Gas separation – Two or more separators – Three or more serially spaced
Reexamination Certificate
2000-06-14
2002-08-27
Hopkins, Robert A. (Department: 1724)
Gas separation
Two or more separators
Three or more serially spaced
C055S486000, C055S492000, C055S510000, C055SDIG003, C015S353000
Reexamination Certificate
active
06440191
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to vacuum cleaners, and more particularly to filters for vacuum cleaners.
BACKGROUND ART
Wet/dry vacuum cleaners generally include a motor which drives an air impeller to create a low pressure area inside of a tank or other receptacle. The tank has an inlet through which dust and debris or liquid material enter into the tank, usually from a hose. The incoming airstream flows through the tank and exits out exhaust ports.
During dry pick-up, the dust or debris may pass into the air impeller, thereby interfering with operation of the air impeller or motor. In addition, the dust or debris may be exhausted back out into the room. To address the problems associated with the particulate-laden airstream, previous vacuum cleaners have typically included a filter for use during dry pick-up to collect the particulate material. Cylindrical or cartridge filters are often used which have large filtering surface areas and may be made of a variety of filtering materials. It has therefore been known to use a cylindrical filter with an open top and a closed bottom which is inserted over a filter cage. The top of the filter may be made of a flexible material such as rubber so that when the filter is pushed over the filter cage, the flexible material deforms and frictionally holds the filter in place. Other systems use cylindrical filters which are open at both ends. Such filters may fit over a filter cage having a closed bottom in order to prevent material from passing around the filter and into the air impeller. Other open-ended filters may use a retainer of some type which holds the filter in place and closes the open bottom end of the filter.
In addition, dual filter assemblies may be used which include two types of filter media concentrically arranged in a single filter unit, such as that disclosed in Newman, U.S. Pat. No. 5,259,854. High efficiency particle air (“HEPA”) filters, which can remove 99.97% of particles larger than 0.3 microns from a stream of air, are useful for removing very small particles of dust or debris from air. Newman discloses a disposable filter cannister including an annular HEPA filter surrounded by a prefilter.
During wet pick-up, an air filter is not necessary and, in fact, may hamper vacuum cleaner performance. Once an air filter has been saturated with liquid, the amount of airflow through the filter is restricted, thereby reducing the capacity of the vacuum cleaner. With the filter in this condition, liquid may be sucked through the filter to collect inside the filter cage, and liquid entrained in the airstream may be pulled through the impeller and motor. As a result, liquid may be ejected out of the air exhaust ports of the vacuum cleaner. To obviate this problem, air filters are typically removed when switching from dry to wet pickup.
To reduce the amount of liquid entrained in the airstream during wet pickup, previous wet/dry vacuum cleaners have employed a foam cuff which is inserted onto the filter cage in place of the air filter. The filter cuff wicks liquid from the airstream and will typically generate a smaller pressure drop than that seen with the air filters. While the foam cuff performs adequately, a user of the wet/dry vacuum cleaner must remember to insert the foam cuff each time the air filter is removed. Replacement of the foam cuff is inconvenient and overly time consuming, and therefore a user may forget or choose not to install the foam cuff, thereby rendering the impeller and motor unprotected. In addition, the foam cuff may be lost or misplaced by the user.
An alternative filter arrangement is described in U.S. Pat. No. 4,906,265, wherein a foam cuff
30
fits over a filter cage
20
during wet operations.
When the vacuum cleaner is used on dry materials, a paper or cloth filter is placed over the foam cuff and attached with a retaining ring. The paper or cloth filter minimizes the amount of particulate material which escapes from the tank and passes to the air impeller. While this filter arrangement allows the foam cuff to remain in place during dry pick-up, the attachment of the cloth filter and retaining ring is cumbersome, and care must be taken so that the filter is properly centered over the foam cuff so that the entire filter cage is covered. As a result, a user may not take the time to insert the cloth filter and ring for dry pick-up, resulting in excess particulate matter passing through the air impeller and into the room.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a filter assembly is provided for a vacuum cleaner having a filter support. The filter assembly comprises a liquid filter mounted on the filter support, and a first air filter removably attached to the filter support, the first air filter having a filter medium disposed about the liquid filter, the first filter defining a lower end. A cover is attached to the lower end of the first air filter.
In accordance with additional aspects of the present invention, a vacuum cleaner is provided comprising a tank, a lid removably attached to the tank, the lid carrying a filter support, and a foam sleeve mounted on the filter support. A first air filter is removably attached to the filter support, the first air filter having a filter medium disposed about the foam sleeve, the first filter defining a lower end. A cover is attached to the lower end of the first air filter.
In accordance with still further aspects of the present invention, a vacuum cleaner is provided comprising a tank, a lid removably attached to the tank, and a filter support carried by the lid. The filter support comprises a shroud depending from the lid defining a central recess and having a bottom wall, and a filter cage is supported inside the central recess. A drain hole is formed in the bottom wall, and a filter is removably attached to the bottom wall, the filter including an upper end cap. The upper end cap of the filter closes off the drain hole when the filter is attached to the shroud.
Other features and advantages are inherent in the vacuum cleaner claimed and disclosed or will become apparent to those skilled in the art from the following detailed description in conjunction with the accompanying drawings.
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Berfield Robert C.
Liu Li H.
Hopkins Robert A.
Marshall Gerstein & Borun
Shop Vac Corporation
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