US1872223A - Mercury switch - Google Patents

Description

1932- P. s. BEAR MERCURY SWITCH Filed June 18. 1930 INVEI VTOR.

e M W TTORNEY.

Patented Au 16, 1932 UNITED STATES PATENT OFFICE PAUL 8. BEAR; OI ELKEAB'I', INDIANA, ASSIGNOB, BY KESNE ASSIGNMENTS, TO m- NEAPOLIS-HONEYWELI: REGULATOR CO CORPORATION 01' DELAWARE MIPANY, OF MINNEAPOLIS, MINNESOTA, A

nan-cosy swrrcn Application filed June 18, 1980. Serial Io. 481,922.

otherwise moved into a position in'which the mercury may flow out of en%gement with the electrodes, the circuit is roken.. Generally speaking, there are two types of these 5 switches now" in general use, one employing an envelope of softglass, such as the lead or lime varieties with the electrodes suspended therein and in such position that they are bridged by'the body of mercury when the 0 tube is moved into a certain position. In this type of mercury switch, the arcing, both at the make and the break of the circuit, has a pronounced deteriorating effect upon the electrodes. As is well known, this action on 5 the electrodes affecting them to such an extent that the life of the switch is materially shortened. Further, soft glass is not adapted to withstand the playing of an are thereon. In the other type of switch referred to, 9 the envelope is made of quartz or hard glass, such as Pyrex or the like,'which, as is well known, is substantially unaffected by the, heat of the arc. In this type of switch, therefore,- owing to the hard glass envelope, the 5 electrodes and mercury may be so arranged that a mercury make and break directl on thesurface of the envelope ma .be utilized, the electrodes in these switches ing usually arranged in .wells or the like, formed in the D envelope, or so positioned relative to one another that each of them isat all times immersed in mercury so that all of the arcing which occurs, occurs directly between mer- 1 cury and mercuryasthe tube is tilted or othi erwise moved to make and breakthe circuit. 'As is well known, a mercury to mercury make and break is desirable fora number of rea sons. Chief among these isthe factthat in such a switch, the electrodes are not-subjectedl I to deteriorating influences of .any,,k;ind;1-

Then too, the arcing is less in a mercury to mercury make and break, as is well known. Furthermore, any arcing which does occur in a switch of this type merely results in a vaporization of a minute portion of the mercury at the point of contact which immediatley condenses upon quenchin of the arc and flows back into the main ody again. Despite the many advantages incident to the utilization of a mercury to mercury contact in switches of this character, they have not come' into general use, principally because of the cost of the hard glass and the difl'iculties encountered in hermetically sealing the leadmg-in wires or electrodes into an envelope made of such glass.

Various types of mercury switches have been designed to overcome the above disadvantages and chief among these is the type employing an inner sleeve of. quartz or Pyrex glass which is cemented to the inner surface of the glass envelope. Such a design.

however, necessitates a hand-sealed switch which materially adds to the cost thereof. In addition to this, another and more serious disadvantage results from the use of cement to hold the inner sleeve in place. After the switch has made a large number of contacts in the field, the mercury begins to leak through the cemented portion and thus cury in the sleeve and the body ofmercury which lies outside the sleeve. Such a condition, of course, destroys the effective operation of the switch and it is no longer useful.

An object, therefore, of my invention is to provide a mercury switch of the innersleeve' type which may be machine-sealed, thusmater'ially reducing the cost thereof.

' Another object is to eliminate the necescauses a connection between the body of meris substantially ing specifications taken in connection with the accompanying drawing wherein:

Fig. 1 is a longitudinal sectional view of a mercury switch constructed in accordance with the present invention, and showing the switch in open or circuit breaking position.

Fi 2 is a similar view showing the switch tilte to the closed or circuit making position.

Fig. 3 is View in section taken on line 3 -3 of Fig. 1, the mercury being omitted for the sake of clearness in illustration.

Fig. 4 is a detail view in end elevation of the ceramic ring.

Fig. 5 is a fragmentary view partly in side elevation and partly in section, showing a modified construction of the ceramicrin 7 Referring more in detail to the drawing, the switch comprises an outer sealed envelo e 1 which, as already stated, is preferably, or commercial and economic reasons, made of glass of the softer varieties. This envelope capsule shaped, through which leading- 1n wires 2 and 3 extend into the interior. These leading-in wires ma be of the usual copper clad type and are ermetically sealed in the wall of the envelope as at 4 at their points of projection'therethrough. Electrodes 5 and 6, preferably formed of some wire which is not afiectedrby the mercury, such, for instance, as iron,

nickel, tungsten or the like, are welded as at 7 to the leading-in wires2 and 3 immediately inwardly of the seals 4. The movable body of mercury in the envelope bears reference character '12 and, as will be observed, in one position, or in other words, the position shown'in Fig. 2 of the drawing, this mercom letes the circuit between the electr I es, w ereas,'as will be'observed, upon tilting "or' oscillation of the, envelope into an opposite'or reverse position the mercury will flow to the otherend "o the envelope,

1 thus interrupting the circuit: The envelope of'these switches is generally filled with an inert s,,such as hydro n,.in order to retard c emlcal actlon an .to assist in suppressing the arcing which results in prolongmg the life of'the switch. j v The switch as'thus far described is much the'same' as switches heretofore develo ed and 'whiclijare at the present time in'rat er a general. use, and-in which the make and break W occurs directly between .the electrodes and mercury, resulting in thedeterioratingefi'ects above pointedout. To, overcome the disadvantages inherent in this type: of switch heretofore. constructed and to, in reality, transform the same into a mercury to mercury make and break type switch, it is proposed,

according tothe present invention, to pro-.

vide means for constantly maintaining a portlon of themercury around each electrode.

, cular iece of'ceramic or other arc resisting material 10 such as high heat resisting porcelain, Alundum, or the like. This ring-like piece 10, is provided with a shallow annular slot 11,.adapted to fit the end of the inner glass tube 9. As before stated, the glass tube 9, is cemented to the ring 10 by means of dipping one end of the tubing in a suitable cement and then pressing it into the annular slot 11 provided in the ring 10. This assem bly is then placed in an oven and baked until the cement is properly set. Following this operation, the inner tubing 9 with the ring 10 attached thereto and the leading-in wire and electrode assembly 2 and 5 is placed in a chuck with the envelope 1. The formation and relative position of envelope l and inner tube 9 at this time is indicated by dotted line in Fig. 3. The whole assembly is then heated until the glass is brought to a melting oint, at which time a sealing head, of the usua construction, is clamped against the assembly on eitherside, thus making a hermetically tight 7 seal andfusing the tubing 9 with the envelope 1 in a pinch seal formation as shown in full lines in Fig. 3. I

The usual tubulation (not shown) is formed in the conventional manner and the leadingin wire and the electrode assembly 3- and 6 1s pmch-sealed into the opposite end of the envelope 1, also in the usual manner. The switch is then filled with the proper amount ofmercury, evacuated and filled with hydrogen or other inert arc-suppressing gas through the tubulation, and the envelope sealed ofi as indicatedby the reference-character1'3. v f

It will be noted that leading-in wires 2 and 3 are sealed into the envelope in a slantwise position, and that consequently the electrodes 5 and 6 are similarly disposed, the electrode 5 trodes 5 and 6 will at all times be'submerged 1n the mercury, whether the switch be in open or closed position.

A body of mercur 12 substantially-in the amount shown is p aced in the envelo 1. This mercury beingpartlyin the inner sleeve 9, and to right of the ring 10, and partly in the envelope proper, such parts being united into a single continuous body when the tube is tilted to circuit lnaking position,'substantially as shown in Fig. 2. As will bev observed, the body of mercury after separation thereof into two portions, one on one side and one on the other side ofthe ring 10, reunites. I in a single body again upon tilting of the be, as shown, and in thus reunitin the tn 7 H p 801131011 to the right of the ring 10 in ig. 2 carrying outthe present invention, a o

tubular piece of glass 9, which may also be ws along the floor of thetubing 9 and over the ring 10, meeting the other portion of the envelope 1. This is done so that the elecmercury which simultaneously flows along the floor of the envelope 1 toward the ring 10, the quantity of mercury and the general construction and arran ement of parts being such as to definitely bring about this making and breaking between these two portions of mercury within the ceramic ring 10. Thus, any arcing which may occur at the make and break occurs at this point which, as will be observed, is located substantially at the longitudinal axis of the envelope and at a sub- 7 stantial distance from both ends thereof.

Thus, the envelope is protected against all the deterioratinginfluences of the arc.

' Referring now to Fig. .5, in which is shown a somewhat different construction of the ceramic ring 10, the ring 10 is made with an extended annular flange 16 slightly less in circumference than that of the ring proper, the reduction in circumference of the flanged portion 16 being enough to allow the tube 9 to slip loosely over said flangedportion 16 of the rin 10. In assembling the tube 9 with the anged ring, a cementitious substance 15, capable of expanding slightly upon being heate is first applied tothe circumferential surface of the flanged portion 16. The tube 9 is then slipped over the flange until the end rests snugly against the shoulder of the ring portion 10. At this time, the

assembly is placed in an oven, as before, and baked until the cement has, properly expanded and set. An expanding cementitious substance is used in order to make a very tight fit between the tube 9 and the ring 10 and flange 16. a

The cement mentioned herein may consist of a pasty mixture of asbestos, sodiumsilicate and water. This cement forms a tight joint between the glass and the refractory ring 10. It is desirable that such cement have av coeflicient of expansion approximately the same as that of the material composing the inner sleeve, as otherwise the alternate heating and cooling of the ring 10 may cause the inner sleeve or the refractory ring to crack by reason of the strain produced by the unequal expansion of the sleeve and ring. A suitable compound for a cement 1s Sodium silicate 2246.7 cc. ,1 Water 394.160. Ground asbestos 857.9 grams The above formula will make approximately ten poundsof cement The nearer the coeflicient of expansion of the glass is to that of the refractory ring, the more asbestos is to be used in the above formula. Magnesium silicate, MgSiO magnesium oxide, MgO, may replace the asbestos. The sodium silicate may also be diluted with some water before use. Another cement that has proven satisfactory is made up of lead This is es ecially desirable when the glassemployed as a high coeflicient of ex ansion.

It will be seen that by my invention, soft glass may be used throughout the mercury switch, and handlabor, to a great extent, is eliminated, thus materially reducing the cost thereof and at the same time making a. mercury switch which is superior to those now manufactured.

It will be appreciated that the invention in its entirety may, of course, take various forms and modifications in addition to the specific example herein illustrated and described, but it is desired that the appended claims be interpreted broadly and .of a scope commensurate with the spirit of the invention and not limited or restricted in any manner to the particular embodiments of the invention shown.

I claim: I

1. A mercury switch comprising an outer envelope, an inner protective sleeve, said en velope and said sleeve being constituted of glass having substantially the same coefli- 'cient of expansion, electrodes extending into envelo e and forming a seal about one at least,

of sai electrodes and a body of mercury cooperable with the electrodes and uniting and dividing on asurface of said sleeve.

2. A mercury switch comprising an outer envelope, an inner protective sleeve, a pinch seal uniting one end of the sleeve to one end of the envelope and a body of mercury within the envelope and uniting and dividing on the inner surface of said sleeve. I

3. A mercury switch comprising an outer soft glass envelope, an inner soft glass rotective sleeve, an electrode projecting into 4. A mercury switch comprising an outer I soft glass envelope, an inner soft glass protectivesleeve, an are resistant collar sup.- ported by said sleeve, an electrode projectmg intotheprotective sleeve, a pinch seal unlting one end of-the sleeve and one endof the envelope and forminga seal about said electrode, a cooperable electrode sealed through the outer envelope and a body of mercury cooperable with the electrodesand imiting and dividing on a surface of the colar.

In testimony whereof he aflixes his signature.

I PAUL S. BEAR.

phosphate, Ph,(PQ.),, and sodium silicate. I

the protectivesleeve, a pinch seal uniting one

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