Electrophotography – Control of electrophotography process – Having temperature or humidity detection
Reexamination Certificate
1999-11-23
2001-04-17
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Having temperature or humidity detection
C399S092000
Reexamination Certificate
active
06219497
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to apparatus and methods of reducing condensation in an image forming apparatus.
2. Description of Related Art
Various systems designed for transporting a copy sheet in a predetermined transfer path have a number of devices to advance and control movement of the sheet while it is advanced along the predetermined path within an image forming apparatus. Examples of such sheet control devices includes sheet grippers, baffles and sheet guides. Some of the sheet devices are fixed at various stationary locations adjacent a predetermined path. Consequently, the stationary sheet control devices act on the sheet as the sheet is transported past each stationary sheet control device. Some systems have multiple sheet control devices that move in and out of operative positions.
SUMMARY OF THE INVENTION
Copy sheet jamming often occurs near the upper turn of a post fuser portion of a transfer path due to moisture forming on the baffles and other sheet control devices of this portion of the transfer path. The moisture evaporates from the hot copy sheet as it passes through the fuser and along the post fuser transfer path. The hot moisture in the air then condenses on the surrounding cooler surfaces. Coated copy sheets, which are less able to absorb moisture and have smoother surfaces, have better contact with the condensed moisture on the baffles and can stall or generate contaminates in the transfer path. Ribs on the baffles have been added to reduce the contact area between the copy sheet and the baffles, which essentially minimizes the contact area and the chance of jamming of the copy sheet in the transfer path. Venting hot moist air near the fuser and along the transfer path will reduce the moisture condensation. Both venting holes for natural convection and ribs have been added to the baffles and tested. These two methods reduce the moisture condensation, but do not eliminate the jamming problems caused by moisture condensation.
One problem within the image forming apparatus is that the various temperatures of the individual components throughout the various regions of the image forming apparatus cause condensation to form within the image forming apparatus and on its various components. Condensation causes many problems within the image forming apparatus and to the copy sheets. First, condensing water on the individual components of the image forming apparatus can damage the parts. Second, the water that condenses on the members and copy sheets causes jams within the image forming apparatus. The condensation causes the copy sheets to stick to surfaces of the image forming apparatus and to other copy sheets within the printing apparatus. Additionally, when condensation forms on transfer guides and the transfer guides come in contact with a copy sheet, the drag coefficient rises dramatically, and can be up to five times higher than without condensation. The combination of condensation and the high drag causes sheet skew and/or sheet stall in the transfer path.
Conventionally, as described above, this condensation problem has been attacked by creating slots within the paper guide. However, this has not completely disposed of the condensation which has formed and has also caused the corners of the leading edge of the copy sheet to jam within the slots.
This invention provides systems and methods that reduce condensation and paper jamming that occurs within an image forming apparatus.
In various exemplary embodiments of the systems and methods of this invention, the critical baffle areas, such as the gate and others where the moist air can not be easily vented, are heated to reduce the moisture condensation at those particular areas
The temperatures of the copy sheets and baffles, the moisture evaporating from the copy sheets, and the moisture condensating from moist air to cold baffles along the post fuser transfer path have been considered by the inventors. At high copy sheet temperatures, for example, at the temperature of the copy sheets right after they leave the fuser, the copy sheets have a high rate of moisture evaporation. The rate of moisture evaporation decreases with time as the copy sheets move through the image forming apparatus. Different types of copy sheets, such as different types of paper, possess different moisture diffusion coefficients. The moisture diffusion coefficients and the temperature of the paper together control the amount and rate of moisture evaporation. The moisture condensation from moist air onto cooler surfaces depends on the moisture content in the air and the temperature of the surrounding cooler surfaces. The inventors have determined that the location and conditions of moisture condensation can be predicted. The moisture condensation is likely to occur shortly downstream of a high temperature region, such as after the fuser area, because of high moisture evaporation from the copy sheet.
In one exemplary embodiment of an image forming apparatus that can beneficially incorporate this invention, after an electrostatic latent image is recorded on a photoconductive member, the latent image is developed by bringing a developer material into contact with the photoconductive member. The toner particles are attracted to the latent image to form a developed image on the photoconductive member.
This developed image is subsequently transferred to a copy sheet. The copy sheet is then heated to permanently affix the toner particles of the developed image to the sheet. After exiting the fuser portion of the image forming apparatus, the copy sheet is relatively warm. The developed copy sheet is then received by a baffle that is much colder. This change in temperature between the warm copy sheet and the cold baffle causes high relative humidity and promotes the formation of water droplets formed from condensation. The condensation that is created occurs when the fuser heats the copy sheet and the moisture that develops from the copy sheet evaporates over time in the transfer guides and other components of the transfer path that follow the fuser portion. Thus, the relative humidity of the air between the transfer guides increases. Eventually, the dew point is reached in this area and condensation forms on the surface of the transfer guides and other various components of the transfer path.
This invention provides systems and methods for reducing condensation by drawing ambient heated air into the vacuum transport.
This invention separately provides an image forming apparatus that is less susceptible to humidity-related faults.
This invention separately provides an image forming apparatus in which condensation is less likely to form.
This invention separately provides an image forming apparatus that has improved air flow and/or humidity control in baffled and vacuum transport areas. In the systems and methods according to this invention, the blower motor of an image forming apparatus is turned on when an image forming apparatus is turned on.
These and other features and advantages of the systems and methods of this invention are described in or are apparent from the following detailed description of the various exemplary embodiments.
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Aurand Susan M.
Harney William M.
Hauman Dewey H.
Hwang Shyshung S.
Vetromile Joseph S.
Chen Sophia S.
Oliff & Berridg,e PLC
Xerox Corporation
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