Recorders – Performance of multiple functions of steam and gas engines – Pressure responsive element
Patent
1990-05-17
1991-09-17
Fuller, Benjamin R.
Recorders
Performance of multiple functions of steam and gas engines
Pressure responsive element
346 75, G01D 1518
Patent
active
050498991
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of high resolution printing in a continuous jet printer and, more particularly, a method of high resolution printing in which satellite drops are used controlled by the electric printing charge.
The conventional technique of writing by ink projection using a continuous jet of calibrated droplets, delivered by a modulation system, consists in charging these droplets electrostatically by means of an appropriate electrode. The passage of these variably charged droplets between electrodes brought to a high electric potential difference leads to deflection of the droplets proportional to their charge. Such deflection combined with the movement of the medium makes matrix printing of characters or graphisms possible.
In ink jet printers of the continuous jet type, the pressurized ink is ejected by the nozzle in the form of a jet which is caused to break up into a succession of droplets to which a charge is then selectively applied, and which are directed towards the printing medium or towards the gutter. Different methods may be used for controlling and synchronizing the formation of the droplets, consisting in causing the nozzle to vibrate or causing disturbances of the pressure of the ink at the level of the nozzle by using particularly a resonator energized by a piezoelectric ceramic upstream of the nozzle. Because of the disturbance, the jet breaks up at the disturbance frequency into uniform droplets, often accompanied by smaller droplets called satellite drops.
In conventional printers the main drops are used for printing and the presence of the satellite drops must be controlled. In fact, at the time of application of the charge of the droplets, the satellites have a higher charge per unit of mass than the main drops. If these satellites pass into the deflection field, they undergo considerable deflection and cause either soiling of the deflection electrodes leading to electric insulation defects, or parasite impacts on the printed medium.
The prior art--see the article by Bogy in the "Annual Review of Fluid Mechanics" 1979--shows that if the physical properties of the ink, the nozzle, the frequency of disturbance, the jet speed, the resonator device and the form of the energization signal applied to the resonator are fixed, it is possible to control the formation of the drops by the amplitude of the disturbance applied to the resonator. It is possible, in particular, to inhibit the formation of satellite droplets by choosing an amplitude adapted to the disturbance.
In the U.S. Pat. No. 4,068,241 to Hitachi, an invention is described which consists in using satellite drops for printing. Depending on whether it is desired to print a satellite droplet or not, the amplitude of the signal applied to the resonator is modulated at the drop formation frequency so as to form or inhibit the satellite drop. All the drops (main and satellite) are charged electrically at the time of their formation by electrostatic influence, through the application of a DC charging voltage to the charging electrode. They are then deflected in a fixed electric field. The main drops whose charge per unit of mass is low are little deflected and recovered in the gutter. The satellite drops whose charge per unit of mass is higher have a more deflected path and impact on the medium to be printed. This technology makes possible a high printing resolution--the size of the satellites and the resultant impacts being very small--while avoiding the use of a small diameter nozzle whose manufacture is always difficult. This also makes it possible to overcome the problems of clogging of the nozzle during its use.
In practice, this technology is difficult to implement. In fact, the method of controlling the formation of the satellites by the amplitude of the signal applied to the resonator is difficult, because it is difficult to correctly control reproducibility in the manufacture of the resonators. It is generally necessary to calibrate each resonator so as to know its electromechanical efficiency. In addi
REFERENCES:
patent: 4150384 (1979-04-01), Meece
patent: 4367476 (1983-01-01), Sagae
patent: 4408211 (1983-10-01), Yamada
patent: 4638326 (1987-01-01), Yamada et al.
Dunand Alain
Margaillan Eric
Fuller Benjamin R.
Imaje (SA)
Plottel Roland
Preston Gerald E.
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