Ink refill unit with incremental ink ejection mechanism

1. An ink refill unit for a print cartridge, said unit comprising:

a housing defining a fluid path in fluid communication with an outlet and configured to be operatively engaged with the print cartridge;

a fluid reservoir having an ejection port arranged in fluid communication with the fluid path inside the housing;

a seal for sealing off one end of the fluid reservoir, the seal being movable within the fluid reservoir;

an ejector assembly comprising a spring biased plunger engaged against the seal, the plunger having defined on a side thereof a number of groves;

an actuator mechanism comprising a rod to which a pawl and an arm are attached, the pawl adapted to engage with the grooves to negate a biasing force of the plunger against the seal; and

an actuator shaft attached to the housing, the actuator shaft being slidable with respect to housing so as to be exposed outside of the housing, wherein

the actuator shaft, when exposed outside of the housing, is operable to engage with the arm of the actuator mechanism to disengage the pawl from a groove, whereby the biasing force of the plunger is allowed to act against the seal.

2. The unit of claim 1 , wherein fluid reservoir is collapsible and includes an.

3. The unit of claim 1 , wherein the ejection port of the fluid reservoir includes a syringe needle arranged to penetrate a valve seal of the print cartridge.

4. The unit of claim 1 , wherein a known and predetermined amount of fluid is ejected from the refill unit with each actuation of the actuator shaft.