Note: Descriptions are shown in the official language in which they were submitted.
CA 02364401 2001-12-05
INKJET PRINTER WITH NOZZLE MAINTENANCE
SYSTEM RELOCATED BY MEDIA CARRIER
Field of the invention
s The invention pertains to the field of inkjet printing and, in particular,
to the
maintenance of inkjet printheads.
Background of the invention
io Drop-on-demand or continuous-stream inkjet printers, such as thermal,
piezoelectric, acoustic, or phase change wax-based printers, have at least
one printhead from which droplets of ink are directed towards a printing
medium (or substrate). Within such printheads, ink is typically contained in a
plurality of channels. By means of power pulses, droplets of ink are expelled
is as required from orifices or nozzles at the end of these channels. The
mechanisms whereby ink ejection works in these various types of machines
are well established and will not be further discussed herein.
An ink jet printhead may be incorporated into a carriage type printer, a
partial
2o width array type printer, or a page-width type printer. A carriage type
printer
typically has a relatively small printhead containing a number of ink channels
and nozzles. The printhead can be attached to a disposable ink supply
cartridge and the combined printhead and cartridge assembly is attached to a
carriage. The carriage is reciprocated to print one swath of information
(equal
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to the length of a column of nozzles) at a time on a recording medium, which
is typically maintained in a stationary position during the reciprocation.
After
the swath is printed, the paper is stepped a distance equal to the height of
the
printed swath or a portion thereof, so that the next printed swath is
contiguous
or overlapping therewith. Overlapping is often employed to address a variety
of undesirable inkjet printing artifacts that may be traced to nozzle
performance. This procedure is repeated until the entire page is printed.
In contrast, a page-width printer includes a substantially stationary
printhead
io having a length sufficient to print across the width or length of a sheet
of
printing medium at a time. The printing medium is continually moved relative
to the page width printhead in a direction which may be substantially normal
to the printhead length. In most cases, the separation between individual
nozzles is greater than the required dot spacing on the media, and hence the
is media may be passed under the page width printhead more than once in
order to print at the interstitial positions or to address a variety of
undesirable
inkjet printing artifacts that may be traced to nozzle performance.
There is a need to maintain the ink ejecting nozzles of an ink jet printhead.
2o For example, the orifices typically need to be cleaned periodically and/or
the
printhead needs to be capped when the printer is out of use or is idle for an
extended period. The capping of the printhead is aimed at preventing
components of the ink in the printhead from evaporating and preventing
contaminants from entering the printhead or contaminating the nozzle plate.
2s There is sometimes a need to prime a printhead before use. This is done to
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insure that the printhead channels are completely filled with ink and contain
no contaminants or air bubbles. Periodic priming may also be necessary to
maintain proper functioning of the orifices. Maintenance and/or priming
stations for the printheads of various types of ink jet printers are described
for
s example, in U.S. Pat. Nos. 4,855,764, 4,853,717, and 4,746,938.
Various methods and apparatus for maintaining the condition of ink jet
printheads are generally known in the art, as illustrated and described in the
following references.
io
U.S. Pat. No. 5,206,666 to Watanabe et al., describes an ink jet recording
apparatus having a full-line type recording head that is rotated between a
recording position and a non-recording position. A cleaning member contacts
the recording head during rotation of the recording head to remove deposited
is ink or foreign matter. In the non-recording position, the printhead is
capped.
U.S. Pat. No. 5,257,044 to Carlotta et al., describes a cap actuation
mechanism for an inkjet printhead maintenance station in a scanning type ink
jet printer. A cap located on a cap carriage in the maintenance station
2o provides the functions of printhead nozzle capping, priming, cleaning, and
refreshing, as well as waste ink management.
U.S. Pat. No. 5,367,326 to Pond et al., describes a pagewidth ink jet printer
having a movable cleaning/priming station adapted for movement parallel to
2s and along an array of printhead nozzles. The cleaning and priming station
is
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slid along a ledge surface so that the cleaning and priming station is
maintained a fixed distance from the face of the printhead.
A number of proposals suggest the use of media sheets for cleaning and
s maintaining inkjet printheads. For example, Japanese patent application JP
4141439A2 discloses a method for cleaning a printhead by pressing the paper
traveling through a printer against the printhead. Similarly, US 4,947,190
suggests the use of an ink-absorbing cleaning sheet that is brought into
contact with the printhead in order to wipe and clean the printhead. Other
1o proposals for cleaning sheets have included sheets with specified surface
roughnesses, adhesives, or absorbent or solvent-soaked pads (e.g., see US
6,030,674, US 5,589,865, US 6,277,457, US 5,751,306, US 5,589,865).
Because media sheets work by coming into physical contact with the nozzle
is orifice plate, they can be made suitable for operations such as wiping off
ink
or debris or applying solvent. However, care must be taken to ensure that
(a) the contact with the orifice plate does not abrade or otherwise damage the
surface,
(b) that the action of the media sheet, or debris from the sheet itself, does
not
2o contribute to the clogging of nozzle orifices, and
(c) that the media sheet makes adequate contact with the surface to be
cleaned.
They also offer the advantage they can be transported past the inkjet
printhead along the existing media carrier path. However, it should be noted
2s the rubbing and wiping printhead surfaces alone does not address all of the
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maintenance needs associated with inkjet printheads, so additional
mechanisms for capping, priming, spitting, and/or suctioning the printheads
will still be required for adequate maintenance. This requirement is reflected
in
US 5,589,865, in which the disclosed cleaning sheet also has an opening in
order to allow the passage of a separate vacuum wand.
As the technology has developed for fabricating ever higher resolution inkjet
heads with ever greater densities of nozzles, and, more particularly, with the
advent of pagewidth systems, the requirements placed on maintenance
io systems have become even more complex. A typical maintenance assembly
may include:
(1 ) a cap assembly to seal around an individual printhead or nozzle plate
to keep the particular inkjet nozzle array from drying out and the nozzle
plate
is free from contaminants.
(2) a wiper that can be moved to engage the nozzle surface of the
printhead and clear away ink, debris and other undesirable matter from the
surface of the nozzle plate area, and which may be moved away from the
2o nozzle surface when wiping is not desired;
(3) a spittoon for receiving ink ejected from the nozzles to remove
contaminated ink from the nozzles and to maintain less used nozzles;
CA 02364401 2001-12-05
(4) a selection of drive assemblies that may include a gear train for moving
the cap, wiper and spittoon;
(5) an absorption pad for absorbing drops of ink ejected during
s maintenance so that the printer may be transported without damaging or
soiling parts of the printer with purged ink; and,
(6) a mechanism for cleaning the cap and wiper to prevent contaminants
being transported onto the nozzle plate during successive maintenance
io procedures.
From these above it is clear that a typical inkjet printhead maintenance
system can be a complex subsystem with many moving parts.
is U.S. Pat. No. 6,179,403 to Xie describes a drum-based inkjet printing
apparatus that includes a maintenance system located at one end of the print
drum. The maintenance system includes assemblies that provide wet wiping
of the nozzles of the printheads as well as vacuuming of the same printheads
for maintenance thereof. The wet wipe nozzles are located within a stationary
2o drum housing and extend through a plurality of apertures when necessary to
provide maintenance functions. The printhead is mounted on a carriage which
moves to the maintenance position, where the wet wipers apply a fluid to the
ink jet nozzles such that any dried ink, viscous plugs or other debris is
loosened on the front face of the ink jet printbars. Once the debris has been
2s sufficiently loosened, a plurality of vacuum nozzles each extending through
a
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plurality of vacuum nozzle apertures vacuum away any of the cleaning fluid as
well as debris loosened thereby.
Other examples are known in the art, where a pad is attached to an extra-
s wide cylinder and the printhead is translated over a long distance to clear
the
nozzles over this pad.
While this approaches address some of the requirements enumerated above,
it nevertheless still requires the entire high precision printhead to be
translated
1o over a considerable distance to a service/maintenance position.
Brief Summary of the invention
A maintenance system for an inkjet printhead assembly is relocated to the
is location of the inkjet printhead assembly to maintain the inkjet printhead
assembly. The relocation is performed by temporarily attaching the
maintenance station to the media carrier of the inkjet printer. The printing
media carrier may also be moved to place the maintenance system in a
position where it may itself be serviced by a docking station.
Brief Description of the Drawings
In drawings which show non-limiting embodiments of the invention:
Figure 1 shows the inkjet printer according to one embodiment of the
2s present invention; and,
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Figure 2 shows a platen-based inkjet printer as an alternative
embodiment of the present invention.
Detailed Description of the preferred embodiment
Throughout the following description, specific details are set forth in order
to
provide a more thorough understanding of the invention. However, the
invention may be practiced without these particulars. In other instances, well
known elements have not been shown or described in detail to avoid
io unnecessarily obscuring the invention. Accordingly, the specification and
drawings are to be regarded in an illustrative, rather than a restrictive,
sense.
Figure 1 shows a cylinder-based inkjet printer with a partial page-width
inkjet
printhead assembly according to an embodiment of the present invention.
is The term inkjet printhead assembly is used herein to describe an inkjet
printer
head assembly that is comprised of at least one, and typically more than one
individual printhead. The term individual printhead is used herein to describe
an array of inkjet nozzles, typically fashioned as a integrated unit, having a
single nozzle substrate, and served with ink either from an ink reservoir
20 located within the integrated printhead unit, or on a more continuous basis
via
a hose system from an ink reservoir separately located. Many commercial
versions of such individual printheads are known and these may be used
individually or in various ways to create an inkjet printhead assembly, some
of
these being described, for example, in U.S. patents No. 5,646,665 and No.
Zs 5,408,746 and in U.S patent application 09/922,150. To the extent that the
s
CA 02364401 2001-12-05
various designs for individual printheads are well known in the field, they
will
not be further described here, nor will the methods for combining them into
inkjet printhead assemblies. The term partial page-width inkjet printhead
assembly is used herein to describe an inkjet printhead assembly that may
s consist of a number of arrayed individual printheads, but which does not
extend across the entire width of the widest media that the machine will print
on.
Printing media carrier 1, being a cylinder in the case of this first
embodiment,
io is capable of carrying paper or transparencies or other sheet-like printing
media. This printing media (not shown) may be of different sizes, textures and
composition. Inkjet printhead assembly 3 is mounted on printhead assembly
carriage 2, which moves on linear track 4. Linear track 4 is arranged
substantially parallel to the rotational axis of printing media carrier 1 and
at
is such a distance as to allow inkjet printing such as by standard inkjet
processes known to practitioners in the field. Carriage 2 is translated along
the width of printing media carrier 1 by the action of lead screw 5 and engine
6. A variety of other controlled translation mechanisms are also known in the
art, and may alternatively be employed for the purposes of moving carriage 2
2o in controlled fashion.
Relocatable inkjet printhead maintenance station 7 is mounted on a stage 8.
When maintenance of inkjet nozzles is not required, this assembly of
relocatable inkjet printhead maintenance station 7 and stage 8 is located in a
Zs storage location which may be within a docking station 9. Docking station 9
9
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services relocatable inkjet printhead maintenance station 7. The term stow
position is used herein to describe the location of relocatable inkjet
printhead
maintenance station 7 within docking station 9.
s To the extent that the various maintenance functions that may be performed
by relocatable inkjet printhead maintenance station 7 requires relocatable
inkjet printhead maintenance station 7 itself to undergo regular service,
docking station 9 is equipped with facilities (not shown) to perform the
servicing of relocatable inkjet printhead maintenance station 7. The term
1o inkjet printhead maintenance station is used herein to describe a unit that
is
used to clean, maintain and/or rejuvenate inkjet nozzles. It may contain, but
is
not limited to contain, facilities for performing one or more of the following
operations:
a) applying vacuum to inkjet nozzles;
is b) priming inkjet nozzles, which may be a combination of applying
vacuum and allowing a nozzle to spit;
c) capping inkjet nozzles;
d) providing a spittoon into which, or a surface onto which inkjet
nozzles may spit;
2o e) wiping of inkjet nozzles; and,
f) blotting of inkjet nozzles.
By way of example, suitable inkjet printhead maintenance facilities that may
optionally be included in relocatable inkjet printhead maintenance station 7
are described in IJ.S. Pat. Nos. 4,855,764, 4,853,717, and 4,746,938 and will
2s not be further detailed here.
to
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When maintenance of one or more individual printheads is required, docking
station 9 is moved such that stage 8 contacts printing media carrier 1. At the
chosen location on printing media carrier 1, stage 8 is temporarily attached
to
s printing media carrier 1. Various means of attachment are possible,
including,
but not limited to, mechanical, vacuum, magnetic and electromagnetic or
combinations of these means. Printing media carrier 1 is rotated, and carriage
2 is moved by means of leadscrew 5 and engine 6, the combined action of the
two motions positioning relocatable inkjet printhead maintenance station 7 in
to opposition to Inkjet printhead assembly 3. This allows such maintenance
actions as may be required at that time to be performed with the aid of
relocatable inkjet printhead maintenance station 7. Advantageously, either
relocatable inkjet printhead maintenance station 7 or inkjet printhead
assembly 3 may be moved towards the other in order to facilitate this
is function.
It is to be noted that inkjet printhead assembly 3 does not have to be moved
outside the printing area of printing media carrier 1 in order to facilitate
this
function. The term printing area is used herein to describe the area defined
2o by the longitudinal section of printing media carrier 1 that can be
traversed by
inkjet printhead assembly 3 during normal full width printing. The printing
area extends substantially around the entire circumference of printing media
carrier 1. It is to be particularly noted that the printing area of printing
media
carrier 1 is determined by the physical extent of inkjet printhead assembly 3
2s and the range over which it can travel during printing, and not by the
presence
n
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or absence of media to print upon. The printing area comprises those parts of
printing media carrier 1 which can be placed adjacent to printhead assembly 3
without moving printhead assembly 3 to a location outside of the range
through which printhead assembly 3 may move during printing.
s
An alternative embodiment of the present invention comprises a translation
system which permits docking station 9 to be moved parallel to the cylindrical
axis of printing media carrier 1. The translation system may comprise, for
example, a translation arrangement of the type employed to translate inkjet
to printhead assembly 3. A variety of other translation mechanisms are also
known and may be employed for this purpose. This arrangement allows inkjet
printhead assembly 3 to maintain its location and the entire relocation
process
falls to the combination of docking station 9, stage 8, relocatable inkjet
printhead maintenance station 7 and printing media carrier 1. This means that
is the high precision drive system of inkjet printhead assembly 3, which is
optimized for precision and may comprise a high-precision lead screw ,
carries less of a systems burden. This reduces the wear and tear on the high-
precision drive system.
2o It is evident that the number of service heads on relocatable inkjet
printhead
maintenance station 7 may be increased such that more than one printhead
may be serviced simultaneously. The term service head is used herein to
describe a unit that comprises an assemblage of one or more facilities
required to maintain at least one individual printhead. Printheads for
printing
2s different colors may require different individual service heads. In a
specific
12
CA 02364401 2001-12-05
embodiment of the present invention, relocatable inkjet printhead
maintenance station 7 is equipped with an array of service heads that map
one-to-one onto the individual printheads arranged in inkjet printhead
assembly 3. This allows any number of the individual printheads, up to and
s including all of them, to be maintained simultaneously, if so required. In a
more general embodiment, the array of service heads comprises a plurality of
service heads and these service heads are used to service another plurality of
individual printheads, without there being a specific numerical relationship
between the two pluralities. Some service heads may be redundant and used
to in case of others failing, while a given service head may service more than
one individual printhead.
It is also evident that docking station 9 may be adapted to maintain more than
one service head on relocatable inkjet maintenance station 7 at the same
is time, and, may indeed be so arranged as to maintain all of the service
heads
on inkjet maintenance station 7 at the same time.
In the embodiment of the present invention shown in Figure 1, inkjet printhead
assembly 3 is shown as a partial page-width inkjet printhead assembly
2o comprising four individual printheads having only one individual printhead
per
row substantially parallel to the cylindrical axis of printing media carrier
1.
There may be more than one such row of one or more individual printheads.
These printheads may be, by way of example, four different color individual
printheads for the industry standard Cyan, Magenta, Yellow and Black colors.
2s In a more general embodiment there is no limitation on the number of
13
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individual printheads, the combination of printed colors from the individual
printheads, or other properties of the individual printheads. For example,
individual printheads having different number of nozzles or different number
of
nozzles per unit distance may be employed.
s
In a further embodiment, inkjet printhead assembly 3 has a plurality of
individual printheads arranged in rows substantially parallel to the
rotational
axis of printing media carrier 1, and there may be more than one such row of
individual printheads. The individual printheads in adjoining rows may also be
to staggered in their layout and/or rotated with respect to the rotational
axis of
the printing media carrier 1. In such an arrangement, inkjet printhead
assembly 3, therefore, comprises an array of individual printheads that may
extend in one or more directions. In this embodiment there is no limitation on
the number of individual printheads, the combination of printed colors from
the
is individual printheads, or other properties of the individual printheads.
For
example, individual printheads having different number of nozzles or different
number of nozzles per unit distance may be employed.
In this embodiment, docking station 9 may be adapted to maintain more than
20 one service head on relocatable inkjet printhead maintenance station 7 at
the
same time, and may be so arranged as to maintain all of the service heads on
relocatable inkjet maintenance station 7 at the same time. In addition, inkjet
printhead assembly 3 may comprise an array of individual printheads
extending in more than one direction for different colors, and may have a
2s different number of printheads and a different arrangement of printheads
for
14
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the different colors. This would be done to allow different colors, different
combinations of colors, different ink drop sizes, different ink compositions,
and/or different resolutions to be printed using fewer total number of heads
than if all were to be done with the same number of heads. The arrangement
s of service heads in relocatable inkjet printhead maintenance station 7 may
be
of any number and type up to and including a complete one-to-one mapping
of service heads onto individual printheads. In this embodiment docking
station 9 may be adapted to maintain more than one service head on
relocatable inkjet printhead maintenance station 7 at the same time, and, may
io indeed be so arranged as to maintain all of the service heads on
relocatable
inkjet maintenance station 7 at the same time.
In a further embodiment, the inkjet printhead assembly comprises an array of
individual printheads with the array extending across the entire width of
is printing media carrier 1 in one dimension, and optionally having additional
rows of individual printheads arranged at different angular positions
concentrically with the circumference of printing media carrier 1. This
embodiment of the present invention constitutes a page width printer with
multiple rows of individual printheads. In this embodiment the total amount of
2o translation of printhead assembly 3 under the action of leadscrew 5 and
engine 6 can be very small, and can therefore, be managed very accurately.
Alternatively, the printhead assembly 3 could remain stationary, in which case
leadscrew 5 and engine 6 would only be required if print modes requiring
translation of the printhead assembly were to be employed along with print
2s modes that did not. For this reason, implementations wherein such a
is
CA 02364401 2001-12-05
printhead is translated over long distances for the purposes of maintenance,
are not preferred, as this would require, for example, a long and expensive,
accurate leadscrew. As with the previous embodiments, the number and type
of service heads in relocatable inkjet printhead maintenance station 7 may be
s of any number and type up to and including a complete one-to-one mapping
of service heads onto individual printheads. In this embodiment it is also
evident that docking station 9 may be adapted to maintain more than one
service head on relocatable inkjet printhead maintenance station 7 at the
same time, and, may indeed be so arranged as to maintain all of the service
to heads on inkjet maintenance station 7 at the same time.
This embodiment of the invention may permit docking station 9 to be
maintained at a fixed position. With a relocatable inkjet printhead
maintenance
station 7 that can have a one-to-one mapping of service heads onto individual
is printheads, the only translation required is totally within the normal
printing
movement range of inkjet printhead assembly 3. This significantly reduces the
complexity of the maintenance system for the page width printer.
In yet a further embodiment of the present invention, the printing media
carrier
20 1 comprises a platen in a flatbed printer arrangement. The term platen is
used
herein to describe a flat plate that is movable in at least one dimension
within
its plane, or on which printing media to be printed on is moved in at least
one
dimension within it's plane. This is shown if Figure 2. All the aspects of the
embodiment of Figure 2 work in the same way as with the cylinder-based
2s implementation, with the exception that the printing media carrier 1 is not
16
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rotated, but rather, translated, to position relocatable inkjet printhead
maintenance station 7 proximate inkjet printhead assembly 3. In this
particular
embodiment, the printing area of the media carrier is again defined, in a
first
dimension, by the longitudinal section of printing media carrier 1 that is
s traversed by inkjet printhead assembly 3 during normal full width printing,
and,
in a second perpendicular dimension, by the full range of relative motion of
the inkjet printhead assembly with respect to the platen. This area will
substantially be a rectangle.
io A further embodiment of the present invention comprises platen printers in
which all the relative motion between platen and inkjet printhead assembly is
performed by moving the inkjet printhead assembly in two dimensions while
the platen remains fixed and stationary. The printing area is as defined for
the
previous embodiment of the present invention, except that both dimensions of
is the printing area are defined by the range of motion of the inkjet
printhead
assembly.
In yet further embodiments, other types of printing media carrier may be
employed, including, but not limited to, platens that have shapes other than a
Zo flat plate. An example is a platen of which the curvature is substantially
a
sector of a circle. Such arrangements are particularly useful by virtue of the
fact they are easier to translate, employing rotary means without the need for
cumbersome mechanical arrangements.
m
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The advantages of the present invention are considerable. Firstly, preferred
embodiments of the invention make optimal use of the translation assemblies
that are fundamentally required for the printing process and thereby
s necessarily present. Secondly, printing apparatus according to the invention
may be compact. Extra space is not required beyond the drive assemblies for
the print media carrier and the precision drive of the inkjet printhead
assembly. It also allows the maintenance system itself to be maintained while
printing is proceeding. It reduces the demands on the highly accurate and
to very busy leadscrew drives of the printhead assembly, thereby reducing the
wear and tear on the system. It furthermore reduces the length of the
precision drive for the inkjet printhead assembly, thereby reducing cost.
There has thus been outlined the important features of the invention in order
is that it may be better understood, and in order that the present
contribution to
the art may be better appreciated. Those skilled in the art will appreciate
that
the conception on which this disclosure is based may readily be utilized as a
basis for the design of other apparatus and methods for carrying out the
several purposes of the invention. It is most important, therefore, that this
2o disclosure be regarded as including such equivalent apparatus and methods
as do not depart from the spirit and scope of the invention.
The invention includes at least the following aspects:
is
