US3150678A - Device utilizing electro-viscous liquid - Google Patents

Description

p 29, 1964 s. E. NUBER 3,150,678

DEVICE UTILIZING ELECTRO-VISCOUS LIQUID Filed July 11, 1960 s Sheets-Sheet 1 Sept. 29, 1964 s. E. NUBER DEVICE UTILIZING ELECTRO-VISCOUS LIQUID 3 Sheets-Sheet 2 Filed July 11., 1960 Sept. 29, 1964 s. E. NUBER 3,150,678

DEVICE UTILIZING ELECTRO-VISCOUS LIQUID Filed July 11, 1960 I5 Sheets-Sheet 5 Wm 's dfredo 6. YLubef' Arrows.

United States Patent 3 150,678 DEVICE UTILIZING ELECTRO-VISCOUS LIQUID Sigifredo E. Nuher, South Beloit, Ill., assignor, by mesne assignments, to Warner Electric Brake & Clutch Company, South Beloit, Ill., a corporation of Delaware Filed July 11, 1960, Ser. No. 41,834 14 Claims. (Cl. 317-262) This invention relates to electrostatic devices such as brakes, clutches, chucks, fluid transfer systems, and the like utilizing the so-called Winslow effect, that is to say, the stiffening or increase in the shear resistance of a thin layer or film of viscous liquid when subjected to an electric field. In such devices, the liquid layer is confined between surfaces across which an electric potential is impressed to stilfen the liquid and bond the same to the confining surfaces thereby controlling the flow of the liquid or its force or torque transmitting ability.

The primary object is to increase shear resistance of the liquid layer in devices of the above character by providing a more effective electric field for activating the layer.

Another object is to increase the intensity or potential gradient of the electric field capable of being sustained by the liquid layer without danger of heating or breakdown while insuring absolute safety in service use of the electro-responsive device.

A further object is to utilize alternating current potential in a novel manner to produce an electric field of increased efiectiveness.

A further object is to provide an electro-rcsponsive device which operates efliciently and safely under high voltage even when exposed to liquids such as conductive coolants or after the accumulation of dirt or other contaminants in the electro-viscous film.

Still another object is to provide a device of the above character in which the holding force may be exerted on a non-conductive surface.

The invention also resides in the novel manner of confining the electro-viscous liquid and imposing the electric field thereon to permit the use of a wider variety of liquid compositions and either a thicker or thinner layer of liquid than has been possible heretofore.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which FIGURE 1 is a fragmentary plan view of an electric chuck embodying the novel features of the present invention including a circuit diagram.

FIG. 2 is an enlarged section taken along the line 2-2 of FIG. 1.

FIG. 3 is a view similar to FIG. 2 showing a modification.

FIG. 4 is a section taken along the line 4-4 of FIG. 1.

FIG. 5 is a diagrammatic view illustrating the path of the electric field. I

FIG. 6 is a longitudinal sectional view of an electric brake embodying the present invention.

FIG. 7 is a fragmentary section taken along the line 77 of FIG. 6.

FIG. 8 is a perspective view of parts of the brake.

3,150,678 Patented Sept. 29, 1964 FIG. 9 is a diagrammatic view of a fluid transfer system including a valve embodying the present invention.

FIG. 10 is a fragmentary section taken along the line 1010 of FIG. 9.

7 FIGS. 11 and 12 are sections taken respectively along the lines 11-11 and 12--12 of FIG. 10.

FIG. 13 is a diagrammatic view of the wave form of the exciting current.

In prior devices utilizing the Winslow effect, the film of electro-viscous liquid has been semiconductive and the exciting electric potential has been applied directly to opposite surfaces of the film, the stiffening of the liquid thus being accomplished by an actual flow of current through the film. With this method, only thin films usually about .001 to .020 of an inch can be used, and the voltage must be limited to a value that will not cause break-down or objectionable heating of the liquid. These inherent characteristics have limited the commercial use of such devices.

I have discovered that the actual conduction of current through an electro-viscous liquid need not be relied on to effect the stiflening of the liquid and that the liquid may be made to respond to the so-called displacement currents such as those produced in the dielectric of an electric condenser when energized by an alternating current voltage. Accordingly, the present invention contemplates interposing a layer of solid dielectric material between at least one electrode and the electro-viscous film so that the resulting sandwich of liquid and solid layers. forms a composite electric condenser capable of withstanding extremely high voltages.

The invention thus generally characterized may be utilized in many different devices and fluid systems, such for example as a chuck shown in FIGS. 1 to- 4 of the drawings for holding a workpiece during machining or other operation thereon, a brake FIGS. 5 to 7 for exerting a retarding torque, and a valve FIGS. 8 to 10 for controlling the flow of liquid in a fluid transfer system. It is to be understood that I do not intend to limit the invention by such illustrative disclosures, but aim to cover all alternative constructions, modifications and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Many different liquids are electro-viscous and will stiffen appreciably and bond effectually to the confining surfaces when an electric potential is impressed across opposite sides of a layer of the liquid so as to create an electric field within the layer. Among the liquids capable of being used to practice the present invention are Examples C and D disclosed in Patent No. 2,661,825 and most of the examples disclosed in a pending application of Willis M. Winslow, Serial No. 19,465, filed April 4, 1960, issued July 31, 1962, as US. Patent No. 3,047,507. Each of the latter examples comprises a mixture of four classes of ingredients namely: (1) an electrically stable, low dielectric constant, oleaginous vehicle of suitable viscosity; (2) finely divided and non-conductive solids having an average diameter of from about 0.1 to about 5 microns and possessing the ability to absorb a significant quantity of a substance such as water or alcohol; (3) an organic surface active dispersing agent; and (4) water or a mixture of water and a water miscible alcohol or other hydroxy compound.

Typical of the suitable liquids given in said application is the following:

Percent by wt.

.A mixture in proportions of about 2: 1 of 4,4-bis hydroxymethyl-2-heptadecencyl-2-oxazoline and oleylamido triethanolmethane-product of Commercial Solvents Co.

Viscosity of 40-50 Saybolt sec. at 100 F.

Specially ground dehydration grade-about 1 micron average diameter. Davidson Chemical Co. SMR-55 6826.

Primarily ,(about 90%) 1 hydroxycthylQ-heptadecenyl imidazoline. The remaining 10% comprises oleic acid amide and N-aminoethyl ethanol-amine. Product sold. by Union Carbide.

A silicate ester base coolant-dielectric fluid sold by Monsanto Chemical Co.

With the present invention, it is possible to employ electr c-viscous mixtures which do not include water as an ingredient. The-following is an example of such a liquid:

Percent by wt. Neutral motor oil (viscosity 90) 30.5 Glycerol mono oleate 5.5 Amine220 10.0 Ethylene glycol 4.0 Silica gel, one micron size 50.0

It has also been found that certain single component liquids can be used to form the electro-viscous .film in devices embodying the present invention. An example of such a liquid is 1,1'-bis(X-chlorophenyl)ethane manufactured by Dow Chemical Company and comprising X- chlorophenyl ethane.

.In the chuck as shown in FIGS. 1 to 5, a workpiece having a generallyfiat bottom surface 11 of conductive material is supported. on a rigid surface 12 of a suitable base-or'composite block 13'through the medium of a layer or relativelythin film 14 of a suitable electro-viscous liquid of the character abovedescribed. The block may be clamped onto a work table or other support 9 as by bolts engaging projecting cars 15. If the workpiece is composed of non-conductive .material such as ceramic, plastic, .glass, wood, etc. having a relatively low dielectric constant, the surface 11 isflashed with metal or otherwise coated with a conductive film suchfor example as a metallicpaint. As'will appear later, workpieces composed of non-metallicmaterial of high dielectric constant, that is, more than 10,'n1ay be chucked without preliminary coating.

The potential for creating the electric field in'the liquid film 14 is applied across electrodes 16, .17 and'lS embedded in the base 13 a uniform distance, usually about .10of an inch, below the top surface 12. In the present instance, each electrode comprises a thin strip of metal such as silver foillying against and preferably bonded to a relatively thin layer 19 of non-conductive or semiconductive material which is set in the base and forms part of the work supporting surface 12. In FIGS. 1 and 2, the layer 19 is composed ofseparate bars laterally spaced apart with the electrode strips covering thebottom surfaces and the top faces flush with each other and defining the surface 12. This relation is maintained by a rigid body of non-conductive material such as plastic 20 preferably cast in and around the electrode bars after attachment of conductors 21, 22 and 23 thereto and while the bars are held in the desired relation within an enclosing frame 24. The latter maybe made of steel with the ears 15 welded or'otherwise secured thereto. The plastic'20 is-preferably a so-called potting compound such as an epoxy resin adapted to be cast while cold.

In the form shown in FIG. 3, the layer 19 may comprise a continuous plate with the electrodes 16, 17 and 18 bonded to the bottom thereof in properly spaced relation as by any well-known technique such as is used in printed circuitry. As before, the plate is backed solidly by the cast body 20 of rigid plastic. In each instance, the plastic below the electrodes and the conductors 21-23 is of suflicient thickness to isolate these parts effectually from work table or other metallic support to which the chuck may be secured in service use.

The electrodes are sized according to the size of the workpieces to be chucked and the number used is preferably suiiicient to provide .an area larger than the bottom of the workpiece. For ceratin work shapes, the electrodes may be of other shapes such for example as concentric rings.

As set forth above, the use of high voltage, for example 2000, for producing a strong electric field in the liquid film 14 is made possible by interposing a layer of rigid dielectric material between at least one side of the film and the electrodes so as to form with the film a composite "electric condenser. In thepresent instance, the bars 19 (FIGS. 1 and-2) or the plate 19 (-FIG. 3) form the dielectric layer. While various dielectric'materials may be employed, optimum voltage across the film may be achieved -byusing amaterial having a high dielectric constant, that is, more than about 10 (measured at 25 (3.), relative to the dielectric constant-of the electro-viscous'liquid which latter is usually about 5 or less.

Among the best such dielectric materials now available is a fired cer-amicsold under the trade name of BT- 15 and described by' the manufacturer, Arnold-Engineering Company of Marengo, Illinois, as produced from a polycrystalline form of barium titanate with varying amounts of lead and calcium titanates and cobalt oxide. A similar-material known as D-51 and supplied by Central Lab Company of Milwaukee is composed of barium titanate-with strontium titanate and ferric oxide additives.

This material has a dielectricconstant of from 5500 to 6500-and an estimated dielectric strength of 35 to 40 voltsper .001 inch of thickness.

In addition to its high dielectric constant, the dielectric strength 'ofithelayer 19 should be as high as possible in order to impart to the liquid-solid sandwich the desired high res'istanceito breakdown under the applied voltage even 'though'the layer is relatively thin. Satisfactory results have been achieved with the materials above described when the layer is .10 of an inch thick.

It will-be observed "that the liquidfilm 14 and the dielectric layer 19' confined as described above between the electrodes and the conductive-bottom surface 11 of the workpiece form in etfect two capacitors connected in series. .In this relation, the so-called. displacement currents in'the film are, for a given value of applied alternating voltage, directly proportional to the frequency of such voltage and the capacitance of the system. Therefore, it is desirable to select an electro-viscous liquid having the highest available dielectric constant and of minimum thickness. The latter, in the case of a work chuck, is determined by the flatness of the bottom surface 11 of the workpiece in order to insure complete coverage of the work and supporting surfaces at all points across the opposed areas.

When, 'as in the work chuck above described, all of the electrodes are mounted in one of the members to be coupled by the viscous liquid, the liquid film and the dielectric layer form two sets of capacitors in series. That is to say, one set is disposed between the conductive bottom surface 11 of the work and an electrode of one polarity, the other set being between this surface and an electrode of opposite polarity. Thus, the work surface serves not only as one plate of the condensers of each set, but also as a conductor for connecting the sets of capacitors in series relation.

With this arrangement, the electric field produced by opposite polarization of adjacent electrodes will be distributed as illustrated in FIG. 5. That is, the displacement currents created by the alternations in the applied voltage will thread the entire areas of the electrodes and the adjacent alined areas of the dielectric layer 19 and film 14, and the latter areas will be bridged by the work surface as illustrated by the lines 26. Shunting of the electric field edgewise between the bars while by-passing of the liquid film may be minimized by spacing the bars apart as shown in FIG. 2.

To minimize variation of the force or torque transmitting ability during alternation of the energizing voltage, the invention, in another of its aspects, contemplates exciting the film 14 by a polyphase voltage with the respective components, three in the present instance, applied to the three electrodes 16, 17 and 18, which are arranged in groups as shown in FIG. 2 with the consecutive numbers of the different electrodes forming each group and successive groups spaced along the supporting surface 12. As a result, the potential at the respective electrodes will change in accordance with the usual wave forms a, b and 0 shown in FIG. 13. These curves intersect each other at successive points 27 of positive potential and similarly at points 28 of negative potential. The

result is that the potential gradient between two electrodes 16 and 17 may fall to zero as at one of the points, but between the other pairs of electrodes 16, 18 and 17, 18 the gradient will be equal to 30. As a consequence, the electric field remains effective to excite and stiffen the liquid of the film 14 at all times in spite of the alternating and changing value of the voltage of each phase. In this way, the desired holding force is exerted continuously on the workpiece. The different components of the polyphase voltage are applied to the three groups of electrodes 16, 17 and 18 through insulated conductors 21-23 which are extended into the chuck base through suitable waterproof fittings.

While the desired polyphase current may be obtained from any suitable source such as a standard alternator, a source more convenient for service use of the chuck in an ordinary machine shop may be derived from a commercial single phase power line by a converter of the type shown in FIG. 1. The single phase voltage from an auto-transformer 31 is adjustable in magnitude by a slider 32 and is applied to a voltage-increasing or step-up transformer 33 when a switch S is closed. The output is impressed across parallel RC phase shift networks including a first resistance 34 and capacitor 35 and a second resistance 36 and capacitor 37, the two being reversely connected to produce one leading phase and a second lagging phase at the output leads 21, 22 and 23. This simple type of converter may be used in the present instance because the creation of the desired electric field within the electro-viscous film does not involve an'actual how or conduction of current through the electro-viscous film 14 but utilizes so-called displacement currents produced by alternating potential as described above.

With the components of the chuck constructed and dimensioned as above described, it is possible to increase the shear resistance of the film mixture to approximate ly 20 pounds per square inch. In addition, all of the electrodes are insulated effectually from each other, from the workpiece and from the supporting work table.

It will be apparent that the electrodes 16, 17 and 18 are spaced equidistant from the conductive bottom surface 11 of the workpiece and also that these electrodes are spaced equidistantly from the support 9 on which the chuck is mounted in service use. As a consequence, there is formed between the work surface 11 and each pair of electrodes an equal capacitive coupling. A similarly balanced coupling exists between each pair of electrodes and supporting metallic structure. These four couplings form a symmetrical bridge circuit for each phase of the energizing potential. Therefore, the machine frame and the workpiece 10 are always at the same potential or at zero potential with respect to each other. This provides absolute safety to the machine operator in spite of the high exciting voltages that may be used.

The dielectric layer 19 associated with the electroviscous film in the manner above described may be used to advantage in torque producing couplings which may take various forms, a typical one of which is the brake shown in FIGS. 6 to 8. In this, electrodes 41, 42 and 43 in the form of thin metal disks are molded into disks 44, 45 and 46 of the fired ceramic material above described, each composite disk having a pair of radially projecting squared teeth 47 snugly splined into inwardly opening grooves 48 in a cylindrical shell 49 of rigid insulating material. The shell is clamped by tie bolts 53 between axially spaced heads 50 also composed of insulating material and bolted to a stationary support 57 supporting bearings 51 in which a shaft 58 is journaled.

Two additional pairs 51 and 52 of grooves are formed in the shell 49 and angularly spaced from the grooves 48 to receive similar spline teeth 47 on the disks 45 and 46. Metallic strips 54, 55 and 56 seated in the bottoms of the grooves 48, 51 and 52 bear against the outer ends of teeth 44 45 and 46 formed on the metal disks within the lugs 47. The respective contact strips 54, 55 and 56 are connected to the three lines 21, 22 and 23 leading from a three phase alternating current source of the type above described.

Interposed between the adjacent disks 44, 45 and 46 are metal disks 60, 61 and 62 spline coupled to the shaft 58 and spaced accurately along the latter by rings 63 separating the adjacent disks from each other, the terminal disks lying adjacent the casing heads 50 in this instance. Narrow axial clearances 65, usually about .010 of an inch, left between the rotating and fixed disks are filled with electro-viscous liquid of the character above described.

With this arrangement, the layer of high dielectric material on each side of the stationary disks 44-46 cooperates with the adjacent liquid film 65 to form a composite capacitor disposed between the adjacent conducting disk 61-63 and the disks 41-43 the same as in the chuck first described. The disks 41-43 which constitute the three electrodes are connected to the different phases of the alternating potential and thus are variably polarized following the wave forms of FIG. 13. As a result, the shear resistance of the disk-like films of liquid spaced along the shaft is increased thus exerting a viscous drag and retarding torque on the disks 60-62 to arrest the motion of the shaft when the capacitors are excited by closure of the control switch S.

Through the use of the present invention, it is possible to form a control valve having no moving parts but operable to regulate and interrupt the flow of liquid in a fluid transfer system. Such an adaptation is shown in FIGS. 9-12 in which liquid is placed under pressure by a motor driven pump 71 and the flow thereof to and from a piston and cylinder type servo 72 is controlled by a valve 73 interposed in the pressure line 74 leading to the servo. The fiuid 70 filling the system may be any one of the electro-viscous mixtures described above.

As shown in FIG. 10, the valve 73 includes a tubular casing 75 composed of insulating material having an internal cylindrical surface 76 concentric with and surrounding the cylindrical external surface of a rod 78, the two surfaces defining between them a tubular space, usually about .010 in radial thickness, through which the liquid may flow freely when not activated.

Herein, the rod 78, which is composed of conductive material or a non-conductive material coated with electrically conductive material or material of high dielectric constant, is seated at opposite ends in disks 79 supported by hollow fittings 74a threaded onto opposite ends of the valve casing 75 and the adjacent portions of the liquid conduit 74. Apertures 89 in the disks allow for the free flow of the liquid through the valve casing when and formed around the interior of the casing 75. Within and in close contact with the electrode rings .are cylindrical rings 85 composed of the fired ceramic material above described having a high dielectric constant. These rings are. about .100 of an inch in radial thickness and their-inner surfaces are substantially flush with the interior of the casing.

One or more groups of the electrodes 81-83 may be employed and the corresponding and consecutively spaced electrodes of each group have terminals extended to the exterior of the casing and connected respectively to the leads 21-23 of .the three phase power source. It will thus be apparent thatthe high dielectric rings 85 and the tube of the electro-viscous liquid enclosed thereby form composite electric condensers in which an electric field and the desired displacement currents in the liquid will beproduced when the three phase potential is applied to the electrodes. As a consequence and as in the chuck and brake above described, the liquid is stiffened and virtually solidifiedthus interrupting the flow to theservo 72. By adjusting the slider 32 and therefore the applied potential, the flow may be regulated and thespeed of the servo piston controlled as desired.

It will be apparent that in each of the devices described above, a layer of the electro-viscous fluid lies in contact with a layer of material having a high dielectric constant and cooperating with the liquid to form an electric capacitor across which an alternating voltage of substantial magnitude may be imposed to produce the desired displacement currents and stiffening of the liquid layer without the actual conductive fiow of current that might other- .wise break-down or carbonize the liquid. Because of this, anelectric field of substantially greater intensity for a given thickness of the electro-viscous film can be produoed and thicker or thinner films may be employed as is desirable for certain applications. Also, the separation of the electro-viscous film from the electrodes by the dielectric insulating layer 19 eliminates any danger of short-circuiting the electrodes as by conductive coolant that may-flow onto the work. For the same reason, the holding power of the film is not reduced by dirt or other contaminants that may be present or enter the liquid in service use.

In different electro-responsive devices such as those illustrated, the electrodes and the dielectric layers may take various forms depending on the use involved and for manufacturing economies. Also, the number of groups of the polyphasc electrodes may be varied as desired to achieve the desired total shear or flow resistance when the electro-viscous layer is activated.

As used in the appended claims, an electro-viscous liquid contemplates and includes a flowable liquid which stifiens and bonds to its confining surfaces when an electric potential is impressed across the latter. A high dielectric constant contemplates a value more than ten.

I claim as my invention:

1. An electrostatic device comprising two electrically conductive members having opposed closely spaced and substantially parallel surfaces, a body of electrical insulation supporting said members and isolating the same from each other, a thin layer of solid material having a high dielectric constant covering and lying against one of said surfaces, a film of electro-viscous liquid disposed between and in electrical contact with said layer and the opposed one of said surfaces and cooperating therewith to form an electric condenser, and selectively controllable means for impressing an alternating current voltage across said members.

2. An electrostatic device comprising means providing a polyphase source of electric potential having a plurality of output terminals for the diiferent phases, a plurality of metallic electrodes respectively connected to said output terminals and providing surfaces laterally spaced apart but substantially flush with each other, means supporting said electrodes in electrically isolated relation, layers of material having a high dielectric constant covering and lying in contact with said electrode surfaces, electro-viscous liquid covering all of said layers and cooperating therewith to form composite electric condensers, and a layer of solid material confining said liquid and providing a bridge across said electrodes for the electric field created in the liquid when subjected to said potential.

3. The combination in an electrostatic device of, a solid base composed of electrical insulation, strips of metal mounted in said base below the surface thereof and disposed substantially flush with each other while being spaced apart laterally, layers of material of high dielectric constant rigid with said base and covering and lying in electrical contact with the outer surfaces of said strips, the opposite surfaces of said layers being flush with'each other and forming a rigid exposed surface, a film of electro-viscous liquid covering said exposed surface, a rigid member lying in contact with the opposite surface of said film and bridging said layers, said strips, said layers, said film and said member constituting two electrical condensers connected in series relation by the member, means providing a source of alternating electric potential, and means connecting said source and said strips to oppositely polarize the latter.

4. An electrostatic device as defined in claim 3 in which the opposed surfaces of said layers and said member are substantially flat and disposed in closely spaced parallel planes.

5. An electrostatic device as defined in claim 3 in which the opposed surfaces of said body and said memher are annular and confine said film in the form of a tube.

6. The combination in an electrostatic device of, spaced metallic electrodes, layers of material of high dielectric constant rigid covering and lying in electrical contact with said electrodes, the opposite surfaces of said layers being exposed, a film of electro-viscous liquid covering said exposed surfaces, a rigid member lying in contact with the opposite surface of said film and bridging said layers, said electrodes, said layers, said film and said member constituting two electrical condensers connected in series relation by the member, means providing a source of alternating electric potential, and means connecting said source and said strips to oppositely polarize the latter.

7. An electrostatic device as defined in claim 6 in which said electrodes and said member are mounted for relative rotation about a predetermined axis.

8. An electrostatic device as defined in claim 7 in which said electrodes, said layers, and said member comprise rings spaced along said axis.

9. An electrostatic device comprising two electrically conductive members having opposed closely spaced and substantially parallel surfaces, a body of electrical insulation supporting said members and isolating the same from each other, a pair of thin layers of solid material having a high dielectric constant covering and lying against each of said parallel surfaces, respectively, a film of electro-viscous liquid disposed between and in electrical contact with said layers and cooperating therewith to form an electric condenser, and selectively controllable means for impressing an alternating current voltage across said members.

10. An electrostatic device comprising at least two electrodes positioned in spaced apart relationship to define therebetween a path of flow of electricity, a layer of material having a relatively high dielectric constant and a film of electro-viscous fluid having a relatively low dielectric constant interposed in the said path of flow of electricity, said layer being sized and positioned to limit said path of flow of electricity, said layer, film and electrodes being in electrical contact with each other to thereby form an electric condenser, and means for applying an alternating electric potential across said electrodes.

11. An electrostatic device comprising a pair of opposed electrodes spaced apart to define therebetween a path of flow of electricity, a layer of material having a relatively high dielectric constant interposed in the said path of flow of electricity and being sized and positioned to overlay and completely cover one of said electrodes, at film of electro-viscous fluid having a relatively low dielectric constant interposed between said layer and the other one of said electrodes, said layer, film and electrodes being in electrical contact with each other to thereby form an electric condenser, and means for applying an alternating electric potential across said electrodes.

12. In an electrostatic device comprising at least two electrodes positioned in spaced apart relationship to define therebetween a path of flow of electricity, a film of electro-viscous fluid having a relatively low dielectric constant interposed in the said path of flow of electricity, and means for applying an alternating electric potential across the electrodes to thereby form an electric condenser, the improvement which comprises means for increasing the intensity of the electrical field in the electroviscous fluid film and thereby increasing the shear resistance of the film comprising a layer of material having a relatively high dielectric constant interposed between the electrodes and being sized and positioned to limit said path of flow of electricity.

13, An electrostatic device comprising means providing a source of electric potential having a plurality of output terminals, a plurality of metallic electrodes respectively connected to said output terminals and providing surfaces laterally spaced apart but substantially flush with each other, means supporting said electrodes in electrically isolated relation, layers of material having a high dielectric constant covering and lying in contact with said electrode surfaces, electro-viscous liquid covering all of said layers and cooperating therewith to form composite electric condensers, and a layer of solid material confining said liquid and providing a bridge across said electrodes for the electric field created in the liquid when subjected to said potential.

14. An electrostatic device as defined in claim 1 in which said layer and the opposed one of said surfaces cooperate to define an annular passage of narrow radial width, and further including means for forcing a flow of said fluid longitudinally through said passage to form said film therein whereby said device constitutes a valve for controlling said flow in accordance with said voltage.

References Cited in the file of this patent UNITED STATES PATENTS 2,417,850 Winslow Mar. 25, 1947 2,859,962 Beveridge Nov. 11, 1958 2,897,424 Waring July 28, 1959 2,897,425 Waring July 28, 1959 2,904,431 MoncrieiT-Yeates Sept. 15, 1959 2,923,390 Fitch Feb. 2, 1960

Claims (1)

1. AN ELECTROSTATIC DEVICE COMPRISING TWO ELECTRICALLY CONDUCTIVE MEMBERS HAVING OPPOSED CLOSELY SPACED AND SUBSTANTIALLY PARALLEL SURFACES, A BODY OF ELECTRICAL INSULATION SUPPORTING SAID MEMBERS AND ISOLATING THE SAME FROM EACH OTHER, A THIN LAYER OF SOLID MATERIAL HAVING A HIGH DIELECTRIC CONSTANT COVERING AND LYING AGAINST ONE OF SAID SURFACES, A FILM OF ELECTRO-VISCOUS LIQUID DISPOSED BETWEEN AND IN ELECTRICAL CONTACT WITH SAID LAYER AND THE OPPOSED ONE OF SAID SURFACES AND COOPERATING THEREWITH TO FORM AN ELECTRIC CONDENSER, AND SELECTIVELY CONTROLLABLE MEANS FOR IMPRESSING AN ALTERNATING CURRENT VOLTAGE ACROSS SAID MEMBERS.

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