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Binary Drop Breakoff Synchronization

IP.com Disclosure Number: IPCOM000079630D
Original Publication Date: 1973-Aug-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Naylor, HE: AUTHOR [+3]

Abstract

In ink jet printing some method is required for automatically synchronizing the breakoff of droplets from the ink stream, with the application of voltage to the charging electrode. In digital approaches to automatic drop breakoff synchronization, the procedure consists of applying a suitable signal to the charging electrode for several drop periods, then sensing the presence or absence of charge on the drops. Possible methods for sensing the presence of charge on the drops include sensing the electrical current of the stream directly, or sensing the induced potential on a noncontacting sensor when charged drops pass close to it.

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Binary Drop Breakoff Synchronization

In ink jet printing some method is required for automatically synchronizing the breakoff of droplets from the ink stream, with the application of voltage to the charging electrode. In digital approaches to automatic drop breakoff synchronization, the procedure consists of applying a suitable signal to the charging electrode for several drop periods, then sensing the presence or absence of charge on the drops. Possible methods for sensing the presence of charge on the drops include sensing the electrical current of the stream directly, or sensing the induced potential on a noncontacting sensor when charged drops pass close to it.

Fig. 1 shows a group of charge electrode signals which could be used in a binary scheme for digital automatic drop breakoff synchronization. An "apply voltage - sense charge" sequence is performed with each of the three signals in turn. The results of the three charge sensing steps indicate the interval at which drop breakoff occurs. For example, if charge is present in each of the three steps, drop breakoff occurs in the interval designated as 111 in Fig. 1.

When the interval of drop breakoff has been determined, the timing of the normal charge electrode signal can be adjusted to yield proper synchronization of the application of charge electrode voltage with drop breakoff.

The use of a group of test signals of the type shown in Fig. 1 has the following advantages:
1) Synchronization is accomplished in the shortest possible time.

(Only N "apply voltage - sense charge" cycles for a resolution

of T/N seconds.)
2) Since no two of the test signals have transitions occurring at

the same point in the drop period, any anomaly in charge

sensing caused by drop breakoff occurring at a transition of

one of the test signals is resolved by the other two test

signals.
3) The shortest pulse needed on the charge electrode is twice the

length of the interval within which the drop breakoff instant

is determined. This greater pulse width makes the pulse rise

time less critical.

The group of three test signals shown in Fig. 1 could be extended...