US3790854A - Apparatus for removing static charge from webs of material - Google Patents

Apparatus for removing static charge from webs of material Download PDF

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Publication number
US3790854A
US3790854A US00178313A US3790854DA US3790854A US 3790854 A US3790854 A US 3790854A US 00178313 A US00178313 A US 00178313A US 3790854D A US3790854D A US 3790854DA US 3790854 A US3790854 A US 3790854A
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United States
Prior art keywords
web
wire means
wire
wires
rolls
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Expired - Lifetime
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US00178313A
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English (en)
Inventor
K Dryczynski
H Kramer
D Messner
W Seifried
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Kalle GmbH and Co KG
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Kalle GmbH and Co KG
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Priority claimed from DE19702044828 external-priority patent/DE2044828C/de
Application filed by Kalle GmbH and Co KG filed Critical Kalle GmbH and Co KG
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05F—STATIC ELECTRICITY; NATURALLY-OCCURRING ELECTRICITY
    • H05F3/00—Carrying-off electrostatic charges
    • H05F3/04—Carrying-off electrostatic charges by means of spark gaps or other discharge devices

Definitions

  • radioactive charge eliminators involving the ionization of the air by means of a radioactive isotope, and preferably, by means of an a-ray producer (e.g. polonium 210).
  • X-rays of suitable wave length or other ionizing rays can be used for ionization of the air. If these charge eliminators are to be sufficiently effective, the intensities of the rays must be relatively high. In the practical use of apparatus of this kind it is therefore essential to provide and maintain expensive means affording protection against radiation. At the industrial level however, such means frequently prevent or interfere with the production cycle and the processing operation.
  • a further disadvantage arising in the use of the above-mentioned rays is the fact that, as a consequence of their high intensity, they cannot be used on all materials since they may cause changes in the material.
  • point ionizing apparatuses Also known for the removal of electrostatic charge are point ionizing apparatuses. When these are placed opposite a charged surface, they develop so great an electrical field strength at the gounded points that discharge occurs. A characteristic feature of these point ionizers is that before they become effective they require a certain minimum charge. Relatively small static charges are therefore not removed by such apparatus.
  • active ionizers In addition to the passive point ionizers, active ionizers, operating on high voltage, are frequently used. Here, an A.C. voltage is applied between the points of the high-voltage ionizer and ground. This causes a corona discharge to occur at the points, whereby the air is in turn ionized and the charge is removed from the affected surfaces.
  • the problem has thus arisen of providing a method whereby an even and satisfactory discharge of webs of material can be achieved in a technically simple manner without however affecting the chemical and/or physical properties of the treated object.
  • the present invention provides a method of discharging a statically charged web of material, wherein the web is uniformly discharged to the extent of at least 99 per cent of the original charge by bombardment, over the entire width of the web, under conditions having no deleterious effect on the material, with charge carriers as herein defined which are produced by a highfrequency A.C. voltage of between 1 and 1,000 kilocycles per second and having a current intensity of between a few 1. amp./cm of web width and several hundred p. amp/cm of web width.
  • charge carriers is to be understood to mean gas ions and electrons.
  • the current intensity and/or the distance between the web of material and the location from which the charge carriers emanate must be so adjusted that for each unit of area at least that number of charge carriers are produced with a polarity opposite to that of the charge on the web as is necessary for discharging to the required extent.
  • the method of the invention it is possible to discharge to the required extent webs of material that may carry a charge of up to the limiting field strength (approximately in the range of 1,000 to 2,000 kV/m). In many cases, residual field strengths of l per cent and less no longer have a critical effect and thus can be ignored. If, however, it is required to remove them completely, the method is preferably carried out several times in succession, in which case, as will be described later, various forms of apparatus can be used.
  • Frequencies of from 5 to 50 kilocycles per second are preferably used, and depending upon the way in which the method is applied, the frequency selected must in some cases be such that it does not occur as an interference frequency.
  • the charge carriers are preferably produced with current intensities of between rt-amp. and 100 [L amp/cm of web width.
  • Another of the method resides in producing the charge carriers not in air, as is customary, but in other readily ionizable gases. In some cases the gas also may be heated.
  • the invention also provides apparatus for performing the method.
  • the apparatus includes at least one wire having a thickness of less than 100 pand preferably 5 to 50 p. or system of such wires, which wire or wire system is dimensioned to extend over the entire widthof the web and arranged to be supplied with AC. under the conditions set forth above.
  • a preferably adjustable A.C. generator is connected to the wire or wire system and the counter electrode is preferably grounded.
  • the apparatus described may be repeated in series, a preferred arrangement being one in which the apparatus is fitted on both sides of the web.
  • a wire system may include a plurality of wires arranged alongside and preferably parallel with one another, and/or located in different planes and offset from one another. An arrangement of this kind has .proved successful especially in the case of webs of material that. are moved particularly rapidly.
  • Another wire system may include a meandering disposition of the wires.
  • the very thin wires used in'the apparatus of the invention are very heavily loaded when current passes through them, it may be advantageous in the case of certain wire materials and large widths of web to mount the wire or wires in insulating support elements to prevent sagging and thus lack of uniformity in the wire arrangement in relation to the plane of the web.
  • the wires are placed in protective elements which on the one hand are intended to prevent damage to the wires when, for example, a web tears, and on the other hand influence the flow of the charge carriers, i.e., the corona characteristic, to some extent, as a result of the way in which they are arranged in relation to the wires and depending upon whether the material used is conducting or non-conducting.
  • the protective elements consist of a base plate containing a number of channels corresponding to the number of wires.
  • the channels may be of particular crosssectional form, rectangular or semi-circular channels being preferred since these are easy to produce.
  • the wires In the case of rectangular cross-sections, it has been found expedient so to arrange the wires so they are spaced by a distance of 5 to 10 mm, and preferably 6 to 8 mm from the side walls, and 10 to 25 mm, and preferably 15 to 20 mm, from the floor of the channels. In the case of semi-circular cross-sections, the distance between the wires and the floor of the channels is preferably up to 25 percent less than that separating them from the side walls of the channels.
  • a dielectric is fitted between the wires and the counter electrode so that depending upon material and thickness, the dielectric, for example in the form of thin films of synthetic material, enables the corona emission to be varied in a predetermined manner.
  • a conducting or non-conducting relatively wide-meshed protective grid may be fitted between the wires and the web, and the corona emission likewise may be influenced by this grid, where necessary by imparting an appropriate profile to it and by using particular materials of construction.
  • means for generating the hot gases in the zone between the web and the wires This may be achieved for example by means of heat radiators or hot-gas producers through which the hot gases can be blown into the zone.
  • a particularly advantageous arrangement is constituted by a variant of the apparatus that uses a roll, since in many production lines rolls are in any case used as the elements for guiding the webs.
  • the wire or wires are fitted inside at least two rotatable rolls containing openings, these rolls being arranged one behind the other or one above the other, as in the generally known roll systems.
  • the number and area of the openings should be as great as possible so as to enable as many zones as possible to be discharged as the material passes over the roll.
  • the corona wires are distributed over the entire circumference of the roll, in which case the corona affects a lengthwise zone that depends upon the looping arc around the roll.
  • the wires may be fitted in a fixed position or they may be mounted to rotate with the rolls, in the latter arrangement, current is supplied through slid- ;ing contacts.
  • An advantageous arrangement isone employing a roll made of thin resistive wires.
  • This apparatus possesses the advantage that the openings are relatively large so that the use of two rolls generally suffices for the purpose of removing the' charge.
  • a further discharging apparatus opposite the roll is expedient to fit a further discharging apparatus opposite the roll.
  • this second charge-removing apparatus is preferably of curved form, the curvature in particular corresponding to the radius of the roll.
  • the apparatus was operated at a high voltage of 6 kV and a frequency of 50 cycles per second. The current intensity was 2 p. amp./cm of web width. After passage through the corona zone, a residual charge having a field strength of 22 kV/m was determined by means of a surface probe instrument.
  • Example 4 was repeated but with the difference that 30 Example 5 was repeated but with the difference that apparatus as in Example 3 was arranged on both sides of the web of film material.
  • the field strength of the residual charge was less than 1 kV/m.
  • ELEM QEJM A 6 u-thick film of polyester was passed through a system of rolls at a speed of m/min.
  • the field strength of the charge on the film was 1,100 kV/m.
  • the film was passed over four wire rolls having a diameter .of 500 mm, the first and-third rolls being in contact with the underface of the film, and the second and fourth rolls being in contact with its top face.
  • the wires constituting the rolls were 1 mm thick and made of V4 A material, andonboths ides they were mounted in rfiigsat disaices apart of 2 mm. mcorfi wires hav ing a thickness of 30 p.
  • Example 3 The driven rolls were so controlled that as the web passed through, there occured each time, in the case of the second roll of a pair, an aperture (gap between the wires) at that place where, in the case of the first roll of the pair, no discharge had taken place as a result of the web bearing on the wires.
  • the field strength of the residual charge was I kV/m.
  • Example 7 was repeated but with the difference-that there was also positioned opposite each of the rolls a counter electrode which likewise comprised five 30 u-thick corona wires which were accommodated in a rectangular protective element. In this case, the field strength of the residual charge was only 0.2 kV/m.
  • the method of the invention in contrast to the known methods, enables an even and approaching complete discharge to be effected. Inter mediate zones in whichthe charge is not satisfactorily removed could not be found, despite the use of a fine resolution probe (for example, a probe as disclosed in German Pat. specification No. 1,281,573). Even at higher speeds of travel of up to approximatley 500 m/min. complete and even removal of the charge could be achieved.
  • a fine resolution probe for example, a probe as disclosed in German Pat. specification No. 1,281,573
  • FIG. 1 shows the principal components of one embodiment of discharge apparatus
  • FIGS. 2 to 6 are plan views of different examples of the corona wire arrangement
  • FIGS. 7 and 8 are elevations showing how the corona wires can be located in protective elements
  • FIGS. 9 and 10 are cross-sections of discharge apparatus in roll form.
  • FIG. 11 is a cross-section of an arrangement for discharge of both sides ofa web by means ofa roll system.
  • FIG. 1 shows an impulse generator 1, which produces square wave impulses of a sequence frequency in the range envisaged by the invention, these impulses being amplified by an amplifier 2.
  • the signal is amplified in a power amplifier 3 and passed to the primary winding of a high-voltage trans-' former 4.
  • the high-voltage terminal of the secondary winding is connected to a corona wire 5.
  • a counter electrode 6 is grounded.
  • a web 7 of material is passed below the corona wire and at a certain distance therefrom.
  • the effective value of the corona voltage is measured in kV on a high-voltage measuring instrument 8.
  • the high-voltage amplitude can be varied at the impulse generator.
  • the current intensity is determined in an independent measurement by means of suitable instruments, and adjustments in accordance with these measurements can be made.
  • a wire is mounted to zig-zag around points 11 provided on the frame.
  • the tension is produced by means of a spring 10.
  • FIG. 4 shows four corona wires 5 which, in contrast to the arrangement seen in FIG. 2 however, are arranged closer together and are additionally held by means of three insulating support elements l2.
  • FIG. 5 shows five individual corona wires 5which' are each tensioned at each end by springs '10 and are staggered in relation to each other. This provides the advantage that, although the entire width of web is covered, shorter lengths of wire can be used.
  • FIG. 6 shows the n're arrangement seen in FIG. 2, but with a protective grid 13 also fitted.
  • FIG. 7 illustrates a rectangular form of protective element 14, and FIG. 8 shows a protective element of semi-circular form.
  • the corona wires 5 are protected in channels 15 which are defined by walls 16 and a floor 17.
  • the protective elements can be used directly as the counter electrode.
  • a dielectric eg in the form of a lining of synthetic film, can be fitted between the corona wires and the interior of the protective elements. 7,
  • FIG. 9 shows a detail of a discharge apparatus in the form of a roll, and also shows a second discharge device disposed opposite the first.
  • the web 7 of the material is passed over the roll which consists of an arrangement of rods 18.
  • the corona wires 5 are fitted inside the roll and distributed around its entire circumference.
  • a counter electrode, ' which consists of a 'protectiveelement 14 with a corresponding number of corona wires 5, is of curved shape.
  • the corona wires are preferably also rotatably mounted.
  • FIG. 10 shows practically the same roll as that of FIG. 9, but with the corona wires 5 positioned only't'o correspond with the looping arc of the web 7 of material.
  • the corona wires are immobilized in relation to the rotatable roll.
  • FIG. 11 illustrates a roll arrangement I, II, III, and IV, for discharging both sides of the web of material, and by means of which particularly low residual charges remain.
  • the rolls which consist of thin rods 19, house co- 7 rona wires 5 and these are fixed in such a way that the corona is produced only over the looping arc of the web.
  • the electrodes disposed opposite the rolls are the same as those shown in FIG. 9.
  • Rollers 20 and 21 are guide rollers known per se.
  • a method of discharging a statically charged web of material which comprises bombarding the web with charge carriers produced by a high-frequency alternating current of 5 to 50 kilocycles per second and having a current intensity of between a few [1, amp/cm of web width and several hundred p. amp/cm of web width.
  • An apparatus for discharging a statically charged web of material which comprises at least one un coated wire means having a thickness less than [L and being adapted to extend over the width of the web, means for supplying high-frequency alternating current of 5 to 50 kilocycles per second to said wire means, and counter-electrode means on the same side of the web as said wire means.
  • a protective element for the wire means is a plate containing channels corresponding in number to the number of wires.

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  • Elimination Of Static Electricity (AREA)
US00178313A 1970-09-10 1971-09-07 Apparatus for removing static charge from webs of material Expired - Lifetime US3790854A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19702044828 DE2044828C (de) 1970-09-10 Verfahren und Vorrichtung zur Entladung von Materialbahnen

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US3790854A true US3790854A (en) 1974-02-05

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US (1) US3790854A (xx)
BE (1) BE772316A (xx)
CA (1) CA942374A (xx)
FR (1) FR2106420B1 (xx)
GB (1) GB1361835A (xx)
LU (1) LU63884A1 (xx)
NL (1) NL7111963A (xx)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4027201A (en) * 1975-10-06 1977-05-31 International Business Machines Corporation Apparatus and method for neutralizing static charges in sheet/web feeding devices
US4110810A (en) * 1977-03-10 1978-08-29 E. I. Du Pont De Nemours And Company Static charge neutralizer and process
US4130852A (en) * 1977-07-29 1978-12-19 Eastman Kodak Company Grounded grid static discharge apparatus
USRE31382E (en) * 1977-03-10 1983-09-13 E. I. Du Pont De Nemours And Company Static charge neutralizer and process
US4672505A (en) * 1984-06-18 1987-06-09 Canon Kabushiki Kaisha Corona discharging device
US5805407A (en) * 1995-09-07 1998-09-08 Fuji Photo Film Co., Ltd. Charge eliminating apparatus for a moving web
US6368675B1 (en) 2000-04-06 2002-04-09 3M Innovative Properties Company Electrostatically assisted coating method and apparatus with focused electrode field
US6475572B2 (en) 2000-04-06 2002-11-05 3M Innovative Properties Company Electrostatically assisted coating method with focused web-borne charges
US20090080956A1 (en) * 2007-09-26 2009-03-26 Montfort David B In-line printing media treatment for printing on non-paper printing media and thick printing media
US11365497B2 (en) * 2016-08-02 2022-06-21 Fitesa Germany Gmbh System and process for preparing polylactic acid nonwoven fabrics

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2556228A1 (de) * 1975-12-13 1977-06-16 Hoechst Ag Coronaeinrichtung
US4064548A (en) * 1976-01-27 1977-12-20 Burlington Industries, Inc. Means for improving ionization efficiency of high-voltage grid systems
DE2643772C2 (de) * 1976-09-29 1985-01-17 Hoechst Ag, 6230 Frankfurt Coronaeinrichtung
US4135085A (en) * 1977-08-10 1979-01-16 The Continental Group, Inc. Charging device for basecoat charging of can ends
US4340926A (en) * 1978-11-23 1982-07-20 Payne John M Device for electrostatically charging sheet material

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US844300A (en) * 1906-02-12 1907-02-12 Chapman Electric Neutralizer Company Process of neutralizing static electricity.
US2867912A (en) * 1956-05-11 1959-01-13 Horace Dawson Method for the decontamination of metal foils
US2879396A (en) * 1957-05-03 1959-03-24 Plastics-treating apparatus
US3376208A (en) * 1964-05-19 1968-04-02 Canadian Ind Method of improving the adhesive properties of polyolefin film by passing a diffuse electrical discharge over the film's surface
US3634726A (en) * 1969-06-03 1972-01-11 Progil Process and device to remove static electricity from plastic films

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US844300A (en) * 1906-02-12 1907-02-12 Chapman Electric Neutralizer Company Process of neutralizing static electricity.
US2867912A (en) * 1956-05-11 1959-01-13 Horace Dawson Method for the decontamination of metal foils
US2879396A (en) * 1957-05-03 1959-03-24 Plastics-treating apparatus
US3376208A (en) * 1964-05-19 1968-04-02 Canadian Ind Method of improving the adhesive properties of polyolefin film by passing a diffuse electrical discharge over the film's surface
US3634726A (en) * 1969-06-03 1972-01-11 Progil Process and device to remove static electricity from plastic films

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4027201A (en) * 1975-10-06 1977-05-31 International Business Machines Corporation Apparatus and method for neutralizing static charges in sheet/web feeding devices
US4110810A (en) * 1977-03-10 1978-08-29 E. I. Du Pont De Nemours And Company Static charge neutralizer and process
USRE31382E (en) * 1977-03-10 1983-09-13 E. I. Du Pont De Nemours And Company Static charge neutralizer and process
US4130852A (en) * 1977-07-29 1978-12-19 Eastman Kodak Company Grounded grid static discharge apparatus
US4672505A (en) * 1984-06-18 1987-06-09 Canon Kabushiki Kaisha Corona discharging device
US5805407A (en) * 1995-09-07 1998-09-08 Fuji Photo Film Co., Ltd. Charge eliminating apparatus for a moving web
US6368675B1 (en) 2000-04-06 2002-04-09 3M Innovative Properties Company Electrostatically assisted coating method and apparatus with focused electrode field
US6475572B2 (en) 2000-04-06 2002-11-05 3M Innovative Properties Company Electrostatically assisted coating method with focused web-borne charges
US6666918B2 (en) 2000-04-06 2003-12-23 3M Innovative Properties Company Electrostatically assisted coating apparatus with focused web charge field
US6716286B2 (en) 2000-04-06 2004-04-06 3M Innovative Properties Company Electrostatically assisted coating method and apparatus with focused electrode field
US20090080956A1 (en) * 2007-09-26 2009-03-26 Montfort David B In-line printing media treatment for printing on non-paper printing media and thick printing media
US11365497B2 (en) * 2016-08-02 2022-06-21 Fitesa Germany Gmbh System and process for preparing polylactic acid nonwoven fabrics
US11920268B2 (en) 2016-08-02 2024-03-05 Fitesa Simpsonville, Inc. System and process for preparing polylactic acid nonwoven fabrics

Also Published As

Publication number Publication date
DE2044828A1 (de) 1972-04-06
LU63884A1 (xx) 1973-03-09
BE772316A (fr) 1972-03-07
FR2106420A1 (xx) 1972-05-05
GB1361835A (en) 1974-07-30
CA942374A (en) 1974-02-19
FR2106420B1 (xx) 1973-06-29
DE2044828B2 (de) 1972-12-14
NL7111963A (xx) 1972-03-14

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