US2911500A - Mercury switches - Google Patents

Description

NOV- 3, 1959 w. G. GusTAFsoN ETAL 2,911,500

MERCURY SWITCHES OriginalA Filed Feb. 18, 1955 3 Sheets-Sheet l w. c. GUSTAFSON WVU/Tof"S H. c. HAM/50N BW C. MW

ATTORNEV Nov. 3, 1959 w. G. GusTAFsoN ET'AL MERCURY SWITCHES original Filed Feb. 18, 1955 3 Sheets-Sheet 2 w. c. GUSTA/"50N NVENTS H. c. HAM/50N rem C.

ATTORNEY Nov. 3, 1959 w. G. GUs'rAFsoN ET AL 2,911,500

MERCURY SWITCHES 3 Sheets-Sheet 5 Original Filed Feb. 18, 1955 W G. GUSTFSON H. C. HARP/SON /NVENTORS ATTORNEY United States Patent Office Patented Nov. 3, 1959 2,911,500 MERCURY SWITCHES 5 f Walter G. Gustafson, New York, and Henry C. Harrison,

Port Washington, N.Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N.Y;, a corporation 4of New York Original application February 18, 19'55, Serial No. 489,046, now Patent N0..2,837,612, dated June 3, 1958.

' Divided and this application October 16, 1957, Serial achim. (c1. zoo-112) This invention relates to circuit controlling devices and more particularly to such devices ofthe type commonly referred to as mercury switches. 'This application is a division of application vSerial No. 489,046, led February 18, 1955, by Walter G. Gustafson and Henry C. Harri- `son (now Patent No. 2,837,612, dated June 3, 1958) in which application are claimed certain features of a mercury contact switch.

Mercury switches comprise, in general, a pair of contacts and a body of mercury, one or both of the contacts or the mercury. being movable to establish a conductive path through these three elements or, conversely, to open such path. Heretofore, primarily because of the uid character of mercury at the temperatures at which the switches usually are utilized, i-t was necessary that the switches be mounted or operated in aparticular position. Also, in such devices of the class wherein one or both of the contacts lare movable to effect closure or opening of the conductive path or circuit, relatively large power eX- penditure has been required to effect operation. Further, in devicesl of this class, chatter uopn making or breaking has been a problem. In addition, and thishas L been of special moment in cases where the switches have .power requisite for operation of such switches, to mini- Amizechatter and to reducethe' voltages developed in circuits including an inductive load, upon opening of 'the circuit.

Additional objects of this invention are to facilitate the fabrication of such switches, to simplify the structure thereof and to reduce the size of' circuit controlling devices .capable of performing multiple functions, for example, make and break of .plural circuits` or transfer.

In one illustrative embodiment of this invention, a

circuit controlling device comprises a'fpair of terminals,

a body of mercury coupled to. one ofthe terminals and an armature connected to the other terminal and actuable to engage with or disengage from the mercury body.

VIn accordance with one `featureof this invention, the

mercury body is confined or localized within a container having therein an aperture through which a contact attached to the armaturemay pass, the container being `constructed and Varranged 'so that irrespective of the position of the' device the mercury remains in operative rela tion with respect'to the contact.

More specifically, in Iaccordance. with this'feature of the invention, the inner wall of the housing includes a portion opposite the contact, which is wet readily by 'mercury, kand the remaining portions are of a material which d oes not wet'` readily. In effect, the mercury adheres to; the readily wettable portion and is not displaceable easily by jarring or even inversion of the container.

In `accordance with another feature of this invention, the aforementioned wettable portion has thereadjacent an annular member adapted to accommodate theA contact and defining a restricted passageway within the container. The Contact, upon actuation to engage the mercury, forces some of the latter through the passageway, whereby a resistive damping of the armature-contact motion is realized.

In accordance with still another feature of thisinvention, vibrational energy dissipative elements are provided for engaging the armature when it operates to disengage the contact from the mercury.

In accordan'ce'with a further feature of this invention, the armature and container are mounted respectively by a pair of substantially parallel magnetic members, the varmature being positioned between the two members and having one end lixed to onemember and its other end free. Actuation of the armature is effected, for example by a signal coil encompassing both the members, by mag-- netization of the members such that one attracts and the other repels the' armature, whereby high sensitivity is real-ized.

In accordance with a still further feature of this invention, the contact and container are correlated toy provide a small and constant gap 'therebetween fduring actuation ofthe contact, whereby the voltage induced with an inductive load in the circuit being controlled is minimized.

In accordance with another featureof this invention, the contactcomprises a portion readily wet by mercury,

' extending froma body which is not readily wet, the ex- 'comitantly or to effect transferbetween` circuits.

tending portion beingat the'end toward the body of mercury. Thus, at least after a single operatiomwhereby theextending portionis wetby mercury, on a make the initial contact is between mercury and mercury, and

hence a quick and low resistanceclosure is attained. Be

cause of the non-wetting character of the contact body, substantial resistance to immersion of the'contact is developed. Hence, a stop is provided upon motion of the con-tact. Further, because of the non-wettingcharactervisftic noted, the force necessary to produce af break, i.e.,

to disengage the contact from the'mercury, is small.'

Theinvention may be embodied in switches for performing a variety of different functions, such as to make or break circuits, tocontrol a plurality of circuits con- Further, one or morernagnets may be' associated with the armature lactuating system to provide polarized operation',o r the armature may be operated by electrostatic means. i' v The inventionand the features thereof will be understood more clearly and fully from the following detailed description withreference to the accompanying drawings, in which:

. j Fig. 1 is a longitudinal view of a mercury switch with the envelope broken away to illustrate one `embodiment of the invention; 1 Fig. 2 is a sectional ViewV taken along the line 2 2 of the switch in Fig. 1;

Fig.' y3 is an exploded perspective view showing the asi sembly of ar container for the body of mercury;

, rainer when the 'switch is'fullyclosedg.

Fig. 4 yis a cross sectioned view of the mercury-.container when the switch is in a fully open position; f

Fig. `5 iis a cross-.sectioned view of the mercury con- Figs. 6' .andi comprise-longitudinaiviews of two mdiaway; j l

Fig. 8V is a longitudinalrviewof another modification 70.* lcations ofthe device with the envelopes thereof broken .made of vitreous material such as glass.

of the device with the armature in a normally closed position; p

Fig. 9 is a perspectiveview of a transfer switch embodying the features of the invention; and s Fig. 10 is an enlarged side view of the tubular electrode shown in Fig. 9, illustrating'the means used to support the armature. v

Referring to Fig. 1 of the drawings, there is shown a .preferred embodiment'of the invention. The elements of the mercury switch are enclosed in an` envelope 11 In order to suppress contact arcing, the envelope maybe filled with laninert gas such as hydrogen, although this is not yessential for operation of the switch. Inserted in the envelope 11 are two electrodes 12 and 13 which comprise the contact terminals. These electrodes may be formed of any suitable material of high electrical conductivity, but

inasmuch -as the switch is operated byl an external magnetic force it is important that the electrodes be made of magnetic material. `In the specific embodiment shown `in Fig. l, the electrode 12 is tubular in shape, thereby facilitating fabrication since both the mercury and the inert gasmay be .inserted into the envelope through this tube.

Attached to the bottom of the electrode 12 is a sup- .porting member 14 which is used to hold the armature 15 in place. These elements may lbe spot welded together so that a continuous current carrying path is formed from the armature 15 to the electrode 12. To insure maximum operating eiciency, the armature should not extend beyond the end of the electrode. It is preferred to make the armature from aL thin permalloy reed so that maximum sensitivity maybe attained. The amature is biased upward so that in its normal position it rests against the damping spring 16 in such amanner that during contact breaks the deleterious elfects of chatter arejreduced to a minimum. The damping spring 16 is made of a'highly resilient material and is spot welded to the electrode 12 so that the vibration ofthe armature 15 is reduced as much as possible. t

Attached to the amature 15 is a contact pin 17, which l `is illustrated in detail in Figs. 4 and-5. The `pin is formed of a material not wettable bymercury and has a currentcarrying shaft 18 along its axis that is mercury wettable and slightly longer than the contact pin 17, so that it protr-udesv from the vbottom of the pin. This configuration has several advantages. The mercury-Wettable shaft 18 retains a thin lm of mercury-thereon which provides a mercury to mercury contact when the armature 15 is energized, whereby a'quickand low resistance closure is attained. vBy makingthe contactpin 17 non-wettable, upon closure, the natural resistance of the contact pin to immersion in mercury prevents the shaft 18 from striking the bottom of the-mercury container 19, thus avoiding all solid contact and greatly increasing the life of the switch. Furthermore, when the contact pin disengages there is verylittle surface tension tending to hold it immersed inthe mercury, and consequently theV sensitivity is greatly increased. A convenient method of fabricat- `ring the contact pin 17 is to `cut it from a chromium plated tungsten wire. The chromium platingshouldbe suiciently thick to provide a large cross sectional area ratio between the contact pin 17 and the shaft- V18, so 'that the above advantages may be fully realized. The chromium is etched until lthe tungsten protrudes from the lower end of the contact pin.l Since tungsten wets readily with mercury while chromium doestnotjthe advantages of a mercury to mercury contact are retained without affecting the sensitivity; l

The Iassembly of a mercuryl container l19 is illustrated in Fig. 3. A centrallyapertured circular plate 20 is inserted Vin the base 21 sothat there is aslight clearance between the plateand the ba'se. A portion of the plate 20 is cut and bent over to form an annular member 2.2',`

which stabilizes the mercury` surface at the center of the container where the the contact pin may be quite liberal but should be small enough toprevent any excess mercury from escaping from the container. Y

Theelements of the mercury container 19 are made of a material that will not amalgam-ate with mercury and are vplated on one side with platinum or other mercury w'ettable substance. `It isof no particular concern whether the container material is magnetic or non-magnetic. However, in embodyingthe inventionfin specific switch designs there may be advantages gained in using one material or the other. *The location-of these wettable surfaces is illustrated in Figs. 4 and"5 and-is of prime importance. The interior of the base 21, the exterior of the cover 23, the upper surface of the plate 20 and the lower surface of the annular-member 22 are all mercury wettable,v so that the mercury -within the container will adhere tothese surfaces. 'When a drop of mercury hits the top of the container 19, capillary forces pull it inside, and the surface tension of the mercury makes it take the shape shown in Figs. 4 and 5. l The mercury surface 24 in the center of the container 19 is coniined between the annular member 22 and the plate 20, so that it is quite stable and its position can be controlled within narrow limits.' The level of the surface 24y would also change very little withV any change in the volume of the mercury pool 25 inside the container, because of the confining nature of thei'mercury wettable surfaces on the annular member 22 andthe plate 20. Besides forming the mercury surface 24,"the annular member `22 provides a small gap through which a portion of the mercury must go when hit by the contact pin 17. Because of the natural adhesion of the mercury to the wettable surfaces, a mechanical resistance, or energy loss, is introduced in the circuit which damps the contact pin 17 and hence the armature 15, thereby preventing chatter when the switch closes. The mercury pool 25 acts as a reservoir for the mercury surface 24, and because of the particular configuration ,of the container 19 itis very diflicult to shake the mercury out,

leither by jarring or even by inversion of the switch. Consequently, the switch may be mounted for operation in any position. During long continuous operation, a certain amount of the mercury may vaporize inside the envelope 11. By plating the upper surface' of the cover 23 with a mercury Wettable material, the vaporized mercury wil-1 condense on this surface, and capillary lforces will cause it to return to the interior of the container 19 through the passageway between the exterior of the cover 23 and the interior of the base 21.

Referring again vto Fig. l, the mercury container 19 is supported by a Vthin non-magnetic plate 26 which is attached to the electrode 13. The other end of the plate supports a magnetic wire 27, so that a .non-magnetic gap is provided between the wire and the electrode. The gap is partly filled by the mercury container 19, thereby completing the magnetic circuit. v

Other details will be understood 'om the following description of the mode of operation of the device.

. When a magnetic field is applied tothe switch of Fig. l, such as by an energizing winding 56 enclosing all or part of the envelope 11, there is a repulsive force between the electrode 12 and the armature 15. At the same time, thereis a force of attractionfbetween the armature 15l and the wire 27. By making the mercury container 19 `of magnetic material and placing it in close .y proximity to the end of the electrodev 13, 'so that there the curved ux pattern will provide an additional `attractive Iforce that will practically double the sensitivity. However, this is not 'essential for successful operation of the switch. The combined forces result in a force which is roughly linear with thetravel of the contact pin 17.

As the contact pin 17 makes contact with the mercury surface 24, a small amount of mercury is forced from underneath the annularv member 22, thus providing a resistive force that will eliminate chatterfon contact makes, as previously described. 'I'he pin 17 andthe mercury container 19 are correlated to provide a small and constant gap therebetween, thereby minimizing the peak voltage induced in the circuit. Because of the wetting characteristics of the annular member Z2, the natural resistance of the mercury will prevent the pin 17 from striking the container base 21, except when a large magnetic force is applied. 'I'his mechanical contact may be presented entirely by reducing theV cross sectional area of the magnetic components until they become magnetically saturated, after which time the amount of external magnetic force applied will have little effect on the distance traveled by the contact pin 17.

When the magnetizing current is removed, the natural resiliency of the armature will move the contact pin 17 out of engagement with the mercury surface 24, thus opening the circuit. As the armature returns to its normal position, it strikes the damping spring 16, thereby reducing vibration.

Fig. 6 illustrates another embodiment of the invention wherein a dilerent means for damping thev armature 15 has been provided. In this modiication the various parts of the structure are substantially similar to those previously described with the exception of a flat spring 28, which has been substituted for the damping spring 16 shown in Fig. 1. The ilat spring is attached to an electrode 29, which is similar tothe electrode 12 (Fig. l) except that it does not extendy as far into the en- 'velope 11. In its normal position the armature 15 is in contact with the llat spring 28, and since the spring 28 is made of a magnetic material the sensitivity of the switch is improved. When the armature 15 returns to normal after the magnetizing current is removed, any

vibrations are communicated to the at spring 28, so

that they are effectively damped. This type of spring is particularly useful in circuits requiring extremely high sensitivity and freedom from chatter.

Another embodiment of the invention is shown in Fig.V

7. The basic structure is retained except for the means used for damping the vibrations of the armature 15. Attached to the wire electrode 30 is a supporting member 31 to which the armature 15 is fastened. A iine wire coil 32 is wrapped around the electrode 30 and is secured thereto at each end by means of a spot Weld or other known method of attachment. As the armature 15 returns to normal, it strikes the coil 32 so that the vibrational energy is dissipated and damping is attained. The electrode 33 is made tubular in shape to facilitate assembly.

Referring to Fig. 8, there is shown a normally closed mercury switch embodying the features of the invention. Enclosed within the envelope 11 are two electrodes 34 and 35. The upper electrode 34v comprises a wire of conductive material with a non-magnetic gap located directly above the contact pin 17. The two portions of the electrode 34 are connected by a non-magnetic plate 36, which has a certain amount of flexibility so that the vibrations of the armature 37 may be reduced when the switch is opened. The armature is attached to the bottom of the electrode 34 by means of the supporting member 38 and is biased in a downward position so that the contact pin 17 attached to its free end is in engagement with the mercury in the container 19. The contact pin and the container are illustrated in -be inserted into the envelope.

39 which is attached to the 'end of the tubular electrode 35, thus maintaining continuity in the magnetic circuit.

When a magnetizing current is applied to a coil encompassing the envelope 11 (see Fig. 1), there is a repulsive force between the lower assembly (the container 19, the.k plate 39zand the electrode 35) and the armature 37. At the same time, there is an attractive force between the armature 37 and the two segments of the electrode 34. These forces combine to raise the armature, thereby `disengaging the contact pin 17 from the mercury in the container 19. It will be noted that the magnitude of these forces necessary to actuate the switch is very small, and consequently the device is highly sensitive in operation. When the magnetizing current is removed, the natural resiliency of the armature v37 returns it to its normal position, thereby causing the contact pin 17' to engage with theumercury inthe container 19 to close the circuit.

In Fig. 9 there is shown .a mercury switch embodying the features of the invention designed to effect transfer between circuits. Three electrodes 40, 41 and 4Z are enclosed within the envelope 43, which is filled with an inert gas. One of the electrodes-may be made tubular inshape so that the inert gas and the mercury can easily A wire support 44 is attached lengthwise along the electrode 41 and has two right angleprojections 45' and 46,4 one of which is encompassedby a roller 47 which is free to rotate thereon. Attached to the lower portions of the roller 47 and the projection 45 is a flat vspring 48, which is held in place by spot welding or other suitable means. An armature 49 is fastened to the roller 47 and pivots about the projection 46. It is so positioned that in its actuated position (left end moved upward) the right end thereof rests against the flat spring 48. The resiliency of the spring 48 therebyprovides ani-effective method of armature damping that will reduce chatter. The positioning of the above-described means for supporting the armature 49 is illustrated in detail in Fig. l0.

Attached to opposite sides of the left end of the armature 49 are two axially aligned contact pins 50 and 51. These pins are identical with those illustrated in Figs. 4 and 5 and conform to the previous description. A mercury container 52 is supported by amagnetic plate 54, which should not extend beyond the tip of the armature 49 in order to insure maximum sensitivity and operating efficiency.y Otherwise, there would be small attractive forces built up between the left end of the plate 54 and the armature 49 which would tend to hamper proper operation of the switch. `A mercury container 53 is supported by a non-magnetic plate 55, which is secured -to the electrode 40 in `such a manner that the outer segment 40 of the electrode is supported thereby. The mercury containers 52 and 53 are -positioned so that they may be engaged by the contact pins 50 and 51, respectively, and are of a construction identical with that hereinbefore described. The various components of the abovedescribed transfer switch are held together by spot welding or other suitable means of attachment.

In its normal position (as shown) the armature 49 is positioned on the roller 47 so that the contact pin 50 is in engagement With the mercury in the container 52,

The mercury container is supported by a magnetic plate thus forming a continuous current carrying path from the electrode 41 to the electrode 42. When an external magnetizing current is applied to a coil encompassing the electrode 43 (see Fig. 1), there is a repulsive force between the armature `49 and the magnetic plate 54. Simultaneously, there is a Iforce of attraction between the armature 49 and the two segments of the electrode 40. These combined forces cause the armature to move to ward the mercury container 53, disengaging the contact pin 50 from the mercury container 52 and engaging the contact pin 51 with the mercury container 53. Hence the circuit is transferred from the electrode 42 to the electrode 40, forming a continuous current carrying path When the magnetizing current is released, the torsional force of the flat spring 48 acting on the roller 47 causes the armature 49 to rotate in a counterclockwise direction about the projection 46. Hence, the contact pin 51 disengages from the mercury container 53 and the contact pin 50 comes into contact with the mercury container 52, thereby returning the switch to its normal position.

It is apparent that the various modifications of the component parts of the switch are, in many instances, interchangeable with each other, and that certain of the mechanical details shown may be modied without departing from the scope and spirit of the invention as dened in the appended claims.

What is claimed is:

1. A switch comprising a pair of magnetic members, one of said members having a non-magnetic strip, a contact mounted on said non-magnetic strip, a magnetic con tact arm extending between said members having one end in proximity to said contact, and magnetizing means disposed in cooperative relationship to said members for moving said contact arm into or out of engagement with said contact.

2. A switch comprising a pair of magnetic members having juxtaposed substantially parallel portions, a magnetic contact arm extending between said members and having one end free and the other end iixed to one of said members, a contact mounted by the other of said members lopposite the free end of said contact arm, and means for magnetizing said members oppositely relative to said contact arm and in the direction to move said contact arm into or out of engagement with said contact.

3. A switch comprising a pair of magnetic members having juxtaposed substantially parallel portions, a magnetic armature extending between said members, said armature having one end free and the other end iixed to one of said members, a iirst contact carried by said armature, a second contact mounted'by the other of said members opposite said rst contact, and means for magnetizing said members oppositely relative to said armature and in the direction to move said first contact into or out of engagement with said second contact.

4. A switch comprising a pair of magnetic members having spaced substantially parallel portionsfoneof said members having a non-magnetic strip, a container mounted upon said strip and having an aperture therein, a body of mercury in said container, a magnetic contact arm extending between said members having one end in proximity to said aperture, and a signal coil encircling said members. i

5. A switch comprising a pair of magnetic members having spaced substantially parallel portions, one of said members having a non-magnetic strip, .a container mounted upon said strip and having an aperture therein, a body of mercury in said container, a magnetic armature between said members, said armature having one end fixed to said other member and its other end in proximity to said aperture, a contact mounted on said armature 'and aligned with said aperture, and means for magnetizing said members oppositely relative to said armature and in the direction to move said contact into or out of engage ment with said mercury.

6. In a switch, a pair of magnetic rods having juxtaposed substantially parallel portions, a non-magnetic strip mounted by one of said rods and extending from one end thereof, a magnetic member extending from the end of said strip remote from said one rod, the other of said rods having an end portion opposite said member, a contact mounted on said strip, a'rnagnetic contact arm between said rods having one end in proximity to said contact and means for magnetizing said rods oppositely relative to said contact arm and in the direction to move said contact arm into or out of engagement with said contact.

7. In a switch, a pair of spaced magnetic rods having juxtaposed substantially parallel portions, a non-magnetic strip mounted by Yone of said rods and extending from one end thereof, a magnetic member extending from the end of said strip remote from said one rod, the other of said rods having an end portion opposite said member, a contact mounted on said str-ip, a rnagnetic contact arm between said rods, said contact arm having one end fixed to said other rod and its other end in proximity to said contact, and signal coil means disposed about said rods.

S. A switch comprising a pair of magnetic rods having juxtaposed substantially parallel portions, a non-magnetic strip mounted by one of said rods and extending from oneend thereof, a magnetic member extending from the end of said strip remote from said one rod, the other of said rods havingl an end portion opposite said member, a first contact mounted on said strip, a magnetic armature between said rods, said armature having one end fixed to said other rod and its other end in proximity to said rst contact, a second contact mounted on said armature and aligned with said rst Contact, and signal coil means disposed about said rods.

9. A switch comprising a pair of spaced magnetic rods having juxtaposed substantially parallel portions, a non-magnetic strip mounted by one of said rods and extending from one end thereof, a magnetic member extending from the end of said strip remote from said one rod, the other of said rods having an end portion opposite said member, a container mounted upon said strip and having an aperture therein, a body of mercury in said container, a magnetic armaturerbetween said rods,

said armature having one end xed to said other rod and its other end in proximity to said aperture, a contact mounted on said armature and aligned with said aperture, and signal coil means disposed about said rods.

References Cited in the tile of this patent UNITED STATES PATENTS 2,797,329 George June 25, 1957

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