A MIXING CHAMBER FOR MIXING A GASEOUS AND A LIQUID COMPONENT

Abstract: A mixing chamber for mixing a gaseous and a liquid component, said mixing chamber being provided with separate inlet connections for the pressurized components for the mixture which is to be formed, and an outlet connection for the formed mixture to a space which is at a lower pressure. According to the invention at least one of the inlet connections consists of narrow channels in a wall of the mixing chamber with a transverse dimension not greater than about 1 mm, and preferably less than about 0.25 mm. In particular the mixing chamber comprises two parts having connecting surfaces which meet at the inner wall, at least one of these surfaces being provided with grooves which, together with the other said surface, delimit the narrow channels, and more specifically one part of the mixing chamber is cup-shaped and is provided with a connection for one component, whereas the other part is a cap which mates with the opening of said cup-shaped part and is provided with a shoulder, the grooves being formed in either this shoulder or in the end face of the cup-shaped part which enters into contact therewith, said grooves being connected externally with an inlet for the other component. The invention relates also to a method for forming narrow channels in a body or object and to a body or object thus manufactured.

Description: A mixing chamber for mixing a gaseous and a liquid component. The present invention relates to a rni incr chamber for mixing a gaseous and a iiαuiα coniPoneπ. , said mixing chamber being provided with separate inlet connections for the pressurized components for the mixture which is to be formed, and an outlet connection for the formed mixture to a space which is at a lower pressure . Mixing a gaseous and a liquid component with a view to forming a ine mist can lead to dif culties when the f ne droplets formed in a sprav nozzle fiow together in the jet to form larger drops. This leads to an irregular distribution of the iiσuid on a sprayed surface. By the use of a propellent gas, which dissolves n the liquid and evaporates easily therefrom, such flowing together may be avoided but there is a growing concern about the use of such propellent gases because of their harmful effects on the environment or their f lammabi lity. When air is used as a propellent, the flowing together of the formed droplets can be prevented by mixing it with the liquid by turbulence in a mixing chamber, but it is diffciult to achieve a satisfactory mix in the case of mixing chambers of small size. This applies especially in the case of aerosol cans, in which the mixing chamber needs to be integrated with the distribution valve and the spray nozzle to a unit of limited size which is to be placed on an aerosol can. This impedes the wider use of aerosols using air as their propellent, so that aerosols using the harmful propellent gases remain in general use. In view of, inter alia, a ban in the foreseeable future of the latter aerosols, there is a great need for a solution to this problem. However, this problem of mixing is not limited to aerosol cans and the finding or " a solution for such aerosol cans may lead to its application in other fields. The solution to the problem is provided by the measures described in Claim 1. It has been found that by the use of such narrow channels a mixing suitable for t e aforementioned purpose can be achieved, while their dimensicns and number may depend on the viscosity of the liquid and the size and construction of the assembly formed by the mixing chamber and the outlet means connected thereto. The forming of such channels is extremely problematical, especially in the case of mixing chambers formed by injection moulding such as are used, in aerosol cans. Tne use of laser beams is not merely expensive, but may lead to inaccuracies if used on plastics. According to the present invention, this drawback may be eliminated by application of the features mentioned in Claim 2. Such grooves may be formed in a perfectly reproducible way, particularly in moulds for forming piastic parts. Further details are enumerated in the other subclaims. The invention further relates in general terms to to a method according to Claims 10 of 11, and to bodies or objects produced using the method. The invention w ll be explained in greater deta l with reference to a drawing, in which: - Fig. 1 is a cross-sectional diagram of an example of a mixing chamber according to the invention; fig. 2A and 2B are views on an enlarged scale of a part of the mixing chamber, and fig. 3 is a section along the line 111—111 in fig. 2A of a somewhat modified, form. The mixing chamber shown in fig. i is part of an aerosol can of which no further description will be given. This mixing chamber i consists of a cup-shaped lower part 2 and a ring-shaped cap 3. The cup 2 is provided on the bottom with a connector pipe for an immersion tube 5 which is immersed in the liquid contained in the aerosol can. A collar 7 of the cap 3 fits onto the upper edge 6 of the cup 2, its internal diameter corresponding to the external diameter of the edge 6 while the internal diameter of the portion of the cap 3 interconnecting with the collar 7 being eα-ial to the internal diameter of at least the upper The upoer edge 5 of the cap 3 is in sealing contact with a ring sea. 9 , which is part of the distribution valve assembly of the aerosol car-. The lower end of a hollow stem 10 projects into a central orifice 10 of this ring seal 9, said stem being connected to the spray head of the aerosol can. The lower end of the stem 11 rests against a pressure body 12 which is biased upwards by a spring 13 which rests against the bottom of the cup 2, th^ uppermost position of the stem being defined by an abutting surface which will not be further described. The lengthwise bore 14 of the stem 11 is in the present case connected with the exterior on either side through a transverse bore 15. which, in the situation here depicted, is above the ring seal 9. The number of transverse bores issuing may be more or less. When the stem 11 is pressed in, it moves within the orifice 10 and the transverse bore 15 comes to be situated on the other side of the ring seal 9, so that the lengthwise bore is connected with the interior of the mixing chamber. The cap 3 has near its transition to the coiiar 7 a transverse shoulder 16 which rests against the end surface 17 of the cup 2 and is provided with a number of grooves 18 whci ' n are more clearly depicted in fig. 2. These grooves together with the end surface 17 delimit channels 19 which connect the exterior of the mixing chamber, in which the propellent ispresent, to the interior of the mixing chamber. To that end, the external wall of the upper edge 6 of the cup 2 is provided with grooves 20 which together with the coiiar 7 define passages 2-i- . It w ll be obvious that the grooves 18 may alternatively be formed in the end surface 17 and that the grooves 20 may also be formed in the coiiar 7. In order to ensure a satisfactory interconnection between the passages 21 and the channels 19, the upper edge 16 of the cup 2 is bevelled on its outside, as is indicated at 22. After the stem il is pressed in, the liquid will be driven out of the aerosol can via the tube 5 into the annular space around the body 12 c i the mixing chamber i, the propellent gas also entering into this space via the channels 19. A turbulence then occurs, by which a satisfactory mixing of liquid and propellent gas is achieved, which will lead to a fine mist as the mixture leaves the nozzle of the aerosol. This is particularly significant if air is used as the propellent gas, since air dissolves so badly in the liquid to be sprayed that the flowing together of droplets is not thereby stopped. By mixing in air in the mixing chamber that can be avoided. This, by the way, also applies for other propellent gases as well, if the formation of mist without mixing them in should be insufficient. The channels must have a diameter such that satisfactory mixing takes place. This, of course, also depends on the shape of the mixing chamber 1 and the nature of the liquid to be sprayed. If air is used as the propellent gas, a total area of the channels 19 of 0.3 mm 1 w ll be suitable, which, divided over, say, seven channels, leads to channels with a width of about 0,2 mm 2 . The number of channels 19 depends on the turbulence to be achieved in the mixing chamber. It is preferable to choose an odd number if the number of transverse bores 15 in the end of the stem is an even one and contrariwise, in order to avoid as much as possible a direct influx from a channel 19 into a transverse bore 15. It is also possible to have the grooves 17 slanted so as to enhance the turbulence. Fig. 3 shows a modified example. In this embodiment, the channels 19 issue into a c rcumferenti l groove 23 in the inner wall of the mixing chamber. This has proved to enhance the mixing. The groove may also, or instead, be provided in the upper portion of the cup, as is shown in fig. 3 in dotted l nes at 23' . Because the mixing chamber is formed of two parts 2 and 3, the various grooves 18 and 20 may be easily formed during injection moulding of these parts, so that inexpensive mass-production is possible. Channels of the aforesaid limited s ze canr-:> be achieved in properly controllable sizes by conventional methods -such as fillers in injection moulds, laser beams and suchlike), especially in mixing chambers of limited size, as is the case with mixing chambers for aerosol cans. It has been found t ' -.at if the channel dimensions are suitably chosen in relation to the dimensions of the immersion tube 5 and/or the annular passage 13, an aerosol can provided with such a mixing chamber 1 will also work satisf ctorily if held upside down, so that the channels 19 interconnect with the liquid space and the tube 5 with the propellent gas space. It will be obvious that the invention is not limited to the examples herein described and may be applied in all cases where small channels are desirable or necessary. Another advantage of the production of such narrow channels using the above method is that as the mould becomes slightly worn, the membranes which may form will not form at the ends of the channels or passages, so that these will never close up.

Claims: 71 T 7v ™ i. -.iixir.g cnamber for mixing a gaseous and a liσuϊά compo¬ nent, said mixin chamber beinσ provided with separate inlet connections for the pressurized orr-ponents for the mixture which is to be formed, and. an outlet connection for the formed mixture to a space which is at a lower pressure, characterized in that at least one of the inlet connections consists of narrow channels in a wall of the mixing chamber with a transverse dimension not greater than about 1 mm, and preferably less than about 0,25 mm. 2. Mixing chamber according to Claim i, characterized in that the mixing chamber comprises two parts having connectinσ surfaces which meet at the inner wail, at least one of these surfaces being provided with grooves which, together with the other said surface, delimit the narrow channels. 3. Mixing chamber according to Claim 2, characterized in that one art of the mixing chamber is cup-shaped and is provided with a connection for one component, whereas the other part is a cap which mates with the opening of said cup-shaped part and is provided with a shoulder, the grooves being formed in either this shoulder or in the end face of the cup-shaped part which enters into contact therewith., said grooves being connected externally with an inlet for the other componen . 4. Mixing chamber according to Claim 3, characterized in that the flange of the cap comprises a collar which fits around the exterior wail of the cup-shaped part, and in that the exterior waii or the coiiar is provided with grooves which, together with the coiiar or the exterioi- waii. respectively, delimit the inlet for the other component. 5. Mixing chamber according to Claim 4, characterized in that the edge of the external wail of the cup-shaped part is bevelled, in order to ensure an interconnection between the grooves at the end face of the CUP and those on its side. 6. Mixing chamber according to one of Claims 1-5, characterized in that the interior wail of the mixing cna oer is p rovide--, at t ' r.÷ mo-i h of the channels, with _ recess . 7. Kixinσ chamber accordinσ to one of Claims l-~6, intended for an aerosol can for spravincr a l qu with a propellent gas provided above the iiαuid surface, in particular compressed air, said propellent gas having to be mixed with the liquid to be sprayed., the outlet of the mixing chamber being comprised of the hollow stem cf an aerosol head the bore of which mav be placed in connection with the mixing chamber by means of a distribution valve, characterized in that the narrow channels normally connect to the propellent gas soace of the aerosol can. 8. Mixing chamber according to Claim 1, it being possible to connect the bore of the stem to the mixing chamber by means of transverse bores which may be closed bv the distribution valve, characterized in that the number of narrow channels is odd or even, respectively, the number of transverse bores being even or odd, as the case may be. 9. Mixing chamber according to one of Claims 1-8, characterized in that ail parts of the mixing chamber are formed by injection moulding. 10. Method for forming narrow channels in a body or object, characterized in that the body or object is produced out of two Parts interconnecting via a surface, in that grooves are formed in at least one of the interconnecting surfaces which, together with the interconnecting surface portion of the other part, delimit the narrow channels, and in that the two portions are put together to form the finished body or object . 11. Method according to Claim 10, carried out using a seif-reieasing injection mould, characterized in that the injection mould is provided on the appropriate form surfaces with grooves, which, together with cooperating mould surfaces, define the grooves in the finished casting. 12. Body or object produced using the method according to Cl ims 10 or 11.

Inventors: VAN DER HEIJDEN EDGAR IVO MARI, VAN DER HEIJDEN, EDGAR, IVO, MARIA
Applicants: AIRSPRAY INT BV, AIRSPRAY INTERNATIONAL B.V.
Application year: 1990
Main classification: B65D83
IPC codes: B23P15, B65D83