Patent Abstract:
An ink supply system for an ink jet printer, comprising:
       an ink cartridge for accommodating a limited volume of liquid ink,   an ink tank having a volume larger than said limited volume and connectable to the ink cartridge, and   an ink supply line including a disengageable coupling, for connecting the ink tank to the ink cartridge,   wherein the coupling includes a valve mechanism which, when the coupling is disengaged, automatically blocks the ink supply line and opens a vent passage for venting the interior of the cartridge.

Full Description:
BACKGROUND OF THE INVENTION 
   This application is a Divisional of co-pending application Ser. No. 10/642,157, filed on Aug. 18, 2003 now U.S. Pat. No. 7,097,288, and for which priority is claimed under 35 U.S.C. § 120, and which parent application claimed priority under 35 U.S.C. § 119(a) on Patent Application No. 02078439.3 filed in Europe on Aug. 16, 2002, each application being incorporated by reference. 

   1. Field of the Invention 
   The present invention relates to an ink supply system for an ink jet printer. 
   2. Related Art 
   Many commercial ink jet printers comprise an ink cartridge which is directly associated with a nozzle head of the printer and is mounted on a carriage for scanning a recording medium to be printed. Since the cartridge is travelling back and forth along with the carriage and the nozzle head, it can only accommodate a limited volume of liquid ink. When the ink cartridge is depleted, it has to be replaced manually. It would therefore be desirable to be able to store a larger volume of ink, especially for printing images with a large format or high volume printers. 
   It is accordingly an object of the present invention to provide an ink supply system in which a large-volume ink tank can be connected to the ink cartridge for replacing the ink that has been consumed. 
   SUMMARY OF THE INVENTION 
   According to the present invention, this object is achieved by providing an ink supply system for an ink jet printer, comprising:
         an ink cartridge accommodating a limited volume of liquid ink,   an ink tank having a volume larger than said limited volume and connected to the ink cartridge, and   an ink supply line including a disengageable coupling for connecting the ink tank to the ink cartridge,   wherein the disengageable coupling includes a valve mechanism which, when the coupling is disengaged, automatically blocks the ink supply line and opens a vent passage for venting the interior of the cartridge.       

   The system according to the present invention, connects the ink cartridge to the large-volume ink tank for supplying ink to the cartridge. When the coupling is engaged, the vent passage is blocked, so that the ink supply system is sealed against atmospheric pressure. As a result, it is possible to create a differential pressure between the ink tank and the ink cartridge and thereby cause the ink to flow from the tank into the cartridge. For example, the ink in the tank may be contained in a collapsible bag, and when the nozzle head is operating and ink is consumed. This will cause a sub-atmospheric pressure in the ink cartridge so that ink can be drawn in from the tank. When the coupling is disengaged, for example, in order to replace the ink cartridge and the nozzle head integrated therewith or in order to exchange the ink tank when it has become depleted, the valve mechanism of the coupling will automatically block the ink supply line so as to avoid leakage of ink from the ink tank and/or the supply line. Simultaneously, the valve mechanism will open the vent passage for venting the interior of the cartridge. Leakage of ink out of the cartridge, e.g. through the nozzles of the nozzle head, is normally prevented by capillary forces of a filling material. However, when the cartridge is closed air-tightly while it is not connected to the tank, a rise in temperature of the cartridge or a decrease in ambient atmospheric pressure creates a differential pressure which causes ink to be squeezed out of the cartridge. According to the present invention, this risk is avoided by automatically venting the cartridge when the coupling is disengaged. 
   Preferably, the ink supply line includes a flexible tube which connects the ink tank to the ink cartridge, and the ink tank is stationarily disposed at a level lower than that of the ink cartridge. As a result, a flow of ink from the tank into the cartridge will be caused only by sub-atmospheric pressure which is created inside of the cartridge when ink is consumed by the nozzle head. As a consequence, the level of liquid ink in the cartridge will automatically be held at a constant level. 
   The disengageable coupling is preferably disposed on the carriage. When the ink cartridge is detachably fitted to a support that is mounted on the carriage, the coupling comprises the cartridge-side connector part and a support-side connector part which are brought into engagement when the cartridge is fitted to the support. In a preferred embodiment, the support defines a pivotal axis for the cartridge, so that the cartridge may be fitted to the support by inserting it into the support in a tilted position and then pivoting the cartridge about said axis until the cartridge is snap-fastened at the support. In this case, the connector parts of the coupling are so arranged at the cartridge and at the support that their direction of mutual engagement is tangential to the pivotal axis. Thus, the coupling will automatically be engaged when the cartridge is snap-fastened in the operating position. 
   Preferably, the support-side connector part comprises a hollow mandrel which, when the coupling is engaged, penetrates an elastic seal member disposed in the cartridge-side connector part. Thus, when the coupling is disengaged and the mandrel is withdrawn from the seal member, the elastic seal member will contract and thereby close the passage from which the mandrel has been withdrawn. This will prevent dust and other contaminants from entering into the ink cartridge, while only the relatively small vent passage will be left open. 
   The vent passage or passages may be defined between the outer circumferential surface of the seal member and a rigid sleeve surrounding the same. Then, the vent passage may automatically be blocked and opened by the expansion and contraction, respectively, of the seal member. 
   The valve mechanism for blocking the ink supply line may be formed by a lateral outlet opening of the mandrel and an elastic sleeve which is slidably disposed on the mandrel so as to cover the outlet opening when the coupling is disengaged. The sleeve is preferably spring-biased into a closed position, and the cartridge-side connector part is arranged to push the sleeve back so as to open the outlet opening of the mandrel when the coupling is engaged and the mandrel penetrates into the cartridge-side connector part. 
   An end face of the slidable sleeve on the mandrel may at the same time serve as a valve member for closing the open end of the vent passage when the sleeve is pushed back by the cartridge-side connector part. 
   Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
       FIG. 1  is a schematic view showing the essential parts of an ink supply system of an ink jet printer; 
       FIG. 2  is enlarged sectional view of an ink cartridge and a coupling forming part of the ink supply system; and 
       FIG. 3  shows the cartridge in a condition in which the coupling is disengaged. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As is shown in  FIG. 1 , an ink supply system for an ink jet printer includes an ink tank  10  mounted on a stationary frame  12  of the printer, a flexible tube  14  and an ink cartridge  16  connected to the tube  14  and hence the to tank  10  through a disengageable coupling  18 . The cartridge  16  has an integrated nozzle head  20  and is detachably fitted to a support  22  which is held on a carriage  24 . The carriage  24  is guided on guide rails  26  and is capable of traveling back and forth along a roller  28 . When the printer is operating, a recording medium, e.g. a sheet of paper (not shown), is fed over the roller  28  via a feed path  30  and a discharge path  32 , so that an image may be printed by the nozzle head  20 . 
   The ink cartridge  16  is capable of accommodating only a relative small volume of liquid ink as compared to the volume of the ink tank  10 . As can be seen in  FIG. 1 , the ink tank  10  is disposed below the level  34  of ink in the ink cartridge  16 . The ink in the tank  10  is contained in a collapsible bag  36  which is connected to the tube  14 . The outer casing of the tank  10  is vented. Capillary forces and the difference between the ink levels in tank  10  and cartridge  16  prevent the ink from leaking out of the ink cartridge  16  through the nozzles of the nozzle head  20 . 
   In the condition shown in  FIG. 1  in which the flexible tube  14  is connected to the ink cartridge  16  through the coupling  18 , the space above the level  34  in the ink cartridge  16  is closed air-tightly. When the nozzle head  20  is operating and ink is consumed, the sub-atmospheric pressure changes in the ink cartridge  16 , and ink is sucked-in from the tank  10  through the tube  14  and replaces the ink that has been consumed. In this way, the level  34  of ink in the cartridge  16  is held essentially constant. 
   As is shown in  FIG. 2 , the support  22  comprises an upright frame  38  and two lower horizontal arms  40  which embrace a lower edge of the ink cartridge  16 . Although not shown in detail in the drawings, the lower arms  40  define a pivotal axis  42  about which the ink cartridge  16  may be pivoted. A downwardly biased locking member  44  is mounted at the top end of the frame  38  and cooperates with a catch  46  of the ink cartridge, so that the cartridge may be snap-fastened in an upright position in which it leans against the frame  38 . 
   The ink cartridge  16  is formed by a vessel  48  which is made of plastic material and is sealingly closed by a cover  50 . A bottom wall of the vessel  48  is formed with an outlet port  52  through which the ink is supplied to the nozzle head which has not been shown in  FIG. 2 . The vessel  48  accommodates a sponge withholding the ink in the vessel  48 , so as to prevent the ink from leaking out of the nozzles of the nozzle head. The sponge  54  is pierced by a hollow needle  56  which is inserted through an opening formed in the cover  50 . This opening is sealingly closed by a plug  58 . The sponge  54  can fill the vessel  48  completely. 
   The coupling  18  comprises a cartridge-side connector part  60  which is integrated in the cover  50  of the ink cartridge, and a support-side connector part  62  which is fixedly mounted to the top end of the support  22 . The connector part  60  communicates with the interior of the ink cartridge  16  through a passage  64  and through the needle  56 . The end of the passage  64  facing the other connector part  62  accommodates an annular seal member  66  made of rubber-elastic material. The seal member  66  is surrounded and held in position by a rigid sleeve  68  fitted onto the open end of the connector part  60 . 
   The support-side connector part  62  comprises an inlet port  70  connected to the flexible tube  14 , and a hollow mandrel  72  which communicates with the inlet port  70  and, in the engaged condition shown in  FIG. 2 , penetrates the seal member  66  and projects into the passage  64  of the connector part  60 . The hollow mandrel  72  is closed at its projecting end and communicates with the passage  64  through a lateral outlet opening  74  which opens into a recess of the seal member  66 . 
   The connector part  62  defines a guide cylinder  76  which is arranged coaxially with the mandrel  72  and the passage  64  and extends tangentially relative to the pivotal axis  42 . The guide cylinder  76  accommodates and guides a slidable piston  78  which is rigidly locked to an elastic sleeve  80 . The sleeve  80  is slidable on the mandrel  72  and has two axially spaced seal portions  82  which tightly engage the outer circumferential surface of the mandrel  72 . The sleeve  80  is biased against the end face of the rigid sleeve  68  by a spring  84 . 
   In  FIG. 3  the cartridge  16  has been tilted about the pivotal axis  42 , so that the catch  46  has slid off from the locking member  44 , and the mandrel  72  which is rigidly held in the connector part  62  has been retracted out of the elastic seal member  66  of the connector part  60 . As a result, the elastic seal member  66  is contracted, and the internal cross-section thereof, which used to accommodate the mandrel  72 , is reduced to zero, and, as a consequence, the passage  64  is closed. 
   Further, due to the contraction of the seal member  66 , an annular gap  86  is formed between the outer circumferential surface of the seal member  66  and the inner circumferential surface of the rigid sleeve  68 . The seal member  66  and the sleeve  68  each have a large diameter portion which serves for holding the seal member  66  in position. Since the connector parts  60  and  62  have been disengaged from one another, the annular gap  86  is open to the outside. The gap  86  communicates with the interior of the ink cartridge  16  through radial passages  88  and through axial passages  90  formed in the wall of the cover  50 . Thus, the annular gap  86  and the passages  88 ,  90  form a vent passage for venting the interior of the ink cartridge  16 , especially for venting the space above the sponge  54 . As a result, the interior of the ink cartridge  16  is held at atmospheric pressure, so that, no ink will leak out of the nozzles of the nozzle head. 
   The labyrinth-like configuration of the passages  88 ,  90  prevents the entry of dust and dirt into the interior of the cover  50 . In any event, such contaminants will be retained by the sponge  54  and thus will not contaminate the ink in and below the sponge. 
   As is further shown in  FIG. 3 , the spring  84  has pushed the piston  78  and the elastic sleeve  80  into an end position which is defined by mating keys  92  of the guide cylinder  76  and the piston  78 . In this end position, the lateral outlet opening  74  of the mandrel  72  is located between the seal portions  82  of the elastic sleeve  80 , so that the ink supply line formed by the flexible tube  14  and the connector part  62  is closed. This will prevent ink from leaking out of the tube  14  and, conversely, will prevent ambient air from entering into the tube  14  when the ink tends to flow back into the tank  10 . 
   As can be seen in  FIG. 3 , the elastic sleeve  82  has an end face which faces the end of the connector part  60 . When the ink cartridge  16  is tilted into the operative position shown in  FIG. 2 , the vent passage formed by the annular gap  86  will reliably be blocked-off by two redundant effects: 1.) When the mandrel  72  penetrates into the seal member  66 , the annular seal member will expand and will be pressed against the internal surface of the rigid sleeve  68 , so that the annular gap  86  is quenched. 2.) The end face of the elastic sleeve  80  engages the open end of the annular gap  86  and closes the same. This latter effect is further enhanced by providing concentric annular bosses at the end faces of the seal member  66  and the rigid sleeve  68 . 
   The elasticity of the seal member  66  and of the elastic sleeve  80  further helps to compensate for a possible slight positional mismatch between the connector parts  60  and  62 . 
   The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Technology Classification (CPC): 1