Patent Application
20070206981
The present disclosure relates to an electrostatographic reproducing machine and, more particularly, to such a machine including a fusing apparatus having a sheet centering stripper assembly.
One type of electrostatographic reproducing machine is a xerographic copier or printer. In a typical xerographic copier or printer, a photoreceptor surface, for example that of a drum, is generally arranged to move in an endless path through the various processing stations of the xerographic process. As in most xerographic machines, a light image of an original document is projected or scanned onto a uniformly charged surface of a photoreceptor to form an electrostatic latent image thereon. Thereafter, the latent image is developed with an oppositely charged powdered developing material called toner to form a toner image corresponding to the latent image on the photoreceptor surface. When the photoreceptor surface is reusable, the toner image is then electrostatically transferred to a recording medium, such as paper, and the surface of the photoreceptor is cleaned and prepared to be used once again for the reproduction of a copy of an original. The paper with the powdered toner thereon in imagewise configuration is separated from the photoreceptor and moved through a fuser apparatus to permanently fix or fuse the toner image to the paper.
One approach to fixing, or “fusing,” the toner image is applying heat and pressure by passing the copy sheet carrying the unfused toner image between a pair of opposed roller members of a fusing apparatus, at least one of the rollers is heated. During this procedure, the temperature of the toner material is elevated to a temperature at which the toner material coalesces and becomes tacky. This heating causes the toner to flow to some extent into the fibers or pores of the sheet. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to become bonded to the sheet.
After the fusing step, the sheet carrying the fused image is stripped from the fusing member and then fed to a subsequent processing station, such as an inverter, collator, stapler, or booklet maker. Sheets or media exiting the fuser or fusing station usually are charged with static electricity, and in addition the just fused images contain toner that is still in a malleable condition.
Despite these conditions, prior art stripper finger assemblies typically involve solid rigid fingers that either slide away from the fuser surface or include expensive articulating assemblies for attempting to achieve similar results.
Examples of fusing apparatus including such prior art stripper finger assemblies are disclosed in the following references. U.S. Pat. No. 6,293,545 issued Sep. 25, 2001 and entitled “Stripper blade assembly” discloses a stripper blade assembly for an ink jet offset printer that has a thin blade fixedly mounted on a top surface of a blade holder. The blade holder includes at a trailing edge flexible eyelet portions that extend downwards to snap over protuberances on mechanical connectors overmolded onto a rotatable shaft in order to secure the blade holder to the shaft. The thin blade engages the surface of an offset drum of the ink jet offset printer along the width of the drum at an appropriate point in the print process to strip the leading edge of a print medium from the offset drum surface, minimizing damage to the offset drum surface and to the printed image on the print medium while also minimizing the risk of a jam.
U.S. Pat. No. 4,929,983 issued May 29, 1990 and entitled “Stripper mechanism” discloses a stripper for separating a printed substrate from a fuser member in an electrostatographic printing machine that has a substantially flat, thin, resiliently flexible finger-like member having a raised dimple-like bump adjacent one end of the finger-like member for contacting the printed substrate when stripped from the fuser member, the finger-like member being coated on both sides with a smooth low surface energy film.
U.S. Pat. No. 4,806,985 issued Feb. 21, 1989 and entitled “Stripper fingers” discloses a sheet stripping device for electrostatographic systems that includes a frame, a member having movable surface for conveying a receiving sheet, and a sheet stripping element for separating the receiving sheet from the movable surface, the sheet stripping element including a stripping element having a leading edge adapted to contact the movable surface and strip the sheet from the movable surface, the leading edge coated with a material including an electrically conductive material comprising a film forming polymer and an electrically conductive additive. The leading edge may include a thermally resistant polymer of cross-linked siloxane-silica hybrid material, a polyimide or a poly(amide-imide). The sheet stripping means may be prepared by coating the leading edges of preformed stripping elements.
U.S. Pat. No. 4,527,509 issued Jul. 9, 1985 and entitled “Dielectric film processor” discloses a processor that is designed to develop imaged film in sheet or roll form, using a leaderless system employing edge guiding of the film. In this design the exposed film is transported in such a manner that no physical contact is made with the image area by any part of the processor until the image has been fused onto the film. The toned and fused image is permanent and smudge proof. The processor, as it is designed, has the capability of using different toners, adjusting film speed to meet toning and fusing requirements, changing fusing temperature depending on the toner at a given film speed, and adjusting the action of the air knife to improve its capability of the toned image prior to fusing. The processor is compact and lightweight, and the design gives due consideration to the health and safety of the operator. An important feature is the toner tray, which has multiple inlets for toner with a central discharge to protect the film that is being processed from scratching.
A conventional form of air sheet stripping assist system has already been introduced in the Xerox corporation iGEN3 and the DocuFamily of products image producing machines (iGEN3 and the Docu are trademarks of Xerox corporation). This conventional air stripping system includes several strategically placed air nozzles that have small individual holes or orifices for producing jets of pressurized air to assist the sheet or media in stripping off the roll/belt. Air knifes that incorporate individual holes to strip media off a roll/belt have been found to cause and show image defects in the locations where the individual air jets initially hit or contact the roll/belt. This is due to minute time differences in releasing the media between locations directly in line with the air holes and locations away or adjacent the hole, that is, locations where no direct air jet is present. This minute difference in time typically manifests itself as a gloss defect.
In accordance to the present disclosure, there is provided a sheet centering stripping assembly for stripping a fused sheet exiting a fusing nip having a still malleable toner image thereon. The sheet centering stripping assembly includes (a) a first air knife device for directing a first flat stream of pressurized air at a first force and a first pressure, the first flat stream of pressurized air adapted to contact a first side of the fused sheet exiting the fusing nip; and (b) a second air knife device for directing a second flat stream of pressurized air at a second force and a second pressure, the second flat stream of pressurized air adapted to contact a second and opposite side of the fused sheet exiting the fusing nip. The pressure balance between the first flat stream and second flat stream acts to prevent smudging of the malleable toner image, and to minimize curling of such fused sheet.
Referring first to
Initially, a portion of the photoconductive belt surface passes through charging station AA. At charging station AA, a corona-generating device indicated generally by the reference numeral 22 charges the photoconductive belt 10 to a relatively high, substantially uniform potential.
As also shown the reproduction machine 8 includes a controller or electronic control subsystem (ESS) 29 that is preferably a self-contained, dedicated minicomputer having a central processor unit (CPU), electronic storage, and a display or user interface (UI). The ESS 29, with the help of sensors and connections, can read, capture, prepare and process image data and machine status information.
Still referring to
ROS 30 includes a laser with rotating polygon mirror blocks. At exposure station BB, the ROS 30 illuminates the charged portion on the surface of photoconductive belt 10. The ROS will expose the photoconductive belt 10 to record an electrostatic latent image thereon corresponding to the continuous tone image received from ESS 29. As an alternative, ROS 30 may employ a linear array of light emitting diodes (LEDs) arranged to illuminate the charged portion of photoconductive belt 10 on a raster-by-raster basis.
After the electrostatic latent image has been recorded on photoconductive surface 12, belt 10 advances the latent image through development stations CC containing the first color toner. Successive imaging stations and developer units containing other color toners, in the form of dry particles. At each developer unit the toner particles are appropriately attracted electrostatically to the latent image using commonly known techniques.
With continued reference to
Referencing
Referring to
After sheets separate from photoconductive surface 12 of belt 10, residual toner/developer and paper fiber particles remaining adhered to photoconductive surface 12 are removed from surface 12 by a cleaning apparatus 150 at cleaning station EE.
Referring now to
Referring to
As illustrated in detail in
The pneumatic means 220 also includes air stream regulating means 240 for regulating aspects such as volume, pressure, direction of the pressurized air 222. The regulating means 240 is controlled for producing laminar flow of first flat stream 210. The regulating means 240 is controlled for producing laminar flow of the second flat stream 212. The sheet centering stripping assembly 200 may further include an ionizing device 250 for ionizing the pressurized air 222 in order to neutralize static build-up on the fused sheet 48. The sheet centering stripping assembly 200 may further include an air temperature controlling device 60 for cooling or heating the pressurized ionized air to a desired temperature.
To recapitulate, the sheet centering stripping assembly 200 includes the uniform air slit SL1, SL2 (over the entire span being equivalent to the media width. The uniform air supply provides for laminar flow and a uniform rate of media removal from the fuser members 72, 74. By using a uniform laminar air flow over the entire sheet width, there are no minute time release differences, and hence less likely to produce stripping related thermal defects since the laminar, uniform air stream 206, 208 remove the sheet as uniformly as possible. The incorporation of the second air knife; located on the underside of the media or sheet, equalizes air pressure on both sides of the sheet, balancing and keeping the media centered in the exit geometry of the post fusing nip region.
Additionally, in order to eliminate the static charge condition on the sheet 48 exiting the fusing nip; sheet centering stripping assembly 200 includes the ionizing device 250 for ionizing the pressurized air 222, to eliminate static electric charges on the sheet. When such ionized air comes in contact with static electric charges of an opposite polarity, those charges are neutralized. The sheet centering stripping assembly 200 thus provides a multiple solutions, (1) effectively addresses the static charge problem, (2) reduces the likelihood of image defects from the malleable toners exiting the fusing nip, and (3) a uniform exit path for media handling.
As can be seen, there has been provided a sheet centering stripping assembly for stripping a fused sheet exiting a fusing nip having a still malleable toner image thereon. The sheet centering stripping assembly includes (a) a first air knife device for directing a first flat stream of pressurized ionized air at a first force and a first pressure, the first flat stream of pressurized ionized air oriented to contact a first side of the fused sheet exiting the fusing nip; and (b) a second air knife device for directing a second flat stream of pressurized ionized air at a second force and a second pressure, the second flat stream of pressurized ionized air oriented to contact a second and opposite side of the fused sheet exiting the fusing nip, thereby preventing smudging of the malleable toner image, and minimizing curling of such fused sheet while improving sheet exit delivery.
It will be appreciated that various adaptations of the above-disclosed and other features and functions of this embodiment, or alternatives thereof, may be desirably combined into other different systems or applications. Therefore, unless specifically defined in a specific claim itself, steps or components of the invention should not be implied or imported from any above example as limitations to any particular order, number, position, size, shape, angle, color, or material. Additionally, it be appreciated that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims:
