US2202569A - Mercury switch - Google Patents

Description

May 28, 1940. F..S..ARMSTRONG 5 MERCURY SWITCH Original Filed Sept. 5, 1931 2 Sheets-Sheet 1 if. I i "2-1 IIIIIII/A Er frzerrfar i' eid rzzszmz 25 Q. I

23, 1940- F. s. ARMSTRONG 2,202,569

MERCURY SWITCH Original Filed Sept. 5, 1931 2 e heet 2 Patented May 28, 1940 Jeiferson Electric Company, Bellwood a corporation of Illinois r A TjflFFicE or to Continuation of application Serial No. 5 1,500, September 5, 1931. This application April 23, 1934, Serial No. 721.9%

34 claims. (or. 200-152 This application is a continuation ofmy pending application Serial No. 561,590, filed September I The present invention has to do with improve ments in mercury switches and the like, and in the specific, construction adapting the switch not only to enable the making and breakingof the circuit at high rate of frequencyfor a number of breaks far exceeding the endurance of any mercury switch heretofore produced,-but also to en-' dure without liability or tendency to rupture of the shell either by the pressure developed in it by the high temperature sometimes resulting from the arcing or by the shock, both mechanical and electric, due to the making and breaking of the circuit. The invention herein disclosed rehates to improvements both in the construction of the mercury switch itself and inthe means" whereby the arcing tendency is reduced and completely suppressed.

The mercury switch herein disclosed includes a casing or envelope of iron or other ferrous material withinwhich the mercury body is located, there being a terminal contact or electrode of iron or ferrous material extending into said casing but insulated therefrom, the casing also being filled with hydrogen or other inert gas under pressure substantially greater than atmospheric. Experience and tests extending over a long intervalof time under arduous conditions 01' operation, clearly demonstrate that the use of the hydrogen under pressure within the casing of iron wherein is contained the mercury body, serves in a very marked degree to suppress the arc which would otherwise be'drawn at the instant of opening'thecircuit. In some cases, the hydrogen may be at a pressure equal to atmospheric or less than atmospheric, but preferably the gas pressure is greater than atmospheric for the most desirable operating condition.

Switches of the above general type are disclosed in my co-pending application for Letters Patent of the United States on Mercury switches and the like, Serial No. 446,268,1lled April 22, 1930, issuing in Patent No. 1,9l6,957, July 4,1933.

The present application concerns itself primarily with improvements in the construction of the switch and the method whereby the'air and oxygenare completely removed from the same, and the inert 'gas such as hydrogen, is introduced under pressu re, if desired, and sealed under said pressure in an absolutely perfect manner. v

The introduction of the gas under pressure and sealing it in place under said pressure, presents certain problems of a highly practical nature so these conditions to the best advantage.

that the construction of the device has been worked out and perfected with a viewlto meeting In this connection, I have provided constructions in which use is made of a compressible gasket of 'yieldable and "sealing material such asrubber or the like, the same being initially introduced ofa size which permits a slight clearance through which the air and oxygen may be withdrawn and through which the inert gas such as hydrogen may he introduced, provision being also made for thereafter compressing said gasket so as to cause the same to swell out in another direction and create the desired perfect seal against the other parts of the device so as to retain the gas under pressure within the same.

In ccnnectionwith the foregoing, it is an object of the invention to provide a very simple arrangement of compressing devices in conjunction with said gasket, so, that the entire switch can be produced at a in cost. At the. same time, the arrangement is such as to avoid the use of parts which will become broken or disabled under ordinary service.

A further object of the invention is to provide means for making it possible to compress the said gasket while the desired pressure is maintained ithin the shell of the switch, such compressing operation being performed by the use of a spe+ cial tool which reaches through or into the gas pressure chamber.

Another feature of the invention relates to the provision of a newand improved construction of bridge piece or lip at the position of which the.

mercury body is broken or reestablished during the circuit breaking and making operations. The

breaker element is formed of suitable vitreous material capable of withstandin the arduous conditions of makingand breaking the circuit under load. In some cases, said breaker is made entirely of said vitreous material, and in other cases, it is formed of. a flange or cup-shaped element of metal such as iron or ferrous material coated over such portion as many be necessary with a layer of vitreous material.

A furtherfeature of the invention relates to the provision of a type'of construction which can;

be readily made from sheet iron or ferrous material, 'dr'awn or otherwise formed into the desired cup formationto establish the principal portion of the chamber or envelope of the switch.

Other objects and uses of the invention will appear from a detailed description of the same, which consists in the features of construction and combination of parts hereinafter described and claimed.

In the drawings:

Figure 1 shows a longitudinal section through a switch device embodying the features of the present invention, the compression nut and stem being released so as to permit the gasket of compressible material to lengthen out and contract in diameter, thereby establishing the desired clearances for removal of air and oxygen and for introduction of inert gas such as hydrogen.

Figure 2 shows a view similar to that of Figure 1, but with the gasket compressed or shortened lengthwise and expanded laterally so as to establish the desired seal.

Figure 3 shows a perspective view of one of the washers which is radially slotted to permit the radial movement of air and gases.

Figure 4 shows somewhat diagrammatically a chamber and connections thereto for exhausting the air on one portion of the operation and for introducing inert gas under pressure under another portion of the operation.

Figure 5. shows a fragmentary longitudinally section through a portion of a switch embodying a modified form of partition or bridgewall of vitreous material.

Figure 6 shows a longitudinal section through still another modified form of construction in which the partition'or bridge wall is made in casing in the form of a pressed or drawn metal cup of iron or other suitable material; and

Figure 8 shows a longitudinal section through a double ended switch embodying the general type of construction of Figure 7, and tilted to make contact at one end.

It will be noted in the first instance that Figures 6 and 7, although illustrating two different. forms of construction, also illustrate the switch in the closed and open circuit positions, respectively; the mercury connecting across the bridge wall in Figure 6 so as to close the circuit and the mercury being severed in Figure 7 by the bridge wall, a small portion or drop of the mercury being retained within the cup-shaped partition, and the remaining portion of the mertherein illustrated includes a thimble or tubular envelope, I0, preferably of iron or steel, closed at its end, The other end, ii,- of said thimble is preferably threaded both interiorly and exteriorly for reasons to be presently explained.

There is a threaded stem, 13 serving as an electrode, having at its inner end the enlarged head, 14, said stem reaching axially into the thimble. A flange, i5, is located on the stem, i3, and against the shoulder of the head, M. In the construction of Figures 1 and 2, said flange, l5, has the inwardly reaching throat, 86, into which there is set an inverted thimble, l1, having the central opening, It), the outer end of said thimble, i1, being seated into the throat, I 8, of the flange, 5, and cemented or sealed in place by the grouting, i9.

.In the particular arrangement illustrated in Figures 1 and 2, the parts, l5 and I1, are made of vitreous material such as porcelain or la e, so that together they establish a small chambe 20, which receives the enlarged head, ll, of the stem, 13, and which chamber also communicates with the interior of the thimble .through the opening, i8.

There is located on the stem, 3, behind the flange, IS, a block of compressible material such as rubber or the like, 2|. A nut or flange, 22, is threaded into the outer end of the thimble, i0, beyond the position of the compressible block, 2|; and for purposes of convenience in manipulating this nut, 22,'the .same is provided with openings, 23, which can be engaged by a spanner wrench itinecessary. Furthermorathe nut, 22, is shown as being provided with a bushing, 24, of insulating material and including an insulating flange, 25, which seats between the nut, 22, andv the end of the block, 2|. In this way, the stem, 13, is insulated from the thimble, ill, at the position of the nut, 22. One or more washers of insulating material, 26, are placed on the stem, I3, beyond the position of the nut, 22, and a tightening nut, 21, is threaded onto the outer end of the stem, 83, beyond the position of the washers, 26, a washer, 28, of metal preferably being located between the nut, 21, and the washers, 26, so as to avoid damage to said washers during the tightening 'up process. I

' The inner washer, 26, is shown in perspective in Figure 3, wherein it will be noted that the same is provided with a series of radial grooves, 29, formed in one face and establishing radially extending gas passages which lead from the position of the stem, E3, to the outer periphery of the washer, 25.

Examination of Figure 1, in particular, shows that when the nut, 21, is loosened up or released, which is the condition illustrated'in said figure,

' the compressible block, 2|, contracts sufliciently the end of the block, 2|, and the face of theinsulating flange, 25. The throat, i6, is also of slightly smaller size than the thimble, it, so as to establish a clearance, 34, between these 7 parts.

All of the above clearances permit a free withdrawal of air and gas from the interior of the casing when the parts are in the release position, and also permit introduction of the desired gas under pressure. Upon tightening up the nut, 21, the stem, I3, is pulled up carrying with it the flange, i5, and compressingthe block, 2|, into the form shown in Figure 2. Thus, said block is shortened lengthwise but is radially expanded to compress solidly against the inner surface of the thimble, i0, and against the stem, l3. As a consequence, the space below the block, 2|, is absolutely sealed oif and whatever condition of vacuum or gas pressure exists therein is perfectly maintained.

Referring to Figure 4, there is provided a chamber structure, 35, communicating at its lower end with a gas pressure connection, 36, and also with an exhausting connection, 31. Inlet and exhausting gate valves, 38 and 39, are provided for the connections, 36, and 31, respectively. The device also includes a-threadecLdpening, 40, opposite to the position of the chamber member, 35, so that the exteriorly threaded portion of thethimble or envelope Ill, can be threaded into said opening, 40. l

A stem, 4|, extends longitudinally into the upper end of the chamber member, 35, being provided with an operating handle, 42, at the exterior of the device. A suitable packing gland, 43, is provided around the stem, M, and can be placed under compression by means of the nut,

The inner end of the stem, 4i, carries a socket wrench, 45, which is adapted to receive the tightening nut, 21, on the stem, I3, of the mercury switch device.

With the above arrangement, the nut, 21, is first loosened up so as to allow the parts to come into the condition illustrated in Figure l. The thimble or chamber, I0, is then threaded up into the opening, 40, and tightened in place. Upon opening the valve, 39, the valve, 38, being closed, the chamber is subjected to suction or vacuum and the air and oxygen are withdrawn from the interior of the thimble, III. Thereupon, the valve, 39, may be closed, and the valve, 38, opened. When this is done, the hydrogen or other inert gas under pressure is forced into the chamber and into the thimble of the mercury switch device. establishing pressure therein. If desired, this operation may be repeated a number of times in succession, first subjecting the device to suction and then to pressure so that it will be very thoroughly flushed out and practically all traces of oxygen removed from the interior of the mercury switch, and at the same time, when the operation is completed, the mercury switch will be filled with theinert gas under pressure. While the valve, 38,-

remains opened, the valve, 39, being closed, the handle, 42, can be turned so as to turn the nut, 21, and tighten the same onthe stem, I3. In this way, the gas under pressure within the thimble will be permanently sealed therein.

In the modified construction shown in Figure 5, the flange I5, is not provided with any throat, I6, but the breaker thimble, I1, is of somewhat larger size and is brought down flush against the edge portion of said flange, I5, to which it is sealed by the cement or grouting, I9, as in the previous case.

In the modified form of Figure 6, there is provided a metal flange, 46, on the stem, I3, and seated against the enlarged head, I4, thereof. In this form, there is a metal thimble or flange, 4'I, threaded onto the flange, 46, said, thimble or flange, 41, being exteriorly coated with poreclain or other vitreous insulating material, 48, as clearly shown .in Figure 6.

In the modified construction of Figure 7,'the exterior envelope or casing is made in the form of drawn orpressed sheet metal, 48, having the peripheral outwardly extending flange, 50. A washer, 5I, is seated against the end of said flange, 50, an insulating bushing, 52, being placed between the washer, 5|, and electrode stem, I3,

' so as to properly insulate these parts from each other; and a sheet metal ring, 53, of U-shaped cross section is crimped or clamped around the edges of the flange, 50, and washer, 5|, as clearly shown in Figure '7.

In each of the switch forms herein illustrated,

a small body of metallic mercury or the like, 54, is placed within the thimble. This is done before the nut, 22, and rubber gasket and related parts are set into place. Upon tilting the switch into position of Figure 6, the circuit is established'betweenthe head, I4, of the electrode stem, I3, and

be; whereas, when the device is tilted down into the position of Figure 7, the mercury body breaks over the flange or breaker, H, leaving a small portion of the mercury, 54, within the cup of the breaker, H, and another portion, 56 in the thimble, 49, outside of said cup, It. It will be noted, therefore, that the break takes place from mercury to mercury and that the contact of the mercury with the electrode head, I4, and with the shell, 49, is maintained unbroken.

Upon tilting the switch back into the position of Figure 6, a reverse action takes place and the circuit is reestablished across the flange, H, by intermingling and contacting of the mercury bodies, 54 and 54 with each other.

In the modified construction of Figure 8, there is shown a double ended switch embodying the general type of construction of Figure 7. This switch can be tilted back and forth so as to make contact first at one end and then at the other, it being understood of course that the body portion of the switch establishes the third terminal. -This is also true of all of the different constructions.

Experience has demonstrated that the operation of the switch in normal service does not affeet the vulcanization of the rubber. This is particularly true in the case of what is called commercially pure rubber having a low sulphur content, meaning by low a percent of sulphur for vulcanization which will not separate from the rubber and constitute free sulphur, which percent for vulcanizing to give proper tenacity and elasticity for the uses for which such rubber is commercially in demand, does not exceed 3% (see Knights American Mechanical Dictionary, volume 2, page 1179, entitled India-rubber.

Preferably the shell and other metallic parts of the device with the exception of the mercury bath, are made of commercially pure iron, by which is meant iron substantially free from carbon impurity, having only a negligible amount of carbon content, the carbon content of the iron used in the mercury switches of the construction shown in this application being less than one-half of one percent. Experience demonstrates that which scum becomes deposited on the surface of the porcelain or other insulator, and in time develops shorts.

I wish to emphasize that the use of hydrogen 7 gas either at pressure greater or less than a-tmospheric, but preferably at greater pressure than atmospheric, in combination with the shell and other parts of iron or ferrous material and with the mercury bath, presents operating conditions of a greatly improved nature; and especially when the gas is relatively heavy pressure as for example from 25 to 100 pounds per square inch, the arcing tendency is very greatly suppressed. Y

The enlarged contact head, I4, of the stem, I3, is preferably made of substantially carbon free iron, and preferably the head and stem are made integral with each other. Furthermore, the exhead is highly polished, the tendency for the same to pit or burn is minimized in those cases in which the mercury may sever connection from said head instead of breaking from.mercury to mercury. I

It may also in some cases be desirable to use, a head, I 4, made of silver or silver alloy, or some such material which will amalgamate with the mercury, in which case the mercury will have a positive meniscus with said head as shown in Figure '7.

I attach la-rge importance to the feature of the mercury switch as above described consisting in that the shell is metallic and highly electrically conductive, as distinguished from such material as glass, because the high pressure of the hydrogen gas desirably produced and maintained in the shell for quenching the arc cannot be relied upon to be produced and maintained in a shell which is hermetically sealed in the process of charging it with gas under said pressure, because the glass, softened'in the process of sealing, is liable to be ruptured by the gas pressure before it has had,

time to become set; and if by any means the sea-ling is effected avoiding rupture of the glass during the process of charging and sealing, the glass is left in condition of such tensional stress that a little mechanical shock or jar causes the fracture of the glass and bursting of the shell. And independently of this liability to fracture and bursting due to mechanical shock and jar, by reason of the electrical non-conductivity of the glass shell making it necessary to provide, extending sealed through the glass from the exterior to the interior of the shell, a second contact for the mercury instead of the shell itself, which, in the present construction, is afforded by the iron shell itself, the electric shock of the mak-. ing and breaking of the circuit produces a mechanical shock communicated to the glass shell from either or both of the circuit contact members which extend sealed through the glass, tending to start cracks which are extended on each repetition of the making and breaking of the circuit, and ending in the bursting of the shell after comparatively short life of the device.

In respect to this defect of mercury switches having glass shells, it is noted that the variation of amperage in the are or spark passing at the breaking of the circuit when the current is taken from a public service source, as a light or heat circuit, is liable to be very wide, varying from a normal of ten (10) to a possible maximum of forty (40) amperage; and in the instances of high amperage, the electric shock above described, and the resulting mechanical shock, is quickly destructive of a glass shell.

The detail structure of the iron shell and means of connecting for charging with gas under pressure and maintaining the shell sealed during the process of charging and completing, are designed to take advantage of the superior adaptation of metallic and electric conductive material over such material as glass for the purpose described.

While I have herein shown and described only certain embodiments of the feature of my present invention, stillI do not intend to limit myself thereto except as I may do so in the claims.

I claim: I

1. As a new article of manufacture, a mercury switch device comprising an iron shell constituting a terminal of an electric circuit, another iron circuit terminal extending longitudinally into said shell and insulated therefrom, a resiliently compressible plug of substantially pure rubber located between the second mentioned iron circuit terminal contact and the shell, a body of metallic mercury within the shell and constituting a circuit-making and-breaking means, subcircuit wires.

2. As a new article of manufacture, a mercury switch comprising an iron shell constituting a terminal of the circuit, another iron terminal extending longitudinally into said shell and insulated therefrom, a compressible plug of rubber located between the iron plug contact and the shell, abody of metallic mercury within the shell and constituting a circuit-making-and-breaking means, inert gas under pressuregreater than atmospheric within the shell, and means for compressing the rubber plug axially with respect to the shell to thereby expand the rubber plug laterally into flrm sealing engagement with the shell and the iron plug, substantially as described.

3. As a newarticle of manufacture, a mercury switch comprising an iron shell, a longitudinally extending terminal contact extending into said shell and insulated therefrom, a cup shaped washer of. vitreous material between the inner end of said terminal and the shell, a compressible plug at the back side of said washer and between the terminal and the shell, said plug when uncompressed being of smaller diameter than the shell, a body of metallic mercury within the shell for establishing electric contacts betweenthe terminal and the shell, inert gas under pressure greater than atmospheric within the shell, and means for exerting a compressing force between the washer and the compressible plug to thereby compress the plug longitudinally and cause the same to expand laterally into full sealing engagement with the terminal and the shell, sub-, stantially as described. I

4. As a new article of manufacture, a mercury switch comprising an iron shell,'a terminal comtact extending longitudinally into the shell and insulated therefrom, a cup-shaped washer of vitreous material located between the inner end of said contact and the shell, a plug of compressible material at the back side of said washer and located between the terminal and the shell, a body of metallic mercury within the shell for establishing and breaking electrical contacts between the terminal and the shell, and means for compressing the plug against the washer to thereby cause the plug to expand laterally into full sealing engagement with the terminal and the shell, substantially as described. i i

'5. As a new article of manufacture, a mercury switch including. ametallic shell, a terminal element extending longitudinally into said shell and insulated therefrom, a plug of compressible elastic material located between said contact and the shell, said plug when uncompressed being of smaller cross-section than the shell, and means for compressing said plug lengthwise to thereby cause the same to expand laterally into sealing engagement with the terminal and the shell,

substantially as described;

6. As a new article of manufacture, a mercury switch having two concentric metallic elements,

one of which constitutes a portion of an enclosing shell, and the other of which constitutes a central terminal element, a plug of compressible elastic material located between said parts and retaining them in concentric relationship and insulating them from each other, said plug when uncompressed lengthwise being of smaller diameter than the shell, and means for compressing said plug longitudinally with respect to the shell to thereby cause said plug to expand laterally and establish sealing engagement with said parts, substantially as described.

7. As a new article'of manufacture, a mercury switch comprising an iron shell of substantially carbon free iron, aterminal contact extending into said shell and insulated therefrom, a cupshaped element of vitreous material carried by the inner end of said terminal interposed betwen said terminal and the shell, a compressible plug of substantially pure rubber interposed between the terminal and the shell for insulating the terminal from the shell, a body of metallic mercury within the shell for establishing electric contacts between the terminal and the shell, inert gas under pressure within-the shell, and means for exerting a compressing force upon the compressible plug to thereby maintain it in sealing engagement with the terminals and the shell, substantially as described.

8. As a new article of manufacture, a mercury switch comprising an iron shell of substantially carbon free iron, a terminal contact extending into said shell and insulated therefrom, a cupshaped element of vitreous material carried by the inner end of said terminal and the shell, a

resiliently compressible plug of insulating material interposed between the terminal and the shell constituting insulation between said iron parts, a body of metallic mercury within the shell for establishing electric contacts between the terminal and the shell, inert gas under pressure greater than atmospheric within the shell, and means for exerting pressure on the cup-shaped element and thereby on the plug to stress the plug into sealing engagement with the terminal and the shell, substantially as described.

9. As a new article or manufacture, a mercury switch comprising a metallic shell, a terminal contact extending into said shell and insulated therefrom, an enlargement on said terminal contact, a plug of substantially pure rubber carried by said terminal contact member by means of said enlargement betwen the terminal and the shell, a body of metallic mercury within the shell for establishing electric contacts between the terminal and the shell, inert gas under superatmospheric pressure within the shell, and means for stressing the plug into resilient engagement with the shell and terminal for sealing the joints between the shell and the terminal respectively and the plug, substantially as described.

10. As a new article of manufacture, a mercury switch comprising a metallic shell, a terminal contact extending into said shell and insulated therefrom, an enlargement on said terminal contact, a plug of substantially pure rubber carried by said terminal contact member by means of said enlargement between the terminal and the shell, a body of metallic mercury within the shell for establishing electric contacts between the terminal and the shell, inert gas under superatmospheric pressure within the shell, and means for stressing the plug in suitable direction for developing its resilient reaction into sealing engage-. ment with the terminal and the shell, substantially as described.

11. A mercury switch device comprising a tubular shell made of iron, said shell being integrally closed at one end for retaining mercury and containing a quantity of mercury occupying a part onlyof the liquid capacity of the shell, and formed at the opposite end with means for mounting on, and admitting intrudedinto, the shell "and stopping longitudinally thereof, a circuit terminal element, means for insulating said element-from the shell at its intrusion there, into,- said insulatin means including resiliently compressible insulating material interposed in the shell between the encompassing wall thereof and the intruded circuit terminal element, the latter having at its inner end portion means adapted and arranged for stopping and being stressed against the inner side of said compressed insulation for developing its resilient reaction. into contact with the intruded element and the wall of the shell, for sealing the cavity of the shell; means associated with said intruded circuit terminal element at the end thereof outside the shell for applying said stress, to initially effoot said sealing of the shell, the shell and mounting means of the intruded circuit terminal ele-',

ment being arranged for connection of the shell 'with a source of gas under super-atmospheric pressure, and said shell being charged with pure hydrogen gas under super-atmospheric pressure.

12. A mercury switch device having a chambered body member comprising two commercially pure iron parts insulatedly mounted one upon the other with means rendering the chamber enclosed gas-tight, and arranged for connection with a source of gas under super-atmospheric pressure, said insulated parts having respectively conductive surface portions exposed interiorly of the chamber insulatedly spaced apart therein a substantial distance, said device being mounted for movement between two positions; a body of mercury enclosed in the chamber in quantity suificient to bridge the insulating space between said exposed surface portions, to establish mercury communication between them when the device is in one of said positions, and hydrogen gas compressed at a substantial degree in excess of atmospheric pressure sealed in said chamber.

13. A mercury switch device having a chambered body member comprising two metal parts insulatedly mounted one upon the other with means rendering the chamber enclosed gas-tight and arranged for connection with a source of gas under super-atmospheric pressure, one of said metal parts being tubular and closed at one end for retaining a limited quantity of mercury, and a quantity of mercury in the chamber small relatively to the liquid capacity of the chamber, I

the other of said metal parts being intruded into said tubular part through the opposite end thereof, the tubular part being provided at said opposite end with means for insulatingly mounting said intruded part, means for sealing the chamber at the intrusion of said otherpart into said tubular part, and means including the path of intrusion of said other part into the chamber for connecting said chamber with a source of gas under super-atmospheric pressure.

14. A mercury switch comprising a tubular shell made of commercially pure iron closed at one end and containing a quantity of mercury occupying part only of the liquid capacity of the shell cavity; a circuit terminal extending into the shell cavity insulated from the shell, the insulating means including a bushing or gasket made of commercially pure rubber; mechanical exteriorly operable means associated with the shell and the intruded circuit terminal member for stressing the rubber bushing in a manner and direction for developing its resilient reaction on the inner wall of the shell and intruded circuit terminal, for sealing the chamber gastight; the shell and said associated parts being formed and arranged for connection with a source of fluid pressure, and hydrogen gas under super-atmospheric pressure occupying the shell cavity, whereby the resilient reaction of the rubber bushing or gasket on the chamber'wall and on the intruded circuit terminal is maintained by the pressure on the commercially pure rubber of a fluid incapable of chemical action on said rubber.

15. The construction defined in claim 14, the bushing uncompressed being fitted to the shell and the intruded circuit terminal element for free air flow past it and said intruded element, and the shell being furnished with means including an exteriorly operable part cooperating for compressing the bushing for sealing, and being arranged for connection with means for evacuating the air from the shell cavity before compressing the bushing for sealing and before the hydrogen gas is supplied.

16. A mercury switch comprising a tubular shell of electrically conductive 'metal closed at one end and containing a quantity of mercury occupying part only of the liquid capacity of the shell cavity; a circuit terminal element mounted on the shell and extending into the shell cavity insulated from the shell, the shell being arranged for connection with a source of gas under superatmospheric pressure and provided withmeans for sealing the shell .cavity gas-tight at the mounting of the intruded circuit terminal element and the connection with the source of gas under pressure, the shell cavity being occupied by substantially pure hydrogen gas under superatmospheric pressure, the sealing means comprising an elastically compressible commercially pure rubber bushing or gasket compressed for eifecting its sealing engagement with the enclosing wall of the shell and the compressing means; whereby the bushing or gasket is maintained in sealing condition by the pressure of the sealed-in gas and the rubber is ensured against hardening and loss of resiliency by the contact of the hydrogen gas excluding other contacts, as of atmosphere, tending to harden and reduce the resiliency of the rubber.-

17. A mercury switch comprising a tubular shell of electrically conductive metal closed at one end and containing a quantity of mercury occupying part only of the liquid capacity of the shell cavity, a circuit terminal element mounted on the shell and extending into the shell cavity, insulated from the shell, said shell being arranged for connection with a source of gas under super-atmospheric pressure and provided with means for sealing the shell cavity gas-tight at the mounting of the intruded circuit terminal element and at the connection with the source of gas under pressure, the shell cavity being occupied by substantially pure hydrogen gas under super-atmospheric pressure, and the sealing means comprising an elastically compressible member of substantially pure rubber compressed .for efiecting its sealing engagement with the enclosing wall of the shell, whereby said elastic member is maintained in sealing condition and insured against hardening and loss of resiliency by thelcontact of the hydrogen gas excluding and containing hydrogen'gas under super-at-' mospheric pressure and also containing a mass of mercury occupying a part only of the liquid capacity of the chamber, said body member being mounted for rocking back and forth between two positions, the quantity of the mercury content of the chamber being such fraction of the liquid capacity of the chamber, that at a position to which the mercury contents gravitate at one of said positions of the body member, a substantial portion of the mercury is separated bodily from contact with said pure iron terminal, and at the other of said positions of the body member the mercury bridges the space between said terminal and the innersurface of the commercially pure iron wall of the chamber.

19. A mercury switch comprising a shell made of highly electrically conductive metal stamping, said shell being arranged for connection exteriorly with an energizing electric circuit, whereby the shell constitutes one terminal of the circuit which is to be subjected to making andbreaking in the functioning of the switch; a second metallic terminal extending into the shell from the outside sealed and insulated from the shell at its extent through the shell wall, the means of sealing and insulation including a yieldingly compressible sleeve or gasket interposed around the intruded second terminal between thev same and the shell, and means associated with the intruded terminalinteriorly of the shell and operable exteriorly thereof for compressing said sleeve or gasket into sealing contact with the shell and the intruded terminal, the shell being formed with the part of its cavity leading from an entrance, parallel-sided, said entrance dimensioned correspondingly to the transverse dimension of said parallel-sided part of the shell cavity; means carried by the intruded circuit terminal at the inner end constituting a head for stopping the compressible gasket or sleeve at the inner end, said means and said sleeve or gasket bein dimensioned for entrance and loose fit in said parallel-sided part of the shell cavity; a plug engageable with the shell at said entrance for stopping the compressible gasket at the end opposite said circuit-terminal-carried head, said plug being apertured for admitting it onto the intruded circuit terminal with freedom for passage of gas under pressure past said plug, and means operatively associated with the terminal outside the plu for stressing the gasket between the plug and said terminal-carried head to compress and expand said gasket into sealing relaelectrical energizing circuit, whereby the shellconstitutes one terminal of the circuit which is to be subjected to making and breaking in the functioning-of the switch; a second metallic terminal extending into the shell from the outside, sealed and insulated from the shell at its ext through the shell wall, the means of sealing and insulation including a yieldingly compressible sleeve or gasket interposed around the intruded second terminal between the same and the shell, and means associated with the intruded terminal interiorly of the shell and operable exterioriy thereof for compressing said sleeve or gasket into sealing contact with the shell and the intruded terminal, the shell at the entrance thereoi through which the second terminal contact is intruded being formed and dimensioned relatively to said intruded terminal for access of fluid pressure into the shell past the intruded terminal said shell bein also formed at the entrance end portion for at least temporary sealing engagement with pipe means for connection with a source of fluid pressure, whereby the junction of the pipe connection for fluid pressure with the shell is not included in the path of access of the fluid pressure to the shell.

21. In a mercury tube switch, the combination of a metallic envelope serving as an electrode, a quantity of mercury in the envelope, an insulating member carried by one end of the envelope,

an electrode sealably extending through the inof a circuit through withdrawal of the mercury between the envelope and the electrode is spaced from the insulating member by the breaker.

22. In a mercury tube switch, the combination of a metallic envelope serving as an electrode, a quantity of mercury in the envelope, an electrode extending into the metallic envelope, an insulating member carried by one end of the envelope encompassing the electrode and compressively urged into sealing contact with the electrode and the envelope, and a breaker. formed to'provide a passage through which the mercury may extend from the envelope to the electrode, said breaker being mounted within the envelope in shielding relation to the insulating member for protecting the latter from the are occurring upon breaking of the column of mercury extending from the envelope to the elec-' trode.

23. In a mercury tube switch of the tilting type, the combination of a metallic tube closed at one end and serving as one electrode, a second electrode coaxially disposed with respect to said tube, an insulating member arranged to space said electrodes from each other and coopv crating therewith to form a sealed chamber, a

breaker carried by said insulating member within the chamber formed to provide a passage through which the mercury may extend in a column connecting the electrodes and being disposed in shielding relation to the insulating member for protecting the latter from the are occurring upon breaking of the column of mercury extending from the envelope to the electrode.

24. In a mercury tube switch, the combination of a metallic envelope, 9. quantity of mercury in the envelope, an insulating member sealably carried by one end of the envelope, an electrode sealably extending through said member andurging the member into compressive contact with the envelope, and a breaker carried by said mem; ber arranged to form a chamber at said elec trode to retain a pool of mercury in contact with trode sealably extending through said member and urging the member into compressive contact with the envelope, and a breaker mounted in the envelope and in position to form a chamber at said electrode to retain a pool of mercury in contact with the electrode, said breaker extending away from the insulating member so as to space from' said member the zone whereinan arc would occur upon breaking of a column of mercury extending between said envelope and said pool,

26. In a mercury tube switch of the tilting type, the combination of a metallic tube closed at one end and'serving as one electrode, a second electrode coaxially disposed with respect to said tube, an insulating member arranged to space said electrodes from: each other and co-.

operating therewith to form a sealed chamber, a quantity of mercury in said chamber and a breaker mounted in the envelope in position to form a chamber at said second electrode to retain a pool of mercury in contact with the electrode, said breaker extending away from the in sulating member so as to-space from said member the zone wherein an arc would occur upon breaking of a column of mercury extending between said envelope and said pool.

ond electrode coaxially disposed with respect to said tube, insulating means arranged to space said electrodes from each other and cooperating therewith to form a sealed chamber, a quantity of mercury in said chamber, and a breaiker mounted in-the chamber providing a passage through which the mercury may extend in a column connecting the electrodes, said breaker having a transaxial surface spaced from a transaxial surface of one electrode to form, between said surfaces, a trapping chamber adapted to retain a pool of mercury in contact with said electrode surfaces when the mercury column is broken upon tilting of the switch.

28. In a mercury tube switch of'the tilting type, the combination of a cylindrical metallic tube closed at one end and serving as one electrode, a second cylindrical metallic electrode, a--

cylindrical breaker of refractory material disposed coaxially in the tube, cylindrical insulating means which includes a portion surrounding and supporting said breaker anda portion compressively disposed between said coaxial electrodes to cooperate therewith in forming a sealed chamber, and a quantity of mercury in said chamber,

said breaker providing a passage through which the mercury may extend in a column connecting the electrodes and the passage through the breaker beingconstructed to determine the point at which the break in the mercury column shall ing with said refractorya recess spaced from said envelope, elastic compressible sealing means 76 the envelope, and compressible sealing means in said envelope floatably supporting said breaker therein.

32. In a mercury switch of the metal envelope type, a breaker of insulating material provided with an axial passage therethrough, an electrode at the outer end of said passage, and resilient sealing means supporting said breaker and electrode with respect to the envelope. 7

33. A mercury switch comprising, in combination, a pair of coaxially disposed electrodes, one

of which electrodes comprises a tubular metallic shell closed at one end; insulating means disposed between the electrodes, said insulating means, said shell and the other one of said electrodes cooperating to provide a closed switch chamber; a quantity of mercury within said chamber; a breaker of insulating material supported by the insulating means and forming with said other one of the electrodes a recess for retaining a quantity of mercury in contact with said other. one of the electrodes.

34. A mercury switch comprising, in combination, a pair of coaxially disposed electrodes,

one of which electrodes comprises a tubular me-.-

tallic shell closed at one end; insulating means comprehending a compressible element disposed between and separating said electrodes, means comprising said electrodes and insulating means cooperating to provide a gas-tight sealed switch chamber; a breaker of insulatingmaterial supported within the chamber and having a passage therethrough; and a quantity of mercury in the chamber adapted to flow through the passage upon tilting of the switch to electrically connect the electrodes, said breaker forming with one of the electrodes a recess adapted .to retain a portion of said mercury in contact with the last mentioned electrode.

.FRED S. ARMSTRONG.

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