fig1 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 fig1 . 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 fig1 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 fig1 . 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 fig1 , 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 fig2 , 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 fig1 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 fig1 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 .