Electrophotography – Image formation – Fixing
Reexamination Certificate
1998-11-20
2001-03-27
Royer, William (Department: 2852)
Electrophotography
Image formation
Fixing
C271S309000, C271S900000
Reexamination Certificate
active
06208827
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to a dual function air skive assembly for a fuser roller, and more particularly to an improved nozzle configuration for a dual function air skive which will substantially prevent damage to the roller and to the fused image on the receiver members stripped from the roller.
BACKGROUND OF THE INVENTION
In a typical commercial reproduction apparatus (electrostatographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member is then brought into contact with the dielectric member. An electric field, such as provided by a corona charger or an electrically biased roller, is applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is separated from the dielectric member and transported away from the dielectric member to a fuser apparatus at a downstream location. There the image is fixed to the receiver member by heat and/or pressure from the fuser apparatus to form a permanent reproduction thereon.
One type of fuser apparatus, utilized in typical reproduction apparatus, includes at least one heated roller and at least one pressure roller in nip relation with the heated roller. The fuser apparatus rollers are rotated to transport a receiver member, bearing a marking particle image, through the nip between the rollers. The pigmented marking particles of the transferred image on the surface of the receiver member soften and become tacky in the heat. Under the pressure, the softened tacky marking particles attach to each other and are partially imbibed into the interstices of the fibers at the surface of the receiver member. Accordingly, upon cooling, the marking particle image is permanently fixed to the receiver member. It sometimes happens that the marking particles stick to the peripheral surface of the heated roller and result in the receiver member adhering to such roller; or the marking particles may stick to the heated roller and subsequently transfer to the peripheral surface of the pressure roller resulting in the receiver member adhering to the pressure roller. Therefore, a skive mechanism, including mechanical skive fingers (or separator pawls), has been employed to engage the respective peripheral surfaces of the fuser apparatus rollers to strip any adhering receiver member from the rollers in order to substantially prevent receiver member jams in the fuser apparatus. Typically a fuser apparatus skive mechanism includes a plurality of skive fingers. The skive fingers are generally formed as elongated members respectively having a relatively sharp leading edge urged into engagement with a fuser apparatus roller. For example, the skive fingers may be thin, relatively flexible, metal shim stock. The respective leading edge of each of the skive fingers is directed, in the opposite direction to rotation of the fuser apparatus roller with which such skive finger is associated, so as to act like a chisel to strip any receiver member adhering to such roller from the peripheral surface thereof.
However, if the marking particle image is particularly heavy, the receiver member may adhere to a fuser apparatus roller with such force that engagement with the skive fingers does not completely strip the receiver member from the roller. When a receiver member transported through the fuser apparatus is only stripped from a roller by some of the skive fingers (and not by others), the receiver member will cause a jam in the fuser apparatus. This destroys the reproduction formed on the receiver member and shuts down the reproduction apparatus. Moreover, as the receiver member moves with the fuser apparatus roller to which it adheres, the stripped portions of the receiver member are forced into engagement with their associated skive fingers by the non-stripped portions of the receiver member. The engagement force of the receiver member on the skive fingers may be sufficient to flex those skive fingers so as to engage the associated peripheral surface of the fuser apparatus roller at a substantially increased attack angle. This increased attack angle may then damage the roller by gouging its peripheral surface or may damage the skive finger itself. Alternatively, as the receiver member is transported through the fuser apparatus, the receiver member may apply such force to the skive fingers on initial engagement therewith so as to cause such fingers to buckle in the direction which will flex those skive fingers to engage the associated fuser apparatus roller at an increased attack angle. Again, this increased attack angle may damage the roller by gouging its peripheral surface or may damage the skive finger itself.
In order to overcome the problems generated by mechanical skive fingers, another mechanism for stripping receiver members from the rollers of a fuser apparatus has been designed which includes air jets directed at the rollers to strip any adhering receiver member from the rollers (see for example U.S. Pat. No. 4,420,152, issued Dec. 13, 1983, in the name of Miyashita). It provides an air chamber with exhaust nozzles which direct escaping air at high speeds for separating receiver members from the fuser rollers. However such arrangement creates a high pressure area near the fusing nip and a low pressure area adjacent to the air skive. Thus after a receiver member is stripped from a fuser roller it is attracted to the skive structure. Since the skive structure is close to the fuser roller, it is at an elevated temperature. Accordingly, the hot skive structure may scratch the image on the receiver member or damage the receiver member itself.
In copending U.S. patent appliciation Ser. No. 09/197,737, a dual function air skive assembly for stripping a receiver member adhering to a fuser apparatus roller from the roller without damage has been proposed. The dual function air skive assembly includes an air plenum having a first nozzle to provide a positive air flow to strip a receiver member adhering to the roller therefrom, and a second nozzle arrangement to provide a positive air flow to cool a stripped receiver member and keep such receiver member from contacting the plenum. However, while such disclosed dual function air skive provides adequate operation with nominal receiver members, it does not necessarily handle the wide variety of receiver member types required by new reproduction apparatus.
SUMMARY OF THE INVENTION
In view of the above, this invention is directed to a fuser apparatus having a pair of rollers in nip relation to transport a receiver member therebetween to permanently fix a marking particle image to such receiver member, and a dual function air skive assembly for stripping a receiver member adhering to a fuser apparatus roller from the roller. The dual function air skive assembly includes a frame engageable with a roller of the pair of rollers of the fuser apparatus. An air plenum is supported by the frame in operative relation to the fuser roller nip. The air plenum has a first nozzle arrangement directed at an angle to the roller so as to provide a positive air flow to strip a receiver member adhering to the roller therefrom. The first nozzle arrangement has a plurality of nozzle heads respectively configured to provide a positive air flow having a substantially oval cross-section. A second nozzle arrangement is directed substantially normal to the first nozzle arrangement to provide a positive air flow to cool a stripped receiver member and keep such receiver member from contacting the plenum.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.
REFERENCES:
patent: 2950989 (1960-08-01), Freeman
patent: 3276425 (1966-10-01), Rabb
patent: 3600215 (1971-08-01), Mervine
patent: 3907280 (1975
Aslam Muhammed
MacLellan Bruce D.
Miura Tsutumu
Eastman Kodak Company
Kessler Lawrence P.
Moldafsky Greg
Royer William
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