Ink refill unit with sequential valve actuators

A refill unit for refilling an ink storage compartment with an interface for releasably engaging with the refill unit, the interface having valves for controlling ink flows into, and out of, the storage compartment, the refill unit comprising: 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 valves in a predetermined sequence.