EP4357713A1

EP4357713A1 - Dual supply system for ovens

Info

Publication number: EP4357713A1
Application number: EP23204567.4A
Authority: EP
Inventors: Piattelli Andrea
Original assignee: Unitech Industries Srl
Current assignee: Unitech Industries Srl
Priority date: 2022-10-19
Filing date: 2023-10-19
Publication date: 2024-04-24

Abstract

A dual supply system (1) for ovens, comprising a substantially box-shaped element (2), which can be associated with an inlet mouth of a duct (C) of an oven (F), with which it is placed in fluid communication; the box-like body (2) includes a first inlet opening (4) and a second inlet opening (5) for respective air flows directed towards the inlet mouth of a duct (C) of an oven (F). The system (1) also includes at least one burner (6), positioned so as to intercept the flow of air entering through the first inlet opening (4), at least one heat exchanger (7), positioned so as to intercept the flow of air entering through the second inlet opening (5), of the first selective occlusion means (8) of the first inlet opening (4), and of the second selective occlusion means (9) of the second inlet opening (5).

Description

TECHNICAL FIELD OF THE INVENTION

The present invention concerns a dual supply system for ovens.
More specifically, the present invention concerns a dual supply system for ovens with different possible configurations of use in relation to specific production needs.

BACKGROUND ART

Numerous types of industrial equipment use an oven to carry out certain treatments on processed products that require the generation and transfer of large quantities of heat.
Some non-limiting examples of such equipment are textile dryers and stenters, which typically include a tunnel-shaped oven through which the product to be treated is passed: a flow of hot recirculation air passes inside the oven, having a temperature suitable for the specific type of treatment to be carried out.
The aforementioned equipment usually also includes an oven supply system, which heats the air flow to carry out the treatment.
Some of the aforementioned supply systems are of the combined type, that is, they are configured to heat the air flow using several energy sources operating together. This choice is dictated by the need to have a supply system that is as flexible and versatile as possible, capable of meeting different operational needs efficiently, with particular attention also to the aspect of resource optimization, and therefore of the energy consumption of the equipment.
For this purpose, combined systems have therefore been developed which use (in the most frequent cases) electrical heating means (typically resistors) together with other steam-type ones (in particular an exchanger, also called battery).
Other existing systems exploit, as an energy source, both a device powered by gas, or LPG, or diesel oil (burner) and, together with the latter, a device comprising an exchanger, or battery, powered by diathermic oil.
In still other cases - less frequent - the combined system includes a burner and a steam-powered exchanger/battery.
Evidently, the combination of the different types of devices used in the same system could be any, to satisfy specific application/production needs.
These combined systems, regardless of the specific types of devices used within them to heat the air flow, are all characterized by the same configuration, which relates to the specific positioning of the devices themselves.
More in detail, in all the aforementioned combined systems, the different heating devices, or exchangers, are positioned in sequence, i.e. one after the other, with reference to the direction of the air flow that passes through the oven.
This configuration of the power system, and therefore this arrangement of the heating/exchanger devices, allows, in some cases, to operate both devices simultaneously, so as to therefore operate in series, in the case of high energy demands.
In other cases, it is also possible to completely exclude one of the devices, so as to use the other one exclusively, to meet certain needs (for example, the scarcity of one of the two energy sources, or its particularly high cost).
The operation of the two devices can, of course, be appropriately regulated so as to dose the thermal power generated by each of them, in relation to the effect one intends to obtain inside the oven.
The aforementioned combined systems present, however, some drawbacks and problems.
Some drawbacks that can arise in this type of system are often due to the poor compatibility of the different heating/exchanger devices, which forces the adoption of often complicated and expensive construction and installation solutions, for example to avoid fire risks or other unexpected events.
Furthermore, the positioning of the two different devices in sequence, one after the other, which is common to all types of existing devices, usually generates high pressure drops in the air flow that passes through them, with a consequent reduction in system performance.
Added to this is that this positioning, in sequence, of the two different heating/exchanger devices is often penalizing from the point of view of maintenance and cleaning, since these devices are preferably installed close to each other (especially in the case combined systems that do not require the use of a burner are used).

OBJECTS OF THE INVENTION

The technical aim of the present invention is to improve the state of the art in the field of supply systems for ovens.
Within such technical aim, it is an object of the present invention to develop a dual supply system for ovens which allows the previously reported drawbacks to be overcome.
Another object of the present invention is to create a dual supply system for ovens which allows solving the compatibility problems between the different heating/exchanger devices which afflict known systems.
A further object of the present invention is to make available a supply system for ovens that allows reducing the pressure drops of the air flow that passes through it. Yet another object of the present invention is to create a dual supply system for ovens simplified from the point of view of cleaning and maintenance.
This aim and these objects are all achieved by the dual supply system for ovens according to the attached claim 1.
The system according to the invention includes a substantially box-shaped element, which can be associated with an inlet mouth of an oven, with which it is placed in fluid communication.
The substantially box-shaped element includes a first inlet opening and a second inlet opening, for respective air flows directed towards the inside of the oven.
The system also includes at least one burner, powered by gas, or LPG, or diesel, positioned so as to intercept the flow of air entering through the first inlet opening of the substantially box-shaped element.
The system also includes at least one heat exchanger, positioned so as to intercept the flow of air entering through the second inlet opening of the substantially box-shaped element.
The system also includes first selective occlusion means of the first inlet opening, and second selective occlusion means of the second inlet opening.
According to an aspect of the invention, in a first configuration of use of the system characterized by a dual supply, both the burner and the heat exchanger are operational, and the air enters the oven duct both through the first inlet opening and through the second inlet opening.
In this first configuration of use, both the first selective occlusion means and the second selective occlusion means are inactive (i.e. removed from the supply system).
According to another aspect of the invention, in a second configuration of use of the system, characterized by a single supply, only the burner is operational; the air enters the oven duct through the first inlet opening, and intercepts the burner since the first selective occlusion means are inactive, while the second selective occlusion means are active, and prevent the entry of air through the second opening.
According to a further aspect of the invention, in a third configuration of use of the system, also characterized by a single supply, only the heat exchanger is operational; the air enters the oven duct through the second inlet opening, since the second selective occlusion means are inactive, while the first selective occlusion means prevent the entry of air through the second opening.
The dual supply system solution according to the invention allows the burner or the heat exchanger to be used in certain production situations as an alternative to each other (in the second and third use configurations respectively).
In other production situations, both devices can also be used simultaneously (in the first use configuration).
In any case, in whatever configuration of use the supply system is used, the solution according to the present invention is advantageous from multiple points of view, as will be seen below.
In fact, the pressure drops of the air flow entering the oven duct are significantly reduced, since in fact there are no heating devices or exchangers installed inside the substantially box-shaped element, which intercept this flow, as happens instead in systems of a known type.
For the same reasons, the conditions for carrying out maintenance and/or cleaning of the supply system are also significantly improved and simplified, precisely due to the absence of exchanger or heating bodies inside the substantially box-shaped element of the system.
Furthermore, numerous risks of various kinds which characterize known systems are eliminated, as clarified below.
The dependent claims refer to preferred and advantageous embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will be more evident from the detailed description of a preferred, but not exclusive, embodiment of a dual supply system for ovens, illustrated by way of example, but not by way of limitation, in the attached drawings in which:

figure 1 is an axonometric view of a two-module oven in which two dual supply systems, according to the present invention, are installed;
figure 2 is an axonometric view of one of the two modules of the oven of figure 1; figure 3 is a cross section of the oven module of figure 2;
figure 4 is an axonometric view of the oven module of figure 2, with some parts removed for greater clarity;
figure 5 is a detailed axonometric view of the module of figure 4, with further parts removed;
figure 6 is an axonometric view of the module of figure 4, sectioned along a horizontal plane;
figure 7 is a top and detailed view of the air supply duct inside the oven module; figure 8 is a cross section of the supply duct carried out according to plane VIII-VIII of figure 7;
figure 9 is a front view of the duct of figure 7;
figure 10 is a detailed axonometric view of another embodiment of the dual supply system according to the invention, in a first configuration of use in which both the burner and the exchanger are operational;
figure 11 is a detailed axonometric view of a phase of preparation of the system of figure 10 in a second configuration of use, in which only the burner is operational;
figure 12 is a detailed axonometric view of a further preparation phase of the system of figure 10, in the aforementioned second configuration of use;
figure 13 is a detailed axonometric view of a phase of preparation of the system of figure 10, in a third configuration of use, in which only the exchanger is operational;
figure 14 is a detailed axonometric view of a further phase of preparation of the system of figure 10, in the aforementioned third configuration of use.

EMBODIMENTS OF THE INVENTION

With reference to the attached figures, the reference number 1 generally indicates a dual supply system for ovens according to the present invention.
The system 1 according to the present invention can be associated with ovens F of industrial equipment of any type, without specific limitations.
In an embodiment of the invention of particular practical interest, the system can be associated with the oven F of an equipment in the textile field, such as dryers, stenters, or similar.
Figure 1 shows an oven F (for example the oven of an equipment in the textile field) in which at least one system 1 according to the present invention is installed.
In particular, the oven F includes two coupled M modules, but which can also work individually.
More in detail, inside each module M of the oven F a duct C is installed, for supplying the air which enters through the system 1 according to the invention, so as to convey it towards the product treatment areas.
The system 1 according to the invention includes a substantially box-shaped element 2.
The substantially box-shaped element 2 can be associated with the inlet mouth 3 of the air supply duct C inside the oven F, with which it is in fluid communication.
As can be seen, for example, in figures 3 and 6, the supply duct C includes fans V which circulate the air in the area of the oven F (the upper one in figure 3) through which the products to be treated pass.
According to one aspect of the invention, the substantially box-shaped element 2 includes a first inlet opening 4 and at least a second inlet opening 5, for respective (recirculation) air flows directed towards the inside of the oven F.
Furthermore, system 1 includes at least one burner 6, powered by gas, or LPG, or diesel (which constitutes the first type of fuel supply of system 1).
The burner 6 is associated with the substantially box-shaped element 2, so as to intercept the flow of air entering through the first inlet opening 4.
The system 1 also includes at least one heat exchanger 7, or battery (more in detail, a battery of tubes inside which a heating fluid flows); the exchanger 7 constitutes the second type of supply of system 1.
The exchanger 7 is associated with the substantially box-shaped element 2, so as to intercept the flow of air entering through the second inlet opening 5.
According to a further aspect of the invention, the system 1 includes first selective occlusion means 8 of the first inlet opening 4.
Furthermore, the system 1 includes second selective occlusion means 9 of the at least one second inlet opening 5.
As will become clearer in the remainder of the description, the features of the present invention, and in particular the first, second selective occlusion means 8, 9 allow the supply system 1 to be used in multiple configurations of use, and therefore with different supplying modes.
In a first configuration of use of system 1, the burner 6 and the exchanger 7 are both simultaneously operating (dual power supply active).
Therefore, in this first configuration, the air enters duct C both through the first inlet opening 4, intercepting the burner 6, and through the second inlet opening 5, intercepting the exchanger 7.
In the first configuration of use, therefore, both the first selective occlusion means 8 and the second selective occlusion means 9 are inactive.
In the first configuration of use, therefore, it is possible to exploit the advantages resulting from the simultaneous use of both types of power supply, appropriately dosed in relation to the specific production condition, to obtain the necessary thermal power.
In a second configuration of use of system 1, only burner 6 is operational (single power condition).
The recirculation air enters the duct C only through the first inlet opening 4 (since the first selective occlusion means 8 are inactive), and therefore intercepts the burner 6.
The second selective occlusion means 9 are instead active, and therefore they prevent the air from entering the oven F through the second inlet opening 5.
This second configuration of use, therefore, can be used in production situations in which it is intended to exploit the peculiar characteristics of air heating obtained with burner 6, powered by gas, or LPG, or diesel (for example, the possibility of quickly reaching high air temperatures).
In a third configuration of use of system 1, the at least one heat exchanger 7 is operational (further single power condition).
The recirculation air enters the duct C through the second inlet opening 5 (since the second selective occlusion means 9 are inactive), and therefore intercepts the exchanger 7.
The first selective occlusion means 8 are instead active, and therefore they prevent the air from entering the oven F through the first inlet opening 4.
This third configuration of use, therefore, can be used in production situations in which it is intended to exploit the peculiar characteristics of air heating obtained with at least one heat exchanger 7 of a specific type.
In this regard, it is specified that the heat exchanger 7, or battery, of the system 1 according to the present invention can be of different types, in relation to the specific production needs.
More in detail, the exchanger 7 can be of the type powered by oil, steam, superheated water, or other types, without limitations to the purposes of the present invention.
According to one aspect of the invention, the substantially box-shaped element 2 includes a first wall 10.
For example, this first wall 10 can be a front (or possibly rear) wall, with reference to the main direction of development of the oven F to which the system 1 is associated.
Through this first wall 10, the burner 6 penetrates inside the volume enclosed by the substantially box-shaped element 2, which is, in turn, in fluid communication with the duct C.
The substantially box-shaped element 2 also includes at least a second wall 11.
At least a second wall 11 can be a side wall, with reference to the main direction of development of the oven F to which the system 1 is associated.
For example, at least a second wall 11 can be perpendicular to the first wall 10.
The second inlet opening 5 is created in the at least one second wall 11.
The exchanger 7 is associated, with the substantially box-shaped element 2, at such second wall 11, in such a way as to be hit by the air flow which circulates inside the oven F and enters the duct C through the second inlet opening 5.
The substantially box-shaped element 2 also includes a third wall 12.
This third wall 12 can be an upper wall, with reference to the main direction of development of the oven F to which the system 1 is associated.
The third wall 12 can therefore be perpendicular to both the first wall 10 and the second wall 11.
The first inlet opening 4 is made in the third wall 12 of the substantially box-shaped element 2.
It is emphasized that the specific positioning, and orientation in space, of the elements that make up the system 1 according to the present invention (in particular the burner 6, the exchanger 7, the first inlet opening 4, the second inlet opening 5), with particular reference to the main direction of development of the F oven, may be different from those described above, in relation to certain application/production needs, which may change from time to time.
All possible alternative solutions, from this point of view, still fall within the scope of protection of the present invention.
According to one aspect of the invention, the system 1 comprises a first filter 13.
The first filter 13 can be associated, in a removable manner, with the first inlet opening 4.
In the specific embodiment illustrated in figures 1-9, the first filter 13 is therefore arranged, in use, along a horizontal plane.
The first filter 13 is preferably of the mesh type; it has the function of preventing impurities (such as fluff, fiber residues) or foreign bodies from entering the duct C through the first inlet opening 4.
The first filter 13 may include a handle portion, to be able to be inserted/extracted into/from the first inlet opening 4 (for example via sliding guides), for cleaning and maintenance reasons.
According to one aspect of the invention, the system 1 comprises a second filter 14. The second filter 14 can be associated, in a removable manner, with the second inlet opening 5.
In the specific embodiment illustrated in figures 1-9, the second filter 14 is therefore arranged, in use, according to a vertical plane.
The second filter 14 is preferably of the mesh type; it has the function of preventing impurities or foreign bodies from entering the duct C through the second inlet opening 5.
The second filter 14 may include a handle portion, to be able to be inserted/extracted into/from the second inlet opening 5 (for example via sliding guides), for cleaning and maintenance reasons.
According to a further aspect of the invention, the first selective occlusion means 8 comprise a first screen 15.
The first screen 15 can be associated, in a removable manner, with the first inlet opening 4.
The first screen 15 includes a solid body with a substantially laminar shape, which completely prevents the passage of air.
The first screen 15 slides along respective guides: it can be moved towards the center of the duct C, to open the first inlet opening 4 without the need to extract it. According to yet another aspect of the invention, the second selective occlusion means 9 comprise a second screen 16.
The second screen 16 can be associated, in a removable manner, with the second inlet opening 5.
More in detail, the second screen 16 is hinged at the second inlet opening 5, and can be moved using a special handle 17, accessible from the outside of the oven F. The second screen 16 is therefore mobile between a raised closing position of the second inlet opening 5, and a lowered opening position of the second inlet opening 5.
It should be noted that, in the specific embodiment of the invention illustrated in figures 1-9, there are two heat exchangers 7, installed at both second (lateral) walls 11 of the substantially box-shaped element 2.
The second screen 16 includes a solid body with a substantially laminar shape, which completely prevents the passage of air.
The way of using the dual supply system 1 for ovens according to the invention is, in light of what has been described, completely intuitive.
In the first configuration of use of the system 1 according to the invention, both the burner 6 and the at least one exchanger 7 are operational (dual power supply active). In this first configuration, both the first selective occlusion means 8 and the second selective occlusion means 9 are inactive (i.e. the first screen 15 and the second screen 16 are removed, respectively, from the first inlet opening 4 and from the second inlet opening 5).
The first filter 13 and the second filter 14 are inserted respectively at the first inlet opening 4 and the second inlet opening 5, to prevent impurities from entering the duct C.
To obtain the second configuration of use of the system 1, in which only the burner 6 is operational (single power condition), the second screen 16 (or each screen 16) is raised to occlude the second inlet opening 5 (or each inlet opening 5) so as to prevent the passage of air through it.
By doing so, therefore, the recirculated air can enter the duct C of the oven F only through the first inlet opening 4, thus intercepting the burner 6.
To obtain the third configuration of use, in which only the (or one) heat exchanger 7 is operational (further single power condition), starting from the second configuration of use, the second screen 16 is lowered from the second inlet opening 5 (or each screen 16 from each inlet opening 5).
Subsequently, the first screen 15 is inserted at the first inlet opening 4, which prevents the passage of air through the aforementioned first inlet opening 4.
By doing so, therefore, the recirculation air can enter the duct C only through the second inlet opening 5, thus intercepting the exchanger 7.
It is completely intuitive that it is possible to easily switch from one to another of the three configurations provided for system 1 simply by inserting, or removing, the first, second screen 15, 16.
Another embodiment of system 1 according to the invention is illustrated in figures 10-14.
This embodiment differs from the previous one due to the conformation and configuration of the first and second selective occlusion means 8, 9.
More in detail, in this embodiment the first selective occlusion means 8 comprise a first filter 13 and a second filter 15 which are extractable and constructionally similar, and therefore interchangeable with each other.
Likewise, the second selective occlusion means 9 comprise a second filter 14 and a second filter 16 which are also extractable and constructionally similar, and therefore interchangeable with each other.
Figure 10 refers to the first configuration of use of the system 1 according to the invention, in which both the burner 6 and the exchanger 7 are operational (dual power supply active).
In this first configuration, both the first selective occlusion means 8 and the second selective occlusion means 9 are inactive (i.e. the first screen 15 and the second screen 16 are removed, respectively, from the first inlet opening 4 and from the second inlet opening 5).
The first filter 13 and the second filter 14 are inserted respectively at the first inlet opening 4 and the second inlet opening 5, to prevent impurities from entering the oven.
Figures 11, 12 refer instead to two successive phases of the preparation of the system 1 in the second configuration of use, in which only the burner 6 is operational (single power supply condition).
In particular, to obtain this second configuration of use (figure 11), the first filter 13 and the second filter 14 are removed respectively from the first inlet opening 4 and from the second inlet opening 5 (as indicated by the arrows).
Subsequently (figure 12) the second screen 16 is inserted at the second inlet opening 5 (as indicated by the arrows), which prevents the passage of air through the aforementioned second inlet opening 5.
By doing so, therefore, the recirculated air can enter the duct C of the oven F only through the first inlet opening 4, thus intercepting the burner 6.
Figures 13, 14 refer instead to two subsequent phases of the preparation of the system 1 in the third configuration of use, in which only the heat exchanger 7 is operational (further single power supply condition).
In particular, to obtain this third configuration of use (figure 13), starting from the second configuration of use, the first filter 13 and the second screen 16 are removed respectively from the first inlet opening 4 and from the second inlet opening 5 (as indicated by arrows).
Subsequently (figure 14) the first screen 15 is inserted at the first inlet opening 4, which prevents the passage of air through the aforementioned first inlet opening 4, while the second filter 14 is inserted at the second inlet opening 5 (as indicated by the arrows).
By doing so, therefore, the recirculation air can enter the duct C of the oven F only through the second inlet opening 5, thus intercepting the exchanger 7.
It is completely intuitive that it is possible to easily switch from one to another of the three configurations provided for system 1 by simply inserting or removing the first, second filter 13, 14, or the first, second screen 15, 16.
The system 1 according to the invention therefore allows the heating of the oven F to be managed as needed, completely independently, without interference, without load losses and with a notable reduction in process energy costs, also eliminating any residual risk and/or contamination between the two heating devices.
According to a practical example - illustrated only for the purpose of a better understanding of the technical advantages of the invention - a user within a company has saturated steam at 10 Bar and for two out of three production shifts. The same user requires distinct processes, which require for example different temperatures (for simplicity, 160°C and 200°C respectively).
Notoriously, saturated steam at 10 Bar has a temperature of 185°C, therefore it is assumed that the indirect exchange with large volumes of air can lead to obtaining a working and air temperature of around 160°C, which however satisfies only part of the work to be carried out.
By using the supply system 1 according to the invention, the user can advantageously carry out both processes on the same system, in particular by operating with the second use configuration, in which only the burner 6 is operational: the burner 6, in fact, allows to reach the temperature of 200°C without any particular problems.
Furthermore, the possibility of using burner 6, instead of exchanger 7, allows the industrial plant (and therefore oven F) to function even during the third shift, in which steam is not available.
Thanks to this, in fact, it is possible to avoid turning on the thermal power plant for the production of steam during the third shift, thus avoiding a probable economic expense.
It has thus been seen how the invention achieves the proposed purposes.
The system 1 according to the invention therefore allows the use of a double supply system, maintaining the technical conditions of a single supply machine unchanged. Furthermore, the system 1 allows to obtain a high versatility of use without generating, for the same energy used, any load loss, and without penalizing the energy used/production ratio.
The system 1 does not present clogging problems greater than those of systems with a single battery or exchanger.
The system 1 also eliminates:

the fire risks affecting combined systems with several devices arranged in sequence;
the risks due to any aqueous residues that can deposit inside the steam batteries;
possible problems of distortion/deformation of the batteries, with possible breakages, due to the high temperatures reached in the flame area of the burner, and also to the high temperatures of the batteries with diathermic oil;
the inevitable oxidation which, due to the modularity of the flame, can form in a battery positioned after the burner, given the high operating temperatures of the same;
the risks of known systems, of the combined type, which involve a battery positioned downstream of a burner, which could retain microfibres, hair, or other things, despite the presence of a filter.

The system 1 according to the invention is also configured to switch in a very practical and quick way from one configuration to another (and therefore from one power system to another).
The invention thus conceived is susceptible to numerous modifications and variations, all falling within the scope of the inventive concept.
For example, in one version of the invention, the system 1 can include two exchangers 7 (of the same type or different types) arranged symmetrically with respect to the burner 6.
Furthermore, all details can be replaced by other technically equivalent elements. In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to needs, without departing from the scope of protection of the following claims.

Claims

Dual supply system (1) for ovens, characterized in that it comprises:
a substantially box-shaped element (2), which can be associated with an inlet mouth of a duct (C) of an oven (F), with which it is placed in fluid communication,

said box-shaped body (2) comprising a first inlet opening (4) and a second inlet opening (5) for respective air flows directed towards the inside of duct (C);

at least one burner (6), positioned so as to intercept the flow of air entering through said first inlet opening (4);

at least one heat exchanger (7), positioned so as to intercept the flow of air entering through said second inlet opening (5);

first selective occlusion means (8) of said first inlet opening (4);

second selective occlusion means (9) of said second inlet opening (5).
System (1) according to claim 1, suitable to operate in a first use configuration in which said burner (6) and said heat exchanger (7) are both simultaneously operative, and in which said first selective occlusion means (8) and said second selective occlusion means (9) are inactive.
System (1) according to claim 1 or 2, suitable to operate in a second use configuration in which only said burner (6) is operative, in which said first selective occlusion means (8) are inactive, and in which said second selective occlusion means (9) are active, and they prevent the air from entering the oven (3) through said second inlet opening (5).
System (1) according to one of the preceding claims, suitable to operate in a third use configuration in which only said heat exchanger (7) is operative, in which said second selective occlusion means (9) are inactive, and in which said first selective occlusion means (8) are active, and they prevent the air from entering the oven (3) through said first inlet opening (4).
System (1) according to one of the preceding claims, wherein said heat exchanger (7) is of the type fed by oil, or by steam, or by superheated water.
System (1) according to one of the preceding claims, wherein said box-shaped element (2) comprises a first wall (10), through which said burner (6) penetrates inside the volume enclosed by said box-shaped element (2), and a second wall (11), in which said second inlet opening (5) is made, and a third wall (12), in which said first inlet opening (4) is made.
System (1) according to one of the preceding claims, wherein said first selective occlusion means (8) comprise a first screen (15) which can be associated, in a removable way, with said first inlet opening (4), said first screen (15) comprising a full body, essentially laminar in shape, which completely prevents the passage of air.
System (1) according to one of the preceding claims, wherein said second selective occlusion means (9) comprise a second screen (16) which can be associated, in a removable way, with said second inlet opening (5), said second screen (16) comprising a full body, essentially laminar in shape, which completely prevents the passage of air.
System (1) according to claim 7, comprising a first filter (13) of the mesh type which can be associated, in a removable way, with said first inlet opening (4), and interchangeable with said first screen (15).
System (1) according to claim 9, comprising a second filter (14) of the mesh type which can be associated, in a removable way, with said second inlet opening (5), and interchangeable with said second screen (16).