U.S. patent number RE46,875 [Application Number 15/072,221] was granted by the patent office on 2018-05-29 for sheet processing apparatus.
This patent grant is currently assigned to Canon Kabushiki Kaisha. The grantee listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Takayuki Fujii, Keiko Fujita, Yasuo Fukatsu, Takako Hanada, Kenichi Hayashi, Daisaku Kamiya, Hideki Kushida, Toshiyuki Miyake.
United States Patent |
RE46,875 |
Fujita , et al. |
May 29, 2018 |
Sheet processing apparatus
Abstract
A sheet processing apparatus includes an aligning member and a
shift conveying unit. The aligning member is movable in a width
direction perpendicular to a sheet conveying direction and presses
a sheet stack loaded on a sheet processing tray so as to align the
sheet stack in the width direction. The unit is provided on the
upstream side of the tray and conveys a sheet, shifting the sheet
in the width direction. Being shifted by the unit, sheets are
loaded at first and second loading positions on the tray. When
sheets are loaded at the first loading position, the aligning
member is moved to a first standby position corresponding to the
first loading position in advance. When sheets are loaded at the
second loading position, the aligning member is moved in advance to
a second standby position corresponding to the second loading
position.
Inventors: |
Fujita; Keiko (Kashiwa,
JP), Kamiya; Daisaku (Abiko, JP), Kushida;
Hideki (Moriya, JP), Fukatsu; Yasuo (Abiko,
JP), Hanada; Takako (Tokyo, JP), Fujii;
Takayuki (Tokyo, JP), Miyake; Toshiyuki (Abiko,
JP), Hayashi; Kenichi (Abiko, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
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|
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
37526970 |
Appl.
No.: |
15/072,221 |
Filed: |
March 16, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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11530792 |
Sep 1, 2009 |
7581725 |
|
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Reissue of: |
12506050 |
Jul 20, 2009 |
7866652 |
Jan 11, 2011 |
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Foreign Application Priority Data
|
|
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|
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Sep 13, 2005 [JP] |
|
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2005-266112 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H
31/38 (20130101); B65H 29/12 (20130101); B65H
9/101 (20130101); B42C 1/12 (20130101); B65H
29/12 (20130101); B65H 31/34 (20130101); B42C
1/12 (20130101); B65H 9/101 (20130101); B65H
31/34 (20130101); B65H 2511/20 (20130101); B65H
2301/363 (20130101); B65H 2301/3613 (20130101); B65H
2404/1424 (20130101); B65H 2220/02 (20130101); B65H
2301/3613 (20130101); B65H 2301/3621 (20130101); B65H
2301/363 (20130101); B65H 2511/20 (20130101); B65H
2404/1424 (20130101); B65H 2301/3621 (20130101); B65H
2220/11 (20130101); B65H 2511/20 (20130101); B65H
2220/02 (20130101); B65H 2220/11 (20130101) |
Current International
Class: |
B65H
39/00 (20060101); B42C 1/12 (20060101); B65H
29/12 (20060101); B65H 9/10 (20060101); B65H
31/34 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaufman; Joseph
Attorney, Agent or Firm: Canon U.S.A., Inc. IP Division
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. patent application Ser.
No. 11/530,792, filed Sep. 11, 2006, which claims priority to
Japanese Application No. 2005-266112 filed Sep. 13, 2005, all of
which are hereby incorporated by reference herein in their
entirety.
Claims
What is claimed is:
1. An apparatus comprising: a shift conveying unit that conveys a
sheet in a sheet conveying direction and shifts the sheet in a
width direction perpendicular to the sheet conveying direction; a
sheet tray on which sheets .Iadd.shifted by the shift conveying
unit .Iaddend.are loaded at a first loading position and a second
loading position that is offset from the first loading position in
the width direction; and an aligning member that aligns the sheet
stacked on the sheet tray in the width direction, the aligning
member is movable .Iadd.between a first position corresponding to
the first loading position and a second position corresponding to
the second loading position .Iaddend.in the width direction,
wherein the aligning member is moved .[.at a first position
corresponding.]. to the first .[.loading.]. position .Iadd.and
thereafter aligns the sheets loaded on the sheet tray at the first
loading position .Iaddend.in the case that .Iadd.the
.Iaddend.sheets are loaded at the first loading position, and
wherein the aligning member is moved .[.at.]. .Iadd.to .Iaddend.the
second position .[.corresponding to.]. .Iadd.and thereafter aligns
the sheets loaded on the sheet tray at .Iaddend.the second loading
position in the case that .Iadd.the .Iaddend.sheets .[.and
aligned.]. are loaded at the second loading position.
2. An apparatus according to claim 1, further comprising a position
detecting unit that detects a position of the sheet in the width
direction, wherein the shift conveying unit shifts the sheet in the
width direction according to the position of sheet detected by the
.[.detecting sensor.]. .Iadd.position detecting unit.Iaddend..
3. An apparatus according to claim 2, wherein the position
detecting unit detects an end edge parallel to the conveying
direction of the sheet.
4. An apparatus according to claim 1, wherein a shift distance of
the sheet by the shift conveying unit is set according to sheet
size.
5. An apparatus according to claim 1, wherein the aligning member
aligns sheets by moving from .[.a standby.]. .Iadd.the first
.Iaddend.position every time .Iadd.the .Iaddend.sheets are loaded
onto the sheet tray .Iadd.in the case that the sheets are loaded at
the first loading position, and the aligning member aligns the
sheets by moving from the second position every time the sheets are
loaded onto the sheet tray in the case that the sheets are loaded
at the second loading position.Iaddend..
.Iadd.6. An apparatus according to claim 1, further comprising: a
discharging member that discharges the sheets aligned by the
aligning member; and a discharging tray on which sheets discharged
by the discharge member are loaded. .Iaddend.
.Iadd.7. An apparatus, comprising: a shift conveying unit that
conveys a sheet in a sheet conveying direction and shifts the sheet
in a width direction perpendicular to the sheet conveying
direction; a sheet tray on which sheets shifted by the shift
conveying unit are loaded at a first loading position and a second
loading position that is offset from the first loading position in
the width direction; and an aligning member that aligns the sheet
stacked on the sheet tray in the width direction, the aligning
member is movable between a first position corresponding to the
first loading position and a second position corresponding to the
second loading position in the width direction, wherein the
aligning member aligns the sheet, loaded at the first loading
position, at the first position in the case that the sheets are
loaded at the first loading position, and wherein the aligning
member aligns the sheet, loaded at the second loading position, at
the second position in the case that the sheets are loaded at the
second loading position. .Iaddend.
.Iadd.8. An apparatus according to claim 7, further comprising a
position detecting unit that detects a position of the sheet in the
width direction, wherein the shift conveying unit shifts the sheet
in the width direction according to the position of sheet detected
by the position detecting unit. .Iaddend.
.Iadd.9. An apparatus according to claim 8, wherein the position
detecting unit detects an end edge parallel to the conveying
direction of the sheet. .Iaddend.
.Iadd.10. An apparatus according to claim 7, wherein a shift
distance of the sheet by the shift conveying unit is set according
to sheet size. .Iaddend.
.Iadd.11. An apparatus according to claim 7, wherein the aligning
member aligns sheets by moving from the first position every time
the sheets are loaded onto the sheet tray in the case that the
sheets are loaded at the first loading position, and the aligning
member aligns the sheets by moving from the second position every
time the sheets are loaded onto the sheet tray in the case that the
sheets are loaded at the second loading position. .Iaddend.
.Iadd.12. An apparatus according to claim 7, further comprising: a
discharging member that discharges the sheets aligned by the
aligning member; and a discharging tray on which sheets discharged
by the discharge member are loaded. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet processing apparatus.
2. Description of the Related Art
Some image forming devices such as photocopiers, printers,
facsimiles, and multifunctional peripheral devices are provided
with a sheet processing apparatus that processes sheets discharged
from the body of the image forming apparatus. For example, the
sheet processing apparatus staples the sheets. Some of such sheet
processing apparatuses load the discharged sheets on a process tray
and align the sheets before stapling.
Japanese Patent Laid-Open No. 2004-51256 discloses an image forming
apparatus whose body is provided with a lateral register correction
unit that detects the side edge in a direction perpendicular to the
sheet conveying direction (hereinafter referred to as "width
direction") of a sheet and moves the sheet in the width direction
so as to correct the position in the width direction of the sheet.
The term "lateral register correction" here means position
correction in the width direction of a sheet.
By providing such a lateral register correction unit, the lateral
register position of a sheet can be aligned with the image forming
position. In addition, since the side edge of the sheet can be
detected and the sheet can be moved while the sheet is being
conveyed, the sheet position can be corrected without reducing the
productivity of the image forming apparatus.
In addition, by performing the lateral register correction of the
sheet, the sheet can be discharged from the body of the image
forming apparatus to the sheet processing apparatus with the
position of the side edge in the width direction of the sheet
aligned.
However, while the sheet is conveyed from the entrance of the sheet
processing apparatus to, for example, a sheet stapling part in the
sheet processing apparatus, lateral register displacement, that is
to say, displacement in the width direction occurs. Therefore, when
sheets are processed, a sheet alignment operation is performed on a
process tray on which sheets are temporarily loaded. That is to
say, it is necessary to perform a sheet alignment operation on the
process tray even after the lateral register correction is
performed in the body of the image forming apparatus.
Recently, high productivity has been required not only for image
forming apparatus but also for a system including sheet processing
apparatus. Therefore, it is necessary to reduce the time for sheet
processing operations such as sheet alignment on the process
tray.
In addition, when the sheet processing apparatus processes a
plurality of copies, during a sheet alignment operation on the
process tray, sheet stacks are offset copy by copy. The sheet
stacks are thereby loaded on the discharge tray, being offset stack
by stack. Thus, the sheet stacks are sorted. However, the larger
the offset distance is, the longer time is required for the
alignment operation on the process tray. Therefore, in order to
achieve high productivity in the entire system, it is necessary to
reduce the alignment time concerning sorting.
If there is a malfunction in the unit that aligns sheets, the
entire system can go down. This is one of the factors that prevents
high productivity from being achieved.
SUMMARY OF THE INVENTION
The present invention provides a sheet processing apparatus that
can achieve high productivity.
In an aspect of the present invention, a sheet processing apparatus
includes a shift conveying unit, a sheet processing tray, an
aligning member, and a discharge member. The shift conveying unit
conveys a sheet in a sheet conveying direction and shifts the sheet
in a width direction perpendicular to the sheet conveying
direction. After being conveyed by the shift conveying unit, sheets
are loaded on the sheet processing tray. By being shifted in the
width direction by the shift conveying unit, the sheets are loaded
at a first loading position and a second loading position that is
offset from the first loading position in the width direction on
the sheet processing tray. The aligning member is movable in the
width direction and presses the sheet stack loaded on the sheet
processing tray so as to align the sheet stack in the width
direction. The discharge member discharges the sheet stack aligned
by the aligning member. When sheets are loaded at the first loading
position, the aligning member is moved to a first standby position
corresponding to the first loading position in advance and then
moves from the first standby position in order to align the sheet
stack loaded at the first loading position. When sheets are loaded
at the second loading position, the aligning member is moved in
advance to a second standby position corresponding to the second
loading position and then moves from the second standby position in
order to align the sheet stack loaded at the second loading
position.
In another aspect of the present invention, a sheet processing
apparatus that aligns sheets loaded on a sheet processing tray
includes a pair of aligning members and a shift conveying unit. The
pair of aligning members are movable in a width direction
perpendicular to a sheet conveying direction and press both sides
of the sheets loaded on the sheet processing tray so as to align
the sheets in the width direction. The shift conveying unit is
provided on the upstream side of the sheet processing tray in the
sheet conveying direction, shifts a sheet to a predetermined
position in the width direction, and conveys the sheet to the sheet
processing tray. The distance in the width direction between the
pair of aligning members at their standby positions when the shift
conveying unit shifts a sheet in the width direction is smaller
than the distance in the width direction between the pair of
aligning members at their standby positions when the shift
conveying unit does not shift a sheet.
In another aspect of the present invention, a sheet processing
apparatus includes a sheet conveying path, a sheet processing tray,
and an aligning member. After being conveyed through the sheet
conveying path, sheets are loaded in a plurality of alternative
discharge positions on the sheet processing tray. The aligning
member presses the edge of the sheets loaded on the sheet
processing tray so as to perform alignment in a width direction
perpendicular to the conveying direction in the sheet conveying
path. The aligning member aligns the sheets by moving so as to
press the edge of the sheets from a standby position. The standby
position of the aligning member is changed according to the
discharge position in the width direction on the sheet processing
tray.
The present invention can reduce the time of sheet alignment
operation performed by the aligning members and can achieve high
productivity.
Further features of the present invention will become apparent from
the following description of exemplary embodiments (with reference
to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a photocopier that is an example of
an image forming apparatus having a sheet processing apparatus
according to a first embodiment of the present invention.
FIG. 2 illustrates the structure of a finisher serving as the sheet
processing apparatus.
FIG. 3 is a control block diagram of the entire photocopier
including the finisher.
FIG. 4 is a control block diagram of a finisher control part of the
finisher.
FIG. 5 is a schematic view showing the structure of a lateral
register correction unit provided in the finisher.
FIGS. 6A and 6B illustrate the operation to shift a sheet to the
left in the conveying path in the lateral register correction
unit.
FIGS. 7A and 7B also illustrate the operation to shift a sheet to
the left in the conveying path in the lateral register correction
unit.
FIGS. 8A and 8B illustrate the operation to shift a sheet to the
right in the conveying path in the lateral register correction
unit.
FIGS. 9A and 9B also illustrate the operation to shift a sheet to
the right in the conveying path in the lateral register correction
unit.
FIG. 10 shows the configuration of a process tray provided in the
finisher.
FIGS. 11A and 11B illustrate the alignment operation performed by
aligning members provided in the finisher in the case where the
lateral register correction is not performed by the lateral
register correction unit.
FIG. 12 also illustrates the alignment operation performed by the
aligning members in the case where the lateral register correction
is not performed by the lateral register correction unit.
FIGS. 13A and 13B illustrate the alignment operation performed by
the aligning members in the case where the lateral register
correction is performed by the lateral register correction
unit.
FIG. 14 also illustrates the alignment operation performed by the
aligning members in the case where the lateral register correction
is performed by the lateral register correction unit.
FIG. 15 is a flowchart illustrating the redundant mode in the
finisher.
FIGS. 16A and 16B illustrate the alignment operation performed by
aligning members provided in a sheet processing apparatus according
to a second embodiment of the present invention in the case where
the lateral register correction is not performed by the lateral
register correction unit.
FIG. 17 also illustrates the alignment operation performed by the
aligning members in the case where the lateral register correction
is not performed by the lateral register correction unit.
FIGS. 18A and 18B illustrate the alignment operation performed by
the aligning members in the case where the lateral register
correction is performed by the lateral register correction
unit.
FIG. 19 also illustrates the alignment operation performed by the
aligning members in the case where the lateral register correction
is performed by the lateral register correction unit.
DESCRIPTION OF THE EMBODIMENTS
Embodiments of the present invention will now be described with
reference to the drawings in detail.
First Embodiment
FIG. 1 is a sectional view of a photocopier that is an example of
an image forming apparatus having a sheet processing apparatus
according to a first embodiment of the present invention.
In the figure, reference numeral 1000 denotes a photocopier. The
photocopier 1000 includes a photocopier body 10, a finisher 500
that is a sheet processing apparatus, and a scanner 200 disposed on
the top of the photocopier body 10.
The scanner 200 scans documents. The scanner 200 includes a
document feeder 100, a scanner unit 104, mirrors 105 to 107, a lens
108, and an image sensor 109. When the scanner 200 scans documents
D, first, the documents D are placed on a tray 100a of the document
feeder 100. The documents D are placed on the tray 100a with the
side to be copied face up.
The document feeder 100 conveys the documents D from the initial
page one by one to the left (in the direction of the arrow in the
figure). After passing along a curved path, the documents D are
conveyed on a platen glass 102 from the left to the right and then
discharged onto a discharged paper tray 112.
When scanning the documents D being conveyed by the document feeder
100, the scanner unit 104 is held at a predetermined position. The
documents D pass over the scanner unit 104 from the left to the
right so as to be scanned.
In the scanning operation, when the documents D move across the
platen glass 102, a lamp 103 of the scanner unit 104 irradiates the
documents D with light. The reflection is guided to the image
sensor 109 via the mirrors 105 to 107 and the lens 108. The image
sensor 109 scans the image data of each document D line by line.
After a predetermined image data processing is performed in an
image signal control part 202 shown in FIG. 3, the image data is
sent to an exposure control part 110.
The scanning of the documents can also be performed by stopping a
document D being conveyed by the document feeder 100 on the platen
glass 102 and then moving the scanner unit 104 from the left to the
right. When a user scans a document without using the document
feeder 100, the user lifts the document feeder 100 and places the
document on the platen glass 102 so as to scan the document.
The photocopier body 10 includes a sheet feeding part 1004 and an
image forming part 1003. The sheet feeding part 1004 feeds sheets P
contained in cassettes 114 and 115. The image forming part 1003
forms images on the sheets P fed by the sheet feeding part
1002.
The image forming part 1003 includes a photosensitive drum 111, a
developer 113, and a transfer charger 116. When an image is formed,
the exposure control part 110 irradiates the photosensitive drum
111 with laser light, thereby forming a latent image on the
photosensitive drum 111. The latent image is changed into a visible
image, that is to say, a toner image by the developer 113. A fixing
unit 117 and a discharge roller pair 118 are disposed on the
downstream side of the image forming part 1003.
Reference numeral 400 denotes an operation display provided on the
top of the photocopier body 10. The operation display 400 includes
a plurality of keys for setting various functions concerning image
formation and a display part that displays the information showing
the setting.
Next, the image forming operation of the photocopier body 10 will
be described.
As described above, the image sensor 109 of the scanner 200 scans
the image data of the document D. After a predetermined image data
processing is performed in the image signal control part 202, the
image data is sent to the exposure control part 110. Next, the
exposure control part 110 outputs laser light according to the
image signal.
This laser light is scanned by a polygon mirror 110a, and the
photosensitive drum 111 is irradiated with the laser light. In this
way, an electrostatic latent image according to the scanned laser
light is formed on the photosensitive drum 111. Next, the
electrostatic latent image formed on the photosensitive drum 111 is
changed into a visible image, that is to say, a toner image by the
developer 113.
On the other hand, a sheet P is conveyed from one of the cassettes
114 and 115, a manual paper feeder 125, and a both side conveyance
path 124 to a transfer part, which includes the photosensitive drum
111 and the transfer charger 116. In this transfer part, the toner
image on the photosensitive drum 111 is transferred onto the sheet
P. The transferred toner image is fixed to the sheet P in the
fixing unit 117. Next, the sheet P with the fixed toner image is
discharged into the finisher 500 by the discharge roller pair
118.
To discharge the sheet P from the photocopier body 10 with the
toner image side face down, a flapper 121 guides the sheet P to a
path 122 after the sheet P has passed through the fixing unit 117.
Next, after the trailing edge of the sheet P has left the flapper
121, the sheet P is conveyed backward. The sheet P is guided to the
discharge roller pair 118 by the flapper 121 and then discharged
from the photocopier body 10.
Therefore, the sheet P is discharged from the photocopier body 10
with the toner image side face down. Such mode of discharge is
called "reverse discharge." Since sheets P are discharged face down
by the reverse discharge, when image formation is performed from
the initial page, for example, when image formation is performed
using the document feeder 100, the sheets P are ordered by page. In
addition, in the case of image formation based on image data from a
computer, sheets P are also ordered by page.
When a hard sheet P such as an OHP sheet is fed from the manual
paper feeder 125 and an image is formed thereon, the sheet P is not
guided to the path 122 and is discharged by the discharge roller
pair 118 with the toner image side face up.
When images are formed on both sides of a sheet P, the sheet P is
guided from the fixing unit 117 straight to the discharge roller
pair 118. Just after the trailing edge of the sheet P has left the
flapper 121, the sheet P is conveyed backward and guided by the
flapper 121 to the path 122 and the both side conveyance path
124.
The sheets discharged from the photocopier body 10 are then taken
in the finisher 500. The finisher 500 is a sheet processing
apparatus that staples or binds the sheets on which images are
formed.
Next, the structure of the finisher 500 will be descried with
reference to FIG. 2.
The finisher 500 takes in sheets from the photocopier body 10 and
performs various processes such as a process to align the sheets
and form a sheet stack, a sort process, a non-sort process, a
stapling process to place staples at the trailing edge of the sheet
stack, and a binding process. The finisher 500 includes a stapling
part 600 and a binding part 800. The stapling part 600 staples a
sheet stack. The binding part 800 folds a sheet stack in half and
binds them.
The stapling part 600 includes a process tray (sheet processing
tray) 630 and a pair of aligning plates (aligning members) 1002.
The process tray 630 is loaded with a sheet stack. The aligning
plates 1002 align the sheet stack on the process tray 630 in the
width direction. The stapling part 600 further includes a stapler
601 that staples the sheet stack.
The binding part 800 includes a binding entrance sensor 831, two
pairs of staplers 810, and a binding intermediate tray (hereinafter
referred to as "binding tray") 830 in which sheets are loaded. The
binding tray 830 is provided with an intermediate roller 803 and a
movable sheet-positioning member 816.
An anvil 811 is provided opposite the two pairs of staplers 810.
The staplers 810 staples a sheet stack in the binding tray 830 in
cooperation with the anvil 811.
A folding roller pair 804 and a pushing member 815 are provided on
the downstream side of the staplers 810. The pushing member 815 is
opposite the folding roller pair 804. The pushing member 815 pushes
the sheet stack in the binding tray 830 into the folding roller
pair 804. A discharged paper sensor 832 is provided on the
downstream side of a conveying roller pair 805.
The finisher 500 further includes an entrance roller pair 502 for
taking in the sheets conveyed from the photocopier body 10. An
entrance sensor 531 is provided between the entrance roller pair
502 and a conveying roller pair 503.
A lateral register correction unit 1001 is provided between the
conveying roller pair 503 and a buffer roller 505. The lateral
register correction unit 1001 operates in the shift sort mode in
which discharged sheet stacks are offset. The lateral register
correction unit 1001 is a shift conveying unit that conveys a
sheet, shifting the sheet to a predetermined position in the width
direction. In the shift sort mode, the lateral register correction
unit 1001 corrects the lateral registration of all sheets taken in
the finisher 500 and conveys the sheets, shifting the sheets to a
predetermined position in the width direction. The lateral register
correction unit 1001 includes conveying rollers 1101a and 1102a and
driven rollers 1101b and 1102b pressed against the conveying
rollers 1101a and 1102a, respectively.
The buffer roller 505 is provided on the downstream side of the
lateral register correction unit 1001. A predetermined number of
sheets conveyed via the conveying roller pair 503 and the lateral
register correction unit 1001 can be wrapped around the buffer
roller 505. The sheets are wrapped around the buffer roller 505 by
the pressing rollers 512, 513, and 514 and are conveyed in the
direction in which the buffer roller 505 rotates.
A switching flapper 511 is provided between the pressing rollers
513 and 514. Another switching flapper 510 is provided below the
switching flapper 511. The switching flapper 511 selectively guides
the sheets wrapped around the buffer roller 505 to a sort path 522
or a non-sort path 521. When guided to the non-sort path 521, the
sheets are peeled off the buffer roller 505. Reference numeral 533
denotes a discharged paper sensor provided in the non-sort path
521.
The switching flapper 510 selectively guides the sheets wrapped
around the buffer roller 505 to the sort path 522 or a buffer path
523. When guided to the sort path 522, the sheets are peeled off
the buffer roller 505. When guided to the buffer path 523, the
sheets remain wrapped around the buffer roller 505. A buffer path
sensor 532 is provided in the buffer path 523. The buffer path
sensor 532 detects the sheets in the buffer path 523.
Another switching flapper 512 is disposed on the downstream side of
the sort path 522. The sheets guided to the sort path 522 is then
guided to the sort discharge path 524 or the binding path 525 by
the switching flapper 512.
The sheets guided to the sort discharge path 524 pass through a
conveying roller pair 507 and are then loaded on the process tray
630. The sheet stack loaded on the process tray 630 is aligned and
stapled, if necessary, and then discharged onto the stack tray
(discharge tray) 700 by discharge rollers (discharge members) 680a
and 680b. In the shift sort mode, a plurality of sheet stacks are
loaded on the stack tray 700. The sheet stacks are loaded
alternately at two positions that differ in the width direction
perpendicular to the conveying direction.
The discharge roller 680b is supported by a swing guide 650. The
swing guide 650 is swung by a swing motor (not shown) so that the
discharge roller 680b comes into contact with the uppermost sheet
on the process tray 630. When the discharge roller 680b is in
contact with the uppermost sheet on the process tray 630, the
discharge roller 680b can discharge the sheet stack on the process
tray 630 onto the stack tray 700 in cooperation with the other
discharge roller 680a.
In the finisher 500 having such a structure, when a sheet is
discharged from the photocopier body 10, the sheet is first passed
to the entrance roller pair 502. At this time, simultaneously, the
timing when the sheet is passed is detected by the entrance sensor
531.
After being conveyed by the entrance roller pair 502, the sheet is
conveyed by the lateral register correction unit 1001, being
shifted in the width direction. Next, the sheet is conveyed to the
buffer roller 505. With the rotation of the buffer roller 505, the
sheet is wrapped around the buffer roller 505 by the pressing
rollers 512, 513, and 514 and conveyed in the direction in which
the buffer roller 505 rotates. The shifting operation of the
lateral register correction unit 1001 will hereinafter be
described.
When the non-sort process is performed, the sheet is peeled off the
buffer roller 505 and guided to the non-sort path 521 by the
switching flapper 511. The sheet is then discharged onto the sample
tray 701 by the discharge roller pair 509.
When the sorting process, the stapling process, or the binding
process is performed, a set of a predetermined number of sheets is
conveyed to the stapling part 600, for example. For this purpose, a
sheet is first sent to the buffer path 523 by the switching
flappers 511 and 510, being wrapped around the buffer roller 505.
In the same way, a predetermined number of sheets are sent to the
buffer path 523, being wrapped around the buffer roller 505.
After a predetermined number of sheets have been sent to the buffer
path 523, these sheets are peeled off the buffer roller 505 by the
switching flapper 510 and sent to the sort path 522. The sheets
conveyed to the sort path 522 pass through the conveying roller
pair 506 and are then guided to the sort discharge path 524 or the
binding path 525 by the switching flapper 512.
When guided to the sort discharge path 524 by the switching flapper
512, the sheets are stacked on the process tray 630. The sheets
stacked on the process tray 630 are aligned by the pair of aligning
plates 1002 and stapled by the stapler 601 according to the setting
from the operation display 400 shown in FIG. 1.
Every sheet stack that has been aligned by the aligning plates 1002
and stapled by the stapler 601 is discharged onto the stack tray
700 by the discharge rollers 680a and 680b. Also in the shift sort
mode, every sheet stack is aligned by the aligning plates 1002 and
discharged onto the stack tray 700 by the discharge rollers 680a
and 680b.
This stapling process is performed by the stapler 601. This stapler
601 is movable along the edge of the process tray 630. Therefore,
the sheets stacked on the process tray 630 can be stapled at the
rearmost position (trailing edge) of the sheets in the sheet
conveying direction (leftward direction in FIG. 2).
On the other hand, the sheets guided to the binding path 525 by the
switching flapper 512 are conveyed to the binding intermediate tray
830 by a conveying roller pair 802 and stapled by the staplers 810
and the anvil 811. Next, being pushed by the pushing member 815
into the space between the folding roller pair 804, the sheet stack
is folded and conveyed downstream by the folding roller pair 804.
The folded sheet stack is discharged onto a discharged paper tray
850 by the conveying roller pair 805.
FIG. 3 is a control block diagram of the entire photocopier
including the finisher 500. In FIG. 3, reference numeral 150
denotes a CPU circuit part. This CPU circuit part 150 includes a
CPU 150A, a ROM 151, and a RAM 152 and controls blocks 101, 201,
202, 209, 301, 401, and 501 according to the control program stored
in the ROM 151. The RAM 152 temporarily stores the control data and
is used as a work area for arithmetic processing necessary for the
control.
The document feeder control part 101 drives and controls the
document feeder 100 on the basis of the instructions from the CPU
circuit part 150. The image reader control part 201 drives and
controls the scanner unit 104, the image sensor 109, and other
components of the scanner 200, and sends an analog image signal
received from the image sensor 109 to the image signal control part
202.
The image signal control part 202 converts the analog image signal
received from the image sensor 109 into a digital signal. Next, the
image signal control part 202 performs various processes so as to
convert this digital signal into a video signal and then sends the
video signal to the printer control part 301. In addition, when the
image signal control part 202 receives a digital image signal from
an external computer 210 through an external interface 209, the
image signal control part 202 performs various processes so as to
convert this digital image signal into a video signal and then
sends the video signal to the printer control part 301. The
processing operation of the image signal control part 202 is
controlled by the CPU circuit part 150.
The printer control part 301 drives the exposure control part 110
on the basis of the video signal received from the image signal
control part 202. The operation display control part 401 performs
information exchange between the operation display 400 shown in
FIG. 1 and the CPU circuit part 150. The operation display control
part 401 receives key signals corresponding to key operation from
the operation display 400 and sends the key signals to the CPU
circuit part 150. On the other hand, the operation display control
part 401 receives signals from the CPU circuit part 150 and
displays the corresponding information on the screen of the
operation display 400.
The finisher control part 501 is provided, for example, in the
finisher 500 and drives and controls the entire finisher by
exchanging information with the CPU circuit part 150.
Alternatively, the finisher control part 501 may be provided in the
photocopier body 10.
FIG. 4 is a control block diagram of the finisher control part 501.
The finisher control part 501 includes a CPU 550, a ROM 551, and a
RAM 552. The finisher control part 501 communicates with the CPU
circuit part 150 in the photocopier body 10 via a communication IC
(not shown) so as to exchange information. On the basis of the
instructions from the CPU circuit part 150, the finisher control
part 501 executes various programs stored in the ROM 551 so as to
drive and control the finisher 500.
FIG. 5 is a schematic view showing the structure of the lateral
register correction unit 1001. Conveying a sheet in the sheet
conveying direction, the lateral register correction unit 1001
shifts the sheet in the direction perpendicular to the sheet
conveying direction (hereinafter referred to as "width direction").
In FIG. 5, reference numeral M1103 denotes a conveying motor. The
conveying motor M1103 drives the conveying rollers 1101a and 1102a
via timing belts 1115 and 1116. The conveying rollers 1101a and
1102a convey sheets together with the driven rollers 1101b and
1102b.
Reference numeral 1104 denotes a lateral register sensor. The
lateral register sensor 1104 is a position detecting device that
detects the position of the edge of a sheet being conveyed. The
lateral register sensor 1104 is mounted in a lateral register
sensor unit 1105. The lateral register sensor unit 1105 is moved
from side to side as shown by arrow 1300 by a lateral register
sensor shifting motor M1106. The home position of the lateral
register sensor unit 1105 is detected by a lateral register HP
sensor 1108.
The lateral register correction unit 1001 is not integral with the
lateral register sensor unit 1105. Reference numeral M1107 denotes
a lateral register correction unit shifting motor, which moves the
lateral register correction unit 1001 from side to side as shown by
arrow 1301. The home position of the lateral register correction
unit 1001 is detected by a lateral register correction unit HP
sensor 1109.
Reference numeral 1112 denotes a trailing edge detecting sensor.
The trailing edge detecting sensor 1112 detects an incoming sheet
and detects that the trailing edge of the sheet has passed between
the conveying rollers 1101a and 1101b in the lateral register
correction unit 1001.
Next, the lateral register correcting operation of the lateral
register correction unit 1001 having such a structure will be
described.
First, with reference to FIGS. 6A, 6B, 7A, and 7B, the case where a
sheet is shifted to the left in the figures in the conveying path
will be described.
First, when a sheet P approaches the lateral register correction
unit 1001 as shown in FIG. 6A, the lateral register sensor shifting
motor M1106 is activated. The lateral register sensor unit 1105 is
thereby moved leftward as shown by the arrow from the home position
to a standby position that is predetermined on the basis of the
sheet size and the offset distance.
Next, when the sheet P enters the lateral register correction unit
1001 as shown in FIG. 6B and is detected by the lateral register
sensor 1104, the lateral register correction unit shifting motor
M1107 is activated and starts to move the lateral register
correction unit 1001 to the left as shown by the arrow in FIG. 7A.
The sheet P thereby starts to be moved to the left, being conveyed.
Soon afterward, the side edge of the sheet P passes over the
lateral register sensor 1104, and the lateral register sensor 1104
thereby stops detecting the sheet P.
When the lateral register sensor 1104 stops detecting the sheet P,
in other wards, when the lateral register sensor 1104 detects the
side edge of the sheet P, the lateral register correction unit
shifting motor M1107 is stopped. By this operation, the lateral
register of the sheet P is corrected, and the sheet P is shifted to
a predetermined position shown by reference letter P'.
The sheet P remains being conveyed. When the trailing edge
detecting sensor 1112 detects the trailing edge of the sheet P, the
lateral register correction unit shifting motor M1107 moves the
lateral register correction unit 1001 to the right as shown by the
arrow in FIG. 7B so as to return the lateral register correction
unit 1001 to the home position shown in FIGS. 6A and 6B.
Next, with reference to FIGS. 8A, 8B, 9A, and 9B, the case where a
sheet is shifted to the right in the conveying path will be
described.
First, when a sheet P approaches the lateral register correction
unit 1001 as shown in FIG. 8A, the lateral register sensor shifting
motor M1106 is activated. The lateral register sensor unit 1105 is
thereby moved leftward as shown by the arrow from the home position
to a standby position that is predetermined on the basis of the
sheet size and the offset distance.
Next, when the sheet P enters the lateral register correction unit
1001 as shown in FIG. 8B and the leading edge of the sheet P is
detected by the trailing edge detecting sensor 1112, the lateral
register correction unit shifting motor M1107 is activated and
starts to move the lateral register correction unit 1001 to the
right as shown by the arrow in FIG. 9A.
The sheet P thereby starts to be moved to the right, being
conveyed. Soon afterward, the side edge of the sheet P is detected
by the lateral register sensor 1104. When the lateral register
sensor 1104 detects the side edge of the sheet P, the lateral
register correction unit shifting motor M1107 is stopped. By this
operation, the lateral register of the sheet P is corrected, and
the sheet P is shifted to a predetermined position shown by
reference letter P'.
The sheet P remains being conveyed. When the trailing edge
detecting sensor 1112 detects the trailing edge of the sheet P, the
lateral register correction unit shifting motor M1107 moves the
lateral register correction unit 1001 to the left as shown by the
arrow in FIG. 9B so as to return the lateral register correction
unit 1001 to the home position shown in FIGS. 8A and 8B.
In this embodiment, after the lateral register correcting operation
is performed by the lateral register correction unit 1001, the
sheet is conveyed to the process tray 630 of the finisher 500. In
this process tray 630, alignment operation is performed.
FIG. 10 shows the configuration of the process tray 630 and
aligning plates that align the sheets stacked on the process tray
630. In FIG. 10, reference numeral M3 denotes a discharge motor.
Being driven by this discharge motor M3, the conveying roller pair
507 discharges the sheets onto the process tray 630.
Reference numerals M1202 and M1201 denote a front alignment motor
and a rear alignment motor, respectively. The front alignment motor
M1202 and the rear alignment motor M1201 drive a front aligning
plate 1002a and a rear aligning plate 1002b, respectively. The
front aligning plate 1002a and the rear aligning plate 1002b
constitute a pair of aligning plates and are independently driven
in the direction shown by arrows 1400 and 1401 so as to align the
sheets. Reference numerals 1203 and 1202 denote a front alignment
HP sensor and a rear alignment HP sensor, respectively. The front
alignment HP sensor 1203 and the rear alignment HP sensor 1202
detect the home positions of the front aligning plate 1002a and the
rear aligning plate 1002b, respectively.
Next, the alignment operation according to this embodiment will be
described. Before that, the alignment operation in the shift sort
mode in the case where the lateral register correction is not
performed by the lateral register correction unit 1001 will be
described with reference to FIGS. 11A, 11B, and 12.
In this embodiment, when the shift sort mode is selected, a sheet
stack P conveyed onto the process tray 630 is shifted by a stack
offset distance La and aligned before the sheet stack P is
discharged onto the discharge tray 700. By switching the shifting
direction between forward and backward (leftward and rightward in
the figures) stack by stack, sheet stacks can be sorted.
As shown in FIG. 11A, when the shift sort mode is selected, the
front aligning plate 1002a and the rear aligning plate 1002b first
stand by at their respective standby positions. The standby
positions are at equal distances from the center of the unit. The
distance between the standby positions is the sum of the sheet
width Lp and twice the stack offset distance La. When the distance
of lateral register displacement that occurs in the photocopier
body 10 is Lb, and the distance of lateral register displacement
that occurs in the finisher 500 is Lc, the stack offset distance La
is set so as to be larger than the sum of the distances of these
lateral register displacements. That is to say, La>Lb+Lc.
Therefore, even if the distance of lateral register displacement
(Lb+Lc) is the maximum, a sheet stack P conveyed onto the process
tray 630 does not collide with the aligning plate 1002a or 1002b at
the standby position to cause conveyance failure.
For example, when a sheet stack P is offset forward by La and
aligned, as shown in FIG. 11B, the front aligning plate 1002a
remains at the standby position and functions as a standard. After
the sheet stack P has entered the process tray 630, the rear
aligning plate 1002b reciprocates a distance approximately twice as
long as the offset distance La. The sheet stack P is thereby
pressed against the front aligning plate 1002a so as to be aligned
(one side standard).
When another sheet stack P is offset backward by La and aligned, as
shown in FIG. 12, the rear aligning plate 1002b remains at the
standby position and functions as a standard. After the sheet stack
P has entered the process tray 630, the front aligning plate 1002a
reciprocates a distance approximately twice as long as the offset
distance La. The sheet stack P is thereby pressed against the rear
aligning plate 1002b so as to be aligned (one side standard).
Next, the alignment operation in the shift sort mode in the case
where the lateral register correction is performed by the lateral
register correction unit 1001 in the finisher 500 will be described
with reference to FIGS. 13A, 13B, and 14.
FIG. 13A shows first standby positions of the aligning plates 1002a
and 1002b in the case where a sheet stack is offset forward and
aligned. Before the sheet stack P is conveyed onto the process tray
630, the lateral register displacement Lb that occurs in the
photocopier body 10 has been corrected by the operation of the
lateral register correction unit 1001. In addition, the sheet stack
P has been shifted by the stack offset distance La by the operation
of the lateral register correction unit 1001. Being offset by the
lateral register correction unit 1001, the sheet stack P is loaded
at the front loading position (first loading position) shown in
FIGS. 13A and 13B.
Therefore, the alignment distance Ld of each of the aligning plates
1002a and 1002b is set slightly larger than the distance Le of the
displacement that occurs in the conveying path from the lateral
register correction unit 1001 to the process tray 630 in the
finisher 500 (Ld>Le). Therefore, the sheet stack P does not
collide with the aligning plate 1002a or 1002b at the standby
position to cause conveyance failure.
After the sheet stack P has been conveyed onto the process tray
630, as shown in FIG. 13B, the front aligning plate 1002a and the
rear aligning plate 1002b are each reciprocated by the alignment
distance Ld so as to align the sheet stack P (center alignment).
That is to say, the aligning plates 1002a and 1002b align the sheet
stack loaded on the process tray 630 from the first standby
positions corresponding to the front loading position. The aligned
sheet stack is discharged onto the stack tray 700 by the discharge
rollers 680a and 680b. The alignment by the aligning plates 1002a
and 1002b is performed every time a sheet stack is discharged onto
the process tray 630.
A similar alignment operation is performed in the case where a
sheet stack is offset backward and aligned. In this case, as shown
in FIG. 14, the center of offset is behind the center of the unit.
That is to say, being offset by the lateral register correction
unit 1001, the sheet stack is loaded at a rear loading position
(second loading position) shown in FIG. 14. In FIG. 14, the
positions of the aligning plates 1002a and 1002b shown by dashed
lines are second standby positions.
The rear (second) loading position shown in FIG. 14 is a
predetermined offset distance away from the front (first) loading
position shown in FIGS. 13A and 13B. When a sheet stack is loaded
at the rear (second) loading position, the aligning plates 1002a
and 1002b stand by at their respective second standby positions
corresponding to the rear (second) loading position (FIG. 14).
The aligning plates 1002a and 1002b align the sheet stack loaded on
the process tray 630 from the second standby positions
corresponding to the rear (second) loading position. In this case,
the alignment distance is the same as that in the case of forward
offset shown in FIGS. 13A and 13B. Therefore, the description
thereof will be omitted. The aligned sheet stack is discharged onto
the stack tray 700 by the discharge rollers 680a and 680b.
When the shift sort mode is selected, first, a sheet stack is
aligned at the front (first) loading position shown in FIGS. 13A
and 13B and then discharged onto the stack tray 700. Next, another
sheet stack is aligned at the rear (second) loading position shown
in FIG. 14 and then discharged onto the stack tray 700. These
operations are repeated alternately. In this way, a plurality of
sheet stacks are loaded on the stack tray 700, being offset stack
by stack. That is to say, a plurality of sheet stacks are loaded on
the stack tray 700, being shifted in the width direction stack by
stack.
In this embodiment, the front alignment motor M1202 and the rear
alignment motor M1201 are stepping motors and self-activated. In
the case of FIGS. 11A, 11B, and 12, the time T required for
alignment operation per reciprocation can be expressed as
T=2*2*La/V where V is the driving velocity of the front alignment
motor M1202 and the rear alignment motor M1201.
In the case of FIGS. 13A, 13B, and 14, the time T can be expressed
as T=2*Ld/V Since La>>Ld, performing the lateral register
correction according to this embodiment can reduce the time by
.DELTA.T=2*2*La/V-2*Ld/V
As described above, a sheet stack P is loaded on the process tray
630, being shifted to a predetermined offset position. Each sheet
constituting the sheet stack is shifted by the lateral register
correction unit 1001. The aligning plates 1002a and 1002b are moved
to positions corresponding to the sheet offset position in
advance.
According to the above-described embodiment, specifically, when a
sheet stack is loaded at the front loading position on the process
tray 630, the aligning plates 1002a and 1002b are moved to
positions corresponding to the front loading position in advance.
When a sheet stack is loaded at the rear loading position, the
aligning plates 1002a and 1002b are moved to positions
corresponding to the rear loading position in advance.
Since the distance between the aligning plates 1002a and 1002b is
smaller than that in the case where the sheets are not shifted, the
time of alignment operation can be reduced, and high productivity
can be achieved.
When the lateral register correction is performed as in this
embodiment, the alignment distance Ld is set slightly larger than
the distance Le of the lateral register displacement that occurs in
the conveying path from the lateral register correction unit 1001
to the process tray 630 in the finisher 500. Hitherto, the offset
distance La has needed to be set larger than the sum of the
distance Lb of the lateral register displacement in the photocopier
body 10 and the distance Lc of the lateral register displacement in
the finisher 500.
Since the minimum offset distance is reduced, the offset distance
can be set more flexibly. Therefore, a more user-friendly and more
productive finisher 500 and an image forming apparatus having the
same can be provided.
In the case of small sized sheets, since the proportion of the
offset distance in the sheet width is great, the sheet stacks
stacked on the stack tray 700 collapse easily. Therefore, in the
case of small sized sheets, the offset distance is set smaller than
that in the case of large sized sheets.
Thus, a larger number of sheet stacks can be stacked in a
well-aligned state. The maximum number of sheet stacks that can be
loaded on the stack tray 700 is increased. In addition, the stacked
sheet stacks do not collapse easily. As a result, a larger number
of copies can be set for a job. In addition, system downtime due to
collapse of sheet stacks is reduced. Therefore, the productivity
can be further improved.
In the staple mode, when each sheet stack is stapled at one place,
difference in height between the front and the rear of the stack of
stapled sheet stacks tends to occur due to accumulated staples. In
contrast, when each sheet stack is stapled at two places,
difference in height between the front and the rear of the stack of
stapled sheet stacks does not occur easily. Therefore, in the case
of two-place stapling, the offset distance is set small. The
two-place stapling is at a disadvantage in productivity by the time
required to move the stapler. However, by setting the offset
distance small, the productivity of the two-place stapling can be
improved.
In this embodiment, if there is a malfunction in the lateral
register correction unit 1001, the function of lateral register
correction can be cut off. That is to say, there is a mode in
which, if there is a malfunction in the lateral register correction
unit 1001, the finisher 500 operates without activating the lateral
register correction unit 1001. The mode in which the finisher 500
operates without activating the lateral register correction unit
1001 will hereinafter be referred to as "redundant mode."
Next, the redundant mode will be described with reference to a
flowchart shown in FIG. 15.
When the finisher 500 is powered on, the initial operation of the
motors is performed for checking the operation of the loads. The
CPU 550 outputs a drive signal of the lateral register correction
unit shifting motor M1107 so as to move the lateral register
correction unit 1001. The lateral register correction unit HP
sensor 1109 functions as a malfunction detecting device. The CPU
550 then monitors whether there is a change in the signal of the
lateral register correction unit HP sensor 1109 to detect a
malfunction in the lateral register correction unit 1001
(S101).
If the lateral register correction unit 1001 can move, that is to
say, if the lateral register correction unit 1001 is normal, there
is a change in the signal of the lateral register correction unit
HP sensor 1109. In this case, the CPU 550 determines that the
lateral register correction unit 1001 is normal. If the CPU 550
determines that the lateral register correction unit 1001 is normal
(in the case of "NO" in S101), the CPU 550 sets the alignment
operation to a first process including the lateral register
correction (S102). Next, a first alignment operation including the
lateral register correction is performed (S103).
On the other hand, if there is no change in the signal of the
lateral register correction unit HP sensor 1109, the CPU 550
determines that there is a malfunction in the lateral register
correction unit 1001. In this case (in the case of "YES" in S101),
the CPU 550 enters the redundant mode.
After entering the redundant mode, the CPU 550 shuts down the
lateral register correction unit shifting motor M1107 and the
lateral register sensor shifting motor M1106 (S104). Next, the CPU
550 sets the alignment operation to a second process in which the
lateral register correction is not performed (S105).
Next, a second alignment operation that does not include the
lateral register correction is performed (S106). The second
alignment operation is the same as the operation in the case where
the lateral register correction is not performed by the lateral
register correction unit 1001 shown in FIGS. 11A, 11B, and 12.
As described above, if there is a malfunction in the lateral
register correction unit 1001, the CPU 550 is switched to the
redundant mode, in which the function of lateral register
correction is cut off and normal operation is continued. Therefore,
system downtime can be avoided. Therefore, high productivity can be
achieved.
Second Embodiment
A second embodiment of the present invention will be described.
In this embodiment, sheet stacks are discharged without being
offset. In the first embodiment, when the lateral register
correction unit 1001 performs the lateral register correction, the
lateral register sensor unit 1105 is moved from the home position
to a standby position that is predetermined on the basis of the
sheet size and the offset distance (see FIGS. 6A, 6B, 8A, and 8B).
In contrast, in this embodiment, the lateral register sensor unit
1105 is moved from the home position to a standby position that is
predetermined on the basis of the sheet size only.
Next, the alignment operation of a finisher that is a sheet
processing apparatus according to this embodiment will be
described. Before that, the alignment operation in the case where
the lateral register correction is not performed by the lateral
register correction unit 1001 will be described with reference to
FIGS. 16A, 16B, and 17.
In this case, the front aligning plate 1002a and the rear aligning
plate 1002b move from their respective initial positions shown in
FIG. 16A to their respective standby positions and stand by there.
These standby positions are determined taking into consideration
the distance of lateral register displacement that occurs in the
photocopier body 10 and the distance of lateral register
displacement that occurs in the finisher 500. These standby
positions are positions such that the alignment operation is
possible even if a sheet stack P2 is displaced from the ideally
corrected position by a maximum distance L22.
Next, as shown in FIG. 16B, when the sheet stack P2 enters the
process tray 630, the front aligning plate 1002a and the rear
aligning plate 1002b move to their respective standby positions
1002a-1 and 1002b-1 according to the sheet size. After the sheet
stack P2 is loaded on the process tray 630, as shown in FIG. 17,
the front aligning plate 1002a and the rear aligning plate 1002b
each reciprocate a distance L12 between the standby positions
1002a-1 and 1002b-1 and pressing positions 1002a-2 and 1002b-2 so
as to align the sheet stack P2. This alignment is performed every
time a sheet stack is loaded on the process tray 630.
Next, the alignment operation in the case where the lateral
register correction is performed in the finisher 500 will be
described with reference to FIGS. 18A, 18B, and 19.
In this case, as shown in FIG. 18A, the lateral register
displacement of a sheet stack P1 is corrected by the lateral
register correction unit 1001 in the finisher 500. Therefore, it is
only necessary to take into consideration the lateral register
displacement that occurs in the sheet conveyance from the lateral
register correction unit 1001 to the process tray 630. Therefore,
the distance L21 of displacement of the sheet stack P1 to be taken
into consideration, that is to say, the distance of displacement
from the ideally corrected sheet stack P is smaller than the
distance L22 shown in FIG. 16A.
Next, as shown in FIG. 18B, when the sheet stack P1 enters the
process tray 630, the front aligning plate 1002a and the rear
aligning plate 1002b move to their respective standby positions
1002a-3 and 1002b-3 according to the sheet size.
After the sheet stack P1 is loaded on the process tray 630, as
shown in FIG. 19, the front aligning plate 1002a and the rear
aligning plate 1002b each reciprocate a distance L11 between the
standby positions 1002a-3 and 1002b-3 and pressing positions
1002a-2 and 1002b-2 so as to align the sheet stack P1. This
alignment is performed every time a sheet stack is loaded on the
process tray 630.
The distance L12 is set larger than the distance L11. That is to
say, the distance between the front aligning plate 1002a and the
rear aligning plate 1002b in the case where the lateral register
correction unit 1001 shifts the sheets in the width direction so as
to perform position correction in the width direction (the distance
between the standby positions 1002a-3 and 1002b-3) is smaller than
the distance between the front aligning plate 1002a and the rear
aligning plate 1002b in the case where the lateral register
correction unit 1001 does not shift the sheets (the distance
between the standby positions 1002a-1 and 1002b-1). The reason that
the standby positions of the front aligning plate 1002a and the
rear aligning plate 1002b are set as above is that the distance of
displacement to be taken in consideration in the process tray 630
in the case where the lateral register correction unit 1001 shifts
the sheets in the width direction so as to perform position
correction in the width direction is smaller than that in the case
where the lateral register correction unit 1001 does not shift the
sheets.
In this embodiment, the front alignment motor M1202 and the rear
alignment motor M1201 are stepping motors and self-activated. In
the case of FIGS. 16A, 16B, and 17, the time T required for
alignment operation per reciprocation can be expressed as T=2*L12/V
where V is the driving velocity of the front alignment motor M1202
and the rear alignment motor M1201. In the case of FIGS. 18A, 18B,
and 19, the time T can be expressed as T=2*L11/V Since L12>L11,
performing the lateral register correction according to this
embodiment can reduce the time by .DELTA.T=2*L12/V-2*L11/V
Since the distance between the aligning plates 1002a and 1002b is
smaller than that in the case where the sheets are not shifted, the
time of alignment operation can be reduced, and high productivity
can be achieved.
As in the first embodiment, the CPU 550 monitors whether there is a
change in the signal of the lateral register correction unit HP
sensor 1109 (malfunction detecting device). If the CPU 550
determines that there is a malfunction in the lateral register
correction unit 1001, the lateral register correction unit 1001
does not perform the lateral register correction.
In both of the above embodiments, a plurality of sheets are wrapped
around the buffer roller 505. The wrapped sheets are then together
discharged onto the process tray 630. However, sheets that are
shifted by a shift conveying unit may be discharged one by one onto
the process tray 630 so as to form a stack.
While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all modifications, equivalent structures and
functions.
* * * * *