U.S. patent application number 11/681529 was filed with the patent office on 2008-09-04 for sheet post-processing apparatus.
This patent application is currently assigned to TOSHIBA TEC KABUSHIKI KAISHA. Invention is credited to Yoshiaki Sugizaki.
Application Number | 20080211164 11/681529 |
Document ID | / |
Family ID | 39732516 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080211164 |
Kind Code |
A1 |
Sugizaki; Yoshiaki |
September 4, 2008 |
SHEET POST-PROCESSING APPARATUS
Abstract
A sheet post-processing apparatus is provided with a first paper
discharge tray that is formed to be able to move up and down and to
stack thereon a sheet of paper discharged by way of a processing
tray after post-processing, and a second paper discharge tray that
is formed to be able to move up and down and to stack thereon the
sheet of paper discharged by way of the processing tray after the
post-processing, and is disposed at a lower stage of the first
paper discharge tray and able to stack sheets of paper of a size
larger than sheets of paper stacked on the first paper discharge
tray.
Inventors: |
Sugizaki; Yoshiaki;
(Sunto-gun, JP) |
Correspondence
Address: |
AMIN, TUROCY & CALVIN, LLP
1900 EAST 9TH STREET, NATIONAL CITY CENTER, 24TH FLOOR,
CLEVELAND
OH
44114
US
|
Assignee: |
TOSHIBA TEC KABUSHIKI
KAISHA
Tokyo
JP
|
Family ID: |
39732516 |
Appl. No.: |
11/681529 |
Filed: |
March 2, 2007 |
Current U.S.
Class: |
271/9.06 ;
271/279; 271/298 |
Current CPC
Class: |
B65H 2511/10 20130101;
B65H 2801/27 20130101; B65H 31/3081 20130101; B65H 2408/1131
20130101; B65H 2511/10 20130101; B65H 31/24 20130101; B65H
2301/42266 20130101; B65H 2220/01 20130101 |
Class at
Publication: |
271/9.06 ;
271/279; 271/298 |
International
Class: |
B65H 3/44 20060101
B65H003/44 |
Claims
1. A sheet post-processing apparatus, comprising: a processing tray
that receives a sheet of paper on which is formed an image from an
image forming apparatus; a processing mechanism that applies
post-processing on the sheet of paper stacked on the processing
tray; a first paper discharge tray that is formed to be able to
move up and down and to stack thereon the sheet of paper discharged
by way of the processing tray after the post-processing; and a
second paper discharge tray that is formed to be able to move up
and down and to stack thereon the sheet of paper discharged by way
of the processing tray after the post-processing, and is disposed
at a lower stage of the first paper discharge tray and able to
stack sheets of paper of a size larger than sheets of paper stacked
on the first paper discharge tray.
2. The sheet post-processing apparatus according to claim 1,
wherein: on the first paper discharge tray are preferentially
stacked sheets of paper of a short size and sheets of paper of
other sizes are preferentially stacked on the second paper
discharge tray.
3. The sheet post-processing apparatus according to claim 1,
wherein: on the first paper discharge tray are stacked sheets of
paper of an A-4 size or a letter size and sheets of paper of a B-4,
a A-3, or a long size are stacked on the second paper discharge
tray.
4. The sheet post-processing apparatus according to claim 1,
wherein: for a bundle of sheets of different sizes, the sheets of
paper are stacked on the second paper discharge tray in a mixed
fashion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image forming apparatus,
such as a copying machine, a printer, and a multi function
peripherals, and more particularly, to a sheet post-processing
apparatus that applies post processing on sheets of paper
discharged after image formation.
[0003] 2. Description of the Related Art
[0004] There is a sheet post-processing apparatus configured to
selectively apply staple processing and punching processing by
accepting sheets of paper on which are formed image inside the
apparatus (for example, JP-A-2002-226118).
[0005] Sheets of paper done with the post-processing are discharged
from the sheet post-processing apparatus, and the apparatus is
equipped with an upper tray and a lower tray capable of stacking
thereon a large number of discharged sheets of paper.
[0006] In addition, the upper tray and the lower tray are disposed
to incline at specific angles, so that discharged sheets of paper
are aligned at the end faces on the sheet post-processing apparatus
side.
[0007] Each of the upper tray and the lower tray is able to move in
a top-bottom direction, and they are used properly depending on the
content of a job the user uses, for example, a copy, a network
printer, and a facsimile. Hence, even the upper tray is able to
stack thereon sheets of paper of a long size.
[0008] However, in a case where sheets of paper of a long size are
stacked on the upper tray, the sheets of paper of the long size on
the upper tray get in the way when the user picks up the sheets of
paper on the lower tray, and there arises a problem that the sheets
of paper on the lower tray are not picked up easily.
[0009] In addition, in a case where a large volume of sheets of
paper of a long size are stacked on the upper tray, the center of
gravity becomes higher due to the weight of the stacked sheets of
paper, which causes an inconvenience that the sheet post-processing
apparatus becomes easy to fall.
BRIEF SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a sheet
post-processing apparatus equipped with plural paper discharge
trays capable of moving up and down.
[0011] In an aspect of the present invention, a sheet
post-processing apparatus includes: a processing tray that receives
a sheet of paper on which is formed an image from an image forming
apparatus; a processing mechanism that applies post-processing on
the sheet of paper stacked on the processing tray; a first paper
discharge tray that is formed to be able to move up and down and to
stack thereon the sheet of paper discharged by way of the
processing tray after the post-processing; and a second paper
discharge tray that is formed to be able to move up and down and to
stack thereon the sheet of paper discharged by way of the
processing tray after the post-processing, and is disposed at a
lower stage of the first paper discharge tray and able to stack
sheets of paper of a size larger than sheets of paper stacked on
the first paper discharge tray.
DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view showing a major portion of a
sheet post-processing apparatus according to one embodiment of the
invention;
[0013] FIG. 2 is a plan view showing the major portion of the sheet
post-processing apparatus according to the embodiment of the
invention;
[0014] FIG. 3 is a view schematically showing the configuration of
the sheet post-processing apparatus according to the embodiment of
the invention;
[0015] FIG. 4 is a perspective view showing a stapler of the sheet
post-processing apparatus according to the embodiment of the
invention;
[0016] FIG. 5 is a view used to describe a portrait alignment
roller according to the embodiment of the invention;
[0017] FIG. 6 is a perspective view showing a paddle according to
the embodiment of the invention;
[0018] FIG. 7 is a functional block diagram showing the relation of
a control system according to the embodiment of the invention and a
control system of an image forming apparatus main body; and
[0019] FIG. 8 is a view used to describe a movement of a stand-by
tray according to one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Throughout this description, the embodiments and examples
shown should be considered as exemplars, rather than limitations on
the apparatus and methods of the present invention.
[0021] Hereinafter, one embodiment of the invention will be
described with reference to the drawings.
[0022] FIG. 1 is a perspective view showing a major portion of a
sheet post-processing apparatus according to one embodiment of the
invention. FIG. 2 is a plan view of the major portion of the sheet
post-processing apparatus.
[0023] FIG. 3 schematically shows the configuration of the sheet
post-processing apparatus disposed adjacently to an image forming
apparatus.
[0024] A sheet post-processing apparatus 7 has a pair of inlet
rollers 22 that takes a sheet of paper P, on which an image is
formed in an image forming apparatus 5 and which is discharged from
a pair of paper discharge rollers 6, inside the sheet
post-processing apparatus 7. The inlet rollers 22 are driven by an
inlet roller motor 26. A paper path ceiling 36 that introduces a
sheet of paper P to a pair of paper feeding rollers 24 is provided
from the inlet rollers 22 to a stand-by tray 10. A processing tray
12 on which is stacked a sheet of paper P supplied by falling from
the stand-by tray 10 is disposed below the stand-by tray 10.
[0025] The processing tray 12 supports and aligns sheets of paper
stacked thereon while the sheets of paper P are subjected to staple
processing by a stapler 14, which is a processing mechanism that
performs post-processing.
[0026] As is shown in FIG. 4, the stapler 14 is allowed to move by
sliding in the direction indicated by an arrow u by a staple
driving unit 49 and is positioned by being rotationally moved in a
staple direction, so that the staple processing is controlled. In
order to align plural sheets of paper P supplied by falling from
the stand-by tray 10 in a portrait direction, which is the carrying
direction, the processing tray 12 has a pair of an upper portrait
alignment roller 38a and a lower portrait alignment roller 38b,
respectively, at top and bottom as shown in FIG. 5. The upper and
lower portrait alignment rollers 38a and 38b also serve as bundle
carrying rollers that nip and take out a bundle of sheets, T (shown
in FIG. 3), from the stapler 14 after the staple processing ends.
The upper portrait alignment roller 38a is driven by a portrait
alignment upper roller motor 40, and the lower portrait alignment
roller 38b is driven by a portrait alignment lower roller motor
42.
[0027] Also, at a position at which the rear end of a sheet of
paper P falls when the sheet of paper P (shown in FIG. 3) is
supplied to the processing tray 12 by falling, a paddle 44 is
disposed, which is capable of rotating to align the uppermost sheet
of paper P stacked on the processing tray 12 in the portrait
direction. As is shown in FIG. 6, the paddle 44 has a reception
unit 44a of a sheet of paper P supplied to the processing tray 12
by falling, a flip unit 44b that flips down a sheet of paper P onto
the processing tray 12, and a sending unit 44c that aligns sheets
of paper P on the processing tray 12, and it is driven by a paddle
motor 46. The paddle 44 is made of a rubber material and therefore
has elasticity.
[0028] A stopper 45 that limits the rear end position by abutting
on the rear end of the sheets of paper P is provided to the
processing tray 12 at the end portion on the stapler 14 side. At
almost the center of the processing tray 12, a carrying belt 50 is
provided, which is a carrying mechanism that carries a bundle of
sheets, T, done with the staple processing and taken out from the
stapler 14 by the upper and lower portrait alignment rollers 38a
and 38b to a first or second paper discharge tray 16 or 18, and it
comes into contact with the lowermost sheet of paper P on the
processing tray 12. The carrying belt 50 is an endless belt that
moves in the direction indicated by an arrow t, and a sending claw
50a to hook up the rear end of a bundle of sheets, T, is attached
to the carrying belt 50.
[0029] The stand-by tray 10 is able to supply sheets of paper P by
letting them fall onto the processing tray 12, while it is able to
carry the sheets of paper P in the direction of the first (upper)
or second (lower) paper discharge tray 16 or 18. The sheets of
paper P are carried in the direction of the paper discharge tray 16
or 18 by bringing a stand-by tray roller 28 that aligns the sheets
of paper P into contact with the sheets of paper P on the stand-by
tray 10. The stand-by tray roller 28 is controlled to move in the
top-bottom direction by a stand-by tray roller driving source 30,
and driven to rotate by a stand-by tray roller motor 32.
[0030] The stand-by tray 10 is disposed with an inclination such
that make the tip end of the sheets of paper P higher than the rear
end. The first or second paper discharge tray 16 or 18 is moved up
or down by a paper discharge tray driving unit 52, and either of
them is selected. The first or second paper discharge tray 16 or 18
moves up or down to the level almost as high as the stand-by tray
10 or the processing tray 12 while the sheets of paper P are
stacked thereon, so that the sheets of paper P to be discharged can
be aligned better.
[0031] The first or second paper discharge tray 16 or 18 is moved
up or down by driving means in the top-bottom direction while being
guided by an unillustrated guiding rail. The paper discharge tray
16 stacks thereon sheets of paper of a size smaller than those on
the paper discharge tray 18, such as those of A-4 size or a letter
size or smaller. Meanwhile, the paper discharge tray 18 stacks
thereon sheets of paper larger than those of A-4 size, such as
those of B-4 size or A-3 size or those of a long size. It goes
without saying that the first paper discharge tray 16 can be
smaller than the second paper discharge tray 18 in the size of an
outer shape.
[0032] In terms of shapes, the first or second paper discharge tray
16 or 18 is disposed with an inclination such that makes the tip
end of the sheets of paper P higher than the rear end.
[0033] FIG. 7 is a functional block diagram showing a relation of
the control system of the sheet post-processing apparatus 7 and the
control system of the image forming apparatus main body. Referring
to FIG. 7, a main body controller 61 of an image forming apparatus
main body 5 is connected to a controller 62 of the sheet
post-processing apparatus 7. More specifically, by operations by
the user or the like, the main body controller 61 of the image
forming apparatus 5 acquires information about the paper size of a
print output together with document data to be printed when it
receives a print job. The main body controller 61 of the image
forming apparatus main body 5 transmits the paper size information
to the controller 62 of the sheet post-processing apparatus 7
together with information about the reception of the print job.
[0034] The controller 62 of the sheet post-processing apparatus 7
has a CPU 63 that controls the sheet post-processing apparatus 7, a
ROM 64 having stored a program or the like to control the sheet
post-processing apparatus 7, and a RAM 65 that is used as a working
area of the program and temporarily stores data necessary for the
control on the sheet post-processing apparatus 7.
[0035] Functions of the sheet post-processing apparatus 7
configured as described above will now be described.
[0036] As the prerequisite, it is necessary for each of the paper
discharge trays 16 and 18 in the sheet post-processing apparatus 7
to stack sheets of paper of various sizes discharged from the image
forming apparatus main body without letting any sheet of paper fall
down. More specifically, whether the paper size is the size of the
largest A-3 size or a long size, or the A-4 size or the letter size
that are assumed to account for about 80% of sheets of paper
actually used, or a further smaller B-5 size, each of the paper
discharge trays 16 and 18 should be able to stack sheets of paper
in a reliable manner.
[0037] Moreover, it is also important that sheets of paper stacked
on each of the paper discharge trays 16 and 18 can be readily
picked up, or even in a state where sheets of papers are stacked on
each of the paper discharge trays 16 and 18, the sheet
post-processing apparatus 7 will no readily fall by losing a
balance.
[0038] In order to satisfy these requirements, the sheet
post-processing apparatus 7 operates in response to respective
modes.
[0039] To be more specific, when images are formed in the image
forming apparatus 5 and sheets of paper P are supplied from the
paper discharge rollers 6, the sheet post-processing apparatus 7
operates differently depending on a case where to post-processing
the sheets of paper P is performed or is not performed or in a case
where a preceding sheet of paper P is being subjected to the
post-processing or done with the post-processing.
(A) A Case Where Post-Processing is not Performed
[0040] The paper size information has been previously transmitted
to the controller 62 of the sheet post-processing apparatus 7 from
the controller 61 of the image forming apparatus main body 5 by the
settings of the print job made by the operator. The controller 62
of the sheet post-processing apparatus 7 controls the position of
each of the paper discharge trays 16 and 18 according to the paper
size information thus transmitted.
[0041] To be more specific, in a case where sheets of paper are of
a paper size as large as an A-4 size or a letter size or smaller,
the upper paper discharge tray 16 moves by sliding to the position
indicated by a dotted line of FIG. 3. Meanwhile, in a case where
sheets of paper are of a B-4 size or an A-3 size or a long size
larger than the A-4 size, the lower paper discharge tray 18 moves
by sliding to the position indicted by a dotted line of FIG. 3.
[0042] In this state, in a case where the post-processing is not
performed, the sheets of paper P carried to the paper feeding
rollers 24 via the paper path ceiling 36 from the inlet rollers 22
are fed to the stand-by tray 10 from the paper feeding rollers 24.
Subsequently, the sheets of paper P are carried by the stand-by
tray roller 28 that is moved down onto the stand-by tray 10 and
rotated in the direction indicated by an arrow f, and discharged to
either the upper paper discharge tray 16 or the lower paper
discharge tray 18 depending on the paper size.
[0043] As has been described, sheets of paper are successively
stacked on each of the paper discharge trays 16 and 18. In this
instance, because each of the paper discharge trays 16 and 18 is
disposed with an inclination such that makes the tip end side of
the sheets of paper P higher than the rear end side, there will be
no event that sheets of paper P stacked earlier on each of the
paper discharge trays 16 and 18 are pushed out by the contact with
the tip end of the following sheet of paper P. In other words, the
order of the discharged sheets of paper P remains intact, and
sheets of papers P are stacked sequentially on each of the paper
discharge trays 16 and 18. In addition, even when the preceding
sheets of paper P undergo positional displacement slightly by being
pushed by the following sheet of paper P, the sheets of paper P
fall with their own weights owing to the angle of inclination.
Consequently, the sheets of paper P are stacked while they are
aligned with the rear end being aligned on each of the paper
discharge trays 16 and 18, whereupon the paper discharge processing
of the sheets of paper P is completed.
[0044] In this case, even when the sheets of papers are stacked on
the paper discharge tray 16 or 18, sheets of paper of a size as
large as the A-4 size or the letter size or smaller are stacked on
the upper paper discharge tray 16 while sheets of paper of the B-4
size or the A-3 size or the long size larger than the A-4 size are
stacked on the lower paper discharge tray 18. Accordingly, it is
possible to pick up the sheets of paper easily whether they are
sheets of paper stacked on the upper paper discharge tray 16 or
sheets of paper stacked on the lower paper discharge tray 18
without being interrupted by the sheets of paper stacked on the
other tray.
[0045] Regarding the stacking on the same paper discharge tray 16
or 18, while sheets of paper of a short size are stacked under the
sheets of paper of a long size, it has been quite difficult to pick
up the sheets of paper of a short size. However, in this
embodiment, because the sizes are assigned to the trays, the
difficulty of picking up sheets of paper can be eliminated.
[0046] By stacking print matter having different sizes on the lower
paper discharge tray 18 as a rule, it is possible to prevent a
problematic event that print matter is stacked separately.
Moreover, because the upper paper discharge tray 16 is small, it is
easy to pick up sheets of paper from the lower paper discharge tray
18 as the sheets of paper of a long size mixed and stacked thereon
serve as a partition.
[0047] In addition, the weight of the sheets of paper stacked on
the lower paper discharge tray 18 is greater than the weight of
sheets of paper stacked on the upper paper discharge tray 16, even
when sheets of paper are stacked on the both paper discharge trays,
the center of gravity of the sheet post-processing apparatus 7
stays at a lower position. The sheet post-processing apparatus thus
becomes difficult to fall and is stabilized.
(B) When Post-Processing is Performed
[0048] As an example of the post-processing, a case will be
described, in which the staple processing is performed when there
is no preceding sheet of paper P on the processing tray 12 that is
being subjected to the staple processing.
[0049] In this case, too, the paper size information has been
previously transmitted from the controller 61 of the image forming
apparatus main body 5 to the controller 62 of the sheet
post-processing apparatus 7 by the settings of the print job made
by the user. The controller 62 of the sheet post-processing
apparatus 7 controls the position of each of the paper discharge
trays 16 and 18 according to the paper size information thus
transmitted.
[0050] More specifically, in a case where the sheets of paper are
sheets of paper of a size as large as the A-4 size or the letter
size or smaller, the upper paper discharge tray 16 moves by sliding
to the position indicated by the dotted line of FIG. 3. Meanwhile,
in a case where the sheets of paper are of the B-4 size or the A-3
size or the long size larger than the A-4 size, the lower paper
discharge tray 18 moves by sliding to the position indicated by the
dotted line of FIG. 3.
[0051] As is shown in FIG. 8, in this state, the stand-by tray 10
opens a fall supply path of sheets of paper P by moving tray
members 10a and 10b by sliding to positions indicated by dotted
lines of FIG. 8 in the directions indicated by an arrow m and an
arrow n, respectively. Also, in order to align sheets of paper P
falling from the paper feeding rollers 24 in the landscape
direction, landscape alignment plates 47a and 47b are disposed in
such a manner that a distance between the landscape alignment
plates 47a and 47b becomes almost the same as the width of the
sheets of paper P. Accordingly, sheets of paper P fed by the paper
feeding rollers 24 are supplied directly by falling onto the
processing tray 12 without being interrupted by the stand-by tray
10 while being carried.
[0052] During the supply by falling, the upper portrait alignment
roller 38a evacuates to an upper position, and the reception unit
44a of the paddle 44 receives the rear end of the sheets of paper
P. The sheets of paper P fall while the both ends are coming into
contact with the landscape alignment plates 47a and 47b so as to be
aligned in the landscape direction. Subsequently, the paddle 44
rotates in the direction indicated by an arrow o to let the rear
end of the sheets of paper P fall from the reception unit 44a and
flips them down onto the processing tray 12 by means of the
flipping unit 44b. Further, the paddle 44 feeds the sheets of paper
P in the direction indicated by an arrow q by means of the sending
unit 44c to let the rear end of the sheets of paper P abut on the
stopper 45, whereupon the alignment of sheets of paper P in the
portrait direction is completed. In this manner, when the sheets of
paper P supplied to the processing tray 12 are aligned in reference
to the stopper 45, the rear end 50c of the carrying belt 50 on the
sheets of paper P side become lower than the supporting plane of
the processing tray 12 for the sheets of paper P. Hence, the
contact friction of the carrying belt 50 to the rear end of the
lowermost sheet of paper P is so small that the alignment of the
sheets of paper P will not be disturbed, which makes it possible to
align the sheets of paper P in a reliable manner. Sheets of paper P
may be aligned in the portrait direction on the processing tray 12
by the upper portrait alignment roller 38a instead of the paddle 44
by moving the upper portrait alignment roller 38a vertically for
each alignment.
[0053] As has been described, sheets of paper P on which are formed
images are directly stacked on the processing tray 12 from the
paper feeding rollers 24 while being aligned successively in the
landscape direction and the portrait direction. When a
predetermined number of sheets of paper P are stacked, the stapler
14 bundles the sheets of paper P on the processing tray 12 by
stapling them at the desired position and makes a bundle of sheets,
T. Thereafter, the upper portrait alignment roller 38a is moved
down above the bundle of sheets to nip the bundle of sheets, T,
between the upper portrait alignment roller 38a rotating in the
direction indicated by an arrow r and the lower portrait alignment
roller 38b rotating in the direction indicated by an arrow s for
the bundle to be carried in the direction of the first paper
discharge tray 16.
[0054] When the rear end of the bundle of sheets, T, passes by the
upper and lower portrait alignment rollers 38a and 38b, it is
hooked by the sending claw 50a of the carrying belt 50 rotating in
the direction indicated by an arrow t and discharged onto the first
paper discharge tray 16 in the form of a bundle. While the bundle
is discharged by the carrying belt 50, the carrying belt 50
inclines so as to protrude from the supporting plane of the
processing tray 12 for sheets of paper P towards the tip end 50b on
the sheets of paper P side. Hence, the contact friction by the
carrying belt 50 becomes gradually larger toward the tip end of the
lowermost sheet of paper P, and a carrying force of the sheet of
paper P in the paper discharging direction by the carrying belt 50
is increased toward the first paper discharge tray 16. The bundle
of sheets, T, is thus carried onto the paper discharge tray 16 or
18 set according to the paper size in the form of a bundle by the
carrying force of the sending claw 50a and the carrying belt 50 in
a reliable manner without being disturbed.
[0055] Because the respective paper discharge trays 16 and 18 are
disposed with inclinations such that makes the tip end of the
sheets of paper P higher than the rear end, there will be no event
that sheets of paper P discharged onto the first paper discharge
tray 16 earlier in the form of a bundle are pushed out by the
contact with the tip end of a following bundle of sheets, T. Also,
even when the preceding bundle of sheets, T, undergoes displacement
by the following sheet of paper P, the bundle of sheets, T, falls
by its own weight owing to the angle of inclination and is stacked
on the paper discharge tray 16 or 18 with the rear end being
aligned for the staple processing on the sheets of paper P to be
completed.
[0056] In this case, too, even when sheets of paper are stacked on
the paper discharge trays 16 and 18, sheets of paper of the A-4
size or the letter size or smaller are stacked on the upper paper
discharge tray 16 while sheets of paper of the B-4 size, the A-3
size or the long size larger than the A-4 size are stacked on the
lower paper discharge tray 18. Hence, it is possible to pick up the
sheets of paper whether they are sheets of paper stacked on the
upper paper discharge tray 16 or sheets of paper stacked on the
lower paper discharge tray 18 without being interrupted by the
sheets of paper stacked on the other tray.
[0057] Regarding the stacking on the same paper discharge tray 16
or 18, while sheets of paper of a short size are stacked under the
sheets of paper of a long size, it has been quite difficult to pick
up the sheets of paper of a short size. However, in this
embodiment, because the sizes are assigned to the trays, the
difficulty of picking up sheets of paper can be eliminated.
[0058] By stacking print matter having different sizes on the lower
paper discharge tray 18 as a rule, it is possible to prevent a
problematic event that print matter is stacked separately.
Moreover, because the upper paper discharge tray 16 is small, it is
easy to pick up sheets of paper from the lower paper discharge tray
18 as the sheets of paper of a long size mixed and stacked thereon
serve as a partition.
[0059] In addition, the weight of the sheets of paper stacked on
the lower paper discharge tray 18 is greater than the weight of
sheets of paper stacked on the upper paper discharge tray 16, even
when sheets of paper are stacked on the both paper discharge trays,
the center of gravity of the sheet post-processing apparatus 7
stays at a lower position. The sheet post-processing apparatus thus
becomes difficult to fall and is stabilized.
[0060] Although exemplary embodiments of the present invention have
been shown and described, it will be apparent to those having
ordinary skill in the art that a number of changes, modifications,
or alterations to the invention as described herein may be made,
none of which depart from the sprit of the present invention. All
such changes, modifications, and alterations should therefore be
seen as within the scope of the present invention.
* * * * *