Inkjet printhead and printhead nozzle arrangement

1. A printhead for an inkjet printer, the printhead comprising:

a wafer assembly defining spaced apart groups of ink supply channels; and

groups of ink ejection nozzle arrangements extending from the wafer assembly and in fluid communication with respective ink supply channel groups, each group of ink ejection nozzle arrangements comprising a pair of rows of ink ejection nozzle arrangements, wherein

each nozzle arrangement includes an ink ejection head from which an actuator tail extends,

each pair of rows of ink ejection nozzle arrangements are arranged such that the ink ejection heads of the ink ejection nozzle arrangements in a first row of the pair face toward and are adjacent to the ink ejection heads of the ink ejection nozzle arrangements in a second row, and

each group of nozzle arrangements comprises an ink spread restriction wall extending from the wafer assembly to border the pair of ink spread restriction pits.

2. A printhead as claimed in claim 1 , wherein the actuator tails of the ink ejection nozzle arrangements in the first row extend outwardly away from the actuator tails of the ink ejection nozzle arrangements in the second row.

3. A printhead as claimed in claim 1 , wherein each nozzle arrangement defines a pair of ink spread restriction pits extending between the rows.

4. A printhead as claimed in claim 1 , wherein each nozzle arrangement comprises:

one of the ink ejection heads in the form of a nozzle chamber structure, the nozzle chamber structure mounted to the wafer assembly and defining a nozzle chamber for receiving ink from one of the ink supply channels and a raised nozzle rim through which ink in the nozzle chamber can be ejected;

an anchor extending from the wafer assembly in a location external to the nozzle chamber; and

one of the actuator tails in the form of an elongate thermal actuator mechanism, the thermal actuator mechanism extending from the anchor and into the nozzle chamber and comprising an elongate arm which terminates in a free end within the nozzle chamber and a pair of layers of conductive material located on either side of the elongate arm, one of the layers being connected to a current supply so that, in use, the free end of the arm can be moved to eject ink in the nozzle chamber through the nozzle rim as a result of differential thermal expansion.

5. A printhead as claimed in claim 2 , wherein each row is staggered and comprises a plurality of linearly arranged sets of nozzle arrangements with adjacent sets being staggered relative to each other along the row.

6. A printhead as claimed in claim 3 , wherein the sets form a plurality of ascending or descending steps.

7. A printhead as claimed in claim 3 , wherein the layers of conductive material are located proximal to the anchor.

8. A printhead as claimed in claim 1 , wherein actuator tails of one group of nozzle arrangements are interleaved with actuator tails of an adjacent group of nozzle arrangements.