US 3826000 A
Terminating of a metallic, electrical conductor is accomplished by heating an end of the conductor until the metal becomes molten and forms a homogeneous mass followed by cooling and solidification of the mass and subsequent shaping of the mass, if desired, to form a terminal having any one of a number of different configurations. That end of the conductor which is to be terminated preferably is supported in a vertical plane with the free end of the conductor lowermost whereupon the surface tension of the molten metal causes the latter to form a pear-shaped enlargement or nodule tapering toward the opposite end of the conductor. Heating of the conductor preferably occurs in an inert atmosphere to prevent oxidation of the molten metal.
Description (OCR text may contain errors)
United States Patent [191 Du Rocher et al. i Q
TERMINATING or ELECTRICAL counuc'roas lnventorsz- GideoniA. Du Rocher; Ellsworth S. Miller, both of Mt. Clemens, Mich.
Assignee: Essex International, Inc., Ft. Wayne,
Filed: May 18, 1972 Appl. No.: 254,530
US. Cl. 29/630 R, 29/475, 29/482, 29/628, 29/630 A, 339/275 T, 228/35 Int. Cl .Q H0lr 9/00 Field of Search 29/475, 482, 628, 629, 29/630; 339/275 R, 275 T; 228/35 References Cited UNITED STATES PATENTS 6/1961 Wagner ct al. 29/630 D 3/1967 8/1968 3/1970 1/1971 2/1971 3/1971 6/1972 [4 ].:July 30,1974
3,718,968 3/1973 Simsetal. 29/482 4 OTHER PUBLICATIONS IBM Technical Disclosure Bulletin, Volume 13, No. 6, November 1970, pg.f1624.
4 Primary Examiner-Charles W. Lanham Assistant Examiner-James R. Duzan Attorney, Agent, or Firm-Learman & McCulloch metal causes the latter to form a pear-shaped enlargement or nodule tapering toward the opposite end of the conductor. Heating of the conductor preferably occurs in an inert atmosphere to prevent oxidation of the molten metal.
3 23 Claims/ 26 Drawing Figures .11 TERMINATINGOF ELECTRICAL CONDUCTORS The invention disclosed herein relates to the terminating of metallic, electrical conductors and morcparticularly to the formation of an integral, homogeneous termination at either or both ends of a conductor.
Conventional terminating of a conductor, is accomplished by stripping insulation fromat least one endof the conductor and joining that'end to a terminal or to another conductor. Aterminal of conventional construction may be formed from the same or different metal as thatfo'rming the conductor and the manner in which the conductor is joined tothe terminal may involve any one of anumber of processes, such as soldering, riveting, crimping,fusing, or the'like. Regardless of the manner in which a separate terminal is joinedto a conductor, there inevitably will be a voltage drop across the juncture of the conductor and the terminal. The voltage drop may be so small as to be'expressed in millivolt units, but it neverthelessresults in electrical losses and generates heat. i
The conventional practice of joining a separate terminal to aconductor also has other disadvantages: For example, it not onlyis necessary to provide machinery for forming the terminal itself, but it also is necessary to provide apparatus for joining the terminal to the conductor. In many instances, the terminal must be joined not only to the conductor, but it also must be rial handling systemsfas well as in factory floor space necessary to accommodate such apparatus.-
In many instances the joining of a separate terminal to a conductor effects weakeningof the conductor at the juncture therof with the terminal, thereby resulting in an assemblywhich .hasless strength than that of the conductor itself or that of the terminal itself. For example, standardl 6-gauge copper wire may be required for some purposes to be capable of withstanding a tensile force of 50 lbs., and the conventional brass or other terminal must'be capable of withstanding a tensile force at least as great. When the terminal is crimped or otherwise joined tothe wire, however, the assembly in many cases is incapable ofwithstanding a tensile force of 50 In those instances in which a conventional, separate terminal is crimped or otherwise joined to one end of a stranded wire conductor, it is impossible to assure that each strand of the conductor conducts its share of a current load. As a consequence,'apparently uniform stranded conductor andterminal assemblies may have greatly differing electrical properties.
Even though'theutmost care may be taken in forming terminals and in joiningthem to conductors, it virtually is impossible to prevent at least some of the terminals from being malformed or improperly joined, to
their conductors, if for no reasonother than thatthe forming and joining machinery cannot always function perfectly'because of wear, for example. If .a terminal is joined improperly to its conductor, or is malformed, it may not be capable of being joined to a mating or companion conductor with proper electrical integrity. If it can be joined to a mating or companion conductor, a malformed or misjoined terminal may increase the voltage drop between the terminal and its conductor. In addition, a terminal which is imperfectly formed or joined to its conductor is difficult to assemble in a connector.
The conventional terminating of insulated magnet wire of the kind used in relays, alternators, motors. and
the like is particularly troublesome inasmuch as the in-' sulation must be either pierced or removed from the wire to enable a terminal to be affixed thereto 'or to enable the, wire to be spliced to another wire. Such wire often is of quite smalldiameter with the resultthat the piercing or removal of the insulation causes substantial weakening of the wire at its juncture with the terminal or the other wire.
Among the objects of this invention is that of terminating either or both ends of an electrical conductor so as to avoid the problems inherent in the joining of conductors to; one another or .to separate terminals and at the same time obtaining advantages superior to those of conventional terminations.
Another object of the invention is to provide simple, inexpensive methods for forming integral terminations at the ends of conductors. I v
A further object of the invention is to provide methods of forming integral terminations at the ends of either'solid or stranded metal conductors. A further object is to provide a method of forming terminations at the ends of conductors and which avoid structural weakening of the conductor while at the same time providing improved electrical and physical properties.
Another object of the invention is to provide methods of joining or splicing conductorsof either the same or different metals, including conductors having insulation thereon, and without necessitating removal of the insulation prior to the joining of the conductors.
Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it isconsidered in conjunction with the appended claims and the accompanying' drawings, in which:
FIG. 1 is a fragmentary, elevational view illustrating the formation of an enlarged, homogeneous termina' tion at one end of an electrical conductor;
FIGS. 2 and 3 are cross-sectional views taken on the lines2+2 and 33, respectively, of FIG. 1;
FIGS. 4 18 are fragmentary, side elevational views illustrating typical terminals which may be formed at the ends of conductors;
FIG. 19 is a fragmentary, elevational view illustrating the terminating or splicing of two conductors according to the invention;
- FIGS. 20 and 21 are transverse sectional views taken on the lines 2020 and 2l2l, respectively, of FIGS. 9 and l2; I
FIG. 22 is a horizontal sectional viewthrough a typical shaping die assembly by means ofwhich a terminal may be formed;
FIG. 23 is a fragmentary view similar to FIG. 1 but illustrating a modified method of splicing a pair of .con-
FIG. 24 is a greatly enlarged, fragmentary view similar to FIG. 1, but partly in section, and illustrating terminating of an insulated wire;
FIG. 25 is a view similar to-FlG. 24 and illustrating a pair of insulated wires supported for splicing; and
FIG. 26 is a view similar toFlG. 25, but illustrating the spliced wires.
Terminations according -to the invention may be formed at either or both ends of a copper or other electrically conductive, metallic conductor 1 composed of either a single, solid wire or a plurality of wire strands. For purposes of illustration, the conductor 1 shown herein is composed of a plurality of parallel strands 2 of copper wire. The conductor 1 may be either bare or insulated. As disclosed, the conductor is positioned within a conventional, polyvinylchloride or the like insulation sheath 3 which has been stripped, in a conventional manner, from one end portion 4 of the conductor, the portion 4 terminating in a free end 5.
The formation of a termination according to the invention comprises heating the exposed conductor portion 4 from the free end 5 thereof to such a temperature and for a sufficient period of time to cause the metal of the conductor to become molten. The temperature to which the conductor must be subjected is at least the melting temperature of a particular metal and such temperature will vary in accordance with the composition of the metal. The melting temperatures of different metals are readily obtainable from metallurgical handbooks or may be determined empirically. The time during which the conductor is exposed to the metalmelting temperature will vary, as will be pointed out hereinafter. I
The preferred method of terminating the conductor '1 comprises supporting the bared end portion 4 in a vertical plane with the free end 5 lowermost. Thatportion of the bared conductor adjacent the end of the insulation 3 may be gripped in an electrically conductive clamp 6 which is connected by a conductor 7 to the negative terminal 8 of a battery (not shown) or other sourceof electrical potential. The clamp 6 provides electrical conductivity between the conductor 4 and the'power source and also locates the free end 5 of the conductor at a predetermined level. To the positive terwhich is joined to 21 preferably tungsten electrode l4 I that is supported in a housing 15. The housing is mounted by means of a bracket 16 or the like in such position that the tip of the electrode 14 initially is positioned directly beneath the bared portion of the conductor 1 and at a predetermined distance d from its free end 5. The housing 15 preferably includes passages (not shown) connected by a conduit 17 to a pressurized source 18 of inert gas such as argon. The timer llcontrols the operation of the machine 12 and also controls a valve 19 mounted in the conduit 17 between the housing 15 and the source 18.
In the operation of the apparatus shown in FIG. 1, closing of a normally open switch 20 in the conductor 10 applies to the electrode 14 a voltage sufficient to establish an are between the electrode and the free end 5 of the conductor. The arc welding machine 12 preferably is of thekind having a variable voltage control so as to assure the application of a sufficiently high voltage to the electrode that the are established between the electrode and the conductor 1 has a temperature sufficient to melt the metal of which the conductor 1 is formed. As a consequence, the establishment of an are causes the free end 5 of the conductor 1 to become molten. The valve 19 normally is closed, but closing of the switch 20 energizes the timer 11 which, in turn,
opens the valve 19 thereby permitting inert gas from the source 18 to be discharged from the housing 15 and envelop the bared portion 4 of the conductor 1. Consequently, oxidation of the metal in its molten state is prevented.
As the metal of which the conductor 1 is formed is melted, the interface between the molten metal and the surrounding inert atmosphere results in the metals possessing surface tension. As a result of the surface tension, continued melting of the metal causes the molten metal to climb the vertical conductor portion 4 so as to produce an enlarged, symmetrical pear-shaped mass of molten metal, the mass tapering toward the opposite or upper endof the conductor portion 4. As the metal continues to be melted, the climbing movement of the molten mass increases the space between the electrode 14 and the lower surface of the mass. When the distance between the electrode and the lower surface of the mass increases to an amount such that the are no longer can be sustained, the are will be extinguished and'no further melting of the conductor 1 occurs. The molten mass thus will cool and solidify so as to form a solid, metallurgically homogenous, pear-shaped termination nodule 21 at the free end of the conductor 1.
Although extinguishing of the are may be effected in the manner above described, it is preferred that the distance d between the electrode 14 and the free end of the conductor be maintained substantially uniform. This result may be achieved simply by mounting the clamp 16 for vertical movements so as to permit the electrode to follow movement of the molten mass. Alternatively, the clamp 6 could be mounted for vertical movements toward and away from the electrode 14.
The maximum size of the molten mass formed by melting of the free end of the conductor 1 is limited to one in which the gravitational force acting on the mass does not exceed the force of the surface tension. Thus, the size of the molten mass cannot be greater than one in which the force of the surface tension slightly exceeds the gravitational force acting on the molten metal. The mass may, however, have any size smaller than the maximum. The size of the molten mass may be determined quite accurately by means of the timer 11 which will act to interrupt the circuit to the electrode 14, and close the valve 19, following the elapse of a predetermined period of time not exceeding that required to form molten mass having the maximum size or weight.
if the conductor 1 is formed of multiple strands 2 of wire, those portions of the strands that are not subjected to the heat of the are are unaffected. See FIG. 2. Those strands which are subjected to the heat of the are, however, lose their identity and become part of the homogeneous nodule 21. See FIG. 3. The metallurgical and electrical properties of the nodule 21, however, are the same as those of the individual strands. Those portions of the strands which are not subjected to the heat of the are emanate from the nodule 21 so that each strand is capable of carrying its full share of an electrical current.
Although the foregoing description has been concerned with a stranded conductor 1, it will be understood that the disclosed process is equally applicable to a solid wire conductor.
If the conductor 1 is composed of aluminum, or some other metal having a lower thermal conductivity than that of copper, it has been found that greater strength at the juncture of the nodule and the conductor may be obtained by the use of an intermittent arc. In this'instance, the timer 11 may constitute a stepping or intermittently operable device capable of interrupting the are at periodic intervals. An intermittent arc causesialternate heating and cooling of the free end of the con-,
ductor and results in a much stronger juncture between the nodule and an aluminum conductor than is obof arc pulses per unit of time can be varied according to the composition of the conductor'and the results sought to be obtained. Thus, if the juncture between a nodule and a conductor must be capable of withstanding a ten sile force of pounds, the procedures followed in the formation of the nodule will be different from those followed in the formation of one which must withstand a tensile force of pounds. These procedures may bedetermined empirically.
Following coolingand solidification of the molten mass to form the nodule 21 it may be shaped by conventional means into any one of a large number of different kinds of terminals, some of which are shown in FIGS. 4 18. Each of these figures discloses a conventional terminal of'the'kind which heretofore has been formed integrally at the free end of theconductorporon 4 and need not'be secured to the insulation sheath The terminal shown in FIG. 4 comprises aneyelet' terminal 22, the terminal shown in FIG. 5 comprises a A distinct advantage of terminations formed in accordance with the invention as thus far described is that the nodule 21 is symmetrical and tapers in a direction toward the opposite end of the conductor. As a result, a terminal formed by shaping or deforming of the nodule merges smoothly along curved lines into the bared portion 4 of the conductor, thereby enabling the juncturebetween the portion 4 and the terminal to be capable of withstanding considerably more tensile force than it could if the juncture were angular. Forexample, conventional pull-off tests conducted on terminals constructed according to the invention have shown that the juncture between the terminal and the conductor is at least as strong in tension as the conductor itself.
The principles of the invention are not limited to the formation of terminals The invention also is applicable to the terminating of two or more conductors in splice joints. FIG. 19 discloses a pair of stranded conductors conductors 43 and 44 are supported at the same level so as to be subjected simultaneously to either a continuousor intermittent arc. The only difference between the formation of the nodule 45 and the nodule 21 is that the free ends of both of the conductors 43 and 44 are subjected to the are so that the metals of both conductors are melted to form a metallurgically homogeneous enlargement.
One of the advantageous characteristics of the invention-is that it enables multiple conductors of either the same ordifferent materials to be terminated or spliced.
For example,both of the conductors'43 and 44 may be formed of copper strands or solid copper wires, or one may be stranded copper and the other solid copper. In
either event the nodule 45 will be a solid, homogeneous button terrn inal 23, the terminal of FIG. 6 comprises a mushroom terminal 24, the terminal of .FIG. 7 comprises an open-ended socket or sleeve terminal 25, the
terminal of FIG. 8 comprises a pin terminal 26, the tercal terminal 34, the terminal of FIG., 16 comprises a cup terminal 35,-the terminal of FIG. 17 comprises a cylindrical terminal 36,. and the terminal of FIG. 18 comprises a spherical terminal 37.
Terminals of the kind disclosed in the drawings, as well as other terminals of conventional configuration,
may befo r'n led by'conventional shaping. or forming apparatus of the kindtypified in FIG.*22. This apparatus comprises a' base 38 having a cavity 39 therein for reception of the nodule 21 and which communicates with an opening 40 in which the conductor portion 4 may be received and clamped. A verticallymovable die 41 having a convex lower surface 42. is adapted to move into and out of the cavity 39 and deform the nodule 21 so as to produce the'mushroom terminal 24 shown in FIG. .6. It will be understood that dies of conventional design will be utilized in the formation of the other kinds of terminals.
mass of copper. Alternatively, if the conductor 43 is formed of copper and the other conductor 44 is formed of aluminum, for example, the nodule 45 will constitute a copper-aluminum alloy that is metallurgically homogeneous. I 1
Such an alloy is quite hard and brittle and, therefore, cannot readily be shaped to form a terminal in the same manner'as has been disclosed heretofore, but if the conductors 43 and 44 are formed of such metals that the nodule 45 is ductile, as is the case of copper, the
nodule 45 can be shaped-to form a terminal, if desired.
In the joining of conductors formed of dissimilar metals, the composition of the nodule may be varied by locating the free ends of the conductor at different levels. This process is illustrated in FIG. 23 wherein a conductor 43a has its free end 43b supported at a level above the level of the free end 44b of a conductor 44a, both of the conductors being located in the path-of an are from the electrode 14, but the distance from the electrode to the end 43b initially being too great to sustain an arc therebetween. In this case the are first will effect melting of the conductor 44a, followed by melting of Although'the preferred manner of terminating the free end of a conductor is to support the free end of the conductor vertically and above the arc-producing electrode, so as thereby to produce a symmetrical, pearshaped nodule, there areother methods by which terminals may be formed. For example, the conductor lv may be laid on a flat, horizontal body of refractory'material and be connected to the negative terminal of the battery, and the electrode 14 moved either mechanically or manually to a position adjacent the free end so as to establish a heat generating are between the electrode and the free end of the conductor. The heat generated by'the arc will melt the metal at the free end of the conductor, and the interface of the molten metal with the surrounding atmosphere will establish surface tension at the surface of the molten metal causing it to remain a cohesive, homogeneous mass-as the melting of the conductor continues toward its opposite end, thereby resulting in an enlarged molten mass at the end of the exposed portion of the conductor. When the conductor lies horizontally on a refractory material, the
molten mass will not be pear-shaped, butthe size. of the molten mass be as large as desired or, stated differently, the time during which the conductor is exposed to heat is that-required to produce a mass of desired size.
When a sufficient quantity of metal has been melted to form a mass of desired size the arc may be extinguished, whereupon the molten mass cools immediately and solidifies to form a termination nodule. The
' nodule then may be formed into a terminal, if desired,
as hereinbefore described. 1
e The invention is particularly adapted to the terminating of magnetwire coated with conventional enamel, varnish, or polymeric insulation, and without requiring prior removal of the insulation. FIG. 24 discloses a conventional, copper magnet wire 46 which carries a coating-of insulation 47 and terminates in a free end 48. The irisulatedwire is supported vertically in the clamp 6 with its free end 48 lowermost and directly over the electrode 14. The free end of the wire is subjected to an are, as earlier described, tocausethe metal to be: come molten and form a pear-shaped mass which subsequently is'permitted to solidifyv and form a termination nodule 49 which may be shaped into a terminal of desired form. v
In the heating of the free end of the insulated wire 46, it is preferable that. the heating tkake place in an oxy- The splicing of a plurality of magnet wires is illustrated in FIGS. 25 and 26 wherein a copper wire 50 coated with insulation 51 is placed adjacent a similar wire 52 coated with insulation 53 and clamped in a clamp 54 having a non-conductive part 55 and a conductive part '56 connected to the terminal 8 of the power source. The insulated wires 50 and 52 bear against each other with the wire 50 bearing against the conductive clamp part 56 and the wire 52 bearing against the non-conductive part 55. The wires 50 and 52 are supported by the clamp 54 with their free ends 57 and 58, respectively, lowermost and directly over the electrode 14. The freeends of the wires are not located at the same level, however, but are staggered or located at different levels. The wire 50 which engages the conductive clamp part 56 is supported in such manher that its free end 57 is at a higher level than that of the free end 58 of the wire 52. As a consequence, the
freeend of the wire 50 is located at a greater distance from the electrode 14 than is the free end of the wire 52.
ln practicing the process illustrated in FIGS. 25 and 26 the-voltage applied to the electrode 14 must be sufficiently high to establish a current path from the part 56 through the insulation 51 to the wire 50, but the distance between the electrode 14 and the free end 57 of the wire 50 must be greater than that at which an arc may be established between the electrode 14 and the free end 57. The voltage also must be sufficiently high to permit a current path to be established between the wires 50 and 52 through the respective coatings of insulation 51-and 53. The distance between the electrode 14 and the free end 58 of the wire 52 must be such as to permit an arc to be established therebetween so as to effect heating of the free end 58 to render the latter molten. The electrode may be moved relatively to the wires 50 and 52 as the latter is melted at its free end so as to reduce the distance between the electrode and the free end 57 of the wire 50. his important that the free ends of both of the wires be positioned in the path of the are so that, when the distance from the free end 57 gen-containing atmosphere such as air, rather than in an inert atmosphere, until just-prior to the extinguishing of the are. This assures sufficient oxygen to enable the insulation adjacent the free end of the wire to be consumed so'that it does not contaminatethe molten metal. Just prior to the extinguishing of the are, however, the inert gas is'caused to envelopethe molten high to establish a current pathbetween the wire 46 andthe clamp 6 through the insulation 47..
and the electrode is such to sustain an arc therebetween, such an arc will be established so as to effect simultaneous melting of the free ends of both of the wires 50 and 52 to establish a homogeneous, pear-shaped molten mass which subsequently may be cooled and solidified to form a termination nodule 59. The nodule may be shaped, if desired, to form a terminal. Again, heating of the wires 50 and 52 preferably occurs in air until just before the arc is extinguished, thereby effecting consumption of the insulation adjacent the molten metal. Just before the arc is extinguished, however, the molten mass is enveloped in an inert atmosphere which is maintained until the mass solidifies and forms the nodule S9.
Heating of the wires 50 and 52 in an oxygencontaining atmosphere causes some oxidation of the molten metal, of course, but the amount of such oxidation, especially when oxidation is prevented during cooling of the metal, does not materially affect the strength or the electrical properties of the nodule.
The voltage to which the electrode must be subjected, the spacing between the electrode and the nearest conductor, and the difference in the levels of the conductors will depend primarily on the electrical and physical properties of the conductors and their insulation. For conductors and insulation of differing propering said nodule to form a terminal.
ties, the voltage and spacing'requirements may be deconductor in a position such that its said end lies in a substantially vertical plane with its free end lowe'rmost;'
heating said conductor from its free end to atemperature at'which the metal at said free end becomes molten; continuing said heating of said conductor for a period of time such that the combined forces of gravity and surface tension shape the molten metal into an enlarged, pear-shaped molten masssuspende'd from said conductor; discontinuing the heating of said conductor prior to the time that theforce of gravity acting on said molten mass causes the latter to separate from said conductor; and solidifying saidmolten mass, thereby forming an enlarged, pear-shaped nodule at the free end of said conductor. i
2. The'method according to claim 1 including enveloping said one end of said conductor in an inert atmosphere during the heating thereof and during the solidification of said molten mass.
3. The method according to claim 1 including shap- 4. The method according to claim 1 wherein said one end of said conductor is heated in an inert atmosphere.
5. The method according to claim 1 wherein said one end of said conductor 'is heated in an oxygencontaining atmosphere.
6. The method according to claim 1 wherein said conductor is composed of a plurality of strands of metal.
7. The method according to claim 6 wherein all of the strands at said one end of said conductor become molto claim 1 whereinthe.
10 I 10. The method according to claim 9 wherein 'said are is applied continuously throughout the heating step.
11. The method according to claim .9 wherein said' conductor has insulation thereon and wherein the voltage of said are is sufficiently high to establish a current path through said insulation.
13; The method according to claim 1 including positioning one end of a second metallic conductor adjacent said one end of the first mentioned conductor and heating said ends to a temperature atwhich both of said endsbecome molten and form a homogeneous mass.
14. The method according to claim 13 wherein said conductors are composed of like metals.
15. The method according to claim 13 wherein said conductors are composed of different metals.
16.The method according ,to claim 13 wherein the free ends ofsaid conductors are staggered.
17. The-method according to claim 13 wherein the heating of the free end of one of said conductors precedes the heating of the free end of the other of said conductors, followed by simultaneous heating of the free ends of both of said conductors.
18. The methodaccording to claim 17 wherein the free ends of said conductor are staggered.
19. The method according to claim 13 wherein the heating of said free ends is effected by an electric arc.
20. The method according to claim 19 including insulation on both of said conductors and wherein the voltage of said are is sufficiently high to establish a current path between said conductors through said insulation.
21. The method according to claim 1 wherein said conductor is composed of solid metal.
22. The method according to claim 1 wherein the heating of said free end initially is conducted in an oxygen-containing atmosphere, and wherein said molten metal is enveloped in an inert atmosphere prior to the termination of the heating step.j 23. The method according to claim 1 including shaping said'nodule to form fa terminal.
12. The method according'toclaim 9 wherein said v