Ink refill unit for an ink reservoir

1. A refill unit for an ink reservoir with an inlet valve for receiving refill ink and an outlet valve for fluid communication with an inkjet printhead, the refill unit comprising:

a docking assembly for docking with the ink reservoir;

an ink bag for storing ink;

a valve actuator configured to close the outlet valve of the ink reservoir and subsequently open the inlet valve upon docking the docking assembly with the ink reservoir;

an ink delivery outlet assembly for establishing fluid communication between the ink bag and the ink reservoir upon docking the docking assembly with the ink reservoir; and

constrictor actuators for increasing pressure in the ink bag upon docking the docking assembly with the ink reservoir, and reducing pressure in the ink reservoir upon disengagement of the docking assembly and the ink reservoir.

2. The refill unit of claim 1 , wherein the valve actuator includes tri-star cross-sectional pins projecting from an underside of the refill unit.

3. The refill unit of claim 1 , which includes an integrated circuit with a plurality of contacts, wherein the ink reservoir is a component of a cartridge for use in a printer housing the printhead, the cartridge having an integrated circuit reader for connection to the contacts to verify that ink in the refill unit is suitable.

4. The refill unit of claim 3 , in which the docking assembly includes a base assembly and a cover assembly, the constrictor actuators projecting from the base assembly.

5. The refill unit of claim 4 , in which the constrictor actuators project from respective corners of the base assembly, are arcuate and have rounded ends to facilitate alignment with corresponding apertures in the print cartridge.

6. The refill unit of claim 4 , wherein the ink delivery outlet assembly has an ink delivery needle extending from the bag to an outlet in the base assembly and surrounded by a seal ring which is spring loaded via a compression spring.

7. The refill unit of claim 4 , having an ink level indicator with a flexible strip with an indicator portion, the strip attached to an upper surface of the ink bag and to an underside of the cover assembly, so that, when the ink within the bag is exhausted, the indicator portion aligns with a transparent window in the cover assembly.