(57) A nozzleless droplet projection system is disclosed. A thin film of fluid (26) with
a constant thickness travels at a constant velocity across a tubular transducer head
(16a, 16b). A smooth perimetrical surface (18) is formed between the input (22) and
the output (24) sides of the transducer head (16a, 16b). An array of electro-acoustic
transducers (15) submerged beneath the transducer head support surface (17) generate
tone bursts (20, Figs 3 and 4) of acoustic energy which are focused by a corresponding
array of acoustic lenses (19) inscribed along the length of the transducer head (16a,
16b). The constant thickness and constant velocity fluid film (26) is generated by
forcing pre-regulated, pressurized fluid through a narrow slit (30) and across the
smooth perimetrical surface (18) of the transducer head (16a, 16b). The fluid film
(26) is maintained at the acoustic focus of the lenses (19) in order to control the
resultant droplet (12) size. A pattern of droplets (12) is ejected by pulsing the
appropriate electro-acoustic transducers (15) as the projection medium (14) is moved
across the droplet formation apparatus at a constant velocity.
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