JPS5973069A - Electrostatic coater - Google Patents

Abstract

PURPOSE:To contrive improvement in safety and work efficiency, while detecting an overcurrent as a true value, by inserting an overcurrent detector into the high-voltage cable of each coating system, and electrically transmitting its detection result as a signal using an optical fiber. CONSTITUTION:When an overcurrent is applied to resistors 23, 24 for detecting an overcurrent in case of accidents such as the short-circuits of coaters 5A, 5B or the damages of high-voltage cables 10, 11, voltages at both ends of the resistors 23, 24 are converted into optical signals by time sharing with signal converters 25, 26 and inputted through optical fibers 27, 28 to switch driving parts 29, 30. Said signals are reconverted into electric ones at said driving parts 29, 30 and compared with predetermined set points. When the overcurrent is distinguished, switches 21, 22 for intercepting high voltage are cut off to stop the impression of high voltage onto the coaters 5A, 5B. Since the interception of high voltage is performed to each cable, coating work with other coaters can be continued as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies a high voltage from a high voltage generator to a coating machine via a high voltage cable, while spraying paint from the coating machine to the object to be coated. This invention relates to an electrostatic coating device that performs electrostatic coating.

Conventionally, as this type of electrostatic coating apparatus, the one shown in FIG. 1 is known. In FIG. 1, 1 is a painting booth, a conveyor 2 is installed in the painting booth 1, and on the conveyor 2 there is a workpiece 4 connected to the ground 3 and at ground potential.
is placed and transported through the painting booth 1 by the compare 2, during which painting work is performed.

Painting machines 5A and 5B (collectively referred to as paint sprayers 5) are installed in the painting booth 1, and each paint sprayer 5 sprays paint onto the object 4 to be coated. ) is connected to a color changing valve 7 via a P-build 6). The color change valve 7 is connected to a paint tank (not shown), an air source, a thinner source, etc., and supplies the paint from the paint tank to the paint machine 5 via the paint pipe f6 to respond to needs such as color change. Clean by supplying sinker and air.

8 is a high voltage generator that boosts the commercial power supply voltage to a high voltage of, for example, -90[:kl; 9 is the high voltage generator 8;
One end of the high voltage cable 9 is connected to the high voltage generator 8, and the other end is branched to a high voltage couple 10. .

5B, respectively.

12 is a high voltage cutoff switch provided in the middle of the high voltage couple 9, and this switch 12 is always connected to the switch 12A.
is connected to the contact 12B, and the high voltage generator 8 and the paint sprayer 5
When an abnormal current (described later) occurs, the switch 12A connects to the other contact 12 connected to the ground 3.
C, and has the function of grounding the paint sprayer 5.

Furthermore, 13 is a resistor for overcurrent detection provided between the high voltage generator 8 and the ground 3, and 14id is a high voltage connection switch 1 when the voltage across the resistor 13 is input.
2 shows a switch operation circuit for activating the high voltage generator 2 and cutting off the commercial power supply to the high voltage generator 8. Here, the switch actuation circuit 14 monitors voltage changes based on the current l flowing through the resistor 13, detects this as an overcurrent when the current flowing through the resistor 13 exceeds a predetermined set value, and detects this as an overcurrent. Device 1
At the same time, the commercial power supply to the high voltage generator 8 is cut off. The high voltage cutoff switch 12 and switch operating circuit 14 of this pole are, for example, manufactured by Japanese Patent Publication No. 55-3598.
No. 8, which is also known from Japanese Patent Publication No. 55-35989.

In the electrostatic coating device configured as described above, the high voltage generated by the high voltage generator 8 is transmitted to each coating machine 5A, 5B via the high voltage cable 9, the high voltage cutoff switch 12, and the high voltage cables io and il. applied. On the other hand, by supplying the paint from the paint tank to the paint machines 5A and 5B via the color change valve 7 and the paint/E iso 6A and 6B, the paint is charged to the same potential as the applied high voltage, and the paint is charged to the same potential as the applied high voltage. By spraying the charged paint from the sprayer 5, the paint is applied in flight along the lines of electric force between the paint sprayer 5 and the object 4 at ground potential. During this time, high voltage generator 8, high voltage cable 9, high voltage cutoff switch 12, high voltage cable 10, 11, paint machine 5A,
5B, the object to be coated 4, the ground 3, and the resistor 13 form a loop, and a current l flows through the loop. The switch actuation circuit 14 then monitors the voltage across the resistor 13 based on the current i.

By the way, although charged paint particles are attracted and fly along the lines of electric force between the coating machine 5 and the object to be coated 4, there is usually a predetermined resistance between them. However, during painting, the paint
In the event of a short circuit accident in which the coating machine 5 abnormally approaches or comes into contact with the object 4 to be coated, the resistance between the coating machine 5 and the object 4 to be coated becomes zero and the resistance 13
Flowing smoothly. In addition, when the paint sprayer 5 is used by being attached to a registration locator, the high voltage cables 10 and 11 connected to the paint sprayer 5 may be bent and damaged due to frequent movement of the paint sprayer 5. There is. In this manner, an overcurrent will flow even in the event of a high voltage cable damage accident in which the core wire of the high voltage cable 10.degree. 11 is short-circuited to the ground 3.

When an overcurrent flows through the resistor 13 due to the reasons described above, the voltage across the resistor 13 increases, so the switch actuation circuit 1
4 switches the switch 12A of the high voltage cut-off switch 12 from contact 12B to 12C when the voltage at both ends due to this overcurrent reaches a predetermined set value, sets the high voltage cable 9 to ground potential, and connects the high voltage generating device. Stop power supply to 8.

This prevents the occurrence of fires due to short circuit accidents and high voltage cable damage accidents.

However, the prior art described above has many drawbacks. First, a resistor 13 for overcurrent detection is inserted between the high voltage generator 8 and the ground 3.
, and does not directly detect the current flowing through the high voltage cables 9 or 10.11. There was a drawback that the current flowing through the high voltage cable 9, 10, 11, etc. could not be detected as a true value due to the influence of internal resistance. Second, although the high voltage cutoff switch 12 is provided in the middle of the high voltage cable 9, the coating machine 5A,
The high voltage cutoff switch 12 will be activated due to either a short circuit accident of the high voltage cable 5B or a damage accident of the high voltage cable 10 or 11.

As a result, there is a drawback that even painting systems that have not caused an accident are stopped. Thirdly, as mentioned above, the high voltage generator 8 frequently stops, which has the drawback of shortening its lifespan.

The present invention aims to improve the drawbacks of the electrostatic coating device according to the prior art described above, and it is possible to detect the overcurrent flowing through a high voltage cable at its true value, and also to The present invention provides an electrostatic coating device in which signals are transmitted using optical fibers so that high voltage cutoff switches and the like are not affected by high voltage.

In order to achieve the above object, the electrostatic coating device adopted in the present invention is characterized by being provided in the middle of a high voltage cable between a high voltage generator and a coating machine, and applying a high voltage through the cable. a high-voltage cutoff switch that cuts off the current flowing through the high-voltage cable; an overcurrent detector installed in the middle of the high-voltage cable between the high-voltage cutoff switch and the coating machine to detect the current flowing through the high-voltage cable; A signal conversion means for converting a detection signal by the detector into an optical signal, an optical fiber for transmitting the optical signal from the signal conversion means, and a signal conversion means for converting the optical signal transmitted by the optical fiber back into an electric signal. and a switch operating means for cutting off the high voltage cutoff switch when the electric signal reaches a predetermined value.

Hereinafter, the present invention will be explained in conjunction with the embodiments shown in FIGS. 2 to 5 in the case where there are two coating systems.
Components that are the same as those of the prior art described above are given the same reference numerals.
The explanation will be omitted.

Reference numerals 21 and 22 indicate high voltage cutoff switches provided in the middle of the high voltage cable 10.11 branched from the high voltage cable 9, and each switch 21.22 is a switch 21A, similar to the high voltage cutoff switch 12 according to the prior art. 22A% contacts 21B, 21C.

It consists of 22B and 22C, and a switch 21A.

22A is normally connected to contacts 21B and 22B, respectively.

Reference numerals 23 and 24 are resistors for overcurrent detection provided in the middle of the high voltage cable 10.11, and each of the resistors 23 and 24 directly detects the voltage at both ends based on the current l flowing through the high voltage cable 10.11. Reference numerals 25 and 26 denote signal converters, each of which has the function of inputting the voltage signal of the resistors 23 and 24, converting this voltage signal into an optical signal corresponding to the signal, and outputting it. have

Reference numerals 27 and 28 each indicate one optical fiber, and 29 and 30 indicate a switch actuator, one end of each of the optical fibers 27 and 28 is connected to a signal converter 25 and 26, and the other end is connected to a switch actuator 29 and 30. It is connected. The optical signals from each signal converter 25.26 are then transmitted to an optical fiber 27.
28 to the switch actuating section 29.30, the electric signal is again converted into a trap, and when the electric signal reaches a predetermined overcurrent flowing through the high voltage cable 10.11, the high voltage cutoff switch 21.22 is activated. Cropped high voltage cable 10
．． 11 to the coating machines 5A and 5B.

Here, each signal converter 25, 26, each switch actuator 2
9.30 have the same configuration, so one of the signal conversion section 25 and switch actuation section 29 will be explained with reference to FIG. The signal converter 25 includes an amplifier 31 that amplifies the input voltage from the resistor 23, and is provided at the next stage of the amplifier 31, and is capable of converting the input voltage into a digital value and latching the highest voltage at predetermined time intervals. An analog-to-digital converter 32 (hereinafter referred to as an A/D converter 32) is provided at the next stage of the converter 32, and converts the latched maximum voltage into a signal consisting of a 9-bit binary serial pulse. Signal/Gruss converter 33 (hereinafter referred to as s
/1) converter 33); and a light emitting diode 34 that emits light every time a pulse is input from the S/1) converter 33.
and a clock oscillator 35 that inputs clock pulses to a 0 converter 32 and an S/'P converter 33.

On the other hand, the switch actuator 29 includes a photoelectric converter 36 that converts the optical signal from the light emitting diode 34 back into an electric signal via an optical fiber 27, and a signal from the photoelectric converter 36 is inputted to the switch actuator 29, and a predetermined set value is input. A switch actuation circuit 37 operates the high voltage cutoff switch 21 when it is determined that there is an overcurrent. Here, the switch actuation circuit 37 has the same configuration as the switch actuation circuit 14 in the prior art, but does not cut off the power to the high voltage generator 8.

Note that in the present invention, no resistor for overcurrent detection is provided between the high voltage generator 8 and the ground 3.

The present invention is constructed as described above, and its operation will now be explained with reference to FIGS. 4 and 5.

Also in the present invention, the high voltage generated by the high voltage generator 8 is applied to the high voltage cables 9, 10.11, the high voltage cutoff switches 21, 22, and the resistors 23.24 in sequence to the coating machine 5A,
5B, and the paint from the color change valve 7 is applied to the paint vibro A.
, 6B, the paint is charged to the same potential as the applied voltage, and the charged paint is sprayed from each coating machine 5 to be applied to the object 4 to be coated.
There is no difference from conventional technology.

Next, the operation of the signal converters 25 and 26 will be described. Now, when a high voltage is applied to the coating machines 5A and 5B by the high voltage generator 8, a current l flows through the high voltage cable 10.
A voltage as shown in (a) is output, and this voltage signal is input to the A//b converter 32 via the amplifier 31 of the signal converter 25.

0 converter 32 converts the voltage signal every instant (for example, 100 [μ
It is converted into a digital signal every 5 ec'), and this is repeated, for example, at a conversion period of 6 m5 ec', as shown in Figure 4 (middle). Then, as shown in FIG. 4(b), if the conversion periods are A, B, C, and D, the A/b converter 32 uses the next 6 (msec) of the conversion period A as the latch time, and the conversion period is Latch the highest voltage at A.

Similarly, the A/1) converter 32 latches the highest voltage of the conversion period B for the next 6 [m5ec] as the latch time. Therefore, in the same time period as conversion period A,
The highest voltage in the previous conversion cycle is latched.

The highest voltage latched by the A/L converter 32 as described above is input to the S//P converter 33, and as shown in FIG.
As shown in FIG. 3, the pulse is converted into a 9-bit binary serial pulse in about 3 msac. That is, FIG. 5 is an enlarged detailed view of the circular part a in FIG.
Data output start/gurus DP is output during the first 200 [μsec] of 5ec), and the next 1 [:m5e
28 + 27 · every 200 [μ5ee) after the elapse of
...Outputs 9-bit binary pulses corresponding to 21 and 2 degrees in a time-division manner. Therefore, in Fig. 4(・), the conversion period A
While latching the highest voltage at P/'i) converter 33Iti3Cm5ec'], the data start pulse DP and the 9-bit signals 28, 27 . ...
2° can be output to the light emitting diode 34.

From the above points, if the highest voltage of, for example, 5 [V] is generated across the resistor 230 in conversion period A, this voltage will be converted to A//b with the next 6 [m5ec] of conversion period A as the latch time. It is latched to the device 31. During this latch time, the S/P converter 33 first outputs the data output start signal DP for 200 [μsec'),
Next, after 2400 [: μ5 ec) have elapsed, the 4 pulse corresponding to K 22 is output for 200 [μsec 1], and then 28
After 00[:μ8ee:] elapses, output the No4 pulse corresponding to 2 for 200 [μsec 1]. These relationships are as shown by the diagonal lines in FIG. 5, which means that a voltage of 5 [V] is converted into a binary serial pulse.

And this data output starts/Gurus DP.

The light emitting diode 34 is caused to emit light by a pulse corresponding to the binary pulse 22, 2°.

Next, the operation of the switch actuators 29 and 30, for example the operation of the switch actuator 30, will be described. Now, as mentioned above
s," each pulse from the p converter 33 is input to a light emitting diode 34 to cause the light emitting diode 34 to emit light,
The 9-bit /4' pulses 28, 27 .・
・The light is received in a time-division manner every time corresponding to 2°,
It is converted back into an electrical signal and input to the switch actuation circuit 37.

The switch activation circuit 37 compares the electrical signal from the photoelectric converter 36 with a predetermined set value, and when it is determined that the electrical signal has resulted in an overcurrent that corresponds to a short circuit accident or a high voltage cable breakage accident, it activates the high voltage cutoff switch. Switch 21A of 21 is switched from contact 21B to 21C, and high voltage cable 10 is set to ground potential.

In this way, the present invention uses the coating machine 5A.

When an overcurrent flows through the overcurrent detection resistors 23 and 24 due to a short circuit accident of the high voltage cable 10.5B or a damage accident of the high voltage cable 10.11, the signal converter 25.
converting the voltage across 24 into an optical signal by time division,
Switch actuator 29. via optical fibers 27, 28.
30, the winter operating section 29.30 converts it into an electrical signal again, compares it with a predetermined setting value, and when it is determined that there is an overcurrent, the high voltage cutoff switch 21.22 is cut off, and the coating machine 5A , 5B can be stopped.

Therefore, since the resistors 23 and 24 can be directly inserted in the middle of the high voltage cables 10 and 11, the overcurrent flowing through each high voltage cable 10 and 11 can be directly detected as the true value, and the detection accuracy can be improved. can. In addition, since the voltage converter 25.26 and the switch actuator 29.30 are connected by optical fibers, the voltage converter 25.26 is at the same potential as the high voltage cables 1.0 and 11. Even if the switch actuating part 29, 30 can be set to the ground potential,
Safety can be increased. Furthermore, high voltage cutoff switches 21 and 22 and resistors 23 and 24 are connected to each high voltage cable 1.
0.11, it is possible to cut off the high voltage cable for each painting system, apply high voltage to the high voltage cables and paint machines of other painting systems that have not caused an accident, and disconnect the conveyor. Since there is no need to stop 2, the coating efficiency can be increased. Furthermore, since there is no need to shut off the power to the high voltage generator 8, the life of the high voltage generator 8 can be extended.

In the above embodiments, the signal converters 25 and 26 optically convert signals by time division, and transmit signals using one optical fiber 27 and 28 under time management. By using a bundle of nine optical fibers 27 and 28, optical signals can be transmitted simultaneously. On the other hand, the coating machines 5A and 5B are used to form two coating systems, and one high voltage generator 8 is branched into two high voltage cables 10 and 11.
．． Although high voltage is applied to each coating machine 5A and 5B from 11 onwards, the number of coating systems may be one, and in this case, one high voltage cutoff switch, one signal converter, one switch actuator, etc. each. Just set it up. Conversely, it goes without saying that three or more coating systems may be combined.

Since the electrostatic coating apparatus according to the present invention has been described in detail above, it achieves the following effects.

■ Since an overcurrent detector can be inserted into each high voltage cable of each painting system, overcurrent can be detected at its true value and detection accuracy can be improved.

(2) Since the overcurrent detection result can be transmitted to the switch actuating part using an optical fiber, the switch actuating part can be set to ground potential, and safety can be improved.

■ It is necessary to detect overcurrent in each painting system and shut off only the painting system where the accident occurred, so high voltage can be applied to other systems and normal painting can be performed, increasing painting efficiency. I can do it.

[Brief explanation of drawings]

Figure 1 is a system diagram of an electrostatic coating device according to the prior art;
The figure is a system diagram showing the electrostatic coating device ii according to the present invention.
The figure is a specific configuration diagram of the signal converter and switch actuator in Figure 2, and Figures 4 (a) to 4) are explanatory diagrams of the operation of the signal converter.
FIG. 5 is an enlarged detailed explanatory view of the circular portion a shown in FIG. 4). 4...Object to be coated, 5A, 5B...Painting machine, 8...High voltage generator, 9, 10, 1.1...High voltage cable, 21.22...High voltage cutoff switch , 23.2
4...Resistor, 25.26...Signal converter, 27.2
8... Optical fiber, 29.30... Switch actuating section.

Claims (2)

[Claims] (1) In an electrostatic coating device comprising a coating machine that sprays paint toward an object to be coated and a high voltage generator that applies high voltage to the coating machine via a high voltage cable, the high voltage generator a high-voltage cutoff switch installed in the middle of a high-voltage cable between the cable and the coating machine to cut off the high voltage applied through the cable; and a high-voltage cutoff switch for detecting the current flowing through the high-voltage cable. an overcurrent detector provided in the middle of a high voltage cable between the overcurrent detector and the coating machine, a signal conversion means for converting the detection signal from the overcurrent detector into an optical signal, and an optical signal from the signal conversion means. optical fibers for transmission, and switch actuating means for converting the optical signals transmitted by the optical fibers back into electrical signals and for cutting off the high voltage cutoff switch when the electrical signals reach a predetermined value. An electrostatic coating device characterized by comprising: (2) By using one high-voltage generator and a plurality of coating machines, the one high-voltage generator and the plurality of coating machines are connected to each other using high normal voltage cables. There are multiple painting systems, and each painting system is equipped with the above-mentioned high voltage cutoff switch, overcurrent detector, signal conversion means, optical fiber, and switch actuation means, and if an abnormality occurs in the - painting system, the system The electrostatic coating apparatus according to claim (1), wherein only the high voltage of the system is cut off, and other systems are allowed to operate normally.