Abstract:
An ink tank, having an ink reservoir separated from an ink supply chamber which contains at least one foam element, is provided with one or more pipes in the partition which separates the ink reservoir from the ink supply chamber. The pipes transport ink from the ink reservoir to a portion of the ink supply chamber which does not contain the at least one foam element. This results in both minimizing leakage from the ink tank when the ink tank&#39;s protective seal is removed prior to inserting the ink tank into a print engine, and in more predictable ink supply pressure and accuracy from the ink tank to a print device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention is directed to construction of ink tanks used in print engines such as, for example, ink jet printers. 
     2. Description of Related Art 
     Conventional ink tank designs typically have seals which are removed when the ink tank is placed into a print engine. These ink tanks have been known to experience problems with leakage of ink when the seal, such as, for example, a foil seal, is removed prior to placing the ink tanks into the print engine. The leakage problem is often exacerbated when the ink tank seal is removed at the somewhat relatively lower atmospheric pressure which exists at high altitude locations. Some conventional tanks have a number of ink reservoir chambers. Any air trapped inside of these one or more ink reservoir chambers expands, when the seal is removed and the tank is directly exposed to relatively lower atmospheric pressure, to reach pressure equilibrium with respect to the relatively lower ambient atmospheric pressure. This expansion of air inside of the formerly sealed ink tank occurs rapidly and causes a rapid surge of ink from the one or more ink reservoir chambers where the air is located into the ink tank foam chamber, where an ink supply opening is located. This ink moves via a path or paths of least resistance, which often includes the ink tank supply opening, resulting in ink dripping out of this opening from the ink tank. 
     Moreover, some conventional ink tanks tend to have relatively poor ink supply consistency and accuracy. In a typical application, an optical sensing system is used to detect when the ink in the ink tank falls below a certain level. In such ink tanks, the amount of ink delivered between the ink reservoir chambers and the ink foam chamber, where an ink supply opening is located, is important in order to provide an accurate measure of how much usable ink remains in the ink tank. The amount of ink remaining in the ink tank when sensed low can be unpredictable due to the variable density and resistance to fluid and air flow that is inherent with foam. In addition, if the resistance of the foam to air flow to the rear chamber is extreme, the ink tank may “deprime” resulting in a severe defect on the customer&#39;s print. 
     SUMMARY OF THE INVENTION 
     This invention provides an ink tank construction which reduces the leakage of ink from an ink tank when the protective seal is removed. 
     This invention separately provides an ink tank construction that is able to reduce the leakage of ink from an ink tank when the protective seal is removed at relatively high altitudes. 
     This invention separately provides an ink tank construction which provides a low impedance path to conduct the ink from an ink reservoir portion of the ink tank into a safe area of the tank. 
     This invention separately provides an ink tank construction that uses a low impedance path to determine and regulate the ink supply pressure of an ink tank to 
     In various exemplary embodiments of the ink tank construction according to this invention, this low impedance path comprises one or more pipes extending between an ink reservoir chamber and an ink supply chamber. In other various exemplary embodiments of the ink tank construction according to this invention, this low impedance path decouples the ink supply of ink to the ink supply chamber from the ink supply of ink from the ink supply chamber. This renders the ink supply consistency and accuracy less dependent on the known variability in density and ink flow resistance of foam. 
     These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various exemplary embodiments of this invention will be described in detail, with reference to the following figures, wherein: 
     FIG. 1 is a cross-sectional view of an ink tank with a removable seal covering the ink supply opening and vent tube; 
     FIG. 2 is a cross-sectional view of the ink tank with its seal removed and an ink manifold pipe inserted in the ink supply opening; 
     FIG. 3 is a cross-sectional view of one exemplary embodiment of an ink tank according to this invention having one or more pipes between an ink reservoir and a foam containing chamber and a removable seal covering the ink supply opening and vent tube; 
     FIG. 4 is a cross-sectional view of the ink tank of FIG. 3 with the removable seal removed; and 
     FIG. 5 is a cross-sectional view of the ink tank of FIG. 3 with an ink manifold pipe inserted in the ink supply opening. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 is a cross-sectional view of a conventional ink tank  10 . The ink tank  10  has an ink supply chamber  110  and an ink reservoir chamber  130 . The ink reservoir chamber  130  is partially filled with ink  20 . The remaining space  30  above the ink  20  is filled with air. The ink supply chamber  110  has an ink supply opening  50 . A large portion of the ink supply chamber  110  is taken up by a foam element  120 , which forms a lower boundary between the ink supply chamber  110  and the ink reservoir  130 . The ink reservoir  130  is separated from the ink supply chamber  110  by a partition wall  75 , which does not completely separate the two chambers, but permits the ink  20  to flow between the ink supply chamber  110  and the ink reservoir chamber  130 , through an opening  121  formed between the partition wall  175  and the bottom of ink tank  10 . In one exemplary embodiment, the opening  121  was about 3mm high and about 9mm wide. 
     The ink tank  10  also has an ink tank vent  52  which opens into a bottom wall  15  of the ink tank  10 . FIG. 1 shows a removable seal  56 , which may be made of any ink impermeable material, such as, for example, a metal foil. The removable seal  56  covers both the ink supply opening  50  and the ink tank vent,  52 . 
     FIG. 2 shows the ink tank  10  after the removable seal  56  has been removed and the ink tank  10  has been positioned on an ink supply pipe  40 . The ink supply pipe  40  has been inserted into the ink supply opening  50  and has displaced part of the foam  120  adjacent to the ink supply pipe  40 . The ink  20  in the ink reservoir chamber  130  is shown as having bubbles. In order for bubbles to form in the ink reservoir  130 , a portion  125  of the foam  120  has to become desaturated. Desaturating a portion  125  of the foam  120  in ink tank  10 , thus providing a free passage for the air bubbles to reach the ink reservoir chamber, has been unpredictable, prior to this invention, due to variations in the properties of the foam, some of which are due to the manufacture of the foam  120 . An arrow indicates the direction of flow of the ink  20  from ink reservoir  130  into the foam  120  across a foam boundary  121 . 
     FIG. 3 shows one exemplary embodiment of an ink tank  100  according to this invention, with its removable seal  56  intact, i.e., prior to removal of the seal  56  and installation of the ink tank  100  on the ink tank supply pipe  40 . The ink tank  100  contains one or more pipes  60  formed in the partition wall  175  which separates ink reservoir chamber  130  and the ink supply chamber  110 . The pipes  60  are molded into the partition wall  175  between the ink supply chamber  110  in which the foam element  120  is located and the ink reservoir chamber  130 . The top of each pipe  60  is located above the top of the foam  120 , which is generally kept below the spacer elements  17  in FIG. 3 in the ink supply chamber  110 . This leaves an air space  31  into which the ink, which can be forced up the pipes  60  in response to a pressure difference between the ink reservoir and ink supply chambers, can enter. In various exemplary embodiments, the air space  31  and the long pipes  60  are formed during the molding process and the opening needed to form the pipes is sealed off with a seal  16  located on the top wall of the ink tank  100 . The pipes  60  can be sized as small as capillaries or larger, and can have capillary sized openings at the bottom of the one or more pipes but be larger in diameter or cross-section above the opening at the bottom end of the one or more pipes  60 . Spacer elements  17  keep the foam element  120  from filling the entire ink supply chamber  110 , and provide an air chambers  31  above the foam element  120 . The air chambers  31  are interconnected by openings  28  in spacer elements  17  so that all of the air above the foam element  120  is at the same pressure. 
     FIG. 4 shows the ink tank  100  after the removable seal  56  has been removed, and prior to insertion of the ink tank supply pipe  40  into the ink tank supply opening  50 . When the ink tank  100  is opened up by removing the removable seal  56 , the air in the top portion  30  of ink reservoir chamber  130  forces the ink  20  up into one or more of the pipes  60 . The ink  20  that is forced up into the pipes  60  overflows onto the top of foam element  120 , where this ink  20  can be absorbed. 
     FIG. 5 shows the ink tank  100  after the ink tank supply pipe  40  has been inserted into the ink tank  100 . During supply of the ink  20  from the ink supply chamber  110  via the ink supply pipe  40 , the air bubbles out of the bottom of pipes  60  into the ink reservoir chamber  130 . The pressure needed to pull the ink  20  through the pipes  60  and to generate an air bubble in the rear, reservoir, chamber, determines the operating or negative pressure of the ink tank  100 . The ink tank operating pressure can be adjusted or tuned by molding a fine hole at the bottom exit of the long pipe  60 . In various exemplary embodiments, the fine hole has a diameter of, for example, between 0.5 mm and 1 mm. 
     In some exemplary embodiments, the pipe  60  may be larger in diameter throughout most of its length than the opening  61  in the bottom of the pipe  60 . This tends to facilitate flow of air bubbles into the space  31  above the pipe  60 . The amount of the ink  20  drawn out of the ink tank  100  before the first bubble occurs between the foam  120  and ink reservoir chamber  130  is relatively more predictable in the ink tank  100  with one or more of the pipes  60 , because the impedance of the foam to air is not a significant factor. 
     This invention provides an ink tank that is configured to substantially reduce the possibility that ink will leak from the ink tank when the protective seal is removed prior to installing the ink tank and after the ink tank is installed on an ink tank supply pipe. 
     In various exemplary embodiments, the pipe is formed in or on the partition wall, where the partition wall defines at least a portion of the surface of the pipe. In other exemplary embodiments, a separate pipe can be placed in the ink tank to connect the ink tank reservoir and the ink tank supply chamber  110 . In this case, the pipe can be attached to the partition wall, but does not need to be so attached. 
     In various exemplary embodiments, as outlined above, the ink is delivered to the ink supply chamber  110  that does not contain the at least one foam element  120 , and thus does not contain the ink  20 . In various other exemplary embodiments, the ink is delivered to a portion of the at least one foam element  120  that, during normal operation, is not saturated with ink, i.e., a portion of the at least one foam element  120  that has subportions that do not contain the ink  20 . In this case, the air space  31  can be omitted, such that the at least one foam element  120  at least substantially fills the ink supply chamber  110 . 
     One other advantage of this invention is the reduction in deprime situations, i.e., situations in which air, instead of ink, is drawn through the foam element  120  to the ink supply orifice  50 . In a deprime situation, the ink supply tube  40  draws air along with, or instead of, the ink  20  into the ink supply tube  40  to the print head (not shown). This happens when air is drawn into the bottom of the foam element  120  and displaces the  20  ink in the bottom of the foam element  120 . In exemplary embodiments of this invention, however, air is displaced from the bottom of the foam element  120  into the ink reservoir chamber  130  and drawn up into the air space  31  on top of the foam element  120  by the one or more pipes  60 . In this manner, the ink is drawn from the ink reservoir  130  into the foam element  120 . As a result, deprime situations occur significantly less often. 
     While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.