Plant and method for producing a continuous web of reconstituted plant material

Abstract

A plant for producing a continuous web from a reconstituted plant material, comprising a forming unit for forming a continuous layer, a first processing unit, and a second processing unit. The plant comprises an intermediate conveyor interposed between the first processing unit and the second processing unit, and an inspection area also interposed between the first processing unit and the second processing unit. The intermediate conveyor is movable between a rearward position suitable for normal operation and in which a rear end of the intermediate conveyor is arranged in the inspection area, and a forward position suitable for access to the inspection area by an operator and in which the intermediate conveyor is away from the inspection area.

Description

The present invention relates to the field of smoking articles and relates to a plant for producing a continuous web of reconstituted vegetable-based material and a method of operating said plant.Within the relevance area of the present invention, plants for producing a continuous web from a reconstituted plant material (tobacco or other plant sources) are known, which comprise a forming unit for forming a continuous layer. By "forming unit" is meant a unit comprising a device for preparing a mixture based on a reconstituted plant material and a device for realizing the above mentioned continuous layer of the mixture itself. In particular, this forming unit is configured for the production of a mixture of the "slurry" type with a high water content (preferably greater than 60%), i.e. liquid or almost liquid, and a subsequent step for depositing a continuous layer of this mixture by means of a nozzle on a conveyor belt. Downstream of the forming unit, this type of plant comprises a first processing unit, typically a drying unit, configured to perform a first drying on the continuous layer. Structurally, this unit comprises a conveyor for transporting the continuous layer through a respective drying chamber configured to remove the moisture present in the continuous layer, whereby the material is suitable for the subsequent processings.Downstream of the first processing unit, this type of plant comprises a further processing unit, typically a second drying unit, configured to perform a second drying on the continuous layer to further dry the continuous layer until the desired consistency for the final product is reached. Generally, the second drying unit has a substantially similar structure to the first drying unit. In other words, this unit comprises a respective conveyor configured to transport the continuous layer through a respective drying chamber.In a position inserted between the above mentioned processing units, this type of plant typically comprises an intermediate conveyor configured to transport the continuous layer from the first processing unit to the second processing unit, and an inspection area allowing one or more operators to enter a zone of the plant to perform inspection, maintenance and / or inspection operations, in particular on the conveyor belt of the conveyor of the first processing unit. In particular, the inspection area is defined by a space at least partially arranged below the outlet zone of the conveyor of the first processing unit. Typically, moreover, the intermediate conveyor extends rearward until it is arranged below the outlet of the conveyor of the first processing unit, since this is necessary because the continuous layer exiting the first drying unit must be picked up, supported and transported forward by the intermediate conveyor. In this situation, however, the intermediate conveyor necessarily occupies at least partially the inspection region.The applicant has pointed out that this technology, although well functional, has some structural and / or functional drawbacks that make it capable of improvement.First, in general, in order to optimize the layout and the space requirement of the installation, a rationalization of the spaces intended for the inspection areas is typically carried out. In particular, with reference to said plant, the intermediate conveyor is structured and / or arranged to be at least partially inserted in the inspection area, so that the plant becomes more compact overall, but has a negative effect on the convenience of access and stay within the inspection area. Second, in known type plants, the applicant has established the persistence of routine manual processes, which often prove slow, inaccurate, and / or generally inefficient. In particular, with reference to said installation, it is known that exceptional control and / or maintenance interventions are carried out on the installation by temporarily stopping the proper operation of the installation for a period of time sufficient to carry out these interventions. After completion of these interventions, a procedure for restarting the installation is implemented. In this step, a portion of the continuous layer exiting the conveyor of the first processing unit is first discarded due to the non-coincidence of the continuous layer with a predetermined quality standard. Once the required specifications are reached, the continuous layer is cut and repositioned on the intermediate conveyor so that the plant can be restarted properly. In particular, the cutting and repositioning of the continuous slice are performed manually by the operator. As a result, these manual procedures can impair the efficiency, accuracy, and productivity of the plant.With reference to the said installation, the applicant also found that the systems currently used for cleaning the conveyors and in particular the intermediate conveyor have a not negligible degree of inefficiency. Such systems often require considerable personnel efforts, which results in an excessive amount of time and resources. Moreover, the cleaning processes may not be fully effective to maintain the plants at maximum performance. Such inefficiencies can affect overall plant productivity and require thorough overtaking to improve the efficiency and durability of the cleaning operations. In other words, the cleaning systems currently used in the above-mentioned type of plant are capable of improvement.The technical object of the present invention is thus to provide a plant for the production of a continuous web from a reconstituted plant material and a method for operating said plant, which are capable of eliminating the disadvantages of the prior art.The main object of the present invention is therefore to provide a plant for the production of a continuous web from a reconstituted plant material and a method for operating said plant, which are optimized from the point of view of managing the spaces and space requirement of the plant.Another object of the present invention is to provide a continuous web manufacturing plant of reconstituted plant material and a method of operating said plant, capable of ensuring a high operating efficiency as well as a high quality product.A further object of the present invention is to provide a plant for the production of a continuous web from a reconstituted plant material and a method for operating this plant, which are capable of ensuring a correct and optimum cleaning of the plant itself.The stated technical object and objects are substantially achieved by a plant for the production of a continuous web from a reconstituted plant material and a method for operating this plant, comprising the technical features set forth in the appended claims 1 and 15 and / or in one or more of the claims dependent thereon and / or in the appended description.In particular, the applicant has found that by moving the conveyor between a rearwardly offset position suitable for normal operative operation and in which the rear end of the intermediate conveyor is located in the inspection area, and a forwardly offset position suitable for access to the inspection area by an operator and in which the intermediate conveyor is remote from the inspection area, it is possible to optimize the spaces of the plant and to improve the accessibility of the inspection area: in fact, the possibility of switching the position of the intermediate conveyor allows to maximize the use of the available space within the inspection area. This can firstly result in better overall plant efficiency by allowing a more efficient arrangement of the other components, and secondly contribute to improving accessibility and comfort in the inspection area and facilitating the work of the operators. Advantageously, a more efficient arrangement of the components of the installation can also contribute to improving the overall safety of the installation.The present invention therefore relates, in a first aspect thereof, to a plant for producing a continuous web based on a reconstituted plant material.Preferably, the term "reconstituted vegetable material based" is understood to mean a vegetable based material (tobacco or non-tobacco) which is processed by milling or other similar procedure to change its particle size to promote its subsequent mixing treatments. In particular, it is to be understood that the continuous web is a semi-finished product obtained by mixing and processing at least one dry vegetable component, such as tobacco or non-tobacco (oilseed rape, hemp, straw or other types, cellulose or cellulose derivatives) with a liquid component, such as water and / or additives. Preferably, the continuous web is used for the realization of smoke products or for the generation of aerosols.The plant comprises a forming unit for forming a continuous layer of the above mentioned reconstituted plant material.The plant comprises a first processing unit having a first conveyor.The plant comprises a second processing unit arranged after the first drying unit and having a second conveyor having an inlet zone arranged at a lower level than an outlet zone of the first conveyor.The plant comprises an intermediate conveyor which is inserted between the first processing unit and the second processing unit and has a front end facing the second conveyor and a rear end opposite the front end. The intermediate conveyor is configured to guide the continuous layer obtained from the first conveyor toward the second conveyor. The plant comprises an inspection area which is located between the first and the second conveyor and is in particular arranged at least partially below the outlet zone of the first conveyor.The intermediate conveyor is movable between a rearwardly offset position suitable for normal operative operation, in which the rear end of the intermediate conveyor is located in the inspection area, and a forwardly offset position suitable for access to the inspection area by an operator, in which the intermediate conveyor is remote from the inspection area, preferably outside the inspection area.Preferably, the rearwardly offset position is suitable for normal operative operation: in this position, the rear end of the intermediate conveyor is located in the inspection area. When the inspection area includes the aforementioned tread or the aforementioned tread, the intermediate conveyor occupies a space above the tread or the tread in the rearward offset position.Preferably, the forwardly offset position is suitable for access to the inspection area by an operator: in this position, the intermediate conveyor is removed from the inspection area, i.e. is arranged outside the inspection area.These features advantageously make it possible to optimize the spaces of the plant and to improve the accessibility of the inspection area: the possibility of switching the position of the intermediate conveyor between the rearward offset and the forward offset positions allows, in fact, to maximize the use of the available space within the inspection area. This can firstly result in better overall plant efficiency by allowing a more efficient arrangement of the other components, and secondly contribute to improving accessibility and comfort in the inspection area and facilitating the work of the operators. Advantageously, moreover, a more efficient arrangement of the components of the installation can contribute to improving the overall safety of the installation itself.The present invention relates, in a second aspect thereof, to a method for operating a plant for producing a continuous web based on a reconstituted plant material.In a preferred embodiment, the process is carried out by means of the abovementioned plant.The method comprises a step of forming a continuous layer, in particular by a mixture based on a reconstituted plant material.The method comprises a subsequent step of supplying the continuous layer to the first processing unit by performing a first processing of the continuous layer.The method comprises a subsequent step of transferring the processed continuous layer from the first conveyor of the first processing unit to the intermediate conveyor and from the intermediate conveyor to the second conveyor of the second processing unit while the intermediate conveyor is maintained in the rearwardly offset position. The method comprises a subsequent step for performing a second processing of the continuous layer in the second processing unit.The method comprises a subsequent step of stopping the operation of the plant.The method comprises a subsequent step, after stopping the plant, bringing the intermediate conveyor to the forwardly offset position and allowing an operator to access the inspection area.In at least one of the aforementioned aspects, the present invention may further include at least one of the preferred features illustrated below.In accordance with one aspect, the continuous layer forming unit may comprise a device configured to prepare a mixture based on a reconstituted plant material and a device for forming a continuous layer from the above mixture.According to one embodiment, the continuous layer forming unit comprises at least one mixer for mixing the solid components and the liquid components to realize the mixing, and downstream of the mixer it comprises at least one continuous layer forming unit.According to one embodiment, the continuous layer forming unit is configured to prepare a mixture of the dough type, i.e. of the type having an amount of water comprised between 30% and 65% and / or having a pasty or viscous, in particular formable, consistency: the continuous layer forming unit is a laminating unit configured to realize the continuous layer by one or more pairs of rolls, in particular a laminating unit.According to an alternative embodiment, the continuous layer forming unit is configured to prepare a "slurry" type mixture, i.e. of the type having an amount of water greater than 65%, and / or: the continuous layer forming unit is a casting unit configured to realize the continuous layer by casting.According to an embodiment, the first processing unit may be a first drying unit configured to perform a first drying on the continuous layer.In alternative embodiments, the plant may comprise another processing unit configured to perform another processing on the continuous layer. Preferably, by the term "first drying" is meant that the unit is configured to remove a predetermined amount of moisture, preferably most of the moisture present in the continuous layer, to obtain a predetermined consistency of the continuous layer and to prepare the continuous layer for subsequent processings.According to an embodiment, the first conveyor of the first processing unit is configured to convey the continuous layer through a respective drying chamber and to unload the dried continuous layer from the outlet zone of the first conveyor.Preferably, the first conveyor is of the conveyor belt type and comprises a continuous conveyor belt slidably bound around return rollers. Preferably, such a conveyor belt is made of a material suitable for supporting the continuous layer during heating, for example a metal or plastic material.Preferably, the first processing unit comprises at least one respective stripping element associated laterally and / or below the deflecting roller and configured to release the continuous layer from the transport belt of the first conveyor. In other words, the outlet zone of the first conveyor comprises a deflection roller and at least one stripper tool associated laterally and / or below the deflection roller.In accordance with one embodiment, the first processing unit comprises a pair of sequentially arranged stripping elements configured to be selectively activated on the conveyor belt.In accordance with one aspect, the second processing unit may be a second drying unit configured to perform a second drying on the continuous layer. Preferably, by the term "second drying" is meant that the unit is configured to further dry the continuous layer until the desired humidity for the final product is reached. This step can also be used to make further changes to the continuous layer, such as changing texture or combustion properties. Preferably, the second conveyor of the second processing unit has an inlet zone which is arranged at a lower level than the outlet zone of the first conveyor of the first drying unit. Preferably, the second conveyor has an inclined position, which in particular defines an upward feed direction. In other words, the second conveyor is not parallel to the floor.In accordance with one aspect, the inspection area allows an operator to pass under the outlet zone of the first conveyor, so that he can perform, for example, control and / or maintenance operations on the at least one stripping element of the first drying unit.In accordance with one embodiment, the inspection region comprises a / n, preferably raised / n, tread surface or running web which is / is accessible by an operator. It is even more preferred that the tread surface or the running web allows an operator to access the at least one stripping element in a maintenance step.In accordance with one aspect, the plant comprises control means configured to at least partially automatically control the plant itself.According to an embodiment, the control means may comprise a control unit and / or an input interface and are configured to receive as input an actuation signal for actuating the plant.According to one aspect, the intermediate conveyor may be of the conveyor belt type and therefore comprises an upper loading branch and a lower return branch.In accordance with one aspect, the intermediate conveyor may comprise a transport belt and has an upper loading branch and a lower return branch defining a transport surface of the transport belt.In accordance with one aspect, the intermediate conveyor may be selectively operated in accordance with a first advancing direction in which the transport surface of the transport belt is moved from the first conveyor toward the second conveyor and in accordance with a second advancing direction in which the transport surface of the transport belt is moved from the second conveyor toward the first conveyor.If present, the control means may be configured to select the first advancing direction or the second advancing direction of the transport surface of the transport belt.In accordance with one aspect, the intermediate conveyor may be movable between the two rearward and forward offset positions along a translatory, rototranslational or rotating trajectory.In accordance with one aspect, the intermediate conveyor may be movable along a direction at least partially parallel to the ground between the rearward offset position and the forward offset position.Preferably, the plant comprises a support frame on which the intermediate conveyor is mounted. The intermediate conveyor is mounted on the support frame so as to be movable between said rearward and forward offset positions relative to the support frame.Preferably, the intermediate conveyor can be mounted on the support frame by means of one or more guides such that the intermediate conveyor is movable between the two rearwardly offset and forwardly offset positions.According to one embodiment, the intermediate conveyor is movable by rototranslational movement between the rearward offset position and the forward offset position: in particular, the intermediate conveyor is movable such that the rear end of the intermediate conveyor moves on a substantially horizontal trajectory, while the front end of the intermediate conveyor moves on a trajectory inclined with respect to a horizontal plane and preferably matching the second conveyor.Preferably, the intermediate conveyor in the rearwardly offset position has a substantially horizontal position, while the intermediate conveyor in the forwardly offset position has an inclined position, in particular with the front end being higher than the rear end.In accordance with one aspect, the one or more guides, if present, may comprise a front linear guide of inclined attitude, preferably parallel to the second conveyor, and a rear guide defining a substantially horizontal movement.Preferably, the rear guide comprises a pinion, preferably having a stationary position, and a rack integral with the intermediate conveyor and engaging the pinion.In accordance with one aspect, the plant may comprise an actuator connected to the intermediate conveyor and configured to move the intermediate conveyor between the two positions. The intermediate conveyor is therefore preferably moved between the two positions in an automated manner.Preferably, the actuator comprises a motoring connected to the aforementioned pinion. Preferably, the actuating drive can be actuated by the control means, in particular the control unit and / or the input interface.In accordance with one aspect, the plant may comprise a continuous layer collecting basin suitable for collecting a fraction of the continuous layer waste. The pool is particularly useful in the steps for restarting the plant.Preferably, the collecting basin is arranged on the side of the intermediate conveyor opposite the inspection region. Preferably, the collecting basin is positioned under the at least one stripping element to cause a falling feeding of the continuous layer stripped by the first conveyor of the first processing unit into the collecting basin during a step of discarding the continuous layer.In accordance with one aspect, the plant may comprise deflecting means configured to move the portion of the continuous layer coming from the first conveyor along a trajectory of movement between a zone above the collecting basin, in which the portion of the continuous layer is fed into the collecting basin, and a zone above the intermediate conveyor, in which the portion of the continuous layer is fed onto the intermediate conveyor.In other words, if present, the deflecting means are activated to deflect this portion of the continuous layer such that the flow path of the continuous layer itself is changed from a downward direction from the scraper towards the collecting basin towards a flow direction from the scraper towards the intermediate conveyor. The section of the continuous layer deflected by the deflecting means is therefore loaded again onto the intermediate conveyor, so that it can be conveyed properly towards the second conveyor. The applicant has found that the use of diverting means makes it possible to optimize the restart of the plant, which allows a fast and easy removal operation of the non-conformal section of the continuous layer. Advantageously, this feature allows the automation of typical manual processes, greatly accelerating the operations in the plant restart steps, reducing downtime associated, in particular, with manual repositioning of the continuous slice, and greatly improving accuracy to improve the quality of the final product. This technical feature also improves the safety of the operators and reduces the risk of injury.The above-mentioned portion of the continuous layer may be any portion thereof. Preferably, a portion of the continuous layer is understood to mean a head end of the continuous layer obtained by the transverse cutting (or tearing) of the continuous layer in the vicinity of the inspection area or, more generally, downstream of the first conveyor.In accordance with one embodiment, the deflecting means may comprise a rod or a roller having a predominant transverse development direction, preferably perpendicular, to the advancing direction of the continuous layer on the deflecting means, which is displaceable transversely to the predominant transverse development direction. Moreover, the deflecting means may comprise at least one shaped guide defining the trajectory of movement of the rod or roller: preferably, the rod or roller comprises at least one lateral support slidably engaging the at least one shaped guide to restrict its movement within the shaped guide. Alternatively, the deflecting means may comprise a movable support (e.g. an arm or a robot support) which engages at least one side of the rod or roller to move the rod or roller along said trajectory.The shaped guide can be realized in accordance with a variety of shapes as long as they are suitable for the above-mentioned purposes.Preferably, the trajectory comprises a first portion with at least one horizontal component when the guide is operational, configured to cause a transverse displacement of the rod or roller between the zone above the collecting basin and the zone above the intermediate conveyor and vice versa. Preferably, the first part has a circular arc configuration.Preferably, the trajectory optionally comprises, after the first section, a second section having at least one vertical and preferably substantially vertical component when the guide is operational, and being adapted to cause raising and lowering of a portion of the continuous layer from the intermediate conveyor. Preferably, the second part has a straight configuration.Advantageously, the first section, if present, is designed to allow a rapid and smooth displacement of the above-mentioned portion of the continuous layer from the zone above the collecting basin to the zone above the intermediate conveyor, in other words to ensure that it is correctly redirected towards the intermediate conveyor.Advantageously, the second vertical portion, if present, has the aim of regulating the vertical position of the continuous layer with respect to the intermediate conveyor, which contributes to improving the tension and consequently the material supply in the subsequent process steps. Together, these two parts of the trajectory ensure an efficient and reliable flow of the continuous layer through the installation.In accordance with one aspect, the deflecting means may comprise at least one actuator active on the rod or roller, which actuator is configured to move the rod or roller along at least a portion of the movement trajectory. Preferably, the actuator is configured to move the rod or roller in particular along the second section. Preferably, the at least one actuator is electrical, hydraulic or pneumatic. Preferably, the actuator is connected to the control means so that it can be activated at least partially automatically. Preferably, the rod or roller is therefore first moved (e.g. manually by the operator) along the first section of the movement trajectory defined by the shaped guide. Preferably, the rod or roller is then moved by the actuator along the second portion of the trajectory of movement defined by the shaped guide, in order to increase the distance of the rod or roller from the intermediate conveyor and to optimize the feeding of the continuous layer.According to one embodiment, the actuator is a linear actuator having a first end articulated to a fixed portion and a second end connected to the rod or roller. Preferably, the linear drive is rotatable about the fixed portion during the movement of the rod or roller along the first section of the trajectory, preferably freely and / or manually. Preferably, the actuator may be activated by the above mentioned control means to actively cause the movement of the rod or roller along the second portion of the trajectory. Preferably, in other words, the deflecting means are at least partially automatically actuated.In accordance with one aspect, in the event of a maintenance intervention that provides for the use of the above-mentioned inspection region, a temporary stopping of the plant is provided.The maintenance intervention can be of any type and require a temporary stopping of the plant. For example, the intervention may relate to the monitoring, maintenance and / or the replacement of components of the first conveyor, such as one of the scraper elements.In the event of an intervention, the plant is stopped and subsequently the intermediate conveyor is displaced from the rearwardly offset position to the forwardly offset position in order to allow an operator to access the inspection area.Preferably, in this plant stopping step, moreover, the continuous layer is transversely cut so as to obtain a head end of the continuous layer in the vicinity of the outlet zone of the first conveyor.Regardless of its type, after completion of the intervention, a restart of the system is provided. Preferably, the restarting of the plant comprises first conveying a first section of the continuous layer exiting the first conveyor of the first processing unit towards the collecting basin. In particular, the aforementioned head end of the continuous layer is conveyed into the collecting basin. The beginning portion of the continuous layer at the moments after restart may have non-conformal features and therefore must be discarded.Preferably, the plant comprises one or more sensors configured to detect one or more characteristics of the continuous layer suitable for determining the conformance of the continuous layer itself, for example by electronic algorithms implemented in the control unit. Such properties may be, for example, the thickness, humidity, temperature or density of the continuous layer.Preferably, in this step, the intermediate conveyor is operated in such a way that the advancing direction of the transport surface of the transport belt is moved towards the collecting basin. In other words, the intermediate conveyor is operated in accordance with the second feed direction (backward).Preferably, when a predetermined time or acceptable quality conditions of the continuous layer exiting from the first drying unit are reached, a reversal of the feed direction of the transport surface of the transport belt, in particular leading from the direction toward the collecting basin in the direction toward the second conveyor, is provided.This can be connected to a light, vision and / or acoustic signal supplied by the control unit, depending on whether the quality conformity of the continuous layer achieved by sensor detection is achieved. Preferably, the continuous layer is cut off in order to obtain a new head end of the continuous layer.At this point, a section of the continuous layer and in particular the new top end of the continuous layer is then moved with the aid of the deflecting means from the zone above the collecting basin to a zone above the intermediate conveyor.The continuous layer is then fed towards the intermediate conveyor and from the intermediate conveyor to the second conveyor. The plant can then operate under normal conditions.In accordance with one aspect, the plant may comprise a cleaning device configured to perform a mechanical cleaning of the intermediate conveyor. Preferably, the cleaning device is equipped with at least one cleaning tool configured to exert a mechanical action adapted to remove residue from the transport surface of the intermediate conveyor.Preferably, the cleaning device further comprises an actuator configured for mutual movement of the intermediate conveyor and the at least one cleaning tool between a release configuration in which the at least one cleaning tool is removed from the transport surface of the intermediate conveyor and an operating configuration in which the at least one cleaning tool is brought towards the transport surface of the intermediate conveyor in order to exert the above-mentioned mechanical effect on the transport surface of the intermediate conveyor.The applicant has found that the use of a special cleaning device enables an optimum renewal of the transport surface of the intermediate conveyor. In particular, the cleaning device is equipped with at least one cleaning tool configured to exert a mechanical action adapted to remove debris from the transport surface of the intermediate conveyor.Furthermore, the possibility of mutually moving the intermediate conveyor and the at least one cleaning tool between a release configuration, in which the at least one cleaning tool is removed from the transport surface of the intermediate conveyor, and an operating configuration, in which the at least one cleaning tool is moved towards the transport surface of the intermediate conveyor in order to exert the mechanical effect on the transport surface of the intermediate conveyor. In particular, the cleaning device can thus be provided with a displacement movement from and towards the intermediate conveyor or the intermediate conveyor can be provided with a displacement movement from and towards the cleaning device (which in this case can be stationary). These technical features contribute to making the cleaning of the conveyor efficient and automated, resulting in better overall plant efficiency and a reduction in operating and / or maintenance costs.Advantageously, this technical feature allows a reduction in cleaning costs and operating times, since the system is fully automated and cleaning interventions on the intermediate conveyor can also be carried out more frequently. In this way, it is firstly possible to ensure a high quality final product, since the plant and in particular the intermediate conveyor are kept at the highest performance level, and secondly it is possible to increase the durability of the plant, since the wear effect caused by the material accumulated on the transport surface is reduced.Preferably, the cleaning device is arranged and / or configured to perform a mechanical cleaning of the lower branch of the intermediate conveyor.Preferably, the cleaning device is arranged below the lower branch of the intermediate conveyor and is movable by an at least partial vertical movement between the operating and release configurations: preferably, the cleaning device is tapped at a support portion, preferably at the support frame (if present), so as to be pivotable between the two configurations about a tilting axis oriented transversely to the feed path of the continuous layer and preferably running horizontally.In accordance with one aspect, the cleaning device can be supported independently of the intermediate conveyor. Preferably, the cleaning device is preferably stationary with respect to the movement of the intermediate conveyor between the forwardly offset and the rearwardly offset positions.Preferably, the operating configuration of the cleaning device is selectable in the forwardly offset position of the intermediate conveyor and preferably only in the forwardly offset position of the intermediate conveyor.In accordance with one aspect, the cleaning device can be moved or movable, in particular in a controlled and / or automated manner, between the release and operating configurations by the respective actuator, preferably by the above-mentioned control means. Preferably, the actuator is electrical, hydraulic or pneumatic.According to one embodiment, the cleaning device comprises a basin-like hold-down body defining a hold-down volume in which the at least one cleaning tool is arranged: the hold-down body is open at the top, such that the at least one cleaning tool faces the lower branch of the transport belt.Preferably, the hold-out body comprises a front holding flap projecting from the top of a front wall of the hold-out body and developing transversely with respect to the lower branch of the conveyor belt: the front holding flap is configured to engage the transport surface of the lower branch of the conveyor belt in the operating configuration of the cleaning device to exert a mechanical scraping action on the transport surface.Preferably, the front retaining flap is made of plastic.Preferably, the detaining body comprises a rear retaining flap projecting from the top of a rear wall of the detaining body and developing transversely with respect to the lower branch of the conveyor belt: the rear retaining flap is configured to engage the transport surface of the lower branch of the conveyor belt in the operating configuration of the cleaning device to exert a scraping action on the transport surface of the conveyor belt in the operating configuration of the cleaning device.Preferably, the hold-out body comprises a pair of side flaps projecting from the top of the respective side walls of the hold-out body and developing along the lower branch of the conveyor belt: the pair of side flaps is configured to at least partially enclose the lower branch of the conveyor belt in the operating configuration of the cleaning device, in order to exert an effect for containing the residues removed from the transport surface of the conveyor belt and / or to exert a scraping effect on the end edges of the transport surface of the lower branch of the conveyor belt.In accordance with one aspect, the cleaning device may comprise two or more cleaning tools arranged with respect to each other such that in the operating configuration of the cleaning device the two or more tools operate simultaneously on the transport surface of the intermediate conveyor.According to an embodiment, the at least one cleaning tool may comprise a motorized roller brush having an axis of rotation oriented transversely to the feed path of the continuous layer: the mechanical action is a brushing action of the transport surface of the intermediate conveyor.Preferably, the cleaning device comprises two motorized roller brushes arranged in series along the transport surface of the transport beltIn alternative embodiments, the cleaning device may comprise only one motorized roller brush or three or more motorized roller brushes.In accordance with one aspect, the cleaning device can comprise at least one spray nozzle which is configured to discharge a pressurized fluid, preferably a pressurized liquid, onto the transport surface of the transport belt in the operating configuration of the cleaning device.Preferably, the at least one spray nozzle is arranged upstream of the cleaning tools in order to wet the residues and the transport surface of the conveyor belt, which facilitates the operations of the cleaning tools, or in order to perform a first removal of the residues on the transport surface of the conveyor belt, and / or it is arranged downstream of the cleaning tools in order to remove particles possibly adhering to the transport surface of the intermediate conveyor.Preferably, the cleaning device comprises a plurality of spray nozzles arranged transversely in a row with respect to the lower branch of the conveyor belt.In accordance with one aspect, the transport surface of the transport belt is made of plastic, in particular polyester. Advantageously, this feature makes the transport surface of the transport belt easy to clean (also due to the low moisture absorption), corrosion-resistant and durable.In accordance with one aspect, the stopping of the installation is also provided in the event of a cleaning intervention of the installation and in particular of the intermediate conveyor, and / or it is possible to carry out a cleaning intervention of the installation during a step for stopping the installation, for example during maintenance of the scrapers as specified above. The cleaning of the plant can be carried out exceptionally, i.e. in a step for temporarily stopping the plant or as a routine at the end of the continuous web production cycle.Regardless of the type of intervention, the interruption of the transfer of the dried continuous layer from the first drying unit to the second processing unit by the intermediate conveyor is provided, and subsequently the arrangement of the cleaning device is provided in the operating configuration. In this configuration, the cleaning device performs cleaning of the intermediate conveyor. In this configuration, the intermediate conveyor is preferably in the rearward offset position. However, it may be arranged that the cleaning step is carried out while the intermediate conveyor is in the forwardly offset position.Preferably, between the step of stopping the transfer of the continuous layer and the step of arranging the cleaning device in the operating configuration, a step of arranging the intermediate conveyor to the rearward offset position when the intermediate conveyor has been previously arranged in the forward offset position is preferably turned on.In the cleaning step, the cleaning device is brought (preferably automatically) to the lower return branch of the conveyor belt and actuated while the transport surface of the conveyor belt is set in motion, whereby a cleaning of the surface of the belt is achieved.Further features and advantages of this invention will become more apparent from the approximate and therefore non-limiting description of an embodiment of a plant for producing a continuous web from a reconstituted plant material and a method of operating such a plant in accordance with the invention. This description is made below with reference to the accompanying drawings, which are provided solely as references and are therefore not restrictive. It shows:FIGS. 1-5 are schematic views of a preferred exemplary and therefore non-limiting embodiment of a continuous sheet manufacturing plant of plant material reconstituted in accordance with the present invention, in a sequence of operating configurations;FIG. 6 is a perspective view of a preferred embodiment of a portion of the plant of FIGS. 1-5;FIG. 7 is a schematic view of the system of FIGS. 1-5 with functional connections to control means.With reference to the accompanying figures, reference numeral "1" indicates a plant for the production of a continuous web based on a reconstituted plant material.In this specification, the term "reconstituted plant material" is understood to mean a vegetable-based material (tobacco or non-tobacco) which is processed by milling or other similar procedure to change its particle size to promote its subsequent mixing treatments. In particular, it is to be understood that the continuous web is a semi-finished product obtained by mixing and processing at least one dry vegetable component, such as tobacco or non-tobacco (oilseed rape, hemp, straw or other types, cellulose or cellulose derivatives) with a liquid component, such as water and / or additives. Preferably, the continuous web is used for the realization of smoke products or for the generation of aerosols. Structurally, the plant 1 comprises a formation unit for forming a continuous layer "S", which is not shown in the attached figures. This unit comprises a device configured to prepare a mixture based on a reconstituted plant material and a device for forming a continuous layer from the above mixture. In the preferred embodiment, the unit for forming the continuous layer "S" is configured to prepare a mixture of the type "Dough", i.e. of the type having an amount of water comprised between 30% and 65% and / or having a pasty or viscous, in particular formable, consistency. Preferably, this unit comprises at least one mixer for mixing the solid components and the liquid components to realize the mixing, and downstream of the mixer it comprises at least one unit for forming a continuous layer by one or more pairs of rolls, in particular a laminating unit.As shown in the accompanying figures, the plant 1 comprises a first processing unit 100 (only partially visible in the accompanying figures). Preferably, this first processing unit 100 comprises a first drying unit 101 configured to perform a first drying on the continuous layer "S".By the term "first drying" is meant that the unit 101 is configured to remove a predetermined amount of moisture, preferably most of the moisture present in the continuous layer "S", to obtain a predetermined moisture (and thus a consistency) of the continuous layer "S" and to prepare the continuous layer "S" for the subsequent processings. In particular, the first drying unit 101 comprises a first drying chamber (not shown) defined by a plurality of side walls, an inlet and an outlet. Within the first drying chamber, a first drying group is provided to dry the continuous layer "S". The first drying group comprises, for example: at least one fan and / or at least one hot air generator and / or steam generator and / or a radiation generator.According to other embodiments, the first processing unit 100 may include a continuous layer thickness control unit "S" (e.g., calibration / laminating rollers) or a continuous layer quality control unit "S" (e.g., at least one camera). Structurally, the first processing unit 100 comprises a first conveyor 102 configured to convey the continuous layer "S" and to unload the continuous layer "S" at the outlet zone 102 bof the first conveyor 102.In the preferred embodiment, where the first processing unit 100 comprises the first drying unit 101, the first conveyor 102 is configured to transport the continuous layer "S" through the respective first drying chamber (e.g., passing between inlet and outlet of the first drying chamber) and to unload the dried continuous layer "S" at the outlet zone 102 bof the first conveyor 102.Preferably, the first conveyor 102 is of the conveyor type and comprises a continuous conveyor belt 103 (only partially visible in the attached figures) constrained during sliding around pulleys, only one of which is shown in the attached figures and is denoted by the reference numeral 104 arranged at the outlet of the first conveyor 102. This conveyor belt is made of a material suitable for supporting the continuous layer during heating, for example a metal or plastic material.The first processing unit 100 further comprises at least one respective stripping element 105, 106 associated laterally and / or below the deflecting roller 104 and configured to release the continuous layer "S" from the transport belt 103 of the first conveyor 102. Preferably, the first processing unit 100 comprises a pair of stripping elements 105, 106 arranged one behind the other, which are configured such that they can be activated selectively on the conveyor belt 103.The plant 1 thus comprises a second processing unit 200 (only partially visible in the accompanying figures) configured to perform a second processing on the continuous layer "S" arranged downstream of the first processing unit 100. Preferably, the second processing unit 200 includes a second drying unit 201 configured to perform second drying on the continuous layer "S" and disposed downstream of the first drying unit 101.By the term "second drying" is meant that the second drying unit 201 is configured to further dry the continuous layer "S" until the humidity desired for the final product (and hence the consistency) is reached. This step can also be used to make further changes to the continuous layer "S", such as changing texture or combustion characteristics. In particular, the second drying unit 201 includes a second drying chamber (not shown) defined by a plurality of side walls, an inlet and an outlet. Inside the second drying chamber, a second drying group is provided to dry the continuous layer "S". The second drying group comprises, for example: at least one fan and / or at least one hot air generator and / or steam generator and / or a radiation generator.According to other embodiments, the second processing unit 200 may include a continuous layer thickness control unit "S" (e.g., calibration / laminating rollers) or a continuous layer quality control unit "S" (e.g., at least one camera).The second processing unit 200 comprises a second conveyor 202 having an inlet zone 202a which is arranged at a lower level than the outlet zone 102b of the first conveyor 102 of the first processing unit 100.In the preferred embodiment, wherein the second processing unit 200 comprises the second drying unit 201, the second conveyor 202 is configured to convey the continuous layer "S" at the inlet of the respective second drying chamber or to convey the continuous layer "S" between the inlet and the outlet of the second drying chamber (situation not shown). The plant 1 further comprises an intermediate conveyor 300 interposed between the first processing unit 100 and the second processing unit 200 and configured to transfer the continuous layer "S" from the first processing unit 100 to the second processing unit 200. The intermediate conveyor 300 is configured to guide the continuous layer "S" obtained from the first conveyor 102 toward the second conveyor 202. Preferably, the intermediate conveyor 300 comprises a conveyor belt 302 provided with a transport surface and having an upper loading branch 303 and a lower return branch 304. The intermediate conveyor 300 has a front end 300 afacing the second conveyor 202 and a rear end 300 bopposing the front end 300 a.Preferably, the intermediate conveyor 300 may be operated in accordance with a first advancing direction in which the transport surface of the transport belt 302 is moved by the first conveyor 102 toward the second transport belt 202, and in accordance with a second advancing direction in which the transport surface of the transport belt 302 is moved by the second conveyor 202 toward the first conveyor 102.Preferably, the plant 1 comprises a support frame 2 on which the intermediate conveyor 300 is mounted.The plant 1 further comprises an inspection area 400 interposed between the first and second conveyors 102, 202 and in particular arranged at least partially below the outlet zone 102 bof the first conveyor 102. In the preferred embodiment, as can be seen from the attached figures, the inspection area 400 allows an operator to access under the outlet zone 102 bof the first conveyor 102, so that he can perform, for example, control and / or maintenance operations on the at least one stripping element 105, 106 of the first drying unit 101.In the preferred embodiment, the inspection area 400 comprises a / n, preferably raised / n, tread or tread 401 that is / is accessible by an operator. More preferably, the tread or tread 401 allows an operator to access the at least one scraper element 105, 106 in a maintenance step.The plant 1 comprises control means "UC" configured to at least partially automatically control the plant 1. The control means "UC" may comprise a control unit and / or an input interface and are configured to receive as input an actuation signal for actuating the plant, as will be clarified in the following of this description.In accordance with a particular aspect of the present invention, the intermediate conveyor 300 is movable between a rearward offset position suitable for normal operative operation, in which the rearward end 300 bof the intermediate conveyor 300 is disposed in the inspection area 400, and a forward offset position suitable for access to the inspection area 400 by an operator, in which the intermediate conveyor 300 is removed from the inspection area 400, preferably outside the inspection area 400.FIGS. 2, 3, 4 and 5 show the rearward offset position of the intermediate conveyor 300. The rearward offset position is suitable for normal operative operation: in this position, the rear end 300 bof the intermediate conveyor 300 is arranged in the inspection region 400. When the inspection area 400 includes the above-mentioned tread surface or the above-mentioned land 401, the intermediate conveyor 300 occupies a space above the tread surface or the land 401 in the rearward offset position. In FIGS. 2-5, the forwardly offset position is designated by the literal reference character "B".In contrast, FIG. 1 shows the position of the intermediate conveyor 300 offset forward. The forwardly offset position is instead suitable for access to the inspection area 400 by an operator: in this position, the intermediate conveyor 300 is removed from the inspection area 400, i.e. arranged outside the inspection area 400. In FIG. 1, the forwardly offset position is designated by the literal reference character "A".Advantageously, this feature makes it possible to optimize the spaces of the plant 1 and to improve the accessibility of the inspection area 400: by the possibility of switching the position of the intermediate conveyor 300 between the rearward and the forward offset positions, the utilization of the available space within the inspection area 400 can be maximized. This may firstly result in better overall efficiency of the plant 1 by allowing a more efficient arrangement of the other components, and secondly contribute to improving accessibility and comfort in the inspection area 400 and facilitating the work of the operators. Advantageously, moreover, a more efficient arrangement of the components of the installation 1 can contribute to improving the overall safety of the installation 1 itself.Preferably, the intermediate conveyor 300 is movable along an at least partially horizontal direction between the rearward offset position and the forward offset position. In other words, the intermediate conveyor 300 is movable along a direction substantially parallel to the ground (the intermediate conveyor 300 being mounted on the frame 2 and being operable). More specifically, the intermediate conveyor 300 is mounted on the support frame 2 so as to be movable between said rearward and forward offset positions relative to the support frame 2.Preferably, the intermediate conveyor 300 is movable between the two rearward offset and forward offset positions along a translatory or rototranslational trajectory. Preferably, the intermediate conveyor 300 is mounted on the support frame 2 by means of one or more guides 305 such that the intermediate conveyor 300 is movable between the two rearwardly offset and forwardly offset positions.In accordance with the preferred embodiment, the second conveyor 202 has an inclined position, which in particular defines an upward feed direction (see FIGS. 1-5 ). In other words, the second conveyor 202 develops in a direction that is not parallel to the floor (with the plant 1 ready for use). According to the illustrated preferred embodiment, the intermediate conveyor 300 is movable by rototranslational movement between the rearward offset position and the forward offset position: in particular, the intermediate conveyor 300 is movable such that the rear end 300 bof the intermediate conveyor 300 moves on a substantially horizontal trajectory, while the front end 300 aof the intermediate conveyor 300 moves on a trajectory inclined with respect to a horizontal plane and preferably matching the second conveyor 202.Preferably, as can be seen from the figures, the intermediate conveyor 300 has a substantially horizontal position in the rearwardly offset position, while the intermediate conveyor 300 has an inclined position in the forwardly offset position, in particular with the front end 300a being higher than the rear end 300b.In accordance with the preferred embodiment, the one or more guides 305 may include a front linear guide 306 of inclined attitude and which preferably extends parallel to the second conveyor 202 and a rear guide defining a substantially horizontal movement. In one embodiment, the rear guide comprises a pinion 308, preferably having a stationary position, and a rack 309 integral with the intermediate conveyor 300 and engaging the pinion 308.Preferably, the plant 1 comprises an actuator (not shown) connected to the intermediate conveyor 300 and configured to move the intermediate conveyor 300 between the two positions. Preferably, the actuator comprises a motoring connected to the aforementioned pinion 308.In accordance with the preferred embodiment, the actuator can be actuated by the control means "UC", in particular the control unit and / or the input interface. The control means "UC" are further preferably configured to select the first advancing direction of the upper guide surface 301 of the intermediate conveyor 300 from the first conveyor 102 to the second conveyor 202 or the second advancing direction opposite to the first.According to the preferred embodiment, the plant 1 comprises a continuous layer collection basin 501 "S" suitable for collecting a fraction of the continuous layer waste "S". As will be explained in more detail below in this description, the collecting basin 501 is particularly useful in the steps for restarting the plant 1.In particular, the collecting basin 501 is arranged on the side of the intermediate conveyor 300 opposite the inspection region 400. Preferably, the collecting basin 501 is positioned under the at least one stripping element 105, 106 to determine a falling feeding of the continuous layer "S" stripped by the first conveyor 102 of the first drying unit 101 into the collecting basin 501 during a step of discarding the continuous layer "S".According to the preferred embodiment, the plant 1 comprises deflecting means 500 configured to move the portion of the continuous layer "S" coming from the first conveyor 102 along a trajectory of movement between a zone above the collecting basin 501 in which the portion of the continuous layer "S" is fed into the collecting basin 501 and a zone above the intermediate conveyor 300 in which the portion of the continuous layer "S" is fed onto the intermediate conveyor 300.In other words, the deflecting means are activated to deflect this portion of the continuous layer "S" such that the flow path of the continuous layer "S" itself is changed from a downward direction from the scraper 105, 106 toward the collecting basin 501 to a flow direction from the scraper 105, 106 toward the intermediate conveyor 300. The section of the continuous layer "S" deflected by the deflecting means 500 is therefore loaded again onto the intermediate conveyor 300, so that it can be conveyed correctly towards the second conveyor 202.The portion of the continuous layer "S" may be any portion thereof. Preferably, as will become more apparent in the further course of the present invention, a portion of the continuous layer "S" is understood to mean a head end of the continuous layer "S" obtained by the transverse cutting (or tearing) of the continuous layer "S" in the vicinity of the inspection area 400 or, more generally, downstream of the first conveyor 102. Advantageously, this feature allows the automation of typical manual processes, greatly accelerating the operations in the steps for restarting the plant 1, in order to reduce the downtime associated, in particular, with the manual repositioning of the continuous slice "S", and greatly improving the accuracy in order to improve the quality of the final product. This technical feature also improves the safety of the operators and reduces the risk of injury.In accordance with the preferred embodiment, the deflecting means 500 comprise a rod or roller 502 having a predominant transverse development direction, preferably perpendicular, to the advancing direction of the continuous layer "S" on the deflecting means 500 and being displaceable transversely to the predominant transverse development direction. Moreover, the deflecting means 500 may comprise at least one shaped guide 503 defining the trajectory of movement of the rod or roller 502: in particular, the rod or roller 502 comprises at least one lateral support slidably engaging the at least one shaped guide 503 to restrict its movement within the shaped guide 503. Alternatively, the deflecting means 500 comprise a movable support (e.g. an arm or a robot support) which engages at least one side of the rod or roller 502 in order to move the rod or roller 502 along said trajectory.According to the illustrated embodiment, the trajectory comprises a first portion 503 awith at least one horizontal component when the guide is operational, configured to cause a transverse displacement of the rod or roller 502 between the zone above the collecting basin 501 and the zone above the intermediate conveyor 300 and vice versa. Preferably, the first part 503 ahas a circular arc configuration.According to the illustrated embodiment, the trajectory optionally comprises, after the first section 503a, a second section 503b having at least one vertical and preferably substantially vertical component when the guide is operational, and adapted to cause a raising and lowering of a portion of the continuous layer "S" from the intermediate conveyor 300. Preferably, the second section 502 bhas a straight configuration.Advantageously, the first section 502a is designed to allow a rapid and smooth displacement of the above-mentioned portion of the continuous layer "S" from the zone above the collecting basin 501 to the zone above the intermediate conveyor 300, in other words to ensure that it is correctly diverted towards the intermediate conveyor 300. Advantageously, on the other hand, the second vertical portion 503 bhas the aim of regulating the vertical position of the continuous layer "S" with respect to the intermediate conveyor 300, which contributes to improving the tension and consequently the material supply in the subsequent process steps. Together, these two portions 503 a, 503 blocateurize for an efficient and reliable flow of the continuous layer "S" through the plant 1.In accordance with the generality of the invention, the shaped guide 503 can be made in accordance with a variety of shapes, so long as they are suitable for the above-mentioned purposes.According to the preferred embodiment, the deflecting means 500 comprise at least one actuator 505 acting on the rod or roller 502 and configured to move the rod or roller 502 along at least a portion 503 a, 503 bof the movement trajectory.Preferably, the actuator 50 is configured to move the rod or roller 502, in particular along the second section 503 b.Preferably, the at least one actuator 505 is electrical, hydraulic, or pneumatic.The actuating drive 505 is preferably connected to the control means "UC" so that it can be activated at least partially automatically.According to the preferred embodiment, the actuator 505 is a linear actuator having a first end 505 a, which is hinged to a fixed portion, and a second end 505 b, which is connected to the rod or roller 502: the linear actuator 505 is rotatable about the fixed portion, preferably freely and / or manually, during the movement of the rod or roller 502 along the first section 503 aof the trajectory. The actuator 505 may instead be activated by the above mentioned control means "UC" to actively cause the movement of the rod or roller 502 along the second portion 503 bof the trajectory.According to the preferred embodiment, the plant 1 comprises a cleaning device 600 configured to perform a mechanical cleaning of the intermediate conveyor 300. Structurally, the cleaning device 600 (see FIG. 6 ) is equipped with at least one cleaning tool 601 configured to exert a mechanical action configured to remove debris from the transport surface of the intermediate conveyor 300. Preferably, the cleaning device 600 further comprises an actuator 602 configured for mutual movement of the intermediate conveyor 300 and the at least one cleaning tool 601 between a release configuration, in which the at least one cleaning tool 601 is removed from the transport surface of the intermediate conveyor 300, and an operating configuration, in which the at least one cleaning tool 601 is approached to the transport surface of the intermediate conveyor 300 to exert this mechanical effect on the transport surface of the intermediate conveyor 300.The release configuration is illustrated in Figures 1-4.The operating configuration is shown in FIG. 5.Advantageously, this technical feature allows for a reduction in cleaning costs and operating times, as the system is fully automated and cleaning interventions on the intermediate conveyor 300 can also be carried out more frequently. In this way, it is firstly possible to ensure a high quality final product, since the plant 1 and in particular the intermediate conveyor 300 are kept at the highest performance level, and secondly it is possible to increase the durability of the plant 1, since the wear effect caused by the material accumulated on the transport surface is reduced.Preferably, the cleaning device 600 is arranged and / or configured to perform a mechanical cleaning of the lower branch of the intermediate conveyor 300.In particular, the cleaning device 600 is arranged below the lower branch 304 of the intermediate conveyor 300 and is movable by an at least partial vertical movement between the operating and release configurations: preferably, the cleaning device 600 is tapped at a support portion, preferably at the support frame 2, so that it is pivotable between the two configurations about a tilting axis oriented transversely to the feed path of the continuous layer "S" and preferably running horizontally.In accordance with the preferred embodiment, the cleaning apparatus 600 is supported independently of the intermediate conveyor 300. In particular, the cleaning device 600 is preferably stationary with respect to the movement of the intermediate conveyor 300 between the forwardly offset and the rearwardly offset positions.Preferably, moreover, the operating configuration of the cleaning device 600 is selectable in the forwardly offset position of the intermediate conveyor 300 and more preferably only in the forwardly offset position of the intermediate conveyor 300.According to the preferred embodiment, the cleaning device 600 is, in particular in a controlled and / or automated manner, moved or movable between the release and operating configurations by the respective actuator 602, preferably by the above mentioned control means "UC". Preferably, the actuator 602 is electrical, hydraulic, or pneumatic.FIG. 6 shows a preferred embodiment of the cleaning device 600.According to this embodiment, the cleaning device 600 comprises a basin-like hold-down body 603 defining a hold-down volume in which the at least one cleaning tool 601 is arranged: the hold-down body 603 is open at the top, such that the at least one cleaning tool 601 faces the lower branch 304 of the transport belt 302.Preferably, the support body 603 comprises a front support flap 604 protruding at the top from a front wall of the support body 603 and developing transversely with respect to the lower branch 304 of the conveyor 302: the front support flap 604 is configured to engage the transport surface of the lower branch 304 of the conveyor 302 in the operating configuration of the cleaning device 600 to exert a mechanical scraping action on the transport surface of the conveyor 302.Preferably, the support body 603 comprises a rear support flap 605 protruding at the top from a rear wall of the support body 603 and developing transversely with respect to the lower branch 304 of the conveyor 302: the rear support flap is configured to engage the transport surface of the lower branch 304 of the conveyor 302 in the operating configuration of the cleaning device 600 to exert a scraping action on the transport surface of the conveyor 302.Preferably, the detaining body 603 comprises a pair of side flaps 606 protruding from the respective side walls of the detaining body 603 at the top and developing along the lower branch 303 of the conveyor 302: the pair of side flaps 606 is configured to at least partially enclose the lower branch 303 of the conveyor 302 in the operating configuration of the cleaning device, so as to exert an effect for containing the residues removed from the transport surface of the conveyor 302 and / or exert a scraping effect on the end edges of the transport surface of the lower branch 304 of the conveyor 302.In accordance with the preferred embodiment, the cleaning device 600 comprises two or more cleaning tools 601 which are arranged with respect to one another such that, in the operating configuration of the cleaning device 600, the two or more tools 601 act simultaneously on the transport surface of the intermediate conveyor 300.According to the preferred embodiment, the at least one cleaning tool 601 comprises a motorized roller brush having an axis of rotation oriented transversely to the feed path of the continuous layer "S": the mechanical action is a brushing action of the transport surface of the intermediate conveyor 300. Preferably, the cleaning device 600 comprises two motorized roller brushes 607 arranged in series along the transport surface of the transport belt 302.In alternative embodiments, the cleaning device 600 may comprise only one motorized roller brush 607 or three or more motorized roller brushes 607.In accordance with an aspect of the present invention, the cleaning device 600 may further comprise at least one spray nozzle 608 which is configured to discharge a pressurized fluid onto the transport surface of the transport belt 302, preferably a pressurized liquid, in the operating configuration of the cleaning device 600. The at least one spray nozzle 608 is arranged upstream of the cleaning tools 601 to wet the residues and the transport surface of the transport belt 302, facilitating the operations of the cleaning tools 601, or to perform a first removal of the residues on the transport surface of the transport belt 302, and / or it is arranged downstream of the cleaning tools 601 to remove particles possibly adhering to the transport surface of the transport belt 302. Preferably, the cleaning device 600 includes a plurality of spray nozzles 608 arranged in a row transversely with respect to the lower branch 304 of the conveyor belt 302.In accordance with the preferred embodiment, the transport surface of the transport belt 302 is made of plastic, in particular polyester.Advantageously, this feature makes the transport surface of the transport belt 302 easy to clean (even due to low moisture pick-up), corrosion resistant, and durable.The present invention also relates to a method for operating the above-mentioned plant 1. the method for operating the above-mentioned plant 1 will be described below of the present invention with reference to an operation cycle of the plant 1 itself. FIG. 4 shows proper operation of the plant. In this configuration, first of all, provision is made for the formation of a continuous layer "S", in particular by a mixture based on a reconstituted plant material.The continuous layer "S" is then supplied to the first drying unit 101 to perform a first drying of the continuous layer "S". Then, the dried continuous layer "S" is transferred from the first conveyor 102 of the first drying unit 101 to the intermediate conveyor 300 and from the intermediate conveyor 300 to the second conveyor 202 of the second drying unit 201. In this step, the intermediate conveyor 300 is held in the rearward offset position. Therefore, a second drying of the continuous layer "S" is performed in the second drying unit 201. In alternative embodiments, the plant comprises a different further processing unit 200 and a different processing is carried out on the continuous layer "S".In the case of a maintenance intervention that provides for the use of the above-mentioned inspection region 400, the temporary stopping of the installation 1 is provided.The plant 1 is stopped and then the intermediate conveyor 300 is displaced from the rearward displaced position to the forward displaced position to allow an operator to access the inspection area 400.Preferably, the intermediate conveyor 300 is moved between the two positions in an automated manner by the use of the respective actuating drive.The maintenance intervention can be of any type and require temporary stopping of the installation 1. For example, the engagement may relate to the inspection, maintenance, and / or replacement of components of the first conveyor 102, such as one of the scraper members 105, 106.In this step of stopping the plant 1, moreover, the continuous layer "S" is transversely cut, so that a head end of the continuous layer "S" is obtained in the vicinity of the outlet zone 102 bof the first conveyor 102.These steps are shown in FIG. 1.Regardless of its type, after completion of the intervention, a restart of the system 1 is provided.The restart of the plant 1 provides first the conveying of a first section of the continuous layer "S" exiting the first conveyor 102 of the first drying unit 101 towards the collecting basin 501. Specifically, the aforementioned leading end of the continuous sheet "S" is conveyed into the collecting basin 501. The initial portion of the continuous layer "S" generally has non-conformal features at the moments after restart and therefore must be discarded.To this end, it is preferable that the plant comprises one or more sensors (not shown) configured to detect one or more characteristics of the continuous layer "S" suitable for determining the conformance of the continuous layer "S" itself, for example by electronic algorithms implemented in the control unit "UC". Such properties may be, for example, the thickness, humidity, temperature or density of the continuous layer "S".In this step, the intermediate conveyor 300 is operated in such a way that the advancing direction of the transport surface of the transport belt 302 is moved in the direction of the collecting basin 501. In other words, the intermediate conveyor is operated in accordance with the second feed direction (backward).After a predetermined time or acceptable quality conditions of the continuous layer "S" exiting from the first drying unit 101 have been reached, the reversal of the feed direction of the transport surface of the transport belt 302, in particular leading from the direction toward the collecting basin 501 in the direction toward the second conveyor 202, is provided.This can be connected to a light, vision and / or acoustic signal supplied by the control unit "UC", depending on whether the quality conformance of the continuous layer "S" achieved by sensor detection is achieved.Preferably, therefore, the method provides for cutting the continuous layer "S" at this point to obtain a new head end of the continuous layer "S".These steps are shown in FIG. 2.At this point, a portion of the continuous layer "S", and in particular the new head end of the continuous layer "S", is then moved by means of the deflecting means 500 from the zone above the collecting basin 501 to a zone above the intermediate conveyor 300.The continuous layer "S" is then fed to the intermediate conveyor 300 and from the intermediate conveyor 300 to the second conveyor 202. Preferably, the deflecting means 500 are at least partially automatically actuated.In particular, the rod or roller 502 is first moved (for example manually by the operator) along the first portion 503 aof the movement trajectory defined by the shaped guide 503, as illustrated in FIG. 3.Subsequently, the rod or roller 502 is moved by the actuator 505 along the second portion 503 bof the trajectory of movement defined by the shaped guide 503 in order to increase the distance of the rod or roller 502 from the intermediate conveyor 300 and optimize the feeding of the continuous layer "S", as illustrated in FIG. 4. Once the step of restarting the plant 1 is completed, it operates properly as shown in FIG. 4.In the case of a cleaning intervention of the installation 1 and in particular of the intermediate conveyor 300, the stopping of the installation 1 is also provided and / or it is possible to carry out a cleaning intervention of the installation 1 during a step for stopping the installation 1, for example during the maintenance of the scrapers 105, 106 as stated above.The cleaning of the plant 1 can be carried out exceptionally, i.e. in a step for temporarily stopping the plant 1 or as a routine at the end of the continuous web production cycle. Regardless of the type of engagement, the interruption of the transfer of the dried continuous layer "S" from the first drying unit 101 to the second drying unit 201 by the intermediate conveyor 300 is provided, and then the arrangement of the cleaning device 600 in the operating configuration is provided as illustrated in FIG. 5. In this configuration, the cleaning device 600 performs cleaning of the intermediate conveyor 300. In this configuration, the intermediate conveyor 300 is preferably in the rearward offset position. However, it may be arranged that the cleaning step is performed while the intermediate conveyor 300 is in the forwardly offset position.Preferably, between the step of stopping the transfer of the continuous layer "S" and the step of arranging the cleaning device 600 in the operating configuration, a step of arranging the intermediate conveyor in the rearward offset position when the intermediate conveyor 300 has been previously arranged in the forward offset position is turned on.In the cleaning step, the cleaning device 600 is brought (preferably automatically) to the lower return branch of the conveyor belt 302 and actuated while the transport surface of the conveyor belt 302 is set in motion, whereby a cleaning of the surface of the belt is effected.This invention fulfills the underlying objects by eliminating the disadvantages of the prior art.In particular, by moving the intermediate conveyor 300 between the rearward offset position and the forward offset position, the spaces of the plant 1 can be optimized and the accessibility of the inspection area 400 can be improved: Due to the possibility of switching over the position of the intermediate conveyor 300, the space requirement of the plant can be rationalized and the inspection area 400 can be optimally utilized.Moreover, the use of the deflecting means enables a quick and simple removal of the non-conformal section of the continuous layer, in particular after the restart of the plant.Moreover, the use of a special cleaning device enables an optimum renewal of the transport surface of the intermediate conveyor.

Claims

Plant (1) for manufacturing a continuous sheet based on reconstituted plant material, comprising: - a forming unit for forming a continuous layer (S) of reconstituted plant material; - a first processing unit (100) configured to perform a first processing on the continuous layer (S) and having a first conveyor (102); - a second processing unit (200) configured to perform a second processing on the continuous layer (S) and arranged downstream of the first processing unit (100), the second processing unit (200) having a second conveyor (202) with an inlet zone (202a) arranged at a lower level than an outlet zone (102b) of the first conveyor (102); an intermediate conveyor (300) interposed between the first processing unit (100) and the second processing unit (200) and having a front end (300a) facing the second conveyor and a rear end (300b) opposite the front end (300a), the intermediate conveyor (300) being configured to guide the continuous layer (S) obtained from the first conveyor (102) toward the second conveyor (202); an inspection area (400) interposed between the first and second conveyors (102, 202) and in particular arranged at least partially below the outlet zone (102b) of the first conveyor (102); characterized in that the intermediate conveyor (300) is movable between a rearwardly offset position suitable for normal operative operation and in which the rear end (300b) of the intermediate conveyor (300) is arranged in the inspection area (400), and a forwardly offset position suitable for access to the inspection area (400) by an operator and in which the intermediate conveyor (300) is located outside the inspection area (400).The plant (1) according to claim 1, wherein the inspection area (400) comprises a / n, preferably raised, tread / n surface or running web (401) accessible by an operator, and wherein the intermediate conveyor (300), in the position offset backwards, occupies a space above the tread or running web (401); in particular, the outlet zone of the first conveyor (102) comprises a deflection roller (104) and at least one scraper tool (105, 106) associated laterally and / or below the deflection roller (104), and wherein the tread or running web (401) allows an operator to access the at least one scraper tool (105, 106) in a maintenance step.Plant (1) according to claim 1 or 2, comprising a support frame (2) on which the intermediate conveyor (300) is mounted by means of one or more guides (305) such that the intermediate conveyor (300) is movable between the two rearward and forward offset positions along a translatory or rototranslational trajectory.Plant (1) according to claim 3, wherein the second conveyor (202) has an inclined position and wherein the intermediate conveyor (300) is movable by rotational movement between the rearward offset and the forward offset position, in particular such that the rear end (300b) of the intermediate conveyor (300) moves on a substantially horizontal trajectory, while the front end (300a) of the intermediate conveyor (300) moves along a trajectory inclined with respect to a horizontal plane and preferably matching the second conveyor (202).Plant (1) according to claim 4, wherein in the rearward offset position the intermediate conveyor (300) has a substantially horizontal position, while in the forward offset position the intermediate conveyor (300) has an inclined position, in particular with the front end (300a) higher than the rear end (300b).Plant (1) according to any one of the preceding claims 3 to 5, wherein one or more guides (305) comprise a front linear guide (306) with inclined position, preferably parallel to the second conveyor (202), and a rear guide defining a substantially horizontal movement.Plant (1) according to any one of the preceding claims, comprising an actuator connected to the intermediate conveyor (300) and configured to move the intermediate conveyor (300) between the two rearwardly offset and forwardly offset positions.Plant (1) according to claim 7 when depending on 6, wherein the rear guide comprises a pinion, preferably having a stationary position, and a rack integral with the intermediate conveyor (300) and engaged with the pinion, the actuator preferably comprising a motorization connected to the pinion.Installation (1) according to claim 7 or 8, comprising control means (UC), in particular an input interface or an automatic controller, connected to the actuator and configured to receive as input an actuation signal for actuating the actuator.Plant (1) according to claim 9, wherein said control means (UC) are further connected to said intermediate conveyor (300) for selecting a first advancing direction of said upper guide surface (301) of said intermediate conveyor (300) from said first conveyor (102) to said second conveyor (202) or a second advancing direction opposite to said first.Plant (1) according to claim 10, further comprising a continuous layer collecting basin (501) suitable for collecting a fraction of the waste of the continuous layer (S) and arranged on the side of the intermediate conveyor (300) opposite the inspection area (400), the second advancement direction of the upper guiding surface (301) of the intermediate conveyor (300) being suitable for a step of discarding the continuous layer (S) from the intermediate conveyor (300) towards the collecting basin (501).Plant (1) according to claim 11, further comprising automatically and / or manually operated or actuatable deflecting means (500) arranged above the collecting basin (501) and configured to move a portion of the continuous layer (S) from a zone above the collecting basin (501) towards a zone above the intermediate conveyor (300) arranged in the rearwardly offset position, wherein the deflecting means (500) preferably comprise a transversely movable rod or roller (502) along at least one shaped guide (503) defining a trajectory of movement of the rod or roller (502).The plant (1) according to any one of the preceding claims, wherein the intermediate conveyor (300) comprises a conveyor belt (302), and wherein the plant (1) further comprises a cleaning device (600) associated with the intermediate conveyor (300) and is configured to perform a mechanical cleaning of the intermediate conveyor (300), in particular of the lower return branch (304) of the conveyor belt (302).Plant (1) according to claim 13, wherein the cleaning device (600) is supported independently of the intermediate conveyor (300) and is in particular stationary with respect to the movement of the intermediate conveyor (300) between the forwardly offset and the rearwardly offset positions; wherein the cleaning device (600) is switchable between a release position in which it is not in contact with the transport belt (302) of the intermediate conveyor (300) and an operating position in which it is in contact with the transport belt (302) of the intermediate conveyor (300), in particular with the lower return branch (304) of the transport belt (302) of the intermediate conveyor (300); wherein the operating position is preferably selectable in the forwardly offset position of the intermediate conveyor (300) and more preferably only in the forwardly offset position of the intermediate conveyor (300).The plant (1) according to any of the preceding claims, wherein the first processing unit (100) comprises a first drying unit (101) and the second processing unit (200) comprises a second drying unit (201); the first drying unit (101) preferably comprises a first drying chamber defined by side walls and a first drying group arranged in the first drying chamber; and the second drying unit (201) preferably comprises a second drying chamber defined by side walls and a second drying group arranged in the second drying chamber.Method for operating a plant (1) according to any one of the preceding claims, comprising: - forming a continuous layer (S), in particular by a mixture based on a reconstituted plant material; - feeding the continuous layer (S) to the first processing unit (100) by performing a first processing of the continuous layer (S); - transferring the continuous layer (S) from the first conveyor (102) of the first processing unit (100) to the intermediate conveyor (300) and from the intermediate conveyor (300) to the second conveyor (202) while the intermediate conveyor (300) is maintained in the rearwardly offset position; - performing a second processing of the continuous layer (S) in the second processing unit (200); - stopping the operation of the plant (1); after stopping the plant (1), bringing the intermediate conveyor (300) into the position offset forward by allowing an operator to access the inspection area (400).Method according to claim 16, further comprising a step of restarting the plant (1) and, after restarting, the following steps carried out by keeping the intermediate conveyor (300) in the position offset backwards: - conveying a first section of the continuous layer (S) exiting the first conveyor (102) of the first processing unit (100), towards a collecting basin (501) arranged on the opposite side of the intermediate conveyor (300) with respect to the inspection area (400); - upon reaching a predetermined time or acceptable quality conditions of the continuous layer (S) exiting the first processing unit (100), feeding the continuous layer (S) exiting the first conveyor (102) of the first processing unit (100) towards the intermediate conveyor (300) and from the intermediate conveyor (300) towards the second conveyor (202) of the second processing unit (200).Method according to claim 17, wherein between the step of conveying the first section of the continuous layer (S) emerging from the first conveyor (102) of the first processing unit (200) towards a collecting basin (501) and the step of feeding the continuous layer (S) emerging from the first conveyor (102) of the first processing unit (100) towards the intermediate conveyor (300) and from the intermediate conveyor (300) towards the second conveyor (202), a step of reversing the advancing direction of the upper support surface of the intermediate conveyor (300), in particular from a direction towards the collecting basin (501) in a direction towards the second conveyor (202), is interposed.Method according to any one of the preceding claims 16 to 18, wherein, between the step of conveying the first section of the continuous layer (S) emerging from the first conveyor (102) of the first processing unit (100) towards a collecting basin (501) and the step of feeding the continuous layer (S) emerging from the first conveyor (102) of the first processing unit (100) towards the intermediate conveyor (300) and from the intermediate conveyor (300) towards the second conveyor (202), a step of moving a portion of the continuous layer (S) by means of deflecting means (500) from a zone above the collecting basin (501) towards a zone above the intermediate conveyor (300) arranged in the position offset towards the rear is interposed.Method according to any one of the preceding claims 16 to 19, wherein the first processing is a first drying of the continuous layer (S) and the second processing is a second drying of the continuous layer (S).

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