IlllllllllllllIlllllllllllll||||||||||||l|||||||||||||l||||l||lllllllllllll
`' U5005324398A
`o
`5,324,398
`[11] Patent Number:
`[19]
`United States Patent
`
`Erickson et a1.
`[45] Date of Patent:
`Jun. 28, 1994
`
`[54] CAPACITIVE DISCHARGE CONTROL
`CIRCUIT FOR USE WITH ELECTROLYTIC
`TRE TIME
`m4
`A
`NT SYS
`FLUID
`S
`Inventors: Robert K. Erickson, Belmont;
`FfaflCOiS X. Prinl, San Jose, both of
`Calif.
`
`[75]
`
`[73] Assignee: Water Regeneration Systems, Inc.,
`361mm: Calm
`[2]] Appl- No.: 901,411
`[22] Filed:
`Jun. 19, 1992
`
`Int. Cl.5 .............................................. C02F 1/461
`[51]
`
` [52] US. Cl. . 204/149; 204/152;
`204/228; 204/305; 204/400; 204/406; 204/412
`[58] Field of Search ............... 204/149, 152, 228, 305,
`204/400, 406, 412
`
`[56]
`
`References Cited
`
`U‘S' PATENT DOCUMENTS
`3,519,550 7/1970 Winslow et a1.
`..
`204/305
`3,532,614 10/1970 Shirley ..............
`
`.. 204/191
`3,679,556 9/1968 Doevenspeck
`204/269
`3,865,710 2/1975 Phipps ...................
`
`~ 204/223
`4,119,520 10/1978 Paschakamis et a].
`" 204/276
`4,263,114 4/1981 Shindell
`................
`" 204/149
`4,382,231
`5/1983 Miller ................
`" 33:73:
`
`..
`4,400,253
`8/1983 Prestridge et al.
`.. 204/228
`4,419,206 12/1983 Frame ...................
`.. 324/464
`4,629,992 12/1986 Nudelmont ...........
`
`4,734,176
`3/1988 Zemba, Jr. et a1,
`................ 204/ 149
`
`4,839,002 6/1989 Pernick ct 8.1.
`..
`.. 204/58
`
`4,917,782 4/1990 Davies .............
`204/152
`340/603
`.
`4,937,557 6/1990 Tucci et 8.1.
`
`204/169
`4,986,906
`1/1991 Dadisman
`
`5,055,170 10/1991 Saito ............
`204/228
`
`
`.. 210/85
`5,057,212 10/1991 Burrows ..
`5,062,940 11/1991 Davies ................................. 204/228
`
`FOREIGN PATENT DOCUMENTS
`0329562
`8/1989 European Pat. orr.
`.
`203896 11/1983 Fed. Rep. of Germany .
`Primary Examiner—John Niebling
`Assistant Examiner—Arm S. Phasge
`Attorney, Agent, or Finn—Christensen, O’Connor,
`Johnson & Kindness
`
`ABSTRACT
`[57]
`An electrolytic filter system (16) is disclosed for use in
`treating fluid provided by a fluid source (12) to a sup-
`plied environment (14). The system includes an electro-
`lytic cell (18), whose operation is governed by a control
`circuit (20) to allow a desired average current to be
`applied to the cell substantially independent of varia-
`tions in fluid resistivity, to allow the cell to simulta-
`neously achieve, for example, the desired removal of
`contaminants, killing of biological materials, and alter-
`ation of the fluid’s chemical characteristics, and to pro-
`vide relatively high levels of energy to the fluid quickly
`.
`and 693°18le-
`
`27 Claims, 6 Drawing Sheets
`
`FROM FLUID
`SOURCE 12
`
`
`
`T0 SUPPLIED
`ENVIRONMENT 14
`
`FLU”
`SENSOR
`
`DC POWER
`SUPPLY
`
`CURRENT
`SENSOR
`
`CAPA CITIVE
`S TORACE
`CIRCUIT
`
`5 W1TCHING
`CIRCUIT
`
` P0 IVER
`
`
`,
`
`INVERTER
`
`CONTROLLER
`
`CONTROL CIRCUIT
`
`,
`7
`T0 ELECTROLYTIC
`CELL 18
`
`20
`
`Tennant Company
`Exhibit 1107
`
`Tennant Company
`Exhibit 1107
`
`

`

`US. Patent
`
`June 28, 1994
`
`Sheet 1 of 6
`
`5,324,398
`
`FLUID SYSTEM
`
`CONTROL
`CIRCUIT
`
`
`
`510
`
`16
`
`12
`
`FLUID
`
`SOURCE
`
`
`
`1 4
`
`SUPPLIED
`
`
`ENVIRONMENT
`
`
`ELEC TR 0L YTIC
`
`4——
`-—>
`CELL
`
`
`
`ELECTROLYTIC
`FILTER SYSTEM
`
`
`
`
`FIG. 7.
`
`

`

`US. Patent
`
`June 28, 1994
`
`Sheet 2 of 6
`
`5,324,398
`
`
`
`FIG. 2.
`
`

`

`US. Patent
`
`June 23, 1994
`
`Sheet 3 of 6
`
`5,324,398
`
`
`
`

`

`US. Patent
`
`June 28, 1994
`
`Sheet 4 of 6
`
`5,324,398
`
`FROM FLUID
`
`SOURCE 12
`
`TO SUPPLIED
`
`ENVIRONMENT 1 4
`
`
`
`
`90
`
`DC POWER
`SUPPLY
`
`
`
`1
`
`0‘2
`
`
`
`FLOW
`SENSOR
`
`
`
`
`
`
`
`
`SWITCHING
`
`
`
`CONTROLLER
`
`92
`
`CURRENT
`
`SENSOR
`
`CAPA CI TI VE
`
`STORAGE
`CIRCUIT
`
`POWER
`
`CIRCUIT
`
`98 "_
`"
`
`INVER TER
`
`
`
`CONTROL CIRCUIT
`
`6
`
`20
`
`T0 ELECTROLYTIC
`CELL 78
`
`FIG. 4.
`
`

`

`US. Patent
`
`June 28, 1994
`
`Sheet 5 of 6
`
`5,324,398
`
`INITIALIZE
`
`S TAR TUP
`
`106
`
`108
`
`MONITOR
`
`CURRENT
`
`
`COMPUTE p
`& AVERA CE
`
`CURRENT
`
` 104
`
`
`
`
`
`
`
`116
`
`INVERT
`
`FIG. 5.
`
`

`

`US. Patent
`
`June 28, 1994
`
`Sheet 6 of 6
`
`5,324,398
`
`V,
`VOL TA GE VZ
`
`FIG. 6.
`
`1
`CURRENT
`I‘— -/T’_—.l
`_-
`__
`.
`-.
`--
`
`
`" AVERAGE
`
`CURREN I
`
`TIME
`'11
`
`
`V1
`VOL TA GE VZ
`
`F]C. 7.
`
`1
`‘6 ”7 +1 --
`- CURRENT
`
`
`__ AVERA CE
`
`CURRENT
`
`TIME
`
`
`11
`
`V,
`VOLTAGE Vz
`
`F]G. 8.
`
`1
`CURRENT
`I‘— ”1—.1
`
`
`HERA CE
`
`CURRENT
`
`TIME
`
`
`11
`
`V,
`
`VOL“ GE ":2
`
`F]C. 9 .
`
`1
`*1 (762%.
`_-
`_
`__
`-
`
`
`""" AVERAGE
`
`CURRENT
`
`
`TIME
`
`CURRENT
`
`I
`
`2
`
`V1
`
`VOLTA CE
`
`v3
`FI C. 7 0.
`
`1
`-
`.-
`- Fifi _
`-
`_- _-
`__
`-
`.-
`
`
`
`------- EMT
`
`I,
`
`
`CURRENT
`
`

`

`1
`
`5,324,398
`
`CAPACITIVE DISCHARGE CONTROL CIRCUIT
`FOR USE WITH ELECTROLYTIC FLUID
`TREATMENT SYSTEMS
`
`FIELD OF THE INVENTION
`
`This invention relates to electrolytic fluid treatment
`systems and, more particularly, to circuits for use in
`controlling such systems.
`BACKGROUND OF THE INVENTION
`
`10
`
`15
`
`20
`
`30
`
`35
`
`Electrolytic fluid treatment systems are widely used
`to, for example, remove impurities and contaminants
`from fluids. In such systems, the fluid to be treated is
`passed between one or more pairs of electrodes. An
`electric potential applied to the electrodes establishes an
`electric current between the electrodes. As a result,
`impurities in the fluid migrate and adhere to the elec-
`trodes, biological materials in the fluid are killed, and
`the fluid’s chemical composition may be altered.
`One fluid that is commonly processed by electrolytic
`fluid treatment systems is water. The electrolytic treat-
`ment of water is, however, complicated by the widely
`varying water characteristics encountered from one
`water source to another. In that regard, the resistivity of 25
`water, which is inversely proportional to conductivity,
`commonly varies over a range extending from 30 to
`1400 ohm-meter. Such resistivity variations may signifi-
`cantly alter the performance of an electrolytic filter
`system.
`the interelectrode resistance is
`More particularly,
`dependent upon the resistivity of the water flowing
`between the electrodes. With a fixed electric potential
`applied to the electrodes, current flow between the
`electrodes will vary in inverse proportion to the water’s
`resistance. If water resistivity is relatively high,
`the
`current may be too low to achieve the desired treatment
`of the water. On the other hand, if water resistivity is
`relatively low, the current may be so high as to damage
`or otherwise decrease the life of system components.
`A variety of different systems have been developed
`that attempt to accommodate such variations in water
`resistivity. For example, circuits have been developed
`to expose water purification and ion generation systems
`to relatively constant load resistances, regardless of 45
`variations in water resistivity. In that regard, U.S. Pat.
`No. 4,769,119 (Grundler) discloses a water ionizing
`device that includes several electrodes. If the resistivity
`of the water being ionized is relatively low, a relatively
`high resistance is introduced in series with the elec-
`trodes. On the other hand, if the water’s resistivity is
`relatively high, a relatively low resistance is introduced
`in series with the electrodes. In either case, by keeping
`the system’s total resistive load constant, a constant
`current flow is maintained between the electrodes.
`U.S. Pat. No. 4,986,906 (Dadisman) describes another
`variation of this approach. The Dadisman water purifi-
`cation system includes a constant current control circuit
`in which changes in water resistance cause opposing
`changes in the effective resistance of a field—effect tran-
`sistor (FET) included in the circuit. These changes in
`FET resistance offset the changes in water resistance,
`allong the current to be kept substantially constant.
`Unfortunately, the approaches taken by Grundler
`and Dadisman have certain limitations. In that regard,
`the Grundler and Dadisman circuits both increase cir-
`cuit resistance to offset decreases in water resistance. As
`a result, energy is dissipated in circuit components
`
`55
`
`65
`
`2
`rather than being used to treat water, making the cir-
`cuits relatively inefficient. In addition, the Grundler and
`Dadisman circuits are both relatively complex.
`An alternative method of handling variations in
`water resistivity is to provide an electronic control
`circuit that allows water purification and ion generation
`systems to maintain constant current flows, substan-
`tially independent of variations in water resistivity. In
`that regard, U.S. Pat. No. 4,119,520 (Paschakarnis et al.)
`discloses a water purification unit that includes such a
`current control circuit. The current to be controlled
`
`flows through a resistor, as well as between the elec-
`trodes. A differential amplifier and transistor coopera-
`tively control the current by keeping the voltage drop
`across the resistor equal
`to the reference potential
`across a diode. As a result, the current flowing between
`the electrodes is kept constant.
`Similarly, U.S. Pat. No. 5,055,170 (Saito) discloses an
`ionic water generator that accounts for variations in
`water resistivity. In that regard, the system employs a
`central processing unit that calculates the appropriate
`voltage to be applied to the electrodes for the water
`being processed. This voltage is computed by multiply-
`ing some voltage corresponding to the desired ion con-
`centration by a factor equal to the resistance of the
`water actually being processed divided by the resis-
`tance of some reference water.
`As will be appreciated, the Paschakamis et a1. and
`Saito systems exhibit several shortcomings. First, the
`control circuits of both systems are relatively complex.
`Because the Paschakarnis et a1. circuit introduces an
`additional resistance into the current path, it is also
`relatively inefficient. The Saito circuit, in turn, disad-
`vantageously requires reference measurements to be
`made for subsequent use in controlling the voltage ap-
`plied to the electrodes.
`Another circuit for controlling an ion generator in a
`water purification system is disclosed in U.S. Pat. No.
`4,734,176 (Zemba, Jr.). The circuit controls the duty-
`cycle of energy applied to the generator to achieve the
`desired level of purification for various applications and
`water conditions. In that regard, an operator apparently
`evaluates water conditions and then manually adjusts
`the control circuit to effect a desired change in duty
`cycle.
`Like the other circuits described above, the Zemba,
`Jr. arrangement has certain limitations. For example,
`the ability of the Zemba, Jr. circuit to handle variations
`in water resistivity is not discussed and is uncertain.
`Also, because the circuit does not automatically re-
`spond to changing water conditions, it may fail to
`achieve the desired regulation in many instances.
`Turning now to another problem experienced in the
`electrolytic treatment of fluids, conventional electro-
`lytic fluid treatment systems typically do not perform
`equally well in removing impurities, killing biological
`materials, and altering the fluid’s chemical composition.
`At best, existing systems achieve one of the desired
`objectives relatively well, while exhibiting compro-
`mised performance with respect to the other objectives.
`More particularly, most such systems fail even to differ-
`entiate between these various objectives, much less
`achieve them fully and simultaneously.
`One final problem encountered in the electrolytic
`treatment of fluids is the limited ability of conventional
`systems to provide large quantities of energy to the fluid
`over brief intervals in an efficient manner. For example,
`
`

`

`5,324,398
`
`3
`while some systems may be suitable for passing rela- ,
`tively low currents through the fluid during short inter-
`vals, they are typically unable to apply higher currents
`to the fluid. Alternatively, while some systems are able
`to provide high currents to the fluid quickly, they are 5
`relatively inefficient.
`In view of these observations, it would be desirable to
`provide a control circuit suitable for controlling the
`operation of an electrolytic fluid treatment system sub-
`stantially independent of variations in the resistivity of 10
`fluid treated by the system. It would also be desirable to
`provide a control circuit that allows several aspects of
`the system’s performance to be optimized, without
`undue circuit complexity, inefficiency, or operator in-
`tervention and that is able to provide relatively large 15
`quantities of energy to the fluid quickly and efficiently.
`SUMMARY OF THE INVENTION
`
`4
`In accordance with yet another aspect of the inven-
`tion, an electrolytic fluid treatment system is disclosed.
`The system includes at least one pair of electrodes defin-
`ing a water flow path therebetween. A capacitor is
`included for storing electrical energy for delivery to the
`pair of electrodes. A switching circuit is included for
`causing energy stored by the capacitor to be delivered
`to the pair of electrodes as a plurality of current pulses.
`If the system is further suitable for treating fluids of
`varying resistivity, an ammeter is included for produc-
`ing an output representative of the current pulses deliv-
`ered to the pair of electrodes. A control circuit is then
`also included for controlling the switching circuit in
`response to the output of the ammeter.
`In accordance with one additional aspect of the in-
`vention, a method and system for electrolytically filter-
`ing water are disclosed. In that regard, water is passed
`between at least one pair of electrodes. A varying volt-
`age is also applied across the electrodes to effect the
`desired filtering of the water. The method and system
`may be, more particularly, for treating several aspects
`of the water and the varying voltage may include a
`range selected to treat the several aspects.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The foregoing aspects and many of the attendant
`advantages of this invention will become more readily
`appreciated as the same becomes better understood by
`reference to the following detailed description, when
`taken in conjunction with the accompanying drawings,
`wherein:
`FIG. 1 is a block diagram of a fluid system employing
`an electrolytic filter constructed in accordance with the
`present invention;
`FIG. 2 is an illustration of an electrolytic cell in-
`cluded in the filter of FIG. 1;
`FIG. 3 is a top perspective of an electrode assembly
`included in the cell of FIG. 2, with parts shown in
`exploded relationship;
`FIG. 4 is a block diagram of a control circuit included
`in the filter of FIG. 1;
`FIG. 5 is a flow chart depicting the operation of the
`control circuit of FIG. 4;
`FIG. 6 is a graph illustrating the output pulses pro-
`duced by the control circuit of FIG. 4 when the fluid
`being treated has some initial resistivity;
`FIG. 7 is a graph illustrating the output pulses pro-
`duced by the control circuit of FIG. 4 when the resistiv-
`ity of the fluid being treated is below the initial resistiv-
`ity;
`FIG. 8 is a graph illustrating the output pulses pro-
`duced by the control circuit of FIG. 4 when the resistiv-
`ity of the fluid being treated is above the initial resistiv-
`lty;
`FIG. 9 is a graph illustrating the output pulses pro-
`duced by the control circuit of FIG. 4 when the average
`current applied to the electrolytic cell is to be increased;
`and
`‘
`FIG. 10 is a graph illustrating the output pulses pro-
`duced by the control circuit of FIG. 4 when the range
`of voltages applied to the electrolytic cell is to be in-
`creased.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`Referring now to FIG. 1, a fluid system 10 con-
`structed in accordance with the invention is shown.
`Fluid system 10 includes a fluid source 12 that provides
`
`A method is described for controlling the operation
`of an electrolytic system used in the treatment of a fluid 20
`exhibiting a potentially variable characteristic. The
`method includes the steps of producing a plurality of
`pulses of electrical energy for application to the electro-
`lytic system. The pulses exhibit parameters including a
`pulse repetition rate, pulse duration, and pulse ampli- 25
`tude. The method also includes the step of evaluating
`the potentially variable characteristic of the fluid. The
`method further includes the step of controlling one of
`the parameters exhibited by the plurality of pulses in
`response to the evaluation of the potentially variable 30
`characteristic of the fluid.
`In accordance with another aspect of the invention, a
`method is disclosed for electrolytically treating water.
`The method includes the step of positioning the water
`between at least one pair of electrodes. The method also
`includes the step of producing a voltage across a capaci-
`tor and selectively coupling the capacitor to the elec-
`trodes, causing the voltage across the capacitor to
`decay and a current to flow through the water between
`the at least one pair of electrodes.
`The method may be further for electrolytically treat-
`ing the water in a manner that is relatively independent
`of variations in the electrical resistivity of the water.
`Thus, the method further includes the steps of sensing
`the resistivity of the water and selectively disconnect-
`ing the capacitor from the electrodes when the voltage
`across the capacitor decays to a pre-determined thresh-
`old. The steps of selectively coupling and selectively
`disconnecting are repeated at a predetermined repeti-
`tion rate and are separated by an interval of time whose
`length is dependent upon the sensed resistivity of the
`water.
`
`45
`
`50
`
`35
`
`In accordance with another aspect of the invention, a
`circuit is disclosed for providing a desired electric cur-
`rent to the electrodes of an electrolytic fluid treatment
`system, substantially independent of variations in the
`fluid passed between the electrodes and treated by the
`system. The circuit includes a sensor for sensing varia-
`tions in the fluid passed between the electrodes. The
`circuit also includes a delivery device for delivering a
`plurality of electric current pulses to the electrodes, the
`electric current pulses exhibiting a pulse duration, pulse
`repetition rate, and pulse amplitude. Finally, a control
`circuit, responsive to the sensor, is included for control-
`ling the delivery device to ensure that the desired elec-
`tric current provided to the electrodes remains substan-
`tially independent of variations in the fluid passed be-
`tween the electrodes.
`
`55
`
`65
`
`

`

`5
`fluid to a supplied environment 14 via an electrolytic
`fluid treatment system, such as filter system 16. As will
`be described in greater detail below, the electrolytic
`filter system 16 is designed to operate in a manner that
`is not adversely impacted by variations in the fluid’s
`resistivity and that is equally effective in removing im-
`purities, killing biological materials, and altering the
`chemical composition of the fluid. The system 16 also
`allows relatively high energy levels to be applied to the
`fluid quickly and efficiently.
`Before discussing the construction and operation of
`system 10 in greater detail, the physics involved will be
`briefly reviewed. In that regard, conventional electro-
`lytic filter systems pass electric current between at least
`one pair of electrodes to effect the desired filtration of
`fluids located between the electrodes. The ability of the
`system to cause impurities to migrate to the electrodes,
`kill biological material, and alter the chemical composi-
`tion of the fluids depends, in part, upon the magnitude
`of the current flow between the electrodes.
`.
`
`Assuming that a fixed voltage V is applied across two
`electrodes, the magnitude of the current I flowing be-
`tween the electrodes varies substantially in accordance
`with the expression:
`
`I= V/R
`
`(l)
`
`where R is the resistance of the fluid between the elec—
`trodes. The resistance R of the fluid can be determined
`in accordance with the expression:
`
`R=pL/A
`
`(2)
`
`where p is the resistivity of the fluid, L is the separation
`of the two electrodes, and A is the cross-sectional area
`of the fluid path between the electrodes. The resistivity
`p, in turn, varies in accordance with the expression:
`
`P=Poll +a(T- T0)]
`
`(3)
`
`where p9 is the resistivity of the fluid at some tempera-
`ture To, T is the actual temperature of the fluid, and a
`is a temperature coefficient. As a result, the resistivity
`and, hence, resistance of the fluid defining the current
`path between electrodes changes in response to both
`fluid and temperature fluctuations.
`As will be appreciated from equation (I), with a fixed
`voltage applied between the two electrodes, the magni-
`tude of the current I flowing therebetween depends
`upon the fluid resistance R. The resistivity p (and its
`reciprocal, conductivity 0') of the fluid may vary con-
`siderably with time, due to differences in the composi-
`tion of the fluid as well as its temperature. Such changes
`alter the interelectrode resistance R and, hence, current
`I and potentially impact the filter’s effectiveness.
`As will be described in greater below, if energy is
`applied to the electrodes in the form of a plurality of
`pulses, some of the characteristics of the pulses can be
`controlled in response to variations in fluid resistivity to
`maintain a relatively constant average current flow
`between the electrodes. The electrolytic filter system 16
`described below maintains the desired current in this
`manner.
`
`Addressing now the construction of the various com-
`ponents of system 10 individually, the fluid source 12
`may take any of a variety of forms. Typically, the fluid
`source 12 will include a fluid supply or reservoir, as
`well as some arrangement for providing fluid to the
`filter system 16 in a controllable and pressurized man-
`
`65
`
`5,324,398
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`6
`ner. To that end, the fluid source 12 may include, for
`example, a pump and various valves.
`One common example of a fluid source 12 is a munici-
`pal water supply. As will be appreciated, the water
`available from many such supplies may exhibit widely
`varying characteristics. For example, it is not uncom-
`mon for the resistivity of water from different munici-
`palities to range between 30 to 1400 ohm-meter.
`Like the fluid source 12, supplied environment 14
`may take a variety of different forms. Examples of sup-
`plied environments 14 include swimming pools, water
`heaters, and drinking water dispensers. In some in-
`stances, although not shown in FIG. 1, the supplied
`environment 14 may use the fluid and return it to the
`source 12 for treatment. In other instances, the supplied
`environment 14 may represent the ultimate destination
`of the fluid.
`The heart of fluid system 10 is the electrolytic filter
`system 16. As indicated in FIG. 1, filter system 16 in-
`cludes an electrolytic cell 18 and control circuit 20. As
`will be described in greater detail below, the electro-
`lytic cell 18 processes fluid flowing from source 12 to
`the supplied environment 14. The control circuit 20
`provides electrical energy to the cell 18 in a controlled
`fashion, allowing cell 18 to effect the desired filtration
`of the fluid substantially independent of variations in
`fluid resistivity.
`Reviewing these two primary components of filter
`system 16 in greater detail, as shown in FIG. 2, the
`electrolytic cell 18 includes an electrode assembly 22
`positioned within a reservoir 24. The electrode assem-
`bly 22, which is shown in greater detail in FIG. 3, in-
`cludes as its primary components a housing 26, a p1ura1~
`ity of electrodes 28, and electrical wiring 30. The hous-
`ing includes a first section 32 and second section 34,
`which cooperatively define an electrode chamber 36
`and inlet chamber 38 therebetween.
`Addressing the construction of the first section 32 of
`housing 26 in greater detail, the portion of the first
`section 32 that defines the electrode chamber 36 in-
`cludes a channel piece 40 formed by a panel 42 and sides
`44 and 46. A rectangular opening 48 is provided in panel
`42, midway between its two ends, and a plurality of
`longitudinally extending, electrode retention grooves
`50 are provided on the inside of panel 42. The first
`section 32 also includes an inlet piece 52, which extends
`from the channel piece 40 and exhibits a tapered cross
`section. A semicircular opening 54 is provided at the
`end of inlet piece 52 to form one-half of a fluid inlet.
`Roughly L-shaped wiring conduits 56 and 58 are
`provided on the sides of the first section 32 of housing
`26. As illustrated in FIG. 3, conduits 56 and 58 are
`substantially rectangular in cross section and include
`openings positioned adjacent the opening 48 in panel 42.
`These openings are provided in a longitudinally stag-
`gered configuration that allows the electrical wiring 30
`received within the conduits to be attached to the vari-
`ous electrodes in a relatively streamlined fashion de-
`scribed in greater detail below. The conduits 56 and 58
`extend axially along the open side of first section 32,
`terminating in openings adjacent the end of inlet piece
`52. The electrical wiring 30 extends from these open-
`ings to the control circuit 20.
`The second section 34 of housing 26 mirrors the first
`section 32, with the exceptions that the opening 48 and
`conduits 56 and 58 are eliminated. In that regard, the
`second section 34 includes a channel piece 60 having a
`
`

`

`7
`panel 62 and two sides 64 and 66. A plurality of elec-
`trode retention grooves 68 are provided on the inside of
`panel 62 for receiving the electrodes 28. A tapered inlet
`piece 70 extends from the channel piece 60 and includes
`a semicircular opening 72, which, in cooperation with
`opening 54, defines a fluid inlet.
`As will be appreciated, the relative size, shape, con-
`struction and materials of the housing 26 can be altered
`as desired.
`In the currently preferred arrangement,
`however, housing 26 is generally rectangular in cross
`section and defines an electrode chamber 36 that is
`roughly 20.5 centimeters by 5.4 centimeters by 5.1 cen-
`timeters. The electrode retention grooves 50 and 68 are
`roughly 0.06 centimeters wide, spaced apart by a dis-
`tance of roughly 0.2 centimeters and may extend the full
`length of the electrode plates or be shorter and spaced
`apart to support the electrode plates at several points.
`The inlet chamber 38 is roughly 8.1 centimeters long
`and tapers to a cross section of roughly 4.8 centimeters
`by 4.5 centimeters. When the first section 32 and second
`section 34 are joined, the semicircular openings 54 and
`72 define a fluid inlet 74 of roughly 9.2 square centime-
`ters. Similarly, the open upper end of housing 26, de-
`fined by the first section 32 and second section 34 pro-
`vides a square fluid outlet 76 of roughly 25.8 square
`centimeters. Sections 32 and 34 are preferably molded
`from a fluid impervious plastic, such as polyethylene
`terephthalate glycol (PETG).
`Having reviewed the construction of housing 26, the
`construction of electrodes 28 will now be considered in
`greater detail. As shown in FIG. 3, seventeen electrodes
`28 are preferably employed. Each electrode 28 includes
`a substantially rectangular body 78 that is positioned
`within housing 26 to contact the fluid to be filtered. A
`connection tab 80, aligned in the same plane as elec—
`trode body 78, projects from one edge of the electrode
`body 78. As will be described in greater detail below,
`the connection tabs 80 are designed to extend through
`opening 48 in the first section 32 of housing 26 to allow
`electrical connections to be made to the electrodes 28.
`The electrodes 28 are preferably made of an electri-
`cally conductive fluid impervious material such as a
`ceramic. The electrode body 78 is roughly 20.3 centi-
`meters by 6.0 centimeters by 0.06 centimeters. Connec-
`tion tab 80 is, for example, roughly 0.6 centimeters by
`0.5 centimeters by 0.06 centimeters. As shown in FIG.
`3, the location of the connection tab 80 between the two
`ends of the electrode body 78 varies from electrode to
`electrode.
`In that regard, the electrodes 28 are separately desig-
`nated 28a through 284 in FIG. 3. The tabs 80 on elec-
`trodes 28a, 28b, 28f, 28f, 281, 2871, and 28g are all spaced
`roughly 8.3 centimeters from one end of their respective
`electrode bodies 78, with the orientation of electrodes
`280, 281', and 28g being reversed from that of electrodes
`28b, 28]; 28], and 2871. The tabs 80 on electrodes 28c,
`28g, 28k, and 280 are spaced midway between the two
`ends of their respective electrode bodies 78. Finally, the
`tabs 80 on the remaining electrodes 28d, 28c, 28h, 281,
`28m, and 28p are spaced roughly 9.2 centimeters from
`one end of their respective electrode bodies 78, with the
`orientation of electrodes 28d, 28h, 281, and 28;; being
`reversed from that of electrodes 28e and 28m. As shown
`in FIG. 3, the varied location of the electrode tabs 80
`effects a staggered alignment that makes it easier to
`provide electrical connections to the electrodes 28.
`With the first section 32 and second section 34 of
`housing 26 secured together by epoxy or other fasteners
`
`10
`
`[5
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`5,324,398
`
`8
`(not shown), the electrodes 28 are retained in slots 50
`and 68 and the tabs 80 on the various electrodes 28
`project from the opening 48 in housing 26, allowing
`electrical connections to be made thereto. In that re-
`gard, the electrical cables 30 are separately identified in
`FIG. 3 as cables 82 and 84. Cable 82 is a standard wire
`cable positioned within wiring conduit 56 and has one
`end connected to the connection tabs 80 of electrodes
`28a, 28c, 28c, 28g, 281', 28k, 28m, 280, and 28g by, for
`example, soldering or fastening hardware (not shown).
`The other end of cable 82 terminates at the control
`circuit 20. Similarly, cable 84 is a standard wire cable
`received within wiring conduit 58. One end of cable 84
`is coupled to the connection tabs 80 of electrodes 28b,
`28d, 28]; 28h, 28f, 281, 2871, and 28p and the other end
`terminates at the control circuit 20.
`Once the housing sections 32 and 36 have been fas-
`tened together and the appropriate connections made
`between cables 82 and 84 and the various electrodes 28,
`the connection tabs 80, electrical connections between
`cables and tabs, and the opening 48 are enclosed by an
`encapsulant, such as an epoxy. As a result, the electrical
`connections are insulated from one another and pro-
`tected from environmental contaminants. Further, by
`closing the opening 48, fluid flow through the electrode
`assembly 22 is confined to a path traversing substan-
`tially the full length of the spaced-apart electrodes 28.
`As noted previously, the electrode assembly 22 is
`positioned in, and axially aligned with, reservoir 24..
`The reservoir 24 is employed to store fluid processed by
`the electrode assembly 22 before it is provided to the
`supplied environment 14. The reservoir 24 may, for
`example, be a roughly cylindrical structure made of a
`fluid impervious plastic such as spun fiber glass (rein-
`forced), acrylonitrite butadiene styrene (ABS). The
`reservoir 24 preferably is roughly 0.6 centimeters thick,
`100 centimeters long and 40.6 centimeters in diameter.
`The fluid inlet 74 of electrode assembly 22 extends
`through the base of reservoir 24, defining a fluid inlet
`into reservoir 24. A fluid outlet 88 is provided in the top
`of reservoir 24. As will be appreciated, the reservoir
`may be equipped with a removable cover, in which the
`outlet 88 would be provided, allowing access to the
`electrode assembly 22.
`Having reviewed the basic construction of electro-
`lytic cell 18, a more detailed discussion of the control
`circuit 20 will now be provided. As shown in FIG. 4, a
`first embodiment of the control circuit 20 includes, for
`example, a DC power supply 90, current sensor 92,
`capacitive storage circuit 94, power switching circuit
`96, inverter 98, controller 100, and flow sensor 102.
`Reviewing these components of control circuit 20
`individually, the DC power supply 90 may be of any
`conventional design and provides energy for use by the
`electrolytic cell 18 in achieving the desired treatment of
`the fluid. As shown in FIG. 4, the power supply 90
`receives inputs from controller 100, allowing the man-
`ner in which energy is output by supply 90 to be con-
`trolled.
`In a preferred embodiment, power supply 90 includes
`a transformer for converting a source of AC input volt-
`age from one level to another, for example, reduced
`level. A rectifier circuit may also be included to convert
`the transformed AC voltage to a suitable DC voltage.
`Finally, a regulation and filtration circuit may be in-
`cluded to ensure that the rectified voltage, available
`between positive and negative output terminals of sup-
`ply 90, has the desired DC characteristics.
`
`

`

`9
`The current sensor 92 is employed to measure the
`current drawn from supply 90. Although the location of
`the current sensor 92 within the control circuit 20 may
`be altered, in the preferred arrangement the sensor 92 is
`coupled between the positive or negative output termi-
`nal of supply 90 and the capacitive storage circuit 94.
`The current sensor 92 may be, for example, an ammeter
`capable of producing outputs representative of currents
`ranging from one to thirty amperes. The output of cur-
`rent sensor 92 is provided to