Fastening structure and fastening method

Abstract

To provide a fastening tool and a fastening method that can easily fasten a first member and a second member.SOLUTION: A fastening tool comprises a first bolt, a second bolt, and a nut. The first bolt comprises a first head part, and a first shaft part extending from the first head part. The second bolt comprises a second head part, and a second shaft part extending from the second head part. The first head part comprises a screw hole capable of receiving the second shaft part. In the first bolt, the first shaft part can be screwed to the nut, and the screw hole can be screwed to the second shaft part. The first bolt and the nut are screwed together via a first member and fixed to the first member, the first bolt and the second bolt are screwed together via a second member, and thereby the second member is fastened to the first member.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fastener and a fastening method using the fastener. [Background technology]

[0002] Conventionally, a method using a fastener consisting of a bolt and a nut has been known as a method for fixing a second member to a first member. A typical fastening method using such a fastener, as described in Patent Documents 1 and 2, includes a method in which a bolt is inserted into a through-hole formed in each of the first member and the second member, and the bolt and the nut are screwed together to fasten the second member to the first member.

[0003] A cooling tower is an example of equipment that uses such fasteners. A cooling tower is used to cool and circulate hot water discharged from air conditioning equipment in a building or the like. It includes a heat exchanger that cools the hot water and a hot water tank that supplies hot water to the heat exchanger. The above-described fasteners are used in this hot water tank. In the hot water tank 5 shown in FIG. 4, the hot water tank 5, which is a second member, is fixed to a U-shaped base 50, which is a first member. The base 50 has an upper plate 503 on which the hot water tank 5 is placed. The hot water tank 5 has a bottom wall 511 with multiple spray holes 511h formed therein, a side wall 512 rising from the outer edge of the bottom wall 511, and a flange 513 extending horizontally from the upper end of the side wall 512. In the conventional method, the hot water tank 5 is fastened to the stand 50 by inserting the bolt b into the bolt holes formed in the upper plate portion 503 of the stand 50 and the flange portion 513 of the hot water tank 5, and then screwing the bolt b into the nut n. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-047810 [Patent Document 2] Japanese Patent Publication No. 2020-193825 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional method using fasteners has a problem in that when fixing a second member to a first member, the bolt and nut must be fastened while the nut is held with fingers, etc., which makes the work difficult. For example, as shown in Fig. 4, when fastening a hot water tank 5 to a frame 50 of a cooling tower, it is necessary to form a construction hole h in a side wall 512 of the hot water tank 5, and insert a finger or the like through the construction hole h to hold the nut n, while inserting a bolt b into the nut n.

[0006] In view of the above problems, an object of the present invention is to provide a fastener and a fastening method that can easily fasten a first member and a second member together. [Means for solving the problem]

[0007] A fastener according to one aspect of the present invention comprises: used to fasten a second member to a first member; A first bolt, a second bolt, and a nut are provided, The first bolt has a first head and a first shank extending from the first head, the second bolt has a second head and a second shank extending from the second head, the first bolt has a screw hole that receives the second shaft portion from the first head portion, The first bolt has a first shaft portion that can be threadedly engaged with the nut and a screw hole that can be threadedly engaged with the second shaft portion, The first bolt and the nut are threadedly engaged with each other via the first member to fix them to the first member, and the first bolt and the second bolt are threadedly engaged with each other via the second member to fasten the second member to the first member.

[0008] A fastening method according to one aspect of the present invention includes: fastening the second member to the first member using a fastener; The fastener includes a first bolt, a second bolt, and a nut; The first bolt has a first head and a first shank extending from the first head, the second bolt has a second head and a second shank extending from the second head, the first bolt has a screw hole that receives the second shaft portion from the first head portion, The first bolt has a first shaft portion that can be threadedly engaged with the nut and a screw hole that can be threadedly engaged with the second shaft portion, The first bolt and the nut are threaded together via the first member to fix them to the first member, and the first bolt and the second bolt are threaded together via the second member to fasten the second member to the first member.

[0009] With this configuration, the first bolt and nut are fixed to the first member, so when fastening the first member and the second member, the second bolt and the first bolt can be screwed together simply by inserting the second shank of the second bolt into the threaded hole of the first bolt, thereby facilitating fastening the first member and the second member. [Effects of the Invention]

[0010] As described above, the present invention can provide a fastener and a fastening method that can easily fasten a first member and a second member together. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a cooling tower with a fastener according to an embodiment. [Figure 2] 2 is a schematic cross-sectional view of a fastening structure including the fastener of FIG. 1. [Figure 3] FIG. 10 is a top view of a fastener according to another embodiment. [Figure 4] 1 is a schematic cross-sectional view of a fastening structure including a prior art fastener; DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a fastener according to one embodiment of the present invention will be described, taking as an example a case where it is applied to a hot water tank of a cooling tower.

[0013] As shown in Fig. 1, the cooling tower 100 includes a rectangular prism-shaped tower body 100a that houses the heat exchange unit 1, a fan 2 that generates an airflow W inside the tower body 100a, a cylindrical fan stack 3 that forms an exhaust path for the airflow W from the tower body 100a, a hot water supply unit 4 that supplies hot water to the heat exchange unit 1, a hot water tank 5 that relays the hot water supplied from the hot water supply unit 4 to the heat exchange unit 1, and a cold water tank 6 that stores the hot water cooled in the heat exchange unit 1 as cold water. Note that, hereinafter, in the cooling tower 100 of Fig. 1, a first direction parallel to the horizontal plane will be referred to as the left-right direction (D1), a second direction perpendicular to the left-right direction D1 and parallel to the horizontal plane will be referred to as the front-back direction (D2), and a third direction perpendicular to both the left-right direction D1 and the front-back direction D2 will be referred to as the up-down direction (D3).

[0014] The tower body 100a has a rectangular prism-shaped cavity V in the center thereof extending in the vertical direction D3. The tower body 100a also has an upper surface portion on which the fan stack 3 and the like are placed. The upper surface portion is formed along a horizontal plane and opens upward so as to connect the cavity V with the exhaust path of the fan stack 3.

[0015] The heat exchange unit 1 is arranged around the cavity V. The heat exchange unit 1 has multiple cooling sections 11 that cool the hot water by bringing it into contact with outside air. Each cooling section 11 has multiple block-shaped fillers stacked in the vertical direction D3. Each filler is composed of multiple filler sheets. The filler sheets are parallelogram-shaped in plan view, with multiple protrusions on one side. Each filler is formed into a block shape by vertically placing multiple filler sheets and arranging them in the front-to-back direction D2. In addition, each filler sheet abuts the tips of the protrusions of one filler sheet against the adjacent filler sheet, forming gaps between the filler sheets that can serve as passages for the airflow W.

[0016] Each cooling unit 11 is formed in the shape of a rectangular pillar by stacking block-shaped filler material in multiple stages in the up-down direction D3. In this embodiment, a pair of cooling units 11 is installed on both sides in the left-right direction D1 with a cavity V interposed therebetween. Each cooling unit 11 is arranged so that the gaps in the filler material communicate with the cavity V. As the fan 2 sucks out the air in the cavity V, outside air is drawn into the gaps in the filler material. The hot water cooled by contact with outside air in the heat exchange unit 1 becomes cold water and is stored in the cold water tank 6 installed below the heat exchange unit 1.

[0017] The fan 2 is disposed above the cavity V. The fan 2 is configured to generate an airflow W that moves upward through the exhaust path of the fan stack 3 when driven. The fan 2 has a rotation shaft 21 extending in the vertical direction D3 and a plurality of rotor blades 22 extending horizontally from the rotation shaft 21. The fan stack 3 extends in the same direction as the rotation shaft 21 of the fan 2 housed therein.

[0018] The hot water supply unit 4 is installed above the hot water tank 5. The hot water supply unit 4 has a hot water discharge unit 41 that discharges hot water into the hot water tank 5.

[0019] The hot water tank 5 is installed above the heat exchange unit 1. More specifically, one hot water tank 5 is installed above each cooling unit 11. As shown in FIG. 2, the hot water tank 5 of this embodiment is composed of a sprinkler tank 51 that sprinkles hot water on the cooling units 11 in the heat exchange unit 1, and a buffer tank 52 installed above the sprinkler tank 51. The hot water tank 5 of this embodiment is placed on a stand 50 made of shaped members.

[0020] The platform 50 is composed of a pair of U-shaped members. The pair of members are installed along the front-rear direction D2 so that each member opens inward. As a result, the platform 50 includes a lower plate portion 501 that is grounded on the upper surface of the tower body 100a and extends in the front-rear direction D2, a side plate portion 502 that rises from the outer edge of the lower plate portion 501, and an upper plate portion 503 that extends horizontally from the tip of the side plate portion 502 so as to face the lower plate portion 501 in the up-down direction D3. The platform 50 may be provided with a grip portion such as a handrail to facilitate various tasks, such as maintenance. Therefore, the platform 50 is installed with an inward opening to facilitate the installation of the grip portion. More specifically, the grip portion is preferably provided on the outer surface of the side plate portion 502. On the other hand, a platform in which such a grip portion is provided on the inner surface of the side plate portion 502 has a more complicated structure and is not preferred.

[0021] Spray tank 51 has a rectangular bottom wall 511 facing the upper surface of cooling unit 11, an annular side wall 512 rising from the outer edge of bottom wall 511, and a flange 513 extending outward from the upper end of side wall 512. Bottom wall 511 is formed with a plurality of circular spray holes 511h for spraying hot water. Hot water that reaches spray holes 511h falls into cooling unit 11 through spray holes 511h by the action of gravity. This enables spray tank 51 to spray hot water to a plurality of locations on heat exchange unit 1 through spray holes 511h. Flange 513 (hereinafter referred to as lower flange 513) is a portion that is placed on upper plate 503 of frame 50, and is formed to fit along a horizontal plane.

[0022] Buffer tank 52 functions to buffer the force of hot water dropping from hot water discharge section 41. Buffer tank 52 is formed in the shape of a rectangular box. Buffer tank 52 has buffer surface section 521, which is a bottom surface disposed between hot water discharge section 41 and bottom wall section 511 of spray tank 51 and buffers the force of the dropping hot water; side surface section 522 rising from the outer edge of buffer surface section 521; and top surface section 523, which closes the upper end of side surface section 522. Top surface section 523 is formed with opening 523h for receiving hot water dropping from hot water discharge section 41 into the buffer tank. Furthermore, buffer surface section 521 is formed in a lattice pattern; in other words, it has a plurality of elongated discharge holes for discharging the received hot water toward bottom wall section 511 of spray tank 51. Furthermore, upper surface portion 523 has flange portion 524 (hereinafter referred to as upper flange portion 524) extending outward from the upper end portion of side surface portion 522. Upper flange portion 524 is a portion placed on lower flange portion 513 of watering trough 51, and is formed so as to fit along a horizontal plane.

[0023] Spray tank 51 and buffer tank 52 are tanks that require regular maintenance or repair because they can become contaminated by foreign matter contained in the hot water that is the fluid supplied. For example, spray holes 511h of spray tank 51 and the discharge holes of buffer tank 52 can be clogged by foreign matter contained in the hot water, making it necessary to remove the foreign matter. Therefore, spray tank 51 and buffer tank 52 are preferably configured to be detachable from stand 50, which can improve the ease of maintenance or repair work.

[0024] Specifically, hot water tank 5 has a fastening structure in which sprinkler tank 51, a second member, and buffer tank 52, a third member, are fixed to frame 50, a first member, by fasteners 7 according to one embodiment of the present invention. Fasteners 7 are composed of detachable bolts and nuts. To enable fastening with fasteners 7, each member is formed with a bolt hole, which serves as a through-hole through which a bolt is inserted. That is, first bolt hole 531 is formed in upper plate 503 of frame 50, second bolt hole 532 is formed in lower flange 513 of sprinkler tank 51, and third bolt hole 533 is formed in upper flange 524 of buffer tank 52. In this embodiment, second bolt hole 532 and third bolt hole 533 have the same diameter, and first bolt hole 531 is larger than second bolt hole 532 and third bolt hole 533. The bolt holes are arranged so that their central axes are aligned on the same straight line. The inner wall defining each bolt hole may be cylindrical with a curved surface without a female thread. Alternatively, the inner wall may have a female thread that screws onto the bolt, or may have a female thread that screws onto the bolt partially or entirely.

[0025] The fastening structure has space S surrounded by lower plate portion 501, side plate portion 502, and upper plate portion 503 of frame 50, and side wall portion 512 of sprinkler trough 51. Space S is directly connected to first bolt hole 531. As a result, the tip of the bolt of fastener 7 and a nut that threads onto the bolt are disposed in space S. The horizontal gap between lower plate portion 501 of frame 50 and side wall portion 512 of sprinkler trough 51 is 10 mm or less. Therefore, it is difficult to insert fingers or a tool into this gap to grasp the nut.

[0026] The fastener 7 of this embodiment includes a first bolt 71 inserted through the first bolt hole 531 and a nut 73 that screws onto the first bolt 71. The fastener 7 of this embodiment also includes a second bolt 72. The first bolt 71 has a head 711 (hereinafter referred to as the first head 711) and a shank 712 (hereinafter referred to as the first shank 712) extending from the head 711. The second bolt 72 has a head 721 (hereinafter referred to as the second head 721) and a shank 722 (hereinafter referred to as the first shank 722) extending from the head 721. Each of the first shank 712 and the second shank 722 of this embodiment has a screw thread on its outer circumferential surface.

[0027] The fastener 7 of this embodiment is not limited to the following, but the first head 711 of the first bolt 71 has a larger diameter than the first shank 712 of the first bolt 71, and the second head 721 of the second bolt 72 has a larger diameter than the second shank 722 of the second bolt 72. The first bolt 71 is thicker than the second bolt 72, and the second bolt 72 is longer than the first bolt 71. More specifically, the first shank 712 has a larger diameter than the second shank 722. The second shank 722 has a length equal to or greater than the entire length of the first bolt 71. The nut 73 is threadably engageable with the first shank 712 of the first bolt 71, and has a threaded hole with a diameter corresponding to the first shank 712.

[0028] The first bolt 71 of this embodiment has a polygonal, plate-shaped (more specifically, hexagonal plate-shaped) first head 711 and a first shank 712 extending from the first head 711. The first head 711 of this embodiment has a larger dimension in the planar direction (left-right direction D1 in FIG. 2 ) than in the thickness direction (up-down direction D3 in FIG. 2 ). The first head 711 has a first surface (bottom surface in FIG. 2 ) that is one of both end surfaces in the thickness direction, and a second surface (top surface in FIG. 2 ) that is the surface opposite the first surface. The first shank 712 extends cylindrically from the center of the first surface of the first head 711 in the thickness direction of the first head 711. The first shank 712 has a male thread portion for threadably engaging with the nut 73. The first bolt 71 is configured to advance toward the nut 73 by rotating clockwise when viewed from above, and to retract from the nut 73 by rotating counterclockwise. The fastening structure has a first fastening portion composed of a first bolt 71, the gantry 50 as the first member, and a nut 73. The first fastening portion fastens each part by applying a compressive force to the upper plate portion 503 with a first head portion 711 that presses the upper plate portion 503 of the gantry 50 from above and a nut 73 that presses the upper plate portion 503 from below. Furthermore, the first fastening portion prevents the first bolt 71 and the nut 73 from loosening by applying an axial force (tensile force) against the compressive force. Thus, the first fastening portion has the first bolt 71 and the nut 73 fixed to the upper plate portion 503 of the gantry 50.

[0029] Furthermore, the first bolt 71 of this embodiment has a threaded hole 713 that opens at the center of the second surface of the first head 711. The threaded hole 713 passes through the first head 711 in the thickness direction and extends to the first shank 712. The threaded hole 713 further extends through the first shank 712 and opens at the tip surface of the first shank 712. In this way, the threaded hole 713 is provided so as to penetrate the first bolt 71 over its entire length, making the first shank 712 cylindrical. The threaded hole 713 has a diameter corresponding to the second shank 722. In other words, the first shank 712 of the first bolt 71 can be threadedly engaged with the nut 73, and the first head 711 can be threadedly engaged with the second bolt 72. Note that the threaded hole 713 may have a female thread formed over the entire length of its inner surface. In addition, the screw hole 713 may have a female thread portion formed partially along the length of the inner surface, in other words, it may be composed of a threaded male thread portion and a cylindrical portion with a curved inner surface.

[0030] The threaded hole 713 may be provided so that its central axis coincides with or does not coincide with that of the first shaft portion 712. In this embodiment, the central axis of the threaded hole 713 coincides with that of the first shaft portion 712 and is on the same straight line as the central axis of the first shaft portion 712.

[0031] 2, in this embodiment, the second surface (upper surface) of first head portion 711 and the third surface (lower surface) of second head portion 721 are planar and parallel to each other. When a compressive force is applied to sprinkler tank 51 or buffer tank 52 for the purpose of preventing inadvertent displacement of these with respect to frame 50, the planar shape as described above can ensure a larger area in contact with lower flange portion 513 and upper flange portion 524 than a curved surface such as a dome shape.

[0032] The second bolt 72 of this embodiment has a polygonal, plate-shaped (more specifically, hexagonal plate-shaped) second head 721 and a second shank 722 extending from the second head 721. The second head 721 has a larger dimension in the planar direction (left-right direction D1 in FIG. 2) than in the thickness direction (up-down direction D3 in FIG. 2). The second head 721 has a third surface (bottom surface in FIG. 2) that is one surface in the thickness direction, and a fourth surface (top surface in FIG. 2) that is the surface opposite the third surface. The second shank 722 extends in a cylindrical shape from the center of the third surface of the second head 721 in the thickness direction of the second head 721. The second shank 722 has a male thread that screws into the threaded hole 713 of the first head 711. Second bolt 72 is configured to advance into threaded hole 713 by rotating clockwise as viewed from above, and to retract from threaded hole 713 by rotating counterclockwise. That is, the advancement of second bolt 72 relative to threaded hole 713 and the advancement of first bolt 71 relative to nut 73 are performed in the same rotational direction (clockwise). The fastening structure has a second fastening portion composed of second bolt 72, sprinkler tank 51 as the second member, buffer tank 52 as the third member, and threaded hole 713 of first bolt 71. The second fastening portion applies a compressive force to upper flange 524 and lower flange 513 between second head 721, which presses upper flange 524 of buffer tank 52 from above, and first head 711, which presses lower flange 513 of spray tank 51 from below, thereby fastening the respective parts.

[0033] Furthermore, according to the fastener 7 of this embodiment, the first bolt 71 and the nut 73 are fixed to the frame 50 in advance, so that the second bolt 72 can be easily attached to and detached from the screw hole 713 of the first bolt 71 simply by rotating the second bolt 72 around its axis, without having to grasp the nut 73 with fingers or a tool.

[0034] Furthermore, by employing fastener 7, the fastening structure allows sprinkler tank 51 and buffer tank 52 to be easily attached and detached from frame 50 for maintenance without the need to form construction holes in side wall 512 of sprinkler tank 51 and grip nuts 73 with fingers or tools, as was necessary in the prior art. Furthermore, it is possible to eliminate hot water leakage caused by the construction holes.

[0035] Furthermore, in the fastening structure, first head 711 of first bolt 71 is sandwiched between upper plate portion 503 of frame 50 and lower flange portion 513 of spray tank 51. Therefore, even if nut 73 on first bolt 71 is inadvertently loosened, the fixed state of first bolt 71 to frame 50 can be maintained.

[0036] Next, a fastening method according to one embodiment of the present invention will be described.

[0037] The fastening method of the present embodiment includes fastening sprinkler tank 51, which is the second member, and buffer tank 52, which is the third member, to frame 50, which is the first member, using fastener 7 of the above embodiment. More specifically, the fastening method of the present embodiment includes a first fastening step of fixing first bolt 71 and nut 73 to frame 50 to form the first fastening portion, and a second fastening step of threading first bolt 71 and second bolt 72 into threaded holes 713 in the state where lower flange 513 of sprinkler tank 51 and upper flange 524 of buffer tank 52 are arranged between first bolt 71 and second bolt 72 (in an overlapping state), thereby forming the second fastening portion.

[0038] In the first fastening step, the first bolt 71 is inserted into the first bolt hole 531, which is a through hole formed in the upper plate portion 503 of the frame 50, and the first bolt 71 and the nut 73 are screwed together to fix the first bolt 71 and the nut 73 to the upper plate portion 503, thereby forming the first fastening portion.

[0039] In the second fastening step, first, the screw hole 713 of the first bolt 71 is aligned with the second bolt hole 532 of the lower flange 513 and the third bolt hole 533 of the upper flange 524. Then, the second bolt 72 is inserted through the second bolt hole 532 and the third bolt hole 533, and the second bolt 72 is screwed into the screw hole 713 of the first bolt 71 to fasten the upper plate portion 503 to the lower flange 513 and the upper flange 524, thereby forming the second fastening portion.

[0040] According to the fastening method of this embodiment, the first bolt 71 and the nut 73 are fixed to the upper plate 503 of the gantry 50 at the first fastening portion. Therefore, the second bolt 72 can be screwed into the threaded hole 713 of the first bolt 71 simply by rotating the second bolt 72 clockwise, without having to grip the first bolt 71 or the nut 73 with fingers or the like. This facilitates fastening between the gantry 50 and each tank. Furthermore, when attempting to remove each tank from the gantry 50, the second bolt 72 can be retracted from the threaded hole 713 of the first bolt 71 simply by rotating the second bolt 72 counterclockwise, without having to grip the first bolt 71 or the nut 73 with fingers or the like. This facilitates attachment and detachment during maintenance or repair.

[0041] The fastener and fastening method according to the present invention are not limited to the above-described embodiment. Furthermore, the fastener and fastening method according to the present invention are not limited by the above-described effects. The fastener and fastening method according to the present invention can be modified in various ways without departing from the gist of the present invention.

[0042] For example, in the fastening structure, the distance between the second surface (upper surface) of the first head 711 and the third surface (lower surface) of the second head 721 may be made slightly larger than the thickness of the member sandwiched between them and fixed to the gantry 50 (specifically, the total thickness of the lower flange 513 and the upper flange 524) to provide play. In other words, in the fastening structure, no compressive force may be applied to the member sandwiched between the first head 711 and the second head 721 and fixed to the gantry 50.

[0043] On the other hand, when a compressive force is applied, the compressive force applied to lower flange 513 or upper flange 524 does not necessarily have to be between the second surface (upper surface) of first head 711 and the first surface (lower surface) of second head 721, and may also be between second head 721 and upper plate 503. For example, as shown in FIG. 3 , by making the shape of second bolt hole 532 larger than first head 711 and setting the thickness of first head 711 equal to or smaller than the thickness of lower flange 513 and positioning first head 711 in second bolt hole 532, a compressive force can be applied to lower flange 513 or upper flange 524 without applying the tightening force of second bolt 72 to first head 711. Furthermore, if it is difficult to make first head portion 711 equal to or smaller than the thickness of lower flange portion 513, third bolt hole 533 can also be made larger than first head portion 711, and second head portion 712 can be made larger than third bolt hole 533, or a flat washer or the like can be interposed between second head portion 712 and upper flange portion 524. As the flat washer, one having an inner diameter larger than second shank portion 722 and smaller than second head portion 721, and an outer diameter larger than third bolt hole 533 can be used. If the lower flange portion 513 is placed on the first head portion 711, the load of the sprinkler tank 51 and the buffer tank 52 will be concentrated on the first bolt 71, but by making the shape of the second bolt hole 532 larger than the first head portion 711 and abutting the lower flange portion 513 against the upper plate portion 503 of the frame 50 without going through the first head portion 711, a larger area can be secured to support the load of the sprinkler tank 51 and the buffer tank 52.

[0044] If compressive force or the load of the watering tank 51 or the buffer tank 52 is not applied to the first head 711, loosening the second bolt 72 while pressure is being applied from above to the upper flange 524 may cause the first bolt 71 to rotate with the nut 73, loosening the fastening. Such inadvertent loosening may result in the nut 73 falling off. To prevent this, the thickness of the nut 73 may be made less than the length of the first shank 712, the first shank 712 may pass through the nut 73, and the tip of the first shank 712 may protrude from the nut 73 on the side opposite to the side where the first shank 712 enters the nut 73, and another nut (second nut) may be attached to this protruding portion to form a double nut structure. In this way, when the length of the first shaft portion 712 is made greater than the thickness of the nut 73 and an area that can protrude from the nut 73 is provided at the tip of the first shaft portion 712, instead of or in addition to a double nut, a resin cap may be attached to the tip of the first shaft portion 712, or the nut and first shaft portion 712 may be bonded together with an adhesive to prevent loosening, such as Loctite (trade name).

[0045] Alternatively, a portion (thin diameter portion) where the diameter of the screw hole 713 is slightly smaller than that of the second shaft portion 722 may be provided at the tip side of the first shaft portion 712, and a notch extending from the tip to the base end of the first shaft portion 712 may be provided at the tip portion of the first shaft portion 712, and these notches may be provided at multiple locations in the circumferential direction, so that when the second shaft portion 722 enters further tip-side than the thin diameter portion, the tip portion of the first shaft portion 712 opens outward and expands in diameter, thereby preventing the nut 73 from falling off.

[0046] Furthermore, the shape of second bolt hole 532 may be such that it interferes with first head 711 when it attempts to rotate around its axis, thereby restricting co-rotation of first bolt 71 when loosening second bolt 72. For example, if first head 711 is shaped like a hexagonal plate, second bolt hole 532 may be shaped like an elongated hole with a width that is equal to or greater than the distance between opposing sides of the hexagon and less than the length of the diagonal of the hexagon, thereby making it possible to prevent free rotation of first head 711 located in second bolt hole 532 and to prevent co-rotation of first bolt 71 with second bolt 72.

[0047] The first head portion may be configured to fit into the second bolt hole and the third bolt hole. That is, the first head portion may have a fitting portion extending opposite (upward from) the first shaft portion and fitting into the second bolt hole and the third bolt hole, and the screw hole may open upward in the fitting portion and extend downward from the fitting portion. Temporary fastening by fitting can further facilitate fastening the sprinkler tank and the buffer tank to the frame. [Explanation of symbols]

[0048] 100: cooling tower, 100a: tower body, V: cavity, 1: heat exchange section, 11: cooling section, 2: fan, 21: rotating shaft, 22: rotor, W: air flow, 3: fan stack, 4: hot water supply section, 41: hot water discharge section, 5: hot water tank, 50: frame, 501: lower plate section, 502: side plate section, 503: upper plate section, 51: sprinkler tank, 511: bottom wall section, 511h: sprinkler hole, 512: side wall section, 513: lower flange section, 52: buffer tank, 521: buffer Face portion, 522: side portion, 523: top surface portion, 523h: opening, 524: upper flange portion, 531: first bolt hole, 532: second bolt hole, 533: third bolt hole, 6: cold water tank, 7: fastener, 71: first bolt, 711: first head portion, 712: first shaft portion, 713: screw hole, 72: second bolt, 721: second head portion, 722: second shaft portion, 73: nut, S: space, D1: left-right direction, D2: front-back direction, D3: up-down direction

Claims

1. A fastening structure using a fastener, the fastener comprises a first bolt, a second bolt, and a nut; The first bolt has a first head and a first shank extending from the first head, The second bolt has a second head and a second shank extending from the second head, the first bolt has a screw hole that receives the second shank from the first head, The first bolt has a first shaft portion that can be threadedly engaged with the nut and a screw hole that can be threadedly engaged with the second shaft portion, the fastening structure includes a first member and a second member fastened to the first member, a first through hole is formed in the first member; a second through hole is formed in the second member; In the fastening structure, the first bolt and the nut are screwed together through the first through hole to fix them to the first member, and the first bolt and the second bolt are screwed together through the second through hole with the first head positioned in the second through hole so that the first member abuts against the second member, thereby fastening the second member to the first member, and the compressive force of the first bolt and the second bolt acts on the first member via the second member.

2. fastening the second member to the first member with a fastener; a first through hole is formed in the first member; a second through hole is formed in the second member; the fastener comprises a first bolt, a second bolt, and a nut; The first bolt has a first head and a first shank extending from the first head, The second bolt has a second head and a second shank extending from the second head, the first bolt has a screw hole that receives the second shank from the first head, The first bolt has a first shaft portion that can be threadedly engaged with the nut and a screw hole that can be threadedly engaged with the second shaft portion, a fastening method including: threading the first bolt and the nut together through the first through hole to fix them to the first member; threading the first bolt and the second bolt together through the second through hole with the first head positioned in the second through hole so that the first member abuts the second member; and fastening the second member to the first member so that a compressive force of the first bolt and the second bolt acts on the first member via the second member.

3. fastening a third member together with the second member to the first member using the fastener; 3. The fastening method according to claim 2, wherein the first bolt and the second bolt fixed to the first member are threadedly engaged with each other via the second member and the third member, thereby fastening the third member together with the second member to the first member.

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