Note: Descriptions are shown in the official language in which they were submitted.
215161 1
SELF-BALANCING BIPOLAR AI IONIZER
Technical Field
This invention relates to apparatus for increasing the
ion content of air and more particularly to air ionizers
which produce both positive and negative ions.
Background of the Invention
Increasing the ion content of the air within a room can
be desirable for a variety of reasons. For example, a high
to negative ion content freshens the air and has beneficial
physiological effects on persons who breathe the air. Air
ions of either polarity act to remove dust, pollens, smoke
and the like by imparting an electrical charge to such
particulates. The charged particles are electrostatically
attracted to walls or other nearby surfaces and tend to
cling to such surfaces.
Some usages of air ionizers require production of both
positive and negative ions. Most notably it has been found
that a high concentration of both types of ions acts to
suppress accumulations of static electricity on objects in
a room. Static electrical charges attract air ions of the
opposite polarity and the attracted ions then neutralize the
static charges. This can be of particular value in certain
industrial operations such as in the clean rooms where
microchips or other miniaturized electronic components are
manufactured. Accumulations of static charge attract
contaminants to such products and may also directly damage
a microchip or the like.
An advantageous type of ionizing device has sharply
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pointed electrodes to which high voltages of the order of
several thousands volts are applied and which are exposed to
the ambient air. Positive and negative high voltages are
applied to separate electrodes or are alternately applied to
the same electrode. The resulting intense electrical field
near the pointed end of the electrode converts the nearby
molecules of the constituent gases of air into positive and
negative ions. Ions with a polarity opposite to that of the
high voltage are attracted to the electrode and neutralized.
Ions of the same polarity as the high voltage are repelled
by the electrode and by each other and disperse outward into
the surrounding air. Dispersal of the ions is usually
accelerated by directing an airflow through the electrode
region and out into the room.
It is usually desirable to produce a predetermined
ratio of positive to negative ions and in many cases such
ions are to be produced in equal numbers. Such balancing
can be accomplished initially by measuring the ion content
of the air flow with an ion detector and adjusting the high
2o voltage on one or more of the electrodes as needed to
achieve the desired balance.
The initial balancing of positive and negative ion
production does not usually persist over a period of time.
Various factors, such as electrode erosion or utility line
voltage fluctuations, can cause a change in the ratio of
positive ion production to negative ion production. This
can have a very detrimental effect. An excess of one type
of ion relative to the other can cause the apparatus to
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impart electrostatic charge to objects in a room rather than
acting to suppress such charge.
The problem has heretofore typically been dealt with by
disposing an air ion sensor in the air flow path to detect
any change in the ratio of positive to negative ions. The
sensor is coupled to a feedback system which responds to
changes in the sensor signal by adjusting electrode voltages
or the durations of periods of electrode energization as
needed to re-establish the original balance of positive and
to negative ion production.
Such ion sensors, feedback components and voltage
adjusting means add substantially to the cost, complexity
and bulk of the ionizing apparatus. An air ionizer which
inherently maintains a balanced production of positive and
negative ions without such complications would clearly be
advantageous.
The positive and negative ions in the air flow should
be thoroughly intermixed if the apparatus is to suppress
static charges on objects rather than creating such charges.
This condition is not met immediately since the ions of
different polarity are produced at separated electrodes or
at different time periods at the same electrode. Such
intermixing does occur gradually as the airflow progresses
away from the ionizing apparatus but it has heretofore been
necessary to keep the ionizer a sizable distance away from
objects that are to be protected to avoid subjecting the
objects to incompletely mixed concentrations of ions of one
polarity. It would be more convenient in many instances if
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the ionizer could be closer to the object on which static
charge is to be suppressed.
The present invention is directed to overcoming one
or more of the problems discussed above.
Summary of the Invention
The present invention provides an air ionizing
apparatus including at least a pair of electrodes which
are spaced apart and exposed to ambient air. A high
voltage supply has a circuit junction, a first high
voltage producing circuit connected between the junction
and a first of the electrodes and a second high voltage
producing circuit connected between the junction and a
second electrode. The high voltage producing circuits
apply voltages of opposite polarities to the first and
second electrodes. The high voltage region of the high
voltage supply including the electrodes and the circuit
junction and the first and second high voltage producing
circuits are electrically isolated from any connection to
ground that is capable of conducting direct current. The
electrodes inherently acquire a D.C. bias voltage that
maintains a balanced output of positive and negative ions
if an incipient imbalance occurs.
Accordingly, in one aspect of the present invention
there is provided a bipolar air ionizing apparatus for
generating and releasing a flow of air including
intermixed positive and negative ions, comprising:
a housing having an air inlet passage and an ionized
air outlet passage that is spaced apart from said inlet
passage;
a fan disposed in said housing to draw a flow of air
into said housing through said inlet passage for
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directing a flow of air and ions through said outlet
passage and out into the external environment, said fan
having a rotary hub and blades which turn about a
rotational axis that is aligned between said air inlet
passage and said air outlet passage;
a cylindrical air duct encircling said fan and being
concentrically oriented on said rotational axis to extend
from said fan to said air outlet passage;
first and second pairs of air ionizing electrodes
disposed in said housing at a location in the air flow
path between said air inlet passage and said fan for
producing positive ions about each of the first pair of
electrodes and for producing negative ions about each of
the second pair of electrodes, each of the electrodes in
said first and second pairs of electrodes being
diametrically oriented about the rotational axis
substantially laterally to the flow of air and
equidistantly spaced from the rotational axis of the fan
and being sufficiently spaced equidistantly apart about
said rotational axis to enable said air flow to carry at
least a portion of the positive and negative ions away
from respective ones of said first and second pairs of
electrodes and out of said housing through said outlet
passage without neutralization of the ions from ones of
the first and second pairs of electrodes by contact with
others of said first and second pairs of electrodes; and
a high voltage supply connected to the first and
second pairs of electrodes for applying high D.C. voltage
of positive polarity to each of the electrodes of the
first pair of electrodes and for applying high D.C.
voltage of negative polarity to each of the electrodes of
the second pair of electrodes to produce supplies of both
y
6 _ 215161 1
positive and negative ions in said flow of air about the
respective first and second pairs of electrodes to be
carried in said air flow through said outlet passage.
Most such ionizers include a voltage step-up
transformer and the referencing is typically accomplished
by connecting one point in the secondary winding of the
transformer directly to a ground or to the neutral wire
of the utility power conductors that supply operating
current to the ionizer. I have now found that such
ionizing apparatus can be caused to inherently maintain a
balanced production of positive and negative ions by
isolating the high voltage side of the high voltage
supply, including the electrodes, from ground provided
certain other conditions are established. The electrodes
are arranged to cause the conductivities of the ion flow
paths from each electrode to other objects to be
approximately equal and to cause leakage current paths
from each electrode to ground to be approximately equal.
When a charged ion of a particular polarity is produced
by an electrode the electrode acquires an equal charge of
opposite polarity. Such acquired charges cancel each
other out within the high voltage circuit if the
production of positive and negative ions is exactly
equal. As there is no path through which D.C. charge can
flow to ground from the high voltage circuit of the
present invention, any momentary decrease in the
production of ions of the opposite polarity causes an
accumulation of charge of the particular polarity. This
creates a D.C. voltage bias on the electrodes that
increases production of the ions of opposite polarity
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thereby rebalancing ion output. Thus the ionizing
apparatus may be less complicated, more compact and more
economical as
v
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it is not necessary to include air ion sensors and feedback
components to assure a balanced ion output.
Fans or the like for creating the airflow that carries
ions away from the electrode region and out into the room
have heretofore been placed upstream from the electrode at
a location between the electrodes and the air intake of the
ionizer. In another aspect of the present invention, the
fan is situated between the electrodes and the outlet of the
ionizer in position to accelerate intermixing of positive
and negative ions. This enables the ionizer to be placed
closer to objects which are to be protected from
electrostatic charge accumulations.
The invention, together with other aspects and
advantages thereof, may be further understood by reference
to the following description of the preferred embodiments
and by reference to the accompanying drawings.
_Brief Description of the Drawings
FIG. 1 is a front elevation view of a D.C. bipolar air
ionizer in accordance with a preferred embodiment of the
invention.
FIG. 2 is an elevation section view of the apparatus of
FIG. 1 taken along lin- -2 thereof.
FIG. 3 is an electrical circuit diagram depicting
electrical components of the apparatus of the preceding
figures.
FIG. 4 is a diagrammatic depiction of an A.C. bipolar
air ionizer embodying the invention.
_ _e_ 215 7 61 1
petailed Descz~~t~on of the Preferred Embodsmon~rs
Referring jointly to FIGS. 1 and 2 of the drawings, a
bipolar air ionizing apparatus 11 in~ accordance with this
embodiment of the invention includes a hollow housing 12
which is a portable rectangular box in this example. The
housing 12 may have any of a variety of other configurations
and in some instances may be defined by pre-existing
structures into which the components of the ionizing
l0 apparatus are installed.
Housing 12 has a back wall 13 with a broad air inlet
passage 14 and a front wall 16 with a similar air outlet
passage 17. Grills 18 and 19, each having a plurality of
open areas 21, are secured to the front and back walls 16
and 13 respectively to prevent entry of human fingers and
other sizable objects into the housing 12.
A portion of the airflow path through housing 12 is
defined by a cylindrical duct 22 situated in the front
region of the housing behind the air outlet passage 17. The
duct 22 is attached to and supported by the housing front
wall 16. The airflow 24 is created by a rotary fan 25
having an electrical motor 26 which is positioned in coaxial
relationship with duct 22 and which is supported by spider
arms 27 which extend to the duct. Motor 26 turns a coaxial
hub 28 from the fan blades 29 extend.
A sub-housing 32 contains components of the electrical
circuit of the ionizer 11 that Will hereinafter be described
and is preferably situated out of the path of the airflow
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24, the sub-housing being centered below the air duct 22 in
this embodiment.
Molecules of the gases in the airflow 24 are ionized by
the intense electrical field in the immediate vicinity of
pointed tips 33 of a plurality of needle-like electrodes 34
and 35 that extend into the airflow and to which high
voltages are applied. Such electrodes 34, 35 are often
referred to as ion emitters although ions do not in fact
emerge from the electrodes but are instead created by the
to interaction of the electrical field with gas molecules that
are near the electrode tips 33. The electrodes 34, 35
extend from electrical insulators 36 which in this
embodiment are attached to the inner walls of housing 12
through insulative brackets 37. Other electrode mounting
techniques may be used.
A minimum of two spaced apart electrodes, including a
positive electrode 34 and a negative electrode 35, are
needed to establish a self-balancing effect in accordance
with the present invention and additional pairs of
electrodes may be present to increase ion output. In this
embodiment, with reference to FIG. 3, there are two positive
electrodes 34 and two negative electrodes 35 situated
between duct 22 and the housing backwall 13. The two
positive electrodes 34 are collinear and the two negative
electrodes 35 are also collinear and oriented at right
angles to the positive electrodes. The four electrodes 34,
are also preferably coplanar and the pointed tips 33 are
equidistantly spaced from the center 38 of the electrode
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array which center is preferably directly behind the
centerline of duct 22 and the rotational axis of fan 25.
A flow of charged ions from an electrode 34, 35 to any
nearby grounded conductor or low resistance path to ground
detracts from the desired self-balancing effect. Referring
again to FIG. 2, this is prevented by forming components
that might otherwise provide a low resistance path to ground
of plastic or other insulative material or by covering such
components with a layer of insulative material. In the
l0 present example, housing 12 including grills 18 and 19, duct
22 and hub 28 and blades 29 of fan 25 are all formed wholly
of insulative plastic. Components which are necessarily
conductive and grounded such as portions of motor 26 and
circuit sub-housing 32, are covered with layers 39 of
insulative material.
Referring again to FIG. 3, the electrical circuit of
this embodiment of the air ionizer 11 includes a control
switch 41 having a sliding conductive member 42 which can be
manually shifted from an OFF position to a LOW position or
to a HIGH position. Switch 41 receives alternating current
from a utility power source through a plug 43 and power cord
44 having a pair of conductors 46 and 47 with conductor 47
being the neutral or grounded conductor. The neutral
conductor 47 is connected to one terminal 48 of fan motor 25
and to one input terminal 49 of a high voltage supply 51.
Control switch 41 further includes a first pair of
spaced apart contacts 52 and 53 which are respectively
connected to the other input terminal 54 of high voltage
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supply 51 and the other fan motor terminal 56. A second
pair of spaced contacts 57 and 58 are each connected to
power conductor 46. A third set of spaced apart contacts 61
and 62 respectively connect to high voltage supply terminal
54 and motor terminal 56, the connection between contact 62
and motor terminal 56 being made through a voltage dropping
resistor 63.
Sliding member 42 bridges only contacts 57 and 58 at
the OFF position of the switch and thus fan 25 and high
voltage supply 51 are unenergized. Member 42 bridges the
power contacts 57 and 58 as well as contact 61 and 62 at the
LOW position of the switch 41 thereby actuating both the
high voltage supply 51 and fan 25. Fan 25 operates at a
relatively slow speed at this switch setting as resistor 63
reduces the voltage received by the fan motor 26. At the
high setting of switch 41, member 42 bridges power contact
57 and 58 and contacts 52 and 53. This again energizes high
voltage supply 51 and sends full power to fan motor 26 to
produce a higher velocity airflow within the apparatus.
High voltage supply 51 applies a continuous positive
voltage to electrodes 34 and a continuous positive voltage
to electrodes 34 and a continuous negative voltage to
electrodes 35, which voltages may typically be in the range
from about 3KV to about 20KV in order to accomplish air
ionization.
Supply 51 includes a voltage step up transformer 64
having a primary Winding 66 which is arranged to receive
only the positive half cycles of the alternating current
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that is transmitted to power input terminal 54 through
switch 41. In particular, terminal 54 is connected to one
end of primary winding 66 through a resistor 67 and diode 68
or other unidirectional circuit element that blocks the
negative half cycles from the winding. A capacitor 69 and
another diode 71 are connected between the other end of
winding 66 and the neutral input terminal 49 with the diode
being oriented to transmit positive current to the tenainal
49 and to block reversed current. Another resistor 72
to connects power terminal 54 with neutral terminal 49 through
the same diode 71. An SCR (silicon controlled rectifier) 73
or similar circuit element is connected across the primary
winding 66 and capacitor 69 to discharge the capacitor
during negative half cycles of the alternating current as
will hereinafter be described in connection with the
operation of the circuit. SCR 73 is triggered into
conduction at such times by a gate connection 74 to neutral
terminal 49. Another diode 76 is connected in parallel with
SCR 73 and is oriented to conduct current in an opposite
direction in order to suppress ringing or oscillation in the
circuit following discharge of the capacitor 69.
Transformer 64 is preferably of the ferrite core type
and has a secondary winding 77 which provides a voltage step
up ratio of 100:1 in this example although other ratios are
also suitable. The ends of secondary winding 77 define
first and second circuit junctions 78 and 79 respectively of
the high voltage region of supply 51. A positive high
voltage storing capacitor 81 is connected between junction
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78 and the positive electrodes 34 and a negative high
voltage storing capacitor 82 is connected between the same
junction and negative electrodes 35. A diode 83 conducts
positive voltage from junction 79 to capacitor 81 and
another diode 84 conducts negative voltage from the same
junction to capacitor 82.
In operation, positioning of switch 41 at either the
LOW or HIGH settings turns on the fan 25 and transmits
alternating current to input terminals 49 and 54 of the high
voltage supply. Capacitor 69 charges through resistor 67
and diode 68 during the positive half cycles of alternating
current. Positive current also flows from input terminal 54
to input terminal 49 during the positive half cycles through
resistor 72 and diode 71. The resulting voltage drop across
diode 71 prevents firing of SCR 73 into a conductive state
during the positive half cycles.
Gate voltage from terminal 49 causes SCR 73 to become
conductive when the voltage at terminal 54 turns negative
following each positive half cycle of the alternating
current. This causes an abrupt discharging of capacitor 69
through primary winding 66 and the SCR. Thus a brief high
voltage spike is induced in the transformer secondary
winding 77 during each ,negative half cycle of the
alternating current. Capacitor 81 charges to a high
positive voltage through diode 83 when the voltage spike is
rising and capacitor 82 charges to a high negative voltage
as the voltage spike decays.
Capacitors 81 and 82 remain continuously charged to
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high positive and negative voltages until the ionizer 11 is
turned off as the charging process reoccurs during each
negative half cycle and there is no discharge path having a
conductivity sufficiently high to enable a sizable discharge
during the course of a single cycle. Thus the capacitors 81
and 82 apply essentially D.C. voltages to the positive and
negative electrodes 34 and 35. Consequently, positive ions
are continuously created at the tips of electrodes 35.
Positive ions are electrostatically repelled by the charge
l0 on the positive electrodes 34 and by each other and are
attracted to nearby objects or surfaces having a less
positive or neutral or negative charge. Similar effects
occur at the tips of the negative electrodes 35.
Consequently, the ions travel away from the electrode 34 or
35 at which they were generated and intermix with the
airflow through housing 12 and with each other.
The above described air ionizing apparatus 11
inherently maintains a balanced equal output of positive and
negative ions and continues to do so in the presence of
changing conditions that have heretofore made it necessary
to use ion sensors and feedback systems for the purpose.
Self-balancing is brought about by several aspects of the
apparatus.
A first such aspect is that the electrodes 34 and 35,
secondary winding 77, circuit junctions 78, 79, the positive
high voltage producing side 86 of the circuit including
capacitor 81 and diode 83 and the negative high voltage
producing side including capacitor 82 and diode 84 are all
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electrically isolated from ground and from any conductive
path capable of conducting direct current. Thus such
components, which constitute the high voltage region of high
voltage supply 1, are in an electrically floating condition
and can acquire a D.C. bias voltage and if there is an
imbalance in the rate at which positive and negative ions
leave the closed system.
If, for example, there is a decrease in the output of
positive ions relative to the output of negative ions,
l0 positive charge accumulates on the negative ion producing
electrode as the rate at which the positive producing
electrode acquires a negative charge decreases since no
drainage path to ground is provided. This results in a
positive D.C. voltage bias in the high voltage region of
supply 51 including at electrodes 34 and 35 and circuit
junctions 78 and 79. This bias increases the positive
voltage at electrodes 34, causing increased positive ion
production, and reduces the negative voltage at electrodes
35 thereby rereducing negative ion output. The production
of positive and negative ions is re-equalized. A similar
re-equalizing occurs if negative ion output decreases
relative to positive ion output although the bias voltage is
negative in this case.
Ions produced by an electrode 34 or 35 are strongly
attracted by the electrodes of opposite polarity if the
electrodes are in proximity to each other. An ion which is
drawn to an electrode of opposite polarity is neutralized by
charge exchange. Ion losses from this effect can be
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minimized by spacing the electrodes apart to the extent that
is practical given the need for intermixing of positive and
negative ions before the ions reach objects that are to be
protected from static charge. In some usages of the present
invention, where very precise balancing of ion outputs is
needed, it may be preferable to provide a relatively close
electrode spacing including in some instances a spacing that
causes ion flow to be predominately between electrodes of
opposite polarity rather than out of the housing 12. This
l0 can be advantageous in some applications of the system as
decreases in the spacing of the electrodes 34 and 35 bring
about a faster response of the system to incipient
imbalances of positive and negative ion outputs. The need
to maintain an adequate ion output limits the minimal
electrode spacing that is practical under most conditions.
Electrode spacing below about one inch cause almost all of
the ion current to be between electrodes leaving very few
ions in the air outflow. The tips of the electrodes 34 and
35 of this particular embodiment are spaced apart by three
2o inches although the spacing may be varied subject to the
considerations discussed above.
Self-balancing is further enhanced by equalizing the
conductivities of the several paths by which charge can
leave the positive and negative electrodes 34 and 35. This
includes the ion current leakage paths through air to
grounded objects within the housing 12. The conductivities
of such paths can be minimized by the hereinbefore described
covering of grounded objects with insulation. Positioning
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the positive and negative electrodes 34 and 35 to be
equidistant from grounded components to the extent possible
aids in balancing leakage of this kind that cannot be
eliminated.
Ion current leakage through air to external objects
that are close to the front of the housing 12 can also tend
to unbalance the system. This is minimized by the placement
of electrodes 34 and 35 towards the back of the insulat:~~e
housing 12, behind the fan 25. Close spacing of t:.e
electrodes 34 and 35 also acts to minimize the effect of any
differences in the length of the ion flow paths from the
positive and negative electrodes to such objects although as
previously discussed electrode spacing must be sufficient to
provide for the needed rate of ion output. The above
described insulation arrangements and placement of the
electrodes 34 and 35 also minimize direct current leakage
paths from the high voltage region of supply 51 and
substantially equalize such leakage to the extent that it
cannot be eliminated.
The above described embodiment of the inv~ .ion is a
D.C. or direct current air ionizer 11 in that high voltage
is continuously present at the electrodes 34 and 35.
Referring to FIG. 4, the invention can also be embodied in
A. C. or pulsed air ionizers lla in which each ion emitter
electrode 88 and 89 produces both positive and negative ions
during alternating intervals.
The A.C. air ionizer lla of this example includes a
voltage step up transformer 64a which is of the iron core
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type in this case. The primary winding of transformer 64a
receives alternating current through an on-off control
switch 41a and an electrical power cord 44a having a
connector plug 43a suitable for engagement with a standard
utility power outlet.
Opposite ends 91 and 92 of the secondary winding 93 of
transformer 64a are coupled to electrodes 88 and 89
respectively. The electrodes 88 and 89, of which there are
only two in this particular, example are spaced apart and
l0 are disposed in a collinear relationship. Air ionizer 11a
has been depicted in schematic form in FIG. 4 as the
mechanical structure, including the housing 12a in which the
electrical components are disposed and including a motor
driven fan 25a for generating an airflow through the
housing, may be similar to corresponding portions of the
previously described embodiment of the invention.
In operation, closure of switch 41a applies alternating
current to primary winding 66a of transformer 64a inducing
cyclical high voltage pulses at the ends 91 and 92 of
secondary Winding 93 and thus at electrodes 88 and 89, the
high voltage pulses which are applied to electrodes 88 and
89 being of opposite polarity at any given instant. Thus
the electrodes 88 and 89 generate air ions of opposite
polarity during the peaks of the high voltage pulses.
As the high voltage side of the circuit, including
secondary winding 93 and electrodes 88 and 89 generate air
ions of opposite polarity during the peaks of the high
voltage pulses.
_19_ 215761 1
As the high voltage side of the circuit, including
secondary winding 93 and electrodes 88 and 89, is isolated
from any conductive path capable of conducting direct
current to ground, an inherent self-balancing of positive
and negative ion output occurs for the same reasons that
have been previously described with respect to the first
embodiment of the invention. The midpoint 96 of secondary
winding 93 is in effect a circuit junction comparable to the
circuit junction 78 of the previously described embodiment
to as one half 97 of the winding constitutes a first high
voltage producing circuit that applies voltage of one
polarity to electrode 88 while the other half 98 of the
winding is a second high voltage producing circuit that
concurrently applies high voltage of opposite polarity to
the other electrode 89. If output of ions of one polarity
starts to drop relative to the output of ions of the other
polarity, an accumulation of charge of the one polarity
occurs at the electrodes 88 and 89 and in secondary winding
93. This creates a D.C. bias voltage on the electrodes 88
and 89 that increases output of ions of the one polarity and
decreases output of ions of the other polarity thereby
causing the ion outputs to remain in balance.
While the invention has been described with respect to
certain particular embodiments for purposes of example, many
modifications and variations are possible and it is not
intended to limit the invention except as defined in the
following claims.
A
