EP2785494B1 - Method for wet-blasting workpieces - Google Patents

Description

The present invention relates to a method for wet blasting according to the preamble of claim 1.

In the prior art, a jet system is known in which a so-called. Injector blasting gun is provided. In addition to the jet nozzle, which extends up to the outlet opening, there is a forward flow nozzle in the flow direction. The suspension is introduced into the blasting gun by means of a supply line and, in the interior of the gun, first passes through a flow space enclosed by the gun housing to the aforementioned front nozzle. The known injector blasting gun additionally has a tubular injector which extends from the outside through the gun housing and through the flow chamber surrounded by the gun housing so far into the gun interior, that the mouth of the injector is leaving a free annular gap within the attachment nozzle. Through the injector a quantitatively strong compressed air flow is blown into the attachment nozzle, which there according to its directed towards the outlet pressure effect or force and the inlet flowing through the annular gap with accelerated and finally pushes out of the blasting gun. at proper operation results on the inlet side of the attachment nozzle and in the flow space of the blasting gun a negative pressure, as its effect further suspension from the supply line is sucked by the suspension container. While such injector blasting guns are well suited for use with a dry blasting medium (ie without the addition of liquid) and offer a cost-effective solution, especially when wet blasting often creates a rather unfavorable spray pattern with a more intensive irradiation in the center and a comparatively weaker blasted scattering zone along the circumference. When wet blasting, in which a suspension containing the blasting agent is irradiated, is added as an aggravation that the performance of such injector blasting guns is low, since the suspension can suck only limited by the compressed air jet from the injector. In order to supply such a jet gun with a significantly larger amount of suspension per unit time than is possible only with the negative pressure, therefore, in a known development of the jet system, the suspension is pumped by a pump to the jet gun, for example. With a conventional or modified Submersible pump, which is usually a centrifugal pump. Then, however, the problem arises that the coming of the pump suspension has a fast-flowing water content and a significantly slower flowing blasting agent content, this Segration is further enhanced with each change in direction in a hose or pipe. These separate streams can mix only partially in the jet gun at most and therefore adversely affect the operation of the jet system. Another difficulty is that in the known injector jet gun due to the comparatively large, supplied by the injector compressed air flow is also the risk that the jet formed from suspension and compressed air pulsates at the outlet of the blasting gun. A disadvantage is also felt that the known Jet system requires a high specific, ie related to the enforced suspension flow compressed air flow rate, which entails high operating costs and also certain restrictions on the application, eg. About the addition of additives to the blasting entails.

In the prior art is off US 3,447,272 A a method for wet blasting known. EP 2 463 058 A2 discloses a blasting nozzle for a device for blasting objects. Out DE 100 10 012 A1 For example, a method and an apparatus for irradiating with various blasting agents are known. DE 10 2005 010 781 A1 discloses a particle beam device.

Against this background, the present invention has the object of developing a generic method for wet blasting advantageous.

The object is achieved according to the invention in conjunction with the characterizing features of claim 1. Notwithstanding the known injector blasting gun, the suspension and the supplied air do not first meet in the nozzle, but already in the supply line, through which the suspension flows to the blasting gun. Investigations and experiments have shown that this, in particular in connection with the below-mentioned possibilities for preferred development, advantageous to the beam result, the constructive Effort and operating costs. The invention is based in particular on the finding that a in the supply line of the suspension (one could also speak of the suspension supply line) supplied air volume flow, which in relation to the same time unit enforced suspension volume flow significantly lower than at the explained prior art already leads to an advantageous effect on the beam result. It has been found that a finely dispersed uniform distribution of very small air bubbles in the suspension causes the air bubbles in the jet nozzle to expand, thereby increasing the exit velocity of the suspension, resulting in a significant increase in jet action. Advantageously, this effect is already achieved with a comparison with the prior art described extremely low amount of compressed air, so that allows lower operating costs and also a pulsation of the beam can be prevented. According to the invention, the supplied small amount of compressed air is not supplied for the purpose of entrainment of the suspension by means of a compressed air jet, but within the scope of the invention, the supply of suspension to the jet device or jet gun is achieved in another way by means of said pressurizing device. The specific, ie based on the suspension volume flow, compressed air flow rate is chosen so low that in a preferred finely dispersed introduction of the air bubbles in the suspension such a sufficient spacing between air bubbles in the suspension results that the air bubbles no or only a relatively small Have a tendency to bond together, allowing a continuous jet of emulsion without undesirable pulsation. On the other hand, it was surprisingly found that even such small amounts of air sufficient to increase the exit velocity of the suspension from the blasting gun appreciably and a considerable increase in the beam effect to reach. This effect is attributed to the expansion of at least part of the air bubbles in the jet nozzle.

There are numerous options for preferred training. In a preferred embodiment of the method, it is provided that the compressed air volume flow supplied by means of the compressed air supply device and the suspension volume flow supplied by the supply line are coordinated so that the ratio of compressed air volume flow to suspension volume flow, if both volume flows to ambient pressure , in particular to 1 bar, converted, is smaller than the value 1 and preferably corresponds approximately to the value 0.5. It is understood that deviating conditions are possible, for example, could take the value 0.1 or 0.2 or 0.3 or the like. In this respect, therefore, only a very small amount of air is supplied to the suspension, in particular with regard to the amount of suspension.

A preferred embodiment also provides that suspension in the container with suspension pressure, which is preferably 3 bar, is applied and that compressed air in the compressed air supply line at least temporarily with air pressure which is higher, preferably by 2 bar higher than said suspension pressure , is charged. In an automatic device or system for wet blasting, devices may be present which are suitable for automatically adjusting or adapting the air pressure as a function of a suspension pressure preselected by the user so as to automatically produce a desired pressure difference, preferably around 2 bar , It is then sufficient that the user selects or regulates only the suspension or jet pressure, while the air pressure in the compressed air supply line then automatically adjusted according to the desired pressure difference becomes. Preferably, a jet device can be used with a jet nozzle whose beam cross-section is, for example, 40 mm ² . Preferably, there is the possibility that the jet device is fed through the supply line, a suspension stream, which, if it is converted to ambient pressure (ie preferably to about 1 bar), corresponds to a volume flow of about 0.8 liters of suspension per second. In particular, in connection with it is preferred that a compressed air flow is supplied through the compressed air supply line, which, if it is converted to ambient pressure (ie relaxed air at preferably about 1 bar), corresponds to a volume flow of about 0.4 liters of air per second , The adjustment of the volume flows can be carried out, for example, by means of tables familiar to the person skilled in the art. The indication of a volume flow of 0.4 liters of relaxed air per second refers to the preferred differential pressure of 2 bar and preferably remains the same or at least in a preferred embodiment of the device, for example, if the suspension pressure changed, but the pressure difference to the Air pressure is kept constant.

While in the injector blasting guns known from the prior art, the compressed air consumption also increases approximately linearly with increasing power or with increasing suspension volume flow, so that large amounts of compressed air are required especially at high blasting rates, this dependency does not exist according to the invention, but also at high suspension volume flows can satisfy a comparatively considerably lower air supply in order to achieve the described advantageous effects.

The method can also be developed advantageously by using for the wet-blasting a suspension comprising at least one liquid, such as water, and blasting agent comprising solid abrasive particles, wherein it is provided that the blasting agent comprises blasting agent particles of a first blasting medium type and blasting agent particles of at least one second blasting medium variety different therefrom.

Inasmuch as it has been stated that the suspension comprises a liquid and blasting medium comprising solid abrasive particles, the phrase "solid abrasive particles" does not indicate a particular strength, but only serves to distinguish between the liquid and solid components of the suspension. The term abrasive particles also does not specify any particular size of these particles, so that, for example, in addition to, for example, granular steel medium particles, powdery abrasive particles are also included. To standardize the use of language is therefore spoken of abrasive particles in this broad meaning and also of abrasive grains, so that for the further description, the usual terms grain size, grain class, etc. can be used. While the term Strahlmittelart in common usage of the blasting means based on a material name and possibly information on extraction or the manufacturing process, the term of blasting abrasive marks a blasting not only by Strahlmittelart, but also by its grain group, grain size, grain shape and hardness of the abrasive. A grain or abrasive grain is understood as meaning a coherent particle of a blasting medium, the typical dimensions depending on the selected grain size ranging from a few μm to a few mm. The term "grain group" refers to a grain size produced with undersize and oversize, characterized by a lower and upper test grain size, in which the permitted proportions are specified outside the two test grain sizes. The so-called. Grain size is a fineness feature with the dimension length, for example. Nominal diameter of the Analysensieböffnung, which can happen just the abrasive grain. The Grain shape indicates the geometric shape of the grain, for example, spherical, cylindrical, cube-shaped, irregular, with a smooth or fissured surface, to. To speak in this respect of two mutually different types of blasting agent is sufficient if they differ in at least one criterion. With certain abrasives, it can be observed that they change certain features or characteristics with increasing duration of use or radiation. For example, in the course of time, the size, the abrasiveness, etc., may decrease. Unless otherwise specified in comparisons of blasting material types, these comparisons apply at least to the as yet unconsumed starting state of the blasting agent particles in question. In order for the suspension used for blasting to be retained as a mixture of liquid and solid particles, the solid blasting agent particles preferably comprise material which is insoluble in the liquid, it being possible in principle to use all blasting agents known for the wet blasting method.

It is regarded as an advantageous possibility that, at least on average, abrasive particles of the first abrasive species have a higher hardness than abrasive particles of the second abrasive species and that, in particular average, the mass of individual (or each) Strahlmittelteilchen in the second Strahlmittelorte larger than in the first Strahlmittelorte is. The at least average comparison means that an average or average value determined for the abrasive particles of the first abrasive species is compared with an average or average value to be determined for the abrasive particles of the second abrasive species. Due to their comparatively larger mass per individual blasting agent particle (or per blasting agent grain), the blasting agent particles of the second blasting medium type have a comparatively larger kinetic when they strike the workpiece surface Energy, on the other hand, but they have a relatively lower hardness than the Strahlmittelteilchen the first type of abrasive. In this respect, it has now surprisingly been found that the use of a suspension with in this way different types of blasting material is particularly suitable for certain jet tasks, where on the one hand at certain surface areas only a small Werkstückabtrag and a high surface smoothness and on the other hand on certain surface sections, the elimination of Burrs is required, and this is now even possible in only one operation. A typical example is jet tasks, in which cutting edge machining tools form the workpieces. For the rounding of the cutting edges an abrasive blasting agent, such as corundum is required. The intention is to achieve a limited rounding of the cutting edges by means of a workpiece removal, while at the same time leaving as little surface roughness as possible. This is achieved by selecting, for example, corundum in comparatively small grain sizes as the so-called first type of blasting medium. For example. For example, grain sizes from # 320 (equivalent to a typical grain size of 16 μm to 49 μm) to No. 500 (equivalent to a typical grain size of 5 μm to 25 μm) can be used. The desired rounding of the cutting edges then takes place by means of the blasting agent particles of the first blasting medium by a grinding and / or polishing process which produces a high surface smoothness. On the other hand, the removal of the grinding burrs by grinding away or polishing off is not possible. However, since the blasting agent particles of the selected so-called second blasting medium have a comparatively larger mass and consequently greater kinetic energy, these can bend over the grinding burrs, eventually break off and possibly level into the surface without the effect of the blasting agent particles of the so-called first blasting medium type (ie the example of Korundstrahlmittels) to influence. The after cutting off the grinding burrs If necessary, remaining on the workpiece surface ridge residues can be removed due to their only small dimensions of the Strahlmittelteilchen the first type of abrasive. In this context, it has been proven in experiments that it is the abrasive particles of the second type of abrasive, for example, to broken Duroplastgranulat, as it is, for example, in dry blasting equipment used. Experiments have shown that when wet blasting with a suspension in which blasting agent particles of the first and second blasting abrasive are included as a mixture, despite the simultaneous effect on the workpiece, the two simultaneously occurring different action mechanisms surprisingly mutually not adversely affect each other, but complement each other advantageous , In particular, this contributes to the fact that the blasting agent particles of the second blasting medium type, which impinge on the workpiece surface with comparatively greater energy, leave no undesirable scratches or damage there at suitably low hardness. In this respect, it is preferable that, at least on average, the mass of the individual blasting agent particles of the second blasting medium is greater by two to four orders of magnitude than the mass of the individual blasting agent particles of the first blasting medium. The different hardness of the two blasting agent types can be advantageously used in particular in a preferred development of the method, in which a workpiece is used whose hardness is less than the hardness of Strahlmittelteilchen the first Strahlmittelsorte and greater than the hardness of Strahlmittelteilchen the second blasting abrasive.

In order to achieve different (average) masses per blasting agent particle or grain at the different types of blasting medium, there is the possibility that the density and / or the volume per blasting agent particle in the second blasting medium type is greater than in the first blasting medium type. insofar For example, it is preferred that the density of the material comprising the abrasive grains is greater than, preferably one (not necessarily integral), several times higher, and more preferably many times higher, than the density of the first abrasive species in the second abrasive species. For example. For example, the material density in the second blasting medium type may be about 4 kg / dm ³ and in the first blasting medium type, for example about 1.3 kg / dm ³ . However, it should be noted that with increasing density difference in the conventional use of pumps, in particular of centrifugal pumps, to promote the suspension, the tendency increases that in the flow, the abrasive particles of the first Strahlmittelorte separate from the particles of the second Strahlmittelorte and in different Enrich flow areas with different flow velocities. In order to avoid this detrimental influence emanating from suspension-flowed pumps and to counteract the effect of the tendency for separation of the suspension components on the jet result, which is also present in reservoirs in principle, suitable possibilities for further development are proposed below, also in connection with the attached figures ,

According to a further aspect, it is preferred that, in particular on average, the abrasivity of the abrasive particles of the first abrasive species is greater than the abrasiveness of the abrasive particles of the second abrasive species. There is the possibility that this distinction either only with respect to at least one selected workpiece material or a material on which for comparison purposes with each of the two abrasive types of workpiece removal, preferably the so-called. Specific, ie to a certain beam time or enforced on a particular Blasting material related, workpiece removal can be determined, applies. On the other hand, the first blasting medium sort in comparison to the second type of abrasive a higher abrasiveness but also compared to a whole group of materials, for example. Against workpieces made of metallic or ceramic materials or plastic (in particular from elastomers or thermosetting plastics), have. It is also preferred that, preferably average, the average maximum surface roughness of the abrasive particles of the first abrasive species is greater than the average maximum surface roughness of the abrasive particles of the second abrasive species.

Blasting agent particles of the first blasting agent type may alternatively or in combination, for example. Corundum, silica, silicon carbide, glass powder, quartz powder, glass beads or the like. Preferably, the abrasive particles of the first abrasive species are mineral material. With regard to the second type of blasting medium, for example, there is the possibility that the blasting agent particles have duroplastic, which may be broken thermoset granules. There is also the possibility that the blasting agent particles of the second blasting medium type have, alternatively or in combination, plastic, fine ceramics and / or zinc or aluminum granules.

According to a further aspect, it is preferred that abrasive particles of the first abrasive species are comparatively angular and that abrasive particles of the second abrasive species are in comparison to smooth, for example cylindrical or spherical, designed.

Another possible area of application, in which a mixture of blasting agents from different blasting agent types brings advantages in the suspension, or actually enables an application, are applications in which powdery blasting abrasives, such as, for example, "polishing red", are to be used for polishing purposes. Embedded in water, such agents alone have hardly any effect when wet-blasting. If the blasting agent particles of the first type of blasting medium are dust-tight and have a particular red polish, the method can advantageously be carried out by selecting, for example, polyamide grains, preferably having a smooth surface, as the blasting agent particles of the second blasting medium, preferably the polyamide grains cylindrical or cube-like shape, whose dimensions are preferably less than 1 mm. There is also the possibility that suspension is used whose blasting agent particles of the second blasting medium type are plastically or elastically deformable. According to a further aspect, it is preferred that suspension is used whose abrasive particles of the second abrasive species are produced as granules, preferably of vegetable material. With such a combination of abrasives is not a processing of flat bodies in the foreground, but it can, for example, polishing and fine sanding tasks on bodies with a highly structured surface or with complex shape rational and efficient. In contrast to the usual sandblasting, where one is bound to certain shapes and dimensions of the jet nozzles for physical reasons, this type of wet blasting opens up a broad field for variations with respect to the type, shape and dimension of the nozzles. With little effort nozzles for a variety of tasks in almost any way possible.

It is preferred that the supply line of the device comprises a valve which can be optionally opened and closed, and that a valve is provided in the compressed air supply line of the device, which can optionally open and close.

One possibility provides that the compressed air supply line with respect to the suspension flow direction before, preferably immediately before, the Blasting gun is connected to the supply line of the suspension. Instead of the also possible term suspension supply line, the more general term supply line is preferred for differentiation from the compressed air supply line, since these, in addition to suspension transported in some areas, depending on the location of the air feed, in turn, with air. The said supply line can be, for example, a supply hose, or the supply line can consist of several components and, for example, comprise a supply hose. There is the possibility that the compressed air supply line is connected to the supply hose or, for example, in relation to the suspension flow direction is connected to the supply line immediately before the hose start.

With respect to the blasting gun, it is preferred that it has at least one blasting agent outlet opening and at least one blasting-agent outlet opening in front of the blasting nozzle upstream of the suspension flow direction. In particular in connection therewith, there is the possibility that the supply line comprises at least one mixing device, which is arranged in front of the jet nozzle, preferably in front of the blasting gun, with respect to the suspension flow direction. Said mixing device may comprise a mixer housing, in which one or more mixer elements in the suspension-flow through housing cross-section position and position fixed (ie static) are arranged, wherein it may preferably be provided that the Compressed air supply line to the mixer housing, preferably in relation to the suspension flow direction in front of the mixer elements or is connected. There is also the possibility that the supply line extends into the blasting gun, wherein, for example, the mixing device of the supply line is arranged in the blasting gun. There is the possibility that the compressed air supply line is connected in or on the blasting gun to the supply line for suspension, preferably to the mixer housing. For example, the supply line for suspension as a hose, as a pipe or the like, or as a mere suitable for flow through opening or cavity (eg. As a bore) in the jet or in particular in the blasting gun extend.

With regard to the mixing device, there is the possibility that it has a plurality of mixer elements which, viewed in the flow direction of the suspension, are arranged one behind the other. The mixer elements may, for example, be lamellar or wing-like flow guide elements which, for example, may be fastened to the mixer housing on the inside. Various mixer elements arranged in spaced-apart flow cross-sections may have installation positions which are different from one another, in particular with respect to one another, in order to improve the effect of thorough mixing of the suspension. It is preferred that the mixer elements are lamellae whose longitudinal ends are rotated relative to one another about an imaginary plane of rotation along the supply line by a quarter turn, wherein it is further preferred that at least one first mixer element is provided on which a first direction of rotation of the Longitudinal ends is selected to each other, and that at least a second mixer element is provided, the longitudinal ends of each other in a second, opposite to the first direction of rotation twisting direction of rotation are rotated. Especially If the mixing device is located only a short distance behind (ie in the flow direction) of the jet nozzle or the blasting gun, the mixing of the solid and liquid suspension components there has an advantageous effect on a uniform spray pattern on the workpiece surface.

A preferred embodiment also provides that the compressed air supply line is connected to an air supply nozzle, which is preferably designed as an injection needle, and that the air supply nozzle opens into the supply line, preferably perpendicular to the flow direction of the suspension. For example. The injection needle can be inserted directly into the wall of the supply tube and held therein according to the radial pressure, without the need for further holding elements. Alternatively, however, separate fasteners can be used. In experiments, it has proven to be advantageous if the air supply nozzle has an inner diameter which is less than or equal to one millimeter and / or that the ratio of inner diameter of the jet nozzle to inner diameter of the air supply nozzle is greater than 10, and preferably about 15. This ratio is many times greater than in the known injector blasting guns, in which typically the jet nozzle has a diameter of 15 mm and the air nozzle has a diameter of 5 mm, so that the ratio has only the value 3.

A further preferred embodiment provides that the pressurizing device is adjusted or adjustable so that the flow velocity of the suspension with respect to the flow direction behind the connection of the compressed air supply nowhere is less than 2 m / sec. It is also preferred that the compressed air supply device is optionally adjustable so that the pressure of the compressed air supplied by the compressed air supply line either higher, preferably about 1 bar or about 2 bar higher than or about the same size or only slightly higher than the pressure of the pressurized by the pressurizing suspension. While compressed air is fed into the supply line in the pressure setting that is higher in this respect, no air is supplied in the alternatively possible setting, in which the pressure in the compressed air supply line corresponds to the suspension pressure, but a suspension return flow into the compressed air supply line and a blockage there avoided.

As regards the pressurizing device, it is preferred that it has at least one first pressurizing line connected to the pressure vessel and connected to a compressed air source by means of a pressure regulator, which can be optionally opened and closed by means of a valve, closure devices being provided for optionally pressure-tight closure of the container , If the container filled proportionately with suspension is pressurized by the pressurizing line, preferably by an upper section of the container housing, this causes the suspension to be displaced and pushed out of the container by the supply line immersed therein and to be pressurized (so-called jet pressure) the blasting gun flows. It is therefore possible to dispense with the existing in conventional wet-jet systems, flowed through by suspension centrifugal pump and the associated separation of the suspension into liquid and solid components are avoided. It is also further preferred that the compressed air supply line has a branching into two line branches on the input side, of which one line branch is connected by means of a selectively openable or closable valve to the aforementioned pressurization line, and of which the other line branch by means of an optional opening or closing Valve is connected to a compressed air line in which there is a higher air pressure compared to the pressurizing line. For the possible effects and advantages, reference is made to the preceding description.

Alternatively, however, it is possible for the pressurization device to have at least one pump through which suspension flows during operation, for example a submersible pump or a centrifugal pump. In particular in this connection it is preferred that a mixing device is present as described above.

The device can be developed advantageously by having, for example, a blast cabinet for receiving one or more workpieces and by having means adapted to the return conveyance of suspension from the blast cabinet into the container, wherein it is preferably provided that the in the device total existing or circulating amount of suspension greater, preferably many times greater than the in the container, preferably on average, recorded amount of suspension. With a dimensioning of the container adapted thereto, the return of the suspension in the container causes a flow which keeps the suspension in motion and mixes it, so that separation or separation into the various suspension components is counteracted. In order to promote the suspension from the container from the blasting gun and thereby act on the required jet pressure, at least one pressurizing device is preferred instead of a pump through which flows suspension, which is the interior of the container in which suspension for the blasting process to displace the Suspension in the beam line pressurized. In this respect, the container can also be spoken of a pressure vessel. In order to further aggravate segregation of the suspension in the container, can the container is preferably made higher than thick. To that extent additionally existing possibilities for the preferred development is also made to the description of the figures.

Fig. 1

schematisch vereinfacht eine erfindungsgemäße Vorrichtung zum Nassstrahlen gemäß einem ersten bevorzugten Ausführungsbeispiel;

Fig. 1a

eine Vergrößerung von Detail Ia aus Fig. 1;

Fig. 2

schematisch eine erfindungsgemäße Vorrichtung zum Nassstrahlen gemäß einem zweiten bevorzugten Ausführungsbeispiel, während der Vorbereitung des Strahlbetriebs;

Fig. 3

die in Fig. 2 gezeigte Vorrichtung, in Strahlbereitschaft;

Fig. 4

die in den Fig. 2, 3 gezeigte Vorrichtung während des Strahlbetriebs;

Fig. 5

die in den Fig. 2 bis 4 gezeigte Vorrichtung, während des Strahlbetriebs mit Rückförderung von Strahlmittel;

Fig. 6

die in den Figuren 2 bis 5 gezeigte Vorrichtung in Strahlbereitschaft mit im Vergleich zu Fig. 3 zusätzlich aktivierter Umwälzung der Suspension in dem zur Aufnahme und Abgabe von Suspension an die Strahlpistole dienenden Behälter;

Fig. 7

in einer Schnittansicht eine Druckschleuse für Suspension der erfindungsgemäßen Vorrichtung gemäß einem von den Figuren 2 bis 6 etwas abgewandelten Ausführungsbeispiel und demgegenüber in Vergrößerung;

Fig. 7a

eine Draufsicht auf den Deckel der Druckschleuse gemäß Fig. 7, wobei Aufbauten und Montageelemente nicht mit gezeigt sind;

Fig. 8

schematisch eine erfindungsgemäße Vorrichtung zum Nassstrahlen gemäß einem noch weiteren bevorzugten Ausführungsbeispiel, bei dem abweichend von dem Beispiel der Fig. 2 bis 6 zwei Druckschleusen für Suspension zum intermittierenden Betrieb vorgesehen sind;

Fig. 9

in einer Schnittansicht einen Behälter zur Aufnahme und Abgabe von Suspension an die Strahlpistole in einer von Fig. 8 etwas abgewandelten Ausführungsform und gegenüber Fig. 8 in Vergrößerung;

Fig. 9a

eine Draufsicht auf den Deckel des Behälters gemäß Fig. 9;

Fig. 10

schematisch eine Gesamtansicht einer erfindungsgemäßen Vorrichtung zum Nassstrahlen gemäß dem in den Figuren 2 bis 6 dargestellten bevorzugten Ausführungsbeispiel, wobei ausgehend von dem Betriebszustand in Fig. 4 eine Druckluft-Zufuhreinrichtung zur Druckluft-Zufuhr in die Zufuhrleitung der Suspension aktiviert wurde;

Fig. 11

in einer im Vergleich zu Fig. 10 vergrößerten und mittels eines Aufbruchs verkürzten Schnittansicht die in Fig. 10 gezeigte Strahlpistole und einen Abschnitt ihrer Zufuhrleitung für Suspension mit daran angeschlossener Druckluft-Zufuhrleitung;

Fig. 12

schematisch eine erfindungsgemäße Vorrichtung zum Nassstrahlen, gemäß einem noch weiteren bevorzugten Ausführungsbeispiel, wobei abweichend von Figur 4 die Druckluft-Zufuhrleitung an das Mischergehäuse einer vor der Strahldüse angeordneten Mischeinrichtung angeschlossen ist, bei noch ausgeschalteter Drucklufteinspeisung in das Mischergehäuse;

Fig. 13

die in Fig. 12 gezeigte Anordnung, jedoch bei aktivierter Drucklufteinspeisung in das von der Zufuhrleitung für Suspension umfasste Mischergehäuse;

Fig. 14

in einer im Vergleich zu Fig. 13 vergrößerten Schnittansicht die dort gezeigte Strahlpistole mit der an das Mischergehäuse angeschlossenen Druckluft-Zufuhrleitung und

Fig. 15

eine schematisch vereinfachte, starke Vergrößerung eines in Fig. 5 mit XV bezeichneten Ausschnitts aus der Strahlmittel enthaltenden Suspension.

The invention will be further described below with reference to the accompanying figures, which show preferred embodiments. It shows:

Fig. 1

schematically simplifies a device according to the invention for wet blasting according to a first preferred embodiment;

Fig. 1a

an enlargement of detail Ia Fig. 1 ;

Fig. 2

schematically a device according to the invention for wet blasting according to a second preferred embodiment, during the preparation of the blasting operation;

Fig. 3

in the Fig. 2 shown device, in beam readiness;

Fig. 4

in the Fig. 2 . 3 shown device during the beam operation;

Fig. 5

in the Fig. 2 to 4 shown device, during the blasting operation with the return of blasting agent;

Fig. 6

in the FIGS. 2 to 5 shown device in beam readiness compared to Fig. 3 additionally activated recirculation of the suspension in the receptacle used to receive and deliver suspension to the blasting gun;

Fig. 7

in a sectional view of a pressure lock for suspension of the device according to the invention according to one of the FIGS. 2 to 6 slightly modified embodiment and in contrast in magnification;

Fig. 7a

a plan view of the lid of the pressure lock according to Fig. 7 , wherein structures and mounting elements are not shown;

Fig. 8

schematically a device according to the invention for wet blasting according to yet another preferred embodiment, in which, by way of derogation from the example of Fig. 2 to 6 two pressure locks are provided for suspension for intermittent operation;

Fig. 9

in a sectional view of a container for receiving and delivering suspension to the blasting gun in one of Fig. 8 slightly modified embodiment and opposite Fig. 8 in magnification;

Fig. 9a

a plan view of the lid of the container according to Fig. 9 ;

Fig. 10

schematically an overall view of a device according to the invention for wet blasting according to the in the FIGS. 2 to 6 illustrated preferred embodiment, wherein starting from the operating state in Fig. 4 a compressed air supply device was activated for supplying compressed air into the feed line of the suspension;

Fig. 11

in one compared to Fig. 10 enlarged and shortened by a riser sectional view in Fig. 10 shown blasting gun and a portion of its supply line for suspension with compressed air supply line connected thereto;

Fig. 12

schematically a device according to the invention for wet blasting, according to yet another preferred embodiment, wherein different from FIG. 4 the compressed air supply line is connected to the mixer housing of a mixing device arranged in front of the jet nozzle, while the compressed air supply is still switched off into the mixer housing;

Fig. 13

in the Fig. 12 shown arrangement, but with activated compressed air feed into the mixer housing comprised of the suspension supply line;

Fig. 14

in one compared to Fig. 13 enlarged sectional view of the blasting gun shown there with the connected to the mixer housing compressed air supply line and

Fig. 15

a schematically simplified, high magnification of an in Fig. 5 designated XV section of the blasting agent-containing suspension.

With reference to the Figures 1 and 1a an inventive method and an inventive device 1, each according to a first preferred embodiment, presented. As in other figures, the representation is simplified schematically, with a partial section comparable to the view of the interior of housings and containers is possible. The device 1 comprises a blasting cubicle 2, in its inner blasting chamber 3 by means of a holder 4 a workpiece 5 for the purpose of a wet-jet treatment of its workpiece surface 6 is temporarily or releasably supported. For the wet-jet method according to the invention, by means of a jet device 8, which in the example is a jet gun 9, suspension 10 is irradiated onto the freely accessible workpiece surface 6 under a jet pressure which is higher than the ambient pressure. As FIG. 1a schematically indicates greatly simplified, the suspension comprises a liquid 11, in the example water, and blasting agent 12, which is composed of a very large number of solid abrasive particles 13, 14. On closer inspection, it is Strahlmittelteilchen 13 of a first type of abrasive and about it different Strahlmittelteilchen 14 a second Strahlmittelorte. In comparison with the blasting agent particles 13, the blasting agent particles 14 have a larger mass per blasting agent particle, ie a greater weight, a comparatively lower hardness and a comparatively smoother surface. In the example, the abrasive particles 13 are corundum and the abrasive particles 14 are thermoset granules. The suspension is initially stored in a container 15, which may also be referred to as a pressure vessel in view of its still-explained function and significance. The container 15 is in fluid communication with the jet device 8 by means of a supply line 16. At 17, a total of greatly simplified a pressurizing device is indicated. The arrow leading from there to the container 15 represents a preferred embodiment, in which the pressurizing device 17 pressurizes the interior 18 of the container 15 to displace suspension 10 into the supply line 16 with overpressure. Preferably, the pressurizing device 17 can have a compressed air source and a pressurizing line leading from there to the pressure-tight sealable container 15, so that no pump through which the suspension 10 flows is required. However, the dashed, arrow extending from the pressurizing device 17 to the supply line 16, that the pressurizing device 17 could alternatively be a pump which could either be inserted into the supply line 16 or, for example, be arranged as a submersible pump in the container 15.

The apparatus 1 comprises for adding relatively small amounts of air into the suspension, a compressed air supply device 19 which includes the components contained in the imaginary system boundary 20 and the compressed air supply line 21, which in the embodiment in the flow direction 22 of the suspension 10 viewed in front of the blasting gun 9 opens from the side into the supply line 16. The compressed air supply device 19 comprises a compressed air source 32, which may be, for example, a compressed air generating pump or a supply line. The compressed air supply line 21 has on the input side a branching into two line branches, of which the one line branch 24 has an optional opening or closing valve 26 and is fed with the valve 26 open by the compressed air source 32, wherein the air pressure in the line branch 24 means a pressure regulator 28 is adjustable. The other line branch 25 has an optionally openable or closed valve 29 and is also supplied with open valve 29 from the compressed air source 32, wherein the air pressure in the line branch 25 by means of a pressure regulator 31 is individually or deviating adjustable. In the example chosen, the pressure set by the pressure regulator 28 for the line branch 24 corresponds to the pressure exerted by the pressurizing device 17 on the suspension 10 in the container 15, whereas with the pressure regulator 31 for the line branch 25 a higher pressure is preselected. Of the valves 26, 29 one valve is closed and the other is opened, this assignment is switchable. Is, as in FIG. 1 indicated by "X", the valve 26 is closed and the valve 29 is opened, the air pressure in the compressed air supply line 21 is greater than the suspension pressure in the supply line 16, so that compressed air is fed into the supply line 16. In the reverse position of the valves 26, 29 corresponds to the air pressure in the compressed air supply line 21, the suspension pressure in the supply line 16 so that no compressed air is fed into the supply line 16, but on the other hand prevents penetration of suspension 10 in the compressed air supply line 21 becomes. For this purpose, the air pressure in the compressed air supply line 21 could also be set slightly higher if necessary. The explained different valve positions can also be clocked in time, in particular automatically, so that air is supplied during beam operation only during one or more time intervals. It has been shown that even by supplying very small amounts of air or an air volume flow which is considerably lower than the suspension volume flow, a significant acceleration of the suspension in the jet nozzle and improvement of the jet effect can already be achieved.

With reference to the FIGS. 2 to 5 a device 1 according to the invention and a method according to the invention are presented according to a further preferred embodiment, wherein, as in the following, for features that correspond to an example described above at least functionally, the same reference numerals are selected for overview. Compared to the example FIG. 1 additional components have been added. In the supply line 16 for the suspension 10, a valve 30, which in the example is a pneumatically actuated pinch valve, is arranged. This is selectively opened or closed by means of a control line 33 arranged in a control line 34. To identify a sealed Valve position, the symbol "X" is used. A return line 35, which extends from a pressure lock 36 arranged below the blast cabin 2 into the container 15, has also been added. In the return line 35 is a valve 62, which is also a pneumatically controllable pinch valve arranged. This is actuated by means of a control line 38 arranged in a control line 38. The container 15 is designed with respect to all ports so that it can be pressure-sealed from the environment, wherein a arranged in the pressurizing line 27 valve 39 is provided to reduce the pressure in the interior of the container 15 if necessary can. The said pressure lock 36 can be closed pressure-tight to the outside environment and in its supply and discharge lines, wherein 40 denotes a valve by means of which the pressure lock with air from the interior of the (not pressure-tight) blasting room or vent , The blast cabin 2 has a funnel bottom 41, which collects sprayed suspension 10 by means of the blasting device 8, so that it can flow off into the pressure lock 36 through a central bottom opening 42 when it is open. From the pressure regulator 28 (it is a pressure control valve) branches parallel to the pressurizing line 27, which has a valve 7, which can be opened and closed optionally, and is connected to the container 15, a further pressurizing line 43 with a valve 44, which can be optionally opened and closed, from and leads into the pressure lock 36. As to FIG. 7 shown by a slightly different embodiment, an opening of the valve 44 has two effects. First, a cone-shaped sealing body 45 is displaced upwards against a seal seat and pressed by the inflowing compressed air, thereby sealing the bottom opening 42 pressure-tight. From an annular gap 46 which bounds between the discharge pipe 47 of the pressurizing line 43 and a central bore in the sealing body 45 When the valve 40 is closed and the valve 62 is opened, this causes suspension contained in the pressure lock 36 to submerge in it through the air pressure applied to the bottom of the pressure lock 36 because of the air pressure acting on it Return line 35 is pumped into the container 15. In the container 15 are the inlet opening 49 of the supply line 16 and the outlet opening 50 of the return line 35 in each case only a small, mutually equal distance above the bottom of the container 15. This is at an inflow of suspension 10 through the return line 35 in the container 15 advantageously causes a suspension flow, which leads to a desired mixing of the suspension components.

51 denotes a pneumatically operated pump, which in the example is a diaphragm pump. This is connected by means of a compressed air line 52, in which a valve 53, which can optionally open and close, is connected to a further pressure regulator 54. The total of three existing in the example pressure regulators 28, 31 and 54 may be known per se control valves, such as preferably proportional valves, act. The pump 51 can serve to mix the suspension 10 received in the container 15, preferably after longer periods of stoppage of the blasting machine, in order to counteract a drop of blasting agent in the liquid. The two connections of the pump 51 are connected to an intake pipe 55 and to an exhaust pipe 56, wherein in the container 15, the opening of the intake pipe 55 is placed well above the opening of the exhaust pipe 56. The opening of the discharge pipe 56 is located only a short distance above the bottom of the container 15. This makes it possible, after longer downtimes, to suck liquid by means of the suction pipe 55 and convey it through the discharge pipe 56 from below into the Mixing suspension 10, whereby a Verwirbelungsströmung arises, which leads to an overall uniform distribution of the blasting agent 12 in the liquid 11, or this uniform mixing favors and maintains.

In the example chosen, the central compressed air source 32 is a compressed air connection. An outgoing central supply line 57 branches off parallel to the pressure regulators 28, 31 and 54. At the output of the branch 58, in which the pressure regulator 28 is located, the line branch 24, the pressurizing line 27 and the pressurizing line 43 connect in parallel with each other. At the output of the branch 59, in which the pressure regulator 31 is located close to each other parallel to the line branch 25, the control line 37 and the control line 33 at. In this respect, in the example, the compressed air supply line 21 is indirectly connected to the compressed air source 32 with regard to the lines and valves connected therebetween. At the output of the branch 59 ', in which the pressure regulator 54 is located, connects only the compressed air line 52 at.

In the following, a preferred method for operating the device 1 will be briefly presented on the basis of various operating states. FIG. 2 shows an operating state for filling the blasting agent or the suspension 10 in the blasting chamber 3 and for its transport through the pressure lock 36 and the return line 35 into the container 15. The pressure lock 36 has an upper level probe 60 which indicates a corresponding filling, and a lower level probe 61, which indicates an evacuation up to this level. The suspension 10 is filled with initially closed valve 44 and can thus flow into the open top pressure lock 36. When the upper level probe 36 is reached, the venting valve 40 is closed, the valve 44 opened and thereby closed the bottom opening 42, the pressure lock 36 pressurized and pumped suspension 10 through the return line 35 and the open valve 62 into the container 15 while the valve 39 is opened.

FIG. 3 shows a subsequent operating state in which the device 1 is in beam readiness. The suspension in the container is pressurized with the valve 7 open by the pressurizing line 27 while the valves 30, 39 and 62 are closed. By means of the air cushion formed above the suspension 10, the suspension 10 in the container is under pressure, in accordance with the pressure set on the regulator 28.

FIG. 4 shows an operating state in which suspension 10 from the jet device 8 is blasted onto a workpiece 5 according to the jet pressure determined by the pressure regulator 28. For this purpose, the valve 30 was opened. The suspension pumped out or out of the container 15 is replaced by inflowing compressed air because of the still open valve 7, the pressure on the suspension 10 remaining the same. In this operating state, the valve 44 is closed and the venting valve 40 is opened, so that the bottom opening 42 is opened and the suspension 10 can flow back into the pressure lock 36.

FIG. 5 shows a further operating state in which an automatic return delivery of suspension 10 takes place during the blasting operation from the pressure lock 36 into the container 15. This operating condition is triggered when the upper level probe 60 is reached. This causes valves 44 and 62 to open and valves 40 and 7 to close. The compressed air flowing through the pressurizing line 43 presses the suspension 10 From the pressure lock into the container 15 and from there to the jet device 8. In the container 15, which is also referred to as a pressure vessel, there is now practically the same pressure as in the lock 36, and from the pressure lock 36 flows the same amount to suspension 10 to the container 15 as emerges from the jet device 8. However, since the transition from the operating state FIG. 4 to the operating state FIG. 5 a short time interruption occurs, during which the blasting process is to be continued, the flow rate of the suspension 10 through the return line 35 can be adjusted slightly higher than the flow rate through the supply line 16 to compensate for the amount of suspension. This can be achieved by lowering the pressure in the container 15 slightly below the pressure in the pressure lock 36 by means of the valve 39. Due to the resulting small pressure difference between pressure lock and container, the level in the latter rises slightly. With this measure, it can also be achieved that the return conveyance is completed slowly when the jet process is interrupted. When the lower level sensor 61 is reached in the pressure lock, it can return to the operating state according to FIG. 4 be switched so that an intermittent operation is possible.

It will be apparent from the foregoing description that the selected pressurizing device 17, which includes the compressed air source 32, the pressurizing lines 27, 43 and their valves, enables reliable operation of the device 1. In this construction, the device 1 advantageously has no pump 10 through which the suspension flows, so that the unwanted separation of the suspension, which is typical for pumps, and the wear occurring thereon are avoided.

FIG. 6 shows a modification of the in FIG. 3 shown operating state in which the device 1 is in beam readiness. In order to mix the suspended in the container 15 under pressure suspension 10, the pump 51 was turned on.

FIG. 8 shows a device 1 according to another preferred embodiment. This has two, parallel to each other connected to the bottom opening 42 pressure locks 36. As can be seen from the valve positions, is during the in FIG. 8 shown jet suspension pumped from the left 36 in the direction of view pressure lock 36 into the container 15, while at the same time from the blasting cabinet 2 effluent suspension 10 is collected in the adjacent pressure lock 36. The switching of these two functions of the pressure locks 36 can be done by means of the respective level sensors 60, 61.

The FIGS. 9, 9a show one of FIG. 8 slightly modified and in contrast enlarged container 15. This has two connecting pipes 35 'for connecting one of the two in FIG. 8 In addition, as a modification of FIG. 8 , a total of four connecting pipes 16 'are provided for the connection of a respective supply line 16, so that at the same time four jet devices 8 can be connected thereto.

FIG. 10 shows an operating state in which during the blasting operation, the compressed air supply means 19 has been set so that the air flowing through the supply line 16 suspension 10 small air bubbles 63 are supplied. In the example shown, the compressed air supply means 19 comprises the compressed air supply line 21 and the compressed air source 32 and the intermediate therebetween lying pneumatic components. These include the line branches 24, 25 with the valves 26, 29. It is envisaged that the line branch 24 with the pressurizing line 27 on the input side, that is connected in front of the valves 26 and 7, so that the pressure in the line branch 24 of the Pressure regulator 28 is dependent. The comparatively in the example by two bar higher pressure in the other leg 25 is determined by the pressure regulator 31. For further development, it is possible to couple the pressure regulators 28 and 31 so that the pressure regulator 31 is automatically readjusted depending on the pressure set on the pressure regulator 28 so that there is always a desired equal pressure difference between the pressures of these two regulators, in particular is preselected, automatically maintained. In the operating state of FIG. 10 the valve 26 is closed and the valve 29 is opened, so that at the junction 64 compressed air with about two bar pressure difference, but in only a small amount, is entered into the suspension 10. In the example of FIG. 10 is the connection point 64 in the region of a supply hose 65, which is part of the supply line 16.

In the FIG. 11 shown jet device 8 has a Strahlmittelaustrittsöffnung 66 and an upstream with respect to the suspension flow direction 22 jet nozzle 67, which viewed in the flow direction before the blasting agent outlet opening in a longitudinal section has a constant flow cross-section. The supply line 16 comprises a mixing device 68. In the tubular mixer housing 69, three mixer elements 70 are fixed one behind the other in the flow direction 22 in the example. These are, for example, made of plastic or steel lamellae, whose two longitudinal ends 71, 72 are rotated relative to each other about an imaginary axis of rotation by a quarter turn each. Compared to the other two mixer elements70 the middle mixer element is twisted in the opposite direction in order to achieve a good mixing effect. FIG. 11 also shows that the compressed air supply line 21 is connected by means of an elbow 73 to the supply line 16, so that the air supply is transverse to the flow direction 22 takes place. Into the angle 73, an air supply nozzle 74 is firmly inserted by means of serving as a transition conical plastic part 75, which is formed in the example as an injection needle and inserted with its tip in the supply tube 65. It can clearly be seen that the inner diameter of the air supply nozzle 74 is significantly smaller than the inner diameter of the compressed air supply line and to a much greater extent smaller than the inner diameter of the supply line 16 of the suspension 10, so that particularly finely dispersed or small air bubbles 63 in the Suspension 10 (in FIG. 11 not shown). In the example, the outer diameter of the air supply nozzle 74 and the injection needle is 1.2 mm.

FIG. 12 differs from the example in FIG. 10 shown embodiment in that the connection point 64 of the compressed air supply line 21 is located on the supply line 16 to the mixer housing 69. While FIG. 5 indicates an operating state in which the pressure in the compressed air supply line 21 corresponds to the pressure of the suspension 10 in the supply line 16 and consequently no air bubbles are supplied FIG. 13 the alternative operating state (see the already explained valve positions), in which finely distributed small air bubbles are introduced into the suspension 10. In this way illustrated FIG. 14 in enlargement, a possible connection of the compressed air supply line to the mixer housing 69 of the supply line 16.

FIG. 15 illustrated, comparable to FIG. 1a schematically the composition of the suspension 10 used in the example for the blasting. This is composed of a liquid 11 and blasting agent 12 distributed therein in the form of very many small solid particles. The blasting agent 12 comprises blasting agent particles 13 of a first blasting medium type as well as different or different blasting agent particles 14 of a second blasting medium type. The Strahlmittelteilchen 13 are significantly smaller than the Strahlmittelteilchen 14 and have, based on each individual Strahlmittelteilchen, a comparatively lower mass. While the abrasive particles 14 are smooth surface spheres, the abrasive particles 13 are irregular and ragged in shape and have a sharp-edged surface. In this respect, have the Strahlmittelteilchen 13 when hitting a workpiece surface 6 in comparison to the Strahlmittelteilchen 14 higher abrasiveness, while the Stahlmittelteilchen 14 have a relatively higher kinetic energy when hitting.

Claims (20)

1. Method for wet-blasting one or more workpieces (5), wherein a device (1) is used for wet-blasting one or more workpieces, wherein the device (1) comprises at least one container (15) for receiving and discharging suspension (10) containing blasting abrasive (12) and at least one blasting apparatus (8), such as a blast gun (9), for blasting suspension (10) onto the workpiece(s) (5), wherein the blasting apparatus (8) is connected to the container (15) by at least one supply line (16), wherein the device (1) comprises at least one pressurisation means (17) for the selective pressurisation of suspension (10), wherein the device (1) comprises at least one pressurised air supply means (19) which comprises at least one pressurised air supply line (21) and at least one pressurised air source (32), and wherein the pressurised air supply line (21) is connected to the supply line (16) and is connected directly or indirectly to the pressurised air source (32), and wherein the pressurised air volume flow supplied by the pressurised air supply means (19) and the suspension volume flow supplied by the supply line (16) are coordinated in such a way that the ratio of pressurised air volume flow to suspension volume flow is less than the value 1 and corresponds in particular approximately to the value 0.5.
2. Method according to claim 1, characterised in that the pressurised air volume flow supplied by the pressurised air supply means (19) and the suspension volume flow supplied by the supply line (16) are coordinated in such a way that the ratio of pressurised air volume flow to suspension volume flow, when both volume flows are converted to ambient pressure, in particular to 1 bar, is less than the value 1 and corresponds in particular approximately to the value 0.5.
3. Method according to claim 1 and/or claim 2, characterised in that a suspension pressure of in particular 3 bar is applied to suspension in the container (15), in that an air pressure which is higher, in particular 2 bar higher, than said suspension pressure is applied at least temporarily to pressurised air in the pressurised air supply line (21), a pressurised air flow being supplied by the pressurised air supply line (21), to which flow, when said flow is converted to ambient pressure, in particular to expanded air at preferably approximately 1 bar, in particular a volume flow of approximately 0.4 litres air per second corresponds, a blasting apparatus (8) comprising a blasting nozzle being used, the blasting cross section of which is in particular 40 mm², and a suspension flow being supplied to the blasting apparatus (8) by the supply line (16), to which flow, when said flow is converted to ambient pressure, preferably to approximately 1 bar, in particular a volume flow of approximately 0.8 litres suspension per second corresponds.
4. Method according to any of claims 1 to 3, characterised in that a blasting abrasive (12) is used which contains blasting-abrasive particles (13) of a first type of blasting abrasive and blasting-abrasive particles (14) of at least a second type of blasting abrasive which is different therefrom.
5. Method according to any of the preceding claims, characterised in that the supply line (16) of the device (1) comprises a valve (30) which can be selectively opened and closed, and in that a valve (26, 29) which can be selectively opened or closed is provided in the pressurised air supply line.
6. Method according to any of the preceding claims, characterised in that the pressurised air supply line (21) is connected to the supply line (16) upstream of, in particular directly upstream of, the blasting apparatus (8) or blast gun (9) in relation to the suspension flow direction (22) in the supply line (16).
7. Method according to any of the preceding claims, characterised in that the supply line (16) is a supply tube (65) or in that the supply line (16) comprises a supply tube (65).
8. Method according to claim 7, characterised in that the pressurised air supply line (21) is connected to the supply tube (65) or is connected to the supply line (16) directly upstream of the start of the tube in relation to the suspension flow direction (22).
9. Method according to any of the preceding claims, characterised in that the blasting apparatus (8) comprises at least one blasting-abrasive discharge opening (66) and at least one blasting nozzle (67) which is upstream of the blasting-abrasive discharge opening (66) in relation to the suspension flow direction (22).
10. Method according to claim 9, characterised in that the supply line (16) comprises at least one mixing unit (68) which is arranged upstream of the blasting nozzle (67), in particular upstream of the blast gun (9), in relation to the suspension flow direction (22).
11. Method according to claim 10, characterised in that the mixing unit (68) comprises a mixer housing (69) in which one or more mixer elements (70) are arranged in a fixed position and location in the hollow cross section of the housing through which suspension (10) flows, it being provided in particular that the pressurised air supply line (21) is connected to the mixer housing (69) upstream of the mixer element(s) (70) in particular in relation to the suspension flow direction (22).
12. Method according to claim 10 and/or claim 11, characterised in that the supply line (16) extends into the blasting apparatus (8), which apparatus is in particular a blast gun (9), in particular the mixing unit (68) of the supply line (16) being arranged in the blast gun (9), and in that the pressurised air supply line (21) is connected to the supply line (16), in particular to the mixer housing (69), in or upstream of the blast gun (9).
13. Method according to any of preceding claims 10 to 12, characterised in that a plurality of mixer elements (70) are arranged one behind the other in the mixing unit (68) when viewed in the flow direction (22) of the suspension (10), it being provided in particular that the mixer elements (70) are blades, the two longitudinal ends (71, 72) of which are each rotated by a quarter turn relative to one another about an imaginary axis of rotation, it further being provided in particular that at least a first mixer element (70) is provided, at which a first direction of rotation of the longitudinal ends (71, 72) relative to one another is selected, and that at least a second mixer element (70) is provided, the longitudinal ends (71, 72) of which are rotated relative to one another in a second direction of rotation which is counter to the first direction of rotation.
14. Method according to any of the preceding claims, characterised in that the pressurised air supply line (21) is connected to an air supply nozzle (74) for connection to the supply line (16), which nozzle is in particular in the form of an injection needle which discharges into the supply line (16), in particular perpendicularly to the flow direction (22) of the suspension (10).
15. Method according to claims 9 and 14, characterised in that the air supply nozzle (74) has an internal diameter which is less than or approximately equal to 1 millimetre, and/or in that the ratio of the internal diameter of the blasting nozzle (67) to the internal diameter of the air supply nozzle (74) is greater than 10, in particular is approximately 15.
16. Method according to any of the preceding claims, characterised in that the pressurisation means (17) is adjusted or can be adjusted in such a way that the flow speed of the suspension (10) in relation to the flow direction (22) downstream of the connection point (64) of the pressurised air supply line (21) is not less than 2 metres per second at any point.
17. Method according to any of the preceding claims, characterised in that the pressurised air supply means (19) can be selectively adjusted in such a way that the pressure of the pressurised air supplied by the pressurised air supply line (21) is either higher, in particular approximately 1 bar or approximately 2 bar higher, than or approximately equal to the pressure of the suspension (10) pressurised by the pressurisation means (17).
18. Method according to any of the preceding claims, characterised in that the pressurisation means (17) comprises at least a first pressurisation line (27) which is in communication with the container (15) and can be fed pressurised air from a pressurised air source (32), which line can be selectively opened and closed by means of a valve (7), and the air pressure of which can be adjusted by means of a pressure regulator (28), closure means being provided for the pressure-tight closure of the container (15).
19. Method according to claim 18, characterised in that the pressurised air supply line (21) comprises a branching (23) into two line branches (24, 25) on the input side, one line branch (24) of which comprises a valve (26) which can be selectively opened or closed and is connected to the pressurisation line (27) according to claim 18, in particular upstream of the valve (7) thereof when viewed in the pressurised air flow direction, and the other line branch (25) of which comprises a valve (29) which can be selectively opened or closed and is in communication with the pressurised air source (32), the air pressure in the line branch (25) being adjusted or being able to be adjusted by means of at least one pressure regulator (31, 28) so as to be higher than the air pressure in the line branch (24).
20. Method according to any of the preceding claims, characterised in that the pressurisation means (17) comprises at least one pump, such as an immersion pump or a centrifugal pump, through which suspension (10) flows during operation.

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