Liquid jet modulator with piezoelectric hemispheral transducer

Abstract

A modulator for the generation of uniform liquid drops over a wide bandwidth of drop rates is provided. The concave and convex surfaces of a hemispherical piezoelectric crystal are electroded, and the transducer formed thereby is seated within and bonded to the wall of a concave well in the face of a solid epoxy crystal backing. A ring gasket is placed contiguous to the ring shaped edge of the transducer, and a nozzle plate is placed in sealed relation with the ring gasket to form a liquid chamber between the plate and the transducer. The physical dimensions of the component parts of the modulator are made smaller than the half wavelength of the shortest standing acoustical wave that can be established at the highest of the operable drop frequency rates in a structure of the same material as the part in question. The bandwidth of operating frequencies may be expanded, the tolerance to ink pressure variations may be increased, and a more stable droplet break-off distance from the nozzle plate may be acquired by enveloping the hemispherical piezoelectric transducer in a solid epoxy crystal backing, and by having a liquid feed bore passing through the center of the transducer to a nozzle. The hemispherical piezoelectric transducer also may be embodied in drop-on-command modulators for the generation of uniform liquid drops singularly.