Radially shrinkable sleeves
AssigneeRaychem Corporation
InventorAnthony R. W. Richardson
Life of this patent
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Abstract
Radially shrinkable sleeves for covering joints and terminations in high voltage cables are made by radially uniform machining of an extrudate comprising an insulating layer and at least one other layer which is conductive or semi-conductive or exhibits stress control properties. Expansion of the sleeve can be effected before or after machining. Novel shrinkable sleeves which are obtainable by this method include an insulating layer which comprises at least one tapered section in which its internal diameter increases gradually from a first diameter to a second diameter.
Claims28
A radially shrinkable sleeve suitable for use in covering a joint or a termination in an electrical cable adapted to carry a voltage of 1 KV or more, said sleeve comprising (a) a first outer tubular layer composed of a first polymeric composition selected from polymeric compositions which exhibit electrical stress control properties and compositions which comprise a polymer and electrically conductive particles dispersed in said polymer in amount sufficient to render said compositions conductive or semiconductive, and (b) a second inner tubular layer composed of a second polymeric composition which is electrically insulating, said second layer comprising at least one outwardly tapered section in which its internal diameter increases gradually from a first diameter to a second diameter such that no part of the inner surface of said second layer is inclined at an angle greater than 30.degree. to the axis of the sleeve.
A method of making a radially shrinkable sleeve suitable for use in covering a joint or a termination in an electrical cable adapted to carry a voltage of 1 KV or more, which method comprises
- (1) preparing a tubular extrudate comprising (a) a first continuous outer tubular layer which is composed of a first polymeric composition selected from polymeric compositions which exhibit electrical stress control properties and compositions which comprise a polymer and electrically conductive particles dispersed in said polymer in amount sufficient to render said composition conductive or semiconductive and (b) a second continuous inner tubular layer composed of a second polymeric composition which is electrically insulating;
- (2) cutting said tubular extrudate into discrete lengths;
- (3) subjecting a discrete length to a machining operation in which a part of said second tubular is layer is removed to provide at least one internal tapered section, the internal diameter of said tapered section increasing towards the closer end of the second tubular layer such that no part of the inner surface of said second layer is inclined at an angle greater than 30.degree. to the axis of the sleeve;
- and
- (4) subjecting said tubular extrudate or discrete length cut therefrom to an expansion treatment which will radially expand it from a first configuration to a second expanded configuration which is storage-stable.
Dependencies are inferred from the claim text.