(19)
(11) EP 0 375 433 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
12.09.1990 Bulletin 1990/37

(43) Date of publication A2:
27.06.1990 Bulletin 1990/26

(21) Application number: 89313455.1

(22) Date of filing: 21.12.1989
(51) International Patent Classification (IPC)5: B41J 2/015, B41J 2/04
(84) Designated Contracting States:
DE FR GB

(30) Priority: 21.12.1988 US 287791

(71) Applicant: XEROX CORPORATION
Rochester New York 14644 (US)

(72) Inventors:
  • Elrod, Scott A.
    Palo Alto, California 94301 (US)
  • Richley, Edward A.
    Mountain View California 94040 (US)
  • Rawson, Eric G.
    Saratoga California 95070 (US)

(74) Representative: Goode, Ian Roy et al
Rank Xerox Ltd Patent Department Parkway
Marlow Buckinghamshire SL7 1YL
Marlow Buckinghamshire SL7 1YL (GB)


(56) References cited: : 
   
       


    (54) Acoustic ink printers having reduced focusing sensitivity


    (57) To improve the tolerance of acoustic ink printers (21) to changes in their free ink surface (25) levels, provision is made for significantly reducing the effect of half wave resonances on the acoustic power density of the acoustic beam (30) or beams that are incident on the free ink surface (25) of such a printer (21), thereby reducing its focusing sensitivity. Some of the approaches that are taken to accomplish this rely upon acoustic losses to damp out the halfwave resonances and anti-resonances, while others employ multi-frequency rf voltage pulses for driving the droplet ejector (23) or ejectors so that the acoustic power perturbations caused by the half wave resonances and anti-resonances of the different frequencies tend to neutralize each other. Indeed, the use of an acoustically lossy ink (26) to dampen the half wave resonances and anti-resonances is compatible with selecting the frequency content of the acoustic radiation to neutralize them, so a combination of those two techniques can be employed, if desired, to carry out this ink printer (21).







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