Information
-
Patent Grant
-
6293190
-
Patent Number
6,293,190
-
Date Filed
Monday, January 31, 200024 years ago
-
Date Issued
Tuesday, September 25, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
-
CPC
-
US Classifications
Field of Search
US
- 101 116
- 101 119
- 101 120
- 101 129
-
International Classifications
-
Abstract
A stencil printer operable with a master wrapped around a print drum includes a rotatable print drum. An ink roller is rotatable in the same direction as the print drum for feeding ink to the inner periphery of the drum. An ink replenishing roller is rotatable in the same direction as the print drum and ink roller and movable between a first position where it is spaced from the inner periphery of the drum and ink roller and a second position where it contacts the inner periphery of the drum and ink roller. An ink collecting member is located downstream of the ink replenishing roller in the direction of rotation of the print drum and movable in interlocked relation to the ink replenishing roller. The printer is capable of surely removing excess ink from the inner periphery of the print drum and desirably forming even the first image after a long time of suspension. The ink collecting member is interlocked to the ink replenishing roller and has its edge initially spaced from the inner periphery of the print drum, so that friction between the ink collecting member and the inner periphery of the print drum is obviated. In addition, ink is prevented from being collected more than necessary. Consequently, there can be obviated noise and short image density.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a stencil printer operable with a master wrapped around a print drum and more particularly to the structure and operation of an ink feeding mechanism included in a stencil printer.
Generally, a thermal digital stencil printer includes a rotatable print drum made up of a porous cylindrical support and a plurality of metallic mesh screens covering the support in a laminate. A stencil to be wrapped around the print drum as a master has a laminate structure consisting of a thermoplastic resin film which is usually 1 μm to 3 μm thick, and a porous substrate to which the resin film is adhered. The substrate is formed of fibers of Japanese paper or synthetic fibers or a mixture thereof. After a thermal head has selectively perforated, or cut, the film surface of the stencil, the resulting master is wrapped around the print drum. Subsequently, ink feeding means arranged within the print drum feeds ink to the inner periphery of the print drum. A press roller or similar pressing means presses a paper or similar recording medium against the print drum with the intermediary of the master. As a result, the ink is transferred to the paper via the porous portion of the drum and the perforations of the master, forming an image on the paper.
A problem with the above stencil printer is that if the ink exists in the print drum in an excessive amount, it leaks from the drum and brings about defective printing. Another problem is that when the printer is not used over a long period of time, the ink is degenerated due to the evaporation of water held in the cylindrical support and mesh screens of the print drum. As a result, when the printer is operated for the first time after such a long time of suspension, it is likely that images are blurred or otherwise effected and causes several to several tens of papers to be wasted.
To solve the above problems, Japanese Patent Laid-Open Publication No. 8-142474, for example, discloses ink collecting means disposed in the print drum and contacting the inner periphery of the drum for collecting excess ink existing in the drum. The ink collecting means, however, constantly contacts the inner periphery of the print drum and produces noise ascribable to friction between the former and the latter. This, coupled with the fact that the ink collecting means collects the ink more than necessary, lowers image density. In addition, the ink collecting means deteriorates rapidly.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 3-164287, 4-296585, 6-135114, 7-52518, 8-25781, and 10-217595.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a stencil printer capable of desirably producing even the first print after a long time of suspension without any noise or short image density.
A stencil printer of the present invention includes a rotatable print drum. An ink roller is rotatable in the same direction as the print drum for feeding ink to the inner periphery of the drum. An ink replenishing roller is rotatable in the same direction as the print drum and ink roller and movable between a first position where it is spaced from the inner periphery of the drum and ink roller and a second position where it contacts the inner periphery of the drum and ink roller. An ink collecting member is located downstream of the ink replenishing roller in the direction of rotation of the print drum and movable in interlocked relation to the ink replenishing roller.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:
FIG. 1
is a front view showing a stencil printer embodying the present invention;
FIGS. 2 and 3
are fragmentary front views showing a print drum included in the illustrative embodiment;
FIG. 4
is a fragmentary side elevation of the print drum;
FIG. 5
is a view showing a sensor also included in the illustrative embodiment; and
FIG. 6
is a block diagram schematically showing a control system further included in the illustrative embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIG. 1
of the drawings, a stencil printer embodying the present invention is shown and generally designated by the reference numeral
1
. As shown, the printer
1
is generally made up of a document scanning section
2
, a sheet feeding section
3
, a master making section
4
, a master discharging section
5
, a sheet discharging section
6
, and a printing section
7
. The sections other than the printing section
7
are identical with conventional ones and will not be described specifically.
The printing section
7
includes a print drum
8
and a press roller
9
. The print drum
8
is rotatably mounted on a shaft
8
a
and caused to rotate by a main motor
29
(see FIG.
6
). A stage, not shown, and a damper
10
are mounted on the outer periphery of the print drum
8
while ink feeding means
11
is arranged within the print drum
8
. Moving means, not shown, causes the press roller
9
to move into and out of contact with the outer periphery of the print drum
8
. The press roller
9
presses a paper or similar recording medium P against the print drum
8
when brought into contact with the press drum
8
, so that an image is transferred from the drum
8
to the paper P.
FIG. 2
shows the print drum
8
in a fragmentary view. As shown, the ink feeding means
11
includes an ink roller
12
, a doctor roller
13
, an ink replenishing roller
14
, and a blade or ink collecting member
15
. The ink roller
12
is journal led to opposite side walls
16
affixed to the shaft
8
a
such that its outer periphery adjoins the inner periphery of the print drum
8
. Ink fed from an ink feed pipe, not shown, is transferred to the inner periphery of the print drum
8
by the ink roller
12
. The rotation of the main motor
29
is transmitted to the ink roller
12
via drive transmitting means, not shown, including gears and a belt, so that the ink roller
12
rotates clockwise, as viewed in
FIG. 2
, in synchronism with the print drum
8
.
The doctor roller
13
is also journal led to the side walls
16
in the vicinity of the ink roller
12
. The rotation of the main motor
29
is transmitted to the doctor roller
13
via drive transmitting means, not shown, causing the doctor roller
13
to rotate in the opposite direction to the ink roller
12
. The outer periphery of the doctor roller
13
is spaced from the outer periphery of the ink roller
12
by a small gap, so that a wedge-like ink well
17
is formed between the outer periphery of the doctor roller
13
and that of the ink roller
12
. The ink in the ink well
17
is passed through the gap between the ink roller
12
and the doctor roller
13
and forms an ink layer on the ink roller
12
.
The ink replenishing roller
14
is positioned downstream of the ink roller
12
in the direction of rotation of the print drum
8
. The ink replenishing roller
14
is mounted on a shaft
14
a
which is, in turn, journal led to a pair of flat arms
18
at its opposite ends.
The end of each arm
18
opposite to the end rotatably supporting the shaft
14
a
is bent to form a receiving portion
18
a
. A slot
18
b
is formed in substantially the intermediate portion of the arm
18
while a slot
18
c
is formed in the arm
18
in the vicinity of the receiving portion
18
a
. The arms
18
are positioned outside of the side walls
16
. Specifically, a pin
19
is studded on the outer surface of each side wall
16
and received in the slot
18
b
of one arm
18
adjoining the side wall
16
. A shaft
20
is journal led to the side walls
16
via bearings
16
a
(see
FIG. 4
that is a view as seen from the right of
FIG. 2
) mounted on the side walls
16
. The shaft
20
has its opposite ends received in the slots
18
c
of the arms
18
. A tie rod
18
d
connects the end portions of the arms
18
adjoining the shaft
14
a
to each other.
Cam disks
21
are mounted on opposite ends of the shaft
20
while a worm wheel
22
is mounted on the center portion of the shaft
20
. Each cam disk
21
is affixed to the shaft
20
at its position offset from the center such that the outer periphery of a larger diameter portion included in the cam disk
21
is capable of contacting the associated receiving portion
18
a
. A bracket, not shown, is provided on the inner surface of the end portion of each arm
18
adjoining the receiving portion
18
a
. Also, a bracket, not shown, is provided on the inner surface of each side wall
16
. A tension spring
23
is anchored to the above brackets at its opposite ends and constantly biases the arm
18
in the direction in which the receiving portion
18
a
tends to contact the circumference of the cam disk
21
.
A stepping motor
24
is affixed to the side walls
16
via mounting members, not shown, in the vicinity of the worm wheel
22
. A worm
25
is mounted on the output shaft of the stepping motor
24
and held in mesh with the worm wheel
22
.
The blade or ink collecting member
15
is located downstream of the ink replenishing roller
14
in the direction of rotation of the print drum
8
and formed of spring steel, resin or similar elastic material. The blade
15
extends over substantially the entire axial width of the print drum
8
. One end of the blade
15
is affixed to a bracket, not shown, extending between the side walls
16
. The other end of the blade
15
is held in contact with the inner periphery of the print drum
8
with a preselected elastic force. The blade
15
has a plurality of bent portions
15
a
at its suitable intermediate position. Specifically, the bent portions
15
a
are positioned such that they contact the tie rod
18
d
when the ink replenishing roller
14
is moved from a second position shown in
FIG. 3
to a first position shown in
FIG. 2
, as will be described specifically later.
The stepping motor
24
causes the cam disks
21
to rotate and thereby selectively moves the ink replenishing roller
14
and blade
15
to the first position or the second position. A controller
28
that will be described later with reference to
FIG. 6
controls the operation of the stepping motor
24
.
Specifically, when the larger diameter portions of the cam disks
21
contact the receiving portions
18
a
of the associated arms
18
, the ink replenishing roller
14
is brought to the first position shown in FIG.
2
. In the first position, the roller
14
is spaced from the inner periphery of the print drum
8
and the outer periphery of the ink roller
12
against the action of the tension springs
23
. When the larger diameter portions of the cam disks
21
move away from the receiving portions
18
a
, the roller
14
is brought into contact with the inner periphery of the print drum
8
and the outer periphery of the ink roller
12
by the action of the tension springs
23
. As soon as the smallest diameter portions of the cam disks
21
face the receiving portions
18
a
, the roller
14
reaches the second position of
FIG. 3
in which it is pressed against the print drum
8
and ink roller
12
by the preselected bias of the tension springs
23
. Each cam disk
21
has such a profile that when its smallest diameter portion faces the associated receiving portion
18
a
, a small gap exists between the former and the latter. Further, the bias of the tension springs
23
is selected such that the roller
14
exerts a greater contact force on the inner periphery of the print drum
8
than on the outer periphery of the ink roller
12
when brought to the second position.
When the larger diameter portions of the cam disks
21
contact the associated receiving portions
18
a
, the tie rod
18
d
raises the bent portions
15
a
of the blade
15
. As a result, the blade
15
is brought to the first position shown in
FIG. 2
with its edge contacting the outer periphery of the ink replenishing roller
14
. When the larger diameter portions move away from the receiving portions
18
a
, the blade
15
is located in the second position shown in
FIG. 3
due to its own elasticity. In the second position, the edge of the blade
15
contacts the inner periphery of the print drum
8
. The blade
15
is positioned such that a small gap x exists between the edge of the blade
15
and the ink replenishing roller
14
in the second position. The elasticity of the blade
15
is selected such that when the ink replenishing roller
14
is brought to the second position, the blade
15
exerts a smaller contact force on the inner periphery of the print drum
8
than the roller
14
.
As shown in
FIG. 5
, a cam
26
is mounted on one of opposite flanges
8
b
of the print drum
8
and rotatable integrally with the print drum
8
. The cam
26
has a notch
26
a
extending over an angular range corresponding to a nonporous portion included in each of a porous support and a mesh screen, not shown, which constitute the print drum
8
. A sensor
27
is positioned in the vicinity of the cam
26
. While the sensor
27
is sensing the cam
26
, it continuously delivers an ON signal to the controller
28
.
Reference will be made to
FIG. 6
for describing a control system including the controller
28
. The controller
28
is implemented as a conventional microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory). As shown, the controller
28
controls the operation of the stepping motor
24
and that of the main motor
29
in response to an operation command input via a control panel
30
. The control panel
30
includes two keys
30
a
and
30
b
respectively used to select an ink collection mode and to set a desired number of times of ink collection. When the ink collection mode is selected on the key
30
a
, the controller
28
locates the ink replenishing roller
14
and blade
15
at the second position,
FIG. 3
, after the end of printing. At the same time, the controller
28
validates a number of ON signals to be output from the sensor
27
corresponding to the number of times of ink collection selected on the key
30
b
and causes the main motor
29
to start rotating the print drum
8
. Every time the ON signal from the sensor
27
disappears, the controller
28
decrements the above number of times by 1 (one). When the number of times reaches zero, the controller
28
stops the rotation of the print drum
8
and returns the ink replenishing roller
14
and blade
15
to the first position, FIG.
2
.
In operation, when the operator selects the ink collection mode on the key
30
a
and sets a desired number of times of ink collection on the key
30
b
, the controller
28
causes the stepping motor
24
to rotate after the end of printing, thereby locating the replenishing roller
14
and blade
15
at the second position.
Subsequently, the controller
28
causes the main motor
29
to rotate the print drum
8
clockwise as viewed in FIG.
1
. The ink roller
12
and doctor roller
13
are rotated together with the print drum
8
. At the same time, the ink replenishing roller
14
is caused to rotate. Because the ink replenishing roller
14
exerts a greater contact force on the inner periphery of the print drum
8
than on the outer periphery of the ink roller
12
, as stated earlier, the roller
14
is rotated clockwise by the print drum
8
.
While the print drum
8
is in rotation, the blade
15
scrapes off excess ink from the inner periphery of the print drum
8
with its edge. The ink scraped off by the blade
15
and transferred to the blade
15
is stored in the gap x. The stored ink is transferred to the ink replenishing roller
14
rotating clockwise and then transferred to the ink roller
12
. As a result, the ink is collected in the ink well
17
which is the regular ink storage. At this instant, because the blade
15
is located as close to the ink roller
12
feeding ink as possible, the excess ink exists on the inner periphery of the print drum
8
only between the ink roller
12
and the blade
15
. It is therefore possible to collect most of the ink existing on the print drum
8
.
When the notch
26
a
of the cam
26
rotating integrally with the print drum
8
meets the sensor
27
, the sensor
27
stops outputting the ON signal. In response, the controller
28
decrements the number of times of ink collection set on the control panel
30
by 1. When the ink collection is repeated the set number of times, the controller
28
stops driving the main motor
29
and thereby stops the print drum
8
at a preselected home position. At the same time, the controller
28
drives the stepping motor
24
in order to return the ink replenishing roller
14
and blade
15
to the first position. As a result, the printer
1
is restored to its initial conditions.
With the above construction and operation, it is possible to surely remove excess ink from the inner periphery of the print drum
8
. Because the number of times of ink collection can be freely selected in accordance with the property of the ink including viscosity, the ink can be collected in an optimal way matching with the kind of the ink. It follows that even the first image formed after a long time of suspension is attractive.
The blade
15
is movable in interlocked relation to the ink replenishing roller
14
and has its edge initially spaced from the inner periphery of the print drum
8
. This obviates friction between the blade
15
and the inner periphery of the print drum
8
and prevents the ink from being collected more than necessary. Consequently, there can be obviated noise and short image density.
The blade
15
exerts a smaller contact force on the inner periphery of the print drum
8
than the ink replenishing roller
14
. Therefore, when the ink replenishing roller
14
feeds ink to the inner periphery of the drum
8
, the blade
15
is successfully prevented from collecting the ink adequately replenished by the roller
14
.
In the above embodiment, the printer
1
executes, after the end of printing, ink collection a desired number of times input on the key
30
b
. Alternatively, the printer
1
may be constructed to automatically bring the ink replenishing roller
14
and blade
15
to the second position for collecting the ink when the print drum
8
makes the last rotation at the end of printing. Although such automatic ink collection collects the ink only once, it can be executed during printing and therefore allows even the first image to be desirably formed after a long time of suspension while reducing the operation time.
If desired, the control panel
30
may additionally include a key
30
c
for causing a plurality of printing operations to be continuously executed. When the operator presses the key
30
c
, the printer
1
will perform ink collection only at the end of the last printing operation. This successfully omits ink collection otherwise effected at the end of each printing operation and again allows even the first image to be desirably formed after a long time of suspension while noticeably reducing the operation time. Ink collection can be executed during printing in the same manner as in the previous construction.
Further, the control panel
30
may include another key
30
d
for allowing ink collection to be executed at any desired timing. Specifically, when a plurality of printing operations are to be continuously executed, the key
30
d
allows the operator to input a desired ink collection timing between the printing operations. This allows even the first image to be efficiently formed after a long time of suspension. In this case, ink replenishment and ink collection may, of course, be executed before the start of printing.
In the illustrative embodiment and above modifications thereof, the ink replenishing roller
14
is pressed against the ink roller
12
and the inner periphery of the print drum
8
by a preselected bias and rotated thereby. If desired, the replenishing roller may be driven by exclusive drive means.
In summary, it will be seen that the present invention provides a stencil printer having various unprecedented advantages, as enumerated below.
(1) It is possible to surely remove excess ink from the inner periphery of a print drum and to desirably form even the first image after a long time of suspension. An ink collecting member is movable in interlocked relation to an ink replenishing roller and has its edge initially spaced from the inner periphery of the print drum. This obviates friction between the ink collecting member and the inner periphery of the print drum and prevents ink from being collected more than necessary. Consequently, there can be obviated noise and short image density.
(2) The ink collecting member exerts a smaller contact force on the inner periphery of the print drum than the ink replenishing roller. Therefore, when the ink replenishing roller feeds ink to the inner periphery of the print drum, the ink collecting member is successfully prevented from collecting ink adequately replenished by the replenishing roller.
(3) Ink collection can be executed during printing and therefore allows even the first image to be desirably formed after a long time of suspension while reducing the operation time.
(4) Ink collection can be executed at any desired timing during printing. This allows even the first image to be efficiently formed after a long time of suspension.
(5) There can be omitted ink collection otherwise effected at the end of each printing operation. This also allows even the first image to be desirably formed after a long time of suspension while noticeably reducing the operation time.
(6) Because ink collection is effected only at the end of the last printing operation, there can be omitted ink collection otherwise effected at the end of each printing operation preceding it. This also allows even the first image to be desirably formed after a long time of suspension while noticeably reducing the operation time.
(7) Because the number of times of ink collection can be freely selected in accordance with the property of ink including viscosity, the ink can be collected in an optimal way matching with the kind of the ink. It follows that even the first image formed after a long time of suspension is attractive.
Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.
Claims
- 1. A stencil printer comprising:a rotatable print drum; an ink roller configured to be rotated in a same direction as said print drum and to feed ink directly to an inner periphery of said print drum during printing; an ink replenishing roller configured to be rotated in a same direction as said print drum and said ink roller and to be moved between a first position where said ink replenishing roller is spaced from the inner periphery of said print drum and said ink roller and a second position where said ink replenishing roller contacts said inner periphery of said print drum and said ink roller; and an ink collecting member located downstream of said ink replenishing roller in a direction of rotation of said print drum and configured to move in inter locked relation to said ink replenishing roller between said first position and said second position.
- 2. The stencil printer as claimed in claim 1, wherein said ink collecting member is configured to contact the inner periphery of said print drum when said ink replenishing roller is brought to said second position.
- 3. The stencil printer as claimed in claim 2, wherein said ink collecting member is configured to exert a smaller contact force on the inner periphery of said print drum than said ink replenishing roller.
- 4. The stencil printer as claimed in claim 2, wherein said ink replenishing roller is configured to gather ink from the inner periphery of said print drum collected by said collecting member in contact with said inner periphery of said print drum.
- 5. The stencil printer as claimed in claim 1, wherein said ink collecting member comprises a flat elastic member.
- 6. The stencil printer as claimed in claim 1, further comprising control means for causing said ink replenishing roller and said ink collecting member to move to said second position when said print drum makes a last rotation during printing.
- 7. The stencil printer as claimed in claim 6, wherein when a printing operation is repeatedly executed, said control means causes said ink replenishing roller and said ink collecting member to move to said second position only at an end of a last printing operation.
- 8. The stencil printer as claimed in claim 1, further comprising control means for causing, after a printing operation, said ink replenishing roller and said ink collecting member to move to said second position and causing said print drum to rotate.
- 9. The stencil printer as claimed in claim 8, wherein when a printing operation is repeatedly executed, said control means causes said ink replenishing roller and said ink collecting member to move to said second position only after a last printing operation.
- 10. The stencil printer as claimed in claim 8, wherein when said ink replenishing roller and said ink collecting member are brought to said second position, said print drum makes a desired number of rotations set by an operator.
- 11. The stencil printer as claimed in claim 1, further comprising control means for causing, at a desired timing set by an operator, said ink replenishing roller and said ink collecting member to move to said second position and causing said print drum to rotate.
- 12. A stencil printer as claimed in claim 1, wherein when said ink replenishing roller and said ink collecting member are brought to said second position, said control means causes said print drum to make a desired number of rotations set by an operator.
- 13. The stencil printer as claimed in claim 1, wherein said ink replenishing roller is configured to gather ink from the inner periphery of said print drum.
- 14. The stencil printer as claimed in claim 1, wherein a gap is formed between the ink collecting member and the ink replenishing roller.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-136790 |
May 1999 |
JP |
|
US Referenced Citations (7)
Foreign Referenced Citations (8)
Number |
Date |
Country |
2638344 |
Jul 1977 |
DE |
3-164287 |
Jul 1991 |
JP |
4-296585 |
Oct 1992 |
JP |
6-135114 |
May 1994 |
JP |
7-052518 |
Feb 1995 |
JP |
8-025781 |
Jan 1996 |
JP |
8-142474 |
Jun 1996 |
JP |
10-217595 |
Aug 1998 |
JP |