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I claim:
1. A shielding membrane for absorbing radiation generated by an
electromagnetic radiation source, the shielding membranes comprising:
first means for absorbing some of the radiation initially passing into the
membrane;
second means for grounding some of the low frequency components of the
radiation that is not absorbed by said first means;
third means for trapping, grounding and absorbing still further radiation
not absorbed or grounded by said first and second means, said third means
including an electromagnetic radiation absorption media, the third means
further causing at least a portion of the unabsorbed radiation to reflect
back and forth through the absorption media.
2. A shielding membrane as recited in claim 1 wherein said third means
includes a pair of grounded plates positioned in a spaced apart
confronting relationship on opposite sides of the absorption media for
reflecting at least a portion of the unabsorbed radiation incident thereon
back and forth across the absorption media.
3. A shielding membrane as recited in claim 1 wherein said first means
includes means for minimizing reflections of electromagnetic radiation
incident on the shielding membrane.
4. A shielding membrane for absorbing radiation from an electromagnetic
radiation source, the shielding membrane having an incident side facing
substantially towards the radiation source and a base side facing
substantially away from the radiation source, the shielding membrane
comprising:
means for minimizing reflection of electromagnetic radiation incident on
the incident surface of the shielding membrane;
a conductive deflection layer formed of a multiplicity of spaced apart
metallic deflection pads for deflecting incident radiation thereabout,
said deflection layer being positioned in spaced apart confronting
relationship with the base side of said reflection minimizing means;
a conductive absorption funneling layer disposed in spaced apart
confronting relationship with the base side of the deflection layer and
having a multiplicity of apertures for passing radiation; and
a grounded reflecting plate spaced apart from the base side of said
absorption funneling layer.
5. A shielding membrane as recited in claim 4 further comprising means for
grounding some of the low frequency components of the radiation that
enters the shielding membrane, the low frequency grounding means being
disposed between the reflection minimizing means and the deflection layer.
6. A shielding membrane as recited in claim 5 wherein said grounding means
includes a conductive mesh that is spaced apart from said deflection
layer, the mesh being grounded.
7. A shielding membrane as recited in claim 6 wherein said reflection
minimizing means includes a waveguide barrier having a multiplicity of
protrusion facing the radiation emitting source for minimizing reflection
of electromagnetic radiation incident on the shielding membrane.
8. A shielding membrane as recited in claim 7 further comprising a first
spacer disposed between said conductive mesh and said deflection layer, a
second spacer disposed between said deflection layer and said absorption
funneling layer and a third spacer disposed between said absorption
funneling layer and said reflecting plate.
9. A shielding membrane as recited in claim 8 further comprising a
plurality of deflection layers and a plurality of absorption funneling
layers disposed in spaced apart relation between said conductive mesh and
said reflecting plate.
10. A shielding membrane as recited in claim 4 wherein said reflecting
plate is formed of a metallic material.
11. A shielding membrane as recited in claim 8 wherein said spacers are
formed of a high density porous foam.
12. A shielding membrane as recited in claim 5 wherein the deflection pads
on said deflection layer have substantially the same geometry as the
apertures on said absorption funneling layer.
13. A shielding membrane as recited in claim 12 wherein said deflection
pads are substantially circular and electrically interconnected.
14. A shielding membrane as recited in claim 8 for use in the walls of a
building.
15. A shielding membrane as recited in claim 8 wherein said conductive
layers are formed of lead and said radiation source emits X-rays.
16. A shielding membrane as recited in claim 8 wherein said shielding
membrane forms a portion of a housing for a video display terminal.
17. A shielding membrane as recited in claim 8 wherein said shielding
membrane forms a housing disposed about a power supply or radiation
source.
18. A shielding membrane as recited in claim 8 wherein said shielding
membrane is substantially tubular.
19. A shielding membrane as recited in claim 18 wherein said shielding
membrane is disposed about electrical power lines.
20. A shielding membrane as recited in claim 7 wherein said waveguide
barrier protrusions are substantially pyramidal.
21. A shielding membrane as recited in claim 8 wherein said deflection
layer, said absorption funneling layer and said reflecting plate are all
stippled to disperse radiation reflected therefrom.
22. A housing for shielding the emission of an appliance having components
that emit electromagnetic radiation, the housing having an incident side
facing substantially towards the radiation emitting components and a base
surface facing substantially away from the radiation emitting components,
the housing comprising:
a waveguide barrier having a multiplicity of substantially pyramid shape
protrusions facing the radiation emitting components for minimizing
reflection of electromagnetic radiation incident on the shielding
membrane;
a conductive mesh disposed on the base side of the waveguide barrier for
blocking low frequency radiation, said mesh being grounded;
a conductive deflection layer formed of a multiplicity of spaced apart
metallic deflection pads for deflecting incident radiation thereabout,
said deflection layer being grounded and positioned in spaced apart
relation from the base side of said conductive mesh;
a conductive absorption funneling layer disposed in spaced apart
confronting relationship with the base side of the deflection layer and
having a multiplicity of apertures for passing radiation, said absorption
funneling layer being grounded;
a reflecting plate spaced apart from the base side of said absorption
funneling layer; and
a plastic casing disposed on the base side of the reflecting plate; and
a plurality of absorption spacers adapted to absorb and disperse at least a
portion of the radiation incident thereon, the plurality of absorption
spacers including a first spacer disposed between said conductive layer
and said deflection layer, a second spacer disposed between the deflection
layer and the absorption funneling layer, and a third spacer disposed
between said absorption funneling layer and said reflecting plate.
23. A shielding membrane for shielding radiation from various electronic
and electrical sources, the shielding membrane having an incident side
facing said components and a base side facing away from said components,
the shielding membrane comprising:
a waveguide barrier having a multiplicity of pyramidal protrusions facing
the radiation source for minimizing the reflection of electromagnetic
radiation incident thereupon;
a plurality of spaced apart and stacked conductive layers, each said
conductive layer being grounded for grounding a portion of the incident
radiation;
a plurality of absorption spacers for absorbing and dispersing radiation
passing therethrough, each said absorption spacer being disposed between
an adjacent pair of conductive layers; and
wherein said conductive layers include, a conductive mesh adapted to block
low frequency radiation, a deflection layer formed of a multiplicity of
spaced apart electrically connected metallic deflection pads for
deflecting incident radiation thereabout, an absorption funneling layer
disposed on the base side of said deflection pad and having a multiplicity
of apertures for passing radiation deflected about said deflection pads,
and a reflecting plate disposed on the base side of said absorption
funneling layer for cooperating with said absorption funneling layer and
said deflection layer to trap radiation passing through said apertures
therebetween.
24. A shielding membrane as recited in claim 4 wherein said deflection
layer is grounded.
25. A shielding membrane as recited in claim 4 wherein said absorption
funneling layer is grounded.
26. A shielding membrane for absorbing radiation from an electromagnetic
radiation source, the shielding membrane having an incident side facing
substantially towards the radiation source and a base side facing
substantially away from the radiation source and comprising:
a conductive deflection layer formed of a multiplicity of spaced apart
metallic deflection pads for deflecting incident radiation thereabout;
a conductive absorption funneling layer disposed in space apart confronting
relationship with the base side of the deflection layer and having a
multiplicity of apertures for passing radiation;
absorption means for absorbing radiation passing through said shielding
membrane, said absorption means including a first absorption layer
disposed on the incident side of said deflection layer and a second
absorption layer disposed between said deflection and absorption funneling
layers; and
grounding means for grounding at least one of the conducting layers from a
group including the deflection and absorption funneling layers. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates generally to a device for shielding
electromagnetic radiation emanating from electronic devices and electrical
power sources. More particularly, the present invention relates to a
shielding membrane that absorbs undesirable radiation emitted by cathode
ray tubes, power sources and other electronic equipment systems.
In recent years, there has been a growing concern that extensive exposure
to electromagnetic radiation and large electrostatic fields may have
adverse implications to a person's health. With the continually increasing
use of video display terminals and power supplies, there has been
extensive research studying the effects of radiation and fields generated
by such devices. During an international conference on "Working With
Display Units" held in Stockholm, Sweden in May, 1986, evidence was
presented showing a correlation between adverse health effects and
extensive exposure to non-ionizing radiation emissions from the video
display terminals. Additionally, some studies have shown that low
frequency emissions from power lines located over residential areas have
adverse health effects on people living in the region.
In addition to health concerns, such emissions may appear as noise to
surrounding electronic equipment, thereby degrading the performance of
neighboring equipment. Additionally, it has been shown that equipment can
be readily constructed to detect radiation emitted from various computers
and that the nature of data being worked with can be deciphered from an
analysis of that radiation. Therefore, data security, particularly in the
environment of embassies, banks and the like, has become a major concern.
Therefore, there is a need for a device capable of effectively absorbing
electromagnetic and RFI radiation as well as static electricity buildups.
In response to such concerns, there have been numerous devices developed
for absorbing electromagnetic radiation. For example, in Japanese Patent
Application No. 55-91870, an electromagnetic wave absorber is disclosed
comprised of a plurality of foamed polystyrol members sandwiched between a
metallic plate and a front surface having a plurality of pyramidal shaped
foam surfaces created from the same material as the wave absorbing
members. The polystyrol members serve as radiation absorbing media.
However, the metallic layer reflects radiation incident thereon. Thus,
even though a large thickness of wave absorbing members is used, there
will be substantial reflection back through the sandwiched materials
towards the radiation source. Unfortunately, such reflected radiation can
have adverse effects on the operation of the electronic equipment.
Particularly, such radiation may be picked up by the equipment as noise
thereby adversely affecting performance. Therefore, it is extremely
important to absorb most of the radiation within the shielding membrane.
Japanese Patent Application No. 55-29599 discloses an alternative
embodiment of a wave absorber that comprises a plurality of triangular
pyramid shape ferrite members disposed over ferrite plates that are backed
with a metal plate. While such a device would effectively absorb some
frequencies, its reliance upon wave length matching principles (due to its
ferrite composition), restricts its usefulness to limited frequency
ranges.
Therefore, there is a need for a shielding membrane that is easy to
fabricate with inexpensive material, effectively absorbs a substantial
percentage of the electromagnetic radiation incident thereupon over a wide
frequency range, while passing virtually none of the radiation and
reflecting only a small percentage of the radiation back into the region
from which it originated.
SUMMARY OF THE INVENTION
Accordingly, it is a primary objective of the present invention to provide
a shielding membrane capable of absorbing a substantial percentage of the
electromagnetic and RFI radiation incident thereupon.
Another object of the invention is to provide a housing suitable for
shielding users from radiation emitted by electronic appliances.
Another object of the present invention is to provide a shielding membrane
that minimizes reflections back to a radiation source.
Another object of the invention is to provide a shielding membrane with a
low radiation transmissivity.
To achieve the foregoing and other objects and in accordance with the
purpose of the present invention, a shielding membrane is provided for
shielding radiation from an electromagnetic radiation source. The
shielding membrane has an incident surface facing the radiation source and
a base surface facing away from the radiation source. The shielding
membrane includes means for minimizing reflection of radiation directed
onto the incident surface of the shielding membrane. Means is also
provided for grounding some of the low frequency electrical components of
the radiation. A conductive deflection layer, formed of a multiplicity of
spaced-apart metallic deflection pads adapted to deflect incident
radiation thereabout, is stacked behind the low frequency grounding means.
A conductive absorption funneling layer is positioned spaced apart behind
the deflection layer in a confronting relationship. The absorption
funneling layer includes a multiplicity of apertures for passing radiation
deflected about the deflection pads. A reflecting plate is placed near the
base side of the absorption funneling layer. The low frequency grounding
means, the deflection layer, the absorption funneling layer and the
reflecting plate are each spaced apart and grounded to facilitate
absorption of various components of the incident radiation. The gaps
between these conductive layers are filled by spacers that are formed of
an absorbing media to maximize radiation absorption. Preferably the
spacers are formed of a high density porous foam.
The low frequency grounding means preferably includes a conductive mesh.
The reflection minimizing means preferably includes a waveguide barrier
having a multiplicity of protrusions facing the radiation emitting source.
The protrusions are preferably pyramidal in shape and the waveguide
barrier is preferably formed of a high density porous foam.
The apertures in the absorption funneling layer preferably have the same
geometry as the deflection pads on the deflection layer. In a preferred
method of construction, the apertures in the absorption funneling layer
are stamped from a metallic foil and the cutout foil materials are used to
form the deflection pads in the deflection layer.
Such a shielding membrane may be used to shield video display terminals,
power supply stations, electronic equipment and the like. Additionally the
walls of buildings and/or rooms, ships, aircraft, and other vehicles that
require data and detection security could be constructed to incorporate
such a shielding device.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention that are believed to be novel are set
forth with particularity in the appended claims. The invention, together
with further objects and advantages thereof, may best be understood by
reference to the following description taken in conjunction with the
accompanying drawings in which:
FIG. 1 is an exploded perspective view of a flat shielding membrane
fabricated in accordance with the present invention.
FIG. 2 is a schematic side view of the shielding membrane shown in FIG. 1
highlighting the travel of an incident wave within the shielding membrane.
FIG. 3 is a front view of a shielding membrane seen in FIG. 1.
FIG. 4 is a schematic of the reflection and transmission characteristic of
a waveguide barrier in accordance with the present invention.
FIG. 5 is a perspective view of the shielding membrane shown in FIG. 1.
FIG. 6 is a side view of the shielding membrane shown in FIG. 1 as applied
to a corner section.
FIG. 7 is a perspective view of a tubular construction of the shielding
membrane.
DETAILED DESCRIPTION OF THE DRAWINGS
As illustrated in the drawings, the shielding membrane 1 of the present
invention includes a waveguide barrier 3, a mesh 5, a deflection layer 7,
an absorption funneling layer 9, a reflecting plate 11, and a plurality of
absorption spacers 15, 15', 15" formed from an appropriate absorption
media. The mesh, the deflective layer, the absorption funneling layer and
the reflecting plate (referred to herein as the conductive layers) are all
formed of highly conductive materials and grounded and spacers 15, 15' and
15" are disposed therebetween to absorb and disperse as much of the
incident radiation as possible. The shielding membrane described is
designed to suppress radiation over an extremely broad frequency range
including high frequency radiation near the visible light spectrum and
extremely low frequency waves.
Referring first to FIG. 1, a preferred embodiment of the present invention
will be described. The shielding membrane 1 has an incident surface 2
facing toward the components that emit radiation sought to be suppressed
and a base surface. Waveguide barrier 3 forms the incident surface 2 of
the shielding membrane 1. The waveguide includes a plurality of pyramid
shaped protrusions that face toward the radiation emitting source (not
shown). The shape of the protrusions may be varied somewhat, although they
are intended to minimize radiation reflections from the incident surface
of the shielding membrane 1 as described below with relation to FIG. 4.
The waveguide barrier is formed from a radiation absorbing material
preferably having micropores dispersed therethrough. The micropores are
used advantageously to disperse radiation within the shielding membrane 1
which enhances the likelihood of absorption.
A mesh 5 formed of a highly electrically conductive material such as a
conductive plastic or metal is disposed behind the waveguide barrier 3. By
way of example, suitable metals include copper, aluminum, steel,
conductively coated nylon or polyester, etc. Suitable plastics include
foam and composites. The mesh is grounded and as will be appreciated by
those familiar with antenna theory, the mesh will appear as a grounding
plate to low frequency radiation. Therefore, a substantial percentage of
the low frequency radiation incident upon conductive mesh 5 will be
absorbed thereby. To secure the conductive mesh 5 in place, waveguide
barrier 3 may be provided with and adhesive backing which adheres to the
mesh 5. By way of example, a suitable adhesive is a 9000 Series type
adhesive manufactured by 3M Company of St. Paul, Minn.
A deflection layer 7 formed of a plurality of electrically conductive
deflection pads 21 is disposed on the base side of spacer 15. A spacer 15
formed of a radiation absorbing medium is disposed between the mesh 5 and
the deflection layer 7 to separate the deflection layer and maintain a
suitable distance therebetween. It should be appreciated that the actual
spacing may be widely varied. By way of example, a 1/8" separation is
appropriate. The deflection pads 21 are in electrical contact with one
another and are suitably grounded. The electrical contact may be
maintained by any suitable means including a conductive copper tape or a
wire mesh. The deflection layer 7 is preferably formed of a metallic
material such as copper, aluminum, stainless steel or nickel, (although
other conductors are appropriate). The actual size of the deflection pads
may be widely varied although, as explained below, they should be sized
such that the expected incident radiation will deflect thereabout. The
deflection pads may take any geometric shape. By way of example, a
circular shape has been found to work well. Further by way of example, 2
cm. diameter disks work well for most applications. The deflection pads 21
must be spaced apart to work effectively. Experimentation has shown that a
spacing of approximately one-fourth the disk diameter works well. Thus,
for the 2 cm. diameter disks described above, a 0.5 cm. spacing works
well. However, it should be appreciated that the actual size, shape and
spacing of the deflection pads 21 may be widely varied. The actual size of
the pads chosen for a particular function may be, in part, dependent on
the wavelength of radiations sought to be suppressed.
Absorption funneling layer 9 includes a plurality of apertures 25 and is
spaced apart from the deflection layer 7 on its base side. A second spacer
15' is disposed between the deflection layer 7 and the absorption
funneling layer 9 to maintain the desired spacing. The spacing between
absorption funneling layer 9 and deflection layer 7 is chosen to allow
radiation deflected about the deflection pads 21 to recombine such that a
substantial percentage of such radiation will regroup and pass through
apertures 25. By way of example, a suitable separation is at least 1/8".
A reflecting plate 11 is positioned on the base side of the absorption
funneling layer 9 with an appropriate spacer 15" disposed therebetween.
The purpose of the reflective layer 11 is to reflect any incident
radiation that is not absorbed thereon. The deflection layer 7, absorption
funneling layer 9 and reflective plate 11 cooperate to trap entering
radiation between the deflection layer and the reflective plate. A
substantial portion of the trapped radiation is reflected back and forth
between deflection layer 7 and the reflective plate until it is ultimately
absorbed. Mesh 5, deflection layer 7, absorption funneling layer 9 and
reflective plate 11 are all connected to appropriate grounds which may
take the form of a common ground.
The spacers 15, 15' and 15" are all formed of a radiation absorbing media.
As with the waveguide, desirable spacer properties include the ability to
effectively absorb and disperse radiation incident thereon. A wide variety
of suitable radiation absorbing materials are known to the art and, by way
of example, a high density porous foam felt, fiberglass and the like all
work well. Indeed, the spacers may be formed of either conductive or
nonconductive material. By way of example, Soundfoam, manufactured by
Soundfoam of Los Angeles, Calif. works well. The deflection pads, the
absorption funneling layer and the reflective plate 11 are all preferably
stippled to enhance defraction of radiation within the shielding membrane.
It will be appreciated that defraction and dispersion of radiation within
the shielding membrane increases the distance any particular wave must
travel within the shielding membrane thereby increasing the likelihood
that the wave will be absorbed and reducing the probability that the wave
will be reflected back towards the source of electromagnetic radiation or
transmitted through the shielding membrane.
Two of the principle objectives of the shield are to minimize reflections
and to minimize transmissivity. Therefore, most of the incident radiation
must be either absorbed or grounded by the shielding membrane.
Conceptually, the shielding membrane 1 is broken down into several
distinct regions. The first region (which comprises waveguide barrier 3)
insures that, radiation incident on the shielding membrane is not
reflected back towards the source of EM radiation. It is important to
minimize the reflection of radiation back towards the source since such
radiations may appear as noise to the source. The waveguide barrier 3, as
well as the spacers 15, are formed from a media that absorbs and disperses
radiation passing therethrough. Dispersion of the radiation is important
since it statistically increases the likelihood that incident radiation
will be either absorbed or grounded within the shielding membrane.
Therefore, the waveguide barrier acts as both an initial reflection
minimizing zone and as an absorption and dispersion zone.
Referring next to FIG. 2, the travel of waves that have entered through
waveguide barrier 3 will be described. The mesh 5 acts as a grounding zone
for low frequency radiation. As will be appreciated by those familiar with
antenna design a wire mesh will effectively ground much of the incident
low frequency radiation. Higher frequency radiation (and lower frequency
radiation that escapes the mesh) passes through an absorption spacer into
a trap region comprising the deflection layer 7, absorption funneling
layer 9, and reflecting plate 11. The intent of the trap region is to
"capture" a substantial portion of the incident radiation behind the
deflection and preferably the absorption funneling layer to ensure that it
is absorbed rather than reflected back towards the radiation source or
transmitted outside the shield.
Some of the radiation directed towards the deflection pads 21 will actually
strike the pads and become grounded. However, most radiation will be
diverted about the grounded metallic deflection pads. Thus, the deflection
pads create a deflection zone 41. Radiation that passes through the
deflection zone 41 travels into a funneling zone 43 which directs the
radiation through apertures 25 in absorption funneling layer 9. The
radiation tend to regroup after it passes the deflection pads and pass
through the apertures 25 in absorption funneling layer 9. Such regrouping
is important to the function of the trap, since the intent is to have
radiation deflected about the deflection pads 21 pass through the
apertures 25. Therefore, it is important that the absorption funneling
layer be spaced far enough behind the deflection pads to allow the
radiation to regroup and divert through the apertures 25. Radiation that
does not pass through the absorption funneling layer will be defracted and
will tend to bounce back and forth between deflection pads 21 and
absorption funneling layer 9 until it either bounces through an aperture
25 or is absorbed by the conducting layers 7 and 9 or the adjacent
spacers. The deflector pads need not be lined up with the apertures of the
funneling layer for proper absorption to take place. This is particularly
true in cases where the incident radiation is not perpendicular to the
membrane. It should be appreciated that radiation escaping the trap region
will likely be absorbed by mesh layer 5, its adjacent spacers, or
waveguide barrier 3.
After passing through the funneling zone the waves pass into a second
absorption zone disposed between the absorption funneling layer and the
reflecting plate 11. The intent is to trap as much of the radiation as
possible between the reflective plate 11 and the deflection layer 7 and to
cause the radiation trapped therein to bounce back and forth between the
reflecting plate and the absorption funneling layer until it is absorbed.
The described construction proves to be very effective at retaining
radiation within the second absorption zone long enough for it to be
either absorbed by spacer 15 or grounded by one of the conductive layers.
It will be appreciated that some radiation will actually be absorbed and/or
dispersed by waveguide 3 and spacers 15 and 15'. Additionally, some
radiation will be grounded by deflection layer 7 or by striking the front
surface of the absorption funneling layer.
Referring next to FIG. 3, the waveguide barrier 3 will be described. The
waveguide includes a plurality of pyramid shaped protrusions 32 that face
toward the radiation emitting source (not shown). The shape of the
protrusions may be varied somewhat, although they are intended to minimize
radiation reflections from the incident surface of the shielding membrane
1. The waveguide barrier 3 is formed from a radiation absorbing material
preferably having micropores dispersed therethrough. The micropores are
used advantageously to disperse radiation within the shielding membrane 1
which enhances the likelihood of absorption. A wide variety of suitable
radiation absorbing materials are known to the art and by way of example,
a high density porous foam works well for this purpose. A suitable high
density foam is Soundfoam, manufactured by Soundfoam of Los Angeles,
Calif. Other suitable materials include felt, fiberglass and the like.
Referring next to FIG. 4, the reflection and transmission characteristics
of a waveguide barrier 3 constructed in accordance with the present
invention will be described. As indicated above, the waveguide barrier
includes a multiplicity of pyramidal shaped protrusions that face the
radiation emitting source. Such a shape reduces the likelihood of
reflecting radiation back toward the radiation source. The pyramidal
geometry facilitates increased absorption since radiation reflected off of
the incident surface 2 is likely to be reflected toward another portion of
the waveguide barrier 3 wherein it may be absorbed on its second or third
contact. The advantages of such a construction is well known to the prior
art. It is important to minimize reflections since such radiation
constitutes noise which in many circumstances can be extremely problematic
for the electronics.
Referring next to FIGS. 5 and 6, the interconnection of membrane sections
and the formation of corners will be described. Membrane sections may be
interlinked by using continuous conducting layers including conductive
mesh 5, deflection layer 7, absorption funneling layer 9 and reflective
layer 11. The waveguide barrier and the spacers may be sized appropriately
to conform to the walls of a housing. To form a corner, two adjoining
sections are bent upon another as shown in FIG. 6 such that the respective
waveguide barriers 3 contact one another. Such a continuous construction
minimizes the possibility of both reflection back toward the electrical
components and emissions of radiation from the appliance. As is
schematically illustrated in FIG. 5, each of the conducting layers may be
joined to a common ground. On membrane structures under 1/2" in aggregate
sandwich thickness, the spacers do not have to be cut for corner bending
as long as they stretch sufficiently to accommodate the extra distance
required.
The sandwich construction described may be manufactured in a laminated
form, as individual components or in other suitable forms. In one of the
preferred embodiments, a metallic foil sheet may be used to form
absorption funneling layer 9, with the apertures 25 being punched
therefrom. The punched portions of the metallic foil may be used to form
the deflection pads 21. Thus, conceptually, the stamped portions of the
absorption funneling layer are moved forward and electrically connected by
suitable means such as copper or other conductive tape or wire.
Referring next to FIG. 7, the shielding membrane may be fabricated in a
tubular construction. Such a tubular configuration lends itself ideally to
the shielding of power lines, conduits and the like.
By way of example the application of a shielding membrane to the plastic
casing walls of a video display terminal will be described. A thin layer
of adhesive is applied to the back surface of the reflecting plate as
uniformly as possible. The shielding layer is then adhered to the casing
wall. Alternatively, the shielding membrane 1 may be integrated into the
housing of an electrical appliance.
Although only one embodiment of the present invention has been described in
detail, it should be understood that the present invention may be embodied
in many other specific forms without departing from the spirit or scope of
the invention. Particularly, it should be appreciated that additional
absorption or grounding layers could be added to further reduce
reflections or transmissivity. Similarly, multiple defraction/absorption
funneling component pairs may be added to improve the efficiency of the
shielding membrane. It should also be appreciated that there are a wide
variety of materials that can be used for each of the components. For
example, the waveguide barrier and spacers may be formed from high density
foams, felt, fiberglass or even particle board. The various conducting
layers should all be highly conductive, such as metal mesh and foils.
Copper, nickel, steel and aluminum are good examples. In an application
designed specifically for shielding X-rays, the conductive layers 5, 7 9
and 11 may be formed of lead. Such a construction would greatly reduce the
weight of conventional shielding aprons necessary to protect against
X-rays. It will be appreciated that the multi-layer structure of spaced
conductive layers obviates the need for an individual conductive barrier
layer that is very thick as is commonly necessary in conventional single
layer X-ray barriers.
Additionally, it will be understood by those skilled in the art that a
shielding membrane as disclosed herein has many applications beyond
housings for cathode ray tubes and electronic components as described
herein. For example, such a shield arrangement could be built into the
walls of power stations to reduce the fields generated therein. Further,
installations which have concerns about the security of data may include
walls formed with the described shielding membrane to prevent the escape
of radiation. Similarly vehicles and installations can be shielded from
electronic jamming with such a membrane. It should also be appreciated
that the shielding membrane of the present invention may be used to
attenuate certain electromagnetic fields. This is accomplished by
suppressing the electrical components of such fields. Therefore, the
present examples of embodiments are to be considered as illustrative and
not restrictive, and the invention is not to be limited to the details
given herein, but may be modified within the scope of the appended claims.
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Description |
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