Information
-
Patent Grant
-
6234076
-
Patent Number
6,234,076
-
Date Filed
Thursday, October 21, 199924 years ago
-
Date Issued
Tuesday, May 22, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 101 118
- 271 314
- 271 401
- 271 408
- 271 1001
- 271 147
- 271 209
- 271 214
- 271 215
- 271 217
- 400 624
- 400 625
-
International Classifications
-
Abstract
An image forming machine includes an image forming section for receiving a sheet supplied in a supplying direction, printing an image on the sheet, and discharging the printed sheet in a discharging direction opposite to the supplying direction while changing the sheet upside-down; a sheet supplying table situated adjacent to the image forming section, the sheet supplying table stacking the sheet to be supplied to the image forming section; a sheet discharging table situated adjacent to the image forming section and disposed vertically relative to the sheet supplying table, the sheet discharging table stacking the sheet having the image printed thereon and discharged from the image forming section; driving mechanism attached to the sheet supplying table and the sheet discharging table for vertically moving the sheet supplying table and the sheet discharging table in directions opposite to each other.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming machine such that both sides printing can be easily conducted although structure of a sheet supplying device and a sheet discharging device is simple.
2. Description of the Related Art
A stencil printing machine will be explained as an example of the image forming machine.
FIG. 5
illustrates an example of a conventional stencil printing machine. A cylindrical printing drum
100
is rotatable around an axis
100
a
thereof. An ink permeable area is formed in a part of a peripheral wall of the printing drum
100
. Inside the printing drum
100
, an ink supplying means
100
b
is situated for supplying ink to an inner circumferential surface of the peripheral wall. A clamping device
101
is attached to an outer circumferential surface of the peripheral wall of the printing drum
100
for holding a leading end of a stencil sheet. The stencil sheet held by the clamping device
101
at the leading end thereof is wound around the outer circumferential surface of the printing drum
100
.
Beneath the printing drum
100
, a cylindrical opposing drum
102
is rotatably situated. The opposing drum
102
is rigid and not deformed during printing. The diameter of the opposing drum
102
is approximately identical to that of the printing drum
100
. An axis of the opposing drum
102
is parallel to the axis of the printing drum
100
. The opposing drum
102
is arranged so as to practically contact the printing drum
100
. A holding claw
103
is attached to an outer circumferential surface of the opposing drum
102
. A recess
104
is formed in the outer circumferential surface of the opposing drum
102
for avoiding interference with the clamping device
101
of the printing drum
100
.
The printing drum
100
and the opposing drum
102
are rotated in synchronization with each other and in directions opposite to each other. The drums convey a printing sheet while holding it therebetween, and conduct printing on it.
Above a sheet supplying table
105
, a sheet supplying roller
106
is situated. Between the sheet supplying roller
106
and the printing drum
100
, a timing roller
107
is situated. On a discharging side of the printing drum
100
, there are disposed a discharging claw,
108
for peeling the printing sheet from the opposing drum
102
, a pinch roller
109
, and a discharging roller
110
for conveying the printing sheet. The printing sheet as printed is fed out by the discharging roller
110
onto a sheet discharging table
113
.
According to the conventional stencil printing machine as explained above, the printing sheet is taken by the sheet supplying roller
106
and the timing roller
107
, held by the holding claw
103
of the opposing drum
102
at the leading end thereof, and then conveyed along the outer circumferential surface of the opposing drum
102
upon rotation of the opposing drum
102
. And, the printing sheet is printed while being held between the printing drum
100
and the opposing drum
102
. The printing sheet as printed is released from the holding claw
103
and sent out by the discharging roller
110
onto the discharging table
113
.
The conventional stencil printing machine includes a driving mechanism for vertically moving the sheet supplying table
105
. Further, the printing machine includes a detecting means for detecting height of the printing sheets stacked on the sheet supplying table
105
. This constitution allows the printing sheet on the sheet supplying table
105
to be situated to an optimum position for being sent out by the sheet supplying roller
106
.
Further, the printing machine includes a driving mechanism for vertically moving the sheet discharging table
113
. Further, the printing machine includes a detecting means for detecting height of the printing sheets stacked on the sheet discharging table
113
. That constitution allows the discharging table
113
to be situated to a position such that the printing sheet as printed is discharged onto the sheet discharging table
113
without crimping and jamming so that the discharged sheets are orderly stacked.
However, according to the conventional stencil printing machine as explained above, the sheet supplying table
105
and the sheet discharging table
113
are situated to a front and a rear side of the printing drum
100
and the opposing drum
102
, respectively, in a direction of conveying the printing sheet. Therefore, the driving mechanism and the detecting means are required to be provided to each of the sheet supplying table
105
and the sheet discharging table
113
. Further, a control means is necessary for each of the sheet supplying table
105
and the sheet discharging table
113
for controlling movement of them. Further, enough space must be ensured for each of the sheet supplying table
105
and the sheet discharging table
113
for allowing them to move vertically. Additionally, the sheet supplying table
105
includes an adjustable sheet supplying fence
115
for guiding an outer edge of the printing sheet, and the sheet discharging table
113
includes an adjustable sheet discharging fence
116
for guiding the outer edge of the printing sheet. And, the sheet supplying fence
115
and the sheet discharging fence
116
must be adjusted according to a size of the printing sheet, respectively.
Further more, in the case where both sides of the printing sheet is needed to be printed, after the printing sheets are printed on one surface thereof, the printing sheets stacked on the sheet discharging table
113
are taken therefrom to be replaced on the sheet supplying table
105
upside-down. However, such operation that the printing sheets are moved from one table to another is troublesome. And, during the operation, the stacked sheets may shift to be rubbed with each other, thereby being deteriorated in printed image quality.
An object of the present invention is to provide an image forming machine of simple constitution that is capable of conducting optimum sheet supplying/discharging operations by moving the sheet supplying/discharging tables interlocked with each other and facilitating handling of the printing sheets during both sides printing.
SUMMARY OF THE INVENTION
An image forming machine defined in a first aspect of the present invention comprises an image forming section for receiving a sheet supplied in a supplying direction, printing an image on the sheet, and discharging the printed sheet in a discharging direction opposite to the supplying direction while changing the sheet upside-down; a sheet supplying table situated adjacent to the image forming section, the sheet supplying table stacking the sheet to be supplied to the image forming section; a sheet discharging table situated adjacent to the image forming section and disposed vertically relative to the sheet supplying table, the sheet discharging table stacking the sheet having the image printed thereon and discharged from the image forming section; and driving mechanism attached to the sheet supplying table and the sheet discharging table for vertically moving the sheet supplying table and the sheet discharging table in directions opposite to each other.
According to an image forming machine as defined in a second aspect of the present invention, in the image forming machine of the first aspect, the image forming machine further comprises sheet cassettes detachably attached to the sheet supplying table and the sheet discharging table for stacking the sheet thereon.
According to an image forming machine as defined in a third aspect of the present invention, in the image forming machine of the second aspect, the sheet cassette at the sheet discharging table and the sheet cassette at the sheet supplying table are exchangeable so that after the sheet supplied from the sheet cassette at the sheet supplying table is printed on one surface thereof by the image forming section and discharged to the sheet cassette at the sheet discharging table, the sheet cassettes at the sheet discharging table and the sheet supplying table are exchanged to allow the sheets in the cassette at the sheet supplying table to be supplied to the image forming section for printing an image on the other surface thereof.
According to an image forming machine as defined in a fourth aspect of the present invention, in the image forming machine of the second aspect, the sheet cassette is variable in shape between a flat form and a concave form directing downwards in a section perpendicular to the discharging direction, the sheet supplying table holds the sheet cassette in the flat form, and the sheet discharging table holds the sheet cassette in the concave form.
According to an image forming machine as defined in a fifth aspect of the present invention, in the image forming machine of the second aspect, the image forming machine further comprises a pair of side plates disposed parallel to the supplying and discharging directions of the sheet on two sides of the sheet cassettes of the sheet supplying table and the sheet discharging table, respectively, the pair of the side plates guides side edges of the sheet stacked on the sheet cassette.
According to an image forming machine as defined in a sixth aspect of the present invention, in the image forming machine of the first aspect, the driving mechanism comprises a first rack fixed to the sheet supplying table, a second rack fixed to the sheet discharging table, a pinion engaging the first rack and the second rack, and a motor for driving the pinion.
According to an image forming machine as defined in a seventh aspect of the present invention, in the image forming machine of the first aspect, the image forming machine further comprises a sensor for detecting the sheet on the sheet supplying table in a sheet supplying position, and control means for controlling the sheet supplying table so that the sheet supplying table moves upwards until the sensor detects the sheet on the sheet supplying table in the sheet supplying position.
According to an image forming machine as defined in an eighth aspect of the present invention, in the image forming machine of the seventh aspect, the image forming machine further comprises a sheet supplying roller situated vertically movably within a vertical range, the sensor is situated above the sheet supplying roller for detecting an upward movement of the sheet supplying roller when the sheet comes in the sheet supplying position.
In the constitution as described above, the printing sheets stacked on the sheet supplying table are successively fed out to the image forming section one by one, thereby decreasing in stack height. The printing sheets as printed are successively received by the discharging table and stacked thereon, thereby increasing in stack height. The driving mechanism moves the sheet supplying table upwards according to feeding-out of the printing sheet from the sheet supplying table. Simultaneously with the upward movement, the driving mechanism also moves the sheet discharging table downwards according to reception of the printed sheets into the sheet discharging table.
The printing sheet fed out from the sheet supplying table is printed on one surface thereof by the image forming section, and then discharged onto the sheet discharging table. Here, when the one surface is a top face of the printing sheet stacked on the sheet supplying table, the printing sheet is discharged onto the sheet discharging table with the printed one surface downward. Now, exchangeable sheet cassettes are attached to the sheet supplying table and the sheet discharging table. The printing sheets on the sheet supplying table and the sheet discharging table are placed on the cassettes, respectively. In this constitution, after all of the printing sheets are printed on one surface thereof, the cassette on the sheet discharging table is detached therefrom and attached to the sheet supplying table, and the cassette detached from the sheet supplying table is attached to the sheet discharging table. Then, printing to the other surfaces of the printing sheets is started. In this way, printing of the printing sheets can be performed successively from one surface to the other without changing the printed sheets stacked on the cassette upside-down.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a front view of a stencil printing machine of one embodiment of the present invention;
FIG. 2
is a front view of a sheet supplying device and a sheet discharging device of the embodiment;
FIG. 3
is a vertical sectional view of the sheet supplying device and the sheet discharging device seen from a right side of the embodiment, namely a sectional view taken along a line III—III of FIG.
4
.
FIG. 4
is a horizontal sectional view of a cassette and side plates of the embodiment, namely a sectional view taken along a line IV—IV of
FIG. 3
; and
FIG. 5
is a schematic view illustrating a conventional stencil printing machine.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will be explained referring to
FIGS. 1
to
4
. This embodiment relates to a stencil printing machine as an image forming machine.
Referring to
FIG. 1
, the entire constitution of the stencil printing machine will be explained. A cylindrical paper drum
1
as a pressing roller is rotatable around an axis
2
. A holding claw
3
is attached to an outer circumferential surface of the paper drum
1
for holding a leading end of a printing sheet. A recess
6
is formed in a part of the outer circumferential surface of the paper drum
1
for avoiding interference with a clamping device
5
of a printing drum
4
, which will be explained later. Rotational frequency detecting means
7
is situated adjacent to the axis
2
.
Four cylindrical printing drums
4
are situated around the paper drum
1
. The four printing drums
4
are arranged to be spaced apart at a predetermined angular interval in a rotational direction of the paper drum
1
. The diameter of the printing drum
4
is approximately identical to that of the paper drum
1
. An axis of the printing drum
4
is parallel to that of the paper drum
1
. The printing drums
4
are each arranged to substantially contact the outer circumferential surface of the paper drum
1
.
The printing drums
4
are rotatable around axes thereof An ink permeable area is formed in a circumferential wall of the printing drum
4
. Inside the printing drum
4
, an ink supplying means
8
is situated for supplying ink to an inner surface of the circumferential wall. A clamping device
5
is attached to an outer surface of the circumferential wall of the printing drum
4
for holding a leading end of a stencil sheet. The stencil sheet is wound around the printing drum
4
with the leading end held by the clamping device
5
.
The printing drums
4
and the paper drum
1
are rotated by a common driving means in synchronization with each other. Rotational direction of the printing drum
4
is opposite to that of the paper drum
1
. During rotation, the clamping device
5
of the printing drum
4
does not contact the outer circumferential surface of the paper drum
1
since it meets the recess
6
of the paper drum
1
. Rotational speed of the printing drum
4
and the paper drum
1
determines printing speed. The printing speed, namely the rotational speed of the printing drum
4
and the paper drum
1
, can be selected for setting from predetermined plural choices.
The four printing drums
4
perform printing with ink colors of cyan, magenta, yellow and black, respectively. The stencil sheets perforated according to the ink colors are wrapped around the outer circumferential surfaces of the printing drums
4
, respectively. That is, an original image of full color is separated into four images of different colors. And, the four stencil sheets are perforated according to the four images of different colors, and the perforated stencil sheets are attached to the printing drums
4
, respectively. The paper drum
1
holds a printing sheet
9
with the holding claw
3
and conveys it along the outer circumferential surface thereof The printing sheet
9
is overprinted by the stencil sheet of each color while being pinched successively between the paper drum
1
and each of the printing drums
4
. Thus, the original image of full color is formed on the printing sheet
9
. Of course, multicolor printing can be performed.
As illustrated in
FIG. 1
, on a discharging side of the paper drum
1
, a paper discharging claw
10
is situated adjacent to the outer
10
circumferential surface of the paper drum
1
. The paper discharging claw
10
peels the printing sheet
9
from the paper drum
1
.
As illustrated in
FIG. 1
, a pinch roller
11
is disposed adjacent to the paper drum
1
. The pinch roller
11
includes two pairs of rollers contacting both side edges of the printing sheet
9
in a width direction thereof, respectively. Since the both side edges of the printing sheet
9
have no images printed thereon, the pinch roller
11
does not contact the printed image.
As illustrated in
FIG. 1
, a discharging roller
12
is situated below a forward side of the pinch roller
11
in a conveying direction of the printing sheet
9
. The discharging roller
12
contacts a bottom surface of the printing sheet
9
. The discharging roller
12
in the present invention is driven by the driving means of the printing drums
4
and the paper drum
1
.
As illustrated in
FIG. 1
, a conveying mechanism
13
is situated adjacent to the discharging roller
12
. The conveying mechanism
13
is continuously operated during printing. The conveying mechanism
13
transfers the printing sheet
9
conveyed by the pinch roller
11
and the discharging roller
12
into a sheet discharging table, which will be explained later, at a speed required for efficient sheet-discharging. The conveying mechanism
13
in the present embodiment includes two belts
15
connecting pulleys
14
and suction means
16
situated below the belts
15
. The suction means
16
holds the printing sheet
9
on the belts
15
. The conveying mechanism
13
may be driven by the driving means of the printing drum
4
, the paper drum
1
, and the discharging roller
12
, or may be driven by other driving source.
As illustrated in
FIG. 1
, a sheet throwing stand
17
is attached to an end of the conveying mechanism
13
. The sheet throwing stand
17
has an upward slope ascending in the conveying direction of the printing sheet
9
for assisting the conveyed printing sheet
9
to be thrown out.
As illustrated in
FIG. 1
, a sheet supplying table
20
and the sheet discharging table
21
are situated adjacent to the conveying mechanism
13
in a throwing direction of the printing sheet
9
. Constitution and operation of the sheet supplying table
20
and the sheet discharging table
21
will be explained referring to
FIGS. 2
to
4
.
FIG. 3
is a sectional view of the sheet supplying table
20
and the sheet discharging table
21
. This is taken along a face perpendicular to the sheet conveying direction or a sheet discharging direction. A pair of frames
22
is situated parallel to the sheet conveying direction and the sheet discharging direction at a predetermined distance therebetween. A motor
23
is situated between the pair of the frames
22
as a driving source for a driving mechanism, and attached to a not-shown frame. A main shaft
24
is rotatably situated between the pair of the frames
22
. A driven gear
25
is attached to an approximately center portion of the main shaft
24
. Two pinions
26
are attached to both ends of the main shaft
24
adjacent to inner surfaces of the frames
22
, respectively. A driving gear
27
attached to a driving shaft of the motor
23
engages the driven gear
25
. When the motor
23
is energized, the main shaft
24
is rotated.
Each of the frames
22
includes vertical guiding grooves
28
,
29
formed therein. The sheet supplying table
20
is vertically movably mounted on the lower guiding grooves
29
,
29
with guiding rollers
30
,
30
. A rack
31
is formed in the sheet supplying table
20
, and the rack
31
engages the pinion
26
on the main shaft
24
. Further, the sheet discharging table
21
is vertically movably mounted on the upper guiding grooves
28
,
28
with guiding rollers
32
,
32
. A rack
33
is formed in the sheet discharging table
21
, and the rack
33
engages the pinion
26
on the main shaft
4
. Accordingly, when the motor
23
is energized, the pinion
26
is rotated to move the sheet supplying table
20
and the sheet discharging table
21
vertically in directions opposite to each other.
Length and position of the guiding grooves
28
,
29
are so arranged that, when the sheet supplying table
20
with the maximum number of the printing sheets stacked thereon is located most distant from the sheet discharging table
21
, the sheet discharging table
21
is situated to the best position for receiving the first printing sheet as printed and discharged. Further, when the sheet discharging table
21
with the maximum number of the printing sheets stacked thereon is located most closest to the sheet supplying table
20
, the sheet supplying table
20
is situated to the best position for supplying the last printing sheet.
Sheet cassettes
40
(hereinafter referred to as “a cassette
40
”) are mounted on the sheet supplying table
20
and the sheet discharging table
21
, and attached thereto. This cassette
40
is adaptable to both the sheet supplying table
20
and the sheet discharging table
21
. As illustrated in
FIGS. 3 and 4
, the cassette
40
includes three members of box-shape, i.e. a rectangular center portion
41
and two side portions
42
,
42
. As illustrated in
FIG. 4
, a recess
43
is formed in an approximately center portion of the side portion
42
. A connecting rod
44
is attached to a front face of the side portion
42
for connecting therewith the sheet supplying table
20
or the sheet discharging table
21
. A circumferential groove
45
is formed on a front end of the connecting rod
44
. The side portion
42
is rotatably attached to the center portion
41
with a rotational axis
46
. A spring
47
fitted on the rotational axis
46
is hooked at an axis
48
attached to the side portion
42
, thereby urging the center portion
41
downwards relative to the side portion
42
. Accordingly, when the cassette
40
is not maintained unchanged in an outer shape thereof by any means, like the cassette
40
mounted on the sheet discharging table
21
illustrated in
FIG. 3
, the cassette
40
shows a concave form with the center thereof projecting downwards. Further, like the cassette
40
mounted on the sheet supplying table
20
illustrated in
FIG. 3
, when the cassette
40
is not allowed to deform while being held with both side edges thereof by retaining members
49
,
49
, the cassette
40
shows a flat form wherein the center portion
41
and the side portions
42
,
42
are approximately in the same surface.
An outer form and dimensions of the cassette
40
is so designed that the printing sheet can be stably stacked thereon during printing by the image forming machine. Further, the cassette is such that it can be held stable in shape when the cassette with printing sheets stacked thereon is attached to or detached from the sheet supplying table and the sheet discharging table, and when the cassette detached from the sheet supplying table or the sheet discharging table is carried by hands.
As illustrated in
FIGS. 1 and 3
, a collision plate
50
is attached to the rear of an upside of the cassette
40
. The collision plate
50
is movable back and forth in the discharging direction of the printing sheet
9
.
As illustrated in
FIG. 2
, a locking device is provided to each of the sheet supplying table
20
and the sheet discharging table
21
for fixing the connecting rod
44
attached to the front part of the cassette
40
. Constitution of the locking device will be explained referring to the sheet supplying table
20
as an example. A connecting member
51
is attached to each of both side portions of the front of the sheet supplying table
20
. The connecting member
51
has a hole formed therein for receiving the connecting rod
44
of the cassette
40
. A lever
52
is disposed adjacent to the connecting member
51
and pivotally attached to the sheet supplying table
20
. Actually, the center of the lever
52
is pivotally attached to the sheet supplying table
20
by an axis. A front end of the lever
52
can be entered and go out of the hole of the connecting member
51
. When the end enters the hole, this engages the circumferential groove
45
of the connecting rod
44
inserted in the hole, thereby locking the cassette
40
. A spring
53
is connected to the rear of the lever
52
, thereby urging the lever
52
to move so that the front end is projected inside the hole. A solenoid
54
is attached to the front of the sheet supplying table
20
. The solenoid
54
has an operating axis downwards. The operating axis of the solenoid
54
is connected to the rear of the lever
52
. When the rear of the lever
52
is lifted up by energizing the solenoid
54
, the front end of the lever
52
moves out of the hole, thereby disengaging the connecting rod
44
from the lever
52
.
As described above, the locking device for fixing the cassette
40
is also provided to the sheet discharging table
21
. Constitution and operation thereof is identical to that of the sheet supplying table
20
.
As illustrated in FIGS,
1
and
2
, a sheet supplying roller
60
is situated adjacent to the sheet supplying table
20
in the present machine. The sheet supplying roller
60
includes two rollers. The two rollers are rotatably supported on a common supporting plate
61
. One roller is a conveying roller
62
situated to one side of the supporting plate near the paper drum. An axis
63
of the conveying roller is attached to a main frame of the present machine. The other roller is a fetching roller
64
situated to the other side of the supporting plate distant from the paper drum. The fetching roller
64
is vertically movable around the axis
63
within a predetermined vertical range. The fetching roller
64
is kept to be slightly lifted up by the printing sheets
9
arranged at a supplying position. In this state, if the sheet supplying roller
60
is driven, a top printing sheet is fed out.
A switch
70
as a sensor is situated above the sheet supplying roller
60
. Height of the printing sheets
9
stacked on the sheet supplying table decreases as the printing sheets
9
are fed out one by one. The fetching roller
64
moves vertically downwardly around the axis
63
. The sheet supplying roller
60
leaves the switch
70
, thereby allowing it to be turned off. A control means not shown here energizes the motor
23
to move the sheet supplying table
20
vertically. The uppermost printing sheet
9
on the sheet supplying table comes to the sheet supplying position, thereby lifting up the sheet supplying roller
60
. The sheet supplying roller
60
pushes up the switch
70
to be turned on while being lifted up. The control means receives a signal from the switch to stop the motor
23
.
As illustrated in
FIGS. 2
to
4
, a pair of side plates
75
,
75
is disposed parallel to the sheet supplying and discharging directions on two sides of the cassettes
40
mounted on the sheet supplying table and the sheet discharging table, respectively. The side plate
75
is detachably attached to a frame of the present machine. The side plate
75
is situated in the recess
43
of the cassette
40
, and can be detached therefrom when the cassette
40
is attached to or detached from the sheet supplying table
20
or the sheet discharging table
21
. The side plate
75
is common to the sheet supplying table
20
and the sheet discharging table
21
. That is, the side plates
75
guide two side edges of the printing sheet
9
supplied from the cassette
40
at the sheet supplying table
20
, and also guide two side edges of the printing sheet
9
discharged onto the cassette
40
at the sheet discharging table
21
.
Both sides printing in the present stencil printing machine will be explained.
Many printing sheets
9
are stacked on the cassette
40
, and the cassette
40
is mounted on the lower sheet supplying table
20
. The connecting rods
44
attached to the front of the cassette
40
are inserted into the holes of the connecting member
51
. The front ends of the lever
52
engage the circumferential grooves
45
of the connecting rods
44
, so that the cassette
40
is fixed to the sheet supplying table
20
. Then, since the both side edges of the cassette
40
are held by the retaining members
49
,
49
, the cassette
40
is fixed to the sheet supplying table
20
as it shows a flat form wherein the center portion
41
and the side portions
42
,
42
are approximately in the same surface.
An empty cassette
40
is attached to the sheet discharging table
21
. The cassette
40
shows a concave form directing downwards since the sheet discharging table has no holding means such as the retaining member
49
formed at the sheet supplying table
20
.
A first process of the both sides printing is started. In this process, the printing sheet is printed on one surface thereof The one surface of the printing sheet faces downward in the printing sheet stacked on the sheet supplying table
20
.
An uppermost printing sheet
9
is took out by the sheet supplying roller
60
from among the printing sheets
9
stacked on the sheet supplying table
20
, and then conveyed to the printing drum
4
and the paper drum
1
. Then, the printing sheet
9
is held by the holding claw
3
by the leading end thereof The printing sheet
9
is conveyed along the outer circumferential surface of the paper drum
1
upon rotation of the paper drum
1
. Four images of different four colors are successively printed on the printing sheet
9
as the printing sheet is conveyed while being pinched between the four printing drums
4
and the paper drum
1
.
After that, the printing sheet
9
is peeled off from the paper drum
1
by the pinch roller
11
and the paper discharging claw
10
, and then conveyed to the discharging roller
12
. The conveying mechanism
13
further conveys the printing sheet
9
, thereby throwing the printing sheet from the sheet throwing stand
17
. The printing sheet
9
collides with the collision plate
50
, and drops onto the sheet discharging table
21
.
The printing sheet
9
printed in the first process enters the cassette
40
at the sheet discharging table
21
with the one surface thereof facing upward. The printing sheet
9
with ink adhered to the upper surface thereof shows a convex form projecting upwards as illustrated by an imaginary line in FIG.
3
. The cassette
40
at the sheet discharging table
21
has the form opposite to that of the printing sheet as printed on the upper surface thereof. Therefore, deformation of the printing sheet can be corrected by stacking the printing sheet on the cassette at the sheet discharging table.
As printing proceeds, height of the printing sheets
9
stacked on the sheet supplying table
20
decreases. The printing sheets
9
as printed are successively stacked on the sheet discharging table, and height thereof increases. The control means energizes the motor
23
to move the sheet supplying table
20
upwards according to supplying of the printing sheets
9
. That movement allows a mechanism to drive the sheet discharging table
21
downward according to receiving of the printing sheets
9
as printed.
That is, since the sheet supplying table
20
and the sheet discharging table
21
are moved together by combination of the racks
31
,
33
and the pinion
26
, the tables
20
,
21
move upwards and downwards, respectively, in the same distance. And, during printing, the printing sheets
9
just transfer to the sheet discharging table
21
from the sheet supplying table
21
, thereby maintaining total weights thereof. Accordingly, the driving source can be common to the sheet supplying side and the sheet discharging side. Further, it is not necessary to detect the printing sheets
9
as discharged for controlling movement of the sheet discharging table
21
. Just controlling the sheet supplying side enables the uppermost printing sheet
9
on the sheet discharging side to be kept in a constant position, thereby allowing the printing sheet as discharged to properly enter the cassette
40
at the sheet discharging table
21
.
Upon completion of the first process of printing for all of the printing sheets
9
, after the side plates
75
are removed, the empty cassette
40
at the sheet supplying table
20
and the cassette
40
at the sheet discharging table
21
are detached. The cassette
40
having printed printing sheets
9
stacked thereon is attached to the sheet supplying table
20
. The empty cassette
40
at the sheet supplying table
20
is attached to the sheet discharging table
21
. During such operation, the printing sheets
9
stacked on the cassette
40
need not be touched. It is not necessary for the printed sheets to be inverted and replaced on the sheet supplying table as is usual in conventional art. The printing sheet
9
is stacked on the cassette
40
with the printed surface facing upward. Just attaching the cassette
40
to the sheet supplying table
20
allows the printing sheet to be printed on the other surface thereof
A second process of the printing is started. In this process, the printing sheet
9
is printed on the other surface thereof. The other surface faces downward in the printing sheet
9
on the cassette
40
at the sheet supplying table
20
.
In the stencil printing machine of the present embodiment, the driving mechanism for moving the sheet supplying table
20
and the sheet discharging table
21
is composed of the racks
31
,
33
and the pinion
26
driven by the motor
23
. Driving force transmission means such as a belt or a chain may be used instead.
The stencil printing machine of the present embodiment as described above includes the rigid paper drum
1
and the four printing drums
4
; however, constitution for enabling printing in the present invention is not restricted to that of the embodiment. For example, the present invention may be adapted to a stencil printing machine comprising one paper drum and one printing drum. Further, the present invention may be adapted to a stencil printing machine comprising a vertically movable pressing roller situated adjacent to the rotating printing drum. In such a machine, a printing sheet is supplied between the printing drum and the pressing roller, and pressed against the rotating printing drum by moving the pressing roller upwards, thereby conducting printing. More further, the present invention may be adapted to a stencil printing machine comprising a printing drum having a deformable circumferential wall, means for supplying ink to an inner surface of the circumferential wall, and pressing means situated inside the circumferential wall for pressing the circumferential wall. In this machine, an opposing roller is situated to a predetermined position adjacent to the printing drum. In such a machine, a printing sheet is supplied between the printing drum and the opposing roller, and pressing means presses the circumferential wall of the printing drum to be deformed outwardly, so that the printing sheet is pinched therebetween, thereby conducting printing.
Additionally, a mechanism for image forming in the present invention is not restricted to that for printing. The present invention may be adapted to any image forming machine of other principles. However, it is necessary that sheet supplying and discharging directions be opposite to each other, and that the printed sheet be changed upside-down when being discharged.
In the image forming machine of the present invention, the sheet supplying table and the sheet discharging table are disposed vertically relative to each other, and moved together by the common driving mechanism. Accordingly, the constitution of the machine is simple, and sheet discharging can be properly conducted by associated movement of the sheet supplying and discharging tables. Further, if the exchangeable cassettes are provided to the sheet supplying table and the sheet discharging table, when both sides printing is conducted, it is only necessary that the cassettes be changed without inverting the printing sheets. That means handling of the printing sheets is simplified.
Claims
- 1. An image forming machine, comprising:an image forming section for receiving a sheet supplied in a supplying direction, printing an image on said sheet, and discharging said printed sheet in a discharging direction opposite to said supplying direction while changing said sheet upside-down, a sheet supplying table situated adjacent to said image forming section, said sheet supplying table stacking said sheet to be supplied to said image forming section, a sheet discharging table situated adjacent to said image forming section and disposed vertically relative to said sheet supplying table, said sheet discharging table stacking said sheet having said image printed thereon and discharged from said image forming section, and a driving mechanism attached to said sheet supplying table and said sheet discharging table for vertically moving said sheet supplying table and said sheet discharging table in directions opposite to each other.
- 2. An image forming machine as claimed in claim 1, further comprising sheet cassettes detachably attached to said sheet supplying table and said sheet discharging table for stacking said sheet thereon.
- 3. An image forming machine as claimed in claim 2, wherein said sheet cassette at said sheet discharging table and said sheet cassette at said sheet supplying table are exchangeable so that after said sheet supplied from said sheet cassette at said sheet supplying table is printed on one surface thereof by said image forming section and discharged to said sheet cassette at said sheet discharging table, said sheet cassettes at said sheet discharging table and said sheet supplying table are exchanged to allow said sheets in said cassette at said sheet supplying table to be supplied to said image forming section for printing an image on the other surface thereof.
- 4. An image forming machine as claimed in claim 2, wherein said sheet cassette is variable in shape between a flat form and a concave form directing downwards in a section perpendicular to said discharging direction, said sheet supplying table holding said sheet cassette in said flat form, and said sheet discharging table holding said sheet cassette in said concave form.
- 5. An image forming machine as claimed in claim 2, further comprising a pair of side plates disposed parallel to said supplying and discharging directions of said sheet on two sides of said sheet cassettes at said sheet supplying table and said sheet discharging table, respectively, said pair of side plates guiding side edges of said sheet stacked on said sheet cassette.
- 6. An image forming machine as claimed in claim 1, wherein said driving mechanism comprises a first rack fixed to said sheet supplying table, a second rack fixed to said sheet discharging table, a pinion engaging said first rack and the second rack, and a motor for driving said pinion.
- 7. An image forming machine as claimed in claim 1, further comprising a sensor for detecting said sheet on said sheet supplying table in a sheet supplying position, and control means for controlling said sheet supplying table so that said sheet supplying table moves upwards until said sensor detects said sheet on said sheet supplying table in said sheet supplying position.
- 8. An image forming machine as claimed in claim 7, further comprising a sheet supplying roller situated vertically movably within a vertical range, said sensor being situated above said sheet supplying roller and detecting an upward movement of said sheet supplying roller when said sheet comes in said sheet supplying position.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-304176 |
Oct 1998 |
JP |
|
US Referenced Citations (6)