Electrophotography – Image formation – Development
Reexamination Certificate
2001-07-13
2003-04-22
Braun, Fred L (Department: 2852)
Electrophotography
Image formation
Development
C399S103000, C399S263000
Reexamination Certificate
active
06553202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for image forming, and more particularly to a method and apparatus for image forming that is capable of performing an effective development process.
2. Description of the Related Art
In a background image forming apparatus such as a copying machine, a facsimile machine, a printer, and so forth, an image forming operation is typically performed by an electrophotographic method that includes various sequential processes. The sequential processes include forming an electrostatic latent image on an image carrying member, developing the latent image with toner into a visual toner image, transferring the toner image on a recording sheet, and fixing the image.
In a two-component development method using a two-component development agent including toner particles and magnetic carriers, the toner particles are charged by friction charge generated between the toner particles and magnetic carriers. The toner particles are captured by the magnetic carriers which are carried by a development agent carrying member because the development agent includes an inner magnet. The development agent is transferred to a development position facing an image carrying member by the development agent carrying member. At the development position, the toner captured by the magnetic carriers is transferred by an electrostatic force to the electrostatic latent image formed on the surface of the image carrying member. Thereby, the image is developed into a visual toner image.
After consuming the toner in the development process, the two-component development agent is carried to a position at which it is.supplied with toner so that the sequential development process can be performed with the two-component development agent containing a sufficient amount of toner. In a development apparatus using such a two-component type development agent, it is necessary to maintain a constant ratio of toner particles to magnetic carriers so as to obtain a stable image density.
For example, a published Japanese unexamined patent application, No. 9-197833 (1997), describes a development apparatus using a two-component development agent. In this development apparatus, a development agent is carried by a development agent carrying member and is supplied with toner from a toner container. When the development agent consumes toner in a development process, the development agent is moved on the development agent carrying member such as to capture toner in accordance with variations in toner density. This development apparatus eliminates the need for a toner density control mechanism including a toner density sensor and so on and therefore it is superior in downsizing and a cost reduction situations.
Generally, it is desirable that a machine separate development agent and toner from each other in respective sealed packages until the user starts to use the machine for the first time after delivery from a manufacturing site, wherein the development agent is adjusted to initially include magnetic carriers with toner at a predetermined toner density or including magnetic carriers only. This is to prevent undesirable dispersion and mixture of the adjusted development agent and the toner.
In one exemplary development apparatus, both containers for the development agent and the toner have openings connected to the development agent carrying member. Each of the openings is initially sealed with a sealing member and is removed when the development apparatus is used. With this structure, the adjusted development agent is initially supplied to the development agent carrying member by removing the sealing member fixed to the container for the development agent and the toner is initially supplied to the development agent carried on the development agent carrying member by removing the sealing member fixed to the container for the toner. However, when both sealing members are removed at the same time or when the sealing member for the toner container is removed earlier than the other, the toner may be supplied to the surface of the development agent carrying member where the development agent is not carried on. Even if the sealing member for the development agent container is first removed, the toner may also be supplied to the surface of the development agent carrying member where the development agent is not carried on when the development agent carrying member is not started. When the toner is directly attached to the surface of the development agent carrying member where the development agent is not present, it is possible that the toner density in an area of the surface is dense and, as a result, an abnormal image such as a dirty background is reproduced, particularly, upon initial use of the machine.
In an attempt to solve the above-described problem, a background development apparatus was developed having a structure in which the opening for the toner is released after the development agent is deposited on a surface of the development agent carrying member facing the opening where the toner is supplied. In this apparatus, the toner supply from the toner container through the opening to the development agent carrying member is prevented with a sealing member, provided near the opening, until the development agent is deposited on a surface of the development agent carrying member in turn facing the opening where the toner is supplied. The sealing member is moved to release the opening after the development agent is deposited on a surface of the development agent carrying member in turn facing the opening where the toner is supplied, and supply of the toner is consequently started relative to the development agent carried on the development agent carrying member. The above-described background development apparatus has a structure in which a single member made of a flexible material is used as a rotary member for transferring the toner contained in the toner container by its rotation and is also used as a sealing member for sealing the opening of the toner container.
FIG. 1
depicts a structure of a background development apparatus
200
. In the background development apparatus
200
, a toner agitator
229
includes a rotary member
229
c
configured to hold a flexible member
229
a
which is located at a position where it closes a toner opening
228
a
formed in a toner container
228
. When the flexible member
229
a
is rotated, supply of toner T contained in the toner container
228
is started through the opening
228
a
relative to a development agent
223
carried on a development agent carrying member
224
. However, the background development apparatus is disadvantageously configured such that it is difficult to completely close the opening
228
a
with the flexible member
229
a
. In this configuration, the opening
228
a
is closed and sealed shut only by pressure on the flexible member
229
a
caused by the weight of the toner T contained in the toner container acting against the flexible member
229
a.
SUMMARY OF THE INVENTION
The present invention provides a novel development apparatus. In one example, a novel development apparatus includes a development agent carrying member, a toner container, an initial development agent container, a flexible feather-like member, and a stopper. The development agent carrying member is configured to carry and transport a development agent including toner and magnetic carriers, and includes an inner magnetic field generating mechanism. The toner container is configured to contain toner, and includes an opening through which the toner is supplied to the development agent carrying member. The opening is located at a position facing the development agent carrying member. The initial development agent container is configured to contain an initial development agent including at least magnetic carriers and to be sealed when the apparatus is in an initially unused condition. The initial development agent container includes a mechanism for supply the initial development agent to the developme
Tamaki Shinji
Yoshizawa Hideo
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