AN ARRANGEMENT FOR PAINTING AN EXTENDED OBJECT MOVING CONTINUOUSLY IN ITS LONGITUDINAL DIRECTION

Abstract: To obtain paint on all sides of a strip, painting must be performed in two stages since the strip must rest on a surface while being painted. This is avoided if moving strips are guided in a manner allowing them to be free from mechanical support from the start of painting until they have passed a drying unit (11), after which they can rest on a support surface without the paint being damaged.

Description: , AN ARRANGEMENT FOR PAINTING AN EXTENDED OBJECT MOVING CONTINUOUSLY IN ITS LONGITUDINAL DIRECTION The present invention relates to an arrangement for painting all sides of extended objects, said objects possibly having different cross sections. Such objects have previously been painted by being placed on a conveyor and painted on all sides except the side in contact with the conveyor. The painted objects were then dried by means of ultraviolet radiation, 5 for instance. When dry, the objects were turned over and painted on the remaining, unpainted side. The disadvantage of this method is that it takes too long to paint extended objects on all sides, and also that special apparatus is needed to turn the objects ready for painting on the surface initially serving as contact surface. Another disadvantage is that paint containing solvent is used, which is unsatisfactory 10 from the environmental aspect. The object of the present invention is to increase the production rate during painting. This is enabled by painting on all sides, the part to be painted and dried being freely suspended and not in contact with any support surface. Guiding the part behind the portion being painted allows the latter to remain freely suspended during painting and 15 while being transported for drying. The drying process can be shortened if very quick- drying paint is used, such as a mixture of binder and monomers that may also contain colour pigment. Such a mixture dries extremely quickly if it is subjected to radiation energy so that polymerization occurs. Drying occurs extremely quickly if the painted surface is radiated with the aid of an electron beam. Painting is suitably performed by 20 allowing the extended object to pass through a closed tank containing the desired paint mixture. The extended object is moved along above the surface of the mixture. Above the surface of the mixture the tank is subjected to a vacuum so that paint from the liquid surface surrounds the portion of the extended object located in the tank. The painted portion then passes two polymerization units, one of which polymerizes the painted % 25 surface from below and the other polymerizes the painted surface from above. The two units are displaced in relation to each other so that electronic radiation is performed first "* from below and then, after a short delav, from above. The use of a paint mixture consisting solely of binder, monomer and possibly colour pigment (i.e. solvent-free), avoids the drawbacks arising out of the use of solvent. The painted surfaces can pass another drying means where they are dried with the aid of ultraviolet light. The ready-painted objects may be packed, for instance, in bundles, parcels or the like. Blanks having rectangular cross section are used for the extended objects, the cross section being sufficiently large to encompass at least two extended objects arranged side by side. Such a blank is machined so that a number of adjacent extended objects are obtained, the objects being held together in pairs by means of a blank remnant. The use of blanks as described above offers the advantage that several extended objects can be fed along beside each other. Instead of only one extended object, a plurality of extended objects located beside each other is obtained, thus increasing the production rate as compared with single objects by the number of blanks lying parallel. Said blank remnants are removed immediately prior to painting. A blank for machining several extended objects is obtained from a stack of similar blanks where the blanks in the stack are arran ■ oge'-d one after the other. A stack of blanks is obtained by sawing one stack at a time from a stack of slabs. The slabs may be produced from optional material such as wood, fiberboard, plastic or metal. Equipment for treating the surface of the extended objects may be arranged along the production line to roughen the surfaces, thereby improving the durability of the finished paintwork. A painting station for priming may also be arranged in the production line, in this case at a point after a number of extended objects disposed side by side have been obtained. The priming station may function similarly to the painting station described above, i.e. the objects are painted on all sides. Here, too, the paint may comprise the same type of mixture as used for painting. However, normally it is sufficient for the extended objects to be painted from above and subsequently dried by means of ultraviolet radiation. The installation described above greatly increases the manufacturing capacity as compared with known methods, thanks both to the use of a quick-drying paint and to several objects being moved along in parallel. Additional features characteristic of the present invention are revealed in the appended claims. One embodiment of the present will be described by way of example with reference to the accompanying drawing showing a block diagram of the various treating stages. According to the drawing a number of slabs stacked one on top of the other, and possibly having an area in excess of 1 m~, are supplied to the unit 1. From this stack of slabs one stack of blanks at a time is sawn off, with rectangular cross section, each blank in the stack being in the nature of a plank. One stack of blanks at a time is supplied to a separating unit 2 where the individual blanks in the stack are arranged one after the other. The blanks are then supplied from said unit 2 to a working-up unit 3 where each blank is machined mechanically by milling, for instance, so that a number of parallel extended objects are obtained, two adjacent objects being joined together by means of blank remnants. The blank with more than two extended objects is supplied to a unit 4 where each blank is roughened, by sand-papering for instance, to prepare it for a first coat of paint. After treatment in the unit 4 the blank is supplied to a painting station 6 where it is painted from above by spray painting, for instance, and where it is subsequently subjected to drying by means of ultraviolet light in a unit 7. A suitable paint for priming consists of binder, monomer and possibly colour pigment and photo-initiator. The primed blank is supplied to a unit 8 for roughening, suitably with sand-paper. After treatment in the unit 8 the blank is ready for more paint. It is therefore conveyed from unit 8 to a unit 9 where all extended objects are separated from each other by means of milling, for instance. From unit 9 the separated extended objects are supplied to a painting unit 10. The objects entering the painting unit 10 are guided in such a manner that portions located in the painting unit 10 are freely suspended allowing them to be painted on all sides. The painting unit 10 suitably comprises a closed container, its lower part containing a mixture of binder, monomer and possibly colour pigment. The portions of the extended objects located insides the closed tank are located above the surface of the paint mixture. The closed container is under vacuum so that paint is drawn up from the surface towards the portions of the objects located therein. The extended objects, painted on all sides and still freely suspended, are conveyed to a drying unit 11. The drying unit 11 has two electron accelerators, one operating from above and the other from below. Painting with electron accelerators is described in detail in a publication from Polymer- Physik GmbH, entitled "Hintergrund und Neueste Anwendungen von Elektronen- bestrahlungsanlagen fur umweltfreundlϊch Beschichtungs- und Laminier-Technologien". Since painted portions of the extended objects in the drying unit 11 should be dried so that the front parts can come into contact with a support surface without the paint being damaged, drying is initiated from below and then continued after a short delay from above. Since the paint used consists of binder, monomer and possibly colour pigment, the electron beams will polymerize the coated paint, resulting in instantaneous drying. The painted and dried extended objects are supplied from unit 11 to a second drying unit 12 where they are dried only from above with the aid of UV light. From unit 12 the painted and dried extended objects are passed to a packing unit 13. The priming unit 6 may be of the same type as the painting unit 10. The extended object blanks are fed continuously along the entire production line. It should be evident that painting under vacuum may be replaced with spray-painting.

Claims: C L A I S 1. An arrangement for painting all sides of an extended object such as rod, strip or the like, said object consisting of optional rigid material such as wood, wood-pulp board, metal, plastic or the like, and moving continuously in longitudinal direction, characterised by a closed container ( 10), its lower part containing a mixture of binder, 5 monomer and pigment, by a passage arrangement for the extended object allowing it to pass through the container ( 10) above the surface of the mixture, by a painting arrangement ( 10) such as a vacuum arrangement (10) so that the extended object within the container ( 10) becomes coated with a layer of the mixture, by guide means such that the coated object is guided in such a way that it remains freely suspended until a drying 10 unit (11) has dried the object from below and it can come into contact with a support surface, and by a second drying unit (11) drying the object from above. 2. An arrangement as claimed in claim 1, characterised in that the two drying units (11) comprise apparatuses that produce a preferably deflectable electron beam or curtain which polymerizes the monomer in the coating layer. 15 3. An arrangement as claimed in claim 1 or claim 2, characterised in that a packing station (13) is arranged after the drying units ( 11), to pack the extended units into bundles, for instance. 4. An arrangement as claimed in claim 1, characterised by a unit (12) for ultraviolet radiation of the object after it has passed the two drying units (11). 20 5. An arrangement as claimed in claim 1 , characterised by an additional painting station (6) for providing a first coat of paint on the extended object prior to its passage through the closed container (10), said painting station (6) preferably coating the object on all sides, the layer of paint being obtained in the same manner as said layer in the closed container (10), or on all sides with the exception of the contact surface. 25 6. An arrangement as claimed claim 5, characterised by a second UV radiation unit (7) disposed after said additional painting station (6). fl 7. An arrangement as claimed in claim 5, characterised in that a working- up machine (3) is disposed before the additional painting station (6), said machine receiving the blank for the extended object and supplying the prepared object to the painting station (6). 8. An arrangement as claimed in claim 7, characterised in that the blank is of such a width that at least two extended objects are encompassed within its cross section. 9. An arrangement as claimed in claim 8, characterised in that at least two extended objects located side by side are obtained from the working-up machine (3), each object being joined to adjacent objects by an easily removed blank remnant 10. An arrangement as claimed in claim 7, characterised in that the working- up machine (3) is supplied with one blank at a time from a separating machine (2), the latter machine taking blanks from a stack and arranging them in a row. 11. An arrangement as claimed claim 10, characterised in that a stock saw (1) is arranged prior to the separating machine (2) to saw off said stacks from a stack of slabs. 12. An arrangement as claimed in any of the preceding claims, characterised in that one or more grinding stations (5, 4 and 8) are arranged along the path of movement of the object. 13. An arrangement as claimed in claim 9, characterised in that a machine (9) is arranged to remove said blank remnants, said machine (9) being preferably located before said closed container ( 10) .

Inventors: LINDBLAD ANDERS, LINDBLAD, ANDERS
Applicants: LINDBLAD ANDERS, LINDBLAD, ANDERS
Application year: 1992
Main classification: B05C13
IPC codes: B05B13, B05C3, B05C9, B05C13, B05D3