The present invention relates to an insulator for sealed covering of an electrical cable termination connector, which produces an electrical connection between a cable termination of a cable and an appliance terminal

In association in particular with electrical switchgear or the like it is often necessary to connect single-pole appliance terminals to at least one single-conductor cable in such a way that the electrical connection is effectively electrically insulated and adequately protected from the penetration of moisture The appliance terminal components to be contacted, for example to produce SF ₆ load break switchgear, in this case have standardised appliance insulators, which are insulated in the form of an outer cone relative to the wall of the switchgear Such an outer cone appliance terminal component is disclosed for example in EN 50181

Hermetically insulated, submersible covering is ensured above all by a specially configured insulator, often also designated as an adapter, which accommodates the appliance terminal on the one hand and the cable termination on the other

With reference to Figs 21 to 23, a known insulator is described below, such as is known for example in the form of an insulated, screwable 630A RlCS 10 kV and 20 kV cable connection from the product range made by TYCO Electronics Raychem

The known insulator 200 here comprises a first insertion channel 202 for accommodating the appliance terminal 208 A second insertion channel 204 is provided for insertion of the cable 206 As is clear m particular from Fig 23, the cable 206 has a cable termination 216 with a cable lug 210, which is connected to the appliance terminal in a connection region, in which the appliance terminal and the cable termination are brought together An open extension piece 212. which is closed by a stopper 214 in the finally assembled state, allows access to the connection region from outside The first insertion channel 202 is pushed in sealing manner over the outer cone 208 of the appliance terminal and the second insertion channel 204 provides a seal directly on the cable termination 216 over of a comparatively large area In order to absorb the forces acting transversely of the cable axis when the cable has been fitted, an annular recess 218 is provided in the insulator 200, in which a metallic insert plate 220 is inserted However, the known insulator 200 comprises a plurality of serious disadvantages In order to ensure the necessary mechanical stability, the known insulator has comparatively thick walls, which leads to the use of large amounts of plastics material Furthermore, a metallic insert plate 220 contributes to the absorption of mechanical forces and inter alia prevents slide-off from the appliance terminal and positions the plug connector The insert plate 220 additionally fulfils functions relating to power transmission, but has the disadvantage that production of the insulator 200 is made substantially more expensive and additional electrical transition resistance arises

In addition to the material costs, the considerable wall thickness leads to the need to apply high assembly forces in order to push the cable termination 216 into the second insertion channel 204 Since the thick walls also stand in the way of extensive resilience in the case of highly resilient plastics materials, the known arrangement in Figs 21 to 23 is also not suitable for a very wide range of cable diameters, such that in each case a relatively large number of injection moulds has to be provided or alternatively appropriate adapters have to be used.

The closing stopper 214, which is produced in the known arrangement from a thermoset and has to be secured by screwing in the open extension piece 212, increases the number of raw materials required, since it is not produced from the same material as the insulator 200, and increases assembly complexity.

The object on which the present invention is based therefore consists in providing an improved insulator for sealed covering of an electrical cable termination connector, which fulfils all the requirements of an electrical connection between a cable termination of a medium and high voltage cable and an appliance terminal with regard to tightness and electric strength, but on the other hand is inexpensive to produce and relatively simple to assemble and allows the assembly of a wider range of cable cross-sections and cable lug geometries without the need for an adapter or similar aid to modify the geometry of the cable terminal connector.

This object is achieved by the subject matter of the independent claims. Advantageous further developments of the present invention constitute the subject matter of the dependent claims. The present invention is here based to the basic concept of reducing the walls of the insulator significantly and ensuring mechanical stability by way of various measures even when using a wide range of cable diameters.

One essential aspect the present invention is that in the second insertion channel a contact region is provided, in which, in the assembled state, the electrically contactable cable termination is accommodated, and a sealing region, which rests sealingly against the termination of the cable, a centre axis of the sealing region being arranged offset relative to a centre axis of the contact region. Through a suitable choice of the offset, which may also be interpreted as eccentricity of the cylinders which in each case form the connection region and the sealing region, it is possible to find a type of compromise between the deflection caused to the second insertion channel by the smallest and largest cables (or cable lugs, or eccentricities) to be used.

According to a further aspect of the present invention, the sealing region is of smaller internal diameter than the contact region. In this way, it is on the one hand ensured that it rests sealingly against the termination while on the other hand sufficient space is made possible for optionally projecting cable lug arrangements. So as to prevent the insertion channel from becoming deformed when the cable is inserted into the narrower sealing region, at least one reinforcing rib is fitted on the outer wall of the sealing region along the insertion direction of the cable.

A funnel-shaped flange may moreover ease insertion and be connected to the reinforcing ribs. In addition to the property of preventing deformation on insertion and removal of the cable, this embodiment also has the advantage of increasing ease of grip for an assembler on insertion of the termination, so increasing the assembly friendliness of the entire arrangement.

In order to ensure the mechanical stability of the connection region even with low wall thickness, further reinforcing ribs may be fitted to the internal wall in the connection region. These may extend both in the circumferential direction and also along the cable axis and be of lattice construction, for example Another essential feature of the reinforcing ribs is that the occurrence of undesirably high electrical field strengths is prevented

According to a further aspect of the present invention, a step is provided at the point of transition between the first insertion channel and the connection region, at which step the cable lug finds a counter- hold in the assembled state Such a step, which may also be interpreted as a limit stop, prevents sliding out from the first insertion channel and from the outer cone of the appliance terminal This effect, which is extremely undesirable, is also known as the "milk off effect Moreover, by avoiding a disc, the number of transition resistances may be reduced According to an advantageous further development of the present invention, a resilient lid (also designated hereinafter as a covering cap) is provided instead of the thermoset stopper provided with known insulators This lid is fixed in the open extension piece by means of a resilient tongue and groove joint The tongue and groove may be provided for example by a recess in the lid and an associated projection on the internal wall of the open extension piece By means of a resilient sealing lip, which may take the form of a collar designed to be brought to rest with its end face against the open limit stop, the lid may be fitted in gap-free, sealing manner without any additional aids In addition to a resilient sealing lip, the collar may also be provided with a bevel, so as to enable resilient application The resilient lid may additionally be made from the same material as the actual insulator, which reduces production complexity and the starting materials required For a better understanding of the present invention, the latter is explained in greater detail with reference to the exemplary embodiments illustrated in the figures below Identical parts are here provided with identical reference numerals and the same component names Furthermore, features or combinations of features from the various embodiments disclosed and described may also in themselves constitute independent inventive solutions or solutions according to the invention In the drawings Fig 1 shows a section through an insulator according to the invention,

Fig 2 shows a perspective, partially sectional representation of the insulator,

Fig 3 shows part of the section 3-3 from Fig 1 ,

Fig 4 shows detail 4 from Fig 1 ,

Fig 5 shows part of a view of the insulator of Fig 1 in the cable insertion direction, Fig 6 shows section 6-6 of Fig 1 ,

Fig 7 shows section 7-7 of Fig 1 ,

Fig 8 shows detail 8 from Fig 1 ,

Fig 9 is a perspective overview of the insulator according to the invention,

Fig 10 is a rotated representation of the insulator according to Fig 9, Fig 1 1 is a schematic representation of the second insertion channel to illustrate the eccentricity of the centre axes, Fig. 12 is a schematic representation of the insulator according to the invention for use with cables of different sizes;

Fig. 13 is a detail view of the arrangement of Fig. 12;

Fig. 14 is a sectional representation of the first insertion channel to illustrate the forces arising when the cable lug is fitted;

Fig. 15 is a perspective representation of the covering cap of the insulator;

Fig. 16 is a rotated perspective view of the covering cap of Fig. 15;

Fig. 17 shows a section through the covering cap according to the invention;

Fig. 18 shows a detail from the representation of Fig. 17; Fig. 19 shows a detail of the fitted covering cap;

Fig. 20 is a plan view of the covering cap according to the invention;

Fig. 21 is a first sectional representation of a known insulator;

Fig. 22 is a sectional representation of a known insulator rotated by 90°;

Fig. 23 is a schematic representation of a known electrical connection between the cable termination of a cable and an appliance terminal using the insulator of Figs. 21 and 22.

The present invention is explained in greater detail below with reference to the figures. Fig. 1 shows a sectional representation of the insulator 100 according to the invention in an advantageous embodiment. The insulator comprises a first insertion channel 102 for accommodating an appliance terminal. A second insertion channel 104 serves to accommodate the cable, not shown in this figure. The first insertion channel provides a seal substantially over the region 102 relative to the appliance terminal.

The two substantially tubular channels are aligned in a connection region 108, in which the actual electrical contact comes into being. The connection region 108 is accessible from the outside via an open extension piece 1 10. A direct comparison with the previously known solution of Figs. 21 and 23 firstly shows in particular the significantly reduced wall thickness of the insulator 100. By reducing the wall thickness in this way and omitting the metallic insert plate, which will be discussed in detail below, marked savings may be made with regard to production of the insulator 100 compared with known insulators and electrical transition resistance may be reduced.

So that a wide range of different cable diameters may be accommodated, essential structural measures are taken with regard to the second insertion channel 104. On the one hand, the second insertion channel 104 is subdivided into a contact region 1 12, in which the cable lug is arranged, and a sealing region 1 14, which comes to rest directly and sealingly against the insulating cable termination. To achieve a compromise with regard to deflection of the second insertion channel 104 on fitting of particularly thin and particularly thick cables and of different cable lug geometries, the centre axes 1 16 and 1 18 of the contact region 1 12 and of the sealing region 1 14 are offset relative to one another. The technical effects of this offset will be addressed in greater detail below with reference to Figs. 1 1 to 13.

The different-sized internal diameters of contact region 1 12 and sealing region 1 14 make it possible, moreover, for cable lugs whose diameters are markedly greater than the cable diameter to be accommodated without difficulty in the second insertion channel 104, and the push-on force is reduced. In this way, in particular, damage to the insulator 100 caused by permanent loading and overstretching may be prevented.

As is clear from the sectional representation of Fig. 1 together with the detail 8 (Fig. 8), latticed reinforcing ribs 120, 121 are arranged in the contact region 1 12 on the inside, in order to lend sufficient mechanical stability to the second insertion channel 104 despite the reduced wall thickness. The cross- sectional shape of the reinforcing ribs 120 is here of essential significance for the electric strength, since the formation of excessive electrical fields and accumulated charges has always to be prevented. Bevelling and rounding of the ribs has proven advantageous. In principle, the sealing region 1 14 could also be provided at its inner wall with sealing lips, wherein the respective requirements relating to forces arising during assembly and operation have always to be complied with. Furthermore, when designing the sealing region 1 14 care must be taken to ensure that electrical requirements are met.

As is also clear from looking at Fig. 1 and 2 together, in the peripheral region of the sealing region 1 14 a funnel-shaped insertion flange 122 is provided, which simplifies insertion of a cable termination. At the outer wall of the sealing region this insertion flange 122 is connected to the outer wall of the contact region 1 12 by way of a total of four reinforcing ribs 124. These outer reinforcing ribs 124, which extend substantially parallel to the insertion direction of the cable, prevent the sealing region 1 14 from being deformed or displaced inwards upon insertion of the cable in the direction of the arrow 126. Furthermore, the ribs 124, which are particularly clearly visible in Figs. 7 and 10, also result in increased ease of grip on fitting of the cable, since they provide, as it were, recessed grips for the user to grasp.

A further advantageous feature of the insulator 100 according to the invention is the limit stop 128 provided in the connection region. As will be explained in greater detail in connection with Fig. 14, this limit stop serves to prevent the milk off effect, and in this way replaces the metallic insert plate, which is used with known insulators. In this way, the number of electrical transition resistances is also reduced.

Detail 4 (Fig. 4) shows the catch projection 130, which is provided on the open extension piece 1 10 and, as will be explained below with reference to Figs. 15 to 20, interacts with an associated groove in the flexible covering cap to fasten the cap to the open extension piece.

Essential aspects and modes of action of the present invention will be described below with reference to the detail representations in Figs. 1 1 to 20. First of all, looking at Figs. 1 1 to 13, the aspect of the eccentricity of the sealing region 1 14 will be explained with reference to the contact region 1 12.

As is clear from these figures, due to the offset 136 according to the invention of the centre axes 1 16, 1 18 of the contact region 1 12 and of the sealing region 1 14, two substantially cylindrical areas, which may also be of conical construction, are arranged eccentrically relative to one another. This eccentricity enables the best possible fitting of cables of different cross section in particular with conventional commercial cable lugs with eccentric tab and/or conductor fixing, such as for example EXRM- 1235 from TYCO Electronics Raychem GmbH. As is clear from Fig. 12 and the associated detail 13 and from Fig. 13, the sealing region 1 14 would bend comparatively far in the direction of the first insertion channel 102 upon fitting of a cable 134 with a relatively small cross-section and so introduce relatively high permanent forces into the connection region 108. Because the offset 136 is provided, markedly reduced deflection of the sealing region 1 14 in the direction of the first insertion channel 102 is achieved in the case of particularly thin cables, while the fitting of thick cables is still problem-free due to the widening of the sealing region in the direction of the open extension piece 1 10. Figs. 12 and 13 show the outlines of a cable termination in one instance for a large cable 132 and in one instance for a small cable 134.

A further essential aspect of the insulator 100 according to the invention will be explained below with reference to Fig. 14. The detail shown in Fig. 14 is the insulator according to the invention fitted on the outer cone 208 of the appliance terminal. Since the insulator 100 according to the invention dispenses with the previously conventional metal insert plate in the region of the first insertion channel 102, the risk of "milk off arises as a result of the force conditions shown in Fig. 14. Because the insulator is widened in the direction indicated by the arrows 138 and the outer cone 208 of the appliance terminal constitutes an inclined region, a sliding movement arises in the direction 140. The limit stop 128 according to the invention provides a counter-hold 142 against the cable lug and prevents slide-off in the direction 140. In this way, the milk off effect can nonetheless be reliably prevented despite cheaper production of the insulator.

The covering cap 144 will now be looked at in detail with reference to Figs. 15 to 20. An essential feature of the covering cap 144 is that it has a mushroom-shaped structure, such that it presses on the one hand from the inside against the inner wall of the open extension piece 1 10 and in so doing latches onto the catch projection 130 of the open extension piece 1 10 by means of the catch groove 146. The insertion bevel 148 allows simplified fitting of the covering cap 144. The snap connection between the catch projection 130 and the catch groove 146 allows secure, defined fitting. The ratios of the diameters of cap and insulator in the region 1 10 should be designed such that the interface is electrically sealed and watertight. Moreover, an internally situated cap 144 allows material usage and structural space requirements to be reduced relative to an externally situated cap. In addition, the interface tends towards comprising a smaller area. The slope 156 in Fig. 18 allows tolerance compensation to allow the parts to rest resiliently one against the other.

Furthermore, however, the covering cap also comprises a collar-like projection 150, which is pressed against an end face 152 of the open extension piece 1 10. When fitted, as illustrated in Fig. 19, gap- free installation is ensured.

Fig. 20 shows a plan view of the covering cap 144. An actuating tab 154, which simplifies removal of the covering cap by an operator, is here in particular visible.

To summarise, the insulator illustrated in Figs. 1 to 10 includes inter alia the following essential improvements relative to the known arrangement of Figs. 21 to 23:

The reduced wall thickness combined with the use of additional reinforcing ribs on the inner surface of the second insertion channel simplifies fitting while retaining mechanical stability. Electrical requirements are complied with thanks to the bevels which the inner reinforcing ribs form with the longitudinal axis of the insertion channel. Because the internal diameter of the contact region 1 12 may be selected to be sufficiently large, cable lugs with a relatively large diameter may also be accommodated without or with only slight stretching of the insulator in the upper region. The actual sealing function in combination with the cable termination is only effected in the sealing region 1 14 with the reduced internal diameter. In this region additional sealing lips may also be provided on the inner wall.

Insertion of the cable may be simplified by the funnel-shaped flange at the end of the sealing region. Furthermore, the funnel-shaped flange is stabilised by four longitudinal ribs on the outside, which do not however clash with demoulding requirements during production, i.e. for example do not create a need for mould undercuts.

The stopper for closing the open extension piece, which consists in known solutions of a thermoset, generally an epoxy resin, has been replaced in the present invention by a covering cap 144 produced in the injection moulding process. This covering cap may be made from the same material as the rest of the insulator 100, for example of a flexible silicone elastomer.

The covering cap is fixed to the insulator by means of a latching connection and, to simplify removal, is equipped with an actuating tab 154. The covering cap could moreover be fixed to the insulator by means of a band, moulded on in one piece for example, in order to prevent loss. The dimensions of the insulator according to the invention are markedly reduced in comparison with known solutions, since instead of the long stopper only a comparatively short covering cap 144 is used, no metal plate is any longer necessary and the connection region for the cable lug is shortened. By shortening the open extension piece 1 10 it is made possible, moreover, to work on the electrical connection with ordinary tools and for the internal diameter to be made smaller while retaining equally good accessibility.

In this way, the costs of the insulator are reduced significantly, while production time is shortened. The forces arising both on insertion of the cable and when the first insertion channel is pushed onto the outer cone of the appliance terminal are lower. A relatively wide range of cable diameters can be covered with one and the same insulator. The sealing properties of the insulator according to the invention are better than those of known insulators. The fact that no metallic insert plate has to be fitted during injection moulding reduces costs and manufacturing complexity and avoids additional electrical contact surfaces. Finally, the insulator according to the invention adapts itself more readily to any bending of the cable which may occur.

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LIST OF REFERENCE SIGNS