US3363205A - Mercury switch - Google Patents

Description

Jan. 9, 1968 R. c. BEcK 3,363,205

MERCURY SWITCH Filed April 26, 1966 ON POSITION I OFF POSITION -INVENTOR.

ROBERT C. BEGK United States Patent 3,3633% MERCURY SWITCH Robert C. Beck, 412 Burkewood Drive, Winst0n-Salem,N.C. 27104 Filed Apr. 26, 1966, Ser. No. 545,313 Claims. (Cl. 335-52) ABSTRACT OF THE DISCLOSURE A magnetically actuated mercury switch installable in any position to energize and interrupt circuit continuity. The switch functions by the selective mating and separating of a pair of complementary tubular insulators, one carried by a movable plunger and the other positioned about one of the two conductors which establish electrical continuity when the switch is closed.

Background, brief summary and objectives of the invention The majority of prior art mercury relays and switches are of the displacer type wherein a mass of mercury is displaced in order to establish contact and circuit continuity between two spaced electrodes. In these switches the conducting path between the spaced electrodes is either normally open or normally closed depending upon the arrangement of standard parts. Switches such as those disclosed in United States Letters Patent Nos. 3,128,358, 3,141,940 and 3,166,654 are representative of those prior art switches utilizing a displacer operation to make or break continuity between prepositioned electrodes whether that displacer, operation be caused by electromagnetic operation or other means. An obvious limitation of the displacer type operation whereupon conductivity depends upon the level of the contained liquid conductor is that the switch can only be operative when placed in a particularly aligned position so that upon displacement of the liquid conductor elevating device, a circuit is completed between the two electrodes.

These limitations and other disadvantages of conventional mercury switches are overcome by the present invention in which there is provided a mercury switch formed by constructing a housing between the terminal ends of two conductors and providing a slidable plunger completely surrounded with mercury in the interior of the housing which is displaced selectively by movement of a permanent magnet or electromagnet. An electrode or conductor sliver extends from one of the prepositioned conductors and is selectively isolated and exposed to the mercury filled interior of the housing by movement of the sli'dably retained plunger so that when the electrode is exposed to the mercury, a circuit is completed and the switch assumes an on, energized or actuated position. Conversely, when the electrode is completely surrounded by interior insulating means within the housing, continuity through the surrounding mercury is interrupted, and the switch assumes a deactivated, de-energized or off position.

From the above discussion it is apparent that an object of this invention is to provide a mercury switch which will complete an electric circuit by displacement of a plunger surrounded by a liquid conductor within a switch housing.

Another object of this invention is to eliminate the necessity of a level installation of the mercury switch by providing a switch housing that is completely filled with a quantity of mercury so that the liquid conductor level has no bearing upon the operation of the switch and its components.

A further object of the present invention is to provide a normally open or normally closed mercury relay which is of simple construction and in which there is a. minimum wear of operating components over a long period of use because of the absence of any appreciable arcing when the switch is opened or closed.

Yet another object of this invention is to provide a mercury relay utilizing the surface tension of the housing contained quantity of mercury to separate that mercury forcibly and interrupt circuit continuity.

A further object of this invention is to provide a mercury relay in which the mercury separating element requires only a minimum insulation and a simple configuration.

These and other objects of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there is shown and described a preferred embodiment of the invention; however, it is to be understood that this embodiment is not intended to be exhaustive nor limiting of the invention but is given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

Figure description FIG. 1 is a perspective, sectional and fragmentary view of the preferred embodiment of a mercury filled magnetically operated switch pictured in the on or activated position,

FIG. 2 is a longitudinal, cross-sectional and fragmentary view of the preferred embodiment of a mercury filled magnetically operated switch illustrating the switch in the off or deactivated position.

Detailed description Referring now to the figures and particularly to FIG. 1, a normally closed mercury switch or relay according to the invention is shown generally at 10 having a housing generally designated 12 which may be of glass, plastic, nylon or other suitable non-conducting materials. A pair of conductors 14 and 16 are connected within the substantially hollow, tubular and non-conducting housing 12, having a wall 17 of thickness suficient to provide strength and rigidity, and these conductors provide a path of current flow in an electric circuit when relay 10 is in the energized or closed position. A plunger 18 is slidably retained within the confines of housing 12 and is movable between two positions which are defined by features to be described subsequently.

Extending from conductor 16 is a conductor sliver or electrode 20 essentially rod-like in configuration which N projects within housing 12 for a distance equal to atleast one-half that chambers length. Also embedded within conductor 16 and surrounding electrode 20 is a glass insulator 22 which extends into housing 12 a portion of the way along the length of the electrode 20, the inwardly extending edge 24 of insulator 22 remaining open to allow free passage of mercury 26 therethrough upon operation of the relay components. The end 28 of conductor 16 is suitably sealed in a well-known manner by epoxy resin 30 or other suitable and similar materials.

Plunger 18 retains an insulator 32 substantially identical in cross-sectional size and length to insulator 22 which extends longitudinally of housing 12 along an axis coinciding with the axis of insulator 22. The outwardly extending end 34 of insulator 32 is also open to permit the selective free flow of mercury 26 therethrough which will be subsequently described. The other end 36 of in sulator 32 is sealed by an epoxy resin 38 or a similarly suitable material to preclude conductivity between mercury contained within insulator 32 and the body of plunger 18.

Surrounding and suitably afiixed to housing 12 is a stop or limiting device 40 which is preferably formed of a band of magnetically sensitive material particularly positioned to position plunger 18 and thus cause relay 10 to assume the off or unactivated position. At the pposite end of housing 12 there is positioned asecond stop or limiting element 42 of similar construction which is also magnetically sensitive that positions plunger 18 so as to place relay 1G in the on or activated position (FIG. 1).

A plunger displacing device 44 surrounds housing 12 in a manner so as to operably displace plunger 18 and its carried insulator 32 within housing 12 upon preselected movement. This displacing element usually takes the form of an electromagnetic energizing coil which surrounds a portion of the housing and which is energizable to urge plunger 18 selectively between stops 40 and 42. The magnetic field associated with device 44 when its coil is energized controls and holds plunger 18 therein so that it will be responsive to the movement of element 44 outside housing 12 in a precise manner. Additionally, since stops 40 and 42 are magnetically sensitive, the displacement of device 44 will be in an abrupt or sharp manner since each of the stops which are being approached by the device 44 have an aflinity to that device by virtue of its magnetic field and thus the switching is accomplished with a clean snap or abrupt movement.

Plunger 18 has been found to slide easily within housing 12 though that housing is filled with a quantity of mercury 26 when one or more of the arcuate sides 45 of the plunger are planed to produce a flat surface 46. Thus mercury 26 can flow down along flat side 46 since some clearance remains between that side and the surrounding wall 17 of housing 12.

Relay is operated by displacing electromagnet 44 to either the on position as shown in FIG. 1 or the off position as illustrated in FIG. 2. When the switch 1 3 is initially examined in the energized or on position as shown in FIG. 1, note that continuity is achieved by tracinga path from conductor 16 through electrode 26 out through the liquid conductor 26 and along fiat wall 46 or through plunger 18 on to conductor 14. The particular feature allowing operation and conductivity of this switch is the separation of insulators 22 and 32 so that the quantity of mercury 26 can act as a conductor from electrode 20.

When relay 10 is shifted to the off or deactivated position as shown in FIG. 2, displacement of magnet 44 in a particular direction (see arrow) will advance insulators 22 and 32 toward each other along their common longitudinal axis so that they eventually become mated and joined to form a substantially continuous tube surrounding, insulating and isolating electrode from the liquid conductor 26 outside the walls of insulators 22 and 32 but within the confines of housing 12. The switch operation in breaking continuity utilizes the natural property of the mercury surface tension since the application of a force against a globule of mercury will cause it to simply separate into two separate quantities rather than splatter or run as would be the case should the substance be a liquid of a different composition. The external tension of the surface of the mercury has a tendency to restrict that substance into its smallest possible volume, i.e., a droplet or globule. Thus when the edges 24 and 3d of insulators 22 and 32 meet to form a single chamber, the force exerted by these edges against each other causes a neat and complete separation of the mercury 26 so that there is no path of conductivity between electrode 20 and conductor 14. Since the plunger 18 is held captive by the force field of the magnet or plunger actuating device 44, all movements of that device are duplicated by the plunger, and this allows the unit to be completely sealed and activated simply by moving the magnet to either activate or deactivate the relay.

Obviously, relay 10 may be operated in any position equally well and is not affected by a liquid conductor level as are most switches of this nature; and it is contemplated that the actuating electromagnet 44 may be in an exterior form of any known and conventional unit such as a toggle switch, push button assembly or double throw switching apparatus.

The insulating resin or material 28 and .36 used along the end of conductor 16 and within plunger 18 serves to establish a completely isolated chamber 48. It has been found advantageous in very small switch construction to form housing 12 from a nylon tube since this particular material can withstand extraordinary wear and will produce a switch of extremely long life.

Since the operating principles of my invention are founded uponthe adaptation of the natural surface tension of conducting fluid, no appreciable arcing occurs when relay 10 is switched from the on to the off position. As insulators 22 and 32 cooperatively mate to form an isolating chamber 48, circuit continuity in interrupted at the point of separation of mercury located on either side of these insulators and thus any arcing that occurs is remote from electrode 20. Thus the switch is of an extremely durable nature and can be expected to function indefinitely without noticeable wear or burning particularly in the extinguishing area.

Obviously this particular construction of a magnetically operated mercury switch can be well adapted to electrical circuits of any size and capacity since the principles of operation are equally applicable to all suc varied arrangements.

It is understood that the form of my invention is embodied in the exemplary illustrations as herewith shown and described which are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangements of the parts including the housing, plunger, plunger actuating means and electrode may be resorted to without departing from the spirit of my invention, which is limited only by the following claims.

What is claimed is:

1. A magnetically operated mercury switch comprising: a pair of electrical conductors; a housing joining said conductors; a plunger slidably movable Within said housing; a quantity of liquid mercury substantially completely filling said plunger-containing housing; means to displace said plunger within said housing; and insulator means carried by said plunger operable to establish and interrupt electrical continuity between said conductors upon sclective actuation of said plunger displacing means.

2. A magnetically operated mercury switch according to claim 1, one of said conductors having an electrode extending therefrom, projecting within said housing and cooperating with said plunger, said insulator means additionally carried by one of said conductors.

3. A magnetically operated mercury switch according to claim 1, said housing being substantially tubular, hollow and of a non-conducting material, said insulator means separating to establish electrical continuity between said conductors and mating contiguously to interrupt electrical continuity between said conductors.

4. A magnetically operated mercury switch according to claim 1, said plunger displacing means including an electromagnetic energizing coil surrounding a portion of said housing and energizable to urge selectively said plunger between proximal and distal limits.

5. A magnetically operated mercury switch according to claim 2, said housing being substantially tubular, hollow and of a non-conducting material.

6. A magnetically operated mercury switch according V to claim 6, said insulator means comprising first and sec- 7 0nd mating tubular insulators, said first insulator held by one of said conductors and substantially shrouding a portion of said electrode and said second insulator retained by said plunger and alignable with said first insulator upon displacement of said plunger to said proximal limit.

8. A magnetically operated mercury switch according to claim 7, said liquid mercury quantity being shiftable within said housing to establish continuity between said conductor pair when said insulators are separated and to interrupt said conductor pair continuity when said insulators are mated and surface tension of the mercury quantity causes the separation thereof Within the housmg.

9. A magnetically operated mercury switch according to claim 8, said housing being substantially tubular, hollow and of a non-conducting material.

10. A magnetically operated mercury switch according to claim 9, said plunger displacing means including an electromagnetic energizing coil surrounding a portion of said housing and energizable to displace selectively said plunger, said plunger formed of a solid magnetically attractive material, said mercury quantity shiftable within said housing along the exterior of said plunger when said plunger is displaced by said plunger displacing means.

References Cited UNITED STATES PATENTS 3,133,998 5/1964 Horowitz 335-52 3,308,405 3/1967 Hurvitz 335-52 BERNARD A. GILHEANY, Primary Examiner. H. BROOME, Assistant Examiner.

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