Jet printing apparatus

[54] JET PRINTING APPARATUS

[75] Inventors: Alessandro Scardovi, Ivrea; Adriano Fetta, Castellamonte; Aldo Chiaro, Caluso, all of Italy

[73] Assignee: Ing. C. Olivetti & G, S.p.A., Ivrea, Italy

[21] Appl. No.: 693,161

[22] Filed: Jan. 22,1985

[30] Foreign Application Priority Data

Jan. 20, 1984 [IT] Italy 67055 A/84

[51] Int. CI* G01D 15/18

[52] U.S. CI 346/140 R

[58] Field of Search 346/140

[56] References Cited

U.S. PATENT DOCUMENTS

3,683,212 8/1972 Zoltan 346/140 X

3,832,579 8/1974 Arndt 346/140 X

4,233,610 11/1980 Fischbeck 346/140

4,415,909 11/1983 Italiano 346/140

4,418,354 11/1983 Perduijn 346/140

4,485,386 11/1984 Dagna 346/140 X

4,528,579 7/1985 Brescia 346/140

Primary Examiner—Joseph W. Hartary

Attorney, Agent, or Firm—Banner, Birch, McKie &

Beckett

[57] ABSTRACT

The apparatus is of the type wherein a piezoelectric transducer (19) is selectively operated to produce a pressure wave in the ink in a duct (16,22), which causes a droplet of ink to be expelled from the nozzle (18). In order to absorb the energy of the pressure wave which is directed towards the ink reservoir (47) the duct comprises a portion (22) of viscoelastic material, which is so dimensioned as to damp the resonance of the duct for frequencies higher than a predetermined cut-off frequency. Frequencies which are lower than the cut-off frequency however are damped by an hour-glass shaped constriction (34) in a tube (33) disposed between the viscoelastic portion (22) of the duct and the reservoir (47). The second portion (22) of the duct comprises a polyamide base material, the modulus of elasticity of which is substantially stable over a wide range of possible operating temperatures. The second portion of the duct may comprise a flexible tube (22) or a double spiral passage (not shown) provided between two substantially square plates. *

14 Claims, 13 Drawing Figures