Patent ID: 6863379

Claim:
An ink jet printhead that comprises a substrate that defines a plurality of ink inlet channels; and a plurality of micro-electromechanical nozzle arrangements positioned on the substrate, each nozzle arrangement comprising a nozzle chamber defining structure positioned on the substrate and having a fixed portion that is fast with the substrate and a movable portion that is displaceable with respect to the substrate and that defines an ink ejection port, the movable portion and fixed portion together defining a nozzle chamber in fluid communication with a respective ink inlet channel and the movable portion being displaceable towards and away from the substrate respectively to reduce and subsequently increase a volume of the nozzle chamber so that ink is ejected from the ink ejection port; and an actuator that is anchored to the substrate and is operatively engaged with the movable portion to displace the movable portion towards the substrate upon receipt of an electrical signal, wherein a restrictive formation is arranged on the substrate and defines an opening in fluid communication with the respective ink inlet channel, the opening having a cross-sectional area that is less than that of the ink inlet channel, such that, when the movable portion is displaced towards the substrate, pressure build-up in the nozzle chamber is enhanced, thereby facilitating the ejection of a drop of ink from the nozzle chamber.