Multi-layer elastic sleeves for electric power cable joints and joints therewith

An electric cable joint between a pair of cables having conductors and encircling insulation of a predetermined size with the insulation cut back to expose the conductors and with the ends of the conductors electrically interconnected, said joint comprising a covering for the interconnected conductor ends and said covering comprising:

• a first elastic sleeve formed from a compound of a cross-lined polymeric material and being electrically insulating for at least part of its radial thickness and said compound having a residual deformation, with an imposed elongation applied for a period of time, of a first predetermined value to which it returns elastically and without heating;
• a second elastic sleeve formed from a compound of a cross-linked polymeric material encircling said first sleeve and in radially expanded condition and said compound from which said second sleeve is formed having a residual deformation, with an imposed elongation applied for a period of time, of a second predetermined value to which it returns elastically and without heating and which is less than said first predetermined value and which causes said firs sleeve to reduce in internal diameter to a size which is less than said first predetermined value and less than said predetermined size of said insulation;
• said covering at its axially central portion encircling said interconnected conductor ends and at its opposite ends elastically gripping at least the portions of said cables adjacent said interconnected cable ends;
• and
• whereby the second sleeve stores sufficient energy to cause the first sleeve not only to follow it during the elastic contraction that takes place during the removal of the tubular support from the joint sleeve but also to cause the first sleeve layer to tighten on the ends of the cables in the joint.

An electric cable joint between a pair of cables having conductors and encircling insulation with the insulation cutback to expose the conductors and with the ends of the conductors electrically interconnected, said joint comprising a covering for the interconnected conductor ends and said covering comprising:

• a first elastic sleeve comprising at least two co-extruded tubular layers of compounds of cross-linked polymeric material, the compound of the radially innermost layer having a percentage ultimate tensile elongation greater than, and a modulus E lower than, the radially outermost layer and said first sleeve being electrically insulating for at least part of its radial thickness an said compounds having a residual deformation, with an imposed elongation applied for a period of time, of a first predetermined value
• a second elastic sleeve formed from a compound of a cross-linked polymeric material encircling said first sleeve and in radially expanded condition and said compound from which said second sleeve is formed having a residual deformation, with an imposed elongation applied for a period of time, of a second predetermined value which is less than said first predetermined value;
• and
• said covering at its axially central portion encircling said interconnected conductor ends and at its opposite ends elastically gripping at least the portions of said cables adjacent said interconnected cable ends.

An electric cable joint sleeve device comprising:

• a rigid tubular support having a predetermined exterior cross-sectional size;
• a first elastic sleeve comprising at least two co-extruded tubular layers of compounds of cross-linked polymeric material, the compound of the radially innermost layer having a percentage ultimate tensile elongation greater than, and a modulus E lower than, the radially outmost layer, said first elastic sleeve having an unstretched cross-sectional interior size less than said predetermined cross-sectional size of said support and being mounted on and encircling said support in elastically radially expanded condition, said first sleeve being electrically insulating for at least part of its radial thickness and said compound having a residual deformation, with an imposed elongation applied for a period of time, of a first predetermined value;
• and
• a second elastic sleeve formed form a compound of a cross-linked polymeric material encircling said first sleeve, and said second elastic sleeve having an unstretched cross-sectional interior size such that when said first sleeve is mounted on said support and said second elastic sleeve encircles said first sleeve, said second sleeve is in radially expanded condition and compound form which said second sleeve is formed having a residual deformation, with an imposed elongation applied for a period of time, of a second predetermined value which is less than said first predetermined value.