DE2954256C2 - Method for forming a sealed connection between a heat-shrunk sleeve and at least two elongated substrates entering the sleeve from the same end - Google Patents

Description

The invention relates to a method for forming a sealed connection between a heat-shrinkable sleeve and at least two elongate substrates entering the sleeve from the same end, such as service lines, in which parts of the sleeve end between the substrates engage parts of the outer surface of the substrates, forming individual channels for each substrate at the end of a heat-shrinkable sleeve, in which at least one clamp is applied to the sleeve end prior to shrink heating and in which the sleeve end is heated with the clamp applied.

Heat-recoverable articles, particularly heat-shrinkable articles, are widely used in many fields where insulation, sealing and encapsulation are required. Typically, such articles return to the original shape from which they were previously deformed when heated. However, the term "heat-recoverable" or "heat-recoverable" as used in the specification includes an article which, when heated, assumes a new different shape even if it has previously been deformed.

In their most common form, such articles comprise a heat-shrinkable sleeve made of a polymeric material having elastic or plastic memory properties, as described, for example, in U.S. Patent Nos. 2,027,962, 3,086,242, and 3,957,372. As can be seen, for example, in U.S. Patent No. 2,027,962, the original dimensionally heat-stable shape may be a transition shape in a continuous process in which, for example, an extruded length of tubing is stretched while hot to a dimensionally heat-unstable shape. In other applications, a preformed dimensionally heat-stable article is deformed to a dimensionally heat-unstable shape in a separate step.

In other articles, such as those described in GB-PS 14 40 524, an elastomeric element, such as an outer tube, is held in the stretched or extended state by a second element, such as an inner tube, which yields when heated so that the elastomeric element can recover.

Heat-shrinkable sleeves or sleeves have a wide range of uses, particularly in the manufacture of joints and connections of wires, cables and pipes or piping. In other applications, however, it is desirable to have a connection, insulation or a heat-recoverable element that serves as protection for elongated objects, such as cables and pipes, whose ends are not accessible, or if their ends are accessible, that they should not be separated from one another or moved in any way. So-called "wrap-around sleeves or wrap-around sleeves" have been developed for such applications.

In particular, these comprise heat-recoverable sheets which can be wrapped around the substrate to form a substantially tubular shape and which generally include fastening means which secure the sheets in their wrapped shape during recovery. Typically, such fastening means are mechanically designed and comprise, for example, rigid clips, pins or channel-shaped elements which cooperate with suitably shaped or extruded protrusions which are provided near the overlapping edges of the heat-recoverable Various types of fastening devices are described, for example, in US Pat. No. 3,379,218 and GB Patent Specifications 1,155,470 , 1,211,988 and 1,346,479. In other applications, however, the sheet material may be held in its wrapped configuration during recovery by means of an adhesive which in some cases may be applied directly in situ.

Heat-recoverable sleeves and turn-over sleeves have been used successfully in a wide variety of fields. However, difficulties can arise when two or more substrates, such as supply lines, particularly cables or pipes, have to be sealed at one point. This difficulty, known as "branching", can occur, for example, at the outlet of a heat-recoverable part. Among other things, this difficulty occurs in particular at the outlet points of splice boxes described in GB-PS 14 31 167, as well as in the feedthrough devices according to GB-PS 12 45 119 and the line seals according to DE-OS 27 48 894.

Tubular sleeves have used molded, heat-shrinkable parts with preformed outlets for the individual supply lines. However, these molded and cast parts are generally only intended for specific applications. Their versatility has been further improved by using end caps which seal the outlets but which are not always required, such as in the embodiments according to DE-OS 27 48 383. Despite this, they are expensive and in many cases their use is not economically viable.

Another less expensive method commonly used is to use a mastic tape to seal the gap between the service lines so tightly that when the heat-recovering part recovers, a seal is formed at the end of the heat-recovering part. However, the use of such a tape is based on experience during installation and is not suitable for large-sized parts. In addition, the mastic can affect the overall appearance and performance of products that have an inner layer or coating of a hot-melt adhesive.

DE-OS 24 13 623 already describes a method for sealing at the input side of at least two cables that enter a sleeve housing in parallel against the sleeve housing. In this method, X-shaped spacers are arranged at the end areas of the shrinkable sleeve between adjacent cables in such a way that the cables and the spacers form wave-shaped surfaces. After the end area of the sleeve has been shrunk on, clamp-like clamping pieces are arranged in the wave troughs formed by the spacers in order to prevent the shrunk-on plastic hose from later bursting open when the sleeve is subjected to greater mechanical stress. Such a seal is structurally complex because not only are spacers required, but these spacers are shaped differently depending on the substrate. In addition, the production of such a seal is complex because after the cable has been inserted into the shrink sleeve, the spacers must first be inserted and then, in order to achieve a perfect seal after the ends of the shrink sleeve have been shrunk onto the cable and spacer, a tool is used that is equipped with clamping jaws that move against each other and are positioned and tightened in such a way that the plastic hose encloses the wave-shaped surfaces of the cable and the spacers arranged between them so tightly that the shrunk plastic hose becomes a molded part. After cooling, this tool is removed and a U-shaped clamping piece is clamped onto the area of the wave troughs.

From DE-OS 25 43 338 a method of the type mentioned above is known in which the sleeve of a clamp is applied and the sleeve and clamp are heated together during heat shrinking.

The invention is based on the surprising discovery that an effective branch can be obtained at the end of a heat-recoverable part by providing individual outlets by means of suitably designed clamps made of a relatively rigid material.

The object of the invention is to further develop a method of the type mentioned at the outset in such a way that a simple, easy-to-handle method is provided for forming a tight connection, i.e. a seal between a heat-shrinkable sleeve and at least two elongated substrates in the entry region of the substrates into the sleeve.

This object is achieved according to the invention in that the channels in the sleeve end are formed by the clamp and that the clamp has at least two legs, at least one of which lies within the sleeve.

Attaching the clamp to the end of the sleeve and inserting the substrates into the sleeve can be done in any order or at the same time. For example, in many applications the clamp is pushed into its final position after the sleeve has been placed around the substrates.

In one embodiment of the invention, the clamp is U-shaped and the two legs slide over the surface of the heat-recoverable sleeve or turn-up sleeve and another cooperating surface (which may itself form part of a heat-recoverable component) so that channel-shaped guides are formed at one end of the sleeve.

It is surprising that such a clamp does not unlatch or pop off during recovery (this effect during thermal recovery is called "milk-off"). Of course, the clamp must be sufficiently long, especially when the substrates are large. The most suitable length can be quickly determined by simple experiments. The resistance to unlatching can be improved if necessary by making the outer surfaces on the legs of the clamp sawtooth or sinusoidal. However, this is generally not necessary.

Another way to prevent the clip from coming off is to apply heat to the clip and the heat-recoverable material in its vicinity before the final recovery is effected. This local heating causes a local increase in the strength of the heat-recoverable material and increases the gripping effect of the clip. If, in preferred embodiments, the sleeve or the turn-up sleeve is additionally provided with an inner layer of an adhesive, the adhesive becomes flowable and thus ensures a satisfactory adhesive bond in the vicinity of the clamp prior to recovery around the substrates. Such local heating can be conveniently carried out in all embodiments of the clamp according to the invention.

In a further preferred embodiment of the invention, which will be described in more detail below, the clamp itself is designed in such a way that the difficulties associated with unlatching or jumping off are eliminated. For this purpose, the clamp can be adjustable so that it can be adapted to the requirements of the respective situation at any time.

The clamp provided according to the invention advantageously consists of a heat-conducting material and/or is designed in such a way that the application of heat to the heat-recoverable material in the vicinity of the clamp is facilitated (see DE-OS 27 56 021). On the other hand, however, the heat-recoverable sleeve can be provided with internal or independent heating devices, in which case the clamp can consist of a non-heat-conducting material.

For these and other reasons, the clamp is conveniently made of a metal including, for example, steel, copper, brass, beryllium copper and, in particular, aluminum. An aluminum clamp may, for example, be formed by injection molding, followed by deburring to remove sharp edges. A steel chamber may be made by stamping, followed by deburring if necessary. In many applications it is desirable to protect the clamp against corrosion. An aluminum clamp, for example, is subjected to a black anodizing treatment or is provided with a chromate layer which may be further protected against mechanical damage, for example by an epoxy resin coating. Such a coating also enables electrical insulation, for example when two lead-sheathed cables are used.

The task of the clamp in the heat transfer to and from the heat-recoverable material and the adhesive in the environment has not yet been recognized. According to BE-PS 8 33 016, a clamp can be made of metal, for example. However, other, non-heat-conductive materials, such as plastics, are also specified, but these are not suitable for the present invention. Polyamide with glass filler is specified as the preferred material. The material of the clamp is not specified in DE-OS 24 13 623.

In certain applications, the metal of the clip may be a memory alloy, such as one of the nickel-titanium alloys described in U.S. Patents 3,174,851, 3,351,463, 3753,700 and 3759,552, or a β- brass alloy as described in U.S. Patents 3,783,037 and 4,019,925. The clip itself is heat-recoverable so that the legs of the clip can move toward each other when the assembly is heated to cause the sleeve to shrink (alternatively, the clip can be heat-recovered before or after final heating). Pretreated memory alloys, particularly β- brass alloys, are preferably used in the clip of the invention. Such alloys and processes for their pretreatment are described in US patents 40 36 669, 40 67 752 and 40 95 999.

In other embodiments, the clamp may be made of a resilient material such as spring steel or beryllium copper so that it has a resilience that assists in the formation of a tight seal. The resiliently deformed outer legs may be held on the outside, for example with the aid of a hot-melt adhesive, so that they move towards one another when heated.

Although the simplest embodiment of the clamp according to the invention is essentially U-shaped, it should be noted that the shape and design of the clamp will depend on the application. For example, in some applications it may be necessary to form more than two outlets at the end of the heat-recoverable component. This can be achieved by means of two or more U-shaped clamps between the outlets, or a single clamp may conveniently be used. Such a clamp has three or more legs, so that any two adjacent legs or arms function in the form of a U-shaped clamp.

According to a preferred embodiment of the invention, the clamp is designed with three prongs, and the middle leg of this clamp goes into the heat-recoverable sleeve, while at least one of the outer legs goes over the outside of the latter. In this case, a layer of heat-recoverable material is clamped between the middle and the outer leg. In such a clamp, the inner surfaces of the outer legs are expediently tapered inwards, so that the space or gap between the outer legs is larger at the open end of the clamp than at the base. The surfaces of the middle leg are also expediently tapered in such a way that they run essentially parallel to the inner surfaces of the outer legs. Such a design makes it easier to attach the clamp to the sleeve, especially in the case of sleeves with large diameters. Once the clamp is attached to the heat-recoverable sleeve, it is practically impossible for it to give way or soften, especially after recovery. It should be noted that in such a clamp the inner surface of the heat-recoverable sleeve does not come into contact with the surroundings of the clamp and that the central leg of the clamp serves to separate the two channel-shaped strands formed from each other. For this reason, the central leg is expediently provided on each side with a layer of a hot-melt adhesive or other heat-active sealant which becomes flowable during recovery in order to seal the gap between the lines or channel-shaped strands. This ensures that the substrates in the channel-shaped strands cannot come into contact with each other.

The sides of the middle leg are therefore suitably roughened or contoured to facilitate adhesion and also to ensure that the adhesive remains in the gripping area of the clamp when heated. An advantageous embodiment of the clamp according to the invention has a waffle-shaped pattern on the surfaces of the middle leg.

The outer legs of the staple are conveniently provided with a thermochromic indicator. The reason for this is that when the staple is heated, a temperature difference of up to 20°C can occur between the outer legs and the middle leg. The use of a thermochromic indicator (such as a melt of white polypropylene powder in a suitable binder) ensures that sufficient heat is applied so that the hot-melt adhesive on the middle leg becomes meltable and flowable.

The clamp can of course also be provided with other indicating devices which indicate that the desired temperature has been reached. For example, a resilient element, such as a spring, in an indicator element attached thereto can be held in a preloaded position by the hot melt adhesive in such a way that it resets the spring when the adhesive melts. Thus, the indicator element moves and indicates that the desired temperature has been reached.

In a similar manner, the clamp may also be provided with a means for indicating that the pressure seal is effective and secure. In a preferred embodiment of the invention, a means is provided for indicating both the desired temperature to be achieved and the pressure so that no leaks are present in the seal at the outlet or outlets of, for example, a pressurized splice housing. For this purpose, an indicator element can be held in a fixed position by means of a hot-melt adhesive. The indicator element can, however, move if the adhesive is melted by the pressure built up inside the tight connection. If the indicator element does not move, either the adhesive has not been melted, i.e. the required temperature has not been reached, or the pressure has not reached the predetermined pressure value, so that a leak has formed in the seal on reset. In the simplest embodiment of this type, the hot melt adhesive (or other hot melt material) itself acts as an indicator by ejecting from the clamp as pressure builds up inside the joint.

In certain applications, in particular when forming branches on splice boxes under pressure and/or for cables with a diameter of 30 mm and more, e.g. from 35 to 80 mm, it is expedient for the inner edges of both outer legs and the edges of the middle leg to be mutually parallel.

In most applications, however, the inner edges of the outer legs and the edges of the middle leg taper inward toward the closed base of the clip. Such a clip has several advantages. Mainly, the tapered inner edges of the outer legs and the edges of the middle leg form two inclined channels so that the clip is positively locked in position when it is pushed onto the sleeve. It should be noted again in this context that the heat-recoverable material thickens as it shrinks, thus bringing the clip closer to the sleeve. A further advantage is that by choosing the angle formed by the outer legs and the maximum width of the middle leg, it is possible to design the clip to conform to the substrates. In this context, it may be expedient for the middle leg to be longer than the outer leg. In this way, the required seal between the branch lines is assisted in its formation.

According to other embodiments where the clip can deform to conform to the substrates and, for example, avoid the risk of adhesive failure, concave outer surfaces are provided on the central leg of the clip to accommodate small sized cables (such as from about 8 mm to 35 mm in diameter) and a central leg can be formed with a reduced thickness at least along part of its length to accommodate large sized cables (such as with a diameter greater than about 30 mm, in particular between 35 and 80 mm).

When the hot-melt adhesive is fluid and fills the gap between the wires, the clamp cannot be removed without detaching the sleeve from the substrates. This eliminates the risk of the clamp slipping off and damaging the branch distribution by detachment.

The three-pronged clamp can be modified to create branches with multiple outlets in the same way as the basic U-shaped clamp. In many cases it is sufficient to design a clamp so that it can be created in the direction of the lines to be provided. In clamps for multiple outlets the central leg is conveniently solid or hollow in the form of a tapered element that works together with several outer legs. In a similar way to the U-shaped clamp, the bottom of the gaps in the three-pronged clamp can be cut out to give the clamp additional rigidity and strength. The thickness of the adhesive coating must be selected so that there is sufficient material to fill the gaps when the clamp is returned. The thickness or strength of the hot-melt adhesive on each side of the central leg is between 2 and 5 mm. If necessary, the thickness of this layer can be varied along the length of the leg, being thicker at the open end of the clip than at the base. As previously mentioned, the outer surface of the central leg is conveniently roughened or wavy or waffled to enable the adhesive to adhere firmly and also to ensure that on recovery it is not forced away from the central leg but rather pressed into the surface irregularities. In these and other embodiments of the invention, it is convenient to pigment the hot melt adhesive so that its diffusion into and coalescence in the clear hot melt lining of the sleeve can be detected to indicate that sufficient heat has been applied.

Another alternative embodiment involves the application of the layer of hot melt adhesive to the center leg. For example, one or more upper and/or lower longitudinal ribs are provided along at least part of the length of the center leg to increase the initial sliding fit force of the clip onto the sleeve and to facilitate secure attachment of the clip to relatively thin, stretched and coated sleeves.

The strength of the clips provided in accordance with the invention is enhanced by the fact that they are made from a flat base material, which means that the width of the legs extending above and below the heat-recoverable sleeve is greater than their thickness which comes into contact with the sleeve. Suitably the width is 1.5 to 3 times the thickness.

According to preferred embodiments of the invention, one or more legs of the clamp, in particular the middle leg of the clamp, can be used to achieve the second purpose. For example, the middle leg can be hollow and form an inlet or outlet for compressed air, jelly, epoxy resins or foaming materials, etc., as is necessary in pressurized splice enclosures. The leg can of course be provided with a valve for this purpose. In some applications, the leg itself can act as a substrate. For example, a branch can be formed from a single cable using a clamp, in particular to provide an inlet valve.

In other embodiments, the clamp may be provided with a device to ensure a uniform passage of current, for example between shielded cables arranged within the channel-shaped strands. For this purpose, for example, jaws or similar elements can be provided on one or more legs of the clamp, which receive and grip loose ends which are cut from the shielding of the cables or which are attached to them.

Although it is not generally contemplated that the clamps will be used in conjunction with other elements, in some applications it may be convenient to provide an insert element cooperating with the clamp and/or to use the method of the invention in conjunction with other techniques including that using a mastic tape. It may also be advantageous to use the clamp to join a heat-recoverable sheet to another component. For example, multiple clamps may be used to form branches around a junction box or to form multiple branches from a single splice housing using another heat-recoverable component such as a closure cap inserted into the heat-shrinkable sleeve. Such embodiments are described in more detail below.

The heat-recoverable sleeve may be a turn-up sleeve and/or have a closed end, i.e. it may form an end cap. The sleeve may also be part of a larger object, such as a larger heat-recoverable object. The invention is in no way limited to the dimensions or shape of the heat-recoverable component. The heat-recoverable sleeve may, for example, be formed from two (or more) sheets of heat-recoverable material. The only requirement of the invention is that the heat-shrinkable component has a high connection section into which substrates are placed.

When the clamps are used in conjunction with a wrap-around sleeve, the clamp can conveniently be designed to cooperate with a fastening device of a wrapping device. The clamp itself can even form part of this fastening device.

Although the clamp is held in place by the heat-recoverable sleeve, the clamp may conveniently be designed to be adjustable so that the gap between the legs can vary according to the thickness of the sleeve. This facilitates the formation of a secure gripping connection upon recovery. It may also be convenient to provide the clamp with one or more elements that cooperate with substrates located outside the heat-recoverable sleeve to thereby facilitate correct positioning of the clamp. For example, a clamp may be provided with a ring element that can surround a pressure transducer located outside a heat-shrinkable splice housing of the connection. According to another embodiment, the clamp may be provided with metal tabs that can be secured around high-performance cables at the end face of a connection to thereby provide stress relief of the connection.

The heat-recoverable material may be made from any polymeric material suitable for use in the manufacture of heat-recoverable articles. In general, the sheet material has a homogeneous and consistent composition overall, but layered materials made from two different polymers bonded together adhesively or by melting may also be used. Suitable polymers include, for example, polyolefins, particularly polyethylene, copolymers of ethylene and vinyl acetate, copolymers of ethylene and ethyl acrylate, chlorinated and fluorinated polymers, particularly polyvinyl chloride, polyvinylidene fluoride and polymers containing units of vinylidene fluoride, hexafluoroethylene and chlorotrifluoroethylene, and rubbers such as ethylene/propylene rubber, chlorinated rubbers such as neoprene, and silicone rubbers which may be used in the form of a mixture with a crystalline or glassy polymer such as an olefin polymer. All of the substances described above may be cross-linked, for example by irradiation and/or chemical substances or chemical treatment.

As previously mentioned, the inner surface of the heat-recoverable component is generally provided with a coating of an adhesive or sealant, such as a hot-melt adhesive or a mastic. Suitable hot-melt adhesives include polyamides, ethylene/vinyl acetate copolymers and terpolymers (with or without incorporated waxes) and polyesters. Such materials are described, for example, in GB-PS 14 40 810 and DE-OS 27 09 717. Also suitable are hardenable elements which melt and become flowable when heated, but which are then no longer hot-meltable. In this context, epoxy resins and conventional mastics should be mentioned in particular, which are based, for example, on butyl and isobutylene rubber modified with corresponding, known substances. The use and selection of materials naturally depends on the specific requirements of the respective application.

In most applications, the force acting on the clamp is within a range of 49.05 N to 147.15 N ( 5 to 15 kp), depending on the diameter of the substrate, the wall thickness and the amount of unused recovery of the sleeve. In connection with the last described dependency, it should be noted that the heat-recoverable sleeve does not have to shrink as much as in the mastic tape method and thus has a smaller expansion ratio because the clamp compresses the sleeve to make it conform to the cables in the central region. In the mastic tape method, the sleeve does not come into contact with the cables in this region. Of course, the amount of expansion in a sleeve is smaller when a three-pronged clamp is used than when only a simple U-shaped clamp is used.

The invention provides a simple method of forming a satisfactory junction, thus eliminating the need for skill in installation and reducing costs. The elongated legs of the clamp ensure that a seal is formed from the edge of the heat-recoverable material to the ends of the legs, effectively separating the substrates in that region.

The invention is explained in more detail below with reference to the drawings, which show

Fig. 1 a preferred embodiment of a trident clamp,

Fig. 2 the application of the trident clamp in the formation of a branch,

Fig. 3a and 3b show a modified embodiment of a three-pronged clamp intended to form a three-way branch,

Fig. 4 a design for forming an asymmetric branch,

Fig. 5 a clamp for forming a four-way branch,

Fig. 6 a clamp to form an eight-way branch,

Fig. 7a and 7b a clamp designed to form a three-way branch,

Fig. 8a and 8b a clamp that can be used as an inlet valve,

Fig. 9a and 9b the application of a clamp to form a branch for an inlet or outlet valve,

Fig. 10a and 10b a preferred embodiment of a trident clamp,

Fig. 11a to 11e the application of another embodiment of the clamp in conjunction with a heat-recoverable sleeve and a distribution box to form a connection with multiple outlets,

Fig. 12a to 12c show a modified embodiment of a connection with several connections,

Fig. 13 a clamp with a temperature display device,

Fig. 14a to 14c a clamp with a combined pressure and temperature display device,

Fig. 15a to 15c the application of a clamp with a device that evens out the current passage,

Fig. 16a and 16b a clamp intended for use in conjunction with a pressure sensor,

Fig. 17a and 17b a clamp that allows stress relief of a formed connection,

Fig. 18a and 18b a self-adjusting clamp,

Fig. 19 shows another embodiment of a clamp intended for connection to a pressurized feed housing,

Fig. 20a and 20b a clamp designed for small diameter cables, and

Fig. 21a to 21c a clamp for cables with large diameters.

In Fig. 1 a trident clamp 31 is shown. The inner surfaces of the outer legs 32 and 33 and the surfaces of the middle leg 34 are tapered including an angle α . The surfaces of the outer legs and the middle leg are substantially parallel to form two oblique passages 35 and 36 , each of which is recessed at the base to increase rigidity in order to achieve stress distribution.

The central leg 34 is provided on one side with a hot-melt coating 37 , and the outer surfaces of the outer legs are provided with a coating 38 of a thermochromic display device.

Such a staple preferably has the following dimensions: thickness 5 mm, width of the middle leg 11 mm, decreasing to 5.5 mm, gap or space between the legs 1 to 2 mm depending on the wall thickness of the casing material.

In Fig. 2, the clamp 31 is shown in connection with a heat-shrinkable sleeve 39 , forming two branching strands 40 and 41. In the retracted position, the center leg 34 forms a separation insulation between the strands.

Fig. 3a and 3b show a modified embodiment of a three-pronged clamp 42 intended to form a three-way branch. The middle leg 43 is designed such that it forms part of a Y-shaped cross section.

Fig. 4, 5 and 6 show various brackets 44 , 45 and 46 intended to form other branches with multiple outlets.

Fig. 7a and 7b show an adjustable clamp for a three-way branch. In this clamp, two of the outer legs 47 and 48 are pivotally attached to an extended part of the inner leg 49 , and the outer leg 50 is fixedly connected to the inner leg 49. Such a clamp can be adapted to the requirements when creating a branch and adjusted accordingly.

In Fig. 8a the application of a trident clamp 51 is shown, which is intended to form an inlet for compressed air within a cable splice 52. In this embodiment, in particular according to Fig. 8b, the middle leg 53 of the trident clamp 51 is hollow and provided with a valve 54 and an inlet channel 55. The middle leg 53 of the clamp 51 serves as a substrate in the branch from the cable 56 .

In Fig. 9a is shown the manner in which two trident clamps 57 and 58 can be used in conjunction with a wraparound feed 59 to form a branching inlet and outlet at the ends. Here, the inlet and outlet are provided with separate devices 60 and 61 (see Fig. 9b) which form the substrates in the branch from the cables 62 and 63 respectively.

Figures 10a and 10b show a further embodiment of a trident clamp 64 according to the invention. The clamp 64 expediently has the feature that the central leg 65 extends beyond the ends of the outer legs 66 and 67 , and that the side surfaces of the central leg 65 have a waffle-shaped pattern which is suitable as a base for an adhesive.

Finally, Figs. 11a to 11b show the manner in which the clamp can be used to form branch outlets from a heat-shrinkable sleeve or sleeve in conjunction with other components interacting with them.

In Fig. 11a, a distribution box 63 is shown, which is provided on its outer surfaces with hot-melt adhesive 69. The distribution box is designed in such a way that it distributes the individual wires from a large supply cable in pairs to several outgoing smaller cables.

The adhesive covers 69 are pre-cut so that the strips can be removed which are slightly wider than the thickness of the clips 70 (see Fig. 11b). The box 68 is then placed in a large diameter heat-recoverable sleeve 71 and the outgoing cables 72 are distributed around the surface of the distribution box 68. As can be seen in Figs. 11c and 11d, the clips 70 are then placed between the cables 72 , over the outer surface of the heat-recoverable sleeve 71 and the inner surface of the distribution box 68. The assembly thus formed can then be heated to recover the sleeve 71 and to cause the adhesive 69 to flow, thus providing the finished distribution box shown in Fig. 11e. As shown, some of the branches can be fitted with devices 73 which are provided with closure caps 74 and can be fitted at a later date.

The distribution box 68 is conveniently made of a durable, thermally conductive metal and may have recesses on its inner surface which serve to facilitate the placement of the clamps. The heat-recoverable sleeve 71 can of course be designed as a wrap-around sleeve and be provided with a coating on its inside which reduces the penetration of water vapor. The other end of the sleeve is shrunk around the large supply cable 75 .

The box 68 can have different shapes, for example circular, elliptical, star-shaped and the like. Differently designed brackets 70 can be used here.

A similar arrangement comprising a plurality of outlet branches is shown in Figures 12a to 12c and is intended for use in connection with a pressurized splice enclosure. As shown in Figure 12a, the splice enclosure 80 , which may consist of two metal shell halves, is protected and insulated by a heat shrink wrap sleeve 81 provided with a conventional fastening device 82. The supply cable 83 is spliced to form four outgoing cables 84. A tight termination is formed at the inlet using a trident clamp 85 having a channel for a pressure valve 86. The seal at the inlet is formed as previously described. At the outlet there is provided a heat shrink closure cap 87 having a coating of hot melt adhesive on its outer surface. As shown, the closure cap is provided with four trident clamps 88 according to the invention. The end cap 87 and clips 88 cooperate with the outlet end of the heat-shrinkable sleeve 81 and the assembly is shown in its pre-recovered condition in Fig. 12b. From this finger it can be seen that the end cap, sleeves and clips form four strands or channels for outgoing cables 84 therebetween. When the assembly of Fig. 12b is assembled, the heat-recoverable sleeve is shrunk using a conventional welding torch and the heat-shrinkable end cap 87 is conveniently shrunk by means of a device referred to as a "heat pack", ie a pyrotechnic heating device which has been previously fitted. The recovered assembly is shown in Fig. 12c. Such a design is particularly useful in forming multi-outlet branches from pressurized splice enclosures where the expansion ratio of the heat-recoverable sleeve should be as low as possible, conveniently about one third, in order to maintain maximum sleeve wall thickness and to keep the unnecessary positions as minimal as possible. This avoids breakage of the sleeve under pressure.

In Fig. 13 there is shown a trident clamp, the central leg 91 of which is provided with a temperature indicating device comprising a rod-shaped indicating element 92 disposed within the leg 91 and comprising a loading spring 93 , held in a compressed condition within the chamber 94 by being embedded in a heat-fusible material (not shown). When the desired temperature is reached, the heat-fusible material melts and the spring 91 resiliently recovers to move the rod-shaped indicating element 92 to the position shown in broken line. This indicates that the desired temperature has been reached.

Fig. 14a to 14c show a clamp 100 provided with a device indicating both the desired temperature and the desired pressure to be maintained within the heat-shrinkable sleeve 101. As shown in Fig. 14b, the central leg 102 of the clamp 100 is provided with a chamber 103 in which a ball valve 104 is arranged. Also arranged within the chamber 103 and in a channel 105 is a heat-melting material 106 which connects the chamber to the closed end 100 .

The mounting of the clamp 100 within a pressurized splice housing at a joint 107 is shown in Fig. 14c. When the desired temperature is reached, the hot melt material 106 melts and the pressure in the joint 107 acts on the ball valve 104 such that that it moves along the chamber 103 when a direct seal has been achieved. This forces a volume of the melted hot melt material out of the end of the clamp, the volume thus forced out being approximately equal to the original volume of the chamber 103. The operator is thus assured that not only has he achieved the desired and correct temperature in making the joint, but also that there is no leakage at the seal formed at the joint.

Fig. 15a to 15c show a three-pronged clamp 110 , the central leg of which is provided on each side with jaw-shaped elements 111. These are designed to receive and grip strips 112 cut out of an aluminum shielding foil for telecommunication cables 113 (see Fig. 15c). This creates a uniform electrical continuity between the cables 113 and an electrical connecting line 114 which is attached to the central leg of the clamp 110 .

In Figs. 16a and 16b there is shown another embodiment of a clamp 116 and its application to form a connection at the end of a pressurized splice housing provided with a pressure transducer. As shown, the clamp 116 is provided with an adjusting ring 117 which is designed to fit into the container 118 of the pressure transducer. If required, the ring 117 can be designed as a closure cap of the container 118 .

In Figs. 17a and 17b there is shown a three-pronged clamp 120 provided with pieces of material 121 and 122 which are designed to be secured around cables 123 and 124 at the point where the cables exit a splice 125. Such a design not only serves to achieve exact placement of the cables and clamp at the splice, but also provides stress relief for the device. At the same time it is ensured that if the cables move outside the splice, no damage to the splice will occur. This design is particularly intended for high power cables or utility lines or the like.

18a and 18b, a clamp 130 is shown which is designed to be self-adjusting so that it can change the gaps between the central leg 131 and the outer legs 132 and 133 in accordance with the thickness of the heat-recoverable sleeve. To this end, the central leg 131 is composed of two parts, a U-shaped member 135 which is slidably mounted on a central member 136 and is normally held in the extended position against the force of a tension spring 137. The entire assembly is embedded in a hot melt adhesive 138 to prevent recovery of the tension spring. When the clamp 130 is heated, the hot melt adhesive 138 melts and the tension spring recovers so that the U-shaped member 135 is moved along the central member 136 towards the base of the clamp as shown in broken lines. This reduces the space between the legs, ensuring that the heat-recoverable sleeve material contained therein is firmly gripped.

In Fig. 19, another embodiment of the clamp 140 is shown which is intended for pressurized splice enclosures. As shown, this clamp 140 has three equal length legs which are generally longer than the clamp. In addition, the width of the center leg 141 is constant throughout its length and as small as possible, such as about 5 mm, to assist in forming a good seal between the heat-recoverable sleeve and the cables in the vicinity of the clamp. Both sides of the center leg 141 are provided with a layer of a hot melt adhesive.

Finally, Fig. 20 and 21 show two further embodiments of clamps. The clamp in Fig. 20 is intended for cables having an outer diameter of approximately 8 to 35 mm. As can be seen in particular in Fig. 20, which is a sectional view near the open end of the clamp, the sides of the central leg 151 are concave, which serve to receive the cables. In addition, the upper and lower surfaces of the hot-melt adhesive layer 152 are each provided with two longitudinally extending ribs 153. The formation of these ribs serves to reinforce the sliding fit of the clamp when it is pushed over the sleeve before shrinking.

The clamp shown in Fig. 21 is designed for larger cables having an outside diameter greater than about 30 mm. In this clamp, the center leg 161 decreases in thickness from the closed to the open end of the clamp to accommodate the cables. Again, a hot melt adhesive layer 162 is provided with longitudinal ribs 163 to assist in proper alignment of the clamp prior to recovery. However, in this embodiment, the ribs 163 extend along part of the length of the center leg 161 to allow for easy initial installation of the clamp.

Claims (11)

1. A method of forming a sealed joint between a heat-shrinkable sleeve and at least two elongate substrates entering the sleeve from the same end, in which parts of the sleeve end between the substrates engage parts of the outer surface of the substrates to form individual channels for each substrate at the end of a heat-shrinkable sleeve, in which at least one clamp is applied to the sleeve end prior to shrink heating and in which the sleeve end is heated with the clamp applied, characterized in that the channels in the sleeve end are formed by the clamp and that the clamp has at least two legs, at least one of which lies within the sleeve. 2. Method according to claim 1, characterized in that a turn-up sleeve is used as the heat-shrinkable sleeve. 3. Method according to claim 1 or 2, characterized in that the heat-shrinkable sleeve is provided with an inner coating of a heat-activatable adhesive or sealant. 4. Method according to one of claims 1 to 3, characterized in that the clamp has a temperature indicator for measuring a temperature sufficient for shrinkage. 5. Method according to one of claims 1 to 4, characterized in that a clamp is used in which a part of the clamp forms one of the substrates. 6. Method according to one of claims 1 to 5, characterized in that after application of the clamp, the sleeve is heated in the vicinity of the clamp. 7. Method according to one of claims 1 to 6, characterized in that a clamp is used to form three or more channel-shaped connecting strands. 8. Method according to one of claims 1 to 7, characterized in that two or more clamps are used to form a branch with several outlets. 9. Method according to one of claims 1 to 8, characterized in that a clamp made of a thermally conductive material, preferably aluminum, steel or beryllium copper, is used as the clamp. 10. Method according to one of claims 1 to 9, characterized in that a clamp is used as the clamp in which the clamp leg or legs located inside the heat-shrinkable sleeve is or are at least partially coated with a heat-activatable adhesive or sealant. 11. Method according to one of claims 1 to 10, characterized in that for the purpose of reinforcement or sealing, the clamp legs move towards one another before, during or after the shrinkage of the sleeve.