Showing papers by "Scott A. Elrod published in 1987"

Spatial stabilization of standing capillary surface waves

Abstract: Provision is made spatially stabilizing standing capillary surface waves in fixed and repeatable locations with respect to stationary external references. For spatially stabilizing such a wave on the free surface of a volume of liquid, the wave propagation characteristics of the free surface of liquid are periodically varied in a spatially stable manner at a spatial frequency equal to the spatial frequency of the standing wave or a subharmonic thereof, thereby locking the crests and troughs of the standing wave in predetermined spatial locations. A spatially periodic pattern of notches in a wall or base plate bounding the free surface of the liquid may be employed to physically modulate its wave propagation characteristics at a suitable spatial frequency. Alternatively freely propagating secondary capillary surface waves may be launched from spatially periodic sites along the free surface of the liquid to actively modulate its wave propagation characteristics at the diesired spatial frequency.

Capillary wave controllers for nozzleless droplet ejectors

Abstract: A nozzleless droplet ejector for ejecting droplets from a free surface of a pool of liquid, such as a pool of ink, comprises a selectively energizeable emission controller for generating a freely propagating capillary wave on the surface of the pool to provide on/off timing control and/or ejection trajectory angle control for the ejector. The controller comprises a conductor and a counter electrode. The conductor is immersed in the pool, whereby a capillary surface wave is generated when a voltage is applied across the conductor and the counter electrode. In one embodiment, a focused ultrasonic acoustic wave or the like perturbs the pressure acting on the free surface of the pool, and the capillary wave supplied by the controller coherently interacts with that pressure perturbence to provide the desired control. Separate controllers may be provided for independently controlling the ejectors of multiple ejector arrays. The functionality of these emission controllers is dependent on the geometry of their conductors, so a few exemplary geometries are disclosed with the understanding that there are others which may be used.

Hot melt ink acoustic printing

Abstract: To facilitate the use of hot melt inks in acoustic ink printers of the type having a printhead including one or more acoustic droplet ejectors for supplying focused acoustic beams, such a printer comprises a carrier for transporting a generally uniformly thick film of hot melt ink across its printhead, together with a heating means for liquefying the ink as it nears the printhead. The droplet ejector or ejectors are acoustically coupled to the ink via the carrier, and their output focal plane is essentially coplanar with the free surface of the liquefied ink, thereby enabling them to eject individual droplets of ink therefrom on command. The ink, on the other hand, is moved across the printhead at a sufficiently high rate to maintain the free surface which it presents to the printhead at a substantially constant level. A variety of carriers may be employed, including thin plastic and metallic belts and webs, and the free surface of the ink may be completely exposed or it may be partially covered by a mesh or perforated layer. A separate heating element may be provided for liquefying the ink, or the lower surface of the carrier may be coated with a thin layer of electrically resistive material for liquefying the ink by localized resistive heating.

Amorphous silicon varactors as rf amplitude modulators and their application to acoustic ink printers

Abstract: Amorphous silicon (aSi) voltage-controlled, variable capacitors (varactors) are utilized as rf amplitude modulators, such as for amplitude modulating the rf applied to an acoustic ink printhead. Large area fabrication processes are employed for vertically integrating these varactors with such printheads or other devices.

Spatially addressable capillary wave droplet ejectors

Abstract: Provision is made for selectively addressing individual crests (64) of traveling or standing capillary surface waves (62) to eject droplets from the selected crests on command. To that end, the addressing mechanisms (65, 85) of this invention locally increase the surface pressure acting on the selected crests and/or locally reduce the surface tension of the liquid within the selected crests. The preferred addressing mechanisms have sufficient spatial resolution to address a single crest substantially independently of its neighbors. Discrete addressing mechanisms having a plurality of individual addressing elements (85) are especially attractive for liquid ink printing and similar applications, not only because their individual addressing elements may be spatially fixed, but also because the spatial frequency of their addressing elements may be matched to the spatial frequency (wavelength λc) of the capillary wave. Such frequency matching enables selected crests of the capillary wave to be addressed in parallel, such as for line printing. Preferably, the capillary wave for a printer is a spatially stabilized standing wave, so that the crests and troughs of the capillary wave are locked in predetermined spatial locations.