System for continuously supplying a paint spraying plant internally within a tube Description Field of the invention The invention relates to an innovative system for supplying nebulized paint to the painting plant which operates with the technique of spraying inside the tubes, optimizing the procedures for putting the paint under pressure, also improving the safety thereof. Prior art In modern industry, painting has become an increasingly automated procedure because it is in great demand in order to customize products of any kind, in large quantities. One of the most used techniques is that of spray painting, which is carried out by putting under pressure, by means of a compressor connected to an electrical outlet, the entire tank, including the paint inside. The system in question, commonly used by the main industries, however, contains several critical issues since, although it includes a relief valve, it does not represent a safe and reliable solution for nebulizing the paint. In fact, operators must pay the utmost attention when working with paint containers since the latter are made up of actual sealed drums which contain very high pressures inside which may even reach 6 bars. If a relief valve does not work correctly, there is a risk of exceeding the limit pressure, thus causing an explosion that could involve the personnel present in the workplace. Given the criticality of said sealed containers, constant maintenance and overhaul is necessary, which entails an essential increase in the management costs of the entire plant. The above problem adds up to the fact that a generic drum, used to contain the paint to be sprayed, has a capacity of about 25 kg which, in a medium-sized industry, is exhausted in less than 8 hours. This problem involves a periodic refilling of said 25kg drums and the consequential interruption of the painting since, on average, a refilling process is performed in 30 minutes. The object of the patent is therefore to solve the aforementioned problems by creating a paint pressurization system which does not endanger workers and which guarantees less frequent refilling of the drums, in order to optimize production and reduce maintenance costs. Description of the invention According to the present invention, a paint spraying system is provided which effectively solves the aforementioned problems. Said system, by breaking down the paint collection and pressurization steps, allows the creation of a spray painting system which protects the operators and optimizes production. The system in question comprises at least a paint container, at room temperature and pressure which, due to the fact that it does not have to be sealed, may contain an amount greater than 25 kg of paint inside. In an embodiment of the system in question, the paint containers are connected in parallel to each other in order to use the same pneumatic pump, in order to optimize consumption and therefore painting costs. At least a pneumatic pump is installed downstream of the container to move and spray the paint before it is sprayed directly inside the product at a pressure between 2 and 6 bar. Said pneumatic pump comprises a one-way circuit inside it, adapted to put the paint that circulates there under pressure through the movement of a piston operated by two air chambers. Said air chambers are operated by at least a compressed air supply line. In order to stabilize the supply line of the pneumatic pump, at least an air pressure tank is installed, comprising, downstream, a pressure gauge suitable for measuring the air supply pressure. Each container comprises an inlet pipe, that is a tube, preferably of plastic material, which carries the paint still at room pressure, inside said pneumatic pump. Once the paint is nebulized, it is transported outside of said pneumatic pump by using a high- pressure tube which leads it to the place where the spray painting takes place. The high-pressure tube, in one of its variants, is made with a flexible rubber which includes a steel track inside which is capable of withstanding pressures up to 20 bar. When the pneumatic pump is switched off, the paint that has already entered circulation is redirected again, through a special discharge conduit, to the container from which its cycle began. Said discharge conduit is suitable for using all the paint and reducing waste due to material dispersions. A plurality of non-return valves are installed inside said pneumatic pump to make the internal circuit one-way, thus promoting the correct operation of the entire system. At least a pneumatically operated pulsation damper is installed downstream of said pneumatic pump to limit pressure oscillations in the supply line of the already nebulized paint. A pressure reducer is instead installed downstream of said pulsation damper in order to limit the supply pressure of the already nebulized paint supply line. At least a discharge valve is installed downstream of the pressure reducer to facilitate the escape of the paint that has already been nebulized at the correct operating pressure. In one of its embodiments, said discharge valve is electronic and remotely adjustable by means of a plurality of installed electronic circuits. This feature therefore allows the operating pressure to be modified by varying it in a range that goes from 2 to 6 bar. A plurality of pressure gauges is installed in the present invention to monitor the pressure values throughout the plant. In particular, a pressure gauge is installed at the first non-return valve in order to check the pressure values before subjecting the paint to nebulization; said pressure gauge, in one of its embodiments, is of the analog type. A second pressure gauge is installed on the discharge valve and, in one embodiment thereof, is of the digital type. The latter digital pressure gauge is suitable for communicating with a common operations center which operates remotely by means of a Wi-Fi connection. Said operating center, by virtue of the information received by the digital pressure gauge and due to the possibility of modifying the operating pressure of the discharge valve, is suitable for managing the entire present invention remotely. The advantages offered by the present invention are clear in the light of the above description and will be even apparent from the accompanying figure and the detailed description. Description of the figures The invention will hereinafter be described in at least a preferred embodiment thereof by way of non-limiting example with the aid of the accompanying figure, in which: - FIGURE 1 shows a simplified diagram of the paint spraying system suitable for nebulizing the paint contained inside said container 10 by means of a pneumatic pump 13 operated by a plurality of air jets, coming from the compressed air supply line 60, which move the piston included therein. A pneumatically operated pulsation damper 40 is installed downstream of said pneumatic pump 13 to limit pressure oscillations in the supply line of the already nebulized paint. A pressure reducer 50 is instead installed downstream of said pulsation damper 40 in order to limit the supply pressure of the already nebulized paint supply line. Once the optimum operating pressure has been reached, the paint is able to go beyond the discharge valve 17 which is calibrated by means of a spring having an elastic constant suitable for promoting the fluid outlet, only when it pushes with a pressure higher than the minimum pre-established one. The nebulized paint leaves the discharge valve 17 and is guided to the spraying station by a high pressure tube 14 specially sized to withstand the 4 bar operating pressure. A digital pressure gauge 15 is installed in proximity to said discharge valve 17 and is suitable for communicating with a common operating center 16 in order to ensure remote monitoring and activation of the present spraying system. Detailed description of the invention The present invention will now be described purely by way of non-limiting or binding example with the aid of the figure, which illustrates an embodiment relative to the present inventive concept. With reference to FIG. 1, a diagram is shown which explains the features of the present invention. The paint spraying system is an optimized system for transforming the liquid paint contained inside special containers 10 into nebulized paint, transported inside a special high-pressure tube 14 to the spraying station. The paint is then taken inside the container 10 through an inlet duct 11 which carries the paint directly to the pneumatic pump 13. In one of its embodiments, a plurality of containers 10 are connected in parallel to each other to use a single pneumatic pump 13 in order to reduce the already minimal labor costs on said pneumatic pump 13. A non-return valve 18 is installed along the inlet duct to prevent the paint from flowing back and thus to ensure that the circuit is one-way. An analog pressure gauge 12 is installed on said non-return valve 18 and is adapted to read the pressure of the fluid upstream of the pneumatic pump 13. Once the paint in the liquid state reaches the pneumatic pump 13, it undergoes the pressurization process in a range between 2 and 6 bars, consequently said paint nebulizes. The paint which fails to nebulize inside the pneumatic pump 13 is led back to the container 10 by using a discharge conduit 19, in order to avoid waste and reduce consumption. Said pneumatic pump 13 is driven by at least a compressed air supply line 60. In order to stabilize the supply line of the pneumatic pump 13, at least an air pressure tank 70 is installed, comprising, downstream, a pressure gauge 80 suitable for measuring the air supply pressure. A pneumatically operated pulsation damper 40 is installed downstream of said pneumatic pump 13 to limit pressure oscillations in the supply line of the already nebulized paint. A pressure reducer 50 is instead installed downstream of said pulsation damper 40 in order to limit the supply pressure of the already nebulized paint supply line. A discharge valve 17 is installed downstream of the pressure reducer 50 and is suitable for allowing only the paint that has reached the predetermined pressure values to escape. A spring inside, in fact, comprises an elastic constant suitable for being compressed only if the sprayed paint reaches the minimum operating pressure values. If the pressure exceeds 4 bar, the sprayed paint can escape from the discharge valve 17 and continue its path to the spraying station by means of a high pressure resistant tube 14 which, in one embodiment, is of flexible rubber material comprising a steel track inside. A digital pressure gauge 15 is installed near the discharge valve 17 and is able, in addition to reading the pressure values reached, to send the values to a common operating center 16. Said operating center 16 is suitable for communicating via a Wi-Fi connection with said digital pressure gauge 15 exchanging information and, in one of its embodiments, for modifying the elastic constant of the spring contained inside the discharge valve 17 in order to change the minimum operating pressure remotely. Finally, it is clear that modifications, additions or variants that are obvious to a person skilled in the art can be made to the invention described so far, without thereby departing from the scope of protection provided by the appended claims.