WO2019106615A1

WO2019106615A1 - Plant for drying pretreated flexible sheet products

Info

Publication number: WO2019106615A1
Application number: PCT/IB2018/059494
Authority: WO
Inventors: Antonio Polato
Original assignee: Officine Di Cartigliano S.P.A.
Priority date: 2017-11-30
Filing date: 2018-11-30
Publication date: 2019-06-06
Also published as: EP3717669B1; CN111417733A; ES2890998T3; CN111417733B; KR20200094158A; PL3717669T3; PT3717669T; EP3717669A1; KR102667839B1; RS62369B1

Abstract

A drying plant (1) for drying pretreated flexible sheet products, having at least one side on which a layer of a chemical compound has previously been deposited, said system (1) comprising feeding means (2) for feeding the sheet products in a direction (L), drying means (3) for drying the products as they are being fed, which have at least open operating unit (5) with a chamber (6) through which the feeding means (2) are designed to pass, and with at least one applicator (10) connected to a respective generator (11) for application of an alternating electromagnetic field in the RF range and a control unit (1 6), for controlling the generator (11) and/or the applicator (10). The field has an oscillation frequency that ranges from 300 kHz to 300MHz and is preferably 27.12 MHz at least one air blowing means (18) (18) for delivering hot air and/or at least one suction means (19) are provided. The control unit (16) is configured to change the speed of the feeding means (2) or to change the electromagnetic field application time. Sensor means are further provided, for detecting one or more physical and/or thermodynamic parameters of the operating unit (5) and the temperature of the sheet and for controlling the means (2, 18, 19) separately from or in combination with each other and carry out complete drying of the chemical compound layer.

Description

PLANT FOR DRYING PRETREATED FLEXIBLE SHEET PRODUCTS

Field of The Invention

[0001] The present invention generally finds application in the field of tanning and particularly relates to a plant for drying pretreated flexible sheet products, such as industrial hides, skins, imitation leather or leather derivatives.

Background art

[0002] After the various tanning, re-tanning and dyeing treatments, hides are known to often exhibit surface defects that were naturally formed during the life of the animals (scratches due to goring, contact with barbed wire or thorns) or caused by poor leather preservation after flaying.

[0003] In these cases, once the hides have been dried, they undergo a surface treatment typically known as finishing, whereby such defects are removed or made less visible, for better use of the hides.

[0004] During chemical finishing, chemical compounds, generally in liquid form, are deposited on the hides, to form a grain side layer that may have various thicknesses or be elastic or tough according to the types of finishing and leather.

[0005] The compound is initially deposited in a predetermined amount on the grain side of the hides and later dried to form a layer that binds with the fibers, to thereby be integrated with the hide.

[0006] The finishing chemical compound is typically applied by spraying or by using rotating rollers that contact the hides as they are being fed.

[0007] Furthermore, the chemical compound drying process is typically carried out using an oven or a tunnel operating with infrared rays, catalytic gas and more often with hot air.

[0008] For this purpose, the plants for surface treatment of hides comprise one or more drying units, with hot air being conveyed thereto by high-flow compressors and blowers, whose flow rates may reach thousands of m³/h. The drying temperatures in these apparatus generally range from 80 °C to 160 °C.

[0009] A first drawback of these plants is that the manufacturing energy costs associated with high hot air flows for drying the hides and with plant operation are very high.

[0010] A further drawback is that the hides dried as described above have a very high surface temperature and cannot be easily handled and stacked.

[0011] Therefore, completely dried hides may be typically cooled using a cooling device, such as a cold air chiller, which has high power consumption.

[0012] Another drawback is that high temperature drying processes are not uniform and tend to alter the "hand" of leather, i.e. make it more rigid and less soft than they were in the unfinished state.

[0013] Finally, any shrinking effect of the hot drying process will cause shrinkage in the hides, thereby leading to a significant reduction of the useful leather area, and to a reduction of the final inherent value of the treated hides.

[0014] In an attempt to at least partially obviate these drawbacks hide drying plants been developed which use electromagnetic fields whose frequency falls within the radiofrequency range.

[0015] EP2935631 , by the proprietor hereof, discloses a plant for drying of the hides with a pair of operating units comprising respective radiofrequency electromagnetic field applicators located in a chamber and connected to respective high-frequency AC voltage generators.

[0016] Namely, the two operating units are configured to dry different finishing chemical compounds that have been previously deposited on the hides by one or more deposition units.

[0017] A first drawback of this arrangement is that this plant does not allow feedback-responsive adjustment of the operation of the generator and the applicator according to the operating conditions of the drying unit.

[0018] A further drawback is that the hides must undergo both drying processes for optimal finishing. This drawback involves an increase of the overall machining costs.

[0019] Another drawback is that electrodes are arranged in the drying unit with a conventional geometry that cannot be changed to optimize the application of the electromagnetic field on the hides as they are being fed.

[0020] Yet another drawback is that the use of a single radiofrequency limits the drying efficiency on chemical compounds and hides and causes an accumulation of residual moisture in the drying units.

Technical Problem

[0021] In the light of the prior art, the technical problem addressed by the present invention is to ensure combined adjustment and control of the various thermal and fluid-dynamic parameters of the plant for efficient and quick drying of finishing chemical compounds after the latter have been deposited on the products.

Disclosure of the invention

[0022] The object of the present invention is to solve the above problem, by providing a drying plant for drying pretreated flexible sheet products that is highly efficient and relatively cost-effective.

[0023] A particular object of the present invention is to provide a plant as described hereinbefore that affords combined and feedback-responsive control and adjustments of the sheet product drying components.

[0024] A further object of the invention is to provide a plant as described hereinbefore that can quickly and efficiently dry the finishing chemical compound, regardless of the amount thereof that has been deposited on the sheet products.

[0025] Another object of the invention is to provide a plant as described hereinbefore that can optimize the overall energy costs.

[0026] Yet another object of the present invention is to provide a plant as described hereinbefore that can use a combination of different drying modes.

[0027] A further object of the present invention is to provide a plant as described hereinbefore that can remove the residual moisture accumulated in the drying units.

[0028] Yet another object of the present invention is to provide a plant as described hereinbefore that can modify the electromagnetic field applicator to optimize application efficiency on the products.

[0029] These and other objects, as more clearly explained hereinafter, are fulfilled by an plant for drying pretreated flexible sheet products as defined in claim 1 , in which the sheet products have at least one side with a layer of a chemical compound previously deposited thereon.

[0030] The plant comprises feeding means for feeding the sheet products in a longitudinal direction and drying means for drying the products as they are being fed.

[0031] The drying means have at least one operating unit with a chamber through which the feeding means are designed to pass, and with at least one applicator therein, connected to a respective generator for application of an AC electromagnetic field in the RF range, to dry the chemical compound deposited on the products during processing.

[0032] The plant also comprises at least one control unit for controlling the generator and/or the applicator. The AC electromagnetic field has an oscillation frequency that ranges from 300 kHz to 300MHz and is preferably 27.12 MHz, with tolerances in the admitted ISM bands, and at least one air blowing means (18) for delivering hot air and/or at least one suction means (19) are provided.

[0033] The blowing means are controlled to deliver hot air at a predetermined temperature and the suction means are configured to draw in the moisture removed during drying from the chamber. The control unit is configured to change the speed of the feeding means or to change the electromagnetic field application time and sensor means are provided in the chamber for detecting one or more physical and/or thermodynamic parameters of the at least one operating unit such as the temperature and/or the residual humidity in the chamber and the temperature of the hides and also for controlling the feeding means, the blowing means and the suction means separately from or in combination with one another to ensure complete drying of the chemical compound layer.

[0034] Advantageous embodiments of the invention are defined in accordance with the dependent claims.

Brief Description of The Drawings

[0035] Further features and advantages of the invention will be more apparent upon reading the detailed description of a few preferred, non exclusive embodiments of a plant for drying pretreated flexible sheet elements such as industrial hides, skins, imitation leather or leather derivatives according to the invention, which are described as non-limiting examples with the help of the annexed drawings, in which:

FIG. 1 is a perspective view of the drying plant of the invention;

FIG. 2 is a lateral view of the plant of Fig. 1 ;

FIG. 3 is a front view of the plant of FIG. 1 .

FIG. 4 is a lateral broken-away view of the plant of Fig. 1 ;

FIG. 5 is a lateral broken away view of the plant of Fig. 4.

Detailed description of a preferred exemplary embodiment

[0036] Referring to above figures, there is shown a plant for drying pretreated flexible sheet products, such as industrial hides, skins, imitation leather or leather derivatives, generally designated by numeral 1 .

[0037] Hides are known to comprise a grain side and a flesh side and have a layer of previously deposited finishing chemical compound on one of the two sides, preferably the grain side.

[0038] The chemical compound drying process that is carried out by the plant 1 of the present invention imparts particular aesthetic and tactile properties to the hide.

[0039] The finishing chemical compound may be deposited by known deposition means, such as spray or roll deposition means. The latter are configured to deposit a layer of chemical compound layer on at least one side of the sheet product with a surface density that ranges from 0.001 g/m² to 500 g/m², preferably from 5 g/m² to 150 g/m².

[0040] By way of example, the deposited chemical compounds may act as a base, color and finishing coat, and may be selected from the group comprising polymeric compounds such as acrylic and polyurethane resins, inorganic compounds such as iron oxides and pigments and natural compounds.

[0041] In a preferred embodiment of the invention, the plant 1 comprises feeding means 2 for feeding the sheet products in a longitudinal direction L and drying means 3 for drying the products as they are being fed.

[0042] As is known per se, the feeding means 2 may comprise an annular belt or wire conveyor 4 with the belt or wires tensioned by end rollers and defining a feeding plane p for the sheet products with their top sections.

[0043] Furthermore, the drying means 3 comprise at least one operating unit 5 with a chamber 6 through which the feeding means 2 pass.

[0044] Namely, the chamber 6 may be at least partially closed and delimited by a box-like structure 7 having an inlet 8 and an outlet 9 for the passage of the feeding means 2.

[0045] As best shown in FIGS. 4 and 5, the drying chamber 6 comprises therein at least one applicator 10 connected to a high-frequency voltage generator 1 1 for applying an AC electromagnetic field with an oscillation frequency that ranges from 300 kFIz to 300MFIz to dry the chemical compound deposited on the products during processing, irrespective of its surface density.

[0046] Preferably, the generator 1 1 is configured in such a manner that the oscillation frequency of the electromagnetic field will have a value of 27.12 MFIz with tolerances within the admitted ISM bands.

[0047] Then, the electromagnetic field applied to the flexible sheet products flexible that are being fed in the operating unit 5 can heat the chemical compound to a predetermined temperature.

[0048] The generator 1 1 may be selected from the group comprising power triodes, inverter-controlled power triodes, modular electronic power amplifiers, converter power amplifiers, possibly with of solid-state technology or a combination thereof.

[0049] The applicator 10 comprises at least one series of electrodes arranged in the drying chamber 6 and connected to a pair of terminals of the generator 1 1 .

[0050] In a first embodiment of the invention, not shown, the electrodes may comprise at least one pair of substantially parallel plates made of a conductive material having the function of an anode and a cathode respectively, for applying the radiofrequency electromagnetic field.

[0051] The plates may be placed below and above the feeding plane p at an adjustable distance, to selectively change the intensity of the electromagnetic field applied to the products during processing.

[0052] Alternatively, the electrodes may comprise first 12 and second series of transverse bars 13 made of a conductive material, which are connected to first and second terminals of the generator 1 1 respectively.

[0053] The electrodes of one series 12 are connected in parallel and have the function of a cathode, and the electrodes of the other series 13 are also connected in parallel and have the function of an anode.

[0054] The bars 12, 13 may be also placed at adjustable distances, to thereby adjust the electromagnetic field intensity, as described above concerning the plates.

[0055] For example, as shown in the figures, the bars of a series 12 may be secured to a longitudinal beam 14 that moves in a respective vertical direction by means of appropriate drive means 15 to move the first bars toward or away from the bars of the other series 13.

[0056] In a second embodiment of the invention, as best shown in FIGS. 4 and 5, the first 12 and second series 13 of bars may be placed below or above the feeding plane p of the conveyor 4.

[0057] Namely, the bars of the first series 12 may be longitudinally offset from and alternated to the bars of the second series 13 and each bar of the first series 12 may define a respective applicator 10, in combination with the bar of the second adjacent series 13.

[0058] In a third alternative embodiment, also not shown, the bars of one series 12 may be placed below the feeding plane p whereas the bars of the other series 13 may be placed above the feeding plane TT.

[0059] Like in the second embodiment, the bars of the first series 12, irrespective of whether they are placed below or above the feeding plane, will longitudinally offset from and alternated to the bars of the second series 13.

[0060] Also in this embodiment, each bar of the first series 12, placed either below or above, defines a respective applicator 10 with the bar of the second series 13, placed either above or below, and longitudinally offset from the first series.

[0061 ] Furthermore, the plant may comprise at least one control unit 16 which is configured to control the generator 1 1 and/or the applicator 10 and/or the feeding means 2 for complete drying of the chemical compound that has been previously deposited on at least one of the sides of the sheet product in the operating unit 5.

[0062] For example, the control unit 16 may be configured to set the speed of the feeding means 2 to a predetermined value ranging from 0.01 m/min to 30 m/min, preferably from 6 m/min to 15 m/min, or to change the electromagnetic field application time or intensity.

[0063] Furthermore, the control unit 16 may comprise a control algorithm installed therein and a memory portion. The latter may store data and information corresponding to a plurality of drying programs.

[0064] The software may be configured to select the most suitable drying program according to the characteristics of the sheet product to be treated.

[0065] In addition, as best shown in FIG. 1 , the control unit 16 may comprise interface means 17 adapted to be actuated by the operator for management thereof.

[0066] Advantageously, the operating unit 5 may comprise at least one air blowing means 18 and/or at least one suction means 19, in fluid communication from the drying chamber 6.

[0067] The blowing means 18 and suction means 19 may also be connected to the control unit 16 to adjust the drying temperature of the sheet products and further dry the chemical compound.

[0068] The blowing means 18 may be controlled to deliver hot air at a predetermined temperature, whereas the suction means may be configured to draw in the moisture removed during drying from the chamber 6.

[0069] Sensor means, not shown, may be further provided in the drying chamber 6 and connected to the control unit 16. [0070] The sensor means are configured to detect one or more physical and/or thermodynamic parameters of the operating unit 5, e.g. the temperature of the chamber and/or the temperature of the hides and/or the residual humidity in the chamber 6.

[0071] Furthermore, the control unit 16 may be configured to manually or automatically control at least one of a generator 1 1 , an applicator 10 and at least one feeding means 2 separately from or in combination with one another, possibly based on the physical and/or thermodynamic parameters as detected by the sensor means.

[0072] Thus, the change of the operating conditions of the aforementioned components by the control unit 16 will be quicker and more accurate as compared with existing plants.

[0073] The temperature of the sheet products as a result of the drying process carried out by the operating unit 5 is determined according to the environmental conditions of use of the plant 1 .

[0074] This feature affords immediate handling and stacking of the sheet products by an operator after drying and hence greatly reduces the overall processing times.

[0075] Also, this feature may avoid the use of cold air chillers, which have high costs and maintenance requirements, downstream from the operating unit.

[0076] The hides, skins and imitation leather that undergo processing by the above described plant have been found to be less prone to reduction of the useful leather area after treatment, and to even increase it, and to have their initial softness unaffected by the various treatment steps.

[0077] In the embodiment of the figures, the system 1 comprises a plurality of operating units 5A, 5B, 5C, one downstream from the other in the longitudinal direction of feed L.

[0078] Obviously, the number of units 5A, 5B, 5C may be also other than that as shown in the figures, without departure from the scope of the present invention. [0079] The units 5A, 5B, 5C may be connected by the above described feeding means 2 otherwise an operator may manually transfer the sheet products from one operating unit to the other at the end of the respective drying treatment.

[0080] Each of the units 5A, 5B, 5C comprises at least one respective generator 1 1 A, 1 1 B, 1 1 C, one respective applicator 10A, 10B, 10C and possibly one respective control unit 16A, 16B, 16C to generate an electromagnetic field of suitable intensity in the respective chamber 6A, 6B, 6C.

[0081] In addition, each of of operating units 5A, 5B, 5c may comprise respective blowing means 18A, 18B, 18C, and/or suction/drying means 19A, 19B, 19C and/or sensors, which are adapted to operate as described above for least one operating unit and are connected to the control unit 16A, 16B, 16C.

[0082] The plant of the invention is susceptible of a number of changes and variants, within the inventive concept as disclosed in the appended claims. All the details thereof may be replaced by other technically equivalent parts, and the materials may vary depending on different needs, without departure from the scope of the invention.

[0083] While the plant has been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Industrial Applicability

[0084] The present invention may find application in industry, because it can be produced on an industrial scale in tanning factories, particularly in surface treatment of hides, skins, imitation leather and derivatives.

Claims

1 . A drying plant (1 ) for drying pretreated flexible sheet products having at least one side with a layer of a chemical compound previously deposited thereon, which plant (1 ) comprises:

- feeding means (2) for feeding the sheet products (M) in a longitudinal feed direction (L);

- drying means (3) for drying the products as they are being fed, said drying means (3) have at least one operating unit (5) with a chamber (6) through which said feeding means (2) are designed to pass, and with at least one applicator (10) therein, which is connected to a respective generator (1 1 ) for application of an AC electromagnetic field in the RF range, to dry the chemical compound deposited on the products during processing;

- at least one control unit (16) for controlling said generator (1 1 ) and/or said applicator (10);

characterized in that said AC electromagnetic field has an oscillating frequency that ranges from 300 kHz to 300MHz and is preferably 27.12 MHz with tolerances within the admitted ISM bands, at least one air blowing means (18) for delivering hot air and/or at least one suction means (19) being provided in said chamber (6), said blowing means (18) being controlled to deliver hot air at a predetermined temperature and said suction means (19) being configured to draw in the moisture extracted during the drying processes from said chamber (6), said control unit (16) being configured to change the speed of said feeding means (2) or to change the electromagnetic field application time, sensor means being provided in said chamber (6) for detecting one or more physical and/or thermodynamic parameters of said at least one operating unit (5) such as the temperature and/or the residual humidity in the chamber and the temperature of the hides respectively and also for controlling said feeding means (2), said blowing means (18) and said suction means (19) separately from or in combination with one another and afford complete drying of the chemical compound layer.

2. Plant as claimed in claim 1 , characterized in that said electromagnetic field generator (1 1 ) is selected from the group comprising at least one of the power triodes, inverter-controlled power triodes, modular electronic power amplifiers, converter power amplifiers, amplifiers with solid- state technology or a combination thereof.

3. Plant as claimed in claim 1 , characterized in that said feeding means (2) comprise a belt or wire conveyor (4) with the belt or wires tensioned by end rollers and defining a feeding plane (TT) with their top section.

4. Plant as claimed in one or more of the 2 and 3, characterized in that said applicator (10) comprises at least one series of electrodes arranged in said chamber (6) and connected to a pair of terminals of said generator (1 1 ).

5. Plant as claimed in claim 4, characterized in that said electrodes comprise at least one pair of substantially parallel plates made of a conductive material having the function of an anode and a cathode respectively for application of said radiofrequency electromagnetic field, said plates being respectively placed below and above said feeding plane (TT) at adjustable distances therefrom.

6. Plant as claimed in claim 4, characterized in that said electrodes comprise first (12) and second series of transverse bars (13) made of a conductive material, which are connected to a first terminal and a second terminal respectively of said generator (1 1 ), said bars being adapted to be placed at adjustable distances from each other.

7. Plant as claimed in claim 6, characterized in that said first (12) and second series of bars (13) are placed below or above said conveyor (4), the bars of said first series (12) being longitudinally offset from and alternated to the bars of said second series (13).

8. Plant as claimed in claim 6, characterized in that the bars of one series (12) are placed below said feeding plane (TT) and the bars of the other series (13) are placed above said feeding plane (TT), the bars of at least said first series (12) being longitudinally offset from and alternated to the bars of said at least one second series (13).

9. Plant as claimed in one or more of the preceding claims, characterized in that it comprises a plurality of operating units (5A, 5B, 5C), one downstream from the other in said feed direction (L).

10. Plant as claimed in claim 9 characterized in that each of said operating units (5A, 5B, 5C) comprises at least one respective generator (1 1 A, 1 1 B, 1 1 C) and/or one respective applicator (10A, 10B, 10C) possibly connected to at least one control unit (16A, 16B, 16C) to generate an electromagnetic field of suitable intensity in the respective chamber (6A, 6B, 6C).