Electric heater

Abstract

To provide an electric heater that complies with seismic class S and prevents the sheathed heater from detaching from the casing or the insulator from being damaged even in the event of a natural disaster. [Solution] The electric heater 1 is installed inside an air conditioning duct and comprises a casing 10 and a plurality of straight-type sheathed heaters 20, one end 21 and the other end 22 of which penetrate the casing 10 and are mounted inside the casing 10. Here, each end 21 is fixed by a first insulator mounted between the end 21 and the casing 10 so as to sandwich the casing 10, a bush mounted on the inside of the first insulator, and a locking nut mounted on the outside of the first insulator. Each other end 22 is fixed by a second insulator mounted between the other end 22 and the casing 10, and a retaining ring mounted on the outside of the second insulator.

Description

Technical Field

[0001] The present invention relates to an electric heater installed in an air conditioning duct.

Background Art

[0002] Conventionally, electric heaters installed in air conditioning ducts are known. For example, the electric heater shown in Non-Patent Document 1 includes a straight-type sheathed heater, and in addition to general building air conditioning, it is also widely used for preheating and reheating air in clean rooms, environmental tests, animal experiments, etc. for special air conditioning. On the other hand, as shown in Non-Patent Document 2, there is also a U-shaped sheathed heater.

[0003] Here, FIG. 6(A) is a diagram for explaining a conventional mounting structure of a straight-type sheathed heater. The straight-type sheathed heater 20 as shown in Non-Patent Document 1 has both ends supported by heater support bushes 31 on a casing 10 with a plate thickness of 1.5 mm.

[0004] On the other hand, FIG. 6(B) is a diagram for explaining a conventional mounting structure of a U-shaped sheathed heater. The U-shaped sheathed heater 20U as shown in Non-Patent Document 2 has both ends fixed to a casing 10 with a plate thickness of 3 mm by insulators 41, bushes 42, and bush nuts 43. The reason why the sheathed heater 20U is U-shaped is that since the sheathed heater is a heating element in which a nichrome wire is covered with a metal sheath (sheath), it expands and contracts when generating heat during operation. However, by making the sheathed heater U-shaped, the curved portion 21U not supported by the bush nut 43 etc., expands and contracts, so that damage to parts and deterioration of quality can be prevented.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] However, the conventional electric heater configuration shown in Figures 6(A) and (B) cannot withstand natural disasters, such as strong earthquakes (shaking). Specifically, in the event of a strong earthquake, in the conventional electric heater configuration shown in Figure 6(A), the sheathed heater 20 is only supported by the heater support bush 31, so the sheathed heater 20 will detach from the casing 10. On the other hand, in the conventional electric heater configuration shown in Figure 6(B), both ends of the sheathed heater 20U are fixed by bush nuts 43, etc., so it can withstand earthquakes up to seismic class A, but if a strong tremor occurs, the insulating insulators 41 at both ends of the fixed sheathed heater 20U may be damaged.

[0007] Furthermore, the Building Equipment Seismic Design and Construction Guidelines classify seismic resistance into three levels (Seismic Class S, Seismic Class A, and Seismic Class B) depending on the importance of the equipment and the installation environment. In facilities requiring the highest level of seismic resistance, such as nuclear power plants, disaster relief hospitals, fire departments, disaster prevention centers, important communication stations, and national research institutions, electric heaters compliant with Seismic Class S are required.

[0008] Therefore, the present invention aims to provide a safe electric heater that complies with seismic class S and prevents problems such as the sheath heater detaching from the casing or the insulator being damaged even in the event of a natural disaster. [Means for solving the problem]

[0009] The present invention relates to an electric heater installed in an air conditioning duct, comprising a casing and a plurality of straight-type sheath heaters, one end and the other end of which penetrate the casing and are mounted inside the casing. Each of the plurality of sheath heaters is fixed at one end with a first insulator mounted between the end and the casing so as to sandwich the casing, a bush mounted inside the first insulator, and a locking nut mounted outside the first insulator. Each of the plurality of sheath heaters is fixed at a second insulator mounted between the other end and the casing, and a retaining ring mounted outside the second insulator.

[0010] As a result, one end of the sheathed heater is securely fixed to the casing by a locking nut or the like, so that it can withstand strong earthquakes (shaking) even if the other end is loosely fixed by a second insulator or the like. Also, because the other end of the sheathed heater is loosely fixed by a second insulator or the like, even if the sheathed heater generates heat and expands and contracts during operation, the other end of the sheathed heater can absorb some of that expansion and contraction, preventing problems such as deformation of the sheathed heater or damage to the insulator.

[0011] In this configuration, it is desirable that one end of each sheathed heater is connected to a power supply, the other ends of each sheathed heater are connected to heaters, and these other ends are connected to each other by a junction board.

[0012] Furthermore, it is desirable that the first insulator consists of multiple parts and is mounted so as to sandwich the casing from both the inside and the outside.

[0013] Furthermore, the casing thickness should preferably be 5 mm or more. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a safe electric heater that complies with seismic class S and does not experience problems such as the sheath heater detaching from the casing or the insulator being damaged even in the event of a natural disaster. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic perspective view of an electric heater according to an embodiment of the present invention. [Figure 2] Figure 1 is a schematic diagram showing the mounting structure of the sheathed heater of the electric heater, where (A) is a schematic diagram showing the mounting structure of one end of the sheathed heater, and (B) is a schematic diagram showing the mounting structure of the other end of the sheathed heater. [Figure 3] Figure 2(A) is a schematic diagram showing the mounting structure of one end of the sheathed heater, where (A) is a schematic diagram showing the mounting structure as seen from inside the casing, and (B) is a schematic diagram showing the mounting structure as seen from outside the casing. [Figure 4] This diagram illustrates how one end of multiple sheathed heaters is connected to an electrical wire. [Figure 5] Figure 2(B) is a schematic diagram showing the mounting structure of the other end of the sheathed heater, where (A) is a schematic diagram showing the mounting structure as seen from inside the casing, and (B) is a schematic diagram showing the mounting structure as seen from outside the casing. [Figure 6] (A) is a diagram illustrating a conventional mounting structure for a straight-type sheathed heater, and (B) is a diagram illustrating a conventional mounting structure for a U-shaped sheathed heater. [Modes for carrying out the invention]

[0016] The embodiments of the present invention will be described in detail below. However, the description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to the following contents as long as it does not deviate from the gist thereof. Also, for configurations having the same function, the same reference numerals are given in the drawings, and detailed descriptions thereof are omitted.

[0017] [Electric heater 1] FIG. 1 is a schematic perspective view of an electric heater according to an embodiment of the present invention. The electric heater 1 includes a casing 10 and a plurality of straight - type sheathed heaters 20 having one end 21 and the other end 22 penetrating through the casing 10 and being attached inside the casing 10.

[0018] The casing 10 of the present embodiment has a thickness of 5 mm and is rectangular in a front view with openings at the front and the back. The casing 10 is made of a stainless - steel plate. In this description, for the sake of convenience, the upper part of the casing 10 shown in FIG. 1 is the power - connection side (the side where one end 21 of the sheathed heater 20 is connected to a power source (not shown)), and the lower part is the heater - connection side (the side where the other end 22 of the sheathed heater 20 is connected to a heater (not shown)).

[0019] Also, in the present embodiment, a box 11 is attached to the top plate on the power - connection side of the casing 10. Although partially omitted in FIG. 1, the box 11 is for covering and protecting one end 21 of the sheathed heater 20 protruding through the casing 10.

[0020] Also, the number and arrangement of the plurality of sheathed heaters 20 attached inside the casing 10 can be arbitrarily changed in design. Hereinafter, the structure in which the sheathed heater 20 is attached to the casing 10 will be described. Since the attachment structures of the plurality of sheathed heaters 20 are all the same, one of the plurality of sheathed heaters 20 will be taken as an example for description.

[0021] [Attachment structure of one end 21 of the sheathed heater 20] Figure 2(A) is a schematic diagram showing the mounting structure of one end 21 of the sheathed heater 20. Figure 3 is a schematic diagram showing the mounting structure of one end of the sheathed heater shown in Figure 2(A), where (A) is a schematic diagram showing the mounting structure as seen from inside the casing, and (B) is a schematic diagram showing the mounting structure as seen from outside the casing. The mounting structure of one end 21 of the sheathed heater 20 will be explained with reference to these drawings.

[0022] One end 21 of the sheathed heater 20 is mounted by passing through a hole 10h provided in the casing 10. The one end 21 of the sheathed heater 20 is also fixed by a first insulator 211 mounted between the one end 21 and the casing 10 so as to sandwich the casing 10, a bush 212 mounted on the inside of the first insulator 211, and a locking nut 213 mounted on the outside of the first insulator 211.

[0023] The first insulator 211 is made of, for example, ceramic. The first insulator 211 consists of multiple parts (in this embodiment, an inner part (see Figure 3(A)) and an outer part (see Figure 3(B))) and is attached to sandwich the casing 10 from the inside and outside, respectively.

[0024] The anti-loosening nut 213 is an anti-loosening nut that, for example, eccentrically fits the convex part of the lower nut with the concave part of the upper nut. One example is the Hardlock® nut manufactured by Hardlock Industries Co., Ltd.

[0025] In this configuration, one end 21 of the sheathed heater 20 is securely fixed to the casing 10 without loosening, via a bush 212 and a locking nut 213, through a first insulating insulator 211 installed between the end 21 and the casing 10 so as to sandwich the casing 10.

[0026] Furthermore, one end 21 of the sheathed heater 20 is provided with a connection part 214 to which an electric wire is connected (see Figure 2(A)). On the power supply connection side of the casing 10, one end 21 of each of the multiple sheathed heaters 10 is connected to an electric wire 215 (see Figure 4).

[0027] [Mounting structure of the other end 22 of the sheathed heater 20] Figure 2(B) is a schematic diagram showing the mounting structure of the other end 22 of the sheathed heater 20. The other end 22 of the sheathed heater 20 is fixed by a second insulator 221 installed between the other end 22 and the casing 10, and a retaining ring 222 installed on the outside of the second insulator 221.

[0028] Similar to the first insulator 211, the second insulator 221 is also made of, for example, ceramic. The second insulator 221 is mounted on the outside of the casing 10.

[0029] In this embodiment, the retaining ring 222 is a C-type retaining ring.

[0030] Thus, unlike the mounting structure of one end 21, the other end 22 of the sheathed heater 20 is loosely fixed by a second insulator 221 and a retaining ring 222, which are attached from the outside of the casing 10.

[0031] Furthermore, the other end 22 of the sheathed heater 20 is provided with a connection section 223 connected by a connection plate (metal plate) (see Figure 2(B)). On the heater connection side of the casing 10, the other ends 22 of the multiple sheathed heaters 10 are each connected by a connection plate 224 (see Figure 5(B)).

[0032] [Mounting structure of the 20mm sheathed heater] In this embodiment, the electric heater 1 has one end 21 and the other end 22 of a plurality of sheathed heaters 20 attached to the casing 10 by the mounting structure described above. Here, one end 21 of the sheathed heater 20 is firmly fixed to the casing 10 without loosening by a locking nut 213 or the like, so even if the other end 22 is loosely fixed by a second insulator 221 or the like, it can withstand strong earthquakes (shaking). In other words, even if a strong earthquake occurs, the sheathed heater 20 will not come off the casing 10. Therefore, the electric heater 1 of this embodiment can also meet seismic class S.

[0033] Furthermore, since the other end 22 of the sheathed heater 20 is loosely fixed by the second insulator 221, etc., even if the sheathed heater 20 generates heat and expands and contracts during operation, the other end of the sheathed heater 20 can absorb some of that expansion and contraction. Therefore, the electric heater 1 of this embodiment does not suffer from problems such as deformation of the sheathed heater or damage to the insulator. In other words, if you firmly fix both ends of a straight-type sheathed heater, the heater will deform because it has nowhere to go when it expands due to the heat generated during operation.

[0034] In this embodiment, the electric heater 1 has the other ends 22 of the sheathed heater 20 connected by a metal plate, the connection plate 224, so there is no problem even if the sheathed heater 20 moves slightly when the electric heater 1 is operating. However, on the power supply connection side, only the wire 215 is connected to one end 21 of the sheathed heater 20. Therefore, if the sheathed heater 20 moves, the wire 215 will also move, which may cause malfunctions such as electrical leakage. For this reason, in this embodiment, one end 21 of the sheathed heater 20 is securely fixed to the casing 10 with a locking nut 213 or the like.

[0035] Furthermore, in this embodiment, the electric heater 1 has a first insulating insulator 211 at one end 21 of the sheathed heater 20 made up of multiple parts, and is attached by sandwiching the casing 10 from the inside and outside, respectively. Therefore, even if the casing 10 is thick, the sheathed heater 20 can be firmly fixed to the casing 10. Also, in this embodiment, the plate thickness of the casing 10 is 5 mm, but it may be 6 mm, 7 mm, or more. [Industrial applicability]

[0036] This invention provides a safe electric heater that complies with seismic class S and prevents problems such as the sheathed heater detaching from the casing or the insulator being damaged even in the event of a natural disaster. Therefore, it can be used in facilities requiring high seismic resistance, such as nuclear power plants, and is industrially useful. [Explanation of Symbols]

[0037] 1 Electric heater 10 Casing 10h hole 11 boxes 20 Sheathed Heater 20U Sheathed Heater (U-shaped) 21U U-shaped sheathed heater curved section 21 One end of a sheathed heater 211 First insulator 212 Bush 213 Locking nut 214 Connection part 215 Electric wire 22 The other end of the sheathed heater 221 Second insulator 222 Retaining ring 223 Connection section 224 Connection board 31 Heater support bush 41 Insulator 42 Bush 43 Bushing nuts

Claims

1. An electric heater installed inside an air conditioning duct, Casing and, It comprises a plurality of straight-type sheathed heaters, one end and the other end of which penetrate the casing and are mounted inside the casing, Each of the plurality of sheathed heaters is fixed at one end by a first insulator mounted between the end and the casing, sandwiching the casing, a bush mounted inside the first insulator, and a locking nut mounted outside the first insulator. Each of the plurality of sheathed heaters is fixed by a second insulator attached between the other end and the casing, and a retaining ring attached to the outside of the second insulator. One end of each of the plurality of sheathed heaters is connected to a power source. An electric heater in which the other ends of the plurality of sheathed heaters are connected to a heater, and the other ends of the multiple sheathed heaters are connected to each other by a connecting plate.

2. The electric heater according to claim 1, wherein the first insulator consists of a plurality of parts and is attached to the casing so as to sandwich it from the inside and the outside, respectively.

3. The electric heater according to claim 1 or 2, wherein the thickness of the casing is 5 mm or more.

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