Patent Publication Number: US-2021162445-A1

Title: Powder coating booth and related coating plant

Description:
TECHNICAL FIELD 
     The present invention relates to a powder coating booth and related coating plant. 
     BACKGROUND ART 
     Coating is a surface coating process carried out both for decorative purposes, coloring the elements to be coated, and for purposes of protection against corrosion and external agents. 
     Such process involves the realization of the coating by spraying organic matrix powders and synthetic resins which, by adhering to the surfaces, color the element being coated. 
     The elements to be coated are inserted in a special booth where, by means of spraying devices such as nozzle guns or the like, they are coated with powders before undergoing subsequent firing and finishing phases. 
     The booths are enclosures which define a substantially closed space within which the coating phase takes place. 
     Inside the booth, a collecting area can be identified above which the element to be coated is made to transit and at which the spraying devices operate to coat the element. 
     The largest amount of excess powder, which does not adhere to the element, commonly called “overspray”, falls to the ground precisely at the collecting area. 
     Usually, the spray booths are connected to suction means which suck up the air and powder inside the booth, first conveying them to subsequent recovery and filtration means and, then, into the atmosphere. 
     Usually, the recovery and filtering means comprise a cyclone, adapted to separate as much powder as possible from the air to recover it, and subsequent filtering units adapted to clean the air before returning it to the atmosphere. 
     Known booths are usually used in coating plants comprising a suction line associated with the suction means which permit sucking up air and powder from the booth. 
     The suction line has a recovery cyclone downstream of the booth wherein the powder is separated from the air for its recovery. 
     Furthermore, the suction line has one or more filtering units located downstream of the recovery cyclone adapted to filter the air before returning it to the atmosphere. 
     One of the drawbacks of known booths relates to the recovery of excess powder. 
     The operation of the cyclone upstream of the filtering units requires a significant consumption of energy as the air flow rate with which it works is proportionate to the volume of the booth. 
     Furthermore, any color change operations would be slowed down by the fact that to recover powder to be reused, the entire booth must be cleaned to prevent residual powder of different colors mixing with other powder and affecting recovery. 
     DESCRIPTION OF THE INVENTION 
     The main aim of the present invention is to devise a powder coating booth and related coating plant which allow facilitating the passage from one coating phase to another. 
     One object of the present invention is to devise a powder coating booth and related coating plant which allow reducing the costs of the coating phase. 
     One object of the present invention is devise a powder coating booth and related coating plant which can facilitate the color change phases. 
     Another object of the present invention is to devise a powder coating booth and related coating plant which allows overcoming the aforementioned drawbacks of the prior art in a simple, rational, easy, effective to use and low cost solution. 
     The objects set forth above are achieved by the present powder coating booth and related coating plant having the characteristics of claim  1  and claim  7 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the present invention will become more evident from the description of several preferred but not exclusive embodiments of a powder coating booth and related coating plant, illustrated by way of a non-limiting example in the accompanying tables of drawings in which: 
         FIG. 1  is an axonometric view of the booth according to the invention; 
         FIG. 2  is an axonometric view of a detail of the booth according to the invention; 
         FIG. 3  is a schematic view of the plant according to the invention; 
         FIG. 4  is an axonometric view of a second embodiment of a detail of the booth according to the invention; 
         FIG. 5  is an axonometric view of a third embodiment of a detail of the booth according to the invention. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     With particular reference to these illustrations, reference numeral  1  globally indicates a powder coating booth. 
     The coating booth  1  has a bottom surface  2  and is delimited by side walls  3  which define the prismatic structure thereof 
     The booth  1  defines an inner space  4  in which is insertable an element to be coated  5 . 
     In particular, the booth  1  comprises a spraying device  6  adapted to spray coating powder on the element to be coated  5 . 
     In the present embodiment, the spraying device  6  comprises a plurality of nozzle guns  7  connected to a system for feeding coating powders, for simplicity not shown in the figures. 
     Solutions cannot be ruled out which provide for spraying devices provided with a single gun or provided with guns different from those illustrated. Furthermore, the booth  1  comprises at least one collecting area  8  defined on the bottom surface  2 . 
     The collecting area  8  can be identified in the proximity of the spraying device  6 . On top of the collecting area  8  the element to be coated  5  passes to be coated with coating powder. 
     The excess powder, commonly called “overspray” which, sprayed on the element to be coated  5 , has not adhered to the surface to be coated, falls in the collecting area. 
     The collecting area  8 , therefore, defines an area identifiable on the bottom surface  2  which is the area where most of the excess powder or “overspray” falls. 
     The booth  1  is associated with first suction means, for simplicity not shown in the illustrations, for the sucking and conveying air coming out of the inner space  4 . 
     The first suction means comprise at least one fan adapted to create a vacuum inside the booth  1  in order to let the air flow from the booth  1  towards a suction line adapted to convey the air and any residual powder. 
     The action of the first suction means prevents the powder being sprayed from coming out into the atmosphere through the slits on the walls of the booth  1 . According to the invention, the collecting area  8  is associated with second suction means adapted to suck and convey the excess powder coming out of said inner space  4 . 
     The collecting area  8 , therefore, is associated with suction means dedicated to it for sucking the overspray. 
     In particular the booth  1  comprises a collecting device  9  positioned in the collecting area  8  to receive the excess powder. 
     The collecting device  9  is associated with second suction means, for simplicity not shown in the figures, adapted to suck up and convey the excess powder out of the inner space  4 . 
     Conveniently, the second suction means comprise at least one fan adapted to create a vacuum at the collecting device  9  so as to suck up the excess powder deposited thereon and convey it out of the booth. 
     In particular, the collecting device  9  comprises at least one conveying channel  10  associated with the second suction means and adapted to convey the excess powder. 
     The second suction means create a vacuum inside the conveying channel  10  sucking up most of the excess powder. 
     The collecting device  9 , in fact, comprises at least one slit  11  communicating with the conveying channel  10  and through which the excess powder can pass to enter the conveying channel  10 . 
     In the present embodiment, the collecting device  9  comprises a collecting surface  12  on which the excess powder falls. 
     The conveying channel  10  is located below the collecting surface  12  and the slit  11  is formed directly on the collecting surface  12 . 
     This way, the action of the second suction means makes it possible to displace and suck up the excess powder from the collecting surface  12  to the conveying channel  10  through the slit  11 . 
     As shown in the figures, the collecting device  9  comprises two conveying channels  10  and two slits  11  communicating with the respective conveying channels  10 . 
     Conveniently, the conveying channels  10  are positioned symmetrically with respect to an axis of symmetry of the collecting device  9  parallel to a conveying direction  13  of the excess powder. 
     In particular, the conveying channels  10  are positioned symmetrically with respect to an axis of symmetry of the collecting surface  12  parallel to a conveying direction  13 . 
     Preferably, the conveying channels  10  are associated with outlet ducts  14  which are connected to each other to form a single recovery duct  15 . 
     In the present embodiment, the collecting surface  12  is arranged at the same height as the bottom surface  2 . 
     Solutions which provide for collecting surfaces that are raised or lowered with respect to the bottom surface cannot be ruled out, just as solutions which provide for different positioning of the conveying channels  10  cannot be ruled out either. 
     Solutions cannot also be ruled out which provide for a different number of conveying channels  10 , or a different number of slits  11 , or other through openings in place of the slits  11 . 
     Preferably, the collecting device  9  comprises at least one blowing element  23  having at least one blowing opening  24  facing the slit  11  and associated with compressor means for blowing air through the blowing opening  24 . 
     This way, the powder deposited on the collecting surfaces  12  is pushed towards the slit  11 , favoring its conveying into the channel  10 . 
     In the present embodiment, the collecting device  9  comprises a single blowing element  23  and has a longitudinal extension substantially parallel to the channels  10 . 
     Conveniently, the blowing element  23  has blowing openings  24  facing both slits  11 . 
     The slits  11  are placed one on the opposite side of the other with respect to the blowing element  23 . 
     In the following, reference numeral  16  globally indicates a coating plant. According to the invention, the coating plant  16  comprises the powder coating booth  1  described above. 
     Still according to the invention, the plant  16  comprises a first suction line  17  associated with the booth  1 , comprising the first suction means and adapted to convey a mixture of air and powder out of the booth  1 . 
     Advantageously, the first suction line  17  comprises at least one filtering unit  18  located downstream of the booth  1  and adapted to intercept the mixture of air and powder before conveying it into the atmosphere. 
     This way, powder residues and other coarse substances can be separated from the air before this is released back into the atmosphere. 
     The first suction line  17  and the filtering unit  18  are illustrated in a simplified manner. 
     The filtering unit  18  comprises at least one of the filters known to the state-of-the-art such as bag filters, gravitational filters or other types of filters. 
     Still according to the invention, the plant  16  comprises a second suction line  19  associated with the collecting device  9 . 
     The second suction line  19  comprises the second suction means and is adapted to convey the excess powder collected from the collecting device  9  to a powder recovery device, indicated with reference numeral  20 . 
     Still according to the invention, the plant  16  comprises the recovery device  20 . 
     The recovery device  20  allows recovering the excess powder and to be able to reuse it later. 
     Usefully, the recovery device  20  is of the type of a centrifugal cyclone. Advantageously, the plant  16  comprises at least one color change device  21  associated with the recovery device  20 . 
     The color change device  21  is schematically illustrated in  FIG. 3 . 
     The excess powder recovered by the recovery device  20  can be sent to the color change device  21 , thereby facilitating its reuse. 
     Such solution is particularly suitable for color change devices which make it possible to load the powder of a first color to feed the spraying device  6  and, at the same time, to unload the powder of a second color in special containers, to be recovered and coming from the booth  1 . 
     Advantageously, the plant  16  also comprises a second filtering unit  22  located downstream of the recovery device  20  and adapted to filter the air coming from the recovery device before returning it to the atmosphere. 
     The operation of the present invention is as follows. 
     The element to be coated  5 , once it has entered the booth  1 , passes on top of the collecting area  8  and is coated with coating powder by means of the operation of the nozzle guns  7 . 
     The excess powder or overspray falls on the collecting surface  12  of the collecting device  9 . 
     Thanks to the vacuum generated by the second suction means, the excess powder is sucked up into the conveying channels  10  passing through the slits  11  and is subsequently conveyed along the direction  13  and, therefore, in the second suction line  19 . 
     The recovery device  20  precipitates the excess powder conveyed in the suction line  19 . 
     The second filtering unit  22  cleans the air coming from the recovery device  20 . Subsequently, the precipitated powder is transferred to be reused later. 
     The first suction means, on the other hand, maintain an air circulation inside the booth  1 , conveying the air from the inner space  4  to the first suction line  17 . The filtering unit  18  separates the residual powder and other impurities present in the air coming from the booth before such air is released back into the atmosphere. 
     A second embodiment of the coating booth and related coating plant is completely similar to the first embodiment described above and differs in that the collecting device  9  comprises two blowing elements  23 , and comprises a single slit  11  and a single conveying channel  10 . 
     The two blowing elements  23  have blowing openings  24  facing the slit  11 . 
     The latter is interposed between the two blowing elements  23 . 
     The blowing openings  24 , therefore, send the air towards the center, pushing the powder deposited towards the slit  11 . 
     Conveniently, the slit  11  is equidistant from the blowing elements  23 . 
     Preferably, the blowing elements  23  are placed at the peripheral edge of the collecting device  9 . 
     A third embodiment of the coating booth and related coating plant is completely similar to the embodiment described above and differs in that the collecting device  9  is shaped like a hopper. 
     In particular, the collecting surfaces  12  are inclined with respect to the horizontal and converge at the slit  11 . 
     This way, the powder is pushed by gravity towards the slit  11  and subsequently conveyed by the channel  10 . 
     In the embodiments shown in the illustrations, the collecting device  9  has smaller dimensions than those of the bottom surface  2 , but solutions wherein the bottom surface  2  and the collecting device  9  have the same dimensions cannot be ruled out. 
     In practice, it has been ascertained that the described invention achieves the intended objects and, in particular, the fact is underlined that the powder coating booth and its related coating plant make it possible to facilitate the transition from one coating phase to another. 
     Compared to known plants, the first suction line does not require a cyclone before the filtering unit, while a second suction line dedicated to the recovery of the overspray has been fitted. 
     The cyclone fitted in the second suction line, the air flow to be sucked up being limited to the collecting device, is much smaller than the cyclones fitted on traditional plants. 
     This way, time is saved as regards cleaning operations, since it is necessary to clean only the collecting device, the cyclone (much smaller than the cyclones used in known plants) and the related channel connecting these. 
     It is no longer necessary to clean the entire booth, but only the collecting device in order to make correct color change. 
     As a result, the time required to change color is reduced, with the transition from one coating phase to another being facilitated. 
     Therefore, the powder coating booth and the related coating plant facilitate the color change phases, speeding them up, with consequent improvements both in terms of execution and in economic terms. 
     This means a significant reduction in downtime between the coating phases with a consequent reduction in operating costs compared to known powder coating booths and related known coating plants.