US2610242A - Impulse counting relay and system therefor - Google Patents

Description

Sept. 9, 1952 T. P. FARKAS 2,610,242

IMPULSE COUNTING RELAY AND SYSTEM THEREFOR Filed March 20, 1948 4 Sheets-Sheet 1 FIG.

m far/6'4 F/G6 INVENTOR I P. FAR/(A 5 Sept. 9, 1952 T. P. FARKAS 2,610,242

IMPULSE COUNTING RELAY AND SYSTEM THEREFOR Filed March 20, 1948 4 Sheets-Sheet 2 FIG. 7

lNl/EN TOR 7. P. FA RKA S A T TORNEY Sept. 9, 1952 T. P. FARKAS 2,610,242

IMPULSE COUNTING RELAY AND SYSTEM THEREFOR Filed March 20, 1948 4 Sheets-Sheet 3 L INE lNl/ENTOR 7. P. FA RKAS Sept. 9, 1952 T. P. FARKAS 2,610,242

IMPULSE COUNTING RELAY AND SYSTEM THEREFOR Filed March 20, 1948 4 Sheets-Sheet 4 FIG. 9 I22 F/G. /0 20 w 1 F0 m m "0 FIG. F IG. /2

OIFFEREN TIAL lNl/ENTOR T. R F ARK/15 ayj A TTORNEV Patented Sept. 9, 1952 IMPULSE COUNTING RELAY AND SYSTEM THEREFOR Thoma P. Farkas, Jackson Heights, N. Y., as-

signor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York AppL cation March 20, 1948, Serial No. 16,091

11 Claims. 1

This invention relates to electrical impulse signaling systems and more particularly to improvements in magnetic counting relays and circuits for selective calling of telephone or teleraph stations of the type disclosed by C. N. Hickman in ccpending application Serial 758,904 filed July 3, 1947 now Patent No. 2,589,806.

An object of this invention is to provide an electrical-impulse counting system responsive to a continuous train of electrical impulses received. in uninterrupted sequence.

Another object of the invention is to eliminate the requirement for a slow-release characteristic in magnetic contact counting relays heretofore employed in a telephone station calling system.

Another object of the invention is to provide an improved magnetic contact relay structure wherein the tendency of such contacts to stick is overcome and wherein a positive break of successive contacts is assured for each impulse cycle.

A further object of the invention is to reduce the space required for selective signaling apparatus of the magnetic contact relay type.

A still further object of this invention is to provide a simplified electrical impulse counting circuit wherein a magnetic contact counting relay is operable directly by such conventional means as a standard telephone dial, without the necessity of an intervening pulsing relay.

In the use of magnetic contact counting relays of the type disclosed by G. R. Stibitz in Patent 2,305,450, issued December 15, 1942, for selective signaling purposes, it has been found that the magnetic contacts sometimes display a tendency to stick when they should open, and this tendency has reduced the speed at which such relays could be operated and even, in some cases, has caused faulty or incorrect operation. This tendency for magnetic contacts to stick has been attributed to residual magnetism remaining in the contact members after deenergization of the operating coil, and in part to leakage flux through magnetic members of one side of the structure from the energizing coil associated with members of the opposite side of the relay structure. Heretofore, the effects of residual magnetism and leakage flux which cause this tendency for contacts to stick have been overcome solely by the application of a more powerful magnetic field to operate the relay against these restraining forces. It is apparent that this solution to the problem has required more power for the operation of the relay than would otherwise have been necessary. In the present invention an additional element has been introduced into the relay whereby the effects of these undesirable forces are overcome and the relay is rendered operable by less power.

Another difiiculty encountered in the use of magnetic contact counting relays for a selective signaling system is the necessity of providing a slow release characteristic for one side of such a relay when used for digit counting, as disclosed by the copending application of C. N. Hickman, Serial No. 758,904 filed July 3, 1947, now Patent No. 2,589,806. Because of the inherent fast operate characteristic of these relays, and because of the relatively low current required for their operation, and the comparatively weak magnetic fields which are set up, as compared with other types of relays, it is more diflicult to provide a slow release characteristic for relays of the magnetic contact counting variety than it is for other types. To overcome this difficulty the inventor has devised a new and improved electrical impulse signaling circuit in which magnetic contact counting relays Without any slow release characteristic are employed.

In all similar systems for signaling or impulse counting, heretofore disclosed in the art, it has been necessary to employ two relay armatures to count each individual electrical impulse, i. e., one armature would operate at the beginning of each impulse and a second armature would operate at the end of each impulse. Although this arrangement is quite satisfactory for systems employing a short train of impulses for each digit or group, it becomes apparent that if larger groups of impulses are required, as may be the case in many signaling applications, the size of the necessary relay stack with two armatures per pulse may become unwieldy, or even so large as to be inoperable. Therefore, the inventor has devised an improved impulse counting circuit wherein only one armature of the counting relay is operated by each complete pulsing cycle. With this arrangement the over-all height of a relay stack as may be required for any particular impulse counting operation may be reduced to approximately one-half that formerly required. With this reduction in over-all size and its attendant reduction in space requirements and cost of apparatus, there is also gained a greater concentration of magnetic field which results in more efiicient operation of the relay, less operating current being required than in the case of the larger structures.

I-Ieretofore, all impulse counting circuits employing magnetic contact counting relays have included a continuity transfer pulsing relay, responsive to dial pulses, by means of which the operating coils of the magnetic contact relay are alternately energized and deenergized. The inventor has discovered that by a rearrangement of the operating coils on the impulse counting relay, the need for a pulsing transfer relay may be eliminated. Thus, in some applications, an additional economy of space and apparatus may be enjoyed by this means.

Still another former limitation of the magnetic contact counting relays has been overcome by the present invention. Th-is ,;1imitation was the impossibility of recycling former types of such relays. This limitation has been overcome in the present invention by the addition of an extra armature tongue at one end of he,.cqunting relay stack. By this means, herein 'discloseda V magnetic contact counting relay may be automatically recycled so that-it willprespond -continuously to an uninterrupted=train ofiimpulses for an unlimited time. With= such an arrange merit the inventors improved magnetic contact counting relay may be used :in: any lja l plication where continuous stepping switches have formerly been employed. Thus the utility-ofthis type of relay may now be extended to many additional operations in systems.

The n re andioneration inf-l the p ese vention may be more; clearly understood from a consideration or thedetailed description which fo wsrwh n studied. in-connectionv with-the -rea e dra ngs wher gl igal is an explodedand; pa tlycutaway isome icd awi e showi g. the; essential operat n elements of a magnetic .contact;counting relay of th yp mbod ed in-the present invention;

- Fi 21 a, ners e tiv drairin ofta singlearmatureilamination otthetype mplcycdinzthe first, third and-fi t layers .ofvtherr lay stacks illus a edla 1;

Fi 3 i p sp ctireedrawineoilapill learmature lam n t on; of the type cmployedinthe secnd, ur h and 3 XQ I$i;:Qf: lhQ. I21a5/"fiiiacks illustrated by Fig. 1;

1 F 4 is a .topp am wioi .thearela-y stacks of Fig. 1 showing therelationship between'operating coils, pole-piecesandahmaliures;

Fig. 5 1s a front viewrelevation -of tithe relay stacks of Figs. 1- and i showing the, relationship between pole-pieces andarmatures;

Fies azschematic,dia ramicfarelay .of the type hereinmsclosedch min an aux li yannaturet n ue .lllat one end of the c ytstac nected with the operating coil andassociated pulsing; relay; whereby theimpulse, countingrelay; may be recycled ,andthusenabled torrespondcontinuously to impulsesas received in; seguence;

Fig. -7 is a schematic. d ia-gram oftwo: impulse counting relays of-the,typephereinidisclo edt interconnected to jcomprise ,a complete digitalase lective signaling system, In.,thi figure-may-be seenv an additional: armature tongue L5!) .in. the digit counting relay stack .wherebyoperating coils of this relay ,are held energized duringiitheeinterval between transmission of; successive digits, thereby eliminating the-need. .ior aslow. release characteristic to be built, into the relay .istructure. Tols plifylt e app ara e of Fi Landreduce the possibility o circuit confusion, the insulated tu whi h ext nd b tween armature tonguesare not illustrated in this drawing. ,fIfongue. .50, unlike all the other tongues,..has :no insulated s ud associatediwith it;

Fig. sis aschematic diagram showin themaner in wh ch a ,maene ic, contaot. counti erelay, of the type embodied in the present invention ma be. inte connected with two pulsing r aysso t at on armature ton ue of. the. counting relay will come ,up for :each complete pulsin yc .In th s. arrangement,- as illustrated, a re.- ay ,stackihavi e only. ten armature tongue may be employed to, count asimanyas ten impulses, whereas: in all arrangements, ,preyiously-disclosed such a relay structure wouldheliniitedto counting .awmaximum of.... n.ly nveinipnlses.

te ephone "plants -.-and

s tongue Ill, have associated insulated studs as shown by. Ei s. l6;

ZJ; Fig.; 9,.is a schematic diagram showing one arrangement in which a magnetic contact counting relayofthertype embodied in the present inven- 11'0" -tion maybeoperated directly-from dial pulses, without the interconnection of a pulsing relayas previously required in all such impulse counting Fig. 10 is a top plan view of a relay stack of the typerepresented schematically in Fig. 9, showing one operating coil positioned around the center armatures, ;an.d:the ;other ,;operating vcoil around the pole-piece leg :of-one. side of. therelay structure;

- 1Fig.1lristaschematiddiagram of an alternative circuitby lneansof which a magnetic counting relay.oLthe-type-embodied. in the present invention-may; be ;operated:directly: from dial impulses; ;'Fig.;121 is atop plan-view of .a relay stack of the ynezrepresented;schematically by Fig. 11, here showing ztheiocationaof a differentially wound operating coil on one legof. the relay pole-piece arms. I 1;Iihezgencral principles involved, 'and'the method ofroperationin magnetic contact counting-rel yszforrin pulse counting, and signalin are described copendin zapplication; of C. N. Hickman.:aSerial.-,No: 753,904,;and byxreference thereto thecdisclosureand drawings of :said application arezherebygincorporated into the specification of heiprescntapplication.i In .the stepping relays previously disclosed, the :advantage of magnetic contacts,rwhichrprovide a high contact pressure for a relativelylow-operating current, were oifset to aklargeidegreebythe disadvantage of residual magnetismand-leakagefiux which tended to hold the-backz-contactsi closed at atime when they should be; Opening .for' the stepping operation. Herctofore .the problemhas been to provide a relay with sumcient contact pressure between the pole-pieces and .back contacts of the armature to-satisfy sthe requirement of noise-free telephone circuits: and at thesame time assure positive st pping operation of: the relay on each energizing cycle. :of- :the ;operating coil. One possible solution-to -the;;pr0b1em of residual magnetism andcleakagev flux is the substitution of non-magneticdiscs for-themagnetic back contacts as disclosed in the prion-art. However,. this solution limits the use of the stepping relay to those applications. where back :contacts are not required in thecircuit.

, :In the; present inven-tion the problems discussed above are, solvedbythe addition of an auxiliary branchleg H l in Fig. .2, -tothe armature laminationsin alternate layers of the relay stack. Auxiliary branch-Elli may=also be seen in Fig. 4, and auxiliary branches l.l,"l3 and l5rmay be clearly seen Fig.5. sEachof. these auxiliary branches carries :a magnetic contact on the lower face of v,its,,-forwar.d extremity, which engages a correspondingmagnetic contact-on the upper face of th vleft-hand.pole-piece to which the auxiliary leg is adjacent. .In the entire .relay structure, when ,.comp-le.tely assembled, these auxiliary branch legs .maymormally be biased downwardly bythespringtension of the leg itself, although such, springitension ,islnot essential inasmuch as an ample contact pressure may beassured bythe passage ofmagneticiiux through this auxiliary branch member andits. associatedmagnetic con-V tacts with the adjacent magnetic pole-piece. By reference to Fig. 5, it will be observed that the main armature tongues in each layer of the relay stacks, as represented by I, 2, 3, 4, 5, and 6 in this view, all carry magnetic contacts on the upper faces of their forward extremities in a position to engage corresponding magnetic contacts on the lower faces of the pole-pieces adjacent to and next above each of the main armature. tongues. However, these armature tongues differ from these previously disclosed in that they are provided with non-magnetic spacers on the underfaces of their forward extremities. These main armature tongues are normally biased in a downward direction sothat even when the relay is completely deenergized, the non-magnetic spacers are held against the pole piece below the armature tongue by means of the spring tension in the tongue. The high reluctance introduced into the magnetic circuit between each 4 of the main armature tongues and the magnetic pole-piece immediately below by means of the non-magnetic spacers eliminates the undesirable effects of residual. magnetism and leakage flux as heretofore encountered. Thus the main armatures are freed from the retarding magnetic ini'iuences formerly exerted through magnetic back contacts and thereby are enabled to come up quickly in succession in response to pulsations of the operating coils.

As in previous magnetic stepping relays, sue cessive operation of the armature tongues is assured by non-magnetic insulating studs which are interposed between armatures in adjacent layers of the relay stack and by means of which all armatures except one are disabled from operating at any time, and operation of the one free armature lifts a restraining stud from the next adjacent armature thereby enabling it to operate on the next pulsing cycle. Referring now to Figs. 1, 3, i and 5, the insulating studs may be seen at ii, iii, I3, 23, 2! and 22. It will be seen that insulating studs are provided for each auxiliary branch leg, as by H, I5 and 2i in Fig. 5, and that these studs are separate from those provided for the main armature tongues as shown by I8, 29 and 22 in Fig. 5. The studs affixed to the auxil iary branch arms are somewhat shorter than the corresponding portion of insulating studs which are fixed to the main armatures. Although this slight difference in length of studs is not clearly apparent in Fig. 5 because the ends, of each stud are hidden from view behind magnetic contacts on the armatures, the spacing referred to is clearly illustrated by Figs. 9 and 11 wherein the studs are not drawn in their true lineal relationship but are shown out from behind the concealing magnetic contacts. Thus it is that the stud it which is affixed to auxiliary branch leg I I in Fig. 5 has a gap between its lower extremity and the upper face of main armature 2, which gap may be of the order of ten one thousandths of an inch to provide lost motion coupling between the adjacent main armature 2 and auxiliary armature I I. Similarly the stud I9 which is afiixed to auxiliary branch leg I3 has a corresponding gap between its lower extremity and the upper surface of main armature 4, and in like manner stud ZI ailixed to auxiliary branch leg 25 has a gap between its lower end and the top face of main armature 6. The gaps thus provided aid in opening the magnetic contacts of the auxiliary branch leg against the forces of residual magnetism and leakage flux through the auxiliary branch. The manner in which these forces are overcome may be better understood from a detailed analysis of the operation of this relay.

Referring now to Fig. 5, we shall trace in detail the process of operation involved in this relay. If we start by energizing left coil LC it is apparent that the first armature tongue I will be attracted upward into magnetic contact with upper lefthand pole-piece 3I. At the same time, auxiliary branch leg II is held down by the magnetic attraction of left-hand pole-piece 33, and armature 2 is similarly held down by the combined forces of its spring tension bias and the magnetic flux flowing through left-hand pole-piece 35. The third armature tongue 3 is also attracted by the magnetic field of left-hand pole-piece 35 but this armature is prevented from rising by the downward force exerted from armature 2 through its protruding insulating stud I8, the force between armature 2 and pole-piece 35 being much greater, than the force exerted by pole 35 on armature 3 because of the difference in spacing. In like manner, armature 5 is restrained from moving upward by the downward force of insulating stud 20 protruding from armature 4 which in turn is held down by the magnetic pull of lefthand pole piece 39. In this initial condition with only the left coil LC energized, all of the auxiliary branch legs are held in magnetic contact with their adjacent left-hand pole-pieces. Now if the right coil RC is energized, all of the main tongues except one will be attracted downwardly so that no movement occurs. The first tongue I which is already up now experiences a pull against upper right-hand ole-piece 32 whereby armature I is held in its upward position. Now if left coil LC is deenergized, the second tongue 2 is no longer held down by a magnetic pull from polepiece 35 but is instead attracted upward by the magnetic pull of right-hand pole-piece 34. At the same time, contact between auxiliary branch leg I I and pole-piece 33 is opened by action of the insulated stud I! which is struck by armature tongue 2 in its upward traverse. At this time, armature tongue 4 is attracted upward through the magnetic pull of right-hand polepiece 38 but is prevented from coming up by the restraining force of stud 20 afiixed to armature tongue 3 which is held downward by the greater magnetic pull of right-hand pole-piece 38. As we have seen before all main tongues below are similarly restrained by the interposed insulating studs. N ow if the left coil LC is again energized, all armature tongues which are up will remain up, while all armatures which are down remain down. If the right coil RC is now deenergized, tongues I and 2 which are already up will be held up by magnetic contact with polepieces 3| and 33 respectively. Armature 3 having been enabled to move by the previous lifting of insulated stud I8 now comes up into contact with pole- pieces 35 and 36, being held in this position by the magnetic attraction of pole-piece 35. The auxiliary branch I3 remains in intimate magnetic contact with pole-piece 31, and a circuit is now closed between pole-pieces 35 and 31. As we have seen previously, none of the remaining armature tongues comes up. However, when RC is once again energized and LC subsequently deenergized, the fourth armature tongue 4 will then rise under the magnetic attraction exerted by right-hand pole-piece 38, and in coming up armature 4 strikes insulated stud I9 thereby opening the magnetic contact between auxiliary branch I3 and pole-piece 31. In like manner, upon successive energization and deenergizationoi'the leftandright coils alternately, the remaining armaturetongues inthe relaystackwill step, upsuocessively. .Thus it is readily. seenthat. in. each complete pulsing cycle, onecircuit betweenadjacent .lpairs of .leftrhand pole pieces is 'closedand ajprevious -.su,ch. .circuit issopencd Thisstepping operation may bacontinued. for as. many. impulses as there are-pairs of armature tongues in the. relay. stack.

... In..reerence to .Eig. 5..itmwillibeiobseryed that although. backma netic contactshaveheeneliminated iromthe underside oithe. .main armature tongues, ,the -non-magnetic spacingprovided between. these -membersnand. .the 1 POIGrPiECBS. .adiacent to. theirnndersideislmuch less than .the normal air-flap. .betwcen :the i ppermagnetic contactsof thearmature. tongues'and the next pole-pieces adjacent .above .the armature. It is byv means of. these -non.-.ma netic .back spacers that .theundesirable effects. of residuahmagnetism and leakage fluxgwhich in previous relays have. .occasioned. unreliable operation clue to armatures sticking when they. :should have stepped. are eliminated -inthe present invention. It .will .beobseryed. that. in the. idle. relay conditionas illustrated by.Fi,g. '5, armature .l,i isiin closerproximity to rightehand pole-piece .34 than it is. to-.eith.e,r of .the.,upper pole-pieces Bland as. It will be, apparentthat if the right coil-RC isiirst. energized, armature I will be subjected to a. magnetieforce irom upper right-hand polepie.ce...32, but that dueto. the greaterair-gap between these .two members as. compared with thespacing. between. armature I. and right-hand 130161131606 34, the. armature, will not be attracted upward but. instead will remainnin its lower po-.

sition held there under .the combined influence of. its downward. spring tension :and the downward magnetic .forceexerted by the attraction of pole-piece .33..v .It is .only whenthe left coil LC is..energized and the right coil .RC ,deenergized, that. armature I yields to the upward attraction otmagnetic .iorce from upper .left-hand-polepieceBl as was seenl in thedetailed analysis of the relay operation. :Siniilarly when onlyleft coil LC is energized, armaturel now. being up in intimate .magnetic contact with pole-piece 3i, armature ,2 issublected to aslight lifting. force due :to themagnetic. attractionof left-hand polepiece..33 but.....this force is. much. less,,than the downward pull of lef.t-,l1and -pole-piece 35, so thatarmature .Zi-Jemains .down until the .next cycleof pulsing.whereuponright coil-RC is energizedand left .coil .LC. .deenergized at. which time armature .2 .ccmesup. under the magnetic. in fluence. of. upper -right1hand pole-piece-.3,4. In likemanner .the spacing and spring :tension- :bias of..all remaining armatures issuch that they remain in. their .downward position until -they are first .enabledto come .up by the lifting .of :an insulated restraining 'studand then are brought up .by the magnetic attractionof an opposite upper pole-piece.. v.Inthepresent invention-therefore, not only are vthe.rundesirable eflects of residual vmagnetismand leakage flux eliminated fromlthemainiarmature tongues-by means of nonrmagnetioback.spacers, .but the contact to be brokenon each successive stepping operation has been transferred to anauxiliary arm wherein positive contactrlosure isassured through the intimate adhesion of magne.tic..contacts, yet the positiveiinterruntion of .this contact is also assured, when desired, .through the. action .of-the next succeeding .main armature, on an insulated stud attached to.th,e...-.auxi1iary.arm. By means oi:.the....s.1ight vgannro.vided between the auxiliary arm.s.insulated.stud andthe next adjacent large armature which,operates-,upon-it,the main armature on every, operation is allowed to start its upward traverseand by means of this lost motion coupling thus acquires sufficient kinetic energy to alwaysinsure opening the, auxiliary contact upon strikingthe insulated stud. The undesirable efiects .ofresidual magnetism and leakage flux in the present invention are minimized in the contacts to be broken by ,virtue of the thin magnetic member, which .carries this contact, and the .resulting increase ,inreluctance through this portion .ofthe ma netiocircuit. The smallsize of .the auxiliary branch arm also-reduces the springtension to be overcome in breaking this magnetic contact, thereby further facilitating the. positiyeinterruption of this circuit as the relaysteps in response tosequential impulses. Inasmuch as the auxiliary branch arm may be stamped .irom the lamination which carries th main armature to gueas illustrated by fi -1 noadditional operation is required to form this member and no added cost is thereby incurred. Although theauxiliary branch armature could be formed. of asep r niececf metal without departing from the spirit or principle of the present inventionanother advantage of the arrangement illustrated by Fig. 2 isthat'internal strapping between the make contact and the break contact members is eliminated, thereby reducing materially the cost of assembly and wiring of such stepping relays. Another advantage aiTorded by the relay of the present inventionis thatindependentuandisolated circuits may be successfully controlled by the device herein disclosed, whereas all previously disclosed magnetic stepping relays were limited to the operation of connecting anyone of a given number of lines to a commonline nnlessanother pole face piece wasadded for. each pulse as in the Stibitz patent. As wasseen .in the detailed analysis of the relay operation in reference to Fig. 5, a circuit isfirst closed between pole-pieces 3| and 33, then on the next pulsing cycle this circuit is openedand another circuit is closed between. pole-pieces 35 and 31. In like manner the next impulse cycle opens the circuit previously completed between pole-piecestli and 37 and then closes another circuit between pole-pieces 39 and Al. 'Thus it may .be seen that a plurality of isolated circuits, each. separate andinsulated from the other, may be controlledby the stepping relay of the present invention.

, ,Eteferringnow to Fig. 6, we see a schematic circuit diagram inwhich the stepping relay ,of the present invention is-connected in amanner to recycle, or in otherwords continuously respond to sequential electrical impulses as received, without limit to the inumber of such impulses which may .be received. Here it will be observed that the circuit for operating the left coil LCis completed through the last contactsin the ,relay stack, Ill, in such, manner that when aseries of vimpulses has been received which operatesall of the armature ton ues in sequence toandrincluding the last, armature tongue, the automatic opening of the contacts 1.0; in responseto the tenth impulse received-will open the battery circuit through left coil .LC' thereby allowingall armatures of the relay'stack to fall oiT intotheir normal .position as biased downward when the both coils of, the relay are deenergizedr :This then automatically resets the relay, thus conditioning it to startStEPping-irom the topall over spond to successive impulses as before.

again in response to the next or eleventh impulse which may be received in sequence without interruption. The recycling contact IE1 may be carried on one of the auxiliary branch arms, in which case it is opened indirectly by operation upon an insulated stud, or it may be of the type illustrated in Fig. 6 which is opened directly by movement of the magnetic armature tongue. We will nowtrace the sequence of operation in the circuit of Fig. 6. Pulsing relay PR is operated by electrical impulses received from battery M in the circuit controlled by operators dial [2, or this pulsing relay may be operated by any sequential series of electrical impulses as employed in telephone signaling. Operation of the stepping relay is identical with that described in reference to Fig. until we come to the last armature tongue l0. Here on the operation of pulsing relay PR for the ninth time, contact 1 closes completing a circuit from battery 16 through contacts ID to energize the left coil LC. Subsequently contact 8 opens, thereby deenergizing coil RC and allowing the next to the last tongue 9 to come up. A circuit is now closed through the ninth pair of pole-pieces on the left side, and all other such circuits are opened. On the release of pulsing relay PR contact ti closes, coil RC is energized, and contact I is opened, thereby deenergizing left coil LC and allowing the last armature tongue I0 to come up. The auxiliary branch arm of the previous tongue is opened by operation of armature ID upon the insulated stud associated with this auxiliary branch, and circuit 9 between the lefthand pole-pieces of the relay stack is thereby opened. Contact ID connected in series with left coil LC is also opened by this operation. Now upon operation of pulsing relay PR. for the tenth time, contact 1 closes but coil LC cannot now be energized since contact Ill is opened. Then when contact 8 of pulsing relay PR subsequently opens right coil RC is deenergized, thus creating a condition in which both operating coils of the stepping relay are deenergized and all of the armature tongues of the relay stack fall off into their normally idle positions. But, in returning to its normal downward biased position the last armature again-closes contact 10 thereby energizing left coil LC through contact I of the pulsing relay PR which is still operated. This energization of coil LC now brings up the first armature tongue and closes a circuit between the first pair of left-hand pole-pieces, O. The stepping relay has now started its second cycle and succeeding armature tongues will re- This recycling feature is considered highly desirable in many applications within the communication industry. Of course, it is to be understood that this recycling arrangement is not limited to a stepping relay having ten external control circuits as illustrated in Fig. 6, but may be employed with any size of stepping relay having either more or less than ten control circuits.

Referring now to Fig. 7 we see a schematic circuit diagram of a complete selective signaling system employing two magnetic contact counting relays of the typ v comprehended in the present invention. A significant advantage which this circuit offers over all previous circuits for digital signaling systems employing magnetic contact stepping relaysis the elimination of the former requirement for-a slow release characteristic in the digit'counting relay. Experience i ha's'indicated that because of the inherent fast 10 operate characteristic of relays of this type it is quite diflicult to build a satisfactory magnetic counting relay of sizeable proportions with an adequate slow release feature.

In the circuit of Fig. 7 the slow release sleeve formerly required on .one operating coil of the digit counting relay has been replaced by an auxiliary armature tongue 50 which engages an additional magnetic pole-piece 5i whenever the left coil LC of digit counting relay DCR is energized, thereby providing a positive means for locking up this side of the relay during th interval of pause between digits. The manner in which this functions will be better understood from a study of the detailed circuit analysis following.

Another advantage which thearrangement of Fig. 7 offers over all previous circuits for selective signaling by means of magnetic contact stepping relays is in the elimination of chains of series contacts through the magnetic contact members of the relays. As described in reference to Fig. 5, the auxiliary armature legs afford a means for controlling a plurality of separate isolated and insulated circuits in succession without the necessity of carrying the control circuits through more than one pair of magnetic contacts, as heretofore was required in all previous circuits. By thus reducing the number of contacts in series, the relay device of the present invention reduces the probability of circuit failure due to noisy or open contact conditions developing between the magnetic contacts. Still another improvement offered by the arrangement of Fig. 7 is a reduction in the over-all power drain required for operation of this selective signaling system. The manner in which these advantages are obtained will be more apparent from a detailed analysis of the sequence of operation involved when considered in reference to Fig. 7.

In general, the operation of this circuit is similar to that of the circuit disclosed in the Hickman application previously referred to. In the latter circuit, if the pulse counting relay is energized the correct number of times an alternate path is established through th contacts of the pulse counting relay and the digit counting relay in such a manner that the left coil of the digit counting relay holds up when the slow release relay falls off during the brief pause at the end of each digit. Since this holding circuit passes through the contacts of the pulse counting relay, it is necessary also to hold up one of the coils, as shown, the right coil, of this pulse counting relay. Then at the start of the next digit, it is necessary to release the pulse counting relay so that it may return to its initial idle position, and this release is accomplished by momentarily opening the holding circuit. Consequently, the left coil of the digit counting relay in that circuit is also opened, and the armatures which have already counted digits will fall off unless a slow release characteristic has been built into this coil of the digit counting relay. Because of the inherent fast operation of relays of this type, it has been found difficult to design suitable relays having a sufficient slow release holdup characteristic. However, in the present invention, by means of the arrangement illustrated in Fig. 7, this problem is solved through .the operation of the auxiliary armature 50 in cooperation with this contacting pole-piece El. The sequence of operation in the circuit of Fig. 7 when the pulsing of a digit is completed and the slow release relay SRR falls off is as followsz'First, assuming r that the "correct "number *ofimpulses had'been -*'received, the leftcoil LG-of =digit counting relay -DGRrwill'beenergized through one pair of contacts on the digit countingrelay andanother pair cf-contacts on the-pulsecounting relay. Simul- -"'taneouslyfithe' armature 50 comes up into intimate 'magneticicontact with the-adjacent "polepiece 5l to-provide an alternate'path for current -through*left coil 13C; thereby'locking ;upthe 'relay DER.- "Next the completerelease-cf the slow rel'e'asei'elay -SRR--opens'-'the battery circuit to the -'operating= -'coil of the pulse-counting relay PRi thereby restoring thatrelay-to its normal idle pcsition. Since the pulse counting relay is thus restcred'to normal at the end of each-digit, there is no power drain holding up thisrelay during the-in'terVal-"betweendigits; and no need "-to rstore this relay *to -normal 'atthe' start of the next succe'eding digit,-a's has heretofore been -required. Thus it" is l clear that with the circuit -"of 'Eig-, 'Yth" left coil of-the ni h-" relay =can now'be-'deenergized 'after the right coil is energized at the start of the-succeeding" digit, sc -that there' "is no need'for a} slow-'releasefeature to beincorporated intheleft coil of this delay. *Since' -"only the coil on "the digit counting --relayis here 'en'e'rgizecl- -at the end of a correct digityandthere is =no energizing "of theleft coil on th digitcount-ing-relayduring'the pulsing of a' di'gitas previously;- the powefdrain required by *this circuit is considerably" less than that required byall"-previous selective signaling systems employing" magnetic contact stepping relays. 'The addition "cf the resistancROinseries with thhdldingcirduitbf digit counting relay 'DCR '-operates to reduce "the current-through "the left *coilLCto a=minimum hold valuei thereby further reducing thepower drain. I

i For a betterfimderstandingof the operation of the -selectivesignalingsystem "illustrated by mg; 7;we Will-now tracetheseque'ncebf operation 'step-by-step. Upon operation of the operators dial -59;-which=may be located at a'remote central oifice-, with theswitchhook 58-closed as illustrated, a series'= (if-"electrical impulses are transmitted from battery 60' through" loop- 51 to pulsing relay PRf When the pulsing relay" 'PR is energized by the first received electrical impulse, contact 6! closes,-"-contact 63opens; and-contact- 62 closes to -"-complete a ci-rcui t frombattery fifi'through slow release relay' SRRf Upon "operation 'of SRR, contact- 65 closes -thereupon"*energizing the righthand coils of digit counting-relay -DCR; and pulse counting r'elay *PGR," respectively. "Now in re- 'sponse to the' magnetic attraction of the upper right-hand pole-pieces inboth stepping relays, the firsttongu't'l; of-PCR and 68 of DCR come up. Gontact 64 of slow -release' relay SRR, opens "-but no 'a'ction now-occurs'as the circuit through armature-'50andspole-piece 5| of digit counting relay DCR is open. "Now at the 'end of the 'first 'impulse, pulsing'relay' PR is'deenergized; contact 62 opens and deenergizes slow release relay SRR, butthis-relay-does-not open due to'its-slow're- "-lease 'characteristic. Contact 63 closes thereby energizing left -'coil LC of pulse counting relay PCR. Contact 6| opens; thereby-deenergizing r htcoil R of pulse counting relay PCR' and allowing the second armature tongue 69 *of "the "pulse counting relayito come upunder the'mag- 'netic attraction ofv the left-hand poleepiecelll.

' At'thestartof the second impulse, pulsing relay 7 'PR- is-again' energized; contact 6| again eloses to energize coiIRCHof pulse counting relay PCR, contact '63now opens, thereby deenergizing coil 12 LCof pulse counting relay P'CR and a'll'owingithe third-"armature" tcngue- 'H' es-Pea kto 'comey-up. Contact 62- closes; completing the operatingcir- -cuitthrough slow release relay SER,*-but-'no turther operation :or this relayl n'ow occurs because 'SRR-had not previously released due to its slow release characteristic. "Whe'rr-"the pulsingrelay ER; is -deenergized='at?the end of thes'econd'fimpulseglcontact R opens thei eby deenergizingfislow i to its slow-release characteristic;=contacir-B3 clcses thereby energizing e011 LG-of pulsecouiitmg re- -lay PCR, and contact fil opens thereby deen'e'rgiz- 'ingcoib RC and allowing" thri -fourth armature 15 tongue -13 of PCR 'to COMe'fupJ "Ihus lt-"is" seen that for every completeipuls' I systerm two armaturetongu'es-bf the pulseeounting relay -cjome' up. Y On -the last impulse-received in a train; the: interval between digits is' 's'ufiig :-cient to allow the slow release relay SRR, to fall off, and at' 'this 'time there are two :possiblee-occurrences, dependingonri wliether' thefinuinber which: was-dialedis'correct or-' not.

If an incorreetnumbenhas been dialed; the -following sequence iresults. TVVhen the slow release relay SRR; finally falls ofi contact 64; closes: but coilLC' of digit'coun'tingrelayDCEcamiotthereby be-energized' smce there is no path establ-ished 1 through' the: contacts Jof the pu-lse :counting relay 9 and 'the digit: counting relayi Contact-2 65* opens and deenergi'zes. :co'ils RC-bf 'DERI and of i thereby allowingialllarmature tonguesiiofiiiboth :stepping relays to fall bfif f lfhusiit is s'een that reception Jot: an incorrect digit 'operates' -toireset the! entire selectivesignaling circuittciits normal ,iidle condition. v

I If,11hOWeVel,' lIhEZ CUI'IECtfCIig'itYhaS- bBGIf dialed, t the following sequenceioccursii when slew release relay SRR? i-finallyi rel'eases, ontactiifide Iclo'ses "thereby completing:- a" :circuit ifrom: batteryiiififi nthrou'gh the fourth:armaturetonguafl aiofiepulse '7 counting-relay? PCRzwhicli -:has closed al' circuit rbetween left-:handapole-piecesil4:and 'IS of -PGR, thence through. the first armature:itongue fiaaof r'digiticounting relayttDCR; WhiChlh'BJS completed a l 'icircuit betweenithe: rightehandmcl'e-pieces flfi and iground. ThussLOiis energizeiiathe:first armature tongueffiti'oflDcRsis heldiup', theeauxiliaryfcontact armature? i -.icloses." contact;mtnap'oleepiece 5'5 l i'thereby lockinggup zleft 10011? LcfoitajpR -andrthe second armatureiton'gue liii of EUR: is enabled:- to

operate. Contact i6 5: of \ES'RBKDPGDS, thereby deenergizing cone-Rent DCR and IiG-b'f- PR thus allowing all the armature -tongues of the pulse counting "relay to releaseand "at the same time bringing up the second-armature tongue |8**of correct digit-brings 'up' two armature tongues 'of the digit counting relay and resets the pulse counting relay to normal. I

At the start 0f' the"neXt-=train: of impulses,

representing the second digity p'ulsing trela'y PR is energized on thefirst impulse; contact 6] closes,

a contact *63aop'ens7 and contact *62 closesf thereby "energizing slowfrelease relay -SRR. 'Contact"65 of SRR,"closesthereby"energizingitheright-hand armaturetongui t 7 iof'PCR comes ;up'. Contact '21E4 opens"th'eiiebyjdeenergizinglthileft. coil-LL6- of 1idigitlcountingvfelay' DOB-whereupon the-,l-th-ird armature .to'ng'u'e 9 "or. 'DCR'. comesqup andlthe au'ii iliary armatureltongue 50.-;fal1s ioffi'd-isengagl ing contactl with poleepiece"'5 I E The: circuit? is now in exactly the same condition as that folrelease r'elay SRR-butyet? thisrelay-holds-up due l3 lowing the first impulse of the first series except for the fact thatnow the first three armature tongues of digit counting relay DCR are up instead of just the first tongue being up. Thus the path necessary through digit counting relay DCR has now been changed and the correct number of pulses required for the second digit may be either the same as or difierent from the number required for the first digit depending upon the manner of interconnection between PCR and DCR. If four correct digits are dialed in sequence, all eight armature tongues of the digit counting relay will come up, and a circuit will be closed between the fourth armature tongue 83 and left-hand pole-piece 8| whereby the signal indicator 82 will be operated. The signal may then be interrupted by the subscribers operation of switchhook 83. The operation of this switchhook can also be used to clear the entire system. If the signal is not answered, the entire system may be restored to normal by the transmission of a single clearing pulse from the Central Office.

Referring now to Fig. 8 we see still another circuit employing a magnetic contact stepping relay of the type comprehended in the present invention. The subject matter of Fig. 8 is shown and claimed in divisional Patent 2,561,730. This circuit difiers from all previous pulse counting circuits employing magnetic stepping relays in that the counting relay of Fig. 8 requires only one main armature tongue for each complete pulse to be counted. That is to say, the ten armature tongues in the relay stack of Fig. 8 will count ten impulses, one tongue responding to each impulse as received, whereas as We have seen in the circuits of Figs. 6 and '7, all previous arrangements of magnetic stepping relays have required the operation of two armature tongues for each complete pulse. An obvious advantage of the ar rangement of Fig. 8 is the reduction of one-half of the number of armature tongues required to count any given number of impulses. A further advantage is that by operating only one tongue per impulse, the circuit of Fig. 8 may inherently require less time per pulse for counting, thus it is apparent that with the arrangement. disclosed in Fig. 8 not only may the size and cost of a magnetic contact stepping relay be reduced but also the speed of operation may be increased.

In Fig. 8, as in Fig. 7, the insulated studs which extend between armature tongues in adjacent layers or" the relay stack have been omitted from the drawings for the sake of clarity and to avoid confusion in tracing the schematic circuit. However, it is to be understood that insulating studs of the type disclosed in Figs. 1, 2, 3, 4, 5 and 6 are also incorporated in the magnetic stepping relay of Fig. 8; it is also to be understood that the left and right operating coils, designated schematically as LC andRC respectively in Fig.

8, are wound around the laminated pole-pieces of the leftand right-hand sides of the relay stack respectively, in a manner similar to the arrangement disclosed by the structure of Figs. 1 and a. The stepping relay structure of Fig. 8 differs from those previously disclosed in that it includes an auxiliary armature tongue I l l interposed between an auxiliary right-hand pole-piece H2 and left-hand pole-piece H3. Thisauxiliary armature and its associated pole-pieces may be placed either at the bottom of the stepping relay stack as illustrated in Fig. 8, or it may be placed at the top of :said stack, or it may be situated anywhere else in the stepping relay amine structure, provided only that it must not interfere with the stepping operation of the relay. The function of this auxiliary armature tongue III is to indicate at all times which of the two operating coils, LC and RC, was the first to be energized whenever both are operating. By reference to Fig. 8, itwill be seen that if the left coil LC is first energized, the auxiliary armature tongue ill will be moved down into conductive engagement with left-hand pole-piece 1 I3, thereby closing contact 9|. If the right coil RC is next energized, tongue Ill will not move since the magnetic force due to the closed contact 92 is much greater than the magnetic force through the open contact 92. However, if the left coil LC is then deenergized, armature tongue Hi will come up into intimate contact with righthand pole-piece H2 thereby closing contact 92. In this situation if the left coil LC is then re energized, the armature tongue 1 l I will not again move until such time as right coil RC is deenergized. Thus it is seen that armature HI always indicates which of the two coils LC and RC was the first to be energized. By means of the two contacts 9! and 9'2 associated with the auxiliary armature Hi, the two pulsing relays PR! and PR2 are alternately operated on each successive impulse. When starting from idle condition, operation of the correct pulsing relay initially is assured by providing armature Hi with a slight pretension in one direction, in the circuit illustrated by Fig. 8 this pretension being downwardly, to insure that contact 9| is always closed when the circuit is idle.

The detailed operation of the circuit of Fig. 8 will now be traced through a step-by-step analysis. The circuit is first conditioned for operation by closing a switch 89 which completes a circuit through coils LC and RC and the battery 90. Armature tongue Ill remains in intimate contact with left-hand pole-piece H3 toward which it was initially biased by spring tension. Now if the operators dial 88, which may be located at a remote ofiice is operated, a circuit will be closed through the dial at the start of the first dial pulse, and-pulsing relay PRI will now be energized through contact 9|. Upon operation of PR] contact 93 first opens, then contact 95 closes to lock up PHI to battery 90, and then contact 9'! opens, thereby deenergizing coil LC, Which in turn causes armature 10! to be .attracted upwardly into intimate contact with the upper right-hand pole-piece. With LC now deenergized, auxiliary armature tongue HI is attracted upwardly into intimate contact with righthand pole-piece H2 thereby closing contact 92. However, this opening of contact 91 has no eiiect on pulsing relay PR! which as we have just seen has already locked up through contact 95. At this instant, the closing of contact 92 has no eifect on pulsing relay PR2 since contact 93 of PR! is open, thereby introducing a discontinuity in the circuit through the operating coil of PR2. Now, at the end of the first dial pulse, the circuit through dial 88 'will open, whereupon pulsing relay PR! is deenergized, contact 91 closes and energizes coil LC, contact 95 opens, andcontact 93 closes, but pulsing relay PR2 cannot yet operate because the dial' contact 88 is still open. The energizing of LC at this moment has no effeet on the auxiliary armature tongue lH since since current is already flowing through coil I28 of RC and the two coils are difierentially wound, the'magnetic fields oppose each other and no flux will flow through the right-hand pole-piece members. However, when the contacts of dial I29 are opened no current will fiow through LC or through l2! of RC, so that the magnetic field created by current flowing through coil I28 of RC is unopposed under this condition and therefore magnetic fiux will flow through the righthand members of the relay structure. It is apparent then that the sequence of operations for the circuit of Fig. 11 is the same as that previously examined in reference to Fig. 9.

It is to be understood that the scope of the.

present invention is not limited to the particular arrangement illustrated by the accompanying drawings, but that numerous modifications may be made, both in the design of the relay structure and in the arrangement of the operating circuit, without departing from the spirit of the present invention as defined by the specification and the appended claims.

What is claimed is:

1. A relay comprising two groups of fixed laminations of magnetic material, principal spring tongues of magnetic material attractable into conductive engagement with fixed laminations in both groups, subordinate spring tongues attractable into conductive engagement with the fixed laminations of one group, laminations of insulating material interposed between said fixed laminations and said spring tongues, energizing coils surrounding said groups of laminations respectively, and lost motion mechanical coupling means interposed between said principal spring tongues and said subordinate spring tongues whereby upon alternate energization and deenergization of said coils respectively, said principal tongues are sequentially attracted into conductive engagement with adjacent fixed laminations, and said subordinate tongues are sequentially disengaged from adjacent fixed laminations by said mechanical coupling means of both groups and said subordinate tongues are sequentially disengaged from adjacent laminations of one group by operation of said lost motion coupling means.

2. A relay comprising two stacks of rigid laminations of magnetic material, a first set of flexible spring tongues of magnetic material interposed between adjacent layers of said rigid laminations and separated therefrom by laminations of insulating material, a second set of flexible spring tongues each in the plane of one tongue of said first set, mechanical coupling means interposed between flexible spring tongues of said first set whereby said springs are normally restrained from conductive engagement with adjacent rigid laminations of both stacks, further mechanical means including lost motion links between tongues of said first and second sets in adjacent layers, energizing coils surrounding each stack of said rigid laminations whereby upon energization and deenergization of said coils alternately said first set of springs are sequentially attracted into conductive engagement with adjacent rigid laminations, and said second set of spring are sequentially disengaged by operation of said lost motion links from contact with adjacent rigid laminations.

3. In a relay structure two adjacent stacks of fixed laminations of magnetic material, laminations of both stacks insulated from each other and from laminations of said adjacent stack by layers of insulating material interposed between the laminations of said stacks, a plurality of primary and secondary spring tongues of magnetic material in adjoining layers interposed between adjacent layers of said insulating material in proximity to said fixed laminations, mechanical coupling studs interposed between primary spring tongues in adjoining layers whereby said primary tongues are normally restrained from conductive engagement with adjacent fixed laminations of both stacks, further mechanical studs interposed between primary spring tongues of alternate layers and secondary spring tongues of an adjoining layer in a manner to include an air-gap between said further studs and said spring tongues of an adjoining layer, magnetic contacts on one side of said primary spring tongues adjacent to and in substantial alignment with corresponding magnetic contacts on facing sides of adjacent fixed laminations in both groups, non-magnetic spacers on the opposite side of said primary spring tongues from said magnetic contacts, further magnetic contacts on each of said secondary spring tongues normally in conductive engagement with a like magnetic contact on an adjacent fixed lamination, and energizing coils surrounding each of said stacks of fixed laminations whereby, upon sequential energization and deenergization of said coils respectively, said primary spring tongues are sequentially attracted into conductive engagement with adjacent fixed laminations of both groups and said secondary spring tongues are successively disengaged from contact with adjacent fixed laminations by said further mechanical studs.

4. An impulse counting system comprising in combination a continuity transfer relay, a source of electrical energy, and a magnetic contact counting relay comprising two adjoining stacks of fixed laminations of magnetic material, laminations of insulating material interposed between adjacent laminations of said magnetic material, a plurality of primary and secondary armatures of magnetic material interposed between adjacent layers of said stacked fixed laminations and insulated therefrom, a tertiary armature of magnetic material, mechanical coupling means interposed between adjacent armatures, energizing coils surrounding each of said stacks of fixed ilaminations, one of said coils connected to said energy source through one contact of said continuity transfer relay, the other of said coils connected to said energy source through said tertiary armature and another contact of said continuity transfer relay whereby upon successive operation of said continuity transfer relay potential is applied from said source of electrical energy to alternately energize and deenergize said coils and successively establish cont-act between said primary armatures and adjacent fixed laminations.

5. A magnetic contact counting relay comprising a plurality of rigid laminations of magnetic material arranged in two adjacent stacks, laminations of each stack insulated from the opposite stack, each stack comprising layers of magnetic members having alternate long and short polepieces in alternate layers, the long pole-pieces in alternate layers of each stack abutting opposite short pole-pieces in alternate layers of the other stack in a manner to provide substantially uniform air gaps between opposing pole-pieces of the two stacks, insulation between adjacent lamin-ations, further laminations of magnetic material in the form of flexible spring tongues inter- 19 posed between adjacent layers of said rigid laminations and isolated therefrom bysaid insulation, one of each such further laminations interleaved between each-two adjacent layers of said rigid laminations, each, of said further laminations comprising a main spring tongue, alternate layers of 'said further laminations comprising a narrow auxiliary springtongue in addition to said main spring tongue, magnetic contact surfaces on the upper face of each of said main spring tongues and non-magnetic spacers on the opposite face of each of said tongues, further magnetic contact. surfaces on. the lower face of each of. said auxiliary spring tongues, magnetic contact, surfaces on the faces of said magnetic polepieces aligned with and adjacent to said contact surfaces'on. said tongues, said spring tongues being normally biased downwardly into engagement with the pole-pieces. of the next adjacent layer of said"rigidlaminations, an insulated stud associated with each of said. auxiliary spring tongues and adapted to be engaged by th main tongue lamination of the next adjacent layer below said auxiliary tongue when said next ad jacent main spring tongue moves into operated position, further insulated studs associated with said main spring tongues in each layer in a manner to bear upon and restrain all main tongues below said layer into their norm-ally downward biased positions, and a pair of operating coils, one of said coils wound around each of said stacks of rigid laminations, whereby upon alternate energization and deenergization of said coils said spring tongues are sequentially moved one at a time into conductive engagement with the next adjacent pair of magnetic pole-pieces, and said auxiliary spring tongues are successively disengaged one at a time from their conductive cont-acts.

6. A magnetic contact counting relay according to claim comprising an additional armature operable only upon operation of the last sequentially operated spring tongues of said relay to open circuits of both operating coils and condition said relay for recycling.

7. A magnetic contact counting relay according to claim 5 in combination with a continuity transfer relay, a source of electrical potential, and means for generating a series of electrical impulses sequentially.

8. A magnetic contact counting relay accord- 'ing to claim 5 in combination with means for generating sequential electrical impulses, and re cycling means comprising an additional auxiliary armature tongue operable at the end of each counting cycle to restore said counting relay to normal.

9. In a magnetic contact counting relay according to claim 5 an armature lamination comprising a plurality of magnetic armatures each bearing magnetic contacts at their outer extremities.

In a relay structure two groups of fixed laminations of magnetic material, a first set of magnetic armatures attractable into conductive engagement with laminationsof both groups but normally disengaged therefrom, a second set of magnetic armatures each of which is normally in conductive engagement with a fixed lamination of one group, energizing coils surrounding each of said groups of laminations respectively for attracting successive armatures of said first set into conductive engagement with adjacent laminations of both groups upon alternate en-- tures of said first set are sequentially attracted into operative engagement.

11. An impulse counting relay comprising a plurality of layers of magnetic laminations in adjacent stacks, each of said laminations insulated from the others and each bearing an electrically conductive magnetic surface on one face thereof, a plurality of layers of magnetic spring armatures interposed between layers of said'magnetic laminations and insulated'therefrom and from.

each other, alternate layers of armatures comprising a main armature and an auxiliary armature, said main armatures having electrically conductive magnetic surfaces on one face thereof and a non-magnetic. surface on the opposite face thereof, electrically conductive magnetic surfaces on one face of said auxiliary armatures, energizing coils surrounding each stack of magnetic laminations, mechanical coupling means extending between main armatures in adjoining layers, means including said mechanical coupling normally holding the electrically conductive magnetic surfaces of said main armatures disengaged from adjacent conductive surfaces of said magnetic laminations, means normally holding the electrically conductive surfaces of said auxiliary armatures in conductive engagement with corresponding surfaces of adjacent mag netic laminations, and further mechanical means including lost motion coupling between said main armatures and auxiliary armatures in adjoining layers whereby upon alternate energization and deenergization of said coils said main armatures are sequentially attracted into conductive engagement with adjacent magnetic laminations and said auxiliary armatures are successively disengaged from electrical contact with said laminations.

THOMAS P. FARKAS.

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

UNITED STATES PATENTS REFERENCES Application 107,156 filed July 28,1949, Patent 2,564,432, Aug. 14, 1951.

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