Abstract:
The invention relates to a powder diffuser nozzle ( 2 ) for an electrostatic dusting device, which is designed to be positioned at the end of an applicator gun. The inventive nozzle ( 2 ) comprises: a lateral wall ( 49 ) which defines a passage that extends from the powder conduit ( 8 ) of the gun ( 3 ), and a base ( 56 ) which seals said conduit ( 8 ) at the end thereof. In addition, a port ( 57 ) is provided in the lateral wall ( 49 ) close to the base ( 56 ) in order to connect the powder conduit ( 8 ) with the exterior of the nozzle ( 2 ). The axis (A 1 ) of the port ( 57 ) forms a determined angle (A) with the axis (A 2 ) of the powder conduit ( 8 ). Moreover, at least one deflector ( 58 ) is provided on the base of the nozzle ( 56 ) or on the lateral wall ( 49 ) close to said base in order to divert the jet of powder from the conduit ( 8 ) along the axis (A 1 ) of the port ( 57 ).

Description:
TECHNICAL FIELD OF THE INVENTION 
   The present invention relates to a powder diffusing nozzle for an electrostatic powder-coating device. 
   BRIEF DISCUSSION OF THE RELATED ART 
   The electrostatic powder-coating of mechanical components is performed in the known way by automatic installations, comprising, for example, a spray booth through which the components pass and spray guns spraying the powder more or less at right angles to the axis of movement of the components through the booth. 
   The geometry of the components being powder-coated may entail orientating the jet of powder from the spray guns by a given angle with respect to the axis of the gun&#39;s support arm so as to reach areas that are occluded with respect to the axis of the support arm. 
   Devices are used for orientating the jet of powder and these rely on the gun or part of the gun being articulated with respect to the gun support arm. 
   However, these devices have two technical problems:
         the articulation is located some distance away from the end of the gun formed with the nozzle, the part that has to pivot is large in size, and this gives rise to a problem of bulkiness which means that the occluded regions cannot readily be attained;   the articulation requires an elbow to be formed in the powder duct of the gun. The rubbing of the powder that may be abrasive then leads to accentuated wearing of the duct at the region of the elbow. Replacing the duct in the gun, which is a complicated operation, has then to be performed more frequently.       

   Furthermore, the guns used are subject to particular safety restrictions. 
   Each gun comprises an interior duct supplying a jet of powder, a terminal nozzle to shape the jet, and a device for ionizing the powder. 
   The latter device in particular comprises a high level voltage source and a spike located near the end of the gun and intended to ionize the powder. 
   The ionization spike may commonly be at an electrical potential of 80 kV with respect to ground. An electric arc can therefore be struck if the end of the gun is brought up close to some other object that is grounded. 
   Since the striking of electric arcs may damage the installation and cause explosions in powder-saturated environments, regulations limit the capacity of the installation as a whole to 5 millijoules. 
   This limitation on the capacity has to be complied with by all the devices used. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides a solution to the aforementioned technical problems while at the same time complying with the restrictions described hereinabove. 
   To this end, the present invention relates to a powder diffusing nozzle for an electrostatic powder-coating device and which is intended to be positioned at the end of a spray gun, the nozzle comprising a side wall delimiting a passage extending the powder duct of the gun and an end wall closing the duct at its end, characterized in that at least one orifice is made in the side wall near the end wall connecting the powder duct to the outside of the nozzle, the axis of the orifice making a determined angle with the axis of the powder duct, and in that at least one deflector is formed on the end wall of the nozzle or on the side wall near the end wall of the nozzle to deflect the powder jet from the duct along the axis of the orifice. 
   This arrangement of the nozzle makes it possible to achieve the desired orientation of the jet while at the same time maintaining a minimum bulk, the entire gun remaining along the same axis. In addition, the component which sustains the most wear due to the orientation of the jet is the deflector rather than the wall of the duct. This arrangement is advantageous because the deflector is readily accessible and easy to replace. 
   According to one possibility, at least one deflector has, when viewed in section on a plane parallel to the plane containing the axis of the duct and the axis of the orifice, a profile made up of a straight segment that, with the axis of duct, makes an angle more or less equal to the angle between the axis of the orifice and the axis of the duct. 
   According to another possibility, at least one deflector has, when viewed in section on a plane parallel to the plane containing the axis of the duct and the axis of the orifice, a profile made of two straight segments, the angle of the first segment lying between a zero value and the value of the angle between the axis of the orifice and the axis of the duct, and the angle of the second segment, closest to the orifice, with respect to the axis of the duct being more or less equal to the angle between the axis of the orifice and the axis of the duct. 
   According to a third possibility, at least one deflector has, when viewed in section on a plane parallel to the plane containing the axis of the duct and the axis of the orifice, a profile forming a curve of increasing gradient, the angle of the tangent to the curve with respect to the axis of the duct near the orifice being more or less equal to the angle between the axis of the orifice and the axis of the duct. 
   The deflector may adopt various shapes, according to the type of powder used or the desired inclination. For example, the arrangement involving two segments is suited to an angle of the order of 90° between the axis of the orifice and the axis of the duct. 
   According to one embodiment, at least one deflector has, when viewed in section on a plane perpendicular to the axis of the duct, a concave profile. 
   According to another embodiment, at least one deflector has, when viewed in section on a plane perpendicular to the axis of the duct, a straight profile. 
   Altering the profile of a deflector in section on a plane perpendicular to the axis of the duct allows the spontaneous distribution of the powder to be modified. For example, a concave profile makes it possible to compensate for a spontaneous distribution that concentrates itself along the two lateral edges of the orifice. This type of profile makes it possible to keep the jet uniform as it leaves the nozzle. 
   Advantageously, at least the terminal part of the nozzle comprising the orifice, the end wall and the deflector is mounted such that it can be orientated about the axis of the duct on the end of a spray gun. 
   The terminal part, mounted such that it can pivot, allows the jet to be orientated along a second axis, still keeping to minimum bulkiness. 
   Advantageously, at least the terminal part of the nozzle comprising the orifice, the end wall and the deflector is fixed removably to the end of a spray gun. 
   Fixing the nozzle such that it can be removed makes it possible, on the one hand, to substitute one nozzle for another with a different jet orientation angle, and also allows all or part of the nozzle to be replaced if the deflector of the orifice becomes worn as a result of the rubbing of the powder. This arrangement is advantageous because the component that sustains the most wear due to the orientation of the jet is readily accessible and easy to replace. 
   According to one possibility, the nozzle comprises an ionization spike for ionizing the jet of powder, this spike being positioned along the axis of the duct and directed in the direction of the jet of powder, the free end of which is situated inside the duct upstream of the end wall in the direction of the jet. 
   According to another possibility, the nozzle comprises an ionization spike for ionizing the jet of powder, the free end of which is situated near the end wall of the nozzle on the outside thereof. 
   Advantageously, the ionization spike for ionizing the jet of powder, positioned along the axis of the duct and directed in the direction of the jet of powder, passes through the end wall of the nozzle via a passage formed in the end wall of the nozzle. 
   According to another possibility, the nozzle comprises an ionization spike for ionizing the jet of powder, the free end of which is situated near the orifice and near the side wall, on the outside of the nozzle. 
   Advantageously, the ionization spike for ionizing the jet of powder, the base of which is positioned along the axis of the duct and directed in the direction of the jet of powder, passes through the end wall of the nozzle forming an elbow to reemerge via the side wall of the nozzle near the orifice through a passage formed in the end wall and the side wall of the nozzle. 
   The various arrangements described for the spike make it possible both to guarantee an installation capacity of less than 5 millijoules and also effective ionization of the jet of powder. 
   Advantageously, the angle between the axis of the orifice and the axis of the powder duct is between 10° and 90°. 
   According to one embodiment, the angle between the axis of the orifice and the axis of the powder duct is between 45° and 90°. 
   Advantageously, the orifice is in the form of a slot directed transversely with respect to the axis of the powder duct. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood with the aid of the description which follows, with reference to the attached diagrammatic drawing which depicts some embodiments of a nozzle according to the invention. 
       FIG. 1  is a view thereof in longitudinal section in a first embodiment, the nozzle being fixed to a spray gun. 
       FIG. 2  is a view thereof in perspective in a first embodiment. 
       FIG. 3  is a view thereof in longitudinal section in a first embodiment. 
       FIG. 4  is a view thereof in longitudinal section in a second embodiment. 
       FIG. 5  is a view thereof in longitudinal section in a third embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  depicts a powder diffusing nozzle  2  according to the invention fixed on the end of a spray gun  3 . 
   The gun  3  comprises a barrel  4  at the front end of which there is formed a shoulder  5  followed by a cylindrical wall  6  comprising an external screw thread  7  over part of its length. 
   The gun  3  also comprises a straight powder duct  8  which extends into the nozzle  2 . A jet of powder is supplied to the duct in the direction of the arrow J. 
   The cylindrical wall  6  delimits a bearing wall  9  perpendicular to the axis of the duct  8 , a passage being formed for the duct  8  in this bearing wall  9 , a cut-out  10  being formed in the portion of the wall of the duct  8  closest to the bearing wall  9 . 
   Furthermore, the gun  3  comprises a device  12  known as a cascade which, via a screw  13 , provides a high-voltage source. The cascade device  12  is a voltage multiplier making it possible for example to generate a high voltage of 80 kV from a supply voltage of 300 V. 
   The screw  13  is housed in an indentation  14  formed in the bearing wall  9 . A polarizing device  15  is formed on the bearing wall  9  to position it with respect to the indentation  14  as described hereinbelow. 
   The nozzle  2  comprises a base  16  comprising a cylindrical portion  17  in which a passage is formed for the powder duct  8 . 
   The rear part  18  of the cylindrical portion  17  has an outside diameter more or less identical to the inside diameter of the cylindrical wall  6  of the barrel  4 . This rear part  18  can thus be housed on the front part of the barrel  4  in the space delimited by the cylindrical wall  6  and the bearing wall  9  of the barrel  4 . 
   As depicted in  FIG. 3 , the base  16  additionally comprises a spindle-shaped support  19  lying along the axis of the duct  8  and connected to the cylindrical portion  17  by a lug  20 . On its front part, the support  19  comprises a shoulder  22  and a tubular portion  23  of a cross section smaller than that of the shoulder  22 , for attaching a resistor tube  24 . This resistor tube  24  is intended to be affixed by one end to the tubular portion  23  and, at its other end, has an opening  25  of a diameter corresponding to the diameter of an ionization spike  26 . This tube  24  and the support  19 , which are intended to nest together, constitute a housing for a damping resistor  27  and an ionization spike  26  passing through the opening  25  of the resistor tube  24 . 
   The damping resistor  27  mounted in series with the ionization spike  26  allows the electrical current exchanged in the event of an electric arc being struck to be reduced. 
   An electrical connection is made between the damping resistor  27  and the high voltage source screw  13  via a conducting insert  28  passing through the support  19 , the lug  20  and the cylindrical portion  17  and connected to a terminal  29  situated on the rear wall  30  of the base  16 . When the rear part  18  is housed on the front part of the barrel  4  as described above, the terminal  29  lies facing the indentation  14  of the bearing wall  9  containing the screw  13 . A spring  32  housed in the indentation  17  then establishes contact between the screw  13  and the terminal  29 . A cut-out  33  is formed on the rear wall  30  of the base  16  to complement the polarizing device  15  formed on the bearing wall  9  of the barrel  4 , and intended to house the latter when the base  16  is in contact with the bearing wall  9  so as to guarantee that the terminal  30  and the indentation  14  are positioned facing each other. 
   The base  16  also comprises a short cylindrical wall  34  formed on its rear wall  30 , projecting and surrounding the passage of the powder duct  8 , this wall  34  being intended to bear against the cut-out  10  formed in the portion of the wall of the duct  8  close to the bearing wall  9  of the barrel  4 . 
   A circular end-stop  35  is formed on the exterior wall  36  of the cylindrical portion  17 . 
   The base  16  additionally comprises a tubular portion  37  comprising a passage for the powder duct  8  and formed at the front end of the cylindrical portion  17 , the thickness of this tubular portion  37  decreasing in the direction away from the cylindrical portion  17 . 
   The nozzle  2  also comprises a nozzle nut  38  intended to fix the base  16  onto the barrel  4  of the gun  3 . This nut  38  has a tubular shape of varying diameter and comprises, from the rear forwards:
         a section  39  in which the internal wall  40  of the nut has a tapping  42  intended to collaborate with the external screw thread  7  of the end of the barrel  4  of the gun  3 ,   a section  43  of constant inside diameter more or less equal to the diameter of the circular end-stop  35  of the base  16 ,   a section  44  of inside diameter smaller than the diameter of the circular end-stop  35  of the base  16 , the shoulder  45  of which is intended to bear against the circular end-stop  35  so as to hold the base  16  in position between the bearing wall  9  of the barrel  4  and the nut  38 ,   a frustoconical section  46  the diameter of which decreases from the preceding section  43 , an opening  47  being formed at the end of this frustoconical section  46  the inside diameter of which is equal to the maximum outside diameter of the tubular portion  37  of the base  16 , this tubular portion  37  being intended to pass through the opening  47  when the base  16  is fixed.       

   The nozzle  2  additionally comprises an end-piece  48  comprising a side wall  49 . 
   This side wall  49  of tubular shape comprises:
         a rear section  50  of a diameter that varies between a maximum valve at the rear edge  52  of the end piece  48  and a minimum value forward of the rear edge. The profile of the interior wall of this section  50  corresponds to the profile of the external wall of the tubular portion  37  of the base  16 . This section  50  can therefore be tightened onto the tubular portion  37  of the base. A housing  53  for a seal  54  is formed on the internal wall of this section  50 . The seal  54  located in this housing  53  enhances the mechanical grip of the end piece  48  on the base  16 , and   a front section  55  of constant diameter, the side wall  49  delimiting a passage for the powder duct  8 .       

   This method of attachment of the end piece  48  to the base  16  allows the end piece  48  to be pivoted about the axis of the duct  8  and thus makes it possible to obtain variable orientations of the jet of powder. Furthermore, this method of attachment allows the end piece  48  to be removed manually and easily in order to replace it when part of it becomes worn. 
   The end piece  48  also comprises an end wall  56  closing the duct  8  at its front end. 
   An orifice  57  is formed in the side wall  49  of the end piece  48  near the end wall  56 , the orifice  57  connecting the powder duct  8  to the outside of the nozzle  2 , the axis A 1  of the orifice  57  forming an angle A with the axis A 2  of the powder duct  8 . In this embodiment, the angle A is equal to 60° and the orifice  57  has the shape of an elongate slot subtending an angle of 90° in the plane of the slot. The plane of the slot intersects the axis A 2  of the duct, forming the angle A, the slot therefore being orientated transversely with respect to the axis A 2  of the duct. 
   A deflector  58  is formed on the end wall  56  of the nozzle  2  to deflect the jet of powder from the duct  8  along the axis A 1  of the orifice  57 . In the embodiment depicted in  FIG. 1 , the deflector  58  has, in section on a plane parallel to the plane containing the axis A 2  of the duct and the axis A 1  of the orifice, a straight profile inclined at 60°, corresponding to the angle A of the axis A of the orifice  57  with respect to the axis A 2  of the duct  8 . The deflector  58  and the orifice  57  are situated close to one another, the front edge  59  of the orifice  57  lying in the extension of the deflector  58 . 
   This end piece  48  comprising an orifice  57  and a deflector  58  both orientated, allows the jet of powder to be orientated without causing problems of bulkiness. Furthermore, the end piece, by virtue of the way in which it is attached, can be replaced and positioned with ease. The duct  8  does not experience excessive wear on its walls because it is straight. 
   In order to comply with the regulations restricting the capacity of the installation, it is preferable for the spike  26  to be emergent and to constitute a point close to an object brought up nearer to the end of the gun. Indeed, the shape of the spike allows a leakage current to form before an arc is struck, thus making it possible either to avoid the striking of an arc or to significantly reduce the electrical current exchanged as the arc is struck. 
   The embodiments presented meet the regulations. 
   In the first embodiment depicted in  FIGS. 1 ,  2  and  3 , the free end  60  of the ionization spike  26  is positioned along the axis of the duct  8  and its end lies upstream of the end wall  56  in the direction of the jet through the duct  8 . 
   According to a second embodiment depicted in  FIG. 4 , the resistor tube  24  and the ionization spike  26  for ionizing the jet of powder pass through the end wall  56  of the nozzle  2 . The ionization spike then forms an elbow to reemerge via the side wall  49  of the end piece  48  of the nozzle  2  near the orifice  57 . 
   A passage  62  is formed in the end wall  56  and the side wall  49  in contact with the end wall  56  of the nozzle  2 , to allow the spike to pass. The free end  60  of the spike  26  is located near the front edge  59  of the orifice  57  on the outside of the nozzle  2 . A seal  64  is contained in a housing  63  formed in the wall of the passage  62 . 
   To form an elbow, the ionization spike is made up of two straight portions  65  and  66 , one of them,  65 , lying along the axis of the duct and the other,  66 , lying in the direction of the free end, and a rubbing electrical contact  67  housed in the elbow of the duct and maintaining an electrical connection between the two straight portions. This contact  67  makes it easier to mount the nozzle  2  and to orientate the latter, the straight portion  65  of the spike  26  remaining in position, while the straight portion  66  pivots with the end piece  48 . 
   According to a third embodiment depicted in  FIG. 5 , the resistor tube  24  and the ionization spike  26  for ionizing the jet of powder pass through the end wall  56  of the nozzle  2  via a passage  62  formed axially in the end wall  56  of the nozzle  2 , the free end  60  of the spike  26  being situated near the end wall  56  of the nozzle  2  on the outside thereof. A seal  64  is contained in a housing  63  formed in the wall of the passage  62 . 
   The profile of the deflector  58  in section on a plane perpendicular to the axis A 2  of the duct  8  may exhibit various shapes, according to the desired effect. By way of example, in the case of an orifice  57  in the form of an elongate slot, the deflector  58  may exhibit a concave profile, so as to compensate for a spontaneous distribution of powder concentrated at the two side edges of the orifice  57 . This type of profile makes it possible to keep the jet leaving the nozzle  2  uniform. 
   The orifice  57  in this case has a slightly curved shape suited to the concave shape of the deflector  58 . 
   In one embodiment that has not been depicted, a deflector has, in section on a plane parallel to the plane containing the axis of the duct and the axis of the orifice, a profile made up of two straight segments, the angle of the second segment with respect to the axis of the duct  8  being equal to the angle between the axis of the orifice and the axis of the duct, the angle of the first segment being equal for example to half the value of the angle between the axis of the orifice and the axis of the duct. 
   This arrangement involving two segments is particularly advantageous when the angle of the axis of the orifice with respect to the axis of the duct is of the order of 90°. 
   In another embodiment that has not been depicted, a deflector has, in section on a plane parallel to the plane containing the axis of the duct and the axis of the orifice, a profile constituting a curve with increasing gradient, the angle of the tangent to the curve near the orifice being equal to the angle between the axis of the orifice and the axis of the duct. 
   According to the various variants, the deflector has a shape and surface area allowing the jet of powder to be deflected in its entirety or allowing at least a substantial proportion, greater than 50%, of the jet to be deflected. 
   In another embodiment that has not been depicted, the end piece of the nozzle and the base are formed as a single orientable component. This component has no polarizing feature and can therefore be orientated in terms of rotation about the axis of the duct when the nut is slackened off. The electrical connection between the ionization spike and the high-voltage source may be achieved by a contact provided axially or by a contact of annular shape centered on the axis of the duct. When the nut is tightened, the nozzle is held in position, maintaining the given orientation. 
   The angle A between the axis A 1  of the orifice  57  and the axis A 2  of the duct  8  may adopt varying values, ranging in particular between 10 and 90°. 
   The invention is not restricted to the embodiments described but, on the contrary, encompasses all variants thereof. Thus, in particular, the deflectors  58  may have different profiles.