Inkjet printhead with shared ink spread restriction walls

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

a wafer assembly defining a plurality of ink supply channels; and

plural groups of ink ejection nozzle arrangements extending from the wafer assembly, each group of ink ejection nozzle arrangements sharing a common ink supply channel, wherein

each group of ink ejection nozzle arrangements includes a plurality of ink ejection nozzle arrangements arranged in a pair of rows,

each group of ink ejection nozzles includes one ink spread restriction wall shared by the group, the ink spread restriction wall being interposed between each ink ejection nozzle of the group and so as to at least partially surround each ink ejection nozzle of the group, and

the shared ink spread restriction wall is spaced apart from each ink ejection nozzle arrangement to define a plurality of ink spread restriction pits between the common ink spread restriction wall and respective ink ejection nozzle arrangements.

2. A printhead as claimed in claim 1 , wherein each ink ejection nozzle arrangement comprises:

a nozzle chamber for receiving ink from an ink supply channel;

a raised nozzle rim through which ink in the nozzle chamber is ejected;

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

an elongate thermal actuator mechanism extending from the anchor into the nozzle chamber, the thermal actuator mechanism 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.

3. A printhead as claimed in claim 2 , wherein the rows of ink ejection nozzle arrangements are arranged so that the thermal actuator mechanisms extend outwardly on either side of the nozzle chambers which, in turn, are centrally located.

4. A printhead as claimed in claim 2 , wherein the plural groups of ink ejection nozzle arrangements are laid out in one or more rows, each group of a row being staggered relative to another group in the same row.

5. A printhead as claimed in claim 4 , wherein the groups forming a row form a plurality of ascending or descending steps.

6. A printhead as claimed in claim 2 , wherein the thermal actuator mechanisms of a group of nozzle arrangements in a row are interleaved with the thermal actuator mechanisms of a group of nozzle arrangements in an adjacent row.

7. A printhead as claimed in claim 2 , wherein the layers of conductive material are located proximal to the anchor.