Patent Application
20070071512
The present invention relates to electrostatographic reproduction machines, and in particular to such a machine including a fuser assembly having a non-gouging sheet stripper assembly for stripping copy sheets from the fuser assembly.
In electrostatographic reproduction machines commonly in use today, a charge-retentive member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the charge-retentive surface in exposed or background areas and creates an electrostatic latent image on the member that corresponds to the image areas contained within the original document.
Subsequently, the electrostatic latent image on the charge-retentive surface is made visible by developing the image with developing powder referred to in the art as toner. Most development systems employ a developer material that comprises both charged carrier particles and charged toner particles that triboelectrically adhere to the carrier particles. During development the toner particles are attracted from the carrier particles by the charge pattern of the image areas on the charge-retentive area to form a powder image on the photoconductive area. This image is subsequently transferred to a support surface, such as copy paper, to that it is permanently affixed by heating or by the application of pressure at a fusing apparatus. Following transfer of the toner image to a support surface, the charge-retentive member is cleaned of any residual toner that may remain thereon in preparation for the next imaging cycle.
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 internally heated. During this procedure, the temperature of the toner material is elevated to a temperature at that 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. 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. 4,929,983 issued May 29, 1990 and entitled “Stripper mechanism” discloses a stripper for separating a print substrate from a fusing member in an electrostatographic printing machine 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 print substrate when stripped from the fusing member, the finger-like member being coated on both sides with a smooth low surface energy film.
U.S. Pat. No. 5,160,130 issued Nov. 3, 1992 and entitled “Thin-tip stripper finger for use with a fuser roll in an electrostatographic apparatus” discloses a stripper finger separates a substrate from a fusing member in an electrostatographic reproduction machines. The stripper finger is a member defining an edge in the form of a symmetrical convex arc across the width of the member. The thickness of the member decreases from a chord through the convex arc perpendicular to the axis of symmetry of the arc, to the edge.
U.S. Pat. No. 6,785,503 issued Aug. 31, 2004 and entitled “Stripper fingers and roller assembly for a fuser in a electrostatographic reproduction machines” discloses stripper fingers that remove the print sheet from a fuser roll in a fuser for xerographic printing. The stripper finger having a tip for stripping a lead edge of a sheet from the fuser roll. A roller assembly, positioned adjacent to the stripper finger; for engaging the lead edge of a sheet and lifting the sheet from further contact with the tip after the tip of the stripper finger strips the lead edge of the sheet from the fuser roll. The roller assembly is removably mounted by using a snap-on mounting structure.
Unfortunately, conventional stripper fingers such as those disclosed herein have a tendency to gouge the surface of the fusing member particularly during an accordion-type jam of a copy coming from the fuser assembly nip. Such gouging undesirably results in subsequent fused images having portions with gloss differentials and marks, and in premature fusing member wear.
In accordance with the present disclosure, there has been provided a non-gouging sheet stripper assembly for stripping copy sheets from a surface of a moving fusing member. The non-gouging sheet stripper assembly includes (a) at least one baffle forming part of a sheet path; (b) a flexible finger shaft having a first end attached to the at least one baffle and a second distal end for forming a sheet directing first angle with the surface of the moving fusing member; and (c) a finger tip located at the second distal end of the finger shaft and having a contour for forming a sheet stripping second angle, that is different from the sheet directing first angle with the surface of the moving fusing member.
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. Preferably a nine-facet polygon is used. At exposure station BB, the ROS 30 illuminates the charged portion on the surface of photoconductive belt 10 at a resolution of about 300 or more pixels per inch. 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, that include four developer units as shown, containing CMYK 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
Fusing station FF includes a fuser assembly of the present disclosure that is indicated generally by the reference numeral 70 for fusing and permanently affixing the transferred toner powder image 213 to the copy sheet 204. Preferably, fuser assembly 70 includes a heated fuser roller 72 and a pressure roller 74 with the powder image 213 on the copy sheet 204 contacting fuser roller 72. The pressure roller 74 is loaded against the fuser roller 72 forming a fusing nip 75 for providing the necessary pressure to fix the heated toner powder image 213 to the copy sheet. The fuser roll 72 for example is internally heated by a quartz lamp 76. The fuser roll surface may be cleaned by a roll 77, and release agent, stored in a reservoir (not shown), may be pumped to a metering roll 79 for application to the surface of the fuser roll after the sheet is stripped by the non-gouging stripper finger assembly 200 into sheet path 202 in accordance with the present disclosure (to be described in detail below) from such surface.
After that, the sheet 204 then passes to a gate 88 that either allows the sheet to move directly via output 17 to a finisher or stacker, or deflects the sheet into the duplex path 100. Specifically, the sheet (when to be directed into the duplex path 100), is first passed through a gate 134 into a single sheet inverter 82. That is, if the second sheet is either a simplex sheet, or a completed duplexed sheet having both side one and side two images formed thereon, the sheet will be conveyed via gate 88 directly to output 17. However, if the sheet is being duplexed and is then only printed with a side one image, the gate 88 will be positioned to deflect that sheet into the inverter 82 and into the duplex loop path 100, where that sheet will be inverted and then fed to acceleration nip 102 and belt transports 110, for recirculation back through transfer station DD and fuser 70 for receiving and permanently fixing the side two image to the backside of that duplex sheet, before it exits via exit path 17.
After the print sheet is separated from photoconductive surface 12 of belt 10, the residual toner/developer and paper fiber particles still on and may be adhering to photoconductive surface 12 are then removed therefrom by a cleaning apparatus 150 at cleaning station EE.
Referring in particular to
Referring now to
As further shown, the non-gouging sheet stripper assembly 200 includes (i) at least one baffle 206 (the lower baffle as shown) forming part of a sheet path 202 downstream from the fusing nip 75; (ii) a flexible finger shaft 212 made of a resilient spring material and having a first end 214 attached to the at least one baffle 206 and a second distal end 216 for forming a sheet directing first angle Al with a tangent T1 to the second surface S2 of movable fusing member 72; and (iii) a finger tip 218 located at the second distal end 216 of the flexible finger shaft 212. In accordance with an aspect of the present disclosure, the finger tip 218 includes a contoured portion 220 for forming a sheet stripping second angle A2 that is different from the sheet directing first angle Al, with a tangent T2 to the second surface S2 of movable fusing member 72.
In
In a second embodiment, the contoured portion 220 can comprise a curved portion 228 that is connected to the flexible finger shaft 212 and that has a radius of curvature Rt that is equal to or slightly greater than the radius Rr of the surface S2 of the fusing member 72. As such, the curved portion 228 will have an axis 230 that is coincident with a tangent T3 to the surface S2 at a point of contact. Accordingly an equivalent sheet stripping second angle A2′ will be zero degrees, which is significantly less than the sheet directing angle A1.
In the machine 8, the non-gouging sheet stripper assembly 200 includes a plural number of the finger shaft 212 aligned from one end to the other of the fuser roll 72 as is well known in the art, and a corresponding plural number of finger tips 218. Again, the flexible finger shaft 212 can be a thin blade-like member that is resiliently bendable between the first end 214 and the distal end 216 thereof by a force Fp of a sheet jam 209 within the sheet path 202. Accordingly, the flexible finger shaft 212 can be made of a spring material such as coated spring steel. The sheet stripping second angle or bend A2 at the tip 218 of the flexible blade-like stripper finger 210 is for decreasing the attack angle with a tangent to the surface S2 of the fuser roll. The net result during an accordion jam as illustrated in
As can be seen there has been provided a non-gouging sheet stripper assembly for stripping copy sheets from a surface of a moving fusing member. The non-gouging sheet stripper assembly includes (a) at least one baffle forming part of a sheet path; (b) a flexible finger shaft having a first end attached to the at least one baffle and a second distal end for forming a sheet directing first angle with the surface of the moving fusing member; and (c) a finger tip located at the second distal end of the finger shaft and having a contour for forming a sheet stripping second angle, that is different from the sheet directing first angle with the surface of the moving fusing member.
The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
