PHASE CONTROL FOR A DROP GENERATING AND CHARGING SYSTEM

• US 3,761,941 A
• Filed: 10/13/1972
• Issued: 09/25/1973
• Est. Priority Date: 10/13/1972
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: John A. Robertson
• Inventors: Robertson, John A.
• Primary Examiner(s): Hartary, Joseph W.
• Application Number:
  US05/297,284
• Time in Patent Office: 347 Days
• Field of Search: 346/75,1 317/3 239/3,15
• US Class Current: 347/80
• CPC Class Codes: B41J 2/115 synchronising the droplet separation and charging time

Abstract

There is disclosed a phase control system for a jet drop generator wherein the phase of drop generation is adjusted by adjusting the amplitude of a stimulating disturbance applied to the jet. A time varying electrical signal, preferably a binary or ON/OFF signal, is applied to a charging electrode located near the point of drop formation, so that newly forming drops are charged or uncharged in correspondence to the signal. During normal operation as a recording device, the charged drops pass through an electrical deflection field for deflection into an appropriately placed catcher. Drops which are uncharged pass undeflected through the deflection field and deposit on a recording sheet. During non recording or dead times a calibrating signal is applied to the charging electrode and the charge carried away by the drops formed during that period is measured by an electrometer connected to the catcher. This measurement provides an indication of the phase of drop generation relative to the phase of the calibrating signal. Deviations of this relative phase from a desired relative phase are corrected by adjusting the amplitude of the drop stimulating disturbance.

Claims

1. Method of sampling a time varying electrical signal comprising the steps of:

1. generating a continuously flowing liquid filament, 2. applying a regular frequency drop stimulating vibration to said liquid Filament, 3. applying a drop charging electrical field to said filament in the region where said vibration causes the filament to break up into drops, 4. sampling said signal by modulating said field in correspondence therewith and thereby inducing in said drops electrical charges which represent samples of said signal, 5. detecting a deviation of the phase of said sampling from a desired phase, and 6. correcting said deviation by adjusting the amplitude of said vibration to alter the length of said filament and change the timing of drop breakoff and charging.

2. In a system for control of liquid drops comprising:

means for generating a continuously flowing filament of said liquid, stimulation means for applying regular frequency disturbances to said filament and causing a series of uniformly sized drops to separate at regular intervals therefrom, and a charging electrode responsive to an input charging signal for inducing electrical charges in said drops during separation from said filament;

the improvement wherein said stimulation means comprises;

means for generating an error signal related to the phase of said drop separation relative to said charging signal, and means responsive to said error signal generating means for correcting said phase by adjusting the amplitude of said disturbances to change the length of said filament and correspondingly change the time required for said disturbances to travel said length.

3. applying a drop charging electrical field to said filament in the region where said vibration causes the filament to break up into drops,

4. The improvement of claim 2 said measuring means comprising means for generating a measuring signal the voltage of which corresponds to the effective current carried by the drops charged and caught as aforesaid.

5. detecting a deviation of the phase of said sampling from a desired phase, and

6. The improvement of claim 4 said means responsive to said error signal comprising:

an integrating network for integrating said error signal to produce a setpoint voltage. an oscillator for generating a periodic stimulating drive signal of continually repeating waveform, a voltage variable attenuator for attenuating said stimulating drive signal in accordance with the magnitude of said setpoint voltage, and means for generating said regular frequency disturbances in accordance with the attenuated amplitude of said stimulating drive signal.

7. The improvement of claim 5 said calibrating signal being a square wave of frequency equal to the frequency of said stimulating drive signal.

8. The improvement of claim 6 said reference voltage being selected to correspond to the magnitude of said measuring signal voltage for the condition when said drops separate from said filament during transition periods for said callibrating signal.

9. In a system for control of liquid drops wherein selected drops are removed from a stream issuing from a drop generator, said drop generator including an orifice from which liquid is expelled along a predetermined path as a filament to separate into drops, a charging electrode spaced from said orifice, means for stimulating the liquid filament to induce regular drop separation at a point adjacent said electrode, and means for selectively applying charging pulses to said charging electrode for electrostatically charging pre-determined ones of the drops;

the improvement comprising means for attenuating the amplitude of the stimulation energy induced into the filament by said stimulating means, and a control for said attenuating means responsive to the quantity of charge on a succession of charged drops and connected to said stimulating means to vary the amplitude of the stimulation energy and thereby to adjust the length of said filament and produce separation of said drops in optimal phase relationship with said charging pulses.

10. A system as defined in claim 8, including means creating a deflection field adjacent said path to change the trajectory of charged drops, means for catching the charged drops, and said control means including a detector connected to said catching means to detect the quantity of charge on the charged drops.

11. A system as defined in claim 9, including means for driving said stimulating means at a preselected constant frequency;

said attenuating means being responsive to changes in the output of said detector means and connected to vary the amplitude of driving energy supplied from said driving means to said stimulating means.