Load cell

Abstract

This invention provides a load cell that can manage the tensile force acting on a tensioning material by connecting it to a control device. [Solution] A load cell comprising a cylindrical strain generating body and a lid, the strain generating body consisting of a cylindrical anchoring joint, a cylindrical fixed object joint, four shear beams connecting the anchoring joint and the non-fixed object joint, the lower surface of the anchoring joint, the lower surface of the shear beams, a bottom plate continuous with the inner circumferential surface of the non-fixed object joint, and strain gauges bonded to the shear beams, the upper surface of the non-fixed object joint and the upper surface of the shear beams being lower than the upper surface of the anchoring joint by a thickness greater than the thickness of the lid, the lid being a hollow disc with a hollow portion and approximately the same diameter as the outer diameter of the non-fixed object joint, and a sensor amplifier unit for measuring load values, a control unit, and a battery housed in the space surrounded by the anchoring joint, the non-fixed object joint, the shear beams, the bottom plate, and the lid, the control unit having a control and recording unit that converts the load values ​​into digital data and records them.

Description

Technical Field

[0001] The present invention relates to a load cell that measures the tensile force acting on a tension member such as an anchor bolt, and more particularly to a load cell that transmits the value of the tensile force measured by wired / wireless communication to an external management device.

Background Art

[0002] Conventionally, various facilities have been installed in tunnels to ensure safety and convenience. Typical facilities include lighting facilities and ventilation facilities, which play an essential role in ensuring visibility for tunnel users and maintaining air quality.

[0003] These facilities are mainly embedded in the tunnel structure made of concrete or fixed to the tunnel wall or ceiling using anchor bolts. An anchor bolt is a metal fixture embedded in the tunnel structure. The anchor bolt is inserted into a hole drilled in the concrete and fixed by mechanical expansion or an adhesive. Then, a fixed fitting for attaching the facility is passed through the male screw portion exposed outside the anchor bolt, and a lock nut is screwed and tightened, so that an axial tensile force acts on the anchor bolt. This tensile force supports the weight of the facility, withstands vibrations and impacts, and firmly fixes the facility.

[0004] Properly installed anchor bolts with the correct tensile force applied provide stable fixation over a long period. However, due to long-term use, continuous vibration, environmental factors such as temperature changes, and moisture, the nut may loosen. As the loosening progresses, the tensile force acting on the anchor bolt decreases, the fixing force of the facility decreases, and there is a risk of the facility falling. If the facility falls, it may cause serious harm to vehicles and personnel passing through the tunnel. To prevent such risks, in addition to visually checking for nut loosening by inspection, it is necessary to appropriately measure the tensile force of the anchor bolt and take measures such as re-tightening as needed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2006-162511 [Patent Document 2] Japanese Patent Publication No. 2021-167793 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1 describes a ground anchor tension detection system for measuring the tensile force (tension) of a ground anchor. Patent Document 1 describes measuring the tensile force of a ground anchor using a strain sensor attached to an anchor plate, but the wiring of the strain sensor is connected to a monitoring device via a connector provided on the outside of the anchor plate. However, the detection system described in Patent Document 1 requires a circuit to operate the strain sensor and an A / D conversion circuit on the connected monitoring device side (see Figure 2). Therefore, simply connecting a general-purpose personal computer that does not have such circuits to the connection connector will not allow for the measurement and monitoring of tensile force. Furthermore, while it is stated that the connection between the strain sensor and the monitoring device will be made by wireless communication (RFID), there is no mention whatsoever of the arrangement of the wireless device on the anchor plate side.

[0007] Patent Document 2 describes a management system that wirelessly monitors the stress value of a sensing washer, which has a sensor and a communication unit, by interposing it between a bolt and a nut. The sensing washer described in Patent Document 2 integrates a strain generating body and a communication unit positioned outside the strain generating body into a single unit housed in a non-metallic casing made of synthetic resin or similar material. Because the sensing washer protrudes from the outside of the strain generating body, it cannot be used when the sensing washer would interfere with the object being fixed. Furthermore, unlike metal casings, non-metallic casings are susceptible to damage due to aging, requiring periodic replacement, but replacement requires loosening and removing the nut.

[0008] The present invention aims to provide a load cell that can manage the tensile force acting on a tensioning material by connecting to a conventional management device such as a personal computer via a wired or wireless connection. [Means for solving the problem]

[0009] The load cell of the present invention, made to achieve the above objective, comprises a cylindrical strain generating body and a lid covering the upper part of the strain generating body, the strain generating body comprising a cylindrical anchoring joint positioned on the inner circumference and having a tension member insertion hole in the center, a cylindrical fixed object joint positioned on the outer circumference, four shear beams projecting in a cross shape in plan view from the outer surface of the anchoring joint and connected to the inner surface of the non-fixed object joint, the lower surface of the anchoring joint, the lower surfaces of the four shear beams, a bottom plate continuous with the inner surface of the non-fixed object joint, and strain gauges bonded to the four shear beams, wherein the upper surface of the non-fixed object joint and the upper surface of the shear beams of the strain generating body are lower than the upper surface of the anchoring joint by a thickness of the lid, and the lid The body is a hollow disc shape with a hollow portion that fits into the upper part of the fixing device joint, and has a diameter approximately the same as the outer diameter of the non-fixed object joint. Inside the strain generating body, in a space surrounded by the outer circumferential surface of the fixing device joint, the inner circumferential surface of the non-fixed object joint, the side surface of the shear beam, the upper surface of the bottom plate, and the lower surface of the lid, houses a sensor amplifier unit connected to the strain gauge for measuring the load value acting on the strain generating body, a control unit connected to the sensor amplifier unit for recording the load value, and a battery for driving the sensor amplifier unit and the control unit. The control unit has a control and recording unit that converts the load value sent from the sensor amplifier unit into digital data and records it. The control unit may be connected to the control and recording unit, and connection terminals for outputting the digital data to the outside may be provided on the side of the strain-generating body or on the top surface of the cover. The system may also have a communication terminal that connects to the aforementioned connection terminal and transmits the digital data to an external source via wireless communication. The control unit has a communication unit that connects to the control and recording unit and transmits the digital data to the outside via wireless communication, and the cover may be made of a non-metallic material. [Effects of the Invention]

[0010] The present invention, by means of solving the above-mentioned problems, can achieve at least one of the following effects. (1) In order to accommodate the sensor amplifier unit, recording unit, and battery inside the strain body, these devices provided protruding outside the strain body do not interfere with the fixed object. (2) In order to save and output the measured load value as digital data, an ordinary personal computer can be used as the management device. (3) By making the lid body made of a non-metallic material that transmits radio waves, even when the communication unit is housed in the internal space and sealed by the lid body, wireless communication can be performed with an external management device. (4) When the lid body is made of a non-metallic material such as synthetic resin, damage due to aging occurs, but it can be replaced without loosening the nut. (5) The lid body can be removed to perform maintenance such as the sensor amplifier unit, recording unit, communication unit, etc., and replace the battery, and measurement can be performed semi-permanently without loosening the nut.

Brief Description of the Drawings

[0011] [Figure 1] Exploded perspective view of the load meter of the present invention [Figure 2] Perspective view (1) of the load meter of the present invention [Figure 3] Plan view of the strain body [Figure 4] Plan view of the load meter of the present invention <F\( [Figure 5] Cross-sectional view taken along line A-A of FIG. 4 (sensor amplifier unit, control unit, battery omitted) [Figure 6] Cross-sectional view taken along line B-B of FIG. 4 [Figure 7] Block diagram (1) of the sensor amplifier unit, control unit, and battery [Figure 8] Perspective view (2) of the load meter of the present invention [Figure 9] Block diagram (2) of the sensor amplifier unit, control unit, and battery [Figure 10] Block diagram (3) of the sensor amplifier unit, control unit, and battery [Figure 11] Perspective view (3) of the load meter of the present invention

Best Mode for Carrying Out the Invention

[0012] Hereinafter, the load cell of the present invention will be described in detail with reference to the drawings.

[0013] [Example 1] (1) Configuration of the load cell (Figs. 1 to 6) The load cell of the present invention has a strain generating body 1, a lid body 2 covering the upper part of the strain generating body 1, a sensor amplifier unit 3, a control unit 4, and a battery 5 housed in the space S inside the strain generating body 1. The load cell is provided between a fixed object 8 and a nut 7 screwed onto the anchor bolt 6, which is fixed by tightening the nut 7 passed through the exposed portion of the anchor bolt 6 fixed to the structure, and measures the load (tensile force acting on the anchor bolt 6) generated by tightening the nut 7.

[0014] (2) Strain generating body 1 The strain generating body 1 is a cylindrical shape made of steel, and includes a cylindrical fixture joining body 11 having a tension member insertion hole 111 arranged on the inner peripheral side and through which the anchor bolt 6 is inserted in the center, a cylindrical fixed object joining body 12 arranged on the outer peripheral side, four shear beams 13 protruding in a cross shape in plan view from the outer peripheral surface of the fixture joining body 11 and connected to the inner peripheral surface of the fixed object joining body 12, the lower surface of the fixture joining body 11, the lower surfaces of the four shear beams 13, a bottom plate 14 continuous with the inner peripheral surface of the fixed object joining body 12, and eight strain gauges 15 adhered to the four shear beams 13 (Fig. 3). The upper surface of the fixture joining body 11 is joined to the nut 7 screwed onto the anchor bolt 6. Also, the lower surface of the fixed object joining body 12 is joined to the fixed object 8. And the bottom plate 14 continuous with the lower surface of the fixture joining body 11 and the lower surfaces of the shear beams 13 is located above the lower surface of the fixed object joining body 12. When the load generated by tightening the nut 7 causes the fixture joining body 11 to be displaced downward, shear force causes strain in the shear beams 13. By measuring this strain as a resistance value with the strain gauges 15, the load generated by tightening the nut 7 is measured. The number of strain gauges 15 is not limited to eight, and can be appropriately selected according to the type of strain gauge 15 used and the measurement method.

[0015] (3) Lid 2 The cover 2 is a member that covers the upper surface of the fixed object joint 12 and the shear beam 13 of the strain generating body 1. The cover 2 is, for example, a non-metallic plate made of synthetic resin, and is made of a material that transmits radio waves generated from the control unit 4 housed inside the strain-generating body 1. The cover 2 is disc-shaped with approximately the same outer diameter as the fixed object assembly 12 and has a hollow portion 21 that fits onto the upper part of the anchoring device assembly 11. Furthermore, the upper surfaces of the fixed object assembly 12 and the shear beam 13 are lower than the upper surface of the anchoring device assembly 11 by at least the thickness of the cover 2, so as not to interfere with the nut 7 or the tool used to tighten the nut 7. The cover 2 is inserted through a screw insertion hole 22 provided on the upper surface of the outer circumference and fixed to the upper surface of the strain generating body 1 by a screw 23 that is screwed into a threaded hole 121 provided on the upper surface of the fixed object joining body 12. If the size of the nut 7 fits within the hollow portion 21, the cover 2 can be removed while the nut 7 is still tightened onto the anchor bolt 6. Since the cover 2 is made of a non-metallic material such as synthetic resin, it may break due to deterioration over time, but it can be replaced without loosening the nut 7.

[0016] (4) Arrangement of sensor amplifier unit 3, control unit 4, and battery 5 Inside the strain generating body 1, there are four spaces S surrounded by the outer surface of the fixing device joint 11, the inner surface of the fixed object joint 12, the side surface of the shear beam 13, and the upper surface of the bottom plate 14. In this embodiment, a sensor amplifier unit 3, a control unit 4, and a battery 5 are housed in each of these spaces S (Figure 3), and the top is sealed with a cover 2. The sensor amplifier unit 3, the control unit 4, and the battery 5 are connected by wiring (not shown). By making the cover 2 a material that transmits radio waves, wireless communication with an external management device can be performed even when the cover 2 is sealed. Furthermore, because the sensor amplifier unit 3, the control unit 4, and the battery 5 are housed inside the strain generating body 1, these devices that protrude from the outside of the strain generating body 1 do not interfere with the fixed object 8. If the size of the nut 7 fits within the hollow portion 21 of the cover 2, the cover 2 can be removed while the nut 7 is still tightened onto the anchor bolt 6, allowing for maintenance of the sensor amplifier unit 3 and control unit 4, as well as replacement of the battery 5. This enables measurements to be taken semi-permanently without loosening the nut 7.

[0017] (5) Sensor amplifier unit 3 The sensor amplifier unit 3 is connected to the strain gauge 15 by wiring, controls the power supply to the strain gauge 15, and acquires the resistance value measured by the strain gauge 15. The acquired resistance value is sent to the control unit 4. The sensor amplifier unit 3 is also connected to the battery 5, and the power required for the operation of the sensor amplifier unit 3 is supplied from the battery 5.

[0018] (6) Control unit 4 (Figure 7) The control unit 4 consists of a control / recording unit 41, a communication unit 42, and a temperature measurement unit 43, and the power required for the operation of each unit is supplied from the battery 5. The resistance value sent from the sensor amplifier unit 3 is converted into digital data by the control and recording unit 41 and stored as a load value. The temperature measurement unit 43 measures the temperature inside the control unit 4, and stores the value as digital data in the control and recording unit 41. The communication unit 42 is a device for transmitting digital data of load values ​​and temperature stored in the control / recording unit 41 to an external management device via wireless communication, and consists of an antenna, a communication control circuit, etc. Since the resistance values ​​and temperature data are converted into digital data by the control / recording unit 41, conventional wireless communication methods such as infrared, Wi-Fi, and Bluetooth (registered trademark) can be used for communication with the management device. Furthermore, a regular personal computer can be used as the management device. The digital data of resistance values ​​and temperature stored in the control / recording unit 41 is transmitted to an external management device at a predetermined time by the communication unit 42. Furthermore, if the external management device fails to receive the transmitted data, it may have a function to transmit all the data at once during the next transmission. In this embodiment, the control / recording unit 41 and the communication unit 42 are integrated, but they may be provided separately.

[0019] (7) Battery 5 Battery 5 supplies power to the sensor amplifier unit 3 and the control unit 4, and can be used with dry cell batteries, rechargeable batteries, etc. In this embodiment, the sensor amplifier unit 3, control unit 4, and battery 5 are separate components, but some or all of them may be integrated into a single unit.

[0020] (8) Waterproof structure (Figures 5 and 6) The space S inside the strain generating body 1 is sealed at the top by the lid 2. A central O-ring 16 is provided between the outer surface of the fixing device joint 11 and the inner surface of the hollow portion 21 of the lid 2. Additionally, an outer O-ring 17 is provided between the upper surface of the object to be fixed joint 12 and the lower surface of the lid 2. This prevents water from entering the space S inside the strain generating body 1. The central O-ring 16 is housed in a central O-ring groove 211 provided on the inner circumferential surface of the hollow portion 21 of the lid 2. The central O-ring groove 211 may be provided on the outer circumferential surface of the fitting portion of the fixing device assembly 11 with the lid 2, or it may be provided at corresponding positions on the inner circumferential surface of the hollow portion 21 of the lid 2 and the outer circumferential surface of the fixing device assembly 11. The outer peripheral O-ring 17 is housed in an outer peripheral O-ring groove 122 provided on the upper surface of the fixed object assembly 12. The outer peripheral O-ring groove 122 may be provided on the lower surface of the cover 2, or it may be provided at corresponding positions on the upper surface of the fixed object assembly 12 and the lower surface of the cover 2, respectively.

[0021] [Example 2] (1) Communication via connection terminal 44 In the above-described embodiment 1, a communication unit 42 was provided in the control unit 4 inside the strain generator 1 (Figure 7) to communicate wirelessly with an external management device. However, a connection terminal 44 such as a USB port may be provided on the side of the strain generator 1 to communicate with the outside of the strain generator 1 and output digital data without using the communication unit 42 (Figure 8). The connection terminal 44 may also be provided on the top surface of the cover 2. Alternatively, a communication terminal 45 such as a USB receiver may be connected to the connection terminal 44 to perform wireless communication with the management device (Figure 9), or a communication cable 46 may be connected between the connection terminal 44 and the management device to perform wired communication (Figure 10). Furthermore, wireless and wired communication may be used in combination by using the communication unit 42 and the connection terminal 44. If wireless communication using the communication unit 42 is not performed, the cover 2 may be made of a metal that does not transmit radio waves.

[0022] [Example 3] (1) Configuration of tensioning material and fixing device In the above-described embodiments 1 and 2, the tensioning member and anchoring device were configured as an anchor bolt 6 and a nut 7. However, the load cell of the present invention is not limited to these configurations. For example, as shown in Figure 11, the tensioning member may be a PC steel wire 61, and the anchoring device may be a wedge 71 that fixes the PC steel wire 61 and an anchor head 72 that fixes the wedge 71 with the PC steel wire 61 inserted through it. The load cell of the present invention can be used with various combinations of tensioning members and anchoring devices. [Explanation of symbols]

[0023] 1 Strain generating body, 11 Fixing device joint, 111 Tensioner insertion hole, 12 Fixed object joint, 121 Screw hole, 122 Outer circumference O-ring groove, 13 Shear beam, 14 Bottom plate, 15 Strain gauge, 16 Central O-ring, 17 Outer circumference O-ring, 2 Cover, 21 Hollow section, 211 Central O-ring groove, 22 Screw insertion hole, 23 Screw, 3. Sensor amplifier unit, 4 control unit, 41 control / recording unit, 42 communication unit, 43 temperature measurement unit, 44 connection terminals, 45 communication cable 5 batteries, 6 anchor bolts, 61 PC steel wires, 7 Nut, 71 Wedge, 72 Anchor head 8 Fixed object, S space

Claims

1. A cylindrical strain-generating body, It has a cover that covers the upper part of the strain-generating body, The strain-generating body is A cylindrical fixing device joint, positioned on the inner circumference and having a tensioning material insertion hole in the center, A cylindrical object-fixing joint positioned on the outer circumference, Four shear beams are provided, projecting in a cross shape in plan view from the outer circumferential surface of the anchoring joint and connecting to the inner circumferential surface of the non-fixed joint, The bottom plate is continuous with the lower surface of the fixing device joint, the lower surfaces of the four shear beams, and the inner circumferential surface of the non-fixed object joint, It consists of strain gauges that are bonded to the four shear beams, The upper surface of the non-fixed joint of the strain-generating body and the upper surface of the shear beam are lower than the upper surface of the anchoring joint by a thickness equal to or greater than the thickness of the cover. The cover is a hollow disc shape having a hollow portion that fits onto the upper part of the fixing device joint, and having a diameter approximately the same as the outer diameter of the non-fixed object joint. Within the interior of the strain-generating body, in the space surrounded by the outer circumferential surface of the fixing device joint, the inner circumferential surface of the non-fixed object joint, the side surface of the shear beam, the upper surface of the bottom plate, and the lower surface of the lid, A sensor amplifier unit connected to the strain gauge measures the load value acting on the strain-generating body, A control unit connected to the aforementioned sensor amplifier unit and recording the load value, The sensor amplifier unit and the battery for driving the control unit are housed together. The control unit has a control and recording unit that converts the load value sent from the sensor amplifier unit into digital data and records it. Load cell.

2. The control unit is characterized by having connection terminals for connecting to the control and recording unit and outputting the digital data to the outside, provided on the side surface of the strain-generating body or on the top surface of the cover. The load cell according to claim 1.

3. The device is characterized by having a communication terminal that connects to the aforementioned connection terminal and transmits the digital data to an external party via wireless communication. The load cell according to claim 2.

4. The control unit has a communication unit that connects to the control and recording unit and transmits the digital data to the outside via wireless communication. The aforementioned lid is characterized by being made of non-metallic material. The load cell according to claim 1.

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