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Method to Establish and Control Drop Velocity and Air Velocity in an Aspirated Ink Jet Printer

IP.com Disclosure Number: IPCOM000052934D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 5 page(s) / 36K

Publishing Venue

IBM

Related People

Damon, BW: AUTHOR [+4]

Abstract

Described in this article is means to establish at printer start-up, and maintained for subsequent printer operation, the ink velocity and air velocity in an aspirated ink jet printer in order to maintain print quality over wide changes in environmental conditions.

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Method to Establish and Control Drop Velocity and Air Velocity in an Aspirated Ink Jet Printer

Described in this article is means to establish at printer start-up, and maintained for subsequent printer operation, the ink velocity and air velocity in an aspirated ink jet printer in order to maintain print quality over wide changes in environmental conditions.

The control method is based on the observation that the flight time of an ink drop between two points in space depends upon the amount of aerodynamic drag that the drop experiences along the flight path between the two points. With motionless air filling the region between the two fixed points in space, the flight time is relatively long since the resultant aerodynamic drag produces a force on the drop which directly opposes drop motion and uniformly reduces the drop velocity along the flight trajectory. Alternatively, with air in motion in the region between the two points and, further, with the magnitude and direction of air motion substantially the same as that of the ink drop at the starting reference point, aerodynamic drag is eliminated, no force to retard drop motion is present, the drop maintains its initial velocity throughout the region, and hence the flight time between the two points is relatively short.

The velocity control method is based on the phenomenon described above in the ink jet apparatus shown in the figure. In the figure, a jet of ink 1 separates at point 2 (within a charge electrode 5) into ink drops 3 which proceed at moderate velocities along the source stream axis 4 and through deflection electrodes 6 to stream catcher or gutter 7. In one embodiment to establish the desired drop velocity, one drop is charged and deflected along trajectory 8 through deflected drop detector 9. The transit time of the deflected drop between the point of separation from the ink stream and a given point on the drop sensor is measured by the machine electronics. This flight time is compared to a first standard flight time which has been determined in a closely toleranced prototype printer in which the drop velocity has been accurately set to the desired value via some secondary means. If the flight time of the ink drop in the operating printer is greater than or less than the first standard flight time, the drop velocity is incrementally increased or decreased by varying the fluid ink supply pressure which establishes the ink jet and regulates the drop velocity. Once the ink supply pressure is incremented, another drop is charged and deflected, the resultant flight time is measured, and this flight time is again compared to the first standard flight time.

This procedure is repeated until the measured flight time equals or is acceptably close in magnitude to the first standard flight time. When this condition is met, the drop velocity has set to the desired value. Note, that since the deflected drop essentially travels through motionless air, the first standard flight time...