CONNECTION TO EARTH PLATE CABLE SHIELDING
Field of the Invention The present invention relates to a ground connection of a shielded flat cable
BACKGROUND OF THE INVENTION Shielded flat cables are often used for signal transmissions in telecommunication and computer applications. A shielded flat cable comprises a plurality of individual insulated wires that are positioned as a ribbon cable having at least one layer of insulated adjacent wires and an electrically conductive shield layer surrounding the ribbon cable. The shielding layer serves to prevent the signals transmitted by means of the individual wires of the ribbon cable from being affected by external noise or by other external influences. The armored layer of the flat cable must be electrically connected to a ground potential, for example, with the cover of an electronic kit. For this purpose, there are so-called spiral wire and drain wire connections, which comprise ground wires electrically connected to the shielding layer and with a ground potential. An example of a drain wire connection is REF. 188128 describes in JP-A-08077836. In this example, a ground wire is placed in electrical and mechanical contact with the shielding layer of a flat cable, where the ground wire extends parallel to the flat cable and protrudes beyond the connectors at the ends of the cable. flat cable. The ends of the ground wire are connected to the ground potential. JP-A-06243731 discloses a ground wire welded with a thin sheet of copper tape which is adhered to the shielding layer of the flat cable. Welding a wire to ground in the shielding layer of a flat cable is a commonly known technique for grounding the shielding layer of a flat cable. However, the welding process is disadvantageous because the application of heat in the shielding layer could damage the ribbon cable below the shielding layer. Also, the electrical connection between the shielding layer and the ground wire is simply established at a location in the shielding layer (the point-shaped connection). Finally, when the cable is bent, the welding connection can be damaged and broken. Another problem with the connection of a cable to ground with the shielding layer of a flat cable is the protection against cable pulls to ground. Without this protection against pulls to the ground wire, there is a risk that the electrical connection between the ground wire and the shielding layer will be destroyed when a voltage is applied to the ground wire. To provide a strain relief and a ground connection to the ground wire, a strain relief sleeve clamp / cable ground connection is offered on the market, for example, through 3M (see for example, the products of the 3504 series). These products comprise two clamps, which apply a clamping force to the shielded flat cable, located between them. The two fastening elements are located in a cabinet wall adjacent to a hole through which the flat cable extends. There is a need for an improved connection to flat cable shielding ground which can be easily established and which also provides sufficient protection against pulls.
SUMMARY OF THE INVENTION In one aspect of the invention there is provided a shielded flat cable comprising: a ribbon cable having at least one layer of a plurality of adjacent single isolated wires,
- an electrically conductive shield layer surrounding the ribbon cable, and a ground wire having a conductor electrically connected to the shield layer, wherein at least two electrically conductive layers of an electrically conductive adhesive tape are adhered at least to a portion of the shielding layer, the adhesive tape has an electrically conductive reinforcement and an electrically conductive adhesive on at least one side of the reinforcement, whereby a superposed array of layers is formed which includes a layer of armor and at least two layers of adhesive tape, - in where the ground wire is formed to comprise at least a first portion and a second portion, at least one of them is at least partially free of an insulation sheath, and the second portion is folded back with respect to to the first portion, and wherein, for the realization of the electrical contact with the shielding layer and to provide the protection against pulls, the first and second portions of the cable to ground are located between the layers of different pairs of adjacent layers of the array superimposed layers. According to this embodiment of the present invention, the ground wire comprises a conductor formed so as to comprise at least a first and a second portion, with the second portion being bent backwards with respect to the first portion. At least one of these two portions is at least partially free of an insulation sheath that could surround the conductor in the remaining part of the ground wire. The first and second folded or bent back portions are located between different pairs of adjacent layers of the superposed array of layers including the shield layer of the shielded flat cable ribbon cable and at least two electrically conductive layers of an electrically adhesive tape conductive By means of the layers of the electrically conductive adhesive tape the ground cable and in particular its first and second portions are fixed in the shielding layer, as well as, between the layers of the electrically conductive adhesive tape for the realization of the electrical contact with the shielding layer and to provide protection against jerks. According to another aspect of the present invention, for the electrical connection of the cable to ground with the shielding layer of the ribbon cable of the shielded flat cable, the following steps are carried out: providing an electrically conductive adhesive tape comprising an electrically conductive reinforcement and an electrically conductive adhesive on at least one side of the reinforcement, - locating a first portion of the cable to ground on the shielding layer, - fixing the first portion of the cable to ground in the shielding layer by means of the first layer of the cable. electrically conductive adhesive tape adhered on both sides of the first portion of the cable to ground, - bend or fold the cable back to ground on the first layer of adhesive tape, so that a second portion of the cable to ground is located on the first layer of adhesive tape, and - fix the second portion of the cable to ground in the first layer of adhesive tape through a second cap a of the electrically conductive adhesive tape, wherein the conductor of the ground cable at least one of the first and second portions is free of an insulation sheath. In a further aspect of the present invention, the ground wire is connected to the shielding layer of the ribbon cable by performing the following steps: providing an electrically conductive adhesive tape comprising an electrically conductive reinforcement and an electrical conductive adhesive to the less on one side of the reinforcement, fix a base layer of the electrically conductive adhesive tape on the shielding layer, - place a first portion of the cable to ground on the base layer, - fix the first portion of the cable to earth in the shielding layer by means of the first layer of the electrically conductive adhesive tape adhered on both lateral sides of the first portion of the cable to ground, - folding or bending back the cable to ground on the first layer of adhesive tape, so that a second portion of the ground cable is placed on the first layer of adhesive tape, and - fixing the second portion of the cable to ground in the first layer of adhesive tape by a second layer of the electrically conductive adhesive tape, in where the conductor of the ground wire at least one of the first and second portions is free of an insulation sheath. The conductor of the ground wire used in the present invention could comprise a solid single wire, a flat bend or braid, or a plurality of individual twisted wires. The driver could be surrounded by an insulation sleeve, although it could also be free of any insulation surrounding the driver. Also, a conductive tape can be used as a ground conductor. To avoid pull-out protection, the driver is bent backwards by flexing the driver by 180 ° at least once. As an alternative, the driver could comprise, for example, three or more portions within which the ground conductor is bent backward, so as to form a Z-shape or a zigzag-bent form. In one embodiment of the present invention, each of the electrically conductive layers comprises individual strips of an electrically conductive adhesive tape, one located on top of the other, at least with the two portions of the ground cable located between them. Normally, the individual electrically conductive layers are formed by wrapping the electrically conductive adhesive tape around the shielding layer of the ribbon cable. Before placing the ground wire on the shielded flat cable, several layers of the electrically conductive adhesive tape can be applied to the shielding layer. In addition, after having fixed the last portion of the cable to ground, more than one layer of the electrically conductive adhesive tape could be applied. In an alternative of the present invention, the first portion of the ground wire is directly placed on the shielding layer of the ribbon cable so that it is fixed in the shielding layer through a first electrically conductive layer of the adhesive tape electrically conductive, with the second portion of the ground wire that is fixed through one of the different electrically conductive layers of the electrically conductive adhesive tape. In order to provide an electrical connection of the cable to ground with the shielding layer, at least one of the portions of the conductor of the cable to ground, which makes contact with the shielding layer and the electrically conductive layers, must be free of the sheath of the cable. isolation. Preferably, the ground wire is free of insulation within all its portions that contact the shield layers and the electrically conductive layers. To extend the electrical connection of the cable to ground through a larger area of the shielding layer, it is suitable to use a ground wire having a plurality of individual twisted wires that are frayed and bent backward within the portions of the cable to ground that makes contact with the shield and the electrically conductive layer arrangement. The electrically conductive adhesive tape which is used in accordance with the present invention, usually comprises a metallic (e.g. made of copper) reinforcement and an adhesive which is most preferably electrically conductive. An electrically conductive adhesive tape suitable for the present invention is for example, a thin sheet of copper with conductive adhesive which is sold by 3M (for example, of the series 1181).
Commonly, the armor layer surrounding the ribbon cable of the shielded flat cable according to the invention comprises a thin sheet of metal placed around the ribbon cable with the opposite lateral ends overlapping each other. As an alternative, the shield layer may also comprise a braided layer made of individual wires or a mesh. Around the connection of the shielded flat cable and the ground wire, an insulation configured as an insulating adhesive tape wrapped around the shielded flat cable or through a heat shrinkable insulation tape could exist. This insulation provided around the connection also improves protection against cable pulls to ground. In a further embodiment, the present invention provides a ground connection for a shielded flat cable having a ribbon cable with at least one layer of a plurality of adjacent single isolated wires and an electrically conductive shield layer surrounding the ribbon cable. , the ground connection comprises: - a ground wire having a conductor and which is formed so that it comprises at least one first and second portions, at least one of them is at least partially free of an insulation sheath , and the second portion is bent rearwardly with respect to the first portion, and at least two superimposed electrically conductive adhesive layers, each of which comprises an electrically conductive reinforcement and an electrically conductive adhesive on at least one side of the reinforcement, - wherein the second portion of the ground wire is located between two adjacent layers of the electrical superimposed adhesive layers. thermally conductive and the first portion is located below the lowermost layer of the electrically conductive superimposed adhesive layers, and wherein, for the realization of the electrical contact between the ground wire and the shielding layer of the shielded flat cable and to provide The protection against pulls to the ground wire, the superimposed electrically conductive adhesive layers with their lowermost layer can be adhered to the armor layer of the shielded cable.
BRIEF DESCRIPTION OF THE DRAWINGS A complete and detailed description of the present invention, including the best mode thereof, allowing a person of ordinary skill in the art to carry out the invention, is pointed out in greater detail in the remainder of the specification, including reference to the accompanying figures, in which: Figure 1 is a side view of a shielded flat cable with an end portion of the outer insulation sheath removed, Figure 2 shows the flat cable shielded with a portion At the end of the shielding layer that is being removed, Figure 3 shows an electrically conductive adhesive tape attached at its end to the shielding layer below the shielded flat cable, Figure 4 shows the situation in which the adhesive tape is rolled around the shielding layer approximately 3/4 of the first winding, Figure 5 shows the situation in which the adhesive tape is rolled around the shielding layer in more than one winding, Figure 6 shows the arrangement of the grounding wire with its individual wires unraveled and placed on top of the outermost layer of the adhesive tape,
Figure 7 shows the situation in which the first portion of the individual wires of the ground wire is fixed by the adhesive tape, Figure 8 shows the additional winding of the adhesive tape around the shield layer, Figure 9 shows the arranging the cable to ground with the protruding portions of its individual wires bent backward on the outermost winding of the adhesive tape, Figure 10 shows the fixing of the bent back portions of the individual wires by means of an additional layer of the adhesive tape wrapped around the shielding layer, Figure 11 shows a side view of the shielded flat cable provided with a connector fixed and coupled with the end portion of the shielded flat cable ribbon cable, Figure 12 shows a cross-sectional view taken along the line XIII -XIII of Figure 10, Figure 13 shows a cross-sectional view taken along line XIII-XIII of Figure 10, Figure 14 shows a view similar to that of Figure 6, although with the portions of end of the individual wires of the ground wire placed on the outer winding of the adhesive tape, Figure 15 shows a view similar to that of the
Figure 7 and showing the attachment of the end portions of the individual wires of the cable to ground through an additional layer of the adhesive tape, Figure 16 shows a side view of the flat armored cable similar to that of the view of the Figure 8 and with the adhesive tape additionally wound around the shielding layer, Figure 17 shows the situation in which the ground wire is folded back over the outermost adhesive tape layer, Figure 18 shows the shielded flat cable of the
Figure 17 although with the adhesive tape additionally wound around the shielding layer for securing the cable to ground in its portion adjacent to the end portions of the individual wires, Figure 19 shows a cross-sectional view taken along the length of the cable. line XIX-XIX of Figure 18, Figure 20 shows a cross-sectional view taken along line XX-XX of Figure 18, Figure 21 shows a cross-sectional view similar to the views of the Figures 13 and 20, respectively, although with the ground wire being bent in-Z between the individual layers of adhesive tape for electrical and mechanical connection and fixing of the cable to ground in the layers of adhesive tape, and Figure 22 shows a perspective view of a prefabricated ground connection.
DETAILED DESCRIPTION OF THE INVENTION Figures 1-13 show a first embodiment of a shielded flat cable with a ground wire that is being connected and fixed to it, as well as the individual steps of making the electrical and mechanical connection between the shielded flat cable 10 and the ground wire. The process starts with the shielded flat cable 10 having an outer insulation sheath 12 located around an electrically conductive shielding layer 14, for example, of a thin sheet of copper which in turn is wrapped around a ribbon cable 16. which comprises an insulation layer 18 into which a plurality of wires 20 is embedded (see also Figures 2 and 12). In the first stage, the outer insulation sheath 12 is removed at the end 22 of the shielded flat cable 10. Subsequently, a portion of the shield layer 14 exposed in this way is removed, so that the situation of the Figure is presented. 2, in which, an end portion of the ribbon cable 16 is exposed, followed by an exposed portion of the shielding layer 14, which in turn is followed by the remaining portion of the shielded flat cable 10 with its outer sheath 12 located around it. In Figure 3 it can be seen that an adhesive tape 24 is adhered to the shielding layer 14, the adhesive tape 24 comprises an electrically conductive reinforcement 26 in the form of a thin sheet of copper and an electrically conductive adhesive layer 28 which is located in one side of the electrically conductive reinforcement 26. As can be seen in Figures 4-6, the adhesive tape 24 is wound around the shielding layer 14 in more than one winding. In this embodiment, the adhesive tape 24 is wound about 1 1/4 of windings around the shielding layer 14 before a prepared ground wire 30 is placed on the first winding of the adhesive tape 24 (see Figure 6). ). As an alternative, the ground wire 30 can also be directly placed on the shielding layer 14. The ground wire 30 comprises a conductor 32 having a plurality of individual wires 34 twisted together. The twisted wires 34 are located inside an outer insulation sheath 36 that is removed at the end 38 of the ground cable 30, so that the individual wires 34 are exposed. Within these exposed end portions, the individual wires 34 are unraveled as shown in Figure 6. The individual unraveled wires 34 are placed on the first winding of the adhesive tape 24., as shown in Figure 6, with a first portion 40 of the individual wires 34 adjacent the outer sheath 36 located on the first winding of the adhesive tape 24, while a second portion 42 of the individual wires 34 protrude beyond of the adhesive tape 24. As shown in Figures 7 and 8, the adhesive tape 24 is wound around the shielding layer 14 through an additional winding, whereby the first portions 40 of the individual wires 34 are fixed. of the ground wire 30 between the first and second windings of the adhesive tape 24. Subsequently, the second projecting portions 42 of the individual wires 34 of the ground cable 30 are bent backwards in the upper part of the second winding of the adhesive tape 24 (see Figure 9), followed by an additional winding of the adhesive tape 24 around the shielding layer 14 (see Figure 10). Subsequently, the adhesive tape 24 can be wound around the shielding layer 14 at least in an additional winding. This is not necessary for the electrical connection, but rather reinforces the mechanical connection of the ground cable 30 in the shielded flat cable 10. Likewise, before laying the wires 34 of the conductor 32 of the ground cable 30 on the adhesive tape 24 wound around the armor layer 14 at least in one winding, the adhesive tape 24 could be wound around the armor layer 14 in more than one winding in order to further strengthen the armor layer 14 below the wires 34 of the ground cable 30. Finally, also between the steps of laying the ground cable 30 on the adhesive tape 24 (see Figure 6) and the folding backward of the second projecting portions 42 of the wires 34 (see FIG. 10), the adhesive tape 24 could be wound around the shielding layer 14 in more than one winding. With the help of the individual steps shown in Figures 1-10 and described above, the electrical connection of the ground cable 30 with the shielding layer 14 of the shielded flat cable 10, as well as, the mechanical connection and the protection against pulls of the cable to ground 30 in the shielded flat cable 10 are established and realized. Subsequently, the connector 44 can be applied to the exposed end portion of the ribbon cable 16. The connector 44 can be an insulating displacement connector (IDC). However, other types of connectors are also possible. The internal construction of the connection between the ground cable 30 and the shielded flat cable 10 can be observed from Figures 12 and 13. Figure 12 shows that the first and second individual portions 40, 42 of the wires 34 of the cable 30 are located between the different pairs of layers of adhesive tape 46, 48 and 50. Instead of applying the layers of adhesive tape 46, 48 and 50 by winding the adhesive tape 24 around the shielding layer 14, the individual sections of the electrically conductive adhesive tape (for example, cut from the length of the adhesive tape 24) could be fixed together in order to form the superposed array of layers 52 on top of a flat surface of the adhesive. shielded flat cable 10 as shown in Figure 12 and could comprise the shielding layer 14, as well as the individual layers of adhesive tape 46, 48 and 50. Figure 13 shows that due to the bent arrangement rearward of the first and second portions 40 and 42 of the wires 34 of the ground cable 30, a reliable strain relief of the cable 30 is realized, together with a reliable electrical contact with the shielding layer 14 either directly or indirectly to through layers 46, 48 and 50 of the adhesive tape 24. With reference to Figures 14-20, another embodiment of the present invention will be described herein. Provided that the elements shown in these figures are identical to those of Figures 1-13, the same reference numbers are used. The main difference between the arrangement of Figures 1-13 and the arrangement of Figures 14-20 is that the ground wire 30 is prepared in a different mode. Namely, as can be seen in Figure 14, the ground wire 30 according to the second embodiment of the invention comprises the individual twisted free wires 34 of the outer insulation sheath 36 simply in one portion (the second portion 42), while the portion of the ground wire 30 adjacent to the portion 42 of the wires 34 is provided with the outer insulation sleeve 36 around the wires 34. After placement of the individual frayed wires 34 on the adhesive tape 24 wrapped around of the shielding layer 14, the individual wires 34 in their exposed portions 42 (second) are fixed through the adhesive tape 24 by the additional winding of the tape 24 around the shielded flat cable 10 (see Figures 15 and 16) . Subsequently, as can be seen in Figure 17, the ground cable 30 is bent backwards, so that its portion 40 provided with the outer insulation sheath 36 is placed on the outer layer of the adhesive tape 24. Subsequently, the cable to ground 30 in its portion 40 is fixed by additional application of the adhesive tape 24, as can be seen from Figure 18. This arrangement of the mechanical and electrical connection of the ground wire 30 and the shielded flat cable 10 can be shown in Figures 19 and 20. Finally, Figure 21 shows a cross-sectional view of a further embodiment of the present invention, wherein the ground wire 30 is bent in a Z-shape to include three portions 40, 42 , 54 in its electrically and mechanically connected section with the shielded flat cable 10 by means of the adhesive tape 24. In the embodiment of Figure 21, one of the portions of the ground cable 30, which is located at Between the adjacent layers 50, 56 of the adhesive tape 24, it is still provided with the outer insulation sheath 36. Also, in this portion the outer sheath 36 of the ground cable 30 could be removed. With respect to all the modalities shown in the figures, it is observed that the number of layers of the adhesive tape 24 between the adjacent individual portions of the ground cable 30 is not limited to one layer but could also be more than one layer. Finally, by arranging the additional material (for example, insulation material) around the electrical and mechanical connection of the ground cable 30 in the shielded flat cable 10, the pull protection can be improved. In addition, protection against environmental influences is provided. In the embodiment of Figure 21, this protection is provided by an insulating material that can be contracted by heat 58 which is located around the superposed array of layers 52. Figure 22 shows a prefabricated wire-to-ground connection similar to connection shown in Figures 19 and 20 although with the individual superimposed layers 46, 48 and 50 formed by the arrangement of electrically conductive adhesive strips one on the other. This superposed array of layers with the first and second portions 40, 42 of the ground cable 30 already positioned therebetween, may be provided with a protective release liner 60 that can be released from the adhesive of the lowermost strip of the electrically adhesive layer. conductive 46. The superimposed strips may be longer than the width of the shielding layer 14 surrounding the ribbon cable 16, so that the superimposed strips at their end may be folded around the shielded flat cable (see arrows 62 in FIG. Figure 22). Although the invention has been described and illustrated with reference to the specific illustrative embodiments thereof, it is not intended that the invention be limited to those illustrative embodiments. Those skilled in the art will recognize that variations and modifications may be made without departing from the true scope of the invention as defined by the claims that follow. Thus, it is intended to include within the invention all these variations and modifications that fall within the scope of the appended claims and the equivalents thereof. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.