Liquid droplet ejection device

A liquid droplet ejection device comprising:

• a piezoelectric actuator comprising:
• a piezoelectric plate member formed of a piezoelectric material and having a first surface and a second surface opposite to the first surface in a thickness direction of the piezoelectric plate member, the piezoelectric plate member being fixed at fixed positions spaced away from each other in an extending direction of the plate member;
• and,
• electrodes for deforming the piezoelectric plate member, each electrode being positioned for imparting an electric field to the piezoelectric plate member so as to expand a part of the piezoelectric plate member in the extending direction, the part being defined between neighboring fixed positions of the piezoelectric plate member, a vacant zone being provided at a position deviating to one of the first and second surfaces in the thickness direction and at a position between the neighboring fixed positions, expansion force of the part of the piezoelectric plate member in the extending direction causing the part to be bendingly deformed between the neighboring fixed positions;
• and
• a liquid chamber constituting member defining a liquid chamber in cooperation with the part of the piezoelectric plate member, each fixed position being positioned adjacent to a contour of the liquid chamber, deformation of the part of the piezoelectric plate member providing a volumetric change of the liquid chamber.

A piezoelectric ink jet printer head comprising:

• a piezoelectric plate member formed from a piezoelectric material and having a first surface and a second surface opposite to the first surface in a thickness direction of the piezoelectric plate member, the piezoelectric plate member extending in an extending direction;
• an ink chamber plate positioned directly below the piezoelectric plate member and formed with a plurality of holes arrayed in the extending direction, the piezoelectric plate member being fixed to solid portions of the ink chamber plate other than the holes;
• a nozzle plate positioned directly below the ink chamber plate and formed with a plurality of nozzles arrayed in the extending direction and positioned in alignment with the holes, a combination of the piezoelectric plate member, the ink chamber plate and the nozzle plate defining a plurality of ink chambers arrayed in the extending direction;
• electrodes for deforming the piezoelectric plate member, each electrode being positioned for imparting an electric field to the piezoelectric plate member so as to expand a part of the piezoelectric plate member in the extending direction, the part being defined in confrontation with the ink chamber, vacant zones being positioned at positions deviating to one of the first and second surfaces and each vacant zone being positioned within a projection area of each hole, expansion force of the part of the piezoelectric plate member in the extending direction causing the part of the piezoelectric plate member to be bendingly deformed toward or away from the ink chamber.