# Patent

## Title
Coating product spraygun and method for resupplying coating product to such a spraygun

## Abstract

This spraygun (1) comprises a body (11) and, housed in a proximal part (11.1) of the body (11), a tank (10) extending along a main axis (X10). This spraygun also comprises atomizing means (5) in a distal part (11.2) of the body (11) comprising an atomizing member (51) designed to atomize the coating product generally in an atomizing direction (Y50). The atomizing direction (Y50) and the main axis (X10) of the tank are convergent.

## Background
RELATED APPLICATIONS
The present application is a §371 U.S. national stage entry of International Application No. PCT/FR2009/052452, filed Dec. 8, 2009, which claims the priority of France patent application No. 08 58414 filed Dec. 9, 2008, all of which are incorporated herein by reference in their entirety.
FIELD
The present invention relates to an atomizer that is designed to be moved by a robot for the purposes of spraying a coating material towards articles to be coated. The present invention also relates to a method of re-supplying such an atomizer with coating material. The term “coating material” is used to designate a liquid material such as a primer, a paint, or a varnish.
BACKGROUND
FR-A-2 887 474 describes an atomizer comprising a body fastened to the wrist of a multi-axis robot that moves the atomizer relative to the articles to be coated. The articles to be coated in that document are vehicle bodies conveyed by a conveyor. That atomizer also has a coating material reservoir that is housed in a proximal portion of the body. The reservoir has a cylindrical shape that extends along a main axis that coincides with the axis of the atomizer. A turbine and an atomizer member in the form of a bell cup are mounted in the body. As shown by comparing FIGS. 1 and 2 of FR-A-2 887 474, the atomizer member sprays the coating material substantially in a spraying direction that extends the main axis of the atomizer and of its reservoir. In other words, the main axis of the reservoir is co-linear with the spraying direction.
The atomizer thus has an elongate shape that limits its agility, i.e. its aptitude for reaching regions that are difficult to access, in particular, on the inside of a motor vehicle body.
In addition, the length and the narrowness of the connection duct and of the feed duct generate large head losses that can reduce the flow rate of solvent, and thus slow down cleaning operations. A specific low head loss duct is necessary for collecting waste when cleaning the atomizer. Thus, in a conventional paint spraying installation, a cleaning stage lasts about 20 seconds (s) and gives rises to paint losses of about 25 cubic centimeters (cm3).
A particular object of the present invention is to remedy those drawbacks, by proposing an atomizer that is agile, compact, and simple to manipulate, by means of a robot.
SUMMARY
To this end, the invention provides an atomizer for spraying a coating material towards articles to be coated, which atomizer comprises:

    
    
        a body equipped with a flange for fastening the atomizer to a robot, the robot and/or the flange defining a terminal axis about which the atomizer is designed to move relative to the articles to be coated;
        a coating material reservoir housed in a proximal portion of the body and extending along a main axis; and
        atomizer means for spraying the coating material, which means are disposed in a distal portion of the body, the atomizer means having an atomizer member arranged to spray the coating material substantially in a spraying direction.
    
    


This atomizer is characterized in that the spraying direction and the main axis of the reservoir are convergent.
By means of the invention, the reservoir housed in the body is offset angularly relative to the spraying direction, thereby facilitating spraying in cavities, and cleaning/filling the reservoir.
According to other advantageous but optional characteristics of the invention, taken in isolation or in any technically feasible combination:

    
    
        the angle between the main axis of the reservoir and the spraying direction lies in the range 50° to 100°, and is preferably equal to 90°;
        the terminal axis forms an angle with the spraying direction that lies in the range 110° to 130°, and that is preferably equal to 120°;
        the distance between the center of gravity of the atomizer and the terminal axis is selected to be less than 80 millimeters (mm), and preferably to be less than 20 mm;
        the height of the atomizer, as measured in the spraying direction is selected to be less than 450 mm, and preferably less than 400 mm;
        the atomizer has at least one orifice for connection to a coating material circuit, said orifice being situated on the outside surface of the atomizer, and it has a connection duct connecting the orifice to the reservoir, the connection duct having a length less than or equal to 50 mm;
        the atomizer also has a valve for controlling the flow of coating material and of a cleaning material through the atomizer, the valve forming a portion of the connection duct;
        the atomizer means have a feed duct for feeding the atomizer member, the feed duct extending from the reservoir to the atomizer member, the feed duct having a length less than or equal to 300 mm, and a maximum diameter less than or equal to 5 mm, and preferably less than or equal to 4 mm;
        the reservoir has a piston for pushing the coating material towards the atomizer means, and the atomizer also has an actuator for moving the piston along the main axis, the actuator being housed in the body between the reservoir and the flange;
        the reservoir is in the shape of a cylinder having a circular base and of volume lying in the range 200 cm3 to 1000 cm3, and the diameter of the cylinder of the reservoir lies in the range 50 mm to 120 mm, and is preferably equal to 100 mm; and
        the atomizer means have rotary drive means for driving the atomizer member in rotation about an axis of rotation that substantially coincides with the spraying direction.
    
    


The invention also provides a method of re-supplying an atomizer as defined above with coating material, said method being characterized in that it comprises the following steps:

    
    
        a) dumping all of any coating material remaining in the reservoir through the feed duct and through the atomizer member;
        b) opening the valve to cause cleaning material to flow into the reservoir and into a cleaning duct, all of the cleaning material flowing, downstream from the reservoir, through the atomizer member; and
        c) opening the valve to cause the coating material to flow into the connection duct and into a cleaning duct in such a manner as to fill the reservoir with the new coating material.
    
    


The invention can be well understood and its advantages also appear from the following description, given merely by way of non-limiting example and with reference to the accompanying drawings, in which:



FIGURES
FIG. 1 is a section view of an atomizer of the invention; and
FIG. 2 is a view on a larger scale of the detail II of FIG. 1.



DETAILED DESCRIPTION
FIG. 1 shows an atomizer 1 including a body 11, a reservoir 10, and atomizer means 5. The atomizer 1 is designed to spray a liquid material, such as a paint, a primer, or a varnish, towards articles to be coated, such as vehicle bodies. The function of the reservoir 10 is to contain the material to be sprayed.
The body 11 is equipped with means for fastening to a robot 2 of the multi-axis type. The casing of the robot 2 is shown in chain-dotted lines in FIG. 1. The robot 2 is designed to move the atomizer 1 relative to the articles to be coated. In order to mount the atomizer 1 on the robot 2, the body 11 is equipped with a flange 19, which is collar-shaped in this example. The means for fastening the atomizer 1 to the robot 2 comprise a set of screws in abutment against the flange 19. The flange 19 is at the interface between the robot 2 and the atomizer 1. In practice, the flange can have various shapes, so long as it makes it possible to link the body to the robot, thereby performing the function of base for the atomizer.
The flange 19 defines a terminal axis Y19 about which the atomizer 1 moves relative to the articles to be coated. The terminal axis Y19 is referred to as being “terminal” because it coincides with the last axis of the robot 2 before the atomizer 1 itself. When the robot 2 is a multi-axis robot, said robot 2 has at least six axes for moving the atomizer 1, including the terminal axis Y19. In the embodiment shown in FIGS. 1 and 2, the terminal axis Y19 is thus defined by the flange 19 and by the robot 2. Alternatively the terminal axis may be defined by the robot only, and not by the flange.
The body 11 is made up of a proximal portion 11.1 and of a distal portion 11.2. The reservoir 10 is received in the proximal portion 11.1, i.e. it is incorporated into the volume defined by a casing 17 of the body 11. In the present patent application, the adjectives “proximal” and “distal” are used with reference to the flange 19. The adjective “proximal” designates an element relatively close to the flange 19, whereas the adjective “distal” designates an element that is further away therefrom.
The reservoir 10 is in the overall shape of a circular cylinder defined by a cylindrical surface 10.1 and by a circular base 10.2. The reservoir 10 extends along a main axis X10 that is horizontal in FIG. 1. The volume V10 indicated herein corresponds to the maximum volume of the reservoir 10. The reservoir 10 has a diameter D10 of 100 mm and a length L10 lying in the range 50 mm to 100 mm. The volume V10 of the reservoir 10 is about 0.8 liters (l), i.e. about 800 cm3. In practice, the diameter D10 lies in the range 50 mm to 120 mm, and the volume V10 lies in the range 200 cm3 to 1000 cm3.
A piston 18.1 in the shape of a disk is arranged in the reservoir 10 so as to expel the coating material therefrom towards atomizer means 5, as described in detail below. The piston 18.1 is mounted to move in translation along the axis X10. The atomizer 1 further includes an actuator 18 for moving the piston 18.1 in translation along the main axis X10. The actuator 18 may be constituted by an electric motor or by any other equivalent actuator. The actuator 18 is of shape that is elongate along the main axis X10. The actuator 18 is received in the proximal portion 11.1 of the body 11, in a space that is defined firstly by the reservoir 10 and secondly by the flange 19.
The atomizer means 5 comprise a bell cup 51 that constitutes an atomizer member, and a turbine 52 that forms means for driving the bell cup 51 in rotation about the axis of rotation Y51. The atomizer means 5 further comprise an injector 53 mounted in a central cavity of the turbine 52, a downstream portion 54 of a feed duct 4, and an atomizer valve 55 that controls the flow of fluids through the injector 53 and thus over the bell cup 51.
During paint spraying, the atomizer valve 55 opens the downstream portion 54 of the feed duct 4, thereby enabling paint to flow through the injector 53 and over the bell cup 51. The turbine 52 drives the bell cup 51 in rotation at high speed. As is known per se, the bell cup 51 atomizes the paint into fine droplets that thus form a spray 50. The spray 50 substantially follows the spraying direction Y50 so as to reach the article to be coated. The bell cup 51 is arranged to spray the paint substantially in the spraying direction Y50. Since the bell cup 51 is circularly symmetrical, the spray 50 is in the shape of a paraboloid or of a bullet that is circularly symmetrical about the spraying direction Y50. The spraying direction Y50 substantially coincides with the axis of rotation Y51 of the bell cup 51.
The spraying means 5 are disposed in a distal portion 11.2 of the body 11. The distal portion 11.2 forms a casing that contains the atomizer means 5. The distal portion 11.2 projects relative to the proximal portion 11.1 at the location of the reservoir 10.
The main axis X10 of the reservoir 10 is perpendicular to the spraying direction Y50, i.e. it forms an angle A10 of 90° with the spraying direction Y50. In practice, the angle A10 lies in the range 50° to 100°. The main axis X10 and the spraying direction Y50 are thus convergent.
In the present patent application, the adjective “convergent” designates two directions that are not co-linear, that do not coincide, and that are not parallel. In other words, when the main axis X10 and the spraying direction Y50 are co-planar, the adjective “convergent” indicates that they are also secant. When the main axis X10 and the spraying direction Y50 are not co-planar, the adjective “convergent” indicates that the orthogonal projection of the main axis X10 in a plane parallel to the main axis X10 and containing the spraying direction Y50 is secant to the spraying direction Y50.
In addition, the distal portion 11.2 extends substantially in the spraying direction Y50. In projection in the plane of FIG. 1, the terminal axis Y19 forms an angle A19 of about 120° with the spraying direction Y50. In practice, the angle A19 lies in the range 110° to 130°. Such an angle A19 imparts high compactness to the atomizer 1, and thus good agility to the robot 2.
As shown in FIG. 2, the atomizer 1 has an orifice 104.1 for connection to a paint circuit (not shown) that is part of a re-supply station. The orifice 104.1 is situated on the docking surface 15 of the distal portion 11.1. The paint and the solvent penetrate into the atomizer 1 via the orifice 104.1 respectively during the stage of filling the reservoir 10 and during the stage of cleaning the atomizer 1.
The atomizer 1 also includes a connection duct 13 connecting the orifice 104.1 to the reservoir 10 and, more precisely, to its base 10.2. The connection duct 13 extends in the distal portion 11.1 in a manner such as to be rectilinear and perpendicular to the base 10.2 and to the docking surface 15. The connection duct 13 has a length L13, measured parallel to the main axis X10. The length L13 is about 50 mm. In practice, the length L13 is less than or equal to 100 mm.
The connection duct 13 is formed in part of a valve 100 that controls the flow of paint and of solvent in the atomizer 1. More precisely, the second duct 112 defines the upstream portion of the connection duct 13.
The valve 100 has a body 101, a first duct 111, and a distinct second duct 112, in which body and in which ducts fluids can flow that are used during the stages of filling the reservoir 10, of spraying, and of cleaning, i.e. that are constituted by paint, solvent, and compressed air. The valve 100 also has a first needle 130 and a second needle 160, which needles serve to allow the fluids to flow or to prevent them from flowing. The body 101 houses the first needle 130 and the second needle 160. In addition, the first needle 130 defines a recess adapted to receive a substantial portion of the second needle 160.
In addition, in this example, the feed duct 4, made up of an upstream portion 14 and of a downstream portion 54, and extending from the base 10.2 of the reservoir 10 to the bell cup 51, has a length of about 260 mm, that needs to be minimized, and a maximum diameter of about 4 mm. In practice, the length of the feed duct 4 is less than or equal to 300 mm and its maximum diameter is less than or equal to 5 mm. The injector 53 has a diameter that can be as large as 3 mm. The injector 53 has a length that is relatively short, so that it generates limited head losses.
The atomizer 1 also has a cleaning duct 16.1 that extends between the valve 100 and the atomizer means 5. The cleaning duct 16.1 is shown diagrammatically in dashed lines in FIGS. 1 and 2. The cleaning duct is connected to a first downstream segment 16.2 and to a second downstream segment 16.3. The first downstream segment 16.2 opens out towards the bell cup 51. The second downstream segment 16.3 opens out into the injector 53.
The cleaning duct 16.1 and then the downstream segments 16.2 and 16.3 channel the solvent towards and into the atomizer means 5, so as to clean or rinse the injector 53, and the surfaces of the bell cup 51. More precisely, the cleaning stage uses streams of compressed air and of solvent to remove paint deposited on the soiled surfaces.
The valve 100 is particularly compact. The length L13 of the duct 13 is relatively short, thereby making it possible to minimize wastage of paint and consumption of solvent during the stages of cleaning and of re-supplying the reservoir 10.
A method of re-supplying the atomizer 1 with coating material, e.g. with paint, consists firstly in a step in which all of any paint remaining in the reservoir 10 is dumped. Any such residual paint is dumped through the second feed duct 4 and through the bell cup 51.
Then, the valve 100 is opened in order to cause all of the solvent to flow into the reservoir 10, into the cleaning duct 16.1, and into the downstream segments 16.2 and 16.3, and, downstream from the reservoir 10, through the bell cup 51, where it can be collected. Then, the valve 100 is opened in order to cause paint to flow into the connection duct 13, so as to fill the reservoir 10 with paint of a new shade of color. In other words, the atomizer 1 can be free of any circuit for collecting waste paint and waste solvent.
In addition, the height H1 of the atomizer 1, as measured in the spraying direction Y50, is about 390 mm. In practice, the height H1 of the atomizer 1 is selected to be less than 450 mm, and preferably to be less than 400 mm.
Such a height H1 makes it easier for the atomizer 1 and for the robot 2 to access and to be removed from regions that are difficult to access, which is important because the minimum distance between the bell cup 51 and the article to be coated is about 200 mm during electrostatic spraying. Thus, the arrangement of the reservoir 10, with its main axis X10 not parallel to the spraying direction Y50 imparts good compactness to the atomizer 1, and thus excellent agility to the robot 2. The term “agility” is used to mean the aptitude of the atomizer 1 or of the robot 2 to reach regions that are difficult to access, in particular on the inside of a vehicle body.
For equivalent weight, the center of gravity G1 of the atomizer 1 is positioned closer to the terminal axis Y19 than the center of gravity of a prior art atomizer. The center of gravity G1 shown in FIG. 1 is the center of gravity of the atomizer 1 when the reservoir 10 is full, as it is during the spraying stage. The center of gravity as empty is relatively close to the center of gravity G1 because the weight of paint contained in the reservoir 10 is negligible compared with the weight of the atomizer 1.
The distance H19 between the center of gravity G1 and the terminal axis Y19 is about 10 mm. The distance H19 is measured “by the shortest route”, i.e. perpendicular to the terminal axis Y19. In practice, said distance H19 is selected to be less than 80 mm, and preferably less than 20 mm. The center of gravity of a prior art atomizer is generally situated more than 100 mm away from the terminal axis.
Such a position for the center of gravity G1, with such a distance H19 makes it possible to minimize the moments of inertia of the atomizer 1 about the terminal axis Y19.
It is thus possible to limit the forces that the robot 2 is required to generate, thereby allowing it to move with higher acceleration than a robot equipped with a prior art atomizer.

## Claims

1. An atomizer for spraying a coating material towards articles to be coated, the atomizer comprises:
a body equipped with a flange for fastening the atomizer to a robot, the robot and/or the flange defining a terminal axis about which the atomizer is designed to move relative to the articles to be coated;
a coating material reservoir housed in a proximal portion of the body and extending along a main axis; and
atomizer means for spraying the coating material, the atomizer means are disposed in a distal portion of the body, the atomizer means having a bell cup atomizer member that rotates about an axis Y51 superimposed with a spraying direction Y50; wherein
the spraying direction Y50 is oriented from the bell cup toward the article to be coated;
the spraying direction Y50 and the main axis X10 of the reservoir are convergent on the body of the atomizer;
the angle between the main axis of the reservoir and the spraying direction lies in the range 50° to 100°, and
the terminal axis Y19 forms an angle with the spraying direction that lies in the range 110° to 130°; on a side of the spraying direction Y50 oriented towards the flange and on a side of the terminal axis oriented toward the bell cup atomizer member.

2. An atomizer according to claim 1, wherein the distance between the center of gravity of the atomizer and the terminal axis is selected to be less than 80 mm.

3. An atomizer according to claim 2, wherein the atomizer also has a valve for controlling the flow of coating material and of a cleaning material through the atomizer, the valve forming a portion of the connection duct.

4. The atomizer of claim 2, wherein the distance between the center of gravity of the atomizer and the terminal axis is selected to be less than 20 millimeters.

5. An atomizer according to claim 1, wherein the height of the atomizer, as measured in the spraying direction is selected to be less than 450 mm.

6. A method of re-supplying an atomizer according to claim 5 with coating material, wherein said method comprises the following steps:
a) dumping all of any coating material remaining in the reservoir through the feed duct and through the atomizer member;
b) opening the valve to cause cleaning material to flow into the reservoir and into a cleaning duct, all of the cleaning material flowing, downstream from the reservoir, through the atomizer member; and
c) opening the valve to cause the coating material to flow into the connection duct in such a manner as to fill the reservoir with the new coating material.

7. The atomizer of claim 5, the height of the atomizer, as measured in the spraying direction is selected to be less than 400 millimeters.

8. An atomizer according to claim 1, wherein the atomizer has at least one orifice for connection to a coating material circuit, said orifice being situated on a docking surface of the atomizer, and wherein it has a connection duct connecting the orifice to the reservoir, the connection duct having a length less than or equal to 50 mm.

9. An atomizer according to claim 1, wherein the atomizer means have a feed duct for feeding the atomizer member, the feed duct extending from the reservoir to the atomizer member, the feed duct having a length less than or equal to 300 mm, and a maximum diameter less than or equal to 5 mm.

10. The atomizer of claim 9, wherein the feed duct extending from the reservoir to the atomizer member has a maximum diameter of less than or equal to 4 millimeters.

11. An atomizer according to claim 1, wherein the reservoir has a piston for pushing the coating material towards the atomizer means, and wherein the atomizer also has an actuator for moving the piston along the main axis, the actuator being housed in the body between the reservoir and the flange.

12. An atomizer according to claim 1, wherein the reservoir is in the shape of a cylinder having a circular base and of volume laying in the range 200 cm3 to 1000 cm3, and the diameter of the cylinder of the reservoir lies in the range 50 mm to 120 mm.

13. The atomizer of claim 12, wherein the diameter of the cylinder of the reservoir is 100 millimeters.

14. An atomizer according to claim 1, wherein the atomizer means have rotary drive means for driving the atomizer member in rotation about an axis of rotation that substantially coincides with the spraying direction.

15. The atomizer of claim 1, wherein the angle between the main axis of the reservoir and the spraying direction is about 90°.

16. The atomizer of claim 1, wherein the terminal axis forms an angle with the spraying direction that is about 120°.