Toner supply device with rotatable agitating element

Electrophotography – Image formation – Development

Reexamination Certificate

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Details

C399S263000

Reexamination Certificate

active

06421517

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a toner supply device for a developer unit provided with electrophotographic apparatus such as laser printers, copiers, facsimile machines and the like, in particular relates to a toner supply device which supplies the toner stored in the developer unit to a predetermined site therein with a conveying sheet whilst agitating the toner with a rotatable agitating element.
(2) Description of the Prior Art
Generally, in an electrophotographic printer, a developing device for creating toner images is provided with a toner supply device called a toner hopper. This toner hopper keeps spare toner in reserve and supplies fresh toner to the developing device as the toner is consumed by the development process. Also this toner hopper has an agitating element for agitating the toner therein and conveying the toner into the developing device. This agitating element is called an agitator or toner agitating shaft and functions to agitate the toner to thereby maintain the proper conveyance of toner and prevent the toner from sticking together in a mass or deteriorating in any other way.
This agitating element is generally formed of a relatively hard material such as metal, resin, etc., and is provided in the form of a rigid ladder structure. Hence, the agitating element has little elasticity or flexibility so that only the toner residing within the effective range of its rotational radius can be agitated and conveyed thereby. Therefore, when the toner in the toner hopper reduces to a certain extent, it becomes impossible to convey a sufficient amount of toner to the developing device because of a lower amount of the toner within the reach of the agitating element. Shortage in the amount of toner in the developing device will cause character voids and light print, producing difficulties in forming high quality images. Therefore, in order to keep the amount of toner in the toner hopper at a level greater than a certain amount, it has been necessary to frequently resupply the toner to the toner hopper, which degraded the operating rate of machine, running efficiency and running cost.
In order to solve the above problem, Japanese Patent Application Laid-Open Hei 6 No. 236110, for example, discloses a toner hopper in which a toner conveying element has a: rectangular conveying sheet having a strong elasticity at the distal end thereof so that the sheet will be able to slide over the inner wall surface of the toner hopper. This arrangement enables a sufficient amount of toner to be brought into the developing device even if only a low amount of toner remains in the toner hopper and makes possible effective use of the toner in the toner hopper and can improve the machine operating rate.
FIG. 1A
shows a configurational example of this toner hopper
2
. Toner hopper
2
in this figure has a toner container
9
for holding the toner and is connected to an unillustrated developing device arranged opposing the photosensitive member by a toner supply portion
10
with a sponge roller
10
a
arranged therein. In this developing device, an unillustrated internal roller is rotationally driven in a predetermined direction by driving means. Toner hopper
2
is enclosed by a top plate
14
, a wall surface (side wall)
22
of toner container
9
and a wall surface
23
of toner supply portion
10
.
FIG. 2A
shows shapes of wall surface
22
of toner container
9
and wall surface
23
of toner supply portion
10
. Toner container
9
is a receptacle of an approximately rectangular parallelepiped, defined by wall surface
22
, unillustrated side walls arranged perpendicular to the wall surface
22
and top plate
14
. Toner supply portion
10
is connected to the upper side part of toner container
9
and is enclosed by a groove defined by wall surface
23
of a semi-cylindrical or other shape and top plate
14
. An agitating element
11
and conveying sheet
12
as shown in
FIG. 2B
are arranged in the toner container
9
thus configured.
Agitating element
11
is provided so as to be rotated about an agitating shaft
11
a
which extends in parallel with the rotational axis of the photosensitive drum (the direction indicated by the arrow W in the drawing). In order to perform efficient toner conveyance, conveying sheet
12
made up of a soft resilient material, such as a PET sheet or the like is fixed at its proximal side
12
b
to the distal part of agitating element
11
away from the rotational axis, by double-sided adhesive tape or the like. The distal end, designated at
12
a
, of conveying sheet
12
is formed in parallel with the axial line of agitating shaft
11
a
and bent in the rotating direction. This shape enhances the rigidity of the distal part of conveying sheet
12
hence makes it possible to convey the toner uniformly toward the developing device. When this agitating element
11
is rotated, conveying sheet
12
rotates with its distal part
12
a
kept in contact with the inner wall (the inner surface of top plate
14
and the inner wall surface
22
) of toner container
9
while stirring the toner in the toner container
9
and conveying it toward the developing device.
FIGS. 1A
to
1
F show the actions in the thus configured toner hopper
2
during toner supply. In the drawings, as agitating shaft
11
a
rotates clockwise, conveying sheet
12
deforms holding and conveying the toner with its distal part
12
a
being in sliding contact with the inner wall surface of toner container
9
, as shown in
FIGS. 1A and 1B
. Then, as shown in
FIGS. 1C and 1D
, the held toner is supplied to toner supply portion
10
. Thereafter, conveying sheet
12
moves over the inner side of top plate
14
and transfers its contact point from the sliding movement over top plate
14
to the sliding movement over wall surface
22
as shown in
FIGS. 1E
to
1
F, restarting a next toner holding and conveying cycle.
Since in the above toner hopper
2
conveying sheet
12
is made to slide over the inner wall of toner container
9
in order to make effective use of the toner, the sheet produces contact noise with the inner wall, increasing the noise level. Of such contact noise, the grating sounds arising while the sheet is sliding over the inner wall are not so intense when a relatively large amount of toner is held because the noise is absorbed by the toner. However, as the amount of toner decreases the grating sounds, instead of being absorbed, are heard outside, reaching the user as uncomfortable noise.
One factor that causes the above-described contact noise is a recoiling or grating sound (to called a colliding sound) which arises when conveying sheet
12
abruptly reverts itself back to the original shape due to elastic force and sharply collides with wall surface
22
in the inner space at the meeting point between top plate
14
and wall surface
22
during the action where conveying sheet
12
moves from the state shown in
FIG. 1E
to the state shown in
FIG. 1F
, that is, the sheet transfers its contact point from the sliding movement over top plate
14
to the sliding movement over wall surface
22
. As the rigidity or mechanical strength of the conveying sheet is enhanced in order to provide more stabilized toner conveyance, this colliding sound becomes more liable to occur and acts as the main source, or cause of the noise. Recently in situations where noise reduction in printer technologies has become more important to meet various needs, there has been a strong demand for sufficient enough countermeasures against noisy sounds of this kind.
Further, there is a risk of the distal part
12
a
of conveying sheet
12
being damaged because the sheet is pressed against the inner wall of toner container
9
and greatly flexed and deformed at that part while agitating element
11
is being rotated. In order to avoid this risk, cutouts
12
c
of various shapes may be formed in the distal part of conveying sheet
12
as shown in
FIGS. 3A
to
3
D. A similar manipulation has been disclosed also in Japanese Patent Applicati

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