FI64482C - VAERMEAOTERHAEMTBAR ANORDNING OCH ANORDNING AV DENSAMMA FOER EN KABELSKARV - Google Patents

Description

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^ ---- ^ (51) Ky.lk.Wl.3 H 02 G 15/113 FINLAND - FINLAND (21) PKenttlhilwmu · - P »Unt» n »öknln | 752666 (22) Htktmltptlvl - Anteknlngidtg 23.09-75 (23) Alkuptlvt — Glltlgh «ttdag 23.09-75 (41) Tullut | ulklMktl - Bllvlt offentllg 28 03 76

Patent · and registered Nghtwucp ™, j. moon new date -

Patent and other registration An * ök * n utltfd och utUkrifttn pubticend 29 * 07,83

(32) (33) (31) Requested * chair — Begird priority 27.09.7U 0U.08.75 USA (US) 509837, 6013UU

(71) Raychem Corporation, 300 Constitution Drive, Menlo Park, California 9U025, USA (72) David August Horsma, Palo Alto, California, Stephen Hunter Diaz, Los Altos, California, USA (7U) Berggren Oy This invention relates to heat-recoverable devices which can be placed around a cable, pipe or switch at a joint or splice and then cause heat to return to its place at the joint or splice. to encapsulate the splice.

There are many applications where it is desirable to provide a sealing, insulating, or protective encapsulating 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, 3,355,336, or 3,770,556. These so-called "wrap-around" closures can be placed around a long piece without accessing its free end. Nevertheless, there is a significant need for a splice, hereinafter referred to as a "splice sleeve", which is suitable for closing electrical cable splices or splices and which provides effective environmental protection, especially for splices with more than two incoming cable ends and / or splices of different sizes. but which can be inserted without access to the free end of the cable.

This invention relates to a heat-recoverable splice sleeve which, in various embodiments, can enclose several different sizes, i. cables of different outer diameters, which sleeve 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 splice sleeve of the present invention uses either a "shell shell" or a structure formed by a separate base plate and capsule body.

In one embodiment, the present invention relates to a splice sleeve 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 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 splice 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 3 64482 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 made to recover simply by connecting it to an electric power source, be it a battery or mains power, e.g.

A 12 or 24 volt battery or 115 volt or other suitable AC power source, and which, when 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 those 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. for 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 virtually inaccessible. Besides, the temperature sensed by the control device is only in its immediate vicinity, while the other areas of the sleeve 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.

“64482 A striking feature of these PTC materials is that when a certain temperature is reached, a rapid increase in resistance occurs. The temperature at which the resistance increases sharply is often defined as the switching temperature (Tg), as the current tends to switch off at this point, thus preventing permanent damage through a continuous rise in temperature to the heating element itself or any object heated by it.

Although numerous theories have been proposed for the sharp increase in resistance of a PTC material, which usually occurs approximately at its melting point of crystals, it is generally believed that this behavior is proportional to the difference in thermal expansion between the conductive filler and the thermoplastic matrix material at the melting point. For a more detailed description of numerous alternative mechanisms for explaining the PTC phenomenon, see "Glass Transition Temperatures as a Guide to the Selection of Polymers Suitable for PTC Materials", J. Meyers, Polymer Engineering in Science, November, 1973, 13, no. 6.

Most self-regulating heating devices using PTC material have steep R = f (T) curves at approximately the T point s, so that above this temperature the device actually closes completely, while below this temperature a relatively constant power output is achieved at a given voltage. At low temperatures, the resistance is at a relatively low and constant level and the current is relatively high at any given voltage. The generated energy is lost in the form of heat, thus heating the material. The resistance remains relatively low up to the T point

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where there is a rapid increase in resistance. As the resistance increases, the power decreases, thus limiting the amount of heat generated, and with very steep R = f (T) curves, the heating actually ceases. As the temperature drops, the resistance drops, which in turn increases power output.

Generally, when voltage is applied through a PTC heating element, the wasted energy causes the PTC element to rapidly heat up to its switching temperature, after which only a little more temperature rise occurs due to a sharp increase in resistance. Due to the sharp rise in resistance, the heating element theoretically reaches a steady state at approximately the switching temperature, thus regulating the power production itself without recourse to fuses or thermostats.

The thermoplastic PTC materials previously disclosed in the art are highly crystalline and have a T 1 point approximately at the melting point of the crystals.

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However, most such materials actually exhibit an "overdrive" effect, i. the resistance drops again at temperatures well above the melting point. This decrease in resistance above the melting point is generally undesirable, especially in cases where the PTC material itself is thermally recoverable or is used in close contact with the thermally recoverable material to effect recovery, as in such conditions it is recommended to heat the heat shrinkable material to its melting point as soon as possible. power densities) and thereafter keep the heater temperature very little above the melting point of the thermoplastic components of the heater to facilitate rapid and efficient shrinkage of the heat recoverable element. However, heat recovery elements such as this invention are intended to be used to encapsulate and seal environmental joints between, for example, telephone cables by shrinking and tightly bonding, usually using glue, to a cable sheath which usually contains a low melting, partially crystalline thermoplastic mixture, e.g. -vinyyliasetaattipolymeeria. Such cable sheaths are almost always uncrosslinked and therefore flow and twist easily if the heater causes them to rise to too high a temperature (i.e., above their melting points) during that time at the temperature required to activate the adhesive. An even more serious consequence would be a heater that does not “close” very positively if the power supply were not cut off from the heat-shrinkable element due to negligence.In such circumstances, it is conceivable that the PTC heater could remain energized for much longer than only ten minutes.The above are even more important if, as is often the case, individual conductors in telephone cables are all insulated with similar thermoplastic alloys.No twisting of such conductor sheaths is acceptable as it will cause this part of the cable to become inoperable.It is therefore recommended that the extension sleeve there is a sharp and large increase in resistance above the point T ^ of the warming element and that it continues to rise when the temperature of the heater is raised above the melting point of the thermoplastic component instead of it "k would be over, "i.e. would deteriorate more or less sharply, as happens with most, if not all, previous heaters in the art.

It is believed that the phenomenon of "over-rotation" and its problems have not been widely recognized in the past.

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Moreover, it has hitherto been generally believed that conductive polymeric materials having PTC properties did not have sufficient heating capacity to provide recovery of the relatively thick portions of thermally recoverable materials shown by the splice of this invention, nor the capacity to activate the high temperature adhesives the invention also shows.

The disadvantages of prior art PTC materials for articles such as the splice sleeve of the present invention can be largely overcome by using structures of the type described in Patent Application No. 752667. However, it should be noted that although prior art PTC materials materials are not recommended, they are suitable for use in the splice sleeve of this invention in many 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, the 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 a telephone cable drops to an unacceptable level of about 0.5 gigaohm / km. At relative humidity below 30%, the properties are acceptable. We have found that the moisture inside the splice sleeve does not need to be kept as low as possible, but should simply be kept below 30 SS 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 relevant conditions.

When outside R.H. is 100% and inside 0% y if the typical water vapor permeability (MVT) of the splice sleeve of this invention is 100 μg / h at 15 ° C, the MVT of the desiccant tank must be> 100 μg / h with an RH of 30%, or > 333 ug / h with 100% RH. Thus, 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 of 100% relative humidity 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 the necessary modifications to the private splices or replacement of any component, the entire splice sleeve can be reinstalled as before and the short reconnection time to the electrical power supply will result in the re-formation of the adhesive bonds to achieve a structural integrity.

8 64482 This ease of reopenability means that if not all cable folds are required for the first installation, a plug or plugs adapted to hold the extra 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. The reopening of the non-self-heating splices can also be performed using an external heat source to melt the adhesive.

It is an object of the present invention to provide a heat recoverable shell system suitable for encapsulating multiple cables.

It is a further object of this invention to provide a heat recoverable shell assembly that can be placed on or wrapped around cables and that can have a self-heating capacity to seal such cables without recourse to external heat sources.

Another object of the present invention is to provide a self-heating shell system which has the ability to self-adjust and not overheat, causing permanent damage to the encapsulated material, and not to turn off below the design temperature.

The present invention provides a heat recoverable element, e.g., a splice sleeve, preferably having an in-house 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., 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.

9 64482 The present invention therefore provides a heat recoverable element which can be placed as it recovers around a wire joint to be covered and sealed therein, the element comprising a heating device connectable to and energized by the device, the device comprising a material formed of an electrically conductive polymer blend, which, when connected to a suitable electrical source, is capable of heating the element to a temperature sufficient to cause it to recover. The characteristic features of the device are given in the appended claims.

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 1'ol polymer mixture is preferably chemically or irradiated crosslinked and the polymer, conductive particles and their amount are selected taking into account the end use and available power source.

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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-activatable layer of sealant or adhesive 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 center portion of the element may be provided with a thermally stable insert that defines a matrix surrounding the splice, while the end portions are shaped to recover separately around each cable, etc. that converges in the splice.

It is preferred that the heating device is self-adjusting and includes 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 to at least the element return temperature at a certain voltage, 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 self-contained heater 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 produce a relative thickness of 64482. a portion of the 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 with two relatively large dimensions and one relatively small dimension, e.g. as a layer such as a film, the flow of current along the small dimension 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 Tg 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 Tg. In other words, the "hot line" 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 in the minimum current path, the ratio between layer length and thickness 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 improve this, a material that gives a constant wattage or Joule heat output at a certain voltage, i. 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 supplying current through the bed compared to the feed along its length and producing a layered composite structure, see Patent Application No. 752667.

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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 to have resistors that are clearly

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Above the T-point resistance, but still to avoid the risk of thermal escape and / or combustion that occurs when prior art PTC alloys 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 heat load. They can also be built to develop very high power T -

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to the point when they are electrically connected to the 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 splice encapsulation devices provided for use in this invention differ substantially from prior art devices and thus overcome to some extent or otherwise avoid 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 opposite heat-recoverable surfaces do not contact each other but press against, for example, opposite surfaces of long-finger brushes 13 64482. on compatible surfaces. 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 itself are not heat-shrinkable, is another significant departure from the foregoing practice.

It has long been 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. Pat. No. 3,555,336, while very useful in most cases, does not solve all 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:! 14 64 4 8 2

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, which shows 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; Figure 10 is a perspective view of the splice sleeve under the non-heat recovery base; Fig. 11 is a longitudinal section through the splice sleeve showing details of the inner matrix; Figures 12 to 19 show details of a preferred method of manufacturing a third preferred form of splice sleeve assembled in accordance with the present invention.

Figure 12 shows the formation of preferred braided 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; Figure 64482 shows a thermally recoverable portion in its thermally stable form after crosslinking; Figure 17 shows the structure of the reinforcing flanges 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 a heat recoverable material, preferably with a self-heating mixture deposited as shown in Figure 5, which will be described in more 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 5, 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 by chamfering them. 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 16. Alternatively, when portions 10 and 12 are formed of the same material, they may be integral at edge 14 using a closure at edge 16, 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 ensured by a suitable 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 heat recovery portion 26 in Figure 1. When the central portion 26 is heat recoverable, it follows the shape of a container that may be 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.

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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 Application No. 752667 ·

Briefly, the laminate consists of an outer insulating layer 30 with heat recovery. Layer 3 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 3 is preferably interposed between layers 32 and 36, which may also be polymer blends in which soot is dispersed, and which layers preferably have a constant heating power 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, 3 and 36 are also preferably heat recoverable. The inner layer may preferably include adhesive layers (not shown) on its free surface to seal and seal against the cabinet.

Embedded in the unchanged layers 32 and electrodes are embedded in a suitable power supply, 18 64482, for example a battery, as shown schematically in Figure 6. This structure causes current to flow through the PTC layer 34 from the electrode 38 to the electrode 40. The recommended 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. It may be a "shell shell" structure with a closure at 50 and self-hinging at 47.

A particularly preferred embodiment of the invention is illustrated in cross-section in Figure 8. It includes upper and lower portions 96 and 80. The upper portion 96 includes an outer housing outer shell 67 firmly attached to a heater consisting of outer and inner layers 68 and 70 of constant wattage material and a core of PTC material. · An adhesive layer 71 is attached to the inner surface of the inner wattage unchanged layer 70. The PTC core 69 of the heater is connected to the unchanged outer layers 68 and 70, which are blends whose thermoplastic polymer components, if any, have lower melting points than the PTC with a polymeric coronary state. Unchanged layers, if they contain thermoplastic polymers, can 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 Figure 9, flexible and adaptive electrodes 19 64482 72 are embedded in the wattage-constant layers, which can be advantageously 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 74 and 74a running along both long sides of the housing. The electrodes 73, 73a, 74 and 74a may be made of a wire braid or a thin metal strip, optionally perforated. Attached to the center portion of the electrode 73 on one side and to the center portion of the electrode 74a 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, 84 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 allows pressure testing of the installed extension housing.

The preferred method of manufacturing the splice case will be described, with particular reference to the embodiments of Figures 8-11, 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 obtained 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 unchanged power 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 14. The material used for the end electrodes may be, in addition to the above-mentioned flattened braid, knitted or woven or galvanized metal rods, conductive fibers or metal-coated polymeric fibers or polymeric 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. Because of these e] ekt rod.i I don't have to go through any significant-; In addition, they may be formed of relatively inextensible and non-conformable materials such as flat metal or otherwise highly conductive strips, which are preferably perforated, and single or multi-stranded yarns.

The structure of the blank for the splice sleeve is shown in Figures 13 and 14. The various layers of the heater, which are made, for example, by extrusion, co-extrusion or hot calendering, are easy to install in a matrix frame. In the specifically described embodiment, the surface layer 6'7 is placed in the frame and then successively a wattage unchanged layer 68a, a first set of electrodes 73 / 73a (with the strip 76 pointing to the right as shown in the drawing), a second wattage unchanged layer 68b, a PTC control layer 69 a constant layer 70a, a second set of electrodes 74 / 74a (with the strip 76 pointing to the left), and a last wattage unchanged layer 70b is 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 preferably sandwiched between the foam rubber sheets 100 and heat treated, e.g., at 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 of up to just two minutes to more than one hour are appropriate, 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 a technique well known to those skilled in the art to ensure a uniform beam shell. 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 all its polymeric components, but not high 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 recoverable" 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 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 the other end of the splice sleeve) is provided with a long "cut-off" strip 91 with set holes 92 for mounting it to the matrix 89 as shown in Figures 17 and 18. All flanges have lowered lips 98 at their outer edges to contain 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 surrounding the electrode strips 75 and 76 and are sized to receive a standard "Quick Disconnect" connector, 6.3 x 0.8 mm in size, as 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 is attached to the surfaces 23 6 4 4 8 2 against 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 94 as shown in Figure 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 are completed and connected to the splice sleeve, the finished splice sleeve is assembled as described above by bringing the tops and bottoms 96 and 80 together and tightening with side clamps 83 and 85 and end clamps 84a 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, e.g. a 12 or 24 volt lead acid battery, heating to cause recovery and / or adhesive activation occurs mainly in folds and flange areas. As a result, the central cavity does not develop enough power to warm up to a mei’kit extent.

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 PTC 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, wetting and sealing 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.

i 64482 24

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 the melting points of commonly used thermoplastic sheath or private conductor insulation materials, electrically connected to a power source for long periods of time (e.g., several hours) after the connection is 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 soften it and any adhesive. The restraint device may consist of rigid, e.g. metal, elements below the parts which are to surround the cable. 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 (13)

A heat recoverable device for introduction around a conduit joint or the like to cover and seal it upon recovery, the device comprising at least in its return part or parts (10) a polymeric material dimensionally converted from a thermally stable form to a thermally unstable form which can be restored by heating -stable shape and towards which the device is further provided with a heating device (32, 314, 36, 38, 140) comprising an electrically conductive dense polymeric material, characterized in that at least part of the heat-recoverable material also forms at least part of the material in the electrically conductive, in a dense material, and that this dense material comprises a material which provides electrical resistance properties therein, including a positive temperature coefficient (PTC) to limit the maximum temperature that the heating device (32, 314, 36, 38, 140) can reach. Device according to claim 1, characterized in that it is provided with electrodes, that the electrically conductive, dense material is shaped to be relatively large in one dimension and relatively small in the other, for example a sheet, and that the electrodes are spaced apart in the smallest dimension, and that the current passes through the thickness of the dense material. Device according to claim 1 or 2, characterized in that the heating device comprises a first layer (310 of conductive polymeric material having a positive resistance temperature coefficient and a surface-to-surface contact with at least one surface of the layer, a second layer (32 or 36) of conductive polymeric material 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 (38, 140) positioned so that the current flowing between them passes through at least partially constant power and the first layer (314) ) from one surface to another. Device according to claim 3, characterized in that the constant power layer (32, 36) is placed against the surface of the first layer (3 * 0) and that the electrodes (38, 40) are all in contact with the unchanged layer. with. Device according to Claim 1, characterized in that it has a device, in particular a clamp (64, 66, 84, 84a, 84b), which is arranged between at least two openings (19, 21, 23) for lines at the same end of the sealing device. to keep opposite parts (10, 12; 96, 80) in contact with each other during recovery. Device according to any one of claims 1 to 5, characterized in that at least part (26) of the device is tubular, at least when it is in place to cover and seal its base part (12). Device according to one of Claims 1 to 6, characterized in that the device has, at least on the surface which comes into contact with the base part (12) to be covered, a coating which is a heat-activated adhesive or sealant (71). Device according to any one of claims 1 to 7, characterized in that the edge regions (16, 50) of the upper part (10) and the lower part (12) of the device are adapted to be brought together and held together during recovery to form a generally tubular device , 52, 54, 83, 85). Device according to claim 1, characterized in that the device has a central part (26) for encapsulating the splice and at least one end of the element is adapted to return and seal on all the cables (20, 22, 24) separately. Device according to Claim 9, characterized in that a rigid, dimensionally stable container part (18, 18a) is arranged in the central part (26) to surround the extension as the reversible central part (26) of the element adapts to the appearance of the part. 27 64482 Device according to any one of claims 1 to 10, characterized in that it also comprises an insulating polymer mixture on at least one side, optionally on both sides, which layers (30, 31) are thermally recoverable. Device according to any one of claims 1 to 11, characterized in that a desiccant container (95) 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. Use of a device according to any one of the preceding claims as a cover for a cable splice. 64482 28