METHOD AND DEVICE FOR APPLYING PARTICLES TO AN OBJECT

Abstract: Paint particles are applied to an object (15), such as an aluminium section, which is conveyed along a horizontal path through a spray booth (1) in which electrically charged paint particles are sprayed onto the object. The spray booth has two belt assemblies (17) which each have a belt (18) comprising an upper run (18') and a lower run (18'') merging with the upper run in a wedge-shaped point and which are arranged one on each side of the path, the point being directed at the path. The upper run (18') of the belts (18) forms the bottom of the spray booth (1). The belt assemblies (17) are set so as to form an air gap between the point and the object (15) and mark a boundary line on the object, paint particles being applied to the object on one side of the boundary line while there is no such application on the other side. Each belt (18) is driven in such a direction (P3) that its upper run (18') is moving away from the path. An exhaust means (32) is provided in the spray booth (1) to generate a negative pressure therein.

Description: METHOD AND DEVICE FOR APPLYING PARTICLES TO AN OBJECT The present invention relates to a method for apply¬ ing paint particles to an object, such as an aluminium section, which is conveyed through a spray booth in which electrically charged paint particles are sprayed onto the object. The invention also concerns a device for imple¬ menting the method. Aluminium sections destined for window casements, window frames and door frames are usually lacquered with a powder coating. The aluminium sections are conveyed through a spray booth in which electrically charged paint particles are sprayed onto the object to be coated. Then, the thus-lacquered aluminium sections are put in an oven where the paint is cured. There is an increasing demand in the market for window casements, window frames and door frames which are lacquered in two different colours. Natu¬ rally, the making of such elements requires aluminium sec¬ tions which are lacquered in the same way. Today, alumi- nium sections are lacquered in two colours by being con¬ veyed first through a spray booth in which a first powder coating is applied and then, after curing of the paint and masking by means of masking tape, through a spray booth in which a second powder coating of another colour than the first powder coating is applied. The masking tape is removed after curing of the second coating. However, both the application and the removal of the masking tape are trying and time-consuming operations. In addition, masking tape is a fairly expensive commodity. One object of the present invention is to obviate this inconvenience and provide a method for applying paint particles to an object, wherein a boundary line, which separates one zone of the object where paint par¬ ticles are to be applied from another zone of the object where no particles are to be applied, is marked without the use of any masking tape. According to the invention, this object is achieved by a method which is of the type mentioned in the intro¬ duction to this specification and which is characterised in that two belt assemblies, which each have a belt com- prising a first run and a second run merging with said first run in a wedge-shaped point, are arranged one on each side of the object, said point being directed at the object, so as to mark a boundary line which is parallel to the direction of travel of the object and on one side of which paint particles are applied to the object and on the other side of which there is no such application, each belt assembly being arranged in such a manner that said first run forms a partition in the spray booth and the point is positioned at a slight distance from the object to form an air gap between the object and the belt assem¬ bly, that the belt of each belt assembly, when the object is conveyed through the spray booth, is driven in such a direction that said first run of the belt is moving away from the object, and that a negative pressure is generated in the spray booth by an exhaust means provided in the booth. Preferably, an endless belt is employed in each belt assembly, the first run of the endless belts being sucked clean by the exhaust means. Another object of the invention is to provide a simple device for implementing the method. This object is achieved by a device which includes a spray booth with means which define a path along which said object is to be conveyed through the spray booth, and a spraying unit provided in the spray booth for spraying electrically charged paint particles onto the object, and which is characterised in that it comprises two belt assemblies which each have a belt comprising a first run and a second run merging with said first run in a wedge- shaped point and which are arranged one on each side of the path, said point being directed at the path, said first run of each belt forming a partition in the spray booth, that each of the belt assemblies is adjustable to form, in the desired position of adjustment, an air gap between the point and the object and mark a boundary line, on one side of which paint particles are applied to the object and on the other side of which there is no such application, that each belt is drivable in such a direc¬ tion that its first run is moving away from the path, and that an exhaust means is provided in the spray booth to generate a negative pressure therein. In a preferred embodiment of the device, each belt is an endless belt, and the exhaust means is adapted to suck clean the first run of the endless belts. The endless belts are preferably made of Teflon ®. The invention will be described in more detail below with reference-to the accompanying drawings, in which Fig. 1 is a schematic plan view of a device according to the- invention, Fig. 2 is a section taken along the line II-II in Fig. 1, Fig. 3 illustrates the portion encircled by the cir¬ cle A of Fig. 2 on a larger scale, Fig. 4 illustrates a connecting means from above, and Fig. 5 illustrates the connecting means of Fig. 4 in the direction indicated by the arrow V. The illustrated device has a spray booth 1 comprising two halves la and lb, each of which has a roof 2, a side wall 3 and two end walls 4. The spray-booth halves la and lb can be horizontally and laterally displaced relative to one another in the direction indicated by the double arrow PI. The spray-booth half la to the left projects a slight distance into the spray-booth half lb to the right, as appears from Figs 1 and 2. Two spraying guns 5 project into the spray booth 1 through an opening 6 in the roof 2 of each spray-booth half la, lb. The two spraying guns 5, which are of conven¬ tional type, are supplied with paint particles via a con¬ duit 7. The paint particles are electrically charged during their passage through the spraying guns 5 and are sprayed into the spray booth 1 through adjustable nozzles 8 in the form of flexible hoses. The spray booth 1 is supported, in a manner which is described in more detail below, by a horizontal stand 9 which consists of two longitudinal beams 10 carried by two support members 11. Each member 11 is made up of two ver¬ tical standards 12 and a horizontal crossbeam 13 extending between the two standards 12. The device illustrated is especially designed for lacquering long aluminium sections which are to be conveyed in their longitudinal direction through the spray booth 1, in the direction indicated by the arrow P2 (Fig. 1). Each crossbeam 13 supports a fix¬ ture 14 for fixing an aluminium section 15 to be lacquer- ed. The lower portion of the end walls 4 of the spray- booth halves la and * lb is formed with openings which con¬ stitute central end-wall openings 16 in the end walls of the spray booth 1 and are aligned with one another to define a horizontal path which is parallel to the side walls 3 and along which the aluminium section 15 is to be conveyed through the spray booth 1. Each spray-booth half la, lb has a belt assembly 17 ® with an endless belt 18, preferably made of Teflon . The belt 18 travels over a rotatable roller 19 and a wedge- shaped guide bar 20, both of which are parallel with the path defined by the end-wall openings 16. The roller 19 is arranged immediately below the side wall 3 of the spray- booth half la and lb, respectively, and is slightly longer than the spray booth 1, as appears from Fig. 1. The width of the belt 18 is substantially equal to the length of the roller 19. The wedge-shaped guide bar 20 is situated close to the path at which its point is directed. The endless belt 18 has an upper run 18' and a lower run 18" which merges with the upper run at the point of the wedge-shaped guide bar 20. The upper run 18' forms the bottom of the spray-booth half la and lb, respectively. Each belt assembly 17 has two supporting bars 21 extending perpendicular to the path. The roller 19 is mounted between the outer ends of the supporting bars 21, and the guide bar 20 is mounted between the inner ends thereof. The supporting bars 21 are fixedly connected to the spray-booth half la, lb at issue by means of an angle strut 22. Each supporting bar 21 is connected to a car¬ riage 23 by means of a connecting bar 24. The carriage 23, which is mounted on wheels 25 that roll on the respective longitudinal beam 10, is designed to be moved along this beam. The carriages 22 of the two belt assemblies 17 can be displaced along the longitudinal beams 10 so as to move the spray booth 1 with associated belt assemblies 17 along the stand 9 between two end positions. Each supporting bar 21 is connected to the associated connecting bar 24 by a connecting means 26, illustrated in more detail in Figs 4 and 5. The connecting means 26 is made up of a sleeve 27 which is slit in its longitudinal direction and through which extends the supporting bar 21, and a vertical sleeve 28 which is connected to the sleeve 27 and slit in its longitudinal direction and through which extends the connecting bar 24. A hole 29 extends horizontally through both the sleeve 27 and the sleeve 28. The part of the hole 29 extending through the sleeve 27 is threaded in the portion farthest away from the vertical sleeve 28. A screw 30 extends through the hole 29 and is in threaded engagement with the threaded portion thereof. The screw 30 can be turned by means of a handle 31. When the screw 30 is not tightened, the bars 21 and 24 can be displaced in the associated sleeves 27 and 28, and the sleeve 27, shown in horizontal position in the drawings, can be turned about the screw 30 to be set at a suitable angle to the vertical sleeve 28. When the screw 30 is tightened, the sleeves 27 and 28 fix the bars 21 and 24 in the desired position at the same time as the sleeves are fixed relative to one another. When the connecting means 26 are released, the two spray-booth halves la and lb can, as mentioned above, be laterally displaced relative to each other, i.e. in the direction indicated by the double arrow PI, and in addi- tion be vertically adjusted relative to the stand 9. By tightening of the screws 30, the spray-booth halves la and lb can be fixed in the desired position of adjustment. A suction box 32 is provided in each spray-booth half la, lb. The boxes 32 are disposed in the lower, outer portion of each spray-booth half la, lb and extend along the lower edge of the side wall 3 over the entire width of the belt. The suction boxes 32 are adapted to generate a negative pressure in the spray booth 1, as well as to clean each belt 18 by drawing paint particles from the upper run 18' thereof, for which reason they are formed with downwardly-directed openings. To enable adjustment of the capacity of the suction boxes 32 for generating a negative pressure in the spray booth 1, they may be formed with laterally directed openings (not shown), whose degree of opening is varied by register means (not shown). The paint particles drawn from the belts 18 may be conducted to a cyclone to be recovered and recycled to the spraying guns 5. When an aluminium section 15 is to be lacquered, the spray booth 1 and associated belt assemblies 17 are moved to one end position. In this position, the section 15 is put on the stand 9 and fixed in the fixtures 14, for con¬ nection to earth. The spray booth and associated belt assemblies 17 have been so set beforehand, depending on the section 15 to be lacquered, that the points of the belt assemblies 17 mark a boundary line on each side of the section, paint particles being applied to the section above the line while no paint particles are applied below the line, and that these points are located at a slight distance from the section, thereby forming an air gap 33 (Fig. 3) between the section and the point of each belt assembly 17. Then, the spray booth 1 is moved to its second end position while electrically charged paint par¬ ticles are sprayed towards the section 15, which is con¬ veyed through the spray booth 1 along the horizontal path defined by the end-wall openings 16. During this displace- ment of the spray booth 1 and associated belt assemblies 17, each roller 19 is rotated to drive the respective belt 18 in the direction indicated by the arrow P3, i.e. in such a direction that the upper run 18' of the belt is moved away from the section 15. During lacquering, the suction boxes 32 draw air from the spray booth 1, which results in an air current P4 in the air gaps 33, thereby preventing the ingress of paint particles to the gaps 33. The upper run 18' of the endless belts 18 is continuously cleaned in the manner described above by means of the suc- tion boxes 32. When the spray booth 1 and associated belt assemblies 17 have reached the second end position, the section 15 is removed from the stand 9 and put in an oven where the paint is cured. If a powder coating of another colour than the coat- ing applied in the first place is to be applied to the aluminium section 15, the section is, after curing, once more put on the stand 9 and fixed in the fixtures 14 in such a manner that the non-lacquered portion is facing upwards. After setting the spray booth 1 and associated belt assemblies 17 in the desired position as described above, the above procedure is again implemented but this time with paint particles of a different colour.

Claims: CLAIMS 1. Method for applying paint particles to an object (15), such as an aluminium section, which is conveyed through a spray booth (1) in which electrically charged paint particles are sprayed onto the object, c h a r ¬ a c t e r i s e d in that two belt assemblies (17), which each have a belt (18) comprising a first run (18*) and a second run (18") merging with said first run in a wedge-shaped point, are arranged one on each side of the object, said point being directed at the object, so as to mark a boundary line which is parallel to the direction of travel (P2) of the object and on one side of which paint particles are applied to the object and on the other side of which there is no such application, each belt assembly (17) being arranged in such a manner that said first run (18') forms a partition in the spray booth (1) and the point is positioned at a slight distance from the object (15) to form an air gap (33) between the object and the belt assembly, that the belt (18) of each belt assembly (17), when the object is conveyed through the spray booth, is driven in such a direction that said first run (18') of the belt (18) is moving away from the object (15), and that a negative pressure is generated in the spray booth (1) by an exhaust means (32) provided in the booth. 2. The method of claim 1, c h a r a c t e r i s ¬ e d in that an endless belt (18) is employed in each belt assembly (17), and that the first run (18') of the endless belts is sucked clean by the exhaust means (32). 3. Device for implementing the method of claim 1 for applying paint particles to an object (15), such as an aluminium section, said device including a spray booth (1) with means (16) which define a path along which said object is to be conveyed through the spray booth, and a spraying unit (5) provided in the spray booth for spray- ing electrically charged paint particles onto said object, c h a r a c t e r i s e d in that it comprises two belt assemblies (17) which each have a belt (18) com¬ prising a first run (18') and a second run (18") merging with said first run in a wedge-shaped point and which are arranged one on each side of the path, said point being directed at the path, said first run (18') of each belt forming a partition in the spray booth (1), that each of the belt assemblies (17) is adjustable to form, in the desired position of adjustment, an air gap (33) between the point and the object (15) and mark a boundary line, on one side of which paint particles are applied to the object (15) and on the other side of which there is no such application, that each belt (18) is drivable in such a direction (P3) that its first run (18') is moving away from the path, and * that an exhaust means (32) is provided in the spray booth (1) to generate a negative pressure therein. 4. The device of claim 3, c h a r a c t e r i s - e d in that each belt is an endless belt (18), and that the exhaust means (32) is adapted to suck clean the first run (18') of the endless belts. 5. The device of claim 4, σ h a r a c t e r i s - e d in that the endless belts (18) are made of Teflon ®.

Inventors: EKSTROEM BO, EKSTROEM, BO
Applicants: EBI PATENT
Application year: 1991
Main classification: B05B15
IPC codes: B05B15