EP0135424A1 - Vorrichtung zur schnellen Entladung, ohne Lichtbogen, der Kapazität einer Hochspannungsquelle - Google Patents

Vorrichtung zur schnellen Entladung, ohne Lichtbogen, der Kapazität einer Hochspannungsquelle Download PDF

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Publication number
EP0135424A1
EP0135424A1 EP84401611A EP84401611A EP0135424A1 EP 0135424 A1 EP0135424 A1 EP 0135424A1 EP 84401611 A EP84401611 A EP 84401611A EP 84401611 A EP84401611 A EP 84401611A EP 0135424 A1 EP0135424 A1 EP 0135424A1
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EP
European Patent Office
Prior art keywords
electrodes
cylinder
piston
pistons
gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP84401611A
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English (en)
French (fr)
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EP0135424B1 (de
Inventor
Laurent Faure
Roger Tholome
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sames SA
Original Assignee
Sames SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sames SA filed Critical Sames SA
Publication of EP0135424A1 publication Critical patent/EP0135424A1/de
Application granted granted Critical
Publication of EP0135424B1 publication Critical patent/EP0135424B1/de
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/02—Details
    • H01H33/04—Means for extinguishing or preventing arc between current-carrying parts
    • H01H33/045—Means for extinguishing or preventing arc between current-carrying parts for arcs formed during closing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • B05B5/10—Arrangements for supplying power, e.g. charging power
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/02—Details
    • H01H33/28—Power arrangements internal to the switch for operating the driving mechanism
    • H01H33/30—Power arrangements internal to the switch for operating the driving mechanism using fluid actuator
    • H01H33/32—Power arrangements internal to the switch for operating the driving mechanism using fluid actuator pneumatic

Definitions

  • the invention relates to a device for the rapid discharge, without an arc, of a direct high voltage source, the capacitance of which, coupled with the impedance of a use circuit, has an excessive value, device where two electrodes, connected respectively to the two poles of the source, are projected towards each other by a triggering means following a path of approximation until coming into contact.
  • the present invention has emerged in the context of electrostatic spraying, where a jet of sprayed material is projected towards a part to be covered, the jet being electrostatically charged at a few tens of kilovolts.
  • the electrodes that charge the jet must be discharged after the sprayer has stopped, without an arc blowing, since the sprayed material is quite generally flammable, containing organic solvents.
  • Patent document FR-A-1,137,824 describes a circuit-breaker device for the short-circuit discharge of the capacity of a coaxial cable connecting a high voltage source of around 40 kV to the electrode of charge of the jet of an electrostatic spray gun.
  • the circuit breaker has a pneumatic control with a piston which moves, driving an axial rod, in a cylinder between two positions. In a first position one end of the rod is in abutment on a ground contact; in the second position the other end of the rod is in abutment on an output terminal of the high voltage source.
  • the cylinder, piston and rod are connected to the core of the coaxial cable for connection to the charging electrode.
  • the operation of the piston is slaved to the control of the gun so that the spray is loaded, and that the capacity of the cable is discharged to earth when the spraying is stopped.
  • the charge energy of the cable which is between approximately 0.01 and 0.1 joule, is suddenly dissipated, on discharge, in an energy spark.
  • the charge of the spray of sprayed material is done by means of "corona" emanations emitted by charging electrodes which have the shape of needles.
  • a needle 10 mm in length, and a few tenths of a millimeter in diameter emits, towards a plane conductor (ground plane) 10 cm apart, a current of approximately 60 p A when the potential difference between needle and plane is 60 kV. This corresponds to an apparent resistance of 1 GJL.
  • the apparent discharge resistance remains of the same order of magnitude.
  • the needle's own capacity with respect to the ground conductor plane at 10 cm is approximately 1 pf, which would determine a time constant of the order of a millisecond; it would be very acceptable.
  • the discharge time increases accordingly.
  • the charging electrode does not produce a corona effluvium, or ceases to produce it before the capacity is discharged, the discharging time can reach several seconds, which is unacceptable. And we have seen that the discharge by a short short circuit causes an energetic spark.
  • the device essentially comprises in an insulating body in bellows, a tapered point connected to a conductive button at the top of the bellows, for the support of the operator's finger, and opposite a plate connected to ground by a resistance.
  • a corona effluvium occurs at the end of the tapered tip, and discharges the capacity formed by the operator's body.
  • the deformation of the bellows brings the tip of the wafer closer, so that the emanation is maintained until the operator has fully discharged, with the tip touching the wafer.
  • the resistance which connects the wafer to ground is determined to prevent the scent from degenerating into a spark.
  • the electric field, at a given voltage is not inversely proportional to the distance which separates the point from an electrically antagonistic surface.
  • a tip In order for a tip not to be a source of corona fragrance at the voltages currently used in electrostatic spraying, it would be necessary for the stroke of this tip for discharging the high voltage source capacity to be prohibitively long.
  • the invention proposes a device for the rapid discharge, without arc, of a direct high voltage source, the capacity of which, coupled with the impedance of a circuit d excessive value, device where two electrodes connected respectively at the two poles of the source, are projected towards each other by a triggering means following a path of approach until coming into contact, characterized in that the electrodes in a dielectric gas are in the form of centered domes on the trajectory, at least one of them being equipped with an erectile needle adapted to protrude out of the dome in the direction of the trajectory during the approach, so that a scent springs from the needle in the gas and discharges a substantial part of the capacity charge, before contact.
  • the general domed shape of the electrodes makes it possible to arrange them, in the dielectric gas, at a sufficiently small distance so that the trajectory to contact is traversed quickly without, however, emanations emanating from the electrodes in the gas, the protrusion of the erectile needle promotes, during the approximation, the emission of scent with sufficient intensity.
  • the source discharge time constant can thus be short enough.
  • the reduction in the distance between electrodes on standby, authorized by their shape, is favorable to efficient confinement of these electrodes in the dielectric gas.
  • the electrodes are produced in the form of pistons capable of sliding in an insulating cylinder, a pipe of pressurized gas, which the triggering means releases into the atmosphere, opening into the middle zone. of the cylinder between the piston electrodes, so that the gas pressure keeps the electrodes apart and their needles retracted against return means.
  • the electrodes are kept apart by the gas under pressure.
  • the disruptive field in the gas increasing with the pressure, one obtains a suitable insulation of the electrodes under tension in spite of a relatively small variation.
  • the venting of the pipeline which brings the gas under pressure not only causes the needles to be erected and the electrodes to be thrown towards each other, but also causes the pressure of the gas to drop between the electrodes, this which is in favor of the emission of effluveso
  • the piston-electrodes are equipped with auxiliary internal pistons integral with the needles, on which the return means act, vents being formed in the auxiliary pistons and piston-electrodes for adjusting the pressure between piston-electrodes and auxiliaries, and their relative displacements, and to allow the circulation of gas under pressure in order to avoid the accumulation of ions in the space between the electrodes.
  • the return means may be metal springs compressed between the auxiliary pistons and end cylinders, pierced with a vent and traversed by a connection connecting to a pole of the source. They can also be formed by pressurizing the spaces between cylinder bottoms and auxiliary pistons, by means of a triggering device constituted by a four-way valve. Pressure variations at the rear of the auxiliary pistons protrude and retract the needles.
  • the needles have complementary ends, one being a tapered point, while the other has a blind hole with an end bevel.
  • the device comprises a cylindrical body 1 made of insulating material, provided at its two ends with bottoms 10 and 11.
  • the inner surface 1a of the cylinder 1 is precisely bored and has in its middle part a groove where the oblique channel 1b opens out, which can be connected to a source of under pressure.
  • cylinder 1 In the cylinder 1 are mounted two metal pistons 2 and 3, the facing ends of which respectively 2a and 3a are in the form of a dome in a spherical cap, with a base diameter less than that of the surface 1a of the cylinder 1. These domes 2a, 3a are connected to the lateral surface of the pistons 2, 3, by rounded shoulders 2d, 3d. O-rings 16, 17, engaged in grooves made in the surface 1a near the bottoms 10, 11, form rear stop for the stroke of the pistons 2, 3.
  • auxiliary pistons respectively 4, 5 coaxial and stopped in the rearward race by rings 4b, 5b housed in the interior of the piston skirts2, 3.
  • the auxiliary pistons 4, 5 carry, in the center of their front face, needles 6, 7 which are engaged in wells 2b, 3b formed in the axis of the domes 2a, 3a, the tip of these needles 6, 7 being however set back from the domes 2a, 3a when the auxiliary pistons 4, 5 are in rear stop on the stop rings 4b, 5b.
  • Metal springs 8, 9 are arranged between the bottoms 10, 11 and the rear face of the auxiliary pistons 4, 5 respectively, these springs 8, 9 being capable of relaxing until bringing the ends of the needles 6, 7 into contact, as shown in figure 2.
  • Vents 2c, 3c were made through the pistons 2, 3, whose domes 2a, 3a form electrodes, 4a, 5a, through the auxiliary pistons 4, 5, and 14, 15 through the bottoms 10, 11, respectively.
  • the triggering device releases the pipe which supplies the central zone of the cylinder 1 to the atmosphere, on the one hand the air pressure between the electrodes 2 and 3 decreases, on the other hand the erect needles 6 and 7 protrude, so that the electric field is concentrated locally in the vicinity of their tips; a relatively intense scent arises in the vicinity of the points of needles with passage of a current between them.
  • the triggering device only comes into action after the power supply to the HV generator has been cut off, so that the current flowing between the needles 6, 7 comes solely from the discharge of the capacity of the high voltage electrode. As the pressure decreases, the needles get closer, and the smell remains until the needles come into contact, the tension gradually decreasing.
  • the shape of the erectile needles 6 and 7, according to the representation of FIG. 5, has been studied to allow the effective emission of effluvium, by reducing the radii of curvature of the terminal surfaces, while avoiding the matting of the tips during contact franc.
  • the needle 6 has a cylindrical end portion 6a of reduced diameter, terminated by an acute cone 6b.
  • the needle 7 ends in a hollow cone 7a, of the same angle at the apex substantially as the cone & b, and connecting to the cylindrical surface of needle 7 by a bevel or tapered edge 7b.
  • This cone hollow 7a is extended by a drill bit 7c, of diameter less than the diameter of the terminal part 6a of the needle 6.
  • FIG. 3 represents a sprayer 20 for electrostatic painting, equipped with a distributor member 20a rotating at high speed (a few hundred revolutions a second), commonly called a bowl.
  • This sprayer 20 is brought to a high voltage of a few tens of kilovolts (typically 80 kV) by the high voltage source 30 supplied with low voltage by the connection 31 and has an edge which constitutes a charging electrode for a liquid sprayed by force. centrifugal.
  • a rapid discharge device 1 is mounted on the high voltage source 30, with a connection 12 connected to the sprayer 20 through the resistor 21 for limiting the discharge current, while the connection 13 is connected to the cylinder head 30b of the high source tension 30, cylinder head which is grounded.
  • the rapid discharge device is supplied with pressurized air through line 1b and the pneumatic turbine of the sprayer 20 through line 32.
  • the rapid discharge device is well associated with a sprayer with a rotating distribution member, which has a relatively high capacity, due to the dimensions of the parts brought to high voltage and directly connected to the high voltage source.
  • the variant shown in Figure 4 uses air pressure to project the electrodes towards each other as well as to separate them.
  • the cylinder 101 are arranged two piston electrodes 102, 103 with a dome in a spherical cap 102a, 103a.
  • the domes 102a, 103a are connected directly to the side wall of the pistons 102, 103, which facilitates machining but has the disadvantage that the device is more sensitive to the risk of discharges which creep on the internal wall of the cylinder.
  • 103a are made wells 102b, 103b for erectile needles 106, 107 mounted on auxiliary pistons 104, 105.
  • the auxiliary pistons 104, 105 are pierced with vents 104a, 105a, while the pistons 102, 103 are pierced with vents 102c. and 103c.
  • Rods 104b, 105b limit rearward movement of the auxiliary pistons 104, 105, while rods 116, 117 limit the movement of the piston electrodes 102, 103.
  • the cylinder bottoms 110, 111 do not have vents .
  • the needles 106, 107 have their ends formed like the needles 6, 7, according to the representation in FIG. 5. Furthermore, the auxiliary pistons 104, 105 are connected by flexible connections 108, 109 to current crossings in the bottoms 110, 111, for the connection to the terminals of the source to be discharged.
  • a pipe for pressurized gas 101b opens into the central region of the cylinder 101, and two pipes 138, 139 open in the vicinity of the bottoms 110, 111 respectively.
  • a four-way reversing valve 120 is arranged to operate the device.
  • a path 120a leads to the atmosphere, a path 120b is connected to a pressurized air source, a path 120e feeds the pipe 101b, while the path 120d jointly feeds the pipes 138 and 139.
  • a rotating bushel connects, in the arrangement shown, track 120c to track 120b, and track 120d to track 120a, By quarter-turn rotation, the plug 121 connect track 120c to track 120a, and track 120d to track 120b .
  • the arrangement shown corresponds to waiting, the high voltage source being in service.
  • the air pressure is applied in the middle zone between the pistons 102 and 103 supported on the stop rods 116, 117.
  • the plug 121 turns a quarter of a turn.
  • Pressure is applied to the rear of the groups of pistons 102, 104 and 103, 105. These are pushed forward and protrude the needles 106, 107, and the pistons 102 and 103 are pushed towards each other. The needles 106, 107 come into contact.
  • the plug 121 when thereafter, for the re-establishment of the high voltage, the plug 121 will again turn a quarter of a turn, venting the pipes 108 and 109, and under pressure the pipe 101b, the chambers between piston electrodes 102, 103 and auxiliary pistons 104, 105 will be in overpressure relative to the ends of cylinder 101, and the auxiliary pistons 104, 105 will be pushed on the stop rings 104b, 105b, while the pistons 102, 103 are pushed back towards the cylinder bottoms 110, 111 by the pressure applied to the central region of the cylinder.
  • one of the piston electrodes 2, 102 or 3, 103 could be replaced by a fixed dome-shaped electrode, this fixed electrode preferably being equipped with an erectile needle. It goes without saying that, if an electrode is fixed, the outlet of the central channel 1b, 101b would be disposed near the fixed electrode.

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  • Electrostatic Spraying Apparatus (AREA)
EP19840401611 1983-08-18 1984-08-01 Vorrichtung zur schnellen Entladung, ohne Lichtbogen, der Kapazität einer Hochspannungsquelle Expired EP0135424B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8313462A FR2550882B1 (fr) 1983-08-18 1983-08-18 Dispositif de decharge rapide, sans arc, de la capacite d'une source haute tension
FR8313462 1983-08-18

Publications (2)

Publication Number Publication Date
EP0135424A1 true EP0135424A1 (de) 1985-03-27
EP0135424B1 EP0135424B1 (de) 1987-03-04

Family

ID=9291697

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19840401611 Expired EP0135424B1 (de) 1983-08-18 1984-08-01 Vorrichtung zur schnellen Entladung, ohne Lichtbogen, der Kapazität einer Hochspannungsquelle

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Country Link
EP (1) EP0135424B1 (de)
JP (1) JPS6075349A (de)
DE (1) DE3462441D1 (de)
FR (1) FR2550882B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2587919A1 (fr) * 1985-10-02 1987-04-03 Sames Sa Appareil de projection electrostatique protege contre l'apparition d'arcs electriques

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1137824A (fr) * 1954-10-04 1957-06-04 Gen Motors Corp Perfectionnements aux installations de revêtement par pulvérisation électrostatique
FR2274155A1 (fr) * 1974-06-07 1976-01-02 Comp Generale Electricite Dispositif de securite pour condensateur
US3935508A (en) * 1974-08-05 1976-01-27 Burroughs Corporation High voltage discharge switch for protecting sensitive electronic equipment and the operators thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1137824A (fr) * 1954-10-04 1957-06-04 Gen Motors Corp Perfectionnements aux installations de revêtement par pulvérisation électrostatique
FR2274155A1 (fr) * 1974-06-07 1976-01-02 Comp Generale Electricite Dispositif de securite pour condensateur
US3935508A (en) * 1974-08-05 1976-01-27 Burroughs Corporation High voltage discharge switch for protecting sensitive electronic equipment and the operators thereof

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2587919A1 (fr) * 1985-10-02 1987-04-03 Sames Sa Appareil de projection electrostatique protege contre l'apparition d'arcs electriques
EP0219409A1 (de) * 1985-10-02 1987-04-22 Sames S.A. Elektrostatisches Spritzgerät mit Vorrichtung zum Verhindern von Lichtbogen
US4737887A (en) * 1985-10-02 1988-04-12 Sames S.A. Electrostatic spray device provided with electric-arc protection means

Also Published As

Publication number Publication date
FR2550882A1 (fr) 1985-02-22
JPS6075349A (ja) 1985-04-27
JPH0380546B2 (de) 1991-12-25
DE3462441D1 (en) 1987-04-09
FR2550882B1 (fr) 1985-11-29
EP0135424B1 (de) 1987-03-04

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