Drop jet apparatus

DETAILED DESCRIPTION An object of the invention is to provide a drop jet apparatus such as an ink-jet printing apparatus which has a good productivity and a small amount of scattering in the characteristic of drop formation.
Another object of the invention is to provide a drop jet apparatus which has a large freedom in the design, is easy to manufacture, and is able to choose any shape of the piezoelectric plate without being restricted by the shape of a pressure chamber.
Further, another object of the invention is to provide a drop jet apparatus, in which the characteristic of drop formation is not directly influenced by a relative position between a diaphragm defining a pressure chamber and a piezoelectric plate adhered to the diaphragm, and by evenness of the adhesion layer.
A feature of the invention is in that a wall such as a diaphragm defining part of the pressure chamber of a nozzle head has a thick central portion at the center of a thin deflective portion surrounding the thick central portion, and an electro-mechanical transducer such as a piezoelectric plate is disposed on said wall to bridge the thin deflective portion and is secured to the thick central portion and portions surrounding the thin portion.
The wall is deflected by the electro-mechanical transducer with the thick central portion being pressed by the deformation of the electro-mechanical transducer.
The thin portion of the wall is not contacted with the thin portion so that securing means between the wall and the central projection has little influence the characteristic of drop formation of the nozzle head.