METHOD FOR TREATING FLEXIBLE LAMINAR SURFACES

METHOD FOR TREATING FLEXIBLE LAMINAR SURFACES

DESCRIPTION The present invention concerns a method for treating flexible laminar surfaces such as leathers, hides and the like in tannery circle, implemented in drums of tanning, re-tanning, dyeing or milling. It is known that, in tannery industry circle the plants for treating flexible laminar surfaces, such as leathers, including, according to a prevalent constructive scheme, a tanning, dyeing or milling drum within which the flexible laminar surfaces are subjected to working. The rotation of the drum around a central axis causes the mechanical working of the flexible laminar surfaces, with the lift and subsequent fall by gravity, in a continuative manner during a treatment cycle, of the laminar surfaces themselves within the volume bounded by the drum.

Generally, the plant also comprises circuits for the circulation from and to the drum of chemical products, dyeing and tanning agents, air and water which, while the drum rotates, carry out the so- called chemical working of the laminar surfaces. For example, milling or flying working into drum dry- occurs with the aim to soften leathers and give a particular grain to the grain side thereof . The operating parameters of the drum during the provided leathers treatment, such as working time, rotation speed of the drum, quantity of leathers introduced into the drum, type and quantity of the treatment products inserted into the drum, are decided and set by the operator on the basis of experience and historical data related to previous similar treatments, considering the type of leather to be treated.

In particular, the time of working leathers into the drum is determined by the operator in empirical way, by simply considering the production history, with the problems of inaccuracy and reliability of the set data that this entails, despite the proven experience of the operator. Let's not overlook the fact that, sometimes, the operator, in order to avoid incomplete workings of the leathers, sets operating times of the drum which exceed even to a great extent those ones necessary for suitable and appropriate treatment . This inevitably leads to not fully optimized working times, unjustified increase in energy consumptions and loss of productivity by the drum.

The present invention seeks to overcome the technical problems of the prior art just complained.

In particular, main purpose of the invention is to develop a method for treating flexible laminar surfaces which involves an optimization of implementation times or at least a precision greater than similar known methods.

In other words, the invention intends to propose a method for treating flexible laminar surfaces whose application depends less and less on the experience of the involved operators thus resulting more reliable than the known art.

Within such a purpose, it is task of the invention to provide a method for treating flexible laminar surfaces which determines an increase of the productivity of a tanning, re-tanning, dyeing and/or milling drum with respect to equivalent methods of the known type . It is another task of the present invention to limit with respect to the prior art the energy consumptions associated with the normal functioning of a flexible laminar surfaces treatment drum.

Said purposes are achieved through a method for treating flexible laminar surfaces in tanning, re- tanning, dyeing and/or milling drums according to the appended claim 1, to which they refer for brevity. Further detail features of the treating method of the invention are reported in the corresponding dependent claims.

A plant for treating flexible laminar surfaces as claim 11, to which they still refer for the sake of brevity, also constitutes integral part of the invention. Other construction features of the plant of the invention are highlighted in the relative dependent claims.

Advantageously, the method for treating flexible laminar surfaces of the invention is able to establish the moment in which the working is actually completed and the processed material is ready, without the need to set any maximum time limit of the drum operation. It is known, indeed, that a working in a drum, whatever it is but in particular the milling, in any case involves a progressive increase in the volume of leathers inside the drum and the change of the position of the barycentre of the overall mass occupied by the leather themselves . Such issues affect in turn the movement of the drum, causing with the prosecution of the working an always stronger imbalance of the rotating drum and a more significant increase in the power absorption by the motorization means which drive the drum. In tannery circle, it is agreed by a long time that the presence of these operative conditions is synonymous of the fact that the working of hides inside the drum is completed. The method of the invention takes advantage right of these issues and, by detecting some operating parameters of the drum, among which exactly the power consumption and/or displacements of the central axis of rotation during operation, stops the movement of the drum as soon as it detects values excessively abnormal with respect to the nominal operating ones. This involves optimization of the working times of flexible laminar surfaces, less energy wastes compared to the known art and a greater productivity by the machine. Still advantageously, the worked flexible laminar surfaces are qualitative better than those ones obtained through known type methods, other factors involved being equal . Said purposes and advantages will result better from the description that follows relating to a preferred embodiment of the drum of the invention and a preferred application of the method of the invention which can be implemented with it, given by illustrative but not limiting way with reference to the attached drawings where : figures 1 and 2 are two perspective views of the plant of the invention; figures 3-5 are enlargements of three distinct details of the plant of figure 1 and 2. The plant for treating flexible laminar surfaces, not represented, is illustrated from two different angles in figures 1 and 2, where it is globally indicated with 1.

As it is observed, the plant 1, according to a traditional constructive form in the tannery circle, comprises a support frame 2, which stands on a reference surface, such as for example the paving of an industrial factory, and a rotating milling drum 3, suitable to contain the flexible laminar surfaces, such as animal leathers, in order to carry out their milling.

The rotating drum 3 defines a central axis of symmetry Z and is coupled with the support frame 2. The plant 1 also includes motorization means, not visible, contained in the box body 4, suitable to put in rotation around the central axis Z the rotating drum 3.

According to the invention, the plant 1 comprises detection means, as a whole numbered with 5, operatively connected with the rotating drum 3 and/or the motorization means, which detect a pair of operating parameters of the plant 1 in order to allow the comparison of the detected value with a predetermined nominal value and the stopping of the moving of the drum 3 if the difference between the detected value of the operating parameters and the nominal value is greater than 0.

Preferably but not necessarily, the detection means 5 comprise two weighing instruments 6, 7, for example load cells, one visible in figure 3 and the other in figure 4, supported by the support frame 2. The weighing instruments 6, 7 are reciprocally opposed, in the sense that the first is positioned at the front of the side wall 3a of the rotating drum 3 and the second is arranged at the front of the side wall 3b- of the rotating drum 3.

Each weighing instrument 6, 7 is placed below a connection hub 8, 9, protruding from the rotating drum 3 in correspondence of the central axis of symmetry Z and coupled with a rotating shaft, not visible, positioned inside the rotating drum 3 and connected with the motorization means through transmission means, not shown.

More in detail, each of the weighing instruments 6, 7 is arranged in a hollowed section 10, 11 of the support frame 2.

In the case at issue, the detection means 5 include, in addition, a plurality of toroidal ammeters 12, better visible in figure 5, cooperating with the motorization means with which they are connected.

In general, the detection means 5 are electrically connected with a central processing and control unit, not represented and constituted for example by a PLC, at operator's disposal. The method for treating the flexible laminar surfaces in the plant 1 for tanning, re-tanning, dyeing and/or milling comprises the following operations: introducing into the drum 3 a plurality of flexible laminar surfaces, such as animal leathers, as already mentioned; rotating the drum 3 in order to carry out the working of the flexible laminar surfaces. According to the invention, the method also comprises the following operations : - detecting some operating parameters of the plant 1; comparing the detected value of the operating parameters with a predetermined nominal value; stopping the movement of the drum 3 if the difference between the detected value of the operating parameters and the nominal value is greater than 0.

In this case, at purely example way, the operating parameters include the power absorbed by the motorization means which drive the drum 3 and the forces applied by the rotating drum 3 on two weighing instruments 6, 7, for example load cells, associate from opposite sides with the rotating drum 3. Other solutions of the invention may include that the operating parameter is any of the quantities selected from the group consisting of:

• lateral displacement of the axis of rotation of the rotating drum;

• barycentre of the flexible laminar surfaces inside the rotating drum or even more .

Moreover, in alternative applications, the method of the invention may comprise the detection of a number of operating parameters of the plant different from that one here considered and referred to the attached drawings . For example, other applicative variants of the method may include only one of aforesaid operating parameters or any combination thereof . The operations of detection and comparison occur automatically by means of the aforesaid central processing and control unit.

In convenient way, the method comprises the operation of displaying on a screen accessible to the operator the detected value of the chosen operating parameters .

Preferably but not necessarily, the method of invention includes the operation of setting up the predetermined nominal value in the central processing and control unit. Such a nominal value of the operating parameter depends at least on the physical and morphological characteristics, weight and/or amount of the flexible laminar surfaces introduced into the rotating drum 3. According to the preferred application form here described of the invention, the method comprises the operation of signalling the operative condition of the plant 1 for which the difference between the detected value and the nominal value is greater than 0. The signalling operation is performed before the stopping operation and could consist in a signal or visual message on the screen accessible to the operator or, alternatively, in a sound signal. The stopping operation occurs automatically or as a result of operator' s intervention after the signalling operation.

In case it is necessary to perform treatment of tanning, re-tanning or dyeing, the method of the invention comprises, according to a custom for the tannery industry, the operation of introducing into the rotating drums products such as dyes, enriching oils, water or air, suitable for the chemical working of the flexible laminar surfaces . Such an operation of introducing the chemical products is performed before or during the operation of moving the rotating drum.

The method of the invention includes, therefore, the operation of extracting the flexible laminar surfaces from the rotating drum 3, performed after the operation of stopping the drum 3 itself .

On the basis of what just stated, it is understood, therefore, that the method for treating flexible laminar surfaces in tanning, re-tanning, dyeing and/or milling plant of the invention reaches the purposes and achieves the advantages mentioned above. In execution, changes may be made to the plant for treating flexible laminar surfaces of the invention consisting, for example, in detection means different from those ones described above. It is stressed that the number, quantity, weight and sizes of the flexible laminar surfaces treated within the rotating drum can be any, depending on the productive choices and needs . It is, finally, clear that many other variations may be made to the method and the plant in question, without for this reason going out of the novelty principles inherent to the inventive idea expressed here, as it is clear that, in the practical implementation of the invention, materials, shapes and sizes of the illustrated details may be any, depending on the needs, and replaced with others technically equivalent.