Fuser Roll Cleaning Apparatus

Abstract

Cleaning apparatus for a dry heated pressure fusing system in which a conformable roll having a sleeve made of a material selected from the group of fluorocarbon resins, silicone or fluorosilicones contacts the dry fuser roll and receives both paper contamination and toner offset to maintain clean copy sheets fixed by the fusing system. The paper contamination is electrostatically attracted to the cleaning roll by electrical charges as well as surface forces from the fuser roll. The toner offset wets or adheres to the sleeve. The contamination and toner offset are removed from the cleaning roll by a wiping member which may be non-tacky or tacky.

Description

This invention relates to an improved cleaning apparatus for use with heated pressure fusing system in an electrostatic reproduction system to produce high quality copies free of toner offset and contaminants.

It has been recognized that one of the preferred ways for fusing a powder image to a substrate is to bring the powder into direct contact with a hot surface, such as a heated roller. The roller surface may be dry, i.e., no application of a liquid release agent to the surface of that roller as described for example, in U.S. Pats. Nos. 3,498,596, 3,539,161 and 3,666,247. Alternatively, the fuser roll surface may be wetted with a release agent such as silicone oil as described in U.S. Pats. Nos. 3,268,351 and 3,256,002.

In the dry fusing system there is a tendency for the fuser roll to collect paper contamination and non-visual or minute toner particles which in turn cause a visual toner offset to build up on the fuser roll surface and be deposited on the copy sheets.

The present invention is an improved cleaning apparatus for cleaning dry fuser rolls to remove undesirable paper contaminants and non-visual as well as visual toner offset.

It is therefore the principle object of the present invention to improve heated pressure fusing roll devices.

It is a further object of the present invention to enable removal of paper contaminants and toner offset particles from a dry heated fuser roll.

It is a further object of the present invention to prevent toner offset from the surface of the fuser roll onto copy sheets.

It is a further object of the present invention to improve copy quality of copy sheets fused by dry pressure heated fuser systems.

These as well as other objects of the invention and further features thereof will be better understood upon reference to the following detailed description of the invention to be read in connection with the drawings wherein:

FIG. 1 illustrates schematically a xerographic reproducing apparatus incorporating a heated pressure fuser roll apparatus constructed in accordance with the present invention;

FIG. 2 is an enlarged portion of FIG. 1 illustrating details of the invention; and

FIG. 3 is a view similar to FIG. 2 illustrating an alternative embodiment.

Referring now to the drawings, there is shown in FIG. 1 a preferred embodiment of the subject invention in a suitable environment such as an automatic xerographic reproducing machine. The automatic xerographic reproducing machine includes a xerographic plate or surface 10 formed in the shape of a drum. The plate has a photoconductive layer or light receiving surface on a conductive backing, journaled in a frame to rotate in the direction indicated by the arrow. The rotation will cause the plate surface to sequentially pass a series of xerographic processing stations. For the purpose of the present disclosure the several xerographic processing stations in the path of movement of the plate surface may be described functionally as follows:

A charging station A, at which a uniform electrostatic charge is deposited on the photoconductive plate;

An exposure station B, at which light or a radiation pattern of copies to be reproduced onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copy to be reproduced;

A developing station C, at which xerographic developing material, including toner particles having an electrostatic charge opposite that of the latent electrostatic image, is cascaded over the latent electrostatic image to form a toner powder image in configuration of the copy being reproduced;

A transfer station D at which the toner powder image is electrostatically transferred from the plate surface to a transfer material or a support surface; and

A drum cleaning and discharge station E at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer and at which the plate is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The preceding description of the xerographic process is sufficient for an understanding of the instant invention. Further details may be had by reference to U.S. Pat. No. 3,578,859 filed July 3, 1969 and commonly assigned herewith.

At the fusing station F the fusing assembly 101 comprises a fuser roll 103 and pressure roll 105 through which the copy sheet to be fused is advanced through the nip formed by contact of the fuser roll and pressure roll. The copy sheet is stripped from the fuser roll 10 by stripper fingers 112. The fuser roll comprises a rotating member 130 having an elastic compressible coating 132 made of silicone rubber or any suitable heat resistant compressible material as described for example in the aforementioned patents. The rotating member may be internally heated by a heat source 134 as described in U.S. Pat. No. 3,666,247 or externally heated as described in U.S. Pats. Nos. 3,498,586 and 3,539,161. The pressure roll comprises a rotating member 140 which is covered with an elastic layer 142 or a slightly higher durometer and the fuser roll coating 132 as described in the aforementioned patents.

Referring specifically to FIG. 2 in accordance with the present invention a cleaning roll apparatus 201 is positioned to clean fuser roll 103 of paper contamination and non-visual as well as visual toner offset particles. Cleaning roll apparatus 201 includes a metal core member 203 which is blanketed in a cylindrical roll 205 made of a soft deformable material. Any suitable soft heat resistant material can be used, such as silicone rubber, Nomex or Dacron, trademarks of duPont Corporation, Wilmington, Del. A sleeve 207 covers cylinder 205. Sleeve 207 is made of a suitable material which attracts by surface forces paper contamination and toner offset. Typical materials are fluorocarbon resins including fluoro-ethylene propylene manufactured under the trademark of Teflon by duPont Corporation. The silicones and fluoro-silicones desirably are moisture flooded as, for example, General Electric RTV 112 and Dow Corning RTV 733.

It has been found that paper contamination on the fuser roll 103 is attracted to sleeve 207 due to an opposite charge generated on the surface. Initially, the fuser roll 103 drives pressure roll 105 generating static charges. When contamination builds up on the rolls the opposite charges occur so that the pressure roll is negative and the fuser roll is positive. When paper copy sheets enter the rolls, the nontoner area of the sheets is more positive than the toner area. As a result additional positive charge induced on the back of the copy sheet causes a decrease in the positive charge thereby increasing the negative charge. Any loose paper fibers and/or background toner particles which are normally negative are attracted by the fuser roll surface which is positively induced. The contamination and toner particles collect on the fuser roll surface and are transferred to the sleeve 207 by virtue of the negatively induced charge thereon. Also, the elastomeric characteristic of silicone rubber enables microconformability for positive transfer. The contamination and toner particles are removed from the sleeve 207 by a wiper pad 210 which is made of wool or synthetic fibers Nomexor Dacron. Pad 210 can be dry or slightly wet with silicone oil. The pad can be a loosely knitted surface to enable contamination to pass through freely or closely knitted to retain the contamination on its surface.

An alternative embodiment is shown in FIG. 3 in which pad 210 is replaced with a sticky roll 212 which is in the form of a heated toner coated roll made of soft material. The tackified toner serves to remove the contamination and toner offset from sleeve 207 continuously. Reference is made to U.S. Pat. No. 3,649,992 for a typical heated toner coated roll and which is commonly assigned with the instant application. Alternatively, the roll 212 may be made out of silicone putty when the sleeve material is a fluorocarbon resin.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

Claims

What is claimed is:

1. In a dry heated pressure fusing system for fusing toner images of an electrostatic copying machine in which a heated dry fuser roll and back-up roll define a contact arc to fuse toner images onto copy sheets, an improved cleaning apparatus to release degrading contaminants from the fuser roll surface comprising

a roller member positioned to contact a dry heated fuser roll surface,

said roller member having a rigid core wrapped in a soft conformable material which is covered by a sleeve portion made of a material selected from the group of fluorocarbon resins, silicones and fluorosilicones and combinations thereof whereby microconformability is attained for positive transfer of contamination, and

wiping means positioned to contact said sleeve portion to remove contamination from said sleeve portion

2. Apparatus according to claim 1 wherein said wiping means has a closely knitted surface made up of a material selected from the group of wool, synthetic fibers, or a combination thereof.

3. Apparatus according to claim 1 wherein said wiping means comprises a sticky roll member.

4. Apparatus according to claim 1 wherein said wiping means has a loosely knitted surface made up of a material selected from the group of wool, synthetic fibers, or a combination thereof.

5. Apparatus according to claim 1 wherein said wiping means is wetted with a silicone oil.

6. Apparatus according to claim 3 wherein said sticky roll member is made out of silicone putty where the sleeve portion is made of a fluorocarbon resin.

7. Apparatus according to claim 3 wherein said stocky roll member has a toner coating.