JPS59109268A - Electrostatic painter - Google Patents

Abstract

PURPOSE:To prevent the firing and electric shock in the event of abnormal approach by connecting an electrode for detecting a grounding object on the front side of an atomizer, and interrupting the supply of a DC high voltage in accordance with the increase in the current flowing in the electrode. CONSTITUTION:If a potential difference between an electrode 21 for detecting a grounding object and a substrate is so set as to be made larger than the potential difference between an atomizer 3 and the substrate in the stage of electrostatic painting, the potential of the atomizer 3 remains postive with respect to the electrode 21 and the suction and sticking of the fine particles of the paint in the direction of the electrode 21 is prevented. Since the electrode 21 is spaced by >=(3-40)mm. from the atomizer 3, spark discharge, etc. are not generated. In case the substrate moves so as to approach to the electrode 21 on account of an accident or the like, the current flowing in the electrode 21 increases and is detected by a current detector 23 in the stage of feeding back to the substrate and its ground line, a ground line 24 and the 2nd high voltage generator 9. The supply of the high voltage from the 1st high voltage generator 1 is interrupted when the current attains a prescribed value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic coating machine that applies electrostatic coating to an object to be coated by utilizing a potential difference between an atomizing device and the object to be coated.

Conventionally, in this type of electrostatic coating machine, the atomizing device is maintained at a negative DC high voltage by a high voltage generator, while the object to be coated is grounded to connect the atomizing device and the object to be painted. A large potential difference is formed between the atomizer and the coating 1'
+1 is attracted to the object to be coated by the potential difference.

By the way, since the atomizer is made of conductive T'l material and is relatively large, it has a large electrostatic capacitance tiii, and therefore the atomizer does not mist during electrostatic coating when a high voltage C1 iri flow is applied by a high voltage generator. The amount of charge on the charging device 6 increases.

For this reason, if an object to be painted abnormally approaches the atomizer due to an accident during electrostatic painting and the distance between the two narrows, the space between the two will be dielectrically broken, spark discharge will occur, and the atomizer will be damaged. Since the amount of charge is large, the energy of spark discharge is also large. However, since electrostatic painting is carried out in an atmosphere containing highly flammable solvents, fires may occur if spark discharges with large amounts of energy occur as described above, and workers may be exposed to electric shock. Then, due to the magnitude of the energy, the work ii′i′:! There is a risk of causing death to J.

Therefore, in order to solve the problems mentioned in -,
There are No. 5-35988 and Special Publication No. 55-35989.

This system focuses on the fact that the current flowing through the atomizer increases as a grounded object such as the object to be painted approaches the coating device, and then generates a high voltage by passing this current from the grounding object through the grounding wire. When the amount of detected current reaches a predetermined value hi, the high voltage generator is cut off, and at the same time the atomization device is grounded to remove the electrical energy stored in the coating device. is released and the temperature drops to a safe level1.
! J, I'm making sea urchins.

However, with the above configuration, an extremely small amount of current increase is detected from the current value that includes disturbances such as noise, so the distance at which it can be determined that the grounding object is approaching abnormally is the distance 1511 where the amount of current increase can be large. limited to very close distances to the converter. For this reason, even if abnormal approach of a grounded object is detected, if the approaching speed of the grounded object is high, the time delay that occurs between each electric circuit from current value detection to voltage drop in the coating device will cause the atomization device 27 to There was a high possibility that the voltage could not drop in time and a dangerous spark discharge would occur. Furthermore,
When the surface area of a grounded object is small, the amount of current increase is also small, so it has been difficult to detect a grounded object with a small surface area.

Moreover, in order to extract an extremely small amount of current increase from a current value that includes a lot of disturbances such as noise, the accuracy of the electric circuit that processes the detected current must be increased, and the electric circuit configuration is therefore complicated. There was a problem in that the manufacturing cost became high.

The present invention has been made in view of the above-mentioned circumstances, and therefore, its purpose is to provide a method to prevent a grounding object such as an object to be coated from abnormally approaching an atomizing device, regardless of the approach speed and surface area of the grounding object. To provide an electrostatic coating machine that can reliably prevent fires caused by spark discharge from an atomizer and electric shock accidents caused by electric shocks, and can reduce manufacturing costs by simplifying the electrical circuit configuration. .

An embodiment of the present invention will be described below with reference to the drawings. First, in FIG. 1 showing the electrical configuration, 1 is a first circuit breaker connected to a first power source 1a via a first circuit breaker 2.
is a high voltage generator, which outputs a negative DC high voltage.

Reference numeral 3 denotes a first high voltage generator 5 - an atomizer connected to the output side of the green mold 1 via a high voltage cable 4, which is a cylindrical metal main body 5 as shown in FIG. The air motor (
The main body 5 and the atomizing head 7 are constituted by a bellmouth-shaped atomizing head 7 which is rotated at high speed by a rotation 116 (not shown), and the main body 5 and the atomizing head 7 are connected to a first high voltage generator. Both are held at a DC high voltage of 0 by 1. Reference numeral 8 denotes a nozzle that discharges paint supplied from a paint supply device (not shown) into the atomizing head 7. On the other hand, in Figure 1, 9
is a second high voltage generator provided in a separate system from the first high voltage generator 1.
The input side of this high voltage generator is connected to the second power supply 9a via the second circuit breaker 10, and the negative DC high voltage is outputted from the output side. 11, one end is the second
The high voltage cable is connected to the output side of the high voltage generator 9, and the other end of the cable is led to the vicinity of the atomizing device 3 as shown in FIG. 12 is a ring-shaped cable holding portion made of J insulating material to which the other end of the high voltage cable 11 is fixed; 13
is an annular electrode holding part made of an insulating material and having a plurality of protrusions 13a directed forward (to the right in FIG. 2) on the same circumference; these cable holding parts 12 and tr; Gokuho 121 part 13 and L together with the main body 5 of the atomizer 3
It is inserted through and supported, and is crimped and fixed to, for example, a 1/1.15 plastic screw. Reference numeral 16 denotes a copper ring held between the cable holding part 12 and the electrode holding part 13, and this is connected to the high voltage cable and the ☆v11 part by a conductive wire 17. Reference numerals 18 and 19 denote annular sealing members arranged at both the inner and outer ends of the copper ring 16, respectively.
We are trying to keep it sealed. Reference numeral 20 denotes a high resistance of, for example, 70 to 100 M0, which is provided inside each protrusion 13a of the electrode holding portion 13, and one end of which is in contact with the copper ring 16. 21 is a wire for detecting a grounded object formed of a stainless steel wire having a conductive element 11 and an elastic f[, for example, a stainless steel wire with a diameter of 0.2 mm and a length of 200 mm. There are 11 poles, the base end of which is embedded and fixed in the tip of each protrusion 13a of the electrode holding part 13 and connected to the high resistance 20, and the part exposed from the protrusion 13a is 40n+m from the atomization device 3. It is spaced apart and spreads forward (to the right in FIG. 2) like an umbrella, and its tip is positioned in front of the atomizing device 3. Then,
In this embodiment, the ground object detection electrode 21 has a diameter of 0.2 mm,
The capacitance of the ground object detection electrode 21 is set to be extremely small (approximately 0.11 pF) by forming it from a stainless steel wire with a length of 20 om to reduce the surface area.

In addition, the second high voltage generator 9 generates a ground object detection voltage 8i.
The potential difference between 21 and the grounded object is set by the first high voltage generator 1 to be larger than the potential difference between the atomizer 3 and the grounded object. This is a coil portion provided on the proximal end side of the object detection electrode 21, and is intended to facilitate elastic deformation of the distal end portion of the grounded object detection electrode 21.In contrast, in FIG. 23 is a current detector connected in series to the grounding wire 2/I of the second high voltage generator 9; The current flowing toward the object is connected to the grounding wire 24 of the second high voltage generator 9.
Detection is performed using a current that returns more, and the current value increases when the grounded object moves in the direction closer to the grounded object detection electrode 21 (in the direction indicated by arrow A in FIG. 2). Therefore, when the current detected by the current detector 23 reaches a predetermined value, the first circuit breaker 2 is opened and the voltage between the first power source 1a and the first high voltage generator 1 is opened. is shut off, and at the same time, the first high voltage generator 1 and the atomizer 3
The first high-voltage relay 27 provided between the atomizer fffi 3 and the atomizer fffi 3 is closed, and the atomizer fffi 3 is grounded, and the electric charge stored in the atomizer 3 and the high-voltage cable 4 is discharged. Furthermore, -1
= 34”r Simultaneously with the operation of the first circuit breaker 2 etc.
The second circuit breaker 10 is opened and the connection between the second lightning block 9a and the second high voltage generator 9 is interrupted, and the connection between the second high voltage generator 9 and the high resistance 20 is interrupted. The installed second high voltage relay 28 is closed and the ground object detection electrode 21. is also grounded.

Two current detectors are connected in series to the grounding wire 30 of the first high voltage generator 1, and these detect the value of the current flowing from the atomization device 3 to a grounded object such as the object to be painted 26. The current detector 29 detects when a grounded object 9- such as a human body approaches from behind the atomizer 3
When the detected current value reaches a predetermined value, the first circuit breaker 2 etc. are activated in the same way as the current detector 23 described above to bring the atomization device 3 and the ground object detection electrode 210 made of silicon to a safe level. I try to raise it up. 31 and 32 are resistors for protecting the first and second high voltage relays 27 and 28, respectively.

Next, the operation of the above configuration will be explained. First, as shown in FIG. 2, the object to be coated 26 is connected to the grounding wire 25, and is installed from the atomizing device 3 at an appropriate distance νjilt1Flu.

After that, the first and second high voltage generators 1 and 9 are energized to apply a negative DC high voltage to the atomizing device 3 and the ground object detection electrode 21, respectively, to separate the atomizing device 3 and the object to be coated. A high potential difference is formed between the object 26 and between the grounded object detection electrode 21 and the object 26 to be coated. When the atomizing head 7 is rotated at high speed by an air motor (not shown), the paint supplied from the paint supply device (not shown) into the atomizing head 7 through the nozzle 8 is atomized, that is, it is atomized into fine particles. Front from head 7 (to be painted object 26 side)
released to. Then, the ejected fine particles of paint move toward the object 26 along the electric lines of force formed by the potential difference between the atomizer 3 and the object 20, and finally reach the object 26. It adheres to the object 26, and electrostatic coating of the object 26 to be coated is performed. During such electrostatic coating, the potential difference between the grounded object detection electrode 21 and the object to be painted 26 is caused by the atomization device 3.
Since the potential difference between the atomizer N3 and the object to be coated 26 is set to be greater than the potential difference between the atomizer N3 and the ground object detection electrode 21, [, therefore, this atomization device 3
Fine particles of paint r1 released from the ground object detection electrode 21
It is not attracted in the direction and is prevented from adhering to the ground object detection electrode 21. Moreover, type 4 for ground object detection
! 1i21 is atomization r? (Since they are provided at a distance of 3 to 40 mm or more, spark discharge will not occur between the grounded object detection electrode 21 and the atomization device 3.

Therefore, if a grounded object such as the object to be painted 26 with a large surface area moves in a direction approaching the grounded object detection electrode 21 (in the direction indicated by the arrow △ in FIG. 2) due to an accident, etc., The current flowing through the ground object detection electrode 21 increases. When this current returns from the object to be coated 26 to the grounding wire 25 to the grounding wire 24 to the second high voltage generator 9, it is transmitted to the current detector 23 by J:
detected. When the object to be coated 26 approaches the ground object detection electrode 21 at a predetermined distance of 1liIt, the current value detected by the current detector 23 reaches a predetermined value, thereby causing the first cutoff. The device 2 is activated to cut off the connection between the first power source 1a and the first high voltage generator 1, and through this bundling, the DC high voltage is supplied from the first high voltage generator 1 to the atomization device 3. is cut off, and at the same time, the high voltage relay 27 is closed and the atomizing device 3 is grounded, whereby the atomizing device 3 is rapidly lowered to the ground potential. Furthermore, simultaneously with the operation of the first circuit breaker 2 and the like described above, the second circuit breaker 10 operates to cut off the connection between the second power source 9a and the second high voltage generator 9, and the second The high voltage relay 28 is closed, the grounding object detection type w121 is grounded, and the atomizing device 3 is rapidly lowered to the ground potential.

By the way, in the conventional structure, the ground object detection electrode 21 detects the current flowing through the atomizer and detects the constant approach of a ground object such as an object to be painted. It is difficult to detect a grounded object until it approaches the discharge start distance, and therefore, if the grounded object approaches at a high speed, there is a risk that the voltage of the atomization device will not drop in time and dangerous spark discharge will occur.

However, in this embodiment, a plurality of ground object detection electrodes 2
1 and its tip is located in front of the atomizing device 3, the approach of the object to be coated 26 can be detected by the ground object detection electrode 21 at a sufficiently distant position from the atomizing device 3 at an early stage. Therefore, even if the approaching speed of the object to be coated 26 is high, the electric potential of the atomizer M3 is surely lowered, and the generation of spark discharge from the atomizer 3 can be reliably prevented. By the way, even if spark discharge is prevented from being generated from the atomization device 3 as described above, if a spark discharge with a large amount of energy is generated from the ground object detection electrode 21, there is a risk of fire etc.
! 1, but in this example, the capacitance of the ground object detection electrode 21 is reduced by forming the ground object detection electrode 21 with a stainless steel wire with a diameter of 2 mm and a length of 200 mm to reduce the surface area. Since the setting is extremely small (approximately 0.11 rlF), even if a spark discharge occurs from the ground object detection electrode 21, the discharge energy will be sufficiently small compared to the minimum ignition energy of the solvent, preventing a fire. There is no danger of this occurring.By the way, when we calculate this discharge energy by addition, we find that the voltage before the start of discharge is Vl = 60KV and the voltage after the end of discharge is V2 = -37KV. is E=C(
Vl-V2) l = 0.03mJ, which is 0.2m which is generally known as the minimum ignition energy of the solvent.
It is understood that it is sufficiently smaller than J. Moreover, since the grounding object detection electrode 21 is connected to the high voltage cable 11 via the high resistance 20 of 70 to 100 MΩ, the electrical energy accumulated in the high voltage cable 11 passes through the high resistance 20 to the grounding object detection electrode 21. Therefore, a large voltage drop occurs due to the high resistance 20, and the voltage of the ground object detection electrode 21 itself becomes lower than the voltage that can be discharged (14), and the discharge is converted into energy. Doing so will be avoided as much as possible.

By the way, in the conventional structure 1), when the surface area of the object to be painted (26 < 1 feature) is small, the increase in current flowing through the atomizer is small, so it is difficult to detect a grounded object with a small surface area. Ta.

However, in this embodiment, even if the object to be painted 26 (grounded object) comes into contact with the grounded object detection electrode 21, there is no risk of fire or the like. On the other hand, when the grounded object contacts the grounded object detection electrode 21 and the current flowing through the grounded object detection electrode 21 increases rapidly, the object to be painted 26 (grounded object) can be detected 1J, In addition, even grounded objects with a small surface area can be detected on the instep 1111 at a distance of -1 from the atomizer 3, eliminating the risk of fire. can. In addition, since the grounding object detection lightning 1421 is made of an elastic stainless steel wire and is further provided with a coil portion 22, even if a grounding object comes into contact with the grounding object detection electrode 21, the grounding object detection electrode 21 can be easily elastically deformed.

By the way, Tokko Akira! No. 15-35988, Special Publication No. 1155
In the method disclosed in No. 35989, the current detected by the current detector had to be processed by a complicated and sophisticated electric circuit, resulting in high manufacturing costs.

However, in this embodiment, since the peak value of the current returning from the grounding object detection electrode 21 to the second high voltage generator 9 via the grounding object is to be detected, the electric circuit configuration is simplified. The manufacturing cost can be reduced.

In this embodiment, the first and second high voltage generators 1.9 are provided independently, and these are connected to the first and second power sources 1a and 9a.
However, the present invention is not limited to this. For example, the primary side of the power transformer of the first and second high voltage generators 1.9 may be made common, and the secondary side of the power transformer may be connected to a separate system, and the first and a second high voltage generator 1.9. Further, in this embodiment, the first and second high voltage generators 1 and 9 are provided independently, but the present invention is not limited to this. For example, the high voltage cable 4 may be connected to the high voltage cable 11, and the first The high voltage generator 1 may be omitted. In this case, if the object 26 to be painted approaches the electrode 21 for detecting a grounded object, the current change may be small and detection may be difficult; however, if the object 26 to be painted comes into contact with the electrode 21 for detecting a grounded object, the current detector The current passing through the atomizer 23 increases from the μAA-der to the order of mA or more and can be easily detected, causing a second interruption before the workpiece 26 approaches the atomizer 3 abnormally and creates a dangerous spark discharge. vessel 10
can be activated to shut off the second high voltage generator 9. In this case, the grounded object detection electrode 21 has a small capacitance, so even if it comes into contact with the object to be painted 26 and generates a spark discharge, the energy of the spark is as small as 0.2 mJ or less.
There is no risk of fire.

However, the present invention is not limited to the embodiments described above and shown in the drawings, and it goes without saying that the present invention can be implemented in various modifications without departing from the scope of the invention.

As is clear from the above description, the present invention is provided with a high voltage generator that supplies a direct current high voltage to the atomizing device, and 17- this high voltage generator is connected to the atomizing device through a resistor in front of or in front of the atomizing device. Connect the ground object detection electrode located on the side,
A current detector detects an increase in the current flowing through the Ti electrode for detecting a grounded object, and when the detected value reaches a predetermined value, the supply of DC high voltage from the high voltage generator to the atomization device is cut off. Since a circuit breaker is installed, when a grounded object such as an object to be painted approaches the atomization device abnormally, the atomization device will not cause a fire or electric shock due to spark discharge, regardless of the approach speed of the grounded object or the surface area. To provide an electrostatic coating machine that is highly effective in that it is possible to reliably prevent electric shock accidents caused by electric shocks and to reduce manufacturing costs by simplifying the electric circuit configuration.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a diagram of the overall electric circuit configuration, and FIG. 2 is an enlarged side view of the main parts. In the figure, 1 is the first high voltage light (L device), 2 is the first breaker,
3 is an atomization device, 9 is a second high voltage generator, 18-10 is a second circuit breaker, 16 is a copper ring, 20 is a high resistance,
21 is a grounding object detection electrode, 23 is a current detector, 24 and 25 are grounding wires, 26 is an object to be painted (grounding object), 27 and 2
8 are first and second high voltage relays, respectively. Applicant Asahi Okuma Sangyo Co., Ltd. 19-1030

Claims (1)

[Scope of Claims] 1. A high voltage generator that generates a high DC voltage, and a workpiece that atomizes and discharges paint, is supplied with the high DC voltage from the high voltage generator, and is connected to a grounding wire. an atomizing device for electrostatically painting objects; an electrode for detecting grounded objects connected to the high voltage generator via a resistor and located in front or to the side of the atomizing device; a current detector that detects an increase in the current flowing through the ground object detection electrode when the ground object moves in a direction approaching the ground object detection electrode or comes into contact with the ground object detection electrode; An electrostatic coating machine comprising: a circuit breaker that cuts off the supply of DC high voltage from the high voltage generator to the atomizer when an increase in current reaches a predetermined value. 2. A first high voltage generator that generates a high DC voltage, and a workpiece that atomizes and discharges paint, is supplied with the high DC voltage from the first high voltage generator, and is connected to a grounding wire. an atomizer for electrostatically painting objects; a second high-voltage generator that is installed in a separate system from the first high-voltage generator and generates a DC high voltage; A grounded object detection electrode connected via a resistor and located in front or to the side of the atomizing device, and when the grounded object such as the object to be painted moves in a direction approaching the grounded object detection electrode, or a current detector that detects an increase in the current flowing through the ground object detection electrode when the electrode contacts the ground object; and a current detector that generates the first high voltage when the increase in the current detected by the current detector reaches a predetermined value. An electrostatic coating machine comprising: a circuit breaker that cuts off the supply of DC high voltage from the atomizer to the atomizer.