TECHNICAL FIELD

J 5 The invention relates to a metallic cloth joint with shape- memory function which is used for connecting, anchoring,

\ reinforcing, securing, or sealing one or more components, such as machine elements, pipes, mouldings, etc.

10 BACKGROUND ART

By the term cloth in this application is meant an essentially two-dimensional body, that is, the width and length of the cloth are considerably greater than the thickness thereof,

15 which exhibits low flexural rigidity and such a coherence that it can be handled in extended state. The cloth according to this application comprises at least one woven, braided, knitted or knotted coherent network built up of one or more threads or tapes of a metallic material. This network may be

20 manufactured by means of different techniques such as weaving, braiding, knotting, knitting, etc. The cloth may constitute an open network of metal wires or metal tapes but the network may also be completely or partially filled with a compound which is adapted to surround and/or cover the wires.

25

By a cloth tape in this application is meant a cloth with thickness « width << length.

By a metal with shape-memory function in this application is 30 meant a metal which, by changes in temperature and/or by application/relief of external forces, may change between different shapes. This is accomplished by a diffusionless phase transformation in solid state, known as martensitic transformation.

35

By a metal with thermal shape-memory function in this applica¬ tion is meant a metal which is deformed and then, by a change in temperature, is transformed into a different shape.

This transformation may be a one-way transformation or be reversible such that the metal may change between the different shapes.

By a superelastic metal is meant in this application a metal which can be greatly deformed by the application of an exter¬ nal force without being plastically changed and then, when the external force has been removed, is transformed into a diffe¬ rent shape. In certain literature this function is referred to as pseudoelastic.

By metal with shape-memory function is meant in this applica¬ tion both superelastic metals and metals with thermal shape- memory function.

The use of metallic cloths as mechanical joints to connect, anchor, reinforce, or secure one or more components such as machine elements, pipes, mouldings, etc., and as joints for sealing pipes, connections and joints as well as containers is known. Such metal cloths, which are substantially used in the form of cloth tape, that is, cloths with thickness « width « length, of conventional metals must, during application, winding on, be greatly prestressed to achieve with the joint the uniting pressure and/or the tightness which is required. This prestressing of the cloth tape is in many cases not possible to achieve during mounting, repair, etc., because of lack of space or other limiting external factors adjacent the location where the joint is to be applied. Further, in many situations it is difficult to apply the great prestressing force which is aimed at.

Mechanical joints based on a sheet or wire winding, so-called Multi-Wire Tension (MWT) windings, are known and used to secure pipe systems and other machine elements (see, e.g., Swedish patent application SE 9000890-5) . In the Swedish application referred to, a joint is described comprising metal with thermal memory function, that is, a joint in which an MWT winding comprising a metal wire or a metal tape with thermal

memory function brings about an inwardly-directed uniting force after mounting. To bring about the inwardly-directed uniting force, the wire has been stretched into a suitable length, before or in connection with the winding on, at a temperature below the transition temperature of the material, in order to achieve the desired contraction of the cloth, when the temperature is subsequently increased above the transition temperature, by a thermally initiated deformation of the wire. Also superelastic metals and metal alloys may be used in this type of mechanical joints, whereby the wire or the tape in connection with the mounting operation is elastically deformed, preferably stretched, by means of an applied force and then, when this force is relieved, the wire strives to recover its previous shape and to achieve an inwardly-directed uniting force acting on the body. In case of complicated geometries, however, it is difficult to apply these MWT windings and achieve through these windings the inwardly- directed uniting force which is required to connect, anchor, reinforce or secure one or more components such as machine elements, pipes, mouldings, etc.

One object of the invention is to suggest a metallic cloth joint which, by application/relief of an external force in connection with mounting, or a change in temperature after mounting, by transformation changes its shape in one or more directions.

Another object of the invention is to suggest a metallic joint cloth, in which the cloth is wound around complicated geome- tries and by deformation, for example contraction after mounting, achieves a mechanical compression joint which acts in a unifying or reinforcing manner on the component or components around which the cloth is applied, regardless of geometry and external limiting factors such as lack of space.

A further object of the invention is to suggest a metallic cloth joint which, by deformation such as, for example, a contraction in one or more directions, achieves a sealing

joint to prevent leakage from a vessel or a pipe.

SUMMARY OF THE INVENTION

A metallic cloth joint in the form of an interplaited network in which the cloth is arranged in the form of a cloth tape, that is, a cloth with thickness << width « length, which comprises one or more wires with shape-memory function. These wires or tapes are oriented essentially in the longitudinal direction of the cloth tape and are arranged to achieve, at a later stage, after the application of the cloth joint, a desired deformation of the cloth when the cloth joint is used as a mechanical and/or a sealing joint, wherein the cloth, during transformation after winding, achieves the desired uniting force.

In one embodiment of the invention, the cloth comprises a metal wire or a metal tape with thermal shape-memory function. Preferably, the cloth comprises a metal wire or a metal tape which, prior to or in connection with the build-up into a network, at a temperature below the transition temperature of the material, has been deformed, preferably has been stretched to a suitable Length, in order to change its shape, by a thermally induced transformation, when the temperature is subsequently increased above the transition temperature, thus achieving a desired deformation of the metal cloth.

A metallic cloth joint according to a further embodiment of the invention comprises one or more metal wires or metal tapes of a superelastic material, wherein the metallic cloth during the application can be greatly deformed under the influence of an external force and then, when the external force is relieved, by a mechanically induced transformation recovers its original shape.

When using a metallic cloth joint comprising one or more wires or tapes of a metallic material with thermal shape-memory function as a mechanical joint for connecting, anchoring,

reinforcing or securing one or more components such as machine elements, pipes, mouldings, etc., or as a sealing joint arranged around a vessel or a pipe, the metal wire or the metal tape has been deformed, at a temperature below the transition temperature of the metallic material, prior to or in connection with the build-up or the application of the cloth joint. In order to achieve, after the winding on, a deformation as a result of a thermally induced transformation in the metallic material, the temperature is increased above the transition temperature. The transformation preferably results in a contraction of the cloth tape in the longitudinal direction, whereby the cloth joint achieves an inwardly- directed pressure against the component which acts in a uniting manner and also counteracts the formation and propagation of cracks in the component.

When using a cloth joint comprising one or more wires or tapes in a superelastic metallic material as a mechanical joint for connecting, anchoring, reinforcing or securing one or more components such as machine elements, pipes, mouldings, etc., or as a sealing joint arranged around a vessel or a pipe, the cloth tape is greatly deformed during the winding on and is then, when relieved, transformed and achieves an inwardly- directed pressure against the component, whereby the cloth joint acts in a uniting manner and counteracts the formation and propagation of cracks in the component.

The elasticity of the cloth and the forces obtained thereby may be varied based on the weaving technique used such as weaving, braiding, knitting, etc., and be adapted to the requirements imposed by different specific uses.

In one embodiment a metallic cloth according to the invention is wound with overlap so as to obtain a cloth joint with an axially uniting force by the friction between the turns. The uniting frictional force then prevents a spontaneous rupture which, in use as a mechanical joint in a tube system, prevents pipe breaks and secures the requirement for "Leak-Before

Break" in critical tube systems.

A cloth joint for sealing in connection with mounting or repair of tube systems or a vessel must be made pressure- tight, that is, the cloth joint must not be permeable to the medium which is present in the tube system or the vessel but must prevent leakage. In one embodiment of the invention, this can be achieved by impregnating or infiltrating a cloth joint according to the invention with a sealing compound to constitute a tight cloth wherein the threads or tapes included in the cloth are surrounded by this sealing compound. The impregnation may be applied to the threads included or to the cloth before or in connection with the application of the cloth by spraying, plating, embedment, etc., in one or more steps. To provide this sealing function, the compound is selected in certain cases so as to maintain its plasticity also when using the compound after application of the joint. Alternatively, a compound is selected which hardens by crosslinking, vulcanization, etc., hereinafter in this application referred to as hardening, after application, preferably in connection with the deformation of the cloth joint. The hardening can be initiated by the temperature increasing. Suitably, a compound is selected which hardens in connection with the transition temperature of the used cloth. Alternatively, a cloth may be used which hardens as a result of the pressure applied to the cloth after the contraction. In certain embodiments, it may be of value for the compound to comprise an incompressible material.

Metallic materials with shape-memory function, especially suitable for use in a cloth joint according to the invention, are so-called memory-metal alloys based on nickel and titanium or iron-based memory-metal alloys.

A cloth joint according to the invention is especially valuable in applications such as:

- prevention of crack growth in pipes,

- prevention of pipe breaks, Leak-Before-Break,

- sealing against leakage,

- securing against pipe breaks,

- where there is a need of great uniting forces, such as in applications in, for example, power plants or process industries but also in more uncomplicated applications such as waste pipes and exhaust pipes.

A particular property of a cloth joint according to the invention is that the joint becomes elastically flexible and resilient, whereby it may be used to advantage in applications which are used in an environment involving mechanical and/or thermal transients.