Information
-
Patent Grant
-
6669189
-
Patent Number
6,669,189
-
Date Filed
Friday, January 25, 200222 years ago
-
Date Issued
Tuesday, December 30, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Walsh; Donald P.
- Joerger; Kaitlin
Agents
- Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
-
CPC
-
US Classifications
Field of Search
US
- 399 364
- 399 388
- 399 390
- 399 394
- 399 395
- 399 396
- 399 401
- 399 402
- 271 186
-
International Classifications
-
Abstract
An image forming apparatus of the present invention includes a conveyance path extending from a sheet tray to an image forming section. A switchback path with a reversing device is connected to the intermediate portion of the conveyance path for switching back a sheet thereon. The switchback path reduces an interval between consecutive sheets being conveyed in the apparatus for thereby enhancing the productivity of image formation. In addition, the switchback path switches back a sheet being conveyed via a refeed path and the above conveyance path in a duplex print mode, thereby obviating the need of an exclusive switchback path for the duplex print mode. The apparatus is reduced in thickness despite the presence of the switchback path.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus and more particularly to an image forming apparatus of the type operable in a duplex print mode and capable of stacking prints face down in order of page.
2. Description of the Background Art
An electrophotographic copier, printer, facsimile apparatus or similar image forming apparatus of the type described usually includes a first path and a second path arranged at the sheet discharge side of an image forming section
102
. The first path conveys a sheet carrying an image thereon toward a sheet outlet section while the second path conveys it in a duplex print mode or to reverse the sheet and then discharge it. A path selector is located at the position where the first and second paths part from each other. The path selector selectively steers a sheet coming out of the image forming section to the first path or the second path.
The second path merges into a switchback path that reverses the sheet by switching it back. A reverse roller is positioned on the switchback pack and movable into and out of contact with the sheet (up-and-down direction). In the duplex print mode, the refeed path again conveys the sheet switched back by the switchback path toward the image forming section. The reverse discharge path discharges the above sheet to a sheet outlet section face down in order of page. The refeed path is positioned below the switchback path. A path selector is located at a position where the refeed path and reverse discharge path part from each other. This path selector selectively steers the sheet switched back by the switchback path to the refeed path or the reverse discharge path.
To reverse the sheet carrying an image on one side thereof and then discharge it, the path selector again delivers the sheet to the second path. In this case, the path selector is so positioned as to steer the sheet driven out of the switchback path to the reverse discharge path. As a result, the sheet is driven out to the sheet outlet section face down via the reverse discharge path.
The conventional image forming apparatus described above has undesirably great height because of the switch back path and refeed path arranged one above the other.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 6-236086 and Japanese Patent No. 2,941,021.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus capable of enhancing the productivity of image formation in a repeat print mode by reducing the interval between consecutive sheets at an image forming section, and obviating the need for an exclusive switchback path for a duplex print mode.
An image forming apparatus of the present invention includes a sheet tray loaded with a stack of sheets. A separating and feeding device feeds one sheet from the sheet tray while separating it from the other sheets. An image forming section forms an image on the sheet fed by the separating and feeding device. A conveyance path conveys the sheet from the sheet tray to the image forming section. A switchback path is connected to the intermediate portion of the conveyance path for receiving the sheet being conveyed along the conveyance path. A reversing device is selectively switchable to a first position for switching back the preceding sheet introduced into the switchback path to thereby feed it to the conveyance path or a second position for allowing the preceding sheet being fed from the switchback path and the following sheet to be introduced into the switchback path after the preceding sheet to at least partly overlap each other. A refeed path is connected to the sheet outlet side of the image forming section and part of the conveyance path upstream of the switchback path. A conveying device conveys the sheet driven into the refeed path to the conveyance path.
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 view showing a conventional image forming apparatus;
FIG. 2
is a view showing an image forming apparatus embodying the present invention;
FIG. 3
is an enlarged front view of a mechanism arranged along a conveyance path in the illustrative embodiment;
FIG. 4
is an isometric view of an inlet roller and a path selector;
FIG. 5A
shows reversing means included in the illustrative embodiment in an open position;
FIG. 5B
shows the reversing means in a closed position;
FIG. 6
is an isometric view showing a roller and another path selector also included in the illustrative embodiment;
FIGS. 7 and 8
are views showing how consecutive sheets are sequentially fed to an image forming section included in the illustrative embodiment;
FIG. 9
is a view showing how a sheet is fed in a duplex print mode;
FIG. 10
shows the order of sheet feed and the interval between sheets, as seen at the junction of the conveyance path and a refeed path in a two-sheet interleaf, duplex print mode;
FIG. 11
is a view how a sheet is fed in a reverse discharge mode;
FIG. 12
is a diagram showing the feed of sheets in a repeat print mode;
FIG. 13
is a view showing the feed of sheets in the reverse discharge mode unique to an alternative embodiment of the present invention;
FIGS. 14 and 15
are views demonstrating sheet feed in the reverse discharge mode particular to the embodiment shown in
FIG. 13
;
FIG. 16
is a view showing a switchback mechanism representative another alternative embodiment of the present invention; and
FIG. 17
is a view showing a switchback mechanism representative of a further alternative embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
To better understand the present invention, brief reference will be made to a conventional image forming apparatus, shown in FIG.
1
. The image forming apparatus to be described is of the type operable in a duplex print mode and capable of discharging prints face down in order of page. As shown, the image forming apparatus includes an image forming section
102
including a photoconductive drum
100
and a developing device
101
. The image forming section
102
prints an image on a sheet.
A first path
104
and a second path
105
are arranged at the sheet discharge side of the image forming section
102
. The first path
104
conveys the sheet carrying an image thereon toward a sheet outlet section
103
while the second path
105
conveys it in the duplex print mode or to reverse the sheet and then discharge it. A path selector
106
is located at the position where the first path
104
and second path
105
part from each other. The path selector
106
selectively steers the sheet coming out of the image forming section
102
to the first path
104
or the second path
105
.
The second path
105
merges into a switchback path
107
that reverses the sheet by switching it back. A reverse roller
108
is positioned on the switchback pack
107
and movable into and out of contact with the sheet (up-and-down direction).
A refeed path
109
and a reverse discharge path
110
are arranged downstream of the switchback path
107
in the direction of sheet conveyance. In the duplex print mode, the refeed path
109
again conveys the sheet switched back by the switchback path
107
toward the image forming section
102
. The reverse discharge path
110
reverses the above sheet and then discharges it to the sheet outlet section
103
face down in order of page. The refeed path
109
is positioned below the switchback path
107
. A path selector
111
is located at a position where the refeed path
109
and reverse discharge path
110
part from each other. The path selector
111
selectively steers the sheet switched back by the switchback path
107
to the refeed path
109
or the reverse discharge path
110
.
In a duplex print mode, the path selector
106
is so positioned as to steer a sheet carrying an image one side thereof toward the second path
105
. In this condition, the sheet is conveyed to the switchback path
107
via the second path
105
. The roller
108
switches back the sheet out of the switchback path
107
. At this instant, the path selector
111
is so positioned as to steer the sheet coming cut of the switchback path
107
to the refeed path
109
, so that the sheet is again conveyed to the image forming section
102
. After an image has been formed on the other side of the sheet, the sheet is driven out to the sheet outlet section
103
via the first path
104
.
To reverse the sheet carrying an image on one side thereof and then discharge it, the path selector
106
again delivers the sheet to the second path
105
. In this case, the path selector
111
is so positioned as to steer the sheet driven out of the switchback path
107
by the roller
108
to the reverse discharge path
110
. As a result, the sheet is driven out to the sheet outlet section
103
face down via the reverse discharge path
110
.
The conventional image forming apparatus described above has great height because of the switch back path
107
and refeed path
109
arranged one above the other, as stated earlier.
Referring to
FIGS. 2 through 12
, an image forming apparatus embodying the present invention will be described. As shown in
FIG. 2
, the image forming apparatus includes a sheet tray
1
loaded with a stack of sheets. An image forming section
2
forms an image on one side of a sheet fed from the sheet tray
1
or the other side of a sheet carrying an image on one side thereof and again fed thereto. A sheet outlet section
3
drives the sheet coming out of the image forming section
2
out of the apparatus. A plurality of paths are arranged inside of the apparatus for conveying a sheet between the sheet tray
1
, the image forming section
2
, and the sheet outlet section
3
.
Specifically, a conveyance path
4
extends from the sheet tray
1
to the image forming section
2
and branches into a switchback path
6
at a point
5
. The switchback path
6
switches back the sheet being conveyed along the conveyance path
4
. More specifically, the sheet conveyed along the conveyance path
4
is steered into the switchback path
6
via the point
5
and then again returned to the path
4
by reversing means, which will be described later specifically.
A roller pair
7
is positioned upstream of the point
5
of the path
4
in the direction of sheet conveyance and rotated by a motor not shown. An inlet roller
8
, an inlet sensor
9
and a path selector
10
are located around the point
5
. A motor, not shown, causes the inlet roller
8
to rotate for introducing the sheet into the switchback path
6
. The inlet sensor
9
is positioned upstream of the inlet roller
8
in the direction of sheet conveyance for sensing the leading edge of the sheet. The path selector
10
steers the sheet from the conveyance path
4
to the switchback path
6
or steers it from the path
6
to the path
4
. In the illustrative embodiment, the sheet sensor
9
is implemented as a reflection type optical sensor made up of a light emitting device and a light-sensitive device, although not shown specifically.
An intermediate roller pair
11
is positioned downstream of the point
5
in the direction of sheet conveyance. A motor, not shown, drives the roller pair
11
for conveying the sheet coming out of the switchback path
6
toward the image forming section
2
. A registration sensor
12
and a registration roller pair
13
are positioned downstream of the roller pair
11
. The registration roller pair
13
starts conveying the sheet sensed by the registration sensor
12
to the image forming section
2
in synchronism with the operation of the section
12
. The registration sensor
12
is also a reflection type optical sensor.
A reversing device, or the previously mentioned reversing means,
14
and a reversal sensor
15
are positioned on the switchback path
6
. The reversing device
14
selectively takes a closed or feed position or an open position. In the closed position, the reversing device
4
again feeds the sheet from the switchback path
6
to the conveyance path
4
. In the open position, the reversing device
14
allows the sheet being again fed to the conveyance path
4
and the subsequent sheet being introduced into the switchback path
6
to at least partly overlap each other. The reversal sensor
15
is responsive to the leading edge of the sheet being introduced into the switchback path
6
and is also implemented by a reflection type optical sensor.
FIGS. 5A and 5B
show the reversing device
14
specifically. As shown, the reversing device
14
is made up of a reverse roller
16
and a driven roller
17
. A stepping motor, not shown, causes the reverse roller
16
to intermittently rotate. The driven roller
17
contacts the reverse roller
16
with the intermediary of the switchback path
6
and is driven by the reverse roller
16
. Part of the circumference of the reverse roller
16
is removed, forming a flat face
16
a
. As shown in
FIG. 5A
, when the flat face
16
a
faces the driven roller
17
, the former and latter form a gap therebetween.
As shown in
FIG. 5
, the reverse roller
16
is rotated in a direction indicated by an arrow in contact with the driven roller
17
, causing the driven roller
17
to rotate. In this condition, the reverse roller
16
and driven roller
17
convey a sheet toward the conveyance path
4
. In the condition shown in
FIG. 5
, a sheet is introduced into the switchback path
6
via the gap between the reverse roller
16
and the driven roller
17
. It should be noted that a sheet moves at a higher speed when fed from the conveyance path
4
to the switchback path
6
than when fed from the latter to the former.
Referring again to
FIG. 2
, a pickup roller
18
pays out the sheets from the sheet tray one by one while a reverse roller
19
separates one sheet being paid out from the other sheets. The pickup roller
18
and reverse roller
19
constitute a separating and feeding device
20
.
The image forming section
2
includes a photoconductive drum
21
. A charger
22
uniformly charges the surface of the drum
21
. A digital, optical writing unit or means
23
optically writes a latent image on the charged surface of the drum
21
. A developing unit
24
develops the latent image with toner to thereby form a corresponding toner image. An image transferring device transfers the toner image from the drum
21
to the sheet. A drum cleaner
26
removes toner left on the drum
21
after the image transfer. A fixing device
27
fixes the toner image on the sheet. The image forming section
2
executes a digital, electrophotographic image forming process.
As shown in
FIG. 3
, the path selector
10
located at the point
5
has a generally triangular contour including a first guide surface
10
a
, a second guide surface
10
b
, and a tip
10
c
with an acute angle between the first and second guide surfaces
10
b
. The first guide surface
10
a
guides the sheet being fed into the switchback path
6
while the second guide surface
10
b
guides the sheet being fed out of the switchback path
6
. The tip
10
c
races the switchback path
6
.
As shown in
FIG. 4
, a plurality of path selectors
10
each having the contour shown in
FIG. 3
are mounted on a shaft
28
, which adjoins and extends in parallel to a shaft
8
a
supporting the inlet roller
8
. The inlet roller
8
is also implemented as a plurality of rollers
8
, as illustrated. The shaft
28
is rotatably supported by bearings not shown. An arm
29
is connected at one end to one end of the shaft
28
. A spring
30
is anchored at one end to the other end of the arm
29
. A stop
31
restricts the rotation of the arm
29
being constantly biased downward by the spring
30
.
The shaft
28
is rotatable to selectively move the path selectors
10
to a first position indicated by a solid line in
FIG. 3
or a second position indicated by a phantom line in FIG.
3
. In the first position, the sheet introduced into the switchback path
6
angularly moves the path selectors
10
due to its own elasticity against the bias of the spring
30
and passes through the gap between the inlet rollers
8
and the first guide surfaces
10
a
of the path selectors
10
. In the second position, no sheets are present between the inlet rollers
8
and the first guides
10
a
of the path selectors
10
; the arm
29
abuts against the stop
31
due to the bias of the spring
30
with the tips
10
c
of the path selectors
10
being positioned radially inward of the circumferences of the inlet rollers
8
. Let the inlet rollers
8
and path selectors
10
be respectively represented by a single inlet roller
8
and a single selector
10
for simplicity hereinafter.
As shown in
FIG. 2
, a direct discharge path
32
extends between the sheet discharging side of the image forming section
2
and the sheet outlet section
3
. A refeed path
33
extends between the sheet discharging side of the image forming section
2
and part of the conveyance path
4
upstream of the point
5
in the direction of sheet conveyance. A path selector
34
is located at a point where the direct discharge path
32
and refeed path
33
part from each other at the sheet discharging side of the image forming section
2
. The path selector
34
selects either one of the direct discharge path
32
and refeed path
33
.
The refeed path includes a vertical portion
33
a
extending downward and a horizontal portion
33
b
extending from the lower end of the vertical portion
33
a
in substantially the horizontal direction The end of the horizontal portion
33
b
remote from the vertical portion
33
a
merges into the conveyance path
4
.
A reverse discharge path
35
branches from the refeed path
33
at the bent portion between the vertical portion
33
a
and the horizontal portion
33
b
. The reverse discharge path
35
is connected to the sheet outlet section
3
.
A refeed roller
36
is positioned on the horizontal portion
33
b
of the refeed path
33
. The refeed roller
36
plays the role of conveying means and reverse discharging means at the same time. Specifically, the refeed roller
36
is selectively rotatable in the forward direction for feeding the sheet out of the refeed path
33
to the conveyance path
4
in the duplex print mode (duplex-print feed state) or rotatable in the reverse direction for switching back the sheet toward the reverse discharge path
35
(reverse discharge state). More specifically, the refeed roller
36
is implemented by a plurality of roller pairs
37
each having a reversible drive roller and a driven roller movable into and out of contact with the drive roller, as illustrated. The drive rollers of the roller pairs
37
each can be driven independently of the others. The refeed roller
36
is capable of nipping the sheet on the horizontal path
33
b
to thereby interrupt conveyance and again driving it toward the conveyance path
4
at a suitable timing in response to, e.g., the output of a sheet sensor not shown.
A roller
38
and a path selector
39
are located at a position where the refeed path
33
merges into the reverse discharge path
33
. The roller
38
is rotated to convey the sheet from the vertical portion
33
a
to the horizontal portion
33
b
of the refeed path
33
. As shown in
FIG. 6
, the path selector
39
is also implemented as a plurality of path selectors
39
mounted on a shaft
40
, which adjoins and extends in parallel to a shaft
38
a
supporting the roller
38
. The roller
38
is also implemented as a plurality of rollers
38
. Each path selector
39
has a generally triangular contour including a first guide surface
39
a
for guiding the sheet being conveyed from the vertical portion
33
a
to the horizontal portion
33
b
, a second guide surface
39
b
for guiding the sheet being switched back toward the reverse discharge path
35
, and a tip
39
c
with an acute angle between the two guide surfaces
39
a
and
39
b
. An arm
41
is connected at one end to one end of the shaft
40
. A spring
42
is anchored at one end to the other end of the arm
41
. A stop
43
restricts the movement of the arm
41
being constantly biased downward by the spring
42
.
The shaft
40
is rotatable to selectively move the path selectors
39
to a first position or a second position. In the first position, the sheet advancing from the vertical portion
33
a
to the horizontal portion
33
b
angularly moves the path selectors
39
due to its own elasticity against the bias of the spring
42
and passes through the gap between the rollers
38
and the first guide surfaces
39
a
of the path selectors
39
. In the second position, no sheets are present between the rollers
38
and the first guides surface
39
a
of the path selectors
39
, as shown in
FIGS. 2 and 6
; the arm
41
abuts against the stop
43
due to the bias of the spring
42
with the tips
39
c
being positioned radially inward of the circumferences of the rollers
38
. In the second position, the tips
39
prevent the sheet switched back from entering the vertical path
33
a
while guiding it toward the reverse discharge path
35
. Again, let the rollers
38
and path selectors
39
be respectively represented by a single inlet roller
38
and a single selector
39
for simplicity hereinafter.
The sheet being switched back from the horizontal portion
33
b
to the reverse discharge path
35
and the sheet being transferred from the vertical portion
33
a
to the horizontal portion
33
b
can pass each other. More specifically, the horizontal portion
33
b
has a height great enough to allow two sheets to pass each other. In addition, assume that the refeed roller
36
, i.e., roller pairs
37
are held in the reverse discharge state for feeding the preceding sheet into the reverse discharge path
35
. Then, as soon as the following sheet enters the horizontal portion
33
b
, the driven rollers of the roller pairs
37
are released from the drive rollers to allow the sheet into the horizontal portion
33
b.
The sheet is conveyed along the refeed path
33
at a speed higher than the image forming process speed of the image forming section
2
. For example, while the process speed of the image forming section
2
is 330 mm/sec, the sheet is conveyed along the refeed path
33
at a speed of 560 mm/sec. This is also true with the conveyance of the sheet along the reverse discharge path
35
.
In the configuration described above, the separating and feeding device
20
feeds one sheet from the sheet tray
1
to the conveyance path
4
while separating it from the other sheets. As soon as the inlet sensor
9
located at the point
5
senses the leading edge of the sheet, the inlet roller
8
is caused to start rotating. Further, when the leading edge of the sheet abuts against the first guide surface
10
a
of the path selector
10
, which is held in the second position, the sheet raises the path selector
10
to the first position due to its own elasticity. The sheet then advances to the switchback path
6
via the gap between the first guide surface
10
a
and the inlet roller
8
. At this instant, the reversing device
14
is held in the open position shown in FIG.
5
A.
As the trailing edge of the sheet moves away from the gap between the first guide surface
10
a
and the inlet roller
8
, the path selector
10
automatically returns to the second position due to the bias of the spring
30
. In the second position, the tip
10
c
of the path selector
10
surely prevents, when the sheet is driven out of the switchback path
6
, the leading edge of the sheet from entering between the inlet roller
8
and the first guide surface
10
a
. This guarantees smooth feed of the sheet from the switchback path
6
toward the image forming section
2
.
To feed the sheet out of the switchback path
6
, the reverse roller
16
of the reversing device
14
is rotated counterclockwise, as viewed in
FIG. 5B
, causing the driven roller
17
to rotate. The reverse roller
16
and driven roller
17
therefore convey the sheet out of the switchback path
6
by nipping it. The intermediate roller pair
11
nips and conveys the leading edge of the sheet coming out of the switchback path
6
. At this time, the reversing device
14
is brought to the condition shown in
FIG. 5A
, releasing the sheet. In the position shown in
FIG. 5A
, the reversing device
14
allows the following sheet into the switchback path
6
.
The intermediate roller pair
11
conveys the sheet until the leading edge of the sheet abuts against the registration roller pair
13
. The registration roller pair
13
starts rotating at a preselected timing to convey the sheet to the image forming section
2
.
Reference will be made to
FIGS. 7 and 8
for describing the flow of consecutive sheets to occur in a repeat print mode As shown, as soon as the preceding sheet a is driven out of the switchback path
6
toward the conveyance path
4
, the following sheet b is conveyed toward the switchback path
6
. More specifically, the reversing device
15
first conveys the sheet a and then releases it, as shown in FIG.
5
A. Subsequently, the intermediate roller pair
11
conveys the sheet a toward the image forming section
2
. On the other hand, the roller pair
7
and inlet roller
8
sequentially convey the following sheet b, so that the sheet b enters the switchback path
6
via the reversing device
14
held in the position shown in FIG.
5
A. At this instant, the trailing edge portion of the preceding sheet a and that of the following sheet b (leading edge when switched back) momentarily overlap each other.
After the preceding sheet a has been fully fed out of the switchback path
6
, the following sheet b is fed out of the switchback path
6
at the time when the trailing edge of the sheet a and the leading edge of the sheet are spaced by an adequate short distance. This successfully enhances the productivity of image formation.
FIG. 12
is a diagram demonstrating the conveyance of the consecutive sheets a and b. As shown, the roller pair
7
and inlet roller
8
convey each of the sheets a and b from the sheet tray
1
to the stop position on the switchback path
6
at a speed of Va. Subsequently, the reverse roller
16
and intermediate roller pair
11
convey the sheet from the above stop position to the image forming section
2
at a speed of Vb equal to the image forming speed. The speed Va is selected to be higher than the speed Vb.
The flow of a sheet to occur in the duplex print mode will be described with reference to FIG.
9
. As shown, a sheet carrying an image on one side thereof (one-sided sheet hereinafter) is conveyed from the image forming section
2
to the refeed path
33
. The refeed roller
36
conveys the one-sided sheet straight to the path
4
. Subsequently, the one-sided sheet, like a sheet fed from the sheet tray
1
, is conveyed to the switchback path
6
and then switched back toward the image forming section
2
via the conveyance path
4
. The one-sided sheet has therefore been reversed when reaching the image forming section
2
. The image forming section
2
forms an image on the other side or reverse side of the one-sided sheet, producing a two-sided or duplex print.
As stated above, the illustrative embodiment switches back a sheet in the duplex print mode by using the switchback path
6
that is originally directed toward high productivity, thereby obviating the need for an exclusive path for the duplex print mode. The image forming apparatus is therefore reduced in height despite the presence of the switchback path
6
.
The illustrative embodiment executes so-called interleaf sheet feed, i.e., interleaves a new sheet and a one-sided sheet in the duplex print mode. More specifically, in the duplex print mode, a plurality of (e.g. two or three) new sheets are continuously fed from the sheet tray
1
to the image forming section
2
. The image forming section
2
prints images on one side of the consecutive sheets in preselected order of page (e.g. the first and third pages in the case of two sheets or the first, third and fifth pages in the case of three sheets). After the resulting first one-side sheet has been positioned in the horizontal portion
33
b
of the refeed path
33
, the refeed roller
36
refeeds the one-sided sheet to the conveyance path
4
at a preselected timing. Thereafter, the one-sided sheets and new sheets paid out from the sheet tray
1
are alternately fed to the path
4
. Two-sided sheets, or duplex prints, are sequentially driven out to the sheet outlet section
3
via the direct discharge path
32
.
The sheet is conveyed along the refeed path
33
at a speed higher than the process speed of the image forming section
2
, as stated earlier. Therefore, in the interleaf, duplex print mode, the sheet being conveyed along the refeed path
33
can be rapidly brought to the junction of the paths
33
and
4
. This successfully reduces the interval between the sheet fed from the sheet tray
1
and the one-sided sheet fed from the refeed path
33
to the path
4
and thereby enhances the productivity of image formation.
FIG. 10
shows the order of sheets being conveyed and the interval between the sheets, as seen at the junction of the paths
4
and
33
, on the assumption that two sheets are continuously fed from the sheet tray
1
in the interleave, duplex print mode. Numbers attached to the sheets indicate the order of feed from the sheet tray
1
while the word “front” attached to the numbers refers to a one-sided sheet. Further, T indicates a time interval between the time when the trailing edge of a sheet fed from the sheet tray
1
(e.g. sheet (
3
)) moves away from the junction of the paths
4
and
33
and the time when the leading edge of the sheet (
3
) “front” to again reach the above junction via the image forming section
2
and path
33
.
In the two-sheet interleaf moved, the time interval T is expressed as:
T
=(2
D+
3
X
)/
V
Eq. (1)
where D denotes the length of the sheet, X denotes the distance between sheets measured at the junction of the paths
4
and
33
, and V denotes a sheet speed also measured at the junction. It is to be noted that in the two-sheet interleaf mode, two sheets pass through the junction of the paths
4
and
33
during the period of time T.
Generally, in an n-sheet interleaf mode, the period of time T is expressed as:
T=[
2(
n−
1)
D
+(2
n
−1)
X]/V
Eq. (2)
In this connection, in a three-sheet interleaf mode, four sheets pass through the junction of the paths
4
and
33
during the period of time T.
When the period of time T increases, the distance X between sheets, of course, increases and lowers productivity. The illustrative embodiment enhances productivity by reducing the interval between sheets in the interleaf, duplex print mode, as will be described hereinafter. First, the sheet speed V included in the Eq. (1) or (2) may be increased to reduce the interval between sheets. This can be done if a sheet is conveyed along the refeed path
33
at a speed higher than the process speed of the image forming section
2
. Specifically, a control unit, not shown, included in the image forming apparatus stores a data table listing distances X and time intervals T in relation to sheet sizes and the number of sheets to be fed first. The control unit finds an adequate distance X and an adequate time interval T out of the data table and substitutes them for the Eq. (1) or (2) to thereby determine an adequate sheet speed V.
Second, a period of time necessary for a sheet to move from the switchback path
6
to the registration roller pair
13
may be reduced. More specifically, the duration of a stop of a sheet on the switchback path
6
maybe reduced to increase the sheet conveying speed from the path
6
to the registration roller pair
13
.
As for the sheet speed V or the duration of a stop, assume that a period of time necessary for a sheet to move from the image forming section
2
to the junction of the paths
4
and
33
is fixed. Then, the control unit subtracts the fixed period of time from the time interval T and then calculates a duration of a stop or a sheet speed V that allows a sheet to move from the switchback path
6
to the registration roller
13
within the remaining period of time.
FIG. 11
shows how a one-sided sheet is driven out to the sheet outlet section
3
after being reversed. As shown, a one-sided sheet is conveyed along the refeed path
33
to the horizontal portion
33
b
. Subsequently, the refeed roller
36
switches back the sheet to the sheet outlet section
3
via the reverse discharge path
35
. As a result, such sheets are sequentially stacked on the sheet outlet section
3
face down in order of page.
When the above one-sided sheet is about to reach the horizontal portion
33
b
, the path selector
39
is held at the second position. The sheet therefore moves the path selector
39
to the first position due to its own elasticity and then enters the horizontal portion
33
b
. As soon as
6
the trailing edge of the sheet moves away from the path selector
39
, the path selector
39
automatically restores the second position due to the bias of the spring
42
. Therefore, when the sheet is switched back toward the reverse discharge path
35
, the path selector
39
surely guides the sheet to the reverse discharge path
35
by preventing it from entering the vertical portion
33
a
and jamming the portion
33
a
. Further, the spring
42
is simpler than a solenoid or similar electronic actuator. In addition, the movement of the path selector
39
effected by the spring
42
is sure and adaptive to high-speed sheet feed.
The sheet switched back to the reverse discharge path
35
and a sheet advancing toward the horizontal portion
33
b
via the vertical portion
33
a
can pass each other, as stated earlier. Therefore, just after the leading edge of the preceding sheet moved away from the path selector
39
into the reverse discharge path
35
has been nipped by a roller pair located on the path
35
, the refeed roller
36
can be switched to its open position so as to allow the following sheet into the horizontal portion
36
. It follows that smooth reverse discharge is achievable despite the short distance between one-sided sheets.
Further, the one-sided sheet is conveyed along the reverse discharge path
35
at a speed higher than the process speed of the image forming section
2
, as also stated earlier. It is therefore possible to increase the distance between consecutive sheets sequentially conveyed along the reverse discharge path
35
to the sheet outlet section
3
. This facilitates punching, stapling or similar finishing that may be executed with the sheets stacked on the sheet outlet section
3
.
Referring to
FIGS. 13 through 15
, an alternative embodiment of the present invention will be described. In the alternative embodiment, as well as in the other alternative embodiments to be described later, structural elements identical with the structural elements of the previous embodiment are designated by identical reference numerals and will not be described specifically in order to avoid redundancy.
As shown in
FIGS. 13 through 15
, first reversible rollers
50
and
51
, a second reversible roller
52
and a reverse roller
53
are arranged in the horizontal portion
33
b
of the refeed path
33
. The first reversible rollers
50
and
51
constitute conveying means, reverse discharging means and refeed rollers at the same time. The second reversible roller
52
constitutes conveying means and reverse discharging means at the same time. The reverse roller
53
also plays the role of reverse discharging means. A trailing edge sensor
54
is positioned in the vertical portion
33
a
of the refeed path
33
in order to sense the trailing edge of a sheet. Further, the roller
38
and path selector
39
are positioned at the junction of the refeed path
33
and reverse discharging path
35
.
The reversible rollers
50
and
51
each are implemented as a drive roller connected to a stepping motor, DC servo motor or similar reversible motor, not shown, and a driven roller constantly held in contact with the drive roller. The rollers
50
and
51
each are selectively rotatable in the forward direction for conveying a sheet from the horizontal portion
33
b
to the conveyance path
4
or in the reverse direction for switching it back to the reverse discharge path
35
.
As shown in
FIG. 14
, the horizontal portion
33
b
includes a passing range X downstream of the junction of the refeed path
33
and reverse discharge path
35
. A preceding sheet A entering reverse discharge path
35
and a following sheet B entering the horizontal portion
33
b
pass each other in the range X. The passing range X varies in accordance with the size and speed of the sheets A and B and varies every moment in accordance with the positions of the sheets A and B being conveyed. The passing range X shown in
FIG. 14
is the maximum range.
The first reversible rollers
50
and
51
are located outside of the passing range X. This obviates an occurrence that the following sheet B reaches the rollers
50
and
51
when the rollers
50
and
51
are conveying the preceding sheet A toward the reverse discharge path
35
. More specifically, when the following sheet B reaches the rollers
50
and
51
, the preceding sheet A has already been released from the rollers
50
and
51
. The rollers SO and
51
can therefore rotate in the forward direction to convey the following sheet B entered the horizontal portion
33
b
to a preselected position downstream of the rollers
50
and
51
. The rollers
50
and
51
therefore do not have to be switched to the open position even when the two sheets A and B pass each other. That is, the rollers
50
and
51
should only be switched in the direction of rotation.
The second reversible roller
52
is identical in basic structure with the first reversible rollers
50
and
51
. The difference is that a driven roller forming part of the roller
52
is movable away from a drive roller forming the other part of the roller
52
. This is effected by a solenoid not shown. Further, the roller
52
lies or does not lie in the passing range, depending on the size of the sheet to be driven into the reverse discharge path
35
. When the preceding sheet A and following sheet B are to pass each other at the position of the roller
52
, the roller
52
is brought to its open position so as not to obstruct the pass.
The reverse roller
53
adjoins the junction of the horizontal portion
33
b
of the refeed path
33
and reverse discharge path
35
. The reverse roller
53
also has a drive roller and a driven roller and so rotates as to drive a sheet toward the reverse discharge path
35
. A solenoid, not shown, selectively brings the driven roller into or out of contact with the drive roller. When the reverse roller
53
rotates to drive the sheet toward the reverse discharge path
35
, the roller
53
and the other rollers
50
,
51
and
52
rotate at the same peripheral speed in synchronism with each other. This prevents the sheet being conveyed toward the reverse discharge path
35
from being pulled or slackened between the rollers
50
,
51
and
52
and the roller
53
.
The trailing edge sensor
54
adjoins the junction of the refeed path
33
and reverse discharge path
35
at a position upstream of the junction. The trailing edge sensor
54
senses the trailing edge of a sheet being conveyed along the refeed path
33
. The direction of rotation of the rollers
50
,
51
and
52
are switched from forward to reverse in accordance with the output of the sensor
54
. Also, the rollers
53
and
52
are brought to the closed position in accordance with the output of the sensor
54
.
A reverse discharge roller
55
is positioned on the reverse discharge path
35
and rotated to discharge a sheet along the path
35
. The reverse discharge roller
55
is positioned such that before the leading edge of the following sheet B being conveyed along the refeed path
33
reaches the reverse roller
53
, the leading edge of the preceding sheet A reaches the roller
55
. In this condition, when the reverse roller
53
is switched to the closed position for allowing the two sheets A and B to pass each other, the roller
55
can nip the leading edge of the sheet A to thereby smoothly discharge the sheet A. Further, the roller
55
and rollers
50
,
51
and
52
drive a sheet toward the reverse discharge path
35
at a speed higher than the speed at which a sheet is introduced into the refeed path
33
. This is achievable by, e.g., assigning a particular motor speed to each of forward rotation and reverse rotation.
FIG. 13
shows a condition in which the preceding sheet A has started moving out of the horizontal portion
33
a
toward the reverse discharge path
35
while the following sheet B is being conveyed toward the horizontal portion
33
b
via the vertical portion
33
b
. At this instant, the rollers
50
,
51
and
52
, as well as the reverse roller
53
, all are rotated in the reverse direction, conveying the sheet A toward the reverse discharge path
35
.
FIG. 14
shows a condition in which the preceding sheet A and following sheet B are passing each other at the horizontal portion
33
b
. At this time, the roller
52
and reverse roller
53
lying in the passing range X are switched to the open position and therefore do not obstruct the following sheet B. The preceding sheet A has its leading edge nipped by the reverse discharge roller
55
and can therefore be smoothly conveyed toward the sheet outlet section
3
even when released from the rollers
50
through
53
.
FIG. 15
shows a condition in which the entire preceding sheet A has entered the reverse discharge path
35
while the following sheet B is being conveyed along the horizontal portion
33
b
toward the path
4
. The rollers
50
through
52
are rotated in the forward direction while the reverse roller
53
is held in the open position. When the trailing edge sensor
54
senses the trailing edge of the following sheet B arrived at the preselected position in the horizontal portion
33
b
, the condition shown in
FIG. 13
is again set up. As a result, the rollers
50
through
52
and reverse roller
53
start switching back the sheet B toward the reverse discharge path
35
. It follows that the sheet B does not become free during the switching of the direction at all and is therefore prevented from skewing or shifting in the widthwise direction.
If the sheet being switched back toward the reverse discharge path
3
S is relatively long, then the roller
52
and reverse roller
53
are omissible; the rollers
50
and
51
can switch back the sheet alone.
FIG. 16
shows another alternative embodiment of the present invention. As shown, a roller
60
, a first and a second roller
61
and
62
facing the roller
60
, a pad or gripping means
63
and a sensor
64
are arranged around the junction of the refeed path
33
and reverse discharge path
35
. The circumference of the roller
60
partly faces the refeed path
33
and reverse discharge path
35
. A motor, not shown, rotates the roller
60
in the direction in which a sheet being conveyed along the refeed path
33
advances and the direction in which a sheet being conveyed along the reverse discharge path
35
advances. The roller
60
includes a cylindrical roller body
60
a
and a number of lugs
60
b
extending radially outward from the circumference of the roller body
60
a
. The lugs
60
b
are formed of an elastic material.
The first roller
61
contacts and is driven by the roller
60
to drive a sheet being conveyed along the refeed path
33
. At the position where the first roller
61
contacts the roller
60
, the lugs
60
b
of the roller
60
yield and become substantially flush with the circumference of the roller body
60
a
. The second roller
62
also contacts and is driven by the roller
60
to drive a sheet being conveyed along the revere discharge path
35
. At the position where the first roller
62
contacts the roller
60
, the lugs
60
b
of the roller
60
yield and become substantially flush with the circumference of the roller body
60
a.
The sensor
64
is positioned upstream of the first roller
61
in the direction of sheet conveyance and senses the leading edge and trailing edge of a sheet. A solenoid or similar actuator, not shown, selectively moves the pad
63
to a gripping position for gripping and stopping a sheet on the refeed path
33
or a releasing position for releasing it.
In operation, a sheet conveyed along the refeed path
33
is conveyed by the roller
61
and first roller, which are rotating in directions indicated by arrows in FIG.
16
. Just after the sensor
64
has sensed the trailing edge of the sheet, but before the trailing edge moves away from the roller
60
and first roller
61
, the pad
63
is moved to the gripping position to grip the sheet for thereby stopping the movement of the sheet. Even after the pad
63
has gripped the sheet, the roller
60
is continuously rotated to convey the trailing edge of the sheet along the refeed path
33
. As a result, the sheet bends between the pad
63
and the roller
60
little by little. When the trailing edge of the sheet moves away from the roller
60
and first roller
61
, the lugs
60
b
of the roller
60
retain the trailing edge of the sheet and convey it toward the reverse discharge path
35
in accordance with the rotation of the roller
60
. AS soon as the trailing edge of the sheet arrives at a preselected position adjoining the reverse discharge path
35
, the bent sheet bounces upward due to its own restoring force. Consequently, the trailing edge of the sheet is released from the lugs
60
b
and enters the nip between the roller
60
and the second roller
62
.
Just after the trailing edge of the sheet has entered the nip between the roller
60
and the second roller
62
, the pad
63
is moved to the releasing position. As a result, the sheet is conveyed by the roller
60
and second roller
62
to the reverse discharge path
35
.
As stated above, the illustrative embodiment does not locate a path selector or similar hard member around the junction of the refeed path
33
and reverse discharge path
35
. This protects a sheet and therefore an image carried thereon from damage ascribable to friction otherwise acting between the sheet and such a path selector. Further, at the time of switchback, the lugs
60
b
convey the leading edge of a sheet (trailing edge before switchback) without causing it to shift in the oblique direction, thereby preventing the sheet from skewing.
FIG. 17
shows a further alternative embodiment of the present invention. As shown, this embodiment is identical with the embodiment described with reference to
FIG. 16
except that a reversible roller
70
is substituted for the pad
63
as alternative gripping and stopping means. In the event of reverse discharge, the roller
70
is rotated in a direction a for conveying a sheet coming in through the refeed path
33
. On the elapse of a preselected period of time since the sensor
64
has sensed the trailing edge of the sheet, e.g., when the trailing edge moves away from the roller
60
and first roller
61
, the roller
70
is caused to rotate in a direction b for again conveying the sheet toward the roller
60
. Consequently, the lugs
60
b
retain the leading edge of the sheet (trailing edge before switchback) and convey it toward the reverse discharge path
35
. This is followed by the conveyance described with reference to FIG.
16
.
The reversible roller
70
substituted for the pad
63
,
FIG. 16
, makes it needless for a sheet to bend between the roller
60
and the roller
70
and therefore frees the sheet from curling.
If desired, at the time when the direction of rotation of the roller
70
is switched, the conveying speed of the roller
70
conveying a sheet on the refeed path
33
may be reduced below the conveying speed of the roller
60
and then stopped and switched in the direction of rotation. In this configuration, when the roller
70
stops rotating while gripping the sheet, the sheet can gently bend between the rollers
60
and
70
. At the time of reverse discharge, the edge of the sheet is prevented from parting from the roller
60
, so that a switchback time is reduced.
In summary, it will be seen that the present invention provides an image forming apparatus having various unprecedented advantages, as enumerated below.
(1) When a preceding sheet is switched back from a switchback path toward a conveyance path, the preceding sheet and the following sheet being introduced into the switchback path at least partly overlap each other. Therefore, by controlling the speed of the sheet being conveyed to the switchback path and the speed and timing of the sheet being driven out of the same path, it is possible to accurately maintain a short distance between sheets to be fed to an image forming section. This can be done without regard to irregularity in the timing of sheet feed from a sheet tray or in the speed of conveyance to the switchback path. Further, in a duplex print mode, the switchback path can be used as a path for switching back a one-sided sheet and again feeding it toward an image forming section. This makes an exclusive path for the duplex print mode needless. The apparatus is therefore reduced in thickness despite the presence of the switchback path
(2) When the one-sided sheet is driven into a refeed path, reverse discharging means switches back the sheet and conveys it into the reverse discharge path. The sheet can therefore be driven out to a sheet outlet section face down in order of page.
(3) A refeed roller for switching the direction of sheet feed plays the role of conveying means and reverse discharging means at the same time, simplifying the structure of the apparatus. At the time of reverse discharge, the refeed roller rotating in the forward direction nips the sheet introduced into the refeed path and then rotates in the reverse direction to thereby drive the sheet toward the reverse discharge path. The sheet therefore does not become free during conveyance to the reverse discharge path and is therefore prevented from skewing.
(4) The sheet being switched back to the reverse discharge path and the following sheet coming in through the refeed path can pass each other. Therefore, the following sheet can enter the refeed path when the trailing edge of the preceding sheet entering the reverse discharge path is still positioned in the refeed path. The preceding sheet can therefore smoothly reversed and discharged even when the distance between sheets being conveyed along the refeed path is short.
(5) When the refeed roller is rotating in the reverse direction to nip and convey the preceding sheet to the reverse discharge path, the following sheet coming in through the refeed path is prevented from reaching the refeed roller. Therefore, even when the preceding sheet and following sheet pass each other, the refeed roller does not have to be opened, but should only be switched in the direction of rotation.
(6) A simple biasing member suffices to switch the position of a path selector that deals with a sheet to enter the refeed path or the reverse discharge path. This not only obviates the need for a solenoid or similar electronic actuator, but also realizes sure, high-speed switching.
(7) The sheet being switched back toward the reverse discharge path does not contact a path selector or similar member and is therefore free from damage ascribable to rubbing, preventing image quality from being degraded. Further, lugs retain the leading edge of the sheet and convey the leading edge to the reverse discharge path side without causing it to shift in the oblique direction. The sheet is therefore from skew when being conveyed along the reverse discharge path.
(8) A pad is movable to a gripping position in order to grip the sheet coming in through the refeed path and stop it. This is also true with a roller that can stop rotating.
(9) The sheet can be driven out of the refeed path to the conveyance path at an adequate timing, implementing interleaf sheet feed.
(10) In an Interleaf, duplex print mode, the sheet being conveyed along the refeed path can be rapidly brought to the junction of the refeed path and conveyance path. This successfully reduces the distance between the sheet being fed from the sheet tray and the sheet being driven out of the refeed path to the conveyance path, thereby enhancing the productivity of image formation.
(11) Punching, stapling or similar finishing is easy to execute with a stack of sheets because the distance between sheets sequentially discharged to the sheet outlet section can be increased.
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. An image forming apparatus comprising:a sheet tray loaded with a stack of sheets; separating and feeding means for feeding one sheet from said sheet tray while separating said one sheet from the other sheets; an image forming section for forming an image on the sheet fed by said separating and feeding means; a conveyance path for conveying the sheet from said sheet tray to said image forming section; a switchback path connected to an intermediate portion of said conveyance path for receiving the sheet being conveyed along said conveyance path; reversing means selectively switchable to a first position for switching back a preceding sheet introduced into said switchback path to thereby feed said sheet to said conveyance path or a second position for allowing said preceding sheet being fed from said switchback path and a sheet to be introduced into said switchback path after said preceding sheet to at least partly overlap each other; a refeed path connected to a sheet outlet side of said image forming section and part of said conveyance path upstream of said switchback path; and conveying means for conveying the sheet driven into said refeed path to said conveyance path.
- 2. The apparatus as claimed in claim 1, wherein said image forming section comprises an eletrophotographic image forming section.
- 3. The apparatus as claimed in claim 1, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
- 4. The apparatus as claimed in claim 1, wherein said conveying means is capable of feeding the sheet driven into said refeed path to said conveyance path at a time interval.
- 5. The apparatus as claimed in claim 4, wherein the sheet is conveyed along said refeed path at a speed higher than an image forming process speed of said image forming section.
- 6. The apparatus as claimed in claim 5, further comprising a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section, wherein the sheet is conveyed along said reverse discharge path at a speed higher than the image forming process speed of said image forming section.
- 7. The apparatus as claimed in claim 6, wherein said image forming section comprises an eletrophotographic image forming section.
- 8. The apparatus as claimed in claim 6, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
- 9. The apparatus as claimed in claim 1 wherein the sheet is conveyed along said refeed path at a speed higher than an image forming process speed of said image forming section.
- 10. The apparatus as claimed in claim 9, further comprising a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section, wherein the sheet is conveyed along said reverse discharge path at a speed higher than the image forming process speed of said image forming section.
- 11. The apparatus as claimed in claim 10, wherein said image forming section comprises an eletrophotographic image forming section.
- 12. The apparatus as claimed in claim 10, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
- 13. The apparatus as claimed in claim 1, further comprising:a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section; and reverse discharging means for switching back the sheet driven into said refeed path toward said reverse discharge path.
- 14. The apparatus as claimed in claim 13, wherein said conveying means and said reverse discharging means comprise a reversible refeed roller positioned downstream of a junction of said refeed path and said reverse discharge path and selectively rotatable in a forward direction for nipping and conveying the sheet driven into said refeed path toward said conveyance path or a reverse direction for switching back said sheet toward said reverse discharge path while nipping said sheet.
- 15. The apparatus as claimed in claim 14, wherein said refeed path allows a preceding sheet switched back and being fed to said reverse discharge path and a following sheet being conveyed along said refeed path to pass each other.
- 16. The apparatus as claimed in claim 15, wherein said refeed roller is positioned outside of a range wherein the preceding sheet and the following sheet pass each other.
- 17. The apparatus as claimed in claim 16, further comprising a path selector positioned at the junction of said refeed path and said reverse discharge path and a biasing member constantly biasing said path selector, wherein said biasing member biases said path selector to a position where the sheet switched back on said refeed path is capable of entering said reverse discharge path, and exerts a force so sized as to allow said path selector to move to another position where a sheet discharged from said image forming section and being conveyed along said refeed path is capable of advancing on contacting said path selector.
- 18. The apparatus as claimed in claim 17, further comprising:a roller located at the junction of said refeed path and said reverse discharge path and rotatable in a direction in which the sheet moves along said refeed path and a direction in which said sheet moves along said reverse discharge path, said roller being formed with a plurality of lugs extending radially outward from a circumference of said roller; a first roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said refeed path by nipping said sheet between said first roller and said roller; a second roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said reverse discharge path by nipping said sheet between said first roller and said roller; and gripping means positioned on said refeed path downstream of said first roller for gripping the sheet being conveyed along said refeed path to thereby stop a movement of said sheet.
- 19. The apparatus as claimed in claim 18, wherein said gripping means comprises a pad selectively movable to a gripping position or a releasing position.
- 20. The apparatus as claimed in claim 18, wherein said gripping means comprises a reversible roller for nipping the sheet.
- 21. The apparatus as claimed in claim 18, wherein said conveying means is capable of feeding the sheet driven into said refeed path to said conveyance path at a desired timing.
- 22. The apparatus as claimed in claim 19, wherein the sheet is conveyed along said refeed path at a speed higher than an image forming process speed of said image forming section.
- 23. The apparatus as claimed in claim 22, further comprising a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section, wherein the sheet is conveyed along said reverse discharge path at a speed higher than the image forming process speed of said image forming section.
- 24. The apparatus as claimed in claim 23, wherein said image forming section comprises an eletrophotographic image forming section.
- 25. The apparatus as claimed in claim 23, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
- 26. The apparatus as claimed in claim 13, wherein said refeed path allows a preceding sheet switched back and being fed to said reverse discharge path and a following sheet being conveyed along said refeed path to pass each other.
- 27. The apparatus as claimed in claim 26, wherein said refeed roller is positioned outside of a range wherein the preceding sheet and the following sheet pass each other.
- 28. The apparatus as claimed in claim 27, further comprising a path selector positioned at the junction of said refeed path and said reverse discharge path and a biasing member constantly biasing said path selector, wherein said biasing member biases said path selector to a position where the sheet switched back on said refeed path is capable of entering said reverse discharge path, and exerts a force so sized as to allow said path selector to move to another position where a sheet discharged from said image forming section and being conveyed along said refeed path is capable of advancing on contacting said path selector.
- 29. The apparatus as claimed in claim 28, further comprising:a roller located at the junction of said refeed path and said reverse discharge path and rotatable in a direction in which the sheet moves along said refeed path and a direction in which said sheet moves along said reverse discharge path, said roller being forced with a plurality of lugs extending radially outward from a circumference of said roller; a first roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said refeed path by nipping said sheet between said first roller and said roller; a second roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said reverse discharge path by nipping said sheet between said first roller and said roller; and gripping means positioned on said refeed path downstream of said first roller for gripping the sheet being conveyed along said refeed path to thereby stop a movement of said sheet.
- 30. The apparatus as claimed in claim 29, wherein said gripping means comprises a pad selectively movable to a gripping position or a releasing position.
- 31. The apparatus as claimed in claim 29, wherein said gripping means comprises a reversible roller for nipping the sheet.
- 32. The apparatus as claimed in claim 29, wherein said conveying means is capable of feeding the sheet driven into said refeed path to said conveyance path at a desired timing.
- 33. The apparatus as claimed in claim 30, wherein the sheet is conveyed along said refeed path at a speed higher than an image forming process speed of said image forming section.
- 34. The apparatus as claimed in claim 33, further comprising a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section, wherein the sheet is conveyed along said reverse discharge path at a speed higher than the image forming process speed of said image forming section.
- 35. The apparatus as claimed in claim 34, wherein said image forming section comprises an eletrophotographic image forming section.
- 36. The apparatus as claimed in claim 34, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
- 37. The apparatus as claimed in claim 13, further comprising a path selector positioned at the junction of said refeed path and said reverse discharge path and a biasing member constantly biasing said path selector, wherein said biasing member biases said path selector to a position where the sheet switched back on said refeed path is capable of entering said reverse discharge path, and exerts a force so sized as to allow said path selector to move to another position where a sheet discharged from said image forming section and being conveyed along said refeed path is capable of advancing on contacting said path selector.
- 38. The apparatus as claimed in claim 37, further comprising:a roller located at the junction of said refeed path and said reverse discharge path and rotatable in a direction in which the sheet moves along said refeed path and a direction in which said sheet moves along said reverse discharge path, said roller being formed with a plurality of lugs extending radially outward from a circumference of said roller; a first roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said refeed path by nipping said sheet between said first roller and said roller; a second roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said reverse discharge path by nipping said sheet between said first roller and said roller; and gripping means positioned on said refeed path downstream of said first roller for gripping the sheet being conveyed along said refeed path to thereby stop a movement of said sheet.
- 39. The apparatus as claimed in claim 38, wherein said gripping means comprises a pad selectively movable to a gripping position or a releasing position.
- 40. The apparatus as claimed in claim 38, wherein said gripping means comprises a reversible roller for nipping the sheet.
- 41. The apparatus as claimed in claim 38, wherein said conveying means is capable of feeding the sheet driven into said refeed path to said conveyance path at a desired timing.
- 42. The apparatus as claimed in claim 39, wherein the sheet is conveyed along said refeed path at a speed higher than an image forming process speed of said image forming section.
- 43. The apparatus as claimed in claim 42, further comprising a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section, wherein the sheet is conveyed along said reverse discharge path at a speed higher than the image forming process speed of said image forming section.
- 44. The apparatus as claimed in claim 43, wherein said image forming section comprises an eletrophotographic image forming section.
- 45. The apparatus as claimed in claim 43, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
- 46. The apparatus as claimed in claim 45, further comprising:a roller located at the junction of said refeed path and said reverse discharge path and rotatable in a direction in which the sheet moves along said refeed path and a direction in which said sheet moves along said reverse discharge path, said roller being formed with a plurality of lugs extending radially outward from a circumference of said roller; a first roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said refeed path by nipping said sheet between said first roller and said roller; a second roller contacting the circumference of said roller and rotatable for conveying the sheet being conveyed along said reverse discharge path by nipping said sheet between said first roller and said roller; and gripping means positioned on said refeed path downstream of said first roller for gripping the sheet being conveyed along said refeed path to thereby stop a movement of said sheet.
- 47. The apparatus as claimed in claim 46, wherein said gripping means comprises a pad selectively movable to a gripping position or a releasing position.
- 48. The apparatus as claimed in claim 46, wherein said gripping means comprises a reversible roller for nipping the sheet.
- 49. The apparatus as claimed in claim 46, wherein said conveying means is capable of feeding the sheet driven into said refeed path to said conveyance path at a desired timing.
- 50. The apparatus as claimed in claim 49, wherein the sheet is conveyed along said refeed path at a speed higher than an image forming process speed of said image forming section.
- 51. The apparatus as claimed in claim 50, further comprising a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section, wherein the sheet is conveyed along said reverse discharge path at a speed higher than the image forming process speed of said image forming section.
- 52. The apparatus as claimed in claim 51, wherein said image forming section comprises an eletrophotographic image forming section.
- 53. The apparatus as claimed in claim 51, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
- 54. The apparatus as claimed in claim 13, further comprising a reverse discharge path extending from an intermediate portion of said refeed path to a sheet outlet section, wherein the sheet is conveyed along said reverse discharge path at a speed higher than the image forming process speed of said image forming section.
- 55. The apparatus as claimed in claim 54, wherein said image forming section comprises an eletrophotographic image forming section.
- 56. The apparatus as claimed in claim 54, wherein said image forming section comprises a digital electrophotographic image forming section including digital writing means.
Priority Claims (5)
Number |
Date |
Country |
Kind |
2001-018687 |
Jan 2001 |
JP |
|
2001-073504 |
Mar 2001 |
JP |
|
2001-101284 |
Mar 2001 |
JP |
|
2001-124133 |
Apr 2001 |
JP |
|
2001-398022 |
Dec 2001 |
JP |
|
US Referenced Citations (5)
Foreign Referenced Citations (2)
Number |
Date |
Country |
6-236086 |
Aug 1994 |
JP |
2941021 |
Aug 1999 |
JP |