Power filter, method for cleaning a filter and system for treating overspray in a coating

Abstract

The invention relates to a power filter, a method for cleaning a filter and a system for treating overspray in coating equipment. A power filter (25) for removing overspray from a gas stream in a coating installation comprises elastically deformable elements to allow it to be easily cleaned and reused. Methods and systems (19) for cleaning filters and coating apparatuses (10) are also described.

Description

[0001] The present invention relates to a dynamic filter for filtering overspray in the air flow of a painting installation, which is easier to clean and reusable. The present invention also relates to a method and a system for cleaning the filter and to a painting installation.

[0002] In the field of spraying techniques of painting installations (in particular for painting the body parts of motor vehicles), a well-known problem is the so-called "overspray", i.e. the problem that atomized paint does not deposit on the part to be painted and must therefore be removed from the painting booth. The removal of overspray is usually carried out by means of a suitable air flow through the booth.

[0003] However, the air flow discharged from the booth must be freed of paint before it can be released into the environment or re-introduced into the booth.

[0004] For this purpose, various systems have been proposed for separating overspray from the air discharged from the booth. For example, electrostatic type known systems for removal using a water film are known, which have filters suitable for filtering liquid particles. These systems are generally complex and, due to the high adhesiveness of the paint, require maintenance.

[0005] Powder inerting systems have also been proposed, i.e. systems in which the air flow is conveyed through a filtering system consisting of chambers, into which a suitable powder inerting product (such as calcium carbonate) is blown, which product absorbs the paint particles and is then intercepted by a normal dust filter. Such a system is described, for example, in US20130122188.

[0006] However, this system requires a relatively large amount of powder, which then has to be processed, resulting in high processing costs. The procurement of the powder is not always easy and can be expensive. In addition, relatively complex techniques are required to move the powder, blow it into the chambers in a uniform manner, intercept it after it has absorbed the paint and effectively discharge it from the air flow, and furthermore to prevent the powder contaminated with paint from soiling and clogging the filter for separating it from the air flow conveying it. These filters are costly and require relatively frequent maintenance to prevent the filter from becoming completely clogged.

[0007] In addition, the substantially random distribution of the powder in the chambers may not be sufficient to prevent the paint from adhering to the walls of the chambers and reliably eliminating all overspray. Furthermore, attempts to provide a higher concentration of powder along the air flow path have proven not to be entirely satisfactory.

[0008] There has also been proposed such a system in which an air stream containing overspray is passed through a filter of dynamic type, i.e., a filter made of a labyrinth, which causes a relatively sudden change in the direction of the air passing through them. In this way, paint particles transported by the air stream and unable to change direction in a corresponding rapid manner impinge on the walls of the labyrinth and adhere to the walls of the labyrinth. The advantage of these filters is that, during use together with an air stream containing liquid overspray, they do not clog the filter with a filtering surface too quickly.

[0009] Once the dynamic filters have accumulated a certain amount of paint, they still have to be replaced and the dirty filters have to be disposed of. Therefore, these dynamic filters are usually made of cardboard and are completely disposable. However, their disposal is problematic because the filters are considered special waste with high pollution due to the paint covering their inner walls. The filters are, for example, incinerated together with the paint in special equipment, at no small cost, and there is a risk of environmental pollution.

[0010] The general object of the present invention is to provide an innovative dynamic filter that can be easily cleaned and reused. Another object is to provide an innovative method and an innovative system for cleaning a dynamic filter, as well as a painting device therewith.

[0011] In view of these objects, according to the present invention, the idea that has emerged is to provide a dynamic filter for removing overspray from an air stream, the dynamic filter comprising a housing containing a dynamic filter element, characterized in that at least the dynamic filter element is elastically deformable.

[0012] Still according to the present invention, the idea that has emerged is to provide a method for cleaning a dynamic filter according to any one of the preceding claims, characterized in that the elastically deformable dynamic filter element of the dynamic filter undergoes a mechanical deformation step after the paint has hardened, in order to detach the hardened paint from the elastically deformable dynamic filter element.

[0013] Still according to the present invention, the idea that has emerged is to provide a system for cleaning a dynamic filter manufactured according to the principles of the present invention described herein and applying a method according to the principles of the present invention described herein, and comprising a unit for elastically deforming the dynamic filter element in order to detach the paint.

[0014] In order to illustrate more clearly the innovative principles of the present invention and its advantages compared to the prior art, examples of embodiments applying these principles will be described below with the aid of the drawings. In the drawings:

[0015] - Figure 1 shows a schematic view of a painting device for removing overspray using a filter according to the present invention;

[0016] -Figure 2 A schematic view of a system for cleaning an overspray removal filter and applying the method according to the present invention is shown;

[0017] - Figure 3 、 Figure 4 and Figure 5 A schematic view of components of a possible embodiment of a filter according to the present invention is shown.

[0018] Referring to the accompanying drawings, Figure 1 a painting apparatus generally designated 10 is shown, which produces overspray that must be removed.

[0019] For example, the apparatus includes at least one chamber 11 for painting an object 12 (such as a motor vehicle body or a component thereof). The object to be painted is advantageously transported into the chamber 11 by a known conveying system 13 (such as an intermittent or continuous conveyor line).

[0020] The chamber 11 is provided with a painting device or operating unit 14, which sprays a liquid paint onto the surface of the object to be painted. Advantageously, the painting device can be implemented in the form of a known robotic arm, which has a spray gun or a paint cup at its end.

[0021] An air flow is passed through the chamber 11 in order to remove overspray from the chamber 11.

[0022] Advantageously, this can be achieved by means of a grid floor 15 of the chamber 11, through which the air in the chamber can be sucked out in order to discharge the overspray from the chamber. There is a corresponding inlet 16 on the ceiling of the chamber, which is advantageously made of a grid for the entry of clean air in order to have a continuous air flow through the chamber from top to bottom during the painting operation. However, other known systems for circulating and extracting air from the chamber can be used. The clean and / or purified air can enter the chamber through one or more ducts 22.

[0023] Thus, there is an air flow containing the paint overspray to be treated in order to remove the overspray from the air.

[0024] In order to remove the overspray, the air flow containing the overspray is sent to at least one unit 17 for removing the overspray. The unit 17 can be located, for example, directly below the grid floor of the chamber, or can be connected to the air flow containing the overspray by means of a suitable conveying duct or passage.

[0025] A suitable known aspirator or fan 21 can also be present along the air flow path (such as at the clean air outlet after the unit 17) in order to move the air flow properly through the unit 17.

[0026] After passing through the overspray removal unit 17 and being cleaned, the air flow can be drawn to the outside and / or conveyed back to the chamber via the duct 22.

[0027] The removal unit 17 includes a chamber 23 having an inlet that receives air from which overspray is to be removed.

[0028] The chamber 23 has a dynamic filter 25 therein through which the air stream passes, releasing the overspray onto the dynamic filter 25. The clean air then exits the chamber through an outlet 26. As is known, the dynamic filter is made with an internal maze for imparting sudden changes in the direction of the air in order to intercept the overspray paint conveyed by the air stream, since the paint droplets cannot change direction as quickly as the air stream and thus strike and remain fixed to the filter walls forming the filter maze.

[0029] During operation of the painting equipment, the dynamic filter 25 accumulates overspray paint. Therefore, it is necessary to periodically replace the dirty filter with a clean one. To determine when the filter contamination requires replacement of the filter, it is possible to simply envisage replacing them periodically on a time basis (e.g., also based on the operating time of the equipment). Additionally or alternatively, a weighing system (e.g., having load cells) can be provided, which gives an indication of when replacement needs to be carried out based on the increase in weight of the filter in the chamber due to the paint accumulation on the filter (and thus the increase in weight of the chamber itself).

[0030] As will be clear below, due to the innovative principle of the present invention, the dynamic filters 25 are made such that they are reusable after a cleaning that can be easily carried out, rather than being disposable filters as in the prior art.

[0031] When it is considered necessary to replace the filter 25 with a clean one, the filter to be replaced or the dirty filter 25 is removed from the chamber 23 and, instead of being discarded, is conveyed along a path 18 towards a cleaning position that can be located within a specially designed cleaning system 19 near or far from the painting equipment, as will become clear below. After cleaning, the filter 25 can be stored for future use or can be transported back along a path 20 to the chamber through which the air stream to be cleaned passes (not necessarily in the same painting equipment), depending on the needs and the operating mode chosen.

[0032] The transfer of the filters towards the cleaning position and their return to the chamber can be carried out using suitable transfer means that are of manual nature (conveyor trolleys and / or containers) and of automatic or semi-automatic nature (e.g., conveyor belts, overhead conveyors, etc.).

[0033] According to the principles of the present invention, the dynamic filter 25 is made of an elastically deformable dynamic filter element (such as an internal labyrinth wall) or includes an elastically deformable dynamic filter element (such as an internal labyrinth wall). The terms "elastically deformable" and "elastically deformable element" are understood to mean that when the elements are deformed, they substantially resume their original form once the deformation applied to them ceases.

[0034] "Elastically deformable" is understood herein to mean at least equal to greater than the elastic deformation capacity of the hardening coating, such that the elastic deformation of the elastically deformable element (continuously or intermittently with a deformation release phase) can cause the fracture and at least partial detachment of the hardening coating.

[0035] Thus, it is possible to obtain a dynamic filter that can be relatively easily cleaned, has low contamination, and limited time and energy consumption.

[0036] To accelerate the hardening of the coating on the element to at least equal to the value required for detachment during the elastic deformation of the dynamic filter element, a heat treatment step can also be applied. According to this solution, when it is necessary to clean the overspray on these dynamic filter elements, the dynamic filter elements are subjected to a heat treatment step for hardening the coating and then to an elastic deformation step to separate the hardened coating from the elastically deformable dynamic filter element.

[0037] In any case, the elastic deformation can also include alternating elastic deformation cycles (such as by compression of the filter or its three-dimensional structured components) and release of the deformation acting on the elastically deformed dynamic filter element (release of compression).

[0038] The cleaning step by means of elastic deformation can be carried out at any distance from the painting equipment and, if necessary, can also be carried out within the same painting equipment.

[0039] The dynamic filter element is advantageously made of an elastically deformable material and preferably made of a material with low wettability compared to the coating, so as not to absorb or retain the coating inside the material. Preferably, the elastically deformable element of the dynamic filter is made of a non-porous and liquid-impermeable material at least on the surface. Also preferably, the dynamic filter element is made of a material that is sufficiently resistant to the adhesion of the coating used in the painting chamber so as to facilitate its detachment after the elastic deformation of the dynamic filter element. An anti-adhesion treatment (such as by means of a suitable liquid or solid coating of known techniques) can also be used.

[0040] The elastically deformable dynamic filter element can advantageously be made of a suitable elastic material, which can be the same as the elastic material of the container and can also be integrated with the container.

[0041] The materials selected for the dynamic filter elements must also be resistant enough to the temperatures to which they are exposed.

[0042] In particular, if heat treatment is used to harden the coating on the element to be cleaned, the dynamic filter elements must withstand the temperature used for the heat treatment for coating hardening without excessive degradation. The value of the treatment temperature will mainly depend on the characteristics of the overspray coating and the time used to achieve the hardening considered sufficient for the coating.

[0043] For example, the selected temperature can be the coating drying temperature. If the coating is polymerizable, the temperature can be selected to be at least equal to or even higher than the polymerization temperature of the coating.

[0044] For coatings commonly used in coating equipment, such as for coating the body of a motor vehicle or its components, the treatment temperature can generally be at least about 80 °C or higher, preferably at least 150 °C and preferably about 200 °C or higher.

[0045] The minimum heat treatment time can also depend on the temperature selected for the treatment, the characteristics of the specific coating to be cleaned, and the thickness of the coating on the dynamic filter element. For example, for coatings commonly used in coating equipment, such as for coating the body of a motor vehicle or its components, in the case of treatment temperatures between 80 °C and 250 °C, a time between about 10 minutes and about 60 minutes can be used, for example.

[0046] Many materials have the required elastic deformation properties and low adhesion of the coating to allow it to detach and withstand the required temperature. Based on the description provided herein, those skilled in the art can select them according to the specific situation. Suitable materials found are, for example, silicone rubber with suitable temperature resistance, stabilized silicone rubber, or other suitable elastic types of synthetic substances.

[0047] Once the dynamic filter elements are made elastically deformable according to the basic principles of the present invention, their elastic deformation allows for their rapid cleaning and can be obtained in various ways. For example, the dynamic filter elements can pass between continuously or alternately compressed or elastically deformed rollers or surfaces with different arrangements, vibration systems, etc.

[0048] Figure 2 A possible example of the cleaning system 19 is shown in schematic form, which cleaning system 19 includes a unit 28 for the elastic deformation of the dynamic filter elements. An automatic or semi-automatic system allows the coating debris to be retained more easily and avoids the risks for human operators.

[0049] System 19 may also preferably include a heating furnace 27 arranged upstream of unit 28 for performing a hardening heat treatment of the coating in order to produce or accelerate the hardening of the coating. In this case, the heating furnace 27 receives the power filter element 25 to be cleaned and performs the heat treatment at an appropriate temperature and for an appropriate time as described above. The furnace may also be of the type with a through-channel and is provided with a transport system (such as a conveyor belt) such that it can be traversed by the power filter element to be cleaned. In any case, the entry / exit of the element into / from the furnace can also be carried out manually or semi-automatically.

[0050] The mechanical treatment unit 28 receives the power filter element 25 with the hardened coating and performs an elastic deformation of the power filter element in order to separate the coating from the power filter element.

[0051] The mechanical treatment unit 28 may for example include means 30 for the compression or elastic deformation of the filter element, through which the power filter element passes in order to be deformed and to dislodge the hardened coating. These means 30 may for example be designed with motor-driven rollers. The rollers may for example consist of a certain number of rollers and are arranged along rotation axes oriented in different directions. In particular, but not exclusively, a plurality of rollers may be arranged at right angles to each other. The elastic deformation may occur between relatively arranged rollers, between a roller and the underlying surface or a undulating path, etc.

[0052] Other elastic deformation systems, such as pressing surfaces, relatively arranged vibrating surfaces, etc., can in any case be used alternatively to each other or additionally or in combination with each other.

[0053] The elastic deformation may occur by means of the power filter element moving continuously or stepwise between the inlet and the outlet of the mechanical treatment unit 28.

[0054] If required, the elastic deformation may be carried out alternately by the power filter element which is introduced into the mechanical treatment unit and is thus held for a sufficient length of time to be elastically deformed to dislodge the coating and is then removed at the end of the treatment.

[0055] The elastic deformation may advantageously be applied in several stages, i.e. elastic deformation stages are alternated with elastic release stages in order to facilitate the detachment of the coating fragments from the surface of the power filter element. This can be obtained by operating the compression or deformation means 30 intermittently and by the spaced arrangement of several compression or deformation means 30 or their components such that the element passes through successive elastic deformation zones and elastic non-deformation zones.

[0056] The mechanical treatment unit advantageously includes a collection area (such as a suitable container) into which the coating detached from the power filter element falls. For example, Figure 2 a container 31 located below the operating area of the means 30 is shown in schematic form.

[0057] When considered useful or necessary, during or after the mechanical treatment step of elastic deformation, the dynamic filter element can also be subjected to an air flow to remove any paint debris remaining above or between the treated dynamic filter elements. Known vibration and / or shaking and / or blowing systems can also be provided, which are also capable of acting during or after the above-mentioned mechanical treatment step. For this purpose, for example, shaking, vibrating, centrifugal or other types of devices 32 can be provided for this purpose, which are composed of, for example, a vibrating surface or support, a rotating drum and / or a blowing device.

[0058] The mechanical treatment step by means of elastic deformation can be considered sufficient for a predetermined time to perform the desired cleaning of the dynamic filter element. The required degree of cleaning obtained can also be detected by a suitable known optical sensor or other known automatic system to ensure the correct treatment time required and sufficient for cleaning. For example, the filter during treatment can be weighed so that when the weight of the filter drops below a predetermined value, which is defined as corresponding to an appropriate degree of cleaning, i.e., a reduction in paint, the cleaning process is determined to stop. For example, the reduction can also be determined as the difference between the weight of the contaminated inlet filter before cleaning and the weight of the filter during cleaning, such that the process ends when the weight difference reaches a predetermined value.

[0059] At the end of the mechanical treatment step, when needed, the dynamic filter element can be used again to remove overspray. In the case where the filter has been divided into multiple components, for the convenience of the cleaning process according to the present invention, the dynamic filter elements forming the filter are separated from each other, and these components can be reassembled to form a complete filter before reuse.

[0060] Figure 3 A possible embodiment of the filter 25 is shown. The filter can include an external structure of side walls 33, which has an inlet end 34 for the air flow with overspray and an opposite end 35 for the purified air to leave after passing through the filter. The external structure 33 contains inside it a filter element composed of an inner wall 36, and the inner wall 36 forms a maze of the dynamic filter.

[0061] The entire filter 25 can be elastically deformable and form the entire deformable filter element, or only the inner wall 36 can be elastically deformable. In the second case, the elastically deformable dynamic filter element will be removed from the external structure before mechanical deformation to detach the paint. Also in the case where the filter is completely elastically deformable, it can be decided to construct the filter with separable or openable components to facilitate the removal of the hardened paint detached due to elastic deformation from the filter element.

[0062] Figure 4Partially shown is a box-shaped housing 37 having grilles at opposite ends 38, 39, the grilles being arranged at an inlet 34 and an outlet 35 for air passing through the filter, whereby the housing can form an outer housing of the filter 35 or can be a housing containing the filter 35.

[0063] The box-shaped housing 37 can also be made inelastic or less elastic than the filter or filter element inserted therein, in order to provide greater rigidity to the filter during use or transport or handling.

[0064] The box-shaped housing 37 can be made, for example, of a rigid plastic material and have at least one wall that can be opened for removing and introducing a powered filter element.

[0065] As Figure 5 shown by way of example, the powered filter can also be designed in modular form, i.e., according to the requirements of the air containing overspray in the filtering device, a plurality of powered filters 25 as described above are assembled to form a larger filter.

[0066] At this point, it is clear how the predetermined objective has been achieved. The powered filter element made elastically deformable can be easily cleaned, overcoming many problems of the prior art. Thus, the method according to the present invention can ensure efficient and effective treatment of the airflow containing overspray with minimal effort, low power consumption and low environmental impact

[0067] In addition, the paint recovered in fragmented form can be easily handled, transported and / or recycled.

[0068] Obviously, the description of the above embodiments applying the innovative principles of the present invention is provided by way of examples of these innovative principles and should not therefore be regarded as limiting the scope of the rights claimed herein. For example, the air source having overspray to be removed can be different from the painting booth shown by way of example herein, there can be multiple units 17 and / or cleaning systems 19 for the same source (e.g., for the same painting booth) in order to treat separated airflows, or conversely, there can be a single unit 17 and / or a single cleaning system 19 that can serve several sources or painting booths. A single cleaning system 19 can also serve multiple overspray removal units of the same source or chamber or several sources or chambers.

[0069] The chamber and / or the device may also include other known components not shown here and not forming part of the subject matter of the present invention, such as means for conditioning or filtering the air entering the chamber or the device, transport systems and additional painting devices, etc. After the dynamic filter according to the present invention, there may also be additional filters, such as bag filters, etc., in order to intercept any impurities still present in the air and that may pass through the dynamic filter, as can be easily imagined by a person skilled in the art. If it is necessary to replace the filter or some of the filters during the operation of the painting device, known means or partitions for blocking or deflecting the air flow may also be provided.

Claims

1. A dynamic filter (25) for removing overspray from an air stream, comprising a housing (33, 37) containing a dynamic filter element, characterized in that, At least the dynamic filter element is elastically deformable.

2. The dynamic filter according to the preceding claim, characterized in that, The housing (33, 37) is more rigid than the elastically deformable dynamic filter element and can be opened to remove the elastically deformable dynamic filter element.

3. The dynamic filter according to claim 1, characterized in that, The elastically deformable dynamic filter element is made of silicone rubber or stabilized silicone rubber.

4. The dynamic filter according to claim 1, characterized in that, The dynamic filter element is made of a material that withstands a temperature of at least about 80 °C or higher, and preferably at least about 150 °C or 200 °C or higher.

5. A method for cleaning a dynamic filter according to any one of the preceding claims, characterized in that, The elastically deformable dynamic filter element (25) of the dynamic filter undergoes a mechanical deformation step after the coating has hardened, in order to detach the hardened coating from the elastically deformable dynamic filter element (25).

6. The method according to claim 5, characterized in that, The mechanical deformation step includes an alternating cycle of deformation and release of deformation of the dynamic filter element (25).

7. The method according to claim 6, characterized in that, The method includes an additional step: before the mechanical deformation step, subjecting the dynamic filter element (25) to a heat treatment to harden the coating.

8. The method according to claim 7, characterized in that, The heat treatment step is carried out at a temperature selected to allow the coating to dry, or if the coating is polymerizable, at a temperature selected to be at least equal to or higher than the polymerization temperature of the coating.

9. The method according to claim 8, characterized in that, The temperature is at least about 80 °C or higher, preferably at least about 150 °C or 200 °C or higher, and the dynamic filter element (25) is made of a material that withstands this temperature.

10. The method according to claim 5, characterized in that, The dynamic filter element (25) undergoes an air flow and / or shaking and / or vibration and / or centrifugation after or during the elastic deformation, in order to facilitate the removal of the hardened coating from the dynamic filter element (25).

11. The method according to any one of claims 5 to 10, characterized in that, The dynamic filter is arranged during use in a chamber (23) through which air with overspray passes, and when the filter needs to be replaced, the dynamic filter is withdrawn from the chamber and sent to a cleaning step, and then used again if necessary.

12. A system for cleaning a dynamic filter 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, The system includes a unit (28) for elastically deforming the dynamic filter element (25) to detach the coating.

13. The cleaning system according to claim 12, characterized in that, The cleaning system includes a furnace (27) for heat treatment of coating hardening, and the furnace (27) is arranged upstream of the unit for elastically deforming the dynamic filter element (25).

14. The cleaning system according to claim 12, characterized in that, The unit (28) for elastically deforming the dynamic filter element (25) includes mechanical compression means (30), through which the dynamic filter element to be cleaned of coating passes between the mechanical compression means (30).

15. The cleaning system according to claim 12, characterized in that, The cleaning system includes blowing and / or shaking and / or vibration and / or centrifugation means (32) within or downstream of the unit (28) for removing coating debris from the dynamic filter element (25).

16. A painting apparatus (10), comprising a painting chamber (11) through which an air stream passes to discharge overspray from the chamber, characterized in that, The coating apparatus (10) includes at least one overspray interception chamber (23), the overspray interception chamber (23) containing a powered filter (25) according to any one of claims 1 to 4, the powered filter (25) being traversed by an air flow leaving the chamber and being associated with a cleaning system (19) according to any one of claims 12 to 15 so as to allow removal of the powered filter (25), cleaning of the powered filter (25) in the cleaning system (19) and reuse of the powered filter (25) in the overspray interception chamber (23).

17. The painting apparatus according to claim 16, characterized in that, The coating apparatus includes 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 (23).

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