Contact system for contacting a braided shield and a contact element

Abstract

The invention relates to a contact system for contacting an aluminium braid (7) to a contact element (1) comprising—an electrically conducting cable (4); —the aluminium braid (7) comprising a plurality of aluminium wires, which is arranged to run at least in sections between a primary isolation (6) and a secondary isolation (8) of the electrically conducting cable (4); —die contact element (1) which can be pushed onto the electrically conducting cable (4) having an outer sleeve (3) and an inner sleeve (2) which can be inserted therein. To achieve a contact system which makes possible, in a simple fashion, a reliable contacting of an aluminium braid to a contact element without additional soldering systems being required, according to the invention the inner sleeve (2) has a first contact surface (2a) and the outer sleeve (3) has a second contact surface (3a), wherein each contact surface (2a, 3a) has areas of different size of cross-section and the contact surfaces (2a, 3a) are designed in such a manner that the aluminium braid (7) is clamped in a contact position by the inner sleeve (2) being pushed axially inside the outer sleeve (3) and contact is made with the contact element (1).

Claims

1. A contact system for electrically contacting an aluminum braided shield with a contact element, comprising an electrically conductive cable having an inner electrical conductor, a primary insulation surrounding the inner electrical conductor, and a secondary insulation surrounding the primary insulation; the aluminum braided shield which comprises aluminum wires and which is arranged so as to extend at least in part between the primary insulation and the secondary insulation of the electrically conductive cable; the contact element, which is pushable onto the electrically conductive cable, comprises an outer sleeve and an inner sleeve, the inner sleeve being pushable at least in part into the outer sleeve, wherein the inner sleeve has a first contact surface and the outer sleeve has a second contact surface for contacting the aluminum braided shield, wherein at least one of: the first contact surface has regions of differently sized cross-sections that change along a longitudinal axis of the inner sleeve, which corresponds with a longitudinal conductor axis of the inner electrical conductor when the inner sleeve is pushed onto the electrically conductive cable, or the second contact surface has regions of differently sized cross-sections that change along a longitudinal axis of the outer sleeve, which corresponds with the longitudinal conductor axis of the inner electrical conductor when the outer sleeve is pushed onto the electrically conductive cable, wherein the first and second contact surfaces are designed such that, in a contact position of the contact element, the aluminum wires of the aluminum braided shield are clamped between the first and second contact surfaces in a way that the first contact surface contacts a first surface of the aluminum wires and the second contact surface contacts a second surface of the aluminum wires that is opposite the first surface of the aluminum wires, and wherein the aluminum wires of the aluminum braided shield are electrically contacted with the contact element by axially pushing together the inner sleeve and the outer sleeve one inside the other.

2. The contact system according to claim 1, wherein the first and second contact surfaces are additionally designed such that, in the contact position of the contact element, by the axially pushing together of the outer sleeve and the inner sleeve, the aluminum wires of the aluminum braided shield are pinched/sheared and the aluminum wires of the aluminum braided shield are cold-welded to the contact element.

3. The contact system according to claim 1, wherein the second contact surface on an inside of the outer sleeve bounds an insertion volume, and the first contact surface on an outside of the inner sleeve is formed by an insertable portion of the inner sleeve, so that the insertable portion of the inner sleeve is insertable into the insertion volume of the outer sleeve.

4. The contact system according to claim 3, wherein the insertion volume of the outer sleeve or the insertable portion of the inner sleeve taper at least in part with respect to the longitudinal conductor axis, when the contact element is pushed onto the electrically conductive cable.

5. The contact system according to claim 3, wherein the inner sleeve is entirely received in the insertion volume of the outer sleeve in the contact position.

6. The contact system according to claim 1, wherein at least one of the first and/or the second contact surface is designed to extend at least in part at an angle to the longitudinal conductor axis in the contact position, when the contact element is pushed onto the electrically conductive cable.

7. The contact system according to claim 1, wherein at least one of the first and/or the second contact surface is conical.

8. The contact system according to claim 1, wherein the first and the second contact surface are conical, and wherein opening angles of at least parts of the conical surfaces of the first and the second contact surfaces are of different sizes in order to define a region between the first and the second contact surface in which, when the inner sleeve and the outer sleeve are axially pushed together axially one inside the other, a pressure peak is formed for clamping the aluminum braided shield.

9. The contact system according to claim 7, wherein at least one of the first or the second contact surface has at least one kink.

10. The contact system according to claim 1, wherein the first and the second contact surfaces each have at least one step.

11. The contact system according to claim 1, wherein the first contact surface has at least one first step and the second contact surface has at least one second step, wherein the first and second steps each form a circumferential contact edge and the aluminum braided shield is contacted by the contact edges in the contact position.

12. The contact system according to claim 1, wherein at least one of the inner sleeve or the outer sleeve is manufactured from copper or a copper alloy.

13. The contact system according to claim 1, wherein one of the inner or outer sleeves is manufactured from copper or a copper alloy, and a respective other of the sleeves is manufactured from aluminum or an aluminum alloy.

14. The contact system according to claim 12, wherein the at least one of the inner or outer sleeve manufactured from copper or a copper alloy has a corrosion-inhibiting coating.

15. The contact system according claim 1, wherein the secondary insulation is removed at least in that region of the electrically conductive cable in which the contact element is arranged in the contact position, wherein the region having the smallest cross-section of the first contact surface adjoins the region of the cable having the secondary insulation.

16. The contact system according to claim 1, wherein the inner sleeve in the contact position is arranged between the primary insulation and the aluminum braided shield.

17. The contact system according to claim 1, wherein 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.

18. The contact system according to claim 9, wherein each kink forms a circumferential contact edge in order to define a region between the first and the second contact surface in which, when the inner sleeve and the outer sleeve are axially pushed together one inside the other, a pressure peak is formed for clamping the aluminum braided shield, and wherein the aluminum braided shield is contacted by the contact edges in the contact position.

19. The contact system according to claim 10, wherein each step forms a circumferential contact edge in order to define a region between the first and the second contact surface in which, when the inner sleeve and the outer sleeve are axially pushed together one inside the other, a pressure peak is formed for clamping the aluminum braided shield, and wherein the aluminum braided shield is contacted by the contact edges in the contact position.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will now be explained in greater detail on the basis of exemplary embodiments. The drawings are given by way of example and are intended to illustrate the concept of the invention but in no way to limit the scope thereof or depict it conclusively.

(2) In the figures:

(3) FIG. 1 shows a sectional view of a contact system according to the invention in a contact position;

(4) FIG. 2 shows an axonometric view of the contact system in the contact position;

(5) FIG. 3 shows an axonometric view of a first exemplary embodiment of the contact system in an intermediate position;

(6) FIG. 4 shows an axonometric view of a second exemplary embodiment of the contact system in an intermediate position;

(7) FIG. 5 shows an enlarged detail view of a contact element of the first exemplary embodiment;

(8) FIG. 6 shows an enlarged detail view of a contact element of a second exemplary embodiment;

(9) FIGS. 7a,b,c,d show sectional views of the first exemplary embodiment in several successive positions;

(10) FIGS. 8a,b,c,d show sectional views of the second exemplary embodiment in several successive positions;

(11) FIG. 9 shows a sectional view of a third exemplary embodiment of the contact system in the contact position;

(12) FIG. 10 shows a sectional view of a fourth exemplary embodiment of the contact system in the contact position.

WAYS OF CARRYING OUT THE INVENTION

(13) FIGS. 1 and 2 show the basic structure of a contact system according to the invention for contacting an aluminium braided shield 7 with a contact element 1. The aluminium braided shield 7 comprises a plurality of aluminium wires and extends between a primary insulation 6 and a secondary insulation 8 of an electrically conductive cable 4. The structure of the cable 4, which can be seen in particular in FIGS. 2 and 4, is as follows:

(14) The core of the cable 4 is formed by an inner electrical conductor 5, which defines a conductor axis 15 that extends in a straight line in the figures. In the present figures, the inner conductor 5 is formed by a plurality of single conductors bundled as a strand and has a substantially circular cross-section. It goes without saying that the number of single conductors of a strand and also the number of strands and the geometry of the cross-section are irrelevant to the invention itself. By way of example, both single conductors and also elliptical or polygonal cross-sections of the inner conductor 5 are therefore conceivable in principle. A primary insulation 6, also referred to as the inner sheath or conductor insulation, is applied to the inner conductor 5 and brings about an insulation between the inner conductor 5 and the aluminium braided shield 7. A secondary insulation 8, also referred to as the outer sheath or cable sheath, is then applied to the aluminium braided shield 7 and insulates the inner conductor 5 and the aluminium braided shield 7 from the surrounding environment.

(15) Before the aluminium braided shield 7 and the contact element 1 can be contacted, usually the electrically conductive cable 4 must be cut to length so that an open end of the cable 4 is formed. The secondary insulation 8 is removed in that region of the electrically conductive cable 4 in which the contact element 1 can be arranged in the contact position. This will hereinafter be referred to as the stripped region. The stripped region is usually arranged in the open end portion of the cable 4 and extends as far as the and of the cable 4, as can be seen in the figures. In addition, an end portion of the cable 4 may also be freed of primary insulation 6, aluminium braided shield 7 and secondary insulation 8, as can be seen in the figures, so that the inner conductor 5 is exposed for electrical connection.

(16) The contact element 1 comprises an inner sleeve 2 having a first contact surface 2a and an outer sleeve 3 having a second contact surface 3a, wherein the contact surfaces 2a, 3a are designed to contact the aluminium braided shield 7 in the illustrated contact position. The inner sleeve 2 can be pushed at least in part into the outer sleeve 3. 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.

(17) Since the contact surfaces 2a, 3a of the sleeves 2, 3 are designed such that the aluminium wires of the aluminium braided shield 7 are clamped between the contact surfaces 2a, 3a and contacted with the contact part 1 in the contact position of the contact part 1 as a result of the inner sleeve 2 and outer sleeve 3 being pushed one inside the other, the aluminium braided shield 7 is securely clamped between the contact surfaces 2a, 3a in the illustrated contact position. In addition, the contact surfaces 2a, 3a in the exemplary embodiments are also designed such that, in the contact position of the contact element 1, a pinching/shearing of the aluminium wires of the aluminium braided shield 7 and a cold welding of the aluminium wires of the aluminium braided shield 7 to the contact element 1 takes place as a result of the outer sleeve 3 and inner sleeve 2 being axially pressed together. This configuration is achieved in that the contact surfaces 2a, 3a have regions of different cross-section, in the present case of different diameter. The electrical connection between the aluminium wires of the aluminium braided shield 7 and the contact element 1 in the illustrated contact position is therefore established by means of cold welding. In other words, the aluminium wires are welded to the contact element 1 in the contact position.

(18) In principle, due to the contact surfaces 2a, 3a surrounding the aluminium braided shield 7, in any case a uniform contacting of as far as possible all the aluminium wires is achieved without there being any need for radial compression, such as crimping, or for additional welding. The electrical contacting can be established simply by pushing and pressing the sleeves 2, 3 together.

(19) Two possible geometric configurations of the contact surfaces 2a, 3a which achieve the two effects mentioned above will be discussed in detail below.

(20) FIG. 3 shows an axonometric view of a first exemplary 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 aluminium 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 diameters normal to the conductor axis 15 vary along the entire longitudinal extent of the sleeves 2, 3. In other words, the two contact surfaces 2a, 3a extend at an angle to the conductor axis 15. It can also be seen that the contact surface 2a has two sections of different slope, which merge into one another at a kink 12. The contact surface 2a has a larger opening angle, that is to say is steeper, in a first portion, which in the present figure faces towards the outer sleeve, than in the second portion.

(21) FIG. 4 shows an axonometric view, analogous to FIG. 3, of a second exemplary 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 portions of differently sized cross-section or diameter, wherein two first steps 13 in each case separate two successive portions from one another.

(22) FIG. 5 shows in detail a contact element 1 of the first exemplary embodiment and FIG. 6 shows in detail a contact element 1 of the second exemplary embodiment, that is to say in each case the inner sleeve 2 and the outer sleeve 3. It can clearly be seen that the inner sleeve 2 and the outer sleeve 3 each have a passage opening and that the inner sleeve 2 can be pushed at least in part into the outer sleeve 3. The passage opening of the inner sleeve 2 is designed as a cable bushing 11, through which the cable 4 can be passed. The first contact surface 2a of the inner sleeve 2 is formed by an outer circumferential surface of the inner sleeve 2.

(23) The passage opening of the outer sleeve 3 is designed as an insertion volume 9 for receiving an insertable portion 10 of the inner sleeve 2 and additionally serves for the passage of the cable 4. In the present exemplary embodiment, the insertable portion 10 comprises the entire extent of the inner sleeve 2, so that the inner sleeve 2 in the contact position is entirely received in the outer sleeve 3. In alternative variant embodiments, it is also conceivable that the insertable portion 10 comprises only a 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 bounds the insertion volume 9.

(24) 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 to the extent that the aluminium braided shield 7 can be clamped and/or cold-welded between the contact surfaces 2a, 3a.

(25) FIG. 5 again shows the conicity of the first contact surface 2a together with the kink 12, as described above in connection with the first exemplary embodiment. 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 a wedge-shaped cross-sectional narrowing is achieved 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 kink 12 defines that region in which a clamping force is exerted on the aluminium wires by the contact surfaces 2a, 3a and/or in which a pressure peak forms for pinching/shearing and cold welding the aluminium wires. The region is thus a circumferential contact edge defined by the kink.

(26) FIG. 6 shows, in contrast, the first steps 13 of the first contact surface 2a, as described above in connection with the second variant embodiment. The second contact surface 3a is now also shown, which has second steps 14 which cooperate with the first steps 13 and which divides the second contact surface 3a into three portions. 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-shaped cross-sectional narrowing is once again achieved by the cooperation of the steps 13, 14. In other words, the steps 13, 14 define the region in which a clamping force is exerted on the aluminium wires by the contact surfaces 2a, 3a and/or in which a pressure peak forms for pinching/shearing and cold welding the aluminium wires. In this exemplary embodiment, each of the steps 13, 14 forms a circumferential contact edge which delineates the aforementioned region.

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

(28) In a first step (which can be seen in FIGS. 7a, 7b and 8a, 8b), the outer sleeve 3 is in each case pushed onto the electrically conductive cable 4. The outer sleeve 3 is pushed beyond the stripped region, 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 the passage opening of the outer sleeve is larger than or equal to the diameter of the cable 4 together with the secondary insulation 8. In other words, the cable 4 is in part received in the insertion volume 9 of the outer sleeve 3.

(29) The second step (which is shown in FIGS. 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 larger than or equal to the diameter of the cable 4 together with the primary insulation 6, so that the inner sleeve 2 can be pushed onto the primary insulation 6.

(30) As can be seen in FIGS. 7c and 8c, the inner sleeve 2 is pushed in between the primary insulation 6 and the aluminium braided shield 7, so that the aluminium braided shield 7 contacts the first contact surface 2a. It is also conceivable that the aluminium braided shield 7 is lifted away from the primary insulation 6 in a separate step and, once the inner sleeve 2 has been pushed on, is folded over the first contact surface 2a, for example by means of the step described below or in a separate step.

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

(32) As the inner sleeve 2 and the outer sleeve 3 are further pressed together, pressure peaks form at the kink 12 or at the steps 13, 14 (that is to say at the circumferential contact edges), which pressure peaks lead first to a compression and, as the pressing-together continues, to an at least partial pinching and/or shearing, preferably to a complete shearing-off, of the aluminium wires, so that a cold welding of the aluminium wires of the aluminium braided shield 7 to the contact element 1 takes place. By virtue of the pinching and/or shearing of the aluminium wires, the surface of the aluminium wires that has the oxide layer is broken open and thus the oxide layer is penetrated and the oxide layer is prevented from forming again, so that an electrical connection which is highly conductive and which is resistant to temperature changes is ensured between the aluminium braided shield 7 and the contact element 1 if the aluminium wires, after the pressing-together, are cold-welded to the contact element 1 in the contact position.

(33) Usually one of the two sleeves 2, 3, that is to say either the inner sleeve 2 or the outer sleeve 3, is designed as a contact sleeve which is manufactured from copper or a copper alloy and preferably has a corrosion-inhibiting coating, for instance made of nickel and/or tin or alloys thereof. By way of this contact sleeve, the potential equalization of the aluminium braided shield 7 with a ground is possible since the contact sleeve can be electrically connected to the ground by means of an equalizing conductor. The respective other sleeve is designed as a support sleeve and is manufactured from aluminium or an aluminium alloy in order to reduce the corrosion of the aluminium wires.

(34) It goes without saying that any combinations of the first and second exemplary embodiment are also suitable for achieving the same technical effects. In addition, geometries differing from the geometry of the contact surfaces 2a, 3a shown in the exemplary embodiments are conceivable if they enable a clamping and/or compression/shearing-off of the aluminium wires of the aluminium braided shield 7.

(35) FIG. 9 shows a third exemplary embodiment of the contact system according to the invention, in which the inner sleeve 2 in the contact position is seated on the secondary insulation 8. In order to be able to clamp the aluminium braided shield 7 between the contact surfaces 2a, 3a, a portion of the aluminium 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, that is to say in the direction of the conductor axis 15, in order to enable the clamping and/or compression/shearing-off of the aluminium wires of the aluminium braided shield 7 between the two contact surfaces 2a, 3a.

(36) The method for contacting the aluminium braided shield 7 with the contact element 1 differs from the methods described above connection with the first two variant embodiments on account of the different structure of the contact systems: In a first step, the inner sleeve 2 is pushed onto the open end of the electrically conductive cable 4 and is pushed onto the secondary insulation 8 beyond the stripped region. If the first contact surface 2a—as in the illustrated exemplary embodiment—has regions with a differently sized cross-section, it is advantageous if the region having the smallest cross-section is directed towards the open end of the cable 4. In the present exemplary embodiment, the contact surfaces 2a, 3a are conical as in the first and fourth exemplary embodiment, but it is also conceivable that the contact surfaces 2a, 3a have steps in a manner analogous to the second exemplary embodiment, or a combination of slopes and steps. In the present exemplary embodiment, the inner sleeve 2 ends flush with the secondary insulation 8, but an offset to the left or to the right is also conceivable. Thereafter, a portion of the aluminium braided shield 7 that has been exposed as a result of the stripping is folded over the first contact surface 2a, so that the aluminium braided shield 7 is folded back and rests on the first contact surface 2a. In the last step, the outer sleeve 3 is then displaced from the direction of the open end of the cable 4 in the direction of the inner sleeve 2, so that the aluminium braided shield 7 is first clamped between the contact surfaces 2a, 3a and then is compressed or sheared off and cold welded as a result of said sleeves being axially pressed together further. By virtue of such a configuration, conventional methods, in which the aluminium braided shield 7 is folded over, can easily be combined with the clamping and cold welding that is advantageous for aluminium, by pushing the sleeves 2, 3 one inside the other and pressing them together.

(37) FIG. 10 shows a fourth exemplary embodiment of the contact system according to the invention, which is constructed in a manner similar to the third exemplary embodiment described above. Here, in contrast to the previously described exemplary embodiment, the inner sleeve 2 in the contact position is seated not on the secondary insulation 8, but instead on an exposed portion of the aluminium braided shield 7. The aluminium braided shield 7 is thus exposed or stripped over a larger region than the region in which it is folded over.

(38) The method for contacting the aluminium braided shield 7 is carried out in a manner analogous to the method described above, wherein the inner sleeve 2 is simply pushed onto the exposed portion of the aluminium braided shield 7 and the portion of the aluminium braided shield 7 that projects beyond the inner sleeve 2 is folded over the first contact surface 2a. The outer sleeve 3 is pushed on in the manner described above. Such a configuration enables a particularly space-saving arrangement of the contact element 1 in the contact position. Only by pushing the sleeves 2, 3 one inside the other and by pressing them together in the manner according to the invention in order to establish the contacting is it possible for the inner sleeve 2 to rest on the aluminium braided shield 7, since the aluminium braided shield 7 located below the inner sleeve 2 could be damaged in the case of conventional radial pressing operations. In addition to this, the secondary insulation 8 can be used as a stop for the positioning of the inner sleeve 2.

LIST OF REFERENCE SIGNS

(39) 1 contact element

(40) 2 inner sleeve

(41) 2a first contact surface

(42) 3 outer sleeve

(43) 3a second contact surface

(44) 4 electrically conductive cable

(45) 5 inner conductor

(46) 6 primary insulation

(47) 7 aluminium braided shield

(48) 8 secondary insulation

(49) 9 insertion volume

(50) 10 insertable portion

(51) 11 cable bashing

(52) 12 kink

(53) 13 first step

(54) 14 second step

(55) 15 conductor axis