Note: Descriptions are shown in the official language in which they were submitted.
CA 02349097 2001-05-29
TITLE OF THE INVENTION
SYSTEM AND METHOD FOR MAINTAINING THE FRONT OF A
FLUID JET DEVICE IN A RELATIVELY CLEAN CONDITION
BACKGROUND OF THE INVENTION
This invention relates generally to the field of fluid jetting
systems and relates, more particularly, to the means and methods used to
maintain a fluid
jet device of a fluid jetting systetr~ in proper working order.
An example of a fluid jet device with which this invention
is concerned is a printer head of an ink jet printer. In some instances, such
a printer head
relies upon capillary action to mono a working fluid (e.g. ink) to the printer
head and
includes means mounted within the head for directing ink through an orifice
toward a
target substrate. Such ink-directing means can include an actuator, such a
piezoelectric
.device or an electrostatic membrane, for directing ink through an orifice
upon appropriate
actuation of the actuator or, in the alternative, can include a thermal device
wherein heat,
which is applied to the ink, serves as the mechanism for directing ink through
an orifice.
Conunonly, a fluid chamber, or ink flow passageway, is
provided in the printer head which conducts ink from a source, by way of a
conduit
connected between the source and the printer head, and past the ink-directing
means to
the orifice. During normal operation of the printer head, ink must be present
in the ink
flow passageway ;~o that operation of the ink-directing means effects a
drawing of ink
into the passageway and a subsequent pushing of ink, under pressure, through
the orifice
and toward a targot surface. If, however, air enters the ink flow passageway
through the
orifice (as could be the case if the printing head were accidentally struck or
jostled) or if
the orifice becomes blocked, for example, by debris or dirt which may become
lodged
within the orifice, operation of the ink-directing means neither draws
additional ink into
the passageway, nor effectively pushes ink through the orifice. Consequently,
for
effective operation of the printer head, the ink flow passageway must be
devoid of air,
and the orifices of the printer head must remain free of blockage.
CA 02349097 2004-O1-23
Air which is present in an ink flow passageway of a
printer head and any blockage (surface or internal blockage) of the orifices
of a printer head
is commonly removed by a purging or head-cleaning operation which requires
that
additional ink be forced through the conduit and ink flow passageways by way
of a purge
bulb, pump or other means for forcing ink through the conduit and toward the
printer head
orifices. Such a purging or head-cleaning process, however, normally pushes
ink, as well
as air or blockage matter (e.g. debris), through the orifices so that ink,
which is pushed
from the orifices, flows downwardly along the front (i.e. the face plate) of
the printer head.
To prevent the ink which flows downwardly along the front of the printer head
from
touching or being smeared upon surfaces desired to remain free of ink, the ink
is manually
wiped from the front of the printing head with an absorbent sheet of material.
However,
such a purging and subsequent cleaning procedure requires manual intervention
in and
disruption of, the printing operation and is usually a messy, undesirable job.
Furthermore,
if such a process is required to be performed on a printer head stationed
along an assembly
line, assembly line production may have to halted in order to satisfactorily
service the
printer head, thereby causing the loss of production time.
It would therefore be desirable to provide a new and
improved system and method for maintairilng the front of a printer head in a
relatively clean
condition, even when ink is pushed through the orifices of the printer head
during a purging
or head cleaning operation wherein air or blockage material is purged from the
ink flow
passageways.
Accordingly, the present invention seeks to provide a
new and improved system and method for use when purging or cleaning a fluid
chamber of
a fluid jet apparatus, such as the printer head of an ink jet apparatus, for
maintaining the
front, or exterior surface of the fluid jet apparatus in a relatively clean
condition.
Further, the present invention seeks to provide such a
system and method which facilitates a purging and cleaning operation in that
such
operations can be performed routinely upon the fluid jet apparatus without the
messiness
associated with purging and cleaning operations of the prior art.
Still further, the present invention seeks to provide such
a system and method which circumvents the need for wiping the front, or
exterior surface of
a fluid jet apparatus during a purging or cleaning operation performed upon
the fluid jet
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CA 02349097 2004-O1-23
apparatus.
Yet further the present invention seeks to provide such
a system and method which is well-suited for automatic operation, thereby
requiring no
manual intervention and can be performed without disruption of a fluid jetting
operation or
any assembly line operation with which the system and method are used.
Further still, the present invention seeks to provide a
system and method which can be used to maintain an orifice of a fluid jet
apparatus
relatively free of blockage matter, such as debris or dirt.
A still further aspect of the present invention seeks to
provide such a system which is uncomplicated in construction, yet effective in
operation.
SUMMARY OF THE INVENTION
This invention resides in an apparatus and method for
use when purging air or blockage from a fluid chamber of a fluid jet apparatus
during a
purging or cleaning operation, wherein the fluid chamber has a chamber wall
with an
exterior surface, an interior surface adjacent the fluid chamber and at least
one orifice
through which fluid is ejected by the fluid jet apparatus during a jetting
operation.
The apparatus includes a cavity adjacent the chamber
wall, wherein the fluid which flows through~the at least one orifice during a
purging or
cleaning operation flows from the at least one orifice into the cavity.
The method of the invention includes the steps of
providing a cavity adjacent the exterior surface of the chamber wall into
which fluid, which
flows from the at least one orifice during a purging or cleaning operation, is
permitted to
flow from the at least one orifice and withdrawing fluid which is contained
within the
cavity.
In another aspect of the apparatus and method, the
cavity can be used to create a zone of above-atmospheric pressure in a region
adjacent the
exterior surface of the chamber wall so that leakage of air from said region
helps to
maintain the at least one orifice in a relatively clean condition. To this
end, air is
conducted, under pressure, to the interior of the cavity so that any leakage
of air from the
cavity into the atmosphere effects a flow of air out of the cavity.
The invention in one aspect provides an apparatus for
purging air, surface blockage or internal blockage from a fluid jet apparatus
during a
3
CA 02349097 2004-O1-23
purging or cleaning operation, the fluid jet apparatus having at least one
orifice through
which fluid is ejected by the fluid jet apparatus during a jetting operation,
the fluid jet
apparatus having a vacuum opening and a purge opening formed therein. The
apparatus
comprises a plate defining an opening therein, the plate configured to overlie
a portion of
the fluid jet apparatus with the plate opening overlying the at least one
fluid jet apparatus
orifice. The plate has a vacuum channel and a purge channel, a portion of the
vacuum
channel overlying the vacuum opening in the fluid jet apparatus and a portion
of the purge
channel overlying the purge opening in the fluid jet apparatus. The vacuum
channel and the
purge channel are in flow communication with the opening in the plate.
Another aspect of the invention pertains to a fluid jet
apparatus for jetting a fluid onto a target, comprising a body having at least
one orifice
through which fluid is ejected by the fluid jet apparatus during a jetting
operation and a face
plate carried by the body, the face plate having an orifice therein through
which the fluid is
ejected, the face plate further including a purge opening and a vacuum opening
formed
therein. A vacuum source is operably connected to the vacuum opening and a
pressurized
air source is operably connected to the purge opening. A cover plate has an
opening therein
configured to overlie a portion of the fluid jet apparatus with the cover
plate opening
overlying the face plate orifice. The cover plate has a vacuum channel and a
purge channel
formed therein, a portion of the vacuum channel overlying the vacuum opening
in the face
plate and a portion of the purge channel overlying the purge opening in the
face plate, the
vacuum channel and the purge channel each being in flow communication with the
opening
in the cover plate. The purge channel and the vacuum channel are configured
for
cooperating with the vacuum source and the pressurized air source to purge
air, surface
blockage or internal blockage from the fluid jet apparatus during a purging or
cleaning
operation.
Still further, there is an apparatus for purging air,
surface blockage or internal blockage , from a fluid chamber of a fluid jet
apparatus during a
purging or cleaning operation, the fluid chamber having a chamber wall with an
exterior
surface, an interior surface adjacent the fluid chamber and at least one
orifice through which
fluid is ejected by the fluid jet apparatus during a jetting operation,
wherein the fluid which
is ejected through the at least one orifice during a jetting operation travels
toward a
substrate. The apparatus comprises a cavity adjacent the clamber wall, wherein
the fluid
4
CA 02349097 2004-O1-23
which flows through the at least one orifice during a purging or cleaning
operation flows
from the at least one orifice into the cavity, the cavity being comprised of
an assembly of
adjacent plates having aligned openings such that fluid which flows from the
at least one
orifice travels toward a target surface unobstructed by the assembled plates.
The assembly
of plates comprises a first plate adjacent the exterior surface of the chamber
wall having a
central opening which is aligned with the at least one orifice and the first
plate further has
channels which are in communication with and extend from the central opening
of the first
plate. The channels of the first plate being out of alignment with the at
least one orifice. A
second plate adjacent the first plate has a plurality of openings including a
central opening,
wherein the central opening of the second plate is aligned with the central
opening of the
first plate and the at least one orifice. At least one other opening of the
second plate is in
communication with at least one channel of the first plate and out of
alignment with the at
least one orifice. The second plate further has a flange, the flange having an
aperture and a
channel which communicates between the at least one other opening and the
aperture in the
second plate. A third plate adjacent the second plate has a central opening
which is aligned
with the central openings of the first and second plates and the at least one
orifice. Thus
fluid which flows from the at least one orifice during a purging or cleaning
operation flows
into the central opening of the first plate, from the central opening of the
first plate into the
at least one channel of the first plate, from the at least one channel of the
first plate into the
at least one other opening of the second plate, from the at least one other
opening of the
second plate into the channel of the second plate and from the channel of the
second plate
into the aperture of the second plate.
Other features and advantages of the present invention
will be apparent from the following detailed description, the accompanying
drawings and the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The benefits and advantages of the present invention
will become more readily apparent to those of ordinary skill in the relevant
art after
reviewing the following detailed description and accompanying drawings,
wherein:
Fig. 1 is a perspective view of an ink jet printing
system within which an embodiment of a purge/clean system in accordance with
the present
invention is utilized.
Fig. 2 is a longitudinal cross-sectional view of a
4A
CA 02349097 2004-O1-23
fragment of a printer head of the prior art illustrating schematically the
components of the
printer head disposed adjacent one embodiment of ink-directing means mounted
within the
head.
Fig. 3 is a perspective view of the printer head of the
Fig. 1 printing system, shown with the cavity-providing assembly of the Fig. 1
purgelclean
system attached thereto.
Fig. 4 is a perspective view of the printer head of Fig.
3, shown exploded.
Fig. 5 is a view of the Fig. 3 cavity-providing
assembly, shown exploded.
Fig. 6 is a view of the Fig. 3 cavity-providing
assembly, shown assembled.
Fig. 7 is a view of a fragment of the gasket of the
cavity-providing assembly as seen in the circle labeled ? - ? in Fig. 5, but
drawn to a
slightly larger scale.
Fig. 8 is a longitudinal cross-sectional view of a
fragment of the Fig. 6 assembly taken generally along lines 8 - 8 of Fig. 6.
4B
CA 02349097 2001-05-29
Fig;. 9 is a cross-sectional view taken about along line 9-9
of Fig. 8.
Fig;. 10 is a cross-sectional view taken about along line
10-10 of Fig. 9.
Fig;. 11 is a view of the flowover plate of the Fig. 6
assembly as seen from the back in Fig. 5.
Fig;. 12 is a view illustrating schematically the purging,
withdrawing and pressure-creating means of the Fig. 1 purge/clean system.
Fig:. 13 is a perspective view of a print head, similar to Fig.
4, illustrating an alternate embodiment of portions of the purge/clean system.
F'ig. 14 is a rear view of the maintenance module plate of
Fig. 13, showing the acid etched regions of the plate.
Fig. 1 S is an enlarged view of the identified region of Fig.
14, illustrating the etched pattern in the plate.
Fig. 16 is a front perspective view of the plate of Fig. 14
illustrating the mounting clips for mounting the plate to the printer head.
DETAILED DESCRIPTION OF THE INVENTION
While the present invention is susceptible of embodiment
in various forms, there is shown in the drawings and will hereinafter be
described
specific embodiments with the understanding that the present disclosure is to
be
considered an exemplification of the invention and is not intended to limit
the invention
to the specific embodiments illustrated. It should be further understood that
the title of
this section, normally, "Detailed lDescription of the Invention," relates to a
requirement
of the United States Patent and Trademark Office, and does not imply, nor
should be
referred to limit the subject matter disclosed and claimed herein.
Turning now to the drawings in greater detail and
considering first I?ig. 1, there is shown an ink jet printing system 20 within
which an
embodiment, generally indicated 22, of a purge/clean system is incorporated.
Furthermore, the printing system 20 is shown utilized in a typical environment
of use
wherein the printing system 20 is used to print indicia, such as a bar code
24, upon the
CA 02349097 2001-05-29
side of a carton 26 being moved along a moving conveyor 28 in the direction
indicated
by the arrow 29. To this end, the printing system 20 includes an ink jet
printer head 30
mounted in a stationary condition adjacent the conveyor 28, a supply 32 of
ink, and a
conduit, or hose 34, for conducting the ink from the supply 32 to the printer
head 30. In
this connection, the ink is conducaed through the conduit 34 to the head 30 by
capillary
action.
The printer head 3U of the depicted system 20 includes
suitable ink-directing means, generally indicated 31, for directing ink
through and out of
the head 30 toward the surface of a target, such as the side of a carton 26.
Although such
ink-directing means 31 can take amy of a number of forms, such as thermal ink
jet
mechanisms (such as are embodied in printer heads available from Canon U.S.A.,
Inc.
under the trade designation "Bubble Jet") and electrostatic transducers, the
ink-directing
means 31 of the depicted system :z0 is piezoelectric-based in that actuation
of
piezoelectric devices within the printer head 30 effects the movement of ink
through and
out of the head 30 toward the surface of a target, such as the side of a
carton 26.
Furthermore, although the system '~0 described herein is an ink jet printing
system, the
principles of the present invention can be embodied in other fluid jetting
systems.
Accordingly, the principles of the present invention can be variously applied.
For controlling the actuation of the ink-directing means 31
of the printer head 30, a control box 36 containing suitable control circuitry
(not shown)
is mounted adjacent the printer head 30, a plurality of wires 38 extend
between the
printer head 30 and the control circuitry positioned within the control box
36. The
printing system 20 is also provided with sensing means, including an electric
eye 40,
which is appropriately wired to the control box 36 for sensing the presence of
a carton 26
moving along the conveyor 28. Daring operation of the printing system 20, the
movement of a carton 26 along the conveyor 28 is detected by the electric eye
40 which,
in turn, initiates a predetermined sequence of events leading to the actuation
of the printer
head 30. In particular, appropriate piezoelectric devices in the head 30 are
actuated, as
desired, to print the indicia 24 upon the side of the carton 26 following a
period of time
necessary for a carton 26 to move from the electric eye 40 to a desired
position in front of
CA 02349097 2001-05-29
the printer head 30. It follows, therefore, that the actuation of the printer
head 30 is
coordinated with the speed of the cartons 26 as they move along the conveyor
28.
The structure and operation of a piezoelectric-based ink jet
printer head is known so that a detailed description of them is not believed
to be
necessary. However, to enhance the appreciation of the contributions of the
Fig. 1
purge/clean system 22, there is sclhematically illustrated in Fig. 2 a
fragment of a prior art
printer head 42 having a body 44, a face plate 46 defining an orifice 48
attached across
the front of the body 44 and a pie~:oelectric device 50 mounted within the
body 44
adjacent the orifice 48. In addition, there is defined within the body 44 an
ink flow
passageway 52 (or fluid chamber) along which ink is permitted to flow from an
ink
supply to the orifice 48. In the depicted head 42, the face plate 46 provides
a chamber
wall of the ink flow passageway 52, and the exterior surface of the face plate
46 provides
the front of the he;~d 42. - _ _ _ _
Due to the surface tension of the ink which normally spans
the orifice 48 between operating cycles of the printer head 42, the ink
normally does not
flow out through the orifice 48 unless forced to do so. However, by energizing
and de--
energizing the piezoelectric device: 50 so that the device SO rapidly
contracts and
expands, ink is drawn into the passageway 52 from the supply and is then
pushed, under
pressure, through the orifice 48 toward the surf ace of a target. If, however,
air is present
in the ink passageway 52, expansion and contraction of the piezoelectric
device SO does
not adequately draw ink into the passageway 52 where it can be subsequently
pushed
through the orifice 48. If, thereforf;, air is injected or drawn into the
passageway 52
through the orifice 48 (as may be the case if the head 42 is jostled or struck
by a carton
26 moving along the conveyor 28), the air must be purged from the passageway
52 to
render the printer head 42 fully operable.
The printer head 42 is similarly rendered inoperable for its
intended purpose if its orifice 48 is blocked with blockage matter, such as
debris or dirt.
More specifically, the blockage matter (which can be surface blockage that
blocks the
orifice 48 at the surface of the face. plate 46 or internal blockage that
becomes lodged
within the orifice 48 or ink flow passageway 52) prevents the passage of ink
out of the
orifice 48 by the actuation of the piezoelectric device 50 and prevents the
flow of ink
CA 02349097 2001-05-29
through the passageway 52 of the head 42 in the desired manner. Therefore, in
the event
that the orifice 48 becomes blocked with blockage matter, such as debris, the
blockage
material must be removed, e.g. purged, from the passageway 52 in a head-
cleaning
operation. As will be apparent herein, the purge/clean system 22 associated
with the
printing system 20 of Fig. 1 is adapted to readily purge air and blockage
matter from the
orifice 48 and passageway 52 in an advantageous manner.
With the foregoing in mind and with reference to Figs. 3
and 4, the printer head 30 of the iiik jet printing system 20 of Fig. 1
includes a face plate
58 (Fig. 4) through which a linear row of orifices 60 are defined, and the
purge/clean
system 22 incorporated within the Fig. 1 system 20 includes means, generally
indicated
62, associated with the face plate :58 for providing, or defining, a
collection cavity 64
(best shown in Fib;. 10) adjacent the face plate 58 for collecting ink which
has been
expelled from the printer head 30 by way of the orifices 60 and means,
generally
indicated 66 in Fig. l, for withdrawing the ink which is collected, or
contained, within
the collection cavity 64. In addition to the face plate 58 and as best shown
in the
exploded view of Fig. 4, the printer head 30 also includes an internal
operating (i.e.
piezoelectric-based) componentry, generally indicated 70, within which ink-
moving
piezoelectric devices are supported and outer housing members 72, 74 which are
secured
about the componentry 70. The internal componentry 70 includes a mount 76 to
which
the face plate 58 is attached so that the face plate 58 is held in a
stationary condition
against the front o:f the componentry 70.
The face plate 58 has front and rear surfaces 78, 80,
respectively, and its row of orifices 60 are arranged along a line 68 which
extends
centrally along the length of the plate 58. In addition, the face plate 58 has
a rectangular
outer periphery and is attached to t:he mount 76 with several (e.g. sixteen
total) screws 82
which are inserted through screw-accepting openings 84 provided along the face
plate 58
and are threadably received by intc;rnally-threaded openings provided in the
mount 76.
As will be apparent herein, four of the screws 82 which are secured at the
corners of the
face plate 58 are removed from thf; face plate 58 and, in turn, used to secure
the
cavity-providing means 62 to the mount 76 with the same screw holes in the
face plate
58.
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Although the collection cavity 64 can be formed by any of
a number of components and.in any of a number of configurations, the depicted
collection cavity 64 is formed by appropriately-shaped cutouts and grooves,
described
herein, formed in a plurality of comity-providing plate members, or plates 86,
88 and 90,
which are arranged in an overlying, or stacked, relationship against the front
surface 78
of the face plate '~8. Each plate 8fi, 88 and 90 is relatively thin and is
held in a stationary
relationship against the face plate 58 with screws 82 (e.g. the aforementioned
four screws
82) and mount openings which are used to attach the face plate 58 to the mount
76.
Accordingly, each of the cavity-providing plates 86, 88 and 90 is provided
within
screw-accepting openings 91 defined at the comers of the plates 86, 88 and 90
which can
be aligned with the screw-accepting openings 84 of the face plate 58 for
acceptance of
the shanks of the screws 82 so that the plates 86, 88 and 90, along with the f
ace plate 58,
are tightly held between the heads of the screws 82 and the surface of the
mount 76. In
addition, each plate 86, 88 and 90 is provided with a pair of through-holes 93
for
accepting alignment pins associated with the head 30 to facilitate the as.
embly of plates
86, 88 and 90 in an aligned condition.
Within the depicted purge/clean system 22 and with
reference to Figs. S and 6, the cavity-providing plates 86, 88 and 90 of the
cavity-providing means 62 includes a first plate 86 (referred to hereinafter
as a gasket 86)
which is positioned in contact with so as to substantially cover the front
surface 78 of the
face plate 58, a second, or flowover plate 88 which is positioned in contact
with so as to
substantially cover the front surface 78 of the gasket 86, and a third, or
cover plate 90
which is positioned in contact with so as to substantially cover the front
surface of the
flowover plate 88.
Wifh reference to Figs. 5-9, the gasket 86 is platen-like in
form and has outer, substantially rectangular dimensions which conform
generally to
those of the face plate 58. In addition, the gasket 86 includes a through-
opening 92 which
extends along the length of the gasket 86 and opposing rows of notches 94
which
communicate with the through-opening 92 (as best shown in Fig. 7) so that the
notches
94 extend laterally from the through-opening 92. The material out of which the
gasket 86
is constructed can be any of a number of materials, but is preferably
stainless steel.
CA 02349097 2001-05-29
The; flowover plate 88 (best shown in Figs. 5 and 11) is also
platen-like in form, but has somewhat of an L shape, and includes three
parallel slot-like
through-openings 96, 98, 100 whiich extend linearly along the length of the
plate 88. The
(middle) through-opening 98 positioned between the other two (outer) through-
openings
96 and 100 is positioned so as to be aligned with the through-opening 92 of
the gasket 86,
and the two outer through-openings 96, 100 are positioned so as to communicate
with the
notches 94 of the gasket 86 when the flowover plate 88 is positioned in its
operative,
overlying relationship with the gasket 86. Furthermore and as best shown in
Fig. 11,
there is defined along one leg of the I~ shape of the plate 88 (and along the
side thereof
opposite the gasket 86) a pair of grooves 102, 103 which extend from one end
(i.e. the
lower end) of the outer through-openings 96, 100 to a pair of internally-
threaded
apertures, or through-bores 106, 108, formed adjacent the end of the
corresponding leg of
the L-shape of the plate 88.
The cover plate 90 (best shown in Figs. 5 and 6) is
plate-like in form having somewhat of an L-shape which corresponds generally
to that of
the flowover plate 88 and is provided with a slot-like through-opening 112
which extends
substantially centrally therealong. The material out of which each of the
flowover plate
88 and the cover plate 90 is constructed is stainless steel, although other
materials can be
used.
When the gasket 86, flowover plate 88 and cover plate 90
are connected to tlae face plate 58 (with the aforementioned four screws 82)
in the
aforedescribed overlying relationship and as best shown in Figs. 8 and 9), the
orifices 60
provided within the face plate 58 are aligned with the central through-opening
92 of the
gasket 86, the middle through-opening 98 of the flowover plate 88 and the
through-opening 112 of the cover plate 90. With the through-openings 92, 98
and 112
aligned with the orifices 60 in this manner, ink which is forcibly pushed
through the
orifices 60 by way of the piezoelectric devices mounted in the printer head 30
is
permitted to travel. toward a target surface, or substrate, unobstructed by
the
cavity-defining plates 86, 88 and 90. In practice, the printer head 30 of the
depicted
printing system 20 has a maximunn throw distance, or distance that the ink is
accurately
thrown from the orifices b0, of about 0.25 inches. C'.onsequently, it is
preferred that the
to
CA 02349097 2001-05-29
collective thicknesses of the gasket 86 and plates 88 and 90 total no more
than about 0.10
inches to enable a target surface, e.g. the side of the carton 26, to pass
across the front of
the cover plate 90 in close proximity, i.e. within about 0.25 inches, of the
orifices 60.
It also follows from the foregoing that with the gasket 86,
flowover plate 88 and cover plate 90 connected to the face plate 58 in the
aforedescribed
overlying relationship, a pair of continuous passages extend between the
orifices 60 and
the through-bores 106, 108 of the flowover plate 88 by way of the notches 94,
outer
through-openings 96, 100 and grooves 102, 103. Therefore, the orifices 60
communicate
with the through-bore 106 by way of the outer through-opening 96 and groove
103, while
the orifices 60 also communicate with the through-bore 108 by way of the outer
through-opening 00 and groove 102. As will be explained in greater detail
herein, a
vacuum is drawn in the cavity 64 by way of the through-bore 108 during a
purging or
head-cleaning operation while pressurized air is introduced into the cavity 64
by way of
the through-bore 106 so that a flow of air is induced across the orifices 60
from the
through-opening ~>6 toward the through-opening 100. This induced air flew, as
well as
the canted condition of the head 30 (as shown in Fig. 1) which disposes the
(pressurized)
through-opening ~~6 above the through-opening 100, effects the flow of ink
which is
expelled from the orifices 60 during a purging or cleaning operation into the
through-opening 100, rather than into the through-opening 96. Consequently and
due to
the influence of gravity and the induced flow of air from the through-opening
96 toward
the through-opening 100, ink which is expelled from the orifices 60 during a
purging or
cleaning operation flows into the portion of the cavity 64 provided by the
through-opening 100, rather than iinto the portion of the cavity 64 provided
by the
through-opening 96.
In addition to the cavity-providing means 62 and with
reference to Figs. 1 and 12, the depicted purge/clean system 22 also includes
means,
generally indicated 114, for purging air from the ink flow passageways and
blockage
matter which has become lodged within the orifices 60 of the printer head 30
and means,
generally indicated 116, for withdrawing ink which has been purged from the
orifices 60
and is present upon the front surface of the face plate 58. In the depicted
purge/clean
system 22, the purging means 114 includes a purge pump 118 which is connected
in-line
11
CA 02349097 2001-05-29
with the conduit 34 leading to the; printer head 30 for pumping, when desired,
a small
volume of ink through the conduiit 34 from the supply 32 so that any air which
is
contained within the ink flow passageways and any blockage matter which is
lodged
within the orifices 60 is pushed, or expelled, through the orifices 60 along
with the ink
which is pumped through the printer head 30 by the purge pump 118. For relief
of the
pump-induced pressure within the printer head 30, a return line 120 (having a
check
valve 122 mounted therein) is connected between the printer head 30 and supply
32 so
that some of the ink which is pumped to the printer head 30 by the pump 118 to
return to
the supply 32.
It follows that actuation of the purge pump 118 expels ink,
as well as air and blockage matter, from the orifices 60 of the printer head
30, and this
expelled ink ordinarily would flow downwardly along the front surface 78 of
the face
plate 58. However, the cavity-providing means 62 described above prevents the
exposure
of this expelled ink to surfaces which are desired to be kept clean and the
withdrawing
means 116 cooperates with the thrnizgh-opening 100 of the cavity-providing
means 62 to
remove this expelled ink from the. face plate 58 so that ink in prevented from
accumulating upon the face plate 58.
With reference still to Figs. 1 and 12, the withdrawing
means 116 of the depicted purge/clean system 22 includes a vacuum pump 124, a
controller 126 within which the vacuum pump 124 is mounted, and an air flow
network
128 connected bel;ween the vacuum pump 124 and the through-bore 108 of the
flowover
plate 88. The air flow network 12.8 of the depicted system 22 includes a first
vacuum
hose 130 which is connected between a collection reservoir assembly 132 and
the inlet of
the vacuum pump 124 and a second vacuum hose 134 which is connected between
the
collection reservoir assembly 132 and the through-bore 108 (Fig. 5) of the
flowover plate
88. To facilitate the attachment of the vacuum hose 134 to the flowover plate
88, an air
hose connector 136 (Figs. 5 and 6) is threadably received by the through-bore
108, and a
sealing ring 138 is interposed bet>veen appropriate surfaces of the connector
136 and the
flowover plate 88 to seal the connector 136 to the plate 88.
With reference again to Figs. 1 and 12, the collection
reservoir assembly 132 includes a reservoir 142 and a lid 144 through which a
pair of
12
CA 02349097 2001-05-29
conduit segments 146, 148 extend. Each conduit segment 146 or 148 is connected
to a
corresponding one of the vacuum hoses 130 or 134, and the lid 144, reservoir
142 and
conduit segments 146, 148 are sealingly connected to one another to prevent
leakage of
the vacuum created by the pump 124 through the air flow network 128. Control
of the
operation of the vacuum pump 12 4, as well as the purge pump 118, is had by
way of
suitable controls mounted within the controller 126 and which are
appropriately wired to
the vacuum pump 124 and the purge pump I 18.
During operation of the purge/clean system 22, the vacuum
pump 124 is actuated to draw air toward the pump 124 from the cavity 64 of the
cavity-providing means 62 through the air flow network 128, and the operation
of the
purge pump 118 is initiated to pmmp a low volume of ink through the printer
head _'
orifices 60 so that any air which rnay be present in the ink passageways and
any blockage
matter which is lodged within the orifices 60 of the printer head 30 is
expelled through
the orifices 60. Since the interior .of the cavity 64 of the cavity providing
means 62
communicates with the atmosphere by way of the notches 94 and aligned
through-openings 92, 98, I 12 of the gasket 86 and plates 88, 90, air is
permitted to be
pulled from the atmosphere and s~o that air flows in sequence toward the
vacuum pump
124 through the cavity 64 of the cavity-providing means 62 and then through
the air flow
network 128 by way of the groove 102 and through-bore 108.
Therefore, any ink which is expelled from the orifices 60
during an air-purging or head-cleaning operation and which begins to flow
downwardly
along the front surf ace 78 of the Mace plate 58 is drawn through the notches
94 and into
the outer through--opening 100 of the flowover plate 88 by the influence of
the vacuum
pump 124, as well as by the influf,nce of gravity. Consequently, the gasket 86
acts as a
manifold through which ink is permitted to be drawn into the outer through-
opening 100
of the flowover plate 88 from the front surface 78 of the face plate 58. Once
the ink
enters the through-opening 100, it is drawn downwardly by the vacuum pump 124
(as
well as by the influence of gravity) toward the through-bore 108 where it is
drawn
through the air flow network 128 toward the vacuum pump 124. Therefore, the
through-opening 100 and groove 102 act as flow channels through which the
expelled ink
moves downwardly through the cavity-providing means 62. Upon reaching the
collection
13
CA 02349097 2001-05-29
reservoir 142 (Fig. 12) by way of the air f low network 128, the ink falls
from the inlet
conduit segment 148 and is collected within the reservoir 142 for reuse or
disposal. Since
ink separates from the combined air and ink contents drawn through the air
flow network
128 at the reservoir 142, only air is moved along the vacuum hose 130 which
extends
from the reservoir 142 to the vacuum pump 124.
7'he; operation of the purge/clean system 22 can be initiated,
for example, by pressing of "start" switch associated with the controller 126
which, in
turn, actuates the vacuum pump 124 and the purge pump 118. Shut-off of the
vacuum
and purge pumps 124, 118 can be~ effected after a predetermined period of time
(e.g. a
few seconds) with appropriate timing controls. The ability to manually
initiate operation
of the purge/clean system 22 is advantageous when, or if, air becomes
entrained within
any ink flow passageway of the printer head 30 during operation or any of the
orifices 60
become blocked, and it is desired that a purging operation be initiated
immediately to
rectify the situation. In the alternative or in addition, actuation of the
purge/clean system
22 can be automatically initiated ;at predetermined intervals to ensure that
the orifices 60
or ink flow passal;eways of the printer head 30 are free from air and orifice-
blockage
matter following those predetermined intervals. For example, with appropriate
programmable co:mponentry mounted within the controller 126, the controller
126 can be
programmed to automatically initiate an operating cycle of the purge/clean
system 22 at
the initiation of an assembly line operation to ensure that the printer head
30 is free from
air and blockage matter at start-up of operation.
If the purge pump 118 which is selected for use with the
purging means 114 possesses appreciably more strength than the vacuum pump
124, it
may desirable that the purge pump 118 be operated intermittently, rather than
continuously, during the operation of the vacuum pump 124. To this end, the
controls of
the controller 126 can be selected (or programmed) to intermittently actuate
and
de-actuate the purge pump 118 while the vacuum pump 124 is operated during an
operating cycle of the purge/clean system 22.
It fcrllows from the foregoing that a purge/clean system 22
has been described which removes ink from the front surface 78 of the face
plate 58
during an air-purging and head-cleaning operation performed upon the printer
head 30.
14
CA 02349097 2001-05-29
Consequently, th<; face plate 58 of the printer head 30 is maintained
relatively free of ink
which is expelled from the oriticf;s 60 during an air-purging and head-
cleaning operation,
and no manual methods are needed to wipe ink from the front of the printer
head 30 to
prevent the expelled ink from contacting or marking a surface desired to
remain free of
ink.
It is also a feature of the purge/clean system 22 that it
includes means, generally indicated 152 in Figs. 1 and 12, for creating a zone
of
above-atmospheric pressure in a region adjacent the front plate 58 of the
printer head 30
of a printing system to help maintain the orifices 60 of the front plate 58
relatively clean,
or in other words, free of matter, ouch as unwanted dust and debris, which
could
otherwise become; lodged within ithe orifices 60. In the depicted system 22,
the creating
means 152 utilizes the cavity 64 of the cavity-providing means 62, and this
provided
cavity 64 surrounds the region adjacent the front plate 58 within which the
zone of
above-atmospheric pressure is desired to be created.
Furthermore, the creating means 152 also includes a
source, indicated 169, of pressuri:;ed air, which can be a fan or a compressor
171, which
is situated to one side of the printer system 20 and further includes a
conduit 170
connected between the pressurized air source 169 and the through-bore 106 for
conducting the pressurized air from the source 169 to the portion of the
cavity 64
provided by the tlurough-opening 96. In this connection, an air flow connector
137 (Figs.
S and 6) is threadably received by the through-bore 106, and the conduit 170
is joined to
the connector 137. The connector 137 is sealed against the flowover plate 88
with a
sealing ring 138. 'Cherefore, during operation of the pressure-creating means
152, air
from the pressurized air source 169 is conducted into the through-opening 96
of the
cavity 64 by way ~f the conduit 1'70 and connector 137 so that the internal
pressure of the
cavity 64 exceeds atmospheric prcasure.
In practice, the internal pressure of the cavity 64 need not
exceed atmospheric pressure by a:n appreciable amount (and can, in fact, be as
small as
I .0 psig) to develop an environment within the cavity 64 wherein any leakage
of air out
of the cavity 64, such as through the aligned through-openings 92, 98, 112
will reduce
any likelihood that unwanted dust or debris will collect at, and thereby lodge
within, the
CA 02349097 2001-05-29
orifices 60. Consequently, the pressure of the air delivered to the cavity 64
from, the
source 169 need not be very great so that the energy ;expended to pressurize
the air at the
source 169 can (for energy-conse-ruing measures j be relatively small.
As long as the pressure-creating means 152 is operating,
the likelihood that unwanted dirt or dust will lodge within and block the
orifices 60 of the
printer head 30 is relatively small. Consequently, it is preferable that the
pressure-creating means 152 be operated continually - even during printing
operations
performed with t1e printing system with which the purge/clean system 22 is
used. During
simultaneous operation of the purge/clean system 22 and the pressure-creating
means 152
and as mentioned earlier, ink which is expelled from the orifices 60 during a
purging or
head-cleaning operation is forced to flow, under the influence of gravity and
an induced
flow of air across the orifices 60 :from the through-opening 96 toward the
through-opening 100, into the through-opening 100 of the cavity 94 for
collection, rather
than into the through-opening 96.
It will be understood that numerous modifications and
substitutions can be had to the aforedescribed system without departing from
the spirit of
the invention. For example, although the aforedescribed purge/clean system 22
has been
shown and described as including; purging means 114 for forcing ink through
the face
plate orifices 60 during a purging or head-cleaning operation, the cavity-
providing means
62 and the withdrawing means 116 can be used without the purging means 114 to
retrofit
the printer head of an existing ink.: jet printing system so that ink which is
expelled from
the face plate with conventional purging means associated with the printing
system can
be removed with the cavity-providing means 62 and the withdrawing means 116.
An alternate embodiment of a portion of the purge/clean
system 222 is shown in FIGS. 13--16. In this embodiment, the vacuum and air
pressure
conduits 234, 270 are formed as part of the print head 230, rather than as
separate
conduits as shown in the embodiment exemplified in Fig. 6. That is, both
conduits 234,
270 penetrate the head 230 and provide openings 236, 272 at the face plate
258. In this
embodiment, a single plate , as indicated at 288, is used to provide a cavity
264 that is
used for ink withdrawal and a cavity 252 to provide positive air pressure. The
plate 288
is commonly referred to as maintenance module.
16
CA 02349097 2001-05-29
The plate 288 includes a front surface 290, which is that
surface opposing the surface-on which printing is carried out (e.g., the
target), and a rear
surface 292 that abuts the print head face plate 258. The plate 288 includes a
slot-like
opening 298 through which the ink is propelled onto the target. This slot-like
opening
298 corresponds to openings 92, 98 and 112 of the previously described
embodiment.
The ink withdrawal cavity 252 is formed as a vacuum
channel, indicated generally at 274, formed in the rear surface 292 of the
plate 288. A
plurality of finger-like notches 276 are formed in the plate 288, and extend
between the
vacuum channel 274 and the slat opening 298. The notches 276 thus provide flow
communication between the slot f.98 and the vacuum channel 274. In a current
embodiment, the channel 274 is oriented generally parallel to the slot 298 and
the notches
276 are formed transverse to both the slot 298 and the channel 274.
The channel 274 terminates at an end 278 that corresponds
to the vacuum opening 236 in the face plate 258. In this manner, the channel
274, at
about the end 278., overlies the vacuum opening 236 in the face plate 25R.
Thus, vacuum
is provided to the plate 288 (and thus to the slot 298, via the notches 276.
by direct
communication of the opening 23ti to the channel 274.
The positive pressure air cavity 252 is formed as a purge or
positive pressure channel 280, andl is also formed in the rear surface 292 of
the plate 288.
Like the vacuum channel 274, the purge channel 280 is oriented generally
parallel to the
slot 298, and finger-like notches 282 extend between the slot 298 and the
channel 280.
The purge channel 280 terminates at an end 284 that overlies the purge or
pressure
opening 272 formed in the face plate 258. Air is provided at a positive
pressure to the
slot 298 (by the channel 280 via the notches 282) to carry out the purge
functions
described above.
In tloe illustrated embodiment, the vacuum and purge
channels 274, 280 are formed in the plate 288, generally parallel to one
another, on
opposing sides of the slot 298. In a preferred embodiment, the vacuum channel
274 is
disposed above the slot 298, and the charmel end 278 is at a downward incline
or angle
relative to the main portion of the channel 274. In this manner, as ink is
drawn from
t7
CA 02349097 2001-05-29
about the slot 298, it flows downward, with gravity, toward the vacuum opening
236 in
the face plate 258.
C'.onversely, the purge channel 280 is located below the slot
298 and the purge; air flow is upward into the slot 298. The purge channel end
284 is
formed generally aligned with the; main portion of the channel 280.
In a~ present embodiment, the plate 288 has a thickness of
about 0.010 inches (about 10 mils), and the channels 274, 280 and notches 276,
282 are
formed by acid etching. The acid etched areas have a depth of about 5 mils. It
has been
found that this plate 288 thickness and etching depth provides sufficient
rigidity to the
plate 288 and sufi:icient flow capabilities at the channels 274, 280 and
notches 276, 282
to carry out the vacuum and purge functions for the maintenance module. Other
depths,
methods and manners for forming the channels and notches will be recognized by
those
skilled in the art a.nd are within the scope and spirit of the present
invention.
A further enhancement of the alternate maintenance
module is that it is configured to readily install on the pricat head 230,
over the face plate
258. In a current embodiment, chip--like portions 238 extend rearwardly from
the plate
288, generally transverse thereto. 'the clips 238 are urged over, and engage
sides 260 of
the face plate 258 to secure the maintenance module plate 288 by a snap-fit.
This
arrangement reduces or eliminates the need for screws or other fasteners to
secure the
maintenance module plate 288 to the print head 230. Thus, by a simple
frictional or
snap-fit over the printing head facie plate 258, the maintenance module plate
288 is held
in place.
The snap-fit configuration permits two or more of the
otherwise used fastener or screw openings to be used to provide the vacuum and
purge
openings 236, 272 in the print head face plate 258. Thus, the print head 230
can be
configured so that. the internally carried conduits 234, 270 have little to no
impact on the
overall size of the print head 230. :(n addition, the snap-fit configuration
also permits
readily aligning the plate 288 over the face plate 258. Such alignment is
necessary to
assure that the jetted ink is directed through the slotted opening 298 in the
plate and onto
the target for printing.
18
CA 02349097 2001-05-29
Additionally, it has been found that during operation,
contaminants can be inadvertently spread onto the maintenance module plate
288. For
example, in a packaging line operation, such as a boxing or crating operation
in which an
adhesive is applied to the boxes or crate, ribbons of adhesive can be land on
the front
surface 290 of the plate 288. As will be appreciated by those skilled in the
art, this
adhesive must be removed, so that it does not build up on the surface 290 of
the plate
288, in order to maintain proper operation of the print head 230.
A maintenance module 288 in accordance with the present
invention can include a coating or layer, as indicated at C in Fig. 16, of a
low friction
material thereon. A present material is a fluoropolymer, such as TEFLON~ or
the like.
Such a material fs~cilitates readily cleaning the front surface 290 of the
plate 288 in the
event that the plate 288 becomes dirty or contaminated by, for example,
adhesive ribbons
and the like. Other readily cleaned, low friction materials will be recognized
by those
skilled in the art, and are within tlhe scope and spirit of the present
invention.
From the foregoing it will be observed that numerous
modifications and variations can be effectuated without departing from the
true spirit and
scope of the novel concepts of thc: invention. It is to be understood that no
limitation
with respect to the specific embodiment illustrated is intended or should be
inferred. The
disclosure is intended to cover by the appended claims all such modifications
as fall
within the scope of the claims.
19
