US2569776A - Electric switch - Google Patents

Description

L. M. PERSONS v ELECTRIC SWITCH 2 Sheets-Sheet 1 Filed Aug. 21, 1946 INVENTORI LAWRENCE M. PERSONS Big Oct. 2', 1951 L. M; PERSONS 2,569,776

ELECTRIC SWITCH Filed Aug. 21, 1946 2 Sheets-Sheetl FIG 4.

l 57 25 4 I 3f 55 I FIG 5 INVE NTOR'.

LAWRENCE M.PERSONS ATTORNEYS.

Patented Oct. 2, 1951 ELECTRIC SWITCH Lawrence M. Persons, Chesterfield, Mo., assignor to McQu-ay-Norris Manufacturing Company, St. Louis, Mo., a corporation of Delaware Application August 21, 1946, Serial No. 692,104

; 1 This invention relates generally to electrical control apparatus and particularly to contractors suitable for use in the power circuits of battery-operated electric trucks and the like.

The control apparatus utilized upon batteryoperated electric trucks has presented a difficult problem because the electric currents being controlled are on the order of magnitude of several hundred amperes, while space is at a premium. Ordinarily, where currents of such magnitude are handled, control devices with operating and structural characteristics (8. g., great amplitude of movement, great air gaps, very large contacts, snap action, arc snuifers and blow-outs) equal to the situation can easily be provided. But, where space is at a premium, such elaborate control devices are eliminated by their intrinsic bulk. It has, for example, been found more economical to tolerate arcing at the contacts of switches utilized on electric trucks (with consequent replacement at frequent intervals) than 9 Claims. (Cl. 200-144) to encumber the vehicle with apparatus which would prevent such arcing.

The object of the present invention, generally stated, is toprovide a contactor compact enough for use in situations of the kind referred to, and which will require less frequent replacement of contact than heretofore.

Another object of the invention is to provide a contact arrangement which is readily reversed for equalizing contact wear and which at the same time is foolproof against reversal of polarity upon reversal of contacts.

Other objects will become apparent to those skilled in the art when the following description is read in connection with the accompanying drawings, in which: 7

' Figure 1 is a perspective view of a contactor constructed in accordance with the present invention;

Figure 2 is a right end elevation of the contactor shown in Figure 1, part being shown in section, to reveal the relation of the parts;

, Figure 3vis a sectional'view taken along line 3--3 of Figure 2;

Figure 4 is a sectional view taken along line 44 of Figure 3 and showing the stationary contact assembly and mounting arrangement without the movable contact;

- Figure 5 is a similar sectional view, but showing a modified form of stationary contact assembly andmounting arrangement therefor; and

Figure 6 is a wiring diagram showing a typical power circuit in which the control apparatus of the present invention is utilized;

In accordance with the present invention, contaictors of the kind generally employed on electric trucks are provided with a, novel arrangement of stationary and movable contacts whereby the arcing upon breaking of the power circuits is reduced and distributed so that the usefullife of the contacts is prolonged. One aspect of the invention involves the provision of electrically separate though physically proximate connected together while like stationary contacts at the opposite side are connected in difierent circuits, the arcing is generally concentrated at one of the last mentioned contacts. This results from the fact that the amplitude movement of the bridge member is too limited to extinguish the are (drawn upon separation at one of the first mentioned stationary contacts) before contact is remade through the other of the first'mentioned stationary contacts. Since, as aforesaid, both of the first mentioned stationary contacts are at the same potential, arcing thereat will not continue after the very brief interval in which neither is in contact with the movable bridge. Consequently, a large arc will be drawn at the other side unless, as contemplated by this invention, the bridge member be composed of a plurality of electrically separate conductors. Such an arrangement not only equalizes the arcing between both contacts upon separation, but synergetically reduces the cumulative arc. The latter action is probably attributable, in part at least, to the fact that, upon completion of a new circuit through the bridge member which had been dead, an electromotive force is induced in the closely adjacent (though electrically separate) bridge member which has just been disengaged and is now arcing at both ends. The E. M. F. thus induced in the arcing bridge member is, however, counter to the arc-producing E. M. F. therein and consequently they tend to neutralize each other and extinguish the arc.

Another aspect of the invention has reference to the organization of the contact members so that they may not only be removed and replaced 7 with facility but also so that pairs of the same plated that the contact sets be so arranged in circuit that the circuits are usually broken at the same set of contacts. Thereby the opposite set is saved from the destructive effects of arcing until the contact is ultimately reversed.

Referring now, to the drawings for an illustrative embodiment of the invention, the apparatus is shown as an electromagnetic'ally operated switch. The switch consists of a pair of station.- ary contact assemblies I and 2, each of which embodies two stationary contacts.

lower contact area 4, while bly 2 has an upper contact 231 The contact 4 fixed in accordance with the usual practice, thereby providing two pairs of contact areas, one pair of conductor I5 and the other pair on conductor I6. In view of the magnitude of currents requ red. ehan by such. a evice. t ductor elements Hi and I 6'; are siib 'n'tially heavy and rigid, having a cross sectional area adequate to conduct currents on the magnitude of several Arranged to bridge the stationary contact areas 3 and .9 4.. and 6 am 'yab q te a em .ths l awines s.-. the od im s fee Stationa cbntacts hen ts rmost eq en. ut hen, its lowermost posit n bridgesv the even numbered Qf mtheemb m tc m the movable co act assembly I is moved back nd rth b tw en ts. u pe d ow 1 95 o eb a su ta e lno rl .8 a n an l y movable core Q ased by a s'p'rin'g It toward its upper position and arranged upon energization of the' solenoid.togattractthe core 9 to the position shown inEiguLr'e' Z, The core 9 has a stem Il extending axially t erefronji aiid passing through, in insulated relation. to; the movable contact asemb e. t m sl r-qvifie l i h a s u der I 2, in order to lirnit movementof. the movable contact assembly the ion onedirection. On the opposite side 6 movable contact assembly, a spring l3,.is prov d ed and heldin position by a collar I4 adjacent the endo fstem I I, 'I 'he spring I3 bjiases the rri'ovablecbntact assembly toward sh'o i ld'er ILbut permits limited relative movement of the assembly I upon stern II against the action'of spring I3, Consequently, when the solenoid is energ' ed; to rnoye the contact assembly. [into engagei e nt with the lower or even number'edstati'onary contacts, it is contemplated that the cor {movie on for a slight degree beyond the point where'a't the. movable contacts have en gag'ed, the. stationary, contacts, so as to subject spring I3 to same compression. Qontrarivvise, when the solenoid, 8 is. deenergized, spring ID forces the core 9 outwardly carrying the movable contact assembly linto engagement with the uppermost or oddnurnbered 'statiqn'ary contacts, so

that, when inthis position, the contacts are urged.

together under the tension of spring "1.. Con"- sequ'ently, inboth contact makin'g positions, the movable contact is spring p'ressed into engagement with the stationary, contacts.

As hereinbefore mentioned, the invention is.

characterizedby the organization of the movable contact assembly 1, so as to provide a pairv of parallel conductors I5 and I5, separated onefrom the other by a layer ofinsulationll, whose thickness is such as. to reduce the physical spacing between conductors l5 and I6 substantially to the minimum consistent with adequate dielec-..

tric to electrically insulate the conductors I5' and I6 one from the other. The conductors I5 and I6 are mechanically secured together by studs of insulating material I8 and also held in mechanical assembly by the arrangement of insulation sleeve I9 and insulating washers and 2 I, as clearly shown in FigureB.

At each endofeach of the conductors I5 and I6; a layer of contact material'22 is suitably af reversed end-for-end without disturb and ig 'hu'ndred amperes. =1 Another aspect of the invention concerns the reabiza qa oi the tationary contact assembly, jet'ail in Figure 4. The staas efmbly I consists of a pair Of k I and 23. Like the conductors I5 and I16; the bars- 2% and 23 are relatively heavy id and are bent so as to provide a central spaced portion of greateig-separation than at their sees. t h entr l. iie o a h of ars. an '2' britact embers {aid id def-suitable can e lb fixfi v he a 2 ha ail s 1 3 h n deed asn'rall hole 2 5 at the other end. Likewisgthe ar, 21 a a are. Ee 61 at on dan a small hole 21 a1; the et er nd. it being no ed a the bars 22-; and 2a are identical, bu rever sed relation in t e assembly. The ends or t e pa s. and: nae ep ate a e id. by an insulation. spacer 2181' Within the large hole 2 4- of tam-z andlarge hole 2610f" bar 13:. n, ns l iqn leev i d' in he insulati n 'sleeve lii a headedcement: 30- ex? tends andis electrically'and' mechanically joined, t 3| tQ the bar argues whosesmaii nci (2% 1 1 1 itextends. The headed po -ti an 'ofe'a'cli connector 3; II=- iselectrically insulated from a'tibit ed that thea may be turned end-{of end to biii" formerly; atone end intothe preci formerlybccup iti thjp ait s a; h i

The contact-assembly j ust'descf'bed-is rnounted upona paii'bf mounting- T33" arm 34; which 1 35* and ai a4 and the same reversab would prevail respect-tothe lower onsets; With tlie arr 'e ment. shown, however, the assembl be ting relation bathecantata-asserts? upo the seats -36=-"and-'3 1 aha witheaeuistursmg tire electrical =re1atiea between contacts and the corres 3-3' and '34;- is anawe to,- severe ar tak' desirabie chime-ts (with at 6%; e n. rder up a tn such reversal of contacts. willnot permit reversal of their polar orientation because, in practice, such reversal of contacts is frequently required to be made by workmen who are electrically unskilled.

, A modified form of reversible contact assembly is shown in Figure 5. In this embodiment, the assembly may be reversed either end-for-end or about a longitudinal axis without changing the polar orientation of the contacts. In this form, two identical contact bars I22 and I23 are'provided with a countersunk hole I24 at each end thereof. The bars I22 and I23 are mechanically connected by an insulation sleeve I25, which spaces the bars I22 and I23 and mechanically connects the same by being peened or molded into the countersunk holes I24, as shown. Mounting post 33 is provided with a seat I36 of I conducting material, while mounting post 34 is provided with a seat I3I of insulating material, but being otherwise identical to seat I36. In order to assure against reversal of polar orientation of the contacts with reference to the mounting posts upon reversal of the contact assembly,

the upper end of post 33 is provided with a connecting means which is not interchangeable with the connecting means at the top of post 34. In the embodiment shown, the upper end of post 33 is provided with a threaded portion I33 of lesser diameter than the threaded portion I34 of post 34. A nut I35 of conducting material is provided for post 34, while a nut I 32of insulating material is provided for post 33. The nut I32 may, if desired, be made of metallic substance if care be exercised that an insulating washer, such as I 3I, be at all times interposed between the nut I32 and bar I22. While this form of contact assembly is less foolproof than the; form illustrated in Figure 4 in that the insertion of a metallic washer at I3I will defeat the purpose of the arrangement, it nonetheless has the virtue that it may be reversed about either ax1s..

In the wiring diagram shown in Figure 6 four contactors of the character hereinbefore described are utilized, asindicated at 12, III, II, and I3. The contactors are provided with operating solenoids 82, 80, 8|, and 83, respectively, as shown. The control circuit for the solenoids just mentioned is not shown, but it will be apparent from Figure 6 that, when contactor III is moved to its lowermost position, a starting circuit is established from the battery 40 through the lower contacts of contactor I0, field M, the upper contacts of contactor II, the upper contacts of contactor I2, resistor 42, resistor 43, and the armature of motor 44. When contactor I2 is actuated to close its lowermost contacts, a second speed circuit is established, as before, to contactor I2, but therefrom shunted about resistor 42. to its lower position (the other contactors remaining in their previously described positions), a third speed circuit is established by throwing the resistors 42 and 43 into paralleL' If now, while contactor 12 remains in its lower position, solenoid 82 be deenergized so as to permit contactor I2 under the influence of its spring III to move to its upper contact-making position, both of resistors 42 and 43 will be shunted out of the circuit and a fourth speed establishedcontactor II, when moved to its lower contactclosing position, establishes the circuit for reverse operation, it being understood in this connection that the control circuits for solenoids 80 Upon the movement of contactor I3 present invention, the action of contactor I2 may beconsidered. When, with the motor operating on starting circuit, contactor 12 is separated from itsupper contacts, an arc will be drawn at each end thereof. Momentarily, after such separation, however, contact-is made between the lower'contacts of contactor I2. The circuit thus established through the lower conductor of con-- tactor" is parallel with, and in the same di-- rection as, the current flowing through the arcs; Theat the upper conductor of contactor I2. magnetic field, which is thrown out as the cur-- rent in the lower conductor of the contactorbuilds up to the high magnitude involved in situations of this type, induces an electromotive force in the arcing upper conductor. Such induced electromotive force is, according to Lenz law, counter to the direction of the impressed electromotive force which is causing the arcs. In order to tend to extinguish the arc lingering at the just-broken contacts, it is necessary that the current traversing the just-engaged contacts be of a high order of magnitude and that the upper and lower conductors of the movable contact be so physically proximate that the current building up in one will induce a substantial counter E. M. F. in the other.

From the foregoing description, those skilled in the art should understand the operation and advantages of the present invention and realize that, While one complete example has been disclosed in full, the invention is not limited to the details of the example, but is susceptible of many modifications without departing from the spirit thereof or the scope of the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In combination with a switch having a pair of stationary contact assemblies, each assembly having an upper and a lower contact insulated from each other, a movable contact member, said movable contact member having two insulated conducting bridges each having a contact at each end thereof, the contacts on one bridge arranged to engage the upper contacts of both stationary contact assemblies and the contacts on the other bridge arranged to engage the lower contacts 'of both stationary contact assemblies, said contact assemblies being identical and symmetrical, and means at each end for mounting the assemblies for reversibility without change of polarity, said mounting means being structurally different at the respective ends.

'2. In a switch having stationary contacts and a movable contact member whose amplitude of movement is limited to less than sufllcient to provide a contact separation of a magnitude such as to provide an air gap across which heavy currents will not maintain an are upon separa-- tion of the contacts, said movable contact member having two pairs of contact areas, one pair of which engage their corresponding stationary contacts only when said member is at one ex-.

treme ofits-movement and the other pair of con-v mum tact; agea's. cnga e their correspondin fitatianary c n ac s, .qnl'y when saidv m'cmbcris at the one pcsite extr me of its mcvemcnt, nneof tha stia tion ry' contacts in each of the pairs thereof being perman ntly el ctrically ccnncc edto me Contact of the thcr pair. the movable ccntact areas of hvpairbe naelectricallyanamccham ally on e e cg ther and mcchanically connected with but ele tricallyinsulatea. from this contact areas of the. other" pain sack of. the said st ti nary c nt cts of one. pair lacin m manen ly assemble with cm of the staticaaml. ntactsfv the other pai 5.0 that one'con: ta t of an assembly is .enza cable bythcmcw-s ablc con ct mber at cmc: ime; of 5.2m assemblies i udin i cntical connector at on Pcsite ends of the contacts. one f saidpcnnectcrs: being lec rically ccnnectc l to" cnc contact-and in la edfrcmthe c her amian thez" cnncctor being 1'BVeI5, y-C@ neC towthccqnt ts where y e. e b ies ar d ascnafly symmetricath an mo nting pasts arran cd to releasabiy' :retain the assemblies in opcrative position,

- 3- A- c t asaembiy campri ina a pair 9f den al on act -c=1cmcn s,- apair of mentical connectors, and a pa r at 'identicat. insulatons; we of the. conn ctors clectricarl'y' cng-a ing one conta t member and inaaiatcdi fmom the o h r contactmember y cf" the in ulator and the ct-hcr Q tnepq mcctcrs clcc rica'lly en a in the n her cf thccontactmambmts' and in ulated from the first-contact mcmberaby the ,other one:

Qfcpa r cf i stflat ns; said parts bein se ured to cther with the :memhezsyofz pair in rever c oricnt ticn wheneby' the assembly is: dia.- ona'liltsxmmetnioal-szhut tnansm s un yma metrical.

4.-.A= ccntia t asaemhm comprisin an upp an ta t bana lQw rccntact-vbar: zidcn ical: with the miner contact tar; 'mealns icr -pc1*v-manem1 ssq iatm bar-' together; a: pair of: con. nec ans rclcasablyccaaaing saidhats .at .opnasit'e ends :thercci, we: cf said connectors qheing: cleict nical l andrme'chanically cQnnectedtovthe-mmer contact. grand mechanically connected ato but clectm. allyiinsulated- 10m the lower contact "bar, and; the other-cf;aajdwconnectorsjbeingamechana ically and electrically connected to the 1OWCP'LQOHI- tact hari andwmcchamcatlw \connectad tmbut :e1e'c ed ircmzthc upper c ntact-bar.

a sembly 4:011:1 )rising an u per cant thc upper con act ba a .ccnnectorqelectrically;

an vmecharlically ccnnectcd :tothe pper-Icon? tact bar 1 and mechanically icunnectedwto but elem-- trically insulated frorn'the :1ower-1ccntact ibarr'; .and-

another c nne or mechanic klyxand electrical- 1y connected to the-lower 3301x1181ctj-ba-riandrnnethfrom the upper :contactharcsai e ric l y i sulated- 6. The combinatmn wvith qla contactias cmhlw hatin ==upper and- ;lower :ccntact" vclcnrnents. 11e

' manently 'mechanicany' connected;vtogether-but ins lated lane tmmhc o hs .Qf za-zn -i Qhmcunt in cp sts. 1forrz-removahly and: reversibly receivin said: contact elemcnta: v:y ach: L ssaidwRosts-.: e lgme .Qne .pf latc mancntlyz imenhnn caillx .coansnteaatoscihc but act bat; at flower ccntactubarr identical; with- 8, inmiaztednna immttfia 01211615, a pair otm'eunting posts for reversibly receiving said contact l-i manta; each at said postspassing: through; both cantact elements, one. at. said mbufiting pasts 5; being insulated from the upper contact elinen't and' the othe'ir from the l'ow er and stl ucturally dissimiiar'means": at each m'cuntinglpost foamtrferirig'fiwith the: i-n'terfit between said ctmt'alct a'nssenwl'y and: the mounting pasts when" the elec tridaii ral'aticn thembetween' is improper;

8'} mioz'hbinatiofi in'a-cntactoi' having amptact c'az-riet movable between two iositibfia wherea't ccn'tatis made-between dificrent-p s or stationar mutants res ectively, a condue liti'dga cmsaid came? eompfiSing two electrical-e ly-sepame cdndtitdi' cn'iof engagei'n each of tfie fislirsfi f' Staticii ccntacta, stationary cofitacts it-i d-ifiercn pairs) ateac end a 0i th bridge 196mg: alce'tri-eany @fid Safetcndqctt's be; togetherwith an intervening layer (if insu atig'rt, saidiaiyef 0f ifisulat ib bing c ntiguogs with bctla ccnauctcrs mac: sjich th infiess' that the induc' fiectmane ccndiictgr 9f incrasi'n'g current th athemcnauctcris sue-h as .taexat-sai'd dine conductor Wheti I fisjtifin wfip'felat said dither condtictcrchgalgea it's" statinaxy contact-11$."

9. In a ctitactei haviiig a bridge movable 'betWeH-tW' iioitilofis at each of which ping lcaa si th l taisza itaa REF K ES c-l rE'ntamin n? at th s

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