Electrical connectors – Metallic connector or contact having movable or resilient... – Screw-thread operated securing part
Reexamination Certificate
1999-12-16
2001-10-23
Abrams, Neil (Department: 2839)
Electrical connectors
Metallic connector or contact having movable or resilient...
Screw-thread operated securing part
C439S886000
Reexamination Certificate
active
06305991
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The invention relates to a method of connecting conductors via a respective contact surface, with the contact surfaces being joined facing one another. The invention further relates to a line-bar connection that is produced in accordance with this method.
2. Prior Art
A typical application of the method is found in so-called line bars (also called bar-type distributors), which are used for supplying power to machines, climate-control systems and lighting systems, and are suited for conducting electrical currents of several hundred amps. These line bars include a plurality of insulated conductors that are guided parallel in the form of solid, flat profiles comprising copper or aluminum. They are produced as individual elements, for example, straight or angled segments, branches, or with connections that branch off laterally, etc. Such elements are then joined to form a system, often long after the production process. In the process, the ends of the conductors are to be connected to one another at the assembly site so as to be mechanically and electrically conductive. Compression joints between overlapping contact surfaces—for example, by means of screw connections—are practically exclusively considered; in contrast, welding the conductors at the site of the line-bar assembly would be very expensive and hardly acceptable for safety reasons.
Connecting solid, copper conductors typically poses no problems. For cost reasons, however, aluminum conductors are also being used in increasing numbers. It is known that a dense layer of hard, brittle aluminum oxide, which is an extremely poor conductor, has already formed on the aluminum after a short period of time. Without special measures, therefore, mechanical (compression) connections between aluminum conductors and aluminum-copper compounds would be affected by high electrical transition resistances, which would be intolerable in, for example, conductors and elsewhere.
One possible remedy is to brush the contact surfaces bare immediately prior to joining the conductors, that is, at the assembly site. This is, however, an extremely time-consuming and laborious process, because the contact surfaces at the ends of the line-bar elements are often difficult to access. The success of the measure also depends heavily on painstaking labor that must be checked precisely. To avoid interfering oxide layers, or to assure bare contact surfaces with a low transition resistance, it is known to provide aluminum conductors with a coating of nickel, tin or silver in the connecting region. Unfortunately, this work step is associated with additional labor and corresponding costs, which increases the cost of the line-bar elements considerably.
It is also known to insert special structural elements between the contact surfaces of the conductors during the connecting process for the purpose of better contacting: U.S. Pat. No. 3,895,853 describes the use of resilient, wavy metal strips forming lamella that protrude on two sides. In contrast, Swiss Patent No. 551 698 proposes a ring that is disposed around a tightening screw and forms a circular, sharp edge at each end face; when the screw is tightened, each of these edges is pressed into one of the contact surfaces. These proposals entail additional mechanical parts, which incur corresponding production costs, and complicate and raise the cost of assembly significantly. The additional parts stipulate a corresponding spacing between the contact surfaces. The connection correspondingly requires more space, which is crucial particularly for conductor elements having multiple conductors and connecting points located in a “packet-wise,” adjacent arrangement. Finally, a disadvantage is that no direct contact is produced between the conductors, but two current transitions are formed in series with a correspondingly-increased transition resistance.
OBJECT AND SUMMARY OF INVENTION
The invention is therefore intended to provide a method that is simple to execute and cost-effective, and assures electrically and mechanically flawless connections in the use of conductors, particularly aluminum conductors, even after a long storage period (the time between production and assembly of the conductors).
In accordance with the invention, this object is, accomplished by a method in which at least the contact surface of the one conductor are provided, prior to the joining process, with grooves, indentations and/or notches that are angled at the surface; the contact surfaces are brought into direct contact and the conductors are pressed together with such a strong force that a mutual, plastic deformation and, consequently, a metallic, electrically-conductive contact are created at a plurality of separate locations at the contact surfaces.
The preparatory machining of the contact surfaces—creation of the grooves, indentations, etc.—need not necessarily be performed immediately prior to the joining of the conductors; rather, a lengthy period of time can pass between these method steps. It has been seen that, in the subsequent pressing of the conductors and the resulting material deformation, a brittle oxide layer that has formed in the interim is broken open at the numerous contact points and splintered on both sides, exposing the bare metal. At the compression points, the material is fluidly compressed, resulting in the desired, permanently-low transition resistance due to a plurality of parallel metallic contacts. The preparatory surface machining of the contact surfaces can be performed at low cost with simple tools during the production of the conductors, for example by means of a correspondingly-shaped pressing ram or through material removal with a comb-like, indented drawing tool. A particular advantage is that no additional parts whatsoever are required for the joining of the conductors, and the contact surfaces lie directly against one another. This makes the assembly extraordinarily simple. The electrical and mechanical contacts distributed over a large portion of the contact surfaces are produced reliably and with uniform quality. Of course, a sufficient surface pressure must be generated to bring about the plastic deformation and the desired low transition resistances at the compression points; a corresponding pressing force is, however, necessary anyway for the stable mechanical connection.
REFERENCES:
patent: 3002173 (1961-09-01), Allen
patent: 3895853 (1975-07-01), Neidecker
patent: 5073121 (1991-12-01), Jaenke et al.
patent: 6089930 (2000-07-01), Matsuoka et al.
patent: 551 698 (1974-07-01), None
patent: 11-185842 (1999-09-01), None
Abrams Neil
Browdy and Neimark
Zarroli Michael C.
Zurecon AG
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