Gas separation: processes – Electric or electrostatic field
Reexamination Certificate
1999-12-06
2002-04-30
Chiesa, Richard L. (Department: 1724)
Gas separation: processes
Electric or electrostatic field
C055S385200, C095S058000, C095S078000, C096S016000, C096S224000, C361S226000
Reexamination Certificate
active
06379427
ABSTRACT:
BACKGROUND OF THE INVENTION
Attempts to protect the human body or surfaces contacted by the human body from various airborne contaminants have taken many forms. Considerable use has been made of air purifiers to remove macroscopic contaminants. For this purpose, air ventilation systems in enclosed areas such as buildings generally include an air filter and/or an electrostatic precipitator. However, it is well known in the art, that while the quantity of contaminants that reach the space to be protected can be reduced by such means it is not possible to completely preclude the entry of small airborne contaminants having a diameter less than 10 &mgr;m, such as bacteria, viruses and the like. As a consequence of ineffective air purification, harmful airborne agents are disseminated throughout the enclosed area and come into contact with exposed surfaces.
In order to overcome the problems associated with small airborne contaminants, filters have been developed with micron sized pore openings. However, due to the small nature of the pore openings these filters became clogged in a short period of time. In order to overcome this problem, an electrostatic charge has been applied to the surface of such filters for repelling particles rather than entraining them in the filtering medium. As an example, U.S. Pat. No. 5,863,312 describes a face mask for covering a wearer's mouth, nose or both, with a single layer of non-entraining filter medium which may have an electrostatic charge applied to it for rejecting particulate matter rather than catching or entraining it. In addition, U.S. Pat. No. 5,492,551 describes a similar means for filtering air by electrostatic rejection.
U.S. Pat. Nos. 5,863,312 and 5,492,551 do not describe a method and apparatus for imparting some or substantially all of the airborne agents with a repellent charge. In the operation of the method and apparatus of these inventions, the air to be purified contained substantial amounts of: (1) uncharged airborne agents; (2) airborne agents with a repellent charge; and (3) airborne agents having an attracting charge with respect to the filter or mask. As such, not all of the airborne agents can be repelled away from the filter or mask. Therefore, the pore size of the filter medium was made to be smaller then the airborne agents for collecting them. In addition, in the use of the method and apparatus of these inventions, naturally occurring oppositely charged particles contained in the particulate laden air are attracted to and also accumulate on the electrostatically charged filter medium. The accumulation of both the neutral and charged particulate matter both clogs the pores of the filter and reduces the efficiency of repulsion by reducing or screening the electrostatic charge on the filter.
Another filtering system that used both rejection and collection of charged agents on a filter is given in U.S. Pat. No. 5,468,488. This patent describes a method and apparatus for restricting the flow of airborne contaminants into a nasal passage. In the operation of the method of U.S. Pat. No. 5,468,488 a spray solution is sprayed onto or around the nasal passages for providing for an electrostatic field. As with the two previously mentioned patents, it involves creating an electrostatic field that either repels or attracts airborne contaminants or both but does not provide for a method and apparatus for electrifying airborne agents with a repellant charge.
Other methods used in the past to shield humans from airborne contaminants have included the use of gas curtains and physical barriers such as surgical garments and masks. An example of the use of air curtains as protective shields is given in U.S. Pat. Nos. 4,140,105 and 4,471,688.
Currently, surgical garments and masks are used as the primary protection for operating room personnel. Surgical garments and masks are not intended to, and do not prevent, the spread of harmful substances and biogenic materials to all parts of the general operating room environment and do not protect certain parts of the practitioner. For example, such equipment often does not protect the eyes and other exposed parts of the body of operating room personnel from contact with fluids in the form of airborne aerosols including bone particles and liquids from direct sprays, streams, or splashes of liquids. Surgical garments that completely cover the body such as those that resemble astronaut's space suit protect only the person wearing it and provide no protection to others in the room against airborne agents. The production of such airborne agents in medical facilities can cause contaminants to come into contact with the mucus membranes of the medical staff. Airborne agents of this type can contain live virus, including AIDS virus, when such is present in the patient. Accidental contamination with airborne aerosols of blood and body fluids of patients having other diseases, such as hepatitis B, may also be communicated by such a mechanism.
When using surgical equipment, the operator often must be able to move in many directions to get the correct point of contact or leverage to use the equipment. Conventional barriers, whether physical or air curtain often limit visibility and/or mobility and/or expose the operator to airborne contaminants. In particular, when using surgical and dental equipment, a medical practitioner must often work between the vacuum source or physical barrier and the operating site, thus exposing the practitioner to infection.
Non-shielding methods used in the past to protect humans from airborne contaminants have included the use of vacuums as described in U.S. Pat. Nos. 3,537,447 4,650,171 and 5,215,539.
Vacuum devices positioned on the instrument itself typically limit the area of protection, as the vacuum only draws in air from the area nearest to the tool. Finally, vacuum devices currently in use and having self-contained vacuum source are often limited in application, as such devices incorporate no means for the containment, destruction, or safe evacuation of contaminants. Such devices are inappropriate for protection from hepatitis and AIDS, as those viruses are dangerous in low concentrations and could be carried to remoter sites by an evacuation system that does not remove contaminants from the gas stream.
In many medical situations open wounds, ulcers, and burned tissue are exposed to airborne agents. As such, wounds and skin ulcers can become contaminated by airborne microorganisms, both pathogenic and non-pathogenic types. Wounds that are heavily contaminated by microorganisms, but not clinically infected, are often characterized by a prolonged period of inflammation as well as a delay in wound repair and healing.
Present shielding systems and other methods for protecting humans from airborne contaminants are inadequate for removing all of the pathogen carrying aerosols produced in a medical procedure. Current air purifiers do not remove bacteria and viruses and provide no protection at all against airborne contaminants in spaces where airborne contaminants are produced, such as medical and dental consultation rooms, operating rooms and the like.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide for a method and apparatus for protecting an exposed surface contained in an enclosed space from harmful airborne agents that may be unintentionally produced.
It is another object of the present invention to provide for a method and apparatus for maintaining a repellant charge on an exposed surface for repelling oppositely charged particles.
It is still another object of the present invention to provide for a method and apparatus for collecting and destroying harmful airborne agents.
It is a further object of the present invention to provide for a method and apparatus for confining potentially harmful airborne agents to the smallest area possible and thus, minimize its dissemination and ultimate spread to other areas or to humans.
It is a still further object of the present invention to provide an improved method of and apparatus for shieldin
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