Electrophotography – Image formation – Charging
Reexamination Certificate
2001-11-02
2003-07-29
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Charging
C399S168000
Reexamination Certificate
active
06600888
ABSTRACT:
BACKGROUND OF THE INVENTION
A prior art liquid charging apparatus is disclosed in Facci et al., U.S. Pat. No. 5,893,663 (hereinafter “Facci Patent”). An elevational schematic view of the liquid charging apparatus of the Facci Patent is shown in
FIG. 1
(which corresponds to
FIG. 1
of the Facci Patent).
FIG. 1
shows a hydrophilic web
100
wound onto a supply roll
110
and a take-up roll
120
. The web
100
is passed over a wetting or moistening device such as a porous roll
130
. The porous roll contains a perforated shaft
131
therethrough. A DC voltage
135
is attached to the shaft to provide charge thereto. The DC voltage can be applied to the electrically conductive liquid by a conductive brush, commutator, wire, or similar device. This voltage application contact can occur at a reservoir, delivery tubing, porous roll, central roller or the wetted section of the web. The porous roll
130
uniformly moistens the web
100
. As copies are made, the web
100
which is initially wound onto the supply roller
110
, is slowly advanced or indexed in a direction (shown by arrow
111
) counter to the photoreceptor
10
motion (shown by arrow
16
), ensuring that any contamination at the entrance nip
17
is kept to a minimum as it is carried away by the web
100
. Also, the contamination is kept out of the nip
18
. The charging web
100
is contacted against the photoreceptor
10
by a contact roll
130
which supplies a charging fluid to the web
100
at a controlled rate. The fluid delivery member (or conduit)
51
, from the reservoir
140
, ensures an even contact pressure across the width of the photoreceptor
10
. The width of the contact pad
130
determines the nip width.
In
FIG. 1
, photoreceptor
10
(which is a drum according to the Facci Patent) contacts the web
100
to result in a tangential contact length. As used herein, the phrase “contact length” refers to the distance in the process direction that two surfaces contact. The phrase “process direction” means the direction of motion of the surface (e.g., photoreceptor) to be charged. The phrase “tangential contact length” refers to two surfaces that slightly contact one another, that is, where the contact length is short. Besides the tangential contact length depicted in
FIG. 1
, another illustration of a tangential contact length is if photoreceptor
10
in
FIG. 1
were a belt where web
100
contacts the linear surface of photoreceptor
10
to result in a short contact length. A tangential contact length depends for instance on the size of the two contacting surfaces. For purposes of discussion, however, a tangential contact length in the context of a nip formed by the contact of web
100
with photoreceptor
10
(whether photoreceptor
10
has the configuration of a belt, a drum or other conventional shape), is one ranging from 1 mm to 5 mm.
A contact length which is tangential is problematic for a liquid charging apparatus in a electrostatographic printing machine because the tangential contact length may lead to nonuniform charging due to variations in the degree of contact between the the charging apparatus and the surface to be charged. In addition, toner particles stuck under the liquid charging apparatus with a tangential contact length may give rise to nonuniform charging. Thus, there is a need for an improved liquid charging method and apparatus which avoid or minimize the problems discussed above.
Conventional liquid charging devices are also disclosed in Tajima et al., JP 57-49964; Facci et al., U.S. Pat. No. 5,457,523; Lewis et al., U.S. Pat. No. 5,781,833; Facci et al., U.S. Pat. No. 5,895,147; Facci et al., U.S. Pat. No. 5,819,141; and Levy et al., U.S. Pat. No. 5,895,148, the disclosures of which are totally incorporated herein by reference.
SUMMARY OF THE INVENTION
The present invention is accomplished in embodiments by providing a method comprising:
(a) dispensing an electrically conductive liquid into a contact member permeable to the liquid;
(b) rubbing the contact member and a surface against each other, at a contact length greater than a tangential contact length, to release the liquid from the contact member to wet the surface with the electrically conductive liquid in a layer ranging in thickness from about 1 to about 100 micrometers; and
(c) electrifying the liquid at any time effective for imparting an electrical charge to the surface.
There is also provided in embodiments an electrostatographic printing machine comprising:
(a) a photoreceptor;
(b) a developer member including toner particles;
(c) a dispensing equipment that dispenses an electrically conductive liquid;
(d) a contact member that receives the liquid and is permeable to the liquid, where the contact member and the photoreceptor rub against each other, at a contact length greater than a tangential contact length, to release the liquid from the contact member to wet the photoreceptor surface with the electrically conductive liquid in a layer ranging in thickness from about 1 to about 100 micrometers; and
(e) a power source that electrifies the liquid.
REFERENCES:
patent: 3835355 (1974-09-01), Tsukada
patent: 4380384 (1983-04-01), Ueno et al.
patent: 5378526 (1995-01-01), Murata
patent: 5457523 (1995-10-01), Facci et al.
patent: 5510879 (1996-04-01), Facci et al.
patent: 5561505 (1996-10-01), Lewis
patent: 5592264 (1997-01-01), Shigeta et al.
patent: 5602626 (1997-02-01), Facci et al.
patent: 5666607 (1997-09-01), Camis
patent: 5781833 (1998-07-01), Lewis et al.
patent: 5819141 (1998-10-01), Facci et al.
patent: 5893663 (1999-04-01), Facci et al.
patent: 5895147 (1999-04-01), Facci et al.
patent: 5895148 (1999-04-01), Levy et al.
patent: 57-49964 (1982-03-01), None
Mishra et al., Ser. No. 09/659,260, “Liquid Charging Apparatus with Greater Contact Length”.
Foley Geoffrey M. T.
Horgan Anthony M.
Mishra Satchidanand
Popovic Zoran D.
Swain Eugene A.
Brase Sandra
Soong Zosan S.
Xerox Corporation
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