Piezoelectric actuator and ink ejector using the piezoelectric actuator

A piezoelectric actuator, comprising:

• first piezoelectric sheets each having inner individual electrodes;
• and
• second piezoelectric sheets each having an inner common electrode, the first and second piezoelectric sheets being laminated alternately,
• wherein first through-holes are formed in the first and second piezoelectric sheets and coated with a conductive material such that the inner individual electrodes are electrically connected with one another in a laminating direction of the first and second piezoelectric sheets, and second through-holes are formed in the first and second piezoelectric sheets and coated with the conductive material such that the inner common electrodes are electrically connected with one another in the laminating direction, and wherein the first through-holes formed in adjacent first and second sheets are not coaxially aligned, and the second through-holes formed in adjacent first and second sheets are not coaxially aligned, and each of the first and second through-holes has a maximum diameter of not less than about 20 μm and not more than about 200 μm.

An ink-jet head, comprising:

• a cavity plate formed with pressure chambers and nozzles each communicating with a corresponding one of the pressure chambers;
• and
• a piezoelectric actuator including:
• first piezoelectric sheets extending across the pressure chambers, each sheet having inner individual electrodes each aligned with a corresponding one of the pressure chambers;
• and
• second piezoelectric sheets extending across the pressure chambers, each sheet having an inner common electrode extending across the pressure chambers, the first and second piezoelectric sheets being laminated alternately, wherein through-holes are formed in the first and second piezoelectric sheets and coated with a conductive material such that the inner individual electrodes are electrically connected, at their end portions, with one another in a laminating direction of the first and second piezoelectric sheets and that the common electrodes are electrically connected, at their at least one end portion, with one another in the laminating direction, and a maximum diameter of each of the through-holes is not less than about 20 μm and not more than about 200 μm.

A printer having at least one ink-jet print head, the at least one ink-jet print head comprising:

• a cavity plate having a plurality of pressure chambers, each pressure chamber associated with an ejection nozzle;
• and
• a piezoelectric actuator comprising:
• a top sheet having a plurality of surface electrodes on a top surface, a through-hole passing through each surface electrode and the top sheet;
• at least one restraining sheet mounted to a bottom surface of the top sheet, each restraining sheet having a common electrode, the common electrode having a plurality of common portions common to the common electrode and a plurality of dummy electrodes separated from the common electrode, a through-hole passing through each common portion and each dummy electrode and the restraining sheet;
• a plurality of first sheets, each first sheet having a plurality of individual electrodes and a plurality of dummy electrodes, one first sheet forming a bottom sheet with no through-holes, remaining first sheets having a through-hole passing through each individual electrode and each dummy electrode and the first sheet;
• and
• a plurality of second sheets, each second sheet having an electrode pattern and a through-hole pattern the same as the at least one restraining sheet, wherein the plurality of second sheets and the plurality of first sheets alternate and the through-holes from the top sheet to the electrodes of the one first sheet are electrically aligned in a substantially linear orientation although having radial offset from sheet to sheet.