DESC:Complete Specification

“Method for increasing the heat-withstanding capacity in electrical wires, its implementing equipment, and applications thereof”

Cross-reference to related applications: This complete specification is filed pursuant to patent application No. 201721038916 originally filed on 01/01/2018 with provisional specification the contents of which are incorporated here, in their entirety, by reference.

Field of the invention
The present invention relates generally to safeguarding and allowing increased tolerance of electrical wires to risks consequential to excessive heat generated within and/ or incident externally upon said wires, therein ensuring their prolonged service life, and also performance throughout said extended service life.

Definitions and interpretations
Before undertaking the detailed description of the invention below, it may be advantageous to set forth definitions of certain words or phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect, with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “Wire” refers a single conductor (material most commonly being copper or aluminum); “Cable” refers two or more insulated wires wrapped in one jacket; “PVC” refers polyvinylchloride; ”RBD machine” refers rod breakdown machine for drawing wires; “MWD” refers multi wire drawing machine designed to draw flux-cored or wire of fine diameters; “OD” refers outer diameter; “Next Peer” refers commercially available / leading brands of electrical wire having rating equivalent / comparable to the product of the present invention.

Background of the invention and description of related art
Electric wiring is most ubiquitous in urbanized locales. Such wiring is expectedly exposed to risks including current overloading and fire. Current overloading causes undesirable heat buildup from within said wiring. On the other hand, fire delivers extrinsic heat to the wire. Irrespectively, occurrence of either has deleterious effect on wiring, most immediate being overheating of the wire, oxidation of conducting core/s, burning of insulation layers, and exposure of conducting elements thereby posing risk of electrocution. These fallouts are grave perils for person and property in immediate vicinity, and hence measures for their avoidance, or at least minimization, are most desirable.

The dangers associated with current overloading and fire can be squarely contained by appropriate insulation and jacketing. In recognition, a variety of efforts are seen to be made to improve materials and method of their use in electrical tape, wire, and / or cable constructions. Inclusion of thermally-resistive and / or fire-retardant materials such as asbestos in insulation and cover wrap materials was widely proposed as an effective solution. However, asbestos fibers have been later identified as potent carcinogens, and hence an effort is underway to phase out the use of asbestos in favor of non-toxic, non-allergenic, neutral materials.

A brief study of immediate art reveals use of ceramics, metal oxides, woven / non-woven glass fabric or their combinations for introducing flame and / or heat retarding properties in electrical wire and / or cable constructs. For example, U.S. Patent No. 3602636 discloses an electrical cable where the conductors are helically wrapped with an open weave glass cloth having a coating of a flame resistant synthetic rubber together with an extruded sheath of polyvinylchloride or the like covering the assembled cable. Another example, U.S. Patent No. 3013902 discloses fabrics coated with colloidal alumina and a final coating of a polymer having a plurality of free carboxylic acid groups. Glass fibers are included in the list of materials which may comprise the fabric substrate.

Additionally, there are few patents such as U.S. Patent No. 3095336 which mentions use of ceramic articles laminated with glass fabric or U.S. Patent no. 3632412 which mentions a pressure sensitive adhesive comprising an interpolymer of acrylates, methacrylates and hydroxyacrylates or hydroxymethacrylates. However, besides disclosing flame / heat retardant wrappings, relevancy of these references to the instant invention is low as no application to manufacturing of electrical tape, wire or cable is disclosed or suggested. Besides, gradual degeneration of wires / cables due to heat or current overloading is almost invisible to the naked eye, thus promulgating continued use till disaster. Hence, it is critical that such eventualities are avoided by ensuring the best raw materials are used for protecting such installations from excess heat generated within and/ or incident externally upon said wires.

Prior art, thus to the limited extent presently surveyed, does not list a single effective solution embracing all considerations mentioned hereinabove, thus preserving an acute necessity-to-invent for the present inventor who, as result of his focused research, has come up with novel solutions for resolving all needs of the art once and for all. Work of the presently named inventor, specifically directed against the technical problems recited hereinabove and currently part of the public domain including earlier filed patent applications or publications or earlier commercialized products, is neither expressly nor impliedly admitted as prior art against the present disclosures.

A better understanding of the objects, advantages, features, properties and relationships of the present invention will be obtained from the following detailed description which sets forth an illustrative yet-preferred embodiment.

Objectives of the present invention
The present invention is identified in addressing at least all major deficiencies of art discussed in the foregoing section by effectively addressing the objectives stated under, of which-

It is a primary objective to provision the ability in electrical wires to function normally while sustaining high temperatures for longer duration than conventionally available electrical wire and / or cable constructions.

It is another objective further to the aforesaid objective(s) to result in an electrical wire construction / cable configuration comprising a unique combination of component materials having characteristic physical and electrical characteristics that allow current and heat to dissipate in controlled manner, instead of accumulating to the point of short circuit.

It is another objective further to the aforesaid objective(s) that the electrical wire construction / cable configuration so reached do not have unduly increased mass, that is, diameters and weights, when compared to wires / cables of the same ratings.
It is another objective further to the aforesaid objective(s) that the electrical wire construction / cable configuration so reached is non-rigid and readily bendable the same way as at least wires / cables of the same ratings are, when implemented over a period of time.

It is another objective further to the aforesaid objective(s) that the methodology to provision the ability in electrical wires to function normally while sustaining high temperatures for longer duration than conventionally available electrical wire and / or cable constructions is not unduly expensive and / or technically complex.

It is another objective further to the aforesaid objective(s) that the electrical wire construction / cable configuration so reached requires no specific knowledge, nor skill, on part of the end-user to implement.

An overall object of the invention is to provide an electric wire / cable having increased endurance against excessive heat build-up for a satisfactory time without developing excessive current leakage.

The manner in which the above objectives are achieved, together with other objects and advantages which will become subsequently apparent, reside in the detailed description set forth below in reference to the accompanying drawings and furthermore specifically outlined in the independent claims. Other advantageous embodiments of the invention are specified in the dependent claims.

Brief description of drawings
The present invention is explained herein under with reference to the following drawings, in which-

Figure 1 is a schematic cross-sectional view of an electrical wire having increased heat-withstanding capacity prepared substantially as per corresponding disclosures in this specification.

Figure 2 is another schematic cross-sectional view of the wire shown in FIGURE 1.

The above drawings are illustrative of particular examples of the present invention but are not intended to limit the scope thereof. The drawings are not to scale (unless so stated) and are intended for use solely in conjunction with their explanations in the following detailed description. In above drawings, wherever possible, the same references and symbols have been used throughout to refer to the same or similar parts. Though numbering has been introduced to demarcate reference to specific components in relation to such references being made in different sections of this specification, all components are not shown or numbered in each drawing to avoid obscuring the invention proposed.

Attention of the reader is now requested to the brief description to follow which narrates a preferred embodiment of the present invention and such other ways in which principles of the invention may be employed without parting from the essence of the invention claimed herein.

Detailed Description
Principally, general purpose of the present invention is to assess disabilities and shortcomings inherent to known systems comprising state of the art and develop new systems incorporating all available advantages of known art and none of its disadvantages. It is with the above considerations in mind that the present invention has been evolved to provide an insulated electrical wire, tape, and/or cable that is heat resistant and will function according to designated electrical load specifications for significant time when exposed to fire or other sources of heat.

Accordingly, a yet-preferred embodiment of the present invention disclosed herein identifies an electrical wire having increased heat-withstanding capacity resulting from inventive layering of thermally-resistive materials arranged coaxially around a central conductive core.

As referred in the accompanying Figure 1, it can be seen that the electrical wire (001) having increased heat-withstanding capacity proposed herein has concentric layers of PVC comprising heat-resistant HR85 (003), fire-resistant FR (004), and heat-and-fire-resistant HRFR (005) grade compounds respectively arranged around a central conductive core (002) being the thin element of electrically conductive material. Amongst cross-sectional area of wire (001), the core (002) admeasures approximately 60%, while layers (003 to 005) account for remaining 40%. In this remaining 40%, the layers (003), (004), and (005) admeasure approximately 15 to 20%, 60 to 65%, and 15 to 20% respectively. The layer (005) has masterbatch (of pigment desired), giving it blue, red, black, green, or yellow color as required (or as per technical standard to be followed).

According to a related aspect of the present invention explained herein with reference to the accompanying Figure 2, logic of using a different grade of PVC compound in every layer is that molecular structure of every layer is different, and therefore distance travelled for a leaked current is far higher against when the same compound is used for the entire insulation or even when used in multiple layers. This causes current and heat to dissipate in controlled manner, instead of accumulating to the point of short circuit.

According to a related aspect of the present invention, the heat-resistant layer of HR85 (003) contacting the central conductive core (002) has capacity to bear a temperature up to 85oC in contrast to conventionally employed PVC which can withstand up to 70oC only. Consequently, the electrical wire (001) has higher heat- withstanding capacity, its degeneration due to over use and prolonged use is not accelerated, therefore increasing its service life without compromising safety in any way and ensure electrical and mechanical performance at higher temperatures than traditional wires.

Additionally, the heat-resistant layer of HR85 (003) contacting the central conductive core (002) has capacity to withstand additional heat and fire conditions, that is, more than 29% oxygen and 250oC temperature index. Consequently, the electrical wire (001) has self-extinguishing properties once removed from direct source of fire.

Reference is now made to certain examples which showcase the manner, particularly sequence of steps, in which the present invention is to be implemented.

Step 1: Initialization of production cycle starting with RBD machine
First step in production of the electrical wire (001) proposed herein commences on a conventional RBD machine, using which a wire of electrically conductive metal, such as copper, used in the industry for making electrical wires / cables and the like, is drawn out. Typically, the RBD machine is deployed to draw a 1.4mm to 2.6mm OD wire from an 8mm input metal rod (raw material, such as copper in the present case). For initialization, the RBD machine is started, control parameters are set as per procedure prescribed by the machine manufacturer. Next, all bobbins are inspected to confirm that they are of requisite / desired dimensions and loaded on pay-off stands as per programme of the RBD machine. At this juncture, the RBD machine is powered ON from its instrument panel, followed by starting circulation of cooling water and RBD lubricant. Usually, RBD lubricant is set to 8% to 10% fat solution with the water being circulated, therein correcting amount of lubricant or water should this value be not reached (fat content being checked once daily by the operator using a refractometer). At this stage, operating parameters of the RBD machine, that is Maximum running speed is set to 225 to 425m*min-1 while Running Line Speed is set to 225 to 425m*min-1 depending on size of wire. Die sizes are selected among 2.6mm, 2.30mm, 2.04mm.Thus the machine is set and operated for a specific wire size – however beforehand, for starting of each and every bobbin, sample of copper wire drawn is sent for quality check. Consequently, stretch film is wrapped over the bobbins produced to end this operating cycle.

Step 2: Initialization and operation cycle of intermediate wire drawing machine
Output (wire drawn) by the RBD machine is fed to a conventional intermediate wire drawing machine, to thereby result in a (thinner) wire of upto 0.5 mm OD. For initialization, the intermediate wire drawing machine is started, control parameters are set as per procedure prescribed by the machine manufacturer. Next, all bobbins are inspected to confirm that they are of requisite / desired dimensions and loaded on pay-off stands as per programme of the intermediate wire drawing machine. At this juncture, the intermediate wire drawing machine is powered ON from its instrument panel, followed by starting circulation of cooling water and wire drawing lubricant. Usually, wire drawing lubricant is set to 8% to 10% fat solution with the water being circulated, correcting amount of lubricant or water should this value be not reached (as mentioned in example 1,using refractometer to check fat concentration once daily). At this stage, operating parameters of the intermediate wire drawing machine, that is Maximum running speed is set to 400m*min-1 while Running Line Speed is set to 245m*min-1. Die sizes are selected among 1.44mm, 1.32mm, 1.22mm, 1.12mm, 1.04mm, 0.95mm, 0.88mm, 0.81mm, 0.75mm, 0.69mm, 0.63mm, 0.58mm, 0.54mm, 0.50mm. Thus the machine is set and operated for a specific wire size – however beforehand, for starting of each and every bobbin, sample of copper wire drawn is sent for quality check. Consequently, stretch film is wrapped over the bobbins produced to end this operating cycle.

Step 3: Initialization and operation cycle of fine wire drawing machine
Output of the intermediate wire drawing machine (that is, wire drawn) is fed next to a conventional fine wire drawing machine. For initialization, the fine wire drawing machine is started, control parameters are set as per procedure prescribed by the machine manufacturer. Next, all bobbins are inspected to confirm that they are of requisite / desired dimensions and loaded on pay-off stands as per programme of the intermediate wire drawing machine. At this juncture, the fine wire drawing machine is powered ON from its instrument panel, followed by starting circulation of cooling water and wire drawing lubricant. Before boiler starts getting heated, boiler drain valve is closed, water level is maintained at marked level, and steam pressure is set at 4kgcm-1. Usually, wire drawing lubricant is set to 4% to 6% fat solution and annealer lubricant is set to 0.5% to 1% fat solution, correcting, in both lubricants, amount of lubricant or water should respective values be not reached (as mentioned in example 1, using refractometer to check fat concentration once daily). At this stage, operating parameters of the intermediate wire drawing machine, that is (line speed, length counter, spooler selection, annealer selection, % of elongation, final diameter) are set as desired by the user / program. Maximum running speed is set to 1800m*min-1 while Running Line Speed is set to 1400 m*min-1. Die sizes are selected among 1.308mm, 1.202mm, 1.103mm, 1.013mm, 0.930mm, 0.854mm, 0.784mm, 0.720mm, 0.661mm, 0.607mm, 0.557mm, 0.511mm, 0.470mm,0.431mm, 0.396mm, 0.364mm, 0.334mm, 0.306mm, 0.281mm, 0.258mm, 0.237mm, 0.218mm, 0.200mm, 0.190mm. Thus the machine is set and operated for a specific wire size – however beforehand, for starting of each and every bobbin, sample of copper wire drawn is sent for quality check. Consequently, stretch film is wrapped over the bobbins produced to end this operating cycle.

Step 4: Bunching
Output bobbins resulting from processes explained at step 3 above (or even former steps 1 or 2, depending on diameter of conducting core of wire desired), are inspected to get total number of strands desired, and loaded onto a bunching machine. Pay-off is adjusted by adjusting the tension manually to make sure the wires do not get bunched up loosely. Said wires are passed through eyelets of the bunching machine, and gears of capstan box provided are laid as per set program/ desired by the user. Said wires are then passed through the bow, and reels loaded in the machine, therein undergoing a clockwise rotation. At this stage, operating parameters of the bunching machine, that is length is set as desired by the user / program. Before starting of each and every bobbin, sample of bunched copper drawn is sent for checking conductor resistance, lay-length and one meter weight of bunched copper (values as per wire / cable product desired by the user). Maximum running speed is set to 200 m*min-1 while Running Line Speed is set to 80 to 120 m*min-1. Lay length size is selected as per Table 1 below. Consequently, stretch film is wrapped over the bobbins produced to end this operating cycle.

Cross sectional diameter of conductor area (mm) 0.50 0.75 1.00 1.50 2.50 4.00 6.00
Lay length size (mm) 60 60 60 60 80 80 80

Table 1

Step 5: Extrusion
Output bobbins resulting from process explained at Step 4 above, are loaded onto pay off stand which feeds a conventional PVC extrusion machine outfitted with a triple layer crosshead. Cooling by circulation of water in barrel and gearbox is ensured ON, before starting of the extruder machine at desired operating parameter conditions defined in Table 2 below. The three grades of PVC as mentioned in the foregoing narration, HR85 grade PVC, FR grade PVC, and HRFR grade PVC are loaded onto respective hoppers of 45mm, 65mm and 45mm extruders respectively. Specifications of these PVC grade compounds are outlined in Table 2 below.

Technical Description Grade- HR85 Grade- FR Grade- HRFR 85
Thermal Stability 215 170 235
Volume Resistivity 1.90 X 1014 1.05 X 1014 1.20 X 1014
Oxygen Index NA 30 30.5

Table 2

Output of aforementioned extruders is simultaneously applied in series by means of the triple layer crosshead to thereby result in that the bunched conductor core fed in is first coated with HR85 grade PVC, followed by a thick FR grade PVC coat, which is then followed by a thin skin of HRFR grade PVC. For every 100 kg of total PVC consumed, 10 to 25 (and preferably 15) % is HR85 grade PVC, 60 to 70 (and preferably 65 percent is FR grade PVC, and 15 to 25 (and preferably 20) percent is HRFR grade PVC. These concentric coatings give the resultant product the molecular diversity needed to impede current, if leaking from the conductor core within.
As mentioned before, specific type of PVC compound is then loaded in hoppers of the PVC extrusion machine as desired / per given programme of the PVC extrusion machine. Temperature of hopper dryer is set as desired / per predefined process control parameter (around 70oC). Next, appropriate weighed quantity, that is 2 to 4% of master batch (of pigment) is weighed and added in the extruder along with each of the aforementioned PVC compounds and then dried in the high speed mixer. Hopper shutter is opened and PVC extrusion machine started after set temperatures of 70oC of different zones of all extruders are reached as listed in Table 3 below.

ZONE TEMP. 65 MM EX 45 MM EX-1 45 MM EX-2
DEG. C SP SP SP
Zone 1 140 145 145
Zone 2 145 150 150
Zone 3 150 155 155
Zone 4 155 NA NA
Neck 155 150 150
Head 150 NA NA
Die 150 NA NA
Ratio (%) 40 80 25
Hopper Temperature 70 70 70

Table 3

Eccentricity of PVC coating obtained, if any, is checked by stripping the insulation and also cutting the cross section of insulation as certain that skin coating is proper. Speed of extruder is then increased gradually by increasing the master ratio of machine. During this process, it is carefully monitored that water cooling is proper, wire passes through air wiper and no water is carried by insulated wire, as well as that entire length of wire is passed through dimensional control gauge and spark tester at test voltage 6 kV upto 16 sq mm and 10 kV above16 sq mm. The resultant wire is marked via printing at every meter ink jet printer or pully printer. Starting sample of each output wire is given for quality check before continuing the operating cycle.

The inventor named herein has used the aforementioned method of preparation to reach multiple varieties of heat and flame tolerant wires, typified by specifications provided in tables 4 and 5 below.
SIZE Configuration Cu.Kg./Km. PVC Kg./Km. Total cable Wt. Kg/km OD in mm No. of Strands Size of Wire Conductor AREA
Tolerance Level NA ± 0.02 ± 0.03 ± 0.05 ± 0.02 NA ± 0.003 ± 0.01
1C X 0.5 16/0.20 3.905 4.513 8.42 2.14 16 0.187 0.439
1C X 0.75 24/0.20 5.86 5.205 11.06 2.34 24 0.187 0.659
1C X 1.00 14/0.30 8.502 7.0600 15.56 2.74 14 0.295 0.956
1C X 1.50 22/0.30 12.73 8.33 21.06 3.04 22 0.288 1.432
1C X 2.50 36/0.30 20.84 12.02 32.85 3.70 36 0.288 2.344
1C X 4.00 56/0.30 30.64 13.484 44.12 4.05 56 0.280 3.446
1C X 6.00 84/0.30 45.959 17.404 63.36 4.70 84 0.280 5.170
Tolerance Level NA ± 0.02 ± 0.03 ± 0.05 ± 0.02 NA ± 0.003 ± 0.01
1C X 0.5 16/0.20 3.904583 4.512759 8.42 2.14 16 0.187 0.439211
1C X 0.75 24/0.20 5.856874 5.204528 11.06 2.34 24 0.187 0.658816
1C X 1.00 32/0.20 7.809 5.761 13.57 2.50 32 0.187 0.878
1C X 1.50 30/0.25 11.464 6.704 18.17 2.76 30 0.234 1.290
1C X 2.50 50/0.25 19.106 10.178 29.28 3.44 50 0.234 2.149
1C X 4.00 56/0.30 30.64 13.484 44.12 4.05 56 0.280 3.446
1C X 6.00 84/0.30 45.959 17.404 63.36 4.70 84 0.280 5.170
1C X 10.00 80/0.40 79.349 29.879 109.23 6.16 80 0.377 8.926
1C X 16.00 126/0.40 124.975 37.671 162.65 7.174 126 0.377 14.058
1C X 25.00 196/0.40 194.406 55.732 250.14 8.80 196 0.377 21.868
1C X 35.00 276/0.40 273.756 67.361 341.12 9.96 276 0.377 30.794
1C X 50.00 396/0.40 392.780 90.485 483.27 11.70 396 0.377 44.182

Table 4

SIZE Configuration Copper in Kg. PVC Ins. In Kg. PVC O. Sheath In Kg. Total cable Wt. Core Diameter No. of Strands Strand diameter Final diameter
Tolerance Level NA ± 0.01 ± 0.01 ± 0.02 ± 0.04 ± 0.02 NA ± 0.003 ± 0.04
2C X 0.50 16/0.20 7.7259 7.946 29.054 44.73 2.023 16 0.186 5.81
2C X 0.75 24/0.20 11.5888 9.171 32.481 53.24 2.217 24 0.186 6.19
2C X 1.00 32/0.20 15.4517 10.237 35.502 61.19 2.381 32 0.186 6.52
2C X 1.50 30/0.25 22.9274 12.039 40.682 75.65 2.647 30 0.234 7.05
2C X 2.50 50/0.25 38.2123 17.998 58.120 114.33 3.279 50 0.234 8.52
2C X 4.00 56/0.30 61.2781 25.896 76.237 163.41 3.991 56 0.280 9.94
2C X 6.00 84/0.30 91.9172 31.425 96.785 220.13 4.537 84 0.280 11.23
3C X 0.50 16/0.20 11.5888 11.919 28.652 52.16 2.023 16 0.186 6.12
3C X 0.75 24/0.20 17.3832 13.756 31.866 63.01 2.217 24 0.186 6.54
3C X 1.00 32/0.20 23.1776 15.356 34.685 73.22 2.381 32 0.186 6.89
3C X 1.50 30/0.25 34.3911 18.059 39.488 91.94 2.647 30 0.234 7.46
3C X 2.50 50/0.25 57.3184 26.997 56.030 140.35 3.279 50 0.234 9.03
3C X 4.00 56/0.30 91.9172 38.844 72.544 203.30 3.991 56 0.280 10.56
3C X 6.00 84/0.30 137.8758 47.138 91.903 276.92 4.537 84 0.280 11.94
4C X 0.50 16/0.20 15.4517 15.892 32.404 63.75 2.023 16 0.186 6.70
4C X 0.75 24/0.20 23.1776 18.342 36.129 77.65 2.217 24 0.186 7.17
4C X 1.00 32/0.20 30.9035 20.474 39.400 90.78 2.381 32 0.186 7.57
4C X 1.50 30/0.25 45.8548 24.079 44.978 114.91 2.647 30 0.234 8.22
4C X 2.50 50/0.25 76.4246 35.996 63.990 176.41 3.279 50 0.234 9.96
4C X 4.00 56/0.30 122.5563 51.791 88.601 262.95 3.991 56 0.280 11.90
4C X 6.00 84/0.30 183.8344 62.851 111.583 358.27 4.537 84 0.280 13.43
5C X 0.50 16/0.20 19.3147 19.864 50.054 89.23 2.023 16 0.186 7.22
5C X 0.75 24/0.20 28.9720 22.927 57.105 109.00 2.217 24 0.186 7.75
5C X 1.00 32/0.20 38.6293 25.593 67.174 131.40 2.381 32 0.186 8.39
5C X 1.50 30/0.25 57.3184 30.099 78.439 165.86 2.647 30 0.234 9.11
5C X 2.50 50/0.25 95.5307 44.994 108.635 249.16 3.279 50 0.234 10.81
5C X 4.00 56/0.30 153.1953 64.739 154.180 372.11 3.991 56 0.280 12.93
6C X 0.50 16/0.20 23.1776 23.837 60.452 107.47 2.023 16 0.186 7.83
6C X 0.75 24/0.20 34.7664 27.512 73.211 135.49 2.217 24 0.186 8.61
6C X 1.00 32/0.20 46.3552 30.712 81.390 158.46 2.381 32 0.186 9.10
6C X 1.50 30/0.25 68.7821 36.118 95.617 200.52 2.647 30 0.234 9.90
6C X 2.50 50/0.25 114.6369 53.993 139.374 308.00 3.279 50 0.234 12.00
6C X 4.00 56/0.30 183.8344 77.687 191.063 452.58 3.991 56 0.280 14.13
7C X 0.50 16/0.20 27.0405 27.810 60.452 115.30 2.023 16 0.186 7.83
7C X 0.75 24/0.20 40.5608 32.098 73.211 145.87 2.217 24 0.186 8.61
7C X 1.00 32/0.20 54.0811 35.830 81.390 171.30 2.381 32 0.186 9.10
7C X 1.50 30/0.25 80.2458 42.138 95.617 218.00 2.647 30 0.234 9.90
7C X 2.50 50/0.25 133.7430 62.992 139.374 336.11 3.279 50 0.234 12.00
7C X 4.00 56/0.30 214.4735 90.635 191.063 496.17 3.991 56 0.280 14.13

Table 5

Step 6: Coiling
Output bobbins resulting from process explained at Step 5 above, are inspected and loaded onto a conventional coiling machine on pay-offs as desired by user /per program set. The wire is passed through accumulator pulleys, therein wire tension is adjusted using air pressure (so that compact coils are formed). The wire is passed then through spark tester, length counter wheel and through wire guide tube. Operating parameters, that is set length, set differ, slow down, and % speed are set as per automated program modes available in the machine. Traverse pitch setting for the coil has to be adjusted during operating cycle. Care is taken that before starting the machine, spark tester is ON at test voltage 6 kV upto 16sqmm. and 10 kV above 16sqmm. After the coil is made, it is immediately bound by means of cotton sutali (coarse string), and filled in packaging material / enclosures of appropriate size.

Step 7: Testing
The electrical wire (001) including the concentric layers of PVC obtained by processes herein above is reached by a unique triple extrusion process which ensures current leakage from the central conductive core (002) through the insulation layers (003 to 005). This leakage, which allows current and heat to dissipate in controlled manner, instead of accumulating to the point of short circuit, has been verified via industrially recognized standard experimental procedures and equipment (standard multimeter), to be 50 to 125 times lower than the international safety norms, as reflected in Table 6 below.

Nominal area of conductor (mm) LEAKAGE CURRENT (mAMPs)
0.50 0.006
0.75 0.007
1.00 0.008
1.50 0.009
2.50 0.010
4.00 0.012
6.00 0.014

Table 6

In independent experiments carried out by the present inventor (Cu 2.5mm2 wires of different manufacturers), the resultant electrical wires obtained as per disclosures hereinabove were found to have significantly enhanced properties as listed in the table 7 below.

Sr
No Name of Test Unit Specified Std. Next Peer 1 Next Peer 2 Next Peer 3 Present invention
1) Conductor Resistance at 20 0C Ohm/km max.7.41 7.42 7.44 7.46 7.15
2) Annealing Test of Copper % min. 13.50 16.0 16.0 15.0 20.0
4) Overall Diameter of Cable mm 4.00 3.60 3.54 3.51 3.70
5)
Thickness of Insulation, Average mm 0.80 0.78 0.76 0.75 0.86
Minimum mm 0.62 0.62 0.64 0.62 0.76
6) Tensile Strength before ageing N/mm2 min. 12.50 13.55 14.25 13.50 16.75
7) Elongation before ageing % min. 150 172 164 160 245
8) Tensile Strength after ageing N/mm2 min. 12.5 14.00 14.95 14.25 17.25
9) Elongation after ageing % min. 150 158 155 145 235
10 variation in T.S. % max.+/- 20 -3.32 -4.91 -5.55 -2.98
11 variation in elongation % max.+/- 20 8.13 5.48 9.37 4.08
12 Loss of mass mg/cm2 max 2.0 1.25 1.16 1.58 1.0
13 Volume Resistivity, at 27 0C Ohm-cm min. 1 x 10 13 4.35 x 10 12 2.45 x 10 13 1.50 x 10 12 6.75x 10 14
14 Volume Resistivity, at 70 0C Ohm-cm min. 1 x 10 10 1.05 x 10 10 8.95 x 10 10 4.65 x 10 9 7.25 x 10 11
15 Insulation Resistance, at 27 0C Mohm-km min. 36.7 45.92 55.35 42.74 85.92
16 Insulation Resistance, at 70 0C Mohm-km min. 4 5.02 5.63 4.02 7.5
17 Shrinkage Test % max. 4.0 1.50 1.25 1.75 0.50
18 Hot Deformation Test, Depth of Indentation % max. 50.0 35.00 30.00 40.00 25
19 Heat Shock Test No Sign of Cracks OK OK OK OK
20 Thermal Stability - Insulation Minute Min. 80 75 85 65 120
21 H. V. AC Test at room temp. 3 KV AC, 5 minute Withstood Withstood Withstood Withstood
22 H.V. AC Test ( water immersion test ) 6 KV AC, 5 minute Withstood Withstood Withstood Withstood
23 H.V. DC Test ( water immersion test ) 1.2 KV DC, 240 Hrs Withstood Withstood FAIL Withstood
24 Flammability Test, Unaffected Portion mm min. 50 280 285 270 295
Period of burning sec max. 60 3 2 4 1
25 Oxygen Index % Min. 29 28 29 28 30
26 Temperature Index 0C Min. 2500C at 21% 270 275 260 290

Contribution of the present invention above prior art can be appreciated from that the resultant electrical wire, tape, and/or cable construct will resist, or at least better withstand, the deleterious effects of high temperatures associated with current overloading and fire as it is:
a) Flame and heat resistant;
b) Self-extinguishing;
c) Exhibits negligible current leakage; and
d) Production optimizes economy in using heat-resistant, fire-resistant, and heat-and-fire-resistant grade PVC compounds

From the foregoing narration, an able technology for safeguarding the well-being and performance of electrical tapes, wires, and cable constructs is thus provided with improved functionality, durability and long service life than any of its closest peers in state-of-art. This invention, which lies more in the engineering than materials included, therefore finds ready acceptance for use in both domestic as well as industrial use-cases as well as high-performance sectors such as ship and submarine circuits, mining operations and so on where fire / heat resistant installations are recommended.

As will be realized further, the present invention is capable of various other embodiments and that its several components and related details are capable of various alterations, all without departing from the basic concept of the present invention. Accordingly, the foregoing description will be regarded as illustrative in nature and not as restrictive in any form whatsoever. Modifications and variations of the invention described herein will be obvious to those skilled in the art. Such modifications and variations are intended to come within ambit of the present invention, which is limited only by the appended claims.

It shall be generally noted that at least a major portion of the foregoing disclosures of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in files or records of the receiving Patent Office(s), but otherwise reserves all copyright rights whatsoever. ,CLAIMS:I Claim,
1] A method for producing an electrical wire (001) having increased heat-withstanding capacity, comprising-
a) Drawing a thin element of electrically conductive metal, being a copper wire in particular;
b) Bunching the thin element to form a central conductive core (002); and
c) Coating the central conductive core (002), in a simultaneous step, with concentric layers (003, 004 and 005) of thermally-resistive dissimilar compounds to thereby result in the electrical wire (001) having increased heat-withstanding capacity.

2] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in claim 1, wherein the increased heat is an incidental consequence arising from a cause selected singly, and alternatively in combination, between undesirable heat buildup due to current overloading and delivery of extrinsic heat due to fire.

3] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in claim 1, wherein the step of drawing the thin element of electrically conductive metal is undertaken by a sub-process involving-
a) drawing a wire of upto 1.4mm outer diameter from an 8mm diameter input copper rod using a rod breakdown machine set to operate at maximum running speed of 225 to 425m*min-1 and running line speed of 225 to 425m*min-1 while maintaining rod breakdown machine lubricant at 8% to 10% fat solution with water being circulated therein for cooling purposes;
b) drawing a wire of upto 0.5mm outer diameter from output of the rod breakdown machine using an intermediate wire drawing machine set to operate at maximum running speed of 400m*min-1 and running line speed of 245m*min-1 while maintaining rod breakdown machine lubricant at 8% to 10% fat solution with water being circulated therein for cooling purposes; and
c) drawing a wire of upto 0.190mm outer diameter from output of the intermediate wire drawing machine using an medium wire drawing machine set to operate at maximum running speed of 1800m*min-1 and running line speed of 1400m*min-1 while maintaining rod breakdown machine lubricant at 4% to 6% fat solution in addition to an annealer lubricant at 0.5% to 1% fat solution, with water being circulated therein for cooling purposes.

4] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in claim 1, wherein the step of bunching is undertaken on an conventional bunching machine set to operate at a maximum running speed of 200 m*min-1 and running line speed of 80 to 120 m*min-1 to result in clockwise-entwined central conductive core (002).

5] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in claim 1, wherein the step of coating the central conductive core (002), in a simultaneous step, with concentric layers (003, 004 and 005) of dissimilar thermally-resistive compounds is undertaken using a PVC extrusion machine outfitted with a triple layer crosshead, said triple layer crosshead comprising three extruder heads of 45mm, 65mm, and 45mm size respectively arranged to serially, and hence simultaneously, apply the thermally-resistive dissimilar compounds to the central conductive core (002) being passed through said PVC extrusion machine.

6] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in claim 1, wherein the concentric layers (003, 004 and 005) are identified being-
a) An innermost layer (003) contacting the central conductive core (002), said layer (003) being made of heat resistant HR85-grade polyvinylchloride compound having thermal stability of 215oC and volume resistivity of 1.90 X 1014;
b) An intermediate layer (004) encasing the layer (003), said layer (004) being made of fire resistant FR-grade polyvinylchloride compound having thermal stability of 170oC, volume resistivity of 1.05 X 1014, and oxygen index of 30%; and
c) An outermost skin layer (005) encasing the layer (004), said layer (004) being made of heat and fire resistant HRFR-grade polyvinylchloride compound having thermal stability of 235oC, volume resistivity of 1.20 X 1014, and oxygen index of 30.5%.

7] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in claim 5, wherein the polyvinylchloride compounds corresponding to layers (003, 004 and 005) are priorly admixed with 2% to 4% of master batch of pigment and dried in a high speed mixer for imparting color if desired to said layers (003, 004 and 005).

8] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in the claims 5, and 6 and 7, wherein for each 100 kg of total polyvinylchloride compound consumed, weighing of the layers (003, 004 and 005), is maintained, on percentage basis, at-
a) From 10% to 25% and 15% in particular of HR85 grade polyvinylchloride;
b) From 60% to 70% and 65% in particular of FR grade polyvinylchloride; and
c) From 15% to 25% and 20% in particular of FRHR grade polyvinylchloride.

9] The method for producing an electrical wire (001) having increased heat-withstanding capacity as claimed in claim 1, wherein the increased heat-withstanding capacity refers-
a) Higher endurance against temperatures of up to at least 85oC compared to conventional electrical wires with polyvinylchloride coating which can withstand only up to 70oC;
b) Higher endurance against excess heat and fire conditions with more than 29% oxygen and 250oC temperature index; and
c) Self-extinguishing effect once the wire (001) is removed from direct source of fire.

10] An electrical wire (001) having 2.5mm2 central conductive core (002) with increased heat-withstanding capacity made by the process recited at claim 1, said wire (001) characterized in having-
a) current leakage being 50 to 125 times lower than the international safety norms;
b) Conductor Resistance of 7.15 Ohm/km at 20oC;
c) 20.0% annealing tested against Copper;
d) Overall diameter of wire being 3.70mm, 0.86mm average thickness of insulation, 0.76mm minimum thickness of insulation, which is equivalent to wires of comparable rating available in the market;
e) Tensile Strength of 16.75 N/mm2 before, and 17.25 N/mm2 after ageing, showing overall variation of -2.98%;
f) Elongation at 245% before, and 235% after, ageing, showing overall variation of 4.08%;
g) Loss of mass of 1.0 mg/cm2;
h) volume resistivity of 6.75x 10 14 Ohm-cm at 27oC, and 7.25 x 10 11 Ohm-cm at 70oC;
i) Insulation Resistance of 85.92 Mohm-km at 27oC, and 7.5 Mohm-km at 70oC;
j) Shrinkage of 0.50%
k) Hot Deformation of 25% maximum indentation;
l) No Sign of Cracks in heat shock testing;
m) Thermal Stability of up to minimum 120oC;
n) Withstanding ably the H. V. AC and H.V. DC tests at room temperature, under water immersion,;
o) 295mm unaffected portion in flammability testing with maximum 1 second of burning period;
p) 30% oxygen index; and
q) 290oC Temperature Index