JP2003001433A - Detector of damage to power feed cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably detect even small damages to insulating coatings of a power feed cable. SOLUTION: A gas layer 35 is formed on the inner side of the power feed cable 31a between a power source part 22 of a spot welding machine 21 and a welding gun 23. Compressed air is fed to the gas layer 35 by a gas pumping means 2, and presence/absence of pressure drop in the gas layer 35 is measured by a pressure gauge 3 to detect presence/absence of damages to the insulating coatings 33a-33c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detector for detecting the presence / absence of damage to a power supply cable arranged between a power source section of a spot welding machine and a welding gun by using gas pressure.

[0002]

2. Description of the Related Art As shown in FIG.
The first welding gun 23 is supported by the lower end of a suspension rod 28 suspended from a horizontal rail 27 so that an operator can hold the welding gun 22 by hand and move it easily. 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 positions. In the figure, 24 is a current breaker, 25 is a connector, 26 is an abnormality detecting means, 41 is a cable damage detecting device, 42 is a detection power source,
Reference numeral 43 is an overvoltage detecting means and 44 is a ground fault current detecting means, which will be described later.

The primary cable 31 has a sectional structure as shown in FIG. 3 (B), and in the figure, 32a and 32b are power supply lines and 3
2c and 32d are signal lines, 32e is a ground line, 33a and 3
3b is an insulating film. Insulation film 3 of primary cable 31
If a crack or a hole is formed in 3a due to damage, there is a possibility that the bare power lines 32a and 32b or the power lines 32a and 32b and the ground line 32e are short-circuited. Furthermore, if the insulating coating 33b of the primary cable 31 is cracked, the power supply lines 32a and 32b may be exposed to the outside and cause electric leakage.

In order to detect that the coating of the power supply lines 32a, 32b or the ground line 32e is damaged before such a short circuit or leakage occurs, a mesh conductor is conventionally provided inside the insulating coating 33b of the primary cable 31. 34 is provided. 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, and is 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 an external conductor, the ground fault current detecting means 44 activates the current breaker 24, and when the mesh conductor 34 comes into contact with the power supply lines 32a and 32b, the overvoltage detecting means 43 shuts off the current. The device 24 is adapted to operate similarly.

When an abnormal symptom of the spot welding machine 21, such as an abnormal temperature rise of the welding gun 23, is detected, the abnormal information is transmitted to the current breaker 24 through the signal lines 32c and 32d, and the current is interrupted. The power supply from the power source unit 22 is shut off by the circuit breaker 24, and the abnormality alarm 26 is activated to notify the operator of the abnormality sign of the spot welder 21.

[0006]

In the conventional cable damage detecting device 41, the power supply lines 32a and 32b or the outer conductors actually become the mesh conductor 34 even when cracks or holes are generated in the insulating coatings 33a and 33b. The current breaker 24 did not operate until the contact, and the power supply 22 continued to supply power to the welding gun 23. Therefore, the worker may continue the welding operation without noticing the damage of the insulating coatings 33a and 33b, and may proceed without knowing the degree of damage of the insulating coatings 33a and 33b.

The present invention has been made in view of the above problems, and an object thereof is to reliably detect even minute damage to the insulating coating of the power supply cable.

[0008]

A damage detection device for a power supply cable according to the present invention encloses a sealed gas of a predetermined pressure inside an insulating coating of a power supply cable wired between a power supply section and an electric device, It is characterized in that the presence or absence of the pressure drop of the enclosed gas is detected by a pressure gauge to detect the presence or absence of damage to the power supply cable.

Further, the power supply cable damage detection device according to the present invention applies a predetermined pressure to the inner space of the insulating coating of the flexible power supply cable that is wired between the fixedly arranged power supply section and the mobile electric device. It is characterized by comprising a gas supply / discharge means capable of supplying / discharging the sealed gas and a pressure gauge capable of detecting the pressure of the sealed gas of a predetermined pressure sealed inside the insulating coating by the gas supply / discharge means.

According to the above configuration of the present invention, when the insulating coating is damaged and minute cracks or pores are generated, the gas enclosed in the insulating coating leaks to the outside to reduce the internal pressure. It is possible to reliably detect and take countermeasures such as repair and replacement of the insulating film early.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a cable damage detection device 1 according to the present invention will be described below with reference to the drawings. In addition, in the present embodiment, air is used as the enclosed gas, and the following description will be made according to this.

The spot welder 21 shown in FIG. 1 has a fixedly arranged power source section 22 and a movable welding gun 23 as in the conventional case, and the power source section 22 and the welding gun 23 have a current breaker 24,
It is connected via the connector 25 and the flexible primary cable 31a. The primary cable 31a has a cross-sectional structure as shown in FIG. 2A, and in the figure, 32a and 32b are power supply lines,
32c and 32d are signal lines, 32e is a ground line, 33a,
33b is an airtight insulating coating. Power supply lines 32a, 32
b and its insulating coating 33a, and the outermost insulating coating 3
A gas layer 35 in which a predetermined pressure of air is enclosed is formed inside 3b.

The cable damage detection device 1 of the present invention comprises a gas supply / discharge means 2, a pressure gauge 3 and a control device 4, and a power supply unit 2
It is arranged in the vicinity of 2. As shown in FIG. 1, the gas supply / discharge means 2 is composed of an air pump (or a compressed air source) 2a and an air hose 2b which 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. Then, the gas supply / exhaust means 2 supplies the air having a predetermined pressure to the gas layer 35 and exhausts the air from the gas layer 35.
The compressed air is supplied to and discharged from the two gas layers 35 between the power supply lines 32a and 32b and the insulating coating 33a and one gas layer 35 inside the outermost insulating coating 33b independently. ing.

A controller 4 is attached to the gas supply / discharge means 2, and the controller 4 controls the supply / discharge of air to the gas layer 35 and the pressure control of the gas layer 35. The pressure gauge 3 includes the gas layer 35 of the primary cable 31a.
The air pressure of the primary cable 31a is detected in the vicinity of the end of the primary cable 31a on the connector 25 side, and the measured value is transmitted to the control device 4.

The damage detection device 1 of the present invention is constructed as described above, and the damage detection device 1 is activated between welding cycles by the welding gun 23 to detect the presence or absence of damage to the primary cable 31a. That is, when the welding process of one work (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 work, the air pump 2a operates and the inside of the primary cable 31a Gas layer 35
The air of a predetermined pressure is supplied to. If there is no abnormality in the insulating coating 33a or 33b, the pressure of the gas layer 35 remains maintained at the predetermined pressure, and therefore the measured value of the pressure gauge 3 does not change. When this stable pressure state is maintained for several seconds, the control device 4 operates to discharge the compressed air from the gas layer 35 in the primary cable 31a to restore the flexibility of the primary cable 31a to the welding gun. The next welding cycle according to 23 is started. In addition, the power supply lines 32a and 32b and their insulating coatings 33
Insulating film 33a or 33b by independently supplying and discharging compressed air to and from two gas layers 35 between a and a and one gas layer 35 inside outermost insulating film 33b. It is possible to individually detect the presence or absence of damage.

Next, when the insulating coating of the primary cable 31a is damaged and cracks or holes occur, the welding gun 23 returns to the standby position, compressed air is supplied to the gas layer 35 of the primary cable 31a, and the gas layer Even if the pressure of 35 temporarily reaches a predetermined pressure, if the supply of compressed air is stopped and held for several seconds, air leakage from the insulating coating 33a or 33b causes the pressure gauge measurement value to decrease. When the measurement result of the pressure drop is input to the control device 4, the current breaker 24 operates 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 always decreases, and the damage of the primary cable 31a is never overlooked.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. For example, in the above embodiment, the power supply unit 2 is used.
Although the present invention is applied to the primary cable 31a connecting the welding gun 23 and the welding gun 23, the present invention is also applicable to a power supply cable connected to general electric equipment other than the welding gun 23,
In that case, when the power supply cable is rigid and fixedly arranged, the gas of a predetermined pressure may be permanently sealed in the gas layer 35. Further, although the pressure gauge 3 is connected to the control device 4 in the above-described embodiment, it may be connected to the abnormality alarm device 26 in addition to the control device 4 to immediately notify the worker of damage to the insulating coatings 33a and 33b. Good. Further, in the above embodiment, the cross section of the primary cable 31a is as shown in FIG.
The cross-sectional structure as shown in (B) to (D) may be adopted. The primary cable 31b shown in FIG. 2 (B) is obtained by separating a plurality of constituent cables. The power supply lines 32a and 32b are covered with a first insulating coating 33a, and the power supply lines 32a and 32b are separated from the first insulation. The gas layers 35 and 35 are formed between the film 33a and the film 33a. Further, the primary cables 31c and 31d shown in FIGS. 2C and 2D are those in which the conventional cable damage detection device 41 is used in combination, and the primary cables 3c shown in FIG.
1c shows the conventional primary cable 31 of FIG. 3B covered with a third insulating coating 33c and a gas layer 35 formed between the primary cable 31 and the third insulating coating 33c. The primary cable 31d of (D) is the first insulating film 3
, 32e covered with 3a are further covered with a second insulating coating 33b, and a mesh conductor 34 is provided on the inner peripheral surface of the second insulating coating 33b. The gas layer 35 is formed on the surface.

[0018]

As described above, according to the present invention, a gas layer having a predetermined pressure is enclosed inside the insulating coating of the power feeding cable, and the presence or absence of pressure drop in this gas layer is detected by a pressure gauge. It is possible to reliably detect damage such as cracks and holes in the insulation coating of the cable, and to start the early repair work of the power supply cable without delay.

[Brief description of 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 supply cable used in the present invention.

FIG. 3A is a schematic view of a spot welding machine equipped with a conventional cable damage detection device, and FIG. 3B is a sectional view of a power supply cable of the welding machine.

[Explanation of symbols]

1 Damage detection device 2 gas supply and discharge means 2a air pump 2b air hose 3 pressure gauge 4 Control means 21 spot welder 22 power supply 23 Welding gun (electrical equipment) 23 Electric equipment 24 current circuit breaker 25 connector 26 Abnormality alarm 27 horizontal rails 28 Suspension rod 31 Primary cable (power supply cable) 32a, 32b power line 32c, 32d signal line 32e ground wire 33a-33c Insulating film 34 reticulated conductor 35 gas layer 41 Cable damage detector 42 Power supply for detection 43 Overvoltage detection means 44 Ground fault current detection means

Claims (2)

[Claims] 1. A sealed gas of a predetermined pressure is sealed inside an insulating coating of a power supply cable wired between a power supply section and an electric device, and the presence or absence of a pressure drop in the sealed gas is detected by a pressure gauge to detect the pressure. A damage detection device for a power supply cable, which is configured to detect whether or not the power supply cable is damaged. 2. A gas supplying / discharging means capable of supplying / discharging a sealed gas of a predetermined pressure to / from an inner space of an insulating coating of a flexible power feeding cable wired between a fixedly arranged power source section and a mobile electric device. And a pressure gauge capable of detecting the pressure of a sealed gas of a predetermined pressure sealed inside the insulating coating by the gas supply / discharge means.