EP1181104A1

EP1181104A1 - Ecological painting and/or washing installation for polyurethane bottoms

Info

Publication number: EP1181104A1
Application number: EP00935464A
Authority: EP
Inventors: Giampietro Ruggeri
Original assignee: RPM Sud SpA
Current assignee: RPM Sud SpA
Priority date: 1999-05-27
Filing date: 2000-05-17
Publication date: 2002-02-27
Also published as: CN1351522A; WO2000072976A1; AU5100200A; IT1309526B1; ITAN990027A1

Abstract

The present invention concerns an ecological installation for the automatic painting and/or washing of polyurethane bottoms; said installation comprises a hermetic booth (1), through which the bottoms moves while hanging from a series of bottom-holding hooks (2) pulled by the cyclic chain (3) of a suitable overhead conveying system; it being provided that the exceeding painting is recovered by the booth to directly fill the tank (6) where the painting is sucked by a pump (5) which sends it to the spray nozzles (4) applied on the walls of the booth.

Description

Ecological painting and/or washing installation for polyurethane bottoms.

The present patent application for industrial invention relates to an ecological installation for the automatic painting and/or washing of polyurethane bottoms.

The installation has been conceived with the specific purpose of improving the realisation of painting and washing operations of polyurethane bottoms from the ecological and economic viewpoint.

Up to now, these operations have been carried out in two alternative ways that are both impaired by significant disadvantages.

According to the first method, the bottoms are painted with nebulized paint sprayed by compressed air guns.

This technology is severely impaired by the fact that the spray painting installations must be provided with disposal system for the powders (or resins) contained in the paint by means of different dry or wet technologies. In particular, this involves all the powders that do not deposit on the bottoms to be painted and are intercepted inside painting booths by means of a suitable water layer that flows on the front side of a vertical panel located behind the bottom being painted.

In this way, the so-called "painting booth mud and water" is produced, which is a highly polluting special waste requiring specific rigorous disposing methods.

During the spraying of the paint, a considerable emission of solvents

(with high concentration) contained inside the paint is produced into the air inside traditional painting booths. These solvents in the gaseous state can only be emitted into the atmosphere after active carbon filtering or filter burning.

Traditional spray painting installations cause a considerable irreparable waste of the paint which does not directly deposit onto the bottoms. As a matter of fact, the paint that does not deposit on the articles to be painted tends to degrade quickly, due to the solvent evaporation, with consequent hardening of its solid parts (or powders) that are intercepted by the water layers and converted into "mud" for final disposal. Other disadvantages of this technology are related to the considerable consumption of paints and compressed air, apart from the need of washing each bottom to be painted to remove from the its surface the residues of silicone that is always sprayed onto the matrix dies to facilitate the extraction of the pieces after consolidation. According to the second method, each bottom is immersed into a tub filled with the desired colour of paint and then extracted from the colour bath with a controlled speed in order to obtain uniform colour coating.

Also the second technology involves the use of aspirators located over the tubs with the paint to capture the dangerous solvent exhalations, which must be disposed of into the atmosphere with the delicate process illustrated above.

Furthermore, the quality of the pieces painted with this technology is not always satisfactory and the areas in which the painting tubs are installed are always considered as highly inflammable explosive areas. The electrical installations must therefore be explosion-proof with a considerable cost increase.

Finally, it must be said that the immersion technique requires a preventive operation by the operators to remove the silicone residues from each bottom to be immersed into the paint tub. The installation according to the present invention is effectively capable of overcoming the drawbacks of the two traditional techniques.

The basic principle of the invention is to avoid the dispersion into the environment of the toxic exhalations of the solvent contained in the paints, as well as to recover the paint that does not deposit directly onto the items to be painted. From this viewpoint, the ecological value of the installation according to the invention can be easily appreciated, together with its capability of ensuring a considerable cost reduction, especially thanks to the close-circuit recovery of all the excess paint in the installation.

The new installation allows for obtaining excellent painting results and is basically made up of a spray painting installation characterised by the fact that the paint is sprayed onto the items inside a hermetic booth, whose internal volume can be permanently saturated with the solvent used in the paint.

Thanks to the saturation of the environment with the solvent, each dose of paint that is sprayed inside the booth and does not deposit onto the bottoms to be painted does not suffer the hardening and viscosity loss processes that would make it impossible to use it.

All the paint that does not deposit on the bottoms falls and drips onto the bottom of the booth due to gravity, without losing its composition and characteristics. The bottom of the booth has a drain hole, which allows the recovered paint to directly fill the tank used by the pump to feed the spray nozzles, which should preferably be of airless type in order to avoid the emission of air into the hermetic booth and reduce the solvent concentration.

When using traditional air compressed nozzles to obtain nebulized paint sprays, it will be necessary to use air saturated with solvent, in order not to alter the saturation degree of the hermetic paint booth. In this perspective, the spray nozzles may be fed with saturated air taken from the hermetic spray booth.

As explained in the description below, the new painting installation is also capable of washing the bottoms to remove the moulding silicone, which must be carried out before painting, in a completely automated sequence. This summary description shows the additional significant advantages of the painting installation according to the present invention.

Apart from the reduced environmental impact, the total absence of special waste, the considerable saving on paint, the new installation is characterised by simple economical functionality and structure, total absence of water disposal systems of painting powders, total absence of compressed air (in its version with airless nozzles), reduction in labour and electrical power, also in consideration of its reduced overall dimensions. For major clarity the description of the invention continues with reference to the enclosed drawing, which is intended for purposes of illustration and not in a limiting sense, whereby fig. 1 is an axonometric schematic view of the installation according to the invention. With reference to this figure, the painting booth (1) of the new installation basically consists in a steel pipe, of the type used in aspirators, whose cross-section is large enough to let the bottoms pass through it.

In the upper part the booth (1) features a longitudinal notch (1a) with seal gaskets, through which a series of bottom-holding hooks (2) moves, pulled by the cyclic chain (3) of a suitable overhead conveying system, so that the bottoms (S) they support can transit inside the booth (1).

The walls of the booth (1) feature a series of nozzles (4) in helicoidal arrangement, so that their sprays do not mutually interfere and, at the same time, each side of the bottom is exposed to the paint sprays. The nozzles (4) are preferably of airless type, that is they operate without the contribution of compressed air, since the paint is nebulized only thanks to the high pressure ensured by a pump (5) that takes the paint from a tank (6) and sends it to the nozzles (4) through a filter (7) and a distribution compartment (8). The painting booth (1) is slightly tilted to favor the flow of the paint to be recovered towards a drain union piece (1 b), located next to one of the booth ends and connected with a pipe (9) to the tank (6).

In order to guarantee the hermetic seal of the painting booth (1), its initial and final sections are closed by double gates (10), whose opening is alternate and obviously synchronized with the passage of the bottoms.

The booth (1) can be used to wash the bottoms before painting them, in order to remove the detachment substances used in the molds to prevent the items from adhering to the walls of the mold, with consequent problems when extracting the piece. In the pre-washing process, the nozzles (4) are fed with suitable detergent or solvent substances - instead of paint - such as acetone or water at 80/90°C. Without exiting the scope of the present invention, an installation assisted by a single conveying chain can be realized, using more booths in a sequence. The booths alternate to drying tunnels and can be used to realize sequences of different operations, such as washing and three-layer painting.

Claims

1) Ecological installation for the painting and/or washing of polyurethane bottoms, characterized in that it comprises a hermetic booth (1 ), in which air is saturated by the solvent used for the paint, whose upper part features a longitudinal notch (1a) with seal gaskets, through which a series of bottom- holding hooks (2) moves, pulled by the cyclic chain (3)of a suitable overhead conveying system; it being provided that the booth is equipped with a series of nozzles (4) in helicoidal arrangement, fed by a pump (5) that takes the liquid to be sprayed from a tank (6) and sends it to the nozzles (4) through a filter (7) and a distribution compartment (8). 2) Installation according to the previous claim, characterized in that the booth (1) is slightly tilted to favor the flow of the paint to be recovered towards a drain union piece (1 b), located next to one of the booth ends and connected with a pipe (9) to the tank (6).

3) Installation according to the previous claims, characterized in that the booth (1) features double gates (10) in its initial and final sections, whose opening is alternate and obviously synchronized with the passage of the bottoms.

4) Installation according to the previous claims, characterized in that the nozzles (4) are fed with air saturated with solvent. 5) Installation according to the previous claims, characterized in that the nozzles (4) are fed with air saturated with solvent taken from the painting booth (1 ).