Square duct, elbow square duct and method for suspending square duct

Abstract

To provide a square duct capable of eliminating welding even when it is made of a thick plate.SOLUTION: A square duct comprises a first half duct 2 and a second half duct 3 each having a substantially U-shaped cross section, and angle members 4, 5 extending along both free edges of the cross sections of the first half duct 2 and the second half duct 3 and provided with shared bolt holes 43, 53. The first half duct 2 and the second half duct 3 are arranged facing each other so that the cross section is a substantially square cylinder, and the angle members 4, 5 are bolted together via the shared bolt holes 43, 53, thereby assembling the first half duct 2 and the second half duct 3 into a cylindrical shape.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a thick plate rectangular duct, an elbow rectangular duct, and a method for suspending the rectangular duct. [Background technology]

[0002] Air conditioning ducts are generally made of steel material with a thickness of 1.2 mm or less, and in the case of rectangular ducts with a roughly rectangular cross section, the rectangular duct is constructed by connecting four side panels with seam joints (see, for example, Non-Patent Document 1). On the other hand, rectangular ducts installed in extra-high temperature rooms such as electrical rooms and boiler rooms have traditionally been made of thicker steel material such as 1.6 mm in order to improve fire resistance, strength, rigidity, etc.

[0003] However, when manufacturing rectangular ducts using such thick steel, it is difficult to join the side panels together, so it is necessary to join adjacent side panels together by welding, and then paint the outer and inner surfaces of the welded parts to protect them from corrosion and improve their appearance. [Prior art documents] [Patent documents]

[0004] [Non-Patent Document 1] "Standard Duct Text" edited and published by the National Duct Industry Association, April 2015, p.36 Summary of the Invention [Problem to be solved by the invention]

[0005] However, welding thick side plates together requires a lot of time and effort, and painting the outer and inner surfaces of the welded parts also requires a lot of time and effort. Furthermore, the welding process generates smoke and dust, which makes the working environment worse and places a heavy burden on the workers.

[0006] In addition, conventionally, four side panels were welded together at the manufacturing plant to form a cylindrical rectangular duct, which was then transported by truck to the construction site or temporarily stored there. This not only required a large area and volume for loading onto the truck and temporary storage at the construction site, but also led to increased transportation and storage costs. Furthermore, because the panels are thick, they are heavier than general ducts with a panel thickness of 1.2 mm or less (about twice as heavy for a duct with the same external dimensions), which placed a heavy burden on workers when transporting or setting them up (hanging, etc.).

[0007] Meanwhile, in recent years, the construction industry has become increasingly conscious of safety, including the working environment, and energy conservation, and there is a demand for technologies that can address these issues.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a square duct, an elbow square duct, and a method for suspending the square duct, which can eliminate the need for welding even when using thick plates. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the invention described in claim 1 is a rectangular duct comprising a first half duct having an approximately U-shaped cross section, a second half duct having an approximately U-shaped cross section, a first connecting portion extending along both free edges of the cross section of the first half duct and having a bolt insertion hole, and a second connecting portion extending along both free edges of the cross section of the second half duct and having a bolt insertion hole, wherein the first half duct and the second half duct are arranged facing each other so that the cross section is approximately square and cylindrical, and the first connecting portion and the second connecting portion are bolted together through the bolt insertion holes, thereby assembling the first half duct and the second half duct into a cylindrical shape.

[0010] The invention described in claim 2 is characterized in that, in the square duct described in claim 1, the first half duct and the second half duct have the same shape and dimensions, and the first connecting portion and the second connecting portion have the same shape and dimensions.

[0011] The invention described in claim 3 is characterized in that, in the square duct described in claim 1, the first connecting portion and the second connecting portion are made of angle iron having a substantially L-shaped cross section and a vertical portion and a horizontal portion, the vertical portion of the first connecting portion is attached along the both free edges of the first half duct, and the vertical portion of the second connecting portion is attached along the both free edges of the second half duct.

[0012] The invention described in claim 4 is characterized in that, in the rectangular duct described in claim 3, when the first half duct and the second half duct are assembled into a cylindrical shape, an axis extends in a straight line, and when the axis is arranged extending approximately horizontally, the horizontal portions of the first connecting portion and the second connecting portion extend approximately horizontally.

[0013] The invention described in claim 5 is characterized in that, in the rectangular duct described in claim 4, hanging bolt holes for inserting hanging bolts are formed in the horizontal portions of the first connecting portion and the second connecting portion.

[0014] The invention described in claim 6 is characterized in that, in the rectangular duct described in claim 5, the hanging bolt hole is a long hole extending in the longitudinal direction of the first connecting portion and the second connecting portion.

[0015] The invention recited in claim 7 is the rectangular duct recited in claim 1, characterized in that an airtight material is provided between the first connecting portion and the second connecting portion.

[0016] The invention described in claim 8 is an elbow angular duct characterized in that a plurality of the angular ducts described in claim 1 are connected at their open ends while changing their axes.

[0017] The invention described in claim 9 is a method for hanging a rectangular duct, characterized in that the rectangular duct is hung from a structure by inserting a lower end of a hanging bolt, the upper end of which is fixed to a structure, into the hanging bolt hole of the rectangular duct described in claim 5 or claim 6. Effect of the Invention

[0018] According to the invention described in claim 1, a rectangular duct can be formed and manufactured by assembling the first and second half ducts, each having a substantially U-shaped cross section, into a cylindrical shape simply by fastening the first and second connecting parts with bolts. In other words, even if the first and second half ducts are made of thick plates and cannot be joined by seam joints, a rectangular duct can be formed simply by fastening them with bolts, making welding and painting of welded parts unnecessary.

[0019] As a result, it is possible to significantly reduce the labor and time required to form the rectangular duct, and moreover, by eliminating welding and painting work, it is possible to improve the working environment and significantly reduce the burden on workers. Also, since the first and second half ducts can be easily assembled, i.e., bolted together, at the construction site, the first and second half ducts can be disassembled and transported to the construction site by truck or temporarily stored at the construction site. This makes it possible to reduce the loading volume of the truck and the temporary storage volume, thereby reducing transportation and storage costs.

[0020] Furthermore, even if the first and second half ducts are made of thick plates, the burden on the worker can be reduced by carrying the first and second half ducts separately. This makes it possible to improve safety, including the work environment, and energy conservation.

[0021] According to the invention described in claim 2, the first half duct and the second half duct have the same shape and dimensions, and the first connecting portion and the second connecting portion also have the same shape and dimensions, which makes it possible to reduce manufacturing costs and facilitate handling.

[0022] According to the invention described in claim 3, the first and second connection parts are made of angle bars and are attached to the first and second half ducts, so that the rectangular duct can be easily formed and manufactured. In other words, if the first and second connection parts are integrally formed with the first and second half ducts, cutting the plate (material cutting) becomes complicated and the yield rate decreases. In contrast, since it is only necessary to attach the angle bars to the first and second half ducts, the rectangular duct can be easily formed and manufactured at low cost.

[0023] According to the invention described in claim 4, when the linearly extending rectangular duct is arranged so as to extend approximately horizontally, the horizontal portion of the angle bar also extends approximately horizontally, so that the rectangular duct can be arranged easily and safely by utilizing this horizontal portion.

[0024] According to the invention described in claim 5, since a hanging bolt hole is formed in the horizontal part of the angle bar, it is possible to easily and safely install (hang) the rectangular duct by inserting a hanging bolt into this hanging bolt hole. Moreover, since the hanging bolt only needs to reach the angle bar that is the connection between the first half duct and the second half duct, the length of the hanging bolt can be shorter than in the past, and the conventional support steel (steel that supports the bottom of the rectangular duct) is also unnecessary. As a result, it is possible to reduce the cost required for installing the rectangular duct.

[0025] According to the invention recited in claim 6, since the suspension bolt holes are elongated holes extending in the longitudinal direction of the angle material (rectangular duct), it becomes possible to easily and appropriately adjust the installation position of the rectangular duct.

[0026] According to the invention recited in claim 7, since an airtight material is provided between the first connecting portion and the second connecting portion, it is possible to ensure the airtightness of the rectangular duct.

[0027] According to the invention recited in claim 8, an elbow angular duct is formed by connecting the open ends of a plurality of the angular ducts recited in claim 1 while changing their axes. That is, even with an elbow angular duct with a bent axis, the same effect as that of claim 1 can be obtained, and it is possible to improve safety, including the working environment, and energy saving.

[0028] According to the invention described in claim 9, by fixing the upper end of the hanging bolt to the structure and inserting and fixing the lower end of the hanging bolt into the hanging bolt hole of the angle bar of the rectangular duct, it is possible to easily and safely hang the rectangular duct from the structure. [Brief description of the drawings]

[0029] [Figure 1] 1 is a perspective view showing a rectangular duct according to a first embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] 2A is a plan view showing the unfolded state (cutting the plate) of the half duct of the rectangular duct in FIG. 1, and FIG. 2B is a plan view showing the unfolded state (cutting the plate) when the half duct and the connecting part are formed integrally. [Figure 4] FIG. 4 is a schematic plan view showing an elbow rectangular duct according to a second embodiment of the present invention. [Diagram 5] FIG. 5 is a schematic perspective view showing a first rectangular duct of the elbow rectangular duct of FIG. 4. [Figure 6] FIG. 1 is a schematic perspective view showing a conventional rectangular duct in a suspended state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, the present invention will be described based on the illustrated embodiment.

[0031] (Embodiment 1) Fig. 1 is a perspective view showing a rectangular duct 1 according to this embodiment, and Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. This rectangular duct 1 is a cylindrical duct with a roughly rectangular cross section formed from thick steel material / plate, and in this embodiment, a straight duct with a straight axis / center axis will be described. Here, a thick plate means a thickness that makes it difficult to form a seam joint, and for example, a plate thickness of 1.6 mm is considered a thick plate.

[0032] The rectangular duct 1 mainly comprises a first half duct 2, a second half duct 3, a first angle member (first connection portion) 4, and a second angle member (second connection portion) 5.

[0033] The first semi-duct 2 is a member having a substantially U-shaped cross section, that is, a member obtained by bending a square plate material into a substantially U-shape. In other words, it is a member obtained by splitting a cylindrical body having a substantially square cross section in half in the axial direction, and has a main surface portion 21 corresponding to the vertical portion of the U-shape, and two side portions 22 corresponding to the two horizontal portions of the U-shape. In addition, flange portions 23 are formed at both ends (both opening ends in the axial direction) of the first semi-duct 2 by bending them outward and raising them up.

[0034] The second semi-duct 3 has the same shape and dimensions as the first semi-duct 2, so a detailed description will be omitted, but what corresponds to the main surface portion 21, side surface portion 22 and flange portion 23 of the first semi-duct 2 are the main surface portion 31, side surface portion 32 and flange portion 33, respectively. Here, the corner piece 7 is adapted to be attached between each of the flange portions 23, 33.

[0035] The first angle member 4 is disposed extending along both free edges of the cross section of the first half duct 2, and is a member provided with a common bolt hole (bolt insertion hole, hanging bolt hole) 43. That is, it is an angle iron material having a substantially L-shaped cross section and a vertical portion 41 and a horizontal portion 42, and the vertical portion 41 is attached by spot welding (at the location indicated by the symbol 4a) along both free edges (edges of both side portions 22) of the first half duct 2. Here, it is attached so that the edges of the side portions 22 and the bottom surface of the horizontal portion 42 (the surface on the side opposite to the vertical portion 41) are substantially flush with each other.

[0036] Furthermore, the common bolt holes 43 are provided for inserting fastening bolts 45 and hanging bolts 101, which will be described later, and are elongated holes extending in the longitudinal direction of the first angle iron 4, with a plurality of them (continuously) formed at prescribed intervals in the horizontal portion 42 along the longitudinal direction of the first angle iron 4. In other words, the common bolt holes 43 function as both bolt insertion holes and hanging bolt holes, and the fastening bolts 45 and hanging bolts 101 can be inserted into any / desired common bolt hole 43.

[0037] The second angle member 5 is a member that is disposed extending along both free edges of the cross section of the second half duct 3 and has a common bolt hole 53, and is disposed in the second half duct 3 in the same manner with the same shape and dimensions as the first angle member 4, so a detailed description will be omitted. Here, the vertical portion 51, horizontal portion 52 and common bolt hole 53 correspond to the vertical portion 41, horizontal portion 42 and common bolt hole 43 of the first angle member 4, respectively. The common bolt hole 53 of the second angle member 5 is formed in the same position (so as to overlap) as the common bolt hole 43 of the first angle member 4.

[0038] In this way, the first half duct 2 and the first angle iron 4, and the second half duct 3 and the second angle iron 5 are arranged in the same manner with the same shape and dimensions. Here, the state in which the first angle iron 4 is attached to the first half duct 2 is called the first half-angle duct 20, and the state in which the second angle iron 5 is attached to the second half duct 3 is called the second half-angle duct 30, and the first half-angle duct 20 and the half-angle duct 30 have the same shape and dimensions.

[0039] The first half duct 2 and the second half duct 3 are then arranged facing each other so that the cross section is a roughly square cylinder, and fastening bolts 45 are inserted into the desired common bolt holes 43, 53 of the angle members 4, 5, and fastening nuts 46 are screwed (bolted) onto the fastening bolts 45, thereby assembling the first half duct 2 and the second half duct 3 into a cylindrical shape to form the rectangular duct 1. In other words, the rectangular duct 1 is formed simply by bolting together the first half-square duct 20 and the half-square duct 30, which are two separate bodies.

[0040] Here, an airtight sheet (airtight material) 47 is provided between the horizontal portion 42 of the first angle iron 4 and the horizontal portion 52 of the second angle iron 5 to make the space between the angle irons 4, 5, i.e., between the semi-ducts 2, 3, airtight.

[0041] In this way, when the first half duct 2 and the second half duct 3 are assembled into a cylindrical shape to form the rectangular duct 1, the axis of the rectangular duct 1 extends in a straight line. That is, the cross section is a cylindrical shape with a substantially rectangular shape, and the axis (center of the cross section) extends in a straight line. And, when the axis extends substantially horizontally, that is, when the rectangular duct 1 is laid on its side so that the main surface portions 21, 31 of the half ducts 2, 3 extend substantially horizontally, the horizontal portions 42, 52 of the angle members 4, 5 extend substantially horizontally.

[0042] Next, a method for installing the rectangular duct 1 having such a structure, including a method for suspending the same, will be described.

[0043] First, the upper end of the hanging bolt 101 is fixed to a structure (for example, the ceiling of a building) according to the installation position of the rectangular duct 1. Next, with the rectangular duct 1 laid on its side so that the main surfaces 21, 31 of the half ducts 2, 3 extend approximately horizontally, the lower end of the hanging bolt 101 is inserted into the desired common bolt holes 43, 53. Then, a nut (not shown) is tightened on the hanging bolt 101 so as to sandwich the horizontal parts 42, 52 of the angle members 4, 5, thereby suspending the rectangular duct 1 from the structure.

[0044] As described above, with this rectangular duct 1, the first half duct 2 and the second half duct 3, each having a substantially U-shaped cross section, can be assembled into a cylindrical shape by simply bolting the first angle bar 4 and the second angle bar 5 together to form and manufacture the rectangular duct 1. In other words, even if the first half duct 2 and the second half duct 3 are made of thick plates and cannot be joined by a seam, the rectangular duct 1 can be formed by simply bolting them together, making welding and painting of the welded parts unnecessary.

[0045] As a result, it is possible to significantly reduce the labor and time required to form the square duct 1, and moreover, it is possible to improve the working environment by eliminating welding and painting work, and significantly reduce the burden on workers. Also, since the first half-angle duct 20 and the second half-angle duct 30 (the first half duct 2 and the second half duct 3) can be easily assembled, i.e., bolted, at the construction site, the first half-angle duct 20 and the second half-angle duct 30 can be disassembled and transported to the construction site by truck or temporarily stored at the construction site. This makes it possible to reduce the loading volume and temporary storage volume of the truck, thereby reducing transportation and storage costs.

[0046] Furthermore, even if the first half duct 2 and the second half duct 3 are made of thick plates, the first half duct 20 and the second half duct 30 (the first half duct 2 and the second half duct 3) can be carried separately, reducing the burden on the worker. This makes it possible to improve safety, including the work environment, and energy conservation.

[0047] In addition, since the first half duct 2 and the second half duct 3 have the same shape and dimensions, and the first angle iron 4 and the second angle iron 5 also have the same shape and dimensions, it is possible to reduce manufacturing costs and make handling easier.

[0048] Moreover, since the first connecting portion and the second connecting portion are made of angle members 4 and 5 and are attached to the semi-ducts 2 and 3, the rectangular duct 1 can be easily and inexpensively formed and manufactured. That is, as shown in FIG. 3(b), for example, when the first connecting portion 40 is integrally formed with the first semi-duct 2, the cutting of the plate (material cutting) becomes complicated and the yield rate decreases. In other words, the four corners of the rectangular plate must be cut, which is time-consuming and costly. In contrast, in this embodiment, the first angle member 4 is simply attached to the first semi-duct 2, and as shown in FIG. 3(a), the rectangular plate is simply bent, so the cutting of the plate (material cutting) is easy and simple, and the rectangular duct 1 can be easily and inexpensively formed and manufactured.

[0049] In addition, when the linearly extending rectangular duct 1 is arranged so as to extend substantially horizontally, the horizontal portions 42, 52 of the angle members 4, 5 extend substantially horizontally, so that the rectangular duct 1 can be arranged easily and safely by utilizing these horizontal portions 42, 52.

[0050] Moreover, because common bolt holes 43, 53 serving as suspension bolt holes are formed in the horizontal parts 42, 52 of the angle members 4, 5, it is possible to easily and safely install (hang) the rectangular duct 1 by inserting the suspension bolt 101 into these common bolt holes 43, 53. Also, because it is only necessary for the suspension bolt 101 to reach the angle members 4, 5, which are the connection parts between the first half duct 2 and the second half duct 3, the length of the suspension bolt 101 can be made shorter than in the past, and furthermore, there is no need for a supporting steel material (steel material supporting the bottom of the rectangular duct) as in the past.

[0051] That is, in the past, as shown in FIG. 6, a plate-shaped support steel material 102 was placed on the bottom side of the rectangular duct 100, and the hanging bolt 101 was inserted into the hanging bolt hole formed at both ends of the support steel material 102 to hang the rectangular duct 100. For this reason, the hanging bolt 101 had to be long so that it could reach the bottom side of the rectangular duct 100, and the support steel material 102 was also required. In contrast, in this embodiment, as shown in FIG. 1, the hanging bolt 101 only needs to reach the angle members 4 and 5 located in the vertical center of the cross section of the rectangular duct 1, so the hanging bolt 101 can be shorter than in the past. Moreover, since the angle members 4 and 5 have common bolt holes 43 and 53 as hanging bolt holes, the support steel material 102 is not required. In this way, it is possible to reduce the cost required for installing the rectangular duct 1.

[0052] Moreover, since the common bolt holes 43, 53 are elongated holes extending in the longitudinal direction of the angle members 4, 5 (rectangular duct 1), the installation position of the rectangular duct 1 can be easily and appropriately adjusted.

[0053] Furthermore, since an airtight sheet 47 is provided between the first angle iron 4 and the second angle iron 5, it is possible to ensure the airtightness of the rectangular duct 1.

[0054] On the other hand, according to the above-mentioned method of hanging the rectangular duct 1, by fixing the upper end of the hanging bolt 101 to the structure and inserting and fixing the lower end of the hanging bolt 101 into the shared bolt holes 43, 53 of the angle members 4, 5, it is possible to easily and safely hang the rectangular duct 1 from the structure.

[0055] (Embodiment 2) FIG. 4 is a schematic front view showing an elbow rectangular duct 6 according to a second embodiment of the present invention, and FIG. 5 is a schematic front view showing a first rectangular duct 1 of the elbow rectangular duct 6. 1This elbow rectangular duct 6 is a schematic perspective view showing a multiple number of rectangular ducts 1 according to the first embodiment, with the open ends of the rectangular ducts 1 being connected together while changing their axes L1 to L4, and the same components as those in the first embodiment are given the same reference numerals and their explanations are omitted.

[0056] That is, in this embodiment, four rectangular ducts 1 are connected at their open ends to form an elbow rectangular duct 6 bent at 90 degrees. In other words, the elbow rectangular duct 6 is formed by dividing a conventional 90° elbow rectangular duct bent at 90 degrees in an arc shape into four rectangular ducts 1 radially from the center of the arc. Here, the first rectangular duct 1 located on the open end side of the elbow rectangular duct 6 is 1 and the fourth square duct 1 4 The second rectangular duct 1 is located between the first rectangular duct 1 and the second rectangular duct 2, and has the same shape and dimensions as the first rectangular duct 1 and the second rectangular duct 2. 2 and the third square duct 1 3 The two have the same shape and dimensions.

[0057] These square ducts 1 1 ~1 4 The first rectangular duct 1 has the same configuration as the rectangular duct 1 in the first embodiment, and detailed explanation will be omitted. 1 This will be explained using an example.

[0058] That is, the device comprises a first half duct 2 and a second half duct 3 each having a substantially U-shaped cross section, and a first angle member 4 and a second angle member 5 disposed extending along both free edges of the cross sections of the first half duct 2 and the second half duct 3. The first half duct 2 and the second half duct 3 are disposed facing each other so that the cross section is a substantially square cylindrical shape, and the first angle member 4 and the second angle member 5 are bolted together to assemble the first half duct 2 and the second half duct 3 into a cylindrical shape.

[0059] When assembled into a cylindrical shape in this manner, both open end faces are formed to form a predetermined angle with respect to the axis L1, and the edges of both open end faces are bent outward to form flange portions 23, 33. By connecting adjacent rectangular ducts 1 with the flange portions 23, 33, the four rectangular ducts 1 are linked while changing the axes L1-L4 (while the axes L1-L4 are bending), and an elbow rectangular duct 6 bent by 90° is formed.

[0060] According to the elbow angular duct 6 having such a configuration, a plurality of the angular ducts 1 of the first embodiment are formed by connecting the open ends of the angular ducts 1 with each other while changing the axes L1-L4. That is, even with the elbow angular duct 6 in which the axes L1-L4 are curved, the same effects as those of the first embodiment can be obtained, and it is possible to improve safety including the working environment and energy saving.

[0061] Although the embodiments of the present invention have been described above, the specific configuration is not limited to the above embodiments, and the present invention includes design changes and the like that do not deviate from the gist of the present invention. For example, in the above embodiment 1, the first half-angle duct 20 and the half-angle duct 30 have the same shape and dimensions, but they may have different shapes and dimensions. Also, in embodiment 1, the case where the rectangular duct 1 is a straight duct has been described, but other rectangular ducts may also be used.

[0062] Furthermore, in the second embodiment, the elbow angle duct 6 is described as being composed of four angle ducts 1 with the axis bent at 90°. However, the elbow angle duct 6 may be composed of less than four or five or more angle ducts 1, or the axis may be bent at an angle other than 90°. [Explanation of symbols]

[0063] 1 Square duct 2 First half duct 3 Second half duct 4 First angle piece (first connection part) 41 Vertical section 42 Horizontal section 43 Common bolt hole (bolt insertion hole, hanging bolt hole) 45 Fastening bolt 47 Airtight sheet (airtight material) 5 Second angle piece (second connection part) 51 Vertical section 52 Horizontal section 53 Common bolt hole (bolt insertion hole, hanging bolt hole) 6 Elbow square duct 101 Hanging bolt

Claims

1. A first semi-duct having a generally U-shaped cross section; A second half duct having a generally U-shaped cross section extending therethrough; a first connection portion extending along both free end edges of the cross section of the first half duct and having a bolt insertion hole; a second connection portion extending along both free end edges of the cross section of the second half duct and having a bolt insertion hole; The first half duct and the second half duct are arranged facing each other so that a cross section of the first half duct is a substantially rectangular cylindrical shape, and the first connection portion and the second connection portion are fastened by bolts through the bolt insertion holes, thereby assembling the first half duct and the second half duct into a cylindrical shape. A square duct characterized by:

2. The first half duct and the second half duct have the same shape and size, and the first connecting portion and the second connecting portion have the same shape and size. The rectangular duct according to claim 1 .

3. the first connecting portion and the second connecting portion are formed of an angle material having a substantially L-shaped cross section and a vertical portion and a horizontal portion, a vertical portion of the first connecting portion is attached along both free edges of the first half duct, and a vertical portion of the second connecting portion is attached along both free edges of the second half duct; The rectangular duct according to claim 1 .

4. When the first half duct and the second half duct are assembled into a cylindrical shape, an axis of the first half duct extends linearly, and when the axis of the second half duct is arranged to extend substantially horizontally, horizontal portions of the first connecting portion and the second connecting portion extend substantially horizontally. The rectangular duct according to claim 3 .

5. A suspension bolt hole for inserting a suspension bolt is formed in the horizontal portion of the first connection portion and the horizontal portion of the second connection portion. The rectangular duct according to claim 4 .

6. The hanging bolt hole is an elongated hole extending in the longitudinal direction of the first connection portion and the second connection portion. The rectangular duct according to claim 5 .

7. An airtight material is provided between the first connection portion and the second connection portion. The rectangular duct according to claim 1 .

8. A plurality of the angular ducts according to claim 1 are connected to each other at their open ends while changing their axes. An elbow square duct characterized by:

9. The rectangular duct according to claim 5 or 6 is suspended from a structure by inserting a lower end of a suspension bolt, the upper end of which is fixed to a structure, into the suspension bolt hole of the rectangular duct according to claim 5 or 6. A method for suspending a square duct.

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