U-bolt, monitoring device and monitoring method

Abstract

A U-bolt (1) according to the present invention is provided with: a pair of shaft portions (111) that are aligned along a first direction and extend in a second direction perpendicular to the first direction; threaded portions (12) respectively provided in the pair of shaft portions (111); and electronic parts (15) that are respectively provided in the pair of shaft portions and detect the descent of a nut (4).

Description

[Technical field]

[0001] The present disclosure relates to a U-bolt, a monitoring device, and a monitoring method. [Background technology]

[0002] Conventionally, U-bolts are used to fix objects such as pipes to objects such as frames and walls. A U-bolt is a U-shaped bolt with two straight shafts connected by a bridge section. The shafts of the U-bolt are inserted into two through holes provided in the object to be fastened while the object to be fastened is sandwiched inside the U-bolt, and the two shafts are tightened with nuts from the ends of each of the two shafts, so that the object to be fastened can be sandwiched and fixed between the U-bolt and the object to be fastened. Figure 22 shows the structure when a U-bolt is used to fix an object to be fastened, such as pipes, to an object to be fastened. When a U-bolt is used to fix an object to be fastened, such as pipes, the left and right nuts are fastened to fix the object to the object to be fastened. However, when the U-bolt is used outdoors for a long period of time, the nuts may loosen due to aging, causing the object to be fastened, such as pipes, to come off, or the metal fittings of the object to be fastened to come off. Furthermore, when the nuts loosen, they may eventually come off the U-bolt, causing the U-bolt to fall and cause an accident in which the U-bolt comes into contact with a person, a car, or the like. Therefore, it is necessary to prevent the nuts from loosening completely and falling.

[0003] Nuts that are less likely to loosen than before have been developed, but when used to tighten a U-bolt, the left and right nuts must be tightened with the same tightening force. Non-Patent Document 1 describes a performance evaluation of a super slit nut (SSN) equipped with a new anti-loosening mechanism. However, since it is very difficult to make the fastening force of the left and right sides of a U-bolt the same in terms of work, the performance of such anti-loosening nuts is not exhibited, and the nuts may loosen and ultimately fall. In addition, as a conventional technology, a technology has been developed to detect falling objects such as falling rocks using a cable sensor. Non-Patent Document 2 describes the results of a study on the applicability of a monitoring system for rock slope collapse or falling rocks using a cable sensor to various locations. However, this technology is intended for falling objects with large weight such as falling rocks that fall a long distance, and is therefore not suitable for detecting the falling nuts of U-bolts that fall a short distance and are light in weight. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Satoshi Izumi and 7 others, "Functional Verification of Super Slit Nuts with Anti-Loosening Performance Using Finite Element Method," Transactions of the Japan Society of Mechanical Engineers (Series A), Vol. 71, No. 703 (March 2005) [Non-Patent Document 2] Masuyuki Uehara et al., "Sensitivity Characteristics of Steel Wire Cable Sensor for Vibration Detection," Proceedings of the Hokkaido Branch of the Japan Society of Civil Engineers, No. 56(A), pp. 204-207, 2000 Summary of the Invention [Problem to be solved by the invention]

[0005] The purpose of this disclosure, made in consideration of such circumstances, is to provide a U-bolt having both a mechanism that prevents the nut connected to the U-bolt from falling even if it becomes loose, and a mechanism that detects the nut's falling due to loosening, and a monitoring device and monitoring method for monitoring the nut's falling from the U-bolt due to loosening. Note that in this specification, "nut falling" refers to the nut coming completely off the shaft, and "nut falling" refers to the nut coming off the threaded portion provided on the shaft and getting caught on a member (such as a base portion, a rod-shaped member, or an insulated electric wire, which will be described later) mounted on the tip side of the shaft. [Means for solving the problem]

[0006] In order to solve the above problems, the U-bolt disclosed herein is a U-bolt that fastens a fastener using a nut, and includes a pair of shanks aligned in a first direction and extending in a second direction perpendicular to the first direction, a threaded portion provided on each of the pair of shanks, and an electronic component provided on each of the pair of shanks for detecting the descent of the nut.

[0007] In order to solve the above problems, the monitoring device of the present disclosure is a monitoring device that monitors the descent of a nut from a U-bolt, and includes a U-bolt having an electronic component that detects the descent of the nut and a transmitting unit that transmits the detection result by the electronic component, a receiving unit that receives the detection result transmitted from the transmitting unit, a control unit that determines whether the nut has been descent based on the detection result, and an alert issuing unit that issues an alert when the control unit determines that the nut has been descent.

[0008] In order to solve the above problems, the monitoring method disclosed herein is a monitoring method for monitoring the descent of a nut from a U-bolt, and includes the steps of detecting the descent of the nut by a monitoring device, transmitting a detection result detecting the descent of the nut, receiving the detection result, determining whether or not the nut has descent based on the detection result, and issuing an alert when it is determined that the nut has descent. Effect of the Invention

[0009] According to the present disclosure, a drop due to a loose nut can be detected and a drop due to a loose nut can be prevented. [Brief description of the drawings]

[0010] [Figure 1] 3A to 3C are diagrams illustrating an example of the configuration of a U-bolt according to the first embodiment. [Diagram 2] This is a diagram showing a structure in which a base part having an elastic member attached to one end is housed in a hole opened in the shaft part of a U-bolt. [Figure 3A] 13 is a diagram showing the state in which the base portion is stored inside the open hole when the nut is attached. FIG. [Figure 3B] 13 is a diagram showing the state in which the base portion protrudes outside the open hole after the nut is attached. FIG. [Figure 3C] 13 is a diagram showing the state in which the base portion becomes a stopper when the nut is lowered. FIG. [Figure 4A] FIG. 13 is a diagram showing a base portion having an elastic member attached to one end thereof in a cylindrical shape. [Figure 4B] FIG. 13 is a diagram showing a base portion having an elastic member attached to one end thereof, which is processed into a tapered shape. [Figure 5A] FIG. 1 is a diagram showing an example of the configuration of a U-bolt equipped with a contact sensor or a distance sensor. [Figure 5B] 11A to 11C are diagrams showing the positional states of the nut and the contact sensor or the distance sensor when the nut is fastened and lowered. [Figure 5C] This is a nut descent determination table. [Figure 6A] FIG. 1 is a diagram showing an example of the configuration of a U-bolt equipped with an electronic component having a switch. [Figure 6B] 11A and 11B are diagrams showing the positional states of the nut and the switch when the nut is fastened and when it is lowered. [Figure 6C] This is a nut descent determination table. [Figure 7A] FIG. 1 is a diagram showing an example of the configuration of a U-bolt on which an electronic component having a metal plate is mounted. [Figure 7B]11A and 11B are diagrams showing the positional states of the nut and the metal plate when the nut is tightened and when it is lowered. [Figure 7C] This is a nut descent determination table. [Figure 8A] FIG. 1 is a diagram showing an example of the configuration of a U-bolt equipped with an electronic component having a reed switch. [Figure 8B] 11A and 11B are diagrams showing the positional states of a nut with an embedded magnet and a reed switch when the nut is tightened and when it is lowered. [Figure 8C] This is a nut descent determination table. [Figure 9] 13A and 13B are diagrams showing an example of the configuration of a U-bolt in which a rod-shaped member is inserted into a through hole that penetrates a shaft portion according to a second embodiment. [Figure 10A] FIG. 1 is a diagram showing the structure of a U-bolt in which a contact sensor is mounted on a rod-shaped member. [Figure 10B] 11A and 11B are diagrams illustrating the positional states of the nut and the contact sensor when the nut is fastened and lowered. [Figure 10C] This is a nut descent determination table. [Figure 11A] This is a cross-sectional view of the contact sensor mounting portion of the U-bolt cut in the Y-axis direction. [Figure 11B] This is a cross-sectional view of the shaft of the U-bolt cut in the Y-axis direction. [Figure 11C] FIG. 4 is a diagram showing a wiring path to a contact sensor. [Figure 12A] FIG. 1 is a diagram showing the structure of a U-bolt in which a distance sensor is mounted on a rod-shaped member. [Figure 12B] 11A and 11B are diagrams illustrating the positional states of a nut and a distance sensor when the nut is fastened and when it is lowered. [Figure 12C] This is a nut descent determination table. [Figure 13A] 1A and 1B are diagrams illustrating an example of the configuration of a U-bolt in which a switch is mounted on a rod-shaped member. [Figure 13B] 11A and 11B are diagrams showing the positional states of the nut and the switch when the nut is fastened and when it is lowered. [Figure 13C] This is a nut descent determination table. [Figure 14A]1A and 1B are diagrams showing an example of the configuration of a U-bolt in which a metal plate is mounted on a rod-shaped member. [Figure 14B] 11A and 11B are diagrams showing the positional states of the nut and the metal plate when the nut is tightened and when it is lowered. [Figure 14C] This is a nut descent determination table. [Figure 15A] FIG. 1 is a diagram showing an example of the configuration of a U-bolt having a reed switch built into a rod-shaped member. [Figure 15B] 11A and 11B are diagrams showing the positional states of the nut and the reed switch when the nut is fastened and when it is lowered. [Figure 15C] This is a nut descent determination table. [Figure 16] FIG. 13 is a diagram showing an example of the configuration of a U-bolt according to a third embodiment, in which an insulated wire is passed through a through hole penetrating the shaft portion and a reed switch connected by the insulated wire is built into the through hole penetrating the shaft portion. [Figure 17A] 1A and 1B are diagrams showing an example of the configuration of a U-bolt in which a reed switch is built into a through hole that passes through the shaft portion. [Figure 17B] 11A and 11B are diagrams showing the positional states of the nut and the reed switch when the nut is fastened and when it is lowered. [Figure 17C] This is a nut descent determination table. [Figure 18] FIG. 13 is a block diagram showing an example of the configuration of a monitoring device according to a fourth embodiment. [Figure 19] FIG. 13 is a block diagram showing an example of the configuration of a monitoring device according to a fifth embodiment. [Figure 20] FIG. 13 is a block diagram showing an example of the configuration of a monitoring device according to a sixth embodiment. [Figure 21] 13 is a flowchart showing an example of a monitoring method executed by a monitoring device according to a fourth embodiment. [Figure 22] This is a diagram showing the structure when piping is fixed with a U-bolt. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0012] (First embodiment) FIG. 1 is a diagram showing an example of the configuration of a U-bolt 1 according to the first embodiment.

[0013] The U-bolt 1 according to the present embodiment is made of a metal such as steel. As shown in FIG. 1, the U-bolt 1 includes a main body 11 including shafts 111A and 111B and a bridge 112, a threaded portion 12, bases 14A and 14B, and electronic components 15A and 15B. The U-bolt 1 is a U-bolt that fastens a fastening object 7 using a nut 4. In the following, when the bases 14A and 14B are not distinguished from each other, they are referred to as the bases 14. In the following, when the electronic components 15A and 15B are not distinguished from each other, they are referred to as the electronic components 15. In the following, the electronic components 15A and 15B are collectively referred to as a pair of electronic components 15.

[0014] The shaft portion 111A and the shaft portion 111B are arranged in a first direction and extend in a direction perpendicular to the first direction. Hereinafter, as shown in FIG. 1, the direction in which the shaft portion 111A and the shaft portion 111B are arranged in a line is referred to as the X-axis direction (first direction), the direction in which the shaft portion 111A and the shaft portion 111B extend is referred to as the Y-axis direction (second direction), and the direction perpendicular to the X-axis direction and the Y-axis direction is referred to as the Z-axis direction (third direction). Hereinafter, the shaft portion 111A and the shaft portion 111B are collectively referred to as a pair of shaft portions 111. Hereinafter, when the shaft portion 111A and the shaft portion 111B are not distinguished from each other, they are referred to as the shaft portion 111.

[0015] The bridge portion 112 connects one end of each of the pair of shaft portions 111. The bridge portion 112 is configured to be symmetrical with respect to an imaginary straight line OY (hereinafter referred to as "imaginary line OY") extending in the Y-axis direction including the apex O of the U-shape formed by the U-bolt 1. The bridge portion 112 is provided at one end of each of the pair of shaft portions 111, and has a shape that is bent in a semicircular shape. Since the bridge portion 112 configured in this manner is provided at one end of the pair of shaft portions as described above, the U-bolt 1 forms a U-shape as a whole.

[0016] The screw portion 12 has a screw thread structure. The screw portion 12 is provided on each of the pair of shaft portions 111.

[0017] As shown in FIG. 1, a fastening object 7 such as a pipe is placed inside the U-shaped U-bolt 1 (a space surrounded by a pair of shaft portions 111 and a bridge portion 112). With the fastening object 7 placed inside the U-bolt 1, the shaft portion 111A and the shaft portion 111B are inserted from one side of the fastening object 8 into a pair of through holes 5 provided in the fastening object 8 such as a support metal. By inserting the shaft portion 111A and the shaft portion 111B into the pair of through holes 5, respectively, the threaded portion 12 of each of the shaft portion 111A and the shaft portion 111B protrudes to the other side of the fastening object 8. The threaded portion 12 protruding from the other side of the fastening object 8 is tightened by a nut 4. The nuts 4 each have a thread that screws into the thread of the threaded portion 12. As a result, the fastening object 7 is sandwiched and fixed between the U-bolt 1 and the fastening object 8.

[0018] The base 14 is a metal or resin base on which an electronic component 15 is mounted. FIG. 2 is a diagram showing a structure in which the base, on which an electronic component having an elastic member attached to one end is mounted, is housed in a hole opened in the shaft of a U-bolt. The U-bolt 1 includes an elastic member s connected to the inner wall of an open hole 13 opened in each of a pair of shafts 111, and a base 14 connected to the elastic member s, and the electronic component 15 is mounted at a position facing the nut 4 of the base 14. As shown in FIG. 2, the open hole 13 is opened in the shaft 111 of the U-bolt 1, and the base 14 on which the electronic component 15 is mounted is attached to the inner wall of the open hole 13 by the elastic member s. This structure serves to prevent the base 14 from falling after the nut 4 is attached. A stopper stp may be provided on the outer periphery of the hole 13 to prevent the base portion 14 from falling off due to the elastic member s being damaged by the impact of the descent of the nut 4 or the elastic member s being in a stationary state for a long time due to aging deterioration. The stopper stp is provided by welding the same metal material as that constituting the shaft portion 111 to the outer periphery of the hole 13. Also, even if the stopper stp is not provided, the base portion 14 can be prevented from falling off by filling the inside of the hole 13 with a resin such as an adhesive to fix the base portion 14. The shape of the hole 13 is not important, but a circular shape is easier to process.

[0019] The electronic components 15 are provided on each of the pair of shaft portions 111. The electronic components 15 detect the descent of the nut 4. The electronic components 15 include: (1) a contact sensor that detects the descent of the nut 4 when it comes into contact with the nut 4; (2) a distance sensor that detects the descent of the nut 4 when the distance to the nut 4 falls below a threshold value; (3) a switch that presses a movable contact when it comes into contact with the nut, closing the movable contact and a fixed contact; (4) a metal plate that, when it comes into contact with the nut 4, closes the electrical circuit formed between the washer 6 of the nut 4; and (5) a reed switch that closes the contacts by the magnetic field formed by the magnet when the distance to the nut 4 with an embedded magnet falls below a threshold value.

[0020] FIG. 3A is a diagram showing a state in which the base part is stored inside the open hole when the nut is attached. As shown in FIG. 3A, one end of the base part 14 is processed into a tapered shape. That is, when the base part 14 is attached to the shaft part 111, it is processed so that it tapers from the apex side of the shaft part 111 toward the tip side. Therefore, when the nut 4 is fastened, when the nut 4 is passed through the shaft part 111 in the upward direction, the base part 14 is pushed into the open hole 13, making it easier to pass the nut 4. FIG. 3B is a diagram showing a state in which the base part protrudes outside the open hole after the nut is attached. As shown in FIG. 3B, after the nut 4 is passed through, the base part 14 protrudes outside the open hole 13 and plays the role of a stopper. FIG. 3C is a diagram showing a state in which the base part 14 becomes a stopper when the nut is lowered. 3C, since one end of base portion 14 is machined into a tapered shape, base portion 14 acts as a stopper when nut 4 is lowered, preventing nut 4 from completely coming off shaft portion 111 and dropping. The shape of open hole 13 provided in shaft portion 111 is not important, but machining is easier when it is circular.

[0021] FIG. 4A is a diagram showing a base part with an elastic member attached to one end in a cylindrical shape. The elastic member s is, for example, a spring. As shown in FIG. 4A, when the elastic force of the elastic member s increases, or when the steady state of the elastic member s becomes longer due to aging or the like, the exposed portion exp where the base part 14 is exposed from the shaft part 111 of the U-bolt 1 becomes longer. When the exposed portion exp becomes longer, the base part 14 is more likely to fall off the shaft part 111 when the nut is fastened or dropped. For this reason, it is desirable to add a function to prevent the base part 14 from falling off even when the elastic force of the elastic member s increases or when the steady state of the elastic member s becomes longer. FIG. 4B is a diagram showing a base part with an elastic member attached to one end in a tapered shape. As shown in FIG. 4B, by machining the tip of the base portion 14 into a tapered shape and fitting a stopper stp made of the same metal material as that constituting the shaft portion 111 welded to the outer periphery of the open hole 13, it is possible to prevent the stopper stp from falling off.

[0022] FIG. 5A is a diagram showing a configuration example of a U-bolt equipped with a contact sensor or distance sensor. The electronic component 15 mounted on the U-bolt 1A is a contact sensor 151 or a distance sensor 152. The U-bolt 1A may detect the descent of the nut 4 using the contact sensor 151 or a distance sensor 152 that measures the distance to the nut 4 by irradiating the object (nut 4) with ultrasonic waves, infrared rays, a laser, or the like. The contact sensor 151 is a sensor that detects the contact of the object (nut 4). In FIG. 5A, the upward dashed arrow indicates that the distance sensor 152 irradiates the nut 4 with ultrasonic waves, infrared rays, a laser, or the like. FIG. 5B is a diagram showing the positional state of the nut and the contact sensor or distance sensor when the nut is fastened and lowered. In FIG. 5B, the left figure shows when the nut 4 is fastened, and the right figure shows when the nut 4 is lowered. When the nut 4 lowers, the base part 14 becomes a stopper and the descent of the nut 4 stops.

[0023] Fig. 5C is a nut descent determination table. Fig. 5C uses a contact sensor as an example. It is desirable for contact sensor 151 to be capable of determining with 0 or 1 whether the nut is in contact with contact sensor 151. When contact sensor 151A comes into contact with the nut (contact), it determines "descent," and when there is no contact (no contact), it determines "no descent." Contact sensor 151B also makes a determination in the same manner as contact sensor 151A.

[0024] FIG. 6A is a diagram showing a configuration example of a U-bolt equipped with an electronic component having a switch. The electronic component 15 mounted on the U-bolt 1B has a switch 153. The U-bolt 1B has the switch 153 mounted on the base 14, so that the electronic component 15 having the switch 153 detects the descent of the nut 4. When the nut 4 loosens and descends onto the switch 153, the switch 153 mounted on the base 14 closes, and the electrical circuit is conducted, thereby detecting the descent of the nut 4. FIG. 6B is a diagram showing the positional state of the nut and the switch when the nut is fastened and descended. In FIG. 6B, the left diagram shows the time when the nut 4 is fastened, and the right diagram shows the time when the nut 4 is descended. When the nut 4 is fastened, the switch 153 is open and the electrical circuit is not conducted. On the other hand, when the nut 4 is descended, the switch 153 is closed and the electrical circuit is conducted.

[0025] 6C is a table showing a nut descent judgment. When the switch 153A is closed due to the nut descent, it judges "descent", and when it is opened without the nut descent, it judges "no descent". The switch 153B judges in the same way as the switch 153A.

[0026] FIG. 7A is a diagram showing a configuration example of a U-bolt equipped with an electronic component having a metal plate. The electronic component 15 to be mounted on the U-bolt 1C has a metal plate 154. In FIG. 7A, the base portion 14 is formed using an insulator. FIG. 7B is a diagram showing the positional state of the nut and the metal plate when the nut is fastened and lowered. As shown in FIG. 7B, a metal plate 154 with an insulated electric wire w attached thereto is provided on the base portion 14, and the insulated electric wire w is attached to the washer 6. The insulated electric wire w refers to an electric wire covered with an insulating coating (hereinafter the same). When the nut 4 is lowered, the metal plate 154, the nut 4, and the washer 6 are in a conductive state, and the descent of the nut 4 is detected by the conduction of a series of electric circuits. Also, when the insulated electric wire w is attached to the U-bolt 1C body instead of the washer 6, the metal plate 154A and the metal plate 154B cannot be distinguished, but the nut 4 and the metal plate 154 come into contact with each other, and the descent of the nut 4 is detected. Furthermore, in the case of a metal base 14, by covering the area other than the contact point between the base 14 and the nut 4 with an insulator, the descent of the nut 4 can be detected without providing an additional metal plate 154.

[0027] 7C is a table showing the descent judgment of the nut. When the washer, nut, and metal plate 154A come into contact with each other and a series of electric circuits are conducted, it is judged as "descent", and when the washer, nut, and metal plate 154A do not come into contact with each other and a series of electric circuits are not conducted, it is judged as "no descent". Metal plate 154B is judged in the same way as metal plate 154A.

[0028] FIG. 8A is a diagram showing an example of the configuration of a U-bolt equipped with an electronic component having a reed switch. The electronic component 15 mounted on the U-bolt 1D has a reed switch 155. In the U-bolt 1D, a magnet 16 is embedded in the nut 4, and the reed switch 155 is mounted on the base 14. FIG. 8B is a diagram showing the positional state of the nut with the embedded magnet and the reed switch when the nut is fastened and lowered. When the nut is fastened, the magnetic field around the reed switch 155, which is a long distance from the nut 4 with the embedded magnet 16, is weak, and the reed switch 155 is open, but when the nut is lowered, the magnetic field becomes stronger due to the descent of the nut 4 with the embedded magnet 16, and the reed switch 155 is closed.

[0029] 8C is a table showing the nut descent judgment. When the magnetic field generated by the magnet becomes strong and reed switch 155A closes, it is judged as "descent", and when the magnetic field around reed switch 155A is weak and reed switch 155A is open, it is judged as "no descent". Reed switch 155B judges in the same way as reed switch 155A.

[0030] In the U-bolt 1 of the present disclosure, the base portion 14 provided on the shaft portion 111 functions as a stopper to prevent the nut 4 from falling, and further, the electronic component 15 mounted on the base portion 14 detects that the nut 4 has fallen.

[0031] Second Embodiment FIG. 9 is a diagram showing a configuration example of a U-bolt according to the second embodiment, in which a rod-shaped member on which an electronic component is mounted is inserted into a through hole penetrating a shaft portion.

[0032] The U-bolt 2 according to this embodiment is made of a metal such as steel. As shown in Fig. 9, the U-bolt 2 includes a main body 11 including shaft portions 111A and 111B and a bridge portion 112, a threaded portion 12, electronic components 15A and 15B, and a rod-shaped member 17. The U-bolt 2 according to this embodiment differs from the U-bolt 1 according to the first embodiment in that it includes a rod-shaped member 17 instead of a base portion 14. The same components as those in the first embodiment are denoted by the same reference numbers as those in the first embodiment, and descriptions thereof will be omitted as appropriate.

[0033] The U-bolt 2 includes a rod-shaped member 17 that is passed through a through hole TH that is opened in a pair of shaft portions 111. The electronic component 15 is mounted or built into the rod-shaped member 17 at a position facing the nut 4. As shown in FIG. 9, the U-bolt 2 has a through hole TH in the shaft portion 111, and the rod-shaped member 17 on which the electronic component 15 is mounted is passed through the through hole TH after the nut 4 is fastened, thereby preventing the nut 4 from completely coming off the shaft portion 111 and falling. The electronic component 15 mounted on the rod-shaped member 17 detects the descent of the nut 4. The top side of the rod-shaped member 17 is processed to be flat so that the electronic component 15 can be easily mounted and the descent of the nut 4 can be easily detected. The electronic component 15 is attached to the rod-shaped member 17 by welding, adhesive, or the like, but the mounting method is not limited. The electronic component 15 may be mounted at any position on the rod-shaped member 17 as long as it is at a position where the nut 4 comes into contact (opposing position).

[0034] A separation prevention member 18 is provided on the outside of the shaft portion 111A and the shaft portion 111B as a separation prevention treatment so that the rod-shaped member 17 does not separate from the shaft portion 111. The separation prevention treatment is performed, for example, by passing the nut 4 through, and then using an adhesive, a nut, or the like, but the method of this treatment is not limited.

[0035] FIG. 10A is a diagram showing the structure of a U-bolt in which a contact sensor is mounted on a rod-shaped member. The electronic component 15 mounted on the U-bolt 2A is a contact sensor 151. The U-bolt 2A detects that the nut 4 has been lowered by mounting the contact sensor 151 that can detect that the nut 4 has been contacted. FIG. 10B is a diagram showing the positional state of the nut and the contact sensor when the nut is fastened and lowered. In FIG. 10B, the left figure shows the positional state of the nut 4 and the contact sensor 151 when the nut 4 is fastened, and the right figure shows the positional state of the nut 4 and the contact sensor 151 when the nut 4 is lowered. When the nut 4 is lowered, the rod-shaped member 17 on which the contact sensor 151 is mounted acts as a stopper, stopping the descent of the nut 4.

[0036] 10C is a nut descent judgment table. Although there is no limitation on the contact sensor 151, it is preferable that the contact sensor 151 can judge whether the nut is in contact with the contact sensor 151 or not with 0 or 1. When the contact sensor 151A comes in contact with the nut (contact), it judges "descent", and when there is no contact (no contact), it judges "no descent". The contact sensor 151B also judges in the same way as the contact sensor 151A.

[0037] FIG. 11A is a cross-sectional view of the area marked AA in FIG. 10A, and is a cross-sectional view of the contact sensor mounting portion of the U-bolt in the Y-axis direction. The AA cross section in FIG. 10A is a cross-sectional view of contact sensor 151B in the Y-axis direction (second direction). FIG. 11B is a cross-sectional view of the area marked BB in FIG. 10A, and is a cross-sectional view of the shaft portion of the U-bolt in the Y-axis direction. The BB cross section in FIG. 10B is a cross-sectional view of shaft portion 111B of U-bolt 2A in the Y-axis direction (second direction).

[0038] Fig. 11C is a diagram showing a wiring path to the contact sensor. In Fig. 11C, when the insulated electric wire w is embedded in the rod-shaped member 17 as shown in the left figure, it is preferable to attach the rod-shaped member 17 on which the contact sensor 151 is mounted in advance to a U-bolt, and when the insulated electric wire w is not embedded in the rod-shaped member 17 as shown in the right figure, it is preferable to attach the contact sensor 151 after attaching the rod-shaped member 17 to the U-bolt.

[0039] FIG. 12A is a diagram showing the structure of a U-bolt in which a distance sensor is mounted on a rod-shaped member. The electronic component 15 mounted on the U-bolt 2A is a distance sensor 152. That is, the U-bolt 2A may detect the descent of the nut 4 by measuring the distance to the nut 4 by irradiating the object (nut 4) with ultrasonic waves, infrared rays, lasers, etc. in addition to contact with the nut 4. In FIG. 12A, the upward dashed arrow indicates that the distance sensor 152 irradiates the nut 4 with ultrasonic waves, infrared rays, lasers, etc. The distance sensor 152 is preferably a simple distance sensor that can determine whether the distance between the object and the nut 4 is equal to or less than a threshold value with 0 or 1. FIG. 12B is a diagram showing the positional state of the nut and the distance sensor when the nut is fastened and when it is lowered. In FIG. 12B, the left figure shows the positional state of the nut and the distance sensor when the nut 4 is fastened, and the right figure shows the positional state of the nut and the distance sensor when the nut 4 is lowered. When the nut 4 is lowered, the rod-shaped member 17 on which the distance sensor 152 is mounted becomes a stopper, and the descent of the nut 4 is stopped.

[0040] 12C is a table showing the descent judgment of the nut. It is preferable that the distance sensor 152 is capable of judging whether the nut is descent or not by using 0 or 1. The distance sensor 152A judges that the nut is "descent" when the distance to the nut is equal to or less than a threshold value, and judges that the nut is "not descent" when the distance is greater than the threshold value (no contact). The distance sensor 152B judges in the same manner as the distance sensor 152A.

[0041] FIG. 13A is a diagram showing a configuration example of a U-bolt in which a switch is mounted on a rod-shaped member. An electronic component 15 mounted on a U-bolt 2B has a switch 153. The U-bolt 2B detects the descent of the nut 4 due to loosening by mounting the switch 153 on a rod-shaped member 17. When the nut 4 loosens and falls onto the switch 153, the switch 153 closes, and the electric circuit becomes conductive, thereby detecting the descent of the nut 4. This mechanism is similar to a tactile switch. FIG. 13B is a diagram showing the positional state of the nut and the switch when the nut is fastened and when it is lowered. When the nut 4 is lowered, the rod-shaped member 17 on which the switch 153 is mounted acts as a stopper, stopping the descent of the nut 4.

[0042] 13C is a table showing a nut descent judgment. When the nut descents and switch 153A is closed, it is judged as "descent", and when the nut does not descent and switch 153A is open, it is judged as "no descent". Switch 153B is judged in the same way as switch 153A.

[0043] FIG. 14A is a diagram showing a configuration example of a U-bolt in which a metal plate is mounted on a rod-shaped member. An electronic component 15 mounted on a U-bolt 2C has a metal plate 154. In FIG. 14A, a rod-shaped member 17 body is formed using an insulator. FIG. 14B is a diagram showing the positional state of the nut and the metal plate when the nut is fastened and lowered. As shown in FIG. 14B, a metal plate 154 with an insulated electric wire w attached thereto is provided on an insulator, and the insulated electric wire w is provided on a washer 6. When the nut 4 is lowered, the metal plate 154, the nut 4, and the washer 6 are in a conductive state, and the descent of the nut 4 is detected by the conduction of a series of electric circuits. Also, when the insulated electric wire w is attached to the U-bolt 2C body instead of the washer 6, A and B cannot be distinguished, but the nut 4 comes into contact with the metal plate 154, and the electric circuit is in a conductive state, and the descent of the nut 4 is detected. On the other hand, when using a metal rod-shaped member 17, by covering with an insulator the area other than the contact area between the rod-shaped member 17 and the nut 4, the descent of the nut 4 can be detected without providing an additional metal plate 154. Also, when the nut 4 descends, the rod-shaped member 17 carrying the metal plate 154 acts as a stopper, stopping the descent of the nut 4.

[0044] 14C is a table showing the nut descent judgment. When the nut descents and the electrical circuit connecting the metal plate 154A, the nut, and the washer is in a conductive state, it is judged as "descent," and when the nut does not descent and the electrical circuit is in an open state, it is judged as "no descent." Metal plate 154B is judged in the same way as metal plate 154A.

[0045] FIG. 15A is a diagram showing a configuration example of a U-bolt in which a reed switch is built into a rod-shaped member. The electronic component 15 mounted on the U-bolt 2D has a reed switch 155. As shown in FIG. 15A, the U-bolt 2D has a magnet 16 embedded in the nut 4 and a rod-shaped member 17 with an insulated electric wire w built in, and the reed switch 155 is built in. The reed switch 155 is connected to the insulated electric wire w. There may be two insulated electric wires w as in the third embodiment described later. FIG. 15B is a diagram showing the positional state of the nut and the reed switch when the nut is fastened and lowered. When the nut 4 is fastened, if the distance from the magnet 16 is long, the magnetic field around the reed switch 155 is weak and the reed switch 155 is open, but when the nut 4 is lowered, the magnet 16 moves above the reed switch 155, so the magnetic field by the magnet 16 becomes stronger and the reed switch 155 is closed. The position of the reed switch 155 is not limited as long as it is within the range affected by the magnetic field, but it is preferable to embed it in the shaft portion 111 where the surrounding magnetic field becomes strongest when the nut 4 with the magnet 16 embedded therein is lowered.

[0046] 15C is a table showing whether the nut has dropped. When the nut with the magnet embedded in it drops and the reed switch 155A closes, it is judged as "dropped." When the nut does not drop and the reed switch 155A is open, it is judged as "not dropped." The reed switch 155B also makes a judgment in the same way as the reed switch 155A.

[0047] According to the U-bolt 2 of the present disclosure, the rod-shaped member 17 passed through the shaft portion 111 functions as a stopper to prevent the nut 4 from falling, and further, various electronic components 15 mounted on the rod-shaped member 17 detect the descent of the nut 4.

[0048] (Third embodiment) FIG. 16 is a diagram showing an example of the configuration of a U-bolt according to the third embodiment, in which an insulated wire is passed through a through hole penetrating the shaft and a reed switch connected by the insulated wire is built into the through hole penetrating the shaft.

[0049] The U-bolt 3 according to this embodiment is made of a metal such as steel. As shown in Fig. 16, the U-bolt 3 includes a main body 11 including shaft portions 111A and 111B and a bridge portion 112, a threaded portion 12, electronic components 15A and 15B, and an insulated wire 19. The U-bolt 3 according to this embodiment differs from the U-bolt 2 according to the second embodiment in that the U-bolt 3 includes an insulated wire 19 instead of a rod-shaped member 17. The same components as those in the second embodiment are denoted by the same reference numbers as those in the second embodiment, and descriptions thereof will be omitted as appropriate.

[0050] FIG. 17A is a diagram showing a configuration example of a U-bolt in which a reed switch is built into a through hole that passes through the shaft. An electronic component 15 mounted on the U-bolt 3 has a reed switch 155. The U-bolt 3 has an insulated electric wire 19 covered with an insulating coating that is passed through a through hole TH opened in a pair of shafts 111. The reed switch 155 is built into each of the through holes TH opened in the pair of shafts 111 and is connected by the insulated electric wire 19. Since the reed switch 155 is built into each of the through holes TH opened in the pair of shafts 111 and each reed switch 155 is individually connected by the insulated electric wire 19, two insulated electric wires 19 are passed through the through holes TH opened in the pair of shafts 111. When the nut 4 with the magnet 16 embedded therein is lowered, the magnet 16 is hooked onto the two insulated electric wires 19 to prevent the nut 4 from falling, so it is desirable that the distance between the two insulated electric wires 19 is close enough to prevent breakage. Any method, such as welding, may be used, but the insulated wire 19 should be fixed with an adhesive or the like so as not to move. Figure 17B is a diagram showing the positional state of the nut and reed switch when the nut is fastened and lowered. When the nut 4 is fastened, the distance between the nut 4 with the magnet 16 embedded in it and the reed switch 155 is long, so the magnetic field around the reed switch 155 is weak and the reed switch 155 is open. However, when the nut 4 is lowered, the distance between the magnet 16 and the reed switch 155 is short and the magnetic field from the magnet 16 becomes stronger, so the reed switch 155 closes.

[0051] 17C is a table showing whether the nut has dropped. When the nut with the magnet embedded in it drops and the reed switch 155A closes, it is judged as "dropped." When the nut does not drop and the reed switch 155A is open, it is judged as "not dropped." The reed switch 155B is judged in the same way as the reed switch 155A.

[0052] In the U-bolt 3 of the present disclosure, the two insulated wires 19 passed through the shaft 111 function as a stopper to prevent the nut 4 from falling, and further, the reed switch 155 built into the through hole in the shaft detects that the nut 4 with the magnet 16 embedded in it has been dropped.

[0053] (Fourth embodiment) FIG. 18 is a block diagram showing a configuration example of a monitoring device according to a fourth embodiment. As shown in FIG. 18, the monitoring device 20 according to the fourth embodiment includes a parent unit 30 and a U-bolt 40. The parent unit 30 has a receiving unit 31, a control unit 32, an alert issuing unit 33, and a first power source 34. The U-bolt 40 has any one of the U-bolts 1, 1A to 1D, 2, 2A to 2D, and 3 described above, and a transmitting unit 41. The monitoring device 20 monitors the descent of the nut 4 from the U-bolt 40. The same configurations as those of the first to third embodiments are given the same reference numbers as those of the first to third embodiments, and the description will be omitted as appropriate. In FIG. 18, the detection result by the electronic component 15 is represented as d, the determination result by the control unit 32 is represented as o, and the power supply by the first power source 34 is represented as e.

[0054] As shown in FIG. 18, the parent unit 30 judges whether the nut 4 has dropped based on the detection result d transmitted from the U-bolt 40, and issues an alert when it judges that the nut 4 has dropped. The parent unit 30 is provided with a first power source 34, and supplies power e to the U-bolt 40 to allow the U-bolt 40 to detect the drop of the nut 4 and to provide power for transmitting the detection result d. When the detection result d is monitored by wire, power supply and monitoring can be performed simultaneously. In addition, the first power source 34 not only supplies power e to the U-bolt 40, but also supplies power e to the receiving unit 31, the control unit 32, and the alert issuing unit 33 of the parent unit 30. Furthermore, the frequency of monitoring can be limited as necessary, such as once a day or once a month, rather than constantly, so that the first power source 34 can be operated efficiently.

[0055] The receiver 31 receives the detection result d transmitted from the transmitter 41 of the U-bolt 40. The receiver 31 outputs the detection result d to the controller 32. The transmission of the detection result d from the transmitter 41 of the U-bolt 40 to the receiver 31 of the master unit 30 may be performed by wired communication, wireless communication such as Wi-Fi, or a combination of these.

[0056] The control unit 32 judges whether the nut 4 has been descent based on the detection result d by the U-bolt 40 input from the receiving unit 31. When the control unit 32 judges that the nut 4 has been descent, it outputs the judgment result o to the alert issuing unit 33. The control unit 32 can respectively judge the cases where only one nut 4A has been descent, only the other nut 4B has been descent, and both nuts 4A and 4B have been descent, and output the judgment result o to the alert issuing unit 33. When the control unit 32 judges that neither the nuts 4A nor 4B have been descent, it continues to monitor the descent of the nut 4 by the U-bolt 40.

[0057] When the control unit 32 judges that the nut 4 is descending, the alert issuing unit 33 inputs the judgment result o that the nut 4 is descending from the control unit 32 and issues an alert. The alert issuing unit 33 issues an alert A when only the nut 4A is descending, and issues an alert B when only the other nut 4B is descending. Also, when both nuts 4A and 4B are descending, the alert issuing unit 33 issues an alert C.

[0058] The first power supply 34 includes a solar panel 341, a charge controller 342, and a battery 343. The first power supply 34 supplies power e to an electronic component 15 for detecting the descent of the nut 4 and a transmitter 41 for transmitting the detection result d, which are provided in the U-bolt 40, and a receiver 31 for receiving the detection result d, a controller 32 for determining whether the nut 4 has been descent, and an alert issuer 33 for issuing an alert, which are provided in the parent unit 30.

[0059] The solar panel 341 generates electricity by generating solar power when exposed to sunlight. However, solar power generation cannot generate electricity at night or during bad weather. For this reason, it is desirable to store the electricity generated by the solar panel 341 in the battery 343 during the daytime when the weather is good.

[0060] Charge controller 342 is connected between solar panel 341 and battery 343. Charge controller 342 is a device that prevents overcharging, over-discharging, or reverse current of battery 343, and is essential for charging battery 343 safely.

[0061] The battery 343 receives and stores electricity generated by the solar panel 341 via the charge controller 342. The electricity stored in the battery 343 provides power for a series of operations for monitoring the detection result d performed in cooperation between the receiving unit 31, the control unit 32, and the alert issuing unit 33 of the parent unit 30, and also supplies power e to the U-bolt 40 connected by wire from the parent unit 30.

[0062] The U-bolt 40 includes an electronic component 15 that detects the descent of the nut 4, and a transmitter 41 that transmits the detection result. The electronic component 15 and transmitter 41 of the U-bolt 40 may receive power e from the first power source 34 of the parent unit 30 that is connected by wire.

[0063] The electronic component 15 constituting the U-bolt 40 is an electronic component having either one of a contact sensor 151 and a distance sensor 152, or either one of a switch 153, a metal plate 154, and a reed switch 155, and detects the descent of the nut 4. The electronic component 15 outputs a detection result d, which detects whether the nut 4 has been descent, to the transmitting unit 41.

[0064] The transmitting unit 41 transmits the detection result d by the electronic component 15 to the receiving unit 31 of the parent device 30.

[0065] FIG. 21 is a flowchart showing an example of a monitoring method executed by the monitoring device 20 according to the fourth embodiment.

[0066] In step S10, the electronic component 15 of the U-bolt 40 detects the descent of the nut 4A or nut 4B.

[0067] In step S20, the transmitter 41 of the U-bolt 40 transmits the detection result d to the receiver 31 of the master unit 30.

[0068] In step S30, the receiver 31 of the master unit 30 receives the detection result d.

[0069] In step S40, the control unit 32 of the master unit 30 determines whether the nut 4A is lowered. If the nut 4A is not lowered, the process proceeds to S50. If the nut 4A is lowered, the process proceeds to S60.

[0070] In step S50, the control unit 32 of the parent unit 30 determines whether the nut 4B has descended. If the nut 4B has descended, the process proceeds to S80. If the nut 4B has not descended, the process returns to S10 and continues monitoring.

[0071] In step S60, the control unit 32 of the master unit 30 determines whether the nut 4B has descended. If the nut 4B has not descended, the process proceeds to S70. If the nut 4B has descended, the process proceeds to S90.

[0072] In step S70, the control unit 32 of the master unit 30 issues an alert A to inform the user that the nut 4A has been lowered.

[0073] In step S80, the control unit 32 of the master unit 30 issues an alert B to inform the user that the nut 4B has been lowered.

[0074] In step S90, the control unit 32 of the master unit 30 issues an alert C to inform the user of the descent of the nuts 4A and 4B.

[0075] The monitoring device 20 according to the present disclosure constantly monitors the descent of the nut 4 from the shaft 111 of the U-bolt 40, and issues an alert when it is determined that the nut 4 has been descent, thereby making it possible to notify the worker of the descent of the nut 4, etc. Furthermore, by providing the parent unit 30 with a first power source 34 having a solar power generation function, the monitoring device 20 can cover the power required to constantly monitor the descent of the nut 4 in a U-bolt 40 installed in a place where electric wires cannot be laid.

[0076] Fifth embodiment FIG. 19 is a block diagram showing a configuration example of a monitoring device according to the fifth embodiment. As shown in FIG. 19, the monitoring device 20A according to the fifth embodiment includes a parent unit 30A and a U-bolt 40A. The parent unit 30A has a receiving unit 31, a control unit 32, an alert issuing unit 33, and a first power source 34. The U-bolt 40A has any one of the above-mentioned U-bolts 1, 1A to 1D, 2, 2A to 2D, and 3, a transmitting unit 41, and a second power source 43. The monitoring device 20A monitors the descent of the nut 4 from the U-bolt 40A. The same configurations as those of the first to fourth embodiments are given the same reference numbers as those of the first to fourth embodiments, and the description will be omitted as appropriate. In FIG. 19, the detection result by the electronic component 15 is represented as d, the determination result by the control unit 32 is represented as o, the power supply by the first power source 34 is represented as e1, and the power supply by the second power source is represented as e2.

[0077] The first power supply 34 supplies power e1 to a receiving unit 31 that receives the detection result d provided in the parent unit 30A, a control unit 32 that determines whether the nut 4 has been dropped, and an alert issuing unit 33 that issues an alert.

[0078] The detection result d may be wirelessly transmitted from the transmitter 41 of the U-bolt 40A to the receiver 31 of the parent unit 30A. By wirelessly transmitting and receiving the detection result d, it becomes possible to monitor the detection result d without exposing the insulated wire.

[0079] The second power supply 43 is composed of a vibration generator 431 and a battery 432 .

[0080] Vibration power generator 431 is a generator that converts pressure generated on the vibrating surface due to vibration into electricity using a piezoelectric element, etc. Bridge-attached equipment using U-bolt 40A is affected by vehicle vibration, so by providing vibration power generator 431 on the main body of U-bolt 40A, power supply from parent unit 30A is not required.

[0081] The battery 432 stores the electricity generated by the vibration generator 431 and supplies power e2 to the electronic components 15 and the transmitter 41 of the U-bolt 40A. Similarly to the first power source 34 of the parent units 30 and 30A, the frequency of monitoring the detection results can be limited as necessary, such as once a day or once a month, rather than constantly, allowing the second power source 43 to be operated efficiently.

[0082] Furthermore, when the installation distance between the parent unit 30A and the U-bolt 40A is short, the power supply e to the U-bolt 40A may be performed by non-contact power supply (wireless power supply).

[0083] Monitoring device 20A according to the present disclosure constantly monitors the descent of nut 4 from shaft 111 of U-bolt 40A, and issues an alert when it is determined that nut 4 has been descent, thereby making it possible to notify an operator of the descent of nut 4, etc. Also, by incorporating second power source 43 having a vibration power generation function in U-bolt 40A in addition to first power source 34 incorporated in parent unit 30A, it becomes possible to cover the power required for constantly monitoring the descent of nut 4 of U-bolt 40A installed in a place where electric wires cannot be laid.

[0084] Sixth embodiment FIG. 20 is a block diagram showing a configuration example of a monitoring device according to the sixth embodiment. As shown in FIG. 20, a monitoring device 20B according to the sixth embodiment includes a parent unit 30B, a U-bolt 40A, and a U-bolt 40B. The parent unit 30B has a receiving unit 31, a control unit 32, an alert issuing unit 33, and a first power source 34. The U-bolt 40A has any of the U-bolts 1, 1A to 1D, 2, 2A to 2D, and 3 described above, and a transmitting unit 41. The U-bolt 40B has any of the U-bolts 1, 1A to 1D, 2, 2A to 2D, and 3 described above, and a transmitting unit 41. The monitoring device 20B monitors the drop of the nut 4 from the U-bolt 40A or the U-bolt 40B. The same configurations as those of the first to fifth embodiments are given the same reference numbers as those of the first to fifth embodiments, and the description will be omitted as appropriate. In Figure 20, the detection result by electronic component 15 of U-volt 40A is represented as d1, the detection result by electronic component 15 of U-volt 40B is represented as d2, the judgment result by control unit 32 is represented as o, power supply by first power source 34 is represented as e1, power supply by the second power source of U-volt 40A is represented as e2, and power supply by the second power source of U-volt 40B is represented as e3.

[0085] The monitoring device 20A monitors the detection results of one U-bolt (U-bolt 40A), whereas the monitoring device 20B according to this embodiment simultaneously monitors the detection results of a plurality of U-bolts.

[0086] Similar to parent unit 30A, first power source 34 constituting parent unit 30B supplies power e1 to receiving unit 31 that receives detection results d1 and d2 provided in parent unit 30B, control unit 32 that determines whether nut 4 has been lowered, and alert issuing unit 33 that issues an alert. Also, similar to U-bolt 40A, battery 432 of U-bolt 40B stores electricity generated by vibration generator 431, and supplies power e3 to electronic component 15 and transmitting unit 41 of U-bolt 40B.

[0087] According to the monitoring device 20B of the present disclosure, the descent of nuts 4 from the shafts 111 of multiple U-bolts 40 is constantly monitored and an alert is issued, thereby notifying the worker of the U-bolt 40 for which the descent of the nut 4 has been determined.

[0088] Although the above-mentioned embodiment has been described as a representative example, it is obvious to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, the present invention should not be interpreted as being limited by the above-mentioned embodiment, and various modifications or changes are possible without departing from the scope of the claims. [Explanation of symbols]

[0089] 1,1A~1D, 2,2A~2D,3, 40, 40A, 40B U-bolt 4,4A,4B Nut 5 Through hole 6 Washer 7. Contracts 8 Object to be fastened 11 Main body 111,111A,111B Shaft part 112 Bridge Section 12 Threaded section 13 Drilled hole (hole drilled in the U-bolt shaft) 14,14A,14B base 15, 15A, 15B Electronic Components 151, 151A, 151B Contact Sensor 152, 152A, 152B Distance Sensor 153, 153A, 153B Switch 154,154A,154B Metal plate 155, 155A, 155B Reed Switch 16, 16A, 16B Magnets 17 Rod-shaped member 18 Anti-detachment member 19 Insulated wire (wire covered with insulating coating) 20,20A,20B Monitoring device 30, 30A, 30B Parent unit 31 Receiving section 32 Control section 33 Alert Issue Department 34 First Power Source 341 Solar Panel 342 Charge Controller 343,422 Batteries 41 Transmitter 42 Second Power Source 421 Vibration Generator

Claims

1. A U-bolt that fastens objects using a nut, A pair of shaft portions aligned in a first direction, extending in a second direction perpendicular to the first direction, and having upper ends connected to each other; A threaded portion provided on each of the pair of shaft portions; an electronic component provided on each of the pair of shaft portions for detecting a descent of the nut; an elastic member connected to an inner wall of an opening hole formed in each of the pair of shaft portions; a base portion connected to the elastic member and having one end tapered; The electronic component is mounted on the base portion at a position facing the nut, The descent of the nut is caused by the nut coming off the threaded portion provided on the pair of shaft portions and becoming caught and retained on the base portion located on the lower end side of the pair of shaft portions, in this U-bolt.

2. A U-bolt for fastening objects using a nut, A pair of shaft portions aligned in a first direction, extending in a second direction perpendicular to the first direction, and having upper ends connected to each other; A threaded portion provided on each of the pair of shaft portions; an electronic component provided on each of the pair of shaft portions for detecting a descent of the nut; a rod-shaped member passed through a through hole formed in the pair of shaft portions, The electronic component is mounted or built into the rod-shaped member at a position facing the nut, The descent of the nut is caused by the nut coming off the threaded portion provided on the pair of shaft portions and getting caught on the rod-shaped member arranged on the lower end side of the pair of shaft portions, in this U-bolt.

3. The electronic component includes: a contact sensor that detects the descent of the nut when it comes into contact with the nut; a distance sensor that detects a descent of the nut when the distance to the nut becomes equal to or less than a threshold; a switch in which, when the nut comes into contact with the movable contact, the movable contact is pressed down to close the movable contact and the fixed contact; a metal plate that, when in contact with the nut, brings an electrical circuit formed between the metal plate and a washer of the nut into a conductive state; and a reed switch that closes the contacts by applying a magnetic field generated by a magnet when the distance to the nut having a magnet embedded therein becomes equal to or less than a threshold value; 3. The U-bolt according to claim 1 or 2, comprising any one of the following:

4. A U-bolt for fastening objects using a nut, A pair of shaft portions aligned in a first direction, extending in a second direction perpendicular to the first direction, and having upper ends connected to each other; A threaded portion provided on each of the pair of shaft portions; an electronic component provided on each of the pair of shaft portions for detecting a descent of the nut; A stopper is disposed on the lower end side of the pair of shaft portions, The electronic component includes: a contact sensor that detects the descent of the nut when it comes into contact with the nut; a distance sensor that detects a descent of the nut when the distance to the nut becomes equal to or less than a threshold; a switch in which, when the nut comes into contact with the movable contact, the movable contact is pressed down to close the movable contact and the fixed contact; a metal plate that, when in contact with the nut, brings an electrical circuit formed between the metal plate and a washer of the nut into a conductive state; and a reed switch that closes the contacts by applying a magnetic field generated by a magnet when the distance to the nut having a magnet embedded therein becomes equal to or less than a threshold value; and The descent of the nut is caused by the nut coming off the threaded portions provided on the pair of shaft portions and being caught and stopped by the stoppers, in this U-bolt.

5. A U-bolt for fastening objects using a nut, A pair of shaft portions aligned in a first direction, extending in a second direction perpendicular to the first direction, and having upper ends connected to each other; A threaded portion provided on each of the pair of shaft portions; an electronic component provided on each of the pair of shaft portions for detecting a descent of the nut; an insulated electric wire covered with an insulating coating and passed through a through hole formed in the pair of shaft portions; The electronic component includes a reed switch, The reed switch is incorporated in a through hole formed in each of the pair of shaft portions and is connected by the insulated wire, The descent of the nut is caused by the nut coming off the threaded portion provided on the pair of shaft portions and getting caught on the insulated electric wire arranged on the lower end side of the pair of shaft portions, in this U-bolt.

6. A U-bolt according to any one of claims 1 to 5, further comprising a transmitter for transmitting a detection result by the electronic component; a receiving unit that receives the detection result transmitted from the transmitting unit; A control unit that determines whether the nut has been lowered based on the detection result; A parent unit having an alert issuing unit that issues an alert when the control unit determines that the nut is lowered; A monitoring device comprising:

7. The monitoring device according to claim 6 , wherein the master unit further comprises a first power source that supplies power to the electronic components, the transmitting unit, the receiving unit, the control unit, and the alert issuing unit.

8. A step of transmitting a detection result of the U-bolt described in any one of claims 1 to 5 detecting the descent of the nut; A step of a parent device receiving the detection result; A step of the parent machine determining whether or not the nut has dropped based on the detection result; When it is determined that the nut is lowered, the parent unit issues an alert; A monitoring method comprising:

Images