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 (X 10 ). 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 (Y 50 ). The atomizing direction (Y 50 ) and the main axis (X 10 ) of the tank are convergent.

Description:
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 (cm 3 ). 
     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 cm 3  to 1000 cm 3 , 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 Y 19  about which the atomizer  1  moves relative to the articles to be coated. The terminal axis Y 19  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 Y 19 . In the embodiment shown in  FIGS. 1 and 2 , the terminal axis Y 19  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 X 10  that is horizontal in  FIG. 1 . The volume V 10  indicated herein corresponds to the maximum volume of the reservoir  10 . The reservoir  10  has a diameter D 10  of 100 mm and a length L 10  lying in the range 50 mm to 100 mm. The volume V 10  of the reservoir  10  is about 0.8 liters (l), i.e. about 800 cm 3 . In practice, the diameter D 10  lies in the range 50 mm to 120 mm, and the volume V 10  lies in the range 200 cm 3  to 1000 cm 3 . 
     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 X 10 . The atomizer  1  further includes an actuator  18  for moving the piston  18 . 1  in translation along the main axis X 10 . 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 X 10 . 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 Y 51 . 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 Y 50  so as to reach the article to be coated. The bell cup  51  is arranged to spray the paint substantially in the spraying direction Y 50 . 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 Y 50 . The spraying direction Y 50  substantially coincides with the axis of rotation Y 51  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 X 10  of the reservoir  10  is perpendicular to the spraying direction Y 50 , i.e. it forms an angle A 10  of 90° with the spraying direction Y 50 . In practice, the angle A 10  lies in the range 50° to 100°. The main axis X 10  and the spraying direction Y 50  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 X 10  and the spraying direction Y 50  are co-planar, the adjective “convergent” indicates that they are also secant. When the main axis X 10  and the spraying direction Y 50  are not co-planar, the adjective “convergent” indicates that the orthogonal projection of the main axis X 10  in a plane parallel to the main axis X 10  and containing the spraying direction Y 50  is secant to the spraying direction Y 50 . 
     In addition, the distal portion  11 . 2  extends substantially in the spraying direction Y 50 . In projection in the plane of  FIG. 1 , the terminal axis Y 19  forms an angle A 19  of about 120° with the spraying direction Y 50 . In practice, the angle A 19  lies in the range 110° to 130°. Such an angle A 19  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 L 13 , measured parallel to the main axis X 10 . The length L 13  is about 50 mm. In practice, the length L 13  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 L 13  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 H 1  of the atomizer  1 , as measured in the spraying direction Y 50 , is about 390 mm. In practice, the height H 1  of the atomizer  1  is selected to be less than 450 mm, and preferably to be less than 400 mm. 
     Such a height H 1  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 X 10  not parallel to the spraying direction Y 50  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 G 1  of the atomizer  1  is positioned closer to the terminal axis Y 19  than the center of gravity of a prior art atomizer. The center of gravity G 1  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 G 1  because the weight of paint contained in the reservoir  10  is negligible compared with the weight of the atomizer  1 . 
     The distance H 19  between the center of gravity G 1  and the terminal axis Y 19  is about 10 mm. The distance H 19  is measured “by the shortest route”, i.e. perpendicular to the terminal axis Y 19 . In practice, said distance H 19  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 G 1 , with such a distance H 19  makes it possible to minimize the moments of inertia of the atomizer  1  about the terminal axis Y 19 . 
     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.