JPH0258846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cable connection, branch or terminal part, a connection part, a branch part and a terminal part themselves,
and metal foil members used therein.

More particularly, the present invention relates to cable connections, branches, and terminations in which thermal recovery of a thermally recoverable member surrounds one or more cable sections.

In cable handling devices such as those described above, particularly those portions of smaller diameter cables (eg, diameters of 15 mm or less) associated with the cable handling device become overheated during the thermal recovery process of the heat recovery member. Such overheating is undesirable in itself and will soften the insulation of the insulated cable sections.
The restoring sleeve severely distorts the shape of the part or presses the part against a hard part, such as an adjacent bifurcated clip, or even against the restoring edge of the sleeve itself.
This can result in partial or even complete penetration of the cable insulation, which can lead to serious problems. Such distortions or burrs in the cable insulation are a potential source of electrical defects, and also if the thermally resilient material surrounds multiple cable sections and one of the cable sections is more rigid than at least one other. This is particularly the case if the diameter is substantially small.

Although many attempts have been made to place thermally insulating materials around such small diameter cable sections, these solutions to the above problem have generally been unsatisfactory. The reason for this is, for example, that it is difficult to handle insulating materials at installation temperatures ranging from -10°C to +40°C. In the present invention,
A completely different approach is taken.

The present invention provides a method for manufacturing a cable connection, branch, or termination in which a heat-restored member surrounds a plurality of cable sections and a portion of the cable extends beyond the end of the heat-restored member. and the method includes forming a cable around at least one cable section (if more than one, each
The hardness of the metal foil member is determined by the process of heat restoring the heat restorable member. The stiffness used is sufficient to substantially prevent diametric distortion or jaggedness of the foil-encased cable section. Placing the foil member in this way, preferably in a wrap-around manner, around at least one cable section (or around each cable section, if more than one) means that the metal shell or liner is It will be appreciated that this is inconsistent with the prior art, which aims to provide a smooth profile to a heat recoverable member that is placed around cable sections en masse and restored onto a shell or liner. In the present invention, typically all cable sections are insulated, but this is not required.

Further, the present invention provides that the heat-restored member has at least one
The present invention provides a method for manufacturing a cable connection, branch, or termination section that surrounds two cable sections, and the cable section extends from the end of a heat recovery member. The process consists of placing a metal foil member around the heat-recoverable member from within the range of the heat-recoverable member to a point beyond the edge of the member, and then thermally restoring the heat-recoverable member, in which case the metal foil member is It must have sufficient stiffness to substantially prevent diametric distortion or jaggedness of the foil-encased cable portion during the thermal recovery process of the heat recoverable member.

Furthermore, the invention provides a connection, a branch or a terminal as defined above, as well as a metal foil member for use therein.

More particularly, the present invention provides a metal foil member suitable for wrapping around or otherwise disposing around a cable section at a junction, branch, or termination. , the member has a thickness of 150 to 250 microns,
It has an aluminum sheet coated with a heat-seal adhesive or a pressure-sensitive adhesive. Preferably, the pressure sensitive adhesive is protected with a release layer before use.
The aluminum sheet also preferably has a mastic attached thereto and preferably has openings through which adhesive can pass during heating during the sleeve restoration process. Preferably, the heat seal adhesive and mastic are in distinct locations on the aluminum sheet to facilitate wrapping of the cable with the sheet. The part of the foil that is not glued acts as a hinge or linchpin. However, it is not necessary to apply the adhesive discontinuously to facilitate envelopment, especially in the case of narrow metal foil tapes.

The principles of the present invention have the great advantage of greatly reducing the bulk of the protective material around the foil-wrapped cable section, and the high thermal conductivity of the metal makes it possible to improve In direct contrast, it has a significant advantage in that the heat-activated adhesive ensures that a suitable seal is formed between the foil member and the cable section.

It is sufficient that the foil previously used around the cable was of a thin and highly flexible construction with a highly heat dissipating surface to reflect heat from the heat source used to restore the sleeve. It will be recognized. In the present invention, at least a portion of the foil comprises:
Specifically, it is intended to be located inside the sleeve to ensure that heat, by conduction, reaches the area between the cables, and in particular the area between the small and large diameter cables to achieve a seal. . In addition, the foil member of the present invention provides a mechanically strong support surrounding the cable for the restoring sleeve.

Although integral tubes of metal foil or half shells of metal foil assembled to form tubes may also be used, it is preferred to use metal foil members that can enclose small diameter cable sections.

The aforementioned adhesive seals are typically formed either by a heat-activatable adhesive deposited on the inner surface of the sleeve, or by other heat-recoverable materials flowing through appropriate openings in the foil member. Although possible, it is preferable to apply the adhesive onto the foil member with the adhesive side facing the cable section. It has been found that this arrangement allows the total amount of heat-activatable adhesive inside the closure to be reduced. The reason is that the amount of adhesive deposited on the heat-resilient component is less if there is no need to form a bond between the metal component and the cable section, regardless of the degree of excess of its amount. This is because the quantity is enough.

If a perforated foil member is used, the adhesive may be applied using a heat recoverable sleeve and may be applied to the inner surface of the sleeve prior to application. The opening in the foil member may be elongated in a direction perpendicular to the direction in which the foil wraps the cable, but is generally rectangular or diamond-shaped and extends to one or both ends of the foil. preferable. It is also preferable that the foil itself is approximately rectangular. The foil member may be such that it can be wrapped once around the cable so that both ends thereof overlap, and the degree of overlap may be as small as at least 20° or as large as 360°.

The heat-activatable adhesive applied to the foil is preferably dispersed at separate locations to facilitate wrapping the cable section with the foil. When wrapping cables in metal foil, it is preferred to place parallel beads of heat-activated adhesive along the length of the cable on the metal foil, but it is also preferred to place the adhesive in dots or other shapes. It's okay.

The type of adhesive may be selected to suit the conditions in question. For certain purposes, U.S. Pat.
4018733 and 4181775, heat-sealing adhesives based on polyamide, ethyl vinyl acetate or mixtures thereof and having good tack at 85-90°C are suitable; For other purposes, mastics based on butyl rubber-based systems, such as polyisobutylene mastics, and EPDM rubber or
Mastics based on EPM are preferred.

However, in some applications, mastic, despite its excellent moisture barrier properties, may not provide sufficient resistance to linear movement of the cable, and heat-seal adhesives may require a greater resistance to such action. Although it has rigidity, it was found that it did not maintain sufficient moisture resistance. A simple solution to this problem has been devised in a preferred embodiment of the invention. That is, in this embodiment, heat-sealing adhesive is applied to one place on the surface of the metal foil, and mastic is applied to another place on the same surface, and the arrangement of both is such that when wrapping the cable in a box, the adhesive and mastic are applied. The mastic is to be located at separate locations along the cable. When the two are arranged in this manner, the heat-sealing adhesive, which preferably has a flow temperature substantially lower than that of the mastic, tends to act as a dam to prevent it from gradually flowing out of the mastic. It is also preferred to use a box coated with a heat seal adhesive on both sides of the mastic coated area, so that it does not matter how the operator actually wraps the cable in foil.

Particularly suitable heat-sealing adhesives for the purposes of the present invention include:
Described in pending US Patent Application No. 8,015,576. The application describes the adhesive composition as being "produced by mixing a thermoplastic polyamide with reactive amine groups attached to the polyamide molecule and a vinyl-terminated rubber." In a further preferred embodiment, a pressure-sensitive adhesive is applied over the heat-sealable adhesive to create a coating to assist in placing the foil on the cable prior to activation of the heat-activatable adhesive. If mastic (usually adhesive) is used, the pressure sensitive adhesive may be omitted. Suitable pressure sensitive adhesives include systems based on polystyrene, polybutadiene or Elvax with suitable tackifiers, but others may be used if desired. In selecting the amount and properties of the pressure sensitive adhesive, it is desirable that the adhesive be mixed with other adhesives during heat activation without degrading the overall adhesive performance.

The foil member is preferably coated with a polyolefin, preferably polyethylene, to improve corrosion resistance and provide a uniform surface for bonding with the adhesive. Polyolefins may be flame treated or corona treated to improve adhesion.

A preferred foil member has a thickness of 150 to 250 microns;
Preferably 200 micron aluminum foil with a thickness of 40-60 microns on both sides, most preferably
Preferably, it is coated with a 50 micron layer of polyethylene. The foil member can also be made from multiple layers of thinner material, but this method is usually not practical.

In a preferred embodiment of the invention, the thermal conductivity of the metal foil is used to direct the appropriateness of heating for activation of the adhesive or sealant on the inside of the heat recoverable member. To do this, the foil member is provided with a temperature indicator, preferably a thermochromic coating, at least on a portion of the foil that can be arranged to protrude from the end of the sleeve. . In the preferred arrangement, the heat conducted along the foil causes a temperature indicator to indicate when the interior of the heat resilient member has reached a suitable temperature. If necessary, install thermal insulation directly adjacent to the edge of the heat resilient member, preferably on top of the foil itself, so that the foil protruding from the edge of the sleeve can be accidentally heated directly and misdirected. may be prevented from being released.

In one aspect of the invention, the thermal barrier member can be mounted, preferably as part of the metal foil member. In this case, the metal foil member can also consist of a metal foil and a thermal barrier bonded thereto. Providing a thermal barrier member is advantageous when the cable is subjected to thermal as well as mechanical forces. Small diameter cables with poor heat absorption or heat sink properties are
This is particularly advantageous from the point of view of installing thermal barrier members. The installation of the insulating member allows air to be used as the insulating medium with only a small amount of extra bulk around the cable. This is advantageous over installing more heat sinks, which requires too much space. There are two preferred methods of attaching the thermal barrier member. 1
One is to adhere the foam material layer to the metal foil, preferably leaving a pressure sensitive adhesive around the edges of the foil to help secure the foil to the cable. A second alternative is to use a ribbed tube through which the cable is passed and a metal foil wrapped around the tube.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic illustration of a roll of adhesive coated aluminum foil suitable for use in the present invention.

FIG. 2 shows the adhesive coated foil in more detail.

FIG. 3 shows a perspective view of the preferred beaded form of heat-activatable adhesive on the foil, with a light coating of pressure sensitive adhesive.

FIG. 4 shows a more detailed cross-sectional view of the arrangement of FIG. 3, with a preferred coating of polyolefin on both sides of the aluminum foil.

FIG. 5 is a perspective view showing a small diameter cable wrapped in coated aluminum foil.

Figures 6a and 6b are schematic diagrams showing in perspective how the heat-sealing adhesive 2 and the mastic 5 are preferably arranged at separate locations on the foil, and the entire surface is optionally coated with a pressure-sensitive adhesive. It has been done.

FIG. 7 shows a foil member coated with a thermochromic indicator.

FIG. 8 shows the foil member of FIG. 7 assembled in a sleeve, with the portion of the member beyond the end of the sleeve provided with a thermochromic composition.

Figures 9 and 10 show foils and assemblies similar to Figures 7 and 8, with thermal insulation provided on the foil and the end of the sleeve being thermally restored during the foil process. Protect from direct heat.

Figures 11 and 12 show a plan view and a partial cross-sectional view, respectively, of a foil member of the present invention.

FIGS. 13 and 14 show cross-sectional views of still other embodiments of the foil member.

FIG. 15 shows a ribbed tube that serves as a thermal barrier member.

FIG. 16 shows a longitudinal section of the thermal barrier tube.

Figure 17 shows how foam sheets can be used as thermal barrier members. Moreover, FIGS. 18 and 19 show modifications of FIG. 17.

Figures 1 and 2 show a relatively narrow tape of aluminum foil 1, 1 cm wide, coated only with a heat-sealable adhesive. The foil is approximately 200 microns thick and the adhesive is coated continuously since the tape is narrow enough to not require any special coats to aid coverage.

Figures 3 and 4 show a preferred beaded coating of hot-seal adhesive 2 on foil 1 (width 250 mm) and Figure 4 shows a preferred coating 3 of polyethylene on both sides of the foil. The preferred top film of pressure sensitive adhesive 4 is shown in dotted lines. Figures 6a and 6
FIG. b is a schematic representation of the preferred arrangement of heat-sealing adhesive 2 and mastic 5 at different points on the foil for the purpose described above, again with a pressure-sensitive adhesive.

In any of the above cases, the aluminum foil 1 has a thickness of approximately 200 microns, and the polyethylene film 3 has a thickness of approximately 200 microns.
50 microns, and the adhesive coating weight is approximately 500 to 1000 microns for hot melt adhesive alone.
g/m ² , preferably 750 g/m ² , and in the case of a combination of heat-fusible adhesive and mastic, the heat-fusible adhesive is 300 to 600 g/m ² and the mastic is 400 to 700 g/m 2 .
m ² and pressure sensitive adhesive (if present)
15-30g/ ^m2 . The preferred heat-seal adhesives described above were used with polystyrene/polybutadiene-based pressure sensitive adhesives.

In use, foil is wrapped around a small diameter cable section and a bead of adhesive is run along the cable, if present, as shown in FIG. This allows the foil to bend more easily between the beads of adhesive, making the coating process easier. Pressure sensitive adhesive is attached to sleeve 6 (Figure 5)
helps hold the foil in place prior to thermal recovery around the small cable 7 and large cable 8. When thermally restoring the sleeve 6,
The cables 7 and 8 will be subjected to compressive forces, and although the smaller cables 7 will tend to overheat, the protective foil 1 will protect them from distortions or depressions etc. caused by the hard edges of the branching clip 9 or the sleeve 6. substantially protected. Additionally, some heat load is absorbed by the foil, helping to reduce overheating. The heat-activatable adhesive applied to the foil 1 is activated during heat recovery to firmly bond the foil to the cable 7, and preferably the mastic 5 (see Figures 6a and 6b) forms a seal against moisture. However, the heat-sealing adhesive 2 acts as a dam to hold the mastic in place and itself participates in the adhesive action of the adhesive. The pressure-sensitive adhesive 4, if present, will be absorbed into the adhesive of the heat-sealable mastic without adverse effects during this operation, so that the mastic is normally below its flow temperature. Since the pressure sensitive adhesive has sufficient adhesive strength, the pressure sensitive adhesive may be omitted.

7 and 8 illustrate a preferred embodiment of the invention.

In the drawing, a polyethylene foil 1, to which beads 2 of adhesive or sealant are applied, has on its surface, apart from the beads, a coating 20 of a thermochromic indicator composition. The thermochromic composition may or may not be reversible. A sleeve 30 of known type, in this example:
The cable 33 has a blocking rail 31 and a blocking channel 32 with an indicator sheath protruding from the sleeve.
When configured as a sleeve 30 surrounding the indicator, the indicator changes color when a sufficient temperature is reached due to heat being transmitted from the inside of the sleeve along the foil. In this way, the appropriately selected indicator is
Inside the sleeve, it can be used to indicate when the activation temperature of the adhesive or sealant on the foil has been reached, typically by providing a thermochromic coating 30 on the outside surface of the sleeve itself. The accuracy of the instructions is significantly improved compared to the instructions that are given. As thermochromic coatings for foils and sleeves, the activation temperature of the foil coating is lower than that of the sleeve coating, such as U.S. Pat. No. 3,816,335, British Patent No. 1,511,053,
and those described in British Patent Application No. 7943636.

The heat recoverable sleeve may be of any suitable type.

Heat-recoverable products, especially heat-shrinkable products, are used for insulation,
It is widely used today in many areas where sealing and encapsulation is required. When heated, these products typically recover from their previously deformed shape to their original shape; however, the term "heat recoverable" as used here refers to It also includes members that take on new forms when heated.

The products described above are most commonly in the form of heat-shrinkable sleeves, which may include, for example:
U.S. Patent Nos. 2027962, 3086242, and
As described in Japanese Patent No. 3,597,372, they are made from polymeric materials exhibiting elastic memory or plastic memory properties.

For example, as disclosed in GB 2027962, a dimensionally and thermally stable initial form may be a transient form during one step of continuous processing. For example, an extruded tube expands upon heating and becomes a dimensionally thermally unstable form, whereas in other applications, a preformed dimensionally thermally stable product is Moreover, it is acceptable even if it deforms into a thermally unstable form.

In other products, for example British Patent No. 1440524
As described in the publication, an elastomeric member, such as a tubular outer member, is held in tension by a second member, such as a tubular inner member, and when heated, the tubular inner member It is adapted to soften and restore the elastomeric member.

Additionally, so-called "wrapping" sleeves have already been developed. Basically, this type of sleeve consists of a heat-recoverable sheet that can be wrapped around a substrate to form a generally tube-like shape, and typically has a fastener to hold the sheet in the wrapped configuration during restoration. It is equipped with Such fasteners are typically mechanical in nature, such as rigid clamps, pins, or channel members, which are placed adjacent the overlapping edges of the heat resilient sheet. As such, it is adapted to cooperate with projections which are integrally molded or extruded into a suitable shape. Various types of fasteners are disclosed, for example, in US Pat. No. 3,379,218, British Patent No.
1155470, 1211988 and 1346479, and UK Patent Application No. 2019120A. However, in other applications, the sheet may be held in an encased configuration during restoration by an adhesive, which may optionally be applied in situ. For some applications, an end cap (or sleeve closed at one end) may be used.

In FIGS. 11 and 12, the foil member 40
consists of a 200 micron thick aluminum sheet 42 of 99.5% softener grade and has a series of rectangular openings 44 in its surface. The shape of these openings may be other shapes, such as diamond-shaped, and preferably extend to both edges of the foil member 40 to aid in wrapping the cable, as shown. It may be something like this. The aperture may extend along the length of the cable to the rear end of the sheet in use. Each side of the sheet 42 is coated with polyethylene 46. The top or outer surface of the sheet 42 is coated with a heat-fusible adhesive 48 and the bottom, or inner surface, is coated with another type of heat-fusible adhesive 50 that is pressure sensitive. The pressure sensitive adhesive 50 is protected with a release paper 52 before the foil 40 is attached.

As in the embodiments of the invention described above, the foil 4
0 wraps around a cable, especially a smaller diameter cable adjacent to a much larger diameter cable, and thus may or may not overlap itself. In the latter case, that is, if the cables are not overlapped, the more susceptible the cables are to damage due to overheating, the more desirably the overlap is, for example, 100%, that is, 360°. If possible, the release paper 52 is removed first and the foil 40 is placed in position around the cable and surrounded by a heat recoverable sleeve. When the sleeve is restored, adhesive from the foil and/or coating on the sleeve flows through the opening 44 and the foil 4
0 to the cable.

As can be seen from Figure 5, if there is a significant difference between the diameters of two cables, heat transfer in the area between them will be empirically difficult;
Along the way, the smaller diameter cable will become overheated.

Thus, when the sleeve is restored, the foil member
Mechanically protects heated small diameter cables and retains them in their original form, even if softened by the heat required to create the seal and surrounded by molten hot adhesive. to be maintained. Such a protection method is particularly suitable for enclosing cables in which the sleeve material is relatively thick and of large diameter, so that the inward forces upon recovery are considerable. Suitable if

13 and 14 show foil members of other embodiments. In these foil members, the aluminum sheet 60 (FIG. 13) is coated with a heat-fusible adhesive 6.
2 has discontinuously attached portions, and the sheet is covered with a continuous coating 64 of pressure sensitive adhesive. The other aluminum sheet (FIG. 14) has a continuous film 65 of heat-fusible adhesive, and the heat-fusible adhesive has discontinuous portions of pressure-sensitive adhesive. It is covered with 66.

It will be appreciated that the features of the embodiments described above, such as those relating to suitable adhesives, are equally applicable to the embodiments of FIGS. 11-14.

As shown in FIG. 15, a ribbed tube, preferably made of nylon, is used as a thermal barrier member. The tube 10 has a raised portion 11 which is formed when the tube 10 is wrapped with a sheet 1 made of aluminum or other metal.
Forms a pocket that insulates the atmosphere. The cable 7 to be protected passes through the cable 10. Although the dimensions do not have to be exact, dimension A is preferably about 10 mm, B is about 1 mm, and C is about
It is said to be 1.5mm. A longitudinal section of this installation is shown in FIG. A heat-fusible adhesive 16 is shown between the metal sheet 1 and the outer heat-recoverable sleeve 6. Each hole 12 is provided through the wall of the tube 10 so that when the sleeve 6 is heated and restored, each hole 12
is intended to be a passageway for the adhesive. 1
The or each hole 12 must be small enough to restrict heat flow, but large enough to allow adhesive to pass through. There is a relationship between the distance between each rib 11 and the thickness of the foil, which means that although it is desirable to reduce the number of ribs to reduce heat conduction, the overlapping metal foil 1 is This is because it must be made so that it does not break. As mentioned above, it has been found that a spacing of 10 mm is sufficient, and the foil has a thickness of approx.
Advantageously, it is 200 microns. The thermal barrier can also be of the helical jacket type, made of a material with poor thermal conductivity and formed so that it can be wrapped around the cable to be protected. It would be convenient to use two layers of metal foil.

Figures 17 and 18 show other embodiments of thermal barrier members. The foil 1 is coated with a foam 13 and has areas 4 to which adhesive is applied. As can be seen from Figure 17, the areas with adhesive are used to secure the entire metal foil element to the cable to be protected. The metal foil member can be wrapped around the cable 7 as many times as necessary, for example, as many as three times, overlapping by 20° or 360° at the ends. The foam is preferably a closed cell cross-linked polymer foam, which provides the necessary thermal insulation for cable protection. metal foil parts,
One or more layers of metal foil can be provided in ways other than simply wrapping around the cable multiple times: for example, by folding the foil in half and wrapping the cable in double thickness. For example, the cross-sectional shape is V
A flat insulating layer can be obtained.
Alternatively, the foil member may itself be twice as thick and form a closed bag that encloses air, other insulating solids, or a fluid such as water. These items may be used in addition to or in place of the foamed thermal barrier layer.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a roll of adhesive-coated aluminum foil used in the present invention; FIG. 2 is a perspective view of the adhesive-coated foil in more detail; FIG. 3 is a perspective view of a roll of adhesive-coated aluminum foil; FIG. 4 is a cross-sectional view of the device of FIG. 3; FIG. Figures 6a and 6b are perspective views showing the heat-sealing adhesive and mastic disposed at separate locations on the foil, and Figure 7 is a foil member coated with a thermochromic indicator. FIG. 8 is a perspective view of the foil member of FIG. 7 assembled in a sleeve; FIG. 9 is a perspective view of a foil assembly similar to FIGS. 7 and 8; FIG. 10 8 is a side view of a device similar to FIG. 8, FIG. 11 is a plan view of the foil member of the present invention, FIG. 12 is a partial sectional view of FIG. 11, and FIG.
15 and 14 are cross-sectional views showing still other embodiments of the foil member, FIG. 15 is a perspective view showing a ribbed tube functioning as a thermal barrier member, FIG. 16 is a longitudinal cross-sectional view of the thermal barrier tube, and FIG. Fig. 17 is an explanatory perspective view showing how the foam sheet is used as a thermal barrier member, Fig. 18 is a plan view showing a modification of Fig. 17, and Fig. 19 is a side view of Fig. 18. . 1...metal sheet, 2...thermal adhesive,
3... Polyethylene coating, 4... Pressure sensitive adhesive, 5... Mastic, 6... Sleeve, 7...
Cable, 8... Cable, 9... Branch clip, 12... Hole, 13... Foam, 20... Coating made of thermochromic indicator composition, 30... Sleeve,
31... Blocked rail, 32... Blocked channel,
33... Cable, 40... Foil member, 44... Opening, 48... Heat-fusible adhesive, 50... Pressure-sensitive heat-fusible adhesive, 52... Release paper, 6
0... Aluminum sheet, 64, 65... Continuous film, 66... Discontinuous portion of pressure sensitive adhesive.

Claims (1)

[Claims] 1. By thermally restoring a sleeve surrounding the cable, the cable is extended from the end of the sleeve, and one or more cables or each cable is surrounded with metal foil. A method of manufacturing cable connections, branches or terminations, wherein the metal foil (i) substantially eliminates radial distortion or irregularities in the cable portion surrounded by the metal foil during thermal recovery of the sleeve; (ii) covered with a heat-activated adhesive and covered with a pressure-sensitive adhesive or mastic at least on the surface facing the cable portion; and (iii) beyond the end of the sleeve. 1. A method of manufacturing a cable connection part, branch part or terminal part, characterized in that the cable connection part, branch part or terminal part extends into the cable. 2. The method of claim 1, comprising at least two cable sections, one of which has a diameter substantially smaller than the diameter of the other cable section. 3. The method of claim 2, wherein the metal foil surrounds the small diameter cable section. 4. A method according to any preceding claim, wherein the heat-activatable adhesive is arranged at appropriate intervals in the circumferential direction of the cable to facilitate the provision of metal foil around the cable portion. 5. The method according to any of the preceding claims, wherein the metal foil comprises aluminum foil. 6. A method according to any preceding claim, wherein the metal foil is 150 microns to 250 microns thick. 7. The heat-activatable adhesive is provided in a heat-recoverable sleeve, and the metal foil is provided with holes through which the adhesive flows for fixing the metal foil to the cable section. The method described in section. 8. A method according to any preceding claim, wherein a heat-activatable adhesive is applied to a metal foil surface and a pressure sensitive adhesive is applied to another metal foil surface. 9. The method according to any of the preceding claims, wherein the metal foil includes a metal foil and a heat insulating material.