Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/08—Plant for applying liquids or other fluent materials to objects
  • B05B5/087—Arrangements of electrodes, e.g. of charging, shielding, collecting electrodes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/08—Plant for applying liquids or other fluent materials to objects
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
  • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
  • B05D1/045—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field on non-conductive substrates

Definitions

• the present invention relates to a method of painting parts of dielectric or weakly conductive material, an electrode for installation of electrostatic painting of parts of dielectric or weakly conductive material and an installation of painting of parts of dielectric or weakly conductive material.
• the present invention is particularly applicable to the wood and furniture industries.
• thermoforming This method cannot fully cover a panel at one time.
• edges of the face against facing reveal the thermoformed film.
• the choice of colors is also very limited here.
• the present invention intends to remedy these drawbacks by proposing a method of painting on parts made of dielectric or weakly conductive material and in particular wood, an electrode and an installation for painting on these materials using said method.
• the method described in the present invention is a method of painting parts made of dielectric or weakly conductive material in which a paint spraying means is used comprising a chamber in relation on the one hand with a paint outlet orifice and on the other leaves with a supply of paint.
• This process is essentially characterized in that it consists in mechanically and electrically connecting at least one electrode to the part to be painted, in creating an electrostatic field between the electrode and the paint spraying means by applying a potential difference electric between the electrode and another electrode housed in the chamber of the projection means, to propel the paint from the reserve, towards the paint outlet orifice by passing through the chamber, to electrically charge this paint and to project this painting towards the part (16) to be painted.
• a solid paint in powder form is used.
• a polyester-based powder paint is used.
• the painting process consists in introducing the electrode into the This arrangement allows you to paint all of the external surfaces of the room.
• the painting process consists in affixing the electrode on at least one of the external faces of the part to be painted. This operating mode limits the painting of the part to the faces not covered by the electrode (s).
• the electrode according to the invention for installation for electrostatic painting of parts made of dielectric or weakly conductive material intended to come into contact with the part to be painted and to be connected to one of the two poles of an electric voltage source fitted to the installation is essentially characterized in that it comprises on its external surface at least one angular region intended to come into contact with the part to be painted, said angular region being the seat of the so-called peak electrostatic effect.
• Figure 1 schematically shows a succession of operations according to the method of the present invention.
• FIG. 2 represents a schematic view of a painting installation provided with an electrode according to the invention and intended for the implementation of the method according to the invention.
• Figure 3 shows a sectional view of a first embodiment of the electrode according to the present invention.
• FIG. 4 represents a front view of the electrode according to FIG. 3.
• Figure 5 shows a sectional view of a second embodiment of the electrode according to the present invention.
• FIG. 6 represents a front view according to FIG. 5.
• FIG. 7 represents, in section, an electric field generated by an electrode according to the present invention.
• FIG. 8 shows in perspective another embodiment of an electrode according to the invention.
• FIG. 9 schematically represents, seen from above, a baking oven for the painting installation according to the present invention.
• the object method of the present invention is applied to a particular example, that of furniture wood.
• This furniture wood can be M.D.F (medium density fiber), i.e. wood made from citrus fruits compressed under high pressure.
• This wood can also be chipboard, and more generally any type of natural or recomposed wood used in the furniture industry.
• the part to be painted, as can be seen in particular in FIG. 2, can be in the form of a polygonal contour panel, for example rectangular or square.
• Figure 1 In Figure 1 are shown a cutout and shaping 1, a hole 2, a sanding and a protection 3 d edges, a sanding 4 of the whole part, an attachment 5 of electrode, an application 6 of tension on an electrode, an application 7 of tension on the paint, a spray 8 of paint, a low flux firing 9, a high flux firing 10, a cutout 11 of margins and an application 12 of varnish.
• the cutting and shaping 1 is of known type. It includes both the rectangle cutting, the rounded edges and possibly the knocking and grooving, for example. It consists in giving the piece its final shape. The other operations relate to the surface condition of this part.
• the wood used should preferably have a hygrometry of 8 to 12 percent.
• Drilling 2 consists in making a first hole in the part so that the electrode can be laid without causing the part to burst. This drilling will advantageously blind and in the case where the part to be painted consists of a panel, will be produced so that its median axis of symmetry is perpendicular to the two large faces of the panel.
• the drilling 2 of electrodes is carried out either in an area which will then be machined, or in an area which will be eliminated by cutting margins.
• the electrode hole 2 is then used, for example for the installation of hinges or hinges or any other mechanical elements participating in the assembly of the panels of a piece of furniture.
• the drilling is not carried out. This drilling is also not carried out if the shape of the electrode allows its insertion into force in the part and this without danger of bursting of the latter.
• the protection of the edges 3 of the panel is a characteristic operation of the present invention.
• the edges of the piece of wood are sanded, for example with a grain of 400 for MDF, with a grain of 220 for the chipboard, then are covered with a blocking primer, consisting for example of wood pulp based barium or a polyurethane varnish.
• This operation therefore consists of closing the pores of the wood or even filling the roughness of the wood.
• This edge protection 3 also includes a drying phase which can last a few hours. It allows the pieces of wood to then undergo heating, that is to say cooking at high temperature.
• Sanding 4 is also one of the characteristic operations of the present invention.
• Sanding is a surface preparation action that precedes the application of a product. Sanding makes the fibers, impurities, traces of grease, scratches disappear on the surface.
• This sanding is carried out according to the method of the present invention with a grain greater than 300 and preferably 400. This grain generally corresponds to a particular sanding operation, called ginning, because of the fineness of the grain used.
• This sanding is carried out on all the surfaces to be painted in the room. The fineness of the grain allows the wood fibers not to be opened in such a way that heating the wood, during cooking operations 9 and 10, does not cause significant bubbling or degassing. Thus, the surface condition of the paint is not altered.
• the attachment of electrode 5 consists in mechanically and therefore electrically fixing the electrode to the part to be painted.
• the electrode is introduced, preferably by force, into the hole drilled during drilling 2.
• the attachment can be carried out by pressing in or by screwing, for example.
• the electrode has straight or curved protrusions or sharp angles.
• the electrode therefore has concave parts. This operation is the main characteristic of the invention because of the shape of the electrode which favors the appearance of a spherical or flattened electric field around the electrode when the latter is connected to a voltage source.
• the application 6 of voltage on the electrode consists in electrically connecting the electrode to a source of electric voltage.
• the practice generally prefers that this tension is zero.
• the electrode is connected by an electric cable or a metal support to said voltage source.
• tension to paint 7 is also of known type. It consists of electrically charging a solid paint powder, for example a polyester powder with a sign voltage opposite to that which charges the part, said voltage being supplied by the voltage source to which the electrode is connected.
• the equipotential lines are distributed in the room and one of them is practically identical to the volume of the room. It is notable that the peak effe applies to the part and that, consequently, the corners are painted the same way as the rest of the room, if not better.
• the spraying of paint 8 is of known type and is generally carried out by an electrostatic paint spray gun. It is the propelling air, the static electricity and the electric field created between the electrode and the gun which cause the movement of the powder of paint towards the part to be painted.
• This electrostatic paint gun is connected to the voltage source and is subject to electrically charging the paint regardless of the positive or negative polarity.
• the spraying of paint is carried out by sweeping, but the powder paint deposited forms a single layer.
• Low-flow cooking 9 is carried out in the first part of an oven, the part in which the painted parts are introduced.
• the flow of hot air, which comes from the bottom of the oven is braked by mechanical protection.
• the thermal shock is limited as well as the mixing of air which could disturb the uniformity of the paint deposition. This is limited to a very short time of two to four minutes, during which the paint begins to adhere to the support.
• High flux cooking 10 is of known type. It takes place in the rest of the oven. Both types of cooking are carried out for example in a gas oven, but it goes without saying that any other type of oven suitable for this function can be used.
• the cutout 11 of margins makes it possible both to bring the part to the required dimensions and to eliminate the drilling 2 of the electrode.
• the application 12 of varnish is of known type, for example curtain, cylinder, automatic or manual spraying. It is understood from the description of Figure 1 that the characteristic steps of the process are in order of decreasing importance. - the use of an electrode which has straight or curved projections or acute angles and which thus favors the appearance of a spherical or flattened electric field around the electrode when the latter is connected to a voltage source .
• edges 3 which are covered with wood pulp that can be diluted or polyurethane varnish.
• This operation therefore consists in sealing the pores of the wood or even filling in the roughness of the wood.
• This edge protection also includes a drying phase which can last a few hours.
• the process which is the subject of the present invention is applied to a particular example, that of furniture wood.
• other examples could have been used, for example, that of plaster, that of earthy materials, bricks, P.V.C, tiles and more generally of all slightly conductive materials.
• the process according to the present invention can also be applied to cardboard products produced from shredded products mixed with glue based on urea formaldehyde and hot-pressed.
• the shredded products may be cartons lined with aluminum foil.
• the paint can be metallized and / or achieve metallization of the part or any other surface effect, such as grain, hammered, structured and smooth effects.
• the products produced according to the process described in FIG. 1 have successfully undergone impact resistance tests with a 110-gram ball, for the qualification of lacquer and varnish paints, the adhesion tests by grid pattern on varnish or lacquer, the resistance tests. from scratches, cigarette burns, stains from household and food products.
• the method comprises a varnishing phase by applying a colorless varnish drying with ultraviolet radiation having a brightness varying between 25 and 100 percent, according to the choice of the user without ginning the support.
• the grammage per square meter preferably reaches 90 to 160 grams with an accuracy and homogeneity of 10 grams.
• the method comprises a varnishing phase by applying a polyurethane varnish with conventional drying or a diluted wood pulp with conventional drying.
• the application methods can be, for example, by robot, by curtain, by spray-painting or manually.
• FIG. 2 schematically represents a painting installation according to the invention.
• a gun 13 a part to be painted 16, an electrode 17, an electrode holder 18 and a voltage source 19, paint 20, a spray of paint 21, a compressor 45 and a tank.
• powder 46 constituting paint reserve 20.
• the gun 13 is adapted to direct the spray of electrically charged paint 21 towards the part 16. It is of known type.
• This gun has an internal chamber formed in a projection barrel and in relation on the one hand with a paint outlet orifice provided at the end of the barrel and on the other hand with the paint reserve 46 via a conduit .
• the powdered paint is propelled by compressed air through the chamber from the reserve 46 to the paint outlet.
• an electrode In the gun chamber is provided an electrode, not shown, electrically connected via the electronic cascade of the gun, to the positive pole of the source of electric voltage 19.
• the other pole of the tensio source 19 is electrically connected to the electrode 17 either directly or indirectly via the support 18.
• a field electrostatic which can be negative or positive depending on the choice of the electronic cascade.
• the paint is electrically charged as it passes through the chamber coming close to or in contact with the gun electrode.
• the source of electric voltage supplied between its terminals a potential difference of several tens of kilovolts.
• the part to be painted 16 is in the paint spraying operation 8 of the process described in FIG. 1.
• the compressor 45 injects compressed air into the powdering tank 46 according to known techniques in order to thin the paint contained in this tank. The fluidized paint is then sprayed.
• the electrode support 18 is adapted to mechanically support the electrode 17 and the part 16 and to electrically connect one of the electrical terminals of the voltage source 19 to the electrode 17.
• the electrode 17 promotes the appearance of a electric song spherical or flattened around it when it is connected a source of tension.
• the electrode 17 is conductive, has angular regions such as for example straight or curved projections or acute angles. Thus the electrode 17 has concave parts. It is electrically connected to an electrical ground and to part 16. To this electrical ground will be connected the negative pole of the voltage source 19. It also serves as a support for part 16.
• Each projection that the electrode may comprise, in a plane normal to the surface of said electrode, may have a triangular cross section or else trapezoidal or any other shape having at a distance from said surface a region of strong curvature.
• Each projection may form a spike or else be elongated and develop in the latter case in a rectilinear manner on the surface of the electrode or else in a curved manner, for example in a helical circle or other curve.
• the electrode may comprise a core, the projection (s) being formed on the external surface of the core and being able to develop radially with respect to the latter.
• An electrode with core is intended to be inserted into a hole previously made in the part to be painted.
• the longitudinal axis of the electrode core is therefore perpendicular to the two large faces of the panel.
• the core may have a polygonal cross section but preferably the cross section of this core is circular.
• This core will be cylindrical or else conical in shape.
• the protrusions of an electrode with a cylindrical or conical core may each develop along one of the generatrices of the cylindrical or conical surface of the outer core or else in a curved manner on this outer surface, for example in a helix, in a circle and the like.
• the protrusions of an electrode with a cylindrical or conical core may also be constituted by pins which will develop radially with respect to the core.
• FIG. 3 shows a sectional view of a preferred embodiment of the electrode object of the present invention.
• FIG. 4 represents a front view of the same embodiment of the electrode.
• This electrode constituted by a cylindrical core, is provided with an external thread and at least one longitudinal groove extending along a generator of the core through the thread.
• an electrode 17 with a cylindrical core comprising an external thread 22, 23, 24, 25, at least one groove, a recess 28, an internal thread 29, a front face 30 and a rod 32.
• the electrode is provided with two diametrically opposite grooves 26, 27.
• the electrode may be equipped with a larger number of grooves which preferably 1ement will be regularly spaced from each other.
• the length of the electrode is adapted to the thickness of the product to be painted.
• the part 16 has been drilled with a hole whose diameter is substantially equal to the bottom diameter of the external threads 22, 23, 24 and 25 and whose depth is substantially equal to or greater than the reentrant length of the electrode in the panel.
• the external thread 22, 23, 24, 25 and the two grooves 26, 27 are formed in a single thread whose pitch for example is of the order of a millimeter.
• Each piece of thread 22, 23, 24 and 25 is therefore substantially equal but less than half a pitch of a helix stopping at the grooves 26 and 27.
• the electrode 17 therefore has curved and helical projections and acute angles.
• the recess 28 of cylindrical shape passes right through the electrode along the longitudinal median axis of the core of the latter.
• the electrode as shown in FIG. 3 does not have a shoulder but as a variant it can be fitted with a shoulder to limit penetration into the part 16.
• the internal thread 29 or internal thread is produced in the recess 28 over the entire length of the latter.
• the metal rod 32 allows the insertion of the electrode 17 into the part 16 by its geometry and the connection of electrical connectors to the electrode 17.
• the rod 32 is preferentially cylindrical and has a thread at the end for engaging, by this end, in screwing in the tapping 29 of the electrode 17. This rod 32 will ensure an electrical and mechanical connection of the electrode to the support of electrode 18. This rod can also constitute an electrode support.
• the shape of the electrode 17 presented in FIGS. 3 and 4 is preferably inserted by screwing. Thanks to the presence of the grooves, the electrode according to this embodiment is self-tapping and its screwing in the hole carries out the tapping of the latter.
• FIG. 5 represents a sectional view of a second embodiment of the electrode object of the present invention.
• FIG. 6 represents a front view of the electrode presented in FIG. 5.
• an electrode 17 comprising a core on the cylindrical surface of which are provided external longitudinal straight projections 33 separated by longitudinal recesses 34, a recess 35, a shoulder 31 and a rod 32.
• This electrode has a cylindrical core.
• the external longitudinal straight projections 33 and the recesses 34 form a prism with a polygonal base, for example in the shape of a star.
• the recess 35 passes right through the electrode and is formed along the longitudinal axis of the core of the latter.
• the shoulder 31 and the rod 32 threaded at the end have the same characteristics and functions as in Figures 3 and 4.
• the shape of the electrode 17 presented in FIGS. 5 and 6 is preferably inserted forcibly into a hole previously made in the panel.
• the electrode 17 therefore has straight projections and sharp angles.
• Electrodes conform to the spirit of the invention, such as, for example, wood screws, threaded rods, or any other element.
• An electrode may also be provided in the form of a plate of reduced thickness and of polygonal outline for example, the projections being formed on at least one of the faces of said plate.
• Such an electrode can be forcibly inserted into the wooden panel without prior drilling thereof, or else be inserted into the hole provided for receiving this electrode or else be affixed to one of the faces of the part.
• the projections provided for this electrode in the form of a plate may be pins of the longiform bosses and the like.
• the protrusions will always each have a cross section of triangular shape, trapezoidal shape and other shapes capable of being the seat of an electrostatic effect called peak.
• the plate may form a succession of protrusions and hollows, thus this plate will be corrugated.
• the corrugations of the plate may be triangular in shape.
• the large faces of the corrugations may be smooth or else have projections like those previously described.
• FIG. 7 represents, in section, an electric field generated by a device which is the subject of the present invention.
• lines of equipotential 36, 37 and 38 generated by the tensioning in air of the inserted part of the electrodes 17.
• These lines of equipotential 36, 37 and 38 are elliptical and, in the space, their surface is ellipsoidal. It is understood that when the electrode 17 is inserted in the part 16, the field lines take on even more flat shapes and that one of them is substantially identical to the shape of the part 16. This is due to the dielectricity of the material constituting the part 16 or at its slight conductivity.
• Figure 8 shows a paint baking oven according to the present invention.
• FIG. 8 In FIG. 8 are shown an oven 39, a room inlet area 40, a room outlet area 41, a high flow heating area 42, a hot air inlet 43 provided with a protection 44.
• the oven 39 has the parts inlet zone 40 which is, for example, at one end and the parts outlet zone 41 which is, at the other end of the oven. Between these two zones there is an intermediate zone 42 In this oven (39) the first heating or baking phase takes place with reduced air movement speeds compared to the following heating or baking phases so that the paint can gel before the part reaches the area with strong air movement.
• the first heating phase is carried out in the air intake zone while the following phase is carried out in the rest of the oven, ie in zones 42 and 41. It should be noted that the entire oven volume is at uniform temperature.
• the high-flow heating region 42 includes the zones 42 and 41.
• the oven is provided over its entire extent with air intake orifices, the air intake being effected by the bottom and the orifices being distributed in the zones 40, 41, and 42.
• the latter is provided with a screen 44 constituted by a removable wall placed on the bottom of the zone 40 in order to hide the air intake orifices of the latter.
• the parts 16 undergo first of all a shock-free cooking. neither thermal nor air mixing, these two events can deteriorate the paints produced on the surface of the parts 16 which are still in the form of powder, solid deposited on the surface of the parts 16. It should be noted that the temperatures and cooking times are those recommended for the powder paints used, the wood being able, once protected on its edges and knockouts by a blocking primer, to withstand high temperatures without thermal expansion.
• the method and the device described in the present invention apply equally to the painting of pieces of agglomerated wood, compressed wood, agglomerated wood coated with polyvinyl film, for example smooth PVC or imitation of natural essence. , MDF wood raw or smooth or coated with smooth P.V.C. or imitation of natural essence, or veneer of natural essence.
• the electrode can be an element of the finished product and for this reason is not removed from the panel.
• This electrode which in this case constitutes an insert can later serve as an anchor point for the panel.

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• Application Of Or Painting With Fluid Materials (AREA)
• Electrostatic Spraying Apparatus (AREA)
• Camera Bodies And Camera Details Or Accessories (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

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• 1994
  • 1994-10-06 FR FR9412130A patent/FR2725385B1/fr not_active Expired - Fee Related
• 1995
  • 1995-10-04 PT PT95933474T patent/PT796151E/pt unknown
  • 1995-10-04 AT AT95933474T patent/ATE202015T1/de not_active IP Right Cessation
  • 1995-10-04 EP EP95933474A patent/EP0796151B1/de not_active Expired - Lifetime
  • 1995-10-04 DE DE69521335T patent/DE69521335T2/de not_active Expired - Fee Related
  • 1995-10-04 JP JP51237796A patent/JP3768531B2/ja not_active Expired - Fee Related
  • 1995-10-04 WO PCT/FR1995/001284 patent/WO1996011063A1/fr not_active Ceased
  • 1995-10-04 US US08/817,816 patent/US5997959A/en not_active Expired - Fee Related
  • 1995-10-04 CA CA002200781A patent/CA2200781C/fr not_active Expired - Fee Related
  • 1995-10-04 ES ES95933474T patent/ES2160715T3/es not_active Expired - Lifetime
  • 1995-10-04 DK DK95933474T patent/DK0796151T3/da active
• 2001
  • 2001-09-13 GR GR20010401476T patent/GR3036618T3/el not_active IP Right Cessation

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