WO2019150268A1

WO2019150268A1 - Industrial plant for milling leathers

Info

Publication number: WO2019150268A1
Application number: PCT/IB2019/050733
Authority: WO
Inventors: Antonio Galiotto
Original assignee: Erretre S.P.A.
Priority date: 2018-02-05
Filing date: 2019-01-30
Publication date: 2019-08-08
Also published as: IT201800002404A1; CN111971399A; EP3749788A1; CN111971399B; EP3749788B1; BR112020015843A2

Abstract

An industrial plant (1; 50) for milling leathers comprising a support framework (2; 51 ) resting on a reference surface (R) of an industrial factory, a rotatable drum (3; 52) coupled with the support framework (2; 51 ) and comprising a hollow body (4; 53) suitable to receive the leathers to be treated by milling, defining a symmetry axis (X) around which the hollow body (4; 53) is put in rotation by motorization means associated with the support framework (2; 51 ) and having a through opening (5; 54) at which a shaped shutter (6) is revolvingly coupled with the hollow body (4; 53) and cooperates with actuation means suitable to place it between a first position, in which the shaped shutter (6) tightly closes the through opening (5; 54), and a second position in which the shaped shutter (6) at least partly opens the through opening (5; 54) for loading into the inner volume (7) of the hollow body (4; 53) of the leathers to be treated and/or discharging from the inner volume (7) of the hollow body (4; 53) of the treated leathers, and a motorized conveyor belt (8; 57), facing and underlying the hollow body (4; 53) and which receives the treated leathers, coming by fall from the hollow body (4; 53), when the shaped shutter (6) takes the second position and which conveys the treated leathers away from the hollow body (4; 53). In particular, in transversal section made in the longitudinal development direction of the conveyor belt (8; 57), the conveyor belt (8; 57) itself presents a curved profile (8') having concavity facing towards the hollow body (4; 53) at least in the linear portion (L) of the conveyor belt (8; 57) on which the treated leathers fall, coming out from the hollow body (4; 53) of the rotatable drum (3; 52) through the through opening (5; 54).

Description

INDUSTRIAL PLANT FOR MILLING LEATHERS

The present invention concerns an industrial plant for milling tannery leathers, or similar flexible and special laminar surfaces (imitation leather, ennobled leather and so on).

It should be noted that, within the tanning industry, the term "milling" refers to the treatment of leathers in a watertight machine, known as "drum", which is performed both to prepare the leather itself for tanning, dyeing o greasing and to subject them to the actual tanning, dyeing or greasing processes.

Typically, among the parameters of a recipe of a milling cycle are included:

• temperature inside the drum and

• in return, relative humidity,

constituting main parameters of a milling cycle to which, anyway, other parameters are also linked such as, for instance, operating (in particular, rotation) drum speed, total time of the milling cycle, chemical products introduced into the drum and type of leathers treated in the drum, purity level of air inserted into the drum and so on. More in detail, the milling is a mechanical process which is carried out on any type of special fabric - in general, animal leathers - in order to give the product the appearance of aging or wrinkling, to make it softer and to eliminate any folds present and, therefore, to prepare it for the subsequent stages of processing.

The material is, indeed, subjected to mechanical action due to its rolling inside the hollow cylindrical (often perforated) basket or barrel that constitutes the main part of the machine (or drum) and which operates by rotating around a generally horizontal transverse axis.

Simultaneously with the mechanical action, it is possible to have a conditioning of the material present inside the cylindrical basket (or barrel) by means of air subjected to predetermined temperature and humidity conditions.

Finally, the product is cooled by circulation of cold air inside the cylindrical barrel which constitutes the main component of the drum. By varying the processing time it is possible to get more or less intense effects on the leather.

In general, an industrial plant for milling leathers - to be submitted for example to a simple fulling operation (word, the latter, commonly used in the tannery sector to indicate that processing - dry or through chemical products allowing to get special fashion effects on the leather - of the leather which provides for its softening by means of mechanical shaking inside the cylindrical barrel of the drum, under controlled temperature and humidity conditions) - comprises a fulling drum which, in turn, includes a hollow, usually cylindrical, body, made for instance of wood, stainless steel or polypropylene and suitable to be rotated around a symmetry axis by motorization means and inside which the leathers to be treated are received. The hollow body arranged horizontally is supported by a hollow shaft, placed on supporting members (such as typically ball or roller bearings) which allow it to rotate under the action impressed by the motorization means; the cavity in the shaft allows to introduce into the cylindrical body the water and the substances necessary for the tanning and the escape of the gases that are formed during the process.

The hollow shaft is provided, at one of its ends, with a toothed crown which, by means of a pinion, is moved by the motorization means which cause the rotation of the cylindrical hollow body.

Conveniently, the inner surface of the hollow body is provided with protruding ribs (pegs, nervations, rounded blades) which increase the movement of the leathers when the cylindrical hollow body of the drum rotates around the symmetry axis.

In addition, the hollow (preferably cylindrical, as said) body of the drum presents a through opening for the introduction and extraction of the material, at which a water-tight revolving shutter (or door) is installed.

In the case of the more traditional drums, the through opening is opened manually, after stopping the drum rotation, while in the highly automated drums, normally called "automatic discharge” ones, the movement of the revolving shutter to open the through opening is impressed by automatic actuation devices (such as pneumatic actuators, electric motors or of other type), without the intervention of the operator and without stopping the drum rotation: in this way the leathers come out of the hollow body of the drum while it is rotating around the symmetry axis.

A central processing and control unit, available to the user who schedules its operation, controls operation of the aforesaid automatic actuation devices and, in return, the movement of the shutter. Suitable actuation means, therefore, selectively and automatically place the shaped shutter between a first position, in which it completely and perfectly hermetically closes the through opening, and a second position in which the shaped shutter at least partly opens the through opening in order to allow the load in the inner volume of the hollow body of the leathers to be treated and/or the discharge from the inner volume of the hollow body of the leathers treated.

Sometimes, indeed, depending on the different size (surface) of the leathers to be treated, the shutter is opened in pre-set or steadily adjustable middle positions.

A typical industrial plant for milling tannery leathers of the type with automatic discharge of the prior art (highlighted, for example, by the prior documents published, respectively, with CN106435052 A and US2282530 A) also includes a motorized conveyor belt (or tape), facing and underlying the hollow body of the drum: this conveyor belt receives the leathers just treated in the hollow body, from which they come by fall - automatic or favoured by the hand action of one or two operators -, when the shaped shutter takes the second position, and conveys the leathers treated far away from the hollow body.

This plant design has been consolidated for years in the leather tanning sector, allowing a more or less efficient management of the leathers discharge phase from the hollow body of the drum where they have just been subjected to a milling cycle.

Such a management of the discharge of the leathers from the drum - especially while it is kept in rotation - is in any case widely improvable and to perfect, in consideration of the fact that, at present, the leathers falling on the motorized conveyor belt are not efficiently and promptly processed by the belt itself, in the sense that they are not so quickly conveyed to the end of the conveyor belt which is placed frontally to the hollow body of the rotatable drum and is accessible by the operators: in practice, this end of the conveyor belt is opposed to that one below the hollow body and closer to the through opening of the hollow body from which the leathers come out while it rotates around the horizontal symmetry axis.

This is due to the fact that the operators, however efficient, are able to withdraw a predefined and limited number of leathers from the conveyor belt in the time unit, much lower than that one which, in the same time unit, falls from the hollow body of the drum rotating and lies on the conveyor belt.

To the substantial impossibility for the operators to follow the fall rate of the leathers from the rotating drum on the conveyor belt - unless to allocate a relevant number (more than two) of operators to pick up the leathers from the conveyor belt, economically disadvantageous choice not always practicable in a company - it comes that leathers discharge operation currently and inevitably includes a little efficient variable sequence of opening and closing of the automatic shutter and an equally little efficient discontinuous operation of the conveyor belt (or belts) arranged below the drum.

Not to mention the fact that, in the prior art, between the hollow body of the drum and the conveyor belt (which, moreover, in some embodiments, is also composed of two or three conveyor belts in series each other) an auxiliary slide is mounted, placed above the conveyor belt and side-by-side to the hollow body of the drum and whose function is to ease the rapid, guided and gentle passage of the leathers from the hollow body to the conveyor belt.

The auxiliary slide is arranged next to the hollow body along an oblique direction defining with the direction defined by the conveyor belt below it an angle of not less than 90°, at the structural discontinuity zone between the auxiliary slide and the conveyor belt.

This general situation causes a relevant disadvantage consisting in that, currently, some (if not many) of the leathers, already exiting from the hollow body of the rotating drum, progressively and however minimally pile up on the conveyor belt at such a structural discontinuity zone between the auxiliary slide and the conveyor belt (especially if it defines an angle of about 90°), with the concrete risk that their accumulation on the conveyor belt increases until it comes into contact and rub against the outer wall of the hollow body, with all the notable disadvantages and dangers that this entails (damage to part of the leathers with consequent their derating, involuntary collection of the leathers from the conveyor belt by the rotatable drum, leaking of the leathers from the conveyor belt and their accidental impact or inclusion in the geared motor-belts towing system of the drum, under stress functioning of the rotatable drum and consequent dangers for the operator). Starting, therefore, from the awareness of the aforesaid drawbacks suffered by the current state of the art herein considered, the present invention proposes to effectively overcome these drawbacks.

Particularly, primary purpose of the invention is to provide an industrial plant (or group of equipment) for milling tannery leathers that avoids or at least considerably reduces with respect to the prior art the risk of accumulation of leathers on the conveyor belt underlying the hollow body of the drum from which they come out while it is rotating.

Otherwise said, main purpose of the invention is to devise an industrial plant for milling tannery leathers allowing a conveyance towards the collection station of the leathers, coming out from a rotating drum inside which they’ve just been treated, more effective and faster than what is offered by equivalent plants of known type. Within this scope, it is therefore task of the present invention to design an industrial plant (or group of equipment) for milling leathers which, with respect to the prior art, greatly reduces the risk of damage to some of the leathers leaving the drum where they’ve just been treated (dry or with water and/or chemicals).

It is a further task of the invention to indicate an industrial plant (or group of equipment) for milling tannery leathers which, compared to the equivalent prior art, lowers the percentage of leather degraded due to their contact with the outer wall of the hollow body of the rotating drum when out of it.

It is another task of the invention to shorten the time for unloading the leathers from a drum of automatic discharge type with respect to the current state of the art, improving the efficiency of this operation with respect to what happens in the known equivalent plants.

In the cognitive sphere of the aforesaid main purpose, it is also task of the same invention to provide an industrial plant (or group of equipment) for milling tannery leathers that, comparing to the prior art, reduces dangers for physical safety of the operator (or operators) responsible for picking up the leathers from the conveyor belt on which they fall, at the exit of an automatic discharge type drum.

It is a last but not least task of the present invention to make concrete an industrial plant for milling tannery leathers that allows almost completely any risk of accidental impact of the leathers in the geared motor-belts towing system which causes the movement of the drum and any risk of under stress functioning of the motorization means which rotate the hollow body of the drum, which can be instead found in the plants comparable to it.

Said purposes are achieved by an industrial plant (or group of equipment) for milling tannery leathers according to claim 1 , as hereinafter referred for the sake of exposition brevity.

Further detailed technical features of the industrial plant (or group of equipment) for milling tannery leathers of the present invention are reported in the related dependent claims.

The aforementioned claims, specifically and concretely defined below, are intended as an integral part of the present description.

Advantageously, the industrial plant for milling tannery leathers of the invention avoids and in any case certainly limits considerably with respect to the plants of the current state of the art the risk that the leathers falling from the hollow body of the rotatable drum dangerously accumulate or pile up on the underlying conveyor belt.

This is due to the fact that, in transversal section made in the longitudinal direction of the conveyor belt, the latter presents a curved profile having concavity facing towards the hollow body at least in the linear portion of the conveyor belt on which the leathers fall just subjected to milling treatment and at the exit of the hollow body of the rotatable drum (of the automatic discharge type) through the through opening, easing their linear release or sliding.

Equally advantageously, therefore, always in function of what has just been explained, the industrial plant for milling tannery leathers of the present invention eases the conveyance towards the collection station (where the operator or operators are placed) of the leathers falling from the hollow body of the rotatable drum of the automatic discharge type.

Still advantageously, the industrial plant for milling tannery leathers of the current invention limits risks of damage (and of degrading if not of destination to waste) of the leathers, by avoiding their contact with the outer wall of the drum hollow body.

In advantageous manner, therefore, the risks for the operator and for the machinery - in particular the rotatable drum and the geared motor-belts towing system associated therewith - are drastically limited by the industrial plant of the current invention, compared to what negatively happens in the known technique. Advantageously, moreover, the industrial plant for milling tannery leathers shortens the time of discharging the leathers from the rotatable drum to the conveyor belt with respect to the current state of the art, since, thanks to the avoidance - through the curved profile of the conveyor belt - the accumulation of the leathers in a certain zone of the conveyor belt itself, it is still possible to foresee, with respect to the similar existing plants, less stoppages of the rotation of the hollow body of the drum and less cycles of movement of the shaped shutter for open and close the through opening of such a hollow body.

Still advantageously, the innovative technical concept underlying the invention can also be extended to industrial plants for milling tannery leathers yet existing and/or operative in the tanning field, by replacing the existing conveyor belts and even the auxiliary slide with the conveyor belt having an at least partly curved profile with concavity facing towards the outer wall of the hollow body of the rotatable drum. Said purposes and advantages will become clearer from the following description, concerning preferred embodiments of the industrial plant (or group of equipment) for milling tannery leathers of the invention, given by indicative and illustrative, but not limitative, way with reference to the attached tables of drawings in which:

figure 1 is a schematic and exemplified side view of a first embodiment of the leathers milling plant of the invention;

figure 2 is a schematic and exemplified side view of a second embodiment of the leather milling plant of the invention.

The industrial plant (or group of equipment or machinery) for milling tannery leathers of the invention is illustrated in an example manner in a first embodiment thereof in figure 1 , where it is globally numbered with 1.

It is noted that the industrial plant 1 for milling leathers comprises:

a support framework 2 adapted to rest on a reference surface R, such as the flooring, of an industrial factory;

a rotatable drum 3 of the automatic discharge type, coupled with the support framework 2 and comprising a hollow body 4 suitable to house the leathers to be submitted to one or more milling cycles, defining a symmetry axis X around which the hollow body 4 itself is rotated by motorization means (not shown for the sake of simplicity) associated with the support framework 2: the hollow body 4 has a through opening 5 at which a shaped shutter 6 is revolvingly coupled with the hollow body 4 and cooperates with actuation means (also not shown for the sake of simplicity) which selectively place it between a first position, in which the shaped shutter 6 hermetically closes the through opening 5, and a second position in which the shaped shutter 6 at least partly opens the through opening 5 for the load into the inner volume 7 of the hollow body 4 of the leathers to be treated and/or the unload from such an inner volume 7 of the hollow body 4 of the treated leathers;

a motorized conveyor belt (or tape) 8, at least partly facing and underlying the hollow body 4 and which:

• receives the treated leathers, coming by fall from the hollow body 4, when the shaped shutter 6 takes the aforementioned second position;

• conveys the treated leathers away from the hollow body 4, towards the collection station where at least one operator P stands.

According to the invention, in transversal section made in the longitudinal direction of the conveyor belt 8, the conveyor belt 8 itself presents a curved profile 8’ having concavity facing towards the hollow body 4 (in this case, this concavity affects almost the entire longitudinal development of the conveyor belt 8), at least in the linear portion L of the conveyor belt 8 onto which the just treated leathers fall from the hollow body 4 of the rotatable drum 3 through said through opening 5.

In particular, moreover, the linear portion L of the curved profile 8’ of the conveyor belt 8 is underlying the hollow body 4 and faces the through opening 5 when the latter takes the spatial position which allows the leaking of the leathers from the inner volume 7 of the hollow body 4.

In this constructive example of the invention, therefore, it is reiterated that the curved profile 8’ of the conveyor belt 8 which has the concavity facing towards the outer wall 4a of the hollow body 4 substantially coincides with the entire longitudinal development of the conveyor belt 8, net of what will be seen shortly. Preferably but not necessarily, the curved profile 8’ of the conveyor belt (or tape) 8 departs from a first end 8a arranged substantially near a point in the space A at the height of which the treated leathers project outwardly from the through opening 5 (shaped shutter 6 in the aforementioned second position) or start coming out from the hollow body 4 through the through opening 5 itself.

In the specific case, by way of pure example, the first end 8a of the conveyor belt 8 is located just beyond the height of the horizontal hollow shaft (not shown for the sake of simplicity) which supports the hollow body 4 and, in essence, little beyond the symmetry axis X of the latter.

In addition, in a preferred but not limiting manner, the curved profile 8’ of the conveyor belt 8, for almost the entirety of its longitudinal development, faithfully follows the profile 4’ of the hollow body 4 from which it is separated by a prefixed distance D which preferably, remains constant along substantially the entire longitudinal development of the curved profile 8‘ of the conveyor belt 8 (which, as said, almost coincides with the entire longitudinal development of the conveyor belt 8) remains constant along substantially the whole longitudinal development. Such prefixed distance D - which creates a gap between the hollow body 4 of the rotatable drum 3 and the conveyor belt 8 - presents a value between 30 cm and 150 cm and, preferably, is equal to 40 cm or 50 cm.

It is underlined, anyway, that the curvature radius of the curved profile 8' of the conveyor belt 8 depends on the curvature radius of the hollow body 4, in the case - as that one described herein purely by preferred way - in which it is cylindrical. Moreover, both the upper surface 8c and the lower surface 8d of the conveyor belt 8 present, in this case, preferably but not exclusively, the same profile, so that the upper surface 8c is concave and the lower surface 8d is convex.

In a preferred but not binding manner, the curved profile 8’ of the conveyor belt 8 extends for a length equal to at least the maximum width dimension T of the hollow body 4, as well illustrated in figure 1.

Preferably, such a maximum width dimension T corresponds to a diameter since, as said, the hollow body 4 is, in a preferred but not exclusive way, cylindrical.

As shown again in figure 1 , in this specific embodiment, the conveyor belt 8 preferably surrounds almost half the perimeter (perimeter which in this case is constituted by a circumference) of the hollow body 4, ensuring effective sliding and conveying towards the collection station of the leathers when they fall on it. More in detail, the conveyor belt 8 presents:

the aforementioned first end 8a placed laterally near a first point Si of the maximum horizontal width dimension (horizontal diameter T, with respect to the reference surface R) of the hollow body 4;

a second end 8b, opposite to the first end 8a, placed near the underlying part of the hollow body 4 and the vertical projection on the reference surface R of a second point S2, opposite to the first point Si, of the maximum horizontal width dimension T of the hollow body 4 of the rotatable drum 3.

According to the preferred embodiment described herein of the invention, the conveyor belt 8 comprises a horizontal end section of collection 9 at the second end 8b to which the treated leathers are conveyed in order to make them available to an operator P ready to pick them up and allocate them for the partial storage. Moreover, the conveyor belt 8 has a transverse development, orthogonal to the longitudinal development, at least partly greater than the maximum width dimension of the through opening 5 of the hollow body 4: generally, such a transversal development of the conveyor belt 8 normally has a value equal to the maximum width dimension T of the hollow body 4 and in any case never less than the maximum width dimension of the through opening 5 which, generally, coincides with a length since the through opening 5 itself has, preferably, a rectangular profile with base parallel to the symmetry axis X of the hollow body 4.

In general, however, the construction composition of the conveyor belt 8 is of the type per se known in the field, providing a continuous and very regular support plane, movable around end rollers and made of plastic material, such as PVC, polyurethane or silicone polymers.

Constructively, the conveyor belt 8 is also, for the most part, interposed between the support framework 2 and the hollow body 4 of the rotatable drum 3, in order to reduce the impact of its overall dimensions as much as possible.

As far as the actuation means are concerned, they comprise any of the linear actuation systems selected from the group consisting of pneumatic actuators, hydraulic actuators, electric motors and/or similar and are operatively connected with a central processing and control unit (not illustrated) available to the operator P which, by activating the actuation means, determines the automatic passage of the shaped shutter 6 from the first position to the second position and vice versa.

It should be noted that, preferably and suitably from an operative efficiency profile, the shaped shutter 6 passes from the first position to the second position while the hollow body 4 of the rotatable drum 3 keeps on rotate around the symmetry axis X. Figure 2 shows a possible embodiment of the invention where the industrial plant for milling tannery leathers, now globally indicated with 50, differs from that one yet described, indicated with 1 and shown in figure 1 , for including also guide means, in the form in this case of an auxiliary slide 58 coupled with the support framework 51 and arranged above a first end 57a of the conveyor belt (or tape) 57 forming its structural continuation, since the auxiliary slide 58 is provided with a first face 58a, facing towards the hollow body 53 of the rotating drum 52, at least partly concave. More specifically and preferably, a lower portion 58b of the auxiliary slide 58 surmounts or overlaps the conveyor belt 57 at the first end 57a closest to the point of fall of the leathers on the conveyor belt 57.

From an operative point of view, the leathers progressively exit from the through opening 5 of the hollow body 4 of the rotatable drum 3 at each rotation of the hollow body 4 around the symmetry axis X: they fall on the underlying linear portion L of the curved profile 8’ of the conveyor belt 8 and are by this conveyed to the horizontal end section of collection 9 where the operator P picks them up and orders them according to the processing requirements downstream the industrial plant for milling leathers 1 of the invention.

Similarly it occurs for the industrial plant 50 of figure 2, where however the leathers coming out from the through opening 54 of the hollow body 53 of the rotatable drum 52 firstly involve the first partly concave part 58a of the auxiliary slide 58 and then the conveyor belt 57: this, however, linearly and without the structural discontinuity between the auxiliary slide 58 and the conveyor belt 57 negatively impacts the fluidity of the conveying of the leathers towards the collection station where the operator P stands.

In accordance with the description just given, it is understood, therefore, that the industrial plant (or group of equipment) for milling leathers of the present invention achieves the purposes and reaches the advantages previously mentioned. Upon execution, changes could be made to the industrial plant (or group of equipment) for milling tannery leathers of the current invention, consisting, for example, in a positioning of the conveyor belt with respect to the hollow body of the drum different from that one detectable in the attached figures, although in the constancy of remaining at least partly underlying it.

In addition to this, other embodiments of the industrial plant for milling tannery leathers that are here exclusively claimed could exist, not illustrated below, in which the actuation means which arrange the shaped shutter in the first position and in the second position are different from those ones previously mentioned, which does not affect the advantage brought by the present invention.

Moreover, in further embodiments of the industrial plant for milling tannery leathers of the invention, unaccompanied by reference figures in the following, the curved profile could have concavity facing towards the hollow body of the rotatable drum only in the linear portion of the conveyor belt on which the leathers in exit of the hollow body fall, or in a length of the conveyor belt greater than such a linear portion but lower than the whole longitudinal development of the conveyor belt itself.

It is pointed out that the innovative technical concept of the invention also extends to rotary drum the hollow body of which has a different shape from the circular shape shown as a preferred feature in the attached figures, for example polygonal and in particular octagonal.

It is, finally, clear that several other changes could be made to the industrial plant for milling tannery leathers concerned, without departing from the principle of novelty intrinsic in the inventive idea expressed herein, as it is clear that, in the practical implementation of the invention, materials, shapes and sizes of the illustrated details could be changed, as needed, and replaced with others technically equivalent.

Where the constructive features and techniques mentioned in the following claims are followed by reference numbers or signs, those reference signs have been introduced with the sole objective of increasing the intelligibility of the claims themselves and therefore they have no limiting effect on the interpretation of each element identified, by way of example only, by these reference signs.

Claims

1. Industrial plant (1 ; 50) for milling leathers comprising:

- a support framework (2; 51 ) suitable to rest on a reference surface (R) of an industrial factory;

- a rotatable drum (3; 52) coupled with said support framework (2; 51 ) and comprising a hollow body (4; 53) suitable to receive the leathers to be treated, defining a symmetry axis (X) around which said hollow body (4; 53) is put in rotation by motorization means associated with said support framework (2; 51 ) and having a through opening (5; 54) at which a shaped shutter (6) is revolvingly coupled with said hollow body (4; 53) and cooperates with actuation means suitable to place it between a first position, in which said shaped shutter (6) tightly closes said through opening (5; 54), and a second position in which said shaped shutter (6) at least partly opens said through opening (5; 54) for loading into the inner volume (7) of said hollow body (4; 53) of said leathers to be treated and/or discharging from said inner volume (7) of said hollow body (4; 53) of said treated leathers;

- a motorized conveyor belt (8; 57), at least partly facing and underlying said hollow body (4; 53) and which:

• receives said treated leathers, coming by fall from said hollow body (4; 53), when said shaped shutter (6) takes said second position;

• conveys said treated leathers away from said hollow body (4; 53), characterized in that, in transversal section made in the longitudinal development direction of said conveyor belt (8; 57), said conveyor belt (8; 57) presents a curved profile (8’) having concavity facing towards said hollow body (4; 53) at least in the linear portion (L) of said conveyor belt (8; 57) on which said treated leathers fall, coming out from said hollow body (4; 53) of said rotatable drum (3; 52) through said through opening (5; 54).

2. Plant (1 ; 50) according to claim 1 ), characterized in that said linear portion (L) of said curved profile (8') of said conveyor belt (8; 57) is underlying said hollow body (4; 53).

3. Plant (1 ; 50) according to claim 1 ) or 2), characterized in that said curved profile (8') of said conveyor belt (8; 57) departs from a first end (8a) disposed substantially near a point in space (A) at the height of which said treated leathers project towards the outside from said through opening (5; 54) or start coming out from said hollow body (4; 53) through said through opening (5 ; 54).

4. Plant (1 ; 50) according to any of the previous claims, characterized in that said curved profile (8') of said conveyor belt (8; 57) follows the profile (4') of said hollow body (4; 53) from which it is separated by a prefixed distance (D) which remains constant along said curved profile (8') of said conveyor belt (8; 57).

5. Plant (1 ; 50) according to any of the previous claims, characterized in that said curved profile (8') of said conveyor belt (8; 57) extends for a length equal to at least the maximum width dimension (T) of said hollow body (4; 53).

6. Plant (1 ; 50) according to claim 5), characterized in that said maximum width dimension (T) corresponds to a diameter when said hollow body (4; 53) is cylindrical.

7. Plant (1 ; 50) according to any of the previous claims, characterized in that said conveyor belt (8; 57) surrounds almost half the perimeter of said hollow body (4; 53).

8. Plant (1 ; 50) according to any of the previous claims, characterized in that said conveyor belt (8; 57) presents:

- a first end (8a) placed laterally near a first point (Si) of the maximum horizontal width dimension (T) of said hollow body (4; 53);

- a second end (8b), opposite to said first end (8a), placed near the underlying part of said hollow body (4; 53) and of the vertical projection on said reference surface (R) of a second point (S2), opposite to said first point (Si), of said maximum horizontal width dimension (T) of said hollow body (4; 53).

9. Plant (1 ; 50) according to any of the previous claims, characterized in that said conveyor belt (8; 57) comprises a horizontal end section of collection (9) at one end (8b) to which said treated leathers are conveyed in order to make them available to an operator (P).

10. Plant (1 ; 50) according to any of the previous claims, characterized in that said conveyor belt (8; 57) has a transverse development, orthogonal to said longitudinal extension, at least partly greater than the maximum width dimension of said opening through (5; 54) of said hollow body (4; 53).

1 1. Plant (50) according to any of the previous claims, characterized in that it comprises an auxiliary slide (58), coupled with said support framework (2; 51 ) and arranged above a first end (57a) of said conveyor belt (57) which constitutes its structural continuation since said auxiliary slide (58) is provided with a first face (58a), facing towards said hollow body (53), at least partly concave.

12. Plant (50) according to claim 1 1 ), characterized in that the lower portion (58b) of said auxiliary slide (58) surmounts or overlaps said conveyor belt (57) at said first end (57a) closest to the point of fall of said leathers on said conveyor belt (57).

13. Plant (1 ; 50) according to any of the previous claims, characterized in that said actuation means comprise any of the linear actuation systems selected from the group consisting of pneumatic actuators, hydraulic actuators, electric motors and/or similar and are operatively connected with a central processing and control unit available to the operator (P) which, by activating said actuation means, determines the automatic passage of said shaped door (6) from said first position to said second position and vice versa.

14. Plant (1 ; 50) according to any of the previous claims, characterized in that said shaped shutter (6) passes from said first position to said second position while said hollow body (4; 53) of said drum (3; 52) continues to rotate around said symmetry axis (X).