GB2145579A

GB2145579A - An assembly for terminating an insulated electrical conductor or for connecting two such conductors

Info

Publication number: GB2145579A
Application number: GB08417155A
Authority: GB
Inventors: Heinz Eilentropp
Original assignee: HEW Kabel Heinz Eilentropp KG
Current assignee: HEW Kabel Heinz Eilentropp KG
Priority date: 1983-08-27
Filing date: 1984-07-05
Publication date: 1985-03-27
Also published as: DD222169A5; FI842187A0; NO164570B; GB2145579B; SU1268116A3; IT1177891B; NL191526B; FR2552279A1; IT8448548A0; SE460163B; FI81221B; FI81221C; BE900096A; FR2552279B1; NL8402214A; CH663296A5; SE8402765D0; ATA176384A; AT386909B; NO164570C

Abstract

The assembly comprises an internally threaded sleeve (35) having at least one open end and a flanged body or bodies (21) having an externally threaded shaft portion (23) adapted to be screwed into the or each open end of the sleeve (35), and an outer flange portion (24). The or each flanged body (21) has an axial bore (26) through which the end of a conductor (30,31) is passed into the sleeve. The interior of the sleeve contains a plastic sealing compound (37). When the flanged body or bodies is or are screwed into the sleeve, the sealing compound is compressed and is forced into the threads to seal the end or ends of the sleeve. Adjacent the flange portion (24), the shaft portion (23) of the or each flanged body is provided with a region of greatly reduced cross-section, e.g. by means of a peripheral groove (39). Further screwing in of the or each flanged body causes the flange portion thereof to break off, thus rendering the termination or connection permanent. <IMAGE>

Description

SPECIFICATION An assemblyforterminating an insulated electrical conductor, or for connecting two such conductors The present invention relates to an assembly for terminating an insulated electrical conductor, e.g. a synthetic resin insulated conductor, or for connecting two such conductors.

At the presenttime, many different methods are used in the coupling and connection of electrical conductors. Thus, it has long been known to provide the points at which electrical conductors are connected together with windings made of self-welding or self-adhesive synthetic resin tapes and subsequentlyto subjecttheseconnection points to a heat treatment. However, the mechanical stability of such connections is inadequate in many applications.

It is also known, after the connection ofthe conductor ends, to surround the connection pointwith a sleeve into which a suitable liquid filler material is subsequently introduced from the outside through an opening. The liquid filler may be,forexample, a heat-hardening or self-cross-linking casting resin which, after having solidified, establishes a bond between the electrical conductors, together with their insulating casing, and the inner walk ofthe sleeve.

Sleeve connections produced in this way have the disadvantage, however, that owing to the difficulty of dispensing the liquid filler material, inclusions of air are difficultto eliminate, and the mechanical stability of such connections is therefore unsatisfactory.

For adaptation to increased operating temperatures, for example, in the case of electrical heating conductors or cables, the insulating materials forthe electrical conductorsfrequentlyconsistoffluorine- containing polymers which practically do not bond with casting resins unless a surface treatment is carried out which can often be accomplished only with difficulty on thefinished cable. Attempts havethere- fore already been made to producethesleeve connection by screwing, using sealing elements, although the seal, in particularwith regard to the penetration of moisture, is unsatisfactory and gives rise to disturbances in the operating behaviourofthe cable or conductor.Neither can such a sleeve connection be used in explosion-protected areas, where only permanent, i.e. non-separable sleeve connections are permitted.

These problems are overcome bythe use of a known sleeve connection (German Utility Patent No.

80 29 424) in which the connection point of the electrical conductors is surrounded byasleeve made of a material which has a high heat resistance and which contains a filler material consisting of a thermoplastic synthetic resin material which has a lower melting range than does the sleeve. This filler material produces an intimate connection between ttte insulations of the conductors, the innerwalls of the sleeve, and the sealing plugs which project into the ends into the sleeve. Such a connection, which also permits pressure-tight insertion in the case of hightemperature resistant cable or conductor insulations, necessitates the simultaneous application of pressure and heat during production.Although this known sleeve connection ensures reliable disturbance-free operation over a period of years, assembly problems canoccurwhena branch point or connection point has to be provided at locations where space is limited, with poor accessibility for assembly.

It is accordingly an object ofthe present invention to provide an assembly for connecting or terminating electrical conductors which satisfies the requirements as regards imperviousness and mechanical stability, but which can also be easily used at locations where space is limited and accessibility is poor. Moreover, for reasons of security, it is often required that the sleeve connection should be non-separable, i.e. that after assembly, the plugs sealing the ends of the sleeve should not be able to be slackened and removed from the sleeve itself.

According tothe invention,there is provided an assemblyforterminating an insulated electrical conductor, or for connecting two such insulated electrical conductors, comprising a sleeve surrounding the end orthe connected ends of the electrical conductor or conductors, and open at least at one end, said sleeve being internallythreaded at least in the region of its open end or ends; a flanged body or bodies adapted to be inserted into the open end or ends of said sleeve, the or each said flanged body having an innershaft portion provided with an external thread co-operating with the internal thread of said sleeve, and an outer flange portion, the shaft portion ofthe or each flanged body having a region adjacent to the flange at which the cross-section of the shaft is reduced to an extent greaterthan that produced by said external thread, and the or each flanged body having an axial bore through which the end of an insulated conductor can be passed into the interior of said sleeve; and a filler material contained in free space within said sleeve, said filler material having a plasticity such that on compression thereof by the screwing of said flanged body or bodies into said sleeve, the filler material is pressed into the free part of said internal thread and againstthethreaded connection of the or each said flanged bodyto said sleeve, so asto seal the end or ends thereof.

The internal thread which is provided along the length of the sleeve, in co-operation with the external thread of the flanged bodies, ensures the formation of a reliable labyrinth seal. This sleeve connection can be used for any desired conductor insulating materials, also, for example, for conductors which are resistant to high temperatures.

The assembly is simpletoform and the space requirement is small. With the sleeve positioned, for example, over a conductor connection point and a flanged body partially introduced at one end, the filler compound is introduced into the sleeve from the other end and the second flanged body is then screwed in.

When the flanged bodies are inserted further into the sleeve, the filler compound is pressed into the cavities inside the sleeve body, and also into the thread. Thus, it is only when the flanged bodies are screwed intothe sleeve thatthe filler compound is subjected to pressure. It has been found to be expedientforthe internal thread to extend along the entire length of the sleeve. Inaccuracies in the dispensing of the required quantity offiller compou nd can be compensated for byturningtheflanged bodies correspondinglyfurth- er, withoutthis leading to inaccuracies in the region of the sleeve.The cross-sectional reduction ofthe shaft oftheflanged bodies in accordance with the invention, meansthat, when theflanged bodies are introduced into the sleeve and the sealing compound is thereby compressed, the flange shears off from the shaft ofthe body atthe location ofthe part of reduced cross-section, as soon as the sealing compound has filled all the spaces in the sleeve and has been sufficiently compressed. When the flanges ofthe flanged bodies have sheared off, the sleeve can no longer be opened without destroying it.

The reduction in cross-section provided means that there is a theoretical shear point at the end ofthe shaft when a maximum torque is exceeded.To enable the shearing-offatthe end oftheshafttotake place reliably and to ensure a clean break, the reduction in the cross-section at the shaft end is preferably formed by a circular groove whose depth exceeds that ofthe threads.

Another possible way of forming the reduction in cross-section atthe shaft end is byforming one or more grooves or recesses which runstangentiallyto the surface of the shaft and whose depth exceeds that ofthethreads.Thisalsopermitsa reliable, non- detachable breaking ofthe sleeve connection.

Afu rther safeguard against the shaft becoming loose in the sleeve can be achieved iftheflanged bodies are recessed at that end of the shaft which projects into the sleeve. This means that when the flanged bodies are inserted into the sleeve, the sealing compound is simultaneously pressed into this recess which it entirely fills and thus prevents self-detachment. The conductors are led through axial bores in theflanged bodies. In orderto achieve an improved sealing in this region also, in the region ofthe shaft, at their surface which faces towards the conductor, the bores may be provided with sealing elements for example, in the form of so-called sealing lips.

It may sometimes be desirable forthe bore in the flanged body to have an enlarged diameterfor facilitating the introduction of the conductors in the region ofthe shaft. This ensures a reliable fixing of the conductor end in the insertion region.

Asthe sleeve connection is required to be nonseparable, to assist in this the flanged bodies may be recessed atthat end of the shaft which projects into the sleeve body. The filler material which engages into this recess in the screwed-together state safely preventstheflange bodies from slackening and thus prevents a self-destruction oftheforce-locking and shape-locking connection.

The flanged bodies are preferably introduced manually into the sleeve body, for example, by rotating them so as to screw them into the ends ofthe sleeve.

Forthis purpose, it has been found to be particularly advantageous to provide the flanged bodies at the flange end with a cross-sectional shape which is other than round, for example, such as to permitthe use of commercially available spanners.

If it is not a question of forming a moisture-tight connection between two conductors, but of connect ing the end of a conductor for example, to a monitoring device or a temperature measuring de vice, or if the conductorend is merely to beencapsu- lated so as to be moisture-tight, together with a corresponding probe, it is also possibleto use an assembly in accordance with the invention. For this purpose, however, it can sometimes prove expedient to use a cylindrical moulded body which is open atone end only, in which case the open end can be used to introduce, for example, a measuring probe with its associated connection line and forthe insertion of a flanged body, after the introduction of a filler material.

In the case of a conductor connection, it may also be advantageous to provide in the interior of the cylindrical sleeve, an additional guide bodyforthe conductor ends on both sides. As a result, these ends remain firmly fixed even when the filler compound is compressed, andthus operating disturbances are avoided from the start. In addition, the use of such a guide body leads to advantages if screened conductors, for example heaterconductors, are connected to one another and the screening wire lay must be carried separately in the region of the sleeve.

In the previously-mentioned case of heater conduc tors,orothercablesorconductorswhich are them- selves provided with insulation which is resistant to relatively high temperatures, it is particularly advantageous if the sleeve and the flanged bodies are made of a synthetic resin which is known to be resistant to the high temperatures likely to be encountered in use.

Examples of such high-temperature resistant resins includepolyamidesandfluoropolymers, particularly tetrafluoropolymers which cannot be processed in the molten form.

Cross-linked or non-cross-linked compounds having a silicone rubber base can be used asthefiller material for the sleeve connection or the end termina tion,and partially cross-linked silicone rubbers can also be used. The latter are particularly advantageous for use in association with sleeves and flanged bodies made offluoropolymers, since, in this case, good adhesive strength is achieved in the boundary surface area without preliminarytreatment ofthe surfaces.

Of course, there may also be used in the invention conventional casting resins which, when hardened, produce a compact connection and by engaging into the threads, ensure the required imperviousness because of the formation of a plurality of seriesarranged labyrinths.

The sealing effect can be improved if the internal and external threads are angular in shape. This serves to lengthen the paths in the labyrinth region and thus furtherto increase their effectiveness.

As already indicated with reference to an end termination, temperature sensors and/or delimiters can be contained, together with the conductorconnec- tion, in the moulded sleeve body. These can serve, for example, to interruptthe circuit when a specified temperature is exceeded in the case of a fault.

Independently ofthe particular application of the invention and ofthefillercompound orfiller material used, it has been found expedient to providethe wall of the sleeve with at least one bore. Such a bore can, onthe one hand, permittheescape of the air initially present within the sleeve during the screwing ofthe flanged bodies into the sleeve, and, on the other hand, it can serve asan optical control indication asto when the pressure oftheflanged bodies has uniformly distributed the compound contained in the interior into all the cavities so that compound spills overtothe outside.

The invention will now befurther described with reference to the drawings, in which Figure lisa schematic side view of a flanged body for use in an assembly according to the invention; Figure 2 is a schematic side view of an assembly according to the invention for connecting two insulated conductors; and Figure 3 is a schematic side view partly in section to illustrate the production of an assembly as shown in Figure 2.

The flanged body 21 shown in Figure 1 has a shaft 23, provided with an external thread 22. The body 21 also has a flange 24 at one end ofthe shaft and a recess 25 atthe opposite end thereof. The body 21 is provided with an axial bore 26 through which the end of a conductorto be connected is led, the interior of the bore 26 being provided with sealing lips 27.

Figure 2 represents the sleeve connection in the final mounted, inseparable state connecting two insulated electrical heater conductors. The conductive connection between the adjacent ends of the two heater conductors 30 and 31 is effected by means of a collet 32, in the interior of a sleeve 35. The connection of the two ends is fixed by means of an additional guide body 33 which is provided with a longitudinal groove 34 in which the conductor ends and the collet 32 are located. On that side of the guide body 33 which lies opposite the groove 34, i.e. on the rear sidle as illustrated, there is provided a corresponding second groove into which are inserted, concentric screening wires ofthe conductors 28 and 29 which are likewise connected by a collet and are assembled to form a bunch.Thus, the additional guide body 33 ensures a clean division of the conductor elements which are to be connected and further ensures an operationally reliable joint.

Flanged bodies as shown in Figure 1 serve to seal the cylindrical sleeve 35 so as to render it moisturetight. The sleeve 35 is provided with a continuous internal thread 36 which co-operates with the thread 22 on the shafts 23 ofthe flanged bodies when these are inserted into the ends of the sleeve.

The sealing or filler compound 37 may be, for example, an entirely or partially cross-linked silicone rubberwhich,whentheflanged bodies 21 are introduced into the ends of the sleeve is pressed into all the cavities in the interior of the sleeve and is simultaneously pressed againstthe enlarged sealing surfaces formed by the threads. A bore 38 in the sleeve 35servesto permitthe escape of residual air remaining in the sleeve and also has a control function. Excess filler material is led to the outside through this bore, and the presence ofthis material is evidence thatthe interior ofthe sleeve is actually full.

The sealing mass 37 also entersthe recesses 25 at the ends of the shafts so as to prevent self-detachment ofthe flanged bodies 21. The connection can therefore be considered to be self-securing.

In order to safeguard this moisture-tight connection against unauthorised or unintentional slackening of the flanged bodies 21, ascan be seen from Figure 1,at the end ofthe shaft 23 an annular groove 39 is provided which leads to a reduction in the crosssectional area ofthe shaft in this region. As can be seen from Figure 2, this reduction in cross-sectional area itself ensures that when the flanged bodies 21 are screwed into the sleeve 35 against the pressure exerted by the sealing compound 37, the flange 24 shears off. The flanges which have sheared off can be finally cut awayfrom the conductors by radial cuts.

The connection so formed producesendswhich are moisture-tight as regards the surroundings and it is no longer possible to separate the sleeve connection without destroying it. The lip seals 27 within the bores intheflanged bodies contributetothefactthat, during assembly, sealing compound is pressed from the interior, and thus in the region of each flanged body, the annular gap between the conductor 28 or 29 and the bore in the flanged body is safeguarded against the penetration of moisture.

In orderto producetheconnection shown in Figure 2, it is possible to proceed, for example, as shown in Figure 3. In this procedure, from the ends ofthe insulated conductors 40 and 41, the flanged bodies 42 and 43 respectively are positioned over the insulation ofthe conductors, which consists for example of polytetrafluoroethylene. At the same time, the sleeve 44 which, like the flanged bodies, is made of a synthetic resin material which is resistant to high temperatures, is placed overthe end of one conductor 40. After the bare electrical conductors 45 and 46 and their shields 47 have been connected together, these connections are pressed into the associated grooves formed in a guide body 48.The flanged body 42 is now partially screwed into the sleeve 44 and a filler material, e.g. a silicone rubber compound, is poured from a supplycontainer49 until approximately half the interior of the sleeve 44 has been filled. The guide body 48 is then drawn into the sleeve body 44 against theflanged body42 andfurtherfiller material is introduced into the sleeve 44to a level slightly below the upper edge thereof.

Finally, by screwing this end ofthe sleeve 44to the flanged body43 and screwing the two flanged bodies further into the sleeve, the filler compound is distributed under pressure into the cavities within the sleeve and presses against the thread to form a seal.

When the two flanged bodies 42 and 43 are turned further, the flanges of these bodies separate from the shafts. Immediately after the separation oftheflanges, the connection in accordance with the invention so produced is readyfor use.

Such a sleeve connection can have very small dimensions and although the assembly can be effected without any further outlay, it is operationally reliable becauseofthe simplicityof its construction and the means which are used. This also applies to the selection of materials, which are selected to be resistant to high temperatures for so-called heatresistant cables and conductors, or heater conductors, e.g. heater conductors insulated with polyfluorinated hydrocarbons, and cold conductors, i.e. the unheated terminal ends of a heater circuit.

Claims

1. An assemblyforterminating an insulated electrical conductor, orfor connecting two such insulated electrical conductors, comprising a sleeve surrounding the end orthe connected ends ofthe electrical conductor or conductors, and open at least at one end, said sleeve being internally threaded at least in the region of its open end or ends; a flanged body or bodies adapted to be inserted into the open end or ends of said sleeve, the or each said flanged body having an inner shaft portion provided with an external thread co-operating with the internal thread of said sleeve, and an outerflange portion, the shaft portion ofthe or each flanged body having a region adjacent to the flange at which the cross-section of the shaft is reduced to an extentgreaterthanthat produced bysaid external thread, and the or each flanged body having an axial bore through which the end of an insulated conductor can be passed into the interior of said sleeve; and a filler material contained in free space within said sleeve, said filler material having a plasticity such that on compression thereof by the screwing of said flanged body or bodies into said sleeve, the filler material is pressed intothefree part of said internal thread and againstthethreaded connection ofthe or each said flanged bodyto said sleeve, so as to seal the end or ends thereof.

2. An assembly as claimed in Claim 1, wherein said sleeve is in the form of a moulded cylindrical body.

3. An assembly as claimed in Claim 1 or Claim 2, wherein the reduction in cross-section at the end of the shaft adjacentthe flange ofthe or each flanged body is formed by a continuous annular groove, the depth of which exceeds that ofthe external thread.

4. Anassemblyasclaimed in any one of Claims 1 to 3, wherein the reduction in cross-section atthe end ofthe shaft adjacenttheflange ofthe or each flanged body is formed by one or more grooves or recesses which run tangentially to the shaft surface and the depth of which exceeds that ofthe thread.

5. An assembly as claimed in any one of the preceding Claims, wherein the or each said flanged body is recessed at its end surface remote from the flange, which projects into the sleeve.

6. An assembly as claimed in any one of the preceding Claims, wherein the axial bore ofthe or each flanged body is provided with sealing elements in the shaft region at its surface which faces towards the conductor.

7. An assembly as claimed in any one of the preceding Claims, wherein the axial bore in the or each flanged body has a diameterwithin the shaft largerthan that ofthe insulated conductor or conductors.

8. An assembly as claimed in any one of the preceding Claims,wherein flange portion of the or each flanged body has a cross-sectional shape other than round.

9. An assembly as claimed in any one of the preceding Claims,wherein the sleeve and the or each flanged body is made of a synthetic resin material which is resistant to high temperature and is based on a polymer which cannot be processed in molten form.

10. An assembly as claimed in any one ofthe preceding Claims, wherein the filler material is a fully or partially cross-linked, or non-cross-linked com pound having a silicone rubber base.

11. Anassembly for connecting two insulated electrical conductors substantially as hereinbefore described with reference to and as illustrated in the drawings.

12. A method of producing a sealed connection between two insulated conductors by the use of an assembly as claimed in any one of Claims 1 to 8, comprising the step at first positioning the sleeve and both the flanged bodiesovertheendsoftheconduc- tors to be connected; connecting the ends of the electrical conductors and any screening which may be present; lightly screwing one of said flanged bodies into the sleeve; introducing a sealing compound into the interior ofthe sleeve from the end which is still open; positioning the sleeve which contains the sealing compound overthe connection point of the conductors; screwing the other of saidflanged bodies into the open end of the sleeve; andfinallyscrewing both the flanged bodies intothe sleeve until thetwo flangesoftheflanged bodiesshearoff.

13. A method as claimed in Claim 12, wherein a further amount of sealing compound is introduced into the sleeve after the latter has been positioned overthe connection point ofthe conductors.

14. A method of producing asealedconnection between two insulated electrical conductors substantially as hereinbefore described with reference to Figure 3 ofthe drawings.