Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2000-06-19
2002-01-01
Grimley, Arthur T. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S105000
Reexamination Certificate
active
06336014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing unit, a process cartridge, and a developing cartridge for developing images using developing agent.
2. Description of Related Art
A conventional image forming device includes a known developing unit that develops electrostatic latent images into visible images using charged particles of toner. This type of developing unit can leak toner. The leaked toner can stain the interior of the image forming device and recording sheets, thereby degrading printing quality. The leaked toner can also stain the user's hands or clothes during replacement of the developing unit.
One such developing unit with this problem includes a developing roller and a layer thickness regulating blade. The developing roller transports toner on its surface, and the layer thickness regulating blade regulates the toner on the surface of the developing roller to a thin layer. The layer thickness regulating blade includes a stainless steel plate spring and a rosin or rubber pressing member, both formed to the same length in their lengthwise direction. Non magnetic single component developing agent is used as toner. The toner easily leaks from around the edges of the developing roller as the developing roller rotates.
Conventionally, various configurations have been provided inside the developing unit in order to prevent toner leakage. As will be described next, side seals, a lower film and sponge seal members are examples of configuration provided for preventing toner leakage.
The side seals are formed from a urethane sponge with a Teflon™ felt attached thereto. The urethane sponge needs to be sufficiently soft and have a low compression set. The side seals are positioned on opposite sides of the layer thickness regulating blade, near one or the other end of the developing roller. The side seals are disposed in sliding frictional contact with the peripheral surface of the developing roller to prevent toner from leaking around the lengthwise ends of the developing roller. The Teflon™ felt can be pressed with sufficient pressing force against the developing roller, without increasing rotational torque required for rotating the developing roller. The sides seals also pressingly contact the layer thickness regulating blade so as to pressingly sandwich the blade therebetween, in order to prevent toner from leaking out between the layer thickness regulating blade and the side seals.
The side seals of one type of developing unit are provided with their side surfaces pressed against the pressing member of the layer thickness regulating blade. However, with this configuration, toner can easily leak from between the layer thickness regulating blade and the side seals.
The side seals of another type of developing unit are disposed with one edge in contact with the free edge of the layer thickness regulating blade. That is, assuming that the layer thickness regulating blade extends downward and the pressing member is at the lowermost end of the blade, then the upper edge of the side seals presses against the lower edge of the pressing member. With this configuration, toner can be prevented from leaking initially. However, over a long period of use, fiber from the Teflon™ felt of the side seals can press up the pressing member and enter between the layer thickness regulating blade and the developing roller. As a result, a gap can open between the pressing member and the developing roller. Toner can leak out through the gap.
Either of these configurations involves a trade off between toner leaks and sufficient pressing force between the side seals and the layer thickness regulating blade. That is, if the side seals press against the pressing member with a force sufficient for preventing toner from leaking, then the side seals can interfere with the function of the layer thickness regulating blade. The pressing force from the side can prevent the thickness regulating blade from uniformly pressing against the developing roller, especially at the end portions of the developing roller. As a result, the layer thickness regulating blade cannot provide a uniform-thickness toner layer on the developing roller. However, when the pressing force blade is reduced to prevent such interference, toner can leak from between the side seal and the layer thickness regulating blade.
The lower film is for preventing toner from leaking between the developing roller and the portion of the developing unit casing below the developing roller. The lower film is maintained in sliding frictional contact with the developing roller at this location. The lower film is usually made from urethane rubber or a polyethylene terephthalate (PET) sheet. Although the urethane rubber provides a sufficiently soft pressing force, it has insufficiently low stiffness on its own, and so needs to be pressed from behind by a sponge or other member. The PET sheet is stiffer than the urethane rubber film and so does not need to be pressed from behind by a sponge member. Therefore, the PET sheet makes assembly processes easier than does the urethane rubber film.
The sponge seal members are also for preventing toner leaks from between the thickness regulating blade and the developing unit casing. The sponge seal members are disposed near lengthwise ends of the layer thickness regulating blade, between the developing unit casing and the rear surface of the layer thickness regulating blade, that is, the surface of the layer thickness regulating blade that faces away from the developing roller. One surface of each sponge seal member is attached to either the layer thickness regulating blade or the developing unit casing by two-sided tape. The opposite surface of the sponge seal member is pressed against the other of the layer thickness regulating blade and the developing unit casing by pressure alone.
The thickness regulating blade itself also functions to prevent toner leakage. Because the thickness regulating blade presses against the developing roller, it prevents toner from leaking between the developing roller and the opening in the developing unit casing.
However, the layer thickness regulating blade vibrates in association with rotation of the developing roller. This vibration is sufficient for producing gaps between the sponge seal member and either the layer thickness regulating blade or the developing unit casing, whichever in not adhered to the sponge seal member. Polymerized toner, which has excellent fluidity, can easily leak through those gaps.
Moreover, the toner can also leak through other sealed areas wherein a sponge seal member merely presses against surfaces of other configurations that vibrate in association with rotation of the developing roller.
SUMMARY OF THE INVENTION
It is an objective of the present invention to reliably prevent toner from leaking between side seals and the layer thickness regulating blade, while maintaining proper pressing force between the layer thickness regulating blade and a developing roller.
It is another objective of the present invention to reliably prevent toner from leaking between the developing unit casing and components that can potentially vibrate even slightly.
To achieve the above-described objectives, a developing device according to the present invention for developing a latent static-electric image into a visible image from developer, includes a developing case, a developer bearing body, a developer layer thickness regulator, and contact members.
The developing case is for holding developer, and is formed with an elongated opening.
The developer bearing body is disposed in the opening of the developing case, with lengthwise ends of the developer bearing body rotatably supported on the developing case.
The developer layer thickness regulator includes a pressing member and a plate spring member. The pressing member is formed from rubber or resin and extends in a lengthwise direction of the developer bearing body. The plate spring member supports the pressing member pressingly against an outer periphery of the develo
Deguchi Hideaki
Horinoe Mitsuru
Kamimura Naoya
Sato Fumikazu
Brother Kogyo Kabushiki Kaisha
Grimley Arthur T.
Ngo Hoang
Oliff & Berridg,e PLC
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