JP2011094913A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner capable of relaxing a stress generated in a bolt or connecting pipe upon starting of a constant speed compressor by a simple structure. <P>SOLUTION: The air conditioner includes constant speed compressors 11a, 11b each having an electric element driving at a substantially constant rotating speed and a rotational compression element driven by the electric element to compress refrigerant, which are stored in a sealed container 61. The constant speed compressor 11a, 11b is fixed to a bottom plate 10 of an outdoor unit 2A with a mount rubber 63 being interposed between a plurality of leg piece portions 62 provided on the sealed container 61 and the bottom plate 10 by fixing each leg piece portion 62 onto the bottom plate 10 by a bolt 65. The air conditioner further includes a connecting member 70 which connects an upper end portion 65B of the bolt 65 disposed on the leg piece portion 62 to the bottom plate 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an air conditioner having a constant speed compressor.

  2. Description of the Related Art Conventionally, an air conditioner including an outdoor unit having a plurality of compressors is known in order to sufficiently secure cooling and heating capabilities. This type of air conditioner includes a variable speed compressor (inverter compressor) whose rotation speed can be controlled by an inverter, and a constant speed compressor (constant speed compressor) that operates only at a constant speed depending on the power supply frequency. ) Is generally provided. (For example, refer to Patent Document 1).

JP 2003-130492 A

By the way, this type of compressor is a hermetic compressor in which an electric element and a rotary compression element that is driven by the electric element and compresses a refrigerant are contained in a cylindrical hermetic container. A plurality of leg pieces are provided, and the leg pieces are fastened to the bottom plate with bolts with a vibration-proof mount rubber interposed between the leg pieces and the bottom plate of the outdoor unit. .
In the compressor, three pipes for refrigerant suction, refrigerant discharge, and oil circulation are connected to an airtight container. In a constant speed compressor, unlike an inverter compressor, a large torque is generated in an airtight container in order to follow a rapid rotational speed at the time of startup. The large torque generated at the time of starting has a problem that a great stress is applied to the bolt and each pipe through the leg piece.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an air conditioner that has a simple configuration and that mitigates stress generated on bolts and connection pipes when a constant speed compressor is started. To do.

  In order to achieve the above object, the present invention provides a constant-speed compressor that houses an electric element that is driven in a sealed container at a substantially constant rotational speed, and a rotary compression element that is driven by the electric element and compresses refrigerant. And the constant speed compressor is fixed to the bottom plate with a fastener with an elastic member interposed between the plurality of leg pieces provided on the sealed container and the bottom plate. The air conditioner includes a connecting member that connects an upper end portion of the fastener and the bottom plate disposed on at least one leg piece.

  In this configuration, the leg piece portion may have an opening that penetrates the fastener and has a diameter sufficiently larger than that of the fastener. Further, the connecting member may be formed by bending a sheet metal.

  Moreover, the said connection member is good also as a structure provided with the part extended above the said leg piece part. Moreover, the said connection member may be comprised so that attachment from the upper direction of the said leg piece part is possible. The fastener may include a bolt and a nut, and the nut may be welded to the bottom plate.

  According to the present invention, there is provided a constant speed compressor that houses an electric element that is driven at a substantially constant rotational speed in a sealed container, and a rotary compression element that is driven by the electric element and compresses a refrigerant. In the air conditioner in which the machine is fixed with a fastener on the bottom plate with an elastic member interposed between the plurality of leg pieces provided on the sealed container and the bottom plate, Since the connecting member that connects the upper end portion of the fastener and the bottom plate disposed on one leg piece is provided, for example, the connecting member receives torque acting on the sealed container at the time of starting the constant speed compressor. Thus, with a simple configuration, the stress acting on the fastener for fixing the sealed container and the piping provided in the sealed container can be relieved.

It is a refrigerant circuit figure of the air harmony device concerning this embodiment. It is a refrigerant circuit diagram which shows the structure of an outdoor unit. It is a fragmentary perspective view of the outdoor unit which shows the arrangement configuration of a constant speed compressor. It is an expansion perspective view which shows a leg piece part periphery. It is a figure which shows the arrangement configuration of a leg piece part, mount rubber | gum, and a control member. FIG. 6 is a side sectional view of FIG. 5. It is a perspective view which shows the arrangement configuration of the connection member concerning another embodiment. FIG. 8 is a front view of FIG. 7. It is an arrangement block diagram of a connecting member concerning another embodiment. It is an arrangement block diagram of a connecting member concerning another embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, the code | symbol 1 shows an air conditioning apparatus. The air conditioner 1 includes a plurality (two) of outdoor units 2A, 2B and a plurality (two) of indoor units 3A, 3B. The outdoor units 2A, 2B and the indoor units 3A, 3B Are connected by a gas pipe 4 and a liquid pipe 5.

  The indoor unit 3A includes an indoor heat exchanger 8 and an indoor expansion valve 9. One end of the indoor heat exchanger 8 is connected to the gas pipe 4, and the other end of the indoor heat exchanger 8 is indoor expansion. The valve 9 is connected to the liquid pipe 5. In addition, the indoor unit 3A is provided with a temperature sensor or the like that detects the inlet / outlet temperature or room temperature of the indoor heat exchanger 8, and an indoor control device that inputs the detection results of these sensors to control the indoor unit 3A. (Not shown). Moreover, since the indoor unit 3B has substantially the same configuration as the indoor unit 3A, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 2 is an enlarged circuit diagram showing the configuration of the outdoor unit 2A. The outdoor unit 2B has substantially the same configuration, and a description thereof is omitted. The outdoor unit 2A includes a plurality of (two) constant capacity type constant speed compressors (AC compressors) 11a and 11b, a variable capacity inverter compressor (DC inverter compressor) 12, an accumulator 13, An oil separator 14, a four-way valve 15, outdoor heat exchangers 16a and 16b, outdoor expansion valves 17a and 17b, a receiver tank 18, and the like are schematically configured.

The constant speed compressors 11a and 11b and the inverter compressor 12 are connected in parallel. Depending on the magnitude of the air conditioning load of the indoor units 3A and 3B, the start and stop of these compressors 11a, 11b and 12 and inverter compression The operating frequency of the machine 12 is controlled. One end of the suction pipe 31 is connected to the suction ports of the compressors 11 a, 11 b, and 12, and the other end of the suction pipe 31 is connected to the four-way valve 15 via the accumulator 13.
One end of a discharge pipe 32 is connected to the discharge port of each compressor 11 a, 11 b, 12, and the other end of the discharge pipe 32 is connected to the four-way valve 15 via the oil separator 14. The four-way valve 15 is switched so that the suction pipe 31 and the discharge pipe 32 communicate with the indoor gas pipe 35 connected to the gas pipe 4 or the outdoor heat exchangers 16a and 16b, respectively.
The outdoor heat exchangers 16a and 16b are connected to the liquid pipe 5 via the outdoor expansion valves 17a and 17b, the receiver tank 18 and the auxiliary cooling circuit 21. In addition, check valves 19a and 19b are connected in parallel with the outdoor expansion valves 17a and 17b. The check valves 19a and 19b allow the refrigerant to flow from the outdoor heat exchangers 16a and 16b to the receiver tank 18. The refrigerant flow in the reverse direction is prohibited.
The auxiliary cooling circuit 21 contributes to the improvement of COP by supercooling the liquid refrigerant condensed in the outdoor heat exchangers 16a and 16b during the cooling operation. The auxiliary cooling circuit 21 is a so-called double-pipe heat exchanger, and an indoor liquid pipe 33 connected to the receiver tank 18 and the liquid pipe 5 is communicated with the inner pipe, and an indoor liquid pipe is connected to the outer pipe. A branch pipe 34 branched from the pipe 33 and connected to the suction pipe 31 communicates. The electric expansion valve 22 is disposed in the branch pipe 34. The refrigerant flowing through the branch pipe 34 evaporates when the refrigerant flowing through the indoor liquid pipe 33 is cooled, and is returned to the suction ports of the compressors 11 a, 11 b, and 12 through the suction pipe 31.

The oil separator 14 is connected to an oil return pipe 36 that returns excess oil to the suction pipes 31 of the compressors 11a, 11b, and 12 when the amount of oil stored in the oil separator 14 is equal to or greater than a predetermined amount. An oil branch pipe 36A is connected to the oil return pipe 36, and the oil branch pipe 36A is connected to the oil balance pipe 6 via a check valve 38. An oil branch pipe 36A extending from the oil separator 14 of another outdoor unit 2B (see FIG. 1) is connected to the oil balance pipe 6 so that the oil amount is balanced between the plurality of outdoor units 2A and 2B. Yes.
Each of the compressors 11a, 11b, and 12 is a high-pressure vessel compressor that has a high pressure inside during a compression operation. The high-pressure portion (inside the high-pressure vessel) of one compressor and the low-pressure portion (suction) of another compressor. And the inside of the pipe 31) are connected by an oil pipe 37 so that the amount of oil in each of the compressors 11a, 11b, and 12 is appropriately adjusted.

The discharge pipe 32 of the outdoor unit 2A is provided with a check valve 25, and the discharge gas flows backward when the operation of each of the compressors 11a, 11b, 12 is stopped, and the compression elements of the compressors 11a, 11b, 12 are reversed. Prevents rotation.
The discharge pipe 32 is provided with a discharge pressure sensor HP that detects the pressure of the discharge gas of each of the compressors 11a, 11b, and 12, and a discharge temperature sensor 40 that detects the temperature of the discharge gas. The suction pipe 31 is provided with a suction pressure sensor LP that detects the pressure of the suction gas of each of the compressors 11a, 11b, and 12, and a suction temperature sensor 41 that detects the temperature of the suction gas. The outdoor heat exchangers 16a and 16b are provided with temperature sensors 42 and 43 for detecting the inlet / outlet temperatures of the outdoor heat exchangers 16a and 16b, respectively. Further, a high pressure switch HPS is disposed between the oil separator 14 and the four-way valve 15, and a low pressure switch LPS is disposed between the four-way valve 15 and the accumulator 13. These pressure sensor, temperature sensor, and pressure switch are all connected to the outdoor control device 50, and the outdoor control device 50 acquires the pressure and temperature detected by each of these sensors and the signal output from each switch. .
The outdoor control device 50 is executed by a CPU (Central Processing Unit), a control program executed by the CPU, a ROM (Read Only Memory) that stores data related to the control program in a nonvolatile manner, and the CPU. A program, a RAM (Random Access Memory) that temporarily stores data relating to the program, and the like are provided.
The outdoor control device 50 of any of the outdoor units 2A and 2B communicates with other outdoor control devices 50 and indoor control devices in accordance with user instructions input via a remote controller (not shown), and this air conditioning Operation control of the entire apparatus 1 is performed. Specifically, in order to realize the operation instructed by the user, the outdoor control device 50 determines the start / stop of the compressor and the operation frequency based on the pressure and temperature detected by the pressure sensor and temperature sensor of the unit. Control and open / close / switch various valves.

FIG. 3 is a partial perspective view of the outdoor unit showing the arrangement configuration of the constant speed compressor 11a.
The constant speed compressor 11a is a hermetic scroll compressor, and includes a hermetic container 61 and a power supply element (not shown) housed in the hermetic container 61 and driven at a substantially constant rotational speed depending on the power frequency. And a rotary compression element (not shown) that is driven by the power supply element to compress the refrigerant. As shown in FIG. 3, the sealed container 61 is a cylindrical container that is long in the height direction, and a plurality of leg pieces 62 extending radially are provided at the lower portion of the sealed container 61.
The constant speed compressor 11a is fixed to the bottom plate 10 with a mount rubber (elastic member) 63 interposed between the leg pieces 62 and the bottom plate 10 of the outdoor unit 2A. Specifically, the leg pieces 62 and the mount rubber 63 are penetrated by bolts (fasteners) 65, and the bolts 65 are screwed to the bottom plate 10.

4 is an enlarged perspective view showing the periphery of the leg piece portion 62, FIG. 5 is a view showing an arrangement configuration of the leg piece portion 62, the mount rubber 63, and the connecting member 70, and FIG. 6 is a side view of FIG. It is sectional drawing.
4 to 6, the leg piece portion 62 includes an upper surface portion 62A and a side surface portion 62B extending downward from an edge portion of the upper surface portion 62A. The side surface portion 62B and the upper end portion of the mount rubber 63 are provided. And overlap in side view. Accordingly, the mount rubber 63 moves following the operation of the sealed container 61 and the leg piece 62, and suppresses vibration of the sealed container 61.
Further, an opening 62A1 (FIG. 6) larger than the diameter of the bolt 65 is formed in the upper surface portion 62A of the leg piece portion 62. When the sealed container 61 and the leg piece 62 are operated, the leg piece 62 swings so that the edge of the opening 62A1 does not touch the bolt 65, thereby preventing contact between the leg piece 62 and the bolt 65. Thus, an excessive step force is prevented from acting on the bolt 65.
As shown in FIG. 6, the mount rubber 63 includes a through hole 63 </ b> A through which the bolt 65 passes. Further, a protrusion 63 </ b> C that protrudes downward and fits into a hole 55 formed in the bottom plate 10 is provided on the lower surface of the mount rubber 63. The protrusion 63C fits into the hole 55, whereby the mount rubber 63 can be positioned.
A nut 66 that is screwed to the bolt 65 is welded and provided below the bottom plate 10 so that the bolt 65 can be easily tightened from above the leg piece 62.

By the way, the constant speed compressors 11a and 11b operate at a constant speed depending on the power supply frequency, and therefore, when the constant speed compressor 11a is started, a large torque is generated to rapidly follow a predetermined rotational speed. It generate | occur | produces in the airtight container 61 of constant speed compressor 11a, 11b, and this airtight container 61 vibrates. As described above, the mount rubber 63 is interposed between the leg piece portion 62 of the sealed container 61 and the bottom plate 10 and functions to suppress vibration. However, when excessive rotational torque is generated in the sealed container 61 as in the case of starting the constant speed compressor 11a, the bolt 65 is tilted with the deformation of the mount rubber 63, so that it is fixed by the nut 66. A large shearing force is generated at the lower end portion 65 </ b> A (FIG. 6) of the bolt 65, and a large stress is applied to the suction pipe 31, the discharge pipe 32, and the oil pipe 37 connected to the sealed container 61.
In this configuration, the connecting member 70 that connects the upper end portion 65B (FIG. 6) of the bolt 65 and the bottom plate 10 is provided, and the tilting of the bolt 65 due to the rotational torque acting on the sealed container 61 when the constant speed compressors 11a and 11b are started. Is regulated.

As shown in FIG. 4, the connecting member 70 is formed by bending a long sheet metal into a substantially S shape, and extends above the upper surface portion 62 </ b> A of the leg piece portion 62. A vertical plate portion 72 that extends downward from the end portion of the portion 71 and is located on the side of the leg piece portion 62 and the mount rubber 63, and an end portion of the vertical plate portion 72 is bent in a direction away from the mount rubber 63. And a fixing portion 73.
As shown in FIG. 6, the horizontal plate portion 71 is provided with a through hole 71A having a diameter similar to that of the screw portion of the bolt 65, and the upper end portion 65B of the bolt 65 is supported by the through hole 71A. In this configuration, when the sealed container 61 vibrates, the bolt 65 is fastened with a clearance that allows the leg piece 62 to swing by the vibration.
Further, as shown in FIG. 5, the vertical plate portion 72 is disposed with a gap between the leg piece portion 62. This prevents the leg piece 62 from coming into contact with the connecting member 70 when the leg piece 62 swings. The fixing portion 73 includes a hole portion 73A for fixing the connecting member 70 to the bottom plate 10 and extends on the bottom plate 10, and is fixed to the bottom plate 10 with a bolt or the like through the hole portion 73A. In addition, you may fix the fixing | fixed part 73 to the baseplate 10 by means, such as welding. According to this, the upper end portion 65 </ b> B of the bolt 65 is fixed to the bottom plate 10 via the connecting member 70. Thereby, for example, even when excessive rotational torque is generated in the sealed container 61 at the time of starting the constant speed compressor 11a, the lower end of the bolt 65 is received by receiving the rotational torque at the bent portion of the connecting member 70. The stress acting on the pipes provided in the portion 65A and the sealed container 61 can be relaxed.

Furthermore, in the present embodiment, since the connecting member 70 includes the horizontal plate portion 71 extending above the upper surface portion 62A of the leg piece portion 62, the sealed container 61 is pulled out from the sealed container 61 and the leg piece portion 62. Even if a load is applied in the direction (Y direction in FIG. 5), the load resistance in the pulling direction is improved by the connecting member 70.
According to the present embodiment, the constant speed compressors 11a and 11b are provided in the sealed container 61. The constant speed compressors 11a and 11b accommodate the electric element that is driven at a substantially constant rotational speed and the rotary compression element that is driven by the electric element and compresses the refrigerant. The constant speed compressors 11a and 11b are configured such that the leg piece portion 62 is mounted in a state where the mount rubber 63 is interposed between the plurality of leg piece portions 62 provided in the sealed container 61 and the bottom plate 10 of the outdoor unit 2A. Since the connecting member 70 is fixed on the bottom plate 10 with the bolt 65 and connects the upper end portion 65B of the bolt 65 disposed on the leg piece 62 and the bottom plate 10, the connecting member 70 is a constant speed compressor 11a, 11b. By receiving a rotational torque acting on the sealed container 61 at the time of starting, the tilting of the bolt 65 is prevented with a simple configuration in which the connecting member 70 is provided, and the bolt 65 and the sealed container 61 are connected. Stress acting on the piping was able to mitigate.

  In addition, the leg piece 62 is formed with an opening 62A1 through which the bolt 65 penetrates and has a diameter that is sufficiently larger than that of the bolt 65, so that even if the upper end portion 65B of the bolt 65 is held by the connecting member 70, The leg piece 62 swings so that the edge of the opening 62 </ b> A <b> 1 does not touch the bolt 65, thereby preventing contact between the leg piece 62 and the bolt 65, and excessive stepping force acts on the bolt 65. Is prevented.

Moreover, according to this embodiment, since the connection member 70 is formed by bending a sheet metal, the bending portion of the sheet metal can absorb stress, and the configuration can be simplified.
Moreover, according to this embodiment, since the connection member 70 is provided with the horizontal plate part 71 extended above the leg piece part 62, it is in the direction which pulls out the said airtight container 61 to the airtight container 61 and the leg piece part 62. Even if a load is applied, the load resistance in the pulling direction is improved by the connecting member 70.
Moreover, according to this embodiment, since the connection member 70 is comprised so that attachment from the upper direction of the leg piece part 62 is carried out, it connects by a simple operation | work, without putting a hand under the baseplate 10 of the outdoor unit 2A. Member 70 can be attached.
Further, according to the present embodiment, the leg piece 62 and the mount rubber 63 are fastened by the bolt 65 and the nut 66, and the nut 66 is welded to the bottom plate 10 of the outdoor unit 2A. The bolt 65 can be easily tightened from above.

Next, another embodiment will be described.
FIG. 7 is a perspective view showing the arrangement configuration of the regulating member according to another embodiment, and FIG. 8 is a front view of FIG. In this other embodiment, the same components as those in the above embodiment are denoted by the same reference numerals and description thereof is omitted.
The connecting member 80 is formed by bending a long sheet metal, and has a horizontal plate portion 81 extending above the upper surface portion 62A of the leg piece portion 62, and a leg piece extending downward from the end portion of the horizontal plate portion 81. A vertical plate portion 82 located on the side of the portion 62 and the mount rubber 63, and a fixing portion 83 for bending an end portion of the vertical plate portion 82 in a direction away from the mount rubber 63. The fixing portion 83 is formed with a hole 83A for screwing the connecting member 80 to the bottom plate 10. However, the fixing portion 83 may be fixed to the bottom plate 10 by means such as welding.
In this embodiment, as shown in FIGS. 7 and 8, an opening 56 is formed in the bottom plate 10, and the lower end of the vertical plate portion 82 is accommodated in the opening 56. The vertical plate portion 82 extends downward from the end portion of the horizontal plate portion 81 along the leg piece portion 62 and the mount rubber 63, and then is bent in the horizontal direction and further upward to form a substantially J-shape. ing.
For this reason, the vertical plate portion 82 can secure a long length of the portion 82A extending downward from the end portion of the horizontal plate portion 81 along the leg piece portion 62 and the mount rubber 63, and the two bent portions 82B. 82C, the stress applied to the connecting member 80 can be absorbed by the bent portions 82B and 82C. For this reason, the tilting of the bolt 65 is prevented with a simple configuration in which the connecting member 80 is provided by receiving the rotational torque acting on the sealed container 61 when the constant speed compressors 11a and 11b are started. The stress acting on the piping connected to the sealed container 61 can be relaxed.

As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to this. For example, the shape of the connecting member can be appropriately changed as long as the upper end portion 65B of the bolt 65 and the bottom plate 10 are connected.
For example, as shown in FIG. 9, the connecting member 90 is formed by bending a long sheet metal into a substantially U shape and extending above the upper surface portion 62 </ b> A of the leg piece portion 62, and the horizontal plate portion. A vertical plate portion 92 that extends downward from the end portion of 91 and is located on the side of the leg piece portion 62 and the mount rubber 63, and is fixed so that the end portion of the vertical plate portion 92 is bent in a direction approaching the mount rubber 63. It is good also as a structure provided with the part 93. FIG.
In this configuration, the fixing portion 93 extends below the bottom plate 10 through a long hole 57 formed in the bottom plate 10, and a nut 66 is welded to the fixing portion 93. For this reason, since the bolt 65 can be fixed at the upper end (horizontal plate portion 91) and the lower end (fixing portion 93) of the connecting member 90, the bolt 65 can be firmly held. Further, in this configuration, since the strength of the bottom plate 10 is reinforced by the thickness of the fixing portion 93, the load resistance in the direction of pulling out the sealed container 61 and the leg piece portion 62 is improved.
Further, as shown in FIG. 10, the connecting member 100 is formed by bending a long sheet metal into a substantially U shape and extending above the upper surface portion 62 </ b> A of the leg piece portion 62, and the horizontal plate portion. A vertical plate portion 102 that extends downward from the end portion of the 101 and is located on the side of the leg piece portion 62 and the mount rubber 63, and is fixed so that the end portion of the vertical plate portion 102 is bent in a direction approaching the mount rubber 63. It is good also as a structure provided with the part 103. FIG. In this configuration, the fixing portion 103 is disposed between the bottom plate 10 and the mounting rubber 63, and is fixed by a bolt 65 that fixes the leg piece portion 62 and the mounting rubber 63. Needless to say, the fixing portion 103 and the bottom plate 10 may be fixed with separate bolts at the tip of the fixing portion 103.
Further, in the above-described embodiment, the connecting members are provided in all the leg pieces 62, but it is sufficient that they are provided in at least one leg piece 62.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2A, 2B Outdoor unit 3A, 3B Indoor unit 10 Bottom plate 11a, 11b Constant speed compressor 12 Inverter compressor 16a, 16b Outdoor heat exchanger 17a, 17b Outdoor expansion valve 31 Suction pipe 32 Discharge pipe 37 Oil pipe 59 Opening 61 Sealed container 62 Leg piece 62A1 Opening 63 Mount rubber 65 Bolt 66 Nut 70, 80, 90, 100 Restricting member 71, 81, 91, 101 Horizontal plate (part)
72, 82, 92, 102 Vertical plate part 73, 83, 93, 103 Fixed part

Claims (6)

  A constant speed compressor containing an electric element that is driven at a substantially constant rotational speed and a rotary compression element that is driven by the electric element and compresses a refrigerant is contained in the hermetic container. In an air conditioner in which an elastic member is interposed between a plurality of leg pieces provided on the bottom plate and the bottom plate, the leg piece is fixed on the bottom plate with a fastener, and at least one leg piece is provided on the air conditioner. An air conditioning apparatus comprising: a connecting member that connects an upper end portion of the fastener to be disposed and the bottom plate.   The air conditioner according to claim 1, wherein an opening having a diameter sufficiently larger than that of the fastener is formed in the leg piece portion.   The air conditioner according to claim 1 or 2, wherein the connecting member is formed by bending a sheet metal.   The air conditioner according to any one of claims 1 to 3, wherein the connecting member includes a portion extending above the leg piece.   The air conditioner according to any one of claims 1 to 4, wherein the connecting member is configured to be attachable from above the leg piece.   The air conditioner according to any one of claims 1 to 5, wherein the fastener includes a bolt and a nut, and the nut is welded to the bottom plate.

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