Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
  • B24C5/00—Devices or accessories for generating abrasive blasts
  • B24C5/02—Blast guns, e.g. for generating high velocity abrasive fluid jets for cutting materials
  • B24C5/04—Nozzles therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
  • B05B1/02—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to produce a jet, spray, or other discharge of particular shape or nature, e.g. in single drops, or having an outlet of particular shape
  • B05B1/04—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to produce a jet, spray, or other discharge of particular shape or nature, e.g. in single drops, or having an outlet of particular shape in flat form, e.g. fan-like, sheet-like
  • B05B1/042—Outlets having two planes of symmetry perpendicular to each other, one of them defining the plane of the jet
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
  • B05B7/1481—Spray pistols or apparatus for discharging particulate material
  • B05B7/1486—Spray pistols or apparatus for discharging particulate material for spraying particulate material in dry state

Definitions

• the present invention relates to a surface treatment nozzle, as well as a method and a device for surface treatment using such a nozzle, for example to strip one or more layers of paint or other coating arranged on a surface. , including an exterior surface of an aircraft.
• the present invention relates to a surface treatment nozzle intended to project solid particles entrained in a flow of gas under pressure, this nozzle being provided with a single inlet for receiving the solid particles mixed with the flow of gas under pressure and a single outlet for projecting the solid particles, the outlet having an elongated slot shape which has a longitudinal axis and extends along this longitudinal axis between two ends, the nozzle comprising a channel having, in the direction of the flow of solid particles, first a convergent section which communicates with the inlet of the nozzle, then a divergent section which opens to the outside of the nozzle through the outlet slot and which has over its entire length a flattened section parallel to said outlet slot, the diverging section further having two lateral edges which extend along said diver
• a nozzle of this type is disclosed in document GB-A-2,191,127.
• This known nozzle has the drawback, however, that the effectiveness of the surface treatment is not evenly distributed over the entire width of the nozzle, this efficiency being very high in the center of the nozzle and low on the sides of the jet of the nozzle.
• the nozzle disclosed in the above-mentioned document has a discontinuity in section which can induce rapid wear of the nozzle and which generates turbulence further disturbing the blasting efficiency, in particular when the nozzle is used with gas speeds. important, and in particular supersonic speeds in the divergent section.
• the object of the present invention is in particular to avoid these drawbacks.
• a surface treatment nozzle of the type mentioned above is essentially characterized in that the channel has progressive section variations over its entire length, in that the converging section has a downstream end which has a flattened section parallel to the outlet slot, and in that the divergent section has, at least towards the outlet slot, two lateral parts of widened section respectively in the vicinity of the two lateral edges, these two lateral parts of widened section separated by at least a narrower section.
• the surface treatment nozzle according to the invention when the surface treatment nozzle according to the invention is moved above a surface, for example perpendicular to its outlet slot, by projecting onto this surface solid particles, this nozzle leaves behind a treated trace of which all the points have received particles which have substantially the same kinetic energy and have been exposed for a time substantially identical to said particles. Consequently, the surface treatment is of the same quality over the entire width of the treated trace.
• the surface treatment nozzle it is in particular possible to strip a layer of paint which covers an underlying surface consisting of a base layer, a composite material or another material without in any way damaging said surface under -ja ⁇ cent.
• the converging section has an upstream end which has a circular section;
• the divergent section comprises, over substantially its entire length, said two lateral parts of enlarged section;
• the divergent section has, at least in the vicinity of its outlet slot, a central part of enlarged section separated from each lateral part of enlarged section by a part of narrower section, so as to further optimize the equalization of the energy kinetics of the particles projected by the nozzle over the entire width of the exit slot.
• the present invention also relates to a surface treatment device comprising a nozzle as defined above and supply means for sending to the inlet of the nozzle the solid particles mixed with the flow of gas under pressure, with a sufficient flow rate. so that the gas flow is supersonic in the divergent section.
• the present invention also relates to a surface treatment device comprising a nozzle as defined above and positioning means for moving the nozzle essentially in translation along a surface to be treated.
• the present invention also relates to a method of treating a surface by spraying solid particles entrained in a flow of gas under pressure, in which:
• the particles are sprayed by means of a nozzle as defined above,.
• the nozzle is supplied with the mixture of solid particles in the pressurized gas flow at a rate sufficient for the gas flow to be supersonic in the divergent section, the longitudinal axis of the outlet slot is disposed substantially parallel to the surface to be treated, and the nozzle is displaced essentially in translation in a direction which is parallel to the surface to be treated, and which may possibly be substantially perpendicular to the longitudinal axis of the outlet slot of the nozzle.
• This process is particularly applicable to the stripping of surfaces.
• the sprayed particles can be starch-based or plastic-based particles.
• the surface treatment method according to the invention tion is particularly suitable for stripping a surface of very precise shape or sensitive to attack, for example an exterior surface of an aircraft.
• FIG. 1 is a sectional view of a surface treatment nozzle according to an embodiment of the invention, the section being taken along line I-I of FIGS. 2 and 3,
• FIG. 2 is an elevation view from the rear of the nozzle of FIG. 1
• FIG. 3 is an elevation view from the front of the nozzle of FIG. 1
• FIG. 3A is a view similar to FIG. 3, for a variant of the nozzle of FIGS. 1 to 3,
• FIG. 4 is a partial perspective view of the nozzle of FIGS. 1 to 3, during operation,
• FIG. 5 is a schematic view of a surface treatment device including a nozzle such as that of FIGS. 1 to 3.
• the surface treatment nozzle of FIGS. 1 to 3 has a central channel which extends longitudinally between an inlet orifice 3 and an outlet orifice 4.
• the inlet port 3 of the channel has a housing 3 X which is adapted to receive one end of a supply duct which brings to the channel of the nozzle a flow of pressurized gas transporting solid particles with possibly liquid droplets.
• This housing 3- is not strictly speaking part of the central channel of the nozzle, since it is not in contact with the flow of gas under pressure or with the solid particles transported by this flow of gas.
• the central channel of the nozzle comprises, in the direction of flow of the solid particles, first a convergent section 6, then a divergent section 7.
• the inlet 3 of the nozzle has a circular section
• the converging section 6 has a section which varies continuously between a circular section at its upstream end, and a flattened section, in particular elliptical, at its end. downstream, that is to say at the level of the neck 5 which separates the converging section 6 from the diverging section 7.
• the converging section 6 flattens progressively between its upstream end and its downstream end.
• outlet orifice 4 of the nozzle is an elongated slot
• divergent section 7 itself has a flattened section parallel to the outlet slot 4.
• the diverging section 7 has, in the vicinity of the neck 5, an elliptical section which corresponds exactly to the section of the downstream end of the converging section 6.
• This elliptical section gradually deforms towards the exit slot 4 by widening slightly in the direction of the longitudinal axis 12 of the exit slot, up to a given width 1 at the exit slot, and increasing thick in the vicinity of the lateral edges 1 1 of the divergent section 7, until forming enlarged lateral parts 4 of thickness e at the ends of the outlet slot 4.
• the ratio 1 / e may for example be greater than 2.
• the divergent section 7 could possibly also include a progressive widening at its center, until it also forms an enlarged part 4 2 at the center of the outlet slot 4, this enlarged central part being separated from the lateral parts enlarged 4 X by section parts more narrow.
• the neck 5 between the converging section 6 and the diverging section 7 is formed by the line of intersection between the interior surfaces of said converging and diverging sections, so that the central channel of the nozzle has no discontinuity in section, that is that is, no surface forming an abrupt obstacle to the flow of compressed gas or an abrupt enlargement.
• the channel of the nozzle preferably has a non-angular section, even at the side edges l x of the convergent section 7, where the section of the channel has a small radius of curvature.
• the surface treatment nozzle of the invention can be produced in various ways.
• this nozzle is produced by molding two parts 1- and 1 2 , from a metallic material of very hardness, these two parts being assembled according to a joint plane 1 3 parallel to the axis longitudinal 12 of the outlet slot 4, by means of screws 2.
• solid particles are brought into a stream of compressed gas, for example air compressed at 2 to 3 bars, at the entrance to the converging section 6.
• This gaseous flow laden with solid particles is accelerated in the converging section 6, and in general becomes sonic at the level of the neck 5 then supersonic just downstream, so that '' it continues to be accelerated in the divergent section 7.
• the nozzle 1 is placed above the surface 8, so that the longitudinal axis 12 of s slot nettle 4 of the nozzle is arranged parallel to said surface 8.
• the nozzle 1 is displaced essentially in translation in a direction 9 (in one direction or the other of this direction) parallel to the surface 8 and in general, but not exclusively, perpendicular to the longitudinal axis 12 of the exit slot.
• the movement of the nozzle 1 may possibly include oscillations parallel to the surface 8 and perpendicular to the direction 9, but the nozzle 1 then always moves in translation, that is to say with its axis 12 always in the same direction .
• the nozzle may undergo movements from time to time causing rotation of its axis 12, in particular during repositioning maneuvers.
• the displacement of the surface treatment nozzle 1 produces a pickled trace 10 which is suitably treated over its entire width, without any attack on the underlying material of the surface 8 at the center of the trace 10.
• the projected particles may in particular be particles based on plastic material or particles based starch, for example particles based on wheat starch.
• the surface treatment nozzle 1 according to the invention can in particular be used in the surface treatment device 20 shown in FIG. 5.
• This device comprises a working head 21 forming an enclosure which is open towards the surface to be treated 8, the outlet of the nozzle 1 opening out inside this enclosure.
• the working head 21 is kept applied on the surface 8, or in the vicinity of the surface 8, and it is also moved along the surface 8 by a system of positioning 22 which can be of any known type.
• the positioning system 22 comprises a guide beam 23 which can be fixed during the operation of the nozzle 1, a carriage 24 movable along the guide beam 23, a robotic articulated arm 25 which is fixed to the carriage 24, and compressed air jacks 26 which hold the working head 21 against the surface 8.
• the guide beam 23 can be mounted at the end of an articulated boom carried by a vehicle (not shown).
• the inlet 3 of the nozzle 1 is supplied with compressed gas, in particular compressed air, charged with solid particles, by a supply duct 30 which is connected on the one hand to a compressor 31, and on the other hand to a feed hopper 32 containing a reserve of solid particles.
• the working head 21 is also connected to a suction pipe 33 to collect the solid particles after their projection, this suction pipe 33 being connected to a suction turbine 34 via a hopper collection 35 which receives the solid particles aspirated.
• the solid particles collected in the hopper 35 can be recycled to the feed hopper 32, in which case they preferably pass through a separation system 36 which can for example separate by screening the particles which are too large or too small, by centrifugation the particles too heavy, possibly by magnetizing the metal particles, to send these separated particles to waste at 37.
• the separation system 36 can also receive new solid particles from a reserve 38.
• the compressor 31 supplies the nozzle 1 with a sufficient gas flow so that the gas flow in the nozzle 1 becomes sonic at the neck 5 then supersonic in the divergent section 7.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Nozzles (AREA)
• Coating With Molten Metal (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1993
  • 1993-11-26 FR FR9314190A patent/FR2712826A1/fr not_active Withdrawn
• 1994
  • 1994-11-25 AT AT95902800T patent/ATE164785T1/de not_active IP Right Cessation
  • 1994-11-25 WO PCT/FR1994/001380 patent/WO1995014536A1/fr active IP Right Grant
  • 1994-11-25 CA CA002177250A patent/CA2177250A1/en not_active Abandoned
  • 1994-11-25 EP EP95902800A patent/EP0730498B1/de not_active Expired - Lifetime
  • 1994-11-25 AU AU11923/95A patent/AU1192395A/en not_active Abandoned
  • 1994-11-25 DE DE69409542T patent/DE69409542T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

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