BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a sheet feeding apparatus for feeding a sheet, and
to image reading apparatus and image forming apparatus provided therewith.
Related Background Art
[0002] As automatic original feeding apparatus there are apparatus of an original circulating
method (RDF) and a non-circulating method (ADF). In the former RDF case, there are
apparatus for completing exposure while an original passes an exposure section, and
discharging the original onto a region above (or below) an original mounting section;
further, in the case of setting of plural sets of copies of originals, there are apparatus
for obtaining plural sets of copies by successively recirculating the originals.
[0003] The combination of RDF with the flow reading mode for finishing exposure during a
moving state of original as described is free of the loss time corresponding to the
moving time of exposure apparatus as against a fixed reading mode for once stopping
the original and then moving the exposure apparatus along an original region. Therefore,
the combination has advantages that it contributes to shortening of changing time
of original and, in turn, to the speed increasing technology and productivity increasing
technology of copying system and that, when comparison is made in a predetermined
original changing time, it enables the original to be circulated at lower moving speed
than in the fixed reading mode, thereby also contributing to the quieting (noise reducing)
technology.
[0004] First describing examples of the combination with RDF, there also exists systems
enabling to achieve the speed increase and productivity increase of copying system
by the combination with the flash exposure technology. The detailed description of
the flash exposure technology is omitted herein, but, when compared with the aforementioned
exposure apparatus, it employs the structure for completing exposure of the all surface
of an original at one time and needs to use a high-power light source and a belt type
photosensitive member, thus increasing the size of apparatus, the cost, and electric
power consumption. It is, therefore, the present status that applications of this
technology are limited to some large-scale high-speed machines.
[0005] The latter ADF apparatus has such structure that an original is fixed at a predetermined
position on a platen, exposure of copying section is repeated a necessary copy set
number times by translationally moving the exposure apparatus, the original is discharged
onto a predetermined discharge tray after completion of exposure, and this operation
is successively repeated to obtain plural sets of copies from a series of originals.
The copying system is combined with a sorter provided on the output side thereof,
which eliminates the need for repetitively circulating the originals many times. Therefore,
this apparatus has an advantage of relatively small damage of original.
[0006] Under the above circumstances of existence of the conventional technology, a variety
of proposals have been made in order to achieve the speed increase and quieting in
recent years.
[0007] A first example of the apparatus devised is a sheet medium conveying apparatus wherein
the originals on a sheet mounting table are fed by automatically selecting one of
two feeding means provided at the both ends of the sheet mounting table, depending
upon the conditions including the size of original and a set mode, and an original
is conveyed up to an image reading section of the copier body to be read there.
[0008] For example, an original-recirculatable system is arranged, as shown in Fig. 8, so
that in the original fixed reading mode (for feeding the original through a first
feeding means) a plurality of sheet originals P loaded on a sheet original mounting
table 304 are separated one by one by first separating means 306, they are conveyed
by feeding means 338 to be successively loaded at an arbitrary position on platen
303, an image of each original is read while moving an image reading section (optical
system) 380 in the direction
a in the copier body 301, and the original is reloaded on the sheet mounting table
304 by discharge means 311. In the original flow reading mode (for feeding the original
through a second feeding means) the plurality of sheet originals P loaded on the original
tray 304 are separated one by one by second separating means 314 to be conveyed by
feeding means 315, the optical system 380 is fixed at a position the distance L apart
from the home position (illustrated by a dashed line) of optical system 380, an image
is read while the sheet original P is conveyed at constant speed on the platen 303
by a wide belt 307, and the original is loaded onto the sheet original mounting table
304 by the discharge means 311.
[0009] When the flow reading mode is selected, for example, under such conditions that a
user puts originals of a small size (A4, B5, LTR, or the like) on the original tray
304, a start key (not illustrated) of the copier body is on, a first entrance sensor
322 is on, and a sheet medium length detecting sensor 368 is off, the operation advances
in the flow reading mode. First, the original tray 304 falls down to a predetermined
position about the fulcrum of 340, a stopper (sheet stack conveying means) 321 conveys
the stack of sheet originals P toward the second separating means 314 to move the
stack up to the position of stack conveying position detecting sensor 328 (before
the stack conveying position detecting sensor 328 becomes on), feeding from the second
feeding means 315 is started to feed the original to the platen 303, the image of
the original is read in the aforementioned original flow reading mode, and then the
sheet original is discharged from the discharge roller 311 onto the original tray
304. The stopper 321 pushes the rear end of sheet original toward the second separating
section every discharge of original so as to enhance alignment. For one more circulation,
after the all sheet originals are discharged, the stack is conveyed together to be
again fed and to be again copied.
[0010] The above devised apparatus was suitable for the productivity increase, because it
is the original recirculating method processing apparatus to achieve the high original
changing speed in the flow reading mode, and also suitable for the quieting, as described
above; however, it required circulation of originals of a setting number times for
obtaining plural copies thereof. The apparatus thus had the structure requiring the
advanced technologies for realizing the system that gave less damage on the originals,
for example, by decreasing the stress on the originals upon passage through the separating
means of the above apparatus, curling of original upon passage through the bent path,
and so on, and that had high reliability by decreasing the probability of conveyance
failure upon handling of original.
[0011] Particularly, in the above apparatus, the separating and feeding means of original
P employs the bottom separating and feeding method of a conventional belt retard system
comprised of a retard belt and a feeding roller, as shown in Fig. 8. This method is
a method for aligning the originals at their leading edges and feeding them, and it
thus has an advantage that even a stack of originals with different sizes mixed can
be separated and fed. However, it has a problem of soiling of original occurring when
a printed surface of the first original P rubs the back surface of the second original
P upon feeding from the lowermost of the originals P mounted in the face-up state.
Various means have been considered to overcome it, and considerable improvements have
been achieved in the soiling.
[0012] When the originals P had poorly fixed images and the number of originals P was large,
the above soiling was conspicuous when seen in a stack of many originals P after copy.
A further improvement was thus demanded. A separating and feeding method using air
is known as feeding means for solving the problem of soiling of original. The structure
of this air feeding is free of not only the problem of soiling of original but also
the problem of abrasion of the belt and rubber in the retard system, and it thus has
advantages of excellent durability and reliability.
[0013] In the above structure of air feeding it is, however, necessary to prevent accompanied
conveyance by making use of the weight of originals P by mounting the originals on
the original mounting tray 2 inclined at an angle of rise in the sheet feeding direction
toward the air separating means, and to align the originals P at the trailing edges
thereof.
[0014] Therefore, the air feeding method has a problem that it is not ready for handling
a stack of originals P of different sizes mixed, different from the aforementioned
retard system.
[0015] Further, in the air feeding method, when the originals have holes at the leading
edges thereof in the original feeding direction, the separation air directed toward
the leading edges of originals leaks through the hole portions, so that the second
and after originals become reluctant to float. The air feeding method thus has another
problem that it is not suitable for the originals with holes at the leading edges
in the original feeding direction.
SUMMARY OF THE INVENTION
[0016] An object of the present invention is to provide a novel sheet feeding apparatus
by making use of the various advantages of the conventional feeding methods and compensating
for their weak points.
[0017] First embodiment of the present invention is provided as a sheet feeding apparatus
comprising a friction separating/feeding means for separating and feeding a sheet
by making use of frictional force, an air separating/feeding means for separating
and feeding a sheet by making use of air and a selecting means for selecting either
one of the friction separating/feeding means and the air separating/feeding means
and for making the selected means separate and feed the sheet.
[0018] Second embodiment of the present invention is provided as a sheet feeding apparatus
applied to an image reading apparatus for reading an image of a sheet existing in
an image reading section, the sheet feeding apparatus comprising a friction separating/feeding
means for separating and feeding a sheet by making use of frictional force, a first
conveying means for guiding the sheet separated and fed by the friction separating/feeding
means to the image reading section, an air separating/feeding means for separating
and feeding a sheet by making use of air, a second conveying means for guiding the
sheet separated and fed by the air separating/feeding means to the image reading section
and a selecting means for selecting either one of the friction separating/feeding
means and the air separating/feeding means and for making the selected means separate
and feed the sheet.
[0019] The selecting means is preferred to select the air separating/feeding means in a
normal mode.
[0020] Third embodiment of the present inveniton is provided as a sheet feeding apparatus
applied to an image reading apparatus for reading an image of a sheet existing in
an image reading section, the sheet feeding apparatus comprising a tray on which a
sheet is to be loaded, a first separating means for separating a sheet loaded on the
tray, the first separating means including feeding means and retard means and a second
separating means for separating a sheet loaded on the tray, the second separating
means including an air knife and vacuum suction conveying means.
[0021] A sheet feeding apparatus is preferred to comprise a switchback conveying means including
a switchback conveying path, the switchback conveying means conveying the sheet separated
by the first separating means through the switchback conveying path from one end of
the image reading section into the image reading section and thereafter switching
the sheet back to convey the sheet through the switchback conveying path out of the
image reading section and a closed loop conveying means including a closed loop conveying
path forming a closed loop, the closed loop conveying means conveying the sheet separated
by the second separating means through the closed loop conveying path, thereby conveying
the sheet from the other end of the image reading section into the image reading section,
the closed loop conveying means conveying the sheet out of the image reading section
from the side opposite to the side where the sheet was conveyed thereinto.
[0022] The switchback conveying means is preferred to temporarily stop the sheet on the
image reading section while the image reading apparatus is reading an image, and the
closed loop conveying means continues conveyance of the sheet conveyed into the image
reading section even while the image reading apparatus is reading the image, and the
closed loop conveying means carries the sheet out thereof from the side opposite to
the side where the sheet was conveyed thereinto.
[0023] The first separating means is preferred to be means for separating an original loaded
on the tray, the means being provided on one side of the tray, and the second separating
means is preferred to be means for separating an original loaded on the tray, the
means being provided on another side of the tray different from the one side of the
tray where the first separating means is provided, and at least one of the switchback
conveying means and the closed loop conveying means returns a conveyed original to
the tray.
[0024] A sheet feeding apparatus is preferred to comprise a moving means for moving a stack
of sheets mounted on the tray to a predetermined separation position on the tray and
a control means for controlling the moving means and the separating means, and the
second separating means is means for separating the lowermost sheet from the other
sheets by blowing of air to a lower portion of a leading edge of the stack of sheets
having been conveyed to the separation position, and the control means controls the
second separating means to start the blowing of air from the second separating means,
prior to arrival of the stack of sheets at the separation position.
[0025] A sheet feeding apparatus is preferred to comprise thickness detecting means for
detecting a thickness of the stack of sheets mounted on the tray at that time, and
the control means changes a blowing amount of air from the second separating means,
according to a detection result of the thickness detecting means.
[0026] The moving means is preferred to comprise pushing means for pushing a trailing edge
of the stack of sheets to move the stack of sheets, and a conveying belt set on a
tray surface of the tray, and the conveying belt rotates in synchronism with the movement
of the stack of sheets by the pushing means.
[0027] Fourth embodiment of the present invention is provided as a sheet reading apparatus
comprising the sheet feeding apparatus and a reading means for reading a sheet having
been fed thereto by the sheet feeding apparatus.
[0028] Fifth embodiment of the present invention is provided as an image forming apparatus
comprising the sheet feeding apparatus, a reading means for reading an image of a
sheet having been fed thereto by the sheet feeding apparatus and an image forming
means for forming the image of the sheet having been read by the reading means, on
a recording medium of a sheet shape.
[0029] Sixth embodiment of the present invention is provided as a sheet feeding apparatus
comprising a sheet tray on which a stack of sheets are to be mounted, a moving means
for moving a stack of sheets mounted on the sheet tray to a predetermined separation
position on the sheet tray, a separating means for separating the lowermost sheet
from the other sheets by blowing of air to a lower portion of a leading edge of the
stack of sheets having been conveyed to the separation position and a control means
for controlling the moving means and the separating means, and the control means controls
the separating means start the blowing of air, prior to arrival of the stack of sheets
at the separation position.
[0030] A sheet feeding apparatus is preferred to comprise a thickness detecting means for
detecting a thickness of the stack of sheets mounted on the tray at that time, and
the control means is preferred to change a blowing amount of air from the separating
means, according to a detection result of the thickness detecting means.
[0031] The moving means is preferred to comprise a pushing means for pushing a trailing
edge of the stack of sheets to move the stack of sheets, and a conveying belt set
on a tray surface of the tray, and the conveying belt rotates in synchronism with
the movement of the stack of sheets by the pushing means.
[0032] Seventh embodiment of the present invention is provided as a sheet feeding apparatus
comprising a sheet tray on which a sheet is to be mounted, a pushing means for pushing
a trailing edge of a sheet mounted on the sheet tray to move the sheet to a predetermined
separation position on the sheet tray, a conveying belt set in a tray surface of the
sheet tray and a control means for controlling the pushing means and the conveying
belt, and the control means controls the conveying belt to rotate in synchronism with
the movement of the sheet by the pushing means.
[0033] Eighth embodiment of the present invention is provided as an image reading apparatus
comprising an image reading means comprising a sheet table, the image reading means
reading an image of a sheet placed on the sheet table and the sheet feeding apparatus
as discribed in fifth, sixth or seventh embodiment for successively conveying sheets
to the sheet table.
[0034] As described above, the sheet feeding apparatus and image forming apparatus of the
present invention can perform secure separation and feeding of original.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035]
Fig. 1 is a drawing to show the schematic structure of an image forming apparatus
as the first embodiment of the present invention;
Fig. 2 is a drawing to show the structure of an automatic original feeding apparatus;
Fig. 3 is a drawing to show the structure for drive of the automatic original feeding
apparatus;
Fig. 4 is a drawing to show the details of an air separating-feeding mechanism;
Fig. 5 is a drawing to show the details of the air separating-feeding mechanism;
Fig. 6 is a drawing to show the structure for control by a controlling device;
Fig. 7 is a flowchart to show the control operation of original conveyance; and
Fig. 8 is a drawing to show the conventional apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] The embodiments of the present invention will be described by reference to the drawings.
[0037] The present embodiment is characterized in that, in transferring an original mounted
on the original tray to an air feedable position (an air separating position), blowing
of separating air (at least preparation for blasting, for example, setting of an air
quantity according to the thickness of original stack) is started prior to arrival
of original at the air separating position. It is also characterized in that upon
the conveyance the adsorption belt is rotated in synchronism with movement of the
original stack.
[0038] First, the image forming apparatus 100 of the present embodiment will be schematically
described referring to Fig. 1.
[0039] The automatic original feeding apparatus 1 conveys an original mounted on the original
tray up to a predetermined read position. The automatic original feeding apparatus
1 will be described in detail hereinafter.
[0040] As well known, the optical system is composed of third mirror 101, second mirror
102, first mirror 103, original illuminating lamp 104, zoom lens 106, fourth mirror
114, and so on. The optical system transmits information of an original on platen
105 onto photosensitive drum 107.
[0041] The above optical system is constructed so as to be capable of both fixed reading
and flow reading. Specifically, upon the fixed reading the original is fixed at a
constant position and an exposure section 133 translationally moves on the platen
to read the image. On the other hand, upon the flow reading the exposure section is
fixed at a predetermined position and the original is moved to read the image. The
home position of the optical system in the fixed reading (original: fixed, optical
system: moving) is at a first image head (fixed reading image head) position G (see
Fig. 2). A second image head (flow reading image head) position H is the fixed position
of the optical system in the flow reading. The second image head position H is located
the distance L right from the first image head position G.
[0042] Next, the image thus read by the optical system is formed on a transfer medium separately
prepared, by an image forming section. The image forming section is provided, as well
known, with drum cleaner 108, pre-exposure lamp 109, primary charger 110, blank exposure
lamp 112, potential sensor 113, hopper section 114 of toner, developing unit 115,
multifeeder 116, side tray 117, roller electrode 118, transfer pre-charger 119, registration
roller 120, refeeding section (for both-side copy) 121, transfer-separation charger
122, upper front tray 123, lower front tray 124, conveying section 125, intermediate
tray 126, second conveying section 127, fixing unit 128, waste toner collecting vessel
129, sheet discharging section 130, copy-sheet-output-side device (sorter) 200, and
so on.
[0043] Each section of the image forming apparatus is generally controlled by control device
300.
[0044] As described previously, the present embodiment is mainly characterized by the automatic
original feeding apparatus 1. Therefore, the following description is focused mainly
on the automatic original feeding apparatus 1.
[0045] The structure of the automatic original feeding apparatus 1 of the present embodiment
will be described referring to Fig. 2 and Fig. 3.
[0046] The automatic original feeding apparatus 1 has two original conveying paths (switchback
path and closed loop path). The two conveying paths are used separately by selection,
depending upon the set mode and the original size.
[0047] The switchback path is used in the case of the originals of a large size (for example,
B4, A3, etc.) and in the case of originals of different sizes mixed. The conveying
direction in the switchback path is indicated by arrow A in the drawing. In feeding
through the switchback path, an original of original stack P mounted on the original
tray 2 is guided through a path PH1 and then is positioned at the predetermined position
on the platen 105 of image forming apparatus 100, and the exposure operation is carried
out thereat by the optical system. After completion of the exposure operation, the
original is returned in the direction C (through a discharge path PH2) again onto
the original tray 2.
[0048] On the other hand, the closed loop path is used in a one-side copy mode of originals
of a small size. In the drawing the conveying direction in the closed loop path is
indicated by arrow B. An original P on the original tray 2 is guided through a predetermined
path PH3 and is positioned at the predetermined position on the platen 105 of the
image forming apparatus 100. After completion of the exposure operation, the original
is returned in the direction C (through the discharge path PH2) again onto the original
tray 2.
[0049] In each of the two conveying paths there are various sensors, rollers, and so on
installed. The structure of each conveying path will be described below. It is, however,
noted that each portion does not always belong to only either one of the conveying
paths, but there are also some portions used in common to the both conveying paths.
[Switchback path]
[0050] The original tray 2 is one for mounting the originals thereon. It is the matter of
course that the original tray 2 is also used upon conveyance through the closed loop
path. The original tray 2 is constructed so as to be movable up and down by tray up/down
motor 59. An original P mounted on the original tray 2 is fed to the right (through
the closed loop path) or to the left (through the switchback path) on the drawing,
depending upon the conveying path used at that time. The original tray 2 is moved
up upon conveyance through the switchback path or down upon conveyance through the
closed loop path. The original tray 2 is inclined at a predetermined angle left side
down from the relation with separating/feeding means (retard belt 5', feeding roller
5'', etc. in the switchback path; adsorption belt 7 and air separating device 426
in the closed loop path) described hereinafter.
[0051] Recycle levers 3 are separating members for separating the original group before
copy from that after copy. The recycle levers 3 are provided in the original mounting
section. The tip of the recycle levers 3 extends through slots provided in side regulating
plate 4 up to the tray of original tray 2. The recycle levers 3 are provided at two
positions in order to be ready for originals of various sizes. The recycle levers
3 are driven by recycle motor 58 mounted in the tray side regulating plate 4. The
recycle levers 3 form parts of stack thickness detecting mechanism 200 described hereinafter.
[0052] Conveying roller 5, retard belt 5', and feeding roller 5'' are members for separating
and feeding the originals when the switchback path is used. These are driven by separating
motor 52.
[0053] The conveying roller 6' is one for guiding the original to the platen 105.
[0054] Inverting flapper 15 is used for inverting the original upon discharge and upon both-side
copy. The inverting flapper 15 is driven by inverting flapper solenoid 73.
[0055] Inverting roller 6 is driving means for registration and inversion of original upon
conveyance through the switchback path and is driven by inverting motor 55. The present
embodiment employs a DC motor as the inverting motor 55 and it is controlled by PLL
control to enable constant speed control between conveying belt 40 and inverting roller
6. Attached to the shaft of inverting motor 55 are a clock disk 56 and a clock detecting
sensor 57 for permitting the PLL control. It can also contemplated that a stepping
motor is adopted as the inverting motor 55 and is controlled in synchronism with the
separating motor 52 (for constant speed control).
[0056] Conveying/discharging roller 16 is used for guiding the original discharged from
the platen 105 again to the platen 105 (or the tray 2). The conveying/discharging
roller 16 is driven by discharge motor 61. The discharge motor 61 is also equipped
with a clock disk 62 and a clock sensor 63 for enabling speed control upon transfer
of original from the inverting roller 6 and upon discharge of original.
[0057] The conveying belt 40 is used for conveying the original on the platen 105. The conveying
belt 40 is driven by stepping motor 51. The stepping motor is used because of its
high controllability, i.e., good control response of start or stop. In addition, the
present embodiment necessitates the constant speed operation at high accuracy between
the conveying belt 40 (a backup roller driven by the conveying belt) and the registration
roller 11, which is also one of reasons for the use of stepping motor.
[0058] The region of the switchback path where the inverting roller 6 and conveying/discharging
roller 16 are set is shared with the closed loop path. Namely, the inverting roller
6 and conveying/discharging roller 16 are also used upon feeding of original through
the closed loop path. The conveying belt 40 is also shared with the closed loop path.
[0059] Various sensors (empty sensor 30, separation sensor 31, switchback registration sensor
32, inversion sensor 33, and discharge sensor 39) for monitoring the conveying status
of original are installed at respective positions of the switchback path. The empty
sensor 30 is used for detecting that the original is set on the tray 2. The separation
sensor 31 is used for detecting that the original is separated. The switchback registration
sensor 32 is used for taking timings of registration of original and correction of
oblique feed. The inversion sensor 33 is used for detecting that the original is moved
back in the switchback from the platen. The discharge sensor 39 is used for detecting
discharge of sheet.
[Closed loop path]
[0060] The adsorption belt 7 is one for adhering to the original and conveying it. This
adsorption belt 7 is set in a notch portion 404 provided in the center of the front
part of original tray 2 (see Fig. 4 and Fig. 5). The adsorption belt 7 is perforated
so as to have many holes 406. A suction duct 20 connected to a suction blower (not
illustrated) is set on the back side (inside the track) of the adsorption belt 7.
When the suction blower is actuated, the air is sucked from the holes 406 of suction
belt 7 through the suction duct 20. This suction causes the lowermost original out
of the originals mounted on the original tray 2 to be adhered to the adsorption belt
7. When the suction belt 7 is rotated in that state, the original thus adhered can
be conveyed. The suction duct 20 is provided with air valve 21 for controlling on/off
of suction (see Fig. 3). The air valve 21 is constructed to be opened or closed by
solenoid 22.
[0061] An air separating device 426 is provided for blowing air obliquely from above to
the lower part of the original stack placed at the predetermined air separating position
of the original tray 2, thereby certainly separating the lowermost original (see Fig.
4 and Fig. 5). The blowing of air is effected by blowing off the air supplied from
a blower (not illustrated) through blowoff port 409 provided in the lower part of
separating air duct 410. An air valve 408 for changing the air quantity according
to the thickness of the original stack is provided in the separating air duct 410.
The air valve 408 is constructed to be drive-controlled by stepping motor 9 so that
the valve travel can be adjusted thereby.
[0062] Shutter 41 (see Fig. 2 and Fig. 3) is provided for pushing the trailing edges of
the originals (the left edges on the drawing) mounted on the original tray 2 to convey
the original stack to the air-separable position. The originals are mounted on the
original tray 2 so that the trailing edges thereof abut the shutter 41. The shutter
41 is driven by stack transfer motor 80. When the originals are conveyed through the
switchback path, the shutter 41 is retracted by solenoid 81 so as to be prevented
from impeding conveyance of original. This stack transfer motor 80 is also used for
jogging the original returning to the original tray 2 through the closed loop path
again toward the separating/feeding means.
[0063] The stack thickness detecting mechanism 200 (see Fig. 2 and Fig. 3) is provided for
detecting the thickness of the original stack mounted on the original tray 2. The
stack thickness detecting mechanism 200 of the present embodiment is arranged to detect
the thickness of the stack of originals, based on an angle of rotation of recycle
levers 3. The stack thickness detecting mechanism 200 is constructed specifically
of a gear system for amplifying an amount of rotation of recycle levers 3, a slit
plate for outputting the amount of rotation amplified as the number of pulses generated,
and a photosensor or the like. Of course, the recycle levers 3 also constitute parts
of the stack thickness detecting mechanism 200. These gear system and other elements
are set inside the side regulating plate 4. The stack thickness detecting mechanism
200 outputs the detection result (specifically, a pulse signal in which the number
of pulses generated vary depending upon the thickness of stack) to the control device
300 described hereinafter.
[0064] The conveying roller 10 is provided for conveying the original separated by the air
separating device 426 etc. and is driven by the separating motor 52.
[0065] Registration roller 11 is driven by stepping motor 64. The stepping motor is used
because the constant speed property relative to the conveying belt 40 is of the significance
(for assuring high-accuracy registration). A clock disk 65 is attached to the drive
shaft of stepping motor 64. A clock detecting sensor 66 is provided for detecting
out-of-step of the stepping motor 64.
[0066] Backup roller 14a is provided in a turn path section in order to make handling of
a thick sheet or the like more advantageous. The backup roller 14a also serves as
a feeding roller for a sheet inserted through feeding port 13 of manual feeding path.
The backup roller 14a is driven by turn roller 8 driven by the conveying belt 40.
The peripheral velocity of the backup roller 14a is arranged so as to be equal to
the velocity of the conveying belt 40.
[0067] Turn flapper 14 is provided for guiding the original under conveyance so as to prevent
the original from being caught by platen edge 105a, and the turn flapper 14 is constructed
so that the position of the height thereof can be adjusted depending upon the circumstances
at that time. For example, when the original is conveyed through the closed loop path
to the platen, the turn flapper 14 is located higher than a platen edge section 105a.
When the original is fed through the manual path feeding port 13, the turn flapper
14 is also located higher than the platen edge section 105a. Conversely, when after
completion of copy the original is again moved back in the direction E, the turn flapper
14 is retracted so as to be lower than the platen edge section 105a in order to scoop
the original up from the platen edge section 105a. The turn flapper 14 is driven by
solenoid 76a.
[0068] Flapper 14' is provided for guiding an original manually fed, to the manual feeding
port 13. The flapper 14' is driven by solenoid 76b. Numeral 12 designates a manual
feeding roller.
[0069] The separating motor 52 is provided for driving the conveying roller 5, retard belt
5', feeding roller 5'', adsorption belt 7, and conveying roller 10. When the separating
motor 52 is rotated forward, it drives the conveying roller 5, retard belt 5', and
feeding roller 5''. When the separating motor 52 is rotated backward, it drives the
adsorption belt 7 and conveying roller 10. Transmission of driving force between the
separating motor 52 and the adsorption belt 7 is effected through clutch 70. Accordingly,
the separating belt 7 can be actuated or stopped without stopping the separating motor
52 by turning the clutch 70 on or off. The separating motor shaft of the separating
motor 52 is equipped with a clock disk 53 and a clock sensor 54 for speed control.
[0070] The stack transfer motor 80 is the stack transfer driving means and is also a drive
source for jogging the original returned after handling of sheet through the closed
loop, again toward the separating/feeding means. In the present embodiment it is a
stepping motor.
[0071] Various sensors (empty sensor 30, original set sensor 34, closed loop separation
sensor 35, closed loop registration sensor 36, image head sensor 37, and manual feeding
set and discharge sensor 38) for monitoring the conveying status of original are provided
at respective positions of the closed loop path. The empty sensor 30 is shared with
the switchback path. The original set sensor 34 is provided for detecting whether
the set original is of a half size (A4, LTR, or B5) or is longer than those, based
on presence or absence of the trailing edge of original when the originals are set.
The original set sensor 34 also functions as an original stack leading edge detecting
sensor. The closed loop separation sensor 35 is a sensor for detecting that the original
is separated. The closed loop registration sensor 36 is a sensor for taking the timings
of closed loop registration and correction of oblique feed. The image head sensor
37 is a sensor for positioning the original on the platen.
[0072] Next, the structure for control in the image forming apparatus, especially in the
automatic original feeding apparatus 1 herein, will be described referring to Fig.
6.
[0073] The automatic original feeding apparatus 1 is generally controlled by the control
device 300. The control device 300 is mainly constructed of the aforementioned microprocessor
unit (MPU) incorporating ROM and RAM. As shown in Fig. 6, signals from the various
sensors etc. described above are supplied to the input ports of the MPU. Further,
the loads described above are connected through a driver to the output ports of the
MPU.
[0074] The control device 300 executes the programs stored in the ROM and RAM to control
the above-stated sections, thereby realizing the various functions. For example, the
control device 300 has a function for adjusting the valve travel of air valve 408
according to the thickness of original stack by controlling the stepping motor 9.
The data necessary for the various controls (for example, information (LUT) indicating
the relation between the number of pulses outputted from the stack thickness detecting
mechanism 200 and the amount of rotation of separating air valve 408) is preliminarily
stored in (or supplied with necessity to) the ROM and RAM. The functions of the control
device 300 will be described in further detail in the description of the operation.
[0075] The "friction separating/feeding means" and "first separating means" in the present
invention are realized by the retard belt 5', feeding roller 5'', separating motor
52, etc. in the present embodiment. The "air separating/feeding means" and "second
separating means" are realized by the adsorption belt 7, air separating device 426,
and so on. The "selecting means" is realized by the control device 300 etc. The "image
reading section" corresponds to the platen 105. The "first conveying means" and "switchback
conveying means" are realized by the feeding roller 6, conveying belt 40, conveying/discharging
roller 16, and so on. The "second conveying means" and "closed loop conveying means"
are realized by the registration roller 11, conveying belt 40, conveying roller 6,
and so on.
[0076] The "sheet" in the present invention corresponds to the original stated in the present
embodiment. The "sheet tray" corresponds to the original tray 2. The "moving means"
corresponds to the shutter 41, adsorption belt 7, and the mechanism for actuating
these members. The "pushing means" corresponds to the shutter 41, stack transfer motor
80, and so on. The "conveying belt" corresponds to the adsorption belt 7, separating
motor 52, and so on. The "separating means" corresponds to the air separating device
426, the blower, and so on. The "separation position" corresponds to the air separation
position where the original can be separated by the air separating device 426. The
"control means corresponds to the control device 300. The "thickness detecting means"
corresponds to the recycle levers 3 and the stack thickness detecting mechanism 200.
[0077] The original conveying operation in the present embodiment will be described.
[0078] The original tray 2 is normally located on the upper side. When the stack of originals
is set on the original tray 2, the control device 300 detects the original size etc.
to determine which conveying path should be used, depending upon the detection result.
For example, when the empty sensor 30 is on and the original set sensor 34 is off,
the control device 300 determines that the size of originals mounted on the original
tray 2 at that time is the half size (A4 or B5 herein) and thus determines use of
the closed loop path. In practice, the control device also determines the size of
either A4, LTR, or B5 by simultaneously carrying out detection of the empty sensor
30, the original set sensor 34, and the original width (though not illustrated). The
operation after this will be described in separate sections of [1] conveyance of original
through the switchback path and [2] conveyance of original through the closed loop
path.
[1] Conveyance of original through the switchback path
[0079] When the user turns the copy button (not illustrated) on, the recycle levers 3 are
placed on the uppermost original.
[0080] Separation-conveyance is carried out in order from the lowermost original of the
stack of originals P mounted on the original tray 2. The original separated is guided
through the path PH1 and is then positioned at the predetermined position on the platen
105 of the image forming apparatus 100. Then the exposure operation by the optical
system is carried out. After completion of the exposure operation, the original is
returned in the direction C (through the discharge path PH2) and again moved back
onto the original tray 2.
[0081] After the all originals have been conveyed, the recycle levers 3 move down to be
lower than the mounting surface of the original tray 2. This causes the control device
to recognize completion of circulation of the originals in one cycle.
[2] Conveyance of original through the closed loop path (see Fig. 7)
[0082] The control device 300 is in a standby state to wait for on of the copy button (not
illustrated) (step 700). When the user turns the copy button (not illustrated) on,
the control device 300 actuates the recycle motor 58 to start descent of the recycle
levers 3 toward the original. The control device also actuates the tray up/down motor
59 to start descent of the original tray 2 (step 702). Then the control device waits
before the original tray 2 is moved down to the position of air-separable height (step
704). After the original tray 2 is lowered down to the predetermined position, the
up/down motor 59 is stopped (step 706).
[0083] During this period, when the recycle levers 3 land on the original stack, the stack
thickness detecting mechanism 200 outputs a pulse signal according to the position
(angle) of the recycle levers 3, i.e., according to the thickness of the original
stack mounted on the original tray 2 at this time, to the control device 300. The
control device 300 checks whether the thickness of the original stack was detected
(step 708), and the control device 300 stops the recycle motor 58 when it is confirmed
(step 710).
[0084] Then the control device 300 determines the valve travel of the separating air valve
408, based on the number of pulses at this time. Then the control device controls
the stepping motor 9 so as to achieve the determined valve travel, thus starting adjustment
of valve travel of the separating air valve 408. In tandem therewith, the control
device 300 actuates the blower to start blowing of air by the air separating device
426 (step 712). Then the control device 300 waits before the separating air valve
408 comes to a set angle (step 714). When it is confirmed that the separating air
valve 408 is set at the set angle (it should be noted that the setting does not always
have to be confirmed, but it may be assumed that the valve becomes set at the set
angle after a lapse of a predetermined time), the control device 300 actuates the
stack transfer motor 80 to make the shutter 41 push the original stack, thus starting
moving of the stack to the air separation position. At the same time as it, the separating
motor 52 and clutch 70 are actuated to start rotation of the adsorption belt 7. At
the same time as it, the rotation of the conveying roller 10 is also started (step
716). At this time the control device 300 controls the stack transfer motor 80 and
separating motor 52 so that the moving speed of shutter 41 becomes equal to the rotating
speed of the adsorption belt 7. Namely, the moving speed of the original stack by
the shutter 41 is synchronized with the rotation of the adsorption belt 7. Accordingly,
the stack will not be disturbed with increase in the moving speed of the original
stack.
[0085] During transfer of the original stack the control device 300 monitors whether the
leading edges (the right edges in Fig. 1) of the originals reach the air separation
position, based on the detection result of the original set sensor 34 (step 718).
When the leading edges reach the air separation position, the stack transfer motor
80 is turned off to stop the movement of the original stack (step 720). In practice,
the arrival at the air separation position is assumed when the original set sensor
34 detects the leading edge of moving original (or after a lapse of a predetermined
time from the time of the detection).
[0086] After this, the control device 300 actuates the suction blower to start suction of
original to the adsorption belt 7 and the control device 300 also turns the clutch
70 on to start the rotation of the adsorption belt 7 (step 722). In this case, the
separating air valve 408 has already started blowing of air in the air quantity suitable
for the thickness of the original stack at that time, and the separation of original
can be done immediately.
[0087] After the start of the separation operation, the control device 300 monitors whether
the original is separated, based on the detection result of the closed loop original
separation sensor 35 (step 724). Then, confirming that the original is separated and
fed, the control device turns the clutch 70 off to temporarily stop the rotation of
the adsorption belt 7. It also closes the air valve 21 (step 726).
[0088] After this, the control device 300 checks whether the original thus separated at
that time is the last original (step 728). If the original is not the last original,
the same process will be repeated, returning to the step 722. On the other hand, if
the original is the last original, the operation will be terminated.
[0089] The original thus separated in this way is guided through the path PH3 to be positioned
at the predetermined position on the platen 105 of the image forming apparatus 100
(see Fig. 2). Then, after completion of the exposure operation, the original is returned
in the direction C (through the discharge path PH2) onto the original tray 2.
[0090] The embodiment described above permits the original stack to be conveyed quickly
to the air-separable position without causing stack deviation of the original stack.
This can decrease the fast copy time (Fcot). Further, since the air quantity of the
separating air is adjusted to the optimum value according to the thickness of the
original stack, prior to the start of air separation-feeding, an original can be separated
by air immediately after the original stack reaches the air-feedable point. This can
also decrease the fast copy time (Fcot).
[0091] In the embodiment described above, the conveying belt 40 and registration roller
11 were driven by the stepping motor. Instead thereof, however, the constant speed
control in the transfer section may be realized by the PLL control of DC motor. In
another arrangement, the conveying belt and registration roller may be simultaneously
actuated by a common drive source through on/off of clutch by use of one drive source
and clutch means or the like.
[0092] In the present embodiment the thickness of the original stack was detected utilizing
the recycle levers. It is, however, needless to mention that a mechanism for detecting
the thickness of the original stack can be provided separately and independently from
the recycle levers.
[0093] In the present embodiment, in transferring the original stack to the air-feedable
position (air separating position) by the shutter 41, the blowing of separating air
was started before the original stack reached the air separation position. However,
the apparatus may be arranged to start at least preparation for blowing (for example,
setting of the air quantity according to the thickness of the original stack), whereby
the fast copy time (Fcot) can be decreased, though the effect thereof is less (than
in the above embodiment). The apparatus may also be modified in such a manner that
adhesion to the adsorption belt 7 is also carried out upon rotation of the adsorption
belt 7 in synchronism with the movement of the original stack.
[0094] As described above, the sheet conveying apparatus of the present invention employs
the separating and feeding method by the retard system in the switchback path and
the air separating and feeding method in the closed loop path.
[0095] Since the separation by air feeding is carried out during the flow reading or the
like through the closed loop path, normally most frequently used, such as processing
of many originals in terms of the productivity, the apparatus of the invention is
free of the problems of the original damage and durability due to the edge soiling
and separation at the leading edge of original. Further, in the case of the originals
having the binding holes, the originals will be set on the original tray so that the
hole side is naturally directed to the left when seen from the user. Therefore, the
hole side of the originals is located in the upstream end in the feeding direction
upon air feeding through the closed loop path, so that the apparatus is free of the
problem of floating failure of original due to leakage of the separating air through
the holes upon the air feeding as described previously.
[0096] In the case of feeding of the originals of different sizes mixed, the originals can
be fed by the retard method through the switchback path, so that the apparatus can
handle a wider range of originals than the apparatus employing only the air feeding
method, thus enhancing the operability.
[0097] The features achieved by the provision of two separating/feeding means of the different
methods are as follows.
[0098] The flow reading of small size sheets (A4, B5, etc.), which are used most frequently,
is set as a standard mode and the air separating/feeding section is used preferentially.
[0099] In analog copiers, it is essential to move the original from right to left on the
platen upon the flow reading, and the air feeding section is thus located on the right
side.
[0100] The friction separating section is used for large-size sheets and for sheets of different
sizes mixed. The conventional apparatus needed a mechanism for sliding the rear edge
regulating plate, for feeding the originals of the small size and large size by use
of one RDF, and the size of the RDF itself was large. The RDF of the present invention
employed the folding tray and friction separating section for the large sizes, thus
compactifying the body of RDF.
[0101] The friction separating/feeding section is used for perforated originals. The perforated
originals, which were hard to deal with heretofore by air separation, can be separated
more certainly by use of the friction separating section.
[0102] According to the feature of air separation and feeding, when the sheets are mounted
on the sheet tray, the thickness detecting means detects the thickness of the sheet
stack. The moving means moves the sheet stack mounted on the sheet tray to the predetermined
separation position. When the moving means is composed of the conveying belt and pushing
means, the conveying belt rotates in synchronism with the movement of the sheet stack
by the pushing means. This permits the stack to retain its shape even with increase
in the speed of movement of the sheet stack.
[0103] The control means makes the separating means start the blowing of air prior to the
arrival of the sheet stack at the separation position. In this case, the blowing amount
of air is set according to the detection result of the thickness detecting means.
Since the separating means has already started blowing of air at the time of arrival
of sheets at the separation position, separation can be done immediately.
[0104] The present invention is provided as a sheet feeding apparatus comprising a friction
separating/feeding means for separating and feeding a sheet by making use of frictional
force, an air separating/feeding means for separating and feeding a sheet by making
use of air and a selecting means for selecting either one of the friction separating/feeding
means and the air separating/feeding means and for making the selected means separate
and feed the sheet.
1. A sheet feeding apparatus comprising:
a friction separating/feeding means for separating and feeding a sheet by making use
of frictional force;
an air separating/feeding means for separating and feeding a sheet by making use of
air; and
a selecting means for selecting either one of said friction separating/feeding means
and said air separating/feeding means and for making the selected means separate and
feed the sheet.
2. A sheet feeding apparatus applied to an image reading apparatus for reading an image
of a sheet existing in an image reading section, said sheet feeding apparatus comprising:
a friction separating/feeding means for separating and feeding a sheet by making use
of frictional force;
a first conveying means for guiding the sheet separated and fed by said friction separating/feeding
means to said image reading section;
an air separating/feeding means for separating and feeding a sheet by making use of
air;
a second conveying means for guiding the sheet separated and fed by said air separating/feeding
means to said image reading section; and
a selecting means for selecting eisaidr one of said friction separating/feeding means
and said air separating/feeding means and for making the selected means separate and
feed the sheet.
3. A sheet feeding apparatus according to Claim 1 or 2, wherein said selecting means
selects said air separating/feeding means in a normal mode.
4. A sheet feeding apparatus applied to an image reading apparatus for reading an image
of a sheet existing in an image reading section, said sheet feeding apparatus comprising:
a tray on which a sheet is to be loaded;
a first separating means for separating a sheet loaded on said tray, said first separating
means including feeding means and retard means; and
a second separating means for separating a sheet loaded on said tray, said second
separating means including an air knife and vacuum suction conveying means.
5. A sheet feeding apparatus according to Claim 4, further comprising:
a switchback conveying means including a switchback conveying path, said switchback
conveying means conveying the sheet separated by said first separating means through
said switchback conveying path from one end of said image reading section into said
image reading section and thereafter switching said sheet back to convey said sheet
through said switchback conveying path out of said image reading section; and
a closed loop conveying means including a closed loop conveying path forming a closed
loop, said closed loop conveying means conveying the sheet separated by said second
separating means through said closed loop conveying path, thereby conveying said sheet
from the other end of said image reading section into said image reading section,
said closed loop conveying means conveying said sheet out of said image reading section
from the side opposite to the side where the sheet was conveyed thereinto.
6. A sheet feeding apparatus according to Claim 5, wherein said switchback conveying
means temporarily stops said sheet on said image reading section while said image
reading apparatus is reading an image, and
wherein said closed loop conveying means continues conveyance of said sheet conveyed
into said image reading section even while said image reading apparatus is reading
the image, and said closed loop conveying means carries the sheet out thereof from
the side opposite to the side where the sheet was conveyed thereinto.
7. A sheet feeding apparatus according to Claim 5, wherein said first separating means
is means for separating an original loaded on said tray, said means being provided
on one side of said tray,
wherein said second separating means is means for separating an original loaded
on said tray, said means being provided on another side of said tray different from
the one side of said tray where said first separating means is provided, and
wherein at least one of said switchback conveying means and said closed loop conveying
means returns a conveyed original to said tray.
8. A sheet feeding apparatus according to Claim 7, further comprising:
a moving means for moving a stack of sheets mounted on said tray to a predetermined
separation position on said tray; and
a control means for controlling said moving means and said separating means;
wherein said second separating means is means for separating the lowermost sheet
from the other sheets by blowing of air to a lower portion of a leading edge of the
stack of sheets having been conveyed to said separation position,
wherein said control means controls said second separating means to start said
blowing of air from said second separating means, prior to arrival of said stack of
sheets at said separation position.
9. A sheet feeding apparatus according to Claim 8, further comprising thickness detecting
means for detecting a thickness of said stack of sheets mounted on said tray at that
time,
wherein said control means changes a blowing amount of air from said second separating
means, according to a detection result of said thickness detecting means.
10. A sheet feeding apparatus according to Claim 8 or 9, wherein said moving means comprises
a pushing means for pushing a trailing edge of said stack of sheets to move said stack
of sheets, and a conveying belt set on a tray surface of said tray,
wherein said conveying belt rotates in synchronism with the movement of said stack
of sheets by said pushing means.
11. A sheet reading apparatus comprising:
the sheet feeding apparatus as set forth in Claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10;
and
a reading means for reading a sheet having been fed thereto by said sheet feeding
apparatus.
12. An image forming apparatus comprising:
the sheet feeding apparatus as set forth in Claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10;
a reading means for reading an image of a sheet having been fed thereto by said sheet
feeding apparatus; and
an image forming means for forming the image of the sheet having been read by said
reading means, on a recording medium of a sheet shape.
13. A sheet feeding apparatus comprising:
a sheet tray on which a stack of sheets are to be mounted;
a moving means for moving a stack of sheets mounted on said sheet tray to a predetermined
separation position on said sheet tray;
a separating means for separating the lowermost sheet from the other sheets by blowing
of air to a lower portion of a leading edge of the stack of sheets having been conveyed
to said separation position; and
a control means for controlling said moving means and said separating means,
wherein said control means controls said separating means start said blowing of
air, prior to arrival of said stack of sheets at said separation position.
14. A sheet feeding apparatus according to Claim 13, further comprising a thickness detecting
means for detecting a thickness of said stack of sheets mounted on said tray at that
time,
wherein said control means changes a blowing amount of air from said separating
means, according to a detection result of said thickness detecting means.
15. A sheet feeding apparatus according to Claim 13 or 14, wherein said moving means comprises
a pushing means for pushing a trailing edge of said stack of sheets to move said stack
of sheets, and a conveying belt set on a tray surface of said tray,
wherein said conveying belt rotates in synchronism with the movement of said stack
of sheets by said pushing means.
16. A sheet feeding apparatus comprising:
a sheet tray on which a sheet is to be mounted;
a pushing means for pushing a trailing edge of a sheet mounted on said sheet tray
to move said sheet to a predetermined separation position on said sheet tray;
a conveying belt set in a tray surface of said sheet tray; and
a control means for controlling said pushing means and said conveying belt,
wherein said control means controls said conveying belt to rotate in synchronism
with the movement of said sheet by said pushing means.
17. An image reading apparatus comprising:
an image reading means comprising a sheet table, said image reading means reading
an image of a sheet placed on said sheet table; and
the sheet feeding apparatus as set forth in Claim 13, 14, 15, or 16, for successively
conveying sheets to said sheet table.