EP0616564B1 - Method for micro-cleaning a support and apparatus for implementing same - Google Patents

Abstract

PCT No. PCT/FR92/01177 Sec. 371 Date Jun. 9, 1994 Sec. 102(e) Date Jun. 9, 1994 PCT Filed Dec. 11, 1992 PCT Pub. No. WO93/11908 PCT Pub. Date Jun. 24, 1993In performing micro-cleaning and micro-blasting, a dry micro-cleaning abrasive powder is sprayed having a very small grain size. This enables high cleaning speeds to be reconciled with exceptionally fine blasting in order to remove dirty stains and encrusted deposits from valuable, delicate, or fragile medium as is the case when having to blast off pollutants and pollution that become stuck to the surfaces of monuments and buildings. Jets of compressed air charged with fine abrasive particles having grain sizes of less than 200 micrometers can also be sprayed towards the surface. The jets are emitted from nozzles at high speeds so that they sweep the surface with at least ten jets, each of which has a cross section lying in the range of 400 micrometers to 4 millimeters, so that very low kinetic energy is imparted to the surface.

Description

The present invention relates to a method and an installation for dry micro-cleaning, by projection of abrasive powders of very fine particle size, method and installation making it possible to reconcile a high cleaning speed with an exceptional fineness of pickling.

The possibilities of application of the process of the invention are numerous and find their main applications in cases where it is necessary to strip quickly with an absolute delicacy of the various stains and foulings on valuable supports, on delicate supports or on fragile supports.

The process thus finds its main application for the stripping of pollutants and pollution coming to stick and adhere to the surface of the facades of monuments and buildings.

The industrial world releases very many chemical pollutants into the atmosphere; these new pollutants stick to the surfaces of the facades of monuments and buildings, which they end up distorting by making them progressively black and dirty.

In addition, this pollution fouling the facade stones, in many cases leads to a more or less rapid acceleration of the weathering processes of the stones used.

Indeed, under the action of pollution, the facade stones of many monuments are weakened on the surface and this in a very variable and very heterogeneous way. As the pollution layer becomes more and more dandruff, it massages more and more the weakened areas, making the work of stripping these surfaces of stone buildings very fine and very delicate.

If facade stones have always been washed with water, today many scientists working on the problems of alteration of facade stones, underline the fact that the cleaning of new pollution by washing, allows pollutants to penetrate either by capillarity, or by more or less defective joints, or by surface points already weakened , and therefore participates in the acceleration of the alteration processes. Water, which acts here as a chemical reaction agent and as a vehicle for harmful salts, is less and less suitable for cleaning up the pollution stuck on the surfaces of dressed stone facades, especially if they are in addition weakened (scaling, alveolization, etc ...).

Unfortunately, the architects responsible for the maintenance and the safeguarding of the facades of the monuments, hesitate all the same with regard to the disadvantages of the techniques of washing with water, to give preference to cleaning by projection of abrasive particles even fine, because more or less significant risk of abrasion of the surface layer of pickled stones.

Indeed, the surface layer of the cut stones used, is covered over time with a thin layer of crystallization harder than the inside of the stone, which has the effect of protecting the stone from external aggressions all sorts. This thin protective layer which varies from 2 to 5 millimeters is called cullet or sulfin in an urban atmosphere. For the protection of the stone, it is therefore essential to avoid abrading this thin layer of crystallization, especially since this thin film becomes more and more fragile under the action of pollution. This blackish pollution also masks the altered and undergoing alteration areas, thus making the visibility of these fragile areas difficult.

Therefore, the cleaning of pollution encrusted and stuck on ashlar surfaces, represents a work which becomes more and more delicate, meticulous, and meticulous, and the current techniques of projection dry abrasives present a more or less significant risk of abrasion and attack of material depending on the state, hardness and uniformity of hardness of the surface layer.

At the base of abrasive projections, sandblasting is a very coarse and very dusty technique, which uses any type of sand, more or less large, unitary and unidirectional fixed jet which is moved manually by more or less labor. less meticulous and meticulous.

The principle of sandblasting therefore consists of spraying dry, under high air pressure (7 to 8 × 10 ⁵ Pa on average), abrasives or sands that are more or less large or more or less fine, through a sandblasting nozzle of 6 or 8 millimeters section, sandblasting nozzle which is manually operated by a sandblaster.

If the cleaning action of stripping obtained by stripping is very effective and very fast, in addition to the abundant very unpleasant dust caused, the supports and mainly the moldings and sculptures are literally abraded, which means that all the architects, companies, etc ... have been forced to no longer use this pickling method, admittedly fast and economical, but much too abrasive, and causing too much nuisance (dust), so that washing and pickling techniques were preferred.

Faced with these drawbacks, particularly abrasion, various solutions have been provided, consisting mainly of replacing sands of too large a volume, with much finer sands, sands often less than 200 micrometers.

At the same time as this progress, the architects responsible for the maintenance and conservation of old monuments are demanding finer stripping work, especially on the part of the applicators.

Indeed, the applicators or sanders, have a lot of trouble, given the performance requirements and physical hardness of the task, to perform regular, metered, neat work, and this for many consecutive hours. The profitability of many companies forces the sandblasters to work at too high pressures (6, 7, 8 or even 10 or even 12 x 10 ⁵ Pa pressure), to use so-called pickling jets (sandblasting nozzle of 6 , 8 millimeters and even more) and to project very large volumes of air, sometimes going up to 12,000 liters of air per minute, which causes even with very fine abrasive particles, a considerable abrasive attack, which manhandles all areas of delicate surfaces (sculptures, joints, cullet of heterogeneous hardness, etc.), not to mention the entire facade, which can be literally abraded, even if the stones are hard, nor the considerable dust emitted , which requires covering the workspace in a complicated and therefore costly manner.

Thus, the lack of application imposed by the performance and the physical hardness of the task increases more or less significantly, the risk and the abrasion effect of the cleaned supports. In addition, these so-called performance jets make it impossible, given the considerable risk of abrasion, to clean valuable architectural supports.

Conversely, certain restorers and certain sculptors, in order to completely avoid the risk of inconceivable abrasive attack on valuable architectural supports and to guarantee a work without alteration of abrasion of pickled supports, arrived at opposite excesses , excess which consists in projecting only a very small air flow (a few tens of liters per minute), at infinitely low pressures (a few hundred grams), through a finest nozzle possible (true projection pen), with the minimum possible powder and using the finest possible powder, powder often not exceeding 10 micrometers.

The small air stream thus obtained is handled as a pen by the restaurateur who follows with infinite patience, millimeter by millimeter, at 2 or 3 centimeters of working distance, the reliefs of the small area he is pickling.

This micro-sandblasting technique, used by a necessarily very patient workforce, makes it possible to guarantee pickling work without any real risk of abrasion, but the very slow speed of this process makes it completely prohibitive to use and apply on complete building surfaces.

If the abrasive jet has the main feature of being roughly stripped and causing considerable dust, even hampering the visibility of the work, this sandblasting jet is very stripping mainly at its center of impact, and therefore , we understand that by wanting to lower to the maximum, as does micro-sanding all the projection parameters (air flow, projection pressure, abrasive size, nozzle section), this center of impact will be mathematically less and less stripper and abrasive, and that the maximum reduction of all the parameters of air flow and abrasive flow will make work easier, by limiting as much as possible the emission of dust.

However, this absence of abrasive and dust characteristics is at the expense of a cleaning speed and incisive characteristics necessary for good cleaning. Indeed, this mini-jet devoid of these incisive characteristics no longer makes it possible to clean certain types of fouling and soiling, and can therefore even become abrasive by reverse effect, since it is necessary to insist too much on areas that can no longer be cleaned, given the lack of natural incisal characteristics of this mini jet.

During previous research, which is the subject of patent publications FR-B-2 640 529, FR-B-2 643 626, FR-B-2 643 673 and EP-B-0 384 873 filed by the plaintiff, the latter realized that throwing an air-powder mixture against the support to be cleaned by means of several rotating nozzles, a good result was generally obtained.

According to EP-B-0 384 873, a particle size indicated for the powder is of the order of 100 to 200 micrometers, and the number of nozzles is two.

A similar technique is also described in the later document DE-U-90 15670 which uses four nozzles, but says nothing about the particle size of the abrasive particles, in this case sand.

None of the prior documents gives any indication relating to the cross section of the air-powder mixture passing through the nozzles.

However, the numerous tests carried out by the applicant have shown that this technique could still be improved in terms of efficiency and yield, in particular for treating certain types of pollution and certain media.

For this, he first thought of increasing the passage section of the nozzles and, correspondingly, the flow rate of the air-powder mixture. This measure was not satisfactory, because it led to an excessive pickling causing deterioration of the treated surface, in particular on fragile and valuable architectural supports, due to the high total kinetic energy of the projected flows.

We also know, from document DE-U-8 912 741, a gun intended to project a sanitation fluid against stone facades. The gun has a fixed distributor ramp pierced with a row of orifices for passage of the fluid, which is in no way defined.

However, such a device is not suitable for performing effective cleaning and micro-etching of a support using an air-powder mixture, and in particular of a fragile support.

The present invention therefore aims to remedy all of these drawbacks, and to do this it proposes a method of micro-cleaning and micro-etching of a support, according to which one projects in the direction of the support jets of compressed air charged with fine abrasive particles whose particle size is less than 200 micrometers, these jets being emitted by nozzles and moved at high speed by scanning the support, characterized in that a multitude of jets are used, the number of which is at least ten, and in that these jets have, at the level of the nozzles, a section having a dimension between 400 micrometers and 4 millimeters, which gives them a very low kinetic energy.

This micro-pickling and dry micro-cleaning process makes it possible to strip very quickly even very delicate and very fragile supports, as are stone supports.

The process of the present invention makes it possible to carry out an extremely rapid pickling work, while guaranteeing work of excellent quality, and this on all types of soiling and on all types of supports. The method of the present invention guarantees a complete absence of abrasion on all the cleaned supports, even if these include in places delicate and more or less fragile areas or more simply of heterogeneous surface hardness (masonry joints, flaking stones , heterogeneous cullet, etc.). The method of the present invention, by the different possible combinations, allows spraying work without nuisance of dust.

• Dans un jet fixe unitaire unidirectionnel, c'est le centre ou "la pointe" du jet, qui est l'élément incisif décapant et donc abrasif, et les paramètres nécessaires à un travail de décapage rapide, obligent à ce que ce jet soit le plus décapant possible, augmentant d'autant la force d'impact de la "pointe" du jet, et donc augmentant ainsi la force et l'impact d'abrasion.

The development of the process of the invention is based on the following observations:

• In a fixed unidirectional jet, it is the center or "the tip" of the jet, which is the incisive stripping and therefore abrasive element, and the parameters necessary for a rapid stripping job, oblige this jet to be the more stripper possible, thereby increasing the impact force of the "tip" of the jet, and therefore increasing the force and impact of abrasion.

To avoid abrasion of the tip of the jet, the method of the invention starts from the principle that the projection parameters should not be reduced, since this reduction takes place at the expense of the speed and the stripping action , but it is necessary to maintain this speed and this quality of stripping to multidivide the jet into a multitude or into multiple fine micro-jets, and to drive these multiple fine micro-jets oriented multidirectionally in very rapid automatic movement.

Thus for example, a jet of 8 millimeters of nozzle section, perhaps multidivisible either in 64 nozzles of 1 millimeter, or in 44 nozzles of 1.2 millimeters, or in 28 nozzles of 1.5 millimeters, or in 12 nozzles 2.5 millimeters, etc ... (the more the jet is multi-divided, the finer the nozzles, and the more the effect is accentuated).

Thus, the stripping action of the "spray tips" is used to the maximum, by multiplying them in quantity, dividing them in volume, and distributing them over a certain surface (disc or projection wheel).

Mainly the abrasive projection nozzles are very fine: they are between 1 and 2.5 millimeters (but which can in principle go from the method of the invention, from 400 micrometers to 4 millimeters in section.)

These very fine spray nozzles require the use of only very fine-grained abrasives (for example 80 to 100 micrometers). These very fine abrasives sprayed by very fine nozzles, have practically no specific kinetic energy, they can only move at high speed, or at a cleaning impact speed if they are transported inside a jet. or a compressed air stream. This jet or this compressed air stream thus serves as a projection guide for very fine particles. Thus the absence of kinetic energy of these very fine particles forces them to remain stored in the compressed air nets, and to strictly comply with the characteristics very fast movements of these fine air streams.

Thus, if we move the whole of the multitude or multiple nozzles at high speed, these achieve multitudes of fractionations of very fine air streams loaded with particles with very low kinetic energy, in small lengths of ends air streams, thus forming a mist of spray tips.

These jets, or very small lengths of fine air streams, loaded with very fine abrasives, resulting from these multitudes of automatic and incessant mechanical fractionation, carry out a scan carried out at high speed, with a surface touch (in area of the surface to be cleaned), scanning then having neither impact time nor impact volume, to be truly abrasive, in the direction of attack of the pickled supports.

The multiplicity, the speed of movement of the jets, the fineness of the nozzles and the fineness of the abrasives used, then form a fog "of micro-abrasive jet tips" with "ultra-fast multidimensional micro-film impact", thus having only the time and the force of impact necessary, to release at any speed, in a superficial, but effective and very fast way, only the particles with not cemented bond between them.

This mist of spray tips then achieves an ultra-fast surface impact stripping. The absence of volume and impact time, combined with the incessant mechanical displacements of the jets multidivided into multiple fine micro-jets, projecting micro-fine particles, thus allows a work of stripping of astonishing finesse, on very supports delicate and very fragile, given the very fast pickling speed achieved

In fact, the multiplicity of nozzles, spaced over a certain surface, makes it possible, by orienting them in a multidirectional manner, to have a multitude of different attack angles, allowing with the relentless mechanical movement of micro-jets to be able to clean all points constituting a relief, and this without having to insist in all directions and without having, as in traditional unidirectional fixed jet techniques, to rotate the nozzle in all directions, and to insistently follow (abrasive), all contours of reliefs of the surface to be stripped

Thus the process of the present invention is a process which consists in projecting towards a support to be cleaned and pickled, a micro-abrasive mist obtained by the very rapid and continuous movement of multiple fine threads of compressed air, charged with abrasive particles with very low kinetic energy, and to displace this micro-abrasive mist obtained, all along the support to be cleaned.

• la granulométrie des particules abrasives est principalement comprise entre 80 et 120 micromètres ;
• la multitude de jets est obtenue par multi-division d'un jet unique ;
• on projette simultanément un brouillard de particules d'eau atomisée ou de fins jets de vapeur.

In preferred embodiments of the method according to the invention, use is also made of one and / or the other of the following arrangements:

• the particle size of the abrasive particles is mainly between 80 and 120 micrometers;
• the multitude of jets is obtained by multi-division of a single jet;
• a mist of atomized water particles or fine jets of vapor is simultaneously projected.

Furthermore, the subject of the invention is also a micro-cleaning and micro-etching installation equipped with a spraying apparatus comprising a rotating wheel provided with nozzles for spraying compressed air loaded with fine abrasive particles, characterized in that said rotary wheel comprises a multitude of nozzles, the number of which is at least ten, which each have an inlet cone and have a particle passage section whose dimension is between 400 micrometers and 4 millimeters.

• la roue comporte une dizaine à plusieurs dizaines de buses ;
• la roue comporte des dizaines à plusieurs centaines de buses ;
• ledit appareil comporte en outre des moyens pour le faire pivoter par rapport à un support de fixation ;
• la dimension de la section de passage des particules dans les buses est comprise entre 1 et 2,5 millimètres ;
• lesdites buses sont disposées selon des orientations de projection angulaires différentes, multidirectionnelles ;
• l'appareil de projection est équipé en outre de buses de projection d'un mélange d'air comprimé et d'eau ;
• l'appareil de projection est équipé en outre de buses de projection de fins jets de vapeur ;
• lesdites buses ne débordent pas, ou pratiquement pas, par rapport à la face de projection de la roue ;
• l'appareil comprend, dans le sens de déplacement des particules abrasives, un tube d'amenée du mélange air-abrasif, qui débouche sur un évasement en forme d'entonnoir ;
• ledit évasement communique avec chacune des buses, ces dernières formant un angle aigu avec l'axe longitudinal dudit tube d'amenée ;
• le fait que le tube d'amenée et l'évasement sont traversés par un conduit indépendant d'aspiration de l'abrasif ;
• l'amenée du mélange air/particules audit évasement se fait à travers un tube fixe et un conduit rotatif, solidaire de ladite roue, l'étanchéité entre les parties fixe et mobile étant réalisée par un embrèvement de la partie fixe dans la partie mobile, avec présence de joints rotatifs du type joints à lèvres.

According to preferred embodiments of the installation according to the invention, recourse is also had to one and / or the other of the following arrangements:

• the wheel has ten to several tens nozzles;
• the wheel has tens to several hundred nozzles;
• said apparatus further comprises means for pivoting it relative to a fixing support;
• the dimension of the section of passage of the particles in the nozzles is between 1 and 2.5 millimeters;
• said nozzles are arranged according to different, multidirectional angular projection orientations;
• the projection apparatus is further equipped with projection nozzles of a mixture of compressed air and water;
• the projection apparatus is further equipped with projection nozzles for fine jets of vapor;
• said nozzles do not project, or practically do not, with respect to the projection face of the wheel;
• the apparatus comprises, in the direction of movement of the abrasive particles, a tube for supplying the air-abrasive mixture, which leads to a funnel-shaped flare;
• said flare communicates with each of the nozzles, the latter forming an acute angle with the longitudinal axis of said supply tube;
• the fact that the feed tube and the flare are crossed by an independent abrasive suction pipe;
• the air / particles mixture is brought into said flaring through a fixed tube and a rotary duct, integral with said wheel, the sealing between the fixed and mobile parts being achieved by a recess of the fixed part in the mobile part, with the presence of rotary seals of the lip seal type.

The number of nozzles is around thirty on average, but can exceed one hundred in some cases.

The section of the abrasive projection nozzles is mainly located around 1 to 2.5 millimeters, but can range from 400 micrometers to 4 millimeters.

Abrasives of very fine particle size, to have an effective pickling action, are of very high hardness (grains or micro-beads of glass, corundum, etc.).

The nozzle-holder projection wheel can cover a large funnel-shaped distribution cone: the distribution cone and the wheel can be made of P.T.F.E (teflon) or ceramic, and the nozzles are ceramic.

Optionally, the projection wheel, when it is not bored and furnished with nozzles, is pierced with multiple fine orifices forming the nozzles (the assembly then being made entirely of ceramic).

Due to the very thin section of each nozzle duct, the interior of each nozzle preferably has a funnel shape. This cone or funnel shape is necessary in order to allow an easy and fluid flow of the projected abrasives, because of the very great narrowness of each nozzle duct.

The nozzle-carrying wheel is driven in automatic mechanical displacement at more or less high speed, in a speed range situated mainly between 0 and 4000 revolutions per minute.

This effect can be accentuated by other automatic mechanical displacements, in particular by the pivoting of the wheel on itself in an arc of a circle on the left, then in an arc of a circle on the right, then in an arc of a circle upwards and towards the low (mechanical and automatic pivoting around a support).

All of the mechanical movements serve to increase the pickling speed of the micro-jets.

It is the smoothness and the multiplicity of projection nozzles, having mainly 1 to 2.5 millimeters of duct section, it is the fairly large projection distance (ranging from 20 to 80 centimeters from the support to be stripped) is very low energy kinetics of the abrasive particles projected (80 to 100 micrometers or mainly 80 to 120 micrometers), allowing them by their very low kinetic energy to follow the characteristics of very fast displacement of the air streams, it is the very great hardness of attack of these very fine particles (grain of glass, corundum etc ...), it is the very high exit speed given by the acceleration ducts of each nozzle, it is the important volume of air projected, several thousand liters per minute, it is the projection pressure (3 to 6 x 10 ⁵ Pa on average), combined with mechanical movements at high speed, which produce this micro-abrasive mist, under compressed air pressure, which is not a dusty abrasive mist, but by the characteristics set out above is a mist of "jet tips", which achieves a scouring sweep by surface brushing, rapid and incessant sweep, allowing to combine a very high pickling speed with no abrasive attack on even very delicate pickling substrates, such as old stone buildings and monuments.

The process of the present invention of spraying fine abrasives under compressed air causes more or less dust, although the process, by its peculiarities (very fine nozzles) consumes 2 to 3 times less abrasive for the same efficiency , and that each fine air stream is adjusted, to project a minimum of abrasive for a large volume of air, since ironing multiple times on the same points.

• soit de positionner dans les espaces entre les buses de projection d'abrasifs, des buses de projection d'eau atomisée ; en effet, pour obtenir le même résultat, sur un jet large classique unidirectionnel de projection d'abrasif ( buse de 8 millimètre), il faudrait projeter beaucoup d'eau simultanément, et la force et le volume du ou des jets d'eau mouilleraient de façon plus ou moins importante le mur, alors que dans le procédé de l'invention, en multidivisant le jet d'abrasif en micro-jets multiples ( par exemple un jet de 8 millimètres de section de buse peut-être multidivisé en 28 buses de 1,5 millimètres ), il faudra alors moins d'eau (28 fois moins dans l'exemple précité) par filet à humidifier, sachant qu'en plus les filets d'air sont réglés pour consommer très peu d'abrasif ; de ce fait, il devient possible, alors en projetant non plus un jet d'eau, mais des particules d'eau atomisées sous pression d'air comprimé, d'humidifier les particules abrasives sans vraiment mouiller les jets ; les jets de projection d'eau atomisés provenant de ces buses 14 d'atomisation pneumatique sont réglés pour envoyer des nuages d'eau atomisés, et ces jets de buse 14 sont dirigés préférentiellement en parallèle aux jets d'abrasifs ;
• soit de positionner dans les espaces entre les buses de projection d'abrasifs, un nombre important de très fines buses de projection de fins jets de vapeur.

The projection of this micro-abrasive mist, a source of dust, makes it possible in the process of the invention, since the jets are fine and dispersed, on the altogether large surface of a projection wheel:

• either to position in the spaces between the abrasive projection nozzles, atomized water projection nozzles; indeed, to obtain the same result, on a classic unidirectional wide jet of abrasive projection (8 mm nozzle), it would be necessary to spray a lot of water simultaneously, and the force and the volume of the water jet (s) would more or less wet the wall, while in the method of the invention, by multidividing the abrasive jet into multiple micro-jets (for example a jet of 8 millimeters of nozzle section may be multidivided into 28 nozzles of 1.5 millimeters), then less will be required of water (28 times less in the above example) per net to be humidified, knowing that in addition the air streams are adjusted to consume very little abrasive; therefore, it becomes possible, then by spraying no longer a water jet, but atomized water particles under compressed air pressure, to humidify the abrasive particles without really wetting the jets; the atomized water spray jets from these pneumatic atomization nozzles 14 are adjusted to send atomized water clouds, and these nozzle jets 14 are preferably directed in parallel to the abrasive jets;
• or to position in the spaces between the abrasive spray nozzles, a large number of very fine spray nozzles for fine jets of steam.

The method of the invention uses compressed air from a compressor, and can produce the air-abrasive mixture by passing through a sandblaster. However, in the process of the invention, it is particularly advantageous not to use a sandblaster. Thus, the compressed air coming from the compressor is sent directly and alone to the multi-nozzle projection device, the air-compressed-abrasive mixture being made inside the projection device just before the nozzle outlet. This system makes it possible to enhance the process of the present invention, by making the best use of the finest nozzles possible, greatly facilitating the regularity of the flow and the flow of abrasive, and consuming very few abrasives. Thus giving more regular jets and can be very weak loaded with abrasive.

Other characteristics and advantages of the invention will appear from the whole of the description and the appended drawings which represent preferred embodiments.

• la figure 1 est une vue schématique de la face de projection d'une roue équipée de 42 buses de projection d'abrasifs,
• la figure 2 est une vue schématique de la face de projection d'une roue équipée de 132 buses de projection d'abrasifs,
• la figure 3 est une vue schématique d'une roue de projection équipée de buses de projection d'abrasifs, et de buses projection de fins jets de vapeur,
• la figure 4 est une vue schématique de l'appareil de projection 21 monté sur un bras de positionnement et de soutien,
• la figure 5 est une vue schématique en coupe de la roue mécanique de projection équipée de buses de projection d'abrasifs,
• la figure 6 est un schéma de principe pour alimenter les buses d'atomisation d'eau,
• la figure 7 est un schéma de principe d'un appareil de projection équipé d'un système de mélange air-abrasif à l'intérieur de l'appareil, par aspiration des particules abrasives juste avant leur projection.

In these drawings:

• FIG. 1 is a schematic view of the projection face of a wheel equipped with 42 abrasive projection nozzles,
• FIG. 2 is a schematic view of the projection face of a wheel equipped with 132 abrasive projection nozzles,
• FIG. 3 is a schematic view of a projection wheel fitted with abrasive projection nozzles, and projection jets for fine jets of vapor,
• FIG. 4 is a schematic view of the projection apparatus 21 mounted on a positioning and support arm,
• FIG. 5 is a schematic sectional view of the mechanical projection wheel equipped with abrasive projection nozzles,
• FIG. 6 is a block diagram for supplying the water atomization nozzles,
• Figure 7 is a block diagram of a projection apparatus equipped with an air-abrasive mixing system inside the apparatus, by suction of the abrasive particles just before their projection.

The installation for implementing the method of the invention comprises a projection device or projection wheel, comprising in the direction of movement of the abrasive particles a tube 2 for cylindrical supply of the air-abrasive particle mixture opening onto a wide flare 4 in the form of a funnel, this flare 4 communicating by means of inlet cones 7 with said nozzles 6 for blasting abrasives, the direction of each of said nozzles 6 forming an acute angle with the longitudinal axis of said supply tube 2. This inclination of different angle on each nozzle 6, allows to obtain a multitude of different projection angles, giving a projection by attack of multidirectional micro-jets.

The apparatus or projection wheel 21 is equipped with a multitude or multiple fine nozzles 6 for projecting abrasives, which are positioned and spaced on a projection disc 15. The positioning is done according to drawing shapes mainly in spirals , in order to accentuate the rotary effect and to cover and sweep the maximum of different cleaning points. The numerous nozzles 6 for blasting abrasives do not project or hardly extend beyond the blasting face 15, thus ensuring a very compact assembly and allowing movement in the air of the blasting apparatus 21 very reliably, in all directions even at very high speed of movement.

This projection wheel 10 is equipped with means allowing its mechanical drive in rotation at very high speed (0 to 4000 revolutions per minute).

This projection wheel 10 is equipped with means allowing it to pivot in mechanical and automatic strokes on itself in an arc of a circle on the left then in an arc of a circle on the right.

This projection wheel 10 is equipped with means allowing it to pivot in mechanical and automatic strokes on itself in an arc of a circle upwards then downwards.

This projection wheel 10 is equipped with means making it possible to automatically modify all of the projection parameters (on, off, mechanical speed variator, flow rate, pressure, air-abrasive metering, etc.).

• un conduit 1 d'amenée fixe du mélange air-abrasif,
• un tube cylindrique 2 d'amenée du mélange air-abrasif : l'ensemble de ce tube 2 est rotatif et est monté par un jeu de roulements 3 à double étanchéité,
• un alésage 4 central, formant un large évasement en forme d'entonnoir, permettant d'approvisionner l'ensemble des buses 6 de projection d'abrasifs au travers de cônes de distribution et de répartition et de multidiviser ainsi le jet central en une multitude de micro-jets. Cet alésage 4 débouche et se ramifie sur les cônes 7 d'entrée de buse en forme aussi d'entonnoir, situés dans la roue 10 de projection,
• des buses 6 de projection: la roue 10 porte-buses 6 est en céramique, elle est percée d'une multitude ou de multiples orifices fins multidirectionnels formant les buses 6 de projection d'abrasifs fins.

This wheel 10 or projection device, is equipped with a distribution and projection system of the air-abrasive mixture. This system includes:

• a fixed supply duct 1 for the air-abrasive mixture,
• a cylindrical tube 2 for supplying the air-abrasive mixture: the assembly of this tube 2 is rotary and is mounted by a set of double-sealed bearings 3,
• a central bore 4, forming a large flare in the form of a funnel, making it possible to supply all of the nozzles 6 for blasting abrasives through distribution and distribution cones and thus to multidivise the central jet into a multitude of micro-jets. This bore 4 opens and branches out on the cones 7 of the nozzle inlet, also in the form of a funnel, situated in the projection wheel 10,
• spray nozzles 6: the nozzle holder wheel 6 is made of ceramic, it is pierced with a multitude or multiple multidirectional fine orifices forming the nozzles 6 for spraying fine abrasives.

• un très large cône 7 d'entrée de buse, en forme d'entonnoir permettant de par la multidivision du jet en jets très fins, et de par l'étroitesse des conduits obtenus, un écoulement fluide et aisé des particules,
• un conduit d'accélération 8 de l'air et des particules abrasives,
• un conduit d'éjection 9 variant d'une forme circulaire à une forme oblongue au niveau de son ouverture de sortie sur la face de projection 15 des particules.

Each nozzle 6 of the wheel 10 comprises:

• a very large cone 7 for the inlet of the nozzle, in the form of a funnel allowing, by the multidivision of the jet into very fine jets, and by the narrowness of the conduits obtained, a fluid and easy flow of particles,
• an air and abrasive particle acceleration duct 8,
• an ejection duct 9 varying from a circular shape to an oblong shape at its outlet opening on the projection face 15 of the particles.

• un embrèvement 26 de la partie fixe dans la partie mobile et dont le guidage en rotation est étanché par des joints rotatifs 5 de type joints à lèvres, ainsi qu'au niveau du guidage en rotation de ce cône d'amenée 4 par rapport au carter 11 fixe par des roulements 3 à double étanchéité. L'étanchéité du couvercle 18 arrière est assurée par un joint plat.

The assembly of this projection wheel 10 is mounted in a completely sealed casing 11. Indeed, the rotational drive of mechanical parts in a medium of very fine abrasives (certain abrasive particles not exceeding a few microns), require a specific manufacturing configuration, and a truly specific seal compared to the fineness of these abrasives very fine.
Thus the device is made completely waterproof by:

• a recess 26 of the fixed part in the mobile part and whose rotation guide is sealed by seals rotary 5 of the lip seal type, as well as at the level of the guiding in rotation of this supply cone 4 relative to the casing 11 fixed by bearings 3 with double sealing. The rear cover 18 is sealed by a flat seal.

With the principle of working without a sandblaster, the configuration of the interior of the projection device 21 is modified by the presence of a central duct 19 for supplying the abrasive (by suction), this duct branching out as many small pipes 20 (supply of abrasives) as there are nozzles 6. The only air not loaded with abrasives arriving in the inlet cone 7 of the nozzle sucks regularly and simultaneously in its passage a small amount of abrasives. This central duct 19 for supplying the abrasive (by suction) is fixed relative to the air supply cone, and it is centered and fixed by fixing lugs connected to the rotary tube 2 and to the distribution cone 4 : This duct is therefore rotated simultaneously with the tube 2 and the distribution cone 4, and therefore comprises a sealed rotary joint at its junction with the abrasive supply pipe.

The projection of abrasive in the form of a mist produced by this projection wheel causes significant dust, so parallel to the projection of fine air streams loaded with very fine abrasive particles, it is advantageous to have on the projection wheel 10 d 'abrasives, a number of very fine nozzles 14 for spraying atomized water or very fine nozzles for spraying very fine jets of vapor 17.

The use of fine air streams and abrasives, the projection nozzles 6 of which are arranged on the altogether large surface which constitutes the surface 15 of the projection wheel 10, makes it possible to dilute the compressed air streams and abrasives in a mist of atomized water particles. This projection wheel 10 also makes it possible by the rotary phenomenon to bring about a homogenization of the water mist which is constantly reforming in the voids of projection of abrasives.

The very fine atomized water particles projected into the projection space are projected in the form of a spray of very fine atomized water particles, the particle size of these atomized water particles being as fine as possible.

Thus this projection wheel 10 is equipped with nozzles 14 for spraying atomized water arranged on the projection face 15.
Water is brought into the spraying apparatus by means of a fixed pipe 22 centered in the cone for supplying the air-abrasive mixture. This conduit 22 is fixed by fixing lugs 13 connected to the rotary tube 2 and to the distribution cone 4. This conduit 22 is rotated simultaneously with the tube 2 and the distribution cone 4 and therefore requires a sealed rotary joint with the pipe 22 for supplying pressurized water. This conduit 22 branches into a series of small channels 25 leading the water to the atomization nozzles 14.

The atomized water spray jets from the pneumatic atomization nozzles 14 are adjusted to send atomized water clouds and these nozzle jets 14 are preferably directed in parallel to the abrasive jets.

In different embodiments, the nozzles 14 for spraying atomized water can be replaced by nozzles for spraying very fine jets of vapor 17.

This wheel 10 for blasting fine abrasives can have a diameter of a few centimeters to several tens of centimeters, this diameter of the blasting wheel 10 being proportional to the number of nozzles fitted to it and to the more or less large spacing given to these.

The process of the invention is a micro-pickling and micro-cleaning process combining speed and very high quality. This high-speed surface touch impact process can be applied to almost all types mainly delicate and very fragile supports (old stones, altered and flaked stones, antiques, old furniture, plasters, etc.), and allows to clean all types of dirt and deposits (oil, various pollutants, tags, graffiti, etc. ).

In a preferred embodiment of the apparatus 21 or of the projection wheel, this projection apparatus 21 is mounted on a support and positioning arm 16. It is equipped with handles 23 for movement and guidance. The projection wheel 10 is equipped with forty eight nozzles 6 for projecting fine abrasives. The section of these nozzles is 2 millimeters. These nozzles are made of ceramic. The assembly comprises, in the direction of movement of the particles, a tube 2 for supplying the air-abrasive particle mixture leading to a wide flare in the form of a funnel 4, this flaring communicating by means of cones 7 inlet with said abrasive spray nozzles 6, the direction of each of said nozzles forming an acute angle with the longitudinal axis of said supply tube 2.

The feed cone 4 which conveys the abrasive in the wheel 10 nozzle holder 6 is made of PTFE (teflon), it is guided in rotation by a sealed needle bushing 24 and a sealed ball bearing 3, housed in a casing 11 itself sealed. The rotation is ensured by a pneumatic motor 12. The sealing of the guide in rotation with the air + abrasive supply pipe is ensured by a rotary seal with double sealing. In order to be able to work without dust, the device is fitted with a set of 24 atomized air-water projection nozzles 14.
The compressed air is supplied by a compressor and the air + abrasive mixture is in this case via a sandblaster, the air-abrasive mixture arriving via the fixed tube 1. The air-water supply is making through a water booster compressor.

The operator is positioned in front of the surface to be stripped, presents the projection device in front of this zone, it starts the rotary motor, it triggers the air-water mixture, it triggers the air-abrasive mixture, and it begins to move gradually, substantially parallel to the surface to be stripped. There is no point of impact the very many jets moving at very high speed over the area to be scoured, sweep gently and superficially (but effective) by micro-abrasive mist this area to be scoured. The presence of delicate or fragile points in this area does not change anything, neither its settings, nor its working speed, which makes it possible to very quickly clean an area without any risk of abrasion or alteration of the pickled surface. The mist of water particles sprayed simultaneously humidifies the dust without wetting the jets, allowing very fine, rapid stripping work without nuisance of dust.

Claims (18)

1. A method of micro-cleaning and of micro-blasting a medium, in which method jets of compressed air charged with fine abrasive particles having grain sizes of less than 200 micrometers are sprayed towards the medium, the jets being emitted via nozzles (6) and being displaced at high speeds so that they sweep the support, said method being characterized in that a multitude of jets are used, the number of jets being at least ten, and in that, at each nozzle (6), respective jet has a cross-section lying in the range 400 micrometers to 4 millimeters, thereby imparting very low kinetic energy to the jet.
2. A method according to claim 1, characterized by the fact that the grain size of the abrasive particles lies mainly in the range 80 micrometers to 120 micrometers.
3. A method according to claim 1 or 2, in which the multitude of jets is obtained by dividing up a single jet (2).
4. A method according to any one of claims 1 to 3, characterized by the fact that a mist of atomized water particles or of fine jets of steam is sprayed simultaneously.
5. A method according to any one of claims 1 to 3, characterized by the fact that compressed air is sprayed without any abrasive, and the spraying pressure of the compressed air is used to suck in fine abrasive particles just before they are sprayed onto the medium.
6. Micro-cleaning and micro-blasting apparatus provided with a spraying device (21) including a rotary wheel (10) provided with nozzles (6) for spraying compressed air charged with fine abrasive particles, said apparatus being characterized in that said rotary wheel (10) is provided with a multitude of nozzles (6), the number of nozzles being at least ten, and each nozzle having an inlet cone (7) and a through section lying in the range 400 micrometers to 4 millimeters through which the particles can pass.
7. Apparatus according to claim 6, characterized by the fact that the wheel (10) is provided with in the range about ten to several tens of nozzles (6).
8. Apparatus according to claim 6, characterized by the fact that the wheel (10) is provided with in the range several tens of to several hundred nozzles (6).
9. Apparatus according to any one of claims 6 to 8, characterized by the fact that said device (21) further includes means for pivoting it relative to a fixing support.
10. Apparatus according to any one of claims 6 to 9, characterized by the fact that the through section for the particles in the nozzles lies in the range 1 millimeter to 2.5 millimeters.
11. Apparatus according to any one of claims 6 to 10, characterized by the fact that said nozzles (6) are disposed at different multidirectional spraying angles.
12. Apparatus according to any one of claims 6 to 11, characterized by the fact that the spraying device (21) is also provided with nozzles (14) for spraying a mixture of compressed air and of water.
13. Apparatus according to any one of claims 6 to 11, characterized by the fact that the spraying device (21) is also provided with nozzles (17) for spraying fine jets of steam.
14. Apparatus according to any one of claims 6 to 13, characterized by the fact that said nozzles (6, 14, 17) do not project from or hardly project from the spraying face (15) of the wheel (10).
15. Apparatus according to any one of claims 6 to 14, characterized by the fact that, in the direction in which the abrasive particles are displaced, the device (21) includes a feed tube (2) for feeding in the air-abrasive mixture, the tube opening out into a funnel-shaped flared portion (4)
16. Apparatus according to claim 15, characterized by the fact that said flared portion (4) communicates with said nozzles (6), each of said nozzles forming an acute angle with the longitudinal axis of said feed tube (2).
17. Apparatus according to claim 15 or 16, characterized by the fact that an independent pipe (19) via which the abrasive is sucked passes through the feed tube (2) and the flared portion (4).
18. Apparatus according to claim 16 or 17, characterized by the fact that the air/particle mixture is fed to said flared portion (4) via a fixed tube (1) and via a rotary pipe (2) that is secured to said wheel (10), sealing between the fixed portion and the moving portion being provided by a recessed joint (26) via which the fixed portion is received in the moving portion, with rotary gaskets (5) of the lip seal type being provided.

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