Patent EP-0744806-A1 (EP)
Inventor: FAUST MICHAEL ALLEN
IPC: H02G15/14
Filed: 1996-05-14
Abstract: It is an object of the invention to provide substantial protection and insulation to the submarine cable joints. It is a further object of the invention to provide such protection and insulation in an efficient manner without utilizing costly molding and x-ray equipment. These and other objects are satisfied, in accordance with the invention, by a novel method for protecting and insulating ajointbox which utilizes a protective covering having at least two hollow elements that are formed from a heat shrinkable material. The heat shrinkable material has an expanded state and an unexpanded state. Upon the application of heat, the heat shrinkable material in the expanded state shrinks such that it substantially returns to the unexpanded state. At least one of the elements forming the protective article is in the unexpanded state while other elements are in the expanded state. The hollow elements are coupled to constitute an integrally-formed single unit having a continuous passageway therethrough. The unexpanded element is positioned against a locating portion of jointbox so as to locate portions of said jointbox and cable segments within the passageway in a predetermined position such that said unexpanded first element and the locating portion undergo insubstantial relative movement as the protective covering is heated. Heating the protective covering causes the expanded elements to shrink such that they are disposed about predetermined portions of said jointbox and cable segments in a substantially close fitting manner. Advantageously, the method described above facilitates installation of the protective covering because the insubstantial relative movement between the unexpanded element and the locating portion of the jointbox allows proper alignment of the protective covering and jointbox to be maintained even as the expanded elements of the covering shrink and move relative to the jointbox during the heating step. In an illustrative example of the invention, the protective covering is formed by from heat shrinkable polyolefin tubes which are arranged as an expanded first substantially cylindrical portion. an expanded second substantially cylindrical portion having a relatively smaller diameter than the first portion, and an unexpanded conical transition portion which couples the first and second portions. The unexpanded conical transition portion functions to precisely locate the protective article against a similarly shaped termination socket portion of the jointbox. An adhesive is applied to portions of the inside surfaces of the article. After cleaning and heating the cable segments andjointbox to enhance adhesion of the adhesive, the article is positioned and heated to cause the cylindrical portions to shrink such that they are disposed around predetermined portions of the jointbox and cable segments in a substantially close fitting manner. The diameters of the cylindrical portions of the article in the expanded state are selected such that a nominal hoop stress is created in these portions during heating to thereby minimize air entrapment and voids in the adhesive. Two protective coverings are overlapped to maximize the dielectric strength of the coverings, and to increase the path length for water egress into the joint.