Gas separation – Combined or convertible – In motor vehicle
Reexamination Certificate
2002-03-26
2004-08-10
Pham, Minh-Chau T. (Department: 1724)
Gas separation
Combined or convertible
In motor vehicle
C055S385100, C055S473000, C055S481000, C055S314000, C362S229000, C353S013000, C128S126100
Reexamination Certificate
active
06773477
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the purification of air, particularly in the passenger cabins of motor vehicles, but also in hospitals, nursing homes, other health care environments, and industrial environments, and especially to the use of a plurality of packed bed filter media packets and a HEPA filter placed in a predetermined sequence within a portable air purifier that can be placed as a console/arm rest at selected locations within a motor vehicle cabin, or by some adaptation in a vehicle trunk or bed of a pickup truck, or placed in any of such other environments, and in the case of a vehicle the air purifier operates independently of the vehicle ventilation system.
2. Description of the Prior Art
The literature in the field of Indoor Air Quality (IAQ) may use the term “ambient air” to refer to the air within an indoor room, while in the context of air quality generally the term often refers to “outside air.” For clarity, the term “ambient air” is used herein in the latter sense, and the air within the motor vehicle cabin that is to be purified is referred to as “cabin air,” although that cabin air will of course be continually supplied with “outside” or “ambient” air by virtue of the vehicle ventilation system, open windows, or the like. More specifically, “ambient air” herein means that air through which the vehicle is being driven.
Considerable effort has been directed toward reducing air pollution inside the cabin of motor vehicles. With hundreds of different kinds of air pollutants around and inside motor vehicles traveling on congested highways, this is no easy task. Most of this effort has targeted dust, pollen, and some odors. Vehicle manufacturers in Europe, Japan and the USA now offer air filtration subsystems for the passenger cabins of some of their new automobiles. These subsystems are typically placed within the ventilation system of new cars and serve as gross particulate filters. Some of these subsystems also have small amounts of activated carbon to reduce odors. These ventilation subsystems are intended to capture particles that are 3 to 8 microns in diameter and larger, but they are not designed to reduce substantially the extensive fine (2.5 micron in diameter and smaller) particulate matter over any extended period of time.
Some of the particulate filters now being installed in the ventilation systems of new cars use electrostatic non-woven filter media. The electric charges on these media help to capture fine particulate matter; however, as the filter media fills, the charge and thus the effectiveness of such media are diminished. The majority of particles by number that appear in the cabin air environment in fact fall within the size range of less than one micron in diameter. These submicron particles are not effectively reduced by current ventilation subsystem designs, but yet they present the greatest health hazard to human beings since they penetrate deeply into the respiratory tract. Also, placement of filters that contain activated carbon within ventilation system does capture some gases, but with no specific standard of effectiveness for individual gases, the object seemingly being simply that of reducing “odors” for purposes of customer satisfaction, but with little or no thought being given to the reduction of any identified pollutants. One major limitation inherent in such systems also is that they have been designed to minimize pressure drop in order to maintain a strong flow of air, for purposes of heating or cooling, but as a result any actual fine particle purification of the air being circulated becomes minimal.
Some inventors have proposed stand-alone cabin air filter systems that are to be permanently mounted in the trunk, the rear window deck, or the ceiling (head liner) of automobiles. Again, most of these proposed systems are designed as gross particulate filters, with small amounts of activated carbon added to reduce smoke and generic odors. These, too, have had little or no capacity to rapidly filter and re-circulate cabin air. Some of these devices are small electronic air cleaners that target fine particulate matter, but also have the potential for generating ozone, itself a pollutant. Such devices also require frequent cleaning to prevent arcing and to minimize ozone production.
In most cases, the stand-alone devices of the prior art have had insufficient air flow to reduce substantially the continuing flow of pollutants that comes into the vehicle cabin through the ventilation system, and through leakage around doors and windows. No device heretofore proposed is portable, re-circulates cabin air at effective rates of cubic meters per minute (m
3
/min) or the corresponding cubic feet per minute (CFM), and employs a specific sequence of filters that has been especially designed to remove specific pollutants, including fine particulate matter, lead, carbon monoxide, ozone, sulfur dioxide, nitrogen dioxide, benzene and other hydrocarbons. A number of the filters used in the invention are of the packed bed type, which type has a long history with respect to purifying air in buildings, but to the inventor's knowledge, there have been no successful attempts to adapt the packed bed technology to cabin air purification. Also, no prior art device intended for vehicle cabin air purification that is known to this inventor has targeted the specific air pollutants for which the EPA or other agencies have established ambient air quality standards, with the goal of reducing the concentration levels of those pollutants at least to below the defined health standards. This seems to have resulted (a) from not being aware until the last several years of the high levels of pollutants that are actually found in a vehicle cabin while driving through crowded urban streets; and (b) from emphasizing in research what particular vehicle manufacturers were doing about cabin air pollution rather than on what needed to be done if those high levels of pollution were to be reduced. Perhaps most significantly, the inventor is aware of no prior test data, such as those reported herein, in which an air purifier was installed in a vehicle that was then driven through the streets, while collecting air quality measurements both with the purifier operating and with it not operating, so that by comparison of those data a practical measurement of the efficacy of the purifier could be established.
Particular patents known to the inventor that relate to air purification, especially in the cabins of motor vehicles, will now be described. U.S. Pat. No. 3,722,182 issued Mar. 27, 1973 to Gilbertson touches on the use of an air filtering device mounted on the rear window deck of an automobile and functions independently of the heater/air conditioner/air intake (plenum) system of the vehicle. (An alternative embodiment that connects directly to the air intake of the vehicle is also described.) For removal of particulate matter, the device employs electrostatic plates, although in the more recent state of the art it is known that HEPA filters better serve that purpose, and do not require the frequent cleaning or replacement that is necessary for electrostatic systems.
U.S. Pat. No. 3,883,637 issued May 13, 1975 to Benedict describes an activated charcoal filter element having dispersed mixtures of copper and chromium oxides, chromates, dichromates and the like for purposes or removal of H
2
S and catalytically, similar air-borne sulfur compounds such as mercaptans, organic sulfides, thiophene compounds, thioethers and organic sulfoxides.
U.S. Pat. No. 3,870,495 issued Mar. 11, 1975 to Dixson, et al., describes the use of non woven fibers of wood, paper, hemp and the like to avoid having periodic gaps in the material as is characteristic of woven fabrics. Secondly, the filters are used in multi-layer or laminated form so as to block any gaps that might occur by way of manufacturing imperfections with respect to particular pieces of fabric.
U.S.
Brown, P.C. Glenn C.
Pham Minh-Chau T.
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