Air filter

Details Air filter Air filter

1999-01-04

2001-01-09

Barry, Chester T (Department: 1724)

Gas separation

Combined or convertible

Involving shielding apparatus

C055S471000

Reexamination Certificate

active

06171357

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to air filters in general and, in particular, to air filters with electromagnetic interference protection properties.
BACKGROUND OF THE INVENTION
Much electronic equipment is required to operate in environments where the air can pick up dust, lint, and other airborne impurities. If these contaminants are permitted to enter the cooling air passages, they might plug up the openings and reduce the air flow, causing overheating of the electronics. To prevent this from happening, air filters are often used. These air filters typically include a layer of demembraned polyurethane, paper, metal, or other plastic material woven or knitted and formed in an egg-crate or repeated pyramid shape.
In addition, in many telecommunications applications, the equipment also requires electromagnetic interference (EMI) protection, also known as RF shielding. These EMI protection devices generally include a metallic material mounted in a frame and inserted in the electronic enclosure.
When both characteristics of dust screening and RF filtration are required, two separate elements are installed, a metallic RF filter and an air filter to trap particulates. Alternatively, these devices can be formed of, for example, layers of corrugated aluminum mesh, which are so aligned to act as an air filter, or layers of crimped or expanded aluminum alloy. In this case, several layers of metallic material of differing aperture size, shape and spacing are required to be mounted in a frame for insertion into the electronic enclosure.
These prior art devices are relatively large in volume, need high maintenance, and are costly to produce.
Accordingly, there is a long felt need for a simple air filter with EMI protection properties.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a combined air filter and EMI shield including an air filter formed of a conducting metal thread mesh.
According to one embodiment of the invention, the metal thread is woven or knitted to form the filter.
According to a preferred embodiment of the invention, the air filter is formed into an egg-crate or repeated pyramid shape.
Further according to a preferred embodiment, the mesh size of the air filter is selected in accordance with electromagnetic interference and air flow requirements.
There is also provided, in accordance with the present invention, a method for providing EMI shielding to an enclosure including the steps of forming a combined air filter and EMI shield of a conducting metal thread mesh, and mounting said combined air filter in the enclosure.


REFERENCES:
patent: 4553499 (1985-11-01), Crone
patent: 4559249 (1985-12-01), Arigaya
patent: 5431974 (1995-07-01), Pierce
patent: 5506047 (1996-04-01), Hedrik
patent: 5680294 (1997-10-01), Stora
patent: 6018125 (2000-01-01), Collins

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