Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
  • B05B7/1481—Spray pistols or apparatus for discharging particulate material
  • B05B7/1486—Spray pistols or apparatus for discharging particulate material for spraying particulate material in dry state
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
  • B05B5/03—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying
  • B05B5/032—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying for spraying particulate materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/02—Spray pistols; Apparatus for discharge
  • B05B7/06—Spray pistols; Apparatus for discharge with at least one outlet orifice surrounding another approximately in the same plane

Definitions

• the present application relates to the field of pneumatic powder feed injectors.
• Pneumatic powder injectors are commonly used to convey fairly fine powders from a reservoir to a device allowing the projection of the powder or its distribution on a surface.
• body paints are applied in powder form by an electrostatic gun supplied from a container of powder paint by an injector.
• the injector operates in the manner of a venturi, that is to say that a supply of compressed air into the injector induces a vacuum zone in a part of the injector connected to the fluidized powder reservoir.
• the vacuum generates the suction of this powder and its movement in a conduit to the electrostatic gun.
• the powder application device is supplied with powder in a homogeneous and continuous manner, that the various conduits traversed by the powder do not become blocked.
• the components of the injector, and in particular the central part or central channel where the compressed air begins to entrain the powder are subjected to significant wear. Indeed, the channel deforms or even cracks or breaks, which leads to an inhomogeneous application of the powder and the need to replace this channel very often.
• the Applicant has therefore deemed it necessary to improve the resistance of the powder injectors over time.
• the present invention provides, for this purpose, a pneumatic powder feed injector comprising a primary channel, connectable to a source of compressed air, and a suction channel, connectable to a powder reservoir, the two channels opening into an internal cavity opening onto a transport nozzle of the powder, the injector being characterized in that the nozzle is a cylinder.
• the nozzle is manufactured from one of the materials on the list consisting of borosilicate glass, quartz, aluminum oxide, ceramic and sintered metal, such as, for example, sintered bronze.
• Sintered metal here designates a porous material obtained by heat treatment of sintering metal powders.
• Examples of sintered metal which can be used in the invention are bronze, iron, steels or any other sintered metal well known to those skilled in the art depending on the field of application of the injector.
• a sintered metal nozzle here designates a cylindrical nozzle manufactured by sintering or heat treatment of metal powder in order to obtain a cylinder which is porous to gases in general and to air in particular.
• the nozzle is preferably completely and only cylindrical.
• the connection between the cavity and the nozzle does not include a frustoconical or funnel-shaped section as is the case in existing pneumatic injectors.
• the nozzle is preferably made only of borosilicate glass, quartz, aluminum oxide, ceramic or sintered metal.
• a cylindrical nozzle allows the use of a shorter nozzle than when it is conical or has a conical section. This makes it possible to limit the rise in temperature during the passage of the powders and all the consequences that this may have on the wear of the nozzle on the one hand and above all, on the degradation of the powders on the other hand.
• EP0962257 discloses a powder feed injector supplied with compressed air to create a vacuum in an area connected to a powder reservoir, the vacuum causing the suction of the powders.
• the vacuum zone opens onto a glass nozzle for transporting the powder having a first section funnel-shaped.
• the glass must be as hard and have a surface as smooth as possible, the blowing technique being for this purpose preferred, in order to avoid accumulations of powder particles in the channels.
• the borosilicate glass nozzle of the invention remains operational after 2500 hours.
• quartz cylinder an exclusively crystalline mineral, obtained by hydrothermal crystallization, makes it possible to obtain a nozzle with performances similar to borosilicate, or even superior. Quartz is in particular not “blowable” like glass and the smooth nature of its surface is therefore not controllable.
• the injector of the invention is not limited to uses in the field of paint powders but also proves to be very advantageous for other applications where fine powders are handled, such as for example the food industry (flour , sugar, etc %) or construction (plaster, etc ).
• the injector according to the invention comprises a secondary channel connectable to a second supply of compressed air, for diluting the air-powder mixture at the outlet of the nozzle.
• this secondary channel runs, at least in part, the outer wall of the nozzle.
• the air introduced through the secondary channel makes it possible to dilute the powders at the outlet of the nozzle. It also makes it possible to cool, or at least to temper, the part of the nozzle which it runs along. This is particularly advantageous for use with thermally unstable powders, such as certain paints containing sensitive pigments or dyes or food powders, in particular containing sugars.
• the secondary channel runs, at least in part, the outer wall of the sintered bronze nozzle.
• the compressed air circulating in the secondary channel passes through the porosities of the nozzle which creates a diffuse air flow on the inner wall of the nozzle, oriented substantially towards the interior of the nozzle. This air flow slows down the powders when approaching the internal surface of the nozzle and limits or even avoids any contact between the powder and the nozzle, thereby limiting wear.
• Figure 1 is a diagram illustrating the hardness of different glasses as well as quartz;
• Figure 2 is a sectional diagram of the injector according to the invention.
• an injector 1 comprises a body 2 or mantle, inside which is hollowed a cavity 3.
• a primary channel 4 and a suction channel 5 each connect respectively the outside of the mantle 2 with the cavity 3.
• the internal cavity 3 extends, in a direction opposite to the arrival of the primary channel 4, towards a generally cylindrical zone 6 into which is introduced a nozzle 7, made of borosilicate, quartz or alumina (aluminum oxide ), cylindrical.
• the interior of the nozzle 7 defines in the zone 6 a channel connecting the cavity 3 to the outlet 8 of the injector.
• the outside of the nozzle 7 is, over part of its length close to the cavity 3, in contact with the material constituting the mantle 2.
• the outside of the nozzle 7 defines the wall internal of an air cylinder 10, the external wall of which is a substantially cylindrical end piece inserted, at least partially into the mantle 2 and the part of which emerges from the mantle 2 constitutes the outlet 8 from the injector.
• the cylinder 10 is in fact a cylindrical envelope around a portion of the nozzle.
• a secondary channel 9 connects the outside of the mantle 2 to the air cylinder 10, at the end of the end piece it inserted into the mantle 2.
• the end piece can be secured to the mantle 2 using '' a screwed ring (not shown here).
• the nozzle can be shaped or include means, such as a stopper, for locking the nozzle in place when using the injector.
• the nozzle can be detached so as to be able to extract the nozzle from the coat 2. Such a removable nozzle makes it easier to clean the interior of the coat.
• the primary channel 4 of the pneumatic injector is connected to a compressed air supply which enters, via the channel 4, into the cavity 3 then into the zone 6 located on the other side of the cavity 3.
• the compressed air induces a vacuum there which causes an aspiration of air from the suction channel 5 to the cavity 3, air which is then entrained with the air compressed towards zone 6 and in particular towards the interior of nozzle 7, up to outlet 8 of the injector.
• the vacuum causes the suction not only of air but also of powder towards the interior of the injector.
• the powder follows the same path: it first crosses the cavity 3 where it meets the flow of compressed air which drives it towards the interior of the nozzle until the outlet of the injector.
• the powder makes a 90 ° turn at the level of the cavity and risks encountering the internal wall of the nozzle 7, then sliding along this wall.
• the nozzle is here made of borosilicate or quartz, which allows friction between the air-powder mixture, which circulates there at high speed, that is to say at speeds reaching 500 to 700 km / h, and the inner wall of the nozzle do not alter the quality of the nozzle, as is the case with the materials usually used, such as a conventional glass or Teflon.
• the wall is smooth enough that the powder particles are not slowed down on contact.
• the nozzle Unlike known injectors where the inlet of the nozzle, that is to say its end close to the cavity, is shaped like a funnel, the nozzle here is cylindrical, that is to say of uniform diameter over its length. No additional part having the shape of a funnel is inserted at the inlet of the nozzle, the cavity 3 also does not include a curved, convex or concave wall, drawing a continuity with at least part of the periphery of the nozzle inlet. This type of curved wall is here, by extension, covered by the term "funnel shape".
• the funnel-shaped configuration makes it possible to avoid or limit the pressure drop, that is to say the reduction in pressure, between the inlet of compressed air and the outlet of the injector.
• the Applicant has nevertheless observed that the conformation in a funnel causes 10 to 15% loss of powder due to the degradation of the powder, in particular by inducing the formation of very fine particles during an impact between the powder entrained at high speed. and the inclined wall of the funnel formed by the entry of the nozzle, as well as the variation in flow. These losses represent a significant financial loss. Fine powder particles are more particularly toxic if they are breathed in by the operator.
• the secondary channel 9 is intended to be connected to a second supply of compressed air and makes it possible to create an air flow in the cylinder 10 around the nozzle which merges with the flow of the air-powder mixture at the outlet of the nozzle and completes it.
• the compressed air supplied by the secondary channel 9 circulates in the same direction as the air-powder mixture at the outlet of the nozzle. It also allows you to adjust this flow without having to play on the primary channel adjustment parameters.
• the air supplied by the secondary channel 9 also makes it possible to “dilute” the powder, that is to say to adjust the concentration in the air flow which is sent to the powder application device. to which the outlet 8 of the injector is connected.
• the air supplied by the secondary channel 9 circulates along the nozzle, over at least part of the length of the nozzle, makes it possible to cool the nozzle, or at least to moderate its heating. This has the consequence of limiting or even eliminating the phenomenon of powder agglomeration inside the nozzle, a phenomenon usually due to the heating of the nozzle. This effect is particularly advantageous when the powder contains organic pigments or other heat-sensitive compounds such as certain food components for example.
• the nozzle of FIG. 2 can alternatively be made of sintered bronze.
• the air passing through the secondary channel passes into the cylinder 10, as described above. Part of the air goes to the outlet 8, another part passes through the porous wall of the nozzle 7 in sintered bronze.
• a diffuse air flow or "air cushion” forms on the inner wall of the nozzle, oriented substantially towards the interior of the nozzle. This air cushion slows down the powder as it approaches the internal surface of the nozzle and limits or even avoids any contact between the powder and the nozzle. This allows on the one hand to avoid wear of the nozzle linked to impacts of the particles against the wall of the nozzle.
• the control of the heating of the nozzle is also amplified. This also makes it possible to avoid fouling of the nozzle, and in particular powder deposits on the internal surface of the nozzle, on imperfections or in porosities for example.
• the mantle 2 is preferably made of metal, preferably of injected aluminum, for better resistance over time.
• FIG. 2 is here illustrative and represents the elements of the injector on a relative scale. Similarly, the precise shape of the mantle 2 can be different as long as the main functionalities of the different elements are ensured.
• the size of the injector and the flow rates it can support depend on the final application. Injectors according to the invention, made of borosilicate and quartz, were tested on 26 guns producing continuously. After 3000 hours of testing, no parts had yet to be replaced, maintenance is reduced by 90% compared to conventional venturis. Whatever the material of the nozzle, the user also noted a lower consumption of powder of at least 10%. It has also been found that the powder leaving the gun has a lower proportion of fine particles resulting from the degradation of the powders in the injector. This is particularly advantageous since fine particles have to be eliminated from the working environment by specialized companies, which has a non-negligible cost.
• the injector of the invention in its general operation, is similar to conventional pneumatic powder injectors with the difference that the nozzle has a particular shape and / or constitution which gives it improved properties.
• the injector of the invention can be used for a wide variety of powders, in particular coating powders, such as for example cold coating powders which can serve as paint, sealer, coatings which conduct heat and electricity, of biocompatible materials or for manufacturing conductive lines on heating glasses, or hot coating powders such as for example flame coating, electric arc coating with wires, plasma coating or coating with an oxygen-gasoline jet at high speed with applications in the electronics industry, the aeronautical industry as well as in the biomedical industry.
• coating powders such as for example cold coating powders which can serve as paint, sealer, coatings which conduct heat and electricity, of biocompatible materials or for manufacturing conductive lines on heating glasses, or hot coating powders such as for example flame coating, electric arc coating with wires, plasma coating or coating with an oxygen-gasoline jet at high speed with applications in the electronics industry, the aeronautical industry as well as in the biomedical industry.
• the injector of the invention can be used in the food industry for fine and / or heat-sensitive powders such as flour, sugar, coffee, cocoa, additives, etc.
• the nozzle or powder transport insert according to the invention overcomes the problems of the nozzles currently on the market, in particular the problems of clogging due to the heating of the internal surface of the nozzle during the passage of the powder and wear problems.
• the choice of the cylindrical shape and of the materials of the invention makes it possible to greatly limit these phenomena.

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Applications Claiming Priority (2)

Publications (1)

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ID=63914732

Family Applications (1)

Country Status (3)

Family Cites Families (4)

• 2018
  • 2018-10-09 BE BE20185691A patent/BE1026693B1/fr not_active IP Right Cessation
• 2019
  • 2019-10-09 EP EP19783055.7A patent/EP3863770A1/de not_active Withdrawn
  • 2019-10-09 WO PCT/EP2019/077378 patent/WO2020074590A1/fr unknown

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