Abstract:
This invention relates to a device for spraying coating material, which comprises a barrel inside which is defined a conduit for circulation of coating material, and a nozzle for shaping the jet of material intended to be mounted on this barrel. Magnetic coupling means are provided between the nozzle and the barrel. These means which are insulated from the conduit, may be formed by one or more magnets associated with a metallic ring. This allows easy and rapid assembly and dismantling of the nozzle on the end of the barrel.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a device for spraying coating material, equipped with a nozzle.  
         BACKGROUND OF THE INVENTION  
         [0002]    In an installation for spraying liquid or particulate coating material, it is known to spray the material by discharging it from the downstream end of a conduit provided in the barrel of a manual or automatic spray gun. A nozzle is generally used to shape the jet of sprayed coating material as a function of the type of application.  
           [0003]    It is known to screw a nozzle on the downstream end of a barrel. Such a screwing operation is relatively long and requires particular care for a thread and a tapping provided respectively on the barrel and the nozzle to cooperate correctly. Such thread and tapping are most often made of the plastic material constituting the barrel and the nozzle, particularly for electrostatic spray guns. Consequently, they may be distorted in the case of poor manipulation. In addition, it may be that coating material accumulates on the thread and tapping, whether it be question of droplets of liquid coating material or of particles of powder. Now, it is often necessary to dismantle and clean a shaping nozzle after several hours of use in order to evacuate agglomerates which may be formed inside and/or outside the nozzle. This involves repeated manipulations of unscrewing and screwing of a nozzle on the barrel, with the drawbacks set forth hereinabove.  
           [0004]    It is a more particular object of the present invention to overcome these drawbacks by proposing an improved solution for a rapid assembly and dismantling of a shaping nozzle at the end of the barrel of a spray gun.  
         SUMMARY OF THE INVENTION  
         [0005]    To that end, the invention relates to a device for spraying coating material, comprising a barrel, inside which is defined a conduit for circulation of coating material, and a nozzle for shaping the jet of material, said nozzle being intended to be mounted on said barrel, characterized in that it comprises means for magnetic coupling between said nozzle and said barrel, such means being insulated from the afore-mentioned conduit.  
           [0006]    Thanks to the use of magnetic coupling means, the assembly and dismantling of the nozzle on and from the barrel are particularly rapid operations, since it suffices to bring the nozzle sufficiently close to the barrel for the magnetic coupling to produce an effective connection. Inversely, dismantling takes place simply by moving the magnetic coupling means apart from one another. These magnetic coupling means also allow a magnetic self-centering of the nozzle with respect to the barrel. In addition, as the coupling means are insulated from the conduit for circulation of material when the nozzle is in configuration mounted on the barrel, they do not risk being soiled or clogged by a deposit of material. This contributes to the durability of the coupling obtained.  
           [0007]    According to an advantageous aspect of the invention, the nozzle is provided with a ring forming a peripheral partition of a terminal part of the conduit, this ring being disposed between this conduit and the magnetic coupling means. This ring efficiently insulates the coupling means from the flow of coating material.  
           [0008]    According to a first embodiment of the invention, the barrel is equipped with at least one magnet adapted to cooperate with a magnetic looping element borne by the nozzle.  
           [0009]    According to another advantageous embodiment of the invention, the nozzle is equipped with at least one magnet adapted to cooperate with a magnetic looping element borne by the barrel.  
           [0010]    Whatever the embodiment in question, the coupling means may be provided to be located around the barrel. In that case, these means are disposed at a distance from the head of the spray gun in which an electrostatic charge, in the case of an electrostatic spray gun, might be likely to accumulate. In other words, the fact of disposing the magnetic coupling elements at a distance from the zones likely to be at a high voltage potential, limits the risks due to the electrical capacitance of the metallic masses constituting these coupling means and, in particular, the magnets and/or metallic rings used.  
           [0011]    According to another advantageous aspect of the invention, the looping means is formed by a metallic ring centred on a longitudinal axis of the conduit and of the nozzle.  
           [0012]    According to another advantageous aspect of the invention, the device comprises means for mechanically centering the nozzle on the barrel, these centering means being adapted to allow a relative pre-positioning of the magnetic looping means when mounting the nozzle on the barrel.  
           [0013]    According to another advantageous aspect of the invention, the magnetic looping means, provided in the nozzle, form contacts of a circuit supplying voltage to means for electrostatically charging the material. In that case, these contacts are advantageously formed by an end of a magnet and by a magnetic looping element in the form of a metallic ring.  
           [0014]    In addition, the device may be provided to comprise controlled means for injection of a separation fluid between the barrel and the nozzle, with a sufficient pressure to overcome the effort of coupling of the coupling means. This makes it possible to create a system for pneumatic dismantling of the nozzle. In that case, the afore-mentioned control means may be mounted in or on the device, preferably in or on the barrel. These means may be controlled manually or automatically.  
           [0015]    According to another advantageous aspect of the invention, the coupling means used, and in particular the magnets and rings, are dismountably installed on the barrel and/or on the nozzle. This facilitates maintenance of the device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention will be more readily understood on reading the following description of three embodiments of a coating material spray device in accordance with its principle, given solely by way of example with reference to the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 is an exploded axial section of the downstream end of a spray device in accordance with a first embodiment of the invention.  
         [0018]    [0018]FIG. 2 is a section along line II-II in FIG. 1.  
         [0019]    [0019]FIG. 3 is an axial section on a larger scale of the device of FIG. 1 in mounted configuration.  
         [0020]    [0020]FIG. 4 is a view similar to FIG. 3 for a device in accordance with a second embodiment of the invention, and  
         [0021]    [0021]FIG. 5 is a side view, with partial longitudinal section, of a device in accordance with a third embodiment of the invention. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    Referring now to the drawings, the device shown partially in FIGS.  1  to  3  comprises a barrel  1  of which only the downstream end has been shown. This barrel is centered on an axis X-X′ which also constitutes the axis of symmetry of a conduit  2  through which the coating material flows. In the example shown, the spray gun is used with a pulverulent coating material, with the result that a mixture of air and powder transits through the conduit.  
         [0023]    The barrel  1  terminates in a sleeve  11  which extends the barrel  1  beyond the opening  21  of the conduit  2 . The sleeve  11  is defined by a cylindrical internal surface  12  with straight generatrix, and by a likewise cylindrical external surface  13  forming an outer shoulder  14 .  
         [0024]    A web  15  extending along a plane substantially perpendicular to axis X-X′ connects the sleeve  11  and the outer surface of the barrel  1  to a sleeve  16  forming housing for receiving the downstream end  22  of the conduit  2 . In the example shown, the conduit  2  is formed by two concentric tubes in its downstream part  22 , but this is not compulsory.  
         [0025]    A nozzle  3  is provided to be mounted on the barrel  1  and comprises a principal body  31  defining a central conduit  32  for circulation of the mixture of air and powder. A rod  33  is disposed in the channel  32  and contains electronic components  34  for supplying high voltage to an electrode  35  provided in the downstream end  33   a  of the rod  33  which forms a deflector for the jet of air/powder mixture. The rod  33  is fast with a ring  36  by means of tabs  37 , the ring  36  being immobilized in the body  31  for example by screwing.  
         [0026]    The body  31  forms an annular housing  38  intended to cover the sleeve  11 , this housing comprising a first section  38   a  of width greater than a second section  38   b  forming the bottom of the housing  38 . The geometry of the housing  38  makes it possible to accommodate the sleeve  11 , the width of the sections  38   a  and  38   b  being adapted to the two successive widths of the sleeve  11  on either side of the shoulder  14 .  
         [0027]    The nozzle  3  is equipped with a steel ring  4  dismountably installed in a housing  39  provided around the ring  36 . The ring  4  may be clipped in the housing  39  or fixed by any other means. However, a dismountable mode of fixation is preferred in order to facilitate maintenance of the nozzle  3 .  
         [0028]    A conductor  41  is provided in the ring  36  and on one of the tabs  37  in order to connect the ring  4  to one of the components  34  when the ring  4  is in position in the housing  39 .  
         [0029]    A contactor  5  is mounted in the barrel  1 , through the web  15 , and comprises a rod  51  projecting beyond the web  15  towards the front of the barrel  1 .  
         [0030]    When the device is in mounted configuration, the axis X-X′ is a longitudinal axis of the conduit  2  and of the nozzle  3 .  
         [0031]    When the device is in mounted configuration, the rod  51  is in electrical contact with the ring  4 , which makes it possible to apply to the components  34  a voltage supplied by the contactor  5  itself supplied via an electric cable  52  from a high voltage generating unit (not shown). In the event of a high-voltage cascade being integrated in the barrel  1 , the contactor  5  is supplied directly therefrom. In any case, it is possible to supply the electrode  35  with high voltage, through the components  34 , in order to create an electrostatic charge at the level of the deflector  33   a.    
         [0032]    Three magnets  6  are removably mounted in the web  15  and extend from the latter over a length  1   6  substantially equal to the length  1   5  of the contactor beyond the web  15 .  
         [0033]    When the device is in mounted configuration shown in FIG. 3, the magnets  6  are therefore in contact with the ring  4  on which they exert an effort of traction F 1  which applies the nozzle  3  firmly on the body  1 .  
         [0034]    In this way, elements  4  and  6  constitute means for magnetic coupling between the barrel  1  and the nozzle  3 .  
         [0035]    It will be noted that, in the configuration of FIG. 3, the ring  36 , which extends the conduit  2 , insulates the volume of circulation of the coating material in the conduit  2  and the conduit  32  with respect to the ring  4  and to the magnets  6 , with the result that the risks of deposit of material on the elements  4  and  6  are minimized. In particular, the front end surface  36   a  of the ring  36  is in firm abutment, under the effect of the effort F 1 , against the downstream end of the conduit  2 . The risks of leakage towards the outside of the ring  36  are thus reduced.  
         [0036]    As is more particularly visible in FIG. 2, the device comprises three magnets  6  regularly distributed around axis X-X′. The number of magnets and their distribution depend on the intensity of the desired effort F 1 .  
         [0037]    It may be envisaged to use an annular magnet centred on axis X-X′. However, this solution presents the drawback of creating a relatively high metallic capacitance near the discharge orifice of the spray gun, which proves detrimental in terms of electrical energy stored in this part of the device.  
         [0038]    The sleeve  11  and the housing  38  allow a relative pre-positioning of the nozzle  3  and of the barrel  1 , and in particular, of the magnetic coupling elements  4  and  6  with respect to one another, during the movement of approach of the nozzle  3  with respect to the barrel  1 , this movement being represented by arrow F 2  in FIG. 1.  
         [0039]    In the second embodiment of the invention, shown in FIG. 4, elements similar to those of the first embodiment bear identical references increased by 100. In this embodiment, the barrel  101  of a spray is equipped with a nozzle  103  and comprises a conduit  102  opening out opposite a central conduit  132  formed by the nozzle  103  around a rod  133  terminating in a deflector  133   a  equipped with a charging electrode  135  supplied by electronic components  134  arranged in the rod  133 .  
         [0040]    A ring  136  belonging to the nozzle  103  abuts, by its end surface  136   a , against the downstream end of the conduit  102  and surrounds conduit  132 , thus guaranteeing that the material remains in the conduits  2  and  102  that it insulates from the outside.  
         [0041]    As hereinbefore, the nozzle  103  is provided with a metallic ring  104  electrically connected to the components  134  by a cable  141 . The ring  104  is supplied with current via a contactor  105  made in the form of a magnet and itself supplied by conducting cables  152 . In this way, the contactor  105  of this embodiment simultaneously performs the role of the elements  5  and  6  of the first embodiment.  
         [0042]    One sole magnet-contactor  105  may be used, as long as the effort of attraction F 1  exerted is sufficient.  
         [0043]    A pneumatic dismantling system  160  is provided, which comprises a pipe  161  traversing the end web  115  of the barrel  101  and connected to a source  162  of pressurized air through an electro-valve  163  controlled by a logic unit  164 . When the nozzle  103  is to be disconnected from the barrel  101 , the electro-valve  163  is opened, so that a flow of air, represented by arrow F 3 , is injected in the volume V defined between the barrel  101  and the nozzle  103 , which has the effect of exerting on the nozzle  103  an effort F 4  which is sufficient to overcome the effort F 1  of magnetic coupling.  
         [0044]    An optional pneumatic dismantling system may, of course, also be used with the device of the first embodiment.  
         [0045]    In the third embodiment of the invention shown in FIG. 5, elements similar to those of the first embodiment bear identical references increased by 200. In this embodiment, the barrel  201  of an automatic liquid paint spray gun is covered by a nozzle  203  which comprises a skirt  203   a  surrounding the barrel  201  over the major part of its length, this skirt being in one piece with the head  203   b  of the nozzle  203 . However, the nozzle  203  might be constituted by two assembled elements.  
         [0046]    The skirt  203  bears, at the level of its edge opposite the head  203   b , a magnet  206  of annular shape and centred on the longitudinal axis X-X′ of the nozzle  203  and of the barrel  201  when the spray gun is in mounted configuration. A metallic ring  204  is permanently mounted around the barrel  201  in a position such that the magnet  206  comes into abutment against the ring  204  when the nozzle  203  is in place on the barrel  201 . An intense magnetic effort F 1  is thus created between the magnet  206  and the ring  204 , this effort guaranteeing an adequate and long-lasting positioning of the nozzle  203  with respect to the barrel  201 .  
         [0047]    The distance d between the magnet  206  and the front face  201   a  of the barrel  201 , taken when the device is in mounted configuration, is such that an electrical insulation is made and that the metallic pieces  204  and  206  do not risk being charged with high voltage, including when the sprayed liquid coating material is charged with high voltage due to an inner charging system or when the head  203   b  is equipped with electrodes for external charging of the liquid material.  
         [0048]    The inner radial surface  203   i  of the skirt  203   a  and the outer radial surface  201   e  of the barrel  201  present corresponding geometries making it possible to guide and to centre the nozzle  203  when it is mounted on the barrel and, consequently, to position the magnet  206  correctly with respect to the ring  204 .  
         [0049]    A pneumatic dismantling system  260  is provided, which comprises a self-closing push button  261  installed in the barrel  201  and connected by a pipe  262  to a source of pressurized air (not shown). The downstream part of the push button  261  is connected by a pipe  263  to the volume V defined between the barrel  201  and the head  203   b . As before, this system makes it possible to inject into the volume V a flow of air, represented by arrow F 3 , to exert an effort F 4  sufficient to overcome the effort F 1  of magnetic coupling. The push button  261  is actuated thanks to a head  261  a easily accessible through an opening  203   c  provided in the skirt  203   a.    
         [0050]    Other variants may, of course, be envisaged and an automatic control system may be used in place of the manual push button  261 .  
         [0051]    The skirt  203   a  may also be shorter than in the example shown in FIG. 5, in which case the distance d is shorter. Nonetheless, this makes it possible to obtain a good insulation of the metallic elements with respect to the high voltage essentially present in or in the immediate proximity of the volume V. In that case, the push button  261  may be located towards the rear of the spray gun with respect to the magnetic coupling elements. It is thus accessible without the need to create an opening in the skirt.  
         [0052]    The skirt  203   d  of the terminal part of the nozzle  203  which bears the magnet  206  abuts against the barrel  201  and the ring  204 , with the result that it insulates the elements  204  and  206  from the volume V which is itself advantageously insulated from the conduit for circulation of the coating material.  
         [0053]    The invention may be used with a spray of manual or automatic type and may be employed for spraying liquid or pulverulent coating material. In particular, the technical characteristics of the different embodiments shown may be combined together.  
         [0054]    According to a variant of the invention (not shown), the rings  4 ,  104  and  204  may be replaced by one or more metal studs capable of cooperating with magnets in order to create a magnetic looping by reducing the electrical capacitance of the nozzle.  
         [0055]    A mixed variant, with magnets and coupling studs provided both on the barrel and the nozzle, may likewise be envisaged.