US1932020A - Electrical relay - Google Patents

Description

Oct. 24, B LAZICH ELECTRI CAL RELAY Filed April 13, 1931 4 Sheets-Sheet l 12 E 26 (sa 9 9 &

8 6 ;3 9 & 55

. NVENTOR.

B. Aaa/ch BY A I e ATTORNEY.

ELECTRICAL RELAY Filed April 13, 1931 4 Sheets-Sheet 5 INVENTOR. B z I o/1 Cka 7/ /V ATTORNEY.

Patented Oct. 24, 1933 ELECTRICAL .RELAX e Branko Lazici, Edgewood, Pal, assigncr to The' Union Switch & Signal Company,jSwissvale, Pa., acorporation of Pennsyivania r Application April 13, 1931. "Serial No. 529534 8 Claims. (Cl. zoo ios) My invention relates to electrical relays, and particularly to that class of electrical relays known as counting relays in which cooperating contact' members are operated from one relative position :to another 'relative position in response to a predetermined number of energizations of one electromagnet and are restore'd to said one relative position in response to a corresponcling number of energizations `of another electromagnet.

I Will describe two forms of counting relays embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a vertical sectional View illustrating one form' of counting relay embodying my invention. Fig. 2 is a top plan View of the relay shown in Fig. 1. 'Figs 3 and 4 are right-hand and left-hand views,

r respectively', of the relay shown in Fig. 1, certain of the parts 'being broken away or removed to more clearly illustrate the construction oi'- the operatingmechanism. Fig. 5 is a diagrammatic view illustrating one circuit arrangement for the relay shown in Fig. 1. Fig. 6 is a vertical sectional View illustrating a mOdified form of the counting relay illustrated in Fig. l and also embodying my invention. i Fig. 7 vis a top plan View 'of the relay shown in Fig. 6. "-Fig. 8 is a View of the .relay shown in Fig. 6 as it appears when viewed from the right in'Fig. 6, certain of the parts being removed to better illustrate the con` struction of the Operating mechanism'. Fig. 9 is -a View'of the relay shown in Fig. 6 as it appears' when viewed from the left in Fig. 6, and illustrating the contact mechanism of the relay. Fig. 10 is a detail view of a portion of the relay shown in Fig. 6.

Similar referencecharacters refer` 'to similar parts in each of theseverlviews;

'Referring first to Figsi' lat@ 4,'inciusive, the reference character A designates a base plate oi' suitable insulating material, such as hard rubber or a pheno-l condensate product, which base plate supports the Operating mechanism'of the relay. 'Mounted onthe base plate A in parallel spaced relation are two electromagn'etsB and' C, 'each comprising a magnetizable core, 1 provided with enlarged pole pieces 2 and 3, and carrying an energizing winding. As here shown, the pole pieces are rectanguiarin'shape and are fastened to the core 1 by means of studs 5 which extend through clearance holes in the pole pieces and are screwed into threaded hcles in the -oores The upper studs extend above the top -of the magnets a sufiicient distance so' that' they can be employed to hold a protective cover in p1ace.- The lower studs 5 of the magnets extend downwardly through the 'base plate the underside of thebase 'plate withnuts 6 which A, and are provided on asten the magnets tothe base plate; as best seen in Fig. 1.

A' pair of laterally spaced vertically extending non-magnetizable plates 7` and's are Secured 'by means of screws 7 '-and 8 respectively, to the pole pieces 2 and 3 of each magnet on opposite sides of the magnets, and together constitute the supporting framework 'o'r the Operating mechanism of the relay.

J ournalled inthe plates 7 and 8 isa horizontal shaft 9. This shaft is intended to 'be rotated viewed in Figs. 2 and 4,

by means ofa spring'19 which is fasten'ed at" one end to' the armature. The other end of the'spring 19 is fastened toan ear 20 provided on the lower side of a' lug 21 which is formed by bending a portion'of the side plate 8 at right angles to the'side plate as' best seen in Figs. 2 and 3.' 'The armature 18 'carries a rigid Operating arm 22, which, in turn, carries a propelling pawl 23. The propelling pawl zs is pivoted inthe tipof: the Operating 'arm *and is biased, b'y' means of a spring`24 carried bythe 'Operating arm (see Fig. 3), to a' position in which i the tip ofthe pawl engages an adjaeent'jtooth of the ratchet wheel 10 Also cooperating'with retaining pawl 11' which ratchet wheel in cne dir 11 is pivotally supporte as shown in Fig. +1.

the ratchet wheel-10 isa prevents rotation of the ection (the clockwise di -rectioh as viewed in Fig 4); The retaining 'pawl dat its upper end ina "brack'et 12,' and is provided with an arm 13 against which a spring 14 carried by the bracket 12 bears.

The function of the spring 14 is to direct the lower end of the retaining pawl into engagement with the successive teeth on the ratchet wheel. The bracketlz'is pivotally attached tothe side `p1ate 7 at 15, and is arranged to bel'ocked in'an adjusted Vertical position'by means of 'a screw 16 which passes through'anarcuate slot 17 in' the plate'7, and is threaded into the bracket 12.

It will be seen that by the bracket 12 may be r the retaining pawl 11 wi .ratchet wheel 10. i i

loos'ening the screw 16,

otated through a limited arc about the pivot 15,' therebygproviding 'a corrvenient means for adjusting the-position in which 11 e'ngage the teetho'fthej f When electromagnet B becomes energized, ar-

'mature 18 moves toward the left as Viewed in Fig. 4, thereby raising the Operating arm 22 and the propelling pawl 23, and hence stepping the ratchet wheel 10 one tooth in a counterclockwise direction as viewed in this figure. This rotation of the ratchet wheel permits the retaining pawl ll'to drop back of thenext successive tooth on the ratchet wheel so that the" ratchet wheel is subsequently held in its stopped position. When' electromagnet B next becomes deenergized, spring 19 draws the armature 18 toward the right as Viewed in Fig. e, thereby restoring the' Operating arm 22 to the position shown, andhence causing the propelling pawl 23 to" drop back of another tooth of the ratchet wheel. is then ready to again step the ratchet wheel the next time electromagnet B becomes energized. It

will be apparent, therefore, that the shaft 9 willtegral with the side plate ,8. A' jamenut 27'is screwed onto the adjusting screw- 110 maintain' the ?screw in its adjusted position.

' *As-best seen in Fig. 1, a-cylindrical casing -is rotatably mounted on the shaft 9 *and this casing' housesa coil spring 29 which is attachedat its inner end tothe shaft9 and at its outer end to the casing. The spring 29 is'soarranged that it always tends to rotatethe casing about the shaft 9 in the clockwise direction as, viewedin Fig. 3. Rigidly fastened to the casing 30 isa second ratchetwheel 31, the teeth of which face in the opposite direction .fromth teethof the `ratchetwheel '10. The ratchet wheel 31 cooperates with a releasing pawl-32 which is rigidlyfastened to an armature 33 controlled by electromagnet C., The armature 33 is similar to the armatures controlled by electroma gnetB, andis pivotally supported at itslower endona rod 34 carried by the A spring 35 is fastened at one end to the armature 33,"and atthe other end toan ear 39 formed on `the lug 26, and this spring biases the' armature toward the rightas-Viewed in Figg3 to a position in which the releasing pawl 32 engages the teeth of -the ratchet wheel 31 and preventsirotation of the casing 30. The ratchet wheelsl also' coi operates with a holding pawl 38 which is attached to an Operating arm Secured to thearmature .33.. ;The-holding pawl 38 is preferably constructed i of resilient material-such as phosphor bronze, and' .whee1'31. An'adjusting screw elcarried' by the Operating arm 40 bears against the underside of ;the pawl 33 near itsfree end, and* holds the pawl r gn'the desired operative relation with `respect to,

` the ratohet' wheelw e v i e 'When 'electromagnet C becomes energized; ar-

n at ure;33 moves toward'. the left as Viewedin' Q F thereby withdrawing thgctaimng The propelling pawl mately *one-'revolution conducting' (ring-50, as hestseen -in Fig 1'.

32 from engagement with the ratchet wheel 31, and noving the holding pawl 38 into a position in which it will engage theratchet wheel after the ratchet wheel'has been rotated approximately one tooth in the clockwse direction by the action of. the spring 29; When' the electromagnet C next becomes deenergized, spring 35 draws armature 33 to the right as seen in Fig; 3, thereby withdrawing the pawl 38 from engagement with the ratchet wheel 31 and moving the pawl 32 back into engagement with the ratchet wheel, the pawls being so arranged'that substantially no rotation of the ratchet wheel is permitted during this latter movement of the armature. It will be apparent, therefore, that each time electromagnet C becomes energized and deenergized, the casing 30 will be rotated about the shait 9 by the' spring 29 an amount represented by one tooth of the ratchet wheel 31, except under certain conditions to be described hereinafter. e

The stroke; of the armature 33 may 'be adjusted by means of an* adjusting screw 42 ,carried bythe lug 21 in thesame manner as the stroke of the armature 18 is adjusted by the adjusting .screw 25. The adjustingsorew 42 is locked inits adjustedpositionby 'a jam nut 43.

The casing 30 also carriesa contact member 44 (se'e Fig. l) which, in the :form here shown' 'conprises a ring 50 of suitable conductingmaterial Secured to the outer edge of an insulating disc49 which; is fixed to the casing 30. As best scen in Fig. 1, the conductingring 50 is of L- shaped cross' section .having a horizontal portion 50 and a vertical portion 50 The verticalportion 50 cooperates with a contact member 45,

'here shown as a contact arm of suitable resilgages the .ccnducting ring 50 at the outer face of the vertical'portion 50'?. u A stop ar; (53 is also clanped` etween the nut %and e washere'ly'and this stoparm cooperates with ai stoppin 51 carried byythecon- V 'tactmember 44, to limit the amount of rotation side plates '7' and 8, in'the same manner as the armature 18 is pivotally supported on the rod-28j of thecasing 30 about the sha'ft' 9 to approxi- It should` be pointed out thatthe Spring 29 constantly biases the casing 30 .to the position in which the stoppin 51 engages' the left-hand side' ofthe stop arm 53 as viewed in Fig.4, this'position of the casingjwith' respect e to'the shaft being hereinafter referredto'as the sulating ;button,52 .wl1ich extends through the The contact member-Eee, also jcc operate's with mounted on,` but insulate'd *rom a 'bracket` 55 in Fig; 1,* andis arrange'd to constantly engage theouter'curved edgepi the horizontal portion member 44.'

whioh'is attached to the side pia-.te 3; as shown External electrioal connections;tothe*relay are in' Figs. 1, 2-and 4. Referring now'also to the wiring diagram for therelay illustrated in Fig. 5";it will be seen that as here-shown, the terminals of winding 4 of electromagnet B` are connected with the binding posts56 and 57 by means oftwo conductors 60 andisi, respectively, and these binding posts, in turn are connected .with abattery 67 over a contact 66. 'It will be i apparent, therefore, that when contact 66 is closed; electromagnet B will become energized. e One r terminal ofwinding 4 of electromagnet C is likewise connected with binding post 59 by means of a, conductor 62 and `the other terminal of this winding, is, connected ,with binding post 58 through a conductor 63 contact finger 54, conclucting ring 50, contact arm 45, the framework of the relay, and a conductor'i. The binding posts 58 and 59 as here shown are connected with a battery 67 over a contact 68. It will be seentherefore from an inspection of Fig. 5, that if contact 63 is closed when arm 45 is engaging' i9' willbe rotated one step each time electromagnet B becomes energized in the manner previously'described. As soon as the shat has been rotated one step, the arm 45 will be moved off of the. insulating button 52 and into engagement 'with the conducting ring 50 so that electromagnet C canthen -be energized by closing contact 68. If this is done, the casing will be rotated one step' by the spring 29 in the same direction as the shaft 9 was previously rotated, and the contact member. 44 will therefore be moved to the position in which the contact arm 45 again engages the insulating button 52. Asa result, electromagnet C cannot again become energized, until after electromagnet B is next energized. If, however, contact 68 remains open while the shaft 9 is being step'ped so that electromagnet C remains deenergized, the casing 30 will be pre- Vented from rotating, and the rotation of. the shaft 9 under these conditions willtherefore causethe contact arm 45 to advance aroundthe conducting ring one step at a time, and will also-wind the spring 29. The shaft 9 will conv tinueto be rotated, and'the contact arm will continue to move around the cond'ucting ring in response to the alternate energization and deenergization of electromagnet B, until the shaft 9-h'as been rotated through approximately one complete revolution, at which time the stop arm 53 will engage the right-hand side of the stop pin 51, as Viewed in Fig. 4, thus preventing further rotation of the shaft'since' the casing 30 is i held in a fixed position under these conditions by thepawl 32 and ratchet wheel 31. It should be pointed out that when the shaft and casing occupy the relative positions in which the stop arm '53 is engaging the right-hand side of the stop pinl, as viewed in Fig. 4, the contactarm 45 still makes electrical contact with the con,- ducting ring 50 of the contact wheel 44.

If, at any time when the contact arm 45 is 'engaging the conducting ring 50,` switch 68 is operated to alternately energize 'and 'deenergize electromagnet C,'the casin so will be moved to'- V ward its normal position by the spring 29 one step each time electrcmagnet C becomes energized and deenergized asflpreviously described. When the casing has been stepped 'by the' spring 29 the samenumber of: timesas the shaft 9. was pre-,- viously stepped in response to the alternate energization and deenergization of electromagnet B,

It will be seen, therefore, that I have provided "a relay in which two cooperating contact members are movedfrom one relative position to another. relative position in response to a pr'edetermined number of Operations of one electromagnet, and are restored to said one-relative position in response to the same number of operations' of another' electroniagnet.

Relays of this type are particularly'suitable for, although in no way limited to", use in connection with certain forms of street car control systems, wherein it is desired to provide' 'a convenient means for determining thenumber of cars which have entered a particular stretch of r track during a measured time interval. When used for this purpose, the contact 66 would be replaced by acar actuated contact so that .this

contact would be operatedand hence the shaft 9 would be stepped, each .time a. 'car entered the stretch. It will be apparent, therefore, that with therelay arranged inthis manner, the number of times contact 68 must be operated at the endof a measured period of. time to restore the parts of the relay to their normal positions would be'an indication of the number of cars that -had entered the stretch during that period of time, within the limitsof the apparatus.

V It shouldbe pointed out that the number of times shaft 9 has to be stepped to move it from theiposition in which the arm 45 engages the insulating button 52 to the positionin which the stop arm 53 engages the right-hand side of stop pin 51 as viewed in' Fig. 4, may be variedby varying the number of teeth on the ratchetwheel 10, and, similarly, the number of times the casing 30has to be stepped by the spring 29 to restore the casing i 30 to -its normal position from therelative position which it occupies when the ,stop arm 53 engagesthe right-hand side of stop pin '51 g as viewed in Fig. 4, may be varied by Varying the number of teeth on the ratchet wheel 31. 10 and 31 will usually be the same, althoughmy invention is not limited to this particular arrangement. r

Referring now to the modified form of relay shown in Figs. 6 to 9, inclusive, as here' shown, the; plates-'I and 8 support-a rotatable` shaft 69 which is constantly urged'in a clockwise direction as viewed in Fig. 8 by means of a spiral spring '72, the inner end of which is fastened to an extension 69 of the shaft 69,' andthe outer endof which is fastened to a spring housing 73 mounted on the side plate'7. Rigidly fastened .to the shaft 69 are two ratchet wheels 70 and 71, the teeth :of

of which face in thesame. direction. The ratchet wheel '11 isioperated by the 'armature 18 through the medium of the Operating arm 22 and propelling 'pawl 23 previously described in connection with the relay shownin Figs. lto 4, inclusive, the

The number of teeth onthe ratchet wheels parts being so arranged that the ratchet wheel, and 'hence' the shaft 69, will be rotated one step in a counter-clockwise direction', as viewed in Fig. 8, each time armature 18 moves to the left due 'to the energzation of electronagnet B. It will be noted that, as here shown, the parts are so adjusted that when the armature l8 occupies'its retracted 'position towhich it is biased by the spring 19, the pawl 23 is out of engagement with the ratchet wheel 71 so that, under. certain con-' and is biased 'by means of a spring 76 to a position in which' it will engage an adjacent .tooth of the ratchet wheel when armature 33 occupies its left-handor'retracted 'position as viewed in Fig. 8. 'When armature 33 moves to the right as viewed in Fig. 8 due to the'energization oi' electromagnet C, the pawl 74 is withdrawn from engagement .with the ratchet wheel 70, and the holding pawl 38 previously described in 'connection with the relay shown in Figs. 1 to 4, inclur sive,'then moves into engagement with the rat'chet wheel 70. The parts are so proportioned that when the paw174 is moved out of engagement with the ratchet wheel and the pawl 38 is moved into 'engagement with the ratchet wheel in the manner just described, the ratchet wheel,'and hence the shaft 69, will be rotated bythe spring 72, in the opposite direction from 'that in which it is impelled by the propellingpawl 23 and ratchet wheel71, through a distance which corresponds to the length of one tooth of the ratchet wheel 70. When the shaft 69 occupies the position shown, a stop 77 attached to the ratchet wheel 71 engages a lug 78 forned on a bracket 79' attached to the side plate 8 (see Fig. 10) and prevents further-rotation of the shaft by the spring 72in the clockwise direction, as Viewed in Fig. 8, and when the shaft has been rotated away from the positions shown through a predetermined distance in a counterclockwise direction, the stop 77 then engages a lug formed on the bracket 79 and prevents further rotation of the shaft in this direction. As shown in the drawings, the lugs 78 and 80 are so arranged that the shaft 69 may be rotated through a total angle of approximately 180 but it will be readily understood that this arrangement may be varied as conditions require.

A contact member, here shown `as a semi-circular disc 81 of suitable conducting material, such as phosphor bronze, is attached to the outer end of the extension 69 of the'shaft 69, and this disc is -arranged to cooperate with a plurality of pairs of contact fingers. As here shown, there are sixteen such pairs'of contact fingers, designated by the reference' characters 82 'to 97, inclusive. The contact fingers of each pairare attached, as by 'eyelets 98,`to the opposite sides of a ring`99 (see Fig. 6) of insulating material formed on a panel 99 attached to :the side plate 7 and are so arf ranged that they extend radially inward toward theextension69 of theshaft 69, inapositio'n' to engagethe opposite sides of the semi-circle disc 81 when the'disc hasbeen rotated to. the proper position. The parts are so adjusted that when the shaft 69. occupies the. position in which the in Fig. 9, it will engage an additional pair of contact fingers.

' External connections with the contact fingers may be made by means of L-shaped conducting bars 100 which are molded in 'thebase plate A of the relay, and each of which conducting bars is adapted to be connected at its' inner end with the fingers of a corresponding ,pair of fingers.

The wires for connecting the bars with the ngers are omitted from the drawings for`- the`sake of clearness. r r r As shown in Fg. 7, the terminals of winding 4 of electromagnet B of the relay shown in Figs. 6 to 9-, inclusive, areconnected directly with the terminal posts 56 and 57 by means of the conductors 60 and 61, and the posts 56 and 57, in turn, are connected with the battery 65 of a contact' 66. The terminals of wincling 4 of electromagnet C are'likewise connected with the binding. posts 58 and 59 by means of conductors 101 and 62, and the binding posts 58 and 59 are connected with the battery 67 over contact 68. i

In explaining the operation of the relay shown 'in Figs. 6 to 9, inclusive, I will assume that with the parts in their normal positions in which they are shown in the drawings and with contact 68 remaining open so that electromagnet C remains deenergized, contact 66 is operated to alternately energize and deenergize electromagnet B. Each time electromagnet B becomes energized, `the shaft 69 'will be stepped one step in a clockwise direction as viewed in Fig. 9 thereby moving the disc ,81 successively into engagement' 'with the pairs of contact fingers 83, 84, 85 and so forth. The shaft .69'wi1l continue to be stepped under these conditions in response to the alternate ,energization anddeenergization of electromagnet B until it has been rotated to the position in which the stop 77 engages the lug 80 at which time further rotation of the shaft is prevented. When the shaft occupies this latter position, the disc 81 will engage the contact fingers of each pair of fingers 82 to 97.

If, when the shaft 69occupies any position fexcept the position in which the stop 77 engagesthe lug 78, and, the contact 66 .remaining open, contact 68 is operated to alternatelyeenergize and deenergize electromagnet C, the shaft 69 will bere:

turned by spring 72 toward the position inwhich the stop 77 engages the lug 78, one step each time electromagnet C becomes energized and deenergized. When the electromagnet C, has been energized and deenergized the proper number of times the disc 81 will be restored to the position in which it is illustrated in the drawings so that the disc will then be engaged by only the fingers of the pair of fingers 82.

Although I have herein shown and described of said conducting ring for sliding contact therev 40- and said shaft to a predetermined relative posiwheel one step each time said one electromagnet 'two electromagnets, means controlled by one casing to one relative position on said shaft, two electromagnets, means controlled by one electromagnet for rotating said shaft one step at a-time, means'controlled by the other electromagnet for at times preventing rotation of said casing and for at other times releasing said casing to permit rotation of said casing one step at a time by said biasing means, acontact member attached to said casing and comprising an insulating disc provided at its outer edge with a conducting ring, a contact arm attached to said shaft for sliding engagement with said conducting ring, and an insulating button extending through said conducting ring in such manner that said contact arm will engage said button when and only when said casing occupies said one position.

2. In combination, a rotatable shaft, a casing journaled on said shaft, means for biasing said casing to one relative position on said shaft, two electromagnets, means controlled by one electromagnet for rotating said shaft one step at a time,`

means controlled by the other electromagnet for at times preventing rotation of said casing and ,contact arm attached to said 'shaft for sliding engagement with one side of said conducting ring,

` an insulating button extending through the side contact arm will engage said button Whenj and only when said casing occupies said one position, and a fixed contact finger engaging the perphery with.

3. In combination, a rotatable shaft, a casing journaled on said shaft, a spring connected with said casing and said shaft for biasing said casing tion, a first ratchet wheel secured to said shaft and a second ratchet wheel Secured to said casing, two electromagnets, means controlled by one electromagnet for advancing said first ratchet is energized, means controlled by the other electromagnet for normally preventing rotation of said second ratchet wheel but for releasing said second ratchet wheel to permit advancement of said second ratchet wheel one step by said spring each time said second electromagnet is energized, and a contact responsive to the relative position 4. In combination, a rotatable shaft, a casing' said casing and said shaft for biasing said casing and said shaft to a predetermined relative position, a first ratchet wheel Secured to said shaft and asecond ratchet wheel secured .to said casing,

electromagnet for advancing said first ratchet wheel one step each time said one electromagnet is energized, means controlled by the other electromagnet for normally preventing rotation 'of said second ratchet wheel but for releasing said second ratchet wheel to permit advancement of said second ratchet wheel one step by said spring each' time said second electromagnet is. .energized, a contact member attached to said casonly when said casing occupies' said, one'po'si 5. In combination, agrotatable shait, acasing mounted to rotate' on said^shaft,`a spring *Secured to said shaft andto said casing for biasing .said shaft and said casing. to a predetermined rela;- tive position, a first ratchet 'wheel fixed to said shaft, a second ratchet -wheel fixed to said casing a first armature biased to a first position, a first electromagnet for at times moving said first armature-from its first position to a second position, a second armature biased to a first position, a secondelectromagfet for moving said second armature from its first position to a second position, 'a first retaining pawl biased into engagement with said first ratchet wheel, a stepping pawl controlled by said first armature and artooth each tine said first armature is moved to its second position, a holding pawl controlled by 4 'said second armature and arranged to engage saiclsecond ratchet wheel when said second armature occupies its second position but not when said second armature occupies its first position,

and a, releasing pawl controlled by said second 'armature and arranged to prevent rotation of said second ratchet wheel when said second armature occupies its first position but to release said second ratchet wheel'to permit rotation of 'said second ratchet wheel one tooth by said spring each time said armature is moved to its second position, and cooperating contact members controlled by said shat and 'said housing.

6. In combination, a rotatable shaft, a casing 'mounted to rotate on said' Shaft, a spring se-' cured to said shaft and to said casing for biasing said shaffl 'and said'casing to a'predetermined i' I relative position, a first ratchet wheel fixed to 'said shaft, a second ratchet wheel 'fixed to said casing, a first armature biased to a first position,

a first electromagnet for at times moving said v first armature from its first'position to a second position, a second armature biased to a first position, a second electromagnet for moving said second armature from itsfirst position 'to a second position, a first retaim'ng pawl biased into engagement with said first ratchet wheel, a step-- ping pawl controlledby said first'armature and arranged to advance said first'ratchet wheel one tooth each time said 'first armature is moved to its second position, a 'holding pawl 'controlled bysaid second armature and'arranged to engage said second ratchet wheel when'said second armature occupies its second position but not when said second armature occupies its first position,

and a'` releasing pawl controlled by said second '.gagement with one side of said conducting ring,

an insulating button extending through the side of said conducting ring in such manner 'that said 4 contact arm will engage said button when and only when said casing occupies said one position, r

and a fixed contact finger engaging the periphery of said conductng 'ring for sliding contact there- Withg v 7. Iflcombnation, a contact; two eleetromagnets; means controlled by cne eleotro nagnet. and effective when said one. eleotromag'net hasbeen members arranged to be moved into engagement witheach other in response to a predetermned amount of movement 'of one contact member in one direction' and to be moved out of engagement 'With each other in response to a correspondngamount of movement of the other contaet member in the same direction, a first electromagnet for moving said one contact member one step at a time in said one direction, and means controlled by a second electromagnetfor moving the other contact member one step at a time in said one direction.

r BRANKO LAZICIL.

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