US2789279A - Electrical connection and method of making the same - Google Patents

Description

1. GEBEL 2,789 279 ELECTRICAL CONNECTION AND METHOD OF MAKING THE SAME April 16, 1957 Filed Aug. '7, 1953 i sill ELECTRICAL CONNECTIGN AND METHOD ()1? MAKING THE SAIl E Application August 7, 1953, Serial No. 372,920

4 Claims. (Cl. 339-276) This application is related to the copending application of Edgar M. Soreng, Serial No. 352,654 filed May 1, 1953 and entitled, Electrical Connection and Method of Making the Same. Like said copending application, the instant invention relates to solderless electrical connectors and refers more particularly to a method for making an improved electrical connection of the type comprising a rolled-up ferrule of sheet metal and a conductor having a bare portion clinched in said ferrule.

in making electrical connections of this type the terrule is usually formed from a blank having a substantially U-shaped or trough-like cross section. The bare end of the conductor to be clinched in the ferrule is placed in the bottom portion of the trough between the upstanding anns thereof, and the arms are thereafter bent inwardly over the conductor and clinched thereonto in any of several different ways.

in one type of clinching the arms are curled substantially abruptly inwardly toward one another and their extremities are directed downwardly into the strands which comprise the conductor to complete the ferrule and efIect permanent clinching of the conductor therein. This type of clinching, however, has been found objectionable for the reason that the relatively sharp edges at the extremities of the opposite arms of the troughlike blank tend to shear the strands of the conductor as they are forcefully curled inwardly toward the bottom of the trough during the clinching operation.

With the type of clinching disclosed in the aforesaid application of Edgar M. Soreng this objection of subjecting the strands of the conductor to shearing is overcome by the expedient of bringing the end portions of the opposite arms of the trough-shaped blank flatwise together at the exterior of the ferrule to form a double thickness flange extending along the length of the ferrule thus formed. This has the advantage of precluding engagement of any sharp edges of the blank or the finished ferrule with the strands of the conductor clinched in the ferrule.

Despite the fact that the clinched joint disclosed in the aforementioned copending application of Edgar M. Soreng represents an improvement in electrical connectors of the type herein concerned, it nevertheless had one disadvantage which resulted from the fact that if the bare end portion of the conductor to be clinched in the trough-like blank did not have its strands tightly bunched or twisted togethenstray strands were very apt to project upwardly out of the open side of the trough-like blank and through the joint between the outwardly directed lips or flanges defining the seam along the exterior of the completed ferrule. When this occurred these lips could not be brought into the desired fiatwise intimate engagement with one another at the exterior of the ferrule, unless, of course, the bare end portion of the conductor was first manually twisted to bunch its strands prior to insertion into the trough-like blank.

Naturally this necessitated a rather close inspection of atent O illustrating the method of deforming the trough-shaped 2,789,279 Patented Apr. 16, 1957 "ice the bare end portion of each conductor before insertion thereof into the blank, and frequent twisting together of the strands to replace any stray strands into the compact bundle necessary for elfecting the best electrical and mechanical joint between the conductor and the ferrule.

'It is therefore an object of the present invention to provide an exceptionally secure clinched joint between the rolled-up sheet metal ferrule of a solderless electrical connector and the bare end portion of a conductor in said ferrule, which electrical connection is effected by a novel method which may be practiced substantially without regard for the condition of the strands at the bare end portion of the conductor, and which will have no tendency to shear the strands of the conductor.

According to the method of this invention the bare end portion of the conductor is placed on a sheet metal blank having a trough-like cross section, between the upstanding arms which define the sides of the trough, and the arms are successively folded inwardly over the bare portion of the conductor. In this way, the arm first folded inwardly will gather any stray strands on the bare end of the conductor and sweep them toward the bottom of the trough prior to completion of the ferrule to assure that all of the strands of the conductor will be bunched together and clinched in the ferrule.

Another object of this invention is to provide an elec trical connection of the type comprising a rolled-up ferrule and a conductor having a bare portion clinched therein, which electrical connection is characterized by the fact that adjoining lengthwise extending portions on the ferrule not only circumferentially overlap one another at one side of the ferrule but are interlocked with one another in such a way as to maintain the pressure exerted on the conductor during the clinching operation.

More specifically it is an object of this invention to provide an electrical connection of the character described wherein said overlapping longitudinal edge portions of the ferrule are depressed inwardly of the ferrule toward opposite wall portions thereof to effect interlocking of said overlapping edge portions and to partially flatten the ferrule and thus crowd the strands of the conductor into a restricted area inside the ferrule to take up all voids therein.

A further object of this invention resides in the provision of an electrical connection of the character described wherein the outer of said overlapping edge portions of the ferrule serves to rigidize the ferrule both lon gitudinally and transversely.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described, and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed in accordance with the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a perspective view of an electrical connection made in accordance with this invention;

Figure 2 is a cross sectional view through the ferrule seen in Figure l;

Figure 3 is a separated perspective view showing the trough-shaped blank from which the ferrule is rolled up, and the bare end portion of a conductor prior to insertion into the trough; and

Figures 4, 5 and 6 are more or less diagrammatic views blank into a "ferrule "and of clinching the conductor therein.

Referring now more particularly to the accompanying drawing, in which like numerals designate I like 7 parts through the several views, the numeral 5 generally designates a'wireterminal connectorof the solderless typehaving a flat body portion 6 apertured to receivea terminal post, and an integral ferrule 7 in which the bare end 8 of an electrical conductor 9 is secured. The body portion of the connector, however, forms no part of the invention, and may be of any suitable type customarily employed to establish an electrical connection between two electrical conductors or between one electrical conductor and a terminal post. For instance, the bod portion may comprise either the male or female element of a readily separable electrical connection of the type shown in the cependin ap lication of Edgar M. Soreng, serial No. 352,654 filed Ma '1, 1953. p

The present invention resides solely in the clinched CO'I'II'IeCfiOfI between the btie end P'Oifiofi 8 of the Conductor and the ferrule surrounding thei'sai'n'e, and the method by which this connection is effected. The method for se curely clinching the bare end of the conductor ih'the fer rule will be first described. 7

Referring to Figure 3 it will be noted that the ferrule portion 7' of the connector initially has a substantially trough or U-shaped cross section on the blank from which the connector is formed. The semicircular b'ight 10 of the U, of course, provides the bottom of the trough; and the opposing upright arms 11 and 12 of the U define the sides of the trough. At one end, the trough-shaped ferrule portion is integrally joined to the flat body portion 6. r I

The bare end 8 of the conductor to be secured to the connector is laid along the bottom of the trough-shaped ferrule portion overlying the bi ght 10 thereof, and between the opposite arms 11 and 12 of the trough. When so placed in the trough, the arm 11 is bent or folded inwardly over the bare end of the conductor so that it extends substantially entirely across the width of the trough with its extremity closely adjacent to the inner surface of the arm 12, in the manner indicated in Figure 5. Thereafter the arm 12 is curled inwardly over the adjacent end portion of the arm 11 and firmly pressed thereagainst in the manner indicated in Figure 6 to not only close the trough and reinforce the ferrule thus formed, but to firrnly hold the inner arm 11 in clinching engagement with the bare end of the conductor inside the ferrule. I

According to this method, therefore, the arms 11 and 12 of the trough-shaped ferrule portion 7 are successively folded inwardly over the conductor to dispose the longitudinally extending marginal edge portions of the rolledup ferrule thus formed in overlapping relationship with one another at one side of the ferrule.

One of the most important features of this method of rolling-up the ferrule is realized when the conductor is comprised of a multitude of strands, as shown. If these strands are frayed at the bare end of the conductor, that is projecting outwardly at divergent angles tothe conductor axis, they are very effectively bunched or gathered together and carried into the Bottom of the trough-shaped blank as the first arrnil of the trough is folded inwardly. This assures that all of the strands will be enclosed within the ferrule and eliminates the need for manually twisting or bunching the strands together into a tight bundle before the rolling-up and clinching operation is started.

After the arms 11 and 12 have been folded inwardly into overlapping relationship with one another as" de scribed, radialin-ward force is applied to the overlapping arms to effect a partial flattening of the ferrule and to spread out the strands of the conductor info intimate cenft'act wiflr all of the surrounding wall surfaces of the ferrule. During the time this force is applied to the over:

' lapp ng the ferrule is held o prevent lateral s rea ing thereof, with the result that the inner 11 forced lengthwise toward the baseof the arm 12. This causes the extremity of the arm 11 to be bent slightly upwardly into the curl of the arm 12, adjacent to the base portion thereof, behind the area of engagement between the outer portion of the arm 12 and the outer side 'of the arm 31.

The partial flattening of the ferrule, therefore, not only assures the best -possible electrical connection between the conductor andthe ferrule, but also effects interlocking of the overlapped arms to assure an excellent mechanical joint therebctween. V

The method is best carried out using cooperating stationary and movable die members 14 and 15, respectively.

The movable die member 15 isprovidedlwith a slot 16 opening to its underside through a taperingly enlarged mouth 17. inwardly of its mouth, the side walls 18 and 1.9 of the slot are substantially parallel and spaced apart a distance to allow the trough-shaped ferrule portion 7 of the connector blank to readily pass upwardly in the slot with its upstanding arms 11 and 12, respectively, closely fiatwise adjacent to the opposite side walls 18 and 2h of the slot. At the bottom of the slot, the side wall 18 terminates in an inwardly curved surface 2% having a radius substantially equal to one-quarter of the width of the slot, white the wall 19 terminates in a similar in wardly curved surface 21 of equal radius but having its center of curvature 'ofiset upwardly from that of the surface 2% a distance corresponding to about one-half of its radius. Where these two vertically offset curved surfaces approach tangency with one another, namely along the vertical centerline of the slot, they define a small downwardly projecting slightly rounded nose 22.

The lower die member slidingly fits the slot 18, and constitutes an anvil having a concave surface 24 at its top of slightly greater radius than that of the bight 10 of the trough-shaped ferrule portion 7.

With the die members separated, the trough-shaped ferrule portion 7 is placed on the anvil with its bight 10 resting upon the concave surface 24 of the anvil and its arms 11 and 12 in upright positions. The bare end portion 8 of the conductor is then placed in the bottom portion of the trough, and the upper die member 15 may then be brought down over the lower die member and .the ferrule port-ion supported thereon, so that the side walls of the slot embrace the opposite arms 11 and 12 of the ferrule portion 7 as shown in Figure 4-. Upon further closing of the dies, the concave surface 20 in the bottom of the upper die member is brought into engagement with the upper or outer end portion of the arm 11 to bend or fold the arm 11 inwardly over the conductor, as indicated in Figure 5. It will be noted that the arm 12 is not caused to be bent or folded inwardly over the exterior of the arm 11 until the latter has been brought to a substantially horizontal position extending almost entirely across the width of the trough, and this results from the vertical offset between the centers of curvature of the concave surfaces 20 and 21.

As the arm 12 begins to fold inwardly over the arm 11 in consequence of continued downward movement of the upper die member 15 from its position seen in Figure 5, the arm 11 is also forced farther toward the bottom of the trough by the engagement of the nose 22 with its exterior surface, and such engagement between the nose and the arm 11 thereafter obtains right up to the time the dies reach their fully closed position seen in Figure 6. It is for: this reason that though the arm 12 of the trough-shaped ferrule portion has the same length as the arm 11', the former is substantially confined by the arm 11 to the space between its exterior and the concave surface 21 during descent of the upper die member beyond its position seen in Figure 5. As a result of such confinement of the arm 11, the metal comprising the same is caused to flow back upon itself and become thickened, as at 25, to provide an exceptionally strong reinforcing rib extending the entire length of the ferrule.

This rib is relied upon to hold the arm 11 firmly pressed against the conductor to permanently clinch its strands in the ferrule.

During the final closing of the dies to subject the ferrule to the desired clinching pressure, both arms 11 and 12 are pressed downwardly to partially flatten the ferrule and to effect interlocking of the arms. This latter feature results from the slight endwise movement of the arm 11 imparted thereto during the final closing of the dies, and which causes its extremity to be deflected upwardly into the curl or slight concavity which obtains at the base of the arm 12.

The engagement of the ferrule with the opposite side Walls of the slot 16, of course, prevents expansion of the ferrule along lines normal to the direction of clinching force applied to the overlapping arms 11 and 12 during the final closing motion of the dies.

Referring to Figure 2 it will be seen that the method of clinching described precludes the engagement of any sharp corners or edges at the ends of the arms 11 and 12 with the bare conductor or the strands comprising the conductor. The inner arm 11 extends all the way across the ferrule and into abutting relationship with the arm 12 adjacent to the base thereof, and all of the strands of the conductor are confined between the inner surface of the arm 11 and the gently curving wall surfaces of the ferrule opposite thereto. Of great importance is the fact that there will be no voids in the ferrule thus formed to assure that the best possible mechanical and electrical connection is efiected between the ferrule and the stranded conductor.

From the foregoing description taken together with the accompanying drawing, it will be readily apparent to those skilled in the art that this invention provides an exceptionally good mechanical and electrical joint between the bare end portion of an electrical conductor and the ferrule of an electrical connector, and that the method by which the joint is efiected assures against the cutting of strands of a multi-strand conductor secured in the ferrule.

What I claim as my invention is:

1. The method of making an electrical connection of the type which comprises a rolled-up ferrule, and a conductor having a bare portion clinchd in said ferrule, which method comprises: laying the bare portion of the conductor along a sheet metal blank of uniform thickness and having a trough-like cross section with said bare portion of the conductor between the upwardly projecting arms which define the sides of the trough; successively folding said arms inwardly over the bare portion of the conductor to form a ferrule in which the bare portion of the conductor is confined and to dispose the outer end portions of said arms in overlapping relationship with one another along one side of the ferrule, with the inner arm in engagement with the conductor; and applying radially inward clinching pressure to said overlapping arms to partially flatten the ferrule and cause the con= ductor portion therein to be securely clamped entirely between the inner of said arms and the opposite wall portion of the ferrule, and simultaneously applying substantiaily edgewise compression to the inner and outer arms to form an outwardly projecting ridge at the extremity of the inner arm along its entire length and to thicken the outer arm and thereby compress it into interlocking engagement around said ridge and to rigidize the ferrule.

2. An electrical connection of the type comprising a rolled-up ferrule having adjoining lengthwise extending flaps, and a stranded conductor having a bare portion clinched in said ferrule: characterized by the fact that said adjoining lengthwise extending flaps circumferentially overlap one another along their lengths at one side of the ferrule; further characterized by the fact that the ferrule is partially flattened in cross section with the side of the ferrule defined by said overlapping flaps and the side opposite them extending across the wider dimension of the ferrule; further characterized by the fact that the inner one of said overlapping flaps extends entirely across the wider cross-sectional dimension of the ferrule so that all of the strands of the conductor are confined between said inner flap and said opposite side wall of the ferrule; and further characterized by the fact that the outer one of said overlapping flaps is curled over said inner one and extends approximately only halfway across said Wider cross-sectional dimension of the ferrule but is thicker than said inner flap to rigidize the ferrule and thus hold the flap portion with its extremity tightly wedged against the adjacent wall portion of the ferrule.

3. The electrical connection set forth in claim 2 further characterized by an interlocking connection between said overlapping flaps comprising an outwardly projecting ridge at the extremity of the inner flap along its entire length projecting into a concavity in the inner surface of the outer flap, whereby the flaps are prevented from separating along both the wider and the narrower crosssectional dimensions of the ferrule.

4. The electrical connection set forth in claim 2 wherein the inner of the overlapping flaps slants inwardly toward said oposite side wall of the ferrule so that the strands of the conductor are distributed through a substantially wedge-shaped cross section providing large contact area with the ferrule.

References Cited in the file of this patent UNITED STATES PATENTS 1,314,641 Fried Sept. 2, 1919 1,836,497 Phelps Dec. 15, 1931 1,873,125 Holmes Aug. 23, 1932 2,451,393 Kershaw Oct. 12, 1948 2,557,126 Macy June 19, 1951 2,567,155 Macy Sept. 4, 1951

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