US2952755A

US2952755A - Electrical relays

Info

Publication number: US2952755A
Application number: US698096A
Authority: US
Inventors: Emil F Brinker; Jr William A Robison
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1957-11-22
Filing date: 1957-11-22
Publication date: 1960-09-13
Anticipated expiration: 1977-09-13
Also published as: FR1212925A; BE572944A; GB892307A

Description

Sept. 13, 1960 E. F. BRINKER ETAL 2,952,755

ELECTRICAL RELAYS 3 Sheets-Sheet l Filed NOV. 22, 1957 Ill! 55e 56 I5 INVENTORS.

Emil E Bl'llaliel and William Abson Jlz BY WAM THEIR ATTRNEY Sept 13,1960 E.. F. BRINKER ETAL 2,952,755

ELECTRICAL RELAYb Filed Nov. 22, 1957 5 Sheets-Sheet 2 INVENTORS. Emil F rmkel' and William A .Robison Jr:

THEIR A TTORNY sept. 13, 1960 Filed Nov. 22, 1957 E. F. BRINKER ET AL ELECTRICAL RELAYS Figi a.

3 Sheecs-Sheet 3 Fly 51).

Insulation Il Z0 INVENTORS.

Emil I-L'nkeland William AJZobiSon J1:

THEIR A TTRN'EY United States Patent ELECTRICAL RELAYS Emil F. Brinker, Blackridge, and William A. Robison, It., Pittsburgh, Pa., assignors to Westinghouse Air Brake Company, Wilmerding, Pa., 4a corporation of Pennsyl- Vania Filed Nov. 22, 1957, Ser. No. 698,096

10 Claims. (Cl. 200--87) Our invention relates to electrical relays, and particularly to a new and improved relay suitable for applications requiring a small lightweight relay of the socalled miniature type.

It is .an object of our invention to provide a relay kcapable of withstanding high temperatures and severe thermal shock.

YIt is another vobject of our invention fto providea relay capable of withstanding mechanical vibration and mechanical shock.

It .is another object of our invention to provide a relay having spring contacts which develop a minimum of contact bounce.

.Itis another object of our invention to provide a .sealed relay having the facility for observing the action of the relay during the calibration operation prior to sealing thereof.

It is another object of our invention to provide a fhermetically sealed relay in which the contacts are shielded from any contaminating gases.

It is yet another object of our invention to provide a relay in which any appreciable internal wear on the relay elements vis eliminated.

It is still another object of our invention to kprovide a relay in which the moving elements of the relay have a small inertia.

In the attainment of the foregoing objects vwe provide a relay including an outer casing, and an inner casing disposed within and spaced from said outer casing. The inner casing is rigidly supported by said `outer casing at essentially only one point. An operating coil, an `associated core piece, and pole pieces are supported within the inner casing. The relay further includes a rotatable armature assembly entirely suspended .on a `tensioned wire extending within the relay. The armature vassembly is biased to an initial position by apermanent magnet. When actuated, the armaturs assembly causes spring contacts to open the `associated `exterior electrical circuitry.

:Other objects and advantages of our invention will become apparent from' the following description andthe accompanying drawings in Vwhich vlike preference charac'rs refer to like elements throughout and in which:

Pig. v1 is an elevational view of the krelay embodying our invention;

Fig. 2 is a cross sectional :taken along rthe center vof .the relay;

Fig. 3 is an isometric view of the inner casing -of the relay;

Fig. 4 Ais an isometric view of the wire suspension, 4the armature assembly, and the permanent magnet;

Fig. 5 is an isometric view of zdiej-permanent magnet Vand the permanent magnet support bracket;

Fig. 6 is a plan Aview partly in cross ysection of Fig. 2 -taken along lines VI-VI in the direction of the arrows, and Iwith the permanent magnet bracket broken away;

Fig. 7 is a plan View partly in cross section Y`of `Fig. 2

taken alonglnes VII-VII in thedirection of .the arrows;

lCC

`Fig. 8a is a plan view partly in cross section of Fig. 2 taken along lines VIII-VIII and in the direction of the arrows, showing one position of the spring contact members;

Fig. 8b is a view similar to Fig. 8a and shows a fragmentary plan view partly lin cross section of another position of one of the spring contact members; and,

Fig. 9 is an isometric view of a spring contact member.

We `shall describe one form of the relay embodying our invention, and shall then point out the novel Vfeae tures thereof in the appended claims. y

In Fig. l there is shown an elevational view of a relay 10 `embodying our invention, the relay in one practical application being about 11/2 inches in length and 1 inch in diameter.

Referring now to Fig. 2 of the drawings, `the relay 410 comprises a housing or outer casing i any suitable material, such as steel, including a cylindrical side wall 12, and a desirably integral circular end wall 13 having a central opening 14 formed therein. Steel in addition to being a rugged material also -in some measure tends to shield the relay elements rfrom external -electric fields. The other end of casing 11 is closed by a base or header disc 15 -of suitable insulating material such for example as alumina The disc 15 -is of material which does not give off gases at high temperatures, whichgases might adversely affect Athe relay contacts. The disc 15 :is also of material having sufficient density to provide a vhermetic seal for the relay 10. The periphery -of disc 15 is suitably metalized for bonding vto the inner surface of side wall 12 of outer casing 11. Aplurality `of ter- .minal pin members 16 extend through the header disc -15 and are bonded Aand sealed thereto as by brazing. Pin members 16 provide electrical Vconnections from relay 10 `to the Iassociated yexternal circuitry, not shown. -Ex- Vhaust opening :19v Vin end wall 13` provides a means vof evacuating and sealing the relay 10 to provide a hermetically sealed unit as -is`well known `in the art. A lbracket r20 `including apertures 20a for mounting the .relay Vin an assigned position is aixed to side wall 12 of outer casing 11, as by welding.

Referring now to Fig. 3 as yWell as Fig. 2, an inner casing member 17 of ferromagnetic vmaterial is inserted within and spaced from .the outer casing -11. Casing member 17 comprises a-cylindrical side wall 18 and an end wall consisting of circular cover plate 21 having a central yopening 22 therein. A short axial tubular ex tension vk23 yis formed along the 'periphery of the opening 22. For.ease in assembly cover plate 21-is formed as a separate unit and aflixed to side wall 18 as by Yspot welding; however the 'two elements -may vbe formed `as .a -single unit. Four symmetrically spaced tabs are punched from inner casing 17 near the lower end thereof land -bent Aradially inward to form `pole pieces 24. .By this construction .thepole pieces are made integral with the -outer casing to effect a reduction -in the -overall weight of -the relay. As will hereinafter be detailed the linner lcasing 17 functions as vpart ofthe magnetic-circuit Aof kthe relay. To facilitate production measurements the oppositely -disposed pole piece 24 have one surface lying in thesame plane extending through the axis of innervcasing 17, see Figs. 7 and8a. Symmetri- Acally spaced legs 25 extend downwardly from side wall '18 at .the `lower-end of `casing-member 17. Legs25'fare kformed with undulations 'or 7corrugations which ,give or yield .in the event the `outer casing 11 contracts due to, ifor instance, thermal shock. fLegs 25 on inner casing l17 Vare received in recesses 26 .formed onithe inner face 4and Yalong the `periphery of header disc 15, see Fig. 2,

of the legs in the recesses is possible for purposes hereinafter described. Legs 25 are not fastened to the header disc. L A core Vpiece' 31 comprising an 'elongatedcylindrical member is 'centrally disposed YwithinV inner 'casing.17: Core piece 31 includes 'a central tubulanportion 31a, an intermediate portion 31b of reduced diameter relativefto the central portion, and a top portion`31d of yet Smaller diameter.

Shoulders

35 and 38 yare formed by the change in diameters between the central portions 31a and the intermediate portion 31b, and between the intermediate portion and the top portion31d, respectively. A radially extendingflange 31'c is formed at the lower end of core piece 31. f The intermediate portion'31b of core piece 31. extends through and is' pressiitted in opening 22 in cover plate 21 of inner casing 17. Top portion 31d further extends .into opening 14 in end Wall 13 of outer casing l1-to 'a point short ofthe outer or top surface of end wall 13. Shoulder 38 bears against the interior or lower surface of end wall 13. Top portion 31d is'press tted in opening 14 to align the core piece within outer casing 11 and is securely aixed, as by weld 39, to the outer ycasing 11.

Intermediate portion 31 b of' core piece 31 is press tted against-tubular extension 23 of cover plate 21 and 'provides a means for securely positioning inner casing 17 within outer casing 11. Shoulder 35 bears against I 31 and consists of a central section 36a, Ka reduced upper 'section 36b, and a lower section 36e of a diameter larger than that ofthe central section. A shoulder 37 is formed -by the change in diameter from the central section 36a tothe diameter ofthe lower section 36e. An operating coil 42 for the relay 10 is formed by 'winding wire on a tubular spool 44 which spool includes radial flanges 45 on opposite ends thereof for containing Vthe coil.V Spool 44 is of a suitable insulative material vwhich does not give oi gases at high temperatures which 'gases might adversely affect the relay contacts. A metallic sleeve 27 is aflixed to the periphery of anges 45 to yseal the operating coil 42 from the remaining elements of the relay. Any gases produced by the coil material will be contained within the sleeve 27 and spool 44 'and will not affect the relay contacts. Wire leads 43, seen also in Figs. 7 and 8a, provide electric connections Ato the operating coil. Leads 43 extend through openings in lower flange 45 which openings are metalized and sealed to prevent any gases developed by the coil wires from escaping.

Spool 44 is mounted around core piece 31 and supported by the flange 31c of core piece 31 in a position adjacent the cover plate 21. A spring 49, placed between cover plate 21 and the adjacent radial ange 45 of spool 44, provides a retaining force to securely aix the spool Within inner casing 17 since excessive movement of the spool might damage the wire leads 43. A core guide 46 comprising an elongated cylindrical member is positioned in alignment with, and in end-toend abutting engagement with the core piece 31. Core guide 46 includes a central tubular portion 46a, an upper portion 46b of a diameter larger than that of the central portion, and a lower portion 46c having a diameter slightly undercut with relation to the central portion. A shoulder or step 47 is formed by thechange in diameter from central portion 46a to the diameter of the upper portion 46b. Arr opening 53 is, formed along the axis of the core guide 46 `and consists of a central section 53a, an upper section 53b of a diameter larger than that of the central section, and a lower section 53e of a diameter smaller than that of the lltral section.

The upper portion 46b of core guide 46 is formed in approximately a U-shape. Parts of the tubular walls of upper portion 46b are cut away, such that in plan view the remaining segments 57 form two diametrically spaced axial arms, see also Fig. 6. The upper portion 46b of core guide 46 is inserted into the lower section 36a` of opening 36 in corepiece 31. Segments 57 are press fitted against shoulder 37 of core piece 31 vand provide a positive engagement between core piece 31 and core guide 46.

The lower end of core guide 46 is slip tted in a header sleeve 58 which is in turn inserted and secured as by welding in a central aligning recess 59 infheader disc 15 which recess has initially been metalized. Header sleeve 58 extends upwardly beyond the lower portion l46c and is caused to bear or is fitted around central portion 46a to align core guide 46 along the axis of the relay 10. The lower` portionf46c might be'slightly deformed during the process Vof assembly, therefore theV central portion 46a Vis desirably used as the reference surfacev for alignment purposes.

'A' wirev 62 of any suitable material such as tungsten, extendsV through the openings 36 yand 53 of core piece 31 and core guide 46, respectively. Tungsten'wire is -used in one practicalembodiment since it can be welded -without annealing. The lower end of the wire 62 extends through the lower section 53C of. opening53 in 'core guide 46 and is fused or welded at a point on 'the llower portion 46c of the core guide. As noted above, the header sleeve 58 extends upwards around the central portion 46a, and any deformation of undercut lower portion 46c caused by heat necessary for the welding process will not affect the alignment reference for core guide 46. The wire 62 is made t-aut or tensioned, and its upper end is secured to the intermediate portion 31b of core piece x31 by means of a pin 63. Pin 63v crimps the wire into the end of a slot drilled in a direction transverse to the axis of core piece 31,` see also Fig. 4.

Referring vnow to Figs. 4 and 6 as well as Fig.4 2, an armature assemblyv65 of ferromagnetic material comprises agammadion o'r4 swastika shaped plate 66 disposed 'in a plane transverse to the axis of the wire 62. Four axial extensions 71 inthe form of rectangular plates are symmetrically spaced about the periphery of plate 66. 'The particular shape of lplate 66 employed aifordsa 'means of producing an armature which is of low mass and whichgcan be fabricated inexpensively from 'sheet material by punching or stamping. The armature extensions 71 provide a large surface, but as noted before of Slow mass, which can Acooperate with the pole pieces 24'. `Plate 66 includesV a central opening 67 through which wire 62 passes. Plate 66 also has a pair of approximately semi-circular openings 68 diametrically spaced from one i another. The segments 57 of core guide 46- extend :through the openings 68 with suflicient clearance to permit the plate 66 to rotate. The flat sidesof the axial extensions 71 'lie in Vplanes extending 'radially inward @toward the axis of the` wire 66. The free ends of extensions 71 are cut in or reduced in width to form tongues 70, A contact actuator vor driving bar 72 ofa suitable nou-gassy insulative material is mounted on each of the tongues 70. Each driving bar 72 is slotted,'therside's"of the slot'beingsuitably metalized, for receiving a tngne extension 71. l

OneV end of an' apertured armature support 1hub 73 is atiixed, as by welding, to the center of plate 66 in'alignment with the centr-alopening 67 thereof. The support hub is in turn affixed to wire 62, as by welding, and provides a'positive means for securely suspending the armature assembly '65 from the wire 62. Wire 62 is tensioned and axed at its ends to provide atorslionally iiex'ible suspension for the armature assembly 6 5. `The angular''distancethe armature asserribly V65 is causedto ll'vli Welll Within the torsional'stress limitslofthe wire 70 and affixing each drivingfbarrto itsrespective axial by the wire 62, no bearing surfaces for rotation are re- `quired, and frictional losses caused by rotation of the armature assembly are reduced to a minimum.

A pair of

elongated sleeve members

83 and 84 are .provided for the wire 62. Sleeve 83 is press -tted around the periphery of support hub 73 and extends upwardly. Sleeve 84 is press fitted in a central recess 85 in support hub 73 and extends downwardly. Both of the

sleeves

83 and 84 rotate with the support hub 73. The free ends of

sleeves

83 and 84 are tapered to form a Small diameter opening which permits only a small clearance `for wire 62. Should the wire 62 for any reason tend to move away from the axis of Ithe relay a low friction side thrust bearing is provided at a point near each end yof the Wire 62.

A permanent magnet 74 for providing a restoring force or bias for armature assembly 65 is also desirably formed in a gammadion shape to cooperate with the armature assembly 65 is positioned such that each of its pole faces 75 coacts with an axial extension 71 of larmature assembly 65. Permanent magnet 74 is formed such that the pole faces 75 adjacent one another are of opposite polarity, for purposes hereinafter described. That is, moving in a circle, the pole faces 75 have a north, south, north, south polarity. To prevent the axial extensions 71 from sticking to the pole faces 75, the usual gore pins 69 are affixed to the axial extensions see also A bracket 76 for supporting the permanent magnet 74 is omitted from Fig. 4, for purposes of clarity in the drawing, but is shown in Fig. 5 and consists of an open ybox-shaped member having sides 77 which are bent up to conform to the sides of the permanent magnet. yThe sides ofthe bracket 76 have openings 80 at each corner to .permit the pole faces 75 of the gammadion-shaped permanent magnet 74 to extend outwardly. Securing tabs 78 spaced along the periphery of the bracket 76 are bent 'against the top of permanent magnet 74. A pair of diagonally spaced legs 79 extend from the bracket V76 and are arranged to be secured as by welding to the flange 31e` on core piece 3'1. Ridges 81 shown on the legs 79 provide a means of concentrating the heat during the welding process. Opening 82 in permanent magnet 74 permits insertion thereof around the central portion 46a of core guide 46.

Referring now to Figs. 8a, 8b, and 9, the contact spring Vassembly includes a plurality of pairs of contact posts 86. A sleeve 87 of a suitable material such as gold alloy is vinserted over each of contact posts 86 to'cooperate with lcontact buttons to provide a contact which will not develop a high resistance with low operating current or voltage. Such contacts can also vhandle higher currents without excessive electrical erosion such as pitting. An

Yapproximately M-shaped contact spring member 88 is associated with each pair of contact posts 86.

AEach M-shaped contact spring member -88 includes a .pair of bifurcated spring legs 89 each of which .cooperates with a respective contact post 86 and the associated sleeve 87. Contact buttons 92 on legs A89 are of suitable .material such as gold alloy to cooperate with the sleeves 87 as noted hereinabove. Reference hereinafter made lto a contact'post 86 will be understood to include the associ- "ated sleeve 87.

The central inward extension '88a of each vof the l"lill-shaped spring members 88 is aixed in position, a's

by welding, to a support pin 91. Inward extension 88a tional rotation.

M-shaped spring members A88. -In Fig. 8a, vthe springs are shown during the deenergized cycle of relay .10 with the driving bars 72 actuated in a clockwise direction, as oriented in the drawing, with legs 89a, of M-shaped Vspring member 88, opened or moved away from their respective contact posts 86. In Fig. 8b, a spring 88 is shown during the energized cycle of the armature assembly 65. At this point the armature assembly 65 .is in its extreme counterclockwise position, in which position the driving bar 72 moves or opens the other leg 8911 of contact spring 88 away from its respective contact post 86.

A desired method of assembling the various subassemblies of the relay will now be described.

Armature assembly 65, including the support hub 73, and the driving bars 72 are initially formed as a subassembly. Wire 62 is next inserted through the central opening 67 in the armature plate 66, and through support hub 73. Wire 62 is then ailixed as by welding to support hub 73 at the predetermined intermediate 4point on the wire. Wire sleeve l84 is next inserted over the lower end of wire 62 and press Vfitted into recess 85 in support hub 73. Wire 62 and sleeve 84 are then inserted into opening 53 of core guide 46. Segments 57 of core guide 46 are inserted through the diametrically opposite opening 68 in armature -plate `66. A jig is employed to set the relative position of the armature plate 66 with respect to the core guide 46. The .end of wire 62 is then afxed, as by welding to the lower section 46c of core guide 46.

Wire sleeve 83 is next inserted Vover the upper end of wire 62 and press fitted on the periphery of support hub 73. Wire 62 and sleeve 83 Yare next inserted into opening 36 of core piece 3=1, and wire 62 is pulled through the opposite end of the core piece and made taut. Pin k63 is then inserted in the slot in core piece 31 to securely crimp the wire 62. The armature assembly 65 will rotate to seek a torsionless position with respect -to wire 62.

The permanent magnet 74 supported in bracket 76 is next slipped over the core guide 46. Since the permanent magnet 74 is free, its pole faces 75 will be attracted toward the respective armature extensions 71. The -permanent magnet 74 thus establishes 7its neutral position. The permanent -magnet 74 is then positioned, that is, manually rotated in =a direction opposite to that in which the armature assembly v65 will rotate during operation. The distance the permanent magnet 74 is manually rotated is equal to approximately one-half of the total operational rotation of the armature assembly 65. Permanent magnet 74 is then secured in this position by welding the legs 79 of bracket 76 to the flange 31e 4on the core vpiece 31.

Next, the cover plate .is .inserted over core lpiece 31 `and the tubular extension 23y on the periphery lof lcentral opening 22 in cover plate 21 is press lfitted onto intermediate portion 31'b. Shoulder 35 on core piece 31 provides vpositive engagement with the Alower end of tubular extension 23. Side wall 18 .is then slipped over cover plate 21 .and the assembled relay elements. Side wall 18 is positioned -such that .the pole pieces 24-are in predetermined spaced relation from their vrespectively cooperating armature extensions 71 to permit operal l When .in position side wall V-18 is-aflxed to cover plate 21, -as by spot welding, to form the complete inner casing 117.

Next, the lower portion 46c-of core guide 46 is vslip fitted into the header Ysleeve A58 which sleeve has been .previously welded in the central aligning recess 59 of disc 15. Note that core guide 46 is not rigidly aixed-.to

the header disc y15 and .that a space between the llower 7 88 and also such that the corrugated legs 25 of inner 'casing l17 rest in the recesses 26 on the header disc. Legsxv25 serve to position the header disc 15 with respect to the other elements of the relay.

IIn an important subassembly operation the contact springs 88 have been initially aflixed to the header disc "15. In the said subassembly operation the central inward extension 88a of each M-shaped spring 88 is po- 'sitioned to cradle against its respective pin 91, and the spring legs `89 are opened sufficiently to straddle their respective pair of contact posts 86. `Because the radius of the central inward extension `88a is larger than the -radius of the pin 91, and since the legs 89 are forcing inwardly against the outsides of the contact posts 86,

v13 of casing 11. Core piece 31 is securely axed to the outer casing 11 by welding the outer casing to the top surface of top portion 31d. This then is the only point or spot by which the relay elements are securely aiiixed to the outer casing 11. Disc #15 is then aixed to outer casing 11 as -by welding to form a sealed relay unit. The relay 10 is then evacuated by means of exhaust opening 19 and sealed, as is well known in the art.

It should be appreciated that all of the relay elements are rigidly fastened to one another at essentially only one point of each element. Each element can expand or contract independently of all other elements and therefore Will not induce mechanical stress or deformation in any of the other elements. The relay is thus insensitive to thermal shock.

lIt will bey appreciated that a principal advantage of employing an inner or outer casing construction for the relay is that normal operation of the relay can be observed during any calibration and adjustment of the relay prior to enclosing therelay in the outer casing 11. In assembly once all the operating elements are positioned within the inner casing 17 the relay may be calibrated. The openings formed in the inner casing -17 when the pole piece tabs 24 are punched inwardly provide windows for viewing the operation of the relay during calibration. After the relay is calibrated the outer casing 11 may be slipped over the assembled unit and affixed to the inner casing 17 and the header disc 15. Heretofore in relays of this type the inability to see the coaction of the operating elements during Referring to Figs. 1, 5' and 8a, operating coil 42 when suitably energized through leads 43 from 4a control source,

not shown, tends to develop an electromagnetic circuit which can be traced from the upper portion 31b of core piece 31, cover plate 21 and side walls 18 of inner casing 17, to pole pieces 24, through the air gaps between the pole pieces and the axial extensions 71 of -the armature assembly 65, up the axial extensions 71 to plateg66, and back through the small air gap between plate 66 and the core piece flange 31C to core piece 31.

lAs is known, the 4air gap between the pole pieces 24 and the axial extensions 71 will tend to be narrowed vand the armature assembly `65, suspended on wire 62,

Iwill be caused to rotate toward the pole pieces and a -first extreme position, Isee Fig. 8b.

' Referring to Figs. 8 apand 8b, as the armature assembly 465 is rotated, the driving bars 72 aixed thereto will force 'against the legs 89h of the Mshaped contacts 88 to open' vor4 move the legs 89b away from their respective contact posts 86. As noted hereinbefore, kspring leg 89a will move toward its respective contact post 86 under the influence of its own restoring force to close its contact. Thus, it should be appreciated that the armature assembly 65 is entirely disconnected from the energized `exterior circuitry at all times except during the momentary transient period when the driving bar 72 initially engages a leg 89 to move said leg away from its respective contact post 86.

When the operating coil 42 is deenergized, the permanent magnet 74 will attract the armature `assembly 65 in a reverse direction to a second extreme position. kAs was noted hereinabove, adjacent pole pieces 75 of permanent magnet 74, are of opposite polarities. Referring to Figs. l, 5 4and 7 permanent magnet 74 tends to develop a magnetic circuit which may be traced from each of its pole faces 75, through the air gap between the pole faces and the respective axial extensions 71 up through the axial extensions to the plate 66, down through an adjacent axial extension 71 to a pole 'face of opposite polarity. The air gap in the magnetic circuit will tend to be narrowed and cause the armature assembly to be rotated toward the pole faces 75 of permanent magnet 74, see Fig. 7. The driving bar 72 will be actuated in a clockwise direction, as oriented in Fig. 8a to open the contact of legs 89a with their respective contact posts 86, and spring legs 89b will move toward their respective contact posts under the influence of their own restoring force to ,close the contact.

In one embodiment of the relay the length of the contact driving bars 72 and the form of the M-shaped spring members 88 are determined such that one of the legs 89 is moved away from its respective contact post `86 just prior to the time the other leg makes contact with its respective contact post, that is, non-bridging contacts are provided. Obviously bridging contacts could be provided by decreasing the length of driving 4bar 72.

The `relay of our invention is constructed to be almost entirely free from contact bounce. The following factors contribute to the elimination of Contact bounce. The M-shaped spring members 88 are arranged to cooperate with the contact posts 86 such that at the instant the legs 89 impinge on their respective contact posts the full contact pressure is effective immediately. As noted above legs 89 are bifurcated such that each of the sides of the legs have a different natural frequency of vibration which tends to dampen any vibrations. Since the spring members are light in weight their natural frequency of 4vibration is high so that the attenuation of the mechanithat the various elements of the relay are rigidly affixed to one another at essentially only one point on each element so that each element can expand or contract independently of the other elements. Deformation of one .element does not therefore induce mechanical stresses or deformation in any of the other elements. It can also be appreciated that the relay of our invention is dynamically balanced. The relay is symmetrical about "the axis of the cylindrical'casings which axis coincides with the line of wire 62. External forces, except those in a rotary direction with respect to the axis of the relay, will-notl inuence the operation of the relay. The low mass of the armature assembly serves to minimize the eect of those 'forces in a rotary direction. The relay can thus be mounted in any position or moved in any ganarse "9 direction 'without adversely aiecting the voperation th'ereof.

Another advantage of a relay constructed with our invention is that problems due to friction vare reduced to a minimum or eliminated. rIn contrast in other types of miniature relays, due to the tight tolerances required and the light assemblies employed, friction is -less controllable and has heretofore been a major problem.

Another advantage of our relay is that the configuration of the contact assembly also eliminates the influence of one contact on another since there is no vibration transfer from one contact to another. Further any vibration of the arm-ature assembly 65 due to external forces does not iniluence the contact which has been made vor .closed since the armature assembly operates in a manner .to actuate the driving bars 72 to open the contacts. The contacts are closed only by the restoring force of '

spring legs

89a and 89b.

It will also be noted that the armature assembly 65 vis interposed between the operating coil 42l and the permanent magnet 74, and effectively shields the permanent magnet from `the electromagnetic flux developed due to the'energization of operating coil 42 and therefore any tendency to demagnetize the .permanent magnet is eliminated. In eect armature assembly 65 provides a shunt path for the electromagnetic llux energy. Armature assembly 65 will also tend to shield the permanent magnet from external yelectrical currents, such as :for instance lightning surges, which would also tend to demagnetize the permanent magnet.

While our invention has been described with reference to a particular embodiment thereof, vit will be understood that various modifications may be made by those skilled in the art without departing from the invention. Although =a relay having fourpolevpiecesis shownand described the invention is applicable for use in relays 'hav- -ing more or fewer lpole pieces. The appended claims are therefore vintended to cover all such modifications within the true spirit and scope of the invention. n Having' th'usl described our invention, whatwe claim is: s l. 'Anelectric "relay'comprising alcasing, an voperating jcoil and 'an associated lcore piece, at least onepole 'piece ie'xtending-:inwardly yfrom-said'casing, a torsionally flexible rnember -lixed Vto spaced-portions in said relay, an a `ature vassemblysuspended yon said member interine'dia'tefthe ends -ofv said member, and a permanent *magnet biasing :saidarmatur'e assembly to one `extreme ngularposition, saidarmature arranged to be attracted .'t'oward said polempiecefandv a lsecond extreme angular ipositionupon energizationof said "coil, said armature assembly being mounted between said permanent magnet, and said core piece and said coil, for shielding said permanent magnet lfrom the magnetic ilux developed due to energization of said coil.

2. An electric relay including an outer casing, an inner `casing `disposed Within said outer casing in spaced 4relation therefrom, said inner casing being aiiixed to said outer casing at essentially one point, tab portions on the walls of said inner casing being bent inwardly to form pole pieces and to form openings in the walls of said inner casin-g, a core piece and an associated operating coil disposed within said inner casing, a tensioned wire extending within said inner casing, an armature assembly supported by said wire, contact springs, and contact drivin-g bars mounted on said armature assembly and arranged to actuate said springs upon operation of said arma-ture assembly, the openings in the wall of said inner casing permitting the viewing of the normal operation of said contact `driving and said contact springs after the relay operating elements are assembled.

3. An electric relay comprising a dynamically balanced structure including a core piece with 4an associated operating coil, said core piece having an opening therein, a core guide athxed in abutting relation to said core piece, said core .guide having van opening therein a tensioned Wire extending through the openings in said co're piece 4and core guide, an armature assembly suspend- 'ed on said wire, 4a relay casing, means axing the relay casing at essentially one point to said core piece, a cup-shaped relay housing disposed around said casing, means aifixing said relay 4housing at essentially one point to said core piece, a header -disc closing the open end' of said relay housing, and means yaflixing said core `guide to said header disc at essentially one point whereby deformation of one of the elements of said relay due to thermal shock does not induce mechanical stress on the other elements of said relay.

4. In an electric relay, a spring contact assembly comprising an M-shaped spring having bifurcated legs, a mounting pin, the central inward extension of said 4M- shaped spring having a radius larger than said mounting pin and being aiiixed thereto, a pair of contact posts, the Ilegs of said M-shaped spring arranged to straddle said contact posts in abutting arrangement, said M-shaped spring being self-positioning against said mounting pin land said contact posts such that its legs apply equal torce against said contact posts, an insulative bar arranged to be inserted between the legs of said M-shaped springs, said insulative bar being actuable to drive one or the other of the legs of said M-shaped springs from its respective contact post, and said legs being returned .to an abutting engagement with their respective contact posts due -to the prestressed restoring force of said M-shaped springs.

5. An armature-contact actuator sub-assembly including in combination -a rotatable magnetic structure, aplurality of axial extensions on the extremities of said structure, a -wire member suspending said magnetic structure',

Van insulative contact actuating member mounted -on the ends of said axial extensions, a permanent magnet having a plural-ity of pole faces, adjacent ones of said pole faces being 4of opposite polarities, said .pole faces of said permanent magnet cooperating with respective ones of said axial extensions for biasing said magnetic structure to one extreme position.

6. An electric relay comprising a cup-like housing,

a -header Idisc of insulative material closing the open end of said housing, yan inner casing Idisposed 4within and spaced from said housing, pole pieces on said casing, a core piece havmg an aperture therein, an operatmg coil associated 'with said core piece, said core piece being Arigidly alxed at essentially only one point lto said housing, said casing being mounted on said core piece and aiiixed thereto at essentially one point, a core guide,

one end of said core guide engaging said core piece and the other end thereof engaging said header disc, said core guide having an aperture therein, a tensioned Wire extending through the apertures in said core piece and said core guide, a rotatable armature assembly mounted on said wire, contact driving bars of an insulative material mounted on said armature assembly, contact springs arranged to be actuated by said driving bars, and `a permanent magnet biasing said armature assembly to one extreme position for actuating said contact springs, said armature assembly cooperating with said pole pieces upon energization of said operating coil and causing said driving bars to actuate said contact springs,

7. An electric relay comprising a tubular outer casing including an end wall, said end wall having an opening therein, a header disc of insulative material closing the open end of said outer casing, an inner casing disposed within and spaced from said outer casing, said inner casing including an end wall having an opening therein, symmetrical tab portions of said inner casing being bent inwardly to form pole pieces, legs on said inner casing for positioning said inner casing relative to said header disc, a core piece having an opening, an operating coil associated with said core piece, said core piece fitting in the openings in said end walls of said inner and outer '11 casing, said inner casing being supported by said core piece, said core piece being rigidly secured to said end wall of said outer casing, a core guide having an opening 'in alignment with the opening in said core piece, one end of said core guide engaging said core piece and the other -end thereof engaging said header disc, a tensioned wire extending through the openings in said core piece and said core guide, said wire being ailixed at one end to said core piece and at the other end to said core guide,

-a rotatable armature assembly suspended on said wire,

said armature assembly including a portion extending in "a 'direction parallel to said Wire, a permanent magnet mounted within said casing to cooperate with said extending portions for biasing said armature assembly to `one extreme position, contact driving bars mounted on said extending portions, and contact springs arranged to 4be actuated by said contact driving bars.

8. An electric relay comprising a tubular outer casing 'including an end wall, said end wall having an opening 'inner casing, legs formed on said inner casing resting in lthe recesses in said header disc, a core piece having an opening, an operating coil associated with said core piece, said core piece tting in the openings in said end walls of said inner and outer casing, one end of said core piece -being affixed to said end wall of said outer casing, a Acore guide having an opening, one end of said core 4guide being in abutting engagement with said core piece 'and the other end thereof being insertable into one of said aligning recesses in said header disc, a tensioned rwire extending through the openings in said core piece 'and said core guide, said wire being aixed at one end 'to lsaid core piece and at the other end to said core guide, a rotatable armature assembly suspended on said Wire,

M-shaped contact springs, insulative contact driving bars mounted on said armature assembly yand disposed be- Atween the legs of said M-shaped springs, pairs of contact leg of said M-shaped contact springs away from its respective contact post, and the other leg of said M-shaped contact springs being actuated toward its respective contact post due to its prestressed form.

9L AnV electric relay comprisinga dynamically balanced structure including an outer and an inner casing,

'polepieces extending inwardly from said inner casing, a

core piece having an opening therein, an operating coil associated with sald core piece, said inner casing being mounted at essentially one point on said core piece,

vsaid core piece in turn being mounted at essentially one point to'saidouter casing for aixing said inner and outer casings in rigid relative position at essentially one point, a tensioned wire affixed to spaced points in said relay and extending through the opening in said core piece, an armature assembly suspended on said wire and being rotatable toward said pole pieces upon energization 'of said coil, a header disc affixed to said outer casing,

and means positioning said core piece centrally with respect to said header disc whereby deformation of any of the elements of said relay due to thermal shock does not induce mechanical stresses on the other elements of said relay.

10. An electric relay including an outer casing and -an inner casing, means for afxing said inner casing to said outer casing at essentially only one point and for positioning said inner casing in spaced relation to said vouter casing, a core piece secured to said inner casing, an

operating coil associated with said core piece, a tenvsioned wire extending within said inner casing, pole pieces on said casing, and an armature assembly supported by 'said wire and arranged for rotation toward and away from said pole pieces in response to the state of energization of said coil.

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