Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
1999-10-22
2001-04-03
Chen, Sophia S. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S103000
Reexamination Certificate
active
06212343
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing device, a process cartridge in which a developing device and a photoconductor unit are integrated, and an image forming apparatus, and more particularly relates to an improved mechanism to prevent toner from leaking out of the developing device.
2. Discussion of the Background
There is known a developing device for developing an electrostatic latent image formed on a photoconductor in which a developing roller to supply toner to the photoconductor and a blade contacting a surface of the developing roller are mounted to a developing case containing toner therein. In such a developing device, the blade restricts the thickness of toner adhering to the developing roller. When single-component toner is used, the blade is pressed to contact the developing roller such that toner passing between the blade and the developing roller is charged by friction. When the blade is made of an elastically deformable metal plate the blade is fixed to the developing case and is pressed to the developing roller while being bent. In this case, because the rigidity of the blade is low, the blade is sandwiched between a blade holder with high rigidity and a supporting member so as to be laminated with each other, and the laminated blade, blade holder and supporting member are attached to the developing case.
If the developing device as described above is dropped during transportation, the developing roller and the blade vibrate and thereby toner intrudes into a gap between the backside of the blade and a blade attaching surface of the developing case and leaks out of the developing case. To prevent such leakage of toner, an opening of the developing case is sealed by a tape, which is peeled off when the developing device is used. This method of sealing an opening of a developing case with a tape requires an operation of taking off the seal when attaching the developing case to an image forming apparatus, which is troublesome.
In order to attach a blade made of a metal plate to a developing case, while laminating the blade with a long blade holder having high rigidity, a blade attaching surface corresponding to the long blade holder must be formed in the developing case. It is hard to form a blade attaching surface having a length corresponding to the long blade holder in a precise manner in the developing case. Generally, the blade attaching surface is formed partly uneven in the longitudinal direction and thereby the blade holder bends in the longitudinal direction together with the blade. Because of this bending of the blade holder and the blade, a contact line between the blade and the developing roller deviates from a line parallel to an axial line of the developing roller and thereby the contact pressure of the blade against the developing roller becomes uneven, causing an undesirable effect on the quality of a resulting image.
It may be conceivable to form protruding blade attaching surfaces in the vicinity of both ends of the developing case so as to support both ends of the blade holder, together with the blade, with the protruding blade attaching surfaces. However, the airtightness between the blade holder and the developing case is lost at the center part of the developing case, i.e., at a part between the blade attaching surfaces at both side ends of the developing case, and thereby toner tends to leak therefrom.
When a developing device is configured such that the amount of toner adhering to a developing roller is restricted by a blade, a roller part of the developing roller is disposed at a toner exit formed in a developing case and axial parts of the developing roller protruding from both ends of the roller part respectively are rotatably supported by supporting walls formed at both sides of the developing case. A lower edge of the blade contacts the roller part of the developing roller such that the blade seals a gap between an upper edge of the toner exit and an upper outer circumferential surface of the developing roller. Further, in order to prevent leakage of toner through a gap between an outer circumferential surface of the developing roller and the toner exit, side seals are provided at both longitudinal ends of the toner exit so as to contact outer circumferential surfaces of both ends of the roller part of the developing roller and an exit seal is provided at a flat surface of the developing case, which is formed in the developing case extending from a lower edge of the toner exit toward a photoconductor, so as to elastically contact the roller part of the developing roller.
In order to decrease the load to the developing roller when the developing roller is driven, the exit seal is generally formed with a thin plastic sheet having low compressibility and is configured such that a part of the exit seal is supported by the flat surface of the developing case and a free end part of the exit seal extending toward the toner exit from the flat surface is pressed against the outer circumferential surface of the developing roller by its own elasticity. The exit seal is generally stuck to the flat surface of the developing case by double-sided adhesive tape.
As described above, because the exit seal contacts the developing roller by its own elasticity and the part of the exit seal stuck to the flat surface of the developing case does not contact the developing roller, both ends of the exit seal tend to be peeled off. If both ends of the exit seal peel off, toner intruded under the exit seal intrudes toward both ends of the exit seal and may leak through a gap between the inner surfaces of the supporting walls formed at both sides of the developing case and the ends of the exit seal.
Further, in order to prevent leakage of toner through a gap between the outer circumferential surface of the developing roller and the toner exit, it is practiced that a free end side of an exit seal attached to a lower part of a developing case elastically contacts a lower outer circumferential surface of the developing roller and outer circumferential surfaces of both ends of a roller part of the developing roller are supported by side seals disposed at both longitudinal ends of the toner exit of the developing case.
When a blade is formed with a thin metal plate having elasticity and is configured such that the blade is bent by a developing roller so as to contact the developing roller by its reacting force when the blade is assembled in the developing device, as described above, the axial center of the developing roller is determined by a bearing of a developing case. In the above configuration, in order to bend the metal blade by pressure of the developing roller, the blade must be shorter than the interval between inner surfaces of side seals arranged at both sides of the developing roller. If the blade is made shorter than the interval between the inner surfaces of the side seals, a gap is generated between both ends of the blade and both inner surfaces of a toner exit, causing leakage of toner through the gap. If the blade is made longer than the interval between the inner surfaces of the side seals, the blade contacts the side seals due to pressure of the developing roller and thereby the blade cannot be bent any further. Such loss in the freedom of bending in the blade causes deformation of the blade and inferior sealing of a gap between the roller part of the developing roller and the side seals.
A known developing device includes a stirring device to stir toner in a developing case, a developing roller and a toner supplying roller to supply toner to the developing roller. In such a developing device, in order to transmit power to the toner stirring device and the toner supplying roller from the outside, rotation axes of these rotating devices protrude from a side wall of the developing case and gears are provided to ends of the protruded axes respectively to transmit rotation power to the axes.
In such a developing device, if sealing around the rotation axes of the stirring device and the toner s
Hosokawa Hiroshi
Nagai Kenichiroh
Osanai Kenetsu
Yamanaka Tetsuo
Chen Sophia S.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Tran Hoan
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