Alarm system, alarm device, and alarm method

Abstract

The system uses the weak induced current flowing through the construction machinery to generate a highly accurate alarm when a construction machine crosses a designated alarm line. [Solution] An alarm system that detects when a construction machine crosses a scheduled alarm line and issues an alarm, comprising: an induction current detector that continuously or intermittently detects the current flowing through the construction machine and measures the current value; and a control unit that controls the issuance of an alarm based on the current value, wherein the control unit includes a threshold setting unit that acquires the current value measured by the induction current detector as a threshold current value and sets the threshold current value as an alarm threshold; a current value monitoring unit that acquires the current value measured by the induction current detector as a determination current value and compares the determination current value with the alarm threshold; and an alarm output unit that issues an alarm when the determination current value exceeds the alarm threshold.

Description

Technical Field

[0001] The present invention relates to an alarm reporting system that can be mounted on construction machinery, an alarm reporting device equipped with the alarm reporting system, and an alarm reporting method using the alarm reporting device.

Background Art

[0002] When working using construction machinery such as a mobile crane near a power transmission line or a distribution line, even if the construction machinery does not directly contact the electric wire, electricity may flow just by approaching, resulting in serious electric shock disasters or power outage accidents. For this reason, for example, Patent Document 1 discloses a proximity alarm device that issues an alarm when a mobile crane approaches a power transmission and distribution line.

[0003] Specifically, a weak induced current flowing through the crane body is detected, and only the signal component of the commercial frequency is extracted through a current transformer and a filter, and then amplification is performed and a comparison with a preset determination value is made. And when this signal component exceeds the determination value, an alarm is issued by an alarm circuit. Also, in detecting the induced current, the induced current is configured to flow in the order of the crane body, the grounding wire, and the ground through a stray capacitance from the power transmission and distribution line, and a detector for the induced current is provided on the grounding wire. And the grounding wire is in contact with the ground and a grounding plate provided on the outrigger via an insulating base.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to Patent Document 1, an alarm can be triggered if a weak induced current exceeds a preset threshold, regardless of which part of the crane body approaches a power transmission line. However, it is susceptible to ambient noise due to improvements in long-range, high-power wireless technology. Furthermore, detection accuracy tends to vary depending on the weather, such as being more likely to detect weak induced currents in rainy weather or high humidity. In addition, the commercial frequency extracted from the induced current may not be completely filtered out by the filter.

[0006] Furthermore, since the grounding wire connected to the crane body is connected to a grounding plate on the outrigger via an insulating base, the induced current is susceptible to the influence of the varying grounding resistance between the grounding plate and the ground surface. In other words, the grounding resistance differs depending on the conditions of the ground surface (sand layer, ballast layer, concrete slab, steel plate, or compacted soil, etc.). In addition, the induced current is also susceptible to the influence of differences in conductivity due to differences in construction machinery.

[0007] Thus, weak induced currents and the commercial frequencies derived from them are susceptible to various influences and prone to errors. When such errors occur, combined with the fact that there is only one threshold value for triggering an alarm, it can lead to a situation where the alarm is not triggered even when part of the crane body approaches the power lines, potentially causing electric shock accidents.

[0008] This invention has been made in view of the above problems, and its main objective is to issue a warning that indicates a construction machine has crossed a designated warning line, using the weak induced current flowing through the construction machine with high accuracy. [Means for solving the problem]

[0009] To achieve this objective, the present invention provides an alarm system that detects when a construction machine crosses a scheduled alarm line and issues an alarm, comprising: an induction current detector that continuously or intermittently detects the current flowing through the construction machine and measures the current value; and a control unit that controls the issuance of an alarm based on the current value, wherein the control unit includes a threshold setting unit that acquires the current value measured by the induction current detector as a threshold current value and sets the threshold current value as an alarm threshold; a current value monitoring unit that acquires the current value measured by the induction current detector as a determination current value and compares the determination current value with the alarm threshold; and an alarm output unit that issues an alarm when the determination current value exceeds the alarm threshold.

[0010] The alarm issuing device of the present invention is an alarm issuing device equipped with the alarm issuing system of the present invention, characterized by comprising: a storage box for housing the alarm issuing system; a connecting wire for connecting the construction machine and the alarm issuing system; and an earth wire for connecting the alarm issuing system to any ground.

[0011] The present invention provides an alarm activation method for detecting when a construction machine crosses an arbitrarily set alarm activation line and issuing an alarm, comprising: a threshold setting step of measuring the current flowing through the construction machine while a part of the construction machine is positioned on the alarm activation line in advance, and setting the current value obtained as a threshold current value and the threshold current value as an alarm activation threshold; a current value monitoring step of measuring the current flowing through the construction machine continuously or intermittently while the construction machine is in operation, and using the current value obtained as a determination current value, and comparing the determination current value with the alarm activation threshold; and an alarm output step of issuing an alarm when the determination current value exceeds the alarm activation threshold.

[0012] The alarm activation method of the present invention is characterized by setting multiple scheduled alarm lines at intervals, and setting an alarm threshold for each of the multiple scheduled alarm lines.

[0013] The alarm activation method of the present invention is characterized in that the scheduled alarm line is set along a power transmission and distribution line.

[0014] The alarm activation method of the present invention is characterized in that the threshold setting step is performed and the alarm activation threshold is updated each time the environment of the site where the construction machinery is operated changes.

[0015] According to the alarm system, alarm device, and alarm method of the present invention, with the construction machine positioned on an arbitrarily set alarm line, the current value of the current flowing through the construction machine is acquired as a threshold current value, and this threshold current value is set as the alarm threshold for alarm activation. This allows the alarm threshold to be adjusted to encompass various uncertain conditions, such as the effects of external disturbances such as ambient noise and weather, and individual differences in construction machines. Therefore, by simply comparing a judgment current value obtained by measuring the weak induced current flowing through the construction machine with the alarm threshold, it becomes possible to issue an alarm that indicates with high accuracy that the construction machine has crossed the alarm line.

[0016] Furthermore, by setting multiple scheduled alarm lines at intervals and establishing an alarm threshold for each line, alarms can be issued in stages. Therefore, by arranging multiple scheduled alarm lines in parallel, for example, along power transmission and distribution lines, it becomes possible to notify site managers and construction equipment operators in stages about the degree of proximity, such as how close the construction equipment is to the power transmission lines.

[0017] Furthermore, the alarm system has a simple configuration in which connection wires and ground wires, which are connected to a storage box housing the alarm system, are connected to the construction machine body and any available ground, respectively. This makes it highly versatile and portable. Therefore, even if the construction machinery used for the work changes as the construction progresses, the alarm system can be installed each time a new piece of construction machinery is brought in to provide the alarm function. [Effects of the Invention]

[0018] According to the present invention, in order to adjust the reporting threshold value including various uncertain conditions such as the influence of disturbances such as ambient noise and weather, and individual differences of construction machines, the reporting threshold value and the weak induced current flowing through the construction machine are measured and obtained. By comparing with the determination current value, it is possible to issue an alarm that notifies with high accuracy that the construction machine has exceeded the reporting scheduled line.

Brief Description of the Drawings

[0019] [Figure 1] It is a figure which shows a state where an alarm reporting device is mounted on the mobile crane of the embodiment of this invention. [Figure 2] It is a figure which shows a state where three reporting scheduled lines parallel to the power distribution line of the embodiment of this invention are provided at intervals. [Figure 3] It is a figure which shows an outline of the alarm reporting method of the embodiment of this invention. [Figure 4] It is a figure which shows the alarm reporting device and alarm reporting system of the embodiment of this invention. [Figure 5] It is a flow of the alarm reporting method using the alarm reporting device of the embodiment of this invention.

Mode for Carrying Out the Invention

[0020] The alarm reporting system, alarm reporting device, and alarm reporting method of the present invention can be adopted for any construction machine and any construction work. In this embodiment, a case where a mobile crane is adopted in the vicinity of a power distribution line supported by a utility pole and a lifting operation is carried out is cited as an example, and the details will be described with reference to FIGS. 1 to 5.

[0021] As shown in Fig. 1(a), when carrying out construction work using the mobile crane 10 in the vicinity of the power distribution line 20 supported by the utility pole 21, safety is considered, and it is obligatory to ensure the construction separation distance L0 recommended by the power company or the like and work. Therefore, a proximity limit E is set with a slight margin with respect to the construction separation distance L0, and an alarm reporting device 30 that issues an alarm when the mobile crane 10 intrudes beyond this proximity limit E and moves to the power distribution line 20 side is attached to the mobile crane 10.

[0022] <<<Outline of Alarm Transmission Method>>> The alarm transmission device 30 is a device that utilizes the fact that a weak induction current on the order of several tens of μA, which has little impact on the human body and equipment flowing through the mobile crane 10, increases as it approaches the power distribution line 20. The procedure for transmitting an alarm using this alarm transmission device 30 is as follows.

[0023] First, as shown in Fig. 1(b), a planned transmission line A extending along the power distribution line 20 is set in advance on the proximity limit E. Next, with at least a part of the mobile crane 10 positioned on the planned transmission line A, the induction current flowing through the mobile crane 10 is measured, and the measured current value is obtained as the threshold current value. After setting this threshold current value as the transmission threshold Ta, construction using the mobile crane 10 is started. During the operation period by the mobile crane 10, the induction current flowing through the mobile crane 10 is measured continuously or intermittently, and the measured current value is obtained as the determination current value.

[0024] This determination current value is monitored and compared with the transmission threshold Ta. When the determination current value exceeds the transmission threshold Ta, it is determined that the mobile crane 10 has crossed the planned transmission line A (that is, has invaded the side of the power distribution line 20 beyond the proximity limit E), and an alarm is transmitted. The timing of transmitting the alarm can be set only when the mobile crane 10 crosses the planned transmission line A as described above, or it can also be set to transmit the alarm step by step before that.

[0025] <<<Outline of Step-by-Step Alarm Transmission Method>>> In Fig. 2, as an example, transmission planned lines B and C parallel to the transmission planned line A extending along the power distribution line 20 are set at two locations at a predetermined separation interval before the mobile crane 10 crosses the transmission planned line A, and the alarm is transmitted in a total of three steps.

[0026] In this case, for example, as shown in the flow chart of Figure 3(a), the induced current flowing through the mobile crane 10 is measured in the order of planned alarm line A, planned alarm line B, and planned alarm line C, with at least a portion of the mobile crane 10 positioned on planned alarm lines A, B, and C, and the measured current values ​​are acquired as threshold current values. Then, the threshold current values ​​acquired for each of the planned alarm lines A to C are set as alarm thresholds Ta to Tc, respectively.

[0027] After this, construction work using the mobile crane 10 is started, and the alarm thresholds Ta, Tb, and Tc are continuously or intermittently compared with the judgment current values ​​obtained by measuring the induced current flowing through the mobile crane 10. This allows for two alarms to be issued before the mobile crane 10 crosses the planned alarm line A and enters the power distribution line 20 side. By changing the alarm pattern for each alarm, it becomes possible to inform the site manager and the operator of the mobile crane 10 of the degree of proximity to the power distribution line 20 in a stepwise and intuitive manner.

[0028] For example, as shown in the flowchart in Figure 3(b), if work using the mobile crane 10 is started near the power distribution line 20, and the mobile crane 10 does not cross the planned alarm line C, no alarm will be triggered. Next, if the crane crosses the planned alarm line C but does not cross the planned alarm line B, alarm pattern 1 will be triggered. Also, if the crane crosses the planned alarm line B but does not cross the planned alarm line A, alarm pattern 2 will be triggered. If the operator of the mobile crane 10 sees alarm pattern 1, they should continue the work; if they see alarm pattern 2, they should be aware that they are working in close proximity and continue the work with caution.

[0029] Furthermore, if a portion of the mobile crane 10 crosses the planned alarm line A, alarm pattern 3 will be activated. Upon seeing this, the operator of the mobile crane 10 can immediately suspend work, thus ensuring that construction proceeds safely. The means of activating the alarm can be any method, such as sounding a buzzer or illuminating a warning light, as long as it can emit visually and / or audibly different information for each of the alarm patterns 1 to 3. For example, with a buzzer, the pitch or tone of the sound can be changed, or with a warning light, the color or flashing pattern can be changed.

[0030] ≪≪≪Alarm device 30≫≫≫ As described above, the alarm device 30, which can progressively notify when a part of the mobile crane 10 approaches the power distribution line 20, is detachably attached to the main body of the mobile crane 10, as shown in Figures 2 and 4(a), and includes a storage box 31, a connecting wire 32, and a ground wire 33.

[0031] As shown in Figures 4(a) and (b), the storage box 31 houses the alarm system 40 and has an operation panel 34 on its surface. The upper side is equipped with a heavy equipment body connection terminal 311 and a ground connection terminal 312. The other end of a connection wire 32, one end of which is connected to the crane body 11, is connected to the heavy equipment body connection terminal 311. The other end of an earth wire 33, the other end of which is connected to the ground of the battery 13 provided in the mobile crane 10, is connected to the ground connection terminal 312.

[0032] Furthermore, the heavy equipment body connection terminal 311 and the ground connection terminal 312 are terminals for connecting the connection wire 32 and the ground wire 33 to the alarm system 40. By connecting them as described above, an electrical circuit without grounding (crane body 11 → alarm system 40 in the storage box 31 → ground wire 33 → battery 13 ground) is formed, as shown in Figure 4(b). Therefore, it is possible to detect the weak induced current flowing through the mobile crane 10, which changes depending on the distance from the power distribution line 20, via the alarm system 40, without being affected by the ground conditions (sand layer, ballast layer, concrete slab, steel plate, or compacted soil, etc.) to which the mobile crane 10 is deployed, as would be the case with grounding.

[0033] Furthermore, as shown in Figure 4(b), the control panel 34 of the storage box 31 is equipped with a stage setting button 341 and a calibration switch 342, which function as input devices for inputting information into the alarm system 40. The stage setting button 341 is used to set the number of stages (i.e., the number of alarm thresholds) when the alarm is issued in stages, and the calibration switch 342 is used to set the aforementioned threshold current value to the alarm threshold. Both of these are operated by the worker.

[0034] Furthermore, the control panel 34 is equipped with a work readiness lamp 343, a buzzer output unit 344, multiple proximity alarm and threshold setting lamps 345, and a contact output unit 346, which function as output devices for outputting information processed by the alarm system 40. The work readiness lamp 343 lights up when the alarm thresholds have been set to the number of levels set by the step setting button 341. The buzzer output unit 344 outputs a buzzer sound assigned to each of the multiple alarm thresholds.

[0035] The proximity alarm and threshold setting lamp 345 consists of multiple lamps of different colors, with one of several alarm thresholds assigned to each color. Figure 4(a) shows an example where alarm activation can be selected from one to five levels (i.e., up to five alarm thresholds). For this reason, five proximity alarm and threshold setting lamps 345 are provided, but the number is not limited to this.

[0036] The contact output units 346 are provided in the same number as the proximity alarm and threshold setting lamps 345. These are terminals used to connect the external multi-color lamps 70 and the alarm activation system 40 by wire. Each color of the external multi-color lamps 70 is assigned one of several alarm thresholds. All of these operate based on commands from the alarm activation system 40.

[0037] ≪≪Warning System 40≫≫ The alarm system 40 includes an induced current detector 50 and a control unit 60 consisting of a microcontroller, as shown in Figure 4(b).

[0038] The induction current detector 50 detects the current flowing through the circuit formed by connecting the alarm system 40 to the connecting wire 32 connected to the crane body 11 and the ground wire 33 connected to the ground of the battery 13 provided in the mobile crane 10, and continuously or intermittently measures current values ​​such as the threshold current value and the judgment current value mentioned above.

[0039] When the control unit 60 receives an operation signal from the control panel 34 via an operator's operation, it executes a predetermined control program stored in a memory unit (not shown) to realize the functions of the alarm activation stage setting unit 61, threshold setting unit 62, current value monitoring unit 63, and alarm output unit 64. As will be described in detail later, the alarm activation stage setting unit 61 sets the number of alarm activation thresholds based on the operation signal related to the number of alarm activation stages N input from the control panel 34.

[0040] The threshold setting unit 62 acquires the current value of the induced current flowing through the mobile crane 10 measured by the induced current detector 50, and sets this as the threshold current value for the alarm thresholds Ta, Tb, Tc, etc., repeating this process for the number of stages N set by the alarm stage setting unit 61. The current value monitoring unit 63 acquires the current value of the induced current flowing through the mobile crane 10 measured by the induced current detector 50, and continuously monitors this as the judgment current value, comparing it with each of the alarm thresholds Ta, Tb, Tc, etc. set by the threshold setting unit 62. Then, the alarm output unit 64 outputs an output signal to the control panel 34 to issue an alarm if the judgment current value exceeds any of the alarm thresholds Ta, Tb, Tc, etc.

[0041] << The alarm activation method using the alarm activation device 30 equipped with the above-described alarm activation system 40 will be explained using the example of a construction project using a mobile crane 10 near a power distribution line 20, where alarms are activated in stages at three locations A to C, as shown in Figure 2, referring to the block diagram in Figure 4(b) and following the flow shown in Figure 5.

[0042] <<Construction Process: Preparation (STEP 1)>> In the preliminary preparation stage before carrying out construction work using the mobile crane 10, the number of stages N for which an alarm will be issued is determined, and an alarm threshold corresponding to the determined number of stages N is set.

[0043] ≪Alarm Stage Setting Process: STEP 1-1≫ First, the worker operates the stage setting button 341 on the control panel 34 to input the number of stages N for which the alarm will be triggered. In Figure 2, since the mobile crane 10 triggers an alarm each time it crosses the three points on the planned alarm lines A to C, "3" is entered as the number of alarm stages N. When the input signal from the control panel 34 is input to the control unit 60, the control unit 60 receives a command from the alarm stage setting unit 61 and stores "3" as the alarm threshold number in its memory unit.

[0044] ≪Threshold Setting Process: STEP 1-2≫ Next, the mobile crane 10 is moved to a position where at least a portion of it reaches the planned alarm line A. In this state, the worker operates the calibration switch 342 on the control panel 34.

[0045] When an input signal from the control panel 34 is input to the control unit 60, the control unit 60 receives a command from the threshold setting unit 62 and acquires the current value measured by the induction current detector 50 as the threshold current value. It also sets this threshold current value as the alarm threshold Ta of the planned alarm line A and outputs an output signal to the control panel 34 to notify that the first alarm threshold has been set. At this point, one of the multiple proximity alarm and threshold setting lamps 345 provided on the control panel 34, corresponding to the color assigned to the alarm threshold Ta, lights up.

[0046] After the worker confirms that the proximity alarm and threshold setting lamp 345 is flashing, the worker moves the mobile crane 10 to a position where at least a portion of it reaches the planned alarm line B. After this, when the worker operates the calibration switch 342 on the control panel 34, the control unit 60 acquires the current value measured by the induction current detector 50 as the threshold current value in the above procedure and sets it as the alarm threshold Tb for the planned alarm line B. Then, among the multiple proximity alarm and threshold setting lamps 345, the lamp of the color assigned to the alarm threshold Tb lights up.

[0047] By repeating the above procedure, once the alarm threshold Tc for the planned alarm line C is set, the control unit 60 receives a command from the threshold setting unit 62 and outputs an output signal to the control panel 34 to notify that all three alarm thresholds Ta, Tb, and Tc for issuing an alarm have been set. Then, not only does the lamp of the color assigned to the alarm threshold for the planned alarm line C among the proximity alarm and threshold setting lamps 345 on the control panel 34 light up, but the work preparation complete lamp 343 also lights up.

[0048] Furthermore, once all alarm thresholds Ta, Tb, and Tc are set, the control unit 60 receives a command from the current value monitoring unit 63 and acquires the current values ​​measured continuously or intermittently by the induced current detector 50 as determination current values, and starts a monitoring process that compares these with each of the three alarm thresholds Ta, Tb, and Tc. Note that the weak induced current flowing through the mobile crane 10 increases as it approaches the power distribution line 20, so the alarm threshold for the planned alarm line A is the largest, and the alarm thresholds decrease in stages for the planned alarm lines B and C.

[0049] <<Construction Flow: Commencement of work with construction machinery (STEP 2)>> Once the alarm system 30 is set up and alarms can be issued, construction work using the mobile crane 10 begins.

[0050] ≪Current Value Monitoring Process: STEP 2-1≫ After commencing construction work using the mobile crane 10, during the operation, the control unit 60 receives commands from the current value monitoring unit 63 and acquires current values ​​measured continuously or intermittently by the induction current detector 50 as judgment current values, and continues to compare these with the three alarm thresholds Ta, Tb, and Tc.

[0051] ≪Alarm output process: STEP2-2≫ For example, the jib 12 of the mobile crane 10, as shown in Figure 2, crosses the planned alarm line C and enters the space between the planned alarm line B and the planned alarm line C. In this case, the control unit 60 detects that the judgment current value exceeds the alarm threshold Tc. Upon receiving a command from the alarm output unit 64, the control unit 60 outputs an output signal to the control panel 34 to announce the alarm pattern 1 corresponding to the alarm threshold Tc.

[0052] As a result, as alarm pattern 1, the proximity alarm and threshold setting lamp 345 on the control panel 34, specifically the lamp of the color assigned to the alarm threshold Tc, is illuminated. In addition, the buzzer output unit 344 sounds a buzzer corresponding to the alarm threshold Tc. Furthermore, the external multi-color lamp 70, which is wired to the alarm activation device 30 via the contact output unit 346, illuminates the lamp of the color assigned to the alarm threshold Tc.

[0053] Furthermore, if the jib 12 of the mobile crane 10 crosses the planned alarm line B and enters the space between the planned alarm line A and the planned alarm line B, the control unit 60 detects that the judgment current value exceeds both the alarm threshold Tb and the alarm threshold Tc. In this way, if the judgment current value exceeds two or more alarm thresholds, the control unit 60 receives a command from the alarm output unit 64, detects the largest alarm threshold, and outputs an output signal to the control panel 34 to notify the corresponding alarm pattern.

[0054] Therefore, if the judgment current value exceeds both the alarm threshold Tb and the alarm threshold Tc, an output signal for announcing alarm pattern 2 corresponding to the alarm threshold Tb is output to the control panel 34. As a result, alarm pattern 2 is activated by illuminating the color of the proximity alarm and threshold setting lamp 345 on the control panel 34 that is assigned to the alarm threshold Tb. In addition, a buzzer sound corresponding to the alarm threshold Tb is sounded from the buzzer output unit 344. Furthermore, the external multi-color lamp 70 illuminates the color of the lamp assigned to the alarm threshold Tb.

[0055] Then, the jib 12 of the mobile crane 10 crosses the planned alarm line A (exceeding the proximity limit E) and enters the power distribution line 20 side. Upon receiving a command from the alarm output unit 64, the control unit 60 detects that the judgment current value has exceeded three alarm thresholds Ta, Tb, and Tc. Therefore, the control unit 60, upon receiving a command from the alarm output unit 64, detects the largest alarm threshold Ta and outputs an output signal to the control panel 34 to notify the alarm pattern 3 corresponding to the alarm threshold Ta.

[0056] As a result, as alarm pattern 3, the proximity alarm and threshold setting lamp 345 on the control panel 34 illuminates the lamp of the color assigned to the alarm threshold Ta. In addition, the buzzer output unit 344 sounds a buzzer corresponding to the alarm threshold Ta. Furthermore, the external multi-color lamp 70 illuminates the lamp of the color assigned to the alarm threshold Ta. Upon confirming these alarm patterns 3, the worker stops the operation of the mobile crane 10 and interrupts the work.

[0057] Furthermore, if environmental changes occur during the construction period, work by the mobile crane 10 will be temporarily suspended. The validity of the three alarm thresholds Ta, Tb, and Tc will then be verified, and they will be readjusted as necessary. Examples of environmental changes include changes in weather or changes in the work location.

[0058] Specifically, it is known that detection accuracy varies depending on the weather; for example, it is easier to detect the induced current flowing through the mobile crane 10 in rainy weather or under high humidity conditions compared to sunny weather. Therefore, for example, if the alarm threshold Ta set for rainy weather is continuously used in sunny weather, even if the mobile crane 10 mistakenly enters the power distribution line 20 side from the planned alarm line A, the judgment current value may not exceed the alarm threshold Ta due to errors in detection accuracy.

[0059] Furthermore, when the mobile crane 10 is moved to perform subsequent work after the preceding work has been completed, the intensity of ambient noise that affects the induced current flowing through the mobile crane 10 may differ before and after the move, potentially resulting in differences in the accuracy of induced current detection. When encountering such environmental changes, the three alarm thresholds Ta, Tb, and Tc are adjusted to correspond to the site environment. This makes it possible to reliably issue alarms for each of the planned alarm lines A, B, and C.

[0060] Furthermore, the alarm device 30 has a simple configuration in which the connection wire 32 and ground wire 33, which are connected to the storage box 31 housing the alarm system 40, are connected to the negative terminals of the crane body 11 and the battery 13, respectively. Therefore, it is highly versatile and can be made smaller and lighter to be portable. In addition, the power supply may be supplied from the vehicle battery or cigarette lighter socket of the mobile crane 10, or a mobile battery can be used.

[0061] Therefore, as the construction progresses, if the construction machinery used for the work changes from the mobile crane 10 to other machinery, the alarm device 30 is attached to the newly delivered construction machinery. Each time it is attached, the alarm thresholds Ta, Tb, and Tc are reset using the procedure described above. This makes it possible to trigger alarms in stages for each planned alarm line A, B, and C, without being affected by individual differences in construction machinery.

[0062] In this way, the alarm issuing device 30 and the alarm issuing system 40 can adjust the alarm thresholds Ta, Tb, and Tc to take into account various uncertain conditions such as the influence of external disturbances such as ambient noise and weather, and individual differences in construction machinery. Therefore, by comparing these with judgment current values ​​obtained by measuring the induced current flowing through the mobile crane 10, etc., it becomes possible to issue an alarm with high accuracy to indicate that the mobile crane 10, etc. has crossed the planned alarm line.

[0063] The alarm system 40, alarm device 30, and alarm method of the present invention are not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

[0064] For example, in this embodiment, we have given the case where the alarm device 30 is mounted on a mobile crane 10, but it is not limited to this, and it can be used in any construction machine as long as the main body is conductive.

[0065] Furthermore, the alarm activation method was explained using the example of carrying out construction work using a mobile crane 10 near a power distribution line 20 supported by a utility pole 21. However, this method can be applied to any construction work where there is equipment that causes the current value of the induced current flowing through construction machinery to change when approached, such as near power transmission lines supported by a steel tower.

[0066] Furthermore, the ground wire 33 provided on the alarm device 30 is connected to the negative (ground) of the battery 13 of the mobile crane 10, as shown in Figure 4(b), but is not limited to this. It may be connected to another ground by any means, or it may be configured to be connected to the earth.

[0067] In this embodiment, as shown in Figure 4(a), the alarm system 40 and the external multi-color lamp 70 are connected by wire via the contact output unit 346. However, instead of the external multi-color lamp 70, it is also possible to connect it to the control unit of the mobile crane 10 and transmit and output a signal to control the operation of the mobile crane 10.

[0068] For example, if the jib 12 of a mobile crane 10 crosses the planned alarm line C and the judgment current value exceeds the alarm threshold Tc, it can output a control signal such as "proximity alarm"; if it crosses the planned alarm line B and the judgment current value exceeds the alarm threshold Tb, it can output a control signal such as "forced deceleration"; and if it crosses the planned alarm line A and the judgment current value exceeds the alarm threshold Ta, it can output a control signal such as "emergency stop". This makes it possible to ensure a higher level of safety when performing construction work near power transmission and distribution lines.

[0069] Furthermore, in this embodiment, Figure 4(a) shows an example where the alarm system 40 can select from 1 to 5 stages of alarm activation (i.e., up to 5 activation thresholds). Also, as shown in Figure 2, an example of the alarm activation method is given where there are 3 stages of alarm activation. However, these are not restrictions, and the number of alarm activation stages N can be set to any value. [Explanation of symbols]

[0070] 10 Mobile Cranes 11 Crane body 12 jibs 13 batteries 20 Power distribution lines 21 utility poles 22 Predetermined area 30 Alarm device 31 Storage Boxes 311 Heavy equipment main unit connection terminal 312 Ground connection terminal 313 Power supply 32 connecting wires 33. Ground wire 34 Control panel 341 Step setting button 342 Calibration Switch 343 Ready to Work Lamp 344 Buzzer output section 345 Proximity alarm and threshold setting lamp 346 Contact output section 40. Alarm System 50 Induction Current Detector 60 Control Unit 61 Alarm stage setting unit 62 Threshold setting section 63 Current Value Monitoring Unit 64 Alarm output section 70 external multicolor light L0 construction distance A Scheduled Signal Line B Scheduled Signal Line C Scheduled Signal Line E Proximity Limit

Claims

1. An alarm system that detects when construction machinery crosses a designated alarm line and issues an alarm, An induction current detector that continuously or intermittently detects the current flowing through the construction machine and measures the current value, The system includes a control unit that controls the activation of an alarm based on the current value, The control unit, A threshold setting unit acquires the current value measured by the induction current detector as a threshold current value and sets the threshold current value as the alarm threshold, A current value monitoring unit acquires the current value measured by the induction current detector as a determination current value and compares the determination current value with the alarm threshold, When the current value used for determination exceeds the alarm threshold, an alarm output unit issues an alarm. An alarm system characterized by including the following.

2. An alarm system comprising the alarm system described in claim 1, A storage box for housing the aforementioned alarm system, A connecting wire that connects the construction machine and the alarm system, An earth wire connecting the alarm system to any ground, An alarm activation device characterized by being equipped with the following features.

3. An alarm activation method that detects when a construction machine crosses an arbitrarily set alarm activation line and issues an alarm, A threshold setting step involves first measuring the current flowing through the construction machine while a part of the construction machine is positioned on the planned alarm line, obtaining the current value as the threshold current value, and setting this threshold current value as the alarm threshold. A current value monitoring step is performed in which the current flowing through the construction machine is measured continuously or intermittently while the construction machine is in operation, the current value obtained is used as a determination current value, and the determination current value is compared with the alarm threshold, When the current value for determination exceeds the alarm threshold, an alarm output step is performed to issue an alarm, An alarm activation method characterized by including the following.

4. In the alarm activation method described in claim 3, An alarm activation method characterized by setting multiple scheduled alarm lines with intervals between them, and setting an alarm threshold for each scheduled alarm line.

5. In the alarm activation method described in claim 3, An alarm activation method characterized in that the scheduled alarm activation line is set along a power transmission and distribution line.

6. In the alarm activation method described in claim 3, An alarm activation method characterized by performing the threshold setting process and updating the alarm activation threshold each time the environment of the construction site where the construction machinery is operated changes.

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