Cable with a cable core, a cable jacket and a tear thread

A cable with a cable core, a cable jacket and at least one tear thread extending therebetween, which tear thread is held in a fixed position by means of at least one auxiliary thread which is preferably wrapped or looped around the tear thread.

BACKGROUND OF THE INVENTION
 The present invention is concerned with a cable with a cable core, a cable
 jacket and at least one tear thread present between the core and the
 jacket. Such cables are widely used in order to facilitate stripping,
 i.e., in order to part or remove a layer of the cable more easily, for
 example, the outer coating, without damaging layers that are situated
 beneath this coating.
 Given specific applications, an exact positioning of the tear thread is
 desirable, wherein the position can be made visible for the installer by
 means of marking the outside covering or jacket. However, it becomes clear
 than an exact positioning is difficult and can get lost given processing
 steps during manufacture. This problem is particularly present when a
 steel grooved jacket is used. For example when a cable that contains a
 steel grooved jacket with two tear threads is to be manufactured, the tear
 threads should preferably lie opposite one another. An approach in order
 to oppose the above-mentioned problem is to introduce a multitude of tear
 threads, so that at least two tear threads are opposite one another or,
 respectively, at least one tear thread is presented in the desired
 position or location.
 Given cables with tear threads having a small length, another problem
 occurs. In a cable of a small length, it is frequently the case that the
 tear threads are pulled out of the cable without parting, tearing or
 breaking the cable jacket.
 SUMMARY OF THE INVENTION
 The present invention is directed to an object of providing a cable wherein
 the movement of one or more tear threads is inhibited or prevented.
 Another object of the invention is to provide a method for manufacturing
 such a cable.
 These objects are achieved by a cable having a cable core, a cable jacket
 and at least one tear thread positioned between the core and the jacket,
 wherein the tear thread is fixed in position by means of at least one
 auxiliary thread. The method of the present invention comprises the steps
 of providing a cable core, arranging at least one tear thread on the cable
 core and arranging at least one auxiliary thread in order to fix the tear
 thread on the core and then arranging a cable jacket that surrounds the
 cable core, the tear thread and the auxiliary thread.
 Given the inventive cable, the at least one tear thread is fixed in
 position by means of at least one auxiliary thread. Therefore, the tear
 thread cannot move out of the imagined position, either during the process
 of manufacturing the cable or given a post-processing, such as laying the
 cable or installation of the cable in cable ducts.
 Advantageously, the inventive cable comprises a plurality of tear threads,
 in particular at least two tear threads. For example, individual layers of
 the cable can be parted independently of each other and can be parted
 following one another by the utilization of a plurality of tear threads.
 Alternatively, the utilization of a plurality of tear threads enables the
 parting of the cable layer, for example enables the parting of the coating
 at a plurality of positions.
 Given the utilization of a plurality of tear threads, these are preferably
 equidistantly arranged around the cable core in a preferred embodiment of
 the inventive cable. For example, when two threads are present for parting
 the outside coating, these should lie diametrically opposite one another.
 Preferably, the tear thread is wrapped by one or more auxiliary thread in
 order to achieve a particularly firm fixing and position. Not only an
 axial movement, but also a radial movement of the tear thread is inhibited
 by the wrapping, which, as warranted, can be supported by a knotting or
 tying.
 Advantageously, the auxiliary thread or threads form a braid or a weave
 which preferably is what is referred to as a KEMAFIL type, which is
 described in a publication "Sonderdruck aus Band- und Flechtindustrie 30
 (1993, 4-10, 76-81, 31 (1994)), 48-52". A more uniform total appearance of
 the cable can be simply achieved when the auxiliary threads are presented
 in such a form. Furthermore, a displacement of the auxiliary threads can
 also be avoided.
 Finally, it is preferred that the tear threads are a part of the
 above-mentioned braid or weave and, in particular, extend parallel to the
 longitudinal axis of the cable.
 At least one tear thread is arranged at the cable core in the inventive
 method for the manufacturing of such a cable. Thus, it should be
 understood that the cable core is an arbitrary structure which, for
 example, can be comprised of a plurality of layers. This particularly
 means that also an inventive cable can be understood as a cable core. At
 the same time or subsequent to the arrangement of at least one tear thread
 at the cable core, the tear thread is fixed in position with an auxiliary
 thread. Finally, a cable coating is arranged, which cable coating
 surrounds the cable core, the tear threads and the auxiliary thread. Thus,
 the inventive cable is manufactured with the inventive method.
 Advantageously, a plurality of tear threads, particularly two tear threads,
 are arranged in order to individually successively part a plurality of
 layers of the cable or in order to part a layer at a plurality of
 positions.
 Preferably, the auxiliary thread at least partially wraps the tear thread
 in order to guarantee an increased fixing of the tear thread given this
 arrangement. This wrapping can additionally comprise a knotting or looping
 and can comprise a multiple wrapping.
 Given a preferred method, the tear thread and the auxiliary thread,
 essentially at the same time, are arranged as a braid or woven fabric. The
 arrangement advantageously occurs according to the known KEMAFIL
 technology, whereby the tear thread or the tear threads are integrated
 into a structure that is being formed.
 Finally, it is preferred that the two tear threads and the two auxiliary
 threads, essentially according to the KEMAFIL technology, are knitted
 around the cable core so that the tear threads extend parallel to the
 longitudinal axis of the cable and are fixed in position by the auxiliary
 threads by means of this wrapping.
 The auxiliary thread preferably exhibits less resistance to tearing than
 the tear threads in order not to impair the function of the tear threads.
 Given pulling of the tear threads, this means that the coating arranged
 thereupon is parted at the same time with the auxiliary threads.
 Therefore, a means is provided with the inventive method and the inventive
 cable in order to avoid an offset of the tear threads. Particularly, an
 exact positioning of the tear threads can be simply achieved and
 maintained given the process of manufacture, the post-processing and also
 the laying or installing of the cables.
 Other advantages and features of the invention will be readily apparent
 from the following description of the preferred embodiments, the drawings
 and claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The principles of the present invention are particularly useful when
 incorporated in a cable shown in FIG. 1, which has a cable core 1, a cable
 jacket formed by two layers 4 and 5 and at least two tear threads 2 and 3
 which extend between the core 1 and the jacket. In this embodiment, the
 layer 4 of the cable jacket comprises a steel grooved jacket and the layer
 5 is a plastic coating. As shown, the tear threads 2 and 3 should be
 present in an equidistant fashion with respect to the cable core 1, and
 this means that they lie diametrically opposite one another.
 The tear threads 2 and 3 are wrapped with auxiliary threads, such as 8 and
 9 (see FIG. 2), in order to guarantee the positioning shown in FIG. 1 of
 the two tear threads. FIG. 2 shows a weaving according to the KEMAFIL
 technology, wherein the tear threads 2 and 3 are components of the
 weaving. The significantly thinner auxiliary threads 8 and 9 are knitted
 with the tear threads 2 and 3 so that the tear threads 2 and 3 can no
 longer move. In the shown embodiment, the auxiliary threads 8 and 9,
 respectively, form a looping knot, as shown with the reference character
 10.
 Although the invention was completely and exemplarily described above with
 reference to the enclosed drawings, someone skilled in the art should
 recognize that different modifications are possible and are to be included
 in the scope of the claimed invention. Exemplary different wrappings and
 looping techniques can be used. In addition, the fabric does not have to
 be of the KEMAFIL type. Finally, it is also not necessary to integrate the
 tear threads into the fabric, since it would be sufficient for the fixing
 at a cable core when the auxiliary thread is arranged over the tear
 threads as a fixing layer.
 Although various minor modifications may be suggested by those versed in
 the art, it should be understood that we wish to embody within the scope
 of the patent granted heron all such modifications as reasonably and
 properly come within the scope of our contribution to the art.