Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2000-02-22
2001-10-30
Brase, Sandra (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S099000
Reexamination Certificate
active
06311031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus and, more particularly, to cleaners of a transferring device to transfer a toner image formed on a photosensitive drum onto a sheet of paper conveyed by adsorbing it to a transferring belt which also functions as a conveying means.
2. Description of the Related Art
In recent years, remarkable progress is observed in the digitization of electro-photographic apparatus and digital data used copiers using digital data comprising images have been widely used. So-called reversal developing system is mainly used for digital copiers and in the transferring process, polarity of a photosensitive drum and that of a transferring member such as a transferring corona are set so that they become different each other.
Accordingly, polarity of a sheet of paper as an image receiving medium and that of a photosensitive drum are reversed and attracted to each other and a paper is adsorbed to the photosensitive drum. So, it becomes necessary to devise a means to separate a sheet of paper from the photosensitive drum.
In conventional laser printers so far available, the process speed of many of them is slow and a small diameter is sufficient for a photosensitive drum and a paper can be separated by its stiffness and further, if necessary, a separation charger is provided as an auxiliary means at the downstream side of a transfer corona, and a paper is discharged to a degree not to disturb a toner image transferred on a sheet of paper.
However, digital copiers have fast process speed and it is required to make the diameter of photosensitive drums large. Therefore, separation of paper by its stiffness becomes difficult.
So, a system has been proposed to transfer a toner image on a photosensitive drum onto a sheet of paper using a transferring belt as a transferring member while conveying the paper by adsorbing it to the transferring belt.
However, when the transferring belt is used as a transferring member, a non-image area of a photosensitive drum contacts directly the transferring belt and after generating a so-called jam, the photosensitive drum having a toner image may contact directly the transferring belt. Because of this, it is indispensable to install a belt cleaner to clean the transferring belt.
As a belt cleaner, a blade cleaner using a blade formed with a rubber elastic body is used in many cases from cost and easiness of construction. As a demerit of a blade cleaner, it can be pointed out that the coating layer of the surface of the transferring belt may be injured as stress applied to the transferring belt is relatively large.
When the coating layer of the transferring belt is injured, the blade edge is damaged and the defecting cleaning is generated. Because of this, it is necessary to mount a lubricant applying mechanism separately to obtain a stabilized cleaning performance in the use for a long period.
From such a problem, many brush cleaners using a conductive brush are proposed as a cleaning member. However, for instance, for removing a large amount of toner after generating jam, a relatively long warm-up time is needed and in addition, there will be generated a problem that it becomes very difficult to remove toner entered into a conductive brush. Therefore, in the use for a long period, there is generated a problem that the back side of a paper is stained by a toner discharged from a conductive brush.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a transferring device equipped with cleaners capable of maintaining reliability in the use for a long period and cleaning a transferring belt stably and an image forming apparatus equipped with this transferring device.
According to the present invention, there is provided a transferring device comprising transferring means for transferring a toner image on a photosensitive body onto an image receiving medium adsorbed electrostatically to a transferring belt and conveyed by the transferring belt; a first cleaning means arranged so as to be able to contact/separate with/from the transferring belt for cleaning toner on the transferring belt when brought in contact with the transferring belt; a second cleaning means arranged so as to be able to contact/separate with/from the transferring belt at the downstream side in the conveying direction lower than the first cleaning means for cleaning the toner on the transferring belt when brought in contact with the transferring belt; and control means for controlling a switching between a first mode to bring the first cleaning means in contact with the transferring belt at the initial stage when starting to use and a second mode to separate the first cleaning means from the transferring belt and bring the second cleaning means in contact with the transferring belt when the running distance of the transferring belt reaches a prescribed value.
Further, according to the present invention, there is provided an image forming apparatus comprising developing means for developing an electrostatic latent image formed on a photosensitive body by supplying toner; a transferring belt configured to electrostatically adsorb an image receiving medium and convey the image receiving medium in one direction; transferring means for transferring a toner image on the photosensitive body developed by the developing means onto the image receiving medium electrostatically adsorbed to the transferring belt; a cleaning blade arranged so as to be able to contact/separate with/from the transferring belt and clean toner on the transferring belt when brought in contact with the transferring belt; a cleaning brush arranged so as to be able to contact/separate with/from the transferring belt at the downstream side in the conveying direction lower than the cleaning blade; and control means for controlling a switching between a first mode to bring the cleaning blade in contact with the transferring belt at the initial stage when starting to use and a second mode to separate the cleaning blade from the transferring belt and bring the cleaning brush in contact with the transferring belt when the running distance of the transferring belt reaches a prescribed value.
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Brase Sandra
Foley & Lardner
Toshiba Tec Kabushiki Kaisha
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