A typical printer of this kind which has been known may consist of feeding ink to a nozzle, applying a very small pressure so that the ink may assume a semicircular form at the tip of the nozzle, establishing an electric field between an acceleration electrode positioned several millimeters in front of the nozzle and the nozzle in order to draw the ink in droplet form, applying an intense electric field between the nozzle and the platen to run the ink drops toward the surface of the printing paper, electrostatically deflecting the ink drops in both the main and sub directions like a cathode ray tube display thereby controlling the position on the printing paper surface to which the ink droplets will be directed in order to print the letters and signs.
Another known typical ink-jet printer consists of feeding ink to the nozzle with a relatively high pressure to blow the ink stream from the nozzle, applying an electric field of an intensity corresponding to the position in the main scanning direction on the printing paper surface to the space between the charging electrode placed at a position where the ink stream divides itself into ink droplets and the nozzle in order to selectively charge the ink droplets and to cause the charged ink droplets to be deflected in the main scanning direction, and moving the printing head at a definite speed and continuously in the subscanning direction to print the letters and signs successively.
The above-mentioned two types are different in regard to their objects that will be controlled according to letter pattern information, and depending on their objects; the former is known as the electric field control type, and the latter the charge control type.
Concerning the electric field control type printers, since it is allowed to fix the relation between the printer head and the printing paper at least during the printing of a letter is fixed, it is desirable to provide a mechanism that intermittently feeds the printer head, such as a typewriter, punching typewriter, or a telegraph printing mechanism. But such printers require the application of a voltage as high as about 10,000 volts. Also for the purpose that the electric field established between a pair of electrostatic deflection plates may cause deflection of the desired ink drops only, the length of the electrostatic deflection plates along the ink drop running direction has to be nearly equal to, or less than, the distance between the ink droplets; hence speeding up the formation of ink drops merely results in the degraded deflection sensitivity.
As for the charge control type printers, the application of a d-c voltage to the electrostatic deflection plate pair provides an advantage in that the deflection sensitivity can be set independently of the ink drop formation rate. But in such printers, since the displacement of ink drops in the lateral direction depends on the movement of the printer head and, tracing performance of the printer head at the time of starting and stopping had always provided problems for the printers interlocked to the key devices.
It is therefore an object of this invention to provide a printer which can feed the printer head either continuously or intermittently by the employment of a printer-head feeding mechanism.
Another object of this invention is to provide an improved printer having increased deflection sensitivity.
Still another object of this invention is to provide a printer which develops reduced printing distortion.
Yet another object of this invention is to provide an improved printer which features increased printing speed when the printer head is being fed continuously.
In the Invention:
Also, in some form of the invention, distortion might develop on a small portion of the letter printed, but by varying the phase of the voltage pulses applied to the charging electrode according to the mode of letter pattern information, distortion of the letter printed can be reduced.