Printing – Stenciling – Rotary machines
Reexamination Certificate
2001-11-26
2004-11-30
Yan, Ren (Department: 2854)
Printing
Stenciling
Rotary machines
C101S118000, C101S420000
Reexamination Certificate
active
06823782
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to stencil printing machines for transferring print medium in pressured state between a printing drum, to which a stencil sheet is mounted, and a press rotary member to press the printing drum to perform a printing operation and, more particularly, to a stencil printing machine having two sets of printing drums and press rotary members for performing a double-face printing operation.
FIG. 1
shows a schematic overall structure of a conventional a stencil printing machine that enables a double-face printing operation. As shown in
FIG. 1
, the stencil printing machine
100
is constructed of upstream and downstream stencil making sections
104
,
105
with respective thermal printing heads
102
,
103
for thermally perforating respective stencil sheets
101
,
101
on the basis of respective image data, an upstream printing section
109
wherein the stencil sheet
101
made in the upstream stencil making section
104
is mounted onto an upstream printing drum
106
and a print sheet
107
, which is fed thereto, is transferred through a path between the upstream printing drum
106
and a press roller
108
in a pressured contact relationship to transfer ink onto an upper surface (one surface) of the print sheet
107
during such a transfer step, a paper feed section
110
which feeds the print sheet
107
to the upstream printing section
109
, an upstream belt-conveyer transfer unit
111
located at a sheet discharge side of the upstream printing section and transferring the print sheet
107
to a downstream side with the action of a belt
121
, a downstream printing section wherein the stencil sheet
101
, which is made in the downstream stencil making section
105
, is mounted onto a downstream printing drum
112
and the print sheet, which is fed from the upstream belt conveyer transfer unit
111
, is transferred through a path between the printing drum
112
and a press roller
114
in a pressured contact relationship to transfer ink onto a lower surface (the other surface) of the print sheet
107
during such a transfer step, and a downstream belt-conveyer transfer unit
117
with a belt
122
located at a sheet discharge side of the downstream printing section
115
for transferring the print sheet
107
to a sheet discharge tray
116
located in a downstream side.
Further, the upstream and downstream printing sections
109
,
115
include squeegee rollers
123
,
123
located inside the printing drums
106
,
112
, respectively, and held in contact with inner surfaces of outer peripheral walls
106
a
,
112
a
of the respective printing drums
106
,
112
, doctor rollers
124
,
124
located in close proximity to the squeegee rollers
123
,
123
, respectively, to form respective given gaps relative thereto, and ink supply units
125
,
125
each for supplying ink to an each area between the rollers
123
,
124
, with the squeegee rollers
123
,
123
being arranged to rotate on inner peripheral surfaces of the outer peripheral walls
106
a
,
112
a
in association with rotations of the respective printing drums
106
,
112
. In addition, as the squeegee rollers
123
,
123
rotate with the rotations of the printing drums
106
,
112
, the outer peripheral surfaces of the squeegee rollers
123
,
123
are adhered with ink in a given film thickness, with the adhered ink being transferred to the outer peripheral walls
106
a
,
112
a
to allow ink to be supplied to an inner side of the stencil sheet
101
at all times.
Now, the double-face printing operation is described below. Rotations of the printing drums
106
,
112
allow the print sheet
107
to be fed from the paper feed section
110
to the upstream printing drum
106
in synchronism with the rotation thereof. The print sheet
107
, thus fed to the printing drum
106
, is brought into pressured contact with the stencil sheet
101
of the printing drum
106
with the press roller
108
to allow ink image to be transferred onto the upper surface of the print sheet
107
, with the print sheet
107
, whose upper surface is printed, being peeled off from the outer peripheral wall of the printing drum
106
and being introduced to the upstream conveyer-belt transfer unit
111
. The upstream belt-conveyer transfer unit
111
causes the belt
121
to move for transferring the print sheet
107
with its lower surface remaining contact with the belt, thereby feeding the print sheet
107
from the most downstream side of the belt
121
to the downstream printing drum
112
. The print sheet
107
, thus fed to the downstream printing drum
106
, is then brought into pressured contact with the stencil sheet
101
of the printing drum
112
with the press roller
114
to transfer ink image onto the lower surface of the print sheet
107
, with the print sheet
107
, whose lower surface is printed, being peeled off from the outer peripheral wall of the printing drum
112
to be introduced to the downstream belt-conveyer transfer unit
117
. The downstream belt-conveyer transfer unit
117
causes the belt
122
to move for transferring the print sheet
107
from the most downstream side of the belt
122
to the sheet discharge tray
116
. The print sheet
107
thus discharged to the sheet discharge tray
116
is placed therein in the stacked state.
Also, a similar technology related to such a stencil printing machine
100
is disclosed in Japanese Patent Provisional Publication No. 8-90893.
By the way, in the aforementioned stencil printing machine for the double-phase printing operation, the print sheet
107
, whose upper surface has been printed with the upstream printing section
109
, is fed to the downstream printing section
115
in a non-fixed ink state to cause the press roller
114
of the downstream printing section
115
to press the upper surface, which remains in the non-fixed ink state, of the print sheet
107
. Accordingly, as shown in
FIG. 2
, the outer circumferential periphery of the press roller
114
and non-fixed ink
130
of the print sheet
107
are brought into surface contact in a wide range. For this reason, when the press roller
114
is separated from the print sheet
107
, non-fixed ink area
130
remaining at the contact surface is caused to be split such that a portion of non-fixed ink
130
is adhered to the press roller
114
. When this takes place, non-fixed ink is transferred to the press roller
114
and is then transferred to the print sheet
107
, providing an issue of contamination in the print sheet
107
.
To address such an issue, it is thought for providing a means for washing ink transferred to the press roller
114
with a waste.
However, with such a means for washing ink adhered to the press roller
114
, a mechanism for washing becomes complicated in structure and, also, a new issues is encountered in that ink is transferred from the print sheet
107
to the press roller
114
, resulting in a decrease in the print density of the print sheet
107
.
On the other hand, with such a stencil printing machine which enables only a single-phase printing operation, when the print sheet is not fed between the printing drum and the press roller to cause the press roller to be brought into direct contact with the stencil sheet owing to a jamming operation, when the print sheet whose size is smaller than a lateral size of the stencil sheet and a portion of the press roller is brought into direct contact with the stencil sheet and when the single-phase printing operation is implemented and the other surface of the print sheet in non-fixed ink state is subjected to the printing operation, there are some instances wherein ink is transferred to the press roller and transferred ink is further transferred to the print sheet, with a resultant contamination in the print sheet.
SUMMARY OF THE INVENTION
The present invention has been made to address the aforementioned issue and has an object to provide a stencil printing machine which is able to prevent print medium from being contaminated with little decrease in a print density of print medium with
Hashimoto Hirohide
Ike Yosuke
Takeno Mitsuru
Berkowitz Marvin C.
Nath Gary M.
Nath & Associates PLLC
Riso Kagaku Corporation
Yan Ren
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