Title: Print medium feed system
Abstract: A print medium feed system comprises a pair of first print medium feed members for feeding a print medium to a print section, a print medium detection section for detecting the print medium, a second print medium feed member for feeding the print medium to the first print medium feed members, and a control section for controlling the first and second print medium feed members. According to the detection by the print medium detection section, the second print medium feed member transports the print medium by a first predetermined distance in the feed direction, then, the first print medium feed members transport the print medium in the feed direction by a second predetermined distance in the feed direction, and then transport the print medium by a third predetermined distance in a backward direction opposite to the feed direction.
Patent Number: 6,845,227 Issued on 01/18/2005 to Nishino, et al.
| Inventors:
|
Nishino; Akinori (Fukushima-ken, JP);
Kitabatake; Totsuya (Fukushima-ken, JP);
Ono; Hiroaki (Fukushima-ken, JP);
Noda; Yasuo (Fukushima-ken, JP)
|
| Assignee:
|
Oki Data Corporation (Tokyo, JP)
|
| Appl. No.:
|
722420 |
| Filed:
|
November 28, 2003 |
Foreign Application Priority Data
| Nov 29, 2002[JP] | 2002-347197 |
| Current U.S. Class: |
399/406; 400/579; 400/630 |
| Intern'l Class: |
G03G 015/00 |
| Field of Search: |
399/18,390,395,406
271/161,184,185,188,209
400/579,596,630
|
References Cited [Referenced By]
U.S. Patent Documents
| 4990011 | Feb., 1991 | Underwood et al. | 400/636.
|
| 5144385 | Sep., 1992 | Tani | 399/406.
|
| 5246224 | Sep., 1993 | Matsuno et al. | 271/242.
|
| 5555083 | Sep., 1996 | Kuo et al. | 399/406.
|
| 5920751 | Jul., 1999 | Chow et al. | 399/97.
|
| 6185403 | Feb., 2001 | Toyoshima et al. | 399/365.
|
Primary Examiner: Yan; Ren
Attorney, Agent or Firm: Takeuchi & Takeuchi
Claims
What is claimed is:
1. A print medium feed system, comprising:
first print medium feed members for feeding a print medium feed to a print
section;
a print medium detection section provided on the upstream side of said
first print medium members in a feed direction of said print medium and
making detection of said print medium;
a second print medium feed member provided on the upstream side of said
print medium detection section in said feed direction and feeding said
print medium to said first print medium feed members; and
a control section for controlling said first and second print medium feed
members, wherein according to said detection of said print medium by said
print medium detection section, said control section, firstly, makes said
second print medium feed member transport said print medium by a first
predetermined distance in said feed direction, secondly, makes said first
print medium feed members transport said print medium by a second
predetermined distance in said feed direction, and thirdly, makes said
first print medium feed members transport said print medium by a third
predetermined distance in a backward direction which is opposite to said
feed direction.
2. The print medium feed system according to claim 1, wherein said control
section makes said second print medium feed member stop transporting said
print medium while said first print medium feed members are transporting
said print medium by said second predetermined distance.
3. The print medium feed system according to claim 1, wherein said control
section makes said second print medium feed member continue transporting
said print medium while said first print medium feed members are
transporting said print medium by said second predetermined distance.
4. The print medium feed system according to claim 1, wherein said second
predetermined distance of said transportation of said print medium by said
first print medium feed members is made small.
5. The print medium feed system according to claim 1, wherein said second
predetermined distance of said transportation of said print medium by said
first print medium feed members is made equal to a maximum size of a curl
of said print medium.
6. The print medium feed system according to claim 1, wherein said second
print medium feed member does not press said print medium while said first
print medium feed members are transporting said print medium in said print
medium feed direction by said second predetermined distance.
7. The print medium feed system according to claim 1, wherein said second
print medium feed member presses said print medium while said first print
medium feed members are transporting said print medium in said print
medium direction by said second predetermined distance.
8. The print medium feed system according to claim 1, wherein said third
predetermined distance of said transportation of said print medium in said
backward direction is made larger than said second predetermined distance
in said print medium feed direction.
9. The print medium feed system according to claim 1, wherein said control
section performs skew correction after said first print medium feed
members transport said print medium in said backward direction.
10. The print medium feed system according to claim 9, wherein when said
control section makes said first print feed members feed said print medium
to said print section after finishing said skew correction, said second
print medium feed member does not press said print medium.
11. The print medium feed system according to claim 9, wherein when said
control section makes said first print feed members feed said print medium
to said print section after finishing said skew correction, said second
print medium feed member presses said print medium.
12. The print medium feed system according to claim 1, wherein said second
print medium feed member is a roller having a shape of substantially D.
13. The print medium feed system according to claim 1, wherein said second
print medium feed member is a roller which is made of a rubber part having
at least one hollow.
14. The print medium feed system according to claim 1, wherein said print
medium detection section is composed of a plurality of print medium
detection sensors.
15. The print medium feed system according to claim 1, wherein said second
print medium feed member is provided at a position corresponding to
positions of said first print medium feed members.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a print medium feed system for feeding a print
medium for an image forming unit, such as a printer, copying machine, and
facsimile.
2. Description of the Related Art
A print medium feed system is provided in an image forming unit, such as a
printer, copying machine, and facsimile, to feed a print medium, such as
paper, to a print section. When a print medium is fed to the print section
from the print medium feed system, it is possible that the print medium
has been skewed. If the print medium is fed to the print section in a
skewed condition, the print medium is transported in the skewed condition
in the print section too. Under the condition, print is skewed on the
print medium, which results in poor printing quality of the image forming
unit. Accordingly, a slip roller is rotatably provided in front of the
print section to correct the skew of the print medium.
FIG. 3 is a top view of a conventional print medium feed system, showing
the operation thereof. FIG. 2 is a sectional view of FIG. 3 taken along
with the line A--A, showing a main part of the print medium feed system.
In FIGS. 2 and 3, reference numeral 21 denotes a print head and 22 is a
platen, which is rotatably provided and opposed to the print head 21. A
print section P1 is provided between the print head 21 and the platen 22.
Reference numeral 23 is a first guide for guiding a print medium 13, 24 is
a second guide which is spaced from the first guide 23 at a predetermined
distance and guides the print medium 13. A transport route Art is formed
between the first and second guides 23 and 24 to transport the print
medium 13 to the print section P1.
A pair of feed rollers 12 are rotatably provided on the upstream side of
the print section P1 in a transport direction of the print medium 13. The
print medium 13 is transported by rotating the feed rollers 12. Each of
the feed rollers 12 is composed of a shaft 12a and a plurality of roller
members 12b provided on the shaft 12a in the axial direction of the shaft
12a. A plurality of table sensors 14 are provided under a table 16 on the
upstream side of the feed rollers 12 in the transport direction the print
medium 13. A plurality of skew sensors 15 are provided under the table 16
on the downstream side of the feed rollers 12.
A slip roller 11 is provided on the upstream side of the feed rollers 12
and the table sensors 14 in the transport direction of the print medium
13. The slip roller 11 is rotatably provided on the side of the second
guide 24 with respect to the transport route Rt and faces the transport
route Rt. The slip roller 11 is composed of a shaft 11a and a plurality of
roller members 11b provided on the shaft 11a in the axial direction of the
shaft 11a.
When the print medium 13 is set on the table 16 such that the print medium
13 is overlapped with at least one of the roller members 11b, the table
sensors 14 detect the set print medium 13 and sends a detection signal to
a control section (not shown).
When the control section reads the detection signal, it drives a skew
correction motor (not shown), rotates the slip roller, and transports the
print medium 13. At this point, the feed rollers are stopped.
As the print medium 13 is transported, the front end (an upper side in FIG.
3) of the print medium 13 abuts against a contact point of a certain
roller member 12b' of the feed rollers 12. The respective roller members
11b are disposed at positions corresponding to those of the respective
roller members 12b. Accordingly, when the front end of the print medium 13
abuts against the contact point of the certain roller member 12b', a
roller member 11b' corresponding to the roller 12b' slips with respect to
the print medium 13 afterwards. Consequently, the roller member 11b' does
not transport the print medium 13. At this point, the roller members 11b
other than the roller member 11b' continue the transportation of the print
medium 13.
When the front end of the print medium 13 abuts against contacts of the
respective roller members 12b one after another, the respective roller
members 11b corresponding to the roller members 12b slip with respect to
the print medium 13. Accordingly, the respective roller members 11b stop
transporting the print medium 13.
As described above, the skew of the print medium is corrected. The roller
members 11b are made of a flexible rubber material to slip sufficiently
with respect to the print medium 13. Also, the pressure of the slip roller
11 against the print medium is adjusted.
After the sip roller 11 rotates at a predetermined travelling amount, which
is more than the distance between the slip roller 11 and the feed roller
12, the control section sends a drive signal to a line feed motor (not
shown) to drive the line feed motor.
After the skew correction is finished, the feed rollers 12 transport the
print medium 13. As the print medium 13 is transported, the front end of
the print medium 13 arrives at the skew sensors 15. The respective skew
sensors 15 detect the arrival and send medium detection signals to the
control section. The control section reads in the respective detection
signals, detects the difference in detection times on right and left sides
of the print medium, and judges if the difference in detection time
exceeds a threshold. When the difference exceeds the threshold, the
control section judges that the skew has not been corrected and drives the
line feed motor in the opposite direction. Then, the feed rollers 12 are
rotated in the opposite direction to expel the print medium 13 in the
left-hand direction in FIG. 2.
When the difference is less than the threshold, the control section judges
that the skew has been corrected and continues driving the line feed
motor. Consequently, the feed rollers 12 are rotated in the feed direction
so that the print medium 13 is supplied to the print section P1. Then,
print is performed in the print section P1.
In the conventional print medium feed system, however, as shown in FIG. 6,
when the front end of the print medium 13 is curled, even if the front end
13b of the print medium 13 is pressed to the feed roller 12 by the
rotation of the slip roller 11, the front end 13b does not abuts against a
contact point 19 of the roller member 12b occasionally. That is, the front
end 13b of the print medium 13 is transported upwardly along the roller
members 12b instead of abutting against them. Consequently, the
transportation of the print medium 13 fails so that the jam of the print
medium occurs. Also, the correction of the skew is not performed surely.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide a print medium
feed system capable of preventing the transportation error of the print
medium and performing the skew correction surely.
According to the invention, a print medium feed system comprises a pair of
first print medium feed members for feeding a print medium to a print
section, a print medium detection section provided on the upstream side of
the first print medium feed members and detecting the print medium, a
second print medium feed member provided on the upstream side of the print
medium detection section and feeding the print medium to the first print
medium feed members, and a control section for controlling the first and
second print medium feed members.
According to the detection by the print medium detection section, the
control section makes the second print medium feed member transport the
print medium by a first predetermined distance in the feed direction, and
then, makes the first print medium feed members transport the print medium
in the feed direction by a second predetermined distance in the feed
direction, and then, makes the first print medium feed members transport
the print medium by a third predetermined distance in a backward direction
opposite to the feed direction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a print medium feed system according to the
first embodiment of the present invention taken along with the line B--B
of FIG. 4.
FIG. 2 is a schematic view of a conventional print medium feed system taken
along with the line A--A.
FIG. 3 is a top view of the conventional print medium feed system, showing
an operation thereof.
FIG. 4 is a top view of the print medium feed system according to the first
embodiment of the invention, showing an operation thereof.
FIG. 5 is a flow chart, showing an operation of the print medium feed
system according to the first embodiment of the invention.
FIG. 6 is a sectional view of the print medium feed system according to the
first embodiment of the invention, showing the first condition thereof.
FIG. 7 is a top view of the print medium feed system according to the first
embodiment of the invention, showing the first condition thereof.
FIG. 8 is a sectional view of the print medium feed system according to the
first embodiment of the invention, showing the second condition thereof.
FIG. 9 is a sectional view of the print medium feed system according to the
first embodiment of the invention, showing the third condition thereof.
FIG. 10 is a sectional view of the print medium feed system according to
the first embodiment of the invention, showing the fourth condition
thereof.
FIG. 11 is a top view of the print medium feed system according to the
first embodiment of the invention, showing an operation of a skew
correction thereof.
FIG. 12 is a flow chart, showing an operation of a print medium feed system
according to the second embodiment of the present invention.
FIG. 13 is a sectional view of the print medium feed system according to
the second embodiment of the invention, showing the first condition
thereof.
FIG. 14 is a top view of the print medium feed system according to the
second embodiment of the invention, showing the first condition thereof.
FIG. 15 is a sectional view of the print medium feed system according to
the second embodiment of the invention, showing the second condition
thereof.
FIG. 16 is a sectional view of the print medium feed system according to
the second embodiment of the invention, showing the third condition
thereof.
FIG. 17 is a top view of the print medium feed system according to the
second embodiment of the invention, showing the third condition thereof.
FIG. 18 is a sectional view of the print medium feed system according to
the second embodiment of the invention, showing the fourth condition
thereof.
FIG. 19 is a top view of the print medium feed system according to the
second embodiment of the invention, showing the fourth condition thereof.
FIG. 20 is a block diagram of the print medium feed system according to the
first embodiment of the invention, showing a control operation.
FIGS. 21(a)-(c) are top views of a feed roller according to the first
embodiment of the invention, showing an opposite-direction transportation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
(First Embodiment)
Embodiments of the invention will now be described below with reference to
the accompanying drawings. A printer will be described as an image forming
apparatus.
In FIGS. 1 and 4, reference numeral 21 denotes a recording device or a
print head, 22 denotes is a platen rotatably provided and opposed to the
print head 21. A print section P1 is provided between the print head 21
and the platen 22. Reference numeral 23 is a first guide for guiding a
print medium 13, 24 is a second guide which is spaced from the first guide
23 at a predetermined distance and guides the print medium 13. A transport
route Rt is formed between the first and second guides 23 and 24 to
transport the print medium 13 to the print section P1.
A pair of first print medium feeders or feed rollers 12 are rotatably
provided on the upstream side of the print section P1 in a transport
direction of the print medium 13. The feed rollers 12 are rotated by a
drive section or a line feed roller (LF) 31. The print medium 13 is
transported to the print section P1 by the rotation of the feed rollers
12. Each of the feed rollers 12 is composed of a shaft 12a and a plurality
of roller members 12b provided on the shaft 12a in the axial direction of
the shaft 12a. A plurality of detection sections for detecting the print
medium or table sensors 14 are provided under a table 16 on the upstream
side of the feed rollers 12 in the transport direction the print medium
13. When the table sensors 14 detect the print medium 13, the table
sensors 14 send detection signals to a control section 33. A plurality of
detection sensors for detecting the skew or skew sensors 15 are provided
under the table 16 on the downstream side of the feed rollers 12 at
positions substantially corresponding to those of the table sensors 14 in
the widthwise direction of the table 16. The skew sensors 15 detect the
print medium 13 and generate detection signals for reporting the condition
of the print medium 13 to send them to the control section 33. The control
section 33 receives the detection signals from a plurality of skew sensors
15 and calculates the differences in the respective detection times. Here,
the pitches between the table sensors 14 and the skew sensors 15 are two
kinds, 38 mm and 52 mm. When a postcard (100 mm.times.148 mm) is set as
the print medium 13, two table sensors 14 or more detect the print medium
13.
A second print medium feeder and skew correction roller, or a slip roller
11 is provided on the upstream side of the feed rollers 12 and the table
sensor 14 in the transport direction of the print medium 13. The slip
roller 11 is rotatably provided on the side of the second guide 24 with
respect to the transport route Art and faces the transport route Rt. The
slip roller 11 is rotated by driving a drive section for the skew
correction or a skew correction motor (MS) 32. When the slip roller 11 is
rotated, the print medium 13 is transported to the feed rollers 12. The
slip roller 11 is composed of a shaft 11a and a plurality of roller
members 11b provided on the shaft 11a in the axial direction of the shaft
11a. The slip roller 11 is made in the form of substantially "D" so that
the slip roller 11 can take two conditions; an evaded condition for
running off the transportation route Rt and a working condition for
working out the skew correction.
A rotation detector for detecting the rotation amount of the slip roller 11
or a rotation sensor 35 is provided at an end of the slip roller 11. The
rotation sensor 35 is composed of a slit 17 attached to an end of the
shaft 11a and a sensor 18 provided at a predetermined position of the
printer and facing the slit 17.
The operation of the print medium feed system will now be described.
When the print medium 13 is set on the table 16 such that the print medium
13 is overlapped with at least one of the roller members 11b of the slip
roller 11, the table sensor 14 detects that the print medium 13 is set,
and sends detection signals to the control section 33.
FIGS. 6-11 and 20 show the operation and conditions of the first embodiment
of the invention.
In FIG. 6, when the control section 33 is waiting for the insertion of the
print medium 13, the slip roller 11 is put in an evaded position in the
rotation direction thereof so that the slip roller 11 does not interfere
with the transportation of the print medium 13. When the slip roller 11 is
in the evaded position, the slip roller 11 is spaced from the
transportation route Art by a predetermined distance so that no friction
is produced between the print medium 13 and the slip roller 11 upon the
insertion of the print medium 13. Accordingly, the print medium 13 is
easily inserted.
As shown in FIGS. 6 and 7, when either front right end 13a or front left
end 13b of the print medium 13 is curled, for example, when the front left
end 13b is curled, if such a print medium 13 is inserted between the first
and second guides 23 and 24, a skew can occur. Accordingly, a
pre-correction means (not shown) in the control section 33 (FIG. 1)
performs pre-correction with the following procedures.
As shown in FIG. 8, the pre-correction means rotates the slip roller 11 by
driving the skew correction motor 32 by a predetermined amount in the
direction of an arrow A. In this embodiment, the slip roller 11 is rotated
by an amount of 1.5 rotations, which is substantially equal to such an
amount of the transportation of the print medium 13 that the print medium
13 is warped by a predetermined amount after the front left end 13b of the
print medium 13 abuts against the feed roller 12. The slip roller 11 stops
after transporting the print medium 13 by the predetermined amount. Here,
the rotation sensor 35 (FIG. 4) detects the amount of the rotation of the
sip roller 11 and sends rotation detection signals to the control section
33. A rotation control means (not shown) in the control section 33
performs rotation control. The rotation control is to calculate the number
of pulses in accordance with the rotation detection signals and controls
the skew correction motor 32 in accordance with the calculated number of
pulses.
At this point, since the feed rollers 12 are not moving, as the print
medium 13 is transported, the front right end 13a of the print medium 13,
which is not curled, abuts against a contact point 19 of the roller member
12b. However, the front left end 13b, which is curled, does not abut
against the contact point 19 but abut against the surface of the roller
member 12b so that the vicinity of the front left end 13b waves.
In this embodiment, the slip roller 11 is rotated by 1.5 rotations in the
pre-correction process. At this point, however, if at least two tables
sensors 14 do not detect the print medium 13, the pre-correction means
judges that the print medium 13 is skewed largely and rotates the slip
roller 11 by 1.5 rotations again. Afterward, if at least two table sensors
14 do not detect the print medium 13 again, an error-judgment means (not
shown) in the control section 33 performs error-judgment. The
error-judgment is to judge the setting-error of the print medium 13 and
indicate the occurrence of the error on a display section (not shown).
Then, as shown in FIG. 9, while the print medium 13 is held by the slip
roller 11, the pre-correction means drives the line feed motor 31 in the
forward direction so as to rotate the feed rollers 12 by a predetermined
amount in the paper-feed direction (the directions of arrows B and C for
the roller members 12b). The front left end 13b, which is abutting against
the roller members 12b, is guided to the contact point 19 by the friction
with the roller members 12b, and then stopped. The front right end 13a
passes between the roller members 12b and the front left end 13b enters
between the roller members 12b at the position of the contact point 19. As
the vicinity of the front left end 13b, which waves, enters between the
roller members 12b, the waves are smoothed out. During this moment, the
pre-correction means stops the drive of the skew correction motor 32 to
stop the slip roller 11. Consequently, the transportation of the print
medium 13 is stopped, and the print medium 13 is pressed to the first
guide 23 by the slip roller and held by the first guide 23. In this
embodiment, the line feed motor 31 is driven by 16 pulses so that the
amount of the transportation of the print medium 13 by the rotation of the
feed rollers 12 is as small as 2.26 mm, which is substantially equal to
the amount of the transportation enabling the curled part of the print
medium 13 to be guided to the contact point 19 of the feed rollers 12.
Next, as shown in FIG. 10, the pre-correction means drives the line feed
motor 31 in backward direction so as to rotate the feed roller 12 by a
predetermined amount in the backward direction (the directions of arrows
of D and E for the roller members 12b). The print medium 13 is transported
by a predetermined distance in the backward direction, and then stopped.
At this point, the slip roller 11 is not moving. Consequently, the front
end of the print medium 13, which has entered between the roller members
12b, comes off the feed rollers 12. The backward movement of the print
medium 13 is a little so that it is impossible that the front left end 13b
is curled upwardly along the roller member 12b again.
The reason why the front left end 13b is not curled and does not abut
against the roller members 12b will be described below with reference to
FIG. 21. FIG. 21(a) shows the status where the print medium 13 is starting
to move backward by the backward rotation of the feed rollers 12, FIG.
21(b) shows the status where the print medium 13 is in the way of the
backward movement, and FIG. (c) shows the status where the print medium 13
is finishing the backward movement. In FIG. 21(a), the print medium 13
receives backward force from the feed rollers 12 in the entire width
thereof so that the whole part of the print medium 13 moves backward. In
FIG. 21(b), the right side of the sheet in the drawing is separated from
the feed roller 12 so that the backward force at that part is lost and
only the left side and center of the sheet are moved. Since the sheet is
held by the slip roller 11, the right side does not move and keeps the
same position. In FIG. 21(c), the right side and center of the sheet are
separated from the feed roller 12 so that the backward force at those
parts is lost and only the left side is moved. Since the print medium 13
is held by the slip roller 11, the right side and center do not move and
keep the same positions. Finally, the left side is also separated from the
feed roller 12 so that the backward force at that part is lost.
Consequently, the whole parts of the print medium 13 stop moving and keep
the position so that the curled front left end 13b does not return up to
the position shown in FIG. 6. That is, the curled front left end 13b stops
moving at the position shown in FIG. 10, therefore, it is prevented that
the curled front left end 13b is curled upwardly along the roller member
12b again.
In this embodiment, the line feed motor 31 is driven by 20 pulses so that
the amount of the transportation (movement) of the print medium 13 by the
backward rotation of the feed rollers 12 is as small as 2.82 mm. That is,
the amount of the backward rotation of the feed roller 12 is made larger
than that of the forward rotation (rotation in the paper-feed direction)
of the feed roller 12. Here, since the line feed motor 31 is driven
forwardly and then backwardly, the actual amount of backward rotation of
the feed roller 12 is two pulses smaller than that by 20 pulses due to the
back lash of gears (not shown) provided between the line feed motor 31 and
the feed roller 12.
Next, a skew correction means (not shown) in the control section 33
performs skew correction. That is, the skew correction means drives the
skew correction motor 32 so as to rotate the slip roller 11 by a
predetermined amount. The skew correction means transports the print
medium 13 to the feed roller 12 to correct the skew, and then stop it.
In FIG. 11, as the print medium 13 is transported by the rotation of the
slip roller 12, the front end of the print medium 13 shown in the dotted
line abuts against the contact point 19 of a certain roller member 12'.
The respective roller members 11b are disposed at positions corresponding
to those of the respective roller members 12b. Accordingly, when the front
end of the print medium 13 abuts against the contact point 19 of the
certain roller member 12b', a roller member 11b' corresponding to the
roller 12b' slips with respect to the print medium 13 afterwards.
Consequently, the roller member 11b' does not transport the print medium
13.
At this point, the roller members 11b other than the roller member 11b'
continue the transportation of the print medium 13. When the front end of
the print medium 13 abuts against contact points 19 of the respective
roller members 12b one after another, the respective roller members 11b
corresponding to the roller members 12b slip with respect to the print
medium 13. Accordingly, the respective roller members 11b stop
transporting the print medium 13.
Thus, the skew of the print medium 13 is corrected as shown in the solid
line in FIG. 11. The roller members 11b are made of a flexible rubber
material to slip sufficiently with respect to the print medium 13. Also, a
rubber part of the slip role 11 is made hollow so that the change in the
pressure of the slip roller 12 against the print medium 13 according to
the thickness of the print mediums 13 is minimized. That is, when the
thick print mediums 13 is inserted, the rubber part is crushed so that the
pressure against the print mediums 13 is reduced. Consequently, even if
the thickness of the mediums is changed, the slip roller 11 presses the
print mediums 13 at substantially constant pressure so that the
transportation force is not changed. Even when a plurality of kinds of
print mediums 13 having different thicknesses are used, the stable
transportation of the print medium 13 is obtained.
After the skew is corrected, the skew correction means brings the slip
roller 11 to the evaded position. Afterwards, a paper feed means (not
shown) in the control section 33 performs paper feed. Namely, the paper
feed means sends drive signals to the line feed motor 31 to drive the line
feed motor 31. Consequently, the feed rollers 12 rotate to transport the
print medium 13 in the direction of the print section P1. The slip roller
11 may be brought to the evaded position after the paper feed is started.
In this case, even when the print medium 13 is pushed in the left
direction in FIG. 9 by the rotation of the feed rollers 12, the slip
roller 11 pushes back the print medium 13 toward the feed rollers 12.
Accordingly, such a transportation error that the print medium 13 is not
transported forwardly because of the pushed-back movement caused by the
backward rotation of the feed rollers 12.
As the print medium 13 is transported by the feed rollers 12, the skew
sensors 15 detect the print medium 13 and send detection signals to the
control section 33. A skew judgment means (not shown) in the control
section 33 performs skew judgement. That is, the skew judgement means
reads the respective detection signals and calculates the difference in
detection times. The skew judgement means judges if the difference in
detection time exceeds a threshold. When the difference exceeds the
threshold, the skew judgement means judges that the skew has not been
corrected and when the difference is less than the threshold, the skew
judgement means section judges that the skew has been corrected.
In case that the first skew correction cannot correct skew sufficiently
(the difference in detection times exceeds the threshold), the skew
judgement means drives the line feed motor 31 in the backward direction
again to rotate the feed rollers 12 in the backward direction by a
predetermined amount. When the print medium 13 is separated from the feed
rollers 12 after the backward transportation by a predetermined amount,
the skew judgement means drives the skew correction motor 32 to rotate the
slip roller 11 by a predetermined amount (in this embodiment, an amount of
0.5 rotation). Then, the print medium 13 is transported forwardly to
correct skew. The same procedure is repeated for the skew correction until
the detection difference becomes less than the threshold. Every time the
skew correction is repeated, the amounts of the forward (paper-feed
direction) and backward rotations of the feed rollers 12 are made large.
If necessary, the rotation speed and rotation amount of the feed rollers
12 may be changed every time the skew correction is repeated. When the
number of the repeat of the skew correction becomes three, the skew
judgment means judges the error of the skew correction occurred and
indicates the occurrence of the error on the display section.
When the skew correction is finished (the detection difference is equal to
or less than the threshold), the paper feed means drives the line feed
motor 31 to rotate the feed rollers 12 for paper feed. Then, the print
medium 13 is fed to the print section P1 for printing.
On the other hand, when the skew judgment means judges that skew did not
occur, the paper feed means continues driving the line feed motor 31 to
rotate the feed rollers 12 for paper feed. Then, the print medium 13 is
fed to the print section P1 for printing.
As described above, since the feed rollers 12 rotate in the feed direction,
while the front end of the print medium 13 is abutting against the feed
roller 12, even when a certain part of the front end of the print medium
13 is curled, the print medium 13 is made flat and the front end of the
print medium 13 can be guided to the contact point 19. Consequently, the
transportation error of the print medium 13 is prevented and the skew of
the print medium 13 is corrected surely.
Also, since the print medium 13 moves back and forth every time the skew
correction is repeated, the print medium 13 is vibrated, which enables
more certain skew correction of the print medium 13.
In this embodiment, the slip roller 11 is rotated by an amount of 0.5
rotation to perform the skew correction after the feed rollers 12 are
rotated in the backward direction by a predetermined amount for separating
the print medium 13 from the feed rollers 12. The rotation amount of the
slip roller 11, however, may be changed in accordance with the detection
difference. For example, when the detection difference is 3 mm or less,
the rotation amount of the slip roller 11 is made 0.5 rotation, and when
the detection difference is more than 3 mm, the rotation amount is made
1.5 rotations.
The flow chart will now be described.
Step S1: Wait until the medium detection sensor 14 detects the print medium
13, while the slip roller 11 is in the evaded position. When the medium
detection sensor 14 detects the print medium 13, go to the step S2.
Step S2: Rotate the slip roller 11.
Step S3: Wait until the slip roller 11 is rotated by a predetermined
amount. Go to the step S4, when the slip roller 11 is rotated by the
predetermined amount.
Step S4: Stop the rotation of the slip roller 11 under the condition that
the slip roller 11 holds the print medium 13.
Step S5: Rotate the feed rollers 12 in the feed direction.
Step S6: Wait until the feed rollers 12 are rotated by a predetermined
amount. Go to the step S7 when the feed rollers 12 are rotated by the
predetermined amount.
Step S7: Rotate the feed rollers 12 in the backward direction.
Step S8: Wait until the feed rollers 12 are rotated by a predetermined
amount. Go to the step S9 when the feed rollers 12 are rotated by the
predetermined amount.
Step S9: Stop the rotation of the feed rollers 12.
Step S10: Rotate the slip roller 11.
Step S11: Wait until the slip roller 11 is rotated by a predetermined
amount. Go to the step S12 when the slip roller 11 is rotated by the
predetermined amount.
Step S12: Stop the rotation of the slip roller 11 under the condition that
the slip roller 11 releases the print medium 13.
Step S13: Feed the print medium 13 by the feed rollers 12 and finish the
process.
As fully described above, according to the invention, a print medium feed
system comprises a pair of first print medium feed members for feeding a
print medium to a print section, a print medium detection section provided
on the upstream side of the first print medium feed members and detecting
the print medium, a second print medium feed member provided on the
upstream side of the print medium detection section and feeding the print
medium to the first print medium feed members, and a control section for
controlling the first and second print medium feed members.
According to the detection by the print medium detection section, the
control section makes the second print medium feed member transport the
print medium by a first predetermined distance in the feed direction, and
then, makes the first print medium feed members transport the print
medium.
Here, the second print medium feed member transports the print medium until
the print medium abuts against the first print medium feed member and
warped. Then, the first print medium feed members transport the print
medium so that even if a certain portion of the front end of the print
medium is curled, the print medium can be certainly transported to the
first print medium feed members. Also, the curled portion of the print
medium can be made flat by the first print medium feed members.
Consequently, the transportation error of the print medium can be
prevented and the skew of the print medium is surely corrected.
(Second Embodiment)
The second embodiment of the invention will now be described. The structure
of a print medium feed system according to the second embodiment is
identical to that of the first embodiment and will be described with
reference to FIG. 1.
The print medium 13 is set on the table 16 such that the print medium 13 is
overlapped with at least one of the roller members 11b of the second print
medium feeder or the slip roller 11. The print medium detection section or
the table sensors 14 detect that the print medium 13 is set and send
detection signals to the control section.
As shown in FIGS. 13 and 14, when either front right end 13a or front left
end 13b of the print medium 13 is curled, for example, when the front left
end 13b is curled, if such a print medium 13 is inserted between the first
and second guides 23 and 24, a skew can occur.
Accordingly, a pre-correction means in the control section 33 performs
pre-correction. That is, the pre-correction means drives the skew
correction motor 32 and as shown in FIG. 15, rotates the slip roller 11 in
the direction of arrow A. The print medium 13 is transported in the
paper-feed direction by the rotation of the slip roller 11 and the front
left end 13b abuts against the roller member 12b. In FIG. 16, the
pre-correction means continues transporting the print medium 13 by
rotating the slip roller 11 in the direction of the arrow A. While
rotating the slip roller 11, the pre-correction means drives the line feed
motor 31 in the forward direction to rotate the first print medium feeder
or the feed rollers 12 by a predetermined amount in the paper-feed
direction (the directions of the arrows B and C for the roller members
12b). The front left end 13b, which has abutted against the roller member
12b, is guided to the contact point 19 by the friction with the roller
members 12b. After the front left end 13b entered between the roller
members 12b, the rotations of the slip and feed rollers 11 and 12 are
stopped.
As shown in FIG. 17, during the time, the print medium 13 is transported in
the direction of an arrow F (the upward direction in FIG. 17). The front
right end 13a passes between the respective roller members 12b and the
front left end 13b enters between the respective roller members 12b at the
position of the contact point 19. Accordingly, the waved portion in the
vicinity of the front left end 13b is stretched by the roller members 12b.
In this embodiment, the line feed motor 31 is driven by the amount of 50
pulses and the transportation amount of print medium 13 in the paper-feed
direction by the rotation of the-feed rollers 12 is made equal to the
maximum curl amount or 7 mm.
As the print medium 13 is transported, the skew condition detection section
or the skew sensors 15 detect the print medium 13 and send condition
detection signals to the control section 33. The skew judgement means
performs skew judgement by reading the respective condition detection
signals and calculate the difference in the detection times. When the
detection difference (difference in the detection times) exceeds the
threshold, the skew judgement means judges that skew has occurred, and
when the detection difference is equal to or less than the threshold, the
skew judgement means judges that skew has not occurred.
When it is judged in the skew judgement process that skew has occurred, the
skew correction means in the control section 33, as shown in FIG. 18,
performs the skew correction again by driving the line feed motor 31 in
the backward direction to rotate the feed rollers 12 in the backward
direction (the direction of the arrows D and E for the roller members 12b)
by a predetermined amount. Accordingly, the front end of the print medium
13 is transported in the backward direction and comes off the roller
members 12b. The transportation amount of the print medium 13 is a little
so that it is impossible that the front left end 13b is curled upwardly
along the roller members 12b again.
In this embodiment, the line feed motor 31 is driven by the amount of 100
pulses and the transportation amount of the print medium 13 by the
rotation of the feed rollers 12 in the backward direction is made 14 mm.
Namely, the amount of backward rotation of the feed rollers 12 is made
twice the amount of the rotation of the feed rollers 12 in the paper-feed
direction.
On the other hand, when it is judged that skew has nor occurred, the paper
feed means continues driving the line feed motor 31 to rotate the feed
rollers 12 for feeding the print medium 13. Then, the print medium 13 is
fed to the print section P1 for printing. During the paper feeding
process, the slip roller 11 is disposed at the evaded position.
Accordingly, the transportation load caused by the friction between the
print medium 13 and the slip roller 11 is reduced so that the stable
transportation of the print medium 13 is enabled.
When the line feed motor 31 is driven in the backward direction to rotate
the feed rollers 12 in the backward direction, as shown in FIG. 18, the
rotation of the slip roller 11 is stopped and the print medium 13 is
pressed against the first guide 23 by the slip roller 11. Accordingly, the
backward force from the feed rollers 12 is applied to the print medium 13
so that the front left end of the print medium 13 retreats and comes off
the contact point 19 to be released from the feed rollers 12 before the
front right end 13a does the same thing. When the front left end 13b is
separated from the roller members 12b, the backward force is lost so that
the front left end 13b remains at the position by the friction with the
slip roller 11.
During the time, the front right end 13a retreats, and then, comes off the
contact point 10 to be released from the feed rollers 12. When the front
right end 13a is separated from the roller members 12b, the front right
end 13a remains at the position by the friction with the slip roller 11.
Consequently, as shown in FIG. 19, the front right and left ends 13a and
13b are stopped at the positions where they come off the contact point 19
and skew is corrected.
Next, the skew correction means drives the skew correction motor 32 to
rotate the slip roller 11 by a predetermined amount. The print medium 13
is transported by the rotation of the slip roller 11 for further skew
correction and stopped after skew is corrected.
Then, the paper feed means in the control section 33 performs paper feed by
sending driving signals to the line feed motor 31 to drive the line feed
motor 3 so that the feed rollers 12 are rotated and the print medium 13 is
transported.
As the print medium 13 is transported, the skew sensors 15 detect the print
medium 13 again and send detection signals to the control section 33. The
skew judgement means reads the respective detection signals and judges
again if skew still occurs. When the detection difference exceeds the
threshold, that is, skew has not been corrected sufficiently in the first
skew correction, the skew correction means drives the line feed motor 31
in the backward direction to rotate the feed rollers 12 in the backward
direction by a predetermined amount so that the print medium 13 is
transported in the backward direction and the front end of the print
medium 13 comes off the roller members 12b.
At this point, the rotation of the slip roller 11 is stopped and the print
medium 13 is pressed against the first guide 23 so that skew is corrected.
The skew correction procedure is repeated until the detection difference
becomes equal to or less than the threshold. Every time the skew
correction is repeated, the amounts of the rotation of the feed rollers 12
in the paper-feed and backward directions increase. Also, if necessary,
every time the skew correction is repeated, the speed and amount of the
rotation of the feed rollers 12 may be changed.
When the skew correction is finished, that is, when the detection
difference becomes equal to or less than the threshold, the skew
correction means brings the slip roller 11 to the evaded position and the
paper feed means drives the line feed motor 31. Consequently, the feed
rollers 12 are rotated to feed the print medium 13 to the pint section P1
for printing.
As described above, the slip roller 11 is rotated to make the front end of
the print medium 13 abut against the feed roller 12 and the feed rollers
12 are rotated in the paper-feed direction, while the slip roller 11 is
rotating. Accordingly, the curled portion of the print medium 13 can be
made flat. Also, the transportation error of the print medium 13 can be
prevented. Accordingly, when the print medium 13 retreats by the backward
rotation of the feed rollers 12, the skew of the print medium 13 can be
corrected certainly.
The flow chart will now be described.
Step S21: Wait until the medium detection sensor 14 detects the print
medium 13. When the medium detection sensor 14 detects the print medium
13, go to the step S2.
Step S22: Rotate the slip roller 11.
Step S23: Wait until the slip roller 11 is rotated by a predetermined
amount. Go to the step S24, when the slip roller 11 is rotated by the
predetermined amount.
Step S24: Rotate the feed rollers 12 in the paper-feed direction to
transport the print medium 13, working together with the slip roller 11.
Step S25: Wait until the feed rollers 12 are rotated by a predetermined
amount. Go to the step S26 when the feed rollers 12 are rotated by the
predetermined amount.
Step S26: Stop the rotations of the slip roller 11 and the feed rollers 12.
Step S27: Rotate the feed rollers in the backward direction, while the slip
roller 11 holds the print medium 13.
Step S28: Wait until the feed rollers 12 are rotated by a predetermined
amount. Go to the step S29 when the feed rollers 12 are rotated by the
predetermined amount.
Step S29: Stop the rotation of the feed rollers 12.
Step S30: Rotate the slip roller 11.
Step S31: Wait until the slip roller 11 is rotated by a predetermined
amount. Go to the step S32 when the slip roller 11 is rotated by the
predetermined amount.
Step S32: Stop the rotation of the slip roller 11.
Step S33: Feed the print medium 13 by the rotation of the feed rollers 12
and finish the process.
In the respective embodiments, the horizontal-type printer, in which the
paper feed is performed in the horizontal direction. The invention,
however, may be applicable to such a printer as has a paper feed section
(paper inserter) capable of receiving the print medium from above. In the
printer with the inserter, cutform is set into the inserter from above and
rollers provided in the inserter has the same functions as the feed
rollers have.
The present invention is not limited to the embodiments and a plurality of
variations are possible in the concept of the invention, and therefore,
the variations should not be excluded from the scope of the invention.
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