SHRINKABLE WRAPPING MATERIAL

This invention relates to a shrinkable wrapping material, for use particularly, but not exclusively, to repair damaged electrical wires or cables without accessible free ends.

Electrically conducting wires or cables need to be insulated and protected to render them safe and to improve performance. Such wires or cables are provided with an electrically insulating sleeve during manufacture. However, the insulating sleeve can be damaged in use, exposing the wires or cables inside.

There are several known ways to repair such damage. One of the most common is self adhesive electrically insulating tape, which can be wound round the damaged section. However known tapes of this kind often have poor adhesive characteristics, in particular at the high temperatures found in many electrical applications, which can lead to the tape unwrapping in use. In addition, these tapes can be difficult to fit in confined spaces, for example when repairing windings within electrical motors.

Another known solution are sleeves of electrically insulating material, which can be passed over a free end of the damaged wire or cable, and manoeuvred into position over the damaged section. Some such sleeves are then heat shrinkable to secure them in position. However, this solution is not possible when the ends of the damaged wire or cable are not accessible, or are provided with terminations which are too large to allow the sleeve to pass over them.

To overcome this particular problem it is know to provide electrically insulating material formed into a tubular roll, which can be unfurled and rolled around the damaged section. However, to be effective these products must be a good fit on the tube or wire or they can move away from the damaged

section. In addition, known devices are awkward to fit in confined spaces. These products can also be complex to manufacture because the material has to be set in the correct tubular formation.

One further problem with known rolls, and with the known sleeves described above, is that they comprise single layers of material, which can often have small "pin-hole" defects which can cause the breakdown of the electrical insulation.

The present invention is intended to overcome some of the above described problems.

Therefore, according to a first aspect of the present invention a shrinkable wrapping material comprises an inner layer and an outer layer connected to one another, in which the inner layer comprises greater permanent shrinkage characteristics than the outer layer, in which the inner layer is shrunk in one direction to a pre-determined degree such that the shrinkable wrapping material is formed into a roll, in which the inner layer and outer layer are resilient such that the roll is unrollable, and in which the inner layer is further shrinkable.

Thus, the present invention provides a device which can be used to repair damaged wires or cables with inaccessible free ends, just as it is possible to do with known tubular rolls described above. However, the use of' two layers, one of which shrinks to a greater extent than the other, provides for a simple manufacturing process as an energy need only be applied to the inner layer such that it will shrink, and the roll will be formed. (There is obviously a degree of control required here, and that is referred to below). In addition, this two layer structure overcomes the problem of pin-hole defects in the materials used. The use of two layers in the one device also meets the requirements of certain international safety standards, where two separate devices were required previously.

The present invention also provides a device which can be set in position on a damaged wire or cable by shrinking it further with the application of energy, for example heat. This allows for one product type to be easily secured in position on wires or cables of different diameters.

In a preferred construction only a first part of the inner layer can be shrunk in one direction to a pre-determined degree, such that the roll can comprise an outer edge portion projecting away from the direction of curvature of said first part.

This construction provides a lip which projects from the roll, which facilitates the ready application of the wrapping material onto a damaged wire or cable. In particular, the lip can be used to easily locate the end of the roll to unfurl it for application. This can be done by hand prior to fitting on a damaged wire or cable, or the lip can be applied directly to the damaged wire or cable and used as an application tab to force the roll open for fitting thereon. This second method may be necessary in very confined spaces, for example when repairing windings within electrical motors.

It will be appreciated that the inner layer can be shrunk in a direction which is oblique to an axis of the roll, so a helical roll is created. However, in a preferred construction the inner layer can be shrunk in a direction normal to an axis of the roll.

In a preferred construction the wrapping material can be rolled through at least 720 degrees. With this construction at least two layers of the wrapping material will surround a damaged wire or cable with a circumference the same or less than that of the roll, which means at least four layers of material are used, providing extra safety and performance. In addition, this construction also allows for the wrapping material to be safely used on wires or cables with a circumference greater than the roll, provided it is no more than twice the circumference of the roll, or the wrapping material will not fully surround it.

It will be appreciated that the present invention includes the use of materials which can be shrunk via the application of any kind of energy. However, in a preferred construction the wrapping material can be heat shrinkable, the inner layer can be heat shrunk to said pre-determined degree, and the inner layer can be further heat shrinkable.

There are a variety of ways the present invention can be performed in terms of the types of material used. In one version of the invention the inner layer can comprise a sheet of polymeric material, the outer layer can comprise a sheet of polymeric material, and the inner layer and the outer layer can be laminated to one another.

However, as an alternative to this construction the inner layer can comprise a sheet material, and the outer layer can comprise a coating applied to the inner layer.

In other versions of the invention the inner layer can comprise a plurality of layered materials each comprising substantially the same permanent shrinkage characteristics. Such a construction may be used to improve shrinkage performance, work performance, or structural integrity.

In yet another version of the invention the inner layer can again comprise a plurality of layered materials, but a first one or more of said layered materials can be shrunk in one direction to a pre-determined degree such that the shrinkable wrapping material is formed into a roll, while a second one or more of said layered materials can be shrinkable such that the inner layer is further shrinkable. With this construction one inner layer does not have to perform the shrinkage which forms the roll, and the shrinkage which attaches the wrapping material to a damaged wire or cable in use. By separating these tasks performance can be further improved in each event by using specifically tailored materials.

It will be appreciated that heat shrinkable materials can shrink in more than one direction, although this can be readily controlled during manufacture. However, it is known to provide materials with a particular shrinkage direction, so preferably the inner layer can comprise one or more materials with a shrinkage direction normal to an axis of the roll. (Materials suitable for this purpose are commonly provided on ply rolls, and the shrinkage direction can be perpendicular to the axis of such a ply, and therefore in the machine direction thereof, or the shrinkage direction can be parallel to the axis of such a ply, and therefore in the transverse direction thereof. In the present case it is preferred to use a ply with a shrinkage direction in the transverse direction, and to cut this into strips for making the inner layers.)

As such, the mere application of heat will result in the roll being formed in a controlled manner.

In one version of the invention an interior or exterior surface of the wrapping material can be provided with a settable adhesive. This can be a hot melt adhesive with a melting temperature above the temperature required to heat shrink the inner layer to said pre-determined degree; or alternatively it can be a thermally setting adhesive with an activation temperature above the temperature required to heat shrink the inner layer to said pre-determined degree. A suitable thermally setting adhesive could be a stage B prepreg based on polyester, polyurethane, acrylic or epoxy technology.

With this construction the wrapping material can be further bonded to itself and/or to the wire or cable to which it is applied in use. As the adhesive is heat settable the roll can still be unfurled prior to application on a wire or cable, and the adhesive will only act as such when the heat is applied to further shrink the inner layer. The heat settable adhesive can fully or partially cover the interior or exterior surface of the wrapping material. For example, the adhesive could be provided only at the inner end of the inner layer, such that it only serves to adhere the wrapping material to the wire or cable.

In one version of the invention the inner layer can comprises an outer edge, and the outer layer can comprise an outer edge portion which can extend beyond the outer edge of the inner layer, and project away from the direction of curvature of said first part. This is a simple way to provide for the lip feature because the outer edge portion will not be formed into a part of the roll as the inner layer does not extend over it and will not force it to curl.

There are a number of different ways that the above described shrinkable wrapping material can be produced. In particular, a subject material can be formed into a roll by a machine before it is subjected to an energy source which effectively sets it in position, or the subject material can simply be subjected to an energy source and allowed to roll up freely.

Therefore, according to a second aspect of the present invention a method of manufacturing a shrinkable wrapping material comprising an inner layer and an outer layer connected to one another, in which the inner layer comprises greater permanent shrinkage characteristics than the outer layer, in which the inner layer is shrunk in one direction to a pre-determined degree such that the shrinkable wrapping material is formed into a roll, in which the inner layer and outer layer are resilient such that the roll is unrollable, and in which the inner layer is further shrinkable, comprises the following steps

i) arranging the inner layer and the outer layer together to form a flat subject material

ii) forming said subject material into a roll in which a first portion overlies a second portion

iii) applying an energy to shrink the inner layer to said predetermined degree.

Apparatus to perform the above described method is known. In particular GB 0723936.1 in the name of the applicant discloses apparatus for manufacturing a tubular product comprising a tube forming means, a tube maintaining means, a drawing means and energy application means, in which the tube forming means comprises a formation aperture or series of apertures adapted to form a subject material drawn therethrough into a tubular shape, in which the tube maintaining means comprises a circular aperture or series of apertures adapted to maintain the subject material drawn therethrough in the tubular shape, in which the drawing means is adapted to draw the subject material through the tube forming means and the tube maintaining means, in which the energy application means is adapted to direct an energy to the subject material, or an energy absorbent component disposed thereon, such that the subject material is set in the tubular shape, and in which the tube maintaining means is adapted to maintain the subject material in the tubular shape during absorption of the energy.

In a preferred version of the this method in step ii) the subject material can be formed into a roll comprising a first rolled part and an outer edge portion projecting away from the direction of curvature of the first rolled part, and in step iii) the energy can be only applied to said first rolled part.

Again, GB 0723936.1 in the name of the applicant discloses apparatus which can perform this method. In one embodiment described therein the formation aperture or series of apertures are adapted to form a subject material drawn therethrough into a tubular shape comprising a tubular section with a flat lateral section extending therefrom, and the tube maintaining means comprises a block provided with an aperture therethrough comprising a circular section with a flat lateral section extending therefrom.

According to a third aspect of the present invention a method of manufacturing a shrinkable wrapping material comprising an inner layer and an outer layer connected to one another, in which the inner layer comprises

greater permanent shrinkage characteristics than the outer layer, in which the inner layer is shrunk in one direction to a pre-determined degree such that the shrinkable wrapping material is formed into a roll, in which the inner layer and outer layer are resilient such that the roll is unreliable, and in which the inner layer is further shrinkable, comprises the following steps

i) arranging the inner layer and the outer layer together to form a flat subject material

ii) applying an energy to shrink the inner layer to said predetermined degree such that the inner layer is formed into a roll.

This particular method is suitable when the inner layer comprises a material with shrinkage direction characteristics sufficient enough to ensure an adequately even roll is formed when heat is applied to a flat panels of the subject material.

In one version of this method in step ii) the energy can be only applied to a first part of the inner layer such that the formed roll can comprise an outer edge portion projecting away from the direction of curvature of said first part. This can be achieved by heat protecting the outer edge portion during application of heat during manufacture.

The invention can be performed in various ways, but one embodiment will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a shrinkable wrapping material according to the present invention;

Figure 2 is a perspective view of the wrapping material shown in Figure 1 prior to forming;

Figure 3 is a cross-sectional end view of the wrapping material shown in Figure 1 ;

Figure 4 is a cross-sectional end view of the wrapping material shown in Figure 1 in a first in use position;

Figure 5 is a cross-sectional end view of the wrapping material shown in Figure 1 in a second in use position;

Figure 6 is a cross-sectional end view of the wrapping material shown in Figure 1 in a third in use position;

Figure 7 is a cross-sectional end view of a second shrinkable wrapping material according to the invention; and,

Figure 8 is a cross-sectional end view of the second shrinkable wrapping material shown in Figure 7 in an in use position.

As shown in Figure 1 , a shrinkable wrapping material 1 comprises an inner layer 2 and an outer layer 3 connected to one another. As described further below the inner layer 2 comprises greater permanent shrinkage characteristics than the outer layer 3, and as is clear from Figure 1 the inner layer 2 is shrunk in one direction to a pre-determined degree such that the shrinkable wrapping material 1 is formed into a roll 4. As also described further below the inner layer 2 and outer layer 3 are resilient such that the roll 4 is unrollable. The inner layer 2 is also further shrinkable.

As is clear from Figure 1 , only a first part 5 of the inner layer 2 is shrunk in one direction to a said pre-determined degree, such that the roll 4 comprises an outer edge portion 6 which projects away from the direction of curvature of said first part 5. In other words the outer edge portion 6 comprises a lip which projects from the roll 4.

The roll 4 passes through more than 720 degrees, so that at all radial points there are at least two layers of the wrapping material 1 , and at least four layers of the component layers 2 and 3. As such, when the wrapping material 1 surrounds a damaged wire or cable with a circumference the same or less than that of the roll 4, at least four layers of material will cover the wire or cable. In addition, this construction also allows for the wrapping material 1 to be safely used on wires or cables with a circumference greater than the roll 4, provided it is no more than twice the circumference of the roll 4.

The wrapping material 1 is manufactured as follows. The inner layer 2 and the outer layer 3 comprise filmic materials which are provided in strips. The inner layer 2 and the outer layer 3 are arranged next to one another and are laminated together in a known way to form a composite strip 7, shown in Figure 2.

The inner layer 2 comprises a commercially available heat shrinkable polyester film, which has a heat shrinkable orientation, indicated by arrow A, which is perpendicular to the machine direction of manufacture of the film, indicated by arrow B. The inner layer 2 can be heat shrunk more than once, and the higher the temperature applied the greater the shrinkage displayed. As such, the inner layer 2 can be shrunk to a first degree to form the roll 4, and shrunk further in use as required. Materials with these properties are known and are not further described here in detail. The outer layer 3 comprises a commercially available non-shrinkable grade of polyester film. Both the inner layer 2 and the outer layer 3 are electrically insulating.

The composite strip 7 is then formed into the roll using apparatus like that described in GB 0723936.1. In particular, the composite strip is drawn through a series of formation apertures adapted to form it into a tubular shape comprising a tubular section passing through 720 degrees, with a flat lateral section extending therefrom. The axis of the roll is normal to the heat

shrinkable orientation A. The composite strip 7 is then drawn through a heating block comprising an aperture corresponding to the formed shape, and the composite strip 7 is heated such that the inner layer 2 shrinks according to its heat shrinkable orientation A, and the composite material 7 sets into the roll 4 illustrated in Figure 3. During this process the outer layer 3 does not shrink, but is forced into the roll shape by virtue of its attachment to the inner layer 2.

It will be appreciated that there are various controllable aspects to this method, for example the degree of heating, the speed the composite strip 7 is drawn through the apparatus and so on, and the skilled man is expected to be

able to apply his common general skills in this area to adjust the manufacturing method to suit. In particular, the temperature and duration of the heating must be sufficient to set the inner layer at the right shrinkage.

The wrapping material 1 is used as follows. Referring to Figure 4 the wrapping material 1 is arranged next to a subject wire 8, with the gap 9 between the outer edge portion 6 and the body of the roll 4 presented thereto. The wrapping material 1 can then be rotated over the wire 8, until the wire 8 is located inside the roll 4, as shown in Figure 5.

It will be appreciated that there are various ways the wrapping material 1 can be manually manipulated to arrive at the configuration shown in Figure 5, however in each case the outer edge portion 6 facilitates the ready unfurling of the roll 4. For example, instead of using the outer edge portion 6 as an application tab as described above, it can be used to simply locate the end of the roll 4 to fully or partially unfurl it manually for ready application.

The subject wire 8 can be a new wire, or it can be a wire which has become exposed through damage. It will be appreciated that the item to which the wrapping material 1 is applied could be anything which has to be electrically insulated, or simply covered for any other purpose.

Heat is then applied to the wrapping material 1 , for example with a heat gun or the like, and the inner layer 2 shrinks further until the wrapping material 1 is snugly attached to the wire 8, as shown in Figure 6. In this process the outer layer 3 may exhibit a degree of shrinkage, depending on the temperature applied, however in most regular instances the outer layer 3 will not exhibit any shrinkage. During this process the outer edge portion 6 is eliminated because heat is applied to the whole of the inner layer 2, and the whole of the wrapping material 1 shrinks into a compact roll shape.

As is clear from Figure 6 the wire 8 is now fully and safely insulated by multiple layers of polyester material.

Figures 7 and 8 show a second shrinkable wrapping material 10, which is similar in construction to the wrapping material 1 described above, but it has one extra feature. In particular the interior surface 11 of the inner layer 12 is provided with a heat settable adhesive 13. This adhesive 13 is applied to the inner layer 12 during an initial manufacturing stage prior to the formation of the wrapping material 10 into a roll for heat shrinkage of the inner layer 12. The adhesive 13 has an activation temperature above that required to heat shrink the inner layer 12 during manufacture, but below the temperature used to further heat shrink the wrapping material 10 in use. The adhesive 13 in this case is a stage B prepreg based on polyester, but such a composition based on polyeurethane, acrylic or epoxy technology could also be used.

Therefore, in use as shown in Figure 8, the wrapping material 10 is applied to a wire 14 in the same way as wrapping material 1 described above, and heat is applied. However, rather than just shrinking into place on the wire

14 like wrapping material 1 , wrapping material 10 is also bonded into position. The application of heat activates the adhesive 13, which bonds the inner layer 12 to the wire 14 where it contacts it as shown at 15, and also bonds the inner layer 12 to the outer layer 16 where they contact each other after the heat has been applied in use, as shown at 17. As such, wrapping material 10 is secured in place on the wire 14 and will not move axially thereon.

The embodiments described above can be altered without departing from the scope of Claim 1. For example, in one alternative embodiment (not shown) the inner layer comprises a sheet material like that described above, but the outer layer comprises a coating applied to the inner layer.

In other alternative embodiments (not shown) the inner layers comprise a plurality of layered materials, each comprising substantially the same permanent shrinkage characteristics.

In other alternative embodiments (not shown) the inner layers comprise a plurality of layered materials, but a first one or more of said layered materials is shrunk during manufacture to form the roll, while a second one or more of said layered materials is shrunk in use to repair a damaged wire. With these constructions one inner layer does not have to perform the shrinkage which forms the roll and the shrinkage which attaches the wrapping material to a damaged wire or cable in use. By separating these tasks performance can be further improved in each event by using specifically tailored materials.

In another alternative embodiment (not shown) the inner layer is shrunk in a direction which is oblique to an axis of the roll, so a helical roll is created.

The invention is not restricted to the use of the above described materials, and in particular, in one alternative embodiment (not shown) the outer layer comprises a woven glass fabric suitably impregnated with an electrically insulating varnish.

In other alternative embodiments (not shown) settable adhesives are applied to only a part of the interior or exterior surface of the wrapping material. For example a heat settable adhesive can be applied to only a part of the interior surface of the inner layer. In one embodiment the adhesive is only applied to the inner end of the inner layer such that it only serves to bond the wrapping material to the wire, and not to itself. In another embodiment the adhesive is only applied to the outer edge portion of the inner layer such that it only serves to bond the wrapping material to itself. Such a construction might be used if it is desired to allow the wrapping material to move axially on the wire. In one further embodiment a settable adhesive is applied to the exterior surface of the outer layer, which serves to bond the outer and inner layers together.

There are also alternative ways that the outer edge portion can be created. For example, in one alternative embodiment (not shown) the inner layer comprises an outer edge, and the outer layer comprises an outer edge portion which extends beyond the outer edge of the inner layer. This outer edge portion is not formed into a part of the roll as the inner layer does not extend over it and will not force it to curl.

The second aspect of the present invention relates to a method of manufacturing a shrinkable wrapping material, and the above described embodiment provides support for that aspect of the invention.

However, in an alternative method of manufacture the formed composite strip can simply be heated without being first formed into a roll. When the inner layer is subjected to this heating it shrinks according to its heat shrinkable orientation and the roll is formed. This particular method is suitable when the inner layer comprises a material with shrinkage direction characteristics sufficient enough to ensure an adequately even roll is formed when heat is applied to the composite strip. In order to provide for the lip

feature the outer edge portion can be heat protected during this process so the inner layer in that area does not perform any shrinkage.

Therefore for the present invention provides a shrinkable wrapping material which is simple to manufacture, and simple to use, in particular in confined spaces.