Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-04-15
2001-11-20
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S034000, C174S0170CT, C248S027100, C361S808000, C361S818000, C361S821000, C361S825000
Reexamination Certificate
active
06320120
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electromagnetic interference (EMI)/radio frequency interference (RFI) shielding devices, and more specifically, to a low profile clip-on EMI/RFI shielding strip.
BACKGROUND OF THE INVENTION
As is well known, selected electric or electronic parts radiate electromagnetic waves which can cause noise or unwanted signals to appear in electric or electronic parts and devices existing in the vicinity of the radiating parts. Accordingly, it is highly desirable to provide shielding and/or grounding for electronic components that use circuitry that emits or is susceptible to electromagnetic radiation. It is known that these components can be shielded to reduce undesirable electromagnetic interference and/or susceptibility effects with the use of a conductive shield that reflects or dissipates the electromagnetic charges and fields. Such shielding may be grounded to allow the offending electrical charges and fields to be dissipated without disrupting the operation of the electronic components enclosed within the shield.
Various types of EMI/RFI shielding devices are known for reducing the transmission of EMI and RFI. Among the known devices are gaskets or strips of a resiliently deformable material which are secured to an openable access panel, door, drawer, or the like (hereinafter “door”), to block the transmission of EMI/RFI through the small clearance between the door and the adjacent structure which forms the opening into and out of which the door is movable. Such strips are useful for shielding openings of housings for electronic components which are highly sensitive to the adverse effects of EMI/RFI.
Such known devices are typically made of one of several materials which have the combined functions of acting as an EMI/RFI shield, and which are resiliently deformable so that they can be compressed between the door when closed, and will spring back to an uncompressed configuration when the door is moved out of the opening.
Prior shielding strips, although providing an adequate level of shielding for the electronic devices, are often difficult to install on an electronics housing and are often not secured to a mounting surface to withstand the forces generated in use without detaching from the surface. For example, one prior strip utilizes a track which is riveted to the mounting surface of the housing, the shielding strip then being slid onto the riveted track to hold the strip in place. Although providing a secure mount for the shielding strip, the riveted track involves a relatively complicated installation procedure, involving several steps, and is therefore labor intensive. Furthermore, a shielding strip which requires a riveted track is relatively expensive, because it requires extra parts (a track and rivets), and added labor to install. The riveted track is also somewhat prone to misinstallation, because installation requires alignment of a rivet with holes in the track.
Another prior shielding strip utilizes an adhesive layer on a portion of the shielding strip which is intended to be mounted on the electronics housing. Although being relatively simple to install, adhesive shielding strips also suffer from particular deficiencies. Specifically, adhesive tends to not be as strong as the riveted track shielding strips, discussed above. If a stronger adhesive is used, the probability of mismounting the adhesive shielding strip increases, requiring destruction of the adhesive shielding strip in order to properly place an adhesive shielding strip on a mounting surface.
Yet another prior shielding strip utilizes one or two long, continuous slots cut into the mounting surface, into which portions of the shielding strip are inserted. If two slots are provided, then the shielding strip is partially expanded, and the entire length of the shielding strip is partially inserted into the slots. The shielding strip is not locked in place, however, and is prone to displacement out of the slots. While providing a good level of shielding when the slots are properly machined, the requirement that precisely machined slots be formed in the mounting surface makes this type of shielding strip more expensive, labor intensive, prone to mismounting, and leads to a heightened potential for EMI/RFI leakage though the slot and past the strip if the slots are machined too wide or long.
There therefore remains a need in the art to provide an inexpensive shielding strip which is easily installed on a mounting surface, which does not require precision machining of the mounting surface, and which locks the shielding strip in place.
SUMMARY OF THE INVENTION
In order to overcome the problems and disadvantages of the prior art, the present invention provides a shielding and/or grounding strip including a strip of material defining a first longitudinal side, a second longitudinal side, a top surface, and a mounting surface. The first longitudinal side of the strip forms a hook member and at least one contact flap is formed on the mounting surface of the strip of material. In a preferred embodiment, a plurality of contact flaps are formed and the contact flaps may preferably have a semicircular shape.
Further, in accordance with a first embodiment of the present invention, at least one and preferably an opposing pair of barbs are provided for mounting the shielding strip. In a further embodiment of the present invention, pressure sensitive adhesive may be utilized for mounting the shielding strip.
Still other objects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings.
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Instrument Specialties Catalog, “RF Shielding Selection: A Guide to Interference Control,” CAT-91, 1991.
BrushWellman Engineering Materials Brochure, “Guide to Beryllium Copper,” pages 4 and 10, Apr. 1992.
Instrument Specialties Catalog, “Engineering Design and Shielding Product Selection Guide,” pp. 62, 64 and 65, Apr. 1998.
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Laird Technologies
Nino Adolfo
Pitney Hardin Kipp & Szuch LLP
Reichard Dean A.
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