Thomson, Andrew Walter Mcrae (Sandford Cottage 54 High Street Avening Gloucestershire GL8 8NF, GB)
| 1. | A synthetic dust compound comprising a mixture of mineral dust, an organic filler and a fibrous material, wherein the fibrous material comprises a multiplicity of fibres made from a material used to manufacture carpets, rugs or other floor coverings and constitutes between 5% and 35% by mass of the compound. |
| 2. | A synthetic dust compound as claimed in claim 1, wherein the multiplicity of fibres are made from one or more of nylon, polypropylene and wool. |
| 3. | A synthetic dust compound as claimed in claim 1 or 2, wherein the shape of each fibre is generally cylindrical. |
| 4. | A synthetic dust compound as claimed in claim 3, wherein each fibre has a cylindrical outer surface which is smooth. |
| 5. | A synthetic dust compound as claimed in claim 3 or 4, wherein each fibre has a diameter of between 10m and 1001lu. |
| 6. | A synthetic dust compound as claimed in claim 5, wherein each fibre has a diameter of substantially 50um. |
| 7. | A synthetic dust compound as claimed in any one of the preceding claims, wherein each fibre has a length of between lmm and 5mm. |
| 8. | A synthetic dust compound as claimed in claim 7, wherein each fibre has a length of substantially 2mm. |
| 9. | A synthetic dust compound as claimed in any one of the preceding claims, wherein the fibrous material constitutes between 8% and 20% by mass of the compound. |
| 10. | A synthetic dust compound as claimed in claim 9, wherein the fibrous material constitutes substantially 10% by mass of the compound. |
| 11. | A synthetic dust compound as claimed in any one of the preceding claims, wherein the mineral dust comprises dolomite dust. |
| 12. | A synthetic dust compound as claimed in claim 11, wherein the dolomite dust includes both coarse and fine fractions thereof. |
| 13. | A synthetic dust compound as claimed in claim 12, wherein the coarse and fine fractions are present in approximately equal proportions. |
| 14. | A synthetic dust compound as claimed in any one of the preceding claims, wherein the organic filler comprises wood flour. |
| 15. | A synthetic dust compound as claimed in any one of the preceding claims, wherein the mineral dust and the organic filler are present in proportions of substantially 3: 1. |
| 16. | A synthetic dust compound substantially as hereinbefore described with reference to the accompanying drawings. |
Consumers of domestic appliances, including vacuum cleaners, require data which enables comparisons to be made between different vacuum cleaners. Therefore, various testing methodologies have been developed over the years with the intention of allowing comparisons to be made. Before the introduction of cyclonic vacuum cleaners, all vacuum cleaners operated under essentially the same principle, i. e. the dirty air was passed through a filter bag in order to collect dirt and dust therein. However, the introduction of cyclonic technology into domestic vacuum cleaners means that different principles of operation are now employed. There is therefore a need for the testing methodologies to be such that reasonable comparisons can be made between different vacuum cleaners, even if the technology employed by each vacuum cleaner is different.
It is believed that a critical aspect of the tests carried out on vacuum cleaners for comparison purposes relates to the material which is used to simulate household dust during the tests. Various different materials have been used in the past, ranging from fine dust to light fibres. For example very fine china clay dust can cause clogging of filter bags in a short time; on the other hand, kapok is a very light and voluminous fibrous material which can form an additional filtering layer within a filter bag and reduce the amount of clogging which might otherwise occur due to the presence of fine dust. Neither of these materials has been endorsed by industry bodies as representative of normal household dust.
It is, of course, very difficult to replicate a material which is variable in nature.
However, there is a need for a synthetic dust compound which closely resembles, on average, the type of material which would be picked up by a domestic vacuum cleaner under normal vacuuming conditions.
It is therefore an object of the present invention to provide a synthetic dust compound which can be used for the comparison testing of different types of vacuum cleaners and which does not favour or disadvantage any specific type of vacuum cleaner which utilises different technology from other vacuum cleaners. It is a further object of the present invention to provide a synthetic dust compound which can be utilise generically and which is capable of forming an acceptable standard for comparison testing of different vacuum cleaners.
The invention provides a synthetic dust compound comprising a mixture of mineral dust, an organic filler and a fibrous material, wherein the fibrous material comprises a multiplicity of fibres made from a material used to manufacture carpets, rugs or other floor coverings and constitutes between 5% and 35% of the mass of the compound.
Preferably, the fibres are made from one or more of nylon, polypropylene and wool.
Further and preferable features of the invention are set out in the subsidiary claims.
A synthetic dust compound according to the invention has the advantage of replicating a typical accumulation of dirt and dust commonly found when vacuuming in a domestic environment. The compound according to the invention does not contain fibres such as kapok which is inclined to agglomerate and cause either abnormal blockage of cyclonic vacuum cleaners or anormal filtration in bag-filter type vacuum cleaners. Neither does the compound according to the invention contain a proportion of very fine dust which is disproportionate to the amount of fine dust normally collected in a household environment. The compound according to the invention also has the advantage of being producable in large quantities to a consistent formulation so that tests performed on vacuum cleaners can be reproduced at will. This has the advantage of increasing the reliability of tests carried out which, in turn, provides consumer confidence in data presented by manufacturers and test houses.
An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a pie-chart representing the relative proportions of the constituents of a synthetic dust compound according to the invention; and Figure 2 is a perspective view, on a greatly exaggerated scale, of a fibre contained within the compound of Figure 1.
A synthetic dust compound according to the invention consists of a mixture of a mineral dust, an organic filler and a fibrous material. In this particular example, the mineral dust consists of dolomite dust. Coarse and fine fractions of the dolomite dust are present in equal proportions by mass. In this embodiment, the coarse fraction of the dolomite dust consists of particles which have a diameter greater than 0.125mm and the fine fraction of the dolomite dust consists of particles which have a diameter less than 0.125mm. The organic filler consists essentially of wood flour. A suitable organic filler is that which is available frorn the manufacturer J. Rettenmaier & Söhne GmbH + Co. under the trade mark ARBOCEL". The mineral dust and organic filler are present in relative proportions of three parts mineral dust to one part organic filler.
The third constituent of the synthetic dust compound is a fibrous material. In the preferred embodiment, the fibrous material consists of a multiplicity of synthetic fibres which are generally cylindrical in shape. An individual fibre is illustrated in Figure 2 of the accompanying drawings. The fibre 10 has a length 1 of substantially 2mm and a diameter d of approximately 501lm. It will be appreciated that these dimensions can be varied and it is envisaged that the length 1 could be anywhere between lmm and 5mm and the diameter d could be varied between lOm and 100pm.
The cylindrical surface 12 of the fibre 10 is essentially smooth, having no projections or surface features by means of which one or more fibres can become attached together.
The fibres 12 are extruded using normal manufacturing techniques for fibres of these dimensions and then cut to the required length 1.
The fibres 10 are manufactured from a material which is normally and commonly used to manufacture carpets, rugs or other floor coverings. The most common materials used to manufacture carpets and rugs are nylon, polypropylene and wool. It is therefore preferred that the fibres 10 are manufactured from one or more of these materials. It is possible for a proportion of the fibres to be manufactured from polypropylene and another proportion to be manufactured from wool, whilst a third proportion is manufactured from nylon. These separate proportions can then be mixed together if required. Alternatively, all of the fibres can be manufactured from just one of the preferred materials or, as a further possibility, all of the fibres can be manufactured from, for example, a wool/nylon mix.
The fibrous material is added to the mineral dust and organic filler mixture so that the proportion by mass of the fibrous material is between 5% and 35% of the compound as a whole. A preferred range of values for this proportion is between 8% and 20%. Tests using a nylon fibre material having individual fibres of approximately 2mm in length and approximately 5ohm in diameter have shown that a proportion of 10% by mass of fibre material produces a synthetic dust compound which closely resembles household dust. It is therefore preferred that the proportion by mass of fibrous material in the synthetic dust compound is substantially 10%.
Figure 1 illustrates the relative proportions by mass of the various constituent components of a synthetic dust compound according to the invention. Portion A represents the proportion (10%) of fibrous material which, as described above, comprises a multiplicity of cylindrical fibres of nylon having a length of substantially 2mm and a diameter of substantially 50pLm. Portion B represents the proportion by mass (24%) of the organic filler material ARBOCEL@. Portion C represents the proportion (33%) of coarse fraction dolomite dust. Portion D represents the proportion (33%) of fine fraction dolomite dust.
The composition of the coarse fraction of the dolomite dust used in the specific example is as follows: ParticleSizeRange(mm)PercentagebyMass(%) 1.0-2.0 3 0.5-1.0 11 0.25-0.5 16 0.125-0.25 20 The composition of the fine fraction of the dolomite dust used in the specific example is as follows: ParticleSizeRange(mm)PercentagebyMass(%) 0.075-0.125 10 0.04-0.075 10 0.02-0.04 10 Lessthan0.02 20 It is believed that the synthetic dust compound described above has many advantages over the compounds which are currently used to test vacuum cleaners in order to produce data for comparison purposes. Firstly, the compound is definable and easily producable in large quantities to consistent standards. At the same time, the synthetic dust compound described above behaves in a manner very similar to that of household dust and therefore does not advantage or disadvantage any particular type of vacuum cleaner which therefore allows tests to be conducted fairly and results to be directly comparable.
The invention is not intended to be limited to the specific features of the embodiment described above. Various modifications and alterations will be apparent to a skilled reader.