Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-06-15
2001-06-26
Lee, Susan S. Y. (Department: 3852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S134000, C347S250000, C347S261000
Reexamination Certificate
active
06252618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic machine, and, more particularly, to a method of controlling print registration in an electrophotographic machine.
2. Description of the Related Art
In an in-line color laser image printing process, the print medium typically passes through four color developing stations in series, with the colors being black, magenta, cyan and yellow. In order for the multi-color laser printer to print at the same speed as a monochrome laser printer, photoconductive drum exposures must occur for all four colors in parallel, shifted in time. Thus, alignment of the four color developing stations in both the process direction (feed direction of the print medium) and scan direction (across the page) is critical.
The process location of each scanning laser beam must overlap in order to prevent color offset in the process direction. Each color must have an adjustment to correct for process direction misalignment because each color has a scanning laser beam following a separate optical path. A particular problem in aligning the outputs of the laser beams in the process direction is that a length of the toner transfer belt between two points at which the belt contacts two respective photoconductive drums is often not an integer multiple of the distance between adjacent scan lines on the photoconductive drums. Consequently, after a scan line is transferred from a first photoconductive drum to the transfer belt, and that point on the transfer belt is advanced to a second photoconductive drum, the scan line on the transfer belt from the first photoconductive drum does not align in the process direction with a scan line to be transferred from the second photoconductive drum.
What is needed in the art is a method of aligning scan lines of multiple photoconductive drums in a process direction which takes into account the possibility that the length of the transfer belt between at least two of the photoconductive drums may not be an integer multiple of the distance between consecutive scan lines in the process direction.
SUMMARY OF THE INVENTION
The present invention provides a method of aligning images in the process direction for a color electrophotographic printer while maintaining a minimal interpage gap.
The invention comprises, in one form thereof, a method of aligning print images of an electrophotographic machine on a print medium or intermediate transfer belt. A plurality of rotating photoconductive drums are provided in the electrophotographic machine. Each of a plurality of laser beams is reflected off of a respective one of a plurality of reflectors. Each reflector rotates relative to the respective laser beam to thereby scan the laser beam across a respective one of the photoconductive drums to produce a scan line in a scan direction. The relative rotation between the laser beams and the respective reflectors is cyclically repeated to thereby produce a plurality of substantially parallel scan lines on each photoconductive drum. Each scan line is displaced from an adjacent scan line by a scan line separation distance in a process direction perpendicular to the scan direction. Toner is applied to each scan line on the photoconductive drums. A moving toner transfer medium contacts each photoconductive drum at a respective toner transfer nip. A first toner transfer nip is associated with a first reflector. A second toner transfer nip is associated with a second reflector. A length of the toner transfer medium between at least the first toner transfer nip and the second toner transfer nip may be a non-integer multiple of the scan line separation distance. The length of the toner transfer medium has an integer portion and a fractional portion when expressed in units of the scan line separation distance. If the fractional portion is not zero, a speed of the rotation of the second reflector is temporarily increased or decreased dependent upon the fractional portion of the length to produce a compensating phase relationship between the respective reflectors. The toner is transferred from the photoconductive drums to the toner transfer medium. The toner is transferred from the toner transfer medium to the print medium.
An advantage of the present invention is that the laser beams of a multicolor electrophotographic machine can be aligned in the process direction in real time while the machine is operating. The machine microcontroller is capable of providing raster scan data synchronized to the rotating reflectors in both scan and process directions.
Another advantage is that the length of the gap between a trailing edge of one page of print medium and the leading edge of the next page can be minimized, thereby increasing the output speed of the electrophotographic machine.
REFERENCES:
patent: 4130838 (1978-12-01), St. John
patent: 4140903 (1979-02-01), Clark
patent: 4845358 (1989-07-01), Asada
patent: 4922266 (1990-05-01), Bidner et al.
patent: 4931815 (1990-06-01), Sato et al.
patent: 4942406 (1990-07-01), Tsuda
patent: 4951065 (1990-08-01), Okino
patent: 4975626 (1990-12-01), Yagi et al.
patent: 5054866 (1991-10-01), Tomita et al.
patent: 5105208 (1992-04-01), Matsuoka et al.
patent: 5121138 (1992-06-01), Schermer et al.
patent: 5181137 (1993-01-01), Koide
patent: 5212570 (1993-05-01), Nacman
patent: 5245637 (1993-09-01), Gersbach et al.
patent: 5260811 (1993-11-01), Morikawa
patent: 5264872 (1993-11-01), Wong
patent: 5331341 (1994-07-01), Egawa et al.
patent: 5331342 (1994-07-01), Shimatani et al.
patent: 5349374 (1994-09-01), Arai et al.
patent: 5424763 (1995-06-01), Komiya et al.
patent: 5448267 (1995-09-01), Sugiura et al.
patent: 5471314 (1995-11-01), Orlicki et al.
patent: 5477330 (1995-12-01), Dorr
patent: 5541637 (1996-07-01), Ohashi et al.
patent: 5550573 (1996-08-01), Serizawa et al.
patent: 5671069 (1997-09-01), Kodama
patent: 5710751 (1998-01-01), Hoover et al.
patent: 5764270 (1998-06-01), Kitigawa et al.
patent: 5818507 (1998-10-01), Genovese
patent: 5821977 (1998-10-01), Nishimura
patent: 5877798 (1999-03-01), Clarke et al.
patent: 5883659 (1999-03-01), Serizawa et al.
patent: 5933184 (1999-08-01), Ishigami et al.
patent: 5982408 (1999-11-01), Overall et al.
patent: 6052143 (2000-04-01), Yoshino et al.
patent: 6094208 (2000-07-01), Oda et al.
Coriale Matthew Christopher
Ream Gregory Lawrence
Richey John Parker
Lee Susan S. Y.
Lexmark International Inc.
Taylor & Aust P.C.
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