Gas separation – With gas flow effecting means – Impeller within or proximate to space encompassed by...
Reexamination Certificate
2000-08-31
2002-06-04
Hopkins, Robert A. (Department: 1724)
Gas separation
With gas flow effecting means
Impeller within or proximate to space encompassed by...
C055S496000, C096S223000
Reexamination Certificate
active
06398835
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to filtration systems and devices, and more specifically to an air filtering device which is removably attachable to a conventional portable electric fan. The present device essentially comprises a filtering element which fits against the back of the fan guard, with a generally toroidally shaped shroud attaching to the periphery of the fan guard at the rear of the fan to guide air past the motor and through the filter.
2. Description of the Related Art
In recent years, people have become more aware of various airborne impurities which are commonly found in indoor environments in the home, office, and other locations. Such impurities range from secondhand tobacco smoke to asbestos dust and other less hazardous materials. Many such hazards, such as those two noted specifically above, are considered to be sufficiently dangerous that indoor smoking has been banned in most areas of the country and considerable sums of money have been spent on asbestos cleanup.
Nonetheless, other undesirable airborne impurities in the form of dust, pollen, etc., generally circulate in most indoor environments, even with centralized filtration systems associated with conventional central heating and air conditioning systems. Accordingly, various systems and devices have been developed in the past in attempts to filter or clean the ambient air within a relatively small localized area, such as a room or individual office space. These devices and systems have generally not provided the efficiency and economy desired in such devices, for various reasons noted further below.
Accordingly, a need will be seen for a filtering device for attaching to the back of a conventional portable electric fan, for guiding air through the back of the fan and for filtering air as it passes through the fan guard to be expelled from the front of the fan. The present air filtering device generally comprises a toroidally shaped solid shroud which may be removably attached to the back of the fan guard to surround the motor. An annulus is defined between the inner edge of the shroud and the motor, to guide airflow past the motor and through the back of the fan guard. A toroidal filter secures about the motor and between the fan guard and shroud, with all air passing through the fan being required to pass through the filter. The filter may be formed of durable material for cleaning and reuse, or may be disposable, as desired.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 2,883,790 issued on Apr. 28, 1959 to Reed J. Blackman, titled “Fan-Type Insect Catching Device,” describes an assembly comprising a screen installed at the outlet side of the fan, with an electric light bulb installed at the inlet side of the fan. The Blackman device is intended to capture insects by means of attracting insects to the light, whereupon they are drawn into the fan and captured by the screen extending from the outlet side. Blackman teaches away from the present invention, as he cannot install the capture screen on the inlet side as it would at least partially conceal the insect attracting light source which of course must be placed at the inlet side of the fan. Moreover, the screen used by Blackman is relatively coarse in comparison with the filtering material of the present invention, as even the smallest insect is many orders of magnitude larger than the particulate matter which is captured by the present filter.
U.S. Pat. No. 4,477,272 issued on Oct. 16, 1984 to Craig E. Hollis et al., titled “Fan Filter,” describes a filter disc which is removably secured to the back of the fan guard of a conventional portable fan. Hollis notes the benefit of placing the filter upstream of the fan to reduce or preclude the buildup of foreign matter on the fan blades, which is a widely recognized problem. Yet, the Hollis et al. filter does not completely cover the inlet side of the fan guard, due to a slot provided in the filter to fit the device over the fan motor in back of the guard. The present filter secures completely and tightly about the fan motor, thereby directing all airflow through the filter.
U.S. Pat. No. 4,750,863 issued on Jun. 14, 1988 to Glenn Scoggins, titled “Fan Shroud Filter,” describes a filter and shroud for installation with a permanently installed ceiling fan, rather than a portable desktop or similar fan as provided with the present fan filter. Scoggins places his filter above the fan, to the inlet side of the fan when the fan is blowing downwardly. As no guard means is conventionally applied to such ceiling fans, the Scoggins filter would tend to be drawn into the fan, whereas the present filter is drawn against the back of the fan guard to help hold it securely in place. Moreover, the Scoggins shroud attaches to the ceiling above the fan or to the suspension shaft of the fan, as no guard is provided for attachment of his filter device.
U.S. Pat. No. 4,781,526 issued on Nov. 1, 1988 to Clarence Mead, titled “Fan And Filter Combination,” describes a filter system for installation to a conventional “box fan,” having a square shroud. The Mead filter device requires modification of the fan shroud by installing guide rails along each side thereof, for sliding the rectangular filter element therein. In contrast, the present filter system does not require any modification of the fan for its placement thereon. Moreover, Mead does not provide any form of close fitting shroud about the fan itself, as provided by the present invention. The Mead filter is more like a conventional central furnace or air conditioning filter, having a rigid structure and periphery, and is not adapted for installation to a tabletop fan or the like, where the flexibility of the present filter element allows it to conform to the back of the fan guard.
U.S. Pat. No. 4,889,543 issued on Dec. 26, 1989 to Jerry D. Burt, titled “Air Filtering System,” describes a rotating filter which is attached to the blades of a ceiling fan. The Burt filter is completely different from the present filtering system, in that (1) no shroud is provided, (2) the filter elements attach to the fan blades and thus rotate with the blades, rather than remaining stationary relative to the moving blades as in the present fan filter system, and (3) the filter elements do not closely envelop the fan motor in order to preclude entrainment of foreign matter through the center of the fan circulation. The Burt filter system can only be used on a relatively slowly turning, large diameter fan such as a ceiling fan, as the high speed of the typical table top fan would throw the filter elements from the blades due to centrifugal force.
U.S. Pat. No. 5,641,340 issued on Jun. 24, 1997 to Anton Kagan, titled “Method For Filtering Air In Laminar Flow,” describes a first embodiment directed to filtering airflow through cooling fans as used in computers and the like. The only embodiment of the Kagan disclosure which is adaptable to portable fans, is shown in FIGS. 7 and 8 of the Kagan '340 U.S. Patent. In those Figures, an annular ring shaped filter is secured to the outer perimeter of the generally circular fan guard. Kagan fails to provide any form of filter for the back of the fan, where incoming air is entrained through the fan blade path by the rotating blades. The present filtration system covers this entire area, to capture dust and other foreign matter before it enters the guard and blade path.
U.S. Pat. No. 5,904,744 issued on May 18, 1999 to Anton Kagan, titled “Fan Filter With Fasterning (sic) Means,” describes further variations on the filtering methods of the '340 U.S. Patent to the same inventor, discussed immediately above. The various embodiments of the '744 Kagan U.S. Patent which are directed to smaller desktop and table type fans are all of essentially the same configuration as those of the '340 U.S. Patent, i. e., the filter does not extend directly into the ai
Hopkins Robert A.
Litman Richard C.
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