Data cable for areas at risk of explosion

Abstract

The invention relates to a data cable. One embodiment of the data cable has at least one pair of wires and a cable sheath surrounding the at least one pair of wires. The at least one pair of wires has two wires twisted together in the longitudinal direction of the data cable. Cavities between the at least one pair of wires and the cable sheath are at least partially filled with a filler. The filler has a viscosity which is such that it adheres in the data cable in such a way as to remain in the data cable at least nearly completely when there is a specified pressure difference between one end of the data cable and the other end of the data cable.

Claims

1. A data cable, comprising: at least one pair of wires with two wires stranded with one another in the longitudinal direction of the data cable; and a cable sheath enveloping the at least one pair of wires; wherein cavities existing between the at least one pair of wires and the cable sheath comprise a first cavity which is delimited outwardly by an electric overall shield lying inside the cable sheath, and at least one second cavity, wherein the at least one second cavity is delimited by a fluid-tight electric shield around the at least one pair of wires and the outer side of a dielectric around each wire of the at least one pair of wires, wherein the first cavity is filled at least partially with a filler, wherein the filler has such a viscosity that it adheres in the data cable in such a way that it remains in the data cable at least nearly completely when there is a specified pressure difference between one end of the data cable and the other end of the data cable, wherein the fluid-tight electric shield prevents at least as far as possible an introduction of the filler into the at least one a second cavity, wherein the viscosity in the event of a pressure difference of up to 1 bar and a processing temperature of 120 C. lies in a range from 10 mPas to 10.sup.3 mPas and the viscosity in the event of a pressure difference of more than 1 bar and a processing temperature of 120 C. lies in a range from 10.sup.4 mPas to 10.sup.8 mPas.

2. The data cable according to claim 1, wherein the dielectric comprises a dielectric surrounding each wire of the at least one pair of wires, wherein the dielectric is a foamed or solid dielectric, and wherein the filler has such a viscosity that at least nearly no deformation of the dielectric occurs around the respective wire.

3. The data cable according to claim 2, wherein the wall thickness and/or the degree of foaming of the respective dielectric are adapted to the filler.

4. The data cable according to claim 1, wherein the filler has the viscosity at room temperature.

5. The data cable according to claim 1, wherein the filler has the viscosity at a temperature lying above room temperature.

6. The data cable according to claim 1, wherein the first cavity is filled with the filler completely.

7. The data cable according to claim 1, wherein the viscosity is selected as a function of the specified pressure difference and/or the processing temperature.

8. The data cable according to claim 1, wherein the at least one pair of wires is formed as several wire pairs, wherein the several wire pairs are stranded with one another in the longitudinal direction of the data cable and form a stranded bundle thereby.

9. A data cable, comprising: at least one pair of wires with two wires stranded with one another in the longitudinal direction of the data cable; and a cable sheath enveloping the at least one pair of wires; wherein cavities existing between the at least one pair of wires and the cable sheath are filled at least partially with a filler, wherein the filler has such a viscosity that it adheres in the data cable in such a way that it remains in the data cable at least nearly completely when there is a specified pressure difference between one end of the data cable and the other end of the data cable, wherein the at least one pair of wires is enveloped by a fluid-tight electric shield, which prevents at least as far as possible an introduction of the filler into a cavity delimited by the fluid-tight electric shield, wherein the viscosity in the event of a pressure difference of up to 1 bar and a processing temperature of 120 C. lies in a range from 10 mPas to 10.sup.3 mPas and the viscosity in the event of a pressure difference of more than 1 bar and a processing temperature of 120 C. lies in a range from 10.sup.4 mPas to 10.sup.8 mPas.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

(1) The present disclosure is to be explained further by means of figures. These figures show schematically:

(2) FIG. 1 a possible configuration of a data cable according to a first exemplary embodiment; and

(3) FIG. 2 a possible configuration of a data cable according to a second exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(4) In the following, without being restricted to these, specific details are set out to provide a complete understanding of the present disclosure. However, it is clear to a person skilled in the art that the present disclosure can be used in other exemplary embodiments that may differ from the details set out below. For example, specific configurations and arrangements of a data cable are described below that should not be regarded as restrictive. Furthermore, various application fields of the data cable are conceivable.

(5) FIG. 1 shows a data cable 1. The data cable 1 in FIG. 1 has, purely as an example and without being limited to the number shown, four wire pairs 30 as an example of at least one pair of wires 30 present in the data cable. Each of the four wire pairs 30 has two wires 10 stranded with one another in the longitudinal direction of the data cable. A wire 10 is formed from a conductor (pure metal), which is surrounded by a dielectric (insulation). Together with the insulation the conductor forms this same wire 10. Each wire 10 (each individual line for data transmission plus insulation) is enveloped by a dielectric 20 to insulate a wire 10 of a pair of wires 30 from an adjacent wire 10 of the pair of wires 30. Each of the wire pairs 30 is surrounded or enveloped by an electric shield 40, for example a foil shield. The pair of wires 30 and electric shield 40 can also be described as a data pair element 60. The four shielded wire pairs 40 (data pair elements 60) are stranded with one another. In the exemplary embodiment in FIG. 1, these four data pair elements 60 adjoin an inner element or central element seen centrally in cross section and are stranded around this inner element acting as a stranding centre. The stranded bundle resulting from the stranding is surrounded or enveloped by an electric overall shield 80, for example a foil shield. The overall structure formed from this, i.e. also the four wire pairs 40, are surrounded or enveloped by a cable sheath 100, which is extruded, for example.

(6) Inside the data cable 1, i.e. inside the cable sheath 100 and the electric overall shield 80, there exist gas-filled, e.g. air-filled, cavities. In cross section these cavities appear as a free area. In FIG. 1, one of these free areas is designated by the reference sign 70. This means that due to the design, the described structure of the data cable 1 has in cross section a considerable free area, which is gas-permeable, e.g. air-permeable. The free areas are often also termed gussets.

(7) In known data cables the areas provided with the reference signs 50 and 90 are likewise formed as such free areas. These free areas lead to gas, e.g. air, being able to flow through the data cable 1 from one end to the other end. However, this is undesirable in explosion-protected zones in particular and when laying cables from explosion-protected zones to non-explosion-protected zones.

(8) In contrast, in the exemplary embodiment from FIG. 1, the areas provided with the reference signs 50 and 90 are provided with a filler/a filling mixture. This means that between each of the wire pairs 30 and the cable sheath 100, more precisely the electric overall shield 80, existing cavities are at least partially filled with a filler/a filling mixture. Expressed another way, at least a portion of the cavities/free areas existing in the data cable 1 are filled with a filler/a filling mixture. In the exemplary embodiment shown in FIG. 1, the area 90 is filled with a filler purely as an example and without being restricted hereto. The area 90 is bordered outwardly by the cable sheath 100, more precisely by the electric overall shield 80. Furthermore, four areas provided with the reference sign 50 are filled with filler. Each of these areas 50 belongs to one of the data pair elements 60. Outwardly each of these areas 50 is delimited by the associated electric shield 40 and inwardly each of these areas 50 is delimited by the outer side of the associated pair of wires 30 (the outer side of the associated dielectrics 20). In the example from FIG. 1, the free area 70 is unfilled purely by way of example. Alternatively the area 70 can also be filled at least partially by a filler.

(9) Since an electric pair shield laid over the entire surface around the individual wire pairs 30 would largely prevent the filling of the free areas between the individual wire pairs 30/in the individual data pair elements 60, in the exemplary embodiment from FIG. 1 an electric shield 40 is used in each case that is permeable, at least in its state during the introduction/during the processing. Each of the electric shields 40 can therefore be formed as a fluid-permeable braided shield for electric pair shielding.

(10) On the one hand, the filler thus acts from the area 90 in a radial direction on each of the electric shields 40. On the other hand, the filler acts from each of the areas 50 in a radial direction on the respective dielectrics 20 of the associated wires 10. The dielectrics 20 can be a foamed or a solid dielectric 20 in each case. Foamed dielectrics 20 in particular, but also solid dielectrics 20 react sensitively to mechanical lateral pressure. Too high a mechanical lateral pressure would irreparably deform the (foamed) dielectrics 20, i.e. the electric insulation layers, for example, of the data pairs/wire pairs 30. This would lead to impairment up to the loss of the transmission properties of the wires 10 and thus of the wire pairs 30.

(11) As already stated, the filler has such a viscosity that it adheres in the data cable 1 in such a way that it remains in the data cable 1 at least nearly completely when there is a specified pressure difference between one end of the data cable 1 and the other end of the data cable 1. The ends of the data cable 1 should be understood as ends in the longitudinal direction of the data cable. The filler can be executed in this case as (highly) viscous fluid. The viscosity of the filler is selected such that it adheres in the data cable 1 on the one hand and is not pressed out of this when there is a defined pressure difference between the two cable ends. Furthermore, the filler should be workable easily in the context of cable manufacturing.

(12) Depending on the pressure difference between the two cable ends and the requirements arising from the production process, the use of a fluid is possible that at room temperature already has the necessary viscosity for the working-up process and for long-term use. However, the possibility also exists of using a fluid that is led to the necessary viscosity by heating during the working-up process and is then cooled down. In the latter case care should be taken to ensure that the cooled fluid, which then acts like an extruded filling mixture, does not lead to deformation of the dielectrics 20 due to the mechanical strength produced and thus to impairment of the transmission properties of the data pairs 30.

(13) One of the requirements of production process, for example, is that the fluid to be introduced fills all cavities (free areas in the cable cross section) if possible to full volume, for example, on the one hand, but on the other hand the fluid does not run back out of the stranded bundle up to application of the cable sheath. The viscosity of the filling material is geared in the solution to the pressure differences to be expected between the explosion-protected zone and the non-explosion-protected zone. At small pressure differences of less than 1 bar, the value can be in the order of 10.sup.2 mPas (at a reference temperature of 120 C. during processing) and at higher pressure differences can lie in a range from up to 10.sup.5 mPas to 10.sup.7 mPas (at a reference temperature of 120 C. during processing). The corresponding viscosity values at lower temperatures, for example room temperature, are then correspondingly higher. As an example of a material for low pressure differences the telephone cable grease TW 3090 could be used; for higher pressure differences Oppanol B12N is suitable, for example. The use of other soft (high-viscosity) filling mixtures is also possible.

(14) As outlined, to avoid impairment of the transmission properties as far as possible the filler should not result in deformation of the wire dielectrics 20 and the geometrical structure of the data transmission pairs 30 both during the working-up process and in the course of cable utilisation.

(15) The data transmission pairs 30 are constructed as outlined above. To reduce or even completely avoid negative influences on the transmission properties, for example due to deformation of the dielectrics 20, the wall thickness of the respective dielectric 20 and/or the degree of foaming of the respective dielectric 20 (in the case of a foamed dielectric 20) can be adapted (compared with a configuration with unfilled free areas). This is based on the fact that gas (e.g. air) located in the free areas enters decisively into the transmission properties. With the use of a filler such as a viscous fluid, the transmission properties of the data transmission pair 30 change. However, to achieve the transmission properties specified in the standard IEC 61156-5, for example, the wall thickness of the dielectric 20 and/or the degree of foaming of a foamed dielectric 20 can be adapted. For example, the wall thickness of the dielectric 20, regardless of whether it is executed as a foamed or as a solid dielectric 20, can be increased to counteract deformation. Furthermore, the degree of foaming (foaming degree) of a dielectric 20 can be reduced to counteract deformation. The filler influences the electric transmission properties of the data pairs 30. Since the dielectric constant of air is approximately 1 and that of the fillers is greater than 1, it must be guaranteed either via the wall thickness of the dielectric (the insulation layer) and/or the degree of foaming of the dielectric that when replacing the air in the cable with the filler, the transmission properties are returned to the original extent that they were with air. Increasing the foaming degree makes the wires more sensitive. The foaming degree must therefore be reduced to counteract deformation.

(16) FIG. 2 shows a data cable 1 according to a second exemplary embodiment. The data cable 1 according to the second exemplary embodiment is based on the data cable 1 according to the first exemplary embodiment from FIG. 1. The components of the data cable 1 from FIGS. 1 and 2 that are provided with the same reference figures correspond to one another. In contrast to the data cable 1 according to the first exemplary embodiment, the four areas 50 are unfilled and are therefore described as four second free areas 55 (four second cavities). This is achieved in that the electric shields 40 are formed around the wire pairs as fluid-tight shields 40, which prevent penetration of the filler into the free areas 55.

(17) The second exemplary embodiment can be regarded as a simplified exemplary embodiment, which can be used with small pressure differences between the ends of the data cable 1, for example. Since with low pressure differences the quantity of gas, e.g. air, flowing through the free areas 55 is smaller and can be regarded as not significant, a fluid-tight electric shield 40, e.g. a fluid-tight foil shield, can be used around a respective pair of wires 30 (data transmission pair). The fluid-tight electric shield 40, e.g. the fluid-tight foil shield, can moreover adapt tightly to the stranded bundle of the wire pair 30 (which has at least nearly an elliptical form), which in turn reduces the quantity of gas, e.g. air, flowing through.

(18) With the aid of the configurations from FIGS. 1 and 2, gas leakage from data cables that are to be used or laid in explosion-protected zones are reduced or even prevented.