BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The invention relates to lightweight rollable power cable covers and methods of covering a cable with said lightweight rollable power cable cover.

Background

[0002] Power cables that are buried are dangerous and require some form of protective covering to prevent electrical shock from digging into the ground and cutting into the power cable. In some jurisdictions, the power cables have to be enclosed in a metal conduit and in other jurisdictions a cover has to be placed over the power cables that is puncture resistant. Polymeric sheets are often used for this purpose as they resist corrosion but have to be made thick to pass the required puncture test. These thick layers of polymer sheeting, such as about 8mm or more, are provided in cable cover segments that are placed over the long length of power cable in incremental sections and sometimes taped or adhered together. Other thick polymeric cable cover material is provided on a spool, but because of the weight, it requires a crane to enable the material to be spooled into the cable ditch to cover the power cables. These thick plastic rolls can have an area weight of about 5kg/m ² or more. In many cases, there is no room to operate a crane in and around the cable ditch.

SUMMARY OF THE INVENTION

[0003] The invention is directed to lightweight rollable power cable cover and methods of covering a cable with said lightweight rollable power cable cover. It has been surprising discovered that a thin and lightweight composite laminate of polymeric material can meet the requirements for puncture resistance of buried cables, in particular power cables. As described in the background, many places require cables to be covered to prevent damage and possible injury from digging. A puncture test that is used is DIN EN 50520:2020-12, the entirety of which is hereby incorporated by reference herein. This test measures a material’s ability to prevent puncture. A tapering puncture implement is dropped from a specified height onto the test specimen material. It is dropped four times onto the same location and there can be no penetration through the test specimen material for the material to pass the test. It was previously believed that thick layers of polymeric material, such as about 10mm or more, were required to meet this test. However, it has been found that much thinner composite laminates of material passes this test, which provides huge benefits for installation of this required cable covering.

[0004] These thinner composite laminates have a much lower area weight, or weight per area, than conventional cable cover tapes, which may be about 10,000g/m2. The area weight of a composite laminate may be about 4,000g/m2 or less, about 3000g/m2 or less, about 2000g/m2 or less, or even 1000g/m2 or less and any range between and including the values provided. The composite laminates may be half or less the area weight of extruded polyethylene which is commonly used in this application.

[0005] Also, the thickness of the composite laminate may be much less than conventional extruded polyethylene, which is commonly 10mm or more. The composite laminate may have a thickness of about 4mm or less, about 3mm or less, about 2mm or less, or even about 1 mm or less and any range between and including the thickness values provided. This much thinner and lower area weight material enables the material to be rolled or spooled onto a core and rolled along a cable ditch by hand to cover cables.

[0006] A very long length of this new composite laminate may be rolled onto a core and still manipulated by hand for installation. The length of material on the core may be about 10m or more, about 50m or more, about 100m or more, about 250m or more, about 500m or more, about 1 ,000m or more and any range between and including the length values provided. This prevents the need for laying down short segments of material that may further require attachment by tapping or gluing to adjacent cover segments and it also eliminates the need for heavy equipment to locate a very heavy spool of material over the cable ditch.

[0007] An exemplary lightweight rollable power cable cover comprises a composite laminate that includes one or more plies of a composite material. This composite material includes three layers with a first and third layer bonded by a second layer configured therebetween. The first and third layers have a higher molecular orientation, and may be a tensilized polymeric film, wherein it is stretched below the melt temperature to produce an increased molecular orientation and also a higher tenacity and flex modulus. These oriented first and third layers are bonded below the melt temperature of these oriented layers by the second layer, which has a substantially lower melt temperature than the first and third oriented layers, such as at least about 5°C lower, at least about 10°C lower, or as much as 20°C lower, as determined by a Differential scanning calorimetry (DSC) test.

[0008] Oriented film layers will have a higher melt temperature as the highly oriented polymer requires more energy to disrupt this orientation, as typically observed on a Differential scanning calorimetry (DSC) test. The first and third oriented layers may be the same polymer and may have the same amount or degree of molecular orientation, which may be quantified by the energy to disrupt this orientation in a DSC scan. The second layer may also be the same polymer as the first and third layers but may be a lower molecular weight polymer and/or may have much less if any molecular orientation. The three layers, or a plurality of plies of this composite material may be heated and pressed below the melt temperature of the first and third layers to bond the composite material together to form the composite laminate. It is well known that when melt laminating and bonding polymers together that “like likes like”, wherein melt bonding the same polymers together is more effective than melt bonding different polymers together. Therefore, orienting the first and third layers increases the melt temperature, as further detailed herein, and enables an effective bond with a less or non-oriented second layer below the melt temperature of the first and third layers.

[0009] A composite laminate may be configured with any number of plies depending on the application requirements and an oriented layer may form one layer of adjacent plies. The composite laminate may have two plies with three oriented layers and two bonding layers, for example. The layers of oriented and bonding layers may be alternating through the thickness of the composite laminate.

[0010] The composite laminate may be made with any suitable polymeric material including but not limited to hydro-carbon type plastics such as polypropylene, polyethylene, polyester, which are examples of a thermoplastic polymer.

[0011] A ply of a composite laminate includes the first and third layers of a tensilized polymer that are bonded together by the second layer of polymer, which is not tensilized or tensilized to a less degree than the first and third layers. In order to meet the combination of properties of puncture resistance while being thin and low weight, the thickness of the first and third layers may be much greater than the thickness of the second bonding layer, wherein the thickness of each of the first and third layers is at least double, four times or more, five times or more, eight times or more, or even ten times or more the thickness of the second layer.

[0012] A first layer and third layer may be a fabric, such as a woven fabric made from tensilized tapes of polymer film that woven together. The weave pattern may be plain, twill, rips, or crepe, for example with plain or twill being preferred. The film may be tensilized and then made into tapes that are then woven or the tapes may be tensilized in tape form and then woven into a woven layer.

[0013] Mechanical and physical properties of the composite laminate compared with a 10mm thick layer of extruded polyethylene, typically used for cable covers are provided in Table 1 :

Table 1

[0014] As shown in Table 1 , three examples of composite laminate are described; all being made from polypropylene polymer, wherein each of the first, second and third layers are polypropylene. Example 1 had a thickness of 4mm and an area weight of 3760g/m2. Example 2 had a thickness of 1 ,3mm and an area weight of 1196g/m2. Example 3 had a thickness of 1 .0 mm and an area weight of 920g/m2. For comparison, the conventional material for cable covers has a thickness of 10mm and an area weight of 9200g/m2, double that of the thickest composite material. The flex modulus according to DIN-EIN-ISO178 are provided along with the tensile modulus in both the warp and weft directions according to DIN 5702. Note that the samples were tested in both the warp and weft directions and the composite laminate is substantially isotropic.

[0015] These composite laminate examples include a plurality of plies of a first layer and third layer, each being an oriented layer, that are bonded together by a second layer, or bonding layer. The first and third layers are a woven layer of tensilized tapes with Example 1 having a plain weave and Examples 2 and 3 having a twill weave. The properties of these Woven Oriented Layers are provided. Then tenacity and elongation at break of the woven oriented layer is measured according to DIN 53857. All test data shown in measured according to the published test method as of November 16, 2021.

[0016] As described herein the composite laminate may be much thinner than conventional cable cover materials, have a much lower area weight and still meet the puncture tests, as detailed in Table 2.

Table 2: Puncture Test according to DIN EN 50520: 2020-12

As shown in Table 2, composite laminates that were 2.02mm thick, 1 ,68mm and 1 ,34mm thick all passed the puncture test, DIN EN 50520. This material is about a fifth or less the thickness of the conventional material and still passes the puncture test.

[0017] A lightweight rollable power cable cover may have a walking layer that is configured on a walking surface or top surface of the cable cover and configured to provide effective footing to prevent falls during installation of said cable cover. The walking layer may be a fabric including a woven or non-woven fabric or a polymeric material that has a texture imparted therein. The walking layer may have a coefficient of friction or 0.3 or more, about 0.4 or, about 0.5 or more as determined via ASTM E303 (Standard Test Method for Measuring Surface Frictional Properties Using the British Pendulum Tester).

Definitions:

[0018] Impact resistant is a material that meets depth of penetration and specimen break requirement according to DIN EN 50520, wherein the penetration into the specimen is less than 100mm and wherein the specimen does not break after four impacts.

[0019] Cables, as used herein, refers to buried cables requiring a cover for protection, such as power cables that require a puncture resistant covering in many countries.

[0020] The summary of the invention is provided as a general introduction to some of the embodiments of the invention, and is not intended to be limiting. Additional example embodiments including variations and alternative configurations of the invention are provided herein.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.

[0022] Figure 1 shows a perspective view of an exemplary cable ditch with four cables extending along the ditch.

[0023] Figure 2 shows a perspective view of cable cover segments being placed over power cable in a cable ditch.

[0024] Figure 3 shows a perspective view of a crane being used to maneuver a large heavy spool of cable cover over the cable ditch.

[0025] Figure 4 shows a perspective photograph of a puncture test wherein the puncture implement is dropped onto a test specimen to determine depth of penetration of the puncture implement into the test specimen.

[0026] Figure 5 shows a cross sectional view of an exemplary lightweight rollable power cable cover having a plurality of plies of composite material and a walking layer configured on a top surface.

[0027] Figure 6 shows a lightweight cable cover spool. [0028] Figure 7 shows a lightweight power cable spool with a length of the lightweight rollable power cable cover extended from said spool.

[0029] Figure 8 shows Differential scanning calorimetry (DSC) scans for exemplary first and third layer tensilized material and also the second layer.

[0030] Corresponding reference characters indicate corresponding parts throughout the several views of the figures. The figures represent an illustration of some of the embodiments of the present invention and are not to be construed as limiting the scope of the invention in any manner. Some of the figures may not show all of the features and components of the invention for ease of illustration, but it is to be understood that where possible, features and components from one figure may be included in the other figures. Further, the figures are not necessarily to scale, some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0031] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Also, use of "a" or "an" are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

[0032] Certain exemplary embodiments of the present invention are described herein and are illustrated in the accompanying figures. The embodiments described are only for purposes of illustrating the present invention and should not be interpreted as limiting the scope of the invention. Other embodiments of the invention, and certain modifications, combinations and improvements of the described embodiments, will occur to those skilled in the art and all such alternate embodiments, combinations, modifications, improvements are within the scope of the present invention.

[0033] As shown in FIG. 1 , an exemplary cable ditch 60 has four cables 62 extending along the ditch. These power cables and other cables may be covered with a puncture resistant cover before the fill dirt is placed back into the cable ditch. The puncture resistant cable cover may prevent unintentional puncture or cutting of the cables from digging. In the case of a power cable, a puncture resistant cover may prevent injury from electrical shock.

[0034] Referring now to FIGS. 2 and 3, cable cover segments 64 may be place over the power cable in a cable ditch. As shown, each of the segments are about a meter in length and may be coupled together with a tape or adhesive to prevent displacement when the fill dirt is placed back into the cable ditch. This manual installation of segments is very labor intensive, but required in some cases, as the cable cover is very thick and not conducive to manipulation in a roll form by hand. Also, the joining of the segments may not prevent displacement during fill thereby leaving exposed cable that may be damaged during digging.

[0035] As shown in FIG. 3, some prior art cable cover material is very thick but can be spooled onto a spool that is very large and heavy, thereby requiring a machine, such as a back-hoe or crane, to maneuver the spool over the cable ditch.

[0036] Figure 4 shows a perspective photograph of a puncture test according to DIN EN 50520. As shown, the puncture implement is dropped onto a test specimen to determine depth of penetration of the puncture implement into the test specimen. In order to pass this test, the puncture implement can not exceed 100mm penetration through the test specimen after four drops of the puncture implement on the same spot on the test specimen and there can be no complete penetration of the puncture implement through the specimen.

[0037] Referring now to FIGS. 5 and 6, an exemplary lightweight rollable power cable cover 10 has a composite laminate 14 that includes a plurality of plies of a composite material 16, 16’, 16” and a walking layer 44 configured on a top surface 40. The walking layer may be a texturized surface to provide effective footing when installing the cable cover. The walking layer may be a fabric including a woven or non-woven fabric or a polymeric material that has a texture imparted therein. The thickness 19 of the lightweight rollable power cable cover 10 from the top surface 40 to the bottom surface 50 may be less than 6mm, and preferably less than 4mm, and even more preferably less than 2mm. Also, the thickness 15 of the composite laminate 14 may be less than 6mm, and preferably less than 4mm, and even more preferably less than 2mm. Each ply has a thickness 17 that includes the thickness 13 of the first layer 11 and third layer 30 as well as the thickness 25 of the second layer 20, which is configured between the first and third layer and adheres the first and third layers together. The thickness of the second layer may be much less than the thickness of either the first and third layer, such as about a half or less, a third or less, a quarter or less, a sixth or less, an eight or less or even a tenth or less and any range between and including the ratios provided.

[0038] As shown in FIG. 6, the lightweight rollable power cable cover 10 is wound about a core 80 to form a lightweight cable cover spool 18 which may be 10m or more in length, 50m or more, 100m or more, 200m or more, 500m or more, 800m or more or even 1 ,000m or more and any range between and including the length values provided. The lightweight cable cover spool may be light enough for manipulation into a cable ditch and unrolling without machines, such as a back-hoe or crane and may be portable by hand, which means they may weigh less than about 60kg, or about 50kg or less, or about 40kg or less. The core 80 may have an outer diameter 85 of about 70mm or more, about 100mm or more, about 150mm or more and any range between and including the diameters provided.

[0039] As shown in FIG. 7, a lightweight power cable spool 18 has a length of the lightweight rollable power cable cover 10 extended from said spool. The lightweight rollable power cable cover is spooled around a core 80. The top surface 40 of the lightweight rollable power cable cover has a walking layer 44 with printed text 46 “Cable Cover Do Not Dig” thereon. This printed text may notify those digging in the area not to disrupt the cover or dig near and certainly not beneath the cover. Also, the lightweight rollable power cable cover has edges 74, 74’ that may be configured to flex downward to more effectively secure the cover in position over the cables. The edges may be folded down into the ground to prevent lateral displacement when the fill dirt is applied over the cable cover. The edges may be defined by a folding feature 76, 76’ which may be a crease in the cable cover or a plurality of perforations and/or a partial slit into the cover, such as through the walking layer 44. Also, the lightweight rollable power cable cover 10 may have a plurality of staking apertures 70 that may be used to stake the cover in place. Short non-electrically conductive stakes, such as plastic stakes may be used for this purpose. [0040] As shown in FIG. 8, the tensilized layer 12, or oriented first layer and third layer of the composite laminate, have a higher melting temperature, (175.8°C) than the non-tensilized or less tensilized second layer 20 (163.1 °C). The melting temperature is the peak before the energy W/g drops as shown by the Differential scanning calorimetry (DSC) scans. This difference in melting temperature of more than 10°C, enables the layers to be bound together while maintaining the molecular orientation of the first and third layers. As described herein, this enables an effective bond of the three layers together through melt lamination below the melt temperature of the first and third layers of polymer film. The increased melting temperature of the tensilized polymeric film is substantially greater than the melting temperature of the second layer, as described herein. Also, the increased melting temperature indicates that the first layer and third layer of polymer film material have been tensilized to produce a higher molecular orientation than the second layer of polymer film. Finally, this enable the same polymer type, such as polypropylene, to be used for all three layers, which promotes bonding and adhesion.

[0041] It will be apparent to those skilled in the art that various modifications, combinations and variations can be made in the present invention without departing from the scope of the invention. Specific embodiments, features and elements described herein may be modified, and/or combined in any suitable manner. Thus, it is intended that the present invention cover the modifications, combinations and variations of this invention provided they come within the scope of the appended claims and their equivalents.