Claims
- 1. In an electrographic process wherein an electrostatic charge pattern on a photoconductive support surface of an imaging medium is developed into a powder image thereon by powder particles attracted to image areas of the charge pattern and a background may result from powder particles adhering to non-image areas of said surface, and wherein a powder image moved with said surface to a transfer station is transferred from said surface there to be received on a receiving material, the process for removing powder particles from said surface which comprises:
- (1) while moving said surface bearing said powder image in a path toward said transfer station and past an electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto, generating between said surfaces an electric field spanning substantially the width of said support surface and having a strength sufficient to attract selectively toward said wall surface background powder particles on said support surface but insufficient to attract objectionably the powder particles forming said image, and flowing air transversely through said field in a thin stream between said surfaces and then away from said support surface through a suction opening extending along said wall surface, thereby removing such background powder particles and sucking them away through said opening; and
- (2) as a said image on said support surface approaches said wall, sensing the presence or absence of a receiving material in position to receive the image at said transfer station and upon sensing the absence thereof increasing the electric field between said surfaces to a strength effective to release and attract toward said wall surface for removal in said air stream the powder particles forming said image.
- 2. A process according to claim 1, said electric field being generated by applying to said wall a direct voltage having the same polarity as said charge pattern, said air stream having adjacent to said suction opening a thickness of about 0.1 to 1 mm and a velocity of between 10 and 300 cm per second.
- 3. A process according to claim 1, said electric field being generated by applying continuously to said wall a direct voltage having the same polarity as said charge pattern and that produces between said surfaces an electric field of between 3 and 10 kV/cm in strength.
- 4. A process according to claim 1, said electric field being generated by applying to said wall a pulsating direct voltage that produces between said surfaces an electric field not exceeding 70 kV/cm in strength.
- 5. A process according to claim 1, said increasing of said electric field being effected by applying to said wall a direct voltage having the same polarity as said charge pattern and that produces between said surfaces an electric field of between 15 and 30 kV/cm in strength.
- 6. A process according to claim 1 which further comprises upon sensing the absence of a receiving material in position to receive the image, subjecting said support surface at a location ahead of or up to said wall to a treatment that reduces the electrostatic attraction between said image areas and the powder particles thereon.
- 7. In our electrographic process according to claim 1
- while moving said support surface beyond said transfer station past a second electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto, generating between said second wall surface and said support surface a second electric field effective to attract toward said second wall surface powder particles remaining on said support surface beyond said transfer station, said second field spanning substantially the width of said support surface, and flowing air transversely through said second field in a thin stream between said support surface and said second wall surface and then away from said support surface through a second suction opening extending along said second wall surface, thereby removing and sucking away such remaining powder particles.
- 8. A process according to claim 7, said second electric field having the same polarity as said charge pattern and being at least five times stronger than the first-mentioned electric field.
- 9. A process according to claim 7, each of said electric fields being generated by applying to the respective electrically conductive wall a direct voltage having the same polarity as said charge pattern, and each of said air streams having at a location adjacent to the respective suction opening a thickness of about 0.1 to 1 mm and a velocity of between 10 and 300 cm per second.
- 10. A process according to claim 7, and at a location between said transfer station and said second wall surface subjecting said support surface to a treatment that reduces the electrostatic attraction between said support surface and powder particles remaining thereon.
- 11. A process according to claim 10, said treatment being by an A.C. corona discharge.
- 12. In an electrographic process wherein an electrostatic charge pattern on a photoconductive support surface of an imaging medium is developed into a powder image thereon by powder particles attracted to image areas of the charge pattern and a background may result from powder particles adhering to non-image area of said surface, and wherein a powder image moved with said surface to a transfer station is transferred from said surface there to be received on a receiving material, the process for removing powder particles from said surface which comprises:
- (1) while moving said surface bearing said powder image in a path toward said transfer station and past an electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto, generating between said surfaces an electric field spanning substantially the width of said support surface and having a strength sufficient to attract selectively toward said wall surface background powder particles on said support surface but insufficient to attract objectionably the powder particles forming said image, and flowing air transversely through said field in a thin stream between said surfaces and then away from said support surface through a suction opening extending along said wall surface, thereby removing such background powder particles and sucking them away through said opening; and
- (2) as a said image on said support surface approaches said wall, sensing the presence or absence of a receiving material in position to receive the image at said transfer station and upon sensing the absence thereof subjecting said support surface at a location ahead of or up to said wall to a treatment that reduces the electrostatic attraction between said image areas and the powder particles thereon so that said electric field will release and attract toward said wall surface for removal in said air stream the powder particles forming said image.
- 13. A process according to claim 12, said treatment being by an A.C. corona discharge.
- 14. A process according to claim 12, said electric field being generated by applying to said wall a direct voltage having the same polarity as said charge pattern, said air stream having adjacent to said suction opening a thickness of about 0.1 to 1 mm and a velocity of between 10 and 300 cm per second.
- 15. A process according to claim 12, said electric field being generated by applying continuously to said wall a direct voltage having the same polarity as said charge pattern and that produces between said surfaces an electric field of between 3 and 10 kv/cm in strength.
- 16. A process according to claim 12, said electric field being generated by applying to said wall a pulsating direct voltage that produces between said surfaces an electric field not exceeding 70 kv/cm in strength.
- 17. In an electrographic process according to claim 12, while moving said support surface beyond said transfer station past a second electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto, generating between said second wall surface and said support surface a second electric field effective to attract toward said second wall surface powder particles remaining on said support surface beyond said transfer station, said second field spanning substantially the width of said support surface, and flowing air transversely through said second field in a thin stream between said support surface and said second wall surface and then away from said support surface through a second suction opening extending along said second wall surface, thereby removing and sucking away such remaining powder particles.
- 18. A process according to claim 17, said second electric field having the same polarity as said charge pattern and being at least five times stronger than the first-mentioned electric field.
- 19. A process according to claim 17, each of said electric fields being generated by applying to the respective electrically conductive wall a direct voltage having the same polarity as said charge pattern, and each of said air streams having at a location adjacent to the respective suction opening a thickness of about 0.1 to 1 mm and a velocity between 10 and 300 cm per second.
- 20. A process according to claim 17, and at a location between said transfer station and said second wall surface subjecting said support surface to a treatment that reduces the electrostatic attraction between said support surface and powder particles remaining thereon.
- 21. A process according to claim 20, said treatment being by an A.C. corona discharge.
- 22. In an electrographic apparatus whereby an electrostatic charge pattern on a photoconductive support surface is developed into a powder image thereon by powder particles attracted to image areas of the charge pattern and a background may result from powder particles adhering to non-image areas of said surface, means for removing powder particls from said surface, comprising an electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto at a location in a path of movement of said support surface with powder particles thereon, means for generating between said wall surface and said support surface an electric field spanning substantially the width of the support surface and effective to attract powder particles therefrom toward said wall surface, a suction opening extending over said support surface along said wall surface, and means for flowing air transversely through said field in a thin stream between said surfaces and then away from said support surface through said suction opening, whereby at least powder particles that lie loose on said support surface and any powder particles loosened from it by said field are removed and sucked away through said opening;
- said wall being the peripheral wall of a tubular member disposed across said path and connected with means for sucking air through said member, said field generating means including means for applying to said wall a direct voltage having a polarity corresponding to that of said charge pattern, and said suction opening being a slot extending through and axially along said peripheral wall over the width of said support surface, said wall surface being surface portions of said peripheral wall bordering said slot;
- said wall surface having thereon a semi-conductive coating preventing arcing between said surfaces, said coating having a resistance of between 10.sup.5 and 10.sup.10 ohm cm.
- 23. In an electrographic apparatus whereby an electrostatic charge pattern on a photoconductive support surface is developed into a powder image thereon by powder particles attracted to image areas of the charge pattern and a background may result from such powder particles adhering to non-image areas of said surface, and wherein said surface is a surface of an imaging medium moved along a path extending through a transfer station having means thereat for transferring a powder image from said surface to a receiving material, means for removing powder particles from said surface comprising:
- (1) an electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto at a location in said path ahead of said transfer station, means for generating between said wall surface and said support surface an electric field spanning substantially the width of the support surface and having a strength sufficient to attract selectively toward said wall surface background powder particles on said support surface but insufficient to attract objectionably the powder particles forming said image, a suction opening extending over said support surface along said wall surface, and means for drawing air through said opening via the space between said surfaces and thus flowing air transversely through said field in a thin stream and then away from said support surface, so that such background particles are loosened selectively from said support surface and sucked away through said opening;
- (2) means operative as a said image on said support surface approaches said wall for sensing the presence or absence of a receiving material in position to receive said image at said transfer station and means responsive to said sensing means upon an absence of such receiving material for subjecting said support surface at a location ahead of or up to said wall to a treatment that reduces the electrostatic attraction between said image areas and the powder particles thereon so that said electric field will release and attract toward said wall surface for removal in said air stream the powder particles forming said image.
- 24. Apparatus according to claim 23, said surface treatment means comprising an A.C. corona.
- 25. Apparatus according to claim 23, said transferring means including an intermediate medium for receiving and carrying said image from said support surface and transferring the image to a receiving material in a zone away from said support surface, said sensing means acting in the path of movement of receiving material to said zone.
- 26. Apparatus according to claim 23, said field generating means including means for applying continuously to said wall a direct voltage that produces between said surfaces an electric field of between 3 and 10 kv/cm in strength.
- 27. Apparatus according to claim 23, said field generating means includng means for applying to said wall a pulsating direct voltage that produces between said surfaces an electric field not exceeding 70 kv/cm in strength.
- 28. In an electrographic apparatus whereby an electrostatic charge pattern on a photoconductive support surface is developed into a powder image thereon by powder particles attracted to image areas of the charge pattern and a background may result from such powder particles adhering to non-image areas of said surface, and wherein said surface is a surface of an imaging medium moved along a path extending through a transfer station having means thereat for transferring a powder image from said surface to a receiving material, means for removing powder particles from said surface comprising:
- (1) an electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto at a location in said path ahead of said transfer station, means for generating between said wall surface and said support surface an electric field spanning substantially the width of the support surface and having a strength sufficient to attract selectively toward said wall surface background powder particles on said support surface but insufficient to attract objectionably the powder particles forming said image, a suction opening extending over said support surface along said wall surface, and means for drawing air through said opening via the space between said surfaces and thus flowing air transversely through said field in a thin stream and then away from said support surface, so that such background particles are loosened selectively from said support surface and sucked away through said opening;
- (2) means operative as a said image on said support surface approaches said wall for sensing the presence or absence of a receiving material in position to receive said image at said transfer station, and means responsive to said sensing means upon an absence of such receiving material for increasing the electric field between said surfaces to a strength effective to release and attract toward said wall for removal in said air stream the powder particles forming said image.
- 29. Apparatus according to claim 28, said wall being the peripheral wall of a tubular member disposed across said path and connected with means for sucking air through said member, said field generating means including means for applying to said wall a direct voltage having a polarity corresponding to that of said charge pattern, and said suction opening being a slot extending through and axially along said peripheral wall over the width of said support surface, said wall surface being surface portions of said peripheral wall bordering said slot.
- 30. Apparatus according to claim 29, said slot having a width of about 2.5 to 3 mm and being located at a distance of about 0.1 to 1 mm from said support surface, said sucking means being operative to draw air through the space between the margins of said slot and said support surface at a velocity of between 10 and 300 cm per second.
- 31. Apparatus according to claim 29, said wall surface having thereon a semi-conductive coating preventing arcing between said surfaces.
- 32. Apparatus according to claim 31, said coating having a resistance of between 10.sup.5 and 10.sup.10 ohm cm.
- 33. Apparatus according to claim 32, said coating being of a butadiene-acrylonitrile rubber.
- 34. Apparatus according to claim 28, said field generating means including means for applying continuously to said wall a direct voltage that produces between said surfaces an electric field of between 3 and 10 kV/cm in strength.
- 35. Apparatus according to claim 28, said field generating means including means for applying to said wall a pulsating direct voltage that produces between said surfaces an electric field not exceeding 70 kV/cm in strength.
- 36. Apparatus according to claim 28, said field increasing means including means for applying to said wall a direct voltage having the same polarity as said charge pattern and that produces between said surfaces an electric field of between 15 and 30 kV/cm in strength.
- 37. Apparatus according to claim 28, said transferring means including an intermediate medium for receiving and carrying said image from said support surface and transferring the image to a receiving material in a zone away from said support surface, said sensing means acting in the path of movement of receiving material to said zone.
- 38. An apparatus according to claim 28 which further comprises means responsive to said sensing means upon an absence of such receiving material for subjecting said support surface at a location ahead of or up to said wall to a treatment that reduces the electrostatic attraction between said image areas and the powder particles thereon.
- 39. In an electrographic apparatus according to claim 28,
- a second electrically conductive wall having a surface extending over and facing said support surface and disposed near thereto at a location beyond said transfer station, means for generating between said second wall surface and said support surface a second electric field spanning substantially the width of said support surface and sufficiently strong to attract toward said second wall surface powder particles remaining on said support surface beyond said transfer station, a second suction opening extending over said support surface along said second wall surface and means for drawing air through said second opening via the space between said second wall surface and said support surface and thus flowing air transversely through said second field in a thin stream and then away from said support surface so that such remaining powder particles are loosened by said second field and sucked away through said second opening.
- 40. An apparatus according to claim 39, said second electric field having the same polarity as said charge pattern and being at least five times stronger than the first-mentioned electric field.
- 41. Apparatus according to claim 39, each of said walls being the peripheral wall of a tubular member disposed over the path of said imaging medium and connected with means for sucking air through said member, each of said field generating means including means for applying to the respective wall a direct voltage having a polarity corresponding to that of said charge pattern, each of said suction openings being a slot extending through and axially along the respective peripheral wall over the width of said support surface, and each of said wall surfaces being surface portions of the respective peripheral wall bordering the respective slot.
- 42. Apparatus according to claim 41, each said slot having a width of about 2.5 to 3 mm and being located at a distance of about 0.1 to 1 mm from said support surface and each said sucking means being operative to draw air through the space between the margins of the respective slot and said support surface at a velocity of between 10 and 300 cm per second.
- 43. Apparatus according to claim 41, each of said wall surfaces having thereon a semi-conductive coating preventing arcing between the respective wall surface and said support surface.
- 44. Apparatus according to claim 43, each said coating having a resistance of between 10.sup.5 and 10.sup.10 ohm cm.
- 45. Apparatus according to claim 44, each said coating being of a butadiene-acrylonitrile rubber.
- 46. An apparatus according to claim 39 and further comprising means for subjecting said support surface at a location between said transfer station and said second wall surface to treatment for reducing the electrostatic attraction between said support surface and such powder particles remaining thereon.
- 47. Apparatus according to claim 46, said surface treatment means comprising an A.C. corona.
Priority Claims (1)
Number |
Date |
Country |
Kind |
7404767 |
Apr 1974 |
NLX |
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Parent Case Info
This application is a continuation-in-part of copending U.S. application Ser. No. 564,413, filed Apr. 2, 1975, now abandoned.
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
1116077 |
Jun 1968 |
GBX |
Continuation in Parts (1)
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Number |
Date |
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Parent |
564413 |
Apr 1975 |
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