Electrophotography – Image formation – Development
Reexamination Certificate
2002-04-29
2003-01-14
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06507721
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to laser printing.
BACKGROUND OF THE INVENTION
FIG. 1
depicts a cross-section view of a typical laser printer
100
. During operation of the printer, a substantially uniform charge is placed on the surface of drum
101
by charge roller
102
, or alternatively, by a corona wire. Laser beam
103
, controlled by a steering mechanism represented by mirror
112
, selectively illuminates areas of drum
101
. This illumination at least partially discharges those areas of drum
101
, for example by photoconduction to a conductive substrate in the drum. The selective discharging of areas on drum
101
forms a latent image on drum
101
.
FIG. 2
shows a magnified view of the resupply roller region of FIG.
1
. Particles of toner
104
carrying an electric charge are taken from a toner supply container
105
by resupply roller
106
and deposited on the surface of developer sleeve
107
. Developer sleeve
107
is depicted as a cylinder in this example printer, but other printers may use other toner receiving surfaces. For example, the toner may be received onto a belt. A leveling blade
113
may assist with the distribution of toner on developer sleeve
107
.
Developer sleeve
107
carries a voltage bias such that when the toner-coated developer sleeve
107
makes rolling contact with drum
101
, the charged toner particles are attracted to the discharged areas on drum
101
, and repelled from the still-charged areas on drum
101
. In this way, toner is collected on selected portions of the surface of drum
101
, forming an image in toner
110
on the drum surface.
As drum
101
rotates further, the toner image
110
is brought into rolling contact with paper
108
between drum
101
and transfer roller
109
. Transfer roller
109
carries a voltage bias such that the charged toner particles are strongly attracted to it, and thus pulled from the surface of drum
101
onto the surface of paper
108
. The toner image
110
is thus transferred to the surface of paper
108
.
The paper, carrying the toner image, then passes through a fuser mechanism
111
. The fuser mechanism
111
may consist of one or more heated rollers that briefly melt the toner particles, fusing them to paper
108
. After passing through the fuser mechanism, paper
108
carries a substantially permanent image.
It is the object of resupply roller
106
to coat developer sleeve
107
with a layer of toner particles. The resupply roller
106
may have longitudinal ribs for assisting in the mechanical transfer of toner
104
to developer sleeve
107
.
While the ribs may greatly facilitate the movement of toner
104
to developer sleeve
107
, they may also affect the quality of the image eventually produced on paper
108
. The mechanical interaction of the ribs with developer sleeve
107
may excite minute vibrations in the printer mechanism, or the toner may not be placed on developer sleeve
107
with perfect uniformity. These effects may cause banding in the final printed image, especially when the image being printed is a photograph or other graphical element.
There is a need for an improvement to the resupply roller so that image artifacts are reduced.
SUMMARY OF THE INVENTION
A toner resupply roller in a laser printer has ribs that are not parallel to the rotational axis of the roller. The ribs form a tilted, helical, herringbone, or other pattern on the roller.
REFERENCES:
patent: 5854961 (1998-12-01), Wibbels et al.
patent: 6026265 (2000-02-01), Kinoshita et al.
patent: 6149564 (2000-11-01), Nozawa et al.
patent: 6196958 (2001-03-01), Shiraki et al.
Boyd David W.
Yergenson Robin P.
Boyd David W.
Campbell Candice C.
Hewlett--Packard Company
Pendegrass Joan
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