US2850602A - Relay contact arrangement - Google Patents

Description

Sept- 2, 1958 L. R. BREESE ETAL 2,850,602

RELAY CONTACT ARRANGEMENT Filed May 16, 1955 INVENToR Ere B Uff Si: arent f.. ce

2,85%,592 Patented Sept. 2, it

RELAY CENTACT ARRANGIENENT Lemuei R. "i-ease and Dorsey D. Simmons, Galion, Ohio, assignors to North Eiectric Company, Gatien, Gino, a corporation of @bio Application May i6, 1955, Serial No. 5%,630

.2 Claims. (Cl. 24343-466) The present invention relates to electrical contact elements, and particularly to novel electrical contact elements for use in relay structures- There has been in recent years a rapid development of the industrial and military fields which has been at least partially accelerated by the increased use of electrical control equipment. Continued use is, of course, dependent upon the ability of the electrical equipment to provide reliable and dependable service; however, the operating conditions in the new uses and applications are such as to seriously deter the accomplishment of such type services with certain known types of contact structures. More specifically, certain newer systems of control require the contacts to control circuits reliably under unusual load conditions.

it is apparent that the provision of reliable and dependable service under the extreme operating conditions encountered in such control circuits is at least partially dependent upon the provision of electrical contact members which are capable of accomplishing repeated circuit control reliably.

Accordingly there is a need in industrial and military elds for electrical contact members which are capable of reducing the number of equipment failures resulting from unreliable operations `of the contact structures in their circuit completing functions. Various attempts have been made to improve the reliability of the contact elements in their operation.

ln certain low voltage `and low current circuits, wherein voltages in the order of two or three volts, and currents in the order of a few milliamperes are encountered, the problems of accomplishing reliable closing and opening of such circuits becomes especially difficult. There seems to be reason to believe that the low order of volage is sometimes unable to start electron flow through contact resistances encountered. Furthermore molecular lms on the surfaces of the contacts tend to interfere with the conductivity of the contact sets. This condition is particularly serious in low voltage applications in that even the lichter lms are sufficient to act `as a barrier to the passage of low voltages and low currents which are applied to the contact sets. This difficulty cannot be overlooked in applications where unreliable circuit completion may have costly consequences.

Accordingly, one object of the present invention is the provision of a contact arrangement of improved reliability.

Another object is the provision of a contact arrangement of improved reliability for controlling low voltage circuits in the order of afew volts.

Another object of the present invention is the provision of a new and novel contact arrangement characterized by an essentially hemispherical member and a cooperating grooved contact member for overcoming such diiiiculties.

The present invention is directed to the provision of a novel contact element which is particularly adapted for reliable operation over an increased number of circuit completing operations, and particularly, to .a novel contact structure which lends itself to simple, economical and practical manufacture. The novel contact structure of the present invention basically comprises an essentially hemispherical contact member arranged to `co-act with a second contact member which comprises a cooperating surface having a longitudinal groove with parallel bridges formed therein, the hemispherical contact member and the groove being so dimensioned that the surface of the hemispherical contact member touches the ridges of the groove at two points while a depression between the ridges is of sufficient ldepth to prevent contact therewith. The hemispherical contact member and ridges on the outer surface of the longitudinal groove are made more reliable in their operation by constructing same of highly conducting precious metals such as gold or platinum.

A feature of the invention is the manner in which the contact elements in one embodiment are mounted upon a relay structure in a contact structure comprised of a plurality of contact sets disposed in adjacent spaced relation, the portion of the respective contacts which depends from the contacting surfaces thereon extending in opposite directions to provide a structure which substantially minimizes crosstalk and reduces the capacitance effect between contacts. At least one -contact carrying member of each of the sets is mounted on a flexible cylindrical reed which, by reason of its exibility, permits .a wiping and transverse action between the surfaces of the mating hemispherical and groove contact Surfaces (as more fully explained hereinafter). As a result of such arrangement the meeting contacts tend to scrape o any insulating molecular lm which normally tends to accumulate on the circuit completing surfaces of the contact structures, and accordingly, further improves the reliability thereof.

The contact burnishing feature of the present invention is also evidenced in another modification thereof in which the groove bearing contact element is rigidly held in position, while the contact carrying element to which is affixed a ball contact member is supported on a flexible reed. Upon the movement of the contact member to- Ward the groove and flexure of the reed, -contact is rst made and subsequently upon further movement of the armature additional iiexure of the reed results in a partial rotation and displacement of the contact member Within the groove to cause an abrasive action which polishes the contacts.

Additionally, should the hemispherical contact through slight misalignment initially make engagement with one ridge only of the cooperating grooved contact member, the complete transverse freedom -of the flexible reed allows the magnetic pull on the armature carrying the hemispherical contact to advance the hemispherical contact along the contour of the ridge until contact is made with the second ridge whereupon the magnetic pull on the armature causes a wedging action at the two points of Contact which aids the establishment of an electrical circuit through the two contact points. This also provides a further type of wiping action.

Tests of the new contact arrangement indicate that they possess unusual reliability in closing circuits with millions of operations. This reliability is particularly appreciated in closing dry circuits or circuits involving potentials in the order of only several volts. Furthermore this reliability in conjunction with the degree of longevity make the contact arrangement particularly attractive for use in higher voltage applications such as telephone switchboard multiples.

The basic contact carrying elements may be constructed of any magnetic material attached to flexible shafts of stainless steel, or the like. A hemispherical or button 3 s type Vcontact memberV of precious metal may be attached to one of the contact carrying elements by spot welding lor other suitable methods. The cooperating contact carrying element Vis formed witha groove extending longitudinally thereof, parallel ridges being providedon either side of a central depression. groove: oftlfiis 'type may *.two Contact carrying members 11 and 15 are disposed be formed by a simple press punch operation on .a gold inlay in the contact carrying member, the gold inlayft'faking` the shape ofthe groove. AlternativelyY thepunch press operation'may.makeV the groovey in the contaet earrying member andra precious -m'etal layer may be plated on the surface and shoulders of the groove.

The'above and further objects, features and advantages of this invention will be recognized by those familiar with the art from theffollowing description of a preferred'emb'odiment thereof, as illustrated in the accompanying drawings in the several figures of which like reference numerals indicate like elementsgand in which:

Figures l and 2 are plan and end views respectively of a bank of movable contact members arranged according to the present invention; Y i

UFigures 3A and 3B are enlarged, partiallycut-away views of the contact arrangements of the present inven-A tion under certain operating conditions thereof;

YFigure `4 is a view, partly in cross-section, taken along line 4 4 of Figure 3A to illustrate a particular feature thereof;Y Y Y Figure 5 VAis a'n enlarged, detailed cross-sectional view taken along the line 5-'-'-5l of Figure 2 illustrating repre'- sentative dimensions of the cooperating contact members of the present invention, and Y Figure 6 is a cross-sectional view of an alternative embodiment of the relay contact arrangement of the present invention. Y Y

Referring now particularly to Figures 1 Vand 2 of the drawings, it will be observed that reference numeral 1'0 designates a group ofjcontact carrying members which are generally similar to those used conventionally in relays` well known 'to those familiar with the telephone art. Such a conventional relaystructu're is disclosed in greater detail in VUnited States Patents numbered 2,396,332 and adjacent each other but in noncontacting relationship prior to the energization of the electromagnet (not shown). A molded strip member 17 serves to position and maintain the reed members 16 in a preset relationship similar to that of reeds 12V so that each of the corresponding contact carrying members 11 and 15 is fixed with respect to one another.

As may be seen from Figure 2, aV contact member 14 is ailixed to the surface of member 11 facing its' cooperating contact carrying member 15. Contact mem ber 14 is in this instance essentially hemispherical or button like in shape and preferably composed of a 2,409,054; issued to Frank R. VMcBerty fonV March l2,

1946 and YOctober 8,V 1946, respectively, andassigned to the. present assignee.` In general the Villustrated contact carrying members are transversely movable into contacting'relatio'nship under the Vinfluence of a suitable magnetc eld generatedby lan electromagnet. For purposes ofY clarityiand brevity only }the pertinent portions Vof the contactcarrying neinbers Vand their individual contactsY are herein illustrated. Y

Since 'corresponding individual contact carrying members ,are identical, only two complementary ones will be described inV detail herein. VContact carrying Vmember 11 comprises magnetic material, such as a nickel-iron alloy having suitable magnetic characteristics, and is of clon gated rectangular shape with its longitudinal dimension exceeding Vgreatly'its width and depth. The specific form 'Y herein shown is illustrative only andpother shapes will readily suggest themselves towthose skilled inthe Vart. Thecontact carrying member 11 is mounted on the upper end of a flexible metallic reed `12Vwhich `is preferably formed of stainless steel. A strip 13 of` insulating ma Vferial engages reeds 12 andisutilized to 'hold theindi-V vidual reeds'12 in fixed relationshipv withfone another and prevent their twisting 'out of alignment withtheir complementary armatures. Electrical Vconnectionto kthe metallic Vreed 12 is provided ats-the lower A'end thereof which projects belowvstrip Y13.V Y Y VReference may `beliad to "Figure -2 whichrillustrat'es' contact` carrying 'member `11 and l its juxtaposed cooperat- `ing contactcarrying Ymember'lS in preset spaced Vrela- Y tionship. The cooperating contactcarrying memb`e`rr15V isl similarV in construction to member 11 'in that itrcniprises av block of magneticpmaterial Vof rectangular form mounted `on the upper end ofja fex'ible. reed YV16. The

carrying member 11 is moved further to theright and` precious metal, such as Vgold or platinum, for greater electrical conductivity and resistance to erosion. Contact member 14 is shaped so as to Contact the corresponding'member 15 in at least two points. In practice contact member 14 may be spot welded to contactcarry ing member 11 nearitsY top and should'be centrally disposed with respect to its width. Alternatively, VYcontact member 14 may be fashioned 'by deformingV member 11 Y in a power press to produce a substantially hemispherical boss thereon. In this latter case the surface of the con tact member should be plated lwith a precious metal for` greater conductivity and longer life.V Opposite contact 14, a groove 18 is formed inrcontact carrying memberV 15 extending along the length thereof for a short distance.

In oneenvironment a length of $56 inch for groove 18 was found suitable. Groove 18 may bestamped out by a punching operation performed on contact bearing member 15Vand is formed in such a manner that its shoulders are spaced so close to each other that the depressed portion of the groove is prevented from contacting 'the contact completing surface of hemispherical contact member 14. The shoulders or ridges (shown in greater detail in Figures 3A-5) on either side of groove 16 alone touch the conducting surface of Contact member 14 to form a two-point contact.

` As before mentioned the surface of Vthe groove is of pre'ciousmetal which may be an inlay which has` taken..

the `form of the groove by a ,punch press operation or which has been deposited by a plating process after the groove has been formed in the member 18.

. Reference has lbeen made to the wiping action between the hemispherical contact V14 and its cooperatinggroove 18. A more -detailed explanation of this feature of the field produced by ak source of electromagnetic energyV i (not shown) is urged to the right to a point where the conductive surface of contact 14 touches the ridges of groove 18, with initial flexure of reed 1-2. A single point on the surface of contact 14 in the horizontal plane of its center-line a-a, touches the rearmost ridge V19 of groove 18. A second point on the surface of contact 14 in the same center-line plane spaced from the first contact point makes contact at the foremost ridge (not shown) of groove 18. An elective wedgingV action caused by the -movement of ,contact carrying member 11 against contact carrying member 1S ensues to force the two points on the surface of -hemispherical Contact 14 Yinto tight engagement with the twospaced ridges or shoulders of groove 18.V As may be seen in Figure 3A the length of groove 18 is such thatit extends a short distance below the center-line'a--a of contact 14. The

purpose of such elongation 4of-g1"oove 18 will be apparent hereinafter. Y* Y v Upon further urging by the magnetic field, contact further exes its supporting reed 12. As kthe Contact points on the surface of contact :14 press `againstrithe ridges of groove 18, the exible reed 16 which supports contact carrying member 15 is also bent. Since the lengths of reeds 12 and 16 are fixed, a sliding action between contact 14 and groove 18 takes place so that member 15 is effectively moved upward with respect to contact carrying member 11 and carrier groove 18 with it. It is now evident that the surface of hemispherical contact 14 makes two point contact with the ridges of groove 18 at new points farther down the length of groove 18. The new points of contact are in a plane containing line b-b. The distance between lines a-a and b-b taken along the outer edge of one of the ridges of groove 18 is indicative of the amount of wiping action taking place between contact 14 and its cooperating groove. Inasmuch as contact 14 rides along the outer surface of the ridges of groove 18 as the two contact carrying members 11 andA 15 move with respect to one another, this wiping action takes place to penetrate any molecular insulating lm which might have accumulated on the surfaces of either contact 14 or the ridges of groove 18, and to bring the cooperating contact surfaces more rmly together.

The two point contact arrangement between contact 14 and the ridges of groove 18 may be more readily seen with reference to Figures 4 and 5 in which Figure 4 is a partly sectional view taken along line 4-4 of Figure 3A and Figure 5 is a sectional view taken along line 5-5 of Figure 2 upon the touching of contact 14 and the ridges of groove 18.

With reference to Figure 4 it may be noted that ridges 19 and 20 of groove V18 extend longitudinally of contact carrying member and form a parallel track upon which the hemispherical surface of contact 14 rides during the relative movement of contact carrying members 11 and 15.

The surface of hemispherical contact 14 touches ridges 19 and 20 of groove 18 at points 21 and 22 respectively. As may he seen from Figures 3A and 3B these points of contact move vertically as the contact carrying members 11 and 15 are moved from their rest position and the iiexure of reeds 12 and 16 occurs.

The two contact points 21 and 22 between the surfaces of hemispherical contact 14 and ridges 19 and 20 respectively are shown in the enlarged cross-sectional view of Figure 5. In this figure, groove 18 comprises two ridges or shoulders 19 and 20 anking a depressed portion 23. The surface of groove 18 consists of a coating Z5 of gold or other highly conducting, erosion resisting metal to form a corrosion and erosion resisting contact, which surface is in the stamped precious metal inlay which has taken the form of the groove. Alternatively the groove can be stamped in the contact carrying member and a precious metal plated on the surface of the groove.

In Figure 5 may be found typical dimensions for the radius of the hemispherical contact 14 and the various surfaces of groove 18. While these dimensions are derived from a practical operating embodiment of the invention, they are for illustrative purposes only and the invention should not be circumscribed by these specific dimensions.

The following chart is a summary of these illustrative dimensions:

Radius of curvature of contact 14 .022 in. Radius of curvature of ridges 19 and 20-- .015 in. Radius of curvature of depression 23 .0135 in. Thickness of gold alloy 25 .005 in. Length of groove 18 1A@ in. approx.

An actual commercial embodiment of the novel contact structure of the present invention is illustrated in Figure 6 wherein the groove carrying contact member is rigidly maintained with respect to the remainder of the relay structure proper shown generally by the reference character 68. Relay 60 comprises an electromagnetic means including a coil 61 disposed on a core 62 of magnetic material which extends upwardly from a U-shaped back bar or pole piece 63 having sides 64 and 65 which extend upwardly forward but fall short of a pole piece 66 to form air gaps. Pole piece 66 is carried by the upper end of coil 61. A block of insulating material 67 in which are embedded the groove bearing contact elements 68 is mounted upon the upper surface of pole piece 66. Each contact member 68 is disposed so that groove 69 is facing outwardly and is maintained in this position by virtue of a reentrant portion 70 embedded in block 67. The complete relay including U-shaped pole piece 63, core 62 and its encompassing coil 61, upper pole piece 66 and insulating block 67 is held together by a countersunk bolt 71 threaded centrally through the above assembly and secured in place by a nut or other fastening means 72. Y

Complementary contact carrying elements or armatures '73 and 73 of magnetic material are vertically disposed adjacent to but spaced from sides 64 and 65 of pole piece 63 and extend upwardly to span the gap between pole pieces 63 and 66. For caonvenience, only armature 73 will be described, it being understood that armature 73 is identical in structure and operation. Contact carrying element 73 is supported by iiexible reed 74 which is embedded in an insulating strip 75 which in turn is held in place by a bolt 76 tapped into pole piece 63. A short distance below armature 73 is disposed a strip of insulating material 77 in which small grooves are cut to guide the reeds in their movement and prevent any eX- cessive sideward movement thereof. At the upper end of armature 73 is a small herispherical contact member 78 which is disposed to engage contact receiving groove 69 to complete an electrical circuit therewith.

In operation the electromagnetic coil 61 is energized by an electrical circuit (not shown) connected thereto and generates a magnetic field which ows in an external circuit through U-shaped pole piece 63, across the air gaps between pole pieces 63 and 66 and through pole piece 66. The armature 73 which spans this gap, being of magnetic material, is therefore attracted toward the pole pieces until contact 78 carried thereby touches groove 69 in member 68 to complete an external electrical circuit (not shown). Because of the tractive force of the magnetic field thus produced, the armature is slightly further moved toward pole pieces 63 and 66. Since the contact carrying end of armature 73 cannot move forward as it is wedged into groove 69 in rigid member 68, the magnetic force causes the lower end of armature 73 to continue its movement toward side wall 64 of pole piece 63 for a short distance but far short of contact with side wall 64. Thise movement of armature 73 after the closure of the contacts causes it to pivot longitudinally about contact 78. This pivotal movement is imparted to the contact member 78 which partially rotates and abrades against the ridges of groove 69 to wipe off any accumulation of molecular lm. Additionally, contact 78 moves up and down in groove 69 to increase the abrasive action and further polish the contacting surfaces. Consequently a polishing action occurs which insures good electrical contact evenl under such adverse conditions as occur in low voltage and low current circuits. If the hemispherical contact should touch one ridge only, it is pulled into contact with the second ridge. Any bouncing back and forth between contacts is rapidly damped and solid two point wedging contact established. Additionally this provides an additional wiping action.

It should also be observed that the two point contact arrangement reduces contact failure if a bit of foreign material lodges between the hemispherical contact and one of the shoulders of the groove.

Factors which make for reliability in the instant invention comprise precious metal contacts, wiping action, two point contact, reduced area of contact, and wedging action.

Thus the contact arrangement of the invention is particularly pertinent providing 'reliability in low .voltage applications :and itsgoad degreeoflonaevityi ,in Conjunction with reliabiltymake it applcablelor higher vvaltag applic-ations Ysuch as -te1ephQne,-Switchh0ards,. etc;

Insummary thefp/resentinyention is directed toward a relay contact structure Whichexhibits a Ygreatly enhanced re1iabi1tyibfmeans-of-a tWofpoin-t labrasive and wedgingcontact between ;a conta/ct member having an essentially hem-isphericalcircuit completing surface and afcooperatinggroove whose'vshoulders'or ridges areidisposed'torreceive the contactrmemben The circuit completing/surfaces off the hemispherical contact member `and the ridges ofthegrooveare'fashioned ofra highlyconductive corrosion resisting zmetal, such as gold or platintim.v VThe contact arrangement produces a wiping and Wedging action Which'inhbits the accumulation of insulatingflms on the'surfaces of ,the cooperating contact areasrand' bites throughlms; v Y

'In short the present invention -is directedl toward a new and novel contactstr-ucture characterized by an increased reliability combined with a simplicity of manufacture Whiehrresults in a more economical and'more desirable relay structure. While What hasbeen ydescribed is regarded to be a v preferred embodiment of the invention it will be apparent that variations,-rearrangement s, modifications and changes Ymay bemade therein Without departing from the scope of theV present invention'as defined by the appendant claims. Y Y

We claim: l

1. A relay arrangement comprising a plurality of @man setssdismssdinsaacsinadiaent relatifenaeaehaf';

ingnrssentl lich Spherleal contact surface therrs 1rY ber having argroovacan E therepnfwth theasidesnf tlsmednrelati e fto Ynachadler,wthe

the groin/ 115; nos! Y Portions .of Lisaid;conta.Clt.carrying members which depend from saidfscontact; surfaces extending in l.opposite A:directions frorn said contactsuriages, support means for .said

rsteand second)contactgcarrying members including la fixed support forcne. of v.said .members `and :a :exible' wirefreed support Afora-the. other of said members to per- Y cludeswmeansorsupporting -said magnetic eld produc- Y ingV means andthe Contact .carrying Amember supported -by saideXible reedtopermit further flexing vof said reed Y kby saidYma-gneticfield producing means subsequenttoY mating Vof said Contact surfacesi Y ,eferencfes Citedin the file of this Vpatent UNITED STATES PATENTS 12,389,429 Y2,525,408 "Grayhill et al. Oct. 10, 1950 Grthk Nov.'20, 1945

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