Electrophotography – Image formation – Fixing
Reexamination Certificate
2000-12-13
2003-05-13
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Fixing
C399S091000
Reexamination Certificate
active
06564030
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to fuser stations for image-forming machines. More particularly, this invention relates to fuser stations having a vented skive assembly to reduce the condensation of water vapor in the fuser station.
BACKGROUND OF THE INVENTION
An image-forming machine transfers images onto paper or other medium. The image-forming machine usually includes a photoconductor, one or more chargers, an exposure machine, a toning station, a fuser station, and a cleaner. The image-forming machine also has an environmental system, which may be an air exchanger, fan, or similar device to pull or push air through the image-forming machine.
Generally, the photoconductor is selectively charged and optically exposed to form an electrostatic latent image on the surface. Toner is deposited onto the photoconductor surface. The toner is charged, thus adhering to the photoconductor surface in areas corresponding to the electrostatic latent image. The toner image is transferred onto a sheet of paper or other medium. In the fuser station, the sheet is heated causing the toner to fix or adhere to the paper or other medium. The photoconductor is refreshed, cleaned to remove residual toner and charge, and is then ready to make another image. The sheet exits the image-forming equipment.
FIG. 13
shows a side view of a typical fuser station for an image-forming machine according to the prior art. The fuser station has a fuser roller, a pressure roller, and upper and lower skive assemblies.
FIG. 14
is a perspective view of an upper skive assembly according to the prior art. The fuser and pressure rollers are disposed to form a nip or pinch region. The pressure roller rotates counterclockwise as indicated by the arrow A. The fuser roller rotates clockwise as indicated by arrow B. One or more heater rollers (not shown) heat the fuser roller. The pressure roller also may be heated. The upper and lower skive assemblies are disposed adjacent to the nip region to help remove and guide the sheet away from the pressure and fuser rollers. The upper skive assembly has finger portions that project toward the nip region.
The fuser station causes the toner to fix or adhere to the sheet. In this fixing process, a sheet of paper or other medium passes through the pressure and fuser rollers in the direction indicated by arrow C. As the sheet passes through the rollers, the constriction of the nip region presses the toner onto the surface of the sheet. At the same time, the fuser roller transfers heat to the sheet, causing the toner to fuse to the sheet. The rotation of the rollers pulls the sheet through the nip region.
The constriction and pressure of the rollers and the heating of the toner in the nip region may cause the sheet to stick or attach to the pressure roller. However, the leading edge of the sheet is guided between the upper and lower skive assemblies. If the sheet is stuck to the pressure roller, the finger portions of the upper skive assembly catch the leading edge of the sheet. The finger portions guide the leading edge between the upper and lower skive assemblies, thus pulling the sheet away from the pressure roller as the sheet moves out of the nip region.
The fixing process is usually done at about 355° F. At this temperature, water evaporates or is driven out of the sheet in the form of water vapor. The water vapor condenses in condensation zones on the surface of the upper skive assembly. The condensed water vapor forms droplets that trickle down the upper skive assembly. The droplets may fall onto a sheet as it passes under the upper skive assembly. The water droplets cause the sheet to swell and leave a deformed spot or track on the sheet. The result is a visual defect on the sheet.
The quantity of water vapor is highly dependent upon the moisture content of the paper. If the moisture content is less than about five percent by weight, there may be less condensation on the upper skive assembly. If the moisture content is more than about five percent by weight, there may be more condensation on the upper skive assembly. The amount of condensation also depends on the number of sheets in an image-forming job. Condensation may accumulate in an image-forming job having a large number of sheets even though the moisture content is low. While the first sheets may be clean, the later sheets may have water droplet defects.
There are several approaches to eliminate or minimize condensation on the upper skive assembly. The image-forming machine may be restricted to use only low moisture paper. However, it is impracticable if not impossible for a user of the image-forming machine to determine the moisture content of the paper or other medium immediately prior to use. The storage method and humidity often affect the moisture content, causing it to vary from time to time. Additionally, the moisture content of the paper or other medium may be reduced or lowered. However, the equipment and time required makes this approach impracticable. It also is impracticable for a user to limit the size of image-forming jobs.
The upper skive assembly or a nearby part may be maintained at a temperature high enough to eliminate the cold surfaces where condensation may occur. However, additional equipment is required such as heating elements or the like for upper skive assembly or the other part. The higher temperature also may expand or distort the upper skive assembly, causing the finger portions to project too far or unevenly into the nip region. Additionally, the energy required to heat the upper skive assembly or other part increases operating costs for the image-forming machine.
The fuser station also may have additional venting or increased airflow to remove water vapor before condensation occurs. The additional venting and increased airflow may require additional equipment such as a larger environmental system or fan. In addition, the configuration of the upper skive assembly may create “dead” zones where the air does not flow well. The water vapor may accumulate and condense in these dead zones rather than flow out of the fuser station.
Accordingly, there is a need for a fuser station in an image-forming machine that reduces the condensation of water vapor.
SUMMARY
This invention provides a fuser station with a vented skive assembly for an image-forming machine. The skive assembly has one or more slots that provide an airflow pattern to reduce condensation in the fuser station. The heat used during the fixing process in the image-forming machine may evaporate water from a sheet. The environmental system or other convective airflows in the image forming machine pass the water vapor through the one or more slots.
The image-forming machine may have a photoconductor, a primary charger, an exposure machine, a toning station, a transfer charger, and a vented fuser station. The primary charger electrostatically charges the photoconductor. The exposure machine optically exposes and forms an electrostatic image on the photoconductor. The toning station applies toner onto the photoconductor. The toner has a charge to adhere to the electrostatic image. The transfer charger transfers the toner from the photoconductor onto a sheet. The fuser station receives the sheet from the transfer charger and fuses the toner onto the sheet.
The fuser station may include a pressure roller, a fuser roller, and a skive assembly. The fuser roller forms a nip region with the pressure roller. The skive assembly catches the sheet as it advances out of the nip region in a sheet direction. The skive assembly has rib sections, which may project from the skive assembly toward the nip region. One or more finger portions may provide the rib sections. The skive assembly also may have a support member connected to the rib sections and the finger portions. The rib sections form one or more slots, which are configured to provide an airflow pattern that reduces condensation on the skive assembly. The skive assembly may have an insert protection device disposed in one or more of the slots. The insert protection device pr
Baughman Richard C.
Morganti Terry N.
Orchard, II James V.
Heidelberger Druckmaschinen AG
Pendegrass Joan
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