Printing – Stenciling – Rotary machines
Reexamination Certificate
1999-06-08
2001-01-16
Funk, Stephen R. (Department: 2854)
Printing
Stenciling
Rotary machines
Reexamination Certificate
active
06173646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stencil printing machine capable of conducting clear printing, and a printing drum used in the printing machine.
2. Description of the Related Art
FIG.
16
and
FIG. 17
are sectional views showing a printing section of a conventional stencil printing machine.
FIG. 18
is a part of a circumferential wall of a printing drum; an essential portion of said printing section. A printing drum
100
has a circumferential wall
101
. The printing drum
100
is rotatably supported by an axis
102
and driven to rotate around the axis by non-illustrated driving means. In the circumferential wall
101
, there is formed an opening portion
104
(printing area) having many through holes
103
formed therein and a non-opening portion
105
(non-printing area) formed around said opening portion
104
. Clamping means
106
is disposed on the non-opening portion
105
in an outer circumferential surface of the circumferential wall
101
. A perforated stencil sheet
107
is clamped with the leading end thereof by the clamping means
106
and wrapped around the outer circumferential surface of the circumferential wall
101
. Inside the printing drum
100
, an ink supplying roller
108
is situated for supplying ink to an inner circumferential surface of the circumferential wall
101
. Below the printing drum
100
, a press roller
109
is situated to be vertically movably relative to the outer circumferential surface of the circumferential wall
101
. At least the surface of the press roller
109
is composed of an elastic material such as rubber and so on. A printing sheet is supplied in synchronization with rotation of the printing drum
100
. The printing sheet is pressed against a stencil sheet
107
on the circumferential surface of the printing drum
100
by the press roller
109
moving upward. Ink is supplied to the inner circumferential surface of the printing drum
100
and passes through the opening portion
104
and a perforated portion (perforations) of the stencil sheet
107
to transfer to the printing sheet, thereby forming an image thereon.
During printing in the aforementioned constitution, as shown in
FIG. 16
, the press roller
109
presses the stencil sheet
107
via a not-shown printing sheet. At the same time, on the opposite side of the press roller
109
relative to the printing drum
100
, the ink supplying roller
108
contacts the inner circumferential surface of the printing drum
100
. In this way, during printing wherein the printing drum
100
, the press roller
109
and the ink supplying roller
108
are superimposed on one another, pressure required for printing is conventionally applied only to a center portion of the printing drum
100
in the axial direction of the drum. Therefore, printing pressures exerted on both end-portions of the printing drum may be not enough and images formed there may be indistinct.
This seems to be due to insufficient ink transferring onto the printing sheet at both end-portions of the printing drum in the axial direction. This is caused by the fact that rigidity of the circumferential wall
101
of the printing drum
100
varies widely from the central opening portion
104
to the non-opening portions on both sides in the axial direction of the printing drum
100
, and that pressing force against both end-portions of the printing drum by the press roller
109
is reduced since the printing drum
100
is deformed while being pressed by the press roller
109
.
If the pressing force exerted on the printing drum
100
by the press roller
109
is increased to improve such problems, enough printing pressure is assured on both the end portions of the opening portion
104
in the axial direction of the printing drum
100
, thereby avoiding indistinct images to be formed there. However, printing pressure on the center of the opening portion
104
consequently increases, and ink transferring onto the center of printing sheet excessively increases. This brings another problems such as seeping-through, enlargement of printed images and so on.
SUMMARY OF THE INVENTION
The present invention is made in view of the problems aforementioned. An object of the present invention is to provide a stencil printing machine capable of uniformly exerting printing pressure on the entire of the opening area of the printing drum, thereby conducting normal printing on all of an effective printing area corresponding to the opening area.
A stencil printing machine as defined in a first aspect of the present invention comprises a printing drum including a cylindrical circumferential wall adapted to receive a perforated stencil sheet wrapped on an outer circumferential surface of itself and driven to rotate around a central axis of itself, the circumferential wall having an opening portion with many through holes formed therein, a non-opening portion formed around the opening portion, and at least one recessed portion formed in at least a part of the opening portion adjacent to the non-opening portion in an axial direction of the circumferential wall; an ink supplying roller situated in the printing drum for supplying ink to an inner circumferential surface of the cylindrical circumferential wall of the printing drum; and a press roller situated adjacent to the printing drum and being urged against the outer circumferential surface of the cylindrical circumferential wall of the printing drum.
In a stencil printing machine as defined in a second aspect of the present invention, the recessed portion communicates with the through hole in the stencil printing machine as defined in the first aspect.
In a stencil printing machine as defined in a third aspect of the present invention, the recessed portion is formed continuously to surround the through holes in the stencil printing machine as defined in the second aspect.
In a stencil printing machine as defined in a fourth aspect of the present invention, the recessed portion interconnects the through holes adjacent to each other in the stencil printing machine as defined in the second aspect.
In a stencil printing machine as defined in a fifth aspect of the present invention, the recessed portion includes a plurality of recesses formed separately from the through holes in the stencil printing machine as defined in the first aspect.
In a stencil printing machine as defined in a sixth aspect of the present invention, each of the recesses is formed between the through holes adjacent to each other in the circumferential wall in the stencil printing machine as defined in the fifth aspect.
In a stencil printing machine as defined in a seventh aspect of the present invention, the recessed portion includes a plurality of recesses, each being formed between the through holes adjacent to each other to extend in a circumferential direction of the printing drum in the stencil printing machine as defined in the second aspect.
In a stencil printing machine as defined in an eighth aspect of the present invention, each of the recesses is formed between the through holes adjacent to each other to extend in a circumferential direction of the printing drum in the stencil printing machine as defined in the fifth aspect.
In a stencil printing machine as defined in a ninth aspect of the present invention, the recessed portion is formed on the outer circumferential surface of the circumferential wall in the stencil printing machine as defined in the first aspect.
A stencil printing drum as defined in a tenth aspect of the present invention comprises a cylindrical circumferential wall adapted to receive a perforated stencil sheet wrapped on an outer circumferential surface of itself and driven to rotate around a central axis of itself, the circumferential wall having an opening portion with many through holes formed therein, a non-opening portion formed around the opening portion, and at least one recessed portion formed in the opening portion adjacent to the non-opening portion in an axial direction of the circumferential wall, wherein rigidity of the
Negishi Hideo
Tanaka Yoshitaka
Funk Stephen R.
Kanesaka & Takeuchi
Riso Kagaku Corporation
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