Tri-layer thermal actuator and method of operating

• Main Authors: TRAUERNICHT, DAVID PAUL, LEBENS, JOHN ANDREW, FURLANI, EDWARD PAUL
• Format: Patent
• Language: English; French; German
• Published: 27.10.2010
• Subjects: CORRECTION OF TYPOGRAPHICAL ERRORS; i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; LINING MACHINES; MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICALDEVICES; MICROSTRUCTURAL TECHNOLOGY; PERFORMING OPERATIONS; PRINTING; SELECTIVE PRINTING MECHANISMS; STAMPS; TRANSPORTING; TYPEWRITERS

An apparatus (27) for and method of operating a thermal actuator (15) for a micromechanical device, especially a liquid drop emitter 110 such as an ink jet printhead, is disclosed. The disclosed thermal actuator comprises a base element (10) and a cantilevered element (20) extending from the base element and normally residing at a first position before activation. The cantilevered element includes a barrier layer (23) constructed of a low thermal conductivity material, bonded between a deflector layer (22) and a restorer layer (24), both of which are constructed of materials having substantially equal coefficients of thermal expansion. The thermal actuator further comprises an apparatus adapted to apply a heat pulse directly to the deflector layer, causing a thermal expansion of the deflector layer relative to the restorer layer and deflection of the cantilevered element to a second position, followed by restoration of the cantilevered element to the first position as heat diffuses through the barrier layer to the restorer layer and the cantilevered element reaches a uniform temperature. When used as a thermal actuator for liquid drop emitters, the cantilevered element resides in a liquid-filled chamber (28) that includes a nozzle (30) for ejecting liquid. Application of a heat pulse to the cantilevered element causes deflection of a free end forcing liquid from the nozzle. The barrier layer exhibits a heat transfer time constant tau B. The thermal actuator is activated by a heat pulse of duration tau P at a repetion time of at least tau C, wherein tau P < 1/2  tau B and tau C> 3 tau B.