US2132920A - Switch - Google Patents

Description

Oct. 1l, 1938.

I swITcH Filed Aug. 5, A1935 2 Sheets-sheet 1v P. s'. BEAR Er'AL `2,132,920

Oct. ll, 1938.

P. s. BEAR Er AL 2,132,920

swITcH Filed Aug. 5, 1935 2 Sheets-Sheet 2 Patented Oct. 11, 1938 swrron y Paul S. iear and Herbert E Bucklen, Elkhart, Ind., assignors to Bucklen-Bear Laboratories, Inc., Elkhart, Ind., a corporation of Indiana Application `August 5, 1935, Serial No. 34,682

26 Claims.

Our invention is concerned primarily with switches of the mercury contactor type, and particularly with switches having a metallic switch envelope in place of the glass type envelope for- 5 merly employed. which has sealed-in metallic electrodes, although certain features of the present invention are applicable to such glass envelope switches. A

The specific embodiments herein disclosed ,are

l heavy duty switches suitable for a heavy schedule of switchingof power current. While our invention is especially useful for heavy duty switches, certain phases of the invention are equally applicable to light duty or small capacity switches.

l In mercury switches of the glass envelope type, the envelope is either evacuated or provided with a filling of hydrogen, neon, or a similar gas, usually under pressure. There are distinct disadvantages in both types of glass envelope 20 switches, since the inability to dissipate heat results in excessive temperature of the inleads'A with resultant leakage about the seal. Such leakage admits oxygen to the interior of the envelore,

resulting in rapid deterioration of the switch. or 25 explosion of the hydrogen filling.

The chief disadvantage of glass envelope switches of the mercury type is that there is a .4

considerable difference in the coeilicients, of

thermal expansion of the glass and of the' me.

1 40 shell type mercury switches, but such constructions present other disadvantages limiting their use. With a metallic envelope type of switch, there is diiiiculty in keeping the parts free of impurities, and surface oxidation particularly, dur- 45 ing the assembling process. Impurities tend to foul the mercury as well as the contact surfaces, and tend to increase the contact resistance. Also, where a thin metal section is employed, the thermal capacity is low andthe rate 50 of heat transmission is 'limited thereby. In such constructions the heat generated by a rapid succession of makingand breaking of relatively high currents cannot be readily dissipated,causing uneven heating up of the parts and tending to 65 break the seals about the electrodes. This tends (Cl. 20o- 152) to permit inltration of air, causing oxidation of the inner surfaces of the shells.

Attempts have been made to fill suchswitches with hydrogen gas, but hydrogen gas is very difficult to retain. Hydrogen will leak through pores 5 that will not pass other gases. It has also been attempted to employ liquid lls in such switches, but thus far no commercially practicable liquid fill switches have appeared on the market or been available. We have found that liquid iilled switches prior `to our present invention would almost invariably explode upon continued inter- "rupting operation at their rating, or upon overload.

Our present invention contemplates a mercury switch of the sealed envelope type, in which the interior of theswitch envelope is cleaned thoroughly prior to assembly, and kept clean during operation. In the preferred form of our invention we employ a cup-shaped metallic shell which has a ceramic insert sealed in one end thereof and having an electrode carried thereby, the shell itself serving'as the second electrode.

In order 'to reduce the localization of heat generated by the arcing produced during opening and closing of the switch as much as possible, we provide a switch construction in which this generation of heat takes place away from the metallic switch parts. 'I'his greatly reduces the tendency for pitting and oxidation of the metal. This construction also secures the beneficial action oi a mercury to mercury making and breaking of the contact. Also, our present construction removes this generation of heat as far as possible from the point of sealing of the ceramic insert into the open end of the shell, serving to protect this seal from the heat. Y

One of the primary objects of our present invention is the use of a liquid iill which is limited in volume with respect to the vapor space in 40 the switch envelope. This limited liquid ll to vapor relation is of distinct advantage in connection with several phases of this type of switch construction. In the first place, the liquid iill which dwe preferably employ is a slightly viscous liquid having a relatively high boiling point. The preferred liquid is triethanolamine. We may utilize a mixture of castor oil and alcohol. We do not wish to be limited to the above named liquids as others may be employed but the foregoing appear to 'ne-suitable for this purpose.

Only a limited quantity of such liquid is employed, the major portion of the interior ofthe switch envelope being employed as a vapor chamber. Upon slight heating of the liquid iill by at a localized 'point in the switch uniformly to the making and breaking of contact within the switch, the liquid starts to boil, and the vapor chamber lbecomes filled with vapor which condenses on the defining surfaces of the envelope and runs back as' a liquid into the main body of liquid. f

The use of alimited amountr of liquid lill with respect to the volume of the chamber produces the beneficial action, that the liquid fill upon boiling and subsequent condensation acts as a highly effective medium for dissipating heat generated all parts ofthe envelope, whereby the heat is rapidly conducted away from the arcing point and dissipated throughout the switch. This prevents the temperature at the heat generating point from rising above the boiling point so long as `there is liquid in contact with the heated part.

Another beneficial action secured by the use of a relatively large vapor space in the envelope compared to the amount of liquid ll employed resides in the limitation of the vapor pressure which can be generated by converting all of it to a vapor. f v

Still another beneficial action secured by this limitation ofthe liquid fill resides in the reduction of resistance to movement of mercury contactor, since it does not have to displace any appreciable quantity of liquid during its movement into and out of lcontacting engagement. The use of a liquid ll of this type is also advantageous in that as the pressure builds up inside the envelope, due to the heat of the arc, the arc value is thereby reduced by the increased pressure, preventing the formation of any appreciable arcs during rapid operation of the switch.

The particular characteristics and advantagesl of liquid fills as to their action on the metallic surfaces and the like are fully disclosed in our copending application, Serial No. 745,842, filed September 28, 1934.

Another feature of the present invention 'is the simplified, compact and eflicient switch structure which we employ in connection with the concept of limiting the liquid fill to vapor relation. The structure which we herein disclose is designed to ,utilize the advantages of the limited liquid fill but obviously many, if not all, of the advantages may be realized in other structures or types of structures, though generally less in degree.

Other objects and advantages of the present invention will appear more fully from the following detailed description, which, taken in oonnection with the accompanying drawings, will dislclose to those skilled in the art the particular con- Figure 4 is a sectional view takensubstantially y' on line 4-.4 of Figure 2, showing the internal construction of th'e switch;

Figure 5 is a detailed view of a modified type of insulating sleeve embodied-in the switch shown in Figure 2; f

Figures 6 and 7 are corresponding views of still further modified types of insulating sleeve;

Figure 8 is a sectional view through a modified type of metal shell switch;

Figures 9 and 10 are similar views through ceramic shell type switches; and

Figure 11 is a fragmentary section through a modified form of electrode and stud.

Referring now in detail tothe drawings, in

Figure 1 we have provided a substantially cupshaped metallic shell I0, having an outwardly flared open end portion I2 adapted to receive the ceramic insert I3, preferably porcelain of the wet process type; which insert is provided with an outwardly flaring tapered spillway or runway I4 extending into the shell I0 toward the closed end thereof. The shell I0 is preferably a drawn sheet metal member formed of iron or stainless steel I or alloy of iron.

, against a suitable resilient conical gasket or packing member I9, which is compressed axially in order to expand it radially. This gasket or packing member I9 preferably is formed of natural b e provided forkeeping the rubber undercompression without completely filling the available space. This allows the washer 41 to rest against the ceramic I3. Alternately, the. washer 41 may rest solely upon the end of the rubber gasket 49.

A conductor 20 is soldered or otherwise suitably secured to'the outwardly extending end of the stud I6.

The electrode I5 is disposed within a substantially cylindrical recess 22 formed at the rear end of the outwardly flaring spillway I4, the recess 22 providing 'a retaining ring or groove adapted to carry a small body of mercury 23 therein which is in engagement with the electrode I5, and which is adapted to .have contacting engagement with a second body of mercury 24 upon tiltingof the switch to move the body of mercury 24 up the inclined spillway I into contact with the body of mercury 23.

'Ihe junction of the spillway I4 with the recess 22 lprovides a lshoulder, the vedge of which is sharp and includes a solid angle of 'less than 90 whereby accurate repeat perfomance is secured.

In assembling the component parts of the switch, the insert I3, is secured in the :flared end I2 of the shell I0 by means `of a sealing gasket 25, which may be formed of natural or synthetic rubber or other suitable material, and which is compressed partly axially and partly radially and laterally of the tapered surfaces 26 and 21 of the insert when the insert is moved into position within the end of the shell I0. A suitable metallic retaining ring 21' of frusto-conical section is carried by the outer end of the insert, and the outwardly defining edge of the flared portion I2 of the shell III-is spun inwardly over the longitudinally extending end of the gasket 25 and 'ring 21', as shown at 28, vto compress and displace the gasket into final position to seal the In the assembly of the switch structure shown 'in Figure 1, the closed and rounded end 32 of the shell I0 is provided with a threadedinwardly extending portion receiving the closing screw or sealing plug 33. When the insert, with its y electrode fixed in position, is sealed within the open end of the shell, the shell is tipped upwardly with the end 32 thereof disposed at the top of the switch, and the mercury 23 and 24, of a predetermined amount, is placed in the switch envelope through the opening closed by the plug 33. A suitable quantity of liquid ll, indicated at 35, is then forced into the interior of the shell I0, the interior of the shell beingfirst evacuated to produce a relatively high vacuum therein, and being washed in any suitable manner to drive out any occluded gases or the like. Before the liquid fill has been introduced, and with a vacuum in the chamber, the chamber may be filled,

able gas which is substantially inert or noncor-rosive with respect to the metal and with respect to the liquid ll. This may be neon, argon, nitrogen, carbon monoxide, hydrogen helium, or the like. The amount of liquid fill 35 which is inserted is predetermined with respect to the volume of the interior of the switch envelope. In a preferred embodiment of the invention the quantity of liquid fill for a switch envelope having approximately a 21 cc. volume comprising about 0.5 cc. of liquid iill, which, together with the mercury and the like, provides for approximately 13.5 cc. of vapor space within the chamber. In a preferred embodiment of our switch, the internal volumeof the switch chamber is 21 cc. and approximately 7 cc. of mercury is employed as a contactor. The liquid ll may run anywhere from 1/2 cc. to 1 cc., leaving a vapor space of approximately 64% of the total volume of the switch chamber. We have shown the liquid as exaggerated in amount in the drawings, for the sake of illustration. In practice, the liquid has a tendency to spread and wet all of the inside surface of the container. as of an exaggerated thickness, for purposes of illustration.

When the connection tothe opening into which the closure plug 33 extends is removed, a por-v tact occurs at the acute angle formed between the sloping spillway I4 and the side wall defining The liquid film is shown with the relatively cool walls throughout the remainder of the switch envelope, is condensed, and runs back down the side wall of the envelope into 'the main body of liquid iill. This ebulltion of the liquid fill and the subsequent condensation of the vapor, due to the use of a definitely limited quantity of ll, prevents any excessively high rupturing pressures within the envelope, even if all of the liquid vaporizes.

We preferably employ triethanolamine as the liquid ll, this liquid having a relatively high boiling point and having the characteristic of maintaining the switch surfacesclean and free from foreign materials. If desired, however, a mixture of castor oil and alcohol may be employed, the castor oil being employed in the form commercially known as Ricinine. Anyliquid of this class which is anhydrous, alkaline in reaction, possesses arc extinguishing characteristics and has about the same viscosity and boiling point, may be employed.

It will also be apparent that the generation of heat at this acute breaking angle will be transmitted directly to the liquid ll, and by reason of the vaporization of this liquid fill will be'dissipated substantially uniformly throughout the `entire switch envelope, whereby the entire surface of the metallic shell I0 can be used for heat conduction away from-the point of generation of heat, whereby the heat will be rapidly dissipated to the surrounding atmosphere. Thus the limited liquid ll performs three important functions in a switch of this type, namely, a maintenance of a relatively low pressure, less than the rupturing or leakage pressure caused by its ebulltion due to the heat generated by arcing of the mercury to mercury contact; secondly, its use as a heat l.

transferring medium for dissipating the localized heat generated by thearc within the switch to all points of the switch envelope; and thirdly, the reduction of the arcing time due to the increased pressure within the switch envelopeV caused by evaporation of the fill, whereby upon increased rapidity of operation the pressure increases and the arcing time, or the length of the arc, decreases. By maintaining the volume of liquid fill employed relatively small with respect to the volume of the vapor space indicated at 35, it occupying only about 3% of this volume, it is apparent that high internal pressures within the switch envelope will not be developed even though all,

or substantially all, of the liquid ll be vaporized.'

Thus by the limited liquid fill both hot spots which are particularly destructive of glass envelope switches and high' pressures which are destructive of all forms of switches are avoided or greatly reduced.

It is to be observed that our system of internal circulation of the liquid flll is unique. The liquid forms a viscous film in contact with the internal surfaces and particularly with the mercury, which is always subject to heat generation by both the flow of current through it and by the arc produced at either making or breaking of the circuit.

This film of liquid is vaporized locally, i. e., at the point where heat is generated. The vapor tends to fill the entire vapor space and selectively flows to the coldest region because it is there most thus elevated by heat, i. e., vaporization, and delivered to the point'where it liquees and returns by gravity. Thus there is an internal circulation of the liquid in the switch. This action is highly z advantageous, and is particularly useful in heavy for Anot only is the heat easily dissipated, but the lss duty metal' shell switches.

There is a peculiarly useful feature in the constitution of the liquid flll as above disclosed. The high boiling point, viscosity, and the limitation of amount provide an ideal coordination of features,

rise of pressure is also limited.

` In the construction ci the porcelain insulator I3 it is advisable to construct the same of two parts joined together because of the 'diculty otherwise encountered in producing the sharp annular shoulder and the annular recess 22. The joint between the two parts is made preferably at a point along the length of the recess 22 where the gasket or seal 25 will prevent any possible leakage of the joint from communicating with the outside; Thus an imperfect joint between the two porcelain parts does not destroy the usefulness of the switch. The parts may be produced and red and then cemented together or they may be joined before firing if desired.

The electrode I5 it will be observed adapted to engage the mercury both on its axially facing or end surface and on its radially facing or side surface. This radial bearingJr or contact reduces the contact resistance between the electrcde..and

the mercury with minimum amount of mercury in the recess 22 while preserving the desired repeat performance.

Considering now Figures 2 to 4, inclusive, the

switch shown-in this embodiment of the invention comprises a drawn metallic shell 40 of iron, stainless steel or suitaole iron alloy, having the flared end 42 adapted to receive a ceramic insert 43 of v porcelain or the like, the insert 43 having a forwardly extending substantially cylindrical sleeve portion44, which sleeve portion is adapted to receive a tubular sleeve electrode 45 which may be of drawn sheet metal ofthe same material'as the shell 40 and which electrode is carried by the headed end of a shank 46 extending outwardly through the rear end of the insert 43. The sleeve 45 and the shank 46 are secured in fixed position with respect to the insert 43 by means of the washer 41 and nut 4e threading over the extending end of the stud there being a suitable lresilient conical rubber bushing or gasket 49 interposed about the stud and compressed ,and expan-ded within the defining wedge-shaped opening in the insert through which the stud extends by endwise pressure of washer 41. A suitable electrical conductor 50 is soldered or otherwise secured tc the outwardly extending end of the. stud 46. The sleeve 45 may be made of iron or stainless steel or the'like with a copper stud,46 brazed to the end ivall thereof, as shown as a modification in Flgure ,11. I

It will be noted that Ithe cuter end of the tubular sleeve electrode 45, indicated at 52, is disposed inwardly of the end of the ceramic sieeve 44, and that a body of vmercury 53 forming part 'of the mercury fill is carried within this sleeve in and the head end of the stud 45. A second body of mercury 5.4 forming the rest of the liquid fdl is carried withirrthe shell 40 about the outer surface of the ceramic sleeve 44, the two bodies of mercury being adapted `to have contacting engagement beyond the outer end of the ceramic Asleeve 44 when the switch is tilted about its longitudinal axis. The insert 43 is secured within the open end of the shell 42 in the same manner as described in connection with Figure 1, there being a suitable resilient gasket 55 and clamping ring 55 interposed therebetween, the outer edge 56 of the shell being spun over the rear portion of the gasket and about the outer surface of the ring to retain the insert in cushioned sealed engagement within the end of the shell 40 substantially. A second conductor 51 is secured at 58 to the external surface ofthe Vshell 40, whereby control of the circuit through the conductors 55 and 51 is provided by movement of the bodies of mercury 53 and 54 within the switch. 'I'he closure plug 59 tioned with respect to the vapor space 62 that free ebullition of the ll is provided for washingV the'internal surfaces of the shell 40, the sleeve 44 and the-tubular electrode 45, as well as the mercury itself. This vapor space 62 also provides for free transmission of the heat generated at the outer end of the sleeve 44 due to rnaking and breaking of contact thereover between the bodies of mercury 53 and 54, to ali parts of the switch envelope, whereby no loeaiized points of heat generation are allowed to build up.

In the operation of the switch shown in Figures 2 and 3, when the switch is in the position shown in Figure the circuit is broken between the bodies of mercury 53 and 54, which are in respective engagement with the electrodes 45 and 40. Upon tilting of the switch in a counterclockwise directionabout its longitudinal axis, as shown in' removed from the electrode seal 49, and from the ceramic seal 55.

In addition, it removes the point of generation of heat away from any of the metal surfaces ofthe electrode 45 or electrode 40, and consequently provides for free action of the liquid fill dissipating this heat to all parts of the switch envelope, and preventing building up of localized heated spots. Also, due to the definite relation of the sleeve 44 withv respect to the shell 40, a positive opening and closing of contact at the same points of inclination is assured, thus giving repeat performance, that is, the opening and closing oi the switch at the same angular positions for successive operations of the switch.

Referring now to Figure 5, we provide a ceramic sleeve 44", which may correspond to the ceramic sleeve 44 of Figures 2 to 4, inclusive, but which is not as great in longitudinal extent. To the extending end of the sleeve 44', whichis provided with the, annular shoulder 65, we secure a modifledtype of breaking edge, which is shown as a f tothe sleeve` 44' by cementing.- The breaking edge formed by the tapered surface 61 is considerably wider in extent, that is, is radiallythickened toprovide for slow motion operation of the switch, whereby the .two bodies of mercury 53 and 54 will not come together with as great a rapidity as provided merely by the sleeve 44. Optionally this edge may be cut back, as shown in Figure '1, to increase the acuteness of the breaking angle.

In Figure 6 we show a still further modified form of breaking edge, comprising a sleeve' member 10, having a suitable recess portion 12 for receiving the end of the stub porcelain sleeve 44', and having a double rounded outwardly extending defining edge 13, which provides a spillover or snap operation of vthe switch; due to the fact that the two bodies of mercury snap over the rounded portion of th-edge 13 and come into engagement in a direction substantially normal to their original direction of movement. This provides for engagement ofthe mercury at an accelerated speed of engagement, which produces a sufficient impact to completely close the circuit without any frying or sputtering between the advancing edges of mercury as the switch should be slowly tilted. It isl to be observed that. in the forms shown in Figures 2 to 7, both bodies of mercury have movementtoward l and away from eachother, with the resultant double speed of engagement and separation.

In the embodiment of the invention shown in Figure 7, we provide a still further modified type y of breaking edge comprising the sleeve 15 having the cutaway annular ring portion -16 for cementing the same to the end of the stub shaft 44', and provided with an externally chamfered acute angle breaking edge 11, cut back from the inner defining periphery of the sleeve 15. This edgev forms a definite and positive point of separating the mercury, whether moved rapidly or rela- .tively slowly, and thereby permits repeat performance, i. e., the feature of making and breaking contact at the same angle'at all times. This feature we believe to be unique in this sleeve type of switch. The present switch requires to be held in no particular angular position about spherical head portion 89, preferably formed of its axis, since it is symmetrical with respect to its longitudinal axis.

In Figure 8 we have provided a switch requiring only a small operating angle. In this construction the metal shell is provided with the usual filler opening 82 and sealing plug 83. At its open end the shell 80 receives the ceramic insert 84 cushioned in sealed engagement within the shell by means of the annular tapered compressible gasket 85 and the frusto-conical ring 86 which is pressed longitudinally against the gasket by the spun-over edge 81 of the shell 8|).`

Extending centrally through the insert 84 Nis a second electrode stud 88, having an inner hemia non-wetting metal, such as stainless steel, projecting outwardly of a central boss formed'on the insert. The surface of the insert adjacent the boss 90 is annularly recessed, as at 92, to position the head 89 of the second-electrode inwardly of adjacent portions of the insert. 'I'he stud 88 is secured in position by a washer 83 and nut 94 engaging the outer end thereof, the insert be- `it will be noted that the lower surface of the electrode head 89 is positioned substantially at the lower edge of the head approximately .015 lowerthan 'the meniscus height of the mercury 91, 4whereby the mercury' will make contact between the shell 80 and the electrode 89 Without rst engaging the ceramic 84. The floor of the envelope is thus maintained level and no'uphill rolling of the mercury is necessary. The ineluded angle of operation of such a switch can be maintained within 1/. The interior of the envelope is provided with a partial fillingA of triethanolamine, or a similar liquid having equivalentproperties, as indicated at 98, in the manner described in connection Awith previous embodiments of the invention.

Figures 9 and 10 are directed to a switch of the ceramic shell type, and disclose switches of the same general construction as indicated by corresponding reference numerals. Thus we provide a ceramic cup-shaped shell |00 having an annular externally thickened portion |02 adja- -cent its open end.A The closed end of the shell |00 is adapted to receive an electrode button |03 having a shank portion |04 extending through the shell and sealed with respect to the shell by the tapered gasket |05 which is axially compressed'into sealing position by the nut |06 engaging the outer end of the shank |04.

At its opposite end, the shell |00 receives the closure cap |01 having the annular clamping portion |08 provided with a spun-over edge |09 engaging the frusto-conical washer ||0 for compressing the resilient gasket ||2 into tight sealing engagement with the external tapered surfaces of the portion |02 of the shell. Welded, or otherwise suitably secured to the inner surface of the cap member |01, is a tubular sleeve member I I3 having a relatively snug fit in the interior of the shell |00 and being closed at its opposite end across the inner face'of the cap member |01. A suitable filler opening is formed in the members |01 and II3, and is closed by the iiller plug Referring 'now specically to Figure 9, a body of mercury ||5 is disposed within the envelope comprising shell'l00 and sleeve H3, and upon tilting of the envelope the mercury is adapted to move toward and away from the electrode button |03, which is preferably formed of stainless steel or other metal not wet by the mercury. This produces contact'- between the sleeve ||3 and button |03, and controls the circuit through the two flexible leads ILS and ||1 electrically connectedto the button and the sleeve. Suitable liquid iill is introduced into the envelope, as indicated at ||8, to take care of heat dissipation and the like.

In Figure 10 we have modied the construction to produce va switch having a larger operating angle and having mercury-to-mercury making and breaking contact. The button |03 of this vembodiment is provided with a` substantially hemispherical cup member |20 held in the closed end ofthe shell |00 by the electrode |03. An annular insulating ring |22, having an'internal frusto-conical spillway surface |23, is inserted into position with the small end of the spillway converging surface, rushes into contact with the mercury |24, closing'the circuit through the switch. Upon opposite tilting of lthe switch, the

vmercury moves down the diverging surface with increased momentum, until finally the gravitational pull'overcomes the cohesion between the bodies |24` and ||5, and themercury is parted over the sharp edge between surfaces |23 and |25, whereby the surface tension snaps the adjacent contiguous edges into receded position. Thus a substantially snap action type of switch is produced.

It will be noted that in both Figures 9 and 10 the actual making and breaking of `the circuit occurs at a point removed from the gaskets ||2, whereby the'gaskets are disposed at the relatively cool portion of the switch.

'It is of paramount importance that the relation of the volumeY of liquid ll to the `volume of the vapor chamber be accurately controlled in order that proper limitation of pressure during heating be obtained. The liquidlm provides for cleansing of the internal surfaces of the switch envelope and keeping them clean. .The vapor produced by boiling, and its condensation, provides for rapid dissipation of heat from a -localized point of heat generation in order that overheating of any particularportion of the switch will be prevented. It is apparent,- however, that this ratio or relationshipbetween these two factors may be varied, depending upon the type of switch which is employed, the currentV which it is required to control, vand other similar factors which must be considered. Therefore, while we have disclosed a particular ratio of approximately 3% of liquid 'fill inI the vapor space, we do not intend to limit the invention to exactly this particular percentage, since it is obvious that the proportions can be regulated or varied as desired to meet certain specified conditions.

One primary concept vinvolved in this phase of the present disclosure is to reduce the amount of liquid fill to the point that when the entire liquid ll is vaporized the pressure of the vapor will then not exceed the strength of the shell or container of the switch. 'I'his medium, i. e., a condensing vapor, is a highly eiiicient means for transferring heat. .'I'he parts are so proportioned that on rated maximum duty the liquid will not all be vaporized, but suiiicient vaporization occurs to carry off the necessary amount of lieat to keep the temperature Within safe limits. If rated maximum is exceededy the pressure may rise, but never to the point of breaking ordey stroying the container. i

We donot intend to be limited to the specic" details shown and-described, nor to the proportions or sizes shown, as mdications of our inventiony will be obvious to'thosef skilled in the art.

We claim: 1. In combination, in a switch of the class described, a cup-shaped metal shell having an en- 2,132,920 adjacent the cup |20, whereby a small body of larged open end, a ceramic insert in the open end of said shell, ,resilient sealing means com- .pressed radially between said insert and the interior of said enlarged opened end, a ceramic sleeve extending longitudinally inwardly from said insert and of a diameter substantially less than the internal diameter of said shell, a tubular electrode within said sleeve and abutting .against the insert at the insert end of said sleeve.

an extension ofthe electrode supportingV said electrode in position and extending outwardly .centrally of said insert, compression seals of yielding material for sealing the ceramic radially.

within the open end of said shell and sealing said electrode with respect to said shell, a body of mercury'in said shell and adapted to make and break contact between said electrode and shell over the extending edge of said sleeve member,

and an anhydrous alkaline liquid fill in said. shell for dissipating heat from said edge to all parts of said shell.`

'2. A switch of the metallic envelope type comprising a tubular cup-shaped metallic shell having an enlarged open end, a ceramic insert closing the open end of said shell, an annular rubber gasket compressed between the external annular surface of said insert and the exterior surface of the open end of said shell, an integral cylindrical sleeve extending longitudinally from said insert into said shell, an annular electrode surface engaging the interior of said sleeve intermediate the ends thereof, a stud securing said electrode in said sleeve and extending outwardly through said insert, a rubber gasket about said lstud and compressed against said insert, an

integral flange'on said insert surrounding said stud and extending axially outwardly beyond the end of said shell, and a body o f mercury vfor bridging said shell and electrode about the inner end of said sleeve upon tilting of said switch.

3. A switch of the metallic envelope type comprising a tubular cup-shaped metallic shell having an enlarged open end, a ceramic insert closing thevopen end of said shell, a rubber gasket compressed between the external annular surface of said insert and the inner surface of the open end of said shell, an integral sleeve extending longitudinally from said insert into said shell, an electrode within said sleeve Iextending to a point adjacent the open end thereof, a stud securing said electrode in said sleeve and extending outwardly through said insert, a rubber gasket about said stud and compressed radially against said insert, insulating ange means on said insert surrounding said stud axially outwardly of the-end of said shell, a body of mercury for bridging said shell and electrode, and means for making and breaking contact between said shell and electrode over the open end of saidsleeve. y

fi. A mercury switch of lthe closed metallic envelope type comprising a liquid fill consisting of an anhydrous alkaline liquid of low vapor pressure and having a substantially constant viscosity within the temperature rangeto which it is subject and being inert with respect to'the of said ll being such that complete vaporizatio thereof will not produce a pressure/sumcie to rupture said envelope and associated parts of said switch.

6. In a mercury switch, a metallic cup-shaped shell, a ceramic insert in the open end thereof,

lcompressiblegasket means between said shell vand insert, an electrode carried on the inner surface of said insert and having an outwardly extending shank, gasket means about said shank and compressible against said insert, abody of mercury in said shell of such quantity that the meniscus height thereof is substantially equal to the radial distance between the inher surface of said shell and the peripheral surface of saidl electrode, and a vaporizingpartial liquid iill in said shell for dissipating heat therein during rapid operation of said switch, said gasket means being so shaped as to relieve excessive internal pressures in said shell but preventing entrance of air thereinto. A r

7. A heavy duty switch comprising a metal shell, an insulator, and an electrode dening an,

envelope which consists chiey in 'a metal heat conducting wall and which is of great strength to resist internal pressure, a body of substantially pure mercury adapted to make and to break contact between the metal shell and the electrode, and a thin film of a viscous anhydrous alkaline liquid of high boiling point which is in contact with the mercury and which is vaporized at the point of heat generationv and condensed upon the metal walls of the envelope to dissipate heat and equalize the temperature of the parts of the switch, the amount of liquid in saidenvelope being so low-that excessive pressure is avoided by vaporization of the liquid as fast as it flows to the point of heat generation.

8. In a mercury switch of the sealed envelope type having iron electrodes and a body of substantially pure mercury for making andV4 breaking circuit betweenl the electrodes, a limited fill of triethanolamine providing not substantially more than a thin film which is adapted to be vaporized locally by the action of makingl or breaking the circuit, the vapor thereof engaging the walls and there being condensed.

9. In a mercury switch, a tubular ferrous envelope, a plug of insulation closing said envelope, the end of said envelope beingl beaded over a portion of the plug 'to retain said plug against internal pressure, a central electrode extending -through and sealed to said plug and having a head upon the inside thereof preventing the expulsion of the electrode by internal pressure, a body of substantially pure mercury in the en- A velope for connecting and disconnecting the shell and electrode, and a small quantity only of ethanolamine in said envelope and in contact with the mercury, said ethanolamine being present -in less than 5% of the free internal volume of the envelope and being capable of being vaporized locally by operation of said switch under load in making and breaking the circuit.

10. In a mercury switch, a tubular ferrous envelope, a plug of insulation closing said envelope,

the end of said envelope being beaded over a portion of the plug to retain said plug against internal pressure, a central electrode extending 1 through and sealed to said plug and having a head upon the inside thereof preventing the expulsion'of the electrode by internal pressure, a

body of substantially pure mercury in the en drous alkaline liquid of a boiling point in excess of that of water, said liquid forming a thin layer of substantially not more than a lm in contact with the mercury at the point of greatest heat generation, said film being locally vaporized andl the vapor carrying the heat to the envelope to equalize the same. l

11.'In a heavy duty mercury switch of the metal-envelope type comprising a metal shell and an insulated electrode sealed together and insulated from each other, a body of substantially pure mercury for making and breaking connection between the shell and the electrode, said shell being beaded over the insulation of the electrode to provide a closed envelope capable of withstanding high internal pressures and temperatures substantially in excess of boiling water, and a small quantity of anhydrous triethanolamine forming a iilm of liquid in contactwith the mercury and being vaporized locally by the heat of the current to transfer heat from the point of vaporization to cooler parts of the envelope, where it is condensed.

12. 'Ina mercury switch, a metallic cup-shaped shell, an insert closingone end of said shell, a body of mercury in said shell, an electrode carried at the inner end of said insert and radially spaced from said shell a distance substantiallyv equal to the meniscus height of said mercury, said insert having an annular recess in the radial inner face thereof about said electrode of a curvature corresponding to the curvature of the approaching edge of said mercury, and a shank on said electrode extending outwardly through said insert. v

13. In a mercury switch, a ceramic cup-shaped' envelope having an open end and having an enlarged annular wall portion about said end, an electrode sealed in the opposite end of said envelope, a second tubular sleeve electrodev extending into the open end of said envelope and terminating within said envelope iat a point open ends thereof in overlapped relation to form@v aA switch envelope, annular sealing means sur-i rounding an end-of one of said members', means carried by the other member for radially compressing said sealing means into sealing engagement to form a sealed switch chamber, a body of mercury in said chamber, one of said members being metallic and the other being formed of refractory insulating material, and an electrode carried within said chamber by said insulating member and spaced from the other member; said mercury bridging between said electrode and said other member upon tilting of the switch chamber.

15. In combination, a cup-shaped ceramic member, a cup-shaped metallic member fitting into and extending toward the closed end of said ceramic member, electrode means carried within the closed end of said ceramic member, an insulating ring within said ceramic member between said electrode means and the inner end vof said metallic member forming -an inclined raceway therebetween, and uid conducting means for eiecting connection between saidmetallic Amember and said electrode means over said raceway upon tilting of said switch.

16.7In combination, an elongated cup-shaped ceramic member having an open end, a -tubular electrode sleeve sealed in the open end ofwsaid/ member, electrode means carried within said member at the closed end thereof and spaced `tension of Leaid mercury and to assist its; movement. the films on said`bodies ofmercury being compressed therebetween upon relative movement toward each other to increase the head of mercury at the-contacting surfaces, andethe potential across s aid bodies of mercurypuncturing said lm to produce instantaneous enlarged surface contact between said bodies for reducing the resistance to passage of current through said contacting surfaces. 18. In a mercury switch, a cup-shaped metallic envelope having an lenlarged open end, a ceramic insert in said open end having an external annular shoulder, resilient sealing means between -sald enlarged vend of Ysaid envelope and saidV shoulder, said enlargedend having its defining edge pressed radially inwardly axially outwardly of said shoulder to lock said insert in sealed'position therein, said insert having a tubular'` sleeve extendingaxiallyiinto Vsaid envelope in spaced relation thereto, a tubular electrode within said sleeve terminating adjacent the inner endthereof and having a shank portion vextending outwardly through said insert, anda body Y'of mercury in saidenvelope for bridging between said electrode and envelope and makingV and breaking contac over the defining edge of said sleeve.

19. Means for dissipating heatv from the*A point of generation thereof in a sealed metallic envelope mercury switch having a ceramic insert in one erel thereof Vcarrying an electrode and havy ing a body of mercury therein adapted to make and break contact betweengsaid envelope and electrodeY over an internal surface of saidinsert, comprising an anhydrous alkaline liquidi-lll of" small volume compared to the internal volume of said switch and adapted to adhere to the mercury, said ll having arelatively high boiling point whereby upon arcing at said surface saidl fill vaporizes and'passes to cooler portions of said `'Witch where it is condensed and flows by gravityS back to the point of heat generation.

20. Means forfdissipating heat from the point of generation thereof in a sealed metallic envelope Y mercury switch having a ceramic (insert in one end thereof carrying an electrode `and having a body of mercury therein adapted to make and break contact between said envelope and elecf trode over an internal surface ofsaid insert, comprisingr an anhydrous alkaline liquid fill of smalilf volume compared to the internal volume of said*- switch 'and adapted to. adhere to the mercury,

said fill: having a relatively high boiling point? whereby upon `arcing at said surface said ll vaporizes and passes' to cooler portions of said switch whereit is condensed and flows by gravity back to the point of heat generation, said vaporization producing an increased pressure in said switch tending to minimize arcing during making l and breaking of contact. 21. In a mercury switch of the heavy duty type, a cup-shaped metal shell forming one electrode and having an enlarged open end, a refractory insert in said open end having an axially taperedbore opening into the interior of said envelope, Yan annular resilient gasket interposed between the external annular surface of said insert and the adjacent internal surface of the enlarged end of said` shell, said shell having its deiining edge forced radially inwardly to eifect radial and axial compression of said gasket, an electrode carried within said bore and having its periphery spacedzfrom the annular defining surface of the smali end of-said bere, a body of mercury retained in said bore in contact Ywith a portion of the face and periphery of said electrode, and a second body of mercury in said shell adapted to makeY and break contact with said rst body of mercury at a. point spaced from said electrode.

22. In a metallic envelope mercury switch having a substantially cup-shaped switch chamber defined by metaliic walls and closed at one end by a refractpry ceramic insulator carrying a metallici electrode, said chamber having a liquid cgntactorY movable upon tilting of said switch to make and break contact between said envelope and said electrode, the method of maintaining the switch cool during operation at its rated capacity which comprises providing a limited flll of an anhydrous alkaline liquid which clings to and-moves with said contacter, eand has .a boiling point below the temperature vto which flow oi! normal rated current-tends to heat said conductor, vaporizingVV said liquid fill at vthe point of said contact bei tween .said envelope and saidelectrode by the heat generated in said contacter, providing unrestricted movement of said vapor into contact with said metallic walis to dissipate said heat therefrom and to condense said vapor, and providing for free return of said condensate into and said tubular portion upon tilting o1' saidswitch. i 24. A ceramic insert for a mercury switch coni;-

prisinga cylindrical portion andan enlarged head i portion having a tapered external surface coriverging toward the cylindrical portion, said insert having imperforate sidewalls and having a conical tapered runway terminating in a sharp peripheral edge defined by a radially extending groove terminating the conical runway.

' 25. In combination in a mercury switch, a bushing of reractorylfinsulation having imperforate side walls and having a peripheral shoul- Y der dening aY wall of a mercury retaining pocket and a bore extending in one direction'from said shoulder and forming a runway for mercury, said bushing having a substantiaiiy cylindrical por-v tion extending in the apposite direction from said .shoulder to form a part of said mercury retaining pocket, alrtubular metal shell having Ian enlarged sealingportion having spaced inwardly extending shoulders for holding the bushing against endwise displacement in either direction relative to the shell, and a resilient annular body of insulation disposed between the shell and saidv bushing and being held in compression uponv the bushing, a resilient deformable sealing bhing external peripheral wail of the bushing whereby surrounding said stem within said refractory i the bushing is also placed under compression. bushing, and ineens for holding said sealing bush- 26. The combination of claim 25 with an elecing in compression to seal the electrode tothe re- 5 trede carried by the bushing, said electrode hav- Iractory bushing. i ing a disc-shaped portion closingof! said cylin- PAUL S. BEAR. v

drical portion and forming a wall of said pocket HERBERT E. BUCKLEN'. and having a stem portion extending outside said v CERTIFICATE 0E coRREcTIoN. Patentl No. 2,152,920. v october 11, 1958.

' PAUL s. BEAR, ET AL.

It is hereby certified that error appears in the printed. specifi-cation of the above numbered patent requiring correctionas follows z Page 6 second column, line 27 claim 2, for the word "exterior" read interior; and that the said Letters Patent should be read with this correction thereinrthat the same may conform to.the record ofthe case in' the Patent Office. Signed and. sealed' this 29th day of November, A. D. 1958;

Henry Van Arsdal e (Seal) I l A Acting` Commissioner of dtents.

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