Brushing – scrubbing – and general cleaning – Machines – With air blast or suction
Reexamination Certificate
1999-10-05
2001-03-13
Warden, Sr., Robert J. (Department: 1744)
Brushing, scrubbing, and general cleaning
Machines
With air blast or suction
C015S001510, C015S383000, C015S415100
Reexamination Certificate
active
06199244
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a vacuum cleaner for cleaning floors or carpets, having a suction mouth, a base plate, which encloses the suction mouth, and a suction line, electrostatic charging of parts of the vacuum cleaner being provided in order to assist the dust intake.
In order to assist the cleaning performance of a vacuum cleaner in an effective manner, it is known to utilize electrostatic forces. By separating non-conductive/poorly conductive components of the vacuum cleaner from an object to be cleaned, the two components come to be electrostatically charged. The level and also the polarity are governed by the individual material pairings. Materials such as polyamide, wool or silk serve as donors and give up electrons easily. Separation results in a positive change on these materials. The substances released from these fibres or materials are negatively charged as a result of the electron uptake. An attraction force in the direction of the floor/carpet acts on the oppositely charged particles, the charge being reversed in the case of carpets made of alternative materials, e.g. polypropylene. However, the effects described are still present. If, then, an element, for example a nozzle, of a vacuum cleaner which is more strongly charged than a dust particle of the carpet, is brought into the vicinity of the carpet/dust system, then the attraction force of this element on the charged, floating particle may be sufficiently great, as a result of which the particle is removed. A basic consideration of the bonding forces between a particle and a surface show that essentially three different types of forces are active: the so-called van der Waals forces, the electrostatic forces (contact potential and reflective force) and the capillary forces. In terms of the charge of particles and the transportation thereof in an electric field, it is possible to distinguish between the basic mechanisms of friction, induction, corona discharge and dielectrophoresis.
The prior art utilizes, for example, the electrostatic bonding forces for the deposition of the particles located in an air volume-flow. For this purpose, the particles, which are taken up in the conventional manner by suction, are charged differently and separated by a filter system. Furthermore, a vacuum cleaner is known for example from DE-A1 196 44 589 which has a dust-attracting grid in the region of the suction mouth. The grid is connected to a high-voltage source and is connected up in the manner of a precipitation electrode. The suction-airstream laden with dust particles can flow through the dust-attracting grid.
In relation to the above-described prior-art, a technical problem of the invention is seen in advantageously developing a vacuum cleaner of the type in question in terms of the dust uptake being assisted by electrostatic charging.
SUMMARY OF THE INVENTION
This problem is solved first and foremost by the fact that the base plate is electrostatically charged, and that the electrostatic charging is carried out by means of a separate generator provided in the vacuum cleaner, it being possible, furthermore, for the electrostatic charge of the base plate to be both positive and also negative. Use is preferably made here of a base plate of metal material which is arranged in an insulated manner in relation to the subassemblies enclosing said base plate. Thus, a desired high voltage is produced by an external generator and applied directly to the base plate. The order of magnitude of the charges which are to be produced depends primarily here on the type of dust and floor covering/carpet, voltages, measured against earth potential, of between 1 and 20 kV being utilized. Consequently, increased dust uptake is achieved simply by applying an external voltage of preferably +5 kV to the base plate on different carpets. This increase in the dust uptake can be explained by a charge separation between particle and carpet fibre when the particle is released from the fibre. The particle obtains a negative charge here and is thus attracted by the positive base plate. Tests have shown that this effect can also be demonstrated without mechanical action, or by rotating brushes or the like. It may alternatively be provided that the base plate consists of a plastic material which is electrostatically charged by frictional contact with a floor covering, for example carpet. The sliding of the vacuum cleaner or of the vacuum-cleaner nozzle or the like on the floor covering as the floor covering is being cleaned results, by way of the friction movement, in the contact being intensified, which, by way of the resulting triboelectricity, brings about the opposite electric charging of the bodies being rubbed against one another, in this case the base plate and floor covering. The dust particles in the carpetting or the like are also released from the fibres by this electrostatic charge.
The invention also relates to a vacuum cleaner according to the introductory mentioned features, the vacuum cleaner also having a brush provided with bristles in order to act on the floor covering. In order to achieve improved dust uptake in this case, it is proposed that, as far as the material is concerned, the bristles be selected to be far apart in the triboelectric series. It is thus possible, in the case of vacuum cleaners with electrically driven cleaning brushes, by way of the specific selection of the bristle materials, to utilize the frictional contact between brush or bristles and carpet fibre as a charge source. The critical factor is for the respective material pairings to be as far apart as possible as far as the triboelectric series is concerned, with the result that an electrostatic charge is achieved by the frictional movement brought about by the rotating brushes. It is thus provided, for example, that the bristles consist of polypropylene for wool carpets or polyamide carpets. Furthermore, it is also conceivable to utilize natural bristles for placement on the brush, triboelectric effects likewise coming to the fore with pure natural-hair mixtures. In a development of the subject matter of the invention, it is provided that the base plate and the material of the suction line are selected in terms of the triboelectric series.
It has been established that, in order to influence the dust uptake positively, a potential, measured against earth, of less than 20 kV should be applied to the base plate. This voltage value is in an order of magnitude which can be applied, for example, by a separate generator in the vacuum-cleaner housing. Furthermore, in the case of a vacuum cleaner with a brush acting on the floor covering, said brush makes a considerable contribution to charge transfer. The usually neutral SiO
2
particles are released from the fibre/dust-particle bond by the volume flow and the mechanical work of the brushes. This results in a positive charge for the fibre and a negative charge on the dust particle. On account of the large-surface-area contact with the carpet, the base plate is likewise positively charged. Assuming that the plate is more positively charged than the individual carpet fibres, the SiO
2
particle will tend to move towards the plate and thus be removed from the carpet.
The invention also relates to a vacuum cleaner wherein, in order to influence the dust uptake positively, the brush can be subjected alternately to an electric potential for providing an electric charge and discharge, or can be grounded. This configuration according to the invention can be used alternatively to, or in combination with, the abovedescribed measures for increasing the dust uptake. Further charging and transporting operations are utilized in this case, for example charging by induction, which can be used in a controlled and reproducible manner. By the additional use of electrostatic effects, there is achieved a significant increase in the dust uptake for different carpets, the carpetting not being exposed to any increased mechanical loading and there being thus no increase in the pushing force. It is t
Hilgers Stefan
Iglseder Heinrich
Jacobs Carsten
Meyer Frank
Rodemann Thomas
Farber Martin A.
Snider Theresa T.
Vorwerk & Co. Interholding GmbH
Warden, Sr. Robert J.
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