Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2000-10-20
2002-02-12
Royer, William J. (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S067000, C399S325000
Reexamination Certificate
active
06347197
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic imaging apparatus, and more particularly to a fuser oiling apparatus life detection system in an electrophotographic imaging apparatus.
2. Description of the Related Art
In the electrophotographic process commonly used in imaging apparatus such as laser printers, an electrostatic image is created upon a photosensitive member such as a roll or belt. Visible electroscopic marking particles, commonly referred to as toner, are applied to the electrostatic image on the photosensitive material. Thereafter, the toner is transferred to the desired media, which may include paper, transparency sheets or the like.
Until the toner is fixed by the application of heat, the toner image applied to the media is not permanent. During fixing, the toner is elevated in temperature sufficiently to cause constituents of the toner to become tacky, and flow into the pores or interstices between fibers of the media. Upon cooling, the toner again solidifies, causing the toner to adhere to the media. Pressure may be applied to enhance the flow of the toner, and thereby improve the subsequent bonding of the toner to the media.
An approach used commonly for thermally fixing the electroscopic toner images is to pass the media, with the toner image thereon, through a nip formed by opposed rolls, at least one of which is heated either internally or externally such that the roll surface is at an elevated temperature. The heated roll, referred to as a fuser roll, contacts the toner image, thereby heating the image within the nip. Under some operating conditions, the tackiness of the toner upon heating can cause the media to adhere to the fuser roll and/or may cause a build up of toner on the fuser roll. By controlling the heat transfer to the toner, transfer of toner to the fuser roll can be minimized. In a duplex imaging apparatus, wherein both sides of the media may be printed, toner transfer or media sticking problems may be enhanced. Further, toner may be transferred to the backing roll of the fuser roll couple, and transferred thereafter elsewhere in the apparatus. The presence of wayward toner particles in the imaging apparatus can degrade the quality of the printed sheets.
In fusers of the type described, it is known to employ an apparatus for applying a release fluid to the surface of the fuser roll. The release fluid creates a weak boundary between the heated roll and the toner, thereby substantially minimizing the offset of toner to the fuser roll, which occurs when the cohesive forces in the toner mass are less than the adhesive forces between the toner and the fuser roll. Silicone oils, having inherent temperature resistance and release properties suitable for the application, are commonly used as release fluids. Polydimethylsiloxane is a silicone oil that has been used for this purpose advantageously in the past.
Various methods and apparatuses have been used to supply oil to the fuser hot roll, including oil wicking systems, oil delivery rolls, and oil webs. Oil wicking systems include reservoir tanks of the desired release agent or oil, and a piece of fabric wick material having one end mounted in the reservoir and the other end spring biased against the hot roll. Oil from the reservoir is drawn through the fabric wick by capillary action, and is deposited against the roll surface. While a wicking system can be effective in supplying oil to the fuser roll, surface deposit of the oil on the roll can be inconsistent, and the replenishment or replacement of the oil and/or system can be difficult and messy.
A variety of oil delivery roll systems have been used in the past, and include a roll nipped against the hot fuser roll. The oil delivery roll may be either freely rotating against the fuser roll or driven against the roll through a gear train. Oil delivered to the surface of the oil delivery roll is deposited on the hot fuser roll as the rolls rotate against each other. Various structures have been used for providing oil to the surface of the oil delivery roll, including reservoirs at the center of the roll providing oil to the surface through small dispersal holes or via capillary action through the outer material. Felts or metering membranes may be used in the oil delivery roll to control the oil flow through the roll. Another style of such roll is referred to as a web wrapped roll, and includes high temperature paper or non-woven material saturated with oil, and wrapped around a metal core. In yet another type of oil delivery roll, the roll rotates in a vat or reservoir of release oil, picking up a coating of the oil or release agent, which is then, in turn applied to the fuser roll. It is also known to use a roll couple in applying the oil from the vat onto the fuser roll. A first pickup roll rotates in the oil contained in the vat and is nipped against an applicator roll. The applicator roll is nipped against the fuser roll. Oil picked up by the pickup roll is transferred to the applicator roll, and is subsequently transferred to the fuser roll. Arrangements of this type can suffer from similar problems of resupply and cleanliness as oil wicking systems.
Oil web systems include a supply spool of web material, generally being a fabric of one or more layers saturated with the desired oil. Non-woven fabrics of polyester and aramid fibers, such as Nomex® manufactured by DuPont, have been used satisfactorily in oil web systems in the past. A take-up spool is provided for receiving the used web. A web path, commonly including one or more guide rolls, extends from the supply spool to the take-up spool. A portion of the web path brings the web material into contact with the hot fuser roll, either by wrapping a portion of the web around the hot roll, or by utilizing a spring-biased idler roll to nip the web material against the hot roll. As the hot roll rotates against the web in contact therewith, oil is transferred from the web to the fuser roll. Periodically, a drive mechanism for the take-up spool activates, rotating the take-up spool and advancing web material from the supply spool to the take-up spool, thereby bringing a fresh section of web material into contact with the fuser roll.
Oil web systems can be used to deliver oil with good uniformity across the fuser roll surface. However, oil deposits on the hot roll are dependent on the amount of web brought in to contact with the hot roll over a given period of time. Simplified drive mechanisms are known, for driving the take-up spool at a consistent interval and for a consistent time. As spent material accumulates on the take-up spool, the diameter of the spool grows, and the length of material brought in to contact with the hot roll increases if the web is indexed, or advanced, for a set duration at constant intervals. However, it has been difficult to determine the precise remaining life of an oil web system. Sheet counters have been used with some success; however, sheet count alone is not a precise indicator of oil web advancement. Indexing the oil web is not always consistent, and the requirements for oil application and web advancement may vary widely for different media types being printed. Unless complex algorithms are used which take in to consideration the media type being printed, sheet count alone can be quite inaccurate of the remaining unused web length. If the oil web runs out, and inadequate lubrication is provided during a printing job, print quality can be adversely affected, and more critically, damage may occur to fuser components. As a result, a preventative maintenance program may involve changing the oil web after a specified sheet count, which may occur with remaining useful life of the web still available, thus being wasteful. Sheet count is also not useful if a web oil system is removed, and later re-installed in the same or another system. Unless a dedicated sheet counter is supplied on the oil web unit, the sheet count is not preserved with nor transported with the oil web unit.
What is needed is a life dete
Maul Michael David
Rush Edward Alan
Shuman David William
Lexmark International Inc.
McArdle, Jr. John J.
Royer William J.
Sanderson Michael T.
Talyor Todd T.
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