METHOD OF SECURING A SHRINK SLEEVE UPON THE OUTER ENDS OF THE INSULATING JACKET OF A THERMALLY INSULATED CONDUIT

Abstract: Method for interconnecting a shrink sleeve (12) upon the outer ends of the insulating jacket (4, 5) of a thermally insulated conduit (1, 2) by inserting an electric conductor (10) into the clearance (9) between the sleeve (12) and the jacket (4, 5) prior to activating the shrinkage of the sleeve (12) whilst after having performed the shrinkage a permanent melt connection is obtained between the sleeve and the jacket by electric heating with the use of said wires.

Description: Method of securing a shrink sleeve upon the outer ends of the insulating jacket of a thermally insulated conduit. The invention relates to a method of securing a shrink sleeve upon the outer ends of the insulating jacket of thermoplastic syn¬ thetic material of a thermally insulated conduit, which shrink sleeve serves to bridge the welded ends of the inner tube and con¬ tains between said tube and the shrink sleeve as well as between the spaced apart ends of the jacket insulating material. Such a method is known in practice. With the shrink sleeve it is possible to seal the joint between two interconnected tube ends and the insulating material placed around it with respect to the environment in a faultless way. The shrink sleeve can be placed with large clearance upon one end of an insulating jacket prior to making the joining weld, subsequently can be placed over the spaced apart ends of the insulating jackets of the interconnected tubes and thereafter can be activated to shrink with a burner or hot air device or by means of a little oven having two halves which are placed around it. Upon shrinkage the sleeve engages the ends of the insulating jacket under tension so that a dense connection is obtained. A disadvantage of said known method is that the initially ex¬ cellent connection in the long run loses quality in that the ten¬ sion by means of which the shrink sleeve engages the insulating jacket gradually gets lost. The initially excellent connection then becomes a bad connection through which moisture can penetrate into the insulating material placed around the welded joint due to which the tube can start to corode there and the insulating material can be affected. Purpose of the invention is to provide a method in which said disadvantage cannot occur. According to the invention this purpose is achieved in that between the outer surface of the insulating jacket and the not yet shrunk sleeve an electric conductor is placed which eventually itself is surrounded by a thermoplastic synthetic material having in principle similar softening and melting properties as the syn¬ thetic material of the insulating jackets and of the shrink sleeve, after which the shrink sleeve is activated to shrink and after completion of said shrink the sleeve and the jacket are welded upon each other by electrical heating by means of the applied wires. According to the invention iπmediately after the shrink connection has been made a melt connection is generated interconnecting the sleeve and insulating jacket permanently with each other due to which it no longer is of importance whether the clamping tension obtained by the shrinkage gets lost in the long run. The shrink sleeve prior to being shrunk has sufficient clearance to apply the electric wire. Said wire can be wound around the jacket after which the shrink sleeve is shifted over it, of course leaving the outer ends free which can be connected to a source of electric energy. After activating the shrinkage the electric wire is firmly clamped. If said wire then is heated electrically up to a temperature at which the coating of the wire melts as well as the adjacent surfaces of the sleeve and of the jacket then, also under the influence of the clamping tension, an excellent melt connection is obtained. According to the invention use is made of the properties of the shrink sleeve and said properties are combined with the somewhere else known possibility of performing a weld by means of electric or inductive heating. The sleeve needs no additional provisions. Accordingly the invention makes it possible by making use of the any how present clearance at the not yet shrunk sleeve to generate a permanent connection without the necessity of more investments than an electric wire and a source of electric energy. The method of the invention can be further simplified by taking as electric wire a-^re having two cores which at one end are interconnected. Such a wire only needs to be cleaned of coating at one end so that the two conductors can be twined after which the wire with at least one winding is put around the jacket whereafter the sleeve is shifted over it. The invention now will be further elucidated with reference to the drawing. Said drawing shows in cross section the place of interconnection of two thermally insulated tube sections. The drawing shows two tube sections 1 and 2 which e.g. by means of a V-welded seam 3 are interconnected. Said tubes 1 and 2 over the largest part of their length are surrounded by an ' insulating jacket 4 and 5 respectively made frcm a synthetic material, ϊhe space between the tubes 1 and 2 respectively and the jackets 4 and 5 respectively has been filled with an insulating material e.g. a foamed synthetic material 6 and 7 respectively. Prior to making the weld 3 a shrink sleeve made from a thermoplastic synthetic material is shi ted over one of the jackets as indicated with interrupted lines at 8. Said shrink sleeve has been stretched such that it has a wide clearance 9 with respect to the jacket. Around each outer end of the jacket 4 and 5 respectively a double core electric conductor 10 is wound in the form of a least one winding. At one end the two cores are interconnected and at the other end connection can take place with the electric source 11 indicated diagrammatically. The shrink sleeve now easily can be shifted over the two windings 10 as indicated with interrupted lines at 12. The space 13 around the welded seam 3 and between the outer ends of the insulating jackets 4, 6 and 5, 7 respectively can have been filled with insulating material prior to placing the sleeve 12 but this can take place at a later time as well by injection of a foaming resin. After shifting the sleeve into the position indicated at 12 said sleeve is heated in a manner known per se due to which the sleeve shrinks and assumes the shape shown in the lower half of the drawing due to which said sleeve, as indicated in the left portion at 14, starts to ly around the electric conductor 10 with the clamping tension. n If thereafter current is supplied through the conductor 10 its coating 15 will melt and said coating merges with the synthetic material of the jacket 5 and of the synthetic material of the sleeve 12 so that the melt connection is generated as indicated at 16.

Claims: CLAIMS 1. Method of securing a shrink sleeve upon the outer ends of the insulating jacket of thermoplastic synthetic material of a thermally insulated conduit, which shrink sleeve serves to bridge the welded ends of the inner tube and contains between said tube and the shrink sleeve as well as between the spaced apart ends of the jacket insulting material, characterized in that between the outer surface of the insulating jacket and the not yet shrunk sleeve an electric " conductor is placed -which eventually itself is surrounded by a thermoplastic synthetic material having in principle similar softening and melting properties as the synthetic material of the insulating jackets and of the shrink sleeve, a ter which the shrink sleeve is activated to shrink and after completion of said shrink the sleeve and the jacket are welded upon each other by electrical heating by means of the applied wires. 2. Method as claimed in claim 1, characterized in that an electric wire is used having two cores which at one end are interconnected. OMPI IPO

Inventors: VAN DER WIEL WILLEM GERRIT, VAN DER WIEL, WILLEM, GERRIT
Applicants: ANIA BV, ANIA B.V.
Application year: 1984
Main classification: F16L59
IPC codes: B29C65, F16L47, F16L59