Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
2002-02-13
2004-01-20
Brase, Sandra (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S124000
Reexamination Certificate
active
06681090
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention generally relates to electrophotographic printers (EPs). More particularly, it relates to those devices and procedures used to access print media (e.g., a sheet of paper) that becomes jammed in the fuser roller units of such EPs. Such jams have become more and more troublesome with current trends toward smaller and smaller EP footprints and shorter heights. These trends have placed a premium on the available space within such printers—especially in the area between their laser printers and fuser units.
EP fuser units usually have two rollers that rotate in pressured, rolling contact with each other. At least one of these two rollers is internally heated by an electrical heater element or a halogen tube. The nonheated roller, or so-called backup roller, is usually the powered roller. It is pressured against the heated roller in order to form a rolling, pressured interface through which print media passes in order to fuse a given toner image to a given sheet. Roller interface pressures between about 10 psi and about 100 psi are normally created between the heated roller and the backup roller.
Unfortunately, one or more sheets of print media sometimes become jammed in and around these fuser units. Consequently, the fuser area must be made accessible to human reach in order to clear such jams. This access is usually gained by doors or panels that are placed in the rear or sides of an EP housing. Access to the fuser area via the rear of such printers is, however, often hampered by the fact that such printers are placed against a wall in order to more fully utilize available work space. Such positioning (near a wall) of a large, heavy EP does not allow for easy access to its rear access door—and hence to its fuser area. Therefore, when a print media jam occurs in an EP unit whose rear is located near a wall, the entire EP unit must be moved in order to open a rear access door.
Once such access is gained, it is advantageous, if not necessary, that the fuser roller pressure on any jammed sheet(s) be relieved in order to facilitate hand removal of such sheet(s). If a jammed sheet is completely wrapped around a fuser roller, release of the fuser roller pressure may be mandatory. Known devices for releasing the pressure between two fuser rollers include providing the fuser roller mechanism with one or more human hand operated pressure release levers. These levers are generally located in the area exposed by opening a rear access door. Indeed, some fuser roller pressure release levers are activated by the act of opening such access doors. In any case, activation of these pressure release levers reduces the grip of the fuser rollers on jammed media and thereby facilitating its removal from a fuser. Use of access door actuated lever systems requires that the access door be reinforced in order to carry the extra load required to release and subsequently reset the fuser roller pressure via automatic actuation of release levers that mechanically cooperate with an access door. Such automatic roller pressure release systems also are mechanically complex and space consuming e.g., long and complex actuating levers are often employed.
Other jam clearing devices include mechanisms for freewheeling the fuser rollers in the process flow direction during jam conditions by automatically disengaging the fuser drive when print media becomes jammed in the fuser. Hand operated jam clearance knobs also have been used to turn the fuser rollers and thereby expel jammed sheets of media from a fuser unit without having to relieve the roller pressure.
Other EPs provide access to the fuser area via access doors in the sides of said printers. Unfortunately, this arrangement suffers from several drawbacks. For example, there is very little room for a human hand to move about in the narrow space between an EP's laser printer and its fuser unit when this space is accessed from the side. These conditions also lead to a tendency to pull on a jammed sheet from its side—and thereby tearing it. Such tearing sometimes leaves a sheet remnant jammed in the fuser. There is also a certain degree of danger associated with the fact that the cramped hand space that is exposed by side access doors is usually in close proximity to still hot heater rollers.
Jam clearing operations also are hindered by the fact that many EP users do not know how to carry out the approved fuser access and/or pressure release procedures. Other users may not have enough working space to readily turn the entire EP unit around in order to properly access a rear access door. Consequently, many user's first course of action in clearing a jam in the fuser area is to open the EP's toner cartridge loading/unloading door—which is usually located in the side of the EP housing—and thereby gaining relatively easy, but limited, access to one or more sheets of print media that are jammed in the fuser area. This course of action is often somewhat aided by the fact that, when an EP's toner cartridge is removed, the trailing edge of a jammed sheet of media is, to some degree, accessible to human reach. Again however, there is very little working room in the space between most EP's laser scanners and their fuser units. Moreover, because the fuser release levers are not necessarily releasable from the toner cartridge loading/unloading area, the fuser rollers may maintain their strong grip on one or more sheets of jammed print media. Under these circumstances, a user often tears off the rear end of a sheet that is jammed between the two, still pressured, fuser rollers. Additionally, when one or more sheets of print media is (are) partially wrapped around a fuser roller, or accordioned within the fuser unit, the leading edge(s) is (are) often not even visible from the toner cartridge side of the fuser. Here again, there also is some danger associated with touching a hot fuser unit when attempting to remove a sheet remnant that is wrapped around a fuser roller in general, and a still pressured fuser roller in particular.
If the rear end of a jammed sheet is torn off, the only remaining practical way of removing the remainder of that torn sheet is by opening its rear access door. Again, when the rear of the EP is near a wall, the entire EP will have to be turned about. After this moving operation is completed, the fuser pressure can be released and the jammed paper cleared. It is, however, also possible that sheet fragments created by tearing a sheet from the other side of the fuser cannot be seen and/or readily removed via the rear access door. In which case, either the printer must be sent to an outside repair facility, or a service agent must be sent to make extensive on-site repairs. Obviously, avoiding or minimizing these measures has great practical and economic value.
SUMMARY OF THE INVENTION
Applicant has found that a more effective print media jam clearance method is to expose the fuser roller area from above. This is done by removal of a toner cartridge that is generally located above the fuser region. In effect, the toner cartridge is removed via the top of the EP unit rather than via its side. Removal of the toner cartridge from the fuser area via the top of the EP allows wide ranging, two-handed, access to that region and thereby allowing jammed media to be more effectively extricated from the fuser area.
This method of clearing a media jam also involves action of a fuser roller pressure release mechanism. Such a pressure release mechanism is automatically deactuated by removal of the toner cartridge from the EP. That is to say removal of the toner cartridge automatically relieves the pressure between the fuser's two rollers. To this end, at least one of the fuser rollers is held in a pressure releasable journal in which a fuser roller axle rotates. Preferably, the drive roller (rather than the heater roller) is provided with such a pressure release journal. Conversely, reinsertion of the toner cartridge back into the EP causes the fuser roller pressure mechani
Brase Sandra
Hewlett--Packard Development Company, L.P.
LandOfFree
EP print media path actuated by insertion/removal of toner... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with EP print media path actuated by insertion/removal of toner..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and EP print media path actuated by insertion/removal of toner... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3249596