US2769965A

US2769965A - Nylon-jacketed connector

Info

Publication number: US2769965A
Application number: US570075A
Authority: US
Inventors: Frey John Nelson
Original assignee: Thomas and Betts Corp
Current assignee: ABB Installation Products Inc
Priority date: 1956-03-07
Filing date: 1956-03-07
Publication date: 1956-11-06
Anticipated expiration: 1973-11-06

Description

Nov. 6, 1956 J, N, FREY 2,769,965

NYLON-JACKETED CONNECTOR Original Filed June 26, 1951 2,769,965 Patented Nov. 6, 1956 2,769,965 NYLON-Mercateo coNNECToR John Nelson Frey, Mountainsidc, N. I., assignor to The Thomas & Betts Co., Elizabeth, N. J., a corporation of New Jersey Continuation of application Serial No. 233,662, June 26, 1951. This application March 7, 1956, Serial No. 570,075

11 Claims. (Cl. 339-276) This application is a continuation of my co-pending application Serial No. 233,662, tiled June 26, 1951.

The invention relates in general to electric terminal tubular sleeves in telescopic coaxial relation, in which the outer sleeve constituted a shield of insulating material and the inner sleeve constituted a ductile wire-barrel adapted to be permanently deformed by the application of a squeeze pressure through the outer sleeve to crimp the inner sleeve into a positive electric and mechanical connection with a wire or cable therein.

More specifically, the invention relates to the wirebarrel portion of a terminal connector of the type which must he made very small, one market requirement of such connector being that the tubular assembly forming the connector be about forty-hundredths of an inch in length and twenty-four hundredths of an inch in outside diameter. It is most important that the elements of the assembly be designed so that they can be made cheaply and in large quantities as a factory product.

One diiiiculty which has been .experienced in the use of such connectors, particularly when made in such small sizes, is to prevent flash-overs and tracking. An electric path is apt to form accidentally, leading from the high potential source in the cable conductors attached to the connector, through, or more often around, the exposed ends of the outer insulating sleeve to ground on some object, and this possibility of a Hash-over or tracking increases with increase of voltage, frequency and lower air pressure at high altitudes.

Tracking as herein used and sometimes referred to as surface leakage or creeping is the passage of current along a path over the surface of an insulator.

4 One of the primary objects of this invention is to provide in such connector a longer leakage or tracking path than has heretofore been economically possible, and thus increase the resistance to electric Hash-overs without necessity of providing additional resistance material particularly for this purpose.

Broadly, this objective -is attained by providing one or msual outer insulating sleeve and the current carrying elements of the connector, and located axially between the exposed ends of the conductors and the exposed ends of the insulating sleeve.

Certain commercial requirements of such devices are that they be capable of use in widely varying temperature conditions, for instance, in Arctic regions and in refrigerat ing apparatus where temperatures often reach minus 40 degrees F., and in fire control circuits and in varnish baking, where the temperature often reaches 400 degrees F. Another ield requirement is that these devices must be capable of withstanding the eifects of acids, alkalies and ketones, as well as salt water, aviation fuel, lubricating oils, carbon tetrachloride, hydraulic iluids and like deleterious agencies with which they might come into contact. In so far as the outer insulating sleeve is concerned, it is required that it be of high tensile and compressive strength; capable of being molded to the required cnfiguration; capable of being made translucent or colored; and having a long life under conditions which tend to destroy its insulating properties. The small all-over size of the connector herein featured necessarily imposes a limitation on the cross section of material of the coinposite members and this, in turn, complicates the problems indicated by these commercial requirements and which the instant disclosure is designed to meet.

l0 It has been suggested in the prior art to form the inner cable-engaging sleeve of the connector of a soft copper and to form the outer sleeve of rubber or of a thermoplastic material such as vinyldichloride or polybutene. When attempts have been made to form such rubber, Vinyl- 15 chloride or polybutene insulating sleeves of the reduced cross section of material featured in this disclosure, the premolded sleeves tended to and in time did collapse. For this reason, in the prior art devices the outer sleeve, irrespective of what material it was formed, was intentionally made to adhere tenaciously to the conductorengaging copper sleeve and being thus internally reinforced the assembly maintained its intended configuration.

These prior art devices otherwise have not proven satisfactory in actual practice for numerous reasons, including,

most seriously, a high production cost. In these known devices, especially where the outer insulating sleeve was thin, the action of the crimping dies thereon had the effect i either of cracking open the insulation or of at least thinning and sometimes actually tearing the insulating material at its point of greatest deformation away from its adherence to the underlying wire-gripping sleeve and thus presenting a spot or area of no insulation or of less than the minimum rated insulating effect required of such devices.

In the form of the invention herein specifically selected for illustration there is disclosed a form of electriciterminal connector, one end of which comprises an apertured tang or tongue formed integral with a wire-barrel or inner sleeve of the improved connector forming the subject-matter of this disclosure. The thickness of the apertured tongue extension of the inner wire-barrel and the size of wire to be secured therein, as well as other factors not involved here, tend to prescribe the dimensions thereof, both internally and externally.

While it is of advantage to make the wire-barrel element of the connector of soft copper, the electrical conductive requirements necessitate that it be made of somewhat thick cross section of material, and apparently this cannot be avoided despite the desire to make the device small.

There is also an advantage in internally reinforcing the outer insulating sleeve and thus permit a reductionthereof in cross section, but it is not required that any such reinforcement possess any conductive capacity and certainly t none comparable to the soft copper required 0f the wirebarrel element.

Accordingly, another object of the invention is to provide a multiple sleeve form of connector whose inner sleeve, while relatively thick as required, is deformable conventionally into crimped engagement with the bare wire or strands of the conductor intruded therein; whose outer sleeve while thin is adequate in its insulating capacity and which provides for a crimping engagement with the insulation of the conductor by an intermediate sleeve 05 which does not necessarily have the conductive capacity members disposed in telescopic coaxial relation, featuring a thin-Walled, rigid, seamless metallic sleeve between the outer insulating sleeve and the inner wire-barrel or sleeve,` operativewto tie thecrimped Yinner` element -to `a portion of the conductor insulation; to give the maximum possible structural strength' and least addition of material for ithis-purpose'to lthe -partsWh-ieh are to' be `radially deformed into al crimping .engagement lwithi the Awire: lor cable .inserted .in the l assembly.

Among the #other '-obiects of t'he invention r is' to Xprovide an electric `terminalconnector of the type above outlined,

which will possess `thecharacteristics#commercially irequired oflsu'chidevices Sas aboveindicatedandt at the same sleeve, las molde'dQibe vfequalto yor lnotf materially greater than the external diameter of the intermediate sleeve. As specifically required -by this disclosure, 'the internal diameter of the insulating sleeve as' molded V`is preferably less than ftheiexternal diameter of the intermedi ate sleeve.

This, in' Iturn, calls'I 'for Aa type of- Athermoplastic wmaterial f which can Abe molded to close tolerances, especially in forming -thebore of the insulating sleeve, and which has atleast a limited plastic-memoryto shrink onto the intermediate 2lining andalimited elastic recovery to form the airfgaps' herein-featured. -The choice of a thermoplastic material capableof being so molded is restricted by other commerciall requirements, lsuch as capacity to make it translucent, to color the same, to provide a narrow plastic range, i. e., 47-5degrees to 5 l() degrees, and it'rnust possess other properties capable of being easily'c'ontrolledduring thel'molding cycle ofthesmall'size articles herein'featured.

`Making `the outer-sleeve of a synthetic' condensation polymeric amide'manuacturedunder the designationof nylon'j -and'oneform of-which `isdisc'l'osed in the patent to GoidonrNol' 2,348,536," granted'MayQ, 1949, hasbeen l' most Ysatisfactory. VWhile this material `hereinafter -referredto generically-as nylonj is not as good an 'insulator as some other thermoplastics, thebetter insulating effects l of Ylsuch other insulating materialsA had 'to'be sacriing-advantages inherent in using nylon.

"On -t-he'flotherhand, it has been foundin the instant situation-:that whenr4 acondensation polymeric-amide is used forthednsulating Vshield its insulatingproperties are improvedduringuse; apparently dneito an orientation'of its crystals incidental 'to =the crimping` actionherein featurd.

While it is the vintent to makethe'outer insulating sleeve of such rigidity as will tend to resist collapsing and'thus maintain 'fits lconfiguration substantially as molded, the intermediate'liningsleeve, `of course, does act as an internal'reinforcement to the outersleeve to resist accidental deformation. The disclosure features for the intermediate sleeveL the use of a length of annealed commercial brass or-bronze, Ihereinafter referredto `generally as copper=`alloy, the basic'stock of which can be purchased in the fopen market las tubing. .Inone form of the inventionv where a'straight tube was used vit was'simply cut oit from-aimarketsize of tubing and used 'as is without any machining. A cheaper methodis'to make the sleeve from flat strips of the alloy fed to an eyelet "machine, While brassfor lbronze'is not a particularlygood electric conductoncompared Vwith copper,` Vthatiproperty is 2 not required' intheiinstant situation and, onthe -other h`and,

making thefsleeve'of brass' or bronze `rather'than' copper ficed somewhat to obtain the vhigl-ily desirable compensati 50 contributes ytothe desireto make the ysleeve very-thin, to give a high degree of strength to the metal part intended to be permanently deformed to resist subsequent elongation, and to reduce as far as possible the presence of a good conductor in the path of a possible flashback. While rigidity is indicated, it is understood vthatlthe-sleeve must not be so rigid in its cross section as would offer any materal resistance to radial'deformation or` otherwise defeat theindicated crimping operatiomnor so rgidas to resist the desired interlocking incidental to the `'crimping operation of the two inner sleevesof `theconneetor -herein featured.

The inner wire-barrel or sleeve is formed of veryvsoft sheet copper which can be rolled into the cylindrical form herein featured and which has a conically flared end which can be easily distended radially, as herein indicated, into the required binding. engagement with 'the rigid intermediate sleeve and to form the funnel-shaped entranceat thefree end thereof, as hereinafter described.

Theinvention also relates to an improved technique in forming an assembly of such a connector withthe wire or' cable' therein topi-Ovide the finished assembly.

Various'other objectsand advantagesof'rthe invention willbe in" part obvious frornan inspection of the accomp'anyingdrawingsand in part will. be more fully forth in the following particular description of one form of connectorv embodying the inventionand of one method of attaching the connector to a cable, and theinventionalso consistsin certain new and novel .features of construction and combination Vof parts hereinafter set forthand claimed.

" In'the accompanying drawings,

Fig.' l' is an enlarged view partly in section showing a preferred embodiment ofthe 'invention deformed into a permanent crimping engagement with an Velectric cable intrudedinto' its wire-barrel end and'ill'ustrating the assembly of' connector and cable in'ithe fin'afform it assume- 1sv following a 'time' delay' after crimping;

Figsj'2 through 5 are each transverse sectional views throughthe assembly shown in Fig. l, 3 being taken ontheline 3--3, `to show substantial recession offthe outer insulating sleeve from the intermediatemet'al sleeve, upon completion of a crimping operation `as in Eig.' 2;

Fig. 4 is taken onthe line' t4-4i of Fig. l, showing anv intermediate stage of thecrimped outer insulating sleeve engagingthel intermediate metal sleeve substantially about its entire periphery;

Fig. 5 is taken on the line S-" of Fig.' l, -showing'the outer insulating sleeve as spaced from the crimped free end' 'ofthe intermediate metal sleeve to'form insulating air gaps therebetween as indicated atV 42 and'43 in Eig l;

Fig.l 6 is a View in end elevation `ofthe connector per seg, considered asv Fig. 7 is a plan viewl of the connector, an articleror manufacture, in its marketed form before being crimped tonto the cable and showing an axial section taken on the line 7-7 of Fig. 6; and

Fig. Sisa viewin axial section of the component elements oftheconnectorlshown in Figs.A 6Aand 7 assembled in position' in' the matrixA of a die-punch machine and'showing a mandrel punch in position about to upset anend of the Vinner sleevelinto engagement with the shoulder ofthe intermediate sleeve to effect a permanent connection therebetween.

In the several viewsoflthe drawingsand 'r'efering'rst to' the. showing of 'the' stock device in Fig. 7, thereis disclosed 'anV electric terminal connector 1t) provided at one 'end with 'an apertured tang'or tongue 'llinand the other end'of which comprises a"cylindrical'portioni'Z formed of three' tubulanmembers in coaxial telescopic relation, particularry' constituting the subject-matter 'of thisdisclosu're. l The tongueincludes a narrow neckjportion 13 which forms an integral extension'from'the'inne ofthe "three'tubular members formingv the 'connector 'as liereinafter1 described.

The outer memberl 14 oflthe improvedconnectorlis a one-piece, preformed, relatively thin, molded "sleeve `of lthe intermediate rigid lining formed of nylon, and thus, as above noted, having at least some insulating properties. The end portions and 16 of the `sleeve 14 are each of cylindrical form and are of diiferent diameters, with an inclined annular shoulder 17 mid-length of the sleeve 14, integrally connecting the end portions and facing the end portion 16 of larger diameter. The nylon sleeve 14 is dimensioned in its process `of being molded so that, when stretched slightly as hereinafter described, the ends of its bore will have diameters exactly equal, respectively, to the outside diameters of an intermediate, rigid lining sleeve 18 of the assembly, and the shoulder 17 will conform more or less exactly to a t with a corresponding shoulder 19 on the in Fig. 1, the smaller provided with an inwardly-projecting annular ange 24) molded integral therewith and forming a stop for the intermediate and inner sleeves of the connector in those cases where such a stop flange is prescribed.

The nylon sleeve 14 is initially molded to have an internal diameter slightly less than the external diameter sleeve 18, and originally the sleeve 14 has the unorientated and substantially unstressed characteristics of molded nylon. The part of the nylon sleeve 14 which telescopes the lining sleeve 18 is stretched slightly as it is located in place. This has the effect of initially working the stretched part radially at least to a limited extent so that, when so stretched, it evidences a greater mechanical strength and a greater resistance to an electric break-down than would be the case if it were not so stretched. At this point the nylon sleeve evidences some plastic memory and in its tendency to shrink to its molded form it adheres to the intermediate `sleeve and in its frictional engagement therewith tends to resist accidental separation therefrom in an axial direction.

The intermediate sleeve 18 has a length in its end 21 of reduced diameter, extending for the length of the corresponding end portion 1S of the outer sleeve, and in its end 22 of larger diameter terminates in spaced relation to the wide-open end of the large diametered portion 16 of the louter sleeve to form an overlap area 23 preferably of sufficient axial length to eliminate, or, at least, tend to eliminate possibility of flash-backs between the inserted cable and articles exterior of and adjacent tothe connector. The inner surface of the nylon sleeve 14 and the outer surface of the copper-alloy sleeve 18 are made smooth at their areas of contact forming the joint 24 therebetween so as to offer, in so far as the surfaces are concerned, minimum resistance to any relative creeping of these members during the subsequent crimping step.

The inner sleeve 25 of the connector is integral with the neck 13 and tongue 11 and is formed as shown in Fig. 6 by bending winged extensions thereof about a mandrel into a closed tube or sleeve 26 with its free edges meeting to form a closed joint 27.

' As shown in Fig. 7, the inner sleeve 25 is a straight cylinder and has initially a press t in the end 21 of reduced diameter of the intermediate sleeve. The purpose of this press fitting of the parts is to prevent opening of the joint 27 when the connector is crimped onto the cable as hereinafter described. The presence of any such open joint would form a crack into which strands of the wire conductors might extend, with resulting impairment of the desired good mechanical and electric contacts. Maintaining the joint closed defeats any such possibility. Initially, the extension 29 does not contact the intermediate sleeve 18 and its conical throat has an angle less than its punch angle as finally formed and shown in Fig. 7. As initially assembled the prestretched nylon sleeve 14 is fast on the intermediate metal sleeve 18 and the sleeve 18 pressatitted on the inner wire-barrel or sleeve `The connector as an article of manufacture is formed in a three-step operation, which steps may take place simultaneously in a die-press operation. First, the,in

termediate copper-alloy sleeve 18 is gently forced against any incidental frictional resistance, with its smaller end in advance, into the momentarily stretched outer nylon sleeve 14 and until the shoulders 17 and 19 abut as shown in Fig. 8. The stretched insulating sleeve is then permitted to contract into a resilient engagement with the sleeve 18. At this time the insulating sleeve and intermediate sleeve are retained in their positions as so set by reason of the tendency of the nylon sleeve to recover its molded configuration with resulting frictional engagement between it and the sleeve 18, and this is sucient to resist any accidental relative separation.

The assembly of the insulating sleeve and intermediate sleeve is inserted in the cavity or matrix a of a diepunch machine fashioned to receive the same as shown in Fig. 8. The inner sleeve 25 is located snugly within the bore of the sleeve 18 approximately in the position it will assume in the completed structure, with its internally tapered free end spaced slightly from the shoulder 19 and its opposite end positioned against or almost against a stop wall b forming the bottom of the cavity.

The die-punch machine includes an upsetting punch or mandrel c movable with its line of thrust coinciding with the axis a*b of the connector. The advance end of the punch is provided with a long cylindrical head d whose diameter is either exactly that of the diameter of the bore 28 of the inner sleeve or of a very slight increase in diameter to force-tit the inner sleeve 25 against the intermediate sleeve, care being exercised not to open the joint 27. The head d is thus `designed of sufficiently small diameter so as to avoid any material expansion of either the inner or intermediate sleeve, as the intent here is to leave these tubular members substantially as originally dimensioned and in their press-t relation. The punch is provided at the inner end of its cylindrical head with a shoulderaforrning enlargement e for upsetting the end 29' of the sleeve 25 to form ange 29 in permanent contact with and conforming in contour with the shoulder 19,. and thus form the wide-open funnel-forming throat 31 shown in Figs. l and 7. In the instant case shoulders 17 and 19 extend at an angle of about 45 degrees with the axis a-b, and the enlargement e likewise extends at an angle of 45 degrees. This means that the extension 29', Fig. 8, has been spread open by the axial advance of the punch from its initial 30 degrees internal Hare into a 45 degree angle with some incidental thinning of the throatforming flange 29 at its outer perimeter as shown in Fig. 7.

In use the cable C is first prepared by stripping back its insulation I to expose an end of the conductor wires W forming its core. is inserted into the large intake end of the connector until the insulation I abuts against the inclined flange 29' and which forms a stop for limiting the insertion thereof. By the use of suitable crimping tools a squeeze pressure is applied to the diametrically opposite sides of the outerv nylon sleeve rst in the region of its smaller diameter, Aalong the pressure lines indicated by the long arrows in Fig. l and thus along the section line 3-3, to transmit the pressure through the three tubular members, deforming the outer nylon sleeve 14 into an interlocking engagement with the intermediate sleeve 18, deforming the intermediate sleeve into an interlocking engagement with the inner sleeve 2S, and deforming the inner sleeve into a permanent crimping engagement with the exposed Wires, somewhat following conventional practice in this respect. rEhen a relatively light squeeze pressure is applied in the plane represented by the short arrows at the right of Fig. 1, thus along the section line 5-5, to transmit pressure through the two tubular members, deforming the outer nylon sleeve into an interlocking engagement with the intermediate sleeve 18 and deforming it into permanent engagement with the cable insulation I. At this time, the right end portion of the nylon sleeve 14 is free to creep towards the right without resistance from the in-4 termediate sleeve 18, which is also free to distend slightly` to the right as may be necessary. j i

The stripped-back end of the cable 'Of course, the cross sectional configuration ofithe 'assembly offFig. 1 in the areas crimped will atleast Vinitially take the form imposed vthereonby the work faces of the crimpingdies or tools. -In the case vherein illustrated the connector is squeezed'between,power-operated dies. The dies which operate along 'the 'line 3 3 have at faces, while those which operate along theline '5-5 have faces with opposing dat arcs and whose faces on opposite sides of the arcs are slightly spaced apart when the dies are in theirpositionof nearest approach.

Considering the init'ally dead soft, copper inner sleeve 25, the disclosure features the use of sufficient cross section of material such as may be necessary to carry the Voltage for which the device is designed, and this, in turn, calls `for the relatively thick-walled wire-barrel or sleeve 2'5 Vherein disclosed. While there is some slight axial elongation of the inner sleeve 25, incidental to the crimping operation, any such axial elongation vis dimensionally about the same as that of the intermediate sleeve 18, so that there is no noticeable Vseparation of thecopper and copper-alloy members. The inner sleeve 25 is not only deformed radially and slightly in an axial direction, but themetal'is coined as the result of the crimping, so that in its viinal form the part `forming the inner sleeve 25 of the connector is harder and stronger as it reaches its final contour than when initially rolled into its cylindrical form as shownl in Fig. 6.

'It will thus be seen that in the `final connector-cable assembly vas shown in Fig. 1 the relatively tough but thinwalled intermediate sleeve 18 is permanently secured at one end to the inner, dead soft copper wire-barrel or sleeve 25 by reason of being crimped thereto in the act of crimping the member onto the exposed ends yof the wires forming the core of the cable. The free end of the sleeve 13 in the portion projecting beyond the wirebarrel or sleeve 25 is permanently secured to the insulated part of the cable, so that the insulation I is tied by the sleeve 1S immovably to the inner sleeve 25 and thus to the bared 4ends of the wires W. In this way any pullapart load on the tongue v11 and cable C will be resisted by both of the crimpings in the planes 3-3 and 5-5 and by the non-distensible intermediate sleeve 18.

Reverting to aconsideration of what takes place during the first squeezing operation, it is noted that the application of pressure on the nylon sleeve tends to elongate both the outer and intermediate sleeves in-both axial directions from the ,plane of the applied pressure indicated by the lQrlg arrow. The .elongation of .the nylon sleeve 14 will be slightly-greater than the elongation ofthe intermediate sleeve 18. As the 'adhesion between the nylo-n sleeve and the` intermediate sleeve is simply that of the initial frictional snug t,.and as the'crimping force must be sufficient to deform the innermost relatively thick coppersleeve 2S, Stuchforce is .sufficient to overcome any frictional resistance .to :relative elongation, 'and the nylon sleeve is free t o readjust ,itself .by creeping valong the surface of the intermediate sleeve 13 without lany noticeable resistance tothe deformation of either of the sleeves. Nylon is capable of being stretched up to five hundred per cent of its'original length. In this way there is avoided any tearing action `of the nylon insulating sleeve, such as would occur-if the insulation were-bonded to the metal sleeve 18. As ythe kintent here is to provide sufficient cross section of material in the insulating sleeve 14 under all service conditions to lgive it the requisite insulating shielding, it is tothe vnoted rthat in molding the sleeve vit be made sufficently :over-size as to itscxtern'al diameter to compensate for any such thinning as -may result from the elongation imposed Ythereon lby the crimping step.

`As the `result of subjecting the initially cylindrical form F of1nylon sleeve tothe squeezing effect of the crimping tools, :the sleeve 14, in the region of the plane indicated bythe section 3-'3, changes from a cylinder into an allover-elliptical form `in cross section, as shown in Fig. 2. At the same time the cross-section-ofmaterialat the point of greatestsqueeze, tends lto Ithin out so that there is "a section ofleastthickness at32. Apparently,'thereis'some cold flow of the plastic, so thatthe roundedends 33, y34 are of lgreater sectionofmaterial than when'intheiriinitial molded Vandislightly distended form.

The inner and intermediate sleeves 2S'andl8take thel constricted-'waistform-with the strands ofthe conductor compressed and `incidentally deformed from 'their 'wire configuration as retained exteriorly of'thecrimpedareas.

Theintermediate sleeve 18 is not materially changed'in its cross section of material, more or lessmaintainingits initial thickness, Vbut the soft copper 'inner sleeve 25 lof -the connector tends to'thin out slightly in the-portion 35'subjected'to the greatest pressure as maybe observed in`Figs. 2 Vand 3, and `there-is some cold ow'of'the copper therefrom into the rounded ends 36. As the result of this action both the intermediate and inner vsleeves become worked and thus coined, with anincrease in strength in the portions so crimped. Of course, the thinned out midportions 32 of the nylon sleeve 14 when squeezed'bythe crimpingtool follow the intermediate sleeve18, or, rather, advance inwardly with it and momentarily adhere tothe same,'as shown in Fig. 2. Thereafter, the deformed nylon sleeve graduallyand slowly recedes outwardly away from the intermediate sleeve 18. The outward recession of the nylon sleeve 'becomes greatestat its point of greatest inward deformation, so that the space 37 forms gaps of greatest width in the .line of the squeeze load, and these gaps, top and bottom, as shown in Fig. 3, gradually reduce in width ktowards points 3S, 'four being shown in Fig. 3. The rounded ends 33, 34 of the nylonsleeve "14 move outwardly slightly along the major axis of the ellipse away from the rounded ends vof the intermediate sleeve 1S to 'form relatively thin secondary end gaps'39.

rThe gaps

37 and 39 are in intercommunication and coact to vform in elect a single .clearance and thus 'anair 'insulating space .between the outer nylon sleeve 14 and the intermediate crimped sleeve 18.

A similar void is established in the region of the squeeze load imposed on the .cable insulation JI in the plane 5-5, Fig. l. As this portion of the connector is squeezed between the faces of crimping dies or tools, the squeeze pressure acts .through the nylon sleeve Vand through the sleeve 18 to compress the cable insulation at least slightly. At .the same time the sleeve 18 .becomes deformed from its initial cylinder into a formresembling in its midportion a fiat ellipse provided at diametrically opposite sides with side portions bent back upon themselves to form

side ribs

40, 41. At this time the nylon sleeve 14 conforms somewhat to the winged contour of the sleeve '18, at least as long as the assembly is under load from crimping apparatus and, in general, the parts take the form shown in Fig. 4. Thereafter the nylon sleeve, in to its initial molded shape, -distends `outwardly andseparates from the intermediate sleeve 18, and thus forms an upper, internal, air-insulating clearance 42 and a-similar lower, internal, lair-insulating clearance 43, as best shown in Fig. 5. Apparently there is not always a complete recovery of the nylon sleeve 14 .either back `to its cylindrical form as molded nor even into its elliptical form resulting from the crimping operation for remnants of the die impressions are often still present after along period of time as four shallo-w indentations 44, shown greatly enlarged.

Considering the finished device as shown in Fig. 1.

it is seen that in order for a dash-over or a tracking ofelectric current tooccur it would have to traversea path from the energized wires W through the inner wire-engaging sleeve 25 and intermediate sleeve 18 to the y'exterior 4of the insulating sleeve 14, lapping about the .open cable-receiving end thereof. mediate sleeve 1S yis not intended to be a particularly good conductor, it i-s possible that the overlap area 23 covered :as 'it more or less is A-by' the insulation lI,-

its inherent tendency to revert more or lessl Realizing that the inter-w -placed on the gap 23 to avoid will tene torpr'eve'nt flash-backs at the open end of the connector. However, the intermediate `sleeve 18 does constitute a conductor and dependence cannot always be dash-backs from the open end of the insulating sleeve 14 to the adjacent edge of the sleeve 18, especially in the presence of currents of high voltage. Tracking which may occur in the presence of currents of low voltage is more likely to develop and, also, possibility of tracking is more likely to occur after the connector has been in use for a long time and where environmental climatic conditions tend to provide an electric path about the insulating sleeve 14 both exteriorly and interiorly. One such possible path is shown by the dots 45 in Fig. l leading from the outer perimeter of the insulating sleeve 14, about its edge encircling the cable insulation I, and then along the inner wall to the point where the sleeve 18 bends inwardly away from the insulating sleeve 14 at about the plane 4-4.

In effect, the presence of the

air spaces

42 and 43 lengthens `the overlap 23 by the distance between the end edge of the sleeve 18 and the plane 4-4 and in this way any leakage path is elongated.

While the

air spaces

37 and 39 are not in the path of any electric tracking, it is noted from the showing in Fig. 3 that these spaces practically encircle the intermediate sleeve, supplement the insulating eifect provided by the outer insulating sleeve; and thus contribute to the provision of a thin insulating sleeve while avoiding electric current penetration therethrough.

These air gaps are eachof some material length meas ured in the direction of any such electric flash-over or tracking and being either iilled with air, or more possibly, in the case of the spaces 37, forming vacuum spaces, function as electric insulators, defeating any possibility of Hash-overs or tracking even in the absence of the flange 20.

While the invention has been illustrated and described with respect to a preferred embodiment thereof, it is to be expressly understood that various changes and modifications may be made therein without departing from the inventive concept underlying the same. Therefore, the invention is not to be limited except insofar as is necessitated by the prior art and the scope of the appended claims.

I claim:

1. In the art` of crimping an electric connector onto a conductor therein, wherein the connector comprises three preformed members in telescopic relation, the inner member being a sleeve of highly conductive malleable metal fashioned toform mechanical and electrical engagement with a conductor therein, the intermediate member being a sleeve of thin malleable metal and the outer member being a sleeve formed of insulating material having plastic memory and capable of automatically distending outwardly towards its original configuration when free of inwardly deforming forces, and wherein the outer `Sleeve initially has an internal diameter slightly of the intermediate sleeve, in momentarily stretching the gouter sleeve, drawing the outer sleeve while so stretched over the intermediate sleeve to cause theouter sleeve to engage the intermediate sleeve friction'ally but otherwise free to creep thereon, subjecting the connector s'o assembled for a limited length area so squeezed to recede outwardly by virtue of its plastic memory from the inwardly deformed portion of theintermediate sleeve, thereby to f'or'm an air spac between the outer and intermediate sleeves at the place so deformed while permitting readjustments to take place automatically between the outer and intermediate sleeves.

2. In the art of crimping an electric connector onto a conductor therein, wherein the connector comprises three performed members in telescopic relation,I the inner member being a sleeve of highly conductive malleable metal fashioned to form mechanical and electrical engagement with a conductor therein, the intermediate member being a sleeve of thin malleable metal and the outer member being a sleeve formed of insulating material having plastic memory and capable of automatically distending outwardly toward its original configuration when free of inwardly deforming forces, and wherein the outer sleeve adheres to said intermediate sleeve frictionally and is otherwise free to creep thereon, the method which consists in subjecting the connector for a limited length thereof to a crimping squeeze force applied from the outside through all three sleeves, with a force suilicient to bend inwardly both the inner and intermediate sleeves beyond their respective elastic limits and thus permanently de form the inner sleeve into a crimped engagement with conductors therein and thus to deform both the inner and intermediate sleeves into an interlocking relation, subjecting the outer sleeve and the intermediate sleeve at oney end thereof to a crimping squeeze force applied through the outer sleeve with a force sulicient to bend inwardlyl the end of the intermediate sleeve beyond its elastic limits, and releasing the connector from all deforming forces acting thereon to permit the outer sleeve in the areas so squeezed to recede outwardly by virtue of its plasticl memory from the inwardly deformed portions of the intermediate sleeve, thereby to form an air space between the outer and intermediate sleeves atthe two places so deformed,

3. An electric connector including three tubular mem bers in telescopic relation and comprising an inner sleevefrictional engageotherwise free to leable metal and of less electric conductive capacity than the inner sleeve, said inner and intermediate sleeves being mutually deformed inwardly each beyond its elastic limit to connect the same permanently into a crimped relation, and the outer member constituting a premolded sleeve formed of a plastic insulating material capable of transmitting squeeze forces therethrough without rupturing to effect such mutual deformation of the inner and intermediate sleeves, said outer sleeve having plastic memory and capable of distending outwardly towards its molded form when free of such squeeze forces, and said intermediate and outer sleeves spaced apart at the portion sov crimped to form an air space therebetween by reason of the outer sleeve receding outwardly from the intermediate: sleeve by reason of its plastic memory and the side of the outer sleeve forming said air space forming a tracking' path.

5. In a device of the class described, an insulated cable having `a bare end of its vconductor projecting beyond its 11 insulation, alterminal connector formed of three telescoping tubular members with the conductor bare ends locatedwithin the innermost member, an intermediate sleeve of malleable metal having one end portion thereof proiect-ing beyond the innermost member, telescoping the insulation of the cable and having said end portion permanently bent inwardlyon the cable insulation, and the outer member beingA premolded approximately to shape and formed of a plastic insulating material having plastic memory and capable of distending outwardly towards its molded formy when free of inwardly-directed deforming forces, with the inwardly bent end of the intermediate sleeve andthe outer plastic member spaced apart to form an airspace therebetween with the part of the plastic member'facing said-space forming a tracking path.

6. VIna device of the classl described, the combination of an outer sleeve of insulating material, a metal tube within the bore of the outer sleeve and in part lining the same, one end of the metal tube being spaced axially inwardly from'thel adjacent end of said outer sleeve to form the outer sleeve with an overlap area providing initially a relatively short tracking path on the inner surface of the outer sleeve, the end of the inner tube at said overlap area being bentv inwardly away from the outer sleeve to formv a space therebetween to lincrease inwardly the length of said short tracking path.

7. In a device of the character described, an insulated cable having a bare end portion of its conductor extending beyond its insulation, a terminal connector formed of three telescoping tubular members as a unit with the bare end portion of said conductor intruded within the innermost member of highly conductive metal, an intermediate member of relatively thin malleable metal having one end portion thereof extending beyond the adjacent free end Vof said innermost member and telescoping the insulation of said cable, said innermost member comprising a tongue and a barrel portion coextensive therewithfwith its said adjacent free end upset within said intermediate member to secure said members against relative movement, and a premolded outer member of liexible insulating material having lastic memory and capable of receding substantially toward its molded form when free of inwardly-directed deforming forces, said innermost member being crimped on the intruded portion of said conductor through said outer member and said extended end portion of said intermediate member being bent inwardly on said cable insulation through said outer member at diametrically opposite points thereon whereby the said extended end portion of Vsaid intermediate member is spaced in part frornportions of the inner periphery of said outer member to lengthen a tracking path thereon'.

8. In an electric terminal connector comprising a plurality ofV telescopically arranged members, the combination of an inner sleeve or" highly conductive metal including an'integral tongue portion, an intermediate sleeve of thin ductile metal having a common wall thickness throughout and opposite end portions of differing diameters forming a shoulder therebetween, said inner sleeve havinga press-tit in one end portion of' said intermediate sleeve with its intruded'free end upset against the inner face of said shoulder to securesaid sleeves against relativeV movement, and an outer sleeve of molded insulating material having a force f1t on said intermediate sleeve with one end portion thereof extending beyond the free end of said intermediate sleeve, said inner sleeve being adapted to be crimped on a bare end portion of an insulated conductor and the free end portion of said intermediate sleeve deformed inwardly on the insulating sheath' of said conductor through said outer sleeve, said outersleeve having plastic memory and capable of receding substantially to its original form when released from inwardly-directed deforming forces whereby portions of said outer sleeve are spaced from deformed portions of saidintermediate sleeve to provide an air space therebetween, the majorV portion of said outer sleeve remaining l2 at all times in tenacious frictional engagement with said'v intermediate sleeve but free to yield thereon in response to inwardly-directed deforming forces.

9. in an electric terminal connector comprising a plu-- rality of telescopically arranged members, the combina tion of an inner sleeve of h1ghly conductive metal including an integral tongue portion coextensive therewith, an intermediate sleeve of thin ductile metal having aA common wall thickness throughout and opposite end portions of diifering diameters forming an inclined shoulder therebetween, said inner sleeve having a press-tit in the reduced end portion of said intermediate sleeve with its intruded end upset on said shoulder therein to secure said sleeves against relative movement, and an outer sleeve of molded insulating material having a force t onV said intermediate sleeve with one end thereof extending beyond the free end of said intermediate sleeve, said inner sleeve being adapted to be crimped on the bare end portion of an insulated conductor through said outer sleeve, and the free end portion of said intermediate sleeve deformed inwardly on the insulating sheath of said said intermediate sleeve to provide an air space therebetween, the balance of said outer sleeve remaining at all times in tenacious frictional engagement with said intermediate sleeve but free to yield thereon in response to a crimping operation. Y

10. In an electric terminal connector comprising a plurality of telescopically arranged members, the combina- -tion of an inner sleeve of highly conductive metal, including a tongue portion coextensive therewith, said inner' sleeve having its free end internally-tapered to reduce the wall thickness thereof, an intermediate sleeve of thin ductile metal having a common wall thickness throughout and opposite end portions of different external and internal diameter defining an inclined annular shoulder' therebetween, said inner sleeve having a press-lit in the smallest end portion of said intermediate sleeve with its tapered free end upset on the inclined shoulder within said intermediate sleeve, and an outer sleeve of molded insulating material having a tenacious frictional t on said intermediate sleeve with one end thereof extending beyond the free end of said intermediate sleeve, said inner sleeve being adapted to be crimped through said intermediate and outer sleeves on the bare end portion of an insulated conductor when intruded therein and the free end portion of said intermediate sleeve deformed inwardly through said outer sleeve into permanent crimped relation with the insulating sheath on said conductor, said outer sleeve having plastic memory and capable of substantially receding toward its normal coniiguration when released from inwardly directed deforming forces whereby deformed areas of the outer sleeve are-spaced from the deformed portions of said intermediyate sleeve to provide an air space therebetween, the balance ofthe outer sleeve remaining at all times in frictional engagement with said intermediate sleeve and free to yield thereon in response to a crimpingoperation.

l-l. In an electric terminal connector comprising a plurality of telescopically arranged members,rthe combination of an inner sleeve of highly conductive metal including a tongue portion coextensive therewith, said inner sleeve having its free end internally tapered to reducethe wall thickness thereof, an intermediate sleeve of thin ductile metal having a common wall thickness throughout andopposite end portions of different external and internal diameter dening an inclined annular shoulder therebetweem said. inner sleeve having a press-fit in thel said intermediate sleeve, an outer sleeve of molded insulating material having plastic memory in tenacious frictional engagement with said intermediate sleeve, one end of said outer sleeve extending beyond the free end of said intermediate sleeve, and an insulated cable having a bare end cportion of its conductor intruded into said inner sleeve from the extended free end of said outer sleeve with the adjacent end of the insulating sheath of said cable intruded in the free end of said intermediate sleeve substantially in abutment with the upset end of said inner sleeve, said inner sleeve being crimped on said intruded conductor por-tion through said outer and in- 10 ing a longer tracking path.

No references cited.