Ink cartridge with variable ink storage volume

1. An ink cartridge for an inkjet printer, the cartridge comprising:

an ink storage compartment having opposed wall sections connected by a flexible wall arrangement to define a variable ink storage volume; and,

an ink feed system for supplying ink to a printhead with an array of nozzles; wherein,

a first wall section of the opposed wall sections is displaceable and biased to expand the variable ink storage volume to create a negative pressure in the ink storage compartment for avoiding inadvertent ink leakage from the nozzles, and

a second wall section of the opposed wall sections has an inlet valve for connection to an ink refill unit and an outlet valve for connection to the ink feed system, the inlet and outlet valves being arranged in the second wall section so that the inlet valve is open and the outlet valve is closed when the ink refill unit is engaged with the ink storage compartment.

2. An ink cartridge according to claim 1 wherein the second wall section is fixed within the cartridge.

3. An ink cartridge according to claim 2 wherein the displaceable wall section is biased by a constant force spring.

4. A cartridge according to claim 1 , wherein the ink storage compartment has a variable storage volume and a displaceable wall section biased to expand the variable storage volume to generate a negative pressure therein, such that ink does not inadvertently leak from the ink ejection nozzles.

5. A cartridge according to claim 1 , wherein:

the negatively pressurized ink storage compartment has an interface for receiving a refill unit for refilling the ink storage compartment, the interface having an inlet valve biased to its closed configuration; and

the refill unit comprises:

a body containing a quantity of ink;

engagement formations for releasably engaging the interface; and

an inlet valve actuator for opening the inlet valve as the refill unit engages the ink interface so that the ink in the body is in fluid communication with the ink storage compartment.

6. A cartridge according to claim 1 , wherein:

the negatively pressurized ink storage compartment has an interface for receiving an ink refill unit for refilling the ink storage compartment, the interface having a normally closed inlet valve and a normally open outlet valve, both in fluid communication with the ink storage compartment; and

the refill unit comprises:

a body containing a quantity of ink; and

a docking portion having an ink outlet and valve actuator formations, the docking portion, during use, releasably engaging the interface to actuate the inlet and the outlet valves so the cartridge fills with ink from the body because of the negative pressure in the ink storage compartment.

7. A cartridge according to claim 1 , wherein:

the negatively pressurized ink storage compartment is arranged to be refilled by a refill unit via a normally open outlet valve; and

the refill unit comprises:

a body containing a quantity of ink;

engagement formations for releasably engaging the ink storage compartment; and

an outlet valve actuator for closing the outlet valve as the refill unit engages the ink storage compartment.

8. A cartridge according to claim 1 , wherein:

the ink storage compartment is arranged to be refilled by a refill unit; and

the refill unit comprises:

a body containing a quantity of ink;

an ink outlet; and

a repressurizing arrangement which, upon engagement of the refill unit with the ink storage compartment, causes part of the unit to be inwardly depressed as the ink from the body is drawn into the ink storage compartment through the ink outlet by the negative pressure until pressure equalization, and which, upon subsequent disengagement of the refill unit from the ink storage compartment, releases the inwardly depressed part of the ink storage compartment to re-establish the negative pressure.

9. A cartridge according to claim 1 , wherein:

the ink storage compartment has an interface for releasably engaging with a refill unit for refilling the ink storage compartment, the interface having valves for controlling ink flows into, and out of, the storage compartment; and

the refill unit comprises:

a body containing a quantity of ink;

an ink outlet; and,

valve actuators for actuating the valves when the refill unit engages the interface, such that the valve actuators actuate the valve in a predetermined sequence.

10. A cartridge according to claim 1 , further comprising an interface for releasably engaging a refill unit for refilling the cartridge,

wherein the inkjet printer incorporates a printhead, control circuitry and the refill unit, the refill unit comprising:

a body containing a quantity of ink;

an ink outlet; and

a memory circuit for storing information relating to at least one characteristic of the ink, which during use, allows the control circuit to interrogate it to verify that the ink in the refill unit is suitable for the printer.

11. A cartridge according to claim 1 incorporating a printhead maintenance assembly for an inkjet printhead of the inkjet printer, the printhead having a nozzle plate with an array of nozzles formed therein,

wherein the printhead maintenance assembly comprises:

a capper to cover the array of nozzles when the printhead is not in use; and

a cleaner for engaging the nozzle plate and wiping across the nozzles, the cleaner being positioned between opposing sides of the capper.

12. A cartridge according to claim 1 , further comprising an interface for engaging an ink refill unit for replenishing the cartridge, the ink refill unit comprising:

an ink storage compartment;

a docking portion for engaging the interface of the cartridge, the docking portion having a base plate with an ink outlet for connection to an inlet port on the interface; and

engagement formations for releasably engaging the interface, the engagement formations being formed on the transverse centre line of the base plate, the centre of the ink outlet being spaced from the transverse centre line.

13. A cartridge according to claim 1 , further comprising an interface for engaging an ink refill unit for replenishing the cartridge,

wherein the ink storage compartment is partially defined by a tubular flexible wall;

the cartridge further comprising a constriction mechanism for constricting the flexible tubular wall by a predetermined amount; and

the ink refill unit comprises:

a body containing a quantity of ink; and

a docking portion for engaging the interface of the cartridge, the docking portion having an ink outlet for connection to an inlet port on the interface, and a plurality of constriction actuators for actuating the constriction mechanism as the ink refill unit engages the interface and releases the constriction mechanism as the ink refill unit disengages the interface.

14. A cartridge according to claim 1 , further comprising a refill unit and an interface for engaging an ink refill unit for replenishing the cartridge, the ink refill unit comprising:

a body containing a quantity of ink;

an ink outlet for engaging a complementary ink inlet in the interface; and

a spigot extending from the body for insertion in an aperture in the interface,

wherein the lateral cross section of the spigot is keyed to the shape defined by the aperture to ensure the ink refill is correctly matched to the cartridge.

15. A cartridge according to claim 1 engageable with an ink refill unit for replenishing the cartridge, the ink refill unit comprising:

a body containing ink;

an ink outlet for engaging a complementary ink inlet in the cartridge; and

a visual indicator to provide a visual indication when a predetermined quantity ink has flowed from the refill unit into the cartridge.