Securing arrangement for securing a refill unit to a print engine during refilling

1. A securing arrangement for securing a printing fluid refill cartridge to a printing unit, the printing unit having refill ports each corresponding to a different colour of printing fluid and a push rod for powered actuation between an extended position and a retracted position, the printing fluid refill cartridge having an outlet arran to be engageable with one of the refill ports, and a syringe assembly containing the printing fluid, the syringe assembly having a plunger biased to discharge the printing fluid from the syringe assembly; the securing arrangement comprising;

a first engagement member;

a second engagement member—for releasable engagement with the first engagement member;

a ratchet for connection to the plunger;

a pawl for releasably engaging the ratchet to stop movement of the plunger thereby preventing discharge of the printing fluid; wherein,

the first engagement member is configured to secure the refill cartridge to the printing fluid such that the outlet engages the refill port corresponding to the printing fluid colour in the syringe assembly and positions the pawl for engagement with the push rod in the extended position to disengage the pawl from the ratchet such that a controlled amount of the printing fluid is dispensed into the printing unit.

2. An arrangement according to claim 1 , wherein the first engagement member is configured so that a syringe needle arranged in the outlet for distributing the printing fluid penetrates and is held within a valve seal of the refill port when engaged with the second engagement member.

3. An arrangement according to claim 1 , wherein the first engagement member is a slot and the second engagement member is a movable protrusion engageable with the slot.

4. An arrangement according to claim 1 , wherein the second engagement member is a slot and the first engagement member is a movable protrusion engageable with the slot.

5. An arrangement according to claim 1 , wherein the refill cartridge further comprises a side wall with a movable region, whereby movement of the movable region provides engagement and disengagement of the first and second engagement members.

6. An arrangement according to claim 5 , wherein the movable region incorporates a depressible region of the at least one side wall.

7. An arrangement according to claim 1 , wherein the printing unit is a printer cartridge mountable to a printer, and the refill port communicates with a printing fluid storage chamber of the printer cartridge which distributes printing fluid to a printhead.

8. An arrangement according to claim 7 , wherein the printhead incorporates a pagewidth printhead arranged to print printing fluid across the width of sheets of print media.

9. An arrangement according to claim 7 , wherein the printhead incorporates a pagewidth printhead arranged as a two-dimensional array of at least 50,000 printing nozzles for printing across the width of sheets of print media.

10. An arrangement according to claim 7 , wherein the printhead incorporates an array of printing fluid ejecting nozzles configured as a pagewidth printhead arranged to print on sheets of print media by ejecting at least 1200 drops of printing fluid per inch across the width of the sheets.

11. An arrangement according to claim 7 , wherein the printhead incorporates an array of printing fluid ejecting nozzles configured as a pagewidth printhead arranged to print on sheets of print media by ejecting drops of printing fluid across the width of the sheets with a drop ejection energy of less than about 250 nanojoules per drop.

12. An arrangement according to claim 7 , wherein the printhead incorporates a pagewidth printhead arranged to print printing fluid across the width of sheets of print media at a rate of at least 60 sheets per minute.

13. An arrangement according to claim 7 , wherein the printhead incorporates an array of printing fluid ejecting nozzles configured as a pagewidth printhead arranged to print on sheets of print media by ejecting drops of printing fluid across the width of the sheets at a rate of at least 500 million drops per second.