Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-06-04
2001-04-17
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S034000, C220S787000
Reexamination Certificate
active
06218611
ABSTRACT:
FIELD OF INVENTION
The invention relates generally to radio frequency (rf) plugs that are inserted into access holes in walls, covers and chassis of radio frequency electrical or electronic equipment to prevent each access hole from acting as an antenna and radiating rf energy to nearby equipment, and more specifically to rf plugs that fit flush, seal in rf energy and are easily installed.
BACKGROUND OF INVENTION
The need for access holes in the walls, covers and chassis of enclosed electronic equipment is well known. These holes allow access for adjusting and/or testing internal components of an assembly while enclosed in radio frequency shielding. Once the adjusting and/or testing is completed, the access holes must be covered or plugged. That is because discontinuities, such as access holes, act as antennae for the electromagnetic fields from the electrical circuitry adjusted or tested by means of such holes, According to well known electromagnetic field theory, the amount and frequency of the electromagnetic energy that is spuriosly emitted depends upon the frequency and power level of the enclosed electrical circuitry. The enclosed circuitry may be for digital logic, computers, radios or telephone equipment. All of these use radio frequency signals that can become spurious emissions if not appropriately contained.
The known cover
100
for access holes , as seen in
FIG. 1
, has a domed or button shaped body
102
and has curved, springy appendages
104
coming out from the bottom circumference of the body. These appendages
104
are crafted such that when the right sized cover
100
is placed over a hole (not shown) and pressed in, the appendages
104
are initially forced inward by the sides of the hole and then as the bottom of the button nears the surface in which the hole is located their springiness and their shapes allow the appendages to expand outward. Also, because of the shape of the appendages
104
, this expanding action against the edges of the hole actually draws the cover
100
down toward the surface and locks it in place. To be effective, the known cover
100
must be bigger than the hole it is in—otherwise the spring action would pull the body portion
102
into the hole. This size difference between the cover
100
and the hole it goes into prevents covering a hole inside of another a hole unless the holes and their respective covers are made progressively and substantially larger towards the outside of the enclosure. Covers within covers are also hard to install. Furthermore, the appendages must be shaped for a range of hole depths and material thicknesses. If the hole is too deep, the pulling action and the locking do not occur. If the hole is very shallow, the pulling action and the locking will not occur either and the cover
100
will be loose and less effective. Furthermore, the appendages
104
as they extend into the enclosure can and will begin to act as antennas for emissions within the enclosure if the effective size of the appendages
104
is approximately a quarter wavelength. This often leads to unintended coupling of circuits when a cover
100
is installed.
Thus, it is an object of the present invention to provide a cover or plug that mounts flush with the top and bottom surfaces of the hole it is inserted into.
It is another object of the invention to provide a cover or plug that can be readily passed through a first hole to cover an interior access/test hole.
It is a further object of the present invention to provide a locking on almost any thickness of material.
SUMMARY OF INVENTION
Briefly stated in accordance with one aspect of the invention, the aforementioned problems are addressed by providing an apparatus for enclosing an electrical circuit. The apparatus includes a conductive enclosure that has an interior surface and an exterior surface. This conductive enclosure has a hole formed therein. The hole is defined in a first portion by a first cylindrical surface that has a first radius. This first cylindrical surface is connected at a first end thereof to the interior surface of the enclosure. The hole also being defined in a second portion by a second cylindrical surface that has a second radius. This second cylindrical surface has multiple semi-cylindrical voids spaced equally around its perimeter. Each of the radii of the semi-cylindrical voids is smaller than the smaller of the first and second radii of the first and second cylinders. The second cylindrical surface is connected at a first end thereof to the exterior surface of the enclosure and extends such that a second end of the second cylindrical surface is coplanar with the second end of the first cylindrical surface;. Also defining the hole is a ring shaped surface that is located between the second ends of the first and second cylinders and located in the common plane of those second ends. A cover is adapted to fit in the hole and engage the surfaces of the conductive enclosure sufficiently to prevent emission of electrical and electromagnetic fields through the hole.
In accordance with another aspect of the invention, the aforementioned problems are addressed by providing an apparatus for enclosing an electric circuit includes a conductive enclosure that has an interior surface and an exterior surface. This conductive enclosure has a hole formed therein. The hole is defined in a first portion by a first cylindrical surface that has a first radius. This first cylindrical surface is connected at a first end thereof to the interior surface of the enclosure. The hole also being defined in a second portion by a second cylindrical surface that has a second radius. This second cylindrical surface has multiple semi-cylindrical voids spaced equally around its perimeter. Each of the radii of the semi-cylindrical voids is smaller than the smaller of the first and second radii of the first and second cylindrical surfaces. The second cylindrical surface is connected at a first end thereof to the exterior surface of the enclosure and extends such that a second end of the second cylindrical surface is coplanar with the second end of the first cylindrical surface. Also defining the hole is a ring shaped surface that is located between the second ends of the first and second cylindrical surfaces and located in the common plane of those second ends. A cover is adapted to fit in the hole and engage the surfaces of the conductive enclosure sufficiently to prevent emission of electrical and electromagnetic fields through the hole. The cover has a first cylindrical portion to fit in said first cylindrical portion of the hole and a second cylindrical portion to fit within the second portion of the hole. The second cylindrical portion of the cover has multiple protrusions adapted to fit into the multiple semi-circular voids. Additionally, the cover has a recess therein for receiving a tool to rotate the cover into sufficient engagement with the surfaces of the enclosure in order to hold the cover in place.
REFERENCES:
patent: Re. 30326 (1980-07-01), van Buren, Jr.
patent: 4179038 (1979-12-01), Rosan, Jr.
patent: 4384165 (1983-05-01), Loving, Jr. et al.
patent: 4620641 (1986-11-01), Beer
patent: 4832234 (1989-05-01), Peterson
Lucent Technologies - Inc.
Oliva Carmelo
Penrod Jack R.
Reichard Dean A.
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