Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-03-15
2001-07-10
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S816000, C361S753000, C174S034000
Reexamination Certificate
active
06259609
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to shielding arrangements for shielding against electromagnetic and radio frequency interference in electronic equipment and pertains, more specifically, to improvements in the construction of shielding gaskets utilized in such equipment.
A wide variety of shielding gaskets currently is available for use in connection with electronic equipment such as computers, wireless telephones and various other information and communication apparatus. Many of these shielding devices are constructed of relatively thin flexible sheets of metal and utilize spring contactors for making electrical contact at multiple locations to effect ground connections in various shielding arrangements. These spring contactors usually are in the form of cantilever spring tabs or fingers biased into contact with surrounding structures by simple bending. Appropriate contact forces generally are attained either by selecting the length of the cantilever arm, or by modifying the cross-sectional configuration of the arm to provide bending characteristics which will attain the desired contact forces. For example, deflection forces are reduced, while effective contact pressure is maintained, by increasing the length of a cantilever contactor arm. However, increased contactor arm length tends to increase stresses at the base of the contactor arm, leading to early mechanical failure and loss of electrical integrity. Modification of the cross-sectional configuration of a contactor arm often leads to a weaker, generally more flimsy gasket construction, and usually one which is more difficult to manufacture, and therefore more expensive. Moreover, the deflection of cantilever contactor arms results in increased contact area, thereby departing further from a more desirable limited point or edge contact and decreasing shielding effectiveness.
Shielding gaskets also have been constructed of elastomeric materials, usually using foamed structures rendered conductive by the incorporation of metal fibers either woven into or around the elastomeric material. The forces required to compress such a shielding gasket usually are much greater than those required for a comparable thin metal gasket because the load is distributed over a much greater area than the point or edge contacts encountered at the spring fingers of a thin metal gasket. Moreover, elastomeric gaskets are prone to oxidation and thermal degradation, both of which will lead to loss of resiliency and concomitant loss of shielding effectiveness.
BRIEF SUMMARY OF THE INVENTION
The present invention provides an improvement in a shielding gasket of the type constructed of a relatively thin sheet of metal, such as stainless steel, the improvement overcoming the shortcomings of thin sheet shielding gaskets which utilize cantilever contactor arms. As such, the present invention attains several objects and advantages, some of which are summarized as follows: Provides improved shielding against electromagnetic and radio frequency interference in electronic devices utilizing a shielding gasket requiring reduced forces for attaining and maintaining effective shielding contact; attains full deflection of the contactors of shielding arrangements with reduced force and without deleterious permanent deformation, for long-term consistent and intimate shielding contact; resists permanent deformations which otherwise could defeat effective shielding contact; assures highly localized contact between the contactors and surrounding structure for effective shielding contact; allows a more compact arrangement with increased shielding effectiveness; enables effective shielding arrangements in connection with circuit boards carrying a dense population of components by utilizing relatively narrow strips carrying contactors, the narrow strips having the ability to follow corresponding narrow traces along such densely populated circuit boards, which traces are to be contacted for shielding purposes; increases longevity through a decreased tendency toward contactor failure and consistent contact force over repeated deflections; enables widespread use in connection with a wider variety of shielding gasket configurations; provides a more rugged, stable and consistent shielding connection over a longer service life.
The above objects and advantages, as well as further objects and advantages, are attained by the present invention which may be described briefly as an improvement in a shielding contactor device in which a relatively thin flexible strip of electrically conductive material extends in a longitudinal direction and has a lateral width between laterally opposite first and second edges, a plurality of contactors extend longitudinally along the strip adjacent the first edge and project in an altitudinal direction from the strip, and a web extends longitudinally along the strip alongside each contactor adjacent the second edge, the improvement comprising: at least some of the contactors each including a contact arm having a length extending longitudinally along a longitudinal axis between a first end and a second end, and a width extending laterally between a first side and a second side, the first end of the contact arm being integral with the strip and the contact arm extending longitudinally adjacent the first edge of the strip, with the longitudinal axis being adjacent the first edge of the strip; and a contact finger adjacent the second end of the contact arm, spaced longitudinally from the first end of the contact arm, and extending laterally from the contact arm in a direction from the first edge toward the second edge of the strip, the contact finger including a contact portion spaced laterally from the longitudinal axis; the contact arm being twisted in permanent deformation about the longitudinal axis for extending the contact portion of the contact finger in the altitudinal direction and torsionally biasing the contact portion in the altitudinal direction.
In addition, the present invention includes an improvement in a method for making a shielding contactor device in which a relatively thin flexible strip of electrically conductive material extends in a longitudinal direction and has a lateral width between laterally opposite first and second edges, a plurality of contactors extend longitudinally along the strip adjacent the first edge and project in an altitudinal direction from the strip adjacent the first edge, a web extends longitudinally along the strip alongside each contactor adjacent the second edge, and at least some of the contactors each include a contact arm having a length extending longitudinally along a longitudinal axis between a first end and a second end, and a width extending laterally between a first side and a second side, the first end of the contact arm being integral with the strip and the contact arm extending longitudinally adjacent the first edge of the strip, with the longitudinal axis adjacent the first edge of the strip, the improvement comprising: providing a contact finger adjacent the second end of the contact arm, spaced longitudinally from the first end of the contact arm, and extending laterally from the contact arm in a direction from the first edge toward the second edge of the strip, the contact finger including a contact portion spaced laterally from the longitudinal axis; and twisting the contact arm to permanently deform the contact arm about the longitudinal axis for extending the contact portion of the contact finger in the altitudinal direction and torsionally biasing the contact portion in the altitudinal direction.
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Gandhi Jayprakash N.
Jacob Arthur
Tran Thanh Y.
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