US2414432A - Timing device - Google Patents

Description

1947. G. c. ARMSTRONG v 2,414,432

TIMING DEVICE Filed Jan. 29, 1944 4 Sheets-Sheet 1 WITNESSES: INVENTOR, Z Geai'ge C. flrmszrony,

' BY M W- ATTORN E-Y Jan. 21, 1947.

G. c. ARMSTRONG TIMING DEVICE Filed Jan. 29, 1944 4 Sheets-Sheet 2 INVENTOR George C/irmszf/fofiy ATTORNEY WITNESSES: 154W,

1947. .G. c. ARMSTRONG ,414,432

TIMING DEVICE Filed Jan. 29, 1944 4 Sheets-Sheet 3 WITNESSES: lNVENT OR ./Y Gea rge C firms fro/7y. M W 35 F 2;

ATTORNEY n- 1947- G; c. ARMSTRONG 2,414,432

TIMING DEVICE Filed Jan. 29, 1944 4 Sheets-SheecA 4 3 2 m a 0 a Q 2 0% a l no :1. 9 .7. 5 w 1 a Q 3 w j 8 u 0 J 4 a y 2 .9 E

24 I INVENTOR- Gearye Cflrmszrony 4 WITNESSES! ATTORNEY Patented Jan. 21,194?

TIMING DEVICE George G. Armstrong, Forest Hills, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 29, 1944, Serial No. 520,191

1 My invention relates to electromagnetic rotary devices and, in particular, to time limit relays of the type dealt with in my Patents Nos. 2,111,550; 2,111,541; 2,111,542; and 2,111,543 and in my copending application Serial No. 523,059 filed February 19, 1944, on Rotor type contactors.

According to my patents, a rotary motion of a driving or timing device is obtained by means of a magnetizable rotor which is subjected :to periodic magnetic flux in movable magnetic and frictional engagement with a magnet structure while permitted to contact one of the magnet poles and biased away from the other pole against the attracting force of the latter. It is also disclosed in some of my patents to dispose such a rotor in a timing device so that it prevents the operation of a magnet armature until the rotor has moved through a given rotary travel.

It is an object of the present invention to improve motor or timing devices of the above-mentioned type in structural as well as operative re spects.

More specifically, one of the aims of this invention is to design a timing device whose timing period can be readily adjusted to a desired duration.

Another object, allied to the one just-mentioned, is to provide a time-adjustable relay or the like apparatus whose adjusting limits are extremely wide, for instance between about seconds down to fractions of one second at a rather simple and space saving construction of the apparatus.

. Another object of my invention is to devise a timing relay of the rotor type in which the rotor mechanism serves to actuate a quick-acting contact as well as a. time delayed contact in order to render this type relay suitable for control circuits in which a contact, such as a holding contact, is to be operated immediately upon energization of the time relay.

is also an object of my invention to simplify and improve the design and operation of a timing relay in which a rotor of the type here referred to serves to delay the operation of a contact controlling armature. According to this object, it is especially intended to eliminate the gearing between the rotor and the armature or armature latch means described in some of my above-mentioned patents, with a view to facilitating the manufacture and reducing the space requirements of such a relay.

A still further object of my invention is to provide a rotor of the type here referred to with control means ior stopping itsrotationmag'net- 14 Claims. (Cl. 200-97) 2 ically notwithstanding a continued energization of the control magnet, especially when the rotor has completed its useful angular travel.

These and other objects of my invention will become apparent from the following description taken in conjunction with the drawings showing different views and detail illustrations of an adjustable time limit relay designed in accordance with the invention.

Figure 1 is a front view, Fig. 2 is a bottom view, and Fig. 3 a side elevation of the relay.

Fig. 4 is a partial front view similar to Fig. 1, but with the cover removed in order to show the interior of the apparatus.

Fig. 5 is a cross section taken along the plane denoted in Fig. 4 by the dot and-dash line marked V-V. 1

Figs. 6 and 7 are front and rear views, respectively, of the rotor assembly of the apparatus separated from its other elements.

Fig. 8 is a section through the rotor assembly taken along the cut indicated in Fig. 6 by the dot and dash line marked VIII-V111.

Figs. 9 and 10 are two different views of the magnet armature forming part of the rotor assembly.

Figs. 11 and 12 are front views similar to Fig. 4. While Fig. 4 shows the apparatus in the inoperative position, Fig. 11 indicates the initial operating position and Fig. 12 the end position assumed by the movable elements of the apparatus when in operation.

Referring to the drawings, numeral I denotes a molded insulating body which forms a casing for the reception of the rotor and armature assembly of the device and is provided with openings for attaching it to a mounting panel or other support. The casing formed by body I is covered by two insulating cover plates 2 and 3 (Figs. 1, 2, 3, 5) which are detachably secured to the body I by means of fastening screws. A magnet frame 4 is rigidly securedto the body I. This frame consists of a laminated structure of substantially U-shaped configuration and has two poles 6 and 8 which traverse the wall ofbody l (Figs. 4, 5). The pole end 6 carries a solid insert or pole piece 1, preferably of stainless steel which has a polished pole surface for coaction with the rotor. The pole end 8 of the magnet frame 4 forms a pole surface at 9, also for cooperation with the rotor, and another pole surface at 10 for coaction with a movable armature (Fig. 4). A stop II is firmly secured to the pole end 8 and forms part of a latching device to be more fully described hereinafter.

A contact carrier |2 in the form of a bellcrank lever of insulating material is pivotally mounted on the stationary structure. The shaft ends 13 of lever l2 engage corresponding bores in the insulating body I and the cover plate 2 (Figs. 1, 3, 4) so that the axis of ends |3 forms the pivot or fulcrum of the contact carrier. A contact bridge is mounted on one end of lever it for cooperation with two stationary contacts I5 and I6 secured to body I and cover plate 2, respectively (Figs. 3 and 4). Similarly, a contact bridge I! carried by the other arm of lever. I2 is provided for cooperation with two stationary contacts I!) and also mounted on body and cover plate 2, respectively. The contact bridge I1 is movably arranged in a saddle, attached to lever I2, which accommodates a contact spring l8 tending to move the bridge I! towards a limit position away from the lever arm in order to produce contact pressure when bridge I! is moved into contact closing position. The lever 12' has a third arm, denoted by 2|, which extends into the main cavity of body and is biased by a hell; cal compression spring 22 (Fig. 4). Due. to the reaction of thespring, the contact bridge [4 is normally held in eng ement with the stationarycontacts l5 and I6 while the contact bridge I! is separated from the appertaining contacts -|9 and 26.

Another movable contact 23 is pivotally mounted on a holding pin 24 which carries also a coiled compression spring 25 tending to maintain the contact 23 into engagement with a stationary contact 23 mounted on body- I as apart of a terminal 21. Another terminal 28, serves to connect a conductor with the movable contact 23 (Figs. 1, 2, 4). An insulating plug 29 is movably mounted on body for transmitting a translating motion from the rotor to the movable contact 23. g

A leaf spring 30 is firmly attached at one end to an angle piece 40 secured to the magnet pole- 8. The spring 30 extends in proximity to the pole surface 9 and rests against the lowermost end of this pole surface. r

A pin 3| is rigidly secured to the bottom of the casing formed by the'insulating body land has. a polygonal portion 32 engaging acorresponding depression in the bottom of the casing in order to prevent a rotation of the pin relative to the stationary structure. Adjacent to the polygonal portion 32 is a conical seat surface for-- accommodating the corresponding; seat surface of a sleeve 34 which is revolvable about the pin. 3|: but, during the operation of the apparatus, usually fixed in a selected angular position relative thereto, (Figs. 5 and 8).. A stop pin 35 is firmly mounted on the disk-shaped bottom portion of the sleeve 34 (Figs. 7, 8),. A washer 36 is placed on the threaded portion of the sleeve and secured in proper position by means of lockingnuts 37 which jam the washer against the shoule der of the sleeve. The upper end 38 of the sleeve has a radial slot at 39 (Figs. 5 and 8).

The just-mentioned sleeve structure forms. a loose bearing for the rotor 4| of'the timing device, The rotor consists of a. solid body, preferably of magnetically permeable stainless steel, andhas a polished peripheral surface for cooperation with the pole surface of pole piece I and the adjacent surface of the leaf spr ng30; (Fig, 4). A cross pin 42 traverses the cylindrical bodyof the rotor so as to project on both axial" sides beyond the rotor front faces. Referring to Fig. 8',

the lower end of the cross pin 42: serves; tollimjit;

the angular motion of the rotor 4! by abutting against the stop pin 35. The upper end of cross pin 42 serves to coact with a latch mechanism and with the armature still to be described. A spring winding 43 is arranged in the annular space between the rotor 4| and the bearing sleeve 34 and has one end in engagement with the rotor while the other end is attached to the sleeve 34. The spring 43 is under torsionaltension in order to bias the rotor 4| for motion so that the rotor has normally the tendency to rotate in the counterclockwise direction, referring to Figs. 4, 6, 7, 11 and 12, until the motion is stopped by pin 35 of sleeve 34. This normal end position is illustrated in Fig. 7.

Two angular bearing plates 44 and 45 engage the rotor 4| on both axial sides and are rotatable relative to the rotor about the geometrical rotor axis (Figs. 4 through 8). Each of the bearing plates 44 and 45 hasa curved arm 46 and 41, respectively, which extends in a substantially ;r'adial direction away from the rotor 4 l, The arms 46 and 41 straddle and carry a laminated magnetarmature 48 which is providedwith. two short circuited shading windings 49 and 59 in order to insure continuous attraction and silent operation when the armature is subjected to the alternating field of the magnet. The armature -48'has a cylindrical pole surface 51' extending in parallel to the peripheral surface of 'the rotor 49. Another pole surface of the armature is formed at 52. This surface is plane and lies oppositethe pole surface id of the magnetpole 8-so that the armature is; attracted when the magnet coil. is

energized (Figs. 4, 6, 7, 9). Thetwo arms'46 and 47 (Figs. 6, l and 8) are-firmly connected with each other bypins or spaces of non-magnetic material located at 53,. 54 and 55. The pin 55 forms a. bearing for the armature 48 which has some clearance so as to permit a slight displace-- ment and rotation of the armature 48 relative to the arm 46. The pin 53 serves also as a guide for cooperation with a latched which is pivoted about a pin 55 (Figs. 6, 8) attachedto arm 45. The latch 65) has an upwardly extending arm 6| (Fig. 4) in proximity to the above-mentioned stationary stop. Ii. Another arm of the latch, extending in the downward direction, forms a cam surface at 62 (Fig. 4). Another portion of the latch 60 straddles the above-mentioned pin 53 so as to limit the rotational motion of the latch 60 (Fig. 4). The latch is biased to rotate against the pin 53 in the clockwise direction and hence assumes normally the position show-n in Fig. .4. In the illustrated example, the biasis effected bygravity although a biasing spring may be pro,- vided for this purpose. Referring to; Fig. 4,,it; will be seen that when the armature is attracted towards the pole surface it of the magnet, the arm 6| of latch fidwill abut-against the .stop H and thus prevent the upward motion of linear.- mature. j

Fig. 4 shows also that when; the rotor: 4| I0: tates. counterclockwise, crosspin 42' will eventually engage the cam, surface 62 of latch 63,, there.- by turning the latch about its, pivot in-the. counterclockwise direction. As aresult, the latch arm 6! is disengaged fromthestQpi H, sothatthe armature can follow. thev attraction, towards the pole surface ill of the magnet pole 8. At theend of its travel, the crosspin 42 will rest directly against the radial arm lii of thebearing plate. 44 and 'lift the armatureinto a'stronger magnetic field; unless. the armature. has already moved tc-' ward;th,e magnet.

It has been mentioned that in the operative condition of the apparatus, the rotor 4| is biased by its spring 43 (Fig. 8), into engagement with the stop pin 35 of the bearing sleeve 34. Consequently, the stopping point of the rotor motion depends on the annular adjustment of the sleeve structure. In order to change this adjustment, an adjusting knob 65 is provided which hasa projection engaging the slot 39 in the upper end 38 of the bearing sleeve 34 (Figs. 5 and'B). The knob 65 carries a plate 6'6 (Figs. 1, 3, 5) which formsa pointer mark 68 cooperating with a dial 69 on the cover plate 3. The plate 66 is radially subdivided into a plurality of lobes which engage a roughened, knurledor toothed surface portion of the cover 3 so as to hold the knob 65 in a selected angular position when a locking nut '61 (Figs. 1, 3, 5) is screwed tight against the knob 65. Upon loosening the nut 61, the knob 65 can be lifted sufiiciently to disengage plate 66 from the locking engagement with the cover plate 3 in order to permit changing the angular adjustment of knob 65 and hence of the entire sleeve structure with its stop pin 35 (Fig. 8). Since the period elapsing from the energization of the apparatus to the actuation of the main relay contacts depends on the extent of the angular travel of the rotor, as will be explained in a later place, a change in the angular adjustment of the knob 65 and plate 66 represents a corresponding change in the timing period. Hence, the dial surface 69 can be calibrated in units of timing periods. For instance, in the illustrated example, a maximum timing period of about five seconds is available, and the pointer 68 can be adjusted gized with periodically variable current, preferI- ably alternating current of 60 cycles frequency, so that a periodic flux is produced in the magnetic structure which reverses its direction at the frequency of the energizing current and is effective in the air gap between the pole surfaces of the magnet poles 6 and 8 so as to traverse the cylindrical rotor body. As a result, the rotor is attracted toward the pole '6 and contacts the pole piece I whil being also attracted toward the pole surface 9 of pole 8 until it abuts against the leaf spring 30. Hence, immediately upon energization of the relay coil, the rotor is moved from the position'of rest shown in Fig. 4 into the posi tion according to Fig. 11. Due to the upward motion of the rotor, the plug 29 is free to follow and permits the sprin 25 to close the contact between elements 23 and 26. This establishes a conductive connection between the terminals 21 and 28 (Fig. 2), thereby closing a circuit serving,v for instance, for maintaining a self-sealing circuit for the relay coil 5 or for any other control purposes requiring an immediate contact operation upon energization of the timing relay. The just-mentioned initial motion of the rotor 4| into the position according to Fig. 11 has no eilect on the contact lever l2 since the armature 48, although immediately exposed to the magnet field between pole surface 40 and the opposite armature surface, is prevented from moving in the upward direction by the latch arm 6| abutting against the stop Furthermore, the field strength inthe armaturegap adjacent the pole surface l0 isrelatively weak because of the rather large distance of the armature.

Under theinfiuence of the periodicfiux and of the bias byyspring 30,- the cylinder 4| will both move to and fro and rotate. At the beginning of the movement, various transients occur, but when the motion has become steady, the rotor will be in its extreme left-hand position at the time the flux is exerting the greatest pull. This is in accordance with the usual action of bodies oscillating steadily. The reversal of motion occurs at the time of greatest force, because it is the time of greatest acceleration.

As the rotor body 4| moves from its extreme left-hand position, friction between itand the pole piece 1 causes the body to rotate. It will reach the extreme right-hand position at or about the time when the flux in the air gap falls to zero. This will be the moment of reversal of flux in the core 4, but it will not be the time of flux reversal in the rotor cylinder 4| because the hysteresis of its material requires that the flux in the gap shall reverse and then rise to a suificient intensity to provide the coercive force needed to overcome the remanence of the cylinder 4| before the polarity of its magnetism will reverse.

At the moment after reversal of flux in the gap, the pole piece I and the adjacent portions of the cylinder 4| will be of the same polarity. Therefore, some repulsion will occur between them. Consequently, the cylinder 4| will move under the influence-of the spring 30 without being caused to roll. That is, it will slide rather than roll during at least part of the time it is moved by the spring toward the left. During the preceding lOlling motion toward the right, the cylinder will have acquired a certain rotational momentum. This will cause its rotation to persist during the motion toward the left until its magnetism has been reversed and there is again attraction between it and the end of the pole piece I. The friction resulting from this attraction must first overcome the rotational momentum before it can reverse the direction of rotation of the cylinder.

The cylinder arrives at its left-hand position with no rotation at that instant or with a rotation smaller than and in the opposite sense to that when reaching the extreme right-hand position. The result is an accumulation of rotational movement in the counterclockwise direction (Fig. 11).

Due to these phenomena, the rotor, upon reaching the initial operative position according to Fig. 11, will start revolving so that its pin 42 moves away from the stationary stop pin 35in the direction marked in Figs. 6 and '7 by the arrows 51 and 58, respectively, until the pin approaches the end of its angular travel and engages the cam surface 62 of latch Bil (Figs. 11 and 12).

The latch is now moved out of engagement with the stop I I so that the armature 48 is free to follow the attraction by the magnet pole 3. If the field strength is insuiiicient to lift the armature, the cross pin 42 will eventually abut against the arm 46 of the bearing plate 44 and lift it with th armature 48 toward the magnet pole 8 until the field strength in the armature gap is suiiicient'to seal the armature against the pole surface Hi. The final position thus reached is represented in Fig. 12.

During the lifting motion of armature 48 toward the magnet pole 8, the connecting pin 53 (Fig. 8) of the armature assembly abuts against the arm 2| of the contact lever l2 and turns it clockwise in opposition to the biasing spring 22. As a result, the contact between bridge I 4 and stationary contacts l5 and I6 is opened and the contact between bridge I1 and stationary contacts l9 and 2!) closed.

*7 V 'In the final operating position, aceor'ding to Fig. T2, the armature l8 establishes :aisu'b'stan tiallyclosed magnetic connection between the pole 'surface I and'tne rotor-'41, thereby shunting the gap between the rotor "and the pole surface '9. -Consequently, the oscillatory motion at leaf spring til ceases and the rotor H is'stopped. Thus-aside from the mechanical arrest of cross pin 42, the rotor-has no -lon'ger the tendency to v brate towards and away from the leaf spring. This renders the operation of theapparatuissil'ent once the switching operation is completed while the "alternating current coil remains energized. Upon d'e'energization of coil 5 by action of the contact spring 18-, and the spring 22, 'the'rnagrieti'c armature is forced away from the pole Hi, the contact armatur 12 rotates counterclockwise, the rotor drops-frdm thefpole 1, opens the contact 23, and, guided by its loose bearing on the sleeve 3'4, "is rotated clockwise by the spring 43. Hence the timing device assumes automatically its starting eondition "after the completionof its operation It will be obvious 'to those skilled in the art upon -studyin g my disclosure that the invention can be modified in various ways without departing from its objects and essential features. Therefore, I wish this specification to be understood as illustrative and not in a limiting sense.

I claim as my invention:

v1. A timing device comprising, in combination, a magnetic structure having two poles forming an 'airga'p and containin energizing means for producing periodic magnetic flux in said gap, a magnetizable rotor disposed in said gap adjacent one of said poles to roll relative thereto and being movable towards said other pole for at traction thereby, means for biasing said rotor away from said other pole so as to cause unidirectional rotation of said rotor when said means are energized, a spring connected with said rotor for biasing it toward an angular starting position when said means are deenergized, and an angularly 'displaceable stop for settin said posi-- tion in accordance with a desired timing period.

2. A timing relay comprising, in combination, a magnetic structure having two poles forming an air-gap and containing energizing means for producing periodic magnetic flux in saicl'ga'p, a magnetizable rotor disposed in said gap adjacent one of said poles to roll relative thereto and being movable towards said other pole for attraction thereby, means for biasing said rotor away from said other pole so as to cause unidirectional ro tation of said rotor when said means are active, contact actuating means controlled by said rotor at the end of said rotation, a spring connected with said rotor for biasing it in the opposite direction towards a starting position when said means are inactive, and an angularly displaceable stop for setting said position'in accordance with a desired timing period.

3. A timing device comprising, in combination, a magnetic structure having two poles forrn ing an airgap and containing energizin means for producing periodic magnetic flux in said gap, a magnetizable rotor disposed in said gap and movable radially towards each of said two poles, a stop associated with one of said poles to be rollably engaged by said rotor when said rotor is: attracted by said latter pole, and elastic meant; for engaging said rotor when the latter is attracted by said other pole so as to bias said rotor away therefrom in order to cause unidirectional.

rotation of said rotor when said'energizing means 8 t '"hi'ea ns at'u'able by said rotor' on its radial motion ofatt'raction towards-sa dstop, andcontactmeans actuaible by said rotor up'o'n its rotation through a givenanguiar'travei. I i I *4. timing-relayfconiprising, infconibination, a 'inagneticstructur'e having two polesfforming "an ai'rgap "and containing energizing means for produc-ing periodic magneti in said, gap, a ana netiz'able motor disposed in said gap and movable radially towards each or said two poles, "a stop associatedwith "one of said poles to be 'rollably engaged by said rotor when said rotor attracted i'by "said latter pole, and elastic means -for engaging'said motor when the latter isfattracted by said'otlier poles'o asto biasfs'aid rotor away therefrom order t cause unidirectional rotation of seawater when said energizing} means are active, contact nie'ans actuabl'e by "said "rotor in dependence upon its-"radial motion of "attractio'n towards said stop, so as to be act'uat'e'd i'm inediately upon energizationof said means, and contact means actuable by "said rotor upon its rotation through agiven angular travel, 'soas to be actuated after 'theelapse of a timing period corresponding to said travel. I o

"5. A timing relay comprising, 'incombination, a 'rn'ag neticstructure having two poles forming 'an jairgap and 'cdntain'ing'energizing means for producing periodic magnetic flux 'in said gap, a magnetizablefrotor disposed 'insaid gap adjacent one or said poles'to rollrelative thereto'and being movable towards said other polejfor attraction thereby, "means for biasing said rotor away from saidother 'p'oleso as to cause unidirectional rotation of said 'rotorwhen s'aid meansare active, contact a-ctuatiri g'ineans controlled'by'said rotor at the end of 'said rotation, and angularly adjustable stop ineans fdrvarying thestarting position of said rotor i'n'o'rder toadjust its length of 'an- 'gular travel in accordance with a desired timing period. g

6. A timing relayfhaving a holdingcontact and a timing'contact and comprising, in'combiiiation, a magnetic structure having two poles forming an air a and containing "energizing means for producing periodic magnetic flux insaid gap, a 'rn'agneti izableiotor disposed in'sa'id gapand movable radially towards each of said two poles, a stbnassociated with one 'of'said poles to be rollably "engaged by'said -rotor when "said rotor is attracted by said "latter pole, said "rotor being biasedaw'ay fromsaid 'stop'andsaid holding contact being m'ec'hanicallycoupled with said rotor so "as to be, closed when said'rotor is attracted against its bias towards said stop, elastic means for'engagings'a id rotor when the latter is "a tracted'by said other polefso as tobia's said rotor away therefrom inorder to cause'unidirectional rotation of said rotorwhen'saidenergizing'mearis 'arej'active, and "means controlled by said rotor for actuating said timing contact upon rotation bf 's'aidrotor througha'given angle. a g V A "7. "A timing relay comprising, in combination, amagn'eticstructure having two poles forming an airgap'and containing energizing means for producing periodic magnetic flux in said gap, a

magn'etizable "roto'r 'diSDosed in said ga adjacent :one of saidpoles to roll relative thereto and being mqvable 'towa'rds "said other polefor attraction 'the'rby means for biasing "said rotor away from s'aidother 'poleso'as tocausefiinidirection'al rotation of said roto'r" hen said means are act ve, a Contact contrblling arina'tiire associated with 's aid structure to 'be attiacfid'thfeby when said energizing means are active, latch means engaging said armature for preventing its contactcon'trolling motion when attracted, and a release member mounted on said rotor' for engaging said latch means so as to move them into releasing position at the end of said rotation.

8. A timing relay comprising, in combination, a magnetic structure having two poles forming an airgap and containing energizing means for producing periodic magnetic flux in said gap, a magnetizable rotor disposed in said gap adjacent one of said poles to roll relative thereto and being movable towards said other pole for attraction thereby, means for biasing said rotor away from said other pole so as to cause unidirectional rotation of said rotor when said means are active, a contact-controlling armature associated with said structure to be attracted thereby when said energizing means are active, a stationary stop and a latch movably mounted on said armature and biased towards engagement with said stop for preventing the contact-controlling armature motion under attraction by said structure, and a release pin mounted on said rotor for engaging said latch at the end of said rotation so as to disengage said latch from said stop.

9. A timing relay comprising, in combination, a magnetic structure having two poles forming an airgap and containing energizing means for producing periodic magnetic flux in said gap, a magnetizable rotor disposed in said gap adjacent one of said poles to roll relative thereto and being movable towards said other pole for attraction thereby, means for biasing said rotor away from said other pole so as to cause unidirectional roi tation of said rotor when said means are active, a contact-controlling armature associated with said structure to be attracted thereby when said energizing means are active, said armature being biased away from said structure so as to form therewith an airgap of normally large width, and means mounted on said rotor for entraining said armature near the end of said rotation so as to reduce said airgap width in order to increase the attraction of said structure on said armature.

10. A timing relay comprising, in combination, a magnetic structure having two poles forming an airgap and containing energizin means for producing periodic magnetic flux in said gap, a magnetizable rotor disposed in said gap adjacent one of said poles to roll relative thereto and bein movable towards said other pole for attraction thereby, means for biasing said rotor away from said other pole so as to cause unidirectional rotation of said rotor when said means are active, a contact-controlling armature associated with said structure to be attracted thereby when said energizing means are active, said armature being biased away from said structure so as to form therewith an airgap of normally large width, latch means engaging said armature for preventing its contact-controlling motion, and means mounted on said rotor for engaging said armature and latch means near the end of said rotation for releasing said latch means and entraining said armature toward said structure to reduce said width of said airgap.

11. An electric motor comprising, in combination, a magnetic structure having two poles forming an airgap and containing energizing means for producing periodic magnetic flux in said gap, a magnetizable rotor disposed in said gap adjacent one of said poles to roll relative thereto when attracted thereby and in engagement therewith, said I rotor" being movable towards said other pole for attraction thereby, means forlbiasing said rotor away from: said other pole so as to cause unidirectional rotation of said rotorwhen said energizing means are active, and a magnetic armature magnetically associated with said rotor and movable toward and away from said other pole for substantially shorting the airgap portion between said rotor and said other pole when moved toward the latter in order to stop said rotor while said means remain active.

12. An electric motor comprising, in combination, a magnetic structure having two poles forming an airgap and containing energizing means for producing periodic magnetic flux in said gap, a magnetizable rotor disposed insaid gap and movable radially towards each of said poles so as to be rollably engaged by one while tending to move toward the other when attracted by said poles, electric means for engaging said rotor when the latter is attracted by said other pole so as to bias said rotor away therefrom in order to cause unidirectional rotation of said rotor when said energizing means are active, and a magnetic armature journalled to said rotor for rotation about its axis and movable toward and away from said other pole for substantially shorting the airgap portion between said rotor and said other pole when moved toward the latter in order to stop said rotor whil said means remain active, said armature having cylindrical surface adjacent to part of the peripheral surface of said rotor.

13. A timing relay comprising, in combination, a magnetic structure having two poles forming an airgap and containing energizing means for produicing periodic magnetic flux in said gap, a magnetizable rotor disposed in said gap adjacent one of said poles to roll relative thereto and being movable towards said other pole for attraction thereby, means for biasing said rotor away from said other pole so as to cause unidirectional rotation of said rotor when said means are active, a contact-controlling armature associated with said structure to be attracted thereby when said energizing means are active, said armature being journalled to said rotor for rotation about its axis and movable toward and away from said other pole for substantially shorting the airgap portion between said rotor and said other pole when moved toward the latter in order to stop said rotor while said means remain active, latch means engaging said armature for preventing its contact-controlling motion, and means mounted on said rotor for engaging said latch means so as, to move them into releasing position when said rotor has rotated through a given angle.

14. A timing relay comprising, in combination, a magnetic structure having two poles forming an airgap and containing energizing means for producing periodic magnetic flux in said gap, a magnetiza'ble rotor disposed in said gap adjacent one of said poles to roll relative thereto and being movable towards said other pole for attraction thereby, means for biasing said rotor away from said other pole so as to cause unidirectional rotation of said rotor when said means are active, a contact-controlling armature associated with said structure to be attracted thereby when said energizing means are active, said armature being journalled to said rotor for rotation about its axis and movable toward and away from said other pole for substantially shorting the airgap portion between said rotor and said other polewhen moved toward: the-latter in.- order'bo stopv said rotor; while said meanslremain active, Ila/coho means engaging said armature for preventjngirts contmuoontrollingmotion, means mounted on said rotor for engaging said latch means; so as. to move, them into releasing position, when said rotor has. rotated through a stop when said energizing. means areinactive;

GEORGE C. ARMSTRONG.

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