Printing – Stenciling – Rotary machines
Reexamination Certificate
2001-07-19
2003-03-04
Evanisko, Leslie J. (Department: 2854)
Printing
Stenciling
Rotary machines
C101S116000, C101S409000
Reexamination Certificate
active
06526881
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing machine having a printing drum onto which a stencil sheet is attached and a pressure drum clamping a print sheet. The printing machine transports the print sheet clamped by the pressure drum along the outer peripheral surface of the pressure drum, whereby the print sheet is pressed against the stencil sheet on a press portion on which the printing drum and the pressure drum press each other.
2. Description of the Related Art
A stencil printing machine as one type of printing machines is constituted so that an image on the print sheet is printed via below-described some steps.
(1) A stencil sheet is thermally perforated so as to correspond to image data.
(2) The stencil sheet thus thermally perforated is wound around and attached onto the outer peripheral surface of a printing drum.
(3) A pressure drum having a sheet clamp section is rotated synchronously with the rotation of the printing drum.
(4) The tip end of a print sheet, which is transported from a paper feed section, is clamped at a rotation upstream position of the press portion on which the printing drum and the pressure drum press each other.
(5) The print sheet thus clamped is transferred along the outer peripheral surface of the pressure drum, whereby the print sheet is transferred while the print sheet is pressed against the stencil sheet attached onto the printing drum.
(6) Ink is transferred to the print sheet in the press and transfer step (that is, (5) step).
The stencil printing machine as described above is required for the sheet clamp section of the rotating pressure drum to receive the print sheet from the paper feed section by clamping the tip end of the print sheet transferred from the paper feed section, and to take over the transportation of the print sheet. The constitution of the printing machine proposed herein is shown in
FIGS. 1 and 2
.
In
FIGS. 1 and 2
, a printing drum
100
is rotatably provided about a rotation center C
1
in an arrow direction. Furthermore, a stencil sheet clamp section (not shown) clamping the tip end of a stencil sheet (not shown) is provided on the outer peripheral surface of this printing drum
100
. The outer peripheral wall of the printing drum
100
is of an ink permeable structure to allow ink to be supplied from inside to the outer peripheral wall. A pressure drum
101
is rotatably provided about a rotation center C
2
below the printing drum
100
in an arrow direction. A sheet clamp section
103
clamping the tip end of a print sheet
102
is provided in the vicinity of the outer peripheral surface of the pressure drum
101
. The outer peripheral surfaces of the printing drum
100
and the pressure drum
101
are opposite each other, and are constituted to be capable of being pressed relatively to each other by pressing means.
A paper feed section
105
includes a primary paper feed roller (not shown) transferring only an uppermost print sheet
102
from print sheets
102
stacked on a paper feed tray (not shown), a pair of secondary paper feed rollers
106
transferring the print sheet conveyed by the primary paper feed roller toward a pressure drum side, and guide members
107
guiding the print sheet
102
transferred by the pair of secondary paper feed rollers
106
toward a predetermined rotation position on the outer peripheral surface of the pressure drum
101
.
In the paper feed section
105
, the printing drum
100
to which the stencil sheet is attached and the pressure drum
101
rotate synchronously with each other in the arrow direction shown in FIG.
1
. As a result, the print sheet
102
is fed from the secondary paper feed rollers
106
so that the tip end of the print sheet
102
is abutted on the sheet clamp section
103
of the pressure drum
101
at timing at which the sheet clamp section
103
is located at the rotation position shown in
FIG. 1
(see a two-dot chain line
102
shown in FIG.
1
). Then, the sheet clamp section
103
clamps the tip end of the print sheet
102
thus fed. The clamped print sheet
102
is transferred along the outer peripheral surface of the pressure drum
101
synchronously with the rotation of the pressure drum
101
. Ink is transferred onto the print sheet
102
on the press portion on which the printing drum
100
and the pressure drum
101
press each other. The sheet clamp section
103
unclamps the print sheet
102
downstream of the press portion in a rotation direction. The print sheet
102
thus unclamped is transferred to a sheet discharge section (not shown). When the sheet clamp section
103
of the pressure drum
101
arrives at the rotation position shown in
FIG. 1
, the above-described operation is repeated, whereby printing operation is executed in succession.
As indicated by a solid line shown in
FIG. 1
, however, if the tip end of the print sheet
102
is warped upward because of the curl, the material or the like of the sheet, the tip end of the print sheet
102
may possibly not be abutted on the sheet clamp section
103
. Then, as shown in
FIG. 2
, the print sheet
102
is transferred to the portion between the pressure drum
101
and the printing drum
100
while the tip end of the print sheet
102
is not clamped by the sheet clamp section
103
. If so, the print sheet
102
cannot be transferred further and sheet clogging occurs. In addition, even if the sheet clamp section
103
cannot clamp part of the print sheet
102
and the print sheet
102
is transferred to the portion between the pressure drum
101
and the printing drum
100
, the tip end of the print sheet
102
may possibly be, for example, flawed, bent or creased.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problems. It is, therefore, an object of the present invention is to provide a printing machine capable of ensuring clamping the tip end of a print sheet by the sheet clamp section of a pressure drum and capable of preventing the flaw or the like of the tip end of the print sheet.
The first aspect of the invention provides a printing machine comprising: a printing drum around which a perforated stencil sheet is wound, and which is provided rotatably about a first axis; a pressure drum having a sheet clamp section for clamping a tip end of a print sheet, and which is provided rotatably about a second axis; and outer peripheral surfaces of the printing drum and the pressure drum, and provided to be freely pressed relatively to each other, the printing drum and the pressure drum opposite to each other on the outer peripheral surfaces, wherein the tip end of the print sheet, which is transferred from a paper feed section synchronously with rotation of both the printing drum and the pressure drum, is clamped by the sheet clamp section at a rotation clamp position upstream of a press position in a rotation direction, the printing drum and the pressure drum press each other on the press portion, the print sheet thus clamped is transferred along the outer peripheral surface of the pressure drum and the print sheet is pressed against the perforated stencil sheet on the press portion, whereby printing is conducted to the print sheet; and wherein the printing machine is provided with a sheet clamp guide member for guiding the tip end of the print sheet, which is transferred from the paper feed section, to a clamp spot of the sheet clamp section located at the rotation clamp position.
According to the first aspect of the invention, even if the tip end side of the print sheet has a curl such as an upstream warp, the tip end of the print sheet, which is transferred from the paper feed section, is guided to the clamp spot of the sheet clamp section by the clamp guide member.
The second aspect of the invention provides a printing machine according to the first aspect of the invention, wherein the sheet clamp section is divided into a plurality of segments in a direction substantially orthogonal to a sheet transfer direction; wherein guide entry spaces are provided between the divided segments
Berkowitz Marvin C.
Evanisko Leslie J.
Nath Gary M.
Novick Harold L.
Riso Kagaku Corporation
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