Background Art Today, the production of containers in different shapes and sizes-for example, plastic bottles or pots made of PET, PP, HDPE, or PEN-suitable to contain different types of foodstuff takes place in production plants that carry out complex processes. Normally, these processes comprise a blow-moulding phase to create the container in its final form, starting from a pre-moulded workpiece. Depending on the properties required of the final container (for example, a container that must contain a special type of liquid), this first blow-moulding phase may be followed by a painting operation to coat the outside of the container. This operation uses products particularly suited to make the container gas-tight, such as to oxygen or carbon dioxide. The issue of the permeability of the container walls to gas is particularly important, for example, when dealing with bottles that must contain carbonated drinks, but also in the case of other foodstuff or drinks that are affected by oxidation, decreasing shelf life.

The painting plants can be of very different sizes, also depending on the productive capacity of the plant that can vary from hundreds to several thousands of bottles per hour given the widespread use of plastic containers in certain markets. Today, these plants are highly automated and are normally controlled by specific or general purpose computers (sometimes even Personal Computers or PCs, that run specific software). The components common to these plants include a station for loading the containers to be painted, a painting station, a paint- reticulation station (for example, comprising ovens of different types), and a station for unloading or transferring the containers to other machines.

In these plants, especially high-output plants, it is important and problematic to achieve and maintain in time containers with a constant painting quality ;

furthermore, it is also necessary to minimize the intervention of human operators and downtime due to failures, damage, and other unscheduled matters. These requirements often also go hand in hand with the need to manage a number of process parameters greater than the number manageable with purely electromechanical means.

Finally, such complex plants must be able to use different types of paint according to the properties required of the containers, and adapt the painting rate to the different productive capacities of the blow-moulding plant containers; essentially, these plants must be very flexible.

Objects of the invention It is an object of this invention-to provide a computerized system for managing a plant for painting containers or other objects made of plastic, such as bottles, that resolves the aforementioned problems carrying out high-quality painting processes in the shortest time possible, compatibly with the adopted painting process and with the required productive capacities.

It is another object of the invention to provide a computerized method for implementing a painting process using the aforementioned computerized system.

It is another object of the invention to create a program for the computer that implements the computerized method in accordance with the invention.

In accordance with a first aspect of the invention, these objects are achieved by means of a computerized control system of a plant suitable for painting containers, especially plastic bottles, comprising many processing stations that carry out the different phases of said painting process. Said computerized control system features centralized control devices for storing the parameters and operating data of the plant and for controlling the values of the process, devices for detecting the signals concerning the operating values of said stations, and actuators for controlling specific devices of the stations. Said stations are grouped together into three functions, specifically: transferring and handling the containers, applying the paint, and drying. Each function involves several stations.

Thanks to the innovative characteristics of the system in accordance with the invention, the painting plant is able to adapt to the most diverse production needs, in addition to operating with parameters that can vary considerably, managing the

painting processes optimally. The particular architecture of the computerized system-grouped together into just three macro functions to represent the entire painting line-makes it possible to manage the painting plant even in different configurations thanks to modular-type modifications.

The architecture of the electronic system for controlling the line is designed to have a centralized console where all the information and data for managing and monitoring the plant and the subordinate stations are available. Settings, adjustments, and detailed checks of the individually controlled areas are carried out in the subordinate stations. The computer program coordinates the different stations by grouping them together into macro functions; thus, it is able to manage optimally-all the functions required of the painting processes that can be-carried out in the plant. Thanks to said system characteristics, interventions by operators are minimized both when carrying out a particular painting process and when switching from one type of process to another using a different type of paint.

In accordance with another aspect of the invention, the above problems are resolved by means of a computerized method for controlling a painting plant of containers, especially plastic bottles, using a computerized system including means for displaying data, processing data, acquiring data, and actuating and controlling the devices. Said method comprises the following stages: a) Managing the container-loading parameters when the containers are loaded onto a first conveyor chain through a loading station, b) Managing the parameters for moving said first conveyor chain, c) Managing the parameters concerning at least one container-pretreatment operation in a pretreatment station, d) Managing the parameters concerning at least one painting operation in. a painting station, e) Managing the parameters concerning the transfer of the containers from said first conveyor chain to a second conveyor chain, f) Managing the parameters concerning feeding through a paint-drying area, g) Managing the parameters concerning the drying operation of the paint on containers in a flash-off area in at least one oven,

h) Managing the parameters concerning the transfer of the containers to another station for further operations.

Other preferred embodiments of the in-line treating device are described in detail in the claims.

Brief description of the drawings Other advantages of the invention will become apparent from the detailed description of embodiments of the computerized system, given by way of non- limiting example and in conjunction with the following accompanying drawings, where: - Fig. 1 shows a block diagram of a painting process implemented with a control system of a painting plant in accordance with the invention; - Fig. 2 shows a schematic three-dimensional view of a painting plant controlled by means of a computerized control system in accordance with the invention; - Fig. 3 shows a block diagram of a part of the plant controlled by the computerized system in accordance with the invention; - Fig. 4 shows a block diagram representing the main components of the painting plant controlled by the computerized system in accordance with the invention; - Fig. 5 shows a block diagram of the computerized control system in accordance with the invention.

Detailed description of the invention Fig. 1 shows a schematic view of a painting process, so-called coating process, of plastic containers-for example, but not necessarily bottles made of PET-that normally includes the phases described below. This description uses the terms "containers"and"bottles"indifferently to refer to the objects to which this invention applies. The containers are made by a known type of blow-moulding plant, not described in this description, and are transported by means of a known type of conveyor to a loading station of the painting plant of the invention. This painting plant feeds the bottles at the appropriate feed rate through a pretreatment station where the bottles are, for example, treated in order to eliminate any residual electric charges, subjecting them to a stream of deionized air if necessary. The means of transport are a part of a first conveying circuit of the closed-ring type.

The next phase involves subjecting the bottles to an electric charge in an electric

field, for example of approximately 100kV, in order to charge the bottles with an appropriate electric charge. Then, the bottles are forwarded to the next phase, which takes place in the painting station. Painting can be carried out preferably through spray painting, immersing the containers in dip tanks, or flow-coating ; however, other painting processes can also be used whenever these are suitable for the particular product chosen to coat the bottles.

After completing the-painting phase, the-bottles. are. transferred from the first conveying circuit to a second conveying circuit that moves the bottles to a flash-off area for a predetermined amount of time (normally ranging from a few seconds to 60 seconds and over), which depends on the type of paint or product used. Then, the bottles are fed through an ovenoven or set of ovenovens for performing reticulation for an amount of time that also varies according to the used type of paint. A particular coating product, marketed as Bairocade0, for PET bottles requires a reticulation time that varies between 5 to 15 minutes at a temperature of approximately 60°C-70°C. When this phase has been completed, the bottles are unloaded and sent off for other uses.

I. n order to implement the described process in the most cost effective, quick, and efficient way a control system is used. In accordance with an essential aspect of the invention, said control system is managed according to the computerized method described below, and implemented by means of a computer program that is the core of the control system of the painting plant.

The control system groups together the different stations that make up the painting line into three macro functions: M1 comprising the functions of transferring and handling the containers to be painted, M2 comprising the painting functions, and M3 comprising the drying functions.

The macrofunction M1 (transferring and handling the plastic containers) comprises the stations of the plant that convey and handle the bottles from the start to the end of the line : the loading station or carousel (1), the primary chain (2), the transfer unit (3), the washing unit (4), the secondary chain (5), and the unloading station or carousel (6).

For the macrofunction M1, the computer program in accordance with the invention manages the motors (10,11) of the conveyor chains, controlling their feed rate by

means of an electric shaft, in order to guarantee the synchronism and timing between the system of the primary chain (2) and the system of the secondary chain (5), according to Fig. 3. The layout also includes some encoders (12,13) placed between the motors and the relating transmission (14,15).

In some work stations, when required by the painting process, the rotating speed of the containers to be painted around their axis is also controlled. The macrofunction M1 also manages the flow of the bottles, and is able to collect data and parameters on the process underway by means of appropriate interfaces in all the concerned areas of the painting plant. Furthermore, it is able to save and separate the acceptable product from the reject; thus, creating a complete map of the-line product, which-can be appropriately saved in the electronic memory of the computer in order to eliminate the rejects at the right time.

In order to carry out the programmed operations, the macrofunction M1 includes several devices that detect the corresponding signals. These devices include the encoder (12) for detecting the feed rate and position of the primary chain 2, the encoder (13) for detecting the feed rate and position of the secondary chain (5), and a photocell detector and a limit stop device for checking the presence of bottles. Actuators and control systems are also used, including a control unit for controlling the motors (10,11) of the conveyor chains, a control unit of the motors for rotating the containers, and electromagnetic valves for controlling the bottle- handling cylinders.

The parameters for controlling the painting process are entered into the monitoring console (20) of the painting plant. These parameters include the feed rate of the bottle-conveying line, the timing difference between the primary chain (2) and the secondary chain (5), and the rotating speed of the containers around their axis.

These values are monitored in real time, making it possible to control the status of the process.

The second macrofunction M2 manages the application of the paint or coating product in the pre-treatment station (7), if included in the painting plant, and in the coating booth (8). Thus, the control system controls the process for preparing the bottles for painting and manages several processes, notably : the deionization of the bottles, the application of any electrostatic charge on the containers or the

plasma treatment of the bottles, the mix and the quantity of paint, and the environment inside the paint booth (8) where the paint is applied.

The stations of the painting plant included in the macrofunction M2 comprise devices that detect the signals required to manage the painting process optimally.

Said devices include pressure transducers for measuring the air-filtering degree in the paint booth ; flowmeters for measuring the flow of air in the booth; and sensors for detecting the temperature and the humidity of the environment, for controlling LEL, and for measuring the level of paint and solvents. Furthermore, flowmeters are used to control the flow of the paint, and devices are used to measure the viscosity and temperature of the paint.

Actuators and control systems are also used, including aspirators and fans placed in appropriate locations; electrodes for generating the electrostatic charge on the containers to be painted; plasma actuators; and valves, pumps, and stirrers for the paint.

For the macrofunction M2, the monitoring console (20) sets the parameters required for controlling the relating phases of the painting process, including the environment temperature and humidity limits, the drying level of the environment, the airflow in the paint booth, the recipes for mixing the paint, and the electrostatic charge for the bottles. Furthermore, the control system monitors in real time the most significant values of the process, even at the different stations if necessary, such as the environment temperature and humidity, the dryness of the environment, and the airflow in the paint booth.

The third macrofunction M3 of the plant, which deals with drying, comprises the different paint-drying stations including the flash-off station (21) and the infrared (22), air (23), and/or ultraviolet (24) ovens. The control system controls the painting process in order to guarantee that the paint on the bottles is dried appropriately, managing the thermal and radiation energy supplied to the bottles.

The electronic circuits of the plant give feedback on certain values such as the temperature of the bottles, the temperature of the air exiting each station, and the supply voltage of the lamps in the case of IR and UV ovens. In this way, the process is constant and the quality of the product is controlled on line.

The macrofunction M3 features devices for detecting respective signals. These devices include optical pyrometers for reading the temperature of the bottles, one or more radiometers for measuring the intensity of the radiation with ultraviolet rays, and a Pt100 device for measuring air temperature. There is also an electronic circuit for reading the supply voltage of the lamps of the ovens, and transducers for measuring the temperature and humidity of the environment.

The actuators and the control systems of the macrofunction M3 comprise power electronic cards for controlling the infrared or ultraviolet lamps, power electronic cards for controlling the resistors of the air oven (s), and fans and aspirators for adjusting the airflow.

The operators enter, in the monitoring console (20), parameters useful for defining the process of this macrofunction M3, including the temperature of the bottles, the acceptable temperature range, and the air temperature and airflow in the ovens.

This part of the painting process is controlled by monitoring in real time the most significant values, including the supply voltage of the lamps, the temperature of the air, the time the bottles remain at the different stations, the temperature of the bottles, and the airflow and air pressure in the ovens.