Liquid jet droplet generator

Abstract

A generator for producing droplets of liquid by subjecting a confined body of such liquid to varying pressures at a given frequency and causing such liquid to issue from a discharge orifice first as a continuous stream and thereafter to break up into a succession of separate droplets. A particular use of the generator is to produce a controlled stream of ink droplets for the purpose of forming printed characters on documents. It accomplishes this object by making use of acoustic and ultransonic vibrations in a body of ink contained in a cavity of tapering dimensions having an ink intake passage and a discharge orifice, and causing periodic variations (or varicosities) in the hydraulic pressure at the discharge orifice which in turn causes the issuing stream of ink to break up into uniformly spaced apart fine droplets of ink. The droplet forming generator includes a resonant vibrating system composed of tapered front and rear horns having their wider ends in surface contact with the opposite sides of a crystal transducer sandwiched therebetween. The ink at the wider end of the cavity receives the pressure oscillations from the front horn and such pressures are concentrated by the shape of the cavity into the immediate region of its discharge orifice. The entire acoustic droplet generator is designed to locate the standing waves of pressure where they are most effective in the operation of the resonant system. Consequently, the generator can use liquids of higher viscosity at greater pressures and at higher frequencies of droplet formation than heretofore achieved. The advantages of thicker viscosity inks and higher pressures enables the attainment of better print quality and greater printing rates.