US2379567A - Electrical connector - Google Patents

Description

y 1945- s. N. BUCHANAN 2,379,567

ELECTRICAL CONNECTOR Filed Dec. 3, 1941 ATTORNE Patented July 3, 1945 Elizabeth,

that .1 ,se1n z a c aims: (or 173 269) The present invention-relates t0 zelfiqtrical connectors of the type adapted. to: be ,connected,.-toelectrical conductors for attachmentto .theQbind ing posts, other connectors,,etc., of ,ele,ctrical. devices. ,1

In thetype-of connectors in which a; substan-; tially flat contact section extends one end of a wire holding ferrule, the base oi this section where it merges into; the ferrule is often structurally weak and subjectto undesirablebending or breakingduring use.

Also, in a solderless .typeof comiector, whether formed with a seamless ferrule'or. with a pair of opposed ears folded; inwardly toiorm thelwire holding ferrule, it: is customary to, anchor the wire in the ferrule by flattening a part or all of V the ferrule.-. Any elastioreturn or subsequent bending of; these flattened portions about the fold lines between them will+loosen-the ferrule grip, on the wires. and-reduce the effectiveness of the. electrical connection-between the wiresand the ferrule;v Bysolderless as usedherein is meant connectors in whichelectrical and. mee, chanical ,connectiomhetweem the terminal pr other electricalelement and thewire or other conductor is made primarily by pressure rather than by a fusedbond 'of'solder or other ioreig n metal; it is not intended to exclude-the presence;

of solder in other.v relations orywhich maybe;

applied before these parts areassembled 0 after asolderlessconnection betweenrthem has been:- formed. l One object; of the presentinvention, is to pro-- vide a connector which is simple, durable, rugged and economical to manufacture,.:and which will efiectively withstand severe service, and meet then,

most rigid electrical requirements...,

A more specific object is to providea new, and improved connector havingv a contact base section capable of effectively withstandingi bending, stresses greater .than are incurred in practice.

A further object is to provide a new and im proved solderless. connector in; which the flattened or crimped ferrule isy efiectively:held;

against bending. and in firm grippinggelectrical' contact with the conductor wir,es.'.,-

Various other. objects of theinvention will apparent from the following particular descrip-,,

tion, and from an inspectionof-theaccompanw mg drawing,in which 1 Fig. 1 is a topplan viewofone .form'of ,7

Figa 2 I is 1 longitudinal section taken on n 2-2 elf-Fig.1.

. V oonn zoj on a I Stephen'N; Buchananywestmoreland Hills, Mil,

" assign'or' "to "Aircraft-Marine Products, -'Inc.,

. being. connected Ito a 3 statemen e we 'f i l'w i h the connector of Figs.v 1' toj3ifisshaped. F .firshowstheconnectoroi.Fi itbflaiteir WWW tcqr a cr' with the lpresentginventi Fig. 6 is a transverse 'sec tiontak n on "a longitudinal "action taken on me Fig. 8 isla .t'opplanview 'othe rfform of. connector feinbodying thgpresent inventio and shown pr" to aptachmentma on'ducr F1g,.,.91. is a longitiidinal seen n taken 'on i and. shown prior Fig.1 l l-i'sla fragmentary ,pers ectl oi the r; nect or 9f 5.Fig.'f 1.3 s qiv attached to "the" ductor.

In the f ormflof the inventionshown. in Figsl 1 to A,,a terminal lug,.-,' 'prermman from sheet-metal 'sfuchfas n'ne'aiew'cop.

a flat blank shdwninrFig". 4.- ,Thislblank a oneend .a rectangular section whichdefines '1 a pairiofhoppjosedears l, "andwhich is a' .ciaptedfv to. be rolled. into a"I,split cylindrical connector: ferrule; l. 2 .(Figs. v.1-3') fort-receiving. th ewiresf'of a conductor. 'ndjtheblanki siorrned ect onlls a'y'mgfa', stud/hole 14' trical device (not shown) .QTlieforrn 'ofijth ntmv The contact section l3 as showni p ith a'as nk. '5 Whi h-h na e ld d e e fo .t'MQ fiQ q i e. se ti i which are substantially wider than said grooves and which have substantially flat crowns in order to afford maximum ferrule area for gripping the wires, and to prevent cutting of the gripped wires. The inner side of the ferrule section at its outer end has a bevel I 8 to flare the inner surface of the inlet end of the cylindrical ferrule l2 formed from said section.

The rectangular section III of the blank is rolled as shown in Figs. 1 to 3 to form the cylindrical wire receiving ferrule I2, with its line of juncture 20 extending substantially centrally with respect to the sides of the lug.

As a feature of the present invention, the base of the contact section I! where it merges into the cylindrical ferrule 12 is wide enough to form a pair of corner braces or flanges 2| between the sides of said section and the end of said ferrule,

when the blank of Fig, 4 is shaped to form said ferrule. These corner flanges 2| desirably follow the curvature of the cylindrical ferrule l2, and serve thereby to effectively brace the lug against transverse bending across said flanges. Likewise, the cylindrical curvature may extend beyond the rectangular portion it into the shank I! as shown to further increase the resistance of the lug against bending.

I have found that by making the width of the contact section at its base where it merges into the cylindrical ferrule l2 substantially equal to the outside diameter of said ferrule, corner bracket flanges 2| of effective size are formed. Expressed in terms of blank. dimensions, such effective flanges 2! may be formed by making the width of the contact section I: where it connects into the rectangular blank section it about one-third the width of said latter section.

It should be noted that the increase in bending resistance of the lug at the base of the contact section I3 is not due merely to an increase in the sectional area of the lug at this region resulting from the increase in the width of said contact base section, but is due mainly to the shape and disposition of this area, and especially to the formation of the reinforcing flanges 2 I.

The provision of a substantially wide shank for the contact section I3 also serves to increase the current-carrying capacity of the lug with minimum amount of resistance and with avoidance of heating- The lug shown in Figs. 1 to 3 constitutes an article of manufacture which can be sold, shipped or stored as such. In clamping this lug to an electrical conductor 23 to form the unit shown in Figs. 5-7, the insulation is stripped off the end of the conductor to expose the stranded wires 24. These wires 24 are then slipped into the cylindrical ferrule i2 until the ends of the insulation abut the bevel edge 18. This bevel edge It forms a flaring mouth to permit entry of the end of the insulation into the interior of the ferrule as well as to guide the wires of the stranded cable into the ferrule; and it may also with advantage be smoothly rounded so as to eliminate any sharp corners that might cut into the wires or insulation during the ferrule crimping operation to be described.

With the conductor wires 2| inserted into the ferrule 12 as described, the ferrule is flattened or collapsed over said wires to form a solderless connection therewith.

In the collapsed condition the width of the contact section It at the region where it connects into the collapsed ferrule is slightly less than the the corner flanges 2| extending from the sides ofsaid contact section to the fold sections of said ferrule follow the curvature of said fold sections, and thereby serve to effectively reinforce the lug against transverse bending across said flanges during use.

In the ordinary construction, prior to the present invention if a ferrule were collapsed or bent onto a wire, after the ferrule bending or collapsing pressure had been released, the two ferrule ears would have a tendency to spring back or reopen outwardly slightly along their fold lines, so that the gripping action on the wires would be somewhat relaxed. Also, if the two ferrule ears were not connected together along their line of juncture, they would tend to bend outwardly along their fold lines under stresses encountered during use.

As a feature of the present invention, the ferrule I2 is crimped in such a way as to reduce the possibility of the collapsed ferrule expanding. For that purpose the ferrule i2 is corrugated on each face by a series of narrow flattened areas formed at spaced positions to give alternate fold sections 25 and 26 of different fold angles as shown. The acutely bent crimped sections 25 serve to grip effectively the wires 24 against withdrawal from the ferrule and resist more effectively any expansive return bending at the fold edge, while the less acutely bent sections 28 afford greater structural stability to the flattened side as a whole by reasons of the wider folds longitudinal of the ferrule, and the formation of comprssively strong zones bracing the fold edges against expansive bending. These less acutely bent fold sections 26 thus serve effectively to resist the outward bending of the crimped sections 25 about their fold lines.

The crimping operation may be effected by a pair of opposed similar dies (not shown) shaped in accordance with the shape of the ferrule areas 25 to be depressed, and serving to flatten the opposed sections of the cylindrical ferrule i2 and to form said areas. A suitable tool for this purpose is described and claimed in my copending application Serial No. 474,935, filed February 6, 1943, or in the application of U. A. Whitaker, Serial No. 455,039, filed August 17, 1942.

Two or more of the depressed areas 25 on each side of the ferrule are preferably provided spaced from the sides and ends of said ferrule to define the raised fold sections 26 at each end of the ferrule and between the two depressed areas 25, and also ridges 21 along thesides of said ferrule between the ralsed fold sections 26. As a result of this construction, there is formed along each fold side of the ferrule a continuous border rib, which adds to the rigidity of the ferrule, and which thereby aids in resisting the spreading or expanding of the opposed depressed wire gripping ferrule sections 25 apart.

In the crimping operation, it is desirable to form first one pair of opposed depressed areas width of the ferrule, but is wide enough so that 7 effective arid corrosion resisting contact.

5; across the crimped area thatithe'metal', rule and.- the metal;1of-;the wires' .:.w thin at. :rule are actually coined so that they 11 2 :t with no -voids;-1eftbe.twecn them. a trated in the lefte-hand.sectiona-of;Fi re celerated. .corrosiontests havei h wnwthat W terminals. madea's described above 11111161118.

- liquid does not penetrate ,intothecrimped area -..e OBpt:.-as it ay c Thus, theelectricalc i outset but issubstanti .pressure is used s I have shown by cutting s pe Etc itable crimping pressure ..an- ;.acid or othepconrosion t its:.way bins ow' rms ontact is. not only equal at its y e ually ent wi 1 n- I a hi h c imn a well solderedconnec there mayeven cold welding between the wires; and ferrule j a ticularly .in the case where tinned-wire is used or other coating of plastic me relativel highplastic flow under the crimpin pressure. .1 A

. Another surprising advantage of theconstruction justdescribed is in its extraordinarily high breaking test: With an ordinary crimped-on terminal the 4 wire tends tobe weakened so that tal which exhibits a be a eg ee 1 tweeiith heirs bi ii db essle in a th nds of he r ml 5 3m? 1 ffih on. 'onstruction', also afford.;maximum dep es d areasji so fi ive v r p-th w res a 'm x me 91 .1? i-Iei ed r sJehn the eld' ide dfthe Ja w re s n e ed ee icr ig ditycrimped; construction.shownserves alsoto lip ioal cross-secti ..serve .il lld latel the sides of the ferrule'along its fold,

edges so. -that the different successivesecti'ons of ,each, fold edge is not} in alignment. .This misit will. break atthe edge-of,the'terminal-iwith a 5 pull very much below the normal tensile strength of the wire. .With a, single crimp, ,Ihavefound licq n nc that if the crimp is, spaced at-least from the end ofzthe ferrule andthe crimp made substantially as; shown,- a pull testbf ,flPP DX 30 mately 90% vof the normal tensilejstrength ,ofthe wire is attained and this falls off rapidly 1 as :the

edge of the crimp approaches closer than /1 ;of

an inch tothe edge of the ferrule, droppingto as o e l 50% or less if the crimp actually overlaps theedge 35 with a sharp edged ferrule. If the; crimp -:25

,which is; closest tothe lug 13-isgmade flrstand the crimp closest :tothe; length, of the wire is, made; a last, and; particularly i if the la e is maderund a lesser pressure thantheformer the-pull testca be even further increased, since =under;;-these.circumstanc the latter crimp :takes a-asupprting holdon he wire yieldable tolessthan the-;break- 1 ing i mw r thecr mp l s stt thelu 13 lds w t r-a ennyiel i e-erip ,and th reb the tension is apparently distributed; between the twogor morecrimps. 1 1 r.

If a single tool is used for making both or all of the crimps simultaneously it is desirable that it should be designed so as to make the deepest crimp at a point more removed from the edge'of ferrule which is toward the length of the wire and to make successively shallower crimps as that edge of the wire is approached. This is more particularly described and claimed in a copending application filed by Uncas A. Whitaker, August 17, 1942, Serial No. 455,039.

Advantageously, the line of juncture 20 extends centrally across the crimped areas so that on [alignment of the successive section of thejffold I edges aids in, resisting the expansive lfbending of v the wire gripped crimped ferrule section .25....

i T e c rru ti nst op o ed acn 'S 'l facescf the ferrule formed by. theI-alternateldepressed and raised ferrule se,ctiohs; and .26,

serve not 7 only to. holdthe "ferr ule as described against relaxing outwardly, but also serve .to wrinkle the wires 24 in said.ferrule ..This wrin- .kling, of [the wires .24, assists; in preventing vsaid res from being pulled outof the ferrule..

In an alternative form shown in -Figs. e

herein, the ferrule isof laminatdconstruction,

and before, attachmenttofthe conductor ,23 comprisesfthe split, cyclindrical part l 211 integral with the terminal lug section 13a, and- ;a thin v cylindricalseamless sleeve 35 of suitable metal, such escopedover said part with a snug lit as; shown in Figs. 3 and-9. This sleeve5is ;substantially co extensive, in len'gth :with the ferrule-part I3a, and; is preferably, retained against axial movement on said partby an inturned spun rim 3; at, one end; of said sleeve embracing the ypinch ing at 31; at its other'end.

correspending rim ofsaidpai-t, andby afsl ight The contact section 13a is shown shapedilwith perin shen sside i andi wie no at its base ire-d m. reinfo c n r ersfi n e L? I f the purpose. described withreference to the corner a'nee in the .c hs i of;

Figs. 1- 8 and 91forms a h a s w no n n Fi s is .com ite unit.) which can ,be sold, shipped and neither side will the stock of the ferrule have to 60 act with an effective cantilever arm greater than one-half the width of the crimped ferrule.

As a further protection against the reduction in tensile strength by crimping, the edge of the points may be cut ofi' by short parallel sides 28,

stored as such. The ferrule liaf35 can be fitted over the bare conductor wires 24, and crimped thereon with alternate depressed and raised sections a and 26a in a manner already described with reference to the construction of Figs. 5-7.

The crimped ferrule part I20. being comparatively thin will be effectively clamped on the wires 24 against expansion. The crimped seamless sleeve will cover the split 20a of the ferrule part I3a and will thereby assist in holding said part against relaxing its grip on the wire, and also will prevent the wires 24 in said part from escaping into or through the split 20a during crimping. Also, this sleeve 35 enhances the neat appearance of the connection.

In Fig. 11 is shown an alternative one-piece construction in which the lug is provided with a second cylindrical split ferrule 40, which is secured to the wire gripping ferrule l2 by an integral connecting piece 4 I, and which is coaxial with said ferrule l2. This second ferrule 40 is larger in diameter than the wire gripping ferrule l2 so as to snugly receive the insulated part of the conductor 23 (Fig. 12).

In clamping the lug of Fig. 11 to the conductor 23, the lug is slipped over the end of the conductor with the ferrule 40 embracing the insulation, and

the ferrule l2 embracing the bared wires. The two ferrules I 2 and 40 are then flattened over the conductor, as shown in Fig. 12.

In Fig. 13 is shown an alternative form of composite lug in which a cylindrical sleeve 35a similar to that shown in Figs. 8-10 extends beyond the ferrule part [2a to embrace a substantial portion of the conductors insulation. The composite ferrule l2a, 35a is crimped over the bare wires 24 to form the alternate depressed and raised sections 25a and 26a, while the rear projecting section of the sleeve 35a extending over the insulation may be left cylindrical, simply flattened thereon or may be crimped as in the case shown in Fig. 12. A hole or opposite holes 42 in the rear projecting section of the sleeve 35a may be provided to serve as an inspection window.

As more particularly described and claimed in a companion application, the gripping power of such a flattened ferrule on a stranded wire increases with increased thickness of the metal in the ferrule only up to a critical thickness. Any greater thickness, which may be found desirable on the one hand, e. g., to impart a necessary structural strength or electrical conduction will be undesirable on the other hand because of the reduced eifectiveness for tightly gripping the wires 24. The thicker ferrule not only is more difficult to crimp tightly onto the wire, but also has greater resilient return after the release of the crimping pressure.

As set forth in said companion application, one way in which this condition can be remedied is by making the ferrule comparatively thick, but reducing its thickness to approximately the critical optimum thickness at the opposite sections where it is to be folded when crimped onto the wire. As will be apparent, the combination shown in Figs. 8-10 and 13-14, is well adapted to use with this invention, both the inner split ferrule H and the seamless ferrule 35 being of less than the critical thickness, whereas taken together they may be of thickness greater than the critical thickness.

In all of the alternative embodiments described, the lug will form a strong electrical connection, capable of withstanding severe service and of meeting the most rigid electrical requirements. This desirable result is obtained without the use of solder, and by comparatively simple expedients,

which do not add materially to the cost of manufacture or impair the ease of attachment to the-- conductor.

As many changes may be made in the above construction, and many apparently different embodiments of this invention may be made without departing from the scope of the invention, it should be understood that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What, is claimed is:

1. An electrical connector of the type intended to be crimped onto an electrical conductor and including a terminal contact portion and a rolled ferrule portion integral therewith having a seam formed by two abutting edges where they are brought together into cylindrical shape for receiving the wire of the conductor, and a seamless sleeve telescoped over and embracing said ferrule portion; said contact and ferrule portions being formed of'a highly conductive, relatively soft material, and said sleeve being formed of a relatively flexible material resistant to stretching and being relatively thin with respect to the material of said ferrule portion.

2. An electrical connector of the type intended to be crimped onto an electrical conductor and including a terminal contact portion and a rolled ferrule portion integral therewith having a seam formed by two abutting edges where they are brought together into cylindrical shape for receiving the wire of the conductor, and a seamless sleeve telescoped over and embracing said ferrule portion; said contact and ferrule portions being 40 of said ferrule portion,

formed of a highly conductive, relatively soft material, and said sleeve being formed of a relatively flexible material resistant to stretching and being relatively thin with respect to the material said sleeve overlapping beyond the end of said ferrule portion remote from said contact portion, whereby said ferrule portion may be positioned over the stripped end of a conductor with said remote end of said ferrule portion abutting the end of the insulation sheath on the conductor and with said sleeve overlapping and embracing the end of said insu-, lation sheath.

STEPHEN N. BUCHANAN.

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