EP0481554A1 - Central device for distribution, recirculation and evacuation of air - Google Patents

Abstract

A central device for the distribution, recirculation and evacuation of air with respect to a plurality of using equipments (A, B, C, D,...), each of which is provided with an air supply pipe (6), a fan (8), an evacuation pipe (9) and, if necessary, a heat exchanger (7), this device comprising a delivery manifold (4), connected to the air supply pipes (6) of the various equipments, a mixture intake manifold (5), connected to the evacuation pipes (9) of the various equipments, a pure air intake pipe (20), an evacuation routing pipe (21), an evacuation fan (10) inserted in this evacuation routing pipe, a valve block (14) comprising three valves (15, 17, 16) inserted, respectively, between the mixture intake manifold (5) and the evacuation routing pipe (21), between the mixture intake manifold (5) and the delivery manifold (4) and between the pure air intake pipe (20) and the delivery manifold (4), at least one driving device (18) disposed for controlling the said valves, and a continuous analyser (13) connected to the mixture intake manifold (5) and disposed to control the driving device (18) by the intermediary of a computer (23) <IMAGE>

Description

The subject of the present invention is a centralized device for the distribution, recirculation and evacuation of air intended to produce the evaporation of a vehicle in user equipment, such as sections of machines for rotogravure printing, processing machines and the like.

The invention will be explained with particular reference to machines for rotogravure printing, which form a characteristic application, but it should be understood that this particular application in no way poses a limit for the more general application of the invention .

In machines for rotogravure printing, the different colors of a subject are printed one after the other on a support in successive sections of the machine, the number of which can vary, for example, from three to ten or more. The ink or lacquer used for printing must be diluted by means of a vehicle, usually a solvent, the purpose of which is to give the ink or lacquer an appropriate viscosity and to allow, in the printing, the desired color tone. This vehicle must be removed by evaporation after the printing of each color, before going on to printing the successive color. To perform this operation, the printing machine includes a number of evaporation tunnels, interposed between the different successive printing sections. In each evaporation tunnel, a current of air is blown, through nozzles provided for this purpose, on the face of the support which has just been printed, in order to produce the evaporation of the vehicle, and the mixture of air and vapor that forms this way is exhausted from the tunnel.

The flow rate, speed and temperature of the air blown into each evaporation tunnel must be chosen in an appropriate manner, on one side to ensure complete evaporation of the vehicle during the period of permanence in the tunnel, and on the other hand so as to obtain an appropriate concentration of the vapor in the evacuated mixture. In most cases the vehicle to be evaporated is a solvent which, with air, forms a flammable and, under certain conditions, detonating mixture. It is therefore necessary, for safety reasons, for the evacuated mixture to contain a lower vapor concentration, while respecting an appropriate safety coefficient, relative to the lower explosion limit of the mixture. On the other hand, the prescriptions concerning the pollution of the environment do not allow to simply discharge into the atmosphere the mixtures of air and vehicle vapor evacuated from the tunnel, and therefore these mixtures must be conveyed to depuration devices. to recover the vehicle vapor contained therein, or else to destroy it, usually by combustion. The costs involved in the management of these depuration devices are all the greater the larger the quantities of mixture to be treated and the smaller the concentration of steam in these mixtures. It is therefore important that, while respecting the safety requirements, the concentration of the vapor in the treated mixture is set to the highest possible value.

To meet these requirements, each tunnel is provided with its own air distribution circuit, which is regulated, generally by hand, so that it can introduce, exhaust and recycle appropriate, regulated air flows. depending on the quality and quantity of vehicle to be evaporated in the tunnel in question. The quantities of vehicle which must evaporate in the successive tunnels of the same machine for printing in rotogravure, during the printing of the same subject, can be very different, considering that the printed subject can have very different surfaces covered by the various colors, and this gives rise to correspondingly different amounts of vehicle to be evaporated in the different sections. However, optimal conditions can only be achieved with a small approximation by manual adjustment of the distribution circuits, while adjustment of the individual distribution circuits, controlled by advanced automatic devices, would be excessively expensive in view of the number of tunnels present in a machine for rotogravure printing. We cannot think of a single distribution circuit which operates all the tunnels without differences, due to the requirements, which can also be very different, which arise in the different sections of the machine.

As already mentioned, the particular requirements indicated for rotogravure printing machines, or similar requirements, are also met in other equipment, such as processing machines and the like.

In view of these problems, the object of the invention is to provide a device making it possible to distribute air to a number of user devices while respecting the different requirements of each of them but, at the same time, by centralizing control equipment intended to optimize the management of the entire system.

This object is achieved, according to the invention, by means of a device for the distribution, recirculation and evacuation of air with respect to user equipment, each of which is provided with an air supply pipe, a fan, a discharge pipe and, if necessary, a heat exchanger, characterized in that the device is centralized for a plurality of said devices and that it comprises a collector of discharge, connected to the air supply lines of the various apparatuses, a mixture suction manifold, connected to the evacuation lines of the various apparatuses, a fresh air suction line, a supply line to the exhaust, an exhaust fan inserted on said evacuation delivery pipe, a valve system comprising three valves inserted, respectively, between said mixture suction manifold and said evacuation delivery pipe, between said mixture suction manifold and said delivery manifold, and between said pure air suction pipe and said delivery manifold, at least one drive device arranged to control said valves, and a connected continuous analyzer to said mixture suction manifold and arranged to control said drive device.

In view of these characteristics, the device according to the invention feeds partially recycled air, through its delivery manifold, to a plurality of devices, each of which uses the air supplied by means of its own fan, adjusted according to requirements. particular of the apparatus itself, and if necessary by heating this air by means of its own heat exchanger, also adjusted according to the particular requirements of the apparatus considered, and the mixture of air and vapor evacuated by the various switchgear is resembled by the mixture suction collector, mixing it with the mixture discharged by the other connected switchgear; this resulting mixture is analyzed to establish the concentration of the vehicle contained therein, and the three valves of the valve system are adjusted by their driving device, under the control of the analyzer, so as to route to the evacuation, under the action of the exhaust fan, a fraction of this mixture, to recycle a fraction of this mixture by routing it to the discharge manifold, and to add to this recycled fraction of mixture a certain amount of pure air from of the fresh air suction line. Since this process is monitored by a continuous analyzer, it can take place in such a way as to meet safety requirements and, at the same time, to adjust the concentration of the vapor in the mixture sent to the discharge to the most suitable value. , and therefore the recovery or destruction of the vapor contained.

The advantages of using a device according to the invention are numerous. The device serves a number of devices, and therefore the installation and management costs are much lower than for a plurality of similar devices arranged to each serve only one device. No air adjustment is no longer necessary in single groups. The device ensures the delivery to the evacuation of the smallest possible quantities of mixture, containing the greatest possible vapor concentration, thus making it possible to reduce the costs of installation and management of the depuration device. The various characteristics of the mixtures discharged by the various devices are brought to average values by the reciprocal mixture, so that the mixtures with a lower vapor content serve to dilute the more concentrated mixtures, and vice versa. The recirculation of the air and steam mixture can be kept at the highest value compatible with the operating conditions and with the safety requirements. A balance is always ensured between the mixture suction and discharge collectors, connected to the various devices. In addition, all these characteristics are obtained by working advantageously on a mixture of average properties, while ensuring the possibility of achieving in each apparatus the optimum local conditions for its particular operating requirements.

Preferably the device further comprises a pressure sensor connected to the mixture suction manifold and arranged to control the operation of the exhaust fan. Preferably, a second continuous analyzer is connected to the discharge collector in order to allow a control of the regular operation of the device. Preferably, a heat exchanger is arranged to operate between the evacuation supply line and the pure air suction line, with the aim of preheating the pure air drawn in at the expense of the heat of the mixture supplied to evacuation. Finally, taking into account the fact that a device for purifying the mixture sent to the evacuation must be connected, a connection can be established between the outlet of this depuration device and the inlet for the pure air drawn in, thus achieving a partially closed air circuit.

The device according to the invention can control, for example, the distribution of air to all the sections of one or more machines for rotogravure printing, or else two or more devices according to the invention can be provided, each of which is connected to a plurality of sections of the apparatus, having requirements compatible with each other but not compatible with the requirements of other sections of apparatus.

The invention will be explained in more detail with reference to an embodiment of the invention, preferred but which should be considered as a non-limiting example, applied to a machine for printing in rotogravure. The only figure in the appended drawing shows the simplified diagram of the apparatus and the device according to the invention, with the valve system shown in section.

Each of the squares distinguished by the letters A, B, C, (D), ... represents the solvent removal device forming part of a section of a machine for rotogravure printing. The number of these sections can be any. Each solvent removal device comprises a tunnel 1 (well known per se and which will not be described), through which the printed support which is to be dried is passed by evaporating the vehicle or solvent from the ink or the lacquer applied to the support. In this tunnel, on the part of the support which has just been printed, an air current is blown coming from an air supply pipe 6, by means of nozzle systems, which are also well known and which do not are not shown, actuated by an electric fan 8 intended to be adjusted locally according to the particular requirements of the section considered. In addition, the supply air can be heated by means of a heat exchanger 7, which is also locally adjusted according to the particular requirements of the section in question. The mixture of air and solvent vapor is carried out of the tunnel 1 by means of an evacuation pipe 9. As can be seen, these components are substantially those of a usual device for removing the solvent, intended to suck in water. air from the medium and to discharge into the medium a mixture of air and vapor of solvent, as it could be used before the adoption of prescriptions relating to protection against pollution of the medium.

In view of the fact that certain sections of the apparatus may remain inactive during certain works, each section also comprises an inlet valve 2, inserted on the air supply line 6, and an outlet valve 3, inserted on the discharge line 9, and these valves 2 and 3 are intended to be closed, thus isolating the section considered, when the latter is to remain inactive.

The air supply lines 6 of several sections are connected, upstream of the respective isolation valves 2, to a discharge manifold 4 of the device according to the invention. Similarly, all the discharge lines 9 of the same sections are connected, downstream of the respective isolation valves 3, to a manifold 5 for mixing suction of the device according to the invention.

The mixture suction manifold 5 is connected to an inlet I of a valve body 14, and in a similar manner the discharge manifold 4 is connected to an outlet Il of the valve body 14. The valve body 14 is provided with another outlet III, which is connected, via a line 21, an electric exhaust fan 10 and, if necessary, a heat exchanger 22, to a depuration device 23. The depuration device 23 can operate by recovering the vapor contained in the mixture it receives, or else by destroying this vapor. In any case, it routes purified air to an outlet 24, which can be discharged into the medium. The valve body 14 is also provided with an inlet IV for clean air coming via a line 20 and, if necessary, the heat exchanger 22, with an air intake 26 which can be opened in the middle. However, it is also possible to establish a connection, indicated at 25 by broken lines, between the outlet 26 and the outlet 24, so as to suck as pure air part of the purified air leaving the depuration device 23. In in this case the air circuit is partially closed. The pure air drawn in, thanks to the heat exchanger 22, can be preheated at the expense of the heat of the mixture of air and steam evacuated; however, the heat exchanger 22 can also be omitted.

The operation of the exhaust electric fan 10 is preferably controlled, according to actual need, by a pressometric sensor 12 connected to the mixture suction manifold 5. This is specially used to proportion the operation of the device to variations in the flow rate of the mixture sucked in by the manifold 5, also taking into account the fact that a variable number of sections of the apparatus served may be inactive and therefore have been isolated by means of the corresponding valves 2 and 3. The electric fan 10 must always maintain a certain degree of vacuum in the mixture suction manifold 5, and therefore in the tunnels 1, in order to prevent the escape of solvent vapors from the tunnels; as a consequence of this depression, a certain amount of air (called "false air") is sucked into the tunnels 1, as indicated diagrammatically by the arrows 11, through the openings provided for the entry and the exit of the support to be treated . Other air can also be sucked around the printing units of the machine in order to prevent small amounts of solvent, released from the containers applied to these groups, being introduced into the medium. As a result, the flow passing through the mixture suction manifold 5 is always somewhat greater than the flow passing through the discharge manifold 4.

In the valve body 14 are installed three valves: a discharge valve 15, arranged between the inlet 1 for mixing suction and the outlet III for delivery to the discharge, a valve 16 for clean air, arranged between the inlet IV for clean air and the outlet outlet Il, and a recirculation valve 17, disposed between the inlet 1 for mixing suction and the outlet outlet Il. These valves, depending on their position, produce a subdivision of the flow of mete lange of air and steam entering through inlet 1 in a partial recirculation flow directed towards the discharge outlet II, and a partial flow directed towards the outlet III to be evacuated, as well as the addition to said recirculation flow of a certain quantity of pure air coming from the IV inlet and also directed towards the discharge outlet II. The valves 15 to 17 can each be controlled by its own drive device, but preferably, as in the example shown, they are controlled collectively by a common drive device 18, for example pneumatic. In any case, the valve drive device is controlled by a continuous analyzer 13, inserted on the mixture suction manifold 5, this analyzer being constituted by an apparatus known per se, capable of determining the concentration of the vapor of solvent in the mixture passing through the collector 5, or else the lower explosion limit of the mixture. The signal produced by this analyzer is received by a computer 27 and, under the control of this computer, the drive device 18 moves the valves 15 to 17 to determine said subdivision of the flow of incoming air and vapor mixture, as well as the addition of pure air, so as to tend towards the achievement of optimal operating conditions. In practice, it can be seen that, independently of the concentration of the vapor contained, it is usually not advisable to recirculate more than 90% of the mixture coming from the collector 5.

A second analyzer 19 can be conveniently inserted on the discharge collector 4. It has no control functions on the device, but it allows an advantageous verification of the correct functioning of the device.

The operation of the device is as follows. At the beginning of the operation, of course, the concentration of the vapor contained in the mixture sucked by the manifold 5 is reduced. The analyzer 13 detects this reduced concentration and therefore the computer 27, through the drive device 18, regulates the valves 15 to 17 by giving the valves 15 and 16 the minimum opening and the valve 17 l maximum opening, so that the maximum percentage of the mixture coming from the manifold 5, admitted for recirculation, is conveyed to the discharge manifold 4, while the smallest possible quantity of this mixture is conveyed to the evacuation via line 21 , and the smallest possible quantity of pure air is introduced via line 20. As operation continues, as a consequence of the recirculation of the air and vapor mixture, the concentration of the solvent vapor in the mixture passing through the manifold 5 gradually increases. If, and when, as a result of this increase, the concentration of vapor in the mixture reaches a preset limit value, detected by the analyzer 13, the computer 27 controls the drive device 18 to move the valves 15 to 17 , and more precisely by opening valves 15 and 16 further and closing valve 17 more, so as to reduce the percentage of mixture which will recirculate and increase the percentage of mixture which is conveyed to the evacuation and the quantity of fresh air added. From this moment the analyzer 13, the computer 27 and the drive device 18 continuously keep the valves 15 to 17 under control, increasing or reducing, as appropriate, the percentage of mixture that is recirculated , so as to maintain the concentration of the vapor in the mixture which is supplied to the depuration device 23 near the optimum preset value.

The correct development of the evaporation operation in the tunnels 1 is ensured by the fact that the concentration of the vapor in the mixture supplied to the delivery manifold 4 is always lower than the concentration of the vapor in the mixture passing through the manifold 5 , and this is either due to the introduction of "false air" 11, or due to the addition of pure air coming from line 20.

In this way, the device according to the invention makes it possible to be as close as possible to the optimal conditions, insofar as the operating conditions and the pre-established safety requirements allow, the mixture of air and steam supplied to the depuration, while allowing local, separate and independent adjustment of the operating conditions in each of the devices served.

The depuration device 23 is not a part of the device according to the invention; it can be of any known genus and will not be described. The heat exchanger 22 makes it possible to recover part of the heat possessed by the mixture conveyed to the evacuation, by transferring this heat to the pure air sucked in. However, this is not always advantageous, and therefore the heat exchanger 22 should not be considered as a necessary element of the device according to the invention. Finally, as already noted, part of the purified air, discharged into the atmosphere through the outlet 24, can be routed via a connection 25 to the pipe 26 for the entry of clean air, thus achieving a partially closed circuit.

Different complementary parts can, of course, be added to the device described, and various modifications, as well as any replacement by technical equivalents, can be made to the device described.

Claims (10)

1. Device for the distribution, recirculation and evacuation of air in relation to equipment ges users (A, B, C, D, ...), each of which is provided with an air supply line (6), a fan (8), an exhaust line ( 9) and, where appropriate, a heat exchanger (7), characterized in that the device is centralized for a plurality of said devices and that it comprises a discharge manifold (4), connected to the supply lines of air (6) from the various devices, a manifold (5) for mixing suction, connected to the exhaust pipes (9) of the various devices, a pipe for suction of clean air (20), a pipe ( 21) for evacuation routing, an exhaust fan (10) inserted on said evacuation routing pipe (21), a valve system (14) comprising three valves (15,17,16) inserted, respectively, between said mixture suction manifold (5) and said evacuation delivery pipe (21), between said mixture suction manifold (5) and the edit delivery manifold (4), and between said clean air suction pipe (20) and said delivery manifold (4), at least one drive device (18) arranged to control said valves, and an analyzer continuously (13) connected to said mixture suction manifold (5) and arranged to control said drive device (18). 2. Device according to claim 1, characterized in that it further comprises a pressometric sensor (12) connected to the manifold (5) of mixture suction and arranged to control the operation of the exhaust fan (10). 3. Device according to claim 1, characterized in that a second continuous analyzer (19) is connected to the discharge collector (4) in order to allow a control of the regular operation of the device. 4. Device according to claim 1, characterized in that a heat exchanger (22) is arranged to operate between the pipe (21) for routing to the evacuation and the pipe (20) for suction of pure air , for the purpose of preheating the pure air drawn in at the expense of the heat of the mixture supplied to the discharge. 5. Device according to claim 1, to which is connected a device (23) for purifying the mixture conveyed to the evacuation, characterized in that it comprises a connection (25) between the outlet of said device (23) for purifying and l inlet (26) for the aspirated clean air, thereby providing a partially closed air circuit. 6. Device according to claim 1, characterized in that it is applied to control the distribution of air to all sections of one or more machines for printing in rotogravure. 7. Device according to claim 1, characterized in that it is connected to a plurality of sections of apparatus, having requirements compatible with each other but not compatible with the requirements of other sections of apparatus, these latter sections being in turn connected to another similar device. 8. Device according to claim 1, characterized in that it comprises isolation valves intended (2,3) to allow to isolate each apparatus served, relative to the collectors (4) of discharge and (5) of aspiration of mixing of the device, during the periods of inactivity of the apparatus considered. 9. Device according to claim 1, characterized in that said valves (15,16,17) of the system (14) of valves are connected to each other, and that the drive device (18) which controls them is unique. 10. Device according to claim 1, characterized in that it comprises a computer (27) which receives the signal produced by said analyzer (13) and provides for the control of said device (18) for driving the valves.

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