DESCRIPTION

Field of the invention The present invention relates to a hood and a relative dust suction plant for paper production and/or processing lines, i.e., a hood and a relative suction plant specifically designed for application in the paper industry.

Background of the invention

As known, paper is made from cellulose fibres and a large amount of dust is generated during its processing into a finished product. The high speed at which the current production lines operate has contributed to an increase in the production of this residue.

The dust produced during processing is a major problem: paper dust in particular is an irritant and can be harmful to the health of operators if present in the work environment in high concentrations; paper dust can also pose a risk to the plant itself, being highly flammable and even explosive if it exceeds defined concentration limits in the work environment.

As it is not possible to avoid the formation of paper dust itself during the processing with the current equipment, there is a particular need to minimise the concentrations of dust within the working environment to limit the risks to the operators and the plant described above.

Currently, one of the ways of achieving this reduction in concentration is to stop the plant at set intervals to stop further dust generation and to remove the already formed dust in the air and which is deposited on the machinery. This strategy unquestionably leads to economic losses due to the stopped production, and therefore the loss of income therefrom during the downtime period.

Other known solutions include the use of suction systems to ensure a continuous removal of dust produced during the operation of the paper machines in order to minimise the downtime of the plant itself. However, the known suction systems have several drawbacks. A first drawback is the low suction efficiency (defined as the ratio between the amount of dust sucked in and the total mass or volume flow rate of air sucked in). In fact, the known systems do not ensure a uniform suction in the transverse direction of the paper layer (which, being developed into a band, has a prevalent longitudinal extension), and therefore only manage to suck up part of the paper dust emitted by the layer. In extractor hood suction systems, it has been found that the suction flow rate is highest near the connection of the main suction pipe in the hood, while moving away from this region there is a decrease in suction performance. Given that the suction efficiency of these known systems is not optimal, periodic shutdowns are therefore necessary to remove the paper dust which is not directly sucked in, using in combination further suction and/or blowing devices to remove the dust deposits from the paper processing machines.

The low suction efficiency of the hoods currently on the market is further a cause of high energy consumption. Moreover, the extractor hoods currently on the market are very bulky and therefore cannot be installed directly next to the paper layer or inside the paper processing machine. The distance from the paper layer and generally from the direct paper processing area contributes to reducing the suction efficiency, considering the fact that it is assumed that a significant proportion of the paper dust is emitted during the folding step of the paper layer.

Further, the known extractor hoods are positioned in a fixed manner, and such a position is influenced by external conditions such as assembly space etc. Such limitations further influence the suction efficiency. Among other things, such a positioning rigidity of the hood also causes a limitation of the maximum flow rate of air which can be sucked. In fact, a fundamental design requirement is that the suction force of the hoods must never be such that it displaces the paper layer from the sliding seat thereof, and thus compromises the operation of the machine itself. The most critical moment for meeting this requirement is during paper roll replacement, where the paper layer loses tension and is more prone to movement. Assuming that the value of the air flow rate sucked in by the plant remains constant, the minimum (fixed) distance between the hood and the paper layer will be determined not by the normal working condition of the hood itself, but by the working conditions present in this particular step of the production process, which is obviously the most critical. Stationary hoods are therefore positioned farther away from the paper layer than that which would be the optimum operating distance, with an inevitable decrease in suction efficiency. Lastly, the currently known extractor hoods have a fixed arrangement; it goes without saying that such arrangement may be effective in some operating conditions but not so effective in others. Therefore, the known hoods do not respond adaptively to different operating conditions in the processing line.

An known extractor hood disclosed in the patent US4690042 provides an elongated body with two distinct internal sections, which develop side by side, or rather overlapping, along a longitudinal axis of the body. However this solution does not allow to achieve among other things, one suction capacity evenly distributed along the extension of the body, nor in general satisfactory suction efficiency.

Summary of the invention The object of the present invention is therefore the realisation of an extractor hood and a consequent dust suction plant for paper processing machines which overcomes the limits of the known art described above.

In particular, it is an object of the present invention to provide an extractor hood having a high suction efficiency, at each processing step of the paper layer and the production line.

It is further an object of the extractor hood according to the invention to be adaptable to different production lines and to be efficient in terms of both suction efficiency and energy consumption.

Another object of the hood and the consequent suction plant is to reduce the level of dust in the air in the working environment, to minimise the risk of damage to property and people accessing the working environment itself, thus minimising or completely eliminating plant downtime.

These and other objects are reached by the extractor hood according to the invention, the essential features of which are defined by the first appended claim. Other important additional features are the subject matter of the dependent claims. It is also an object of the invention to provide a suction plant using an extractor hood according to the first and following claims.

Brief description of drawings

The features and advantages of the hood will appear more clearly from the following description of an embodiment thereof, provided by way of non-limiting example with reference to the appended drawings in which:

- figure 1 is an isometric view of an extractor hood, with parts not shown for clarity of interpretation of the drawing;

- figure 2 is a bottom view of the hood of figure 1 ;

- figure 3 is a top view of the hood of the previous figures;

- figure 4 is a sectional view of the hood, according to the section line AA shown in figure 3;

- figure 5 shows in isometric view a variant of the hood according to the previous figures;

- figure 6 shows in isometric view a suction plant with several extractor hoods, each as shown in the previous figures;

- figure 7 is a side view (with parts omitted for clarity of interpretation) of the plant according to figure 6;

- figures 8a to 8d show, respectively in isometric right and left view, side and sectional view according to line AA of figure 8c, a variant of a suction plant inserted within a paper layer transport roller of a paper processing line;

- figure 9 is an isometric view of the hood from the previous figures showing adjustment movements of the hood itself;

- figure 10 is a top view of a plant with two extractor hoods with moving means of the plant;

- figure 11 is a side view of the plant of figure 10;

- figure 12 is a bottom view of the plant of figure 10 and figure 11 ; and

- figures 13 to 16 show the above mentioned moving means in isolation, in particular figure 13 is a front view, figure 14 is a side view, figure 15 is a rear view and figure 16 is a top view.

Detailed description of the invention With reference to the figures, an extractor hood C according to the invention comprises a frame body 1 of substantially box-like shape, defining an internal compartment 10 in fluid communication with an air intake inlet 11 and an air intake outlet 12. The sucked air flows in the hood from the inlet 11, within the internal compartment 10, towards the outlet 12.

The frame body 1, and consequently the internal compartment 10, have a main development according to an axis X between a first and a second longitudinal ends.

More in detail, the frame body 1 comprises at least a first wall 1a and a second wall 1b, mutually facing each other; in use, the first wall 1a is arranged facing a work area with respect to which the hood is installed and with respect to which it performs the suction function thereof. In a preferred application solution, the work area is relative to that of a paper processing machine, thus the first wall 1a faces, in use, a paper strip or layer being processed. In this situation, the longitudinal axis X of frame body 1 is substantially transversal to the movement direction of the paper layer that, being in a continuous strip, travels in the work area.

The air intake inlet 11 is made on the first wall 1a, visible in figure 2, arranged in a distributed manner between the longitudinal ends of the body. Such an inlet is intercepted by a grille to allow the passage of the sucked air into the internal compartment 10. In the solution illustrated in figures 1 to 7, the outlet 12 of the sucked air is made on the second wall 1b in proximity of one of the two longitudinal ends of the body. Such an outlet takes the form of a hole (figure 3) which defines a connection for a pipe outside the hood (of a known type, therefore not described and not shown in the figures). The pipe connects the hood to the vacuum generation plant, which obtains the suction effect of the air.

It goes without saying that depending on the application, the outlet 12 may also be alternatively provided on the frame body 1, for example on a side wall 1c (arranged between the first and second walls), as shown in the solution illustrated in figures 8a to 8d, for example. Having said this, there is nothing to prevent the extractor hood from being arranged with respect to the layer in a different way, i.e. , not substantially perpendicular to the direction of development of the paper layer, but inclined towards it. This choice can be a function of specific working conditions.

Returning to the description of the hood, within the compartment 10 there are uniform distribution means for the flow rate of air sucked in along the axis X. Such means essentially concern the internal development of the compartment along the axis X.

Refer in particular to figures 1 and 4.

A plurality of bulkheads 13 are mounted within the compartment 10. The plurality of bulkheads is mounted in a regular array along the axis X, standing substantially perpendicular to the air inlet 11 and consequently to the wall 1 a. Each pair of contiguous bulkheads 13', 13" defines a suction channel 14. The plurality of contiguous bulkheads shall then define a plurality of contiguous suction channels 14 arranged inside the compartment 10 in at least an orderly array along the axis X in a number one unit less than the total number of bulkheads.

In the example shown in the figures, there are sixteen bulkheads, thus the number of suction channels defined thereby is fifteen. It goes without saying that other solutions with numbers other than those taken as examples can be envisaged. For example, the number of bulkheads (and consequently channels) may vary depending on the length along the axis X of the hood, or on design specifications (suction force, etc.).

Returning to the channels 14, each channel defines an air inlet 14a thereof and an air outlet 14b thereof. The flow of sucked air runs through each individual channel 14 from the inlet 14a, towards the outlet 14b and develops from the air inlet and the air outlet of the channel perpendicularly to the longitudinal axis X.

The air inlet 14a therefore relates to the air inlet 11 of the hood, while the air outlet 14b is directed towards the inside of the compartment 10. In detail, all the outlets 14b of the individual channels face a free zone 100 of the internal compartment 10, zone 100 into which the outlet 12 of the hood leads.

According to an aspect of the invention, each channel 14 has a divergent shape, i.e. , the inlet 14a is larger than the outlet 14b.

According to a further aspect of the invention, each outlet 14b of each channel 14 has different dimensions from the other and in particular, the outlets 14b have increasing dimensions moving away, along the axis X, from the suction outlet 12. Therefore, if the channels are progressively counted starting from the suction outlet 12 and moving away therefrom along the axis X, in the direction of 14', 14", 14’", 14 ⁿ , the outlets 14b of each channel thereof, in the direction 14b', 14b", 14b"’, 14b ⁿ will be such that the outlet 14b ⁿ is larger than the outlet 14b ^{n 1} , 14b ^{n 2} , 14b ^{n 3} , 14b'", 14b", 14b’.

In a design solution, such as for example shown in the figures, the inlets 14a', 14a", .... 14a ⁿ have constant dimensions. However, other design variants can also be provided in which the inlets do not have constant dimensions but vary therebetween.

A further aspect of the invention includes separating partitions 15 to be housed within each channel 14. The partitions are arranged in a fan shape, following the divergent structure of the channel, spaced angularly evenly. The separating partitions 15 divide the channel 14 into a sub-plurality of channels 150.

The number of separating partitions 15 and the inclination thereof is a function of the individual channel 14. The rule is inverse with respect to that of the dimensions of the outlets 14b, i.e. , the channels 14 farthest from the suction outlet 12 have a lower number of partitions than the channels closest to the outlet, according to the axis X. Therefore, referring to the previous description, if the channels are counted progressively starting from the suction outlet 12 and moving away therefrom along the axis X, in the direction 14', 14", 14”’, ...., 14 ⁿ , the number of partitions of the channel 14 ⁿ will be lower than the number of partitions of the channel 14b ^n_1 , 14b ^{n 2} , 14b ^{n 3} , ...., 14b’", 14b", 14b’.

Similarly, having the channels 14 ⁿ , 14b ^{n 1} , 14b ^{n 2} , 14b ^{n 3} ,... , 14”’, 14”, 14’ progressively an angle a of incremental divergence (i.e., more and more inclined side walls), the partitions of the channels farther from the outlet 12 will have an arrangement with a lower degree of inclination with respect to the partitions of the channels closer to the outlet 12. Therefore, considering the fan-shaped distribution of the partitions described above, the partitions of the channels from 14 ⁿ ,14b ^n_1 , 14b ^n_2 , 14b ^{n 3} ,... , 14”’, 14”, 14’ will have a fan-shaped distribution with gradually decreasing angular spacing.

Take the specific example in figure 1. As mentioned above, there are fifteen channels. The channel 14 ¹ (that closest to the outlet 12) has a more divergent shape with respect to the channel 14 ¹⁵ , which is farthest from the outlet 12. Therefore, the outlet 14b ¹ of the channel 14 ¹ is smaller with respect to the outlet 14b ¹⁵ of the channel 14 ¹⁵ . Generally speaking, the outlets of the individual channels have increasing dimensions in the direction of the axis X according to the sequence 14b ¹ , 14b ² , 14b ¹⁴ , 14b ¹⁵ . The number of partitions is decreasing within each channel in the direction of the axis X in the sequence 14 ¹ , 14 ² , 14 ¹⁴ , 14 ¹⁵ therefore the channel 14 ¹⁵ will have less partitions than 14 ¹ . Further, the angular spacing between the individual partitions of each channel will be increasing in the direction of the axis X according to the sequence 14 ¹ , 14 ² ,

14 ¹⁴ , 14 ¹⁵ thus the channel 14 ¹⁵ will have partitions with greater angular spacing than those of the channel 14 ¹ .

Both the channels and partitions bring specific advantages which will be discussed in more detail below. To anticipate, the channels create a uniform suction distribution along the whole length X of the hood, therefore the channel farthest from the outlet 12 will have the same suction power, i.e., the same suction efficiency as the channel closest to the outlet 12.

The partitions, on the other hand, ensure that the flow rate of the sucked air is the same in the different sub-channels 150 of each channel 14; they also prevent flow separation phenomena.

Still with particular reference to figures 1 to 7, the bulkheads 13 may not occupy the entire length of the compartment 10 along the axis X. A further side channel 140 may therefore exist downstream of the last end channel 14n (i.e., the distal one with respect to the outlet 12 along the axis X). Such a further channel 140 is made between an end bulkhead 13 ⁿ and the side wall 1c of the frame body adjoining it. In a preferred, but not limited, solution, the further side channel 140 is non-divergent (the inlet and outlet thereof have similar dimensions); furthermore, the further side channel may be free of internal partitions. In more detail, consider the bulkhead 13 ⁿ as the last bulkhead in the row, i.e., the one farthest from the outlet 12. Such a bulkhead faces a side wall 1c of the frame body 1 , which is substantially perpendicular to the axis X. The further channel 140 is therefore defined by the bulkhead pair 13 ⁿ and the side wall 1c. Such a further channel 140 is not divergent but has a regular trend. The above-described configuration may be understood as mirroring the one indicated in the figures, or further the outlet 12 may be in any position of the second wall 1b, also in a central position with respect to the development of the body of the hood according to the axis X. In this case there will be two rows of channels (one to the right, one to the left of the outlet 12 with respect to the direction X), as described above, each of which defining as a start channel the one near the outlet 12. Referring now to figure 5 at the sides of the intake inlet 11, wing surfaces 2 may be provided, arranged according to the axis X. The wing surfaces 2 have the function of conveying the sucked air towards the intake inlet 11, thereby contributing to improving the suction efficiency of the hood. If necessary, the wing surfaces 2 can be mobile, i.e. , they can be rotated around a rotation axis parallel to the axis X for a more effective conveying effect. For this purpose they are mounted rotatably to the frame body 1 of the hood.

Referring now to figures 6 and 7, a suction plant for a paper processing line comprises two or more extractor hoods C as described above. Figures 6 and 7 specifically show an example of a suction plant with two extractor hoods C, C". Each hood of the plant is installed in series with the other, in continuity along the axis X. Each hood is independent from the other and has an air intake inlet 11 ', 11" and an outlet 12', 12" thereof, connected to a relative pipe thereof connecting to the plant generating the vacuum responsible for the suction effect.

The extractor hood C as described can also be installed within a roller 3 of a paper layer moving system (figures 8a to 8d). There can be one or two or more hoods, depending on the length of the roller. In this case, the outlet 12 of each hood is arranged on a side wall 1c, to project outside the roller 3 from a respective head end thereof. The hood C obtains the suction of the paper dust directly from the paper layer through slots 30 made on the surface of the roller 3. Refer now to figures 9 to 16. In such images, a hood moving system is described, comprising moving means 4, which allows the extractor hood to be moved at least in rotation thereon around the axis X and in translation along an axis Y perpendicular to the axis X (figure 9).

In use, such movement along the axis Y allows the hood C to be brought closer to/farther away from the working area, i.e., the paper layer, while the rotation around X allows the angle of the intake inlet 11 of the hood to be varied with respect to the working area, i.e., the paper layer.

Such movement of the hood is obtained by the moving means 4 described below.

The translation of the hood C according to the axis Y is obtained through a system consisting of two connecting rods 40, 41 set in motion by a rotary actuator 42. The connecting rods move a plate 43 on a linear guide 44 arranged along the axis Y.

If necessary, the translation system can also comprise a gas piston 45, which supports part of the hood's own weight and reduces the power required by the rotary actuator. The rotation of the hood C around the axis X is achieved by using a second rotary actuator 46 which is housed on the plate 43. The second rotary actuator 46 rotates a shaft 47, arranged according to the axis X, which is connected at the head to a flange 48 which is in turn integrally connected to a side wall 1c of the hood C. The moving system of the hood is, in the illustrated example, fixed by means of a flanged support 49 to a fixed plate 6 which is integral or belongs to a paper processing machine or to a frame of the paper processing plant with respect to which the hood is installed.

There can be one unit or two units of moving means 4 mounted on the hood, fixed to opposite side walls 1c of the hood.

Further, the moving means 4 can be used indifferently on a single hood C or on a plant with one or more hoods in series as shown in the figures and described above.

In one embodiment variant, the movement of the hood can be managed automatically by an automatic management and control system. The system can, for example, operate the moving means during the paper roll replacement operations, moving the hood away from the paper layer when the latter decreases the sliding speed thereof and loses tension as a result of the roll replacement operations, thus preventing an unwanted displacement of the paper layer from the sliding seat thereof. Once the paper roll has been replaced, as soon as the machine resumes normal operation, the system controls the moving means 4 of the hood C in translation along the axis Y to bring the hood closer to the layer, stopping in the work position, i.e., the position which maximises the suction capacity of the hood. The automatic management and control system is associated with sensor means; for example, but not limited to, such sensor means comprise a sensor which measures the speed of the paper layer: when the speed of the paper layer falls below a preset threshold value, the automatic management and control system operates the moving means to move the hood away from the layer. Conversely, when the measured speed is above the threshold value, the hood is moved closer to the layer and returned to the work position thereof.

The automatic management and control system also allows to adjust the position of each hood in relation to the paper strip to maximise the suction thereof. The optimal position is defined in terms of distance and inclination of the hood with respect to the paper layer. The automatic system manages the correct positioning of each of the plant's hoods by the moving means described above and in particular by moving the hood along the axes Y and X.

For each hood, the optimal position is determined according to the local angle of curvature of the paper layer where the hood is installed and for each type of paper which can be processed by the machine (for each length of paper fibre to be sucked). For each type of paper, the maximum suction setting of each hood is determined after a preliminary exploration of a predefined number of positions and orientations. During this step, also known as the "self-learning step", the automatic management and control system acquires data on the measurement of the quantity of dust sucked by each hood with a dedicated sensor. After this self-learning step, it will be sufficient to enter the type of paper used in a control panel of the suction plant and the automatic management and control system will autonomously move each hood to the position which maximises suction. The automatic management and control system described above can also intervene in the management of the movement of the wing surfaces 2 described above. The best set-up of the wing surfaces 2 can be determined during the self-learning base of the system, synergistically and functionally to the overall positioning of the hood according to the axes X and Y. For low-cost construction solutions, a manual wing surface 2 positioning system can also be provided. The hood described so far and the associated dust suction plant in a paper processing line overcome the above-described drawbacks of the background art and have many unique advantages.

A first advantage is that the flow rate of air sucked in by the hood is evenly distributed between the channels 14. This is made possible by the divergent shape of the channels, which have progressively larger outlets the farther they are positioned from the main intake pipe 12.

The channels closer to the outlet 12 with smaller restricted outlets 14b have a reduced suction capacity. The outlets 14b gradually increase in size away from the outlet 12. In fact, as a result of the passage of the working fluid (air and dust) in the diverging channels, pressure losses are created, and therefore resistance to the passage of the fluid itself, which are inversely proportional to the passage section. However, by sizing the diverging channels as described, it is possible to distribute the sucked air evenly therebetween. The hood therefore has the same suction capacity over the entire length thereof along the axis X and thus along the entire transverse extension of the paper layer.

Turning to the partitions 15, they allow more efficient operation of the diverging channels by equalising the suction speed along the axis X in output from the extractor hood. The partitions 15 ensure that the flow rate of air sucked into the different sub- channels of each channel is the same, avoiding flow separation phenomena. Without the internal partitions, the air flow would only be sucked in, or in any case mainly in the internal part of the channel 14, with a clear loss of suction efficiency.

Therefore, the hood as described achieves a surprisingly high suction efficiency, i.e. , a high ratio between the amount of air and dust sucked in and the nominal suction power.

The hood is also extremely small and compact compared to the known hoods, which allows the hood to be integrated directly into the paper processing machine.

Such advantages are also inherent in the plant according to the invention which installs one or more hoods as described. In fact, the hood can be considered a repeatable module to define a suction plant. Furthermore, by virtue of the automatic management and control system, the hood/plant is fully movable and adaptable in position with respect to the paper layer and the work position in general, with obvious advantages in terms of optimising suction efficiency. If the automatic management and control system is associated with a learning system as described, the suction plant is in fact fully automated and able to self-adjust to the optimal position as a function only of the indication of the type of paper/material to be processed.

The present invention has been described herein with reference to preferred embodiments thereof. It is to be understood that there may be other embodiments that relate to the same inventive nucleus, all falling within the scope of protection of the claims provided below.