US3356789A - Band-like crimp - Google Patents

Description

Dec. 5, 1967 j V PATTEN Q 3,356,789

BAND-LIKE CRIME Filed Aug. 11, 1965 :4 INVENTOR.

JOHN R. V/IN P/777'EN United States Patent 3,356,789 BAND-LIKE CRIMP John R. Van Patten, Waynesboro, Va., assignor to General Electric Company, a corporation of NewYork Filed Aug. 11, 1965, Ser. No. 478,917 7 Claims. (Cl. 174--74) ABSTRACT OF THE DISCLOSURE A crimp consisting of two or more bands of radial indentations is applied to a sleeve to hold a cable therein. The bands of indentations are spaced apart along the sleeve by a distance equal to or less than the width of each band to provide a strain relief between the bands. The method of making the crimp obtains substantially an inversion of the original arc of the sleeve at each indentation in a band so that minimal stress to the sleeve wall is realized.

The present invention relates to a crimp and a method of crimping and more particularly to the method and apparatus for holding a cable within a sleeve by the use of band-like crimps.

Since miniaturization in the electronic industry has become widespread, compact wiring provisions have become a necessity. In many instances, new concepts of packaging and component coupling must be devised since mere reduction of the size of components has not proved satisfactory. In the process of examining each element used in an assembly to see if it can be made smaller, the strain relief which prevents any cable strain from reaching the wires at the point of electrical connection has become subject to such scrutiny. It has been found that this device, which is generally three to four times the diameter of the cable to be held, may be replaced by a crimp which satisfactorily performs the same function yet does not increase the size of the connection.

The art of crimping is most often associated with fastening an electrical conductor or wire to a terminal connector lug with the wire inserted into the sleeve or barrel portion of the connector. A tool is used to depress a portion of the wall of the metal sleeve so that the wire is pinched by the collapsed wall and electrical connection to the lug is thereby secured. Such is basically the method employed in crimping to effect strain relief, where a cable containing a plurality of wires is desired to be held within a sleeve element so that any strain placed on thecable is not translated to the wires at the point of electrical connection but is absorbed by the crimp. Here, however, the degree of crimp and manner of holding the cable is more critical. The insulation of the cable is often slippery and therefore a better clamp must be devised. Because the cable contains a plurality of wires spaced in different configurations within the cable, indiscriminate and nonsymmetrical placement of the crimp may often be harmful because of the different materials within a cable. Extreme pressure applied to the cable by the crimp often requires that a pressure relief be provided.

It is, accordingly, an object of the present invention to provide means for holding a cable within a sleeve without damaging the sleeve element or the cable.

Another object of this invention is to provide a crimp for holding a cable within a sleeve element having radial holding power and minimal sleeve deformation.

A further object of this invention is to provide a crimp for holding a cable within a sleeve element which contains a pressure relief to absorb the outflow of the material of the cable from the crimped area.

Another object is to provide a stronger crimp for holding a cable within a sleeve element wherein a pair of circular crimps and the spacing therebetween form a sandwich trapping the insulation of the cable.

Another object is to provide a method of crimping a cable to be held within a sleeve element with a band-like crimp containing a pressure release.

A further object is to provide a method of crimping a cable to be held within a sleeve element where the thickness of the sleeve wall is maintained constant.

In carrying out the objects of the invention, there is provided in one embodiment thereof a plurality of bandlike crirnps separated to allow stress relief. Each band or ring includes a plurality of indentations or concave segments, the ends of each of which are coincident with the circumference of the sleeve. The method of providing such a crimp may include first the step of compressing the cylindrical sleeve until its circumference is changed into a plurality of linear segments or chords arranged in a band about the sleeve and further compressing each of the segments into the form of arcuate indentations so that each arcuate indentation presses radially inwardly to hold the cable. Another embodiment of the method for making such a crimp includes radially pressing into the sleeve with a plurality of arcuate dies so that the crimp is made in a single step.

Other advantages of the invention will become more fully apparent and better understood from the following description of an embodiment of the invention selected by way of example as illustrated in the drawings, in which:

FIGURE 1 shows an electrical element having a crimped sleeve portion securing a cable therein;

FIGURE 2 is a line drawing illustrating one of the preliminary steps in the method of making the crimp; and

FIGURE 3 is a line drawing of an end view of a crimped element also showing a second method of crimping.

Referring now to the drawings wherein like reference characteristics relate tolike parts throughout, there is shown in FIGURE 1 an electrical element, which for convenience is shown as a light element 12, having a sleeve portion 14 encompassing a cable 13. In general, the sleeve should be of slightly greater diameter than the diameter of the cable so that a close fit is obtained. To hold the cable within the sleeve of the electrical element the sleeve has been crimped as shown in this figure. This crimp 16 includes a plurality of bands of which two, 18 and 20, are shown. Each of these circular bands or rings includes a plurality of compressed segments 32 which provide .the cable holding function. A relief for the cable from the pressure of the crimp is provided by spacing 23 between bands 18 and 20. This spacing is of greater diameter than the crimped portion of the sleeve and thus provides a relief or reservoir for the material of the cable extruded by the compressive forces of the crimp. The pressure release of this space between bands will be discussed further below.

As shown more clearly in FIGURE 3, each of the segments 32 of the sleeve within a band of the crimp is in the shape of a concave depression or indentation pressing in on the cable. Each segment has its ends coincident with the original circumference of the sleeve 14 as indicated by the circle so referenced. The purpose of maintaining the ends of each segment at the original circumference of the sleeve is to obtain a minimum of deformation of the sleeve thereby reducing the likelihood of fracture of the electrical component at this point due to work hardening and reduction of the diameter of the sleeve. FIG- URES 2 and 3 further illustrate this characteristic by showing that the distance between ends of diametrically opposite segments is D, the original diameter of the sleeve.

While the number of segments within a band is not indicated by the illustration of FIGURE 1, there is shown in FIGURES 2 and 3 a band containing six segmentsfor purposes of illustration. The number of segments should be chosen so that there is not so many that the depth of the indentation is large compared to the length of the segment to provide the holding force required to secure the cable. A large number of short segments requires sharp indentations for each segment thereby risking fracture of the sleeve wall. In addition, the segments should not be so limited in number as to provide an uneven distribution of the radially inward forces on the cable thereby risking damage to the conductors within the cable. It is preferred that the number of segments be sufficient to permit a gentle curve for each segment approximating an inversion of the circumference of the sleeve.

FIGURE 3 shows a symmetrical crimp which is necessary for even distribution of forces on the wires of the cable. Insulated wires 38 are shown suspended by a fill 37 within the insulation 36 of the cable 13. Uneven forces on the wires would cause them to be flattened either against each other or the wall of the cable, a different picture from that shown. When shielded cables are used and the electrical conductors are subject to the unequal forces of a nonsymmetrical crimp, the possibility of a short between conductors or between conductor and shield has substantially increased.

The methd.-In FIGURE 2 there is shown a line drawing of the cross section of a sleeve after undergoing the first step of the crimping process. While maintaining the original circumference of the sleeve at the ends thereof, linear segments are compressed into the wall of the sleeve such that, if six be selected as the number of segments desired within a band, a hexagon is formed as shown. Each section of this symmetrical figure is designated 32, the sleeve before compression being shown as circle 14.

FIGURE 3 illustrates the shape taken by the sleeve which has been further compressed into arcuate indentations in place of the linear segments shown in FIGURE 2. The two-step process of compression to linear segments and further compression to concave segments is often necessary where an up and down press is the tool used for applying the crimp. With this sort of device, a single impression to form the band of arcuate segments is not predictably obtainable without loss of dimension, such as is desired to be maintained by having the ends of each segment coincident with the original circumference of the sleeve.

Also illustrated in FIGURE 3 is a single step crimping process. Here, a plurality of tool bits 34 are shown, each capable of moving in a radial direction to the center of the sleeve for individually compressing each of the segments in a band of the crimp. With individual pressure applied at the points desired, greater certainty of maintaining the dimension of the end points of the segments unchanged is obtainable.

Since it is an object of the present invention to maintain minimum deformation of the components subject to the crimping process, it is desirable that the number of segments within a band of the crimp be selected so that the final arc of each segment most closely approximates the original curve of the circumference of the sleeve. It is thought that by having the arc of the circumference inverted at each segment the deformation of the wall of the sleeve will be maintained at a minimum. When the sleeve is first compressed into a plurality of linear segments, the compression results in a thickening of the sleeve wall in each of these portions. By further compressing each segment, the sleeve wall is stretched and thus thinned, and if the compression stops at the point at which the original arc of the sleeve has been inverted, the original thickness of the wall is obtained.

It should be noted that the six-sided figure shown in FIGURES 2 and 3 consumes all of the circumference of the sleeve so that the segments within a band are contiguous with each other. This close association of segments results in sharp points at the circumference which may be either rounded ofi or, in fact, a number of segments less than six may be selected thereby providing proportionally larger areas of unaltered sleeve wall therebetween while maintaining the desired inversion of the arc of the sleeve wall at each segment. Here, however, the selection is restricted by the obligation of providing equally distributed radially applied forces to the cable.

It is well known that when a material is compressed it is caused to flow out from the area of compression and the material thus necks down and becomes thinner and weaker. Thus, the electrical cable is caused to neck down under the crimp. This reduction in area can prove serious if the insulation is extruded to the point of hazarding an electrical short between the conductors. Also, where the crimp consists of a single wide compression band, the filler material 37 in the cable can compact to a degree where the crimping pressure is transmitted through the compacted filler to the conductors causing the material of the conductors to flow out of the crimp area in both directions from the center of the crimp. This flow away from the crimp center results in the necking down of the conductors at this point and their possible fracture.

To provide relief from the necking down caused by the crimp the bands or rings of the crimp are spaced from each other thereby allowing a pressure relief between bands. This relief portion 23 is of greater diameter than the crimped portion of the sleeve which allows the material of the cable to flow into this portion. It should be pointed out that the combinations of the two crimps sandwiching the bulged pressure release provides extra holding power for the cable as the spacing between bands provides what may be considered a trap for the cable material. To enhance this extra holding power, the distance between bands should be less than or at most equal to the width of a band since it is desired that the bulge the release provides be abrupt and the space between bands actually trap the extruded material of the cable.

It will be recognized that while the holding technique of the present invention has been described as a strain relief, i.e., holding a cable to avoid the strain to the conductors occasioned by unavoidable pulls on the cable, the crimp hereinbefore described is readily adaptable to making electrical connection such as to the shield of a shielded cable or to a conductor itself, Here too, the advantages of maximum holding power with minimum deformation to the sleeve portion of the electrical element may be realized.

From the foregoing, it is apparent that the technique of holding a cable within a sleeve element described and the method of achieving the crimp for this purpose provides maximum protection for the cable and the electrical element crimped. This is primarily because with minimum deformation of the sleeve of the electrical element the circular bands of indentations in the sleeve provide equal radial forces on the wires inside the cable during the crimping operation and the insulation on individual wires is thus thinned out evenly on all sides thereby minimizing the possibility of wire-to-wire or wire-to-shield shorts caused by the high forces involved.

Since various changes and modifications may be made in the practice of the invention herein described without departing from the spirit or scope thereof, it is intended that the foregoing description shall be taken primarily by way of illustration and not in limitation except as may be required by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of holding a cable within a close fitting sleeve, comprising inserting one end of said cable intosaid sleeve, crimping said sleeve into at least two pluralities of linear segments around the circumference thereof, said pluralities of linear segments being spaced from each other to permit stress relief therebetween, further crimping each of said linear segments into arcuate segments substantially equal in radius. to the ra i of said sleeve so that each segment presses in on said cable to inhibit movement of said cable with respect to said sleeve.

2. A method of holding a cable within a close fitting sleeve, comprising compressing said sleeve radially inward about said cable in at least two rings of concave segments, s-aid rings being spaced from each other to permit pressure relief therebetween, and controlling the compression of said sleeve to obtain a substantial inversion of the original convex segments of said sleeve while maintaining the original circumference of said sleeve at the ends of each of said concave segments, each segment being formed to press radially in on said cable to prevent relative movement between said cable and said sleeve.

3. A method of holding a cable within a close fitting sleeve, comprising thickening the wall of said sleeve by compressing said sleeve at a plurality of rings in linear segments about said cable, and thinning the wall of said sleeve by further compressing each of said rings so that each of said segments in a ring is stretched into a concave configuration substantially the inverse of the original convex configuration of said sleeve and each segment is thereby caused to press into said cable to prevent relative movement between said cable and said sleeve.

4. A crimp for holding a cable within a close fitting sleeve, comprising a plurality of circular bands of arcuate indentations in said sleeve, the ends of each of said arcuate indentations forming unaltered portions of the surface of said sleeve, each of the arcuate indentations in the wall of said sleeve being substantially a reversal of the original convex curve of said sleeve and bearing radially on said cable to prevent relative movement between said sleeve and said cable, said bands of arcuate indentations being spaced from each other to provide a pressure relief for said cable.

5. A crimp as defined in claim 4 wherein the arcuate indentations within a band are contiguous with each other.

6. A crimp as defined in claim 5 wherein the space between bands is equal to or less than the width of one of said bands.

7. A strain relief for securing a cable within the sleeve of an electrical element, comprising a plurality of rings of arcuate indentations in said sleeve, each of said indentations being equal in length and depth and bearing radially on said cable to prevent relative movement between said sleeve and said cable, the depth of each indentation, measured from a plane through the end points of the indentation, being substantially equal to the height of the original arc of the sleeve above said plane, and the number of indentations Within a ring being chosen so that the depth of each indentation is not large compared to the length thereof and so that the forces on said cable are evenly distributed, each of said rings about said sleeve being separated to form a pressure release for said cable, the spacing between said rings being less than or equal to the width of one of said rings so that the portion of the cable caused to flow into said pressure release by the pressure of said indentations is trapped by the rings about the spacing thereby effecting a greater bond between the electrical element and cable.

References Cited UNITED STATES PATENTS 2,816,276 "12/1957 Fuller et al 339-223 X 3,123,663 3/1964- Muldoon 17484 3,203,078 8/1965 Ustin 174-84 X FOREIGN PATENTS 790,536 2/1958 Great Britain.

LEWIS H. MYERS, Primary Examiner.

H. HUBERFELD, Assistant Examiner.

Claims (2)

1. A METHOD OF HOLDING A CABLE WITHIN A CLOSE FITTING SLEEVE, COMPRISING INSERTING ONE END OF SAID CABLE INTO SAID SLEEVE, CRIMPING SAID SLEEVE INTO AT LEAST TWO PLURALITIES OF LINEAR SEGMENTS AROUND THE CIRCUMFERENCE THEREOF, SAID PLURALITIES OF LINEAR SEGMENTS BEING SPACED FROM EACH OTHER TO PERMIT STRESS RELIEF THEREBETWEEN, FURTHER CRIMPING EACH OF SAID LINEAR SEGMENTS INTO ARCUATE SEGMENTS SUBSTANTIALLY EQUAL IN RADIUS TO THE RADIUS OF SAID SLEEVE SO THAT EACH SEGMENT PRESSES IN ON SAID CABLE TO INHIBIT MOVEMENT OF SAID CABLE WITH RESPECT TO SAID SLEEVE.

4. A CRIMP FOR HOLDING A CABLE WITHIN A CLOSE FITTING SLEEVE, COMPRISING A PLURALITY OF CIRCULAR BANDS OF ARCUATE INDENTATIONS IN SAID SLEEVE, THE ENDS OF EACH OF SAID ARCUATE INDENTATIONS FORMING UNALTERED PORTIONS OF THE SURFACE OF SAID SLEEVE, EACH OF THE ARCUATE INDENTATIONS IN THE WALL OF SAID SLEEVE BEING SUBSTANTIALLY A REVERSAL OF THE ORIGINAL CONVEX CURVE OF SAID SLEEVE AND BEARING RADIALLY ON SAID CABLE TO PREVENT RELATIVE MOVEMENT BETWEEN SAID SLEEVE AND SAID CABLE, SAID BANDS OF ARCUATE INDENTATIONS BEING SPACED FROM EACH OTHER TO PROVIDE A PRESSURE RELIEF FOR SAID CABLE.

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