|Publication number||US3128214 A|
|Publication date||Apr 7, 1964|
|Filing date||Dec 27, 1960|
|Priority date||Apr 6, 1959|
|Publication number||US 3128214 A, US 3128214A, US-A-3128214, US3128214 A, US3128214A|
|Inventors||Lay Norman R|
|Original Assignee||Ling Temco Vought Inc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (3), Referenced by (21), Classifications (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
April 7, 1964 N. R. LAY 3,123,214
METHOD oF MAKING MULTICONDUCTOR CABLE original Filed April 6, 1959 s sheeissheet 1 FIG 4 FlG. 3
Norman R. Lay
AGENT April 7, 1964 N. R. LAY 3,128,214
METHOD OF MAKING MULTICONDUCTOR CABLE Original Filed April 6, 1959 3 Sheets-Sheet 2 6 Norman R. Loy
BYjevL'C'o-QM AGENT April 7, 1964 N` R, LAY
METHOD OF MAKING MULTICONDUCTOR CABLE Filed April 6, 1959 5 Sheets-Sheet 3 Original OAV@ Norman R. Lay
United States Patent O 3,128,214 METHOD F MAKING MULTICNDUCTQR CABLE Norman R. Lay, Arlington, Tex., assigner, by mesne assignments, to Ling-'i'lemco-l/ollgllt,y lne., Dallas, Tex.,
a corporation of Delaware Original application Apr. 6, 1959, Ser. No. 864,177, now
Patent No. 2,991,323, dated July 4, 1961. Divided and this application Dec. 27, 1960, Ser. No. 78,718 Claims. (Cl. 156-55) This invention relates to multiconductor cables and more particularly to a method for making a relatively rigid multiconductor cable. s n The instant application is a division of my copending application forfMulticonductor Cable, Serial No. 804,177, tiled April 6, 1959, and since issued as US. Patent 2,991;
lt has been common practice for electrical wires to be tied together to form harnesses. For protection against chaing, each wire has been provided with an outer, protective layer of fabric or other material which overlies the electrical insulating layer or layers on the conductor in the wire. f
ln other cases, the outer, abrasion-protective layer has been left oil each wire and the entire bundle of wires inserted in a protective casing. Thus, it has been the common practice to draw a bundle of wires through a flexible casing or'sleeve made of' vinyl plastic or some other dielectric material. The outer sleevings employed have themselves been subject, to an undesirable extent, to chafing and abrasion; and because harnesses made with tlexible sleevings tend to sag and are easily deflected, they must be clamped at relatively close intervals to the structural itemsfon which they are mounted, and, to prevent chang, adequate and relatively wide clearances must be left between them and adjoining items against which they might be deected under vibration or other conditions.
The ilexible, outer jackets or sleevings have been of round cross-section. Use of jackets of such cross-section has been compelled by practical considerations including the diihculties which would be encountered in pulling wires through a sleeve which, for example, had a rectangular cross-section, to the end that the bundle of wires would thoroughly fill the jacket. Further, in case, of a ilexible jacket, the rectangular cross-section is distorted by pressures of the wires and tends to become of circular cross-section as it becomes tightly filled with the wires. In many, probably in most, ,applications a multiconductor cable of circular cross-section is quite wasteful of space; for example, where it is strung along one or more substantially iiat surfaces, space would be saved (in most cases) if the cable were of rectangular cross-section. ideally, of course, space would best be conserved by making the cross-section of the cable, at anypoint along its length, such as best to lit against and among the other kitems with which it must be associated.
distinct limitations upon the compactness and density.
ymode of construction is of little orno advantage in reducing weight or cross-sectional area of the harness because it is not practically possible to space wires of any considerable length very closely together without having some of them Contact or cross each other in a short-cirice cuited relation which is made permanent when the wires are cast into the insulating material. the wires must be spaced well apart, with added spacing for safety; and a great weight and volume of insulating material must be used in making the solid block or strip into which they are cast. For reasons concerning their electrical properties and their producibility, the yconductors which most often are used in electrical harnesses are made of single or stranded wires of circular cross section. Even ir the spacing of wires of circular cross-section could be controlled so reliably and well that the wires could be spaced so closely that the insulation about each wire was, at its thinnest point, of the minimum thickness for preventing arc-over to an vadjoining wire, the embedding of the wires in a solid, common, insulating block requires, by its very nature, the filling of all of the spaces between the round wires and thus, of course, requires the use of a great weight of insulating material above that actually necessary merely for the insulation of the Wires. n
A cable made of a plurality of wires cast into a single piece of insulating material tends to behave under llexure, from vibration or other causes, as a single bar and does not lhave the advantages which, as will become apparent, accrue to a multiconductor cable in which each'wire is slideable, with its insulating sheath, lengthwise of and against adjoining wires. The same disadvantage may, and ordinarily does, appear in cables made of a large number of individually insulated wires pulled through a protective sheath: as more wires are introduced into a sheath of given diameter in an attempt to produce a highly compact cable, wire-to-wire friction becomes yso high that the individual wires no longer are slideable against each other within the sheath, and the cable behaves as a solid, though not necessarily rigid, bar. This behavior becomes a detect where, for example, vit causes the cable to display a resonance to mechanical vibrations and thus further aggravate the problems of chang, clamping, etc. lt is, accordingly, a` major object of the invention to provide a method for making a rigid multiconductor cable of improved low weight and volume and resistance to heat and abrasion.
Another object is to provide a method for making a rigid multiconductor cable which is pre-shaped to conform to surfaces against or near to which it is to be mounted yand which is accurately and stably locatable relative to such surfaces, y
A further object is to provide a method for making a high-density, rigid multiconductor cable which is substantially non-resonant to mechanical vibration and which requires a minimum number of mounting points.
A still further object is to provide a method for making a inulticonductor cable of improved resistance to electrical overloading of individual wires in the cable and possessing a greater current-carrying capacity of the wires individually and as a whole. y
Yet another object is to provide a method for making a high-density multiconductor cable having branches that re ofone-piece, unitary construction with each other and to supply a practical and eillcient method for making the same. Still other objects and advantages will be apparent from the specification and claims and from the accompanying drawing which illustrates an embodiment of the invention.
ln the drawing: Y FGURE 1 is a perspective View of a multiconductor cable produced by the instant method; n
FlGURE 2 is an enlarged view in elevation oa segment of the cable in which portions of the cover have been removed to show the wires and the reinforcing plate; FIGURE 3 is a cross-sectional View of the cable taken as at line lll-lll in FGURE l; v
FIGURE 4 is a longitudinal sectional view'taken as For this reason, n
a along the line and looking in the direction shown by the arrows at IV-IV in FIGURE l;
FIGURE is a cross-sectional view through several typical conductors of the cable shown in other figures;
FIGURE 6 is a plane View of a branched portion of the cable shown in FIGURE l in .vnich some of the outer cover is removed to show the cover interior;
FIGURE 7 is a perspective view of a harness of wires prepared for incorporation into a multiconductor cable such as shown in FIGURE i;
FIGURE 8 is a cross-sectional View taken as at VIII- VIII in FIGURE 9 and with the male mold member shown not yet inserted into the female mold member; and
FIGURE 9 is a perspective view of the meld with the multiconductor parts being molded therein.
With reference now to FIGURES l and 2 of the drawing, the multiconductor cable 10 made according to the present method comprises an elongated, tubular cover 11 through which extends a plurality of elongated, individually insulated conductors such as the Wires 12. The ends of the wires 12 may be provided with suitable terminals or connectors, such as, for instance, the multiconnector plugs or receptacles 13. The outer shape of the cover 11, in the example shown, is rectangular at the location of the cross-section shown in FIGURE 3, but is by no means limited to the cross-sectional shape shown; for it may be made in square, circular, oval, triangular, or still other cross-sectional shapes as desired. Moreover, the cover 11 need not be of one same cross-sectional shape along all its length, and it is preferable that this shape be varied, in manufacture of the cable, Where and if this offers a decisive advantage of giving it a predetermined cross-sectional shape which enables it to fit with best economy of space among or against items near or on which it is to be mounted. The cover 11 similarly is made with curves or bends along its length, as at 14, 15 (FIGURE I), for shaping it to lie exactly along a desired routing through a computer cabinet, aircraft or missile compartment, or other location within which it may be desired to t it with considerable exactitude.
As seen in FIGURE 3, the cover 11 has a Wall I6 whose inner surface defines an inner volume or cavity which extends lengthwise within and through the cover from one of its ends 17, 18 (FIGURE l) to the other, and this cavity is substantially filled with the Wires 12. The elongated conductors 20 (see FIGURE 5) included in the wires 12 are individually provided, each one of them, with a separate insulating sheath 19. The sheaths 19 of the wires I2 are of course made of a dielectric material; and it is preferable that this material be a resilient plastic which has a low coefficient of friction and which is free of adhesive compatability with the material of the outer cover 11 even at high operating temperatures or at temperatures which may be employed, as will be described, for curing the outer cover. To fit the multicenductor cable I@ for operation in environments in which the temperature is very high, the sheaths I9 of the conductors Ztl are made of a material whose electrical insulating properties do not break down at high temperatures and which is not subject to physical changes such as softening which could allow shifting of the conductors 2t) within the sheaths 19 or result in Welding of one of the sheaths 19 to another sheath 19 with which it is in contact or with the cover 11 where the particular sheath 19 is one which contacts the latter. Meanwhile, it is desirable that the sheath material employed, while possessing the other qualities enumerated above, should be (at least among the class of resilient, dielectric materials) in itself` a fair conductor of heat.
The specific material employed in the wire sheaths 19 may be varied according to the conditions under which the cable 10 will be expected to perform. Materials generally preferred because of their superior electrical, thermal, and mechanical properties are the tetrauorethylene resins, marketed under the trade name of Teflon by E. I. du Pont de Nemours & Company of Wilmington, Delaware. Though not generally capable of withstanding as high a temperature as Teflon and not possessing, for example, as extremely low a coefficient of friction as the latter, materials entirely suitable for many applications are found among the silicone rubbers, and still other materials are satisfactory, for instance those presently used for the insulating of electrical Wires and listed in the U.S. Government Specification MIL-W-l6878C (Navy) of April 3, 1958. As far as consistent with it having the other desirabilities noted herein, it is preferred that the material chosen be of the highest obtainable dielectric strength per mil of thickness since this permits the use of sheaths 19 of minimum thickness and closer spacing of the conductors 2t); and this aids in reducing the weight and overall size of the multiconductor cable 10. The thicknesses of the sheaths 19 must be great enough to prevent voltage breakdown between the conductors 20 at the voltages or over-voltages they may reasonably be predicted to encounter in service of the cable 10.
The desired relationship of the conductors 20 and their sheaths 19 with each other and with the wall of the cover 11 shown `in the cross-sectional view presented in FIGURE 3 is generally typical along all the length of the cover. The later-described compacting of the wires is such that substantially every sheath 19, in all its length within the cover 11, has intimate contact with adjoining sheaths 19; and all the conductors 20 are confined to this contacting relationship by `contact `of sheaths 19 of conductors 2i) lying at the borders of the group of wires 12 with the inner surface of the cover 11. The Wires 12 are compacted as tightly as is consistent with achieving an optimum relationship between the density of the group of wires 12 Iand a desired degree of freedom from lack of pressure-induced deformation of their sheaths 19 sufficient to squeeze and hence deform any sheath 19 such that it, together with the material of adjoining sheaths 19, would not be thick enough to provide suicient dielectric material between its conductor 20 land adjoining conductors 20. Further, the compacting is such that the density of the group of wires 12 is that at which virtually no space is Wasted between the wires: all the space Within the interior volume of the cover 11 should be lled with Wires 12 arranged to lie as closely together and preferably with as much contact with each other as their cylindrical cross-sections permit, thus reducing to a minimum the voids between them and hence making the Volume 0ccupied by the group as small as possible. In practice, some slight deformation may be acceptable; but since the wall thickness of the sheaths 19 is, to begin with, at (or near) a practical minimum, and since the dielectric strength of a sheath 19 tends to be no greater than that at its thinnest point, compressing the wires 12 so tightly as, for instance, to change their respective sheaths 19 from circular to hexagonal cross-section tends to defeat the invention and its object of providing a light-weight cable. This will be clear upon consideration of the following. Depending upon the voltages at which the wires 12 are to be used and upon the material of which the sheaths 19 are made, there is a certain minimum thickness of sheath material which must interlie adjoining conductors 2@ to prevent voltage break-down between them. When a conductor Ztl of circular cross-section is spaced from the nearest-approaching points of surrounding conductors 2t) of similar section by its own and other sheaths 19 whose combined thickness between adjoining conductors equals this required thickness of dielectric material, the lightest weight, electrically effective insulation of the conductors 2t? is effected by sheaths 19 of annular crossseetion. To ll in, in effect, between these round sheaths until they were, for instance, hexagonal would be to add weight without increasing the effective thickness of the insulation or adding to the dielectric strength between the Wires 20, and hence is to be avoided.
The shape of the inner cavity of the cover 11 generally corresponds to the exterior shape of the cover v11; and the cover wall 16, through contact with outer ones of the wires 12, constrains the wires to a relationship in which mutual contact of the sheaths 19 of neighboring Wires 12 isy close and intimate throughout their length Within the cover 11. The cross-sectional shape of the group or core of wires 12 thus also corresponds, as seen in FIGURE 3, to that of the exterior of the cover 11.
The materials of the cover 11 are selected to produce a rigid, unitary structure of excellent dielectric properties and resistance to high and low temperatures and to abrasion. For these purposes, the wall 16 preferably is made ofy dielectric fibers (for example, a glass fiber cloth) irnpregnated with a hard-curing resin. The resin preferably is adhesively incompatible with the material of the ysheaths 19 provided on the conductors 20. Other of its qualities being in accordance with the requirements stated herein, it is entirely suitable that the resin be of the thermo-setting or heat-curing variety. For a cable 1ntended for operation at temperatures ranging from, for instance, 65 F. to 200 F., ka woven glass fabric meeting the requirements of U.S. Government Specification MlL-lE `-9()S44 and impregnated with a polyesterftype resin conforming to Specification MIUR-7575, Type II 1s suitable. Adequate materials for a cover 11 made for use throughout a greater temperature range, for instance from 65 F. to 500 F. or above, include a glass cloth conforming to Specification MlL-Y-ll40, No. 181 or 182 and a resin meeting the requirements of Specification MlL-R 9299, Type 1I. The outer surface of the cover wall 16 preferably is smooth, while its inner surface complements the shape of the group of conductors 20 and compensates for variations between the shape of the group and the outer shape of the cover 11. The materials listed are given to provide specific examples of acceptable materials, and still others are entirely suitable. The construction of the multiconductor cable described herein provides it with a superior degree of rigidity which is importantly contributed to by the dielectric cover 11; and the latter, of course, is subject to stresses imposed upon the cable '11i by bending loads. Forces urging deflections of the multiconductor cable generally are most apt to cause ultimate cracking or other failure of the cover at relatively pronounced bends in the cable, such as at 14 or 1:5 in FlGURE 1, if the deflections urged are such as would tend to increase or diminish the sharpness of the particular bend. Such failures are prevented as described below.
To enforce and add to the rigidity of the multiconductor cable at, for example, the bend 14, there is provided the construction shown in FIGURES 2 and 4. The Wall of the cover 11, in the example shown, is made up of at least two plies of resin-impregnated fabric. The inner ply (or plies) is made to lie closely along the wires 12 which the cover 11 encloses; and in each of a facing pair of sides 27, 28 of the wall of the cover 11, a plate 29, preferably made of a light, strong metal and of such thickness and width as required for adding the needed reinforcement to the bent portion of the cable, overlies the yinner ply 23 within and preferably somewhat beyond each end of the bend 14. The outer ply (or plies)-24 of the cover 11 separates from the inner ply 23 at one end of the plate 29, passes tightly over the latter, and rejoins the inner ply 23 at the other end of the plate. It will be f understood that, except where they are `separated by the bly is narrower than the outer dimension of the respective side 25er 26which it reinforces, and thus the entire plate is enclosed between the inner and outer plies 23, 24. Rigid bonding of the plies 23, 24 of the cover 11 is ensured by providing, in thek plate 29, a liberal number of holes 3t`whi'ch are filled as at 31' with resin of the cover 11 and through'which resin in the outer ply 24 is continuous with resin of the inner ply 23. Addition of the plates 29 necessarily adds to the thickness of the cover sides 25, y26 receiving thern, and it is preferable that this added thickness result in an increase of the over-all width of the exterior dimensions of the cover 11 rather than that the inner surface of the Wall of the cover 11 be displaced inwardly to any extent causing any excess of compressive deformation, as discussed above, of the ysheaths on the wires 12. Reinforcement of the bend 14 is shown and describedby way of illustration, and similar reinforcement ofcourse may be employed at other portions, such as at 15, or may be omitted altogether where vibrations, etc. to which the cable 10 is submitted are not excessively heavy or severe.
Thus far, the multiconductor cable 10 made by the instant method has been described as if it were elongated, bent as at 14, 1S or Wherever necessary to shape it to fit properly along its intended route, and typified as having two ends 17, 18 between which there are no branches. The multiconductor cable 10 indeed may be made in just suchmanner; but an importantly advantageous feature of the cable 1li is that it may be provided with integral branches as required for dividing the Wires 12 and running dilferent ones of them to different locations. With reference also to lilGURE 6 and designating the part of the cover 11 extending between the ends 17, 18 as a first wall or cover yportion 32, the multiconductor cable 10 shown by Way of example is provided with a second Wall or cover portion 33 ywhich is continuous with and'whch branches olf at an angle from the first portion 32y at a point between the two ends 17, 18 of the first cover portion. s As explained, the inner cavity of the cover 11 extends through the first cover portion 32, including the bends 14, 15, from one of its ends 17 to the other end 18. The second cover portion 33is integral with the first portion 32 yand in all important respects made in exactly the same way as the latter; and the inner cavity of the cover portion 32 branches into the second cover portion 33 and extends to its outer end 34. The cross-section of the first cover portion 32 shown in FIGURE 3 is generally typical of cross-sections which might be taken Within the length of the second portion 33, and the interior cavity is bounded at all locations Within both portions 32, 33 by the inner surface of the cover wall 16.
f The ends 17, 18, 34 of the first and second cover portions 32, 33 define openings providing communication between the exterior of the cover portions 32, 33 aud the elongated, branched cavity within it. The wires 12 Within the cover cavity extend outwardly beyond the cover ends 17, 1S, 34 to electrical connectors, such as 13, with which they may be provided, as required, at their ends. Wires 12 entering the cover through a first opening at, for instance, the end 17 extend through and out of the cover 11 through a second opening defined by another end 18. Again, some wires 12 may, as at 35, enter the outer end of the branch 33 and pass into the first portion 32 and toward either end 1'7 or 1S of the cover. Voids which would be left, as at 3d, Within the cover interior where a group of wires is deflected from a straight course topass from one cover portion 32 or 33 to another preferably are filled by the complementary local thickening 36 of the Wall of the cover 11.
. The interchange of wires 12 from the first cover portion 32 to the branch 33 will in some cases result in there being a smaller number of wires in the cover first portion 32 on one side of the location where the second portion 33 branches from it than in it on the other side of this location. ln this event, the dimensions of the cover 11 preferably should be reduced, as atk 37 (FIGURE 1k), in the side where there is the smaller number of wires 12 until the inner cavity within that side is sufficiently small to maintain the wires 12 in the previously described, close- 1y compacted relationship wherein the sheath of each wire 12 is in close, intimate contact with the sheaths of other wires 12 throughout its length enclosed in the cover 11.
For protection of the wires 12 Where they extend outside the cover, it is in many cases desirable to protect them with a flexible outer jacket which lies in encasing relation to them. As a feature of the invention, the breakout opening 3S or any of the other openings at the ends 17, 1S, 34 of the cover 11 are provided as desired with a. exible jacket 41 mounted in the particular opening in firm attachment to the cover 11. A preferred material for the flexible jacket 41 is a glass cloth covered tube made of tetrafluorethylene and provided with a convolution or spiral corrugation which may run, in the manner of a screw thread, from one end of the jacket to the other. Such a jacket 41, because of its Teflon interior, has very little abrasive effect on the wires 12 within it upon bending and detiections that cause its wall to rub on the wires, and the glass cloth exterior has good resistance to abrasion. The jacket 41 readily yields and shows good iiexibility when there is imposed upon it forces tending to lengthen, compress, or bend it. The convoluted, glass fiber exterior of the jacket 41 interlocks firmly with and becomes integral with the wall of the cover 11 to thus ensure an excellently secure mounting of the flexible jacket 41 in the end of the cover 11. Where the jacket 41 must withstand high temperatures, it should be made of temperature-resistant materials; and those suggested above are adequate in this respect. While a flexible jacket 41 is shown only for the wires 35 extending from the outer end of the second portion or branch 33 of the cover 11, it may similarly be employed at any opening of the cover, including the breakout opening 3S.
Where a flexible section is desired Within the length of the multiconductor cable 1t), such is provided by terminating the cover 11 (FIGURE 1) at one end of the desired exible section 45 and employing a second cover 46 which is spaced from the irst and which re-encases the wires 12 where, at the other end of the tiexible section 45, they pass into the second cover 46 through the opening defined at its end 34 by the wall of the cover 11. The second cover 46 may be constructed in the same general manner and of the same materials as the first cover 11. The Wires 12 pass through its interior cavity and are constrained to the same relation with each other and the second cover 46 as described in connection with the first cover 11. It is preferred that the bundle of wires 12 in the iiexible section 45 lying between the first and second covers 11, 46 be twisted as a group, for this greatly enhances the flexibility of the group of wires 12 where they lie outside the covers 11, 46. For the same reason, the groups of wires 12 leaving the other openings of the covers 11, 46 also may be twisted.
The wires 12 which it is desired to include in the cable are built up into a harness as shown in FIGURE 7. The wires 12 employed should of course conform to the requirements as to materials, etc. set forth in previous paragraphs. The wires 12 preferably should not be marked by any stamping which could cause mechanical and electrical weakening of the insulating sheaths of the wires. Care should be taken that neither the conductor (FIGURE 5) or the insulating sheath 19 of any wire 12 used is broken, cut, or nicked. Assembly of the wires 12 is such as to produce a harness 5@ of a shape which generally fits the applicable mold 51 (FIGURES 8, 9) in which, as will be described, the harness 50 is brought to its final, desired shape. Since the intricacies of assembly of a wire harness are well known in the art, no further description of this step is required beyond mentioning that the harness St) preferably is held together by mechanical means such as, for instance, temporary spot ties of twine 52 made at, for example, 10- to l2-inch intervals along the harness Stb and preferably removed therefrom prior to the step of molding described below. In the completed harness 50, wires which are intended to pass through a break-out opening 38 (FIGURE l) or into a branch 33 of the multiconductor cable 1t) should branch away from the main body of the harness 5t) (FIGURE 7) approximately as they will in the completed cable. Within the harness 5e, the wires 12 should lie as nearly as practicable in parallel relation to each other, and excessive crossing of wires should be avoided, though some crossing of the wires 12 is acceptable and generally will not diminish the quality of the finished cable.
The mold 51 (FIGURES 8, 9) employed for making the multiconductor cable is shaped, branched, etc. as required to cause the materials of the cable 1t), when formed in it, to have the shape desired at all points in the finished article. Where a needed change in shape can be made by introducing a deviation from a plane surface at one side only of the cable, it is generally preferable that such change be made on its upper side 25 (FIGURE 1) since it is generally more feasible to make corresponding variations in the surface of the male part S3 of the mold 51 which forms this side 25 of the cable 1t). The mold 51 shown in FIGURE 8, for example, is intended for making a multiconductor cable 11i of square or rectangular cross-section as shown in FIGURES 1 and 3. Accordingly, a female part 54 of the mold 51 (FIGURE 9) contains a channel whose three sides 55, 56, 57 have the shape and dimensions of the three sides 26, 27, 2S of the cable lltl (FIGURES 1 and 3), and the lower surface of the male piece 53 of the mold is shaped and dimensioned to correspond to the remaining, upper side 25 of the cable. Similarly, the parts of the complete mold 51 (FIGURE 9) are bent as at 58 and 59 and branched as at 6i) in correspondence with the bend 14 and 15 and branch 33 of the completed multiconductor cable 10 (FIGURE l). Whereas one mold section 51 with male and female parts 53, 54 is used for making the first section 11 of the cable 10, a second mold section 61, spaced from the first by an interval equal to the length of the iiexible section 45, is employed for the second section 46 of the cable.
The impregnated fabric previously described is Wrapped about the harness Sil, or, according to a preferred procedure, it is laid up in the female mold sections to form a lining in the latter as shown at 62 in FIGURE 8. The width of the material 62 should be sufficient to provide an overlap of its edges 63, 64 when, as will be described, it is folded over the wires 12. As many plies of the fabric 62 as required should be employed for making a cover 11 or 46 (FIGURE 1) with adequate Wall thickness. Since this requirement will vary with the fabric employed and with the cross-section and other dimensions of the cable to be made, and since known technics of laying up impregnated fibers in molds are well developed, specific instructions will not be given in regard to the number of plies to be used nor of the manner of laying them one over the other since one skilled in the art can readily proceed without such direction. Several procedures peculiar to the making of the multiconductor cable 1t? require specific explanation, however, in connection with laying the materials of the cover 11 in the mold female parts 54, and these explanations follow.
Where required at bends in the cable, as at 14 (FIG- URE l), the reinforcing plate 29 (FIGURES 2, 4) is introduced during the laying up of the impregnated cloth 62 in the molds. At least the outer ply or plies 24 of the cloth 62 are laid in the mold female part 54, then the plate 29 is set in place. Next, the inner ply or plies 23 are laid up over the plate 29 to produce the relation shown in FIGURE 4 between outer plies 24, plate 29, and inner plies 23. If the cloth 62 is not heavily enough impregnated to ensure filling of the holes 3th of the plate 29 with resin V31 when the wires 12 and cloth 62 are placed under pressure in the mold, it is helpful, for securing best bonding of the plate 29 with the cover 11, to add more resin locally, as needed, at the plate 29 for complete filling of the holes 311.
If a iiexible jacket 41 is to be employed in the multiconductor cable 1t) at one of the openings of the cover 11, a piece of tubing, preferably of the kind described above and shown at 41 in FIGURE 7, is placed on the part of the harness 50 which will lie at the opening concerned. Other jackets such as 41 similarly are placed as kin it within the mold female part 54 and the edges 63, 64
of the cloth are folded over the wires 12 and lapped over each other as shown in dotted lines in the drawing. Before or as this is done, the flexible jacket or jackets 41, if such are employed in the particular multiconductor cable under construction, are checked for location and slipped along the harness 50 as necessary to bring them into proper overlapping relationship with the material of the cover 11 at the cover opening or openings involved as shown in FIGURES 7 and 9.
The male part S3 of the mold then is brought down on the cloth-wrapped wires 12 with pressure enough to compact and form them and material of the cover 11 to the shape and relationships with each other previously described. Any gaps which occur between ones of the wires 12 lying next to the cover 11 are filled in the molding process by resin and fabric squeezed into them as at 65 in FIGURES; thus, the inner surfaceof the cover 11 complements the outer `periphery of the group of conductors 12, and the outer surface of the cover 11 is smooth and done during the application of heat to the cable 10 while it is retained in the mold. The temperature employed should be appropriate for proper curing of the resin and should not be high enough to be ya factor resulting in permanent dimensional or other changes in the individual insulating sheaths 19 of the conductors 20. When the cover 11 is properly cured, the cable 10 is removed from the mold. Some or all of the plugs'13 or other connectors or terminals provided on the wires 12 may be added thereto before the molding step, or, as may be expedient, they may be added after the wires 12 are molded into the cover or covers 11, 46, the latter mode of procedure being preferred in the majority of instances.
The methoddisclosed above results in a multiconductor cable 19 of superior low weight and volume since it makes possible the utilization of the conductors 20 whose individual sheaths 19 contain only the amount of material` necessary, withk adequate safety margin, for preventing7 shorting and arc-over between the wires 12. Further, the weight of individual abrasion-resistant covers on the wires is eliminated, the cover 11 providing excellentabrasion protection, at great saving in weight, for all the wires 12. The wires 12 preferably are held by the cover 11 in as close association with each other as is practically possible without sofdeforming the individual insulating sheaths 19 of the wires by excessive wire-to-wire pressures that their insulating ability would be significantly reduced; consequently, they are held by the cover 11 in a group of as high a density and low a volume as is practically possible.
' The density is much higher and the volume lower than ever could be obtained by pulling conductors into place within a cover, and the stretching, breakage, and other damages to the wires resulting from being pulled into a cover are obviated. Preshaped by the molding process, the cable 14) conforms to the surfaces of the bodies such as 43, 49 against or near which it is designed to be mounted; of rigid construction, it is not deflectable when clamped to a fixed body and consequently remains in a fixed accurately known location relative to that and other bodies of accurately predictable position.
Upon the cable 1@ being subjected to a vibratory force which tends to make it oscillate in resonance with the vibration, any deflection of the cable 1i? away from its normal position would cause a small bending of the cable 1d. Wires of the cable 1d at the outside of the bend would tend to be stretched and wires on the inside to be compressed. Because of their low coefficient of friction, the wires 12 in such caseslide upon each other, thus expending much 'of the energy that causes the bending in friction losses and making it unavailable for causing a rebound to and/or beyond the normal position of the cable 10. The multiconductor cable 10 thus is nonresonant as compared with a cable in which the wires are all embedded in one common block of insulating material or in which their coefficient of friction is so high that the individually insulated wires are bound to each other by friction and behave as if enclosed by a solid block of insulating material; for, in such a construction, the energy expended in forcing a cable segment through one half-y cycle of a Vibratory motion is stored in the material of the wires and their insulating sheaths and supplies energy causing or aiding the cable to move through the next halfcycle of vibration. Previous cables, for this reason, have had to be clamped at quite close intervals to prevent the i formation of standing waves which otherwise would form as the cables came into resonance with vibrations of bodies yon which they might be mounted, Because of its rigidity, which prevents its drooping or sagging between clamps, and because of its substantial freedom from resonance with vibrations of the objects with which it is associated, the multiconductor cable 1) requires a quite favorably small number of clamps 47, and these may be spaced at wide intervals; thus, the cable 10 is much more easily, quickly, and inexpensively mounted than previously employed cables.
Weil able to withstand abrasion, blows, etc. because of its hard, rough cover 11, the multiconductor cable 10 has greatly improved resistance to electrical overloading of its wires 12. When an excessive current is passed through one or several of the wires 12, they of course tend to overheat. The individual sheaths 19 of the conductors are, however (among the class of resilient insulating materials), fair conductors of heat, while the metallic conductors 2@ are themselves excellent heat conductora Each wire 12 is preferably in intimate contact, all along its length, with other wires 12; and these other wires act as heat sinks which carry oif the excessive heat produced by overloaded ones of the wires. If a wire 12 is overloaded so greatly that it eventually fails, the heatsink relationship between the wires 12 prevents failure within the cover 11; and it is a great advantage of the multiconductor cable 10 that the failure consistently occurs outside the cover 11 at the uncovered, accessible ends of the wires, In the same manner, a segment of the cable 10 locally exposed to what would otherwise tend to be excessive ambient temperatures is cooled by the heat-sink action of other segments of the cable located in cooler areas. High ambient temperatures and/ or heavy electrical loading of the entire cable is well withstood by virtue of the heat resistant materials of the cover 11 and of the individual insulating sheaths 19 of the wires 12. The multiconductor cable 1t) rfurthermore is substantially water-proof and airtight, and it is substantially immune to the effects of acids and bases and their reaction products. Being able to stand up well in chemical environments in which other cables could not survive, the multiconductor cable is excellent, for example, foruse underground as well as in many other applications including those previously mentioned.
While only one embodiment of the invention has been described herein and shown in the accompanying drawing, it Will be evident that various modifications are possible in the method of making the multiconductor cable ll 'l without departing from the scope of the invention.
l. The method of producing a multiconductor cable comprising the steps of: arranging individually insulated, elongated conductors in a group in which they lie in generally parallel relation with Veach other; providing on the group of conductors a wrapping made of a cloth impregnated with a hard-setting resin adhesively incompatible with the individually insulated conductors; reducing the cross-sectional area of the group of conductors and forming the latter and the wrapping to a desired cross-sectional shape by pressing them between dies; and curing the resin of the wrapping under pressure of the dies until it has substantially solidified to a rigid state.
2. The method of making a high-density multiconductor cable comprising the steps of: massing in a group in which they lie in generally parallel relation with each other a plurality of elongated conductors having individual insulating sheaths; providing on the group of conductors a wrapping of inorganic iibers impregnated with a resin which is adhesively incompatible with said individual insulating sheaths and which can be thermally set to a rigid form at a temperature having substantially no permanent effect on the sheaths of the conductors; reducing the cross-sectional area of the group of conductors and forming the latter and the wrapping to a desired crosssectional shape by pressing them between dies; and heatcuring the resin oi the Wrapping, at a temperature having substantially no permanent effect on the sheaths of the conductors, until the resin has set while continuing to press the group of conductors and the wrapping between dies.
3. For making a high-density multiconductor cable of a kind comprising: a tubular, rigid, one-piece cover made of a dielectric material and having a wall, the cover further having an elongated inner volume enclosed by the wall, and individually insulated, elongated conductors compactly grouped together within and extending along the length of the inner volume of the cover and lying in generally parallel relation with each other, the conductors being confined through Contact of at least some of the conductors with the wall in a relationship wherein substantially every one of the conductors, throughout substantially all its extension through the interior volume of the cover, has contact with at least another of the conductors, the method comprising the steps of: arranging individually insulated, elongated conductors in a group in which they lie in generally parallel relation with each other; providing on the group of conductors a wrapping made of a cloth impregnated with a hard-setting resin; reducing the cross-sectional area of the group of conductors and forming the latter and the wrapping to a desired cross-sectional shape by pressing them between dies; and curing the resin of the wrapping under pressure of the dies until it has substantially solidified to a rigid state.
4. The method of making a high-density, substantially rigid and non-resonant multiconductor cable of predeterl2 mined size and shape comprising the steps of: assembling a harness composed ot wires provided with individual insulating sheaths of low coetiicient of friction and minimum thickness for preventing arc-over between the wires under predictable voltage overloads and arranged in a configuration generally corresponding to that of the desired cable; placing on the harness a wrapping of glass iber cloth impregnated with a resin which is adhesively incompatible with the material of the individual insulating sheaths of the wires and which can be thermally set to a rigid form at a temperature having no permanent effect on the insulating sheaths of the wires; reducing the crossseetional area of the harness and forming it and the wrapping to the desired conguration by pressing the wrapped harness between dies under a pressure sutiicient to tightly compact the wires and below that which would deform the cross-section of individual sheaths on the wires; and heat-curing the resin of the wrapping, at a temperature having substantially no permanent elfect on the individual sheaths ofthe Wires, while continuing to press the wrapped harness between dies and until the resin has set to a rigid,
, dimensionally stable state.
5. The method of making a high-density multiconductor cable of the type having a rigid, molded cover and a flexible jacket extending from a cover opening comprising: arranging individually insulated, elongated conductors in a group in general parallel relation with each other; slipping over the end of the group of conductors a convoluted exible jacket that has a dielectric material with low coeiicient of friction for its inside wall, slipping the encircling jacket along the group of conductors to where one end thereof is positioned around the conductors where the conductors and the jacket are to extend from an opening in the rigid cover; providing on the group of conductors over the length desired for the rigid cover and over the one end of the positioned jacket a continuous wrapping made of a cloth impregnated with hardsetting resin that is adhesively incompatible with the individually insulated conductors, reducing the crosssectional area of the group of conductors and forming them within their wrapping including the wrapped end of the jacket to a desired cross-sectional shape by pressing them between dies, and curing the resin of the Wrapping under pressure of the dies until it has substantially solidiiied to a rigid state.
References Cited in the tile of this patent UNITED STATES PATENTS 2,299,140 Hanson Oct. 20, 1942 2,601,243 Botts et al June 24, 1-952 2,675,421 Dexter Apr. 13, 1954 OTHER REFERENCES Du Pont, Teflon, Tetrauoroethylene Resins, Properties, Uses, 3l pages, copyright 1957, E. I. Du Pont de Nemours and Co. (Inc.).
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|U.S. Classification||264/258, 174/72.00A, 156/56|
|International Classification||H01B7/00, H01B13/012, H01B13/00|
|Cooperative Classification||H01B13/012, H01B7/0045|
|European Classification||H01B7/00D, H01B13/012|