US3902845A

US3902845A - Metal foam under conformable surface replaceable

Info

Publication number: US3902845A
Application number: US430991A
Authority: US
Inventors: Richard J Murphy
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-12-26
Filing date: 1973-12-26
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02
Also published as: NL7415830A; JPS5099156A; CA1053319A; GB1484160A

Abstract

Fuser apparatus for affixing toner images to a substrate by means of heat and pressure. The apparatus is characterized by a heated fuser roll which is internally heated and has a reservoir of offset preventing material supported by a tubular member comprising the core or base of the fuser roll. A resilient, low surface energy layer of a lesser thickness than the reservoir is adhered thereto. The reservoir comprises a porous, thermally conductive member through which offset preventing material diffuses during operation of the apparatus. The offset preventing material also diffuses through the resilient layer and forms a thin coating on the surface thereof to form a boundary layer for preventing toner from offsetting to the resilient material.

Description

United States Patent Murphy Sept. 2, 1975 [54] METAL FOAM UNDER CONFORMABLE 3,452,181 6/1969 Stryjcwski 432/60 SURFACE REPLACEABLE 3,514,312 /1970 Gandiner 29/132 3.612.170 /1971 Juppet 100/93 RP Inventor: Richard J. Murphy, Webster. NY 3,731,358 5 1973 Artl 29/132 [73] Assignee: Xerox Corporation, Stamford,

Conn. Primary bxammer.lohn J. Camby Assistant Examiner-Henry C. Yuen [22] Filed: Dec. 26, 1973 21 Appl. No.: 430,991 ABSTRACT Fuser apparatus for affixing toner images to a sub- 52 us. c1. 432/- 29/132- 100/93 RP- rate by means of heat pressure The apparatus is 118/60 118/70 432/258 219/l69 219/385; characterized by a heated fuser roll which is internally Int. CL Bzlb 31/08 heated and has a reservoir of offset preventing mate- [58] Field 01525121......................IIIIIIIIII.43259-60, Suppmed by a tubular r. comprsmg Hz/227L228. 219/216 388 469. 100/93 core or base of the fuser roll. A res1l1ent, low surface l lie/6O 637 energy layer of a lesser thickness than the reservoir 15 adhered thereto. The reservoir comprises a porous, References Cited thermally conductive member through which offset preventing material diffuses during operation of the UNITED STATES PATENTS apparatus. The offset preventing material also diffuses 2,679,572 5/1954 Workman /93 RP through the resilient layer and forms a thin coating on M1110 1 the urface thereof to form a boundary layer for pre i f l 2 3 22 venting toner from offsetting to the resilient material. ser 0 a 3,437,032 4/1969 Manghirmalani et al 29/132 17 Claims, 3 Drawing Figures PATENTEDSEP' 2:915 3, 902 845 SHEET 1 UF 2 FIG. I 5

METAL FOAM UNDER CONFORMABLE SURFACE REPLACEABLE BACKGROUND OF THE INVENTION This invention relates generally to Electrostatography apparatus and, more particularly, to a contact fusing system for fixing electroscopic toner material to a support member.

In the process of Electrostatography an image of an original to be copied is typically recorded in the form of a latent electrostatic image upon a member with subsequent rendering of the latent image visible by the application of electroscopic marking particles, commonly referred to as toner. The visual image can be either fixed directly upon the member or transferred from the member to a sheet of plain paper or other suitable substrate with subsequent affixing of the image thereto.

In order to permanently affix or fuse electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This action causes the toner to be absorbed to some extent into the fibers of the support member which, in many instances, constitutes plain paper. Thereafter, as the toner material cools, solidification of the toner material occurs causing the toner material to be firmly bonded to the support member, In both the xerographic as well as the electrographic recording arts, the use of thermal energy for fixing toner images onto a support member is old and well known.

One approach to thermal fusing of electroscopic toner images onto a support has been to pass the support with the toner images thereon between a pair of opposed roller members, at least one of which is heated. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the heated roll to thereby effect heating of the toner images within the nip. By controlling the heat transferred to the toner, virtually no offset of the toner particles from the copy sheet to the fuser roll is experienced under normal conditions. This is because the heat applied to the surface of the roller is insufficient to raise the temperature of the surface of the roller above the hot offset" temperature of the toner whereat the toner particles in the image areas of the toner would liquify and cause a splitting action in the molten toner to thereby result in hot offset. Splitting occurs when the cohesive forces holding the viscous toner mass together is less than the adhesive forces tending to offset it to a contacting surface such as a fuser roll.

Occasionally, however, toner particles will be offset to the fuser roll by an insufficient application of heat to the surface thereof (i.e. cold offsetting); by imperfections in the properties of the surface of the roll; or by the toner particles insufficiently adhering to the copy sheet by the electrostatic forces which normally hold them there. In such a case, toner particles may be transferred to the surface of the fuser roll with subsequent transfer to the backup roll during periods of time when no copy paper is in the nip.

Moreover, toner particles can be picked up by the fuser and/or backup roll during fusing of duplex copies or simply from the surroundings of the reproducing apparatus.

One arrangement for minimizing the foregoing problems, particularly that which is commonly referred to as offsetting has been to provide a fuser roll with an outer surface or covering of polytetrafluoroethylene, commonly known as Teflon, to which a release agent such as silicone oil is applied, the thickness of the Teflon being on the order of several mils and the thickness of the oil being less than 1 micron. Silicone based oils, which possess a relatively low surface energy, have been found to be materials that are suitable for use in the heated fuser roll environment where Teflon constitutes the outer surface of the fuser roll. In practice, a thin layer of silicone oil is continuously maintained on the surface of the heated roll to thereby form an interface between the roll surface and the toner images carried on the support material.

In order to supply silicone oil for such purposes, an oil sump or reservoir and associated structures are provided internally of the recording or reproducing apparatus. In addition to increasing the cost of the overall apparatus, the oil applying means requires periodic maintenance. Moreover, it is undesirable too have quantities of oil contained in the apparatus due to the possibility of spillage.

Accordingly, it is the principle object of this invention to provide a new and improved contact fusing apparatus for fixing toner images to a substrate.

A more particular object of this invention is to provide a fuser roll structure having an integral reservoir of offset preventing liquid to thereby render unnecessary the need for structure separate from the fuser roll for applying offset preventing liquid thereto.

Another object of this invention is to provide a removable reservoir for a fusing member which can be replaced when the offset preventing liquid thereof has been depleted.

BRIEF SUMMARY OF THE INVENTION Briefly, the above-cited objects are accomplished by the provision of a contact fuser apparatus comprising nip forming roll structures one of which is internally heated in order to elevate the surface temperature thereof to a level necessary to soften toner material forming images on a substrate passed through the nip with the toner images contacting the heated roll structure.

The heated roll structure comprises a rigid, thermally conductive core having a heating element supported therein. In the preferred embodiment, as set forth hereinafter in greater detail, a sleeve fabricated by powdered metal techniques serves as a reservoir for offset preventing liquid and is removably supported by the core. A thin layer of elastomeric material, for example, silicone rubber is adhered to the sleeve which during operation of the fuser apparatus is coated with the offset preventing liquid by diffusion of the liquid from the reservoir through the thin layer of silicone rubber to thereby form a barrier between the rubber layer and the toner forming the images.

Other objects and advantages of the present invention will become apparent when read in conjunction with the accompanying drawings and detailed description of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of an electrostatic reproducing apparatus incorporating the present invention;

FIG. 2 is a pictoral front elevational view of a fuser apparatus representing the present invention; and

FIG. 3 is a cross-sectional view taken on the line 111- III of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, particularly FIG. 1,

reference character 9 designates a reproducing apparatus employing an image recording drum-like member 10 the outer periphery of which is coated with a suitable photoconductive material 11. One type of photoconductive material is disclosed in US. Pat. No. 2,970,906 issued to Bixby in 1961. The drum 10 is suitably journaled for rotation within a machine frame (not shown) by means of a shaft 12 and rotates in the direction indicated by arrow 13, to bring the image retaining surface thereon past a plurality of Xerographic processing stations. Suitable drive means (not shown) are provided to power and coordinate the motion of the various cooperating machine components whereby a faithful reproduction of the original input scene infor mation is recorded upon a sheet of final support material such as paper or the like.

Since the practice of xerography is well known in the art, the various processing stations for producing a copy of an original are herein represented in FIG. 1 as blocks A to E. Initially, the drum moves photoconductive surface 11 through a charging station A. At charging station A an electrostatic charge is placed uniformly over the photoconductive surface 11 of the drum 10 preparatory to imaging. The charging may be provided by a corona generating device of a type described in US. Pat. No. 2,836,725 issued to Vyverberg in 1958.

Thereafter, the drum 10 is rotated to exposure station B where the charged photoconductive surface 11 is exposed to a light image of the original input scene information, whereby the charge is selectively dissipated in the light exposed regions to record the original input scene in the form of a latent electrostatic image. A suitable exposure system may be of the type described in US Patent Application, Ser. No. 259,181 filed June 2, 1972 now US. Pat. No. 3,832,057.

After exposure, drum 10 rotates the electrostatic latent image recorded on the photoconductive surface 11 to development station C, wherein a conventional developer mix is applied to the photoconductive surface 11 of the drum 10 rendering the latent image visible. A suitable development station is disclosed in US. Patent Application Ser. No. 199,481 filed Nov. 17, 1971 now abandoned. This application describes a magnetic brush development system utilizing a magnetizable developer mix having carrier granules and toner comprising electrophotographic resin plus colorant from dyes or pigments. A developer mix is continually brought through a directional flux field to form a brush thereof. The electrostatic latent image recorded on photoconductive surface 11 is developed by bringing the brush of developer mix into contact therewith. The developed image on the photoconductive surface 11 is then brought into contact with a sheet of final support material 14 within a transfer station D and the toner image is transferred from the photoconductive surface 11 to the contacting side of the final support sheet 14. The final support material may be plain paper, gummed labels, transparencies such as Polycarbonate, Polysulfane and Mylar, etc., as desired.

After the toner image has been transferred to the sheet of final support material 14, the sheet with the image thereon is advanced to a suitable fuser assembly 15 which fuses the transfer powder image thereto. After the fusing process, the final support material 14 is advanced by a series of rolls 16 to a copy paper tray 17 for subsequent removal therefrom by a machine operator.

Although a preponderence of the toner powder is transferred to the final support material 14, invariably some residual toner remains on the photoconductive surface 11 after the transfer of the toner powder image to the final support material 14. The residual toner particles remaining on the photoconductive surface 11 after the transfer operation are removed from the drum 10 as it moves through cleaning station E. Here the residual toner particles are first brought under the influence of a cleaning corona generating device (not shown) adapted to neutralize the electrostatic charge remaining on the toner particles. The neutralized toner particles are then mechanically cleaned from the photoconductive surface 11 by conventional means as for example, the use of a resiliently biased knife blade as set forth in US. Pat. No. 3,660,863 issued to Gerbasi in 1972.

The sheets of final support material 14 processed in the automatic xerographic reproducing device may be stored in the machine within a removable paper cassette 18. A suitable paper cassette is set forth in US Patent Application Ser. No. 208,138 filed Dec. 15, 1971 now US. Pat. No. 3,767,187.

The copier can also have the capability of accepting and processing copying sheets of varying lengths. The length of the copy sheet, of course, being dictated by the size of the original input scene information recorded on the photoconductive surface 11. To this end, the paper cassette 18 is preferably provided with an adjustable feature whereby sheets of varying length and width can be conveniently accommodated therein.

In operation, the cassette 18 is filled with the stack of final support material 19 of pre-selected size and the cassette 18 is inserted into the machine by sliding along a baseplate (not shown) which guides the cassette 18 into operable relationship with a pair of feed rollers 20. When properly positioned in communication with the feed rollers 20 the top sheet of the stack 19 is separated and forwarded from the stack 19 into the transfer station D by means of registration rollers 21.

It is believed that the foregoing description is sufficient for purposes of present application to illustrate the general operation of an automatic xerographic copier which can embody the teachings of the present invention.

The fuser assembly 15 comprises a heated roll structure 31 including a cylindrical core or base member 32 having a conventional heating element 34 disposed internally thereof and extending substantially coextensive therewith. The core is fabricated from any suitable material capable of readily conducting heat picked up from the heating element 34. To this end, the core 32 preferably is fabricated from copper or a copper alloy which is overcoated with a thin layer of aluminum.

A porous layer 36 approximately 0.25 inch thick is supported by the core 32 and has affixed thereto a rela: tively thinner layer 38 (i.e. on the order of 4 mils thick) of deformable material. The layer 38 comprises an elastomeric material, for example, cured silicone rubber, however it will be appreciated by those skilled in the art that other materials may be employed, for example, fluorosilicone rubber or other heat resistant materials that have a low affinity for the types of toners employed in electrostatic recording processes and which are capable of diffusing offset preventing liquids therethrough.

The porous layer 36, in the preferred embodiment, comprises a removable sleeve impregnated with offset preventing material which is preferably a liquid at room temperature. Suitable offset preventing materials are silicone or silicone based oils having a viscosity on the order of 100 to l000cs. Accordingly, the sleeve forms a reservoir for the oil which during operation of the fusing apparatus will diffuse outwardly to the surface of the layer 38 to thereby provide a uniform coating thereon which acts as a barrier between the layer 38 and the toner materials being fused. While in the preferred embodiment the layer 36 comprises a porous sleeve which is removable, other structures may be employed, for example, a porous layer of aluminum or other suitable material could be flame sprayed onto the core 32.

The sleeve 36 is preferably fabricated by well known powdered or foamed metal techniques to thereby provide a reservoir having the desired porosity, for example, l030% by volume. Typical materials, for example, bronze, utilized for the fabrication of the sleeve are selected for their good thermal properties. The sleeve 34 may comprise a single member approximately inches in length or a plurality of smaller segments having a combined length of approximately 15 inches. 3

The core 32 has a circumferential flange 40 against which the sleeve 36 abuts when installed on the core. A threaded collar 42 disposed adjacent the other end of the core 32 serves to captivate the sleeve 36 thereby retaining it in its operative position. When in position the ends of the sleeve abut the collar 42 as well as the circumferential flange 40. This abuting relationship precludes flow of oil from the ends of the sleeve. Other methods of captivating the sleeve on the core 32 may be employed, for example a tongue and groove arrangement could be provided or conventional fasteners could be employed to fix or assist in fixing the position of the sleeve on the core.

The fuser assembly 15 further comprises a backup roll structure 44 which cooperates with the fuser roll structure 31 to form a nip 46 through which a copy paper or substrate 48 passes such that toner images 50 thereon contact the fuser roll structure. The backup roll structure may comprise any suitable construction. but preferably comprises a rigid steel core 52 having a layer 54 of silicone rubber thereover with a relatively thinner layer 56 of polytetrafluoroethylene carried thereby.

Means (not shown) for applying a loading force in a conventional manner to the fuser assembly 15 serves to create pressures on the order of 15 to 150 psi average thereby forming the nip 46. Also, means (not shown) are provided for separating the

rolls

32 and 44 during periods of inoperativeness and for effecting reengagement of the rolls during operative periods. Such means may comprise structures well known in the art or obvious in view of the known art.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in'the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention.

What is claimed is:

1. Apparatus including a fuser member for utilization in fixing toner images to a substrate by pressure and heat comprising:

a core;

a thermally conductive relatively non-deformable porous layer on said core, said porous layer forming a reservoir containing offset preventing liquid;

a deformable layer carried by said thermally conductive porous layer. said deformable layer comprising a material having a relatively low affinity for the toner forming said images;

said layers being capable of allowing passage of said offset preventing liquid therethrough to form a coating on said deformable layer for preventing offsetting of toner to said deformable layer.

2. Apparatus according to claim 1 wherein said porous layer comprises a removable sleeve structure.

3. Apparatus according to claim 2 wherein said porous sleeve comprises a powdered metal structure.

4. Apparatus according to claim 3 wherein said dcformable layer comprises cured silicone rubber.

5. Apparatus according to claim 4 wherein said offset preventing liquid comprises silicone oil.

6. Apparatus according to claim 5 including means for elevating the surface temperature of said deformable layer to provide sufficient heat for softening toner forming said toner images.

7. Apparatus according to claim 6 wherein said means for heating said deformable layer is supported internally of said core and said core is thermally conductive.

8. Apparatus according to claim 7 wherein said core comprises a rigid cylinder.

9. Apparatus according to claim 8 including a backup roll cooperating with said fuser member to form a nip therebetween through which said substrate passes with said toner images contacting said fuser member.

10. A fuser member adapted to be supported on a core member for use in fixing toner images by pressure and heat, said fuser member comprising:

a thermally conductive means having an outer surface and constituting a reservoir containing offset preventing material; and

a layer on said outer surface adapted to pass said offsetting preventing material therethrough to thereby form a toner barrier coating thereon, said layer having a relatively low affinity for toner.

11. A fuser member according to claim 10 wherein said layer comprises cured silicone rubber.

12. A fuser member according to claim 11 wherein said offset preventing material comprises silicone oil.

13. A fuser member according to claim 10, wherein said thermally conductive means comprises a generally cylindrical sleeve adapted to be supported by said core.

14. Means adapted to be supported on a based member for handling substrates having softened toner images thereon, said means comprising first means comprises a generally cylindrical sleeve adapted to be removably supported on said base member.

16. The structure according to claim 15 wherein said second means comprises a silicone rubber layer.

17. The structure according to claim 16 wherein said offset preventing liquid comprises silicone oil.

Claims

1. Apparatus including a fuser member for utilization in fixing toner images to a substrate by pressure and heat comprising: a core; a thermally conductive relatively non-deformable porous layer on said core, said porous layer forming a reservoir containing offset preventing liquid; a deformable layer carried by said thermally conductive porous layer, said deformable layer comprising a material having a relatively low affinity for the toner forming said images; said layers being capable of allowing passage of said offset preventing liquid therethrough to form a coating on said deformable layer for preventing offsetting of toner to said deformable layer.

4. Apparatus according to claim 3 wherein said deformable layer comprises cured silicone rubber.

8. Apparatus according to claim 7 wherein said core comprises a rigid cylinder.

10. A fuser member adapted to be supported on a core member for use in fixing toner images by pressure and heat, said fuser member comprising: a thermally conductive means having an outer surface and constituting a reservoir containing offset preventing material; and a layer on said outer surface adapted to pass said offsetting preventing material therethrough to thereby form a toner barrier coating thereon, said layer having a relatively low affinity for toner.

14. Means adapted to be supported on a based member for handling substrates having softened toner images thereon, said means comprising A first means having an outer surface forming a reservoir containing offset prevent liquid; a second means carried by said first means and forming an integral assembly therewith, said second means being adapted to pass said offset preventing liquid therethrough to thereby form a toner barrier coating thereon, said second means having a relatively low affinity for said toner.

15. The structure according to claim 14 wherein said first means comprises a generally cylindrical sleeve adapted to be removably supported on said base member.