GB1438069A - Ink jet printer - Google Patents

Abstract

1438069 Ink jet printers INTERNATIONAL BUSINESS MACHINES CORP 1 May 1974 [22 June 1973] 18994/74 Addition to 1426803 Heading G4H In liquid-droplet recording apparatus, droplet charge is detected to control the relative timing of a clock-driven counter. An ink jet printer includes a transducer 15 for vibrating a nozzle 14 to produce droplets, a charging electrode 16 for varying deflection of the droplets in an electric field between deflecting electrodes 18, and means for controlling the phase relation between the transducer 15 and the charges applied to the electrode 16 comprising: circuit means 28, 29, 30 connected to the charging electrode 16 for applying, in response to an initiation signal, input information signals to the droplets and, in the absence thereof, applying a calibration signal to droplets to be discarded; a counter 31 cyclically counting clock pulses 25 and producing the initiation signal during each counting cycle; means 20 for catching the discarded droplets having a plurality of impact locations 20a, 20b and producing output signals indicative of the location; and means responsive to the output signals to alter the number of clock pulses fed to the counter 31 and change the time of the counting cycle and thereby the initiation signal. Contacts 45 in location 20a are connected across capacitor 50 and resistor 49 in a filter 47, whereby ink droplets in location 20a complete the circuit and provide a low impedance path to ground for the filter output. Ink droplets in location 20b produce no such action. Comparator 51 produces a 0 or 1 output for droplets in locations 20a, 20b respectively. Normally, irrespective of where the droplets land, counter 31 is driven by clock pulses 25 via path 33 or 34 and AND 36 or 39 according to the output of comparator 51 which thus makes no difference. However, whenever a sampling signal is produced at 69 in response to 62 &c. (see Fig. 1), an extra pulse is produced by single shots 70, 71 and fed to the counter 31 via AND 36 if the output of comparator 51 is 0 whereas if the output of comparator 51 is 1, counter 31 receives one clock pulse less due to the influence of the sampling pulse on NAND 53 since now clock pulses reach the counter 31 only via AND 39. The initiation signal for character generator 28 and discard waveform circuit 30 is the reset output of counter 31, the time position of which is thus varied. Driver 29 passes the discard waveform from 30 only in the absence of output from the character generator 28. There is one initiation signal per droplet since the capacity of counter 31 equals the division ratio of divider 26 shown, viz. 8.