Gas separation: processes – Electric or electrostatic field
Reexamination Certificate
1999-05-07
2001-01-09
Chiesa, Richard L. (Department: 1724)
Gas separation: processes
Electric or electrostatic field
C015S347000, C015S352000, C055S382000, C055S486000, C055S487000, C055SDIG002, C055SDIG003, C095S078000, C095S287000, C096S015000, C096S069000
Reexamination Certificate
active
06171369
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel disposable vacuum cleaner bag, composition which is notably superior to existing vacuum cleaner bag constructions in terms of dust holding capacity, minimal increase in pressure drop with dust loading, and in ease of bag fabrication and shape retention, while achieving filtration efficiency values which compare most favorably with premium commercially available bags.
BACKGROUND OF THE INVENTION
Over the last few years, a number of companies have developed raw materials and components for vacuum cleaner bags to replace the older single layer paper bag and the well-known two-ply bag, having a downstream filter paper and an upstream tissue paper, with bags having upstream layers of either wet-laid tissues or fibrous fleeces such as meltblown (MB) ultra-fine webs occasionally referred to herein as “filtration grade MB fleece.” Some manufacturers of vacuum cleaners have even marketed bagless vacuum cleaners to avoid the cost of bags. However, this type of vacuum cleaner has less suction and the compartment holding the dust must be emptied manually, and this largely nullifies its advantages by exposing the worker and the environment to the concentrated dust. Nevertheless, the bagless cleaner has prompted manufacturers to continue to improve the overall performance of bags.
The prior art addressed the problem of providing a vacuum cleaner bag with improved filtration efficiency. U.S. Pat. No. 5,080,702, Home Care Industries, Inc. discloses a disposable filter container-like bag which comprises an assembly of juxtaposed plies, namely an inner and outer ply of air pervious material. U.S. Pat. No. 5,647,881 (EPO 0 822.775 B1) discloses a three layer composite of an outer support layer, middle charged fibrous filter layer having specific properties and an inner diffusion layer unbonded except at least at one seam to the fibrous filter layer. The diffusion layer is described to provide the filter bag as its main function, with resistance to shock loading. EPO 0 338 479 to Gessner discloses a dust filter bag with a fibrillated fleece-lined outer layer of filter paper. The filtration grade fibrillated fleece layer is upstream of the filter paper.
In the vacuum bag of the invention the principal function of the inner layer is that of high dust-holding capacity, a property of this magnitude not yet disclosed in the prior art.
The disclosures of the above-mentioned patents are incorporated herein in their entirety by reference.
With the advent of electrostatically charged MB fleeces, it has been possible to produce bag laminates with filtration efficiencies on the order of 99.8-99.9% to fine dust at a moderate airflow. However, conventional MB webs are essentially flat filters. Consequently, filter structures that utilize MB webs quickly load up with dust, reduce the air suction, and lose further dust pick up ability by the vacuum cleaner. Today, the standard dust bags have an air permeability of 200 to 400 L/(m
2
×s). It is desirable to have a combination of paper types and other liners, including MB liners that would yield a high efficiency of up to 99.9% and also, am allow a high flow with minimal pressures gradient increase measured by the DIN 44956-2 Test.
A primary object of this invention is to provide a novel vacuum cleaner bag composition capable of extremely high filtration efficiency to fine dust and of maximum performance of a vacuum cleaner in terms of continuous high suction for picking up dust without a notable increase in pressure drop until the bag is filled.
A second objective of this invention is to provide a bag with a composition such that it has the rigidity needed for it to be fabricated and shaped on conventional vacuum cleaner bag making equipment.
A third objective of this invention is to construct a vacuum cleaner bag media that by virtue of its excellent filtration efficiency and superior non-blocking, high airflow performance, will be most suitable to the new European trend of small vacuum cleaners, with of course, smaller vacuum dust bags.
These and other objectives of this inventor will become apparent to one skilled in the art from the following disclosure.
The Nonwoven Fabrics Handbook of the Association of the Nonwoven Fabrics Industry, 1992, is incorporated herein in its entirety by reference.
SUMMARY OF THE INVENTION
A disposable vacuum cleaner bag that has an air permeability of greater than 400 L/(m
2
×s) was developed. This was accomplished by placing a filter paper on the upstream air side of a filtration grade MB fleece/spunbond two-ply component, instead of placing a filter paper on the outside (i.e., downstream air side) of the bag, as is typically done. It should be noted, however, that prior art bag constructions often place a lightweight (typically 13 g/m
2
) tissue fleece upstream of the MB fleece for support and to protect the MB fleece from abrasion. This lightweight tissue fleece only filters some of the largest dust particles.
In the new filter bag construction, it is possible to use a coarse filter paper ocassionally referred to herein as “high dust holding capacity,” “multipurpose” or “capacity” paper or layer, on the most upstream layer inside the bag. This invention also allows for optional use of lightweight tissue fleece, netting or other scrim on the most inside layer upstream of the filter paper. Thus, large dust particles are removed by the coarse filter paper (and possibly to a minor extent by the light weight tissue fleece, if used). The filtration grade MB part of the bag fabric can serve more effectively as a filter without clogging up, since it does not need to hold the bulk of the dust. If desired, a wet-laid tissue may also be used in front of the coarse paper. This construction is very much unlike the earlier constructions that used MB liners on the inside of the bag, and which depended upon the MB web for both dust holding and filtration. Furthermore, the paper gives the bag the rigidity needed to fabricate and shape the novel bag composition on conventional vacuum cleaner bag making equipment.
The novel vacuum cleaner bag thus comprises a flat composite of a coarse filter layer comprising at least one of (a) a wet-laid high dust holding capacity paper, (b) a dry-laid high dust holding capacity paper, (c) a high bulk meltblown nonwoven, (d) a Spunblown (Modular) nonwoven, and (e) a microdenier spunbond nonwoven positioned upstream in the direction of air flow of a filtration grade meltblown fleece layer formed into the bag having at least one air inlet defining means in the flat composite and at least one seam forming the flat composite into the bag. The filter layer operative according to this invention which is positioned downstream of the course, capacity layer is sometimes referred to herein as a “secondary” or “high efficiency filtration” layer.
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patent: 55
Schultink Bas
Schultink Jan
Airflo Europe N.V.
Chiesa Richard L.
Schnader Harrison Segal & Lewis LLP
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