CS276831B6 - Coaxial cable for higher ambient temperatures - Google Patents

Abstract

Material composition of the structural elements of a coaxial cable, meeting all the requirements in terms of reducing the ability to spread fire and intended for environments with a high concentration of people and property. The cable is a suitable replacement for coaxial cables with Teflon insulation, which do not meet the requirement of halogen-free materials used, as well as coaxial cables with silicone rubber insulation with worse mechanical and electrical parameters. The essence of the solution lies in the fact that the insulation (2) of the inner core of the cable is made of cross-linked polyethylene and the sheath (5) is made of a material with an oxygen number equal to or greater than 22. Under the sheath (5) at least one covering layer (4) can be formed from a material with an oxygen number greater than 40.

Description

1 CS 276831 B6

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the material composition of the coaxial cable constituents intended to be used in environments with higher ambient temperatures. in environments where halogen-free, non-flammable cables are needed. The purpose of the solution is to create such coaxial cables that meet all the requirements placed on these types of cables in view of reducing the ability to spread fire, while still being safe from the point of view of health protection.

The conditions for using coaxial cables in an environment with elevated ambient temperature are several types of cables. The most widespread types with the so-called Teflon insulators, which in the composition of fluoroethylene propylene, polytetrafluoroethylene-propylene or perfluoroalkoxyethylene, are responsible for the temperature requirements! insulation resistance 130 to 200 ° C. However, their disadvantage is the fluorine content of this insulating material. I. Fluorine at high temperatures or during core punching causes poisonous and highly corrosive gases. Thus, cables with such insulation do not meet the requirements for halogen-free application of materials. Another type of cable for this purpose is a coaxial cable with an insulated core core insulation. These cables resist! temperatures up to 130 to 150 ° C, I reach! thus also a relatively high heat resistance. However, their advantage is that, although such insulation is non-polar, and therefore high frequency characteristics of the cable independent of frequency, they have! however, greater specific damping, and the higher loss factor and relative permittivity of the liqueur rubber. A further disadvantage of these cables is their high mechanical properties resulting from the relative softness of the silicone rubber, which, when subjected to more radial stress, does not allow the shortening of both concentric cable cores to be avoided. pressed magnesium. The temperature resistance of these cables is even higher than in the previous solutions, but their cost does not allow their use in conventional areas, but only in the most demanding projects, eg the transmission of high-frequency signals in space loops or in the military industry. Another disadvantage of these large bending radii, that is to say in terms of mechanical properties, does not suit many purposes for many purposes.

The above-mentioned disadvantages of the prior art are eliminated by the solution of the qax cable according to the invention, which is based on the fact that it is designed to isolate the inner cable! of silane, peroxide or radiation crosslinked polyethylene, and the outer shell of the coaxial cable is made of a material with an oxygen number equal to or greater than 22. If the cable is constructed with one or more multi-layer coating layers, these are made of an oxygen number material greater than 40.

To isolate the coaxial cable that decisively determines the transverse electromagnetic wave transmission (TEM) the crosslinked polyethylene is stabilized against degradation from interaction with the metal cores. This results in a lower specific damping value due, among other things, to the loss factor tg 6raax. 10 4 and relative permittivity ε. r - 2.3 compared to, for example, CS 276831 B6 2 1 iconic isolation of ,63,6- · The temperature resistance of such insulation is 120 to 130 ° C. Crosslinked polyethylene insulation allows additional coating layers to be applied over the outer core, as well as being coated with materials with a higher oxygen number, so that these cables can meet the requirements for fire-resistant cables, eg according to IEC 332-3. In this case, the insulation is sufficiently hard, so that even at radial pressure of the cable, respectively. when combining tension and bending, the kernel is not short-circuited. Compared to the Teflon insulations proposed by the invention, the use of halogen-free rays only makes it possible to substantially increase the safety of persons in the vicinity of cables in the event of fire. Significantly, the reduction of gas aggressiveness compared to the Teflon-insulated gas gasses is also significant, resulting in a very significant corrosion of the metal parts of the electrical equipment in the vicinity of the installed cables. Another significant advantage of the present invention is the economic benefit, since all of these solutions are up to 15 times more expensive.

In the accompanying drawing, a coaxial cable according to the invention is shown schematically in FIG. 1 with an inner core 1 on which the insulation 2 and the outer core 3 are. Below the jacket 5 of the co-axial cable is a coating layer 4.

The solution is further documented by several examples of a particular embodiment of high frequency coaxial cables of the invention. Example 1

Coaxial cable with inner core 1 formed by a strand of tinned copper drots with a diameter of 0.17 mm, with insulation of 2 of crosslinked polyethylene with a diameter of 2.5 mm. an outer core 3 formed by braiding of tinned copper wires with a diameter of 0.10 mm and a jacket 4 of burning a retarding, very low density polyethylene with a diameter of over 4.4 mm. Example 2

Coaxial cable with inner core 1 of seven tinned copper drots 0.3 mm thick forming a strand, with 2 braided polyethylene, 5.5 mm in diameter, outer core 3 formed by braiding copper tinned wires 0.15 mm in diameter and sheath 4 of polyethylene terephthalate silk, impregnated with silicone lacquer, increases elasticity to a final cable diameter of 5.8 mm. Example 3

Coaxial cable with inner core 1 consisting of tinned copper copper diameter of 1.15, with insulation 2 of silane crosslinked low strength polyethylene, diameter of 7.25 mm, outer core 3 consisting of a combination of polyethylene terephthalate and aluminum foil and supporting tinned copper drots, of filler sleeve 4, of a material having an oxygen number of 45, concentrically deposited on the outer core 3 of a cable of 2 mm thickness and a sheath 5 of fire-retarding ethylene vinyl acetate with a resulting cable diameter of 14.5 mm -

Claims (2)

Coaxially, the cables of the present invention find particular use in apparatuses with a high level of property and personality, such as hospitals, hotels, banks, underground transport stations, and the monitoring of nuclear power plant premises in the case of conventional levers. where they are used to transfer images from cameras. PATENT'S CLAIMS A coaxial cable over higher ambient temperatures consisting of an inner radius, an insulation, an outer core and a sheath, possibly x from other sheathing layers below the sheath, characterized in that the insulation (2) of the inner sheath is made of cross-linked polyethylene and the sheath (5) It is made of a material with an oxygen number equal to or greater than 22. 2. A coaxial cable over a higher ambient temperature according to claim 1, characterized in that it has at least one layer (4) made of a material having an oxygen number greater than 40 below the jacket (5). 1 drawing