Patent Application
20050199414
The present invention basically relates to composite electrical conductors having a desirable combination of excellent tensile strength, acceptable levels of current carrying capacity, reduced weight and preferably, high temperature resistance. As such, these composite conductors are particularly useful for automotive and aircraft wire and cable.
In automotive and aircraft wire and cable applications, weight reduction is deemed highly desirable due to the long lasting and positive impact it has on the performance (e.g., speed, fuel economy), as well as the cost of the vehicle in question. This is especially true in racing applications, where fractions of a second can mean winning or losing a race. Weight, therefore, is an important, if not critical factor in the overall design of wire and cable products for these applications.
In addition to the desirable property of being lightweight, insulated electrical wire products used in automotive and aircraft applications must also satisfy rigorous mandatory requirements that include, but are not limited to, high temperature resistance, high tensile strength, and adequate current carrying capacity.
A need continues to exist for lighter weight electrical conductors that qualify for higher use-temperatures, while demonstrating excellent tensile strength and while providing acceptable levels of current carrying capacity.
It is therefore an object of the present invention to provide such a lightweight conductor.
It is a more particular object to provide a composite electrical conductor that employs a plastic core or matrix for improving the strength while reducing the weight of the resulting conductor.
It is a further object of the present invention to provide a cable that employs one or more such composite conductors.
The present invention therefore provides a lightweight composite electrical conductor that comprises:
The present invention also provides a cable incorporating one or more composite electrical conductors, as described above.
Other features and advantages of the invention will be apparent to one of ordinary skill from the following detailed description and accompanying drawings.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
In the course of the description which follows, reference is made to the drawings, in which:
The composite electrical conductor of the present invention has a desirable combination of excellent tensile strength, acceptable levels of current carrying capacity, reduced weight and preferably, high temperature resistance.
As will be readily appreciated by those skilled in the art, conductors that match the dimensions of prior art conductors have the added benefit of being suitable for use with existing coupling means or connectors. The present inventors have, therefore, directed their efforts toward designing a reduced weight composite conductor that not only demonstrates the combination of properties noted above but, in a preferred embodiment, matches the physical dimensions of prior art conductors, rendering it suitable for use with conventional connectors.
As will also be readily appreciated by those skilled in the art, the plastic core or plastic matrix of the above-referenced composite conductor uses space that could have been occupied by additional electrical conductors, thereby reducing the current carrying capacity of these conductors. By way of the present invention, it has been discovered that such reduced current carrying capacities are not a disadvantage in that these conductors continue to be suitable for use in a large percentage of the signal transmitting circuits in transportation equipment such as aircraft and automobiles, which are able to operate at substantially reduced current levels.
Referring now to
Plastic materials suitable for use in matrix 14 are flexible, flame resistant plastic materials. For higher-use temperatures (e.g., ≧150° C.), suitable materials include thermoplastic fluoropolymers such as ethylene-tetrafluoroethylene (ETFE) copolymers and fluorinated ethylene-propylene (FEP) and perfluoroalkoxy (PFA) resins. For lower-use temperatures (e.g., <150° C.), polyesters, polyamides, and polyolefins may be used provided flame-retardants and preferably antioxidants are incorporated into these materials to impart flame retardant and anti-aging properties.
The outer diameter of plastic matrix 14, in this one embodiment, ranges from about 0.35 to about 0.90 millimeters (mm), and preferably ranges from about 0.50 to about 0.65 mm.
In FIGS. 2 to 4, reference numeral 18 has been used to generally designate a more preferred embodiment of the inventive composite conductor. In this more preferred embodiment, conductor 18 comprises a plastic core 20, a plurality of substantially continuous, longitudinally positioned and stranded conductive materials 22 arranged in a layer that circumferentially surrounds the plastic core 20, and a layer of insulating material 24.
The plastic core 20 of conductor 18 is a relatively stiff or rigid solid, substantially solid, or hollow tubular structure that extends along the length of conductor 18 and may adopt any cross-sectional shape (e.g., circular, triangular, square). Plastic materials suitable for use in forming plastic core 20 are strong and relatively stiff materials that demonstrate high temperature resistance (i.e., maintain substantial tensile strength and deformation resistance at temperatures of up to about 150° C.). Examples of such materials include liquid crystal polymers, polyether ether ketone (PEEK), polyether sulfone, polyimide and polyimide-amide plastic materials.
In one such more preferred embodiment, which is shown in
In another such embodiment, which is shown in
In yet another such embodiment, which is shown in
The outer diameter of the plastic core 20, in these more preferred embodiments, may range from either from about 0.25 to about 1.00 mm (preferably, from about 0.30 to about 0.40 mm) for smaller sized conductors, or from about 2.80 to about 15.00 mm (preferably, from about 4.19 to about 11.28 mm) for larger sized conductors.
The plurality of electrical conductors 12, 22 used in the embodiments described above are stranded conductive materials that include stranded copper, copper alloys, nickel, nickel-clad copper, nickel-plated copper, silver, silver-plated copper, tin-plated copper and tin.
In a preferred embodiment, the electrical conductors 12, 22 are prepared from stranded copper with tin plating. The tin plating is applied by electroplating (or hot-dipping) a uniform thickness of high purity tin to the individual copper wires comprising the strand. The tin plate is intended to protect the underlying stranded copper from oxidation effects. Also, the tin plating helps improve the integrity of electrical connections.
In the embodiment generally shown in
The thickness of the layer(s) formed by the strands 22, in the more preferred embodiments of the present invention, may range from either from about 0.10 to about 0.32 mm (preferably, from about 0.13 to about 0.20 mm) for smaller sized conductors, or from about 0.28 to about 3.00 mm (preferably, from about 0.58 to about 2.30 mm) for larger sized conductors.
Insulating layer 16, 24 serves as a protective shield and is applied directly to the outer surface of the polymer matrix 14, or to the layer(s) formed by electrical conductors or strands 22.
Insulating layer 16, 24 is preferably a fluoropolymer layer formed by either (1) extruding a fluoropolymer material along a portion or length of the polymer matrix 14, or the layer(s) formed by electrical conductors or strands 22, or (2) wrapping a fluoropolymer film, in an overlapping fashion, along the length of the polymer matrix 14, or conductor layer(s).
Fluoropolymers which may advantageously be utilized in insulating layer 16, 24 of the composite electrical conductor 10, 18 include, perfluoromethylvinylether (MFA), perfluoroalkoxy (PFA), polytetrafluoroethylene (PTFE), ethylene-chlorotrifluoroethylene (ECTFE) copolymers, ethylene-tetrafluoroethylene (ETFE) copolymers and terpolymers, polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride (THV), polyvinylfluoride (PVF) resins, and mixtures thereof.
The fluoropolymer of insulating layer 16, 24, in a preferred embodiment, is an ETFE copolymer which comprises 35 to 60 mole % (preferably 40 to 50 mole %) of units derived from ethylene, 35 to 60 mole % (preferably 50 to 55 mole %) of units derived from tetrafluoroethylene and up to 10 mole % (preferably 2 mole %) of units derived from one or more fluorinated comonomers (e.g., HFP, HFIB, PFBE, VDF and VF). Such copolymers are available from DuPont under the trade designation TEFZEL HT 200, and from Daikin America, Inc. (“Daikin”), Orangeburg, N.Y., under the trade designation NEOFLON EP-541.
In a more preferred embodiment, insulating layer 16, 24 is extruded and the fluoropolymer(s) contains (as extruded) from about 4 to about 16% by weight of a crosslinking agent. Preferred crosslinking agents are radiation crosslinking agents that contain multiple carbon-carbon double bonds.
In yet a more preferred embodiment, crosslinking agents containing at least two allyl groups and more preferably, three or four allyl groups, are employed. Particularly preferred crosslinking agents are triallyl isocyanurate (TAIC), triallylcyanurate (TAC) and trimethallylisocyanurate (TMAIC).
In yet a more preferred embodiment, the fluoropolymer(s) contains a photosensitive substance (e.g., titanium dioxide), which renders the insulating layer 16, 24 receptive to laser marking. The term “laser marking,” as used herein, is intended to mean a method of marking an insulated conductor using an intense source of ultraviolet or visible radiation, preferably a laser source. In accordance with this method, exposure of the fluoropolymer insulating layer 16, 24 to such intense radiation will result in a darkening where the radiation was incident. By controlling the pattern of incidence, marks such as letters and numbers can be formed.
In yet a more preferred embodiment, the fluoropolymer(s) contains from about 1 to about 4% by weight, of titanium dioxide.
In addition to the above component(s), the fluoropolymer(s) may advantageously contain other additives such as pigments (e.g., titanium oxide), lubricants (e.g., PTFE powder), antioxidants, stabilizers, flame retardants (e.g., antimony oxide), fibers, mineral fibers, dyes, plasticizers and the like. However, some such additives may have an adverse effect on the desirable properties of the composite electrical conductor 10, 18 of the present invention.
The components of the insulating layer may be blended together by any conventional process until a uniform mix is obtained. In a preferred embodiment, a twin-screw extruder is used for compounding. The insulating layer 16, 24 is preferably formed by melt-extrusion, and then crosslinked using known techniques, which include beta and gamma radiation crosslinking methods.
In another preferred embodiment, insulating layer 16, 24 is formed by wrapping a fluoropolymer film, in an overlapping fashion, along the length of the polymer matrix 14, or conductor layer(s). The fluoropolymer film may be a heat-sealed or a non-heat-sealed fluoropolymer film. It is noted that wrapped fluoropolymer tapes or films will fuse or bond to themselves in overlapping regions at temperatures at or above the melting point of the fluoropolymer, thereby obviating the need to employ a heat-sealable adhesive with such films.
The thickness of insulating layer(s) 16, 24 of the composite electrical conductor 10, 18 may range from about 0.05 to about 0.30 mm (preferably, from about 0.10 to about 0.21 mm) for smaller sized conductors, or from about 0.20 to about 0.50 mm (preferably, from about 0.25 to about 0.41 mm) for larger sized conductors.
Composite electrical conductor 18, in one more preferred embodiment, comprises: a solid plastic core 20 prepared from one or more PEEK resins; a plurality of stranded tin-plated copper wires 22 contained in a single layer that circumferentially surrounds the plastic core 20; and an extruded, crosslinked ETFE insulating layer 24 circumferentially surrounding the layer formed by electrical conductors or strands 22.
This more preferred embodiment of composite conductor 18, when sized to 24 American Wire Gage (AWG), may be prepared by wrapping eleven strands of tin-plated copper wire, each having a diameter of 0.128 mm, around a solid PEEK plastic core having a diameter of 0.35 mm, using a multi-stranding machine. Lay lengths of the strand-winding around the core preferably range from about 0.34 to about 0.36 mm, with strand winding preferably done with a left-hand lay. A quantity of ETFE is then extruded over the copper wire layer using conventional extrusion techniques and the resulting assembly exposed to approximately 18 megarads of electron beam irradiation to crosslink the ETFE layer.
In another more preferred embodiment of composite electrical conductor 18, plastic core 20 is a hollow tubular PEEK plastic core, and (as shown in
The composite electrical conductor 10, 18 of the present invention is lightweight, and preferably may be used in environments where temperatures exceed 150° C. In addition, the inventive conductor 10, 18 demonstrates excellent tensile strength and acceptable levels of current carrying capacity.
Composite conductor 10, 18 has an outer diameter that may range either from about 0.40 to about 1.62 mm (preferably, from about 0.56 to about 0.80 mm) for smaller sized conductors, or from about 3.28 to about 18.50 mm (preferably, from about 5.35 to about 15.88 mm) for larger sized conductors, and weighs from about 1.0 to about 7.0 kilograms (kg) per kilometer (km) (preferably, from about 1.2 to about 4.0 kg/km) for smaller sized conductors, or from about 11.5 to about 950 kg/km (preferably, from about 15.5 to about 609 kg/km) for larger sized conductors.
Preferred embodiments of the composite conductor 10, 18 of the present invention qualify for use temperatures ranging from about −65° C. to about 260° C.
In addition to the above, preliminary test results indicate that the composite conductor 10, 18 of the present invention demonstrates improved breaking strength (ASTM B246-00) and acceptable levels of electrical resistance (ASTM B193-01) when compared to similarly sized conventional wire products. Further testing has indicated that the pull off tensile load for the composite conductor 10, 18 with crimp setting no. 24 greatly exceeds the minimum pull off load of 36 Newtons for #24 AWG Crimp (as required in Military Specification MIL-C-39029 entitled “Contacts, Electrical Connector, General Specification for,” and dated May 2, 1988).
The subject invention will now be described by reference to the following illustrative examples. The examples are not, however, intended to limit the generally broad scope of the present invention.
In the Working Examples set forth below, the following components and materials were used:
Eleven CONDUCTORs were wrapped around the PEEK CORE using a WATSON (model number HK-630L) multi-stranding machine. Lay length of the strand-winding around the core, which was done with a left-hand lay, was 9.6 mm.
A quantity of ETFE was compounded with 8% by wt. TAIC and 2% by wt. TiO2 and was then extruded over the layer of ELECTRICAL CONDUCTORs using a single-screw extruder having four heating zones which were set at 200° C., 240° C., 275° C., and 290° C., respectively. The thickness of the extruded ETFE layer was 0.15 millimeters.
Test samples were then irradiated using electron-beam radiation, with air-cooling. Total beam dosage was 18 megarads, while the applied voltage was 800 kilovolts (KV).
The subject wire constructions are described in Tables 1 and 2, hereinbelow.
The prepared test samples and Commercial Wire Products were then subjected to the test procedures identified below.
For these examples, the prepared composite electrical conductor samples and Conductors I and II were tested for breaking strength and electrical resistance. The results are set forth in Table 1, hereinbelow.
The results shown in Table 1, demonstrate that the composite conductor of the present invention (Example 1) achieves a level of current carrying capacity that is acceptable for signal transmitting circuits. More specifically, signal transmitting circuits need only the current carrying capacity of 30 AWG wires or conductors. As such, conductors having electrical resistance levels as high as 375% of conventional 24 AWG wires or conductors will function properly in these circuits. The electrical resistance level of Example 1 is only 145% of Conductor I (24 AWG tin-plated copper), which means that it has more current carrying capacity than these circuits require. In addition, it is noted that the inventive composite conductor increases wire breaking strength by approximately 39%, while reducing weight by approximately 20%, when compared to similarly sized Conductor I.
For these examples, the prepared composite electrical conductor samples and Conductor III were tested for pull off tensile load. The results are set forth in Table 2, hereinbelow.
1Sample Lost
The results shown in Table 2 generally demonstrate the strength of the composite electrical conductor of the present invention (Example 2), with composite conductors with crimp setting no. 24 generating the most reliable and consistent results. In fact, the pull off tensile load for the composite conductor with crimp setting no. 24 greatly exceeded the minimum pull off load of 36 Newtons for #24 AWG Crimp (as required in Military Specification MIL-C-39029 entitled “Contacts, Electrical Connector, General Specification,” and dated May 2, 1988).
Although the present invention has been shown and described with respect to detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.
This application claims priority from U.S. Provisional Patent Application Ser. No. 60/552,091, filed Mar. 10, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60552091 | Mar 2004 | US |
