A pressure-compensation cartridge for ink jet printers, which is able to adjust the backpressure inside the cartridge within a proper range to prevent ink leakage from the print head or failure caused by ink dropping problems. The cartridge is a sealed container with an air duct on the top and a print head on the bottom. The pressure-compensation device, located inside the cartridge, includes an ink bag, a tension spring, and a motion element. The ink bag accommodates a substantial amount of ink for the print function of the print head and is made of a soft material. The tension spring has a first end engaged with the upper end of the ink bag and a second end engaged with the motion element. The resilience of the tension spring restrains the contraction of the ink bag caused by the running off of the ink so as to maintain a stable backpressure inside the ink bag, which prevents ink leakage or ink dropping problems through the print head of the cartridge.
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.
