Electrophotography – Document handling – Copy
Reexamination Certificate
2002-08-27
2003-11-25
Ngo, Hoang (Department: 2852)
Electrophotography
Document handling
Copy
Reexamination Certificate
active
06654587
ABSTRACT:
The present application claims priority to Japanese Patent Application No. 2001-255866 filed Aug. 27, 2001, the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a continuous paper printer that uses the heat roll fusing method, and more particularly, to a continuous paper printer using which stable paper conveyance and printing performance can be obtained without the use of a buffer mechanism that would otherwise be included in order to provide appropriate tension to the continuous paper.
2. Description of the Related Art
Continuous paper printers using the heat roll fusing method have been available in the conventional art, in which folded continuous paper or rolled-up paper is placed in the apparatus and toner images are transferred and fused while the paper is supplied on a continuous basis. The paper conveyance speed provided by the fusing roller is determined in this type of apparatus by the diameter and the rate of rotation, or rpm, of the fusing roller. However, because the fusing roller becomes hot, the diameter thereof fluctuates due to thermal expansion. Therefore, it is difficult to completely match the conveyance speed of the fusing roller to the image conveyance speed of the image formation area. In addition, where continuous paper is used, because the paper is continuous, once a difference arises between the conveyance speed of the fusing roller and the image conveyance speed of the image formation area, such difference accumulates, causing either a gradual increase in the slackening of the paper or the application of excessive tension to the paper.
Accordingly, continuous paper printers equipped with a buffer mechanism that maintains the tension of the continuous paper between the transfer area and the fusing area at an appropriate level are commercially available. Such a continuous paper printer detects the tension of the continuous paper using the buffer mechanism, and by controlling the rate of rotation of the fusing roller in response to the detected tension, an appropriate level of tension is applied to the continuous paper.
A basic construction of a continuous paper printer equipped with a buffer mechanism (so called buffer arm) is shown in FIG.
8
. As shown in
FIG. 8
, a tractor
102
that supplies and conveys continuous paper
101
, conveyance rollers
103
and
105
, a conveyance motor
112
that drives these components, a conveyance guide
104
and other components are located in the paper supply area of the continuous paper printer. An image forming unit
110
to form toner images on the surface of the photoreceptor drum
107
, a transfer roller
106
and other components are located around the photoreceptor drum
107
in the image formation area. The image forming unit
110
includes a charger, an optical system and a developing device. Because the constructions of these components are in the public domain, they will not be described herein.
A fusing roller
108
that performs heat-roller fusing is located in the fusing area, and a paper eject roller
109
is located downstream therefrom in terms of the paper conveyance direction. Here, if the continuous paper
101
were in contact with the fusing roller
108
while the apparatus is standing by for printing, various problems would occur due to the heat supplied to the fusing roller
108
, such as burning of the continuous paper. Therefore, in order to avoid such problems, the apparatus is designed such that the fusing roller
108
separates from the continuous paper while the apparatus is standing by for printing.
A buffer arm
116
, a suction fan
111
and other components comprising a buffer mechanism are located between the transfer area and the fusing area. A buffer arm detection plate
117
to detect the paper tension is mounted to this buffer arm
116
. The rate of rotation of the fusing roller
108
is then controlled based on the tension thus detected. In addition, a buffer arm retracting mechanism (comprising a retracting motor, for example)
115
that retracts the buffer arm
116
downward is connected to the buffer arm
116
. Using this buffer arm retracting mechanism
115
, when continuous paper
101
is placed in the printer, the buffer arm
116
can be retracted downward, such that after the leading edge of the continuous paper
101
is introduced to the fusing roller
108
, the buffer arm
116
is returned to its original position. The suction fan
111
is used to suck the continuous paper
101
onto the buffer arm
116
so that the leading edge of the continuous paper
101
is reliably led to the fusing roller
108
without separating from the buffer arm
116
.
In the continuous paper printer described above, the continuous paper
101
is conveyed to the transfer area for the photoreceptor drum
107
via the tractor
102
, the conveyance rollers
103
and
105
and the conveyance guide
104
. The continuous paper
101
comes into contact with the photoreceptor drum
107
therein, and the toner image on the photoreceptor drum
107
is transferred to the continuous paper
101
by the transfer roller
106
. The continuous paper
101
is then conveyed to the fusing roller
108
via the buffer arum
116
, whereby the toner image is fused onto the continuous paper
101
. The continuous paper
101
is then ejected outside the printer by the paper eject roller
109
.
However, the conventional continuous paper printer described above includes a buffer arm
116
between the transfer area and the fusing area in order to supply an appropriate tension to the continuous paper
101
. Therefore, the problem of a large apparatus size has arisen. In addition, when the leading edge of the continuous paper
101
is conveyed toward the fusing roller
108
, the buffer arm
116
becomes an obstruction. Therefore, in order to avoid this problem, a retracting mechanism
115
by which to temporarily retract the buffer arm
116
downward is also included. As a result, the apparatus also entails the problem of high cost.
These problems can be eliminated by removing the buffer arm
116
. However, removing the buffer arm
116
would make it impossible to supply an appropriate tension to the continuous paper
101
between the transfer area and the fusing area. In other words, due to the changes in the rate of rotation of the fusing roller
108
, the tension of the paper would fall outside the proper range. If the fusing roller
108
were to pull the continuous paper
101
with an excessive strength, tearing (deformation or ripping of the tracking holes formed on either side of the paper) would occur. It would then become impossible to control the amount by which to convey the continuous paper
101
, and the initial printing position on each page would be likely to shift. Conversely, if the continuous paper
101
were too slack, the tension of the continuous paper
101
would become insufficient, resulting in creasing, and a loop would form in the continuous paper
101
, resulting in the contact between the unfused toner image and the printer components, which would lead to smudging of the image. As described above, removing the buffer arm
116
would prevent stable conveyance and printing performance from being achieved.
SUMMARY OF THE INVENTION
A main object of the present invention is to provide a continuous paper printer by which it is possible, via the provision of an appropriate tension to the continuous paper and the control of the initial printing position, to obtain stable paper conveyance and printing performance without using a buffer mechanism.
In order to resolve the problems identified above, the continuous paper printer pertaining to the present invention has paper conveyance means to supply and convey continuous paper, an image carrier that carries images, transfer means that transfers the image carried on the image carrier to the continuous paper conveyed by the paper conveyance means, fusing means that causes the continuous paper onto which the image has been transferred by the transfer means to pas
Minolta Co. , Ltd.
Morrison & Foerster / LLP
Ngo Hoang
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