ABRASIVE PARTICLES.

FIELD OF THE INVENTION

The present invention relates to a nozzle, that would not easily be clogged or worn out from abrasive media in a stream of detergents or water.

BACKGROUND OF THE INVENTION

Nozzles for shot-blasting with detergents, that contain abrasive media hitherto had diameters sized a multiple of that of the particles for to avoid clogging.

However, the abrasive effect of this cleaning method depends on the pressure of the cleaning fluid. This to one part depends on the power of the pressure pump, but as well on the compression ratio that results from the ratio between the gauges of inlet and ejecting orifices.

Not only for this reason as fine a nozzle as possible is preferred: A finer pressure jet also results in a more sharply contured cut or erosion, which usually is aimed at.

Contrary to systems, where air or a gas jet presses the abrasive components through a nozzle, as known with sand-blasting or shot-peening, or with the use of compressed gases as carriers for finer abrasive media - e.g. for dental cleaning- (see to US patents 4.608.018, 4.540.365, 4.462.803, 4.482.322, 4.595.365, 5.094.615, 5.186.625, 5.558.474, 5.733.174, 5.746.596, 5.857.851 , 5.857.900, 5.918.817, 6.485.304, 6.752.685, 6.837.709, 6.935.576 and 6.964.569), as well as on nozzles for blasting a combination of liquid and gas or compressed air, (as in US 4.253.610, 4.776.794, 5.203.698, 5.385.304, 5.551.909, 5.553.784 and 5.595.346) the employment of insoluble particles mixed into liquid media as such is the main cause for blocking and thus the breakdown of such devices.

PRIOR ART However, there are well-known measures, which can solve the problem to a certain degree: The classical paradigm is, to manufacture a nozzle with plain and smooth walls from materials, as hard as possible and resistant to wear and tear- i.e. highly compressed ceramics, rubies or diamonds - as found in EP 0.476.632 B1 in detail and also in US 4.252.768, 4.545.157, 5.052.624 and US 7.757.971.

One of the few exceptions to this is found in US 4.494.698, similarly in US 4.611.759, which describe a nozzle from PU, which there is offered for blasting with abrasive media, however is known to be applied only to sputter gypsum milk in exhaust ports of desulfurization plants. On the other hand, superhard materials are expensive and their treatment is intricate, even if only implemented to the nozzle bore, or when lining their walls with it, as suggested in DE 3528137 A1 and US 5.335.459. A possible way to avoid the employment of superhard materials is to buffer the abrasive medium with a surrounding stream of other media, in order to prevent the wear of the nozzle walls, as suggested in EP 0258 242 B1 (claim 2), EP 0573 957 B1 , US 4.478.368, 4.707.952, 5.018.317, 5.601.478, 6.077.152, 6.824.453 and US 6.846.211. Other suggestions are ducting and smoothing the abrasive jet with lamella nozzles (DE 196 49 921 , EP 0691 183 B1 , US 5.169.065) and/or guiding it in a laminar flow along the nozzles walls (DE 3622292 A1 ), or to reduce contact to it by an accelerated nuclear jet, that would keep it convergent within the tubular walls. (DE 19640921 d and US 5.056.718).

However, inevitable turbulences often make the effect of such measures nearly ineffective after few millimeters way.

Another essay was made with injecting the abrasive means into the jet at the nozzle outlet (US 6.119.964). However, as foreseeable, radiation quality must strongly impaire wit this measure, while regularly most efforts were made to achieve an even spray pattern, as described in DE 10 2006 015 805 A1 .

Other proposals refer to sequentially cleaning the nozzle either mechanically with a tappet like in US 4.945.688, or with a pressure surge of the medium (US 5.312.040) or with additional liquids or filtrates (US 5.226.565), or again with gas pressure (see above). Moreover, it was tried to lubricate the inner wall of a nozzle of porous material by incasing it in a chamber that contains lubricants under high pressure (US 5.921.456 and 6.688.947) - which might be quite intricate. Other solutions refer to a fast replaceability of nozzles (EP 0.810.038 B1 , EP 0.526.087 A1 , as well as US 7.762.812 and 6.601 .783, or to unite nozzle and mixing chamber (US 5.114.766) - the effect of which seems questionable.

The above mentioned paradigm for past nozzle constructions - to make these from as hard a material as possible, in order to reduce their wear - was also transferred to devices with lower pressure, as far as abrasive components were applied.

However, for application with comparatively low pressure (4 to 10 bar at the nozzle) and ap- plications of limited cleaning intensity, like e.g. the removal of biofilm these measures appear inadequately intricate - whereas particularly here the risk of clogged nozzles is quite high with water containing abrasive components. Thus, due to the high cost of adequately resistant nozzles, such cleaning equipment hitherto remained infeasible for the consumer range. PROBLEM TO BE SOLVED

The inventive task therefore is to find a nozzle design with regular- or low cost materials, that would avoid clogging and fast wear when applied as jet-nozzle for fluids, that contain abrasive media.

PROBLEM APPROACH - INVENTIVE STEP

An actuating variable with regard to possible blockages is nozzle geometry. While it is on the one hand obvious that "dead volumes", in which deposits may adhere due to the lack of sufficiently flowing medium are to be avoided, different pressure zones and vortex reflux caused by turbulences in the narrowing of tubes can not so easily be investigated and therefore are only incompletely understood and only insufficiently representable in computer simulation. Even though these are crucial for the accumulation of blast grains at the walls of tubes and nozzles, they could sofar - without much expenditure- only be analyzed post facto from the deposits.

Due to above mentioned paradigm, institutional research for the investigation of relevant conditions related to nozzles made of hard ceramics etc., whereas the inventive approach was based on research with simple means, i.e. with nozzles from acrylic glass for in situ observation of the flow attitude. Surprisingly it was found, that there were substantially smaller deposits and also less wear in comparison to much harder metallic nozzles with similar cross section and surface smoothness.

This was recognized to fulfil the task to implement nozzles in such an economical way, that they avoid blockages, even if its diameter is only little larger than the grain size of the firm components within the medium.

The inventive step follows the perception won from the experiments: that the material of the nozzle must have a certain flexibility on a microscopic scale, to deform itself under turbulences in a water jet of appropriate pressure, so to release accumulated particles from their walls by vibration. Besides it was found, that also the wear and tear of the nozzles is reduced, if they consist of somewhat flexible material instead of a hard one.

Both obviously is based on the fact that turbulences in the medium and periodic irregularities of the primary pressure lead to resonance effects, which release or prevent possible accumulations at the nozzle.

This is comparable to the conventional approach to employ sound generators in nozzles. However, the transmission of vibrations in hard nozzles is, due to the high periodic resonance, only effective in a very high frequency range with low amplitudes -and therefore seems to be less promising- disregard the much higher expenditure for this procedure. SUMMARY OF THE INVENTION

One embodiment of the invention therefore comprises a nozzle made of semi-hard plastic, as is standard PMMA , which avoids expensive materials and laborious methods of manufacturing. Besides, due to their low cost, such nozzles may simply be replaced, if necessary.

Another embodiment pertains to the geometry of the nozzle:

It was found that a vortrex movement is favorable, that is induced proximately to the front of the compression zone and which then is led as laminarly as possibly along the sidewalls up to the nozzles orifice, which itself is bevelled at 45° within a wall thickness of 0.5 mm.

Thus, in contradiction to hereditary constructions and the ideas to smoothen the stream with straight lamellae, a nozzle has been constructed, wherein twisted lamellae or a screw-type guide transform the current flow into vortices in a compression zone to enter a straight pass- way and re-expand in a bevelled orifice, thus forming a fine-spraying cone of high speed particles.

This usually could not have been done in conventional constructions, since lamellae and screw-type spiral cone usually would be clogged quite easily when applying media that contains abrasive particles of nearly the size of their keyways.

But vibrations due to the turbulences in combination with the regarded flexibility of the materials applied, obviously provoke blasts that carry it away.

DETAILED DESCRIPTION OF THE INVENTION IN DRAWINGS

In Fig. 1 the medium enters the inlet hose 3 to be led to the nozzle unit 1 , that is held in a bushing 2, by drillings or slots 7 in the terminal 6 to be led into the pressure chamber 8, where screw-type spin bodies 11 or twisted lamellae 18, held by an axle 10 lead into a conical compression chamber 12.

The therein enclosed and through the in turning turbulence accelerated medium is pressed out through a guideway 13 into the conically bevelled orifice 14.

So particularly for the tooth cleaning with abrasive particles the jet at the nozzle mouth 14 is again expanded to form a conical spray.

Fig. 2 shows a more simply producible version with similar effect: here a cylindrical spin body of parallel lamellae 18 procures the turning turbulence with which the medium with the abrasive particles enters the compression chamber 17, which -as in Fig. 1- leads through a guideway into the bevelled orifice. List of Cited Patents

In sucession of their citation In alphabetical and nummerical order

No. view PAGE LINE No. No. view PAGE LINE

4.608.018 2 24 DE 10 015 805 Al 3 20

4.462.803 2 25 DE 19 640921 CI 3 13

4.482.322 2 25 DE 19 649 921 3 10

4.540.365 2 25 DE 3.528.137 Al 3 3

4.595.365 2 25 DE 3.622.292 3 12

5.094.615 2 25 EP 0-810.038 Bl 3 27

5.186.625 2 25 EP 0.258.242 Bl 3 7

5.558.474 2 25 EP 0.476.632 Bl 2 38

5.733.174 2 25 EP 0.526.087 Al 3 28

5.746.596 2 26 EP 0.573.957 Bl 3 7

5.857.851 2 26 EP 0.691.183 Bl 3 11

5.857.900 2 26 US 4.253.610 2 28

5.918.817 2 26 US 4.252.768 2 38

6.485.304 2 26 US 4.462.803 2 25

6. 752.685 2 26 US 4.478.368 3 7

6.837.709 2 26 US 4.482.322 2 25

6.935.576 2 26 US 4.494.698 2 40

6.964.569 2 27 US 4.540.365 2 25

4.253.610 2 28 US 4.545157 2 39

4.776.794 2 28 US 4.595.365 2 25

5.203.968 2 28 US 4.608.018 2 24

5.385.304 2 28 US 4.611.759 2 40

5.551.909 2 28 US 4.707.952 3 7

5.553.784 2 29 US 4.776.794 2 28

5.595.346 2 30 US 4.945.688 3 22

0.476.632 Bl 2 38 US 5.018.317 3 8

4.252.768 2 38 US 5.052.624 2 39

4.545157 2 39 US 5.056.718 3 13

5.052.624 2 39 US 5.094.615 2 25

7.757.971 2 39 US 5.114.766 3 29

4.494.698 2 40 US 5.169.065 3 11

4.611.759 2 40 US 5.186.625 2 25

3.528.137 Al 3 3 US 5.203.968 2 28

5.335459 3 3 US 5.226.565 3 23 .258.242 Bl 3 7 US 5.312.040 3 22 .573.957 Bl 3 7 US 5.335459 3 3

4.478.368 3 7 US 5.385.304 2 28

4.707.952 3 7 US 5.551.909 2 28

5.018.317 3 8 US 5.553.784 2 29

5.601.478 3 8 US 5.558.474 2 25

6.077.152 3 8 US 5.595.346 2 30

6.842.453 3 8 US 5.601.478 3 8

6.846.211 3 8 US 5.733.174 2 25

19 649 921 3 10 US 5.746.596 2 26 .691.183 Bl 3 11 US 5.857.851 2 26

5.169.065 3 11 US 5.857.900 2 26

3.622.292 3 12 US 5.918.817 2 26

19 640921 CI 3 13 US 5.921.465 3 26

5.056.718 3 13 US 6. 752.685 2 26

6.119.964 3 18 US 6.077.152 3 8

10 015 805 Al 3 20 US 6.119.964 3 18

4.945.688 3 22 US 6.485.304 2 26

5.312.040 3 22 US 6.601.783 2 28

5.226.565 3 23 US 6.688.947 3 26

5.921.465 3 26 US 6.837.709 2 26

6.688.947 3 26 US 6.842.453 3 8 -810.038 Bl 3 27 US 6.846.211 3 8 .526.087 Al 3 28 US 6.935.576 2 26

7.762.812 3 28 US 6.964.569 2 27

6.601.783 2 28 US 7.757.971 2 39

5.114.766 3 29 US 7.762.812 3 28