Printhead having nested modules

1. A printhead comprising:

an elongate support having a plurality of internal webs protruding from a base section to define a plurality of parallel fluid supply channels;

a shim supported by the support and defining a plurality of rows of openings through which fluid from respective supply channels is supplied; and

a plurality of elongate printhead modules supported serially on the shim, each module defining a plurality of fluid supply passages through which fluid passes to fluid ejection nozzles from respective rows of the openings, either end of each module defining complementary formations such that adjacent modules nest together.

2. A printhead as claimed in claim 1 , wherein the complementary formations are stepped.

3. A printhead as claimed in claim 1 comprising a pair of molded endcaps mounted on either end of the support which is extruded.

4. A printhead as claimed in claim 3 , wherein one of the endcaps defines a plurality of fluid inlet tubes in fluid communication with respective fluid supply channels.

5. A printhead as claimed in claim 4 , wherein the other endcap defines a plurality of serpentine grooves to equalize the gas pressure in respective fluid supply channels.

6. A printhead as claimed in claim 1 , wherein each module has a shield plate covering the ejection nozzles and defining slots in register with the ejection nozzles so that fluid can be ejected through the slots.

7. A printhead as claimed in claim 1 , wherein the support is shaped to provide a form-lock for retaining opposite edges of the shim as a snap fit.