JPH0380546B2 - - Google Patents

Description

[Detailed Description of the Invention] [Detailed Description of the Invention] The present invention provides a method for rapidly discharging devices without arcing when the capacitance connected to the impedance of the load circuit in a DC high voltage power supply exhibits an excessive value. This relates to a device in which two sets of electrodes, each connected to two poles of a power source, protrude from each other by means of a tripping means as they approach each other to the point where they are alternately connected. It is.

The present invention was developed in the field of so-called electrostatic spray painting, in which a powder spray material is sprayed onto a member to be painted, and the spray jet is applied at several tens of kilovolts. It is electrostatically charged up to.

For obvious safety reasons, the electrode charging this jet must complete its discharge after the sprayer has stopped, especially without arcing. The reason for this is that most sprayed materials are usually flammable and contain organic solvents.

There are various known processes for discharging power supplies that can be used. For example, a discharge caused by a “corona-like” glow discharge from a high-voltage electrode,
Examples include discharge due to a free short circuit between power supply terminals or through a leakage resistor permanently connected to the power supply.

The patent specification of FR-A-1137824 describes a coaxial cable that connects a high voltage power source of about 40KV to the electrode that charges the jet from the electrostatic spray gun.
A fuse cutout device for capacitance discharge is described. The safety circuit breaker has a pneumatic actuator with a piston adapted to actuate an axle to move it in a cylinder between two positions. In the initial position, one end of the rod rests in contact with the body. In the second position, the other end of the rod rests in thrust at the output terminal of the high voltage source. The cylinder, piston, rod, etc. is connected to the core web of the coaxial cable, which connects the charging electrode. The movement of the piston serves to control the operation of the gun so that the spray jet is charged and the capacitance of the cable is discharged to ground upon ceasing to spray. The cable's charge energy is approximately between 0.01 and 0.1 joules, but when it discharges, it emits a powerful spark and quickly dissipates.

In some cases, charging of the jet of atomized material is accomplished via a "corona-like" glow discharge produced by a charging electrode, in which case the electrode is needle-shaped. From a typical point of view, it has a needle with a length of 10 mm and an emission diameter of several tenths of a mm, and this diameter is 10 cm in the direction of the planar conductor that is the mass plan.
The potential difference between the needle and the plane is 60KV.
If , the current will be about 60μA, and this condition is 1G
This corresponds to the apparent resistance value of Ω. Even if the needle of the mass plan is gradually approached during the discharge operation, the apparent discharge resistance still shows the same value. Compared to a mass planar conductor separated by 10 cm, the needle's self-capacitance is about 1 pF, which determines the constant time on the order of milliseconds. This value can be said to be fully acceptable.

However, if the discharge capacitance exhibits a very high value, for example of the order of 100 pF, as in the device described in the FR-A-1137824 patent, the discharge time will consequently be longer. Furthermore, if the charged electrode does not produce a glow discharge due to the corona effect or before the electrostatic capacitance is discharged,
When the glow discharge stops occurring, the discharge time can reach several seconds, and such a situation is unacceptable. Further, as is well known, discharge due to a short circuit generates a powerful spark.

In this case, it is also possible to discharge high-voltage electrostatic capacitance without generating an arc by utilizing glow discharge caused by the corona effect. For example, as is known, US Pat. It is also known that it does not cause unpleasant shocks and does not generate sparks from overcurrents that can interfere with the operation of sophisticated and complex electrical equipment. The present invention originally consisted of a bellows-type insulating material including a pointed tip with a conductor contact connected to the top of the bellows, a plate on which an operator's finger rests, and a plate facing this and grounded through a resistor. It is equipped with the following. When the operator places his finger on the contact key, a corona glow discharge occurs at the tip, discharging the capacitance created by the operator's body. The deformation of the bellows moves to the tip of the tip and the glow discharge continues until the tip of the tip touches and the operator is completely discharged. The resistance value at which the chip plate is installed is selected so that sparks do not occur and the glow discharge loses its effectiveness.

An analysis of the mechanism of this device reveals that this device is not suitable for solving the troubles that arise from discharging the electrostatic capacitance of a high-voltage power supply without generating sparks.

In fact, it cannot be said that in the vicinity of the electrode tips, the electric field with a constant voltage is inversely proportional to the distance separating the tips on electrically opposing surfaces. A certain chip
In order to prevent electrostatic sputtering from becoming a glow discharge source due to corona operation under the voltage actually used, the stroke of the chip for capacitance discharge of the high voltage power source should have a prohibited length.

What should be noted is that there is no problem with the scope of application of rice patents. The reason for this is that when discharge is not a problem, the problem that must be added to the insulation between the electrode tip and the chip plate is the insulation between the operator's finger and the contact connected to the tip. Furthermore, in the embodiments contemplated in the US patent specification, it is said to be advantageous if the glow discharge appears immediately when the operator-to-ground voltage causes trouble.

Now, if we organize and look at the problems that have been described so far, we can summarize them as follows. The present invention relates to a device for rapidly discharging a high voltage source continuously without arcing, the capacitance of which exhibits an excessive capacitance value when connected to the impedance of the circuit in which it is used. In this device, two sets of electrodes are each connected to both poles of a power source, and are operated to protrude by a release device along the approach trajectory until they come into phase contact with each other, and are operated in a dielectric gas. The electrodes are in the shape of a dome that is concentrated on the orbital stroke, and one of the electrodes is provided with an erectile needle to facilitate the outward protrusion of the dome in the direction of at least the approaching actuation stroke, and the glow discharge is caused by the needle in the gas. The present invention relates to a device characterized in that it discharges a portion of the charge of an electrostatic capacitance to a noticeable extent before contact.

Since the shape of the electrodes is generally dome-shaped, this group of electrodes can be placed at a sufficiently small distance in the dielectric gas, and the process of bringing them together will not take place rapidly. , so much glow discharge does not scatter from the electrode in the gas, and the overhang of the upright needle also favors a sufficiently intense glow discharge emission during the approach operation. The power supply discharge time constant can therefore be kept sufficiently short. As warranted, the small distance between the prospective electrodes is highly effective and advantageous in confining these electrodes within the dielectric gas.

Preferably, the electrodes, each with a rigid needle, are in the form of a piston capable of sliding within an insulated cylinder and are provided with a conduit for pressurized gas;
Opening means communicate with the atmosphere and open into the center of the cylinder between the piston and the electrodes, and are adapted to hold the electrodes separated by gas pressure and the retraction needle that occurs when a link return device is used.

With this type of arrangement, the electrodes are held apart by the gas under pressure. Bursting discharges in the gas increase with pressure and can adequately separate electrodes under pressure even over relatively small distances. Aeration of the conduit conducting the gas under pressure not only assists in erecting the needle, directing the voltage between each other, but also reduces the gas pressure between the electrodes, which is favorable for producing a glow discharge. This is a major factor.

In addition, an auxiliary inner piston with a needle integrated into the piston-electrode is provided, on which a return action device operates, and a ventilation path is provided between the auxiliary piston and the piston-electrode to adjust the pressure between the piston/electrode and the auxiliary piston. In order to control the gas flow and their relative movement and to avoid accumulation of ions in the interelectrode space, it is advantageous to be able to cycle the gas under pressure.

The link return means may be a metal spring trapped between the end portions of the cylinder of the auxiliary piston, provided with a ventilation passage and a coupling passage to one pole of the power supply.
The return means (reversing device) can also be configured to open the space between the cylinder cover and the auxiliary piston under pressure using a four-way valve configuration opening device. Pressure fluctuations at the rear of the auxiliary piston ensure the protrusion and retraction movement of the needle.

The desired needle has auxiliary ends, one of which is a sharp corner and the other with a blind hole cut at an angle at the end. In this way, free contact can be obtained between the needles without deterioration of the terminal portions.

The apparatus shown in FIGS. 1 and 2 comprises a cylindrical body 1 made of insulating material, the ends of which constitute cylinder heads 10, 11. The inner surface 1a of the cylinder 1 is finely polished and has a ring groove 1c in its central part, through which an inclined conduit 1b leads, with which a source of pressurized air can be communicated.

Two sets of metal pistons 2 and 3 are built into the cylinder 1, and their respective front ends 2a and 3a have a ball-and-socket joint-like dome shape, and the diameter of their base is the same as the inner surface 1a of the cylinder 1. is smaller than the diameter of This kind of dome 2a, 3a is 2d,
The ring cages 16 and 17 are connected to the side surfaces of the pistons 2 and 3 by circular shoulders 3d, and the ring cages 16 and 17 fit into groove rings provided in the surface 1a near the cylinder heads 10 and 11. It constitutes the rear thrust bearing for the stroke.

Attached to the pistons 2 and 3 are reinforced metal pistons 4 and 5, respectively, which are coaxially jammed toward the rear by bearing retaining rings 4b, 5b provided inside their skirts.
The auxiliary pistons 4, 5 hold needles 6, 7 at the center of their front surfaces, and the needles are installed in conducting portions 2b, 3b provided in the shafts of the domes 2a, 3a. However, at the tips of the needles 6 and 7, the auxiliary pistons 4 and 5 are attached to the bearing retaining rings 4b and 5.
If the thrust is formed above b, dome 2
It is located recessed from a and 3a. metal spring 8
and 9 are provided between the cylinder heads 10, 11 and the rear faces of the auxiliary pistons 4, 5, respectively, and these spugs 8, 9 are in phase contact with the ends of the needles 6, 7, as shown in FIG. It shows a tendency to expand and loosen up to.

Spring 8 in contact with auxiliary pistons 4 and 5
and 9 are connected to passages 12 and 13, which conduct the heads 10, 11 and permit connection with a piston-electrode having both ends for a high-voltage power supply (not shown).

Ventilation passages 2c and 3c are provided through the pistons 2 and 3, and the dome portions 2a and 3a form electrodes, and 4a and 5a pass through the auxiliary pistons 4 and 5.
14 and 15 are cylinder heads 10 and 1, respectively.
It passes through 1.

If the passage 1b and the compressed air source are connected under a pressure of 3 to 6 bar, the air pressure will increase the cylinder 1 until the pistons 2, 3 are supported on the wheel gauges 16, 17.
Push it towards the heads 10 and 11. In addition, the ventilation passages 2c, 4a, 14 on one side, and 3c, 14 on the other side.
The air passing through the air passages 2c and 15 expands sequentially, and the pressure gradually rises from atmospheric pressure, passes through the air passages 14 and 15, and rises to the pressure within the central zone of the cylinder. 1
0,11 and the auxiliary pistons 4,5 and between the auxiliary pistons 4,5 and the piston-electrodes 2,3. In practice, the internal diameter of the air passage is adjusted so that the compressed air consumption does not become excessive. Thus, as long as the source pressure remains at the applied value in the middle of the cylinder 1, the piston 2
and 3 are not only pressurized to the ring gauges 16 and 17, but also the auxiliary pistons 4 and 5 are pressurized to the bearing retaining rings 4b and 5b, and the springs 8 and 9 are compressed. In this way, the air between the electrodes is sufficiently ventilated without using an excessive amount of air.

On the other hand, the tripping device introduces air into the passage, which extends towards the inclined tube 1b and the stress of the springs 8, 9 is applied behind the auxiliary pistons 4, 5, the piston-electrode 2, The relatively high pressure state in the gap between the domes 3 and the auxiliary pistons suddenly disappears, and air passes through the ventilation passages 2c, 3c and 4a, 5a, and the auxiliary pistons 4, 5 are pushed out in the direction of the domes 2a, 3a. , needles 6 and 7 will protrude from the front surface of the domes of 2a and 3a. The piston-electrode 2, 3 and auxiliary piston 4, 5 assembly is propelled from one side to the other under the extension of the springs 8, 9, this extension being added to the residual pressure in the cylinder head. The needles 7 and 8 will be in contact as shown in FIG.

Now that the mechanical operation has been described, the electrical mechanism will be described.

When the device is in the stage of FIG. 1, the pressure in the central zone is 3-6 bar, but the ring gauges 16
Piston/electrode 2, 3 on the thrust bearing on 7
When the needles 6 and 7 are retracted behind the front surfaces of the electrode domes 2a and 3a, even if a relatively high voltage is applied between the passages 12 and 13 and, as a result, between the electrodes 2 and 3, the Moreover, no current leakage occurs. This is because the dielectric strength has increased due to the pressurized air, and the shape of the radius of curvature of the electrode is rounded, which prevents the concentration of electrostatic field on the electrode surface and increases the degree of glow discharge. by. As is well known, in practice, the concentration of the electrostatic field in the vicinity of a protrusion exhibiting a very low radius of curvature causes free electron acceleration, resulting in a glow charge due to ionization.

If, on the other hand, the tripping device supplies air to a conduit, which leads to the central zone of the cylinder 1, the air pressure between the electrodes 2 and 3 is reduced on the one hand, and on the other hand the stiffening needle 6 and 7, the electric field is locally concentrated near the tip, and when a current is passed between the needles, a glow discharge of relatively high intensity occurs near the point where the needles operate. As is well known, the trip device only takes effect after the high voltage generator has been depleted. In this case, the current circulating in the needles 6, 7 is only caused when the capacitance of the high voltage electrode is discharged. As the pressure decreases,
The needles approach each other and the glow discharge continues until the needles touch and the voltage decreases successively.

The shapes of the rigid needles 6 and 7, as shown in FIG. 5, are designed to generate efficient glow discharge by reducing the radius of curvature of the terminal surfaces and avoiding caulking of the tips at the time of free contact. researched. As is well known, the needle 6 exhibits a small diameter cylindrical end 6a and terminates in an acute cone 6b. On the other hand, the needle 7 is a hollow cone 7a.
It ends at the same angle as the cone 6b at a point that is almost the top. In addition, it is connected to the cylinder surface of the needle 7 by a sharp edge or a diagonal cut edge of 7b. This hollow cone 7a is penetrated by a drill hole 7c, and its diameter is smaller than the diameter of the end portion 6a of the needle 6. When the needles 6 and 7 are in contact with each other, the end portion 6a of the needle 6 has a cavity. Penetrates inside the cone. And this contact penetrates the side surface 7a of the cone. Also, contact is made between the sides of the cones 6b and 7a. For this purpose, the tip of the needle 6 and the edge of the needle 7 are protected by mechanical staking.

FIG. 3 shows an electrostatic coating sprayer equipped with a supply regulating device 20a, commonly referred to as a ball, which rotates at high speed (on the order of several hundred revolutions per second). The atomizer 20 is charged to a voltage of several tens of kilovolts (typically 80 kv) by a high voltage power supply 30 connected to a low voltage supply by a connection 31. The ball 20a has an end that constitutes a charging electrode for the liquid to be atomized by centrifugal force.

The rapid discharge device 1 is mounted on a high-voltage power source 30 connected to the atomizer 20 by a connection port 12 via a discharge current limiting resistor 21. On the other hand, the connection 13 is connected to the cylinder head 30b of the high voltage power supply 30,
This cylinder head is grounded. The rapid discharge device is supplied with pressurized air using a conduit 1b, and a pneumatic turbine of the atomizer 20 is attached via a conduit 32.

It is understood here that rapid discharge devices and atomizers with rotary distributors can be combined well, and that the electrostatic capacitance is relatively low due to the dimensions of the high-voltage components as well as the dimensions of the materials directly connected to the high-voltage power source. can be considered high.

The modification shown in FIG. 4 is an example of an embodiment in which pneumatic pressure is used to project the electrodes from one side to the other and to separate the electrodes. Inside the cylinder 101 are provided two dome-shaped piston-electrode pairs 102, 103 with a kind of ball joint 102a, 103a. Here, the domes 102a, 103a are directly connected to the piston side walls of 102, 103,
Although this makes machining easier, this device has the inconvenience and risk that electrical discharge is likely to propagate onto the inner wall of the cylinder. Dome 102
Grooves 102b and 103b are provided in the axes of pistons a and 103a to serve as needles 106 and 107 mounted on auxiliary pistons 104 and 105, respectively.
The auxiliary pistons 104 and 105 have a ventilation passage 104.
a, 105a, while the pistons 102 and 103 have the same ventilation passages 102c, 105a.
You can see that 3c is open.

The retaining rings 104b and 105b are connected to the auxiliary piston 1.
04, 105, while rings 116, 117 serve to prevent movement of the piston-electrodes 102, 103. The cylinder heads 110, 111 are not provided with ventilation passages.

What you notice here is that needles 106 and 107
In this case, the end portions are configured as needles 6, 7 shown in FIG. Note that the auxiliary pistons 104 and 105 have flexible connecting parts 108 and 109.
It is connected to the conductor through terminals in the cylinder heads 110, 111 using the terminals 110 and 111, and connected to the edge of the discharge source.

The pressure gas conduit 101b is connected to the cylinder 101.
It opens into the central zone of the
39 open near the cylinder heads 110 and 111, respectively.

A four-way check valve 120 is installed for operation of this device, with the conducting portion 120a being connected to the atmosphere and the conducting portion 120b being connected to the atmosphere.
is connected to a pressure air source, and the conducting portion 120c is connected to the conduit 1.
01b, while the pipe 120d is also connected to conduits 138 and 139 at the same time. As shown in the figure, the conducting portion 120c is similarly connected to 120b, and the conducting portion 120d is connected to 120a by rotating short tubes. By turning 1/4, the short tube 121 becomes 12
0c could be connected to 120a and 120d to 120b.

The illustrated embodiment is adapted for use with high voltage power supplies, as desired. Air pressure is applied to the piston 10 supported on retaining rings 116, 117.
Introduced in the central area between 2,103 and 2,103. When the high voltage electrode has to be discharged, 121 briefly rotates 1/4 turn. The pressure is the piston group 102, 104, and 1
Add after 03,105. After these pistons are driven forward, the needles 106, 107 and the pistons 102, 103 are pushed out from each other. Needles 106 and 107 begin to make contact.

In addition, regarding high voltage installation,
Turn the short tube 121 1/4 turn again and connect the conduits 138 and 13.
9 and supply air under pressure to the conduit 101b, the piston-electrode 102,
The chamber between 103 and the auxiliary pistons 104 and 105 is
There will be an overpressure condition compared to the ends of the cylinder 101, and the auxiliary pistons 104, 105 will be forced onto the retaining rings 104b, 105b, while the pistons 102, 103 will be forced out of the cylinder by the pressure applied to the center of the cylinder. Head 11
It will be pushed out again towards 0,111.

As is well known, a ring groove in the inner surface of the cylinder 101 can be suitably arranged at the opening of the 101b conduit to cut off leakage on this inner surface. Also, if you are an expert in that field, conduit 101
Of course, it is possible to avoid uncontrolled current loss by considering the linearity and properties of B, 138, and 139 and appropriately designing a leakage line for high voltage. Also, in implementing the cylinder design, by choosing an insulating material with a resistivity lower than the best known insulating material, a false charge was applied in the surface reaction area, and the surface reaction during the precursor to the generalized discharge phenomenon was also applied. The occurrence of sparkling micro-discharges may be avoided.

Furthermore, as is well known, the description of the present invention is not limited to the above-described embodiments. In particular, either the piston or the electrodes 2, 103, 3, 103 could be replaced with a dome-shaped fixed electrode. Preferably, this fixed electrode is equipped with a durable needle. If an electrode is fixed, opening 1 of the central conduit
It goes without saying that electrodes b and 101b should be attached near the fixed electrode.

[Brief explanation of drawings]

FIG. 1 shows an axial sectional view of the device according to the invention depending on the desired position, FIG. 2 shows a diagram of the device of FIG. 1 under short-circuit conditions, and FIG. FIG. 4 shows a perspective view of a rotating ball nebulizer, FIG. 4 shows a sectional view of a variant of this device, and FIG. 5 shows an embodiment of an erectile needle. 1: Cylindrical body, 1a: Cylinder inner surface, 2, 3: Piston-electrode portion, 2a, 3a: Opposite end dome portion, 1
c: Ring groove, 1b: Conduit, 2b, 3b: Suction port, 2c, 3c: Air passage, 2d, 3d: Circular shoulder, 4, 5: Auxiliary metal piston, 4b, 5b: Bearing retaining ring, 4a, 5a : Ventilation passage, 6, 7: Needle, 6a: Reduced diameter cylinder end, 6b: Acute cone end, 7a: Cavity cone, 7c: Drill hole, 7
b: Acute corner, 8, 9: Metal spring, 10, 1
1: Cylinder head, 12, 13: Connection piping,
14, 15: Ventilation path, 16, 17: Wheel gauge, 2
0: Sprayer, 20a: Supply adjustment device, 21: Resistor, 12, 31, 13: Connection, 30: High voltage power supply,
30b: cylinder head (110, 111),
32, 1b: conduit, 101: cylinder, 10
2,103: Piston-electrode part, 102a, 10
3a: Ball joint, 102b, 103b: Suction port, 1
02c, 103c: Ventilation path (104a, 105
a, 120a, 120c, 120d), 104,
105: Auxiliary piston, 104b, 105b: Retaining ring (116, 117), 106, 107: Rising needle, 101a: Cylinder inner surface, 101
b, 138, 139: Conduit, 108, 109: Flexible connection, 120: Tripping device (check valve), 12
0b: Pressurized gas source, 121: Short tube.

Claims (1)

[Scope of Claims] 1. In a rapid discharge device without arc generation when the capacitance of a DC high-voltage power supply connected to a circuit in use exhibits an excessive value, two sets of electrodes 2, each connected to both poles of the power supply, are provided. At least one of the electrodes 3 is pushed out to the other through a relatively close path until they come into contact with each other by the open trip device 120, and the electrode of this type has a dome shape having its center on its orbital path in the dielectric gas. 2a, 3a,
102a, 103a, and the erectile needles 6, 7, 1 have a shape in which at least one of the electrodes protrudes outward from the dome along the direction of the orbit when performing an approach operation.
06,107, and characterized in that a kind of glow discharge is emitted from this needle into the gas, so that a considerable part of the charge of the capacitance is discharged before contact. 2. The pistons 2, 3, 102, 103 are configured to slide within the insulating cylinders 1, 101, with one protruding needle on each electrode, and the pressure gas conduits 1b, 101b connect the pistons to the electrodes 2, 101.
A tripping means opened at the center of the cylinder between 3, 102, and 103 is provided with air, and the gas pressure maintains the separated electrodes while operating the needle to retract when a return action is applied. An apparatus as claimed in claim 1. 3 Piston - auxiliary piston inside the electrode - 4,
5, 104, 105 are provided with integrated needles, on which the return device acts, and the ventilation passages 4a, 5a, 104a, 105a are inserted into the auxiliary piston, and further ventilation passages 2c, 3 are provided.
c, 102c, 103c are provided in the piston-electrode, and the piston-electrode 2, 3, 102, 10
3. The device according to claim 2, characterized in that the pressure between the auxiliary piston 3 and the auxiliary piston 4, 5, 104, 105 can be adjusted and their relative displacements possible. 4. The link return device is a metal spring 8,9 clamped between the auxiliary pistons 4,5 and the end portions 10,11 of the cylinder 1, the end of which is provided with a set of ventilation passages 14,15. connecting passage 12 between the power supply pole and the corresponding spring;
4. The device according to claim 3, characterized in that the device is electrically connected by 13. 5. The cylinder 101 is provided with conduits 108, 109 that are open in the terminal area, and the tripping device 120
is expected to be connected to a source of gas under pressure 120b, and the vent passage 101b is closed to the central zone, further vent passages 138, 139 are open to the atmosphere 120a at the termination zone, and a trip operation is performed. 4. The apparatus of claim 3, wherein the air passages 138, 139 are connected to a source of gas under pressure 120b, while the air passage 101b opening into the central zone is under atmospheric conditions 120a. 6. Any one of claims 2 to 5, characterized in that the electrode domes 2a, 3a having a diameter smaller than the inner diameter of the cylinder 1 are connected to the piston-electrode by circular shoulders 2d, 3d. The device described in Crab. 7. Claim characterized in that the needle has auxiliary ends 6a, 7a, one of which 6a has the shape of an acute cone, while the other end is provided with a hollow cone 7a terminating in a terminal acute part 7b The device according to any one of items 2 to 6 of the range. 8 The ring groove 1c is located on the inner surface 1a of the cylinder 1.
8. The device according to any one of claims 2 to 7, characterized in that the device is installed in a pressurized air conduit 1b and is open to a pressure air conduit 1b.