Hermetic cable joint

Details Hermetic cable joint Hermetic cable joint

1999-09-02

2001-08-07

Sanghavi, Hemang (Department: 2874)

Optical waveguides

Optical transmission cable

C385S097000, C385S072000, C385S087000, C385S098000, C385S099000

Reexamination Certificate

active

06272273

ABSTRACT:

The present invention relates to an apparatus and method for jointing cables. In particular, the present invention includes a fiber optic cable joint with a varying inside crimp diameter, wherein the sharing of force transfer between layers of the wire strands of the fiber optic cables and the crimp can be maximized, to permit the minimum possible overall outside diameter and length.
BACKGROUND OF THE INVENTION
In conventional cable crimp joints, the crimp sleeve has always been sized such that a small diameter and length was very difficult to obtain. For example, when conventional optical fiber cable ends are cut flush and butted together, a crimp of a single inside diameter and sufficient cross-sectional area would be required to carry the entire load, resulting in a larger outside diameter and longer length.
The cable joints disclosed by Jones et al, U.S. Pat. No. 5,048,921, and Jenkins, U.S. Pat. No. 4,784,459, are typical of the prior art in which the joints are large in diameter and are neither flexible nor simply configured.
In particular, Jones et al disclose fibers spliced together at
28
at the center of the cable joint and encapsulated with a thin plastics coating. A tubular member
10
is fitted over the spliced fiber and exposed metal tube
2
. Metal ferrules
27
are slid over the member
10
, and a tapered hollow insert
26
is slid into position over the wires
6
A. Sleeve-like intermediate inserts
25
are positioned over the wires
6
A, and collars
24
are clamped towards each other. An outer casing
32
acts as a bridging member connecting the collars
24
. Thus, with the quantity of components needed, the cable joint is large in diameter and complicated to attain.
Jenkins is similar in that the reference discloses a submarine cable joint which includes two cables
2
,
3
, each including an annular tensile layer
28
surrounding at least one optical fiber
4
,
5
wherein the annular tensile layers
28
are connected to opposed positions on a coupling member
8
, and leading a length of each fiber to be joined to a position outside the coupling member
8
. After the tensile layers
28
are fixed to the coupling member
8
, the fiber lengths are joined together and a housing fitted around the joined fibers and the coupling member
8
. Thus, the cable joint in Jenkins suffers from the same disadvantages as the one in Jones et al, wherein the cable joint is neither compact, flexible, or simply configured.
Ziebol et al, U.S. Pat. No. 5,159,655 discloses an optical fiber crimp with a first crimping portion
52
and a second crimping portion
54
biased toward one another, to securely crimp a fiber within a cut-away ferrule
14
. This connector subassembly is not designed to maximize tensile strength.
Thus, the above cable joints are not optimized with respect to compactness, tensile strength, and cable handling. In addition, the cable joints are complicated and require excess components.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a cable joint for the inline connection of fiber optic cables which is simple to assemble, includes low cost components, maximizes the coupling of tensile forces, and which includes a short assembly time. A second object of the invention is to provide a small diameter joint, in order to improve cable handling. A third object of the present invention is to provide a hermetically sealed cable joint, in order to maximize resistance to hydrogen ingress.
In attaining these and other objects, the present invention provides a cable joint for the inline connection of fiber optic cables, in which two opposed ends of light-weight fiber optic cables are joined. The two fiber optic cables are cut to expose each wire strand of each cable, and a tube joint is formed by joining the optical fibers of the two cables such that the tube joint is located under the wire strand of the first cable. The tube joint includes a capillary tube which extends under the cable joint to provide additional hoop strength for crush resistance.
A tapered crimp sleeve is applied over the exposed inner layer and outer layer of each of the wire strands of the two cables, the inner layer and outer layer forming stepped portions within the crimp sleeve. The staggered different inside diameters provide complete coupling to the inner wire nest allowing a maximum cross-sectional area of the crimp sleeve for strength.
The crimp sleeve tapers outwardly from a central portion, such that its two ends are of a larger diameter than the central portion of the crimp sleeve. When the inner layer and outer layer of each wire strand is crimped, the crimp sleeve attains approximately the same diameter along its length.
A raised circumferential ring is integrally formed within one end of the crimp sleeve to provide a further hermetic seal when crimped to one of the cables. The crimp sleeve is crimped over the ring, providing a hermetic seal between the conductive tube of one of the cables and the crimp sleeve.
The present invention further incorporates a soldered spring which surrounds an exposed outer wire strand in one of the cables, providing a hermetic seal. The spring is soldered to the crimp sleeve and to the cable. The tube joint is located under the spring. The hermetic seal prevents hydrogen ingress. The soldered spring provides the additional benefits of strength and flexibility for cable handling.
With the above configuration, the sharing of force transfer between the two wire layers in each of the cables and the crimp sleeve is maximized. This configuration also permits a reduced outer diameter and length for the cable joint because the crimp carries the total load only at the maximum cross sectional area. In addition this invention combines carbide grit with crimping and an epoxy adhesive to increase the coupling forces in the joint.


REFERENCES:
patent: 4784459 (1988-11-01), Jenkins
patent: 4804252 (1989-02-01), Betzler et al.
patent: 5005940 (1991-04-01), Modrey
patent: 5048921 (1991-09-01), Jones et al.
patent: 5159655 (1992-10-01), Ziebol et al.
patent: 5317664 (1994-05-01), Grabiec et al.
patent: 5321784 (1994-06-01), Cubukciyan et al.
patent: 5455880 (1995-10-01), Reid et al.
patent: 5455881 (1995-10-01), Bosisio et al.
patent: 5475782 (1995-12-01), Ziebol

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