(19)
(11) EP 0 273 664 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
24.05.1989 Bulletin 1989/21

(43) Date of publication A2:
06.07.1988 Bulletin 1988/27

(21) Application number: 87311224.7

(22) Date of filing: 18.12.1987
(51) International Patent Classification (IPC)4B41J 2/065, B41J 2/205
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 19.12.1986 US 944286

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

(72) Inventors:
  • Elrod, Scott Alan
    Menlo Park California (US)
  • Khuri-Yakub, Butrus T.
    Palo Alto California (US)
  • Quate, Calvin F.
    Stanford California (US)
  • Vanzandt, Thomas Roy
    Menlo Park, California (US)

(74) Representative: Weatherald, Keith Baynes et al
Rank Xerox Ltd Patent Department Parkway
Marlow Buckinghamshire SL7 1YL
Marlow Buckinghamshire SL7 1YL (GB)


(56) References cited: : 
   
       


    (54) Droplet ejectors


    (57) Provision is made for varying the size of the pixels or spots printed by an acoustic printer of the type in which one or more droplet ejectors (12) are driven by rf voltage pulses to produce focused acoustic beams (22) for ejecting droplets (25) of ink on demand from a free surface (24) of an ink supply (23). It has been found that the size of the individual droplets (25) of ink that are ejected from the free surface (24) of the ink can be varied by modulating the frequency, duration or amplitude of the pulses applied to such a droplet ejector (12). Furthermore, it also has been found that the trajectory along which the ink droplets (25) are propelled from the free surface (24) of the ink supply to a nearby record medium (11) is sufficiently well defined and repeatable that multiple droplets (25) can be deposited on the record medium (11) in rapid sequence, one on top of the other, before the ink has time to dry, to print variable diameter pixels or spots. The control techniques discribed in this application may be employed for variable resolution printing and for imparting a controlled pseudo-gray scale shading to the printed image. Each of the pixels of the printed image may be composed of a single cell for one spot per pixel printing or may be subdivided into a plurality of cells for multiple spot per pixel printing.







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