U.S. patent application number 11/000989 was filed with the patent office on 2005-06-23 for sheet feeding apparatus and image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Koga, Hiroto.
Application Number | 20050133980 11/000989 |
Document ID | / |
Family ID | 34674865 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133980 |
Kind Code |
A1 |
Koga, Hiroto |
June 23, 2005 |
Sheet feeding apparatus and image forming apparatus
Abstract
A middle plate for piling a sheet bundle is provided elevatably.
A duct opened to the side surface of the upper part of the sheet
stack supported on the middle plate. A vacuuming belt for vacuuming
and feeding the uppermost sheet of the sheet stack supported on the
middle plate is provided. A first height detecting means for
detecting the uppermost part of the sheet stack supported on the
middle plate reaching a first position and a second height
detecting means for detecting the uppermost part of the sheet stack
supported on the middle plate reaching a second position higher
than the first position are provided. At the time the uppermost
surface of the sheet stack supported on the middle plate is
detected by the first height detecting means, the controller stops
the middle plate and commands the air blowing operation from the
duct opening, and then at the time the uppermost surface of the
sheet bundle is detected by the second height detecting means
according to the middle plate raising operation, it commands the
vacuuming and feeding operation of the uppermost sheet by the
vacuuming belt.
Inventors: |
Koga, Hiroto; (Abiko-shi,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
TOKYO
JP
|
Family ID: |
34674865 |
Appl. No.: |
11/000989 |
Filed: |
December 2, 2004 |
Current U.S.
Class: |
271/97 |
Current CPC
Class: |
B65H 3/0816 20130101;
B65H 3/48 20130101; B65H 2406/3662 20130101; B65H 1/08
20130101 |
Class at
Publication: |
271/097 |
International
Class: |
B65H 001/08; B65H
003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2003 |
JP |
2003-407026 |
Claims
1. A sheet feeding apparatus comprising: sheet supporting means for
moving the uppermost surface of a sheet stack to a predetermined
position, air blowing means having a duct for blowing the air from
a direction substantially perpendicular to the side surface of the
uppermost part of the sheet stack supported on the sheet supporting
means, and sheet feeding means for vacuuming and feeding the
uppermost sheet of the sheet stack supported on the sheet
supporting means by vacuuming the air, wherein the air blowing
means blows the air to the uppermost part of the sheet stack
supported on the sheet supporting means at a first position which
the uppermost sheet of the sheet stack is faced to an opening of
the all blowing means, and the uppermost sheet is vacuumed and fed
by the sheet feeding means at a second position above the first
position.
2. The sheet feeding apparatus according to claim 1, wherein the
feeding operation is stopped temporarily after the continuous
feeding operation of a predetermined number of sheets at the second
position for moving the uppermost sheet of the sheet stack to the
first position, and after operating the air blowing means for a
predetermined time, the uppermost sheet is moved again to the
second position for resuming the feeding operation.
3. The sheet feeding apparatus according to claim 1, further
comprising an air blowing speed varying means for changing the air
blowing speed blown out from the air blowing means.
4. The sheet feeding apparatus according to claim 3, wherein the
sheet feeding means is operated for vacuuming and feeding the
uppermost sheet after moving from the first position to the second
position after operating the air blowing means and the air speed
varying means at the first position for a predetermined time.
5. The sheet feeding apparatus according to claim 4, wherein the
feeding operation is stopped temporarily after the continuous
feeding operation of a predetermined number of sheets at the second
position for moving the uppermost sheet of the sheet stack to the
first position, and after operating the air blowing means and the
air blowing speed varying means for a predetermined time, the
uppermost sheet is moved again to the second position for resuming
the feeding operation.
6. The sheet feeding apparatus according to claim 3, wherein the
air blowing means and the air blowing speed varying means can be
operated also at the time the uppermost sheet of the sheet stack
supported on the sheet supporting means is between the first
position and the second position.
7. The sheet feeding apparatus according to claim 3, wherein the
air blowing speed varying means is a channel moving means for
moving the air channel blown out from the air blowing means in the
substantially vertical direction in the vicinity of the sheet stack
side surface.
8. The sheet feeding apparatus according to claim 3, wherein the
air blowing speed varying means increases or reduces the air supply
from the air supply source of the air blowing means.
9. The sheet feeding apparatus according to claim 3, wherein the
air blowing speed varying means is an air blocking means for
blocking or opening the air channel from the air blowing means.
10. The sheet feeding apparatus according to claim 1, further
comprising an air orientation varying means for changing the air
orientation blown out from the air blowing means.
11. The sheet feeding apparatus according to claim 10, wherein the
sheet feeding means is operated at the second position above the
first position for vacuuming and feeding the uppermost sheet after
operating the air blowing means and the air orientation varying
means for a predetermined time at the first position.
12. The sheet feeding apparatus according to claim 11, wherein the
feeding operation is stopped temporarily after the continuous
feeding operation of a predetermined number of sheets at the second
position for moving the uppermost sheet of the sheet stack to the
first position, and after operating the air blowing means and the
air orientation varying means for a predetermined time, the
uppermost sheet is moved again to the second position for resuming
the feeding operation.
13. A sheet feeding apparatus comprising: a middle plate provided
elevatably which supports sheet stack, a duct opened to the side
surface of a upper part of the sheet stack supported on the middle
plate, and said duct blows out the air from a opening of the duct
to the side surface of a upper part of the sheet stack, a vacuuming
belt for vacuuming and feeding a uppermost sheet of the sheet stack
supported on the middle plate by vacuuming the air, first height
detecting means for detecting the uppermost sheet of the sheet
stack supported on the middle plate reaching a first position,
second height detecting means for detecting the uppermost sheet of
the sheet stack supported on the middle plate reaching a second
position higher than the first position, and a controller for
commanding the execution of the air blowing operation of the duct
when the uppermost surface of the sheet stack supported on the
middle plate is detected by the first height detecting means, and
commanding the execution of the feeding operation of the vacuuming
belt when the uppermost surface of the sheet stack raised by the
elevation of the middle plate is detected by the second height
detecting means.
14. The sheet feeding apparatus according to claim 13, further
comprising a shutter having a slit, vertically movably between the
duct opening and the sheet stack such that the shutter is
controlled by the controller so as to be moved vertically at the
time the air is blown out from the duct opening.
15. The sheet feeding apparatus according to claim 13, further
comprising a swing nozzle to be rotated vertically in the duct such
that the air is blown out from the swing nozzle at the time the
uppermost surface of the sheet stack is detected by the first
height detecting means.
16. An image forming apparatus comprising: an image forming unit
for forming an image on a sheet, and the sheet feeding apparatus
according to any of claims 1 to 15, for separating and feeding
sheets one by one to the image forming unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sheet feeding apparatus
for separating and feeding the uppermost sheet of a sheet stack, in
particular, it relates to a sheet feeding apparatus to be used for
an image forming apparatus such as a copying machine, a printer and
a facsimile equipment.
[0003] 2. Description of the Related Art
[0004] Conventionally, according to the image forming apparatus
such as a copying machine and a printer, cut sheet to be fed
continuously have been limited to in general good quality paper or
plain paper designated by the copying machine manufacturer. Since
the sheets have a low surface smoothness and a low air
permeability, air can easily be introduced between the sheets.
Therefore, sticking of the sheets and generation of superimposition
can hardly be generated at the time of taking out the sheets one by
one from the stacked sheets.
[0005] However, recently, according to the variation of the
recording media, in addition to the thick papers, the OHP papers,
the tracing papers, or the like, from the demand for the colors
from the market, image formation on the sheets having a smooth
surface such as art papers, coat papers, with a coating process
applied on the sheet surface for providing the whiteness and the
glossiness has been more and more required. However, since the OHP
papers, the tracing papers, the art papers, the coat papers, or the
like have a high smoothness and a high air permeability,
particularly in the case of piling the above-mentioned sheets in a
high humidity environment, the sheets stick with each other. In the
case the sheets stick with each other, a problem is involved in
that superimposition and feeding error are generated frequently
according to the friction separation method commonly used in the
conventional image forming apparatus such as a copying machine and
a printer.
[0006] On the other hand, those of the air feeding method of
separating and feeding one by one from the upper sheet by a
vacuuming device and a feeding belt disposed above while separating
a sheet bundle by blowing the air from the side surface of a sheet
stack supported and stored in an image forming apparatus at the
same time have been adopted in the printing industry and a part of
the copying machines, or the like. According to the air feeding
method, compared with the friction separation method, there are
advantages such as (1) a wide setting latitude of the feeding
conditions with respect to various sheets of different materials,
(2) capability of high speed feeding, (3) a high durability, and
(4) a low running cost.
[0007] A number of proposals have been given for the air feeding.
For example, a paper feeding apparatus disclosed for example in the
official gazette of the Japanese Patent Application Laid Open
(JP-A) No. 62-249835 can be presented. According to the paper
feeding apparatus, a method of blowing the air in the direction
parallel to the sheet upper surface by an air blowing device onto
the sheet top end side surface supported on a paper feeding stand
and at the same time having the vacuuming cylinder opened above the
sheets in a negative pressure by a negative pressure generating
device for vacuuming is proposed. According to the paper feeding
apparatus, the sheets are separated by lifting the uppermost sheets
from the sheets stacked on the paper feeding stand by the vacuuming
function from the opening and blowing the air from the air blowing
device into the gap formed between the uppermost sheet and the next
sheet.
[0008] However, as mentioned above, since the sheets of the OHP
papers, the tracing papers, the art papers, the coat papers, or the
like have a high smoothness and a high air permeability,
particularly in the case the sheets are stacked in a high humidity
environment, the sheets stick with each other. Here, in the case
the air feeding method is adopted, since the air blown from the
side surface of the sheet bundle is a constant flow, the sheet
bundle in the upper part may be lifted on the sheet bundle in the
lower part out of the sheet bundle at the interface of the sheets
with a relatively weak sticking force. Therefore, the sheet bundle
in the upper part lifted on the sheet bundle in the lower part
cannot have the air introduction between the sheets (gaps) in the
sheet bundle so that it has been extremely difficult to certainly
separate the uppermost sheet one by one.
[0009] FIG. 7 is an explanatory diagram for the conventional air
feeding method. According to the air feeding method shown in FIG.
7, the uppermost sheet is vacuumed by a vacuuming belt 104 by the
vacuuming static pressure of a vacuuming fan 103 disposed above
while blowing the air from a blowing fan 101 via duct 102 to the
upper part side surface of a sheet stack S disposed at a
predetermined position (a position capable of feeding the uppermost
surface of the sheet bundle) so as to be fed by driving the
vacuuming belt 104. However, according to the conventional
configuration, since the blowing air for separating the sheet
bundle is blown to the sheet bundle at the predetermined position
simultaneously with the vacuuming operation by the vacuuming fan,
and furthermore, the above-mentioned blowing air is a constant flow
as shown in FIG. 7, the sir introduced between several to several
tens of the sheets stuck with each other relatively weakly from the
upper part of the sheet bundle S so that the upper part sheet
bundle Su with respect to the sheets with the air introduction is
lifted above the lower part sheet bundle Sd, and thus it is
difficult to certainly separate the uppermost sheet one by one.
SUMMARY OF THE INVENTION
[0010] The present invention has been achieved in view of the
above-mentioned problems, and an object thereof is to provide a
sheet feeding apparatus capable of certainly releasing sticking of
the sheets in a simple configuration for preventing generation of
the feeding error or the superimposition in the air feeding method,
which is superior in terms of the compatibility to the sheet
materials, the high speed feeding, the high durability, or the
like. Furthermore, it is to improve the miniaturization of the
apparatus, reduction of the product cost and the running cost, and
the reliability.
[0011] In order to achieve the above-mentioned object, the present
invention provides a sheet feeding apparatus comprising:
[0012] A sheet supporting means for moving the uppermost surface of
a sheet stack to a predetermined position,
[0013] An air blowing means having a duct for blowing the air from
a direction substantially perpendicular to the side surface of the
uppermost part of the sheet stack supported on the above-mentioned
sheet supporting means, and
[0014] A sheet feeding means for vacuuming and feeding the
uppermost sheet supported on the above-mentioned sheet supporting
means by vacuuming the air,
[0015] Wherein the above-mentioned air blowing means blows the air
to the uppermost part of the sheet stack supported on the
above-mentioned sheet supporting means at a first position which
the uppermost sheet of the sheet stack is faced to an opening of
the above-mentioned air blowing means, and the above-mentioned
uppermost sheet is vacuumed and fed by the above-mentioned sheet
feeding means at a second position above the above-mentioned first
position.
[0016] Moreover, the present invention provides a sheet feeding
apparatus comprising:
[0017] A middle plate provided elevatably which supports sheet
stack,
[0018] A duct opened to the side surface of a upper part of the
sheet stack supported on the above-mentioned middle plate, and said
duct blows from a opening of the duct to the said surface of a
upper part of the sheet stack,
[0019] A vacuuming belt for vacuuming and feeding a uppermost sheet
of the sheet stack supported on the above-mentioned middle plate by
vacuuming the air,
[0020] A first height detecting means for detecting the uppermost
part of the sheet stack supported on the above-mentioned middle
plate reaching a first position,
[0021] A second height detecting means for detecting the uppermost
sheet of the sheet stack supported on the above-mentioned middle
plate reaching a second position higher than the above-mentioned
first position,
[0022] And a controller for commanding the execution of the air
blowing operation of the above-mentioned duct when the uppermost
surface of the sheet stack supported on the above-mentioned middle
plate is detected by the above-mentioned first height detecting
means, and commanding the execution of the feeding operation of the
above-mentioned vacuuming belt when the uppermost surface of the
sheet bundle raised by the elevation of the middle plate is
detected by the above-mentioned second height detecting means.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic cross sectional view of a copying
machine comprising a sheet feeding apparatus according to an
embodiment of the present invention.
[0024] FIG. 2 is a schematic cross sectional view of a sheet
feeding apparatus according to a first embodiment.
[0025] FIG. 3 is a schematic cross sectional view of the sheet
feeding apparatus according to the first embodiment.
[0026] FIG. 4 is a schematic cross sectional view of a sheet
feeding apparatus according to a second embodiment.
[0027] FIG. 5 is a schematic cross sectional view of the sheet
feeding apparatus according to the second embodiment.
[0028] FIG. 6 is a graph for explaining the sticking force between
the sheets in the case of coat papers under a high humidity
environment.
[0029] FIG. 7 is a block diagram of the embodiment.
[0030] FIG. 8 is a schematic cross sectional view for explaining
the conventional air feeding configuration.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] Hereinafter, with reference to the drawings, preferable
embodiments of the present invention will be explained in detail.
However, the size of the component parts, the material, the shape,
the relative arrangement thereof, or the like disclosed in the
following embodiments can optionally be changed according to the
configuration and the various conditions of an apparatus with the
present invention applied, and thus the scope of the present
invention is not limited thereby.
[0032] (Entire Configuration)
[0033] FIG. 1 is a cross sectional view showing the principal part
configuration of an embodiment of a copying machine as an image
forming apparatus comprising a sheet feeding apparatus according to
the present invention.
[0034] As shown in FIG. 1, the copying machine comprises an image
reader 20 as an image reading part for reading a document image, a
printer 30 as an image forming part for recording the image on a
sheet, and a sheet feeding part 40 capable of separating and
feeding the sheet one by one. The sheet feeding part 40 comprises
paper decks 40A, 40B as a sheet feeding device having a common
sheet feeding mechanism. The paper deck 40
[0035] A can store 1,000 sheets and the paper deck 401B can store
1,500 sheets, and the paper decks 40A, 40B have the same
configuration. The sheet feeding part 40 will be explained later in
detail.
[0036] A document feeding device 10 is mounted in the image reader
20. The document feeding device 10 feeds a document with the image
surface set upward on a document tray 11 one by one from the top
page in the leftward direction in the figure via a curved path on a
platen glass 12 from the left side to the rightward direction
through a flow reading position, and then discharges the same onto
an outside discharging tray 13. At the time the document passes the
flow reading position on the platen glass 12 from the left side to
the right side, the document image is read out by a scanner unit 21
supported at a position corresponding to the flow reading position.
The reading method is a method in general called the document flow
reading. Specifically, at the time the document passes by the flow
reading position, the document reading surface is irradiated by the
light beam of a lamp 22 of the scanner unit 21 so that the light
beam reflected from the document is guided to a lens 26 via mirror
23, 24, 25. The light beam passes through the lens 26 is focused
onto an imaging surface of an image sensor 27.
[0037] Accordingly, by feeding the document from the left side to
the right side so that it passes by the flow reading position, a
document reading scan with the direction perpendicular to the
document feeding direction provided as the main scanning direction
and the feeding direction provided as the sub scanning direction is
executed. That is, by feeding the document in the sub scanning
direction while reading the document image per each line in the
main scanning direction by the image sensor 27 at the time of
having the document pass by the flow reading position, the entire
document image is read out so that the image optically read out is
converted to an image data by the image sensor 27 so as to be
outputted. The image data outputted from the image sensor 27 are
inputted to an exposure control part 30A of the printer 30 as a
video signal after applying a predetermined process at an unshown
image signal control part.
[0038] It is also possible to read out the document by scanning
with the scanner unit 21 from the left side to the right side in a
state with the document fed onto the platen glass 12 by the
document feeding device 10 so as to be stopped at a predetermined
position. The reading method is a method so called the document
fixed reading.
[0039] In the case of reading the document without using the
document feeding device 10, first, the document feeding device 10
is opened and closed by a user for placing the document onto the
platen glass 12. Then, the document is read out by scanning with
the scanner unit 21 from the left side to the right side. That is,
at the time of reading out the document without using the document
feeding device 10, the document fixing reading is executed.
[0040] The exposure control part 30A of the printer 30 modulates
and outputs a laser beam based on the inputted video signal so that
the laser beam is directed onto a photosensitive drum 31 while
being scanned by a polygon mirror. An electrostatic latent image is
formed on the photosensitive drum 31 according to the scanned laser
beam. Here, the exposure control part 30A outputs a laser beam so
as to form a correct image (an image, which is not a mirror image)
at the time of the document fixing reading.
[0041] The electrostatic latent image on the photosensitive drum 31
is visualized as a developing agent image by a developing agent
supplied from an unshown developer. Moreover, a sheet is fed
selectively from the paper decks 40A, 40B as the sheet feeding
device to be described later at a timing synchronously with the
start of the laser beam irradiation so that the sheet is fed
between the photosensitive drum 31 and a transfer part 33 by a
resist roller pair 32. The developing agent image formed on the
photosensitive drum 31 is transferred onto the sheet fed by the
transfer part 33.
[0042] The sheet with the developing agent image transferred is fed
to a fixing part 34 so that the fixing part 34 fixes the developing
agent image on the sheet by heating and pressuring the sheet. The
sheet passed through the fixing part 34 is discharged onto a first
discharging tray 37 via a first discharging roller 36 or onto a
second discharging tray 39 via a second discharging roller 38
according to the changeover of a flapper 35.
[0043] Next, the paper decks of the air feeding method as the sheet
feeding device according to the present invention will be explained
in detail with reference to the embodiments. Although the numbers
of the sheets to be stored in the paper decks differ, since the
other configuration is same, the paper deck 40A will be explained
in the following description and the same, numerals are applied to
the members having the same function of the paper deck 40B so as to
omit the explanation.
First Embodiment
[0044] FIGS. 2, 3 are schematic cross sectional view for explaining
the operation of the paper deck 40A of the air feeding method in
the first embodiment. The paper deck 40A has a sheet stack
supported and stored on a middle plate 43 provided in a storage
bank 41 as a sheet supporting means. The sheet stack S supported
and stored in the storage bank 41 has the top end part thereof
limited by a pre-separation plate 44 and the rear end part and the
side end parts limited each by an unshown rear end limiting plate
and side limiting plates at a predetermined position.
[0045] A feeding unit 45 as a sheet feeding means for vacuuming and
feeding by the air the uppermost sheet of the sheet stack S
supported on the above-mentioned middle plate 43 is provided above
the sheet stack supported and stored on in the storage bank 41. The
feeding unit 45 comprises a vacuuming means 45a capable of
generating a vacuuming static pressure, such as a fan and a
vacuuming duct 45b. Furthermore, a vacuuming belt 45c comprising a
large number of holes, surrounding the vacuuming duct 45b, is
provided rotatably in the sheet feeding direction.
[0046] Moreover, an air blowing unit 46 as an air blowing means,
comprising a duct for blowing the air from the direction
substantially perpendicular to the side surface of the upper part
of the sheet stack S supported on the above-mentioned middle plate
43 is provided on the top end side of the sheet stack supported and
stored in the storage bank 41.
[0047] Next, with reference to FIG. 2, the configuration and the
operation of the air blowing unit 46 provided on the top end side
of the sheet stack will be explained in detail. The installation of
the air blowing unit 46 is not limited to the sheet bundle top end
side, but it can be installed optionally at any sheet bundle side
surface. However, according to the experiment of the present
inventor, relatively good results are obtained in terms of the
separation performance at the time it is installed at the sheet
feeding direction top end side. Moreover, in the case in particular
the image formation reference position is at the center of the
sheet feeding direction and various sheet sizes need to be dealt
with, a simpler configuration can be provided compared with the
case of installing the air blowing unit on the side limiting plate
side, and thus it is advantageous.
[0048] In FIG. 2, the air blowing unit 46 as the air blowing means
is provided on the sheet bundle top end side. The air blowing unit
46 comprises the blowing duct 46b having an unshown blowing fan,
and an duct opening 46a interlocked with the blowing fan and opened
toward the side surface of the sheet stack supported and stored in
the storage bank 41. Moreover, an air blowing speed varying means
for changing the air blowing speed blown out from the
above-mentioned air blowing unit 46 is provided between the
above-mentioned air blowing unit 46 and the sheet bundle top end
side. The air blowing speed varying means according to this
embodiment is a shutter 47a movable in the substantially
perpendicular direction between the sheet bundle side surface and
the duct opening 46a, comprising a slit 47b having a width
substantially smaller than the width of the duct opening 46a in a
part thereof. That is, the shutter 47a functions as a channel
moving means for moving the channel of the air blown out from the
duct opening 46a of the above-mentioned air blowing unit 46 in the
substantially perpendicular direction in the vicinity of the sheet
bundle side surface. Moreover, a detecting means 47c for detecting
the position at the time the shutter 47a is at the uppermost part
in the moving direction.
[0049] FIG. 7 is a control block diagram of this embodiment.
[0050] To the controller, the material and the size of the sheets
to be piled on the paper decks 40A, 40B are inputted by an user
from an inputting means I. Moreover, the temperature, the humidity,
or the like inside and outside the storage bank 41 are inputted
form an environment sensor SE. Furthermore, a detection signal of
the upper surface of the sheet bundle S is inputted from a first
sheet height detecting means 48 and a second sheet height detecting
means 49 to be described later. Then, based on the information, the
controller C carries out the elevation control of the middle plate
43 by a lift up motor 43a (shown in FIG. 7), the sheet feeding
control by the feeding unit 45, the drive control of the shutter
47a, the air blowing control of the air blowing unit 46, or the
like.
[0051] Next, the sheet separation feeding operation in the
above-mentioned paper deck 40A will be explained in detail. In the
case the sheet bundle is set in the storage bank 41 of the paper
deck 40A and the paper deck 40A is inserted into the image forming
apparatus man body, the middle plate 43 is lifted up by the lift up
motor 43a to a pre-separation height (first height) H1 set by a
first sheet height detecting means 48 (see FIG. 2A) for executing
the pre-separation operation to be described below. As shown in
FIG. 2A, the pre-separation height as the first position is a
position at which the uppermost surface of the sheet stack S
supported on the middle plate 43 in the storage bank 41 is in the
width range in the vertical direction of the above-mentioned
blowing duct 46b. At the pre-separation height H1 as the first
position, first, the unshown blowing fan is operated so as to blow
the air from the duct opening 46a toward the sheet bundle side
surface. Here, the shutter 47a has the drive transmission from an
unshown driving source so as to be moved reciprocally in the
substantially vertical direction between the sheet bundle side
surface and the blowing duct opening 46a. First, the shutter 47a is
moved downward and the slit 47b is moved accordingly. Here, at the
time the slit 47b is at the duct opening 46a, the air blowing speed
passing through the slit 47b is increased by the difference between
the slit width and the duct opening width. The air passed through
the slit 47b with the height air blowing speed is blown
continuously to the sheet bundle side surface while moving downward
(see FIGS. 2B, 2C). At the time the shutter 47a is reached at the
lowermost point in the moving direction shown in FIG. 2C, then it
starts the upward movement (see FIG. 2D) so as to move to the
uppermost point again in the moving direction while blowing the air
continuously to the sheet bundle side surface in the same manner
(see FIG. 2C). Since the air with the height air blowing speed
blown from the slit 47b formed in the shutter 47a to the sheet
bundle side surface can be blown by a plurality of times toward the
sheet bundle upper part by repeating the reciprocal motion of FIGS.
2B to 2E, a certain sheet separation effect can be expected without
lifting up of the sheet bundle upper part by the air of the
constant flow to be blown out directly as in the case of the
conventional duct opening.
[0052] The number of the reciprocal motion and the moving speed of
the shutter 47a in the above-mentioned pre-separation operation can
be set optionally by the material and the size of the sheet, and
the environmental conditions. Here, the present inventor collected
the sticking force data between the sheets as to the coat paper to
be stuck easily at a high humidity (temperature 30.degree.
C./humidity 80%). Results are shown in FIG. 6. As it is apparent
from FIG. 6, the sticking force between the sheets is maximally
about 9.8N at the sheet bundle uppermost part and it tends to be
lowered gradually toward the lower part. From the results, since
the separation ability in the conventional friction separation
method is about 0.98N at most, it is apparent that separation
cannot be carried out thereby. Moreover, it is apparent that the
sheets are lifted up at a part with a relatively weak sticking
force between the sheets at about 10 sheets from the uppermost
sheets so as to easily generate superimposition at which the sheet
surface height is close to the vacuuming belt according to the
above-mentioned conventional air feeding method. Accordingly, since
the sticking force between the sheets is high at the uppermost part
of the sheet bundle, it is effective to execute the vacuuming
feeding operation by the feeding unit 45 to be described later
after executing the above-mentioned pre-separation operation at the
first position (pre-separation height) to have the uppermost
surface of the sheet stack S in the range in the vertical direction
of the blowing duct 46b before the sheet feeding operation by the
vacuuming feeding as in this embodiment.
[0053] Next, as shown in FIG. 3, after executing the
above-mentioned pre-separation operation, the middle plate 43 is
lifted up by the lift up motor 43a such that the uppermost surface
of the sheet stack reaches at the feeding sheet surface height
(second position) H2 to be detected by the second sheet height
detecting means 49 so as to execute the sheet feeding operation by
the feeding unit 45. As shown in FIG. 3, the feeding sheet surface
height H2 as the second position is a position for operating the
above-mentioned feeding unit 45 (the vacuuming means 45b and the
vacuuming belt 45) above the first position. By starting the
vacuuming operation by the upper vacuuming means 45a and driving
and rotating the vacuuming belt 45c at the feeding sheet surface
height H2 as the second position, a preferable separation feeding
operation can be carried out certainly for each sheet from the
uppermost sheet of the sheet bundle after the above-mentioned
pre-separation operation. Moreover, the separation duct 46c
interlocked with an unshown separation fan supplies the separation
air toward the vacuuming belt 45c through the duct opening 46d from
the sheet feeding direction downstream side. Although the
separation air is effective for vacuuming only the uppermost sheet
by the vacuuming belt 45c and then separating and dropping the
following sheets, the configuration without the separation air may
be employed as well.
[0054] The timing of the air blowing operation by the
above-mentioned air blowing unit 46 to be carried out while
reciprocally moving the shutter 47a having the above-mentioned slit
47b is not limited to the pre-separation operation at the first
position but also it can be operated while the uppermost surface of
the above-mentioned sheet bundle is moved between the
above-mentioned first position H1 and the above-mentioned second
position H2 or it is at the second position H2. That is, the air
blowing operation can be carried out by the above-mentioned air
blowing unit 46 while reciprocally moving the shutter 47a having
the above-mentioned slit 47b during the sheet feeding operation
after the above-mentioned pre-separation operation.
[0055] As heretofore explained, according to this embodiment, since
the pre-separation height (first position) H1 is set in the
reciprocal movement range of the slit 47b of the shutter 47 having
a high sheet separation effect (in the range of the vertical
direction width of the duct opening 46a) and the sheet bundle
separated sufficiently is moved to the feeding sheet surface height
(second position) H2 above the pre-separation height H1 for
vacuuming and feeding the sheets, even in the case of a bundle of
special sheets such as a coat paper of a material different from a
plain paper, or the like, that is, a bundle of sheets having a
relatively high sticking force between the sheets, the stickiness
can be released by certainly introducing the air between the
sheets. Thereby, according to the air feeding method superior in
terms of the compatibility to the sheet materials, the high speed
feeding, the high durability or the like, a sheet feeding apparatus
capable of certainly releasing the stickiness between the sheets in
a simple configuration and preventing generation of the feeding
error and the superimposition can be provided.
[0056] Furthermore, since it has a simple configuration of
executing the pre-separation operation by the blowing air of the
air blowing unit 46 at the first position H1 with the uppermost
surface of the sheet stack in the vertical direction width range of
the duct opening 46a and the vacuuming feeding operation by the
feeding unit 45 at the second position H2 above the first position
H1, the sheets can be separated and fed certainly in a simple
configuration without the need of additionally providing new parts
of the bulkiness of the apparatus, or increasing the parts cost or
the running cost so as to improve the reliability.
[0057] Although the case of having the initial position of the
shutter 47a at the uppermost position in the moving direction has
been explained above, it is not limited thereto and thus it can be
provided at an optional position. Moreover, the vacuuming means 45a
or the unshown blowing fan may be a fan such as a sirocco fan, a
compressor, or the like.
[0058] Moreover, in order to further improve the separation effect
during continuous feeding according to the conditions such as the
environment and the material, it is also possible to provide the
control of temporarily stopping the sheet feeding operation even in
the case there is a remaining feeding job at the time of a
continuous feeding job of a certain number or more sheets, moving
the uppermost surface of the sheet stack from the feeding sheet
surface height H2 to the pre-separation height H1 by lowering the
middle plate 43, and again lifting the same up to the feeding sheet
surface height H2 after executing the pre-separation operation so
as to execute the remaining feeding job.
Second Embodiment
[0059] The second embodiment of the present invention will be
explained with reference to FIGS. 4, 5. As to the numerals in the
figures, the same numerals are applied to the same elements as in
the above-mentioned first embodiment, and the explanation is
omitted here.
[0060] This embodiment comprises a swing nozzle 47d capable of
rotating the sheet bundle upper side end part in the vertical
direction in the blowing duct 46b provided on the sheet bundle top
end side. The swing nozzle 47d is an air direction varying means
for changing the orientation of the air blown out from the air
blowing unit 46 such as a blowing fan, which executes the
pre-separation operation for the sheet bundle lifted up to the
pre-separation height (first position) H1 as in the first
embodiment. The above-mentioned swing nozzle 47d blows the air to
the sheet bundle side surface while changing the orientation
thereof from the initial position (upward) shown in FIG. 4A to
substantially horizontally, downward, substantially horizontally,
upward (in the order of FIGS. 4B to 4E. Since the air blowing
operation is executed while vertically rotating the swing nozzle
47d, the air with the air orientation changed continuously can be
provided to the sheet bundle, the effect of separating the sheets
stuck with each other or the sheets piled slightly displaced with
each other by introducing the air is extremely high. The number of
the reciprocal operation or the moving speed of the swing nozzle
47d by the pre-separation operation can be set optionally according
to the material and the size of the sheets and the environmental
conditions.
[0061] After executing the above-mentioned pre-separation
operation, like the above-mentioned first embodiment, as shown in
FIG. 5, the middle plate 43 is lifted up by the lift up motor 43a
until the feeding sheet surface height (second position) H2 with
the uppermost surface of the sheet stack detected by the second
sheet height detecting means 49 so as to execute the sheet feeding
operation by the feeding unit 45. As shown in FIG. 5, the feeding
sheet surface height H2 as the second position is a position for
operating the above-mentioned feeding unit 45 (vacuuming means 45a
and the vacuuming belt 45c) above the first position H1. At the
feeding sheet surface position height H2 as the second position,
the vacuuming means 45a provided above starts the vacuuming
operation and the vacuuming belt 45c is driven and rotated so as to
execute certainly a preferable separation feeding operation for
each sheet from the uppermost sheet of the sheet bundle after the
above-mentioned pre-separation operation. Moreover, the separation
duct 46c interlocked with an unshown separation fan supplies the
separation air from the sheet feeding direction downstream side
through the duct opening 46d toward the vacuuming belt 45c.
Although the separation air is effective for vacuuming only the
uppermost sheet by the vacuuming belt 45c and then separating and
dropping the following sheets, the configuration without the
separation air may be employed as well.
[0062] The timing of the air blowing operation by the
above-mentioned air blowing unit 46 to be carried out while
rotating the above-mentioned swing nozzle 47d is not limited to the
pre-separation operation, but also it can be operated while at
least the uppermost surface of the above-mentioned sheet bundle is
between the above-mentioned first position H1 and the
above-mentioned second position H2. That is, the air blowing
operation can be carried out by the above-mentioned air blowing
unit 46 while rotating the swing nozzle 47d during the sheet
feeding operation after the above-mentioned pre-separation
operation.
[0063] As heretofore explained, also according to this embodiment,
since the pre-separation height (first position) H1 is set in the
duct swing operation range of the swing nozzle 47d having a high
sheet separation effect (in the range of the vertical direction
width of the duct opening 46a) and the sheet bundle separated
sufficiently is moved to the feeding sheet surface height (second
position) H2 above the pre-separation height H1 for vacuuming and
feeding the sheets, even in the case of a bundle of special sheets
such as a coat paper of a material different from a plain paper, or
the like, that is, a bundle of sheets having a relatively high
sticking force between the sheets, the stickiness can be released
by certainly introducing the air between the sheets. Thereby,
according to the air feeding method superior in terms of the
compatibility to the sheet materials, the high speed feeding, the
high durability, or the like, a sheet feeding apparatus capable of
certainly releasing the stickiness between the sheets in a simple
configuration and preventing generation of the feeding error and
the superimposition can be provided.
[0064] Furthermore, since it has a simple configuration of
executing the pre-separation operation by the blowing air of the
air blowing unit 46 at the first position H1 with the uppermost
surface of the sheet stack in the vertical direction width range of
the duct opening 46a and the vacuuming feeding operation by the
feeding unit 45 at the second position H2 above the first position
H1, the sheets can be separated and fed certainly in a simple
configuration without the need of additionally providing new parts
of the bulkiness of the apparatus, or increasing the parts cost or
the running cost so as to improve the reliability.
[0065] Although the case of having the initial position of the
swing nozzle 47d at the uppermost position (upward) in the moving
direction has been explained above, it is not Limited thereto and
thus it can be provided at an optional position. Moreover, the
vacuuming means 45a or the unshown blowing fan may be a fan such as
a sirocco fan, a compressor, or the like.
[0066] Moreover, in order to further improve the separation effect
during continuous feeding according to the conditions such as the
environment and the material, it is also possible to provide the
control of temporarily stopping the sheet feeding operation even in
the case there is a remaining feeding job at the time of a
continuous feeding job of a certain number or more sheets, moving
the uppermost surface of the sheet stack from the feeding sheet
surface height H2 to the pre-separation height H1 by lowering the
middle plate 43, and again lifting the same up to the feeding sheet
surface height H2 after executing the pre-separation operation so
as to execute the remaining feeding job.
Other Embodiments
[0067] Although an example of the shutter (channel moving means)
47a having the slit 47b in a part has been explained as the air
blowing speed varying means for changing the air blowing speed to
be blown out from the air blowing means in the above-mentioned
embodiment, it is not limited thereto. For example, one having the
air supplied from the air supply source of the blowing air
increased or reduced by the on/off changeover, or an air blocking
means capable of blocking or opening the air channel provided
inside the blowing duct opening 46a can be adopted as well. In any
case, by setting the pre-separation height (first position) H1 in
the opening width (in the vertical direction width range) of the
blowing duct opening 46a for executing the pre-separation operation
thereat, the sheets can be separated certainly at the feeding sheet
surface height (second position) H2 above the pre-separation
height.
[0068] Moreover, although the cases of providing the positions of
the blowing duct 46b and the shutter 47a, the positions of the
blowing duct 46b and the swing nozzle 47d at the sheet bundle side
surface top end part have been explained in the above-mentioned
embodiments, it is not limited thereto, and an optional position at
the sheet bundle side surface can be used as well.
[0069] Furthermore, although the configuration of providing the air
blowing means only at the sheet bundle side surface top end part
has been explained, it is not limited thereto, and as needed, it
can be disposed at a plurality of points facing the sheet bundle
side surface. Moreover, it is also possible to use in a combination
with the air blowing speed varying means or the air pressure
varying means explained in the above-mentioned first and second
embodiments.
[0070] Moreover, although the example of the sheet feeding
apparatus having only the air feeding method ha been explained as
the sheet feeding mechanism for separating and feeding the sheets,
a configuration having another separating means can be adopted as
well.
[0071] Furthermore, although the case of a copying machine has been
explained as the image forming apparatus in the above-mentioned
embodiments, the present invention is not limited thereto, and for
example, another image forming apparatus such as a scanner, a
printer and a facsimile equipment, another image forming apparatus
such as a composite machine combining the functions thereof, an
image forming apparatus using a transfer material supporting member
for successively superimposing and transferring toner images of
various colors onto a transfer material supported by the transfer
material supporting member, or an image forming apparatus using an
intermediate transfer member, successively superimposing and
transferring toner images of various colors onto the intermediate
transfer member, and transferring the toner images supported by the
intermediate transfer member onto a transfer material collectively
may be adopted as well. By adopting the present invention to the
sheet feeding apparatus used in the image forming apparatus, the
same effect can be obtained.
[0072] Moreover, although the example of the sheet feeding
apparatus provided integrally in the image forming apparatus has
been explained in the above-mentioned embodiments, the present
invention is not limited thereto, and by adopting the present
invention to the sheet feeding apparatus, the same effect can be
obtained.
[0073] Furthermore, although the example of the sheet feeding
apparatus for separating and feeding the sheets of a plain paper, a
coat paper, or the like as the recording subject has been explained
in the above-mentioned embodiments, the present invention is not
limited thereto. For example, by adopting the present invention to
the sheet feeding apparatus for feeding the documents (sheets) of a
plain paper, an OHP paper, or the like as the reading subject to an
image reading part, the same effect can be obtained.
[0074] Moreover, although the example of the electron photography
method has been explained as the recording method in the
above-mentioned embodiments, it is not limited thereto. For
example, another recording method such as an ink jet method can be
used as well.
[0075] This application claims priority from Japanese Patent
Application No. 2003-407026 filed Dec. 5, 2003, which is hereby
incorporated by reference herein.
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