Printhead assembly with composite support beam for a pagewidth printhead

1. A pagewidth printhead assembly comprising:

a support beam assembly having a composite shell of metals selected so that the shell has a coefficient of thermal expansion substantially the same as that of silicon and a core located within the shell and defining a number of longitudinally extending ink reservoirs for containing respective inks; and

at least one printhead mounted on the support beam assembly to receive inks from the ink reservoirs the, or each, printhead including a silicon-based printhead integrated circuit.

2. A pagewidth printhead assembly as claimed in claim 1 , in which the shell is a composite of two metals.

3. A pagewidth printhead assembly as claimed in claim 2 , in which the shell is a laminate of the two metals.

4. A pagewidth printhead assembly as claimed in claim 3 , in which the shell is a trilayer laminate with a first metal layer sandwiched between two layers of a second metal.

5. A pagewidth printhead assembly as claimed in claim 4 , in which the layers of the second metal are symmetrically disposed about the layer of the first metal.

6. A pagewidth printhead assembly as claimed in claim 4 , in which the laminate is hot rolled.

7. A pagewidth printhead assembly as claimed in claim 1 , in which the core is an extrusion of a plastics material.

8. A pagewidth printhead assembly as claimed in claim 6 , in which the, or each, printhead circuit is mounted on a micro-molding bonded to the core.