Printhead assembly with two-material supporting structure

#The present invention relates to modular printheads for digital printers and in particular to pagewidth inkjet printers.

#Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee of the present invention on 24 May 2000:

#PCT/AU00/00578 PCT/AU00/00579 PCT/AU00/00581 PCT/AU00/ 00580 PCT/AU00/00582 PCT/AU00/00587 PCT/AU00/00588 PCT/AU00/ 00589 PCT/AU00/00583 PCT/AU00/00593 PCT/AU00/00590 PCT/AU00/ 00591 PCT/AU00/00592 PCT/AU00/00584 PCT/AU00/00585 PCT/AU00/ 00586 PCT/AU00/00594 PCT/AU00/00595 PCT/AU00/00596 PCT/AU00/ 00597 PCT/AU00/00598 PCT/AU00/00516 PCT/AU00/00517 PCT/AU00/ 00511

#A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing in which:

#FIG. 1 is a schematic longitudinal cross section of a first embodiment of a printhead assembly according to the present invention; and,

#FIG. 2 is a schematic longitudinal cross section of a second embodiment of a printhead assembly according to the present invention.

#Referring to FIG. 1, the printhead assembly has a support beam 1 supporting a plurality of printhead modules 2 each having a silicon MEMS printhead chip. The support beam 1 is a hot rolled three-layer laminate consisting of two different materials. The outer layers 3 and 4 are formed from invar which typically has a coefficient of thermal expansion of about 1.3×10−6 meters per degree Celsius. The coefficient of thermal expansion of silicon is about 2.5×10−6 meters per degree Celsius and therefore the central layer 5 must have a coefficient of thermal expansion greater than this in order to give the support beam as a whole a coefficient of thermal expansion substantially equal to that of silicon.

#It will be appreciated that the effective coefficient of thermal expansion of the support beam will depend on the coefficient of thermal expansion of both metals, the Young's Modulus of both metals and the thickness of each layer. In order to prevent the beam from bowing, the outer layers 3 and 4 should be the same thickness.

#Referring to FIG. 2, the printhead assembly shown as an elongate support beam 1 supporting the printhead modules 2. Each printhead module has a silicon MEMS printhead chip.