Casing member for forming a connection between tubular sections and use thereof for forming connections
A casing member for forming a connection between two tubular sections, said casing member having a first, cross-linked, heat shrinkable plastic layer, and a second, inner, non-crosslinked (or less cross-linked) layer. The casing member also has an electrically heatable member spaced inwardly from the first layer, for fusion bonding the second layer to the tubular sections.
1. A casing member for forming a connection between two tubular sections, the casing member having at each side a side portion for connecting on a respective adjacent end surface of a tubular section adjacent the connection, and a middle portion that spans between the end surfaces of the tubular sections, each said side portion comprising a first crosslinked plastics material layer to be disposed relative to said end surfaces outwardly from a second plastics material layer that is uncrosslinked or has a degree of crosslinking substantially less than said first layer, at least said first layer being heat shrinkable in the direction of the circumference of the adjacent tubular section, and an electrically heatable member spaced inwardly from said first layer for heating the second layer to cause it to fusion bond with a plastics material jacket of a tubular section when disposed adjacent thereto, wherein the first crosslinked plastics material layer and the second plastics material layer comprise high density polyethylene.
2. A casing member according to claim 1 , wherein the member spans continuously between the two tubular sections and the middle portion is formed integrally with the side portions.
3. A casing member according to claim 1 wherein the first layer extends substantially the full width of the casing member.
4. A casing member according to claim 1 wherein said second layer comprises portions extending adjacent the sides of the casing and the middle portion of the casing member is free from said second layer.
5. A casing member according to claim 1 wherein said second layer extends substantially the full width of the casing member.
6. A casing member according to claim 1 wherein said second layer is heat shrinkable.
7. The casing member according to claim 1 wherein the electrically heatable member is adapted to be disposed inwardly from the second layer.
8. The casing member according to claim 1 wherein the electrically heatable member is embedded integrally within the second layer.
9. The casing member according to claim 1 wherein the electrically heatable member comprises electrically resistively heatable elements.
10. The casing member according to claim 1 wherein the electrically heatable member comprises electrically inductively heatable elements.
11. The casing member according to claim 1 having a wall thickness at its thickest wall portion before heat shrinking of 2 to 15 mm.
12. A casing member according to claim 1 , having a wall thickness at its thickest wall portion before heat shrinking of 8 to 25 mm.
13. Use of a casing member according to claim 1 for forming a connection between tubular sections including the steps of applying a heat source external of the casing member to heat shrink said first layer to conform said second layer tightly to an adjacent end surface of a tubular section under compressive hoop stress generated at least in part by the heat shrunk first layer, and heating the second layer to cause fusion bonding thereof to the end surface of the tubular section by electrically activating said electrically heatable member.
14. The casing member according to claim 1 wherein the second plastics material layer is crosslinked, and has a degree of crosslinking substantially less than said first layer.
15. A casing member according to claim 1 including a third layer of plastics material at least partially co-extensive with the middle portion.
16. A casing member according to claim 15 wherein the third layer is disposed inwardly from the second layer.
17. A casing member according to claim 15 wherein the third layer is heat shrinkable.
18. A casing member according to claim 1 in the form of a wrap-around sleeve comprising a sheet of which at least a portion is heat shrinkable along a heat shrink direction and that is, or of which sections are, adapted to be formed into a tubular sleeve by connecting together edges opposed in the heat shrink direction.
19. A casing member according to claim 18 wherein said sheet comprises a crosslinked heat shrinkable first plastics material layer and laminated thereto a second plastics material layer that is non-crosslinked or substantially less crosslinked than the first layer.