Inkjet printer having stably mounted printhead

1. An inkjet printer comprising;

an elongate support member; and

an elongate inkjet printhead mounted to the printer at the support member,

wherein the elongate support member comprises:

an elongate core having a portion mounting the elongate inkjet printhead; and

a laminated shell encasing the core about said portion, the shell and core together having an effective coefficient of thermal expansion substantially equal to that of the inkjet printhead.

2. An inkjet printer according to claim 1 , wherein the outer shell is formed from different materials laminated together, the laminate having inner and outer layers which are of the same metal.

3. An inkjet printer according to claim 1 , wherein the outer shell has an odd number of longitudinally extending layers, being at least three in number, layers being arranged symmetrically about a central layer.

4. An inkjet printer according to claim 1 , wherein a coefficient of thermal expansion of the core and a coefficient of thermal expansion of the shell are different.

5. An inkjet printer according to claim 4 , wherein the laminated shell comprises two or more different materials, each having a different coefficient of thermal expansion.

6. An inkjet printer according to claim 1 , wherein the core comprises adjacent reservoirs which collectively lead to the portion for mounting the printhead.

7. An inkjet printer according to claim 2 , wherein the laminated shell comprises inner and outer layers of invar about the central layer.

8. An inkjet printer according to claim 1 , wherein the core is an extruded and elongated body having a plurality of internal reservoirs, the reservoirs each having an ink exit opening, the openings converging into the portion for mounting the printhead.

9. An inkjet printer according to claim 8 , wherein the body is a plastic extrusion.

10. An inkjet printer according to claim 8 , wherein the body incorporates the portion for mounting the printhead as a protrusion beyond the shell.

11. An inkjet printer according to claim 8 , wherein the body is internally subdivided by extruded membranes to define the reservoirs.

12. An inkjet printer according to claim 11 , wherein the reservoirs are four in number.

13. An inkjet printer according to claim 1 , wherein the core has a coefficient of expansion which is less than the coefficient of expansion of silicon, and the shell has a coefficient of expansion which is greater than the coefficient of expansion of silicon.

14. An inkjet printer according to claim 1 , wherein the shell comprises at least two materials bonded to one another and having coefficients of expansion which are different than the coefficient of expansion of silicon, one material having a coefficient of expansion which is greater than the coefficient of expansion of silicon and another material having a coefficient of expansion which is less than the coefficient of expansion of silicon.

15. An inkjet printer according to claim 1 , wherein the laminated shell comprises hot rolled layers of metal.

16. An inkjet printer according to claim 1 , wherein the elongate inkjet printhead is a modular printhead comprising a plurality of printhead modules.