IL45011A - Fusible inserts - Google Patents

Description

Fusible inserts RAfCHBK COfiPG lOH C. 43080 It has long been known that recoverable articles are useful for covering, protecting and/or encapsulating ^ T^ other articles. For example, elastomer sleeves have often been used to cover cylindrical articles merely by choosing a sleeve which, in its relaxed condition, has a diameter less than that of the article to be covered. The tendency of the sleeve to retract when it has been expanded and placed over the article results in a covering for the article which, for some few purposes, is satisfactory. Heat-recoverable articles have been used i a somewhat similar manner and generally found superior to elastomer covers in many applications. However, many of the previously proposed heat-recoverable encapsulating articles have not been completely satisfactory, particularly under circumstances where a strong and impervious bond between the recoverable article and the workpiece which is to be covered is desired. For example, it is common practice to install insulating coverings over electrical components such as conductors. The insulating material must, of course, be securely bonded to the conductor in order to protect the conductor from water or air or other media with which it may come into contact. Furthermore, it is also highly important that there be no air spaces between the covering and the conductor. The occurrence of air spaces is particularly troublesome where the insulating material is applied to a substrate having an irregular surface, for example a plurality of wires which have been twisted together to form a cable or braided structure. Thus, as is well-known to those skilled in the art, there has been a long standing need for heat-recoverable coverings which are easy to apply, and yet are capable of forming a secure, intimate, impervious bond with the article which is covered.

U.S. Patents Nos. 3,243,211 and 3,396,460 disclose heat-recoverable articles capable of being applied to substrates in such a manner that a secure, intimate and impervious bond was formed. Furthermore, Belgian Patent No. 781,546 describes the use of heat-recoverable sleeves to repair breaks in mine cables. These specifications disclose, inter alia, a heat-recoverable, hollow article provided with a fusible insert or liner. If the liner is positioned in abutting relationship with both the recoverable member and the substrate to which the recoverable member is to be applied, a heat-induced change, i.e., recovery, of the recoverable member will urge the fusible member toward the substrate and bring it into compressive abutment therewith.

In order, however, to obtain a secure, intimate and impervious bond between the recoverable member and the substrate, the interposed fusible member must become "fluid", that is it must be reduced in viscosity to an extent sufficient for it to flow and "wet" the adjacent surfaces of the substrate and of the recoverable member and thereby form a bond therebetween. With polymeric substances, the term "flow temperature" may be used to denote the temperature at which the polymer has a sufficiently low viscosity to "wet" surfaces it contacts. With substantially crystalline polymers the flow temperature approximately corresponds to the melting point of the polymer and the melting point is taken herein as the flow temperature of ϋϋ or to be flowable if it has substantially no stability of form under the pressure exerted on it by the recoverable — member.

The invention makes it possible to provide a composite structure comprising a hollow heat-recoverable sleeve and a fusible liner and a method of using same whereby even the most unskilled workman will be certain that sufficient heat has been applied completely to melt the fusible liner and thereby bond said recoverable sleeve to any workpiece telescoped within same. The invention also makes it possible to provide a means whereby simple visual and/or tactile examination of the workpiece after heating of the aforementioned composite structure to encapsulate said workpiece will be sufficient to determine if sufficient heat has been applied to melt the fusible liner.

Although the following discussion will be directed primarily towards heat-recoverable members of tubular form (sometimes for convenience referred to as "sleeves" or "jackets"), it should be understood that the present invention is equally applicable to and therefore encompasses structures wherein the recoverable member is in the form of an end cap (for example, a cup), a T, X or Y, a ring or any other hollow configuration having at least one open end which can receive a substrate workpiece.

Furthermore, a heat-recoverable member may be either heat-shrinkable or heat-expansible. i According to the present invention, the surface of a fusible member or liner is provided with a protuberance, or a plurality of separate upstanding protuberances, which may be formed from for example either the same material as the fusible liner or other compatible material (as hereinafter defined). These protuberances may be present on either the surface of the liner disposed towards the ' substrate or the surface disposed towards the recoverable member, or both. If the heat applied to effect recovery of the heat-recoverable member is sufficient to also melt the fusible liner, then the protuberances will melt (if they comprise a fusible material - see below) and the recovered composite structure will have a smooth outer surface (for example, the outer surface of an encapsulating sleeve will be smooth). Conversely, if the amount of heat supplied is sufficient to effect recovery of the recoverable member, but insufficient completely to melt the fusible liner, then the protuberances on the liner will not melt and will form corresponding bulges showing on the surface of the recovered member. Even under conditions of poor visibility, such bulges can readily be felt by running the hand over the recovered member. The heating referred to in this specification as being required to effect recovery of the heat-recoverable member and melting of the fusible insert may be by any positive application of heat, for example, radiation heating, induction heating, electric resistance heating or heat generated by an exothermic reaction.

The number, form and manner of disposition of the protuberances on the fusible member according to the invention is not critical provided the basic objective of the invention is adhered to. With respect to number, obviously if only a very limited number of protuberances are present, the operator after recovery will be less certain that all the fusible liner, including the areas thereof which are furthest from any protuberance, has been sufficiently heated. It is therefore apparent that sufficient protuberances should preferably be present so that their disappearance on heating is a clear indication that all of the fusible liner has been melted. Likewise, to achieve this objective the protuberances are preferably distributed over substantially the entire surface of the fusible liner. Such distribution can be random or in any conceivable geometric pattern. Viith respect to the form of the protuberances, they can be, for example, discrete (for example bumps or pimples) or in the form of continuous or discontinuous lines (for example, ridges). Preferably such bumps or ridges will be sharp sided and relatively high in proportion to their cross-sectional area so that if they are not fully melted they will form readily apparent corresponding bumps or ridges on the surface of the recoverable member. Thus it is preferable that the height of the protuberances be equal to at least about the diameter or width, as the case may be, of the base of the protuberance. It is further preferred that the height of the protuberances be at least about equal to the thickness of the recovered member with which they are associated. Obviously, the most appropriate number and form of the protuberances will vary with the thickness and shape of the recoverable member and the contemplated heating means and for any given type of recoverable member can readily be determined by a few simple experiments.

The inserts can be functionally combined with the heat-recoverable member in any suitable manner. For example, the fusible material may be applied to either the recoverable member or to the substrate as a coating thereon with the protuberances being disposed on either or both surfaces of the insert. For example, the fusible insert can be coated on the inner surface of the heat-recoverable member, i.e., the surface which is disposed towards a substrate telescoped therewithin, the outer surface or both. Normallyj the protuberances will be present on the surface of the fusible insert which is not bonded to the heat-shrinkable member and will therefore be disposed towards the substrate. Conversely, if the fusible insert is applied to the outer surface of the be substrate the protuberances will typically/on the other surface of the fusible insert, being thereby disposed towards the inner surface of the enveloping recoverable member. However, if desired, the side containing the protuberance(s) may readily be bonded to the substrate or sleeve, for example, by bonding the liner at points between the protuberances. Alternatively, the fusible insert in sheet form can first be wrapped around the substrate followed by telescoping the encased substrate within the sleeve.

Or, a separate integral tube of fusible insert can be interposed between the substrate and the recoverable member. Under these circumstances the fusible insert can have protuberances present on either or on both of its surfaces, that is, the surface disposed towards the substrate and/or on the surface disposed towards the recoverable member.

If the fusible insert is to be positioned on the inner surface of the heat-recoverable member this would, 480 - of course, be done subsequent to the deformation of said member to its heat-recoverable condition. If desired, *** although this is not preferred, the fusible insert need not coat or envelop the entire surface of the substrate or coat the entire surface of the recoverable member but can be deposited on either the substrate or recoverable member in the form of rings, strips or other discontinuous areas of fusible material on the substrate outer surface or jacket inner surface, respectively.

In general, the protuberances will be of the same material as the liner and will have the same melting point as the liner. However, in some cases, it may be desirable for the protuberances to melt or flow at a temperature different from that of the rest of the liner. For example, the protuberances may melt or flow at a temperature higher than the temperature at which the rest of the liner melts or flows. In such a case, there would be a heat margin, thus insuring that the rest of the liner had melted or flowed when the protuberances disappeared. Further, if the protuberan melt at a temperature higher than the melting temperature of the liner, they may dig into either the substrate or the sleeve thus providing for maintenance of good gripping between the liner and substrate, liner and sleeve or all three prior to fusing of the liner. Indeed, the protuberances may be infusible at the heating temperatures so that they remain in contact with the substrate and/or sleeve after the rest of the liner has melted. For this purpose, pieces of, for example, metal, ceramic or a thermosetting plastics material, which may be applied, for example, by sprinkling them onto the insert, may be used as protuberances. Protuberan which mechanically engage the sleeve and/or the substrate may increase the mechanical strength of the joint. In particular, when the substrate comprises two articles having a joint or splice therein, such protuberances may provide mechanical reinforcement of the joint or splice against stress in use and may assist in preventing, for example, longitudinal or torsional sli^age.

Alternatively, the protuberances may melt or flow of the liner. Use of such lower melting or flowing protuberances may be desirable where timed heating is to occur. For example, when applying sleeves with fusible liners to cold pipelines, it is desirable to heat the sleeve covering the pipeline for a set period of time after a predetermined temperature has been reached. Thus, if the protuberances are set to melt at the predetermined temperature, timing can be started from that point.

The protuberances may be used for purposes other than indicating whether fusing of the liner has occurred.

Thus, it is sometimes desirable to have a layer of foamed material as a liner for imparting desired dielectric properties. The protuberances may be fusible or hollow and fusible so that they allow sufficient volume for controlled foaming of the balance of the liner. Thus, foaming agents placed in the liner could result in the production of a foam which would occupy, in part, the space originally occupied by the hollow protuberances.

The protuberances on the fusible member can be formed in a wide variety of ways, the choice being primarily dependent upon whether the fusible insert is to be used as a separate sheet or tube or on the recoverable member or substrate, as described above. Where a separate sheet or tube of fusible insert is used, such a sheet or tube may be prepared by extrusion. Thus, the sheet or tube may be extruded using a die shaped to extrude a sheet or tube profile with ridges integrally formed thereon. Alternatively, a transfer coating apparatus can be used to emboss any desired pattern of protuberances on either or both of the sheet surfaces. A tube, sheet or a coating of fusible material can be provided with protuberances by sprinkling ^— pellets, preferably of the fusible insert material, onto the surface of the tube, sheet or coating which will preferably be warmed sufficiently to ensure adherence of the pellets.

A tube interiorly coated, that is, lined, with a fusible material can be provided with internal ridges, either longitudinal or helical, by passing the lined tube over a vertical spray head which is received within the tube and sprays molten material onto the interior surface of the fusible member. If the lined tube is simultaneously rotated as it traverses the spray, helical ridges are formed. Alternatively, an internal rotating spray head can be used to provide a series of ridges on the inside surface of the fusible member where the tube is stationary and the head rotates and then either the tube or the head is displaced in stages longitudinal Another method is to partly heat-recover a heat-recoverable tube with a fusible liner onto an engraved mandrel which will thereby emboss any desired pattern of ridges or bumps on the liner inner surface.

Under some circumstances, it may be desirable to bring the fusible insert to a temperature somewhat higher than its flowing or melting point or range. In these cases, the protuberances may be made by sprinkling or otherwise applying, as described above, onto the surface of the fusible member protuberances of a material with a melt or flow temperature higher than that of the fusible insert, the material being compatible vrith the fusible insert. In some cases, the desired temperature corresponds to the Boftening temperature of a cable upon which the heat-shrinkable jacket is being applied. The term "compatible"^\^ as used herein, merely indicates that at the melting or flow temperature of the higher melting protuberance material, said material will become dissolved or otherwise dispersed into the already melted fusible member material. In many instances the melting point or flow temperature of the protuberances is substantially the same as that of the fusible insert so that flowing and elimination of the protubera indicates flowing of the fusible material. In other instances (see above) the melting point or flow temperature of above or protuberances may advantageously be substantially/below that of the fusible insert.

The recoverable member used according to the invention may be extruded or moulded in the desired shape.

Where a simple tubular shape is desired, it may also be fabricated from a flat sheet of material simply by rolling it into a tube and suitably sealing the seam. Preferably, the recoverable member comprises a material having the property of elastic memory, for example those materials disclosed in United States Specification No. 3,086,242.

As is well-known to those skilled in the art, materials having the property of elastic memory are dimensionally heat-unstable and may be caused to change shape and/or dimension simply by the application of heat. Elastic memory may be imparted to polymeric materials by first extruding or otherwise moulding the polymer into a desired shape. The polymer is then crosslinked by exposure to high energy radiation, for example, a high energy electron beam, exposure to ultra-violet irradiation, or by chemical means, for example, incorporation of peroxides when polyolefins are used. The crosslinked polymeric material is then heated and deformed and then locked in that deformed condition by quenching or other suitable cooling or, alternatively, the same process can be carried out at room temperature by using greater force to deform the polymer. The deformed material will retain its shape almos indefinitely until exposed to an elevated temperature sufficient to cause recovery, for example, approximately 250°!' in the case of polyethylene. Among the polymers which can be processed in this way are polyolefins (for example, polyethylene and polypropylene), polyamides, polyurethanes, polyvinylchloride, polytetrafluoroethylene and polyvinylidene fluoride. The property of elastic memory can also be imparted without actual crosslinking to materials having the properties of crosslinked polymers (fo example polytetrafluoroethylene, polyolefins, or vinyl polymers) which have a sufficiently high molecular weight to give the polymer appreciable strength at temperatures above the crystalline melting poin . inorganic fusible materials, for example, solder and Suitable materials for the fusible insert include/ conventional thermoplastics materials, for example polyolefins (for example, polyethylene and polypropylene), polyamides (for example, Nylon 6 and Nylon 66), polyesters (for example polyethylene terephthalate) , and polyether sulphones (for example, 4,4'-phenylene ether sulphone).

Particularly preferred are hot melt adhesives, for example those disclosed in Belgian Patent Specification No 80 2 It is to be understood, however, that the present invention is not limited to the use of conventional thermoplastics as the fusible insert and initially flowable thermosetting materials are also suitable.

Materials such as epoxy resins, polyurethane resins, phenol-formaldehyde resins and the like may, therefore, also be used either alone or in combination with a thermoplastic material to form the fusible insert.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figures 1 and 2 are enlarged, fragmentary views of two different fusible liners for use according to the invention; Figure 3 is a view of recoverable sleeve, fusible- liner and substrate; Figure 4 is a view of a substrate having positioned around it a fusibleliner and a recoverable sleeve; Figure 5 is a view illustrating bumps visible through the sleeve when the liner has not been heated sufficiently to flow; Figure 6 is a view illustrating a method of making the fusible liner for use according to the invention ; Figure 7 is a cross-section through a sleeve and liner illustrating embossing of the liner; and Figure 8 is a view, partly in cross-section, illustrating the formation of a liner In Figure 4, a substrate 9 is covered with a fusible liner in the form of a tube 10. This liner has ^ protuberances 11 again illustrated as bumps. A recoverable sleeve 12 is then placed over the fusible liner 10 and heat-recovered. In this case, the protuberances are preferably disposed toward sleeve 12.

When either sleeve 6 or sleeve 12 is heat-recovered, the sleeve may recover before enough heat has been applied to cause the fusible insert or liner to flow. In that case, the protuberances will be visible on the outer surface of the sleeve. This condition is illustrated in Figure 5· As can be seen, a substrate 13 is covered by a heat-recoverable sleeve 14. A fusible liner 15 has not yet become flowable and, as a result, the protuberances are visible at 16 on the outer surface of heat-recoverable sleeve 14. When this condition exists, it can be seen and the workman applying the sleeve can thus readily determine, either visually or by feel, that insufficient heat has been applied and that more heat should be applied. When the outer surface of sleeve 14 becomes smooth, this indicates that the fusible liner has reached a flowable condition, and that sufficient heat has been applied.

Figure 6 illustrates a method of manufacturing a fusible J.iner according to the present invention. A sheet of fusible material 17 is warmed and then pellets of fusible material 18 are sprinkled onto the surface to form protuberances 19. The pellets should be compatible with the material 17 so that they adhere thereto when material 17 is warmed.

As illustrated in Figure 7, protuberances can also be formed while using an engraved mandrel. A tube of ea^ recoverable material 20 is provided with an inner liner 21 of fusible material. The tube is then placed over a mandrel 22 having grooves or indentations 23 therein. The heat-recoverable sleeve is then partially heat-recovered over the mandrel. The heat causes the inner fusible sleeve 21 to flow into the indentation 23 thus forming protuberances on the inner surface of the liner 21. The sleeves 20 and 21 are then removed from the mandrel, and a heat-recoverable tube 20 having an inner fusible liner with protuberances on the inner surface is obtained.

A method for forming protuberances in the form of ridges on the fusible liner is illustrated in "Figure 8. A heat-recoverable tube is indicated generally at 24. It comprises an outer heat-recoverable sleeve 25 and an inner fusible liner 26. The liner has protuberances in the form of ridges 27. These ridges are applied by spraying fusible material through a spray head 28. The ridges 27 are formed helically by rotating tube 24 and at the same time moving it laterally. Alternatively, the spray head 28 could be rotated as tube 24 moves laterally.

In addition to the embodiments specifically disclosed in the Figures above, it should be understood that this invention is applicable to any type of protuberance on the fusible liner and any method of forming such a protuberance. Thus, protuberances in any form may be employed, the only restriction being that the protuberances be discernible by sight or feel when the recoverable sleeve is recovered without causing the fusible layer to become flowable. Further, any method of forming the protuberance^, which is desired may be employed.

In those aspects of the invention that involve the use of a recoverable member the fusible article of the invention may be a corrugated article which may have one or more corrugations.

It will also be appreciated that the invention is applicable to recovery over any type of substrate which may be in the form of one or more articles.

Claims (9)

1. 45011-3 1. A recoverable article which comprises a recoverable member and an article positioned in abutting relation to, and in the direction of recovery of, the recoverable member, the article either comprising fusible material (as hereinbefore defined) and being corrugated or comprising a fusible member (as hereinbefore defined) and at least one protuberance on a surface of the fusible member, the protuberance or corrugation(s) being of such a size and shape that it can be detected through the recoverable member after recovery of the recoverable member but before application of an amount of heat which is sufficient to cause the fusible material or the fusible member to flow (as hereinbefore defined), and being such that it can indicate when sufficient heat has been applied to cause the fusible material or the fusible member, and/or the protuberance or corrugation, to flow (as hereinbefore defined).

2. A recoverable article as claimed in claim 1 , wherein the article is in sheet form.

3. A recoverable article as claimed in claim 1, wherein the article is .in the form of a tube.

4. A recoverable article as claimed in any one of claims 1 to 3» wherein the protuberance is in the form of a bump.

5. A recoverable article as claimed in any one of claims 1 to 3» wherein the protuberance is in the form of a ridge.

6. A recoverable article as claimed in any one of claims 1 to 5» wherein the- height of the protuberance is equal to or greater than the diameter or width, as appropriate, of the base of that protuberance.

7. A recoverable article as claimed in any 45011-2 one of claims 1 to 7» wherein the protuberance has been formed by extrusion. "~ 9. A recoverable article as claimed in any one of claims 1 to 7, wherein the protuberance has been formed by embossing. 10. A recoverable article as claimed in any one of claims 1 to 7, wherein the protuberance has been formed by warming a pellet of fusible material to cause it to adhere to said surface. 11. A recoverable article as claimed in any one of claims 1 to 7, wherein the protuberance has been formed by a spray nozzle. 12. A recoverable article as claimed in any one of claims 1 to 11, wherein the protuberance comprises a fusible material (as hereinbefore defined). 13. A recoverable article as claimed in claim 12, wherein the protuberance comprises the same fusible material as the fusible member. 14. A recoverable article as claimed in claim 12 or claim 13» wherein the protuberance comprises a fusible material which is different from the fusible material of the fusible member. 15. A recoverable article as claimed in claim 14, wherein the fusible material of the protuberance is compatible with (as hereinbefore defined) the fusible material of the fusible member. 16. A recoverable article as claimed in any one of claims 12 to 15» wherein the protuberance becomes flowable (as hereinbefore defined) at a temperature which is not less, han that nt.jjfh ch^J±Le_ usible^membe ii ^come8 45011/3 flowable (as hereinbefore defined). 17. A recoverable article as claimed in anj 1—' one of claims 12 to 15» wherein the protuberance becomes flowable (as hereinbefore defined) at a temperature which is substantially the same as that at which the fusible member becomes flowable (as hereinbefore defined). 1

8. A recoverable article as claimed in anyone of claims 12 to 1 » wherein the protuberance becomes flowable (as hereinbefore defined) at a temperature which is less than that at which the fusible member becomes flowable (as hereinbefore defined). 19· A recoverable article as claimed in any one of claims 12 to 15» wherein the protuberance becomes flowable (as hereinbefore defined) at a temperature which is higher than that at which the fusible member becomes flowable (as hereinbefore defined). 20. A recoverable article as claimed in anyone of claims 1 to 19» wherein the article comprises a thermoplastic polymeric material. 21. A recoverable article as claimed in claim 20, wherein the thermoplastic polymeric material is a polyolefin, a polyamide, a polyester, or a polyether sulphone. 22. A recoverable article as claimed in any one of claims 1 to 21 , wherein the article comprises a hot melt adhesive. 2?. A recoverable article as claimed in any one of claims 1 to 22, wherein t e article comprises an initially flowable thermosetting material or a formable material. 24. A recoverable article as claimed in any one of claims 1 to 23, wherein the article comprises solder. 45011/3 25. A recoverable article as claimed in l^-' any one of claims 1 to 1 1 , wherein the protuberance is infusible at the recovery temperature of the recoverable member or at the temperature of fusion of the fusible article . 26. A recoverable article as claimed in claim 25 , wherein the protuberance comprises a metallic, ceramic, or thermosetting plastics material. 27. A recoverable article as claimed in any one of claims 1 to 23 , wherein the article comprises a plurality of protuberances, which may be the same or different from one another. 28. A recoverable article as claimed in claim 24, wherein the protuberancesare distributed over substantially the whole of the said surface. 2

9. A recoverable article as claimed in any one of claims 1 to 28, wherein the recoverable member is heat-shrinkable. 30. A recoverable article as claimed in any one of claims 1 to 29 , wherein the recoverable member has the property of elastic memory. 31. A recoverable article as claimed in any one of claims 1 to 30, wherein the recoverable member comprises a crosslinked polymer. 32. A recoverable article as claimed in any one of claims 1 to 31 , wherein the recoverable member is in the form of a tube. 33» A recoverable article as claimed in any one of claims 1 to 32, wherein the surface of the 45011/3 38. A method as claimed in claim 35 or claim 36, wherein the protuberances are infusible at the recovery temperature of the article or at the temperature at which the fusible article flows (as hereinbefore defined). 39. A method as claimed in claim 38 wherein, after recovery of the recoverable member and fusion of the fusible article, the protuberances mechanically engage the substrate and/or the recoverable member to increase the strength of the joint between the substrate and the recoverable member. 40. A method as claimed in any one of claims 35 to 39» wherein the recoverable member and the article are in the form of a recoverable article as claimed in any one of claims 1 to 34. 41. A method as claimed in any one of claims 35 to 39, wherein, before heating takes place, the article is positioned in contact with the substrate. 42. A method as claimed in claim 41 , wherein the surface of the article which is in contact with the substrate is free of protuberances. 43. A method as claimed in any one of claims 35 to 40, wherein, before heating takes place, at least a substantial part of the article is in contact neither with the recoverable member nor with the substrate. 44. A method as claimed in claim 43» wherein both the surface of the article which is presented to the recoverable member and the surface of the article which is presented to the substrate have at least one protuberance thereon.