TECHNICAL FIELD

The present invention relates, generally, as indicated, to electrical contacts, and, more particularly, to electrical fork contacts having high conductivity inlay material, such as gold, in the tines thereof. The invention also relates to electrical connectors using such contacts.

BACKGROUND OF PRIOR ART

Planar electrical contacts of the fork type are well known as are connectors that use such contacts. A typical prior fork contact is shown in U.S. Patent No. 4,030,799. Such fork contact has a pair of tines that extend out from a base. A member, such as a pin contact, may be inserted between a pair of tines to make an electrical connection therewith. Such patent also discloses an electrical connector using such contacts. The connector is of the cable termination assembly type, which includes the contacts, a housing, and at least a portion of a multiconductor cable. The present invention may be used with such cable termination assemblies and with other types of electrical connectors,' such as a cable termination, which is like the noted assembly but without necessarily including the cable as a part thereof.

It is well known that such fork contacts may be formed by die cutting or die stamping the same from a relatively thin sheet of metal material. However, such stamping often leaves the finished product with a smooth side, which is the one that the cutting die strikes first, and a burr side or surface. The sharp, rough burrs at such burr side usually are undesirable because they can damage pin

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contacts inserted to engagement therewith, for example by scoring off high conductivity coatings or the like applied to such pin contacts. It would be desirable to permit such die cutting of fork contacts while eliminating with facility such scoring and like problems created by such burrs.

To improve the electrical conductivity and possibly for other reasons electrical contacts often are plated with certain materials, such as high conductivity materials. For example, a contact formed of nickel silver may by plated with gold or palladium silver in order substantially to improve the electrical conductivity thereof, especially at the surface area of the contact where it engages with or wipes against a pin contact or other- member inserted to engage the same. Plating materials, though, sometimes are applied non-uniformly, which may result in uneven wear; and there may be voids ift the plating allowing undesirable oxidation to occur. Also, plating is unnecessarily relatively expensive because the entire contact usually is plated, which wastes plating material at portions of the contact that do not perform a contacting function.

The use of relatively highly conductive or high conductivity inlay material has eliminated the need for plating an entire electrical contact, but contacts using inlay material usually are non-planar and relatively large in comparison to the required dimensions of a planar fork contact ^" or the like. An advantage of inlay material over plating is the former would be denser and more uniform in thickness than the latter. Also, the inlay material usually would present a contacting surface area for engaging an inserted member, e.g. a pin contact, that is smoother and, therefore, a better contacting surface, than the plated or unplated surface, say of a conventional fork contact. The usual technique for applying inlay material to sheet material has been to force by pressure, e.g. by a rolling process, a strip of inlay material into a shallow groove in the sheet material from which the contact would be cut. Then, the contact would have to be deformed, for example in the shape of a hairpin curve or in the form of a full

or three quarters folded box that has contact arms extending, say upwardly, from respective opposite sides of the box and parallel thereto, in order to locate the inlay material at a position of contacting exposure to a pin contact inserted to 'engagement therewith.

In contrast, though, a planar fork contact is a secure, integral device that requires minimum space while assuring a highly effective contacting/wiping function to establish a connection with, for example, a pin contact or other member inserted between the tines thereof to engagement therewith. A planar fork contact would be one that has the tines and preferably, although not necessarily, the base, which holds the tines thereto, all substantially in a single narrow plane, i.e. that plane of the sheet material from which the contact is formed, especially by the noted die cutting. It would be desirable to provide inlay material at the contacting/wiping areas of the tines of such planar fork contacts.

Another problem sometimes encountered in electrical con¬ nectors using resiliently deformable contacts, such as the tines of a fork contact, is over-stressing beyond the elastic limit causing permanent damage to the contact. It would be desirable _, to reduce the possibility of such over-stressing and/or damage.

SUMMARY OF THE INVENTION

Briefly, the invention relates to improvements in electrical contacts and in electrical connector devices, such as cable terminations and cable termination assemblies, employing such contacts. The invention permits the application of inlay material, such as gold, palladium silver, or the like, in one plane, i.e. that of the sheet material from which fork contacts are cut, and use thereof in another plane, i.e. that of the contacting/wiping area of the respective tines of the fork contacts.

Fundamentally, the invention resides in an electrical contact

of the fork type, wherein each of the tines is substantially parallel and coplanar and has a contacting or wiping area facing that of the other tine for wiping engagement and direct surface to surface contact with a member, such as a pin, inserted between the tines to engagement therewith. Importantly at least one of the tines has inlay material at the contacting or wiping area thereof to improve the electrical connection with such member and/ or for similar reasons that plating traditionally may have been provided on electrical contacts.

The noted inlay material, such as gold, palladium silver, or the like, preferably is applied only to the relatively limited area of each tine that maintains direct engement with such inserted member. A twist is provided in each tine to align the respective contacting areas that contain such inlay material with each other in confronting relation for such wiping engagement with the inserted member. The contact, moreover, may be die cut or stamped; however, the twist provided in each tine enables alignment of the respective smooth side surfaces of each in respectively confronting relation with each other, allocating the back of each tine, i.e. that portion not intended to engage such inserted member, for the burr side surface.

Accordingly, one aspect of the present invention relates to an electrical contact, including a pair of tines, each tine having a contact wiping area, inlay material in at least part of the wiping area of at least one of the tines, and holding means for holding the tines in generally parallel, coplanar relation.

Another aspect relates to a planar fork contact including a pair of tines for engaging a member inserted therebetween, and inlay material in at least one of the tines for directly engaging such inserted member.

An additional aspect relates to a die cut electrical contact, including plural tines, each having a smooth side and a burr side, the lattα' being created upon the die cutting of the contact, and holding means for holding the tines in generally fixed relative position with the smooth sides facing an area for connection with a member

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inserted to engagement with the contact, and the burr sides facing away from such area.

A further aspect relates to an electrical fork contact, including plural tines, each having a contact area (contact area, contacting and a twist at substantially the area, and wiping area are used interchangeably herein) same respective portion to place the contact areas in opposed confronting relative position to engage a member inserted therebetween.

Still another aspect concerns a multiconductor cable termination, including a multiconductor electrical cable having a plurality of conductors and electrical insulation about the conductors maintaining the latter electrically insulated from each other, a plurality of electrical contacts, each including terminals connecting with at least one of the conductors directly through said electrical insulation to form an electrical junction, each of the electrical contacts being of the types mentioned in the several paragraphs of this summary, and a housing including a base for directly holding the contacts and the cable in relatively fixed position, the base means comprising a body integrally molded about at least a portion of each of the contacts and a portion of the cable, whereby tlie base, contacts and cable form an integral structure.

Still an additional aspect of the invention concerns the combination of one or more such electrical contacts with an electrical cable including at least one electrical conductor and electrical insulation about the conductor maintaining the latter electrically insulated, wherein the contact includes a terminal for connecting with a respective conductor directly through the electrical insulation to form an electrical junction, and a housing for holding the contact and cable in fixed relative position to form a secure cable termination assembly.

Still a further aspect relates to an improvement in an electrical contact having plural tines defining an area therebetween for receiving a member inserted therein, and each tine having a

contact area for engaging such member, such improvement being directed to inlay material in at least one of the tines at such contact area, and mounting means for mounting the tines at least substantially in a common plane.

With the foregoing in mind, a primary object of the present invention is to provide an electrical contact that is improved in the noted respects.

Another object is to provide a cable termination and/or cable termination assembly improved in the noted respects.

An additional, object is to enable use of inlay material in an electrical contact that is formed in a single plane.

A further object is to facilitate use of inlay material in an electrical contact.

Still another object is to minimize the cost of using specialized materials, e.g. gold, in electrical contacts.

Still an additional object is to provide reliable . high conductivity for the contact wiping area of an electrical contact at relatively minimum cost, and preferably without requiring plating.

Still a further object is to minimize the amount of high conductivity material needed in an electrical contact, especially while assuring adequate amount of such material at the contact area.

Even another object is to reduce the effect of undesirable burrs and sharp edges in an electrical contact.

Even an additional object is to- obtain a smooth surface at the contact wiping area or connection area or an electrical contact, especially of the planar type.

Even a further object is to improve the ability of an electrical contact to withstand deformation abuse.

Yet another object is to achieve the above objects par¬ ticularly in a fork contact, and especially a fork contact.

Yet an additional object is to achieve the foregoing objects in a cable termination assembly or other electrical connector device.

These and other objects and advantages of the present

invention will become more apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises tlie features hereinafter fully described in the specification and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the invention may be employed.

BRIEF DESCRIPTION OF DRAWING

In the annexed drawing:

Fig. 1 is a plan view of a plurality of electrical contacts in accordance with the present invention;

Fig. 2 is an exploded isometric view of a cable termination assembly type of connector in accordance with the present invention using the contacts of Fig. 1;

Figs. 3 and 4 are section views of one contact of Fig. 1 looking generally in the direction of the respective section arrows identified by the same numbers; and

Fig. 5 is an isometric view of a single electrical contact in accordance with the present invention in the midst of being manufactured.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring, now, in detail to the drawings, wherein like reference numerals designate like parts in the several figures, an electrical contact in accordance with the present invention is ^" generally indicated at 1. In Fig. 1 there are three contacts 1 shown connected to a breakaway strip 2 formed during the manufacturing of the contacts and used to facilitate manipulating the contacts, for

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example, just prior to incorporating the contacts in a connector, such as the cable termination assembly 3 shown in Fig. 2. In Figs. 3 and 4 are shown section views of the contact 1 of the invention, and in Fig. 5. the contact 1 is shown prior to finishing the manufacturing thereof.

Each of the contacts 1 that are illustrated in the drawings is a planar fork contact; the contacts are formed by die cutting or die stamping the same from a planar sheet of metal, such as nickel silver, so that the two tines 4, 5, the base 6, and the terminal legs 7, 8 are all in a common plane of the sheet material, such as is exhibited by the breakaway strip 2. The tines 4, 5 have respective straight leg portions 10, 11 and curved leg portions 12, 13, the latter portions being more remote from the base 6 than the former. A contacting or wiping area 14, 15 of each tine is intended to engage a member inserted into the space 16 between a respective pair of tines of a given fork contact 1. Usually the wiping areas 14, 15 wipe against a member inserted into the space 16, as the resilient force of the respective tines urges such areas into wiping engagement with such member. The wiping helps to clean the tines and the surfaces with which they are to connect to form a reliable electrical con¬ nection. Thus, the areas 14, 15 perform both a wiping function and a contacting function with respect to such member.

In the broadest sense of the invention the wiping areas 14, 15 and the portions of the tines 4, 5 at which they are formed should- be coplanar to achieve the various advantages of planar fork contacts. However, in the preferred embodiment and best mode of tlie invention the tines 4, 5, base 6, and terminal legs 7, 8 all are coplanar.

To improve the electrical connection between a contact 1 and a member inserted into the space 16, at least one of the tines 12, 13, and preferably both of them, has inlay material 17, 18 at the wiping area 14, 15. The inlay material 17, 18 preferably is gold, palladium silver, or other material, as may be desired. Usually, though, such inlay material would have a higher electrical conductivity, i.e. be a better conductor and/or have a greater

resistance to impedance causing oxidation, than the material of which the remainder of the contact 1 is formed, such as the above-noted nickel silver. Since the inlay material 17, 18 is located generally only in the contacting area 14, 15 of each tine 4, 5, only a minimum amount of such relatively costly material is required for the contact 1. The thickness of such inlay material may be on the order of several, say about twenty, millionths of an inch to on the order of about fifty millionths of an inch in thickness; and preferably the inlay material is about thirty millionths of an inch thick.

Moreover, the inlay material 17, 18 may be applied in a conventional inlay applying technique to the sheet material of which the contact 1 is formed prior to the die cutting of the respective contacts 1 from such sheet material. For example, such inlay material in the form of a relatively thin strip of narrow width may be force fit into a shallow groove in the sheet material at the portion thereof that will become the contacting areas 14, 15 when the contact 1 is formed.

An example of a method for manufacturing the contacts 1 in accordance with the present invention is disclosed in commonly assigned, concurrently filed U.S. patent application- entitled "Method and Apparatus for Making Fork Contacts" and the entire disclosure of such application hereby is incorporated by reference. Briefly, referring here to Fig. 5, a manufacturing technique for the contact 1 may include, after having inlaid the inlay material in the sheet material, for example by a rolling process, and having die cut the contact shape to form the respective tines 4, 5, base 6, and terminal legs 7, 8, deforming the tines to bow the same generally in that portion thereof that will become the contacting areas 14, 15. It is noted, too, that during the die cutting operation weakening cut-outs 20, 21 are formed in the tines near the base ends 22, 23 thereof, and twisting flags or tabs 24, 25 are formed at the leading ends 26, 27 of tlie tines. Also, some of the metal of the terminal legs may be coined to provide sharpened edges 28, 29 of the terminal legs 7, 8 to

facilitate slicing into and through the insulation of a cable, such as that shown at 30 in Fig. 2.

During die cutting of the contact 1, that portion of the contac remote from the cutting blade portion of the die often has sharp burr formed thereon, as is well known, and will be referred to herein as th burr side 31 of the contact. Tlie other side 32 of the contact 1 is usuall quite smooth because it will have been rolled, for example, durin application of the inlay material. The burr side, of course, preferably i on the side of the contact 1 remote from the inlay material to avoi loosening of the latter during the cutting or stamping process.

One of the final* steps involved in manufacturing the contact involves twisting the tines by applying clockwise and counter-clockwis (relative to Fig. 5) twisting torques to the respective tabs 24, 25. Suc twisting of the tines 4, 5, then, brings the respective wiping areas 14, 1 into directly opposed confrontation with each other with the curved le portions 12, 13 of the tines being convex toward each other in substantiall direct spaced-apart confrontation, as is seen in Figs. 1 and 2. It is th purpose of the weakening cut-outs 20, 21 to facilitate the mentione twisting and substantially to confine the twist 33, 34 of each tine 4, 5 t the areas of such cut-outs and, thus, in the straight leg portions 10, 11 o the tines. By so confining, and, therefore, effectively controlling th twisting, equal lengths of the respective tines 4, 5 and good alignment o the contacting/ wiping areas 14, 15 is achieved, and the normal forces tha each contact 1 would apply to a member inserted between the contact tine will be equal. The tabs 24, 25 may be cut off after twisting has bee completed.

The finished contacts 1 are seen in Figs. 1-4. The space 1 between the convex wiping areas 14, 15 is relatively narrow so as to permi such wiping areas to engage securely a member, such as a pin contact printed circuit board, or the like, inserted into such space. The space 3 between the straight leg portions 10, 11 of the contact 1 is relatively wide than the space 16 to accomodato a portion of such an inserted member.

Due to the relatively gradual slope or curvature of the curve

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leg portions 12, 13 of the tines 4, 5, upon insertion of a member into t space 16 down toward the space 35, there will be a relatively smoo movement of such member and a corresponding relatively smooth resilie bending or elastic deformation of the respective tines, as the wiping are 14, 15 will tend to part in response to force exerted by such member. Th wide inlet 36 to the space 16 helps to guide such a member during th insertion procedure, while the relatively narrow width of the space 1 assures wiping engagement of the contacting areas 14, 15 with such membe during such insertion.

The weakest portion of planar fork contacts usually is at th junctures of the tines 4, 5 and the base 6. The nature of the contact provides for effectively strengthening the contact, and particularly suc junctures. This is accomplished using the straight 10, 11 and curved 12, 1 leg portions in conjunction with respective support walls of a housing o the like in which the contact 1 is used to form a connector. Specifically such support walls are shown schematically at 40 in Fig. 1. The walls 4 are stepped, having a relatively thick support portion 42 intended directl to support the respective straight leg portions 10, 11, after they hav undergone a predetermined amount of resilient deformation by a membe inserted into the space 16. The relative spacing of the tines 4, 5 wit respect to the support portions 42 is such that the latter will preven over-stressing of such straight leg portions and the noted junctures in th event that an over-size member is inserted into the space 16 or such member is inserted in an askew manner. There is a recessed or concave wall portion 44 of each wall 40, as well, which permits further resilient deflection of the curved leg portions 12, 13 of the tines 4, 5 even after the straight leg portions or the junctions thereof with the respective curved leg portions have bottomed against the wall 42. Such curved leg portions are capable of suc added deflection due to tl e nature of their curvature.

Preventing such over-stressing also may be accomplished by using curved leg portions 12, 13 that have their leading ends 26, 27 terminating closer to the center-line of the contact 1, i.e. a line drawn between and parallel to the straight leg portions 10, 11 of tlie tines through the space 16,

than a line parallel to the outside surfaces 44, 45 of the straight le portions. In such embodiment the support walls 40 may be straight whil still providing the described support function because the junctions of th straight and curved leg portions would abut, and, therefore, be supporte by, the walls 40 before the straight leg portions would be over-stressed while still permitting subsequent resilient deflection of the curved le portions until the leading ends thereof abut such walls.

Turning, now, briefly to Fig. 2, the cable termination assembly there illustrated is a representative connector in which the contact 1 o the invention may be employed. Such cable termination assembly include the cable 30; the contacts 1, the terminal legs 7, 8 of which pierce throug the cable insulation 50 to engage respective conductors 51, which enter th slots 52 between respective legs 7, 8; a body 53 of electrically non conductive material molded about parts of the contacts 1 and cable 30 forming an integral structure therewith; and a cover 54. A similar cabl termination assembly is disclosed in the above-mentioned U.S. patent No. 4,030,799. The body 53 preferably is molded to enclose fully the junction of respective conductors 51 and terminal legs 7, 8 to maintain the same i an air-free environment, thus minimizing the possibility of oxidation or electrolytic action at such junctions. Accordingly, the combination of suc excellent electrical connection between the contacts 1 and conductor 51 and of the wiping areas 14, 15 via the inlays 17, 18 with members inserted t engagement therewith provides a highly effective and reliable couplin ultimately between such conductors and members.

The cover 54 is like the one in the noted patent. It fits on the body 53 at the step 55 and may be ultrasonically welded in place. The front wall 56 of the cover has openings 57 for guiding pins or like members to engage respective contacts. Compartments partly shown in Fig. 1 at 58 in the cover 54 provide some measure of isolation of respective contacts while the walls of such compartments provide the support walls 40 described above.

STATEMENT OF INDUSTRIAL APPLICATION .

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It will be appreciated that the contacts and electrical connect of the invention may be used to connect respective conductors to provi an electrically conductive path for respective electrical signals.