The present invention relates to a rotary sprayer for spraying a coating material, and to an installation for spraying a coating material and including at least one such sprayer.
Conventional atomization by means of rotary sprayers is used for applying a primer, a base coat, and/or a varnish to articles that are to be coated, such as motor vehicle bodywork. A rotary sprayer for spraying a coating material includes an atomizer member rotating at high speed under drive from rotary drive means, such as a compressed air turbine.
Such an atomizer member is generally in the form of a bowl presenting symmetry of revolution and it includes at least one atomizer edge suitable for forming a jet of coating material. The rotary sprayer also has a stationary body housing the rotary drive means and also means for feeding the atomizer member with the coating material.
The jet of coating material atomized by the edge of the rotary member presents a shape that is generally conical and that depends on parameters such as the speed of rotation of the bowl and the flow rate of the coating material. In order to control the shape of this jet of material, prior art rotary sprayers are generally fitted with a plurality of primary orifices formed in the body of the sprayer and disposed on a circle centered on the axis of symmetry of the bowl. The primary orifices serve to deliver primary air jets that together form air for shaping the jet of material, which shaping air is sometimes referred to as “skirt” air.
JP-A-8 071 455 describes a rotary sprayer having primary orifices designed to deliver primary air jet for shaping the jet of material. Each primary air jet is inclined relative to the axis of rotation of the bowl in a primary direction presenting an axial component and a circumferential component. The primary air jets thus generate a turbulent air stream around the axis of rotation of the bowl and of the jet of coating material. This turbulent air stream, sometimes referred to as a “vortex”, is used, in particular by adjusting its flow rate, to shape the jet of material atomized by the edge as a function of the intended application.
The body of the rotary sprayer shown in FIG. 6 of JP-A-8 071 455 is provided with a plurality of secondary orifices disposed on the same circle as the primary orifices and offset therefrom. Each secondary air jet from one of the secondary orifices is inclined relative to the axis of rotation in a secondary direction presenting an axial component and a radial component. These components are determined in such a manner as to inject air streams in front of the downstream face of the bowl, so as to reduce the suction caused by the bowl rotating at high speed.
Thus, the secondary air jets are intended to obtain a uniform film of deposited paint. For this purpose, it is necessary that the secondary air jets come directly into the suction zone situated facing the bowl and downstream therefrom. The direction of each secondary air jet is thus determined in such a manner as to avoid the secondary air jets striking the rear surface of the bowl.
Nevertheless, such secondary air streams require tricky adjustments in order to avoid damaging the shape of the jet of coating material. Furthermore, secondary air jets inclined in that way do not enable the shape of the jet of material to be adjusted and consequently do not enable the impact area of the atomized droplets on the article for coating to be adjusted.
The present invention seeks specifically to remedy those drawbacks by proposing a novel rotary device for spraying a coating material, which device provides great latitude in adjusting the shape of the jet of material.
To this end, the invention relates to a rotary sprayer for spraying a coating material, the sprayer comprising:
a material sprayer member presenting at least one sprayer edge suitable for forming a jet of material;
means for driving said member in rotation; and
a stationary body presenting primary orifices disposed on a primary contour surrounding the axis of rotation of said member, and secondary orifices disposed on a secondary contour surrounding the axis of rotation of said member in a manner that is offset relative to the primary orifices, the primary and secondary orifices serving respectively to emit primary and secondary air jets, each primary air jet being inclined relative to the axis of rotation in a primary direction presenting at least an axial component and a circumferential component, such that said primary air jet freely crosses the region where the edge is located, each secondary air jet being inclined relative to the axis of rotation in a secondary direction presenting at least an axial component and a radial component. According to the invention, the components of each secondary air jet are such that said secondary air jet strikes an outside surface of the sprayer member.
By means of the invention, the secondary air jets burst against the atomizer member, thereby enabling the jet of atomized material to be adjusted finely and uniformly.
According to other characteristics of the invention that are advantageous, but optional, whether taken in isolation or in any technically feasible combination:
the body also presents tertiary orifices disposed on a tertiary outline surrounding the axis of rotation and designed to emit tertiary air jets, each tertiary air jet being inclined relative to the axis of rotation in a tertiary direction presenting axial, radial, and circumferential components such that said tertiary air jets freely cross the region where the edge is located;
at least one of the contours presents a shape that is regular and non-circular, e.g. elliptical or rectangular;
the orifices disposed on each contour are associated in subgroups of orifices that are juxtaposed from one to the next, each of the subgroups being connected to an independent compressed air feed source via a valve, the valves being controllable independently of one another;
the primary and secondary contours coincide with a circle centered on the axis of rotation;
the secondary direction presents a zero circumferential component;
the body presents primary and secondary channels opening out respectively via the primary and secondary orifices, the primary and secondary channels being inclined relative to the axis of rotation respectively along the primary and secondary directions;
the primary and secondary channels are made by drilling through an outer jacket and/or are constituted by gaps formed between the outer jacket and an inner jacket, the jackets being disposed around means for driving the member in rotation and a rear portion of the member;
the primary and secondary channels are connected respectively to a primary common chamber and to a secondary common chamber, said chambers being defined in the body and constituting two independent compressed air feed sources;
the primary orifices are arranged on the circle in alternation with the secondary orifices;
the components of the primary air jet are determined in such a manner that the primary air jets flow at a radial distance from the edge lying in the range 0 to 25 millimeters (mm), and that is preferably equal to 1.5 mm;
the components of the secondary air jets are determined in such a manner that the secondary air jets strike the member at an axial distance from the edge that lies in the range 0 to 10 mm, and that is preferably equal to 2.8 mm;
the circle on which the primary and secondary orifices are disposed has a diameter lying in the range 58 mm to 80 mm, and preferably equal to 68 mm, for a bowl having a diameter equal to 55 mm.
Furthermore, the invention also provides an installation for spraying a coating material, the installation being characterized in that it includes at least one rotary sprayer as specified above.
The invention can be better understood and other advantages thereof appear more clearly in the light of the following description of a rotary device and an installation in accordance with the invention, given purely by way of example and made with reference to the accompanying drawings, in which:
A dispenser 3 is secured to the upstream portion of the bowl 1 to channel and spread the coating material. The speed of rotation of the bowl 1 in operation, i.e. when it is atomizing the material, may lie in the range 30,000 revolutions per minute (rpm) to 70,000 rpm.
The bowl 1 presents symmetry of revolution about the axis X1. The bowl 1 has a spreader surface 11 on which the coating material spreads out under the effect of centrifugal force until it reaches an atomizer edge 12 where it is micronized into fine droplets. The set of droplets forms a jet J1 of the material leaving the bowl 1 and travels towards an article to be coated, not shown, on which it produces an impact surface. The outside rear surface 13 of the bowl 1, i.e. its surface that does not face towards its axis of symmetry X1, faces towards the body 2.
The body 2 has primary orifices 4 and secondary orifices 6 disposed on a common circle C centered on the axis of symmetry X1 of the bowl 1. The primary and secondary orifices 4 and 6 are designed to emit respective jets of primary air and secondary air that are represented in the figures by their respective directions J4 and J6.
The edge 12 is at an axial distance L1 from the circle C, which distance is equal to 10 mm in this example. The distance L1 thus represents the extent to which the bowl 1 projects out from the body 2.
The primary and secondary directions J4 and J6 in this example are determined respectively by the angles of inclination of primary channels 40 and of secondary channels 60 defined in the body 2. In the example shown in the figures, the channels 40 and 60 are rectilinear and open out respectively via the primary and secondary orifices 4 and 6. Upstream, the channels 40 and 60 are connected to two independent sources, described below, for providing compressed air in order to form the jets J4 and J6.
As shown in
In other words, the primary jets J4 do not strike the rear surface 13 of the bowl 1. A primary direction J4 is thus oblique relative to the axis X1, which it does not intersect. Together, the primary jets J4 generate a turbulent air stream or vortex air suitable for influencing the shape of the jet of coating material. The components A4 and O4 of a primary air jet J4 are determined in such a manner that the jet flows at a radial distance l4 from the edge 12 that is equal to 1.5 mm. In practice, the distance l4 may lie in the range 0 to 25 mm. The distance l4 depends in particular on the axial distance L1. Thus, when the distance L1 is 50 mm, the distance l4 may lie in the ratio 0 to 50 mm.
Each secondary air jet is inclined relative to the axis of rotation X4 in a secondary direction J6 that presents an axial component A6 and a radial component R6. In addition, the components A6 and R6 are determined in such a manner that a secondary air jet J6 strikes the rear surface 13 of the bowl 1, as can be seen clearly in
In other words, the secondary direction J6 extends transversely relative to the axis of rotation X4. Furthermore, the secondary direction J6 in this example presents a circumferential component that is zero, thus enabling it to be considered as being a generator line of a cone having its vertex lying on the axis X1.
The secondary air jet J6 shown in
The diameter D of the circle C, which depends in particular on the diameter of the edge 12, is equal to 68 mm in this example for a bowl 1 having a diameter equal to 55 mm. In practice, it may lie in the range 58 mm to 80 mm for such a bowl.
On the circle C, the primary orifices 4 are arranged to alternate with the secondary orifices 6. As shown in
The number and the distribution of primary and secondary orifices 4 and 6 is determined as a function of the accuracy desired for controlling the shape of the jet of material and as a function of the uniformity that is desired for the impact area. Thus, the greater the number of orifices 4 and 6, the greater the extent to which the impact area is uniform. In a variant, provision can be made for the numbers of primary and secondary orifices to be different.
The primary and secondary orifices 4 and 6 have respective diameters d4 and d6 that are equal to 0.8 mm and 0.8 mm. Such dimensions enable primary and secondary air jets to be delivered at flow rates that are respectively equal to 700 liters per minute (L/min) and to 500 L/min, when they are fed with respective pressures of 6 bars and 6 bars. In practice, the diameters d4 and d6 of the primary and secondary orifices 4 and 6 may lie respectively in the ranges 0.5 mm to 1.5 mm and 0.5 mm to 1.5 mm. In particular, the diameters d4 and d6 may be different from each other.
As shown in
In this example, the primary and secondary chambers 23 and 25 are formed between the outer jacket 22 and an inner jacket 24, and they are separated by a sealing O-ring 26. The adjective “internal” is used herein to designate an article that is close to the axis of rotation X1, while the adjective “outer” is used to designate an article that is further away therefrom. The jackets 22 and 24 present globally a symmetry of revolution around the axis X1.
Alternatively, the primary and/or secondary channels 40 and 60 may be defined by gaps formed between the outer and inner jackets 22 and 24. Under such circumstances, these gaps may be made by machining notches in one and/or the other of the facing surfaces of the inner and outer jackets 24 and 22.
This rotary sprayer for spraying a coating material comprises a bowl 101 analogous to the bowl 1 that is partially received within a stationary body 102. The bowl 101 may be driven in rotation at high speed about an axis X101 and it is fed with material via a dispenser 103.
The bowl 101 has a spreader surface 111 over which the coating material spreads out until it reaches an atomizer edge 112 where it is micronized into fine droplets.
The body 102 presents primary, secondary, and tertiary orifices 104, 106, and 108 that are disposed respectively on primary, secondary, and tertiary contours C104, C106, and C108. The contours C104, C106, and C108 are plane and respectively elliptical, circular, and rectangular. The orifices 104, 106, and 108 are for delivering respective primary, secondary, and tertiary air jets that are represented in
The primary and tertiary contours C104 and C108 are centered on the axis of rotation X101 and they present shapes that are elongate along the same main direction, being respectively elliptical and rectangular with rounded corners. Thus, the primary and tertiary air jets J104 and J108 serve to shape the jet of sprayed material by flattening it. This serves to optimize the overlap of impacts on the article to be coated, and consequently to optimize the uniformity of the thickness that is deposited.
Furthermore, for each contour C104, C106, or C108, the orifices 104, 106, or 108 are associated in four subgroups of orifices so as to form four quadrants I, II, III, and IV. The orifices in a given subgroup defined by a quadrant are juxtaposed from one to the next, i.e. they form an uninterrupted sequence.
Each subgroup is connected to an independent compressed air feed source via a valve, not shown. The four valves of the four subgroups of a given contour are independent from one another, thus making it possible to modulate the shapes of the primary, secondary, and tertiary air jets. For this purpose, it is possible to feed the orifices of some of the quadrants with compressed air while not feeding the orifices of the remaining quadrants.
Where necessary, the subdivision into subgroups could be implemented other than by quadrant.
Furthermore, in the embodiments of
The characteristics of the embodiments described above may be combined. For example, the air jets of the sprayer of
Number | Date | Country | Kind |
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07 04217 | Jun 2007 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FR2008/000813 | 6/12/2008 | WO | 00 | 12/14/2009 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/010646 | 1/22/2009 | WO | A |
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