Patent ID: 7073881

Claim:
A method of controlling the temperature of an ink jet printhead, said printhead including an array of nozzles formed on a substrate, each nozzle including a thermal actuator which is thermally connected to and relatively displaceable from the substrate, a portion of the thermal actuator being heated to cause displacement of the thermal actuator whereby ejection of ink through a nozzle opening of an associated nozzle is caused, said heated portion of the thermal actuator being thermally insulated from portions of the thermal actuator in physical contact with said ink in said associated nozzle, said method including the steps of: (a) obtaining at least one first temperature signal representing a temperature of a part of said substrate; (b) comparing one of the at least one first temperature signal and a derivative thereof with a predetermined threshold; (c) if said one of the at least one first temperature signal and a derivative thereof is below said predetermined threshold, supplying energy to at least one of said actuators so as to heat at least part of the substrate and thereby heat the ink via the substrate until said one of the at least one temperature signal and a derivative thereof is above said predetermined threshold, wherein step (c) does not cause the ejection of ink from said printhead and further wherein said thermal actuator is a thermally actuated lever arm.