US2674725A - Electrical connector - Google Patents

Description

April 6, 1954 S. N. BUCHANAN ELECTRICAL CONNECTOR Original Filed June 28, 1949 I NVENTOR. gepfiem M fiacamm q l v6 Patented Apr. 6, 1954 ELECTRICAL CONNECTOR Stephen N. Buchanan, Westmoreland Hills, Md.,

assignor to Aircraft Harrisburg, Pa.

-Marine Products Inc.,

Original application June 28, 1949, Serial No. 101,839. Divided and this application May 29, 1951, Serial No. 228,789

1 Claim. 1

The present invention relates to electrical connectors of the type adapted to be connected to electrical conductors for attachment to the binding posts, other connectors, etc., of electrical devices. It is a division of my application Serial No. 101,839 filed June 28, 1949 now abandoned which is a continuation-impart of my application Serial No. 570,004 filed December 27, 1944 now abandoned which is a division of my application Serial No. 421,408 filed December 3, 1941, Patent No. 2,379,567, issued July 3, 1945.

In a solderless type of connector, Whether formed with a seamless ferrule or with a pair of opposed ears folded inwardly to form the wire holding ferrule, it is customary to anchor the wire in the ferrule by flattening a part or all of the ferrule. By solderless as used herein is meant connectors in which electrical and mechanical connection between the terminal or other electrical element and the wire or other conductor is made primarily by pressure rather than by a fused bond of solder or other foreign metal; it is not intended to exclude the presence of solder in other relations or which may be applied before these parts are assembled or after a solderless connection between them has been formed.

It is an object of the present invention to provide a solderless connector which is simple, durable, rugged and economical to manufacture, and which will effectively withstand severe service, and meet the most rigid electrical requirements.

A further object is to provide a new and improved solderless connector in which the flattened or crimped ferrule effectively holds in firm gripping electrical contact with the conductor wires.

Various other objects of the invention will be apparent from the following particular description and from an inspection of the accompanying drawings, in which:

Figure 1 is a top plan view of one form of connector embodying the present invention, and here shown prior to being connected to a conductor;

Figure 2 is a longitudinal section taken on line 2-2 of Figure 1;

Figure 3 is a transverse section taken on line 3-3 of Figure 1;

Figure 4 is a plan view of a blank from which the connector of Figures 1 to 3 is shaped;

Figure 5 shows the connector of Figures 1 to 3 after being connected to a conductor in accordance with the present invention;

Figure 6 is a transverse section taken on line 86 of Figure 5; and a Figure 7 is a longitudinal section taken on line 'l! of Figure 5.

In the form of the invention shown in Figures '1 to 4, a termina1 lug is preliminarily stamped from sheet-metal such as annealed copper into a flat blank shown in Figure 4. By preliminarily stamped from sheet metal I mean that the cutting and punching of the blank to give it the external configuration is done by stamping methods as well as the formation of the surface grooves and the edge beveling visible in Figure 4 regardless of the sequence of the stamping steps should more than one be employed. This blank has at one end a rectangular section In, which defines a pair of opposed ears II, and which is adapted to be rolled into a split cylindrical connector ferrule 12 (Figures 1-3) for receiving the wires of a conductor. At its other end the blank is formed with a contact section l3 having a stud hole [4 for attachment to the binding post of an electrical device (not shown). The form of this contact section is not essential to the present invention, and is merely shown as representative of any desired electrical device which is to be connected to the wire.

The contact section 13 as shown is provided with a shank I5 which has parallel side edges but which, for the purpose of the present invention, may be of any other suitable shape.

The inner surface of the ferrule section I 0 is stamped to form thereon a series of fine parallel grooves [6 extending across its full width, and defining a series of wire gripping ridges H, which are substantially wider than said grooves and which have substantially fiat 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 is swaged to form a bevel l8 to flare the inner surface of the inlet end of the cylindrical ferrule I 2 formed from said section.

The rectangular section it of the blank is rolled as shown in Figures 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 l3 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 Figure 4 is shaped to form said ferrule. These corner flanges 2| desirably follow the curvature of the cylindrical ferrule I2, and serve thereby to brace'efi'ectively the Iugagainst transverse bending across said flanges. Likewise, the cylindrical curvature may extend beyond the rectangular portion l into the shank l as shown to increase further the resistance of the lug against bending.

The lug shown in Figures 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 Figures 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 l2 until the ends of the insulation about 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 is with advantage swaged to a smoothly rounded contour so as to eliminate any sharp corners that might cut into the wires or insulation during the ferrule crimping operation to be described. Furthermore, by producing the smoothly rounded contour of the bevel at I8 by swaging a step is saved as compared to producing the same type of surface by machining for it has been found that a machined surface is so rough as to cause wire damage unless it is polished before use, whereas by the swaging method the requirement for a polish ing step is eliminated. Furthermore, soft copper, which is a very satisfactory material from which to make connectors, is very diflicult to machine whereas it is quite amenable to stamping and swaging operations.

With the conductor wires 24 inserted into the ferrule I2 as described, the ferrule is flattened or collapsed over said wires to form a solderless connection therewith.

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 12 is corrugated on each face by a series of narrow flattened areas formed at spaced positions to give alternate fold sections 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 26 afford greater structural stability to the flattened side as a whole by reason of the wider folds longitudinally of the ferrule and the formation of compressively strong zones bracing the fold edges against expansive bending. These less acutely bent fold sections 25 thus serve effectively to resist the outward bending of the crimped sections 25 about their fold lines.

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 the sides of said ferrule between the raised 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 apart or expanding of the opposed depressed wire gripping ferrule sections 25.

A surprising advantage of the construction just described is in its extraordinarily high breaking test. With an ordinary crimped-on terminal the yvire tends to be weakened so that it will break iii at the edge of the terminal with a pull very much below the normal tensile strength of the wire. With a single crimp on the connector described above, I have found that if the crimp is spaced at least of an inch from the end of the ferrule and the crimp made substantially as shown, a pull test of at least of the normal tensile strength of the wire is attainable. If the crimp 25 which is closest to the lug I3 is made deeper than the crimp closest to the length of the wire the pull test can be even further increased, since under these circumstances the latter crimp takes a supporting hold on the wire yieldable to less than the breaking tension, whereas, the crimp closest to the lug l3 holds with an unyielding grip and thereby the tension is apparently distributed between the two or more crimps.

If a tool provided with a single pair of indenting dies is used, this can be best accomplished by making the crimp closest to the lug IS with a pressure a little greater than will produce the maximum pull out strength with a single crimp, and then to make the second crimp closest to the extended wire with a pressure a little less than will produce the maximum pull out strength if a single crimp were used. Advantageously, both crimps are made simultaneously with a single tool having double indenters, but the one nearest the extended wire extending a little beyond the other so as to form a slightly deeper crimp. Such a tool is shown in the Carlson Patent No. 2,385,792. By reason of the band [8 forming the flared mouth of the connector ferrule extending substantially tangentially to the wire and for a substantial distance nearly parallel to the wire before the grooves i6 are encountered, the pull out strength of the crimped connection is improved and especially if against an angular pull, that is to say, in the pull along a direction at an angle to the axis of the ferrule.

As a, further protection against the reduction in tensile strength by crimping, the edge of the ferrule towards the wire, as illustrated in Figure 2, is rounded or sloped gently at I8; and this also serves to protect to a. substantial extent against weakening the wire by over-crimping near the end of the ferrule; so that, even if the crimp is carelessly placed so as to overlap the edge, excessive reduction in the pull test strength would be avoided.

In the foregoing discussion it has been stated that the steps may be performed in various sequences. By this it is meant that the grooves l6 and the bevel l8 may be stamped in the blank before the ferrule portion is cut or that the ferrule portion may be cut first and then the beveled edge l8 and the grooves I1 stamped thereon. It is apparent that the rolling of the ferrule must be subsequent to the cutting of the blank from which it is formed but that the rolling may be precedent or subsequent to the stamping out of the terminal portion l3.

As various embodiments may be made of the above invention and as changes might be made in the embodiment above set forth, it is to be understood that all matter hcreinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

What is claimed is:

A sheet metal electrical connector of the type adapted to be pressure formed about a conductor into intimate electrical and mechanical connection therewith comprising a ferrule portion for receiving a conductor portion, a bell mouth in one end of said ferrule portion smoothly flaring from the inner surface toward the outer surface there of, a plurality of steep-sided grooves disposed in the interior surface of said ferrule portion substantially perpendicularly of the longitudinal axis thereof, and the end groove of said grooves being longitudinally spaced from said cell mouth to provide a smooth wire-engaging surface in said ferrule portion between said bell mouth and said. end groove, whereby any tendency of the ferrule portion to form a sharp line of stress in the conductor at the inner edge of said bell mouth is minimized.

References Cited in the file of this patent UNITED STATES PATENTS Number Number 15 Number Name Date Stratford et al Mar. 9, 1926 Persons Dec. 28, 1926 Prince Oct. 25, 1927 Dibner June 12, 1928 Jones Dec. 10, 1929 Paulus Jan. 9, 1934 Linde Oct. 17, 1939 Knapp Feb. 13, 1940 Warren Aug. 26, 1941 Thomas, Jr Mar. 3, 1942 Pous Oct. 19, 19 8 FOREIGN PATENTS Country Date Great Britain June 19, 1919 Great Britain Nov. 19, 1926 Germany Dec. 19, 1935

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