SERVO CONTROL OF INK JET PUMP

• US 3,787,882 A
• Filed: 09/25/1972
• Issued: 01/22/1974
• Est. Priority Date: 09/25/1972
• Status: Expired due to Term

• Current Assignee: IBM Information Products Corp. (Ninestar Corporation)
• Original Assignee: Donald L. West, Gary L. Fillmore, Hugh E. Naylor III
• Inventors: Naylor, Hugh E. III, West, Donald L., Fillmore, Gary L.
• Primary Examiner(s): Hartary, Joseph W.
• Application Number:
  US05/293,300
• Time in Patent Office: 484 Days
• Field of Search: 346/75,140 417/412,32,42,43,326 318/127,129,130
• US Class Current: 347/6
• CPC Class Codes: B41J 2/125 Sensors, e.g. deflection sensors nozzle clogging detection for cleaning reasons B41J2/16579; detection for compensation for failed nozzles B41J2/2139
• CPC Class Codes: B41J 2/17596 Ink pumps, ink valves
• CPC Class Codes: F04B 43/04 Pumps having electric drive
• CPC Class Codes: F04B 49/065 and making use of computers

Abstract

An important factor in quality of printing with an ink jet printing apparatus is the velocity of the ink jet stream. The present case describes a number of servo systems for controlling velocity of the stream. This can be done indirectly by sensing pressure and/or temperature or directly by sensing velocity of the stream and controlling the pump frequency or pump drive currents.

Claims

1. In an ink printing apparatus, a servo system for monitoring and maintaining parameters, affecting quality of printing, such as velocity of the jet, within predetermined ranges, which determines jet placement during printing of information, comprising:

jet forming means for forming and propelling an ink jet in a predetermined path of travel, pump means interconnected with said jet forming means for maintaining a predetermined level of ink jet pressure in said jet forming means;

sensor means proximately positioned in relation to said ink jet for sensing a characteristic of said ink jet and for developing a signal representative of said characteristic;

comparator means for comparing said developed signal with a reference signal in order to further develop a corrective signal; and

means for applying said corrective signal to said pump means in order to maintain pressure exerted by said pump means in said jet forming means within a predetermined range, thereby maintaining jet velocity, jet placement, and printing of information within a predetermined range of printing.

2. The apparatus of claim 1, further comprising:

pump control means interconnected with said pump means for directing corrective signals from said comparator means to said pump means; and

timing logic interconnected with said pump control means for controlling activation and deactivation of said pump control means.

3. The apparatus of claim 2 wherein said ink jet is directed to a medium for recording of information in the form of character intervals, each separated by an inter-character interval;

and further comprising;

recognition means interconnected with said logic means for recognizing said inter-character intervals and for activating said pump control means during said intercharacter intervals.

4. The apparatus of claim 3 wherein said ink jet forming means and said medium are relatively moved from a home position to record information, and further comprising:

means in said recognition means for activating said pump control means while said apparatus is at home position.

5. The apparatus of claim 1, wherein said sensor means comprises:

a temperature sensor for monitoring temperature characteristics of said ink jet.

6. The apparatus of claim 1, wherein said sensor means comprises:

a pressure sensor for monitoring pressure characteristics of said ink jet.

7. The apparatus of claim 1, further comprising:

a temperature sensor and a pressure sensor incorporated in said sensor means and interconnected with said pump means for monitoring temperature and pressure, respectively; and

circuit means responsive to signals developed by said temperature and pressure sensors and interconnected with said pump means for controlling pump pressure in order to maintain said pump pressure within a predetermined range.

8. The apparatus of claim 1, further comprising:

a first proximity sensor aNd a second proximity sensor incorporated in said sensor means and connected for input to said comparator means, said proximity sensors being positioned a predetermined distance apart and adjacent the path of travel of said ink jet;

means for developing signals from said proximity sensors indicative of the passage of ink as it moves past said proximity sensors; and

said comparator means developing a corrective signal responsive to the signals derived from said first and second proximity sensors for application to said pump means in order to maintain pressure in said pump means within a predetermined range.

9. The apparatus of claim 8, wherein said comparator means further comprises:

activatable gate means;

means interconnecting said proximity sensors as inputs to said gate means;

count means;

means interconnecting said gate means and said count means to initiate operation of said count means under control of said gate means during an activate mode of said gate means in order to develop digital count representations; and

means for activating said gate means and thereby said count means upon sensing passage of ink moving past said first proximity sensor and for deactivating said gate means and said count means upon sensing passage of ink past said second proximity sensor.

10. The apparatus of claim 9, wherein said comparator means further comprises:

digital-analog converter means interconnected between said count means and said pump means for converting digital representations from said count means to an analog signal for application to said pump control means.

11. The apparatus of claim 8, wherein said comparator means further comprises:

a ramp generator circuit providing a ramp signal having predetermined slope and duration characteristics;

means interconnecting said proximity sensors as inputs to said ramp generator;

an analog holding circuit;

means for initiating operation of said ramp generator circuit upon sensing passage of ink by said first proximity sensor and for terminating operation of said ramp circuit upon sensing passage of ink by said second proximity sensor;

means interconnecting said ramp generator to said analog holding circuit in order to provide the ramp level attained by said ramp circuit to said analog holding circuit; and

means interconnecting said holding circuit to said pump means in order to correct pressure in said pump means.

12. The apparatus of claim 1 wherein said ink jet passes through a charge electrode and between deflection electrodes for charging and deflection within a predetermined deflection monitoring range, and further comprising:

means for applying a charging potential to said charging electrodes in order to deflect said ink jet into said monitoring range;

sensor means positioned adjacent the path of travel of said ink jet for developing signals from said ink jet during passage thereof past said sensor means indicative of velocity characteristics in said monitoring range, and means for applying said velocity characteristics signals to said pump control means in order to correct pressure in said pump means.

13. The apparatus of claim 12, further comprising:

first and second sensor probes incorporated in said sensor means, said probes being positioned a predetermined distance apart and in proximity to said ink jet when said ink jet passes through said monitoring range; and

means interconnected with said probes and said pump means and responsive to signals developed by said probes for developing corrective signals for application to said pump means in order to increase or decrease pump pressure, as required, in order to maintain jet velocity within a predetermined range.