EP1844859A1 - Powder metering and transport device - Google Patents

Abstract

The system has a porous plate for fluidizing a portion of a powder e.g. food powder, in a pressurized pot (4). A tube dipping into the fluidized powder is discharged to an outside of the pot. A pipe continuously supplies gas for pressurizing the pot, and for mixing the gas with the fluidized powder leaving the tube. The pipe has an adjustable constriction that creates a head loss between upstream and downstream ends. A hose (7) connected to the downstream end of a mixing chamber, transports the powder mixed with the gas.

Description

The invention relates to a device for dosing and continuous transport of powdery product as well as to a use of such a device and to a coating product spraying installation comprising such a device.

In the field of spraying powder coating product, it is known to supply a pneumatic or rotary projector coating product from a tray in which the coating product is fluidized with air, while a plunger tube enters the bed of fluidized product and a suction system of the Venturi type is mounted in the upper part of this plunger tube, which allows to suck up a portion of the fluidized product. The tank is possibly subjected to vibrations in order to improve the fluidization. In this type of equipment, only a small product flow can be obtained and the product transport distances are limited, which can be detrimental for some applications. In addition, the contact of the coating product on certain essential parts of this material as regards the driving of the product has the effect of premature wear of these parts, this wear resulting in a drift of the value of the product flow rate obtained. . As a result, the product flow supplied to the projector is not really insured and expensive and time-consuming preventive maintenance operations must be undertaken.

In order to remedy these limitations of flow rates and transport distances, it is also known to use for the same purpose a closed tank fed sequentially with powdery product, in which the coating product is fluidized and driven towards the projector by repression. in a pipe whose mouth is disposed opposite a driving air ejector. This ejector has the role of pressurizing the enclosure of the closed tank and the dosage of the powder to be transported. The ejector is sometimes located directly in the bed of powdery product, as in the equipment marketed by the Applicant under the reference CSV216. It can also be located near the mouth of the pipe, the powdery product being then sucked by a dip tube. This type of equipment overcomes the limitations of flow rates and transport distances mentioned above, but does not completely remedy the wear of certain parts due to the presence of an ejector. In addition, the control of the powder flow in a wide range is not easy.

In addition, a pressure pot as described in FR-A-1,279,167 can be used to transport a powdered product continuously, with a high flow rate and over long distances, without using a Venturi system with rapid wear. However, in this system, no control of the product flow can be carried out, this flow rate evolving during the emptying of the pot because it is difficult to control both the air flow required to fluidize the product and the pressure internal of the pot. It is also difficult to keep the coating product in the fluidized state waiting for use without initiating the pressurizing of the pot and the delivery of the product. In addition, the dip tube and the conduits to which it is connected must have a relatively large diameter when it is desired to transport the product over a long distance, of the order of several meters, and with a high flow rate, in order to limit the pressure drops to the flow.

It is also known from EP-A-1,454,675 to use a pressure pot to feed a projector fluidized powder coating product in the form of dense. The product flow supplied to the projector can be controlled by establishing and controlling the pressure in the pot using, for example, an air vent. An independent air injection device is provided to stop the flow of the air / powder mixture and clean the supply duct of the projector when necessary. This kind of material and the transport method in dense form do not allow to power a projector over a long distance and are incompatible with successive stops and restarts of the power supply.

The problems mentioned above arise in fact in any dosing system and continuous transport of powdered product and, for example, in food, pharmaceutical or agricultural powder transport systems.

In these applications indeed, as in the field of coating product spraying installations, it is often important to transport a powdered product continuously, that is to say without pulsation or shaking may adversely affect the operation of equipment powered by powdery product, while controlling the product flow and avoiding systematic use of large diameter conduits that are not always compatible with the applications envisaged, especially in the case of supplying mobile equipment.

In this spirit, the invention relates to a device for metering and conveying powder product continuously from a closed reservoir, this device comprising means for fluidizing at least part of the product in this reservoir, a dip tube in the fluidized product and opening out of the tank, and means for pressurizing the reservoir. This device is characterized in that it comprises means for permanently feeding the pressurizing gas from the reservoir to a mixing chamber of this gas with the fluidized product leaving the dip tube, this gas supply means being equipped or constituting a restriction on the flow of gas, while a pipe for transporting the powdery product mixed with the gas is connected downstream of the mixing chamber.

Thanks to the invention, the pressure drop induced by the restriction on the path of the pressurizing gas to the mixing chamber makes it possible to establish a pressure difference between the pressure prevailing in the internal volume of the reservoir and the pressure prevailing in the mixing chamber. This pressure difference is in fact applied on both sides of the dip tube, so that it determines the flow of fluidized product in this tube when the density of this product is controlled in the zone where the dip tube is in contact. contact with the product. In other words, the determination and, possibly, the control of the pressure drop obtained by the pressurizing gas supplying means make it possible to control the flow of fluidized product into the dip tube, when the density of the product is mastered. Rejecting the pressurizing gas to the mixing chamber at the outlet of the dip tube makes it possible to dilute the fluidized product as desired by adjusting the flow of pressurizing gas and / or the restriction. Dilution of the product through this addition of gas facilitates its continuous transport with a large flow and over significant distances.

The invention also relates to a particular use of the device mentioned above and more specifically, its use for supplying a projector with a coating product.

The invention also relates to a powder coating product projection installation which comprises at least one coating product projector and at least one device as mentioned above, this device supplying the projector coating product. Such an installation is easier to install and operate than those of the state of the art and the quality of the coating obtained is improved to the extent that the flow of coating product can be controlled sufficiently accurately to ensure operation. optimal projector.

• la figure 1 est une représentation schématique de principe d'une installation de projection de produit de revêtement conforme à l'invention, incorporant un dispositif de transport de produit pulvérulent conforme à l'invention ;
• la figure 2 est une coupe longitudinale de principe à plus grande échelle du dispositif de transport utilisé dans l'installation de la figure 1 ;
• la figure 3 est une vue à plus grande échelle du détail III à la figure 2 ;
• la figure 4 est une représentation schématique de principe d'un dispositif de transport conforme à un second mode de réalisation de l'invention ;
• la figure 5 est une vue analogue à la figure 4, pour un dispositif de transport conforme à un troisième mode de réalisation de l'invention ;
• la figure 6 est une vue à plus grande échelle du détail VI à la figure 5 ;
• la figure 7 est une vue analogue à la figure 6, pour un dispositif de transport conforme à un quatrième mode de réalisation de l'invention ;
• la figure 8 est une vue analogue à la figure 4 pour un dispositif conforme à un cinquième mode de réalisation de l'invention
• la figure 9 est une vue analogue à la figure 4 pour un dispositif conforme à un sixième mode de réalisation de l'invention ; et
• la figure 10 est une vue analogue à la figure 4 pour un dispositif conforme à un septième mode de réalisation de l'invention.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an embodiment of a coating product spraying equipment in accordance with its principle and seventh. Embodiments of a powdery product transport device also in accordance with its principle, given by way of example only and with reference to the accompanying drawings in which:

• Figure 1 is a schematic representation of principle of a coating product spray installation according to the invention, incorporating a powdery product conveying device according to the invention;
• Figure 2 is a longitudinal sectional view of the larger scale of the transport device used in the installation of Figure 1;
• Figure 3 is an enlarged view of Detail III in Figure 2;
• Figure 4 is a schematic representation of a transport device according to a second embodiment of the invention;
• Figure 5 is a view similar to Figure 4, for a transport device according to a third embodiment of the invention;
• Figure 6 is an enlarged view of Detail VI in Figure 5;
• Figure 7 is a view similar to Figure 6, for a transport device according to a fourth embodiment of the invention;
• FIG. 8 is a view similar to FIG. 4 for a device according to a fifth embodiment of the invention
• Figure 9 is a view similar to Figure 4 for a device according to a sixth embodiment of the invention; and
• Figure 10 is a view similar to Figure 4 for a device according to a seventh embodiment of the invention.

The installation I shown in FIG. 1 is intended for the electrostatic coating of objects O displaced by a conveyor 1 in a direction perpendicular to the plane of FIG. 1. The objects O pass in front of an electrostatic projector 2 of powder coating product connected to a high-voltage unit 3 and supplied with coating material from a pressurized pot 4 held in place by means of a support 5.

The projector 2 is connected to the unit 3 by means of a high-voltage cable 6, while it is connected to the pot 4 by means of a flexible hose 7. The projector 2 is mounted on an arm 8 extending through a window 9 formed in a partition 10 of a coating cabin C. The arm 8 is vertically movable, as represented by the double arrow F ₁ , and supported by a mast 11 extending vertically from a base 12 of a reciprocator 13.

In operation, a cloud of powder coating material is directed from the projector 2 towards the objects O along the electrostatic field lines.

Alternatively, the projector may not be electrostatic, in which case the path of the powder constituting the coating product is determined essentially by aeraulic and gravitational forces.

Given the vertical movement of the arm 8, the path of the pipe 7 varies with time and this pipe can not be too large diameter, except to hinder the movements of the moving part of the reciprocator.

As is more particularly apparent from FIGS. 2 and 3, the pressurized pot 4 comprises a bottom 101 and a cover 102 between which a cylindrical wall with a circular base 103 is arranged. When the cover 102 is in place on the wall 103, the pot 104 constitutes a sealed reservoir vis-à-vis the outside.

The bottom 101 is equipped with a porous plate 104 disposed above a distribution chamber 105 supplied with air under controlled pressure or with a controlled flow, by means of a conduit 106 formed in the bottom 101 and opening towards the outside by a connector 107 which is connected to a conduit C ₁ fed from a regulated source S ₁ of pressurized air.

A platen 108 fixed to the bottom 101 supports a vibrator 109 for transmitting vibrations to the entire pot 4 and thus agitating the fluidized mixture, to facilitate its fluidization and to avoid the formation of preferential flows or d agglomerates within the powdery product.

When the chamber 105 is supplied with pressurized air, the air flows through the plate 104 as represented by the arrows F ₂ , which has the effect of fluidizing the amount of powder coating product present in the interior volume V ₄ of the pot 4 and to create a bed L ₄ of fluidized coating product which extends above of the plate 103 on a height H ₄ which depends both on the amount of the coating product present in the volume V ₄ , the pressure and the feed rate of the chamber 105.

A dip tube 110 extends downwardly from the lid 102 to the vicinity of the plate 104. This tube has an inner diameter d ₁₁₀ relatively narrow and passes through the cover 102 being disposed in a sleeve 111 which protrudes toward the top from the cover 102 and on which is disposed a nozzle 112 which is connected to the pipe 7.

110A is the lower end of the tube 110 and 110B its upper end.

The upper part of the tube 110 is disposed in a central bore 113 of the sleeve 111 which is cylindrical and circularly based and whose inside diameter d ₁₁₃ is strictly greater than the outside diameter D ₁₁₀ of the tube 10. In order to maintain the tube 110 in position in the bore 113, a ring 114 is provided around the tube 110 and engaged in the bore 113.

Above the bore 113, the sleeve 111 is provided with a second bore 115 aligned on an axis ZZ 'common to the elements 110, 113 and 114 and having a diameter d ₁₁₅ greater than the diameter ₁₁₃ .

A liner 116 is disposed in the bore 115 and its inner diameter d ₁₁₆ is greater than the diameter D ₁₁₀ of the tube 110.

A second duct C ₂ connects a source S ₂ of pressurized air to the part W ₄ of the volume V ₄ which is not occupied by the bed L ₄ of fluidized coating product, that is to say the portion which extends between the upper surface of the bed L ₄ and the inner face of the cover 102, over a height H ' ₄ .

Taking into account the supply of the volume W ₄ in pressurized air, a pressure P ₄ prevails in this part W ₄ of the volume V ₄ , which has the effect of exerting on the upper surface of the bed L ₄ an effort which has tendency to drive some of the coating product inward from the end 110A of the tube 110.

A third duct C ₃ connects the source S to a sewing 117 formed in the sleeve 111 in a direction generally radial to the axis ZZ 'and opening into the bore 113, at a distance from the end 110B.

The conduit C ₃ is provided with an adjustable restriction R ₃ which makes it possible to create a pressure drop ΔP between the upstream end and the downstream end of the conduit C ₃ .

At the upper end 110B of the tube 110, two different fluid flows can be considered. The first flow is that of the air coming from the conduit C ₃ through the restriction R ₃ . The second flow is that of the mixture of powdery product and fluidizing air rising in the tube 110.

At the right end 110B and in the bulk of the interior volume V ₆ of the jacket 116, there is a pressure that is noted P ₆ and that we can consider, for simplicity, as applied within each of these flows. This pressure P ₆ depends directly on the flow of the mixture of pulverulent products and air downstream of the end 110B, that is to say in the internal volume V ₆ of the jacket 116, in the pipe 7 and in the the projector 2. This pressure P ₆ is stable if the flows and the operating regime downstream of the end 110B are stabilized in steady state.

The volume V ₆ constitutes a chamber in which the flow E ₁ of fluidized coating product coming from the bed L ₄ and the flow E ₂ of gas arriving via the pipe C ₃ are mixed.

ou ΔP dépend du débit de gaz circulant au sein de la restriction R₃.If we now consider only the flow E ₂ of gas through the restriction R ₃ , this restriction induces a pressure drop ΔP which depends directly on the flow of air flowing in the duct C ₃ and in the restriction R ₃ . In steady state, once the tank 4 under pressure, the pressure losses in the conduit C ₂ can be considered negligible compared to ΔP. Similarly, the pressure losses in the parts of the duct C ₃ situated respectively upstream and downstream of the restriction R ₃ can be considered as negligible compared to ΔP, just as the pressure losses in the annular space surrounding the tube 110 inside the bore 113. P ₄ is noted the air pressure prevailing in the volume W ₄ . Given the above observations, the following equation is verified: $${\mathrm{<figure-callout\; id="4"\; label="P"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{4}}\mathrm{=}{\mathrm{P}}_{\mathrm{6}}\mathrm{+}\mathrm{.DELTA.P}$$

or ΔP depends on the flow rate of gas flowing within the restriction R ₃ .

où p est la densité du lit fluidisé L₄, g l'accélération de la pesanteur et h₄ la hauteur sur laquelle le tube 110 plonge dans le lit L₄ au-dessus de l'extrémité 110A.Moreover, the pressure P ' ₄ in the fluidized bed L ₄ near the end 110A can be estimated as follows: $${\mathrm{P\text{'}}}_{\mathrm{4}}\mathrm{=}{\mathrm{<figure-callout\; id="4"\; label="P"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{4}}\mathrm{+}{\mathrm{<figure-callout\; id="4"\; label="\rho gh"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\rho gh</figure-callout>}}_{\mathrm{4}}$$

where p is the density of the fluidized bed L ₄ , g the acceleration of the gravity and h ₄ the height over which the tube 110 dips into the bed L ₄ above the end 110A.

Under these conditions, the pressure difference ΔP ₁₁₀ between the ends of the tube 110 can be expressed as follows: $${\mathrm{.<figure-callout\; id="110"\; label="DELTA.P"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">DELTA.P</figure-callout>}}_{110}={\mathrm{P\text{'}}}_{\mathrm{4}}-{\mathrm{P}}_6={\mathrm{<figure-callout\; id="4"\; label="P"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">P</figure-callout>}}_4\mathrm{+}{\mathrm{\rho gh}}_{\mathrm{4}}-{\mathrm{P}}_6=\mathrm{.DELTA.<figure-callout\; id="4"\; label="P\; +\; \rho gh"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">P\; </figure-callout>}+{\mathrm{\rho gh}}_{}{\mathrm{}}_4$$

Thus, the pressure difference between the inlet and the outlet of the tube 110 is equal to the pressure difference created by the restriction R _3, to which is added a factor dependent on the height of the fluidized bed L ₄ , which factor can be determined by the calculation.

Under these conditions, it is possible to control the pressure difference ΔP ₁₁₀ by controlling the pressure drop ΔP induced by the flow E ₂ of gas within the restriction R ₃ , at the influence of the variation of the height H ₄ and provided that the density p is kept substantially constant.

However, the control of the pressure difference ΔP ₁₁₀ makes it possible to control the mass flow rate of fluidized powdery product in the tube 110 since this flow rate is a univocal function of this pressure difference ΔP ₁₁₀ , the characteristics of the powdered pulverized product as well as the characteristics The control of the mass flow rate of pulverulent products is therefore all the easier as the term ΔP allowing to define ΔP ₁₁₀ is preponderant in front of the term pgh4, which makes it possible to overcome any variations in height H. ₄ .

In order to vary the pressure drop induced by the flow of gas in the restriction R ₃ and thus to modify the mass flow rate of powdered product discharged through the tube 110, it is possible to act on the flow of gas flowing at within the restriction R ₃ and / or on the geometry of this restriction in the case of a variable restriction. If this restriction is calibrated, a simple control of the flow of gas circulating within them makes it possible to control the flow of powdered product discharged through the tube 110 and then conveyed to the projector 2.

The volume V ₆ constitutes a mixing chamber of the flow E ₁ of fluidized powder product and the flow E ₂ of the air coming from the pipe C ₃ , the fluidized coating product being itself a mixture of the powdery product. and fluidizing air from chamber 105.

It should be noted that, at the end 110B of the tube 110, the flow E ₂ opens out around this end while being centered on the axis of the tube 110, which induces a regulation effect of the flow rate of the product mixture. coating and air and avoids jerks in the flow downstream of the 110B end.

A second stitching 118 is optionally provided in the sleeve 111 and also opens into the bore 113. This second stitching is connected by a conduit C ₄ to a source S ₃ of pressurized air and makes it possible to near the end 110B of the tube 110 of the additional dilution air of the air / powder mixture created in the chamber V ₆ .

The taps 117 and 118 are arranged upstream of the downstream end 110B of the tube 110, which prevents the return of untimely products to the ducts C ₃ and C ₄ and prevents clogging.

It can be provided that the liner 116 is interchangeable and that its internal diameter d ₁₁₆ is chosen as a function of the inside diameter d ₇ of the pipe 7. In practice, the diameter d ₁₁₆ is preferably chosen to be substantially equal to the inside diameter d ₇ of the pipe 7 .

The bore 113 and / or the jacket 1216 may be cylindrical with a straight generatrix or provided on their internal face with a thread or a helical relief intended to improve the mixing of the air and the product by rotating stirring or vortex effect. Such a net is partially shown in phantom in FIG. reference 116a, on the inner face of the liner 116. In a variant, such a thread may be provided in the bore 113, upstream of the end 110B, which makes it possible to obtain a Vortex effect on the flow E ₂ .

The length L ₁₁₆ of the liner 116 which is equal to the length of the mixing chamber V ₆ , is chosen at least three times greater than the diameter d ₁₁₆ , preferably equal to about ten times this diameter, which allows a good homogenization of the air / powder mixture coming from the tube 110 and the air coming from the bore 113. In the case where a Vortex or rotational stirring effect is used, the ratio L ₁₁₆ / d ₁₁₆ may be chosen equal to about five .

The invention makes it possible to convey, to a large distance, a continuous mixture of air and coating product, with a large and controlled flow rate, while the tube 110 and the pipe 7 have small diameters and that the pipe 7 is relatively long and liable to deform depending on the movements of the arm 8.

In the second embodiment of the invention shown in FIG. 4, the elements similar to those of the first embodiment carry identical references increased by 200. The pressure pot 204 of this embodiment is equipped with a tube plunger 310 which extends from a cover 302 into a bed L ₄ fluidized coating product through a device 303 supplied with fluidization air through a conduit C ₁ connected to a source S ₁ of pressurized air . A vibrator 309 is mounted on the bottom 301 of the pot 204. The volume W ₄ of the pot 204 which is not occupied by the bed L ₄ of fluidized coating product is supplied with pressurized air from a conduit C ₂ connected to a second source S ₂ of pressurized air.

A mixing chamber V ₆ is disposed above the pot 204, the downstream end 310B of the tube 310 opening into this chamber.

A duct C ₃ provided with an adjustable restriction R ₃ connects, through the lid 302, the volume W ₄ and the mixing chamber V ₆ , which makes it possible, as previously to control the flow rate of the product mixture of coating / gas of fluidization flowing in the conduit 310 by means of the pressure drop created by the restriction R ₃ in the conduit C ₃ .

A vent 318 is mounted on the cover 302 and makes it possible to vent the volume W ₄ , in particular when the apparatus to which the pot 204 is connected by a flexible duct 207 is not in operation or before its manual filling in. coating product.

In the third embodiment of the invention shown in FIGS. 5 and 6, elements similar to those of the first embodiment carry identical references increased by 400. The pressure pot 404 of this embodiment is equipped with a porous plate 503 supplied with pressurized air, from a source S ₁ , via a conduit C ₁ which opens into a distribution chamber 505.

A bed L ₄ pulverulent food product, for example sugar or flour, is created, while leaving a free volume W ₄ in the upper part of the pot 404, this volume W ₄ being supplied with pressurizing air by a conduit C ₂ connected to a regulated source S ₂ of pressurized air.

A pipe 407 connects the pot 404 to a product use station which is not shown.

E _{1 is} the flow of the product mixture / dilution air in the conduit 510.

As is more particularly apparent from FIG. 6, an annular duct C ₃ is formed around the upper part 510B of a tube 510 immersed in the bed L ₄ and opening inside a sleeve 513. The duct C ₃ is created by the difference between the outside diameter of the tube 510 and the inside diameter of the sleeve 513. This duct C ₃ has an annular section of relatively small area with respect to its length L ₃ , so that it creates in it even a restriction on the flow E ₂ of the pressurizing air, between the volume W ₄ and a mixing chamber V ₆ formed in the sleeve 513, downstream of the tube 510. The restriction R ₃ of the conduit C ₃ induces a pressure drop of the same kind as that resulting from the restrictions R ₃ of the first and second embodiments.

The pressure P ₆ in the chamber V ₆ is less than the pressure P ₄ in the upper part of the pot 404 by a value determined, inter alia, by the geometry of the duct C ₃ and by the flow rate of gas flowing through this duct . Thus, the control of the flow rate of gas flowing through the conduit C ₃ makes it possible to control the flow rate of the flow E ₁ of the fluidized mixture circulating in the conduit 510. This flow rate of gas flowing through the conduit C ₃ depends in fact on the flow of fluidization gas conveyed by the conduit C ₁ and the flow rate of pressurizing gas tank 404 conveyed by the conduit C ₂ .

If the flow rate of the fluidization gas is kept constant, a substantially constant fluidized product density is obtained and the only parameters to be controlled to control the flow of product in the product 510 are then the pressure and / or the gas flow rate. pressurizing the reservoir through the conduit C ₂ . The restriction formed by the conduit C ₃ can be designed in such a way that the flow rate of the fluidization gas is not sufficient to generate, on its own, a flow rate within the led 510, which allows to constantly maintain the bed L ₄ of fluidized products without delivering products in the conduit 110 while the powder product remains available at any time by "pumping" when necessary.

According to a not shown variant of the invention, the section of the duct C ₃ or of its inlet zone can be adjustable, which makes it possible to modulate the air flow in this duct and, thus, the pressure drop and the flow in the tube 510.

In the embodiment of Figure 7, the conduit C ₃ is replaced by a restriction R ₃ in the form of a ring around a portion of the dip tube 510. This restriction alone is sufficient to create a pressure drop on the flow E ₂ of air resulting from the difference between the pressure P ₄ in the volume W ₄ of the pressure vessel and the pressure P ₆ in a mixing chamber V ₆ formed in a sleeve 513, in a manner analogous to that of the third embodiment. The restriction R ₃ can be calibrated or adjustable.

In the fifth and sixth embodiments of the invention shown in Figures 8 and 9, the elements similar to those of the first embodiment bear identical references. The pressure pot 4 of the embodiment of Figure 8 has a wall 103 converging downwards and its bottom 101 is open facing a porous plate 104 for fluidizing the coating product in the pressure pot. The porous plate is fed from a source S ₁ of pressurized air whereas a source S ₂ of pressurized air makes it possible to feed the volume W ₄ of the pot 4 which is not occupied by the product fluidized. A restriction R ₃ is provided on a conduit C ₃ which opens in the vicinity of the upper end 110B of a plunger tube 110, the air coming from the conduit C ₃ mixing with the fluidized product mixture coming from the tube 110 in a mixing chamber whose interior volume is V ₆ .

The tank 4 is equipped with a vibrator 109 and a scale 150 for continuously determining the weight of product contained in the tank. This scale sends a signal Σ1 to a control unit U of the installation in which the tank 4 is integrated. It is thus possible to monitor the consumption of a powered projector from the tank 4 by comparing the weight of the product at the beginning and at the end of the application. It is also possible to monitor the product flow consumed by the projector by integrating, over a longer or shorter period of time, the variations in product weight detected by the scale.

A cylindrical partition 160 is held inside the tank 4 by unrepresented lugs bearing on the wall 103. This partition 160 is cylindrical, circular base and centered on the tube 110. It defines, in the interior volume V ₄ of the tank 4, two unit volumes, namely a volume V ₁₆₀ , in the form of a column defined inside the partition 160, and a volume W ₁₆₀ , located around the partition 160 inside the tank.

The plate 104 is disk-shaped with a radius close to the inside radius of the partition 160. The lower edge 160A of the partition 160 is also disposed at a height h _{160 which is} not zero relative to the bottom 101. The fluidizing air flowing through the plate 104, as represented by the arrow F ₂ , makes it possible to create a bed L ₄ of fluidized product in the volume V ₁₆₀ , this bed L ₄ being permanently supplied with coating product stored in unpowdered form in the volume W ₁₆₀ and flowing by gravity towards the center of the plate 104. The flow of the product fluidizing coating, the volume W ₁₆₀ to the volume V ₁₆₀ , is represented by the arrows F ₁₆ .

The air flow through the plate 104 is adjusted so that the bed L ₄ extends to the upper edge 160B of the partition 160 and overflows therefrom, a portion of the coating product being discharged by gravity to the volume W ₁₆₀ , as represented by the arrows F ₁₇ .

Thus, the height h ₄ of the fluidized bed L ₄ above the lower end 110A of the tube 110 is constant insofar as the height H ₄ of the fluidized bed is itself constant. This avoids fluctuations in the amount of the coating product directed to the mouth 110A of the tube 110.

In other words, the partition 160 makes it possible to maintain in the tank 4 a column L ₄ of fluidized product of height H _{4 which is} constant or almost constant, despite the consumption of product and despite the fact that the reservoir is not re-heated. powered during an application. The volume W ₁₆₀ constitutes, within the tank 4, a product reserve area to be fluidized which makes it possible to compensate for the consumption of the product.

To facilitate the movement of the product to be fluidized in the direction of the arrows F ₁₆ , a vibrator 109 is mounted at the bottom of the tank 4.

The embodiment of FIG. 9 is close to that of FIG. 8. The same references are used to designate the same elements and only the differences with respect to the embodiment of FIG. 8 are explained here. The porous plate 104 of the tank 4 has an area greater than the section of the interior volume of the partition 160, which fluidizes the coating product both in the volume V ₁₆₀ and partially in the volume W ₁₆₀ . This facilitates the feeding of the volume V ₁₆₀ to the fluidizing coating product in the direction of the arrows F ₁₆ . This makes it possible to dispense with the use of the vibrator 109 of the embodiment of FIG. 8.

Other means may be provided for maintaining a predetermined height of fluidized coating product over the mouth 110A of the tube 110. For example, manual or automatic adjustment means may be provided for adjusting the position of the tube 110 with respect to the lid of the pressurized pot so that the lower end 110A is depressed by a substantially constant height h ₄ in the fluidized bed L ₄ . It is also possible to maintain the total height H ₄ of the bed of fluidized product L ₄ by keeping the overall quantity of fluidized coating product contained in the tank substantially constant, by supplying the tank continuously or almost continuously.

A scale may also be used with the reservoir of the embodiment of Figure 9, as with those of the embodiments of Figures 1 to 7.

The use of a scale such as scale 150 makes it possible to use the information relating to the weight of the product present in the reservoir to estimate the fluidized product height and to ensure the filling of the reservoir to a maximum height of fluidized product which corresponds, in practice, to a maximum product weight that can hold the reservoir. Such a scale also makes it possible to estimate in real time the evolution of the fluidized product height in order to perform, if necessary, an automatic correction of the flow rate supplied by the device to the projector that it supplies. This makes it possible to compensate for any drift in the flow rate resulting from the fluidised product height variation that may occur in the devices of the first four embodiments in the absence of a partition of the type of the partition 160.

The invention has been described during its implementation in a coating product installation and for the transport of agri-food product. It is however not limited to these applications, even if the application in the field of installations of the coating product is very advantageous. In particular, the invention can be used in the pharmaceutical field, for the transport of drugs in pulverulent form or in the agricultural field for the transport of herbicide, fungicide or fertilizer in powder form.

Depending on the nature of the powdery product to be transplanted, the nature of the fluidizing gas and the pressurizing gas can be adapted.

In the first two embodiments shown, the restrictions R ₃ have been represented as variables. However, it is possible to predict that these restrictions are calibrated. Control of the total flow of gas entering the tank and gas passing through the restriction then controls the flow of powdered product taken from the tank. These restrictions may, where appropriate, be the subject of a standard exchange depending on the characteristics of the product to be transported and the characteristics of the installation downstream of the mixing chamber.

The restrictions of the third and fourth embodiments may be adjustable.

These restrictions may be constituted by tubes of relatively small inner diameter by diaphragms or by any other suitable means.

Whatever the embodiment considered, the restriction in the gas supply duct to the mixing chamber or constituting this duct may be adjustable or calibrated.

In practice, a calibrated restriction makes it possible to easily control the flow of powdery product since the control of the flow rate and / or the pressurization gas pressure of the reservoir is relatively easy, for example with a solenoid valve. In addition, it is preferable that the restriction has a simple shape, devoid of a retention zone because the gas passing through such a restriction can be slightly loaded with particles of coating product, especially in the case of the installation of FIG.

In practice, it can be ensured that the flow rate of the fluidization gas is negligible compared to the flow rate of the pressurizing gas of the reservoir, so as to enable the control to be separated from the powder product flow, on the one hand, and the fluidization, on the other hand. This makes it possible, in particular, to keep the coating product in the form of a fluidized bed waiting to be pumped into the tank, without the airflow necessary for this fluidization being sufficient to create a pressure drop across the restriction. and generating a pumping of the product.

The invention has been shown with certain materials in which all the powdery product is fluidized. It also applies to the case where only a part of this product is fluidized. In addition, whatever the embodiment considered, there is provided a system, known per se, for supplying the reservoir with powdery product. The supply of the tank with such a system can be continuous or sequential. In a simple case, the tank lid is periodically removed and the product is discharged by an operator into the tank.

The invention has been described when it is used with separate air sources S ₁ , S ₂ and / or S ₃ . These In practice, sources are fed from the same main network and pressure or flow control devices are interposed upstream of the sources S ₁ , S ₂ and / or S ₃ to allow their independent management. Alternatively, two of these sources or three sources could be grouped together.

In the seventh embodiment shown in FIG. 10, elements similar to those of the first embodiment bear identical references. The pressurized pot 4 of this embodiment is used to feed a projector 2 of powder coating material, this projector being mounted on the movable arm 120 of a multi-axis robot. Alternatively, this projector 2 could be mounted on any type of support, including the arm of a reciprocator.

The pressurized pot 4 has a cylindrical wall 103 and its internal volume is separated by a porous plate 104 into a distribution chamber 105 and a volume of production of a fluidized bed L ₄ of powder coating product. The chamber 105 is supplied with air under controlled pressure from a source S ₁ of compressed air, this compressed air passing through the plate 104, as represented by the arrows F ₂ , to fluidize the bed L ₄ .

From the lid 102 of the pot 4, a tube 110 dips into the fluidized bed L ₄ and allows to extract a portion of the product, as explained above. The tube 110 is connected, in the upper part, to a hose 117 which extends from the upper end 110B of the tube 110 to a volume V ₆ defined inside the arm 120 and in which the powdery product in dense phase passing through the tubes 110 and 117 may be mixed with additional air. For this purpose, the volume V ₆ is fed through a conduit C ₃ of relatively small diameter. from a conduit C ₂ connected to a second source of pressure S ₂ .

The duct C ₂ is also connected to the internal volume V ₄ of the pot 4 situated above the fluidized bed L ₄ by a duct section C ' ₃ .

Downstream of the volume V ₆ , the coating product mixed with air flows in a pipe 7 for supplying the projector 2.

In practice, the length of the pipe 117 may be of the order of 6 to 8 m, while the length of the pipe 7 is greater than 10 cm and less than 2 m. However, the length of the pipe 7 could be increased to 50% of the total length of the flow path between the pot 3 and the designer 2.

The pipe C ₃ constitutes a means for permanently supplying pressurizing gas from the source S ₂ into the mixing chamber formed by the volume V ₆ . Given its length and its diameter, which is in practice less than 5 mm, the conduit C ₃ induces a pressure drop on the flow of air from the source S ₂ , this pressure loss resulting from the restriction. constituted by the conduit C ₃ .

According to one aspect of the invention which is not shown, the conduit C ₃ could also be equipped with a variable restriction such as that R ₃ mentioned with reference to the embodiments of Figures 4, 8 and 9.

Compared to the first embodiment described, the seventh embodiment corresponds to a case where the coating product is transported in dense phase over a relatively long length, namely the length of the pipe 117, and in diluted phase over a relatively long length. low, namely the length of the pipe 7. For the rest, the principle used in this embodiment is close to that of the first embodiment.

The characteristics of the different embodiments can be combined in the context of the present invention.

Claims (22)

Device for dosing and continuous conveying of powdery product from a closed reservoir, said device comprising means for fluidizing at least part of said product in said reservoir, a tube immersed in said fluidized product and opening into the outside said tank and means for pressurizing said tank, characterized in that it comprises means (C ₃ , 113, R ₃ ) for permanently feeding the pressurizing gas of said tank (4; 204; 404 ) to a chamber (V ₆ ) for mixing said gas with the fluidized product exiting said tube (110; 310; 510), said supplying means being equipped or constituting a restriction (C ₃ , R ₃ ) to the flow of the pressurizing gas, while a pipe (7; 207; 407) conveying the powdery product mixed with said gas is connected downstream of said mixing chamber. Device according to claim 1, characterized in that said supply means (C ₃ ) is supplied with gas directly from a line (C ₂ ) supplying said tank (4) with pressurizing gas. Device according to claim 1, characterized in that said supply means (C ₃ , R ₃ ) is supplied with gas from the volume (W ₄ ) of said reservoir (204; 404) not occupied by the fluidized product (L ₄ ). Device according to one of the preceding claims, characterized in that said restriction (R ₃ ) is adjustable, so that the pressure drop (ΔP) induced on the flow of gas in said supply means (C ₃ ) is adjustable. Device according to one of claims 1 to 3, characterized in that said restriction (C ₃ , R ₃ ) is calibrated, the pressure drop (ΔP) induced on the flow gas in said supply means being controlled mainly by the flow of gas through said restriction. Device according to one of the preceding claims, characterized in that said mixing chamber (V ₆ ) is arranged immediately downstream of said tube (110; 310; 510). Device according to claim 6, characterized in that said mixing chamber with a length (L ₁₁₆ ), in the direction of flow of the product, greater than three times its internal diameter ( d ₁₁₆ ), preferably of the order of ten times said diameter. Device according to one of claims 1 to 5, characterized in that said mixing chamber (V ₆ ) is arranged in the vicinity of a projector (2) and at a distance from the dip tube (110). Device according to one of the preceding claims, characterized in that said feed means (C ₃ ) comprises an annular volume (C ₃ , 113) arranged around the downstream portion of said tube (110; 310; 510), upstream its outlet (110B). Device according to one of the preceding claims, characterized in that said supply means comprises a duct (C ₃ ) connecting a pipe (C ₂ ) supplying said reservoir with pressurizing gas and said mixing chamber (V ₆ ) or the volume (W ₄ ) of said reservoir not occupied by the fluidized product and said mixing chamber (V ₆ ). Device according to claim 10, characterized in that said duct (C ₃ ) is generally annular and arranged around said tube (510). Device according to one of claims 1 to 8, characterized in that said feeding means is formed by a restriction (R ₃ ) calibrated or adjustable (Figure 7). Device according to one of the preceding claims, characterized in that it comprises means (C ₄ , 118) for supplying said mixing chamber (V ₆ ) with additional dilution gas, said supply means being distinct from said gas supply means and able to be controlled independently. Device according to one of the preceding claims, characterized in that said mixing chamber (V6, 116) and / or a passage (113) for feeding said gas to said mixing chamber is / are provided with at least one relief (116a) for improving the mixing of the gas and the coating product by stirring or vortexing. Device according to one of the preceding claims, characterized in that it comprises means (150) for continuously weighing the quantity of coating product present in said reservoir (4). Device according to one of the preceding claims, characterized in that it comprises means (104, 160) for maintaining the height (h ₄ ) of fluidized product (L ₄ ) above the mouth (110A) of said tube (110). Device according to claim 16, characterized in that said means comprise a partition (160) for separating the internal volume (V ₄ ) of said reservoir into a first (V ₁₆₀ ) and a second (W ₁₆₀ ) unit volumes, the product being fluidized (4) in said at least one first unit volume, while said volumes are in communication to allow the supply (F ₁₆ ) of said first volume of product to be fluidized from the second volume and the discharge (F ₁₇ ) of fluidized product into excess of the first volume to the second volume. Device according to claim 17, characterized in that the supply (F ₁₆ ) of said first volume from of said second volume and the discharge (F ₁₇ ) of fluidized product in excess takes place by gravity. Device according to one of claims 17 or 18, characterized in that said product is partially fluidized in said second volume (W ₁₆₀ ). Use of a device (4-117; 204-310; 404-513) according to one of the preceding claims for supplying a projector (2) with powder coating material. Coating projection installation (I) comprising at least one coating material projector (2) and at least one device (4-117; 204-310; 404-513) according to one of claims 1 to 19 feeding said projector in coating product. Installation according to claim 21,
characterized in that said projector (2) and said mixing chamber (V ₆ ) are carried by the mobile arm (120) of a robot.

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