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STREAM BREAK-OFF LENGTH CONTROL IN AN INK JET PRINTER

IP.com Disclosure Number: IPCOM000025280D
Original Publication Date: 1984-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 6 page(s) / 210K

Publishing Venue

Xerox Disclosure Journal

Abstract

Ink jet printing of the continuous stream type is achieved by induction charging of droplets of ink as they separate from the grounded ink stream emanating from the drop generator orifice. It is necessary that the drop separation point be located within the charge tunnel to achieve accurate charging. However, operating with a break-off length which is too long rather than too short, is clearly the more dangerous situation, since the drops would be charged by the high DC deflection field and be drawn into the deflection plates; this would, of course, foul the plates and short out the deflection voltage.

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Page 1 of 6

KEROX DISCLOSURE JOURNAL

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STREAM BREAK-OFF LENGTH CONTROL IN AN INK JET PRINTER
Dale R. Ims

Proposed Classification
U.S. C1. 346/75

Int. C1. Gold 15/18

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Volume 9 Number 3 May/June 1984 183

[This page contains 1 picture or other non-text object]

Page 2 of 6

STREAM BREAK-OFF LENGTH CONTROL IN AN INK JET PRINTER (Cont'd)

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184

 XEROX DISCLOSURE JOURNAL Volume 9 Number 3 May/June 1984

[This page contains 1 picture or other non-text object]

Page 3 of 6

STREAM BREAK-OFF LENGTH CONTROL IN AN INK JET PRINTER (Cont'd)

Ink jet printing of the continuous stream type is achieved by induction charging of droplets of ink as they separate from the grounded ink stream emanating from the drop generator orifice. It is necessary that the drop separation point be located within the charge tunnel to achieve accurate charging. However, operating with a break-off length which is too long rather than too short, is clearly the more dangerous situation, since the drops would be charged by the high DC deflection field and be drawn into the deflection plates; this would, of course, foul the plates and short out the deflection voltage.

While there are schemes for visually detecting break-off length and adjusting it to an acceptable value, large arrays of jets and structural interference make this difficult. Thus, it is desirable to have a technique to automatically adjust break- off length to an acceptable value. In addition, variations in ink viscosity or aging of the piezoelectric driver may necessitate such an automatic system.

With the bipolar ink jet device 10 shown in Figure 1, the break-off point of each stream begins to encounter a field component from the deflection plates 12 as the break-off points 14 move toward the end of the charge tunnels 16. It has been shown that the last approximately 25% of the length of the charge tunnel 16 contains an increasing deflection field component as one moves toward the downstream end. The result of this deflection field component will be to reduce the drop charge and the resulting drop trajectory 18.

Bipolar refers to the fact that the drops may be charged both positive and negative with the corresponding deflections either left or right. The gutters 24 collect unprinted droplets and are physically located within or beyond the grounded deflection plate set 12. The center-null stich point sensor 22 is located beyond the gutters and is used to calibrate the individual ink jet trajectories to enable accurate stitching of the neighboring trajectories.

A technique for controlling break-off length 14 within the charge tunnels 16 for each of the ink jet streams 26 from a long array of orifices 20 in which the droplets are charged in a bipolar manner and stitched together at the printing plane is as follows:

(1) Utilize a large set-up gutter 28 positioned at or beyond the print plane to catch all ink droplets. (2) Set the acoustic drive voltag...