Underwater Marine Cable

Abstract

1. The combination of a new and improved flexible marine cable and a wateght end coupler formed thereon, comprising A multistrand center conductor, A first inner layer of insulation of high density polyethylene surrounding said center conductor to provide good electrical insulation, A second outer layer of insulation of nylon covering said inner layer of insulation to provide good mechanical strength, A braided coaxial outer conductor surrounding the insulation and supported thereby, A high density polyethylene jacket encasing said outer conductor to provide corrosion protection and abrasion resistance, A swaged assembly including a collar through which the combination of said outer conductor, insulation, and center conductor passes, the strands of said outer conductor being laid back over said collar, and a collet swaged over said collar, the center conductor extending beyond said swaged assembly, A generally cylindrical cable end fitting having a first axial bore therethrough through which the combination of said outer conductor, insulation, and center conductor passes, and a second larger diameter axial bore part way therethrough which receives said swaged assembly, A first seal comprising a potting compound filling the cavity in said second bore, and A second seal comprising a tapered polyurethane section molded over said end fitting and over a portion of said polyethylene jacket encasing said outer conductor.

Description

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates generally to underwater marine cables, and more particularly to a new and improved flexible marine cable having watertight end couplers formed thereon.

The usual construction for electrical cables required to carry substantial mechanical loads is a double-armored, counterwound construction. This construction, however, is too inflexible for many applications.

It is therefore an object of the instant invention to provide an improved marine cable which is capable of sustaining high mechanical loads and withstanding severe flexing without impairing the conductor or the conductor insulation.

It is another object of this invention to provide a highly flexible underwater electrical cable having end couplers formed thereon which provide both mechanical and watertight electrical termination that is a fraction of the size of available fittings.

It is a further object of the invention to provide a flexible cable for underwater use which is able to sustain high mechanical loads for substantial periods of time and not leak water at high hydrostatic pressures.

According to the present invention, the foregoing and other objects are attained in a preferred embodiment by providing a coaxial cable formed by a multistrand center conductor, a first insulating layer of polyethylene, a layer of nylon for mechanical strength, an outer conductor, and an outer polyethylene jacket for corrosion and abrasion protection. The ends of the cable are made watertight by means of swaged end fittings sealed by potting material.

The specific nature of the invention, as well as other objects, aspects, uses and advantages thereof, will clearly appear from the following description and from the accompanying drawing, in which:

FIG. 1 is a cross-sectional view of the marine cable and an end coupler according to the invention which shows the construction thereof; and

FIG. 2 is an end view of the end coupler shown in FIG. 1.

Referring now to the drawing, and more particularly to FIG. 1, the marine cable according to the invention comprises an insulated center conductor 101 which is stranded to promote flexibility. The insulation is in two layers; an inner layer 102 of high density polyethylene to provide excellent electrical insulation, and an outer layer 103 of nylon to provide protection for inner layer 102. A stranded coaxial outer conductor 104 surrounds the insulation and is supported thereby. Outer conductor 104 is preferably made of steel and is the principal strength member of the cable. A high density polyethylene jacket 105 encases the cable to provide corrosion protection and abrasion resistance. Alternatively, the abrasion resistance of the cable can be enhanced by using nylon or polyurethane in place of the high density polyethylene for jacket 105.

The end coupler shown in FIGS. 1 and 2 includes a swaged assembly secured to the cable. This assembly comprises a collar 106 through which the cable, except for jacket 105, passes. As is shown in FIG. 1, jacket 105 terminates some distance before the end of the cable. The strands of conductor 104 are untwisted and, uniformly distributed, laid back over collar 106. A collet 107 is swaged on over the strands of conductor 104 and collar 106, the excess wire lengths extending beyond collet 107 being trimmed off. The end coupler additionally comprises a generally cylindrical cable end fitting 108. Fitting 108 has a main body portion 109, a smaller diameter tail portion 111, and a larger diameter head portion 112. An axial bore having a diameter slightly larger than the swaged assembly including collar 106 and collet 107 extends through the head 112 and a substantial distance into the main body portion 109 of fitting 108. A smaller diameter axial bore slightly larger than the cable without jacket 105 extends through the tail portion 111 of fitting 108 and communicates with the larger diameter bore in the body portion 109. The swaged assembly rests on the shoulder formed by the junction of the two axial bores, and the cable extends out through the bore in tail portion 111. An axial recess having a slightly larger diameter than the bore receiving the swaged assembly is provided in the face of the head portion 112 of fitting 108. This recess receives an insert 113 which supports a central pin connector 114. The central conductor 101 of the cable extends beyond the swaged assembly and is electrically connected to the base of pin connector 114 as by crimping the conductor into a recess thereof, for example. A second electrical connector in the form of an annular disk 115 having a plurality of outwardly extending and forwardly projecting tabs 116 surrounds pin connector 114 but is electrically insulated therefrom. As illustrated, disk 115 and insert 113 are provided with a plurality of holes drilled therethrough which are in registry. To provide connection to the outer coaxial conductor 104 of the cable, a plurality of uninsulated, soft, coated copper wires 117, less in number than the number of holes in disk 115 and insert 113, extend from the swaged assembly through insert 113 and are bent over and soldered to disk 115. Preferably, wires 117 are placed between collar 106 and collet 107 before the swagging process to ensure a good electrical and mechanical connection. The fitting 108 is made watertight by potting the swaged assembly and the extending center conductor in a suitable epoxy resin generally indicated at 118, the cavity in fitting 108 being filled through one of the empty holes in disk 115 and insert 113. Alternatively, polyurethane may be used as the potting compound instead of an epoxy resin. A second seal is provided by molding a tapered polyurethane section 119 over the tail portion 111 of fitting 108 and the cable including jacket 105. The molded section 119 also protects the cable end against sharp bends. Adhesion between the polyurethane section 119 and the metal tail portion 111 of fitting 108 is mechanically enhanced by providing a collar 121 about tail portion 111 a short distance from the main body portion 109. Adhesion is further chemically enhanced by priming the surface of tail portion 111 with a suitable primer and flame treating and priming the surface of the polyethylene cable jacket 105. Polyurethane is used as the molding material because it can be molded at moderate temperatures (160.degree. F). Elevated temperatures, for an appreciable period of time, cause flow of the conductor insulation and allow leakage between the insulation and the epoxy potting. Further, the polyurethane is a good adhesive, tough and abrasion resistant. As an alternative, tapered section 119 may be injection molded using a medium or low density polyethylene. Since the time required to mold is short the heat does not destroy the bond between the epoxy and the center conductor insulation.

The end coupler is secured to a connector (not shown) by means of a securing threaded cap 122. Cap 122 is conjoined to the head portion 112 of fitting 108, extending about the periphery thereof, and may, as illustrated, extend over the shoulder formed between head portion 112 and main body portion 109 of fitting 108. Alternatively, securing cap 122 may be integrally formed on head portion 112. The seal between the end coupler and another connector to which the coupler is secured is made by O-ring 123 which is supported in an annular groove in the face of head portion 112 near the outer edge thereof.

It will be apparent that the embodiment shown is only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

Claims

I claim as my invention:

1. The combination of a new and improved flexible marine cable and a watertight end coupler formed thereon, comprising

a multistrand center conductor,

a first inner layer of insulation of high density polyethylene surrounding said center conductor to provide good electrical insulation,

a second outer layer of insulation of nylon covering said inner layer of insulation to provide good mechanical strength,

a braided coaxial outer conductor surrounding the insulation and supported thereby,

a high density polyethylene jacket encasing said outer conductor to provide corrosion protection and abrasion resistance,

a swaged assembly including a collar through which the combination of said outer conductor, insulation, and center conductor passes, the strands of said outer conductor being laid back over said collar, and a collet swaged over said collar, the center conductor extending beyond said swaged assembly,

a generally cylindrical cable end fitting having a first axial bore therethrough through which the combination of said outer conductor, insulation, and center conductor passes, and a second larger diameter axial bore part way therethrough which receives said swaged assembly,

a first seal comprising a potting compound filling the cavity in said second bore, and

a second seal comprising a tapered polyurethane section molded over said end fitting and over a portion of said polyethylene jacket encasing said outer conductor.

2. A new and improved flexible marine cable as recited in claim 1 wherein said end fitting further has an axial recess larger in diameter than said second bore at the entrance of said second bore, said end coupler further comprising

an insert received by said recess, and

and pin connector supported by said insert and extending therethrough, said center conductor being electrically connected to the base of said pin connector.

3. A new and improved flexible marine cable as recited in claim 2 wherein an annular groove is cut in the end of end fitting around said recess, said groove supporting a third seal in the form of an O-ring.

4. A new and improved flexible marine cable as recited in claim 3 wherein said potting compound is an epoxy resin.

5. A new and improved flexible marine cable as recited in claim 3 wherein said potting compound is polyurethane.