Method of operating a thermal actuator and liquid drop emitter with multiple pulses

Abstract

Methods of operating a thermal actuator, especially for use in a liquid drop emitter for ink jet printing, are disclosed. Methods are disclosed for operating a thermal actuator comprising a base element, a thermo-mechanical element extending from the base element, having a moveable portion residing in a first position and reliably operating at temperatures below a maximum temperature Tand including apparatus adapted to apply energy pulses to the thermo-mechanical element to cause a temperature increase therein and movement of the moveable portion to a second position. The methods for operating comprise determining a first energy pulse having a first energy, E, and a first energy pulse time, t, for suddenly increasing the temperature of the thermo-mechanical actuator, but not above T. Further, determining a second energy pulse having a second energy, E, and a second energy pulse time, t, that when applied after the first energy pulse, causes the moveable portion to move to or remain at the second position. Also, determining a first delay time, t, selected, at least, to avoid increasing the temperature of the thermo-mechanical element above T. The first energy pulse is applied to the thermo-mechanical element; then, after waiting a first delay time t, applying the second energy pulse to the thermo-mechanical element so that the moveable portion moves to or remains at the second position and the maximum temperature is not exceeded. When used to operate liquid drop emitters, the disclosed methods cause liquid drop emission without exceeding the maximum temperature of reliable operation of the thermo-mechanical element.