EP3422481B1 - Contact system for contacting a braided shield and a contact element - Google Patents

Description

FIELD OF THE INVENTION

The invention relates to a contact system for contacting an aluminum braided shield with a contact element
an electrically conductive cable with an electrical inner conductor, a primary insulation surrounding the electrical inner conductor and a secondary insulation surrounding the primary insulation;
the aluminum braided screen comprising a plurality of aluminum wires, which is arranged to run at least in sections between the primary insulation and the secondary insulation of the electrically conductive cable;
the contact element which can be pushed onto the electrically conductive cable and which comprises an outer sleeve and an inner sleeve which can be pushed into the outer sleeve at least in sections.

STATE OF THE ART

Electrical cables, the inner conductors of which carry high voltages, require electrical shielding in order to prevent any influence on electrical or electronic components in the vicinity. At the same time, the shield can also be provided to protect the inner conductor against external electrical and / or magnetic interference. For the purpose of shielding, a braided shield, which consists of a large number of strands made of an electrically conductive material, is provided, which encloses the electrical inner conductor. The braided shield is usually located within a cable jacket and is arranged between primary insulation, also called inner jacket, which is arranged between the inner conductor and braided shield, and secondary insulation, also called outer jacket or cable jacket, which surrounds the braided shield on the outside. To increase the shielding effect of the braided shield, you can also use either between the primary insulation and the braided shield or between the braided shield and the secondary insulation, a shielding foil can be provided, which is usually a plastic-laminated aluminum foil. This shielding film does not transmit any noteworthy currents and is not also contacted if the braided shield is contacted, but is separated when the braided shield is exposed.

In order to ensure the shielding of the inner conductor or the equipotential bonding of the braided shield, it is necessary that the braided shield can be connected to a ground in the end regions of the electrical cable. For this purpose, at least one contact element is usually provided at each end of the cable, which are electrically conductively connected to the braided shield and can be connected to ground.

Known method for connecting a braided shield made of copper to a contact element, for example in the DE 10 2015 004 485 B4 are usually realized in that a support sleeve is pushed onto the secondary insulation of the cable and the exposed braided shield is folded back over the support sleeve. The contact part is then passed over the support sleeve and the braided shield resting on it and, for contacting, it is radially pressed, for example crimped, with a suitable tool. During the pressing process, the braided shield is clamped between the support sleeve and the contact part. These methods can only be used for materials with good transverse conductivity, as the braided shield is only pressed at certain points.

Also suitable as conductive material for braided shields are aluminum or aluminum alloys, which due to its low mass is used in many areas of application, for example in the automotive sector, in particular in electrically powered automobiles. However, if aluminum wires made of aluminum or an aluminum alloy are pressed together, these wires naturally only have one very difficult to penetrate oxide layer on its surface. A contacting process for a braided shield, which is common in copper technology, is not able to establish contact with all the aluminum wires of the braided aluminum shield with the contact element due to the radial compression, since the oxide layers that form on the aluminum wires prevent transverse conductivity in the pressed areas. Thus, the oxide layers for all wires in the braided shield cannot be broken through by known methods. It has also been shown that with known contacting methods in the case of aluminum braided shields, it is not possible to achieve a connection that is stable through thermal cycling.

In order to enable uniform shield contact with these materials, known connection methods for aluminum braided shields make use of additional measures in order to secure the contact of all aluminum wires and, if necessary, to be able to break up the oxide layer. For example, from the DE 10 2012 00 137 B4 It is known that when connecting an aluminum braided shield to a sleeve, the braided shield is folded back over the sleeve and the connection is made using ultrasonic welding. In this process, a material connection between the braided shield and the contact part is established by supplying heat.

On the one hand, this type of connection technology has the disadvantage that the quality of the braided shield always also influences the quality of the connection; in this case, adhering substances from the previous processes are mainly disturbing factors. On the other hand, the production of such electrically conductive connections between an aluminum braided shield and a contact element is dependent on the existence of expensive welding systems, which are also not portable and therefore cannot be used flexibly.

The EP 2 874 236 A1 describes a contact system consisting of a first inner contact part and a second outer Contact part by means of which an aluminum wire screen comprising several individual wires can be clamped and contacted. In this case, the wire screen is pressed between a conical outer surface of a contact area of the first contact element and a conical inner surface of the second contact element via clamping means of the contact system.

The U.S. 5,508,475 describes a contact system in which a sleeve is pushed onto an end piece so that a cable shield is clamped between the end piece and the sleeve by moving it axially.

OBJECT OF THE INVENTION

It is therefore an object of the invention to overcome the known contact systems of the prior art and to propose a system that enables reliable contacting of an aluminum braided shield with a contact element in a simple manner, the clamping force in defined areas of the contact surfaces through structural measures should be increased.

DISCLOSURE OF THE INVENTION

This object relates to a contact system according to the invention for contacting an aluminum braided shield with a contact element of the type mentioned above, the inner sleeve having a first contact surface and the outer sleeve having a second contact surface for contacting the aluminum braided shield, the first and / or second contact surface each having areas with cross-sections of different sizes in relation to a conductor axis of the electrically conductive cable,
and wherein the contact surfaces are designed such that the aluminum wires of the aluminum braided shield are clamped in a contact position of the contact part by axially sliding the inner sleeve and the outer sleeve between the contact surfaces and are in contact with the contact part.

As electrical inner conductors made of electrically conductive material, preferably copper, aluminum or alloys containing at least one of these metals, both individual conductors and of several conductors are understood in the context of the invention Single conductors consisting of strands or a package of two, three, four or more strands, which are covered by the primary insulation. The electrical inner conductor defines a conductor axis which follows the course of the electrical cable, that is to say can run straight, curved or angled in sections. However, at least in the area of the contact, the conductor axis generally runs straight.

The term sleeve is usually understood to mean an element which comprises a, preferably central, through opening and a preferably rotationally symmetrical jacket body having the through opening. In principle, the through opening can have any geometric cross section as long as at least one section of the electrically conductive cable is guaranteed to pass through. The inner sleeve is that sleeve which, in the contact position, is arranged closer to the inner conductor in the radial direction. In other words, the inner sleeve can be pushed onto the electrically conductive cable, so that the through opening of the inner sleeve, hereinafter referred to as the cable bushing, is advantageously adapted to the geometry of the electrical inner conductor of the cable, for example circular, elliptical or essentially polygonal. The jacket body of the inner sleeve is designed in such a way that the inner sleeve can be pushed into the outer sleeve at least in sections, the first contact surface of the inner sleeve usually being formed by a radially outer peripheral surface of the inner sleeve. In general, the ability to be pushed in is achieved in that the outer dimensions of the inner sleeve are smaller than or equal to the inner dimensions of the through opening of the outer sleeve. The second contact surface of the outer sleeve is generally formed by a radially inner circumferential surface, that is to say by the boundary surface of the through opening of the outer sleeve.

The contact surfaces are in any case defined by a surface of the inner sleeve or the outer sleeve and conceptually enclose a volume. If in light of the invention of A cross section of a contact surface is spoken of, this is understood to mean the cross section of the enclosed volume which is oriented normal to the conductor axis.

In the contact position, the aluminum braided shield is arranged between the contact surfaces so that the aluminum wires of the aluminum braided shield, preferably all aluminum wires if possible, contact both the first contact surface and the second contact surface. Due to the different sized cross-sections of at least one of the contact surfaces of the inner sleeve and outer sleeve, which are usually arranged correspondingly in the contact position, the aluminum wires of the aluminum braided shield contacting the contact surfaces are already clamped by axially sliding the outer sleeve and inner sleeve into one another. Due to the different cross-sections, with a circular cross-section, these correspond to the diameter, in different areas at least one of the interacting contact surfaces, which areas either continuously or abruptly merge into one another, at least one area is defined in which, when the sleeves are pushed into one another, one from the contact surfaces onto the aluminum - Braided shielding force is exerted. Each of the contact surfaces preferably has regions with a different cross-section.

Thus, either an electrical contact is established between the outer sleeve and / or the inner sleeve and the aluminum wires in order to enable potential equalization. For the choice of the geometry of the interacting contact surfaces of the sleeves, a variety of shapes are possible, as long as the design of the contact surfaces and their cross-sections define at least one area through which a clamping force is exerted on the aluminum shield when the sleeves are pushed into one another.

In the context of the invention, axial pushing into one another or pressing together means that the two sleeves are pushed or pressed into one another in the direction of a conductor axis and the pressing is not achieved, as is known from the prior art, by subsequent radial pressing, e.g. crimping becomes. Uniform contact between the aluminum wires and the contact element is thus achieved by pushing the sleeves into one another, since the pressing is no longer carried out radially or punctually, but runs evenly over the contact surface and the aluminum wires.

Although the invention relates to an aluminum braided screen made of aluminum wires, it should be expressly pointed out that the contact element according to the invention is also suitable for braided screen made of other materials or alloys, for example made of copper or copper alloys.

In order to achieve clamping and / or pinching / shearing of the aluminum wires of the aluminum braided shield between the contact surfaces of the sleeves, it is provided according to the invention that the first contact surface has at least one step. The second contact surface preferably also has a step. A step is understood to mean a sudden increase or decrease in the cross-sectional area defining the corresponding contact surface normal to the conductor axis. Such a configuration can be combined with any geometric shape of the contact surfaces, for example the first and / or second contact surface can have a cylindrical shape or the conical shape described above. It is advantageous if both contact surfaces have mutually corresponding first and second steps. The at least one first and / or second step defines the area in which, in the contact position, the pressure peak for exerting the clamping force or for pinching / shearing and cold welding of the aluminum wires is located of the aluminum braided shield. Advantageous effects are already observed if only one of the contact surfaces has a step. However, variants are also conceivable in which a contact surface has several steps or both contact surfaces have one or more steps.

In order to ensure the contact between the aluminum wires of the aluminum braided shield and the contact element in a simple manner, in particular to be able to safely penetrate the oxide layer of the aluminum wires, one embodiment variant of the invention provides that the contact surfaces are further designed so that in the Contact position of the contact element by axially compressing the outer sleeve and inner sleeve, pinching / shearing of the aluminum wires of the aluminum braided shield and cold welding of the aluminum wires of the aluminum braided shield to the contact element takes place.

The contact between the aluminum braided shield and the contact element is achieved in the variant in that the contact surfaces of the inner sleeve and the outer sleeve are designed in such a way that the surface containing the oxide layer of as many aluminum wires as possible of the aluminum braided shield is broken when the inner sleeve and the outer sleeve are axially pressed together, so that a cold weld can occur between at least one contact surface and the aluminum braided shield. To break up the surface, the aluminum wires are squeezed or at least partially sheared / sheared off when they are pressed together, so that a cold weld occurs between the aluminum wires and at least one of the sleeves, i.e. the inner sleeve and / or the outer sleeve. The areas of different cross-section of the contact surfaces, which preferably correspond to one another, in turn define at least one area in which a pressure peak is formed when the contact surfaces are pressed together. This area usually corresponds to the area in which the clamping force is also exerted. A cold-welded state can can thus be achieved when the sleeves are axially compressed, for example starting from the contact position in which the aluminum braided shield is clamped between the contact surfaces.

Cold welding exploits the effect that aluminum tends to flow when very high pressure is applied and can therefore be cold-welded with contacting materials. Such a connection is permanent and electrically conductive.

In other words, the choice of the geometry of the interacting contact surfaces, taking into account the areas with different sized cross-sections, ensures that the oxide layer is reliably broken through when the sleeves are axially compressed by squeezing or squeezing the aluminum wires of the aluminum braided shield in an area defined by the contact surfaces . be sheared off. At the same time, the connection by means of the contact system according to the invention is insensitive to superficial contamination of the aluminum braided shield due to the local shearing / crushing and the cold welding that takes place there. For the choice of the geometry of the interacting contact surfaces of the sleeves, a large number of shapes are possible, as long as the design of the contact surfaces and their areas with different cross-sections define at least one area in which a pressure tip is formed when axially compressed, which can cause pinching / Shear of the aluminum wires and ultimately leads to cold welding.

As a rule, one of the sleeves is made of copper or a preferably coated copper alloy and serves as a contact sleeve while the other sleeve functions as a support sleeve. The cold welding advantageously takes place both between the contact sleeve and between the support sleeve and the aluminum braided shield.

In a further embodiment of the invention it is provided that the second contact surface of the outer sleeve delimits an insertion volume for the inner sleeve and the first contact surface of the inner sleeve is formed by a section of the inner sleeve that can be inserted into the insertion volume. The insertion volume of the outer sleeve is generally formed by a section of the through opening, preferably completely through the through opening. The interaction of the contact surfaces can be achieved in a simple manner through the design of the insertion volume of the outer sleeve and the insertable section of the inner sleeve.

According to a further embodiment variant of the invention it is provided that the insertion volume and / or the insertable section taper at least in sections with respect to the conductor axis. Due to the tapering of at least one, preferably both, element (s) forming the contact surfaces, a geometry of the contact surfaces is achieved in a simple manner, which causes a clamping or pinching / shearing of the aluminum braided shield in the contact position. In the tapering section, that area is formed which exerts a clamping force on the aluminum wires or causes the aluminum wires to be crushed / sheared. It goes without saying that two, three, four or more tapering sections can also be provided. In other words, the contact surfaces can be designed in such a way that in an intermediate position of the contact part, in which the inner sleeve is pushed into the outer sleeve in sections, a gap for receiving the aluminum braided shield is formed between the contact surfaces and the gap has at least one cross-sectional constriction.

A particularly space-saving design of the contact element is achieved in a preferred embodiment variant in that the inner sleeve in the contact position is completely received in the insertion volume of the outer sleeve. In other words, the entire inner sleeve is designed as an insertable section.

In order to be able to easily produce and define the areas with different cross-sections in the contact surfaces, a further variant embodiment of the invention provides that the first and / or the second contact surface in the contact position are at least partially designed to run obliquely to the conductor axis . In other words, the imaginary extensions of the first and / or second contact surface intersect the conductor axis.

In a particularly simple manner, clamping and / or compression / shearing of the aluminum wires of the aluminum braided shield between the contact surfaces can be achieved in a preferred embodiment variant in that the first and / or the second contact surface is conical. The conicity, which usually relates to the conductor axis, of at least one contact surface, preferably both contact surfaces, ensures that the contact surfaces exert a clamping force on the aluminum wires or a pressure tip for squeezing through an axial displacement of the sleeves into the contact position / Form shear (i.e. cold welding) of the aluminum wires. It goes without saying that the contact surfaces are designed to correspond to one another, at least if both contact surfaces are designed to be conical.

An increase in the clamping force or a particularly efficient definition of an area in which a cold weld is generated is achieved in an example not claimed in that the first and second contact surfaces are conical, the opening angles of the cones being at least partially different. Due to the different opening angles in relation to the conductor axis, there is on the one hand an increase in the axial sliding into one another Clamping force in the area in which the clear distance between the contact surfaces is minimal. On the other hand, an area between the contact surfaces can be defined in which a pressure peak is formed when the sleeves are pressed together. Due to this pressure peak, the aluminum wires can be sheared / crushed to produce the cold weld.

The effects mentioned above in connection with the conical contact surfaces can be further improved in that the first and / or the second contact surface has at least one kink. A kink is understood to mean the change in the slope in the conical or frustoconical contact surface or, in other words, the continuous transition between two mutually merging sections with different opening angles of the contact surface. Each bend defines a circumferential contact edge on which a pressure peak forms and / or which exerts a clamping force on the aluminum braided shield. Advantageous effects are already observed if only one of the contact surfaces has a kink. However, variants are also conceivable in which a contact surface has several kinks or both contact surfaces have one or more kinks. The kinks, in turn, define the area in which the clamping force is exerted on the aluminum wires in the contact position or in which the pressure tip is formed in the contact position.

In order to reinforce the advantages mentioned above in connection with the steps, a further particularly preferred embodiment of the invention provides that the first contact surface have at least one first step and the second contact surface have at least one second step, the steps each forming a circumferential contact edge and the aluminum braided shield is contacted by the contact edges in the contact position. The contact edges in turn define the area in which the pressure tip is in the contact position Exercise of the clamping force or for pinching / shearing and cold welding of the aluminum wires of the aluminum braided screen.

It is advantageous for equipotential bonding if one of the sleeves is designed as a contact sleeve, via which potential equalization is enabled, and the other sleeve is designed as a support sleeve. In order to achieve good connection properties between the aluminum wires of the aluminum braided screen and the contact sleeve, it is particularly advantageous if the contact sleeve is made of copper or a copper alloy. Depending on the application, either the inner sleeve or the outer sleeve can be designed as a contact sleeve. It is also conceivable that both the contact sleeve and the support sleeve are made of copper or a copper alloy. Therefore, in further embodiment variants of the invention it is provided that the inner sleeve and / or the outer sleeve is made of copper or a copper alloy.

Particularly good clamping properties or cold welding properties and electrical conduction properties are achieved in a further embodiment variant in that one of the sleeves is made from copper or a copper alloy and the other sleeve is made from aluminum or an aluminum alloy. The sleeve made of aluminum or an aluminum alloy, that is to say the sleeve designed as a support sleeve, furthermore minimizes the tendency of the aluminum wires to corrode in the area of the contact element. In order to achieve a particularly high strength of the support sleeve, it can also be made of stainless steel, which is preferably protected against corrosion, for example by means of a corrosion-inhibiting coating.

In order to also improve the corrosion properties of the sleeve made of copper or a copper alloy, preferably the contact sleeve, and the tendency to corrosion To reduce aluminum wires, a further particularly preferred embodiment of the invention provides that the sleeve made of copper or a copper alloy has a corrosion-inhibiting coating. Nickel and / or tin or alloys containing nickel and / or tin are particularly suitable as coating materials for such a corrosion-inhibiting coating.

In order to be able to contact the aluminum braided shield arranged between the primary insulation and the secondary insulation with the contact element, it is usually necessary to cut the cable to length and to strip the aluminum braided shield at one open end of the cable, i.e. at least remove the secondary insulation and the inner sleeve relatively to position electrical conductor. Therefore, in a further embodiment of the invention it is provided that the secondary insulation is removed at least in that area of the electrically conductive cable in which the contact element is arranged in the contact position, the area having the smallest cross section of the first contact surface being adjacent to the area having the secondary insulation of the cable is adjacent.

While it is known according to the prior art that the contact element sits in the contact position on the secondary insulation of the cable and the braided shield is folded back over the contact element so as not to damage the inner conductor through the subsequent radial compression or welding, it is the case according to the invention Design of the inner sleeve and outer sleeve, however, possible to arrange the contact element in a space-saving manner in the stripped area of the cable, that is to say in the area in which the secondary insulation is removed. The reason for this is that the clamping or cold welding is only achieved by sliding the inner sleeve and outer sleeve into one another or axially pressing them together, so there is no risk of the inner conductor being damaged by the axial compression of the sleeves. The inner sleeve is preferably between the primary insulation and the aluminum braided screen inserted so that the inner sleeve contacts the primary insulation on the one hand and the aluminum braided screen on the other. Therefore, in a further preferred embodiment of the invention, it is provided that the inner sleeve is arranged in the contact position between the primary insulation and the aluminum braided shield, a cable bushing of the inner sleeve preferably making contact with the primary insulation. Both the inner sleeve and the outer sleeve or at least their contact surfaces are thus located in the radial direction in the stripped area of the cable.

In a further embodiment variant of the invention it is provided that the aluminum braided shield is folded over the first contact surface of the inner sleeve and a cable bushing of the inner sleeve contacts the secondary insulation or the aluminum braided shield. If the inner sleeve is in the contact position on the secondary insulation and thus the cable bushing, i.e. the passage opening, of the inner sleeve contacts the secondary insulation, the aluminum braided screen must be folded over to make contact over the first contact surface. A particularly space-saving design is achieved in that the inner sleeve is pushed over the aluminum braided shield in the stripped area of the cable and then the aluminum braided shield is folded over the first contact surface. The cable bushing makes contact with the section of the aluminum braided shield resting on the primary insulation and the first contact surface makes contact with the part of the aluminum braided shield that is folded back.

• gegebenenfalls Entfernen eines Abschnitts einer das Aluminium-Schirmgeflecht umgebenden Sekundärisolation und/oder eines Abschnitts einer den Innenleiter umgebenden Primärisolation im Bereich eines offenen Endes des elektrischen Kabels;
• gegebenenfalls Aufschieben von Innenhülse und Außenhülse auf das elektrisch leitende Kabel;
• Platzieren der Innenhülse zwischen Aluminium-Schirmgeflecht und Innenleiter, wobei das Aluminium-Schirmgeflecht an der ersten Kontaktoberfläche anliegt;
• Verschieben der Außenhülse in Richtung der Innenhülse in eine Kontaktposition des Kontaktteils in dem die zweite Kontaktoberfläche der Außenhülse das Aluminium-Schirmgeflecht kontaktiert und die Aluminiumdrähte des Aluminium-Schirmgeflechts zwischen den Kontaktoberflächen festgeklemmt wird.

One possibility for using the contact system according to the invention relates to a method for contacting an aluminum braided screen and a contact element, which is formed from aluminum wires and surrounds an electrical inner conductor of an electrically conductive cable, the contact element comprising an inner sleeve with a first contact surface and an outer sleeve with a second contact surface, taking the following steps be performed:

• optionally removing a section of secondary insulation surrounding the aluminum braided shield and / or a section of primary insulation surrounding the inner conductor in the area of an open end of the electrical cable;
• if necessary, sliding the inner sleeve and outer sleeve onto the electrically conductive cable;
• Placing the inner sleeve between the aluminum braided shield and the inner conductor, the aluminum braided shield resting against the first contact surface;
• Moving the outer sleeve in the direction of the inner sleeve into a contact position of the contact part in which the second contact surface of the outer sleeve contacts the aluminum braided shield and the aluminum wires of the aluminum braided shield are clamped between the contact surfaces.

First, the electrically conductive cable is cut to length and the resulting open end of the cable is stripped, with at least the secondary insulation being removed in that or up to that area in which the contact is to be made with the contact element. It goes without saying that an already cut cable with a stripped open end can also be used.

The inner sleeve and outer sleeve are then pushed onto the cable, the cable being guided through the through opening of the sleeves, respectively the insertion volume and the cable bushing. However, it is also conceivable for the electrical cable to be delivered already prefabricated, so that the outer sleeve and inner sleeve only need to be pushed or pressed together.

If the contact element is to be arranged in the contact position in the non-stripped area of the cable, it is necessary to first slide the inner sleeve onto the secondary insulation, then fold the aluminum braided screen over the secondary insulation or over the inner sleeve and then slide the outer sleeve from the direction of the stripped area of the cable in the direction of the inner sleeve. In other words, the inner sleeve is placed between the secondary insulation and the folded-back section of the aluminum braided shield. According to a further variant of the method it is therefore provided that first the inner sleeve is pushed over the secondary insulation and then the aluminum braided shield is folded over the first contact surface before the outer sleeve is shifted in the direction of the inner sleeve. In this case, the outer sleeve is shifted from the direction of the open end of the cable in the direction of the area of the electrically conductive cable having the secondary insulation in order to be brought into the contact position.

If, however, the contact element is to be arranged in the contact position in a space-saving manner in the stripped area of the cable, as is provided in a preferred variant of the method, the outer sleeve is first pushed onto the secondary insulation of the cable. The inner sleeve is then inserted between the primary insulation and the aluminum braided shield so that it is no longer necessary to fold over the aluminum braided shield. The outer sleeve is then pushed in the direction of the stripped area of the cable or in the direction of the inner sleeve. According to a further variant of the method it is therefore provided that first the outer sleeve is pushed over the secondary insulation and then the inner sleeve is inserted between the aluminum braided shield and the primary insulation before the outer sleeve is moved in the direction of the inner sleeve. In this case, the outer sleeve is displaced from the area of the electrical cable which has the secondary insulation in the direction of the open end of the cable in order to be brought into the contact position.

It is particularly space-saving if the inner sleeve in the stripped area is pushed directly onto the aluminum braided shield attached to the primary insulation and that Aluminum braided shield is folded over the first contact surface in the stripped area of the electrically conductive cable. The aluminum braided shield is exposed to such an extent that a section protrudes beyond the pushed-on inner sleeve and can be turned over. The outer sleeve is then subsequently shifted in the direction of the area of the electrically conductive cable having the secondary insulation. According to a further variant of the method, it is therefore provided that the inner sleeve is first pushed over the aluminum braided shield and then a section of the aluminum braided shield protruding over the inner sleeve is folded over the first contact surface before the outer sleeve is shifted in the direction of the inner sleeve. In this case, the outer sleeve is shifted from the direction of the open end of the cable in the direction of the area of the electrically conductive cable having the secondary insulation in order to be brought into the contact position.

In all of the above-mentioned variants, the inner sleeve is placed between the inner conductor and the braided shield when viewed in the radial direction, if necessary with the primary insulation and / or the secondary insulation in between.

By axially sliding the outer sleeve and inner sleeve into one another, the aluminum wires of the aluminum braided shield are clamped between the contact surfaces, as described in detail at the beginning in connection with the contact system.

• Weiterverschieben und Pressen der Außenhülse in Richtung der Innenhülse sodass durch die Druckbeaufschlagung der Kontaktoberflächen eine Quetschung/Scherung der Aluminiumdrähte des Aluminium-Schirmgeflechts und Kaltverschweißung der Aluminiumdrähte des Aluminium-Schirmgeflechts an den Kontaktoberflächen des Kontaktelements stattfindet.
  Besonders vorteilhaft ist es, wenn ein erfindungsgemäßes System in Kombination mit dem beschriebenen Verfahren verwendet wird bzw. wenn ein erfindungsgemäßes System durch das beschriebene Verfahren herstellbar ist.

In order to ensure the contact between the aluminum wires of the aluminum braided shield and the contact element in a simple manner, in particular to be able to safely penetrate the oxide layer of the aluminum wires, one variant of the method provides for the following method step to be carried out:

• Moving and pressing the outer sleeve in the direction of the inner sleeve so that the pressurization of the contact surfaces squeezes / shears the Aluminum wires of the aluminum braided shield and cold welding of the aluminum wires of the aluminum braided shield takes place on the contact surfaces of the contact element.
  It is particularly advantageous if a system according to the invention is used in combination with the method described or if a system according to the invention can be produced by the method described.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in more detail on the basis of exemplary embodiments. The drawings are exemplary and are intended to explain the concept of the invention, but in no way restrict it or reproduce it conclusively.

Fig. 1

eine Schnittansicht eines erfindungsgemäßen Kontaktsystems in einer Kontaktposition;

Fig. 2

eine axonometrische Ansicht des Kontaktsystems in der Kontaktposition;

Fig. 3

eine axonometrische Ansicht eines ersten Ausführungsbeispiels des Kontaktsystems in einer Zwischenposition;

Fig. 4

eine axonometrische Ansicht eines zweiten Ausführungsbeispiels des Kontaktsystems in einer Zwischenposition;

Fig. 5

eine vergrößerte Detailansicht eines Kontaktelements des ersten Ausführungsbeispiels;

Fig. 6

eine vergrößerte Detailansicht eines Kontaktelements eines zweiten Ausführungsbeispiels;

Fig. 7a,b,c,d

Schnittansichten des ersten Ausführungsbeispiels in mehreren aufeinanderfolgenden Positionen;

Fig. 8a,b,c,d

Schnittansichten des zweiten Ausführungsbeispiels in mehreren aufeinanderfolgenden Positionen;

Fig. 9

eine Schnittansicht eines dritten Ausführungsbeispiels des Kontaktsystems in der Kontaktposition;

Fig. 10

eine Schnittansicht eines vierten Ausführungsbeispiels des Kontaktsystems in der Kontaktposition;

It shows:

Fig. 1

a sectional view of a contact system according to the invention in a contact position;

Fig. 2

an axonometric view of the contact system in the contact position;

Fig. 3

an axonometric view of a first embodiment of the contact system in an intermediate position;

Fig. 4

an axonometric view of a second embodiment of the contact system in an intermediate position;

Fig. 5

an enlarged detailed view of a contact element of the first embodiment;

Fig. 6

an enlarged detailed view of a contact element of a second embodiment;

Figures 7a, b, c, d

Sectional views of the first embodiment in several successive positions;

Figures 8a, b, c, d

Sectional views of the second embodiment in several successive positions;

Fig. 9

a sectional view of a third embodiment of the contact system in the contact position;

Fig. 10

a sectional view of a fourth embodiment of the contact system in the contact position;

WAYS OF CARRYING OUT THE INVENTION

The Figures 1 and 2 show the basic structure of a contact system according to the invention for contacting an aluminum braided shield 7 with a contact element 1. The aluminum braided shield 7 comprises a large number of aluminum wires and runs between a primary insulation 6 and a secondary insulation 8 of an electrically conductive cable 4. The structure of the cable 4 , which is especially in Figure 2 and 4th can be seen, looks like this:
The core of the cable 4 is formed by an electrical inner conductor 5 which defines a conductor axis 15 which runs in a straight line in the figures. In the present figures, the inner conductor 5 is formed by a multiplicity of individual conductors bundled as a strand and has an essentially circular cross section. It goes without saying that the number of individual conductors of a strand and the number of strands or the geometry of the cross section are irrelevant for the invention itself. In principle, both individual conductors and also elliptical or polygonal cross-sections of the inner conductor 5 are therefore conceivable. A primary insulation 6, also called an inner jacket or conductor insulation, is applied to the inner conductor 5, which causes insulation between the inner conductor 5 and the aluminum braided shield 7. A secondary insulation 8, also called an outer jacket or cable jacket, is then applied to the aluminum braided shield 7, which insulation insulates the inner conductor 5 and the aluminum braided shield 7 from the environment.

Before contact can be made between the aluminum braided shield 7 and the contact element 1, the electrically conductive cable 4 must usually be cut to length so that an open end of the cable 4 is formed. In that area of the electrically conductive cable 4 in which the Contact element 1 can be arranged in the contact position, secondary insulation 8 is removed. In the following, therefore, we will speak of the stripped area in this context. As a rule, the stripped area is arranged in the section of the open end of the cable 4 and, as can be seen in the figures, extends to the end of the cable 4. Furthermore, as can be seen in the figures, an end-side section can also be used of the cable 4 must be freed from primary insulation 6, aluminum braided shield 7 and secondary insulation 8, so that the inner conductor 5 is exposed for electrical connection.

The contact element 1 comprises an inner sleeve 2 with a first contact surface 2a and an outer sleeve 3 with a second contact surface 3a, the contact surfaces 2a, 3a being designed for contacting the aluminum braided shield 7 in the contact position shown. The inner sleeve 2 can be pushed into the outer sleeve 3 at least in sections. At least one of the two sleeves 2, 3 is designed as a contact sleeve and can be electrically connected to a ground for the purpose of potential equalization.

Since the contact surfaces 2a, 3a of the sleeves 2, 3 are designed in such a way that the aluminum wires of the aluminum braided shield 7 are clamped in the contact position of the contact part 1 by axially sliding the inner sleeve 2 and outer sleeve 3 between the contact surfaces 2a, 3a and with the contact part 1, the aluminum braided shield 7 is clamped in the illustrated contact position between the contact surfaces 2a, 3a. Furthermore, the contact surfaces 2a, 3a in the exemplary embodiments are also designed in such a way that in the contact position of the contact element 1 by axially compressing the outer sleeve 3 and inner sleeve 2, the aluminum wires of the aluminum braided shield 7 are crushed / sheared and the aluminum wires of the aluminum braided shield 7 are cold-welded with the contact element 1 takes place. This design is achieved in that the contact surfaces 2a, 3a have areas of different cross-sections, in the present case different diameters. Therefore, the electrical connection between the aluminum wires of the aluminum braided screen 7 and the contact element 1 is established in the contact position shown by means of cold welding. In other words, the aluminum wires are welded to the contact element 1 in the contact position.

In principle, the contact surfaces 2a, 3a surrounding the aluminum braided shield 7 achieve uniform contact with as many aluminum wires as possible, without the need for radial compression, such as crimping, or additional welding. At the same time, the electrical contact can be established by simply pushing or pressing the sleeves 2, 3 together.

Two possible geometrical configurations of the contact surfaces 2a, 3a, which achieve the two above-mentioned effects, are discussed in detail below.

Figure 3 shows an axonometric view of a first embodiment of the system according to the invention in an intermediate position in which the contact surfaces 2a, 3a of the sleeves 2, 3 are not yet in contact with the aluminum braided shield 7. It can clearly be seen that the first contact surface 2a of the inner sleeve 2 is conical, so that the size of the cross-sections or diameter changes normal to the conductor axis 15 along the entire longitudinal extent of the sleeves 2, 3. In other words, the two contact surfaces 2a, 3a run obliquely to the conductor axis 15. It can also be seen that the contact surface 2a has two sections of different gradients which merge into one another at a bend 12. In this case, the contact surface 2a has a larger opening angle in a first section facing the outer sleeve 3 in the present illustration, that is to say it is steeper than in the second section.

Figure 4 shows one to Figure 3 analog axonometric view of a second embodiment of the system according to the invention in the intermediate position. It can be seen here that the first contact surface 2a of the inner sleeve 2 is composed of three cylindrical sections of different sizes or diameters, with two first steps 13 separating two successive sections from one another.

In Figure 5 is a contact element 1 of the first embodiment, in Figure 6 a contact element 1 of the second exemplary embodiment, that is to say the inner sleeve 2 and the outer sleeve 3, are shown in detail. It can be seen immediately that the inner sleeve 2 and outer sleeve 3 each have a through opening and that the inner sleeve 2 can be pushed into the outer sleeve 3 at least in sections. The through opening of the inner sleeve 2 is designed as a cable bushing 11 through which the cable 4 can be guided. The first contact surface 2 a of the inner sleeve 2 is formed by an outer peripheral surface of the inner sleeve 2.

The through opening of the outer sleeve 3 is designed as an insertion volume 9 for receiving an insertable section 10 of the inner sleeve 2 and also serves to lead through the cable 4. In the present exemplary embodiment, the insertable section 10 covers the entire extent of the inner sleeve 2, so that the inner sleeve 2 is in the contact position is completely received in the outer sleeve 3. In alternative design variants, it is also conceivable that the insertable section 10 comprises only part of the longitudinal extent of the inner sleeve 2, so that a part of the inner sleeve 2 protrudes out of the outer sleeve 3 in the contact position. The second contact surface 3a is formed by an inner circumferential surface of the outer sleeve 3a and delimits the insertion volume 9.

In both exemplary embodiments it can be seen that the geometry of the first contact surface 2a corresponds to that of the second Contact surface 3a corresponds to the extent that the aluminum braided shield 7 can be clamped or cold-welded between the contact surfaces 2a, 3a.

In Figure 5 the conicity of the first contact surface 2a, described above in connection with the first exemplary embodiment, is shown again including the bend 12. In addition, the conical design of the second contact surface 3a of the outer sleeve 3 can now also be seen. In the present exemplary embodiment, the opening angles of the cones of the contact surfaces 2a, 3a differ from one another, so that when the inner sleeve 2 is pushed into the outer sleeve 3 or when the outer sleeve 3 is pushed onto the inner sleeve 2, a wedge-like cross-sectional constriction is achieved. The kink 12 defines the area in which a clamping force is exerted on the aluminum wires by the contact surfaces 2a, 3a or in which a pressure peak for pinching / shearing and cold welding of the aluminum wires is formed. The area is thus a circumferential contact edge defined by the bend.

In Figure 6 on the other hand, the first steps 13 of the first contact surface 2a described above in connection with the second embodiment variant can be seen. The second contact surface 3a is now also shown, which has second steps 14 cooperating with the first steps 13 and dividing the second contact surface 3a into three sections. When the inner sleeve 2 is pushed into the outer sleeve 3 or when the outer sleeve 3 is pushed onto the inner sleeve 2, the interaction of the steps 13, 14 again results in a wedge-like cross-sectional constriction. In other words, the steps 13, 14 define the area in which a clamping force is exerted on the aluminum wires by the contact surfaces 2a, 3a or in which a pressure peak for pinching / shearing and cold welding of the aluminum wires is formed. In this embodiment, a circumferential contact edge is formed by each of the steps 13, 14, which represents the above-mentioned area.

The Figures 7a, b, c, d and 8a, b, c, d show different positions of the contact element 1 or the inner sleeve 2 and the outer sleeve 3 during the contacting process, the first-mentioned figures showing a system according to the first embodiment and the last-mentioned figures showing a system according to the second embodiment.

In a first step (see in Figures 7a, 7b or 8a, 8b) the outer sleeve 3 is pushed onto the electrically conductive cable 4. The outer sleeve 3 is pushed out over the stripped area so that the outer sleeve 3 comes to rest over the secondary insulation 8. In order to be able to ensure that the outer sleeve 3 can be pushed onto the secondary insulation 8, the smallest diameter of its passage opening is greater than or equal to the diameter of the cable 4 including the secondary insulation 8. In other words, the cable 4 is received in sections in the insertion volume 9 of the outer sleeve 3.

The second step (shown in the Figures 7b, 7c and 8b, 8c ) consists in that the inner sleeve 2 is pushed onto the electrically conductive cable 4. The smallest diameter of the cable bushing 11 is greater than or equal to the diameter of the cable 4 including the primary insulation 6, so that the inner sleeve 2 can be pushed onto the primary insulation 6.

As in the Figures 7c and 8c it can be seen that the inner sleeve 2 is pushed between the primary insulation 6 and the aluminum braided shield 7 so that the aluminum braided shield 7 makes contact with the first contact surface 2a. It is also conceivable that the aluminum braided shield 7 is lifted off the primary insulation 6 in a separate step and, after the inner sleeve 2 has been pushed on, is slipped onto the first contact surface 2a, for example by means of the step described below or in a separate step.

In the last step, the outer sleeve 3 is then moved in the direction of the inner sleeve 2 until the second contact surface 3a and the first contact surface 2a contact the aluminum braided shield 7 in the contact position and the aluminum wires of the aluminum braided shield 7 are clamped between the contact surfaces 2a, 3a and the electrical contact between the contact element 1 and the aluminum braided shield 7 is established. In the first embodiment, the wedge-shaped taper or bend 12 and in the second embodiment the steps 13, 14 define that area of the contact surfaces 2a, 3a in which the clamping force is exerted on the aluminum braided shield 7 in the contact position.

When the inner sleeve 2 and outer sleeve 3 are pressed together further, pressure peaks form at the bend 12 or at the steps 13, 14 (i.e. on the circumferential contact edges), which first lead to compression and, when further pressed together, to at least partial crushing or shearing, preferably a complete shearing, the aluminum wires lead, so that a cold welding of the aluminum wires of the aluminum braided screen 7 with the contact element 1 takes place. By squeezing or shearing the aluminum wires, the surface of the aluminum wires with the oxide layer is broken open and the oxide layer is broken through and a new formation of the oxide layer is prevented so that an alternating temperature-resistant, highly conductive electrical connection between the aluminum braided screen 7 and the contact element 1 is ensured, if the aluminum wires are cold-welded after being pressed together in the contact position with the contact element 1.

As a rule, one of the two sleeves 2, 3, i.e. either the inner sleeve 2 or the outer sleeve 3, is designed as a contact sleeve made of copper or a copper alloy and preferably a corrosion-inhibiting coating such as nickel and / or tin or alloys from it. The potential equalization of the aluminum braided shield 7 is connected to a Ground possible in that the contact sleeve can be electrically connected to ground by means of a compensating conductor. The other sleeve is designed as a support sleeve and is made of aluminum or an aluminum alloy in order to reduce the corrosion of the aluminum wires.

It goes without saying that any combination of the first and second exemplary embodiments are also suitable for achieving the same technical effects. Geometries deviating from the geometry of the contact surfaces 2a, 3a shown in the exemplary embodiments are also conceivable if they enable the aluminum wires of the aluminum braided screen 7 to be clamped or compressed / sheared off.

In Figure 9 a third embodiment of the contact system according to the invention is shown, in which the inner sleeve 2 is seated on the secondary insulation 8 in the contact position. In order to be able to clamp the aluminum braided shield 7 between the contact surfaces 2a, 3a, a section of the aluminum braided shield 7 is folded back over the first contact surface 2a. The outer sleeve 3 can be pushed onto the inner sleeve 2 in the axial direction, i.e. in the direction of the conductor axis 15, in order to enable the clamping or compression / shearing of the aluminum wires of the aluminum braided screen 7 between the two contact surfaces 2a, 3a.

The method for contacting the aluminum braided shield 7 with the contact element 1 differs from the method previously described in connection with the first two design variants due to the different structure of the contact systems: In a first step, the inner sleeve 2 is placed on the open end of the electrically conductive cable 4 pushed on and pushed over the stripped area onto the secondary insulation 8. If the first contact surface 2a - as in the illustrated embodiment - has areas with different cross-sections, it is advantageous if the area with the smallest cross-section in Direction of the open end of the cable 4 is directed. In the present exemplary embodiment, the contact surfaces 2a, 3a are conical as in the first and fourth exemplary embodiments, but it is just as conceivable that the contact surfaces 2a, 3a have steps, analogously to the second exemplary embodiment, or a combination of bevels and steps. In the present exemplary embodiment, the inner sleeve 2 ends flush with the secondary insulation 8, with a left-hand or right-hand offset also being conceivable. Subsequently, a section of the aluminum braided shield 7 exposed by the stripping is folded over the first contact surface 2a, so that the aluminum braided shield 7 is folded back and rests on the first contact surface 2a. In the last step, the outer sleeve 3 is then shifted from the direction of the open end of the cable 4 in the direction of the inner sleeve 2, so that the aluminum braided shield 7 is first clamped between the contact surfaces 2a, 3a and further compressed or sheared and cold-welded by axial compression. By means of such a configuration, conventional methods in which the aluminum braided shield 7 is folded over can be combined in a simple manner with the clamping or cold welding, which is advantageous for aluminum, by pushing the sleeves 2, 3 into one another or pressing them together.

Figure 10 shows a fourth embodiment of the contact system according to the invention, which is constructed similarly to the third embodiment described above. In contrast to the previously described embodiment, the inner sleeve 2 does not sit on the secondary insulation 8 in the contact position, but on an exposed section of the aluminum braided shield 7. The aluminum braided shield 7 is therefore exposed or stripped over a larger area than when it is turned over becomes.

The method for contacting the aluminum braided shield 7 is carried out analogously to the method described above, with the inner sleeve 2 being flat on the exposed Section of the aluminum braided shield 7 is pushed on and the portion of the aluminum braided shield 7 protruding beyond the inner sleeve 2 is folded over the first contact surface 2a. The outer sleeve 3 is pushed on as described above. Such a design enables a particularly space-saving arrangement of the contact element 1 in the contact position. Only when the sleeves 2, 3 are pushed into one another or pressed together to establish the contact, the inner sleeve 2 can rest on the aluminum braided shield 7, since the aluminum braided shield 7 underneath the inner sleeve 2 could be damaged during conventional radial pressing processes. In addition, the secondary insulation 8 can be used as a stop for positioning the inner sleeve 2.

REFERENCE LIST

1

Contact element

2

Inner sleeve
2a first contact surface

3

Outer sleeve
3a second contact surface

4th

electrically conductive cable

5

Inner conductor

6th

Primary isolation

7th

Aluminum braided screen

8th

Secondary isolation

9

Insertion volume

10

insertable section

11

Cable entry

12

Kink

13

first stage

14th

second step

15th

Ladder axis

Claims (16)

1. Contact system for contacting an aluminium braided shield (7) with a contact element (1), comprising

   - an electrically conductive cable (4) having an inner electrical conductor (5), a primary insulation (6) surrounding the inner electrical conductor (5), and a secondary insulation (8) surrounding the primary insulation (6);

   - the aluminium braided shield (7) which comprises a plurality of aluminium wires and which is arranged so as to extend at least in part between the primary insulation (6) and the secondary insulation (8) of the electrically conductive cable (4);

   - the contact element (1) which can be pushed onto the electrically conductive cable (4) and which comprises an outer sleeve (3) and an inner sleeve (2) that can be pushed at least in part into the outer sleeve (3),

   wherein the inner sleeve (2) has a first contact surface (2a) and the outer sleeve (3) has a second contact surface (3a), wherein the first (2a) and/or second contact surface (3a) has regions with a differently sized cross-section with respect to a conductor axis (15) of the electrically conductive cable (4), wherein the contact surfaces (2a, 3a) are designed to clamp and to contact the aluminium wires of the aluminium braided shield (7),
   wherein the contact system can be brought into a contact position by axially pushing the inner sleeve (2) and the outer sleeve (3) one inside the other with the interposition of the aluminium wires of the aluminium braided shield (7), in which contact position the aluminium wires of the aluminium braided shield (7) are clamped between the contact surfaces (2a, 3a) and are contacted with the contact element (1),
   characterized in that
   the first contact surface (2a) has at least one step (13) with a circumferential contact edge so as to define a region in which, when the inner sleeve (2) and the outer sleeve (3) are axially pushed one inside the other, a pressure peak forms in order to clamp the aluminium braided shield (7), and in that the aluminium braided shield (7) is contacted by the contact edge in the contact position.
2. Contact system according to claim 1, characterized in that the contact surfaces (2a, 3a) are additionally designed to enable a cold welding of the aluminium wires of the aluminium braided shield (7) to the contact element (1), wherein the outer sleeve (3) and the inner sleeve (2) are axially pressed together in the contact position so that the aluminium wires of the aluminium braided shield (7) are pinched and/or at least partially sheared/sheared off and are cold-welded to at least one of the contact surfaces (2a, 3a).
3. Contact system according to any one of claims 1 to 2, characterized in that the first contact surface (2a) has a plurality of steps (13) each having a circumferential contact edge.
4. Contact system according to any one of claims 1 to 3, characterized in that the second contact surface (3a) has a cylindrical shape.
5. Contact system according to any one of claims 1 to 3, characterized in that the second contact surface (3a) has a conical shape.
6. Contact system according to any one of claims 1 to 5, characterized in that the second contact surface (3a) of the outer sleeve (3) bounds an insertion volume (9) for the inner sleeve (2), and the first contact surface (2a) of the inner sleeve (2) is formed by an insertable portion (10) of the inner sleeve (2) that can be inserted into the insertion volume (9).
7. Contact system according to claim 6, characterized in that the inner sleeve (2) is entirely received in the insertion volume (9) of the outer sleeve (3) in the contact position.
8. Contact system according to any one of claims 1 to 7, characterized in that the first contact surface (2a) are designed to extend at least in part at an angle to the conductor axis (15) in the contact position.
9. Contact system according to any one of claims 1 to 8, characterized in that the first contact surface (2a) is conical.
10. Contact system according to claim 5 or 9, characterized in that the first contact surface (2a) and/or the second contact surface (3a) has at least one kink (12).
11. Contact system according to any one of claims 1 to 10, characterized in that the inner sleeve (2) and/or the outer sleeve (3) is manufactured from copper or a copper alloy.
12. Contact system according to any one of claims 1 to 11, characterized in that one of the sleeves (2, 3) is manufactured from copper or a copper alloy, and the respective other sleeve (3, 2) is manufactured from aluminium or an aluminium alloy or stainless steel.
13. Contact system according to any one of claims 11 to 12, characterized in that the sleeve (2, 3) manufactured from copper or a copper alloy has a corrosion-inhibiting coating.
14. Contact system according to any one of claims 1 to 13, characterized in that the contact system is in the contact position, wherein the secondary insulation (8) is removed at least in that region of the electrically conductive cable (4) in which the contact element (1) is arranged,
    wherein the region having the smallest cross-section of the first contact surface (2a) adjoins the region of the cable (4) that has the secondary insulation (8).
15. Contact system according to any one of claims 1 to 14, characterized in that the contact system is in the contact position, wherein the inner sleeve (2) is arranged between the primary insulation (6) and the aluminium braided shield (7).
16. Contact system according to any one of claims 1 to 15, characterized in that the aluminium braided shield (7) is folded over the first contact surface (2a) of the inner sleeve (2) and a cable bushing (11) of the inner sleeve (2) contacts the secondary insulation (8) or the aluminium braided shield (7) .

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