US2965147A

US2965147A - Crimping methods and apparatus

Info

Publication number: US2965147A
Application number: US441277A
Authority: US
Inventors: Norman E Hoffman
Original assignee: AMP Inc
Current assignee: TE Connectivity Corp
Priority date: 1954-07-06
Filing date: 1954-07-06
Publication date: 1960-12-20
Anticipated expiration: 1977-12-20
Also published as: DE1084337B; FR1137368A; CH344113A; GB811996A; NL198024A; NL102635C

Description

Dec. 20, 1960 N. E. HOFFMAN 2,965,147

CRIMPING METHODS AND APPARATUS Filed July 6, 1954 2 Sheets-Sheet 1 INVENTOR f /VoRMA/v E. HoF/:MAN

nDlc. 20, 1960 N. E. HOFFMAN 2,965,147

CRIMPING METHODS AND APPARATUS Filed July 6, 1954 2 Sheets-Sheet 2 lNvENToR /VORMAN HWMAN ATTOR United States Patent() CRIMPING METHODS AND APPARATUS Norman E. Hoffman, Rutherford Heights, Pa., assigner to AMP Incorporated Filed July 6, 1954, Ser. No. 441,277

Claims. (Cl. 153-1) This invention is in the lield of electrical connectors of the type having ferrule portions adapted to receive conductors and be crimped thereto and relates to improved crimps and crimping dies and methods for applying the connectors to the conductors.

In order to produce a high quality connection in this field, there are a number of criteria which must be met both during the crimping of the ferrule onto the conductor and in the resulting crimp. For example, the connection should be mechanically strong to resist tension, vibration and torsion, and be tight against corrosion, and maintin a high electrical conductvity over a long period of time. It should be economical to make and to apply. The form of the connection should be such that -the gradations in crimping pressures exerted upon the various areas of the outside of the ferrule are within reasonable limits and the maximum crimping pressures are not unduly high, thus preventing shearing or puncture in the wall of the ferrule; and yet the metals of the ferrnle and conductor must be forged together under the crimping pressures used so as to produce a connection .in which the ferrule and conductor are essentially integral. Where the ferrule is of the type that carries an external insulation sheath through which the crimping pressure is transmitted, these latter criteria are very important in providing a well insulated yet strong connection. Moreover,

Vthe amount of metal required to be used in the ferrule` should be as small as possible to reduce cost and weight, the latter being of prime importance in aircraft.

As is understood by those skilled in this field, many of these criteria tend to be mutually exclusive; however, it is among the advantages of the method and apparatus of the present invention that these various antagonistic factors are so controlled as to be caused to work together to produce a connection of highly superior electrical and mechanical qualities.

An important advantage of the present invention is that it enables connections to be formed with the use of lower maximum crimping pressures and smaller total crimping forces than those which have heretofore been required for the same size of conductor, while the resulting connections actually have a higher tensile strength and a greater strength against torsional stress than other crimped connections of comparable dimensions. These lower pressures and forces actually permit the use of thinner walled ferrules, and yet the resulting connections have superior mechanical and electrical properties.

Among the further advantages of the present invention are those resulting from the fact that it enables a given connector ferrule to accommodate a wide range of sizes and kinds of conductors, including solid and stranded wires, and wires of polygonal as well as circular cross sections, or combinations of these, and yet produces a crimp of superior strength throughout the entire range. -Also it enables a single set of dies to be used with a wide range of conductors.

Yet another advantage of the present invention is that it enables larger insulated connections to be made of the ice type having a ferrule surrounded by an insulation sheath, the crimping forces being applied through this insulation sheath, by virtue of the lower crimping forces and thinner ferrule walls which can be used with the present invention.

Among the further advantages of my invention are that it provides a crimped connection which can be easily and economically made under mass production conditions and which is highly resistant to corrosion, is mechanically strong both in torsion and in tensile stress for both solid and stranded conductors. Moreover, the present invention produces excellent results not only with ordinary electrical copper but also with other metals, including for example, aluminum, brass, Phosphorbronze, berylliumcopper, hard-drawn copper, iron, etc.

One of the important advantages of the present invention is that during a crimping operation the curve of the required crimping force as a function of die travel has the highly desirable characteristic of a gentle slope over the major portion of die travel, whereby the effort required to close the dies over this major portion of the die travel is low; with a suddenly increased slope occurring when the connection is forged to solid cross-section, .whereby the normal operation of the dies is also the desired operation. If dies of this invention are used with toggle-type force-multiplying linkages connected so that themecnanical advantage (and therefore the force output) is low over most of the travel of the dies but increases greatly as the toggle nears its dead-center position, asy the dies near full closure, the result is substantially constant force during the full stroke of the handles. This steep increase of crimping force near full closure acts as a stop to prevent over-crimping with mechanically- -actuated tools provided with a resilient member in the force linkages and with hydraulic tools having pre-set by-pass valves which release at a predetermined crimping force.

In this specification and the accompanying drawings, I have described and shown some embodiments of my invention; but it is to be understood that these are not intended to be exhaustive or limiting of the invention, but are given for the purpose of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in various forms, each as may be best suited to the conditions of the particular use. Various other aspects, objects, and advantages of my invention are pointed out hereinafter or will be understood from a consideration of the accompanying drawings in connection with the following description.

:In the drawings:

Figure 1 is a perspective view of an electrical connector applied to the end of a wire;

Figure 2 is a cross sectional view of the connection taken through the center of the crimp, on the line 2-2 of Figure 1;

Figure 3.is a cross sectional view of a connection similar to that shown in Figure l but wherein a larger size conductor has been used with the same size of ferrule and dies;

Figure 4 is a perspective view of an electrically insulated end connector crimped onto a number of wires;

Figure 5 is a transverse sectional view taken along the line 5--5 of Figure 4;

Figure 6 is a longitudinal sectional view taken along the line 6 6 of Figure 5;

Figure 7 is a sectional elevation view taken through a pair of crimping dies with a solid electrical conductor and the ferrule portion of an electrical connector between the dies in their fully open position;

Figure 8 is a View similar to that of Figure 7 but showing the dies in a partially closed position;

Figure 9 is a view similar to that of Figures 7 and 8 but showing the dies nearing their fully closed position;

Figure 10 is a plan sectional view of the dies taken along the lines 10-10 of Figure 9;

Figure l1 is an enlarged geometrical diagram of 'the outline of a crimped connection made in accordance with the present invention for example as shown in Figure 2;

Figure l2 is an enlargement of the upper Vertex p0rtion of the outline of Figure ll, for purposes of further explanation; and

Figures 13 and 14 show enlarged elevational views of the nest die and indenter die, respectively.

In Figure l is shown an electrical connector, generally indicated at 20, including a ferrule portion 22 telescoped over and crimped to the bare end 24 of an insulated electrical conductor 26 with a contact portion 28 integrally extending from the ferrule, shown here as a ring tongue. As shown in Figure 2, an integral connection is Vformed by crimping the ferrule 22 inwardly against the bare end 24 of conductor 26 and compressing it by three approximately equally spaced elongated longitudinally extending

indentations

30, 30, 32, respectively. These indentations, as shown, are parallel-sided with rounded ends 34 and rounded bottoms and are impressed in the wall of the ferrule to engage it with the conductor 24 and to coin and cold ow the metal of the ferrule into a substantially solid integral body with the metalV of the conductor. It is an advantage of this invention that compression forging of the metal can proceed to the stage where the cross-section is free from voids before the mechanical strength and integrity of the connection are seriously impaired at any part. Two of these indentations 30 are ofthe same size but the third indentation 32 is somewhat wider. I have found it advantageous to have 'this third indentation from about fifteen to about forty percent wider than 'either of `the other two and for 'r'nost applications a very high quality connection is formed by having the width of indentation 32 about 4twenty-five to thirty percent wider than the others.

I have found it desirable to have the length of these indentations within the range from somewhat less to somewhat more than the outside diameter of the ferrule. For many applications a highly satisfactory connection is obtained when the lengths of the indentations are just slightly less than the ferrule O D. Moreover, rounded ends 34 of these indentations are preferably spaced at least short distances from the respective ends of the ferrule so that the inside of the uncrimped ends of the ferrule are from the triangular crimped form to one which retains to a large degree the original shape, herein shown as circular. Thus, the uncrimped ends form effectively a reinforcing flange at both ends of the ferrule. Also, by leaving the end of the ferrule toward the conductor uncrimped, a bell mouth in effect results to 'support the conductor strands against sharp bending as they leave the end of the ferrule. This is` quite apparent, for example, from Figure 6.

The resulting body of the ferrule and conductor as seen in Figure 2 in cross section, presents a generally three-sided configuration with the appearance of a scalloped triangle having concave sides formed by the

indentations

30 and 32 which are defined transversely by circular arcs of radii R2 (Figure 1l) and having

vertices

3S, 35, and 36, respectively, rounded to circular arcs of smaller radii R1 and R3 tangent to the concave arcs.

The two vertices 35 adjacent the larger indentation 32 are more actute than the third vertex 36 so that the over-all cross section of the connection has a generally isoceles-triangular appearance. As seen from a Vcomparison of Figures l and 2, one of the advantages of the present invention is that in a connection with a terminal tongue the outline of the connection blends with the tongue portion 28, the two actute vertices 35 being more ,l

or .less aligned with the edges ofthe tongue, do not cause objectionable distortion and the less acute vertex 36 Ying stress.

aligning with the seam 38 keeps it under compression during crimping. Thus, any stresses in the contact tongue are taken by the reinforcing circular flange 37, while the ribs formed by vertices 35 withstand bending, tensile and torsion stresses.

Among the advantages of Ya connection in accordance with my invention are those resulting from the fact that indentations V30 and 32v may be voriented in any position with respect to a seam in the ferrule. For example, as 'shown in Figure 3, the connection has been made with a seam 38 lying near the center of the wider indentation 32. This is particularly advantageous with through-type (butt or parallel connectors) or acorn type (end connectors). The searnwill ordinarily be brazed, but the invention is of great advantage with butt seams because it subjects the ferrule to peripheral compression.

Figure 3 is a cross sectional view ofa connection madev wit-hthe same dies and with a ferrule 22 of the same size `as 'that shown in Figures 1 and 2, but with a conductor crimping operation is performed in a press or tool with sufficient force to move the dies to the same extent as in Figure 2, the result will be that the ferrule wall and the wire are thinned by greater longitudinal extrusion under the action of the crimping dies, leaving a larger area within the ferrule 22 to accommodate the larger (although reduced) cross section of conductor end 24a. It is desirable thus to provide a limited percentage reduction i cross section of the conductor 24a.

The metal of ferrule 22 and of conductor 24a are integrallyforged together in Figure 3, as in Figure 2, to produce 'a connection of great tensile and torsional strength.

Among the reasons for the high torsional strength of a connection as shown in Figures 2 and 3 is that the method -of crimping controls both the shape of the ferrule and the shape 4'of the conductor to produce a forged junction 39 between conductor and ferrule which at no point conforms to the periphery of the original conductor shape.

Thus, when the conductor is placed under torsion no sig nificant part of junction 39 is subjected to a purely shear- Hence the junction has a very high resistance to-torsional stress.

Another reason for the high torsional strength of a conneetion as described is that the crimped conductor cross section has a generally triangular shape with concave sides. Theresulting three fairly

sharp interface vertices

40, 40 and 41, respectively, of junction 39 create abutments extending almost radially outwardly from the axis of the connection substantially at right angles to the torsional stressto resist it. To illustrate, in Figure 3 a dotted radial line 42 is drawn from the axis of the connection vthrough an interface vertex 40. It is seen that a tangent 43 to one of the abutments is almost parallel to line 42. Moreover, these abutment faces near interface vertices `40 and 42 are at maximum radial distances from the axis 'of the connection, whereby to have maximum effective moment arms in resisting torsion.

As shown in Figures 2 and 3 another of the advantages ofthe present invention is that the ribs formed by the

rounded vertices

35 and 36 of the ferrule provide reinforcement adjacent -both sides of each of the

indentations

30 and 32 and thus serve to hold the indented metal of the ferrule firmly against the conductor therein and to resist any tendency for the ferrule indentations to spring ,back away from the conductor. Moreover, these ribs reinforce the connection in the regions of the iunction vertices 40 and 42 to aid in resisting the torsional stresses discussed above.

'I have found that with a connection as described here nest die 60 and ,a male indenter ydie 62.

in a substantially thinner ferrule wall can be used than with prior connections having comparably good strength against torsional and tensile stresses. For example, with my connection I use a ferrule wall thickness which is only 58% of that used with a Freedom connection of the type shown in U.S. Patent 2,535,013. The use of the thinner wall not only saves material cost but enables me to use between 15% and 20% less force than Freedom during the crimping operation. Moreover, even with a ferrule wall of the same thickness 20% to 25% less force is re# quired. Thus, the total gain is effciency by the use of my crimp with the thinner walled ferrule enables me to use between 35% and 45% less force while producing a connection of greater strength. At the same time the initial cost and weight of the machinery, tools and dies used for crimping are less and the wear is less because of the lower forces involved.

In Figure 4 is shown an insulated end connection on four

insulated conductors

26, 26a of different sizes. `As shown in Figures 5 and 6, the end connector 20a used to make the connection includes a metal ferrule 22a telescoped over the bared conductor ends 24. Surrounding ferrule 22a is an insulation sheath 50 having a closed end portion of smaller diameter tightly embracing the out- 'side of the metal ferrule 22a and having an open skirt the ferrule and conductor therein.

When used with insulated ferrules, -the smaller forces used and the action of the dies in closing against the insulation sheath enables a larger size of insulated ferrule to be crimped. Moreover, the action is such that during the final stages of crimping, when the pressures increase, pressure is distributed over substantially the entire periphery of the insulation sheath, thus avoiding serious weakening or puncture. A slight circumferential plastic flow occurs away from the centers of the

indented regions

30 and 32 toward the

rounded vertices

34 and 36. This is advantageous for it somewhat increases the thickness of insulation along the rib-

like vertices

35 and 36 where 'the connection is most likely to touch other objects and where abrasion might occur.

'Following crimping, if the insulation sheath 50 is not bonded to the metal, it draws back slightly in the regions of the indentations to leave thin crescent shaped voids 52 vunderneath the insulation, which provide additional protection against short circuiting contacts and a longer leakage path to the ferrule if the insulation should be damaged at any time. Because the insulation sheath over the crescent shaped voids 52 can yield resiliently to impact, such damage is very unlikely.

The orientation of the crimp away from the ferrule seam 38 is not essential, but it is advantageous as the crimp tends to subject the

portions

35, 36 to the `highest circumferential compression. With insulated connectors of the type shown in Figures 5 and 6, the deformation from circular to triangular form may thus take place at any convenient angular orientation, for the insulation layer reduces the variations in circumferential stress differences in the ferrule.

As shown in Figures 7, 8, 9, 13, and 14, a set of dies for making a connection as described includes a Afemale Die 60 has .a nest, generally indicated at 63, adapted to receive the ferrule longitudinally therein and having substantially straight ,sides 64 inclined'inwardly at a small angleI with respect to fthe direction of closing shown by a dashed line 66 (see Figure 8). The bottom of nest 63 is defined by a longitudinal central indenter, shown as au arcuate hump 68 between concave valleys '6 9 of small radius and'` tangent fwith the straight sides 64vas well as with the hump 68;

Male die 62 includes a pair of longitudinally extending lateral camming tynes 70 having polished camming surfaces 72, with -a longitudinally extending forming throat 73 therebetween. v

The indenter 68 and tynes 70 are arranged longitudinally of the ferrule and are a little shorter than the outside diameter of the ferrule so that they make indents as shown in Figures 1 and 4.

The ferrule with the conductor therein is placed within nest 63 (Figure 7) which has an average width only slightly greater than the O.D. of the ferrule. The nest sides and die faces 72, 73 confine the ferrule and align it over the hump 68.

The dies close (Figure 8) together along the direction 66, which, although shown straight, for use in straightaction type tools, can also be arcuate for pliers-type and other types of tools. Accordingly, where parts are designated as parallel to the die path 66, it includes concentric orientation for arcuate action.

The tynes 70 enter the nest with their outsides 74 extending parallel with the direction 66 and in sliding con'- tact or spaced only a slight distance from the respective sides 64 of the nest. Sides 64 advantageously converge slightly (see also Figure 13), which may compress the ferrule slightly. This slight convergency is advantageous for it provides positive lateral supporting by action of the sides of the nest, as the male die 62 drives the ferrule down into the nest.

As male die 62 enters the nest, the tynes 70 provide force multiplication and deflection action to squeeze the ferrule Itransversely until the ferrule is deformed into sub'- stantial conformity with the cooperating die Afori-hing surfaces and the conductor into substantial conformityI tothe inside of the deformed ferrule. This initial transverse squeezing and camming of the ferrule and conductor ,occur before the voids are eliminated, and when the throat 73 is filled, then the major force is imposed on the ferrule and conductor by a direct ycompression action by the force of the male die driven into the nest to assure a solid cross section. Because of the initial transverse camming and distortion of ferrule and conductor into mutual conformity, the final compression more readily obtains a solid cross section without excessive reduction in cross section of conductor or ferrule. During the completion of the camming action and during the final compression, tynes 70 are supported, tynes 70 are supported laterally by sides 6 4 of the nest to prevent undue stress on throat 73 of die 62. Moreover, throat 73 is protected from undue stress, for as the applied force is increased during the fin-al stages of crimping, throat 73 is filled and the camming action ceases.

The sides of the nest may advantageously each be inclined to the direction 66 by an anglein the range from 1/2 to 3 (i.e., an included angle of convergence from l to 6). An inclination of about 1 for each side (an included convergence angle of about,2) is considered an optimum. v

The present invention provides both the advantages of close lateral confining of the ferrule during substantially the entire crimping operation and also ease of removal of 4the completed connection from the nest.

' As tynes 70 enter the nest cavity, their inner camming and crimping surfaces 72 first contact the ferrule tangentially thereto at points 76 on opposite sides of the center line of the nest and on opposite sides of the axis of the ferrule. Lines 77 are drawn' to indicate that points 76 are above the side walls of the ferrule in the direction 66. These points 76 are less than one-fourth the widthl 'of nest V63 from the sides of the nest. When the camming surfaces 72 initially strike the ferrule at points 76,'-tlie effective portions of these surfaces4 are inclined at angles of about 30 with respect to direction 66. Thus, the camming action produces indenting forces acting perpen- .S F1 cosecant 30=F1 These forces overcome the arch strength of the ferrule and buckle the ferrule wali in against the conductor 24 at three places, as shown in Figure 8. The portion ofthe 'top of the ferrule which is buckled up toward thoatr73 4engages portions of camming surfaces 72 which are even more nearly parallel with direction 66, thus enhancing the force multiplication effect acting laterally on the top ferrule portion jcircumferentially to compress the ferrule wall and vform ridge 36.

As the dies continue closing, the camming surfaces 72 contact an increasing portion of the circumference of the ferrule and drive it inwardto overcome the arch strength of the conductor, and eventually to forge the ferrule and conductor together with substantial metal ow.

The buckling of the ferrule Wall produces an initial indent which lits itself substantially to the hump 68 and surfaces 73 and further indenting increases the area of eng-agement by the camming surfaces. This is advantageous, for, as the crimping forces increase, there is a concomitant increase in the area of the ferrule wall used to transmit the crimping forces to the conductor, so that the lpressures on the outside of the ferrule are not excessively increased in any point, and puncture or objectionable weakening of the ferrule wall can then be avoided. This is particularly `adr/antagemis for insulated fer'ru'les.

The force multiplication effect of the dies minimizes the required applied force, whilethe metal of ferrule and wire are extruded up into hollow 73 and laterally into hollows 69 to form their scalloped isosceles triangular shape, as shown in Figure 9.

At this stage in the crimping operation the connection has become substantially voidles's. Moreover, the connection is now completely confined between the male and female dies, and longitudinal extrusion must, therefore, occur during the final increment of closing motion, i.e., in moving from the position shown in Figure 9 until the limit elements 80 on the male die cooperate With limit elements 82 on the female die to limit further entry of the tynes 72 into Vnest 63. This final longitudinal extrusion assures fresh metal contact and conforming of the conductor to the ferrule, reduces spring back, and increases the strength of the completed connection by work hardening the metal.

, During this final extrusion stage, when the dies are moving beyond the position shown in Figure 9, the camming action ceases so that the required applied force increases sharply, with the advantageous results mentioned above.

The heavy line l90 in Figure 1l shows the outline of an enlarged cross section of the crimped connection at the longitudinal center of the crimp. One important factor in attaining the yhigh quality and performance of such a connection is longitudinalv extrusion of the metal, which may be expressed as percent reduction in the cross sectional area of metal in the region of the crimp, including the metal of the conductor and of the ferrule.

`This percent reduction (also called the reduction ratio) is preferably in the range from to 48%, for this range provides the maximum torsion andi tension strengths in the completed connection.

M It is found that the optimum size for the dimens-fon Z is equal to the maximum diameter 'of the ferrule plus gasli'ght clearance, eg. from .001 of an inch to .010 of top portion 92 of this curve being dotted. This curve 90, Y92 is referred to as a scalloped 'equilatera curve, and the curve ,'90, without the portion 92, is referred to as a scalloped isosceles curve. Y

' Figure 11 shows a large equilateral triangle ABC formed by four-identical smaller e'quilateral triangles AED, BFE, CDF, and DEF, the latter central triangle 91 being the one around which the scalloped equilateral curve is circumscribed.

I have found it usually preferable to modify the scalioped equilateral shape to the scalloped isosceles shape by omitting the dotted portion 92 of the upper vertex or. ridge formed between

indents

30, 30. A slightly larger radius R3 is shown defining this ridge, with its center at a position F at an angle, below the line BC. This strengthens the indenter 62 and makes it easier for the metal of the ferrule to extrude fully into the valley v73 even when harder copper or other metal is used for the ferrule.

For crimping most connections, the angle preferably is in the range from about 10 to about 30, and over a wide variety of applications a value of 20 proves a good compromise, with a thus having a value of 70.

kFrom analyses and tests, I have determined that certain ranges `in the above dimensions are advantageous. For example, the ratio .R2/R1 may be varied from about 6 to 9, with 6.5 being very nearly the value shown in Figure 11 and with 7.5 or 8 being used in certain instances where it is desired to obtain somewhat more pronounced ribs in the completed connection. The ratio of R3/R1 may lie in the range from about 1.2 to 1.7 with approximately 11.5 being most advantageous for many applications. The ratio of the height HI of the scalloped isosceles c urve to its width Z may lie in the range from about .5 to .8 with about two-thirds being most satisfactory for many applications.

As used herein conductor is intended to include any solid or stranded Wires or groups of them or any conductor regardless of cross sectional shape.

From the foregoing, it will be understood that the embodiments of the invention described above are well suited to provide the advantages set forth and that the various features of the invention may be subject to a variety of modifications as may be desirable in adapting the invention to different applications and in some instances certain features of the invention may be used without the use of other corresponding features.

What is claimed is:

l. The method of making an electrical connection between a ferrule and a conductor comprising the steps of applying a first force over a relatively small area of a ferrule-forming connector portion, said force being directed inwardly of the ferrule, applying a second opposing force, with force multiplication and deflection by camming actions on the ferrule to two spaced areas on the opposite sides of an axial plane of the ferrule parallel to the direction in which the first-named force is applied, said camming actions producing radially in- Wardly directed forces on said second-named areas, respectively, all of said inwardly directed forces being comparable in magnitude, to indent the wall of said ferrule inwardly in three places against the conductor, increasing said inwardly directed forces and also increasing the circumferential extent of the indented areas until the entire periphery of the ferrule is confined by said inwardly directed forces and the ferrule and connector are forged together into substantially solid cross section, coining the connection with forces exerted on the entire periphery to a scalloped triangular cross seetion, and controlling the amount of coining of the connectien by the steep increase in total force occurring when the entire periphery of the ferrule becomes coniined'.

2. The method of making an 'electrical connection between a ferrule 'and a conductor comprising the steps of applying a first force to a rst area of the ferrule of small circumferential extent relative to the circumference of the ferrule, said force being directed radially inwardly toward the axis of the ferrule, applying a second opposing force, with force multiplication and defiection by camming actions on the ferrule to second and third spaced areas of the ferrule, said second and third areas both being on the opposite side of an axial plane of the ferrule perpendicular to the direction in which the first-named force is applied, said second and third areas each being spaced from said first area a distance approximating the spacing between said second and third areas, said camming actions producing second .and third forces on said second and third areas, respectively, which are directed inwardly toward the axis of the ferrule, said second and third forces each being comparable in magnitude to the magnitude of said first force, to indent the wall of said ferrule inwardly in three places against the conductor, increasing said inwardly directed forces and also increasing the circumferential extent of said first, second, and third areas, until the entire periphery of the ferrule is confined by said inwardly directed forces and the ferrule and conductor are forged together into substantially solid cross section, coining the connection with forces exerted on the entire periphery to a scalloped triangular cross section, and limiting the Aamount of said coining by the steeply increasing forces Adeveloped upon the confinement of the entire periphery.

3. The method of making an electrical connection be- .tween a ferrule and a conductor comprising the steps of applying a first force to a first area of the ferrule of relatively small circumferential extent, said force being directed radially inwardly of the ferrule, applying camming actions to second and third spaced areas of the ferrule, said second and third areas both being on the `opposite side of an axial plane of the ferrule from said first area and each being spaced from said first area a distance approximately equal to the spacing between said second and third areas, said camming actions producing second and third forces on said second and third areas, respectively, which are directed radially inwardly of the ferrule, said second and third forces each being comparable in magnitude to the magnitude of said first force, to collapse the wall of said ferrule inwardly in three places against the conductor therein, increasing said first force and said camming actions while increasing the circumferential extent of said first, second, and third areas until said areas extend around substantially the entire circumferences of the ferrule in a scalloped triangular configuration, whereby to produce a confined crimping action, and extruding the material of the ferrule and conductor in an axial direction to produce a reduction in the sum of the cross-sectional areas of the conductor and ferrule in the range from about a 15% reduction to about a 48% reduction.

4. Apparatus for crimping a ferrule into a generally triangular cross sectional form comprising a first die member having a nest adapted to receive the ferrule longitudinally therein and a second die member having a pair `of spaced tynes, said die members being adapted to close along a path with said tynes straddling the full width of the ferrule and entering said nest, sad nest having a `pair of straight sides almost parallel with said path and converging in a direction toward the bottom of the nest at an angle in the range from about 1 to about 6, each of said tynes having an outer surface and an inner carn- .ming surface a tangent to which at the mid point thereof is oriented at an acute angle with respect to said path, :said inner camming surfaces converging toward each lother with the inner portions of said cammingv surfaces defining a throat therebetween, theouter surfaces of said tynes near their ends engaging said straight sides before said die members are fully closed, thereby to provide l: positive lateral Isupport for said tynes. i- 5.App'aratus for crimping a ferrule into a generally triangular cross sectional form comprising a first -die l@ member having a nest adapted to receive the ferrule longi tudinally therein and a second die member having a pair of spaced tynes, said die members being adapted to close along a path with said tynes straddling the full width of the ferrule and entering said nest, said nest having a pair of sides almost parallel with said path and converging toward the bottom of the nest at an angle in the range from about 1 to about 6, each of said tynes having an inner camming surface a tangent to which at the mid point is oriented at an acute angle with respect to said path, said inner camming surfaces converging toward each other with the inner portions *of said camming surfaces defining a throat therebetween,- the extremities of said ferrule camming surfaces beingl spaced apart a distance greater than the width of the ferrule, said tynes having outer surfaces extending substantially parallel to said path and bearing against said sides of the nest during the final stages of closure of the die members, thereby to provide positive lateral support for the tynes to resist spreading of the tynes.

6. Apparatus for crimping a ferrule into a generally scalloped isosceles triangular cross sectional form comprising first and second die members movable toward each other along a path, said first die members having a nest adapted to receive the ferrule longitudinally therein, said nest being defined by a pair of spaced sides extending almost parallel with said path but converging in a direction toward the bottom of the nest at a small angle lying in the range from about 1 to about 6 and with the bottom of the nest being defined by a pair of concavities each near one of said sides with a hump therebetween, said second die member having a pair of spaced `tynes entering said nest when said die members; are

moved along said path, each of said tynes having anv inner camming surface a tangent to which at the point of initial contact with the ferrule is oriented at an acute angle with respect to said path, said inner camming surfaces converging toward each other with the inner portions of said camming surfaces defining a throat therebetween, said die members in their fully closed position defining an opening having a scalloped isosceles triangular shape as seen in cross section including three rounded vertices and three concave sides between respective vertices, the over-all height HI of the isosceles triangular shape being in the range from .5 to .8 times the over-all width Z.

7. Apparatus for crimping a ferrule into a generally scalloped triangular cross sectional form comprising first and second die members movable toward eachother along a path, said first die member having -a nest adapted to receive the ferrule longitudinally therein, said nest being defined bya pair of spaced sides extending almost parallel with said path but converging toward the bottom of the nest at a small angle lying in the range from about 1 to about 6 and with the bottom of the nest being defined by a pair of concavities each near one of said sides with a hump therebetween, said second die member having a pair of spaced tynes entering said nest when said die members are moved along said path, each of said tynes having an inner camming surface a tangent to which at the point of initial contact with the ferrule is oriented at an acute angle with respect to said path, said tynes having tps spaced apart a distance greater than the width of the bottom of the nest, said tynes having outer surfaces bearing against said sides of the nest during the final stages of motion of the die members along said path, said die members in their fully closed position outlining an opening having a scalloped isosceles triangular configuration, the ratio of the over-all height 4.HI of the scalloped isosceles triangularv configurationsto l a path, said first 'die member having awnest adaptedio receive the ferrule longitudinally therein, said ,nest

ing defined by a pair of spaced sides extending almost parallel with said path but converging toward the bottom of the nest at a small angle and with the bottom of the nest being defined by a pair of concavities each tangent to one of said sides and with a longitudinally extending hump therebetween, said second die member having a pair of spaced tynes entering said nest when said die members are moved along said path, each of said tynes having an inner convex camming surface which con'- verges toward the convex camming surface of the other tyne in a direction away from said nest.

'9. Apparatus for crimping a 'ferijule into a generally scalloped triangular cross sectional form comprising rst and second die members movable toward each other along a path, said first die member as seen in elevation having a nest adapted to receive the ferrule longitudinally therein, said nest being defined by a pair of spaced sides extending almost parallel with said path but converging at a small angle toward the bottom of the nest and with the bottom of the nest being defined by a pair of concavities each near one of said sides with an arcuate longitudinally extending hump therebetween, said second die member as seen in elevation having a pair of spaced tynes entering said nest when said die members are 'moved along said path, each of said tynes having a camming surface, tangent to all portions of said respective camming surfaces being oriented at acute angles with respect vto said path, each of said camming surfaces including longitudinally extending convex surfaces, with the inner portions of both of said camming surfaces converging toward each other and defining a concave throat therebetween, said dies in their fully closed position defining an opening having a scalloped triangular shape. y Y

l0. Crimping apparatus for crimping ferrules onto electrical conductors vforming electrical connections having scalloped triangular cross sectional form comprising rst and second die members movable toward each other along a path, said first die member having a nest adapted to receive the ferrule longitudinally therein, said nest including a pair of spaced sides extending almost parallel with -said path but converging at a small angle lying in the range from about 1 to about 6, the bottom of the nest being defined by a pair of concavities extending longitudinally and each tangent to a respective one of said sides with a longitudinally extending hump therebetween and tangent to said concavities, said concavities having a radius of curvature R1 and said hump having -a radius of curvature R2, ysaid second die member including a pair of spaced tynes straddling the full width of the ferrule and entering said nest, the outer surfaces of said tynes engaging said nest sides in the fully closed position, said tynes having a central cylindrical cavity therebetween extending longitudinally and having a radius of curvature R3, said tynes each having an inner convex camming surface each tangent to a respective side of said cylindrical cavity, said convex camming surfaces each having a radius of curvature R2, said tynes each having a longitudinally extending concave surface tangent to the con- Vex camming surface and located near the end of the tyne, said concave surfaces each having a radius of curvature R1, said die members in the fully closed position defining a scalloped isosceles triangular opening having three concave sides and three convex vertices, the ratio between R2 and R1 lying in the range from 6 to 9, the ratio between R3 and R1 lying in the range from 1.2 to 1.7.

ll. Crimping apparatus for crimping ferrules onto electrical conductors for forming electrical connections having scalloped triangular cross-'sectional shape comprising rst and second die members movable toward each other along a path, said vfirst die member having a nest adapted to receive the terrine longitudinally therein, said nest including a pair of spaced sides converging toward the bottom of the nest, the bottom of the nest being defined by a pairof longitudinally 'extending ccnl cave cylindrical surfaces each tangent to a respective `side with 'a longitudinally extending convex cylindrical hump 'therebetween tangent to both of said concave surfaces, said second die member including a pair of spaced tynes entering opposite sides of the nest closely adjacent to said converging side surfaces of the nest and straddling the full width of the ferrule, said tynes having a longitudinally extending central concave cylindrical cavity therebetween, said tynes each having an inner converging camming face tangent to a respective side of said cavityl and defined by a longitudinally extending convex cylindical surface, said tynes each having a longitudinally extending concave cylindrical surface tangent to the convex surface and near to the tip, said dies in their fully closed position defining a scalloped triangular opening having three convex vertices and three concave sides.

l2. Crimping apparatus as claimed in claim l1 and wherein said three convex sides have a radius of curvature lying in the range from 6 to 9 times the radius of curvature of the concave vertices.

13. Crimping apparatus for forming crimped electrical connections between ferrules and conductors inserted therein including rst and second dies movable toward each other along a path, said first die having a nest for receiving a ferrule longitudinally therein and including a pair of spaced side walls 'each converging with 'respect to said path toward the bottom of 'the nest, the bottom of the nest being defined by a central longitudinally extending cylindrical hump and by a pair of longitudinally extending cylindrical cavities each tangent to said hump and to respective side 'walls of the nest, said second die including a pair of spaced tynes entering opposite sides of the nest adjacent to said side Walls, said tynes having a central longitudinally extending cylindrical hollow therebetween and each having a longitudinally extending convexvcylndrical camming surface tangent to opposite sides of said hollow, said tynes each having a longitudinally extending cylindrical cavity near the end and tangent to the camming surface, said dies in the fully closed position outlining a scalloped triangular opening traced by arcs swung about centers in common the respective cylindrical cavities near the ends of the tynes and with said convex cylindrical camming surfaces being tangent to straight lines passing through said respective common centers. v

14. Crimping apparatus for forming crimped electrical connections between ferrules and electrical conductors telescoped therein, 'said apparatus including first and second crimping dies adapted to move towards each other along a path, said rst die having a nest for receiving a ferrule longitudinally therein, said nest having a pair of spaced side walls each converging with respect to said path, the bottom of said nest being defined by a central humpy and by a pair of cavities tangent to opposite sides of said hump and to a respective side wall, said second die including a pair of spaced tynes entering opposite Vsides of the nest and closely adjacent to respective side walls in the fully closed position, said tynes having a central hollow therebetween and convex camming surfaces tangent to opposite sides of said hollow, with a cavity near the end of each tangent to the camming surface, said hump having a convex surface between 15% and 40% wider than said convex camming surfaces, said dies in their fully closed position outlining a scalloped isosceles triangular opening having three concave sides and three convex vertices. j

15. Crimping apparatus for forming crimped electrical connections between ferrules and electrical conductors telescoped therein, said apparatus includingvfir'st andsecond crimping dies adapted to move towards each other, said first die having a nest including a pair of spaced side walls, the bottom of the nest including a central hump and Aa pair of concavities tangent to opposite sides of the hump and to a respective side wall, said second die including a pair of spaced types entering opposite sides of the nest and closely adjacent to the respective side walls when the dies are in their fully closed position, said tynes having a central hollow therebetween and convex camming surfaces tangent to opposite sides of said hollow and with a concavity near the end of each tyne tangent with the convex cammng surface, said hump and said convex camming surfaces when said dies are in their fully closed position being tangent to the respective sides of an equilateral triangle, said concavities at opposite sides of the hump and near the ends of said tynes being respectively centered at a pair of the vertices of said equilateral triangle, and said hollow being centered at a point within the other vertex of said equilateral triangle.

References Cited n the le of this patent UNITED STATES PATENTS 308,087 McDonald Nov. 18, 1884 14 Sherman Dec. 9, 1919 Rowley May 17, 1932 Douglas May 21, 1935 Douglas Dec. 31, 1940 Klein Aug. 5, 1941 Douglas Sept. 16, 1941 Carlson Mar. 19, 1946 Johnson Nov. 2, 1948 Dupre Dec. 28, 1948 Freedom Dec. 19, 1950 Andreu Aug. 21, 1951 Homan July 27, 1954 Wells Mar. 15, 1955 FOREIGN PATENTS France Apr. 4, 1906