Abstract:
A high efficiency, liquid supply vessel is provided. The liquid supply vessel includes a chamber, either an open-foam or septum-based fluidic interconnect, a tower, and at least one gas-permeable vent. The tower includes a valve which remains closed when the vessel is inserted into a printer and the fluidic interconnect is engaged, thereby retaining the liquid in the vessel. When the printhead is operated, a sufficient vacuum is created to open the valve, thereby supplying the liquid to the printhead. Whereas the vacuum pressure may otherwise rise to unacceptable levels, the gas-permeable vent enables the pressure to be equalized. Similarly, the vent equalizes pressure during altitude and/or temperature changes, thereby preventing pressure increases or decreases which would otherwise be associated with such changes.

Description:
BACKGROUND  
       [0001]     Liquid supply vessels, such as, for example, ink cartridges for printers have a liquid yield which is a generally defined volume of liquid (e.g., ink) expunged from the vessel divided by the volume of liquid originally present in the vessel. Improving the yield lengthens the life of the vessel and, therefore, improves the value of the vessel.  
         [0002]     In ink cartridges, often the liquid yield may be around 0.75. As a result, roughly 25% of the ink originally present in the cartridge is “lost,” i.e., it remains in the cartridge and is unable to be dispensed. One reason that ink remains in the cartridge is due to mechanical stranding where ink gets trapped in low lying areas inside the cartridge. The ink gets trapped due to inefficiencies caused by geometry (i.e., a flaccid bag used to contain the ink), or by the variation in capillary sizes if foam is used to contain the ink. By extending the life of an ink cartridge, printer downtime will be reduced. Moreover, by improving the ink yield, the cost associated with printing will also be reduced.  
         [0003]     Accordingly, what is needed is a liquid supply vessel, such as, for example, an ink cartridge, which addresses one or more of the aforementioned deficiencies in the prior art.  
       SUMMARY  
       [0004]     One embodiment of the invention addresses a liquid supply vessel comprising: (a) a chamber adapted to contain a liquid, wherein the chamber comprises a floor having an opening thereon; (b) a liquid dispensing apparatus having an intake and an outtake, wherein a valve is positioned between the intake and the outtake, and wherein the outtake is aligned with the opening; (c) a supply line having an inlet adjacent the floor and an outlet in fluid communication with the intake, wherein the supply line extends from the floor and is substantially housed within the chamber; and (d) at least one vent formed in a wall of the chamber, wherein the at least one vent is adapted to be exposed to a liquid contained within the chamber, and wherein the at least one vent is permeable to gas but impermeable to liquid.  
         [0005]     The invention also addresses a method of preventing back-pressure from developing in a chamber in a liquid supply vessel when the amount of liquid in the chamber decreases, and of equalizing pressure in a chamber in a liquid supply vessel when the altitude and/or temperature at which the vessel is maintained is changed. This method includes: (a) providing a chamber containing the liquid; (b) expunging at least some of the liquid from the chamber through an opening; and (c) sucking gas into the chamber in a manner that is impermeable to liquid to equalize the pressure in the chamber with the ambient pressure exterior of the chamber, to prevent back-pressure from developing in the chamber.  
         [0006]     These and other features, aspects, and advantages of the present invention will become more apparent from the following description, appended claims, and accompanying exemplary embodiments shown in the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a cross-sectional view of a liquid supply vessel according to one exemplary embodiment of the invention having an open-foam fluidic interconnect;  
         [0008]      FIG. 2  is an inverted view of the exemplary embodiment of  FIG. 1  showing how a supply line may act as an inverted snorkel or siphon; and  
         [0009]      FIG. 3  is a cross-sectional view of a liquid supply vessel according to a second exemplary embodiment of the invention in which a needle/septum fluidic interconnect replaces the open-foam of the previous embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0010]     Reference will now be made in detail to various embodiments of the invention, which are illustrated in the drawings. An effort has been made to use the same reference numbers throughout the drawings to refer to the same or like parts.  
         [0011]      FIG. 1  shows a cross-sectional view of a liquid supply vessel  100  according to one embodiment of the invention. The vessel  100  is formed of two parts, a cover  10  and a base  20  which may be joined and sealed together by at least one fastener and gasket (not shown). As shown, the cover  10  and the base  20  have recessed portions such that when the cover  10  is placed on top of the base  20 , a chamber  90  is formed. The chamber  90  is designed to contain a liquid  12 , such as, for example, ink.  
         [0012]     When the cover  10  is placed on top of the base  20 , a top wall  14  of the cover  10  is opposite a floor  24  of the base  20 . At least one vent  30  is formed in the top wall  14  and/or the floor  24 . The vessel  100  may have at least four vents  30 , two of which will be formed in the top wall  14  and two of which will be formed in the floor  24 . Further, each of the vents  30  is gas permeable, but substantially liquid impermeable. One example of such a vent  30  may be an oleophobic membrane with a 0.45 μm pore size and a polypropylene backer which engages a polypropylene fitting (not shown) that is threaded in the top wall  14  or floor  24 . To protect the vent  30  physically, the vent  30  may be recessed from the outer surface of the vessel (not shown); a labyrinthine pathway (not shown) may also be interposed between the vent  30  and the ambient air to reduce the water vapor transmission rate (WVTR) from the vessel.  
         [0013]     As a result of being gas permeable, but substantially liquid impermeable, the liquid  12  within the chamber  90  is unable to pass through the vents  30 . Further, to equalize the pressure within the chamber  90  with the ambient pressure exterior of the chamber  90 , gas (e.g., air) can be exhausted or sucked through the vents  30 , as hereafter described in detail.  
         [0014]     As a result of the vents  30 , if the altitude and/or the temperature at which the vessel  100  is maintained increases (such as, for example, if the vessel  100  were in an ascending plane and/or placed near a heat source), the pressure in the chamber  90  will not increase (as would normally be the case for a closed container) due to exhaustion of some of the gas in the chamber  90  through the vents  30 . Similarly, when the altitude and/or temperature at which the vessel  100  is maintained decreases (such as, for example, if the vessel  100  were in a descending plane and/or placed near a cooling source), the pressure in the chamber will not decrease (as would normally be the case for a closed container) due to gas being sucked into the chamber  90  through the vents  30 .  
         [0015]     The vents  30  also eliminate (or at least substantially reduce) any back-pressure in the chamber  90  that would otherwise be caused by liquid  12  being expunged from the chamber  90 . Rather, as the liquid  12  is expunged, gas is sucked into the chamber  90  through the vents  30  thereby enabling the pressure in the chamber  90  to remain equalized with the ambient pressure exterior of the chamber  90 , i.e., the vents  30  prevent the formation of a vacuum in the chamber  90 .  
         [0016]     To expunge the liquid  12  in the chamber  90 , it is pumped into a dispensing tower  50  by means of a supply line  40  (also referred to as an “inverted snorkel” or “siphon”  40 ). The supply line has an inlet  44  adjacent the floor  24 . This inlet  44  serves as an intake port for the supply line  40 . A filter  42 , which substantially prevents the passage of air bubbles when wetted, due to surface tension, is provided in the inlet  44 . The filter may be a low-micron screen which greatly reduces the likelihood that any impurities in the liquid  12  in the chamber  90  will be transmitted into the supply line  40 .  
         [0017]     As previously mentioned, the filter  42  in the inlet  44  substantially blocks gas bubble when wetted; the importance of this feature is shown in  FIG. 2 , which shows the vessel  100  of  FIG. 1  in an inverted state. Although the vessel  100  may be kept in the upright orientation shown in  FIG. 1 , it is practically understood that the vessel  100  will likely be inverted during its lifetime such as, for example, when a box of vessels  100  is improperly stored upside-down by a vender or when a consumer puts a box containing a vessel  100  upside-down in a bag.  
         [0018]     In the inverted state shown in  FIG. 2 , the liquid  12  in the chamber  90  falls (under the force of gravity) to the top wall  14 . As a result, the inlet  44  of the supply line  40  may project out of the surface of the liquid  12  in a manner similar to that of a snorkel projecting out of the surface of an ocean. In this position, the inlet  44  of the supply line  40  may be exposed to the gas in the chamber  90  which fills that portion of the chamber  90  which is not occupied by the liquid  12 . If the filter  42  were not provided, the gas in the chamber  90  could enter the supply line  40 , thereby negatively impacting print quality. As a result of the filter  42 , however, the gas in the chamber  90  is substantially prevented from entering the supply line  40 .  
         [0019]     With respect to  FIG. 1 , the liquid  12  which is sucked through the filter  42  and into the supply line  40 , passes through the supply line  40  and exits through an outlet  46 . The liquid  12  exiting the outlet  46  passes into a tower  50 . The tower  50  contains an intake  48  which is in fluid communication with the outlet  46  and with a valve  60 . The tower  50  rests within an upper bore  22  which projects upward from the floor  24 . A lower bore  23 , which is concentric with the upper bore  22 , is designed to house a fluidic interconnect  80 .  
         [0020]     For the vessel  100  to be compatible with some existing printheads, it may have an outtake (a.k.a. “fluidic interconnect”)  80  which is open-foam  70  based in combination with a filter screen  71 . Similarly, in a vessel  200  according to another embodiment (shown in  FIG. 3 ), the fluidic interconnect  80  may be designed to engage printheads having a needle (not shown) which pierces a septum  72 .  
         [0021]     If the foam-based  70  fluidic interconnect  80  is employed, the fluidic interconnect may have a large surface area that is exposed to the atmosphere before the vessel  100  inserted in to a printer, after the customer removes the label protecting the fluidic interconnect  80 . As a result, the valve  60  must operate reliably and the internal supply pressure must never rise above the cracking pressure of the valve  60 ; else, liquid  12  could leak out of the fluidic interconnect  80 . To achieve these requirements, the vents  30  serve to reduce back-pressure and the valve  60  design also reduces the potential for leakage.  
         [0022]     In choosing a valve  60 , it should be appreciated that the vessel  100  will likely operate in the 1″-8″ Water back-pressure range. In addition, as a result of the small size of the chamber  90 , the valve  60  must be miniaturized to fit within the tower  50 . As a result of these considerations, in one embodiment the valve  60  may be an umbrella valve. Further, the umbrella valve may be about 6.4 mm in size, may have a cracking pressure of about 5.7″ Water, and may be designed to operate in a 3″-5″ Water pressure range. In addition, the reliability of the valve  60  is enhanced by placing it towards the upper end of the tower  50 , as shown in  FIGS. 1 and 3 . By placing the valve  60  near the upper end of the tower  50 , the positive head pressure acting on the valve is reduced.  
         [0023]     Regardless of the vessel embodiment, when the vessel  100 ,  200  is manufactured, the chamber  90  may be filled with liquid  12 . After the chamber  90  is filled, the supply line  40  and the tower  50  are primed, i.e., liquid  12  is sucked through the supply line  50  and into the tower  50  up to the valve  60 . By filling the supply line  40  and tower  50  with liquid  12 , air expansion in the supply line  40  and/or tower  50  during altitude/temperature changes is minimized, thereby substantially reducing the likelihood of breakage and leakage. In addition, upon insertion of the vessel  100 ,  200  into a printhead, a pocket of gas will not be driven into the printhead upon start-up.  
         [0024]     When the vessel  100 ,  200  is inserted in a printhead and a request for liquid is initiated, suction applied to the valve  60  will cause it to open. When the valve  60  opens, liquid will flow through the tower  50  and out the fluidic interconnect in the direction of the arrows shown in  FIGS. 1 and 3 .  
         [0025]     The invention herein described can, in some exemplary embodiments, reduce the “stranded” ink in a container to about 3%, compared to about 30% or more in a foam-based container. Moreover, these improved yields may occur at a flow rate of 0.5-1.5 cc per minute. In addition, in some embodiments, the simplicity of the design yields low manufacturing costs. Further, in some embodiments there is no flow restriction to limit the print speed.  
         [0026]     Some embodiments of the invention also reduce mechanical stress by eliminating (or at least substantially reducing) back-pressure caused by ink expulsion. Similarly, the gas permeable vents equalize the pressure within the chamber with the ambient pressure exterior of the chamber, thereby eliminating (or at least substantially reducing) any mechanical stress which would otherwise act on the vessel as a result of a change in altitude and/or temperature. As a result, the invention is more durable, decreases the number of customer interventions, is significantly more cost effective and, is significantly more environmentally friendly.  
         [0027]     Although the aforementioned describes embodiments of the invention, the invention is not so restricted. It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments of the present invention without departing from the scope or spirit of the invention. Accordingly, these other liquid supply vessels are fully within the scope of the claimed invention. Therefore, it should be understood that the apparatus and method described herein are illustrative only and are not limiting upon the scope of the invention, which is indicated by the following claims.