US2951968A

US2951968A - Apparatus for removal of electrostatic charges from the surfaces of materials of lowconductivity by means of a stabilized electrical glow-discharge

Info

Publication number: US2951968A
Application number: US496853A
Authority: US
Inventors: Leupi Robert
Original assignee: Messen-Jaschin GA
Current assignee: Messen-Jaschin GA
Priority date: 1954-03-26
Filing date: 1955-03-25
Publication date: 1960-09-06
Anticipated expiration: 1977-09-06
Also published as: CH326862A; CH319039A

Description

2,951,968 CHARGES FROM THE Y MEANS Sept. 6, 1960 R. LEUPl APPARATUS FOR REMOVAL OF ELECTROSTATIC SURFACES OF MATERIALS 0F LOW CONDUCTIVITY E OF A STABILIZED ELECTRICAL GLOW-DISCHARGE Filed March 25, 1955 4 Sheets-Sheet 1 m m L E V u M t w M b I .3 W a, R 2 m a... F 4 4 l n #4 5/ 5 F \3 J 3 2 Q\v\\\\\\ 2,951,968 FROM THE SURFACES OF MATERIALS 0F LOW CONDUCTIVITY BY MEANS Sept. 6', 1960 R. LEUPl APPARATUS FOR REMOVAL OF ELECTROSTATIC CHARGES OF A STABILIZED ELECTRICAL GLOW-DISCHARGE Filed March 25, 1955- 4 Sheets-Sheet 2 FIG,6

IN VE N TOR ROBERT LEUP/ 5v V V Richards d 6616/ Attorneys -APPARATUS FOR REMOVAL Di ELECTROSTATIC CHARGES FROM THE Sept. 6, 1960 R LEU 2,951,968

SURFACES OF MATERIALS OF LOW CONDUCTIVITY BY MEANS OF A STABILIZED ELECTRICAL GLOW-DISCHARGE Filed Mafch 25, 1955 4 Sheets-Sheet s I Fig.8

Fig.9 I 18 INVENTOR ROBE T LEUP/ mu/A3 05 4 GE/LQ ATTORNEYS Sept. 6, 1960 R. LEUPl 2,951,968

APPARATUS FOR REMOVAL OF ELECTROSTATIC CHARGES FROM THE SURFACES OF MATERIALS 0F LQW CONDUCTIVITY BY MEANS OF A STABILIZED ELECTRICAL GLOWDISCHARGE Filed March 25, 1955 4 Sheets-Sheet 4 \INVENTOR:

ROBERT LEUPI'" B91 R/cH/MDS f 6.5/51? ATTORNE Y5 United States atent APPARATUS FOR REMOVAL OF ELECTROSTATIC CHARGES FROM THE SURFACES F MATE- -RIALS:OF LOW .CONDUCTIVITY 'BY MEANS OF A STABILIZED ELECTRICAL GLOW-DISCHARGE kobertiLeupL'zsarnen, Switzerlandassignorto G. A.

Messen-Jaschin, SarnenySwitzerland .Fil8d'M2l'.'2 5,1955,. Ser. No. 496,853

tfil'aimsipriority, .applicationSwitzerland Mar. 26,: 1954 '4 Claims. (Cl.3I5-57) 5.flf his,inve,ntionrelates toa device of the kindserving to remove electrostatic charges from the surface of ill-conduqtipgwmaterials. It is especiallysuited ,to discharge .,materials;.that.arepassing it in the form of ribbons and endless webs but it also permits to remove electrostatic r charges-from the-surfaces. of solid immovable or hardly icharged-amayrdeeply penetrate the space of discharge be- :tween: the; electrodes.

. Tfhejrnethodgperlse, is alreadywell .known andsuffiacientlyzproved.

Up=to':;nowh0wever, no"practioal design-of the elecut-rodesshasrbeenyfound that would have satisfiedin rpracnticexwitharespect to operation :and moreover ensured a imiflicientrrapiddischarge of the charged objects.

:Hitherto designs ofelectrodes have been proposed .and .;realized where the glowing electrode was equippedby rsharpipoints.andsurrounded by a tube of insulating material leaving :thepoints "free in corresponding openings. Thexinsulatingrt-ubehas the purpose of a PI'OtBCtiVCIdCViCG :against' accidental contact with the high tension :electrode rand: thezfine :points.

:Substantiallymore eifectivethan these electrodes with .=points.. areielectrodes having glowing .edges or wires, beaoause the :number :of glowing ions is necessarily..pro- .-portionedato:the.area.of the glowing surface. In-this kind rioiielectrodesrthesinsulating tube serves to receive at least aonetglowing'wire or. at least one metal foil that when conynecteduto a high-tension source glows at the outwardly r directed edge.

I-n-order to make the discharge of a ribbon running over these glowing portions most effective this ribbon should move along said tube or rod in a very little distance or even slide-over it. T his is disadvantageous in the case where the tension of the ribbon cannot be:kept sufficiently constantyto ensure a constant distance from the tube. Since due to friction of the ribbon on the tube of insulatiingmaterialanew charge will be generated on the ribbon.

It is'anobject of thepresent invention to avoid this disadvantage to a great extent partly by a greater discharging e'ifeot, generated by the approaching of acounter electrode-andpartly in that it is made possible for the field -to-penetnate deeply in the space of discharge of the stabilizing glow-discharge. This opens the possibility ofa substantialsimplification and economization of the design.

A 'furtherobject of the invention is to providea cylinfidrical body forming one-of the electrodes and serving .at the-same time as support for at least one metal wire in- -sul-ated-from 'the support and forming the second elec- -trddefthat extends parallel to the axis of the cylinder and'exterior'ly ofthe latter.

It has been found that 'not'only ansasymmetricahposi- ;tion' of the glowing wire but also an asymmetrical-position of its counter electrode inthe insulating body-may beof great importance.

.In the device according to thepresent invention there- 'fore' the cylindrical bodyisan insulating body enclosinng at least one cylindrical axially directed metallic body parallel ,to ,the insulating body and coated byit andfilling out aqsmaller portion of the section of the insulating body, the metallicbody being outwardly displaced with-respect to" the axisoftheinsulating body in the-direction to the glowingwire in such a-inanner, that only anarrowzone of the insulating bodyis-traversed by the field generating 'the glow discharge.

By this arrangement two substantial advantages are gained. On the one hand the capacity of-the electrode coated by the insulating body may be kept much lower without suffering any loss of field intensity nearthe glowingwire, and on theother hand in the case of highfrequency operation of the device, the high frequency thereof.

'In order to get a correct screening of the highfrequency field'emitting-from the inner .or the counter electrode respectively, the cylindrical body for screening thehigh frequency field may be surrounded by at least onenot glowing groundedmetalpart, which leaves the grounded glow wire generating ions free. Suitably the not glowing meta'l part-is not arranged nearer tothe glowwire than theglow wire-is distantfrom the cylinder, so that the field extending from the material to be discharged is able to penetrate deep-enough in the space of discharge between glow wire and counter electrode.

By way of-example specificembodiments of the present invention are represented in the accompanying .drawings.

"Figspl to 4 and 1a to 4a are axial-andcross-sections illustrating --four discharging :devices according to the invention.

Figs. "5 6 show variousarrangements of the high .frequency transformer in the device according to Figs. 14. Fig. 7 illustrates the simultaneous application of the high "frequency transformer as .a mechanicalsupport. for 'a' cantilever cylindrical electrode.

Figs.'8, 8a are axialand-cross-sections, respectively,

"of a first-example.

*-Figs..9--and 9a are axial-andcross-seotions of:a. second example.

Figs. 10 and 10a are axialand cross-section .of :a modification with respect to Figs. 2, 2a, respectively.

Figs. 11, 11a show in side View and section,:respective- 'ly,-a. further modification of the example according to -Figs.'-9, 9a.

Fig. -12 aside view ofa part of the first embodiment of the device.

. ignates-a;cylindrical metallic'hollow or solid body,-which at both of its'ends is provided with two metallic supports The latter are insulated from the body by meansof insulatingportions "3. The supports 2 serve for the .attachmen't of wires 4, which extend parallel with respect tO=th6- 3.XiS Of the .cylindrical body :1 and are-covered by a glow-layer as soon as sufiiciently high electrical voltage is present between the support'2 and the cylindrical metal body 1 by connecting these parts with a suitable source of voltage. The voltage can be led to the in axial direction, form a wire-electrode, which may be earthed. The electrode 1 carrying the voltage is then screened by an earthed wire-electrode, forming a cage and protecting that electrode from being contacted. The

, separate wires of the wire-electrode glow during operation despite being earthed, since the glow discharge is only dependent of the field erected above said wires and not of the absolute potential of the wires. Also in the case of the Saint Elmos fire, the luminous objects are connected to earth.

The spacing between two adjacent wires 4 should at least be equal to their distance from the cylindrical electrode 1 in order that the field of the body to be discharged will reach sufiiciently into the discharge space of the glow discharge and thereby will be fed with the ions necessary for discharge.

The wire cage-electrode provides an effective protection against touching since the field at the wires will be homogenised upon approach of a hand to the extent that it will no more be sufficient to keep up the glow discharge and no electrifying effects are experienced.

An effective protection of the voltage-carrying electrode can also be achieved with less wires in that according to Fig. 2 the cylindrical metallic body 1 is provided with an insulating layer 5 of good dielectric break-down properties or in that according to Fig. 3 the voltage-carrying electrode is arranged as a conductive layer 6 in a tube 7 of insulating material. In order to prevent flash-overs the ends of the insulating tube 7 can be provided with stoppers of insulating material which are glued into the tube to give a certain break-down safety to the assembly.

Another embodiment of the device is shown in Fig. 4. Here the voltage carrying electrode is formed by a metallic body 8 such as a metal tube, which is only supported by the tube covering portions 9 at both of its ends or insulators, inserted into this tube. Also in this case the tube covering portions may be glued in for break-down safety.

In order not to necessitate a high tension cable for feeding the high voltage, which would be unhandy, suitably high-frequency currents are used, which are transformed in a small Tesla-transformer it) to high voltage,

which transformer may suitably be attached to one end of the device. The coil body of the secondary coil of this Tesla-transformer may at the same time have the mechanical function of one of the insulation coils 3 or 9, respectively, in one of the embodiments according to Figs. 1, 2 or 4, as for instance shown in Figs. 5 and 7. When using a tube of insulating materials the Teslatransformer it is suitably mounted into this tube as shown in Figs. 6 and 7. This provides a certain protection for this transformer against damage and there will I be less danger of inadvertently touching said transformer.

In all cases where the wire electrode is connected to earth there will be no difliculties in insulating the feed ,tallic support 2 of the suspended wire may be fixed at the height of this winding at the tube as shown in Fig.

7 without charging the secondary winding with an additional capacity. In the same manner also the other support 2 may be fixed on the insulating tube 7 if the tube is extended correspondingly over the voltage carrying electrode at this point. This manner of attachment of the supports 2 has the advantage that the device may suitably be secured at both of its ends by means of brackets or that the tube ends serve at the same time as handles.

In the embodiment according to Figs. 8 and 8a a cylindrical insulating body 12 is provided, which is formed as a round bar. The insulating body 12' is provided with an eccentric longitudinal bore, in which a metallic rod 13 forming one of the electrodes is arranged. By means of end plates 14 two wires 15 diametrically and parallely extending with respect of the axis of the insulating body are suspended. The wire 15 being shown as situated above the other wire in these figures, serves as glow electrode.

In the embodiment according to Figs. 9, 9a the cylindrical insulating body is formed by a tube 16 in which a cylindrical rod-electrode 13 is eccentrically arranged with respect to the tube 16 but parallel to the axis of the latter by means of the holder 17. Otherwise the constiuction of the device is the same as in the first described embodiment.

in the modification according to the Figs. 10, 10a of the previously described embodiment, two cylindrical metallic electrodes 18 are diametrically arranged within 7 the tube 16, forming the insulating body and eccentrically with respect to the axis of the latter.

These two metallic electrodes 18 are electrically connected with each other.

In the modification shown in Figs. 11 and 11a the cylindrical insulating body is formed by a two-part tube 19, its two-parts being diametrically opposed to each other. Also in this case a cylindrical metal electrode 18 is eccentrically arranged within this tube. By means of the two-part configuration of the tube 19 longitudinal slots 20 are formed, which permit a further reduction of the high-frequency loss. Thereby the insulating body must naturally fill out a sufficiently large space between the metal electrode and the glow-wire, in order to stabilize the discharge in that space with respect to a spark or arc discharge. t will be understood that also in this case two metallic electrodes 18, corresponding to the modification according to Figs. 10 and 10a might be provided.

Similarly the insulating

bodies

12 and 16 ofthe embodiments according to Figs. 8 to 10 might be provided with longitudinal slots to reduce the high frequency losses. In all described embodiments the

cylindrical metal body

13 and 18, respectively, forming the inner electrode is eccentrically arranged with respect to the axis of the insulating body, and towards the corresponding glow wire 15, such that only a narrow zone of the cross-section of the insulating body will be situated between the metal electrode and the glow wire, which will be penetrated by the strong field generating the glow discharges. Further this

metal electrode

13 and 18, respectively, will fill out in all cases only a small portion of the total cross-section of the insulating body.

In order to minimise the glow-losses of the electrode built into the insulated body, these electrodes are given a circular or elliptic cross-section and are provided with ball-shaped end portions.

In Figs. 12 to 14, M. designates the cylindrical body, which in the embodiments shown, is formed as a tube.

7 Two holding rings 22 are seated on the tube 21 and are axially spaced from each other. Between these holding rings a glow-wire is extended distanced from the outer surface of the tube 2.1; and parallel with respect to the tube axis by means of screws 23.

In the embodiment according to Figs. 12 and 13 a second wire 24 is extended between the holding rings 22 parallel with respect to the tube axes and diametrically opposed to the first glow-wire. The tube 21 is constituted by an insulating body. In the same diameter as the wire i electrodes 24, one of which is formed as a glow-electrode,

a counter-electrode formed by a cylindrical metal rod 25 is arranged within the tube 21. The metal rod 25 is distanced from the tube axis and extends parallel thereto. At the rings 22 a screening cover 26 is secured, which surrounds a part of the insulating body 21 in trough-shaped configuration without obstructing thereby the upper glowelectrode 2 4. The distance of the cover 2 6 from the insulating body 21. must at least be equal to the distance of the glow-electrode 24 from the insulating body 21. In the embodiment shown the firstment-ioned distance is somewhat larger than the second-mentioned distance. The wires 24 and the cover 26 are connected to earth, while the counter electrode 25 carries voltage.

In most cases it will be sufiicient to give the remaining spacing 27 (Fig. 13) double the width of the distance between the glow-electrode 24 and the electrode 25 or the insulating body 21, respectively. Thereby the field emitted by the material to be discharged may penetrate sufliciently into the discharge space between the glow electrode 24 and the electrode 25 or the insulating body 21, respectively and it will thus be possible to collect the ions from this space necessary for the discharge of the material.

Tests have shown that in many cases a metallic protecting-cover will already by sufficient, the edge tangent surface of which will just contact the insulating body 21 if the glow electrode 24 connected to earth will extend in the middle of this spacing 27 as shown. In order to prevent glowing of the protecting cover the latter is crimped at its ends 28 with a sufiiciently large radius.

In the embodiment according to Figs. 14 and 15 a plurality of metallic wires 29, which are suspended in the same manner as the glow wire 24 between the holding rings 22 and with the same angular spacing with respect to each other or the glow wire 24, respectively, serve as a screen. The metallic wires 29 include a larger radial distance with respect to the tube axis than the glow wire 24- and further their cross-section is larger than that of the glow Wire. In this case the tube 21 is made of metal and forms the voltage carrying electrode 29.

It will be understood that also when using a counterelectrode 25 according to Figs. 12 and 13, eccentrically arranged in the insulating body, the screen may be formed by suspended wires 29.

In both embodiments shown, the plane of symmetry extending through the longitudinal axis of the device and through the glow wire 24 will be perpendicular to the plane of the material to be discharged.

The screen metal portion could also be formed by an other suitable apparatusor machine-pant.

I claim:

1. An apparatus for the removal of electrostatic charges from the surfaces of materials of low conductivity by means of a stabilized electrical glow-discharge comprising a metallic cylindrical body forming an elongated electrode, an insulating member at each end of said body, supporting means carried by each insulating member, and a metallic wire forming a second electrode extended between said supporting means at both ends of said cylindrical body in parallel relation to the axis thereof exteriorly of said cylindrical body forming the firstmentioned electrode, wherein a hi h-voltage transformer is mounted between one end of the cylindrical electrode and the adjacent supporting means, in order to generate the voltage required for operating the glow-electrode.

2. An apparatus as claimed in claim 1, in which the secondary of said high voltage transformer is wound on a coil body serving as support for said cylindrical metal body.

3. An apparatus for the removal of electrostatic charges from the surface of materials of low conductivity by means of a stabilized electrical glow-discharge comprising a metallic cylindrical body forming an elongated electrode, an insulating member at each end of said body, supporting means carried by each insulating member, and a metallic wire forming a second electrode extended between said supporting means at both ends of said cylindrical body in parallel relation to the axis thereof exteriorly of said cylindrical body forming the first-mentioned electrode, wherein a high voltage transformer generating the voltage required for operating the glow-electrode is built into one end portion of said cylindrical body formed of insulating material.

4. An apparatus as claimed in claim 3, in which the end of said hollow cylindrical body remote of said transformer is provided with a glued-in stopper for preventing electrical break-down.

References Cited in the file of this patent UNITED STATES PATENTS 414,356 Wirt Nov. 5, 1889 565,777 Moore Aug. 11, 1896 1,249,429 Lewis Dec. 11, 1917 1,260,750 Bryant Mar. 26, 1918 1,985,058 Rath Dec. 18, 1934 2,071,464 Henderson Feb. 23, 1937 2,228,276 Le Van Jan. 14, 1941 2,505,993 Rogers May 2, 1950 2,624,858 Greenlee Jan. 6, 1953 2,629,839 Greenlee Feb. 24, 1953 2,651,004 Acton Sept. 1, 1953 2,660,685 Johnson Nov. 24, 1953