Electrophotography – Control of electrophotography process
Reexamination Certificate
2000-02-22
2001-09-25
Grainger, Quana M. (Department: 2852)
Electrophotography
Control of electrophotography process
C399S160000
Reexamination Certificate
active
06295424
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electrostatographic reproduction apparatus such as copiers and printers, and more particularly to such a copier or printer that includes an imaging member having imaging and non-imaging portions and methods of use therewith.
DESCRIPTION OF THE PRIOR ART
Electrostatographic reproduction apparatus for producing copies of an original document are well known. Such copies typically are produced on suitable receiver sheets through a repeatable process that normally includes the steps of (1) using electrostatic charges and first and/or second stations in some manner to form a latent image on the surface of an imaging or image-bearing member; (2) developing the latent image at a third station with developer material that includes toner particles; (3) transferring the developed image at a fourth station from the imaging member to a suitable receiver sheet for subsequent fusing; and (4) cleaning the image-bearing surface of the imaging member thereafter at a fifth station by removing residual toner and other particles therefrom.
In such reproduction apparatus in which the imaging member is repeatedly reused, ordinarily the imaging member has an endless shape for example in the form of a drum or of a flexible web. The endless flexible web form has certain advantages and disadvantages relative to the drum form. Among the advantages is the fact that such a flexible web can be disposed in a flat orientation along one portion thereof, and in a curved orientation along another portion thereby facilitating placement of operating stations thereabout. More importantly, the flexible web form of an imaging member can allow for multiple images to be in the formation process at any given time and still retain some compactness and overall machine size.
Among the disadvantages, however, is the presence of a web splice or seam, that is where two ends of the web material usually have been splice-joined together in order to form its endless shape. Unfortunately, the portion of the web including an area immediately adjacent to either side of the splice may be not suitable for forming quality images, and so is regarded as a non-imaging area. Accordingly, in order to avoid forming images on such a non-imaging area, it is conventional to move the web about its path in the reproduction apparatus until the splice is detected by a detector located at a fixed location selected so that the imaging portion of the web is then in a position to run in proper registration with the fixed electrostatographic process stations of the apparatus as described above. The splice may be detected by the detector by providing on the web adjacent to the splice area a permanent mark or indicium such as a perforation or patch of density that can be detected by the detector.
In U.S. Pat. No. 4,556,311 there is described an electrophotographic copying apparatus that is particularly concerned with the production of a plurality of sizes of images on the image forming surface of a photosensitive member such as a photoconductor. This patent teaches that the same number of images of different sizes may be formed on the photoconductor by dedicating certain start areas of each image frame as a common start area for each of the different sizes. As an improvement, the patent teaches that higher productivity can be obtained by providing plural parallel tracks of permanent image frame markings so that detection of at least two marks can be used to identify the location of any particular one frame for forming an image. Thus, as taught in this patent, an A4 size image may be formed on each of four image frames of the photoconductive member, a B4 size image may be formed on each of three image frames of the photoconductive member, and an A3 size image may be formed on each of two image frames of this photoconductive member.
A problem with the approach suggested by the aforementioned patent is the requirement for plural tracks of permanent marks and necessity of providing plural sensors along such tracks. It is therefore an object of the invention to provide a method and apparatus that includes an electrostatographic image forming member that has permanent indicia for producing multiple image sizes yet does not require the use of plural rows of sensors for detecting permanent indicia on plural tracks.
In U.S. application Ser. No. 08/841,008, filed Apr. 29, 1997, in the names of Ziegelmuller et al, there is disclosed an electrophotographic recording apparatus wherein contamination of the transfer roller is reduced. The transfer roller is normally electrically biased to attract toner particles forming an image on a photoconductive web or belt. The electrical voltage bias or potential on the transfer roller is such as to attract the electrostatically charged toner particles forming the developed image to the receiver sheet which is advanced into a nip formed between the photoconductive web or belt and the transfer roller. In order to control process setpoints for the various electrophotographic operating stations, it is desirable to record process control patches and develop the patches with toner particles. It is not usually desirable to transfer these patches to a receiver sheet, so the patches are typically measured for density and then removed from the photoconductive belt. In order to maintain productivity of the machine, it is desirable to form the process control patches in areas of the belt not overlapping with image areas so that the image areas can be used for recording images. A problem with operating a photoconductive web at high speed is that in order to minimize contamination of the transfer roller when engaging a process control patch or area that tends to collect toner, such as a seam, it is desirable to reverse bias the transfer roller so that the roller tends to repel the charge on the toner particles and thereby avoids attracting the toner particles from the patch or the seam onto the transfer roller. In order to reverse bias the roller properly, it takes time for this reverse bias to be implemented. It is, therefore, another object of the invention to provide an electrostatographic recording apparatus and method that is adapted to provide for sufficient time for an operation to be enabled, such as switching bias of the transfer roller from one polarity to an opposite polarity and then back to the one polarity wherein the primary image forming member such as a photoconductive web, belt or drum is moving at high speed.
The above and other objects and advantages will become more apparent upon reading of a detailed description of the preferred embodiments of the invention provided below.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an electrostatographic recording apparatus comprising a primary image forming member (PIFM) moving along a closed path, the PIFM having a row of image frame synchronizing indicia, the image frame synchronizing indicia being spaced from each other in the direction of movement of the PIFM, and the image frame synchronizing indicia not all being uniformly spaced from one another so that an interframe area larger than other smaller interframe areas on the PIFM can exist, a recording device that is enabled to record a series of electrostatic images on the PIFM, a development station that develops the electrostatic images, a transfer device for transferring the developed images from the PIFM, a sensor for detecting image frame synchronizing indicia, and a controller responsive to sensing of the image frame synchronizing indicia for synchronizing recording of the image frames by the recording means, the control means also being operative for controlling an operation at the larger interframe area for which sufficient time is not available at a smaller interframe area.
In accordance with a second aspect of the invention, there is provided an electrostatographic recording method comprising the moving of a primary image forming member (PIFM) along a closed path, the PIFM having a row of image frame synchronizing indicia, the image
Anthony James D.
Lairmore Anne F.
Regelsberger Matthias H.
Stern Philip A.
Grainger Quana M.
Heidelberg Digital L.L.C.
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