Ink jet printing apparatus with balanced thermal actuator

摘要

An ink jet nozzle assembly includes a nozzle chamber having an inlet receiving ink from a reservoir and a nozzle through which ink from the chamber can be ejected. The chamber includes a fixed portion and a movable portion configured such that relative movement in an ejection phase reduces an effective volume of the chamber and alternate relative movement in a refill phase enlarges the effective volume of the chamber. A pair of spaced apart actuating arms is connected with the movable portion and undergo selective differential thermal expansion upon heating so as to effect the relative movement. The inlet is positioned and dimensioned relative to the nozzle such that ink is ejected preferentially from the chamber through the nozzle in droplet form in the ejection phase, and ink is alternately drawn preferentially into the chamber from the reservoir through the inlet in the refill phase.