US3929094A

US3929094A - Roll fuser

Info

Publication number: US3929094A
Application number: US537881A
Authority: US
Inventors: Raghulinga R Thettu
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1975-01-02
Filing date: 1975-01-02
Publication date: 1975-12-30
Anticipated expiration: 1992-12-30

Abstract

A contact fuser assembly for use in an electrostatic reproducing apparatus including an internally heated metal core cooperating with a resilient backup roll to form a nip through which substrates carrying toner images are moved with the toner images contacting the metal core. The fuser assembly is characterized by the provision of a sump of release agent material which material coats the fuser roll structure. A polymer covered cleaning member immersed in a mini-sump containing some of the release agent material contacts the fuser roll structure for removing nonvisual toner and other contaminates offset thereto during the reproduction process. The mini-sump is removably disposed in a larger sump and serves to prevent contamination of the main sump.

Description

United States Patent [1 1 Thettu 1 1 ROLL FUSER [75] Inventor: Raghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: Jan. 2, 1975 211 Appl. No.2 537,881

[ Dec. 30, 1975 3,811,821 5/1974 Ariyama ct al. 118/60 Primary ExaminerMervin Stein Assistant ExaminerDouglas Salser 57 ABSTRACT A contact fuser assembly for use in an electrostatic reproducing apparatus including an internally heated metal core cooperating with a resilient backup roll to form a nip through which substrates carrying toner images are moved with the toner images contacting the metal core. The fuser assembly is characterized by the provision of a sump of release agent material which material coats the fuser roll structure. A polymer covered cleaning member immersed in a mini-sump containing some of the release agent material contacts the fuser roll structure for removing non-visual toner and other contaminates offset thereto during the reproduction process. Themini-sump is removably disposed in a larger sump and serves to prevent contamination of the main sump.

'-7 Claims, 1 Drawing Figure US. Patent Dec. 30, 1975 3,929,094

ROLL FUSER BACKGROUND OF THE INVENTION This invention relates generally to xerographic copying apparatus and, more particularly, to a contact fusing system and cleaning mechanism therefor for fixing electroscopic toner material to a support member.

In the process of xerography, a light image of an original to be copied is typically recorded in the form of a latent electrostatic image upon a photosensitive 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 photosensitive member or transferred from the member to a sheet of plain paper 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 internally 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 are less than the adhesive forces tending to offset it to a contacting surface such as a fuser roll.

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 problems attendant the foregoing, 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 applied to the surface of the heated roll to thereby form an interface between the roll surface and the toner images carried on the support material. Thus a low surface energy layer is presented to the toner as it passes through the fuser nip and thereby prevents toner from offsetting to the fuser roll surface. The foregoing notwithstanding, non-visual offsetting (i.e. offsetting of very fine particles of toner) does occur. In prior art constructions (fuser structures where the outer surface comprises Teflon or silicone rubber) such offsetting has been combated by the employment of various cleaning members, the wick material employed for applying the silicone based oil to the fuser roll serving this purpose.

However, it has been found that cleaning systems which are known to work with the aforementioned types of fuser roll surfaces are not acceptable for utilization with metal roll fusers.

Accordingly, the primary object of this invention is to provide a new and improved contact fuser system for fixing toner images to substrates.

A more particular object of this invention is to provide a fuser roll-cleaning structure for utilization with a metal roll fuser.

Another object of this invention is to provide a contact fuser system employing a metal fuser roll structure and a sump of release agent material wherein a cleaning memb'rfor said fuser roll structure is immersed in a mini-sump containing some of the release agent, the mini-sump being removable from a main sump and serving to prevent contamination of the main sump.

BRIEF OF THE INVENTION Briefly, the above-cited objects are accomplished by the provision of a contact fuser apparatus comprising a metal fuser roll structure cooperating with a resilient backup roll to form a nip through which substrates carrying toner images are passed with the toner images contacting the fuser roll structure.

A sump of release agent material, preferably polyethylene, is provided for coating the fuser roll structure to enhance the release of toner particles and other contaminates from the surface of the fuser roll structure. A polymer coated cleaning roll structure which is supported adjacent the fuser roll structure and rotated thereby is immersed in a mini-sump containing some of the polyethylene release agent material. The mini-sump is removably disposed in the main sump and prevents contamination thereof.

The cleaning roll is coated with a polymer which at the operating temperatures of the fuser apparatus is in a tacky state, in which condition, together with the aid of the release agent material is useful in cleaning toner and other contaminates from the fuser roll structure.

3 Other objects and advantages of the present invention will become apparent when read in conjunction with the accompanying drawing.

DESCRIPTION OF THE DRAWING The FIGURE is a side elevational view of a contact fuser representing the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Since the xerographic reproducing process is well known, a detailed description thereof is omitted. For those who would consider a description of the xerographic process necessary for a complete understanding of the present invention reference may be had to US. Pat. Nos. 3,718,116 and 3,745,972.

As shown in the FIGURE the present invention comprises a fuser assembly 15 including a heated roll structure 30 including a hollow cylinder or core 31 having a suitable heating element 32 disposed in the hollow portion thereof which is coextensive with the cylinder. The heating element 32 may comprise any suitable type heater for elevating the surface temperature of the cylinder to operational temperatures, therefore, 250400F. For example, it may be a quartz lamp. The cylinder or core 31 is fabricated from any suitable material capable of accomplishing the objects of the present invention. Typical materials are copper, anodized aluminum and alloys thereof, steel, stainless steel, nickel and alloys thereof, nickel plated copper and chrome plated copper. The resulting structure has an outside diameter on the order of 1.5 to 3.0 inches and has a length on the order of to inches. Power requirements for the foregoing are 500-2500 watts peak power with an average power of 300-2000 watts and 75-250 watts for standby.

The surface temperature of the fuser roll structure is controlled by contacting the surface thereof with a thermistor probe 45 in a manner described in US. Pat. No. 3,327,096, issued in 1967 to Bernous and incorporated herein by reference.

The fuser assembly 15 further comprises a backup roll structure 33 which cooperates with the fuser roll structure to form a nip 34 through which a copy paper or substrate 35 passes such that toner images 36 thereon contact the fuser roll structure. The backup roll structure may comprise any suitable construction, for example, a steel cylinder, but preferably comprise a rigid steel core 37 having a Viton elastomer surface or layer 38 thereon. A suitable roll has a core approximately 1.8 inches in diameter with a 0.1 inch cover or layer structure of Viton elastomer or other suitable high temperature elastomeric layer structure, for example, silicone rubber and a combination of Viton or silicone rubber with Teflon thereon. Viton is a trademark of the E. I. duPont de Nemours and Company. The specific dimensions of the members making up the backup roll will be dictated by the requirements of the particular copying apparatus wherein the fuser assembly 15 is employed, the dimensions being greater or less depending upon the process speed of the machine. The heated roll and backup roll structures may be mounted on fixed axes, therefore not requiring movement in and out of engagement or they may be mounted in accordance with prior art devices wherein the backup roll is moved into and out of engagement with the fuser roll structure.

Means (not shown) for applying a loading force in a conventional manner to the fuser assembly 15 serves to create nip pressures on the order of 15 to 150 psi average. The durometer of the backup roll is chosen such that dwell times of 5 to milliseconds can be obtained with loading forces within the aforementioned range of pressures. Dwell time is proportional to the ratio of the nip length to the surface speed of the rolls. For a given angular velocity the surface speeds will vary depending upon the diameter of the rolls. For example, with a 2 inch fuser roll, speeds of 0 to 30 inches per second are attainable and for a 3 inch fuser roll, speeds of O to 45 inches per second have been attained. Accordingly, it can be seen that the aforementioned dwell times can be obtained by varying one or the other or both of the dwell time relationships. Durometers of 20-90 Shore A have been found to provide satisfactory results.

The aforementioned materials from which the fuser roll structure 30 may be fabricated are relatively high surface energy materials, consequently, hot toner material contacting such surfaces would readily wet the surface of the fuser roll. Accordingly, there is provided a main sump 39 for containing release material 40 capable of interacting with the fuser roll. The release material is preferably a low molecular weight material which is solid at room temperature and which has a relatively low viscosity at the operating temperatures of the fuser roll structure. An example of such a material is polyethylene hopolymer manufactured by Allied Chemical Co. and having the designation AC-8 hopolymer. A resistance heater 38 which may be of the brush-on film type is provided for melting the polyethylene.

A metering blade 41 preferably of silicone rubber is mounted to the sump 39 by conventional means such that an edge 42 thereof contacts the fuser roll structure serving to meter the release agent 40 in its liquid state onto the fuser roll. In the preferred embodiment, a blade 0.060 inch thick and having a width of 1.0 inch and length of 15 inches has been employed. By means of such a construction a 0.1-0.5 micron thickness of release agent is applied to the surface of the fuser roll.

A pair of end seals 47, preferably of sponge rubber are provided to contain a release agent material in the sump 39. One or more stripper fingers 50 are provided for insuring removal of the substrate from the fuser roll.

Although the interaction of the polyethylene material with the surface of the fuser roll structure is not well understood, it is believed that a thermal degradation of the polyethylene takes place to form a by-product of carboxylic acid which chemically reacts with the surface of the fuser roll structure. It has been noted that where the polyethylene and the fuser roll surface form a boundary layer with the ambient air, beading of the surface of the fuser roll structure takes place along such boundary. Accordingly, a wiper blade 60 is supported adjacent to the sump 39 in any suitable manner such that it contacts the core 31 to form a wiper blade/- polyethylene/air boundary 62 and thereby prevent the formation of a core/polyethylene/air boundary which would result in the aforementioned formation of a bead on the core which would print out on the copy sheets 14 and also disrupt proper operation of the combination seal and metering blade 41. The wiper blade 60 is preferably fabricated from a material which is compatible with the polyethylene (i.e. does not chemically react therewith and to a lesser degree is dimensionally stable in the presence thereof). To this end, the wiper blade comprises an elastomeric material, for example, silicone rubber.

In accordance with the objects of the present invention, a cleaning roll structure 64 is positioned to clean the fuser roll structure 30 of paper contamination and non-visual offset as well as visual toner offset particles. The cleaning roll structure comprises a metal core member 66 which is covered by a cylindrical sleeve member 68 made of polyester polymer material. Any suitable polyester polymer material having a melting or softening point ranging from about 120 to about 275C can be employed. Typical materials are aliphatic, aromatic or mixtures of aliphatic, aromatic polyesters. Examples of these classes of materials are polyethylene oxolate, poly-pp xylelene terephthalate, polyethylene/neopentyl terephthalate. Preferred materials of the mixed class of polyesters are PE-IOO or PE-ZOO, trademarks of Goodyear Company, of Akron, Ohio. The sleeve member 68 has a thickness of about 0.005 to about 0.030 inches. The sleeve member may be applied to the metal core member 66 by any suitable technique such as solvent spraying, extrusion wrapping, hot melt rolling or combinations thereof. Preferably the final application is by heat shrinking the extruded polyester tube over the core member. Desirably, hot rolling is applied during the heat shrinking process.

It has been found that paper contamination on the fuser roll structure 30 is physically attracted to the sleeve 68 due to good adhesion at high temperature. The viscosity of the polyester material is such that it has high elongation at the operating temperatures coupled with excellent wetting properties.

Any loose paper fiber and/or background toner particles attracted by the fuser roll surface collect thereon and transfer to the sleeve member 68 by virtue of the physical adhesion of the contamination to the polyester polymer material. As can be observed from the FIG- URE of the drawing, the cleaning roll member 64 is immersed in the polyethylene release agent material. it has been found that the adhesion action of the polymer material along with the action of the polyethylene release agent material effectively removes the toner material and other contaminates from the fuser roll structure. However, the cooperative action is not understood. Cleaning of metal fuser rolls was attempted with a cleaning member such as the roll member 64 which was not immersed in the release agent. The foregoing yielded unacceptable results.

The cleaning roll member 64 is disposed in a minisump structure 70 which is removably disposed in a conventional means (not shown) within the volume delineated by the main sump 39. It will be appreciated 6 that contaminates removed from the fuser roll structure 30 will accumulate in the release agent material contained in the mini-sump and will, therefore, minimize the contamination of the main sump. Accordingly, the release agent material which is utilized for coating the fuser roll structure 30 and supplied from the main sump 39 is highly effective for its intended purpose since it is substantially free of deleterious contaminates.

While the invention has been shown and described in conjunction with the preferred embodiment thereof, it will be understood that various modifications thereto may be made by those skilled in the art without departing from the spirit of the invention and such modifications are intended to be covered by the claims appended hereto.

What is claimed is:

l. Fuser apparatus for fixing toner images to support members, said apparatus comprising:

a heated metal fuser member;

a resilient member cooperating with said metal fuser member to form a nip through which said support members pass in order to soften said toner images;

a first sump containing release agent material to .be

coated on said metal fuser member;

a second sump smaller in size than said first sump and disposed within an area delineated by said first sump, said second sump also containing release agent material; and

means for cleaning toner particles from said fuser members, said cleaning member being disposed in said second sump whereby the toner particles removed from said fuser member are prevented from contaminating the release agent material contained in said first sump.

2. Apparatus according to claim 1, wherein said second sump is removably disposed within said area.

3. Apparatus according to claim 2, wherein said cleaning member comprises a polymer material on the surface thereof that is tacky at the operating temperature of the fuser apparatus.

4. Apparatus according to claim 3, wherein said release agent material comprises polyethylene.

5. Apparatus according to claim 4, wherein said fuser member is internally heated and said support member moves through said nip with said toner images contacting said fuser member.

6. Apparatus according to claim 5, wherein said members comprise roll structures.

7. Apparatus according to claim 6, wherein said fuser member comprises a copper outer surface.

i l l l l

Claims

1. Fuser apparatus for fixing toner images to support members, said apparatus comprising: a heated metal fuser member; a resilient member cooperating with said metal fuser member to form a nip through which said support members pass in order to soften said toner images; a first sump containing release agent material to be coated on said metal fuser member; a second sump smaller in size than said first sump and disposed within an area delineated by said first sump, said second sump also containing release agent material; and means for cleaning toner particles from said fuser members, said cleaning member being disposed in said second sump whereby the toner particles removed from said fuser member are prevented from contaminating the release agent material contained in said first sump.