US3184566A - Liquid displacement float switch - Google Patents

Description

May 18, 1965 E. W. KLEINPETER LIQUID DISPLACEMENT FLOAT SWITCH Filed March 30, 1961 United States Patent 0 3,184,566 LIQUID DISPLACEMENT FLOAT SWITCH Edward W. Kleinpeter, Baton Rouge, La., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia Filed Mar. 30, 1961, Scr. No. 99,427 1 Claim. (Cl. 200-112) This invention relates to electrical switch apparatus. More particularly, the invention relates to new and improved electrical switching apparatus for currents of high amplitude, and at low voltages.

It has long been necessary to provide make and break switch contacts for high amplitude electrical currents, particularly in the electrometallurgical or electrochemical industry. Multiple blade knife switches are frequently used, particularly for shunting service, using a plurality of bus bar sections or the like as the switch contact elements. However, such types of switch apparatus is, in many respects, unsatisfactory in the process industries, wherein the apparatus must be employed in atmospheres which include corrosive components resulting from process operations, or a high degree of dirt, humidity and heat. Under these circumstances, the contact services corrode or oxidize, and it becomes quite difficult to establish a closed circuit with minimum resistance drop at the actual junctions. Hence, when dealing with current flows of the order of amplitude of twenty to forty thousand amper-es, for example, appreciable power is lost at such points, during operations, and in addition, the resistance at the actual junctions causes temperature increases which aggravate the corrosion and oxidation problem. Hence, heretofore there has not been a highly effective switch gear for such types of installations.

The object of the present invention is to provide a new and improved switch gear for high amplitude electrical current control, and particularly when the circuit is to be closed or opened only under low voltage conditions. More particularly, an object is to provide such an apparatus which is not subject to degradation by surrounding atmospheres or corroding or oxidizing gases.

In all forms of the invention, a receptacle is provided, which is capable of being entirely sealed oif from the atmosphere, to prevent access of corrosive, moist, or oxidizing gases. The electrical conductor, or conductors between which connection is to be made or broken, project into the interior of the said receptacle or container, and have terminal surfaces or termini which are in vertically spaced apart relationship. By spaced apart relationship is meant that there is a gap, in vertical orientation, between the termini .of these conduit branches. As will be described hereinafter, the precise configuration of the gap between the termini can vary, but in general, it will be seen that the configuration must necessarily be capable of being filled or voided, that is by movement of a liquid by vertical displacement, as shown more fully below.

Also positioned within the said container is a supply of normally liquid metal, having a high and satisfactory electrical conductivity, which supply is sufiicient to occupy only a portion of the total space defined by the receptacle or container. Lastly, an essential feature of the apparatus is means whereby the liquid level of said liquid metal is alterable at will to a degree sufiicient to establish a continuous contact, electrically, between the two conductor 3,184,566 Patented May 18, 1965 "ice termini, or to entirely dis-establish such a contact. Various means for providing said adjustment in liquid surplus level can be provided, as described below. It will be understood that the receptacle construction, or other elements of the construction include the necessary means to prevent short circuiting of the conductors through the walls of the receptacle or by the various apperturances thereto.

The details of the invention will be more readily understood from the following description and from the figure, which is a schematic representation of a typical and highly preferred embodiment of the invention.

Referring to the figure, this illustrates an embodiment wherein the displacing element, for altering the liquid level surface of the liquid within the receptacle, is highly efficient in achieving a rapid change therein, as desired, and further, the means for causing movement of a displacing device is effective and simple, responsive to outside signals without mechanical linkage.

Referring to the figure, a container 11 is provided, which consists of a bottom portion 12 and a cover portion 13. Projecting from the exterior of the container 11 to the interior thereof are conductor segments 31, 32 which pass through openings in the bottom portion 12 and the cover portion 13 respectively. The junction point of the conductors 3 1, 32 with the walls of the container 11 are tightly sealed for fluid tightness by appropriate sealing means 18, 19 or g-asketing means. These conduct-or segment-s terminate in accurately finished or ground surfaces or termini 31 32 in this embodiment being in precisely aligned, ventically spaced apart, parallel relationship A body of liquid metal 33 is provided in the container 11, this being, typically, and preferred, a low melting or eutectic mixture of sodium and potassium. For example, the eutectic mixture of 78 atom percent potassium with sodium has a melting point of about l2 C. Normally, the surface of this supply of liquid metal 33 is below the terminus surface 32,, of the conductor 32, or at least is not as high as the terminal surface 31,, of the upper conductor 31.

A displacing element 21 is provided, normally positioned slightly above or adjacent to the surface of the liquid metal 33, and having a volume at least equal to or greater than the void space between the termini 31,, 32,, of the conductors 31, 32. The displacing element 21 can be a solid block of metal, or a hollow chamber, and it is suspended or positioned in place by a guide rod 22, which is per-ferably of an insulating material such as a rod coated with a phenolic resin.

A nozzle 23 is provided as a projecting portion of the cover element 13 of the container 11. The nozzle terminates in or is connected tightly to a bellows 24, which is closed to the external atmosphere by a cover plate 25.

The insulating rod 22, which supports the displacing member 21, extends downwardly therefrom, also, and is affixed to a terminal portion or member 26, which is made of a ferromagnetic material. Surrounding the member 26 is a sump member 28 which is a downward extension of the bottom portion 12 of the container 11. The sump 28 is of relatively small diameter, and is encircled by an electrical coil 27, whereby an electromagnetic field can be generated tending to move the ferromagnetic member 26 into the confines of said coil 2'7, upon closure of the switch member 29 and passage of current from a source not shown.

The top member 13 of the receptacle or container 11 is tightly affixed to the flanged portion of the bottom member 12 thereof. Threaded fastenings 14, 15 are employed to provide the desired gas or fluid tight seal of these two parts, a gasketing material 16 being provided between the two portions, the gasket material 16 being of an insulating nature. It will be clear that to avoid short circuiting between the conductor elements 31, 32, that full insulation, electrically, must be provided between the top and bottom members 13, 12, and hence insulating washers 15 14 and insulating sleeves 1'7, 18 are provided.

In operation of the embodiment of the figure, it is clear that in the position as shown, there will be no electrical contact between the conductors 31, 32 Upon closure of the switch 29 and energizing the coil 27, ferromagnetic element 26 is pulled downwardly into the coil, thereby moving the displacement member 21 a corresponding distance into the liquid 33, causing the upper surface thereof to rise further past the terminus 32 and promptly thereafter to make contact with the terminus 3%, thus closing the circuit. The downward movement of the displacing element 21 is accompanied by a compression of the bellows or spring member 24. Upon opening of the control or energizing circuit which energizes the coil 27, the spring action of the bellows 2d raises the displacing element 21, dropping the level of the liquid 33, and breaking the principal circuit through the conductors 31, 32. The displacing member is of sufiicient volume to, of course, displace a volume sufficient to cause the desired rise of liquid level in the entire chamber.

Normally, and particularly in the case of a strongly chemically reactive liquid alloy such as the sodium-potassium eutectic, the vapor space 34 of the space defined by the container 11 is filled with an entirely inert gas such as argon or nitrogen. In certain embodiments, duct work or nozzles are provided so that a stream of gas can be passed through the vapor space, or occasionally the vapor space can be purged with fresh, dry, inert gas.

It will be apparent to one skilled in the art that appreciable variation in the structure can be provided to give various other embodiments, which nevertheless are fully within the scope of the invention. For example, the conductor elements, instead of being single conductor elements of rectangular cross section as illustrated, can be a plurality of parallel bars, and in some cases the actual terminus of the separate sets of said conductor bars will be inter-meshing similar to intermeshing fingers. It will be appreciated, of course, that even in this instance a gap is provided between the surfaces of the terminal ends of u the conductor portions, so that as the level of the conductive metal liquid surface drops that a void or gas space is created between the terminal surfaces of the conductor elements.

The degree of vertical displacement between the terminal surfaces of the electrical conductors is not highly critical. However, the vertical displacement is subject to the requirement that the vapor space established between the terminal surfaces, when the switch is in the open position, is not so limited that there is the possibility of arcing at the service voltages involved. As the apparatus is intended for service at only nominal voltages, e.g., of the order of one to about 10 volts, vertical separation of the order of /z to 2 inches is quite satisfactory. The lateral amplitude of the flow path between the termini, in which current flows through the liquid metal conductor when the switch is closed, is also not critical. The identity of the liquid metal and its electrical properties, particularly conductivity, does affect the necessary magnitude. Thus, when the eutectic alloy of sodium and potassium is employed, the transverse area of the current transmission path between the termini can be ordinarily from one to about three times the transverse area of the main portions of the conductors 31, 32. On the other hand, when a liquid metal with low conductivity, such as mercury, is

used, deliberate extension of flow pattern area is desirable to prevent overheating in the liquid metal between the tenmini. Such extension of the transverse area of the current path can be achieved, as already mentioned, by arranging the conductors as a plurality of element in intermeshing fashion. Alternatively, the conductor elements can include segments extending laterally in parallel planes to create an extended path between the terminals thereof.

It will be apparent in the specific embodiment described above, that the location of the switch 29 for actuating the closure elements, can be at a point remotely situated from the apparatus, hence, the switch can be used to establish a closed circuit by closure of the switch 29 at a remote point. It will also be apparent that the embodiment described is susceptible of mechanical closure by manually depressing the top of the bellows element 25, to depress the displacing element 21, and cause the rise of the liquid metal 33 in the manner already described.

In preferred embodiments a supplemental, locking mechanism is provided, whereby, once the circuit is closed, through the actuation of the coil 27 as already described, the failure of said circuit will not automatically result in the rise of the displacing element and the opening of the circuit. Such locking means can consist of a latch means for retaining the top of the bellows element 25 in a depressed position, corresponding to the position when the switch is closed, which latching device is capable of being disengaged by manual release, or by associated separate actuating means.

With respect to the displacement member employed in all forms of the apparatus, it is not essential that the displacement element be a solely vertically movable element such as is specifically illustrated in the figure. Alternatively, a circle-segmental chamber, arranged to be pivoted at a point adjacent the wall of the container, by the point of the segment, and actuated by a lever projecting through appropriate sealing means through the wall of the chamber or container, can be employed to cause rapid and effective movement of the surface of the conductive liquid up, or down, as the case may be and as is desired.

When the displacement member is actuated by an electromagnetic coil as is specifically illustrated, it will be understood that the container in which the ferromagnetic element is moved, is necessarily of a non-magnetic material, which can be a cuprous material, or, for example, a stainless steel.

Instead of the sodium potassium eutectic alloy which is employed in numerous embodiments of the process, other low melting metallic materials can be readily employed, for example, gallium metal or alloys thereof, or if desired mercury, although the quantity of mercury required for a large switch means is relatively high. The materials of construction of the chamber, other than as noted above, is ordinarily of appropriate ferrous metal.

Having fully described the apparatus of the invention and its mode of construction, what is claimed is:

An electrical switch comprising:

(1) container means being vapor proof and further comprising a bottom portion and a top portion when oriented vertically in its operable position, said bottom portion containing a liquid alloy consisting essentially of sodium and potassium, and the space thereabove being filled with an inert medium,

(2) said top portion further comprising nozzle means mounted so that its longitudinal axis extends in a vertical direction,

(3) said bottom portion further comprising a sump member extending in a vertical direction coaxially with said top portion nozzle means,

(4) conductor means further comprising at least two segments, one of said segments constituting a positive terminal and the other of said segments constituting a negative terminal, said segments projecting into said container means and being attached thereto in a fixed vertical spaced relationship so as to provide. a space between the ends of said segments,

5 (5) bellow means mounted upon said top portion nozzle means,

(6) fluid displacing means positioned within said container means, said displacing means further comprising a guide rod operably oriented in a vertical direction with one of its ends extending into and conneoted to said bellow means mounted upon said top portion nozzle means, the other of its ends extending into said bottom portion sump member, the longitudinal axis of said guide rod being coaxial with the axes of said nozzle and sump,

(7) said guide rod fuurther comprising a ferro-magnetic member aflixed to that end extending into said sump member, and

(8) electrical coil means positioned relative to said sump member such that upon being energized said ferromagnetic member by virtue of said bellow means is caused to move in a downward direction easeee whereby said dis-placing means is immersed in said liquid conductor material so as to raise the level thereof and cause it to fill the space between the ends of said segments and establish continuity therebetween.

References filited by the Examiner UNITED STATES PATENTS ROBERT K. SCHAEFER, Acting Primary Examiner.

RICHARD M. WOOD, BERNARD R. GILHEANY,

Examiners.

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