U.S. patent application number 11/211146 was filed with the patent office on 2006-08-17 for paper feeding method and paper feeder.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Akinobu Nakahata, Tomoyuki Shiiya, Keiichi Taguchi.
Application Number | 20060180991 11/211146 |
Document ID | / |
Family ID | 35427980 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060180991 |
Kind Code |
A1 |
Nakahata; Akinobu ; et
al. |
August 17, 2006 |
Paper feeding method and paper feeder
Abstract
An image-forming apparatus has a limitation pad 31c and a retard
roller 34, which separately feed recording paper P on an elevation
tray 31 in an MPT cover 30 by bringing the recording paper P
against an outer peripheral surface 33a of the feeding roller 33.
In this image-forming apparatus (paper feeder), when the feeding
roller is stopped by passing recording paper to be separately fed
to a pair of relay transport rollers, the elevation tray is lowered
before stoppage of the feeding roller, thereby separating an
extremity of the recording paper from the outer peripheral surface
of the feeding roller.
Inventors: |
Nakahata; Akinobu; (Nagano,
JP) ; Taguchi; Keiichi; (Nagano, JP) ; Shiiya;
Tomoyuki; (Nagano, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
500 S. GRAND AVENUE
SUITE 1900
LOS ANGELES
CA
90071-2611
US
|
Assignee: |
SEIKO EPSON CORPORATION
|
Family ID: |
35427980 |
Appl. No.: |
11/211146 |
Filed: |
August 24, 2005 |
Current U.S.
Class: |
271/121 |
Current CPC
Class: |
B65H 2701/1311 20130101;
B65H 2601/521 20130101; B65H 2513/514 20130101; B65H 1/14 20130101;
B65H 2511/514 20130101; B65H 3/0669 20130101; B65H 2220/01
20130101; B65H 2220/01 20130101; B65H 2220/02 20130101; B65H
2220/11 20130101; B65H 2220/01 20130101; B65H 2220/02 20130101;
B65H 2220/02 20130101; B65H 2513/512 20130101; B65H 2511/21
20130101; B65H 2511/13 20130101; B65H 2405/11162 20130101; B65H
3/5261 20130101; B65H 2701/1768 20130101; B65H 2511/21 20130101;
B65H 2511/13 20130101; B65H 2513/514 20130101; B65H 2511/514
20130101; B65H 2513/512 20130101 |
Class at
Publication: |
271/121 |
International
Class: |
B65H 3/52 20060101
B65H003/52 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2004 |
JP |
2004-243877 |
Nov 11, 2004 |
JP |
2004-327976 |
Claims
1. A paper feeder for separately feeding a sheet of paper from
plural sheets of paper along a transfer path, said paper feeder
comprising: a feed roller; a retard roller in pressed contact with
the feed roller and forming a first nip between the feed roller and
the retard roller, wherein an axis-to-axis distance between the
feed roller and the retard roller is fixed; a lift plate on which
plural sheets of paper can be set, the lift plate being located in
an upstream side of the transfer path with respect to the feed
roller and being movable between a first position where a front end
of the plural sheets of paper set on the lift plate is brought into
contact with the feed roller and a second position where the front
end of the plural sheets of paper set on the lift plate is
separated from the feed roller; a pair of transport rollers in
contact with each other to form a second nip, and being located in
a downstream side of the transfer path with respect to the feed
roller; and a controller which moves the lift plate from the first
position to the second position in a state in which the sheet of
paper is held between the feed roller and the retard roller at the
first nip and is also held between the transport rollers at the
second nip.
2. The paper feeder according to claim 1, wherein when the
controller moves the lift plate from the first position to the
second position, the controller stops rotation of the feed
roller.
3. The paper feeder according to claim 2, wherein controller moves
the lift plate from the second position to the first position when
the controller restarts the rotation of the feed roller.
4. The paper feeder according to claim 1, wherein the plural sheets
of paper set on the lift plate is of cardboard.
5. The paper feeder according to claim 1, wherein the controller is
communicatable with an interface by which a user can selectively
enter cardboard and plan paper as information of the plural sheets
of paper set on the lift plate to set a first mode and a second
mode, respectively, in the first mode, a controller moves the lift
plate at the first position to the second position before the sheet
of paper completely passes through the first nip.
6. The paper feeder according to claim 5, wherein in the second
mode, the controller maintains the lift plate at the first position
until the sheet of paper completely passes through the first
nip.
7. The paper feeder according to claim 5, wherein in the second
mode, the controller moves the lift plate at the first position to
the second position when the controller stops rotation of the feed
roller and before the sheet of paper completely passes through the
first nip.
8. The paper feeder according to claim 5, wherein in the first
mode, the controller moves the lift plate from the second position
to the first position after the sheet of paper completely passes
through the first nip, to thereby feed a subsequent sheet of paper
to the first nip.
9. The paper feeder according to claim 7, wherein in the second
mode, the controller moves the lift plate from the second position
to the first position after the sheet of paper completely passes
through the first nip and when the controller restarts the rotation
of the feed roller, to thereby feed a subsequent sheet of paper to
the first nip.
10. A paper feeder comprising: a separation-and-feeding section for
separating a sheet of paper from plural sheets of paper set in a
load position and feeding said sheet of paper downstream; a
transport section which transports said sheet of paper sent from
said separation-and-feeding section further downstream to feed said
sheet of paper to a processing position on an apparatus main body;
a transfer path for guiding said sheet of paper to be sent from
said load position to said processing position using said
separation-and-feeding section and said transport section; and a
control section for controlling driving action of individual
sections of said apparatus so that said sheet of paper is fed from
said load position to said processing position in synchronism with
processing timing of said apparatus main body, wherein said
separation-and-feeding section includes a feeding roller for
feeding, to a downstream transfer path, said sheet of paper brought
into pressed contact therewith, a separation roller which is
rotationally driven or subjected to limited rotation according to
frictional force developing between said separation roller and said
sheet of paper while bringing said sheet of paper into pressed
contact with said feeding roller, thereby separating, from said
plural sheets of paper, said sheet of paper to be fed by said
feeding roller, and a movement mechanism which is configured so as
to be able to carry said plural sheets of paper and which moves an
extremity of said plural sheets of paper in a direction in which
said extremity is brought into contact with or separated from a
portion of an outer peripheral surface of said feeding roller, said
portion of said outer peripheral surface being located upstream of
said separation roller; said separation-and-feeding section is
designed to such a configuration that said separation roller
remains in pressed contact with said feeding roller at all times;
and said control section drives and controls said movement
mechanism such that said extremity of said plural sheets of paper
is separated from said feeding roller at a timing at which said
feeding roller comes to a stop.
11. The paper feeder according to claim 10, wherein said transfer
path is designed to a transfer path length over which feeding of
said sheet of paper to said processing position of said apparatus
main body by said transport section is commenced before said sheet
of paper passes through a nipping position existing between said
feeding roller and said separation roller of said
separation-and-feeding section; and when transfer of said sheet of
paper received from said separation-and-feeding section is
temporarily stopped before said sheet of paper passes through said
nipping position between said feeding roller and said separation
roller so that said transport section feeds said sheet of paper to
said processing position in synchronism with a processing timing of
said apparatus main body, said control section stops said feeding
roller of said separation-and-feeding section.
12. The paper feeder according to claim 11, wherein said control
section stops said feeding roller even after said sheet of paper
transported by said transport section has passed through said
nipping section between said feeding roller and said separation
roller.
13. The paper feeder according to claim 10, wherein, when transfer
of said sheet of paper received from said separation-and-feeding
section is temporarily stopped before said sheet of paper passes
through said nipping position between said feeding roller and said
separation roller so that said transport section feeds said sheet
of paper to said processing position in synchronism with said
processing timing of said apparatus main body, said control section
controls driving of said movement mechanism such that said
extremity of said plural sheets of paper is separated from said
feeding roller before occurrence of temporary stoppage of said
sheet of paper until said sheet of paper passes through said
nipping position.
14. A paper feeding method for a paper feeder including a paper
feeding roller which comes into contact with a topmost sheet of
paper in stacked sheets of paper to thereby feed said topmost sheet
of paper, a retard roller which comes into contact with said paper
feeding roller to separate said topmost sheet of paper from a
subsequent sheet of paper in said stacked sheets, and a lift plate
which supports said stacked sheets of paper to be fed by said paper
feeding roller and presses a front portion of said stacked sheets
of paper against said paper feed roller, wherein when said paper is
plain paper, said paper is fed while said lift plate remains
pressed; and when said paper is cardboard, said paper is fed while
said lift plate is lifted and lowered every time one sheet of
cardboard paper is fed.
15. A paper feeder comprising: a paper feeding roller which comes
into contact with a topmost sheet of paper in stacked sheets of
paper to thereby feed said topmost sheet of paper; a retard roller
which comes into contact with said paper feeding roller to separate
said topmost sheet of paper from a subsequent sheet of paper in
said stacked sheets; a lift plate which supports said stacked
sheets of paper to be fed by said paper feeding roller and presses
a front portion of said stacked sheets of paper against said paper
feed roller; a lift plate lifting-and-lowering mechanism for
lifting or lowering said lift plate; and a controller which selects
either a plain paper mode, where paper is fed while said lift plate
remains pressed by said lift plate lifting-and-lowering mechanism
when said paper is plain paper, or a cardboard mode, where paper is
fed while said lift plate is lifted and lowered by said lift plate
lifting-and-lowering mechanism every time one sheet of cardboard is
fed when said paper is cardboard.
16. The paper feeder according to claim 15, further comprising: a
first tray which has said lift plate and is tilted at a tilt angle
with respect to a horizontal plane; and a second tray which is
coupled to a rear portion of said first tray, supports a rear
portion of said stacked sheets of paper, and has a smaller tilt
angle with respect to said horizontal plane than the tilt angle of
said first tray, wherein a paper support face of said second tray
falls within a range of angle made between a paper support face of
said lift plate at a lift-up position where said lift plate is
lifted when the stacked sheets of paper is maximum in number that
can be set on said first tray and a paper support face of said lift
plate at another lift-up position where said lift plate is lifted
when one sheet of paper is supported by said first tray.
17. The paper feeding method according to claim 14, wherein
lifting/lowering of said lift plate performed when said paper is
cardboard is effected by: lowering said lift plate after one sheet
of cardboard has been fed and before a trailing edge of said
cardboard passes through a contact section between said paper
feeding roller and said retard roller, and lifting said lift plate
before initiation of feeding of a next sheet of cardboard.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a paper feeding method and
paper feeder.
[0002] The present invention is applicable to a paper feeding
method and a paper feeder which can separately feed set paper to a
desired position without fail by preventing backward movement of
paper from a position where a plurality of sheets of paper are
separately fed one at a time to a pickup-impossible position.
[0003] The present invention is also applicable to a paper feeding
method and a paper feeder, which feed paper (plain paper,
cardboard, a card, an envelope, an OHP sheet, or other recording
material) stacked on a tray one at a time to an image-forming
apparatus, or the like.
[0004] A paper feeder, which sets a plurality of sheets of paper in
a loaded state and feeds paper by separating and feeding paper one
sheet at a time to a desired position, has hitherto been used
heavily. This paper feeder feeds, e.g., an original (paper) loaded
in an image reader, to an image reading position. Alternately, the
paper feeder is set in an image-forming apparatus, and feeds
recording paper to a position where an image is to be recorded and
formed (hereinafter called an "image recording-and-forming
position").
[0005] The paper feeder of this type comprises: a feeding roller
for downwardly feeding paper to be brought into pressed contact; a
lift plate which is designed so as to be able to load a plurality
of sheets of paper and which lifts or lowers a front edge thereof
in a direction to come into contact with or out of contact from an
outer peripheral surface of the feeding roller; and a retard roller
(a separation roller) which comes into pressed contact with the
outer peripheral surface of the feeding roller at a position
downward of the front edge of the lift plate in a rotational
direction and which is rotated so as to follow the feeding roller
under the load exceeding the set value. This paper feeder enables
the outer peripheral surface of the feeding roller to come into
pressed contact with the front edge of paper on the lift plate, to
thus directly pick up the paper. The paper is nipped between the
feeding roller and the retard roller, thereby separating the paper
one sheet at a time and feeding the thus separated paper
downwardly. Therefore, the paper feeder enables an attempt to
reduce space and cost by omitting setting of a so-called pickup
roller which picks up paper on the lift plate.
[0006] In the configuration of such a paper feeder, paper is fed
downward as if it were withdrawn while being nipped between the
feeding roller and the retard roller or the lift plate. Even after
having been passed to a downward pair of rollers, the paper
produces a great load. For this reason, in connection with the
paper feeder set in the image-forming apparatus, it has been
proposed to sequentially separate the lift plate and the retard
roller from the feeding roller after the document has been passed
to the pair of rollers downward of the feeding roller is described
(see, e.g., Patent Document 1). Even in connection with the paper
feeder provided in the image-forming apparatus, it is described to
separate the lift plate and the retard roller from the feeding
roller after a document has been passed to a pair of rollers
downstream of the feeding roller (see, e.g., Patent Document
2).
[0007] Patent Document 1: JP-A-11-334917
[0008] Patent Document 2: JP-UM-A-5-89344
[0009] However, in such a conventional paper feeder, the lift plate
usually has the function of lifting and lowering the front edge of
paper in a pinchable manner between the lift plate and the feeding
roller. If an attempt is made to provide the paper feeder with a
mechanism for separating the paper from the feeding roller until
arrival at the retard roller, the paper feeder must be provided
with a special mechanism, as described in the above-described
publications, which in turn adds to cost.
[0010] Here, the feeding roller rotates in a paper feeding
direction while rotating the retard roller. In contrast, the paper
fed by the feeding roller is fed to a desired position while being
firmly nipped between a pair of transport rollers and a pair of
gate rollers, both of which are disposed in downstream positions.
For this reason, after paper has been passed to the pair of
transport rollers and the pair of gate rollers, the chance of
feeding accuracy of the paper being deteriorated can be
lessened.
[0011] However, when the paper feeder attempts to feed paper to a
processing position in the image-forming apparatus main body, there
may arise a case where the feeding roller is stopped for reasons of
processing of the image-forming apparatus main body. For instance,
in order to make a gap (a so-called gap between sheets of paper)
between a trailing edge of one sheet of paper and a front edge of a
subsequent sheet of paper, the feeding roller is temporarily
stopped. In particular, in the case of a paper feeder set in the
image-forming apparatus, before being fed to the image
recording-and-forming position, recording paper is temporarily
stopped in synchronism with image-forming timing of the
image-forming apparatus main body while being nipped between the
pair of downstream gate rollers. At this time, thanks to recent
miniaturization of equipment, in the case of a paper feeder whose
path to a processing position of the image-forming apparatus main
body is designed to be short, there may arise a case where the
recording paper is temporarily stopped before passing through the
nipping position existing between the feeding roller and the retard
roller.
[0012] However, when the feeding roller is stopped while the retard
roller and the lift plate remain in pressed contact with the
feeding roller, load induced when the feeding roller is moved a
short distance backward in reaction to stoppage of the retard
roller is imparted to the feeding roller. At this time, when the
front edge of paper on the lift plate remains in pressed contact
with the outer peripheral surface of the feeding roller, force for
backwardly moving the feeding roller is cumulatively exerted on the
front edge of the paper. As a result, there arises so-called
backward movement; that is, a phenomenon of paper being moved
backwardly to such an extent that paper cannot be fed by bringing
the paper into pressed contact with the outer peripheral surface of
the feeding roller by means of the lift plate.
[0013] Accordingly, the present invention aims at providing an
inexpensive paper feeder capable of reliably separating and feeding
set paper to a desired position without provision of a mechanism
for moving a separation roller, by preventing backward movement of
paper to a position where separated feeding of paper is impossible,
which would otherwise arise as a result of stoppage of a feeding
roller.
[0014] Available paper feeding methods include a method for
continuously feeding a plurality of sheets of paper without regard
to the kind of paper while the lift plate is held in a pressing
state, and a method for feeding paper by lifting or lowering the
lift plate every time one sheet of paper is fed, without regard to
the kind of paper.
[0015] According to the technique for continuously feeding a
plurality of sheets of paper without regard to the kind of paper
while the lift plate remains in a pressing state, when paper is
cardboard (including a postal card, an envelope, an OHP sheet, and
the like, in addition to the cardboard), the next sheet of paper
becomes likely to move backward because of reaction of a torque
limiter of a retard roller. Consequently, overlapping transfer of
paper or transfer failure of paper becomes likely to arise.
[0016] In the meantime, according to the technique for feeding
paper by lifting or lowering the lift plate every time one sheet of
paper is fed without regard to the kind of paper, when paper is
plain paper (including thin paper), the lift plate is lowered when
the topmost paper is fed, whereby the paper is released from a
supported state. Therefore, the paper trembles in the vicinity of a
nipping section located between the paper feeding roller and the
retard roller, thereby causing chattering sound (noise).
[0017] Another object of the present invention is to provide a
paper feeding method and a paper feeder, which enable reliable
feeding of cardboard one at a time simultaneously with feeding of
plain paper without causing chattering sound.
SUMMARY OF THE INVENTION
[0018] A first aspect of the invention is directed toward a paper
feeder for separately feeding a sheet of paper from plural sheets
of paper along a transfer path. The paper feeder includes: a feed
roller; and a retard roller in pressed contact with the feed roller
and forming a first nip between the feed roller and the retard
roller. An axis-to-axis distance between the feed roller and the
retard roller is fixed. The paper feeder further includes a lift
plate on which plural sheets of paper can be set, the lift plate
being located in an upstream side of the transfer path with respect
to the feed roller and being movable between a first position where
a front end of the plural sheets of paper set on the lift plate is
brought into contact with the feed roller and a second position
where the front end of the plural sheets of paper set on the lift
plate is separated from the feed roller. The paper feeder further
includes a pair of transport rollers in contact with each other to
form a second nip, and being located in a downstream side of the
transfer path with respect to the feed roller. The paper feeder
further includes a controller which moves the lift plate from the
first position to the second position in a state in which the sheet
of paper is held between the feed roller and the retard roller at
the first nip and is also held between the transport rollers at the
second nip.
[0019] Since the lift plate is moved from the first position to the
second position in the state in which the sheet of paper is held
between the feed roller and the retard roller at the first nip and
is also held between the transport rollers, an adverse effect by
the retard roller to a subsequent sheet of paper can be
eliminated.
[0020] A second aspect of the invention is directed toward a paper
feeder having: a separation-and-feeding section for separating a
sheet of paper from plural sheets of paper set in a load position
and feeding the sheet of paper downstream; a transport section
which transports the sheet of paper sent from the
separation-and-feeding section further downstream to feed the sheet
of paper to a processing position on an apparatus main body; a
transfer path for guiding the sheet of paper sent from the load
position to the processing position by the separation-and-feeding
section and the transport section; and a control section for
feeding the sheet of paper from the load position to the processing
position in synchronism with processing timing of the apparatus
main body by controlling driving action of individual sections of
the apparatus. The separation-and-feeding section includes a
feeding roller for feeding, to a downstream transfer path, the
sheet of paper brought into pressed contact therewith, a separation
roller which is rotationally driven or subjected to limited
rotation according to frictional force developing between the
separation roller and the sheet of paper while bringing the sheet
of paper into pressed contact with the feeding roller, thereby
separating the sheet of paper from the plural sheets of paper, and
a movement mechanism which is configured so as to be able to carry
the plural sheets of paper and which moves an extremity of the
plural sheets of paper in a direction in which the extremity is
brought into contact with or separated from a portion of an outer
peripheral surface of a feeding roller. The portion of the outer
peripheral surafce of the feeding roller is located upstream of the
separation roller. The separation-and-feeding section is designed
to such a configuration that the separation roller remains pressed
contact with the feeding roller at all times. The control section
drives and controls the movement mechanism such that the extremity
of plural sheets of paper is separated from the feeding roller at a
timing when the feeding roller comes to a stop.
[0021] In this aspect, an extremity portion of the upstream plural
sheets of paper can be moved so as to separate from the outer
peripheral surface of the feeding roller at the timing at which the
feeding roller comes to a stop while the separation roller remains
in a pressed contact state. Even when the feeding roller is rotated
backward as a result of reaction of the separation roller stemming
from stoppage of the feeding roller, the paper located before the
nipping position between the feeding roller and the separation
roller can be prevented from undergoing force of backward movement.
Consequently, there can be prevented backward movement of paper to
such an extent that the paper cannot be separately fed, which would
otherwise be caused as a result of paper being moved backward every
time the feeding roller stops.
[0022] In addition to the specific items of the second aspect, a
third aspect of the invention is characterized in that the transfer
path is designed to have a transfer path length over which feeding
of the sheet of paper to the processing position of the apparatus
main body by the transport section is commenced before the sheet of
paper passes through a nipping position existing between the
feeding roller and the separation roller. When transfer of the
sheet of paper received from the separation-and-feeding section is
temporarily stopped before the sheet of paper passes through the
nipping position between the feeding roller and the separation
roller so that the transport section feeds the sheet of paper to
the processing position in synchronism with a processing timing of
the apparatus main body, the control section stops the feeding
roller of the separation-and-feeding section.
[0023] In this aspect, the paper transport path is short. Even when
the feeding roller comes to a temporary standstill before the sheet
of paper passes through the nipping position between the feeding
roller and the separation roller, paper located before the nipping
position can be prevented from undergoing force of backward
movement. Therefore, even in the course of paper feeding action,
accumulation of force for moving backward the next paper to be
separately fed can be avoided, and backward movement of paper to
such an extent that the paper cannot be separately fed can be
prevented with high reliability.
[0024] In addition to the specific items of the third aspect, a
fourth aspect of the invention is characterized in that the control
section stops the feeding roller even after the sheet of paper
transported by the transport section has passed through the nipping
section between the feeding roller and the separation roller.
[0025] In the fourth aspect, even when the feeding roller comes to
a temporary standstill after paper has passed through the nipping
position between the feeding roller and the separation roller, the
paper located before the nipping position can be prevented from
undergoing force of backward movement. Therefore, for instance,
even when the feeding roller stops such that a clearance exists
between sheets of paper to be fed, accumulation of force for moving
backward the next paper to be separately fed can be avoided, so
that backward movement of paper to such an extent that the paper
cannot be separately fed can be prevented with high
reliability.
[0026] In addition to the specific items of the second aspect, a
fifth aspect of the invention is characterized in that, when
transfer of the sheet of paper received from the
separation-and-feeding section is temporarily stopped before the
sheet of paper passes through the nipping position between the
feeding roller and the separation roller so that the transport
section feeds paper to the processing position in synchronism with
a processing timing of the apparatus main body, the control section
controls driving of the movement mechanism such that the extremity
of the plural sheets of paper is separated from the feeding roller
before occurrence of temporary stoppage of the paper until the
sheet of paper passes through the nipping position.
[0027] In this aspect, the paper transport path is short. Even when
the feeding roller comes to a temporary standstill before the sheet
of paper passes through the nipping position between the feeding
roller and the separation roller and when the feeding roller
temporarily stops even after the sheet of paper has passed through
the nipping position, the next sheet of paper to be separately fed
is left in a receded position and can be prevented from undergoing
force for moving the paper backward. Therefore, paper which is
brought into pressed contact with the feeding roller to be
separately fed does not need to be moved uselessly, and there can
be avoided accumulation of force for backwardly moving the next
paper to be separately fed. Thus, backward movement of paper to
such an extent that the paper cannot be separately fed can be
prevented with high reliability.
[0028] As mentioned above, according to the present invention, the
extremity of plural sheets of paper is separated at a timing at
which the feeding roller is stopped, without provision of a
mechanism for moving the separation roller and while the separation
roller is left in a pressed contact state. As a result, there can
be prevented backward movement of paper, which would otherwise be
caused by reverse rotation of the feeding roller as a result of
reaction of the separation roller stemming from stoppage of the
feeding roller. Backward movement of paper to such an extent that
the paper cannot be separately fed, which would otherwise be caused
by accumulation of backward movement of paper, can be prevented.
Therefore, by means of only an inexpensive configuration which
actuates an existing mechanism for bringing the extremity of plural
sheets of paper into pressed contact with an outer peripheral
surface of the feeding roller, set paper can be separately fed to a
desired position with high reliability.
[0029] A sixth aspect of the invention is directed toward a paper
feeding method for a paper feeder including a paper feeding roller
which comes into contact with a topmost sheet of paper in stacked
sheets of paper to thereby feed the topmost sheet of paper, a
retard roller which comes into contact with the paper feeding
roller to separate the topmost sheet of paper from a subsequent
sheet in the stacked sheets of paper, and a lift plate which
supports stacked sheets of paper and presses a front portion of
stacked sheets of paper against the paper feed roller. In the
method, when the paper is plain paper, paper is fed while the lift
plate remains pressed. When the paper is cardboard, paper is fed by
lifting/lowering the lift plate every time one sheet of cardboard
paper is fed.
[0030] A seventh aspect of the invention is directed toward a paper
feeder including: a paper feeding roller which comes into contact
with a topmost sheet of paper in stacked sheets of paper to thereby
feed the topmost sheet of paper; a retard roller which comes into
contact with the paper feeding roller to separate the topmost sheet
of paper from a subsequent sheet of paper in the stacked sheets of
paper; a lift plate which supports stacked sheets of paper to and
presses a front portion of the stacked sheets of paper against the
paper feed roller; a lift plate lifting-and-lowering mechanism for
lifting or lowering the lift plate; and a controller which selects
either a plain paper mode, where paper is fed while the lift plate
remains pressed by the lift plate lifting-and-lowering mechanism
when the paper is plain paper, or a cardboard mode, where paper is
fed while the lift plate is lifted and lowered every time one sheet
of cardboard is fed by the lift plate lifting-and-lowering
mechanism when the paper is cardboard.
[0031] According to the sixth and seventh aspect, when paper to be
fed is plain paper, paper is fed while the lift plate remains
pressed. Hence, the lift plate becomes pressed (lifted) when the
topmost sheet of paper is fed, whereby supporting of paper is
achieved.
[0032] Therefore, occurrence of tremble vibrations in paper, which
would otherwise arise in the vicinity of a nipping section between
the paper feeding roller and the retard roller, is prevented, which
in turn suppresses occurrence of chattering sound (noise).
[0033] Further, when paper to be fed is plain paper, paper is fed
while the lift plate remains pressed. There is no necessity for
lifting or lowering the lift plate every time one sheet of paper is
fed. Hence, a plurality of sheets of plain paper can be
continuously fed with efficiency.
[0034] In contrast, when paper to be fed is cardboard, the lift
plate is lifted and lowered every time one sheet of cardboard is
fed. Therefore, even when the next sheet of paper has been moved
rearward by means of reaction of a torque limiter of the retard
roller, the extent to which the next sheet of paper is moved
rearward is diminished by the lifting-and-lowering actions of the
lift plate.
[0035] Consequently, overlapping transfer of paper or transfer
failure of paper, which would otherwise be caused when paper is
cardboard, is unlikely to arise.
[0036] As mentioned above, according to the present invention,
cardboard can be fed one sheet at a time without fail, and plain
paper can be fed without causing chattering sound.
[0037] Preferably, the paper feeder further includes a first tray
which has the lift plate and is tilted with respect to the a
horizontal plane; and a second tray which is coupled to a rear
portion of the first tray, supports the rear portion of the paper,
and makes a smaller tilt angle with respect to the horizontal plane
than that formed by the first tray. A paper support face of the
second tray falls within a range of angle made between a paper
support face of the lift plate achieved at a position where the
lift plate is lifted when a maximum number of sheets of paper that
can be set on the first tray are stacked on the first tray and a
paper support face of the lift plate achieved at a position where
the lift plate is lifted when one sheet of paper is supported by
the first tray.
[0038] In this case, the paper support face of the second tray
achieved when the maximum number of sheets of paper that can be set
on the first tray are stacked on the first tray turns into a slope
which makes the same angle as that made between the horizontal
plane and the paper support face of the lift plate achieved at the
position where the lift plate is lifted, or turns into a slope
which makes a smaller angle of inclination with respect to the
horizontal plane.
[0039] Consequently, occurrence of a downward flexion in the paper
support plane of the lift plate and the paper support face of the
second tray, which would otherwise arise when the lift plate has
lifted the front portion of paper, is prevented. Even when the
stacked paper is cardboard, both ends of the cardboard are not
supported, whereby a transfer failure of paper is unlikely to
arise.
[0040] Meanwhile, the paper support face of the second tray
achieved when one sheet of paper is supported by the first tray
turns into a slope which forms the same angle as that made between
the horizontal plane and the paper support plane of the lift plate
achieved in the position where the lift plate is lifted, or turns
into a slope which makes a larger angle of inclination with respect
to the horizontal plane.
[0041] Consequently, when a plurality of sheets of paper are set in
the first tray (and the second tray), even when force--which causes
rearward movement by reaction of the torque limiter--has been
exerted on the next sheet of paper as a result of use of a retard
roller having a torque limiter, the paper becomes easy to slip over
the slope (or the upper surface of paper), and hence overlapping
transfer or transfer failure of paper becomes unlikely to
arise.
[0042] This paper feeder can yield an additional advantage of the
ability to feed a plurality of sheets of paper one by one without
fail until the last sheet of paper.
[0043] Desirably, lifting/lowering of the lift plate performed when
the paper is cardboard is effected by: lowering the lift plate
after one sheet of cardboard has been fed and before a trailing
edge of the cardboard passes through a contact section between the
paper feeding roller and the retard roller, and lifting the lift
plate before initiation of feeding of a next sheet of
cardboard.
[0044] In this case, the lift plate has been lowered before the
trailing edge of the cardboard passes through a contact section
between the paper feeding roller and the retard roller. Hence,
rearward movement of the next sheet of paper, which would otherwise
be caused by reaction of the torque limiter of the retard roller,
can be reliably prevented.
[0045] The present disclosure relates to the subject matter
contained in Japanese patent application Nos. 2004-243877 (filed on
Aug. 24, 2004) and 2004-327976 (filed on Nov. 11, 2004), each of
which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 is a view showing an example image-forming apparatus
equipped with an embodiment of a paper feeder of the present
invention; that is, a front perspective view showing the
substantially-entire configuration thereof.
[0047] FIG. 2 is a view for describing a mechanism for opening and
closing an exterior cover of the image-forming apparatus, wherein
FIG. 2A is a phase diagram of the exterior cover when the cover is
closed, and FIG. 2B is a phase diagram of the exterior cover when
the cover is opened.
[0048] FIG. 3 is a view showing that an MPT cover is opened so as
to make available a multipurpose tray (MPT) set on the exterior
cover; that is, a fragmentary cross-sectional side view of the
cover.
[0049] FIG. 4 is a perspective side view showing the multipurpose
tray of the exterior cover.
[0050] FIG. 5 is a plan view showing the multipurpose tray of the
exterior cover.
[0051] FIG. 6 is a related block for describing controlling of
feeding of paper from the multipurpose tray.
[0052] FIG. 7 is a timing chart describing operation for
controlling feeding of recording paper from the multipurpose tray
of the exterior cover.
[0053] FIG. 8 is a schematic front view showing an example internal
structure of a color image-forming apparatus using an embodiment of
a paper feeding method and that of a paper feeder, both of which
pertain to the present invention.
[0054] FIG. 9 is an enlarged fragmentary view of FIG. 8.
[0055] FIG. 10 is a plan view of the principle section shown in
FIG. 9.
[0056] FIG. 11 is a block diagram of a paper feeder.
[0057] FIG. 12 is a flowchart showing a paper feeding method.
[0058] FIG. 13 is a descriptive view of operation of the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0059] The best mode of the present invention will be described
hereinbelow by reference to the drawings.
First Embodiment
[0060] FIGS. 1 through 7 are drawings showing an example
image-forming apparatus equipped with one embodiment of a paper
feeder of the present invention.
[0061] In FIG. 1, an image-forming apparatus 10 is a printer which
is connected to and utilizes an external device, such as a personal
computer, which prepares and outputs an image such as characters.
This image-forming apparatus 10 comprises an image recorder which
receives image data used for forming an image, such as characters,
and records and forms an image on one or both sides of recording
paper by means of electrophotography; and a paper transport device
which separately feeds a plurality of sheets of loaded recording
paper one at a time to the image recorder and which transports the
recording sheet, on which the image has been recorded and formed,
to the outside of the image-forming apparatus and stacks the
thus-transported recording paper.
[0062] In simple terms, the image recorder comprises: a laser beam
scanning device 11 for effecting scanning of a laser beam L on the
basis of image data; a photosensitive drum (image-carrying body) 12
which is exposed to radiation and scanning of the laser beam L
emitted from the laser beam scanning device 11, whereby an
electrostatic latent image based on image data is formed on the
surface of the photosensitive drum 12 through exposure; an
electrifying device 13 for electrifying an outer peripheral surface
of the photosensitive drum 12 so that an electrostatic latent image
can be formed by means of radiation of the laser beam L;
development cartridges 14a (only one of which is illustrated) of
respective colors which store toner of yellow (Y), cyan (C),
magenta (M), and black (K) color and transfer the toner to the
electrostatic latent image on the photosensitive drum 12 by means
of a development roller 14c, to thus cause the toner to adhere to
the latent image, thereby effecting toner development; a rotary
development device 14 which houses the development cartridges 14a
in setup spaces 14b of respective colors and which performs
switching of the development cartridges 14a to be operated (used
for development) while facing the photosensitive drum 12; an
intermediate transfer belt (an intermediate transfer medium) 15
which receives the toner images of respective colors developed on
the photosensitive drum 12 and forms a transferrable-and-recordable
toner image (a monochrome image or a color image) on the recording
paper; a transfer roller 16 which transports the conveyed and fed
recording paper downstream such that the recording paper is nipped
between the transfer roller 16 and the intermediate transfer belt
15 and which transfers the toner image carried by the intermediate
transfer belt 15 to the nipped and transported recording paper; a
pair of fusing rollers 17 which fuse the toner image by subjecting
the recording paper, on which the toner image has been transferred
and which has been transported, to heating and pressed contact and
which transports the recording paper in a nipped manner in a
further downstream direction; a waste toner tank 18 which recovers
the toner still remaining on the photosensitive drum 12 by means of
a blade 18a and stores the thus-recovered toner; and a waste toner
tank 19 which, similarly, recovers the toner still remaining on the
intermediate transfer belt 15 by means of a blade and stores the
thus-recovered toner. The intermediate transfer belt 15, the
transfer roller 16, and the pair of fusing rollers 17, all of which
belong to the image recording device, each have the function of
transporting the recording paper. For this reason, the intermediate
transfer belt 15, the transfer roller 16, and the pair of fusing
rollers 17 constitute a portion of the paper transport device to be
described below.
[0063] In simple terms, the paper transport device comprises: a
paper cassette 21 which is removably set in a lower portion of the
image-forming apparatus main body 10 and which houses a plurality
of sheets of recording paper loaded on an elevation plate 21a at
the bottom; a pickup roller 22 which is brought into pressed
contact with a bundle of sheets of recording paper lifted by a lift
plate 21a of the paper cassette 21 and which rotates so as to be
pressed against a separation pad 21b, thereby picking up
(withdrawing) the topmost sheet of recording paper and delivering
the thus-picked-up sheet of recorded paper to a paper transport
path "f"; a pair of first relay transport rollers 23 which receive
the recording paper fed from the paper cassette 21 by the pickup
roller 22 and transport the thus-received recording paper in a
nipped manner to the downstream transport path "f"; a pair of
second relay transport rollers 24 which receive the recording paper
transported in a nipped manner by the pair of first relay transport
rollers 23 and transport the thus-received recording paper to a
further downstream transport path "f"; a pair of gate rollers
(so-called registration rollers) 25 which receive the recording
paper transported by the pair of second relay transport rollers 24
in the transport path "f" and transport (feed), in a nipped manner,
the thus-received recording paper to a position where an image is
recorded and formed (transferred) by the intermediate transfer belt
15 and the transfer roller 16, both of which belong to the image
recording device; and a pair of first paper output rollers 26 and a
pair of second paper output rollers 27 which receive from the pair
of gate rollers 25 the recording paper--on one surface of which the
image has been fused as a result of the recording paper having been
transported over the transport path "f" between the intermediate
transfer belt 15 and the transfer roller 16 and between the pair of
fusing rollers 17--and transport and output, in a stacking manner,
the thus-received recording paper to a paper output table 29
located in the upper portion of the image-forming apparatus main
body 10. This paper transport device has a re-transport path "r"
which inverts the recording paper, on one surface of which the
image is formed, and delivers the thus-inverted recording paper to
the transport path "f" upstream of the pair of gate rollers 25; and
a pair of third intermediate transport rollers 28 disposed in the
path "r." The pair of third intermediate transport rollers 28
receive the recording paper that has been delivered to the
re-transport path "r" as a result of reverse rotation of the pair
of first and second paper output rollers 26, 27, and pass the
thus-received recording paper to the pair of gate rollers 25,
whereby images can be formed on both surfaces of the recording
paper.
[0064] As a result, the image-forming apparatus 10 can form images
by transferring, on one surface or both surfaces of the recording
paper by way of the intermediate transfer belt 15, the toner images
that have been formed by causing toner to adhere to the surface of
the photosensitive drum 12 to thus develop the electronic latent
image. In this way, an image can be formed by transferring, to the
recording paper, the color image that has been formed by
superimposing yellow (Y), cyan (C), magenta (M), and black (K)
toner on the surface of the intermediate transfer belt 15, or
transferring a monochrome image formed from black (K) toner to the
recording paper.
[0065] A reclosable cover (an exterior cover) 100 is provided on a
side surface, shown in FIG. 1, of the paper transport device of the
image-forming apparatus 10 so as to enable opening and closing of
the inside of the image-forming apparatus main body 10. A cover
(general-purpose cover) 30 for use with a multipurpose tray--which
carries a plurality of types of recording paper used for interrupt
processing other than paper fed from the paper cassette 21--s
provided integrally and reclosably in the reclosable cover 100.
This paper transport device has an MPT transport path "m" used for
feeding the recording paper set on this multipurpose tray cover
(hereinafter abbreviated as an "MPT cover") 30 to the transport
path "f" upstream of the pair of gate rollers 25. An MPT feeding
roller 33 disposed in the MPT transport path "m" separately feeds
the recording paper one at a time, thereby passing the recording
paper to the pair of second intermediate transport rollers 24 and
the pair of gate rollers 25. As a result, the recording paper can
be fed to a position where an image is recorded and formed by means
of the intermediate transfer belt 15 and the transfer roller 16,
both belonging to the image-recording device, whereby an image can
be formed on the recording paper.
[0066] Specifically, in this image-forming apparatus 10, the
reclosable cover (exterior cover) 100 on the side is pivotally
supported by rotary shafts provided on both lower ends. As shown in
FIG. 2, the reclosable cover 100 is supported so as not to
unlimitedly pivot and fall, by means of link members 102 to 105,
which are attached to positions on both sides of the transported
recording paper in a transverse direction thereof to thus
constitute a link mechanism, and a traction spring 106. As a
result, an upper edge of the reclosable cover 100 is pivoted in a
direction approaching and departing from the image-forming
apparatus main body 10 (a horizontal direction in FIG. 1) by
detaching an unillustrated lock mechanism, thereby opening and
closing the inside of the image-forming apparatus main body 10. The
reclosable cover is pivoted in a clockwise direction in FIG. 1 to
thus provide access to the inside of the image-forming apparatus
main body 10. As a result, there can be performed operation for
removing the recording paper having jammed during the course of
transportation, by releasing (exposing) the transport paths "f" and
"r" of the paper transport device. The photosensitive drum 12 in
the image recording device and the development cartridges 14a in
the rotary development device 14 can be subjected to maintenance by
opening and closing an unillustrated front reclosable cover.
[0067] In the link members 102, 103 of the link mechanism, base end
sections 102a, 103a are pivotally attached to the image-forming
apparatus main body 10 and the reclosable cover 100, respectively,
and extremity sections 102b, 103b are coupled so as to be able to
relatively pivot, thereby allowing the reclosable cover 100 to
approach and depart from the image-forming apparatus main body 10.
As shown in FIG. 2A, the reclosable cover 100 can close the link
members 102, 103 in a collapsed manner. As shown in FIG. 2B, when
the reclosable cover 100 is opened, the link members 102, 103 are
pivoted so separate the base end sections 102a, 103a, whereby the
link members 102, 103 can be supported in a suspended manner on a
part of the image-forming apparatus main body 10 and maintained at
a set release (pivot) angle.
[0068] In the link member 102, an outer peripheral surface of the
base end section 102a is formed into a cam surface 102c. The link
members 104, 105 are coupled to the cam surface 102c, to thus limit
pivotal movement of the link members 102, 103. Thus, pivotal
movement (releasing action) of the reclosable cover 100 is adjusted
to be stopped in a multistage manner.
[0069] In more detail, the link member 104 axially supports a
rotary shaft 17c of one roller 17b of the pair of fusing rollers
17. The link member 104 is pivotally attached to the image-forming
apparatus main body 10 by taking an upper portion of the rotary
shaft 17c as a pivot 104a. The traction spring 106, which urges the
fusing roller 17b in a direction approaching the other fusing
roller 17a to thus impart pressing force, is attached to the
extremity of the link member 104 which is spaced from the pivot
104a to a position lower than the rotary shaft 17c. The link member
105 is pivotally attached to the image-forming apparatus main body
10 while taking an intermediate portion of the link member 105 as a
pivot 105a. One end section 105b of the link member 105 remains in
pressed contact with a pin 104b located at the extremity of the
link member 104 pulled by the traction spring 106, and the other
end section 105c remains in slidable contact with the cam surface
102c of the link member 102.
[0070] The cam surface 102c of the link member 102 is designed to
pivot the link member 105 by changing an interval between the
position where the cam surface 102c comes into slidable contact
with the other end section 105c of the link member 105 and the base
end section 102a of the pivot, in accordance with the amount of
pivotal movement. When the reclosable cover 100 is stopped, the
traction spring 106 is allowed to pull the link member 104 in a
direction where the fusing roller 17b is brought into pressed
contact with the fusing roller 17a. In contrast, when the
reclosable cover 100 is released, the link member 104 is pivoted in
a direction where the fusing roller 17b is caused to depart from
the fusing roller 17a in defiance of the restoration force (elastic
force) of the traction spring 106. The pair of fusing rollers 17
(17a, 17b) are released from a pressed-contact state, thereby
releasing nipping pressure for nipping the recording paper. The
reclosable cover 100 does not naturally return from a released
state to a closing direction, which would otherwise be caused when
the restoration force of the traction spring 106 has surpassed
pivotal force stemming from the weight of the reclosable cover
100.
[0071] As a result, when released from the lock of the
image-forming apparatus main body 10, the reclosable cover 100
attempts to pivot in an opening direction. However, pivotal
movement of the link members 102, 103 is limited by the link
members 104, 105 pulled by the traction spring 106 joined to the
cam surface 102c of the link member 102, and the link members 102,
103 are held in their pivotal positions. Consequently, the
reclosable cover 100 is retained at the position where an upper
portion of the reclosable cover 100 is slightly opened. Thus,
occurrence of fracture or impact sound, which would otherwise be
caused when the reclosable cover abruptly pivots and falls to a
fully-opened position shown in FIG. 2B, can be prevented.
[0072] As shown in FIG. 3, the MPT cover 30 is integrally provided
inside of the reclosable cover 100 with a portion of the MPT cover
located close to the outer edge of the reclosable cover 100 being
left outside. As in the case of the reclosable cover 100, the MPT
cover 30 is pivotally supported by the pivots located on both lower
ends. As a result of the upper end portion of the MPT cover 30
being pivoted in a direction (a horizontal direction in FIG. 1) in
which the MPT cover approaches and departs from the reclosable
cover 100, the MPT transport path "m" in communication with the
transport path "f" can be opened or closed. A closing mechanism 50
maintains the MPT cover 30 such that the exterior surface of the
MPT cover 30 becomes essentially flush with the reclosable cover
100. This closing mechanism 50 comprises an engagement piece 100b
formed into the shape of a tongue by cutting a wall surface 100a of
a recessed section of the reclosable cove 100; and an elongated
engagement hole 30d formed by cutting a side wall 30a of the MPT
cover 30. Specifically, the engagement piece 100b of the reclosable
cover 100 advances or recedes in the front-and-back direction of
drawing paper of FIG. 3 by means of only pivoting the reclosable
cover 100 in an approaching/departing direction with an
unillustrated grip section provided on the upper end of the MPT
cover 30 (by only applying force for opening/closing the MPT cover
30). As a result, the engagement piece 100b is engaged with or
disengaged from the elongated engagement hole 30d, so that the MPT
cover 30 can be held in either a closed state or an open state.
[0073] When the MPT cover 30 is pivoted in such a direction that
the upper end thereof departs from the reclosable cover 100 (in the
clockwise direction in FIG. 3), the portion of the MPT cover 30
close to the lower end thereof is supported by the reclosable cover
100 so as to guide the set recording paper to the MPT transport
path "m" and such that the external upper end of the MPT cover
comes to an elevated position. As shown in FIGS. 4 and 5, the
feeding roller 33 and the retard roller (the separation roller) 34
are opened (exposed) in an available manner in conjunction with an
elevation tray 31 and an extended tray 32, both of which are
provided inside as MPT trays. The recording paper P set on the
elevation tray 31 or the extended tray 32 is separately fed to the
MPT transport path "m" one at a time by means of the feeding roller
33 and the retard roller 34. Specifically, the elevation tray 31,
the extended tray 32, the feeding roller 33, and the retard roller
34 constitute a separation feeding section. The pair of relay
transport rollers 24 and the pair of gate rollers constitute a
transport section, and the transport paths "f" and "m" constitute a
transfer path.
[0074] The elevation tray 31 is supported by a pivot 30b provided
on an interior surface of the side wall 30a of the MPT cover 30
such that a rear end section 31a departed from the image-forming
apparatus main body 10 is pivotally supported. A limitation pad 31c
is provided in the center of an extremity section 31b so as to be
able to approach or depart from the feeding roller 33 provided in
the image-forming apparatus main body 10. As shown in FIG. 3, the
lift plate 35, which is connected in communication with the
image-forming apparatus main body 10 and vertically moves, is
situated between the elevation tray 31 and the MPT cover 30 located
below. While being forced upwardly at all times by an unillustrated
forcing member (e.g., a torsion spring), the lift plate 35 is
pressed downward in defiance to the force of the forcing member in
accordance with a rotational angle of an eccentric cam 36 (shown in
FIG. 5) which is rotationally driven by a controller (control
section) 40 to be described later. As a result, the lift plate 35
is vertically moved. Specifically, the elevation tray 31, the lift
plate 35, and the eccentric cam 36 constitute a movement mechanism.
The extremity P1 of the recording paper P set on the upper surface
of the elevation tray 31 can be caused to approach or depart from
an outer peripheral surface 33a of the feeding roller 33. This
elevation tray 31 can limit withdrawal of the recording paper P
pressed against the outer peripheral surface 33a of the feeding
roller 33 by means of the limitation pad 31c. The frictional
surface of the limitation pad 31c is set to such an extent that
withdrawal of the final one sheet of recording paper P is withdrawn
by the outer peripheral surface 33a of the feeding roller 33.
[0075] The elevation tray 31 is provided with a pair of side guides
37 separated from each other in the widthwise direction (the
vertical direction in FIG. 5) of the set recording paper P. The
side guides 37 are provided so as to be slidable in the widthwise
direction while maintained upright on the upper surface of the
elevation tray 31. The side guides 37 extend in the widthwise
direction of the recording paper P on the back of the elevation
tray 31, and are coupled to a pair of racks 39 separated in a
lengthwise direction (the horizontal direction in FIG. 5) of the
recording paper P. The racks 39 mesh with a pinion 38 arranged in
the center between the racks 39. As a result, the side guides 37
are designed to slide evenly in the widthwise direction of the
recording paper P on the elevation tray 31, thereby restricting the
side edges of the recording paper. As a result, the recording paper
P is separately fed to the MPT transport path "m" while being
oriented in an appropriate attitude.
[0076] The extended tray 32 is inserted and housed in a space S
defined between the back surface of the elevation tray 31 and the
MPT cover 30. When the recording paper is loaded on the elevation
tray 31, the extended tray 32 is designed to be withdrawn to
support a trailing edge section P2 of the recording paper P. This
extended tray 32 is supported by the MPT cover 30 in such an
attitude as to become essentially flush with an extended plane of
the elevation tray 31 (illustrated by a dashed line in FIG. 4) that
causes the extremity section 31b to approach the outer peripheral
surface 33a of the feeding roller 33 when the extended tray 32 is
withdrawn. When the extended tray 32 is withdrawn, protrusions 32a
provided at the extremity of the extended tray 32 catch ribs 30c
provided upright on the side walls 30a of the MPT cover 30, thereby
preventing removal of the extended tray 32. Extended sides 32b
formed on both sides of the extended tray 32 are supported so as to
assume a desired attitude by the ribs 30c of the MPT cover 30. An
auxiliary tray 32d is provided on a rear end section of the
extended tray 32 so as to be pivotable around a pivot 32c. When
very long recording paper P is set on the elevation tray 31, the
auxiliary tray 32d is pivoted, thereby enabling extension of a load
surface.
[0077] The feeding roller 33 is provided in a position
corresponding to the limitation pad 31c in the center of the
extremity section 31b of the elevation tray 31. The feeding roller
33 is rotationally driven by the controller 40 to be described
later. This feeding roller 33 rotates clockwise in FIG. 4 to pick
up (withdraws) the recording paper P on the elevation tray 31, on
the outer peripheral surface 33a of which the extremity section P1
is pressed, and feeds the thus-picked-up recording paper to the MPT
transport path "m."
[0078] The retard roller 34 is rotationally supported while the
feeding roller 34 remains in pressed contact with the outer
peripheral surfaces 33a, 34a, and is attached to a stationary shaft
34b fixed in a nonrotatable manner to the image-forming main body
10, so as to rotate in conjunction with a torque limiter 34c. The
torque limiter 34c is set as follows. When the outer peripheral
surface 33a of the feeding roller 33 and an outer peripheral
surface 34a of the retard roller 34 are in direct pressed contact
with each other or in direct pressed contact with the recording
paper P withdrawn by the feeding roller 33, the retard roller 34 is
rotationally driven by the feeding roller 33 by means of frictional
force developing therebetween. Meanwhile, the retard roller 34 is
stopped by the frictional force developing between the retard
roller 34 and the recording paper P withdrawn by the feeding roller
33, thereby stopping the recording paper P remaining in a pressed
contact with the retard roller.
[0079] As shown in FIG. 6, the controller 40 is connected to, e.g.,
a personal computer PC which prepares and outputs an image, such as
characters, and exchange various types of control data and image
data with the PC. In accordance with previously-prepared programs,
various types of data processing control operations and drive
control operations of individual sections of the image-forming
apparatus are performed. As a result, the individual sections of
the image-forming apparatus 10 are collectively controlled, to thus
form an image on the recording paper P and produces a printout.
[0080] In this controller 40, for example, a group of motors 41 for
driving individual sections of the controller and step clutches 42,
43 coupled to the group of motors by way of an unillustrated gear
trains so as to be able to transmit driving force from drive shafts
of the motors 41. The step clutch 42 is coupled to an unillustrated
drive gear for rotationally driving various types of drive rollers,
such as the pickup roller 22 and the feeding roller 33. The
controller 40 connects or disconnects transmission of driving force
of the motors 41 to the feeding roller 33 by means of the step
clutch 42, thereby driving or stopping, e.g., the feeding roller 33
of the MPT transport path "m". An unillustrated drive gear for
rotationally driving the eccentric cam 36 is coupled to the step
clutch 43. The controller 40 connects or disconnects transmission
of driving force of the motors 41 to the eccentric cam 36 by means
of the step clutch 43. Thus, the eccentric cam 36 is driven and
stopped, thereby lifting or lowering the elevation tray 31 by way
of the lift plate 35.
[0081] Specifically, upon detection of the MPT cover 30 having been
opened with respect to the reclosable cover 100 through use of an
unillustrated sensor, the controller 40 drives the groups of motors
41 to thus rotate the eccentric cam 36 so as to lower the lift
plate 35 to the lowermost position by way of the step clutch 43. As
a result, the extremity section 31b of the elevation tray 31 is
lowered so as to depart from the outer peripheral surface 33a of
the feeding roller 33 so that the recording paper P can be set on
the elevation tray 31. When a start key in an unillustrated control
section is pressed in this state, the controller 40 starts driving
the groups of motors 41, and rotates the eccentric cam 36 so as to
release the lift plate 35 from the pressed state, thereby lifting
the elevation tray 31. Thereby, after the extremity section P1 of
the set recording paper P has been pressed against the outer
peripheral surface 33a of the feeding roller 33, the feeding roller
33 is rotationally driven by way of the step clutch 42.
[0082] Thereby, when the feeding roller 33 picks up the recording
paper P on the elevation tray 31 to thus feed the paper to the MPT
transport path "m," the limitation pad 31c located in the center of
the extremity section 31b of the elevation tray 31 is brought into
pressed contact with the lowermost sheet of recording paper P,
thereby preventing from sequential feeding of the recording paper P
from the lowermost sheet thereof. Even when a plurality of sheets
of recording paper P are delivered between the feeding roller 33
and the retard roller 34, the recording paper P other than the top
sheet thereof is stopped by the outer peripheral surface 34a of the
retard roller 34, and only the topmost sheet of recording paper P
can be separately fed one at a time.
[0083] At this time, as shown in FIG. 7, the controller 40 starts
driving operation of the image recording device and that of the
paper transport device, both of which are provided in the
image-forming apparatus main body 10. The recording paper P on the
elevation tray 31 is separately fed in synchronism with recording
and formation (transfer) of an image while a sensor signal for
detecting one rotation of the intermediate transfer belt 15 is
taken as a reference signal, thereby feeding paper to the position
where an image is recorded and formed by the intermediate transfer
belt 15 and the transfer roller 16. Lifting and lowering of the
elevation tray 31 and rotation of the feeding roller 33 are
controlled as follows in accordance with the amount of recording
paper P fed to the MPT transport path "m" continual to the
transport path "f" for the pair of relay transport rollers 24 and
the pair of gate rollers 25.
[0084] In detail, the eccentric cam 36 is rotated to lift the
elevation tray 31 (the lift plate 35) at a timing which is delayed,
only a preset period, from the timing of a sensor signal (Vsync)
for detecting one rotation of the intermediate transfer belt 15
before recording and formation of an image. Thereby, the extremity
section P1 of the recording paper P set on the load surface is
brought into pressed contact with the outer peripheral surface 33a
of the feeding roller 33, thereby preparing feeding of the
recording paper P. Subsequently, rotational driving of the feeding
roller 33 is started at a timing delayed by only a sufficient time
t1 from when lifting of the elevation tray 31 is started until when
lifting operation is completed. Thus, the recording paper P on the
elevation tray 31 is separately fed one at a time in conjunction
with the limitation pad 31c of the extremity section 31b and the
retard roller 34, thereby causing the recording paper P to travel
from the MPT transport path "m" to the inside of the ordinary
transport path "f."
[0085] When an unillustrated paper detection sensor provided in
front of the pair of relay transport rollers 24 has detected the
recording paper P fed over the transport path "f," rotational
driving of the pair of relay transport rollers 24 is commenced,
thereby nipping and transporting the recording paper P traveling
over the transport path "f." At this time, the eccentric cam 36 is
further rotated to thus lower the elevation tray 31 at a timing
delayed from the timing at which the paper detection sensor
provided in front of the pair of relay transport rollers 24 have
detected the recording paper P, by a time t2 sufficient for nipping
and transporting the recording paper P. The extremity P1 of unfed
recording paper P set on the load surface is separated from the
outer peripheral surface 33a of the feeding roller 33 until
commencement of separation feeding of the next sheet of recording
paper P. Thereby, the bundle of sheets of recording paper P
awaiting on the elevation tray 31 until the pieces of paper are fed
enter a standby condition while being temporarily separated from
the feeding roller 33 and the retard roller 34. Reference symbol
"t3" shown in FIG. 7 denotes a time lag from when the paper sensor
for the pair of relay transport rollers 24 has detected the
recording paper P until when the pair of relay transport rollers 24
are started to be rotationally driven. Variations exist in the
time, in FIG. 7, at which the elevation tray 31 is lifted or
lowered are attributable to the shape of the outer peripheral
surface of the eccentric cam 36 that slidably contacts the lift
plate 35; that is, a difference in rotational angle required for
lifting or lowering the elevation tray 31.
[0086] When the unillustrated paper detection sensor provided in
front of the pair of gate rollers 25 has detected the recording
paper P nipped and transported by the pair of relay transport
rollers 24, nipping and transporting of the recording paper P is
left to the pair of relay transport rollers 24, and rotational
driving of the feeding roller 33 is stopped until separation
feeding of the next sheet of recording paper P is started, and the
feeding roller 33 is driven (driven so as to follow) in conjunction
with the recording paper P to be nipped and transported.
Specifically, the feeding roller 33 stops driving operation before
the trailing end section P2 of the recording paper P passes through
the nipping position between the feeding roller 33 and the retard
roller 34. When active rotation of the feeding roller 33 has
stopped, the load for directly driving the retard roller 34
remaining in pressed contact with the outer peripheral surface 33a
of the feeding roller 33 is released. As a result, the torque
limiter 34c attempts to its natural state with respect to the
stationary shaft 34b. Hence, the retard roller 34 slightly rotates
reversely in a direction opposite to the feeding direction of the
recording paper P (the clockwise direction in FIGS. 3 and 4).
Therefore, in relation to the bundle of sheets of recording paper P
awaiting on the elevation tray 31 until they are fed, force of
backward movement stemming from reverse rotation of the retard
roller 34 is not exerted on and accumulated in the bundle of sheets
of paper, even in the case of a structure where the feeding roller
33 and the retard roller 34 remain in pressed contact with each
other. Backward movement of the extremity section P1 of the
recording paper P to a position where the extremity section P1
cannot be nipped by the outer peripheral surface 33a of the feeding
roller 33 does not arise.
[0087] The pair of relay transport rollers 24 and the pair of gate
rollers 25, which are located in positions subsequent to the
position where the recording paper P has been detected by the paper
detection sensor located in front of the pair of gate rollers 25,
are not distinguished from each other by means of the transport
path. The recording paper P having passed is nipped and transported
to the image recording-and-forming position. The pair of relay
transport rollers 24 continually nip and transport the recording
paper P for only a period of time t4 during which the extremity of
the recording paper P is sufficiently brought into collision with
the nipping section of the pair of gate rollers 25, thereby
correcting skewing (oblique traveling) of the recording paper P and
temporarily stopping the recording paper P.
[0088] Subsequently, after having awaited for only a period of time
t5 required for synchronization with the timing at which a toner
image is transferred to the intermediate belt 15, the pair of relay
transport rollers 24 and the pair of gate rollers 25 start
rotational driving such that the recording paper P is fed to the
image-recording-and-forming position between the intermediate
transfer belt 15 and the transfer roller 16. Operation for nipping
and transporting the recording paper to the
image-recording-and-forming position is continued, and the trailing
end section P2 of the recording paper P is detected to have passed
through the nipping position. Then, the rotational driving of the
pair of relay transport rollers 24 and the rotational driving of
the pair of gate rollers 25 are stopped.
[0089] In a case where the recording paper P to be subjected to
operation for recording and forming an image is in numbers,
analogous control operation for separately feeding the next sheet
of recording paper P from the elevation tray 31 is started before
the trailing end section P2 of the recording paper P is detected to
have passed through the nipping position between the pair of relay
transport rollers 24 and the pair of gate rollers 25 by means of
the paper detection sensor located in front of the rollers 24, 25.
FIG. 7 illustrates a case where images are formed on two sheets of
recording paper P.
[0090] As mentioned above, in the present embodiment, the elevation
tray 31 is lowered at the timing at which the feeding roller 33 is
stopped while the retard roller 34 remains in pressed contact with
the feeding roller 33, thereby releasing the feeding roller 31 from
the pressed contact with the extremity section P1 of the awaiting
recording paper P. Even when the retard roller 34 has slightly
reversely rotated in reaction to stoppage of the feeding roller 33,
backward movement of the recording paper P on the elevation tray 31
can be avoided. Moreover, backward movement of the recording paper
P to such an extent that the recording paper P cannot be nipped by
the outer peripheral surface 33a of the feeding roller 33, which
would otherwise be caused by accumulation of backward movement, can
be prevented. Therefore, the recording paper P, on which an image
is to be formed next time, can be brought into pressed contact with
the outer peripheral surface 33a of the feeding roller 33 without
fail and separately fed with high reliability by means of the
limitation pad 31c on the extremity section 31b of the elevation
tray 31 and the retard roller 34, so that the recording paper can
be fed to a position where an image is recorded and formed.
[0091] In another mode of the above-described present embodiment,
the elevation tray 31 is lowered and the feeding roller 33 is
maintained in a stationary state until when separate feeding of the
next sheet of recording paper P during the course of the recording
paper P being transported by the pair of relay transport rollers 24
and the pair of gate rollers 25. For instance, in a case where
rotational driving of the feeding roller 33 is continued and
temporarily stopped in conjunction with the pair of gate rollers 25
even after the recording paper P has been passed to the pair of
relay transport rollers 24, the essential requirement is to lower
the elevation tray 31 immediately before stoppage of the feeding
roller 33 at the same time when the feeding roller 33 is stopped.
Even in this case, a similar working-effect can be yielded, and the
recording paper P can be fed along with the pair of relay transport
rollers 24 and the pair of gate rollers 25. However, in a case
where the recording paper P is not a type which requires a
plurality of pieces of feeding load, lifting and lowering the
elevation tray 31 are troublesome. Hence, drive control, such as
that mentioned in the above embodiment, is preferable.
Second Embodiment
[0092] A paper feeding method and a paper feeder, both of which
pertain to the present invention, will be described hereinbelow by
reference to the drawings.
[0093] FIG. 8 s a schematic front view showing an example internal
structure of a color image-forming apparatus using an embodiment of
the paper feeding method and that of the paper feeder, both of
which pertain to the present invention.
[0094] The image-forming apparatus is a color image-forming
apparatus capable of longitudinally feeding A4-size paper
(including letter-size paper) and forming a full-color image on
both surfaces of the paper. The image-forming apparatus is equipped
with a case 310; an image carrier unit 320 housed in the case 310;
an exposure unit 330 serving as exposure means; a developer unit
(development device) 340 serving as developing means; an
intermediate transfer member unit 350; and a fusing unit (fuser)
360 serving as fusing means.
[0095] The case 310 is provided with an unillustrated frame of the
apparatus main body, and the respective units are mounted on this
frame.
[0096] The image carrier unit 320 has a photosensitive member 321
having a photosensitive layer on a circumferential surface thereof,
and a corona charger (scorotoron charger) 322 serving as
electrifying means for uniformly electrifying the outer
circumferential surface of the photosensitive member 321. The outer
circumferential surface of the photosensitive member 321 having
been uniformly charged by the corona charger 322 is selectively
exposed to a laser beam L output from the exposure unit 330,
thereby forming an electrostatic latent image. Toner serving as a
developing agent is imparted to the electrostatic latent image by
means of the developer unit 340, thereby forming a visible image
(toner image). This toner image is transferred to an intermediate
transfer belt 351 of the intermediate transfer member unit 350 by a
primary transfer section T1 through primary transfer operation.
Moreover, a secondary transfer section T2 transfers the toner image
onto paper, which is an object of transfer, through secondary
transfer operation.
[0097] Provided in the case 310 are a transport path 316 for
transporting the paper, on one side of which an image is formed by
the secondary transfer section T2, toward a paper output section
(paper output tray section) 315 on the upper surface of the case
310, and a return path 317 which switches back the paper
transported from the transport path 316 toward the paper output
section 315, to thus return the paper toward the secondary transfer
section T2 in order to form an image on the other surface.
[0098] Reference numeral 370 designates a double-sided unit
removably attached to the apparatus main body, and the return path
317 is formed as a result of attachment of the double-sided unit
370.
[0099] Paper feeding cassettes 318 for retaining a plurality of
sheets of paper in a stacked manner are provided in two layers in
the lower portion of the case 310. Each of the paper feeding
cassettes 318 is provided with a paper feeding roller 319 for
feeding paper one at a time toward the secondary transfer section
T2.
[0100] A multipurpose tray 400 constituting a paper feeder 380 of
the present invention is provided below the double-sided unit 370.
The apparatus main body is provided with a paper feeding roller 390
which feeds, one at a time, the paper set in the multipurpose tray
400.
[0101] This paper feeder 380 will be described in detail later.
[0102] The developer unit 340 is a rotary developer unit (a rotary
development device), and a plurality of developer cartridges (not
shown) housing toner are removably attached to a rotary member main
body 341. As a result of the rotary member main body 341 rotating
at a pitch of 90 degrees in the direction of arrow R, the
development rollers (not shown) provided with the respective
developer cartridges are selectively brought into contact with the
photosensitive member 321, thereby enabling selective development
of the surface of the photosensitive member 321.
[0103] The exposure unit 330 radiates the laser beam L toward the
photosensitive member 321.
[0104] The intermediate transfer member unit 350 is equipped with
an unillustrated unit frame; a drive roller 354 rotatably supported
by this frame; and the intermediate transfer belt 351 tensilely
passed across a plurality of follower rollers. The intermediate
transfer belt 351 is driven in a circulatory manner in the
direction of an illustrated arrow. The primary transfer section T1
is formed in the section where the photosensitive member 321 and
the intermediate transfer belt 351 come into contact with each
other. The secondary transfer section T2 is formed in a nipping
section existing between the drive roller and a secondary transfer
roller 310b provided in the main body.
[0105] The secondary transfer roller 310b can come into contact
with or detach from the drive roller 354 (in turn from the
intermediate transfer belt 351). Upon coming into contact with the
drive roller 354, the secondary transfer roller 310b forms the
secondary transfer section T2.
[0106] Therefore, when a color image is formed, toner images of a
plurality of colors are superimposed one on top of the other on the
intermediate transfer belt 351 while the secondary transfer roller
310b remains separated from the intermediate transfer belt 351, to
thus form a color image. Subsequently, the secondary transfer
roller 310b comes into contact with the intermediate transfer belt
351, whereupon the paper is supplied to the contact section (i.e.,
the secondary transfer section T2). As a result, the color image
(toner image) is transferred to the paper from the intermediate
transfer belt 351 (through secondary transfer operation).
[0107] The paper, on which the toner image has been transferred,
passes through the fusing unit 360, whereby the toner image is
fixedly fused. The paper is then discharged toward the paper output
tray section 315.
[0108] Feeding of paper to the image-forming section is performed
selectively by any one of the above-described two paper feeding
cassettes 318 and the multipurpose tray 400.
[0109] In general, plain paper, or the like, is steadily set in the
paper feeding cassettes 318. However, various types of paper are
set in the multipurpose tray 400, as required. Specifically, plain
paper (including thin paper), cardboard (a post card, an envelope,
or an OHP sheet other than the cardboard), or another recording
material is set in the multipurpose tray 400, in accordance with a
user's requirement.
[0110] FIG. 9 is an enlarged fragmentary view of FIG. 8 and
corresponds to a front view of a paper feeder 380. FIG. 10 is a
plan view of the principal section of the paper feeder 380.
[0111] As shown in these drawings (chiefly in FIG. 9), the paper
feeder 380 has a paper feeding roller 390 which comes into contact
with the topmost sheet of paper of stacked paper S to thus feed the
topmost sheet of paper; a lift plate 411 which supports a front
section S1 of paper to be fed by the paper feeding roller 390 and
presses a front portion S1 of paper against the paper feed roller
390; a first tray 410 which is inclined with respect to the
horizontal plane H (at an angle of inclination .theta.1); and a
second tray 420 which is coupled to a rear portion of the first
tray 410, supports a rear section S2 of the paper S, and makes a
smaller angle of inclination .theta.2 with respect to the
horizontal plane H than that made by the first tray 410.
[0112] A paper support face 421 of the second tray 420 is
configured to fall within a range of angle .theta. made between a
paper support face 411a1 of the lift plate acquired at a position
411a where the lift plate 411 is lifted when a maximum number of
sheets of paper that can be stacked on the first tray 410 are
stacked and a paper support face 411b1 of the lift plate 411
acquired at a position 411b where the lift plate 411 is lifted when
one sheet of paper is supported by the first tray 410.
[0113] Reference numeral 430 designates a retard roller with a
torque limiter which comes into contact with the paper feed roller
390, and the topmost sheet of paper and the sheet of paper directly
below the topmost sheet of paper are separated from each other by
the retard roller 430.
[0114] The retard roller 430 is attached, in a rotatable manner, to
a fixed shaft 431 by way of a torque limiter 432 (see FIG. 10), and
is forced at all times in the direction of an arrow (in the same
direction as that of the paper feeding roller 390; that is, in a
clockwise direction in FIG. 9) by means of a spring fitted in the
torque limiter 432.
[0115] Consequently, in a case where, when the sheet of paper
directly below the topmost sheet of paper and subsequent sheets of
paper are about to be fed during the course of the topmost sheet of
paper being fed by the paper feeding roller 390, rotation of the
retard roller 430 is hindered by load torque stemming from the
torque limiter 432, thereby hindering feeding of the sheet of paper
directly below the topmost sheet of paper. Feeding of the sheet of
paper directly below the topmost sheet of paper is hindered, and
only the topmost sheet of paper is nipped between the paper feeding
roller 390 and the retard roller 430. When the upper limit torque
of the torque limiter 432 is exceeded, the retard roller 430 is
driven by the paper feeding roller 390 by way of the topmost sheet
of paper, whereupon only the topmost sheet of paper is fed.
[0116] As shown in FIG. 8, the multipurpose tray 400 (which is, in
turn, the first tray 410) is reclosably attached to a side cover
402 of the main body case 310 of the image-forming apparatus 310 by
means of a shaft 401. The side cover 402 is configured so as to be
able to open/close with respect to the image-forming apparatus main
body by means of the shaft 403. FIG. 8 shows a state where the side
cover 402 is closed; and where the multipurpose tray 400 is opened
so as to be usable.
[0117] As shown in FIGS. 9 and 10, the first tray 410 comprises an
essentially-box-shaped tray main body 412, and the lift plate 411
that is attached to both side plates 413 of the tray main body 412
in a pivotable manner by means of a shaft 414.
[0118] As shown in FIG. 8, the image-forming apparatus main body is
provided with a push plate 391 used for pushing the lift plate 411.
The base section of the push plate 391 is attached to the
image-forming apparatus main body, and the extremity of the push
plate 391 moves into a position below the lift plate 411.
[0119] The push plate 391 is provided with an unillustrated forcing
member (e.g., a tension spring) which forces the push plate 391 in
the pushing direction at all times. When the multipurpose tray 400
(which, in turn, is the first tray 410) is opened as shown in FIG.
8, the extremity of the push plate 391 forces the lift plate 411
upward at all times. Thereby, the extremity of paper is pressed
toward the paper feeding roller 390, but the image-forming
apparatus main body is provided with a cam (e.g., an eccentric cam)
392 (see FIG. 10) forming a lift plate lifting-and-lowering
mechanism for lifting or lowering the lift plate 411. When the push
plate 391 is lowered by the cam 392, pressing of paper against the
paper feeding roller 390 by the lift plate 411 is released, whereby
the lift plate 411 is lowered.
[0120] As shown in FIG. 10, side guides 415, 416, which can slide
in a widthwise direction thereof (i.e., the vertical direction in
FIG. 10), are attached to the lift plate 411. The side guides are
for guiding side edges of paper to be fed. A rack 417 is provided
integrally on each of the bottoms of the side guides 415, 416. The
racks 417 mesh with a gear 418 provided on the lift plate 411.
Consequently, when either the side guide 415 or 416 is slid, the
other side guide is also slid. The center of paper coincides with
the position of the paper feeding roller 390.
[0121] The second tray 420 is configured so that it can be housed
in the first tray 410 (a position below the lift plate 411) and
withdrawn.
[0122] As shown in FIG. 9, when the second tray 420 is withdrawn
from the first tray 410, projections 422 provided at both ends of a
lower portion of the extremity of the second tray 420 come into
contact with extremities of ribs 419 provided on interior surfaces
of the side plates 413 of the first tray 410, thereby preventing
slipping-out of the second tray 120. Moreover, as shown in FIG. 10,
ribs 423 provided on both side sections of the second tray 420 come
into contact with the ribs 419 provided on the first tray 410,
thereby defining the angle of inclination of the second tray
420.
[0123] As mentioned above, the paper support face 421 of the second
tray 420 falls within the range of angle .theta. made between the
paper support face 411a1 of the lift plate 411 acquired at the
position 411a where the lift plate 411, which carries a maximum
number of sheets of paper that can be stacked on the first tray
410, is lifted and the paper support face 411b1 of the lift plate
411 acquired at the position 411b when one sheet of paper is
supported by the first tray 410.
[0124] As shown in FIGS. 9 and 10, an auxiliary tray 424 is coupled
to the rear portion of the second tray 420 in a pivotable manner by
means of a shaft 425. The auxiliary tray 424 is rotatable through
180 degrees about the shaft 425. FIGS. 9 and 10 show the opened
status of the auxiliary tray 424. However, the auxiliary tray 424
can be rotated through 180 degrees and housed in a recessed section
426 in the upper surface of the second tray 420 (see FIG. 10). The
auxiliary tray 424 is opened for use when legal-sized paper is to
be supported.
[0125] The paper feeding method of the present embodiment is a
paper feeding method to be performed by the above-described paper
feeder 380. According to this method, when the paper S is plain
paper, paper is fed while the lift plate 411 is held in a pressed
state. When the paper S is cardboard, the lift plate 111 is lifted
and lowered every time one sheet of cardboard is fed.
[0126] Lifting and lowering of the lift plate 411 performed when
the paper is cardboard is effected such that the lift plate 411 is
lowered after feeding of one sheet of cardboard and before the
trailing edge of the cardboard passes through the contact section
between the paper feeding roller 390 and the retard roller 430 and
such that the lift plate 411 is lifted before initiation of feeding
of the sheet of cardboard located directly under the topmost sheet
of cardboard.
[0127] The paper feeder 380 has a plain paper mode and a cardboard
mode, as well as having a controller for selecting either the plain
paper mode or the cardboard mode. In the plain paper mode, when the
paper S is plain paper, paper is fed while the lift plate 311 is
held in a pressed state by means of the lift plate
lifting-and-lowering mechanism 392. In the cardboard mode, when the
paper S is cardboard, the lift plate lifting-and-lowering mechanism
392 feeds paper by lowering or lifting the lift plate 411 every
time one sheet of cardboard is fed.
[0128] FIG. 11 is a block diagram of the paper feeder 380, and FIG.
12 is a flowchart showing the paper feeding method.
[0129] As shown in FIG. 11, the paper feeder 380 has a controller
500 for controlling the overall image-forming apparatus; a motor
501 whose driving operation is controlled by the controller 500; a
first step clutch 511 which is interposed between the motor 501 and
the drive mechanism 393 of the paper feeding roller 390 and whose
activation/deactivation is controlled by the controller 500; a
second step clutch 512 which is interposed between the motor 501
and the lift plate lifting-and-lowering mechanism (cam) 392 and
whose activation and deactivation are controlled by the controller
500; the drive mechanism 393 of the paper feeding roller 390; and
the lift plate lifting-and-lowering mechanism (cam) 392.
[0130] The plain paper mode and the cardboard mode are stored in
memory of the controller 500.
[0131] The controller 500 is connected to a personal computer P-C
to which the image-forming apparatus of the present embodiment is
connected.
[0132] In this embodiment, when "plain paper" or "cardboard" has
been selected as the kind of paper used by the user on a setting
screen of the printer driver installed in the personal computer
P-C, the controller 500 selects either the ordinary paper mode or
the cardboard mode in accordance with the result of selection, as
shown in FIG. 12, and activates the paper feeder 380 in the
thus-selected mode. Selection operation can also be performed by
user's operation on the control panel provided in the image-forming
apparatus.
[0133] Operation of the paper feeder 380 will be described by
reference primarily to FIG. 12.
[0134] (i) Upon receipt of a print command signal (which is, in
turn, print data) sent from the personal computer P-C, the
controller 500 determines whether the print data correspond to data
for plain paper or data for cardboard, in step S2 by way of step
S1. As mentioned previously, this determination is rendered by the
user by way of the personal computer P-C in response to selection
of "plain paper" or "cardboard" as the kind of paper.
[0135] Now, when no print data are input, the controller 500 enters
a standby condition for awaiting input of print data.
[0136] (ii) When having determined, in step S2, that the image data
correspond to data for plain paper, the controller 500 selects the
plain paper mode in step S3. In step S4, the controller 500
activates the motor 501 and the second step clutch 512 (see FIG.
11); releases the pushing force on the push plate 391 imposed by
the cam 392 (see FIG. 10), to thus push the paper S against the
paper feeding roller 390 by means of the lift plate 411; activates
the first step clutch 511 while maintaining the pressing state to
rotate the paper feeding roller 390; and feeds paper to the
image-forming section of the image-forming apparatus until printing
operation (formation of an image) specified by the print data is
fully completed.
[0137] Consequently, when the print data run to a plurality of
sheets of paper, a plurality of sheets of plain paper are
continuously fed while the lift plate 411 is held in a pressed
state.
[0138] After completion of feeding of paper for printing all of
sets of print data, the controller 500 deactivates the first step
clutch 511, and activates the second step clutch 512, thereby
rotating the cam 392 to thus push the push plate 391, thereby
lowering the lift plate 411. Thus, the controller 500 enters a
standby condition.
[0139] (iii) When having determined the image data as data for
cardboard in step S2, the controller 500 repeatedly performs the
following operations until printing specified by the print data
(i.e., image forming operation) is fully completed; namely,
operations for: selecting the cardboard mode in step S5; activating
the motor 501 in step S6; alternately activating and deactivating
the second step clutch 512 and the first step clutch 511; releasing
the pushing force on the push plate 391 imposed by the cam 392 (see
FIG. 10) to cause the lift plate 411 to push the paper S against
the paper feeding roller 390 and to rotate the paper feeding roller
390, thereby feeding paper; and lowering the lift plate 411 by
pushing the push plate 391 by means of the cam 392 before the
trailing edge of the paper S passes through the contact section
(i.e., the nipping section) between the paper feeding roller 390
and the retard roller 430.
[0140] Therefore, when the print data run to a plurality of sheets
of paper and when paper is cardboard, paper is fed by lifting or
lowering the lift plate 411 by means of the cam 392 every time one
sheet of cardboard is fed.
[0141] After feeding operation for printing all sets of print data
has been completed, the controller 500 deactivates the first step
clutch 511; activates the second step clutch 512 to thus rotate the
cam 392; lowers the lift plate 411 by lowering the push plate 391
downward; and then enters a standby condition.
[0142] The paper feeding method of the present embodiment is for
use with the paper feeder having the paper feeding roller 390 which
comes into contact with the topmost sheet of paper among the
stacked sheets of paper to thus feed the topmost sheet of paper;
the retard roller 430 which comes into contact with the paper
feeding roller 390 to thereby separate the topmost sheet of paper
from the sheet of paper directly thereunder; and the lift plate 411
which supports paper to be fed by the paper feeding roller 390 and
presses a front portion of the paper against the paper feeding
roller 390. This method is to feed paper while the lift plate 411
remains pressed when paper corresponds to plain paper and to lift
or lower the lift plate 411 every time one sheet of cardboard is
fed when paper corresponds to cardboard.
[0143] Moreover, a paper feeder of the present embodiment includes
the paper feeding roller 390 which comes into contact with a
topmost sheet of paper among stacked sheets of paper to thereby
feed the topmost sheet of paper; the retard roller 430 which comes
into contact with the paper feeding roller 390 to separate the
topmost sheet of paper from the sheet of paper directly thereunder;
the lift plate 411 which supports paper to be fed by the paper
feeding roller 390 and presses a front portion of paper against the
paper feed roller 390; the lift plate lifting-and-lowering
mechanism 392 for lifting or lowering the lift plate 411; and the
controller 400 which selects either a plain paper mode, where paper
is fed by the lift plate lifting-and-lowering mechanism 392 while
the lift plate 411 remains pressed when the paper is plain paper,
or a cardboard mode, where paper is fed by lifting or lowering the
lift plate 411 every time one sheet of cardboard is fed by means of
the lift plate lifting-and-lowering mechanism 392 when the paper is
cardboard. According to this paper feeding method or the paper
feeder 380, the following working-effect can be achieved.
[0144] Specifically, when paper to be fed corresponds to plain
paper, paper is fed while the lift plate 411 remains in a pressed
state. Hence, when the topmost sheet of paper is fed, the lift
plate 411 is brought into a pressed state (a lifted state),
whereupon paper is supported.
[0145] Accordingly, tremble vibration, which would otherwise arise
in the nipping section between the paper feeding roller 390 and the
retard roller 430, is prevented, and occurrence of chattering sound
(noise) is prevented.
[0146] When paper to be fed corresponds to plain paper, paper is
fed while the lift plate 411 remains in a pressed state. There is
no necessity for lifting or lowering the lift plate 411 every time
one sheet of paper is fed, and hence a plurality of sheets of paper
can be efficiently, continuously fed.
[0147] Consequently, forming of images on a plurality of sheets of
paper can be speeded up.
[0148] Meanwhile, when paper to be fed corresponds to cardboard,
the lift plate 411 is lifted or lowered every time one sheet of
cardboard is fed. The lift plate 411 remains lowered when the
trailing edge of paper passes through the contact section between
the paper feeding roller 390 and the retard roller 430. Backward
movement of the next sheet of paper and subsequent sheets of paper,
which would otherwise be caused by reaction of the torque limiter
432, is prevented.
[0149] Therefore, overlapping transfer of paper and transfer
failure of paper, which would otherwise arise when paper is
cardboard, becomes less likely to arise.
[0150] As mentioned above, according to the second embodiment,
sheets of cardboard can be fed one at a time without fail
simultaneously with feeding of plain paper without causing
chattering sound.
[0151] The paper feeder 380 of the present embodiment includes the
paper feeding roller 390 which comes into contact with a topmost
sheet of paper among stacked sheets of paper S to thereby feed the
topmost sheet of paper; the lift plate 411 which supports the front
section S1 of paper to be fed by the paper feeding roller 390 and
presses the front portion S1 of paper against the paper feed roller
390; a first tray 410 which is tilted (an angle of inclination is
denoted by .theta.) with respect to the horizontal plane H; and a
second tray 420 which is coupled to a rear portion of the first
tray 410, supports a rear portion S2 of the paper S, and makes a
smaller tilt angle .theta.2 with respect to the horizontal plane H
than that made by the first tray 410.
[0152] Further, a paper support face 421 of the second tray 420
falls within a range of angle .theta. made between a paper support
face 411a1 of the lift plate achieved at a position 411a where the
lift plate 411 is lifted when a maximum number of sheets of paper
that can be set on the first tray 410 are stacked on the first tray
and a paper support face 411b1 of the lift plate 411 achieved at a
position 411b where the lift plate 411 is lifted when one sheet of
paper is supported by the first tray 410. Accordingly, the paper
support face 421 of the second tray 420 achieved when the maximum
number of sheets of paper that can be set on the first tray 410 are
stacked on the first tray turns into a slope which makes the same
angle as an angle .theta.3 made with respect to the horizontal
plane H by the paper support face 411a1 of the lift plate at the
lifting position 411a of the lift plate 411, or turns into a slope
whose angle of inclination with respect to the horizontal plane H
is smaller. The unillustrated paper support face 421 forms a slope
whose angle .theta.2 of inclination with respect to the horizontal
plane H makes an angle smaller than the angle .theta.3.
[0153] Therefore, when the lift plate 411 has lifted the front
portion S1 of paper, the paper support face 411a1 of the lift plate
411 and the paper support face 421 of the second tray 420 are
prevented from buckling downward into a dogleg shape. Therefore,
even when the stacked sheets of paper S correspond to cardboard,
both ends are not supported, whereby transfer failure becomes
unlikely to arise.
[0154] FIG. 13 is a diagram for describing the above-described
working-effect.
[0155] As shown in FIG. 13, under the assumption that the paper
support face 421 of the second tray 420 achieved when the maximum
number of sheets of paper that can be set on the first tray 410 are
stacked on the first tray 410 turns into a slope which makes an
angle .theta.4 larger than the angle .theta.3 made by the paper
support face 411a1 of the lift plate with respect to the horizontal
plane H at the lifting position 411a of the lift plate 411, the
paper support face 411a1 of the lift plate 411 and the paper
support face 421 of the second tray 420 are buckled downward into a
dogleg shape when the lift plate 411 lifts the paper front portion
s1. When the stacked sheets of paper S correspond to cardboard,
both ends of the sheets of paper are supported as illustrated.
[0156] Therefore, force F2--which cancels the lift force F1
(pressing force against the paper feeding roller) exerted by the
lift plate 411--becomes larger, transport failure is likely to
arise.
[0157] As mentioned, according to the second embodiment of the
present invention, the paper support face 421 of the second tray
420 achieved when the maximum number of sheets of paper that can be
set on the first tray 410 are stacked on the first tray turns into
a slope which makes the same angle as an angle .theta.3 made with
respect to the horizontal plane H by the paper support face 411a1
of the lift plate at the lifting position 411a of the lift plate
411, or turns into a slope whose angle of inclination with respect
to the horizontal plane H is smaller. Therefore, when the lift
plate 411 has lifted the front portion S1 of paper, the paper
support face 411a1 of the lift plate 411 and the paper support face
421 of the second tray 420 are prevented from buckling downward
into a dogleg shape. Therefore, even when the stacked sheets of
paper S correspond to cardboard, both ends are not supported,
whereby transfer failure becomes unlikely to arise.
[0158] In the meantime, according to the present embodiment, when
one sheet of paper is supported by the first tray 410, the paper
support face 421 of the second tray 420 turns into a slope which
forms the same angle as the angle .theta.2 made with respect to the
horizontal plane H by the paper support plane 411b1 of the lift
plate 411b at the lifting position of the lift plate 411, or turns
into a slope which makes a larger angle of inclination with respect
to the horizontal plane H. The paper support face 421 shown in FIG.
9 forms a slope which makes an angle essentially identical with
that made between the paper support face 411b1 of the lift plate
411b and the horizontal plane H.
[0159] Therefore, in a case where a plurality of sheets of paper
are set in the first and second trays 410 and 420, even when force
which would cause backward movement because of reaction of the
torque limiter of the retard roller 403 has been exerted on the
next sheet of paper, paper becomes likely to slide over the tilt
surfaces 411b1 and 421 (or an upper surface of paper). Hence,
overlapping transport of paper or transport failure of paper
becomes less likely to arise.
[0160] Under the assumption that the paper support face 421 of the
second tray 420 achieved when one sheet of paper is supported by
the first tray 410 turns into a slope which makes an angle smaller
than the angle .theta.2 made by the paper support face 411b1 of the
lift plate 411 with respect to the horizontal plane H at the
lifting position 411b of the lift plate 411 (in a state where the
paper support face has pivoted clockwise in FIG. 9 to thus form a
horizontal plane such as that achieved in the previously-described
related art), the trailing edge of the paper supported by the
second tray 420 becomes less likely to slide over the tray.
Consequently, the entirety of paper becomes less likely to slide
over the tray.
[0161] Therefore, in a case where a plurality of sheets of paper
are set in the first and second trays 410 and 420, the next sheet
of paper is likely to undergo backward movement stemming from
reaction of the torque limiter of the retard roller 430.
Consequently, overlapping transport of paper or transport failure
of paper becomes likely to arise.
[0162] In contrast, according to this embodiment of the present
invention, when one sheet of paper is supported by the first tray
410, the paper support face 421 of the second tray 420 turns into a
slope which forms the same angle as the angle .theta.2 made with
respect to the horizontal plane H by the paper support plane 411b1
of the lift plate 411b at the lifting position of the lift plate
411, or turns into a slope which makes a larger angle of
inclination with respect to the horizontal plane H. Therefore, in a
case where a plurality of sheets of paper are set in the first and
second trays 410 and 420, backward movement of the sheet of paper
immediately below the topmost sheet of paper, which would otherwise
be caused by reaction of the torque limiter of the retard roller
430, becomes difficult to arise. Consequently, overlapping
transport of paper or transport failure of paper becomes less
likely to arise.
[0163] Therefore, this paper feeder additionally yields an
advantage of the ability to reliably feed a plurality of sheets of
paper one at a time until the final sheet of paper.
[0164] In a case where the paper support face 421 of the second
tray 420 achieved when the maximum number of sheets of paper that
can be set on the first tray 410 are stacked on the first tray
turns into the slope which makes the same angle as an angle
.theta.3 made with respect to the horizontal plane H by the paper
support face 411a1 of the lift plate at the lifting position 411a
of the lift plate 411, the lifting position of the lift plate 411
lifts (the lifting position shifts from the position 411a to the
position 411b) as the number of sheets of paper on the first tray
410 is decreased as a result of feeding of paper. The first tray
410 and the second tray 420 become buckled into a dogleg shape
which gradually recesses downwardly. Consequently, when stacked
sheets of paper S correspond to cardboard, both ends of the sheets
of paper become gradually supported.
[0165] However, in the meantime, the number of stacked sheets of
paper decreases. As a result, the force F2 that cancels the lifting
force F1 stemming from the lift plate 411 is also decreased, and
hence overlapping transfer of paper remains less likely to
arise.
[0166] Although the first and second embodiments of the present
invention has been described, the present invention is not limited
to the above-described embodiments. Needless to say, the present
invention can be carried out in various different forms within the
scope of the technical concept of the present invention.
[0167] For instance, each of the above-described embodiment has
provided a description by taking, as one example, a case where the
present invention is applied to a location where the MPT cover 30
is opened and the loaded recording paper P is separately fed.
However, the present invention is not limited to this application,
but can also be applied to a case where a similar configuration is
adopted for a separate-paper-feeding mechanism of a paper
cassette.
[0168] In each of the first and second embodiments, a description
is provided by taking, as one example, an image-forming apparatus
which forms an image on recording paper by means of an
electrophotographic image-recording device equipped with a paper
transport device. However, the present invention is not limited to
this image-forming apparatus. For instance, the present invention
may be applied to a paper feeder in the paper transport device of
the image reading apparatus. Alternatively, needless to say, the
present invention may be applied to an image-forming apparatus
which adopts an ink-jet recording method.
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