U.S. patent application number 16/570208 was filed with the patent office on 2020-01-02 for vacuum within a pallet conveyor for a printing system.
The applicant listed for this patent is HP SCITEX LTD.. Invention is credited to Itshak Bushmits, Yaron Dekel, Yuval Dim, Alex Veis.
Application Number | 20200002118 16/570208 |
Document ID | / |
Family ID | 57218781 |
Filed Date | 2020-01-02 |
United States Patent
Application |
20200002118 |
Kind Code |
A1 |
Dekel; Yaron ; et
al. |
January 2, 2020 |
VACUUM WITHIN A PALLET CONVEYOR FOR A PRINTING SYSTEM
Abstract
In one example, a pallet conveyor for a printing system is
described, having a track, a pallet to support a print substrate
and move on the track, and a vacuum mechanism to selectively apply
a vacuum at the pallet. A boundary of the vacuum applied at the
pallet is synchronised with an edge of the print substrate.
Inventors: |
Dekel; Yaron; (Gan -
Yeoshaya, IL) ; Dim; Yuval; (Moshav Haniel, IL)
; Bushmits; Itshak; (Netanya, IL) ; Veis;
Alex; (Kadima, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HP SCITEX LTD. |
Netanya |
|
IL |
|
|
Family ID: |
57218781 |
Appl. No.: |
16/570208 |
Filed: |
September 13, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15681718 |
Aug 21, 2017 |
10450159 |
|
|
16570208 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 2406/3223 20130101;
B65H 2406/3222 20130101; B65H 2801/21 20130101; B41J 11/06
20130101; B41J 11/0085 20130101; B41J 11/007 20130101; B65H 29/242
20130101 |
International
Class: |
B65H 29/24 20060101
B65H029/24; B41J 11/00 20060101 B41J011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2016 |
EP |
16196632.0 |
Claims
1-9. (canceled)
10. A printing system comprising: a printing mechanism defining a
print zone to apply printing fluid to a print substrate; a conveyor
comprising: a track; a plurality of pallets operably coupled to and
conveyable on the track through the print zone, to support the
print substrate through the print zone as the pallets are conveyed
on the track; and a vacuum mechanism to selectively apply a vacuum
at the pallets, such that a boundary of the vacuum applied at the
pallets is synchronised with an edge of the print substrate.
11. The printing system according to claim 10, wherein the vacuum
mechanism comprises a plurality of elongate vacuum chambers spaced
orthogonally to a conveyance direction of the pallets, each
parallel to the conveyance direction, and connected to a first
valve and a second valve for communicating vacuum to the elongate
vacuum chamber.
12. The printing system according to claim 11, wherein each
elongate vacuum chamber comprises a piston defining: a first
partition of the elongate vacuum chamber coupled to the first
valve; and a second partition of the elongate vacuum chamber
coupled to the second valve; wherein the piston is moveable
longitudinally within the elongate vacuum chamber to vary the
boundary of the vacuum applied when either of the first valve and
the second valve is open and the other is closed.
13. The printing system according to claim 11, comprising a
plurality of pulleys driveable by a rotatable shaft to synchronise
each piston, wherein each pulley comprises a belt extending a
length of the elongate vacuum chamber that is moveable about the
pulley, and wherein each piston is fixably coupled to a respective
belt.
14-15. (canceled)
16. The printing system according to claim 10, wherein the conveyor
comprises a plurality of sliders operably coupling the pallets to
the track to convey the pallets on the track through the print
zone.
17. The printing system of claim 11, wherein the conveyor comprises
a plurality of sliders operably coupling the pallets to the track
to convey the pallets on the track through the print zone, each
slider slidable along the vacuum mechanism and each slider having
an inlet to communicate vacuum from an aperture in the elongate
vacuum chambers to the pallets in the print zone.
18. The printing system according to claim 10, wherein the track
comprises an endless track, the pallets operably coupled to and
conveyable around the endless track.
19. A printing system comprising: a printing mechanism defining a
print zone to apply printing fluid to a print substrate; a track; a
pallet to move on the track to support the print substrate as the
pallet passes through the print zone; a slider to operably couple
the pallet and the track to convey the pallets on the track through
the print zone; and a vacuum mechanism to selectively apply a
vacuum at the pallet, such that a boundary of the vacuum applied at
the pallet is synchronised with an edge of the print substrate.
20. The printing system according to claim 19, wherein the vacuum
mechanism comprises an elongate vacuum chamber arranged parallel to
a conveyance direction of the pallet, and connected to a first
valve and a second valve for supplying vacuum to the elongate
vacuum chamber.
21. The printing system according to claim 20, wherein the vacuum
mechanism comprises a moveable surface arranged within, and
moveable along a length of, the elongate vacuum chamber, such that
the moveable surface defines the boundary of the vacuum applied
when one of the first valve and the second valve is open and the
other is closed.
22. The printing system according to claim 20, wherein the slider
is slidable along the vacuum mechanism, and comprising an inlet to
communicate the vacuum from an aperture in the elongate vacuum
chamber to the pallet.
23. The printing system according to claim 22, wherein the slider
comprises hinged slidable elements, the slidable elements extending
in a conveyance direction and having a hinged axis perpendicular to
the conveyance direction.
24. The printing system according to claim 20, wherein the elongate
vacuum chamber is one of a plurality of elongate vacuum chambers
arranged substantially parallel to one another, and wherein the
pallet comprises internal sections, each internal section in
communication with each of the plurality of elongate vacuum
chambers.
25. The printing system according to claim 20, wherein the vacuum
mechanism comprises a rotatable tube arranged within the elongate
vacuum chamber, the rotatable tube comprising openings regularly
spaced along a length of a surface the rotatable tube.
26. The printing system according to claim 25, wherein: each of the
openings is circumferentially transposed with respect to a
preceding opening; and a surface of the elongate vacuum chamber
comprises regularly spaced apertures, such that rotation of the
rotatable tube varies alignment between the openings in the surface
of the rotatable tube and the apertures in the surface of the
elongate vacuum chamber to define the boundary of the vacuum.
27. The printing system according to claim 19, wherein the track is
an endless track and the pallet circulates on the track.
28. The printing system according to claim 19, wherein the pallet
comprises a train pallet.
29. The printing system according to claim 19, wherein the pallet
comprises a wagon pallet.
Description
BACKGROUND
[0001] Pallet conveyors for printers may be arranged to convey
pallets on a track in a printing system. The track may be an
endless track. The pallets support and move print media during
printing. The pallets may support the print media as it passes
through a print zone of the printer. The pallets may include a
driving mechanism, such as an electromagnetic element or magnetic
responsive material, so that the velocity of individual pallets may
be controlled as they move on the track. A vacuum may be generated
to apply a pressure gradient to the print media through a pallet.
The vacuum may be used to draw and removably secure the print media
to a surface of the pallet during printing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Various features and advantages of the present disclosure
will be apparent from the detailed description which follows, taken
in conjunction with the accompanying drawings, which together
illustrate, by way of example, features of the present disclosure,
and wherein:
[0003] FIG. 1 is a side view schematically illustrating a pallet
conveyor for a printing system according to an example;
[0004] FIG. 2 is a top-down view schematically illustrating a
pallet conveyor for a printing system according to an example;
[0005] FIG. 3a is a schematic illustration showing a top-down
cutaway view of a vacuum mechanism for a pallet conveyor according
to an example;
[0006] FIG. 3b is a schematic illustration showing a side-on
cutaway view of the vacuum mechanism of FIG. 3a;
[0007] FIG. 4 is a schematic illustration showing a perspective
view of a vacuum mechanism for a pallet conveyor according to an
example;
[0008] FIG. 5 is a schematic illustration showing a top-down view
of a vacuum mechanism for a pallet conveyor according to an
example; and
[0009] FIG. 6 is a flow diagram showing a method of conveying
pallets in a printing system according to an example.
DETAILED DESCRIPTION
[0010] Certain examples described herein relate to printing systems
with pallets to convey print media. These pallets comprise moveable
platforms or surfaces that support a supplied print media. A sheet
of print media may rest on top of a pallet or train of pallets and
be driven through a print zone. In the print zone, printing fluid
may be applied, e.g. using inkjet print-heads mounted above the
pallet conveyor. In certain systems, a vacuum mechanism may be used
to secure the print media to the pallets via suction, e.g. by
maintaining a low pressure chamber underneath the pallet conveyor
that draws air at an ambient pressure above the pallet conveyor. In
these systems, there may be leakage of the vacuum. At the beginning
or end of a printing operation, most of the vacuum mechanism may be
exposed to the atmosphere, e.g, a large proportion of conduits to a
low pressure chamber forming part of the vacuum mechanism may be
exposed rather than covered by a sheet of print media. This can
cause vacuum to leak and vacuum pressure in the vacuum mechanism to
drop, e.g. due to the inflow of higher pressure air from the
atmosphere. For example, when sheets of print media are conveyed on
pallets in a conveyance direction through the print zone, the
vacuum mechanism may be substantially covered by the print media.
Thus, there may be minimal leakage. However, when a first sheet of
print media is loaded and conveyed by the pallets through the print
zone, the vacuum mechanism ahead of the first sheet (in the
conveyance direction) may be exposed to atmosphere. Similarly, when
a last sheet of print media is exiting the print zone, the vacuum
mechanism behind the last sheet may be open to atmosphere, again
causing vacuum leakage.
[0011] Certain examples described herein act to reduce vacuum
leakage during operation of a printing system utilising a pallet
conveyor. In these examples, the vacuum mechanism is constructed to
selectively apply a vacuum or negative pressure at the pallets. The
application of the vacuum is controlled such that a boundary of the
vacuum applied at the pallet is synchronised with an edge of a
print substrate, e.g. a sheet or section of print media.
[0012] In certain examples, the edge of the print substrate may be
a leading edge of the print substrate, for example a leading edge
of a first sheet of print media. In other examples, the edge of the
print substrate is a trailing edge of the print substrate, for
example a trailing edge of a last sheet of print media. In some
examples, the boundary of the vacuum may be synchronised at both
the leading and trailing edge of the print substrate, e.g. for a
set of sheets of print media. The print substrate may comprise a
single sheet of print media or multiple sheets.
[0013] In these examples, the vacuum mechanism may comprise an
elongate vacuum chamber arranged parallel to the conveyance
direction of the pallets. The pallets may be conveyed above and
along the vacuum chamber, with vacuum or low pressure supplied to
(or generated within) the vacuum chamber. The vacuum may be
communicated to the print substrate via the pallets, e.g. through
apertures or inlets in the chamber and pallets. In certain cases,
suction cups on a surface of the pallets may act as conduits to the
vacuum chamber.
[0014] In certain examples, the elongate vacuum chamber may be
partitioned into a plurality of sub-chambers, each sub-chamber
having a vacuum supply via a valve connecting the chamber to a
vacuum source. Prior to loading print media into the printing
system, all valves are closed and no vacuum is supplied to the
sub-chambers. After a first sheet of print media is loaded, and as
it is conveyed along the elongate vacuum chamber, a vacuum
sub-chamber immediately ahead of a leading edge of the first sheet
may be activated by opening the corresponding valve. During
conveyance of a last sheet of print media through the printing
system, a vacuum sub-chamber immediately behind the last sheet may
be disengaged from its vacuum supply after the trailing edge of the
last sheet has passed the sub-chamber by closing the corresponding
valve. In these examples, some vacuum leakage may occur, limited to
a surface area of a single vacuum sub-chamber. A vacuum source may
be powerful enough to keep the vacuum pressure constant with this
amount of leakage.
[0015] In other examples, vacuum leakage may be reduced by a vacuum
mechanism to selectively apply vacuum at the pallets in a more
continuous manner. For instance, in these examples, the vacuum
boundary may be controllably positioned within the vacuum
mechanism.
[0016] Certain examples will now be described with reference to the
Figures.
[0017] FIG. 1 is a side view schematically illustrating a pallet
conveyor 110 for a printing system 100 according to an example. The
pallet conveyor 110 comprises a track 115 and a pallet 120. The
pallet 120 is arranged to support a print substrate 125 and move on
the track 115. The pallet conveyor 110 also comprises a vacuum
mechanism 130 to selectively apply a vacuum at the pallet 120, such
that a boundary of the vacuum applied at the pallet 120 is
synchronised with an edge of the print substrate 125. The print
substrate 125 may comprise one sheet of media for printing, for
example, or multiple sheets that are conveyed by the pallet
conveyor 110. The edge of the print substrate may be a leading edge
of the first sheet of print substrate 125 in one example, or may be
a trailing edge of the same or another succeeding sheet of print
substrate 125 in another example.
[0018] In the example shown in FIG. 1, the pallet 120 is a train
pallet which may tow a wagon pallet 122. As used herein, "train
pallet" means an active pallet bearing at least part of the driving
mechanism of the train-and-wagon configuration and "wagon pallet"
means a passive pallet dragged or towed by a train pallet either
directly or indirectly. The train and wagon pallets 120, 122 may
support the print substrate 125. In the example of FIG. 1, the
train pallet 120 tows only one wagon pallet 122, however, the
number of wagon pallets may vary in implementations. A train pallet
may tow a wagon pallet configuration that may comprise a single
wagon pallet or a plurality of wagon pallets coupled between them
in a successive manner. The number of wagon pallets in a wagon
pallet configuration may be limited by a size or power of a driving
mechanism 121 of the train pallet. As the number of wagon pallets
in a wagon pallet configuration increases the train-and-wagon
configuration may become more flexible. Accordingly, a wagon pallet
configuration with fewer pallets may require a train pallet with
smaller driving mechanism parts, such as motors.
[0019] The train pallet 120 may be the leading pallet of the
train-and-wagon configuration and the wagon pallet 122 may be the
leading pallet of the wagon pallet configuration. In the example of
FIG. 1, as there is only one wagon pallet in the wagon pallet
configuration, the wagon pallet 122 is also the last pallet of the
train-and-wagon configuration. A coupling 123 may maintain the
distance between the two pallets substantially constant as the
pallets are conveyed on the track 115. In certain cases, the
distance maintained by the coupling 123 may be such that no print
substrate 125 may be trapped between the pallets 120, 122. The
train pallet 122 may comprise at least part of the driving
mechanism 121 that provides the motive power to the train-and-wagon
configuration and may be operably coupled with the track 115. The
driving mechanism 121 may comprise at least part of a motor,
drivers, controllers and encoder heads. The track 115 may be an
endless track. The wagon pallet 122 may be merely dragged by the
train pallet 120 along the endless track and may not be
individually controlled. The pallet conveyor 110 may include
multiple train-and-wagon configurations, as shown in the example of
FIG. 1. A wagon pallet may be directly dragged by a train pallet
when it is directly coupled to a train pallet. However, a wagon
pallet may form part of a wagon pallet configuration, i.e. a series
of wagon pallets coupled together. In such a scenario, a particular
wagon pallet may be indirectly dragged by a train pallet when it
belongs to a wagon pallet configuration that is being dragged by a
train pallet even though the particular wagon pallet is not
directly coupled to the train pallet.
[0020] In the example of FIG. 1, the vacuum mechanism 130 comprises
an elongate vacuum chamber 135 arranged parallel to a conveyance
direction 140 of the pallet 120. The elongate vacuum chamber 135
may be connected to a first valve 145 and a second valve 147 for
supplying vacuum to the elongate vacuum chamber (the vacuum supply
via the first and second valves 145, 147 is labelled V in FIG. 1).
The first and second valves 145, 147 may control a supply of
vacuum, or negative pressure, to the elongate vacuum chamber 135
from a vacuum source (not shown in FIG. 1). For example, when one
of the first and second valves 145, 147 is open, a vacuum may be
applied from the vacuum source to the elongate vacuum chamber 135
by that valve. Similarly, when one of the first and second valves
145, 147 is closed, vacuum may not be applied to, i.e. it is
blocked from, the elongate vacuum chamber 135 by that valve.
[0021] In one case, the vacuum mechanism 130 comprises a moveable
surface 150 arranged within, and moveable along the length of, the
elongate vacuum chamber 135, such that the moveable surface 150
defines the boundary of the vacuum applied when one of the first
valve 145 and the second valve is open 147 and the other is closed.
The moveable surface 150 may, in one example, comprise a piston to
move longitudinally within the elongate vacuum chamber 135. The
moveable surface 150 may partition the elongate vacuum chamber 135
into two sub-chambers, with the moveable surface 150 being a
boundary between the two sub-chambers. Thus, in an example where
one of the sub-chambers is coupled to the first valve 145, and the
other is coupled to the second valve 147, the moveable surface 150
may be the boundary of the vacuum applied when one of the first
valve 145 and the second valve is open 147 and the other is closed.
An example of a mechanism for the moveable surface 150 moving along
the length of the elongate vacuum chamber 135 is described below
with reference to FIG. 3.
[0022] In one case, synchronisation of the boundary of the vacuum
applied at the pallet 120 and the edge of the print substrate 125
may be via an optical detector to detect a position and velocity of
the edge and feedback to a controller to control the moveable
surface 150 accordingly. For example, the moveable surface 150 may
be synchronised with the leading edge of the print substrate such
that it moves ahead of the leading edge by a small amount, e.g. by
a proportion of the length of the pallet or print substrate.
[0023] In the example of FIG. 1, the pallet 120 comprises a slider
155 to operably couple the pallet 120 and the track 115. The slider
may be slidable along the vacuum mechanism 130, for example along
the elongate vacuum chamber 135. The slider 155 may, in one case,
comprise an inlet to communicate the vacuum from an aperture in the
elongate vacuum chamber 135 to the pallet 120. In this case, the
elongate vacuum chamber 135 may comprise one or more apertures
along a surface facing the pallet 120. A vacuum in a portion or
sub-chamber of the elongate vacuum chamber 135 may therefore be
applied from the elongate vacuum chamber 135 via the one or ore
apertures, for example. The size of the inlet in the slider 155 may
be very small relative to a surface area of the pallet 120 for
drawing the print substrate 125 towards the pallet 120.
[0024] In one case, the slider 155 has hinged slidable elements, or
runners, for example two runners hinged together as shown in FIG.
1. The elements may extend in the conveyance direction 140 and may
have a hinged axis, i.e. an axis about which the elements hinge,
perpendicular to the conveyance direction. The hinged axis may also
be in the same plane as the conveyance direction 140, in one
example. The inlet in the slider 155 may, for example, comprise a
slit along a length of one or more of the hinged slidable elements
or runners. Each slider 155 may run within a suitable channel. The
channel may form part of the track 115 and may act to slidably
couple the pallet to the track 115. In certain examples, the track
115 is an endless track, and the pallet 120 circulates on the track
115.
[0025] The printing system 100 shown in FIG. 1 comprises a printing
mechanism 102 defining a print zone to apply printing fluid to a
print substrate 125. In one case, the printing mechanism 102 may
include printing fluid supplies 104, for example ink supplies, for
supplying printing fluid to a print-head assembly 106. The
print-head assembly 106 may include an arrangement of print-heads
for dispensing printing fluid on to a sheet or continuous web of
paper or other print substrate 125. The print-head assembly 106 may
be stationary with an array of print-heads that may span the
maximum width of the print substrate 125, or may be a carriage
mounted to scan the print-head(s) back and forth across print
substrate 125. The print-head assembly 106 may be positioned in the
print zone to print onto the print substrate 125 carried by the
pallet 120 in the print zone.
[0026] In certain cases, the vacuum mechanism 130 may comprise a
plurality of elongate vacuum chambers 135 spaced orthogonally to
the conveyance direction 140 of the pallets 120, 122, with each one
arranged parallel to the conveyance direction 140. Each of the
plurality of elongate vacuum chambers 135 may be an implementation
of the example elongate vacuum chambers 135 herein described, and
may be connected to a first valve and a second valve for
communicating vacuum to the respective elongate vacuum chamber 135.
In certain examples, each elongate vacuum chamber 135 may comprises
a moveable surface defining a first partition of the elongate
vacuum chamber 135 coupled to the first valve 145, and a second
partition of the elongate vacuum chamber 135 coupled to the second
valve 147. The moveable surface 150 may be moveable longitudinally
within the elongate vacuum chamber 135 to vary the boundary of the
vacuum applied when either of the first valve 145 and the second
valve 147 is open and the other is closed.
[0027] In certain examples, the printing system 100 may comprise a
plurality of pulleys driveable by a rotatable shaft to synchronise
each moveable surface 150, wherein each pulley comprises a belt
extending the length of the elongate vacuum chamber 135 that is
moveable about the pulley, and wherein each moveable surface 150
comprises a piston fixably coupled to a respective belt. This
mechanism for moving each moveable surface 150 of the vacuum
mechanism 130 is described in more detail below with reference to
FIGS. 3a and 3b. Features in FIGS. 3a and 3b that may correspond,
in certain cases, to a feature in FIG. 1 are referenced by their
numeral in FIG. 1 incremented by 200.
[0028] FIG. 2 is a top-down view schematically illustrating a
pallet conveyor 210 for a printing system according to an example.
Pallet conveyor 210 comprises a track 215a, 215b and a pallet 220
to support a print substrate (not shown). The pallet 220 moves on
the track 215a, 215b, The pallet conveyor 210 also comprises a
vacuum mechanism 230 to selectively apply a vacuum at the pallet
220, such that a boundary of the vacuum applied at the pallet 220
is synchronised with an edge of the print substrate. The edge of
the print substrate may be a leading edge of the first sheet of
print substrate in one example, or may be a trailing edge of the
same or another succeeding sheet of print substrate in another
example.
[0029] In the example shown in FIG. 2, the pallet 220 is a train
pallet which may tow a wagon pallet 222 in a conveyance direction
240. A coupling 223 may couple the pallets 220, 222 and may, in
certain cases, maintain the distance between the two pallets 220,
222 substantially constant as the pallets are conveyed on the track
215a, 215b. The train pallet 220 may provide the motive power and
may be operably coupled with the track 215a, 215b. The train pallet
220 and the track 215a, 215b may be operably coupled together via a
first portion 221a disposed on the train pallet 220 and a second
portion 221b disposed along a length of the track 215a, 215b. One
of the respective first and second portions 221a, 221b may comprise
an electromagnetic element and the other of the respective first
and second portions 221a, 221b may comprise a magnetically
responsive material. For example, the train pallet may comprise at
least part of a driving mechanism, such as a coil motor 221a on one
or both sides, as shown in FIG. 2. The track may be equipped with
the rest of the driving mechanism in the form of a plurality of
magnets 221b along the sides of the track 215a, 215b, The train
pallets 220 may also comprise encoders to provide feedback
controls. The wagon pallet 222 may be dragged by the train pallet
220 along the track 215a, 215b and may not be individually
controlled. Accordingly, a train-and-wagon configuration may
comprise the train pallet 220 coupled to the wagon pallet 222 with
one or more couplings 223, and coil motors 221a on the sides of the
train pallet 232.
[0030] The pallet conveyor 210 may, in certain examples, also
comprise a central controller to individually control the velocity
of each train-and-wagon configuration along the track 215a, 215b by
controlling the velocity of each train pallet 220. The central
controller may communicate wirelessly with the train pallet
controllers and transfer any motion control signals. Electricity
may be transferred via sliding brushes. This described driving
mechanism is provided as one example. One skilled in the art may
appreciate that any other driving mechanism may be used to drive
the train pallets.
[0031] In one example, the vacuum mechanism 230 comprises a
plurality of elongate vacuum chambers 235 arranged substantially
parallel to one another as shown in FIG. 2. The plurality of
elongate vacuum chambers 235 may in certain cases be arranged
substantially parallel to the conveyance direction 240 and may be
spaced orthogonally to the conveyance direction 240, as shown in
FIG. 2.
[0032] In certain examples, each of the plurality of elongate
vacuum chambers 235 may be an implementation of the elongate vacuum
chamber 135 described with reference to FIG. 1. For example, each
elongate vacuum chamber 235 may comprise a first valve and a second
valve, separated longitudinally from one another along a length of
the respective elongate vacuum chamber 235.
[0033] In one case, each elongate vacuum chamber 235 comprises an
aperture 260 along a surface facing the pallets 220, 222. A vacuum
in a portion or sub-chamber of the elongate vacuum chamber 235 may
therefore be applied from the elongate vacuum chamber 235 via the
aperture 260, for example. In this case, shown in FIG. 2, each
elongate vacuum chamber 235 comprises one aperture 260, however, in
other cases each elongate vacuum chamber 235 may have a plurality
of apertures. Vacuum, or negative pressure (as compared to an
atmospheric pressure), present in each elongate vacuum chamber 235
may therefore be communicated with the pallets 220, 222 via the
aperture 260. Vacuum conduits comprised within the pallets 220, 222
may draw and removably secure the print substrate, for example a
print media, against and relative to a top surface (facing the
print substrate) of the pallets 220, 222. In one example, the
pallets 220, 222 may comprise cups 265 on the top surface, e.g, at
a conduit mouth or exit, for contacting the print substrate and
communicating the vacuum to a surface of the print substrate to
draw and removably secure the print substrate to the respective
pallet 220, 222. The cups 265 may allow print substrate such as
warped boards or corrugated sheets to be drawn to the pallet 220,
222 with less vacuum leakage compared to a flat surface of the
pallet 220, 222 with apertures therein for applying the vacuum.
[0034] In certain examples, the pallets 220, 222 may each comprise
a slider to slide along the surface of the vacuum mechanism 230: in
one case the slider may be an implementation of the slider 155
described with reference to FIG. 1. In this case, vacuum may be
communicated from each elongate vacuum chamber 235 to the pallets
220, 222 via an inlet in the slider. For example, the surface of
the elongate vacuum chamber 235 may comprise a channel within which
the slider slides. The channel and slider may comprise apertures to
fluidicly couple conduits within the pallet to the vacuum chamber
235.
[0035] Each pallet 220, 222 may, in one case, comprise internal
sections, as shown in FIG. 2 by the dotted lines subdividing each
pallet 220, 222 orthogonally to the conveyance direction 240. Each
internal section may be in communication with each of the plurality
of elongate vacuum chambers 235, as shown in FIG. 2: each internal
section of the pallet 220, 222 may be aligned with one of the
elongate vacuum chambers 235. Thus, in this case, vacuum may be
selectively applied to the plurality of elongate vacuum chambers
235 via the valves coupled to each elongate vacuum chamber 235. In
turn, vacuum may be selectively applied to the internal sections of
the pallets 220, 222 such that only selected internal sections may
be in communication with the vacuum supply via the plurality of
elongate vacuum chambers 235. This may allow different sized print
media to be conveyed by the pallet conveyor 210, as the width of
the vacuum supply perpendicular to the conveyance direction 240 may
be controlled and selected. Thus, for relatively narrower print
media, selected elongate vacuum chambers 235 may be closed via the
coupled valves such that vacuum is not exposed to outside
atmosphere through the pallets 220, 222.
[0036] In certain examples, the track 215a, 215b is an endless
track, and the pallets 120, 122 circulate on the track 215a,
215b.
[0037] FIG. 3a is a schematic illustration showing a top-down
cutaway view of a vacuum mechanism 330 for a pallet conveyor
according to an example. FIG. 3b is a schematic illustration
showing a side-on cutaway view of the vacuum mechanism of FIG. 3a.
The vacuum mechanism 330 may comprise a plurality of elongate
vacuum chambers 335a, 335b, 335c spaced orthogonally to a
conveyance direction 340 of the pallets (not shown in FIG. 3a). In
certain examples, each of the elongate vacuum chambers 335a, 335b,
335c may be an implementation of the elongate vacuum chamber 135
described with reference to FIG. 1. For example, each elongate
vacuum chamber 335a, 335b, 335c may be parallel to the conveyance
direction 340, and connected to a first valve and a second valve
for communicating vacuum to the respective elongate vacuum chamber
335a, 335b, 335c.
[0038] In certain cases, each elongate vacuum chamber 335a, 335b,
335c comprises a moveable surface or piston 350a, 350b, 350c
defining a first partition of the elongate vacuum chamber coupled
to the first valve and a second partition of the elongate vacuum
chamber coupled to the second valve. The piston 350a, 350b, 350c
may be moveable longitudinally within the respective elongate
vacuum chamber 335a, 335b, 335c to vary the boundary of the vacuum
applied when either of the first valve and the second valve is open
and the other is closed.
[0039] In the example of FIG. 3b, the vacuum mechanism may comprise
a plurality of pulleys, with each pulley 375c associated with one
of the elongate vacuum chambers 335c. Each pulley 375c may be
driveable by a rotatable shaft 380 to synchronise the pistons 350a,
350b, 350c, For example, each pulley 375c may comprise a belt 370c
extending the length of the elongate vacuum chamber 335c, the belt
370c being moveable about the pulley 375c. Each piston 350c may be
fixably coupled to the respective belt 370c. As can be seen in FIG.
3b, in certain cases the belt 370c may extend beyond the length of
the elongate vacuum chamber 335c, and may be arranged about pulleys
at either end of the elongate vacuum chamber 335c. In these cases,
the belt 370c is arranged within the elongate vacuum chamber 335c
along one length and along an underside of the elongate vacuum
chamber 335c along the other length.
[0040] In the example shown in FIG. 3a, driving the rotatable shaft
380 may turn each of the pulleys associated with the elongate
vacuum chambers 335a, 335b, 335c such that the belts 370a, 370b,
370c synchronously move the respective coupled pistons 350a, 350b,
350c along the elongate vacuum chambers 335a, 335b, 335c in the
conveyance direction 340.
[0041] FIG. 4 is a schematic illustration showing a perspective
view of a vacuum mechanism for a pallet conveyor according to an
example. The pallet conveyor may comprise a track, a pallet to
support a print substrate and move on the track, and a vacuum
mechanism, as described in examples herein with reference to the
Figures. The vacuum mechanism selectively applies a vacuum at the
pallet, such that a boundary of the vacuum applied at the pallet is
synchronised with an edge of the print substrate.
[0042] In this example, the vacuum mechanism 430 comprises a
rotatable tube 490 arranged within an elongate vacuum chamber 435.
The rotatable tube 490 may comprise openings 495 regularly spaced
along a length of a surface the rotatable tube, as shown in FIG. 4.
The elongate vacuum chamber 435 may be arranged parallel to a
conveyance direction of a pallet to move on a track of the pallet
conveyor, and may be connected to a first valve and a second valve
for supplying vacuum to the elongate vacuum chamber 435.
[0043] In the example of FIG. 4, each of the openings 495 may be
circumferentially transposed with respect to a preceding opening,
and a surface of the elongate vacuum chamber 435 may comprise
regularly spaced apertures 460. Thus, in this case, rotation of the
rotatable tube 490 varies the alignment between the openings 495 in
the surface of the rotatable tube 490 and the apertures 460 in the
surface of the elongate vacuum chamber 435. This alignment may
define the boundary of the vacuum applied via the elongate vacuum
chamber 435. At a position where an opening 495 in the surface of
the rotatable tube 490 is aligned with an aperture 460 in the
surface of the elongate vacuum chamber 435 (e.g. such that the
opening 495 and aperture 460 overlap), a vacuum supplied to the
rotatable tube 490 may be communicated via the aligned opening 495
and aperture 460, and may be applied at the pallet. At certain
rotational positions of the rotatable tube 490, multiple openings
495 and apertures 460 may be aligned in such a way. The boundary of
the vacuum applied at the pallet may therefore be a position where
an opening 495 and aperture 460 overlap, and an adjacent opening
495 and aperture 460 do not overlap. There may be one or two
boundaries of the vacuum delimited in this way, in some examples.
In one instance, this example vacuum mechanism 430 described with
reference to FIG. 4 may be implemented in place of the previously
described vacuum mechanism 130 described as part of the pallet
conveyor example shown in FIG. 1.
[0044] Rotation of the rotatable tube 490 may advance, in the
conveyance direction of the pallet, the boundary of the vacuum
applied to the pallet via the apertures 460 in the surface of the
elongate vacuum chamber 435. In some cases, this rotation of the
rotatable tube 490 may be synchronised with a leading edge of the
print substrate supported and conveyed by the pallet, such that the
boundary of the vacuum applied at the pallet is synchronised with
the leading edge. For example, the boundary of the vacuum applied
at the pallet may advance ahead of the leading edge of the print
substrate such that minimal or no vacuum is applied to the pallet,
or a top surface of the pallet, where the print substrate is not
supported. This may allow vacuum leakage to be minimised and
improve the efficiency of the vacuum mechanism and pallet conveyor.
In other cases, the rotation of the rotatable tube 490 may be
synchronised with a trailing edge of the print substrate supported
and conveyed by the pallet, such that the boundary of the vacuum
applied at the pallet is synchronised with the trailing edge.
Similarly, the boundary of the vacuum applied at the pallet may
advance slightly behind the trailing edge of the print substrate
such that minimal or no vacuum is applied to the pallet, or a top
surface of the pallet, where the print substrate is not supported,
for example.
[0045] FIG. 5 is a schematic illustration showing a vacuum
mechanism 530 for a pallet conveyor according to an example. In the
example of FIG. 5, the vacuum mechanism 530 comprises a plurality
of elongate vacuum chambers 535a, 535b, 535c arranged substantially
parallel to one another. In one case, the elongate vacuum chambers
535a, 535b, 535c may be spaced orthogonally to a conveyance
direction of pallets conveyed by the pallet conveyor, and each
elongate vacuum chamber 535a, 535b, 535c may be substantially
parallel to the conveyance direction. The elongate vacuum chambers
535a, 535b, 535c may each be connected to a first valve and a
second valve for communicating vacuum to the respective elongate
vacuum chamber 535a, 535b, 535c. In one example, each elongate
vacuum chamber 535a, 535b, 535c may comprise a rotatable tube 590a,
590b, 590c arranged within the respective elongate vacuum chamber
535a, 535b, 535c. The rotatable tubes 590a, 590b, 590c may each
comprise openings 595a, 595b, 595c regularly spaced along a length
of a surface the respective rotatable tube 590a, 590b, 590c, for
example in accordance with the example rotatable tube 490 described
with reference to FIG. 4.
[0046] In one case, the elongate vacuum chambers 535a, 535b, 535c
may be rotatable synchronously, for example by a single driving
mechanism, such that alignments between openings 595a, 595b, 595c
in the surface of the rotatable tubes 590a, 590b, 590c and the
apertures 560a, 560b, 560c in the surface of the respective
elongate vacuum chamber 535a, 535b, 535c vary synchronously. In
this case, a boundary 597 of vacuum applied at a pallet may advance
in the conveyance direction 540, and may be synchronised with an
edge of print substrate supported by the pallet.
[0047] The examples of FIGS. 1-5 show components of a printing
system that enable more efficient transfer of vacuum from a source
to print media with minimal leakage. For example, utilising a
moveable piston or rotatable tube within elongate vacuum chambers
allows for a position of a vacuum boundary in the vacuum chamber to
be moved continuously along the vacuum chamber. Thus, said vacuum
boundary may be synchronised with an edge of print media. In
certain cases, synchronisation may be controlled using an optical
detector to detect the edge of the print substrate and provide
feedback to a controller to control the moveable piston or
rotatable tube. During printing of a first or last sheet of print
media, the vacuum communicating with pallets may therefore be
limited by the vacuum boundary so that vacuum does not leak through
apertures in the vacuum mechanism that are not covered by the sheet
of print media, for example.
[0048] FIG. 6 shows a method 600 of conveying pallets in a printing
system according to an example. The printing system may comprise
one of the printing system examples previously described. At block
610, a moveable surface within an elongate vacuum chamber is
positioned at a first end portion of the elongate vacuum chamber.
The moveable surface and elongate vacuum chamber may be
implementations, respectively, of one of the moveable surfaces (or
pistons) or elongate vacuum chambers previously described with
reference to the examples shown in FIGS. 1-5. At block 620, a first
vacuum valve coupled to the first end portion of the elongate
vacuum chamber is opened. At block 630, a conveyance mechanism
between a track and the pallets is operated to convey the pallets
to support a print substrate along the elongate vacuum chamber. The
conveyance mechanism may correspond to an example conveyance
mechanism previously described with reference to FIGS. 1 and 2, for
instance the driving mechanisms 121, 221a and 221b. At block 640,
the moveable surface within the elongate vacuum chamber is
synchronised with a leading edge of the print substrate. At block
650, a second vacuum valve coupled to a second end portion of the
elongate vacuum chamber is opened upon the leading edge of the
print substrate passing a position of the second vacuum valve.
[0049] In certain examples, the method 600 of conveying pallets in
a printing system may further comprise: resetting the moveable
surface at the first end portion of the elongate vacuum chamber;
closing the first vacuum valve; synchronising the bar with a
trailing edge of the print substrate; and closing the second vacuum
valve upon the trailing edge of the print substrate passing a
position of the second vacuum valve.
[0050] The preceding description has been presented to illustrate
and describe examples of the principles described. This description
is not intended to be exhaustive or to limit these principles to
any precise form disclosed. Many modifications and variations are
possible in light of the above teaching. It is to be understood
that any feature described in relation to any one example may be
used alone, or in combination with other features described, and
may also be used in combination with any features of any other of
the examples, or any combination of any other of the examples.
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