Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
1999-08-19
2001-02-27
Pendegrass, Joan (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S105000
Reexamination Certificate
active
06195515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a developing apparatus which can be used in an image forming apparatus such as an electrophotographic copying apparatus or an electrophotographic printer.
2. Related Background Art
Heretofore, an image forming apparatus using, for example, an electrophotographic system has been provided with, for example, a rotatable drum-like electrophotographic photosensitive body, i.e., a photosensitive drum, as an image bearing body, in substantially the central portion thereof, and charging means uniformly charges the surface thereof. Thereafter, the surface of the photosensitive body is subjected to exposure and an electrostatic latent image corresponding to an image signal is formed on that surface. This electrostatic latent image comes to a position opposed to a developing apparatus with the rotation of the photosensitive body, and is visualized by a developer, and a so-called toner image is formed on the photosensitive body. Thereafter, this toner image is electrostatically transferred onto a recording material by transferring means and further, is fixed by heat and pressure in a fixing device, whereby a permanent image is formed on the recording material. A cleaning device for removing any toner or the like remaining on the photosensitive body after the termination of the transfer is disposed at a desired location.
As the developing apparatus in the image forming apparatus adopting the construction as schematically described above, various ones using a dry type monocomponenet developer as the developer have been proposed and put into practical use. Particularly, there is known a developing apparatus using only non-magnetic toner particles (hereinafter simply referred to as the “toner”) as the dry type monocomponent developer.
Such a developing apparatus is provided with a rotatable sleeve-like developer bearing body, i.e., a developing sleeve, in order to carry the toner to a developing position opposed to the photosensitive drum, make the toner adhere to the electrostatic latent image on the photosensitive drum and form a toner image thereon. In any developing apparatuses, however, it is not easy to form a thin layer of the monocomponenet developer, i.e., the toner, on the developing sleeve, and it is a main point in the image forming operation.
Nowadays, improvements in the resolution, clearness, etc. of an image formed by the image forming apparatus have been further required, and in the developing apparatus as described above, there have been made various proposals regarding a method of forming a thin layer of toner on the developing sleeve and a developing apparatus embodying it.
For example, in a developing apparatus disclosed in Japanese Patent Application Laid-Open No. 54-43038, an elastic blade as developer layer thickness regulating means made of rubber or a metal is made to be abutted against the surface of the developing sleeve. That is, the toner is made to pass through the abutting portion of contact between this elastic blade and the developing sleeve and the layer thickness of the toner is regulated to thereby form a thin layer of the toner on the developing sleeve and, in this abutting portion, triboelectricity (frictional charging amount) sufficient for development is imparted to the toner.
In the prior art as described above, to regulate nonmagnetic toner particles by the elastic blade, means for supplying the toner onto the developing sleeve becomes separately necessary. That is, as is heretofore known, in the case of a developing apparatus using magnetic toner particles as a monocomponent developer, it is possible to supply the toner onto a developing sleeve by a magnetic force produced by a magnet provided in the developing sleeve, whereas this is impossible in the case of a developing apparatus using nonmagnetic toner particles.
So, in order to effect the supply of the toner to the developing sleeve, it has been variously proposed to make a roller-like member having elasticity using a foamed rubber material such as polyurethane foam or sponge or a brush material abut against the developing sleeve.
FIG. 9
of the accompanying drawings shows an example of the prior art developing apparatus using a monocomponent developer.
The developing apparatus
4
contains non-magnetic toner particles (toner) in a developing container
41
, and a portion of that side of the developing container
41
on which the developing apparatus
4
and a photosensitive drum
1
are opposed to each other opens, and in such a manner as to expose a circumferential portion from this opening portion, a developing sleeve
42
as a developer bearing body is supported on the developing container
41
for rotation in the direction of arrow B. Also, spacers (not shown) as gap regulating members are provided on the lengthwisely opposite end portions of the developing sleeve
42
, and these spacers abut against the surface of the photosensitive drum
1
, whereby the surface of the photosensitive drum
1
and the surface of the developing sleeve
42
are opposed to each other with a predetermined distance therebetween.
An elastic blade
44
as developer layer thickness regulating means for regulating the quantity of toner abutted on the surface of the developing sleeve
42
bears against the developing sleeve
42
, and at a position upstream of this elastic blade
44
with respect to the direction of rotation of the developing sleeve
42
, an elastic roller
43
as developer supplying and scraping means abuts against the developing sleeve
42
.
When the developing apparatus
4
starts its developing operation, the toner is agitated by the rotation of an agitating member
45
in the direction of arrow C and is carried to the elastic roller
43
side. The toner is borne on the surface of the developing sleeve
42
while being preliminarily charged by the friction thereof with the elastic roller
43
rotated in the direction of arrow D, whereafter the toner is carried to the abutting portion between the elastic blade
44
and the developing sleeve
42
with the rotation of the developing sleeve
42
, and has its layer thickness regulated and becomes a thin layer. By the friction at this time, desired charging is imparted to the toner.
Thereafter, the toner borne and carried to a developing position opposed to the photosensitive drum
1
with the rotation of the developing sleeve
42
flies onto the photosensitive drum
1
by a developing bias voltage applied to the developing sleeve
42
, and selectively adheres to the electrostatic latent image on the surface of the photosensitive drum to thereby form a toner image. Any toner remaining on the surface of the developing sleeve
42
without contributing to development is again carried into the developing container
41
by the rotation of the developing sleeve
42
, and is scraped off by the elastic roller
43
, whereby it is mixed with the toner in the developing container
41
.
When in such a prior art developing apparatus, a metal material is used as the developing sleeve
42
, if a blade made of a metallic thin plate is used as the elastic blade
44
, it will abrade the developing sleeve
42
, and this is not preferable. To obtain a good thin layer of toner, it is necessary to use a rubber material such as urethane or silicone rubber.
By adopting the construction schematically described above, it has become possible to well effect the formation of a thin layer of toner on the developing sleeve
42
.
However, a developing apparatus using nonmagnetic toner particles (toner), unlike a developing apparatus using magnetic toner particles, cannot utilize a magnetic adsorbing force and therefore, cannot powerfully hold the toner on the developing sleeve
42
. Accordingly, it is difficult to prevent the leakage of the toner to the outside of the developing apparatus
4
.
That is, the other toner than the toner which has slipped out of the portion of pressure contact between the elastic blade
44
and the developing sleeve
42
and has been sufficiently charged has no adsorbing for
Fujita Akiyoshi
Horikawa Tadashi
Matsuda Kenji
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Pendegrass Joan
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