Printing – Stenciling – Rotary machines
Reexamination Certificate
2001-05-02
2003-08-12
Colilla, Daniel J. (Department: 2854)
Printing
Stenciling
Rotary machines
C101S116000, C101S129000
Reexamination Certificate
active
06604460
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stencil printing machines and more particularly to a stencil printing machine equipped with plural printing drums for achieving a multi-color printing and a method of controlling the same.
2. Description of the Related Art
Various research and development work has been undertaken to provide an improved stencil printing, a typical example of which is disclosed in
FIG. 6
which shows a part of a structure of the earlier stencil printing machine. In
FIG. 6
, first and second printing drums
101
and
102
and a press drum
103
are rotatably supported in a frame body (not shown) such that the first and second printing drums
101
and
102
are located in close proximity to an outer periphery of the press drum
103
at positions angled at 90 degrees of a central angle of the press drum
103
. Outer circumferential peripheries of the respective first and second printing drums
101
and
102
carry thereon stencil clamping bases
101
a
and
102
a
, respectively, which support thereon sheet clamping segments
101
b
and
102
b
for clamping stencil sheets (not shown) onto the stencil clamping bases
101
a
and
102
a
, respectively.
Further, screens
105
are wound on the outer circumferential peripheries of the first and second printing drums
101
and
102
in a stretched state with the use of the stencil clamping bases
101
a
and
102
a
and springs
104
, with each of the screens
105
being formed of a mesh structure which allows printing ink to permeate. Inner press rollers
106
and
107
, which serve as ink supply rollers, respectively, are located inside the screens
105
of the first and second printing drums
101
and
102
, respectively, with the inner press rollers
106
and
107
being moveable between a wait position not to press the screens
105
and a press engagement position to press the screens
105
.
During printing operation, the inner press rollers
106
and
107
are maintained in the press engagement position, in which the screens
105
are expanded outward. Also, it is arranged such that the screen
105
of the first printing drum
101
is supplied with printing ink in a first color by the inner press roller
106
and the screen
105
of the second printing drum
102
is supplied with printing ink in a second color by the inner press roller
107
. The outer circumferential periphery of the press drum
103
is provided with a print sheet clamping segment
109
, for clamping a leading edge of a print sheet
108
, which clamps the leading edge of the print sheet
108
transferred from a paper feed section
110
and release the leading edge of the print sheet
108
at a position in the vicinity of an inlet portion of a sheet discharge section
111
.
Now, the stencil printing machine thus arranged operates as follows. A leading edge of a first stencil sheet, which has been made on the basis of image data in a first color of an original is clamped with the sheet clamping segment
101
b
of the first printing drum
101
, and a leading edge of a second stencil sheet, which has been made on the basis of image data in a second color of the original, is clamped with the sheet clamping segment
102
b
of the second printing drum
102
, with the stencil sheets being mounted onto the outer circumferential peripheries of the respective screens
105
. Next, the first and second printing drums
101
and
102
and the press drum
103
are rotated in synchronism with one another in directions as shown by arrows in
FIG. 6
, thereby causing the print sheet
108
to be transferred between the first printing drum
101
and the press drum
103
from the paper feed section
110
. The print sheet
108
thus transferred is clamped with the print sheet clamping segment
109
of the press drum
103
, allowing the print sheet to pass along the outer circumferential periphery of the press drum
103
between the first printing drum
101
and the press drum
103
.
During this passing step of the print sheet, the inner press roller
106
is brought into press engagement with the screen
105
of the first printing drum
101
which is consequently expanded outward, allowing printing ink to be transferred to the print sheet
108
to reproduce a desired image pattern with a first color via a perforated image area of the first stencil sheet. The print sheet
108
, which has passed between the first printing drum
101
and the press drum
103
, then passes between the second printing drum
102
and the press drum
103
. During this passing step of the print sheet, the inner press roller
107
is brought into press engagement with the second screen
105
which is consequently expanded outward, allowing printing ink to be transferred to the print sheet
108
to reproduce a desired image pattern with a second color. As the sheet clamping segment
109
of the press drum
103
is rotated to a position near the inlet of the sheet discharge section
111
, the sheet clamping segment
109
is released, with the released print sheet
108
being discharged to the given discharge position by the sheet discharge section
111
. In this manner, two-color printing is completed.
SUMMARY OF THE INVENTION
As noted above, the first and second printing drums
101
and
102
are located at the rotational positions spaced by 90 degrees of central angle of the press drum
103
, in which the first and second printing drums
101
and
102
are rotated with the rotational phase angle of 180 degrees such that the respective printing positions of the first and second printing drums
101
and
102
are aligned with one another relative to the press drum
103
. As a consequence, the stationary rest positions of the respective printing drums
101
and
102
are kept in opposing positions of 180 degrees at the termination of the printing operation.
By the way, in the earlier practices, since no consideration has been undertaken to the rotational stop positions of the respective printing drums
101
and
102
at the termination of the printing operation, when, for example, the first printing drum
101
, which is one of the printing drums, is stopped at the stationary rest position in an upper area, the second printing drum
102
, which is the other remaining printing drum, is caused to stop at the stationary rest position located in a lower area, with this stationary rest position being left until the start of next printing operation.
On the other hand, in the event ink pools are located at upper circumferential positions of the respective inner press rollers
106
and
107
and supply printing ink to the inner press rollers
106
and
107
, the printing ink is liable to gradually flow downward in a long time period along the respective outer peripheries of the inner press rollers
106
and
107
. Consequently, when the stencil clamping bases
101
a
and
102
a
remain at the lower positions, the dropped printing ink.flows through a gap between the each screen
105
and each stencil clamping base
101
a
or
102
a
onto a surface of each stencil clamping base
101
a
or
102
a
, causing that surface to be stained with the printing ink.
The present invention has been made to address various issues encountered in the earlier practices and has an object of the present invention to provide a stencil printing machine which can prevent stains with printing ink as little as possible in a stationary rest position of each printing drum.
According to a first aspect of the present invention, there is provided a stencil printing machine having a frame body, which comprises a press drum rotatably supported in the frame body, a plurality of printing drums rotatably supported in the frame body in close proximity to the press drum and each including an outer circumferential periphery having a first portion formed with a stencil clamping base, which has a stencil clamping segment and a second remaining portion formed with an ink permeable member, and a plurality of ink supply rollers located inside the printing drums, respectively, for supplying ink to res
Berkowitz Marvin C.
Colilla Daniel J.
Culler Jill E
McGee Sheldon M.
Nath & Associates PLLC
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