Patent Application
20220305514
The present invention relates to the technical field of apparatuses for applying paint on mainly flat pieces such as panels and/or three-dimensional pieces, known in the art as spray booths. In particular, the present invention relates to a cleaning station for the cleaning and the color changing of spraying tools, said cleaning station being arranged adjacently to said spray booth.
Mainly flat panels are panels, in which two of the three dimensions are bigger, by an order of magnitude, than the third dimension. Typically, said panels have measures ranging between 100×300×18 mm and 1250×2400×30 mm.
Three-dimensional pieces are pieces, in which the three dimensions of a piece are comparable. Indicatively, said three-dimensional pieces are provided with dimensions ranging between 200×400×100 mm and 1300×3000×200 mm.
In the art, spray booths are known, which typically are provided with a closed space (a booth), inside which the pieces to be painted are conveyed through a conveying system. Typically, said conveying system comprises at least two rollers, one of which is usually motorized while the other one is an idle roller, and a closed belt, on which the pieces to be painted lay. The conveying system can work so that the pieces are painted while passing (i.e., without stopping the closed belt) or intermittently.
It is worth mentioning that in the present invention said spray booth works preferably in an intermittent way: a payload (comprising one to some tens of pieces to be painted) is conveyed inside the spray booth; the conveying of pieces is stopped; the pieces are painted, and once the painting is completed, said pieces are conveyed out of the spray booth. A production batch, painted with a single painting product (a single color) ranges one payload to any number of payloads. Typically, the pieces to be painted are painted in production batches painted with the same color, e.g., blue. Subsequently, the spray booth must be cleaned to change color, e.g., to paint the successive batch with yellow. Alternatively, the pieces could be painted in continuous, without stopping the conveying of pieces.
It is known to provide said spray booths with reading systems of the pieces to be painted, a plenum, and air filtering systems. In this context, plenum means a ceiling able to distribute an airflow entering into the closed space of the booth while painting takes place. Fans force air into the booth, which can be adjusted in order to vary the speed and the quantity of air input into the spray booth in a time unit. The distribution of air must be as uniform as possible, while the speed of air must be controlled. In some points of the plenum the 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 said plenum is maintained inside optimal pre-set limits. Said plenum is in fluidic connection with a suction tower arranged on one of the sides of the spray booth.
Spray paint application entails that not all the sprayed paint hits the parts to be painted; the paint not hitting parts partly hits the 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 spray booth suction system, which can be, in a known way, of different kinds, and comprise or not a suction tower.
Finally, it is known to arrange said spray booth inside a production line, wherein a plurality of machines making different operation are placed in series upstream and downstream said spray booth. E.g., upstream said spray booth there may be provided a machine making a pre-treatment of the pieces to be painted, while downside said spray booth there may be provided a drying oven and/or a vertical storage.
Spray booths are known that through automatic devices (reciprocators, rotating spraying systems, gantry-robots, anthropomorphic-robots) spray paint on parts to be painted.
It is known to provide said spray booths with two spraying arms, each of which bears at least a spraying tool, e.g., in the form of known spraying guns. In this context it is worth specifying that according to the present invention said spraying tools are preferably Cartesian robots or anthropomorphic robots.
The current productive system is based on batch-and-queue production, and generates long lead times; moreover, it requires to produce panels in advance with respect to shipping. Even with the more accurate forecast, the emergency production of panels that are not in the finished goods warehouse is inevitably necessary, or alternatively obsolescence is generated when such warehouse inventories are dimensioned so as to have a greater safety margin.
All this is antithetic with the most modern techniques for organizing production, based on methods known as Toyota Production System (TPS) or Lean Production or Just in Time (JIT). Market drivers are: delivery speed and product customization, lead time reduction, reduced dimensions of production batches, developing and producing special pieces. The production for a more modern warehouse as performed up to now is possible just for non-customized product (mass production). The market requirement is to produce lots size one, with a huge range of finish and dimensions of the panels, and with pull manufacturing.
For mechanical processing the problem was tackled, and now there are provided sundry solutions on the market. For painting, the problem is more complex.
The set-up time of the painting machines, although was reduced to few minutes, inevitably is very expensive due to material waste and need of cleaning solvents (in addition to the purchase cost, there is also the disposal cost to be considered). Therefore, to reduce these costs, the production is scheduled according to daily shipping, grouping the panels to be produced as much as possible according to the kind of paint applied. Despite these methods, the number of paint changes in a working shift went from about some units to several tens.
CN111822210A of Fuzhou Zhibuqu Tech CO LTD, WO2019053590A1 of Carlisle Fluid Tech INC, WO2015010018A1 of Graco Minnesota INC describe cleaning systems for the lumen of tubings and color changes.
CN110605208A of Jiangsu Zonghu Coating Equipment Ind Res Inst CO LTD, DE202012104930U1 of Metso Paper INC, EP300248B2 of Uni Ram CORP describe cleaning systems for nozzles and spray guns.
CN106513217A of Shanghai Kafer Automation Equipment CO LTD, CN111632785A of Hefei Haoming Intelligent Tech CO LTD, CN106362898B of Qingdao Jinguanghong Intelligent Machinery Electronics CO LTD, CN107321538A of Shenzhen Taida Robot CO LTD describe automated cleaning systems.
The present invention aims to provide a spray booth allowing to perform color changing, while minimizing the downtimes due to color changes.
This object is achieved by an apparatus and a method having the features of the independent claims. Advantageous embodiments and refinements are specified in claims dependent thereon.
This object is achieved through a spray booth according to the present invention, which is provided with:
at least two arms provided with a spraying tool comprising a plurality of spray guns for applying paint on pieces; and
at least one, preferably two, cleaning stations of the spraying tool, which cleaning stations are arranged outside said spray booth,
said combination allowing the first spraying tool to be cleaned while the second spraying tool paints pieces and vice versa, so that color changing is performed in masked time, without downtime, i.e., without stopping the painting of pieces.
Said spray booth is provided with at least one cleaning station according to the present invention, which is provided with a substantial box-shape and arranged adjacent to the spray booth. The arrangement is such that it allows to access the suction tanks. Said cleaning station comprises:
a draining tube for collecting paint and solvent. Said tubing is provided with a mouth; said draining tube drains paint/solvent in a (not shown) barrel generally placed outside the cleaning station; said barrel is manually emptied by a human operator;
at least a slot supplying compressed air; and
a cleaning brush.
Said devices are placed inside a mobile drawer provided with two positions:
a rest position, wherein said mobile drawer is inside the perimeter of the cleaning station;
a cleaning position, wherein said mobile drawer protrudes in the spray booth.
In a first preferred embodiment, the spray booth is provided with two arms, each carrying a spraying tool, and with two cleaning stations. In said embodiment, the two said cleaning stations can be arranged on the same side of the suction tower, or alternatively they can be arranged on the opposed side, called operator's side, of the spray booth.
In a second embodiment, the spray booth is provided with four arms, each carrying a spraying tool, and with four cleaning stations.
The method according to the present invention comprises the following steps:
a. Inserting the cleaning station drawer inside the spray booth;
b. Inserting the spraying tool provided with spray guns inside said drawer;
c. Draining the spray gun supply circuit which channels a first painting product, by positioning each spray gun in front of the mouth of the draining tube through an actuator;
d. Optionally, supplying a solvent to spraying guns, by positioning each spray gun in front of the mouth of the draining tube through an actuator;
e. External brushing of spray guns, in the form of dry brushing or wet brushing through said brush;
f. External blowing of the spraying tool through compressed air supplied through at least a slot;
g. Supplying a new painting product up to the spray guns; the spray guns are positioned in front of the draining tube in order to supply the new painting product up to the nozzle while they are open to allow the passage from the solvent/old painting product to the new painting product; the spraying tool is ready to resume painting;
h. Leaving of the spraying tool from the cleaning drawer;
i. Closing of the cleaning station, with the return of the drawer into the inside of the cleaning station.
It is worth specifying that in the case the two successive painting products are of similar colors and chemically compatible, e.g., two paints with a similar composition, the first of which is pale brown and the second dark brown, the step d) with the solvent can be omitted.
The first advantage of the present invention is due to the prevention of downtimes for color changing: this allows to maximize the working time of the spray booth wherein painting is performed, with an apparent economical advantage.
The second advantage of the present invention is the possibility of working on production batches as small as needed, and the possibility of using Just In Time production techniques, while minimizing the quantity of finished products in storage.
The third advantage of the present invention is that the cleaning stations are arranged adjacent to the mobile walls with which typically said spray booths are provided. This allows to use the cleaning stations according to the present invention even in spray booths already installed in production lines (retrofit).
The fourth advantage is that the present spray booth can be used for intermittent painting or in continuous painting.
Additional advantages and properties of the present invention are disclosed in the following description, in which exemplary embodiments of the present invention are explained in detail on the basis of the drawings:
A spray booth according to the invention is provided with two cleaning stations 1, 1′, the first one being disposed on the ingress side of the pieces, and the second one on the egress side. The cleaning stations 1 are mobile, i.e., they can be connected to and disconnected from the spray booth for maintenance.
It is known in the art to provide spray booths 100 with at least one mobile, transparent wall 108, which enables access to the inside of the spray booth. Said cleaning stations 1 are placed in a position adjacent to said spray booth, with their mobile portion (see below) placed in correspondence of said mobile wall 108. This allows providing even spray booth that are already installed in productive lines with at least one cleaning station according to the present invention as a retrofit.
The cleaning station 1 is tied to the spray booth 100 using fasteners such as screw). Moreover, the cleaning station 1, on the perimeter that comes into contact with the spray booth 100, is provided with suitable seals, e.g., made from polythene, which allow the sealing between said two components and prevents the dispersion of the overspray into the environment outside of the spray booth.
In a first, more common, embodiment, the spray booth is provided with two arms a spraying tool 10 being provided on each arm. Therefore, normally just two cleaning stations are provided on one of the two sides, two cleaning stations on the suction tower side, or alternatively two cleaning stations on the operator's side. In a second embodiment, said spray booth can be provided with four arms, a spraying tool being provided on each arm. Therefore, four cleaning stations are needed, two on the suction tower side and two on the operator's side.
Said drawer 5 is provided with a mobile protective wall 4, hinged and blocked with a magnet and a sensor, so that the spray booth 100 is stopped when the wall 4 is hit by the spraying tool. This is a safety mechanism: when the spraying tool 110 moves from its cleaning position toward the inside of the spray booth, generating a risk of collision, the painting is stopped.
Said cleaning station 1 comprises:
A draining tube 6 for collecting painting products and solvents, provided with a mouth 7; said draining tube drains painting products/solvents in a (not shown) barrel generally placed outside the cleaning station. Said barrel is manually emptied by a human operator;
At least a slot 8 supplying compressed air;
A cleaning brush 9.
Said devices are meant for cleaning the spraying tools 110 with which the spray booth 100 is provided.
Said spraying tool 110 is provided with a supporting structure on which there are provided:
Four spray guns 101, 102, 103, 104 provided for painting the main surfaces of the pieces to be painted;
A spray gun 105 provided for the edges of the pieces to be painted;
An optional draining gun 106, whose function is draining more rapidly the tubings channeling the painting product/solvent to the spraying tool 110.
It is known that the spraying tools 110, 110′ are provided with four degrees of freedom in their movement:
A longitudinal direction corresponding to the conveying direction of the pieces to be painted, thanks to the movement of arms 60, 60′ on which spraying tools 110, 110′ are supported;
A transversal direction, corresponding to the width of the spray booth 100, wherein the spraying tools 110, 110′ move sliding on their respective arm 60, 60′;
A vertical direction, wherein the spraying tools 110, 110′ come closer/move away to the pieces to be painted;
Finally, the spraying tools 110, 110′ pivot around their longitudinal axis.
In normal working, when one of the spraying tools must be cleaned e.g., 110, the drawer 5 is moved through its actuator and brought in its cleaning position wherein it protrudes in the spray booth, as shown in
The method according to the present invention is applied to a spray booth 100 comprising preferably two cleaning stations 1, 1′ placed indifferently on the suction tower side (
Said method comprises the following steps:
a. Inserting the drawer 5 of the cleaning station 1 inside the spray booth 100 (cleaning position);
b. Inserting the spraying tool 110 provided with spray guns 101, 102, 103, 104, 105 and optionally with a draining gun 106 inside said drawer 5 of the cleaning station 1;
c. Draining the spray gun supply circuit which channels a first painting product; Obviously said spraying tools 110 are supplied by a (not shown) circuit supplying said painting product to the spraying tool 110, which circuit withdraws said painting product from a reservoir. In order to supply said spraying tools 100 with solvent, the painting product reservoir must be replaced with a solvent reservoir; such replacement can be made manually or automatically, see below;
d. Optionally, supplying a solvent to spraying guns 101, 102, 103, 104 provided for plane painting and to spraying gun 105 provided for painting edges. The guns 101, 102, 103, 104, 105 are placed one by one in front to the mouth 7 of the draining tube 6. In order to place the edge spray gun in front of the draining tube the tube 6 is to be moved through a pneumatic actuator;
e. External brushing of spray guns 101, 102, 103, 104, 105, through said brush 9;
f. External blowing of the spraying tool 110 through compressed air supplied through at least a slot 8. This step has the aim to dry the spraying tool 110 to prevent that drops of solvent or painting product remained on the outside of the spraying tool fall on the pieces to be painted;
g. Supplying a new painting product to spray guns (of a different color/composition with respect to the previous one) to spray guns 101, 102, 103, 104, 105. Spray guns are positioned in front of the mouth 7 of the draining tube 6 in order to supply the new painting product up to the nozzle while they are open to allow the passage from the solvent/old painting product to the new painting product; the spraying tool 110 is ready to resume painting;
h. Having the spraying tool 110 leave from the drawer 5 of the cleaning station 1;
i. Closing the cleaning station 1., and having the drawer 5 return into the inside of the cleaning station in the rest position shown in
The draining spray gun 106 is optional. When provided in the spraying tool 110, the draining steps of the old painting product, of the solvent and of the new painting product are faster. As spray gun 106 is not provided with a spraying nozzle, the diameter of the outlet hole is larger than that of the spraying guns, so as to allow a bigger flow rate than that of spray guns.
Supplying the subsequent product pushes the previous product out from the supplying circuit, for example, supplying the solvent pushes the old painting product out of the circuit, and the new painting product pushes the solvent out of the circuit. The changes are made upstream, manually replacing the supplying reservoir from which the pump draws, or automatically by using a known system for changing colors.
When two subsequent painting products are of similar colors and are chemically compatible, e.g., two paints have similar composition, the first one being pale brown and the second one being dark brown, the step d) with the solvent can be omitted.
The operation of the brush 9 for cleaning the outside of the spray guns may be different:
In a first case, the brush 9 is at least partially immersed in a small tank containing solvent, from which it is wetted. In this case, the supply of solvent, which is provided to the small tank through the same supplying circuit supplying the inside of spray guns, preferably occurs at a reduced pressure with respect to the normal supply pressure of the circuit of the painting product (e.g., 3 atmospheres in lieu of 100 atmospheres);
In a second case, the brush 9 dry-brushes the spray guns.
It should be noted that the cleaning of the outside of the spray guns is performed just for spray guns 101, 102, 103, 104, 105 and not for the draining gun 106.
The entire above-described method is automatic: the opening/closing of the drawer 5, the approaching of the mouth 7 of the draining tube 6 to one of the spray guns 101-106, the rotation of the spraying tool 110 to bring each spray gun in correspondence of the mouth 7, the replacement of the painting product or solvent to supply the supplying circuit of the spraying tool 110, the actuation of the brush 9, the supply of compressed air through at least one s1o68, are all performed by specific actuators, placed under the control of a PLC which is part of the spray booth 100.
In a completely automatic spray booth, there is provided a plurality of reservoirs containing different painting products and a plurality of pumps. When it is necessary to automatically pass to a different painting product (or to a solvent), changing color systems are used, i.e., systems provided with valves which can supply the supplying circuit of the spray booth by selecting from said plurality of reservoirs placed upstream the control valves. Such changing color systems are well known in the art.
As mentioned, the cleaning of one 110′ of the two spraying tools is performed by the cleaning station 1′ while the other spraying tool 110 is spraying the pieces to be painted, freely moving inside the spray booth 100. At the end of the method steps, the spraying tool 110 can start the cleaning steps according to the above-specified method, while the spraying tool 110′ can start painting the subsequent payload of pieces to be painted. Basically, the cleaning operation on the first of the spraying tools 110, 110′ occurs at the same time as the painting operation by the second spraying tool 110′, 110. Consequently, no downtime is needed to clean the spraying tools, which occurs in masked time.
This way, the hourly productivity of the spray booth 100 is maximized, enabling work on production batches as small as needed. Potentially, every single payload can be painted with a different color.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021000007592 | Mar 2021 | IT | national |
