Patent Application
20220355327
The present invention relates to the technical field of apparatuses for applying paint to mainly flat products (panels), known on the market as automatic sprayers. In particular, the present invention relates to a particularly advantageous shape of plenum, characterized by an M-shape, and to different advantageous forms of the support for spray guns. A preferred embodiment of the invention refers to the advantageous combination of said M-shaped plenum and to a particular form of the support for spray guns, in particular to a rotating device having an oval shape having the two long sides parallel to one another and perpendicular to the feeding directions of the parts to be painted.
In this context, plenum means a ceiling or upper wall that is able to distribute an airflow entering the closed space of the booth while painting takes place. Fans force air into the booth, the fans can be adjusted in order to vary the speed and the quantity of air input into the spray booth in the time unit. The distribution of air must be as uniform as possible and the air speed must be controlled. In different points of the plenum the dispensed airflow can vary, while it must be constant over time in that specific point. The adjustment of inlet fans is intended to compensate the pressure drop, so that the distribution of air to the plenum is maintained within optimum pre-set limits.
Spray booths are known that through automatic devices (reciprocators, carousels, rotating arms) apply spray paint to products to be painted.
Spray paint application entails not all the sprayed paint hitting the product; the paint not applied to the product partly hits the product conveying system, and partly hovers in the air inside the spray booth itself. This last portion of sprayed paint is called overspray, and is partially intercepted by a suction plant with which the spray booth is equipped.
Non-intercepted overspray tends to contaminate spray booth internal walls, gathering on them up to the point of compromising manufacturing quality, and leading to a significant quantity of painted products being rejected. This thus makes costly cleaning/maintenance of the spray booth itself obligatory.
The overspray intercepted by the suction plant is channelled towards spray booth filters, thanks especially to an airflow generated by the suction plant itself. In this path, the overspray is controlled in a more orderly manner owing to the emission of an airflow from the plenum.
FR2405758 of Manuel Garcia Sanchez discloses a mobile roof for a spray painting booth. This booth is provided for the manual painting of motor vehicles, performed by a human operator. Said roof, which is a filtering ceiling, not a plenum, has three portions, a central portion 2, and two side sectors 3 and 4 which rise in an opposite direction; in other words, overall the ceiling has a convex shape. Said ceiling can move vertically, i.e. rise and lower, in response to the pressure conditions that form inside the booth itself, in order to prevent explosions due to the paints and fuel of the motor vehicles painted inside the booth.
JP2002128578A of Tono Yogyo KK and GB1393202A of Atlas Copco AB describe a rotating support for spray guns. The rotating support is moved along two parallel, rectilinear paths joined by two half-circles. This allows a plurality of guns to be obtained spraying at the same time in a direction perpendicular to the items to be painted in transit.
The present invention seeks to provide a spray booth having a plenum with an improved air circulation in the booth in order to control as much as possible the phenomenon of overspray. This can be obtained generating an airflow more similar to the geometry of the vortex generated by the combined effect of the spray guns and of the suction.
This object is obtained with an apparatus having the features of the independent claims. Advantageous embodiments and refinements are specified in claims appended thereto.
The object is obtained with a spray booth according to the present invention, which has an M-shaped plenum, i.e. a plenum with the central portion lower than the immediately adjacent lateral portions; more peripherally, the plenum lowers again, reaching two end points that are lower than the central portion.
In the preferred embodiment, in the spray booth a rotating device is also present in which the spray guns follow a closed oval path, provided with two parallel sides and two half-circles. This device supports spray guns and can be moved vertically, moving to/away from the object to be painted. Each arm is provided with a distributor block supplying the gun; this distributor block allows the painting product to recirculate.
The M-shape of the plenum forms two expansion chambers in which the kinetic energy of the paint dispensed by the gun is spontaneously and progressively reduced: this allows the suction plant to intercept the overspray.
The apparatus according to the present invention has very high productivity combined with a quality of painted items that is just as high. Indicatively, the speed of transit of the items to be painted can range from 8 to 20 m/min, while the weight of paint applicable to said items ranges from 80 to 300 g/m2. The apparatus can work over three work shifts, i.e. 24/24 h.
The advantages of the present invention are due to the improvement in the control of overspray flow. This has several consequences:
With respect to the rotating spray gun support, provided with an oval shape with two parallel sides, the advantages are connected to the following features:
The present invention will be disclosed below in one of the embodiments thereof with the help of the following figures, which show:
It is worthwhile pointing out that, for particular applications, the air inlet groups 4 can be absent, replaced by alternative groups having the same function but providing hyper-filtered air.
From the periphery of the apparatus toward the centre, said plenum 20 has two first external descending portions 21 tilted toward the periphery, which do not touch a conveying belt 25 to permit the transit of the products to be painted. Following said portions 21, there are two lateral surface portions 22, parallel to the conveying belt 25 conveying the parts. Therefrom, there are provided two tilted central surface portions 23, descending towards the rotating device 40 (therefore, having a tilt opposite the first portions 21). The two central descending portions 23 are connected through a parallel central portion 24 which is parallel to the conveying belt 25, and is placed lower (i.e. nearer the conveying belt 25) than the parallel lateral portions 22. The M-shaped plenum 20 is symmetric, and the structure that has just been disclosed of the portions 21, 22, 23, 24 is identical on the two sides. The various surface portions 21, 22, 23 and 24 will be indicated simply as “portions” hereinafter.
It is worthwhile noting that the air exiting the various portions 21, 22, 23, 24 of the plenum always exits perpendicularly to each surface 21, 22, 23, 24.
The speed of the air exiting the descending external portions 21 is such as to contrast the residual kinetic energy of the paint dispensed by spray guns 26, so that the overspray tends to recirculate towards the lateral parallel portion 22, to be then suctioned by the suction plant.
In the portions 22 and 23 of the plenum the exit speed of air exiting the surface of said plenum can be lower than that of the air exiting the portion 21, because they are in a zone in which the kinetic energy of the overspray is lower. The reduction of speed of the inlet air in the areas underneath the portions 22 and 23 of said plenum allows to an overall airflow to be obtained that is lower than in the apparatuses in which the air speed exiting the plenum is homogeneous for all the portions 22, 23, 34, air speed being equal to the airflow of portion 21.
Also in said central parallel portion 24 of the plenum there is an airflow exiting said plenum 20 that has the function of preventing that overspray generated by spray guns 26 dirtying the spray guns 26 themselves and the support arms 41 thereof.
The choking of the air speed in the different portions 21, 22, 23, 24 of the plenum is achieved by controlling the airflow delivered to the spray both by fans 4, adjusting the airflow itself through separating baffles 34, 35, which bound the chambers 31, 32, 33 of the plenum itself. Owing to the presence of the chambers 31, 32, 33 formed by the respective separating baffles 34, 35, just two inlet air groups can be used, placed on the respective sides of the apparatus 1. By modifying the crossing surface of the separating baffles 34, 35 the airflow in the different portions 21, 22, 2324 of the plenum can be varied, so adjusting also the speed of the air entering the spray booth 2.
It is worthwhile noting that two walls 36 bound the volume in which air is moved. Said walls 36 delimit a volume 37, inside which the rotating device 40 is placed, and into which no forced air is conveyed.
For the sake of clarity, the portion indicated with 3 in
In an alternative embodiment that is not shown, the separating baffles 34, 35 are not perpendicular to the ground as in the Figures, but can be tilted, or have a different extent, or have a different degree of permeability.
The filtration system is provided in the form of lateral suction tanks 27, better observable in
The dimensions and the shape of the plenum 20 represent the best compromise between the overall dimensions of the apparatus 1 on the one hand, and on the other hand the speed and quantity of air needed for containing the overspray, preventing the generation of paint accumulation inside the apparatus. In other words, a bigger apparatus would spontaneously lead to a lower overspray accumulation, but would be too cumbersome and too expensive to find a place in a production line. Indicatively, the dimensions of the spray booth 2 are 3.5 m×6.5 m, with a distance of 1.5 m between parallel lateral portion 22 and conveying belt 25.
Said tanks 27 are a known water filtration system. Alternatively, this water filtration system can be replaced by a dry filtration system, known in the prior art, too, or alternatively by other filtration systems or paint/air separation systems known in the prior art.
Experimentally, the best performance of the apparatus according to the present invention are obtained by combining the M-shaped plenum 20 with an oval rotating device 40, which combination is the preferred embodiment. Nonetheless, providing an apparatus provided with the oval rotating device (40) without M-shaped plenum, i.e. combined with a known plenum, is possible.
The M-shaped plenum 20 can also be combined with spraying devices of different shape, e.g. a rotating carousel in which the spray guns follow a circular path, or any configuration of a spraying device in which the spraying direction goes from the centre to the periphery of the apparatus. For example, in an alternative not shown embodiment, the same M-shaped plenum 20 can be used combined with spray guns placed in the centre of the apparatus that guns move with a rectilinear alternating movement along a direction orthogonal to the conveying direction of the products 30 to be painted, with a direction so that the paint jet goes from the centre of the apparatus to the periphery.
The spray gun supports 41 are supported by the pair of moving chains 42 which move along the oval trajectory of the guns between a pair of motorized sprocket wheels 57 and a pair of idle sprocket wheels 58 (both visible in
Each tube-support chain 44 contains the pipes supplying and removing paint for each gun 26. The two ends of each tube-support chain 44 are fixed:
The two rotating supports 61 and 62, which are constructively identical, allow the rotation of the two ends of the tube-support chain 44, allowing the two ends to move always on the same plan, preventing mechanical warping which would lead to breakage thereof. In fact, the rotating disc 56 is in phase with moving chains 42, i.e. a full circle of the rotating disc 56 corresponds to a full circle of the moving chains 42.
In order to understand the operation of the oval rotating device 40, the three
The same gearmotor 59, again with a chain transmission, moves the disc 56 too, which moves the first end 61 of the tube-support chain 44 and a rotating joint 43.
Said rotating joint 43 (visible also in
The rectilinear tracts of the oval rotating device 40 are perpendicular to the feeding direction of the parts to be painted, indicated by the bold arrow in
Through supply pipes and a supply pump (which are not shown), the painting product is sent from the storage reservoirs (which are not shown), placed outside the apparatus 1 to the rotating joint 43 placed at the centre of the rotating device 40. From a distributor that is not shown connected to said rotating joint 43 the supply pipes (which are not shown) depart, directed to each spray gun 26. In order to allow the correct movement of the pipes from the central portion of the rotating joint to the peripheral portions on which the spray guns 26 move, said tube-support chains 44 are used. For the sake of simplicity, in
Through the gearmotor 59 the moving chains 42 and the disc 56 are moved at the same time: a relative movement is generated between the two ends of the tube-support chain 44. During the gun movements, the rotating supports 61 and 62 move on two different trajectories: the rotating support 61 follows a circular trajectory on the disc 56, while the rotating support 62 follows an oval trajectory on the moving chains 42.
It is worthwhile highlighting that the tube-support chains have to move their mobile ends on their working plane only, in order to function properly. Otherwise, if the mobile ends of the tube-support chain 44 are moved on different planes, transverse loads are generated, which would lead to the breakage of the tube-support chain 44 itself. In the known art, such tube-support chains 44 normally are used to guide the movement of pipes or cables between two mobile ends that move on rectilinear and coplanar pathways. In this case, unlike the known art, the tube-support chain is used on a pathway provided with a rototranslation movement, provided with a rectilinear and a rotatory component.
It is worthwhile remembering that paint tends to settle, and therefore preferably the supply circuits of painting apparatuses are provided with a return branch to form a recirculation system keeping the paint in motion. As a consequence, the aforesaid number of pipes must be doubled, in order to dispose of a system of paint delivery and return.
The paint inlet branch goes from the paint storage reservoir (not shown) to a recirculating block 45 (visible in
A further feature of the rotating device 40 is that the whole device can be moved, moving the rotating device, and therefore the spray guns 26, to/from the transiting products 30 to be painted. All the device 40 is supported by two support columns 51, visible in
The two
This rotating brush has the object of cleaning the nozzles of the spray guns 26 when it is brought into a position that is such as to interfere with the gun 26.
During spraying, when spray guns 26 are active, said cleaning device 65 is in the resting position (lower position, shown in
The position of the cleaning device 65 is defined: in order to perform the cleaning of all the guns 26, the cleaning device 65 is raised until it is at the same height as the guns 26. The passage of a spray gun 26 to the following occurs while the cleaning device 65 is in the resting lower position, while when the following gun arrives at the cleaning device 65, the device 65 is lifted to the working position. In other words, during a cleaning cycle the cleaning device undergoes a number of translations upwards and downwards corresponding to the number of guns present. This translation movement occurs through a pneumatic cylinder 69, visible in
Not all commercially available spray guns are identical, therefore adjusting means is provided to allow the correct positioning of the brush 66 with respect to the nozzle of the specific spray gun 26.
Finally, it is worthwhile specifying that in addition to the automatic cleaning working as explained above, also focused manual cleaning can be performed of the single spray gun 26.
Each spray gun 26 with the respective support arm 41 thereof is marked by a consecutive number, e.g. from one to twelve or from one to twenty-four, which allows the spray gun 26 to be identified univocally. For example, let us consider the case in which gun number eleven is spraying badly because the nozzle thereof is clogged. The apparatus 1 is provided with a program allowing the desired gun, e.g. said gun number eleven, to be taken to the greater axis of the oval. A human operator can remove the corresponding glass protection 6 and proceed to the manual cleaning of the nozzle of the gun number eleven.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019000009714 | Jun 2019 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/055870 | 6/22/2020 | WO |
