U.S. patent application number 12/338359 was filed with the patent office on 2009-06-25 for image forming apparatus, sheet finisher, and method for driving stacking tray.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Ken IGUCHI, Yasunobu TERAO.
Application Number | 20090160115 12/338359 |
Document ID | / |
Family ID | 40787656 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090160115 |
Kind Code |
A1 |
IGUCHI; Ken ; et
al. |
June 25, 2009 |
IMAGE FORMING APPARATUS, SHEET FINISHER, AND METHOD FOR DRIVING
STACKING TRAY
Abstract
An image forming apparatus according to the present invention
includes a printer, a stapler, a stacking tray, a driving
mechanism, a detecting unit, a storage unit, and a controller. The
printer prints image data on a sheet. The stapler staples a sheet
bundle including the sheet. The stacking tray receives the sheet
bundle at a standby position. The driving mechanism lifts and
lowers the stacking tray. The detecting unit detects an upper
surface of the sheet bundle on the stacking tray. The storage unit
stores number of sheet bundles on the stacking tray. The controller
controls the driving mechanism to increase a distance from the
detecting unit to the stacking tray at the standby position
according to an increase in the number stored in the storage
unit.
Inventors: |
IGUCHI; Ken; (Shizuoka-Ken,
JP) ; TERAO; Yasunobu; (Shizuoka-Ken, JP) |
Correspondence
Address: |
PATTERSON & SHERIDAN, L.L.P.
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
TOSHIBA TEC KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
40787656 |
Appl. No.: |
12/338359 |
Filed: |
December 18, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61015182 |
Dec 19, 2007 |
|
|
|
61016944 |
Dec 27, 2007 |
|
|
|
Current U.S.
Class: |
270/58.09 |
Current CPC
Class: |
B65H 2511/30 20130101;
B65H 2801/27 20130101; B65H 2701/18292 20130101; B65H 2511/22
20130101; B65H 2511/152 20130101; B65H 31/18 20130101; B65H
2511/152 20130101; B65H 2220/01 20130101; B65H 2511/22 20130101;
B65H 2220/02 20130101; B65H 2220/11 20130101; B65H 2511/30
20130101; B65H 2220/01 20130101 |
Class at
Publication: |
270/58.09 |
International
Class: |
B65H 39/00 20060101
B65H039/00 |
Claims
1. An image forming apparatus comprising: a printer configured to
print image data on a sheet; a stapler configured to staple a sheet
bundle, the sheet bundle including the sheet; a stacking tray
configured to receive the sheet bundle at a standby position; a
driving mechanism configured to lift and lower the stacking tray; a
detecting unit configured to detect an upper surface of the sheet
bundle on the stacking tray; a storage unit configured to store the
number of sheet bundles on the stacking tray; and a controller
configured to control the driving mechanism to increase a distance
from the detecting unit to the stacking tray at the standby
position according to an increase in the number stored in the
storage unit.
2. The apparatus according to claim 1, wherein the storage unit
stores the number of sheets included in the sheet bundle, and the
controller controls the driving mechanism to reduce the distance
according to an increase in the number of sheets included in the
sheet bundle stored in the storage unit.
3. The apparatus according to claim 1, wherein the controller
controls the driving mechanism to increase the distance according
to an increase in a size of the sheet.
4. The apparatus according to claim 1, wherein the controller
controls the driving mechanism to keep the distance if the number
is equal to or smaller than a specified value.
5. The apparatus according to claim 1, wherein the controller
controls the driving mechanism to change the distance corresponding
to a thickness of a plurality of sheet bundles.
6. A sheet finisher comprising: a stapler configured to staple a
sheet bundle, the sheet bundle including a sheet; a stacking tray
configured to receive the sheet bundle at a standby position; a
driving mechanism configured to lift and lower the stacking tray; a
detecting unit configured to detect an upper surface of the sheet
bundle on the stacking tray; a storage unit configured to store
number of sheet bundles on the stacking tray; and a controller
configured to control the driving mechanism to increase a distance
from the detecting unit to the stacking tray at the standby
position according to an increase in the number stored in the
storage unit.
7. The finisher according to claim 6, wherein the storage unit
stores the number of sheets included in the sheet bundle, and the
controller controls the driving mechanism to reduce the distance
according to an increase in the number of sheets included in the
sheet bundle stored in the storage unit.
8. The finisher according to claim 6, wherein the controller
controls the driving mechanism to increase the distance according
to an increase in a size of the sheet.
9. The finisher according to claim 6, wherein the controller
controls the driving mechanism to keep the distance if the number
is equal to or smaller than a specified value.
10. The finisher according to claim 6, wherein the controller
controls the driving mechanism to change the distance corresponding
to a thickness of a plurality of sheet bundles.
11. A method for driving a stacking tray comprising acts of:
stapling a sheet bundle, the sheet bundle including a sheet; and
controlling driving of a stacking tray to increase a distance from
a detecting unit that detects an upper surface of the sheet bundle
on the stacking tray to the stacking tray at a standby position
according to an increase in number of sheet bundles on the stacking
tray.
12. The method according to claim 11, wherein the act of
controlling controls the driving of the stacking tray to reduce the
distance according to an increase in the number of sheets included
in the sheet bundle.
13. The method according to claim 11, wherein the act of
controlling controls the driving of the stacking tray to increase
the distance according to an increase in a size of the sheet.
14. The method according to claim 11, wherein the act of
controlling controls the driving of the stacking tray to keep the
distance if the number is equal to or smaller than a specified
value.
15. The method according to claim 11, wherein the act of
controlling controls the driving of the stacking tray to change the
distance corresponding to a thickness of a plurality of sheet
bundles.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from U.S. provisional application 61/015,182, filed on
Dec. 19, 2007, and U.S. provisional application 61/016,944, filed
on Dec. 27, 2007, the entire contents of each of which are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to an image forming apparatus,
a sheet finisher, and a method for driving a stacking tray, and,
more particularly to an image forming apparatus, a sheet finisher,
and a method for driving a stacking tray for stacking a sheet
bundle to be subjected to stapling.
BACKGROUND
[0003] Recently, image forming apparatuses of an
electrophotographic system such as a laser printer, a digital
copying machine, and a laser facsimile include, for example, a
sheet finisher disclosed in JP-2007-76893-A1 that staples a sheet
bundle with a staple and sorts the sheet bundle.
[0004] As disclosed in, for example, JP-5-305786-A1, if a sheet
bundle subjected to stapling is stacked on a stacking tray, in a
sheet finisher, there is a technique for changing a lowering amount
of the stacking tray more if a sheet bundle is discharged than if
unstapled sheets are stacked on the stacking tray. The use of the
technique can improve alignability during stacking on the stacking
tray.
[0005] As disclosed in, for example, JP-11-310362-A1, there is a
technique for providing, in a sheet finisher, an upper surface
detection sensor for detecting an upper surface of a sheet bundle
stacked on a stacking tray and lowering, if an upper surface of the
stacking tray or the sheet bundle is detected, the stacking tray by
a fixed amount.
[0006] However, if a large number of sheet bundles subjected to
stapling are stacked on the stacking tray, a portion subjected to
the stapling swells compared with a portion not subjected to the
stapling. Therefore, an upper surface of the stacked sheet bundles
cannot be normally detected. The problem is more conspicuous, for
example, if sheet bundles subjected to the stapling in one place at
one end of sheets are stacked than if sheet bundles subjected to
the stapling in plural positions symmetrically are stacked.
[0007] If the sheet bundles subjected to the stapling in one place
at one end of sheets are stacked as explained above, a portion
subjected to the stapling swells. Therefore, even if an upper
surface of the sheet bundles is detected near the center of the
sheet bundles, if a large number of sheet bundles are stacked, a
top surface of the stacked sheet bundles cannot be accurately
detected.
[0008] Therefore, since an original upper surface is present in a
position higher than a detectable upper surface and a swelling
portion closes a discharge port of a processing tray, a jam occurs.
If a large number of sheet bundles are stacked, the sheet bundles
are unaligned because, for example, the sheet bundles bump against
sheet bundles already stacked. The stacked sheet bundles fall from
the stacking tray. This problem is more conspicuous if bundles of
two sheets are stacked than if, for example, bundles of fifty
sheets are stacked.
SUMMARY
[0009] The present invention has been devised in view of the
circumstances and an object of the present invention is to provide
an image forming apparatus, a sheet finisher, and a method for
driving a stacking tray that can stack a large umber of sheet
bundles subjected to stapling on the stacking tray and stack the
sheet bundles with high alignability.
[0010] In order to attain the object, an image forming apparatus
according to an aspect of the present invention includes: a printer
configured to print image data on a sheet; a stapler configured to
staple a sheet bundle, the sheet bundle including the sheet; a
stacking tray configured to receive the sheet bundle at a standby
position; a driving mechanism configured to lift and lower the
stacking tray; a detecting unit configured to detect an upper
surface of the sheet bundle on the stacking tray; a storage unit
configured to store number of sheet bundles on the stacking tray;
and a controller configured to control the driving mechanism to
increase a distance from the detecting unit to the stacking tray at
the standby position according to an increase in the number stored
in the storage unit.
[0011] In order to attain the object, a sheet finisher according to
another aspect of the present invention includes: a stapler
configured to staple a sheet bundle, the sheet bundle including a
sheet; a stacking tray configured to receive the sheet bundle at a
standby position; a driving mechanism configured to lift and lower
the stacking tray; a detecting unit configured to detect an upper
surface of the sheet bundle on the stacking tray; a storage unit
configured to store number of sheet bundles on the stacking tray;
and a controller configured to control the driving mechanism to
increase a distance from the detecting unit to the stacking tray at
the standby position according to an increase in the number stored
in the storage unit.
[0012] A method for driving a stacking tray according to still
another aspect of the present invention includes acts of: stapling
a sheet bundle, the sheet bundle including a sheet; and controlling
driving of a stacking tray to increase a distance from a detecting
unit that detects an upper surface of the sheet bundle on the
stacking tray to the stacking tray at a standby position according
to an increase in number of sheet bundles on the stacking tray.
DESCRIPTION OF THE DRAWINGS
[0013] In the accompanying drawings:
[0014] FIG. 1 is a perspective view of an example of an external
appearance of an image forming apparatus according to an embodiment
of the present invention;
[0015] FIG. 2 is a diagram of a detailed configuration example of a
sheet finisher of the image forming apparatus according to the
embodiment;
[0016] FIG. 3 is a schematic diagram of a configuration of the
sheet finisher;
[0017] FIG. 4 is a perspective view of the structure showing mainly
inlet rollers, outlet rollers, a processing tray unit, and a
stacking tray;
[0018] FIG. 5 is a perspective view of a first example of the
structure of the processing tray unit;
[0019] FIG. 6 is a perspective view of a second example of the
structure of the processing tray unit;
[0020] FIG. 7 is a perspective view of the processing tray unit
viewed from an angle different from an angel shown in FIG. 5;
[0021] FIGS. 8 to 11 are schematic side views showing mainly a
configuration example of a belt driving mechanism;
[0022] FIG. 12 is a perspective view of a main part of the sheet
finisher viewed from the stacking tray side;
[0023] FIG. 13 is a side view of the main part of the sheet
finisher;
[0024] FIG. 14 is a block diagram of a first example of functions
of the image forming apparatus according to the embodiment;
[0025] FIG. 15 is a schematic diagram for explaining a function of
a lifting controller;
[0026] FIGS. 16 to 20 are schematic diagrams for explaining a
function of a lowering amount calculating unit;
[0027] FIG. 21 is a flowchart of a first example of acts of the
image forming apparatus according to the embodiment;
[0028] FIG. 22 is a block diagram of a second example of the
functions of the image forming apparatus according to the
embodiment; and
[0029] FIG. 23 is a flowchart of a second example of the acts of
the image forming apparatus according to the embodiment.
DETAILED DESCRIPTION
[0030] An image forming apparatus, a sheet finisher, and a method
for driving a stacking tray according to an embodiment of the
present invention are explained with reference to the accompanying
drawings.
[0031] FIG. 1 is a diagram of an example of an external appearance
of a copying machine (or an MFP) as a typical example of the image
forming apparatus according to this embodiment.
[0032] An image forming apparatus 100 according to this embodiment
is shown in FIG. 1. The image forming apparatus 100 includes an
image forming apparatus main body (a printer, etc.) 1 and a sheet
finisher 2. The image forming apparatus main body 1 includes a
scanning unit 3, a printer 4, and a paper feeding unit 5.
[0033] The scanning unit 3 of the image forming apparatus main body
1 optically scans an original placed on a document table and an
original received by an ADF (auto document feeder) and generates
image data.
[0034] The printer 4 prints the image data on a sheet received from
the paper feeding unit 5 using an electrophotographic system. The
printer 4 has a control panel 6 with which a user performs various
kinds of operation, and a display panel 7 on which various kinds of
information are displayed.
[0035] The sheet finisher 2 is a device that applies post
processing such as sorting and stapling by a staple to sheets P
which the image forming apparatus main body 1 prints.
[0036] FIG. 2 is a diagram of a detailed configuration example of,
in particular, the sheet finisher 2 of the image forming apparatus
100 according to this embodiment. FIG. 3 is a schematic diagram of
a configuration of the sheet finisher 2.
[0037] The sheet finisher 2 adjacent to the image forming apparatus
main body 1 has inlet rollers 11a and 11b on a side thereof. The
inlet rollers 11a and 11b receive a printed sheet P discharged by
the image forming apparatus main body 1. The inlet rollers 11a and
11b transport the received sheet P to outlet rollers 12a and
12b.
[0038] The sheet finisher 2 has a waiting tray 13 ahead of the
outlet rollers 12a and 12b. The waiting tray 13 temporarily holds
the sheet P which the outlet rollers 12a and 12b transport.
[0039] If a holding period passes and the waiting tray 13 is
opened, the waiting tray 13 drops and feeds the sheet P temporarily
held therein to a processing tray 14. On the processing tray 14, a
plurality of the sheets P are placed one on top of another to form
a sheet bundle B.
[0040] The sheet finisher 2 has the processing tray 14 to incline
in an up to down direction. The sheet finisher 2 includes a stapler
19 ahead of a lower end side of the processing tray 14. The sheet
finisher 2 includes a stacking tray (a movable tray) 23 which
stacks the sheet bundle B ahead of an upper end side of the
processing tray 14.
[0041] The sheet finisher 2 has a sheet guide 18 above the lower
end side of the processing tray 14. The sheet guide 18 guides a
trailing end of the sheet bundle B received by the processing tray
14 in the direction of the stapler 19.
[0042] The sheet finisher 2 has a jogger fence 16 on both sides of
the processing tray 14. The jogger fence 16 laterally aligns the
sheet P on the processing tray 14. The sheet finisher 2 has
longitudinal alignment rollers 17 on a rear end side of the
processing tray 14, and a paddle 15 on an upper side of the
longitudinal alignment rollers 17. The paddle 15 and the
longitudinal alignment rollers 17 strike a trailing end of the
sheet P on the processing tray 14 against a rear stopper 26 and
longitudinally align the sheet P.
[0043] The sheet finisher 2 sequentially guides the sheet P to the
processing tray 14 through the waiting tray 13 and guides a
plurality of the sheets P to the stapler 19 as the sheet bundle B.
The stapler 19 staples the vicinity of a trailing end of the sheet
bundle B with a staple.
[0044] In the sheet finisher 2, ejectors (hook members) 20 fixed to
eject belts (toothed belts) 30 (shown in FIG. 5) and a bundle pawl
(a transporting hook member) 21a fixed to a bundle pawl belt (a
transport or belt) 21 hook the trailing end of the sheet bundle B,
and transport the sheet bundle B in the direction of the stacking
tray 23 by the driving of the eject belts 30 and the bundle pawl
belt 21. The sheet finisher 2 fixes push rods 25 on the opposite
side of the ejectors 20 on the eject belts 30. The sheet finisher 2
projects the sheet bundle B in the direction of the stacking tray
23 with a lower surface thereof supported by the push rods 25 and
discharges the sheet bundle B to the stacking tray 23 by
discharging rollers 22.
[0045] The stacking tray 23 can stack a large number of the sheet
bundles B. The stacking tray 23 gradually falls as a stacking
amount of the sheet bundles B increases.
[0046] FIG. 4 is a perspective view of the structure showing mainly
the inlet rollers 11, the outlet rollers 12, a processing tray unit
50, and the stacking tray 23. FIG. 5 is a perspective view of a
first example of the structure of the processing tray unit 50.
[0047] As shown in FIG. 5, the processing tray 50 includes the
processing tray 14 on which the sheet bundle B is placed. The sheet
finisher 2 has the jogger fence 16 on both the sides of the
processing tray 14. The jogger fence 16 aligns side ends of the
sheet bundle B before stapling by being moved in the width
direction. The two longitudinal alignment rollers 17 strike the
trailing end of the sheet bundle B on the processing tray 14
against the rear stopper 26 to longitudinally align the sheet
bundle B.
[0048] Post processing performed by the sheet finisher 2 includes
sorting in addition to the stapling. In the sorting, with a sheet
bundle to be laterally aligned and longitudinally aligned set as a
sorting unit, the sheet finisher 2 alternately shifts the sheet
bundle in the horizontal direction (left and right) for each
sorting unit, and discharges the sheet bundle to the stacking tray
23. The jogger fence 16 shifts the sheet bundle in the horizontal
direction.
[0049] The sheet finisher 2 discharges the sheet bundle B from the
processing tray 14 to the stacking tray 23 via a belt driving
mechanism 60 (shown in FIGS. 8 to 11) and the four discharging
rollers 22. The sheet finisher 2 includes, in the belt driving
mechanism 60, the bundle pawl belt 21, the bundle pawl 21a fixed to
the bundle pawl belt 21, the two eject belts 30 of both sides of
the bundle pawl belt 21, and the ejectors 20 and the push rods 25
fixed to the eject belts 30.
[0050] FIG. 6 is a perspective view of a second example of the
structure of the processing tray unit 50.
[0051] The processing tray unit 50 shown in FIG. 6 includes four
push rods 25. Both outer sides of the two push rods 25 fixed to the
eject belts 30 may have the same two push rods 25, respectively.
The two push rods 25 on the outer side and the two push rods 25 on
the inner side move in synchronization with each other. In the
processing tray unit 50, the sheet bundle B can be supported in a
range wide in the horizontal direction and projected in the
direction of the stacking tray 23. Therefore, the sheet finisher 2
can perform stable transport with little positional deviation.
[0052] FIG. 7 is a perspective view of the processing tray unit 50
viewed from an angle different from an angle shown in FIG. 5.
[0053] The processing tray unit 50 has a motor 51 as a driving
source for the bundle pawl belt 21 and the eject belts 30, and an
electromagnetic clutch 52 for connecting and releasing transmission
of driving force to the eject belts 30 in a lower part thereof.
[0054] FIGS. 8 to 11 are schematic side views of a configuration
example showing mainly the belt driving mechanism 60.
[0055] As shown in FIGS. 8 to 11, the belt driving mechanism 60
includes the bundle pawl belt 21, the bundle pawl 21a fixed to the
bundle pawl belt 21, the two eject belts 30 of both the sides of
the bundle pawl belt 21, and the ejectors 20 and the push rods 25
fixed to the eject belts 30.
[0056] FIG. 8 is a diagram of a state in which the eject belts 30
is in a home position (a first position) The ejectors 20 may be in
a home position of the ejector 20. The push rods 25 fixed to the
eject belts 30 may be in a home position of the push rods 25. The
ejectors 20 stops in a state in which the ejectors 20 hook the
trailing end of the sheet bundle B in a position substantially the
same as the rear stopper 26.
[0057] If the ejectors 20 are in the home position, the belt
driving mechanism 60 applies lateral alignment and longitudinal
alignment to the sheet bundle B using the jogger fence 16 and the
longitudinal alignment rollers 17, and staples by the stapler
19.
[0058] If the eject belts 30 are in the home position, the
electromagnetic clutch 52 (shown in FIG. 7) are off and a toothed
pulley 31 is disconnected from the rotation of the motor 51.
[0059] Even if the ejectors 20 are in the home position, the bundle
pawl belt 21 continues the consecutive rotation in the
counterclockwise direction. Immediately before the ejectors 20
start to move from the home position, the bundle pawl 21a on the
bundle pawl belt 21 moves, for example, in the vicinity below a
toothed pulley 32 (a driven roller) located on the right side.
[0060] FIG. 9 is a diagram of a state after some time elapses after
the electromagnetic clutch 52 is turned on in the state shown in
FIG. 8. If the electromagnetic clutch 52 is turned on in the state
shown in FIG. 8 (the state in which the eject belts 30 are in the
home position and the bundle pawl 21a is moving in the vicinity
below the toothed pulley 32 (the driven roller), the toothed pulley
31 starts the rotation in the counterclockwise direction. The eject
belts 30 (and the ejectors 20 and the push rods 25) start to move
in the left direction in the figure (a forward path direction)
according to the rotation of the toothed pulley 31. The ejectors 20
hook the trailing end side of the sheet bundle B. The push rods 25
support the leading end side of the sheet bundle B. The ejectors 20
transports the sheet bundle B to the stacking tray 23 side.
[0061] A torsion coil spring (an elastic member) inserted into one
end of a pulley shaft of the toothed pulley 31 is wound up by the
rotation of the toothed pulley 31 and elastic force is gradually
accumulated.
[0062] On the other hand, the bundle pawl belt 21 continues the
rotation. In the state shown in FIG. 9, the bundle pawl 21a is
approaching the ejectors 20 from behind the ejectors 20.
[0063] As shown in FIG. 10, when the bundle pawl 21a overtakes the
ejectors 20 and contacts an end of the sheet bundle B, the
electromagnetic clutch 52 is turned off. For example, at a point in
time when the ejectors 20 reached a second position, the
electromagnetic clutch 52 turns off. The bundle pawl 21a which the
sheet bundle B contacts transports the sheet bundle B.
[0064] If the electromagnetic clutch 52 is turned off, as shown in
FIG. 11, the toothed pulley 31 starts to rotate in the opposite
direction (the clockwise direction) by the elastic force
accumulated in the torsion coil spring. The ejectors 20 move to the
home position in a backward path direction while increasing
speed.
[0065] FIG. 12 is a perspective view of a main part of the sheet
finisher 2 viewed from the stacking tray 23 side. FIG. 13 is a side
view of the main part of the sheet finisher 2.
[0066] As shown in FIGS. 12 and 13, a driving mechanism for the
stacking tray 23 of the sheet finisher 2 mainly includes a stacking
tray motor 71 as a driving source, which is a DC (direct current)
motor, a motor timing belt 72, a worm gear 73, gear and pulley 74a
and 74b, a driving side pulley 75, a timing belt 76, an encoder
sensor 77, and a driven side pulley.
[0067] The rotation driving of the stacking tray motor 71 transmits
power to the worm gear 73, the gear and pulley 74a and 74b, and the
driving side pulley 75 in this order via the motor timing belt 72.
The rotation driving of the stacking tray motor 71 transmits the
power to the timing belt 76 stretched between the stacking tray
motor 71 and the driven side pulley.
[0068] The number of revolutions of the stacking tray motor 71,
which is a driving amount of the stacking tray 23, is managed
according to a count number of the encoder sensor 77 attached to
the worm gear 73. If the stacking tray motor 71 is a pulse motor,
the number of revolutions of the stacking tray motor 71 is managed
according to a pulse number.
[0069] The sheet finisher 2 has upper surface detection sensors 78
below the four discharging rollers 22. In FIG. 13, the sheet
finisher 2 has two upper surface detection sensors 78 below the two
discharging rollers 22 in the center, respectively.
[0070] FIG. 14 is a block diagram of a first example of functions
of the image forming apparatus according to this embodiment.
[0071] According to the execution of programs by a CPU (central
processing unit) of the sheet finisher 2, the sheet finisher 2
functions as a sheet-information acquiring unit 101, a lifting
controller 102, a lowering-amount calculating unit 103, and a
lowering controller 104. The sheet finisher 2 may have the
respective units 101 to 104 as hardware.
[0072] The sheet-information acquiring unit 101 has a function of
acquiring, from the CPU of the image forming apparatus main body 1,
sheet information of the sheet P discharged from the image forming
apparatus main body 1 to the sheet finisher 2. The sheet
information means a size of the sheet and sheet thickness of the
sheet P. The sheet thickness may be calculated from the size of the
sheet and sheet weight.
[0073] The lifting controller 102 has a function of, if a sheet
bundle is discharged to the stacking tray 23 in the standby
position, controlling the stacking tray motor 71 (shown in FIGS. 12
and 13) and lifting the stacking tray 23 until the upper surface
detection sensors 78 detect the upper surface of the stacking tray
23 or the upper surface of the sheet bundle B.
[0074] FIG. 15 is a schematic diagram for explaining the function
of the lifting controller 102.
[0075] As shown in FIG. 15, if the sheet bundle B is discharged
from the processing tray 14 to the stacking tray 23 by the sheet
pawl 21a and the discharge rollers 22, the stacking tray 23 stays
on standby in a position below the upper surface detection sensors
78 (a position of a broken line in FIG. 15) If the sheet bundle B
is discharged to the stacking tray 23, the lifting controller 102
lifts the stacking tray 23 until the upper surface detection
sensors 78 detect the upper surface of the sheet bundle B.
[0076] The lowering-amount calculating unit 103 shown in FIG. 14
has a function of calculating a lowering amount of the stacking
tray 23. The lowering amount of the stacking ray 23 is a lowering
amount of the upper surface of the sheet bundle B stacked on the
stacking tray 23.
[0077] The lowering-amount calculating unit 103 calculates a
lowering amount L of the stacking tray 23 such that a distance
(I+L) obtained by adding up a distance I from a discharge port for
discharging the sheet bundle B to the stacking tray 23 to detecting
sections of the upper surface detection sensors 78 and a lowering
amount L of the stacking tray 23 is equal to an optimum distance
for discharging the sheet bundle B onto the stacking tray 23.
Lowering mount=L(fixed value) (1)
[0078] The function of the lowering-amount calculating unit 103 is
explained in detail with reference to FIGS. 16 to 19.
[0079] FIGS. 16 to 19 are schematic diagrams for explaining the
function of the lowering-amount calculating unit 103.
[0080] It the sheet bundle B subjected to stapling, in particular,
the sheet bundle B subjected to the stapling at a corner on one
side is stacked on the stacking tray 23, as shown in FIG. 16, a
difference occurs between the height z1 of a first end on a side
subjected to the stapling and the height z2 of a second end on a
side not subjected to the stapling.
[0081] If the difference occurs between the height z1 of the first
end and the height z2 of the second end, as shown in FIG. 17, an
error ze occurs between the height z1 of the one end as the actual
height of the sheet bundle B and the height z3 of the sheet bundle
B actually detected by the upper surface detection sensors 78. If
the sheet bundle B has a sheet size large in sheet width, the error
ze is larger because a distance y1 in the width direction from the
upper surface detection sensors 78 to the sheet end is large
compared with that in the case of a size with small sheet
width.
[0082] Therefore, if the number of the sheet bundles B stacked on
the stacking tray 23 gradually increases and the error ze gradually
becomes larger, the error ze exceeds the distance (I+L) at certain
timing. If the stacking tray 23 is lowered by the lowering amount L
and the stacking tray 23 is put on standby despite the fact that
the error ze exceeds the distance (I+L), because of the friction
between the front end of the sheet bundle B discharged from the
processing tray 14 next and the sheet bundle B to be stacked, the
sheet bundles B are not stacked with high alignability. The sheet
bundle B discharged from the processing tray 14 next pushes out the
sheet bundle B to be stacked in an upper part of the stacking tray
23.
[0083] On the other hand, if the lowering amount L calculated by
the above equation (1) is set to a value not exceeding the error
ze, in particular, if a stacking amount of the stacking tray 23 is
small, a falling distance of the discharged sheet bundle B is
large. The discharged sheet bundle B is not stacked on the stacking
tray 23 with high alignability.
[0084] Therefore, the lowering-amount calculating unit 103
calculates the error ze as a conversion error ze' using the sheet
information (the size and the thickness of the sheet P) acquired by
the sheet-information acquiring unit 101 and information (the
number of stacked sheet bundles, the thickness of a staple C, and
the number of sheet bundles subjected to stapling) stored in a
storage device such as a memory. The lowering-amount calculating
unit 103 calculates a lowering amount (L+ze') of the stacking tray
23 using a following equation (2):
Lowering amount=L+ze' (2)
[0085] The lowering-amount calculating unit 103 calculates the
conversion error ze' according to a following equation (3) using
the thickness of the staple C as a stapling material shown in FIG.
18:
ze'=(thickness of the staple C-(sheet thickness.times.number of
sheet bundles subjected to stapling)).times.sheet width
coefficient.times.number of stacked sheet bundles (3)
[0086] The lowering-amount calculating unit 103 calculates the
sheet width coefficient using a distance y1 (shown in FIG. 17) for
each size of the sheet P. An example of the sheet width coefficient
for each sheet size is shown in FIG. 19. When the sheet finisher 2
includes the plural upper surface detection sensors 78 as shown in
FIG. 13, the lowering-amount calculating unit 103 only has to
calculate the sheet width coefficient using the upper surface
detection sensor 78 closest to a stapling position of the sheet
bundle B.
[0087] If the conversion error ze' is negative in the calculation
by the above equation (3), the lowering-amount calculating unit 103
may regard the conversion error ze' as zero. If the conversion
error ze' is negative, the lowering-amount calculating unit 103
calculates a lowering amount L shown on the left in FIG. 20. On the
other hand, if the conversion error ze' changes from negative to
positive, the lowering-amount calculating unit 103 changes the
lowering amount L to a lowering amount (L+ze') shown on the right
in FIG. 20.
[0088] The lowering controller 104 shown in FIG. 14 has a function
of controlling the stacking tray motor 71 (shown in FIGS. 12 and
13) to lower the stacking tray 23 by a lowering amount calculated
by the lowering-amount calculating unit 103.
[0089] FIG. 21 is a flowchart of a first example of acts of the
image forming apparatus according to this embodiment.
[0090] First, the sheet finisher 2 of the image forming apparatus
100 acquires, from the CPU of the image forming apparatus main body
1 (shown in FIG. 16), sheet size information of a sheet discharged
from the image forming apparatus main body 1 to the sheet finisher
2 (Act 1).
[0091] Subsequently, the sheet finisher 2 controls the stacking
tray motor. 71 (shown in FIGS. 12 and 13) to lift the stacking tray
23 until the upper surface detection sensors 78 detect the upper
surface of the stacking tray 23 or the upper surface of the sheet
bundle B stacked on the stacking tray 23 (Act 2).
[0092] The sheet finisher 2 calculates the conversion error ze'
using the above equation (3) (Act 3). The sheet finisher 2
determines whether the conversion error ze' calculated in Act 3 is
positive (Act 4). If the sheet finisher 2 determines that the
conversion error ze' is positive ("YES" in Act 4), the sheet
finisher 2 calculates, on the basis of the sheet information (the
size and the thickness of the sheet P) acquired in Act 1 and the
information (the number of stacked sheet bundles, the thickness of
the staple C, and the number of sheet bundles subjected to
stapling) stored in the storage device such as a memory, a lowering
amount (L+ze') of the stacking tray 23 using the above equation (2)
(Act 5).
[0093] On the other hand, if the sheet finisher 2 determines that
the conversion error ze' is negative ("NO" in Act 4), the sheet
finisher 2 regards the conversion error ze' of the above equation
(2) as zero and calculates the lowering amount L of the stacking
tray 23 (Act 6).
[0094] The sheet finisher 2 controls the stacking tray motor 71
(shown in FIGS. 12 and 13) to lower the stacking tray 23 by the
lowering amount calculated in Act 5 or Act 6 (Act 7). According to
the lowering of the stacking tray 23 in Act 7, the stacking tray 23
stays on standby in a position after the lowering.
[0095] The sheet finisher 2 determines whether the discharge of the
sheet bundle B to the stacking tray 23 should be finished (Act 8).
If the sheet finisher 2 determines that the discharge of the sheet
bundle B to the stacking tray 23 is finished ("YES" in Act 8), the
sheet finisher 2 finishes the acts.
[0096] On the other hand, if the sheet finisher 2 determines that
the discharge of the sheet bundle B to the stacking tray 23 is not
finished ("NO" in Act 8), the sheet finisher 2 discharges the sheet
bundle B from the processing tray 14 to the stacking tray 23 (Act
9). Subsequently, the sheet finisher 2 controls the stacking tray
motor 71 to lift the stacking tray 23 until the upper surface
detection sensors 78 detect the upper surface of the sheet bundle B
stacked on the stacking tray 23 (Act 2).
[0097] FIG. 22 is a block diagram of a second example of the
functions of the image forming apparatus according to this
embodiment.
[0098] According to the execution of programs by the CPU of the
sheet finisher 2, the sheet finisher 2 functions as the
sheet-information acquiring unit 101, the lifting controller 102, a
lowering-amount calculating unit 103A, and the lowering controller
104. In the sheet finisher 2, the respective units 101 to 104 may
be provided as hardware. In the second example of the functions of
the sheet finisher 2 shown in FIG. 22, units same as those in the
first example of the functions of the sheet finisher 2 shown in
FIG. 14 are denoted by the same reference numerals and signs and
explanation of the units is omitted.
[0099] The lowering-amount calculating unit 103A has a function of
regarding, if the conversion error ze' calculated by the above
equation (3) is equal to or smaller than a specified value (a
positive number), the conversion error ze' as zero and, on the
other hand, if the conversion error ze' exceeds the specified
value, taking into account the conversion error ze' to calculate
the lowering amount (L+ze') of the stacking tray 23 using the above
equation (2).
[0100] As explained about the function of the lowering-amount
calculating unit 103 shown in FIG. 14, if the conversion error ze'
is taken into account to calculate the lowering amount (L+ze') of
the stacking tray 23 in all cases in which the conversion error ze'
is positive, a lowering amount of the stacking tray 23 by the
lowering controller 104 and a lifting amount of the stacking tray
23 by the lifting controller 101 increase and performance falls.
Therefore, the lowering-amount calculating unit 103A regards the
conversion error ze' as zero until the conversion error ze' exceeds
the specified value.
[0101] The lowering-amount calculating unit 103A sets the
conversion error ze' to a specified value (a ratio to (I+L)) and
calculates, using the distance I, the lowering amount L, the sheet
thickness, the sheet width coefficient, and the number of sheet
bundles subjected to stapling, the number of sheet bundles at which
the conversion error ze' exceeds the specified value for the first
time.
[0102] For example, the distance I is set to 20 [mm], the lowering
amount L is set to 15 [mm], the specified value is set to 28 [mm]
(80% of (20+15)), and the thickness of the sheet P is set to 0.1
[mm]. Under these conditions, two A4 plain papers (the sheet width
coefficient: 2.2) are stapled. The lowering-amount calculating unit
103A calculates, on the basis of the following formula, the
lowering amount (L+ze') of the stacking tray 23 using the above
equation (2) starting from a twelfth sheet bundle.
Number of sheet bundles=28/(1.3-(0.1.times.2)).times.2.2=11.57
[0103] Ten A4-R plain papers (the sheet width coefficient: 1.1) are
stapled under the same conditions. The lowering-amount detecting
unit 103A calculates, on the basis of the following formula, the
lowering amount (L+ze') of the stacking tray 23 using the above
equation (2) starting from an eighty-fifth sheet bundle.
Number of sheet bundles=28/(1.3-(0.1.times.10)).times.1.1=84.84
[0104] The lowering-amount calculating unit 103A may calculate a
lowering amount of the stacking tray 23 at an interval of plural
sheet bundles rather than calculating a lowering amount of the
stacking tray 23 using the conversion error ze' calculated at an
interval of one sheet bundle. For example, the lowering-amount
calculating unit 103A calculates, for fifty-first to sixtieth sheet
bundles, a lowering amount of the stacking tray 23 using the
conversion error ze' calculated at a fifty-first sheet bundle.
[0105] FIG. 23 is a flowchart of a second example of the acts of
the image forming apparatus according to this embodiment. In the
second example of the acts of the image forming apparatus 100 shown
in FIG. 23, acts same as those in the first example of the acts of
the image forming apparatus 100 shown in FIG. 21 are denoted by the
same reference numerals and explanation of the acts is omitted.
[0106] The sheet finisher 2 determines whether the conversion error
ze' calculated in Act 3 exceeds the specified value (Act 10). If
the sheet finisher 2 determines that the conversion error ze'
exceeds the specified value ("YES" in Act 10), the sheet finisher 2
calculates the lowering amount (L+ze') of the stacking tray 23
using the above equation (2) (Act 5).
[0107] On the other hand, if the sheet finisher 2 determines that
the conversion error ze' is equal to or smaller than the specified
value ("NO" in Act 10), the sheet finisher 2 calculates the
lowering amount L of the stacking tray 23 using the above equation
(1) (Act 6).
[0108] As explained above, the image forming apparatus 100, the
sheet finisher 2, and the method for driving the stacking tray 23
according to this embodiment can stack a large number of the sheet
bundles B subjected to stapling on the stacking tray 23 and stack
the sheet bundles B with high alignability.
* * * * *