US3404418A

US3404418A - Sheet transport apparatus

Info

Publication number: US3404418A
Application number: US618978A
Authority: US
Inventors: Fantuzzo Joseph
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1967-02-27
Filing date: 1967-02-27
Publication date: 1968-10-08
Anticipated expiration: 1985-10-08

Description

Oct. 8,- 1968 FANTUZZO 3,404,418

SHEET TRAN 5 PORT APPARATUS Filed Feb. 27, 1967 INVENTOR. JOSEPH FANTUZZC BY ML;

ATTORNEYS United States Patent 3,404,418 .SHEET TRANSPORT APPARATUS Joseph Fantuzzo, Rochester, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Feb. 27, 1967, Ser. No. 618,978 4 Claims. (Cl. 15-l.5)

ABSTRACT OF THE DISCLOSURE An automatic copying machine of the type in which a powder image is transferred to a support material electrostatically carried on a dielectric web characterized by an improved apparatus for removing powder electrostatically attracted to the web. The apparatus comprises an electrically conductive member positioned to momentarily neutralize electrostatic fields on the web while a brush removes the powder from it. A variable source of potential is connected to the electrically conductive member to control the flow of powder onto the brush.

This invention relates to electrostatic copying apparatus, and, in particular, to apparatus used to transfer powder images from an electrostatic latent image to a sheet of support material moved in contact therewith.

More specifically, the invention is drawn to an improvement over apparatus described in copending application Ser. No. 500,945, now Patent No. 3,357,325, which describes a xerographic machine in which powder images are transferred from a moving xerographic surface onto support material transported therepast on an electrostatic conveyor.

In the process of xerography as described, for example, in US. Patent No. 2,297,691 to Carlson, powder images are developed on a photoconductive surface and transferred to suitable support material. These images are developed by placing in the absence of light a uniform electrostatic charge on the surface of a photoconductive material. The photoconductive material is then exposed to a light image of copy to be reproduced, and the electrostatic charge is drained off the surface of the photoconductive material as the light from the optical image renders the photoconductive material conductive and thus there is a latent electrostatic image remaining on the photoconductive surface corresponding to the optical image of the copy to be reproduced. The latent electrostatic image is then contacted with finely divided powder material or toner which is attracted to the surface of the photoconductor by the electrostatic charge and held thereon until transferred to a sheet of paper or support material.

In the copending application referred to above, transfer of the image to support material is accomplished at a transfer station wherein a conveyor in the form of a dielectric belt carries sheets of support material electrostatically into surface contact with the xerographic surface. An electrostatic charging device is positioned at the area contacted to provide an electrostatic charge sufficient to cause the powder image on the xerographic surface to transfer and adhere to the surface of the support material which may be paper. It has been found that electrostatic forces emanating from the conveyor belt attract toner particles from the xerographic surface which is especially noticeable in the case of a paper misfeed. Due to the strength of these fields and the relatively large size of toner, as compared, for example, to dust particles, it is difiicult to remove the toner from the belt by normal cleaning modes, such as by a vacuumcleaner. This problem becomes increasingly acute during low humiditycondition because of the greater electrostatic attraction forces present. As a result smudge marks are Patented Oct. 8, 1968 ice made on copies produced detracting from the overall quality of these copies.

In accordance with the present invention, it is possible to remove toner particles electrostatically bonded to the conveyor belt in an extraordinarily simple manner thereby rendering high quality prints. This is accomplished generally speaking, by momentarily breaking the electrostatic fields emanating from the belt at a predetermined location for a sufficient time to wipe the toner from it thereby rendering a clean electrostatic conveyor for continuously transporting sheets of support material.

It is, therefore, an object of this invention to improve apparatus used for transferring images from a xerographic surface to a sheet of support material.

It is a further object of this invention to facilitate the cleaning of an electrostatic conveyor in an automatic xerographic machine without deleteriously affecting the conveyor.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description to be read in conjunction with the accompanying drawing in which the figure is a schematic representation of a preferred embodiment for carrying out the invention.

Referring now to the drawing there is shown a xerographic system adapted for continuous and automatic operation employing an electrostatic conveyor apparatus generally designated 10 for transporting sheets of support material toward and away from a transfer station. As is usual in xerographic systems, a xerographic member 12 having a photoconductive layer and formed in the shape of a drum is mounted on a shaft 14 for movement past several xerographic processing stations in a direction indicated by the arrow. The elements of the systems are conventional with the exception of those at the transfer station which forms the basis of the present invention.

For purposes of the present disclosure, the several xerographic processing stations in the path of movement of the xerographic surface may be briefly described as follows:

A charging station at which a uniform electrostatic charge is deposited on the xerographic surface of the drum by means of a corotron 16.

An exposure station at which a light or radiation pattern of an original to be reproduced is projected onto the drum surface by an optical projector 18 to dissipate the drum charge in the exposed areas thereof to thereby leave an electrostatic latent image.

A developing station 20 at which a xerographic developing material, which includes toner particles having an electrostatic charge opposite to that of the latent image, is moved into contact with the drum surface whereby the toner particles adhere to the latent image to form a powder image.

A transfer station at which the powder image is electrostatically transferred by means of a corotron 22 from the drum surface to a sheet of support material to which it may be subsequently fused to produce a permanent print. Sheets of support material are continuously transported toward and away from the transfer area by electrostatic conveyor apparatus 10 which is maintained clean of toner deposited on the drum as will be described hereinafter.

A drum cleaning and discharge station at which the drum surface is moved past a preclean corotron 23 and contacted by a fibrous web 24 taken from a supply roller 26 around a roller 27 in contact with the drum surface and finally onto a take-up roller 28. Also the drum surface is exposed to a relatively bright light source 29 to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

It is believed that the foregoing description is sufficient for the purposes of this application to show the general operation of the xerographic system.

As shown in the figure, a developed image is transferred to a sheet of support material advanced into contact with the xerographic drum by electrostatic conveyor apparatus 10. Conveyor apparatus comprises a dielectric web supported at the ends thereof on a pair of rollers 34 and 36. Roller 34 is connected to a drive motor (not shown) to advance the Web in the same direction as xerographic surface 12. Web 30 is made from any suitable dielectric mate-rial, such as, Mylar, a polyethylene terephthalate resin available from E. I. du Pont de Nemours and Company.

A sheet of support material to receive the image from the drum is placed in contact with web 30 by insertion between roller 34 and an idler roller 44. Just beyond the point of contact between roller 34 and idler roller 44 is an electrostatic discharge member or corotron similar to those stationed around the xerographic drum. At this time, corotron 50 is energized to place a charge on the surface of support material 40 causing it to adhere electrostatically to the belt on a principle well known to those familiar with static electricity. Potentials ranging from 4000 to 8000 volts are suitable for web thicknesses ranging from about .003 to about .007 inch. The electrostatic attraction between support material 40 and web 30 causes the support material to be carried forward into contact with the drum surface.

The developed image on the drum surface is transferred to the sheet of support material by energizing corotron 22 as previously mentioned. The potential on corotron 22 ranges from about 4000 to 8000 volts and is the same polarity as corotron St). The powder image, which has a charge opposite to the corotron charge, is attracted to support material 40. It should be noted that corotron 50 is tilted at a slight angle. This is because if the charge preceded the transfer point, an arc would be produced between the web and the drum resulting in disruption of the image on the drum.

After the toner image has been transferred, support material 40 is advanced to a point adjacent roller 36 where it is separated from the web. The sharpness of the angle that the web makes with roller 36 and the natural rigidity of the support material combine to overcome the electrostatic attraction between the Web and the support material. Support material 40 is received between the nip of

rollers

56 and 58, the latter being a heated roller for fusing the image to the support material to render a permanent print.

Loose toner on the drum as Well as from the latent image itself, in the case of sheet misfecds, of support material is electrostatically deposited on the web. As a result the web is unsuitable for transporting support material at that location. The electrostatic force between toner and the web is so great as to make removal by ordinary cleaning mechanisms, such as a vacuum, wholly unsatisfactory.

In accordance with the instant invention, toner, as well as other dust, is removed from the web by a brush 62 which is mounted for rotation in a housing 63. Brush 62 is driven at a rate which ranges as high as 10 times the linear speed of the web by a drive motor (not shown) and is made from any suitable material which will not abrade or otherwise damage the web, such as, rabbit fur. Positioned opposite brush 62 is an electrically conductive backing member 65 which contacts the web moving relative thereto for a sufiicient time to momentarily interrupt or neutralize the electrostatic fields emananting on the web enabling brush 62 to wipe the toner from it. Conductive backing member 65 can be in the form of a plate, as shown, or a roller.

The flow of toner onto the brush may be controlled by electrically biasing conductive member 65. To accomplish this, a variable source of DC. potential 67 of the same polarity as the toner particles is connected to con- 4 ductive member 65. Toner is removed from brush62 by exerting a vacuum pull in the interior of housing 63 through an exhaust port 69.

After the belt has been cleaned, it is next passed through the nip of idlers 72 and 74. Roller 74 is connected to a variable D.C. source of potential 76 ranging from 0 to 3000 volts of a polarity opposite to that of

corotrons

22 and 50 to discharge any electrostatic fields remaining on the web.

It will be appreciated that with the web cleaned from toner particles and with no charge remaining thereon, it is ready for another cycle to advance another sheet of support material into contact with the xerographic surface to produce the desired number of copies.

Above is described a sheet transfer apparatus including an electrostatic conveyor to continuously feed support material into contact with the developed image on a Xerographic drum. Heretofore toner particles becoming electrostatically attracted to the conveyor were difficult to remove by conventional cleaning devices without deleteriously affecting the conveyor. Now with the inventive apparatus, albeit extraordinarily simple, it is possible to remove toner particles from the conveyor without incurring any damage thereto thereby readying the machine for another cycle in which high quality prints are produced.

While the invention has been described with reference to the structure disclosed herein, it is not confined to the details set forth and is intended to cover such modifications or changes as may come within the purposes of the improvements or scope of the following claims.

What is claimed is:

1. In an automatic copying machine in which a Xerographic member is moved past xerographic processing stations including a transfer station at which a powder image is electrostatically transferred from said xerographic member to support material transported on a dielectric web mounted for movement in a path contacting the surface of said xerographic member at the place of image transfer, characterized by an improved apparatus for removing charged powder electrostatically attracted to said web after transfer comprising a brush mounted for rotation positioned in the web path downstream from the place of image transfer, drive means to rotate the brush at a rate greatly exceeding the speed of the web, and

an electrically conductive member positioned in the web path opposite to said brush to neutralize momentarily the electrostatic fields on said web for a time sufiicient for the aforementioned powder to be removed from said web onto said brush.

2. Apparatus according to claim 1 wherein said brush is enclosed in a housing, an opening arranged in said housing, a source of vacuum in communication with said opening to exert a vacuum pull on the interior of said housing for removing powder from said brush.

3. Apparatus according to claim 2 wherein a variable source of DC. potential of a polarity opposite to the electrostatic fields on said web is connected to said conductive member to control the movement of charged powder onto said brush.

4. Apparatus according to claim 3 wherein said brush is constructed from rabbit fur.

References Cited UNITED STATES PATENTS 2,832,977 5/1958 Walkup et al. 151.5 2,920,987 1/1960 Landry et a1. 15-1.5 XR 2,990,278 6/1961 Carlson 118-637 X 3,239,863 3/1966 Gardner 151.5 3,357,325 12/1967 Eichorn et a1. 1.7

PETER FELDMAN, Primary Examiner.