not limited to fryers and can also be applied to other liquid heating cookers such as noodle boilers.

[0012] FIG. 1 is an exterior view of one embodiment of a fryer 100 and shows the front door being opened to remove a food basket. The fryer 100 is composed of three sections: an upper section 1a, a middle section 1b, and a lower section 1c. The upper section 1a houses an elevator and other components, and the middle section 1b has a door opening at the front, providing space for loading and unloading a food basket 12. The lower section 1c houses a liquid tank 7, and a door at the front of the lower section 1c can be opened to check the status of the liquid tank 7. An additional section may be added below the lower section 1c to provide space for a liquid container to be used when disposing of the liquid in the liquid tank 7.

[0013] FIG. 2 is a perspective view of a portion of the mechanism housed in the upper section 1a. FIG. 3 is a schematic cross-sectional view of the liquid heating cooker 100. The upper section 1a is equipped with a magnetron and a waveguide 4 built into a microwave generator 3, in addition to an elevator (not shown). Microwaves from the magnetron are guided to the upper portion of the top plate 8 via the waveguide 4. While being stirred by a microwave stirring motor 5 located above the top plate 8, which rotates a microwave diffusion propeller 6, the microwaves are irradiated into the liquid tank 7 through an opening in the top plate 8 (which may be covered with a non-conductive thin plate such as a glass plate). The microwave irradiation output and duration can be controlled depending on the type and amount of food to be heated. Furthermore, any device capable of generating desired microwaves, other than a magnetron, can also be used as the microwave generator 3.

[0014] The lifting device (not shown) has a hanging rod 10 that engages with the food basket 12. Note that the lifting device itself may have any structure, and therefore a detailed description thereof will be omitted. In the present embodiment, there are four hanging rods 10 for suspending the food basket 12 from the four corners. The hanging rods 10 move up and down within the liquid cooking appliance 100 by a lift motor of the lifting device, and as a result, the food basket 12 suspended from the lower end of the hanging rods 10 moves up and down between the food basket loading / unloading space in the middle section 1b and the liquid tank 7 in the lower section 1c (hereinafter, the food basket loading / unloading space and the liquid tank 7 will be collectively referred to as the "cooking unit space").

[0015] In this embodiment, each hanging rod 10 is composed of two parts: a non-conductive portion 10a and a metal portion 10b. These parts are connected in any manner to form a single rod-like structure. As shown in FIG. 2 , each hanging rod 10 moves up and down through a hole 9 provided in a top plate 8. The top plate 8 is a metal plate fixed to the ceiling of the food basket loading / unloading space located in the middle section 1b. The top plate 8 and the doors of the middle section 1b and the lower section 1c form an enclosed space for the cooking unit. In other words, the top plate 8 forms the upper surface of the food basket loading / unloading space in the middle section 1b and also functions as a lid to prevent microwaves generated by the microwave oscillator 3 in the upper section 1a from escaping from the cooking unit space in the middle section 1b and the lower section 1c.

[0016] In this embodiment, the liquid tank 7 housed in the lower section 1c is a non-cylindrical tank composed of an upper tank 7a and a lower tank 7b, but it may also be a cylindrical tank. In this embodiment, both the upper tank 7a and the lower tank 7b are made of conductive stainless steel and have a substantially rectangular cylindrical shape, with the lower tank 7b having a smaller horizontal cross-sectional area than the upper tank 7a. The bottom of the upper tank 7a has a horizontal bottom that connects to the sidewall and is connected to the vertical sidewall of the lower tank 7b. Cooking oil is stored from the bottom of the lower tank 7b to a predetermined height (position A shown in Figure 4) of the upper tank 7a. The size of the food basket 12 for placing heated food materials, such as frozen foods, is appropriately determined according to the shape of the upper tank 7a. The bottom of the lower tank 7b has a drain port 14 for discharging cooking oil from the oil tank 7 to the outside as waste oil. As shown in Figure 4, the bottom of the lower tank 7b has a sloped surface to facilitate collection of waste oil that accumulates at the bottom, but it may also be horizontal.

[0017] Figure 4 shows the position of the hanging rod 10 when the food basket 12 is raised or lowered. Figure 4(A) shows the state before or after cooking (i.e., while microwaves are not being generated). The lift motor of the lifting device pulls the hanging rod 10 upward so that the food basket 12 is in the food basket loading / unloading space in the middle section 1b. Figure 4(B) shows the state during cooking (i.e., while microwaves are being generated). The hanging rod 10 is pulled downward so that the food basket 12 is immersed in the liquid bath 7 in the lower section 1c. A in the figure indicates the position of the liquid surface.

[0018] It is important to note here that, in the case of the position of the food basket 12 during cooking (i.e., while microwaves are being generated) shown in FIG. 4(B), the hanging rod 10 is composed of a metal portion and a non-conductive portion, as described above, but the position is controlled so that the non-conductive portion 10a of the hanging rod 10 penetrates the hole 9 in the top plate 8. The metal portion 10b in FIG. 4(B) is below the oil tank 7, and the non-conductive portion 10a penetrates the hole 9. During cooking, if the non-conductive portion 10a of the hanging rod 10 passes through the hole 9 in the top plate 8, even if microwaves are being radiated, no discharge occurs due to the formation of an incomplete contact between the metal parts, thereby preventing sparks. Outside of cooking (i.e., while microwaves are not being generated), the metal portion 10b may penetrate the hole 9 in the top plate 8, or the non-conductive portion 10a may penetrate the hole 9, as in cooking. Figure 4(A) shows the electromagnetically shielded guide pipe 11 as seen through, showing that the metal portion 10b penetrates through the hole 9 in the top plate 8, with the connecting portion 10c and part of the non-conductive portion 10a existing inside the electromagnetically shielded guide pipe 11.

[0019] An electromagnetically shielding guide pipe 11 made of metal or the like, installed above the hole 9 in the top plate 8, prevents lateral shaking when the hanging rod 10 lifts up and down a food basket 12 containing food to be cooked. The hanging rod 10 passes through the electromagnetically shielding guide pipe 11 above the hole 9. As described above, the hanging rod 10 of this embodiment has a structure in which the non-conductive portion 10a and the metal portion 10b are connected and integrated by the connecting portion 10c. The non-conductive portion 10a and the metal portion 10b can be separated at the connecting portion 10c. Therefore, since the connecting portion 10c is particularly susceptible to load, the electromagnetically shielding guide pipe 11 guides the connecting portion 10c and the entire hanging rod 10. Furthermore, when ceramic is used for the non-conductive portion 10a, the electromagnetically shielding guide pipe 11 serves to protect the ceramic, which is vulnerable to impacts. Therefore, it is desirable to adjust the length and the amount of lifting of the suspension rod 10 and the electromagnetically shielding guide pipe 11 so that this connecting portion 10c enters inside the electromagnetically shielding guide pipe 11. In other embodiments, the suspension rod 10 may be configured as a single lift support member with an inseparable structure in which the non-conductive portion 10a and the metal portion 10b are arranged, and it is also possible that no electromagnetically shielding guide pipe is provided.

[0020] In addition, if the microwave frequency used in the fryer 100 of this embodiment is, for example, 2.45 GHz, the half-wavelength is approximately 6 cm. Therefore, the diameter of the hole 9 in the top plate 8 through which the hanging rod 10 passes can be set to 6 cm or less to prevent microwaves from passing through the hole 9. While in principle, microwaves will not pass through a hole with a diameter of 6 cm or less, in reality, the range of microwave frequencies is wide, and some microwaves will pass through a hole with a set diameter. Therefore, the electromagnetically shielding guide pipe 11 not only functions to prevent lateral shaking when the hanging rod 10 is lifted up and down as described above, but also functions to prevent microwaves within the cooking unit from leaking to the outside through the hole 9 in the top plate 8. From the perspective of preventing microwave leakage, the length of the electromagnetically shielding guide pipe 11 may be any length as long as it is long enough to sufficiently attenuate microwaves.

[0021] In the first embodiment described above, the material of the hanging rod 10 is changed to a non-conductive material such as ceramic instead of metal to prevent discharge, but in the fryer of the second embodiment, the inner walls of the holes 9 in the top plate 8 are covered with a non-conductive material. An example of using a non-conductive material such as ceramic is shown in Figure 5.

[0022] FIG. 5 is a schematic cross-sectional view of the interior wall surface of the hole 9 in the top plate 8 covered with ceramic 15. The ceramic 15 can be attached to the interior wall surface using any adhesive or the like. Therefore, the top plate 8 only needs to be provided with a hole with a diameter that includes the thickness of the ceramic 15. However, it goes without saying that the thickness of the ceramic 15 can be arbitrarily chosen. This prevents discharge even if the suspension rod 10 is made entirely of metal or if the metal portion 10b of the hole 9 passes through during microwave oscillation. Even when discharge is avoided by covering the interior wall surface of the hole 9 with a non-conductive material such as ceramic 15, it is desirable to reinforce the suspension rod 10 with the electromagnetic shielding guide pipe 11 described above.

[0023] In the case of the hole 9 shown in Figure 5, the inner wall surface is made of a non-conductive material such as ceramic, so the hanging rod 10 passing through the hole 9 may be made entirely of metal (even when the inner wall surface is covered with ceramic or the like, the entire hanging rod 10 may be made of only the non-conductive portion 10a). Furthermore, dividing the hanging rod 10 makes maintenance easier. Even when the inner wall surface is covered with ceramic or the like, it is useful to make the hanging rod 10 multiple (for example, divided into two) rather than a single piece. As in the first embodiment, the hanging rod 10 may be made of two parts, the non-conductive portion 10a and the metal portion 10b, or may be further separated by a connecting portion 10c.

[0024] Although the present invention relates to a liquid heating cooker that uses microwaves as a heating source, an electromagnetic induction coil for electromagnetic induction heating may be disposed as an additional heating source, surrounding the bottom or side of the liquid tank 7. In this case, heating by microwave energy efficiently irradiated from the microwave oscillator and heating by convection of high-temperature cooking oil heated by electromagnetic induction make it possible to achieve heating and cooking in a short time.

[0025] 3 Microwave oscillator 7 Liquid tank 8 Top plate 9 Hole 10 Hanging rod 10a Non-conductive part of hanging rod 10b Metal part of hanging rod 10c Connection part of hanging rod 11 Electromagnetic shielding guide pipe 12 Food basket 100 Fryer

Claims

1. A liquid heating cooker comprising: a cooking unit including a liquid tank for storing liquid for heating food, wherein a space is formed above the liquid tank for loading and unloading a food basket in which food is placed; a microwave radiating unit that radiates microwaves to the cooking unit; a lift mechanism that raises and lowers a food storage unit in which food is placed; and a metal top plate provided on the top of the cooking unit to prevent the microwaves from being exposed to the outside, wherein the lift mechanism includes a hanging member that engages with the food storage unit, and the food storage unit is raised and lowered by the up and down movement of the hanging member that passes through a hole in the top plate, at least a portion of the hanging member includes a non-conductive portion, and the liquid heating cooker is position-controlled so that the non-conductive portion of the hanging member is present at the position of the hole in the top plate during the period in which microwaves are irradiated by the microwave radiating unit.

2. A liquid heating cooker comprising: a cooking unit including a liquid tank for storing liquid for heating food; a microwave radiating section for radiating microwaves to said cooking unit; a lift mechanism for raising and lowering a food storage section on which food is placed; and a metal top plate provided on the top of said cooking unit to prevent said microwaves from being exposed to the outside, wherein said lift mechanism includes a hanging member that engages with said food storage section, and said food storage section is raised and lowered by the up and down movement of said hanging member that passes through a hole provided in said top plate, and the inner wall of the through hole in said top plate is covered with a non-conductive material.

3. A liquid heating cooker according to claim 1 or 2, further comprising a hollow electromagnetically shielded guide pipe above the top plate through which the hanging member passes.

4. A liquid heating cooker according to claim 1, wherein the hanging member has a non-conductive portion and a conductive portion that are integrated at a connecting portion and can be separated at the connecting portion.

5. The liquid heating cooker according to claim 2, wherein the hanging member is made up of a plurality of detachable sections.

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