The present invention relates to a solution for accomplishing a cable lead-through particularly for cables having a large diameter.
In practice, the lead-through of high-frequency signal cables in particular, such as motor cables of frequency converters, into a cabinet or a casing is problematic. Sufficient sealing in view of the environment (IP protection) and also sufficient protection against electromagnetic emission (EMC) have to be taken into account in the lead-through. Various ready-made lead-through fittings are available for small cable diameters, but for large cables whose lead-through components require not only the above-described properties, but also effective draught elimination, adequately operating lead-through components are not available.
Another problem associated with lead-through components is that the diameters of interface cables of a high-power frequency converter may be 55 mm while the width of the casing of the frequency converter is only 200 mm. Accordingly, there is not much space for the lead-through component of the cable, and it should therefore have a structure that does not require much space in the wall in which it is installed.
An object of the present invention is to achieve a solution that is suitable particularly for implementing a lead-through for cables having a large diameter. This object is achieved by the method of independent claim 1 and the lead-through component of independent claim 5.
The invention utilizes a combination of an electrically conductive lead-through bushing and a shrinkable sleeve to accomplish an effective lead-through. A conductive material layer arranged on the inner surface of the shrinkable sleeve comes into contact with the conductive lead-through bushing that is fastened to a wall and with the cable. This results in efficient EMC protection at the lead-through point. By heating, the shrinkable sleeve is sealed against the cable, resulting in effective IP protection in addition to draught elimination.
Preferred embodiments of the method and lead-through component of the invention are described in the attached dependent claims 2 to 5 and 7 to 9.
In the following, the invention will be described by way of example with reference to the accompanying figures, of which
FIGS. 2 to 4 illustrate alternative manners of installation of the lead-through component of the invention.
A wall 1, through which a cable is led, may be the metal wall of an electric installation cabinet, for example. In the case of
A shrinkable sleeve 3 to be threaded onto the lead-through bushing 2 may be made from polyolefin. This allows the shrinkable sleeve 3 to be dimensioned for instance in such a manner that its length is 50 to 100 mm depending on the diameter, and its wall thickness about 2 to 3 mm after the shrinkage.
In accordance with the invention, an electrically conductive material layer 5 is arranged on the interior surface of the shrinkable sleeve 3. In the case of
Depending on the cable material to be used, any adhesive layer 4 to be arranged onto the interior surface of the shrinkable sleeve is preferably selected such that it provides a good adhesion to the cable and the lead-through bushing 2 when the shrinkable sleeve is heated for reducing its diameter. A glue line may be involved, which is activated by heating, and adheres to the cable and the lead-through bushing. Should the material in the cable with which the adhesive layer 4 comes into contact be PVC or XLPE, for example, the adhesive layer 4 may be hot melt adhesive, for example. The use of an adhesive layer 4 brings the advantage of the cable lead-through becoming more rigid, whereby it operates more effectively as a draught eliminator, and also seals the contact surfaces between the cable, the lead-through bushing and the shrinkable sleeve in a manner enhancing the IP protection of the structure against dust and water.
At least the lead-through bushing 2 can be fastened to the wall of the cable cabinet during manufacture of the cable cabinet. Such a cable cabinet may be delivered to the client together with a suitably dimensioned shrinkable sleeve including electrically conductive material layer (as a fixed component with the shrinkable sleeve or as a component separate from it). In this case, in connection with the electric installation the lead-through may be implemented for instance with a fan heater, with which a first end of the shrinkable sleeve 3 threaded onto the lead-through bushing 2 is heated for shrinking it and for activating any adhesive layer 4 in such a manner that the shrinkable sleeve adheres to the lead-through bushing. The cable is then peeled and threaded through the shrinkable sleeve. Finally, a second end of the shrinkable sleeve is heated in such a manner that it adheres to the cable by shrinkage (or by means of any adhesive layer).
It is also feasible not to fasten the lead-through bushing to the cable cabinet in connection with the manufacture, but it is delivered, together with the shrinkable sleeve, as a separate delivery to the installation site, where the implementation of the lead-through is initiated by fastening the lead-through bushing to the wall of the cable cabinet.
It is further feasible that the lead-through bushing 2 is fastened to the wall of the cable cabinet during manufacture, in addition to which the shrinkable sleeve 3 is fastened at its first end onto the lead-through bushing. This being so, in the actual electric installation it is sufficient to thread the cable through the lead-through bushing and the shrinkable sleeve, after which the second end of the shrinkable sleeve is heated with a fan heater in order to complete the cable lead-through.
FIGS. 2 to 4 illustrate alternative manners of installation of the lead-through component of the invention.
The case in
The case in
It is to be understood that the above specification and the related figures are only intended to illustrate the present invention. Different variations and modifications of the invention will be apparent to those skilled in the art, without deviating from the scope of the invention.
Number | Date | Country | Kind |
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20055682 | Dec 2005 | FI | national |