Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
2001-01-12
2004-07-13
Markoff, Alexander (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S006000, C134S007000, C015S001510
Reexamination Certificate
active
06761773
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing dust and particles, which may include allergens, found in carpet and fine fabric material as well as to an apparatus for delivering electrostatically charged particles to the said material.
The invention, we believe functions, by the dust and fine particles agglomerating with electrostatically charged particles, after which the resulting agglomerates can be removed, for example by vacuuming.
It is well known to remove dust and fine particles from carpets by vacuuming. Although most commercial vacuum cleaners will remove some dust and fine particles from carpets, there will always be some fine dust particles left in the carpet that due to their size cannot be sucked into the vacuum cleaner. It is normally the very fine particles which are the most difficult to remove. Particles below 10 &mgr;m in diameter, commonly called PM
10
s, which are lodged deep in the carpet pile near the backing, are always difficult to remove efficiently. It is these particles that are considered to be most hazardous in terms of health implications.
In addition even those PM
10
s which are removed by the vacuum cleaner may well not be retained in the vacuum cleaner filter and may therefore subsequently be released into the atmosphere through the filtration system of the vacuum cleaner. As a result it is often necessary to have special filter bags to retain the dust and fine particles actually in the vacuum cleaner.
During vacuum cleaning of such materials as carpets, those particles which are not removed have a tendency to be disturbed and thus become airborne. Thus a high level of airborne particles (which may include allergens) may occur. Particles of up to 10 &mgr;m in diameter can remain airborne for long periods of time and are small enough to be inhaled into the human respiratory system. In this way, the faeces of the house dust mite (Dermatophagoides pteronyssinus or Dermatophagoides farinae)—now recognised as the most common allergen carrier associated with asthma, enters the respiratory system. These allergens are known as known as the Der p and Der f allergen series. In addition, the feline allergen (Fel d series) can also be transmitted to the respiratory system.
It is an aim of the present invention to provide an improved method and apparatus for controlling and removing dust and other fine particles, especially the Der f and Der p allergens in, for example, a carpet.
It is a further aim of the present invention to provide an improved method of dispensing charged particles to a surface.
SUMMARY AND GENERAL DISCLOSURE
According to one aspect of the present invention there is provided a method for controlling and removing dust and other fine particles in a material, such as a carpet or fine fabric material, comprising
i) electrostatically charging carrier particles (for example by tribo-electric charging, induction charging or corona charging) in powder form to give the carrier particles a minimum charge to mass ratio of +/−1×10
−4
C/kg,
ii) delivering the electrostatically charged carrier particles to the material, whereby the dust and other fine particles in the material agglomerate with the charged carrier particles and
iii) removing the resultant agglomerates from the material.
The agglomerates can be removed from the carpet or other material by a vacuum cleaning process or by a brush. The agglomerates, which are significantly larger than individual dust particles, will be easier to remove by vacuum cleaning, especially where the cleaning process includes mechanical agitation and vacuum suction.
In addition, the agglomerates are less likely to become airborne than the individual dust particles and certainly will not be able to remain airborne for long periods of time. In addition, once the small particles (PM
10
s) are in a vacuum cleaner as a component of the agglomerates, their escape through the filtration system of the vacuum cleaner will likewise be significantly reduced.
Where the material to be treated is a carpet, the charged carrier particles penetrate right down to the backing of the carpet and attract dust and other fine particles from the depths of the carpet, so that these can also be removed more efficiently.
The carrier particles used in the method of the invention may be electrostatically charged as they are being applied to the carpet or other material. For example, the carrier particles may be stored in the container or a device having a delivery system which is designed so that on delivery an electrostatic charge is imparted, eg by tribo-electric charging, to the particles.
In such an apparatus the carrier particles will become charged as they are expelled through the delivery system onto the carpet or other material.
Alternatively, the carrier particles may be charged and stored in a container before they are applied to the carpet or other material. A process for the preparation of electrostatically charged particles of a high resistivity is described in European Patent Application No. 95921916.3. The already charged particles are then delivered from the container and applied directly to the carpet or other material.
The electrostatically charged carrier particles are preferably powder particles formed from compounds selected from celite, maize, cyclodextrin, polyvinylpyrrolidone, polyester, nylon, calcite treated with oils, polyvinyl chloride (PVC), polytetra fluoroethylene, polystyrene, polycarbonate, polyimides, “immobilised tannic acid” (as defined below) and wax materials (such as a synthetic paraffin wax or a natural wax, for example Carnauba wax).
By the term “Immobilised tannic acid” as used herein is meant tannic acid immobilized on polyvinylpyrrolidone beads. “Immobilised Tannic Acid” is prepared as follows:
100 mg of tannic acid dissolved in water, 50 mg of Polyclar 10 (ISP, Guildford Sumg) polyvinylpyrrolidone beads were added and stirred for one hour. The beads were filtered from the solution and washed with a few mls of iced water until no colour was seen in the washings. They were then dried in an oven at 50° C.
The minimum level of charging required on the carrier particles is such as to provide a charge to mass ratio of ±1×10
−4
C/kg, although ratios in excess of ±1×10
−3
C/kg may be achieved using the charged particle application system hereinafter described with reference to
FIGS. 2
,
3
and
4
of the accompanying drawings.
The electrostatic charge on the carrier particle may be of positive or negative polarity, or may be a mixture of both when the particles are frictionally charged mixtures of different electrically insulating materials.
The charged particles used in the method of the invention preferably have a diameter in the range of from 10 to 500 &mgr;m, more preferably 100 to 300 &mgr;m.
In carrying out the method according to the invention, at the same time as (or after) the electrostatically charged carrier particles are applied to the material, the surface of the material is preferably agitated in order to ensure that the dust and small particles agglomerate with the charged carrier particles and are therefore captured. Agitation may be carried out at the same time as the electrostatically charged particles are delivered to the carpet, or as an intermediate agitation step between delivery of the electrostatically charged carrier particles and their final removal, or during the final removal step.
The method of the invention therefore enhances the removal of small particles from the carpet or other material (“Mop-Up”), restricts the number of particles becoming airborne during the removal of the small particles (“Damp-Down”), and increases the capacity of a vacuum cleaner to retain the small particles (“Stay-Put”).
It has been found that the charging levels on the powder are increased when the velocity of the particles through the charging tube or pipe is increased. Generally the velocity of the particles being passed down the tube or pipe will be in the range of from 10 to 80 m/sec, preferab
Gaynor Paul Terence
Hughes John Farrell
McKechnie Malcolm Tom
Swingler Jonathan
Fish & Richardson P.C.
Markoff Alexander
Southampton University
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