CA2127668A1

CA2127668A1 - Electric welding sleeve

Info

Publication number: CA2127668A1
Application number: CA002127668A
Authority: CA
Inventors: Alfred Thalmann
Original assignee: Streng Plastic AG
Current assignee: Streng Plastic AG
Priority date: 1993-07-23
Filing date: 1994-07-08
Publication date: 1995-01-24
Also published as: EP0635354A1

Abstract

A B S T R A C T

The invention relates to an electric welding sleeve (5) for welding tubular welding ends (R1, R2) made from thermoplastic materials or weldable plastics and provided with a filament winding (2) and contacts (3, 3') for supplying electric power, so that said electric welding sleeve (5) has a welding sleeve member (5.1) for receiving the filament winding (2) and a terminating means (5.2), that both of these has in each case positive anchoring points for simulta-neous radial and axial-tight connection and that the anchoring points are in the form of interengaging cavities (6, 6') and bulges (7, 7') and/or in the formof terminating means (5.2) engaging over the welding sleeve member (5.1).
(Fig. 4)

Description

P0768US 1 21276~8 ELECI'RIC '~ELDING SLEEVE

The invention relates to joints or moulded parts of tubular welding ends and relates to an electric welding sleeve for pressure pipes made from thermopla~
stics in accordance with the claims.

S ~ ,' ' :,, '-' ' In the case of electric welding sleeves for joining tubular welding ends made from thermoplastics, according to the prior art the sleeve body and the tubu~
lar welding ends to be joined are made from the same material, e.g. polyole-fins such as polyethylene. The sleeve body wall thickness is selected in materi-10 al-specific manner in such a way that the mechanical strength for both radialand axial loads corresponds at least to the mechanical strength of the tubular part to be welded. Such electric welding sleeves are e.g. known from DE-AS
28 23 455 and EP 222 287.

, The heater coil or electric s]eeve welding method is now mainly used in poly-ethylene pressure pipe networks for the gas and water supply. ll~e aforemen-tioned design principle of material uniforrnity has proved extremely satisfacto-ry for small and medium size pipe diameters of 20 to 225 mm. ~ -~~- P0768US - 2 - 2 ~ 2 7 ~ ~ 8 Increasing interest is being attached to polyethylene for use with larger pipe cross-sections. The joining procedure can be in the form of heating element butt welding and electric sleeve welding. For joining larger pipes and pipe components there is an ever increasing demand for electric welding sleeves of 5 corresponding size.

However, disadvantages result from such pipe dimension increases. Based on the material uniformi~y principle with increasing pipe diameter there is also 10 an increase in the wall thicknesses of the electric welding sleeves. In order to withstand the operating pressure, the wall thicknesses of material-uniform electric welding sleeves are at least as thick as the wall thicknesses of the pipes to be welded. Weldable plastic pipes for pressure pipe lines with a large internal diameter, particularly those made from polyethylene, have relatively 15 large wall thicknesses, which leads to the use of corresponding thick electric welding sleeves. The consequence thereof is that the weight and volume are so great that handling, transportation, storage, etc. are made difficult and more expensive. The manufacture of such large, thickwalled and heavy sleeve bodies, e.g. by injection moulding is expensive, because it leads to uneconomi-20 cally long machine cycle times, to high costs for correspondingly large andpowerful injection moulding machines and finally has a considerable material requirement.

25 Apart from these economic and production aspects, account must also be taken of welding requirements. Electric welding sleeves for large pipes with large wall thicknesses must be gi-en correspondingly large weld surfaces. For melting large thermoplastic quantities the latter require more electric power, which in turn must be introduced into the joining zone over the extended 30 welding time. Long welding times mean that a larger part of the sleeve body is heated, which causes an increase in the heated volume parts. This effect is . ~..

" P0768US - 3 ~ 2 1 2 7 6 ~ 8 used from the welding standpoint in order to build up the necessary joining pressure for a material connectio~ in the melting zone. However, this is only brought about if the sleeve body has a sufficiently large temperature gradient and remains mechanically load bearing and dimensionally stable. Such areas 5 compensating the joining pressure, separated by a large wall thickness, can bethe outer areas of the sleeve bod~. Thus, sleeve bodies for large pipe diame-ters are provided for purely welding reasons with overdimensioned wall thick-nesses.

For solving these problems DE 39 32 807 and EP 222 287 describe electric welding sleeves, which have externally applied reinforcements. These reinfor-cements are characterized in that the sleeve body is stiffened in the radial direction, so that the wall thickness of the sleeve body for optimi7.ing the 15 weldin~ parameters does not have to be thiclcened and stiffened beyond the thickness necessary for the opera~ng pressure. For axial loads, e.g. caused by external influences such as land slips, damage by tools, etc., said reinforce-ments remain largely ineffective. The minimum perrnitted sleeve wall thick-ness is consequen~ly determined by the amount of tbe wall thickness of the 20 pipe to be welded, so as to ensure in this way the uniformity of the radial and axial load bearing charac~eristics of the pipe string and also those of the joi-ning points of the entire pipe system.

25 It would be desirable to have an electric welding sleeve ensuring with a mini-mum material expenditure on the one hand optimum conditions for the wel-ding process, such as producing a necessary welding pressure for material--uniform welds and on the other optimum mechanical strength values for the subsequent use.

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- -~ P0768US - 4 -21~76~8 The problem of the invention is to provide an electric welding sleeve and a method for the production thereof permitting mechanically stable cormections between the electric welding sleeve and the tubular welding ends, so that radi~
al and axial forces which occur are absorbed. This problem is solved by the S invention defined in the claims ~ , The present invention relates to a design concept and to a rational manufac-turing method for an electric welding sleeve for the completely satisfactory 10 joining of large pipes with correspondingly large wall thicknesses made from thermoplastic material. The idea of the invention is to make a logical distinction between aspects of the correct material long term sealing and the mechanical strength of the pipe junctions.

The best material-correct long term sealing of a pipe joint is achieved by a material-uniforrn welding, such as :is known in plastic pipeline construction with the aid of electric welding sleeves for small to medium pipe sizes. For the medium tightness it is merely necessary to have a relatively thin-walled 20 sleeve, which is made from a weldable therrnoplastic pipe material and which is equipped with a filament winding.

The mechanical strength during subsequent use of such mediumtight arran-25 gements involves the absorption of the radial and axial forces occurring on the pipe string. Such forces lead to a flux of force via the welding joints of the tubular welding ends to the electric welding sleeve. According to the invention these forces are absorbed by a terminating means or reinforcement super-imposed on the sleeve and cormected thereto in transverse and longitudinal 30 force closure manner. These terminating means do not come into contact with the medium in the pipeline. Thus, compared with the pipe material, they are P0768US 5 2 1 2 7 6 ~ 8 : ~`

subject to comp]etely different selection criteria, greatest importance being ~-attached to optimum mechar~ical strength Yalues.

The invention is described in greater detail relative to figs. 1 to 5.

Fig. 1 shows the prior art of a material-uniform pipe connection in longi-tudinal section.

Fig. 2 shows a first embodiment of a pipe connection according to the invention in longitudinal section.

Figs. 3a to d show a first method variant and method steps for the manufac-ture of a first embodiment of an inventive electric welding sleeve with the sleeve and terminating means in accordance with fig. 2, the individual representations being longitudinal sections through parts of semifinished products.
: ' Fig. 3a shows the shaping of the semifinished product welding sleeve, ma-nufactured by mechanical worldng of a pipe section or rnanufactur-ed as an injection moulding.

Fig. 3b shows the shaping of the sernifinished product sleeve body with a semifinished product terrninating means formed on the semifinished product welding sleeve. `

Fig. 3c shows the shaping of the semifinished product sleeve body with a sleeve bore worked in dimensionally accurate manner for the in-troduction of the filament winding into the semifinished product welding sleeve and radially drilled positioning points for the assem-~ P0768US - 6 - -2127~

bly of the components for the subsequent contacting of the fi]ament winding.

Fig. 3d shows the finished electric welding sleeve for large pipes according to the invention.

Fig. 4 shows in longitudinal section parts of a second embodiment of an inventive electric welding sleeve with a terminating means in the form of a metallic or thermosetting material cage, which can be manufactured in a second method variant.

Fig. 5 shows in longitudinal section parts of a third embodiment of an inventive electric welding sleeve with a terminating means in the form of a metallic or thermosetting material cage.

Fig. 1 shows the prior art of a material-uniform pipe connection ir~ longitudi-nal section. The tubular welding ends Rl and R2, as well as the electric wel-ding sleeve 1 are made from the same thermoplastic material, e.g. a polyolefin 20 such as polyethylene. The electric welding sleeve 1 is fitted to the outside of the pipes Rl and R2 to be joined. For welding purposes a filament winding 2 supplies by means of the contacts 3, 3' a given welding current. During wel-ding said filament winding 2, e.g. passing in spiral manner over the inner face of the electric welding sleeve becomes hot. Then the thermoplastic material of 25 the inner area of the elçctric welding sleeve surrounding the filament winding 2 and the outer area of the pipe ends Rl, R2 become hot and said ends Rl, R2 are joined to the welding sleeve. However, the outer area of the electric welding sleeve remains hard and ensures the necessary mechanical stability.

- P0768US - 7 - 2 1 2 7 ~ f) 8 The wall thicl;ness of the electric welding sleeve for materialuniform welding must be chosen in such a way that during the power supply period, i.e. also in the case of a long welding period, a sufficiently dimensioned outer jacket layerremains cold and mechanically adequately load bearing in order to force 5 radially effectively against one another the thermal volume enlargements of the sleeve body and the welding ends occurring in the heating area. In this way there is a swelling against one another of the joining faces fitted with clearance in the cold state, so that an adequate joining or melting pressure is produced. With increasing pipe diameters the assembly clearances to be brid-10 ged by thermal expansion increase, so that the compensating times up to theweld-tight contact of the joining faces become longer, the welding energy required due to the larger welding faces increases superproportionally, so that there is a significant heat penetration into the sleeve body. This leads to a marked decrease of the radial stiffness or annular stiffness, so that the joining 15 ~conditions can be significantly disturbed and the possibility of a tight weld is prejudiced. If as a result of the circumferentially different clearance distribu~
tions in the joining area there are partial areas with an inadequate welding pressure, then welding errors are unavoidable. An increase in the sleeve body wall thickness naturally obviates this problem. However, the welding-caused 20 measure is superfluous for the mediurri tightness and the compression strength of the welding joint and, as described hereinbefore, leads to disadvantages during manufacture and assembly.

25 The prior art electric welding sleeve 1 according to fjg. 1 is consequently provided with large wall thicknesses only for dissipating the welding energy.
Thus, it forms an adequately large heat sink so as to ensure that during wel-ding its outside does not become soft and as a result of the large mass also withstands the necessary contact pressure, i.e. it does not or only slightly de-30 forms under the latter.

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~ - P0768US - 8 - 2 1 2 7 6 ~ ~

Fig. 2 sho~s a pipe connection according to the invention in longitudinal section. This first embodiment of an electric welding sleeve 5 according to the invention is applied to the outside of two tubular welding ends Rl and R2 to be joined. It has a filament winding 2 with contacts 3, 3' by means of which a 5 given welding current is supplied and in this way the tubular welding ends Rl,R2 are welded. Unlike in the known embodiment according to fig. 1, the electric welding sleeve S forms a compound sleeve body made from different materials. The inside of the electric welding sleeve 5 comprises a welding sleeve member 5.1, which is advantageously made from the same material as 10 the tubular welding ends Rl and R2, e.g. from polyolefin such as polyethylene, so that the optimum material-correct, materialuniform welding thereof is guaranteed. However, the outside of the electric welding sleeve S is a termina-ting means 5.2 and is made from a different material, which does not soften and melt at the welding temperature. Numerous specifically designed materi-15- als are available for this purpose. They must satisfy certain mechanical strength criteria such as hardness, stiffness, thermal expansion, corrosion resi-stance, etc. Ideal characteAstics in this connection can e g. be obtained w-ith metals and fibre-reinforced therrnosetting materials. With the knowledge of the present invention a large number of different embodiments in the most 20 varied materials are made available to the expert.

This clear separation between aspects of the material-correct long term sea-ling and the mechanical strength of the pipe connections permit an optimiza-25 tion of each of these functions. With a minimum material use of materialssuitable in optimum manner for each partial function a long term, material--uniform electric welding sleeve joint is obtained, which particularly for large pipe diameters requires a much smaller sleeve body wall thickness than other material-uniform designs. The mechanical strengthening of the electric wel-30 ding sleeve is provided by a terminating means having devices for absorbingradial and axial forces. It is located outside the welding sleeve and the wel-~ P0768US - 9 -ding zones, is made from a material which does not soften and melt during the welding process and during the welding process supports same against both radial and axial forces. The terminating means absorbs the flux of force of external forces -via the welding joints of the tubular welding ends to the 5 electric welding sleeve. The thin-walled, internal welding sleeve member and the external terminating means, advantageously shaped onto one another, form an electric welding sleeve of light and small construction.

10 Thus, the terminating means 5.2 absorbs radial and axial forces. Radially occurring forces are compensated by the slight thermal expansion and the non-melting and non-softening of the thermosetting materials used during the welding process, so that there is no external widening in the form of a radial expansion. Axially occurring forces, e.g. due to land slips or different thermal15 expansions between the pipeline and the soil surrounding it at different times of the year are compensated by anchoring points in the form of matched cavities 6, 6' and bulges 7, 7' preferably at right angles to the longitudinal axis of the electric welding sleeve 5 and located in the welding sleeve member 5.1 and the terminating means 5.2. These forces can be normal or shear forces.
20 The cavities 6, 6' can be closed or partly closed grooves running round the outer surfaces of the welding sleeve member 5.1. The bulges 7, 7' can be cor-respondingly worked webs on the inner surfaces of the terminating means 5.2.
It is also possible to have matched cavities 6, 6' on the inner surfaces of the terminating means 5.2 and bulges 7, 7' on outer surfaces of the welding sleeve 25 member 5.1. According to fig. 2, considered in the longitudinal axis of the tubular welding ends Rl, R2 and the electric welding sleeve 5, there are in each case two pairs of matched worked cavities 6, 6' and bulges 7, 7' with a constant spacing from the welding zone close to the outer boundary of the~
welding sleeve 5.

-- P0768US - 10 - 2 1 2 7 g ~ ~

The central area Z of the tubular welding ends Rl, R2 to be welded is the area in ~hich they come into contact with one another if they are inserted in the welding-ready form into the welding sleeve 5. Fig. 2 shows that the tubular welding ends ~l, R2 do not rest against one another but, as a result of assem-5 bly conditions, are separated by a gap. The filament winding 2 has two areasof welding zones 8.2, 8.2', which are separated from the central area Z of the tubular welding ends Rl, R2 to be joined and which are symmetrically left and right of the central area Z. Thus, the filament winding 2 produces a non-ho-mogeneous thermal fiel on the inner face of the welding sleeve member 5.1 10 and the outer faces of the tubular welding ends Rl, R2 to be welding, so thatthey are welded in the welding zones 8.2, 8.2' in melting islands under welding pressure and in the form of a pasty melt.

15 Figs. 3a to 3d show a first method variant and method steps for producing an electric welding sleeve 5 according to the invention in longitudinal section through parts of preliminary products thereof. This is the same first embodi-ment as described relative to fig. 2.

Fig. 3a shows the shaping of a semifinished product welding sleeve member 5.1' of an electric welding sleeve 5. In this method variant the welding sleeve member 5.1' is produced by mechanically working a tubular portion or injec-tion moulding made from thermoplastics such as polyolefins, e.g. polyethylene.
25 This sernifinished product welding sleeve member 5.1' has a geometrical pre-ferred axis, e.g. along the longitudinal axis of two tubular welding ends to be joined and is consequently produced in such a way that they can be inverted over the external diameter of tubular welding ends. Advantageously the semi-finished product welding sleeve member 5.15 with said flat extension surrounds 30 in ring-c]osed manner the welding zone of the tubular welding ends to be welding and consequently is produced as a thin sleeve of uniform thickness, so P0768~iS - 11 - 2127~8 that the thermoplastic material melts in uniform manner corresponding to the heati~g power of the uniformly inserted filament winding. Naturally it is possi-ble to have other embodiments with non-uniform thicknesses of the welding slee-e member 5.1' and filament windings 2 inserted with irregular spacings.
5 Furlher details are provided in this connection in the description of fig. 3d.With the knowledge of the present invention there are numerous design possi-bilities open to the expert.

10 On the outside of the semifinished product welding sleeve member 5.1' are formed cavities 6, 6', so that subsequently matching bulges 7, 7' of a termina-ting means 5.2 can be joined to these cavities 6, 6', so as to form anchoring pOil~tS. The cavities 6, 6' can be closed or partially closed on the outer surfa-ces of the welding sleeve member 5.1'. The shape of the cavities 6, 6' can be - 15 freely varied. Thus, they can be in the form of straight, elongated grooves, circular or oval blind holes or complicated three-dimensional structures, simi-lar to the profile or tread of car tyres, regularly or irregularly ribbed notches (cf. fig. 5), etc. The depth of the cavities 6, 6' is also freely selectable. The cavities 6, 6' can be produced by using suitable tools in a completely automa-20 tic manner, e.g. by making grooves.

Fig. 3b shows how a semifinished product terminating means 5.2' is placed on a semifinished product welding sleeve member 5.1' of an electric welding 25 slee-e 5. The terminating means 5.2' is e.g. made from fibre-reinforced ther-mosetting materials. The latter can be wound as resin-impregnated cords or threads in cavities 6, 6' of the welding sleeve member 5.1', which gives rise tobulges 7, 7'. The remainung terminating means can either be wound crosswise as resin-impregnated threads or cords on the welding sleeve member 5.1' or is 30 produced from resin-impregnated mats or fabrics. In this way the terminating means can be formed by layerwise application. By curing the resin this shape 21~7~8 of the welding sleeve member 5.1' and terminating means 5.2' is mechanically stabilized. For easy assembly purposes it is appropriate to provide the semifi-nished product terminating means 5.2' with a sirnilar geomet~y to the semifi-nished product welding sleeve member 5.1', so that it is also in the form of a 5 closed, tubular sleeve.

Fig. 3c shows how the semifinished product sleeve body is provided with di-mensionally accurate sleeve bore and radially drilled positioning points for the10 assembly of components for the subsequent contacting of the filament v~in-ding. As is e.g. described in Swiss patent application 1275/93-6 of 27.4.1993, in the inner face of the welding sleeve member 51' grooves can be formed in accordance with fig. 3b and are used for receiving the filament winding 2.
These grooves are not shown in fig. 3c. In parts of the anchoring points are made openings 9, 9' for receiving the contacts 3, 3'. The openings 9,9' have steps so as to permit a better positioning of the contacts 3, 3'. Finally, on the inner edges 4, 4' of the semifinished product welding sleeve member 5.1' are made bevels, which facilitates the engagement of the electric welding sleeve on such tubular welding ends.

Fig. 3d shows the ~llament winding 2 placed on the inner face of the semifinis-hed product welding sleeve 5.1' according to fig. 3c. After inserting the fila-ment winding 2 the sen~ifinished product welding sleeve 5.1' is complete and 25 is then known as the we!ding sleeve member 5.1. The insertion product of the ~llament winding 2 can take place fully automatically with suitable tools. In the embodiment according to fig. 3d the filament winding 2 in areas is equidi-stant, e.g. spirally or helically on the inner face of the welding sleeve member5.1. The filament winding 2 is consequently in the form of two areas of spiral 30 or helical, equidistant windings. These actively heatable areas of the welding sleeve member 5.1 form the welding zones 8.2, 8.2' for welding tubular wel-ding ends. The welding zones 8.2, 8.2' are separate from the central area of the tubular welding ends to be joined and symmetrically surround the same.
They are not located in the central area, because the tubular parts to be wel-ded are not necessarily in contact here and instead, for assembly reasons, of -ten leave a small gap between them. Following the fitting of the contacts 3, 3' in the openings 9, 9' electric current is supplied to the filament winding 2 forwelding purposes and the semifinished product terminating means 5.2' is then called the terrninating means 5.2. ~ ;~

~'' ' Fig. 4 shows a second embodiment of an electric welding sleeve according to the invention with a terminating means in the form of a metallic or thermo- -setting material cage in a longitudinal section through part of the welding sleeve. Compared with the first embodiment of figs. 2 and 3d, this second - 15 embodiment has a terminating means 5.2, which surrounds the outer and lateral faces of the welding sleeve member 5.1 by outer boundaries 10, 10'. On welding tubular welding ends the welding sleeve member 5.1 is surrounded on the outer and lateral faces by terminating means 5.2, but on the inner faces by the tubular welding ends Rl, R2 to be welding.
~

These boundaries 10, 10' of the welding sleeve member 5.1 can e.g. be produ- ;
ced by flanging the end portions of a thin-walled, metal sleeve, like the end portions of the terminating means of the first variant of figs. 3a to 3d. Howe-ver, it is also possible to choose a second variant, in which initially a semufinis-hed product terminating means 5.2' is produced, e.g. by mechanically working a tubular portion made from metal or fibre-reinforced thermosetting materials and on the inside of said terminating means 5.2' are formed bulges 7, 7' and outer boundaries 10, 10'. The sernifinished product welding sleeve member 30 5.1' is then filled into the sernifinished product terminating means 5.2' by injecting thermoplastic material in an injection moulding process and in this '~

~ P0768US - 14-21276~8 way the terminating means 5.2' and welding sleeve member 5.1' are joined together in radially an axially tight manner by means of anchoring points in the form of cavities 6, 6' and bulges 7, 7'. Otherwise the second embodiment of the electric welding sleeve 5 and its manufacturing method are identical 5 with the ~lrst embodiment according to figs. 3a to 3d.

A further embodiment of the inventive electric welding sleeve with an enga-geable terrninating means 5.2 in the form of ~wo annular elements or parts 10 can be used for equipping radially reinforced sleeves, so as to solve the pro-blem of the invention.

In this embodiment, unlike in the two embodiments of figs. 2 and 3d, the 15 welding sleeve member 5.1 is formed from one or more elements, which e.g.
form welding zones 8.2, 8.2' in each case and which are engaged on the tubu-lar welding ends Rl, R2 to be joined and which by means of a tension-exerting terminating means 5.2, are so interconnected on their outsides by means of anchoring points that radial and axial tight forces occur. An already radially 20 reinforced sleeve and two terminating rings or elements or parts form a unit.One terminating ring is engaged on a pipe end and the pipe ends are inserted in the reinforced sleeve. The terminating rings e.g. are circumferentially provi-ded with pin-like anchoring points by means of which a tensioning means can be guided. If e.g. a taut wire is fixed to an anchoring point of a terminating 25 means and alternatively guided by means of the anchoring points of two ter-minating rings and under tension is again fixed to an anchoring point, then between the two terminating means there is an axial force combined on wel-ding with the radial forces of the reinforcement. The same action is obtained by a type of bayonet catch between the sleeve reinforcement and the terrnina-30 ting means and e.g. holding cams can be placed on the sleeve reinforcementand tension slots on the terminating rings.

~ P0768US - 15 - 2 1 2 7 ~ 6 8 ~ ~

.
Fig. S shows a third embodiment of an inventive electric welding sleeve with a terminating means in the form of a metallic or thermosetting material cage in a longitudinal section through part of said sleeve. This embodiment has a 5 terminating means 5.2, which surrounds the outer and lateral faces of the welding sleeve member 5.1 by external boundaries 10, 10', the bulges 7, 7' being in the form of holding cams. Thus, this embodiment is similar to those according to figs. 2, 3d and 4 and their descriptions again apply. It is a combi-nation of the embodiments of figs. 3d and 4. Thus, there is a radially reinfor-ced sleeve with bulges 7, 7' in the outer boundaries 10, 10'. As these bulges 7,7' are formed in the outer boundaries 10, 10', they are inclined to the axial extension of the welding sleeve. The anchoring points are consequently in the form of bulges 7, 7' in one or more terminating means 5.2 engaging over the welding sleeve member 5.1.
."~ - '.
All the different embodiments of the invention can be combined. Thus, e.g. a welding sleeve member 5.1 comprising one or more elements can be prefixed by means of bulges 7, 7' and cavities 6, 6' on one side and have on the other 20 side a terminating ring with a bayonet catch. Such an embodiment permits the insertion of a welding part into an outer sleeve absorbing the radial forces positively engaged (form-fit) on one side and anchored in axially acting man-ner with the facing terminating ring prior to welded. Numerous constructional possibilities are open to the expert through the knowledge of the present 25 invention.
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Claims

1. Electric welding sleeve (5) for welding tubular welding ends (R1, R2) made from weldable plastics, with a filament winding (2) having contacts (3, 3'), which is supplied with electric current for welding purposes, the electric welding sleeve (5) having a welding sleeve member (5.1) for receiving the filament winding (2) and a termina-ting means (5.2) with in each case positive anchoring points for si-multaneous radial and axial-tight joining.

2. Electric welding sleeve (5) according to claim 1, characterized in that the anchoring points are in the form of interengaging cavities (6, 6') and bulges (7, 7') and/or as terminating means (5.2) engaging over the welding sleeve member (5.1).

3. Electric welding sleeve (5) according to claim 2, characterized in that a terminating means (5.2) is applied to the outside of the electric welding sleeve (5) and that the welding sleeve member (5.1) is ap-plied to the inside of the welding sleeve (5).

4. Electric welding sleeve (5) according to claim 3, characterized in that the terminating means (5.2) is made from metals or fibre-reinforced thermosetting materials which do not soften during the welding pro-cess.

5. Electric welding sleeve (5) according to claim 3, characterized in that the welding sleeve member (5.1) is made from weldable, thermopla-stic material for material-uniform welding.

6. Electric welding sleeve (5) according to one of the claims 1 to 5, characterized in that the welding sleeve member (5.1) can be enga-ged on the welding ends (R1, R2) to be joined and that the welding sleeve member (5.1) is reduced to a minimum wall thickness for a material-uniform, tight welding to the welding ends (R1, R2).

7. Electric welding sleeve (5) according to one of the claims 1 to 6, characterized in that the cavities (6, 6') and the bulges (7, 7') of the anchoring points are worked so as to match one another and that they are made on the outer surfaces of the welding sleeve member (5.1) and on the inner surfaces of the terminating means (5.2).

8. Electric welding sleeve (5) according to one of the claims 1 to 7, characterized in that the terminating means (5.2) have boundaries (10, 10'), which prevent an external widening as a radial or axial expansion of the thermoplastic material of the welding sleeve mem-ber (5.1) which becomes elastic and soft as a result of the heat pro-duced during welding.

9. Electric welding sleeve (5) according to one of the claims 1 to 8, characterized in that the terminating means (5.2) provides an axial reinforcement, which absorbs the flux of external forces via the wel-ding joints to the tubular welding ends (R1, R2) on the electric wel-ding sleeve (5).

10. Electric welding sleeve according to claim 1, characterized in that the terminating means (5.2) comprises a part absorbing the radial forces and one or two parts absorbing the axial forces and that the radial and axial force parts are provided with fixing means in order to si-multaneously absorb both forces.

11. Electric welding sleeve according to claim 10, characterized in that the fixing means are pins on terminating rings and tension means on the pins of both rings.

12. Electric welding sleeve according to claim 10, characterized in that the fixing means are bayonet catches on terminating rings and sleeve reinforcement.

13. Method for the manufacture of an electric welding sleeve (5) accor-ding to one of the claims 1 to 12, characterized in that a semifinished product welding sleeve member (5.1') is produced by mechanical working of a tubular portion or as an injection moulding, that to the outside of the semifinished product welding sleeve member (5.1') are applied cavities (6, 6'), that a semifinished product terminating means (5.2') is formed by winding resin-impregnated cords and mats, so that bulges (7, 7') of the semifinished product terminating means (5.2') engage in cavities (6, 6') of the semifinished product welding sleeve member (5.1') and consequently form anchoring points, that in the semifinished product terminating means (5.2') and the semifinished product welding sleeve member (5.1') are formed openings (9, 9') for the fitting of contacts (3, 3'), that a filament winding (2) is placed of the inner face of the semifinished product welding sleeve member (5.1'), so that the latter becomes a welding sleeve member (5.1), that contacts (3, 3') are fitted, so that the semifinished product termina-ting means (5.2') becomes a terminating means (5.2) and that the filament winding (2) is supplied by means of the contacts (3, 3') with electric current for welding purposes.

14. Method for the manufacture of an electric welding sleeve (5) accor-ding to one of the claims 1 to 12, characterized in that a semifinished product terminating means (5.2') is produced by the mechanical wor-king of a tubular portion made from metal or fibrereinforced thermo-setting materials, that to the inside of the semifinished product termi-nating means (5.2') are applied bulges (7, 7') and/or outer bounda-ries (10, 10'), that a semifinished product welding sleeve member (5.1') is formed by injecting thermoplastic material into the semifinis-hed product terminating means (5.2'), so that bulges (7, 7') of the semifinished product terminating means (5.2') engage in cavities (6, 6') of the semifinished product welding sleeve member (5.1') and consequently form anchoring points and so that the outer and lateral faces of the semifinished product welding sleeve member (5.1') are surrounded by the outer boundaries (10, 10'), that in the semifinished product terminating means (5.2') and the semifinished product wel-ding sleeve member (5.1') are formed openings (9, 9') for the fitting of the contacts (3, 3'), that a filament winding (2) is placed on the inner face of the semifinished product welding sleeve member (5.1'), which then becomes a welding sleeve member (5.1), that contacts (3, 3') are fitted, so that the semifinished product terminating means (5.2') becomes a terminating means (5.2) and that electric current can be supplied by means of the contacts (3, 3') to the filament win-ding (2) for welding purposes.