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Publication numberUS3701868 A
Publication typeGrant
Publication dateOct 31, 1972
Filing dateMay 18, 1970
Priority dateMay 18, 1970
Publication numberUS 3701868 A, US 3701868A, US-A-3701868, US3701868 A, US3701868A
InventorsLucian Arsene N
Original AssigneeLucian Arsene N
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Liquid-state switching device
US 3701868 A
Abstract
A liquid-state switching device utilizes movement of a column of liquid, resulting from a change in surface tension of the liquid caused by electrocapillary action, to operate various switch means. The electrocapillary effect is induced across a single interface sets of single of mercury and an electrolyte or electrolytes. Filter partitions are installed to maintain the liquids in a proper relationship throughout variations in position of the switching device. Means are provided to assist the return of the column of liquids to their normal positions including a bias voltage, a permanently installed resistance, and/or pressurized gas pockets.
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Description  (OCR text may contain errors)

United States Patent Lucian [54] LIQUID-STATE SWITCHING DEVICE [58] Field Inventor:

Filed:

Appl.

Street, Manasquan Park, NJ. 08736 May 18, 1970 US. Cl. ..200/192, 200/194, 200/211 Int. Cl. ...H01h 29/00, l-lOlh 29/06, H0lh 29/02 of Search...200/l52 K, 152 L, 83.34, 81.8, 200/839, 83.3; 335/49, 50, 52

References Cited UNITED STATES PATENTS 8/1955 Pettigrew et al ..200/83 5/1956 Bellamy ..335/49 8/1957 Boyle ..335/49 X 7/1962 Corrsin ..200/l52 X 12/ 1964 Bourdel ..200/15'2 X 6/1965 Huston "ZOO/81.8

Arsene N. Lucian, 2405 Cherry 5/1966 l-lurvitz ..335/49 X 3/1967 Hurvitz ..335/52 Primary Examiner-Robert K. Schacfcr Assistant ExaminerWilliam J. Smith Attorney-Darby & Darby [57] ABSTRACT A liquid-state switching device utilizes movement of a column of liquid, resulting from a change in surface tension of the'liquid caused by electrocapillary action,

to operate various switch means. The electrocapillary effect is induced across a single interface sets of single of mercury and an electrolyte or electrolytes. Filter partitions are installed to maintain the liquids in a proper relationship throughout variations in position of the switching device. Means are provided to assist the return of the column of liquids to their normal positions including a bias voltage, a permanently installed resistance, and/or pressurized gas pockets.

24 Claims, 12 Drawing Figures PATENTEDIJBI 31 1912 sum 2 or 4 ATTORNEYS.

PATENTEDncm m2 3.701.868

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INTERFACIAL TENSION EXTERNAL VOLTAGE APPLIED ACROSS INTERFACE I NV ENTOR ARSENE N. LUC/AN BY 6 m w uA 7 W his ATTORNEYS.

1 LIQUID-STATE SWITCHING DEVICE BACKGROUND OF THE INVENTION This invention relates to liquid-state switching devices and, in particular, to novel and highly effective switching devices that' respond to electrocapillary forces generated by electrical inputs of very low voltage and current.

Many difficulties, which are well known to those versed in the switching and relay arts, are encountered in constructing electrical switching devices which dependably actuate contact means in response to very low input voltages and currents. The common electromechanical relay, for example, has been designed to respond to very low voltages; however, either the actuating current is high or the required mechanism is so delicate that the dependability of the switch is relatively low. At low input voltages and currents, the available actuating power is low, and thus it has been difficult to construct a switch having a short response time. In switching mechanisms which use movable contacts to break the electrical circuit, problems have also been encountered with contact arcing and deterioration from exposure to the atmosphere, and encapsulation of the contact means has provided additional problems, such as poor serviceability and excess bulk. Often, the solution to one problem leads to further difiiculties in another area.

SUMMARY OF THE INVENTION There is provided in accordance with the present invention a novel and useful switching device that is highly suitable for actuation by an electrical input of low voltage and very low current. The invention applies the well-known principles of electrocapillary phenomena, which involve interactions between a double layer of electrical charges at a single interface between two partiallyconducting liquids in contact with each other in a capillary tube, and the surface tension of the liquids. The result of these interactions is a change in surface tension at the single interface of the liquids when an electromotive force of low voltage, such as small fractions of a volt, and negligible current are impressed across the interface. A conducting liquid and an electrolyte immiscible with the conducting liquid are placed in contact in a capillary tube and a suitably low voltage is applied to generate a motive force which is then utilized to actuate various switch means. It is a significant feature of the invention that the switching operations are accomplished without the aid of externally imposed electromagnetic or electrostatic fields. Various switch means are provided which are susceptible to direct hydraulic actuation by one of the liquid phases comprising the switch. Since intermediate mechanical components are eliminated, the dependability of the switch is increased.

The switch according to the invention also includes sealed switch means to prevent atmospheric contamination. Furthermore, some embodiments employ a liquid contactor to minimize malfunctions caused by arcing the pitting of the contacts. To shorten the total response time of the switching device, various means are provided to assist the return of the capillary columns to their normal positions including enclosed gas pockets which exert a slight counter pressure on the liquids, a bias voltage which operates on removal of the ,2 control voltage to quickly return the interfacial potential to its original value, and a resistor, permanently installed across the control contacts, to dissipate the counter electromotive, or back e.m.f., force developed upon actuation of the switch. I

BRIEF DESCRIPTION OF THE DRAWINGS An understanding of additional aspects of the invention may be gained from a consideration of the following detailed description of several representative embodiments thereof, in conjunction with the appended figures of the drawing, wherein:

FIG. 1 is an elevation view in enlarged longitudinal section of a prior art'device used to illustrate the principles of operation of the subject invention;

FIGS. 2 through 8 are views similar to FIG. 1 showing various embodiments of the invention;

FIGS. 9 through 11 are schematic representations of electrical biasing means;

FIG. 12 is a representative electrocapillary curve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is first made to FIG. 1 which shows a prior art device for an explanation of theoretical background to aid in the understanding of the subject invention. FIG. 1 shows an envelope 10 of suitable dielectric material, which may, for example, be glass. The envelope consists of three functional sections: a tube 12, a reservoir 14, integrally fused with the tube at one end thereof and having a common fluid path 15 with the tube, and a reservoir 16, integrally fused with the tube 12 at the other end thereof, and also having a common fluid path 17 with the tube. The tube 12 has a bore with transverse dimensions which are of capillary magnitude; however, the interior transverse dimensions of the reservoir 14 are not critical and may be greater than the corresponding dimensions of the capillary tube 12.

The envelope contains a column of mercury 18, which partially fills the reservoir 14 and extends into the capillary tube 12, a first globule of mercury 20, which is located in the capillary tube section, and an electrolyte 22, such as acidulated water, which forms an interface or meniscus 19 with the column of mercury 18. The electrolyte also maintains the mercury globule 20 in a spaced relationship tothe column of mercury 18. The envelope 10 also contains a second globule of mercury 24, which is spaced from the globule 20 by a dielectric liquid 26, which may, for example, be transformer oil, and a third globule of mercury 28, which is spaced from the globule 24 by a similar dielectric liquid 30. Other suitable metallic liquids may be substituted for the mercury; however, the metallic liquid and the electrolyte must be immiscible.

Excessive movement of the globule 28 to the right as represented in FIG. 1 is prevented by a barrier 32, comprising, for example, a spring or gauze pad. A pair of electrodes 34 and 36 are integrally fused in the envelope, the electrode 34 contacting the mercury colunm 18 and the electrode 36 contacting the mercury globule 20. Integrally fused into the capillary tube 12 are a plurality of electrodes 38,40,42,and 44 to provide two normally-opened circuits.

also to aid in the return of the system to its normal state.

The electrocapillary effect is well known, and derives from interactions between interfacial potential and surface tension. It has been theoretically established, as a corollary of the Helmholtz double-layer theory, that a double layer of opposite electrical charges exists at a single interface of a metal and an electrolyte in contact, and that the metal is positively charged with respect to the electrolyte. With no external voltage applied, these two oppositely charged layers attract each other, and remain in equilibrium. It has been observed that if this steady-state charge distribution is altered by applying an external voltage across the single interface, the interfacial tension is concurrently altered. It is this change in surface tension of the liquids which causes movement of the liquids in the switch according to the invention.

The relationship between the voltage applied across the single interface 19 and the surface tension of the mercury column 18 is considered with reference to the curve in FIG. 12. This curve corresponds to the known electrocapillary curve; however, the ordinate corresponds to the surface tension of the mercurycolumn rather than the often-depicted height of a column of liquid supported by a capillary surface. The abscissa corresponds to the control voltage applied across the interface 19 with the polarity of the voltage being measured with reference to the mercury column 18.

For a mercuryelectrolyte single interface to which an increasingly positive voltage is applied (thus making the mercury surface a cathode), it is apparent from the curve that the surface tension initially increases, which corresponds to the reduction of the positive charge on the mercury surface. The surface tension reaches a maximum value, represented by the apex of the electrocapillary curve, when the electron flow to the mer cury side of the interface reduces the positive charge on the mercury surface to zero. Further increase in the applied voltage causes the mercury surface to become increasingly negative with respect to the electrolyte surface and the surface tension decreases. Ifthe voltage is reversed and the mercury is made an anode, no such neutralizing occurs, the interfacial potential increases in proportion to the applied voltage and the surface tension decreases proportionally to the magnitude of the applied voltage.

Four modes of switch operation are possible. First, the mercury can be made a cathode with a relatively small voltage applied, whereby the interfacial tension increases and there is movement of the interface 19 to the left as represented in FIG. 1. In the second mode, the mercury can bemade an anode and upon application of any magnitude of voltage the interfacial tension decreases and there is movement to the right as represented in FIG. 1. In the third mode of operation,

the mercury can again be made a cathode with, however, a large voltage applied, so that the interfacial tension first increases and then decreases, thus resulting in an initial movement to the left followed by movement to the right as represented in FIG. 1. An additional, fourth, mode of operation is available if a steady-state bias voltage is applied across the mercury-electrolyte interface, with a control voltage applied in series to vary the total applied interfacial potential from the steady-state bias voltage. In this fourth mode the value of the mercury-electrolyte interfacial tension is a function of the sum of the bias voltage and the control voltage. For example, if the bias voltage level is set so that for the steady-state condition the switch is operating at the apex of the electrocapillary curve shown in FIG. 12 (by reducing the positive charge distribution on the mercury surface to zero), then the application of a control voltage in series with the bias voltage in either'a positive or a negative direction decreases the interfacial tension, since, for both voltages taken together, the switch is caused to operate at some point not at the apex of the electrocapillary curve. A bias voltage is also employed in a second manner according to the invention, not in series with the control voltage, but supplementary to it to cause the interface to more quickly return to the steady-state position after the control voltage is removed. The principle of operation and ef' feet on the switch of a bias voltage in the last-mentioned application is analogous to the application of a voltage in any of the first three modes presented above.

Although it is possible to operate a device of this kind in which a mercury column is made an anode, such as in mode two above, chemical reactions may develop which render such a construction less desirable than one wherein the mercury column is made the cathode, e.g., oxidation of the mercury surface (see Dole, M., Principles of Experimental and Theoretical Electrochernistry,N.Y., McGraw-Hill Book Company,. 1935, Chapter 27, p. 467), or formation. of mercurous sulfate (see Findlay, A., Practical Physical Chemistry, London, Longmans, Green & Co.,l91l, p. 198). Such chemical reactions will detract from the reliability of the device. It is realized that according to the embodiment shown in FIG. 1 the double interface 21, which is defined between the electrolyte 22 and the mercury globule 20, constitutes a second mercury-electrolyte interface in which the mercury globule 20 must be an anode if the mercury column 18 is made a cathode. This presents the disadvantages above discussed for anode operation, and, in accordance with the invention, a construction substantially reducing the problems inherent in necessarily operating one of the transfer interfaces as an anode is shown in FIGS. 2-8 which are discussed hereafter.

Returning to FIG. 1, the switch is preferably operated with the mercury column 18 made a cathode and values of control voltage are applied which are sufficiently small that the interfacial tension increases in direct relationship to the magnitude of the applied voltage.

Upon application of such a preferred voltage, the mercury interface 19 moves to the left as represented in FIG. 1 and a differential pressure is exerted on the liquid in the capillary tube 12, causing such liquid to move towards the left. Since the interior of the tube 12 is of capillary transverse dimensions, no fluid or gas can by-pass the globules of mercury 24 and 28. The fluid movement thus causes the mercury globule 24 to move towards the left, thereby completing an electrical path between the electrodes 38 and 40, and also causes the mercury globule 28 to move a similar distance to the left to complete an electrical path between the electrodes 42 and 44. The mercury globule 20 is positioned so that when it is at maximum operative displacement to the left or to the right, and for any position therebetween, it is in continuous contact with the electrode 36. FIGS. 2 through 8 illustrate means according to the present invention by which the pressure exerted by the moving mercury column actuates various switching means. FIGS. 2 through 8 also illustrate various means by which the electrocapillary switch may be designed to decrease susceptibility to positional variations. The embodiments of these figures also show means for applying the proper polarity voltage to the electrolyte mercury single interface which substantially avoids the disadvantages presented above which are associated with anode operation of an interface.

In the embodiment shown in F IG. 2, the envelope 10 comprises the capillary tube 12, a reservoir 56, integrally fusedwith the capillary tube at one end thereof and having a common fluid path 57 with the tube, a reservoir 58, integrally fusedwith the tube 12 at the other end thereof and also having a common fluid path 59 with the tube, asleeve 60, integrally fused with the reservoir 56 and having a common fluid path 61 therewith, and a reservoir 62, integrally fused with the reservoir 58 and having a common fluid path 63 therewith.

The mercury column 18 substantially fills the reservoir 56, and extends into and partially fills both the capillary tube 12 and the sleeve 60. The electrolyte 22 substantially fills the reservoir 58, and extends into and partially fills the capillary tube 12, forming an interface 19 in the capillary tube with the mercury column 18. A quantity of gas, which may be air, substantially fills the reservoir 62, preferably at a pressure slightly greater than atmospheric, creating a gas pocket 64 therein. The electrode 34 is integrally fused into the envelope 10 at the reservoir 56, and contacts the mercury column 18. A mercury pool 66 is contained within the reservoir 58 and contacts the electrolyte 22. A terminal 68 is integrally fused into the envelope 10 at the reservoir 58, and contacts a mercury pool electrode 66. It is an important feature in this embodiment that the interior dimensions of the reservoir 58 are sufficiently large and the quantity of mercury 66 sufiiciently great that the surface-area of the interface 65 is large compared to the surface area of the interface 19. This construction yields a non-polarizable electrode so that the undesirable effects of operating the metallic liquid at interface 65 in an anode configuration are substantially reduced, and the efficacy of the electrode to establish the desired potential in the electrolyte is increased. Similar non-polarizable electrodes may be employed, and it is apparent to one skilled in the art that the mercury 66 may readily be substituted by other materials, for example mercurous chloride, in which case a calomel electrode is obtained.

A filter partition 70 is positioned in the fluid path 63 between the reservoir 58 and the reservoir 62 and sub stantially fills the path 63 so that all fluid flow must pass through the filter partition 70. The filter partition is impervious to the electrolyte 22 and completely pervious to the gas contained in the gas pocket 64. A second filter partition 72 is positioned in, and substantially occopies, the fluid path 59 so that all fluid flow must pass through the filter partition 72. The filter partition 72 is impervious to mercury and completely pervious to the electrolyte. The filter partitions 70 and 72 increase the positional stability of the switching device by restricting the motion of the interface 19 to the capillary tube 12, thereby preventing the flow of the mercury or electrolyte to an improper cavity.

An insulating plunger 74 is carried within the sleeve 60 and travels in an axial direction therewithin. The mercury column 18 contacts the insulating plunger 74, which substantially occupies the interior transverse area of the sleeve 60 so that no mercury can by-pass the plunger 74 at the bearing surface between the plunger and the sleeve wall. An insulating spacer 78 seals the open end of the sleeve'60 and carries a pair of spaced electrodes 82 and 84. A cavity 80 is located within the sleeve 60 between the plunger 74 and the spacer 78.

The electrodes 82 and 84 extend through the spacer 78 into the cavity 80. When a suitably low voltage of preferred polarity is impressed across the electrodes 34 and.68 the resultant electrocapillary force causes the mercury column 18 to exert a pressure on the plunger 74 to cause the plunger to move upward, contact, and deflect the electrode 84 at a curved end 85. The electrode 82 is positioned in the cavity 80 so that the deflection of the electrode 84 causes it to contact the electrode 82 to complete an electrical circuit between the electrodes 82 and 84. I

The embodiment shown in FIG. 3 is similar in operation to FIG. 2, but an overlapping contact arrangement is shown. A housing 86 is formed integrally with the sleeve 60. A plurality of spaced electrodes 88, 90, 92, and 94 pass through, and are affixed to the housing 86. The insulating plunger 74 travels longitudinally in the sleeve 60 and is caused to move by the electrocapillary force produced as described in conjunction with FIG. 2. The plunger 74 firstcontacts the electrode 88 and deflects it to contact the electrode 90,"thus completing an electrical circuit between the electrodes 88 and 90. As additional force is exerted on the plunger 74 by the mercury column 18, the plunger moves further outward, causing the electrode 90 to deflect. The electrode 90, through an insulating spacer 96, deflects the electrode 92, which then contacts the electrode 94 to complete an electrical path between the electrodes 92 and 94. When the plunger 74 retracts into the sleeve 60, the electrodes 92 and 94 break contact prior to the electrodes 88 and 90, thus creating an overlapping sequence of operation. It is apparent to a person skilled in the art that the electrodes 88, 90, 92, and 94 may readily be rearranged to provide simultaneous operation.

FIG. 4 illustrates another switching means. A hollow resilient coil 98, which may be glass, is carried within the sleeve 60. One end 97 of the glass coil 98 is joined to the wall of the reservoir 56 with the interior of the reservoir 56 in fluid communication with the cavity of the glass coil 98. The other end 99 of the glass coil 98 is sealed. A pair of spaced electrodes 100 and 102 are mounted by the housing 86 in operative relationship to the glass coil. The mercury column 18 substantially fills the glass coil 98, as well as filling the reservoir 56 and partially filling the capillary tube 12. When a control voltage is applied to the electrodes 34 and 68 as described in conjunction with FIG. 2, the electrocapillary force produced causes the mercury column 18 to exert an internal pressure on the glass coil 98, thereby causing the glass coil to increase in length in the direction of the axis of the sleeve 60. As the glass coil 98 increases in length, it contacts the electrode 100 and causes it to deflect and contact the electrode 102 to complete an electrical circuit between the electrodes 100 and 102.

FIG. is similar in operation to FIG. 4, except that a resilient bellows 110, which preferably is metal, but which may also be glass or rubber or neoprene, replaces the glass coil 98. Similarly to the glass coil 98, the metal bellows 110 is carried within the sleeve 60 and has one end 111 attached to the wall of the reservoir 56 by means preventing the by-pass of fluid between the bellows and the wall. The bellows 110 is in fluid communication with the reservoir 56, and is sealed at its other end 113. When a proper control voltage is applied to the electrodes 34and 68, the resultant electrocapillary force increases the internal pressure of the mercury column 18 to cause the bellows to lengthen in the direction of the axis of the sleeve 60. As the bellows 110 increases in length, it contacts the electrode 100 and deflects it to contact the electrode 102, thus completing an electrical circuit between the electrodes 100 and 102.

In the embodiment shown in FIG. 6, a sleeve 112 is formed integrally with the reservoir 56 and has a common fluid path 113 therewith. The mercury column 18 extends into and partially fills the sleeve 112, as well as substantially filling the reservoir 56 and partially filling the capillary tube 12. An insulating plunger 114 travels longitudinally within the sleeve 112, and is in intimate contact with the mercury column 18. The plunger 114 substantially occupies the transverse area of the housing 112 to prevent by-pass of mercury between the plunger and the housing wall. A pair of electrodes 116 and 118 pass through, and are affixed by, the sleeve 112. A bellows 120, which may, for example, be metal, is contained within the housing 112 and is integral with the electrode 118. An insulating spacer 122 maintains the bellows 120 in a spaced relationship to the electrode 1 16. When a proper voltage is applied to raise the interfacial tension of the mercury column 18, the electrocapillary force causes the plunger 114 to travel upward in the housing 112 and contact the bellows 120. Further motion of the plunger 114 causes the bellows 120 to contact the electrode 116, thereby completing an electrical circuit between the electrodes 116 and 118. i

In the embodiments of the invention shown in FIGS. 2-6, a single capillary tube 12 is provided having reservoirs located at either end. FIG. 7 shows an embodiment of the invention in which the electro-capillary force is generated by a pair of interfaces in parallel. A mercury reservoir 140 and an electrolyte reservoir 142 are provided which are substantially identical to the reservoirs 56 and 58 respectively of FIG. 2; however, it is understood that any of the respective reservoirs in FIGS. 2-6 may readily be substituted. A tube 144, which may, for example, be glass, extends between and connects reservoirs and 142. Extending through the tube 144 are two spaced passageways 146 and 148, each passageway communicating at one end with the interior of reservoir 140 and at the other end with the interior of reservoir 142. The passageways 146 and 148 each duplicate the bore of tube 12 and accordingly each has transverse dimensions which are of capillary magnitude and carries a mercury-electrolyte interface, 150 and 152 for passageways 146 and 148 respectively. It is understood that the embodiment shown in FIG. 7 is merely exemplary, it being clear that any number of capillary passageways may be provided in the tube, and that the relative position of the passageways need not be parallel, but may be oblique, and that the respective lengths of the passageways may vary substantially depending on the path. 7

When a proper control voltage is applied to electrodes 34 and 68 the movement of each of the interfaces 150 and 152 will be approximately the same as the movement experienced for the interface 19 in the figures previously considered. Since interfaces 150 and 152 undergo simultaneous displacement, the total fluid displaced is multiplied by a factor corresponding to the number of passageways, in this case two, over the fluid displaced by a single capillary interface as in the previously considered embodiments. Therefore, the travel of the plunger 74 is approximately twice that experienced previously and the dependability of the switch is accordingly increased.

Another embodiment of an'electrocapillary switch is shown in FIG. 8. As with the switchshown in FIGS.

2-7, a suitable control voltage is applied to the terminals 68 and 154 to cause movement of the interface 156 to the left as shown in FIG. 8. Movement of the interface 156 to the left, also causes globule of mercury 158 to move to the left. Three insulating spherical balls 160, which may be glass, are arranged within the capillary tube in adjacent relation to each other and to the mercury globule 158. The glass balls 160 substantially occupy the interior transverse dimensions of the capillary tube; however, it is understood that the glass balls may be of any diameter smaller than the interior transverse dimensions of the capillary tube provided that the motion of globule 158 is effectively transmitted to globule 162 as next described. Upon movement of the globule 158 to the left, it exerts a pressure on the glass balls 160 which in turn exert pressure to cause the mercury globule 162 to move to-the left and complete an electrical circuit between the electrodes 164 and 166.

FIG. 8 also shows an enclosed gas chamber 168 located to the left of the mercury globule 162. The gas in the chamber is slightly compressed by the globule 162 when no voltage is applied across the electrodes 68 and 154. Upon movement of the interface 156 to the left as above described, the gas in the pocket 168 is further compressed, and upon removal of the voltage, the gas pocket exerts a reactive pressure to restore the mercury globule 162 back to its normal position.

As mentioned above in conjunction with the modes of operation of an electrocapillary switch, a bias voltage may be applied across the metal-electrolyte interface to facilitate the return of the interface to its normal position after removal of a control voltage. FIG. 9

shows a representative embodiment for applying such a bias voltage, it being understood that any of the switch arrangements shown in FIGS. 2-8may be utilized, and that a switch outline similar to FIG. 2 is shown by way of example. In the switch according to FIG. 9, the polarity of application of the control voltage is indicated by the positive and negative signs 170 and 172. A DC bias voltage source 174, which may be a battery, is connected in series with a resistance 176 across the terminals 34 and 68. For a control voltage of approximately one-half volt, the bias voltage is approximately 0.1 volt, and the value of the resistance 176 is approximately lOK ohms. The polarity of the battery 174 is opposite that of the control voltage as indicated "by the positive and negative signs 178 and 180. For a properly selected value of resistance 176 itmay be seen from an analysis of the network that the effect of the bias voltage 174 may be ignored when a control voltage is applied to the terminals 34 and 68. Upon removal 'of the control voltage, the bias voltage 174 becomes effective to apply a reverse potential across the interface to facilitate the return of the interface to the original position.

It is a further feature of the invention that the return of the interface may also be facilitated by permanently installing a resistance 186, which may be in the range of 2K-3K ohms, across the terminals 34 and 68 as shown in FIG. 10. The resistance 186 facilitates the return of the interface to normalby dissipating the counter electromotive force (back e.m.f.) developed when a'control voltage is applied across the terminals 34 and 68, analogously to the resistance braking employed in electric motors, or breaking the closed circuit of an electrolytic primary cell.

The bias voltage 174 may also be applied to terminals 34 and 68 intermittently and without the resistance 176 (FIG. 9) as shown in FIG. 11. The intermittent application enables the bias voltage to cause the interface to return to its original position after removal of the control voltage without interfering with the control voltage during its application. A timer 188 for accomplishing this type of operation is commonly known in the art and is described as having a time delay upon de-energization. Upon application of the control voltage, the timer contacts open and the bias voltage 174 is removed from the terminals 34 and 68. Upon removal of the control voltage a timed contact closes and the bias voltage 174 is applied across terminals 34 and 68 until either the timed contact opens or, alternatively, until the control voltage is reapplied.

While the invention has been described in terms of the above preferred embodiments, it is recognized that others skilled in .the art may apply the novelfeaturejs in a wide variety of combinations and switching arrangements without departing from the spirit and scope of the invention. For example, the hollow glass coil 98 of FIG. 4 may be applied in FIGS. 2, 3, 6, or 7 to actuate the contact means therein contained. Another readily obtained modification of the above embodiments involves substitution of normally-closed contact configurations for the normally-open configurationsshown. A still further modification, for example, is to vary the interior transverse area of the capillary tube 12, within capillary dimensions, whereby the interface between the mercury column 18 and the electrolyte22 moves in a portion of the capillary tube havingasmaller transverse area than that portion carrying the mercury globules, thereby facilitating installing of the electrodes into the envelope. Therefore, the invention is to be construed as including all of the embodiments thereof within the scope of the appended claims.

I claim:

1. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverse interior dimensions;

a metallic liquid contained within said envelope and extending into said tube portion;

an electrolyte contained within said envelope and extending into said tube portion, said metallic liquid and said electrolyte being immiscible in each other and forming a' single interfacein said capillary tube portion;

means for applying an electromotive force across said metallic liquid and said electrolyte effective't o change the interfacial tension of said liquids at said single interface whereby electrocapillary movement of said interface isinduced; and

contact means including a plurality of spaced globules of a third conducting liquid located within said capillary tube portion, a plurality of pairs of spaced electrodes operatively associated with a respective globule of said third electrically conductive'liquid so that said motion of said interface causes each globule of conducting liquid to close an electrical circuit between the respective pair of electrodes, and at least one quantity of gas operatively located between at least one pair of said globules, whereby the globule of said pair of globules which is located farther from said interface actuates an electrical circuit between the respective pair of spaced electrodes at some time subsequentto the time at which the globule of said pair of globules which is located nearer said interface actuates an electrical circuit between the respective pair of spaced electrodes.

2. A liquid-state switching device for electrical circuits, comprising: I

an envelope including a tube-portion having capillary transverse interior dimensions;

a metallic liquid contained within saidenvelope and extending'into said tube portion;

an electrolyte contained within said envelope and extending into said tube portion, said metallic liquid and said electrolyte being immiscible in each other and forming a single interface in said capillary tub means for applying an electromotive force across said metallicliquid and said electrolyte effective to change the interfacial tension between said liquids whereby electrocapillary movement of said single interface is induced;

contact means having at least one movable element for actuatingan electrical circuit; and

translating means for moving said movable element rmponsive to movement of said single interface including a hollow resilient coil closed at one end, the interior of said coil being in fluid communication with said interface, whereby movement of said interface causes said coil to change in length in the axial direction to actuate said contact means.

3. A switching device according to claim 2, wherein said hollow resilient coil is made of glass,

4. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverse interior dimensions;

a metallic liquid contained within said envelope and extending into said tube portion;

an electrolyte contained within said envelope and extending into said tube portion, said metallic liquid and said electrolyte being immiscible in each other and forming a single interface in said capillary tube;

means for applying an electromotive force across said metallic liquid and said electrolyte effective to change the interfacial tension between said liquids whereby electrocapillary movement of said interface is induced;

contact having at least one movable element for ac tuating an electrical circuit and translating means for moving said movable element responsive to movement of said single interface.

5. A switching device according to claim 4 wherein said translating means includes a resilient bellows having one side in fluid communication with said single interface.

6. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverse interior dimensions;

a metallic liquid contained within said envelope and extending into said tube portion;

an electrolyte contained within said envelope and excontact means having at least one movable element 4 for actuating an electrical circuit and translating means for moving said movable element responsive to movement of said single interface including at least one substantially spherical ball made of a insulating material.

7. A switching device according to claim 6, wherein said spherical ball is located within said capillary tube portion, the diameter of said ball being less than said capillary tubes so that said ball may travel longitudinally within said capillary tube responsive to movement of said interface.

8. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverse interior dimensions;

a metallic liquid contained within said envelope and extending into said tube portion;

an electrolyte contained within said envelope and extending into said tube portion, said metallic liquid and said electrolyte being immiscible in each other and having a single interface in said capillary tube;

a. source of electromotive force;

first and second substantially polarization resistant electrodes for applying said electromotive force to and across said metallic liquid and said electrolyte respectively, said second electrode comprising a calomel electrode, whereby the interfacial tension between said liquid and said electrolyte is changed so that electrocapillary movement of said interface is caused; and

contact means having at least one movable element actuated by said motion of said interface.

9. A switching device according to claim 8, wherein said envelope includes a reservoir, and said electrolyte is contained within said reservoir and extends into said capillary tube, and wherein said second electrode has a second interface in said reservoir with said electrolyte, the surface area of said second interface being large with respect to the first interface between said electrolyte and said metallic liquid, whereby a substantially non-polari2able electrode is provided.

10. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverse and interior dimensions;

a metallic liquid contained within said envelope and extending into said tube portion;

an electrolyte contained within said envelope and extending into said tube portion, said metallic liquid and said electrolyte being immiscible with each other and forming a single interface in said capillary tube;

means for applying a first electromotive force across said metallic liquid and said electrolyte effective to change the interfacial tension between said metallic liquid and said electrolyte and cause movement of said single interface; contact means having at least one movable element actuated by said motion of said interface; and

means efiective upon removal of said first electromotive force for causing return movement of said interface to an initial position occupied prior to application of said first electromotive force, whereby the response timeof the switching device is improved.

11. A switching device according to claim 10, wherein said means for causing return movement of said interface includes means for applying a second electromotive force across said metallic liquid and said electrolyte to cause movement in a direction opposite to said first electromotive force.

12. A switching device according to claim 11, wherein said means for causing return movement of said interface further includes resistance means in series with said means for applying a second electromotive force of sufficiently high value that the electrocapillary effect due to said second electromotive force is negligible compared to the electrocapillary effect due to said first electromotive force when both said first electromotive force means and said second electromotive force means are operatively connected across said interface.

13. A switching device according to claim 11, wherein said means, for applying a second electromotive force across'said first and second liquids includes an electrical control circuit operatively connected to interlock said second electromotive force responsive to ILL application of said first electromotive force and to apply said second electromotive force for a predetermined length of time responsive to removal of said first electromotive force.

14. A switching device according to claim 10, wherein said means for causingreturn movement of said interface includes a resistance operatively connected across said first and second electrodes.

15. A switching device according to claim 10, wherein said means for causing return movement of said interface includes at least one quantity of gas contained within said envelope and operatively associated with said interface to change volume responsive to movement of said interface caused by said first electromotive force means and to exert a reaction force on said interface effective to cause said interface to return to said initial position upon removal of said first electromotive force applying means.

16. A switching device according to claim 15, wherein said quantity of gas is initially at a pressure greater than atmospheric, and wherein movement of said interface responsive to said first electromotiveforce means compresses said quantity of gas.

17. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverse interior dimensions;

a first conducting liquid containedwithin said envelope and extending into said tube portion;

a second conducting liquid contained within said envelope and extending into said tube portion, said first and second liquids being immiscible in each other and forming a single interface in said capillary tube;

means for applying an electromotive force across said first and second liquids effective tochange the interfacial tension between said first and second liquids and cause movement of said single interface and said first and second liquids;

contact means having at least one movable element actuated by said motion of said interface; and

filter means operatively associated with said first and second liquids for restricting said motion of said interface to said capillary tube.

18. A switching device according to claim 17, wherein said envelope includes first and second reservoirs, said first reservoir is joined with said capillary tube at one end thereof and has a common fluid path therewith, said electrolyte extends into and partially fills said first reservoir, and wherein said second reservoir is joined with said first reservoir and has a common fluid path therewith, and further comprising a gas filling said second reservoir, a first filter partition mounted in the fluid path between said capillary tube and said first reservoir and substantially separating said capillary tube and said first reservoir from'each other, said filter partition being pervious to said electrolyte and impervious to said metallic liquid, and a second filter partition mounted in the fluid path between said first reservoir and said second reservoir and substantially separating said first reservoir and said second reservoir from each other, said second filter partition being pervious to said gas and impervious to said electrolyte.

19. A liquid-state switching device for electrical cira e l o p e ii cluding a plurality of passageways having capillary transverse interior dimensions;

a first conducting liquid contained within said envelope and extending into the respective passageways; v

a second conducting liquid contained within said envelope and extending into the respective passageways, said first and second conducting liquids being immiscible with each other and forming a single interface with each other in each of said plurality of passageways respectively;

vmeans for applying an electromotive force across said first and second liquids effective to'change the interfacial tension between said first and second liquids at each interface in the respective passageways and cause movement of each said interface, whereby motion of said first and second liquids is caused responsive to motion of said plurality of said interfaces; and

contact means having at least one movable element actuated by said motion of said first and second liquids.

20. A switching device according to claim 19, wherein each said capillary passageway having one and only one interface between said first 'and said second liquids.

21. A switching device according to claim 19 further comprising filter means operatively associated with said first and second liquids for restricting said motion of said interfaceto said capillary tube.

22. A liquid-state switching'device for electrical circuits, comprising:

an envelopeincluding a tube portion having capillary transverse and interior dimensions; a metallic liquid contained within said envelope and extending into said tube portion; an electrolyte contained within said envelope and extending into said tube portion, said metallic liquid and said electrolyte being immiscible with each other and forming a single interface in said capillary tube; means for applying a first electromotive force across said metallic liquid and said electrolyte effective to change the interfacial tension between said metallic liquid and said electrolyte and cause movement of said single interface;

switching circuit means having portions located within said envelope; and

means responsive to the movement of said interface for changing the state of said switching circuit means coacting with the portions of the switching means within said envelope.

23. A switching device as in claim 22 further comprising a source of first electromotive force, said electromotive force applied across said metallic liquid and said electrolyte so that the electrolyte is positive with respect to said metallic liquid.

24. A switching device as in claim 23 wherein said metallic liquid is mercury.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5472577 *Jun 30, 1994Dec 5, 1995Iowa State University Research FoundationFluid pumping system based on electrochemically-induced surface tension changes
Classifications
U.S. Classification200/192, 200/211, 200/194
International ClassificationH01H29/00
Cooperative ClassificationH01H29/00
European ClassificationH01H29/00