Electrophotography – Image formation – Development
Reexamination Certificate
2001-01-04
2002-09-17
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Development
C399S239000
Reexamination Certificate
active
06453141
ABSTRACT:
This application is based on application No. JP 2000-000793 filed in Japan, the contents of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an improved liquid material supply device that causes a liquid material (such as ink, for example) to be carried on the continuous outer circumferential surface (liquid material carrying surface) of a continuous carrier (such as a roller or a belt, for example), as well as to an image forming apparatus incorporating such liquid material supply device.
2. Description of the Related Art
Among various types of liquid ink supply devices are those that use a blade to cause the ink adhering to the outer circumferential surface of a rotating roller to become a thin uniform-thickness layer, and transfer this thin layer of ink to an image (comprising convex areas, or a latent image) carried on a plate, image carrier, etc.
In an ink supply device of this type, a prescribed pressure is applied to the blade such that it is in pressure contact with the outer circumferential surface of the rotating roller. The excess ink adhering to the roller is removed by the blade when the ink passes through the area of contact between the blade and the roller. As a result, a uniform thin layer of ink is formed. In addition, the thickness of the ink layer may be varied by adjusting the pressure applied to the blade that is in contact with the roller.
FIG. 11
shows a conventional ink supply device
1
using a blade as described above. This ink supply device
1
includes a container (developer container)
2
. An ink cartridge
4
is located in the housing of the container
2
such that it may be removed. Ink
6
is supplied from the cartridge
4
to the container
2
such that the depth of the ink
6
is maintained at a prescribed level in the container
2
. A roller (developing roller)
10
, which has a shaft
8
that runs parallel to the surface of the ink
6
and extends in the direction perpendicular to the sheet, is located in the upper area of the container
2
such that the bottom of the roller is below the ink surface. The shaft
8
is connected to a motor
12
, so that the roller
10
rotates in the direction of an arrow
13
in the drawing as the motor
12
rotates. A regulating blade
16
, which comprises a plate-shaped elastic member supported by a pressing member
14
, is located downstream from the area of the roller submerged in the ink
6
in terms of the roller rotational direction
13
. This regulating blade
16
protrudes essentially tangentially to the roller
10
and in the downstream direction of the rotation of the roller
10
, such that it is in contact with the roller
10
under a prescribed pressure. In addition, an image carrier (image carrying roller)
22
, which has a shaft
20
that is parallel to the surface of the ink
6
and extends in the direction perpendicular to the sheet, and carries a latent image in accordance with image information, is located above and near the roller
10
. The shaft
20
is connected to a motor
24
, and the image carrier
22
rotates in the direction of the arrow
25
of the drawings as the motor
24
rotates.
The operation of the ink supply device
1
will be explained below with reference to FIG.
11
. When the roller
10
rotates via the motor
12
, the ink
6
adhering to the surface of the roller
10
reaches the regulating blade
16
as it is carried on the roller
10
as the roller
10
rotates. Here, excess ink
6
is removed by the regulating blade
16
through the receipt of a prescribed pressure therefrom. A uniform thin layer of ink
6
having a desired thickness (several &mgr;m to several tens of &mgr;m) is formed on the surface of the roller
10
in accordance with the pressure from the regulating blade. The thin layer of ink
6
is then transferred to the image carrier
22
in the transfer area
26
. For the method by which to transfer the ink
6
to the image carrier
22
from the roller
10
, either a contact method or a non-contact method may be used.
In the ink supply device
1
described above, where the opening
28
(the area indicated by dotted lines in the drawing) through which the interior of the container
2
is exposed to the outside atmosphere is large, the amount of solvent (i.e., water in the case of a water-based ink) of the ink
6
in the container
2
that evaporates and escapes through the opening
28
is large, and consequently, the viscosity of the ink
6
increases. If the container
2
were completely closed off, the water component of the ink
6
would be maintained in equilibrium between the ink
6
housed in the container
2
and the remaining space in the container
2
, and therefore the viscosity of the ink
6
would change very little. However, in actuality, the container
2
is never completely closed during development due to the mechanical construction of the device. When the viscosity of the ink increases, an ink layer that is thicker than the desired thickness is formed on the roller
10
. Such an increase in the ink layer thickness increases the amount of ink transferred to the image carrier
22
, and in turn, image failure when an image is formed on the sheet using this ink (such as the so-called cockling in which the sheet warps as a result of shrinking due to absorbed ink, resulting in a wavy sheet surface, for example) as well as ink bleed-through. (In this application, ‘the outside atmosphere’ refers to the atmosphere that exists outside the opening
28
of the container
2
, and is distinguished from the gas that exists inside the opening
28
of the container
2
).
OBJECTS AND SUMMARY
The present invention was created in view of the situation described above, and the object thereof is to provide an improved ink supply device. In other words, an object of the present invention is to provide an ink supply device that can supply ink under stable conditions. More particularly, an object of the present invention is to provide an ink supply device that prevents the solvent, which is the main ingredient of the ink inside the developer container, from evaporating and escaping from the container, in order to maintain the ink viscosity at an essentially fixed level, and that consequently forms a layer of ink having an essentially uniform thickness on the surface of a liquid carrier such as a roller
10
.
In order to attain this and other objects, the liquid material (ink) supply device according to one aspect of the present invention has a rotational shaft; a liquid material carrier having a continuous liquid material carrying surface around the rotational shaft; a motor that causes the liquid material carrier to rotate in a prescribed direction around the rotational shaft; and a container that houses a liquid material such that a part of the liquid material carrying surface may be submerged in the liquid material, so that the liquid material may be supplied onto the liquid material carrying surface, and the top part of which is open, wherein the liquid material supplied onto the liquid material carrying surface is conveyed to the transfer area through the rotation of the liquid material carrier that occurs based on the rotation of the motor, and is supplied to the liquid material receiving member in the transfer area. The liquid material supply device further has a liquid material supply mode in which the liquid material is supplied from the liquid material carrier to the liquid material receiving member, and a liquid material non-supply mode in which the liquid material is essentially removed from the liquid material carrier.
In this liquid material supply device, according to one aspect of the present invention, a part of the liquid material carrier is located outside the opening of the container, and the liquid material is supplied from the liquid material carrier to the liquid material receiving member using one area of the above part of the liquid material carrier, and the opening area A and the liquid material surface area B defined below satisfy the relationship (A/B)<
Kitoba Utako
Sasai Kosuke
Grainger Quana M.
McDermott & Will & Emery
Minolta Co. , Ltd.
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