EP0478537A1 - Process for removing fouling deposits from dielectric surface of electrostatic charge target electrode - Google Patents
Process for removing fouling deposits from dielectric surface of electrostatic charge target electrodeInfo
- Publication number
- EP0478537A1 EP0478537A1 EP89905992A EP89905992A EP0478537A1 EP 0478537 A1 EP0478537 A1 EP 0478537A1 EP 89905992 A EP89905992 A EP 89905992A EP 89905992 A EP89905992 A EP 89905992A EP 0478537 A1 EP0478537 A1 EP 0478537A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- dielectric surface
- bristles
- process according
- brush
- brush assembly
- 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.)
- Ceased
Links
Classifications
-
- 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
Definitions
- This invention relates to a process for cleaning of dielectric surfaces of target electrodes during operation thereof in the application of electrostatic charge to fibrous structures, and relates more particularly to a process for removal of fouling deposits accumulating upon target electrodes in the application of electrostatic charge to multifibrous webs during manufacture thereof by flash-spinning, subsequent charging and spreading, and depositing onto a moving surface. 2.
- the high-resistance dielectric surface covering is provided to reduce a problem-causing effect associated with flash-spinning and electrostatic charging of fibrous structures, namely the generation of small separated particles which become attracted to the target electrode and build up an electrically insulating film thereupon.
- a problem-causing effect associated with flash-spinning and electrostatic charging of fibrous structures namely the generation of small separated particles which become attracted to the target electrode and build up an electrically insulating film thereupon.
- the high-resistance dielectric surface covering spreads out the charging field, thereby reducing current density, and it restricts the amount of current that may be drawn to points of breakdown.
- U.S. Patent No. 3,860,369 to Brethauer et al also discloses an apparatus for making non-woven fibrous sheets, and including electrostatic charging of the web in a corona discharge zone that includes a metal target disc electrode which is preferably covered with a dielectric insulating surface as disclosed in U.S. Patent No. 3,578,739.
- Brethauer et al indicates use of a rotating brush for clearing of any debris from the target plate and from adjacent parts.
- the present invention is intended to substantially reduce the aforesaid problems caused by flash-spun particles depositing upon target electrodes that have resulted in relatively short useful target electrode operating life, and accordingly, the invention has as a primary object the provision of a process for removal of fouling deposits from target electrode surfaces during operation thereof by a self-cleaning rotating brush apparatus, so that target electrodes cleaned thereby achieve useful in-process operating lifetimes that are significantly longer than heretofore possible.
- regions on the target electrode surface upon which accumulate fouling deposits comprising tiny solidified polymer particles generated during flash-spinning and electrostatic charging of fibrous web structures, are brushed by a self-cleaning rotating brush apparatus during the manufacture of the fibrous web structures, whereby fouling deposits are removed and charging efficiency for fibrous web structures is improved, so that useful in-process operating lifetimes of target electrodes are significantly increased.
- the process of the invention comprises brushing the revolving target electrode surface with a cylindrical brush having substantially radial bristles whose tips thereby remove fouling deposits from the target electrode surface.
- the brush is rotated about its axis and is adjustably spring-loaded against the moving target electrode surface.
- the brush is continuously cleaned by brushing against a cleaning bar that flicks away fouling deposits collected on the bristles.
- FIG.l is a schematic cross-sectional elevation of a flash-spinning apparatus including a brush apparatus for use in the process according to the present invention
- FIG.2 is an enlarged schematic view of a portion of FIG.l, showing schematically the vicinity of a target electrode fouled by deposits;
- FIG.3 is an enlarged schematic sectional view of a brush apparatus for use in the process according to principles of the invention.
- a flash-spinning apparatus 10 is schematically depicted therein that is used in production of multifibrous web structures.
- the shown apparatus comprises charging means for electrostatically charging such structures.
- the charging means includes an ion gun 12 and a target electrode 14; the latter being generally shaped in form of an annular disc.
- Target electrode 14 is provided with a dielectric surface layer 16, and is concentrically disposed about a baffle 18.
- Baffle 18 is revolved about axis 20, as indicated by arrow 22.
- a spinneret 24 is supplied with a pressurized polymer solution that issues from orifice 28 and forms a fibrous structure 26.
- An aerodynamic shield comprises a first member 30 and a second member 32.
- Target electrode 14 together with second member 32 are adapted to be rotated independently of baffle 18, but concentrically therewith, by means not shown here.
- a collecting surface 34 is comprised in an endless belt 36 that is carried by rolls of a powered conveyor means 38.
- Ion gun 12 comprised in first shield member 30, is supplied with a potential of 50 to 100 kilovolts.
- Target electrode 14 is connected to electrical ground via a here not shown contact ring and brush arrangement.
- a corona discharge is produced between ion gun 12 and target electrode 14, and continuously charges fibrous structure 26, thereby causing spreading thereof.
- Collecting surface 34 is electrically conductive and is grounded or given an opposite charge relative to the charge imposed on fibrous structure 26. Consequently, fibrous structure 26 is attracted to and deposited upon collecting surface 34 in flattened sheet-like form and is conveyed by powered conveyor means 38 to an accumulating means 42.
- uniform electrostatic charging of fibrous structure 26 is required to maintain spread of its partially interconnected filaments and to effectively deposit the structure in flattened form onto collecting surface 34.
- An electrostatic charge is imparted to fibrous structure 26 during its passage between ion gun 12 and the portion of target electrode 14 nearest thereto.
- Fibrous structure 26 passes through the unipolar region formed over the surface of target electrode 14. The unipolar region is established by the flow of ions from the corona discharge device, namely ion gun 12, to target electrode 14.
- the charge captured by fibrous structure 26 has the same polarity as the charge of ion gun 12.
- Coulomb repulsion forces spread such components apart.
- Tiny solidified polymer particles generated as a by-product of flash-spinning, also issue from spinneret 24 and are also charged by ions emitted from ion gun 12. While charged fibrous structure 26 is carried to the oppositely charged collecting surface 34, the charged polymer particles are attracted to and predominantly deposited upon dielectric surface layer 16.
- a brush apparatus 45 is disposed in a distal region from the charging region between ion gun 12 and target electrode 14. Particle-fouled surface regions of dielectric surface layer 16 are brought within reach of brush apparatus 45 by the rotation of the annular target electrode 14, and the deposited particles are removed by brushing.
- fibrous structure 26 issues from spinneret 24, is deflected downwardly along baffle 18, continues to move downwardly through a charging region between ion gun 12 and target electrode 14, and is carried to the oppositely charged collecting surface 34.
- Target electrode 14 comprises a metal target base 48 and dielectric surface layer 16.
- charged tiny polymer particles are deposited upon dielectric surface layer 16 and form thereupon a fouling layer 50.
- Build up of fouling layer 50 is detrimental to the charging process and causes rapid degradation of charging efficiency. Consequently, prevention or elimination of accumulation of fouling layer 50 is highly desirable.
- Fouling layer 50 is a nonconducting film upon target electrode 14.
- the present invention provides a process for removal of the fouling particle layer, during the aforesaid flash-spinning process, by use brush apparatus 45 for in-process removal of fouling layer 50.
- brush apparatus 45 is shown therein as it is disposed in spatial relationship to target electrode 14.
- Target electrode 14 has the general shape of an annular ring and it comprises metal target base 48 and dielectric surface layer 16.
- Target electrode 14 is disposed concentrically about revolving baffle 18, and is rotated about its axis independently therefrom.
- Brush apparatus 45 comprises a brush assembly 52 securely mounted upon a shaft 54 that is rotatably borne in a gearbox 56, a compression spring-loading device 58 disposed between a support 60 and gearbox 56, a compression adjusting means 62 mounted on gearbox 56 and bearing upon an adjustment support 64, and a brush cleaning bar 66 borne in gearbox 56.
- Brush cleaning bar 66 is preferably rotated about its axis, although it can be stationary.
- Shaft 54 extends through gearbox 56, as indicated, and is driven by a power drive means not shown here, for instance via a flexible drive shaft.
- brush cleaning bar 66 When brush cleaning bar 66 revolves, it is driven from shaft 54 via gearing in gearbox 56 and it is preferably provided with a substantially triangular cross-sectional shape to promote cleaning and clearing of bristles in brush assembly 52, although other cross-sectional shapes can be used therefor effectively.
- Support 60 and adjustment support 64 are rigidly mounted to structural members of flash-spinning apparatus 10 (not shown here) .
- Gearbox 56 is pivotably mounted to structural members of flash-spinning apparatus 10, having a pivot axis parallel to shaft 54, so that substantially tangential contact along a length of brush assembly 52 is maintained with dielectric surface layer 16 by the action of compression spring-loading device 58, while brush contact preloading is selectively adjusted by compression adjusting means 62.
- Brush assembly 52 preferably comprises a plurality of cylindrical brushes 68, having substantially radially oriented bristles, that are assembled upon shaft 54 and secured thereto, for instance by threaded nuts and locking arrangements, as shown here.
- each cylindrical brush is .76 centimeters wide and 6.4 centimeters in diameter and comprises about 2000 nylon filament bristles, each bristle having a diameter of '° 41 centimeters.
- brush assembly 52 is adjusted by compression adjusting means 62 onto dielectric surface layer 16 within a resilient brush contact interference range between about zero and .51 centimeters and preferably between about .1 to .25 centimeters, having a brush contact preloading force provided by compression spring-loading device 58 of between .68 and 3.41 to 3.64 kilograms.
- Shaft 54 is powered and revolves at a speed of about 150 to 190 RPM and preferably about 170 RPM to result in a bristle tip speed of between about 50.8 and 63.5 centimeters per second.
- Brush cleaning bar 66 is disposed parallel to shaft 54 and at a distance therefrom to result in a resilient brush contact interference between the bristles and the surface of brush cleaning bar 66. This contact interference effects substantial removal of particles collected upon bristles by flicking such particle off the bristles.
- brush apparatus 45 in flash spinning apparatus 10 significantly prolongs the useful in-process lifetime of target electrodes 14 by effectively removing fouling layer 50 from dielectric surface layer 16. Since brush apparatus 45 is self-cleaning by the action of brush cleaning bar 66, as hereinbefore described, its own service-free operating life vastly exceeds the life of critical components of flash-spinning apparatus 10. Dielectric surface lifetimes during in-process operation without the use of a fouling layer removing brush apparatus have been found to be increased at least about two and one half times when a process according to principles of the present invention is applied.
Abstract
L'invention concerne un procédé d'élimination à partir d'une surface diélectrique (16) d'électrode cible électrostatique, de dépôts d'encrassement (50) se présentant sous la forme de minuscules particules de polymère solidifiées au cours du "flash-spinning" de structures en bandes fibreuses. Les particules sont attirées et déposées sur la surface diélectrique (16) de l'électrode cible (14) utilisée pour la charge à effet de couronne de ladite structure en bande fibreuse, le dépôt d'encrassement résultant (50) augmentant la vitesse de perte d'efficacité de charge de structures fibreuses. Ledit procédé consiste à éliminer par brossage les dépôts d'encrassement à l'aide d'un agencement (45) de brosses rotatives autonettoyantes, afin d'empêcher l'accumulation des dépôts (50) sur la surface (16) de l'électrode cible électrostatique (14), et ainsi d'augmenter de manière significative l'efficacité de charge et la durée de vie de surfaces diélectriques d'électrodes cibles.The invention relates to a method for removing, from a dielectric surface (16) of an electrostatic target electrode, fouling deposits (50) which are in the form of tiny particles of polymer solidified during "flashing". spinning "of structures in fibrous bands. The particles are attracted and deposited on the dielectric surface (16) of the target electrode (14) used for the corona charge of said fibrous band structure, the resulting fouling deposit (50) increasing the rate of loss. loading efficiency of fibrous structures. Said method consists in brushing off the deposits of fouling using an arrangement (45) of rotary self-cleaning brushes, in order to prevent the accumulation of deposits (50) on the surface (16) of the electrode. electrostatic target (14), thereby significantly increasing the charging efficiency and the lifetime of dielectric surfaces of target electrodes.
Description
Claims
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1989/002005 WO1990014172A1 (en) | 1989-05-15 | 1989-05-15 | Process for removing fouling deposits from dielectric surface of electrostatic charge target electrode |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0478537A1 true EP0478537A1 (en) | 1992-04-08 |
EP0478537A4 EP0478537A4 (en) | 1993-05-19 |
Family
ID=22215004
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19890905992 Ceased EP0478537A4 (en) | 1989-05-15 | 1989-05-15 | Process for removing fouling deposits from dielectric surface of electrostatic charge target electrode |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0478537A4 (en) |
JP (1) | JPH04505186A (en) |
WO (1) | WO1990014172A1 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5558830A (en) * | 1994-12-02 | 1996-09-24 | E. I. Du Pont De Nemours And Company | Wand purging for electrostatic charging system in flash spinning process |
US5643524A (en) * | 1994-12-30 | 1997-07-01 | E. I. Du Pont De Nemours And Company | Corona charging of flash spun plexifilamentary film-fibril webs in poor charging environments |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3278972A (en) * | 1964-09-30 | 1966-10-18 | Xerox Corp | Xerographic plate cleaning apparatus |
US4148595A (en) * | 1977-09-28 | 1979-04-10 | E. I. Du Pont De Nemours And Company | Coating for aerodynamic shield in apparatus for making non-woven web |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3565979A (en) * | 1968-09-18 | 1971-02-23 | Du Pont | Flash spinning |
US3578739A (en) * | 1969-05-13 | 1971-05-18 | Du Pont | Apparatus for applying electrostatic charge to fibrous structure |
US3804569A (en) * | 1972-09-08 | 1974-04-16 | Du Pont | Spinneret wiper |
US3860369A (en) * | 1972-11-02 | 1975-01-14 | Du Pont | Apparatus for making non-woven fibrous sheet |
DE2825356C2 (en) * | 1978-06-09 | 1985-08-14 | Akzo Gmbh, 5600 Wuppertal | Device for cleaning spinnerets |
JPS61132609A (en) * | 1984-12-03 | 1986-06-20 | Toray Ind Inc | Apparatus for cleaning spinneret face |
DE3511797C1 (en) * | 1985-03-30 | 1986-05-22 | Klöckner Ferromatik Desma GmbH, 7831 Malterdingen | Molding press |
-
1989
- 1989-05-15 WO PCT/US1989/002005 patent/WO1990014172A1/en not_active Application Discontinuation
- 1989-05-15 EP EP19890905992 patent/EP0478537A4/en not_active Ceased
- 1989-05-15 JP JP50601489A patent/JPH04505186A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3278972A (en) * | 1964-09-30 | 1966-10-18 | Xerox Corp | Xerographic plate cleaning apparatus |
US4148595A (en) * | 1977-09-28 | 1979-04-10 | E. I. Du Pont De Nemours And Company | Coating for aerodynamic shield in apparatus for making non-woven web |
Non-Patent Citations (1)
Title |
---|
See also references of WO9014172A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO1990014172A1 (en) | 1990-11-29 |
JPH04505186A (en) | 1992-09-10 |
EP0478537A4 (en) | 1993-05-19 |
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Legal Events
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STAA | Information on the status of an ep patent application or granted ep patent |
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