AU616114B2 - Machine for the spraying of a coating comprising powder and/or fibrous products, process for the spraying of such coating and coating thus obtained - Google Patents

Description

I ~k I dP DATE 22/10/A0 PCI 4OJP DATE 29/11/90 APPLN. ID 534614 PCT NUMBER PCT/FR90/00189 DEMANDE INTERNATIONALE PUBLIEE EN VERTU DU TRAITE DE COOPERATION EN MATIERE DE BREVETS (PCT) (51) Classificati'n Internationale des brevets 5 (11) Num~ro de publication Internationale: WO 90/111531 B22D 41/02, F27D 1/16 Al (43) Date de publi :ation Internationale: 4 octobre 1990 (04.10.90) (21) Numrno de ]a demande Internationale: t'CT/FR90/00 189 (74) Mandataire: BOUJU, Andr6; 38, avenue de la Grande-Arm~e, F-75017 Paris (FR).

(22) Date de d~p6t international: 21 mars 1990 (21.03.90) (81) Etats d~sign~s: AT (brevet europ~en), AU, BE (brevet euro- DonaJ~es relatives AX In priorit6: p~en), BR, CA, CH (brevet europ~en), DE (brevet euro- 89/03899 24 rn- 1989 (24.03,89) FR pden), DK (brevet europ~en), ES (brevet europ~en), FR (brevet europ~en), GB (brevet europ~en), HU, IT (brevet europ~en), KR, LU (brevet europ~en), NL (brevet euro- (71) D~posant (pour ious les Ei'ats d~sign~s saif US); DAUSSAN p~en), NO, RO, SE (brevet europ~en), US.

ET COMPAGNIT 29-33, route de Rombas, F- 57140 Woippy (FR).

Publi~e (72) Inventeurs;1 et Avec rapport de rechlerche International, Inveniteurs/D~posants (US seulem'ent),I DAUSSAN, Jean Avat l'cxpirat ion du d~Iai pr~i'u pour la ,nodufcation des EFR/FR]; 42, rue Saint-M:'rcel, F-5700 Metz revendications, sera repubike si de telles modif/ications sont DAUSSAN, Gerard [FR/Fix]; 32, nte du Fort, F-57050 reques.

Longeville-les-Met:- (1FRP D)AUSSAN, Andr6 EFR/FR]; 52, rue des P~pini~res, F-57050 Longeville- les- Metz

(FR).

(54)Title: MACHINE FOR filE SPRAYING OF A COATING COMPRISING POWDER AND/ORk FIBROUS PRO- DUCTS, PROCESS FOR THE SPRAYING OF SUCH COATING AND COATING THUS OBTAINED (54) Tltre: MACHINE A PROJETER, UN REVETEMENT COMPORTANT DES MATIERES PULVERULENTES ET/OU FIBREUSES, PROCEDE POUR PROJETER UN TEL REVETEMENT ET REVETEMENT AINSI OBTENU (57) Abstract The machine comprises tileanis for receiving the mixture of products constituting the coating, means for direct- Ing the mixture towards the lower part f the machine, means forming a handling chamber for distributing the mixture towards a transport line (13) in which said mixture is pnieumatically driven to a spray nozzle (14) Into which arpt injected pulverized water, or air 4nd pulverized water for m'aking the mixture uniform so that it can be sprayed and tnke hold, It also comprises at least one water, or air plus wator pulverizing apparatus for pre-humidifying the mixture, whereby the quantity of water injected at this stage Is adjusted so that the mixture retains the features of an essentially dry product.

(57) Abr~g6 18 La machine comprend des moyens de rt~ception du mblange des matlbres constituant to rev~tement, des moyens (6) pour achominer le m~lnnge ver5 le bas de la machine, des moyens formanit sas pour dktriluer Ic melange vers une canalisation de transport (13) dans laquelle te melange est propuls6 pneumnatiqueinent jtsqu'A une tWbuiure de projection (14) dans laquelle sont injectbs de l'eau pulv6ris~e, out de 'alr at de lVeau pulv~ris6e, pour rendre te m~lttnge piteux afin de permettre sa projection et sa prise. Elie comporte en outre au momns un pulvbrisateur (16) d'eau, ou d'alr at d'eau, pour pr~humnidifier le mdlange, Ia. quantit6 d'eau inject~e 4 ce stade 6tant rbgt~c pour qua te m~Iange conserve les caract6ristiques d'un produit sensiblement or verso -1- The present invention relates to a machine for continuously spraying a coating containing high percentages of pulverulent and/or fibrous substances and intended to set after wetting with water, in particular a fire-protection coating or a coating for thermal or sound or acoustic insulation, or alternatively a coating for insulating and/or protecting the walls of a metallurgical vessel intended to receive liquid metal.

The invention also relates to a method for spray. ig such a coating, as well as a coating obtained by using the abovementioned machine or method.

EP-A-0,286,513 filed by the Applicant discloses a machine and a method for spraying a coating consisting of at least two layers: an aqueous, pasty and hardenable product containing all the water required for spraying and setting the coating is prepared for each layer, and this product is pumped to a spraying nozzle. Such a machine and such a method are 1Zot suitable for spraying a material containing high percentages of pulverulent and/or fibrous substances.

It is known that such a material may be transported only when dry by blowing with air, the pulverulent and/or fibrous substances being held in suspension in the b,.owing air. The method thus consists in transporting the substances dry and in injecting all the water required at the end of the spraying tube.

Numerous machines of the abovementioned type are known which comprise in a general manner means for receiving the mixture of the substances forming the coating, means for conveying the mixture to the lower part of the machine, rotating lock chamber and distributor means for distributing the mixture by gravity into a blow chamber, blowing means for propelling the mixture by blowing air from the blow chamber into a duct for transporting it to a spraying tube at the end of which atomized water, or air and atomized water, are injected in order to make the said mixture pasty so as to enable it to be sprayed and to set, SThese machines have numerous disadvantages, many aib It is n pote onywe r yboigwihar h uvrln 7~I~YIL~CL~LPI~I~PL~NI~DI~~ -2 of them related to the presence of the pulverulent substances, whether they be refractory particles which themselves have a certain hydraulic-setting effect such as, for example, particles of Aighly calcined magnesia, or particles of binder, which may be a hydraulic-setting binder such as, for example, cement, or a chemical" setting binder such as, for example, silicate. The pric art teaches the person skilled in the art to carry out the moistening of the mixture only at the end of the spraying tube for fear of the binder, and in particular the cement, and/or the said refractories, setting or of the fibres matting together causing the binder, and in particular the cement, to set at any point in the machine.

Because of the insufficient mixing together of the sprayed substances and water, the spraying of a coating of the abovementioned types is accompanied, unless corrective measures are taken, by a high degree of dust formation which, not to mention the discomfort and harm caused to the operators, may result in losses of substance and appreciable and detrimental differences between the composition of the coating applied and that intended.

One of the possible corrective measures consists in significantly increasing the proportion of water added before spraying. Such a measure effectively reduces the formation of dust but the excessively wet mixture is too heavy and too fluid and tends to run along, or fall from, the wall onto which it is applied, which considerably limits the thickness which may be applied in one go.

Moreover, when water used in an excessively large quantity evaporates, it gives a coating whose porosity is too great and may cause the creation of cracks.

In the light of these disadvantages, a mixture containing, for example, a small quantity of dedusting oil,, added when this mixture is prepared, is generally preferably used. The percentage of oil added depends on current regulations, in particular in the case of fire- Sprotection coatings or coatings for protecting the walls n -3 of metallurgical vessels, and is never more than a few percent. However, this oil burns at a high temperature when in contact with liquid metal or in the event of fire, and pollutes the steel or the environment, which significantly reduces the quality of the protection provided by the coating in question.

The object of the invention is to provide a machine of the abovementioned type which overcomes the disadvantages of the known machines and which enables a coating to be sprayed containing high percentages of pulverulent and/or fibrous substances and intended to set after wetting with water, this coating containing no, or virtually no, dedusting oil without giving excessive formation of dust, the quantity of water corresponding substantially to the quantity required to provide the water for tempering the substances and optionally the water of crystallization of the hydraulic or chemical (silicate) binders of the coating.

According to the invention, the spraying machine of the abovementioned type is characterized in that it furthermore comprises, between the receiving means and the spraying tube 14, at least one atomizer of water, or of air and water, in order to premoisten the mixture.

Indeed, the Applicant noticed that it was possible to premoisten the mixture as long as the latter preserves the properties of a dry or substantially dry product, in other words in particular as long as the pulverulent and/or fibrous substances may remain in suspension in the blown air and do not exhibit any segregation likely to influence adversely the homogeneity and the uniformity of the mixture.

In these conditions, and counter to the fears of the person skilled in the art, there is no risk of hydraulic and/or chemical setting, and/or of sticking or matting, inside the machine, of the substances forming the coating.

This injection of water, even in ei smal.! quantity, enables the formation of dust to be considerably reduced, and therefore a coating to be sprayed which

LLI_-

-4 contains only a reduced quantity of oil, or no oil at all, without having to use an excessively high quantity of water which would give rise to the disadvantages mentioned above.

According to an advantageous alternative of the invention, the machine comprises several injectors of atomized water, or of air and atomized water or of air alone, distributed in the receiving means and/or around the means for conveying the mixture to the lower part of machine and/or around the distribution means, and one or more atomizers of air and/or water into the transport duct.

According to another alternative of the invention, the end of the spraying tube is provided with a spreading plate capable of retaining the materials after rebounding and of limiting the emission of dust.

This spreading plate promotes the application and the thorough mixing of the various substances forming the mixture with water and enables both the emission of dust and the loss of substance by rebounding to be reduced, ard the total quantity of water used for spraying the coating to be reduced.

According to an advantageous alternative of the invention, the spreading plate comprises, on at least one of its edges, a flap or a roller with a spindle parallel to this edge.

The roller or rollers and/or the flap or flaps complete the action of the spreading plate on its sides and provide an additional "spreading" and levelling function for the sprayed coating.

i According to another aspect of the invention, the method for spraying a coating containing high percentages of pulverulent and/or fibrous substances and intended to set after wetting with water, in particular by means of a machine of the type defined hereinabove, is characterized in that atomized water or air and atomized water is injected at at least one point in the machine in order H to premoisten the mixture of substances, the quantity of "f water thus injected being less than the quantity usually 17 or rotating fingers or combs or a screw or a required to ensure the spraying and setting of the mixture.

According to an advantageous alternative of the invention, atomized water or air and atomized water is injected at several places in the machine and the duct for transporting the mixture, and the quantity of water injected is optimized at each of these places in order to obtain at each of them a mixture having a moisture content predetermined as a function of the nature, the diameter and the quantity of the fibrous substances and as a function of the nature, the particle size and the quantity of the pulverulent substances, so that the mixture preserves the properties of a substantially dry product.

Each of these methods enables the emission of dust to be reduced and the quantity of water necessary to perform the spraying to be reduced, the second of which enables the spraying conditions and the quality of the coating obtained to be optimized.

According to another aspect of the invention, the coating containing high percentages of pulverulent and/or fibrous substances and intended to set after wetting with water and spraying is characterized in that it is obtained by means of a spraying machine according to the invention and/or that it is formed using a method according to the invention.

S-uc a coating only contains a reduced quantity of oil, or none at all, has a porosity determined beforehand as it may be applied without using an excessive quantity of water, does not run along, or fall from, the wall on which it is sprayed, and may therefore be sprayed, in most cases, in one go with the necessary, thickness, Because of the reduced degree of dust emission, once in place this coating has exactly the composi- tion intended.

Other features and advantages of the invention will emerge from the description below.

lii in the attached drawings, given by way of nonk limiting examples: 11 18r 18 i-i -s -I rI- 6 Figure 1 is a schematic view in longitudinal cross-section with cut-aways of a spraying machine according to the invention; Figure 2 is a view in cross-section along II- II in Figure i, the lid of the machine being partially open, Figure 3 is a top view of a spreading plate according to the invention positioned in order to apply a coating inside a continuous-casting tundish, shown partially in plan view, Figure 4 is a top view of the spreading plate in Figure 3; Figure 5 is a view in cross-section, along V-V in Figure 3, of a spreading plate in operation inside a continuous-casting tundish, this plate being shown in a first position at rest on the base, and in a second position during the spraying of a coating onto one of the side walls of the tundish; Figure 6 is a view in axial cross-section of a vent of a spreading plate according to the invention, along VI-VI in Figure 4; Figure 7 is a view similar to Figure 4 of another embodiment of the spreading plate according to the invention; Figure 8 is a view similar to Figure 5 of a spreading plate according to another embodiment of the invention; Figure 9 is a view similar to Figure 8 of a spreading plate according to another embodiment of the invention.

In the embodiment shown in Figures 1 and 2, the spraying machine according to the invention is adapted for spraying coatings containing high percentages of pulverulent and/or fibrous substances and intended to be sprayed after wetting with water, in particular fireprotection coatings or coatings for thermal or sound or acoustic protection, or coatings for protecting the walls of a metallurgical vessel intended to receive liquid metal.

T IC L 1 I__I i 7 It may, for example, spray coatings composed of a hydraulic binder such as, for example, cement, or a chemical binder such as, for example, a silicate and/or a resin, and/or refractory particles having a hydraulic effect and serving as a binder, and inorganic and/or organic fibres whose nature is appropriate for the function of the coating; the composition of the latter may vary from 0.5% binder and 99.5% fibres to 0% fibres and 100% binder and other pulverulent and granular materials. The machine may, in particular, spray coatings composed of a binder and/or cement, of fibres and pulverulent or granular materials such as perlite or vermiculite in the expanded or non-expanded state, it being possible for the fibres to be, for example, wool fibres for insulating coatings.

It may also spray all sorts of mixtures containing pilverulent and/or fibrous substances, granular substances, and an inorganic and/or organic binder, in particular refractory coatings having refractory partides, and optionally a binder and fibros, in one or more layers, for protecting the walls of a metallurgical vessel intended to receive liquid metal, and in particular refractory coatings such as those described in FR-A-2,393,637, in FR-A-2,458,519 or in FR-A-2,585,273 filed by the Applicant.

In each of these examples, the quantity of water may be adjusted to the exact quantity required to provide the tempering water for the substances and, in certain cases, the water of crystallization of the hydraulicsetting and/or chemically setting binders or substances.

In the embodiment shown in Figures 1 and 2, the spraying machine, of a known type, comprises a hopper 1 with a substantially rectangular horizontal section inside which two parallel lump breakers 2 are mounted, rotating, for example, in opposite directions to each other under the action of a motor, not shown. Each of the lump breakers 2 has several blades 3 distributed along its axis and each having, for example, a different orientation on this axis.

iimmiiImn I 2 47I-r7 7-- -8- In the lower part of the hopper 1, whose width narrows towards the bottom, and below the lump breakers 2, an Archimedes screw 4 is installed which may be driven by the same motor as the lump breakers 2.

The screw 4 pushes the substances towards one of its ends up to a card 6 which, in the example shown, is mounted directly on the shaft 5 of the screw 4. The card 6 carries combs and/or fingers 7 diametrically opposite in pairs, which impart a downward movement to the substances.

A horizontal-axis paddle distributor 8, comprising for example eight to twelve paddles 9 regularly distributed about its shaft and which are flush with the inner wall of the casing 10 of the distributor, is mounted below the card 6. The distributor 8 may also be driven by the same motor as the lump breakers 2 and the screw 4.

A blow chamber 11, in which blowing air is introduced, produced by a blower 12 driven by a motor, not shown, is arranged below the paddle distributor 8.

A transport duct 13, for example a flexible duct, leaves the blow chamber 11 and terminates in a spraying tube 14 of a known type.

According to the invention, the spraying machine has a set of pipes 15, which are rigid in the example shown, equipped with injectors 16 of any known type arranged at various points of the hopper 1, above the card 6 and in the distributor 8. These pipes 15 and atomizers 16 enable water or, preferably, a mixture of air and water to be injected so as to premoisten the mixture.

Similarly, a flexible pipe 15a accompanies the flexible duct 13 for transporting the mixture, and supplies water, or a mixture of air and water, to one or more pulverizer 17 of known type arranged substantially In the axis of the duct 13. The pulverizer may be of the type whose walls have been cut out to a corkscrew shape.

SThe remainder of the water necessary to ensure SWO 90/11153 PC/FR90/00189 1 WO090/11153 PC/FR90/00189 1/3

I,

9 good spraying and setting conditions for the mixture forming the coating is injected into the spraying nozzle 18 of a known type placed at the end of the spraying tube 14. Such a nozzle 18 may comprise, in a known manner, at the periphery of the tube, radially directed openings or openings directed along certain generatrices of a cone converging towards the downstream end of the nozzle, or alternatively, in the axis of the tube, a simple injector or a pulverizer whose walls have been cut-out to a corkscrew shape.

The upper part of the hopper 1 may be closed by a leaktight lid 19 which pivots about a pin 20. The lid 19 is, in its closed position, locked to the hopper 1 by any known means, not shown, which enable the machine to operate under pressure.

In the embodiments shown in Figures 3 to 9, a spreading plate 21 is fastened to the spraying nozzle 18 of the spraying tube 14.

Figures 3 and 5 show a spreading plate 21 according to the invention in operation on the side walls 22 and 23 and on tie base '4 of a continuous-casting tundish the spreading plate 21 serving to form a wear coating 27 on top of the permanent coating 26 of this tundish In the embodiment in Figures 3 to 6, the spreading plate 21 has a trapezoidal shape which is particularly suited to accomplishing the wear coating 27 on the inclined side walls 22 and 23 of the tundish On two of its adjacent sides, the spreading plate 21 has a flexible flap 28 which retains the materials which rebound and the dust. The flexible flaps 28 are, for example, made from rubber or from plastic, are fastened in any known manner to the plate 21 and project perpendicularly to the latter in the direction of the surface to be coated.

As indicated in Figure 5, the flaps 28 have, of course, a height which is substantially equal to or greater than the thickness of the coating 27 to ba A. applied.

P

I, 2 i I- *1 L:' -7i The spreading plate 21 is traversed substantially 10 in its centre by the spraying nozzle 18. It may also be traversed by one or more vents 29, two in the example shown, comprising for example a valve 30 urged towards its seat in the direction of the surface to be coated by a spring 31 (see Figure which makes it easier to remove the air for transporting and spraying the mixture.

Figure 5 shows, on the one hand, a spreading plate 21 at rest, placed on a coating 27 applied to the base 24 of a continuous-casting tundish 25, the flap 28 thus being raised, and, on the other hand a spreading plate 21 executing the coating 27 on the wall 22 of this tundish, the sprayed substances being retained, in the plane of the cross-section, between the wall 22, the spreading plate 21, the coating 27 already in place and the flap 28.

In the embodiment in Figure 7, the spreading plate 21 has a rectangular shape and carries flaps 28 on its four sides.

In the embodiment shown in Figures 8 and 9, the spreading plate 21 has a rectangular shape. It is equipped on two of its opposite sides with rollers 32 which rotate freely about their respective spindles which are parallel to the said sides.

In the embodiment in Figure 8, the spindles of the two rollers 32a, 32b are fixed but are situatec at different distances from the surface 21a of the spreading plate 21 opposite the wall to be coated 33. The roller 3 2 c, termed front roller, is intended to roll on the wall 33 and maintains the surface 21a at a distance from the latter which is constant and substantially equal to, or slightly greater than the thickness of the coating which it is desired to apply to this wall. The function of the rear roller 32b is to spread and level the sprayed substances and it is intended to roll on the coating in place. In the example shown, a flap 28 is fastened to the plate 21 beyond the rear roller 32b.

In the embodiment in Figure 9, the spindles of the two rollers 32c can move in the direction perpendicular to the plate 21. Each of the ends of these t

I

'1 S11 spindles is carried by a rod 34 perpendicular to the plate 21 and which can slide in its longitudinal direction between the two arms of a U-shaped support 35. A stop 36 integral with the rod 34 limits the displacement of the latter in each direction. A spring 37 urges the rod 34 and the roller 32c towards the wall to be coated 33.

As in the embodiment in Figure 8, the roller 32c indicated on the left in Figure 9 is, for example, intended to roll on the wall to be coated 33, the other roller 32c being intended to roll on the applied coating in order to spread it and level it. A flap 28 is provided behind this second roller 32c serving as a rear roller.

The mode of operation of the spraying machine according to the invention will now be described.

Apart from the periods at the beginning and end of spraying, which may require common and known special precautions which depend on the nature of the sprayed substances, the mode of operation of the machine shown in Figures 1 and 2 when working continuously is as follows.

The mixture to be sprayed in the hopper 1 is turned around by the blades 3 of the lump breakers 2 and then transported by the screw 4 to the card 6 whose fingers 7 roughly separate the fibres and impart a downward movement to the mixture. Below the card 6, the paddle distributor 8 provides the blow chamber 11 with a substantially constant flow of mixture which is carried along in the' transport duct 13 by the blowing air coming from the blower 12.

According to the nature of the pulverulent and/or fibrous substances forming the mixture to be sprayed, at least one or a certain number, which can vary, of the injectors 16 are employed, distributed at various points in the hopper, and/or above the card 6 and/or the paddle distributor 8, and/or of the pulverizers 17 in the transport duct 13, and the flow of water, or air and water, into each injector 16 or pulverizer 17 is regulated V such that the water content of the mixture increases in N) 12 a predetermined' manner as the i.tet-, progresses inside the machine and in the transport duct; at any suitable point in the machine and in the duct, the mixture may thus be given a moisture content which is predetermined as a function of the nature, the diameter and the quantity of the fibrous substances and as a function of the nature, the particle size and the quantity of the pulverulent substances, so that the mixture preserves the properties of a substantially dry product: this amounts to saying that the pulverulent and/or fibrous substances may become and remain suspended in the blown air and have no segregation likely to influence adversely the homogeneity and the uniformity of the mixture.

A quantity of water, which represents, depending on circumstances, between approximately and 40% of the weight of the mixture to be sprayed, may thus be injucted progressively, the mixture preserving the properties of a substantially dry product and flowing naturally into the various elements of the machine which it traverses successively up to the end of the spraying tube 14.

The machine shown in Figures 1 and 2 may, in particular, with its card 6 and its paddle distributor 8, spray coatings having extremely high percentages of fibrous substances: these percentages may b- eonsiderably greater than 50% by weight and reach the abFiovjlntioned upper limit of 99.5%.

Experiments show that a mixture containing a high proportion of pulverulent and/or fibrous substances may thus be sprayed without any dust and without having to add to this mixture either dedusting oil likely to burn and pollute or excess water causing an excessive porosity_ and fluidity of the sprayed mixture, it being possible for the quantity of water used to be strictly equal to that required for the tempering water of the mixture and optionally for the water of crystallization of the hydraulic-setting and/or chemically setting materials of the mixture.

If a spreading plate 21 fastened to the end of the spraying tube 14 beyond the spraying nozzle 18 is YIIL~L~-L-~I- L i

I

-13used, a considerable restriction of the rebound of substances, and optionally the emission of dust, is witnessed. Furthermore, a spreading effect by the surface of the spreading plate 21 is witnessed, and possibly the flap 28 or the roller 32 which spread and level the substances after application. It will be understood that at least two flaps, or one -oller and one flap, fastened on two adjacent sides oZ the spreading plate 21, are preferably used, so as to substantially close the space between the spreading plate 21 and the surface to be coated, which ij already limited on two sides by a layer already formed and the layer being applied.

It will be understood that the spraying machine according to the invention may be used and the corresponding methods employed in order to apply coatings having high percentages of pulverulent and/or fibrous substances such as those mentioned above, The avidity for water of the fibres, in particular wool, rock wool or slag-wool, paper,.and certain grain or powder substances such as vermiculite and/or perlite, partly explains that the mixture of fibres and binder and/or cement (and optionally other substances) <aybe moistened without, fear,of..the.binder-or the cement setting in the machine.

The invention is not, of course, limited to the embodiments described above and numerous modifications may be made to them without departing from the field of the invention.

The spraying machine may thus have a conical hopper, and not a parallelepipedal one, a se aper arm provided with fingers being displaced in a conical trajectory along the inner wall of the hopper, it being possible for the latter to be provided at its base with a vertical-axis comb forming a card, or with another appropriate stirring mechanism.

Similarly, whatever the shape of the hopper, the machine moy be equipped, instead of with a paddle 4 distributor, with a barrel distributor, also termed a

TIC

J INTERNATIONAL SEARCH REPORT lhlrntmatlonal AppllZon No PCT/FR 90/00189 1. CLASSP ICATION OF SUPJCT MATTtR (if sevaeat clasSinittlon symbal atppty. Indlcaate alft A0otdtog to Internationa Patnt Classineatla n (IPC) ar to both National Classlrloatlon and IPC I A OF MATE (I -e a .ct sybl t y I t al l n 14 rotor distributor, known per se: a vertical-axis rotor, arranged in the lower part of the hopper, has several rotor chambers which pass successively, when the rotor rotates, beneath an inlet orifice through which the mixture to be sprayed arrives in the rotor chamber, and then above an outlet orifice opening into the blow chamber from which the material is propelled into the transport duct by the blowing air.

One or other piece of equipment which would or would not be necessary may also be added or removed, depending on the composition of the mixture or mixtures to be sprayed.

The type of the distribution means or of the machine may thus be chosen as a function of the nature of the mixture to be sprayed. For example, it is known that barrel or rotor distributors enable mixtures to be sprayed at high speed and high pressure. Such distributors will thus be used preferably for this type of spraying.

This is the case for spraying fire-protection coatings: a grid, fastened and held at a distance from the surfaces to be protected, for ex. -ple by "pig's tail" or "bishop's crook"-shaped fasteners welded onto these surfaces, is generally positioned in front of these surfaces: the mixture to be sprayed, which may contain fibres, may traverse the meshes of the grid, which have for example a size of the order of a centimetre, by being sprayed preferably at high pressure and at high speed.

This is also the case for certain coatings for which it is desired to obtain a certain density, in particular for certain coatings for protecting the walls of a metallurgical vessel intended to receive liquid metal, in order to increase the resistance of this coating to erosion by metal or liquid slag, or for certain coatings for protecting construction elements subjp-ted to wind erosion.

On the other hand, barrel or .'otor distributors are not suited to spraying mixtures having very high quantities of iibtes. These quantities of fibres natu- I 4 f C, _5 li r 4 ANNEX TO THE INTERNATIONAL SEARCH REPORT ON INTERNATIONAL PATENT APPLICATION NO.

FR 9000189 SA 35785 n'k nv V e bt h th. -16.t r -hu -In 'na 11- nniont A-imant~n e ol#&r In ih. A 0V*:nil carcr ~r) 15 rally depend a great deal on the nature and the dimensions of the fibres, but rarely exceed percentages of the order of approximately 50% by weight.

It is clear that the number and type of the injectors 16 and pulverizers 17 may be modified, it being possible to adjust the latter individually or otherwise.

A premoistening device, comprising means for receiving the mixture to be sprayed, means for conveying this mixture, such as one or more Archimedes screws or blades, and one or more atomizers of water, or of air and water, may be installed upstream from the spraying machine. Such a premoistening device may naturally supply the spraying machine, either directly by pouring the premoistened mixture into the hopper of the machine, or indirectly by interrupting charging and the premoistened mixture, it then being possible for the premoistening device to operate so as to supply several spraying machines.

The spreading plate may be equipped with a variable number of rollersand/or flaps, have any shape, be handled manually by a worker or by a .,bhot equipped with any means enabling the said plate to be held at a constant distance from the wall to be coated. The flaps may also be formed from a flexible or unflexible metal sheet.

It is possible for the spreading plate not to have vents, or to have vents of a type other than that described.

If a spreading plate is not used, the end of the spraying tube may be provided with a length of flexible pipe, for example a few tens of centimetres, preferably about 30 centimetres, long to which it would be possible, by shaking the tube in a suitable manner, to communicate gyratory and/or pendulum movements, facilitating the spraying of the coating.

7I -tj I S RAPPORT DE RECHERCHE

INTERNATIONALE

Domand Intem.atioan.l$ N PCT/FR 90/00189 i. CLASSMENT D LINVINTION (si pl urs symboli do classification sont modliehIabl. i. Indm.u. iAn.% 7

Claims (12)

1. Machine for continuously spraying a coating containing high percentages of pulverulent and/or fibrous substances and intended to set after wetting with water, in particular a fire-protection coating or a coating for thermal or sound or acoustic insulation, or a coating for protecting the walls of a metallurgical vessel intended to receive liquid m6tal, the said machine comprising, from upstream to downstream, means for receiving the mixture of the substances forming the coating, means for conveying the mixture to the lower part of the machine, rotating lock chamber and distributor means for distributing the mixture by gravity into a blow chamber blowing means (12) for propelling the mixture by blowing air from the blow chamber (11) into a duct (13) for t:cansporting it to a spraying tube (14) at the end of which atomized water, or air and atomized water, are injected in order to make the said mixture pasty so as to enable it to be sprayed and to set, the said machine being characterized in that it furthermore comprises, between the receiving means and the spraying tube (14), at least one atomizer (16, 17) of water, or of air and water, in order to premoisten the mixture.

2. Spraying machine according to Claim 1, charac- terized in that the receiving means comprise a premois- tening device having means for conveying the mixture, such as one or more screws and/or blades, and at least one atomizer of water or of air and water.

3. Spraying machine according to one of Claims 1 or 2, characterized in that it comprises several atomizers (16) of water or of air and water distributed in the receiving means and/or around the means for conveying the mixture to the lower part of the machine and/or around the distribution means, and one or more atomizers (17) of water or of air and water into the transport duct.

4. Spraying machine according to one of Claims 1 to 3, characterized in that the means for conveying the mixture to the lower part of the machine comprise a card 'T i i CI I 1~4~~eqRB~e~ lslLpll~ 17 or rotating fingers or combs or a screw or a stirring mechanism. Spraying machine according to one of Claims 1 to 4, characterized in that the lock chamber and distri- butor means for distributing the mixture comprise a paddle distributor or a barrel distributor or a bucket-wheel distributor.

6. Spraying machine according to one of Claims 1 to characterized in that the end of the spraying tube (14) is provided with a spreading plate (21) capable of retaining the materials after rebounding and of limiting the emission of dust.

7. Spraying machine according to Claim 6, charac- terized in that the spreading plate (21) comprises a flap (28) on at least one of its edges.

8. Spraying machine according to Claim 6, charac- terized in that the spreading plate (21) comprises, on at least one of its edges, a roller (32, 32a, 32b, 32c) with a spindle parallel to this edge and with a length sub- stantially equal to the length of this edge, it being possible for this roller (32, 32a, 32b, 32c) to rotate freely about its spindle.

9. Spraying machine according to Claim 8, charac- terized in that the spindle of the roller (32c) may slide in a direction perpendicular to the plane of the plate a spring (37) urging the roller (32c) into its position furthest from the plate (21). Spraying machine according to one of Claims 8 or 9, characterized in that the plate comprises, on at least one of its edges adjacent to the edge having a roller (32b, 32c), a flap (28).

11. Spraying machine according to one. of Claims 6 to characterized in that the plate (21) has at least one vent (29) enabling the spraying air to escape.

12. Method for spraying a coating containing high percentages of pulverulent and/or fibrous substances and intended to set after wetting with water, by means of a spraying machine according to one of Claims 1 to 11, characterized in that atomized water, or air and atomized ;I- ir '7 (1i i "V y P~ 18 water, is injected at at least one point in the machine or upstream from the latter in order to premoisten the mixture of the substances, the quantity of water thus injected being less than the quantity required to ensure the spraying and setting of the mixture.

13. Method according to Claim 12, characterized in that atomized water, or air and atomized water, is injected at several places in the machine and the duct for transporting the mixture and in that the quantity of water injected is optimized at each of these places in order to obtain at each of them a mixture having a moisture content predetermined as a function of the nature, the diameter and the quantity of the fibrous substances and as a function of the nature, the particle size and the quantity of the pulverulent substances, so that the mixture preserves the propertie of a substantially dry product.

14. Coating containing high percentages of pulveru- lent and/or fibrous substances and intended to set after wetting with water and spraying, characterized in that it is formed by means of the spraying machine according to one of Claims 1 to 11. Coating containing high percentages of pulveru- lent and/or fibrous substances and intended to set after wetting with water and spraying, characterized in that it ia obtained by the method according to one of Claims 12 or 13. I ABSTRACT Company called: DAUSSAN ET COMPAGNIE "Machine for spraying a coating containing pulverulent and/or fibrous substances, method for spraying such a coating and coating thus obtained" (An invention of Jean Charles DAUSSAN, Andr6 DAUSSAN and Gerard DAUSSAN) The machine comprises means for receiving the mixture of the substances forming the coating, means (6) for conveying the mixture to the lower part of the machine, lock chamber means for distributing the mixture to a transport duct (13) in which the mixture is propelled pneumatically to a spraying tube (14) into which atomized water, or air and atomized water, are injected in order to make the mixture pasty so as to enable it to be sprayed and to set. It furthermore comprises at least one atomizer (16) of water, or of air and water, in order to premois- ten the mixture, the quantity of water injected at this stage being adjusted so that the mixture preserves the properties of a substantially dry product. Use in particular for reducing the emission of dust and lessening the quantity of water required when spraying coatings containing high percentages of pul- verulent and/or fibrous substances and intended to set after wetting with water, in particular fire-protection coatings or coatings for thermal or acoustic or sound insulation or coatings for protecting the walls of a metallurgical vessel intended to receive liquid metal, and for at least partially eliminating the addition of dedusting oil to these coatings. See Figure 1.