US2474742A

US2474742A - Electromagnetic switch

Info

Publication number: US2474742A
Application number: US493811A
Authority: US
Inventors: Clarence W Kuhn
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1943-07-08
Filing date: 1943-07-08
Publication date: 1949-06-28
Anticipated expiration: 1966-06-28
Also published as: GB580279A

Description

June 2s, 1949. C. w. KUHN 2,474,742A

ELECTROMAGNETIC SWITCH June 28, 1949. c. w. KUHN 2,474,742

ELEGITROMAGNETIC swuca Filed July 8, 1 943 2 Sheets-Sheet 2 Patented June 28, 1949 .EL,rze'rraQMA.GrNE'rIC4 swrron Clarence W. Kuhn, Wemuwatoszn,V Wis., assigner to E'Cutier-'Hem`n r1'er,"Inc., Milwaukee, Wis., acorportion (of vDelaware 4 Y. nation July ,8, 1943, Serial 493,811y

Rs., te. electromagnetic oseol, electromegneti switch. or lterntingf ourr'e'ntwhioh meeevery seiner, ejer-arg1y.` high rpositely' moving-commi nl, melf The pr ont 1 tomschrgeneral o of Lariel. has v among1 its` objects. Inodioatr n` the o; to lrend 1'v hex current.

Another. objet is togproyide,@switchof., the aforf'e'rnentone .l hldlng. flaflif he and, of satisfactory AAnother.objec w i A' Y aieremeiieed cherleier,Wbihmilrbe quiet, in

El mentionne. lrlveeiionis illustere@ in ,th afebme'yine'drawies Whih Willrp. 'be dsqrbei, it Qld. that' themheq.- mentlilirgfsirat i plee View.;

` ieW,l taken, on e linet 21-2l kpliirigers 5k and,` 'L respectively" .oarry'ljrisuleting' blocks s and 9 of iike' form, Shown inleg. 4,. which eitend trnsversely ofthe 'x'is of' the electromagnem earch. carrying etA oposite extremities contacts'y of the aforementioned-two pairs'- 'of contcts. More 'spoieally'bleck 8 oarries at ed fino' prevent.

17 Clainzism (Cl. 2007-403) 2.. opposite extremities., thereof contacts Z and ll,x While'.block'r ily cerriesto- 'tenets' I veind. 3. yThe plungerjs 'Bend 'i have' ass c'itled springs IB arl'd" il., respectively," Wl'iiohy bis.s'aidf`plurgers Aepzr'ii normally to separel'teveontots I and `2 and coni' talets `3 ,and 4- "as 4'shoifvn in'Figg l. Onmthe'l other hand, the electromagnetfis Aen'ergizlatblevto dr'iir' theplungers togetljueijf `o enggecontaots sind 2 en@ also contacts 3 andfk' hollin'gffthem in' engagement so long as fitf 're'rnginvs,ie nergiz'ecl"Itv Will'be noted. that thestrliotilre'fclescribed is'genfj erally symmetrical with respet4 tothey axis ofr the electromagnet fwith respect to an @uns passing,trensverselyvthrough thef magnet through the spaces between `the'.coniiznets' of the two pairs of,ContatsWhendiserigeged.

Referring tol'ig`A 3,'tl"ie'e'letromaglnetic lWinding Eris carried wit/hina' substantially re'tiline magnet frarne l5,` sai'dffrjame llevii'g' rearwardly extendingsetsofpostsflii I'l forfthllt toe supporting r'i'agrlel 18 the arrangement shown'l being such as to proyile "for 'vertieal break *by thefoontats with' tlielsyiitch xd. to a 'Vertical supportingpanel.n The niaget framefals is"` seotiorialfoornprisng f U-shabedfpert to Weigh the, SupQrjtrie. poets 16. fnd; l1 arle and @liront ple/te*2lisfclilredy asby screws 2l t thefree endsv *of` thefQ-shabe lpart.l Snelly front pleite'inolv the oppos'eydlw'a-lff theU r-shapedSerti have enged openings to 'reoeir'fe and'supprtfa',

tube

2,24 on whichr the Winding@islmounted land' inv` which the plungers AG 'ndA 'l re reoiproeably supported. As shown the tiiloe22 berries a spring' Wesher 23 `irlterposed between. the y Winding `5 and the djaeent Wall ofutlie'n'iagnet frame and for al purpose latter set forth Ythe frn't plate 2l) 'is pro/idedwith a' pair oi" spaed projecting pins Further referring to Fig. 3, the insulating bloolrs ywelnrl' uwhichearrif the ontacts each comprise peri;A of an assembly f'urtherrillustratd inliig. 4, fitting'ontof'redlioed outerend por# tion of its resillective') p1iriger,'ibeing"suitably secured thereo'nfiri Vengei'ge'me'n't withv an annular shoulderfZl on the pliY ger. Elh of seid. es` semblies is shown'as'c'rprising a. flat oblong plete 28 and 'atl forme'dplite 29 holding there; between the insulating eontaotvcarrying block which preferably is recessed to` reeive the flat' plate for interlock aginst rotary movement relf attive theretol The '

pltes

28 and 29 are prefer-r ably secured together as by rivets'3ll`andpreferably the insoletingfbloo'k'i's secured to the formed plate 2'9' as by'ri'v'ets' 31|. "The springs In and Il whic'hbiasthe plnngers apart surround the plungers and are interposed between the magnet frame and the plates 28 of the contact carrying assemblies. The plunger l is shown as provided with a tapered end portion 32 adjacent the plunger 6 and the latter plunger is shown as provided with a tapered recess 33 to receive said tapered end portion of plunger 1. This construction of the adjacent end portions of the plungers has been found advantageous in various respects, but generally satisfactory results have been obtained without the tapered formation.

The two contact carrying assemblies have portions disposed between the supporting posts i6 and Il in the case of the rear assembly and between the pins 24 in the case of the front assembly for restraint against turning about the axis of the plungers. Also the contact carrying assemblies are interlocked for prevention of movement independently of one another and for limitation of their relative movement, preferably by the means illustrated in Fig. 1. This means comprises a disk 35 oscillatable about a fixed axis and having engaged therewith by crank pins 36 and 31 at diametrically opposed points two

reciprocable bars

38 and 39, the bar 39 being connected to the front contact carrying assembly, and the bar 38 being connected to the rear contact carrying assembly. More specifically referring to Figs. 3 and 4, the front contact carrying assembly has xed to the upper end f its plate 28 as by screws a plate 49 with an upstanding lug 4| which projects through an opening in the bar 39 while the rear contact carrying assembly has a similar plate with a lug 4| projecting through an opening in the bar 38. Thus since the

bars

38 and 39 have crank pin connections with the disk 35 it will be apparent that any motion of either assembly will be transmitted to the other through the bars and the connecting rotary oscillatable disk. Also the bar 39 is provided with laterally extending lugs 44 and 45 coacting with laterally extending lugs 416 and 41 on the bar 38 to limit relative rectilinear motion of the bars and thereby correspondingly limiting relative movement of the contact carrying assemblies. Preferably the disk 35 is set in a circular opening in an insulating plate 50 suitably fixed to the top of the magnetic frame, said disk being confined to a rotary motion about a fixed axis through engagement with the insulating plate into which it is set and preferably also the insulating plate 59 is recessed to provide a channel 52 to receive the bars 3B and 39. A cover plate 53 secured to the magnet frame as by screws 54 serves to clamp the interlocking assembly to the top of the magnet frame. A like interlocking mechanism is preferably provided on the bottom of the frame to similarly interlock the contact carrying assemblies at their lower ends also, and such interlocking mechanism is illustrated in Fig. 3. This second interlocking mechanism being structurally the same as that described further description thereof is unnecessary beyond pointing out that it preferably has its

bars

33 and 33 arranged so the bars 3S as well as the bars 39 of the two interlocking mechanisms lie on opposite sides of the axis of the plungers.

Referring to Fig. 2 which shows the contacts |-2, each contact is shown as comprising an angular element fixed by a bolt -60 to a formed inverted U-shaped rocking element 6|, said element having a struck-up portion 62 forming an abutment for the contact to prevent turning of the latter on the bolt. The rocking element 6l has its downwardly extending portions spaced to straddle a supporting post 63 of rectangular cross section to which said rocking element is pivotally connected by a pin 54. The supporting post 63 is fixed to the insulating block of one of the aforede ibed contact carrying assemblies. As shown in 'l g. 2, the post `53 has a reduced portion 65 passing through its respective insulating block and having a fiat surface thereof enga-ged by a shoulder 53 on the block to prevent turning of the post. The post 53 has on its reduced end a washer iii to bear against the insulating supporting block and the reduced end of the post is turned over onto the washer to rivet the post to the block, Threaded into post 53 is an upstanding pin "5B extending into a slot in the rocking member `f5! and having at its upper extremity a vwasher y69 to engage the upper side of the member 6! to form a stop therefor, said washer being secured to the pin by a screw 10. Also the pin carries a second washer 'll engaging the under side of member 6i, said washer being under the bias of a coil spring i2 surrounding the pin and interposed between said washer and post 63. Thus considering contact 2 of Fig. 2, the spring 12 biases the rocking member 6l to rotate counterclockwise on its pivot 64 to a limit established by the washer 39 on the pin 98 and initially adjustable by turning the pin, whereas said spring permits member 6l to rotate clockwise on its pivot when contact 2 meets with resistance within the range of movement of its respective plunger, On the other hand, the contact l which is mounted in a like manner on its respective contact carrying assembly is biased by its respective spring in a clockwise direction, and as will be understood

contacts

3 and 4 are mounted on the contact carrying assemblies in the same manner as contacts I and 2.

Further referring to Fig. 2, the same shows contacts l and 2 and is likewise exemplary of

contacts

3 and 4, with the plungers of the electromagnet spread apart under the influence of the springs lll and Il, the contacts of each pair under such conditions having a predetermined suitable air gap therebetween. On the other hand, when the plungers are drawn together by the electromagnet the contacts of each pair are engaged, each of the contacts yielding with a slight rocking motion against the action of its respective spring l2 until the plungers seal, bringing the cont-acts to rest. Such resiliency in the support of the contacts affords cushioning thereof when brought into engagement, whereas the energy stored in the springs 72 resists rebound of the contacts and insures intimate engagement thereof while the electromagnet remains energized. In view of the slight rocking motion of the contacts incident to engagement thereof their adjacent faces are preferably formed as illustrated with their upper portions receding slightly. Thus provision is made for contact over a substantial area adjacent the upper ends of the contacts when they first engage through rectilinear movement, whereas upon subsequent rocking of the contacts the area of engagement shifts downwardly to the surfaces which in spread relation of the contacts diverge slightly in a downward direction.

Thus it will be observed that since the switch unit as a whole is symmetrical, comprising two structurally identical parts oppositely disposed with respect to a vertical plane midway of the ends of the electromagnet, balancing of such 5 pants iny V1.csr eclj,..o massgwill adapt,t1'1e.y :uniti-,to meetrhigh shocletest. As will be observed,-Whern the: sets --of contactsfare; outof. engagement :ann shock tending-rte movereithercontact carrying assembly `Will be counteractedby the Iother conve, 5

inclosing hasfbeen foundytobe enhanced bill-usw 15 l ing-plungers of .the .tapered yform shown l ForV extinguishing larcsviorn-ied upon separation of the .two pairsof contacts eachpai-rj isf.- preferel ably provided Withi fan electromagnetic r blowout-A device as shownl inFigsfl and 2. The -blowoutazu devices may. in practice assume vvariousdifferent forms andas the devices illustrated are distincrtive. only in specificconstruction for ruggedness,y durability, etc., they w-ilLnot-be describedin cle-.-I

tailf Brieyfdescribed' each blowoutydeviceas 25,.

shown in Fig.. 2 comprises ,avblowout winding.15- arranged below; its ,respective :contactsy with; its' axisat right .angles to ithe plane oimovement` oisaidfcontaetsr I.The winding .15 issupioorted on a core JIS in turnsupported by a-bracleet TI- car-.- riedby an insulating block` .-'lS iinedf to the .sup-` poigtingg.panel1;-I-3..-The-iranie 7'?. which is pref-'- erablyformedot nonsmagnetic. material carriesi at -opposite'ends of the winding 'i5 upstanding. magnetic plates 19, which `plateshave nxed there 35 to suitable-insulating arc shielclswlill.:l As will lbeunderstood,v thenlates- Til are spaced-to receive therebetween'the contactsof their-respective?. pairs ofacontacts, Whilethe insulating shieldsY 80 are ,interposed (between the plates 1.9 and theu enclosed contacts', theshieldsfadjacent :their respectivecontacts ybeingenlarged upwardly' and laterally.

Asshown in l, the supportingy paneli18- has iixed thereto adjacenty the top triereoi` insnlatine blocks 82 andS .respectivelyl earryingftera, minal studs 84 yandpto nth-icharecarried;-the,= terminal leads. of the electromagnetic winding and also terminal studsf and B1. to which. areY carried. pigtails from.; the contacts-l and' 3v, re-z spectively. Thetfrafmesf-'ll of the two blowout-v. devices carry insulating blocl s- 381ancl9, respectively, which carryterminal studsilllrto which.- areled pigtails from the contacts 2 andy 4, respectively, one such-terminal stud 90 beingy shownin 2. As shown-in Fig. 2, theblowfout winding has one terminal connected'to -the terminal stud-til and itsr other terminal con-. nectedfto -la termi-nal stud y9i carried-by thein; sulfati-ng blocl:Il,zand-,as will be understood Vthei other :blowout-Winding. has similar connections` v #Switchesl of. character commonly require-A forV maintainingcircuitsgand -other purposes a'ux. iliary switches landya preferable form of switch'. is illustrated in partsr in Fig. 3. As here shovvn..55 thel auxiliarycontacteere carried by an insulatinfgybloclrfi-li secured :to the underside of therI switch unit directly beloiiv and against-the afore-.. described lov/ier yinteriocliine.- mechanism for the tivo- Contact` carryingiassembliesi These auxiliary; switches are of the,sliding-,engagement type, and-y of [a designrto meet high shocktest. While the. drawing, showson-ly .two stationary contacts 94-1-95 and one movable contactxthe auxiliary; svvitohi` mechanism, .would ,Y in practice; ordinarily.

ycontacts 8.4 ,.andiil. selectively,according tothet` have-.more of ,the samerlineliof .statioeatawur tacts, -and preerablygltwoffof .the samekindk movablecontacts. Each stationary-contactcom prises a pair of spring clips carried by anderer... cured -to the insulating- 13100112.83 by fa terminal stud f 91,. Whereas, `v each imovablez- .contact corn-fl1 pri es a sliding-bladato enter between v.andto spreaclythe .clipsmf A.the stationary contacts. As.;` willbe .'noted,.the clips of .each stationarycon-LE tact have outwardly.bentfextremities.which ifa-A.,

cilitate.entryy of theA cooperating .sliding contact., therebetween and which by abutment ,with the., adjacentv insulatlin34 parts. limit possible lspread-Av ingroi the .,clips.. Prefer-ablyspreading .of .the 5. clins l is thus limited.. .tothe smallest amount sui-7 ficient to enable entry of .thesliding contact., The sliding,` contacts areA ,preferablyioi a form to bridgev two or .more .stationary .contacts-l ar,. ranged in a. sideby ,side relatiomandas. showE the .contact 93 is. slida-lale. to engage. the v.oppose position.- ci one. yof .the .contact carrying, assem-.-,. bliesto Whicliit. is. operatively.. connected... AST., su employmentoitwo movable contacts- 95,-', each would be .operable througlithe Amediuvmof.. one of two sliding. barsi. shown,` as respectively... connected. to the iront, andrear. contact. .arr ingassemblies, these bar sinrespectof mounts.. ing .and connection. to the. .contact rv,carrying as.jl sernbliesy being .si iilar .to .thebarsof the afoije-r.. described interlocking .clevices.. As. vshown Fig.. 4, eachfplateniil .nasa secondlug 9.9 to be ,re-:.1 ceived in anopeningin l@nepi the'.bars.98,. but as will. be` understooct`onlywthe,lugsl` of the. lower platesof thetwo contactcarryingesserne, blies .Wculdfbe required for operati/elyiconnect?. ing title tivobarsl illustrated .in Fie. ,3. As. will be .understoomwhenftne contacts l-2 and ile-..4 arefengagedthe magneticpull thereol'i.l must be maintained to insure c.onti;oued, engagel,. ment thereof under shock. .which lof course re-., quires maintaining Atnevcircuit. of Winding. l.5. throughthe mediu1n..of .shockeproof auxiliary contactsandthe aforedescribedtype yoi auxiliary.l contact YhasY beeniound veryefiectiveto so supf.-A plement .the required shoclq'oroof characteristics.: of the .switchitseli..y Thus the combination of ,theg herein. disclosed.. switch and. .auxiliary.contacts will. meetV higlifshoclc test in either openv or closedf,

i position of the switchand. Withoutneedof any..

latching. mechanisms,r Whereas as aforeindicatedi the switch has capacity foncontrolling directx current circuits subjected. to currentof relatively A high value.

What; I claimU as ,newanddesire to secure by I Letters Patent is:

1. In anelectric-switch `to meet shockftest,the..` combination. With-a pairl `-of coacting contacts,=` both movable. of .individuali actuating. means .fonJr said contacts having like. n'iovernents oppositely of one anotherto move `said, contacts-into and, out yoi? abutting relation,..and .means -b.yi-whicl1- said. actuating means are. interconneotedto pref ventl at any tirnesuch movements thereof inde-n pendently of lone anot herwhereby ,they-fare. Ysulo-vr iected` -to counteractionaone. by another fundenI shock.

2. In ,an electric `sit/itelito meet shock test, the; combination with a pair of cooperating contacted 'fbothfmovabla of individualV -atuatina means for said, contacts by Whichvt/said, contacts are whpllyff supported.y and which lhave 1ike-.movements Opf-ir positely of one another tto fmove.- .said .contact'sy into. and out oi aloijlttirig` relatiom and` rmeans 1interconnectinsSeidfentaetsupporting arles-emv'.

ating means to prevent at any time such movements thereof independently of one another thereby to effect counteraction one by another under shock.

3. In an electric switch to meet shock test, the combination with a pair of coacting contacts, both movable, of individual supporting and actuating means for said contacts conned to rectilinear movements at right angles to the plane of engagement of said contacts for engaging and disengaging said contacts, and means interconnecting said contact supporting and actuating means to prevent at any time such rectilinear movements thereof independently of one another, thereby to subject them to counteraction one by another under shock.

4. In an electric switch to meet shock test, the combination with a pair of coacting contacts, both movable, of individual supporting and actuating means for said contacts confined to rectilinear movements at right angles to the plane of engagement of said contacts, for engaging and disengaging said contacts, and means interconnecting said 4contact supporting and actuating means to prevent at any time such rectilinear movements thereof independently of one another, thereby to subject them to counteraction one by another under shock, said contacts having limited rocking play on their respective supporting and actuating means to yield when brought into engagement and having spring biasing means opposing such yielding thereof.

5. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, coacting contacts wholly supported by said plungers, and means interconnecting said plungers to prevent at any time independent movements thereof, and to limit their biased movements, subjecting them to counteraction one by another under shock.

6. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, contacts movable by said plungers, and means interconnecting said plungers to prevent at any time independent movements thereof and to subject them to counteraction one by another r under shock, said interconnecting means comprising an element oscillatable about a fixed axis and bars linking said plungers to said oscillatable element.

7. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, contacts movable by said plungers, and means interconnecting said plungers to prevent at any time independent movements thereof and to subject them to counteraction one by another under shock, said interconnecting means comprising an element oscillatable about a fixed axis and bars linking said plungers to said oscillatable element, said bars having interengaging parts to limit relative movement thereof and thus limit the extent of separation of said plungers under the bias thereof.

8. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, means interconnecting said lplungers to prevent at any time independent movements thereof and to subject them to counteraction one by another under shock, said means including means to limit biased movement of said plungers away from one another, and contacts wholly supported by said plungers to be engaged one with another upon movement of said plungers electromagnetically.

9. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, means interconnecting said plungers to prevent at any time independent movements thereof and to subject them to counteraction one by another under shock, said means including means to limit biased movement of said plungers away from one another, and contacts wholly supported by said plungers to be engaged one with another upon movement of said plungers electromagnetically, each of said plungers having for support of each Contact thereof a spring biased rocker limited in range of movement, rendering said contacts upon engagement thereof yielding against their bias.

10. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, said plungers respectively having a tapered end and a correspondingly tapered recess, means interconnecting said plungers to prevent at any time independent movements thereof and to subject them to counteraction one by another under shock, and contacts wholly supported by said plungers to be engaged one by another upon movement of said plungers electromagnetically, each of said plungers having for support of each contact thereof a spring biased rocker limited in range of movement, rendering said contacts upon engagement thereof yielding against their bias.

11. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, coacting contacts wholly supported by said plungers, a xed blowout device and means interconnecting said plungers to prevent at any time independent movements thereof subjecting them to counteraction one by another under shock and to bring about final engagement of said contacts always in substantially the same relation to said xed blowout device.

12. In an electric switch to meet shock test, in combination, electromagnetic means comprising axially aligned magnetic plungers biased apart and adapted to be drawn ltogether electromagnetically, coacting contacts wholly supported by said plungers, a fixed blowout device and means interconnecting said plungers to prevent at any time independent movements thereof subjecting them to counteraction one by another under shock and to bring about final engagement of said contacts always in substantially the same relation to said xed blowout device, said contacts affording a vertical break and said blowout device comprising a blowout winding below said contacts and vertically extending magnetic elements spaced to receive therebetween said contacts,

13. In an electric switch to meet shock test, in combination, spaced pairs of coacting contacts, electromagnetic actuating means disposed between said pairs of contacts and comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, said plungers wholly supporting all of said contacts and each supporting one contact of each pair, and means interconnecting said plungers to prevent at any time independent movements thereof and to limit spread of said plungers under the bias thereof, the two sets of movable parts comprising the plungers and contacts carried thereby being balanced and counteracting one another under shock.

14. In an electric switch to meet shock test, in combination, spaced pairs of coacting contacts, electromagnetic actuating means disposed between said pairs of contacts and comprising axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetcally, said plungers wholly supporting all of said contacts and each supporting one contact of each pair, and means interconnecting said plungers to prevent at any time independent movements thereof and to limit spread of said plungers under the bias thereof, the two sets of movable parts comprising `the plungers and contacts carried thereby being balanced and counteracting one another under shock and said interconnecting means comprising duplicate complete devices one on either side of the axis of said electromagnetic means for symmetry and balance of the switch as a whole.

15. In an electric switch to meet shock test, in combination, electromagnetic means having axially aligned magnetic plungers biased apart and adapted to be drawn together electromagnetically, said electromagnetic means also having means for attachment thereof to a vertical panel with the axis of said plungers perpendicular to said panel, coacting contacts wholly supported by said plungers to aord vertical break, and means interconnecting said plungers to prevent at any time independent movements thereof, subjecting them to counteraction one by another under shock and to limit separation of said plungers under the bias thereof.

16, In an electric switch to meet shock test, the combination with a pair of oppositely moving coacting contacts, of individual actuating means for said contacts having like movements oppositely of one another in a plane at right angles to the plane of engagement of said contacts to move said contacts into and out of abutting relation, and means by which said actuating means are interconnected to prevent at any time such movements thereof independently of one another, thereby to render them subject to counteraction one by the other under shock, said individual actuating means together with their respective contacts and their respective intercon necting parts being substantially identical in respect of structure and weight.

17. In an electric switch to meet shock test, the combination with a pair of oppositely moving ,f coacting contacts, of individual actuating means for said contacts having like movements oppositely of one another in a plane at right angles to the plane of engagement of said contacts to move said contacts into and out of abutting relation, and means by which said actuating means are interconnected to prevent at any time such movements thereof independently of one another, thereby to render them subject to counteraction one by the other under shock, said individual ac tuating means together with their respective contacts constituting substantially floating units substantially identical in respect of structure and weight,

CLARENCE W. KUHN.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 987,441 Dickinson Mar. 21, 1911 1,155,157 Lewis Sept. 28, 1915 1,166,030 Willower et al Dec. 28, 1915 1,183,159 Barnum May 16, 1916 1,226,697 Rinsche May 22, 1917 1,227,568 Barber May 29, 1917 1,533,251 Johnston Apr. 14, 1925 1,566,122 Roberson Dec. 15, 1925 2,016,448 Milne Oct. 8, 1935