U.S. patent number 3,826,000 [Application Number 05/254,530] was granted by the patent office on 1974-07-30 for terminating of electrical conductors.
This patent grant is currently assigned to Essex International, Inc.. Invention is credited to Gideon A. Du Rocher, Ellsworth S. Miller.
United States Patent |
3,826,000 |
Du Rocher , et al. |
July 30, 1974 |
TERMINATING OF ELECTRICAL CONDUCTORS
Abstract
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.
Inventors: |
Du Rocher; Gideon A. (Mt.
Clemens, MI), Miller; Ellsworth S. (Mt. Clemens, MI) |
Assignee: |
Essex International, Inc. (Ft.
Wayne, IN)
|
Family
ID: |
22964634 |
Appl.
No.: |
05/254,530 |
Filed: |
May 18, 1972 |
Current U.S.
Class: |
29/857; 228/155;
439/874; 219/137R; 228/164; 228/180.1 |
Current CPC
Class: |
H01R
43/16 (20130101); H01R 4/026 (20130101); Y10T
29/49174 (20150115) |
Current International
Class: |
H01R
4/02 (20060101); H01R 43/16 (20060101); H01r
009/00 () |
Field of
Search: |
;29/475,482,628,629,630
;339/275R,275T ;228/3.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
IBM Technical Disclosure Bulletin, Volume 13, No. 6, November 1970,
pg. 1624..
|
Primary Examiner: Lanham; Charles W.
Assistant Examiner: Duzan; James R.
Attorney, Agent or Firm: Learman & McCulloch
Claims
We claim:
1. A method of terminating an end of at least one metallic,
electrical conductor comprising holding said conductor in a
position such that its said end lies in a substantially vertical
plane with its free end lowermost; heating said conductor from its
free end to a temperature 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
mass suspended from said conductor; discontinuing the heating of
said conductor prior to the time that the force of gravity acting
on said molten mass causes the latter to separate from said
conductor; and solidifying said molten mass, thereby forming an
enlarged, pear-shaped nodule at the free end of said conductor.
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 shaping said nodule to
form a terminal.
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 oxygen-containing 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 molten and form a homogeneous
mass.
8. The method according to claim 1 wherein said nodule tapers
toward the opposite end of said conductor.
9. The method according to claim 1 wherein the heating of said one
end of said conductor is effected by an electric arc.
10. The method according to claim 9 wherein said arc is applied
continuously throughout the heating step.
11. The method according to claim 9 wherein said arc is applied
intermittently throughout the heating step.
12. The method according to claim 9 wherein said conductor has
insulation thereon and wherein the voltage of said arc 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 at which
both of said ends become 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 of said
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 method according 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 arc 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.
23. The method according to claim 1 including shaping said nodule
to form a terminal.
Description
The invention disclosed herein relates to the terminating of
metallic, electrical conductors and more particularly 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 from at least one end of the conductor and
joining that end to a terminal or to another conductor. A terminal
of conventional construction may be formed from the same or
different metal as that forming the conductor and the manner in
which the conductor is joined to the terminal may involve any one
of a number of processes, such as soldering, riveting, crimping,
fusing, or the like. Regardless of the manner in which a separate
terminal is joined to 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 nevertheless results in electrical losses and
generates heat.
The conventional practice of joining a separate terminal to a
conductor also has other disadvantages. For example, it not only is
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 crimped or otherwise
secured to the insulation surrounding the conductor. The terminal
forming machinery and the terminal joining apparatus frequently
represent a substantial investment in machinery and material
handling systems, as well as in factory floor space necessary to
accommodate such apparatus.
In many instances the joining of a separate terminal to a conductor
effects weakening of the conductor at the juncture therof with the
terminal, thereby resulting in an assembly which has less strength
than that of the conductor itself or that of the terminal itself.
For example, standard 16-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 to the wire, however, the assembly
in many cases is incapable of withstanding a tensile force of 50
lbs.
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 and terminal assemblies may
have greatly differing electrical properties.
Even though the utmost care may be taken in forming terminals and
in joining them 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 reason other than
that the 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 insulation 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 small diameter with the result that 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.
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 conductors of 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 is considered 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 termination at one end of an
electrical conductor;
FIGS. 2 and 3 are cross-sectional views taken on the lines 2--2 and
3--3, 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
20--20 and 21--21, respectively, of FIGS. 9 and 12;
FIG. 22 is a horizontal sectional view through a typical shaping
die assembly by means of which 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 conductors;
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 FIG. 24 and illustrating a pair of
insulated wires supported for splicing; and
FIG. 26 is a view similar to FIG. 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 metal-melting
temperature will vary, as will be pointed out hereinafter.
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. That portion 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 source of
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 terminal 9 of the battery or the like is connected a
conductor 10 which is connected through a known, adjustable timer
11 to a conventional arc welding machine 12. From the machine 12
extends a conductor 13 which is joined to a preferably tungsten
electrode 14 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 11 controls 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 arc between the
electrode and the free end 5 of the conductor. The arc welding
machine 12 preferably is of the kind having a variable voltage
control so as to assure the application of a sufficiently high
voltage to the electrode that the arc 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 arc 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 metal's 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 end of
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 arc no longer can be
sustained, the arc 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 arc 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
arc are unaffected. See FIG. 2. Those strands which are subjected
to the heat of the arc, 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 arc 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 arc at
periodic intervals. An intermittent arc causes alternate heating
and cooling of the free end of the conductor and results in a much
stronger juncture between the nodule and an aluminum conductor than
is obtained if the arc is continuous. Nevertheless, the shape of
the nodule is the same as has been described.
When utilizing an intermittent arc process the voltage applied to
the arcing electrode, the duration of the arc, the time between
successive arcs, and the number of 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 tensile
force of 10 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 20 pounds. These
procedures may be determined empirically.
Following cooling and 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 crimped
or otherwise secured to the free end of a conductor or to the free
end of the conductor and to the adjacent end of the insulation
sheath. Terminals constructed according to the invention, however,
are formed integrally at the free end of the conductor portion 4
and need not be secured to the insulation sheath 3.
The terminal shown in FIG. 4 comprises an eyelet terminal 22, the
terminal shown in FIG. 5 comprises a button terminal 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 terminal of
FIG. 9 comprises a socket terminal 27 having one closed end and one
or more axially extending slits 28, the terminal of FIG. 10
comprises a spade terminal 29, the terminal of FIG. 11 comprises a
blade terminal 30, the terminal of FIG. 12 comprises a corner
terminal 31, the terminal of FIG. 13 comprises a tap terminal 32,
the terminal of FIG. 14 comprises a 90.degree. offset spade
terminal 33, the terminal of FIG. 15 comprises a conical 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 be formed by
conventional shaping or forming apparatus of the kind typified 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 vertically movable 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.
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 juncture
between the portion 4 and the terminal to be capable of
withstanding considerably more tensile force than it could if the
juncture were angular. For example, 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 43 and 44 the free ends of which have been
joined in an enlarged, pear-shaped termination nodule 45 formed in
the same manner as the nodule 21 previously described. In forming
the nodule 45 the free ends of the conductors 43 and 44 are
supported at the same level so as to be subjected simultaneously to
either a continuous or 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 arc 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 or different
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
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.
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 arc 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 arc first will effect melting of the conductor 44a,
followed by melting of the conductor 43a as the electrode is moved
to follow the molten mass. The nodule 45a thus formed will
constitute a solid, homogeneous alloy of the materials from which
the conductors are formed, but the predominant material in the
nodule will be that from which the conductor 44a is formed. This
process may be utilized to reduce the brittleness of a
copper-aluminum alloy.
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, pear-shaped nodule, there are other methods by which
terminals may be formed. For example, the conductor 1 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
5 so as to establish a heat generating arc 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, but the 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.
The invention is particularly adapted to the terminating of magnet
wire 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 insulated wire 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 arc, as earlier described, to
cause the metal to become molten and form a pear-shaped mass which
subsequently is permitted to solidify and form a termination nodule
49 which may be shaped into a terminal of desired form.
In the heating of the free end of the insulated wire 46, it is
preferable that the heating tkake place in an oxygen-containing
atmosphere such as air, rather than in an inert atmosphere, until
just prior to the extinguishing of the arc. This assures sufficient
oxygen to enable the insulation adjacent the free end of the wire
to be consumed so that it does not contaminate the molten metal.
Just prior to the extinguishing of the arc, however, the inert gas
is caused to envelope the molten metal and to continue to envelope
the mass until such time as it has solidified to form the nodule
49. Enveloping the molten mass in an inert atmosphere as the mass
cools prevents oxidation of the molten metal during its cooling and
solidification stage. The time between the envelopment of the
molten metal by an inert gas and the termination of the arc may be
of extremely short duration such as 0.25 - 0.5 second, for
example.
In practicing the process illustrated in FIG. 24 the voltage
applied to the electrode 14 must be sufficiently high to establish
a current path between the wire 46 and the clamp 6 through the
insulation 47.
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
free ends 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 manner
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 free end of the wire 50 is
located at a greater distance from the electrode 14 than is the
free end of the wire 52.
In 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. It is
important that the free ends of both of the wires be positioned in
the path of the arc so that, when the distance from the free end 57
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 59.
Heating of the wires 50 and 52 in an oxygen-containing 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 properties,
the voltage and spacing requirements may be determined
empirically.
This disclosure is intended to be illustrative rather than
definitive of the invention. The invention is defined in the
claims.
* * * * *