Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-08-16
2001-07-17
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S152000, C347S232000
Reexamination Certificate
active
06262753
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic imaging apparatus such as a laser printer, and, more particularly, to such an imaging apparatus including multiple printhead assemblies and photoconductive drums.
2. Description of the Related Art
An electrophotographic imaging apparatus, such as a laser printer, may be configured as a multi-color imaging apparatus for producing color images on a print medium. In a tri-color imaging apparatus, it is known to provide four separate toner reservoirs which contain different color toners. For example, a first toner reservoir may contain yellow toner; a second toner reservoir may contain magenta toner; a third toner reservoir may contain cyan toner; and a fourth toner reservoir may contain black toner. Each toner reservoir is positioned in association with a photoconductive (PC) drum on which a latent image is formed using a laser beam which is projected from a printhead assembly. The laser beam projects against the peripheral surface of the PC drum at an angle of incidence relative to a line extending through an axis of rotation of the PC drum and the point of incidence of the laser beam. The laser beam is scanned across the peripheral surface of the PC drum along a line extending parallel to the axis of rotation of the drum. In an image forming apparatus as described above, the printhead assemblies may be configured substantially identical to each other. Moreover, the printhead assemblies are configured to project the scanned laser beam at identical angles to the PC drum along lines of incidence which are positioned at the same relative position from one drum to another. Although such a configuration provides high quality printing, geometric constraints associated with such an arrangement tend to increase the packaging size of the imaging apparatus.
What is needed in the art is an EP imaging apparatus which provides high quality printing with a reduced overall packaging size.
SUMMARY OF THE INVENTION
The present invention provides an electrophotographic imaging apparatus, such as a laser printer, with a reduced packaging size by increasing the distance between adjacent printhead assemblies and decreasing the distance between adjacent PC drums.
The invention comprises, in one form thereof, an electrophotographic imaging apparatus for printing on a print medium, including a plurality of photoconductive drums and a plurality of printhead assemblies. Each drum has an axis of rotation and a photoconductive peripheral surface. A plurality of the axes of rotation of the drums lie in a generally common plane. Each peripheral surface rotates in a common direction defining an advance direction of the print medium. Each printhead assembly is associated with a respective drum and is configured for generating a laser beam which impinges upon the respective drum along a line of incidence. The laser beam is disposed at an angle of incidence relative to a perpendicular extending through the line of incidence and the axis of rotation. The angle of incidence sequentially increases from one printhead assembly to another along the advance direction.
The invention comprises, in another form thereof, an electrophotographic imaging apparatus including a plurality of photoconductive drums and a plurality of printhead assemblies. Each drum has an axis of rotation and a photoconductive peripheral surface. A plurality of the axes of rotation of the drums lie in a generally common plane. The peripheral surface of each drum rotates in a common direction defining an advance direction of the print medium. Adjacent drums are disposed at a first distance away from each other between the axes of rotation. Each printhead assembly is associated with a respective drum and is configured for generating a laser beam which impinges upon the respective drum along a line of incidence. The printhead assemblies are disposed at a second distance from one to another which is greater than the first distance.
An advantage of the present invention is that the packaging size of the electrophotographic imaging apparatus is reduced.
Another advantage is that the distance between adjacent printhead assemblies may be increased by either sequentially increasing the angle of incidence or sequentially moving the line of incidence from one photoconductive drum to another along an advance direction.
Yet another advantage is that the printhead assemblies may be precisely and easily located relative to one another in the image forming apparatus using precisely located support channels attached to a frame.
REFERENCES:
patent: 4494103 (1985-01-01), Jarosz et al.
patent: 4761046 (1988-08-01), Funato
patent: 4916547 (1990-04-01), Katsumata et al.
patent: 5278589 (1994-01-01), Wong
patent: 9-269683 (1997-10-01), None
patent: 11-95520 (1999-04-01), None
Chee Christopher Gregory
Horrall Paul Douglas
Ream Gregory Lawrence
Ward II Earl Dawson
Lexmark International Inc.
Pendegrass Joan
Taylor & Aust P.C.
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