Dispensing – With discharge assistant – Fluid pressure
Patent
1993-12-09
1995-07-04
Shaver, Kevin P.
Dispensing
With discharge assistant
Fluid pressure
22218906, B65D 8314
Patent
active
054292794
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a mixing chamber for mixing together a pressurised gaseous and liquid constituent, which mixing chamber is provided with separate feed connections for the pressurised constituents of the mixture to be formed, and with a discharge connection for the mixture formed to a chamber with lower pressure, at least one of the feed connections being formed by narrow passages in the wall of the mixing chamber.
The mixing together of a gas and a liquid with a view to forming a fine mist can lead to difficulties if the fine droplets formed in a spray nozzle merge into larger droplets in the jet. This leads to an irregular distribution of the liquid on a sprayed surface. If a propellant which dissolves in the liquid and evaporates easily again from it is used, this merging can be avoided, but there is an increasing objection to the use of such propellants on account of their harmful effects on the environment, or on account of their combustibility.
If air is used as the propellant, mixing it well with the liquid by turbulence in a mixing chamber can actually prevent the droplets formed from merging, but it is difficult to obtain a good mix in the case of small mixing chambers. This applies in particular in the case of aerosols in which the mixing chamber with the dispensing valve and the spray nozzle has to be combined to a small unit for placing on an aerosol. This stands in the way of a more widespread use of aerosols working with air as the propellant, so that the aerosols with harmful propellants still remain in general use. A likely ban on the latter aerosols in the future is part of the reason why there is a great need for a solution to this problem. Besides, this mixing problem is not limited to aerosols, and finding a solution for such aerosols can lead to applications in other fields.
One solution is described in NL-A-89 01877 of Applicant, which describes a mixing chamber made up of two parts which have surfaces touching each other and abutting the inside wall of the mixing chamber. The narrow passages are in this case formed by grooves in at least one of the abutting surfaces which together with the other surface bound the narrow passages.
The present invention provides another simple solution to the provision of narrow passages in the wall of the mixing chamber, and to that end is characterised in that the narrow passages are formed by at least one porous part present locally in the wall of the mixing chamber.
It has in fact been found that through the use of such a porous part with narrow passages a mixing suitable for the abovementioned purpose can be obtained, in which the dimensions of the passages can depend on the viscosity of the liquid and the dimensions and layout of the assembly of mixing chamber and discharge means connected to it.
The invention also relates to an aerosol intended for atomising a liquid by means of a propellant, in particular air, which aerosol contains a mixing chamber according to the invention.
The invention will be explained in greater detail below with reference to the appended drawing, in which:
FIG. 1 shows a schematic section of an example of an embodiment of a mixing chamber according to the invention;
FIG. 2 shows a schematic section of another example of an embodiment of a mixing chamber according to the invention.
The mixing chambers shown in FIGS. 1 and 2 form a part of an aerosol not shown in any further detail. The mixing chamber 1 in FIG. 1 comprises a beaker-shaped bottom part 2 and an annular top piece 3, separated by an annular porous part 4, which can be, for example, a porous plastic, a sintered material, or a porous ceramic material. Apart from materials with a relatively random pore distribution, materials which are provided in a very accurate way with narrow passages are also suitable. An example which can be mentioned in this connection is plastic which is provided with narrow passages using a laser, which passages nave a very accurately determined orientation and size.
It will be clear that the position and dimensions of th
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Airspray International B.V.
Shaver Kevin P.
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