GB2152298A - Multi-leaf electrical contact - Google Patents

Abstract

An electrical contact comprises spaced cantilever contact leaves 22 with (a) distal ends normally spaced but adapted to mutually engage on insertion into socket 14 and (b) outwardly bowed central longitudinal portions. Because of their construction, the contacts may be used repeatedly without loss of resiliency. The contact may be made by extruding a seamless cylinder, forming slots 30A (fig 3) then moving the distal end of the slotted cylinder into engagement with die 32. <IMAGE>

Description

SPECIFICATION Electrical contact This invention relates to a multi-leaf electrical contact, and more particularly pertains to a low insertion force contact adapted for repeated use without ioss of contact efficiency.

The development ofoomputertechnology is accom- panied by an attendant need for micro miniature contacts having low insertion forces for repeated connect-disconnect capabilities. Such contacts are needed in an ever-growing number of both civilian and military applications. Because ofthe tremendous numbers of such contacts which may be employed in a single installation, the need is also constantly growing for contacts which assure desired electrical cummunication while possessed of cycle durability and yet are at low cost.

In accordance with this invention a novel lowinsertion-force leaf pin contact is provided which satisfies all of the above noted desiderata. The contact construction hereinafter described is particularly adapted for micro miniature size manufacture without any loss of contact efficiency or reliability, after repeated insertion and withdrawal relative to a contact socket employed in completing an electrical connection. One embodiment of the provided contact employs a multi-leaf contact portion integrally formed with a conductor receptacle or sleeve portion for securely engaging the end of an electrical conductor.

The multi-leaf contact portion is adapted to inwardly resiliently flex in the course of insertion into the receptacle or socket of a mating connector element.

The use of electrical contacts having compliant insertable contact portions is well-known, as is the use of contacts requiring low insertion forces.

Thus, Griffin U.S. patent 4,166,667 discloses a circuit board connector system employing contacts having barrel portions of C-shaped cross-section which deform in the course of being received in electrically conductive openings of a circuit board.

Tax burr U.S. patent 4,076,356 discloses an interconnection pin for printed circuit boards having a compliant section of generally C-shaped sectional configuration with raised pressure ridges formed in the outer surface adapted to engage inner electrically conducting peripheries of circuit board openings in which received.

Schramm U.S. patent 4,191,440 discloses an elec- tricalconnectorforcompling leads to circuit boards employing pin contacts having compliant sections of C-shaped cross-section and tapered ends for reception in plated openings of circuit boards.

Knowles U.S. patent 4,017,143 discloses a solderless electrical contact having a compressible, compliant barrel portion of C-shaped cross-section for reception in the plated openings of a circuit board.

Kurtz et al. U.S. patent 3,783,433 discloses contacts similarto those disclosed in the Knowles patent but which have compliant barrel portions of various sectional configuration, as well as detents for locking said contacts in fixed position relative to a receiving circuit board.

Gluntz U.S. patent 3,992,076 discloses a circuit board contact having cantilever spring arms which are insertable in the receiving openings of an insulating board. Solder is employed for effecting electrical contact between the contacts which are permanently set in place, and a printed circuit on the surface of the board. The arms of the Gluntz contact are inadequate for providing the desired electrical contact and interlocking with the inner peripheries ofthe insulation board even were the latter peripheries coated with an electrically conducting material. There is no suggestion of contacts made in accordance with this invention in the Gluntz patent.

It is thus an object of this invention to provide an improved contact construction providing desired electrical contact with a mating socket and which effects redundant contacts for desired electrical conductivity between the contact and socket defining an electrical connection.

It is a further object of this invention to provide a novel electrical contact of excellent cycle durability which requires low insertion forces while at the same time assuring a desired secure engagement with a receiving socket.

It is a further object ofthis invention to provide an embodiment of a contact employing an unbroken, continuous crimp barrel for desired engagement with an electrical conductor.

It is a further object of this invention to provide a novel one piece unitary contact construction employing resilient contact leaves integrally formed with an extending from a cylindrical barrel portion which securely engages an electrical conductor by means of a crimp engagement.

It is yet another object ofthis invention to provide a methodforforming a novel contact made in accordance with this invention by simple extrusion and slotting steps which enable the contacts to be manufactured in a rapid manner although of a precise uniform construction maintained within desired dimensional tolerances.

It is yet another object of this invention to provide electrical contacts adapted for micro miniature use in which the contacts may be arranged in close-packed arrangement, as on centers of approximately .035 inch.

It is another object ofthis invention to provide a novel multi-leaf contact which is readily adaptable for incorporation with a contact portion having a compliant section, whereby the resulting contact may be received in adjacent receptacle portions such as openings in adjacent printed circuit boards.

The above and other objects ofthis invention will become more apparent from the following detailed description when read in the light of the accompanying drawing and appended claims.

In one embodiment of the provided invention an integral cylindrical contact body is formed by extrusion. One end of the cylindrical body has longitudinal slots formed therein so as to form spaced cantilever arms or leaves. An endwise force is applied to the distal endsofsuch leaves so asto urgesuch ends together while simultaneously uniformly, outwardly bowing each of the central portions of such leaves.

Such outwardly bent portions form a maximum leaf periphery which is insertable in a cylindrical socket or receptacle which is electrically conductive orhas an electrically conductive inner periphery so as to effect an electrical connection therewith. Such socket is of smaller diameterthan the diameter ofthe maximum periphery defined by the contact leaves so as to insure an efficient multi-point contact.

The contact also employs a crimp barrel portion adapted to receive one end of an electrical conductor for secure engagement therewith.

In a modified contact construction, the integral barrel portion ofthe contact opposed to the leaves may be elongated and slotted so as to define a second male contact portion having a compliant center section. The resulting contact may be recieved at opposed ends in female receptacle portions for purposes of effecting two electrical connections as will hereinafter be disclosed in greater detail.

Fora more complete understanding ofthisinvention reference will now be made to the drawings wherein: Fig. 1 is a fragmentary elevational view of a slug of e'ectrically conductive material which is adapted to be extruded into a contact made in accordance with this invention; F;g. 2 is an elevational view illustrating the slug of Fig. 1 after the same has been subjected to an extrusion step; Fig. 3 isan elevational view illustrating the ex t::- ided generally cylindrical member of Fig. 2 afterthe rower portion thereof has been slotted so as to torm parallel slots therein, such slots defining the illustrated parallel contact leaves or arms; Fig. 3 also illustrates in section a die member adapter to move against the distal ends of the contact leaves; F;C. is a pian view of a slotted sheet fragment which may be employed for forming a contact made in accordance with this invention; F:g.4 illustrates in side elevation a contact made in accordance with this invention in which the parallel contact leaves of Fig. 3 following die engagement have the distal ends thereof urged into adjacent relationship and, are bowed outwardly; the outward bows formed in each ofthe leaves defining points on a maximum leaf circumference; Fig. 5 is an end view ofthe contact leaves of Fig. 4; Fig. 5A is an end view illustrating a modified contact which has flat contact leaves; Fig. 6 is a perspective view illustrating one embodiment of a contact made in accordance with this invention in crimped engagement with an electrical conductor and in spaced relation with the female socket also illustrated in crimped engagement with an electrical conductor; Fig. 7 is an elevational view, partly broken away, illustrating the contact and socket of Fig. 6 in mated engagement for purposes of effecting a desired electrical connection; Fig. 8 is a perspective view partly broken away, illustrating a plurality ofthe contacts and sockets of Figs. 6 and 7 mounted in connector insulating housings; and Fig. 9 is an elevational view partly in section illustrating a modified contact construction made in accordance with the teachings of this invention.

Referring more particularly to Fig. 6 a contact 10 made in accordance with this invention is illustrated having a multi-leaf contact portion 12 adapted to be received in a female socket or receptacle 14. It will be noted from Fig. 6that both the contact 10 and the socket 14 have integral barrel portions 16 and 18 respectively which are crimped to electrical conductors extending through illustrated tubular insulating members 20. There may, of course, be applications in which the provided contacts 10 and/or sockets 14 are employed in which the conductors are in an environment not requiring outer insulation, in which event the coverings 20 may be eliminated.

The leaved portion 12 of each contact 10 comprises a plurality of leaves or blades 22 which, are cantilver spring arms extending from adjacent an inner contact annulus 24. Annulus 24 interconnects the barrel or conductor receiving receptacle portion 16 and the contact portion 12.

In accordance with a preferred embodiment of this invention, each contact 10 comprises seamless elementwhich is extruded from a slug of an electrically conducting material, such as slug 28 illustrated in Fig.

1. As a result of an extrusion step extrusion 28A of Fig.

2 is formed having concentric and integ rally formed tubular portions 1 6A and 1 2Afrom which the contact portions 16 and 12 of Fig. 6 are formed.

Although the portions 1 6A and 1 2Aare of different diameter as illustrated to accommodate a conductor of precise size at its barrel portion and to form spaced contacts 22 of desired peripheral arrangement at opposed end 12, a barrel of uniform diameter may be extruded from which contact portions 12 and 16may be formed. Contact 10 is then formed by slotting the barrel portion 1 2A of the exruded elements 28a of Fig.

2, resulting in the parallel leaves 22A of Fig. 3.

Separated by four slots 30A, one of which is illustrated in side elevation.

It will be noted from Figs. 4 and 6 of the drawing that slots 30 which are formed in the completed contact 10 mayvary in width with a resulting variance in the width of each of the leaves 22. Thus it will be noted that each slot 30 begins inwardly of each contact portion 12, extending from a curved periphery, widens in the course of progressing along the length of the contact barrel portion in which formed, whereafter the slot narrows upon approaching the distal end of the barrel portion 12. Each leaf 22 is thus seen to widen as it proceeds outwardly toward the distal contact end after which itwill again taper upon approaching such distal end.

Following slotting ofthe extrusion 28a of Fig. 2 resulting in the configuration of Fig. 3, die 32 having surface 34 and the distal ends of the spaced leaves 22A of Fig. 3 are moved into engagement. Following die engagementtheslotted extrusion will become the completed contact 10 of Fig. 4 in which the distal ends of the four leaves are brought into mutual contact or closely spaced relationship (see Fig. 5). Simultaneously with the converging of the leaves bythe die 32, the central portion of each leaf 22 will be bowed outwardly to form a maximum leaf circumference as represented by dotted line C of Fig. 6, which will effect contact with the inner periphery of a receiving socket or receptacle such as the socket l4ofthedrawing.

Figure 7 of the drawing illustrates the contact leaves 22 and socket 14 of Fig. 6 in the normal mated condition. A comparison of the positions ofthe leaves 22 in Figs. 6 and 7 demonstrates the manner in which such leaves are inwardly resiliently flexed in the course of effecting contact with the inner periphery of the socket 14. It is apparent from Fig. 7 that each leaf 22 of contact portion 12 comprises in effect a cantilever spring arm touching at its outermost end with the adjacent leaves 22 at least during socket engagement, and extending at its inner end crom adjacent annulus or periphery 24 with which each leaf is integrally formed. The leaves are thus seen to engage in a complementary self-biasing engagementattheirdis- tal ends when in mating engagement with a socket.

In accordance with this invention, each contact 10 is preferablyformed of an extrudable, electrically con ducting material such as a berylium copper alloy or a copper nickel tin alloy. Such alloys and comparable alloys are known in the art and provide desired electrical conductivity in addition to providing desired resiliency in each ofthe leaves or cantilever spring arms 22 of each contact 10. Because each leaf 22 is supported or in biasing engagement at opposed ends in the mated condition with the receiving socket as illustrated in Fig. 7, each leaf 22 is provided with a desired resistance to inward flexing as each leaf is forced to flex inwardly from its maximum periphery C illustrated in Fig. 6.Figure 5 illustrates the adjacent relationship of distal ends of the leaves 22 in the normal position of rest as well as their complementary structural relationship. In accordance with this invention the leaf ends may be in mutual contact or slightly spaced apart in a position of rest. The normal gap between spaced leaf tips is of the order of a few thousandths of an inch.

Although Figs. 6 and 7 illustrate the connection of a single contact and mating socket, it is, of course, apparenttothoseskilled in the artthat a plurality of such contacts and sockets may be mounted in electrically insulating housings for purposes o-form- ing a multi-conductor connector. In Fig. 8 a plurality of electrical connections is simultaneously effected by mating housing 34 in which thefemalesockets 14are mounted in aligned relationship with housing 36 in which the contacts 10 are correspondingly aligned.

Latching members not illustrated butwell-known in the art may be employed in conjunction with the housings 34 and 36 so thatupon engagement of the lower surface of housing 34 and upper surface of housing 36, not only are the contacts in desired electrical engagement with its associated mating socket in the manner illustrated in Fig. 7 but, in addition, the housing members 34 and 36 are latched together.

Itwill be appreciated bythoseskilled intheartthat the arrangement of Fig. 8 is illustrative of one manner only of employing contacts made in accordance with this invention. The provided contacts may also be employed for purposes of effecting electrical com munication as with a circuit on a PC board. The contact structure above described lends itself to ready incorporation in micro miniature applications, that is, for packaging in installations in which the contacts are packaged on centers less than .050 inch such as approximately .038 inch.

It will be further appreciated that the contact embodiment 10 illustrated in the drawing utilizing four substantially parallel leaves 22 is provided byway of illustration only. It has been found that a minimum ofthree leaves should be employed for purposes of assuring a stable interconnection with a receiving socket. Each leaf 22 provides a separate point of contact with the electrically conductive surface of its mating socket. Accordingly, the greaterthe number of leaves 22, the greaterthe number of electrical contacts and the resulting electrical communication.The provision of eight separate leaf members would provide eight separate pointsofcontact; the possible number of leaves formed is dictated in part by the size of the original barrel which is slotted for leafformation.

It will be appreciated that the contacts of this application comprise most satisfactory substitutes for the more complex twist pin connectors ofthe type disclosed in Phillips U.S. patents 3,255,430 and 3,319,217. Methods of forming such pins are disclosed in Phillips patent 3,402,466. It will be noted that in forming these twist pins a plurality of wires are employed for conforming compliant male pin portions including seven outerwireswound about an inner core which may comprise one or more core wires. Atypical twist pin construction is composed of eleven discrete elements. The plurality of elements and method of manufacturing such twist pins entail an expense which is approximately five times that of manufacturing the contact pins ofthis invention.

It is apparent from the foregoing description and the illustrations ofthe drawing, that the provided contact by employing in the preferred embodiment a unitary extruded construction, has eliminated any seams which may comprise points of weakness in a formed contact. Such seams may separate after a crimping operation in which a barrel portion ofthe contact is crimped to an electrical conductor. By the utilization of the continuous barrel with integral cantilever leaf contact elements a contact construction is provided possessed of excel ien t cycie durability.

The basic structure provided readily lends ,tse!f to custom manufacture. For instance, the number of leaves may be altered for purposes of determining the number of contacts with the female receptacle; it is contemplated that normally the number of leaves would comprise any number between 4and 8, although 3 would appearto be workable as would be greater leaf number if the contacts are of adequate size and/or satisfactory materials are available for forming the discrete leaf members.

The basic leaf construction provided in the abovedescribed contact may be incorporated in a contact formed from rolled sheet material such a sheet segment 37 of Fig. 3Awhich has been predeterminately stamped or otherwise appropriately formed so as to form spring arms 39 separated by slots 41. Following rolling ofthe segment 37 into a cylindrical form the unslotted sheet portion may be crimped to conductors 41 extending from tubular insulator 20. The sheet portion may first be rolled into a cylindrical form prior to slotting. Such a rolled sheet will, of course, not have the unitary construction above described and would obviously be more susceptible to separation along the seam than would be an integral barrel construction.

However, it is apparent that in certain applications crimping a contactto a conductor may serve to securely lock the contactto the encompassed conduc torso thatthe danger of seam separation is extremely small or nonexistent. Also, a separate manufacturing step may be employed to secure the seam defining portions ofthe contact tgether. Such sheet construction would work to equal advantage with the contacts 10 illustrated in the drawing, and, the resulting contacts would looksimilarto contacts 10 but have a longitudinal seam.

A modified contact construction 40 is illustrated in Fig. 9 wherein a contact portion lOB substantially identical to the contact 10 above described is formed integ rally with a contact portion 42 having a compliant barrel portion 46. The barrel portion 46 has an elongate slot 48 which tapers at opposed longitudinal ends. In the normal course of utilization of the contact of Fig. 9, the contact portion 1 0b may be recieved in a socket in the manner above described, whereasthe compliant barrel portion 46 may also be received in a female receptacle for purposes of effecting electrical connection. Thus the contact illustrated in Fig. 9 has opposed male portions each ofwhich is adapted to be received in a female receptacle.The contacts of Fig. 9 may serve many applications as, for instance, the connection of circuits on PVC boards, barrel portion 46 being illustrated in Fig. 9 received in a plated opening of a PC board 50.

Another feature ofthe provided contacts which er 3bles the sameto be customized for particular use --7mpnsesthe ablility to control the length ofthe slots 50 formed in an extruded cylindrical element or in a rold sheet element for purposes offorming the spaced parallel leafs orspring arms. It is apparentthat the lorgertheslots3othelongereach cantilever spring leaf, and as a result such longer leaf is more susceptible to flexing upon receipt in a receiving socket. Accordingly, by lessening the length of the slots formed in a contact, the more resistantto bending the resulting leaves become.Thus, by regulating the length ofthe slots 30 a ready means is available for controlling the insertion forces necessary for effecting an interconnecction with a mating receptacle element. The slot 30 need not extend the length ofthe portion 12 as in the illustrated contact embodiment 10.

A further modification of the provided contacts 10 comprises the flattening of one or more of the leaves 22 after formation. Such leafflattening will result in contact being effected by each leaf along opposed longitudinal edges upon insertion in a cylindrical socket. Fig. 5A illustrates such a flat-leaved contact 10F.

By way of example only, a contact made in accordance with this invention may havethefollow- ing dimensions. The contact, such as contact 10 illustrated in the drawing, may beformed from a copper nickel tin alloy and be approximately .005 inch in thickness. The contact may be approximately 1/4 inch in length with the leaf contact portion 12 and the barrel portion 16 each constituting approximately one-half ofthe overall length. The maximum diameter ofthe maximum periphery formed in the bowed central portions of the leaves of such contact would be approximately .028 inch, and the diameterofthe barrel portion 16 of such contact would be approximately .0375 inch. The terminal ends ofthe leaves of such a contact are in adjacent relationship at rest, i.e., eithertouching or have a gaptherebetween of approximately .005 inch. The foregoing dimensions may, of course, be modified while still retaining the various inventive features above described in detail.

It is believed thatthe foregoing description has made apparenta number of modifications which may be made in the illustrated contact embodiments without departing from the spirit of this invention.

Accordingly, this invention is to be limited only by the scope ofthe appended claims.

Claims (19)

1. A low insertion force contactformed of resilient material, and having a first portion comprising at least three spaced cantilevercontactleaves having proximal ends extending from an inner, continuous periphery; said leaves having terminal distal ends in adjacent relationship; said leaves being in substantially parallel, spaced relationship relative to the contact longitudinal axis; portions of said leaves between said proximal and distal ends being bowed outwardly relative to said longitudinal axis so as to define portions of a maximum circumference defined by said leaves whereby insertion of said first contact portion in a mating socket having a receiving opening smallerthan said maximum circumference results in inward resilientflexing of the leaf portions defining said maximum circumference with said distal ends of said leaves in mutual engagement.

2. The contact of claim 1 in which said contact first portion is connected with a receptacle portion for receiving an electrical conductor in crimped engagement therewith.

3. The contact of claim 2 in which said contactfirst and receptacle portions comprise an integral extruded, generally cylindrical member; said first and receptacle portions being of different diameters and said inner, continuous periphery being adjacent a juncture between said first and receptacle portions.

4. The contact of claim 1 in which said contactfirst portion is connected to a second contact portion having a slotted, compliant barrel portion adapted to reduce in cross-section in the course of being received in the opening of a receiving socket having a cross-section smallerthanthatdefined by said compliant barrel portion.

5. The contact of claim 4 in which said contact second contact portion is of substantially C-shaped cross-sectional configuration and has a slot of greater width intermediate the ends of said second contact portion whereby said intermediate slotted portion of said second contact portion may resiliently deform when received in such socket opening.

6. An electrical contact comprising a first contact receptacle portion for receiving the end of a first electrical conductor; a second low insertion force contact portion connected to said first receptacle portion for reception in a receiving aperture of a socket of a second electrical conductor; said contact portion comprising spaced cantilever leaves having proximal ends extending from adjacent one end of said receptacle portion; said leaves being in adjacent relationship atthe distal terminal ends thereof, and bowed outwardly at portions disposed between said distal terminal ends and said proximal ends.

7. An electrical contact comprising an integral, substantially cylindrical body having a slotted end portion defining a plurality ofsubstantially parallel cantilever leaves with proximal ends extending from a continuous annulus; said leaves having distal end portions in adjacent relationship; said leaves being bowed outwardly intermediate said proximai and distal ends so asto define portions of a leaf circumference of maximum diamater whereby insertion of said leaves in a socket having a receiving diameter iessthanthat ofthe leaf maximum diameter forces said leaf bowed portions to resilientlyflex inwardly; said leaf distal end portions being configured so as to be urged into conplementary, mutually contacting engagement upon flexing of said leaves in the course of being received in a socket.

8. The contact of claim 1,6or7 in which said contact comprises an integral, extruded, generally cylindrical body in which said leaves are substantially curvilinear in cross-section.

9. The contact of claim 6 in which said receptacle portion is substantially cylindrical and is formed integrallywith an annulusfromwhichfourofsaid leaves extend uniformly in spaced relation.

10. The contact of claim 6 in which said receptacle and contact portions are extruded from a slug of a copper nickel tin alloy and said cantilever leaves have excellent resiliency.

11. The contact of claim 1,6 or 7 in which said cantilever leaves are substantially flat.

12. The contact of claim 1 or 6 in which said contact is formed of a sheet of an electrically conductive material which is rolled into substantially cylindrical form and crimped to one end of an electrical conductor.

13. Thecontactofclaim 1 or6 in which said leaves are four in number and each leaf is of such crosssection as to effect engagement along opposed longitudinal edges when received in a cylindrical socket of such size as to receive said contact portion and force said leaves together.

14. The electrical contact of claim 1,6 or 7 in which said contact is approximately one-quarter inch in length, is formed of an electrically conductive material of approximately .005 inch in thickness, and is adapted for micro miniature applications.

15. In a method offorming an electrical contact the steps comprising extruding a seamless hollow element; slitting one portion of said element along the length thereof so asto form at leastthree spaced, cantilever leaves, exerting an endwise axial force againstthe distal ends of said leaves so as to bring said ends into engagement and outwardly bow central portions of said leaves.

16. In a method offorming an electrical connector the steps comprising extruding a cylindrical contact portion of a first diameter contiguouslywith a cylindrical receptacle portion of a second diameter; slitting said contact portion along the length thereof so as to form at Ieastthree cantilever leaves; applying force to the ends of said leaves so as to outwardly bow such leaves intermediatethe distal ends and said receptacle portion and force the ends of said spaced leaves into close proximity.

17. The method of claim 15 or 16 in which said leaves are forced into mutual engagement at their distal ends, and an electrical conductor is inserted into said connector receptacle portion and the latter portion is crimped into engagement with said conductor.

18. Any ofthe electrical contacts substantially as herein described with reference to the accompanying drawings.

19. Any ofthe methods offorming an electrical contact substantially as herein described with reference to the accompanying drawings.