Kinetic filters, method for cleaning the filters and systems for treating the overspray in painting plants

Abstract

Kinetic filters, method for cleaning the filters and systems for treating the overspray in painting plants A kinetic filter (25) for removing overspray from the air flow in a painting plant comprises elastically deformable elements for allowing easily cleaning and reuse thereof. A method and a system (19) for cleaning the filter and a painting plant (10) are also described.

Description

[0001] Kinetic filters, method for cleaning the filters and systems for treating the overspray in painting plants

[0002] Description

[0003] The present invention relates to a kinetic filter for filtering the overspray in the air flow of a painting plant, which is easier to clean and reusable. The present invention relates also to a method and a system for cleaning the filter and to a painting plant.

[0004] In the technical sector of paint spraying in painting plants (in particular the painting of bodywork parts of motor vehicles) a well-known problem is that of the so-called “overspray”, namely the problem of the atomized paint which is not deposited on the parts to be painted and which must therefore be removed from the painting booth. The removal of the overspray is usually performed by means of a suitable air flow which crosses the booth.

[0005] The air flow evacuated from the booth must, however, be cleaned of the paint before it can be released into the environment or introduced again into the booth.

[0006] For this purpose various systems for separating the overspray from the air extracted from the booth have been proposed. For example, known systems of the electrostatic type, for performing removal using a film of water, with filters suitable for filtering the liquid particles, are known. These systems are generally complex and require a high degree of maintenance owing to the adhesive nature of the paint.

[0007] Powder inerting systems have also been proposed, i.e. systems in which the air flow is conveyed across a filtering system composed of a chamber inside which a suitable powder inerting product (for example calcium carbonate) is blown, said product absorbing the particles of paint and being then intercepted by normal dust filters. Such a system is described for example in US20130122188.

[0008] This system requires, however, a relatively large quantity of powder which must then be disposed of, with high disposal costs. The procurement of the powders is not always easy and may be costly. Moreover, relatively complex techniques are necessary for moving the powder, blowing it in a uniform manner inside the chamber, intercepting it and evacuating it effectively from the air flow after absorption of the paint, moreover preventing the paint-soiled powder from soiling and clogging the filters used to separate it from the air flow conveying it. These filters are costly and require relatively frequent maintenance in order to prevent them from becoming completely blocked up.

[0009] Moreover, the substantially random distribution of the powder inside the chamber may not be sufficient to prevent the paint from adhering to the walls of the chamber and to eliminate securely all the overspray. Also attempts to provide a greater concentration of powder along the path of the air flow have proved to be not entirely satisfactory.

[0010] Systems have also been proposed where the air flow containing the overspray is made to pass through filters of the kinetic type, namely filters made with labyrinths which cause relatively sudden changes in direction of the air crossing them. In this way, the particles of paint which are transported by the air flow and which do not manage to change direction in a correspondingly rapid manner strike the walls of the labyrinth and adhere thereto. The advantage of these filters is that, during use with air flows which contain a liquid overspray, they clog less rapidly the filters with a filtering surface.

[0011] Once the kinetic filters have accumulated a certain amount of paint, they must nevertheless be replaced and the dirty filter must be disposed of. Usually these kinetic filters are therefore made of cardboard and are entirely disposable. The disposal thereof, however, is problematic because the filter is to be regarded as highly polluting special waste owing to the paint which covers the internal walls thereof. The filter is for example incinerated together with the paint in special plants, at a not insignificant cost and with the risk of environmental pollution.

[0012] The general object of the present invention is to provide an innovative kinetic filter which can be easily cleaned and reused. A further object is to provide an innovative method and an innovative system for cleaning the kinetic filter and also a painting plant together therewith.

[0013] In view of these objects the idea which has occurred, according to the invention, is to provide a kinetic filter intended for the removal of overspray in an air flow, comprising a housing containing kinetic filter elements, characterized in that at least the kinetic filter elements are elastically deformable.

[0014] Still according to the invention, the idea which has occurred is to provide a method for cleaning a kinetic filter according to any one of the preceding claims, characterized in that the elastically deformable kinetic filter elements of the kinetic filter are subjected to a mechanical deformation step after hardening of the paint, in order to cause detachment of the hardened paint from the elastically deformable kinetic filter elements.

[0015] Still according to the invention, the idea which has occurred is to provide a system for cleaning a kinetic filter made in accordance with the here mentioned principles of the invention and applying a method according to the here mentioned principles of the invention and comprising a unit for elastic deformation of the kinetic filter elements for the detachment of the paint.

[0016] In order to illustrate more clearly the innovative principles of the present invention and its advantages compared to the prior art, examples of embodiment applying these principles will be described below with the aid of the accompanying drawings. In the drawings:

[0017] - Figure 1 shows a schematic view of a painting plant applying a filter for removal of the overspray according to the invention;

[0018] - Figure 2 shows a schematic view of a system for cleaning the overspray removal filters and applying a method according to the invention;

[0019] - Figures 3, 4 and 5 show schematic views of parts of possible embodiments of filters according to the invention.

[0020] With reference to the figures, Figure 1 shows, denoted generally by 10, a painting plant which produces overspray which must be removed.

[0021] For example, the plant comprises at least one booth 11 for painting objects 12 (for example motor vehicle bodies or parts thereof). The objects to be painted are advantageously transported into the booth 11 by means of a known conveyor system 13, for example an intermittent or continuous conveying line.

[0022] The booth 11 is provided with painting devices or operator units 14 which spray liquid paint onto the surfaces of the object to be painted. Advantageously, the painting devices may be realized in the form of known robotic arms which have spray guns or cups at their ends.

[0023] An air flow is made to pass through the booth 11 in order to remove the overspray from it.

[0024] Advantageously, this may be obtained by means of a grilled floor 15 of the booth 11 through which the air in the booth may be sucked out so as to evacuate the overspray from the chamber. In the ceiling of the booth there are corresponding inlets 16 which are advantageously made with grilles, for the entry of clean air, so as to have a continuous air flow which crosses the booth from the top downwards during the painting operations. Other known systems for circulation and extraction of the air from the booth may however be used. The clean and / or purified air may enter into the booth through one or more ducts 22.

[0025] There is therefore an air flow containing paint overspray to be treated in order to remove the overspray from the air.

[0026] For removal of the overspray, the air flow containing the overspray is sent to at least one unit 17 for removal of the overspray. The unit 17 may be situated for example directly underneath the grilled floor of the booth or may be connected to the air flow containing overspray by means of suitable conveying ducts or passages.

[0027] Suitable known aspirators or fans 21 may also be present along the air flow path (for example at the clean air outlet after the unit 17) in order to move suitably the air flow through the unit 17.

[0028] The air flow, after crossing the overspray removal unit 17 and being cleaned, may be evacuated externally and / or be conveyed back into the booth via the ducts 22.

[0029] The removal unit 17 comprises a chamber 23 which has an inlet which receives the air from which the overspray is to be removed.

[0030] The chamber 23 has, inside it, kinetic filters 25 which are crossed by the air flow which release the overspray onto them. The cleaned air then exits the chamber through an outlet 26. As is known, kinetic filters are made with internal labyrinths for imparting a sudden change in the direction of the air so as to be suitable for intercepting the overspray paint conveyed by the air flow owing to the fact that the paint droplets do not manage to change direction as rapidly as the air flow and therefore strike against the walls of the filter which form the labyrinth of the filter and remain fixed thereto.

[0031] During operation of the painting plant the kinetic filters 25 accumulate overspray paint. Periodically it is therefore necessary to replace the dirty filter with a clean filter. In order to establish when soiling of the filters requires replacement of the latter, it may be simply envisaged periodically replacing them on a time basis (for example depending also on the operating time of the plant). In addition or alternatively a weighing system (for example with load cells) may be provided, this providing an indication when it is required to perform replacement depending on the increase in weight of the filters inside the chamber (and therefore increase in weight of the chamber itself) resulting from accumulation of the paint on the filters.

[0032] As will be clear below, owing to the innovative principles of the present invention, the kinetic filters 25 are made so that they are reusable after cleaning which may be easily performed, instead of being disposable filters as in the prior art.

[0033] When it is considered necessary to replace a filter 25 with a clean filter, the filter or dirty filters 25 to be replaced are extracted from the chamber 23 and, instead of being disposed of, are conveyed along a path 18 towards the cleaning location, which may be inside a specially designed cleaning system 19 situated close to or far from the painting plant, as will become clear below. After cleaning, the filters 25 may be stored for future use or may transported back into a chamber crossed by an air flow to be cleaned (not necessarily in the same painting plant) along a path 20, depending on the needs and the chosen operating mode.

[0034] The transfer of the filters towards the cleaning location and their return inside the chamber may be performed using suitable transfer means both of a manual nature (conveyor carriages and / or containers) and of an automatic or semiautomatic nature (for example conveyor belts, overhead conveyors, etc.).

[0035] According to the principles of the invention, the kinetic filters 25 are made with or comprise kinetic filter elements (for example internal labyrinth walls) which are elastically deformable. The terms “elastic deformation” and “elastically deformable elements” are understood as meaning that, when the elements are deformed, they essentially reassume their original form once the deformation applied to them ceases.

[0036] “Elastically deformable” is understood as meaning here an elastic deformability at least equal to greater than that of the hardened paint, such that the elastic deformation of the elastically deformable elements (performed either continuously or with intermittent deformation release phases) may result in breakage and at least partial detachment of the hardened paint.

[0037] As a result it is possible to obtain kinetic filters which can be cleaned with relative ease, low pollution and limited expenditure of time and energy .

[0038] In order to accelerate the hardening of the paint on the elements to a value at least equal to that required for detachment during the elastic deformation of the kinetic filter elements, it is also possible to apply a heat treatment step. According to this solution, when cleaning of the overspray on these kinetic filter elements is required, the kinetic filter elements are subjected to a heat treatment step for hardening the paint and then to the elastic deformation step in order to cause separation of the hardened paint from the elastically deformable kinetic filter elements.

[0039] In any case, the elastic deformation may comprise also alternate elastic deformation cycles (for example by means of compression of the filter or its parts with a three-dimensional structure) and release of the deformation (release of the compression) acting on the elastically deformed kinetic filter elements.

[0040] The cleaning step by means of elastic deformation may take place at any distance from the painting plant and, if desired, also within the same painting plant.

[0041] The kinetic filter elements are advantageously made using a material which is elastically deformable and preferably has a low wettability compared to the paint so as not to absorb or retain paint inside the material. Preferably, the elastically deformable elements of the kinetic filter are at least superficially made of non- porous and liquid-impermeable material. Again preferably, the kinetic filter elements are made at least superficially of a material which is sufficiently resistant to adhesion of the paint used in the painting booth, so as to facilitate the detachment thereof following the elastic deformation of the kinetic filter elements. Also anti-adhesive treatments may be used (for example by means of suitable liquid or solid coatings of the known art).

[0042] The elastically deformable kinetic filter elements may be advantageously made of a suitable elastic material which may be identical to that of the container and which may also form one piece therewith. The material chosen for the kinetic filter elements must also be sufficiently resistant to the temperature to which they are exposed.

[0043] In particular, if a heat treatment is used to harden the paint on the elements to be cleaned, the kinetic filter elements must withstand without excessive degradation the temperature used in this paint hardening heat treatment. The value of the treatment temperature will depend mainly on the characteristics of the overspray paint and the time which is to be used to achieve the hardening considered sufficient for the paint.

[0044] For example, the chosen temperature may be a paint drying temperature. If the paint is polymerizable the temperature may be chosen to be at least equal to the polymerization temperature of the paint or even higher.

[0045] For paints usually used in the painting plants, for example for painting motor vehicle bodywork or parts thereof, the treatment temperature may be generally a temperature at least of about 80°C or higher, preferably at least 150°C and preferably about 200°C or higher.

[0046] The minimum heat treatment time may also depend on the temperature chosen for the treatment, the characteristics of the specific paint to be cleaned and also the paint thickness on the kinetic filter elements. For example, for paints usually used in painting plants, for example for painting motor vehicle bodywork or parts thereof, with a treatment temperature of between 80°C and 250°C a time of between about 10 minutes and about 60 minutes could be used for example.

[0047] Many materials have the desired characteristics of elastic deformability and low adhesiveness of the paint for allowing detachment thereof and resistance to the desired temperature. The person skilled in the art, on the basis of the description provided here, may choose them depending on the specific circumstances. Materials found to be suitable are for example silicone rubbers with a suitable temperature resistance, stabilized silicone rubbers or other suitable synthetic substances of an elastic type.

[0048] Once the kinetic filter elements are made elastically deformable according to the basic principles of the present invention, their elastic deformation allows rapid cleaning thereof and may be obtained in various ways. For example the kinetic filter elements may be passed between continuous or alternate compression or elastic deformation rollers or surfaces which are varyingly arranged, vibrating systems, etc.

[0049] Figure 2 shows in schematic form a possible example of a cleaning system 19 comprising a unit 28 for elastic deformation of the kinetic filter elements. An automatic or semi-automatic system allows the paint flakes to be more easily retained and avoids risks for human operators.

[0050] The system 19 may also preferably comprise a heating oven 27 arranged upstream of the unit 28 for performing a hardening heat treatment of the paint so as to produce or speed up hardening of the paint. In this case, the heating oven 27 receives the kinetic filter elements 25 to be cleaned and performs the heat treatment at a suitable temperature and for a suitable time, as described above. The oven may also be of the type with through-passage and provided with a transport system (for example a conveyor belt) so that it can be crossed by the kinetic filter elements to be cleaned. The entry and the exit of the elements into / from the oven may in any case be performed also manually or semi-automatically.

[0051] The mechanical treatment unit 28 receives the kinetic filter elements 25 with the hardened paints and performs the elastic deformation of the kinetic filter elements, so as to cause the separation of the paint from the kinetic filter elements.

[0052] The mechanical treatment unit 28 may for example comprise devices 30 for compression or elastic deformation of the filter elements, between which the kinetic filter elements pass so as to be distorted and cause detachment of the hardened paint. These devices 30 may for example be designed with motor- driven rollers. The rollers may for example consist of a certain number and be arranged along differently oriented axes of rotation. In particular, but not exclusively, several rollers may be arranged at right angles to each other. The elastic deformation may take place between oppositely arranged rollers, between rollers and an underlying surface or undulating path, etc.

[0053] Other elastic deformation systems, such as press surfaces, oppositely arranged vibrating surfaces, etc., may in any case be used instead of each other or in addition or in combination with each other.

[0054] The elastic deformation may take place with kinetic filter elements which are moved continuously or stepwise between an inlet and outlet of the mechanical treatment unit 28.

[0055] If necessary, the elastic deformation may be performed alternately with kinetic filter elements which are introduced into the mechanical treatment unit and remain therefore for a sufficiently long time to be elastically deformed in order to cause the detachment of the paint and then extracted at the end of treatment.

[0056] The elastic deformation may be advantageously applied in several stages, namely with elastic deformation phases alternating with elastic release phases in order to facilitate the detachment of the paint flakes from the surface of the kinetic filter elements. This may be obtained both by operating intermittently the compression or deformation devices 30 and by the spaced arrangement of several compression or deformation devices 30 or parts thereof so that the elements pass through successive elastic deformation zones and elastic nondeformation zones.

[0057] The mechanical treatment unit advantageously comprises a collection zone (for example a suitable container) inside which the paint detached from the kinetic filter elements falls. For example, Figure 2 shows in schematic form a container 31 situated underneath the operating zone of the devices 30.

[0058] Where considered useful or necessary, the kinetic filter elements, during or after the mechanical treatment step by means of elastic deformation, may also be subjected to an air flow for the removal of any flakes of paint left above or between the treated kinetic filter elements. Known vibration and / or shaking and / or blowing systems may also be provided, these being able to act also during or after the aforementioned mechanical treatment step. For this purpose, shaking, vibration, centrifuging or other types of devices 32 may be provided for example for this purpose, these consisting for example of vibrating surfaces or supports, rotating drums and / or blowing devices.

[0059] The mechanical treatment step by means of elastic deformation may last a predetermined time considered sufficient to perform the desired cleaning of the kinetic filter elements. The desired degree of cleaning obtained may also be detected by means of suitable known optical sensors or other known automatic systems, so as to ensure the correct treatment time which is required and sufficient for cleaning. For example, the filters during treatment may undergo weighing so as to determine stoppage of the cleaning process when the weight of the filter falls below a predetermined value which is defined as corresponding to a suitably degree of cleaning, i.e. loss of paint. For example, said loss may also be established as being the difference between the weight of the soiled incoming filter before cleaning and the filter during cleaning, so that the process ends when the difference in weight reaches a predetermined value.

[0060] At the end of the mechanical treatment step, the kinetic filter elements may be used again for removal of the overspray, when required. In the case where the filter has been divided into parts, separating from each other the kinetic filter elements which form it in order to facilitate the cleaning treatment according to the invention, these parts may be reassembled to form the complete filter, before it is used again.

[0061] Figure 3 shows a possible embodiment of a filter 25. The filter may comprise an external structure of side walls 33 with an entry end 34 for the air flow with overspray and an opposite end 35 for exit of the purified air after the passage through the filter. The external structure 33 contains, inside it, filter elements consisting of internal walls 36 which form labyrinths of the kinetic filter.

[0062] The entire filter 25 may be elastically deformable and form the entire deformable filter element or only the internal walls 36 may be made elastically deformable. In this second case the elastically deformable kinetic filter elements will be extracted from the external structure before they are mechanically deformed for detachment of the paint. Also in the case of a filter which is entirely elastically deformable, it may be decided to construct it with parts which are separable or can be opened in order to facilitate the removal of the hardened paint from the filter elements, which is detached owing to the elastic deformation.

[0063] Figure 4 shows, partially, a box-shaped housing 37 with grilles at the opposite ends 38, 39, arranged at the inlet 34 and outlet 35 for the air which crosses the filter, whereby said housing may form the external housing of the filter 35 or may be a housing containing the filter 35.

[0064] The box-shaped housing 37 may also made so as to be non elastically deformable or less elastically deformable than the filter or the filter elements which are inserted inside it so as to provide the filter with a greater rigidity during use or transport or handling.

[0065] The box-shaped housing 37 may for example be made of rigid plastic material and have at least a wall which can be opened for the extraction and the introduction of the kinetic filter elements.

[0066] As shown by way of example in Figure 5, the kinetic filter may also be designed in a modular form, namely with several kinetic filters 25 as described above assembled to form a larger filter, depending on the requirements for filtering the air containing overspray in a plant.

[0067] At this point it is clear how the predefined objects have been achieved. The kinetic filter elements which are made elastically deformable may be easily cleaned overcoming the many problems of the prior art. The method according to the invention is thus able to ensure efficient and effective treatment of the air flow containing overspray with minimum effort, low power consumption and low environmental impact

[0068] Moreover, the paint recovered in the form of flakes may be easily treated, transported and / or recycled.

[0069] Obviously the description given above of embodiments applying the innovative principles of the present invention is provided by way of example of these innovative principles and must therefore not be regarded as limiting the scope of the rights claimed herein. For example, the source of air with overspray to be removed may be different from the painting booth shown here by way of example, there may be several units 17 and / or cleaning systems 19 for the same source (for example for the same booth) so as to treat air flows which are divided up, or on the contrary there may be single unit 17 and / or a single cleaning system 19 which may serve several sources or booths. A single cleaning system 19 may also serve several overspray removal units of the same source or booth or of several sources or booths.

[0070] The booth and / or the plant may also comprise other known parts, not shown here and not forming the subject of the invention, for example for conditioning or filtering the air entering the booth or plant, transport systems and additional painting devices, etc. The kinetic filters according to the invention may also be followed by further filters, for example bag filters or the like, so as to intercept any impurities which are still present in the air and which may pass beyond the kinetic filter, as may be easily imagined by the person skilled in the art. There may also be provided known devices or partitions for blocking or deviating the air flows should it be required to replace the filters or some of the filters while the painting plant is in operation.

Claims

Claims1. A kinetic filter (25) intended for the removal of overspray in an air flow, comprising a housing (33, 37) containing kinetic filter elements, characterized in that at least the kinetic filter elements are elastically deformable.

2. Kinetic filter according to the preceding claim, characterized in that the housing (33, 37) is more rigid than the elastically deformable kinetic filter elements and can be opened for extraction of the elastically deformable kinetic filter elements.

3. Kinetic filter according to claim 1 , characterized in that the elastically deformable kinetic filter elements are made of silicone rubber or stabilized silicone rubbers.

4. Kinetic filter according to claim 1 , characterized in that the kinetic filter elements are made of a material resistant to a temperature of at least about 80°C or higher and, preferably, of at least about 150°C or 200°C or higher.

5. Method for cleaning a kinetic filter according to any one of the preceding claims, characterized in that the elastically deformable kinetic filter elements (25) of the kinetic filter are subjected to a mechanical deformation step after hardening of the paint, in order to cause detachment of the hardened paint from the elastically deformable kinetic filter elements (25).

6. Method according to claim 5, characterized in that the mechanical deformation step comprises alternating cycles of deformation and deformation release of the kinetic filter elements (25).

7. Method according to claim 6, characterized in that it comprises the further step, prior to the mechanical deformation step, of subjecting the kinetic filter elements (25) to a heat treatment for hardening the paint.

8. Method according to claim 7, characterized in that the heat treatment step takes place at a temperature selected to allow drying of the paint or, if the paint is polymerizable, at a temperature selected to be at least equal to or higher than the polymerization temperature of the paint.

9. Method according to claim 8, characterized in that the temperature is at least about 80°C or higher and, preferably, at least about 150°C or 200°C or higher and the kinetic filter elements (25) are made of a material resistant to this temperature.

10. Method according to claim 5, characterized in that the kinetic filter elements (25) are subjected, after or during the elastic deformation, to an air flow and / or to shaking and / or vibration and / or centrifuging to facilitate the removal of the hardened paint from the kinetic filter elements (25).

11. Method according to any one of claims from 5 to 10, characterized in that the kinetic filter, during use, is arranged in a chamber (23) crossed by the air with overspray and, when the filter needs to be replaced, it is extracted from the chamber and sent to the cleaning step to then be used again if necessary.

12. System for cleaning a kinetic filter made according to any one of claims 1 to 4 and applying a method according to any one of claims 5 to 11 , characterized in that it comprises a unit (28) for elastic deformation of the kinetic filter elements (25) for the detachment of the paint.

13. Cleaning system according to claim 12, characterized in that it comprises an oven (27) for the paint hardening heat treatment, arranged upstream of the unit for elastic deformation of the kinetic filter elements (25).

14. Cleaning system according to claim 12, characterized in that the unit (28) for elastic deformation of the kinetic filter elements (25) comprises mechanicalcompression devices (30) between which the kinetic filter elements to be cleaned of the paint pass.

15. Cleaning system according to claim 12, characterized in that it comprises, within or downstream of the unit (28), blowing and / or shaking and / or vibrating and / or centrifuging devices (32) for removing flakes of paint from the kinetic filter elements (25).

16. Painting plant (10) comprising a painting booth (11 ) which is crossed by an air flow for the evacuation of overspray from the booth, characterized in that it comprises at least one overspray interception chamber (23) containing a kinetic filter (25) according to any one of claims 1 to 4 to be crossed by an air flow exiting the booth and associated with a cleaning system (19) according to any one of claims 12 to 15, so as to allow extraction of the kinetic filter (25), cleaning thereof in the cleaning system (19) and use thereof again in the overspray interception chamber (23).

17. Painting plant according to claim 16, characterized in that it comprises a first outward path (18) between the chamber (23) and the cleaning system (19) and a second return path (20) between the cleaning system (19) and the chamber

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