Automatic ink refill system for disposable ink jet cartridges

An active ink refill system for an ink jet printer having a print carriage that traverses across a print medium, the ink refill system comprising:

• (a) a disposable ink jet cartridge removably mountable in the print carriage and constructed as a self-contained unit that includes a print head and an ink supply container that stores a first quantity of liquid ink at a given sub-atmospheric pressure hydrodynamic condition;
• (b) an ink reservoir that stores a second quantity of ink for replenishing the first quantity of ink in the ink supply container;
• (c) tubing means, operatively coupled to the ink reservoir and the ink supply container, for supplying ink from the second quantity of ink to the first quantity of ink during operation of the ink jet printer as the print carriage traverses across the print medium;
• (d) sensor means for sensing when the first quantity of ink is below a predetermined threshold:
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• (e) refilling means, operatively coupled to the tubing means, for refilling the ink supply container from the ink reservoir during operation of the ink jet printer as the print carriage traverses across the print medium in response to the sensor means sensing when the first quantity of ink is below the predetermined threshold such that the refilling of the ink supply container is accomplished in a manner that maintains the sub-atmospheric pressure hydrodynamic condition of the ink jet cartridge.