US2927150A

US2927150A - Insulation piercing crimp

Info

Publication number: US2927150A
Application number: US554176A
Authority: US
Inventors: Paul M Amigh; Rossiter R Potter
Original assignee: Aircraft Marine Products Inc
Current assignee: TE Connectivity Corp
Priority date: 1955-12-20
Filing date: 1955-12-20
Publication date: 1960-03-01
Anticipated expiration: 1977-03-01

Description

March 1, 1960 P. M. AMIGH ET AL 2,

INSULATION PIERCING CRIMP Filed Dec. 20, 1955 2 Sheets-Sheet 1 INVEN Ross'figr R. Potter an I Paul M,Amvgh BY March 1, 1960 P. M. AMIGH ETAL 2,927,150

INSULATION PIERCING CRIMP 2 Sheets-Sheet 2 Filed Dec. 20, 1955 INVENTOR. Ross'flzer R, Putt-r and Paul M, Amish BY 1M We. 1 J M United States PatentO INSULATION PIERCING ennu Paul M. Amigh, Marysville, and Rossiter R. Potter, Harrisburg, Pa., assignors to Aircraft-Marine Products, .Inc., Harrisburg, Pa.

1 Application December 20, 1955, Serial No. 554,176

I 3 Claims. c1. 174-74 This invention relates to methods and apparatus .for making solderless electrical connections and, more particularly, to the method and apparatus for effecting an electrical connection between a connector and the metallic core of an insulated conductor through the insulation covering thereof.

In the art of making solderless connections with insulated conductors, it heretofore has been the practice to dispose a conductor in an open ferrule connector which then is closed or crimped, the base of the ferrule having one or more preformed insulation piercing spears or prongs struck up therefrom was to pierce the insulation and part the strands of the conductor during the crimping operation. The connections thus produced, however, at best provide a joint of relatively high electrical resistance and low mechanical strength which has operated to limit the field of use oftheprinciple of insulation piercing in electrical. connectors.

In such connections electrical continuity between the conductor and the body of the connector body is accomplished by virtue of the core strands pressing against the sides of the insulation piercing spear. In this type of electrical connection, the quality and characteristics of the joint depend primarily on the amount of pressure forcing the contacting surfaces together and in part on the area of contact. Accordingly, the high resistance usually encountered .in insulation piercing connectors heretofore designed may be traced to insufficient contact pressure being maintained between the surfaces in contact. This relatively low contact pressure is assignable .to two primary causes. First, the energy maintaining the conductor strands pressed against the insulation piercing spear isstored in theinsulation material surrounding. the conductor core, which insulation, being under constant pressure from the confining andcrimped connector ferrule, tends to relax and be extruded out of the crimped area. Secondly, as the connector ferrule usually is simply wrapped around the conductor, leaving an open scam, the inherent resiliency of the metal pro- 'method of producing such connections f I Another object is to provide in the insulationpiercing connector art, a connection, and a methodfor producing it, having a sustainable high contact pressure.

Still another object of the invention is to provide a method and apparatus for crimping a connector to an insulated wire wherein the conductor metallic core is directly pressed between opposed portions of the, metallic ice ferrule thus avoiding reliance on the conductor insulation to sustain the contact pressure in use.

V! ing of the ferrule during the crimping operation.

A still further object is to provide in an insulation piercing connector'utilizing a seamless or closed ferrule a method and apparatus for applying the connector with minimum distortion of the ferrule in cross-section over the crimped length.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there are shown and described several embodiments of the invention; 'it is to be understood, however, that these embodiments are not intended to be exhaustive nor limiting of the invention but are given for purposes 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 practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

In the drawings:

Figure 1 is a plan view of a metallic ferrule crimped onto the end of an insulated conductor in accordance with the present invention;

Figure 2 is an enlarged fragmentary sectional view taken along lines 2-2 of Figure 1;

Figures 3 and 4 are views similar to Figure 2 illustrating slightly modified connections formed in accordance with the basic principles of the present invention;

Figure 5 is a sectional view taken along lines 5-5 of Figure 2; Figure 6 is a sectional view taken along lines 6-6 of Figure 4;

Figures 7 and 8 are sectional views similar to Figures 5 and 6 illustrating further modified forms of the connection;

Figure 9 is a fragmentary front view of the crimping dies for effecting the connections generally illustrated in Figures 1 through 8;

Figure 10 is a sectional view taken at lines 1010 of Figure 9;

- Figures 11 and 12 are fragmentary perspective views of the forming and severing blades employed in connection with the dies shown in Figures 9 and 10; and

Figure 13 is an enlarged fragmentary sectional view taken at lines 13-43 of Figure 10 for the purpose of illustrating the cooperation of the blades shown in Figures l1 and 12 with the dies of Figures 9 and 10.

With reference to Figures 1 and 2, in accordance with one embodiment of the invention, a ferrule 10 is crimped onto the end of an insulated conductor 12 and serves to couple electrically and mechanically the conductor with a pin or plug member 14 formed as an integral extension of ferrule 10. It is to be understood, however, that member 14 may take any form suitable for a particular use, such as a wire ring or spade terminal, or may be a ferrule duplicate of ferrule 14 thereby to serve as a means for spicing a pair of conductors. Conductor 12 may consist of a multiple strand metallic core 16 surrounded by a concentric covering 18 of a suitable insulating material. In general, the principles of the presentinvention are applicable in connection with confductors having any of the common types of insulation, for example, good electrical connections have been made utilizing a conductor covered with a primary serving J of a vinyl-base plastic material and an outer serving of cotton braiding.

To efiect the electrical connection with core 16, ferrule it) is provided with a plurality of peripherally aligned rectangular, or angular, tangs or tabs 20 severed from ferrule so as to have a free end contact portion 22 that extends through insulation 18 to contact in intimate engagement with core 16. Preferably, electrical contact by ferrule 10 with core 16 is had over relatively wide surfaces substantially transverse to the longitudinal axis of the conductor core and at a plurality of opposed points so that the conductor core may be tightly compressed between relatively rigid metal portions under high pressures. More particularly, it is desired that the tabs 20 of ferrule 10 in contact with the core be at diametric points about the periphery of the conductor so as to mutually assist each other in maintaining any contact pressures originally imposed on the core thus to avoid placing any reliance on the insulating material to hold the core strands against the insulation piercing portions of the ferrule. To this end, the generally rectangular tangs or tabs 20 are severed from opposite sides of ferrule It) with the leading and free end edges 23 of contact portions 22 being substantially transverse to the longitudinal axis of the conductor so that upon turning the tabs inwardly about a transverse bending axis, the conductor core may be compressed between opposed metal surfaces as shown in Figure 5.

longitudinally displaced from tabs 26 along ferrule 10 are a series of indentations 24 which serve to increase the mechanical strength of the connection by firmly grasping the insulation in a manner to be more particularly described. The connection shown in Figures 1 and 2 may convenientiy be eifected by automatic or semi-automatic crimping machines well-known generally in the-art, which machines conventionally include a press bed and a ram movable toward and away from the bed to complete a crimping cycle, the ram being driven by a power source either electrical or mechanical in nature as desired. A cooperating die set including upper and lower forming die members or blocks affixed to the ram and bed respectively of the machine serve to operate on the ferrule according to the design of the operating die faces for producing the end result desired.

To achieve the specific connection of the present invention, forming die member 32, Figures 9 and 10, the lower member of a die set, is provided with anelongated recess 30 contoured to receive ferrule '10 in position to be crimped. The die set also includes an upper forming die member 34 adapted to be moved by-the machine ram in the. crimping stroke toward die member 32, die member 34 also havingin its operative face a recess 36 in alignment with recess 30 for forming a ferrule-confining cavity 37 when opposed faces 38 and respectively of the die blocks abut.

Any method of presenting the ferrules to be shaped in proper crimping position between the die set will suffice. For example, the connectors may be fed one at a time from a hopper into the crimping region as an automatic operation of the machine, or the connectors may be manually positioned as desired. Withthe end portion of an insulated conductor assembled within the ferrule and therewith disposed within recess 39 of forming die32, the initial phase of thecrimping operation is completed when the die set is closed, at which time surfaces 33- and 40 of the respective die blocks are in abutting relation thereby confining the ferrule within the similarly contoured cavity 37.

For effecting the desired forming and severing operations on ferrule 19 a plurality of

formingblades

42, 44 and 46 and 48, 59, 52 in die blocks 32 and 34 respectively are slidably movable in a like number of

radiating slots

43, and 47, and 49, 51 and53, in the associated die blocks.

As will be discussed in detail the forming blades are adapted to be driven under high pressure into cavity 37 in a second phase of crimping machine operation, which is preferably initiated subsequent to the bottoming of die34 with respect to die 32 forming cavity 37.

Each of the forming blades, Figures 11 and 12, have at their leading side that is projectable in cavity 37, an elongated multiple die face arranged lengthwise relative to cavity 37, which die face includes a generally rounded and elongated die 54 for effecting the indentations 24. There being a combined total of six blades and dies 54, for example, a like manner of elongated indentations 24 will be produced, longitudinally oriented and preferably equally spaced about the periphery of ferrule 10 as shown in the embodiment of Figure 1.

At least one and preferably a pair of forming blades, such as blades 44 and 50, in diametric positions in the respective die blocks are provided with severing and curling dies 56, Figure 11, which are so shaped as to strike tangs or tabs 29 from the body of ferrule 10 and turn them inwardly towards core 16 through insulation 18. On the

remaining blades

42, 46, 48 and 52, a holding or supporting die 58, Figure 12, in peripheral alignment with severing die 55, is provided for a purpose to be described hereinafter.

In the illustrated embodiment of the crimping dies, die 56 is shown to be an integral extension of die blades 44 or 50 and substantially triangular. in shape for presenting a substantially planar face 60 inclined inwardly toward the axis of the cavity 37, and hence, the axis of ferrule 10 and inserted lead 12. The side edges 62 of die face 60. are relatively abrupt and sharp to cooperate with asharp and transverse leading edge 63' of the die thus to be capable of severing the metal ferrule 10 on being urged inwardly under pressure into cavity 37.

Ingeneral, in the art of making cold-forged solderless connections it has been found that optimum electrical characteristics are achieved when the metallic core of the conductor is compressed within the encompassing terminating connector to a degree sufficient to produce a voidless cross-section of metal in the crimped area. Further, the compression should be accomplished at pressuressuificient to extrude the metal comprising the metallic core from its original cross-sectional area to a final area significantly less than the original area, a reduction of 20% being typical for a gas tight crimp. On pressing the opposed tabs 20 together at their end portions to-the'extent necessary to produce a voidless cross-section of metal, it has been found that such pressure concentration proves at least adequate to eliminate completely insulation from between the contact surfaces 22 of the tabs'and-the underlying conductor core. The insulation piercing action thus occurs as aresult of imposing high pressures along lateral lines, atleast as defined by the leading free edges of the tabs, on opposite sides of the conductor, the action being effective to pierce such insulating materials as are in common use and depending in nature, i.e., whether a severing, extruding, or both, upon the type insulation to be parted.

It will be appreciated that the extent to which tabs 26 are-bent radially inwardly and the tab width depend upon the width of die face 60 and'the length and angle this face makes with respect to the longitudinal axis of the: cavity 37, and further, the 'extent to; which the die 56.is:projected into cavity 37'. The length and width ofthe tab and the angle at which it is turned inwardly determine, of course, the area of contact made with the metallic-core 16 at free end portion 22. To obtain optimum electrical characteristics in the contact the width of the'tab should be approximately as wide as the conductor corein its compressed condition thereby trapping and essentially surrounding the strands'of the conductor as illustrated in Figure 5. As a minimum, the tab width should not be so diminished that the strands ofthe'conductor core may be appreciably extruded around the tab side edges during crimping although some slight mushrooming effect, as shown, of the conductor is desirable for stabilizing the tab against lateral movement inrresponse to sidewise pulls on the conductor. Conversely, the tabs should not be so wide as to weaken significantly the ferrule mechanically, it being understood that the number of tabs and the width thereof are designed to retain adequate structural strength for the particular use involved.

Where only a pair of piercing tabs are to be used it is especially desirable that the side walls of the ferrule in peripheral alignment with the tabs be supported, or preferably slightly indented, during the crimping operation to permit sufficiently high pressures at the 'exact piercing station for effective severing and extruding or both. To furnish lateral support for the ferrule side walls, supporting dies 58 on forming

blades

42, 46,48 and 52 have operating faces dimensioned to produce indentations 64, Figures 1 and 5, which cover as much of the ferrule side walls between the tabs as is practical. Indentations 64 advantageously absorb the lateral pressure of the conductor core during crimping thus assuring that the metal of the conductor and the insulation are extruded longitudinally, rather than laterally, while maintaining the side walls of the ferrule within their original configuration. I

For many applications the mechanical strength of the connection aiforded by tabs 20 and indentations 64 will be sufficient. It is preferred, however, that the electrical contact area at tab portions 22 be isolated when stresses of significant magnitude are expected to be applied in normal use to conductor 12. The mechanical strength addedto "the joint by indentations 24 also serves to isolate the electrical contact area, the characteristics, such as the size, shape and the number of indentations 24 depending upon the conditions of a particular use. In general, however, the indentations should be as deep as possible without significantly damaging or rupturing the underlying insulation, and as long and narrow as possible for minimizing distortion of the original configuration of the ferrule without acting as a piercing instrument relative to the insulation.

As thus made, the connection provides electrical contact at end edges 22 of the tabs 20 with the conductor core along diametrically opposed surfaces between which the conductor core may be compressed under high pressures to achieve insulation piercing and retainable high contact pressures over effective surfaces of contact. From Figure 5 it can be seen that the major portion of the conductor perimeter is in contact with metal portions of the ferrule. To increase still further the proportional contact area and to provide a system which can be subjected to higher crimping pressures, it is preferred that three mutually opposed insulation piercing tabs be struck from the ferrule, Figure 7. In this embodiment, of course, the width of the tabs should be designed so as not to mutually interfere during the crimping operation.

In another embodiment, for a two tab system, the face 60 of shearing dies 56 may be made with a slight transverse concavity thereby to impart a like contour to contact surfaces 68 of tab end portions 70 as shown in Figure 8. The concave configuration obviously reduces the tendency of the conductor core strands to extrude laterally and escape contact with the contact surfaces of the tabs during crimping while an advantageously high linear proportion of the core perimeter is contacted by the tabs.

Additional mechanical strength and rigidity may be imparted to the tab structure by curling the tab portions, as they are moved radially inwardly towards the conductor core, as compared with the fiat bend form described in connection with Figures 1 and 2. By having the operating face 60 of severing die 56 gradually curved, not shown, relative to its length, as illustrated by the contour of the tabs in Figure 3, during the crimping l of the die block relative to the recess therefor.

operation leading edges'72 of the tabs are caused to part the conductor insulation and engage the metal core. Further inward curling of the tabs causes edges 72 to slide along, as well as into, the conductor core thereby to effect a grooving action along opposite sides of the conductor core. During this grooving action the high pressures involved in crimping results in both extrusion of the conductor core metal and coining or burnishing of the relatively sharp edges 72 to the rounded configuration indicated in Figure 3. There is thus assured a good clean electrical contact and complete removal of insulation from within the contact area. In addition, metal of the conductor is disposed axially behind the leading edges 72 of the tabs. Consequently, metal of the conductor core must first be deformed before any tensile stresses imposed on the conductor, either to the right or left of the conductor axis in Figure 3, can result in relative movement of the conductor and ferrule. Furthermore, relative to a pull on the conductor to the right in Figure 3, a camming action arises at the free end of the tabs which tends to draw the tabs further inwardly and more tightly against the conductor core thereby substantially increasing the resistance of the conductor to mechanical displacement from the ferrule.

The principles discussed in connection with the embodiment of Figure 3 may be applied in instances where it is desired to employ only a single insulation piercing tab, as shown in the embodiment illustrated in Figures 4 and 6. As shown, application of sufficient pressure between the free end portion of tab 74 and diametric supporting indentation 76 has caused extrusion of insulation from under the tab and from between the core and side wall 78 of the ferrule opposite indentation 76. The degree of pressure required, and the length of tab 74 to be struck and other like considerations depend, of course, on the characteristics of the insulation such as thickness, toughness, etc.

As alluded to above, in the crimping operation die blocks 32 and 34 are first closed to define cavity 37 whereupon the forming blades are driven into the cavity to operate on and effect the connection between the assembled ferrule and conductor. To accomplish these operations in the sequence desired, in the illustrated embodiment, die blocks 32 and 34 take the form of a split hexagonal block, the block halves being associated with the press bed and ram respectively of the crimping machine, not shown. Each die block, for example, block 34 is rigidly affixed as by bolts 82 to a carrier plate slidably mounted in a die block holder 84 which is rigidly connected to the press ram 86, or the press bed as the case may be. Each of the die block holders 84 is provided with a semihexagonal recess 88 which corresponds in dimensions to its associated die block 34 for receiving the block in a close fit. The die blocks are urged or biased out of the associated recesses 88 by virtue of normally compressed springs 90 which act between the base 92 of the die block holder and a bearing surface 94 on the die block carrying plate 80. A pin 96 in die block holder 84 cooperating with slot 98 in the carrying plate 80 limits the extent of movement The forming blades, for example,

blades

48, 50 and 52 in die block 34 are freely slidable in their

respective slots

49, 51 and 53, but are restrained from dropping altogether out of the slots by means of flat stop keys 100 e received in recesses 102 in die block 34, the recesses 7 Figure 10, the blade dies 54, 56 and 58 project to the desired degree in cavity 37.

As thus constructed, in the open position of the apparatus, Figure 9-, die blocks 32 and 34 are projected out of recesses 88 with the forming blades resting or idling in their associated slots. On movement of the press ram' towards the press bed the die block holders 84 move relatively towards one another to cause the die blocks 32 and to close, forming and closing cavity 37 about the ferrule to be crimped. Further movement of die block holders 84 seats recesses 88 about the hexagonal faces of the die blocks. As a result, the surfaces of recesses 88 are forcefully brought tobear against therear ends of the forming blades, driving them inwardly along their associated slots, and causing the die faces thereof to project within cavity 37 operating on the ferrule as has been described. On upward or opening movement of the ram, the die blocks are biased by springs 90 out of the recesses permitting the forming blades again to idle Within the die block slots, thus completing the cycle of crimping operation.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made Without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.

We claim:

1. In-an electrical connection with an insulated electrical conductor, a substantially cylindrical metallic ferrule receiving an insulated section of the conductor, at least a pair of opposed tab portions intermediate the length of said ferrule having substantially transverse free end edges relative to the longitudinal axis of the conductor core, the length of said edges being approximately equal to the original diameter of said core, said tab portions being turned inwardly With said edges penetrating the conductor insulation and compressing said core along opposed lines of contact, said opposed lines lying in the least a pair of: opposed tab portions intermediate the length of. saidferrule having substantially transverse free end edges relative to the longitudinal aXis of the conductor core, said tab portions being turned inwardly with said edges. penetrating the/conductor insulation and compressing said core along opposed lines of contact, said tab portions being transversely bowed at said edges withan inward concavity so as substantially to encompass said core along said lines of contact, said opposed lines lying in the same transverse plane relative to the longitudinal axis of the ferrule.

3. In an electrical connection with an insulated electrical conductor, a substantially cylindrical metallic ferrule; receiving an insulated section of the conductor, at least three circumferentially spaced tab portions in said ferrule having substantially transverse free end edges relative to the longitudinal axis of the conductor core and substantially encompassing said core, said tab portions being turned inwardly with said edges penetrating the conductor insulation and compressing said core along lines of contact substantially encompassing said core, said opposed lines lying in the sarne transverse plane relative to thelongitudinal axisof the ferrule.

References Cited in the file of this patent UNKTED STATES PATENTS 1,706,005 Thompson Mar. 19, 1929 2,291,434 Hollopet'er July, 28, 1942 2,604,508 Bergan July 22, 1952 2,646,554 Pollock July 21, 1953 2,694,188 Poupitch Nov. 9, 1954 2,783,442 Burnosky Feb. 26, 1957 2,799,721 Floyd July 16, 1957 FOREIGN PATENTS 607,276 France Mar. 23, 1926 UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 2,927,150 March 1, 1960 Paul M. Amigh et al It is hereby certified" that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

lines 2 and 3, for "assignors to Aircraft- In the grant,

Pennsylvania," read Marine Products, Inc., of Harrisburg, assignors to AMP Incorporated, a corporation of New Jersey, line 12, for "Aircraft-Marine Products, Inc. its successors" read AMP Incorporated, its successors in the heading to the printed specification, lines 4 and 5, for "assignors to Aircraft-Marine Products, Inc. Harrisburg, Pa." read assignors to AMP Incorporated, a corporation of New Jersey Signed and sealed this 27th day of September 1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT c. WATSON Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,927, 150 March 1, 1960 Paul M. Amigh et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 2 and 3, for "assignors to Aircraft- Marine Products, Inc., of Harrisburg, Pennsylvania," read assignors to AMP Incorporated a corporation of New Jersey, line 12, for "Aircraft-Marine Products, Inc. its successors" read AMP Incorporated, its successors in the heading to the printed specification, lines 4 and 5, for "assignors to Aircraft-Marine Products, Inc. Harrisburg, Pa." read assignors to AMP Incorporated, a corporation of New Jersey Signed and sealed this 27th day of September 1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents