BACKGROUND
Description of the Art
Substantial developments have been made in the micro-manipulation of fluids in fields such as electronic printing technology using inkjet printers. Fluid ejection cartridges and fluid supplies provide good examples of the problems facing the practitioner in preventing the formation of gas bubbles in the supply container, microfluidic channels, and chambers of the fluid ejection cartridge. The fluid supply in inkjet printing systems is just one common example.
Currently there is a wide variety of highly efficient inkjet printing systems in use, which are capable of dispensing ink in a rapid and accurate manner. Generally a printhead is mounted to a carriage that is moved back and forth across a print media, a print controller activates the printhead to deposit or eject ink drops onto the print media to form images and text. Ink must be delivered to the printhead by an ink supply that is either carried by the carriage or mounted to the printing system in a fixed manner, typically, with a flexible ink delivery system connected between the supply and the printhead.
There has been a demand by consumers for ever-increasing improvements in speed, image quality and lower cost in printing systems. In an effort to reduce the size of ink jet printers and to reduce the cost per printed page, efforts have been made to optimize the performance of three basic configurations: 1) print cartridges with integral reservoirs, 2) small semi-permanent or permanent printheads with replaceable ink reservoirs mounted on the printheads, and 3) small semi-permanent or permanent printheads with a fixed ink supply that is either continuously connected or intermittently connected to the printhead. For the last case the ink supply is mounted off of the carriage and either connected to the printhead via a flexible conduit providing continuous replenishment or else intermittently connected by positioning the printhead proximate to a filling station that facilitates connection of the printhead to the ink supply. In the first case the entire printhead and ink supply is replaced when the ink is exhausted. In the second case the ink supply is separately replaceable, and is replaced when exhausted and the printhead may be replaced at the end of printhead life. Regardless of where the ink supply is located within the printing system, it is desirable that the ink supply reliably, efficiently, and cost effectively deliver as much of the total volume of ink contained in the supply to the printhead as possible.
An example of an inkjet cartridge with an integral fluid supply is shown in FIGS. 1a-1c. The fluid supply of print cartridge 102 consists of unitary cartridge body 121 that is configured to hold free ink in printhead support section or snout region 112 and to hold ink in porous media section 114 as shown in a cross-sectional view in FIG. 1b. Standpipe 139, shown in a top-plan view in FIG. 1a and in cross-sectional views in FIGS. 1b-1c generally has filter 156 mounted to the top portion of the standpipe. Ink stored in the porous media section flows through filter 156 into standpipe 139 as ink is ejected from the printhead (not shown). Typically, printhead support region 112 will have several support members such as standpipe supports 125a, 125b, 125c, and 125d which increase the rigidity of both the standpipe and the printhead support section in general, providing greater resistance to cracking of the printhead when the print cartridge is subjected to shock such as through inadvertent dropping. In addition, the ink delivery system of such a print cartridge should function properly in the presence of shaking, vibration, trapped air, particle contamination, and a broad range of operating temperatures and pressures.
In addition to providing ink to the printhead, the ink supply also provides additional functions. Typically, replaceable ink supplies are provided with seals over the fluid interconnects to prevent ink leakage and evaporation, and contamination of the interconnects during distribution and storage. In addition, the ink supply also provides for some pressure regulation to deliver the ink to the printhead at the optimum backpressure (i.e. a negative pressure). The printing system strives to maintain the backpressure of the ink within the printhead to within as small a range as possible. The backpressure needs to be sufficiently negative so that the head pressure associated with the ink supply is kept at a value that is lower than the atmospheric pressure to prevent leakage of ink from either the ink supply or the printhead, such leakage is typically referred to as drooling. In addition, the ink supply should provide a backpressure over a wide range of temperatures and atmospheric pressures to which the printhead may be subjected in storage, shipment, and operation.
Changes in back pressure, of which air bubbles are only one variable, may greatly effect print density as well as print and image quality. In addition, even when not in use the volume of air entrapped in a fluid supply may increase when subjected to stress such as dropping. Subsequent altitude excursions typically cause this air to expand and displace ink ultimately leading to the displaced ink being expelled from the supply container. The expelled ink will cause damage to the product package or other container in which it is located.
If these problems persist, the continued growth and advancements in inkjet printing and other micro-fluidic devices, seen over the past decade, will be reduced. Current ink supply technology continually struggles with maximizing the amount of ink delivered for a given container size while continuing to meet shipping stress and altitude specifications. Consumer demand for cheaper, smaller, more reliable, higher performance devices constantly puts pressure on improving and developing cheaper, and more reliable manufacturing materials and processes. There is an ever present need for ink supplies which make use of low cost materials and are relatively easy to manufacture. In addition, there is a continuing desire for ink containers that are volumetrically efficient producing compact ink supplies that provide for ever smaller printing systems. The ability to optimize fluid ejection systems, will open up a wide variety of applications that are currently either impractical or are not cost effective.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
a is a top plan view of a prior art print cartridge storing ink in a free ink section and a porous media section.
FIG. 1
b is a cross-sectional view along 1b-1b of the print cartridge shown in FIG. 1a.
FIG. 1
c is a cross-sectional view along 1c-1c of the print cartridge shown in FIG. 1a.
FIG. 2
a is a top plan view of a fluid container according to an embodiment of the present invention.
FIG. 2
b is a cross-sectional view along 2b-2b of the fluid container shown in FIG. 2a.
FIG. 2
c is a cross-sectional view along 2c-2c of the fluid container shown in FIG. 2a.
FIG. 2
d is a cross-sectional view along 2d-2d of the fluid container shown in FIG. 2a with a capillary material disposed within the container and the container filled with a fluid according to an embodiment of the present invention.
FIG. 2
e is an expanded view showing the compression region formed by the free fluid compartment sidewall as illustrated in FIG. 2d according to an embodiment of the present invention.
FIG. 3
a is a top plan view of a fluid container according to an alternate embodiment of the present invention.
FIG. 3
b is a cross-sectional view along 3b-3b of the fluid container shown in FIG. 3a.
FIG. 3
c is a cross-sectional view along 3c-3c of the fluid container shown in FIG. 3a.
FIG. 4
a. is a top plan view of a fluid ejection cartridge according to an alternate embodiment of the present invention.
FIG. 4
b is an expanded top plan view of a portion of the outlet compartment of the alternate embodiment shown FIG. 4a.
FIG. 4
c is a cross-sectional view along 4c-4c of the fluid ejection cartridge shown in FIG. 4a.
FIGS. 5
a-5b are cross-sectional views of compression shoulders of a free fluid compartment sidewall according to alternate embodiments of the present invention.
FIGS. 5
c-5e are cross-sectional views of compression edges of a free fluid compartment sidewall according to alternate embodiments of the present invention.
FIG. 5
f is top plan view of the intersection of two free fluid compartment sidewalls according to an alternate embodiment of the present invention.
FIG. 5
g is a cross-sectional view along 5g-5g of the two free fluid compartment sidewalls shown in FIG. 5f.
FIG. 6
a is perspective view of a fluid ejection cartridge according to an alternate embodiment of the present invention.
FIG. 6
b is a cross-sectional view along 6b-6b of the fluid ejection cartridge shown in FIG. 6a.
FIG. 7
a is a top plan view of a fluid container according to an alternate embodiment of the present invention.
FIG. 7
b is a cross-sectional view along 7b-7b of the fluid container shown in FIG. 7a.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
This invention is directed to various fluid containers and fluid ejection cartridges that utilize, for fluid containment, a volume of capillary material along with a free fluid chamber. The present invention provides a container or cartridge that reduces the amount of free fluid that can be displaced by air from a given air path or leakage path reaching the free fluid volume. If gaps, between the capillary material and the edges of the container or cartridge, allow air to reach the free fluid, the capillary force in the capillary material will draw the free fluid into the material until the material is saturated to the point the material stops absorbing fluid into it. Once the capillary material is saturated the excess free fluid can leak out through vent holes or outlet ports, or in the case of cartridges through the nozzles of the fluid ejector head and drool out of the container or cartridge potentially causing damage. In addition, during either or both increases in ambient temperature or deceases in air pressure, any air trapped within the container or cartridge will expand further exacerbating this drool problem.
The present invention advantageously utilizes a free fluid chamber partitioned into compartments with each compartment defined by various combinations of the peripheral walls of the container, compartment sidewalls and a surface of the capillary material. Each compartment sidewall has a compression region that extends into the capillary material. The volume of capillary material defines a fluid capillary volume of the container or cartridge. The compression region of the compartment sidewall compresses the capillary material along the compression region. These compressed cells of the capillary material have a higher capillary pressure, which causes them to saturate with fluid preferentially over less-compressed cells. The saturated cells adjacent to the compression region of each sidewall severely hinder and/or restrict air from migrating beyond the particular sidewall with which it comes in contact. Such a structure allows for over ten percent of the fluid stored in the container or cartridge to be stored as free fluid outside the capillary material. The combination of partitioning the free fluid chamber into at least two compartments, and the utilization of the compression regions of the compartment sidewalls hinders and/or limits an air path from reaching more than the 1 compartment exposed to the air path. This limitation allows the capillary material to continue to function properly since the capillary material absorbs only the smaller amount of free fluid contained in the one compartment and does not absorb the entire amount of free fluid held within the container or cartridge.
The present invention reduces the amount of capillary material utilized to provide a given amount of fluid to a customer. In addition, it allows the use of less expensive simple geometric shapes of capillary material such as simple cylinders, cubes, and rectangular shapes rather than more complex shapes that fill the entire volume of the container or cartridge. Further, since up to about twenty percent of the fluid absorbed by the capillary material may remain in the material at the end of life, the amount of fluid filled into a container or cartridge is increased by the amount held in the free fluid chamber. However, the amount of fluid stranded in the container or cartridge is not increased thereby providing for a higher percentage of the volume of fluid contained to be dispensed.
It should be noted that the drawings are not true to scale. Further, various elements have not been drawn to scale. Certain dimensions have been exaggerated in relation to other dimensions in order to provide a clearer illustration and understanding of the present invention. In particular, vertical and horizontal scales may differ and may vary from one drawing to another. In addition, although some of the embodiments illustrated herein are shown in two dimensional views with various regions having height and width, it should be clearly understood that these regions are illustrations of only a portion of a device that is actually a three dimensional structure. Accordingly, these regions will have three dimensions, including length, width, and height, when fabricated on an actual device.
Moreover, while the present invention is illustrated by various embodiments, it is not intended that these illustrations be a limitation on the scope or applicability of the present invention. Further, it is not intended that the embodiments of the present invention be limited to the physical structures illustrated. These structures are included to demonstrate the utility and application of the present invention to presently preferred embodiments.
A top plan view of an embodiment of fluid container 200 employing the present invention is illustrated in FIG. 2a. In this embodiment, fluid container 200 includes body 220 configured to contain a fluid. Body 220 has straight or vertical body sidewalls 222a, 222b, 222c, and 222d; however, in alternate embodiments, body 220 may have sloping sidewalls that provide for easy insertion of a capillary material such as capillary material 218 (see FIG. 2d). In addition, although body 220 is depicted as having a rectangular shape, body 220 may have any of a variety of different shapes and configurations. In this embodiment, body 220 is formed by injection molding utilizing a polyethylene terephthalate polymer (PET) that is 15 percent filled with glass; however, in alternate embodiments, any suitable metal, glass, ceramic, or polymeric material that is compatible with the fluid being stored also may be utilized. For example, polypropylene, polyethylene, liquid crystal polymers, glass, stainless steel, and aluminum are just a few materials that also may be utilized to form body 220.
Body 220 includes capillary material stops 232a, 232b, 232c, and 232d on which capillary material 218 is supported. The volume above the capillary material stops is the capillary fluid volume. In this embodiment, body 220 also includes free fluid compartments 224a and 224b which form a free fluid chamber. In alternate embodiments, the free fluid chamber may be partitioned into any reasonable number of free fluid compartments. Free fluid compartment 224a is formed by body sidewalls 222a and 222d and free fluid compartment sidewalls 226a and 226b. Free fluid compartment 224b is formed by body sidewalls 222c and 222d and free fluid compartment sidewalls 226a and 226c. Free fluid compartment sidewalls 226a and 226b and free fluid compartment sidewalls 226a and 226c each intersect at an angle of about 120 degrees; however, in alternate embodiments, the free fluid compartment sidewalls may intersect at other angles less than about 120 degrees. The actual angle utilized will depend on the amount of free fluid volume held in container 200 and the surface tension of both the fluid being stored and the surface free energy of the sidewall material. Larger angles, generally will be less efficient in generating a capillary path where the sidewalls intersect. The capillary path is advantageous for efficient uptake of the free fluid stored in that compartment. In addition, body 220 further includes outlet compartment 240 formed by body sidewalls 222b, 222a, and 222c and free fluid compartment sidewalls 226b and 226c. Outlet compartment 240 also includes fluid outlet 242 formed in body sidewall 222e through which fluid held in container 200 is dispensed as illustrated in FIG. 2b.
In this embodiment, as illustrated in FIGS. 2b-2d the compartment sidewalls extend from bottom or base surface 230 of body 220 toward opening 238. The portion of the compartment sidewalls extending above capillary material stops 232a, 232b, 232c, and 232d, as shown in cross-sectional views in FIGS. 2b-2d, form compression edges 234. As illustrated in FIG. 2d capillary material stops 232a, 232b, 232c, and 232d limit the distance that capillary material 218 may be inserted into body 220. When the capillary material is fully inserted, into the body, compression edges 234 generate a compressive region in the capillary material proximate to the compression edges as illustrated, in an expanded cross-sectional view, in FIG. 2e. This compressive region increases the capillarity of the cells or pores in this region and thus reduces the possibility of an air path penetrating from one free fluid compartment to another. Free fluid compartment sidewall 226a, in this embodiment, is flush with, or at the same height with, free fluid compartment sidewalls 226b and 226c which also form a portion of outlet compartment 240. In this embodiment, compression edges 234 extend about 1 millimeter above the capillary material stops; however, in alternate embodiments, the compression edges may extend from about 0.5 millimeters to about 3 millimeters above the capillary material stops. The particular amount that the compression edges may extend will depend on various factors such as the particular material utilized for the capillary material, the surface tension of the fluid, the surface free-energy of the capillary material, and the localized compressibility of the capillary material in the region proximate to the compression edges.
The structure of the present invention may be compared with print cartridge 102 shown in FIG. 1c. Print cartridge 102 includes standpipe supports 125b and 125d that extend from standpipe walls 143 to the peripheral walls of snout region 112 of cartridge body 121. In print cartridge 102 stand pipe supports are lower in height than the top of standpipe 139 onto which filter 156 is mounted. Thus, as illustrated in FIG. 1c, air gaps 110, generally, are formed between the top edge of the standpipe supports and capillary material 118 in the region of the intersection of standpipe supports 125b and 125d with standpipe walls 143, and air gaps 110 are also, generally, formed in the region of intersection with the peripheral walls of snout region 112. In FIGS. 1b and 1c the interface between the capillary material that is proximate to the air gaps is shown with a dashed line, whose dash length changes in certain regions solely for purposes of clarity. A gap between the capillary material and the support walls or compartment sidewalls that is greater than the nominal pore or cell size of the capillary material, allows air that finds a path into one free fluid compartment to continue to pass into an adjacent compartment.
As noted above and as shown in FIGS. 2b-2c, in the present invention the barrier between compartments is generated along compression edges 234, which form, in the capillary material due to the localized compression, a region of smaller-sized pores that have a bubble pressure greater than the backpressure in the fluid container. In the embodiment shown in FIGS. 2a-e, the radius of curvature in the plane of free fluid compartment sidewalls 226a, 226b, and 226c at the intersection with body sidewalls 222d, 222a, and 222c respectively is essentially square having a radius of curvature less than 0.1 millimeters. Fluid container 200 shown in FIGS. 2a-2e further includes cap or lid 228 having an air vent tube or labyrinth (not shown) formed in the lid for supplying or replenishing air to the internal volume as fluid is removed from the container. Lid 228 may have various ribs or other structures formed on the internal portion to further provide compression of capillary material 218 against compression edges 234 of the free fluid compartment sidewalls. In this embodiment, capillary material 218 is generally referred to as polyurethane foam; however, in alternate embodiments, other materials such as bonded polyester fiber (BPF), bonded polypropylene or polyethylene fibers, nylon fibers, or rayon fibers also may be utilized to form capillary material 218. Any material having a surface energy higher than the liquid being stored may be utilized including surface modified materials.
An alternate embodiment of a fluid container is shown in a top plan view in FIG. 3a. In this embodiment, fluid container 300 includes body 320 having peripheral walls 322a, 322b, 322c, and 322d formed by injection molding. Body 320, in this embodiment, includes capillary material stops 332a, 332b, 332c, and 332d having curved walls that extend between the two closest peripheral walls of body 320 forming capillary stop compartments 323a, 323b, 323c, and 323d in which additional free fluid may be stored. In addition, in this embodiment, body 320 further includes capillary material stop ledges 332e and 332f. The capillary material (not shown) is supported by the capillary material stops and ledges. In alternate embodiments, other structures may be utilized, such as a ledge that either entirely or partially circumscribes the peripheral walls of body 320, which advantageously reduces the volume of the structures utilized to form the stops so that the volume of free fluid which may be stored within fluid container 300 is maximized. The volume between container opening 338 and capillary material stop surfaces 333 forms capillary fluid volume 314.
In this embodiment, body 320 also includes free fluid volume 315 that is the volume between container base surface 330 and material stop surfaces 333 excluding the volume of fluid outlet 340. Free fluid volume 315, in this embodiment, is partitioned into 10 free fluid compartments labeled as 324a-324j. Each compartment includes at least one free fluid compartment sidewall 326a-326j. Body 320 further includes outlet compartment 340 formed by outlet compartment walls 344 and also includes fluid outlet 342 through which fluid held in container 300 is dispensed. Each free fluid compartment sidewall is flush with outlet wall surface 346 of outlet compartment walls 344, where the region of each free fluid compartment sidewall that extends above capillary material stop surfaces 333 forms compression edges 334 as illustrated in a cross-sectional view in FIGS. 3b and 3c.
An alternate embodiment of the present invention is shown in a top plan view in FIG. 4a where fluid container 400 is an integral part of fluid ejection cartridge 402. In this embodiment, fluid ejection cartridge 402 includes cartridge body 420 having peripheral walls 422a, 422b, 422c, 422d, 422e (see FIG. 4c), 422f (see FIG. 4c), and 422g (see FIG. 4c) where the internal surface of peripheral wall 422e forms capillary material stop 432. The volume between cartridge lid 428 (see FIG. 4c) and capillary material stop surface 433 forms capillary fluid volume 414. Cartridge body 420 also includes free fluid volume 415 that is the volume between internal cartridge base surface 430 and capillary material stop surface 433 excluding the volume of fluid outlet 440. Free fluid volume 415, in this embodiment, is partitioned into free fluid compartments 424a, 424b, 424c, and 424d. Each compartment includes at least one free fluid compartment sidewall 426a-426e. Cartridge body 420 further includes cylindrically shaped standpipe 440 formed by standpipe wall 444. Standpipe 440 typically includes a filter (not shown) mounted to standpipe wall surface 446 to provide filtration of air bubbles and solid particles when fluid flows from the capillary material (not shown) into standpipe 440. In this embodiment, standpipe wall 444 has 4 recessed grooves 448a, 448b, 448c, and 448d that provide separate conduits to transmit fluid between the capillary material, that is in intimate contact with the filter, and standpipe 440. These recessed grooves extend over a substantial length of standpipe 440. In this embodiment, the recessed grooves have a rectangular cross-section; however, in alternate embodiments, any non-circular or non-smoothly rounded interior cross-section may be utilized. The vertex or corner regions along the length of the recessed grooves define bypass channels that function to allow fluid flow past a large bubble that may form in the standpipe and effectively block fluid flow. The addition of the recessed grooves limits the expansion of any large bubble into the recessed grooves which remain filled with fluid to maintain a continuous fluid path between fluid container 400 and outlet 442. The fluid surface tension will substantially hinder an air bubble from completely filing the recessed groove so long as the width of the groove is less than 8(γ)/P where γ is the surface tension of the fluid and P is the internal pressure of the bubble assuming the bubble is characterized as cylindrical in shape. In this embodiment, the width of the recessed grooves is less than about 0.5 millimeters with a depth in the range from about 0.35 millimeters to about 0.46 millimeters. In alternate embodiments, cylindrically shaped free fluid compartments having recessed grooves may also be utilized in free fluid volume 415 to provide a wide variety of compartment geometries that may be utilized in the present invention.
At the base of standpipe 440 fluid outlet 442 provides a fluidic orifice through which fluid held in cartridge body 420 is fluidically coupled to printhead substrate 450 via fluid flow channel 452. Printhead substrate 450 may be any of the wide variety of fluid ejector heads known in the art such as thermal resistor, piezoelectric, flex-tensional, acoustic, and electrostatic. In this embodiment, printhead substrate 450 is a thermal resistor type fluid ejector having a plurality of thermal resistors formed on printhead substrate 450 and a plurality of orifices or nozzles in fluid communication with the thermal resistors.
In this embodiment, each free fluid compartment sidewall is flush with the top standpipe wall 444, where the region of each free fluid compartment sidewall that extends above capillary material stop surface 433 forms compression edges 434 as illustrated in a cross-sectional view in FIG. 4c. In addition, in this embodiment, the radius of curvature in the plane of free fluid compartment sidewalls 426a, 426b, and 426d at the intersection with peripheral walls 422d, 422a, and 422c respectively is curved upward toward lid 428 having a radius of curvature of 1 millimeters forming compression shoulder 436. In alternate embodiments, the radius of curvature may be in the range from about 0.25 millimeters to about 2.5 millimeters. The geometric configuration of the peripheral walls of cartridge body 420 and the spacing between the capillary material and the peripheral walls generally provides the most advantageous path for air leakage into the free fluid compartments. The addition of a radius of curvature proximate to the peripheral walls provides increased protection against leakage of air between two adjacent compartments in this region.
Alternate embodiments of a compression shoulder that may be utilized in the various embodiments of the present invention are shown in expanded cross-sectional views in FIGS. 5a-5b. In FIG. 5a compression shoulder 536, formed on compartment sidewall 526, decreases linearly moving away from body sidewall 522 of the container or cartridge body. In FIG. 5b compression shoulder 536′ forms a tab at the sidewall of the container or cartridge body. The particular length over which the compression shoulder extends and the particular height of the compression shoulder will depend on various factors such as the compression characteristics of the capillary material, the surface free energy of the capillary material, the surface tension of the fluid, the geometric configuration of the walls and the typical gap between the walls and the capillary material.
Alternate embodiments of the compression edge of the free fluid compartment sidewalls that may be utilized in the various embodiments of the present invention are shown in expanded cross-sectional views in FIGS. 5c-5e. In FIG. 5c, compartment sidewall 526 includes compression edge 534 that has a knife edge cross section, which provides for the highest compression of the capillary material at the apex of the knife edge. In FIG. 5d, compression edge 534′ includes compression channel 537 that runs parallel with the compression edge. In FIG. 5e compression edge 534″ includes a fully rounded edge. These embodiments provide a few examples of the wide variety of geometrical shapes that may be utilized to form the compression edge in the present invention.
An alternate embodiment of the intersection between two free fluid compartment sidewalls that may be utilized in various embodiments of the present invention is shown in a top plan view in FIG. 5f. In this embodiment, free fluid compartment sidewall 526a intersects with free fluid compartment sidewall 526b at an angle of ninety degrees. In addition, sidewall projection 527 having a rectangular cross-section extends out from free fluid compartment sidewall 526a proximate to free fluid compartment sidewall 526b forming fluid capillary channel 516 between sidewall 526b and projection 527. Fluid capillary channel 516 extends from base surface 530 of body 520 to compression edge 534 of free fluid compartment sidewall 526a providing a capillary channel for conducting free fluid from the base or bottom of a free fluid compartment to the capillary material as illustrated, in a cross-sectional view, in FIG. 5g.
An exemplary embodiment of the present invention is shown in a perspective view in FIG. 6a. In this embodiment, fluid ejection cartridge 602 includes cartridge body 620 having peripheral walls 622a, 622b, 622c, 622d, and 622e where the internal surface of peripheral wall 622e forms capillary material stop surface 633. The volume between container opening 638 and capillary material stop surface 633 forms capillary fluid volume 614 (see FIG. 6b). Cartridge body 620 also includes free fluid volume 615 (see FIG. 6b) that is the volume between internal cartridge base surface 630 and capillary material stop surface 633 excluding the volume of fluid outlet 640. Free fluid volume 615, in this embodiment, is partitioned into five free fluid compartments formed by compartment sidewalls 626a, 626b, 626c, 626d and 626e. Cartridge body 620 further includes square shaped fluid outlet 640 formed by outlet walls 644. Fluid outlet 640 also includes fluid feed slot 660 formed in bottom body sidewall 622g through which fluid held in fluid ejection cartridge 602 is dispensed to the printhead substrate (not shown).
As illustrated in a cross sectional view in FIG. 6b, in this embodiment, sidewalls 626a and 626e each have compression edges 634 that vary in elevation or height in moving from outlet walls 644 to peripheral walls 622a and 622c respectively. In this embodiment, compression edges 634 of sidewalls 626a and 626e are each flush in elevation with their respective outlet wall surface 646 of outlet walls 644, moving from the outlet wall toward the peripheral wall compression edges 634 each smoothly decrease in height reaching a minimum elevation in concave region 635. In this embodiment, the change in elevation between the outlet wall and the point of minimum elevation is about 0.5 millimeters; however, in alternate embodiments, other values, generally in the range from about 0.3 millimeters to about 1 millimeter also may be utilized. The particular value will depend on various factors such as the compression characteristics of the capillary material, the surface free energy of the capillary material, the surface tension of the fluid, the geometric configuration of the walls and the typical gap between the walls and the capillary material. Continuing toward peripheral wall the compression edges smoothly increase in height ending with compression shoulder 636 formed in the compression edge of the compartment sidewall at the intersection with the peripheral wall. In this embodiment, compression shoulder 636 has a radius of curvature of 2 millimeters; however, in alternate embodiments, the radius of curvature may vary from about 0.5 millimeters to about 3 millimeters. By varying the elevation of the compartment sidewall the amount or degree of compression of the capillary material, along the compression edge, may be varied. For example, the compression characteristics of the capillary material may be taken into account to produce a compression region having uniform compression over the entire length of the sidewall. Alternatively, the elevation may be varied to generate a region of high compression in the region of the outlet wall and the peripheral wall with a region of lower compression formed between these two regions of high compression.
Another exemplary embodiment of the present invention is shown in a top plan view in FIG. 7a. In this embodiment, fluid container 700 includes body 720 having peripheral walls 722a, 722b, 722c, 722d, and 722e (see FIG. 7b) where the internal surface of peripheral wall 722e forms base surface 730. Free fluid compartment 724a is formed by peripheral walls 722a-722d and circumjacent compartment sidewall 726a. Free fluid compartment 724b is formed by compartment sidewall 726a, cylindrical sidewall 726e and straight sidewalls 726d and 726c. Free fluid compartment 724c is formed by compartment sidewall 726a and straight sidewalls 726b and 726d, whereas free fluid compartment 724d includes compartment sidewall 726a and straight sidewalls 726b and 726c. Free fluid compartment 724e is formed between cylindrical sidewall 726e and cylindrical outlet wall 744. Outlet fluid compartment 740, in this embodiment, is formed by cylindrical outlet wall 744. In addition, fluid outlet compartment 740 also includes fluid outlet 742 formed in peripheral wall 722e through which fluid stored in fluid container 700 is dispensed. In this embodiment, each free fluid compartment is also bounded by peripheral wall 722e and capillary fluid volume 714 as illustrated in a cross-sectional view in FIG. 7b. Free fluid compartment sidewalls 726a-726e as well as cylindrical outlet wall 744 extend from base surface 730 to capillary fluid volume 714. In this embodiment, compression edges 734 of each compartment sidewall are flush with outlet wall surface 746 of outlet wall 744. Each compression edge of the free fluid compartment sidewalls generates a compressive region in the capillary material (not shown) proximate to the compression edges as described above. In this embodiment, compression edges 734 act as capillary material stops limiting the distance the capillary material may be inserted into body 720 of fluid container 700. In alternate embodiments, compression edges 734 may be lower in height than outlet hall surface 746 but extend sufficiently into capillary fluid volume to form a compressive region in the capillary material (not shown). As described above, the region between the capillary material and the peripheral walls typically is the dominant path for air leakage to a particular free fluid compartment. Thus, by utilizing free fluid compartment sidewall 726a to form free fluid compartment 724a having a narrow gap between and circumjacent to the peripheral walls of body 720, typically, the fluid uptake of the capillary material upon creation of the first air leakage path is substantially limited to the volume contained in free fluid compartment 724a.
Patent Grant
7478901
