US3340429A - Apparatus adapted to apply an electrostatic charge to moving fibrous elements - Google Patents

Apparatus adapted to apply an electrostatic charge to moving fibrous elements Download PDF

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Publication number
US3340429A
US3340429A US549436A US54943666A US3340429A US 3340429 A US3340429 A US 3340429A US 549436 A US549436 A US 549436A US 54943666 A US54943666 A US 54943666A US 3340429 A US3340429 A US 3340429A
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United States
Prior art keywords
path
needle
needles
fibrous elements
ion gun
Prior art date
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Expired - Lifetime
Application number
US549436A
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English (en)
Inventor
Owens John Edward
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.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
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Filing date
Publication date
Priority claimed from US137575A external-priority patent/US3163753A/en
Priority to LU42298D priority Critical patent/LU42298A1/xx
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Priority to US549436A priority patent/US3340429A/en
Application granted granted Critical
Publication of US3340429A publication Critical patent/US3340429A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T19/00—Devices providing for corona discharge
    • H01T19/04—Devices providing for corona discharge having pointed electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/0007—Electro-spinning
    • D01D5/0061—Electro-spinning characterised by the electro-spinning apparatus
    • D01D5/0092—Electro-spinning characterised by the electro-spinning apparatus characterised by the electrical field, e.g. combined with a magnetic fields, using biased or alternating fields
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/04—Dry spinning methods
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/11—Flash-spinning
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F13/00—Recovery of starting material, waste material or solvents during the manufacture of artificial filaments or the like
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
    • D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
    • D04H3/16—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
    • Y02P70/62—Manufacturing or production processes characterised by the final manufactured product related technologies for production or treatment of textile or flexible materials or products thereof, including footwear

Definitions

  • This invention relates to an apparatus for placing electrostatic charges on dielectric material and particularly to corona discharge means employed in charging continuously forwarded dielectric materials, particularly those materials in the form of continuous filaments and still more especially those of synthetic organic polymeric structure.
  • a corona discharge is the electrical discharge occurring in a gas surrounding a conductor when the potential gradient at a point in a non-uniform electric field exceeds the critical value for ionization causing a local selfsustained discharge. It is a phenomenon particularly associated With sharp-edged electrodes and essentially occurs in a limited region near the electrodes, the rest of the gap carrying a so-called dark current.
  • the magnitude of the electric field gradient required to produce a corona discharge is the same as that required to produce arcing; the difiference between the two being that in corona the critical value has been reached only in a limited region of the breakdown path between electrodes.
  • the apparatus of the present invention is useful in supplying a corona field particularly in applying an electrostatic charge to a fibrous web.
  • an apparatus through which a web of fibrous elements is forwarded in a path of advance or flow-path while an electrostatic charge is placed upon the said elements by a corona discharge assembly.
  • the corona discharge assembly consists of an ion gun and a target electrode positioned on opposite sides of and adjacent to the path of advance of the web. Forwarding means are provided to convey the web into the zone of corona influence in order to impose an electrostatic charge upon it.
  • the ion gun of the present invention consists of a row of parallel needles rigidly held in a fixed lateral spacial relationship.
  • each needle is connected to a common source of high voltage current through an individual resistor of relatively high impedance, i.e., at least 1 megohm.
  • FIGURE 1 is a perspective view partially in section of the ion gun of the present invention.
  • FIGURE 2 is an elevation of a plug-in corona discharge needle of the ion gun of FIGURE 1.
  • FIGURE 3 is a top view with the top cover removed -velocity vapor currents of a second embodiment of the ion invention.
  • FIGURE 4 is a cross-sectional elevation indicating schematically the arrangement of the various elements in a system wherein the ion gun of the present invention is useful. This system is described and claimed in US. application No. 372,623 to Hollberg and Owens, filed June 4, 1964.
  • corona discharge needles 25 are rigidly fixed in supporting face 24 of the ion gun illustrated. Connection of each needle to the main power supply through a port 33 is through a separate lead 32 in series with a resistor 28.
  • the unit illustrated is particularly useful in applications where high are experienced, the curved electrically insulating top 23 and flat electrically insulating face 24 providing a path of low turbulence for such vapor flow.
  • needle 25 has a sharp point 22 and is conveniently of a plug-in variety with a conducting socket attached to prongs 34 adaptable for making electric contact with lead 32.
  • FIGURE 3 Another embodiment of the ion gun is shown in FIGURE 3, wherein a row of conducting needles is mounted parallel in side 27 of a housing 26 (the top of the housing being removed in the drawing). Each needle is connected through an individual resistor 28 to a conducting bar 29. Terminal 30 is provided along conducting bar 29 for connecting the device to a high voltage source such as 35, shown in FIGURE 4.
  • a high voltage source such as 35, shown in FIGURE 4.
  • the top (not shown) of housing 26 is secured in place and encloses resistor 28 and bar 29.
  • Use of a resistor in series with each needle and the high voltage source provides needle-toneedle uniformity of corona flow which is especially important when operating at a low current per needle such as is necessary in the production of sheet products formed from plexifilaments such as those described in US. Patent No.
  • Efiicient operation under these conditions requires that a targetto-ground current no greater than that required to apply the peak charge be employed. Furthermore, operation at corona currents above that required to produce a peak charge on the web results in non-uniformity of sheet product. Generally a corona current at each needle from about 5 to about 30 microamps is adequate; between 10 and 20 microamp per needle is preferred for charging a plexifilamentary web. At this relatively low current per needle small changes in emitted current magnify the eifect of non-uniformity.
  • the ion gun described herein provides a high impedance circuit from the high voltage source to each needle so that normal fluctuations in the effective dynamic resistance of corona discharge have little effect on emitted current.
  • the nature of the target electrode is not critical. It may be a round bar variety as illustrated in US. Patent No. 3,163,753, dated Dec. 29, 1964.
  • the fiat target plate described and claimed in combination in the aforementioned application to Hollberg and Owens is preferred.
  • the present invention is particularly useful in electrostatically charging a freshly-spun plexifilamentary web. A suitable systern for this operation is shown in FIGURE 4 which is described in detail below.
  • a spinneret device 1 is connected to a source ofv polymer dissolved in an organic solvent.
  • Polymer solution 2 under pressure is fed through extrusion orifice 3 into intermediate pressure or let-down pressure zone 4 and then through spinning orifice 5 into web forming chamber 6.
  • the extrudate from spinning orifice 5 is a plexifilament 7. Due to the pressure drop at spinning orifice 5 vaporization of solvent creates a vapor blast which, by virtue of impingement upon baffie 8 concomitantly with plexifilament 7, generally follows the path of advance of the plexifilament 7 from spinning orifice 5 to collecting surface 9, thereby creating a flow pattern within chamber 6 as indicated by the arrows.
  • Bafile '8 is mounted on shaft 10 which in turn is oscillatably mounted in bearing 11 and is powered to oscillate by means not shown. While oscillation of the bafiieis not essential, it is preferred in the spreading of the plexifilament, at the beginning of the path of advance.
  • Target plate 13 and ion gun 14 are disposed on opposite sides of the path of advance of the plexifilament web, downstream from the web forming and spreading devices.
  • Target plate 13 is so disposed that the vapor blast originating at 5 and the air flow pattern in chamber '6 holds plexifilament 7 in brushing contact with its charging surface.
  • Target plate 13 is connected to ground by wire 15 and microammeter 16, the latter indicating target plate current. The position of needles 25 with reference to target plate 13 is important for efficient operation.
  • the clearance between the needle points 22 and plate 13 should be as small as efficient operation will permit. Generally a clearance of from about 0.2 to about 2 inches is satisfactory although this will vary with the design and capacity of the particular equipment.
  • the total applied voltage across the resistor and the gap should be reduced to keep the current per point in the 5 to 30 rnicroampere range.
  • the needle point-toelectrode distance is decreased, it is desirable to increase the number of points per inch in order to deposit a uniform charge on all parts of the web of fibrous elements.
  • the voltage should be increased and/ or the number of points per inch decreased. For optimum operation, the points should be equally spaced along the conducting bar.
  • Placement of the ion gun at a point further upstream results in pinning or clinging of the web to the target plate. This results in bunching for an instant, an uneven diselectric charge by power charge across the web width, and a falling free of the bunched web to give a non-uniform sheet.
  • the web charge curve is very abrupt, making the process more difiicult to control.
  • secondary ionization will develop at the edge of the target plate providing charged ions of opposite polarity which will discharge the web unevenly. The web will then collapse and give a ropey strand which in turn gives a non-uniform sheet.
  • the discharged web will not pin well to the belt because of loss of charge.
  • plexifilament 7 After passing through the charging zone, plexifilament 7, as shown in FIGURE 4, is deposited upon a collecting surface 9.
  • the surface illustrated is a continuous belt forwarded by drive rolls 36.
  • the belt is given an opposite source 37 to that imposed on plexifilament 7 in the charging zone. Due to differences in their electrostatic charge, the plexifilarnent 7 is attracted to surface 9 and clings to it in its arranged condition as a sheet 38 with suflicient force to overcome the disruptive influences of whatever vapor blast may reach this area.
  • Surface 9 carries sheet 38 out of chamber 6 through port 39. Flexible elements 40 across port 39 and also across port 41, which permits reentry of the unloaded continuous belt, assist in retention of vapor within chamber 6. The sheet is then lightly compacted by compacting roll 44 and is collected on wind up roll 42.
  • a conventional solvent recovery unit 43 may be beneficially employed to improve economic operation.
  • a typical gun of the type shown in FIGURE 1, has 41 needles each attached to a distant 600 megohm resistor 28 by means of a small conducting wire 32.
  • the conducting wires are electrically insulated from one another and were further encased in a bar of polyacetal resin which supports the needles, The
  • resistors are encased in a box-like housing 26 located outside the vapor stream from the jet.
  • the needles of the ion gun extend 0.48 em. out of the polyacetal resin face 24.
  • the needles are 0.14 cm. in diameter at the shank and .007 cm. in radius at the tip. They are mounted on 0.95 cm. centers apart on the bar.
  • This gun is particularly useful in charging a plexifilamentary web using the apparatus of FIGURE 4.
  • Mounted opposite a flat target plate extending 12.7 cm. along the path of advance and 40.7 cm. across the said path and having a straight, thin trailing edge (to promote smooth vapor flow), it may be conveniently located 3.8 cm. away from the target, with its needles on a line 1.3 cm. above the trailing edge of the target plate.
  • the gun of the present invention is of a flat face construction at 24 with a streamlined top surface 23 as shown in FIGURE 1.
  • the needles are recessed within shielding or focusing cavities along the gun face.
  • the gun has been described as particularly useful in the charging of plexifilamentary webs, it is broadly applicable to the charging of all filamentary materials, particularly man-made filaments of a continuous structure.
  • An apparatus adapted to apply an electrostatic charge to fibrous elements, said apparatus comprising, in combination, means for forwarding the said fibrous elements in a linear path, a corona discharge device consisting of an ion gun and a grounded target electrode therefore disposed on opposite sides of the said path, the said ion gun being comprised of a row of parallel conducting needles fiXed rigidly in a fixed lateral spacial relationship arranged transverse to and completely across the said path with the points of the said needles facing the said target electrode, a direct current source of high voltage power, and means connecting each said needle to said source of high voltage, each connecting means including a high impedance resistor, the said voltage and resistor providing a corona current at each needle of from about 5 to about 30 microamps, each said resistor providing a voltage drop of at least about 3,000 volts.
  • said housing includes a dielectric bar as its fiat face, said bar being provided with a plurality of longitudinally aligned sockets for receiving said needles.

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Elimination Of Static Electricity (AREA)
US549436A 1961-09-12 1966-04-04 Apparatus adapted to apply an electrostatic charge to moving fibrous elements Expired - Lifetime US3340429A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
LU42298D LU42298A1 (en, 2012) 1961-09-12 1962-09-01
US549436A US3340429A (en) 1961-09-12 1966-04-04 Apparatus adapted to apply an electrostatic charge to moving fibrous elements

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US137575A US3163753A (en) 1961-09-12 1961-09-12 Process and apparatus for electrostatically applying separating and forwarding forces to a moving stream of discrete elements of dielectric material
US549436A US3340429A (en) 1961-09-12 1966-04-04 Apparatus adapted to apply an electrostatic charge to moving fibrous elements

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US3340429A true US3340429A (en) 1967-09-05

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3932760A (en) * 1967-12-22 1976-01-13 Inoue K Powder activation in an inert atmosphere
FR2395150A1 (fr) * 1977-03-25 1979-01-19 Knopf Franz Procede d'assistance electrostatique pour machines d'impression
EP0010756A1 (en) * 1978-10-31 1980-05-14 E.I. Du Pont De Nemours And Company Process for preparing a nonwoven web and apparatus for carrying out said process
US4968238A (en) * 1989-09-22 1990-11-06 E. I. Du Pont De Nemours And Company Apparatus for making a non-woven sheet
US5045248A (en) * 1989-09-22 1991-09-03 E. I. Du Pont De Nemours And Company Process for making a non-woven sheet
WO1994024737A1 (de) * 1993-04-16 1994-10-27 Eltex-Elektrostatik Gmbh Aufladeelektrode

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1782712A (en) * 1930-01-11 1930-11-25 Chapman Electric Neutralizer C Method of controlling electrostatic charges on moving surfaces
US2163294A (en) * 1936-11-21 1939-06-20 Simons Julius Static eliminator
CH368877A (de) * 1959-03-13 1963-04-30 Hans Dipl Ing Gruenenfelder Vorrichtung zur Ableitung der statischen Elektrizität aus Werkstoffbahnen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1782712A (en) * 1930-01-11 1930-11-25 Chapman Electric Neutralizer C Method of controlling electrostatic charges on moving surfaces
US2163294A (en) * 1936-11-21 1939-06-20 Simons Julius Static eliminator
CH368877A (de) * 1959-03-13 1963-04-30 Hans Dipl Ing Gruenenfelder Vorrichtung zur Ableitung der statischen Elektrizität aus Werkstoffbahnen

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3932760A (en) * 1967-12-22 1976-01-13 Inoue K Powder activation in an inert atmosphere
FR2395150A1 (fr) * 1977-03-25 1979-01-19 Knopf Franz Procede d'assistance electrostatique pour machines d'impression
EP0010756A1 (en) * 1978-10-31 1980-05-14 E.I. Du Pont De Nemours And Company Process for preparing a nonwoven web and apparatus for carrying out said process
US4968238A (en) * 1989-09-22 1990-11-06 E. I. Du Pont De Nemours And Company Apparatus for making a non-woven sheet
US5045248A (en) * 1989-09-22 1991-09-03 E. I. Du Pont De Nemours And Company Process for making a non-woven sheet
WO1994024737A1 (de) * 1993-04-16 1994-10-27 Eltex-Elektrostatik Gmbh Aufladeelektrode

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LU42298A1 (en, 2012) 1962-11-02

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