Printing – Stenciling – Rotary machines
Reexamination Certificate
2001-07-19
2003-01-07
Evanisko, Leslie J. (Department: 2854)
Printing
Stenciling
Rotary machines
C101S114000, C101S116000, C101S416100
Reexamination Certificate
active
06502506
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a stencil printing machine wherein a perforated stencil sheet is mounted onto a printing drum against which a print sheet is pressed during transfer thereof to allow ink to be transferred to the print sheet through a perforated area of the stencil sheet to generate a desired image thereon, and more particularly to a stencil printing machine effectively preventing paper dusts from being adhered to the stencil sheet mounted onto the printing drum.
Several researches and developments have been undertaken to provide a stencil printing machine of the type which enables printing with the use of a printing drum and a rotary back press roller, a typical example of which is disclosed in
FIG. 9
which shows an essential part of a structure of the prior art stencil printing machine.
In
FIG. 9
, the stencil printing machine
10
includes a paper feed section
12
adapted to feed a print sheet S one by one from a stack of print sheets (not shown), and a print section
14
which enables printing on the print sheet S, which has been fed from the paper feed section
12
, to reproduce a desired image thereon.
The paper feed section
12
includes plural paper feed roller pairs
12
a
,
12
b
which are arranged to be held in press contact with the print sheet S, creating frictional pressure during rotation of the roller pairs
12
a
,
12
b
to cause the print sheet S to be transferred to the print section
14
at predefined timings. The print section
14
includes a printing drum
16
, and a back press roller
18
located in close proximity thereto and serving as a rotary printing press member for imparting printing pressure to the printing drum
16
. In particular, the printing drum
16
and the back press roller
18
are rotatably supported under a condition wherein respective outer circumferential peripheries are partially located in substantially close proximity to one another. The printing drum
16
carries on its outer circumferential periphery a stencil clamping base
20
which clamps a leading edge of a stencil sheet
22
. The stencil sheet
22
has a perforated image area or pattern which is formed by perforating with a thermal printing head based on image data. The outer circumferential periphery of the printing drum
16
also carries a flexible screen
24
over an area except for the stencil clamping base
20
, with the flexible screen
24
being constituted with an ink permeable porous sheet. An inner press roller
26
is located inside the printing drum
16
, which is moveable between a press contact position wherein the inner press roller
26
remains in press contact with an inner peripheral wall of the screen
24
and a wait position wherein the inner press roller
26
is held out of press contact with the inner peripheral wall of the screen
24
. An outer periphery of the inner press roller
26
is supplied with ink, with the thickness of an ink layer adhered onto the inner press roller
26
being regulated with a gap formed by a doctor roller
28
to maintain the quantity of the ink to be applied to the screen
24
at a given constant level substantially at all times in the operation.
In the operation with such a structure, the perforated stencil sheet is made by perforating the stencil sheet
22
over a given area thereof on the basis of image data to produce a desired perforated area, and the perforated stencil sheet
22
is mounted onto the outer circumferential periphery of the printing drum
16
. The printing drum
16
, to which the stencil sheet
22
is mounted, is rotated in synchronism with the back press roller
18
as shown by an arrow in
FIG. 9
, with the print sheet S being transferred between the printing drum
16
and the back press roller
18
from the paper feed section
12
. In this instance, the inner press roller
26
is moved to the press contact position to cause the screen
24
, which adjacently has the stencil sheet
22
, to be expanded outward during transfer of the print sheet S for thereby allowing the print sheet S to be held in press contact between the screen
24
and the back press roller
18
while transferring the print sheet S. During such a transfer step of the print sheet S in press contact with the screen
24
and the back press roller
18
, the ink is transferred from the inside of the screen
24
to the print sheet S through the perforated area of the stencil sheet
22
, reproducing the desired image on the print sheet S in dependence on the perforated area of the stencil sheet
22
.
SUMMARY OF THE INVENTION
Due to further investigations performed by the present inventors, it is thought that the print sheet S encounters paper dusts that are produced due to friction caused with the paper feed roller pairs during travel thereof or paper dusts that are produced when the print sheet S has been cut and are adhered to the print sheet S. With such paper dusts adhered onto the print surface of the print sheet S, the paper dusts are transferred onto the stencil sheet
22
mounted onto the printing drum
16
when the print sheet S is pressed against the printing drum
16
such that the paper dusts are adhered to the stencil sheet
22
. The paper dusts, that are separated from the print sheet S in a floating state, are adhered to the surface of the stencil sheet
22
.
The paper dusts adhered to the stencil sheet
22
readily absorb the ink, thereby causing inadequate quantity of the ink to be transferred onto the print sheet S. As a result, the printed sheet S tends to have a thin area (i.e., a white area) of image corresponding to that of the stencil sheet adhered with the paper dusts. Also, in the event that the print sheet S and the paper dusts remaining thereon are sufficiently wet, a large quantity of the ink permeates into the paper dusts, and such ink is transferred onto the print sheet S. This causes the print sheet S to be transferred with more quantity of the ink than required, with the printed image being reproduced at more density in an area (i.e., a black area) corresponding to that of the stencil sheet adhered with the paper dusts than required.
That is, it is thought that, when the paper dusts are adhered to the stencil sheet
22
of the printing drum
16
, the printed image are apt to involve the white and black areas, with a deteriorated quality in the printed image reproduced on the print sheet S. Such a deterioration in the print image becomes more conspicuous especially when the print section employs oily ink such as UV ink.
The present invention has been made through the above investigations by the present inventors and has an object to provide a stencil printing machine which prevents paper dusts from being adhered to a stencil sheet mounted onto a printing drum for thereby enabling a print sheet to be reproduced with a print image at a high quality.
According to one aspect of the present invention, there is provided a stencil printing machine which comprises: a paper feed section feeding a print sheet in a paper feed path, the print sheet being allowed to have paper dusts thereon; a print section to which the print sheet is transferred, and including a printing drum carrying thereon a stencil sheet having a perforated image area formed on the basis of image data and a rotary printing press member located in close proximity to an outer circumferential periphery of the printing drum to impart printing pressure thereto to allow the print sheet to be transferred in press contact between the printing drum and the rotary printing press member such that printing ink is transferred onto the print sheet to generate a desired image thereon through the perforated image area; and a liquid applying mechanism applying liquid, which is permeable to the paper dusts, onto a print surface of the print sheet to allow the paper dusts to be permeated with the liquid at an upper stream position than a position where the printing drum and the rotary printing press member are in press contact with each other in the paper feed path.
According to another aspect of the present invention, the
Endo Toshihiro
Yamamoto Yasuo
Berkowitz Marvin C.
Evanisko Leslie J.
Nath Gary M.
Novick Harold L.
Riso Kagaku Corporation
LandOfFree
Stencil printing machine having moistener mechanism does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stencil printing machine having moistener mechanism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stencil printing machine having moistener mechanism will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3062870