FI68933C - FOERFARANDE FOER ATT FOERSLUTA EN SKARV MELLAN TVAO ELLER FLERE KABLAR ELLER ROER SAMT VAERMEREGENERERBART FOERSLUTNINGSELEMENT FOER UTFOERANDE AV FOERFARANDET - Google Patents

Description

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(51) Kv.lk//lncCL* H 02 G 15/18 SUOMI FINLAND (21) Patent application - Patentansöknlng 79 29 ** 6 (22) Application date - Ansöknlngsdag 21.09.79

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'* (23) Start date— Giltighetsdag 23.09.75 (41) Has become public - Blivit offentlig 21 09 79

National Board of Patents and Registration of Finland Date of display and publication - 07 8ζ

Patent- oeh registerstyrelsen '' Ansökan utlagd och utl.skrlften publicerad -5 · '· ° 5 (32) (33) (31) Privilege claimed— Begärd prloritet 27.09.7 ** 04.08.75 USA (US) 509837, 601344 ( 71) Raychem Corporation, 300 Constitution Drive, Menlo Park, California 94025, USA (72) David August Horsma, Palo Alto, California, Stephen Hunter Diaz, Los Altos, California, USA (7 **) Berggren Oy Ab (54) Method for sealing a joint between two or more cables or pipes and a heat-recoverable element for carrying out the method This invention relates to a method according to the preamble of claim 1 for sealing a connection between two or more cables or pipes by means of a heat-recoverable closure element.

There are many applications in which it is desirable to provide a sealing, insulating or protective encapsulation or sealing body for long objects such as cables or pipes. Such encapsulation is particularly important when connecting or extending pipes or cables, especially in the case of a connection involving several pipes or cables. In many cases, the ends of long objects (hereinafter referred to as cables, although the invention is naturally useful for sealing or encapsulating long substrates of pipes, cables, wires, ducts, etc., especially between them) generally do not readily allow a tubular sealing body to be placed around it. To overcome this disadvantage, closures have been developed which are suitable for wrapping around long objects. See, e.g., U.S. Patents 3,379,218, 3 ** 55,336, or 3,770,556. These so-called "wrap-around" 2,68933 closures can be placed around a long body without access to its free end. Nevertheless, there is a significant need for a splice, hereinafter referred to as a "splice sleeve", suitable for closing electrical cable joints or splices and providing effective environmental protection, especially for splices with more than two incoming cable ends and / or splices between cables of different sizes, but which can be inserted without access to the free end of the cable.

The present invention also relates to a heat-recoverable closure element for applying the method, which in different embodiments can enclose several different sizes, i. cables of different outer diameters, which element can be removed and, in some embodiments, re-applied over the splice and which does not require access to the free end of the cable. The structure in question is not called "wrap-around" because it encapsulates the splice somewhat differently from the "wrap-around" shells mentioned above. In alternative embodiments, the closure element of the present invention uses either a "shell shell" or a structure formed by a separate base plate and capsule body.

The method according to the invention is characterized by what appears from the appended claim 1. The closing element required to carry out the method is characterized by what appears from the appended claim 3. The means by which the parts of the closing element are held together may comprise e.g. a press or tensioner which may be flexible.

In one embodiment, the present invention provides a splice sleeve as a closure element that recovers and encapsulates a cable or other splice when exposed to an external heat source, e.g., a propane burner or hot air blower.

Many applications for splice sleeves involve on-site use where the splice is relatively inaccessible or in a potentially hazardous environment and great care must be taken when installing the splice sleeve.

For example, when connecting aerial telephone cables or in mines or other places that may contain flammable gases, the use of an open 3 63933 flame burner for recovery is often not only dangerous but sometimes even prohibited. Under such conditions, the shell to be wrapped around, i.e. an extension sleeve that does not require the use of external heat, especially a flame, would be particularly advantageous.

Therefore, in a preferred embodiment, the extension sleeve of the present invention has a built-in heating device, i. the splice sleeve includes an independent electric resistance heating element which, when combined with a suitable external electrical power supply, is capable of generating sufficient heat to cause the splice sleeve to recover and encapsulate the splice.

This heat-recoverable splice sleeve does not require an external heating source, but can instead be recovered simply by connecting it to an electrical power source, be it a battery or mains power, e.g. 12 or 24 volt battery or 115 volt or other suitable AC power source, and which combined with such a power supply recovers and can also activate the adhesive or sealant on its inner surface.

Arrangements and compositions for providing uniform heating are important in forming materials that include an independent heating element for use in the splice sleeves of this invention. In addition, for applications where the heating element must provide thermal activation of the adhesive or sealant as well as heat recovery of the element, relatively high temperatures in the order of 120-200 ° C must be achieved, but also carefully controlled. If temperatures are reached which are above what is required for heat recovery of the splice sleeve and activation of the adhesive, permanent damage to the sealing element, i.e. to the splice sleeve and / or the piece to be sealed, e.g. the base cable, which damage is often not apparent when the visually restored splice sleeve and the areas of the cable immediately associated with it are visually inspected.

Thermostats and / or other temperature control devices can be used to control the temperature of the recovered and recovered element. But for many applications, this nullifies the idea of using what is inherent in it, i. a self-heating shell system in the sense that expensive, sensitive and / or clumsy external temperature control devices must be used in places that are sometimes in fact inaccessible towers. Moreover, the temperature sensed by the control device is only in its immediate vicinity, while the other areas of the sleeve il 63933 can be at significantly lower or higher temperatures.

In recent years, a new approach in electric heaters has been to use self-regulating heating systems that utilize plastic materials with positive temperature coefficient properties of electric resistance (hereinafter referred to as PTC properties or materials). Such materials generally contain crystalline thermoplastics with a conductive particulate filler.

The disadvantages of prior art PTC materials for articles such as the splice sleeve of this invention can be largely overcome by using structures of the type described in U.S. Patent No. 65,522 (Pat. No. 752667). It should be noted, however, that while prior art PTC materials are not preferred, they are suitable for use in the splice sleeves of this invention under a variety of conditions.

During the use and operation of telephone cables, especially when individual conductors are wrapped with paper-based insulating material, it is required that water be excluded, because if the moisture content of the wire insulation exceeds a relatively low critical level, the electrical properties of the wire become unacceptable. For this reason, when extending cables, it is customary to place a small desiccant (usually silica gel) paper bag with sufficient desiccant in the assembly just prior to sealing to keep the internal moisture of the splice very low throughout the life of the splice, whatever the external moisture. Typically, about 50 g of silica gel may be used. As might be expected, the desiccant is often overlooked or, even if not forgotten, bags (usually tightly closed for storage) are sometimes left unsealed for long periods before being placed in place or, in extreme cases, even dropped into water or moist soil and nevertheless set in place. A preferred embodiment of the present invention provides relief from this problem.

Excessive moisture will lead to an unacceptable decrease in the property level of the paper insulated cable. At 30% relative humidity (R.H.) and 15 ° C, the insulation resistance of paper-insulated stranded wires of the type often used in telephone cables drops to an unacceptable level of 5,68933 at about 0.5 gigaohm / km. At relative humidity below 50%, the properties are acceptable. We’ve found that the moisture inside the splice sleeve doesn’t need to be kept as low as possible, but should simply be kept below $ 30 whenever possible. Unexpected and astonishing advantages are obtained by encapsulating the desiccant in a container whose water vapor permeability properties are carefully matched to the properties of the splice itself so that the relative humidity inside said splice can be kept below 30% under all normally applicable conditions. .

When outside R.H. is 100% and inside 0 JS, if the typical water vapor permeability (MVT) of the splice sleeve of this invention is 100 ug / h at 15 ° C, the MVT value of the desiccant tank must be> 100 ug / h with an RH of 30% or ^ 333 / ug / h with 100% RH. Therefore, if the MVT value of the desiccant tank is 500 μg / h, the requirement is satisfied.

It is assumed that the container draws about 100 g of desiccant, such as silica gel, which is capable of absorbing about 50 g of water. Under storage conditions with a relative humidity of 100 and without other protective layers, the desiccant thus packaged loses half of its absorption capacity in about six years. Thus, this type of container, which is permanently placed inside the splice sleeve, does not suffer a significant loss of power, even if the splice sleeve is removed from its protective wrapper for storage and many months before use.

A particularly useful feature of certain self-heating splice sleeves of this invention is the ability to reopen them. The sleeve can be reopened simply by electrically connecting the installed splice to the power supply, waiting a few minutes for the adhesive to soften, removing the electrical contacts and side and end closures (if left on) and separating the upper and lower splice halves. If desired, after making the necessary modifications to the private splices or replacing any of the components, the entire splice sleeve can be reinstalled 6,68933 as before and a short reconnection time to the electrical power supply will result in re-bonding of the adhesive bonds to a structural integrity. This ease of reopenability means that if not all cable folds are required in the first installation, a plug or plugs adapted to hold the additional folds in a stretched state during the first installation can be used. In a subsequent reopening, new cables can be added at any time and all added components will be sealed as effectively as any of the original components. Reopening of non-self-heating splices can also be performed using an external heat source to melt the adhesive.

The present invention comprises a method of sealing a joint with an element and provides a heat recoverable element, e.g. a splice sleeve, preferably having an integral heating device associated with a material having a positive resistance temperature coefficient (PTC) to control heat production without recourse to external temperature control devices. The element is shaped so that it can be placed around the joint and then made to recover by heat and seal the joint. The phrase "self-contained heater" or "self-heating" means that an extension sleeve having this feature is associated with an electric resistance heater unit which, when connected to a suitable electric power source, e.g., a battery or AC power source, generates sufficient heat to shrink and activate (e.g.) any glue in the splice sleeve. The present invention also provides the use of a splice sleeve which does not have a self-heating feature (i.e., does not involve an electrical resistance element) and in which shrinkage and adhesive activation are accomplished using an external heating source.

The present invention thus provides a method of sealing a joint and performing a method of recovering a heat recoverable element which may be placed around a wire joint to be covered and sealed therewith, the element alternatively comprising a heating device connectable to and energized by the device, preferably comprising a material formed an electrically conductive polymer blend capable, when connected to a suitable electrical source, of heating the element to a temperature sufficient to cause it to recover.

7 6 S 9 3 3

The conductive polymer blend material preferably has a positive resistance temperature coefficient and preferably the material is shaped to be large in length and width relative to its thickness and is preferably in the form of a layer or film, and the electrodes are positioned so that current passes through the material thickness, i. in the case of a layer or film, from one surface to another.

It is preferred that the thermally recoverable portions of the element comprise a polymeric material that has been dimensionally modified from a heat-stable form or to form a dimensionally heat-unstable structure capable of recovering to or towards a stable form when heat is applied.

Preferably, at least a portion of the material that forms the heating device also forms a dimensionally heat unstable portion of the element.

It has, of course, been found that the particular heating device and the properties of the mixture and the electrodes are selected in each case, bearing in mind the nature of the electric power source available to the user.

The mixture is preferably a crystalline polymeric material and is preferably dispersed with carbon particles, especially carbon black. The polymer blend is preferably crosslinked chemically or by irradiation and the polymer, conductive particles and their amount are selected taking into account the end use and the power source available.

Those parts of the surface of the element which face the substrate to be covered and those which contact each other when the element is placed on the substrate preferably have a heat-activated sealant or adhesive layer on their surface, which is preferably activated at approximately the recovery temperature of the element. The interlocking parts are preferably provided with means for keeping them connected to each other during recovery. The central part of the element can be provided with a thermally stable insert, which defines the matrix surrounding the joint, while the end parts are shaped to return. separately around each cable, etc., which join together.

It is preferred that the heating device be self-adjusting and include a first layer of conductive polymeric material having a positive resistance temperature coefficient and in contact with at least one surface of the layer against the surface, a second layer of conductive polymeric material having a substantially constant resistance until at least the element return temperature and at least one pair of electrodes positioned so that the current flowing between them passes at least partially through a wattage-constant material and from one surface of the first layer to another.

It is recommended that the wattage layer be in contact with the surface against the surface and the electrodes are both in contact with the wattage layer.

The element preferably includes an insulating layer, which may also be heat recoverable.

In some cases, the element assembled according to the invention can be restored by an external heating device, and in these cases the conductive layers and electrodes can, of course, be omitted.

The optional built-in heating device preferably consists of a polymer in which an electrically conductive filler is dispersed to enable it to conduct current at a given voltage (e.g. 12 or 24 volts from the battery) while having sufficient resistance at its operating temperature to be capable of generating heat

II

9,68933 to cause a relatively thick portion of heat recoverable materials, on the order of a few millimeters, to warm to its recovery temperature and recover around the encapsulated joint. In addition, it is preferred that the heating device be capable of providing sufficient heat production to activate the high temperature thermoplastic or disposable plastic adhesive or seal.

When the PTC material is in the form of a structure having two relatively large dimensions and one relatively small dimension, e.g. as a layer such as a film, a small dimension along the flow of current is recommended for more uniform heating. When the current flows along the level of the PTC layer, local heating along certain conductive roads may result, resulting in uneven heat production. This, in turn, can cause an even greater problem, rendering the entire heater unusable for most of its heating cycle. If local heating causes the material to reach a T point along a line perpendicular to the current path, it prevents current from flowing across the path, effectively causing the heater to shut down until the temperature of the "hot line" thus formed falls below the T point. In other words, the "hot line"

O

across the layer between the end electrodes effectively shuts off the heating device, even if only a small area of the layer has reached the T point. This makes the heater so inefficient that it turns out to have a very low heating capacity. The problem of hot line formation can be minimized by placing PTC material between the electrodes in a manner that minimizes the length of the conductive paths through which hot line formation can occur. To obtain maximum efficiency on the minimum current path, the ratio between the length and thickness of the layer must be minimized. This is achieved, for example, by a film in which the electrodes deposit a PTC material between them. However, due to the short current path and the limited surface area required by some applications, insufficient heating for such a structure can occur at lower power outputs. To enhance this, a material that; gives a constant ti number or Joule heat output at a given voltage, i.e. a material that does not have PTC properties is preferably laminated with the PTC layer so that the laminate has a good heating efficiency and is still self-adjusting without hot line formation. For a more detailed description of the advantages of feeding current through a bed over feed along its length and making a layered composite structure, see Patent No. 65,522.

68933 10

Suitable PTC blends, which are preferred for use as the layers used in this invention, include blends of thermoplastic and elastomeric materials in which conductive materials are dispersed. As emphasized in the specification, such blends have a sharp rise in resistance at approximately the melting point of the thermoplastic component, with the resistance continuing to rise with temperature thereafter. Due to the increased safety margin provided by additional increases in resistance above the melting point, such heaters can be constructed to regulate ("disconnect") temperatures above the theoretical T-point and have resistors well above the T-point resistance, but still avoid thermal resistance. - the risk of burning and / or combustion which occurs when prior art 'f'TCs' are used in such structures. Such heaters, especially when the increase in resistance with temperature above the T point is very steep, are very "demandingly insensitive", i. The operating temperature of the PTC material varies very little with the thermal shell. They can also be built to generate very high powers up to the T point when electrically connected to a power supply. Due to their excellent temperature control, they can be used to activate adhesives and cause heat recoverable devices such as the devices of the present invention to recover around substrates such as thermoplastic telephone cable sheaths with reduced risk of substrate melting or warping, even if left on for considerable periods.

It should be noted that many different sealing means, including the adhesive described above, can be used for splice sleeves. The barrier means must be such as to withstand the heat recovery forces at the recovery temperature, for examples of which see U.S. Patents 3,379,218 and 3,455,336.

The method and apparatus for splicing encapsulation provided for use in the present invention differs substantially from prior art apparatus and methods and thus overcomes to some extent or otherwise avoids some of the disadvantages inherent in the latter. For example, in one of the preferred embodiments of the invention, heat-recoverable corrugations wrapped around a substrate, e.g., cables, wrap the substrate so that opposing heat-recoverable surfaces do not contact each other but press against, for example, opposing surfaces of long-fingered brushes. on compatible surfaces of the base. Forming a shell or splice sleeve from a combination of a heat-shrinkable and heat-stable part, as in certain preferred embodiments such that the areas of the parts that abut each other defining the cable splice matrix are not themselves heat-shrinkable, is another significant departure from the foregoing practice.

If it is long understood that when a heat-recoverable body is wrapped or wrapped around a substrate and shrunk to an area where the heat-recoverable body is brought into contact with and attached to the shell portion, it forms a weak area both mechanically and environmentally resistant to water intrusion. The aforementioned U.S. patent describes ways to solve this problem using a structure having an overlapping strip under the contiguous edges of the heat recoverable portion and secured to the top layer with an adhesive to provide a long leakage path. However, this solution has failed unless the substrate provides a solid foundation against which the heat-recoverable barrier layer can compress the strip to cause the adhesive to flow and wet the corresponding surfaces. Adding to this factor the difficulty of constructing a multi-hole splice with overlapping heat recovery regions, it can be seen that an element constructed in accordance with U.S. Patent 3,455,336, while very useful in most cases, does not solve all of the problems solved by this invention.

These problems are solved in a surprisingly simple and highly effective manner by the preferred approach of this invention. The optional use of an intervening brush or finger in the non-heat recovery base together with clamps and flanges in the heat recovery part, which flanges can be used accurately because the heat recovery part in these areas contains non-heat recovery segments, facilitates this highly desirable result.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: 12 68933

Figure 1 is a perspective view of the heat recoverable element i.e. a first embodiment of a splice sleeve assembled in accordance with the present invention and in which a plurality of cables of different dimensions are arranged and connected together; Figure 2 is an end view of the element of Figure 1 before being stretched to heat unstability, i. in its heat recoverable form; Figure 3 is an end view of this element after stretching it to a thermally unstable shape; Figure 4 is an end view of this element after it has been made to recover heat around the cables; Fig. 5 is taken along line 5 ~ 5 »of Fig. 3 showing in more detail the layered structure of the element; Figure 6 is a perspective view of the element prior to cable insertion; Figure 7 is a perspective view of an alternative embodiment of an element assembled in accordance with the present invention.

It should be noted that, with the exception of the schematic circuit of Figure 5 and Figure 6, Figures 1-7 illustrate the splice sleeve whether or not it includes a self-heating device. Figure 5 shows a layered structure as an example of an embodiment in which the splice sleeve includes a self-heating device. Figures 8-11 show the structure of another preferred embodiment of an extension sleeve assembled in accordance with the present invention.

Figure 8 is a cross-section through one end of the splice sleeve; Figure 9 is a perspective view of one cross-sectional end to show details of the structure; Fig. 10 is a perspective view of a 'crush' under the heat-irreversible base; Fig. 11 is a longitudinal section through the splice sleeve showing details of the inner matrix; Figures 12-19 show details of a preferred method of manufacturing a third preferred embodiment of an extension sleeve assembled in accordance with the present invention.

Figure 12 shows the formation of preferred pnose electrodes; Figure 13 shows the placement of the electrodes on the open rails and their attachment to the latter; Figure 14 shows the different layers of the preform of the heat recoverable body placed in the mold prior to lamination (cut open for ease of understanding); Figure 15 shows a blank currently being shaped into the basic shape of a heat recoverable part; 13,62933 Figure 16 shows a thermally recoverable portion in its thermally stable form after crosslinking; Figure 17 shows the structure of a reinforcing flange for the ends and sides of the heat recoverable part; Figure 18 shows the placement of flanges on a heat recoverable part placed in a mold prior to stretching; Figure 19 shows the heat recoverable part at the end of the stretching step; Figure 20 shows a perspective view of lower portions of the upper splice to show the interior of the additional details; Figure 21 shows a particularly preferred embodiment after it has been installed around the cable splice.

Referring now to the drawings, Figure 1 shows a heat recovery barrier device made in accordance with the present invention and adapted to receive a plurality of cables and having an enlarged center portion to accommodate a splice between the cables therein. Such an appearance is particularly suitable for low-voltage telephone cables, in which case several cables must be connected quickly and efficiently at the lowest possible cost.

The device shown in Figure 1 may be made entirely of heat-recoverable material, preferably with a self-heating mixture deposited as shown in Figure 5, which will be described in detail below. Alternatively, only the part of each end of the splice sleeve that contains the corrugations, i. the part of the splice sleeve between its ends and the dashed lines 18 can be made heat recoverable with the central part being heat irreversible. The layer or layers of thermally recoverable material are crosslinked, for example, by irradiation to render them thermally recoverable. The thermally recoverable portion containing the layer 10 is placed in its stable, unstretched state with the folds 11, as shown in Fig. 2. The unstretched corrugations may, of course, be of any shape, including the general shape of the cable, provided that there is sufficient excess material to allow stretching. The corrugations are stretched by a known technique to a larger dimension than the diameter of the cables to be sealed, as shown in Figure 3. The material is flexible and pliable enough to allow the cable to be pressed into the opening in the corrugation. As best seen in Figures 3 and 4, the openings may vary in dimension depending on the size of the cable to be inserted, although it should be borne in mind that one opening size may return over a wide cable size range tiiiv w 68933. The heat recoverable portion 10 is matched to the base portion 12 of the splice sleeve, which is not heat recoverable, although, as shown in Figure 7, for example, it may be heat recoverable in some embodiments. The base portion 12 can act as a permanent detent for the cable splice, providing rigidity to the system. Alternatively, portions 10 and 12 may have a common hinge at one edge 14 (Figure 4) and a closure device at opposite edge 6. Alternatively, when portions 10i and 12 are formed of the same material, they may be integral at edge 14 using a closure at edge 6, or portions 10 and 12 may be separate parts separate from both edges 14 and 6, in which case the heat-shrinkable part 10 is simply lifted off the part 12 for the insertion of cables. If desired, the parts 10 and 12 may have reinforcing strips embedded in them along their longitudinal axis, preferably next to the edges 14 and 16. These strips can also act as busbars.

When closing the cable splices according to the method of the present invention, the parts 10 and 12 are separated from each other and the cables 20, 22 and 24 are placed inside them. Referring in more detail to Figures 2, 3 and 6, in which parts 10 and 12 are neither integral nor hinged, a compression device is used, for example, hinged clamps 52 and 54, which are tightened by means of a bolt 56 and a wing nut 58. The tensioners can operate while holding parts 10 and 12 together during expansion (Figure 2) and during cable insertion and recovery (Figure 4). Although these tensioners could form a permanent part of the installation, it is recommended that they be removed after installation and that an adhesive, such as that described in U.S. Patent 3,770,556, be used to permanently seal the edges.

Also at the ends, a suitable distance between the cables is more suitably ensured by a tightening device. As best seen in Figure 6, this may be a plate separator 62 with openings for receiving the corrugations 11 (Figure 2), which plate seals the parts 10 and 12 with tensioners 64 and 66 during expansion and sealing operations.

In order to increase the strength and further protect the system and, if necessary, to provide water vapor penetration protection or radio frequency protection, the cable splice itself may optionally be encapsulated in a rigid container having a housing defined by dashed lines 18 and 18a generally below the center of the heat recovery portion. 1. When the central portion 26 is heat recoverable, it conforms to the shape of a container suitably made of any rigid material, including metals or molded plastics. The end openings 19, 21 and 23 are adapted to receive private cables of varying dimensions. The other end of the heat-recoverable part generally includes openings of similar dimensions for receiving the cables to be connected, although all the openings may have been placed on the same side.

When a rigid container is used to cover the splice, sealing with a heat-recoverable portion from the center may not be necessary. Therefore, as mentioned above, the heat recoverable part of the article of the present invention can be limited to the end areas so as to seal the private incoming cables up to the container. In this case, the central part 26 may be of non-recoverable material or, if it is reversible, it need not be returned. Alternatively, the material need not extend across the container so as to allow the container to remain exposed, or only a secreting layer, e.g., layers 30 or 31 in Figure 5, need to extend over the container with the other layers confined to the ends.

Referring now in more detail to Figure 5, the heat recoverable housing preferably includes a self-heating laminate embedded with electrodes that can be connected to a suitable power supply. A suitable laminate is more fully described in Patent No. 65,522.

In short, the laminate consists of an outer insulating layer 30 which is heat recoverable. Layer 34 contains a polymer or polymer blend, for example a mixture of highly crystalline polyolefin and ethylene-propylene rubber, in which a conductive carbon black is dispersed. Layer 34 is preferably interposed between layers 32 and 36, which may also be polymer blends dispersed with carbon black, which layers preferably produce constant wattage at a certain voltage over a wide temperature range and do not exhibit significant resistance temperature coefficient properties. An insulating inner layer 31 may also be present. Layers 31, 32, 34 and 36 are preferably also heat recoverable. The inner layer may preferably include an adhesive layer (not shown) on its free surface to join and seal against the cable.

Embedded in the constant watts layers 32 and 36 are electro-dies 38 and 40 which can be connected to a suitable power supply, 16 68933, for example a battery, as schematically shown in Fig. 6. This structure causes current to flow through the PTC layer 34 from the electrode J> & to the electrode 40. The preferred type of electrode structure and configuration is described more fully below.

Referring now in more detail to Figure 7, there is shown an alternative configuration of the present invention. Such a configuration can be formed and stretched from a single sheet of material, which is generally the layered configuration of Figure 5. Once the cables have been inserted through the openings 44, 46 and 48 as previously described, the device is closed by bringing the opposite edges 50 of the plate together with a suitable closure device 51. Such a device can, of course, be adapted to different cable diameters and shapes as shown. with locking device in position 50 and self-hinging in position 47 ·

A particularly preferred embodiment of the invention is described in cross section. in Figure 8. It includes upper and lower portions 96 and 80. The upper portion 96 includes an extension housing outer shell 67 firmly attached to a heater consisting of outer and inner layers 68 and 70 of a wattage-free material and a core layer 69 of PTC material. an adhesive layer 71 is attached to the inner surface of the unchanged layer 70. The PTC core 69 of the heater is connected to the wattage unchanged outer layers 68 and 70, which are blends whose thermoplastic polymer components, if any, have lower melting points than the pTC blend thermoplastic polymer component. Non-wattage layers, if they contain thermoplastic polymers, may be made thermally recoverable, and preferably an additional outer shell 68 consisting of a layer of thermally recoverable polymer blend having a recovery temperature lower than the melting point of the thermoplastic component of the PTC blend is also included. An additional layer 71 of hot melt adhesive or mastic may also be included, the hot melt adhesive, when used, having a melting point similar to that of the heat recovery portion and an activation temperature lower than the melting point of the thermoplastic component of the PTC mixture. Such an embodiment has been found to be particularly advantageous when the substrate is heat sensitive, i. when heated above its melting point, it twists or drains.

As shown in more detail in Fig. 9, flexible and adaptive electrodes li 17 6 S 9 3 3 72 are embedded in the layers having a constant wattage, which can advantageously be formed of braided wires. Each heat-shrinkable end pleat contains six electrodes 72, three connected to be connected to one terminal and the other three to the other, facing each other in pairs and running perpendicular to the longitudinal axis of the housing. The first polarity electrodes are connected (e.g., by welding, soldering, or gluing with a conductive adhesive from the cutting area) to the collection electrodes 73 and 73a and the second polarity electrodes to the collection electrodes 79 and 7a running along both long sides of the housing. The electrodes 73, 73a, 7, and 79a may be made of a wire punch or a thin metal strip that is perforated in a horizontal manner. Attached to the center portion of the electrode 73 on one side and to the center portion of the electrode 7A> a on the other side are strips 75 and 76 adapted to be easily connected to an electrical power supply. Reinforcement flanges 77, 78 and 79 made of any rigid material are attached (by gluing or otherwise adhering) to the primary heat-shrinkable layer (see also Figure 8) along both sides and between the heat-recoverable end pleat structures. Particularly suitable materials are metals and technical thermoplastics, for example polycarbonates, acrylonitrile-butadiene-styrene or SAN resins, and filled polymers, for example polyamides or polyolefins. Glass-filled polyamide (nylon) is especially recommended. The lower portion 80, which is not thermally recoverable, preferably has protruding ribs 81 for better rigidity and optionally internal ribs 82 which correspond to and are adapted to join the open sides of the thermally recoverable pleats, as also shown in Figure 10. The extension housing can be mounted by bringing the top and bottom together and securing them with spring retainers 83, 89 and 85 suitably made of materials similar to flanges 77, 78 and 79. Turning now to Figure 11, it shows a section along the longitudinal axis of the housing. The central cavity 86 operates to include private extended wires from the cables. Optionally and preferably, a small container 95 (filled with desiccant) is present, the walls of which allow water to diffuse through at a rate greater than the diffusion rate into the inner cavity, as described in more detail above. The housing may be provided with a valve to allow access to the cavity 86, which. enables pressure testing of the installed splice case.

The preferred method of manufacturing the splice case will be described with particular reference to the embodiments of Figures δ-11 with reference to Figures 12-21.

The electrode material, preferably a metallic braid, which may be formed, for example, of sixteen conductors, each consisting of four 38 AWG (diameter about 0.010 cm) tinned copper filaments braided at the largest possible braid angle (to achieve a high degree of conformation), is formed into a thin conductive or around the non-conductive thermoplastic pipe. Excellent results have been achieved with a 75 ° 'braid angle around a pipe with an outer diameter of 6.25 mm and a wall thickness of 0.25 mm, which is the same mixture as a material with a constant wattage. The braided tube is heated to or above the melting point of the thermoplastic tube and flattened to avoid carefully stretching the braid. These steps are shown in Figure 12.

The next step in the process is the construction of an electrode assembly electrode system comprising the steps of attaching the strip 75 to the side electrode 73a, followed by attaching the end electrode 72. Suitable fastening methods include spot welding, soldering and gluing. When the electrode consists of a wire braid around a conductive core of the same material as the wattage-constant layer, it has been found that excellent results are obtained by heat bonding using a conductive thermoplastic core to bond the electrodes together. Attaching the electrodes to each other to form the basic configuration is facilitated by using a matrix as shown in Figure ± 4. The material used for the end electrodes may be, in addition to the above-mentioned flattened braid, knitted or woven or galvanized metal wires, conductive fibers or metal-coated polymer fibers or polymer fibers containing conductive particles and treated to be highly conductive in the fiber direction.

In all of these embodiments, it is recommended that the resulting electrode be highly stretchable and adaptable so as not to provide any significant resistance to the expansion or recovery of the heat-recoverable portions of the splice case that occurs during fabrication and installation of the splice case.

Similar materials can be used for side or assembly electrodes. In addition, since the exemplary electrodes do not have to undergo any significant deformation during manufacture and installation, they may be formed of relatively inextensible and non-lint-free materials such as flat metal or otherwise highly conductive strips, which are preferably perforated, and single or multi-strand yarn.

The structure of the blank for the splice sleeve is shown in Figures 13 and 1. The various layers of the heater, which are made, for example, by extrusion, co-extrusion or separation from the mandrel, are easy to install in a matrix frame. In the specifically described embodiment, the surface layer 67 is placed in the frame and then successively the wattage-constant layer 6Sa, the first set of electrodes 73 / 73a (with the strip 76 pointing to the right as shown in the drawing), the second wattage-constant layer 68b, the PTC control layer 69 , a second wattage unchanged layer 70a, a second set of electrodes 7/7 ^ a (with the strip 76 pointing to the left) and a last wattage unchanged layer 70b are applied. The entire structure is sandwiched between the protective polytetrafluoroethylene layers 97 and laminated together by heating under pressure. The matrix is used to keep the different layers and electrodes in a fixed relationship with each other during lamination using minimum pressure. After lamination and removal of the polytetrafluoroethylene layers, the assembled splice blank is to be sandwiched between the foam rubber sheets 100 and heat treated at, for example, about 185 ° C for a sufficient period of time with minimum compression pressure to allow the sublayers to release their stress thoroughly. Depending on the materials in question, heat treatment times, even from just two minutes to more than one hour, are suitable, with 5_15 minutes being the recommended time. The blank is removed while still at the processing temperature and adapted to the male mold as shown in Figure 15 using pressure as indicated by the arrows to form the unstretched splice configuration 87 shown in Figure 16. As in the above procedure, care must be taken to ensure that the heater is not stretched during the forming operation. · If desired. the upper surface of the flanges 77, 78 and 79 may have a plurality of brushes, preferably wedge-shaped, which brushes act to direct the compressive forces provided by the tensioners 83 and 85.

The basic splice sleeve 87 is then irradiated with ionizing radiation using techniques well known to those skilled in the art to ensure uniform irradiation. Suitable ionizing radiations include gamma rays, X-rays, and accelerated electrons. The dose required should be sufficient to ensure the cohesiveness of the configuration. above the melting point of the crystals of its polymeric constituents, but not large enough to adversely affect the elongation behavior during the stretching operation to form it in the heat recoverable configuration. A suitable irradiation dose has been found to be 2-50 megarads, with 5-20 megarads being recommended.

The preform, which after irradiation can be considered a "thermally stable" configuration, is then formed into a "heat recovery" configuration 88 in the sequence shown in Figures 17-19 · After the body 87 is preheated to heat it approximately to the melting point of its crystalline polymer components, the formed preforms are placed in a matrix 39 18 as shown. Reinforcing flanges 77, 78 and 79, the contact surfaces of which are coated with adhesive 90 as shown in Fig. 17, are placed on the sides and ends of the formed blank 87. The end flange 78 (and the corresponding flange at one end of the splice sleeve) is provided with a long "cut" strip 91 with insertion holes 92 for mounting to the matrix 89 as shown in Figures 17 and 18. All flanges have turned-down lips for $ 9 on their outer edges to hold and protect the edges of the heater from mechanical damage. The side flanges 77 and 79 have a small shoulder 99 in the center of the outer edge that surrounds the electrode strips 75 and 76 and is sized to receive a standard 6.3 "0.8 mm 0.8" connector, such as those supplied by Arc-Less Company.

The pressure is directed to the side and end flanges and the pleats and central cavity of the splice sleeve are formed by a suitable stretching device. Such a stretching technique is well known in the art in the past and involves spindle stretching and pneumatic or vacuum forming. Care must be taken in this procedure to avoid longitudinal compression of the folds when using a spindle. A suitable way to minimize such compression is to use a radially expanding or circumferentially segmented sleeve portion between the mandrel and the pleat, which acts to dissipate from the pleat the longitudinal insertion forces provided by the mandrel. Alternatively, pneumatic or hydraulic expansion of the longitudinally forced elastomeric tube can be used. It is recommended to form the central cavity of the extension sleeve pneumatically. The expanded preform is then cooled while forced, as in Figure 19, removed from the matrix and the adhesive layer 93 adhered to the surfaces 21 63933 facing the bottom and against the inner surfaces of the pleats. The adhesive layer can also be attached to the joint surface of the part 80. At this point, the desiccant-filled container 95 may, if desired, be attached to the inner surface of the central cavity 9 as shown in Fig. 20, which is a view of the finished heat-recoverable top 96 from which the ratio of pleats to central cavity can be seen. Alternatively, the desiccant may be attached to the base plate as shown in Figure 11.

In use, after the splices have been completed and connected to the splice sleeve, the finished splice sleeve is assembled as described above by bringing the upper and lower portions 96 and 80 together and tightening with side clamps 83 and 85 and end clamps 8½ and 84b. The heater is then electrically connected to the power supply.

Due to the placement of the electrodes in the top of the splice and the relative resistances of the wattage and PTC layer, when the heater is connected to a power source, such as a 12 or 24 volt lead acid battery, heating to recover and adhesive activation occurs mainly in the folds and flange areas. Thus, the central cavity does not generate enough power to heat significantly.

As mentioned above, the mixtures used in the heating layers can be selected to provide very rapid heating of the splice sleeve. For example, using preferred FTC blends of the type mentioned above, it has been found that the heater in the pleat area typically heats to II5-120 ° C in less than one minute. When this temperature is reached, the pleated areas begin to recover. In about two minutes, the pleated areas have shrunk around the substrate, e.g., the cable, and after another eight to thirteen minutes, the adhesive layers have been thoroughly activated and have moistened and sealed the cable sheath and the heat-irreversible base. Thus, in typical cases, the heater is suitably connected to the power supply for about 10-15 minutes, during which time the assembly can be safely ignored, allowing the installer to continue other operations. Those skilled in the art will recognize that the time that a heater is effective will vary depending on the temperature requirements of the adhesive, the heat load, and other factors. Surprisingly, it has been found that the time required is relatively insensitive to ambient temperature. It is believed that this may be due to the very sharp cutting temperature of the PTC layer made possible by the particularly advantageous structural combination of the present invention.

'22 6 8 9 3 3

After a suitable period of time, the electrical power supply is removed and the splice sleeve is allowed to cool to ambient temperatures. In this case, the side and end clamps can be removed or left in place to provide additional mechanical protection if desired.

A particularly advantageous result of the combination of components of the present invention is that since the heater itself is able to maintain itself in a very limited temperature range no matter the ambient heat load, even when this temperature range is very close to melting points of commonly used thermoplastic sheath or private conductor insulation materials, leave electrically connected to the power supply for long periods (eg several hours) after the connection has been made and damage to telephone wires or cables can be avoided.

To facilitate reopening, the product may be provided with a retaining device to prevent complete recovery of the returnable part when the installed part is reheated to strain it and any adhesive. The restraint device may consist of rigid, e.g. metal, parts below the parts which are to surround the cabinets. Referring to Figure 9, a tongue having the same width as the planar portion 78 between the cable entry openings is disposed on the surface of the planar portion with one portion extending axially upwardly therefrom. Similar tongues can be placed on the outer planar surfaces 77 and 79 and all axially extending parts are joined together by suitably shaped connecting rings to provide a retaining device forming a whole. If desired, this device can be left in place during use.

Claims (19)

23 6 89 3 3 A method of sealing a joint between two or more cables or pipes with a heat recovery closure element (10, 96), wherein the ends of the cables or pipes are inserted into the element and the end of the element is heated to return and seal around the cable or pipe, characterized in that that two or more cables or pipes are placed at one end1 (19, 21, 23; 44, 46, 48) of the closure element and the opposite parts of the end of the closure element are held together between the cables or pipes during heat recovery. Method according to Claim 1, characterized in that the parts are held together by a clamp or clamp (64, 66, 84). A heat-recoverable sealing element (10, 96) for sealing a connection between two or more cables or pipes, the ends of the element through which the cables or pipes extend are heat-recoverable and sealable around the cables or pipes, characterized in that the end is shaped (19 , 21, 23; 44, 46, 48) for receiving two or more cables or pipes and provided with means (64, 66, 84) for holding two opposite parts together between the cables or pipes during heat recovery. Element according to claim 3, characterized in that the element comprises a heating device comprising a material formed of an electrically conductive polymer blend having a positive resistance temperature coefficient. Element according to any one of claims 3 to 4, characterized in that at least the reversible part (10) or parts of the element consist of a polymeric material dimensionally converted from a thermally stable form to a thermally unstable form capable of recovering to or towards its thermally stable form, from which polymeric material at least a portion also forms at least a portion of the material of the conductive polymer blend (32, 34, 36) of the heating device. 2I> 68933 Element according to one of Claims 3 to 5, characterized in that the conductive polymer mixture (32, 34, 36) consists of a polymer in which conductive carbon particles are dispersed. Element according to Claim 6, characterized in that the carbon is carbon black. Element according to any one of claims 3 to 7, characterized in that at least part of it, at least when it is in place to cover and seal its base, is tubular. Element according to one of Claims 3 to 8, characterized in that it has, at least on the surface which comes into contact with the substrate (12) to be covered, a coating which is a heat-activated adhesive or sealant. Element according to any one of claims 3 to 9, characterized in that its first and second opposite edge regions (14, 16) are arranged to be brought together to form a generally tubular device and have means (51, 52, 54) for to connect and hold them together during recovery. Element according to Claim 10, characterized in that the edge regions (14, 16) have a heat-activated sealant or adhesive on their interconnected surfaces. Element according to Claim 3, characterized in that it has a central part for encapsulating the splice and at least one end of the element is adapted to return and seal on all the cables separately. Element according to Claim 12, characterized in that a rigid, dimensionally stable container part (18, 18a) is arranged in the central part to surround the joint as the reversible central part of the element adapts to the appearance of the part. Element according to any one of claims 4 or 5 to 13, characterized in that the heating device is self-adjusting and comprises a first layer of conductive polymeric material (3 * 0 * having a positive resistance temperature coefficient and a surface in contact with at least one layer). with the surface of a second layer of conductive polymeric material (32, 36) having a substantially constant resistance up to at least the recovery temperature of the element, providing a substantially constant power at a certain voltage, and having at least a pair of electrodes positioned so that the current flows at least partially in watts through the unchanged material and from the surface of the first layer to the second. An element according to claim 14, characterized in that the wattage constant layer (32, 36) is placed against the surface of the first layer in contact with both surfaces of the first layer and in that the electrodes (38, 40) are all in contact with the wattage constant layer. Element according to one of Claims 3 to 15, characterized in that it also contains an insulating polymer mixture (30, 31). Element according to one of Claims 3 to 16, characterized in that the heating device is heat-recoverable. Element according to one of Claims 3 to 17, characterized in that the insulating polymer layer (30) is heat-recoverable. Element according to any one of claims 3 to 18, characterized in that a desiccant container is attached to its inner surface, the water vapor permeability of which is such that it keeps the relative humidity below 30% below ambient conditions, which is achieved after the element has been recovered around his platform. 26 6 8 9 3 3