Transfer apparatus having a transfer member with vacuum means
First Claim
1. Apparatus for transferring a toner image from an image-bearing member to a receiving sheet, which apparatus includes:
- a transfer member having a conductive surface and having vacuum holes to said surface,means for applying a vacuum to said vacuum holes to hold a receiving sheet on the surface of the member,means for creating an electric field urging a toner image toward said transfer member, anda conductive insert positioned in each of said vacuum holes, said insert being sufficiently conductive to improve the continuity of said electric field and having or defining with the inside of the vacuum hole small vacuum openings thinner in cross section than said vacuum hole.
3 Assignments
0 Petitions
Accused Products
Abstract
A transfer member, for example, a transfer drum utilizes a vacuum applied through vacuum openings to the drum surface for holding a receiving sheet. A toner image is transferred to the sheet under the urging of an electric field. The vacuum openings are made small enough to prevent a visible artifact caused by nontransfer of toner in the vicinity of the opening but large enough to still maintain a vacuum contributing to the holding force of the sheet. According to a preferred embodiment, larger vacuum holes are formed in the drum and a conductive insert defining or helping define small vacuum openings is inserted in each vacuum hole. The insert maintains the continuity of the electric field in the hole region, but its geometry provides the small openings to maintain the vacuum. The invention is particularly useful in apparatus in which more than one color toner image is transferred in registry to the receiving sheet.
19 Citations
24 Claims
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1. Apparatus for transferring a toner image from an image-bearing member to a receiving sheet, which apparatus includes:
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a transfer member having a conductive surface and having vacuum holes to said surface, means for applying a vacuum to said vacuum holes to hold a receiving sheet on the surface of the member, means for creating an electric field urging a toner image toward said transfer member, and a conductive insert positioned in each of said vacuum holes, said insert being sufficiently conductive to improve the continuity of said electric field and having or defining with the inside of the vacuum hole small vacuum openings thinner in cross section than said vacuum hole.
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2. Apparatus for transferring a toner image from an image-bearing member to a receiving sheet, which apparatus includes:
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a transfer drum having an outer surface formed by a layer of conductive material having a given thickness, said layer having vacuum holes to said surface, means for applying a vacuum to said vacuum holes to hold a receiving sheet on the surface of the drum, means for creating an electric field urging a toner image toward said drum, and a conductive insert positioned in each of said vacuum holes, said insert being generally hollow but having a closed end generally coplanar with the outer surface of the drum, the closed end having small vacuum openings through said closed end, said openings having a length substantially less than the thickness of the outer layer of the drum. - View Dependent Claims (3, 4, 5)
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6. Apparatus for transferring a toner image from an image bearing member to a receiving sheet, which apparatus includes:
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a transfer drum having a conductive surface formed by a conductive layer having a given thickness, said layer having vacuum holes to said conductive surface, which vacuum holes have a particular cross-sectional shape, means for applying a vacuum to said vacuum holes to hold a receiving sheet on the surface of the drum, means for creating an electric field urging a toner image toward said drum, and a conductive insert positioned in each of said vacuum holes, said insert being sufficiently conductive to improve the continuity of said electric field and having a cross-sectional shape sufficiently different from the cross-sectional shape of said hole to form with the inner surface of the vacuum hole small vacuum openings sufficiently large to maintain a vacuum at the surface of the transfer drum. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. Apparatus for transferring a toner image from an image bearing member to a receiving sheet, which apparatus includes:
a transfer drum having a conductive surface formed by a conductive layer having a given thickness, said layer having vacuum openings to said conductive surface, said vacuum openings being wider at their end away from the surface than they are at the surface.
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14. Apparatus for transferring a toner image from an image-bearing member to a receiving sheet, which apparatus includes:
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a transfer drum having a conductive surface formed by a conductive outer layer having a given thickness, said layer having vacuum holes to said surface, means for applying a vacuum to said vacuum holes to hold a receiving sheet on the surface of the drum, means for creating an electric field urging transfer of a toner image to a receiving sheet so held, and a conductive insert positioned in said vacuum holes the insert having a cylindrical outer surface,, a hollow center with one closed end, at least a portion of said closed end having a diameter smaller than the cylindrical outer surface to form an annular recess from the inner wall of the vacuum hole, and said insert further having at least one vacuum opening between the annular recess and the hollow center.
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15. Apparatus for forming multicolor toner images on a receiving sheet, said apparatus including
means for forming a series of electrostatic images on an image bearing member, means for toning said electrostatic images with toners of different colors, and means for transferring a plurality of said images to a receiving sheet in registry with each other image, to form a multicolor image on said receiving sheet, said transferring means including a transfer member having a conductive surface and having vacuum holes to said surface, means for applying a vacuum to said vacuum holes to hold a receiving sheet on the surface of the member, means for creating an electric field urging a toner image toward said transfer member, and a conductive insert positioned in each of said vacuum holes, said insert being sufficiently conductive to improve the continuity of said electric field and having or defining with the inside of the vacuum holes small vacuum openings thinner in cross section than said vacuum hole.
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17. Apparatus for transferring a toner image from an image-bearing member to a receiving sheet, which apparatus includes:
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a transfer member having an outer layer of material sufficiently conductive to help form an electric field, said layer having an outer surface, and said member having vacuum openings through said layer to said surface, means for applying a vacuum to said vacuum openings to hold a receiving sheet on the surface of the member, and means utilizing said layer for creating an electric field urging a toner image toward said transfer member, characterized in that said vacuum opening has a cross-sectional dimension at said surface that is less than 1.0 mm. - View Dependent Claims (18)
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19. Apparatus for transferring a toner image from an image bearing member to a receiving sheet, which apparatus includes:
a transfer drum having a conductive surface formed by a conductive layer having a given thickness, said layer having vacuum openings to said conductive surface, said vacuum openings being generally tapered, with the cross-section of the opening at the surface of the layer having a maximum dimension less than 1.0 mm and the other end of the opening having a maximum dimension larger than the maximum such dimension at the surface.
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20. Apparatus for forming multicolor toner images on a receiving sheet, said apparatus including
means for forming a series of electrostatic images on an image bearing member, means for toning said electrostatic images with toners of different colors, means for transferring a plurality of said images to a receiving sheet in registry with each other image, to form a multicolor image on said receiving sheet, said transferring means including a transfer member having an outer layer of material sufficiently conductive to help form an electric field, said layer having an outer surface, and said member having vacuum openings through said layer to said surface, means for applying a vacuum to said vacuum openings to hold a receiving sheet on the surface of the member, and means utilizing said layer for creating an electric field urging a toner image towards said transfer member, characterized in that each of said vacuum openings has a cross-sectional dimension at said surface that is less than 1.0 mm.
- 22. A transfer drum having an outer layer of material sufficiently conductive to help form an electric field, said layer having an outer surface, and said drum having vacuum openings through said layer to said surface, said openings being less than 1.0 mm in diameter at their narrowest.
Specification