TECHNICAL FIELD

This invention relates to a vertical booth for powder painting.

It is a booth for powder painting parts which move in succession along a line which passes through a unit for powder spraying which is symmetrical in all its components, giving important advantages, relative to the traditional solutions, from the point of view of uniformity in application of the powder.

According to the invention, the powder painting booth gives a high efficiency due to the particular profile of the booth and by the guns located in the four sides of the profiles which allow the surfaces to be processed to the maximum extent with the minimum overspray and with a very precise management in the dispensing of the paint powders, with a limitation in the waste and with a clear overall saving.

This invention can be advantageously applied in the sector of systems for synthetic resin-based powder painting and subsequent polymerisation by passing through a controlled temperature oven.

BACKGROUND ART

It is known that powder painting is a process with which it is possible to coat metal surfaces with an organic film, for decorative purposes and/or protection against corrosion and aggressive agents.

It is also known that the parts being processed are coated with synthetic resin-based powder paint, which adheres due to the electrostatic effect, and then pass through an oven in which the paint in a first step melts and in a second step polymerises giving the consistency of an adherent layer.

Powder painting is generally performed in systems which, if they are of the continuous type, involve the use of an aerial chain transport belt where the parts to be painted are hung, usually sheets, pipes and profiles or elongate parts of various types, which advance progressively passing through spraying booths with electrostatic, or triboelectric, guns, an oven for polymerisation and a system for washing the parts.

It is also known that the colour change is particularly critical in powder painting systems, especially in the continuous cycle systems, since it is necessary that in these steps that the powder knocked down by the ventilation air of the booths is recovered by the ducts on which it normally adheres, so as to avoid the possibility of mixing between the previous colour and the next colour.

In cases in which it is necessary to changing the paint being processed it is essential to clean extremely carefully not only the spraying apparatuses and the booths and their bases, but also the entire air circuit and the powder circulation circuit. Unlike the old booths made of sheet iron, modern powder paint booths are made of dielectric material such as fibreglass resin and this allows a fast cleaning of the walls.

To overcome any problems regarding the change of colour, the more modern versions of paint booths forming part of the continuous cycle systems for powder painting are. eguipped with means for automatic removal of the colour which fall within the self-cleaning types of booths .

They are booths substantially parallelepiped in shape with a height greater than that of the parts being processed which move in a suspended fashion advancing in a vertical position, open at the front for introducing parts during their painting and equipped with base walls, bottom walls and two opposite lateral walls, which, in order to avoid having to clean them at every colour change, may be covered with disposable sheets, or slidable belts on rollers intercepted by special scrapers which make it possible to keep constantly clean the inside of the wall.

The problem found with the use of such systems relates to the so-called "overspray", which means a surplus of paint sprayed that does not deposit on the surface to be painted.

Due to its very nature, the overspray does not bring any advantage to the coating process; in fact, it is a burden since it increases the quantity of material which must be disposed of, increases the load on the filters, soils the booth and increases the atmospheric emission levels: its reduction, therefore, can only represent a saving .

Moreover, the overspray which deposits on the parts already painted has an adverse affect on the quality of the coating process, by reducing the brightness of the surface and contributing to the "orange peel" effect.

In order to limit the effect of the overspray the traditional solutions provide for the increase in the air flow at the nozzles in the paint booth, which however has an even more deleterious effect on the final result, as it prevents the pigmented powder particles from adhering to the surfaces, causing a further increase in the guantity of paint powder which must be disposed of and not recovered, with a conseguent increase in the waste of paint powder and all the above-mentioned problems.

DESCRIPTION OF THE INVENTION

The aim of this invention is to provide a vertical booth for powder painting which is eguipped with means designed to create a slowing down of the air in the spraying booth, thereby creating a condition which can eliminate or at least reduce the drawbacks described above .

The invention aims in particular to provide a booth for powder painting in which the slowing down of the air, allowed by a suitable shaping of the booth and in particular by a suitable widening of the spraying compartment in which the objects to be painted advance hung on the transport line, associated with a particular arrangement of the spraying nozzles, gives more time for the powder to be attracted by the profiles by the electrostatic effect, thus achieving a consequent reduction in the overspray effect.

This is achieved by means of a powder paint booth, which is positioned along a line for transferring the parts being processed, whose features are described in the main claim.

The dependent claims of the solution according to this invention describe advantageous embodiments of the invention .

The main advantages of this solution relate to the fact that the distribution of the pigmented powder on the part being processed is much more homogeneous and the effect is limited, thereby achieving a final result with a higher quality and above all a better dosing and a saving of the paint powder.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become clear on reading the description given below of one embodiment, provided as a non-limiting example, with the help of the accompanying drawings, in which:

Figure 1 is a schematic perspective view of a paint booth according to the invention located along a painting system with parts to be painted hung along an advancement line;

Figure 2 is a schematic plan view of the paint booth;

Figure 3 is a schematic plan view of a detail of the paint booth.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

With reference to the accompanying drawings, and initially in particular to Figure 2, the numeral 10 indicates generally a booth for spraying synthetic resins in its entirety which is located along an aerial transport line of the part 11 being processed hung on a chain 12.

The aerial chain transport line 12, which is located in the upper part of the powder painting system, allows the feeding at a controlled speed of the parts being processed, consisting of extruded bars or profiles of various types and length, through various processing stations .

The paint booth 10, in which the synthetic resin- based pigment is sprayed through pneumatic guns 13 allowing adhesion of the powders on the parts being processed by the electrostatic effect, is located between a pre-treatment station, where the degreasing, washing and drying of the parts is performed, and a polymerisation oven.

The distinctive feature of the invention refers to the features of the paint booth 10, which is designed to optimise the spraying process and to improve the adhesion of the pigmented powder, limiting as much as possible the overspray effect with the consequent result of improving the dosing and achieving a saving of the painting powder.

As shown in Figure 2 and in detail in Figure 3, the paint booth 10, which is crossed centrally by the line 11 for advancing the parts hung on the chain 12, has on the inside of it self-cleaning walls 14 which are positioned in pairs which face each other, where each of the two walls which form each pair is inclined symmetrically relative to the other on a vertical axis relative to the feed line, forming an arrangement which is substantially rhomboidal consisting of pairs of inclined walls which face each other.

At the inlet zone A and the outlet zone B of the paint booth 10 there are groups of spray guns 13 which also have an inclined arrangement formed by four groups of guns arranged in symmetrical pairs which similarly face the self-cleaning walls.

Moreover, between each pair of inclined walls 14, which are slightly and mutually separated by a slit, there is a respective aspiration line 15 consisting of vertical pipes connected to an air duct, which is not illustrated, which allows suction of the powders which are collected by a separating cyclone 16 to which the air duct is in turn connected.

The substantially rhomboidal and symmetrical arrangement of the self-cleaning walls passed through centrally by the line for advancing parts to be painted allows, close to the inlet zone A and the outlet zone B, for there to be two narrower sectors of the booth which widens centrally in the proximity of the spraying zone, and this determines a widening of the central section of the booth with a slowing down of the suction air entering from the outside.

This slowing down of the suction air makes it possible for the colouring powder sprayed to remain longer in suspension inside the booth, giving more time for the deposit of the powder on the profiles due to the effect of the above-mentioned electrostatic attraction, which also allows a reduction in the overspray.

It should be noted that according to the prior art the speed of the air suction is increased in the zone of applying the powder and precisely for this reason the powder was removed without giving it time to adhere to the profile, whilst with the solution according to this invention the slowing down of the air speed allows a greater length of time of permanence of the pigmented powders, and a consequent better adhesion of them on the surfaces to be processed.

The guns 13 for spraying the pigmented powder are positioned in perfect symmetry on four sides of the booth and are moved by four robots located inside the booth itself, in proximity of the four self-cleaning walls 14.

In this way it is possible to coat with the painting all the corners of the profiles to obtain an optimum coating . The profiles hanging on the aerial transport line pass in a straight sector inside the self-cleaning walls 14, and it is precisely the linearity together with the symmetry which offer the important advantage of a perfect distribution on the parts during the application of the powder .

A further advantage offered by the solution according to the invention relates to the possibility to paint very large parts and sheets which are impossible to be treat with the use of the traditional solutions.

The symmetrical arrangement of all the components comprising the self-cleaning walls 14 and the spray guns 13 which are located inside the booth results in important advantages in terms of uniformity in application of the powder, and a high efficiency given on the one hand by the sections which widen centrally and on the other hand by the guns located on the four sides of the profiles, with the a consequent reduction to a minimum of the overspray effect.

The solution described also makes it possible to achieve another important advantage compared with the prior art solutions, which is that of preventing the rotation of the parts the during injection of the powders, an operation which was previously necessary for the purpose of a correct distribution.

The invention as described above refers to a preferred embodiment. It is nevertheless clear that the invention is susceptible to numerous variations falling within the scope of the disclosure, in the context of technical equivalents.