A METHOD TO JOIN TWO ELEMENTS,AND A JOINT ACCORDING TO THE METHOD

Abstract: A method to join two elements (4, 5), and a joint according to the method, a first element (4) to be joined having an internal peripheral surface located surrounding and at a distance from an external peripheral surface of a second element (5). A mainly ring-shaped expandable tubular member (1), arranged surrounding an explosive charge (2) with associated igniter means is located in an intermediate position between the elements (4, 5), and when the explosive charge (2) is detonated, the tubular member (1) is expanded to a contact position with the adjacent surfaces of the elements (4, 5), the explosive force also influencing enclosed, integrated or adjacently located holding and sealing members (6, 6'; 7, 7'; 8, 8', 9, 9'; 10, 10'), arranged to prevent deflection of the expanded tubular member (1) from the contact position taken up against the elements (4, 5), and/or to establish mechanical contact with the elements (4, 5), thus improving the sealing and/or holding properties of the established joint.

Description: A method to join two elements, and a joint according to the method The present invention relates to a method to join two elements, and a joint according to the method. For numerous applications, it is desired to join two elements, one of the elements being located surrounding the second element. Such a joint can be used for attachment purposes, or to join together two elements, in the latter case either by the use of a separate surrounding member, e.g. a tubular member located surrounding the end portions of two pipes, or two members, one having a larger internal diameter than the outside diameter of a second member, the first member " arranged*.: surrounding the second member. A joint can be accomplished by means of welding, provided that the distance between the adjacently located surfaces of the elements is rather small. However, since welding is a rather time-consuming method to accomplish a joint, and since welding also requires skilled personnel, other methods to accomplish a joint have been proposed. With regard to the method and the joint according to the present invention, the most relevant prior art is disclosed in NO-PS 136.223 and NO-PS 141.128, which disclose a joint accomplished by the use of one, or a number of explosive charges, arranged to cause expansion of a surrounding tubular member, thereby forming a frictional joint between two elements. However, the prior art as disclosed in the above two patents only facilitates accomplishment of a joint in a minimum of time, but the joint lacks certain desired features, since it requires that one of the elements is specifically arranged to hold the expandable tubular joint, and since it only accomplishes a joint of frictional type, without any sealing elements. The object of the present invention is to disclose an improved meth.od and joint, which removes all disadvantages with previously known types of explosive joints, and which makes it possible to accomplish a joint having desired holding and sealing properties, and without any need for one of the elements being prepared in a certain fashion to hold the expandable element. The present invention makes it thus possible to accomplish a joint having improved holding and sealing properties in relation to prior art, and said properties can be altered in any desired fashion. Furthermore, none of the elements to be joined ne to be pre-machined to facil tate use of the joint according to the present invention. However,, for certain applications, it may be regarded as advantageous to arrange a groove in at least one of the peripheral surfaces facing each other at the elements to be joined. A major advantage is that the joint can be established between two elements having large diametrical tolerances, and that there is a minimum requirement for surface finish with regard to the surfaces to be joined. Furthermore, the joint according to the present invention can also be arranged including an element which prevents deflection of the joint from a contact position against the facing surfaces of the elements joined. Sealing and holding properties can be varied as desired, by reducing or increasing the number of sealing elements included in the joint, and by increasing or decreasing the total area of contact established between the elements by means of the joint. The method to join two elements according to the present invention is mainly characterised in that a mainly ring-shaped tubular member is arranged with longitudinally extending depressions, thereby reducing the internal and external diameter of same, is located between two elements to be joined, one of said elements having an internal surface facing and located at a distance froπrthe external surface of a second element, said.tubular member surrounding an explosive charge and an associated igniter means, said explosive charge being arranged to expand the tubular member when ignited, thereby forcing same into a contact position with the facing surfaces of the two elements, thus establishing a joint between same. The expansion of the tubular member is preferably also arranged .to force at least one sealing member, located adjacent to the expandable tubular member, inte a contact - .position with the elements to be joined. The explosive force can also be arranged to influence as a first " step a member located embraced by the expandable tubular member, arranged to take up contact with the internal surface of the tubular member, and to ' prevent deflection from an expanded position in contact with the elements " to be joined. Further characteristic features of the method according to the present inventio and of a joint according to the method, are disclosed in the claims. A number of embodiments of joints according to the present invention are more fully described, reference being made to the accompanyinc drawi ngs , i n whi ch :- Fig. 1 is a cross-sectional view of a first embodiment of an expandable tubular member, shown before expansion. Fig. 2 is a cross-sectional view corresponding to Fig. 1, showing a second embodiment of a tubular member. Fig. 3 is a cross-sectional view corresponding to Figs. 1 and 2, showing a third embodiment of an expandable tubular member. Fig. 4 is a cross-sectional view of the embodiment shown in Fig. 1, arranged with two adjacently located sealing . and holding members and arranged in an intermediately located position between two elements, shown before expansion into a position joining the elements together. Fig. 5 is a cross-sectional view of the embodiment shown in Fig. 4, when a joint has been established between the elements. Fig. 6 is a cross-sectional view corresponding to Fig. 4, showing a number of sealing and holding members located adjacently to each side of the expandable tubular member. Fig. 7 is a cross-sectional view of a further embodiment of a joint according to the present invention, shown before the establishment of an expanded position, joining two elements together. Fig. 8 is a cross-sectional view corresponding to Fig. 7, showing the established joint. Fig. 9 is a cross-sectional view of an embodiment having integrated sealing members, shown in an intermediate position between two elements before expansion into a position joining the elements together. Fig. 10 is a cross-sectional view corresponding to Fig. 9, showing the established joint. Fig. 11 is a cross-sectional view of a further embodiment having tv wedge-acting ring members enclosed within the expandable tubular member shown before the establ shment of a joint between two elements. Fig. 12 is a view corresponding to Fig. 11, showing the established joint. Fig.13 is a cross-s * ectional view of the embodiment shown in Fig. 2, shown before expansion and including a tubular member, arranged to be expanded into a contact position with the internal wall surface of the outer tubular member, shown before expansion. Fig. 14 is a cross-sectional view of the embodiment shown in Fig. 13, showing the established joint. Fig. 15 is a perspective view of a portion of the expandable tubular members shown in Fig. 13. Fig.16 is a cross-sectional view of the embodiment shown in Fig.9, enclosing two expandable tubular members, shown before expansion. •Fig. 17 is a cross-sectional view of the embodiment shown in Fig. 16, showing the established joint. Fig. 18 is a cross-sectional view of the embodiment shown in Fig. 11, including an expandable tubular member located in an intermediate position to the wedge-acting ring members. Fig. 19 is a cross-sectional view of the embodiment shown in Fig. 18, showing the established joint. Fig.20 is a side-view of a telescopically interconnected portion of an expandable tubular and mainly ring-shaped member. Fig.21 is a perspective view of a helically wound expandable tubular member according to the present invention. Fig.22 is a cross-sectional view of the embodiment shown in Fig.21, arranged to form a joint between two elements, having a numbeχ---Qf--_ sealing and holding elements arranged adjacent to the outer end portions of the helically wound tubular member. Fig. 23 is a cross-sectional view corresponding to Fig. 22, the outer expanded tubular member being arranged surrounding an internal tubular member. Fig. 24 is a cross-sectional view, showing how a number of expandable tubular members can be arranged, having intermediately located sealing and holding members. The method according to the present invention is based on the use of a expandable tubular member, which can be expanded by means of an explos charge, located within said member. With reference to the embodiment- shown in Fig. 1, the expandable tubul member-has been denominated with reference numeral 1, and it encloses explosive charge 2, which can be detonated by means of an igniter (not shown), e.g. a mechanically or electrically operated igniter. In order to -facilitate expansion, and to reduce the external diameter and incre the internal diameter before expansion, said tubular member 1 has four longitudinally extending deformations, directed towards the centre of the tubular member.!. The number of longitudinally extending deformed portions may be varied in a number of ways, and two further examples are shown in Figs. 2 and 3. However, it is obviously possible to vary the shape and the number of deformations in many other ways, sirice the outside diameter can be decreased, and the internal diameter can be increased, using any other number or shape of deformat ons. For a large number of applications, the tubular member 1 should not only expand diametrically, but also in width. Accordingly, deformations directed towards each other from at least three different planes are normally preferred. Fig. 4 shows the tubular member 1 disclosed in Fig. 1, located in a peripheral groove 3 taken up in the internal wall surface of a first tubular element 4, located surrounding and at a distance from the external wall surface of a second tubular element 5. A spring ring 6, 6', having a frusto-conical cross-section, is located at each side of the expandable tubular member 1, located in an intermediate position between the side surfaces of the groove 3 and the tubular member 1. When the explosive charge 2 is detonated, the tubular member 1 is expanded diametrically into a contact position with the bottom surface of the groove and the external surface of the second element 5, and it is also expanded towards the side wall surfaces of the groove 3, thereby flattening the frusto-conical spring rings 6, 6' against the side wall surfaces of the groove 3. The external diameter of each spring ring 6, 6' is thus expanded, and the internal diameter is . reduced, whereby the spring rings 6, 6' are forced into contact against the bottom surface of the groove 3 and the external peripheral surface of the second element 5. Each spring ring 6, 6' is thus acting as a sealing and holding element i.n conjunction with the expanded tubular member 1, and since the expanded tubular member 1 mainly takes up a frictional contact between .the two elements 4, 5, the sealing and holding properties are considerably improved by the mechanical contact taken up by means of the outside and inside edge portions of the spring rings 6, 6', which in fact slightly cut into the bottom surface of the groove and the outside wall surface of the second . element 5. This final joined position is shown in Fig. 5. The number of spring r ngs 6, 6' at each side of the expandable tubular member 1 may be further increased, as shown in Fig. 6. According to this embodiment, four spring rings &--JS are shown located at each side of the tubular member 1, each individual spring ring 6, 6' being turned 180 in relation to adjacently located spring rings 6, 6 l . This embodiment illustrates how the number of spring rings 6, 6' can be varied as desired, in order to increase sealing and holding properties of the established joint. The shown embodiment may be further modified, since more than one expandable*tubular member 1. may ' be ;used, spaced from each other by means of intermediately located spring rings 6, δ'. Such a modification would increase the area of frictional contact, and also facilitate the use of a larger number of spring rings 6, 6', i.e. a larger number of sealing and holding elements. A further modified embodiment of a joint according to the present • invention is shown in Figs. 7 and 8. The expandable tubular member 1 OR. in this embodiment is arranged with two supporting ring members 7, 7', arranged spaced from each other and enclosed within the tubular member 1. The grrove 3 for the expandable tubular member 1 has a trapezoidal cross-section, thereby increasing the contact surface against the second element 5. When the explosive charge 2, located within the expandable tubular member 1, is detonated, the tubular member 1 is expanded into the position shown in Fig. 8, thereby forming a joint between the elements 4, 5. The ring members 7, 7' now prevent the tubular member 1 from being deflected away from the second element 5. Obviously, other cross-sectioήal configurations can be used than the trapezoidal cross-section shown, in order to facilitate use of sealing and holding members located adjacent to the expandable tubular member. 1, e.g. as disclosed with reference to the embodiments shown in Figs. 4 - 6. The expandable tubular member 1 may also be arranged with integrated and outwardly directed sealing members, and an example of this is shown in Figs. 9 and 10. The expandable tubular member 1 includes two mainly wedge-shaped sealing members 8, 8', extending outwardly in direction from each other and in a mainly parallel relationship to the external surface of the second element 5. The term "wedge-shaped" refers to the cross-sectional configuration of said members 8, 8 1 , since same extend along the entire length of the expandable tubular member 1. When the explosive charge 2 is detonated, the tubular member 1 is expanded, and the wedge-shaped sealing members 8, 8' move in direction from each othe thereby establishing contact with the elements 4, 5 to be joined. This final position is shown in Fig. 10. A further modified embodiment is shown in Figs. 11 and 12, having two wedge-acting ring members 9, 9 1 enclosed within the expandable tubular member 1, the explosive charge 2 being located in an intermediate position between said ring members 9, 9'. Before the explosive charge 2 is detonated, the ring members 9, 9' are located adjacently to each other, as shown in Fig. 11. The explosive force from said charge 2 moves the wedge-acting ring members 9, 9' in direction from each other, thereby expanding the tubular member 1 into a contact position against the elements 4, 5, and said ring members 9, 9' prevent the tubular member 1 from being deflected away from the surfaces contacted atJΛerr- elements 4, 5. Accordingly, a frictional joint is established between the elements 4, 5, and since the wedge-acting ring members 9, 9' are completely enclosed with the tubular member 1, there is no mechanical damage on either of the elements 4,* 5 to be joined by means of the ring members 9, 9', when same move away from each other. In order to prevent deflection of the tubular member 1 when expanded •into a contact position with the elements 4, 5 to be joined, a further modification is shown in Fig. 13. This embodiment corresponds mainly with the embodiment shown in Fig. 2, but includes a second expandable tubular member 10 located within'jthe first expandable tubular member 1 Said second tubular member 10 is arranged with a number of holes or apertures 11, 11*, spaced from each other, and the explosive charge is located within said second tubular member 10. When the explosive charge 2 is detonated, the explosive force expands the second member 1 and the combustion gases are also distributed throug existing holes or apertures 11, IT in said member 10 into the first expandable. ember 1 which is expanded into a contact position with the" elements 4, 5 to be joined. As shown in Fig, 14, the second tubular member 10 now acts a reinforcing tubular member within the first member 1 in contact with the elements 4, 5, thereby preventing deflection of same from the ' contact position with the elements 4, 5. Obviously, this embodiment can also be combined with adjacently located sealing and holding : members, as disclosed with reference to Figs. 4 - 6. The fi st and second expandable tubular member, 1 and 10 respectively, are shown more in detail in Fig. 15, in which a portion of same is shown as a perspective view, the inside expandable tubular member 10 being shown extending out from the outside tubular member 1. The number of inside tubular members 10, located within the first tubular member 1, may also be larger than one, as shown in Fig. 16. This embodiment corresponds to the embodiment disclosed with reference ■ to Fig. 9, but in order to remove the risk for deflection from an expanded position, two expandable tubular members, denominated 10 and 10' respectively, are located within the first expandable tubular member 1, each one enclosing an explosive charge, 2 and 2' respectively When the explosive charges 2, V are detonated, the enclosed tubular members 10, 10' are expanded within the outer tubular member 1, and since the combustion gases from the explosion pass through the holes or apertures 11, 11' taken up in each internal tubular member 10, 10', the outer tubular member 1 is also expanded- into a contact position against the elements 4, 5 to be joined. This final position is shown in Fig. 17, and the expanded tubular members 10, 10' now act as two reinforcement means within the outer expanded tubular member 1, thus preventing deflection of said outer member 1 from the contact position taken up against the elements 4, 5. The embodiment previously discussed with reference to Fig. 11 can also be modified by means of an internal expandable tubular member.10, as shown in Fig. 18. Said member 10 is located in an intermediate position between the wedge-acting rings 9, 9', enclosing the explosive charge 2. When said charge is detonated, the tubular member 10 enclosing the charge 2 is.expanded, simultaneously as the wedge-acting rings 9, 9' move in direction away from each other. When the joint has been established, as shown in Fig. 19, the expanded tubular member 10 acts as a means preventing the wedge-acting rings 9, 9 1 from moving back towards each other. The joint established is thus more secure than the joint shown in Fig. 12, which is obvious when compared with the established joint shown in Fig. 19. The joint according to the present invention can be manufactured with the expandable tubular member 1 having a ring-shaped configuration, e.g. from a tubular member formed into a preferably mainly circular configuration, and with adjacent end portions being joined together by means of welding or any other previously known method. However, in order to facilitate adjustment to the diameter of the members 4, 5 to be joined, and to avoid the risk for cracks or other damage in the joint at the portion where the tubular member 1 has been joined, it is also possible to accomplish a mainly ring-shaped member without the above disadvantages. As shown in Fig. 20, the free end portions of the tubular member 1 can also be telescopically interconnected, i.e. one end portion being arranged having an internal configuration mainly corresponding to the outside configuration of the other end portion. When the enclosed explosive charge 2 is detonated, the tubular member 1 is expanded both diametrically and longitudinally, and the internal force from the combustion gases also expand the enclosed tubular end portion into contact with the surrounding tubular end portion. The expandable tubular member 1 has been referred to as a mainly ring- shaped member, but this term is also intended to include a helically wound tubular member 1, as shown in Fig. 21. According to the present invention, it is possible to use either separate ring-shaped tubular members 1, arranged as single elements, or as a combination of rings, adjacently located to each other. A helically wound tubular member 1 can be regarded as a number of mainly.. ing-shaped members, each turn forming one such member. To use a helically wound tubular member 1 can be regarded as advantageo for certain applications, and it " also facilitates the use of members 1 which are formed to des red diameter from a longitudinally extending length. The end portions are sealed, e.g. folded over, and the igniter for the explosive charge 2 is preferably inserted immediatel prior to this sealing operation. The total length of the joint is easily pre¬ determined, since desired number of adjacently located turns can be applied. Furthermore, the tubular member 1 may also include at least one enclose second expandable tubular member 10, having through holes or apertures 11, 11' and surrounding the explosive charge 2. The enclosed second tubular member 10 will thus act as a rei forcing member, preventing deflection of the outer tubular member 1 from an expanded position in contact with the elements 4, 5 to be joined, as previously discussed with reference to the embodiments shown in Figs. 13 - 19. A helically wound tubular member 1 may also he used together with a number of adjacently located sealing and holding members, as disclosed with reference to Figs. 4 - 6. This is shown τn Fig. 22, which shows a helically wound tubular member 1, having a supporting tubular member 10 enclosing the explosive charge 2 located inside the outer tubular member 1. When the explosive charge 2 is detonated, the joint is established between the elements 4, 5, as shown τn Fig. 23. / ^}R.E As previously mentioned, a number of ring-shaped tubular members 1 can be used for the establishment of one joint, and Fig. 24 shows how two tubular members 1 are arranged with spring rings 6, 6' located in an intermediate position, and also located adjacent to the outside surfaces of each tubular member 1. When the explosive charges are brought to detonate, by actuating associated igniting means, the • expansion of the tubular members 1 will obviously force the spring rings 6, 6' to take up contact with the elements 4, 5, thus acting as sealing and holding members, improving the holding properties of the established joint. The above described embodiments, shown in the accompanying drawings, are only intended to serve as examples of embodiments within the scope of the present invention and following claims. As shown, a:-large number of embodiments can be combined in different ways, depending on the requirements of the joint to be established, i.e. strength, sealing, and other properties. The risk of deflection from an expanded contact position can be eliminated by the use of enclosed expandable tubular members 10, 10', and sealing and holding properties can be improved • as desired by the use of external sealing and holding members, either being integrated with the outer expandable tubular member 1, or being applied as separate members 6, 6'. The explosive charge 2 can be ignited mechanically or electrically, and the igniters are of previously known type. Since the igniter can be initiated in so many different fashions, only the explosive charge 2 has been shown, but electrical wires, or a mechanical striking pin, • can obviously be arranged extending out from the expandable tubular member 1. Accordi ngly, the present inventi on i s i n no way restri cted to only the - embodiments shown and described, si nce many modi fi cations obviously are possibl e wi thi n the scope of the inventi on and the fol l owing cl aims , Final ly, the spring rings 6 , 6 ' may al so be arranged wi th a curved cross-secti onal confi gurati on, or any other sui tabl e confi gurati on , facil i tati ng expansi on when compressed .

Claims: CLAIMS 1. A method to join two elements (4, 5), a first element (4) having an internal peripheral surface located in a- surrounding relationship at a distance from an external peripheral surface of a second element (5), at least one mainly ring-shaped expandable tubular member (1) with at least one explosive charge (2) and associated igniter being arranged ■located in an intermediate position between said peripheral surfaces, characterised in that detonation of the explosive charge (2) is arranged to expand the tubular member/members (1) into a contact position against adjacently located peripheral., surfaces of the elements (4, 5), and also influence enclosed, integrated. or adjacently located holding and sealing members (6, 6'; 7, 7'; 8, 8'; 9, 9'; 10, -10'), arranged to prevent deflection of the expanded tubular member (1) from the contact position taken up against the elements (4, 5) and/or to establish mechanical contact with the elements (4, 5)-, thus improving the sealing and/or holding properties of the established joint. 2. A method according to claim 1, characterised in that at least one second tubular expandable member (10, 10') is arranged to surround the explosive charge (2) located within the first and outer expandable tubular member (1), said second tubular member (10, 10') being arranged with a number of through holes or apertures (11, 11'}, detonation of the explosive charge causing said second tubular member (10, 10') to expand to a contact position with at least two mainly opposed internal wall portions of the first tubular member (1), the combustion gases from the explosion being arranged to flow through said holes or apertures (11, 11'} into the interior of the first tubular member (1), thereby expanding same simultaneously into a contact position against the adjacently located surfaces of the elements (4, 5] to be joined, 3. A method according to claim 1 or 2, characterised in that at least one mainly frusto-conical spring ring (6, 6'} is arranged located adjacently to -the .expandable tubular member (1), said spring ring(sj (6, 6') being deformed to increase the external diameter and decrease the internal diameter when the tubular member (1) is expanded by means of explosive force from the explosive charge (2), thereby establishing a mechanical connection between the facing peripheral elements (4, 5) to be joined. 4. A method according to claim 1, 2 or 3, characterised in that the tubular members (1, 10, 10'), expandable by means of the explosive force, are arranged with mainly. longitudinally extending depressions, arranged to decrease the external diameter and to increase the interna diameter, and preferably also arranged to decrease the width of the tubular members (1, 10, 10') from a larger cross-sectional configurati 5. A joint according to the method disclosed in claim 1, 2, 3 or 4 including at least one mainly- ring-shaped expandable tubular member (1) with at least one explosive charge (2) and an associated igniter means being enclosed within said tubular means (1), characterised in that the detonation of said explosive charge (2) is arranged to expand the tubular member (1) into a contact position against adjacently located surfaces of the elements (4, 5) 'to be joined, and also influence enclos integrated or adjacently located holding and sealing members (6, 6'; 7, 7'i 8, 8'; 9, 9'; 10, 10'), arranged to prevent deflection of the expanded tubular member (1) from the contact position taken up against the elements (4, 5) and/or to establish mechanical contact with the elements (4, 5), thus impr-ving the sealing and/or holding properties of the established joint. 6. A joint according to claim 5, characterised in that at least one second expandable tubular member (10, 10') is arranged to surround the explosive charge (2) located within the first expandable tubular member (1), said second tubular member (10, 10') being arranged with a number of through holes or apertures (11, IT) to facilitate a combustion gas flow from the explosive charge (2) into the first tubular member (1), said second tubular member (10, 10') being arranged to be expanded by the explosive force into a contact position with at least two mainly opposed internal wall portions of the first tubular member (1). 7. A joint according to claim 6, characterised in that the second expandable tubular member (10, 10') is arranged to take up a mainly- circular cross-sectional configuration after expansion. 8. A joint according to claim 5, 6 or 7, characterised at least one external side surface of the expandable tubular member (1) is arranged to form a first restricting surface for at least one spring ring (6, 6') having a preferably frusto-conical cross-sectional con¬ figuration, a second restricting surface being arranged at the opposed side of the spring ring/rings (6, 6'), said expandable tubular member (1 being arranged to deform said spring ring/rings (6, 6') when expanded by means of the explosive force, thereby reducing the internal diameter and increasing the external diameter of the spring ring/rings (6, 6') and causing same to take up contact with the facing peripheral surfaces of the elements (3, 4) to be joined. 9. A joint according to claim 8, characterised in that at -least two spring rings (6, 6 f ) are arranged adjacent to at ' least one side surface of the expandable tubular member (1), each spring: ring (6, 6') being turned 180° in relation ~to adjacently located spring rings (6, 6'). 10. A joint according to claim 5, 6, 7, 8.or 9, characterised in tha the expandable tubular member (1) is arranged with outwardly directed and preferably wedge-shaped, sealing members, arranged to take up contac with at least one of the peripheral surfaces of the elements (3, 4) to be joined when the tubular member (1) is expanded by means of explosive force. 11. A joint according to claim 5, 6, 7, 8, 9 or 10, characterised in that the expandable tubular member (1) is arranged with at least one supporting ring, enclosed within the tubular member (1) and preferably forming an integrated part with same. 12. A joint according to claim 5, 6, 7, 8, 9, 10 or 11, characterise in that the expandable tubular member (1) is arranged with at least one wedge-acting ring member (9, 9'), arranged to be moved mainly transversely under the influence of the explosive force and to act as a force-applying internal member, imposing a force directed towards the elements (4, 5) to be joined. 13. A joint according to claim 5, 6, 7 , 8, 9 , 10, 11 or 12, characterised in that the mainly ri ng-shaped expandabl e tubular member (1 ) is formed by means of a number of adjacently wound hel i extending turns with the free end portions sealed, e.g. by a folding operation. 14. A joint according to claim 5, 5, 7, 8, 9, 10, 11 or 12, characterised in that the mainly ring-shaped expandable tubular membe (1) extends in mainly one plane, the free end portions being joined telescopically together. 15. A joint according to claim 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, characterised in that the expandable tubular member (1) is arranged with a number of longitudinally extending deformations, arranged to decrease the external diameter and to increase the internal diameter, and also preferably reduce the width of the tubular member (1). •^SϊlEΛ J y OMPI K IPO Λ

Inventors: GEBELIUS SVEN R
Applicants: GEBELIUS SVEN R
Application year: 1981
Main classification: B21D39
IPC codes: F16L13