Background art Some embodiments of drums for the treatment of hides, generally called milling drums, are known.

GB-A-2,081, 303 and WO-A-0132937 describe two examples of drums, each of which comprises a substantially cylindrical drum-like container which is driven to rotate about its horizontal axis of symmetry. The container is shaped so as to receive internally hides or similar products and, by means of its rotation, exerts a mechanical action on the latter. Both machines are also provided with a forced- ventilation and suction device which draws the internal air through a hole coaxial with one of the two rotation hubs of the drum-like container, conveys it through an external filtering device and brings it back inside by means of a second hole coaxial with the other of the two hubs.

The above solutions have the disadvantage that the mechanical action exerted on the hides is always substantially the same during the whole operating cycle of the drum. At present, no device is known for producing different mechanical actions upon rotation. This feature limits the uniformity of the mechanical action on the hides and generates preferential area for absorption of any chemical products used during the process.

A second drawback lies in that air is fed through a hollow hub and is sucked

through the opposite hub. The air flow inside the drum-like container follows the path where there is the least resistance, which in these examples of embodiment is essentially the rotation axis. By contrast, the hides and dust are located, as a result of the centrifugal force, along the external circumference of the container.

This results in the further disadvantage that air passes through the hides to a minimum extent and undesirable accumulations of dust may occur.

A further drawback present in the above solutions is that the air suction and filtration device is arranged externally and laterally with respect to the drum-like container. This arrangement results in increased overall dimensions, which could be troubling.

EP-A-0,960, 948 discloses of a drum for the treatment of hides, in which a circuit for introducing water into the drum-like container and a further circuit for the introduction of chemical agents are provided, in addition to the air circulation circuit. These circuits allow to increase the possibilities for treatment of the hides, but do not solve the above mentioned problems.

IT-A-VI960186 discloses a drum for treatment of the hides, comprising a prism- shaped container adapted to receive the hides and formed by two end walls which are spaced from each other and connected together by means of a shrouding fixed along the external periphery of the end walls. Vanes are arranged radially along the shrouding. The two end walls and the shrouding are formed by means of panels with raised edges connected adjacent to each other. The ventilation system envisages the introduction and the suction of air into the prism-shaped container by means of holes formed in the two end walls. Air flow introduced passes through the hollow hub, flows into cavities in one of the two end walls, formed between the panels with raised edges and suitable external covering panels, and enters the prism-shaped container through the holes formed in the panels with raised edges. The suction air flow continues its reverse path through the other end wall and the other hub.

This solution allows the dust to be drawn into a zone which is closer to the shrouding than in the previous embodiments, but no suction holes are envisaged directly on the shrouding. This limits the effective suction of dust since the latter tends to accumulate just on the internal surface of the shrouding, particularly close to the internal vanes.

Also this latter solution does not provide any variation in the mechanical action exerted on the hides, which is capable of improving the uniformity of the treatment.

Moreover, the air suction and filtration device is, also in this case, arranged outside the drum, with a consequent increase in its overall dimensions.

A further inconvenience consists in that the ventilation and suction air flows pass through cavities formed in the two end walls which may be inspected and cleaned only by disassembling the covering panels, resulting in complex and costly maintenance operations.

Disclosure of the invention A general object of the present invention is that of eliminating the aforementioned drawbacks, by providing a drum for the treatment of hides, fabrics and the like which is strong and reliable over time.

A main object is concerning a drum which ensures a high degree of uniformity in the treatment of all the hides loaded inside it.

A particular object is that of providing a drum having a form which allows different mechanical actions to be exerted on the hides in a continuous manner.

A further object of the invention is that of providing a drum which has a uniform air flow inside it and which prevents the undesirable accumulation of dust inside it.

Another particular object is that of providing a drum, the maintenance and cleaning

of which are facilitated.

A further particular object is that of designing a drum which can be easily transported and which, once installed, has limited overall dimensions.

These objects together with others, which will appear more clearly hereinafter, are achieved in accordance with Claim 1 by a drum for the treatment of sheet-like products such as hides, fabrics and similar articles, comprising a container for the hides to be treated, having a substantially cylindrical side wall and a pair of substantially flat end walls defining an axis of symmetry, support means for rotatably supporting the container about an axis of rotation coinciding with said axis of symmetry, actuating means for rotating the container, ventilation and suction means able to generate an air flow inside the container, and at least one opening for allowing loading and unloading of the hides, in which the side walls and the end walls comprise a plurality of sheet-metal panels, characterized in that said panels are removably secured to a cage-like reinforcement structure which comprises one or more planar framework structures in correspondence of the end walls, joined together by a plurality of elongated connecting elements and by a plurality of reinforcement frames in correspondence of the side wall.

Thanks to this particular configuration, it will be possible to obtain a drum having a high degree of rigidity able to ensure reliable operation over time.

Preferably, each planar framework structure comprises at least one link element in the form of a circle segment and at least one polygonal link element, which are joined together so as to form in a same flat meshwork structure a substantially polygonal structure adjacent to a portion substantially in the form of a quarter of circle.

Thanks to this particular configuration, it will be possible to exert in a continuous manner different mechanical actions on the hides and thus obtain a high degree of uniformity of treatment.

Suitably, the ventilation and suction means comprise a plurality of suction holes arranged along elongated connecting elements and able to draw air and dust from inside the container.

By means of this particular configuration it will be possible to generate a uniform air flow inside the drum and prevent the undesirable accumulation of dust internally thereof.

Brief description of the drawings Further features and advantages of the invention will be more clearly understood from the detailed description of some preferred, but not exclusive embodiments of a drum according to the invention, illustrated by way of a non-limiting example with the aid of the accompanying drawings in which: FIG. 1 shows a side view of a drum according to the invention; FIG. 2 shows a perspective view of the cage-like structure of the drum according to Fig. 1; FIG. 3 shows an exploded view of a detail of the drum according to Fig. 1; FIG. 4 shows a side view of a detail of the drum according to Fig. 1; FIG. 5 shows a second side view of the detail according to Fig. 4; FIG. 6 shows an exploded side view of a detail of the drum according to Fig. 1.

Detailed description of a preferred embodiment (s) With particular reference to the above figures, a drum according to the invention used for the treatment of hides, fabrics and similar products is shown, overall denoted with reference number 1. Drum 1 comprises a container 2 inside which the hides P to be treated are loaded and which has a substantially cylindrical side wall 3 and a pair of substantially flat end walls 4 defining an axis of symmetry L.

Container 2 is supported by means of support means 5 which are able to support it rotationally about an axis of rotation coinciding with the axis of symmetry L.

Support means 5 may consist of a metal structure 6 fixed to the ground and able to support the container 2. Suitably, a pair of hubs 7,7'situated in the vicinity of the intersection of the axis of symmetry L with the pair of end walls 4 allows the free rotation of the container 2. Actuating means 8 for causing rotation of the container 2 are also envisaged.

Drum 1 is characterized by a cage-like reinforcement structure 9 which forms the load-bearing structure of the container 2 and comprises one or more planar framework structures 10 in correspondence of the end walls 4, which are joined together by a plurality of elongated connecting elements 11 and by a plurality of reinforcement frames 12 in the region of the side wall 3.

Sheet-metal panels 13 are removably secured to the cage-like structure 9, in correspondence of the pair of end walls 4 and the side wall 3, said panels allowing the container 2 to be substantially closed.

Each of the planar framework structures 10 comprises at least one mesh element 14 in the shape of a circular portion and suitably at least one mesh element 15 of polygonal shape. This polygonal-shaped mesh element will be preferably but not exclusively of substantially triangular shape.

In order to produce the flat framework structures 10, the mesh elements 14,15 are arranged adjacent to each other and combined so that each planar framework structure 10 comprises a portion 16 which is substantially polygonal, for example rectangular or square, and optionally chamfered, adjacent to a portion 17 having substantially the shape of a quarter of circle. The sides 18 of the polygonal portion 16 have a length different from the radius of the adjacent quarter circle portion 17.

Suitably, at least one pair 19 of framework structures 10, adjacent to each other and arranged symmetrically with respect to the axis of symmetry L, is provided in the proximity of each of the two end walls 4. In this way the polygonal portion 16

of a planar framework structure 10 is adjacent to the quarter of circle portion 17 of the other planar framework structure 10 belonging to the same pair 19.

During treatment of the hides P, it is very important that air is allowed to circulate inside the container. Suitable ventilation and suction means 20, comprising a plurality of suction holes 21, are used. The suction holes 21 are located on the elongated connecting elements 11 so as to suck air and dust inside the container 2 and convey them inside internal cavities 22 of the elongated connecting elements 11.

The internal cavities 22 are in fluid communication with a plurality of radial ducts 23 formed inside and at least planar framework structure 10. Advantageously, the radial ducts 23 are formed inside the pair 19 of flat meshwork structures 10 in the region of one of the two end walls 4. An air extraction duct 24, in fluid communication with the radial ducts 23 and substantially coaxial with the axis of symmetry L, is also provided. Air and dust are collected by the suction holes 21 situated on the elongated connecting elements 11, pass through the internal cavities 22 of the latter and are conveyed by the radial ducts 23 towards the axis of symmetry L, in proximity of which they enter into the extraction duct 24.

The mixed air and dust is drawn via the extraction duct 24, is conveyed to suitable filtering means 25 and is finally introduced again into the container 2 by means of an entry duct 26 coaxial with the axis of symmetry L and passing through one of the end walls 4. Thus, air is introduced into the container 2 centrally in the region of one of the two end walls 4, is sucked in by the suction holes 21 in the region of the side wall 3 and is collected inside the extraction duct 24 in the region of the other of the two end walls 4.

Radial ducts 23 are provided with inspection openings 27 which are positioned on planar framework structures 10 and can be selectively opened to allow inspection and cleaning of the radial ducts.

The elongated connecting elements 11 may be of different types and in particular comprise a first series of larger vanes 28 projecting radially towards the axis of symmetry L of the container 2. Each larger vane 28 is connected, on the planar framework structures 10, to a joining beam 29 between the polygonal portion 16 and the quarter of circle portion 17. Moreover, the larger vanes 28 have a connecting portion 30 with a flank 31 on the inside of the container 2 and a flank 32 on the outside of the said container. This connecting portion 30 forms a portion of the side wall 3.

The elongated connecting elements 11 comprise a second series of smaller elongated vanes 33 projecting radially towards the axis of symmetry L of the container 2 by an amount smaller than that of the larger vanes 28. Each smaller vane 33 is connected, on the planar frame structures 10, to a cross member 34 of the quarter of circle portion 17.

Moreover, the elongated connecting elements 11 comprise a plurality of cross members 35, each of which is connected, on the planar framework structures 10, proximate to a vertex 36 of the polygonal portion 16.

The elongated connecting elements 11 of all types are provided with suction holes 21 so that, inside the container 2, all the possible dust accumulation zones, such as for example the zones in the vicinity of concave edges or corners, are constantly cleaned. Moreover, the arrangement of the suction holes 21 and the entry duct 26 is such that, inside the container 2, the air flows, indicated in the figures by the number 37, are distributed in a uniform manner.

The actuating means comprise a motor 38 connected to the container 2 by means of belt-type power transmission means 39. Motor 38 is mounted at a height from the ground which is substantially equal to or greater than the height of the axis of symmetry L, so that the force exerted by the power transmission means 39 on the axis of symmetry L is not added to the force of gravity acting on the said axis.

Moreover, mounting of the motor 38 in a raised position allows the filtering means

25 to be positioned below the said motor. As a result of this arrangement, the dual advantage is obtained that the load on the hubs 7,7'is not increased and the overall dimensions of the drum 1 are reduced.

An opening 40 is provided on side wall 3, to allow loading and unloading of hides P.

In use, during operation, container 2 is rotated and the hides P are raised and made to rotate as a result of the internal form of the container 2 until the force of gravity causes them to fall into the bottom of container 2. The larger vanes 28 and smaller vanes 33 facilitate conveying of the hides P upwards and assist the overall mechanical action exerted on the said hides, in particular when the latter fall into the bottom zone of the container 2. The use of the rectangular portions 16 and quarter of circle portions 17 allows different mechanical actions to be exerted on the hides P. In particular, hides P are subject to a mainly compressive action in correspondence of the rectangular portions 16, while they are subject to a mainly distensive action in proximate of the quarter of circle portions 17.

From the foregoing description, it is obvious that the drum according to the invention achieves the intended objects and in particular allows different mechanical actions to be exerted on the hides and thus obtain a high degree of uniformity of treatment. Moreover, it is possible to produce a uniform air flow inside the drum and prevent the undesirable accumulation of dust.

The drum according to the invention may be susceptible of numerous modifications and changes all falling within the inventive concept expressed in the accompanying claims. Al the details may be replaced by other technically equivalent elements and the materials may be different according to requirements, without departing from the scope of the invention.

Even though the drum has been described with particular reference to the accompanying figures, the reference numbers used in the description and in the

claims are used to improve understanding of the invention and do not limit in any way the scope of protection claimed.

The instant application is based upon and claims priority of patent application no.

Vl2002A000120, filed on 04.06. 2003 in Italy, the disclosure of which is hereby expressly incorporated here in reference thereto.