EP2429716B1 - Projector and member for spraying a coating material, and spraying method using such a sprayer - Google Patents

Description

The present invention relates to a rotary projector coating product. The present invention also relates to a rotating device for spraying coating product. Furthermore, the present invention relates to a coating product spraying process which implements such a rotating projector.

Conventional spraying by means of rotating projectors is used to apply a coating product to objects to be coated, such as motor vehicle bodies. By coating product is meant any product intended to be projected in the form of droplets on an object to be coated, such as a primer, a paint, a varnish or a plant protection product to be sprayed on plants etc.

A rotary coating product projection projector comprises a spraying member rotating at high speed under the effect of rotating drive means, such as a compressed air turbine. Such a spraying member generally has the shape of a rotationally symmetrical bowl and it comprises at least one spraying edge capable of forming a jet of coating product. The rotating projector also comprises a fixed body housing the rotating drive means as well as means for supplying the spray member with coating material.

The jet of coating material sprayed from the edge of the rotating member has a generally conical shape which depends on such parameters as the rotation speed of the bowl and the flow rate of the coating product. To control the shape of this jet, the rotating projectors of the prior art are generally equipped with several orifices. These orifices are formed in the body of the rotating projector, on a circle which is located on the outer periphery of the bowl and which is centered on the axis of symmetry of the bowl. These orifices are intended to emit air jets to conform the jet of coating product.

JP-A-8,071,455 describes such a rotating projector for which the air jets emitted from the outer periphery of the bowl are intended to reduce the existing depression downstream of the bowl and to obtain a uniform deposited paint film.

However, such a rotating projector induces relatively high air velocities, which may degrade, qualitatively and quantitatively, the application of the coating product on the object to be coated.

In a qualitative way on the one hand, an object coated with such a rotating projector has impacts whose profiles are sometimes irregular and generally not robust. The robustness of an impact resulting from a rotary projector of a coating product corresponds substantially to the regularity of a curve representing, as a function of a determined parameter such as the skirt air flow, the "width of the 'impact', that is, the width of the area of median or greater deposited thickness, considered in a direction perpendicular to the direction of relative movement between the rotating projector and the object to be coated.

In a quantitative manner, on the other hand, the deposition efficiency of such a rotating projector is relatively limited. The deposition efficiency, also referred to as transfer efficiency, is the ratio of the amount of coating product deposited on the object to be coated to the amount of coating product sprayed by means of the rotating projector.

DE-A-10 2007 012 878 discloses a projector in which an airflow is used to shape a central spray of paint and to press a peripheral flow against a flow surface of a bowl. The air injection means located outside the flow surface of the bowl do not affect the robustness of the impact of the coating product or the deposition efficiency.

The present invention aims in particular to overcome these disadvantages by providing a rotating coating product projector to fill the depression downstream of the bowl, to obtain a good robustness of the impacts of coating products on the objects to be coated and to limit the dirt on the bowl components.

For this purpose, the subject of the invention is a rotary coating product projector, as defined in claim 1.

Thanks to the invention, in particular to the arrangement of the air distributor, air can be injected into the spray member during the painting feed, which improves the robustness and deposition efficiency when spraying. Within the meaning of the invention, the fact that the air distributor is arranged in the upstream part of the flow surface means that it is surrounded radially by this surface and located axially at least at least part of this area. area.

Other advantageous but optional features of the invention, taken alone or in any technically permissible combination, are defined in claims 1 to 14.

In addition, the subject of the present invention is a rotatable coating product spraying device as defined in claim 15.

On the other hand, the subject of the invention is a method for projecting a coating product, as defined in claim 16.

• la figure 1 est une vue en perspective avec arraché d'un projecteur rotatif conforme à l'invention, comprenant un organe de pulvérisation conforme à l'invéntion ;
• la figure 2 est une vue en coupe, à plus grande échelle et selon le plan Il à la figure 1, d'une partie du projecteur ;
• la figure 3 est une vue analogue à la figure 2 d'une partie d'un projecteur et d'un organe de pulvérisation conformes à un deuxième mode de réalisation de l'invention ;
• la figure 4 est une vue analogue à la figure 2 d'une partie d'un projecteur et d'un organe de pulvérisation conformes à un troisième mode de réalisation de l'invention ;
• la figure 5 est une vue analogue à la figure 2 d'une partie d'un projecteur et d'un organe de pulvérisation conformes à un quatrième mode de réalisation de l'invention ;
• la figure 6 est une vue analogue à la figure 2 d'une partie d'un projecteur conforme à un cinquième mode de réalisation de l'invention ;
• la figure 7 est une vue analogue à la figure 2 d'une partie d'un projecteur conforme à un sixième mode de réalisation de l'invention ;
• la figure 8 est un graphique illustrant certains avantages du projecteur rotatif et de l'organe de pulvérisation conformes à l'invention par rapport à l'art antérieur.

The invention will be well understood and its advantages will also emerge in the light of the description which follows, given solely by way of nonlimiting example and with reference to the appended drawings in which:

• the figure 1 is a perspective view broken away from a rotating projector according to the invention, comprising a spraying member according to the invention;
• the figure 2 is a sectional view, on a larger scale and according to the plan Il to the figure 1 , part of the projector;
• the figure 3 is a view similar to the figure 2 a part of a projector and a spraying member according to a second embodiment of the invention;
• the figure 4 is a view similar to the figure 2 a part of a projector and a spraying member according to a third embodiment of the invention;
• the figure 5 is a view similar to the figure 2 a part of a projector and a spraying member according to a fourth embodiment of the invention;
• the figure 6 is a view similar to the figure 2 a part of a projector according to a fifth embodiment of the invention;
• the figure 7 is a view similar to the figure 2 a part of a projector according to a sixth embodiment of the invention;
• the figure 8 is a graph illustrating certain advantages of the rotating projector and the spraying member according to the invention compared to the prior art.

The figure 1 shows a rotating projector P for projecting coating product comprising a spraying member 1, hereinafter referred to as a bowl. The bowl 1 is housed partially within a fixed body 2. The bowl 1 is shown in a spray position where it is rotated at high speed about an axis X ₁ by rotation drive means, such as an air turbine T whose envelope is represented in dashed lines at the figure 1 . The axis X ₁ is therefore the axis of rotation of the bowl 1. The speed of rotation of the bowl 1 in charge, that is to say when spraying the coating product, can be between 25000 rpm and 100000 rpm.

The fixed body 2 is said to be "fixed" because it does not rotate about the axis X ₁ . The fixed body 2 may be mounted on a not shown support such as a multiaxis robot arm.

As shown in figure 2 , the bowl 1 has a symmetry of revolution about the axis X ₁ . The bowl 1 comprises a flow surface 11, which is intended to receive the coating product in a film which spreads, under the effect of the centrifugal force, to an edge 12 where this product is micronized into fines droplets. By flow surface is designated the hollow inner surface of the bowl 1, that is to say, its surface facing the axis X ₁ . The edge 12 and the flow surface 11 are in fluid communication, so that the coating material film can flow from the flow surface 11 to the edge 12 which borders the surface of the flow surface 11. flow downstream.

The set of droplets sprayed at the edge 12 forms a coating product jet, not shown, which leaves the bowl 1 and goes towards an object to be coated, not shown, on which this jet produces an impact. The bowl 1 has an outer surface 13 which faces the fixed body 2. The outer surface 13 is called "external" because it is not turned towards the axis X ₁ . By contrast, the flow surface 11 can be described as "internal" because it is turned towards the axis X ₁ .

As shown in figure 2 , the flow surface 11 consists of an upstream portion 11.1, which is frustoconical of axis X ₁ , and a downstream portion 11.2 which consists of two frustoconical surfaces of axis X ₁ juxtaposed and connected together, the vertex angle of the frustoconical surface connected to the edge 12 being less than the vertex angle of the frustoconical surface connected to the upstream portion 11.1.

The edge 12 has the overall shape of a circle of diameter D ₁₂ centered on the axis X ₁ . Not shown notches are made between the flow surface 11 and the edge 12 to improve the control of the size of the sprayed droplets at the edge 12. The diameter D ₁₂ may be, for example, equal to 65 mm .

As shown in figure 1 , the rotating projector P further comprises a pipe 24 for bringing fluids, liquid or gaseous, involved in the operation of the bowl 1 object of the invention. The duct 24 is illustrated in dashed lines at figure 1 and its downstream portion 22 is partially illustrated at figure 2 .

During a spraying phase, the duct 24 makes it possible to supply air and coating product at the level of the bowl 1. During a cleaning phase of the rotating projector P and the bowl 1, the duct 24 can bring solvents and cleaning air to the bowl 1.

As shown in figure 2 the downstream section 22 of the duct 24 comprises an air duct 20 and a duct 21 for feeding the bowl 1 with a coating product. The downstream section of the air duct 20 has a cylindrical shape that extends upstream of the bowl 1 and coaxially with the axis X ₁ . Alternatively, the downstream section of the air duct 20 may extend generally parallel to and near the axis X ₁ .

The terms "upstream" and "downstream" refer to the direction of flow of the coating product from the base of the rotating projector P, located to the right of the figure 1 , to the ridge 12, located to the left of the figure 1 .

Line 21 forms means for feeding bowl 1 with a coating product. The downstream section of the pipe 21 consists of a cylindrical bore which extends substantially parallel to the air duct 20, and therefore to the axis X ₁ , at a radial distance R ₂₁ from the axis X ₁ . In other words, the pipe 21 is eccentric in the duct 22 with respect to the air duct 20. In addition to the duct 21, in particular upstream thereof, the rotating projector P may comprise other supply means to bring the duct coating product in line 21.

The term "axial" refers to an entity, part or direction, which extends along the axis X ₁ of rotation and symmetry of the bowl 1. The term "radial" applies to an entity, part or direction, which extends in a direction perpendicular to the axis X ₁ , such that the direction Y ₁ in the plane of the figure 2 .

Alternatively, the pipe 21 may have, as the pipe 121 described below in connection with the figure 3 , a tubular shape extending around the air duct and coaxial with the axis of rotation. Such a tubular shape makes it possible to evenly distribute the coating product on the periphery of the air distributor and in the space separating the upstream face of the air distributor and the downstream face of the duct.

As shown in figure 2 , the rotating projector P further comprises an air distributor 30 which is disposed near the end surface 23 of the downstream section 22 of the duct 24. The end portion of the downstream section 22 extends through an upstream opening 14 of circular shape arranged in the bowl 1. The air distributor 30 is disposed in the upstream portion 11.1 of the flow surface 11. The air distributor 30 is disposed downstream, with respect to the direction of flow of the air, of the air line 20.

In the first embodiment illustrated in figure 2 , the air distributor 30 is integral with the bowl 1. The air distributor 30 and the bowl 1 are secured by fastening means which extend around the axis X ₁ , but not in the plane of the figure 2 where they are not represented. These fixing means may for example consist of magnets or screws.

The air duct 20 and the air distributor 30 form means 3 for injecting air into a region located radially inside the volume delimited by the flow surface 11 and upstream of the edge 12 This region is delimited, on the one hand, by the air distributor 30 and, on the other hand, by the downstream part 11.2 of the flow surface 11.

In the present application, the expression "to inject air" refers to the injection of air within the volume delimited by the flow surface of the bowl, if although this air then flows beyond the bowl 1. In addition to this air that can be described as "central", the rotating projector can be equipped with skirt air injection means, right and / or oblique (vortex), as is known per se.

The means 3 for injecting air, namely the air duct 20 associated with the air distributor 30, are distinct from the means for supplying the bowl 1 with the coating product, which in particular comprise the duct 21. Thus, it is possible, during the spraying of the coating product, to inject air concomitantly with the supply of coating material at the level of the bowl 1.

In the first embodiment of the invention, which is illustrated in FIG. figure 2 , the air distributor 30 is arranged to inject air into a central region 11.3 which belongs to the volume delimited by the flow surface 11. The term "central" applies to the position of the central region 11.3 as well. well in the radial direction Y ₁ than in the axial direction X ₁ . The air distributor 30 has an opening 35 which is arranged on the upstream side of the air distributor 30 so as to receive a flow of air coming from the air duct 20. For this purpose, the opening 35 is placed in position. in the vicinity of the downstream end of the air duct 20. The diameter of the opening 35 corresponds substantially to the diameter of the air duct 20.

The air distributor 30 has a plurality of channels 32, 34 and 36 which extend rectilinearly into the air distributor 30. The channels 32, 34 and 36 converge in a common chamber 31 located downstream of the opening 35 In addition to the channels 32, 34 and 36 shown in the plan of the figure 2 , the air distributor 30 comprises channels which extend out of the plane of the figure 2 and whose inlet ports are visible at the common chamber 31. In other words, the air distributor 30 has the shape of a knob. In practice, the number of channels is between 1 and 30.

The air distributor 30 comprises a pair of channels 32 and a pair of channels 34 which respectively have a symmetry with respect to the axis X ₁ . The jets of air produced by the channels 32, 34 and 36, when they are supplied by the air duct 20, are represented by straight arrows, even if they are actually air jets substantially. conical or cylindrical.

The extent of the central region 11.3 may vary depending on the geometry and the parameters of use such as the air flow or the orientation of the channels 32, 34 and 36.

The direction of each channel 32 forms, with the axis X _1, an angle A ₃₂ . The direction of each channel 34 forms, with the axis, an angle A ₃₄ . The direction of the channel 36 forms, with the axis X ₁ , a zero angle. In practice, the angles A ₃₂ , A ₃₄ and A ₃₆ are between 0 ° and 80 °. The respective directions of the channels 32, 34 and 36 are therefore distributed in a solid angle of less than 2n sr.

In other words, the channels 32 and the channels 34 are directed towards the flow surface, whose upstream portion 11.1 forms with the axis X ₁ an angle A ₁₁ . The respective directions of the channels 32, 34 and 36 are therefore distributed in a solid angle which is greater than the solid angle inscribing the flow surface 11. Thus, the means for injecting air, the air channel 20 and the air distributor 30, are arranged to direct a portion of the air towards the flow surface 11. This part of the injected air makes it possible in particular to thin the film of coating product spread on the surface 11 by "rolling" it.

In the first embodiment, illustrated in FIG. figure 2 , the downstream axial surface 37 of the air distributor 30 is in the form of a totally planar disc where the outlets of the channels 32, 34 and 36 open out. The flat or flattened shape of the downstream axial surface 37 defines a distributor of Air 30 simple to manufacture and provides continuous or less disturbed air flows and reduced soiling areas.

The positions of these outlets, as well as the respective lengths and diameters of the channels 32, 34 and 36, are determined for injecting air into the central region 11.3. Combined with the rotation of the air distributor 30 with the bowl 1, this makes it possible to push back further from the bowl 1, to attenuate or even to fill the existing depression downstream of the bowl 1.

The air distributor 30 has an outer surface 30.1 which is generally frustoconical axis X ₁ . The apex angle of the outer surface 30.1 is equivalent to the apex angle of the upstream portion 11.1 of the flow surface 11. In other words, the outer surface 30.1 extends parallel to the upstream portion 11.1 . Thus, the outer surface 30.1 and the upstream portion 11.1 define between them a passage 11.4 for the coating product. The passage 11.4 directs the coating product from the pipe 21 to the flow surface 11 where it spreads to form a film.

In operation, during the spraying of the coating product, the bowl 1 and its air distributor 30 are rotated by the air turbine T. The coating product flows in the pipe 21, inside of the duct 22, to fill the space separating the end surface 23 from the upstream face 33 of the air distributor 30. Then, the coating product flows through the space 11.4 and spreads on the surface flow 11 to the edge 12 where it is sprayed into fine droplets.

Prior or concomitantly with this supply of coating material, the means 3 for injecting air, which comprise the air duct 20 and the air distributor 30, are supplied with compressed air which they drive and distribute in the air. Central region 11.3. The air supply is maintained as long as the bowl is fed with coating material. The air thus injected then flows downstream of the bowl 1 and then mixes with the jet of sprayed coating product. The air thus injected thus makes it possible to compensate for the depression existing downstream of the bowl 1.

More specifically, a brief initial phase may consist in delivering the compressed air into the air duct 20 and into the air distributor 30 before discharging the paint into the duct 21. This initial phase makes it possible to avoid the recovery of painting on and in the air distributor 30.

In addition, air ejected through the channels 32 and 34 is directed to the flow surface 11, which aids in spreading or rolling of the coating material film on the flow surface 11.

In addition, the air thus injected into the central region 11.3 limits the returns of coating material inside the flow surface 11 and on the downstream face 37 of the air distributor 30, which reduces the soiling of the bowl 1, so the amount of solvent needed for cleaning.

In addition, this air injection improves the application performance of the coating product on the object to be coated, as is detailed hereinafter in connection with the figure 8 . Furthermore, it has been found that the injection of air at the center of the bowl 1 does not decrease the deposition efficiency, otherwise known as the transfer efficiency, of the application.

The figure 8 shows a graph illustrating, as a function of the skirt airflow SA to conform the jet of sprayed product, the variations of the impact width W50 of the dynamic impact, that is to say on, an object in movement, measured at the median thickness of the deposition profile, as indicated above in connection with the state of the art.

A curve C ₀ represents the robustness curve of the impact width W50 of a rotary projector of the prior art, while a curve C ₃ represents the robustness curve of a rotating projector according to the invention, that is to say comprising means 3 for injecting air within the volume delimited by the flow surface 11.

Each of the curves C ₀ and C ₃ has an area where the impact width W 50 evolves discontinuously. These zones are denoted Z ₀ and Z ₃ respectively for the curves C ₀ and C ₃ . The zones Z ₀ and Z ₃ are said to be "non-robust" because the impact width W 50 evolves therein discontinuously when the skirting air flow SA is modified, so that the non-robust zones Z ₀ and Z ₃ are not usable for spraying coating product. Indeed, in a non-robust zone Z ₀ or Z ₃ , a small variation of an external parameter, such as the rotation speed of the bowl 1, the product flow or the displacement of the multiaxis robot arm on which the rotary projector P, can strongly change the air flow around the bowl 1 and vary unevenly the width of impact W50.

The non-robust zone Z ₃ , with air injection in the center of the bowl 1, represents a relatively small variation of the impact width W50, while the robust zone Z ₀ , without air injection in the center of the bowl 1, represents a greater variation of the W50 impact width. A rotating projector P according to the invention, with air injection in the center of the bowl 1, thus reduces the amplitude of the non-robust zone Z ₀ and bring it back to the non-robust zone Z ₃ . The decrease of this amplitude is materialized at the figure 8 by the zone Z ₀ - Z ₃ which represents a variation of the diameter W50 of about 200 mm.

Consequently, the variations of the impact width W50 along the curve C ₃ are lower, which allows the application of coating product in revoilage, to superpose a thin layer of coating product on a base coat already applied. . Revoiling is an application in which the Skirt airflow is relatively low and the rotation speed of the bowl is relatively high.

Moreover, it is possible to optimize the method of use of the rotating projector P. For this purpose, it is necessary to use all the areas of the curves C ₀ and C ₃ where the impact width W 50 is robust.

In the example of the figure 8 when increasing the skirt air flow SA from a few NL / min to 600 NL / min, first spray the coating product without air injection in the center of the bowl 1 to follow the robust part initial of the curve C ₀ to a point 51. Then, it is preferable to inject more or less air flow in the center of the bowl 1, to be placed at a point 52 starting a robust zone of the curve C ₃ . It is then necessary to follow the curve C ₃ to a point 53, maintaining the air injection in the center of the bowl 1. Then, in the same sequence, it is possible to continue to follow the curve C ₃ from the point 53 when increasing the skirt air flow SA.

Alternatively, it is possible to follow the curve C ₀ , thus to interrupt the injection of air at the center of the bowl 1, from a point 54, when increasing the skirt air flow SA. The air flow within the bowl 1 can thus be injected either in sequenced mode, or in continuous mode, that is to say at constant value, or in variable mode.

This maximum and juxtaposed exploitation of the robust zones of the curves C ₀ and C _{3 also} makes it possible to minimize the skirt air consumption SA, by following the curve C ₀ rather than the curve C ₃ between the flow rates corresponding to the points 51 and 54. .

The figure 3 illustrates a second embodiment of the invention, in which the bowl 1 is identical to the bowl 1 of the figure 2 . The description of the bolus 1 given above in relation to the figure 2 can be transposed to the bowl 1 shown in figure 3 . Elements of the rotating projector of the figure 3 Like or corresponding to those of the rotating projector P have the same numerical references increased by 100. Thus defines a duct represented by its downstream section 122, an air duct 120 and a duct 121.

The rotating projector partially illustrated at figure 3 differs from the rotating projector P of the figure 2 by the structure of the feeding means of the bowl 1 in coating product and their position relative to the means for injecting air into the center of the bowl 1.

The downstream section of the duct 122 comprises the air duct 120 which is identical to the air duct 20 of the downstream section 22 of the duct 24. In particular, the air duct 120 is coaxial with the axis X ₁ . The means 3 for injecting air, which comprise the air duct 120 and the air distributor 30, are therefore identical to the means 3 illustrated in FIG. figure 1 .

In particular, the air leaving the pipe 120 enters the common chamber 31 of the distributor 30 through an opening 35 formed on the upstream side of this distributor.

The section 122 differs from the downstream section 22 of the duct 24 in that the coating product supply means comprises the duct 121 which has a tubular shape extending around the air duct 120 and coaxially with the duct. X axis ₁ , while the pipe 21 consists of a single hole eccentric relative to the axis X ₁ . The tubular shape of the pipe 121 makes it possible to evenly distribute the coating product on the circumference of the air distributor 30 and in the space separating the upstream face 33 of the air distributor 30 and the downstream face 123 of the pipe duct 122.

Alternatively, the pipe 121 may comprise, as the pipe 21 described above in relation to the figure 2 , a bore extending parallel to the air duct, thus to the axis of rotation, and eccentrically in the duct.

The figure 4 illustrates a bowl 101 according to a third embodiment of the invention, wherein the downstream section 122 of the pipe is identical to the section 122 of the figure 3 and the bowl 101 similar to the bowl 1. The description of the bowl 1 and the section 122 given above in relation to the figure 3 can be transposed to bowl 1 and section 122 of the figure 4 , taking into account the differences set out below. Elements of the rotating projector of the figure 4 similar or corresponding to those of the rotating projector P have the same numerical references increased by 100. Thus defines an air distributor 130, a common chamber 131, channels 132, 134, 136 and 138, an opening 135 for access to the chamber 131, a downstream axial surface 137, an outer surface 130.1.

The bowl 101 differs from the bowl 1 because it comprises an air distributor 130 whose shape and the number of channels differ from those of the air distributor 30. The other characteristics of the air distributor 130 are identical to the corresponding characteristics of the air distributor 130. air distributor 30, in particular its upstream axial surface 133 and its external surface 130.1.

The pipe 120 of the section 122 and the air distributor 130 together form means 103 for injecting air into a central region of the bowl 101 situated radially inside its flow surface 11.

Firstly, the air distributor 130 differs from the air distributor 30 in that its downstream axial surface 137 is curved and convex, in this case in the form of a sphere portion, while it is flattened in the case of the downstream axial surface 37. The shape of the air distributor 130 makes it possible to produce an air distribution different from the distribution obtained with the air distributor 30, which may be useful depending on the application. desired. According to a variant not shown, the downstream axial surface of the air distributor 30 may be curved and concave, that is to say hollow.

In addition, the air distributor 130 has more channels 132, 134, 136 and 138 than the air distributor 30. The distribution of the channels 132, 134, 136 and 138 is similar to the distribution of the channels 32, 34 and 36 that has been described above in relation to the figure 2 .

The figure 5 illustrates a bowl 201 according to a fourth embodiment of the invention, wherein the downstream section 122 of the pipe is identical to the section 122 of the figure 3 . The description of the bowl 1 and the duct 122 given above in relation to the figure 3 can be transposed to bowl 201 and section 122 of the figure 5 , taking into account the differences set out below. Elements of the rotating projector of the figure 5 similar or corresponding to those of the rotating projector P have the same numerical references increased by 200. Thus defines a flow surface 211, an edge 212, an outer surface 213, an air distributor 230, a common chamber 231, channels 232 and 234, an opening 235 for access to the chamber 231, a downstream axial surface 237, an external surface 230.1, as well as a central region 211.3 and air injection means 203 formed by the pipe 120 of the distributor 122 and the air distributor 230.

The flow surface 211, the ridge 212 and the outer surface 213 are identical, respectively to the flow surface 11, to the edge 12 and to the outer surface 13. The bowl 201 differs from the bowl 1 by the structure and by the number of channels of its air distributor 230. The channels 232 and 234 are in fact machined in a downstream portion 239 of the distributor 230 which protrudes from the downstream axial surface 237. The downstream axial surface 237 is therefore partially flat, because it is composed of a flat crown and a protruding and frustoconical portion. The common chamber 231 extends to this projecting portion. A large flat portion of the downstream axial surface 237 is thus disengaged from the channels 232 and 234.

The downstream end of the section 222 enters the common chamber 231, through the opening 235, with a radial clearance, which forms a baffle locally generating pressure losses that limit the rise of paint in the air distributor 230 For the same purpose of preventing the return of paint between the distributor 230 and the outer radial surface of the chamber 231, the upstream axial surface 235.2 is provided with a frustoconical rim or bead 235.1 which abuts radially on the outside, the opening 235 and the chamber 231.

The other characteristics of the air distributor 230 are identical to the corresponding characteristics of the air distributor 30 and 130, in particular the outer surface 230.1 of the air distributor 230 has a frustoconical shape.

The air distributor 230 makes it possible to produce a more localized air distribution in the center of the central region 211.3 than the air distributor 30 or 130 allows.

The figure 6 illustrates a bowl 301 according to a fifth embodiment of the invention. The description of the bowl 1 and the duct 24, in particular of its downstream section 22, given above in relation to the figure 1 can be transposed, in the figure 6 , at the bowl 301 and the pipe represented by its downstream section 322, taking into account the differences set out below. Elements of the rotating projector of the figure 6 similar or corresponding to those of the rotating projector P have the same numerical references increased by 300. This defines a flow surface 311, upstream portions 311.1 and downstream 311.2, a central region 311.3, an edge 312, an outer surface 313, an air distributor 330, a common chamber 331 and channels 332 and 334.

The air distributor 330 has channels 332, 334 similar to the channels 232, 234 of the bowl 201. The air distributor 330 differs from the distributors 30, 130 and 230 in that it is disjointed from the bowl 301 and fixed relative to the fixed body of the rotating projector. On the contrary, the air distributors 30, 130 and 230 are respectively integral with the bowls 1, 101 and 201, so that the air distributors 30, 130 and 230 rotate around the axes X ₁ , X ₁₀₁ and X ₂₀₁ , relative to the fixed body of the rotating projector P.

Line 320 of duct 322 and air distributor 330 together form means 303 for injecting air into a region of bowl 301 located radially inside flow surface 311.

In the embodiment illustrated in figure 6 , the air distributor 330 is formed at a downstream portion of the air duct 320. In practice, the air distributor 330 is machined in the downstream portion of the section 322 so as to form a projection through the upstream opening 314 of the bowl 301 and in the central radial portion of the bowl 301. The air distributor 330 and the section 322 are therefore integral. Alternatively, the air distributor can be attached to the pipe by screwing, gluing or the like.

The pipe 320 and the chamber 331 are in line with each other and are connected at an opening 335, which is in fact constituted by an inner subassembly zone 322-330. The air thus enters the pipe 320 into the chamber 331 through the opening 335.

The bowl 301 further comprises a distributor 340 which fulfills the function of distribution of the coating product on the upstream portion 311.1 of the flow surface 311. The distributor 340 is integral with the bowl 301 and rotates with it about the X axis ₃₀₁ . The distributor 340 has an external surface 340.1 which defines, with the upstream portion 311.1, a passage 311.4 for the coating product.

In addition to the channels 332 and 334, the air distributor 330 has side channels 333. The side channels 333 extend radially and are distributed about the X axis ₃₀₁ . Air flows through side channels 333 to an annular gap 339 between dispenser 330 and manifold 340 so that paint does not flow into gap 339. For the same purpose, prevent the repainting of paint between the distributor 330 and the distributor 340, the upstream axial surface 335.2 is provided with a rim or frustoconical bead 335.1 similar to the rim 235.1 of the embodiment of the figure 5 .

For the bowl 301, the means for injecting air comprises the bore which defines the gap 339, since the air distributor 330 injects the air also through this bore. The means for injecting air are distinguished from the paint supply means which are formed by the distributor 340.

The air distributor 330 makes it possible to produce static air jets, as opposed to the dynamic or rotary air jets produced by the air distributors 30, 130 and 230. Static air jets have the advantage that they 'to be particularly directive and have a local impact relatively more important than dynamic jets.

The figure 7 illustrates a bowl 401 according to a sixth embodiment of the invention. The description of the bowl 301 and the downstream pipe section 322 given above in connection with the figure 6 can be transposed, in the figure 7 , at the bowl 401 and the pipe represented by its downstream section 422, taking into account the differences set out below. Elements of the rotating projector of the figure 7 similar or corresponding to those of the rotating projector of the figure 6 have the same numerical references increased by 400. A flow surface 411, an edge 412, an outer surface 413, an air distributor 430, a common chamber 431, channels 432 and 434, an opening 435, are defined. access to the room 431 and a splitter 440.

The pipe 420 of the section 422 and the air distributor 430 together form means 403 for injecting air into a region of the bowl 401 located radially inside the flow surface 411. One (or more) pipes not shown allows the supply of the bowl 401 coating product. Each duct extends in the section 422 and opens upstream of the distributor 440. Each duct may be similar to a duct 21, 121, 221 or 321 as described above, that is to say rectilinear and parallel to the X axis ₄₀₁ or tubular and coaxial with the X axis ₄₀₁ .

Unlike the air distributor 330, the air distributor 430 comprises a nozzle which is attached to the end of the section 422. More specifically, the air distributor 430 comprises an upstream portion of tubular shape which is screwed into the pipe 420 whose downstream end portion is threaded 433. The distributor Air 430 is easily removable and cleanable because it has a twist-off tip. Alternatively, the tip can be fixed in the duct by fins.

The air distributor 430 is disjointed from the bowl 401 and fixed relative to the fixed body of the rotating projector. The air distributor 430 has a channel 434 similar to the channel 334 of the bowl 301. The downstream portion of the air distributor 430 has a frustoconical shape in the center of which is pierced the channel 434 along the X axis ₄₀₁ . The air supplying the channel 434 comes from the common room 431.

An interstitial space, or clearance, is formed between the frustoconical surface of the air distributor 430 and the coinciding terminal surface of the section 422. This interstitial space forms a channel 432 of lamellar shape extending around the axis X ₄₀₁

The air reaches the channel432 through several radial holes, three of which are visible at the figure 7 with the references 437, 438 and 439. The radial bores 437 and 438 extend in the radial direction Y ₄₀₁ contained in the plane of the figure 7 . These radial bores 437, 438 and 439 are made in the upstream tubular portion of the air distributor 430 and they open into an annular chamber 428 which is formed in the duct 422.

Thus, the nozzle forming the air distributor 430 makes it possible to inject a stream of lamellar air into the region located radially inside the flow surface 411.

The embodiments described above, in particular in relation to the Figures 1 to 7 , offer all the main advantages of the invention, namely to fill the depression downstream of the bowl, to obtain a good robustness of the impacts of coating products on the objects to be coated and to limit the soiling of the components of the bowl.

According to another variant not shown, the pipe for the coating product and the air duct can be machined in two different parts assembled by conventional fastening means.

In addition, the air injected at the center of the bowl can be replaced by any other harmless and neutral gas vis-à-vis the coating product, such as nitrogen.

In all the embodiments, the air duct 20, 120, 220, 320 or 420 is centered on the axis of rotation X ₁ , ... X ₄₀₁ of the bowl 1, ... 401 and the distributor 30, 130, 230 or 430 is also centered on this axis. The flow of air between the pipe and the distributor is therefore along this axis.

In all embodiments, the air distributor or equivalent is arranged in the volume defined by the upstream portion, 11.1 or equivalent, of the flow surface, or equivalent, of the bowl. In other words, the air distributor 30 or equivalent is inscribed in the volume defined by the flow area, 11 or equivalent, of the bowl. This location of the dispenser allows it to effectively distribute the air both to the flow surface and to the center of the bowl, which allows in particular to fill a possible depression in the central region of the bowl or downstream of this region. The robustness of the impact and the deposit efficiency are improved.

Claims (16)

1. A rotary projector (P) for a coating material, comprising

   - a fixed body (2),

   - a coating material spraying member (1; 101; 201; 301; 401),

   - means (T) for rotating the spraying member (1; 101; 201; 301; 401) around a rotational axis (X₁; X₁₀₁; X₂₀₁; X₃₀₁; X₄₀₁),

   - means (21; 121; 321) for supplying the spraying member (1; 101; 201; 301; 401) with a coating material,

   the spraying member (1; 101; 201; 301; 401) for the coating material comprising:

   - at least one flow surface (11; 211; 311; 411) for receiving the coating material,

   - at least one edge (12; 212; 312; 412) for spraying the coating material, the edge (12; 212; 312; 412) being in fluid communication with the flow surface (11; 211; 311; 411),

   the rotary projector (P) also comprising means (3; 103; 203; 303; 403) for injecting air into a region located radially (Y₁; Y₄₀₁) inside the space defined by the flow surface (11; 211; 311) and upstream from the edge (12; 212; 312; 412), the air-injecting means (3; 103; 203; 303; 403) being separate from the coating material supply means (21; 121; 321), the air-injecting means (3; 103; 203; 303; 403) including an air dispenser (30; 130; 230; 330; 430) characterized in that the air dispenser (30; 130; 230; 330; 430) is arranged in an upstream portion (11.1; 311.1) of the flow surface (11; 211; 311; 411) to inject air into a central area (11.3; 211.3), radially (Y₁; Y₄₀₁) and axially (X₁; X₄₀₁), of the flow surface (11; 211; 311; 411).
2. The rotary projector (P) according to claim 1, characterized in that the air-injecting means (3; 103; 203; 303; 403) are arranged so as to orient all or some of the air toward the flow surface (11; 211; 311; 411).
3. The rotary projector (P) according to claim 1, characterized in that the air dispenser (330; 430) is separate from the spraying member (301; 401) and stationary relative to the fixed body.
4. The rotary projector (P) according to claim 3, characterized in that the air dispenser (430) comprises a nozzle that is removably fastened to the means (403) for injecting air and/or the supply means.
5. The rotary projector (P) according to one of the preceding claims, characterized in that the means (3; 103; 203; 303; 403) for injecting air comprise an air pipe (20; 120; 320; 420) extending upstream of the spraying member (1; 101; 201; 301; 401), the downstream section of the air pipe (20; 120; 320; 420) extending substantially parallel and close to the axis of rotation (X₁; X₁₀₁; X₂₀₁; X₃₀₁; X₄₀₁), said downstream section preferably being coaxial to the axis of rotation (X₁; X₁₀₁; X₂₀₁; X₃₀₁; X₄₀₁).
6. The rotary projector (P) according to claim 5, characterized in that the means (21; 321) for supplying the coating material comprise a tubing (21; 321) whereof the downstream section extends generally parallel to the air pipe (20; 320) and spaced away from the axis of rotation (X₁; X₁₀₁; X₂₀₁; X₃₀₁).
7. The rotary projector according to claim 5, characterized in that the means (121) for supplying the coating material comprise a tubing (121) that is tubular and extends around the air pipe (120).
8. The rotary projector according to claim 3 and claim 6 or 7, characterized in that the air dispenser (330) is made at a downstream portion of the air pipe (320).
9. The rotary projector (P) according to one of the preceding claims, characterized in that the air dispenser (30; 130; 230) is secured to the spraying member (1; 101; 201).
10. The rotary projector (P) according to one of the preceding claims, characterized in that the air dispenser (30; 130; 230; 330; 430) has at least one opening (35; 135; 235; 335; 445) arranged upstream of the air dispenser (30; 130; 230; 330; 430) to receive a stream of air, as well as at least one channel (32, 34, 36; 132, 134, 136; 232, 234; 332, 334; 432, 434) extending downstream of the opening (35; 135; 235; 335; 435).
11. The rotary projector according to claim 10, characterized in that the air dispenser (30; 130; 230; 330; 430) has several channels (32, 34, 36; 132, 134, 136; 232, 234; 332, 334; 432, 434) that converge downstream of the opening (35) and the discharge directions of which are distributed in a solid angle greater than the solid angle inscribing the flow surface (11; 211; 311; 411) and smaller than 2π steradians (sr), certain channels (32, 34, 36; 132, 134, 136; 232, 234; 332, 334; 432, 434) being oriented toward the flow surface (11; 211; 311; 411).
12. The rotary projector (P) according to one of claims 9 to 11, characterized in that the downstream axial surface (37; 237) of the air dispenser (30; 230; 330) is completely or partially planar.
13. The rotary projector according to one of claims 9 to 11, characterized in that the downstream axial surface (137) of the air dispenser (130) is curved, preferably in the shape of a sphere portion.
14. The rotary projector (P) according to one of claims 9 to 13, characterized in that the flow surface (11; 211; 311; 411) generally has a symmetry of revolution relative to the axis of rotation (X₁; X₁₀₁; X₂₀₁; X₃₀₁; X₄₀₁) and the air dispenser (30; 130; 230; 330; 430) has a globally tapered outer surface around the axis of rotation (X₁; X₁₀₁; X₂₀₁; X₃₀₁; X₄₀₁), the outer surface (30.1, 130.1; 230.1) defining, with the flow surface (11; 211; 311; 411), a passage (11.4; 311.4) for the coating material.
15. A rotary member (1; 201; 301; 401) for spraying a coating material comprising:

    - at least one flow surface (11; 211; 311; 411) intended to receive the coating material conveyed by the means (21; 121; 321) for supplying the coating material,

    - at least one edge (12; 212; 312; 412) for spraying said coating material, the edge (12; 212; 312; 412) being in fluid communication with the flow surface (11; 211; 311; 411),

    the rotary member (1; 201; 301; 401) also comprising means (3; 103; 203; 303; 403) for injecting air into a region situated radially (Y₁; Y₄₀₁) inside the volume delimited by the flow surface (11; 211; 311; 411) and upstream of the edge (12; 212; 312; 412), the air-injecting means (3; 103; 203; 303; 403) being separate from the means (21; 121; 321) for supplying coating material, the air-injecting means (3; 103; 203; 303; 403) comprising an air dispenser (30; 130; 230; 330; 430),
    characterized in that the air dispenser is arranged in an upstream part (11.1; 311.1) of the flow surface (11; 211; 311; 411) to inject air into a central region (11.3; 211.3), radially (Y₁; Y₄₀₁) and axially (X₁; X₄₀₁), of the flow surface (11; 211; 311; 411) and in that said air dispenser is integral with the spraying member (1; 101; 201; 301; 401).
16. A method for projecting a coating material, using a rotary projector (P) according to one of claims 1 to 14 and in that it comprises the following steps:

    - supplying the spraying member (1; 101; 201; 301; 401) with coating material;

    - injecting air into a region situated radially (Y₁; Y₄₀₁) inside the volume delimited by the flow surface (11; 211; 311; 411) using the air dispenser (30; 130; 230; 330; 430) arranged in an upstream part (11.1; 311.1) of the flow surface (11; 211; 311; 411) of the spraying member;

    - selecting one or more air flow(s), in a continuous, variable or direct mode, flowing into the air-injecting means (3; 103; 203; 303; 403).

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