Continuous medium printing apparatus

Details Continuous medium printing apparatus Continuous medium printing apparatus

1999-12-29

2003-08-19

Yan, Ren (Department: 2854)

Printing

Rolling contact machines

Rotary

C101SDIG029

Reexamination Certificate

active

06606945

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates generally to a continuous medium printing apparatus, and more particularly to a continuous medium printing apparatus suitable for use as a printer that performs printing on both sides of continuous paper formed at predetermined intervals with perforations by an electrophotographic method.
(2) Description of the Related Art
In continuous paper (continuous medium) on which printing is performed by a continuous medium printing apparatus, there is one in roll form and one folded and stacked at predetermined intervals. Furthermore, in some continuous paper, a plurality of perforations are formed in parallel with the lateral direction of the continuous paper at regular intervals depending on paper size. The continuous paper with perforations can easily be stacked by alternately folding it into mountains and valleys at the perforations or can easily be cut at the perforations.
A conventional continuous medium printing apparatus, which performs printing on both sides of such continuous paper by an electrophotographic method, attaches, for example, continuous paper folded and stacked alternately into mountains and valleys at perforations to a paper hopper. This continuous paper is conveyed while it is being stretched successively by a conveyance system. In an image forming process section, toner images are formed on the obverse and reverse sides of the continuous paper by image forming drums, respectively. Furthermore, the toner images formed on both sides of the continuous paper are fixed by image fixing sections, respectively. In this manner, duplex printing is performed on the continuous paper.
FIG. 13
shows the stretched continuous paper
1
. If the continuous paper
1
, folded and stacked alternately into mountains and valleys at perforations
1
a
, is stretched in order to perform printing, mountains and valleys with perforations
1
a
as apices will be produced in the continuous paper
1
, as shown in FIG.
13
.
Because of the mountains and valleys with perforations
1
a
as apices, in the image forming process section, a space will arise between the image forming drum, which transfers a toner image to the continuous paper
1
, and the continuous paper
1
and therefore a print trouble area will arise near the perforations
1
a.
There are cases where when printing is performed on continuous paper, an identification mark or the like is printed near the perforations
1
a
. In such a case, it is desirable to make such a print trouble area as small as possible.
Hence, in the continuous medium printing apparatus, the conveyance system is provided with a scuff section, which is constituted by a scuff roller and a pinch roller disposed opposite to each other at a downstream position of the conveying path of the continuous paper
1
from the image forming process section and the image fixing section. In this scuff section, the continuous paper
1
is conveyed by freely sliding and rotating the scuff roller in the conveying direction of the continuous paper
1
, with the continuous paper
1
clamped between the scuff roller and the pinch roller. That is, the continuous paper
1
is stretched by the scuff force (feed force) produced by the scuff roller in the scuff section, and the tension produced in the continuous paper
1
makes the mountains and valleys (unevenness) at the perforations
1
a
smaller, thereby stabilizing the behavior of the continuous paper
1
in the image forming process section.
Note that the difference d (see
FIG. 13
) between the mountain and the valley at the perforations
1
a
in the above-mentioned continuous paper
1
varies depending on the kind of the continuous paper
1
, that is, paper basis weight (paper thickness), paper stem, paper size and the like. As shown in
FIG. 13
, the difference d between the mountain and the valley is defined, for example, as a distance measured in the direction perpendicular to the paper conveying direction.
However, there are cases where the conventional continuous medium printing apparatus cannot cope with various kinds of continuous paper, because of scuff force produced by the scuff section is constant. For instance, in changing the kind of the continuous paper
1
, if scuff force is too strong, paper tear will occur at the perforations
1
a
or there is a possibility that the feed holes formed at regular intervals in the continuous paper
1
will crumble. If, on the other hand, scuff force is insufficient, the continuous paper
1
cannot be sufficiently tensioned, and consequently, there is also a possibility that printing quality will be degraded.
There is also a continuous medium printing apparatus provided along the conveying path of the continuous paper with a plurality of image forming drums for forming images on the continuous paper. In such a continuous medium printing apparatus, however, it is difficult to stretch the continuous paper
1
in each of a plurality of image forming process sections, by the feed force produced by the scuff section disposed at a downstream position of the conveying path of the continuous paper
1
from the image forming process section. Particularly, in the image forming drum disposed at a position away from the scuff section along the conveying path of the continuous paper
1
, there is also a problem that print trouble will easily occur near the perforations
1
a.
In addition, in the continuous medium printing apparatus which performs printing on both sides of the continuous paper
1
, unevenness near the perforations la in the continuous paper
1
cannot be effectively removed by the feed force produced by the scuff section, because a guide member, a roller and the like, which apply tension to the continuous paper
1
in contact with the opposite side of the continuous paper
1
from the image forming drum, cannot be provided near the image forming process section in order to protect the unfixed toner images formed on both sides of the continuous paper
1
.
Furthermore, in the scuff section, the continuous paper
1
is conveyed with the frictional force produced between the outer circumferential surface of the scuff roller and the continuous paper
1
, but there are cases where the coefficient of surface friction of the continuous paper
1
is reduced due to matter such as ink or dust on the continuous paper land the like. As a result, there is also a fear that because of the reduction in the coefficient of friction, (1) the feed force produced by the scuff section will be reduced, (2) the continuous paper
1
will slacken because it cannot be stretched, and (3) the contact of the continuous paper
1
with the guide surface or the glass surface of the fixer in the conveying path will damage a formed printed image and reduce printing quality or will damage the guide surface or the fixer.
Incidentally, in order to prevent the occurrence of print trouble near the perforations
1
a
in the continuous paper
1
, a method is known which stabilizes the behavior of the continuous paper
1
in the image forming drum, by disposing tractors for paper conveyance (tractor mechanisms), respectively, at upstream and downstream positions of the conveying path of the continuous paper
1
from the image forming drum and by conveying the continuous paper
1
with the feed pins of the tractor mechanisms fitted into feed holes formed at regular intervals in the laterally opposite portions of the continuous paper
1
.
Such a method, however, requires a large space for installing the tractor mechanisms. Therefore, in a continuous medium printing apparatus provided within the same case with a plurality of image forming drums, like a duplex printing apparatus which performs printing on both sides of the continuous paper
1
by an image forming drum for the obverse side and an image forming drum for the reverse side, the tractor mechanisms have to be disposed between these image forming drums in the paper conveying path, and consequently, there is a problem that the size of the apparatus cannot be reduced.
In addition,

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