Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-09-13
2004-08-24
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06779876
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electrostatic printing device for forming an image using toner particles in printers, facsimiles, copying machines and so on, and parts therefor.
2. Description of the Prior Art
Printing devices, by which electric signals output from computers, word processors, facsimiles, or the like are formed as visible images on a recording medium such as paper or the like, include an electrostatic printing device
1
shown in
FIG. 5
, in which an electrode unit is arranged between a particle carrier and a back electrode.
The electrostatic printing device
1
generates an electric potential difference between the particle carrier
20
and the back electrode
30
to create an electric field, by which toner particles are conveyed toward the back electrode
30
from the particle carrier
20
, and the electrode unit
10
arranged between the particle carrier
20
and the back electrode
30
controls conveyance of toner toward the back electrode
30
from the particle carrier
20
to enable forming of a desired image on a recording medium
50
, such as paper or the like, or an intermediate recording medium, such as a transfer belt or the like, disposed between the particle carrier
20
and the back electrode
30
.
The above-mentioned electrode unit
10
comprises apertures
11
and control electrodes
12
surrounding the apertures
11
at least partially (see FIG.
6
), and voltage applied on the control electrodes
12
has an influence on an electric field, by which toner particles are conveyed toward the back electrode
30
, so that toner particles conveyed toward the back electrode
30
from the particle carrier
20
determine positions, sizes and the like of dots formed on the recording medium
50
.
The electrode unit
10
is formed from a base material of a resin film or resin sheet composed of, for example, a resin material such as polyimide or the like and having a thickness of around 25 to 200 &mgr;m, the base material being formed with a plurality of apertures
11
aligned in a predetermined direction, and the apertures
11
being formed to be at least partially surrounded by, for example, mutually intersecting control electrodes or the control electrodes
12
formed in a ring-shaped fashion.
When being assembled into the printing device
1
, the electrode unit
10
is disposed between the particle carrier
20
and the back electrode
30
such that rows of the apertures (L
1
to L
4
) of the unit
10
are made in parallel to an axis of the particle carrier
20
, which is formed as a column or cylinder-shaped rotating body.
In the example shown in
FIG. 5
, the electrode unit
10
is formed with four rows of apertures (L
1
to L
4
) disposed in parallel. In the case where the plural rows of apertures (L
1
to L
4
) are provided in the electrode unit
10
, a distance between the surface of the particle carrier
20
and the apertures
11
formed on the electrode unit
10
varies depending upon, for example, to which of the rows of apertures (L
1
to L
4
) the apertures
11
belong, when the electrode unit
10
is positioned in a planar manner.
In the specification of the present application, assuming that Lk denotes a distance between the respective apertures
11
of the electrode unit
10
and the surface of the particle carrier
20
, Lk is large between the apertures
11
belonging to the right and left rows (L
1
, L
4
) in FIG.
5
and the surface of the particle carrier
20
and small between the apertures
11
belonging to the central rows (L
2
, L
3
) and the surface of the particle carrier
20
. Also, since even with an electrode unit
10
comprising one or two rows of apertures, it is difficult to arrange the row or rows of apertures in completely parallel to the axis of the particle carrier, Lk is in some cases varied in the apertures
11
belonging to the same row. Therefore, as Lk is varied, the control electrodes
12
have different influences on an electric field formed between the particle carrier
20
and the back electrode
30
even in the case where the same voltage is applied to the control electrodes
12
surrounding the apertures
11
in the respective rows (L
1
to L
4
) of apertures, so that dots formed on the recording medium
50
, such as paper or the like, vary in size and density depending upon which of the control electrodes
12
surrounding the apertures
11
has controlled the forming of the dots.
By way of example, in the case where dots are formed on the recording medium
50
assuming that all the control electrodes
12
surrounding the apertures
11
(L
1
to L
4
) formed on the electrode unit
10
in the printing device
1
shown in
FIG. 5
are the same in electric potential, when the apertures
11
belonging to the rows L
2
, L
3
and having a relatively small distance Lk between them and the surface of the particle carrier
20
form relatively deep and large dots, and the apertures
11
belonging to the rows L
1
, L
4
and having a relatively small distance Lk between them and the surface of the particle carrier
20
form light and small dots, quantity of toner particles adhered to a printed surface finished and sizes of dots formed differ depending upon, through which of the apertures
11
adherence of toner particles and formation of dots are made, when dots are consecutively shown in, for example,
FIG. 6
, so that there are produced areas being uneven in density and not printed, such unevenness and non-printed areas being visually recognized as lines.
Such phenomenon is called “white line noise”, which causes degradation in printing quality, and removal of which is contemplated. In order to prevent generation of such “white line noise”, distances Lk between the surface of the particle carrier
20
and the apertures
11
formed on the electrode unit
10
are made constant to eliminate variation &Dgr;Lk in the distances, thereby solving the problem of “white line noise”. Therefore, there has been proposed a printing device (see
FIG. 7
) constructed such that distances Lk between the apertures
11
of the electrode unit
10
and the surface of the particle carrier
20
are made uniform in all the rows (L
1
to L
4
) by bending that area of the electrode unit
10
, in which the apertures
11
are formed, so that all the apertures
11
are adjusted to be disposed on a circle concentric with an outer periphery of the particle carrier
20
.
As described above, with the printing device
1
, in which the area of the electrode unit
10
formed with the apertures
11
is bent in compliance with the surface configuration of the particle carrier
20
, all the distances Lk between the surface of the particle carrier
20
and the respective rows (L
1
to L
4
) of the apertures of the electrode unit
10
are uniform, and therefore it is possible to prevent that degradation in printing quality, which is attributed to unevenness in such distances.
When the electrode unit
10
formed from a base material of a resin film or resin sheet is bent in a certain direction, the cross section of the bent portion itself undergoes deformation in its inner surface with the result that such deformation causes the electrode unit
10
to change in shape.
For example, when an X—X axis of an electrode unit
10
put in a state of being disposed in a planar position shown in
FIG. 8
is bent into a shape shown by a broken line X′—X′ as shown in
FIG. 9
, the electrode unit
10
generates warp &rgr; at both ends in the direction along a Z—Z axis perpendicular to the X—X axis thus bent (see FIG.
9
).
FIG. 10
shows a state of a minute space containing an origin O and cut from the bent portion of the electrode unit
10
put in the state shown in FIG.
9
. When the electrode unit
10
is bent in a widthwise direction in a square column above the origin O (above the broken line) in
FIG. 10
, normal stress acts to compress the electrode unit
10
in the direction along the X—X axis, thereby generating longitudinal strain &egr;
x
and lateral strain &egr;
x
(=−&ngr;&egr;
x
) in t
Gordon Raquel Yvette
Harness & Dickey & Pierce P.L.C.
Matsushita Electric - Industrial Co., Ltd.
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