WO2018172837A1

WO2018172837A1 - Improved drum for the milling treatment of leathers

Info

Publication number: WO2018172837A1
Application number: PCT/IB2017/057604
Authority: WO
Inventors: Antonio Galiotto
Original assignee: Erretre SpA
Current assignee: Erretre SpA
Priority date: 2017-03-23
Filing date: 2017-12-04
Publication date: 2018-09-27
Anticipated expiration: 2019-09-23
Also published as: CN110402291A; BR112019019398A2; BR112019019398B1; EP3601622B1; IT201700031928A1; EP3601622A1; CN110402291B

Abstract

An improved drum for the milling treatment of the leathers comprising a bearing frame (2) resting on a reference surface of an industrial factory, a movable hollow body (3), coupled with the bearing frame (2) and made of at least partly thermally conductive material, receiving in its inner volume (4) the leathers to be treated by milling, motorization means operatively connected with the movable hollow body (3) in such a way as to place it in rotation around a linear axis (X) when the leathers must be treated in the inner volume (4) of the hollow body (3), an outer casing (5) coupled with the bearing frame (2) and surrounding the movable hollow body (3) with which it defines an annular space (6). In particular, the improved drum (1) comprises a conditioning circuit (7) cooperating with the movable hollow body (3) through air (A1) which the conditioning circuit (7) conveys within the annular space (6) at a given temperature, varied by adjustment means depending on the contingent needs of treatment of the leathers inside the hollow body (3) in rotation, so that the outer wall (3a) of the hollow body (3) is kept at a predefined temperature, deemed to be adequate for each phase of the treatment of the leathers in the hollow body (3), and a structural assembly (8) formed by the outer casing (5) and the movable hollow body (3) defines a heat exchanger in which the air (A1) which is conveyed into the annular space (6) and flows around the outer wall (3a) of the hollow body (3) stands for a first one of the heat exchange fluids and is at least hot in the initial stage of the treatment of the leathers, in order to contribute to the heating of the leathers in the inner volume (4) of the hollow body (3), and cold in the advanced stage of the treatment of the leathers in order to dissipate the heat in excess developed by friction by the leathers moving in the inner volume (4) of the hollow body (3).

Description

IMPROVED DRUM FOR THE MILLING TREATMENT OF LEATHERS

DESCRIPTION

The present invention generically concerns a leather processing machine such as an improved drum for the milling treatment of leathers in the tanning industry.

It is clear from the outset that with the term "milling", within the tanning industry, it is meant a mechanical type processing in which the leathers are immersed into a drum which, when rotated by motorization means, moves them, usually dry, to make them softer and to eliminate any existing folds and, therefore, to prepare them for the subsequent stages of processing.

The material is, indeed, subjected to mechanical action due to its rolling inside the cylindrical (often punched) body which constitutes the main part of the machine (or drum) and which works 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 drum by means of air subjected to predetermined temperature and humidity conditions.

Finally, the product is cooled by means of circulation of cold air. By varying the processing time it is possible to have more or less intense effects.

In essence, therefore, the milling cycle to which the leathers are subjected inside the cylindrical body of a tannery drum is made according to a determined "recipe" which is essentially composed of pre-established temperature and humidity conditions, cylindrical body rotation speed imparted by appropriate motorization means operatively connected with it, type and quantity of leathers treated inside the drum and time duration of the milling cycle.

Such a "recipe" allows to get, in a general and hypothetical way, the desired and expected level of softness for the dry leathers processed in a milling cycle.

In the tanning industry, a drum is a processing equipment which, by rotating, softens the leathers using a centrifugal force: the leathers are softened inside the rotating hollow body (drum) where they are contained by means of rectangular or trapezoidal deflectors (or blades) uniformly distributed on the inner wall of the hollow body itself.

Generally speaking, a tannery milling drum includes two types of structure, a first one of which provides that the rotating hollow body which contains the leathers is circular, while a second one provides that the aforesaid rotating hollow body is octagonal.

These two types of drum used for several years in the leather tanning industry simply exploit the centrifugal force, generated by the hollow body in rotation, to soften the leathers: it follows that the efficiency of softening and, in general, the quality and the surface yield of the leathers is rather low or at least can be widely improved.

Moreover, the continuous impact of the leathers contained inside the rotating hollow body of the drum, especially if it is cylindrical, during the milling treatment, i.e. while the hollow body is rotating around a linear, generally horizontal, axis, over time reduces the structural integrity of the same, with the obvious economic disadvantages coming from that.

A tannery drum having the particular constructive conception described in the patent publication CN203247270 (U) have tried to remedy to some extent to these drawbacks providing, in a nutshell, for the insertion of a heating mechanism between the movable hollow body of the drum, placed in rotation by motorization means about the linear axis when the leathers must be treated in its inner volume, and an outer casing which surrounds the movable hollow body in such a way as to define an annular space in which the heating mechanism is precisely housed which operates by irradiation on the structure of the rotating hollow body and, in return, on the leathers to be milled, contributing to their treatment actuated by means of hot or cold air blown inside the hollow body itself. However, also the evolution of drum for the milling of leathers described in this prior patent document CN203247270 (U) presents some undeniable and recognized drawbacks, a first one of which is undoubtedly represented by the fact that the heating mechanism inserted into the annular space between the outer casing and the inner hollow body (drum) can only work, by definition, only by heating the latter and, therefore, in return, the leathers contained therein.

It follows that such a constructive solution does not anyway allow to dissipate the excess heat that notoriously develops during the milling treatment inside the rotating hollow body - due to the mutual rubbing of the leathers as well as to the impact of the leathers, during the rotation of the latter, against the inner wall of the hollow body and against the deflecting blades - and that during the milling process is inconvenient and unwanted with respect to the set processing temperatures.

On the contrary, the heating mechanism installed in the drum referred to in the prior document CN203247270 (U) negatively teaches in the opposite direction to the need, often stringent and relevant for the final quality of the leathers, to dissipate the heat that the leathers themselves generate on the rotating cylindrical hollow body while subjected to milling.

A second drawback of the drum described in the prior art document CN203247270 (U) is related to its complexity of construction and assembly, given the particular type and specific location of the heating mechanism provided by it, increased by the fact that the latter must be designed keeping in mind that it is integral with the hollow body which, during operation, rotates.

A last but not least drawback of the prior art closest to the invention, constituted as said by the prior art document CN203247270 (U), is linked to the need to adopt suitable and onerous constructive safety measures for managing the electrical powers deriving from the installation of a heating mechanism in an inner compartment - the annular space formed by the outer casing and the inner hollow body - of a drum where heat develops. Starting, therefore, from the awareness of the aforementioned drawbacks of the current state of the art, the present invention seeks to remedy them.

In particular, main purpose of the invention is to provide an improved drum for the milling treatment of leathers which allows to keep substantially at a given predetermined temperature, during the entire milling treatment, the inner hollow body which contains the leathers being processed.

Otherwise said, primary purpose of the present invention is to implement an improved drum for the milling treatment of leathers which, contrary to what happens in the equivalent drums of known type, allows to manage, dissipating it, the heat developed by the moving leathers inside the rotating hollow body, during the milling cycle.

Within this scope, it is task of the present invention to create an improved drum for the milling treatment of leathers which, with respect to similar known drums, allows to get at the end of the treatment a finished product of better quality in terms of softness, uniformity and superficial homogeneity.

It is another task of the invention to tune an improved drum for the milling treatment of leathers which increases production efficiency with respect to the equivalent prior art. It is another purpose of the present invention to indicate an improved drum for the milling treatment of leathers which presents constructional conception and/or assembly procedure simpler than those ones of the drums of the nearest known and more advanced art comparable to it.

It is another purpose of the invention to devise an improved drum for the milling treatment of leathers whose operation, also in terms of safety, is easier to design than the equivalent drums of known type.

It is a last but not least purpose of the present invention to provide an improved drum for the milling treatment of leathers which has a competitive production cost, even in the increased functionalities which enable the other purposes listed above to be achieved. The aforesaid purposes are achieved by means of an improved drum for the milling treatment of leathers according to the attached claim 1, as hereinafter referred for the sake of brevity of exposure.

Further constructive features of detail of the improved drum for the milling treatment of leathers according to the invention are contained in the respective dependent claims. The aforementioned claims, specifically and concretely defined below, are integral part of the present description.

Advantageously, the improved drum for the milling treatment of leathers of the invention allows to control and keep substantially constant, during the entire milling treatment, the internal and external temperature (and therefore also the humidity) of the rotating inner hollow body which contains the leathers being processed.

This depends on the fact that the drum of the invention includes in particular a conditioning circuit cooperating with the movable hollow body through air which the conditioning circuit itself conveys within the annular space at a given temperature, varied by adjustment means according to the contingent needs of treatment of the leathers inside the rotating hollow body, in such a manner that the outer wall of the hollow body is kept at a predefined temperature, deemed to be adequate for each phase of the treatment of the leathers in the hollow body.

Moreover, the main advantage associated with the invention depends on the fact that the structural assembly formed by the outer casing and the movable hollow body defines a kind of heat exchanger in which the aforesaid air which is conveyed into the annular space and flows around the outer wall of the hollow body stands for a first one of the heat exchange fluids and is at least:

• hot in the initial stage of the treatment of the leathers in the rotating hollow body, in order to contribute to the heating of the leathers in the inner volume of the hollow body;

· cold in the advanced stage of the treatment of the leathers in order to dissipate the heat in excess developed by friction by the leathers moving in the inner volume of the hollow body.

Equally advantageously, therefore, the improved drum for the milling treatment of leathers of the invention, by means of appropriate adjustment of its specific and peculiar conditioning circuit, allows dissipation of the heat developed by the moving leathers inside the rotating hollow body, during the milling cycle, guaranteeing an optimal quality of the finished product at the end of the treatment, or at least certainly better than that one offered by equivalent drums of known type.

In advantageous manner, therefore, the improved drum of the invention achieves values of production efficiency and of overall quality in leathers greater than those ones of similar drums comparable to it, thanks to the temperature and humidity control it provides.

Equally advantageously, the improved drum for the milling treatment of leathers, which is the subject of the present invention, presents a construction concept simpler than equivalent drums of know type, resulting in particular with respect to the latter easier to be assembled, to all the advantage of its production cost which is rather competitive, the manpower and raw materials used for its construction being equal.

Said purposes and advantages, as well as other ones that will emerge later, will result to a greater extent from the following description, relating to a preferred embodiment of the improved drum for the milling treatment of leathers of the present invention, given by indicative and illustrative, but not limitative, way with the aid of the attached drawing tables in which:

- figure 1 is a schematic and simplified top plan view of the improved drum of the invention, in an operative condition;

- figure 2 is an enlargement of a constructive assembly of figure 1;

- figure 3 is another enlargement of the constructive assembly of figure 1;

- figure 4 is an enlarged detail of figure 3.

The improved drum of the invention, specifically and exclusively used for the milling treatment of leathers, is schematically and illustratively shown in figure 1 where it is globally numbered with 1.

As it can be observed, such an improved drum 1 includes:

- a bearing frame, generically numbered with 2 and only partly visible (not contributing to the innovative technical concept underlying the current invention), suitable to rest on a reference surface (not shown) of an industrial factory;

- a movable hollow body 3, coupled with the bearing frame 2 and made of at least partly thermally conductive material (for instance stainless steel), suitable to receive in its inner volume 4 the leathers to be treated by milling;

- motorization means, not represented for the sake of exposition convenience, operatively connected (or keyed) with the movable hollow body 3 in such a way as to place it in rotation around a linear axis X when the leathers must be treated in the inner volume 4 of the hollow body 3;

- an outer casing 5 coupled with the bearing frame 2 and completely surrounding the movable hollow body 3 with which it defines an annular space (or peripheral chamber) 6 which presents dimensions in width depending on the overall dimensions of the improved drum 1, generally not more than 20÷25 cm.

According to the invention, the improved drum 1 comprises a conditioning circuit, in the whole signaled with 7, cooperating with the movable hollow body 3 through air Ai which the conditioning circuit 7 conveys inside the annular space 6 at a given temperature, varied by adjustment means (not indicated) depending on the contingent needs of treatment of the leathers inside the hollow body 3 in rotation, in such a manner that the outer wall 3a of the hollow body 3 is kept at a predefined temperature, deemed to be adequate for each phase of treatment of the leathers in the hollow body 3, and a structural assembly, as a whole indicated with 8, formed by the outer casing 5 and the movable hollow body 3, defines a heat exchanger in which the air Ai is conveyed in the annular space 6 and flows around the outer wall 3a of the movable inner hollow body 3 represents a first one of the heat exchange fluids and is at least:

• hot in the initial stage of the treatment of the leathers in the hollow body 3 in rotation, in order to contribute to the heating of the leathers in the inner volume 4 of the hollow body 3;

· cold (or at a colder temperature) in the advanced stage of the treatment of the leathers in order to dissipate the heat in excess developed by friction by the leathers moving in the inner volume 4 of the hollow body 3.

In particular, a second of the heat exchange fluids of the aforesaid heat exchanger defined by the structural assembly 8 consists of air A2 independent and distinct from the air Ai circulating in the annular space 6 and introduced into the inner volume 4 of the hollow body 3 by an auxiliary conditioning circuit, as a whole reported with 9 cooperating with the hollow body 3.

In this constructive solution, as it is well evident also from figure 2, the air Ai and the air A2 are, by way of pure example, in flow agreement or in co-current.

In addition, the outer casing 5 is made of any of the materials selected from the group consisting of wood, plastic material (such as typically polypropylene), metallic material and/or combinations thereof (traditional materials for these applications in the tanning sector), and substantially has a function of support and formation of the annular space (or peripheral chamber) 6.

Preferably, furthermore, the outer casing 5 comprises an inner insulating coating 10, fixed to the inner surface 5a of the outer casing 5 and facing the outer wall 3a of the inner hollow body 3 in such a way as to be contained in the annular space 6. In detail, the inner insulating coating 10 is arranged on the entire inner surface 5a of the casing 5, both on the lateral sides 5b, 5c and on the side wall 5d.

Preferably but not necessarily, the inner insulating coating 10 has a thickness of 4 cm and is made of any of the foamed materials selected from the group consisting of polyurethane (PU), polyethylene (PE) and/or the like and is coupled with the outer casing 5 through junction means of the type known per se to the person skilled in the art, for example adhesives substances, screws, bolts and/or similar.

It is understood that the outer casing of the improved drum of the invention will be advantageously and hopefully, though not necessarily, made of metallic material if, in the annular space, the inner insulating coating is provided which, especially in such a case, will properly perform the function of preventing the dispersion of heat through the metallic structure of the outer casing.

Under the constructive point of view, in this case but purely as a preferred and non- binding title, the outer casing 5 is movable integrally and synchronously with the hollow body 3, rotating around the linear axis X during the treatment of the leathers: this in order to increase the efficiency of the treatment itself ensuring a greater reflux of air Ai in the annular space 6.

It should be understood that in other embodiments of the improved drum of the invention, not shown, the outer casing could constitute a fixed or movable component asynchronously with respect to the inner hollow body, at a different speed.

Moreover, the movable inner hollow body 3 and the outer casing 5 are mutually coaxial and preferably have a cylindrical profile laterally closed by the respective lateral flanks 3b, 3c and 5b, 5c.

According to the preferred embodiment described herein of the invention, the conditioning circuit 7 is advantageously arranged outside the movable hollow body 3 and the outer casing 5 and is at least partly supported by the bearing frame 2 resulting extraneous to the rotation around the linear axis X.

This constructive arrangement allows the improved drum 1 of the present invention to be significantly different from the closest known art, constituted for example by the document CN203247270 (U) in which the (pure) heating mechanism is contained into the interstitial space defined between the inner hollow body and the outer casing: indeed, the constructive solution associated with the invention allows greater safety both for the mechanical components and for the operators in factory with respect to the prior art, since the conditioning means 7 are released from the rotation of the inner hollow body 3 (and of the outer casing 5) during operation and are not affected by the high temperatures that develop in the structural assembly 8 and which, however, are advantageously managed by suitable adjustment of the operation of the conditioning means 7.

In the invention, therefore, the installation of the conditioning circuit 7 outside not only of the inner hollow body 3 but also of the outer casing 5 allows the improved drum 1 to avoid the technical-constructive and plant engineering complications which can be found in the aforementioned closest prior art the (it should be considered the need to manage the installation and operation of transmission elements mounted in the annular space, as it happens in CN203247270 (U), which from an the electric point of view place limitations and risks of manoeuvre).

In addition, in the preferred embodiment described herein of the improved drum 1 of the invention, the conditioning circuit 7 also presents the non-negligible advantage of being more easily subjected to inspection, maintenance, repair and/or replacement with respect to the current state of the art equivalent to it, with consequent further advantages both in terms of operator intervention and in economic terms.

More in detail, figure 1 shows that the conditioning circuit 7 comprises in the specific case:

- a first fan 11 in contact with the external environment adjacent to the hollow body 3 and suitable for conveying the air Ai into the annular space 6;

- a first diverter or exchange valve 12, placed downstream the first fan 11 considering the direction of flow of the air Ai entering into the annular space 6;

- first heating means, indicated as a whole with 13, arranged between the first diverter valve 12 and the movable hollow body 3.

In particular, the conditioning circuit 7 defines a closed loop path in such a manner that the air Ai introduced into the annular space 6 through an axial inlet 14 made in the outer casing 5 comes out from the annular space 6 through a axial outlet 15, clearly visible also in the attached figure 3, made in the outer casing 5 and is recovered by the first fan 11. It is stated precisely that the aforementioned adjustment means determine that the first heating means 13 are operated when the first diverting valve 12 is closed and inhibits the passage therethrough of air coming from the external environment at room temperature. In presence of excessive overheating of the inner hollow body 3 during its rotation around the linear axis, caused mainly by the leathers moving in the inner volume 4 of the hollow body 3, the adjustment means properly control the conditioning circuit 7, closing the heating means 11 and opening the exchange valve 12 to allow entry into the annular space 6 of colder air - at room temperature - able to cool the outer wall 3a of the hollow body 3. It follows, in given limited phases of the entire milling cycle, a kind of "cold" milling allowing to disperse the heat in excess produced by the mutual rubbing of the leathers as well as of the same leathers against the inner wall 3d of the hollow body 3 and against the deflecting blades (partly visible in the enlargement of figure 4 where they are numbered with 22) during milling, not disadvantageously verifiable in any way in the prior art.

More specifically, the first heating means 13, such as for example at least one electrical resistance, are arranged upstream the axial inlet 14 made in the outer casing 5.

As far as the auxiliary conditioning circuit 9 is concerned, figure 1 illustrates that it preferably but not exclusively includes:

- a second fan 16 in contact with the external environment adjacent to the hollow body 3 and suitable for conveying air A2 into the inner volume 4 of the hollow body 3 itself; - a second diverter or exchange valve 17, placed downstream the second fan 16 considering the direction of flow of the air A2 at the input into the movable hollow body 3;

- second heating means, generally indicated with 18, arranged between the second diverter or exchange valve 17 and the movable hollow body 3.

Also in this case, in particular, the auxiliary conditioning circuit 9 defines a closed-loop path in such a manner that the abovementioned air A2 introduced into the hollow body 3 through an axial entry duct 19 made in the hollow body 3 comes out of the latter through an axial exit duct 20 made in the hollow body 3 and is recovered by the second fan 16.

In advantageous but non-binding manner, the axial inlet 14 is arranged at the axial entry duct 19, while the axial outlet 15 is arranged at the axial exit duct 20, as it can be observed in figures 2 and 3. Furthermore, by observing figure 1, it is possible to state that also for the second heating means 18, comprising for example at least one electrical resistance, they are arranged upstream the axial entry duct 19 made in the hollow body 3.

Preferably but not necessarily, the auxiliary conditioning circuit 9 also includes filtering means, generally numbered with 21 and visible in figure 1, interposed between the exit duct 20 and the second fan 16, suitable to restrain the powders present in the air A2 coming from the hollow body 3 and in contact with the leathers while the latter were subjected to the milling treatment.

From an operative point of view, the motorization means, the conditioning circuit 7 and the adjustment means, as well as the auxiliary conditioning circuit 9, are electrically connected with a central processing and control unit (not shown) at the operator's availability in a location adjacent to the movable hollow body 3 and to the outer casing 5 associated therewith which manages its operation: in particular, the central processing and control unit manages the activation of the heating means 13 and of the exchange valve 12, according to the operating requirements in the inner volume 4 of the inner hollow body 3 necessary to obtain optimally softened leathers.

On the basis of the description just given, it is understood, therefore, that the improved drum for the milling treatment of leathers, object of the present invention, achieves the purposes and reaches the advantages mentioned previously.

Upon execution, changes could be made to the improved drum for the milling treatment of leathers of the current invention, consisting, for example, in motorization means of different type and composition compared to that one previously described and visible in the attached figures and also including proper transmission and/or referral means.

Furthermore, other constructional embodiments of the invention, not accompanied herein by reference drawings, could provide that the conditioning circuit comprises components which are different but equivalent by technical effect from those ones described and illustrated in the figures of the following drawing tables.

In addition, other embodiments of the improved drum for the milling treatment of leathers exclusively claimed herein could be, in which the conditioning means could be different from those ones described above with particular reference to the preferred embodiment of the improved drum claimed herein by exclusive, which does not affect the advantage provided by the present invention.

It should be noted that in case in which the outer casing is fixed (embodiment however provided for by the invention), the introduction of the air inside the annular space could not necessarily be axial, since, if the inner hollow body (or drum) rotates inside a fixed outer box element, the air intakes can be made in any point of the latter in that case being no particular constructive constraints other than that one to provide an additional rotatable wing on the outer casing, beyond to that one on the rotating inner hollow body. It is, finally, clear that several other changes could be made to the improved drum for the milling treatment of the 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. Improved drum (1) for the milling treatment of the leathers comprising:

- a bearing frame (2) suitable to rest on a reference surface of an industrial factory;

- a movable hollow body (3), coupled with said bearing frame (2) and made of at least partly thermally conductive material, suitable to receive in its inner volume (4) the leathers to be treated by milling;

- motorization means operatively connected with said movable hollow body (3) in such a way as to place it in rotation around a linear axis (X) when said leathers must be treated in said inner volume (4) of said hollow body (3);

- an outer casing (5) coupled with said bearing frame (2) and surrounding said movable hollow body (3) with which it defines an annular space (6),

characterized in that it comprises a conditioning circuit (7) cooperating with said movable hollow body (3) through air (Ai) which said conditioning circuit (7) conveys within said annular space (6) at a given temperature, varied by adjustment means depending on the contingent needs of treatment of said leathers inside said hollow body (3) in rotation, in such a manner that the outer wall (3a) of said hollow body (3) is kept at a predefined temperature, deemed to be adequate for each phase of said treatment of said leathers in said hollow body (3), and a structural assembly (8) formed by said outer casing (5) and said movable hollow body (3) defines a heat exchanger in which said air (Ai) which is conveyed into said annular space (6) and flows around said outer wall (3a) of said hollow body (3) stands for a first one of heat exchange fluids and is at least:

• hot in the initial stage of said treatment of said leathers in said hollow body (3) in rotation, in order to contribute to the heating of said leathers in said inner volume (4) of said hollow body (3);

· cold in the advanced stage of said treatment of said leathers in order to dissipate the heat in excess developed by friction by said leathers moving in said inner volume (4) of said hollow body (3).

2. Drum (1) according to claim 1), characterized in that a second of the heat exchange fluids of said heat exchanger defined by said structural assembly (8) is constituted by air (A2) independent from said air (Ai) circulating in said annular space (6) and introduced into said inner volume (4) of said hollow body (3) by an auxiliary conditioning circuit (9) cooperating with said hollow body (3).

3. Drum (1) according to claim 1) or 2), characterized in that said outer casing (5) is made of any of the materials selected from the group consisting of wood, plastic material, metallic material and/or combinations thereof.

4. Drum according to any of the preceding claims, characterized in that said outer casing (5) comprises an inner insulating coating (10), fixed to the inner surface (5a) of said outer casing (5) and facing said outer wall (3a) of said hollow body (3) in such a way as to be contained into said annular space (6).

5. Drum (1) according to claim 4), characterized in that said inner insulating coating (10) is made of any of the foamed materials chosen from the group consisting of polyurethane (PU), polyethylene (PE) and/or the like.

6. Drum (1) according to any of the preceding claims, characterized in that said outer casing (5) is movable integrally with said hollow body (3), rotating around said linear axis (X) during said treatment of said leathers.

7. Drum (1) according to any of the preceding claims, characterized in that said movable hollow body (3) and said outer casing (5) are mutually coaxial and have a cylindrical profile.

8. Drum (1) according to any of the preceding claims, characterized in that said conditioning circuit (7) is arranged outside said movable hollow body (3) and said outer casing (5) and is at least partly supported by said bearing frame (2).

9. Drum (1) according to any of the preceding claims, characterized in that said conditioning circuit (7) comprises:

- a first fan (11) in contact with the external environment adjacent to said hollow body (3) and suitable to convey said air (Ai) into said annular space (6);

- a first diverter or exchange valve (12), placed downstream said first fan (11) considering the direction of flow of said air (Ai) at the input into said annular space

(6);

- first heating means (13) arranged between said first diverter valve (12) and said movable hollow body(3), said conditioning circuit (7) defining a closed loop path in such a manner that said air (Ai) introduced into said annular space (6) through an axial inlet (14) made in said outer casing (5) comes out from said annular space (6) through an axial outlet (15) made in said outer casing (5) and is recovered by said first fan (11).

10. Drum (1) according to claim 9), characterized in that said first heating means (13) are operated when said first diverter valve (12) is closed and inhibits the passage therethrough of air coming from said external environment.

11. Drum (1) according to claim 9) or 10), characterized in that said first heating means (13) are arranged upstream said axial inlet (14) made in said outer casing (5).

12. Drum (1) according to any of the claims from 2) to 11), characterized in that said auxiliary conditioning circuit (9) includes:

- a second fan (16) in contact with the external environment adjacent to said hollow body (3) and suitable to convey air (A2) into said inner volume (4) of said hollow body (3);

- a second diverter or exchange valve (17), placed downstream said second fan (16) considering the direction of flow of said air (A2) at the input into said movable hollow body(3);

- second heating means (18) arranged between said second diverter valve (17) and said movable hollow body (3),

said auxiliary conditioning circuit (9) defining a closed loop path in such a manner that said air (A2) introduced into said hollow body (3) through an axial entry duct (19) made in said hollow body (3) coming out from said hollow body (3) through an axial exit duct (20) made in said hollow body (3) and is recovered by said second fan (16).

13. Drum (1) according to claim 12) when dependent on claim 9), 10) or 11), characterized in that said axial inlet (14) is arranged at said axial entry duct (19) and said axial outlet

(15) is arranged at said axial exit duct (20).

14. Drum (1) according to claim 12) or 13), characterized in that said auxiliary conditioning circuit (9) includes filtering means (21), interposed between said exit duct (20) and said second fan (16), suitable to restrain the powders present in said air (A2) coming from said hollow body (3) in which said leathers are subject to said milling treatment.

15. Drum (1) according to any of the preceding claims, characterized in that said motorization means, said conditioning circuit (7) and said adjustment means are electrically connected with a central processing and control unit available to the operator which manages their functioning.