CN112423898B - Coating equipment with overspray removal system, removal method and device - Google Patents

Abstract

A liquid paint application apparatus (10) comprising: a coating chamber (11) in which the liquid coating material is sprayed; and means for drawing an air flow from the chamber (11) to the filter unit (17) to remove overspray particles from the air flow. The apparatus further comprises a microwave device (22), the microwave device (22) treating the air stream drawn from the chamber (11). This ensures effective elimination of overspray. A purging method and a purging device are also described.

Description

Coating equipment with overspray removal system, removal method and device

The invention relates to a painting installation provided with an innovative system for removing overspray. The invention also relates to a method and a device for removing overspray.

In spray coating technology, the problem of so-called "overspray" is known, i.e. excess coating material particles do not deposit on the object to be coated and must therefore be removed from the coating booth. The removal of overspray is typically performed by a suitable air flow through the chamber.

Thus, the air stream exhausted from the chamber is contaminated with coating particles and must be cleaned before being released into the environment or reintroduced back into the chamber.

For this purpose, various removal systems have been proposed, for example of the electrostatic type or with integrated filters suitable for filtering liquid particles. These systems are often complex and require a high degree of maintenance due to the high adhesion of the coating.

Systems are known for eliminating overspray in which a continuously circulating stream of water is used to capture paint particles present in an air stream.

The water contaminated with the paint particles must be purified before being reintroduced into the booth or else disposed of.

This overspray removal system, although widely used, is not without drawbacks, since it requires dedicated labour for water purification operations; furthermore, the management of the chamber with air recirculation is particularly expensive from an energy point of view, since the air must be reconditioned before being reintroduced into the chamber, where it passes through the stream of water and is therefore subject to variations in its temperature and humidity conditions.

Systems for eliminating overspray by powder inerting have also been proposed, in which a stream of air is conveyed through a filtering system consisting of a chamber into which a suitable powder inerting product (for example calcium carbonate) is blown, said powder absorbing the coating particles and then being intercepted by a conventional powder filter.

The advantage of this system is that it does not change the temperature and humidity conditions of the air and thus makes recirculation of the air in the room more cost-effective.

However, this system requires a relatively large amount of powder, which must then be processed, resulting in high processing costs. Furthermore, the procurement of powders is not always easy and may involve more costs.

Furthermore, relatively complex techniques are required to move the mass of powder, blow the powder into the chamber in a uniform manner, intercept the powder and efficiently expel it from the air stream after absorbing the coating.

The filter itself is costly and requires relatively frequent maintenance to prevent complete clogging of the filter.

Furthermore, the substantially random distribution of powder within the chamber may not be sufficient to fully neutralize the overspray and prevent the coating from adhering to the chamber walls.

Other overspray removal systems are also known in which the air stream is forced to travel along a path of abrupt change in direction, so that paint particles (heavier, non-redirecting-prone paint particles) eventually strike and adhere to the paper filter along which they encounter their path.

However, in order to eliminate all the paint particles present in the air stream, a large number of filters arranged in succession are required. Furthermore, the system requires continuous monitoring of the status of the filters, maintenance and their disposal, which are expensive operations.

A general object of the present invention is to provide a paint booth with an overspray removal system and an overspray removal method which overcome the disadvantages mentioned above with reference to the prior art.

It is another object of the present invention to achieve effective elimination of overspray (or paint particles).

A further object is to ensure less maintenance, lower management and operating costs and ultimately fewer disposal problems than known systems.

In view of these objects, the idea according to the invention is to provide a liquid paint application apparatus as claimed in claim 1 and a device for removing overspray of liquid paint from an air flow as claimed in claim 15.

Another idea of the invention is to provide a method for removing overspray from an air flow discharged from a chamber in a liquid paint application installation as claimed in claim 10.

In order to illustrate more clearly the innovative principles of the present invention and its advantages compared with the prior art, an example of an embodiment applying these principles will be described below with the aid of the accompanying drawings. In the drawings:

fig. 1 shows a schematic front view of a first embodiment of a paint booth applying the principles of the present invention;

fig. 2 shows a schematic front view of a second embodiment of a paint booth applying the principles of the present invention;

fig. 3 shows a schematic front view of a third exemplary embodiment of a painting booth applying the principles of the invention.

Referring to the drawings, FIG. 1 shows a first embodiment of a coating installation according to the invention, generally designated 10.

The apparatus 10 includes a paint booth 11 for painting an object 12 (e.g., a motor vehicle compartment). The objects 12 to be painted are advantageously transported into the painting booth 11 by means of known conveyor belts 13, for example intermittent or continuous conveyor lines.

The booth 11 contains an automatic or manual painting device 14, which painting device 14, when activated, sprays liquid paint onto the surface of the object to be painted. Advantageously, the painting device 14 can be realized in the form of a known mechanical arm provided at its end with a spray gun or a spray cup.

The air flow passes through the chamber 11 so that overspray is removed from the chamber 11 by an air flow extraction device, such as that indicated at 18. These means, for example comprising a fan or a suction unit, can be implemented in various ways, as will be apparent per se to the person skilled in the art.

Advantageously, the extraction is performed through the floor 15 of the chamber 11, consisting of a grille through which the air in the chamber is extracted in order to expel the overspray from the chamber.

The ceiling of the booth 11 is therefore advantageously formed with a corresponding air intake 16, the air intake 16 also being advantageously provided with a grille and a filter in order to have a continuous air flow vertically through the booth from the top downwards during the painting operation.

The air stream leaving the chamber 11 contains overspray in the form of excess paint particles and is conveyed to a removal device which may comprise a filter unit 17.

Suitable suction units or fans 18 present along the air flow path can be formed or included in the extraction device in order to move the air flow appropriately towards the filter unit 17, the cleaned air leaving the filter unit 17 and being discharged to the outside through a duct 19 and/or being conveyed back to the ceiling of the chamber through a duct 20.

The air supply system 21 may have a related known regulating system with the possibility of recirculating or completely renewing the air.

The apparatus according to the invention comprises means for removing overspray which also use microwaves.

In particular, along the transport path between the chamber 11 and the filtering unit 17, the air flow is subjected to the action of the microwave device 22, so as to at least reduce the adherence of the particles.

In particular, the preferred microwave device 22 includes at least one microwave emitter 221, the microwave emitter 221 being capable of suitably irradiating a stream of air for an exposure time sufficient to at least partially dry the overspray particles.

Advantageously, for the purposes of the present invention, the period of time during which the air stream comprising overspray particles is exposed may vary between 0.5 and 4 seconds.

The microwave generator or emitter per se is well known to the person skilled in the art and is therefore not further described or shown here.

The at least one microwave emitter 221 may be selected from known microwave generating devices, such as solid state devices or vacuum tubes.

The at least one microwave emitter 221 is preferably selected to emit electromagnetic radiation in the range of 2450MHz +/-50 MHz.

The transmitting power of the microwave emitter 221 will also depend on the amount of air to be treated per unit time.

Advantageously, for the purposes of the present invention, at least one microwave emitter 221 may emit an intensity of between 2 and 5mW/cm ² Electromagnetic waves in between.

Advantageously, the apparatus 10 can also be provided with a plurality of microwave emitters 221, these microwave emitters 221 being arranged in succession along the path for conveying the air flow from the chamber 11 to the filtering unit 17. For example, as can be seen in fig. 1, a plurality of emitters 221 may be arranged along a vertical portion of the apparatus 10 downstream of the paint booth 11, for example within the chamber 24 of the duct 26 for conveying the air flow from the floor of the paint booth 11 to the filter unit 17.

The apparatus 10 may also be provided with a plurality of microwave emitters 221, the microwave emitters 221 being arranged transversely in parallel with respect to the path for conveying the air flow from the floor 15 to the filtering unit 17. For example, as can be seen in fig. 1 and 2, the microwave emitters 221 may be disposed on both sides of the air stream and/or spaced apart from each other in order to better illuminate the air stream.

In accordance with the principles of the present invention, all air streams carrying overspray may be irradiated by microwaves and, thus, as the coating particles are conveyed towards the filter unit 17, the coating particles may be at least superficially dried before they contact and adhere to the interior of the apparatus 10 (e.g., to the walls of the conveying chamber 24).

Therefore, according to the invention, the filter unit 17 has to handle an air stream in which coating particles which are no longer or less adherent are dispersed.

The filtration unit 17 may for example comprise one or more conventional solid particle filters 171 (depending on the desired degree of filtration), such as bag filters, cartridge filters, plate filters or rigid membrane filters, depending on the desired separation efficiency of the system.

According to a preferred configuration, as shown in fig. 1, the filtering unit 17 has 171 filters through which the air flow passes in the vertical direction.

Thus, the hopper 172 may advantageously be located below the filter 171, such that dried paint particles fall through the hopper 172 into the storage container 23.

The cleaning of the filter with the reverse flow of the compressed air may be performed cyclically so that the particles intercepted by the filter 171 fall down.

If the overspray particles are still partly adherent after the microwave treatment, the powder overspray removal system can be used again, for example by introducing the powder into the air flow which reaches the filter unit 17.

The use of powders is in any case limited compared to the prior art due to the reduced adhesion of the microwaved overspray.

In accordance with the principles of the present invention, the air flow must in any case be separated from a smaller number of particles, and therefore the amount of waste of the apparatus 10 is smaller. It is also advantageous that the waste can be reused directly for other applications (e.g. as a filling material).

Various delivery systems may be provided to deliver the air stream contaminated with coating particles from the chamber 11 to the filter unit 17.

The conveying system may comprise, for example, at least one conveyor 25 connected to the area below the grate floor 15 and a discharge pipe 26 connected to the air flow filter unit 17.

Advantageously, at least one conveyor 25 has the form of an inverted pyramid.

Further, the inner wall of at least one conveyor 25 may be coated with a known anti-adhesive material.

For example, as shown in fig. 1, the apparatus 10 may be provided with a single conveyor 25 covering the entire grid floor 15 of the paint booth 11.

On the other hand, fig. 2 shows an alternative embodiment with a plurality of conveyors 25 below the grid floor 15. For purposes of clarity, similar elements in the various embodiments will be identified with the same reference numbers.

Advantageously, at least one microwave emitter 221 is arranged in the region of at least one conveyor 25.

The apparatus 10 may also be provided with an electromagnetic wave shield (faraday cage), not shown, to prevent microwaves from escaping from the apparatus.

Advantageously, the at least one microwave emitter 221 is suitably shielded by a faraday cage.

As shown in dashed lines in fig. 1, the emitter 221 may also be placed along a narrow portion or duct for conveying the air flow to the filtering unit 17, or even directly inside the filtering device 17 itself.

Fig. 3 shows another possible variant of the device 10 according to the invention. In this variant, the air flow with overspray from the coating booth 11 through the grille floor 15 is guided into a conveying chamber 24, in which conveying chamber 24 a conveyor partition 25 guides the air flow through the microwave device 22. These microwave devices 22 comprise a chamber 223, which chamber 223 is advantageously integrated in a chamber below the coating booth 11, and the microwaves are acted upon in this chamber 223 by a microwave generator 221. The generators 221 are advantageously placed on opposite side walls of the chamber so as to impinge the air flow with microwaves transversely to the air flow.

The chamber 223 has an inlet and an outlet for the air flow, which are advantageously located on opposite sides of the chamber. This opposite side is advantageously delimited by a screen 224, 225 of a type known per se (for example a suitable metal grid), the screen 224, 225 allowing the passage of overspray air but preventing the escape of microwaves of dangerous intensity.

After passing through the chamber 223, the air flow with the overspray at least partially dried by microwaves is conveyed to the duct 26 in order to reach the filter unit 17.

The remaining components of the device may be similar to those described above. The arrangement in fig. 3 is particularly compact and efficient.

So far it is clear how the predefined objects are implemented.

The device obtained according to the invention allows to implement an efficient method for removing overspray while limiting the complexity of the removal system.

The system according to the invention allows the plant to reduce the number of machine maintenance stoppages.

Furthermore, the cleaning operations required are reduced, since overspray particles after microwave treatment are less likely to adhere to the interior of the apparatus. Over time, this also leads to better wear of the equipment parts (e.g. conveyor) over time, so that cleaning with abrasive products is not necessary.

The waste will be dry, in the least amount, and can also be recycled, thus constituting an added value rather than a disposal cost.

It is evident that the above description of an embodiment applying the innovative principles of the present invention is given by way of example of such innovative principles and must therefore not be considered as limiting the scope of the claims claimed herein.

For example, the conveyor may be in direct communication with the filtration unit, or an additional connection system may be provided.

The device according to the invention for removing overspray from an air stream of liquid coating material using at least one microwave emitter and possibly a subsequent filter device can of course also be incorporated in coating installations other than those illustrated here.

Claims (15)

1. A liquid paint application apparatus (10) comprising:

-a painting booth (11) in which the liquid paint is sprayed;

-a filtering unit (17);

-means (18) for drawing an air flow from said chamber (11) towards said filtering unit (17) to remove overspray from said air flow,

a conveying path for conveying the air flow from the chamber (11) to the filtering unit (17);

characterized in that the filtering unit (17) comprises one or more conventional solid particle filters (171) and in that a microwave device (22) is placed in the conveying path before the filtering unit (17), the microwave device (22) treating the air flow extracted from the chamber (11) so as to at least reduce the adherence of overspray before it reaches the filtering unit (17).

2. The apparatus (10) according to claim 1, wherein said microwave device (22) comprises at least one microwave emitter (221).

3. The apparatus (10) according to claim 2, wherein said microwave device (22) comprises a microwave emitter (221), said microwave emitter (221) being arranged in succession along a path for conveying said air flow from said chamber (11) to said filtering unit (17).

4. The plant (10), as claimed in claim 2, characterized in that said microwave means (22) comprise a microwave emitter (221), the microwave emitter (221) being arranged transversely in parallel with respect to the path for conveying said flow from said chamber (11) to said filtering unit (17).

5. The apparatus (10) according to any one of claims 2-4, wherein the microwave device (22) emits electromagnetic radiation in the range of 2450MHz +/-50 MHz.

6. The apparatus (10) according to any one of claims 2 to 4, characterized in that said microwave means (22) emit an intensity of between 2 and 5mW/cm ² Electromagnetic radiation in between.

7. Device (10) according to any one of claims 2-4, characterized in that the device (10) is provided with a shield designed to prevent the escape of microwaves.

8. The plant (10) according to any one of claims 1 to 4, characterized in that said chamber (11) comprises a grille floor (15) and at least one conveyor (25), said grille floor (15) being intended to discharge said air flow towards said filtering unit (17), said conveyor (25) having an inlet arranged near and below said grille floor (15).

9. The plant (10) according to claim 8, characterized in that said microwave device (22) is located in the region of said at least one conveyor (25).

10. A method for purging overspray from an air stream exhausted from a chamber in a liquid coating material dispensing apparatus, comprising the steps of:

-treating the air stream with microwaves, thereby at least reducing the adherence of overspray; and

-subsequently filtering the air stream containing overspray with a unit (17) for filtering the overspray in the air stream after the air stream has been subjected to microwave treatment.

11. The method of claim 10, wherein the microwave frequency is in the range of 2450MHz +/-50 MHz.

12. Method according to claim 10, characterized in that the intensity of the microwaves is between 2 and 5mW/cm ² In the meantime.

13. The method of claim 10, wherein after the microwave treatment, the air stream is passed through a powder system to remove the overspray.

14. The method of claim 10, wherein the microwave treatment is performed until at least surface drying of the overspray particles occurs.

15. The method according to claim 10, characterized in that the method comprises using one device comprising an overspray air flow path along which there is at least one microwave emitter (221) for at least partially drying the overspray and a filter unit (17) for filtering the overspray.

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