Information
-
Patent Grant
-
6311614
-
Patent Number
6,311,614
-
Date Filed
Thursday, September 14, 200024 years ago
-
Date Issued
Tuesday, November 6, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Hilten; John S.
- Crenshaw; Marvin P.
Agents
- Nath & Associates PLLC
- Nath; Gary M.
- Berkowitz; Marvin C.
-
CPC
-
US Classifications
Field of Search
US
- 101 116
- 101 119
- 101 124
- 101 129
-
International Classifications
-
Abstract
According to the stencil printing machine of the present invention, ink that has entered the gap between a circumferential wall and a stencil sheet is allowed to escape to the outsides of an inner pressing roll in the axis direction. When it reaches the outer circumferential face of an ink free passage section of a screen, the escape ink is allowed to pass through the ink free passage section by a pressing force from the pressure drum, and directed to the inner circumferential side; therefore, it is possible to prevent the escape ink from reaching the right and left ends of the stencil sheet, and consequently to eliminate the limitation to the number of prints in endurance printing processes that is imposed due to ink leakage from the stencil. Moreover, since it is not necessary to form a raised portion along the circumferential face, the printing drum can be easily manufactured at low costs.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stencil printing machine of an inner press system in which a printing pressure is exerted from the inner circumference side of a printing drum, and also relates to a technique for preventing ink leakage from the sides of the printing drum (in the center axis direction of the printing drum).
2. Description of the Related Art
As shown in
FIGS. 1 and 2
, a printing section of a stencil printing machine is provided with a printing drum
100
and a pressure drum
101
, and the printing drum
100
and the pressure drum
101
are respectively installed so as to freely rotate, with respective portions of their outer circumferential faces being closely located with each other. The printing drum
100
is provided with a pair of cylindrical flanges (not shown) aligned face to face with each other with a predetermined gap, and a stencil sheet clamp section
100
a
, which clamps the leading edge of a stencil sheet
104
, is placed on a part of the outer circumferential face of each flange. A flexible screen
102
is stretched over the outer circumferential faces of the flanges of the printing drum
100
other than the stencil sheet clamp section
100
a.
As shown in
FIGS. 3 and 4
, the screen
102
, which forms a circumferential wall of the printing drum, consists of an area which is subjected to a pressing force applied by an inner pressing roll
106
and which is constituted by a rough mesh screen section
102
a
and a dense mesh screen section
102
b
that are overlapped with each other so as to form a pressing-time ink passage section
112
(indicated by a diagonal hatched portion in
FIG. 3
) through which ink
103
is only allowed to pass upon application of the pressing force, and an area which is not subjected to the pressing force and which is formed by the rough mesh screen section
102
a
to which a coating material is injected so as to provide an ink non-passage section
113
(indicated by a cross hatched portion in
FIG. 3
) through which no ink
103
is allowed to pass even upon application of the pressing force. All the circumferential portion of the dense mesh screen section
102
b
is affixed to the rough mesh screen section
102
a
through a bonding section
102
c
formed by using the coating material injected to the rough mesh screen section
102
a
as a bonding agent. On the inner circumferential face of the screen
102
as well as on the ink non-passage section
113
located on one of the outer circumferential sides of the pressing-time ink passage section
112
, a raised portion
114
a
is formed, and on the other outer circumferential side that is rotation-delay side of the ink non-passage section
113
of the pressingtime ink passage section
12
, a raised portion
114
b
is formed. In other words, on the Inner circumferential face of the screen
102
, the raised portions
114
a
and
114
b
are formed in a U-letter shape.
Moreover, an inner press mechanism
105
is installed inside the screen
102
forming the circumferential wall of the printing drum
100
. The inner press mechanism
105
is provided with an inner pressing roll
106
, and this inner pressing roll
106
is formed on a roll support member
107
so as to freely rotate thereon. This roll support member
107
is supported so as to freely pivot centered on a support shaft
108
so that the inner pressing roll
106
is allowed to shift between a pressing position at which the inner pressing roll
106
is allowed to press the inner circumferential face of the screen
102
with the roll support member
107
being pressed in the direction of arrow a in
FIG. 2
, and a stand-by position at which the inner pressing roll
106
is apart from the inner circumferential face of the screen
102
with the roll support member
107
being rotated in the direction of arrow b in FIG.
2
. The inner pressing roll
106
is located at the pressing position at the time of printing and is also located at the stand-by position in cases other than the printing process.
Moreover, a doctor roll
109
and a driving rod
110
are respectively installed on the roll support member
107
. The doctor roll
109
has a column shape, and is secured to the roll support member
107
in the vicinity of the inner pressing roll
106
. The driving rod
110
is supported on the roll support member
107
so as to freely rotate thereon and is placed in an upper space that is formed by the outer circumferential faces of the inner pressing roll
106
and the doctor roll
109
on the respective sides located close to each other. Ink
103
is supplied to this upper space from an ink supplying section, not shown.
Next, an explanation will be given of the outline of the printing operation in succession. A stencil sheet
104
is subjected to a stencil making process by forming perforations in predetermined positions thereof, and the leading edge of the stencil sheet
104
thus subjected to the stencil making process is clamped by a stencil sheet clamp section
100
a
of the printing drum
100
, and attached to the outer circumferential face of the screen
102
forming the circumferential wall of the printing drum
100
. Next, the printing drum
100
and the pressure drum
101
are rotated in a direction indicated by an arrow in
FIG. 1
in synchronism with each other. Moreover, at the time of printing, the inner pressing roll
106
is allowed to press the screen
102
, and in this pressing state, the inner pressing roll
106
is rotated following the printing drum
100
. Ink
103
, which has passed through the gap against the doctor roll
109
, is allowed to adhere to the outer circumferential face of the inner pressing roll
106
, and the adhering ink
103
is successively transferred onto the inner circumferential face of the screen
102
by the rotation of the inner pressing roll
106
. Moreover, the screen
102
is expanded to the outer circumferential side by the pressing force of the inner pressing roll
106
so that the screen
102
is made in contact with the pressure drum
101
.
In this state, as shown in
FIG. 1
, a sheet of printing paper
111
is transported to the gap between the printing drum
100
and the pressure drum
101
, and the sheet of printing paper
111
is successively transported by the printing drum
100
and the pressure drum
101
.
The printing paper
111
, transported between the printing drum
100
and the pressure drum
101
, is further transported while being pressed between the inner pressing roll
106
and the pressure drum
101
together with the screen
102
and the stencil sheet
104
. This pressing force allows the ink
103
on the screen
102
side to be transferred onto the printing paper
111
side through the perforations of the stencil original paper
104
so that a printing process in accordance with an image formed on the stencil sheet
104
is carried out.
In the above-mentioned printing operation, the inner pressing roll
106
supplies ink
103
to the inner circumferential face of the screen
102
, and also presses the screen
102
so as to exert a pressing force thereon, while pressing the raised portions
114
a
of the screen
102
at both of the ends of the inner pressing roll
106
so that side leakage of the ink
103
(ink leakage in the center axis direction of the printing drum) is prevented.
More specifically, as shown in
FIG. 5
, some of the ink
103
located between the inner pressing roll
106
and the rough mesh screen section
102
a
is not allowed to escape outwards in the axial direction of the inner pressing roll
106
, since the inner pressing roll
106
presses the raised portions
114
a
so as to form a closely contact state between the inner pressing roll
106
and the raised portions
114
a
. Some of the ink
103
located between the rough mesh screen section
102
a
and the dense mesh screen section
102
b
is blocked in its shift outwards in the axial direction of the inner pressing roll
106
by a bonding section
102
c
so that it is not allowed to escape in the axial direction of the inner pressing roll
106
. Moreover, some of the ink
103
located between the dense mesh screen section
102
b
and the stencil sheet
104
is not allowed to escape outwards in the axial direction of the inner pressing roll
106
, since the inner pressing roll
106
presses the raised sections
114
a
from above so that the pressing force forms a closely contact state between the dense mesh screen section
102
b
and the stencil sheet
104
. With the above-mentioned arrangements, side leakage of the ink
103
on the inner circumferential side as well as on the outer circumferential side of the screen
102
is prevented.
However, as shown in
FIG. 6
, when the raised portions
114
a
, etc. are worn out after a long time use, the pressing force of the inner pressing roll
106
applied to the raised portions
114
a
becomes weaker, and in the worst case, it hardly exists. As a result, since the closely contact state between the dense mesh screen section
102
b
and the stencil sheet
104
is no longer maintained, the ink
103
located between the dense mesh screen section
102
b
and the stencil sheet
104
is allowed to escape outwards in the axial direction of the inner pressing roll
106
. Then, the amount and spread of the ink
103
escaping in the axial direction of the inner pressing roll
106
increase in proportion to the number of the printing operations, with the result that when the ink
103
has reached the right and left ends of the stencil sheet
104
, the ink
103
stains the pressure drum
101
, etc. Therefore, because of the ink leakage from the sides of the screen
102
, a limitation has to be imposed on the number of prints in endurance operations (the number of prints with guaranteed quality for one sheet of stencil sheet
104
).
Moreover, as the wear of the raised portions
114
a
develops, the ink
103
located between the inner pressing roll
106
and the rough mesh screen section
102
a
escapes outwards in the axial direction of the inner pressing roll
106
over the raised portions
114
a
, and since the escaped ink
103
gradually accumulates on the inner circumferential face of the screen
102
, resulting in problems such as stains inside the machine due to leakage ink.
Furthermore, in the conventional screen
102
, it is necessary to provide the raised portions
114
a
in addition to the structures such as the mesh screen section
102
a
and
102
b
; therefore, the manufacturing process becomes complex with high costs.
SUMMARY OF THE INVENTION
The present invention has been devised to solve the above-mentioned problems, and its object is to provide a stencil printing machine which can eliminate the limitation to the number of prints in endurance printing processes that is imposed due to ink leakage from the printing drum side portions, and which allows a printing drum to be manufactured easily at low costs, and which is also free from problems such as stains inside the machine due to ink leakage from the inner circumferential face of the printing drum.
One of the features of the present invention is that, in a stencil printing machine in which: a printing drum and a pressure drum are installed so as to be freely rotated with respective portions on the outer circumferential faces being virtually located closely; a stencil sheet is detachably attached onto the outer circumferential wall face of the printing drum; an inner pressing roll, which supplies ink from the inner circumferential face side of the circumferential wall, is supported inside the circumferential wall so as to freely rotate thereon, the inner pressing roll being allowed to freely press the inner circumferential face of the circumferential wall; the printing drum and the pressure drum are allowed to rotate so that the respective closely-located outer circumferential faces are shifted in the same direction; and the inner pressing roll is allowed to press the inner circumferential face of the circumferential wall so that this pressing force allows the stencil sheet attached to the circumferential wall and a printing medium passing through the stencil sheet and the pressure drum to contact each other, thereby carrying out a stencil printing process, the above-mentioned circumferential wall is constituted by a pressing-time ink passage portion which allows ink to pass through an area pressed by the inner pressing roll with the pressing force being applied thereto, an ink free passage portion that is located on the respective outside areas of the pressing-time ink passage portion in the direction of the center axis line of the printing drum and that allows ink to pass through it even in a state where no pressing force is applied thereto, and an ink non-passage portion that is located the respective further outside areas of the ink free passage portion and that does not allow the ink to pass through it even when the pressing force is exerted thereon.
With this arrangement, ink, located between the circumferential wall of the printing drum and the stencil sheet, is allowed to escape outward in the axial direction of the inner pressing roll by a pressing force exerted between the inner pressing roll and the pressure drum, and when the ink has reached a position on the outer circumferential face of the ink free passage portion of the circumferential wall of the printing drum, the escape ink is allowed to pass through the ink free passage portion by the pressing force from the pressure drum, and directed to the inner circumferential face side; thus, no escape ink is allowed to reach the right and left ends of the stencil sheet, and it is not necessary to provide a raised portion along the circumferential wall.
It is preferable to install an ink return unit for returning the ink stored on the inner face side of the ink free passage portion of the circumferential wall to a position at which the ink is re-used.
In this arrangement, the ink, stored on the inner face side of the ink free passage portion of the circumferential wall, is returned to the position at which the ink is re-used by the ink return unit.
Also, it is preferable that the ink return unit is provided with an ink passage that is formed between the roll supporting member for supporting the inner pressing roll so as to freely rotate thereon and the side end face of the inner pressing roll; thus, ink adhering to the side end face of the inner pressing roll is raised upward by the rotation of the inner pressing roll and allowed to rise through the ink passage, and the surface tension of the ink thus raised upward serves to raise the ink located below successively so that the ink is allowed to rise through the ink passage, and directed to the outer circumferential face side above the inner pressing roll.
In this arrangement, of the ink accumulated on the inner circumferential side of the ink free passage portion of the circumferential wall, the ink adhering to the side end face of the inner pressing roll is raised upward by the rotation of the inner pressing roll, and allowed to rise through the ink passage, and the surface tension of the ink thus raised upward serves to raise the ink located below successively so that the ink is allowed to rise through the ink passage, and directed to the outer circumferential face side above the inner pressing roll.
And also it is desirable to install an ink wiping member which is placed inside the printing drum, on the rotation downstream side of the printing drum with respect to the inner pressing roller, and which returns ink flowing over the ink non-passage portion to the ink free passage portion.
In this arrangement, of the ink accumulated on the inner circumferential side of the ink free passage portion of the printing drum, the ink flowing over the ink nonpassage portion is wiped by the ink wiping member, and returned to the ink free passage portion.
Other and further objects and features of the present invention will become obvious upon understanding of the illustrative embodiments about to be described in connection with the accompanying drawings or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employing of the invention in practice.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1
, which shows a conventional example, is a structural diagram showing one portion of a printing section of a stencil printing machine.
FIG. 2
, which shows the prior art structure, is a cross-sectional view showing a mechanism for supplying ink to the printing section.
FIG. 3
, which shows the prior art structure, is a perspective view showing members such as an inner pressing roll and a developed screen.
FIG. 4
, which shows the prior art structure, is a cross-sectional view showing the inner pressing roll and the screen.
FIG. 5
, which shows the prior art structure, is a cross-sectional view of an essential portion showing a state in which the inner pressing roll is pressing the raised portion of the screen.
FIG. 6
, which shows the prior art structure, is a cross-sectional view of an essential portion showing a state in which the raised portion of the screen is worn out, with the result that ink is allowed to flow from the respective sides of the screen.
FIG. 7
, which shows one embodiment of the present invention, is a schematic structural diagram showing a stencil printing machine.
FIG. 8
, which shows one embodiment of the present invention, is an exploded perspective view showing an inner press mechanism.
FIG. 9
, which shows one embodiment of the present invention, is a perspective view showing an inner unit.
FIG. 10
, which shows one embodiment of the present invention, is a structural side view showing the inside of a printing drum in which an inner pressing roll is located at a stand-by position.
FIG. 11
, which shows one embodiment of the present invention, is a structural side view showing the inside of the printing drum in which the inner pressing roll is located at a pressing position.
FIG. 12
, which shows one embodiment of the present invention, is a structural side view showing the inside of the printing drum in which the inner pressing roll is located at a pressing position, and also in a state so as to avoid a stencil sheet clamp section.
FIG. 13
, which shows one embodiment of the present invention, is a structural side view showing the inside of the printing drum in which ink is supplied.
FIG. 14
, which shows one embodiment of the present invention, is a perspective view showing an ink return unit in the vicinity of the end face of the inner pressing roll.
FIG. 15
, which shows one embodiment of the present invention, is a perspective view showing members such as the inner pressure roll and a developed screen.
FIGS. 16A and 16B
, which show one embodiment of the present invention,
FIG. 16A
is a cross-sectional view taken along the line A—A of FIG.
15
and
FIG. 16B
is a cross-sectional view taken along the line B—B of FIG.
15
.
FIG. 17
, which shows one embodiment of the present invention, is a diagram showing the locus of a relative shift of the inner pressing roll with respect to the screen.
FIG. 18
, which shows one embodiment of the present invention, is a cross-sectional view of an essential portion showing a state in which escape ink is directed to the inner circumferential side of the ink free passage portion of the screen and the ink is allowed to rise through the ink passage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various embodiments of the present invention will be described with reference to the accompanying drawings. It is to be noted that the same or similar reference numerals are applied to the same or similar parts and elements throughout the drawings, and the description of the same or similar parts and elements will be omitted or simplified.
As shown in
FIG. 7
, a stencil printing machine
1
is mainly constituted by a document-reading section (not shown), a stencil making section
3
, a printing section
4
, a paper feeding section
5
, a paper-discharging section
6
and a stencil disposal section
7
.
The document-reading section (not shown) reads a document as electric signals. The information thus read is designed so as to be processed based upon a predetermined instruction (such as enlargement, reduction, etc.).
The stencil making section
3
is constituted by a stencil sheet housing section
11
for housing an elongated stencil sheet
10
wound into a roll, a thermal head
12
placed on the downstream side of the stencil sheet housing section
11
in the transporting direction of the elongated stencil sheet
10
, a platen roller
13
that is placed at a position opposing to the thermal head
12
and that is driven by a driving force of a write pulse motor (not shown), a pair of stencil sheet feeding rollers
14
that is placed on the downstream side of the platen roller
13
and the thermal head
12
in the transporting direction of the elongated stencil sheet
10
and that is driven by a driving force of a write pulse motor (not shown) and a stencil sheet cutter (not shown) that is placed between the pair of stencil sheet feeding rollers
14
and the platen roller
13
as well as the thermal head
12
.
The printing section
4
is provided with a printing drum
16
and a pressure drum
17
, and the printing drum
16
and the pressure drum
17
are placed so as to be freely rotated with respective portions on the outer circumferential faces virtually closely located with each other. The printing drum
16
has a pair of circular flanges that are placed face to face with each other with a predetermined gap. A stencil sheet clamp section
18
is formed on one portion of the circumferential face of the flange so that the leading edge of a stencil sheet
15
is clamped by this stencil sheet clamp section
18
. Onto the outer circumferential face of the flange of the printing drum
16
except the stencil sheet clamp section
18
, a flexible screen
19
, which forms a circumferential wall of the printing drum
16
, is attached in a stretched manner. With respect to the structure of the screen
19
forming the circumferential wall of the printing drum
16
, an explanation will be given below. Inside the screen
19
of the printing drum
16
, an inner pressing roll
47
of an inner press mechanism
20
is installed, and with respect to the inner press mechanism
20
, a detailed explanation will be given below. Moreover, a paper clamp section
21
is placed at a predetermined position on the outer circumferential face of the pressure drum
17
so that the leading edge of a sheet of printing paper
22
that is a printing medium is clamped by the paper clamp section
21
.
The paper-feeding section
5
is constituted by a paper-feeding tray
23
on which sheets of printing paper
22
are stacked, a scraper
24
for pressing and contacting the sheets of printing paper
22
on the upper-most position from the paper-feeding tray
23
, a pickup roll
25
and a sorting roll
26
that are placed on the downstream side of the scraper
24
at virtually proximate positions from each other, a guide roll
27
and a timing roll
28
that are placed on the downstream side of the pickup roll
25
and the sorting roll
26
at virtually proximate positions from each other. With respect to sheets of paper
22
shifted by the rotation of the scraper
24
, only one sheet of paper
22
on the uppermost position is allowed to be transported by the pickup roll
25
and the sorting roll
26
, and this sheet of printing paper
22
, thus allowed to be transported, is transported in synchronism with the rotation of the pressure drum
17
by the rotations of the guide roll
27
and the timing roll
28
.
The paper-discharging section
6
is provided with an upper regulating guide section
30
for guiding the leading edge of a sheet of printing paper
22
that has been subjected to printing, a sheet separator claw
32
for scraping a sheet of printing paper
22
that has been stacked on the pressure drum
17
, a paper-transporting mechanism
33
for transporting the sheet of printing paper
22
guided by the guiding section
30
, or scraped by the sheet separator claw
32
, and a stacker section
34
for placing the sheets of printing paper
22
transported by the paper-transporting mechanism
33
in an accumulated state.
The stencil disposal section
7
is provided with a discharged stencil guiding belt
35
for guiding the leading edge of the stencil sheet
15
released from the stencil sheet clamp section
18
of the printing drum
16
, a pair of discharged stencil conveyor belts
36
for transporting the stencil sheet
15
directed from the discharge stencil guiding belts
35
while allowing the stencil sheet
15
to separate from the printing drum
16
, and a discharged stencil box
37
for storing the stencil sheet
15
transported thereto by the pair of discharged stencil conveyor belts
36
.
In
FIGS. 8 through 12
, the inner press mechanism
20
is provided with an inner unit
38
placed inside the printing drum
16
, and torque-transmitting unit
39
for transmitting a torque to the inner unit
38
, which is placed outside the printing drum
16
. The inner unit
38
has a roll support member
40
, and the roll support member
40
is supported by a securing member (not shown) centered on a support shaft
41
so as to freely rotate thereon. A teeth portion
42
is formed on the roll support member
40
, and the teeth portion
44
of an inner arm portion
43
is engaged with the teeth portion
42
. The inner arm portion
43
is supported so as to freely rotate, with a driving shaft
43
a
serving as a fulcrum, and one of the ends of the driving shaft
43
a
is allowed to stick outside from the printing drum
16
. The torque from the torque transmitting unit
39
is transmitted to this driving shaft
43
a
sticking out in this manner.
When the inner arm portion
43
is rotated clockwise as shown in
FIGS. 10 through 12
, the roll support member
40
is allowed to pivot counterclockwise so that the inner pressing roll
47
is placed at a pressing position at which it presses the screen
19
forming the circumferential wall of the printing drum
16
onto the outer circumference side (state shown in FIG.
11
), and when the inner arm portion
43
is rotated counterclockwise as shown in
FIGS. 10 through 12
, the roll support member
40
is allowed to pivot clockwise so that the inner pressing roll
47
is placed at a stand-by position at which it retreats inward from the screen
19
(state shown in FIG.
10
).
A gear
45
is supported by the support shaft
41
so as to freely rotate thereon, and this gear
45
is engaged with an inner circumferential gear section
46
of the printing drum
16
. The inner pressing roll
47
is supported on the roll support member
40
so as to freely rotate thereon, and a first gear
48
and a roller member
49
are secured to the respective ends of the inner pressing roll
47
. The first gear
48
is engaged with the gear
45
of the support shaft
41
so that the inner pressing roll
47
is rotated in synchronism with the rotation of the printing drum
16
. Moreover, in the case of the stand-by position of the inner pressing roll
47
, the roller member
49
is placed at a position apart from the flange cam face
50
of the printing drum
16
, and in the case of the pressing position, it is placed at a position in the proximity of the flange cam face
50
of the printing drum
16
or in press-contact therewith; thus, in the pressing position, the inner pressing roll
47
is allowed to move up and down along the flange cam face
50
. The flange cam face
50
is arranged so that the diameters thereof from the rotation consists of a large-diameter range, a small-diameter range and a slanting range that continuously connect these ranges. Here, at the portion corresponding to the stencil sheet clamp section
18
, the diameter from the rotation center is set in the small diameter range so that when the inner pressing roll
47
is positioned at the stencil sheet clamp section
18
, it is placed apart therefrom so as not to cause any intervention; when it passes through the stencil sheet clamp section
18
, the inner pressing roll
47
is returned to a position from which it presses the screen
19
; and when it approaches the stencil sheet clamp section
18
, a pressing start position and a pressing release position are placed at predetermined positions so that the inner pressing roll
47
is gradually separated from the screen
19
. The following description will discuss the detailed positions of the pressing start position and pressing release position.
As shown in
FIG. 8
, the torque transmitting unit
39
is provided with a motor
72
secured to a mounting member
70
outside the printing drum
16
through a bracket
71
, and a worm gear
73
is secured to the rotary shaft of the motor
72
and a rotation position detection disc
74
is also secured thereto. On the periphery of the rotation position detection disc
74
, a rotation position detection sensor
75
is placed in the proximity thereof, and based upon the detection output of the rotation position detection sensor
75
, the stroke of a spring
79
, which will be described below, is calculated.
A worm wheel
77
is engaged with the worm gear
73
, and a flat gear
76
is integrally secured to the worm wheel
77
. The flat gear
76
is engaged with a teeth section
78
a
of an arm member
78
so that the arm member
78
is supported so as to freely pivot centered on a support shaft
79
a
. A spring hooking pin
78
b
is secured on the other end of the arm member
78
opposite to the teeth section
78
a
, and one end of the spring
79
is hooked on the spring hooking pin
78
b
. Moreover, the spring hooking pin
78
b
is inserted into a long groove
80
a
on one end of link plate
80
, and the spring hooking pin
78
b
and the link plate
80
are stopped by a screw
81
and a washer
82
so as not to come off. The other end of the spring
79
and the other end of the link plate
80
are secured to an outer arm portion
83
with a screw
84
and a washer
85
. The outer arm portion
83
is secured to the circumferential outer face of a rotation support body
86
, and an engaging hole (not shown) to which the driving shaft
43
a
is inserted is formed in the rotation support body
86
. The driving shaft
43
a
is inserted into the engaging hole so that the rotation of the rotation support body
86
is transmitted to the driving shaft
43
a.
In other words, when the arm member
78
is allowed to pivot clockwise (in the direction of arrow a in
FIG. 8
) by the driving operation of the motor
72
, the spring force of the spring
79
allows the outer arm portion
83
to rotate counterclockwise (in the direction of arrow c in
FIG. 8
) so that the inner pressing roll
47
is placed at the pressing position shown in
FIGS. 11 and 12
. A pressing force by the spring force of the spring
79
is always exerted on the inner pressing roll
47
at the pressing position, and this forms a printing pressure. Moreover, when the arm member
78
is allowed to pivot clockwise (in the direction of arrow b in
FIG. 8
) by the driving operation of the motor
72
so that the spring hooking pin
78
b
presses the bottom end face of the long groove
80
a
of the link plate
80
, the link plate
80
presses the outer arm portion
83
so that the outer arm portion
83
is allowed to pivot clockwise (in the direction of arrow d in FIG.
8
), with the result that the inner pressing roll
47
is placed at the stand-by position shown in FIG.
10
.
Moreover, as shown in
FIGS. 9 and 13
, a doctor roll
51
and a driving rod
52
are attached to the roll support member
40
. The doctor roll
51
is secured to the roll support member
40
at a position in the proximity of the inner pressing roll
47
. The driving rod
52
is supported by the roll support member
40
so as to freely rotate thereon, and placed in an upper space that is formed by the outer circumferential faces of the inner pressing roll
47
and the doctor roll
51
on the sides facing each other closely. Ink
53
is supplied to the upper space from an ink supplying section, not shown. A gear
54
is secured to one end of the driving rod
52
, and this gear
54
is engaged with a second gear (not shown) of the inner pressing roll
47
. The second gear (not shown) is supported on the shaft of the inner pressing roll
47
through a one-way clutch (not shown), and the driving rod
52
is rotated in synchronism with the printing drum
16
in the same manner as the aforementioned inner pressing roll
47
.
When ink
53
is supplied to the upper space by the ink supplying section (not shown), the ink
53
is stirred by the driving rod
52
, and of the stirred ink
53
, some of ink
53
adhering to the outer circumferential face of the inner pressing roll
47
is apt to rotate together with the rotation of the inner pressing roll
47
due to its tackiness. Then, by making it pass through the gap against the doctor roll
51
, only a predetermined amount of the ink
53
is always allowed to adhere thereto, and since the inner pressing roll
47
is made in press-contact with the screen
19
on the downstream side of the doctor roll
51
, this predetermined amount of ink
53
is transferred onto the inner circumferential face of the screen
19
. In other words, the inner pressing roll
47
has a function for applying the printing pressure to the screen
19
from inner circumferential side and also has a function for supplying ink
53
to the screen
19
.
Moreover, as shown in
FIGS. 9 and 14
, ink returning unit
60
are respectively placed near both of the side end faces of the inner pressing roll
47
. In the ink returning unit
60
, each of portions of the roll support member
40
facing the side end faces
47
a
of the inner pressing roll
47
is formed into a cut face
40
a
, and this cut face
40
a
provides an ink passage
61
between the side end face
47
a
of the inner pressing roll
47
and the roll support member
40
. The Ink
53
adhering to the side end face
47
a
of the inner pressing roll
47
that is shifted upward by the rotation of the inner pressing roll
47
is raised upward by the rotation of the inner pressing roll
47
through the ink passage
61
, and the surface tension of the ink
53
thus raised upward serves to successively raise ink
53
located below, and the ink
53
is raised through the passage
61
and directed to the upper outer circumferential face side of the inner pressing roll
47
.
Moreover, as shown in
FIGS. 10 through 12
, a pair of right and left ink wiping members
62
are installed on the rotation downstream side of the screen
19
with respect to the inner pressing roll
47
inside the screen
19
. As shown in
FIG. 15
, each of the ink wiping members
62
has its lower end made in press-contact with the ink non-passage section
65
of the screen
19
in a state where it is pressed by a pressing unit such as a spring so that its lower end is inclined in a direction so as to return ink
53
flowing over the ink non-passage section
65
to the ink free passage section
64
.
Next, a detailed explanation will be given of the screen
19
that forms the circumferential wall of the printing drum
16
.
FIG. 15
is a perspective view showing a developed state of the cylinder shaped printing drum
16
, and
FIG. 16A
is a cross-sectional view taken along the line A—A of
FIG. 15
, and
FIG. 16B
is a cross-sectional view taken along the line B—B of FIG.
15
. In
FIGS. 15 and 16
, the screen
19
is constituted by a rough mesh screen section
19
a
that allows ink
53
to pass through it without an application of a pressing force and a dense mesh screen section
19
b
that only allows ink
53
to pass through it when a pressing force is applied thereto. Here, an area on which the inner pressing roller
47
applies a pressing force is provided as a pressing-time ink passage section
63
(indicated by a diagonally hatched portion in
FIG. 15
) which is an overlapped portion of the rough mesh screen section
19
a
and the dense mesh screen section
19
b
and which allows ink
53
to pass through it only when the pressing force is exerted thereon. In both of the outside areas of the pressing-time ink passage section
63
in the center axis direction of the printing drum
16
that are not pressed by the inner pressing roll
106
, only rough mesh screen sections
19
a
are formed so as to provide ink free passage sections
64
(indicated by white void portions in FIG.
15
). In both of the further outside areas of the ink free passage section
64
and in the rotation uppermost stream side area and the rotation lowermost stream side area of the screen
19
that form a cylinder portion of the printing drum
16
, a coating material is injected into the rough mesh screen section
19
a
so as to form these areas as ink nonpassage sections
65
,
65
a
and
65
b
(indicated by cross hatched portions in
FIG. 15
) wherein ink
53
is not allowed to pass through them even when the pressing force is exerted thereon.
Moreover, the rotation uppermost stream side portion and the rotation lowermost stream side portion of the dense mesh screen section
19
b
are bonded to the rough mesh screen section
102
a
through a bonding section
19
c
by utilizing the coating material injected into the rough mesh screen section
19
a
as a bonding agent. Therefore, these portions are provided as ink non-passage sections
65
c
and
65
d
(indicated by crosshatched portions in FIG.
15
).
Moreover, an ink free passage section
64
a
(indicated by a white void portion in
FIG. 15
) is formed between the ink non-passage section
65
d
that is the rotation lowermost stream side portion of the dense mesh screen section
19
b
and the ink non-passage section
65
b
that is the rotation lowermost stream side of the rough mesh screen section
19
a.
Next, an explanation will be given of a position at which the inner pressing roll
47
starts a pressing operation onto the screen
19
and a position at which this pressing operation is removed.
FIG. 17
is a diagram showing the locus of a relative shift of the inner pressing roll
47
with respect to the screen
19
. In
FIG. 17
, when the inner pressing roll
47
is rotated beyond the position (corresponding to the stencil sheet clamp section
18
) at which the inner pressing roll
47
is separated from the inner circumferential face of the screen
19
, the inner pressing roll
47
gradually approaches the inner circumferential face of the screen
19
and comes into contact with it; and in this case, the position at which the pressing operation is started by using a predetermined force is set to be located at least on the upstream side of the pressing-time ink passage section
63
. In other words, it is set to be located at the ink non-passage section
65
a
and
65
b
of the screen
19
. Then, from the state in which it is pressing the screen
19
with a predetermined pressing force, the inner pressing roll
47
gradually decreases its pressing force, and the inner pressing roll
47
is separated from the screen
19
to completely release its pressing force; and in this case, this pressing force releasing position is set to be located at the ink free passage section
64
a.
Next, a brief explanation will be given of the operation of the stencil printing machine
1
. In the stencil making section
3
, the platen roller
13
and the stencil sheet feeding roller
14
are rotated so that the elongated stencil sheet
10
is transported, and based upon image information read at the document reading section (not shown), the respective heat-generating elements of the thermal head
12
are selectively allowed to generate heat so that the elongated stencil sheet
10
is perforated through the heat-sensitive process; thus, the elongated stencil sheet
10
, subjected to the stencil making process, corresponding to one-stencil length is cut with a stencil sheet cutter (not shown) so as to form a stencil sheet.
15
.
In the printing section
4
, the leading edge of the stencil sheet
15
subjected to the stencil making process at the stencil making section
3
is clamped at the stencil sheet clamp section
18
, and in this clamped state, the printing drum
16
is rotated so that the stencil sheet
15
is wrapped around and attached to the outer circumferential face of the screen
19
that forms the circumferential wall of the printing drum
16
.
In the paper-feeding section
5
, a sheet of printing paper
22
is transported in synchronism with the rotations of the printing drum
16
and the pressure drum
17
, and then transported between the printing drum
16
and the pressure drum
17
with the leading edge of the sheet of printing paper
22
being clamped at the paper clamp section
21
of the pressure drum
17
.
In the printing section
4
, the inner pressing roll
47
is maintained at a stand-by position as shown in
FIG. 10
in cases other than the printing process; thus, the inner pressing roll
47
is placed at a position apart from the screen
19
. In the case of the printing process, the inner pressing roll
47
is placed at the pressing position and the printing drum
16
is rotated. Then, the inner pressing roll
47
is rotated on the inner circumferential face of the screen
19
while the inner pressing roll
47
is pressing the inner circumferential side of the screen
19
, as shown in
FIG. 11
, except that at the periphery of the stencil sheet clamp section
18
it is placed at a retreated position, as shown in FIG.
12
. Since ink
53
is continuously supplied onto the outer circumferential face of the inner pressing roll
47
, this rotation transfers the ink
53
onto the screen
19
. Moreover, the pressing force of the inner pressing roll
47
makes the screen
19
extend on the outer circumferential side so as to come Into contact with the pressure drum
17
. Then, the sheet of printing paper
22
is transported between the printing drum
16
and the pressure drum
17
from the paper-feeding section
5
as described above, and the sheet of printing paper
22
thus transported is further transported while being pressed together with the screen
19
and the stencil sheet
15
between the inner pressing roll
47
and the pressure drum
17
. In this pressing process, the ink
53
is transferred on the sheet of the printing paper
22
through the perforated portion of the stencil sheet
15
so that an image is formed. When the leading edge of the sheet of printing paper
22
passes through the position of the inner pressing roll
47
and comes to the downstream side, the paper clamp section
21
releases the leading edge thereof.
In the paper discharging section
6
, the leading edge side of the sheet of printing paper
22
is guided by the upper regulating guide section
30
, or the leading edge side of the sheet of printing paper
22
is scraped from the pressure drum
17
by the sheet separator claw
32
, and this is transported to the stacker section
34
through the paper-transporting mechanism
33
.
Moreover, in the stencil disposal section
7
, upon starting a new stencil making process, it is necessary to remove the stencil sheet
15
wrapped around and attached to the outer circumferential face of the screen
19
of the printing drum
16
, that has been used in the previous printing process; therefore, in this case, prior to the step for wrapping a new stencil sheet that has been subjected to a stencil making process around the outer circumferential face of the circumferential wall of the printing drum
16
so as to be attached thereto, the stencil sheet clamp section
18
of the printing drum
16
is released, and the leading edge of the stencil sheet
15
thus released is directed by the discharge stencil guiding belt
35
while the printing drum
16
is being rotated, and transported by the pair of discharge stencil conveyor belts
36
and housed in the discharge stencil box
37
.
In the above-mentioned printing operation, the ink
53
, supplied to the screen
19
, is applied onto the inner circumferential face of the rough mesh screen section
19
a
, and also injected inside the rough mesh screen
19
a
, between the rough mesh screen section
19
a
and the dense mesh screen section
19
b
, and between the dense mesh screen section
19
b
, and the stencil sheet
10
. Here, the ink behaves so as to avoid the pressing force exerted between the inner pressing roll
47
and the pressure drum
17
.
More specifically, as shown in
FIG. 18
, some ink
53
located between the rough mesh screen section
19
a
and the dense mesh screen section
19
b
and some ink
53
located between the dense mesh screen section
19
b
and the stencil sheet
15
are not blocked in their shift outward in the axis direction of the inner pressing roll
47
, and allowed to escape to the outsides of the inner pressing roll
47
in the axis direction. When they reach the outer circumferential face of the ink free passage section
64
of the screen
19
at which no pressing force from the inner pressing roll
47
is exerted, the escape ink
53
is allowed to pass through the ink free passage section
64
by a pressing force from the pressure drum
17
, and directed to the inner circumferential side of the screen
19
. Therefore, it is possible to prevent the leakage ink
53
from reaching the right and left ends of the stencil sheet, and consequently to eliminate the limitation to the number of prints in endurance printing processes that is imposed due to ink leakage from the stencil. Moreover, since it is not necessary to form a raised portion along the screen, which has been required in conventional arrangements, the screen
19
can be easily manufactured at low costs.
Moreover, in the present embodiment, as shown in
FIG. 18
, some ink
53
, located between the inner pressing roll
47
and the rough mesh screen section
19
a
, also is not blocked in its shift outward in the axis direction of the inner pressing roll
47
, and allowed to escape to the outsides of the inner pressing roll
47
in the axis direction. Then, the ink
53
, escaped from the inner circumferential side and the outer circumferential side of the screen
19
, is accumulated on the inner circumferential face of the ink free passage section
64
, that is, in the vicinity of each of the side end face
47
a
of the inner pressing roll
47
. Of the accumulated leakage ink
53
, the ink
53
adhering to the side end faces
47
a
of the inner pressing roll
47
, is raised upward by the rotation of the inner pressing roll
47
, and allowed to rise through the ink passage
61
, and the surface tension of the ink
53
thus raised upward serves to raise ink
53
located below successively so that this ink
53
is allowed to rise through the ink passage
61
, and directed to the upper outer circumferential face side of the inner pressing roll
47
. The ink
53
, thus directed to the upper outer circumferential face side of the inner pressing roll
47
, is again supplied to the screen
19
by the rotation of the inner pressing roll
47
. Therefore, it is possible to solve problems, such as stains inside the machine due to ink leakage on the inner circumferential face of the screen
19
.
Moreover, in the present embodiment, the ink
53
flowing to reach the ink non-passage section
65
further outside from the ink free passage section
64
of the screen
19
is wiped by the ink wiping member
62
, and returned to the ink free passage section
64
; therefore, it Is possible to positively solve problems, such as stains inside the machine due to ink leakage on the inner circumferential face of the screen
19
.
Additionally, in the arrangement of the present embodiment, with respect to the ink return unit
60
, the ink passage
61
is installed and the ink
53
is allowed to shift upward onto the inner pressing roll
47
through the ink passage
61
by utilizing the rotation of the inner pressing roller
47
and the surface tension of the ink
53
; however, any means other than the surface tension, such as an ink suction process, may be utilized, and with respect to the return position of the ink
53
, not limited to the upper outer circumferential face of the inner pressing roll
47
, any position may be used as long as it allows the ink
53
reused. In other words, any means may be used as long as it allows the ink
53
accumulated on the inner face side of the ink free passage section
64
of the screen
19
to be reused.
Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without depending from the scope thereof.
Claims
- 1. A stencil printing machine comprising:a printing drum rotatable about an axis and having an outer circumferential wall having an inner face and an outer face, said outer circumferential wall defining an interior space in said printing drum, said outer face adapted to detachably receive a stencil sheet; a rotatable pressure drum axially parallel to said printing drum, said pressure drum having an outer circumferential face having a portion thereof disposed close to said outer face of said printing drum and forming a nip therebetween; and a rotatable inner pressing roll having an outer circumferential face disposed axially parallel to said printing drum, in said interior space, and that can supply an ink from said inner circumferential face side of said circumferential wall, a portion of said inner pressing roll being pressed against a portion of said inner circumferential face of said circumferential wall so that the stencil sheet attached to said circumferential wall and a printing medium passing through the stencil sheet and said pressure drum contact each other; said circumferential wall further comprising: a centrally disposed first portion through which the ink can pass only in an area where said inner pressing roll applies a pressure to said inner face, said first portion having a periphery; a second portion disposed axially to said first portion and outside the periphery thereof, said second portion being adapted so that the ink can freely pass there-through, said second portion having an axially outer peripheral side; and a third portion disposed axially to said second portion and outside the outer peripheral side thereof, said third portion being adapted so that the ink can not pass there-through.
- 2. The stencil printing machine of claim 1, further comprising:an ink return unit for returning the ink from an area of said inner face of said circumferential wall near said second portion to a position at which the ink can be reused.
- 3. The stencil printing machine of claim 2, wherein the ink return unit comprises:an ink passage between a supporting member of said inner pressing roll and a side end face of said inner pressing roll, wherein the ink adhering to said side end face is raised upward by a rotation of said inner pressing roll and allowed to rise through said ink passage, and whereby surface tension of the ink thus raised upward successively raises the ink located there-below, and is directed to above said outer circumferential face side of said inner pressing roll.
- 4. The stencil printing machine of claim 1, further comprising:an ink wiping member disposed in said interior space of said printing drum, on a rotation downstream side thereof with respect to said inner pressing roll, and which returns the ink from said third portion to said second portion.
- 5. A stencil printing machine comprising:a printing drum rotatable about an axis and having an outer circumferential wall with an inner face and an outer face, said outer circumferential wall defining an interior space in said printing drum, said outer face being adapted to detachably receive a stencil sheet; and a rotatable inner pressure roll having an outer face that can supply an ink, said inner pressure roll disposed axially parallel to said printing drum, in said interior space thereof, a portion of said outer face of said inner pressure roll pressingly in contact with a portion of said inner face of said circumferential wall; said circumferential wall further comprising: a centrally disposed first portion through which the ink can pass only in an area where said inner pressure roll applies a pressure to said inner face, said first portion having a periphery; a second portion disposed axially to said first portion and outside the periphery thereof, said second portion being adapted so that the ink can freely pass there-through, said second portion having an axially outer peripheral side; and a third portion disposed axially to said second portion and outside the outer peripheral side thereof, said third portion being adapted so that the ink can not pass there-through.
- 6. The stencil printing machine of claim 5, further comprising:an ink return unit for returning the ink from an area of said inner face of said circumferential wall near said second portion to a position at which the ink can be reused.
- 7. The stencil printing machine of claim 6, wherein the ink return unit comprises:an ink passage between a supporting member of said inner pressing roll and a side end face of said inner pressing roll, wherein the ink adhering to said side end face is raised upward by a rotation of said inner pressing roll and allowed to rise through said ink passage, and whereby surface tension of the ink thus raised upward successively raises the ink located there-below, and is directed to above said outer circumferential face side of said inner pressing roll.
- 8. The stencil printing machine of claim 5, further comprising:an ink wiping member disposed in said interior space of said printing drum, on a rotation downstream side thereof with respect to said inner pressing roll, and which returns the ink from said third portion to said second portion.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-264471 |
Sep 1999 |
JP |
|
US Referenced Citations (3)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0 963 856 A1 |
Dec 1999 |
EP |
0 976 569 A1 |
Feb 2000 |
EP |