Information
-
Patent Grant
-
6672902
-
Patent Number
6,672,902
-
Date Filed
Wednesday, December 12, 200122 years ago
-
Date Issued
Tuesday, January 6, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 174 35 R
- 439 607
- 361 816
- 361 818
-
International Classifications
-
Abstract
A system includes a chassis having at least one wall, the chassis housing electrical components and a layer of flexible foam electromagnetic interference (EMI) emission absorption material covering an interior surface of the wall. A system also includes a chassis containing slots, the chassis housing electrical components and a layer of flexible foam electromagnetic interference (EMI) emission absorption material covering at least one of the slots.
Description
FIELD OF THE INVENTION
This invention relates to reducing electromagnetic interference (EMI) emissions.
BACKGROUND
During the operation of computers, or other similar electronic components, electromagnetic interference (EMI) emissions, or radiation, are generated by motors, drives, processors, chips and circuits. One way to contain these emissions is to surround the circuit in a metal panel. Further, in some situations, these emissions must be contained in order to comply with certain regulations.
DESCRIPTION OF DRAWINGS
FIG. 1
is a block diagram of a first embodiment.
FIG. 2
is a block diagram of a second embodiment.
FIG. 3
is a block diagram of a third embodiment.
FIG. 4
is a block diagram of a fourth embodiment.
DETAILED DESCRIPTION
Referring to
FIG. 1
, a computer
10
includes a metal or plastic chassis
12
in which a motherboard
14
is mounted. A chassis is the physical frame or structure of a computer that houses the main electronic components, including the motherboard
14
with places (not shown) to insert or replace microchips for the main and possibly specialized processors and random access memory (RAM) and places for adding optional adapters like audio or video capabilities, for example. Typically, room is also provided for a hard-disk drive and a CD-ROM drive. A processor
16
is connected to the motherboard
14
. A number of memory devices or modules
18
and two input/output (I/O) devices
20
are also mounted to the motherboard
14
. Two buses
16
a
and
16
b
are also provided on the motherboard
14
and connect the processor
16
to the memory modules
18
and to the input/output devices
20
, respectively. A power supply
22
is connected to the motherboard
14
and a pair of cable assemblies
24
a
and
24
b
connect the motherboard
14
to a hard drive unit
26
and a disk drive
28
. Other components (not shown), electrical traces, electrical circuits and related devices may also be provided in the chassis
12
.
At least part of the interior walls of the chassis
12
is covered with a layer
30
of electromagnetic interference (EMI) emission absorption material. The layer
30
is affixed to the interior walls of chassis
12
and absorbs electromagnetic emissions. For example, in a personal computer where the chassis
12
may be expected to provide 6 dB attenuation of EMI emission, the layer
30
can absorb 6 dB of the EMI emission. In another example, the layer
30
can protect sensitive components in a wireless device from emissions from circuitry or transmitting antenna. Rather than containing EMI emissions, the layer
30
absorbs the EMI emissions. One or more layers of EMI emission absorption materials can easily be applied to all computer-type systems, such as work stations, desktop computers, servers, as well as any electronic device, such as personal data assistants (PDAs), wireless devices, internet tables, game consoles and peripherals.
Referring to
FIG. 2
, the layer
30
is shown attached to an interior of a side panel
32
of the chassis
12
. An adhesive is used to bond the layer
30
to the side panel
32
during manufacturing and assembly of the chassis
12
and sized to the dimensions of the interior portion of the side panel
32
of the chassis
12
. No electrical grounding is required. The layer
30
may be fabricated in a variety of thicknesses to cover a wide range of EMI emission ranges. For example, the layer
30
may be constructed as a lightweight, flexible, low density, and high-loss foam. Thickness may range, for example, from 0.01″ to 1.0″, and densities may range, for example, from 0.05 to 5.0 pounds per cubic foot, however the thickness and densities are not limited to these values. The layer
30
may be single layer, multilayer, weatherproof, reticulated and or rigid. Suitable EMI emission absorber material is supplied, for example, by R+F Products of San Marcos, Calif. and ARC Technologies of Amesbury, Mass.
Referring to
FIG. 3
, in another approach, the chassis
12
may be fitted with a molded, i.e., rigid, EMI emission absorption panel
34
that replaces a metal or plastic panel of FIG.
1
. The panel
34
is, for example, a reticulated foam with a continuously graded lossy coating produced using a two part closed cell polyurethane filler to provide structural integrity. Thus, rather than bonding a layer
30
to the interior walls of the chassis
12
, the front panel
34
replaces the front wall of the chassis with a rigid material capable of EMI emission absorption.
Referring to
FIG. 4
, in still another approach, the chassis
12
includes a front panel
40
of rigid EMI absorption material and two side panels
42
a,
42
b
of rigid EMI absorption material. A back panel
44
has attached on an interior surface
46
a panel
48
of flexible EMI absorption material.
In other examples, one or more of the interior and/or exterior metal or plastic walls of the chassis
12
are replaced with solid molded EMI emission absorption panels. Use of the molded EMI emission absorption panels also provides thermal venting since it is porous and not impermeable. Further, combining a different EMI emission absorption material in a single panel or layer covers a very wide frequency band.
In still other examples, layers of EMI emission absorption materials are used to line internal bays within the chassis, like, for example, a bay in which the power supply
22
resides.
In another example, where slots are common in computer peripherals for assembly and thermal reasons, radiation from these slots may cause EMI problems. Layers of EMI emission absorption materials are used to suppress EMI around slots in computer peripherals, such as CD-ROMs, DVDs, CD-RWs and floppy/disk drives.
Other embodiments are within the following claims.
Claims
- 1. A system comprising:a chassis having at least one wall, the chassis housing electrical components; and a layer of flexible, lightweight, low density, high-loss foam electromagnetic interference (EMI) emission absorption material covering an interior surface of the wall, the material having a thickness of 0.01″ to 1.0″ and a density of 0.05 to 5 pounds per cubic foot.
- 2. The system of claim 1 wherein the layer comprises a single layer of lossy foam.
- 3. The system of claim 1 wherein the layer comprises multiple layers of lossy foam.
- 4. The system of claim 1 wherein the layer comprises a layer of weatherproof lossy foam.
- 5. The system of claim 1 in which the layer covers all walls within the chassis.
- 6. The system of claim 1 in which the layer covers more than one wall within the chassis.
- 7. The system of claim 1 in which another wall is made entirely of a rigid EMI emission absorption material.
- 8. Apparatus comprising:an electrical chassis, at least one rigid reticulated foam with a continuously graded lossy coating produced using a two part closed cell polyurethane filler connected to a plurality of non-shielded walls.
- 9. Apparatus comprising:panels joined to form a chassis; at least one bay located within an interior of the chassis, the bay having at least one wall; and a layer of flexible, lightweight, low density, high-loss foam EMI emission absorption material affixed to an interior surface of the wall of the bay, the material having a thickness of 0.01″ to 1.0″ and a density of 0.05 to 5 Pounds per cubic foot.
- 10. The apparatus of claim 9 in which a second wall is constructed from a rigid foam EMI emission absorption material.
- 11. An enclosure comprising:a front panel constructed from a rigid reticulated foam with a continuously graded lossy coating produced using a two part closed cell polyurethane filler and joined to two side panels, an upper panel and a lower panel; and a rear panel joined to the two side panels and upper and lower panels.
- 12. The enclosure of claim 11 in which the two side panels are constructed of a rigid reticulated foam EMI emission absorption material.
- 13. The enclosure of claim 11 in which the upper and lower panels are constructed of a rigid reticulated foam EMI emission absorption material.
- 14. The enclosure of claim 11 further comprising internal bays having walls lined with a flexible foam EMI emission absorption material.
- 15. The enclosure of claim 11 further comprising internal bays having walls constructed of a rigid reticulated foam EMI emission absorption material.
- 16. A method comprising:forming a front panel from a rigid reticulated foam with a continuously graded lossy coating produced using a two part closed cell polyurethane filler; and joining the front panel to a top and bottom panel, two side panels and a back panel.
- 17. The method of claim 16 further comprising:providing internal bays having metal walls; and covering the metal walls with a first layer of flexible foam EMI emission absorption material.
- 18. The method of claim 17 further comprising covering the metal walls with a second layer of foam EMI emission absorber material.
- 19. The method of claim 16 further comprising covering an interior side of the top and bottom wall with a flexible foam EMI emission absorption material.
- 20. The method of claim 16 further comprising covering an interior surface of the back panel with a flexible foam EMI emission absorption material.
- 21. The method of claim 16 further comprising covering an interior surface of the two side panels with a flexible foam EMI emission absorption material.
- 22. A system comprising:a chassis containing a plurality of slots, the chassis housing electrical components; and a layer of flexible, lightweight, low density, high-loss foam electromagnetic interference (EMI) emission absorption material covering at least one of the slots, the material having a thickness of 0.01″ to 1.0″ and a density of 0.05 to 5 pounds per cubic foot.
- 23. The system of claim 22 wherein the layer comprises a single layer of lossy foam.
- 24. The system of claim 22 wherein the layer comprises multiple layers of lossy foam.
- 25. The system of claim 22 wherein the layer comprises a layer of weatherproof lossy foam.
- 26. The system of claim 22 in which the layer covers more than one slot.
US Referenced Citations (24)