Apparatus and method for jet deflection and recording

A jet drop recorder produces a continuously flowing stream of recording liquid and has a pair of deflection electrodes positioned therealongside but offset therefrom. The stream of recording liquid is stimulated to break up into uniformly sized and regularly spaced drops, and the electrodes are positioned such that at least portions thereof are upstream from the break-off point. Drops produced by the stream are steered to different laterally separated printing positions by application of a cyclic differential charging signal to the electrodes. This causes a stepped cyclic deflection of the unbroken stream, which in turn directs the drops toward the desired printing positions. There is no need to provide a drop deflection field. Furthermore the filament need not have any particular level of conductivity, as the disclosed electrode configuration produces a gradient electrical field capable of polarizing and deflecting a perfectly dielectric liquid. A selective drop catching technique is employed in combination with the above mentioned lateral steering. Such catching is accomplished by means of a cooperative charging signal applied simultaneously to the deflection electrodes. This cooperative charging signal causes the unbroken stream to be deflected in a dumping direction perpendicular to the above mentioned direction of lateral deflection. A catcher is positioned for catching of those drops deflected in the dumping direction. A large number of such jet drop recording devices may be arranged in two parallel rows.

BACKGROUND OF THE INVENTION 
This invention relates to the field of jet deflection and has specific 
application to a recording or printing process wherein one or more jets of 
recording liquid are controlled to reproduce graphic information on a 
print receiving medium. An early example of such a device is disclosed in 
Ranger et al U.S. Pat. No. 1,817,098, wherein a pair of electrodes are 
positioned on opposite sides of a jet. Control signals are applied to the 
electrodes to deflect the jet against a catching surface for achieving a 
no-print condition. A print receiving medium is transported through the 
active printing region of the jet (or three such jets of different 
colors), and pictorial information is reproduced by programmed application 
of no-print or catching signals to the control electrode. Hansell U.S. 
Pat. No. 1,941,001 discloses a somewhat more advanced symmetrical 
electrode arrangement for use in facsimile recording. 
The Ranger and Hansell patents relate to the control of jets comprising 
continuously flowing streams, which break up into drops on a random basis 
in accordance with physical principles described by Lord Rayleigh in the 
middle of the 19th century. More recently the quality of jet drop 
recording has been improved by stimulating the stream at a frequency near 
its natural frequency to create drops which are uniformly sized and 
regularly spaced. An application of such a technique to character printing 
is disclosed in Lewis et al U.S. Pat. No. 3,298,030. 
In the Lewis patent a plurality of streams are stimulated for drop 
generation, and the drops are directed toward laterally separated 
positions by charging the drops to different levels and directing them all 
through electrostatic deflection fields. Under the action of the 
deflection fields all drops are deflected in proportion to their level of 
charge. A series of charge rings are utilized for drop charging and the 
deflection fields are produced by a pair of deflection electrodes. 
Character generating circuitry causes the printing of predetermined 
characters by selectively applying a catching potential to the charge 
rings. Drops which are charged in response to this catching potential are 
deflected into an appropriately positioned catcher. 
A somewhat more compact arrangement for jet drop printing is disclosed in 
Sweet et al U.S. Pat. No. 3,373,437, wherein a row of closely spaced 
streams are produced by a common manifold and are commonly stimulated for 
drop generation. A series of charging electrodes charge the drops on a 
binary basis in response to desired "print" or "no-print" conditions. The 
"no-print" drops are charged to a predetermined level for deflection into 
a catcher. The "print" drops are uncharged. 
The recording head arrangement taught by Sweet et al has been improved and 
made more compact by using a laminated plate arrangement, including a 
notched charge plate as shown in Culp U.S. Pat. No. 3,618,858. For 
application of the Sweet et al technique to a twin row print head, 
reference may be made to Mathis U.S. Pat. No. 3,701,998. Utilization of 
the Mathis invention requires a row-to-row switching delay as taught in 
Taylor et al U.S. Pat. No. RE28,219. 
It will be appreciated that binary or on/off printing as taught by Sweet et 
al requires extremely close jet spacing for high resolution printing. As 
taught in King U.S. Pat. No. 3,739,395, such spacing requirements may be 
somewhat relaxed by lateral drop deflection in a manner similar to that of 
Lewis et al. As shown in King, selective drop catching is achieved by 
deflection in a direction perpendicular to the lateral scanning direction. 
Another patent, Robertson U.S. Pat. No. 3,656,171, teaches a recording 
technique which eliminates the requirement for drop deflection fields, 
thereby enabling closer spacing than electrical considerations previously 
would permit. The Robertson technique, however, is an on/off process, so 
there remains a packing density problem caused by the necessity of 
providing apparatus for creating a very great number of closely spaced 
jets. 
SUMMARY OF THE INVENTION 
In accordance with the present invention a novel electrode arrangement 
enables a marked improvement in recording resolution within prior art jet 
spacing constraints. The novel electrode arrangement enables a liquid 
stream to be deflected laterally toward a plurality of operating 
directions and to be deflected in a dumping direction perpendicular to the 
lateral deflection direction for print/no-print control. By this means any 
drops which break off from the stream can be directed to any of a 
plurality of laterally separated printing locations or into a 
perpendicularly displaced catcher, all without the aid of an electrical 
deflection field. 
The electrodes are placed on opposite sides of the stream, but they are 
offset from the stream axis. Thus a single pair of electrodes is able to 
produce stream deflection (and drop positioning) in two perpendicular 
coordinate directions. For stream deflection in the lateral direction a 
cyclic differential deflection signal having a net stepping effect is 
applied to the electrodes. For deflection in the dumping direction a 
cooperative or common charging signal is applied to the electrodes. 
It has been found in accordance with this invention that fairly substantial 
changes in drop positioning may be achieved with relatively little 
deflection of the stream itself. This means that the control electrodes 
may be placed quite close to the stream, at which placement a rather 
substantial electrical field gradient may exist. This field gradient in 
turn is capable of polarizing and deflecting a stream of non-conductive or 
dielectric printing liquid. Thus this invention makes it possible to 
achieve jet printing with a wide variety of conductive and non-conductive 
liquids. 
In accordance with this invention a plurality of streams may be generated 
by orifices placed side by side in one or more rows, with each stream 
passing closely adjacent a pair of electrodes. The electrodes are 
preferably flat strips plated inside notches on the edge of the charge 
plate. A cyclic charging potential is impressed upon each plate of each 
pair to create a differential field for laterally stepped stream 
deflection and laterally stepped drop positioning. 
Catching is accomplished by simultaneous application of a common dumping 
voltage to both electrodes of an electrode pair. This causes the 
associated stream to be pulled inwardly toward the electrodes, so that its 
drops are steered toward an appropriately positioned catcher. Since each 
stream is laterally deflected for drop deposition at any of a plurality of 
print positions, it is possible to decrease the size of the stream, while 
maintaining a relatively large stream spacing. 
It is therefore a primary object of this invention to produce a jet drop 
recorder of improved recording resolution. 
Another object of this invention is to provide an array of closely spaced 
recording jets, each of which is capable of recording in a plurality of 
laterally separated recording positions. 
Still another object of this invention is to provide an improved method for 
positioning a stream of liquid. 
Other and further objects of the invention will be apparent from the 
following description, the accompanying drawings and the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Jet drop printing in accordance with this invention may be accomplished 
with apparatus as illustrated in the simplified schematic drawings of 
FIGS. 1 and 2. As illustrated therein, a stream of recording liquid 20 
flows continuously through an orifice 21 in an orifice plate 22. A pair of 
deflection electrodes 23 and 24 are disposed on opposite sides of stream 
20 but are offset from the axis thereof, as illustrated in FIGS. 3 and 4. 
As hereinafter employed the term "offset" will be understood to mean that 
the deflection electrodes are so positioned relative to the stream axis 
that the application of a common voltage to the electrodes will produce 
stream deflection in a direction generally therebetween. For deflection 
electrodes of the type illustrated in FIGS. 3 and 4, the offset may be 
great enough to produce a small gap between the illustrated lateral 
deflection plane L and the electrode leading edges 38 and 39. The height 
of electrodes 23 and 24 is great enough to straddle the drop breakoff 
point, and the top surfaces 28 and 29 thereof should extend upwardly above 
that point. 
The stimulation of stream 20 to break up into drops 25 is accomplished by 
well known techniques and need not be discussed in detail herein. As 
described in detail below, the generation of drops 25 is accompanied by 
application of differential charging potentials to electrodes 23 and 24. 
This causes drops 25 to deposit successively on a moving web of paper 27 
in three different positions labelled 90, 91 and 92. It will be 
appreciated that drops 25 may be deposited at any number of laterally 
separated printing positions and that the three positions 90, 91 and 92 
are shown for illustrative purposes only. For such positioning it is 
convenient to drive the drop stimulation transducer 30 (illustrated 
schematically in FIG. 9) with the same clock signal which controls the 
generation of the above mentioned differential charging potentials. As 
shown in FIG. 9, the same clock signal may drive a control motor 31 
arranged for driving a take-up roll 32 for the web 27. 
Drops 25 are directed toward the laterally separated positions 90, 91 and 
92 as a result of deflection of stream 20 by electrodes 23 and 24. The 
recording liquid in stream 20 travels at a reasonably high velocity, so 
that when it is deflected in different operating directions the drops are 
"aimed" in a manner somewhat analogous to pointing a rifle bore and aiming 
bullets toward a target. Depending upon the conductivity of the recording 
liquid, the vertical positioning of electrodes 23 and 24 relative to the 
drop formation point, and the phase relation between drop charging and 
drop formation drops 25 may or may not carry a significant electrical 
charge. However, there is no requirement for a deflection field downstream 
from the drop formation point. 
The catching action for non-printing drops is best illustrated in FIG. 2. 
To accomplish catching a common cooperative deflection potential is 
applied to electrodes 23 and 24, and this deflects stream 20 in what might 
be termed the dumping direction. Such dumping deflection of stream 20 
causes drops 25 to impact against the face of a catcher 26. A vacuum is 
applied to catcher 26 to cause ingestion of such drops. 
As hereinafter discussed, the recording liquid may be either conductive or 
dielectric but is preferably conductive. In the case of a conductive 
recording liquid, lateral deflection of stream 20 to cause printing in 
position L of FIG. 1 may be accompanied by an electrical field 
configuration as illustrated schematically in FIG. 3. FIG. 3 illustrates a 
series of equipotential lines 33 as actually measured in a scaled up two 
dimensional model. Since the corresponding electrical field is represented 
at any point by the gradient of the potential function, the electrical 
field may be visualized as being perpendicular at all points to the lines 
33. A dumping plane D and a lateral deflection plane L, both passing 
through the axis of the stream, are illustrated in the figure. 
In order to obtain the plot for the lines 33, a two dimensional area of 
conductive material representative of stream 20 was electrically grounded 
as was another area representative of the right hand deflection electrode 
24. A deflection voltage V.sub.1 was connected to an area simulating the 
left hand electrode 23, and this produced the illustrated potential field. 
The naturally resulting electrical field exerts a force against stream 20, 
and it can be seen that this force acts in a direction as illustrated by 
the arrow 34. It will be seen that the arrow 34 does not point precisely 
in the lateral direction but has a small component in the dumping 
direction. This gives rise to a small printing error, which may be 
compensated as hereinafter discussed. 
For deflection of stream 20 in the dumping direction a common potential 
V.sub.0 is applied to electrodes 23 and 24 produces equipotential lines 33 
as illustrated in FIG. 4. The plot of FIG. 4 was obtained the same general 
manner as the plot of FIG. 3. Here we see that stream 20 is attracted 
toward electrodes 23 and 24 as illustrated generally by the arrows 35 and 
36, but the vector sum of all forces acting on streams 20 is in the 
dumping direction as illustrated by arrow 37. In the limiting case when 
V.sub.0 is 0 (i.e. at ground potential) the arrow 37 shrinks to a length 
of 0. This is the situation for printing in the center position C of FIG. 
1. 
In general the most satisfactory performance is obtained when the 
centerline of stream 20 is centered between the leading edges 38 and 39 of 
electrodes 23 and 24. However a small positioning error in the order of 
about 1 mil in any direction can easily be tolerated. For the plots of 
FIGS. 3 and 4 the stream 20 is positioned outwardly and to the left of the 
ideal position. 
Test results for a series of three dimensional experiments are illustrated 
by curves 75 and 76 of FIGS. 5 and 6 respectively. Curve 75 illustrates 
lateral drop positioning actually achieved as a function of the voltage 
V.sub.1, when applied differentially (e.g. applied to one electrode only). 
For this experiment the drops were generated at a frequency of 110 kHz 
from an orifice having a 1 mil diameter. Electrodes 23 and 24 were 
arranged symmetrically with respect to the dumping plane D but were offset 
with respect to the lateral deflection plane L such that their leading 
edges 38 and 39 were separated therefrom by a distance of about 0.1 mil. 
The separation distance between deflection electrodes 23 and 24 was 5.9 
mils, and the deflection data was measured at a distance of 0.550 inches 
below the stream forming orifice. The liquid rate for this test was 0.39 
milliliters per minute, and the drops formed printed spots of 3 mil 
diameter. For satisfactory three position recording using such drops, the 
system should be designed to achieve a lateral drop positioning shift of 
about 2.2 mils. An electrically conductive, water base printing ink was 
used for the test. 
Curve 75 of FIG. 5 indicates that a recording head operating in accordance 
with this invention can achieve the desired 2.2 mil lateral positioning 
shift by application of a potential difference of about 75 volts to the 
deflection electrodes. For satisfactory catching, a dumping direction 
shift in the order of about 5 mils is considered to be desirable. Curve 76 
of FIG. 6 indicates that such dumping positioning can be accomplished by 
application of a voltage V.sub.0 in the order of about 100 volts to each 
of electrodes 23 and 24, the stream 20 being connected to a source of 
ground potential. 
As further indicated by the supra linear nature of curve 75 of FIG. 5, 
there is an increasing lateral drop positioning shift sensitivity with 
increasing differential voltage. Thus while 62 volts produces a shift of 
only 2 mils, 90 volts produces a shift of 4 mils. This increasing 
sensitivity makes drop positioning less accurate when larger deflections 
are employed, and therefore the above mentioned three position recording 
system is preferred over five or seven position recording. The shape of 
curve 75 also indicates that the recording system of this invention is 
less sensitive to crosstalk positioning errors than prior art systems 
having a linear voltage response. 
As mentioned above it is not necessary that the recording liquid be 
electrically conductive. This can be understood by referring to the 
following equation, which sets forth the force F acting on a small body 
located within an electrical field: 
EQU F = qE+p.multidot..gradient.E 
where q is the electrical charge on the body, E is the electrical field 
vector, and p is the polarization vector or moment of the charge 
polarization. Since both q and p are proportional to E, the force F is 
proportional to the square of the voltage applied to the field generating 
electrode. In the case of a non-conductive liquid q is zero, so that only 
the second term of the above equation is applicable. In the case of a 
uniform electrical field the second term is likewise zero. However, for 
deflection electrodes of the type and arrangement herein of interest, the 
electrical field has a considerable gradient. Quite obviously a dielectric 
liquid stream will have a sizable polarization moment when subjected to a 
strong electrical field, and in the case of a field having a substantial 
gradient, the resulting force on the filament can have a not insignificant 
value. The above expression is, of course, quite complex, because a dyadic 
field is specified by .gradient.E. 
Quite naturally one would expect that a dielectric liquid stream would be 
deflected less than a corresponding conductive liquid filament for the 
same applied electrical field. Experimentation has confirmed, however, 
that a dielectric material such as ethanol can be deflected far enough to 
obtain 3 mils of lateral drop positioning shift by application of a 
differential voltage V.sub.1 of 175 volts to one of the deflection 
electrodes. A cooperative dumping potential V.sub.0 of like amount has 
been observed to produce a corresponding dumping shift of 3 mils. This 
data was taken under conditions similar to those applicable for the data 
of FIGS. 5 and 6. 
An examination of the above set out force equation will reveal that the 
right hand term is merely the classical expression for the force on an 
electrical dipole situated within an electrical field. The corresponding 
expression for a continuously flowing stream of dielectric liquid 
necessarily is quite complex and has not been derived. However, it will be 
apparent that the force in any event will be a gradient function and will 
go to zero in an uniform field. Thus the operation of a dielectric jet 
recorder in accordance with this invention becomes closely analogous to 
the operation of a ferrofluid jet recorder as described in Johnson, U.S. 
Pat. Nos. 3,510,878 and in Fan et al 3,805,272. 
In cases where the recording liquid is not perfectly dielectric but has 
some conductivity, then an electrical charge is available for augmentation 
of stream deflection. Generally speaking, the deflection due to the 
presence of an electrical charge is the dominant contributor for a liquid 
of even moderate conductivity. With this invention, however, it becomes 
possible to deflect and switch a continuously flowing stream of liquid 
without restriction to any particular conductivity range and without 
requiring any special magnetic properties. This enables printing with 
non-conductive organic liquids such as alcohol base textile dyes. It is 
even possible to switch a dielectric liquid such as kerosene for fuel 
injection purposes. Other applications will be readily apparent. 
The preceding discussion describes the invention in terms of only a single 
stream. A recording head 40 in preferred form is illustrated in FIG. 7. In 
the preferred form there are two rows of orifices 21 regularly spaced 
along orifice plate 22. A recording liquid supply manifold is defined by 
orifice plate holder 41, which is sealed against orifice plate 22. A pair 
of electrode plates 42 are spaced below orifice plate 22 and above a pair 
of catchers 26. 
The general twin row arrangement is similar in some respects to the 
recording head arrangement disclosed in Brady et al U.S. Pat. No. 
3,805,273. In the arrangement of Brady et al, however, it is necessary 
that the stream forming orifices be sufficiently close together for solid 
printing coverage without any lateral deflection of the streams. In 
accordance with this invention, orifices 21 can be reduced in diameter for 
production of smaller drops; solid printing coverage being achieved by 
lateral deflection of each of the streams. As taught by the prior art 
referred to in Brady et al, it is necessary that the control of drops in 
one row be delayed in time with respect to the drops in other rows of 
jets. Such a timing delay is necessary to produce registration of the 
print on the print receiving medium. The discussion which follows will 
relate to only one row of streams and to deflection of only one stream 
within such a row. 
FIG. 8 illustrates a portion of deflection plate 42, with reference numeral 
usage corresponding to the usage of FIGS. 1 through 4. It will be 
understood that the offset and the lateral positioning of liquid streams 
20 relative to the deflection electrodes is as previously described with 
reference to the lateral deflection plane L and the dumping plane D. 
As illustrated in FIG. 8, deflection electrodes occur in pairs, with the 
left member of each pair being denoted by the reference numeral 23 and the 
right member of each pair being denoted by the reference numeral 24. The 
leading edges of electrodes are denoted by the reference numerals 38 and 
39 respectively. Electrodes 23 and 24 are plated inside a series of 
notches 44 and are connected to a series of control lines 45. Typically 
the streams may be spaced at a spacing of about 75 streams per inch, so 
that the effective spacing of the twin row arrangement is 150 streams per 
inch. Since each stream directs its drops toward three printing positions, 
the recording head has 450 printing positions per lateral inch of print 
receiving medium 27. Orifices 21 may have a diameter of about 1 mil, and 
deflection plate 42 may be spaced about 10 mils below orifice plate 22. 
The lateral spacing between the surfaces of the electrode pairs is about 6 
mils, all as described above in connection with FIGS. 5 and 6. 
A simplified schematic of electrical circuitry for controlling the charging 
of electrodes 23 and 24 is illustrated in FIG. 9. As illustrated therein a 
master clock signal is applied to a line 46, which is connected to the 
input terminal of a counting and decoding unit 47. Unit 47 comprises a 
two-bit counter for counting clock pulses on input lines 46. Unit 47 
further comprises a decoder, which decodes the two-bit count to provide 
sequential output signals on output lines 48 through 51. Output line 51 
resets the counter after every fourth count, and output lines 48 through 
50 synchronize the generation of differential deflection control signals 
for electrodes 23 and 24. Clock signal 46 is also applied to a pair of 
amplifiers 58 and 59 for control of drive motor 31 and stimulation 
transducer 30. 
The signals or decoded counts on lines 48 through 50 are utilized as inputs 
to sets of NOR gates such as gates 52 through 54 and 55 through 57 as 
illustrated. A set of three such NOR gates is provided for each stream, 
and each such NOR gate has a data input line, such as one of the 
illustrated lines D.sub.1 through D.sub.6. Each data line carries binary 
printing information for one laterally spaced print position for drops 
from an associated stream. 
As further illustrated in FIG. 9 there are four transistors 60 through 63, 
which are switched from conducting to non-conducting states by output 
signals from NOR gates 52 through 54. A similar switching arrangement is 
provided for each pair of deflection electrodes 23 and 24. A voltage 
V.sub.0 representing the cooperative deflection voltage for dumping 
control is applied to a terminal 64, and this potential in turn is applied 
to both of deflection electrodes 23 and 24 unless one of transistors 60 
through 63 has been switched into a conducting state. Whenever any of 
transistors 60 through 63 is rendered conductive, there is a voltage drop 
across at least one of four collector resistances 67 through 70. 
So long as no signal representing a no-print or dumping command is present 
on any of the input data lines, then transistors 60 through 63 are 
cyclically rendered conductive in pairs as follows: first transistors 61 
and 62, then transistors 60 and 62 and finally transistors 60 and 63. 
Thereafter the sequence is repeated. A pair of OR gates 65 and 66 are 
connected as illustrated to enable the aforementioned switching sequence. 
Appearance of a dumping signal on a data line during any of the switching 
steps gates off the two transistors, which otherwise would be conductive 
during that step. As a result the potential V.sub.0 applied to terminal 64 
is not dropped across any of the collector resistances 67 through 70, and 
the stream 20 is deflected in the offset direction toward catcher 26. 
As a result of the above described switching sequence a pair of deflection 
control signals 71 and 72 are generated, as illustrated generally in FIG. 
10. The signal 71 is the charging voltage which appears on the left 
deflection electrode 23, while signal 72 is the charging voltage which 
appears on the right deflection electrode 24. It will be seen that both of 
signals 71 and 72 are stepped from a level of 0 to V.sub.1 and back to 0 
with a relative phase shift such that the two signals are never 
simultaneously on any non zero voltage. Thus the application of the two 
signals to the deflection electrodes creates what might be termed a 
differential charge. 
Whenever a dumping signal is applied to one of the data lines, then both of 
signals 71 and 72 jump simultaneously to a voltage V.sub.0 for cooperative 
application to electrodes 23 and 24. Such a cooperative signal is 
illustrated in FIG. 10 by the portions of duration d as illustrated for 
both of signals 71 and 72. The illustrated cooperative charging signal 
replaces the differential charging signal illustrated by dotted lines and 
is shown as occurring for three consecutive time periods. This would be 
produced by sequential application of dumping signals to NOR gates 53, 54 
and 52. 
As previously discussed in connection with the description of FIGS. 3 and 
4, the application of a lateral deflection voltage V.sub.1 to only one of 
the electrodes of a deflection electrode pair causes a slight deflection 
of the stream in the offset direction. This offset movement, while 
normally quite small, causes a slight shifting of the left and right 
printing positions relative to the center printing positions. This can be 
compensated for by adding a slight voltage correction, V.sub.2, to the 
deflection control signals 71 and 72 as indicated by reference numerals 77 
and 78 of FIG. 12. 
The circuitry for producing the V.sub.2 voltage correction is illustrated 
in FIG. 11 and is seen to be quite similar to the circuitry of FIG. 9. 
Corresponding reference numerals in FIGS. 11 and 9 represent components 
having corresponding functions. It will be seen that the main difference 
between the two circuits is that the circuit of FIG. 11 has eliminated OR 
gates 65 and 66 and has added transistors 73 and 74, together with 
associated voltage dropping resistors 79 and 80. FIG. 11 omits stimulation 
transducer 30 and drive motor 31, but it will be understood that 
appropriate stream stimulation and web driving apparatus are provided. 
Referring now to FIG. 9 it will be seen that an output from NOR gate 53, 
which corresponds to a center position print command, causes both of 
transistors 60 and 62 to become conductive, thereby grounding both of 
electrodes 23 and 24. This produces the zero level during the time period 
T = 1 through T = 2 on both of signals 71 and 72 as illustrated in FIG. 
10. 
For the arrangement of FIG. 11 an output from NOR gate 53 causes 
transistors 73 and 74 to become conductive. This causes a voltage drop 
across resistor 79 to produce the step 77 of FIG. 12 and a voltage drop 
across resistor 80 to produce the step 78. The actual magnitude of the 
steps 77 and 78 depends upon the voltage V.sub.0 applied to terminal 64 
and the voltage dividing effect produced by the resistance values of 
resistors 79 and 80 relative to resistors 67 and 69. In general the 
required drop positioning shift in the dumping direction for compensation 
of the effect described with reference to FIG. 3 has been found to be less 
than 1 mil. FIG. 6 indicates that a voltage drop in the order of about 25 
volts across resistors 79 and 80 should be sufficient. Assuming that 
V.sub.0 has a value of 100 volts for normal dumping deflection, resistors 
79 and 80 should have resistances about 1/3 those of resistors 67 and 69. 
FIG. 13 illustrates an electrode arrangement in alternative embodiment. The 
view of FIG. 13 corresponds generally to the view of FIGS. 3 and 4, there 
being illustrated the stream 20, the left electrode 81 and a right 
electrode 82, all in horizontal cross section. The axes of electrodes 81 
and 82 are parallel to the axis of stream 20 and are offset from the 
lateral deflection plane L by a distance M. While equipotential lines have 
not been constructed for the arrangement of FIG. 13, it should be apparent 
that the application of a cooperative charging signal to electrodes 81 and 
82 will produce a deflection of stream 20 in the dumping plane D as 
illustrated generally by the arrow 83. The arrow 83 may be viewed as being 
the vector sum of the illustrated arrows 84 and 85, which represent the 
differential deflections obtained by application of charging voltages of 
appropriate magnitude to each of electrodes 81 and 82 separately. 
It should be clear that many alternative deflection electrode 
configurations are possible, but the electrodes should be provided in 
pairs positioned generally symmetrical with respect to the dumping plane D 
and offset with respect to the lateral deflection plane L. 
While the methods and forms of apparatus herein described constitute 
preferred embodiments of the invention, it is to be understood that the 
invention is not limited to these precise methods and forms of apparatus, 
and that changes may be made therein without departing from the scope of 
the invention.