CA1199382A - Electric wiring terminal and method of making same - Google Patents

Abstract

Abstract of the Disclosure An electrical terminal having a wire clamping tab connected thereto by an essentially thin neck portion about which a wire coated with a resin-type, high temperature insulation is adapted to be wound so that, when the tab is bent back against the terminal by opposed, energized elec-trodes to clamp a portion of the wire extending from the neck portion therebetween, resistance of the latter to flow of current heats both the neck portion and the wire wrapped therearound sufficiently to explode the insulation from the wire to assure a good electrical connection. At the same time the relatively large area of the terminal and its clamping tab maintains the clamped portion of the wire below its annealing temperature so that it is resistant to breakage in use.

Description

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ELECTRIC WIRING TERMINAL
AND METHOD OF ~KING SAME
Background of the Inven~iDn Certain electrical components, such as the coils conventionally used with throttle positioners on automotive ; ~ehicles, and the actuating solenoids for diaphragm valves used in some pollution control systems of automotive vehicles, for example, necessarily use wire coated wi~h high temperature resin-type insulation which must be stripped from the wire to assure good electrical connections at the terminals Ordinarily, the wire at the ends of the coil are simply soldered to the terminals, and the soldering temperature of approximately 6~0F. is sufficient to strip the insulativn from the wire; however, in the examples referred to3 the high temperature polyamid insulating coating is not removed from the wire at this temperature. Attempts have been made to solve the problem by connecting the wire to the terminals mechanically using splice clips having knurled surfaces that penetrate the insulating coating during the mechanical clamping operation, but this method does not always produce a good electrical connection and it adds significantly to the cost particularly w}lere high production is involved. I~ also has been proposed to weld wire coated wi~h high temperature insulation to its terminals as welding temperatures are sufficiently high to explode the insulation from the wire;
however, welding temperatures are above the annealing tem-perature of the wire so tnat the welding operation leavesthe wire ex~remely soft and easily broken. In many automo-ti~e environmentsj such as those referred to specifically abovç, the coils are mounted where they are subjecced in ` .
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use to vibration that flexes the wire baoX and ~orth at the terminal connections and soon causes it to break.

Brief Summary of ~he Invention The pTesent inven~ion embodies a novel ~e~hod ~f attaching wire costed with a high temperature insulation par-ticularly of the resin-type to ~ unique terminal constructioD
using electrodes that assures a good electrical coDnection between the wire and ~he terminal and that is adap~able ~o mass production operations.
More particularly, the present invention utilizes an electrical terminal having a relatively large tab or fla~
disposed laterally or to one side of and in acute angular relation to a main portion o the terminal body to which it is connected at one edge thereof by an essentially thin neck portion. By reason ofthis construction and arr~ngement of parts, a good electrical connection is established between the terminal and a wire coated with high temperature insula-tion that is wound aro~nd the neck of the terminal by placing the 1ag and the portion of the terminal to ~hich it is co~-nected between opposed electrodes which are urged toward eachother at a pressure that is insufficie~t to bend the neck in its normal state. Under these conditions, current necessarily flows between the electrodes through the neck which, because of its thin dimension, acts as a hea~ concentra~or and quickly becomes heated to a tempera~ure high enough ~o ex-plode the insulation from the wrapped portion of ~he wire and simultaneously to anneal and sGften the metal of the neck sufficiently so that it then yields under pressure of the electrodes ~o clamp an unannealed portion of ~he wire extending from the neck mechanically be~ween ~he flag and ~he adjacen~

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~ody of the terminal. As a consequence, a good electrical connection is established between the ~ire and the terminal 2t the neck of the latter, but the annealed and softened portion of the wiTe at ~he neck through which the connection is established is protected from breakage due to vibrations or other conditions of use.
In a typical coil assembly, the terminal is mounted in any suitable way on the spool and the wire coming off the spool is wrapped several times around the neck with the portion of the wire extending from the spool to the neck disposed between the flag and the terminal. In manufacture of the assembly, ~he terminal with the wire attached and disposed in the manner described, is positioned between the electrodes with the latter contacting the flag and the portion of the terminal to which it is attached. When the terminal is thus positioned, the current is turned on, a~d this current flows between the el~ctrodes through the terminal. While this is occurring, the terminals are ad~anced toward each other under predetermined pressure to clamp the wire between ~he flag and the terminal. In a typical spot welding machine of the type used in this operation, the electrodes are conven-tionally moved toward each other either pneumatically OT
mechanically through a spring at a controlled pressure that can 'oe adjusted within prede~ermined limits. The particular pressure used for the purpose of this invention will vary de-pending on the size of the terminal and the ga~e of the metal from which i~ is made. In actual practice, a large terminal made of relati~ely heavy gage metal used an electrode pres-sure of 16 psi, whereas a small terminal made of relatively light gage metal used an electrode pressure of only 2 psi.

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These are the electrode pressures at which the wire clamping flags on the two terminals referred to resisted the pressures of the electrodes until the neck portions of the terminals had become heated sufficiently to explode the insulation rom the wire and to anneal tb the polnt where they collapsed ~nd clamped the wire adjacent ~o the neck. Also, spo~ welders of the above ~ype are conventionally equipped with con~rols for regulating the amount of current flowing between the electrodes and the length of time the current is on. The entire operation is performed quickly. Typically, the cur-rent flows between the electrodes through the terminal only for about 4 cycles of the 60 cycle current or for about one-fifteenth of a second.
Description of the Drawings Fig. 1 is a side elevational view showing a typical coil with the ends of the wire attached to electTical terminals embodying the present invention;

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~ig. 2 is a top plan Yiew thereof showing the flag portions of the terminals in ~he initial unclamped position;
Fig. 3 is a view similar to Fig. 2 but showing th~
flag portions of the terminals in the wire clamping position;
Fig. 4 is a view similar to Fi~. 3 but showing the terminal bent as it sometimes is following the welding operation;
Fig. 5 is an enlarged vie~ showing the terminal attached to a lead cable and with its flag in its normal unclamped position and disassocia~ed fTom ~he wire to which it is adapted to be connected;
Fig. 6 is an elevational view looking in the direction of the arrows 6-6 in Fig. 5;
Fig. 7 is an enlarged view of the terminal, per se, with its flag in the normal unclamped position;
Fig. 4 is a view looking in the direction of the arrows 8-8 in Fig. 7; and Fig. 9 is an end elevational Yiew looking in the direction of the arrows 9-9 in Fig. ~ and showing, in addi-tion, the terminal in operative association with the elec-trodes of a spot welder or he~t .staker.

Description of the Preferred Embodiment The terminal here shown by way of illustration com-prises an elongate body 10 of a suitably formable, electrically and heat conductive material such as pretinned and tempered cold rolled steel. At one end of the body 10 is an elongate post portion or me~ber 12 having longitudinally spaced pairs .
of wire or cable clamping tabs 14 and 16 ex~ending from the ~o ~ ~

opposite edges thereof. The ~erminal conYeniently may be q formed by conventional metal stamping and forming operatio~s and, initially prior to forming, both pairs of ~ire clamping tabs 14 and 16 ex~end laterally in the same plane as the bDdy 10 and its post portion lZ. However~ during the forming . operation, the tzbs 14 and 16 are bent upwardly or at right angles ~o the plane of the terminal body to accept the wire or cable 18 to which the terminal is to be attached, as shown in Figs 5 and 6. Typically, the post end of the terminal is adapted to be attached to a relatively heavy wire 20 (such as 16 gage wire, for example) having an outer insulating sheath 22. Since the sheathing 22 is necessarily larger in diameter than the wire 20, ~he rear clamping tabs 16 are spaced farther apart than the front clamping tabs 14. In practice, the sheathing 22 i5 stripped back from the end of the wire 20 and, at the time of attachment of the terminal to the cable, the latter is laid on the post portion 12 with the end portion of the sheathing 22 between the rear tabs 16 and the projecting portion of the wire 20 from which the sheathing has been stripped between the front tabs 14. The front tabs 14 are then wrapped tightly around and crimped to the wire 1~ and the rear tabs 16 are wrapped tightly arsund and crimped to the insulating sheathing 22 to fasten the terminal and the cable seeurely together.
In the typical environments previously described9 the terminal is adapted to interconnect the relatively heavy-gage wire 20 mechanically and electrically ~o a relatively light wire ~such as 30 gage, for example) ~ypically used in 5.

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~he manufac~ure of a solenoid or other type of electrical coil~ To t~:is end, the body 10 is formed at the end theTeof opposite the post member 12 with a connector portion 24 in-te~rally with and extending longitudinally from the body at one side thereof, as perhaps ~est shown in Fig. 8. At the free end of the connector portion 24, laterally thereof, and attached to the inner edge 26 by an essentially thin integral neck portion 28 is a wire clamping tab or flag 30.
At the time of the initial stamping operation, the neck 28 and the flag 30 are disposed in the same plane as the connector portion 24; however, during forming of the stamped blank, the neck 28 is bent back toward the connector portion 24 to position the wire clamping flag 30 in acute angular relation with the connector portion, as perhaps best shown in Fig. 9. Bending of the neck 28 in the manner described positions the flag 30 so that ~he neck 28 can be ben~ farther in the direction of the arrow 32 in Fig. 9 to press the flag against the adjacent side of the connec~or portion 24, as shown by broken lines in Fig. 9. HoweYer, until this final bending step is performed, the flag 30 is disposed in acute angular relation to the connector portion 24 as previollsly described, and this is the position of the par~s at the time the terminal is assembled on the bobbin 34 and the light-gage coil wire is attached ~o the terminal.
In practice, the terminal will, in most instances, be assembled with and connected to the bobbin 34 on which the coil wire is wound, and in the particular constr~ction here shown by way of illustration, the coil wire is connected to the terminal after the latter has been attached to ~he 3~ bobbln. It will be observed that the bobbin 34 is construc~ed 6._ .

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so that the terminal can be assembled thereon with the tab or flag 30 in the partially bent but open position shown in Fig. 2. Nore particularly, the bobbin 34 is foTmecl at one end thereof with a centrally disposed, tubular, longitudinal extension 36 of redueed diameter, and the latter has a pair of laterally spaçed, radially extending, longitudinal ribs 35 and 40. Two aligned slots 42 and 44 extend through the ribs at substantially the midsec~ions ~hereof, as shown in Fig. 2, and two transverse slots 46 and 48 extend from the outer faoes of the ribs 38 and 40 and radially of the exten-sion 36 so that they intersect the slots 42 and 44 at sub-stantially their middle. It will be observed (Fig. 1) that the neck 28 is disposed at about the longitudinal center-line of the terminal so that, when the flag 30 is in the partly open position shown in Fig. 2, the terminal ean be passed through the slots 42 and 44 from left to right, as viewed in Fig~ l. As the terminal is inserted into the slots 42 and 44, the neck 28 passes through the transverse slots 46 and 48 with the paTtly open flag 30 outside the ribs 35 and 40. It is desirable that the terminal fit the slots 42 and 44 rela$ively snugly so that it is held r~la-tively firmly in the assembled condition.
In order to hold the terminal assembled with the bobbin, the terminal is formed at opposite sides thereo~
with rearwardly extending longitudinal fingers 50 and 52 having laterally ben~ tabs or stops 54 and 56 that sea~
against t'ne rib 3~ to limit the insertion movement of the terminal in the slots 42 and 44 to substantially the position shown in Fig. 1. Also, laterally of the connector portion 24 and to the right of the finger 52 as viewed in ~he drawing, ~he terminal is formed with a transverse, inwardly ex~.ending locking tab 58 that passes entirely through the slots 42 and 44 when the terminal i5 inserted and which just clears the rib 40 when the stops 54 and 56 seat against the rib 38 so that it can be bent laterally to form a fron~ stop tha* pre-vents retraction of the terminal and thus securely holds the latter assembled with the bobbin 34.
The light-gage coil wire 60 of course is wound around the bobbin 34 in the conventional manner and the end portion of the wire coming off the coil at the extension 3$
passes upwardly ~as shown in Fig. 1) toward the terminal in any suitable or conventional manner. In the particular bobbin construction here shown by way of example, the coil wire 60 extends through a slot 62 in the adjacent bobbin flange 63 and thence under the rib 38 which is foreshortened, as shown in Fig. 1, and then upwardly between the ribs 38 and 40 and laterally through the transverse slot 4~ from which it passes upwardly behind the connector portion 24 and then forwardly over the upper edge of the connector portion where it is positioned by a recess 64. If desired, the por~ion of the coil wire 60 passing through the slot 48 may also pass through the opening 66 that defines the front locking tab 58 to position and hold the wire properly with respect to the connector portion 24 and also to hold the portion of the wire extending between the coil and the slot ~8 relatively taut.
The portion of the coil wire 60 extending from the positioning notch 64 is passed downwardly as shown in ~he drawing aad wrapped once or twice around the terminal neck 2B. It is desirable that some slack be left in the coil wire between 30 the slot 48 and the neck 2B so that the connector portion of .

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the *erminal extending forwardly beyond the rib 40 can be bent to any position necessary or desirable ~o accommodate the bobbin and terminal assembly ~o the particular environ-ment in which it is adapted to be used.
S After the coil wire has been attached to the ter-minal in the manner hereinabove described, the flag 30 and the connector 24 are placed between the elec~rodes 68 and 70 of a spot ~elder or heat staker (not shown) and 2he electrodes are moved toward ach other to explode the insu-lation from the ~ire and ultimately to bend the flag 30 from the full-line, partly open position shown in Fig. 9 to the closed, broken-line position 30' (Fig. 9) in the manner pre-~iously described As previously suggested, ~he heat staking operation takes place very quickly. As soon as the elec~
trodes 68 and 70 contact the terminal, current flows between the electrodes through the neck ~8 and resistance to flow of the current through the relatively thin neck 28 causes the latter to heat up to or above the annealing temperature of the metal from which the terminal is made. In fact 9 the neck 28 may become red-hot. This blows or explodes the high te~perature resin-type of insulation with which the coil wire is coated from the portion of the wire wrapped around ~he neck 28. It also anneals the metal in the neck 28 so that the flag 30 bends to the closed position 30', and clamps the wire between the flag and the coil 60. As the lag 30 reaches the fully closed position, it becomes heat staked to the under-lying connector portion 2~. Normally, this entire action takes place in about 4 cycles of the 60 cycle welding current or one-fifteenth o a second. Curren~ IS permi~ed ~o flow between the electrodes o~ly for this period of time, and the ~.

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duration of flow of the current is con~rolled by a timer with which welders or hea~ stakers of the ~ype used in this opera-ti~n conventionally are equippedO
The portion of the coil wire extending between the S positioning notch 64 and the neck 28 passes behind ~he flag 3Q and consequently is clamped between the flag and the connector portion 24 of the terminal. However, while the neck 28 is heated ~o a very high temperature because of its thin configuration and consequential resistance to flow of current between the electrodes, the flag 30 and the connec~or portion 24 which are in direct contact with the electrodes are not heated to a temperature above the annealing tempera-ture of the wire because of their much greater size and mass.
Cons~quently, the portion of the coil wire coming off the neck 28 and clamped between the flag 30 and the connecto~
portion 24 is not heated to the same high temperature as the por~ion that is wrapped around the neck and it therefore retains its strength to such a degree that vibrations or other conditions that heretofore have tended to cause the wire to break at the terminal in use no longer have this effect.
As a result, the coil has a much longer life.
Fig. 2 shows the terminal just described at the upper end of ~he bobbin 34, as viewed in Figs~ 2, 3 and 4, and it shows a similar but modified terminal 72 at the underside of the bobbin. The coil wire coming off the bottonn end of the bobbin 34 is wrapped around and connected to the connector por~ion of ~he bottom terminal 72 in ~he same way it is connec~ed to ~he upper terminal, but the mounting portion of the terminal 72 that attaches ~o ~he bobbin is modified. In both instances, however, the two ',' 10, .~ .

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terminals project similarly from the portion of the bobbin 34 to which they are attached and the wire wrapping and hea~
staking operations performed thereon are identical. After these operations aTe completed, the terminals are ben~ back out of the way, as shown in Fig. 4, to accommodate an en-vironmental condition with which the particular coil he~e shown is adapted to be used.
While it will be apparent that the invention here-in described is well calculated to achieve the benefits and advantages as hereinabove set forth, it will be appreciated that the invention i5 susceptible to modification, variation and change without departing from the spirit thereof.

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Claims (17)

Having thus described the invention, we claim:

1. An electrical terminal adapted to be physically and electrically connected to wire coated with a resin-type of high temperature insulation and suitable for use particularly in situations that subject the wire to vibrations or other condi-tions likely to result in a high incidence of wire breakage at the terminal, said terminal being of a metallic material and having a pair of spaced apart, angularly related relatively large electrode-seating portions having a relatively low resistance to flow of electrical current therethrough interconnected by a bendable relatively narrow neck portion having a relatively high resistance to flow Of electrical current therethrough, said neck adapted to have said coated wire wrapped therearound and said electrode-seating portions adapted to be pressed together by opposed elec-trodes to clamp said wire extending from said neck therebetween, whereby engagement of said electrode-seating portions by and between said electrodes at a pre-determined pressure less than the pressure re-quired to bend said neck in the normal state of said terminal causes current to flow between the electrodes through said neck to heat the latter and the portion of said wire wrapped therearound 12.

to a temperature above the annealing temperature of the metallic material to explode the insulation first from the mentioned portion of said wire to assure a good electrical connection between said wire and said terminal and then to press said electrode-seating portions together to clamp at insulation coated portion of said wire there-between the relatively low resistance character-istic of said electrode-seating portions preventing the latter from being heated sufficiently to blow the insulation from the clamped portion of said wire and thus maintaining the resistance thereof to breakage due to vibrations and other adverse conditions occurring in use.

An electrical terminal as defined by claim 1 including means adjacent to one of said electrode-seating portions for locating and positioning at least one portion of the wire extending from said neck.

An electrical terminal as defined by claim 2 wherein the means for locating and positioning the men-tioned portion of said wire comprises a recess in a portion of said terminal extending from and formed integrally with one of said electrode-seating portions.

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4. An electrical terminal as defined by claim 3 including slot means provided in a portion of the terminal opposite and remote from said recess and disposed farther than the latter from said electrode-seating portions for accepting and loosely retaining at least one of said wire portions extending from said neck portion and located and positioned by said recess.

5. An electrical terminal as defined by claim 4 wherein said slot means has an essentially keyhole-shape terminal portion disposed substantially trans-versely of said terminal and a wire accepting slot portion communicating with and extending from said keyhole-shaped portion through an adjacent edge of said electrode.

6. An electrical terminal as defined by claim 1 wherein said electrode-seating portions and said neck portion are disposed at one end of said terminal, and including a cable connecting portion at the end of said terminal remote from said electrode-seating and neck portions.

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7. An electrical terminal as defined by claim 6 including mounting and fastening means intermediate said electrode-seating portions and said cable connecting portion for associating and detachably connecting said terminal to a spool or the like about which wire extending from said neck portion is adapted to be wound.

8. An electrical terminal as defined by claim 7 wherein said mounting and fastening means comprises flexible and resilient spring arms disposed at opposite sides of said terminal and extending longitudinally thereof.

9. An electrical terminal as defined by claim 8 wherein said flexible and resilient spring arms extend longitudinally in a direction away from said electrode-seating portions and said neck portion.

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10. A method of connecting wire coated with a resin-type high temperature insulation to an electrical terminal of metallic material having a relatively large flag portion connected thereto by an essen-tially narrow neck portion and disposed in acute angular relation with respect to the potion of said terminal to which it is attached, said method comprising the steps of wrapping said wire around said neck portion with a portion thereof extending from said neck portion and between the mentioned portion of said terminal and said flag portion, then electrically contacting spaced electrodes with the mentioned portion of said terminal and said flag portion and passing current therebetween so that resistance to passage of said current by said neck portion heats the latter and the wire wrapped therearound sufficiently to explode the insulation from said wire whereby to establish a good electrical connection between said wire and said terminal at said neck portion, and simultaneously moving at least one of said electrodes toward the other to bend the neck portion and to press said flag portion against the mentioned por-tion of said terminal to clamp the extending portion of said wire therebetween.

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11. The method defined by claim 10 wherein said electrodes are moved toward each other by a force less than that required initially to bend said neck portion, whereby the latter physically resists such movement until electrical resistance to passage of said current there-through due to its relatively small size causes it to become heated sufficiently not only to explode the insulation from the wire wrapped therearound but also to anneal and soften so that the force of said electrodes is able to collapse the same so as to clamp the wire between the flag and said electrodes.

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12. A method of connecting wire coated with a resin-type high temperature insulation to an electrical terminal of metallic material having a relatively large flag portion connected thereto by an essen-tially narrow neck portion and disposed in acute angular relation with respect to the portion of said terminal to which it is attached, said method comprising the steps of wrapping said wire around said neck portion with a portion thereof extending from said neck portion and between the mentioned portion of said terminal and said flag portion, and then squeezing said flag portion and the mentioned por-tion of said terminal between electrodes between which an electrical current is passed through said flag, neck and terminal portions, said current being sufficient to heat said neck portion by re-sistance thereof to passage of said current to a sufficiently high temperature to explode the insu-lation from the wire wrapped therearound and to anneal the metal in said neck portion,and the squeezing force applied by said electrodes being sufficient to bend said neck portion at least after annealing thereof so as to collapse said flag portion against said terminal to clamp the extending portion of said wire therebetween.

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13. The method defined by claim 12 including the steps of limiting the duration of current flow to an interval of time sufficient only to explode the insulation from the wire wrapped around said neck portion and to anneal the latter to clamp the wire between the flag portion and the terminal so that the relatively large mass of said flag and said terminal portions maintain the clamped portion of said wire at a temperature below the annealing temperature of said clamped portion whereby the strength of said clamped portion is not significantly affected.

14. A method of connecting wire coated with a high temperature insulation to an electrical terminal of a heat and electrically conductive material, said terminal having a relatively large flag por-tion connected thereto by a relatively small neck portion, said method comprising the steps of wrapping said wire around said neck portion with a portion thereof extending from said neck portion and between the mentioned portion of said terminal and said flag portion, and then bending said neck portion to bring said flag portion into overlapping relation with the mentioned portion of said terminal to clamp the extending por-tion of said wire therebetween using electrodes between which electrical current is passed through said flag, neck and terminal portions.

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15. The method defined by claim 14 including the steps of maintaining the current at a level sufficient to blow the insulation from the wrapped portion of the wire and to anneal said neck portions.

16. The method defined by claim 15 including the steps of maintaining the current at a level sufficient to blow the insulation from the wrapped portion of the wire and to anneal said neck portions but insufficient to anneal the metal in said flag and terminal portions and the clamped portion of said wire.

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17. A method of connecting wire coated with a high temperature insulation to an electrical terminal of a heat and electrically conductive material, said terminal having a relatively large flag por-tion connected thereto by a relatively small neck portion, said method comprising the steps of wrapping said wire around said neck portion with a portion thereof extending from said neck portion and between the mentioned portion of said terminal and said flag portion, and then bending said neck portion to bring said flag portion into overlapping relation with the mentioned portion of said terminal to clamp the extending portion of said wire therebetween using electrodes between which electrical current is passed through said flag, neck and terminal portions and maintaining current flow for a predetermined limited interval of time during which the relatively small cross-sectional dimensions of said neck portion and the resistance thereof to passage of said current heats both said neck portion and the portion of said wire wrapped therearound to a temperature above the annealing temperature of said wire to explode the insulation from the wrapped portion of said wire while the relatively large mass of said flag and terminal portions keeps the portion of said wire clamped therebetween at a temperature below the annealing temperature of said wire, whereby the latter retains its strength and its ability to maintain its integrity when subjected to vibration and other adverse conditions in use.

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