US2471957A - Electrical connector - Google Patents

Description

May 31, 1949.

D. c. HUBBARD ELECTRICAL CONNECTOR Filed oct. 25, 1945 A Y INVENT'o-R. arda'd' Clfaard Patented May 31, 1949 ELECTRICAL CONNECTOR David C. Hubbard, Centrala, Mo., assignor to A. B. Chance Company, Centralia, Mo., a corporation of Missouri Application October 25, 1945, Serial No. 624,497

8 Claims.

The present invention relates to electrical connectors and is particularly concerned with an improved construction of split-bolt electrical connector of the type which is used for fastening taps, jumpers, etc., to either primary or secondary lines.

One of the defects of the connectors of this type of the prior art is that pressure which exerted upon the conductors by the connectors of the prior art is such that it causes the soit conductor material to ow out from under the gripping surfaces of the connectors of the prior art. This makes such connectors loose, even though they have been initially tightened, and, being loose, they become pitted or burned, and the sparking which results from the looseness of the connector is a source of radio interference.

One of the objects of the present invention is the provision of an improved split-bolt connector which has a greatly increased contact area so that the pressure per unit area on the conductor can be reduced to such an extent that there is no longer any marked tendency for the soft metal of the conductors to flow out from under the clamping surfaces, yet provides adequate pressure for a sound electrical contact.

Another object of the invention is the provision of an improved split-bolt connector of the class described which is provided with a resilient spring clamping member which has sufcient ileXibility and resiliency to take up any tendency toward loosening which might result from the ow of the soft metal of the conductors out from under the clamping members.

Another object of the invention is the provision of an improved connector of the class described in which the resilient clamping member is so arranged in connection with the clamping nut that neither of these parts can be lost when they are attached to the bolt.

Another object of the invention is the provision of an improved construction of split-bolt connector adapted to effect a better electrical contact engagement with the conductors to which the connectors are attached, thus reducing contact resistance.

Another object of the invention is the provision of an improved electrical connector which may be economically manufactured, which is sturdy and serviceable, and which may be used over and over again for a long period of time without the necessity for repair or replacement of its parts, and which is adapted to maintain a connection of low contact resistance for an unlimited time on-ce it has been placed in clamping engagement With a pair of conductors.

Another object of the invention is the provision of an improved electrical connector of the split-bolt type which is adapted to have its parts so locked on the conductors that vibration has no eiect in or tendency toward loosening the nut, and in which the contact areas are so greatly increased that the tendency toward extrusion of the conductors from the points between the clamping members is substantially eliminated.

An additional object of the invention is the provision of an improved split-bolt connector having elongated, hooded ends whose side walls, by extending further from the center of the bolt, will assist in reducing the tendency of the bolt to kink the conductor when the nut is being tightened, especially when the connector is applied to energized conductors.

Other objects of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the single sheet of the drawings accompanying the specification,

Fig. 1 is a side elevational view of an electrical connector of the split-bolt type shown in connection with a pair of conductors to which it is attached.

Fig. 2 is an end elevational view taken from the left end of Fig. 1 with the wires in section.

Fig. 3 is another sectional view taken on the plane of the line 3-3vof Fig. 2, looking in the direction of the arrows.

Fig. 4 is another sectional view taken on the plane of the line 4-4 of Fig. 1, looking in the direction of the arrows.

Fig. 5 is a view in perspective showing the clamping spring.

Fig. 6 is a top plan view of the bolt.

Referring to Figs. 1 and 2, I0 indicates the line conductor and II a tap-off wire which is secured to the line conductor I 0 by means of a split-bolt connector indicated in its entirety by the numeral I2.

The split-bolt connector I2 preferably comprises three parts, the split-bolt I3, the nut Ill, and the spring clamping member I5. The splitbolt I3 and the nut I 4 may be made of any suitable metal, such as brass, copper or aluminum, the metal used depending upon the type of conductors with which it is to be employed.

The nut I4 may consist of any type of threaded member having an internally threaded bore It-,

In other words, the size of the nut may be suchy that when it is engaging the spring I5, and one of the corners I9 passes the portion-:203er the spring, the corner -must press the spring inwardly and ride up slightly over the-portion 2D. V"I'hus the spring acts as a nut lock.

In other embodiments of the invention, however, the nut I4 may be smallergqits corners having no engagement with the portions 20,0f the spring I5, but its fiat upper surface 22 engaging the fiat lower surface 234m the legs of the spring.

The split-.bolt I3-maytbe1 made from a-blank which may be cast'orfdrop-forged,lor=made-by any other of theconventionalmethods. :This bolt is preferably -provided with anV elongated-head 24 which-is-best showminlFig.' 6. ".Ihishead is elongated for the purposei ofv providing it withl an increased area of contact 'in the partially cylindrical groovef25. Thus lthe head124is=morelthan twice as long as itis wide,=and\thegroove'125 extends longitudinally .of `the head on: its lower side.

The head 24 is preferably provided with. a-p1u rality of at sides, suchasgfor example,.26+33. Howevenit is not necessary thatthese-surfaces all be plane,` and 2 it -is vsufficient .if :the `twol opposed surfaces"2 1,*3l .belplanesancl-parallel so that they may be gripped byawrench.

In other embodiments of thefinvention the. head may take various shapes,.provide'd'lit` isrelatively narrow and elongatediforlthe.purposes .set.forth.

Thehead 24 supportsthe ishankill, which consists of a pair of legs-'34,f35 vseparatedby a'parallel-sided groove' 36. vl.The` groove. 36 -terminates at itsupper end adjacent the head-24 inv-thepartially cylindrical end surface 25 which entendsv up.V into the head 24. and ispreferably'substantially cylindrical throughout soas toengagea straight cylindrical wire. or substantiallyY cylindrical cable.

The size of the-partiallycylindrical grooveor the radius of this curved surface is preferablysa few thousandths of an inch less than theeradius of the wire on which-'ituisto beused-sothatas the wire or cable is-resiliently forced into the groove at the cylindrical-surfacedlthe wire can fit itself to the groove by extrudingsorne slight portion of the material necessaryifor Ithisaction in the wire, thus providing amaximumarearof Contact betweenthe wire III and :the groove e25.

It should be noted that they groovel36 yhas its sides preferably only substantiallyV parallel, as some manufacturing methods require :a small amount of draft such.as,f forexample, 1onrthe orderof five degrees .per Yside .longitudinallylwith respect to theaxis of the-bolt.

The shank I8 of -thezbolt is .substantially cylindrical and is provided withthreads: I1 andpreferably with a grooved cylindrical portion 31 which aids in locating the nut on'thebolt and in starting the nut on the threads.

The sides 38, 39 of the groove 31 are preferably substantially plane andparallel, but the groove is also preferably slightly `widened,.as indicated at 40, adjacent each lateral opening ofthe groove. This may also be accomplishedv byfmakingwthe groove sides 38, 39j slightly convex.

The threads I1 on theflegs .34, L35.0i`fshanls LI8 iii) 4 are, of course, substantially helical, being interrupted only by the fact that a. portion of the material is cut away at the slot 36.

The clamping spring I5 may be made of various types of metal, preferably spring steel or spring bronze, and if the former, they are preferably cadmium or copper plated. This spring is preferably made of sheet metal, so that itrmay be formed out of a -strip by various stamping and bending operations at a minimum expense.

The amount of resiliency of the spring is preferably -such that it may be compressed even to a solid condition without passing its elastic limit.

The -shapeof 'the spring may vary, depending upon-variousembodiments of the invention, but it is preferably of substantially the shape shown in'Figs. 3 and 4. jIt has a pair of legs 4I, 42 which are parallel to each other and located to pass through lthe bore of thenut I4 when the spring is in the bolt.

-The legs-4I, 42 may-fbevflat, lbut. arepreferably partially cylindrical, theexternal cylindricalsurface 43 conforming.substantially.to thevinside. of the nut so that there-are no sharp cornerson the spring engaging anddamaging the threads of the nut.

At the lower end of.eachleg.f4l,f42 therelis a laterally turned retaining portion 144,145, which is located adjacent the endofthe shank-.I3 when the spring is clamped onl a pair of conductorslll, Il.

Thefwidth of the stockof which the Aspring vI5 is made may vary,.but.it is ypreferablyof a Iwidth slightly narrower than the widthof the `slot.or groove 36 in the bolt.I3..so that 4the springhas a freely sliding engagement in' the :slot of 'the bolt.

At the upper end of eachzleg 4I, '42 the spring is bent outwardly and laterally. at.-4B, preferably at substantially rightfangles, .so that the radial portions 41, 48 of .the springhave theirlowerzat surfaces 23vlocatedlto `engage ltheupper at surface 22 of the nut.

At a point radially outwardly of :the nut I4, indicated by the numeral 49,' each leg ofthe spring is bent outwardlyin Fig. 3, forming anpintegral, partially cylindrical, easy bend 5D. These; easy bend portions 50;50@ are integrallyfjoinedgto the upper elongated clamping portion5 I` of ,thespring which engages the lower -side of the wire I I. This clamping portioni5I is also -formed--fwithva 4V- shaped or-partially -cylindrical=groove52 Ywhichis preferably a few thousandths of, an inch, suchas one or-two or three thousandths of an inch, 4smaller in radius than the radiusA of Ythewire.l I which it is intended to engage,

The method of assembly of vthepartslis asiellows:

The spring I5 mayhave itslegs 4 I,142.b ent,to gether far enough so that Ythe retaining janges 44, 45 clear the inner threaded portions of 'the nut and then the legs 4I;42,rnayA be inserted into the nut. Then'the clamping portion y5Igof the spring is inserted into the slot- 36 of'thenut, and the nutis threaded on'the 'shankw'l8- of'thebolt I3, the nut rotating as 'the-spring II 5l merely lslides longitudinally into the slot 36.

This operation of my split-bolt connector vis as follows:

This connector is adaptedto-be-ap-plied -to line conductorswhen energizedv by`-means-0f the improved tool which-is shown yinrny copending. application, `Serial No. .639,438, Lle'd `.lanua1y'15, 1946, entitled .Tools forapplying. connectors .to energized.. transmission :lines and. the llike. It can, of course, alsobe appliejdto- .deenergized con- 5 ductors by means of the usual wrenches and other tools.

When the connector is to be applied to the line the head of the bolt I3 is clamped in the connector tool, the tap wire II is held by a pair of `clamping members in proper position to be inserted inside the slot, and the nut I4 is held by a wrench member of the tool below and spaced from ie bolt so that the bolt can iirst be placed on the line. Then the wrench is driven upward with respect to the bolt until the nut brings the spring into engagement with the tap wire which is forced up into the slot until the nut is in position to engage the threads of the bolt.

Rotation of the tool then causes the nut to be threaded on the shank I8, the clamping spring I5 resiliently engaging the lower wire II', which is forced into the groove 52, and which forces the upper wire I into the groove 38.

It will be recalled that these wires are slightly larger by a few thousandths than the groove into which they are to be forced, and this causes the groove surfaces to have an increased contact engagement with each wire.

When the wires are subjected to a. continued resilient pressure by the nut and spring which tends to force the wires into the grooves which are one or two thousandths of an inch smaller than the wires, this pressure tends to cause the metal of the wires to iiow and to shape itself to that of the grooves.

The flow of the material of the conductors quickly ts the conductors snugly in the grooves so that the bearing area equals substantially oneiourth of the conductor surface and extends over a considerable length due to the elongated nature of the groove in the spring and elongated groove in the head.

Instead of two lines of contact, as would be the case with a V-shaped groove, this connector has two cylindrical areas of contact, these areas being also elongated.

As the spring I is compressed the bending takes place at the easy bends 50, and the spring may be compressed without injury until the radial legs Lil, 48 engage the lower surface of the clamping portion 5|.

As the nut rotates on the shank I8, engaging the threads Il, the spring I 5 slides in the slot 36. The flexibility and resiliency of the spring is such that a relatively low unit pressure is applied to the conductors, and the tendency of the relatively soft conductor material to flow out from under the clamping surfaces of the connector is substantially reduced.

In any event, sucient tension may be placed upon the spring so that any tendency of the extrusion effect on the conductors to loosen the conductors is taken up by following movement of the spring.

rihe spring also acts frictionally to prevent the loosening of the nut by vibration, and in some embodiments of the invention may actually act as a nut lock, the corner of the nut being unable to pass the portion 2l) of the spring without extraordinary rotative force applied to the nut.

While the unit pressure in pounds per square inch applied to the rconductors is low enough to substantially eliminate ow of the conductors out from under the clamping surfaces, it is still sufficient to provide an adequate pressure for sound electrical contact.

It will thus be observed that I have invented an improved connector of the class described which is adapted to be maintained in tight contact with the conductors on which it is placed so that there will be no loosening, and, consequently, no arcing or sparking or pitting or burning.

The present connector has a greatly increased area of contact with the conductors, and it also has a tendency to reduce the extrusion effect on the soft conductors beyond that required to bring the grooves into actual close contacting fit with the wires. The contact resistance of the present connector is greatly reduced over the devices of the prior art.

While I have illustrated a preferred embodiment of :my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the Unite-d States, is:

1. In an electrical connector, a clamping member comprising a standard nut provided with a threaded bore and a spring clamping member carried by said nut, said spring clamping member having a pair of legs extending through the bore of the nut and provided with outwardly turned flanges forming retaining means at their outer ends for engaging one side of the nut, the said legs having portions extending radially outward on the other side of the nut and backwardly bent and integrally joined to each other at an elongated clamping portion which is formed With a partially cylindrical groove for engagement with a wire, the said legs of the spring being provided with a partially circular, easy bend at the end of each radial portion wherein resilient bending may take place until the radial portions of the leg engage the lower part of the clamping portions of the legs without exceeding the elastic limit.

A2. A spring clamping member for electrical connectors comprising a resilient metal strip which is formed with an upper yoke having a partially cylindrical clamping surface, the said yoke carrying at each end a partially circular, easy bend which is integrally joined to a pair of inwardly and radially extending portions which are adapted to engage one of the ends of a nut, said radial portions carrying a pair of substantially parallel legs which are adapted to extend through the bore of the nut and one of said legs being provided with a retaining flange for engaging the opposite side of the nut and retaining the spring in the nut.

3. A spring clamping member for electrical connectors comprising a resilient metal member comprising a strip which is formed with an upper yoke having a partially cylindrical clamping surface, the said yoke carrying at each end a partially circular, easy bend which in integrally joined to a, pair of inwardly and radially extending portions which are adapted to engage one of the ends of a nut, said radial portions carry-- ing a pair of substantially parallel legs which are adapted to extend through the bore of the nut and one of said legs being provided with a retaining flange for retaining the spring in the nut, the said legs being partially cylindrical form and substantially concentric to the inner threaded surface of the nut to prevent damage to the threads of the nut.

4. In an electrical connector, the combination of a threaded bolt having a head anda shank,

said nut relative to the location of the easy bends 10 on said clamping member being such that the corners of the nut engage the inwardly facing portions of said easy bends upon rotation of the nut so that the easy bends act to prevent rotation of the nut after the manner of a lock nut.

DAVID C'. HUBBARD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,217,724 Dwork Feb. 27, 1917 1,714,779 Harris May 28, 1929 2,164,075 ORussa June 27, 1939 FOREIGN PATENTS Number Country Date Great Britain June 26, 1940

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