Electrophotography – Image formation – Development
Reexamination Certificate
2001-10-17
2003-11-18
Braun, Fred L (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06650855
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a color image forming apparatus that can be applied to a color printer, a color copying machine or a color facsimile, and it relates, in particular, to a color image forming apparatus that forms a color image by overlapping multicolor toner images by electrophotography.
BACKGROUND ART
In such a color image forming apparatus, development units of four colors (yellow, magenta, cyan and black) usually are used. These development units are contained in a carriage supported rotatably within a perpendicular plane in a main body of the apparatus, so that a photosensitive body of the development unit for each color is moved sequentially between an image forming position and a waiting position, whereby the development units can be switched.
In this type of color image forming apparatus in which a plurality of the development units are contained in the carriage and rotated within the perpendicular plane as described above, it is necessary to provide a mechanism for preventing each of the development units from dropping out of the carriage. In the following, the configuration around a carriage of a conventional color image forming apparatus having such mechanism will be described with reference to FIG.
12
.
As shown in
FIG. 12
, the interior of a carriage
1041
is provided with four carriage reinforcing plates
109
that are arranged radially from a rotation center of the carriage
101
and spaced away from each other by 90°. These carriage reinforcing plates
109
also serve as partition plates for dividing an inner space of the carriage
101
into four spaces. A development unit
102
is contained in each of these four spaces.
Each of these four spaces in the carriage
101
is provided with a carriage guide groove
105
and a guide pin groove
106
for guiding the development unit
102
. The end of the carriage guide groove
105
is formed to be slightly larger than the other portion. Also, near the end of the guide pin groove
106
, a unit lock member
107
is provided such that its tip is located inside the guide pin groove
106
, and the unit lock member
107
constantly is forced by a unit lock spring
108
toward the guide pin groove
106
. On the other hand, each of the development units
102
is provided with a development unit rotating shaft
103
to be guided along the carriage guide groove
105
and a development unit guide pin
104
to be guided along the guide pin groove
106
. The development unit rotating shaft
103
has an oval-shaped cross-section. After being inserted in the carriage
101
from above, each of the development units
102
is rotated toward an arrow direction, so that the development unit guide pin
104
advances over the unit lock member
107
and then is locked. At this time, the development unit rotating shaft
103
comes to engage the end of the carriage guide groove
105
. The above-described double lock state makes it possible to prevent each of the development units
102
from dropping out of the carriage
101
.
However, in the conventional color image forming apparatus described above, because the lock mechanism is provided, two actions are needed for attaching the development unit to the apparatus main body or removing the development unit from the apparatus main body, causing a problem in that the attaching/removing of the development units becomes complicated.
DISCLOSURE OF INVENTION
The present invention was made in order to solve the conventional problem mentioned above, and it is an object of the present invention to provide a color image forming apparatus that can prevent a development unit from dropping out of a carriage, without any lock mechanism.
In order to achieve the above-mentioned object, a first configuration of a color image forming apparatus according to the present invention includes a plurality of development units, each development unit having a toner for a different color and a developing member, a carriage for supporting the plurality of development units so as to be attachable/removable with respect to an apparatus main body, a carriage driving system for rotating the carriage so as to move the plurality of development units sequentially and switch them between an image forming position and a waiting position, a unit positioning system for positioning the development unit at a normal position with respect to the apparatus main body in the image forming position, guide rails for restricting a moving track of the development unit during a rotation of the carriage, and a transfer system for transferring a toner image formed by the plurality of development units onto a printing medium. With this first configuration of the color image forming apparatus, since the development unit can be rotated in such a manner as to be held between the carriage and the guide rails, the moving track of the development unit is stabilized. Also, since a lock mechanism or the like for preventing the development unit from dropping out of the carriage becomes unnecessary, the development unit can be attached or removed in a single action when it is located in an upper side of the carriage.
In the first configuration of the color image forming apparatus according to the present invention described above, it is preferable that the guide rails are fixed to left and right side plates of the apparatus main body, and both ends of the development unit are supported by the guide rails. With this preferable example, the guide rails can be formed using relatively small members.
In the first configuration of the color image forming apparatus according to the present invention described above, it is preferable that the guide rails are formed to have an arc shape whose center corresponds to a rotation center of the carriage, and a bisectional point of the arc shape (a point bisecting the arc) of each of the guide rails is located lower than the rotation center of the carriage. With this preferable example, the development unit reliably can be prevented from dropping out.
In the first configuration of the color image forming apparatus according to the present invention described above, it is preferable that at least one of the plurality of development units can be attached to/removed from the apparatus main body when located outside a fan-shape formed by the guide rails and a rotation center of the carriage. With this preferable example, the development unit can be removed only by lifting it up and attached only by dropping it in.
In the first configuration of the color image forming apparatus according to the present invention described above, it is preferable that the development unit does not contact the guide rails when the development unit is positioned in the image forming position by the unit positioning system. With this preferable example, since the development unit does not contact the guide rails in the image forming position, the development unit can be positioned accurately. After the positioning, it also is possible to prevent an external force inhibiting an excellent image formation from being applied to the development unit.
In the first configuration of the color image forming apparatus according to the present invention described above, it is preferable that each of the plurality of development units integrally includes a photosensitive body having a surface on which a static latent image is formed, and development unit guide portions that slide in contact with the guide rails during the rotation of the carriage are provided on left and right ends of the photosensitive body. With this preferable example, while avoiding the contact of the exposed photosensitive body with the guide rails and other components on the main body side, it is possible to restrict the moving track of the development units reliably during the rotation of the carriage. In this case, it is preferable that the development unit guide portions are provided on a line connecting a rotation center of the carriage and a center of the photosensitive body. With this preferable example, it is possible to minimize the contact length
Braun Fred L
Merchant & Gould P.C.
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