JP2021183305A - Electrostatic atomizer - Google Patents

Abstract

To provide an electrostatic atomizer whose management can be executed easily with high safety.SOLUTION: An electrostatic atomizer 10 by an electrospray method includes: an electric field adjusting electrode 35 formed of a conductive material or a semi-conductive material, which is electrified by applying a voltage at least between a liquid atomizing part 20 and a different polarity part 40, and influences an electric field generated between the liquid atomizing part 20 and the different polarity part 40; and an element 51 having voltage-current characteristics by which a flowing current increases rapidly when a voltage of a fixed voltage level or higher is applied, and which keeps an electric potential of the electric field adjusting electrode 35 at a fixed electric potential level or lower by being electrically connected between the electric field adjusting electrode 35 and a coated material 40.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrostatic spraying device using an electrospray method.

Patent Document 1 describes a state in which a liquid such as a paint is charged by an electrostatic force generated by applying a voltage between a liquid spray portion and a different electrode portion (object to be coated) having a different electrode with respect to the liquid spray portion. In an electrostatic spray device using an electrospray method that separates from the liquid spray part and atomizes it and sprays the atomized liquid on the object to be coated, a proximity electrode is placed near the tip of the liquid spray part and the liquid spray part is used. Disclosed is an electrostatic spray device that suppresses the adhesion of liquid to the proximity electrode by reducing the potential difference between the proximity electrode and the outside electrode and adjusting this potential difference with respect to the potential difference between the proximity electrode and the outside electrode. Has been done.

Japanese Unexamined Patent Publication No. 2016-137479

In the above-mentioned conventional technique, a voltage is applied to the liquid spray portion by a high voltage generator such as a Cockcroft-Walton circuit, and the object to be coated, which is a different electrode portion, and the proximity electrode are electrically connected via a variable resistor. It was configured to adjust the potential of the proximity electrode by dividing the voltage applied between the liquid spray part and the different electrode part.
However, a very high voltage of 10 kV or more may be applied between the liquid spray part and the different electrode part, and when this high voltage is divided by a resistor to adjust the voltage of the object to be coated and the proximity electrode. There is a risk of ignition or electric shock to the human body due to the discharge of the paint using an organic solvent, and there is a problem in safety.
Further, in order to suppress the current to 0.1 mA or less, which is a safe level, by connecting a resistor, a very high resistor of about 100 MΩ is required. However, such high resistance requires consideration not only of the electric circuit but also of the surrounding resistance such as the surrounding air, circuit board, circuit storage case, etc., which fluctuates greatly depending on humidity, etc., and its management is extremely difficult. was there.

Therefore, it is an object of the present disclosure to provide an electrostatic spray device having high safety and easy management.

The present invention is grasped by the following in order to achieve the above object.
(1) In the electrostatic spraying device of the present invention, the liquid is charged by the electrostatic force generated by applying a voltage between the liquid spraying portion and the different electrode portion having a different pole with respect to the liquid spraying portion. An electrostatic spray device by an electrospray method that separates from the liquid spray portion to atomize and sprays the atomized liquid onto an object to be coated, which is a different electrode portion, and is formed from a conductive material or a semi-conductive material. At least, an electric current adjusting electrode that is charged by applying a voltage between the liquid spraying portion and the different electrode portion and affects the electric current generated between the liquid spray portion and the different electrode portion, and a constant voltage. It has a voltage-current characteristic in which the current that flows rapidly increases when the above voltage is applied, and the potential of the electric field adjustment electrode is constant because it is electrically connected between the electric field adjustment electrode and the object to be coated. It includes an element that keeps the voltage below the potential.
(2) The electrostatic spraying device of the present invention sprays a liquid by an electrostatic force generated by applying a voltage between a liquid spraying portion having a nozzle and a different electrode portion having a different pole with respect to the liquid spraying portion. It is an electrostatic spray device by an electrospray method that separates from the liquid spray portion in a charged state to atomize it and sprays the atomized liquid onto an object to be coated, which is a different electrode portion, and is formed of a conductive material. A discharge electrode and an electric field adjusting electrode formed of a conductive material or a semi-conductive material, which is charged by at least the discharge from the discharge electrode and affects the electric field generated between the liquid spray portion and the different electrode portion. It has a voltage-current characteristic in which the current that flows rapidly increases when a voltage higher than a certain voltage is applied, and the potential of the electric field adjustment electrode is electrically connected between the electric field adjustment electrode and the object to be coated. It is provided with an element that keeps the voltage below a certain potential.
(3) In the above (2), the discharge electrode is arranged near the outer periphery of the tip of the nozzle and has the same potential as the liquid spray portion.
(4) In either (1) or (3) above, the element is grounded.
(5) In any of the above (1) to (4), the element is a varistor.
(6) In the above (2) or (3), the discharge electrode appears in the vicinity of the front side of the nozzle when the discharge electrode is not arranged, and the like on a plane including the central axis of the nozzle. The shape is such that at least a part of the equipotential curve is in the state of the equipotential curve that draws a gentler curve with respect to the state of the potential curve.
(7) In the above (2), (3) or (6), the discharge electrode is attached to the liquid spray portion.
(8) In the above (2), (3), (6) or (7), the position of the discharge electrode can be changed along the nozzle.
(9) In any of the above (1) to (8), the electric field adjusting electrode is attached to the liquid spraying portion.

According to the present disclosure, it is possible to provide an electrostatic spray device having high safety and easy management.

It is sectional drawing which shows the electrostatic spraying apparatus which concerns on 1st Embodiment of this invention. It is a perspective view which shows the electric spray device which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the liquid spray part of the electrostatic spraying apparatus which concerns on 1st Embodiment of this invention. It is an enlarged view which shows the tip side of a liquid spray part (the tip of a mandrel is rearward). It is an enlarged view which shows the tip side of a liquid spray part (the tip of a mandrel is the front). It is a figure which shows the voltage change when there is no constant voltage device. It is a figure which shows the voltage change when there is a constant voltage device. It is sectional drawing which shows the electrostatic spraying apparatus which concerns on 2nd Embodiment of this invention. It is an exploded sectional view which shows the liquid spray part and the discharge electrode which concerns on 2nd Embodiment of this invention. It is a perspective view which shows the liquid spray part which concerns on 2nd Embodiment of this invention. It is a figure which shows the state of the equipotential curve when the voltage is applied without arranging the discharge electrode in the electrostatic spraying apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the state of the equipotential curve when the discharge electrode is arranged and the voltage is applied in the electrostatic spraying apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the electrostatic spraying apparatus which concerns on 3rd Embodiment of this invention. It is a perspective view which shows the liquid spray part which concerns on 3rd Embodiment of this invention. It is sectional drawing which shows the electrostatic spraying apparatus which concerns on 4th Embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. The same elements are numbered the same throughout the description of the embodiment.
Unless otherwise specified, expressions such as "front (end)" and "front (direction)" represent the spraying direction side of the liquid in each member, etc., and "rear (end)" and "rear (direction)". The expression "" or the like represents the side opposite to the spraying direction of the liquid in each member or the like, and the "connection" represents an electrical connection.

(First Embodiment)
FIG. 1 is a cross-sectional view showing the overall configuration of the electrostatic spraying device 10 according to the first embodiment of the present invention, and FIG. 2 is a perspective view showing an outline of the electrostatic spraying device 10.
As shown in FIGS. 1 and 2, the electrostatic spray device 10 is an electrostatic spray device used in the electrospray method, and has a different electrode from the liquid spray unit 20 having a nozzle 22 and the liquid spray unit 20. It is provided with a voltage applying means (voltage power supply) 50 for applying a voltage between the different electrode portion 40 and the different electrode portion 40. Further, an electric field adjusting electrode 35 that affects the electric field generated between the liquid spraying portion 20 and the different electrode portion 40 is provided between the nozzle 22 of the liquid spraying portion 20 and the different electrode portion 40, and the electric field adjusting electrode 35 is provided. A constant voltage device 51, which is an element electrically connected to the device, is provided. The constant voltage device 51 is an element having a voltage-current characteristic in which the flowing current rapidly increases when a voltage higher than a certain voltage is applied.

In this embodiment, the case where the electric wiring from the voltage applying means 50 is directly connected to the object to be coated and the object to be coated itself is the different electrode portion 40 is shown. However, for example, the object to be coated is mounted. An electric wiring from the voltage applying means 50 is connected to the mounting portion (not shown) to be placed, and the object to be coated is electrically connected to the voltage applying means 50 via the mounting portion by using this mounting portion as a different electrode portion 40. It may be connected to the target.
In the following description, the different electrode portion 40 or the object to be coated 40 is used.

The object to be coated 40, which is the different electrode portion 40, is grounded by the grounding means 60.
This grounding means 60 is not an indispensable requirement, but in the case of something like the object to be coated 40, it is preferable to provide it from the viewpoint of safety because the operator may touch it.

(Liquid spray part)
FIG. 3 is a cross-sectional view showing a liquid spraying portion 20 of the electrostatic spraying device 10 according to the first embodiment of the present invention.
In addition, in FIG. 3, a state in which a liquid such as a paint is sprayed from the liquid spraying unit 20 is also illustrated as described later.
As shown in FIG. 3, the liquid spray unit 20 has a body portion 21 made of an insulating material having a liquid flow path 21b having a liquid supply port 21a to which the liquid is supplied, and a through hole for the liquid flow of the body portion 21. A nozzle 22 provided at the tip of the body portion 21 so as to communicate with the path 21b, and a mandrel 23 made of a conductive material arranged in the liquid flow path 21b of the body portion 21 and in the through hole of the nozzle 22 are provided. There is.

The body portion 21 is provided with a hole portion 21c communicating with the liquid flow path 21b in order to take out the mandrel 23 to the rear end side, and a gap between the mandrel portion 23 is sealed in the hole portion 21c. A sealing member 24 is provided to prevent the liquid from leaking.
In the present embodiment, the O-ring is used as the seal member 24, but the seal member 24 is not limited to the O-ring and may be any one that can be sealed.

A knob portion 23a made of an insulating material is provided at the rear end of the mandrel 23 located on the rear end side of the body portion 21 through the hole portion 21c, and is provided so as to penetrate substantially the center of the grip portion 23a. An electric wiring connection portion 23b made of the conductive material is provided.

As shown in FIG. 1, the electrical wiring from the voltage applying means 50 is connected to the electrical wiring connection portion 23b.
Then, as shown in FIG. 3, the mandrel 23 and the electric wiring connecting portion 23b are electrically connected by making the electric wiring connecting portion 23b come into contact with the mandrel 23.

In the present embodiment, the mandrel 23 is used as an electrode on the liquid spraying portion 20 side. For example, the nozzle 22 of the liquid spraying portion 20 is made of a conductive material, and the nozzle 22 is electrically wired from the voltage applying means 50. May be connected and the nozzle 22 may be used as an electrode on the liquid spraying portion 20 side.

Further, a female screw structure 21e for screwing and connecting the grip portion 23a is provided on the inner peripheral surface of the rear end opening portion 21d of the body portion 21, while a male screw is provided on the outer peripheral surface of the tip of the grip portion 23a. The structure 23c is provided.

Therefore, the mandrel 23 is detachably attached to the body portion 21 by screwing the male thread structure 23c on the outer peripheral surface of the tip of the knob portion 23a into the female thread structure 21e of the rear end opening portion 21d of the body portion 21.
Further, the mandrel 23 can be moved in the front-rear direction by adjusting the screwing amount of the grip portion 23a, and the position of the tip surface 23d of the mandrel 23 can be adjusted in the front-rear direction.

Here, generally, the nozzle for spraying the liquid of the electrostatic spraying device is a fine liquid flow path having a small diameter of the through hole through which the liquid flows.
It is presumed that this is because if the opening diameter of the tip of the nozzle through which the liquid flows is large, a stable liquid atomization state cannot be obtained.
For example, generally, the opening diameter of the nozzle tip is less than 0.1 mm.

Therefore, as soon as the liquid dries, the opening at the tip of the nozzle is clogged, but there is a problem that it is difficult to clear the clogging because the opening diameter is small.

However, as will be described later, it has been found that by using the mandrel 23, good atomization can be achieved even if the opening diameter of the nozzle tip is large as compared with the conventional case. The opening diameter of the opening 22b at the tip of the nozzle 22 of the present embodiment has a large opening diameter of 0.2 mm.
As a result, the frequency of clogging can be significantly reduced.

The opening diameter of the opening 22b of the nozzle 22 is not limited to 0.2 mm, and in the form of using the mandrel 23, there is no problem even if the opening diameter is about 1 mm.

The opening diameter of the opening 22b of the nozzle 22 is preferably 0.1 mm or more, more preferably 0.2 mm or more, and further 0. It is preferably larger than 2 mm.

On the other hand, the opening diameter of the opening 22b of the nozzle 22 is preferably 1.0 mm or less, more preferably 0.8 mm or less, and further preferably 0.5 mm or less in consideration of the stability of atomization. Is good.

Further, in the present embodiment, as described above, the mandrel 23 can be moved in the front-rear direction, so that even if clogging occurs, the mandrel 23 can be moved to eliminate the clogging.
Further, since the inner diameter of the through hole of the nozzle 22 is also large enough to allow the mandrel 23 to be arranged, it is possible to remove the mandrel 23 and flow a large amount of cleaning liquid for cleaning.

FIG. 4 is an enlarged view of the tip end side of the liquid spray portion 20, FIG. 4A is a case where the tip surface 23d of the mandrel 23 is located rearward, and FIG. 4B is a mandrel 23 from the state of FIG. 4A. This is the case where the tip surface 23d of the above is located in the front.

As shown in FIG. 4A, the nozzle 22 has a tapered inner diameter portion (see range A) in which the inner diameter is tapered toward the opening 22b side and the taper angle is α, and the mandrel 23 has a tip. It has a tapered shape portion (see range B) in which the taper angle at which the outer diameter becomes smaller toward the surface 23d is β.

The taper angle α of the tapered inner diameter portion of the nozzle 22 is made larger than the taper angle β of the tapered shape portion of the mandrel 23.
The diameter of the tip surface 23d of the mandrel 23 is smaller than the diameter of the opening 22b of the nozzle 22, but the tapered portion of the mandrel 23 gradually increases in diameter toward the rear end side. Therefore, it is formed so as to have a portion having a diameter larger than the opening diameter of the opening 22b of the nozzle 22.

As described above, by forming the tip side of the nozzle 22 and the mandrel 23, as can be seen by comparing FIGS. 4A and 4B, the mandrel 23 is formed by moving the mandrel 23 in the front-rear direction to form the nozzle 22 and the mandrel 23. The width of the gap can be adjusted, and the amount of liquid discharged from the opening 22b of the nozzle 22 can be adjusted.

Further, by moving the mandrel 23 further forward than in the state shown in FIG. 4B, the mandrel 23 comes into contact with the inner peripheral surface of the nozzle 22 and the opening 22b of the nozzle 22 can be closed.
Therefore, it is possible to block the opening 22b of the nozzle 22 with the mandrel 23 in a state where the liquid such as paint is not sprayed, to prevent the liquid in the nozzle 22 from drying, and to suppress clogging of the nozzle 22. can.

(Different pole part 40)
In the present embodiment, as described above, the case where the object to be coated is used for the different electrode portion 40 is shown, and the electric wiring on the opposite side to the mandrel 23 of the voltage applying means (voltage power supply) 50 is shown. By being connected to the object to be coated 40, the object to be coated 40 itself is made to have a different electrode to the liquid spray portion 20.

However, as mentioned above, for example, when the object to be coated is transported to a position where a liquid such as paint is applied by a transport device or the like, the electrical wiring from the voltage applying means 50 is transferred to the transport device. The object to be coated may be electrically connected to the voltage applying means 50 via the mounting portion so that the object to be coated is connected to the mounting portion on which the object to be coated is placed.

Next, with reference to FIG. 3, first, a state in which the liquid is sprayed from the liquid spraying unit 20 will be described.

The liquid supplied to the liquid supply port 21a of the body portion 21 is supplied to the tip end side of the nozzle 22, and the electrostatic force due to the voltage applied between the different electrode portion 40 (object to be coated) and the mandrel 23. Pulls forward and separates and atomizes forward.

The liquid may be supplied in sequence as long as the amount of liquid lost from the liquid spray unit 20 due to consumption by spraying is sequentially supplied, and the opening 22b of the nozzle 22 (more accurately, the opening 22b and the mandrel). It is not necessary to pump and supply the liquid at a pressure such that the liquid is ejected from the gap between the 23 and 23), and in a state where the liquid is vigorously ejected, atomization may not be possible.

More specifically, as shown in FIG. 3, the electrostatic force that pulls the liquid forward is balanced against the adhesive force due to the surface tension and viscosity of the mandrel 23 to the tip surface 23d and the tip outer peripheral edge 22a of the nozzle 22. A tailor cone 80 having a conical shape is formed at the tip of the liquid supplied to the tip side of the nozzle 22.

The tailor cone 80 is formed in a conical shape due to the separation of positive and negative charges in the liquid due to the action of an electric field and the deformation of the meniscus at the tip of the nozzle 22 charged with excess charge.
Then, the liquid is pulled straight from the tip of the tailor cone 80 by electrostatic force, and the liquid is electrostatically exploded at the tip of the jet portion 82 extending linearly from the tip of the tailor cone 80, so that the liquid is sprayed over a wide range.

The sprayed liquid, that is, the liquid that has separated from the nozzle 22 and becomes liquid particles, has a dramatically larger area in contact with air than the state before the separation, so that the vaporization of the solvent is promoted, and the solvent of the sprayed liquid is promoted. With vaporization, the distance between the charged electrons becomes shorter, electrostatic repulsion (electrostatic explosion) occurs, and the liquid particles have a smaller particle size.

When this split occurs, the surface area that comes into contact with the air increases compared to before the split, so the vaporization of the solvent is promoted, an electrostatic explosion occurs as described above, and a liquid with a smaller particle size is further generated. It splits into particles.
By repeating such electrostatic explosion, the liquid is atomized.

Here, in the present embodiment, the mandrel 23 is provided in the nozzle 22.
Assuming that the mandrel 23 is not provided as in the conventional electrostatic spraying device, the portion to which the liquid can adhere is only the outer peripheral edge 22a of the tip of the nozzle 22.

If the opening diameter of the opening 22b of the nozzle 22 is increased in such a state, the liquid can adhere only to the outer peripheral edge 22a of the tip of the nozzle 22, so that the liquid sways up, down, left and right of the nozzle 22, for example. The stability of the liquid particles that separate from the nozzle 22 (stability of the particle size, number, charge state, etc.) because the tailor cone 80 cannot be easily formed and the tailor cone 80 itself cannot be maintained. As a result, it is presumed that stable atomization of the liquid cannot be obtained.

On the other hand, in the present embodiment, the mandrel 23 is arranged in the nozzle 22, and the liquid adheres not only to the outer peripheral edge 22a of the tip of the nozzle 22 but also to the tip surface 23d of the mandrel 23.
Therefore, even if the opening diameter of the opening 22b of the nozzle 22 is large, the tip surface 23d of the mandrel 23 to which the liquid can adhere exists in the center of the opening 22b, so that a stable tailor cone 80 can be formed and the liquid can be formed. It is considered that stable atomization is possible.

If the tip surface 23d of the mandrel 23 protrudes too far forward from the outer peripheral edge 22a of the tip of the nozzle 22 (that is, the tip surface of the opening 22b of the nozzle 22), it becomes difficult for an electric field to act on the liquid discharged from the nozzle 22, while the mandrel If the tip surface 23d of the 23 is retracted too far rearward from the tip surface of the opening 22b of the nozzle 22, the state is the same as if there is no portion where the liquid can adhere to the central portion of the opening 22b.

From this, the position of the tip surface 23d of the mandrel 23 is the position of the nozzle 22 in the front-rear direction along the central axis of the mandrel 23 with reference to the tip surface of the opening 22b of the nozzle 22 in the state of spraying the liquid. It is preferably located within 10 times the opening diameter of the tip opening 22b, more preferably within 5 times, and even more preferably within 3 times. be.

For example, in the present embodiment, the opening diameter of the opening 22b of the nozzle 22 is 0.2 mm, and when electrostatic force is not taken into consideration, the liquid discharged from the opening 22b of the nozzle 22 has a diameter of about the tip of the nozzle 22. It comes out in a hemispherical shape of 0.2 mm.

Then, the tip of the mandrel 23 often exists near this liquid so that an electric field (electrostatic force) acts on the liquid that has come out at the tip of the nozzle 22 to form a conical tailor cone 80. Therefore, it is preferable that the tip of the mandrel 23 is located within 2 mm forward (in the direction of exit) from the tip surface of the opening 22b of the nozzle 22, while the tip of the mandrel 23 acts on the adhesion of the liquid. It is preferable that the opening 22b is located within 2 mm rearward (in the retracting direction) from the tip surface of the opening 22b.

As described above, by providing the mandrel 23, stable liquid atomization can be performed even if the opening diameter of the opening 22b of the nozzle 22 is increased.
Therefore, the opening diameter of the opening 22b of the nozzle 22 can be made large so that clogging can be suppressed.
Further, since the opening diameter of the opening 22b of the nozzle 22 can be increased, the nozzle 22 can be manufactured by machining.

In the present embodiment, the case where the tip of the mandrel 23 is a flat flat surface as the tip surface 23d is shown, but the tip of the mandrel 23 does not necessarily have to be a flat flat surface, and a stable tailor cone 80 is formed. For example, the tip of the mandrel 23 may have a curved surface that protrudes toward the front side, such as an R shape.

The liquid sprayed from the liquid spraying portion 20 (nozzle 22) in this way becomes an atomized liquid while repeating electrostatic explosion, and since this atomized liquid is in a charged state, the different electrode portion 40 ( It is attracted to the object to be coated) side by electrostatic force and is applied to the object to be coated 40.

In FIG. 1, as the constant voltage device 51, an element having a voltage-current characteristic in which the flowing current rapidly increases when a voltage of a certain voltage or higher is applied can be used. In particular, an element having a characteristic that the current does not flow up to a certain voltage or is extremely small even if it flows, but the current that flows rapidly increases when the voltage exceeds a certain value is suitable.
As an element exhibiting such characteristics, for example, a varistor can be used. The varistor has a characteristic that the internal resistance drops sharply when the applied voltage reaches a predetermined voltage, as it is sometimes called a non-linear resistance or a voltage-dependent resistance. It is an element having a voltage-current characteristic in which the flowing current rapidly increases when applied. Varistors generally prevent high voltages such as lightning surges, static electricity, and counter electromotive voltage when the power of direct current equipment (DC motors, etc.) is cut off from flowing into the circuit, and are used as surge protection devices (SPDs) in each circuit. Used for the purpose of protecting elements and electronic devices.

In the present embodiment, the varistor is not intended to protect each element or electronic device of such a circuit, but is to electrically connect a varistor, which is a constant voltage device 51, between the electric field adjusting electrode 35 and the object to be coated 40. It is used for the purpose of keeping the potential of the electric field adjusting electrode 35 below a certain potential.
In addition, the laminated chip varistor has a structure similar to a capacitor in which a metal oxide is sandwiched between electrodes, and has a capacitance component, that is, a function of storing electric charge like a capacitor, so that a sudden change in voltage is suppressed. In terms of having an action, it is also suitable for use in the constant voltage device 51 in the present embodiment.

In FIG. 1, when the power of the voltage applying means 50 is turned on, electric charges are accumulated in the liquid spraying portion 20 and a potential difference is generated between the electric field adjusting electrode 35 to which the negative electrode of the voltage applying means 50 is connected. This potential difference increases as the electric charge is accumulated in the liquid spray unit 20.

Then, the electric field adjusting electrode 35 is charged by turning on the power of the voltage applying means 50, that is, by applying a voltage at least between the liquid spraying portion 20 and the object to be coated 40 which is a different electrode portion. become.
The charge of the electric field adjusting electrode 35 is generated by the action of the atomized liquid 87 sprayed from the liquid spray unit 20 by turning on the power of the voltage applying means 50 and the discharge from the liquid spray unit 20. This discharge is not limited to that generated by the liquid spray unit 20. It may be provided in the vicinity of the liquid spray unit 20 and may be configured to discharge from an electrode having the same polarity as the liquid spray unit 20.

When the constant voltage device 51 is not electrically connected between the electric field adjusting electrode 35 and the object to be coated 40, the electric charge is accumulated in the liquid spraying unit 20 due to the potential difference between the liquid spraying unit 20 and the electric field adjusting electrode 35. It gets bigger with the. The voltage of the electric field adjusting electrode 35 is not equal to the power supply voltage due to its own discharge, and is charged to the voltage between the positive electrode and the negative electrode of the voltage applying means 50.

On the other hand, as shown in FIG. 1, when the constant voltage device 51 is electrically connected between the electric field adjusting electrode 35 and the object to be coated 40, the electric field adjusting electrode 35 is charged and the voltage is increased. When the potential of the electric field adjusting electrode 35 with respect to the negative electrode of the applying means 50, that is, the voltage applied across the constant voltage device 51 reaches a constant voltage (rated voltage) or more defined by the rating of the constant voltage device 51. As the internal resistance of the constant voltage device 51 drops sharply, the current flowing from the liquid spray unit 20 to the constant voltage device 51 via the electric field adjustment electrode 35 suddenly increases, and the negative voltage of the voltage applying means 50 becomes negative. The potential of the electric field adjusting electrode 35 as a reference, that is, the voltage applied across the constant voltage device 51 acts to be maintained at the rated voltage of the constant voltage device 51.

In this way, the atomized liquid 87 is sprayed from the nozzle 22 by applying a voltage between the liquid spraying portion 20 and the object to be coated 40 by the voltage applying means 50. The constant voltage device 51 is electrically connected to the electric field adjusting electrode 35 provided between the liquid spraying unit 20 and the object to be coated 40, so that the electric field adjusting electrode 35 has the same polarity as the liquid spraying unit 20. Therefore, the potential of the rated voltage of the constant voltage device 51 is maintained.

As shown in FIGS. 1 and 2, the electric field adjusting electrode 35 maintained at such a potential affects the electric field generated between the liquid spray portion 20 and the object to be coated 40, and fog in the vicinity of the electric field adjusting electrode 35. The chemical liquid 87 has an inwardly deformed distribution. The atomized liquid 87 charged to a potential of the same polarity as the liquid spray unit 20 is similarly deformed by receiving a repulsive force by the electric field adjusting electrode 35 having the same polarity.

That is, the electric field adjusting electrode 35 is provided between the liquid spraying unit 20 and the object to be coated 40, and the rated voltage of the constant voltage device 51 is appropriately selected to adjust the potential of the electric field adjusting electrode 35, thereby causing the liquid spraying unit 20 and the liquid spraying unit 20. The electric field between the objects to be coated 40 can be affected to deform the object into a desired shape, and the distribution of the atomized liquid 87 sprayed can be adjusted as appropriate.

In this way, the constant voltage device 51 is electrically connected to the electric field adjusting electrode 35 without directly connecting a high voltage power supply to the electric field adjusting electrode 35 or connecting a very high resistance. By configuring the electric field adjusting electrode 35 to maintain the potential at a predetermined potential, according to the present embodiment, it is possible to obtain an electrostatic spraying device 10 having high safety and easy management.

The electric field adjusting electrode 35 is formed of a conductive material, a semi-conductive material having a surface resistance of ^{10 10 Ω or less, and an antistatic material.}

The shape and size of the electric field adjusting electrode 35 and the position where the electric field adjusting electrode 35 is installed are appropriately determined by the distribution of the target electric field. Therefore, the electric field adjusting electrode 35 is not limited to the shape and arrangement shown in FIGS. 1 and 2.

FIG. 5 is a diagram showing a change in voltage with respect to the object to be coated 40 when the object to be coated 40 is connected to the ground with and without the constant voltage device 51. FIG. 5A shows the change in the voltage of the electric field adjusting electrode 35 when the constant voltage device 51 is not present, and FIG. 5B shows the change in the voltage of the electric field adjusting electrode 35 when the constant voltage device 51 is present.

In FIG. 5A, when the power of the voltage applying means 50 is turned on, an electric charge is stored in the liquid spraying portion 20 and the potential gradually rises. Along with this, the electric field adjusting electrode 35 is charged and the electric field adjusting electrode 35 is charged. Raises the potential of. This potential is substantially maintained when the potential rises to around 9 kV due to the balance between the charge from the liquid spray unit 20 and the discharge of the electric field adjusting electrode 35 itself.

In FIG. 5B, when the power of the voltage applying means 50 is turned on, an electric charge is stored in the liquid spraying portion 20 and the potential gradually rises. Along with this, the electric field adjusting electrode 35 is charged and the electric field adjusting electrode 35 is charged. Raises the potential of. When the potential of the voltage adjusting electrode 35 with respect to the negative electrode of the voltage applying means 50, that is, the voltage applied across the constant voltage device 51 becomes around 5 kV, which is the rated voltage of the constant voltage device 51, the internal resistance of the constant voltage device 51 drops sharply. As a result, the flowing current suddenly increases, and the voltage becomes almost constant at around 5 kV.
That is, by electrically connecting the constant voltage device 51 to the electric field adjusting electrode 35, the potential of the electric field adjusting electrode 35 with reference to the negative electrode of the voltage applying means 50 is the voltage across the constant voltage device 51, that is, It is kept equal to the rated voltage of the constant voltage device 51. In this way, the constant voltage device 51 is electrically connected between the electric field adjusting electrode 35 and the object to be coated 40, so that the potential of the electric field adjusting electrode 35 is kept below a certain potential.

The object to be coated 40 is connected to the negative electrode of the voltage applying means 50, and the object to be coated 40 has the same potential as the negative electrode of the voltage applying means 50. Therefore, the potential difference between the liquid spray portion 20 connected to the positive electrode of the voltage applying means 50 and the object to be coated 40 is irrespective of whether or not the constant voltage device 51 is electrically connected to the electric field adjusting electrode 35. It becomes equal to the power supply voltage of the voltage applying means 50.

On the other hand, when the constant voltage device 51 is electrically connected to the electric field adjusting electrode 35, the potential of the liquid spraying portion 20 is the highest, then the electric field adjusting electrode 35 is the highest, and the object to be coated 40 is the lowest. Become a relationship. Then, the potential difference between the electric field adjusting electrode 35 and the object to be coated 40 becomes the rated voltage of the constant voltage device 51. That is, when the object to be coated 40 is used as a reference potential, the electric field adjusting electrode 35 has a positive potential and has the same polarity as the liquid spray portion 20.

Therefore, when the constant voltage device 51 is electrically connected to the electric field adjusting electrode 35, the liquid spray unit 20 and the electric field adjusting electrode are selected by selecting the power supply voltage of the voltage applying means 50 and the rated voltage of the constant voltage device 51. 35, the potential of the object to be coated 40 can be set to a predetermined relationship.

The object to be coated 40 and the constant voltage device 51 are connected to the negative electrode of the voltage applying means 50, but as shown in FIG. 1, they may be further connected to the grounding means 60 and grounded. This makes it possible to increase the safety.

(Second Embodiment)
FIG. 6 is a cross-sectional view showing an electrostatic spraying device 10 according to a second embodiment of the present invention.
The electrostatic spraying device 10 according to the second embodiment is different from the electrostatic spraying device 10 according to the first embodiment in that a discharge electrode 30 is provided, and other than that, it is the same as that of the first embodiment. be.

As shown in FIG. 6, in the electrostatic spraying device 10, the electrostatic spraying device 10 is located between a liquid spraying unit 20 having a nozzle 22, a discharge electrode 30, and a different electrode portion 40 which is a different electrode with respect to the liquid spraying unit 20 and the liquid spraying unit 20. It is provided with a voltage applying means 50 for applying a voltage to the voltage, an electric field adjusting electrode 35, and a constant voltage device 51.

FIG. 7 is an exploded cross-sectional view showing the liquid spray portion 20 and the discharge electrode 30 according to the second embodiment of the present invention.
FIG. 8 is a perspective view showing the liquid spray unit 20 according to the second embodiment of the present invention.

As shown in FIG. 7, the discharge electrode 30 has a screw hole 31a provided with a female screw structure.
Then, after the discharge electrode 30 is mounted on the nozzle 22 of the liquid spraying portion 20, the fixing screw 31 is screwed into the screw hole 31a of the discharge electrode 30 and the outer periphery of the nozzle 22 is pressed by the fixing screw 31. It is fixed to the nozzle 22 by tightening the fixing screw 31.

In this way, as shown in FIG. 8, the discharge electrode 30 is attached so as to be arranged near the outer periphery of the tip of the nozzle 22 of the liquid spray unit 20.
More specifically, in the present embodiment, as shown in FIG. 6, the discharge electrode 30 is fixed to the outer periphery of the nozzle 22 so as to be arranged behind the outer peripheral edge 22a of the tip of the nozzle 22.

Then, as described above, since the discharge electrode 30 is fixed by the fixing screw 31, it can be moved along the nozzle 22 by loosening the fixing screw 31, and the discharge electrode 30 can be moved along the nozzle 22 before and after. It is possible to change and adjust the arrangement position in the direction.

In this embodiment, the case where the discharge electrode 30 is fixed to the nozzle 22 is shown, but the fixing itself may be performed to the body portion 21 of the liquid spray portion 20, and the discharge electrode may be fixed by an arm structure or the like. It suffices if the 30 is arranged near the outer periphery of the tip of the nozzle 22.

The discharge electrode 30 is made of a conductive material, and as shown in FIG. 6, an electric wiring branched from the electric wiring connected to the electric wiring connection portion 23b from the voltage applying means 50 is connected.
Therefore, the discharge electrode 30 has the same potential as the liquid spray unit 20. However, the discharge electrode 30 is not limited to having the same potential as the liquid spray unit 20.

FIG. 9 is a diagram showing a state of the equipotential curve 58 when a voltage is applied without arranging the discharge electrode 30 in the electrostatic spray device 10 according to the second embodiment of the present invention.
FIG. 10 is a diagram showing a state of an equipotential curve 58 when a discharge electrode 30 is arranged and a voltage is applied in the electrostatic spray device 10 according to the second embodiment of the present invention.

In FIG. 9, the central axis of the nozzle 22 is shown as the Z axis, and one axis orthogonal to the Z axis is shown as the X axis, and when a voltage is applied to the cross section in the X axis direction along the Z axis. The state of the equipotential curve 58 that appears is also shown in the figure.
That is, FIG. 9 is a diagram showing a state of the equipotential curve 58 on a plane including the central axis of the nozzle 22.

As shown in FIG. 9, when a voltage is applied, an equipotential curve 58 appears so as to surround the nozzle 22.
Then, the liquid discharged from the nozzle 22 is pulled by an electrostatic force in a direction orthogonal to the tangent line of the equipotential curve 58, and at this time, the surface tension on the tip surface 23d of the mandrel 23 and the tip outer peripheral edge 22a of the nozzle 22. As shown in FIG. 3, the liquid supplied to the tip side of the nozzle 22 is formed into a conical shape at the tip of the tailor cone 80 by balancing the electrostatic force pulling the liquid with the adhesive force due to the viscosity and viscosity. It becomes a state. Then, the liquid is pulled straight from the tip of the tailor cone 80 by electrostatic force, and then electrostatically explodes.

The pulling force to the front side leading up to this electrostatic explosion becomes the inertial force of the sprayed liquid, and further, the spreading force (repulsive force) at the time of electrostatic explosion and the direction perpendicular to the tangent line of the isopotential curve 58. The liquid is sprayed forward as a result of interactions such as tensile forces due to electrostatic forces. Then, the liquid is atomized by repeating such electrostatic explosion.

As shown in FIG. 9, the equipotential curve 58 that appears so as to surround the nozzle 22 by applying a voltage appears so as to draw a circle around the nozzle 22.
Considering that the tensile force of the electrostatic force acts in the direction orthogonal to this tangent line when the tangent line is drawn on the equipotential curve 58, the direction orthogonal to the tangent line of the equipotential curve 58 is the forward direction with respect to the liquid to be separated. Not only that, there can be various directions such as diagonal direction and lateral direction, so the liquid that separates is pulled by electrostatic force from various directions, and this electrostatic force, inertial force, and electrostatic explosive force (repulsive force). It will be sprayed over a wide area on the front side in consideration of such factors.

Therefore, in the present embodiment, the discharge electrode is formed of a conductive material that adjusts the state of the equipotential curve 58 and has the same potential as the liquid spray portion 20 in order to match the spreading state of the liquid according to the application of the liquid. 30 is provided.

FIG. 10 is a side view showing only the tip end side of the nozzle 22 that sprays the liquid, as in FIG. 9, but further, a discharge electrode 30 is provided, and the state of the equipotential curve 58 in that state is combined. It is the figure shown.
Note that the Z-axis and the X-axis of FIG. 10 are views showing equipotential curves 58 on a plane including the central axis of the nozzle 22, similar to that shown in FIG.

As shown in FIG. 10, by providing the discharge electrode 30, a plane including the central axis of the nozzle 22 that appears near the front side of the nozzle 22 when the discharge electrode 30 shown in FIG. 9 is not arranged. It can be seen that the equipotential curve 58 is partially drawn with a gentler curve than the equipotential curve 58 in the above state, and the equipotential curves 58 approach the state of being arranged in parallel toward the front side. The action of the discharge electrode 30 on the equipotential curve 58 may be configured so that not only a part of the equipotential curve 58 but the whole of the equipotential curve 58 is in the state of the equipotential curve 58 which draws a gentle curve.
The vicinity of the front side of the nozzle 22 is within 150 mm or 100 mm in the direction orthogonal to the center axis with respect to the center axis of the nozzle 22, and is within 150 mm or 100 mm in front of the nozzle 22. It is a range that does not exceed the range of the columnar shape in front of the tip.

In such a state of the isopotential curve 58 shown in FIG. 10, the direction orthogonal to the tangent line of the equipotential curve 58 with respect to the liquid to be discharged is mainly the forward direction, so that the static electricity at the time of the liquid withdrawal or after the liquid is discharged. Although the liquid spreads due to an electric explosion or the like, it is difficult to spread as compared with the state where the discharge electrode 30 is not provided. As a result, the sprayed liquid will be sprayed without spreading too much.

If the discharge electrode 30 is arranged too far behind the nozzle 22, the action of adjusting the equipotential curve 58 is reduced, so that the discharge electrode 30 is in a state where the discharge electrode 30 is not arranged. It is necessary to be able to arrange it in the vicinity of the outer periphery of the tip of the nozzle 22 which can be in the state of the equipotential curve 58 which draws a gentler curve than the state of the equipotential curve 58 which sometimes appears on the front side of the nozzle 22.

Further, as shown in FIG. 8, in the present embodiment, the tip portion 30a of the discharge electrode 30 is formed of a flat surface, and by doing so, as shown in FIG. 10, the tip portion of the discharge electrode 30 is formed. The equipotential curve 58 appearing between the 30a and the nozzle 22 is not curved to the rear side of the tip portion 30a of the discharge electrode 30.

By arranging the discharge electrode 30 in the vicinity of the outer periphery of the tip of the nozzle 22 formed of the conductive material in this way, the shape of the equipotential curve 58 can be appropriately adjusted, and the distribution of the sprayed liquid can be adjusted. be able to.

The shape, size, and position of the discharge electrode 30 can be appropriately selected according to the target shape and distribution of the equipotential curve 58. In FIG. 8, the shape is a cylinder, but the shape is not limited to this, and it may be a polygon such as a rectangle or a fan shape.

In FIG. 6, when the power of the voltage applying means 50 is turned on, electric charges are accumulated in the liquid spraying portion 20 and the discharge electrode 30, and a potential difference is generated between the electric field adjusting electrode 35 to which the negative electrode of the voltage applying means 50 is connected. Occurs. This potential difference increases as the electric charge is accumulated in the liquid spray portion 20 and the discharge electrode 30.

Then, by turning on the power of the voltage applying means 50, that is, by applying a voltage at least between the liquid spraying unit 20 and the discharge electrode 30 and the object to be coated 40 which is a different electrode portion, the liquid spraying unit 20 The electric field adjusting electrode 35 is charged by the action of the atomized liquid 87 to be sprayed and the discharge from the liquid spraying portion 20 and the discharge electrode 30.
In the present embodiment, the discharge electrode 30 is provided in the vicinity of the liquid spray portion 20, so that the electric field adjusting electrode 35 is charged by at least the discharge from the discharge electrode 30.

As described above, in the second embodiment, by providing the discharge electrode 30 in the vicinity of the liquid spray portion 20, the electric field adjusting electrode 35 is charged to raise its potential, and the voltage becomes equal to or higher than the rated voltage of the constant voltage device 51. By the action of the constant voltage device 51, the electric field adjusting electrode 35 can be kept at a predetermined potential, and the shape of the equipotential curve 58 can be appropriately adjusted to adjust the distribution of the sprayed liquid. can.

Although the object to be coated 40 and the constant voltage device 51 are connected to the negative electrode of the voltage applying means 50, as shown in FIG. 6, the object to be coated 40 and the constant voltage device 51 may be further connected to the grounding means 60 and grounded. This makes it possible to increase the safety.

(Third Embodiment)
FIG. 11 is a cross-sectional view showing an electrostatic spraying device 10 according to a third embodiment of the present invention.
FIG. 12 is a perspective view showing the liquid spray unit 20 according to the third embodiment of the present invention.
The electrostatic spraying device 10 according to the third embodiment is different from the electrostatic spraying device 10 according to the first embodiment in that the electric field adjusting electrode 35 is attached to the liquid spraying unit 20, and the other parts are the same. 1 It is the same as the embodiment.

As shown in FIGS. 11 and 12, an electrode holder 25 for mounting the electric field adjusting electrode 35 is provided on the outer peripheral surface of the nozzle 22. The electrode holder 25 has an annular structure made of an insulating material provided on the outer periphery of the nozzle 22, and an electrode mounting portion 25a for mounting the electric field adjusting electrode 35 is provided at the tip of the annular structure.

As shown in FIGS. 11 and 12, the electric field adjusting electrode 35 is a member made of a ring-shaped conductive material formed to have a diameter larger than the outer diameter of the nozzle 22, and is a voltage applying means via a constant voltage device 51. It is connected to the negative electrode of 50.
In the present embodiment, the case where the electric field adjusting electrode 35 has a circular ring shape is shown, but it may be a polygonal ring shape, an arc shape, or the like. Further, the shape is not limited to a closed shape such as a ring shape, and may be a rod shape or a plate shape.
The electric field adjusting electrode 35 is fixed to the outer periphery of the nozzle 22 via an electrode holder 25 made of an insulating material, but the electrode holder 25 is not limited to being fixed to the nozzle 22. , May be fixed to the body portion 21.

In the present embodiment, the electric field adjusting electrode 35 is attached to the liquid spraying unit 20, so that the electric field adjusting electrode 35 particularly in the work of spraying the liquid while moving the liquid spraying unit 20 with respect to the object to be coated 40. Since it moves integrally with the liquid spray unit 20 and the positional relationship between the electric field adjusting electrode 35 and the liquid spray unit 20 is fixed, the electric field generated between the liquid spray unit 20 and the object to be coated 40 can be stabilized. ..

(Fourth Embodiment)
FIG. 13 is a cross-sectional view showing an electrostatic spraying device 10 according to a fourth embodiment of the present invention.
The electrostatic spray device 10 according to the fourth embodiment is different from the electrostatic spray device 10 according to the first embodiment in that the discharge electrode 30 and the electric field adjustment electrode 35 are attached to the liquid spray unit 20. Others are the same as in the first embodiment.

In the present embodiment, since the discharge electrode 30 and the electric field adjusting electrode 35 are attached to the liquid spraying unit 20, the electric field is particularly applied in the work of spraying the liquid while moving the liquid spraying unit 20 with respect to the object to be coated 40. Since the adjusting electrode 35 moves integrally with the liquid spraying portion 20 and the positional relationship between the electric field adjusting electrode 35 and the liquid spraying portion 20 is fixed, the electric current generated between the liquid spraying portion 20 and the object to be coated 40 is stabilized. Further, the shape of the isopotential curve 58 can be appropriately adjusted to adjust the distribution of the sprayed liquid.

In the third embodiment and the fourth embodiment, the object to be coated 40 and the constant voltage device 51 are connected to the negative electrode of the voltage applying means 50, but as shown in FIGS. 11 and 13, further grounding means. It may be configured to be connected to 60 and grounded. This makes it possible to increase the safety.

As described above, according to the present embodiment, by providing the electric field adjusting electrode 35 and electrically connecting the electric field adjusting electrode 35 to the constant voltage device 51, the electrostatic spraying device 10 having high safety and easy management can be obtained. Can be provided.

Although the present invention has been described above based on the specific embodiment, the present invention is not limited to the above embodiment, and modifications and improvements may be carried out as appropriate.

For example, the liquid spray portion 20 is described as having a positive potential and the object to be coated 40 is described as having a negative potential through the above description, but the present invention is not limited thereto. Even if the liquid spray portion 20 has a negative potential and the object to be coated 40 has a positive potential, the same effect can be obtained. In this case, the electric field adjusting electrode 35 has a negative potential having the same polarity as the liquid spraying portion 20.
Further, the case where the liquid spray unit 20 is one is described through the above description, but the present invention is not limited to this. A plurality of liquid spraying units 20 are provided, and the same effect can be obtained even if the electric field adjusting electrodes 35 are arranged in the vicinity of the tips of the plurality of liquid spraying units 20. For example, the liquid spraying unit 20 may be arranged in a regular polygon, and the electric field adjusting electrode 35 may be arranged between the vicinity of the tips of the liquid spraying units 20.

As described above, the present invention is not limited to a specific embodiment, and those which have been appropriately modified or improved are also included in the technical scope of the present invention. It is clear from the description of the scope of claims.

10 Electrostatic spray device 20 Liquid spray part 21 Body part 21a Liquid supply port 21b Liquid flow path 21c Hole part 21d Rear end opening 21e Female screw structure 22 Nozzle 22a Tip outer peripheral edge 22b Opening 23 Mandrel 23a Picking part 23b Electrical wiring connection Part 23c Male screw structure 23d Tip surface 24 Seal member 25 Electrode holder 25a Electrode mounting part 30 Discharge electrode 30a Tip 31 Fixing screw 31a Screw hole 35 Electricity adjustment electrode 40 Different electrode part (object to be coated)
50 Voltage applying means 51 Constant voltage device 58 Equipotential curve 60 Grounding means 70 Electrode (different electrode)
71 Electrode holder 80 Tailor cone 82 Jet part 87 Atomized liquid

Claims (9)

The liquid is separated from the liquid spraying part in a charged state by the electrostatic force generated by applying a voltage between the liquid spraying part and the different pole part having a different pole with respect to the liquid spraying part, and atomization is performed. , An electrostatic spraying device by the electrospray method that sprays an atomized liquid onto an object to be coated, which is a different electrode.
Formed from a conductive material or a semi-conductive material, it is charged by applying a voltage between at least the liquid spray portion and the different electrode portion, and an electric field generated between the liquid spray portion and the different electrode portion is generated. Influencing electric field adjustment electrodes and
It has a voltage-current characteristic in which the current that flows rapidly increases when a voltage above a certain voltage is applied, and the potential of the electric field adjustment electrode is electrically connected between the electric field adjustment electrode and the object to be coated. An electrostatic spraying device characterized by comprising an element that keeps the voltage below a certain potential. The liquid is separated from the liquid spraying part in a charged state by the electrostatic force generated by applying a voltage between the liquid spraying part having a nozzle and the different electrode part having a different pole with respect to the liquid spraying part, and atomizing. It is an electrostatic spraying device by the electrospray method that sprays the atomized liquid onto the object to be coated, which is a different electrode.
A discharge electrode formed from a conductive material and
An electric field adjusting electrode formed of a conductive material or a semi-conductive material, which is charged by at least the discharge from the discharge electrode and affects the electric field generated between the liquid spray portion and the different electrode portion.
It has a voltage-current characteristic in which the current that flows rapidly increases when a voltage above a certain voltage is applied, and the potential of the electric field adjustment electrode is electrically connected between the electric field adjustment electrode and the object to be coated. An electrostatic spraying device characterized by comprising an element that keeps the voltage below a certain potential. The electrostatic spray device according to claim 2, wherein the discharge electrode is arranged near the outer periphery of the tip of the nozzle and has the same potential as the liquid spray portion. The electrostatic spray device according to any one of claims 1 to 3, wherein the element is grounded. The element is a varistor.
The electrostatic spray device according to any one of claims 1 to 4. With respect to the state of the equipotential curve on the plane including the central axis of the nozzle, which appears near the front side of the nozzle when the discharge electrode is not arranged, at least the equipotential curve of the discharge electrode. The electrostatic spray device according to claim 2 or 3, wherein a part of the electrostatic spray device has a shape having an equipotential curve that draws a gentler curve. The electrostatic spray device according to claim 2, claim 3 or claim 6, wherein the discharge electrode is attached to the liquid spray portion. The electrostatic spray device according to claim 2, claim 3, claim 6 or claim 7, wherein the discharge electrode can be repositioned along the nozzle. The electrostatic spraying device according to any one of claims 1 to 8, wherein the electric field adjusting electrode is attached to the liquid spraying portion.

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