| 摘要 |
1. A foldable tube (1) comprising a tubular wall having at least three elongate relatively flexible areas (2-9) where the wall is more flexible than other areas of the wall, which areas are oriented in a substantially parallel direction relative to each other along at least a substantial part of the length of the tube (1) so that in use said areas form hinges which define wall segments that are inwardly foldable to bring the tube into a contracted shape and that can be unfolded to bring the tube into a substantially cylindrical or elliptical shape, characterized in that the tube (1) is a liner tube for providing a lining within a substantially cylindrical or elliptical tubular cavity (27) and the hinges of the unfolded tube are in use located in the vicinity of the wall of the cavity (27) such that the wall segments between the hinges inhibit refolding of the unfolded liner tube. 2. The foldable tube of claim 1 wherein said relatively flexible areas are formed by trough-shaped grooves (2-9) in the wall of the tube (1), which grooves are oriented in a parallel or helical direction relative to a longitudinal axis of the tube (1). 3. The foldable tube of claim 2 wherein at least one set of four grooves (2-5, 6-9) is arranged in the wall of the tube such that each set of four grooves defines a tube segment that can be folded as a delta- or U-shaped recess (12,13) inwardly into the tube. 4. The foldable tube of claim 3 wherein two sets of four grooves (2-5, 6-9) are arranged symmetrically at opposite sides of the tube (1) such that if the tube (1) is folded into a contracted shape two delta- or U-shaped recesses (12,13) are formed at opposite sides of the tube. 5. The foldable tube of claim 3 wherein a single groove (16,31) is arranged in the inner wall at one side of the tube (15,25) and a set of four grooves (17-20, 32-35) is arranged at an opposite side of the inner wall of the tube (15, 25). 6. The foldable tube of claim 5 wherein a branch tube (36) is secured around a window (37) in the wall of the tube (25) which window (37) is located between said single groove (31) in said one half of the tube and an adjacent groove (32) of said set of four grooves (32-35) at said opposite side of the tube (25). 7. The foldable tube of any preceding claim wherein the foldable tube is a well tubular which is insertable in a contracted shape into the well and expandable downhole into a substantially cylindrical shape. 8. The foldable tube of claim 6 wherein the tube (35) is a well casing at a branchpoint in an underground well and the branch tube (36) forms part of a well casing or liner in a well branch (29), and the tube is insertable in a contracted shape into the well and expandable downhole into a substantially cylindrical shape such that the branch tube (36) is positioned at the entrance of the branch well (29) near the branchpoint. 9. The foldable tube of claim 1 wherein the tube (1) is made of steel. 10. The foldable tube of claim 1 wherein the tube (1) is made of a plastic material. 11. A method of placing a foldable tube (25) according to claim 1 in a tubular cavity (27), the method comprising inserting the tube (25) folded in its contracted shape into the cavity (27), unfolding the tube (25) into its substantially cylindrical shape at a selected location within the cavity (27) and securing the tube within the cavity, wherein the cavity (27) has a substantially cylindrical or elliptical shape and the tube (25) is unfolded such that the hinges (31-35) are located in the vicinity of the wall of the cavity (27) thereby inducing the wall segments of the unfolded tube between the hinges to inhibit refolding of the unfolded tube. 12. The method of claim 11 wherein the tube (1) comprises at least one set of four grooves (2-5, 6-9) according to claim 4 which grooves define a delta- or U-shaped recess (12,13) when the tube is inserted into the cavity and a tubular container containing a sealing agent is arranged within said recess when the tube is inserted into the cavity, which container is squeezed and breaks open as a result of the unfolding of the tube within the cavity and sealing agent is released into the annular space between the unfolded tube and the wall of the cavity, which sealing agent is then allowed to create an annular seal between the unfolded tube and the cavity wall. 13. The method of claim 11 wherein the tube (1) is unfolded by inserting a sealing plug at one end of the tube (1) and pumping a high pressure fluid into the other end of the tube. |
