Abstract: The particle diameter of droplets is controlled without improvements on a nozzle plate. An ultrasonic wave causes a radiation pressure to be intermittently applied to an opening in a cycle having a period shorter than the fundamental vibration period of a liquid surface in the opening. A high-order standing wave is then generated at the liquid surface in the opening to cause a plurality of droplets to be emitted simultaneously. Since the plurality of droplets are simultaneously emitted from a plurality of mounds of the high-order standing wave, the droplets have a diameter smaller than the diameter of the opening and are emitted vertically upwardly. The diameter of the droplets is controlled by the order of the high-order standing wave to be generated. The order of the standing wave is increased by shortening the period for which the radiation pressure is applied to the opening.

Abstract: A liquid ejector increases the density of acoustic energy to eject droplets efficiently. Acoustic waves are introduced in generally planar form from a piezoelectric transducer into a liquid ink in a reservoir and are reflected from a reflecting wall of the reservoir. The reflecting wall defines a parabola in cross section. An ejection opening is located near a focal point of the parabola, opposite the transducer. The acoustic waves focus at the ejection opening, increasing the density of the acoustic energy in the ink at the ejection opening. Thus, ink droplets are ejected efficiently from the ejection opening.

Abstract: A scroll-type apparatus having a main journal bearing which journals the drive shaft of the apparatus and is capable of pivoting by small angles with two degrees of freedom. The main journal bearing comprises three or more arcuate pads whose inner surfaces journal the drive shaft and which are pivotably supported by a stationary main bearing housing. In a preferred embodiment, each of the pads has a spherical protrusion and two rotation-preventing pins secured to its back surface. The protrusions contact the inner surface of the main bearing housing and pivotably support the pads, while the rotation-preventing pins are inserted into grooves formed on the inner surface of the main bearing housing.