SE447434B - PROCEDURE FOR ENCAPLING A CONNECTOR BETWEEN MULTIPLE TWO CABLES OR SIMILAR LONG-TERM FORMAL - Google Patents

Description

15 20 25 30 35 447 454 can again be applied to a joint, and which does not require access to a free end of the cable. The new construction is not attributable to the so-called the type of cover because it encapsulates a joint in a slightly different way than the above-mentioned "cover closures". In alternative embodiments, the splice case is based on the use of either a "collet structure" or a base plate and lid.

An embodiment of the invention is based on the use of a splice casing capable of recovering and encapsulating a cable or other splice when exposed to an external heat source, e.g. a propane flame or hot air blower. Many applications for splice covers include use on site where the splice is relatively inaccessible or in a potentially hazardous environment and great care must be taken when mounting the splice cover.

When connecting overhead telephone cables, or in mines and other premises that may contain flammable gases, for example, the use of an open flame for recovery is often not only risky but sometimes prohibited. In such cases, a cover closure, ie. a splice casing, which does not require the supply of external heat, in particular a flame, can be particularly advantageous.

In a preferred embodiment, the splice housing is therefore provided with a built-in heating device, i.e. the splice cover contains an integral electric resistance heater which, when connected to a power source, has the ability to generate heat in a sufficient amount for the splice cover to be recovered and encapsulate the splice. This heat-recoverable splice housing does not require an external heat source but can instead be made to recover by simply connecting it to a power source, either an accumulator or an electrical network, e.g. a 12 or 24 V battery or a 115 V or other suitable electrical network, and which when connected to the power source will recover and can also activate an adhesive or sealant on its inner surface. 91 10 15 20 25 30 35 447 434 When assembling the materials that provide the integral heating element for use in the splice housings, arrangements and compositions that provide even heating are important. For applications where the heating element must provide heat activation of an adhesive or sealant, as well as heat recovery of the device, relatively high temperatures of the order of 120-200 ° C must be achieved, but are carefully controlled. If the temperature were to exceed that required for the recovery of the splice casing and the activation of the adhesive, the sealing device, i.e. the joint cover, and / or the part intended for sealing, e.g. the cable, is permanently damaged, which is often not shown by visual inspection of the recovered splice case and immediately adjacent areas of the cable.

Thermostats and / or other heat-regulating devices can be used to regulate the temperature of the device during recovery and after completion of recovery. For many applications, however, this overturns the purpose of using a built-in, ie. self-heating, sealing systems, as expensive, sensitive and / or bulky external temperature control devices must be used in places that are sometimes virtually inaccessible. In addition, the control device only senses the temperature in its immediate vicinity, while other areas of the casing may have significantly lower or higher temperatures.

In recent years, a new approach for electric heating devices has been the use of self-regulating heating systems based on the use of plastic materials which exhibit electrical resistivity properties with a positive temperature coefficient (hereinafter referred to as PTC properties or materials). Such materials generally consist of crystalline thermoplastics with an electrically conductive granular filler.

The distinguishing feature of these PTC materials is that a rapid increase in resistance occurs upon reaching a certain temperature. The temperature at which the resistance increases sharply is often called the switching temperature (TS) because the current at this point tends to turn off, whereby permanent damage to the heating device itself or to any object heated thereby is prevented by a further rise in temperature.

Although a number of theories have been proposed to explain this sudden increase in the resistance of the PTC material, which usually occurs around the crystallite melting point of the material, it is generally assumed that such behavior is related to the difference in thermal expansion of the conductive filler and thermoplastic matrix. at the melting point. For a more detailed discussion of a number of 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, lay, No. 6.

In most self-regulating heating devices with a PTC material, steep R = f (T) curves are calculated at approximately the TS temperature so that the device is switched off completely above this temperature but that a relatively constant output power at a given voltage is achieved below this temperature. At low temperatures the resistance is kept at a relatively low and constant level and the current is relatively high for a given voltage.

The generated energy is given off in the form of heat, whereby the material is heated. The resistance is kept at the relatively low level up to the TS temperature, when a rapid increase in resistance occurs. With the increased resistance, the effect and thus the amount of heat developed is reduced, and for extremely steep R = f (T) curves, the heating is stopped. When the temperature drops, the resistance decreases, whereby the output power in turn increases.

When a voltage is applied across a PTC heating element, the developed energy generally causes a rapid heating of the PTC element up to its TS temperature, after which little further temperature reduction will occur due to the fire. UI 10 15 20 30 35 447 '434 take the increase in resistance with temperature. Due to the steep increase in resistance, the heating element will theoretically reach a state of durability approximately at the TS temperature and thereby automatically regulate the heating effect without having to rely on fuses or thermostats.

Thermoplastic PTC materials, previously considered, are highly crystalline and have a TS temperature approximately at the crystallite melting point. In most such materials, however, the resistance decreases again at a temperature much higher than the melting point. This reduction in resistance is generally undesirable, especially when the PTC material itself is heat recoverable or used in the immediate vicinity of a heat recoverable material to cause it to recover, as in such conditions it is preferred to heat the heat shrinkable material as quickly as possible. to its melting point (ie using high power densities) and then keep the temperature of the heater very insignificant above the melting point of the thermoplastic component or components of the heater to facilitate rapid and efficient shrinkage of the heat recoverable device. However, such heat recoverable devices as are encompassed by the present invention are intended to be used for encapsulating and sealing joints between, for example, telephone cables by crimping against and securely bonding, usually using an adhesive, to the cable sheath, which usually consists of a low melting, partially crystalline, thermoplastic composition, e.g. a carbon black filled ethylene vinyl acetate copolymer. Such cable sheaths are almost always non-crosslinked and will therefore easily float and warp if heated to too high a temperature (ie above their melting points) for the time required at such a temperature to activate an adhesive. An even more serious result would be the result of a heating device which does not "switch off" in a very positive way, if the power supply of oversight was not switched off from the heat-shrinkable device. Under such circumstances, it would be conceivable for the PTC heater to remain switched on for periods which are far longer than what is required to complete the encapsulation process, which only needs, for example, 10 minutes. The above considerations are even more important if the individual conductors in telephone cables, as is often the case, are each insulated with similar thermoplastic compositions. Any disturbance of such wire insulations is unacceptable because the section of the cable in question thereby becomes inoperable. The joint housing heater should therefore preferably undergo a steep and far-reaching increase in resistance above the Ts temperature of the heating element, and this increase in resistance should continue as the temperature of the heater rises above the melting point of the thermoplastic component, instead of decreasing more or less steeply. , as happens with most, not to mention all prior art heaters. This reduction in resistance at temperatures above the TS element's temperature is a problem that generally does not seem to have been noticed before.

Furthermore, it has previously been generally assumed that conductive polymeric materials with PTC properties do not have sufficient heating capacity to effect recovery of relatively thick sections of such heat-recoverable materials which are suitable for the splice casing according to the invention, nor sufficient heat capacity to activate the high melting glues which have also been proposed for use according to the invention.

The shortcomings of the prior art PTC material for devices such as the splice case according to the invention can be largely remedied by using the compositions described in our patent application 7510846-4, and by using constructions of the type described in our patent application 7510844 -9, both submitted today. It should be noted, however, that prior art PTC materials, although not preferred, are in many circumstances suitable for use in the splice case. During use and operation of telephone cables, especially when the individual wires are insulated with paper dielectric, it is required that moisture be kept out, as the electrical properties of the wire deteriorate if the moisture content of the wire insulation rises above a certain, relatively low critical level. . Therefore, when splicing cables in the assembly immediately before closing, place a small paper bag with a desiccant (usually silicic acid gel) in sufficient quantity to keep the joint's internal moisture at a very low level for the entire life of the joint, regardless of the humidity. outside.

In a typical case, about 50 g of silica gel could be used. However, it may be that the desiccant is sometimes forgotten or that the bags (which are usually sealed for storage) are sometimes forgotten in an unsealed state for a long time before use or that they are even dropped into water or wet dirt and nevertheless placed as desiccant. at the joint.

However, an excessively high moisture content leads to an unacceptable decrease in the insulation capacity of a paper-insulated cable.

At 30% relative humidity and 15 ° C, the insulation resistance of paper-insulated wires of the type often used in telephone cables decreases to an unacceptable level of about 0.5 Gohm / km.

Below 30% relative humidity, the insulation resistance is acceptable. We have found that the moisture inside the joint casing does not need to be kept at the lowest possible value, but that it should as far as possible be <30%. Unexpected and surprising advantages are obtained by encapsulating the desiccant in a container whose water vapor permeability has been carefully matched to that of the splice casing itself so that the relative humidity inside the splice casing under all normally expected conditions can be kept below 30% independent of the relative humidity outside. of the following calculation.

If a typical splice casing according to the invention described in SE patent specification 7510845-6 at 15 ° C has a permeability for water vapor of 100 pq / h at 100% relative humidity on the outside and Ut relative humidity on the inside, the container for the desiccant permeability of> 100 pg / h at 10 15 20 25 30 35 447 434 30% relative humidity or> 333 ng / h at 100% relative humidity. Thus, if the container for the desiccant has a moisture permeability of 500 pg / h, the requirement is satisfied.

Let us assume that the container holds about 100 g of desiccant, e.g. silica gel, capable of absorbing about 50 g of water. Under storage conditions at 100% relative humidity without other protective cover, the desiccant stored in the container would thus lose half its absorbency within approximately 6 years. A container of this type permanently placed inside the splice case will thus not lose significant drying effect even if the splice cover is removed from its protective cover during storage and periods of several months before use.

A particularly advantageous feature of some of the self-heating splice covers according to the invention described in SE patent specification 7510845-6 is their potential re-insertability.

The cover can be reconnected by simply connecting the assembled splice cover to a power source, waiting a few minutes for the adhesive to soften, removing the electrical contacts and clamps at the sides and ends (if left on the splice cover) and separating the top and bottom halves of the splice cover. After necessary changes to the individual joints or replacement of any part, the entire joint housing can, if desired, be reassembled as before and briefly connected to a power source so that the adhesive joints are re-established to provide an assembly with maintained structural integrity. The ease with which the splice case can be put back into operation means that, if not all cable folds are required during the initial assembly, one or more plugs can be used, which are dimensioned to keep the excess folds in an extended condition during the original assembly. During the following re-insertion, additional cables can be added at any time and any new components sealed as effectively as any of the original components. Re-insertion of the self-heating splice covers can also be accomplished using an external heat source to melt the adhesive. kfl 10 20 25 30 447 434 An object of the invention according to SE patent specification 7510845-6 is to provide a heat-recoverable closure device which is suitable for encapsulating a plurality of cables of different sizes.

Another object of the invention according to the patent specification is to provide a heat-recoverable closing device which can be threaded over or laid around cables, and which can have self-heating ability to seal such cables without the aid of external heat sources.

A further object of the invention according to the patent specification is to provide a self-heating closing device with self-regulating ability which prevents overheating and thereby caused permanent damage to the encapsulated object but which on the other hand is such that the current does not switch off at a temperature below the calculated the temperature.

The invention according to the patent specification provides a heat-recoverable device, e.g. a splice housing, preferably with a built-in heating device, which heating device preferably comprises a material with a resistivity which has a positive temperature coefficient (PTC material) so that the emitted heating effect is regulated without the aid of external temperature control devices. The device is designed in such a way that it can be placed around a joint and then brought back to heat and seal the joint by heating. By the terms "built-in heating device" or "self-heating" is meant that a splice case with such a feature comprises an electrical resistance element which, by connection to a current source, e.g. a battery or AC mains, will emit heat in sufficient quantity to shrink the shrinkable part of the splice case and activate (eg melt) any glue present in the splice case. The invention also provides a collar cover without the self-heating feature (ie does not contain an electrical resistance element), but shrinkage and activation of glue is achieved using an external heat source.

The invention according to the patent specification 7510845-6 thus provides a heat-recoverable device which is capable of being placed around a pipe joint which is to be covered and sealed by it through its recovery, whereby for the device in particular characterized in that it has a heating device connectable to a power source, comprising a material formed of an electrically conductive polymer composition capable of heating the device to a temperature sufficient for its power when connected to a power source. recovery.

The material of the electrically conductive polymeric composition suitably has a resistance with a positive temperature coefficient and is suitably shaped in such a way that its length and width are large compared to its thickness, and preferably have the shape of a layer or a disc, and electrodes are placed in such a way that current will flow through the thickness of the material, ie. in the case of a layer or a disc, from one side to the other.

The heat-recoverable parts of the device suitably consist of a polymeric material which has changed dimensionally from a heat-stable configuration or shape to a dimensionally heat-stable one, with the ability to recover to or in the direction of the stable shape upon application of heat. At least a part of the material forming the heating device preferably also forms the dimensionally heat-unstable part of the device.

It should be emphasized that the special heating device and the properties of the composition and the electrodes in a special case will of course be chosen with special regard to the nature of the current source available to the user.

The composition is suitably a crystalline polymeric material, in which suitably carbon particles, in particular carbon black, are dispersed. The polymeric composition is suitably crosslinked by chemical means or by irradiation, and the polymer, the conductive particles and the proportion thereof will be selected in view of the end use and the available power source.

The parts of the surface of the device which will face the substrate to be covered and the parts which will come into contact with each other when the device is placed over the substrate are suitably provided with a coating of a heat-activatable sealant or glue, which is preferably activatable approximately at the device's recovery temperature. The interlocking parts are preferably provided with means for holding them in engagement during recovery. The central part of the device may be provided with a heat-stable insert, which will define a cavity for enclosing the joint, while the end parts are shaped to recover individually around each of the cables etc., which are joined in the joint.

The heating device is suitably self-regulating and comprises a first layer of electrically conductive polymeric material with a positive temperature coefficient of resistance, and in surface contact with at least one side of the layer, a second layer of electrically conductive polymeric material with a substantially constant resistance at least up to the recovery temperature of the device to provide a substantially constant output power at a given voltage, and at least a pair of electrodes positioned so that current passing between them will pass through at least a portion of the constant power material and from one of the first layers side to its other side.

Preferably, a constant power layer is provided in surface contact with the first layer, and each of the electrodes is in contact with a constant power layer.

The device preferably contains an insulating layer, which can also be heat-recoverable. In some cases, the device described in SE patent specification 7510845-6 can be made to recover by means of an external heating device, and in such cases the conductive layers and electrodes can of course be omitted.

The present invention relates to a method for encapsulating a connection point between more than two cables or similar elongate objects, wherein an at least partially heat-shrinkable sleeve is arranged around the connection point and the parts of the sleeve which are heat-shrinkable are heated to at least recovery temperature. The method is characterized in that the sleeve is arranged around the connection point in such a way that at least two cables pass into the sleeve through one end of the sleeve and that two opposite points on the sleeve between at least a pair of cables which pass in or out at one end and which are almost parallel to each other are brought to rest securely against each other during recovery to form an input to each cable.

The optional built-in heater suitably consists of a polymer with an electrically conductive filler dispersed therein to enable the polymer to conduct current at a given voltage (eg 12 or 24 volts from a battery), at the same time in that at its operating temperature it has sufficient resistance for its emitted heat effect to be able to bring a relatively thick section of heat-recoverable material, of the order of a few millimeters in thickness, to warm to its recovery temperature and recover around the joint intended for encapsulation. . In addition, the heating device is suitably capable of emitting sufficient heat output to activate a thermoplastic or curable high temperature adhesive or sealant.

When a PTC material has the shape of a structure with two comparatively large dimensions and a comparatively small dimension, e.g. a layer such as a wafer, current passage along the down small dimension is preferred for more uniform heating. When the current flows along the plane of the PTC layer, this can result in localized heating along certain conductive paths, which results in an uneven heat development.

This in turn can give rise to even greater problems that make the entire heating device unusable for a larger part of its heating cycle. If localized heating causes the material to reach the TS temperature along a line perpendicular to the current path, this will impede the current flow in the transverse direction of the path, and in fact cause the heating device to switch off until the temperature of the "hot line" thus formed falls. The "hot line" across the layer between end electrodes thus effectively shuts off the heater even if only a small area of the layer has reached the TS temperature, making the heater so inefficient that it appears to have very low heating capacity. The problem of the formation of a hotline can be minimized by placing the PTC material between the electrodes in such a way that the length of the conductive paths over which a hotline can occur is minimized.To maximize efficiency with the shortest possible current path, the ratio of the layer length must and thickness is minimized, this is achieved, for example, with a disc in which electrode are laminated on both sides of the PTC material. However, due to the short current path and the limited surface area required for some applications, the heating for such a configuration may be insufficient at lower inputs. In order to remedy this, a material capable of emitting constant power or Joule heat at a given voltage is preferably laminated, i.e. a material that does not exhibit PTC properties, with the PTC layer so that the laminate provides a good heating effect and despite this is self-regulating, without any hotline being formed. For a more detailed discussion of the advantages of conducting a current through the layer as opposed to conducting it in its longitudinal direction, and the manufacture of a layered self-regulating heating device, reference is made to patent application 7510844-9. For a more detailed discussion of suitable PTC compositions which are preferably used as layers, especially at relatively high temperatures, reference is made to patent application 7510846-4.

Such compositions consist of mixtures of thermoplastic and elastomeric materials with conductive materials dispersed therein. As previously mentioned, such mixtures show a steep rise in resistance approximately at the melting point of the thermoplastic component, and the resistance then continues to rise with temperature. Due to the increased safety margin ensured by the continued increase in resistance above the melting point, such heating devices can be used to control ("switch off") at temperatures above the theoretical TS temperature and have resistances that are significantly higher than the resistance at the Ts temperature, but nevertheless eliminates the risk of heat rush and / or burn-out, which occurs when previously known PTC compositions are used in such constructions. with the thermal load, especially when the increase in resistance with temperature is very steep at temperatures above TS.They can also be designed to generate very high effects up to TS temperature when connected to a power source.Due to their excellent temperature control, they are used to activate adhesives and bring heat-recoverable devices, such as according to the present invention, to recover around substrate, e.g. thermoplastic telephone cable sheaths, with reduced risk of melting or deformation of the substrate, even if they would be connected to the power source for a longer period of time.

It should be emphasized that a number of sealing means for the splice casing can be used, including an adhesive as discussed above.

The sealing means should be such that it resists the heat recovery forces at the recovery temperature, see e.g.

U.S. Pat. Nos. 3,379,218 and 3,455,336. The method provided for encapsulating joints according to the invention differs substantially from previous methods and thereby remedies to some extent or otherwise avoids some of the shortcomings that characterize these. For example, when the heat recoverable folds in one of the preferred embodiments of the invention are placed around the substrate, e.g. the cable, they enclose the substrate in such a way that the opposite heat-recoverable surfaces do not come into contact with each other but meet opposite surfaces of, for example, long fingers which form ridges on the mating surfaces of the non-heat-recoverable base part. As will be apparent from the following more detailed discussion, another significant departure from the prior art is the fabrication of a cover or splice case of a combination of a heat shrinkable and a heat stable member as well as in some preferred embodiments so that the surfaces of the adjacent ones the abutting parts delimit the cavity containing the cable joint.

It has long been known that when a heat-recoverable part is folded or wrapped around a substrate and shrunk, the area in which the heat-recoverable part is joined and fixed with a closure part forms a weakness area both mechanically and in its resistance to the environment, e.g. ex. against water penetration. The above-mentioned Ellis patent describes ways to solve this problem by using a structure with an overlapping flap below the abutting edges of the heat-recoverable part and attached to the overlying layer by means of an adhesive to provide a long path for leakage. However, this solution fails if the substrate does not provide a stable substrate against which the heat-recoverable seal can press the flap to cause the adhesive to float and wet the facing surfaces. If one adds to this factor the difficulty of constructing a splice casing with several inputs with overlapping heat-recoverable areas, it will be appreciated that a device constructed according to Ellis' patent does not solve all the problems solved according to the invention, although in most cases it is extremely useful. . These problems have been solved in a surprisingly simple and highly efficient manner by the preferred approach according to the invention. The optional arrangement of an intermediate ridge or finger on the non-heat-recoverable base part in combination with the clamps and flanges on the heat-recoverable part, which flanges can be fitted exactly because the heat-recoverable part in these areas contains non-heat-recoverable segments, facilitates the possibility of achieve this highly desirable result.

The invention will be described in more detail below with embodiments selected by way of example only with reference to the accompanying drawings.

Fig. 1 is a perspective view showing a first embodiment of a heat recoverable device, i.e. a splice sheath, in which a plurality of cables of different dimensions have been placed and spliced; Fig. 2 is an end view of the device according to Fig. 1 before expansion to its heat unstable, i.e. heat recoverable form; Fig. 3 is an end view of the device after expansion to its heat unstable shape; Fig. 4 is an end view of the device after it has been recovered around cables; Fig. 5 is a sectional view taken along line 5-5 of Fig. 3 showing in more detail the layered construction of the device; Fig. 6 is a perspective view showing the device before the insertion of the cables; Fig. 7 is a perspective view showing an alternative embodiment of a device constructed according to the invention; It should be noted that Figs. 1-7, with the exception of Fig. 5 and the schematic electrical circuit of Fig. 6, are illustrative examples of a splice housing whether or not it is provided with a built-in heating device. or not. Fig. 5 shows a sandwich construction which exemplifies an embodiment in which the splice housing is provided with a self-heating device. Figs. 8-11 show the construction of a second preferred embodiment of a splice casing constructed according to the invention.

Fig. 8 shows a cross section through one end of the splice housing; Fig. 9 is a perspective view of one end cut through to show the details of the structure; Fig. 10 is a perspective view showing the splice case seen from below the non-heat recoverable base portion; Fig. 11 shows a longitudinal section through the joint housing with details of its inner cavity; Figs. 12-19 show details of the preferred method of making a third preferred embodiment of a splice case; Fig. 12 shows the fabrication of the preferred electrodes in the form of flat wire braids; Fig. 13 shows the laying of electrodes over the busbars and the attachment thereto; Fig. 14 shows different layers of the blank for the heat-recoverable part placed in a jig before lamination; Fig. 15 shows the blank during molding to the basic shape of the heat-recoverable part; Fig. 16 shows the heat-recoverable part in its heat-stable configuration after the bridging of the plastic material; Fig. 17 shows the construction of the reinforcing flanges for the ends and sides of the heat-recoverable part; Fig. 18 shows how the Elänsarna were placed on the heat-recoverable part clamped in a jig before expansion; Fig. 19 shows the heat recoverable part at the end of the expansion step; Fig. 20 shows the upper and lower parts of the joint housing in perspective to show further details of the interior; Fig. 21 shows the especially preferred embodiment after mounting around a cable splice; Fig. 1 shows a closing device for receiving a plurality of cables and with an extended central part for receiving a joint between the cables. Such a configuration is particularly suitable for low current cables, e.g. telephone cables, where a number of cables must be spliced quickly and efficiently at the lowest possible cost.

The device shown in Fig. 1 may be made exclusively of a heat-recoverable material, preferably with a self-heating composition laminated therein, as shown in Fig. 5, as will be explained in more detail below. Alternatively, only the part of each end of the splice case which comprises the folds, i.e. the part of the splice housing which is located between the ends thereof and the dashed lines 18, be heat-recoverable while the central part is non-heat-recoverable. The material in the layer or layers of the heat-recoverable material is cross-linked, e.g. by irradiation, to make it heat recoverable. A heat-recoverable part, consisting of a layer 10, is in its stable, unexpanded state placed with folds 11 as shown in Fig. 2. The unexpanded folds can of course have any shape, including the general shape of the cable, provided that the material is in sufficient excess to be able to expand 10 15 20 30 35 447 454 19. The folds are expanded in a known manner to a dimension which is larger than the diameter of the cables intended for splicing, as shown in Fig. 3. The material is sufficiently elastic and flexible that the cable can be threaded into the opening in the fold. As best seen in Figures 3 and 4, the openings may be of varying dimensions depending on the size of the cable to be inserted, although it should be borne in mind that a fold with a single size of the opening is capable of recovering over cables. with different sizes and seal these. The heat-recoverable part 10 is mated to a bottom part of the splice housing 12, which is not recoverable, although, as shown in Fig. 7, for example, in some embodiments it may be heat-recoverable. The bottom part 12 can serve as a permanent assembly for the cable joint and give the system rigidity. Alternatively, the parts 10 and 12 may be connected by a hinge at one edge 14 (Fig. 4) with a closing device at the opposite edge 6.

In the case where the parts 10 and 12 are formed of the same material, they may alternatively be integral with each other at the edge 14, a closing device being used at the edge 16, or the parts 10 and 12 may be completely separate from each other at both edges 14. and 16, in which case the heat-shrinkable part 10 only needs to be lifted from the part 12 for the insertion of the cables. If desired, the parts 10 and 12 can be provided with embedded reinforcement bands in the longitudinal direction, preferably next to the edges 14 and 16. Such bands can also serve as busbars.

When closing the cable joints, the parts 10 and 12 are separated and cables 20, 22 and 24 are placed therein. With reference to Figs. 2, 3 and 6, where the parts 10 and 12 are neither made continuous with each other nor connected with hinges, a tensioning device is used, e.g. conductive clamps 52 and 54, such clamps being clamped by means of a screw 56 and a wing nut 58. The clamps can serve to hold the parts 10 and 12 together during the expansion (Fig. 2) as well as during the insertion of the cables and the recovery of the parts. 20 25 30 35 447 434 20 (Fig. 4). Although such clamps could form a permanent part of the assembly, they are preferably removed after assembly and an adhesive, e.g. that described in U.S. Pat. No. 3,770,556 is used to permanently seal the edges. Even at the ends, it is also best to ensure a correct distance between the cables with the help of a clamping device.

As best seen in Fig. 6, this may consist of a plate separator 62 with openings therein for receiving the folds 11 (Fig. 2).

This plate holds the parts 10 and 12 tightly together by means of clamps 64 and 66 during the expansion and sealing operation. .

In order to provide the device with increased strength and additional protection and, if necessary, be made impermeable to water vapor and shielded against radio interference, the cable joint itself may be encapsulated in a rigid sheath inside the housing, with an outer structure limited by the dashed lines. 18 and 18a below the central part of the heat-recoverable part 26 in Fig. 1. If the central part 26 is heat-recoverable, it will adapt to the shape of the jacket, which can suitably be made of any rigid material. at any time, including metal fl clay molded plastic. The end openings 19, 21 and 23 are adapted to receive individual cables of varying dimensions. The other end of the heat-recoverable part is usually provided with openings of similar dimensions to receive the splicing cables, although all the openings may be located on one side.

When a rigid jacket is used to cover the joint, sealing at the central part by means of the heat-recoverable part may be unnecessary. As mentioned earlier, the heat recoverable part of the device can therefore be limited to the end parts so that it will seal the individual incoming cables up to the rigid sheath. In this case, the central part 26 may consist of a non-recoverable material or need not be made to recover, if it is recoverable. Alternatively, the material need not extend 10 15 20 25 30 35 40 M 447 434 across the jacket, but this may be left exposed, or only need an insulating layer, e.g. layer 30 or 31 in Fig. 5, extend over the casing since the remaining layers are limited to the ends.

The heat-recoverable casing shown in Fig. 5 preferably consists of a self-heating laminate with electrodes embedded therein which are connectable to a suitable current source. A suitable laminate is described in more detail in co-pending patent application 7510844-9. The laminate consists of an outer insulating layer 30, which is heat-recoverable, a layer 34 consists of a polymer or polymer mixture, e.g. a mixture of a highly crystalline polyolefin and an ethylene-propylene rubber, with conductive carbon black dispersed therein. The layer 34 preferably has a resistivity with a positive temperature coefficient for controlling the heating. The layer 34 is preferably laminated between layers 32 and 36, which may also consist of polynermic mixtures with carbon black dispersed therein, these layers at a given voltage preferably giving constant output effects over a wide temperature range and not exhibiting any significant properties of resistivity with a positive temperature coefficient. . An inner insulating layer 31 can also be provided. Layers 31, 32, 34 and 36 are preferably also heat recoverable. The inner layer may advantageously contain an adhesive layer (not shown) on its free surface for bonding and sealing to the cable.

Electrode grids 38 and 44 have been embedded in the constant power layers 32 and 36 for connection to a suitable current source, e.g. a battery as schematically shown in Fig. 6. This configuration causes the current to pass through the PTC layer 34 from the electrode 38 to the electrode 40. A preferred type of electrode construction and shape will be described below.

Fig. 7 shows an alternative configuration of the device.

Such a configuration can be formed and expanded using a single board, generally with the laminated configuration according to fic. 5. After the cables have been inserted through the openings 44, 46 and 48, the device is closed by joining the opposite edges 50 of the disc by means of a suitable locking device 51. Such a device can of course be adapted to the shape. of different cable diameters and shapes as shown.

It can be a "collet structure" with a locking device at 50 and self-guided at 47.

A particularly preferred embodiment is shown in cross section in Fig. 8. It consists of upper and lower parts 96 and 80. The upper part 96 consists of an outer joint housing 67 attached to a heating device, which consists of outer and inner layers 68, 70 of constant power material. and a core layer 69 of PTC material. An adhesive layer 71 has been applied to the inside of the inner constant effect layer 70. The PTC core 69 of the heating device, which is preferably constructed as described in patent application 7510846-4, is combined with surrounding layers 68 and 70 of compositions whose thermoplastic polymer constituents, if such are present, have a lower melting point than that of the thermoplastic polymer component of the PTC composition. If the constant effect layers contain thermoplastic polymers, they can be made heat-recoverable, and in addition an additional outer shell 68 is preferably provided, which consists of a layer of a heat-recoverable polymer composition whose recovery temperature is lower than the melting point of the thermoplastic component of the PTC composition. . An additional layer 71 of a hot melt adhesive or a mastic may also be provided, the hot melt adhesive or mastic then having the same melting point as the thermoplastic component of the PTC composition and an activating temperature below its melting point. Such an embodiment has proved to be particularly advantageous when the substrate is heat-sensitive, i.e. if it deforms or floats when heated above its melting point.

As shown in more detail in Fig. 9, flexible and compliant electrodes 72 are embedded in the constant power layers. These electrodes can advantageously be formed of braided wires.

Each heat-shrinkable end fold contains six electrodes 72, three of which are interconnected for connection to one power outlet and three to another, the electrodes being arranged in pairs opposite each other and running perpendicular to the longitudinal axis of the housing. . Electrodes of one polarity are (for example by welding, soldering or gluing with a conductive adhesive in the contacting surfaces) connected to busbars 73 and 73a, and with the other polarity to bushes 74 and 74a, which extends along each side of the housing. The busbars 73, 73a and 74, 74a may be constructed of wire braid or thin metal strip, which may be perforated. At the center of the busbar 73 on one side and at the center of the busbar 74a on the other side, ears 75 and 76 have been attached for connection to a power source. On the top of the primary heat-shrinkable layer (see also Fig. 8), reinforcing flanges 77, 78 and 79, made of a suitable rigid material, are attached along each side and between the heat-recoverable folds (eg by gluing). . Particularly suitable materials are metals, thermoplastics, e.g. polycarbonate, acrylonitrile butadiene-styrene and SAN plastics and filled polymers such as polyamides or polyolefins. Particularly preferred is a glass-filled polyamide (nylon). The lower part 80, which is not heat-recoverable, is preferably provided with external reinforcing strips 81 and possibly also inwardly directed cams 82 adapted to the open sides of the heat-recoverable folds, as also shown in Fig. 10. The splice cover can be closed by the upper and lower the parts are joined and locked with spring clamps 83, 84 and 85 which are suitably constructed of similar materials as the flanges 77, 78 and 79.

Fig. 11 shows a section along the longitudinal axis of the housing. A central cavity 86 serves to receive the individual spliced wires and cables. A small container 96 (filled with a desiccant) can advantageously be placed in the cavity, the walls of which allow water to diffuse through at a rate greater than the diffusion rate into the cavity of the splice casing, as previously explained in more detail. A valve may be provided to provide access to the cavity 86 to enable pressure testing of the assembled splice housing.

The preferred method of manufacturing a splice casing will be described in the following with particular reference to the embodiment of Figs. 8-11, with reference to Figs. 12-21.

The electrode material, preferably a metal braid, which can be formed, for example, of 16 support wires, each composed of four tinned approximately 0.1 mm copper wires, braided with the largest possible braid angle (to achieve a high degree of compliance), is formed around a thin, conductive or non-conductive thermoplastic tube. Excellent results have been achieved with a braid angle of 750 around a pipe with the same composition as the constant power material and with an outer diameter of 6.25 mm and a wall thickness of 0.25 mm. The braided tube is then heated to a temperature higher than the softening temperature of the thermoplastic tube and flattened, ensuring that the braid is not stretched. These steps are shown in Fig. 12.

The next step in the process is the construction of the electrode current collector system, consisting of attaching the ear 75 to the busbar 73a and then attaching the ends of the electrodes 72 thereto. Suitable fastening methods consist of spot welding, soldering and gluing. When the electrode consists of a wire braid around a conductive core of the same material as the constant power layer, it has been found that excellent results are obtained by hot bonding using the conductive thermoplastic core to bond the electrodes. The attachment of the electrodes to each other to form the basic configuration is facilitated by the use of a jig as shown in Fig. 14. In addition to the above-mentioned flattened braid, the material used for the electrodes may comprise knitted or woven or plated metal wires, conductive fibers or metallized polymer fibers or polymers. fibers containing conductive particles that have been treated in such a way that they have been made highly conductive in the fiber direction.

In all these embodiments, it is preferred that the resulting electrode be highly extensible and compliant so that it does not provide appreciable resistance to expansion or recovery _ _.._ ._ _.___........- ... ..mn _ 10 15 20 25 30 35 447 434 25 the heat-recoverable parts of the splice cover, as occurs during the splice cover's manufacture and assembly in operation.

Similar materials can be used for the busbars. Since these do not have to undergo any significant deformation during manufacture and assembly, they can also be formed from such relatively unstretchable and inflexible materials as sheet metal or otherwise high-conducting strips, preferably perforated and single or multi-strand material.

The construction of the blank for the splice case is shown in Figs. 13 and 14. The various heating layers, which are produced, for example, by extrusion, co-spraying or hot calendering, are suitably mounted in a jig gram. In the embodiment shown in particular, a surface layer 67 is placed in the frame and in turn a constant power layer 68a, the first group of electrodes 73 / 73a (with the ear 75 pointing to the right as shown in the figure), a further constant power layer 70a, the second group electrodes 74 / 74a (with the ear 76 pointing to the left), and a final constant power layer 70b laid on top. The entire structure is placed between protective layers 97 of the polytetrafluoroethylene and laminated together by heating under pressure. A jig is used to keep the different layers and electrodes fixed in relation to each other during lamination, whereby the lowest possible pressure is applied. After lamination and removal of the polytetrafluoroethylene layers, the assembled blank to the splice case is preferably laminated between foam rubber sheets 100 and heat treated, e.g. at about 185 ° C, for a time sufficient to allow the constituent layers with the lowest applied pressure to be thoroughly relaxed.

Depending on the materials used, heat treatment times of 2-60 minutes and more are suitable, with 5-15 minutes being preferred.

While the blank is still at the heating temperature, it is removed and formed over a convex mold as in Fig. 15 under pressure, as shown by the arrows, to form the unexpanded splice housing configuration shown in Fig. 16. In this operation as before, care is taken to ensure that the heating device 10 is not stretched during the forming operation. If desired, a plurality of, preferably wedge-shaped, cams can be arranged on the upper surface of the flanges 77, 78 and 79, which serve to conduct the compression forces exerted by the clamps 83 and 85.

The splice housing 87 is then irradiated with ionizing radiation using techniques known to those skilled in the art to ensure even irradiation. Suitable types of ionizing radiation include gamma rays, X-rays and accelerated electrons. The radiation dose must be sufficient to ensure the integrity of the structure over the crystalline melting point of any of its polymeric constituents, but on the other hand must not be so large as to adversely affect the extensibility of the material during the expansion step to form it into the heat recoverable form. A suitable radiation dose has been found to be 2-50 Mrad, preferably 5-20 Mrad. The blank, which after irradiation can be considered to be in a "heat stable" configuration, is then formed into the "heat recoverable" configuration 88 in the sequence of operations shown in Figs. 17-19. After a preheating sufficient for the article 87 to be heated to a temperature approximately corresponding to the melting point of its crystalline polymeric constituents, the shaped blanks are introduced into a jig 89 (Fig. 18). The reinforcing flanges 77, 78 and 79, the contact surfaces of which are coated with an adhesive 90 (Fig. 17) are placed on the sides and ends of the molded blank 87. The end flange 78 (and the corresponding flange at the other end of the splice case) is provided with a long interruptible tongue 91 with locating holes 92 for mounting in the jig 89 as shown in Figs. 17 and 18. All the flanges have folded lips 98 at their outer edges to serve to enclose and protect the edges of the heater from mechanical damage. The side flanges 77 and 79 have a small groove 99 in the middle of the outer edge which surrounds the electrode tongues 75 and 76 and is dimensioned to accommodate a 6.3 x 0.8 mm connection connector of standard type. 10 15 20 25 30 35 447 434 27 Pressure is applied to the side and the end flanges and the seams' folds and central cavity are formed by suitable expansion means. Such expansion technology is well known in the art and includes expansion with mandrel and pneumatic forming or vacuum forming. In this operation, care must be taken to prevent longitudinal compression of the folds when a mandrel is used. Suitable means for minimizing such compression include the provision of a radially expandable or peripherally segmented sleeve member between the mandrel and the crease, which serves to disengage the longitudinal insertion forces exerted by the mandrel from the crease. Alternatively, pneumatic or hydraulic expansion of a longitudinally blocked elastic hose can be used. The central cavity of the splice housing is preferably formed pneumatically.

The expanded blank is then cooled while being held in place as shown in Fig. 19, removed from the jig and coated with an adhesive layer 93 on the surfaces to be abutted against the lower part and on the inner surfaces of the folds. An adhesive layer can also be applied to the contact surface of the part 80. At this stage, if desired, a desiccant-filled container 95 may be attached to the inner wall of the central cavity 94 as shown in Fig. 20, illustrating the finished upper heat recoverable portion 96 where the relationship between the folds and the central cavity can be seen. Alternatively, the desiccant may be attached to the base plate as shown in Fig. 11.

After completion of splicing and insertion of the splices into the splice housing, this is assembled in the manner described above by joining the upper and lower parts 96 and 80 together and locking them with the side clamps 83 and 85 and the end clamps 84a and 84b. The heating device is then connected to a power source.

Due to the placement of the electrodes in the upper part of the splice case and the relative resistances of the constant power and PTC layers, when the heating device is connected to a current source, e.g. a 12 or 24 V heat accumulator, developed the heat for recovery and / or glue activation 10 15 20 25 30 35 447 454 28 mostly to take place at the folds and in the flange areas.

The central cavity thus does not develop sufficient power to be heated to a significant extent.

As mentioned earlier, the comf positions used in the heating layers can be selected in such a way that they give an extremely fast heating of the splice casing. When using the preferred PTC compositions of the above-mentioned type, it has been found, for example, that the heating device in the weekly area typically heats to 115-120 ° C in less than one minute.

Upon reaching this temperature, the weekly areas begin to recover. In about two minutes, the soft areas have shrunk around the substrate, e.g. the cable, and after a further 8-13 minutes, the adhesive layers have been thoroughly activated and have been wetted and sealed against the cable sheath and against the non-heat-recoverable base member. In a typical case, the heating device has thus been connected to the power source for about 10-15 minutes, during which time the installation can be left without supervision so that the fitter can continue with other operations. It will be easy for those skilled in the art to realize that the time during which the heating device is switched on will vary according to the temperature requirements of the adhesive, the thermal load and other factors. Surprisingly, it has been found that the required time is relatively insensitive to the ambient temperature. This is believed to be due to the extremely sharp PTC disconnection made possible thanks to the particularly advantageous construction according to the invention.

When a suitable time has elapsed, the power source is disconnected and the splice case is allowed to cool to ambient temperature, as the side and end clamps can be removed or left in place to provide extra mechanical protection if desired.

A particularly advantageous result of the combination of elements in the device according to the invention is that the splice case can be left electrically connected to the power source for a longer time (eg several hours) after the splice has been made, without damaging the telephone wires or cables, because heating device - U! 10 15 20 447 454 29 has a self-regulating ability to keep its temperature in a particularly limited range regardless of environmental thermal load, even if this temperature range is very close to the melting points of commonly used thermoplastic cable sheathing or individual wire insulation material.

To facilitate re-insertion, the device may be provided with shut-off means to prevent the complete recovery of the assembled recoverable part during its reheating in order to soften itself and to melt any glue. The barrier means may consist of rigid, e.g. metallic, tongues that will lie under the parts that will enclose the cable. A tongue with the same width as the flat part 78 between the cable inlets is shown in Fig. 9 placed on the surface of the flat part with a part extending axially outwards therefrom. Similar tongues can be placed on the outer flat surfaces 77 and 79 and all the axially extending parts are connected to each other by means of suitably shaped connecting links to form a continuous restraining device. This can, if desired, be left in position during use.

Claims (2)

10 15 20 _3. The method of claim 2, 447,434 A method for encapsulating a connection point between more than two cables or similar elongate objects, wherein an at least partially heat-shrinkable sleeve is arranged around the connection point and the parts of the sleeve which are heat-shrinkable are heated to at least recovery temperature, k ä characterized in that the sleeve is arranged around the connection point in such a way that at least two cables pass into the sleeve through one end of the sleeve and that two opposite points on the sleeve between at least a pair of cables passing in or out at one end and which are substantially parallel to each other are brought to abut securely against each other during the recovery to form an input to each cable. 2. A method according to claim 1, characterized in that a special cohesive member is applied to the end of the sleeve to provide the abutment. characterized in that a clamping device is fitted at the end of the sleeve to provide the abutment.