Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
1999-05-27
2001-03-06
Moses, Richard (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S113000, C399S116000
Reexamination Certificate
active
06198891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus of tandem type which includes a plurality of photoreceptors disposed along a linearly extending sheet transportation path.
2. Description of Related Art
In recent years, color image forming apparatuses of tandem type have been provided in which four photoreceptor drums respectively adapted to form cyan, magenta, yellow and black monochromatic toner images are disposed in series along a linearly extending sheet transportation path.
In such a tandem color image forming apparatus, the four photoreceptor drums for cyan, magenta, yellow and black image formation are disposed in parallel as extending perpendicularly to a sheet transportation direction. The monochromatic toner images of the respective colors are formed on surfaces of the respective photoreceptor drums. In the course of transportation of a sheet along the sheet transportation path, the monochromatic toner images formed on the respective photoreceptor drums are successively transferred onto the sheet. After the transfer of the fourth color toner image, the toner images on the sheet are subjected to a fixation process, whereby a full color image is recorded on the sheet.
Since the tandem image forming apparatus is constructed so that four toner images are successively transferred in superimposition on a sheet, there is a possibility of misregistration of the respective color toner images, which will show up as a color offset in the resulting image.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus which is less liable to cause a color offset in an image formed on a sheet.
The image forming apparatus of the present invention comprises: a plurality of photoreceptors provided along a sheet transportation path and each extending perpendicularly to the sheet transportation path; an imaging mechanism for forming toner images on surfaces of the respective photoreceptors; and a pair of support plates which receive opposite end circumferential portions of the respective photoreceptors to support the photoreceptors together in a parallel relation.
The sheet transportation path may be a linear transportation path.
The imaging mechanism may be adapted to form different color toner images on the respective photoreceptors. The pair of support plates may support the plurality of photoreceptors in a rotatable manner.
The photoreceptors may be of a drum shape.
With this arrangement, the plurality of photoreceptors are supported with their opposite end circumferential portions received by the pair of support plates and, hence, there is no likelihood of a color offset which may otherwise occur due to wobbling of the photoreceptors during the driving thereof.
In a conventional arrangement in which photoreceptors each have a drum shaft extending therethrough and opposite ends of the drum shaft are supported by bearings, the photoreceptors may wobble due to off-centering of the drum shaft during the driving thereof if the rotation center of the photoreceptor does not exactly coincide with the drum shaft. On the contrary, the aforesaid arrangement is such that the photoreceptors have no drum shaft and the circumferential portions of the photoreceptors are supported and, therefore, the photoreceptors never suffer from wobbling which may otherwise occur due to the off-centering of the drum shafts. Hence, there is no danger that the respective color toner images are misregistered on the sheet to cause a color offset in the resulting image. Thus, formation of a high quality image can be ensured.
It is preferred that bearings are fitted around the opposite end circumferential portions of the respective photoreceptors, and the pair of support plates each have the same number of cut-away portions as the number of the photoreceptors, the cut-away portions being formed in a spaced apart relation for receiving outer rings of the bearings.
The cut-away portions are preferably formed equidistantly.
Further, the pair of support plates are preferably conformal members which are formed by stamping flat plates by means of the same stamping die.
With this arrangement, the pair of support plates are formed with the use of the same stamping die and, hence, the cut-away portions formed in one of the support plates are arranged at the same interval as the cut-away portions formed in the other support plate. Since the plurality of photoreceptors supported by the pair of support plates are arranged parallel to each other, there is no possibility that any one of the photoreceptors is disposed at angles with respect to the other photoreceptors to cause misregistration of the respective color toner images on the sheet. In addition, the parallel arrangement of the photoreceptors can be achieved simply by supporting the photoreceptors on the pair of support plates. Accordingly, there is no need for adjustment of the parallelism of the photoreceptors.
The image forming apparatus may further includes a squareness adjustment mechanism for properly positioning one of the pair of support plates with respect to the other support plate along the sheet transportation path, so that the plurality of photoreceptors are each disposed perpendicularly to the sheet transportation path.
With this arrangement, the position of the one support plate with respect to the other support plate along the sheet transportation path can easily be adjusted by means of the squareness adjustment mechanism and, therefore, the plurality of photoreceptors supported by the pair of support plates can each easily be disposed perpendicularly to the sheet transportation direction. Thus, the plurality of photoreceptors can be prevented from being arranged in parallel on the skew with respect to a direction perpendicular to the sheet transportation direction. Therefore, the image is prevented from being formed on the skew with respect to an edge of the sheet, so that the quality of the image can further be improved.
The imaging mechanism may include the bearings fitted around the opposite end circumferential portions of the photoreceptors, a frame including the pair of support plates and detachably supporting image forming sections including the photoreceptors, a pair of fixture plates supporting the bearings attached to the opposite end portions of each of the photoreceptors, engagement portions respectively projecting from the pair of fixture plates outwardly of the frame, and a fixture mechanism fixing the pair of fixture plates to the frame in engagement with the engagement portions. In this case, the cut-away portions which receive the outer rings of the bearings are provided in upper edge portions of the support plates.
With this arrangement, the bearings fitted around the opposite end portions of the photoreceptors are fixed to the pair of fixture plates, and then the engagement portions provided on the pair of fixture plates are brought into engagement with the fixture mechanism, whereby the photoreceptors each supported on the pair of fixture plates can be fixed to the frame. More specifically, the attachment and detachment of the photoreceptors to the frame can be achieved by such a simple action that the fixture mechanism is brought into and out of engagement with the engagement portions provided on the pair of fixture plates. This remarkably facilitates the assembly of an imaging unit.
Further, the positioning of the photoreceptors can readily be achieved by fitting the bearings fitted around the opposite end circumferential portions of the photoreceptors in the cut-away portions of the pair of support plates.
Where the present invention is applied to a color image forming apparatus of tandem type, replacement of the image forming sections can easily be achieved. Since the respective image forming sections can be kept in a consistent positional relationship, a color offset in an image formed on a sheet can be prevented.
The fixture mechanism may include slide plates attached to the frame slidably along the length of the support plat
Ishida Hideki
Kamidaira Kazuya
Kusuda Toshiaki
Miyamoto Kiyoaki
Nakano Kuniaki
Kyocera Mita Corporation
Moses Richard
Smith , Gambrell & Russell, LLP
LandOfFree
Image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2474235