Patent Application
20130087636
The present invention relates to a spray nozzle according to the preamble of claim 1.
Generally, it is known to admix further substances such as fillers, reinforcement substances, additives, etc. (hereinafter referred to as additional substance) to reactive mixtures, comprised for example of a polyurethane mixture, i.e., of isocyanate and polyol elements or of another multi-component system.
This can be done by mixing the solids outside of a mixing head into a spray jet. In this regard, reference is made for example to EP 1 458 494 B1. This process is however unsuitable for processing fillers having a very low density (for example so-called micro-glass bubbles of only a few μm diameter and a density of 0.2), because these substances for the most part are blown off from the added component by ambient air and only partially absorbed by the liquid.
Further admixture can be realized by introducing the additional substance or the additional substances into a mixing chamber in which the individual reactive components are added separately and mixed together. However, there are some materials, for example, those that are very sensitive and cannot be admixed as so-called batch component into the reactive mixture, in particular into the mixing chamber of a mixing head.
Oftentimes the isocyanate and polyol components—or the other components of a multi-component system—are atomized under high pressure in a mixing head and mixed together. This pressure—and the resultant force development can cause destruction of the particle structure, when sensitive substances are involved, and thus can lead to loss of the property that is desired later. This also applies to the afore-mentioned micro-bubbles of glass, as well as to expanded graphite or other sensitive materials.
It is an object of the present invention to provide a spray nozzle which allows introduction of also sensitive materials into a reactive mixture, with the entire mixture being atomizable subsequently.
This object is attained by the features set forth in claim 1.
Accordingly, the reactive mixture is initially prepared in a (conventional) mixing head, and supplied to the spray nozzle that is—preferably separate or provided at the end of the mixing head—via a connection. The connection has an inlet which is connected with a further mixing chamber. The sensitive material to be added is introduced into this mixing chamber via a separate supply and mixed homogeneously with one another in the mixing chamber under lesser high pressure.
Furthermore, air is subsequently introduced via an air supply and air supply openings into the mixing chamber by which the previously prepared mixture of the reactive mixture and the substance to be added is ejected. For that purpose, the air supply openings are preferably distributed about the mixing chamber at the end of the mixing chamber in flow direction. According to a preferred embodiment, the air supply has an annular space in the housing of the spray nozzle, which is connected with the plurality of air supply openings circumferentially disposed about the end of the mixing chamber, so that an even introduction of air across the periphery is possible. Further, it is advantageous when the air guide channels and/or the air supply openings are formed such that a swirl can be produced so that a fanned jet can be produced in a defined manner. Air supply is however not necessarily required. In the event, the mixture should simply be introduced into a molding tool, air supply may also be omitted.
In addition, the venturi effect may also be utilized. For this purpose, a venturi nozzle is formed at the outlet-side end of the (material) inlet and is connected to the same or further air inlet. Arranged between venturi nozzle and air inlet in the area of the (material) inlet is an air collecting space (e.g. annular space) which in particular surrounds the (material) inlet and across which the additionally supplied air is distributed into the venturi nozzle. With this preferred configuration, air flows at high speed into the mixing chamber, for example via the annular gap between the nozzle housing and a lance forming the (material) inlet. Suction is hereby generated at the inflow nozzles of the solid material as a result of the venturi effect and the filler is likewise drawn in. This causes an even transport of the substance being admixed into the reactive material mixture. The gap dimension may, for example be between 0.1 and 0.5 mm.
In order to be able to gently admix the substance being added into the reactive mixture within the mixing chamber, the injection nozzle has in terms of flow in its mouth region an orientation which preferably extends at an acute angle to the flow direction of the mixing chamber. In this way, the material flows are mixed together without great pressure and force impact on the particles.
Overall, the present invention is able to attain an introduction of even sensitive fillers (e.g. fragile fillers) into the reactive material mixture already within the nozzle in order to effectively prevent a release to the outside and to incorporate the substances to be introduced as completely as possible into the reactive material mixture.
A single exemplary embodiment of the invention will now be described in greater detail with reference to the accompanying drawings. The drawings show in
Two channels 20 of two material supply devices 18 feed into this mixing chamber 30 for supply of the substances to be added to the mixing chamber 30 via respective lines and supply devices. It should be noted that this mixing chamber 30 is different from the mixing chamber of a mixing head, which latter mixing chamber is used for mixing the reactive components with one another. As a result, a reactive mixture is already being supplied to the mixing chamber 30 of the spray nozzle.
Examples of added substances include sensitive particles, such as micro-bubbles of glass or expansion graphite.
The channels 20 feed here at the upper end of the mixing chamber 30 at an acute angle into the mixing chamber 30 so that the sensitive substances can be added into the reactive material mixture within the mixing chamber 30 without being subject to great pressure and force. It is hereby also useful that the mixing chamber has a greater diameter than the inlet channel 16.
Air is being injected into the mixing chamber 30 via two air supply inlets 22 (see
The core component of the afore-described spray nozzle is the presence of an insert 32 which is insertable, in particular threadably engageable, into the housing 12 and allows realization of the mixing chamber 30, air supply as well as air injection.
The thus produced total mixture of the reactive mixture and the substance being added is sprayed out via a discharge opening 28 and applied onto the surface of a body to be coated.
The construction of the spray nozzle 10′ differs from the one of the spray nozzle 10 in particular by the arrangement in the housing 12 of a further air supply 34 which ends in an annular space 36 that is arranged about the inlet 16 configured in the shape of a lance. A venturi nozzle 38 is formed by a corresponding taper of the lance (cf.
In this configuration, air introduced via the inlet 34 flows at high speed into the mixing chamber 30 via the annular gap 36 between nozzle housing 12 and the lance forming the inlet for the reactive mixture. Suction is hereby generated at the ends of the inlet nozzles of the solid material (inflow channel 20) due to the venturi effect and the filler is aspirated. This causes an even transport of the substance being admixed into the reactive material mixture. The gap dimension shown in the figures may, for example, range between 0.1 and 0.5 mm.
Moreover, the spray nozzle 10′ has an outlet-side end (discharge opening 28) which is configured differently than the one of the spray nozzle 10.
The present spray nozzle enables even a pressure-sensitive substance to be admixed into a reactive mixture and to inject it therewith.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102010025501.7 | Jun 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/060006 | 6/16/2011 | WO | 00 | 12/19/2012 |
