U.S. patent application number 13/947164 was filed with the patent office on 2015-01-22 for compact inverter for cut sheet media.
The applicant listed for this patent is Harsha S. Bulathsinghalage, Michael Joseph Piatt. Invention is credited to Harsha S. Bulathsinghalage, Michael Joseph Piatt.
Application Number | 20150021849 13/947164 |
Document ID | / |
Family ID | 52342958 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150021849 |
Kind Code |
A1 |
Piatt; Michael Joseph ; et
al. |
January 22, 2015 |
COMPACT INVERTER FOR CUT SHEET MEDIA
Abstract
A media inverting system is described for a cut sheet printing
system. A first media transport advances a media sheet in a first
direction, the media sheet having a first side that contacts the
first media transport and an opposing second side. A rotatable
member having a rotation axis that is substantially parallel to the
first direction receives the media sheet from the first media
transport and rotates to advance the media sheet around the
rotatable member. A rotatable member force mechanism is switchable
between a first state where the second side of the media sheet is
held to the rotatable member, and a second state where the media
sheet is released. A second media transport receives the media
sheet from the rotatable member and advances the media sheet in an
inverted orientation in a second direction that is substantially
parallel to the first direction.
Inventors: |
Piatt; Michael Joseph;
(Dayton, OH) ; Bulathsinghalage; Harsha S.;
(Miamisburg, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Piatt; Michael Joseph
Bulathsinghalage; Harsha S. |
Dayton
Miamisburg |
OH
OH |
US
US |
|
|
Family ID: |
52342958 |
Appl. No.: |
13/947164 |
Filed: |
July 22, 2013 |
Current U.S.
Class: |
271/225 |
Current CPC
Class: |
B65H 15/00 20130101;
B65H 2301/3421 20130101; B65H 85/00 20130101; B65H 5/021 20130101;
B65H 2301/33216 20130101 |
Class at
Publication: |
271/225 |
International
Class: |
B65H 85/00 20060101
B65H085/00 |
Claims
1. A media inverting system for a cut sheet printing system,
comprising: a first media transport for advancing a media sheet
along a first media transport path in a first direction, the media
sheet having a first side that contacts the first media transport
and an opposing second side; a rotatable member adapted to receive
the media sheet from the first media transport at a first transfer
position and rotate to advance the media sheet around the rotatable
member to a second transfer position, the rotatable member having a
rotation axis that is substantially parallel to the first
direction, wherein the second transfer position is on an opposite
side of the rotatable member from the first transfer position,
wherein the rotatable member is a belt system including a belt
travelling along a belt path around a plurality of rollers having
substantially parallel roller axes, and wherein the rotation axis
is substantially parallel to the roller axes; a rotatable member
force mechanism switchable between a first state and a second
state, wherein when the rotatable member force mechanism is in the
first state the second side of the media sheet is held to the
rotatable member, and when the rotatable member force mechanism is
in the second state the media sheet is released from being held to
the rotatable member; and a second media transport for receiving
the media sheet from the rotatable member at the second transfer
position and advancing the media sheet along a second media
transport path in a second direction that is substantially parallel
to the first direction, the rotatable member being positioned
between the first media transport and the second media transport;
wherein the first side of the transferred media sheet contacts the
second media transport, and wherein an orientation of the first and
second sides of the media sheet is inverted while the media sheet
is advanced along the second transport path relative to an
orientation of the first and second sides of the media sheet while
the media sheet is advanced along the first transport path.
2. The media inverting system of claim 1 further including a
control mechanism for controlling the rotatable member and the
rotatable member force mechanism according to a control sequence
including: switching the rotatable member force mechanism to the
first state to transfer the media sheet from the first media
transport to the rotatable member and hold the second side of the
media sheet to the rotatable member while it is advanced around the
rotatable member; rotating the rotatable member to advance the
media sheet around the rotatable member to the second transfer
position; and switching the rotatable member force mechanism to the
second state to release the media sheet from being held to the
rotatable member in synchronization with the media sheet being
transferred to the second media transport.
3. (canceled)
4. The media inverting system of claim 1 wherein the rotatable
member is a drum.
5. The media inverting system of claim 1 wherein the rotatable
member continuously rotates.
6. The media inverting system of claim 1 wherein the rotatable
member force mechanism is a vacuum force mechanism that provides a
vacuum force in the first state to hold the second side of the
media sheet to the rotatable member.
7. The media inverting system of claim 6 wherein the rotatable
member force mechanism blows air through holes in the rotatable
member onto the second side of media sheet in the second state,
thereby actively releasing the media sheet from being held to the
rotatable member.
8. The media inverting system of claim 1 wherein the rotatable
member force mechanism is an electrostatic force mechanism that
provides an electrostatic force in the first state to hold the
second side of the media sheet to the rotatable member.
9. The media inverting system of claim 1 wherein the rotatable
member force mechanism provides an attractive force between the
media sheet and the rotatable member in the first state and a
repelling force between the media sheet and the rotatable member in
the second state.
10. The media inverting system of claim 1 further including a first
media transport force mechanism for holding the first side of the
media sheet to the first media transport.
11. The media inverting system of claim 10 wherein the first media
transport force mechanism is a vacuum force mechanism that provides
a vacuum force for holding the first side of the media sheet to the
first media transport, or an electrostatic force mechanism that
provides an electrostatic force for holding the first side of the
media sheet to the first media transport.
12. The media inverting system of claim 10 wherein the first media
transport force mechanism is switchable between a first state and a
second state, such that when the first media transport force
mechanism is in the first state the first side of the media sheet
is held to the first media transport, and when the first media
transport force mechanism is in the second state the media sheet is
not held to the first media transport, and wherein the control
system also controls the first media transport force mechanism
according to a control sequence including: switching the first
media transport force mechanism from the first state to the second
state to transfer the media sheet to rotatable member when it
arrives at the first transfer position; wherein the control system
switches the first media transport force mechanism to the second
state in synchronization with switching the rotatable member force
mechanism to the first state.
13. The media inverting system of claim 1 further including a
second media transport force mechanism for holding the first side
of the media sheet to the second media transport.
14. The media inverting system of claim 13 wherein the second media
transport force mechanism is a vacuum force mechanism that provides
a vacuum force for holding the first side of the media sheet to the
second media transport, or an electrostatic force mechanism that
provides an electrostatic force for holding the first side of the
media sheet to the second media transport.
15. The media inverting system of claim 13 wherein the second media
transport force mechanism is switchable between a first state and a
second state, such that when the second media transport force
mechanism is in the first state the first side of the media sheet
is held to the second media transport, and when the second media
transport force mechanism is in the second state the media sheet is
not held to the second media transport, and wherein the control
system also controls the second media transport force mechanism
according to a control sequence including: switching the second
media transport force mechanism from the second state to the first
state to transfer the media sheet to the second transport mechanism
when it arrives at the second transfer position and to hold the
first side of the media sheet to the second media transport as it
is advanced along the second media transport path; wherein the
control system switches the second media transport force mechanism
to the first state in synchronization with switching the rotatable
member force mechanism to the second state.
16. The media inverting system of claim 1 wherein one or both of
the first media transport and the second media transport are
transport belt systems.
17. The media inverting system of claim 16 wherein each of the
transport belt systems includes a transport belt travelling along a
transport belt path around a plurality of rollers.
18. The media inverting system of claim 16 wherein at least one of
the transport belt systems is a vacuum belt system.
19. The media inverting system of claim 1 further including one or
more sensors to detect a position of the media sheet, wherein the
control system switches the rotatable member force mechanism to the
first state in response to detecting that the media sheet is at the
first transfer position.
20. The media inverting system of claim 19 wherein the control
system switches the rotatable member force mechanism to the second
state in response to detecting that the media sheet is at the
second transfer position.
21. The media inverting system of claim 1 wherein the first media
transport advances the media sheet from an output of a printing
module, and wherein the second media transport advances the media
sheet to an input of the same printing module.
22. The media inverting system of claim 21, wherein the second
media transport is a belt system including a belt travelling along
a belt path around a plurality of rollers, and wherein the second
media transport is adapted to advance the media sheet around at
least one of said plurality of rollers, thereby reversing a
direction of travel of the media sheet.
23. A media inverting system for a cut sheet printing system,
comprising: a first media transport for advancing a media sheet
along a first media transport path in a first direction, the media
sheet having a first side that contacts the first media transport
and an opposing second side; a rotatable member adapted to receive
the media sheet from the first media transport at a first transfer
position and rotate to advance the media sheet around the rotatable
member to a second transfer position, the rotatable member having a
rotation axis that is substantially parallel to the first
direction, wherein the second transfer position is on an opposite
side of the rotatable member from the first transfer position; a
rotatable member force mechanism switchable between a first state
and a second state, wherein when the rotatable member force
mechanism is in the first state the second side of the media sheet
is held to the rotatable member, and when the rotatable member
force mechanism is in the second state the media sheet is released
from being held to the rotatable member; and a second media
transport for receiving the media sheet from the rotatable member
at the second transfer position and advancing the media sheet along
a second media transport path in a second direction that is
substantially parallel to the first direction, the rotatable member
being positioned between the first media transport and the second
media transport; wherein the first side of the transferred media
sheet contacts the second media transport, and wherein an
orientation of the first and second sides of the media sheet is
inverted while the media sheet is advanced along the second
transport path relative to an orientation of the first and second
sides of the media sheet while the media sheet is advanced along
the first transport path; wherein the rotatable member is a belt
system including: a first belt travelling around a first plurality
of rollers; and a second belt travelling around a different second
plurality of rollers; wherein the first and second belts are
adapted to invert first and second media sheets, respectively, that
are advanced adjacent to one another by the first media transport.
Description
FIELD OF THE INVENTION
[0001] This invention pertains to the field of media handling for
cut-sheet printing systems, and more particularly to an apparatus
inverting the media sheets for printing on a second side.
BACKGROUND OF THE INVENTION
[0002] In a digitally controlled printing system, a receiver media
(also called a print media) is directed through a series of
components for printing an image. The receiver media can be a
continuous web of media or a sequential flow of cut sheets of
media. In the case of a cut-sheet printing system, a media
transport system physically moves the receiver media sheets through
the printing system. As the receiver media sheets move through the
printing system, a printing process is carried out on a first side
of the receiver media sheets. For example, in an inkjet printing
system, liquid (e.g., ink) is applied to the receiver media sheet
by one or more printheads through a process commonly referred to as
jetting of the liquid.
[0003] In many printing applications it is desirable to print on
both sides of the receiver media sheets, thereby saving cost and
being more environmentally friendly. Some printing systems are
capable only of printing on a single side of the receiver media
sheets. In this case, a user who wishes to print on both sides of
the receiver media sheets can print the odd numbered pages, reload
the stack of print media sheets, and then print the even numbered
pages. However, this is slow and cumbersome. A more user-friendly
printing system is one that includes a media inverter, also called
a duplexer, for duplex printing.
[0004] Desktop printing systems typically use a carriage to move a
printhead across the receiver media sheet to print a swath of an
image and advance the receiver media sheet between swaths in order
to form the image swath-by-swath. Such printing systems are small
and low-cost, but printing throughput on single sides of
letter-sized receiver media sheets is typically limited to around
20-30 pages per minute. Because the distance the receiver media
sheet is moved through a desktop printing system is small, the
transport system can be a series of rollers. Printing of all of the
colors of the image is performed in a relatively small print zone
compared to the length of the receiver media sheet. For printing a
single side, the receiver media sheet is advanced swath-by-swath
sequentially past the print zone. For duplex printing, the receiver
media sheet is typically driven through a duplexer by one or more
rollers to turn the receiver media sheet over and return the
receiver media sheet to a point prior to the print zone so that the
second side can be printed.
[0005] High-volume cut-sheet printing systems typically print one
color of an entire line of the image essentially all at once, for
example using a page-width printhead or some other page-width
printing process in a printing station for that color. The receiver
media sheet is advanced past the printing station as sequential
page-width lines of the same color are printed. To print all colors
(typically cyan, magenta, yellow and black), the receiver media
sheet is moved from printing station to printing station, each
printing station printing a different color. In a high volume
inkjet printing system, there are typically dryers between some or
all of the printing stations in order to remove some of the carrier
fluid of the ink and make the ink less mobile so that it is less
susceptible to bleeding into the next color that is printed.
[0006] In web printing systems, tension in the continuous web of
receiver media can be used to pull the web through the various
printing stations. In high-volume cut-sheet printing systems, a
media transport system, which typically includes components such as
belts or drums, is used to move the receiver media sheets through
the printing system from one printing station to the next.
High-volume cut-sheet printing systems tend to be significantly
larger and more costly than desktop printing systems. However, the
printing throughput is also typically significantly higher.
[0007] Because of the successive printing stations, and other
stations such as dryers or fusers, in a high-volume cut-sheet
printing system, the distance between the input to the first
printing station and the output of the last printing station can be
relatively large compared to the length of the receiver media
sheet. A simple roller-driven duplexer that can position the lead
edge of the receiver media sheet close enough to the print zone
that a feed roller can begin to pull the leading edge before
trailing edge of the receiver media sheet passes the duplexer drive
roller is not adequate in such a large high-volume cut-sheet
printing system. Furthermore, some high-volume cut-sheet printing
systems include a first printing module including all of the color
printing stations for printing a first side of the sheets, and a
second printing module including all of the color printing stations
for printing a second side of the sheets. A media inverter is
positioned between first printing module and the second printing
module.
[0008] Although high-volume cut-sheet printing systems can be
inherently large, it is desirable that they not be excessively
large. In addition, since high volume cut-sheet printers have
capability for high printing throughput, other components of a
printing system should be able to keep up with the printing
throughput so that they do not compromise the overall throughput of
the system. Therefore, there is an ongoing need for a media
inverter that is compact and high speed in turning the cut receiver
media sheets over and providing the cut receiver media sheets in a
proper orientation to the beginning of the printing process for the
second side, either using the same printing module or in a
different printing module.
SUMMARY OF THE INVENTION
[0009] The present invention represents a media inverting system
for a cut sheet printing system, comprising:
[0010] a first media transport for advancing a media sheet along a
first media transport path in a first direction, the media sheet
having a first side that contacts the first media transport and an
opposing second side;
[0011] a rotatable member adapted to receive the media sheet from
the first media transport at a first transfer position and rotate
to advance the media sheet around the rotatable member to a second
transfer position, the rotatable member having a rotation axis that
is substantially parallel to the first direction, wherein the
second transfer position is on an opposite side of the rotatable
member from the first transfer position;
[0012] a force mechanism of the rotatable member force mechanism
switchable between a first state and a second state, wherein when
the force mechanism of the rotatable member force mechanism is in
the first state the second side of the media sheet is held to the
rotatable member, and when the force mechanism of the rotatable
member force mechanism is in the second state the media sheet is
released from being held to the rotatable member; and
[0013] a second media transport for receiving the media sheet from
the rotatable member at the second transfer position and advancing
the media sheet along a second media transport path in a second
direction that is substantially parallel to the first direction,
the rotatable member being positioned between the first media
transport and the second media transport;
[0014] wherein the first side of the transferred media sheet
contacts the second media transport, and wherein an orientation of
the first and second sides of the media sheet is inverted while the
media sheet is advanced along the second transport path relative to
an orientation of the first and second sides of the media sheet
while the media sheet is advanced along the first transport
path.
[0015] This invention has the advantage that the media sheet is
inverted in a compact space.
[0016] It has the additional advantage that the media transports
and the rotatable member can be continuously operated without the
need to reverse directions, thereby providing a high throughput
required for high-speed printing systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows a side view of a cut-sheet printing system
including a first printing module, a media inverter and a second
printing module;
[0018] FIGS. 2A-2E show an exploded perspective of a media inverter
according to an exemplary embodiment with a media sheet being
advanced through an inverting process;
[0019] FIG. 3 is a side view of the media inverter of FIGS.
2A-2E;
[0020] FIGS. 4A-4B are side views of belt systems where the hold
down force for the media sheet is provided electrostatically by
charging rollers and by corona charging units, respectively;
[0021] FIG. 5 is an exploded perspective of a media inverter
according to an alternate embodiment where the rotatable member is
a drum;
[0022] FIG. 6 shows a side view of a cut-sheet printing system
including a printing module and a media inverter that inverts media
sheets and returns them to the input of the printing module;
[0023] FIGS. 7A-7B show an exploded perspective of the media
inverter of FIG. 6 according to an exemplary embodiment with a
media sheet being advanced through an inverting process; and
[0024] FIGS. 8A-8B show an exploded perspective of a portion of a
media inverter capable of inverting two adjacent media sheets at
the same time.
[0025] It is to be understood that the attached drawings are for
purposes of illustrating the concepts of the invention and may not
be to scale.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The present description will be directed in particular to
elements forming part of, or cooperating more directly with, an
apparatus in accordance with the present invention. It is to be
understood that elements not specifically shown, labeled, or
described can take various forms well known to those skilled in the
art. In the following description and drawings, identical reference
numerals have been used, where possible, to designate identical
elements. It is to be understood that elements and components can
be referred to in singular or plural form, as appropriate, without
limiting the scope of the invention.
[0027] The invention is inclusive of combinations of the
embodiments described herein. References to "a particular
embodiment" and the like refer to features that are present in at
least one embodiment of the invention. Separate references to "an
embodiment" or "particular embodiments" or the like do not
necessarily refer to the same embodiment or embodiments; however,
such embodiments are not mutually exclusive, unless so indicated or
as are readily apparent to one of skill in the art. It should be
noted that, unless otherwise explicitly noted or required by
context, the word "or" is used in this disclosure in a
non-exclusive sense.
[0028] The example embodiments of the present invention are
illustrated schematically and not to scale for the sake of clarity.
One of ordinary skill in the art will be able to readily determine
the specific size and interconnections of the elements of the
example embodiments of the present invention.
[0029] Cut sheets, also referred to as media sheets, refer to
individual sheets of receiver media that are moved along a
transport path through a printing system (or through some other
type of media handling system). Cut-sheet printing systems are
commonly used for printing on sheets of paper; however, there are
numerous other materials for which cut-sheet printing is
appropriate. For example, the media inverter described herein is
compatible with media sheets made using flexible materials such as
vinyl sheets, plastic sheets, or textiles.
[0030] The terms "upstream" and "downstream" are terms of art
referring to relative positions along the transport path of the
receiver media; points on the receiver media move along the
transport path from upstream to downstream.
[0031] Referring to FIG. 1, there is shown a simplified side view
of a portion of a cut-sheet printing system 100 including a first
printing module 10, a second printing module 20, and a media
inverter 30 positioned downstream of first printing module 10 and
upstream of second printing module 20. A media sheet 2 (sometimes
referred to as a "cut sheet") is shown at input 11 and output 12 of
first printing module 10, and also at input 21 of second printing
module 20 after passing through media inverter 30. In this example,
at output 12 of first printing module 10, a media sheet 2 is shown
moving along a media transport path 45 in a first direction 15 with
a first side 4 held against the media transport path 45 and an
opposite second side 3 facing away from media transport path 45,
and with a leading edge 5 being the most downstream edge of media
sheet 2. This is the same orientation as media sheet 2 had at input
11 of first printing module 10. As media sheet 2 is moved through
the first printing module 10, the media sheet is oriented so that
the second side 3 is printed on by printing stations 14. After
media sheet 2 exits media inverter 30, it moves along media
transport path 65 in second direction 25, with the orientation of
the media sheet 2 being inverted so that the second side 3 is held
against media transport path 65 and the first side 4 is facing away
from media transport path 65. The leading edge 5 is still the most
downstream edge of media sheet 2. (While the second direction 25 is
the same as the first direction 15 in this example, this is not a
requirement.) Thus as media sheet 2 enters second printing module
20 at input 21 and passes through second printing module 20, first
side 4 is properly oriented for printing on by printing stations
24.
[0032] FIGS. 2A-2E show an exploded perspective of a media inverter
30 of the type described above relative to FIG. 1 according to an
exemplary embodiment. In FIG. 2A, media sheet 2 is being advanced
along a first media path by first media transport 40 in first
direction 15. In this embodiment, first media transport 40 is a
belt system including two belt strips 46 that travel around a first
roller 41 and a second roller 42. Rollers 41 and 42 have parallel
roller axes 43 that are substantially perpendicular to first
direction 15. Upper belt portions 46a of belt strips 46 travel in
first direction 15, while lower belt portions 46b travel in an
opposite direction. In this example, it is the upper belt portions
46a of the belt strips 46 that define the first media path. First
side 4 of media sheet 2 is in contact with upper belt portions 46a
of belt strips 46, with second side 3 facing away from the belt
strips 46.
[0033] In a preferred embodiment, the first side 4 of the media
sheet 2 is held to the upper belt portions 46a by a vacuum force
applied through vacuum holes 47. Vacuum belt systems for applying a
vacuum force to a media sheet 2 to hold the media sheet 2 to the
belt are well-known in the art, and any such system can be used to
provide the vacuum force in accordance with the present invention.
In more general terms, first media transport 40 is provided a
hold-down force by first media transport force mechanism 70, where
the hold-down force is applied through force transfer element 71.
For example, first media transport force mechanism 70 can include a
vacuum pump that can be switched on and off, and force transfer
element 71 can include tubing and a plenum for applying the vacuum
to vacuum holes 47 in belt strips 46. In a preferred embodiment,
the first media transport force mechanism 70 is switchable between
a first state and a second state. In the first state, the first
side 4 of media sheet 2 is attracted to and then held by first
media transport 40. In the second state of rotatable member force
mechanism 72, the media sheet 2 is released from being held to the
first media transport 40. Because media sheet 2 is transported
horizontally on the upper belt portion 46a of belt strips 46, in
some embodiments gravity can be used to hold the media sheet 2 onto
belt strips 46 and no separate first media transport force
mechanism 70 is used.
[0034] Although in this example the first media transport 40
includes a pair of belt strips 46, in other embodiments more than
two belt strips 46 or a single wide belt strip 46 can be used. In
FIG. 2A the belt strips 46 are shown as somewhat widely separated
in order to show other portions of the apparatus more clearly. More
typically the belt strips 46 would be located closer to one another
to provide better support for the media sheets 2. Providing more
than two belt strips 46 can be advantageous for accommodating a
variety of widths of media sheets 2.
[0035] In addition to first media transport 40, the illustrated
embodiment shown in FIG. 2A also includes a rotatable member 50
that is adapted to receive media sheet 2 from the first media
transport 40 at a first transfer position 48 (FIG. 2B), and advance
the media sheet 2 to a second transfer position 59 (FIG. 2D),
thereby inverting it as is described in further detail below with
reference to FIGS. 2B-2D. The illustrated embodiment shown in FIG.
2A also includes a second media transport 60 for receiving the
media sheet 2 from the rotatable member 50 at the second transfer
position 59 (FIG. 2D) as is described in further detail below with
reference to FIGS. 2D-2E.
[0036] Rotatable member 50 is positioned between the first media
transport 40 and the second media transport 60. In the exemplary
embodiment of FIGS. 2A-2E the first media transport 40, the
rotatable member 50 and the second media transport 60 are all belt
systems including belts travelling along respective belt paths
around a plurality of rollers. Such a configuration can be
advantageous for successively transferring media sheet 2 from first
media transport 40 to rotatable member 50 to second media transport
60 in a compact apparatus. In particular, the rotatable member 50
includes belt strips 56 with vacuum holes 57 traveling along a belt
path around rollers 51, 52 with roller axes 53, and the second
media transport 60 includes belt strips 66 with vacuum holes 67
traveling along a belt path around rollers 61, 62 with roller axes
63.
[0037] The rotatable member 50 has a rotatable member force
mechanism 72 with force transfer element 73, and the second media
transport 60 has a second media transport force mechanism 74 with
force transfer element 75. In a preferred embodiment, the rotatable
member force mechanism 72 is switchable between a first state and a
second state. In the first state, the second side 3 of media sheet
2 is attracted to and then held by rotatable member 50. In the
second state of rotatable member force mechanism 72, the media
sheet 2 is released from being held to the rotatable member 50.
Similarly, the second media transport force mechanism 74 is
switchable between a first state and a second state. In the first
state, the first side 4 of media sheet 2 is attracted to and then
held by second media transport 60. In the second state of rotatable
member force mechanism 72, the media sheet 2 is released from being
held to the second media transport 60.
[0038] FIG. 2B shows the media inverter 30 of FIG. 2A with the
media sheet 2 having arrived at first transfer position 48. Arrival
at first transfer position 48 can be detected by sensor 90, which
can be an optical sensor or a mechanical sensor, for example.
Alternatively if first media transport force mechanism 70 includes
a vacuum that is applied through force transfer element 71 to belt
strips 46, the coverage of the vacuum holes 47 between first roller
41 and second roller 42 at upper belt portion 46a of the belt
strips 46 can optionally be monitored by sensing vacuum pressure in
order to determine when media sheet 2 arrives at the first transfer
position 48. First transfer position 48 is indicated as an upward
arrow, because when media sheet 2 arrives at the first transfer
position 48, the media sheet 2 is transferred upwardly in the
direction of the arrow to rotatable member 50.
[0039] When it is detected that media sheet 2 has reached first
transfer position 48 (e.g., as detected by sensor 90), a controller
80 switches the first media transport force mechanism 70 from its
first state to its second state to release the media sheet 2 from
being held to the first media transport 40 in synchronization with
switching the rotatable member force mechanism 72 to its first
state, thereby attracting the media sheet 2 to the rotatable member
50 and holding it there. Switching the first media transport force
mechanism 70 to its second state in synchronization with switching
the rotatable member force mechanism 72 to its first state does not
necessarily mean that the switching is simultaneous. In some
embodiments, the switching of the rotatable member force mechanism
72 to the first state can be before or after the switching of the
first media transport force mechanism 70 to the second state by
some predefined time interval. Typically such a time interval would
be less than 1 second, and in some embodiments would be between
0.0-0.1 seconds.
[0040] FIG. 2C shows the media inverter 30 of FIG. 2A with the
media sheet 2 being rotated around rotatable member 50 toward
second transfer position 59 (FIG. 2D) on the opposite side of the
rotatable member 50 from the first transfer position 48 (FIG. 2B).
By "opposite side" it is not necessarily meant that second transfer
position 59 is directly opposite first transfer position 48, such
that media sheet 2 has been rotated by a full 180.degree. in
travelling from the first transfer position 48 to the second
transfer position 59, but that media sheet 2 has been rotated by
more than 90.degree..
[0041] In the exemplary embodiment shown in FIGS. 2A-2E, the
rotatable member 50 is a belt system including belt strips 56
travelling along a belt path such that lower belt portions 56b of
belt strips 56 move in lower belt portion direction 55b toward a
first roller 51, then rotate around roller 51 in rotation direction
58. Upper belt portions 56a of belt strips 56 then move in upper
belt portion direction 55a toward a second roller 52.
[0042] In FIG. 2C, the media sheet 2 can be seen travelling with
belt strips 56 as it is held to the belt strips 56 by the rotatable
member force mechanism 72. Rotatable member 50 has a rotation axis
54 that is parallel to the roller axes 53 of the rollers 51, 52. It
can be seen that the rotation axis 54 is substantially parallel to
the first direction 15 of the first media transport 40. (By
"substantially parallel" it is meant that rotation axis 54 is
parallel to first direction 15 to within 10.degree..) It should be
noted that while the rotation axis 54 is substantially parallel to
first direction 15 near first transfer position 48 (FIG. 2B), it is
not necessarily substantially parallel to the direction of the
first media transport 40 at points along the media path farther
from first transfer position 48.
[0043] In some embodiments, rotatable member 50 continuously
rotates, although its speed may change. In other embodiments, the
rotatable member 50 occasionally stops, for example when no media
sheets 2 are in the media inverter 30 or closely approaching the
media inverter 30. In a preferred embodiment, the rotatable member
50 rotates in a single direction (e.g., rotation direction 58)
rather than reversing direction during the process of turning media
sheet 2 over, although this is not required.
[0044] FIG. 2D shows the media inverter 30 of FIG. 2A with the
media sheet 2 having arrived at the second transfer position 59.
Second transfer position 59 is indicated as an upward arrow,
because when media sheet 2 arrives at second transfer position 59,
media sheet 2 is transferred upwardly to second media transport 60.
Arrival at the second transfer position 59 can be detected by
sensor 92, which can be an optical sensor or a mechanical sensor,
for example. Alternatively if rotatable member force mechanism 72
includes a vacuum force that is applied through force transfer
element 73 to vacuum holes 57 in belt strips 56, the coverage of
vacuum holes 57 between first roller 51 and second roller 52 in
upper belt portions 56a of the belt strips 56 can optionally be
monitored by sensing vacuum pressure in order to determine when
media sheet 2 arrives at the second transfer position 59.
[0045] When it is detected that the media sheet 2 has reached
second transfer position 59, the rotatable member force mechanism
72 is switched from its first state to its second state, thereby
releasing the media sheet 2 from being held to the rotatable member
50. In synchronization with switching the state of the rotatable
member force mechanism 72, the second media transport force
mechanism 74 is switched to its first state, thereby attracting the
media sheet 2 and holding it to the second media transport 60.
Switching the states of the second media transport force mechanism
74 and the rotatable member force mechanism 72 in synchronization
does not necessarily mean that the switching is simultaneous. In
some embodiments, the switching of the rotatable member force
mechanism 72 to the second state can be before or after the
switching of second media transport force mechanism 74 to the first
state by some predefined time interval. Typically, such a time
interval would be less than 1 second, and in some embodiments would
be between 0.0-0.1 seconds.
[0046] FIG. 2E shows the media inverter 30 of FIG. 2A with the
media sheet 2 having been transferred to the second media transport
60. In this example, second media transport 60 includes belt strips
66 that travel around first roller 61 and second roller 62. In a
preferred embodiment, the media sheet 2 is held to the belt strips
66 by applying a vacuum force from second media transport force
mechanism 74 via force transfer element 75 through vacuum holes 67.
In particular, first side 4 of media sheet 2 contacts lower belt
portions 66b of belt strips 66. The media sheet 2 is then advanced
in a second direction 25 that is substantially parallel to first
direction 15. By "substantially" parallel it is meant that second
direction 25 is parallel to first direction 15 within 10.degree..
It should be noted that while the second direction 25 is
substantially parallel to first direction 15 near second transfer
position 59 (FIG. 2D), it is not necessarily substantially parallel
at points along the media path farther from second transfer
position 59. As will be discussed with reference to FIGS. 7A-7B, in
some embodiments the second direction 25 is substantially parallel
to the first direction 15, but is in the opposite direction to the
first direction 15.
[0047] Comparing FIG. 2E with FIG. 2A, it can be seen that the
orientation of first side 4 (facing upward in FIG. 2E and downward
in FIG. 2A) and second side 4 (facing downward in FIG. 2E and
upward in FIG. 2A) is inverted. It can also be seen that leading
edge 5 continues to be the most downstream edge of media sheet 2.
With reference also to FIG. 1, media sheet 2 can subsequently be
optionally transferred to the top side of belt strips 95 that are a
downstream portion of media transport path 65 leading to input 21
of second printing module 20, so that first side 4 of media sheet 2
can be printed on by corresponding printing stations 24. This
transfer can take place, for example, by switching second media
transport force mechanism 74 of second media transport 60 to its
second state to release the media sheet 2 when it has advanced to a
position above the belt strips 95. This can be done in
synchronization with switching a force mechanism associated with
the belt strips 95 so that the media sheet 2 is attracted to and
held to the belt strips 95.
[0048] The exploded perspectives of FIGS. 2A-2E are useful for
showing the details of the individual components of the media
inverter 30, as well as the orientation of the media sheet 2 as it
travels through the media inverter 30, but the exploded
perspectives do not provide an adequate appreciation of the
compactness of the media inverter 30. FIG. 3 shows a non-exploded
side view of the media inverter 30 of FIGS. 2A-2E. As was described
above relative to FIG. 2A, media sheet 2 is advanced along first
direction 15 by first media transport 40, and is transferred to
rotatable member 50, which is positioned between first media
transport 40 and second media transport 60. (Only the front-most
roller 51 of rotatable member 50 is visible in FIG. 3.)
[0049] The upper belt portion 46a of belt strips 46 of first media
transport 40 is spaced apart from the lower belt portion 56b of
belt strips 56 of rotatable member 50 by a first separation
distance d.sub.1. Similarly the upper belt portion 56a of the belt
strips 56 of the rotatable member 50 is spaced apart from the lower
belt portion 66b of the belt strips 66 of the second media
transport 60 by a second separation distance d.sub.2. It is
advantageous for the first separation distance d.sub.1 and the
second separation distance d.sub.2 to be less than 2 cm, and
preferably to be less than 1 cm in order to facilitate the transfer
of media sheet 2 from the first media transport 40 to the rotatable
member 50 to the second media transport 60. The belt system
embodiments of media inverter 30 shown in FIGS. 2A-2E and FIG. 3
with rotatable member 50 being positioned at a close spacing from
the first media transport 40 and the second media transport 60 can
be advantageously compact both horizontally and vertically.
[0050] By contrast U.S. Pat. No. 4,019,435 to Davis, entitled
"Sheet inverting," shows an inverter having lower conveyor belts
positioned below the first media transport and upper conveyor belts
positioned above the second media transport. The turnover mechanism
includes an arcuate surface along which the sheets are driven by
the lower conveyor belts until they are handed off to the upper
conveyor belts. Such a media inverter has the disadvantage that it
is not as compact as embodiments of the present invention,
especially in the vertical direction. In addition, some types of
media sheets do not have appropriate stiffness or have too short of
a length to be pushed around arcuate surface. To solve this
problem, the rotatable member 50 in the embodiment of the present
invention described above holds onto the media sheet 2 across its
surface as the media sheet 2 is being inverted.
[0051] U.S. Pat. No. 4,027,870 to Frech et al., entitled "End for
end document inverter," shows a media transport in the form of a
first belt that transfers a document to an inverting mechanism.
Inverting mechanism uses a second belt at right angles to the first
belt. Transfer from the upper side of first belt to the lower side
of the second belt occurs as vacuum is turned off for the first
belt and turned on for the second belt. The second belt then moves
the document to a drum, which turns the document over and transfers
the inverted document back to the lower side of the second belt.
The second belt then reverses direction and returns inverted
document to the first belt. The described inverting mechanism is
compact vertically, but is not compact horizontally. In addition,
because the second belt reverses direction requiring deceleration
and acceleration times, the inverting mechanism is inherently
slower than embodiments of the present invention, where the
rotatable member 50 can rotate constantly in a single
direction.
[0052] Referring again to the example shown in FIGS. 2A-2E, the
controller 80 is used for controlling various components of the
media inverter 30. An example of a control sequence that can be
used by controller 80 includes a) controlling the first media
transport 40 to advance the media sheet 2 in the first direction 15
to the first transfer position (as sensed for example by sensor
90); b) switching the rotatable member force mechanism 72 to its
first state in synchronization with switching the first media
transport force mechanism 70 to its second state to transfer the
media sheet 2 from the first media transport 40 to the rotatable
member 50 and hold the second side 3 of the media sheet 2 to the
rotatable member 50; c) controlling the rotatable member 50 to
advance the media sheet 2 around the rotatable member 50 to the
second transfer position 59 (as sensed for example by sensor 92);
d) switching the rotatable member force mechanism 72 to its second
state in synchronization with switching the second media transport
force mechanism 74 to its first state to release the media sheet 2
from being held to the rotatable member 50 and transfer the media
sheet 2 to the second media transport 60 and hold the first side 4
of the media sheet 2 to the second media transport 60; and e)
controlling the second media transport 60 to advance the inverted
media sheet 2 in the second direction 25.
[0053] In the previous examples, the first media transport force
mechanism 70, rotatable member force mechanism 72 and second media
transport force mechanism 74 are vacuum force mechanisms that can
be switched on (i.e., switched to a first state) or off (i.e.,
switched to a second state). In other words, in the first state an
attractive vacuum force holds the media sheet 2 to the respective
first media transport 40, rotatable member 50, or second media
transport 60, and in the second state the attractive force holding
the media sheet 2 is removed, thereby passively releasing media
sheet 2 from being held to rotatable member 50. In some
embodiments, at least one of the first media transport force
mechanism 70, rotatable member force mechanism 72 and second media
transport force mechanism 74 provides a repelling force in the
second state. For example, in some embodiments, the rotatable
member force mechanism 72 includes a vacuum source that applies an
attractive force by providing suction at vacuum holes 57 in the
first state, and an air source for blowing air through vacuum holes
57 onto the second side 3 of media sheet 2 in the second state,
thereby actively releasing media sheet 2 from being held to
rotatable member 50.
[0054] Alternatively, one or more of the first media transport
force mechanism 70, rotatable member force mechanism 72 and second
media transport force mechanism 74 can provide an electrostatic
hold down force. FIG. 4A shows a belt 76 having an electrically
insulating surface. A belt charging roller 77 is provided a high
voltage by voltage source 81 and applies a charge to the
electrically insulating surface of belt 76. A sheet charging roller
78 is provided a high voltage of the opposite polarity by voltage
source 82 to charge the media sheet 2 with an opposite charge, so
that the media sheet 2 is attracted to the belt 76, thereby
providing the first state. A discharging roller 79 is connected to
ground and bleeds charge off at least one of the belt 76 and the
media sheet 2, thereby removing the attractive force and providing
the second state.
[0055] FIG. 4B shows another embodiment of an electrostatic hold
down belt system where non-contact corona units are used for
supplying the charge (to provide the first state) and for
neutralizing the charge (to provide the second state). Belt 86 has
an electrically insulating surface. At least one corona charging
unit 89 includes a wire 83 that is provided a high DC voltage by DC
voltage source 87. Typically, a shield 84 partially surrounds the
wire 83 but is open where the corona charging unit 89 faces belt
86. The high voltage causes ionization and charged particles
(electrons or ions) are showered onto the belt 86 or the media
sheet 2 to provide the attractive force. Optionally a grid (not
shown) between wire 83 and belt 86 can be used to control the rate
of flow of charge from the corona charging unit 89. A corona
discharging unit 85 is provided a high AC voltage by an AC voltage
source 88. Charges of both signs are directed toward at least one
of the media sheet 2 and the belt 86. Charges of the same polarity
as the charge on the media sheet 2 or the belt 86 are repelled,
while opposite polarity charges are attracted, thereby at least
partially neutralizing the charge and removing the attractive
force.
[0056] In the embodiments described above, rotatable member 50 is a
belt system. FIG. 5 shows an exploded perspective of a media
inverter 30 similar to that of FIGS. 2A-2E, but where the rotatable
member 50 is a drum 96 having a drum axis 97. The drum 96 rotates
about the drum axis 97 in a rotation direction 98 to invert media
sheet 2 from its orientation at first transfer position 48 to an
opposite orientation at the second transfer position 59.
[0057] Cut-sheet printing system 100 described above with reference
to FIG. 1 has a media inverter 30 between first printing module 10
and second printing module 20. Such a printing system is
advantageous for very high printing throughput. Referring to FIG.
6, there is shown a simplified side view of a portion of cut-sheet
printing system 200 according to an alternate configuration. In
this case, the cut-sheet printing system 200 includes a printing
module 110 having printing stations 114. The media sheet 2 enters
the printing module 110 along an initial media transport path 140
at input 111, and exits at output 112. A media inverter 130 is
provided for inverting a media sheet 2 and returning it to input
111 of printing module 110. Such a printing system is still capable
of high printing throughput but has further advantages of lower
cost and smaller overall size.
[0058] For clarity, the original orientation of media sheet 2 at
input 111 of printing module 110 is not shown in FIG. 6 as it
enters printing module 110 in entry direction 105, but (similar to
FIG. 1) it is the same as the orientation at output 112 after
second side 3 of media sheet 2 has been printed on by printing
stations 114, such that first side 4 faces down, second side 3
faces up and leading edge 5 is the most downstream edge.
[0059] Media sheet 2 enters the media inverter 130 along first
media transport path 145 in first direction 115 and exits the media
inverter 130 along second media transport path 165 in a second
direction 125, which is opposite the first direction 115. Media
inverter 130 inverts the media sheet 2 such that at its exit onto
second media transport path 165, the second side 3 still faces up
and first side 4 still faces down. However, the orientation of the
leading edge 5 has been inverted so that it is still the most
downstream edge, even though media sheet 2 is traveling in the
opposite direction.
[0060] FIGS. 7A-7B show an exploded perspective of a media inverter
130 of the type described above relative to FIG. 6 according to an
exemplary embodiment. In this configuration, second media transport
160 includes belt strips 166 that travel around a rollers 161, 162
having roller axes 163. In an exemplary embodiment, the belt strips
166 include vacuum holes 167 for providing a vacuum force supplied
by second media transport force mechanism 74. Media sheet 2 is
transferred from the rotatable member 50 to the underside of lower
belt portion 166b at second transfer position 59 in similar fashion
as described above with reference to FIG. 2D. However, in this
embodiment, the media sheet 2 is initially advanced along in an
initial direction 124 (which is the same as the first direction
115) toward roller 162. The media sheet 2 is then rotated around
the roller 162 thereby bringing the media sheet to the top of the
second media transport 160 so that the first side 4 of media sheet
2 is held to the top side of upper belt portion 166a with second
side 3 facing up as shown in FIG. 7B. The media sheet 2 is then
carried by the second media transport 160 in a second direction
125, which is reversed relative to the first direction 115.
[0061] With reference again to FIG. 6, as the media sheet 2 exits
the media inverter 130, it is advanced along a second media
transport path 165, with the first side 4 of media sheet 2 being
held to the upper side of upper belt portion 166a. The media sheet
2 is carried around first turn roller 191 and then travels in a
return direction 195 toward second turn roller 192. After turning
around the second turn roller 192, the first side 4 of media sheet
2 is now held to the underside of lower belt portion 166b, with the
leading edge 5 continuing to be the most downstream edge. At this
point, the media sheet 2 is advancing again in the original entry
direction 105. By switching off the holding force (at least
locally) for lower belt portion 166b, the media sheet 2 is released
and is transferred to the initial media transport path 140, where
it enters input 111 of printing module 110 for a second time, this
time with the second side 4 facing upward for printing on by the
printing stations 114. In this way, a compact system is provided
where a single printing module 110 is used to print on both sides
of the media sheet 2. The belt continues around third turn roller
193 and fourth turn roller 194, and returns to the media inverter
130.
[0062] FIGS. 8A-8B show exploded perspectives of a portion of a
media inverter 230 having increased throughput according to another
exemplary embodiment. In this configuration, a first media
transport 240 includes four belt strips, the upper belt portions
46a of which are shown carrying a first media sheet 2a and a second
media sheet 2b adjacent one another in a tandem arrangement. As in
the embodiment of FIGS. 2A-2E, the first side 4 of first media
sheet 2a and second media sheet 2b is in contact with upper belt
portions 46a of the belt strips. Rotatable member 250 includes a
first set of belt strips 156 that travel around first roller 251
and second roller 252, as well as a second set of belt strips 256
that travel around third roller 253 and fourth roller 254. The
first set of belt strips 156 are spaced apart from the second set
of belt strips 256 such that the media sheets 2a, 2b can be
transferred to rotatable member 250 and inverted at the same time
as shown in FIG. 8B. As the media sheets 2a, 2b are carried around
the rotatable member 250, the second side 3 of first media sheet 2a
is in contact with belt strips 156 and the second side 3 of second
media sheet 2b is in contact with belt strips 256. First media
sheet 2a is turned over by travelling around first roller 251 in
rotation direction 58, while second media sheet 2b is turned over
by travelling around third roller 253 in rotation direction 58. The
second media transport of media inverter 230 is not shown, but can
also have four belt strips, for example, similar to first media
transport 240. Other details of the media inversion process are
similar to that described earlier with respect to FIGS. 2A-2E.
[0063] The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
PARTS LIST
[0064] 2 media sheet [0065] 2a first media sheet [0066] 2b second
media sheet [0067] 3 second side [0068] 4 first side [0069] 5
leading edge [0070] 10 first printing module [0071] 11 input [0072]
12 output [0073] 14 printing stations [0074] 15 first direction
[0075] 20 second printing module [0076] 21 input [0077] 24 printing
stations [0078] 25 second direction [0079] 30 media inverter [0080]
40 first media transport [0081] 41 roller [0082] 42 roller [0083]
43 roller axis [0084] 45 media transport path [0085] 46 belt strips
[0086] 46a upper belt portion [0087] 46b lower belt portion [0088]
47 vacuum holes [0089] 48 first transfer position [0090] 50
rotatable member [0091] 51 roller [0092] 52 roller [0093] 53 roller
axis [0094] 54 rotation axis [0095] 55a upper belt portion
direction [0096] 55b lower belt portion direction [0097] 56 belt
strips [0098] 56a upper belt portion (rotatable member) [0099] 56b
lower belt portion (rotatable member) [0100] 57 vacuum holes [0101]
58 rotation direction [0102] 59 second transfer position [0103] 60
second media transport [0104] 61 roller [0105] 62 roller [0106] 63
roller axis [0107] 65 media transport path [0108] 66 belt strips
[0109] 66a upper belt portion [0110] 66b lower belt portion [0111]
67 vacuum holes [0112] 70 first media transport force mechanism
[0113] 71 force transfer element [0114] 72 rotatable member force
mechanism [0115] 73 force transfer element [0116] 74 second media
transport force mechanism [0117] 75 force transfer element [0118]
76 belt [0119] 77 belt charging roller [0120] 78 sheet charging
roller [0121] 79 discharging roller [0122] 80 controller [0123] 81
voltage source [0124] 82 voltage source [0125] 83 wire [0126] 84
shield [0127] 85 corona discharging unit [0128] 86 belt [0129] 87
DC voltage source [0130] 88 AC voltage source [0131] 89 corona
charging unit [0132] 90 sensor [0133] 92 sensor [0134] 95 belt
strips [0135] 96 drum [0136] 97 drum axis [0137] 98 rotation
direction [0138] 100 cut-sheet printing system [0139] 105 entry
direction [0140] 110 printing module [0141] 111 input [0142] 112
output [0143] 114 printing stations [0144] 115 first direction
[0145] 124 initial direction [0146] 125 second direction [0147] 130
media inverter [0148] 140 initial media transport path [0149] 145
first media transport path [0150] 156a belt strips [0151] 156b belt
strips [0152] 160 second media transport [0153] 161 roller [0154]
162 roller [0155] 163 roller axis [0156] 165 second media transport
path [0157] 166 belt strips [0158] 166a upper belt portion [0159]
166b lower belt portion [0160] 167 vacuum hole [0161] 191 first
turn roller [0162] 192 second turn roller [0163] 193 third turn
roller [0164] 194 fourth turn roller [0165] 195 return direction
[0166] 200 cut-sheet printing system [0167] 230 media inverter
[0168] 240 first media transport [0169] 250 rotatable member [0170]
251 roller [0171] 252 roller [0172] 253 roller [0173] 254 roller
[0174] 256 belt strips [0175] d.sub.1 first separation distance
[0176] d.sub.2 second separation distance
* * * * *