SOLVENT EVAPORATION SYSTEM IN PAINT DRYING PROCESSES

Description

B092A000402 SOLVENT EVAPORATION SYSTEM IN THE PROCESSES OF DRYING OF PAINTS. DESCRIPTION The present invention relates to the drying process of paints, of the type comprising solvents which must be evaporated during said drying process. In fact, a conventional paint drying system consists of an evaporation zone and a drying zone. In the evaporation zone, the parts with the paint applied to them are subjected to aeration. This aeration occurs inside a tunnel where forced circulation of air from outside is achieved. The air velocity reaches one meter per second (Im / sg); the direction is opposite to that of the parts' circulation, and the air temperature during this process is around thirty degrees Celsius (30°C). The direction of air movement is opposite to that of the circulation of the parts. The air, duly filtered, enters from the end of the tunnel where the parts exit, and exits from the opposite end, where the parts enter. This ensures that the air entering the tunnel maintains a minimum concentration of the solvent to be evaporated. As it travels through the tunnel, the concentration of the solvent to be evaporated progressively increases, and when it exits the tunnel, the air has the highest concentration of solvents. Therefore, the tunnel exit is the point where the air is purest and the solvent absorption capacity is maximum; while at the tunnel entrance, due to the saturation of the air with solvents, the absorption capacity is practically zero and thus the solvent elimination is also practically zero. In this way, due to the very design of conventional processes for drying paints with solvents applied to the surface of different pieces, the exposure times of said pieces are very long and, furthermore, the required temperature and air velocity conditions negatively affect the quality of the resulting surface. In fact, in traditional evaporation tunnels, the times recommended by paint manufacturers before starting the drying process are relatively long, on the order of 10 minutes; this, at a speed of five meters per minute, represents a transport length of fifty meters. This presupposes very large tunnels. to large, that is, with a large space occupied by the system. In accordance with the present invention, a new system for evaporating paint solvents is proposed and the fundamental variant proposed consists in changing the direction of air movement. In fact, in all the solutions known up to now, the direction of the air is parallel to the direction of the painted pieces j while in accordance with the solution proposed here the direction of the air is perpendicular to the theoretical horizontal plane containing the painted pieces. From a direction of air parallel and inverse to the movement of the pieces, we move to a direction perpendicular and from bottom to top. With this new trajectory in the direction of the air S-ì- obtains that, at any point of the evaporation tunnel, the conditions for the evaporation of the solvent are optimal, since the air enters clean, without any concentration of solvent and in these conditions it comes into contact with the painted pieces at all points along the entire length of the tunnel. On the other hand, the movement of air from bottom to top establishes an ascending current of air which allows for the acceleration of a natural movement of air from the affected surface towards the top. This creates the ideal conditions for maximizing solvent transfer to the air carrying it, resulting in accelerated evaporation. This means the time required to enter the drying phase is much shorter than with traditional systems. Likewise, accelerating evaporation means that, at the same speed as conventional solutions, a shorter path is required, thus reducing the length of the evaporation tunnels and consequently the space they occupy. On the other hand, it should be noted that in traditional evaporation systems, solvents are removed by the transverse movement of air over the painted surface. This can cause undulations or curling on the surface. In contrast, with the system in question, since the air moves in a vertical, upward direction, there is no tangential movement of the air at the surface level, and as a consequence, such irregularities do not occur on the surface. All these improvements change the essential conditions of the system, differentiating it from everything that has been known up to now. To better understand the nature of the invention, the attached tables show, by way of a purely illustrative and non-limiting example, a preferred form of industrial embodiment to which reference is made in the description, and in said tables: - fig. 1 shows a schematic representation of the traditional system used for the evaporation of solvents in the drying process of painted pieces; - Fig. 2 shows a schematic representation of the system now proposed for the evaporation of solvents in the paint drying process; - fig.3 shows a cross-section representation of an example of practical implementation of the system for the development of the system which is the object of the invention; - Figures 4 and 5 illustrate corresponding means seen from above and in plan of an example of the mentioned system for the development of the system according to a straight aligned arrangement; - Figures 6 and 7 illustrate top and plan views of an example of the system in a semicircular arrangement. ILLUSTRATIVE DETAILS 1. - Evaporation tunnel. 1.1 - Entry ends of the pieces. 1.2 - Output ends of the pieces. 2. - Direction of air circulation. 3. - Painted pieces. . - Median transporter. 5. - Air intake. 6. - Turbine. 7· - Heating battery. 8. - Filter. 9· - Lung. 10. - Collection bell. 11. - Aspirator. 12. - Evacuation exit. 13. - Direction of the path of the pieces. The object of the present invention is a system for the rapid evaporation of solvents in paint drying processes. As schematically shown in Fig. 1, traditional systems are equipped with an evaporation tunnel 1 into which the corresponding painted pieces 3 enter, transported by a conveyor belt 4 or any similar means. In accordance with traditional solutions, the pieces 3 enter tunnel 1 following a direction of travel indicated by the black arrows 5 in Fig. 1; while inside tunnel 1 a forced flow of filtered air is established which moves in a direction parallel to that of the pieces 3, but opposite to it, as indicated by the white arrows 2 in the aforementioned Fig. 1. This conventional solution shown in Fig. 1 means that the filtered and clean air enters from end 1.2 of tunnel 1, that is, it enters where the pieces 3 exit, and in this area the concentration of the solvent eliminated by the pieces 3 progressively increases; so that at inlet 1.1 of tunnel 1 the air is saturated with solvents. Because of this, at the beginning of tunnel 1.1 the solvent absorption capacity of the air is practically zero, while on the contrary the maximum absorption capacity is reached at outlet 1.2. This conventional solution requires considerable evaporation times and, consequently, very wide tunnels 1 that occupy large spaces. Likewise, the fact that the air flows in the opposite direction to the movement of the pieces 3 gives rise to a tangential movement at the surface of the latter, which can cause undulations or curling on the surface of the same pieces 3. To avoid these inconveniences, the system which is the subject of the invention was designed, schematically represented in fig. 2. In accordance with the new system, the direction of the air movement is changed from a movement parallel to that of the pieces 3 to a movement in a direction perpendicular to the pieces 3 as represented by the arrows 2 in fig. 2. Likewise, the direction of air movement from bottom to top, as indicated by the aforementioned arrows 2. With this change in the direction of air movement, it follows that at any point inside the evaporation tunnel 1 the air has practically the same level of solvent concentration, this translates into an optimal condition for evaporation, thus allowing for a reduction in the times of this process and, consequently, the length of the tunnel 1. On the other hand, since the air movement is in an ascending direction, the natural displacement of evaporation from the applied surface is accelerated and irregularities such as waviness or curling on the surface of the pieces are avoided 3. Fig. 3 shows, as a non-limiting example of practical implementation, a possible implementation of the system proposed above. According to this solution, air enters from the outside through the inlet port 5 and is pushed by a turbine 6 to a heating battery 7, then passes through a filter 8 and reaches the reservoir 9, which uniformly projects the air from the bottom upwards, creating a laminar flow that meets the conveyor 4 on which the painted pieces 3 are placed. Once the air passes the pieces 3, causing the solvent to evaporate from the paints, it flows towards a collection bell 10 from which it is evacuated by means of an aspirator 11 to the outlet port 12. In a preferred embodiment, the system assembly is envisaged to comprise an air inlet 5 and two outlets 12 for evacuation, although the number of inlets 5 and outlets 12 can be completely variable, remaining in accordance with the object of the invention; the aforementioned system assembly can be arranged in a straight line as can be seen in figures 4 and 5, or following a curved path such as a semicircle, as can be seen in figures 6 and 7. Having sufficiently described the nature of the present invention, as well as its industrial realization, it is therefore necessary to add that changes in shape, material and arrangement can be made to the complex and its constituent parts without departing from the scope of the invention itself, since such changes do not alter its functioning. The Applicant reserves the right to submit appropriate modifications to make any necessary improvements to the present invention. _ . ~ . .. ? -rh - - · -Λ'-rfe*

Claims

CLAIMS 1) Solvent evaporation system in paint drying processes, characterised in that the movement of the solvent evacuation air is carried out in a direction 2 perpendicular to the upper surface of the painted pieces 3, i.e. perpendicular to the theoretical horizontal plane of advancement of said pieces 3 and that the direction of the air movement is from bottom to top; so that an ascending vertical movement of the entire mass of air is generated which drags the solvents of the paint applied to the surface of the pieces 3. 2) Solvent evaporation system in paint drying processes according to claim 1, characterized in that a particular practical embodiment of the plant for implementing the system is constituted by an air inlet 5, provided with a door, beyond which is located a turbine 6 and subsequently a heating battery 7, to open the duct, through a filter 8, and a lung 9 located below the median conveyor 4 of the painted pieces 3, and above said conveyor of the aforementioned pieces 3, an air collection bell 10 which gives access to an evacuation outlet 12 in which is incorporated an aspirator 11 to accelerate the evacuation. 3) Solvent evaporation system in paint drying processes in accordance with the provisions of Rule 2, characterised by the fact that in the system the inlets 5 for the evaporation air and the evacuation outlets 12 can be multiple in variable number and independent of each other. 4) Solvent evaporation system in paint drying processes in accordance with the provisions of the rules 1 and 3, characterized in that the system assembly can be distributed according to a straight alignment or following a curved path. Bologna, 05 / 11 / 1992 The Master Engineer Giaric rio D. Olio (Register prot. 193D) IT IS DECLARED THAT THIS IS A TRANSLATION CONFORMING TO THE ORIGINAL TEXT OF THE SPANISH PATENT FOR INVENTION No. 9201530 OF 22 July 1992. OFFICE OF THE HOWNCIMI OF BOLO OFFICE 11. 9