[0001] This invention relates to ink reservoirs for thermal ink-jet ("TIJ") print cartridges.
[0002] TIJ technology is widely used in computer printers. Very generally, a TIJ includes
a print head typically comprising several tiny controllable ink-jets, which are selectively
activated to release a jet or spray of ink from an ink reservoir onto the print media
(such as paper) in order to create an image or portion of an image. TIJ printers are
described, for example, in the Hewlett-Packard Journal, Volume 36, Number 5, May,
1985, and Volume 39, Number 4, August, 1988.
[0003] An ink-jet printer for ink-jet printing onto a print media is described, and includes
an ink-jet cartridge including an ink-jet print head and a closed spring-bag primary
reservoir in fluid communication with the print head for holding a first supply of
liquid ink under negative pressure. The primary reservoir includes at least one movable
side wall and an internal spring for biasing the movable side wall against collapsing
as ink is withdrawn from the reservoir and ejected from the print head onto a print
medium during printing operations. The printer includes means for effecting relative
motion between the print medium and the print head during printing operations.
[0004] A closed auxiliary reservoir holds a second supply of liquid ink. A connection tube
runs between the primary reservoir and the auxiliary reservoir for providing a closed
fluid path to provide passive ink replenishment from the auxiliary reservoir to the
primary reservoir during normal printing operation.
[0005] In accordance with another aspect of the invention, a method of replenishing liquid
ink in a closed spring-bag primary reservoir in an ink-jet printing system is described.
The method comprising the following steps:
providing an ink-jet cartridge including an ink-jet print head and a closed spring-bag
primary reservoir in fluid communication with the print head for holding a first supply
of liquid ink under negative pressure, the primary reservoir including at least one
movable side wall and an internal spring for biasing the at least one movable side
wall against collapsing as ink is withdrawn from the reservoir and ejected from the
print head onto a print medium during printing operations;
providing a closed auxiliary reservoir for holding a second supply of liquid ink;
providing a closed ink path running between the primary reservoir and the auxiliary
reservoir to provide passive ink replenishment from the auxiliary reservoir to the
primary reservoir during normal printer operation.
[0006] These and other features and advantages of the present invention will become more
apparent from the following detailed description of an exemplary embodiment thereof,
as illustrated in the accompanying drawings, in which:
[0007] FIG. 1 is an isometric view of a thermal ink-jet pen cartridge embodying the invention,
shown with its covers in an exploded form.
[0008] FIG. 2 is an enlarged view of the snout region of the pen of FIG. 1.
[0009] FIG. 3 is a cross-sectional view of the pen of FIG. 1, taken lengthwise through the
pen snout region.
[0010] FIG. 4 is a broken away cross-sectional view of the snout region of the pen of FIG.
1.
[0011] FIG. 5 is a view of the snout region of the pen of FIG. 1, taken prior to installation
of the air check valve.
[0012] FIG. 6 is an isometric view of the thermal ink-jet pen cartridge of FIG. 1.
[0013] FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 6.
[0014] FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7.
[0015] FIG. 9 is a cross-sectional view similar to FIG. 7 but showing the insertion of the
sealing ball.
[0016] FIG. 10 is a side view of the external plastic frame member comprising the pen cartridge
of FIG. 1.
[0017] FIG. 11 is a cross-sectional view taken along line 11-11 of FIG. 10.
[0018] FIG. 12 is a side view of the external and inner plastic frame members comprising
the pen cartridge of FIG. 1.
[0019] FIG. 13 is a cross-sectional view taken along line 13-13 of FIG. 12.
[0020] FIG. 14 is a cross-sectional view taken along line 14-14 of FIG. 12.
[0021] FIG. 15 is a cross-sectional view taken along line 15-15 of FIG. 12.
[0022] FIG. 16 is a cross-sectional view taken along line 16-16 of FIG. 6.
[0023] FIG. 17 is an enlarged view of the region within circle 17 of FIG. 16.
[0024] FIGS. 18 and 19 show alternate techniques of locking the inner plastic member to
the external plastic member comprising the pen cartridge of FIG. 1.
[0025] FIG. 20 is a partial isometric view of a spring bag cartridge swath printer employing
an auxiliary reservoir in accordance with a further aspect of the invention.
[0026] FIG. 21 is a front view of the swath printer of FIG. 20.
[0027] FIG. 22 is partial cross-sectional view, taken along line 22-22 of FIG. 21.
[0028] FIG. 23 illustrates in isolation the fluid connection between the spring bag cartridge
primary reservoir and the auxiliary reservoir.
[0029] FIG. 24 is a bottom view of the spring bag cartridge and the auxiliary reservoir
of FIG. 23.
[0030] FIG. 25 is a close up view of the fitment element and the surrounding portion of
the auxiliary bag.bottom cross-sectional view of tine auxiliary reservoir bag.
[0031] FIG. 26 is a cross-sectional view of the fitment element, taken along line 26-26
of FIG. 25.
[0032] FIG. 27 is a cross-sectional view of the closed fluid path between the auxiliary
reservoir and the cartridge, taken along line 27-27 of FIG. 24.
[0033] FIG. 28 is a cross-sectional view taken along line 28-23 of FIG. 23, showing the
tube connection to the cartridge fill port.
[0034] FIG. 29 is a partial front view of an alternate embodiment of a swath printer employing
a plurality of spring bag cartridges and auxiliary reservoirs in accordance with the
invention.
[0035] FIG. 30 is a cross-sectional view of the swath printer of FIG. 29, taken along line
30-30 of FIG. 29.
[0036] FIG. 31 is a bottom view of the cartridge carriage employed in the swath printer.
[0037] FIG. 32 is an isometric view of the cartridge carriage of FIG. 31.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] FIGS. 1-17 illustrate a thermal ink-jet pen cartridge 50 embodying the present invention.
The pen 50 comprises an external frame structure 60 which defines a closed band or
loop defining the periphery of the pen 50. The pen structure 60 comprises two chemically
dissimilar plastic members 78 and 68. The external plastic member 78 is molded from
a relatively rigid engineering plastic such as a glass-filled modified polyphenylene
oxide, such as the material marketed under the trademark "NORYL" by General Electric
Company. An inner plastic member 68 is injection molded to the inner periphery of
the external plastic member 78, and is fabricated of a plastic material suitable for
attaching the ink reservoir membranes 64 and 66. A plastic suitable for the inner
plastic member 68 is a polyolefin alloy or 10 percent glass-filled polyethylene.
[0039] The frame 60 defines a generally rectilinear open volume region 110 and a snout region
75 protruding from one corner of region 110. The external plastic member 78 is molded
to form a standpipe 93 with an interior opening or channel 94 formed therein. The
standpipe channel 94 communicates with a TIJ printhead 76 secured across the the standpipe
channel 94 to supply the printhead 76 with ink. As drops of ink are forced outwardly
through the printhead nozzles, ink flows through the standpipe 94 from the reservoir
62 via the fluid paths indicated generally by arrows 97 and 99 to replenish the ink
supply available to the printhead 76.
[0040] The inner plastic member 68 further includes a support rib 120 which extends across
the throat of the snout region 75, separating the snout region from the main ink reservoir
area 62. A generally rectangular chamber area 122 is formed by a surrounding structure
of the inner member 68 extending between the rib 120 and the inner opening of the
standpipe channel 94.
[0041] First and second membranes 64 and 66 are attached to the inner plastic member 68
through heat staking, adhesives or other bonding processes, to form a leak-proof seal
between the inner plastic member 68 and the membranes. The membranes 64 and 66 are
formed of a material which is impermeable to the ink to be stored within the ink reservoir,
and compatible with the plastic of material from which the inner plastic member 68
is fabricated. A preferred material for the membranes 64 and 66 is ethylenevinyl acetate
(EVA). The ink delivery system includes a spring 74 which applies a separating force
against two opposed piston plates 72A and 72B inside the ink reservoir to separate
the membranes 64 and 66. The spring and piston elements maintain negative pressure
or. the ink in the reservoir to keep the ink from drooling from the printhead 76.
As ink is consumed from the reservoir, atmospheric pressure on the membranes 64 and
66 result in compression of the spring with the plates 72A and 72B drawn toward each
other.
[0042] The membranes 64 and 66 extend over the standpipe region, and in this embcdiment
are heat staked along the edge regions 63A, 63B and 63C (FIG. 4) to maintain the sealing
of the membranes along the periphery of the snout region 75. The membranes 64 and
66 are not sealed to the region of the rib 120. Standoffs 69A and 698 comprising the
inner plastic member 68 hold the membranes off the area of rib 120, to ensure the
membranes do not sag against the support rib structure and thereby close off the ink
flow from the ink reservoir to the standpipe 93.
[0043] An air check valve is provided in the fluid path between the printhead 76 and the
ink reservoir 62, to prevent air bubbles from travelling from the printhead into the
reservoir 62. The valve also serves the function of a filter to prevent particulate
contaminates from flowing from the ink reservoir 62 to the printhead 76 and clogging
the printhead nozzles. In this embodiment, the valve includes two valve members 90,
92 one on each side of the frame. The valve members 90 and 92 each comprise, in this
exemplary embodiment, a section of finely woven stainless steel mesh, the edges of
which are attached to the inner plastic member. The mesh has a nominal passage dimension
of 15 microns between adjacent mesh strands, and has a typical thickness of less than
0.005 inches. In this embodiment, each mesh member 90 and 92 is square, and covers
an area of about one centimeter by one centimeter. A mesh marketed under the tradename
RIGIMESH-J by Engle Tool and Die, Eugene, Oregon, is suitable for performing the function
of the check valve. The mesh passage size is sufficiently small that, while ink may
pass through the passages of the mesh, air bubbles under normal atmospheric pressure
will not pass through the mesh passages which are wetted by the ink. The required
air bubble pressure necessary to permit bubbles to pass through the mesh, in this
embodiment, about 30 inches of water, is well above that experienced by the pen under
any typical storage, handling or operational conditions. As a result, the mesh serves
the function of an air check valve for the pen.
[0044] A second function fulfilled by the mesh valve is that of a particulate filter, preventing
particles as small as 15 microns from passing through the mesh. It is known to use
a mesh of this mesh opening size in a particulate filter in vented, foam-filled ink
reservoirs. Such reservoirs have no need for an air check valve.
[0045] There is a pressure drop across the mesh members 90 and 92. If the mesh opening size
is too small, not enough ink will flow through the mesh, and the printhead will starve.
Two separate mesh members 90 and 92 are employed to ensure sufficient ink flow from
the reservoir 92 into the chamber 94.
[0046] FIGS. 4 and 5 illustrate the snout region 75 of the pen 50. FIG. 4 is a cross-section
taken along line 4-4 of FIG. 3. FIG. 5 is a view of the snout without the covers and
valve element 90 and 92 in place. The frame member 73 includes a pair of inwardly
facing tabs 78A and 78B which provide suppcrt to the portion of inner frame member
68 molded around the inner periphery of the snout region 75. The tabs 78A and 78B
also serve as coring features for molding of the inner member 68. The frame member
68 defines inner chamber 122, with a rectilinear frame portion extending around the
periphery of the chamber. The frame portion is defined by side regions 68A-D. As shown
in FIG. 3, the width of member 68 defines the width of the chamber 122. The side regions
68A-D thus define a window into the chamber 122 on each cover-facing side of the member
68. Each side of the chamber 122 which extends in a perpendicular sense to the plane
of the covers 70 and 80 is defined by the plastic comprising member 68.
[0047] During operation, air bubbles may accumulate in the chamber 122. The printer in which
the pen 50 is installed may include a priming station to apply a vacuum to the printhead
to withdraw the air bubbles through the printhead, and draw ink from the reservoir
to fill the standpipe opening and the chamber 122. Such priming stations are known
in the art.
[0048] The frame member 68 is molded to define a thin lip 124 which protrudes from the side
regions 68A-D and extends around the periphery of the frame portion. Such a lip is
defined on each cover-facing side of the member 68; only lip 124 is visible in FIG.
5. During the heat staking operation used to attach the mesh screen members the heated
die member is positioned over the mesh member, and brought downwardly against the
mesh member with force. The temperature of the die member is sufficient to soften
or melt the plastic material defining the lip 124, so that some of the molten plastic
flows into the adjacent interstices of the mesh. Upon removal of the die member and
cooling of the plastic, the mesh member is firmly attached to the member 68 all around
the periphery of the window into the chamber 122.
[0049] FIGS. 6-9 illustrate the location and structure of the ink fill port 130 of pen 50.
As shown in FIG. 6, in this embodiment, the fill port 130 is located in a flat surface
60A of the frame 60 adjacent the pen snout region 75. The ink reservoir 62 is filled
with ink via the port 130, which is thereafter sealed off by insertion cf a stainless
steel ball 132.
[0050] The external frame member 73 is molded to form an opening of circular cross-section,
whose diameter transitions abruptly from a smaller diameter in the region 134 in which
the ball 132 is captured, to a larger diameter in the region 136 adjacent the surface
60A. In this embodiment, the ball 132 has a diameter of .187 inches (4.76 mm), the
smaller diameter of the frame member 78 in the region 134 is .236 inches (6.0 mm),
and the larger diameter of the frame 73 in the region 136 is .283 inches (7.2 mm).
[0051] During the molding of the inner plastic member 68 onto the previously fabricated
outer frame member 73, the molten plastic flows through the opening formed for the
ink fill port in the member 78 and around a mold pin inserted therein to form the
fill port structure comprising the inner member 68. Thus, the molten plastic flows
around the material forming the member 78 at region 134, providing a lining thereover.
Moreover, the inner member 68 thus formed defines the fill port opening 130 which
communicates with the ink reservoir 62. The diameter of the fill port opening 130
tapers from a first diameter of the opening adjacent the surface to a second, smaller
diameter at 138 adjacent the reservoir 62 which is substantially smaller than the
diameter of the ball 132. In this exemplary embodiment, the first diameter is .179
inches and the second diameter is .120 inches.
[0052] To fill the reservoir 62, the pen is held with the snout region 75 in an upright
position as shown in FIG. 6. A needle is lowered through the fill port opening 130
down into the ink reservoir nearly touching the bottom of the reservoir. This is done
so that the in falls the shortest distance possible, as some inks will foam if they
fall, which makes priming difficult later. The pen reservoir is then filled with ink
through the ink fill needle by a pumping means to the point that the ink in the reservoir
is nearly touching the inside of the ink fill hole. At this point the needle is drawn
out of the pen and a ball 132 is placed over the ink fill opening 130. The ball fits
tightly within the opening 138, as it must displace some of the plastic material surrounding
the opening 130, due to its size relative to the opening size. The ball 130 is then
pressed into the in fill 130B by a pressing tool 140 (FIG. 9) such that it just touches
the inner diameter at 138 at the bottom of the ink fill opening 130. At this point
the ink is contained in the pen reservoir; however, an air path exists from the top
of the free surface of the ink through the printhead nozzles which must be removed
to establish the initial pen back pressure.
[0053] The air is pulled from the pen with the pen 50 tilted on a 30 degree angle such that
the highest point is the snout region 75. This is done because the air will float
to the highest point which then is the snout region, and thereby facilitating pulling
the air from the pen by the primer. A suction head is then placed over the nozzle
region of the thermal ink-jet head and vacuum pulled. As the vacuum removes air from
the pen and the ink level will rise, wet out the filter, and eventually make its way
up to and through the printhead nozzles. This process has been characterized such
that a known amount of ink will be pulled through the nozzles to establish the initial
back pressure in the pen at -1 inch of water. After the pen is primed, the top surface
of the printhead is washed with clean water and an air knife to remove any excess
ink from the priming process. After the pen has been primed it, of course, may be
turned in any orientation with the ink remaining in the pen.
[0054] FIGS. 10 and 11 show in isolation the outer plastic member 78 comprising the pen
50. In particular, it can be seen in FIG. 11 that the plastic member 78 presents an
exterior flat surface 142, but that the inner side of member 73 presents several steps
to increase the thickness of member 78, forming a plateau 146. A rib feature 144 is
formed along the center of the member 78 extending from plateau 146, and includes
undercut sides 144A and 144B. The rib 144 extends along part or nearly all of the
sides of the frame member 78, as shown in FI.G. 10.
[0055] FIG. 12 is a side elevation view corresponding to FIG. 10, but showing the inner
frame member 78 molded onto the outer frame member 78. The frame member 78 extends
along the plateau 146, and covers the rib 144. The undercut sides of the rib provide
a locking means for locking the member 68 onto the member 68. In this embodiment,
the member 68 has a thickness T (.059 inches) and a width W (.354 inches) in the area
shown in FIG. 13. The sides 148 and 150 of the member 68 which extend generally perpendicular
to the frame member 78 provide surfaces to which the ink reservoir membranes 64 and
66 may be attached.
[0056] The material forming the inner member 68 has a shrink rate as it cools from the molten
state. This material is molded inside the outer frame 78 and tends to shrink away
from the frame 78 as it cools. To keep the inner plastic member 68 attached to the
exterior frame member 78, it is molded onto the undercut features 144 which are molded
as part of the member 78. As the material forming member 68 cools, it locks onto the
external frame 78 by these features 144, thereby countering the forces of the material
forming member 68 to pull away from the external frame 78 due to the shrinkage of
that material. The locking rib 144 shown has a simple cross section which is easy
to mold.
[0057] A soft polyolefin alloy can be used as the material for member 68, as it adheres
chemically to the surface of the NORYL material and has a shrink rate that is very
low (about equal to the NORYL 2.5 mills/inch) so that the forces created during the
shrinking process are lower than, for example, pure polyethylene which is about 20
mils/inch. An exemplary material suitable for construction of member 68 is described
in application serial number 08/058,730, filed May 3, 1993, entitled "Two Material
Frame Having Dissimilar Properties For Thermal Ink-Jet Cartridge."
[0058] FIGS.14 and 15 show the structrure of the members 68 and 78 in the snout region in
further detail. The material of the inner member 68 flows over the ribs 78A and 78B,
and covers the standpipe 93, locking onto the rib 93A.
[0059] FIG. 16 is a cross-section taken along line 16-16 of FIG. 6. Elements defining the
ink reservoir are visible here. Attachment of the spring bag membranes 64 and 66 to
the opposed side surfaces 143 and 150 of the inner member 68 is illustrated. FIG.
17 in particular is an enlarged view illustrating the heat staked attachment of the
membrane 66 to surface 148 of the inner frame member 68. Heat staking per se is well
known in the plastics art.
[0060] FIGS. 18 and 19 illustrate two alternate embodiments of the locking features which
may be formed on the inner surface of the frame member 78, instead of the undercut
rib 144. Thus, FIG. 18 shows a frame member 78' which employs locking features 144',
essentially small handle-like features with an opening 160 into which the molten plastic
flows when the inner member 68' is molded. FIG. 19 shows a frame member 78" which
includes locking features 144" which include rounded undercut openings 162 formed
therein. The molten plastic flows into the undercut openings 162 when the inner member
68" is molded.
[0061] Another aspect of the invention is shown in FIGS. 20-32. This aspect is illustrated
in a drum printer application, but it is applicable to other types of swath printers
as well. The drum printer utilizes the spring bag pen cartridge described above with
respect to FIGS. 1-19, and a closed auxiliary in reservoir. There are two illustrated
embodiments. The first is a single cartridge swath printer. The paper is secured to
the periphery of the drum by a vacuum (or other attachment means, such as adhesive
tape), and the drum rotated relative to a cartridge carriage. The carriage is moved
in two alternate ways. One way is to incrementally step or move the carriage from
one swath to the next. The other is a continuous, very slow movement, so that the
printhead moves in a spiral relative to the paper surface. To provide higher ink volume
capacity in accordance with this aspect of the invention, a closed auxiliary reservoir
is connected via a tube to the spring bag internal reservoir. For the single cartridge
drum printer, the auxiliary reservoir is held by a platform mounted on the carriage.
As the carriage moves, the auxiliary carriage moves with the carriage. To prevent
ink from unduly sloshing around in the auxiliary reservoir, the use of the continuous,
slow movement of the cartridge carriage works best. For a multiple cartridge printer
using two cartridges, each having a different color ink, one auxiliary reservoir is
held on a platform mounted on the cartridge carriage as in the single cartridge embodiment,
and a second reservoir mounted on a platform secured to the printer body, there being
relative motion between the second reservoir and the cartridge and paper. In each
embodiment, the auxiliary reservoirs are connected via flexible tubes to the respective
internal reservoir of the spring bag cartridge through the existing fill hole defined
through the softer inner plastic material. The auxiliary reservoir for each embodiment
is a flat, high capacity bag. The inner diameter of the tubes is sufficient to supply
ink under heavy printing loads to maintain the ink supply in the primary spring-bag
reservoir; the system does not rely on capillary flow through the tubes.
[0062] FIGS. 20-26 illustrate the single cartridge embodiment of a swath printer 200 with
an auxiliary reservoir. The printer includes a printer body 202 which provides support
for the printer elements. The printer includes a hollow cylindrical drum 204, which
is perforated with a number of holes 206. The drum 204 is mounted on the body 202
for rotational movement about its axis, and is driven by motor 208. A source of vacuum
(not shown) is connected to the interior of the hollow drum, which tends to draw air
into the interior of the drum through the holes 206. This tends to secure a print
medium such as paper tightly about the periphery of the drum for printing operations.
[0063] The printer 200 further includes a cartridge 50 having a spring bag reservoir 62,
mounted in a carriage 210 for movement along a carriage axis which extends generally
parallel to the center axis of the drum 20. The carriage is mounted on rods 212 and
214 for sliding movement along the extent of the drum over which printing operations
are to be performed. The carriage 210 is driven by a leadscrew 218 which is rotated
by motor 220. The carriage 210 has mounted thereon a leadscrew follower nut (not shown)
which is engaged on the leadscrew. The motor 220 can be operated to rotate the leadscrew
218, which in conjunction which the leadscrew follower translates the rotation movement
of the leadscrew into linear movement of the follower and carriage.
[0064] The motors 208 and 220 can be operated to precisely position a given point on the
print medium surface relative to the printhead carried by the spring bag cartridge
50.
[0065] In accordance with the invention, the swath printer further includes a closed auxiliary
reservoir 230, connected to the primary reservoir 62 of the spring bag cartridge 50
by a flexible tube 240. In this exemplary embodiment, the auxiliary reservoir 230
is carried on the cartridge carriage 210, which includes a reservoir platform 244.
Thus, as the carriage is moved along the carriage axis during printing operation,
the auxiliary reservoir 230 is carried with the carriage. Because the carriage typically
moves slowly in a continuous movement, or in small incremental swath steps, the liquid
in held in the reservoir 230 is not subjected to large accelerations/decelerations,
and so does not slosh about within the reservoir to a large degree.
[0066] The tube 240 has a primary reservoir end 240A which is connected to the existing
fill port 130 formed in the frame 60 of the cartridge 50. The external diameter of
the tube 240 is selected to be slightly larger than the nominal opening size of the
fill port 130. After the primary cartridge reservoir has been filled with in as described
above, the tube end 240A is connected to the fill port through a right angle "L" fitting
243 (FIG. 23). This interconnection between the tube end 240A and the inner plastic
member 68 is illustrated in FIG. 23.
[0067] The tube 240 is further connected at its second end 240B to the auxiliary reservoir
230, as illustrated in FIGS. 23 and 24. The reservoir 230 includes a fitment element
232 which provides a structure to attach the tube 240. The fitment 232 includes a
tube 232A extending transversely to a "q" shaped fitment flat structure portion 232B.
There is a tube opening 232C extending through the tube and flat structure portion.
The flat structure portion 232B has a flat surface 232E which is attached to the bag
material, and a series of channels 232D formed in the surface opposed to the flat
surface. The channels lead to the tube opening 232C, and serve to prevent the opening
from being closed by the bag material as the bag empties and collapses. Thus, the
channels allow the bag to be more completely emptied of ink. The fitment 232 in the
exemplary embodiment is a one piece structure molded from low density polyethylene.
[0068] In a preferred embodiment, the auxiliary reservoir 230 is a bag fabricated of a flexible
material impervious to the liquid ink, and can be the same material as that used for
the spring bag membranes in the spring bag cartridge. A suitable bag material is a
commercially available assembly of two thin layers adhered together, a two mil thick
layer of polyethylene, and a .75 mil thick layer of polyester (MYLAR) on the bag exterior.
The auxiliary reservoir bag can be fabricated in accordance with the following exemplary
method.
[0069] First, a piece of the bag material about six inches wide and twenty-four inches long
is cut. Next, a 1/4 inch hole is punched in the very center of the bag material for
the fitment element 232. The piece of bag material is placed over the fitment 232
with the fitment tube 232A inserted through the hole in the material. The fitment
position is adjusted so that its long dimension is parallel to the long side of the
piece of material. Next, a two-inch-by-two-inch piece of teflon cloth with a 1/4 inch
hole punched in it is placed over the fitment tube 232A, so that the bag material
and teflon cloth sandwich the fitment element 230. A fitment welder is used to heat
weld the fitment to the bag material. The fitment welder can be a hollow aluminum
cylinder attached to a soldering iron, with the cylinder defining a clearance opening
larger than the diameter of the fitment tube. The temperature can be controlled by
unplugging the soldering iron, etc., to get the best fitment seal. A cylinder of rolled
teflon cloth is placed over the fitment tube 232A to protect it from melting. A second
cylinder of rolled teflon cloth is placed inside the clearance hole of the fitment
welder. The welder is carefully lowered over the fitment tube and pressed down to
melt the bag material and the fitment together. This welding will require a rather
fast rolling motion to prevent melting the fitment tube or excess melting of the bag
but also must assure a complete bag to fitment seal.
[0070] Once the fitment is in place, the periphery of the bag can be sealed with impulse
heat sealers typically used on plastic bags. The piece of bag material is folded over
in the long direction to end up with a bag six-inches-by-twelve inches with the fitment
tube protruding out of one side wall of the bag. The long edges of the bag material
are lined up, and the short end of the bag is heat sealed about 11-1/2 inches from
the fitment end. A second seal right can be placed next to the first one for added
sealing security. Then each of the long edges of the bag are sealed about one inch
from the edge. A second seal can be placed right next to the first seal for added
sealing security. The bag should now have a sealed area of about four-inches-by-eleven-and-one-half-inches
with the fitment tube 232A protruding from one side wall of the bag. When the bag
is filled with ink, it will have a typical height of about 1-1/2 inches.
[0071] The auxiliary reservoir bag 230 can be filled by at least two exemplary methods.
One method is syringe filling. Ink is pulled into a syringe, the syringe is connected
to the bag fitment tube through a luer fitting, and the ink is pushed into the bag.
Another method is siphon filling. The bag 230 is placed at a lower level than the
free liquid level in an ink bottle. A tube is placed in the ink bottle. A "tee" is
connected between a luer fitting on the bag 230 and the tube from the bottle. A syringe
is attached to the open end of the "tee." When the syringe is used to evacuate the
tube and bag of air, the ink that is pulled out of the bottle starts a siphoning action
into the bag 230. Once the bag has the required amount of ink in it, the luer fitting
can be capped with a male luer plug. To remove any air bubbles, the bag is oriented
to get any air bubbles to collect at the fitment and the plug is opening enough to
let the air escape. The auxiliary reservoir bag 230 can be refilled by the same techniques.
[0072] The cartridge 50 shown in FIGS. 1-19 is employed in the printer 200, with modifications
to permit the connection of tube 240. Consider a cartridge 50 which has been filled
with ink and the fill port sealed with a ball 132 as shown in FIG. 9. With the cartridge
oriented as shown in FIG. 9, the ball 132 is pushed into the cartridge reservoir 62.
To permit a sealed connection to the reservoir at the fill port 130, the fill port
opening is enlarged with a drill bit, e.g., a number 21 bit for a port opening size
of .159 inches, either by hand or with a drill press. Using a clean stainless steel
#10/32 screw, threads are formed in the inner plastic member 68 defining the fill
port opening by threading the screw into the opening. The threads are formed only
in the inner plastic material 68, and do not expose or cut into the external plastic
frame member 78. The screw is then withdrawn and replaced with a #10-32 "L" fitting
243 with a barbed end. The L fitting is turned in as far as it will go and still have
the barb end point away from the pen snout. The threaded engagement between the fitting
and the port opening sidewall results in a joint which is leak-free over a range of
environmental parameters to which an ink-jet cartridge is typically exposed. The tube
end 240A is then attached to the barb end of the fitting 243 by pressing the tube
end over the barb. The length of tubing is preferably kept as short as feasible (e.g.,
less than 6 inches) to reduce the back pressure but still allow connection to the
bag 230. At least some portion of the tube 240 is capable of being pinched off with
a clamp. A tubing clamp is placed on the tube, and a male luer barbed connector is
pressed onto the tube end. To reset the spring bag reservoir, a syringe is attached
to the tube 240, to pull out the air in the cartridge reservoir until ink comes out
into the tube. The clamp is closed and the syringe removed. The cartridge is ready
for any testing and may be connected to an auxiliary bag at any time.
[0073] Of course, instead of starting the process with a filled, sealed cartridge, one could
start the process with a cartridge whose reservoir is empty. If the fill port 130
is sealed with a ball 132, the ball can be pushed into the reservoir as before. If
the port 132 is not sealed, this step will of course not be necessary. The port is
opened with a drill bit, threaded with a screw, the L fitting installed, and a tube
connected to the barbed end of the L fitting. The spring bag reservoir can then be
filled through the tube, and air drawn out with a syringe as described above. The
cartridge is then ready to be connected to the auxiliary bag 230.
[0074] To attach the cartridge 50 to the auxiliary reservoir bag 230, it is helpful if a
tube is attached to the L fitting attached to the fitment tube 232A and capped with
a female luer fitting and a luer plug. In an exemplary embodiment, the tube has an
inner diameter of 1/8 inches to permit adequate flow and without relying on capillary
flow. The end of the bag tube is held above the height of the bag itself, and the
luer plug removed. The male luer fitting attached to the cartridge tube is twisted
into the female luer at the end of the bag tube. The clamp on the cartridge tube is
opened. While handling cartridges with untaped printheads connected to the reservoir
bag, care should be taken to keep the cartridge nozzle plate within four vertical
inches of the top of the bag 230 or cartridge depriming or drooling may result. It
is desirable to clamp off the cartridge tube if the cartridge 50 and bag 230 are being
moved around. The amount of ink in the cartridge reservoir 62 can be decreased when
the cartridge is attached to the bag 230 by raising the cartridge relative to the
bag and increased by lowering the cartridge relative to the bag.
[0075] In a particular exemplary embodiment, it has been found that the cartridge-bag system
will work well with the bag's upper surface between one and four inches below the
cartridge nozzle plate. The system can accommodate a moderate degree of air, though
the tube from the cartridge to the auxiliary reservoir should be kept below the top
of the cartridge to avoid the formation of an air lock.
[0076] The cartridge spring-bag reservoir creates a negative pressure as it collapses, and
the pressure gets more negative throughout the collapse. The auxiliary reservoir bag
230 will also create a negative pressure as it collapses but of much less magnitude.
To consider the operation of the continuous refill system, assume that the spring
bag cartridge reservoir is nearly empty, and that the auxiliary reservoir bag is full
and mounted below the cartridge reservoir. Further assume that the cartridge reservoir
and auxiliary reservoir are connected with a tube with a valve blocking flow between
them. Now assume that the valve is opened. Ink will flow up hill from the bag 230
to the cartridge reservoir so long as the suction (negative pressure) in the cartridge
reservoir is greater than necessary to collapse the auxiliary bag and pull the ink
uphill. The cartridge reservoir will refill to an equilibrium point depending on the
height difference between the cartridge reservoir and the auxiliary bag, the cartridge
and bag pressure-volume relationships, and the starting ink volumes in the cartridge
reservoir and the auxiliary reservoir. This equilibrium point will vary as the auxiliary
bag is emptied of ink. The location of the tube connection to both the cartridge reservoir
and the auxiliary reservoir will affect the effective cartridge/auxiliary bag height
difference. The height differential at issue for this closed system is the height
differential between the free surface of the ink within the auxiliary reservoir and
the ink meniscus formed at the cartridge printhead.
[0077] There is a narrow range of cartridge/auxiliary reservoir heights that will work correctly;
too small a height differential and the cartridge reservoir will overfill and drool
ink from the printhead due to too low a back pressure, too great a height differential
and the cartridge reservoir will underfill and will not be able to print due to too
high a back-pressure. It is desired that the system be set up so that the spring-bag
plates never touch the outer frame covers due to overfilling, and the plates do not
collapse completely until the auxiliary reservoir ink supply has been depleted. The
height difference can determined empirically by testing a statistically significant
pcpulation of cartridges. The ideal height differential is one which will not cause
a statistically "worst case" cartridge to drool or puddle, i.e. a cartridge having
a spring-bag reservoir with the highest back pressure at which the system will be
designed to operate. These cartridges have higher than normal back pressure, and as
such, may cause ink to flow when other cartridges may not. To ensure these "worst
case" cartridges do not puddle or drool, the vertical height difference is increased
from a nominal distance to give some margin. The nominal distance is based on average
back pressures for a given "filled" cartridge, say 40cc of ink which may correspond
to 3 inches of water. The typical range of back pressure for a spring-bag cartridge
is between 2 and 10 inches of water, with a typical preferred operating range of 3-7
inches for production cartridges. The print head type and spring construction will
have some effect on the desired operating range.
[0078] FIGS. 27 and 28 show an alternate embodiment of a drum printer 200' employing the
auxiliary ink reservoir system. The printer 200' has two spring-bag reservoir cartridges
50' and 50'' mounted in respective carriages 210' and 210", each mounted on carriage
support structure 215. The orientation of the two cartridges is shown in the cross-sectional
view of FIG. 28. Each is oriented such that its longitudinal axis if extended would
intersect the center of the drum 204.
[0079] The auxiliary reservoir 230' for cartridge 50' is mounted on platform 244' in a similar
manner as in the printer 200 embodiment shown in FIGS. 20-21. A tube 240' connects
the primary reservoir in the cartridge 50' and the auxiliary reservoir 230'. Thus,
the reservoir 230' is carried along with the cartridge 50' as the carriage structure
215 is advanced/retracted by the leadscrew 218.
[0080] The auxiliary reservoir 230" for cartridge 50" is mounted on platform 244", which
is secured to the printer body 202. A tube 240" connects the primary reservoir in
the cartridge 50'' and the auxiliary reservoir 230".
[0081] When the cartridge and auxiliary reservoir are not installed in a printer, e.g.,
during shipping or in inventory, there is the risk that the height differential between
the cartridge and auxiliary reservoir will not be at the correct differential to prevent
ink flow from the reservoir to the cartridge, allowing ink drool from the print head.
To prevent this, a shut-off valve will typically be installed in the fluid path between
the auxiliary reservoir and the cartridge to prevent ink flow when the cartridge/auxiliary
reservoir are not installed in a printer. This may be a simple pinch valve for closing
the tube, for example. Such valves are schematically illustrated in FIG. 24 as elements
241A and 241B.
[0082] It is understocd that the above-described embodiments are merely illustrative of
the possible specific embodiments which may represent principles of the present invention.
Other arrangements may readily be devised in accordance with these principles by those
skilled in the art without departing from the scope and spirit of the invention.
1. An ink-jet printer (200) for ink-jet printing onto a print media, characterized by:
an ink-jet cartridge (50) including an ink-jet print head (76) and a closed spring-bag
primary reservoir (62) in fluid communication with said print head for holding a first
supply of liquid ink under negative pressure, said primary reservoir including at
least one movable side wall (64) and an internal spring (74) for biasing said at least
one movable side wall against collapsing as ink is withdrawn from said reservoir and
ejected from said print head onto a print medium during printing operations;
apparatus (204,208) for effecting relative motion between the print medium and the
print head during printing operations;
a closed auxiliary reservoir (230) for holding a second supply of liquid ink;
a connection tube (240) running between the primary reservoir and the auxiliary reservoir
for providing a closed fluid path to provide passive ink replenishment from said auxiliary
reservoir to said primary reservoir during normal printer operation.
2. A printer according to Claim 1, further characterized in that said auxiliary reservoir
(230) comprises at least one movable wall element.
3. A printer according to Claim 1 or Claim 2, further characterized in that said auxiliary
reservoir (230) comprises a collapsible bag comprising a sheet of flexible material
impervious to liquid ink.
4. A printer according to Claim 3, further characterized in that the auxiliary reservoir
(230) further includes a fitment structure (232) attached to said sheet of flexible
material, said fitment structure including a planar surface (232E) attached to said
sheet, an opening (232C) defined through the planar surface and the sheet, and a tube
connecting structure (232A) for attaching an end of said tube (240) in communication
with said opening.
5. A printer according to any preceding claim, further characterized in that said primary
and auxiliary reservoirs (62, 230) and said connection tube (240) are cooperatively
arranged so as to provide automatic ink replenishment of said primary reservoir (62)
without operation of any valves in said closed fluid path.
6. A printer according to any preceding claim, further characterized by apparatus (244)
for positioning said auxiliary reservoir (230) at a height relative to said primary
reservoir (62) to maintain a sufficient liquid ink pressure head in said closed fluid
path to provide continuous replenishment of said primary ink reservoir from said auxiliary
reservoir.
7. A printer according to Claim 6, further characterized in that said liquid ink pressure
head is insufficient to diminish said negative pressure sufficiently so as to allow
ink to drool from the print head (76).
8. A printer according to any preceding claim, further characterized in that said primary
and auxiliary reservoirs (62, 230) and said connection tube (240) are cooperatively
arranged so as to provide automatic ink replenishment of said primary reservoir (62)
without operation of any sensors to indicate a level of ink in said primary reservoir.
9. A printer according to any preceding claim, further characterized in that said apparatus
for effecting relative movement comprises:
a drum (210) for holding a print medium;
a carriage (210) for holding said spring bag cartridge (50) in a closely arranged
position relative to a surface of said drum;
apparatus (208) for rotating the drum so as to move the print medium in relation to
the printhead of the cartridge; and
apparatus (218, 220) for moving the carriage along a carriage axis.
10. A printer according to any preceding claim, further including a second cartridge (50")
with a second primary reservoir, a second auxiliary reservoir (230") and a second
connection tube (240") running between the second primary reservoir and said second
auxiliary reservoir, said second cartridge held by said carriage and translated along
the carriage axis with said first cartridge, said printer further including a stationary
printer body, said carriage translating relative to said body, and wherein said second
auxiliary reservoir is secured relative to said body and remains stationary as said
carriage is translated along said axis during printing operation.
11. A method of replenishing liquid ink in a closed spring-bag primary reservoir (62)
in an ink-jet printing system, characterized by the following steps:
providing an ink-jet cartridge (50) including an ink-jet print head (76) and a closed
spring-bag primary reservoir (62) in fluid communication with said print head for
holding a first supply of liquid ink under negative pressure, said primary reservoir
including at least one movable side wall (64) and an internal spring (74) for biasing
said at least one movable side wall against collapsing as ink is withdrawn from said
reservoir and ejected from said print head onto a print medium during printing operations;
providing a closed auxiliary reservoir (230) for holding a second supply of liquid
ink;
providing a closed ink path (240)running between the primary reservoir and the auxiliary
reservoir to provide passive ink replenishment from said auxiliary reservoir to said
primary reservoir during normal printer operation.
12. A method according to Claim 11 further characterized by the step of effecting relative
movement between the ink-jet printhead and a print medium during printing operations.
13. A method according to Claim 11 or Claim 12, further characterized in that said primary
and auxiliary reservoirs and said connection tube provide automatic ink replenishment
of said primary reservoir without operation of any valves in said closed fluid path.