WO2007148947A1

WO2007148947A1 - Cyclone generator for collecting a pollutant, collection device having it, and collection unit for a pollutant

Info

Publication number: WO2007148947A1
Application number: PCT/KR2007/003048
Authority: WO
Inventors: Ho-Sung Lee
Original assignee: Ho-Sung Lee
Priority date: 2006-06-22
Filing date: 2007-06-22
Publication date: 2007-12-27
Also published as: KR100742560B1

Abstract

Provided are a cyclone generator for collecting pollutants, which generates a cyclonic flow in the air so that pollutants such as a dust, a hazardous gas, a mist and the like floating in the air are collected by the cyclonic flow, a collection device having the same, and a pollutant collection unit. Therefore, it is possible to enhance pollutant collection performance and reduce noise and energy consumption. The cyclone generator for collecting pollutants, which is coupled to a hollow duct having an inlet for sucking pollutants, includes: a hollow housing having a suction hole into which the pollutants are sucked, and a communication hole communicating with the inlet of the duct; and a pair of blocking members disposed in the housing so as to face each other in a direction from the suction hole toward the communication hole, and respectively having through-holes passing in the direction from the suction hole toward the communication hole.

Description

CYCLONE GENEARATER FOR COLLECTING A

POLLUTANT, COLLECTION DEVICE HAVING IT, AND

COLLECTION UNIT FOR A POLLUTANT

Technical Field

[1] The present invention relates to a cyclone generator for collecting pollutants, a collection device having the same, and a pollutant collection unit, and more specifically, to a cyclone generator for collecting pollutants, which collects pollutants such as a dust, a hazardous gas, a mist and the like, and then discharges them, a collection device having the same, and a pollutant collection unit. Background Art

[2] Devices for collecting pollutants such as a dust, a hazardous gas, a mist and the like are widely used in a variety of fields. For example, in a working area where an operation such as coating, soldering, refining or the like is performed, a discharge system may be installed, which collects various pollutants generated during the operation and then discharges the same to the outside of the working area. Further, ventilation and exhaust systems for ventilating and exhausting the inside of a tunnel or building may be installed in the tunnel or building. Further, a hood for removing food smell or cigarette smoke may be used in a kitchen or smoking room.

[3] Meanwhile, a conventional pollutant collection device includes a hollow duct and a fan which is installed in the duct so as to suck air outside the duct into the duct. Therefore, when the fan is driven, the air outside the duct is sucked into the duct. Simultaneously, pollutants are sucked into the duct together with the air.

[4] In the conventional pollutant collection device, pollutants are collected by a suction force of the fan. Therefore, when high collection performance is required, for example, when a wide area is ventilated or minute pollutants are collected, a high-power fan should be installed. However, the high-power fan not only consumes an excessive amount of energy, but also generates noise while being driven.

[5] Therefore, there is a demand for a pollutant collection device which has excellent pollutant collection performance, consumes a smaller amount of energy, and generates little noise. Disclosure of Invention

Technical Problem

[6] In order to solve the foregoing and/or other problems, it is an objective of the present invention to provide a cyclone generator for collecting pollutants, which generates a cyclonic flow in the air such that pollutants such as a dust, a hazardous gas, a mist and the like floating in the air are collected by the cyclonic flow, a collection device having the same, and a pollutant collection unit. Therefore, it is possible to enhance pollutant collection performance and reduce noise and energy consumption. Technical Solution

[7] In one aspect, the present invention is directed to a cyclone generator for collecting pollutants, which is coupled to a hollow duct having an inlet for sucking pollutants, the cyclone generator including: a hollow housing having a suction hole into which the pollutants are sucked, and a communication hole communicating with the inlet of the duct; and a pair of blocking members disposed in the housing so as to face each other in a direction from the suction hole toward the communication hole, and respectively having through-holes passing in the direction from the suction hole toward the communication hole.

[8] In another aspect, the present invention is directed to a pollutant collection device including: a hollow housing having an inlet for sucking pollutants and an outlet for discharging the pollutants sucked through the inlet; a fan for sucking air including the pollutants such that the pollutants are sucked into the housing; and a pair of blocking members disposed in the housing so as to face each other in a direction from the inlet toward the outlet, and respectively having through-holes passing in the direction from the inlet toward the outlet.

[9] In still another aspect, the present invention is directed to a pollutant collection unit including: a plurality of hollow ducts, each of which has an inlet for sucking pollutants and an outlet for discharging the pollutants sucked into the inlet; a hollow main duct having a plurality of communication holes, which communicate with the outlets of the respective ducts, and a main outlet into which air sucked through the ducts is discharged; a fan for sucking air including the pollutants such that the pollutants are sucked into the respective ducts; a plurality of blocking members installed inside the respective ducts, and having through-holes passing in directions from the inlets to the outlets of the respective ducts; and a main blocking member installed inside the main duct, and having a through-hole passing in a direction from the communication hole toward the main outlet of the main duct.

Advantageous Effects

[10] According to the present invention, a cyclonic flow is generated in the air such that pollutants such as a dust, a hazardous gas, a mist and the like floating in the air are collected by the cyclonic flow, and thus it is possible to enhance pollutant collection performance and reduce noise and energy consumption. Brief Description of the Drawings [11] FIG. 1 is a schematic cross-sectional view of a cyclone generator for collecting pollutants according to an exemplary embodiment of the present invention;

[12] FIG. 2 is a schematic cross-sectional view of a pollutant collection device according to an exemplary embodiment of the present invention;

[13] FIG. 3 is a schematic side view of a pollutant collection unit according to an exemplary embodiment of the present invention; and

[14] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3.

Best Mode for Carrying Out the Invention

[15] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[16] FIG. 1 is a schematic cross-sectional view of a cyclone generator for collecting pollutants according to an exemplary embodiment of the present invention.

[17] Referring to FIG. 1, a cyclone generator 100 for collecting pollutants according to this exemplary embodiment is detachably coupled to a conventional duct 10 for collecting pollutants so as to generate a cyclonic flow. The duct 10 has a hollow shape. The duct 10 has a circular inlet 11 formed in one side thereof, and the other side thereof is connected to a ventilation system (not shown). A fan 12 for sucking pollutants 2 is installed inside the duct 10. In FIG. 1, a region indicated by a dashed- two dotted line represents the inside 1 of a building. The cyclone generator 100 includes a housing 20, a cyclone generating portion 30, and a guide member 40.

[18] The housing 20, which is hollow, has a curved inner surface, or more specifically, a circular curved inner surface. The housing 20 includes a suction hole 21, a communication hole 22, and a groove portion 23. The pollutants 2 present in the building are sucked through the suction hole 21. The communication hole 22 communicates with the inlet 11 of the duct 10. The groove portion 23 is formed at an end of the housing 20. The groove portion 23 is formed in a shape corresponding to an end of the duct 10. As the end of the duct 10 is inserted into the groove portion 23, the housing 20 is coupled to the duct 10. As the end of the duct 10 is separated from the groove portion 23, the housing 20 is separated from the duct 10. The suction hole 21, the communication hole 22, and the groove portion 23 are formed in a circular shape.

[19] The cyclone generating portion 30 includes a pair of blocking members 31 and 32 disposed in the housing 20. The blocking members 31 and 32 are spaced at a predetermined distance in a direction from the suction hole 21 toward the communication hole 22 of the housing, that is, in a vertical direction so as to face each other. The blocking members 31 and 32 are disposed in such a manner that the outer surfaces thereof come into contact with the inner surface of the housing 20. In this exemplary embodiment, one of the blocking members 31 and 32, i.e., the blocking member 31 is disposed at the suction hole 21 of the housing. The blocking members 31 and 32 respectively have through-holes 311 and 321 passing in a vertical direction. The through- holes 311 and 321 of the blocking members 31 and 32 are disposed coaxially with each other. Further, the through-holes 311 and 321 are disposed coaxially with the suction hole 21 and the communication hole 22 of the housing.

[20] The blocking members 31 and 32 are installed in the housing 20, thereby reducing a cross-sectional area of air flow. Therefore, when the air outside the housing, i.e., the air in the building, is sucked by the fan 12, air pressure in one side of the inside of the housing 20 is reduced compared with air pressure in the other side of the inside of the housing 20. That is, air pressure at the through-holes 311 and 321 of the respective blocking members is reduced compared with air pressure between the blocking members 31 and 32. Further, as indicated by a helical line in FIG. 1, a cyclonic flow is generated in the air sucked into the suction hole 21 of the housing. The cyclonic flow is generated to the inside and the outside of the housing. Therefore, the pollutants 2 present in the building are sucked with the air into the suction hole 21 of the housing by the cyclonic flow, and are then discharged through the duct 10 into a ventilation system of the building connected to the duct.

[21] The guide member 40 is coupled to the housing 20. The guide member 40 is shell- shaped and has a coupling hole 41 passing through the center thereof such that the end of the housing is inserted into the coupling hole 41. The guide member 40 guides the flow of pollutants and air present in the building such that the pollutants and the air are induced toward the suction hole 21 of the housing 21.

[22] The cyclone generator 100 constructed in the above-described manner is coupled to the conventional duct 10 for collecting pollutants so as to change pressure distribution in the housing 20. Then, a strong cyclonic flow is generated in the air sucked when the fan 12 is driven, in contrast to the conventional art. Therefore, while the pollutants 2 present in the building are swept along and rotated by the cyclonic flow, they are guided in the upper direction so as to be sucked into the duct 10. Then, the sucked pollutants 2 are discharged to the ventilation system. In this exemplary embodiment, a cyclonic flow is generated, and a strong suction force of the cyclonic flow is utilized to effectively collect pollutants present in a building. Therefore, even when a conventional fan is used, it is possible to exhibit more excellent collection performance than in the conventional art.

[23] In addition, since the cyclone generator 100 in this exemplary embodiment has the guide member 40, pollutants which may randomly flow in a building are guided by the guide member 40 so as to circulate around the suction hole 21 of the housing. Therefore, the pollutants 2 are effectively collected.

[24] Further, when the cyclone generator 100 in this exemplary embodiment is coupled into the duct 10 connected to a conventional ventilation and exhaust system, the installation is carried out easily. Further, while the conventional ventilation and exhaust system is used without modification, the cyclone generator 100 can generate a cyclonic flow, thereby exhibiting high collection performance.

[25] In addition, since the inner surface of the housing 20 is formed in a circular shape, friction between the air and the inner surface of the housing 20 is reduced during the suction of air. Therefore, it is possible to minimize noise generated during the suction of air.

[26] In this exemplary embodiment, the blocking members are separately manufactured from the housing and then coupled to the housing. However, the blocking members may be formed integrally with the housing.

[27] Further, the inner surface of the housing has a circular curved surface. However, the inner surface of the housing is not limited to the circular curved surface, but may have an elliptical curved surface or rectangular planar surface.

[28] In addition, the suction hole, the communication hole, and the groove portion are formed in a circular shape. However, they are not limited to the circular shape, but may be formed in various shapes such as a rectangle, a triangle, an ellipse and the like.

[29] FIG. 2 is a schematic cross-sectional view of a pollutant collection device according to an exemplary embodiment of the present invention.

[30] Referring to FIG. 2, a pollutant collection device 200 according to this exemplary embodiment is portable and may be used in a place where pollutants should be collected, for example, a work table 3 on which coating, soldering, refining and the like are performed. The pollutant collection device 200 includes a housing 20a, a sucking portion 50, a cyclone generating portion 30a, and a guide member 40a.

[31] The housing 20a, which is hollow, has a curved inner surface, for example, a circular curved surface. The housing 20a has an inlet 21a and an outlet 22a formed therein. Through the inlet 21a, pollutants 4 generated from the work table 3 are sucked. Through the outlet 22a, the pollutants 4 sucked through the inlet 21a are discharged. The outlet 22a is connected to a duct 5 included in a ventilation system (not shown), and thus the pollutants 4 sucked through the inlet 21a are discharged to the ventilation system through the duct 5.

[32] The sucking portion 50 sucks the air outside the housing 20a such that the pollutants 4 included in the air are sucked through the inlet 21a of the housing. In this exemplary embodiment, a fan is used as the sucking portion 50. The fan 50 is installed inside the housing 20a. More specifically, the fan 50 is disposed between the inlet 21a and the outlet 22a of the housing.

[33] The cyclone generating portion 30a includes a pair of blocking members 31a and

32a disposed in the housing 20a. The blocking members 31a and 32a are spaced at a predetermined distance in a direction from the inlet 21a toward the outlet 22a of the housing, i.e., in a horizontal direction so as to face each other. The respective blocking members 31a and 32a are disposed in such a manner that the outer surfaces thereof come into contact with the inner surface of the housing. In this exemplary embodiment, one of the blocking members 31a and 32a, i.e., the blocking member 31a is disposed at the inlet 21a of the housing. The blocking members 31a and 32a respectively have through-holes 311a and 321a passing in a horizontal direction. The through-holes 311a and 321a of the blocking members are disposed coaxially with each other. Further, the through-holes 311a and 321a are disposed coaxially with the inlet 21a and the outlet 22a of the housing.

[34] The blocking members 31a and 32a are installed in the housing 20a, thereby reducing a cross-sectional area of air flow. Therefore, when the air outside the housing is sucked by the fan 50, air pressure in one side of the inside of the housing 20a, i.e., air pressure at the through-holes 311a and 321a of the respective blocking members is reduced compared with air pressure in the other side of the inside of the housing 20a, i.e., air pressure between the blocking members 31a and 32a. Further, as indicated by a helical line in FIG. 2, a cyclonic flow is generated in the air sucked into the inlet 21a of the housing. Specifically, the cyclonic flow is generated to the inside and the outside of the housing. Therefore, the pollutants generated from the work table 3 are sucked into the inlet 21a of the housing with the air by the cyclonic flow, and are then discharged through the duct 5 into a ventilation system (not shown) connected to the duct.

[35] The guide member 40a is coupled to the housing 20a. The guide member 40a is shell-shaped and has a coupling hole 41a passing through the center thereof such that the housing 20a is coupled to the coupling hole 41a. The guide member 40a guides the flow of pollutants generated from the work table and air such that the pollutants and the air are induced toward the inlet 21a of the housing.

[36] Since the pollutant collection device 200 constructed in the above-described manner is portable, it may be used portably in various kinds of work tables 3 in which pollutants need to be collected. Particularly, since pollutants 4 can be sucked by the cyclonic flow, it is possible to enhance collection performance and reduce energy consumption and noise compared to the conventional art.

[37] In this exemplary embodiment, the blocking members are separately manufactured from the housing and then coupled to the housing. However, the blocking members may be formed integrally with the housing.

[38] FIG. 3 is a schematic side view of a pollutant collection unit according to an exemplary embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3.

[39] Referring to FIGs. 3 and 4, a pollutant collection unit 300 according to this exemplary embodiment is installed in a place such as a building, a tunnel, an underground space or the like, where pollutants are generated. In this exemplary embodiment, it is assumed that the pollutant collection unit 300 is installed in a tunnel 6. The pollutant collection unit 300 includes a plurality of ducts 60, a main duct 70, a sucking portion 50b, a cyclone generating portion 30b, and a guide member 40b.

[40] The respective ducts 60 are hollow, and the inner surface of each of the ducts 60 is formed of a curved surface, for example, a circular curved surface. Each of the ducts 60 has an inlet 61, an outlet 62, and a groove portion formed therein. Pollutants 7 present in the tunnel are sucked through the inlet 61 and discharged through the outlet 62.

[41] The main duct 70, which is hollow, has a curved inner surface, for example, a circular curved surface. The diameter of the main duct 70 is larger than the sum total of diameters of the respective ducts 60. The main duct 70 has a plurality of communication holes 71, a main outlet 72, and a plurality of projections 73 formed therein. The communication holes 71 are formed in one side of the main duct 70 so as to communicate with the outlets 62 of the respective ducts. Through the main outlet 72, the pollutants 7 sucked through the communication holes 71 are discharged. The main outlet 72 is formed in the other side of the main duct 70 and is connected to a ventilation system (not shown). The projections 73 are disposed between the communication holes 71 and are formed in a shape corresponding to the groove portions 63 of the respective ducts. The projections 73 are inserted into the groove portions 63 of the respective ducts. Therefore, as the projections 73 are coupled to and separated from the groove portions 63, the main duct 70 is coupled to and separated from the respective ducts 60.

[42] The sucking portion 50b sucks the air in the tunnel 6 such that the pollutants 7 included in the air are sucked through the inlets 61 of the respective ducts into the main duct 70. In this exemplary embodiment, a fan is used as the sucking portion 50b. The fan 50b is installed inside the main duct 70. The fan 50b is disposed between the communication holes 71 of the main duct and the main outlet 72.

[43] The cyclone generating portion 30b includes a plurality of blocking members 3 Ib and a main blocking member 32b. The blocking members 31b are installed inside the respective ducts 60. In this exemplary embodiment, the blocking members 31b are disposed in the upper portions of the inlets 61 of the respective ducts. The blocking members 31b are disposed in such a manner that the outer surfaces thereof come into contact with the inner surfaces of the respective ducts 60. The respective blocking members 31b have through-holes 31 Ib passing in directions from the inlets 61 to the outlets 61 of the respective ducts. The through-holes 31 Ib of the respective blocking members are disposed coaxially with the inlets 61 of the respective ducts. The main blocking member 32b is installed inside the main duct 70. In this exemplary embodiment, the main blocking member 32b is disposed between the communication hole 71 and the fan 50b. The main blocking member 32b is disposed in such a manner that the outer surface thereof comes into contact with the inner surface of the main duct 70. The main blocking member 32b has a through-hole 321b passing in a direction from the communication holes 71 of the main duct toward the main outlet 72, that is, in a vertical direction. The through-hole 321b of the main blocking member is disposed coaxially with the communication holes 71 of the main duct.

[44] The blocking members 31b and the main blocking member 32b are installed in the ducts 60 and the main duct 70, respectively, thereby reducing a cross-sectional area of air flow. When the air outside the respective ducts 60, i.e., the air in the tunnel is sucked by the fan 50b, air pressure in one sides of the insides of the respective ducts 60, i.e., air pressure in the through-holes 31 Ib of the respective blocking members is reduced compared with air pressure in the other sides of the insides of the respective ducts, i.e., air pressure between the through-holes 31 Ib of the blocking members and the communication holes 71 of the main duct. Further, air pressure in one side of the inside of the main duct 70, i.e., air pressure in the through-hole 321b of the main blocking member is reduced compared with air pressure in the other side of the inside of the main duct, i.e., air pressure between the through-hole 321b of the main blocking member and the communication holes 71 of the main duct. Further, as indicated by a helical line in FIG. 4, a cyclonic flow is generated in the air sucked into the inlets 61 of the respective ducts. The cyclonic flow is generated to the insides and outsides of the ducts 60 and the inside of the main duct 70. Therefore, the pollutants 7 generated in the tunnel 6 are sucked into the inlets 61 of the respective ducts with the air by the cyclonic flow and are introduced into the main duct 70 through the ducts 60. Then, the pollutants 7 are discharged to a ventilation system (not shown) connected to the main duct.

[45] The guide member 40b is coupled to the respective ducts 60. As shown in FIG. 3, the guide member 40b includes a plane portion 41b and a curved portion 42b. The plane portion 41b is formed in a plate shape. The plane portion 41b has coupling holes 41 Ib passing therethrough such that the respective ducts 60 are coupled to the coupling holes 41 Ib. The curved portion 42b is connected to an end of the plane portion 41b and is formed in a curved-surface shape. The curvature center of the curved portion 42b is positioned between the plane portion 41b and the curved portion 42b. The guide member 40b guides the flow of pollutants and air present in the tunnel such that the pollutants and the air are induced toward the inlets 61 of the respective ducts.

[46] In the pollutant collection unit 300 constructed in such a manner, since the plurality of ducts 60 are coupled to the main duct 70, the pollutants 7 generated in the tunnel 6 can be collected from a wider area than in the conventional art. That is because, since the ducts 60 are disposed in a range of diameter larger than the diameter of the main duct 70, the area from which pollutants are collected becomes wider than in the conventional art. Further, in this exemplary embodiment, since the pollutants are collected by the cyclonic flow, it is possible to enhance collection performance and reduce energy reduction and noise compared to the conventional art.

[47] Further, after one main duct 70 is installed in a building with a plurality of spaces, the ducts 60 may be disposed in the respective spaces. In this case, pollutants generated from the respective spaces can be collected and discharged through the main duct 70. Therefore, the pollutant collection unit can be easily installed in a building with a plurality of spaces. Specifically, when the respective ducts are made of flexible materials such as flexible plastics, the installation of the ducts is more easily carried out.

[48] In this exemplary embodiment, the blocking members and the main blocking member are manufactured separately from the respective ducts and the main duct and are then coupled to the ducts and the main duct. However, the blocking members and the main blocking member may be formed integrally with the ducts and the main duct, respectively.

[49] While this invention has been described with reference to exemplary embodiments thereof, it will be clear to those of ordinary skill in the art to which the invention pertains that various modifications may be made to the described embodiments without departing from the spirit and scope of the invention as defined in the appended claims and their equivalents.

Claims

[1] A cyclone generator for collecting pollutants, which is coupled to a hollow duct having an inlet for sucking pollutants, the cyclone generator comprising: a hollow housing having a suction hole into which the pollutants are sucked, and a communication hole communicating with the inlet of the duct; and a pair of blocking members disposed in the housing so as to face each other in a direction from the suction hole toward the communication hole, and respectively having through-holes passing in the direction from the suction hole toward the communication hole.

[2] The cyclone generator according to claim 1, wherein the respective blocking members are disposed such that outer surfaces thereof come into contact with an inner surface of the housing, and the through- holes of the blocking members are disposed coaxially with each other.

[3] The cyclone generator according to claim 2, wherein the blocking members are formed integrally with the housing.

[4] The cyclone generator according to claim 1, further comprising: a guide member coupled to the housing to guide an air flow such that the air flow is induced toward the suction hole of the housing.

[5] The cyclone generator according to claim 4, wherein the guide member is shell-shaped and has a coupling hole passing therethrough such that the housing is coupled to the coupling hole.

[6] The cyclone generator according to claim 1, wherein the inner surface of the housing has a circular curved surface.

[7] The cyclone generator according to claim 1, wherein the housing is detachably coupled to the duct.

[8] A pollutant collection device comprising: a hollow housing having an inlet for sucking pollutants and an outlet for discharging the pollutants sucked through the inlet; a fan for sucking air including the pollutants such that the pollutants are sucked into the housing; and a pair of blocking members disposed in the housing so as to face each other in a direction from the inlet toward the outlet, and respectively having through-holes passing in the direction from the inlet toward the outlet.

[9] The pollutant collection device according to claim 8, wherein the respective blocking members are disposed such that outer surfaces thereof come into contact with an inner surface of the housing, and the through- holes of the blocking members are disposed coaxially with each other.

[10] The pollutant collection device according to claim 9, wherein the blocking members are formed integrally with the housing.

[11] The pollutant collection device according to claim 8, further comprising: a guide member coupled to the housing to guide an air flow such that the air flow is induced toward the inlet of the housing.

[12] The pollutant collection device according to claim 11, wherein the guide member is shell-shaped and has a coupling hole passing therethrough such that the housing is coupled to the coupling hole.

[13] The pollutant collection device according to claim 8, wherein the inner surface of the housing has a circular curved surface.

[14] A pollutant collection unit comprising: a plurality of hollow ducts, each of which has an inlet for sucking pollutants and an outlet for discharging the pollutants sucked into the inlet; a hollow main duct having a plurality of communication holes, which communicate with the outlets of the respective ducts, and a main outlet into which air sucked through the ducts is discharged; a fan for sucking air including the pollutants such that the pollutants are sucked into the respective ducts; a plurality of blocking members installed inside the respective ducts, and having through-holes passing in directions from the inlets to the outlets of the respective ducts; and a main blocking member installed inside the main duct, and having a through- hole passing in a direction from the communication hole toward the main outlet of the main duct.

[15] The pollutant collection unit according to claim 14, wherein the respective blocking members are disposed such that outer surfaces thereof come into contact with inner surfaces of the respective ducts, and the main blocking member is disposed such that an outer surface thereof comes into contact with an inner surface of the main duct.

[16] The pollutant collection unit according to claim 15, wherein the blocking members are formed integrally with the ducts, respectively, and the main blocking member is formed integrally with the main duct.

[17] The pollutant collection unit according to claim 14, further comprising: a guide member coupled to the respective ducts to guide an air flow such that the air flow is induced toward the inlets of the ducts.

[18] The pollutant collection unit according to claim 17, wherein the guide member comprises a plane portion, which is formed in a plate shape and has coupling holes passing therethrough such that the respective ducts are coupled to the coupling holes, and a curved portion which is connected to an end of the plane portion and is formed in a curved- surface shape.