Abstract:
An ink-jet print cartridge includes a body with a lid. The body defines a vent structure communicating between ambient and an ink reservoir internally of the body. One embodiment of the vent structure includes a straight cylindrical bore opening through the lid of the print cartridge body between ambient and the ink reservoir. This vent structure includes a tapered annular surface surrounding the opening of the straight cylindrical bore on a surface of the lid, so as to direct ink away from the opening of the bore. An annular ink well surrounds the tapered annular surface so as to catch and hold ink flowing along this surface away from the opening of the straight cylindrical bore.

Description:
RELATED APPLICATIONS 
     This application is related to the following copending utility patent applications, each filed concurrently on Jan. 5, 2000: 
     Ser. No.: 09/477,644, by Junji Yamamoto et al., entitled “Horizontally Loadable Carriage For An Ink-Jet Printer”; 
     Ser. No.: 09/477,646 by Ram Santhanam et al., entitled “Ink-Jet Print Cartridge Having A Low Profile”; 
     Ser. No.: 09/477,644 by Junji Yamamoto et al., entitled “Horizontally Loadable Carriage For An Ink-Jet Printer”; 
     Ser. No.: 09/477,649 by Junji Yamamoto et al., entitled “Method And Apparatus For Horizontally Loading And Unloading An Ink-Jet Print Cartridge From A Carriage”; 
     Ser. No.: 09/478,148 by Richard A. Becker et al., entitled “Techniques For Providing Ink-Jet Cartridges With A Universal Body Structure”; 
     Ser. No.: 09/477,843 by Ram Santhanam et al., entitled “Techniques For Adapting A Small Form Factor Ink-Jet Cartridge For Use In A Carriage Sized For A Large Form Factor Cartridge”; 
     Ser. No.: 09/478,190 by James M. Osmus, entitled “Printer With A Two Roller, Two Motor Paper Delivery System”; 
     Ser. No.: 09/477,860 by Keng Leong Ng, entitled “Low Height Inkjet Service Station”; 
     Ser. No.: 09/477,648 by Matt Shepherd et al., entitled “New Method of Propelling An Inkjet Printer Carriage”; 
     Ser. No.: 29/116,564 by Ram Santhanam et al., entitled “Ink Jet Print Cartridge”; and 
     Ser. No.: 09/477,940 by Ram Santhanam et al., entitled “Multiple Bit Matrix Configuration For Key-Latched Printheads”, all of which are incorporated by reference. 
    
    
     FIELD OF INVENTION 
     The present invention generally relates to ink-jet print cartridges and, more particularly, to their construction. 
     BACKGROUND OF THE INVENTION 
     The general construction and operation of an ink-jet print cartridge using reticulated polyurethane foam is disclosed in U.S. Pat. No. 4,771,295 entitled “Thermal Ink Jet Pen Body Construction Having Improved Ink Storage and Feed Capacity” by Baker et al. issued Sep. 13, 1988. 
     The ink reservoir of such a print cartridge is vented to the atmosphere so that when ink is being expelled during operation of the cartridge, a vacuum is not created in the reservoir and the pressure of the ink behind the print head can be properly maintained by the foam at about −2″ of water. 
     The size of the vent must be sufficiently large so that at the maximum printing speed of the cartridge such a vacuum is not produced, affecting the operation of the cartridge. On the other hand, the size of the vent must not be so large that the water in the ink evaporates too quickly, causing the cartridge to dry out and become useless before the end of its intended life. 
     There are other challenges as well in the design of vents for ink-jet print cartridges. The size of the vent and its construction must be such that when the print cartridge is held with the vent downward, the ink does not run out into the printer or onto the user. Further, the vent should be designed so that it is not easily clogged by debris and dried ink and is also not blocked by liquid ink drawn into the vent by the capillary effect. 
     Lastly, prior vent designs have been unable to withstand harsher environments than the normal office. A vent is needed for a print cartridge that will be used in a printer designed to be stacked in a home entertainment center. Such an environment is hotter, more dusty, and drier than offices and commercial facilities. 
     Thus, it should be apparent from the foregoing that the design and construction ink-jet print cartridges offer many challenges and trade offs. There is still a need for an approach that sufficiently vents at maximum cartridge printing speed, minimizes water loss through evaporation, avoids leakage, and withstands harsh environments. 
     SUMMARY OF THE INVENTION 
     Briefly and in general terms, an apparatus according to the invention includes a vent for an ink-jet print cartridge having a body and a lid. Communicating through the lid is a straight bore having an opening and a tapered annular surface surrounding the opening of the bore. 
     In an alternative embodiment, the invention includes a straight bore communicating through the lid and an annular ring located on the lid surrounding the opening of the bore. 
     In a second alternative embodiment, the invention includes a straight bore communicating through the lid and having an opening that flares outwardly into the body of the print cartridge. 
     Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view, partially exploded, of a ink-jet print cartridge having a vent embodying the principles of the invention. 
     FIG. 2 is a perspective of the bottom side of the lid of FIG.  1 . 
     FIG. 3 is a bottom elevational view of the lid of FIG.  1 . 
     FIG. 4 is a side elevational view, partially cut away, taken along line  4 — 4  of FIG.  1 . 
     FIG. 5 is a side elevational view, partially cut away, of an alternative embodiment of the vent of the present invention. 
     FIG. 6 is a side elevational view, partially cut away, of a second alternative embodiment of the vent of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the drawings for the purposes of illustration, the invention is embodied in a vent for an ink-jet print cartridge. 
     The apparatus offers a simple, reliable solution that sufficiently vents at maximum cartridge printing speed, minimizes water loss, avoids leakage and clogging, and withstands harsh environments. 
     Referring to FIG. 1, reference numeral  14  generally indicates an ink-jet print cartridge having a body  16  and a lid  18 . Although the print cartridge is illustrated with the lid removed, the cartridge is filled with foam, not shown, and ink, likewise not shown, during manufacturing and the lid is ultrasonically welded shut. The lid  18  is not intended to be removed from the body  16  by the user. The body  16  contains three ink chambers  20 ,  21 ,  22  that are isolated from each other for holding inks of different hues. The three chambers are each connected to a separate series of nozzles, not shown, that are independently energized to expel droplets of ink in the conventional manner. 
     Referring to FIG. 1, each chamber  20 ,  21 ,  22  within the body  16  of the print cartridge  14  is independently vented to the atmosphere by three vents  24 ,  25 ,  26  that are described in detail below. As ink is expelled from the print cartridge, air at atmospheric pressure passes through the vents and refills the chambers. 
     Referring to FIGS. 2,  3 , and  4 , each of the vents  24 ,  25 , and  26  contains an unobstructed bore  30  that communicates through the lid  18 . The bore has a tapered surface  32  in the shape of a frustrum of a cone, and the edge  33  of the opening to the bore  30  is sharply defined. The tapered surface  32  leads to an annular ink well  34  in the shape of an annular trough that surrounds the bore and is co-axial with it. Referring to FIGS. 2 and 3, the ink well  34  is connected by two tortuous conduits  36  to two ink reservoirs  38  on the chamber-side of the lid  18 . In the embodiment that has actually been constructed the bore was fifty thousandths of an inch (0.050″) long and twenty thousandths of an inch (0.020″) in diameter. 
     Each chamber  20 ,  21 ,  22 , FIG. 1, is filled with foam, not shown, and the ink primarily resides in the foam. If the print cartridge is inverted and the vent is pointed downward, any free ink, that is to say not in the foam, will fall on to the chamber-side of the lid  18 . The sharp edge  33  around the opening of the bore breaks up any drops of free ink that approach the bore by over coming their surface tension. The sharp edge and the tapered surface  32  also act to direct any free ink away from the bore  30 . Any free ink that flows down the tapered surface  32  and into the ink well  34  is thereafter directed away from the vent by the tortuous conduits  36  and is retained in the ink spill reservoirs  38 . The sharp edge  33 , the tapered surface  32 , the tortuous conduits  36  and the ink spill reservoirs  38  all operate together to keep the ink from blocking the bore  30  and to direct any free ink within the chambers  20 ,  21 , 22 , FIG. 1, as far away from the bore as possible. 
     Referring to FIG. 4, reference numeral  40  indicates the wall of a counter bore  42 . This counter bore compresses the foam thereby keeping the foam away from the sharp edge  33  and the bore  30 . The counter bore also acts as a further barrier to any free ink coming into contact with the bore  30  and blocking it. 
     As much as one would like to avoid it, there is always the possibility of ink spilling out of the bore  30 , FIG. 4, through volumetric changes induced by thermal cycling or pressure changes. To prevent the ink from flowing into the printer or onto the user, a second ink fountain  46  is molded into the top of the lid  18 , FIG.  4 . The bore has a tapered surface  48  in the shape of a frustrum of a cone, and the edge  50  of the opening to the bore  30  is sharply defined. The tapered surface  48  leads to an annular ink well  52  in the shape of an annular trough that surrounds the bore and is co-axial with it. The ink well is formed by the wall  54  of circular counter bore  57 . 
     Referring to FIG. 4, if ink flows upward and out the opening  50  of the bore  30 , the sharp edge  51  of the opening  50  will break up the drops and the ink will flow down the tapered surface  48  into the ink well  52 . The ink is thereby trapped by the ink fountain  46 . In time the liquid ink will dry in the ink well and the threat of clogging is eliminated. This construction also eliminates the need to draw the ink back into the print cartridge through the bore  30  or the need to relocate the ink to a less troublesome location. 
     Referring to FIG. 5, reference numeral  60  generally indicates a vent according to an alternative embodiment of the invention. The vent  60  is located in a lid  62  and permits air at atmospheric pressure to flow into one of the chambers  20 ,  21 ,  22 , FIG.  1 . The vent includes a straight bore  64  that communicates through the lid  62 . Located on the top surface of the lid is an annular ring  66  that prevents dust and debris from clogging the vent. Located on the chamber-side of the lid is a second annular ring  68  that prevents ink from being drawn up into the vent by the capillary effect. In one embodiment of the vent  60  that was actually constructed, the bore was the bore is fifty thousandths of an inch (0.050″) long and twenty thousandths of an inch (0.020″) in diameter. 
     Referring to FIG. 6, reference numeral  74  generally indicates a vent according to a second alternative embodiment of the invention. The vent  74  is located in a lid  76  and permits air at atmospheric pressure to flow into one of the chambers  20 ,  21 ,  22 , FIG.  1 . The vent includes a straight bore  78  that communicates through the lid  76 . The bore has a narrow upper cylindrical section  80  and an outwardly flaring section  82 . The flaring section has the shape of a frustrum of a cone and opens up into the body  16 , FIG. 1 of the print cartridge. The flaring section eliminates the capillary effect of drawing ink up into the bore  78  when the print cartridge is located in an upright position. Located on the top surface of the lid  76  is an annular ring  86  that prevents dust and debris from clogging the vent. Located on the chamber-side of the lid is a second annular ring  88  that additionally prevents ink from being drawn up into the vent by the capillary effect. 
     While the print cartridge described above contains three ink reservoirs and three vents, it is contemplated that a print cartridge with one or more reservoirs with one or more vents can also be used. In the printer that is planned for this print cartridge, one print cartridge having one reservoir containing only black ink will be installed adjacent to a second print cartridge having three reservoirs containing inks of the three primary hues. 
     Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangement of parts so described and illustrated. The invention is limited only by the claims.