JP3827144B2 - Damage detection device for power supply cable - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a detection device that detects the presence or absence of damage to a power supply cable wired between a power supply unit of a spot welder and a welding gun by using gas pressure.
[0002]
[Prior art]
As shown in FIG. 3A, the welding gun 23 of the spot welder 21 is supported by the lower end of a suspension rod 28 suspended from a horizontal rail 27, and the operator can easily move the welding gun 22 by hand. It is like that. The welding gun 23 is connected to the power supply unit 22 via a welding transformer primary cable 31 supported at the lower ends of the suspension rods 29a and 29b at several points. In the figure, 24 is a current breaker, 25 is a connector, 26 is an abnormality detection means, 41 is a cable damage detection device, 42 is a power supply for detection, 43 is an overvoltage detection means, and 44 is a ground fault current detection means. These will be described later.
[0003]
The primary cable 31 has a cross-sectional structure as shown in FIG. 3B, in which 32a and 32b are power lines, 32c and 32d are signal lines, 32e is a ground line, and 33a and 33b are insulating coatings. If the insulation coating 33a of the primary cable 31 is cracked or holed due to damage, the power wires 32a and 32b, which are bare wires, or the power wires 32a and 32b and the ground wire 32e may be short-circuited. Further, if the insulation coating 33b of the primary cable 31 is cracked, there is a possibility that the power lines 32a and 32b are exposed to the outside and cause electric leakage.
[0004]
In order to detect that the covering of the power supply lines 32a, 32b or the ground line 32e is damaged before such a short circuit or electric leakage occurs, a mesh conductor 34 is conventionally arranged inside the insulating coating 33b of the primary cable 31. It is done. As shown in FIG. 3A, the mesh conductor 34 is grounded via the connector 25, the detection power source 42, and the ground fault current detecting means 44, while being connected to the overvoltage detecting means 43 via the connector. ing. When the mesh conductor 34 comes into contact with the ground wire 32c or the external conductor, the current breaker 24 is actuated by the ground fault current detecting means 44. When the mesh conductor 34 comes into contact with the power supply lines 32a and 32b, the overvoltage detection means 43 cuts off the current. The device 24 is operated similarly.
[0005]
When an abnormality sign of the spot welder 21 such as an abnormal temperature rise of the welding gun 23 is detected, the abnormality information is transmitted to the current breaker 24 via the signal lines 32c and 32d, and the current breaker 24 As a result, the power supply from the power supply unit 22 is cut off, and the abnormality alarm 26 is activated to notify the operator of an abnormality sign of the spot welding machine 21.
[0006]
[Problems to be solved by the invention]
In the conventional cable damage detection device 41, even if the insulation coatings 33a and 33b have cracks or holes, the current breaker 24 is used until the power lines 32a and 32b or the external conductors actually contact the mesh conductor 34. The power supply from the power supply unit 22 to the welding gun 23 was continued without operating. For this reason, there is a possibility that the worker may continue the welding operation without noticing the damage to the insulating coatings 33a and 33b and proceed without knowing the degree of damage to the insulating coatings 33a and 33b.
[0007]
The present invention has been made in view of such a problem, and an object of the present invention is to reliably detect even a minute damage of an insulating coating of a power feeding cable.
[0008]
[Means for Solving the Problems]
The power supply cable damage detection device according to the present invention supplies a sealed gas of a predetermined pressure to the inner space of the insulating coating of the flexible power supply cable wired between the power supply unit having a fixed arrangement and the mobile electric device. A gas supply / discharge means capable of exhausting, and a pressure gauge capable of detecting the pressure of a predetermined pressure of the sealed gas sealed inside the insulating coating by the gas supply / discharge means, and the mobile electric device stops. In this state, the gas supply / exhaust means supplies the sealed gas of a predetermined pressure to the inner space of the insulating coating of the flexible power supply cable, and detects the pressure drop of the sealed gas with a pressure gauge, thereby insulating the insulation. The presence or absence of damage to the coating is detected, and if the insulation coating is not damaged, the sealed gas of a predetermined pressure is exhausted from the inner space of the insulation coating of the flexible power supply cable to restore the flexibility of the flexible power supply cable. Move the mobile electrical equipment through the street Characterized in that the the cause.
[0009]
According to the above configuration of the present invention, when the insulating coating is damaged and fine cracks or holes are formed, the gas contained in the insulating coating leaks to the outside and the internal pressure decreases. Thus, countermeasure work such as repair and replacement of the insulating coating can be performed at an early stage.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a cable damage detection apparatus 1 according to the present invention will be described with reference to the drawings. In the present embodiment, air is used as the sealed gas, and the following description will be made according to this.
[0011]
The spot welder 21 in FIG. 1 has a power supply unit 22 and a movable welding gun 23 that are fixedly arranged as in the prior art. The power supply unit 22 and the welding gun 23 are connected to a current breaker 24, a connector 25, It is connected via a flexible primary cable 31a. The primary cable 31a has a cross-sectional structure as shown in FIG. 2A, in which 32a and 32b are power lines, 32c and 32d are signal lines, 32e is a ground line, and 33a and 33b are airtight insulating coatings. It is. A gas layer 35 in which air of a predetermined pressure is sealed is formed between the power lines 32a and 32b and the insulating coating 33a and inside the outermost insulating coating 33b.
[0012]
The cable damage detection device 1 according to the present invention includes a gas supply / discharge means 2, a pressure gauge 3, and a control device 4, and is disposed in the vicinity of the power supply unit 22. As shown in FIG. 1, the gas supply / discharge means 2 includes an air pump (or compressed air source) 2a, and an air hose 2b that communicates the discharge port of the air pump 2a with the gas layer 35 of the primary cable 31a. Is connected to the vicinity of the end of the primary cable 31a on the welding gun 23 side. The gas supply / discharge means 2 supplies air of a predetermined pressure to the gas layer 35 and exhausts air from the gas layer 35. The supply and discharge of compressed air to and from the two gas layers 35 between the power lines 32a and 32b and the insulating coating 33a and the one gas layer 35 inside the outermost insulating coating 33b are performed independently. ing.
[0013]
A control device 4 is attached to the gas supply / discharge means 2, and supply / discharge of air to / from the gas layer 35 and pressure control of the gas layer 35 are performed by the control device 4. The pressure gauge 3 detects the air pressure of the gas layer 35 of the primary cable 31 a, is connected to the vicinity of the end of the primary cable 31 a on the connector 25 side, and transmits the measured value to the control device 4. It has become.
[0014]
The damage detection apparatus 1 according to the present invention is configured as described above, and the damage detection apparatus 1 is operated between welding cycles by the welding gun 23 to detect whether the primary cable 31a is damaged. That is, when the welding process of one workpiece (not shown) is completed by the welding gun 23 and the welding gun 23 returns to a predetermined standby position in preparation for welding of the next workpiece, the air pump 2a is activated and the inside of the primary cable 31a is operated. A predetermined pressure of air is supplied to the gas layer 35. If there is no abnormality in the insulating coating 33a or 33b, the pressure of the pressure gauge 3 does not change because the pressure of the gas layer 35 is maintained at a predetermined pressure. When this pressure stable state is maintained for several seconds, the control device 4 operates to exhaust the compressed air from the gas layer 35 in the primary cable 31a and restore the flexibility of the primary cable 31a to the welding gun. The next welding cycle according to 23 is started. The supply and discharge of compressed air to the two gas layers 35 between the power lines 32a and 32b and the insulating coating 33a and the one gas layer 35 inside the outermost insulating coating 33b are shifted in time. By performing it independently, it is possible to individually detect the presence or absence of damage to the insulating coating 33a or 33b.
[0015]
Next, when a crack or a hole is generated due to damage to the insulating coating of the primary cable 31a, the welding gun 23 returns to the standby position, and compressed air is supplied to the gas layer 35 of the primary cable 31a. Even if the pressure reaches a predetermined pressure temporarily, if the supply of compressed air is stopped and held for several seconds, the measured value of the pressure gauge decreases due to air leakage from the insulating coating 33a or 33b. When the measurement result of the pressure drop is input to the control device 4, the current breaker 24 is activated and the power supply to the welding gun 23 is automatically stopped. Note that the compressed air is supplied to the gas layer 35 in the primary cable 31a from the side opposite to the side to which the pressure gauge 3 is connected. The measured value of the total 3 is surely lowered, and the primary cable 31a is not overlooked.
[0016]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the power supply unit 22 and the welding gun 23 are connected. Although the present invention is applied to the primary cable 31a, the present invention can also be applied to a power supply cable connected to electrical equipment other than the welding gun 23. In this case, when the power supply cable is rigid and has a fixed arrangement, a gas layer is used. A gas having a predetermined pressure may be permanently sealed in 35. In the above embodiment, the pressure gauge 3 is connected to the control device 4. However, in addition to the control device 4, the pressure gauge 3 is also connected to the abnormality alarm device 26 so as to immediately notify the operator of damage to the insulating coatings 33a and 33b. Good. Moreover, in the said embodiment, although the cross section of the primary cable 31a was made into FIG. 2 (A), it is good also as a cross-sectional structure as shown to FIG. 2 (B)-(D). A primary cable 31b shown in FIG. 2 (B) is obtained by separating a plurality of constituent cables. The power lines 32a and 32b are covered with a first insulating film 33a, and the power cables 32a and 32b are separated from the first cables. Gas layers 35, 35 are formed between the coating 33a. Moreover, the primary cables 31c and 31d shown in FIGS. 2 (C) and 2 (D) are obtained by using the conventional cable damage detection device 41 together, and the primary cable 31c in FIG. 2 (C) is shown in FIG. 3 (B). The conventional primary cable 31 is covered with a third insulating film 33c, and a gas layer 35 is formed between the primary cable 31 and the third insulating film 33c. The primary cable shown in FIG. 31d further covers various wire bodies 32a, ..., 32e covered with the first insulating coating 33a with the second insulating coating 33b, and a mesh conductor 34 is disposed on the inner peripheral surface of the second insulating coating 33b. A gas layer 35 is formed inside the mesh conductor 34.
[0017]
【The invention's effect】
In the present invention, as described above, a gas layer having a predetermined pressure is sealed inside the insulation film of the power supply cable, and the presence or absence of a pressure drop in the gas layer is detected by a pressure gauge. Damages such as cracks and perforations can be reliably detected, and early repair work of the power supply cable can be started without delay.
[Brief description of the drawings]
FIG. 1 is a schematic view of a spot welding machine equipped with a cable damage detection device according to the present invention.
2A to 2D are cross-sectional views of a power feeding cable used in the present invention.
3A is a schematic view of a spot welder equipped with a conventional cable damage detection device, and FIG. 3B is a cross-sectional view of a power supply cable of the welder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Damage detection apparatus 2 Gas supply / discharge means 2a Air pump 2b Air hose 3 Pressure gauge 4 Control means 21 Spot welding machine 22 Power supply part 23 Welding gun (electric equipment)
23 Electrical equipment 24 Current breaker 25 Connector 26 Abnormality alarm 27 Horizontal rail 28 Suspension rod 31 Primary cable (power supply cable)
32a, 32b Power supply line 32c, 32d Signal line 32e Ground wire 33a-33c Insulating coating 34 Reticulated conductor 35 Gas layer 41 Cable damage detection device 42 Power supply for detection 43 Overvoltage detection means 44 Ground fault current detection means

Claims (1)

A gas supply / exhaust means capable of supplying / exhausting gas with a predetermined pressure to / from an inner space of an insulating coating of a flexible power supply cable wired between a power supply unit having a fixed arrangement and a mobile electric device; A pressure gauge capable of detecting the pressure of a predetermined gas sealed inside the insulating coating by a discharge means, and is flexible by the gas supply / discharge means in a state where the mobile electric device is stopped. Supplying a predetermined pressure of the sealed gas to the inner space of the insulating coating of the conductive power cable and detecting the presence or absence of pressure drop of the sealed gas with a pressure gauge to detect the damage of the insulating coating, If there is no damage, the mobile electric device is moved while the flexibility of the flexible power supply cable is restored by exhausting the sealed gas of a predetermined pressure from the inner space of the insulating coating of the flexible power supply cable. feeding cable, wherein the thing Damage detection device.

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