DE8713072U1 - Plastic hose for conveying liquid or gaseous media with an embedded heating conductor - Google Patents

Description

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Plastic hose for conveying liquid or gaseous media with an embedded heating conductor

The innovation is aimed at a plastic hose for the transport of liquid or gaseous media, namely hoses in which a heating conductor is embedded for heating the transported medium. Hoses of this type can be used in areas in which it is important to bring a wide variety of media to a certain temperature, to ensure a constant temperature or to prevent them from freezing. In certain circumstances they can also be used to convert a substance from a solid to a liquid state. Hoses of this type are used, for example, in windscreen wiper systems in motor vehicles. Other possible uses are, for example, feeds for heated test systems or air or water-carrying hoses in dentists' offices. Although the plastic hose can therefore be used for the transport of a liquid or gaseous medium according to the innovation, in order to simplify the description, only the transport or the transport of a liquid is referred to below.

A hose of this type is known from DE-GMS 85 20 557, in which a heating cable is connected to a flexible plastic hose by a braid that holds both parts together. A special,

the braid preventing the braid from splitting up A braid termination must be present* This and the fact that the flexible braid allows the heating conductors attached to the hose to move under pressure and that the braid is permeable to moisture and dirt were considered to be disadvantageous.

Furthermore, a hose of this type has become known from DE-GMS 86 22 603, in which the lumen of the hose is offset on one side to form a longitudinal cross-sectional connection, with the heating conductor being inserted into the cross-sectional thickening at a distance from the lumen in such a way that the hose wall area between the lumen and the heating conductor is thinner in cross-section than the hose wall area between the heating conductor and the surface of the hose. This avoids the disadvantages mentioned above and ensures good heat transfer due to the small distance to the heating conductor caused by the lateral offset of the lumen from the central axis, but in return a large overall cross-section is accepted, which is perceived as disturbing for many safety purposes and, for example, particularly in motor vehicle construction, in which there is often little space available for such liquid guides and which may have to be bent with small radii. What both of the above-mentioned designs have in common is the relatively low heat output per unit length due to the straight heating conductor.

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Accordingly, the innovation was based _on the task of creating a plastic hose with an embedded heating conductor* whose total cross-section can be kept very small while maintaining high heating output.

This object is achieved by the means defined in the claims.

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Examples of embodiments are shown schematically in the drawing, based on which the innovation is described below. They show:

Fig. 1 shows a cross-section through a hose according to the innovation on an enlarged scale;

Fig. 2 is a longitudinal section through the object of Fig. 1;

Fig. 3 another embodiment of the innovation in

the representation and in scale of Fig. 1 in cross section;

Fig. 4 is a longitudinal section through the object of Fig. 3.

In Fig. 1, 1 is an inner tube made of e.g. PVC with a clear width of e.g. about 4 mm and a wall thickness of e.g. 2 mm, when it comes to hoses for windscreen washer systems for motor vehicles. In order to

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A heating element 2 made of nickel with a thickness of 0.2 mm is wound spirally in such a way that the ends or, in certain intervals adjusted to average hose bend lengths, have an area with a small gradient 3 and the space between these areas has a wide gradient 4. This ensures a secure electrical connection at the hose ends, e.g. by stripping the sheath and attaching a clamp, but also e.g. by using a socket plug with claws that presses from the outside, similar to a television plug, without or after only partial sheathing.

On the other hand, the different pitch and the compression of the turns at certain points can create a certain ohmic resistance over a certain length, which can be determined in such a way that it provides good heat output on the one hand and prevents overheating on the other hand, which has a detrimental effect on the plastic material of the inner tube carrying the liquid as well as on the insulation and can even cause it to melt.

The heating conductor 2 is covered with an elder winding, generally designated 5, which can be made of polyester or glass fibers, for example, and which connects with the material of the hose 1 and serves to relieve tension and/or pressure, thus preventing the heating conductor winding from shifting. It can consist of a spiral wound around the inner

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tube, wound thread or strand or even a fabric.

6 is an insulating sheath made of e.g. PVC foam.

Such a hose can have a total thickness of only about 12 mm or less and can be bent with a small radius, as is particularly desired in automotive construction.

The embodiment according to Figs. 3 and 4 differs from that according to Figs. 1 and 2 in that instead of the strain relief winding 5 made of, for example, glass fiber fabric or strands, only individual, e.g. three longitudinal strands 7, 7a, 7b made of, for example, glass fiber are provided, which are embedded in the insulation jacket 6 and serve to relieve pressure in this arrangement. Of course, strain and pressure relief can also be used in combination.

In addition, at certain intervals of the endlessly extruded hose, the areas 8 of tight winding are arranged, e.g. with seven windings each, so that the extruded hose can be divided into sections along the line 9 using a saw or other suitable cutting device, thus creating two hose ends with windings of a small pitch.

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The transition from a narrow to a wide pitch of the heating conductor winding can of course be more gradual than shown.

Hoses according to the innovation can be manufactured in one operation in successive stages, where the extrusion of the inner hose is followed by the winding of the heating conductor, then the application of the strain relief and finally the application of the insulation jacket.

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Claims (2)

1·· · « I ■ Patent Attorney DipL-lng. C-H. Huss Griesstrasse 3 a G 628 Garmiseh-Partenkirchen, 28 September 1987 Hs: A Verwaltungsgesellschaft Geiger Plastic GmbH & Co.KG Breitenauer Strasse 1 8100 Garmiseh-Partenkirchen Protection claims 1. Plastic hose for conveying liquid or gaseous media with an embedded heating conductor, characterized by the central arrangement of an inner hose (1) made of plastic and a heating conductor (2) made of metal wound around it in a spiral shape in such a way that at the ends of a piece of hose or in regular sections of an endlessly extruded hose the winding has a region of narrow pitch (3) and in the areas between them (4) a wide pitch) and also an insulation layer (6) firmly connected to the inner hose* * t *·<! 4 MH t* III« Il ·* # * «III i 10* I «II« I * 9 · ■ I I 11 lit! lilt ■ » · ||*t Il &igr; I at··) } iiit) I &igr; > · &igr;&igr;&eegr;&igr;&igr;&igr; III· ·· » » *"i l fc *" I I I 2. Hose according to claim 1, characterized in that a tension and/or pressure relief layer (5) made of spirally wound polyester or glass fiber strands, fabric or longitudinal strands (7) is connected between the inner hose (1) and the insulation jacket (6). 3- Hose according to claim 1, characterized in that the endlessly extruded hose has a region (8) of narrow heating conductor winding at predetermined intervals, which allows subsequent separation into hose pieces with narrow heating conductor winding at both ends. IfIIfIfVlIl it >&igr;&igr;&igr; 4 i i t' I I I I I f f &igr;&igr;&igr;&igr;&igr;&igr;&igr; i &igr;&igr; I* I III It Il I III!