Information
-
Patent Grant
-
6786664
-
Patent Number
6,786,664
-
Date Filed
Friday, October 26, 200122 years ago
-
Date Issued
Tuesday, September 7, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
-
CPC
-
US Classifications
Field of Search
US
- 271 276
- 400 648
- 400 656
- 400 617
- 400 618
- 346 134
- 346 136
-
International Classifications
- B41J1108
- B41J1310
- B41J1102
- B65H522
-
Abstract
A media advancing device for a hardcopy apparatus includes at least one roller having an outer surface and being rotatable for advancing media, and a negative pressure mechanism. The outer surface further comprises a plurality of openings and a contact region for engaging the media, wherein the negative pressure mechanism is capable of creating negative pressure through at least a portion of the openings in the contact region.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to hardcopy apparatus, such as copiers, printers, scanners, and facsimiles, and more particularly to improved media advancing devices for such apparatus.
2. Description of the Prior Art
In hardcopy apparatus and particularly in apparatus handling media of large size, such as large format printers, printed media is outputted from the printer by means of outputting devices that may damage the quality of the printout. Conventional outputting devices, in order to advance the printed media, employ elements for holding the media having direct contact with the printed surface. This may cause markings on the media, ink smearing and other adverse affects on the print appearance.
As an example, the prior art has employed pinch wheels on top of the overdrive roller for outputting printed media. These devices may damage the printout with pinch wheel marks and further require the need to employ a mechanism or a structure to hold the pinch wheels.
To overcome the problem of adverse affects on the print appearance, U.S. Pat. No. 6,234,472 discloses a media holddown device including a vacuum holddown output unit for holding at least a portion of the media down onto a surface of the outputting mechanism. Thus, the device allows holding of the media without direct contact with the printed surface. The vacuum holddown output unit includes a platen having a continuous waved slot that allows for even distribution of a vacuum along the print zone. To advance the media, this device employs a plurality of overdrive wheels with a gap between the overdrive wheels and the surrounding platen. The vacuum is supplied through these gaps and tangentially results in a negative pressure distribution upon the overdrive roller in the area of the outer surface that engages the back of the media. Rotation of the overdrive wheels, that are frictionally engaging a portion of the back of the media due to the negative pressure distribution, advances the media for output. However, the negative pressure distribution of this device provides a limited traction force as a result of the vacuum being tangentially applied to the area of media contact on the overdrive wheels.
Experiments by the present applicant show that such conventional designs behave in such a way that the overdrive wheels begin to act as a friction load for the media advance when the vacuum levels are increased.
The present invention provides an improved media advancing device and method for advancing a printed media in a hardcopy apparatus with increased traction force. The present invention also provides an advancing device that allows for smaller trailing margins.
SUMMARY OF THE INVENTION
A media advancing device for a hardcopy apparatus comprising at least one roller having an outer surface and rotatable for advancing media, and a negative pressure mechanism; the outer surface comprising a plurality of openings and a contact region for engaging the media, wherein the negative pressure mechanism is capable of creating negative pressure through at least a portion of the openings in the contact region.
Preferably, the negative pressure mechanism comprises one vacuum source in fluid communication with one vacuum chamber, the vacuum chamber being in fluid communication with at least a portion of said openings in said contact region. More preferably, the vacuum chamber further comprises at least one slot, wherein the at least one roller is partially housed in the at least one slot such that the openings in the contact region provide the only entrance for air through the at least one slot into the vacuum chamber.
The present invention will be described further, by way of example only, with reference to an embodiment thereof as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view of an inkjet printer incorporating the features of the present invention;
FIG. 2
is a diagram of a media advancing device of the printer of
FIG. 1
without a shim;
FIG. 3
depicts a cutaway, perspective view of a portion of the media advancing device of
FIG. 2
with a shim;
FIG. 4
is a cross-sectional view of the media advancing device of
FIG. 2
; and
FIG. 5
depicts a cutaway, perspective view of a portion of a second embodiment of a media advancing device of the present invention; and
FIG. 6
is a flow chart depicting a method for advancing media according to the apparatus of FIG.
2
.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIG. 1
, a printer
110
includes a housing
112
mounted on a stand
114
. The housing has left and right drive mechanism enclosures
116
and
118
, and a cover
122
. A control panel
120
is mounted on the right enclosure
118
. A print media
130
, such as media, is positioned along a media axis denoted as the X axis. A second axis, perpendicular to the X axis, is denoted as the Y axis.
Referring now to
FIG. 2
, a media outputting device is globally referenced as
200
and includes the media advancing device globally referenced as
340
that will be discussed in more detail with respect to FIG.
3
. The outputting device
200
is located between the left and right drive mechanism enclosures
116
and
118
. The width of the outputting device
200
measured along the Y axis (shown in
FIG. 1
) is at least equal to the maximum allowable width of the media. In this embodiment, the width of the outputting device
200
should allow the advancement of media having width up to 36 inches, i.e., 914 mm. However, a larger or smaller media may be advanced according to the capabilities of the hardcopy apparatus in which the media outputting device is being utilized.
A carriage assembly
100
is adapted for reciprocal motion along carriage bar
124
. The carriage assembly
100
comprises four inkjet printheads
102
,
104
,
106
,
108
, each having printhead nozzles and adapted to store ink of different colors, e.g., black, magenta, cyan and yellow ink, respectively. Inkjet printheads
102
,
104
,
106
,
108
, are held rigidly in movable carriage
100
so that the nozzles are above the surface of a portion of media
130
that lays substantially flat on flat stationary platen
400
. As carriage assembly
100
moves relative to media
130
along the X and Y axis (shown in FIG.
1
), selected nozzles of printheads
102
,
104
,
106
,
108
are activated and ink is applied to media
130
. The colors from the color printheads are mixed to obtain any other particular color.
Referring to
FIG. 3
, media outputting device
200
includes platen
400
and media advancing device
340
. Platen
400
is a flat surface that extends from the front of printer
110
to main driving roller
300
. Platen
400
comprises a plurality of vacuum holes
330
connected to atmosphere and to vacuum chamber
380
. Vacuum chamber
380
is in fluid communication with a vacuum source, which in this embodiment is a fan that is not shown in the drawings, such that the vacuum source generates an air flow by sucking air from the atmosphere through holes
330
into vacuum chamber
380
. Due to the pressure differential between atmospheric pressure on the surface of media
130
and the vacuum applied through holes
330
to the back of media
130
, the portion of the media closest to holes
330
adheres to platen
400
. In order to reduce the loss of air from vacuum chamber
380
, holes
330
are distributed at a certain distance from main roller
300
. According to this embodiment, a plurality of holes
330
lay in a line at a distance preferably between about 10 mm to about 30 mm from main roller
300
, and more preferably about 19 mm from main roller
300
.
Platen
400
further comprises a plurality of substantially linear grooves
315
having a wave like shape such that the top of the wave is closest to main roller
300
and the bottom of the wave is farthest from main roller
300
. Grooves
315
are linked together to form continuous wave channel
320
, which crosses substantially the whole width of platen
400
. Preferably, channel
320
has a depth greater than about 0.5 mm, and more preferably about 1 mm, and a width between about 3 mm to about 8 mm, and more preferably about 5 mm. Furthermore, a high vacuum may crease the media if the grooves of channel
320
are wide and run parallel to the media advance direction. Therefore, grooves
315
preferably run at an angle of about 45° with respect to the media axis X. Thus, the angles of grooves
315
optimize the channel width in order to minimize creases in the media and to evenly distribute the vacuum.
The plurality of vacuum holes
330
are positioned in wave channel
320
, preferably at the bottom of the wave, farthest from main roller
300
. Holes
330
have a diameter between about 1.5 mm to about 3.5 mm, and more preferably about 2.5 mm.
The continuous shape of wave channel
320
evenly distributes the vacuum along print zone
450
. Although the preferred embodiment links the plurality of grooves
315
together in order to form a continuous channel
320
for achieving the above described advantage, alternatively, the plurality of grooves may be separated.
Platen
400
further comprises slot
420
extending along the Y axis about a length equal to, or slightly less than the maximum allowable width of the media. Slot
420
partially houses overdrive roller
345
which will be discussed later in more detail.
A plurality of pinch wheels
310
are positioned above a rear portion of platen
400
and are controlled to periodically index or convey media
130
across the surface of platen
400
. In this embodiment, for example, there are 12 pinch wheels
310
, of which only four are shown in FIG.
3
. However, the number of pinch wheels may vary according to the hardcopy apparatus being utilized. The force between each pinch wheel
310
and main roller
300
is preferably between about 3.33 N to about 5 N, and more preferably about 4.15 N. This pinch wheel distribution and force help to drive media
130
straight with irrelevant lateral slippage.
Main roller
300
has an outer surface having a plurality of circumferencial recesses
305
housing a corresponding plurality of protrusions
405
of platen
400
. Protrusions
405
extend from the rear of platen
400
towards the rear of printer
110
. This combination of features allows media
130
to reliably move between main roller
300
and platen
400
.
Referring to
FIGS. 3 and 4
, media advancing device
340
comprises an overdrive roller
345
and may include vacuum chamber
380
. Overdrive roller
345
is a hollow cylinder and is rotatably mounted partially within slot
420
between first platen edge
356
and second platen edge
358
. Overdrive roller
345
has a length slightly less than the length of slot
420
and an outer surface
350
having a plurality of openings
352
and a contact region
355
. Openings
352
are preferably circular in shape but other shapes may be used in order to facilitate the flow of air through the openings. Openings
352
preferably have a radius of about 0.5 mm to about 1.0 mm. Openings
352
are positioned along outer surface
350
in order to equally distribute the negative pressure along overdrive roller
345
. In this embodiment, openings
352
are positioned in offsetting rows, equidistantly set apart, along the entire outer surface
350
. The distance between openings
352
is preferably about 4 mm to about 10 mm.
Although this embodiment of advancing device
340
has a continuous overdrive roller
345
that extends almost the length of slot
420
in order to supply equal traction to each part of media
130
, a plurality of rollers, in strict contact with one another or separated from one another, may also be employed.
Overdrive roller
345
may also have a coating with a high coefficient of friction on outer surface
350
. Preferably, the coating is made from rubber, silicone, ceramic or metal grit and the like. Combinations of these materials may also be used. More preferably, the coefficient of friction for the coating is about 0.6 to about 1.1.
In this embodiment, running axially beneath slot
420
and overdrive roller
345
, is a vacuum chamber
380
such that the overdrive roller is partially housed in the chamber through slot
420
. In this embodiment, vacuum chamber
380
is in fluid communication with slot
420
through openings
352
.
Contact region
355
of roller
345
is that area of the roller that is located between first and second edges
356
and
358
, and which engages the back of media
130
. As a result of the vacuum created by the vacuum source, air flows from atmosphere through openings
352
in contact region
355
through openings
352
in the remaining portion of outer surface
355
and into vacuum chamber
380
. Preferably, the vacuum level is about 2 to about 8 inches of H
2
O. This vacuum creates a negative pressure distribution directly upon overdrive roller
345
in the area of contact region
355
. The negative pressure distribution causes the back of media
130
to engage with contact region
355
.
The traction force, resulting from the negative pressure distribution, between media
130
and overdrive roller
345
is preferably between about 0.6 N to about 1 N, and more preferably about 0.8 N.
A shim
430
may be positioned over slot
420
, extending the length and width of the slot and having a gap
440
. Shim
430
may also include at least one transversal rib
435
transversing gap
440
such that a plurality of smaller gaps are formed in shim
430
. Preferably, these smaller gaps are of equal size in order to equally distribute the negative pressure along contact region
355
. Gap
440
is aligned over contact region
355
and engages with first and second platen edges
356
and
358
providing for an entrance for air through slot
420
into vacuum chamber
380
. Preferably, gap
440
is engaged with slot
420
so that openings
352
in contact region
355
are the only entrance for air through slot
420
into vacuum chamber
380
. The size of gap
440
can be varied according to the rigidity of media
130
that is being advanced and the amount of adherence of the media to overdrive roller
345
that is sought.
Alternatively, annular grooves may be formed in outer surface
350
to house transverse ribs
435
. To transmit the proper traction force to media
130
, the overdrive interference, i.e., the distance between the surface of platen
400
and the top of overdrive roller
345
, would preferably be between about 0.3 mm to about 0.6 mm. Below 0.25 mm the traction force reduces rapidly, towards zero traction force at zero interference; while an interference larger than 0.65 mm may result in wrinkles created by overdrive roller
345
extending to print zone
450
.
Referring to
FIG. 5
, an alternative embodiment of the media advancing mechanism is shown. Overdrive roller
345
further comprises at least one axial exhaust
370
. In this alternative embodiment, there is one axial exhaust
370
but a plurality of axial exhausts may be used in order to facilitate the flow of air. Axial exhaust
370
is in fluid communication with the vacuum source and openings
352
such that air flows from atmosphere through openings
352
in contact region
355
through axial exhaust
370
to the vacuum source. This vacuum creates a negative pressure distribution directly upon overdrive roller
345
in the area of contact region
355
. The negative pressure distribution causes the back of media
130
to engage with contact region
355
.
Media advancing device
340
utilizes a negative pressure distribution directly upon overdrive roller
345
to create the necessary traction force for advancement or outputting of media
130
. By distributing the negative pressure directly upon overdrive roller
345
through the plurality of openings
352
, the present invention increases the traction force as compared to devices that apply the negative pressure tangentially to the overdrive roller. This increase of traction force further allows for smaller trailing margins because the overdrive roller is capable of exclusively advancing the media after the media has been released from the main drive roller.
Advancing Operation
Referring to
FIG. 6
, an advancing operation may be activated either automatically when a printing operation has been completed or aborted, or manually by a user's request, as shown in step
800
.
When the operation is activated, printer
110
verifies if media
130
to be outputted is a cut sheet or a roll (step
810
). If media
130
is a roll a cutting step is performed. This means that media
130
is advanced to the cutting position and the vacuum source is powered creating a negative pressure distribution through roller
345
and through platen
400
in order to tension the media and hold the media substantially flat while minimizing movement (step
815
). This allows a blade (not shown) to traverse media
130
along the Y axis to cut the media, as shown in step
817
.
Once the roll has been cut or if media
130
is a cut sheet, the media is advanced along the X axis towards the front of printer
110
away from main roller
300
(step
830
).
The advancement of media is performed by engagement of a portion of the back of media
130
with contact region
355
, due to the negative pressure generated by the vacuum source through openings
352
in contact region
355
, and rotation of overdrive roller
345
.
If the ink printed onto media
130
requires additional drying time (step
840
), the overdrive roller rotation may be stopped when most of the printout is advanced out of the printer (step
845
), e.g., as shown in FIG.
1
. The vacuum source is kept on for the required time to tension media
130
and assist in drying.
Media
130
can then continue its advancement or output from printer
110
(step
850
), preferably into a conventional collecting bin, as shown in step
860
. The vacuum source is then powered off (step
870
).
The present invention having thus been described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims. Furthermore, the skilled artisan will appreciate that, in accordance with the preferred embodiment, the same media advancing device may be capable of being employed to perform a plurality of different operations, such as loading and feeding operations, through use of the above-described “direct” negative pressure distribution.
Claims
- 1. A media advancing device for a hardcopy apparatus comprising:a main drive roller that advances a media toward at least one overdrive roller having an outer surface and being rotatable for further advancing said media, said outer surface comprising a plurality of openings and a contact region for engaging said media; and a negative pressure mechanism for creating negative pressure through at least a portion of said openings, wherein said roller is partially housed in at least one slot in said negative pressure mechanism such that said opening provide an entrance for air through said slot into said negative pressure mechanism.
- 2. The media advancing device according to claim 1, wherein said negative pressure mechanism comprises at least one vacuum source in communication with at least one vacuum chamber, wherein said vacuum chamber is in communication with at least a portion of said openings.
- 3. The media advancing device according to claim 2, wherein said roller is partially housed in at least one slot above said vacuum chamber, and said openings are in said contact region and provide the only entrance for air through said slot into said vacuum chamber.
- 4. The media advancing device according to claim 1, wherein said openings are circular.
- 5. The media advancing device according to claim 1, wherein said opening are equidistantly spaced apart.
- 6. The media advancing device according to claim 1, wherein said outer surface further comprises a coating having a high coefficient of friction.
- 7. The media advancing device according to claim 1, wherein said roller further comprises at least one axial exhaust and said negative pressure mechanism comprises at least one vacuum source in communication with said axial exhaust, said axial exhaust being in communication with at least a portion of said openings.
- 8. A media advancing device for a hard copy apparatus comprising:at least one roller having an outer surface and being rotatable for advancing media, said outer surface comprising a plurality of opening and a contact region for engaging said media; a negative pressure mechanism for creating negative pressure through at least a portion of said opening, wherein said negative pressure mechanism comprises at least one vacuum source in communication with at least one vacuum chamber, wherein said vacuum chamber is in communication with at least a portion of said opening, and wherein said roller is partially housed in at least one slot above said vacuum chamber, and said opening are in said contact region and provide the only entrance for air through said slot into said vacuum chamber; and at least one shim disposed above said slot and having a gap, said gap aligning over at least a portion of said contact region.
- 9. The media advancing device according to claim 8, wherein said shim further comprises at least one transverse rib forming a plurality of smaller gaps.
- 10. The media advancing device according to claim 9, wherein said smaller gaps are about equal in size.
- 11. The media advancing device according to claim 8, wherein said shim is made of a flexible material.
- 12. A media advancing device for a hardcopy apparatus comprising:a main drive roller that advances a media toward at least one overdrive roller having an outer surface with a contact region for engaging said media and rotatable for further advancing said media; and a negative pressure mechanism for creating negative pressure that is radial to at least a portion of said contact region, wherein said outer surface further comprises a plurality of openings and said negative pressure mechanism comprises at least one vacuum source in communication with at least one vacuum chamber, said vacuum chamber being in communication with at least a portion of said openings, and wherein said roller is partially housed in at least one slot in said negative pressure mechanism such that said openings provide an entrance for air through said slot into said negative pressure mechanism.
- 13. The media advancing device according to claim 12, wherein said roller is partially housed in at least one slot above said vacuum chamber, and said openings are in said contact region and provide the only entrance for air through said slot vacuum chamber.14.The media advancing device according to claim 12, wherein said openings are circular.
- 15. The media advancing device according to claim 12, wherein said openings are equidistantly spaced apart.
- 16. The media advancing device according to claim 12, wherein said outer surface further comprises a coating having a high coefficient of friction.
- 17. The media advancing device according to claim 12, wherein said roller further comprises at least one axial exhaust, said outer surface further comprises a plurality of openings and said negative pressure mechanism comprises at least one vacuum source in communication with said axial exhaust, said axial exhaust being in communication with at least a portion of said openings.
- 18. A media advancing device for a hard copy apparatus comprising:at least one roller having an outer surface with a contact region for engaging media and rotatable for advancing said media; a negative pressure mechanism for creating negative pressure that is radial to at least a portion of said contact region, wherein said outer surface further comprises a plurality of openings and said negative pressure mechanism comprises at least one vacuum source in communication with at least one vacuum chamber, said vacuum chamber being in communication with at least a portion of said openings, and wherein said roller is partially housed in at least one slot above said vacuum chamber, and said openings are in said contact region and provide the only entrance for air through said slot into said vacuum chamber; and at least one shim disposed above said slot and having a gap, said gap aligning over at least a portion of said contact region.
- 19. The media advancing device according to claim 18, wherein said shim further comprises at least one transverse rib forming a plurality of smaller gaps.
- 20. The media advancing device according to claim 19, wherein said smaller gaps are about equal in size.
- 21. The media advancing device according to claim 18, wherein said shim is made of a flexible material.
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