Patent Application
20130137316
The present description relates generally to electrical connections and more particularly, to methods and apparatus for preventing oxidation of an electrical connection.
The electrical industry uses an antioxidant to help keep electrical connections from getting oxidation in-between the conductive surfaces of the connections. An antioxidant may be particularly important when the connection is made through an aluminum to aluminum or an aluminum to copper connection.
In particular, most metals (with a few exceptions, such as gold) oxidize freely when exposed to air. In the specific case of aluminum, aluminum oxide is not an electrical conductor, but rather an electrical insulator. Consequently, the flow of electrons through the oxide layer can be greatly impeded. However, because the oxide layer is only a few nanometers thick, the added resistance is not noticeable under most conditions. When an aluminum wire is terminated properly, the mechanical connection breaks the thin, brittle layer of oxide to form an excellent electrical connection. Unless this connection is loosened, there is no way for oxygen to penetrate the connection point to form further oxide, and thus the connector operates with little change.
However, as is typically the case, this connection does loosen over time, and once oxygen penetrates the connection point to form an oxide, the electrical connection may be compromised. For instance, aluminum, steel, copper, each expand and contract at different rates under thermal load, so connections utilizing multiple metals can become progressively looser over time. In one instance, the expansion/contraction cycle results in the connection loosening slightly, overheating, and allowing intermetallic steel/aluminum oxidization to occur between the conductor and the screw terminal. This may result in a high-resistance junction, leading to overheating.
Another issue is the joining of aluminum wire to copper wire. As aluminum and copper are dissimilar metals, galvanic corrosion can occur in the presence of an electrolyte and these connections can become unstable over time.
To prevent oxidation, many types of antioxidants have been developed in the industry. These antioxidants, however, are typically either a grease or gel-like material. For example, in one instance, a twist-on connector, such as a Twister® Al/Cu Wire Connector, available from Ideal Industries, Inc., Sycamore, Ill., has been designed for the purpose of joining aluminum to copper wire. This twist-on wire connectors use a special polypropylene, zinc plated steel, antioxidant grease to prevent corrosion of the connection. In another example similarly available from Ideal Industries, a grease-like antioxidant includes a polybutene (<80% wt), zinc dust (20% wt), and silicon dioxide (<5% wt).
While the prior antioxidants are oftentimes suitable for their intended purposes, there remains a need for a malleable antioxidant for use with some electrical connections.
In particular, in the example antioxidant disclosed herein, a malleable wax-based antioxidant is provided for use between two electrical connectors. To form the example antioxidant, a wax base is melted and metal particles, such as, for example, zinc particles, are provided in suspension with the melted wax base. The wax suspension is cooled and formed into a shape by, for example, molding, extrusion, die cutting, and/or other suitable forming method. In use, the zinc particles keep the connections running cool, particularly with aluminum to aluminum connections.
The following description of example methods and apparatus is not intended to limit the scope of the description to the precise form or forms detailed herein. Instead the following description is intended to be illustrative so that others may follow its teachings.
Referring now to
Continuing with the illustrated example, each of the example connectors 12, 14 includes at least one wire insert 22 adapted to accept a wire connector (not shown) such as an aluminum and/or copper wire. Each of the wire inserts 22 includes a fastener 24 such as a set screw to retain an inserted wire connector in the wire insert 22.
As previously noted, the example connectors 12, 14, may be any suitable electrical connector including a mechanical lug, such as a dual-rated (aluminum/copper) two-barrel mechanical connector 12 and/or a single-barrel mechanical connector 14, comprising a high strength aluminum alloy. It will be appreciated, however, that the connectors 12, 14 may be constructed of any suitable material, including, for example, a copper material as desired. As previously noted, the connectors 12, 14 are electrically coupled and in at least one example, are UL listed at 600V and are acceptable for use through 2000V.
To prevent oxidation between the two conductive surfaces the example connector 10 includes an antioxidant 30. In this example, the antioxidant 30 is a die-cut wafer sized to insert utilized during assembly of the electrical connector to sufficiently cover the portions of the mating contact surfaces 12a, 14a that are brought into contact when the electrical connector 10 is assembled. As illustrated in
As mentioned, the example antioxidant 30 is a wax-based antioxidant which prevents oxidation and helps to keep the electrical connections between the two electrical connectors 12, 14 operating at an optimal level. Specifically, the antioxidant 30 comprises a wax base, such as a material similar to beeswax and/or a microcrystalline wax impregnated with metal particles in suspension, such as for example, a powdered zinc. The percentage of metal particles suspended in the wax base is preferably about 10% to 95% by weight of the suspension.
In one instance, the wax base is a wax material available from The International Group, Inc., of Wayne, Pa., and provided under the product number 5799A. In determining the wax base, it is preferable that the melting temperature of the wax base be relatively high so that the wax does not melt under normal operating temperatures of the electrical connectors under load. This melting temperature can be readily obtained by one of ordinary skill in the art.
With the example material, the drop melting temperature of the chosen wax base is approximately about 73° C. to 81° C. The example wax base also includes an oil content of less than approximately 2.5% by weight, and has a needle penetration of approximately about 20 dmm to 30 dmm at 25° C. Because of these properties, the wax base does not melt and/or flow under normal operating conditions and the antioxidant 30 does not easily “run out” or “ooze” all over the electrical connectors 12, 14 under normal operating circumstances. In particular, the kinematic viscosity of the example wax base is between approximately 13.0 centiStokes (cSt) and 17.0 cSt at 100° C. Beneficially, with the example viscosity, the antioxidant 30 remains malleable and can be manipulated like clay to conform to any desired shape including the shape of the mating surfaces, etc.
Turning to
After mixing, the suspension is allowed to cool at a block 414. Before, during, and/or after the cooling period, the suspension may be molded, extruded, and/or otherwise formed into a particular shape. In this example, the cooling suspension is poured into a mold or otherwise formed into a sheet or web. Once cooled sufficiently, the final shape of the antioxidant 30 may be formed at a block 416. It will be appreciated that the final shape may be any suitable shape, including a plug, sphere, cylinder, torus, disk, washer, square, rectangle, etc. It will be further appreciated that the final shape may be custom created by the user, and/or other entity during installation and/or the manufacturing process. Additionally, as noted previously, the final shape may be formed to define and/or include an aperture(s) as desired.
In use, the antioxidant 30, is utilized between the two electrical connectors 12, 14, as illustrated. For example, in one instance, the antioxidant 30 is formed to be rectangular in shape and to include the aperture 32. The antioxidant 30 is placed between the two electrodes 12, 14 by an end-user and the connectors 12, 14 and the contact surfaces 12a, 14a are brought together in any suitable manner, including, for example, by tightening the fastener 20. Because the antioxidant 30 is malleable, the material will flow between the contact surfaces 12a, 14a during tightening, to cover the contact surfaces 12a, 14a and prevent oxidation regardless of whether the connection between the connectors 12, 14 loosens slightly as is typical over time. Furthermore, because the antioxidant 30 is malleable, the shape of the antioxidant 30 may be modified before placement (e.g. like molding clay) between the electrical connectors 12, 14 as desired to ensure a proper coating of the antioxidant 30 over the contact surfaces 12a, 14a. For instance, in one example, the antioxidant 30 may be shaped into a ball and/or other shape and utilized to fill a pocket for a wire with the antioxidant 30 such that insertion of the wire into the pocket sufficiently coats and/or covers the wire. Furthermore, it will be appreciated that because the normal operating temperature of the electrical connection is below the melting point of the wax base, and thus the melting point of the suspension itself, the antioxidant will not flow, ooze, and/or otherwise run out over time, ensuring that the contact surfaces 12a, 14a will not be exposed over time.
While the example antioxidant 30 is illustrated as connecting a pair of mechanical lugs, it will be understood that the antioxidant may be utilized in any suitable manner, to connect any suitable electrical connector as desired, including for example, between wires and the electrical lug as well. Additionally, while the example antioxidant 30 is illustrated as a wafer-shaped insert, the shape, thickness, and/or form of the antioxidant may vary as desired. Still further, the choice of materials in the antioxidant (e.g., the choice of a wax base and/or the type of suspended particle) may vary without departing from the scope of the present disclosure. Finally, while not illustrated in the present disclosure, the antioxidant may be provided with various other inert and/or active ingredients to enhance and/or otherwise supplement the characteristics of the present antioxidant as desired.
Accordingly, although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.
