Claims
- 1. In an acoustic ink printer including a printhead having a supply of liquid ink with a free ink surface; an acoustic cavity of finite length containing said ink, with one end of said cavity being defined by said free ink surface; a droplet ejector acoustically coupled to said ink: and a pulse modulated rf signal source coupled to said droplet ejector for exciting said droplet ejector to radiate said free ink surface with substantially focused acoustic power pulses, whereby individual droplets of ink of controlled size are ejected from said free ink surface on command at a controlled ejection velocity; the improvement wherein
- said signal source supplies a plurality of rf frequency components for exciting said droplet ejector, said frequencies being selected to produce resonant and anti-resonant reflections within said cavity that substantially counteract each other at said free ink surface, thereby inhibiting said reflections from materially perturbing the acoustic power at said free ink surface.
- 2. The improvement of claim 1 wherein
- said signal source supplies a pair of rf frequencies at amplitude levels which are scaled to cause their resonances and anti-resonances to substantially equally and oppositely perturb the acoustic power at said free ink surface.
- 3. The improvement of claim 1 wherein
- said signal source has a broad frequency spectrum and a substantially uniform signal amplitude across said frequency spectrum, and
- said printhead is configured to couple many of the frequencies within said spectrum into said ink within the passband of a single resonance of each of said frequencies within said ink,
- whereby the acoustic power perturbations caused by the resonances and anti-resonances of said frequencies tend to neutralize each other at the free ink surface.
- 4. The improvement of claim 3 wherein said signal source includes a pseudo-random bit generator for supplying a cyclical bit sequence signal, and means for frequency modulating a rf carrier in accordance with said pseudo-random signal.
- 5. The improvement of any of claims 2 through 4, inclusive, or 1 wherein
- said means for suppressing said power perturbations further includes an acoustically lossy ink for amplitude attenuating the reflected radiation sufficiently to significantly dampen said resonances and anti-resonances.
- 6. The improvement of any of claims 2 through 4, inclusive, or 1 wherein
- each of said droplet ejectors comprises a spherical acoustic focusing lens for launching said converging acoustic radiation into said ink.
Parent Case Info
This is a continuation of application Ser. No. 07/462,275, filed Dec. 16, 1989, which, in turn, was a continuation of application Ser. No. 07/287,791 filed Dec. 21, 1988
US Referenced Citations (5)
Continuations (2)
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Number |
Date |
Country |
Parent |
462275 |
Dec 1989 |
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Parent |
287791 |
Dec 1988 |
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