EP2673843B1

EP2673843B1 - Electrical connector for connecting electrical cables to electrical terminals

Info

Publication number: EP2673843B1
Application number: EP12707920.0A
Authority: EP
Inventors: Giovanni Rosani
Original assignee: Cembre SpA
Current assignee: Cembre SpA
Priority date: 2011-02-09
Filing date: 2012-02-07
Publication date: 2016-03-23
Anticipated expiration: 2032-02-07
Also published as: EP2673843A1; ITMI20110192A1; IT1403926B1; WO2012107873A1

Description

The object of the present invention is an electrical connector for connecting electrical cables to electrical terminals. DE102007005810A1 indicates a state of the art for such connectors. Furthermore, WO 2004/047 227 A1 indicates a connector according to the preamble of claim 1.
Single piece electrical connectors made of copper are known, which form a cable connection portion, for example a tubular or C-shaped seat suitable for receiving one end of an electric cable and for being compressed around such an end so as to obtain, a press-fit connection, as well as a terminal connection portion suitable for being connected in pressing contact, for example through a bolt, against an electrical terminal of a use.
This known type of electrical connector can be applied to make electrical contacts in the civil, industrial and rail fields.
However, due to a considerable increase in the cost of copper and to the consequent frequent theft of conductors made from such a metal, over the last years there has been an increase in the use of conductors made from aluminium for transportation and distribution of electrical energy.
The electric conductors made of aluminium must be connected to the pre-existing terminals made of copper and also to the more common recently installed terminals which are still now very frequently made of copper.
Therefore, a requirement has arisen of being able to have electrical connectors for connecting cables made of aluminium to existing terminals made of copper.
Analogous requirements have arisen for connecting cables made of copper to terminals made of aluminium, for connecting cables of steel to terminals made of copper and vice versa, as well as for connecting cables made of steel to terminals made of aluminium and vice versa.
There are connectors (so called cable terminal connectors) made of aluminium the use of which however leads to a contact which is exposed to the environment between metals with different galvanic potential, such as copper and aluminium, with consequent risks of galvanic crevice corrosion in the contact area between the connector made of aluminium and the terminal made of copper.
In order to avoid the problem of the galvanic corrosion which could occur in the contact area between the aluminium and the copper, bi-metal connectors are currently sold on the market having a cable seat in aluminium that is suitable for being compressed onto the conductor, as well as a terminal connection portion made of copper that is suitable for being connected in contact with a terminal, in which the cable seat and the terminal connection portion are welded to one another.
Such a solution, although solving the problem of the crevice corrosion in a satisfactory manner, is not without drawbacks.
The manufacturing process of the single parts made of aluminium and copper and their subsequent joining through welding is, on one hand, complex and costly and, on the other hand, is not able to obtain a copper-aluminium connection that is sufficiently reliable and resistant for applications in which the connectors undergo vibrations. One example of electrical connections exposed to the external environment and undergoing vibrations and cyclical mechanical stress is the connection between electrical cables and train rails.
The purpose of the present invention is therefore that of proposing an electrical connector (so called cable terminal) for the connection of electrical cables made of a first metal (for example aluminium) to terminals made of a second metal (for example copper), having characteristics such as to withstand mechanical stress, in particular vibrations, and avoid the phenomenon of galvanic crevice corrosion.
These and other purposes are achieved with a connector (cable terminal) according to claim 1 for connecting an electric cable to a terminal, comprising a tubular body that forms a cable connection portion that is suitable for receiving one end of an electric cable and a terminal connection portion suitable for being connected in contact with a terminal, in which the tubular body comprises one inner layer that is substantially made of a first conductive metal that forms an inner surface of the tubular body and one outer layer that is substantially made of a second conductive metal that is different from the first conductive metal and that forms an outer surface of the tubular body, in which the outer surface forms a terminal contact surface of the terminal connection portion and the inner surface forms a cable contact surface of the cable connection portion, in which said inner layer and said outer layer are metallurgically bonded. The connection between the two layers can be made through melting of the material in the transition area between the outer layer and the inner layer, for example through the manufacture of the bi-layer or multi-layer tubular body through drawing or co-extrusion.
The cable terminal thus configured makes it possible to obtain the specific advantages of a bi-metal cable terminal (no difference of galvanic potential in the area of contact between the cable terminal and the terminal) with low costs and with mechanical resistance that is suitable for applications undergoing vibrations.
Moreover, the use of a multi-layer tubular body manufactured through drawing or co-extrusion allows a production of the connector on a large scale with low costs and with a close and resistant joining between the layers themselves.
In the present description the terms "substantially made of a first metal" and "substantially made of a second metal" or, more specifically "substantially made of copper" and "substantially made of aluminium" do not exclude alloys of such metals as long as the metals indicated form the main portion of the alloy itself. In the preferred embodiment, the expressions "substantially made of copper" and "substantially made of aluminium" refer to the two metals as usually found on the market and used as conductors for the electrical and electro-technical industry.
In order to better understand the invention and to appreciate the advantages thereof, in the following description we shall describe some of its embodiments given as an example and not for limiting purposes, with reference to the attached figures, in which:

figures 1A - 1E are side, front and rear views of a connector (cable terminal) for connecting an electric cable to a terminal of a user, according to a first embodiment;
figure 1F is a longitudinal section view of the connector in figure 1A;
Figure 1G is a perspective view of the connector in figure 1A;
figures 2A - 2E are side, front and rear views of a connector (cable terminal) for connecting an electric cable to a terminal of a user, according to a second embodiment;
figure 2F is a longitudinal section view of the connector in figure 2A;
figure 2G is a perspective view of the connector in figure 2A;
figure 3 illustrates the connector of figure 1 applied to an electric conductor;
figure 4 is a longitudinal section view of the conductor - connector group in figure 3;
figures 4A and 4B illustrate variant embodiments of the connector;
figure 5 is a cross-section view of the conductor - connector group in figure 3;
figure 6 illustrates an application of the connector for the electrical connection of a cable to a train track;
figure 7 is a section view of the connection in figure 6.

With reference to the figures, a connector 1 (so called cable terminal) for connecting an electric cable 2 to a terminal 3 comprises a tubular body 8 that forms a cable connection portion 4 that is suitable for receiving an end of the electric cable 2 and a terminal connection portion 6 that is suitable for being connected in contact with the terminal 3. The tubular body 8 comprises an inner layer 9 that is substantially made of a first conductive metal (for example aluminium, alternatively steel, copper) that forms an inner surface 17 of the tubular body 8 and an outer layer 10 substantially made of a second conductive metal (for example copper, alternatively aluminium, steel) that is different from the first conductive metal and that forms an outer surface 18 of the tubular body 8, in which the outer surface 18 forms a terminal contact surface of the terminal connection portion 6 and the inner surface 17 forms a cable contact surface of the cable connection portion 4.
The inner layer 9 and the outer layer 10 are connected to one another with continuity of material substantially over the entire surface, for example through melting of the material in the interface or transition area 19 between the outer layer and the inner layer. Consequently the inner layer is to all effects welded to the outer layer. This can be obtained for example through the manufacture of the bi-layer or multi-layer tubular body 8 through drawing or co-extrusion.
According to one aspect of the invention, in the interface or transition area 19 between the two layers, the latter are metallurgically bonded. Such a metallurgical bond between the two metal layers can be obtained for example through the manufacture of the bi-layer or multi-layer tubular body through drawing. According to one embodiment a bi-layer or multi-layer tube previously preassembled is equipped with an inner floating mandrel and is cold drawn through one or a series of outer matrices so that the high pressure between the tube layers generates the aforementioned metallurgical bond.
Alternatively, the metallurgical bond between the two metal layers can be obtained by manufacturing the bi-layer or multi-layer tubular body through co-extrusion or, in other words, through co-extrusion welding (CEW) in which the two different metals are, for example, extruded simultaneously and together through the same matrix so that the high pressure and the high temperature generate the metallurgical bond in the transition area 19 between the two adjacent layers of the tube.
According to a further aspect of the invention, the metallurgical bond between the two metal layers can be obtained through the manufacture of the bi-layer or multi-layer tubular body through roll welding (ROW) in which the different metals are joined during their forced passage between the lamination rollers so that the high pressure and, if foreseen, the high temperature generate the metallurgical bond between the layers of the tube.
In technical jargon the connection between the two layers thus obtained, that is to say the metallurgical bond of the two different metal materials, is sometimes called "metallurgical cladding". This connection is obtained through layers having preferably uniform thicknesses and not too thin and provides, together with minimum thicknesses of the metal layers involved of at least 0.5 mm, preferably from 0.5 mm to 10 mm, the most favourable mechanical and galvanic characteristics for the electrical connector.
In accordance with one embodiment, the tubular body 8 is a two-layer tubular body with the inner layer 9 made of aluminium and the outer layer 10 made of copper, in which the inner layer 9 has a thickness ranging from 0.5 mm to 10 mm and the outer layer 10 has a thickness ranging from 0.5 mm to 2 mm.
In the present invention by the term "metallurgical bond" we mean that the lattice structure of the two metals is forced in mutual conformance with sharing of electrons in the interface between the two layers which generates a bond at the atomic level.
Advantageously, in the interface (transition area 19) between the two layers, the latter are metallurgically bonded and locally interpenetrated.
According to one aspect of the invention, the transition area 19 with metallurgical bond extends continuously and uninterruptedly for the entire extension of the interface between the two layers. Preferably, both metal layers (and also the interface between them) substantially extend on the entire extension of the tubular body, the wall of which is therefore multi-layer all over and substantially without monolayer portions.
The cable terminal thus configured makes it possible to obtain the specific advantages of a bi-metal cable terminal (no difference of galvanic potential in the contact area between the cable terminal and the terminal) with low costs and with mechanical resistance that is suitable for applications undergoing vibration.
Moreover, the use of a multi-layer tubular body manufactured through drawing or co-extrusion allows a production of the connector on a large scale at low costs and with a close and resistant connection between the layers themselves.
In accordance with one embodiment, the terminal connection portion 5 is formed by a flattened end, for example through cold plastic deformation, of the multi-layer tubular body 8 and can be equipped with a through hole 11 that is suitable for receiving a bolt 12 or a connection screw.
This facilitates making a connection in pressing contact through bolting down the connector 1 to the terminal 3, for example to a terminal of a train rail 13 (Figures 6, 7).
In accordance with one embodiment, the cable connection portion 4 is formed by one open end portion (tubular, for example cylindrical) of the tubular body 8, opposite to the flattened end, and suitable for receiving an end of the electric cable 2 as well as for being compressed around it so as to make a press-fit and shape connection (Figures 3, 4).
In accordance with a further embodiment, at at least one or both the free ends 14, 15 of the tubular body 8 and, therefore, at the terminal connection portion 6 and/or at the cable connection portion 4, the outer layer 10 extends beyond the inner layer 9, so that only the outer layer 10 is exposed to the external environment.
Such a configuration of the free edges of the tubular body 8 can be made for example through boring or milling of the ends of the tubular body 8 so as to eliminate an end section of the inner layer 9. The end section of the outer layer above the inner layer can be folded towards the inside of the tubular body 8 to prevent exposure of the inner layer to the environment.
This makes it possible to eliminate also the residual galvanic differential in the free edges of the connector.
In the embodiment illustrated in figures 2A - 2G, the flattened terminal connection portion is substantially symmetrical with respect to the cable connection portion.
Alternatively, in the embodiment illustrated in figures 1A - 1G, the flattened terminal connection portion 6 defines a contact plane 16 that is substantially tangent to the outer surface 18 of the cable connection portion 4 or radially outside of it or inclined with respect to it, so that said contact plane 16 does not intersect the cable connection portion 4.
This facilitates the connection of the connector 1 to extended flat terminals or flat and extended surfaces in general.
From the description given, a man skilled in the art will appreciate how the connector 1 synergically reconciles the requirements of:

an electrical connection between two different metals, such as for example aluminium and copper, and the consequent problems of galvanic corrosion,
a mechanical and electrical connection that can withstand vibrations and adverse weather conditions,
a simple structure that can be manufactured on a large scale and at low cost.

Of course, a person skilled in the art, with the purpose of satisfying contingent and specific requirements, may carry out further modifications and variants to the connector according to the present innovation, all moreover covered in the scope of protection of the invention, as defined by the following claims.

Claims

Connector (1) for connecting an electric cable (2) to a terminal (3), said connector (1), comprising a tubular body (8) that forms a cable connection portion (4) suitable for receiving the electric cable (2) and a terminal connection portion (6) suitable for being connected in contact with the terminal (3),
wherein the tubular body (8) is a multi-layer tubular body having an inner layer (9) of a first conductive metal that forms an inner surface (17) of the tubular body (8) and an outer layer (10) of a second conductive metal different from the first conductive metal and that forms an outer surface (18) of the tubular body (8),
in which the outer surface (18) forms a terminal contact surface of the terminal connection portion (6) and the inner surface (17) forms a cable contact surface of The cable connection portion (4)
characterized in that the tubular body (8) is a multi-layer tube selected from the group consisting of:
drawn multi-layer tubes,

coextruded multi-layer tubes,

laminated multi-layer tubes,

and said outer (10) and inner (9) layers are metallurgically bonded.
Connector (1) according to claim 1,
wherein the inner layer (9) and the outer layer (10) substantially extend on the entire extension of the tubular body (8).
Connector (1) according to claim 1 or 2, wherein said outer layer (10) and said inner layer (9) are metallurgically bonded and locally interpenetrated.
Connector (1) according to one of the previous claims, wherein the terminal connection portion (5) is formed from a flattened end of the tubular body (8).
Connector (1) according to any one of the previous claims, wherein the terminal connection portion (5) defines a through hole (11) suitable for receiving a bolt 12 or a connection screw, said through hole (11) extending through both the outer and inner layers (10, 9,).
Connector (1) according to any one of the previous claims, wherein the cable connection portion (4) is formed from an open end portion of the tubular body (8), opposite to the flattened end, and suitable for receiving an end of the electric cable (2) as well as for being compressed around it so as to make a press-fit connection.
Connector (1) according to any one of the previous claim, wherein at at least one free end (14, 15) of the tubular body (8) the outer layer (10) extends beyond the inner layer (9), so that only the outer layer (10) is exposed to the external environment.
Connector (1) according to the previous claim, wherein an end section of the outer layer (10) above the inner layer is bent towards the inside of the tubular body (8).
Connector (1) according to any one of the previous claims, wherein the terminal connection portion (6) is flattened and defines a contact plane (16) oriented so as not to intersect the cable connection portion (4).
Connector (1) according to any one of the previous claims, wherein said first conductive metal is selected from the group consisting of aluminium, copper, steel,
and said second conductive metal is selected from the group consisting of copper, steel, aluminium.
Connector (1) according to any one of the previous claims, wherein the thickness of the inner layer (9) is substantially uniform and equal to or greater than 0.5 mm. and the thickness of the outer layer (10) is substantially uniform and equal to or greater than 0.5 mm.
Connector (1) according to claim 12, wherein the tubular body (8) is a two-layer tubular body with the inner layer 9 made of aluminium and the outer layer 10 made of copper, wherein the inner layer 9 has a thickness ranging from 0.5 mm to 10 mm and the outer layer 10 has a thickness ranging from 0.5 mm to 2 mm.