EP3277848B1

EP3277848B1 - Leathers drying and/or conditioning plant

Info

Publication number: EP3277848B1
Application number: EP16722373.4A
Authority: EP
Inventors: Antonio Galiotto
Original assignee: Erretre SpA
Current assignee: Erretre SpA
Priority date: 2015-04-02
Filing date: 2016-03-30
Publication date: 2021-08-25
Anticipated expiration: 2036-03-30
Also published as: CN107567504B; EP3277848A1; WO2016157088A1; CN107567504A; BR112017021086B1; BR112017021086A2

Description

The current invention concerns a drying and/or conditioning plant of leathers or similar laminar surfaces, especially tannery leathers typically although not exclusively wet leathers just undergone tanning, re-tanning or dyeing working for example in a machine known as "drum" in the tannery field, or leathers still partially drenched in humidity which must be stabilized by means of a treatment known as "conditioning" in the tannery industry itself, or dry leathers (which always contain a humidity value variable between 5% and 15%) to which it is desired to impart certain features thanks to the tension and simultaneous conditioning. The particularity of the plant of the invention consists predominantly in that it comprises specific means for adjusting the level of tension or traction of the leathers, when they have just been introduced into the operating tunnel of such a drying and/or conditioning plant and/or during the progressive passage of the leathers themselves through said operating tunnel in order on the one hand to improve with respect to the current state of the art the uniformity of the tension setting among leathers of the same batch and on the other hand to avoid damage to the leathers due to an excessive traction potential applied to them or the failed expansion of the leathers to the maximum value effectively possible.
The adjustment means of the drying and/or conditioning plant of leathers of the present invention are associated with each support frame of the leathers to be dried and/or conditioned within the operating tunnel and, being of purely mechanical type, allow a very precise spontaneous automatic adjustment - as punctual and continuous (seamless) - of the tension setting of the leathers which is kept constant at a nominal level (considered optimal by the manufacturer for that type of leathers) which is predetermined in consideration of:

chemicals with which they are treated in the tanning, re-tanning or dyeing step;
humidity degree which distinguishes them or water percentage which they're drenched in;
type of article to be obtained.

In essence, the salient feature of the invention consists in the fact that the innovative drying and/or conditioning plant of leathers which is claimed responds and adapts in real time to the changing tension conditions to which the leathers are inevitably subjected during the process of drying and/or conditioning.
In conceptual principle, the present invention also relates to a support frame for leathers to be dried and/or conditioned suitable to be used in such a drying and/or conditioning plant. As known, in the tanning industry of leathers drying (or desiccation) of the leathers themselves is a basic process that is typically performed in the middle phase of the entire production process of tanning (in which the leathers already take the connotation of semi-finished products) with the aim of drying the leathers from the excess of water accumulated in the previous processing.
When they must undergo the drying process, the leathers have, indeed, already been subjected to at least the typical chemical and mechanical workings of the tanning industry such as soaking, liming, fleshing, splitting, descaling, degreasing, tanning, re-tanning, shaving, dyeing and greasing, in their proper and consolidated operating sequence, and appear as wet semi-finished products.
According to the prior art, the drying process is carried out with various plant solutions, depending on the type of leathers and the final destination of the finished product: in this regard, drying by suspension or hanging, drying for nailing, drying for "pasting", vacuum drying are herewith cited, for example.
In the major essential aspects, a typical and current drying and/or conditioning plant of leathers of the frames type includes an operating tunnel which mainly develops along a linear direction and is provided with air conditioning devices, (for example fans of axial type) and/or traction organs (for example pneumatic organs installed in the operating tunnel), suitable to operate on the leathers in such a way as to respectively dry and/or spread them according to pre-defined cycles and values of treatment and/or tension.
A drying and/or conditioning plant of the known type also includes a plurality of support frames, each of which receives at least a leather so as to keep it spread, as well as moving means, operatively connected with the support frames in order to convey them along the aforesaid linear direction according to a predetermined speed within the operating tunnel, in order to allow drying and/or conditioning of the leathers, and the outside the operating tunnel itself in order to allow discharge of these leathers dried and/or conditioned in a given processing cycle and load of other leathers to be dried and/or conditioned in the next processing cycle.
The leathers are coupled, often by nailing, by an operator but more often by at least a pair of operators with the relative support frames which, subsequently, are conveyed one at a time inside the plant operating tunnel where drying (or conditioning) of the leathers is got by properly varying and modulating, depending on the settings chosen, the inner temperature and humidity conditions along the longitudinal extension of the operating tunnel.
Having stably coupled them with the various support frames (as said, at least one leather for at least one of the side faces of the latter), the operators expand, widen or put in traction the leathers by means of an initial manual action which, however carefully performed and however proven both the operative capacity and the expertise of the operators involved are, it is inherently empirical and does not take into account the type, conformation and condition of the various leathers which, as known in the field, vary from batch to batch, and sometimes, also from leather to leather within the same batch.
In addition, the physical state itself (fatigue, tiredness, concentration level and even more) of the operators varies during a working day, as well as from one working day to another, so that the force with which the operators are able to spread or open the leather on the support frames is evidently variable in the short-medium term.
Such a situation concretely represents a widely felt drawback in the tanning field if it is considered how, in the prior art, the leathers thus loaded on the support frames by the operators are further and mechanically spread or stretched by actuation means which, as mentioned, the drying and/or conditioning plant concerned is provided with: see in this connection the prior document GB1432966 A .
Indeed, as soon as the support frames, complete with leathers to be dried, reach or approach the operating tunnel, they are subjected to the mechanical action of actuation means which enlarge the support frames according typically to a vertical direction (as known, for example from prior art document GB1432966 A , these support frames are usually, in the technical solutions mainly used, formed by two half-frames which are spaced apart and partially telescopically coupled each other) with consequent extension of the surface of the leathers, previously secured to the support frames by one or more operators at the loading station arranged upstream the operating tunnel.
Alternatively, as shown by the prior art document FR2187913 A1 , the actuation means operate directly on the stretched leathers in order to widen them at a plurality of perimetrical points in which they have been engaged by means of tongs to the various support frames. The enlargement or distension value of the leathers to be dried is generally, according to an operative methodology consolidated for years in the field, preset and adjusted at the beginning of the treatment cycle in of the drying and/or conditioning plant and as a fixed distance (that determines the application of a given tension to the fibres of the leathers) for a certain batch (for example, 200 mm), instead varying from batch to batch.
In this way it is not disadvantageously and minimally possible to consider, on one hand, the initial conditions of expansion of the leathers manually positioned by the operators and, on the other hand, the dimensions of the leathers belonging to the same batch, properties that, as just mentioned, are inevitably and often variable.
Yet this first situation, today widely seen in the tanning industry, involves, at the end of the drying and/or conditioning cycle, that the leathers of a given batch are stretched or expanded in a uniform manner in terms of distance, but to such an expansion corresponds a nonuniform tension of the fibres of the dried material: this effect is currently causing inhomogeneity between batches of the same product resulting from working of different leathers and typically translates into a reduction of the generally expected quality for the leathers (with consequent choice downgrading) or in a surface yield lower than that one which might be expected or that one optimal.
In addition, in the remainder of the drying and/or conditioning cycle inside the operating tunnel, the wet leathers inevitably and automatically shrink due to the loss by evaporation of water in which they are drenched: this occurs at a different extent depending on the type of leather - which depends on the animal's morphological features - and on the type of treatment which the same leathers have previously undergone - which depends on the practiced temperature and humidity conditions and on the chemical tanning, re-tanning and dyeing products used in the leather processing.
In this phase, therefore, as a result of their drying inside the operating tunnel of the plant, the fibres of tannery leathers (initially manually hooked to the support frames by the operators and subsequently mechanically spread by the actuation means) are subjected to a higher tension, which cannot be measured or modified during the drying phase: also this situation (detectable in the already cited prior documents FR2187913 A1 and GB1432966 A ) often causes damage to the leathers, with the consequence of generating disadvantageous downgrades or production waste.
To overcome the above drawbacks leathers drying and/or conditioning plants of somewhat technological nature have been recently proposed on the market by the same applicant, described in particular in the patent publication WO2014/191910 A1 : these plants implement a particular operational methodology that provides a control stage of the level of expansion of the leathers, both upstream and inside the operating tunnel of the plant, based on the adjustment of the tension of the fibres of the leathers themselves.
Such a control phase includes a series of basic operations, such as identification or programming of a predetermined nominal tension value of the leathers (considered ideal for the leathers of a given batch), the detection of the tension value of the fibres of the leathers, spread following the operation of the actuation means on the support frames, within the operating tunnel, the comparison of the detected tension value with the predetermined nominal tension value, with related calculation of the tension deviation and, finally, the adjustment of the operation of the actuation means as a function of this measured deviation in such a way as to keep the leathers spread and/or tensioned substantially to the predetermined nominal tension value.
The aforesaid operative sequence can be implemented several times during drying and/or conditioning of the leathers, according to what set by the operator: it follows, therefore, that there may also be many predetermined nominal tension values during the process of drying and/or conditioning.
This operating method thus allows to keep constant - at the predetermined nominal value, fixed at design point - the tension which the fibres of the leathers are subjected to during the drying and/or conditioning process by controlling it and, if necessary, modifying it accordingly: preferably, modification of the tension of the leathers fibres until the predetermined nominal value is achieved by increasing or decreasing the level of expansion of the leathers on the support frames.
The drying and/or conditioning method described in WO2014/191910 A1 allows leathers, during the step of crossing the whole operating tunnel, to keep a constant tension, considered optimal in a given operating situation, without subjecting the leathers to excessive stresses as it happens traditionally, thanks to the possibility of modifying the traction force with which the actuation means operate on the support frames which stably hold the leathers.
The force of traction automatically applied by the actuation means on the leather does not consider only the length of opening or distension of the leathers themselves, attached to the support frames, necessary to reach a standard prefixed expansion value (and a consequent nominal tension value), as it happens in the traditional known art (for example in the prior art documents FR2187913 A1 and GB1432966 A ), but the actual tensile state in which the tannery leathers are during the whole drying process: in this way, the force actually applied by the actuation means compensates for the manual force applied by the operator and each tannery leather of a given production batch is spread or enlarged of the same and constant predetermined nominal tension value of the leather fibres, set optimal by the manufacturer for that production batch.
In any case, even such method of more recent and modern conception operated for drying and/or conditioning the leathers by a plant having a more evolved technology which implements such a method are not free from some drawbacks, the main of which is constituted by the fact that its construction concept requires some rather complex tricks even in the operating (or drying) tunnel which must allow the installation of the control means (or unit) as described in the patent publication WO2014/191910 A1 .
Indeed, the method and the plant described in the patent publication WO2014/191910 A1 provide, in substance, installation of the actuation means on opposite sides of the operating tunnel (when seen from the front, from its inlet mouth) which must be moved by the moving means along the entire operating tunnel or at least a portion of it (in case the operating tunnel is divided into a number of drying chambers consecutive each other, operatively independent and possibly separated each other by a movable partition) in order to be able to contact, interact or cooperate with the support frames that from time to time the operator decides to check within the operating tunnel.
It is therefor evident that such a leathers drying and/or conditioning plant, necessary to implement the methodology briefly described above presents a relevant constructive complexity which impacts considerably on production, installation, maintenance and operation costs, generic factors involved in the calculation of these costs, such as manpower cost, raw materials cost, energy costs and so on, being equal.
A second drawback of the prior art closest to the invention, consisting of the PCT application published under WO2014/191910 A1 in the name of the same applicant of the present patent application, is due to the fact that in the implementing and operative practice, checking and eventual adjustment of the applied tension to the leathers on the support frames during drying and/or conditioning - in order to keep the tension constant at the nominal value initially programmed - are still left to the decision of the operator who performs it on the basis of his own experience or on a preset controls plan, pre-established on the paper.
In essence, the control and the intervention of adjustment of the leathers tension on a given support frame are decided by the operator who performs them at a certain time deemed appropriate by the same but which may not necessarily be the optimal one for the leathers fixed at a given support frame, with the obvious disadvantage of being able only in part in the aim of solving the drawbacks of the more traditional processing methods yet previously indicated (inhomogeneity among batches of the same article, reduction of the generally expected quality for the leathers or of their surface extension, damage to the leathers, choice downgrade, production waste).
In other words, one of the drawbacks of the leathers drying and/or conditioning plant described in the cited patent publication WO2014/191910 A1 is due to the fact that it allows to adjust the opening of the half-frames of the support frames (or expansion frames) only in a discrete manner during a working cycle, i.e. giving discrete opening increments (or decrements) of the two half-frames, thereby obtaining a tension regulation not continuously adjustable on all values and, thus, not optimal and precise at the highest level.
Starting, therefore, from the awareness of the abovementioned drawbacks of the current state of the art, the present invention intends to give accomplished remedy to them.
In particular, main purpose of the invention is to provide a drying and/or conditioning plant of leathers, especially tannery ones which is able to control and adjust the level of tension which the leathers are subjected to within the operating tunnel in such a way to keep it constant at a predetermined nominal value programmed by the operator more easily than equivalent known plants having the same purposes, shown for example in the patent publication WO2014/191910 A1 .
Within this purpose, it is task of the present invention to develop a leathers drying and/or conditioning plant which presents production, installation, maintenance and operation costs lower than the corresponding prior art drying and/or conditioning plants and support frames for leathers.
It is a second purpose of the invention to implement a drying and/or conditioning plant of leathers, and in particular a support frame for leathers to be dried and/or conditioned suitable to be used in such a plant that, contrary to the equivalent known art, perform a punctual (i.e. timely) and continuous control of the leathers tension level on each support frame during the drying and/or conditioning process upstream and inside the plant operating tunnel and, if necessary, adjust it in real time at the programmed nominal value.
It is, therefore, a purpose of the invention to realize a drying and/or conditioning plant of leathers, and in particular a support frame for leathers to be dried and/or conditioned suitable to be used in such a plant which are sensitive to the inevitable changes of the tension suffered by the leathers during the drying and/or conditioning process and are able to immediately and mechanically adapt to these leathers tension changes on each support frame while drying, self-adjusting themselves in a spontaneous, automatic way, not induced by external agents but seamless in their intrinsic regulating action.
In the conceptual sphere of this second purpose, it is task of the present invention to make available a leathers drying and/or conditioning plant, and in particular a support frame for leathers to be dried and/or conditioned suitable to be used in such a plant, which allow to avoid, or at least drastically reduce over the prior art, on one side damages - and consequent downgrades and production waste - of the leathers due to an excess tension of their fibres during the drying and/or conditioning process, on the other side inadequate and not optimal expansion levels of the leathers due to a lack of tension of their fibres.
Always in connection to the aforesaid second purpose, it is another task of the invention to provide a drying and/or conditioning plant of leathers, and in particular a support frame for leathers to be dried and/or conditioned suitable to be used in such a plant, which allow to achieve a greater uniformity in the tension of the dried leathers and a greater correspondence to the expected quality for the leathers compared to the current state of technique.
It is another purpose of the invention to devise a drying and/or conditioning plant of leathers, and in particular a support frame for leathers to be dried and/or conditioned suitable to be used in such a plant, which contribute to achieve these purposes and tasks efficiently even from a structural point of view.
It is a last but not least purpose of the present invention to indicate a drying and/or conditioning plant of leathers which is advanced, versatile and reliable, even in its simplified construction compared to the similar known art.
The foregoing purposes are achieved through a drying and/or conditioning plant of leathers according to claim 1 attached hereto, as hereinafter referred for the sake of brevity. Further constructive features of detail of the plant of the invention are indicated in the corresponding dependent claims.
Contributes to the solution of the drawbacks mentioned above also a support frame for leathers to be dried and/or conditioned, suitable to be used in the drying and/or conditioning plant just mentioned, according to claim 13 attached, as again hereinafter referred for the sake of brevity.
Additional technical features of detail of the support frame of the invention are contained in the respective dependent claims.
The above-mentioned claims, in the following specifically and concretely defined, are considered an integral part of the present description.
Advantageously, the leathers of a given production batch treated by the drying and/or conditioning plant of the invention present a more uniform tension level with respect to the leathers treated with equivalent plants of the known art.
Still advantageously, the drying and/or conditioning plant of leathers of the invention presents a construction concept simpler than that one of similar plants of the prior art, while allowing a punctual, timely, immediate and continuous adjustment - in other words, in real time - of the tension level of the leathers in order to keep it tensioned for the same nominal programmed or predetermined value.
These advantages derive from the fact that the actuation means and the detection means are incorporated in elastically yielding means (or damping means), stably coupled with each of the support frames and cooperating with the adjustment means in such a way as to obtain a spontaneous continuous adjustment of the effective tension value which each of the leathers secured on the support frames is subjected to during their relative processing cycles, keeping the leathers constantly tensioned according to the nominal tension value during the entire processing cycles, in particular within the operating tunnel.
The constructive simplification and the most accurate (as continuous, timely and spontaneous, without any dead time) adjustment capacity associated with the invention is a consequence of the fact of providing elastic or elastically yielding means which operate as actuation means and, simultaneously, as detection means and react in real time to any, even minimal, variation of the tension level of the leathers during the processing cycle in a drying and/or conditioning plant of the operating tunnel type.
These elastically yielding means in which, in the invention, the actuation means and detection means construed according to claim 1 attached are incorporated, therefore perform a function which cannot be found in the known art document GB 1,432,966 A yet mentioned above (especially to highlight its drawbacks which the present invention intends to solve) where the damping spring, fulfilling a function purely of safety, specifically serves to avoid that one of the two telescopic half-frames forming a support frame abruptly (and therefore dangerously) returns in the rest position, re-entering in the other half-frame: no detection and actuation function on the support frame when the tension which the leather is subjected to during its drying outside and inside the operating tunnel varies (concept claimed by the current invention) is, therefore, associated with the damping spring described in such a prior document.
Similarly with regard to the prior document EP 0028918 A2 , where the helical springs, which are coupled with the two half-frames, only operate when the shape memory material with which they're made reaches the transition temperature, but while the leathers are already within the operating tunnel and partly have been already dried and are drying, and only in expansion causing the mutual spacing of the two half-frames which slide on guide rods: as a consequence, the leather supported by two half-frames is only stretched and tensioned while it is drying inside the operating tunnel.
At the light of this overall operative situation, the leather which is drying inside the operating tunnel of the drying plant described in EP 0028918 A2 exactly suffers from the drawbacks which have been listed above and that the present invention, instead, solves: the inventive concept proposed by the invention, summarized above, does not find application and confirmation in EP 0028918 A2 , where, instead, the elastic means operate at certain times in (negatively) opposite way with respect to the elastically yielding means of the plant exclusively claimed herewith, because subjecting the leathers during the drying phase to a tension that, over time, is certainly excessive for the fibres that form it, causing an effect contrary to that one intended (increase of the useful leather surface) since they seriously damage the leather, with the obvious disadvantages that this entails.
The use of helical springs made of shape memory material obliges to operate as a function of their typical transition temperature, regardless of the type of leathers treated, with the evident and already mentioned drawbacks that this entails and which are instead solved by the invention described herein.
Said purposes and advantages, as well as other ones which will emerge later on, will result at a greater extent from the following description, relating to a preferred embodiment of the drying and/or conditioning plant of the invention and to a preferred applicative embodiment of the method of the invention implemented by such a plant, given by indicative, but not limitative, example way with reference to the attached drawings, in which:

figure 1 is a simplified front view of the drying and/or conditioning plant of leathers and the support frame both object of the invention;
figure 1a is an enlarged detail of figure 1;
figure 2 is a simplified front view of a first possible variant embodiment of the drying and/or conditioning plant of leathers and the support frame of figure 1;
figure 2a is an enlarged detail of figure 2;
figure 3 is a simplified front view of a second possible variant embodiment of the drying and/or conditioning plant of leathers and the support frame of figure 1;
figure 3a is an enlarged detail of figure 3.

The leathers, especially tannery leathers, industrial drying and/or conditioning plant of the invention is shown in figure 1, where it's globally numbered with 1, in partial and schematic way (particularly without operating tunnel and drying and/or conditioning equipment associated with it) but still reproducing the inventive kernel of the invention itself.
Such a drying and/or conditioning plant 1 of leathers includes:

an operating tunnel (as mentioned not shown for the sake of exposition simplicity since it does not involve fundamental components for the purposes of the inventive concept expressed by the present invention), which mainly develops along a linear direction and is provided with air conditioning devices, not represented, suitable to operate on the leathers in such a way as to dry and/or condition them according to pre-defined treatment cycles;
a plurality of support frames, of the type visible in a single specimen in figure 1 where it is indicated with 2, each of which is suitable to receive on at least one of the side faces 2a, 2b at least one leather in order to keep it in the spread position;
actuation means, operatively connected with the support frames 2 and suitable to be operated in such a way as to stretch the leathers to a nominal tension value set by the operator;
moving means, numbered on the whole with 3, operatively connected with the support frames 2 in order to convey them along the linear direction according to a predetermined speed inside the operating tunnel, in order to allow the leathers to be dried and/or conditioned, and outside the operating tunnel in order to allow discharge of the leathers dried and/or conditioned in a processing cycle and loading of the leathers to be dried and/or conditioned in the next processing cycle;
detection means, operatively connected with the actuation means and suitable to measure the tension value of the fibres of the leathers during a processing cycle;
adjustment means, generally numbered with 4, operatively associated with the actuation means with which they cooperate according to the difference in tension between the tension value measured by the detection means and the nominal tension value so as to keep the leathers tensioned substantially to the set nominal tension value during the aforesaid processing cycle.

In accordance with the innovative features of the invention, the actuation means and the detection means are incorporated, embedded or gathered in elastically yielding means, as a whole indicated with 5, coupled with each of the support frames 2 together with the adjustment means 4 with which cooperate in such a way as to obtain a spontaneous continuous adjustment of the actual tension value which each of the leathers secured on the support frames 2 is subjected to during a processing cycle of the leathers, keeping the actual tension value of the leathers constantly and substantially equal to the nominal tension value during a processing cycle.
In essence, therefore, the elastically yielding means 5 operate, on one hand, as detection means and, simultaneously and/or at the same time, on the other hand, as actuation means in the functional sense just described, without this implying the use of different and separated mechanical members as it happens in the prior art; in such a manner, it is ensured an automatic and continuous adjustment, spontaneous and not induced, of the effective tension value which each of the leathers secured on the support frames 2 is subjected to, during a given processing cycle, keeping it constantly and substantially equal to the nominal tension value during a processing cycle.
It is reiterated that the nominal tension value at which, in the invention, the treated leathers are constantly kept can be suitably varied and thus take different numbering during a drying and/or conditioning cycle, in function of the program set by the operator.
In particular, the elastically yielding means 5 and the adjustment means 4 are stably fixed to the lateral portions 2c, 2d of each of the support frames 2 of the leathers, when the support frames 2 themselves are viewed from the front (as shown in figure 1).
Still more in detail, in this specific constructive example, the elastically yielding means 5 are fixed to a first movable portion 6 of each of the support frames 2 while the adjustment means 4 are fixed to a second fixed portion 7 of each of the support frames 2: in this case, the first movable portion 6 is slidingly and telescopically coupled with the second fixed portion 7 and, in applicative conditions, is positioned above the latter.
Preferably but not necessarily, although only advantageously, the elastically yielding means 5 and the adjustment means 4 are internally (and respectively) coupled with the first movable portion 6 and with the second fixed portion 7 of each of the support frames 2, so as to be totally hidden from view: in such a case, the support frames 2 of the leathers drying and/or conditioning plant 1 object of the invention present from the outside as those ones of a traditional drying and/or conditioning plant of the prior art but advantageously devoid of the cumbersome plant equipment and instrumentation of the latter, provided for the same operational purposes of the elastically yielding means 5 and of the adjustment means 4 belonging to the plant 1 of the invention.
In other embodiments of the invention, not illustrated, the elastically yielding means and the adjustment means, while remaining totally hidden from view, could be internally coupled only with the first movable portion or only with the second fixed portion of each support frame, so as, on the other hand, they could remain at sight and be coupled externally with the first movable portion and/or the second fixed portion of each support frame.
In a suitable although not binding manner, the elastically yielding means 5 comprise for example a typical torsion spring 13 of industrial type and are provided with a preload force (expressed in kilograms) set by the operator according to the type of leathers temporarily secured to the frames support 2, i.e. for the time required for their drying and/or conditioning within the operating tunnel.
This does not exclude that in other embodiments of the invention, not illustrated in the appended drawings, the elastically yielding means could include mechanical damping components or systems of other type, such as for example a helical spring of industrial type. In this regard, it should be noted how, at the time of fixing to the support frame 2, each leather to be dried and/or conditioned is not subjected to tension on the support frame 2 itself if not purely by the tension due to the normal application of the tongs through which it is hooked such a support frame 2.
As soon as positioned in vertical position, the support frame 2 is locked in position by a light preload of the elastically yielding means 5 (or by other locking systems used in traditional plants, although they are believed to be constructively more complex) which, in return, move a hooking system for coupling with the support frame 2 and the leather hooked to the latter undergoes a substantial release (this is, indeed, an elastic material drenched in a large quantity of water).
Preferably, the support frame 2, once locked in vertical position, and with it the leather that supports is then immediately subjected to a controlled expansion by providing to the load (or compression) of the elastically yielding means 5 (such as the torsion spring 13) which, in doing so, convey a reaction on the support frame 2 (this is the position of the elastically yielding means 5 taken as the zero reference point).
The leather thus undergoes a force that, on the whole, is the result of two components:

force of the elastically yielding means 5 which tends to move apart the two half-frames which make up the support frame 2;
intrinsic resistance strength to be enlarged of the leather.

Since it is a fibrous material, the leather is a material that requires a certain time interval - which depends on its dimensions, its thickness, type of chemical treatment which it is subjected to, and so forth - to redistribute across its own surface the forces applied to it and thus transform them into enlargement of the two semi-frames of the support frame 2.
This phase, in which the elastically yielding means 5 are loaded for the first time, is often referred to, incorrectly, as "preload" (to be understood however in a different sense from that one described above, in the previous page) and determines a simple stretch of the leather and a moderate enlargement of the two half-frames of the support frame 2 with the result that the leather is not properly subjected to tension.
In the plant 1 of the invention, therefore, the nominal tension value - at which the leathers outside the operating tunnel and/or inside the same are constantly kept during the entire processing cycle - is suitably set from time to time by the operator through adjustment/variation of the preload force of the elastically yielding means 5 performed for each of the leathers to be treated or, at least, for each batch of leathers similar each other for physical properties, previous chemical treatment, type and origin of the animal from which they are obtained and other parameters considered during drying and/or conditioning in an operating tunnel of such a plant 1.
In the invention, the operator adjusts/varies the preload force of the elastically yielding means 5 initially provided (depending on the leather type) mechanically acting on the adjustment means 4, whose constructive preferred composition is shown in the remainder of the present description.
This allows to get the most uniform and effective possible levels of treatment of the leathers, certainly better than those ones which can be obtained in the prior art with respect to which the invention limits the drawbacks previously mentioned and which can be, for example, found in the prior document published with no. US2,828,575 A , in which such an operation of initial adjustment - allowed, it is confirmed, by the adjustment means 4 in the plant of the invention - not only is not described and not deductible by a man skilled in the art but is not always practicable (especially when the support frame, complete with leathers to be dried, is in the vertical position which is conveyed to the operating tunnel with), since the various springs are inside the inner angular bodies slidingly connecting the outer side parts of the support frame, and therefore they are not in any way accessible in order to operate an adjustment.
Confirming this position which can be actually found in US2,828,575 A , it should be also observed that, in the embodiment described in such a document, before loading the leathers on the support frame (thus, in the very first stage of the treatment cycle), the external lateral parts of the frame are pressed against one another, for example by means of a mechanical press, in such a way as to define the closed position of the frame, which, subsequently, takes again the opening position, as a result of the opening of the mechanical press, after the leathers have been fixed to the frame by means of tongs.
It follows that, in the prior document US2,828,575 A , the springs are compressed (therefore, load) when the support frame of the leathers is also only partly closed (i.e., its component parts are at least partly approach each other): when the support frame, complete with one or more leathers attached to it by means of the tongs, is released as a result of the opening of the mechanical press, it is therefore no longer possible in any way to intervene on the springs and adjust the preload thereof, contrary to what happens in the invention where this manoeuvre is if necessary but advantageously allowed by the adjustment means 4.
In addition, it is should be noted that the elastically yielding means 5 and the adjustment means 4 are in this case coupled with each of the support frames 2 through fixing means, overall indicated with 8.
At purely preferred but not exclusive title, the drying and/or conditioning plant 1 of the invention comprise end-of-stroke means, numbered on the whole with 9, associated with the elastically yielding means 5 and/or with the adjustment means 4 and suitable to stop pulling movement downwardly and/or upwardly of the elastically yielding means 5 and, accordingly, the telescopic entry and/or exit movement of the first movable portion 6 in/from the second fixed portion 7.
According to the preferred embodiment described here of the invention, the adjustment means 4 comprise a mechanical adjustment system constituted in this case by screw means, overall indicated with 10, of the type nut screw 11 and worm screw 12, better visible in the detail of figure 1a.
Figure 2 shows another embodiment of the invention in which the drying and/or conditioning plant differs from the drying and/or conditioning plant described above and indicated with 1 first of all for the fact that the elastically yielding means, now on the whole numbered with 55, and the adjustment means, now overall numbered with 54, are fixed only to a first movable portion 56 of each of the support frames 52.
Another substantial difference between the plant of figure 2 now under description and the drying and/or conditioning plant 1 of the invention described above and shown in figure 1 relates to the fact that the elastically yielding means, overall indicated with 55, and the adjustment means, indicated as a whole with 54, are externally (and respectively) coupled with a first movable portion 56 of each support frame 52 in order to be placed in the linear slot 58 defined between the first portion 56 and the second portion 57 and an outer frame 59 of each of the support frames 52 integral with the first movable portion 56 and/or the second fixed portion 57.
This arrangement, together with the fact that the elastically yielding means 55 and the adjustment means 54 are substantially contained in the overall dimensions of the respective support frame 52, gives the drying and/or conditioning plant the advantage of minimizing also in this case the constructive impact of the main innovative feature of the invention which, as already highlighted, is represented by the elastically yielding means 55 which operate as actuation means and as detection means and are associated with each of the support frames 52.
In this way, indeed, the elastically yielding means 55 and the adjustment means 54, while remaining at sight from the outside, are substantially protected from accidental impacts, always unwanted and harmful, and their presence has a negligible effect on the storage and transportation of the support frames 52.
It is understood that in other embodiments of the invention, not illustrated in the figures that follow, the elastically yielding means and the adjustment means could be coupled with a first movable portion and/or with a second fixed portion of each of the support frames without being placed in the slot defined by the first movable portion and the second fixed portion aligned to it (preferably telescopically) with the outer frame of the support frames.
In addition, further optional embodiments of the drying and/or conditioning plant of the invention, not illustrated, could provide that the elastically yielding means and the adjustment means, while remaining totally in the overall dimensions of the respective support frame, could be externally coupled only with the first movable portion or only with the second fixed portion of each of the support frames.
The detail of figure 2a shows the position of the elastically yielding means 55 and the adjustment means 54, as well as that the adjustment means 54 are in this case of the same type of the adjustment means 4 of the drying and/or conditioning plant 1 (screw means, generically indicated with 60, of the type with nut screw 61 and screw 62 and placed below the torsion spring 63 which are operatively connected with).
In the next figure 3 another possible embodiment of the invention is shown in which the drying and/or conditioning plant differs from those ones already described before for the composition of the adjustment means, on the whole numbered with 104 and which in this case include a mechanical adjustment system constituted by locking means of the type with successive shots, indicated as a whole with 110, of the type tooth 111/rack 112 and placed below the torsion spring 113 which are operatively connected with.
Also in this constructive example, as figure 3a highlights, the elastically yielding means 105 and the adjustment means 104 take the same position of the elastically yielding means 55 and of the adjustment means 54 of the drying and/or conditioning plant of figure 2.
It is understood that in further embodiments of the drying and/or conditioning plant of the invention, not accompanied by appended reference drawings, the adjustment means could comprise a mechanical adjustment system which differs from those ones previously described.
As already mentioned above, object of the present invention is also the support frame, of the type indicated with 2, 52 and 102 in the attached figures, for leathers to be dried and/or conditioned.
It should be observed that the support frame 2, 52, 102 comprises a composite bearing structure 14 suitable to be introduced through the moving means 3 into an operating tunnel of a drying and/or conditioning plant of leathers and to be accessible to the operator in a working station, not shown, arranged upstream of the operating tunnel in order to ensure at least one of the leathers on at least one of the side faces 14a, 14b of the composite bearing structure 14.
According to the invention, the support frame 2, 52, 102 comprises the elastically yielding means 5 firstly introduced that:

are coupled with the composite bearing structure 14 itself;
operate as actuation means, suitable to be operated in such a manner as to spread the leathers to a nominal tension value set by the operator, and at the same time as detection means, operatively connected with the actuation means and suitable to measure the tension value of the fibres of the leathers during a processing cycle;
are operatively associated with the adjustment means 4 with which they cooperate according to difference in tension between the tension value measured by the detection means and the nominal tension value in such a way as to keep the leather substantially tensioned to the nominal tension value and to obtain a spontaneous continuous adjustment of the actual tension value which each of the leathers secured on the composite bearing structure 14 is subjected to during a processing cycle of leathers, keeping the aforesaid actual value of the leathers constantly and substantially to the nominal tension value during such a processing cycle.

In particular, the composite bearing structure 14 comprises a metallic foldable grid plane in order to facilitate the stable application of the leathers in a spread position on both the side faces 14a, 14b of the composite bearing structure 14.
It should be observed in the attached figures that the elastically yielding means 5, 55, 105 and the adjustment means 4, 54, 104 are symmetrically arranged with respect to a vertical symmetry axis Y and to a horizontal symmetry axis X of the composite bearing structure 14 of the support frame 2, 52, 102.
With reference to this last constructive detail, it is underlined that if the leathers supported by support frames, due to their more markedly irregular area, are tensioned in a different manner on a first of the lateral portions relative to the second opposite one (looking frontally the support frames), the elastically yielding means and the adjustment means will continue to be symmetrically arranged with respect to a vertical symmetry axis and to a horizontal symmetry axis of the composite bearing structure of each support frame but, in such a case, the operator will set a preload force on the elastically yielding means arranged at a first lateral portion different from the preload force on the elastically yielding means arranged at the second lateral portion.
In operating terms, at the beginning - before entering into the operating tunnel of the drying and/or conditioning plant of the invention - the wet leathers, applied by the operator by means of special tongs (operation known in the state of the art of the field as "nailing") on both the side faces 2a, 2b of each support frame 2, 52, 102, settle in their position increasing their surface extension and, thanks to the presence of the elastically yielding means 5, 55, 105 and the adjustment means 4, 54, 104, move away each other of the minimum distance the two half- frames 6, 56 and 7, 57 of each support frame 2, 52, 102, causing the output of the first telescopic movable portion 6, 56 from the second fixed portion 7, 57.
During the crossing of the operating tunnel of various support frames 2, 52, 102 where they are subjected to a drying and/or conditioning treatment cycle, the leathers shrink and, thus, inevitably would tend to reduce their surface area and to increase their tension by virtue of the constraint given by the tongs at the perimeter of the leathers themselves: thanks to the elastically yielding means 5, 55, 105 and the adjustment means 4, 54, 104 cooperating each other, the leathers, instead, release on the support frames 2, 52, 102 the greatest tension which they're subjected to, thereby approaching the two half- frames 6, 56 and 7, 57 of the support frames 2, 52, 102 (the first movable portion 6, 56 partly re-enters into the second fixed portion 7, 57) up to the point in which the preload of the elastically yielding means 5, 55, 105 balances the tension of the leather which is brought back to the nominal value initially set by the operator.
On the basis of the description just given, it is understood, therefore, that the leathers drying and/or conditioning plant, and the support frame for leathers to be dried and/or conditioned, both object of the present invention, achieve the purposes and reach the advantages yet mentioned.
The innovative technical concept underlying the invention is also applicable to leathers drying and/or conditioning plants already existing and operative providing the latter of the elastically yielding means and adjustment means as previously described: this, in particular, if the existing leathers drying and/or conditioning plants are provided with locking means of the tooth/rack type that stable retain in a well precise and fixed position, initially established by the operator, the two half-frames of each support frame during a certain processing cycle of the leathers supported by that support frame in that specific processing cycle.
Upon implementation, changes could be made to the leathers drying and/or conditioning plant of the invention, consisting, for example, in elastically yielding means (or damping means) different from those ones described and shown in the drawings that follow, and this in function of the tension values required to leathers, the type of leathers to be treated (surface, breed, thickness and so on) and the size and structural shape of the support frames. Moreover, other embodiments of the drying and/or conditioning plant of the invention, not shown, could provide that at least one of the support frames withholds only one leather on one of the side faces, or a single leather for each of the side faces.
It is stated precisely that the drying and/or conditioning plant of the present invention could include any number of support frames, that number varying according to the constructive choices, the operating requirements and/or the available space in the manufacturer's factory. It is, finally, clear that several other changes could be made to the leathers drying and/or conditioning plant and the support frame concerned, without departing from the principle of novelty intrinsic in the inventive idea expressed herein or from the scope of the claims, 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

Leathers drying and/or conditioning plant (1) comprising:
- an operating tunnel which mainly develops along a linear direction and is provided with air conditioning devices suitable to operate on the leathers in such a way as to dry and/or condition them according to pre-defined treatment cycles;

- a plurality of support frames (2; 52; 102), each of which is suitable to receive on at least one of the side faces (2a, 2b) at least one of said leathers in order to keep it in the spread position and formed by two half-frames or portions (6, 7) spaced apart and partially coupled each other so that a first half-frame or portion (6) is movable with respect to a fixed second half-frame or portion (7);

- actuation means operatively connected with said support frames (2; 52; 102) and suitable to be operated in such a way as to extend said leathers to a nominal tension value set by the operator, by opening or spacing said half-frames or portions (6, 7);

- moving means (3), operatively connected with said support frames (2; 52; 102) in order to convey them along said linear direction according to a predetermined speed within said operating tunnel, in order to allow drying and/or conditioning of said leathers, and outside said operating tunnel in order to allow discharge of said leathers dried and/or conditioned in a processing cycle and load of said leathers to be dried and/or conditioned in the next processing cycle;

- detection means, operatively connected with said actuation means, whereby said actuation means and said detection means are incorporated in elastically yielding or elastic means (5; 55; 105);

- adjustment means (4; 54; 104), operatively associated with said actuation means and cooperating with said actuation means to keep said leathers tensioned substantially to said nominal tension value during said processing cycle,
characterized in that said adjustment means (4; 54; 104) are coupled with each of said support frames (2; 52; 102) and are of mechanical and self-adjusting type, cooperating with said elastically yielding or elastic means (5; 55; 105), coupled with each of said support frames (2; 52; 102), in such a way as to obtain a spontaneous continuous self-adjustment of said first movable portion (6) with respect to said second fixed portion (7) of said support frames (2; 52; 102) and, thus, of the actual tension value which each of said leathers secured on said support frames (2; 52; 102) is subjected to during said processing cycle of said leathers keeping said actual tension value of said leathers constantly to said nominal tension value during said processing cycle, wherein said elastically yielding or elastic means (5; 55; 105) are provided with a preload force set by the operator according to the type of said leathers temporarily secured to said support frames (2; 52; 102).
Plant (1) according to claim 1), characterized in that said elastically yielding means (5; 55; 105) and said adjustment means (4; 54; 104) are firmly fixed to the lateral portions (2c, 2d) of each of said support frames (2; 52; 102) of said leathers, when said support frames (2; 52; 102) are viewed from the front.
Plant (1) according to claim 1) or 2), characterized in that said elastically yielding means (5) are fixed to said first movable portion (6) of each of said support frames (2) and said adjustment means (4) are fixed to said second fixed portion (7) of each of said support frames (2), said first movable portion (6) being slidably and telescopically coupled with said second fixed portion (7).
Plant according to claim 1) or 2), characterized in that said elastically yielding means (55; 105) and said adjustment means (54; 104) are fixed to said first movable portion (56) of each of said support frames (52; 102).
Plant according to any of the preceding claims, characterized in that said elastically yielding means (55; 105) and said adjustment means (54; 104) are externally coupled with said first movable portion (56) and/or with said second fixed portion (57) of each of said support frames (52; 102) in order to be placed in the linear slot (58) defined between said first portion (56) and said second portion (57) and an outer framework (59) of each of said support frames (52; 012), said outer framework (59) being integral with said first movable portion (56) and/or said second fixed portion (57).
Plant (1) according to any of the claims 1) to 5), characterized in that said elastically yielding means (5) and said adjustment means (4) are internally coupled with said first movable portion (6) and/or with said second fixed portion (7) of each of said support frames (2).
Plant (1) according to any of the preceding claims, characterized in that said elastic or elastically yielding means (5; 55; 105) comprise any of the mechanical damping components or systems selected from the group consisting of torsion springs (13) of industrial type and helical springs of industrial type.
Plant (1) according to any of the preceding claims, characterized in that said elastic or elastically yielding means (5; 55; 105) react in real time to any variation of said tension level of said leathers during said processing cycle.
Plant (1) according to any of the preceding claims, characterized in that said preload force of said elastic or elastically yielding means (5; 55; 105) is adjusted/varied by mechanically acting on said adjustment means (4).
Plant (1) according to any of the preceding claims, characterized in that said elastically yielding means (5; 55; 105) and said adjustment means (4; 54; 104) are coupled with each of said support frames (2; 52; 102) through fixing means (8).
Plant (1) according to any of the preceding claims, characterized in that it comprises end-of-stroke means (9), associated with said elastically yielding means (5; 55; 105) and/or said adjustment means (4; 54; 104) and suitable to stop pulling movement downwardly and/or upwardly of said elastically yielding means (5; 55; 105).
Plant (1) according to any of the preceding claims, characterized in that said adjustment means (4; 54; 104) comprise any of the mechanical adjustment systems selected from the group consisting of screw means (10) of the type nut screw (11)/screw (12) and locking means (60) of the type with successive shots (tooth 61/rack 62) which said elastically yielding means (5; 55; 105) are operatively connected with.
Support frame (2; 52; 102) for leathers to be dried and/or conditioned comprising a composite bearing structure (14):
• formed by two half-frames or portions (6, 7) spaced apart and partially coupled each other so that a first half-frame or portion (6) is movable with respect to a fixed second half-frame or portion (7);

• suitable to be introduced through moving means (3) into an operating tunnel of a leathers drying and/or conditioning plant (1) and to be accessible to the operator in a working station placed upstream said operating tunnel in order to assure at least one of said leathers on at least one of the side faces (14a, 14b) of said composite bearing structure (14);

• comprising actuation means operatively connected with said support frames (2; 52; 102) and suitable to be operated in such a way as to extend said leathers to a nominal tension value set by the operator, by opening or spacing said half-frames or portions (6, 7);
- comprising detection means, operatively connected with said actuation means, whereby said actuation means and said detection means are incorporated in elastically yielding or elastic means (5; 55; 105),

characterized in that it comprises adjustment means (4; 54; 104) which:
- are coupled with said composite bearing structure (14);

- are of mechanical and self-adjusting type, cooperating with said elastically yielding or elastic means (5; 55; 105) to keep said leathers tensioned substantially to said nominal tension value and to obtain a spontaneous continuous self-adjustment of said first movable portion (6) with respect to said second fixed portion (7) of said composite structure (14) and, thus, of the actual tension value which each of said leathers secured on said composite structure (14) is subjected to during said processing cycle of said leathers, keeping said actual tension value of said leathers constantly to said nominal tension value during said processing cycle, wherein said elastically yielding or elastic means (5; 55; 105) are coupled with each of said support frames (2; 52; 102) and are provided with a preload force set by the operator according to the type of said leathers temporarily secured to said support frames (2; 52; 102).
Frame (2; 52) according to claim 13), characterized in that said composite bearing structure (14) comprises a metallic foldable grid plane in order to favor the stable application of said leathers in a spread position on both of said side faces (14a, 14b) of said composite bearing structure (14).
Frame (2; 52) according to claim 13) or 14), characterized in that said elastically yielding means (5; 55; 105) and said adjustment means (4; 54; 104) are symmetrically arranged with respect to a vertical symmetry axis (Y) and to a horizontal symmetry axis (X) of said composite bearing structure (14).