FORAMINOUS VACUUM BIAS ROLL TRANSFER SYSTEM

• US 3,832,055 A
• Filed: 06/05/1973
• Issued: 08/27/1974
• Est. Priority Date: 06/05/1973
• Status: Expired due to Term

• Current Assignee: Ralph A. Hamaker
• Original Assignee: Ralph A. Hamaker
• Inventors: Hamaker, Ralph A.
• Primary Examiner(s): Greiner, Robert P.
• Application Number:
  US05/367,279
• Time in Patent Office: 448 Days
• Field of Search: 355/3R 96/1.4 118/621
• US Class Current: 399/313
• CPC Class Codes: G03G 15/1685 Structure, details of the transfer member, e.g. chemical composition

Abstract

In electrostatographic apparatus for applying a high bias voltage between a bias roller electrode and an original support surface to provide an electrical field for development material transfer to a cut sheet therebetween without arcing or undesired corona, a roller electrode having an electrically conductive core to which said high voltage is applied and a normally thick roller body of foraminous convolute open cell material compressed between the conductive core and the support surface and a vacuum applied through said foraminous material to hold said cut sheet against said roller electrode.

Claims

1. In electrostatographic apparatus wherein a transfer bias voltage is applied between a roller electrode and a first support surface to provide an electrical field for image transfer to a sheet providing a second support surface there-between while relative movement is provided between said roller electrode and said first support surface and said sheet, and said roller is variably deformed by said first support surface at a roller nip area with pre-nip and post-nip areas at each side of said Nip area, the improvement in said roller electrode comprising:

an electrically conductive core to which said bias voltage is applied, spaced from said first support surface; and

a highly compressible and air permeable roller body of foraminous convolute open cell material extending between said conductive core and said first support surface and having a substantial normal uncompressed thickness, said foraminous material occupying the space between said conductive core and said first support surface with a multiplicity of small convolute air passage discontinuities provided by said cells in said material and providing an ionization control barrier, said foraminous material being compressed between said conductive core and said first support surface in said nip area to a thickness substantially less than said normal uncompressed thickness, to close air passages therein, said foraminous material being less compressed in said pre-nip and post-nip areas than in said nip area and having a greater thickness and porosity between said conductive core and said first support surface therein over a substantial area of said surface for ionization control in said pre-nip and post-nip areas; and

vacuum means for applying a vacuum through said roller body for aminous material to provide vacuum retention of said sheet on said roller body.

2. The apparatus of claim 1 wherein said first support surface is a photoreceptor and said roller electrode is a xerographic bias transfer roller for electrostatic image transfer of xerographic developer material from said first support surface to said second support surface.

3. The apparatus of claim 1 wherein said foraminous roller body is non-conductive to said bias voltage and electrically insulates said conductive core from said first support surface and does not affect the electrical field therebetween.

4. The apparatus of claim 1 wherein said conductive core and said foraminous roller body are curvalinear and said core has a radius greatly smaller than the normal uncompressed radius of said foraminous roller body.

5. The apparatus of claim 1 wherein said open cells of said foraminous roller body are air filled.

6. The apparatus of claim 1 wherein said foraminous material in said nip is compressed to at least approximately one-half of said normal uncompressed thickness.

7. The apparatus of claim 1 wherein said foraminous material in said nip is compressed sufficiently to collapse a substantial portion of said open cells in said nip to correspondingly close said air passages in said nip.

8. The apparatus of claim 1 wherein said conductive core and said roller body are cylindrical and coaxially mounted with said conductive core uniformly wrapped with said foraminous material, and said conductive core is a hollow perforated tube with said vacuum means communicating with the interior thereof.

9. The apparatus of claim 1 wherein said foraminous material is electrically resistive and conducts said transfer bias, and wherein the resistivity of said material in said normal state is rendered substantially greater than its compressed resistivity in said nip by a substantial percentage of compressively collapsed cells in said nip, to provide increased nip transfer field strength.

10. The apparatus of claim 9 wherein foraminous material in said nip is compressed to at least approximately one-half of said normal uncompressed thickness.

11. The apparatus of claim 1 wherein said conductive core is hollow and air permeable and said vacuum means communicates with the interior thereof.

12. The apparatus of claim 1 further including air blowing means blowing into said post-nip area for assisting stripping of said sheet from said roller.

13. The apparatus of claim 1 wherein said first support surface is a photoreceptor and said roller electrode is a xerographic bias transfer roller for electrostatic image transfer of xerographic developer material from said first support surface to said second support surfAce. said conductive core and said roller body are cylindrical and coaxially mounted with said conductive core uniformly wrapped with said foraminous material, and said conductive core is a hollow perforated tube with said vacuum means communicating with the interior thereof.

14. In electrostatographic apparatus wherein a transfer bias voltage is applied between a roller electrode and a first support surface to provide an electrical field for image transfer to a sheet providing a second support surface therebetween while relative movement is provided between said roller electrode and said first support surface and said sheet, and said roller is variably deformed by said first support surface at a roller nip area with pre-nip and post-nip areas at each side of said nip area, the improvement in said roller electrode comprising:

an electrically conductive core to which said bias voltage is applied, spaced from said first support surface; and

a highly compressible and air permeable roller body of foraminous convolute open cell material extending between said conductive core and said first support surface and having a substantial normal uncompressed thickness, said foraminous material occupying the space between said conductive core and said first support surface with a multiplicity of small convolute air passage discontinuities provided by said cells in said material and providing an ionization control barrier, said foraminous material being compressed between said conductive core and said first support surface in said nip area to a thickness substantially less than said normal uncompressed thickness, said foraminous material being less compressed in said pre-nip and post-nip areas than in said nip area and having a greater thickness and porosity between said conductive core and said first support surface therein over a substantial area of said surface for ionization control in said pre-nip and post-nip areas; and

vacuum means for applying a vacuum through said roller body foraminous material to provide vacuum retention of said sheet on said roller body, further including vacuum cleaning apparatus spaced from said nip area deformably engaging the surface of said roller for vacuum cleaning it.

15. In electrostatographic apparatus wherein a transfer bias voltage is applied between a roller electrode and a first support surface to provide an electrical field for image transfer to a sheet providing a second support surface there-between while relative movement is provided between said roller electrode and said first support surface and said sheet, and said roller is variably deformed by said first support surface at a roller nip area with pre-nip and post-nip areas at each side of said nip area, the improvement in said roller electrode comprising:

an electrically conductive core to which said bias voltage is applied, spaced from said first support surface; and

a highly compressible and air permeable roller body of foraminous convolute open cell material extending between said conductive core and said first support surface and having a substantial normal uncompressed thickness, said foraminous material occupying the space between said conductive core and said first support surface with a multiplicity of small convolute air passage discontinuities provided by said cells in said material and providing an ionization control barrier, said foraminous material being compressed between said conductive core and said first support surface in said nip area to a thickness substantially less than said normal uncompressed thickness, said foraminous material being less compressed in said pre-nip and post-nip areas than in said nip area and having a greater thickness and porosity between said conductive core and said first support surface therein over a substantial area of said surface for ionization control in said pre-nip and post-nip areas; and

vacuum means for applying a vacuum through said roller body foraminous materiAl to provide vacuum retention of said sheet on said roller body, further including sheet registration lip means providing a sheet edge detaining surface discontinuity in said foraminous material, which discontinuity is suppressed in said nip by said compression of said foraminous material to maintain a smooth and continuous nip engagement by said roller.

16. The apparatus of claim 15 wherein the dimensions of said sheet registration lip means are substantially less than the thickness of said foraminous material.

17. The apparatus of claim 16 wherein said roller is cylindrical and said sheet registration lip means comprises an integral projecting rib extending along the outer surface of said roller parallel to the axis of said roller.