Patent Application
20120312579
The present invention relates to a jacket for a cable that includes an embedded shield and the method for making the jacket. More specifically, the jacket includes a shield that is a shielding tape with discontinuous conductive shielding segments. The shielding tape is embedded with the jacket by co-extruding the shielding tape with the jacket.
Conventional communications cables typically include a core of twisted pairs of insulated conductors that are enclosed in a protective jacket. To avoid crosstalk with other cables, often referred to as alien crosstalk, conventional cables often include at least one shielding layer disposed around the core of twisted pairs of conductors. A non-conductive barrier layer between the shielding layer and the pairs must also be provided to insulate the core of pairs of the cable.
Such cables, however, are often bulky because of the requirement of both a shielding layer and a barrier layer. Therefore, a need exists for a cable that protects against alien crosstalk and that is not bulky.
Accordingly, the present invention may provide a cable jacket that comprises first and second jacket layers each formed of a jacket material. At least one shielding tape may be embedded between the first and second jacket layers. The shielding tape is formed of a substrate material and the substrate material has at least one conductive segment. In a preferred embodiment, the substrate material and the jacket material are the same, although different materials may be utilized. In another embodiment, the substrate material includes a plurality of conductive segments disposed in a spaced discontinuous arrangement. In yet another embodiment, a plurality of shielding tapes are embedded between the first and second jacket layers.
The present invention may also provide a cable that comprises at least one twisted pair of insulated conductors and a jacket that encloses the twisted pair of insulated conductors. The jacket is formed of a jacket material. A shielding tape may be embedded in the jacket. The shielding tape is formed of a substrate material that has at least one conductive segment. The cable does not include a barrier layer.
The present invention may further provide a cable assembly that comprises a plurality of cables that are bundled together. Each of the plurality of cables includes at least one twisted pair of insulated conductors, a jacket enclosing the at least one twisted pair of insulated conductors where the jacket is formed of a jacket material, and at least one shielding tape embedded in the jacket. The at least one shielding tape is formed of a substrate material and the substrate material has at least one conductive segment, whereby the cable does not include a barrier layer enclosed by the jacket.
The present invention may also provide a method for making a cable jacket that comprises the steps of providing at least one shielding tape that has a substrate formed of a substrate material where the substrate includes at least one conductive segment; inserting the at least one shielding tape between first and second jacket layers of the cable jacket and each of the layers is formed of a jacket material; and co-extruding the shielding tape with the first and second jacket layers, wherein the substrate material of the shielding tape and the jacket material of the first and second jacket layers are the same such that during the co-extrusion step, the substrate and the first and second jacket layers bond together.
Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
Referring to
As seen in
The shield 200 may be a shielding layer or tape made up of a substrate 202, as seen in
The shielding tape 200 may include a plurality of conductive segments 204, such as aluminum, copper, ferrite, or any other conductive bricks. The segments 204 may be applied to the surface of the substrate 202 by adhesive, heat pressing, laser ablation, vapor deposition, or by spraying conductive particles onto the substrate 202 to form the segments. Alternatively, the conductive segments 204 can be sandwiched between two layers of the substrate 200. The conductive segments 204 are preferably spaced from each other, thereby forming a discontinuous shield, as seen in
According to an exemplary method of the present invention, one or more of the shielding tapes 200 is inserted into the jacket 100 during the jacket extrusion process. Specifically, the shielding tape 200 is pulled through the actual die/crosshead or tooling for the jacket 100 in between the inner and outer layers 110 and 120 of the jacket. Thus, one or more shielding tapes 200 may be sandwiched by the inner and outer jacket layers 110 and 120. During that co-extrusion process, the material of the jacket layers 110 and 120 is in a molten or near molten state. When the shielding tape or tapes 200 come into contact with the molten jacket material, bonding/melting of the shielding tape or tapes occurs within the jacket material. Alternatively, the two jacket layers may be preformed materials (not in a molten state) that are bonded together.
Preferably, the material of the jacket 100 and its layers 110 and 120 are the same as the substrate 202 of the shielding tapes 200, so that the materials readily mix and bond to each other. This creates a near seamless dispersing of the shielding tape 200 within the jacket 100. Alternatively, the jacket layers 110 and 120 may be formed of a different material than the substrate 202 of the shielding tapes 200. In that case, the jacket layers 110 and 120 may be bonded to the substrates 202 of the shielding tapes by any know method, such as adhesive bonding, high pressure, or the like. On the other hand, the outer jacket layer 120 may suffice as a barrier to hold the shielding tape 200 and the inner jacket layer 110 in place.
During the co-extrusion process, the conductive segments 204 are encased in the jacket 100 while also maintaining the original orientation of the segments on the shielding tape 200. That orientation of the segments insures consistent electrical properties of the cable, such as return loss and attenuation. Thus, the method of the present invention allows conductive shielding segments 204 to be inserted into the jacket 100 without negatively impacting the physical properties of the jacket, such as tensile strength and elongation. That is because the near continuous material of jacket 100 (incorporated with one or more shielding tapes 200) maintains its original tensile strength as well as elongation properties.
Referring to
While particular embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.
