US1967953A - Mercury switch - Google Patents

Description

July 24, 1934. Q J- WARNKE I 1,967,953

MERCURY SWITCH Filed Feb. l. 1932 Patented Judy 249 y lg3di Cari .,U, Warnke, Elkhart, End., assigner, hy directan'd mesne assieme, to The Adams it li'ilesti liaise Company, Chicago, lill., a corporation of )Iliinois Application February il, 31932, Seriali No.. who@ 2 Claims.

My invention relates to mercury switches or sealed containers in general, and. is concerned more particularly with providing a device of this character in which the outer envelope or container is protected against the ordinary disintegrating inuences present in the operation of the switch.

@ne object of-my invention vis to devise a mercury switch which 'is constructed and arranged to i@ materially shorten thelength 'of the current path through the switch with a view of correspondingly reducingthe electrical resistance and accompanying heat effects which would otherwise obtain owing to the relatively low conductivity of meri5 cury.

A further object is to provide a switch of the type comprising an outer envelope and an inner structure disposed in spaced relation thereto and sealably connected to provide an integral .unit

a@ characterized by strength and rigidity, the inner structure substantially dividing the outer envelope into two chambers andhaving a ceramic sleeve attached thereto composed of arc resisting material that readily permits the switch to be employed under high wattage conditions. .l

A further object is to devise a -switch o the character described in which the ceramic sleeve is preferably composed of a material, such as zirconium oxide or an equivalent substance, which 3o is characterized by a melting point several times that of glass and a coeicient of thermal expan-` sion substantially equal to that of glass, thus pro- 1 tecting-the switch against the erosive conditions Ynsually obtaining and permitting the sleeve 'to be attached to the inner tube without creating any internal strains arising from heat effects under conditions of operation.

`f A further object is toiprovide a switch as above set forth which is characterized by a mercury to o mercury contact owing to the interposition of the inner tube whichinsures a merging and dividing of the mercury mass in the 'circuit making and breaking positions of the switch, respectively, and consequent lengthening of the operative life of the 145 electrodes since they are not subjected to the erosive eiectsof the electric arc.

A further object is to provide av mercury switch which incorporates the above noted advantages and which is further simply constructed and ar- .o ranged to withstand the rigors of daily operation over a long period, and whose manufacture is comparatively inexpensive and susceptible of .being practiced under large scale manufacturing n'con-- ditlona y o5 in the operation of a mercury switch whether employing a mercury to metal contact or a mercury tol mercury contact, when theelectrical circuit is interrupted or is about to be completed by an appropriate actuation of the switch con=1 tainer, the tendency of the current to break down t@ the dielectric strength ofthe intervening air or gas gap resultsin the creation of an electric are of relatively high temperature which has a marked owing to the high-voltage arc which is induced at the breaking yof the circuit and the resulting rapid changes of temperature whichv subsequently are obtained within the switch envelope. This rise in temperature occurs within a relatively short period of time, as does the temperature recession downwardly therefrom to the normal temperature of the switch, so that the glass envelope l isl subjected to a highly destructiveeiect `in both so instances, the glass being actually eroded with a consequent decrease 'in the wall thickness, so

that excessive stresses are established in the envelope whichare in addition to and superimposed on the actual stresses present in the glass. The g5 glass accordingly breaks at the indicated point and the switch is therefore removed from service. Similar rapid .temperature changes occur in induction switches when employed in circuits which are subject to high current surges, that is in in 9o ductive circuits through which the current iiows intermittently and in which the loads are heavy, such as the lamp banks-of advertising signs and similar installations. K 4

g Many structural solutions have been hereto- 95 fore proposed as remedies for the above disadvantages, one such typeproposed being in the nature of an outer envelope which encloses an` inner, protected structure which alone is subjected to the ravages of the electric arc and which is therefore especially constructed to resist the same; It is accordingly possible to make both the outer envelope andthe inner structure of a cheaper material and one that is less expensive toA work during' the manufacturing operation, 105 While particularly treating the inner structurel to eiectively resist the high temperature conditions obtaining. The switch comprising the present `invention belongs generically to the latter type of mercury switch, but in addition embodiesgcer-ff tain specific advantages as regards the relative locations of the inner structure, the mercury masa and the electrodes, which are so disposed as to provide a considerably shorter path for the 'electric current when the switch is in a circuit making position, than Anow obtains generally in the art. Mercury is characterized by a relatively high resistance and by so disposing' the above parts in the manner indicated, it is possible to minimize to a considerable extent the low conductivity of the mercury, as well as protecting the glass and the electrodesfagainst the ravages of the electric arc.

'Ihese and further objects of my invention will be set forth in the following specification, reference being had to the accompanying drawing, and the novel means bywhich said objects are effectuated will be definitely pointed out in the claims.

In the drawing:

Figure 1 is a sectional elevation showing my improved switch in circuit breaking position.

Figs. 2 and 3 are views similar to Fig. 1, but showing the switch in two different, circuit making positions.

l Fig. 4 is a perspective view of the ceramic sleeve utilized in my improved switch to protect the glass structure against erosion.

The switch shown in the drawing is intended merely as illustrative of switches of this general character and it will be understood that the de- 'tails of construction may be modified as appears desirable, dependent upon the external shape of the switch container, the disposition and number of the lead-,in conductors employed, and miscellaneous other factors.

Referring to Fig. 1, the switch comprises an -outer envelope or :container 10 which may be composed of soft glass or any other suitable material that is customarily employed in the manufacture of Amercury switches and in the type shown has a generally elongated shape, although the precise nature of the latter forms no part of the present invention. However shaped, the container 10 will have positioned therein an 'inner element or structure 11 which is shown as tubular in conformation, although it may assume other forms, and is preferably composed of the same kind of glass asis the outer envelope 10. The tub 11 is preferably concentrically disposed with reference to the envelope 10 and at. one end thereof is fusibly connected with said envelope'by means of an annular wall 12, thus dividing the interior of the envelope 10 into chambers 1'3a'nd 14 which havecommunication thrcugh the tube 11.y `The' opposite -end of -said tube terminates short of the adjacent .end wall l5 of the envelope 10 and the opposite end wall 16 may be pinchs ealedduring the manufacture` of the switch-in the usual manner in order to hermetically seal the envelope.

Positioned within the open end of the tube 11 i is a'ceramic sleeve 17 having an annular shoulder 18 which abuts against'` the end edge ofthe sleeve 11. The sleeve 17 is fused or sealed, or attached in any other convenient mannerto the inner tube 11 and is preferably composed of znconium oxide, or an equivalent material which has substantially the same coemcient of thermal expansion as the glass composing the tube 11. This sleeve, when composed of the indicated material or materials, is characterized by a melting point which isfrom three to five times that of glass or, generally speaking, is considerably higher than the latter, so that it is well adapted to withstand rapid temvany required length of path with a view of minperature changes, as well as the deteriorating effects of the electric arc. Extending through the end wall 15 are electrodes 19, 20 and 21, electrode 19 being substantially axially aligned with the inner tube and projecting within the ceramic sleeve 17, with the other electrodes disposed above and below the electrode 19 in the form of construction shown in Fig. 1. The electrodes may be of any desired shape and material and are connected externally of the envelope by means of lead-in conductors of the customary type which are sealed through theend wall 15 in a manner to prevent leakage at these points.

In the circuit breaking position of the switch, as shown in Fig. 1, the chamber 13 encloses a mass of' mercuryl 22 which is located entirely to the left of the sleeve 17, while the chamber 14. carries a mass of mercury `23 in which is continually immersed the electrode 2l.

such that, when the envelope 10 is tilted into the position shown in Fig. 2, the electrical circuit is completed through the switch by a uniting of the mercury masses 22 and 23 over the surface presented by a portion of the sleeve 17. Similarly, when the envelope 10 is returned to the position shown in Fig; 1, the then single mass of mercury divides substantially over the same surface to form the separate masses' 22A and 23, thus breaking the electrical circuit. It will be particularly observed that, when the switch is moved to a circuit making position, the mercury mass 22 establishes contact with the electrode 19 prior to joining with the other mercury mass 23, and, similarly, when the switch is moved to a circuit breaking position, the division of the single mercry mass occurs prior to the separation of the mercury mass 22 from the electrode 19.

Accordingly, such sparking as may occur will be substantially directed against the specially formed sleeve 17 which along is subjected to the erosive action obtaininglduring these operative phases of the switch.

Referring to Fig. 2 whichshows one circuit making position of the switch, it will be noted imizing the relatively low electrical conductivity which characterizes mercury. Resistance losses within the switch are therefore considerably less- '.-ened as well as the heat effects which 'flow from such a condition. The switch is therefore capacitated foruse more particularly under conditions requiring the carrying of a relatively high amperage whichrenders the switch highly advantageous for use under heavy load conditions. The switch is further characterized by a relatively long life, particularly as regards the substantial freedom of the glass composing the principal portion of the switch from erosion and the avoidance of any tendency of the electrodes to become pitted.

vThe switch is illustrated as being provided with ias j the extra electrode 20 in order to enable it to be employedunder conditions wherein the switch substantially occupies the position shown in F1g.

.i under circuit making conditions, wherein the Where it is contemplated take on the part of the mechanic installing the switch arising from uncertainty as to whether the switch should be so positioned as to place, the electrode 20 above the electrode i9 or vice versa. The electrode 2o enables the switch to be placed either in the position shown in Fig. l, or in a position in which the electrode 2l occupies the position shown by the electrode 20 without affecting in any way the normal operation of the switch.

Wln'le have shown one set or elements and combinations thereof for eectuating my iniproved mercury switch, it will be understood that the saine is intended :for purpose of illustration only and in no wise to restrict my device to the exact forms and structures shown, for many changes may be made therein without departing fromn the spirit of my invention.

claim:

l. .ln a mercury switch, a glass envelope, spaced conductors sealed through one end of the en= velope, a glass tube secured within the envelope adjacent to the other end thereof, a mass of mercury cooperating with the conductors to rnake or break an electrical circuit according to the position of the switch, the inner projecting ends of said conductors being arranged so that the mercury mass will divide over the free end of the tube to break the electrical circuit and will sub1 stantially cover the conductors adjacent to their seals when the circuit is closed, whereby heat within the conductors is dissipated by the nier= cury.

2. In a mercury switch, a glass envelope, spaced conductors sealed through one end of the en= velope, a glass tube secured within the envelope adjacent to theother end thereof, a mass oi mercury cooperating with. the conductors to make or break an electrical circuit according to the position of the switch, the inner projecting ends of said conductors being arranged so that the mercury mass will divide over the free end of the tube to break the electrical circuit and will substantially cover the conductors adjacent to their seals when the circuit is closed, whereby heat Within the conductors is dissipated by the mercury, and a refractory sleeve at the free end of the tube.

CARL J. WARNM.

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