Information
-
Patent Grant
-
6356293
-
Patent Number
6,356,293
-
Date Filed
Friday, June 30, 200024 years ago
-
Date Issued
Tuesday, March 12, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
-
CPC
-
US Classifications
Field of Search
US
- 347 221
- 347 116
- 347 152
- 347 262
- 347 264
- 399 96
- 399 117
- 346 138
- 346 132
- 101 79
- 101 85
- 101 110
- 101 114
- 101 116
- 101 485
- 101 486
-
International Classifications
-
Abstract
A printer of the present invention includes at least a first and a second drum unit each including a respective print drum. Angular position sensing device each are assigned to the respective print drum. A main motor included in drum drive mechanism is controlled on the basis of the output of a first or a second drum unlock key such that the print drum of the first or second drum unit is brought to a preselected home position. The printer has a compact configuration and promotes easy, efficient manipulation without resorting to conventional top-bottom movement adjustment mechanism including top-bottom moving device.
Description
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a stencil printer or similar printer and more particularly to a color printer including a plurality of print drums around which masters are to be wrapped.
DISCUSSION OF THE BACKGROUND
A thermal, digital master making type of stencil printer belongs to a family of relatively simple printers. In this type of stencil printer, a stencil is caused to contact a thermal head having fine heat generating elements arranged thereon. While the stencil is conveyed, the heat generating elements are selectively energized in accordance with image data so as to selectively perforate the stencil with heat. The perforated stencil, or master as referred to hereinafter, is wrapped around a print drum implemented as a porous hollow cylinder. Ink feeding means arranged in the print drum feeds ink to the inner periphery of the print drum. A press roller or similar pressing member presses a paper sheet or similar recording medium conveyed thereto against the print drum via the master. As a result, the ink is transferred from the print drum to the paper sheet via the porous portion of the print drum and the perforation pattern of the master, printing an image on the paper sheet.
Assume that a master making device and a master discharging device are physically separate from the printer, that the print drums of the printer are mechanically interlocked to each other, and that all of the print drums are removed from the printer in the event of master making and master discharging and again inserted into the printer. Then, the print drums cannot be removed from or inserted into the printer at the same time unless the distance between nearby print drums is an integral multiple of the circumferential length of each print drum in order to provide all of the print drums with an identical home position. This, however, makes the entire printer bulky. In light of this, the distance between nearby print drums may be made shorter than the circumferential length of each print drum with a preselected initial phase difference provided between the drums, thereby making the printer compact. This kind of scheme is taught in, e.g., Japanese Patent Application Nos. 9-321702 and 10-167322 and Japanese Patent Laid-Open Publication Nos. 11-138961 and 11-151852.
Specifically, the above Laid-Open Publication Nos. 11-138961 and 11-151852 disclose technologies that free the operator of a single drum type stencil printer from troublesome operation in the event of color printing. Further, assume that a color stencil printer including a plurality of print drums produces, e.g., a tetracolor or full-color print. Then, the operator of such a printer sometimes desires to replace two print drums assigned to a first and a second color, respectively, at the same time or to remove a paper sheet jamming a path between the two print drums without scratching mesh screens wrapped around the drums. To meet such a demand, in a printer of the previously described type spacing nearby drums by a distance shorter than the circumferential length of each print drum and providing an initial phase difference between the print drums, the above technologies automatically move the individual print drum to a dismount position by using top-bottom movement adjusting means including top-bottom moving means. The top-bottom movement adjusting means is essential for multicolor printing.
However, the problem with Laid-Open Publication No. 11-138961 is that the top-bottom movement adjusting means must rotate the individual print drum by a phase corresponding to the circumferential length of several ten millimeters or to adjust the top-bottom movement (amount of phase adjustment) by an angle of 90° or more with the top-bottom moving means. The adjusting means therefore makes the printer bulky although the initial phase difference makes it compact.
Moreover, the above conventional technologies have been proposed in the initial stage of development and, of course, have various problems left unsolved as to making the operation easy and efficient for the operator to perform.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Utility Model Laid-Open Publication No. 64-46258, Japanese Patent Laid-Open Publication Nos. 5-229243, 6-71998, 6-293175, 7-1817 and 7-17013, Japanese Utility Model Laid-Open Publication No. 61-85462, and Japanese Patent Laid-Open Publication Nos. 8-39916, 8-39918, 10-109470, 10-846, and 64-18682.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved compact printer not needing the top-bottom movement adjusting means and allowing a plurality of print drums to be mounted thereto by simple operation.
It is another object of the present invention to provide a printer that is easy and efficient to operate.
A printer of the present invention includes a plurality of drum units removably mounted to a printer body and each including a respective print drum allowing a particular master to be wrapped therearound. Nearby print drums are provided with a preselected initial phase difference therebetween beforehand when the drum units are present in the printer body. The drum units each are removable from the printer body when the respective print drum is brought to a preselected phase. The printer wraps masters around the print drums, feeds ink of particular color to each master, and presses a recording medium against the consecutive masters to thereby effect continuous printing. Individual removal setting devices each are assigned to a particular drum unit for making the drum unit removable from the printer body. Angular position sensing means each sense the angular position of the drum of a particular drum unit. A drum drive arrangement causes the print drum of the drum unit to be removed to rotate. A controller controls, based on the output of the individual removal setting device assigned to the drum unit to be removed and the output of the angular position sensing means assigned to the print drum of the same drum unit, the drum drive arrangement such that the print drum of the drum unit to be removed is brought to the preselected phase.
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 the general construction of a stencil printer embodying the present invention, as seen from the front of a housing printer body;
FIG. 2
is a fragmentary isometric view showing mounting/dismounting means and a drum unit included in the illustrative embodiment together with members associated therewith;
FIG. 3
is a view showing the engagement of locking means included in the illustrative embodiment;
FIG. 4A
is an isometric view showing drum drive means and mechanical locking means included in the illustrative embodiment, as seen from the rear of the housing;
FIG. 4B
is a fragmentary isometric view of a coupling portion arranged in the housing;
FIG. 4C
is a front view of the coupling portion;
FIG. 5
is a schematic block diagram showing a control arrangement around the drum drive means;
FIG. 6A
is a front view schematically showing paper egress sensors included in the illustrative embodiment;
FIG. 6B
is a timing chart representative of the operation of the paper egress sensors;
FIG. 7
is a perspective view showing LEDs (Light Emitting Diodes) and a door cover mounted on the housing;
FIG. 8
is a plan view showing a specific configuration of an operation panel included in the illustrative embodiment;
FIG. 9
is a block diagram schematically showing a control system included in the illustrative embodiment;
FIGS. 10 and 11
are views for describing an initial phase difference provided between nearby print drums in the illustrative embodiment;
FIG. 12
is a view showing a mount/dismount position assigned to a first drum included in the illustrative embodiment;
FIG. 13
is a view showing a mount/dismount position assigned to a second drum included in the illustrative embodiment;
FIG. 14
is a front view showing a positional relation between the print drums included in the illustrative embodiment; and
FIGS. 15 through 20
are flowcharts each demonstrating a particular specific operation of the illustrative embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A stencil printer embodying the present invention will be described hereinafter with reference to the accompanying drawings. In the figures and description to follow, structural elements identical in configuration and function are designated by identical reference numerals and will not be repeatedly described in order to avoid redundancy. To simplify the figures and description, parts and elements not relevant to the understanding of the illustrative embodiment will not be described. Further, as for parts and elements provided in pairs and not needing distinction, only one of them will be described for simplicity.
Referring to
FIG. 1
of the drawings, a stencil printer embodying the present invention is shown and generally designated by the reference numeral
500
. As shown, the printer
500
includes a box-like housing or printer body
501
. A first print drum
1
a
and a second print drum
1
b
are positioned side by side in a direction X in which a paper sheet
22
is conveyed (direction of paper conveyance X hereinafter). In this sense, the print drums
1
a
and
1
b
are located at an upstream side and a downstream side, respectively. The print drums
1
a
and
1
b
are removably mounted to the housing
501
. Masters
33
a
and
33
b
are wrapped around the print drums
1
a
and
1
b,
respectively. Ink of a particular color is fed to each of the masters
33
a
and
33
b
via the associated print drum
1
a
or
1
b.
In this condition, the paper sheet
22
is sequentially pressed against the masters
33
a
and
33
b.
As a result, a color image (bicolor image in the illustrative embodiment) is printed on the paper sheet
22
.
While the illustrative embodiment includes only two print drums
1
a
and
1
b
spaced in the direction of paper conveyance X, three or more print drums can, of course, be sequentially arranged in the direction X in order to produce a color print.
FIGS. 4A through 4C
and
FIG. 5
show drum drive means
80
for causing the print drums
1
a
and
1
b
to rotate.
FIG. 2
shows mounting/dismounting means
50
a
and
50
b
for respectively allowing the print drums
1
a
and
1
b
to be mounted and dismounted from the housing
501
.
FIG. 8
shows a specific arrangement of an operation panel
110
for allowing the operator to operate the printer
500
.
FIG. 9
shows control circuitry including a controller
200
.
Home positions different from the home positions taught in Japanese Patent Laid-Open Publication No. 11-138961 mentioned earlier are assigned to the print drums
1
a
and
1
b.
For example, the home positions are such that dampers
5
a
and
5
b
(see
FIG. 1
) mounted on the print drums
1
a
and
1
b,
respectively, are positioned substantially at the bottoms of the drums
1
a
and
1
b.
The general construction of the printer
500
will be described first with reference to
FIG. 1
, and then details of the mounting/dismounting means
50
a
and
50
b,
drum drive means
80
, operation panel
110
and controller
200
will be described. It is to be noted that master making devices
41
a
and
41
b
and master discharging devices
42
a
and
42
b
are indicated by phantom lines because they are not used or arranged in the illustrative embodiment.
The print drums
1
a
and
1
b
are substantially identical in configuration and function, and so are the mounting/dismounting means
50
a
and
50
b.
Also, ink feeding means assigned to the print drum
1
a
and ink feeding means assigned to the print drum
1
b,
as will be described specifically later, are substantially identical in configuration and operation. Such identical structural elements are distinguished from each other by suffixes a and b, and only one of them will be described as far as possible in order to avoid redundancy.
The printer
500
is generally identical with a printer shown in
FIG. 4
of Japanese Patent Application No. 10-167322 mentioned earlier except for the above-described unique arrangements. Specifically, as shown in
FIG. 1
, a sheet feeder
20
is positioned below and rightward of the print drum
1
a
around which the master
33
a
is wrapped. The sheet feeder
20
feeds paper sheets
22
stacked on a paper tray
21
one by one. A pressing device
32
a
is arranged below the print drum
1
a
for pressing the paper sheet
22
conveyed thereto against the master
33
a
so as to print an image of a first color on the paper sheet
22
. An air knife
7
a
peels off the paper sheet
22
carrying the above image thereon from the print drum
1
a.
A pressing device
32
b
is positioned below the print drum
1
b,
around which the master
33
b
is wrapped, and presses the paper sheet
22
against the master
33
b
in order to print an image of a second color on the paper sheet
22
over the image of the first color. An intermediate conveying device
17
conveys the paper sheet
22
from the pressing device
32
b
to the pressing device
32
b.
An air knife
7
b
peels off the paper sheet
22
carrying the resulting bicolor image thereon from the print drum
1
b.
A paper discharging device
35
conveys the paper sheet or bicolor print
22
to a print tray
37
and includes the air knife
7
b.
In the illustrative embodiment, the master making devices
41
a
and
41
b,
master discharging devices
42
a
and
42
b
and a scanner usually arranged above the devices
41
a
through
42
b
are absent. Specifically, assume an integrated stencil printer with a thermal digital master making capability and equipped with a scanner, a master discharging device and a master making device separate from the printer
500
. Then, the used masters
33
a
and
33
b
wrapped around the print drums
1
a
and
1
b,
respectively, are discharged via drum units
100
a
and
100
b
while new masters
33
a
and
33
b
are wrapped around the drums
1
a
and
1
b,
respectively, via the drum units
100
a
and
100
b,
as shown in
FIG. 4
of the previously mentioned Application No. 10-167322. The printer
500
shares the same drum units and other structural parts with the above-described type of integrated stencil printer and is therefore simple, small size and low cost.
The print drum
1
a
is a conventional porous hollow cylinder rotatable about a shaft
2
a
and extending in the axial direction of the shaft
2
a.
The print drum
1
a,
like a print drum shown in
FIG. 4
of Laid-Open Publication No. 11-138961 mentioned earlier, has a double layer structure made up of a metallic, hollow cylindrical core and a mesh screen layer wrapped around the core, although not shown specifically. The core is formed with a number of pores permeable to ink. The mesh screen layer is formed of resin or metal. More specifically, the core has a printing area formed with the pores and a non-printing area not formed with the pores and not permeable to ink. The printing area extends over a preselected circumferential range of the core except for a position where the damper
5
a
is located. The non-printing range is also formed at opposite axial edge portions of the core.
As shown in
FIG. 1
, the damper
5
a
is openably mounted on the print drum
1
a
and extends in the axial direction of the drum
1
a
for clamping the leading edge of the master
33
a.
The damper
5
a
is angularly movably mounted on the print drum
1
a
via shaft
6
a.
Opening/closing means, not shown, is located at a suitable position around the print drum
1
a
for causing the damper
5
a
to open and close at a preselected position.
As shown in
FIG. 2
, the print drum
1
a
has opposite ends thereof fastened to the circumferential surfaces of two end plates
68
by screws. A roller bearing, not shown, is interposed between the center of each end plate
68
and the shaft
2
a.
The print drum
1
a
is rotatably mounted on the shaft
2
a
via the roller bearings while the shaft
2
a
is supported by a front frame
55
and a rear frame
56
. A main motor
81
(see
FIGS. 4A and 5
) drives the ink drum
1
a.
As shown in
FIG. 1
, ink feeding means is arranged in the print drum
1
a
for feeding ink of a first color from the inner periphery to the outer periphery of the drum
1
a.
Likewise, ink feeding means is arranged in the print drum
1
b
for feeding ink of a second color from the inner periphery to the outer periphery of the drum
1
b.
In the illustrative embodiment, the first and second colors are assumed to be black and magenta, respectively. The ink feeding means arranged in the print drum
1
a
includes an ink roller
3
a
for applying the black ink to the inner periphery of the drum
1
a.
A doctor roller
4
a
is parallel to the ink roller
3
a
and spaced from the ink roller
3
a
by a small gap, forming an ink well
1
a
therebetween. An ink feed tube
2
a
for feeding the ink to the ink well
1
a
serves as the shaft
2
a
at the same time.
The drum unit
100
a,
which will be described specifically later with reference FIG.
2
and other figures, includes an ink cartridge
64
a
and an ink pump
66
a
for feeding compressed ink from the cartridge
64
a.
The ink fed from the ink cartridge
64
a
is delivered to the ink well
1
a
via the ink feed tube
2
a.
Ink sensing means (see, e.g., FIG. 5 of Laid-Open Publication No. 5-229243 mentioned earlier) senses the amount of ink existing in the ink well
1
a.
The delivery of the ink from the ink pump
66
a
is controlled on the basis of the output of the ink sensing means.
The ink roller
3
a
is formed of, e.g., aluminum, stainless steel, metal or rubber and caused to rotate clockwise by a gear train, not shown, together with the print drum
1
a.
A preselected ratio is set between the rotation speed of the ink roller
3
a
and that of the print drum
1
a.
The doctor roller
4
a
is formed of iron, stainless steel or similar metal and caused to rotate counterclockwise by a gear train not shown. A preselected ratio is also set between the rotation speed of the doctor roller
4
a
and the print drum
1
a.
The master
33
a
is implemented by a laminate of a film formed of polyester or similar thermoplastic resin and a porous base implemented by, e.g., Japanese paper. Alternatively, use may be made of a master substantially consisting only of an extremely thin thermoplastic resin film 1 μm to 8 μm thick), a thin master (20 μm to 30 μm thick) not as thin as the above master, but thinner than the master
33
a
(about 40 μm to 50 μm thick), and including a base that contains a substantial amount of synthetic fibers, e.g., a base entirely implemented by polyethylene terephthalate (PET).
The sheet feeder
20
includes the previously mentioned paper tray
21
driven by a motor, not shown, in the up-and-down direction in accordance with the increase/decrease in the amount of the sheet stack
22
. A pickup roller
23
and a separator roller
24
are journal led to opposite sidewalls, not shown, included in the sheet feeder
20
. A separator roller
25
is pressed against the separator roller
24
for preventing two or more paper sheets
22
from being fed together. An upper and a lower registration roller
29
and
30
convey the leading edge of the paper sheet
22
toward a gap between the ink drum
1
a
and the press roller
9
a
at a preselected timing. An upper and a lower guide plate
28
and
27
guide the leading edge of the paper sheet
22
to a nip between the registration rollers
29
and
30
. An upper and a lower registration guide plate
31
guide the paper sheet
22
further to the gap between the ink drum
1
a
and the press roller
9
a.
A paper feed motor
44
independent of the main motor
81
causes the pickup roller
23
and separator roller
24
to rotate. A registration motor
47
also independent of the main motor
81
causes the registration rollers
29
and
30
to rotate. A paper lead edge sensor
48
is located on a paper transport path between the separator roller
24
and the registration rollers
29
and
30
for sensing the leading edge of the paper sheet
22
. A registration sensor
49
is located in a paper transport path between the print drum
1
a
and the registration rollers
29
and
30
for sensing the leading edge of the paper sheet
22
.
The pickup roller
23
and separator rollers
24
and
25
contact the top sheet
22
existing on the paper tray
21
. While the pickup roller
23
pays out the top paper sheet
22
from the paper tray
21
, the separator rollers
24
and
25
and separator plate
26
cooperate to separate the top paper sheet
22
from the under lying paper sheets
22
. The pickup roller
23
, separator rollers
24
and
25
and separator plate
26
constitute paper feeding means for feeding the leading edge of the top paper sheet
22
toward the registration rollers
29
and
30
.
The paper feed motor
44
is implemented by a stepping motor and plays the role of paper feed drive means for causing the separator roller
24
and pickup roller
23
to rotate. The paper feed motor
44
is drivably connected to the separator roller
24
via a toothed endless belt
45
. The belt
45
is passed over a drive pulley mounted on the output shaft of the motor
44
and a driven pulley mounted on the shaft of the separator roller
24
. In this configuration, the motor
44
causes the separator roller
24
to rotate clockwise. A one-way clutch, not shown, is arranged on each of the shafts of the rollers
23
and
24
, so that the rollers
23
and
24
are rotatable only in the clockwise direction via the belt
45
.
The leading edge of the paper sheet
22
fed from the paper tray
21
abuts against a portion of the registration rollers
29
and
30
just short of the nip between the rollers
29
and
30
. The paper sheet
22
then forms a loop convex upward along the upper guide plate
28
. The registration rollers
29
and
30
then nips the leading edge of the paper sheet
22
and conveys it to the gap between the print drum
1
a
and the press roller
9
a
at a preselected timing.
The registration motor
47
is implemented by a stepping motor and plays the role of registration drive means for causing the lower registration roller
30
to rotate. A toothed endless belt
46
is passed over a drive pulley mounted on the output shaft of the registration motor
47
and a driven pulley mounted on the shaft of the registration roller
30
. The motor
47
is therefore drivably connected to the registration roller
30
via the belt
46
.
The paper lead edge sensor
48
and registration sensor
49
each are implemented by a reflection type optical sensor having a light emitting portion and a light-sensitive portion. The upper guide plate
28
and upper registration guide plate
31
are formed with holes for passing light issuing from the light emitting portions and holes for passing the light reflected from the leading edges of the paper sheet
22
, although not shown specifically. The paper lead edge sensor
48
responsive to the leading edge of the paper sheet
22
detects a jam occurred at the upstreamside, including the paper feeding means, in the direction of paper conveyance X. In addition, the sensor
48
implements part of a function of adjusting the amount of the loop that the leading edge of the paper sheet
22
forms.
The registration sensor
49
also responsive to the leading edge of the paper sheet
22
detects a jam occurred at the upstream side, including the registration rollers
29
and
30
, in the direction of paper conveyance X. In addition, the sensor
49
sends its output to a control unit, not shown, for correcting the amount of slip of the paper sheet
22
that occurs at the registration rollers
29
and
30
and varies in accordance with the kind of the paper sheet
22
.
The pressing device
32
a
includes a bracket
11
a,
tension spring
13
a
and a cam
12
a
having a pear-shaped profile in addition to the ink roller
3
a
and press roller
9
a.
The press roller
9
a
plays the role of pressing means for pressing the paper sheet
22
against the print drum
1
a,
as stated earlier. The press roller
9
a
is rotatably supported by one end of the bracket
11
a
such that it is movable into and out of contact with the print drum
1
a.
The tension spring
13
a
is anchored to the other end of the bracket
11
a
and determines the pressure that the press roller
9
a
exerts on the print drum
1
a.
The end of the bracket
11
a
is pressed against the profile of the cam
12
a
by the bias of the tension spring
13
a.
The cam
12
a
is connected to the drum drive means
80
, including the main motor
81
, and caused to rotate thereby in synchronism with the paper feed from the paper feeder
20
and the rotation of the print drum
1
a.
When the paper feeder
20
does not feed any paper sheet
22
, a larger diameter portion included in the cam
12
a
contacts the end of the bracket
11
a
facing the cam
12
a.
When the paper feeder
20
feeds the paper sheet
22
, the cam
12
a
is rotated to brings its smaller diameter portion into contact with the end of the bracket
11
a,
causing the press roller
9
a
to rotate clockwise as viewed in FIG.
1
. At this time, the pressure derived from the tension spring
13
a
is transferred to the print drum
1
a.
The air knife
7
a
has its edge implemented as a nozzle for preventing the paper sheet
22
from adhering to the print drum
1
a
and rolling up. Specifically, a pump or compressed air source, not shown, delivers air under pressure to the nozzle of the air knife
7
a.
As a result, a jet of air is sent from the nozzle to the leading edge of the paper sheet
22
at a high velocity. The air knife
7
a
is angularly movable about a shaft
8
a
between an operative position where it adjoins the print drum
1
a
for peeling off the paper sheet
22
from the print drum
1
a
and an inoperative position where it is spaced from the print drum
1
a.
That is, the air knife
7
a
is movable between the two positions in synchronism with the rotation of the print drum
1
a
so as not to interfere with the damper
5
a.
A blast fan
34
is located at the left-hand side of the other air knife
7
b.
The blast fan
34
helps the air knife
7
b
separate the paper sheet
22
from the print drum
1
b
and prevent it from rolling up together with the print drum
1
b.
The intermediate conveying device
17
includes a porous belt
16
passed over a drive roller
15
and a driven roller
14
, a suction fan
18
, and a casing
19
. At least the surface of the belt
16
is formed urethane rubber or similar material having a great coefficient of friction with respect to the paper sheet
22
. The belt
16
therefore pulls the paper sheet
22
to the left, as viewed in FIG.
1
. At this time, however, the upstream portion of the paper sheet
22
in the direction of paper conveyance X is still nipped between the print drum
1
a
and the press roller
9
a.
The paper sheet
22
therefore moves to the left at a speed equal to the peripheral speed of the print drum
1
a.
The belt
16
is driven in synchronism with the print drum
1
a
at a speed equal to or slightly higher than the peripheral speed of the print drum
1
a.
The belt
16
therefore conveys the paper sheet
22
while applying leftward tension thereto. The suction fan
18
is disposed in the casing
19
and generates vacuum in the casing
19
.
The paper discharging device
35
includes a porous belt
40
passed over a drive roller
38
and a driven roller
39
, a jump board
40
A, a suction fan
36
, and a casing
36
A. The belt
40
is driven in synchronism with the print drum
1
b
at a speed substantially equal to the peripheral speed of the drum
1
b.
Air sent from the blast fan
34
hits against the surface of the paper sheet or print
22
from a position above and leftward of the air knife
7
b.
This air not only prevents the paper sheet
22
from rising above the belt
40
, but also promotes the drying of the ink existing on the paper sheet
22
. The jump board
40
A causes the center portion of the paper sheet
22
to deform in the form of a letter U, i.e., provides the paper sheet
22
with an adequate degree of stiffness, so that the consecutive paper sheets
22
can be neatly stacked on the print tray
37
.
As shown in
FIGS. 1 and 6
, a first paper egress sensor or sensing means
74
is positioned downstream of the print drum
1
a
of the drum unit
100
a
in the direction of paper conveyance X. The paper egress sensor
74
is responsive to the roll-up and defective egress, or egress error, of the paper sheet
22
. Likewise, a second paper egress sensor or sensing means
75
is positioned downstream of the print drum
1
b
of the drum unit
100
b
in the direction of paper conveyance X and also responsive to the roll-up and defective egress of the paper sheet
22
.
The paper egress sensors
74
and
75
each are implemented as a reflection type photosensor similar to a roll-up sensor
50
shown in
FIG. 6
of Laid-Open Publication No. 11-151852 mentioned earlier. The belt
16
included in the intermediate conveying device
17
is divided into a plurality of spaced segments. The first paper egress sensor
74
is positioned beneath a gap between the segments of the belt
16
. Likewise, the second paper egress sensor
75
is positioned beneath a gap between spaced segments constituting the belt
40
of the paper discharging device
35
.
As shown in
FIG. 2
, the drum unit
100
a
is removably mounted to the housing or printer body
501
via the mounting/dismounting means
50
a.
Likewise, the drum unit
100
b
is removably mounted to the housing
501
via the mounting/dismounting means
50
b.
Openings
501
a
and
501
b
are formed in the front end of the housing
501
for allowing the drum units
100
a
and
100
b,
respectively, to be mounted and dismounted from the housing
501
. As shown in
FIGS. 3 and 4A
through
4
C, coupling portions for respectively receiving the rear end portions of the shafts
2
a
and
2
b,
as viewed in
FIG. 2
, and the drum drive means
80
are arranged in the housing
501
behind the openings
501
a
and
501
b.
As shown in
FIG. 2
, the drum unit
100
a
includes a cartridge holder
65
a,
a grip
63
, a front frame
55
, a rear frame
56
and a handle
57
in addition to the print drum
1
a,
end plates
68
, shaft
2
a,
ink feeding means, ink pump
66
a,
and ink cartridge
64
a
storing black ink and received in the cartridge holder
65
a.
Likewise, the drum unit
100
b
includes a-cartridge holder
65
b
for holding an ink cartridge
64
b
storing magenta ink, an ink pump
66
b,
a grip
63
, a front frame
55
, a rear frame
56
and a handle
57
in addition to the print drum
1
b,
end plates
68
, shaft
2
b
and ink feeding means.
The drum units
100
a
and
100
b
can be removed from the housing
501
only when the print drums
1
a
and
1
b
thereof are located at their home positions via a structure and means that will be described specifically later.
The above-described configuration of the drum units
100
a
and
100
b
is extremely convenient when the operator, intending to change the colors, replaces the print drums
1
a
and
1
b
with other print drums. Further, the operator is capable of removing a paper sheet jamming the path between the print drums
1
a
and
1
b
without scratching or otherwise damaging the masters
33
a
and
33
b
wrapped around the drums
1
a
and
1
b,
respectively, or the mesh screens of the drums
1
a
and
1
b.
The drum units
100
a
and
100
b
are substantially identical in construction and operation, as stated earlier. The print drums
1
a
and
1
b,
shafts
2
a
and
2
b,
structural elements constituting the ink feeding means, mounting/dismounting means
50
a
and
50
b,
ink cartridges
64
a
and
64
b,
cartridge holders
65
a
and
65
b
and ink pumps
66
a
and
66
b
respectively assigned to the print drums
1
a
and
1
b
are distinguished from each other by the suffixes a and b. When one of the corresponding parts is described in detail, the other part will not be described in order to avoid redundancy.
As shown in
FIG. 2
, the mounting/dismounting means
50
a
includes a pair of rollers
58
, a guide rail
53
and a pair of inlet rollers
60
as well as the shaft
2
a,
front frame
55
, rear frame
56
, and handle
57
. The mounting/dismounting means
50
a,
part of which is not shown in
FIG. 2
, may be constructed in the same manner as a drum support arrangement shown in
FIG. 4
of Laid-Open Publication No. 61-85462 mentioned earlier.
Annular affixing members, not shown, are mounted on opposite ends of the shaft
2
a.
The front frame
55
and rear frame
56
through which the shaft
2
a
is passed are fastened to the inner surfaces of the affixing members by screws. The upper ends of the frames
55
and
56
are affixed to opposite ends of the handle
57
, which has a top-open channel configuration. The handle
57
supports the rollers
58
at its rear end via a shaft.
The guide rail
53
having a bottom-open channel configuration is affixed to the housing
501
in the upper portion of each of the openings
501
a
and
501
b.
The guide rail
53
extends in the axial direction of the print drum
1
a.
The inlet rollers
60
each are rotatably mounted on the front end or inlet of the guide rail
53
via a respective shaft.
The drum unit
100
a
is inserted into the guide rail
53
with the rollers
58
of the handle
57
at the head, while being guided by the rollers
60
. The drum unit
100
a
is pulled out of the guide rail
53
with the rollers
58
at the tail. The guide rails
58
roll on a pair of flanges
53
a
protruding from the side walls of the guide rail
53
toward each other. When the handle
57
is fully received in the guide rail
53
, the rear end of the shaft
2
a
is connected to the coupling portion arranged in the housing
501
.
As shown in
FIGS. 3 and 4A
, an annular portion
93
protrudes outward from the rear frame
56
and has a notch
93
A at its lower end. The annular portion
93
has an outer inside diameter slightly smaller than an inner inside diameter and is generally L-shaped in a sectional view. A tapered pin
94
is studded on the end plate
78
at a position corresponding to the home position of the print drum
1
a.
The end plate
78
is rotatably supported by the rear end of the shaft
2
a
via the previously mentioned roller bearing. A hole
91
is formed in the lower portion of the rear frame
56
for positioning the drum unit
100
a.
As shown in
FIG. 7
, a door or openable member
503
is mounted on the housing
501
via hinges
507
so as to selectively cover or uncover the openings
501
a
and
501
b.
The door
503
is implemented by a molding of synthetic resin. A screen member
506
protrudes from the bottom right portion of the door
503
, as viewed in
FIG. 7
, in such a manner as to face the housing
501
. In
FIG. 7
, the screen member
506
is scaled up relative to the door
503
for the sake of illustration.
A door sensor or open/close sensing means
504
is mounted on the bottom left portion of the housing
501
, as viewed in
FIG. 7
, for determining whether or not the door
503
is closed. The door sensor
504
is a transmission type optical sensor including an opening
505
. When the door
503
is closed, the screen member
506
enters the opening
505
and causes the door sensor
504
to turn on. A power switch
95
is located on the right side wall of the housing
501
and turned on when power should be fed to the printer
500
.
Indicators for showing the operating conditions of the printer
500
are arranged on the housing
501
above the openings
501
a
and
501
b.
Specifically, a first “Ready” LED
96
and a first “Unready” LED
97
are positioned above the opening
501
a
and respectively show that the drum unit
100
a
can be mounted or dismounted and that it cannot be done so. Likewise, a second “Ready” LED
98
and a second “Unready” LED
99
are positioned above the opening
501
b
and respectively show that the drum unit
100
b
can be mounted or dismounted and that it cannot be done so.
The first and second “Ready” LEDs
96
and
98
and first and second “Unready” LEDs
97
and
99
constitute ready/unready displaying means for displaying whether or not the drum units
100
a
and
100
b
can be mounted or dismounted. The “Ready” LEDs
96
and
98
may be green LEDs and may be caused to blink or glow by an LED driver. Also, the “Unready LEDs
97
and
99
may be red LEDs and may be caused to blink or glow by an LED driver.
As shown in
FIGS. 4A through 4C
and
5
, the drum drive means
80
includes drive transmitting means connected to the main motor
81
, which is shared by the print drums
1
a
and
1
b.
The drive transmitting means transmits the rotation of the main motor
81
to the print drums
1
a
and
1
b
of the drum units
100
a
and
100
b.
The main motor
81
is implemented by a DC motor provided with conventional brake means.
The drive transmitting means is arranged on a rear wall, not shown, affixed to the casing
501
and includes a drive pulley
82
mounted on the output shaft of the main motor
81
. A first drum pulley
84
is rotatably supported by the rear wall in alignment with the print drum
1
a
and implemented by a double pulley. A timing belt
83
is passed over the drive pulley
82
and first drum pulley
84
via a plurality of tension pulleys. A second drum pulley
85
is rotatably supported by the rear wall in alignment with the print drum
1
b.
A timing belt
86
is passed over the first and second drum pulleys
84
and
85
.
In addition to the above-described function, the main motor
81
has a function of rotating the print drum
1
a
of the drum unit
100
a
and/or the print drum
1
b
of the drum unit
100
b,
which is to be removed, and a function of rotating drum drive plates
87
assigned to the print drum
1
a
and/or the print drum
1
b,
which is to be inserted, as will be described specifically later. The drum drive plates
87
each are included in the respective coupling portions. While top-bottom moving means is not shown in order to clearly show the characteristic of the drum drive means
80
, the illustrative embodiment includes second top-bottom moving means
245
shown in
FIGS. 13 and 16
of Laid-Open Publication No. 11-138961 mentioned earlier.
Because the coupling portions respectively assigned to the print drums
1
a
and
1
b
are identical in configuration, let the following description concentrate on the coupling portion assigned to the print drum
1
a.
As shown in
FIGS. 3 and 4A
through
4
C, the coupling portion includes the drum drive plate
87
formed integrally with the first-drum pulley
84
and capable entering the annular portion
93
of the rear frame
56
. A lug
88
protrudes downward from the bottom of the drum drive plate
87
and is capable of mating with the notch
93
A of the annular portion
93
. When the lug
88
mates with the notch
93
A, it locks the drum unit
100
a
due to the rotation of the drum pulley
84
and drum drive plate
88
and prevents the drum unit
100
a
from being pulled out. An elongate hole
89
is formed in the drum drive plate
87
for receiving the pin
94
of the print drum
1
a.
A tapered positioning pin
90
is studded on the rear wall of the housing
501
and capable of mating with the hole
91
of the drum unit
100
a.
When the drum unit
100
is inserted into the housing
501
via the mounting/dismounting means
50
a
in the previously described manner, the drum drive plate
87
enters the annular portion
93
of the rear frame
56
with the notch
93
A and lug
88
aligning with each other. At the same time, the pin
90
of the coupling portion enters the hole
91
of the rear frame
56
. As a result, the drum unit
100
a
is positioned relative to the housing
501
only at its home position.
Further, the pin
94
of the print drum
1
a
mates with the hole
89
of the coupling portion, so that the rotation of the main motor
81
can be transferred to the print drum
1
a.
When the main motor
81
rotates clockwise or counterclockwise by a presented amount, the lug
88
of the drum drive plate
87
is displaced relative to the notch
93
A of the rear frame
56
via the first drum pulley
84
in FIG.
3
. Consequently, the drum unit
100
a
is locked in position and inhibited from being pulled out of the housing
501
.
As stated above, the drum units
100
a
and
100
b
can be mounted to or dismounted from the housing
501
only when the print drums
1
a
and
1
b,
respectively, are held at the home positions relative to the housing
501
. The coupling portion of the illustrative embodiment may be replaced with a stop mechanism for restricting the removal of the drum units
100
a
and
100
b
from the housing
501
(see, e.g.,
FIG. 5
of Laid-Open Publication No. 8-39916). Further, use may be made of a meshing mechanism in which drum gears, not shown, respectively mounted on the print drums
1
a
and
1
b
mesh with drive gears, not shown, only when the print drums
1
a
and
1
b
are held at their home positions, and can be released from the drive gears.
A connector, not shown, similar to a connector taught in Laid-Open Publication No. 11-138961 is mounted on the rear wall of the housing
501
. A connector, not shown, is mounted on the outer surface of the rear frame
56
of the drum unit
100
a
and connectable to the above connector of the housing
501
. The connector of the housing
501
is connected to an external power source and the controller
200
shown in FIG.
9
. The connector of the drum unit
100
a
is connected to an encoder sensor (see
FIG. 9
) and the ink sensing means and ink pump
66
a.
When the drum unit
100
a
is inserted into the housing
501
via the mounting/dismounting means
50
a,
the connector of the drum unit
100
a
is connected to the connector of the housing
501
. In this condition, power supply and signal exchange are effected while the presence of the drum unit
100
a
on the housing
501
is electrically detected. This is also true with the other drum unit
100
b.
The connector of the drum unit
100
a
and the connector of the housing
501
respectively constitute a first drum sensor
77
and a second drum sensor
78
(see FIG.
9
).
The drum unit
100
a
and
100
b
each include a device, not shown, for fixing, when the drum unit is removed from the housing
501
, the home position of the print drum where the damper
5
a
or
5
b
is positioned at the bottom of the print drum. Such a device allows the drum unit to be inserted into the housing
501
in the same position as during removal. The grip
63
includes an unlock lever for mechanically unlocking the drum unit
100
a
from the housing
501
when the operator holds the grip
63
. The drum unit
100
a
further includes locking means for mechanically locking the drum unit
100
a
to a locking portion included in the housing
501
when the drum unit
100
a
is fully set on the housing
501
. The locking means may have a structure shown in, e.g.,
FIG. 5
of Laid-Open Publication No. 8-39916. The locking means is combined with the locking structure of the coupling portion for enhancing sure operation and safety.
The drum units
100
a
and
100
b
and mounting/dismounting means
50
a
and
50
b
may be replaced with drum units
10
provided with respective drum stop mechanisms
20
and means for removably supporting them, which are shown in, e.g.,
FIGS. 1 through 5
of Laid-Open Publication No. 10-109470.
To better understand the illustrative embodiment, why the distance between nearby print drums is made shorter than the circumferential length of each drum with an initial phase difference being provided between the drums will be described with reference to
FIGS. 10 through 14
.
As shown in
FIG. 14
, assume that the print drums
1
a
and
1
b
each have a circumferential length A, and that the two drums
1
a
and
1
b
are spaced from each other by a distance L. The paper sheet
22
carries the image of the first color represented by black rectangles and the image of the second color represented by outline rectangles. The paper sheet
22
is conveyed by the print drum
1
a
being rotated counterclockwise, while being nipped between the drum
1
a
and the press roller
9
a.
The paper sheet
22
is then conveyed by the intermediate conveying means
17
toward the print drum
1
b
at a speed equal to the peripheral speed of the print drum
1
a.
The prerequisite with such conveyance is that the reference position of the image on the paper sheet
22
be exactly coincident at both of the print drums
1
a
and
1
b.
It follows that the print drum
1
b
must be provided with a delay corresponding to the distance L relative to the print drum
1
a.
For example, as shown in
FIGS. 10 and 11
, assume that the home positions of the print drums
1
a
and
1
b
are contrary to the home positions of the illustrative embodiment, but the paper sheet
2
is conveyed in the above-described conditions. Specifically, assume that the home positions of the print drums
1
a
and
1
b
are set at a reference angle of 0° (mechanical origin) such that the dampers
5
a
and
5
b,
respectively, are positioned on the top. Further, assume that the distance L is not equal to the circumferential length A and is shorter than A for a compact configuration, and that L and A are 100 mm and 300 mm, respectively. Then, the phase difference (delay angle) of the print drum
1
b
relative to the print drum
1
a
is 360×(100/300)=120°.
A positional relation that allows the print drums
1
a
and
1
b
shown in
FIGS. 10 and 11
to be inserted into the printer body will be described with reference to
FIGS. 12 and 13
. As shown, only when the home positions of the print drums
1
a
and
1
b
(reference angle of 0°) are coincident with the mechanical origin of 0° of the printer body, the former can be mounted to or dismounted from the latter. Stated another way, the print drums
1
a
and
1
b
cannot be mounted or dismounted at the same time if L is not equal to A. In
FIG. 12
, only the print drum
1
a
coincident with the mechanical origin of 0° can be mounted or dismounted. In
FIG. 13
, only the print drum
1
b
coincident with the mechanical origin of 0° can be mounted or dismounted because the phase difference (delay angle) of the print drum
1
a
relative to the print drum
1
b
is 120°.
In the illustrative embodiment, L is not equal to A and is shorter than A for a compact configuration while L and A are selected to be 240 mm and 180π (565) mm. Therefore, as shown in
FIG. 1
, the phase difference between the print drums
1
a
and
1
b
is 153° with respect to the positions of the dampers
5
a
and
5
b.
Why the above phase difference is selected will be described on the assumption that the masters
33
a
and
33
b
existing on the print drums
1
a
and
1
b,
respectively, have the same size, and that images formed in the masters
33
a
and
33
b
both are solid images. The print drums
1
a
and
1
b
are connected to each other such that they rotate at the same peripheral speed, while the path between the print positions of the print drums
1
a
and
1
b
has a certain length. Obviously, therefore, to transfer the entire contour of the solid image from the print drum
1
b
to the paper sheet
22
over the solid image transferred from the print drum
1
a
without any positional deviation in the direction of paper conveyance X, the print drum
1
b
must be provided with an initial phase difference corresponding to the length of the above path.
It will be seen from the above that the print drums
1
a
and
1
b
cannot be brought to the respective mount/dismount positions at the same time. That is, the print drums
1
a
and
1
b
are brought to the mount/dismount positions by being rotated one by one or successively. This can be done with the simple drum drive means
80
including a single main motor
81
, i.e., without resorting to the sophisticated topbottom movement adjusting means taught in Laid-Open Publication No. 11-138961.
The illustrative embodiment selects the distance L not equal to the circumferential length A and shorter than A and includes two print drums
1
a
and
1
b
and two paper egress sensors
74
and
75
respectively neighboring the print drums
1
a
and
1
b.
Of course, the illustrative embodiment is applicable even to a stencil printer including three or more print drums and three or more paper egress sensors respectively assigned thereto.
Reference will be made to
FIG. 8
showing a specific configuration of the operation panel
110
. As shown, the operation panel
110
includes various keys for allowing the operator to operate the printer
500
and various indicators and displays for displaying the operation statuses of the printer
500
as well as the operator's manipulation. Specifically, a print key
111
starts the paper feed, print and paper discharge procedure when pressed. Numeral keys
112
are available for inputting, e.g., a desired number of prints. A stop key
113
interrupts the paper feed, print and paper discharge procedure when pressed. A first drum unlock key or individual removal setting means
114
makes the drum unit
100
a,
which includes the print drum
1
a
to be removed, removable when pressed. A second drum unlock key or individual removal setting means
115
makes the drum unit
100
b,
which includes the print drum
1
b
to be removed, removable when pressed.
The first drum unlock key
114
plays the role of individual insertion setting means at the same time for making the drum unit
100
a,
which includes the print drum
1
a
to be inserted, insertable when pressed. Likewise, the second drum unlock key
115
plays the role of individual insertion setting means at the same time for making the drum unit
100
b,
which includes the print drum
1
b
to be inserted, insertable when pressed. When the keys
114
and
115
are pressed at the same time, they set up conditions that allow the drum units
100
a
and
100
b
to be successively prepared for removal and, in this sense, serve as successive removal setting means.
A first “Ready” LED
116
and a first “Unready” LED
117
are also arranged on the operation panel
110
and respectively show that the drum unit
100
a
can be mounted or dismounted and that it cannot be done so. A second “Ready” LED
118
and a second “Unready” LED
119
respectively show that the drum unit
100
b
can be mounted or dismounted and that it cannot be done so. An LCD (Liquid Crystal Display)
120
displays whether or not a mounting/dismounting operation is allowed drum unit by drum unit. The first and second “Ready” LEDs
116
and
118
and first and second “Unready” LEDs
117
and
119
constitute ready/unready displaying means for displaying whether or not the drum units
100
a
and
100
b
can be mounted or dismounted. The “Ready” LEDs
116
and
118
may be green LEDs and may be caused to blink or glow by an LED driver. Also, the “Unready LEDs
1117
and
119
may be red LEDs and may be caused to blink or glow by an LED driver.
If desired, only the first and second “Ready” LEDs
116
and
118
may be arranged on the operation panel
110
, i.e., the first and second “Unready” LEDs
117
and
119
may be omitted. In such a case, the LEDs
116
and
118
will be caused to blink or glow by an LED driver if the drum units
100
a
and
100
b
can be mounted or dismounted, and will be turned off if otherwise. Further, the LEDs
116
and
118
may be caused to blink while the associated drum units
100
a
and
100
b
are rotating toward the respective mount/dismount positions.
The LCD
120
is connected to an LCD driver and may display the rotation of the drum units
100
a
and
100
b
toward their mount/dismount positions in the form of a picture or characters. Also, the LCD
120
plays the role of informing means for informing, based on the outputs of the first and second paper egress sensors
74
and
75
, the operator of the drum unit
100
a
and/or the drum
100
b
where defective paper egress has occurred.
Referring to
FIGS. 5
,
6
A,
6
B and
9
, a control system including the controller
200
will be described. As shown in
FIG. 5
, the main motor
81
is connected to a CPU
201
, which is included in the controller
200
, via a motor controller
81
A. The main motor
81
interchanges ON/OFF signals, data signals and command signals with the CPU
201
via the motor controller
81
A. Home position sensors
70
a
and
70
b
are located at preselected positions on the housing
501
facing the rear end plates, not shown, of the print drums
1
a
and
1
b.
The home position sensors
70
a
and
70
b
are respectively responsive to the home positions of the print drums
1
a
and
1
b
and implemented by transmission type photosensors similar to photosensors shown in
FIG. 6
of Laid-Open Publication No. 11-138961 or
FIG. 7
of Laid-Open Publication No. 11-151852.
Screen members, not shown, respectively protrude outward from the rear end plates, not shown, of the print drums
1
a
and
1
b
in such a manner as to selectively meet the home position sensors
70
a
and
70
b,
respectively. The screen plates are configured in the same manner as in
FIG. 6
of Laid-Open Publication No. 11-138961 or
FIG. 7
of Laid-Open Publication No. 11-151852. In the illustrative embodiment, it is not necessary to sense a master feed position or a master discharge position.
An optical, incremental rotary encoder
72
formed with a number of slits is mounted on the rear end plate of the print drum
1
a.
An encoder sensor
73
is mounted on the rear frame
56
of the drum unit
100
a
and embraces the peripheral portion of the encoder
72
. The encoder sensor
73
is implemented by a transmission type photosensor and determines the amount of rotation (rotation angle) of the print drum
1
a.
The CPU
201
calculates, based on the output signals of the home position sensors
70
a
and
70
b
and encoder sensor
73
, the absolute rotation angles of the print drum
1
a
and
1
b
from the home positions (mechanical origins), thereby determining the angular positions of the drums
1
a
and
1
b
and those of the drum drive plates
87
. The home position sensors
70
a
and
70
b,
screen members, encoder
72
and encoder sensor
73
constitute angular position sensing means responsive to the angular positions of the print drums
1
a
and
1
b.
The belts included in the rotation transmitting means of the drum drive means
80
may be replaced with gears if consideration does not have to be given to cost reduction. The DC motor used as the main motor
81
may be replaced with a stepping motor or similar pulse-driven motor, in which case the encoder
73
is omissible. Further, if consideration does not have to be given to the stretch of the belts and other factors effecting the home position sensing accuracy, a single home position sensor may be assigned to either one of the print drums
1
a
and
1
b
because the print drum
1
b
is driven by belt connection.
As shown in
FIG. 9
, the controller
200
is implemented as a microcomputer including a RAM
202
(Random Access Memory), a ROM
203
(Read Only Memory)
203
and an I/O (Input/Output) port, not shown, in addition to the CPU
201
. The CPU
201
, RAM
202
, ROM
203
and I/O port are interconnected by, e.g., a signal bus. The CPU
201
receives the ON/OFF signals and data signals from the home position sensors
70
and
70
b,
encoder sensor
73
, first and second paper egress sensors
74
and
75
, first and second drum sensors
77
and
78
, power switch
95
, and door sensor
504
. Also, the CPU
201
receives ON/OFF signals from the various keys of the operation panel
110
including the first and second drum unlock keys
114
and
115
.
The CPU
201
sends various command signals to the first and second “Ready” LEDs
116
and
118
, first and second “Unready” LEDs
117
and
119
, and LCD
120
. Further, the CPU
201
sends various command signals to the first and second “Ready” LEDs
96
and
98
and first and second “Unready” LEDs
97
and
99
. In addition, the CPU
201
sends various command signals to the main motor
81
.
In response to the output of the first or second drum unlock key
114
or
115
and the output of the angular position sensing means associated with the print drum
1
a
or
1
b
to be removed, the CPU
201
(controller
200
hereinafter) controls the main motor
81
such that the print drum
1
a
or
1
b
to be removed is brought to its home position (first function).
In response to the outputs of the paper egress sensors
74
and
75
, first or second drum unlock key
114
or
115
and angular position sensing means associated with the print drum
1
a
or
1
b
to be removed, the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
to be removed and where defective egress has occurred is brought to its home position (second function).
Assume that after one of the drum units
100
a
and
100
b
has been removed, the other drum unit should also be removed. Then, when the operator opens the door
503
, removes the drum unit
100
a
or
100
b,
and again closes the door
503
, the door sensor
504
sends its output to the controller
200
. In response to the output of the door sensor
504
, the output of the drum unlock key
114
or
115
assigned to the drum unit
100
a
or
100
b
to be removed next, and the output of the angular position sensing means assigned to the same drum unit
100
a
or
100
b,
the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
of the drum unit to be removed is brought to its home position (third function).
Assume that the operator presses the drum unlock keys
114
and
115
at the same time. Then, in response to the outputs of the keys
114
and
115
and the output of the angular position sensing means assigned to the drum unit
100
a
or
100
b
to be removed, the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
of the above drum unit is brought to its home position. Subsequently, in response to the output of the angular position sensing means assigned to the print drum
1
a
or
1
b
of the other drum unit to be removed next, the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
of the drum unit to be removed is brought to its home position (fourth function).
Again, assume that the operator presses the drum unlock keys
114
and
115
at the same time. Then, in response to the outputs of the keys
114
and
115
, the outputs of the paper egress sensors
74
and
75
, and the output of the angular position sensing means assigned to the drum unit
100
a
or
100
b
to be removed, the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
of the drum unit
100
a
or
100
b
to be removed and where defective egress has occurred is brought to its home position. Subsequently, in response to the output of the angular position sensing means assigned to the print drum
1
a
or
1
b
of the other drum unit
100
a
or
100
b
to be removed next and where defective egress has occurred, the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
of the drum unit to be removed next is brought to its home position (fifth function)
Assume that the operator, intending to remove both of the drum units
100
a
and
100
b,
opens the door
503
, removes one of the drum units
100
a
and
100
b,
and again closes the door
503
. Then, in response to the resulting output of the door sensor
504
and the output of the angular position sensing means assigned to the print drum
1
a
or
1
b
of the drum unit
100
a
or
100
b
to be removed next, the controller
200
controls the main motor
18
such that the print drum
1
a
or
1
b
of the drum unit to be removed next is brought to its home position (sixth function).
In response to the output of the paper egress sensor
74
or
75
representative of an egress error, the controller
200
controls the LCD
120
in such a manner as to inform the operator of the drum unit
100
a
or
100
b
where the egress error has occurred (seventh function).
In response to the output of the door sensor
504
and the outputs of the paper egress sensors
74
and
75
, the controller
200
determines whether or not a printing operation is allowed (eighth function).
The controller
200
controls the LEDs
96
through
99
, LEDs
116
through
119
and LCD
120
on the basis of the outputs of the home position sensors
70
a
and
70
b
and the output of the encoder sensor
73
(ninth function).
The controller
200
controls the LEDs
96
through
99
, LEDs
116
through
19
and LCD
120
on the basis of the outputs of the drum sensors
77
and
78
(tenth function).
In response to the outputs of the paper egress sensors
74
and
75
and the output of the angular position sensing means assigned to the print drum
1
a
or
1
b
of the drum unit
100
a
or
100
b
to be removed, the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
of the drum unit to be removed and where an egress error has occurred is brought to its home position. Subsequently, in response to the outputs of the sensors
74
and
75
and the output of the angular position sensing means assigned to the print drum
1
a
or
1
b
of the other drum unit to be removed next, the controller
200
controls the main motor
81
such that the print drum
1
a
or
1
b
of the same drum unit is brought to its home position (eleventh function).
Assume that the power switch
95
is turned on. Then, in response to the output of the drum unlock key
114
or
115
and the output of the angular position sensing means assigned to the print drum
1
a
or
1
b
of the drum unit
100
a
or
100
b
to be inserted, the controller
200
controls the main motor
81
such that the drum drive plate
87
of the casing
501
assigned to the print drum
1
a
or
1
b
of the above drum unit is brought to its home position (twelfth function).
Again, assume that the power switch
95
is turned on. Then, in response to the output of the drum sensing means assigned to the print drum
1
a
or
1
b
of the drum unit
100
a
or
100
b
to be inserted, the controller
200
controls the main motor
81
such that the drum drive plate
87
assigned to the print drum
1
a
or
1
b
of the above drum unit is brought to its home position. Subsequently, in response to the output of the drum sensing means assigned to the print drum
1
a
or
1
b
of the other drum unit to be mounted next, the controller
200
controls the main motor
81
such that the drum drive plate
87
assigned to the print drum
1
a
or
1
b
of the same drum unit is brought to its home position (thirteenth function).
Assume that neither one of the drum units
100
a
and
100
b
is present on the housing
501
and that the operator inserts one of them into the housing
501
. Then, in response to the outputs of the drum sensors
77
and
78
, the controller
200
controls the main motor
81
such that the drum drive plate
87
assigned to the print drum
1
a
or
1
b
of the other drum unit
100
a
or
100
b
absent on the housing
501
is brought to its home position (fourteenth function).
The ROM
203
stores data for controlling the main motor
81
, LEDs
96
through
99
, LEDs
116
through
119
and LCD
120
and programs for executing specific procedures to be described with reference to
FIGS. 15 through 20
later. The RAM
202
temporarily stores data signals received from the various sensors. In addition, the RAM
202
stores. rotation priority order for allowing the drum units
100
a
and
100
b
to be continuously mounted to or dismounted from the housing
501
. Specifically, if the drum unit
100
a
is provided with priority over the drum unit
100
a,
the drum drive plate
87
assigned to the print drum
1
a
is rotated to its mount/dismount position, and then the drum drive plate
87
assigned to the print drum
1
b
is rotated to its mount/dismount position. If the drum unit
100
b
is provided with priority over the drum unit
100
a,
the rotation occurs in the reverse order.
Before the specific procedures shown in
FIGS. 15 through 20
, the general sequence of paper feeding step, printing step and paper discharging step will be described. After the used masters
33
a
and
33
b
have been removed from the print drums
1
a
and
1
b,
respectively, new masters
33
a
and
33
b
are wrapped around the print drums
1
a
and
1
b.
The drum units
100
a
and
100
b
respectively loaded with such print drums
1
a
and
1
b
are inserted into the housing
501
(initial condition shown in FIG.
1
). Then, the paper feeding step and printing step begin. At this instant, the print drum
1
a
is rotated to its home position where the damper
5
a
is positioned at the bottom. The other print drum
1
a
is rotated to a position where the damper
5
b
takes an obliquely upper rightward position. In this manner, in the illustrative embodiment, a phase difference is initially provided between the print drums
1
a
and
1
b
when the drums
1
a
and
1
b
are present in the housing
501
.
The operator turns on the power switch
95
, inputs a desired number of prints on the numeral keys
112
, and then presses the print key
111
. In response, the printing step begins. The paper tray
21
is raised beforehand to a level where the top sheet
22
contacts the pickup roller
23
. When the paper feed motor
44
drives the separator roller
24
and pickup roller
23
, the rollers
24
and
23
pay out the top sheet
22
. At the same time, the separator rollers
24
and
25
and separator plate
26
cooperate to separate the top sheet
22
from the underlying sheets
22
. The top paper
22
is therefore conveyed toward the registration rollers
29
and
30
in the direction of paper conveyance X while being guided by the guide plates
27
and
28
. The leading edge of the paper sheet
22
abuts against a portion of the registration rollers
29
and
30
just short of the nip and forms a loop along the upper guide plate
28
, as stated earlier.
On the start of the printing step, the print drum
1
a
assigned to the first color starts rotating at a preselected printing speed. The ink distributor delivers black ink to the ink well
1
a
between the ink roller
3
a
and the doctor roller
4
a.
The ink uniformly deposits on the ink roller
3
a
while being kneaded by the ink roller
3
a
and doctor roller
4
a
in rotation. When the amount of ink becomes short, as determined by the previously mentioned ink sensing means, the ink distributor replenishes ink to the ink well
1
a.
Rotating in the same direction and at the same speed as the print drum
1
a
in contact with the inner periphery of the drum
1
a,
the ink drum
3
a
applies the ink to the inner periphery of the drum
1
a.
The registration motor
47
and therefore the registration rollers
29
and
30
are rotated at a preselected timing so as to convey the leading edge of the paper sheet
22
in synchronism with the rotation of the print drum
1
a
loaded with the master
33
a.
The leading edge of the paper sheet
22
therefore arrives at the gap between the print drum
1
a
and the press roller
9
a
such that it meets the leading edge of the image formed in the master
33
a.
At this time, the press roller
9
a
is raised toward the print drum
1
a
until it has been pressed against the master
33
a.
As a result, the master
33
a
closely adheres to the print drum
1
a
due to the viscosity of the ink penetrated the porous portion of the drum
1
a.
The ink further penetrates the perforation pattern of the master
33
a.
Consequently, the ink is transferred from the print drum
1
a
to the paper sheet
22
, forming a black image on the paper sheet
22
.
When the leading edge of the paper sheet
22
with the black image approaches the edge of the air knife
7
a,
the air knife
7
a
is rotated about the shaft
8
a
toward the print drum
1
a
in synchronism with the rotation of the drum
1
a.
A jet of air sent from the edge of the air knife
7
a
peels off the leading edge of the paper sheet
22
from the print drum
1
a.
The intermediate conveying device
17
conveys the paper sheet
22
separated from the print drum
1
a
to the downstream side in the direction of paper conveyance X. Specifically, the belt
16
, turning counter clockwise as indicated by an arrow in
FIG. 1
, conveys the paper sheet
22
toward the next pressing device
32
b
while easily retaining it thereon by suction effected by the fan
18
.
The belt
16
conveys the paper sheet
22
at a speed (linear velocity) equal to or higher than the linear velocity or peripheral speed of the print drum
1
a.
However, because the upstream portion of the paper sheet
22
is still nipped between the print drum
1
a
and the press roller
9
a,
the paper sheet
22
moves to the left at a speed equal to the peripheral speed of the drum
1
a,
as stated earlier. The paper sheet
22
is therefore conveyed with leftward tension acting thereon. In a more strict sense, the belt
16
moves at a higher speed than the paper sheet
22
, so that the belt
16
and paper sheet
22
slip on each other.
At this instant, the print drum
1
b
assigned to the second color starts a printing operation in synchronism with the print drum
1
a,
i.e., starts rotating at a printing speed. The ink roller
3
b,
contacting the inner periphery of the ink drum
1
b,
feeds magenta ink to the drum
1
b
while rotating at the same speed as the print drum
1
b.
The initial phase difference is set between the print drums
1
a
and
1
b,
as stated earlier.
The leading edge of the paper sheet
22
arrives at the gap between the print drum
1
b
and the press roller
9
b
at a preselected timing synchronous to the rotation of the drum
1
b
while being pulled by the belt
16
in the direction of movement. Then, the press roller
9
b
is raised toward the print drum
1
b
and pressed against the master
33
b
existing on the drum
1
b
due to the action of the tension spring
13
b.
As a result, the master
33
b
closely adheres to the print drum
1
b
due to the viscosity of the ink penetrated the porous portion of the drum
1
b.
The ink further penetrates the perforation pattern of the master
33
b.
Consequently, the ink is transferred from the print drum
1
b
to the paper sheet
22
, forming a magenta image on the paper sheet
22
over the black image existing on the paper sheet
22
.
While the press roller
9
b
is released from the print drum
1
b
during printing so as not to interfere with the damper
5
b
protruding from the drum
1
b,
it is pressed against the drum
1
b
before the leading edge of the paper sheet
22
arrives at the gap between the roller
9
b
and the drum
1
b.
When the leading edge of the paper sheet
22
with the bicolor image, i.e., black-and-magenta image approaches the edge of the air knife
7
b,
the air knife
7
b
is rotated about the shaft
8
b
toward the print drum
1
b
in synchronism with the rotation of the drum
1
b.
A jet of air sent from the edge of the air knife
7
b
peels off the leading edge of the paper sheet
22
from the print drum
1
b.
The paper discharging device
35
conveys the paper sheet
22
separated from the print drum
1
b
to the print tray
37
in the direction of paper conveyance X.
Air sent from the blast fan
34
hits against the surface of the paper sheet or print
22
from a position above and leftward of the air knife
7
b.
This air not only prevents the paper sheet
22
from rising above the belt
40
, but also promotes the drying of the ink existing on the paper sheet
22
. The jump board
40
A causes the center portion of the paper sheet
22
to deform in the form of a letter U, i.e., provides the paper sheet
22
with an adequate degree of stiffness, so that the consecutive paper sheets
22
can be neatly stacked on the print tray
37
.
The paper sheet
22
peeled off by the air knife
7
b
is retained on the belt
40
by the suction fan
36
while being prevented from rising above the belt
40
by the blast fan
34
. The belt
40
, turning counterclockwise, conveys the paper sheet
22
toward the print tray
37
. As a result, the paper sheet
22
is neatly laid on the print tray
37
via the jump board
40
A as a trial print. The press rollers
1
a
and
1
b
are retracted away from the print drums
1
a
and
1
b,
respectively, to their initial positions or stand-by positions shown in FIG.
1
.
Assume that the operator, looking at the trial print, determines that the image should be adjusted in position in the direction of paper conveyance X. Then, the operator may adjust the position of the image via top-bottom movement adjusting means
212
taught in Laid-Open Publication No. 11-138961 mentioned earlier. If the trial print is acceptable, the operator inputs a desired number of prints on the numeral keys
112
and then presses the print key
111
. In response, the previously described paper feed, print and paper discharge procedure is repeated a number of times corresponding to the desired number of prints.
First Specific Operation
Assume that the paper sheet
22
adheres to the master
22
a
or
22
b
due to the viscosity of the ink too closely to be peeled off by the air knife
7
a
or
7
b
or a conventional peeler and rolls up, or that the paper sheet
22
jams the transport path around the print drum
1
a
or
1
b
or between the print drums
1
a
and
1
b.
Then, one or both of the drum units
100
a
and
100
b
must be successively removed from the housing
501
. A first specific operation to be described with reference to
FIG. 15
relates to a manual error removal mode for allowing the operator to perform the above operation.
First, how the events including the roll-up and egress error. of the paper sheet
22
are detected will be described with reference to
FIGS. 6A and 6B
.
(1) Assume that the first paper egress sensor
74
does not sense the paper sheet
22
, i.e., it remains in an OFF state even when the print drum
1
a
rotates to a given angle K
1
after the start of conveyance of the paper sheet
22
. Then, the paper sheet
22
has rolled up and is staying around the print drum
1
a.
If the sensor
74
turns on when the print drum
1
a
reaches the angle K
1
, the paper sheet
22
is being conveyed in the expected manner.
(2) Assume that the first paper egress sensor
74
remains in an ON state even when the print drum
1
a
further rotates to a given angle K
2
, an egress error has occurred, and the paper sheet
22
is again staying around the print drum
1
a.
If the sensor
74
turns off when the print drum
1
a
reaches the angle K
2
, the paper sheet
22
is being conveyed in the expected manner.
(3) If the second egress sensor
75
does not sense the paper sheet
22
, i.e., it remains in an OFF state when the print drum
1
b
rotates to a given angle K
3
, the paper sheet
22
has rolled up and is staying around the print drum
1
b.
(4) If the second egress sensor
75
remains in an ON state even when the print drum
1
b
further rotates to a given angle K
4
, an egress error has occurred, and the paper sheet
22
is staying around the print drum
1
b.
In the first specific operation relating to the manual error removal mode, the previously described second, third and seventh to tenth functions of the controller
200
are used.
As shown in
FIG. 15
, assume that the controller
200
determines, based on the outputs of the first and second paper egress sensors
74
and
75
, that any one of the above events (1) through (4) has occurred at the beginning of printing or during printing. Then, the controller
200
interrupts the printing procedure (step S
1
). The controller
200
then deenergizes the main motor
81
when the drum unit
100
a
or
100
b
reaches a preselected phase (in the illustrative embodiment, the home position of the drum unit
100
a
or
100
b
). At the same time, the controller
200
displays an error message on the LCD
120
.
Referencing information appearing on the LCD
120
, the operator sees a location where the roll-up or the defective egress of the paper sheet
22
has occurred (step S
2
). The operator determines whether or not the error has occurred at the print drum
1
a
side (step S
3
). If the answer of the step S
3
is positive (YES), the operator turns on the first drum unlock key
114
(YES, step S
4
). In response, the controller
200
drives the main motor
81
with the result that the print drum
1
a
starts rotating via the rotation transmitting means (step S
5
). At this instant, the first “Ready” LED
116
blinks in green while the second “Unready” LED
119
glows in red, urging the operator to wait until the end of rotation of the print drum
1
a.
Subsequently, the controller
200
controls, based on the outputs of the home position sensor
70
a
and encoder sensor
73
, the main motor
81
such that the print drum
1
a
reaches its home position (dismount position). When the print drum
1
a
reaches its home position (YES, step S
6
), the controller
200
stops driving the main motor
81
and thereby stops the print drum
1
a
at the home position (step S
7
). At the same time, the first “Ready” LED
116
glows in green.
The step S
7
is followed by a step S
8
for urging the operator to remove the error by hand. Specifically, watching the first “Ready” LED
116
glowing in green, the operator sees that the print drum
1
a
is located at the home position or dismount position. The operator then opens the door
503
in order to pull out the drum unit
100
a.
In response to the resulting output of the door sensor
504
, the controller
200
causes the first “Ready” LED
96
to glow in green and causes the second “Unready” LED
99
to glow in red. The operator sees such statuses of the LEDs
96
and
99
and then pulls out the drum unit
100
a.
Specifically, the operator holds the grip
63
and pulls the drum unit
100
a
out of the housing
501
via the opening
501
a
and the mounting/dismounting means
50
a.
At this instant, the unlock lever or the stop mechanism interlocked to the grip
63
is operated. The operator removes the paper sheet
22
jamming the path around the print drum
1
a
and again closes the door
503
. In response, the controller
200
causes both of the first and second “Unready” LEDs
117
and
119
to glow in red. At the same time, the controller
200
determines whether or not a printing operation is allowed on the basis of the outputs of the door sensor
504
and first paper egress sensor
74
. The removal of the drum unit
100
b
is effected in exactly the same manner as the removal of the drum unit
100
b
and will not be described specifically.
If the answer of the step S
3
is negative (NO) or after the step S
8
, the controller
200
determines whether or not the error has occurred at the print drum
1
b
side (step S
9
). If the answer of the step S
9
is YES and if the operator presses the second drum unlock key
115
(YES, step S
10
), the controller
200
drives the main motor
81
and thereby starts rotating the print drum
1
b
via the rotation transmitting means (step S
11
). At this instant, the controller
200
causes the second “Ready” LED
118
on the operation panel
110
to blink in green while causing the first “Ready” LED
116
to turn off. This informs the operator of the fact that neither the drum unit
100
a
nor the drum unit
100
b
can be mounted or dismounted, and urges the operator to wait until the end of rotation of the print drum
1
b.
Subsequently, the controller
200
drives, based on the outputs of the home position sensor
70
b
and encoder sensor
73
, the main motor
81
in order to bring the print drum
1
b
to its home position or dismount position. When the print drum
1
b
reaches the home position (YES, step S
12
), the controller
200
stops driving the main motor
81
and thereby stops the print drum
1
b
at the home position (step S
13
). At the same time, the controller
200
causes the second “Ready” LED
118
on the operation panel
118
to glow in green.
The step S
13
is followed by a step S
14
for manual error removal assigned to the print drum
1
b
side. Specifically, watching the second “Ready” LED
118
on the operation panel
110
glowing in green, the operator sees that the print drum
1
b
is located at the home position or dismount position. The operator then opens the door
503
in order to pull out the drum unit
100
b.
In response to the resulting output of the door sensor
504
, the controller
200
causes the second “Ready” LED
98
to glow in green and causes the first “Unready” LED
97
to glow in red. The operator sees such statuses of the LEDs
98
and
97
and then pulls out the drum unit
100
b.
The operator removes the paper sheet
22
jamming the path around the print drum
1
b
and again closes the door
503
. In response, the controller
200
causes both of the first and second “Unready” LEDs
117
and
119
to glow in red. At the same time, the controller
200
determines whether or not a printing operation is allowed on the basis of the outputs of the door sensor
504
and second paper egress sensor
75
.
The drum units
100
a
and
100
b
each are inserted into the housing
501
in the same manner as will be described in relation to a third specific operation.
Second Specific Operation
One or both of the drum units
100
a
and
100
b
are sometimes successively removed from the housing
501
due to the same errors as in the first specific operation. A second specific operation to be described with reference to
FIG. 16
relates to an automatic error removal mode for successively removing the drum units
100
a
and
100
b.
The second specific operation mainly uses the previously described seventh to eleventh functions available with the controller
200
.
As shown in
FIG. 16
, assume that the controller
200
determines that any one of the events (1) through (4) has occurred at the beginning of printing or during printing. Then, the controller
200
interrupts the printing procedure (step S
20
). Subsequently, the controller
200
determines whether or not the error has occurred at the print drum side
1
a
(step S
21
). If the answer of the step S
21
is YES, the controller
200
drives the main motor
81
(step S
22
).
After the step S
22
, the controller
200
controls, based on the outputs of the home position sensor
70
a
and encoder sensor
73
, the main motor
81
such that the print drum
1
a
reaches its home position (dismount position). When the print drum
1
a
reaches its home position (YES, step S
23
), the controller
200
stops driving the main motor
81
and thereby stops the print drum
1
a
at the home position (step S
24
). At the same time, the controller
200
causes the first “Ready” LED
116
to glow in green and displays an error message on the LCD
120
.
The step S
24
is followed by a step S
25
for manual error removal as in the first specific operation. Specifically, the operator pulls the drum unit
100
a
out of the housing
501
and then closes the door
503
. In response to the resulting output of the door sensor
504
, the controller
200
executes a step S
26
and successive steps.
In the step S
26
, the controller determines whether or not an error has occurred at the second print drum
1
b
side. If the answer of the step S
26
is YES, the controller
200
drives the main motor
81
to thereby start rotating the print drum
1
b
via the rotation transmitting means (step S
27
). At this instant, the controller
200
causes the second “Ready” LED
118
on the operation panel
110
to blink in green while causing the first “Ready” LED
116
to turn off and causing the first “Unready” LED
117
to glow. This informs the operator of the fact that neither the drum unit
100
a
nor the drum unit
100
b
can be mounted or dismounted, and urges the operator to wait until the end of rotation of the print drum
1
b.
If the answer of the step S
21
is NO, the step S
21
is also followed by the step S
26
.
Subsequently, the controller
200
drives, based on the outputs of the home position sensor
70
b
and encoder sensor
73
, the main motor
81
in order to bring the print drum
1
b
to its home position or dismount position. When the print drum
1
b
reaches the home position (YES, step S
28
), the controller
200
stops driving the main motor
81
and thereby stops the print drum
1
b
at the home position (step S
29
). At the same time, the controller
200
causes the second “Ready” LED
118
on the operation panel
118
to glow in green and displays an error message on the LCD
120
.
The step S
29
is followed by a step S
30
for manual error removal assigned to the print drum
1
b
side as in the first specific operation.
The drum units
100
a
and
100
b
each are inserted into the housing
501
in the same manner as will be described in relation to the third specific operation.
Third Specific Operation
The drum units
100
a
and
100
b
are sometimes successively dismounted from the housing
501
in order to, e.g., replace the colors of ink or the masters
33
a
and
33
b
or for a cleaning purpose. A third specific operation to be described with reference to
FIG. 17
relates to a manual successive removal mode for allowing the operator to successively remove the drum units
100
a
and
100
b
from the housing
501
. The third specific operation mainly uses the first, third and eighth to tenth functions of the controller
200
.
As shown in
FIG. 17
, when the operator presses the first drum unlock key
114
(YES, step S
40
), the controller
200
drives the main motor
81
and thereby rotates the print drum
1
a
via the rotation transmitting means (step S
41
). At this instant, the controller causes the first “Ready” LED
116
to blink in green and causes the second “Unready” LED
119
to glow in red. This informs the operator of the fact that neither the drum unit
100
a
or the drum unit
100
b
can be mounted or dismounted, and urges the operator to wait until the end of rotation of the print drum
1
a.
Subsequently, the controller
200
controls, based on the outputs of the home position sensor
70
a
and encoder sensor
73
, the main motor
81
such that the print drum
1
a
reaches its home position or dismount position. When the print drum
1
a
reaches the home position (YES, step S
42
), the controller
200
stops driving the main motor
81
to thereby stop the print drum
1
a
at the home position (step S
43
). At the same time, the controller
200
causes the first “Ready” LED
116
on the operation panel
110
to glow in green.
The step S
43
is followed by a step S
44
. In the step S
44
, the operator sees the “Ready” LED
116
glowing in green and then opens the door
503
in order to pull the drum unit
100
a
out of the housing
501
. In response to the resulting output of the door sensor
504
, the controller
200
causes the first “Ready” LED
96
to glow in green while causing the second “Unready” LED
99
to glow in red. Watching such statuses of the LEDs
96
and
99
, the operator pulls out the print drum
100
a.
After the print drum
1
a
has been stopped at the home position, the operator pulls the drum unit
100
a
out of the housing
501
as in the first specific operation, replaces the ink of the print drum
1
a,
replaces the master
33
a
or performs cleaning, and again closes the door
503
. The removal of the drum unit
100
b
from the housing
501
is effected in the same manner as the removal of the drum unit
100
a
and will not be described specifically.
Subsequently, when the operator presses the second drum unlock key
15
(YES, step S
45
), the controller
200
drives the main motor
81
and thereby starts rotating the print drum
1
b
via the rotation transmitting means (step S
46
). At this instant, the controller
200
causes the second “Ready” LED
119
on the operation panel
110
to blink in green, causes the first “Ready” LED
116
to turn off, and causes the first “Unready” LED
117
to glow. This informs the operator of the fact that neither the drum unit
100
a
not he drum unit
100
b
can be mounted or dismounted, urging the operator to wait until the end of rotation of the print drum
1
b.
In a step S
47
following the step S
46
, the controller
200
controls, based on the outputs of the home position sensors
70
b
and encoder
73
, the main motor
81
in order to bring the print drum
1
b
to its home position or dismount position. When the print drum
1
b
reaches its dismount position (YES, step S
47
), the controller
200
stops driving the main motor
81
and thereby stops the print drum at the home position (step S
48
). At this instant, the controller
200
causes the second “Ready” LED
118
on the operation panel
110
to glow in green.
Subsequently, in a step S
49
, the operator sees the second “Ready” LED
110
glowing in green and then opens the door
503
in order to remove the drum unit
100
b.
In response to the resulting output of the door sensor
504
, the controller
200
causes the second “Ready” LED
98
to glow in green and causes the first “Unready” LED
97
to glow in red. Watching such statuses of the LEDs
98
and
97
, the operator pulls the drum unit
100
b
out of the housing
501
. The operator then performs the replacement of the ink of the print drum
1
b
or the master
33
b
or cleaning and again closes the door
503
.
How the drum units
100
a
and
100
b
are inserted into the housing
501
will be described hereinafter. For the mounting operation, use is mainly made of the ninth, tenth and fourteen functions available with the controller
200
.
For example, assume that the operator replaces the masters
33
a
and
33
b
of the drum units
100
a
and
100
b
and then inserts the drum unit
100
b
into the housing
501
. Then, because the operator pulled out the drum unit
100
b
after the drum unit
100
a
at the time of removal, the second “Ready” LED
98
and first “Unready” LED
97
on the housing
501
are glowing in green and red, respectively. Also, he second “Ready” LED
118
and first “Unready” LED
117
on the operation panel
110
are glowing in green and red, respectively. This shows the operator that the drum drive plate
87
of the coupling portion assigned to the print drum
1
b
is held in its home position (dismount position or mount position), allowing the print rum
100
b
to be inserted into the housing
501
.
When the operator inserts the drum unit
100
b
into the housing
501
via the opening
501
and mounting/dismounting means
50
b,
the drum unit
100
b
can be easily received in the housing
501
and set because of the home position of the drum drive plate
87
.
Subsequently, the operator closes the door
503
. At this instant, the output of the second drum sensor
78
is indicative of the presence of the drum unit
100
b.
In response to this output of the second drum sensor
78
, the output of the door sensor
504
and the outputs of the home position sensor
70
b
and encoder sensor
73
, the controller
200
drives the main motor
81
until the drum drive plate
87
of the coupling portion assigned to the other drum unit
100
a
reaches its home position. The controller
200
then causes the first “Ready” LED
116
on the operation panel to glow in green.
Seeing the first “Ready” LED
116
glowing in green on the operation panel
110
, the operator opens the door
503
in order to insert the drum unit
100
a.
In response to the resulting output of the door sensor
504
, the controller
200
causes the first “Ready” LED
96
and second “Unready” LED
99
to glow in green and red, respectively, urging the operator to insert the drum unit
100
a.
When the operator inserts the drum unit
100
a
into the housing
501
via the opening
501
a
and mounting/dismounting means
50
a,
the drum unit
100
a
can be easily received and set because of the home position of the drum drive plate
87
assigned to the print drum
1
a.
When the operator closes the door
503
, the controller
200
determines, in response to the resulting output of the door sensor
504
and the outputs of the drum sensors
77
and
78
, that the printer is capable of operating.
Alternatively, the operator may first press the first drum unlock key
114
in order to insert the drum unit
100
a
before the drum unit
100
b.
In such a case, the controller
200
brings the drum drive plate
87
assigned to the print drum
1
a
to its home position. Thereafter, when the operator closes the door
503
, the automatic mode operation occurs in substantially the same manner as described above. Specifically, the controller
200
automatically brings the drum drive plate
87
assigned to the print drum
1
b
to the home position, allowing the operator to insert the drum unit
100
b.
Fourth Specific Operation
To replace the ink of the print drums
1
a
and
1
b,
to replace the masters
33
a
and
33
b
or to perform cleaning, the operator sometimes intends to successively remove the drum units
100
a
and
100
b
from the housing
501
. A fourth specific operation to be described with reference to
FIG. 18
relates to an automatic successive removal mode for effecting the above operation. The fourth specific operation mainly uses the fourth, sixth and eighth to tenth functions of the controller
200
.
As shown in
FIG. 18
, the operator presses the first and second drum unlock keys
114
and
115
at the same time for selecting successive drum removal (step S
50
). At this instant, an automatic successive removal signal is generated to set up an automatic mode. The automatic successive removal signal is sent to the controller
200
. In response, the controller
200
drives the main motor
81
and thereby starts rotating the print drum
1
a
via the rotation transmitting means (step S
51
). At the same time, the controller
200
causes the first “Ready” LED
116
and second “Unready” LED
119
on the operation panel to blink in green and to glow in red, respectively. This shows the operator that neither the drum unit
100
a
nor the drum
100
b
can be mounted or dismounted, urging the operator to wait until the end of rotation of the print drum
1
a.
Subsequently, the controller
200
controls, based on the outputs of the home position sensor
70
a
and encoder sensor
73
, the main motor
81
in such a manner as to bring the print drum
1
a
to its home position or dismount position. When the print drum
1
a
reaches the home position (YES, step S
52
), the controller
200
stops driving the main motor
81
and thereby stops the print drum
1
a
at the home position (step S
53
). At the same time, the controller
200
causes the first “Ready” LED
116
to glow in green. In this condition, the operator pulls out the print drum
100
a
in the same manner as in the step S
44
of the third specific operation (step S
54
).
After the step S
54
, the controller
200
drives the main motor
81
and thereby starts driving the print drum
1
b
via the rotation transmitting means (step S
55
). At the same time, the controller
200
causes the second “Ready” LED
118
on the operation panel
110
to blink in green while causing the first “Unready” LED
117
to glow. This informs the operator of the fact that neither the drum unit
100
a
nor the drum unit
100
b
can be mounted or dismounted, urging the operator to wait until the end of rotation of the print drum
1
b.
Subsequently, the controller
200
controls, based on the outputs of the home position sensor
70
b
and encoder sensor
73
, the main motor
81
in such a manner as to bring the print drum
1
b
to its home position or dismount position. When the print drum
1
b
reaches the home position (YES, step S
56
), the controller
200
stops driving the main motor
81
and thereby stops the print drum
1
b
at the home position (step S
57
). At this time, the controller
200
causes the second “Ready” LED
118
to glow in green on the operation panel.
In the above condition, the operator pulls out the drum unit
100
b
in the same manner as in the step S
49
of the third specific operation. The drum units
100
a
and
100
b
may be inserted into the housing
501
in the same manner as in the third specific operation.
In the fourth specific operation, the operator should only press the two drum unlock keys
114
and
115
at the same time. The fourth specific operation therefore makes the operator's manipulation simple and easy, compared to the third specific operation.
Fifth Specific Operation
A fifth specific operation to be described with reference to
FIG. 19
relates to a manual insertion mode for allowing the operator to successively insert the drum unit
100
a
and
100
b
into the housing
501
. For this specific operation, use is mainly made of the ninth, tenth and twelfth functions of the controller
200
. Neither one of the drum units
100
a
and
100
b
is assumed to be initially present in the housing
501
.
As shown in
FIG. 19
, the operator first turns on the power switch
95
(step S
60
). In response, the printer
500
becomes ready to perform a printing operation. Specifically, the LEDs
116
through
119
and LCD
120
on the operation panel
110
and the LEDs
96
through
99
adjoining the openings
501
a
and
501
b
are prepared for display. The operator watches the LCD
120
to see if the drum unit
100
a
(print drum
1
) is present in the housing
501
or not (step S
61
). For this purpose, an exemplary message “Please insert drum units
100
a
and
100
b.
” is displayed on the LCD
120
. If desired, such a message may be replaced with LED sensors arranged on the operation panel
110
and responsive to the presence of the print drums
1
a
and
1
b.
Further, if it is not necessary to promote efficient operation, the operator may, of course, open the door cover
503
and see if the drum units
100
a
and
100
b
are present in the housing
501
or not.
Subsequently, the operator presses the first drum unlock key
114
ih order to insert the drum unit
100
a
into the housing
501
(YES, step S
62
). In response, the controller
200
drives the main motor
81
and thereby starts rotating the drum drive plate
87
assigned to the print drum
1
a
via the rotation transmitting means (step S
63
). At the same time, the controller
200
causes the first “Ready” LED
116
on the operation panel
110
to blink in green while causing the second “Unready” LED
119
to glow in red. This informs the operator of the fact that the drum unit
100
b
cannot be mounted, urging the operator to wait until the end of rotation of the drum drive plate
87
.
When the drum drive plate
87
assigned to the print drum
1
a
reaches its home position (YES, step
64
), the controller
200
stops driving the main motor
81
and thereby stops the above drum drive plate
87
at the home position (step S
65
). At the same time, the controller
200
causes the first “Ready” LED
116
to glow. in green, showing the operator that the coupling portion assigned to the print drum
1
a
is ready to receive the drum unit
100
a.
Subsequently, the operator inserts the drum unit
100
a
into the housing
501
(step S
66
). Specifically, watching the first “Ready” LED
116
glowing in green on the operation panel
110
, the operator opens the door
503
. In response to the resulting output of the door sensor
504
, the controller
200
causes the first “Ready” LED
96
and second “Unready” LED
99
to glow in green and red, respectively. The operator, seeing such statuses of the LEDs
96
and
99
, inserts the drum unit
100
a
into the opening
501
a
via the mounting/dismounting means
50
a.
The drum unit
100
a
can be easily inserted and set because of the home position of the drum drive plate
87
assigned to the print drum
1
a.
The operator then closes the door
503
.
After the operator has closed the door
503
, an exemplary message “Drum unit
100
b
is absent.” appears on the LCD
120
of the operation panel
110
, showing the operator that the drum unit
100
b
is absent (step S
67
). Watching this message, the operator presses the second drum unlock key
115
(YES, step S
68
). In response, the controller
200
drives the main motor
81
and thereby starts rotating the drum drive plate
87
assigned to the print drum
1
b
via the rotation drive means (step S
69
). At the same time, the controller
200
causes the second “Ready” LED
118
to blink in green, causes the second “Unready” LED
119
to turn off, and causes the first “Unready” LED
117
to glow in red. This informs the operator of the fact that the drum unit
100
b
cannot be mounted, urging the operator to wait until the end of rotation of the above drum drive plate
87
.
When the drum drive plate
87
assigned to the print drum
1
b
reaches the home position (YES, step S
70
), the controller
200
stops driving the main motor
81
and thereby stops the drum drive plate
87
at the home position (step S
71
). Also, the controller
200
causes the second “Ready” LED
118
to glow in green, showing the operator that the coupling portion assigned to the print drum
1
b
is ready to receive the drum unit
100
b.
Thereafter, the operator inserts the drum unit
100
b
into the housing
501
in the same manner as the drum unit
100
a
(step S
72
). Specifically, watching the second “Ready” LED
118
glowing in green on the operation panel
110
, the operator opens the door
503
for inserting the drum unit
100
b.
In response to the resulting output of the door sensor
504
, the controller
200
causes the second “Ready” LED
98
to glow in green and causes the first “Unready” LED
97
to glow in red. When the operator, watching the LEDs
98
and
97
, inserts the drum unit
100
b
into the opening
501
b
via the mounting/dismounting means
50
b,
the drum unit
100
b
can be easily inserted and set because of the home position of the drum drive plate
87
.
Sixth Specific Operation
A sixth specific operation to be described with reference to
FIG. 20
pertains to an automatic insertion mode that allows the operator to successively insert the drum units
100
a
and
100
b
for the same purpose as the fifth specific operation. For the sixth specific operation, use is mainly made of the ninth, tenth and thirteenth functions available with the controller
200
. Again, neither one of the drum units
100
a
and
100
b
is assumed to be initially present in the housing
501
.
As shown in
FIG. 20
, the operator first turns on the power switch
95
(step S
80
). In response, the printer
500
becomes ready to perform a printing operation. Subsequently, the controller
200
automatically determines whether or not the drum unit
100
a
is present on the basis of the outputs of the drum sensors
77
and
78
(step S
81
). Because the drum unit
100
a,
i.e., the print drum
1
a
is absent at this stage, as indicated by the output of the first drum sensor
77
(NO, step S
81
), the controller
200
executes a step S
82
. If the answer of the step S
81
is YES, the controller
200
executes a step S
86
. The steps S
82
to S
85
are identical with the steps S
63
to S
66
of the fifth specific operation, FIG.
19
.
Subsequently, the controller
200
automatically determines whether or not the drum unit
100
b
is present on the basis of the outputs of the drum sensors
77
and
78
(step S
86
). If the answer of the step S
86
is NO, the controller
200
executes a step S
87
; if otherwise, the controller
200
ends the procedure shown in FIG.
20
. The steps S
87
to S
90
are identical with the steps S
69
to S
72
of the fifth specific operation shown in FIG.
19
.
The RAM
202
stores priority order as to the insertion of the print drums
1
a
and
1
b
into the housing
501
, as stated earlier. The controller
200
may therefore sequentially set the print drums
1
b
and
1
a
in this order in accordance with the priority order.
A first modification of the illustrative embodiment will be described hereinafter. The modification differs from the illustrative embodiment in the following aspect. The mechanical locking means associated with the drum units
100
a
and
100
b
are replaced with electric locking means respectively assigned to the drum units
100
a
and
100
b
for locking them to the housing
601
. The first and second drum unlock keys
114
and
115
play the role of unlock setting means for canceling locked states set up by the electric locking means in addition to the previously stated function. The controller
200
controls the electric locking means for canceling the locked state of the drum unit
100
a
or
100
b
to be dismounted on the basis of the output of the drum unlock key
114
or
115
.
The electric locking means each may be implemented as, e.g., electric locking means
175
shown in FIGS. 8 and 9 of Laid-Open Publication No. 10-846 mentioned earlier. Obviously, the controller
200
combined with the electric locking means
175
is capable of executing any one of the first to sixth specific operations.
A second modification of the illustrative embodiment differs from the illustrative embodiment in the following respect. Again, the mechanical locking means associated with the drum units
100
a
and
100
b
are replaced with electric locking means respectively assigned to the drum units
100
a
and
100
b
for locking them to the housing
601
. The first and second drum unlock keys
114
and
115
play the role of unlock setting means for canceling locked states set up by the electric locking means for the drum units
100
a
and
100
b
to be continuously dismounted in addition to the previously stated function. The control means
200
controls, in response to a signal to appear when the operator presses the keys
114
and
115
at the same time, the electric locking means in such a manner as to unlock the drum unit
100
a
or
100
b
to be dismounted.
Again, the electric locking means each may be implemented as, e.g., electric locking means
175
shown in
FIGS. 8 and 9
of Laid-Open Publication No. 10-846 mentioned earlier. Obviously, the controller
200
combined with the electric locking means
175
is capable of executing any one of the first to sixth specific operations.
A third modification of the illustrative embodiment will be described hereinafter. The third modification is implemented as a stencil printer designated by the parenthesized reference numeral
700
. The stencil printer is identical with the stencil printer
500
except that it additionally includes the master discharging devices
42
a
and
42
b
and master making devices
41
a
and
41
b
indicated by phantom lines as well as a scanner not shown.
The master making devices
41
a
and
41
b,
master discharging devices
42
a
and
42
b
and scanner are constructed in the same manner as in, e.g.,
FIG. 8
of Laid-Open Publication No. 5-229243. The scanner includes a group of mirrors and a lens. Interposed between the mirrors and the lens is an arrangement having various functions necessary for color separation essential with color printing, e.g., a filter unit including a plurality of color filters as taught in, e.g., Laid-Open Publication No. 64-18682. The above devices automatically effect master making, master discharging and other procedures in the same manner as taught in Laid-Open Publication NO. 64-18682. Data for making masters may be generated by a computer or similar data processing apparatus in place of the scanner, if desired.
The operation of the printer
700
is identical with the operation described in paragraphs (0088) through (0096) of Laid-Open Publication No. 11-138961 and will not be described specifically. The printer
700
can, of course, perform the first to sixth specific operations.
In the illustrative embodiment and modifications thereof, the print drums
1
a
and
1
b
are assumed to be located at home positions when the dampers
5
a
and
5
b,
respectively, are located at the bottoms of the drums
1
a
and
1
b.
Alternatively, the home positions may be such that the dampers
5
a
and
5
b
are positioned at the tops of the print drums
1
a
and
1
b,
respectively. The crux is that the home positions be identical throughout the printer
500
or
700
.
The construction and arrangement of the individual device included in the printer
500
or
700
is only illustrative and may be replaced with any other conventional device and arrangement. For example, the air knives
7
a
and
7
b
may be replaced with conventional angularly movable peelers adjoining the print drums
1
a
and
1
b.
The present invention is, of course, applicable to a stencil printer having three or more print drums. Further, the present invention may be implemented as a stencil printer including a plurality of print drums to each of which ink of particular color is fed from outside the print drum, as disclosed in, e.g., Laid-Open Publication No. 7-17013 mentioned earlier.
Moreover, for the mounting/dismounting means for allowing the print drums to be mounted and dismounted from the housing, use may be made of an arrangement shown in
FIG. 1 and 2
of Laid-Open Publication No. 64-46258, holding means
36
and a print drum device
55
shown in
FIG. 2 and 3
of Laid-Open Publication No. 5-229243, an arrangement shown in
FIG. 3
of Laid-Open Publication No. 6-71998, an arrangement shown in
FIG. 1
of Laid-Open Publication No. 6-293175, or an arrangement shown in
FIG. 2
of Laid-Open Publication No. 7-1817.
In summary, it will be seen that the present invention provides a stencil printer with a plurality of print drums having various unprecedented advantages, as enumerated below.
(1) A print drum to be dismounted can be dismounted without resorting to conventional top-bottom movement adjusting means including top-bottom moving means, so that the printer has a compact configuration. Only if a drum unit to be dismounted is brought to a removable condition via individual removal setting means, the print drum of the drum unit can be automatically moved to a preselected phase and easily removed from a printer body. This eliminates the need for conventional sophisticated manual operation, i.e., returning each print drum to its home position or similar dismount position and then removing it. The operator of the printer can therefore easily remove drum units for the purpose of, e.g., successively replacing the print drums of first and second colors in the event of four-color printing, removing a paper sheet or a master jamming a path between nearby print drums, or performing cleaning.
(2) The operator can surely operate the printer because of controlled unlocking operation.
(3) Only if at least two drum units are successively brought to their dismount positions via successive removal setting means, the print drums of such drums units can be automatically and consecutively moved to a preselected phase and easily removed from the printer body.
(4) The individual removal setting means plays the role of successive removal setting means at the same time, so that the number of parts is reduced.
(5) The operator can immediately see a drum unit to be dealt with as to the defective egress of a paper sheet.
(6) The operator is prevented from forgetting to deal with defective paper egress that would cause another defective paper egress to occur.
(7) Drum drive means is simple in configuration.
(8) The phase of the individual print drum can be surely sensed while angular position sensing means responsive to the angular position of the print drum can be simplified in configuration.
(9
1
) Whether or not the individual print drum is ready to be mounted or dismounted is indicated at a position easy for the operator to see, enhancing efficient operation. In addition, a particular color is assigned to each of a ready state and an unready state, further enhancing efficient operation.
(10) Only if the operator turns on a power switch and conditions the printer for the insertion of a desired drum unit via individual insertion setting means, a coupling portion included in the printer and assigned to the above drum unit is automatically moved to a preselected phase. In this condition, the operator can easily insert the drum unit into the printer body. This is also successful to enhance efficient operation.
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 printer including a plurality of drum units removably mounted to a printer body and each including a respective print drum allowing a particular master to be wrapped therearound, nearby print drums being provided with a preselected initial phase difference therebetween beforehand when said drum units are present in said printer body, said plurality of drum units each being removable from said printer body when said respective print drum is brought to a preselected phase, said printer wrapping said particular master around said respective print drum, feeding ink of particular color to each master, and pressing a recording medium against consecutive masters to thereby effect continuous printing, said printer comprising:individual removal setting means each being assigned to a particular drum unit for making said drum unit removable from the printer body; angular position sensing means for sensing an angular position of the drum of the individual drum unit; drum drive means for causing the print drum of the drum unit to be removed to rotate; and control means for controlling, based on an output of said individual removal setting means assigned to the drum unit to be removed and an output of the angular position sensing means assigned to the print drum of said drum unit, said drum drive means such that said print drum of said drum unit to be removed is brought to the preselected phase.
- 2. A printer as claimed in claim 1, further comprising locking means each being assigned to a particular drum unit for locking said drum unit to the printer body, wherein said individual removal setting means includes individual unlock setting means for unlocking the drum unit to be removed and locked by said locking means to thereby make said drum unit removable, and wherein said control means controls, based on an output of said individual unlock setting means, said locking means in such a manner as to unlock said drum unit to be removed.
- 3. A printer as claimed in claim 1, further comprising:an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; wherein when another drum unit should be removed, said control means controls, based on an output of said open/close sensing means appearing when an operator of said printer opens said openable member for removing the drum unit to be removed and then closes said openable member, an output of said individual removal setting means assigned to said another drum unit and an output of said angular position sensing means assigned to said another drum unit, said drum drive means such that the print drum of said another drum unit is brought to the preselected phase.
- 4. A printer as claimed in claim 3, further comprising displaying means each being assigned to a particular drum unit for displaying whether or not said drum unit can be mounted or dismounted, said displaying means being positioned at least around said openings or on an operation panel.
- 5. A printer as claimed in claim 4, wherein said displaying means comprises LEDs indicating whether or not the individual drum unit can be mounted or dismounted in color.
- 6. A printer as claimed in claim 1, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said printer further comprising:paper egress sensing means each being located downstream, in said direction, of the print drum of a particular drum unit present in the printer body for detecting a roll-up, defective egress or similar egress error of the recording medium; and informing means for informing, based on an output of each of said paper egress sensing means, an operator of said printer of the drum unit where the egress error has occurred.
- 7. A printer as claimed in claim 6, further comprising:an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; said control means determining whether or not to perform a printing operation on the basis of an output of said open/close sensing means and outputs of said paper egress sensing means.
- 8. A printer as claimed in claim 1, wherein said drum drive means comprises a single drive source and rotation transmitting means for transmitting a rotation of said single drive source to the print drums of the drum units present on the printer body.
- 9. A printer as claimed in claim 8, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said angular position sensing means each comprising:home position sensing means for sensing a home position assigned to the respective print drum and corresponding to the preselected phase; and a pulse encoder mounted on a most upstream drum unit in said direction for sensing a phase of the print drum of said most upstream drum unit.
- 10. A printer as claimed in claim 1, wherein the drum units each comprises locking means for selectively locking or unlocking the respective drum unit to or from the printer body in interlocked relation to an insertion or a removal of said drum unit to or from said printer body.
- 11. A printer including a plurality of drum units removably mounted to a printer body and each including a respective print drum allowing a particular master to be wrapped therearound, nearby print drums being provided with a preselected initial phase difference therebetween beforehand when said drum units are present in said printer body, said plurality of drum units each being removable from said printer body when said respective print drum is brought to a preselected phase, said printer wrapping said particular master around said respective print drum, feeding ink of particular color to each master, and pressing a recording medium against consecutive masters to thereby effect continuous printing, said printer comprising:successive removal setting means for successively making at least two drum units removable from the printer body; angular position sensing means for sensing an angular position of the print drum of the individual drum unit; drum drive means for causing the print drum of the drum unit to be removed to rotate; and control means for controlling, based on an output of said successive removal setting means and an output of said angular position sensing means assigned to the print drum of one drum unit to be removed, said drum drive means such that said print drum of said one drum unit is brought to the preselected phase, and then controlling, based on an output of said angular position sensing means assigned to the print drum of another drum unit to be removed, said drum drive means such that the print drum of said another drum unit is brought to said preselected phase.
- 12. A printer as claimed in claim 11, further comprising individual removal setting means each being assigned to a particular drum unit for making said drum unit removable from the printer body, wherein said successive removal setting means comprises at least two individual removal setting means.
- 13. A printer as claimed in claim 11, further comprising locking means each being assigned to a particular drum unit for locking said drum unit to the printer body, wherein said successive removal setting means comprises successive unlock setting means for unlocking the drum units to be successively removed and locked by the respective locking means to thereby make said drum units to be successively removable, and wherein said control means controls, based on an output of said successive unlock setting means, the locking means assigned to one drum unit to be removed in such a manner as to unlock said one drum unit, and controls the locking means assigned to another drum unit to be removed in such a manner as to unlock said another drum unit.
- 14. A printer as claimed in claim 11, further comprising:an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; wherein said control means controls, based on an output of said open/close sensing means appearing when an operator of said printer opens said openable member for removing one drum unit to be removed and then closes said openable member and an output of said angular position sensing means assigned to the print drum of another drum unit to be removed, said drum drive means such that said print drum of said another drum unit is brought to the preselected phase.
- 15. A printer as claimed in claim 14, further comprising displaying means each being assigned to a particular drum unit for displaying whether or not said drum unit can be mounted or dismounted, said displaying means being positioned at least around said openings or on an operation panel.
- 16. A printer as claimed in claim 15, wherein said displaying means comprises LEDs indicating whether or not the individual drum unit can be mounted or dismounted in color.
- 17. A printer as claimed in claim 11, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said printer further comprising:paper egress sensing means each being located downstream, in said direction, of the print drum of a particular drum unit present in the printer body for detecting a roll-up, defective egress or similar egress error of the recording medium; and informing means for informing, based on an output of each of said paper egress sensing means, an operator of said printer of the drum unit where the egress error has occurred.
- 18. A printer as claimed in claim 17, further comprising:an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; wherein said control means determines whether or not to perform a printing operation on the basis of an output of said open/close sensing means and outputs of said paper egress sensing means.
- 19. A printer as claimed in claim 11, wherein said drum drive means comprises a single drive source and rotation transmitting means for transmitting a rotation of said single drive source to the print drums of the drum units present on said printer body.
- 20. A printer as claimed in claim 19, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said angular position sensing means each comprising:home position sensing means for sensing a home position assigned to the respective print drum and corresponding to the preselected phase; and a pulse encoder mounted on a most upstream drum unit in said direction for sensing a phase of the print drum of said most upstream drum unit.
- 21. A printer as claimed in claim 11, wherein the drum units each comprises locking means for selectively locking or unlocking the respective drum unit to or from the printer body in interlocked relation to an insertion or a removal of said drum unit to or from said printer body.
- 22. A printer including a plurality of drum units removably mounted to a printer body and arranged side by side in a direction in which a recording medium is conveyed and each including a respective print drum allowing a particular master to be wrapped therearound, nearby print drums being provided with a preselected initial phase difference therebetween beforehand when said drum-units are present in said printer body, said plurality of drum units each being removable from said printer body when said respective print drum is brought to a preselected phase, said printer wrapping said particular master around said respective print drum, feeding ink of particular color to each master, and pressing a recording medium against consecutive masters to thereby effect continuous printing, said printer comprising:paper egress sensing means each being located downstream, in said direction, of the print drum of a particular drum unit present in the printer body for detecting a roll-up, defective egress or similar egress error of the recording medium; angular position sensing means for sensing an angular position of the print drum of the individual drum unit; drum drive means for causing the print drum of the drum unit to be removed to rotate; and control means for controlling, based on outputs of said paper egress sensing means and an output of said angular position sensing means assigned to the print drum of one drum unit to be removed due to an egress error, said drum drive means such that said print drum of said one drum-unit to be removed is brought to the preselected phase, and then controlling, based on the outputs of said paper egress sensing means and an output of said angular position sensing means assigned to the print drum of another drum unit to be removed due to an egress error, said drum drive means such that the print drum of said another drum unit is brought to said preselected phase.
- 23. A printer as claimed in claim 22, further comprising:an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; wherein said control means controls, based on an output of said open/close sensing means appearing when an operator of said printer opens said openable member for removing the one drum unit to be removed and then closes said openable member and an output of said angular position sensing means assigned to the print drum of another drum unit to be removed, said drum drive means such that said print drum of said another drum unit is brought to the preselected phase.
- 24. A printer as claimed in claim 23, further comprising displaying means each being assigned to a particular drum unit for displaying whether or not said drum unit can be mounted or dismounted, said displaying means being positioned at least around said openings or on an operation panel.
- 25. A printer as claimed in claim 24, wherein said displaying means comprises LEDs indicating whether or not the individual drum unit can be mounted or dismounted in color.
- 26. A printer as claimed in claim 22, further comprising informing means for informing, based on an output of each of said paper egress sensing means, an operator of said printer of the drum unit where the egress error has occurred.
- 27. A printer as claimed in claim 22, further comprising:an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; wherein said control means determines whether or not to perform a printing operation on the basis of an output of said open/close sensing means and outputs of said paper egress sensing means.
- 28. A printer as claimed in claim 22, wherein said drum drive means comprises a single drive source and rotation transmitting means for transmitting a rotation of said single drive source to the print drums of the drum units present on the printer body.
- 29. A printer as claimed in claim 22, wherein said angular position sensing means each comprises:home position sensing means for sensing a home position assigned to the respective print drum and corresponding to the preselected phase; and a pulse encoder mounted on a most upstream drum unit in said direction for sensing a phase of the print drum of said most upstream drum unit.
- 30. A printer including a plurality of drum units removably mounted to a printer body and each including a respective print drum allowing a particular master to be wrapped therearound, nearby print drums being provided with a preselected initial phase difference therebetween beforehand when said drum units are present in said printer body, said plurality of drum units each being insertable into said printer body when said respective print drum is brought to a preselected phase, said printer wrapping said particular master around said respective print drum, feeding ink of particular color to each master, and pressing a recording medium against consecutive masters to thereby effect continuous printing, said printer comprising:a power switch for selectively setting up or interrupting power supply to said printer; individual removal setting means each being assigned to a particular drum unit for making said drum unit insertable into the printer body; angular position sensing means for sensing an angular position of the drum of the individual drum unit; drum drive means for causing the print drum of the drum unit to be inserted to rotate; and control means for controlling, after a turn-on of said power switch and on the basis of an output of said individual removal setting means assigned to the drum unit to be inserted and an output of said angular position sensing means assigned to the print drum of said drum unit, said drum drive means such that a coupling portion arranged in the printer body and assigned to said print drum of said drum unit to be inserted is brought to the preselected phase.
- 31. A printer as claimed in claim 30, further comprising:an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; wherein when another drum unit should be inserted, said control means controls, based on an output of said open/close sensing means appearing when an operator of said printer opens said openable member for inserting the drum unit to be removed and then closes said openable member, an output of said individual removal setting means assigned to said another drum unit and an output of said angular position sensing means assigned to said another drum unit, said drum drive means such that said coupling portion is brought to the preselected phase.
- 32. A printer as claimed in claim 31, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said printer further comprising paper egress sensing means each being located downstream, in said direction, of the print drum of a particular drum unit present in the printer body for detecting a roll-up, defective egress or similar egress error of the recording medium, said control means determining whether or not to perform a printing operation on the basis of an output of said open/close sensing means and outputs of said paper egress sensing means.
- 33. A printer as claimed in claim 31, further comprising informing means for informing, based on an output of each of said paper egress sensing means, an operator of said printer of the drum unit where the egress error has occurred.
- 34. A printer as claimed in claim 31, further comprising displaying means each being assigned to a particular drum unit for displaying whether or not said drum unit can be mounted or dismounted, said displaying means being positioned at least around said openings or on an operation panel.
- 35. A printer as claimed in claim 34, wherein said displaying means comprises LEDs indicating whether or not the individual drum unit can be mounted or dismounted in color.
- 36. A printer as claimed in claim 30, wherein said drum drive means comprises a single drive source and rotation transmitting means for transmitting a rotation of said single drive source to the print drums of the drum units present on the printer body.
- 37. A printer as claimed in claim 30, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said angular position sensing means each comprising:home position sensing means for sensing a home position assigned to the respective print drum and corresponding to the preselected phase; and a pulse encoder mounted on a most upstream drum unit in said direction for sensing a phase of the print drum of said most upstream drum unit.
- 38. A printer including a plurality of drum units removably mounted to a printer body and each including a respective print drum allowing a particular master to be wrapped therearound, nearby print drums being provided with a preselected initial phase difference therebetween beforehand when said drum units are present in said printer body, said plurality of drum units each being insertable into said printer body when said respective print drum is brought to a preselected phase, said printer wrapping said particular master around said respective print drum, feeding ink of particular color to each master, and pressing a recording medium against consecutive masters to thereby effect continuous printing, said printer comprising:a power switch for selectively setting up or interrupting power supply to said printer; drum sensing means each being assigned to a particular drum unit for determining whether or not said drum unit is present on the printer body; angular position sensing means for sensing an angular position of the drum of the individual drum unit; drum drive means for causing the print drum of the drum unit to be inserted to rotate; and control means for controlling, after a turn-on of said power switch and on the basis of an output of said drum sensing means assigned to one drum unit to be inserted and an output of said angular position sensing means assigned to the print drum of said drum unit, said drum drive means such that a coupling portion arranged in the printer body and assigned to said print drum of said drum unit to be inserted is brought to the preselected phase, and then controlling, based on an output of said drum sensing means assigned to the print drum of another drum unit to be inserted and an output of said angular position sensing means assigned to said print drum of said drum unit, said drum drive means such that a coupling portion arranged in said printer body and assigned to said another drum unit is brought to said preselected phase.
- 39. A printer as claimed in claim 38, wherein the plurality of print drums are arranged side by side in a direction in which the recording medium is conveyed, said printer further comprising:paper egress sensing means each being located downstream, in said direction, of the print drum of a particular drum unit present in the printer body for detecting a roll-up, defective egress or similar egress error of the recording medium; an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; said control means determining whether or not to perform a printing operation on the basis of an output of said open/close sensing means and outputs of said paper egress sensing means.
- 40. A printer as claimed in claim 39, further comprising displaying means each being assigned to a particular drum unit for displaying whether or not said drum unit can be mounted or dismounted, said displaying means being positioned at least around said openings or on an operation panel.
- 41. A printer as claimed in claim 40, wherein said displaying means comprises LEDs indicating whether or not the individual drum unit can be mounted or dismounted in color.
- 42. A printer as claimed in claim 38, further comprising informing means for informing, based on an output of each of said paper egress sensing means, an operator of said printer of the drum unit where the egress error has occurred.
- 43. A printer as claimed in claim 38, wherein said drum drive means comprises a single drive source and rotation transmitting means for transmitting a rotation of said single drive source to the print drums of the drum units present on the printer body.
- 44. A printer as claimed in claim 38, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said angular position sensing means each comprising:home position sensing means for sensing a home position assigned to the respective print drum and corresponding to the preselected phase; and a pulse encoder mounted on a most upstream drum unit in said direction for sensing a phase of the print drum of said most upstream drum unit.
- 45. A printer including a plurality of drum units removably mounted to a printer body and each including a respective print drum allowing a particular master to be wrapped therearound, nearby print drums being provided with a preselected initial phase difference therebetween beforehand when said drum units are present in said printer body, said plurality of drum-units each being insertable into said printer body when said respective print drum is brought to a preselected phase, said printer wrapping said particular master around said respective print drum, feeding ink of particular color to each master, and pressing a recording medium against consecutive masters to thereby effect continuous printing, said printer comprising:drum sensing means each being assigned to a particular drum unit for determining whether or not said drum unit is present on the printer body; angular position sensing means for sensing an angular position of the drum of the individual drum unit; drum drive means for causing the print drum of the drum unit to be inserted to rotate; and control means for controlling, when one drum unit is inserted into the printer body on which no drum units are present, said drum drive means on the basis of outputs of said drum sensing means such that a coupling portion arranged in said printer body and assigned to another drum unit to be inserted is brought to the preselected phase.
- 46. A printer as claimed in claim 45, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said printer further comprising:paper egress sensing means each being located downstream, in said direction, of the print drum of a particular drum unit present in the printer body for detecting a roll-up, defective egress or similar egress error of the recording medium; an openable member mounted on the printer body for selectively opening or closing openings formed in said printer body and each opening being assigned to a particular drum unit; and open/close sensing means for determining whether said openable member is open or closed; said control means determining whether or not to perform a printing operation on the basis of an output of said open/close sensing means and outputs of said paper egress sensing means.
- 47. A printer as claimed in claim 46, further comprising informing means for informing, based on an output of each of said paper egress sensing means, an operator of said printer of the drum unit where the egress error has occurred.
- 48. A printer as claimed in claim 45, wherein said drum drive means comprises a single drive source and rotation transmitting means for transmitting a rotation of said single drive source to the print drums of the drum units present on the printer body.
- 49. A printer as claimed in claim 45, wherein the plurality of drum units are arranged side by side in a direction in which the recording medium is conveyed, said angular position sensing means each comprising:home position sensing means for sensing a home position assigned to the respective print drum and corresponding to the preselected phase; and a pulse encoder mounted on a most upstream drum unit in said direction for sensing a phase of the print drum of said most upstream drum unit.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-184842 |
Jun 1999 |
JP |
|
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