Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-10-16
2002-04-09
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C399S162000, C430S127000
Reexamination Certificate
active
06369842
ABSTRACT:
Cross-reference is made to a commonly assigned co-pending U.S. application Ser. No. 09/692,236, filed Oct. 20, 2000 by Martin E. Hoover et al, entitled “Two Dimensional Surface Motion Sensing System Using Registration Marks and Linear Array Sensor”.
Disclosed is an improvement in permanent registration markings for the accurate registration of an image bearing member of an image reproduction system, in particular, the photoreceptor of a xerographic reproduction apparatus, such as a plural color printer. A method is disclosed for forming permanent registration (fiducial) marks in desired areas of a photoreceptor belt, by making those areas transparent, and thus readily optically detectable relative to other belt areas, without requiring apertures or other physical impairment of the photoreceptor belt.
The photoreceptor belt permanent registration marking system and method of manufacture disclosed in the specific embodiment herein can be accomplished with low manufacturing cost and complexity, yet provide accurately optically detectable belt position signals with available optical sensors, by providing sharply and distinctly produced transparent areas in an otherwise opaque photoreceptor belt. It does not require composition or manufacturing changes in existing photoreceptor materials or the belts made therefrom. In particular, it can provides precise belt positional signals, or ROS raster positional signals relative to the belt position, without weakening or damaging the belt or reducing its effective life, unlike belt holes or apertures previously provided for those functions.
The disclosed method may be utilized for making transparent areas in different types of photoreceptors, although it may be more suitable for some than others, as will be apparent to those skilled in that art. For example, the photoreceptor with a metallic ground plane layer of Xerox Corp. U.S. Pat. No. 4,780,385 issued to Fran Weiloch et al, and other art cited therein.
By way of background, belt holes or slots through photoreceptor belts desirably allow light transmissive optical detection, but have problems. They can cause increased stress and wear, or even belt tearing, in the areas of the belt holes or slots. Especially since typical photoreceptor (PR) belts in xerographic copiers and printers must flex and partially rotate around relatively small diameter driving and supporting rollers for many tens of thousands of cycles of use as imaging substrates.
Thus, the need for non-destructive permanent marks on photoreceptor belts is well known and long-standing. Holes are usually cut through the entire belt, near the belt edges, making belt areas that are weak and subject to damage. Yet, this is commonly done, in order to provide for the belt motion and the position of belt imaging panels to be determined with such marks by various sensing means. The (normally opaque) belt can be illuminated from one side, and when a hole or other cut in the belt passes by the illuminator, a optical sensor on the other side of the belt conventionally senses the change in light level through the hole and provides an electrical signal. That electrical signal can indicate, for example, the belt position for the intended start of an image panel, or the presence of a non-imagable seam in the belt which must be tracked so that it does not appear in any image panel. Further, in order to monitor and correct for belt motion anomalies, which cause image artifacts, marks which are alternately opaque and transmissive have also been cut or laser burned into the belt outside the image areas, such as near the belt edge, so that specific positions on the belt can be tracked as the belt moves. In such cases the belt is being physically cut or abraded to provide these belt marks, so the belt becomes physically weaker at these marker areas. Many belt failures are thus caused by belt hole tearing.
Further, the belt hole is normally cut into the ground strip along the belt edge to avoid cuts in the basic photoreceptor area, which can delaminate quickly. However, in typical xerographic machines a ground brush must make continuous contact with that ground strip along the back of the belt, and therefore may ride over this belt hole in every cycle, leading to failures in both sensing and continuous grounding. This has required in some cases the use of two contact brushes, so that one is always in contact with the ground strip, and/or cutting less holes, since they are so troublesome.
Permanent registration marks printed or painted on the belt surface avoid such hole problems, but can wear, and may not provide sufficient optical contrast. If the marks are printed on the imaged side of the belt, which may often be desirable for other reasons, wear can be caused by abrasion from the xerographic cleaning and development systems, or, the belt marks may become contaminated with toner. Yet printed belt marks must depend on light reflective contrast levels different from the adjacent unmarked areas of the photoreceptor, rather than light transmissive detection systems. For that and other reasons they may not provide sufficiently sharp-edged light reflectance mark detections for sufficiently accurate registration.
The system and method disclosed herein can provide the same registration functions as belt holes, or other functions. For example, labeling, timing, and/or registering of images on photoreceptor belts, and/or belt seam skipping. However, the present system does not require belt holes. It provides such sensing cursor functions by providing transparent areas in the belt instead. The present system creates permanent fiducial markings in the belt which are not on the surface and thus not subject to being worn off in use. That is, creating internal selected images of desired fiducial markings which are transparent areas through which light can be transmitted through the belt for light transmissive detection systems.
The system of the embodiment herein can thus, if desired, utilize the same or pre-existing registration sensors and controls designed or used for belt hole registration marks, or other conventional or simple light transmissive detection systems.
To summarize, with the disclosed embodiment and method of making transparent registration marks in the photoreceptor belt, the marks can last as long as the belt lasts mechanically in the machine, since there is no required physical cutting or abrading of the belt. Further, if the marks are made outside of the basic image areas of the belt, the marks can last throughout the entire electrical life of the belt, and the area around it will not change its contrast level. As noted, these marks can easily be used in place of belt holes with current belt registration systems and sensors, compatibly with those systems and sensors, yet prevent belt hole caused belt failures and ground strip contact failures.
An additional possible utility of the disclosed method could be to produce photoreceptors with permanent small “watermark” images therein. If produced in image areas, those images could even produce copies in which those images are negatively reproduced on the final copy substrates, so as to identify the photoreceptor on which they were printed. By way of further background, in various reproduction systems, including xerographic printing, the control and registration of the position of imagable surfaces such as photoreceptor belts, and/or images being placed thereon, is critical, and a well developed art, as shown by exemplary patents cited below. It is well know to provide various single and/or dual axes control systems, for adjusting or correcting the lateral position and/or process position or timing of a photoreceptor belt or other image bearing member of a reproduction apparatus, such as by belt lateral steering systems and/or belt drive motor controls, and/or adjusting or correcting the lateral position and/or process position or timing of the placing of images on the belt with adjustable image generators such as laser beam or raster scanners.
The following exemplary U.S. patents are noted for d
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