Roller leather finishing machine

Abstract

The invention relates to a spreading machine for roller leather finishing.

Description

Technical Field

[0001] The invention relates to a spreading machine for roller leather finishing. Background Art

[0002] Currently, two types of spreading machines for reverse roller natural leather finishing (i.e. spreading machines utilizing a carved spreading drum that rotates in the opposite direction relative to the direction of the underlying transport system) coexist:

[0003] The first type consists of spreading machines equipped with a rubber conveyor belt which performs a corresponding / contrasting function and at the same time serves as a means of transport for the hides output from the spreading area.

[0004] The second type consists of spreading machines equipped with counter / contrast rubber rollers, which require an automatic hide transport system in order to be able to convey the hides towards the outlet.

[0005] In the case of a detailed analysis of what occurs in the contact zone between the spreading roller and the underlying contrast and / or transport system, i.e. the leather is subjected to the mechanical action of contact with the spreading roller which, by friction, releases the finishing chemical product contained in the cavities created by the engraving on its surface, in the case of a first type of machine, what occurs is as follows:

[0006] a) A large contact surface is provided by the conveyor belt, which obviously has a contact area of ​​generally flat or flat shape. As a result, the specific pressure for a given load applied between the paving roller and the comparison roller will be relatively low.

[0007] b) Taking into account the necessarily inexact geometry of conveyor belts made of rubber / cloth, the shape of the contact area will be irregular; this shape will even depend on its operating conditions, i.e. on the required tension, which depends on the distance acting on the external idler rollers and the actual state of the conveyor belt surface and its level of flatness.

[0008] In contrast, in the case of the second type of machine, there will be:

[0009] a) The relative reduction in the contact surface between the paving roller and the comparison roller (relative to the previous case) is directly proportional to the diameter difference between the two rollers. Therefore, in a hypothetical comparison between a conveyor belt system and a rubber comparison roller system, where the loads applied between the paving roller and the rollers are equal, the specific pressure in the latter case will be significantly higher.

[0010] b) The geometry of the contact surface is much clearer due to the regular shape provided by the rubber roller; this makes it possible to obtain a very high control of the contrast pressure, ie the uniformity of the high pressure provided by the machine over the entire span of the table.

[0011] Whatever the solution adopted, the rubber layer must have a high thickness in order to ensure the required "squeezing" of the hide between the spreading roller and the contrast roller. In fact, hides of animal origin have relevant thickness differences between their different areas and corresponding to the different anatomical parts of the animal (in addition to the presence of natural wrinkles, folds, protrusions and local depressions). Therefore, in order to be able to ensure the most uniform possible contact between the spreading roller and the surface of the hide to be covered, when passing between the spreading roller and the contrast roller (whether roller or rubber conveyor belt), the hide must be able to "sink" easily in the rubber layer, which tracks and absorbs its shape on its bottom side and, on the other hand, provides a surface that is as flat as possible for the "flower" side, that is, the upper part that comes into contact with the spreading roller; this is because the leather surface must be spread and finished with a layer of chemical products (resins, pigments, etc.) as evenly as possible.

[0012] However, in the case of spreading machines equipped with rubber conveyor belts, one must rely on the fact of a very high rubber thickness in the contact area between the spreading rollers and the contrast conveyor belt, the purpose of which is to be able to effectively compensate for the natural thickness unevenness and surface irregularities of the leather and then put the machine in a state that can spread a layer of the finishing product as evenly as possible on its surface. The natural consequence is that the rubber conveyor belt (rubber / cloth) must have a high thickness (14-20 mm). This involves the following limitations:

[0013] a) A high circumferential speed difference between the area wrapped around the drive roller (of the relevant diameter) and the area immediately downstream of the paving area. In fact, the circumferential speed of the rubber section wrapped around the corresponding roller (also called the traction or drive roller, if motorized) is a direct function of the diameter of the traction roller (DT [m]), the thickness of the conveyor belt (ST [m]), and the rotation speed of the transport roller (VT [rpm]). Thus: Vperif1. Wrapped section [m / min] = (D + 2ST) × n × VT. In contrast, the circumferential speed of the horizontal branch is proportional only to the diameter of the corresponding roller (DT [m]) and its rotation speed VT [rpm]. Thus: Vperif2. Horizontal branch [m / min] = (DT × n × VT).

[0014] b) It is necessary to use drive (traction) rollers which have a relatively large diameter and then a large radius of curvature, around which the thickness of the conveyor belt will be wound without damaging it due to fatigue stresses.

[0015] Thus, in case a), there will be a situation where the (front) part of the hide exiting the spreading area (where it is anchored to the conveyor belt travelling at speed Vperif1) is subjected to an immediate deceleration after leaving where it travels at speed Vperif2, and then, since the front part of the hide is not as elastic as the rubber spread on it, it will tend to become shrunken and rise from the conveyor belt, by forming a wave with a more relevant range, the greater the difference between the two speeds, and therefore the greater the difference between the two diameters. The range / severity of the wave will ultimately be directly proportional to the thickness of the wrapped conveyor belt.

[0016] In case b), on the contrary, there will be a need to equip the machine with a hide separating mechanism (also called a hide separating roller conveyor).

[0017] The aforementioned hide separation device / roller conveyor represents an additional element subject to constant maintenance and a potential source of dangerous leather blockages, which, under certain conditions, can snag and / or lock the hides, leading to total or partial destruction of the hide and associated costly machine downtimes. Moreover, due to the continuous contact of this device with the chemical products applied by the spreading rollers to the leather surface (the flower), it becomes dirty, inevitably contaminating its underside (the flesh) during the subsequent leather processing, thus causing economic losses due to the waste of the contaminated parts.

[0018] In contrast, in the case of a paving machine equipped with a contrast / corresponding rubber roller, the presence of a contrast / corresponding rubber roller of the relevant diameter and without a conveyor belt involves the need to equip the machine with:

[0019] a) An effective leather separation mechanism (leather separation roller conveyor), which must essentially rest on the surface of the rubber roller, leaving as little gap as possible. However, compared to similar leather separation roller conveyors with rubber belts, the leather separation roller conveyor acting on the corresponding rubber roller must be more precise, given the greater difficulty in effectively separating the leather. The leather tends to adhere to the surface during delivery through the "vacuum effect", which is kept appropriately moist by a cleaning system equipped with brushes and scrapers.

[0020] b) An independent transport system which receives the hides from a separate roller conveyor, keeps them properly spread, and transfers them to an adjacent machine or drying cabinet.

[0021] Therefore, in case a), the hide separation device / roller conveyor represents an element subject to constant maintenance and a potential source of dangerous blockage of the hides, which, under certain conditions, can snag and / or lock the hides, leading to total or partial destruction of the hides and associated expensive machine downtimes. Moreover, due to the continuous contact of this device with the chemical products applied to the hide surface (flower) by the spreading rollers, it becomes dirty, inevitably contaminating its underside (flesh) during the subsequent processing of the hides, thus causing economic losses due to the waste of the contaminated parts.

[0022] In the case of b), it is the additional equipment (with multiple forked belts or a single belt) that must be used to collect the hides to which a layer of chemical product (paint) has previously been applied. This is a new, semi-liquid product that is easily transferred by contact and, similar to the separate roller conveyors described, also contaminates the movable elements of the independent transport system (belts), which in turn contaminates other hides, resulting in economic losses due to waste. If, for technical reasons, a spreading machine is placed in line or in series with another equivalent and / or similar machine without the intervening drying system, the inclusion of additional machine parts forming the conveyor supply system will further exacerbate the problems described, and contamination by the chemical product will spread from one machine to another with a multiplier effect.

[0023] For example, machines of known technology are described in the following documents.

[0024] CN107961945A belongs to the technical field of roller leather coating and roller spreading devices, and particularly relates to a reverse roller spreading machine for sheepskin garments.

[0025] CN105396748A relates to the technical field of roller coating devices, and in particular describes a roller spreading machine with a high soft leather throughput rate.

[0026] CN108774653A belongs to the field of leather processing technology, and particularly relates to a machine for pre-coating leather with a water-based coating agent, a device for leather surface processing, and related processes. Summary of the Invention

[0027] The object of the present invention is to solve the problems existing in the prior art by providing a machine as defined in claim 1 .

[0028] Additional features of the invention are defined in the respective dependent claims.

[0029] In order to do this, a system has been devised which comprises a soft rubber counter roller which transmits the motion to a still soft rubber transport / conveyor belt.

[0030] The transport system of the rubber conveyor belt is equipped with idler rollers that perform the function of leather separating rollers.

[0031] Furthermore, the system can advantageously be provided with a movable idler roller positioned between the drive roller serving as contrast and the hide-separating idler roller, so as to be able to vary the output angle of the hides from the spreading area.

[0032] This combination allows for high mechanical results without losing the uniformity of pressure on the leather to be spread, typical of machines equipped with rubber counter rollers, and, on the contrary, a reduction in pressure when necessary, thanks to the increase in contact surface, typical of machines equipped with a conveyor belt, which serves both as a contrast and as a means of transport. This increase in contact surface, and consequently a reduction in specific pressure, is achieved by raising a movable roller positioned against the underside of the conveyor belt; this increase is necessary when spreading chemical products with very high viscosities (mixtures of resins and sometimes pigments), such as with plasters and for various properties.

[0033] The combination represented by a conveyor belt of reduced thickness wrapped around a rubber counter roller allows the behavior of a rubber conveyor belt of related thickness to be simulated, by causing the hide to "sink" in the rubber thickness resulting from the sum of the thickness of the conveyor belt plus the thickness of the counter roller rubber. The thickness irregularities of the hide are then compensated for, and the chemical product layer can be spread evenly over the surface.

[0034] The use of a transport rubber belt with reduced thickness further prevents ripples in the leathers exiting the spreading area due to different circumferential speeds between the rubber sections wound onto the respective rollers. This circumferential speed is proportional to the total roller diameter (DT [m]), the belt thickness (ST [m]), and the transport roller's rotational speed (VT [rpm]). Thus: Vperif1. Wrapped section [m / min] = (D + 2ST) × n × VT. In contrast, the circumferential speed of the horizontal section is proportional only to the corresponding roller's diameter DT [m] and its rotational speed VT [rpm]. Thus: Vperif2. Horizontal section [m / min] = (DT × n × VT).

[0035] In fact, the (front) part of the hide that exits the spreading area (where it is anchored to the conveyor belt traveling at speed Vperif.1) undergoes a deceleration after leaving it, where it travels at speed Vperif.2, and since the front part of the hide is not as elastic as the rubber spread on it, it will tend to become shrunken and rise from the conveyor belt, forming a wave with a more relevant range, the greater the difference between the two speeds, and therefore the greater the difference between the two diameters. The range / severity of the wave will ultimately be proportional to the thickness of the wrapped conveyor belt.

[0036] Taking into account the use of rubber conveyor belts having a thickness of at least about 14 mm in currently existing machines, by using in their place a conveyor belt with a thickness equal to / less than 8 mm, the difference between the two peripheral speeds goes from about 7.5% to a value equal to / less than 4%.

[0037] However, results with values ​​of 4% or less are quite acceptable since it is easy to compensate by pulling the remaining (rear) part of the hide in the opposite direction while it is kept under pressure between the spreading rollers and the conveyor belt rotating in the opposite (reverse) direction.

[0038] Excessive waviness of the leather in existing machines can easily lead to surface defects in the new finish (paint) layer just applied by the spreading rollers, thus affecting the quality of the finished product.

[0039] The use of a transport belt with reduced thickness allows the use of even leather-separating idler rollers with reduced diameters. The use of idler rollers with reduced diameters significantly facilitates the final separation of the leather from the rubber conveyor belt (for transfer to another machine or drying cabinet), and it allows the process to be carried out without mechanical leather-separating systems (known as roller conveyors), which become dirty through continuous contact with chemical products applied to the leather surface (flower) by the spreading rollers, inevitably contaminating even the underside (flesh) during subsequent leather processing. Furthermore, these leather-separating devices / roller conveyors represent additional components subject to constant maintenance and a potential source of dangerous leather blockages. Under certain conditions, the leather can become hooked and / or locked, leading to total or partial destruction of the leather and associated costly machine downtime. This problem affects both machines equipped with transport belts of greater thickness and, even more severely, machines equipped with corresponding rubber rollers, which must be equipped with very powerful leather-separating roller conveyors in order to separate the leather and subsequently transfer it to a separate transport system.

[0040] Other advantages, together with the features and modes of use of the invention, will become apparent from the following detailed description of the preferred embodiment thereof, which is shown by way of illustration and not for purposes of limitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the following description reference will be made to the figures shown in the accompanying drawings, in which:

[0042] · Figure 1 is a schematic overall view of the machine according to the invention in a first operating configuration;

[0043] · Figure 2 is a detailed view of the contact area between the paving roller and the underlying contrast and / or transport system in a first operating state;

[0044] · Figure 3 is an overall schematic diagram of the machine according to the present invention in a second operating state;

[0045] · Figure 4 is a detailed view of the contact area between the paving roller and the underlying contrast and / or transport system in a second operating state;

[0046] · Figure 5 Here is a detailed view of the leather separation roller;

[0047] · Figure 6 is an overall view of the output portion of the machine; and

[0048] · Figure 7 This is an overall view of the output section of the machine, with the rubber conveyor belt made transparent in order to show a possible configuration of the leather separating rollers. DETAILED DESCRIPTION

[0049] Hereinafter, the present invention will be described with reference to the above-mentioned drawings.

[0050] In particular, by way of example and according to the schematic diagram, Figure 1 A machine according to the invention is shown, at least in the part relevant to the invention.

[0051] Figure 1 The machine 1 shown is intended for reverse finishing of leather.

[0052] It comprises a traction drum 2 and a carved paving drum 3 .

[0053] Furthermore, the machine 1 comprises a rubber conveyor belt 4 wound between a traction drum 2 (acting as a driving roller) and at least one idler roller 5, 8, 9. The traction drum 2 in turn comprises a rubber layer 6.

[0054] The machine is configured so that, in every operating configuration, the conveying surface 7 of the rubber conveyor belt 4 is tangential to the engraved paving drum 3 at a point of tangency P.

[0055] Advantageously, one of the idler rollers 5 , 8 , 9 provided is a leather separating roller 5 and, according to the invention, such leather separating roller 5 has a diameter DS comprised between 10 mm and 80 mm.

[0056] The advantages of a hide separating roller having a reduced diameter DS have been discussed previously.

[0057] According to an embodiment of the present invention, the leather separating roller 5 has a diameter DS of less than 60 mm.

[0058] Figure 5 A detail of the leather separating roller 5 is shown.

[0059] According to a further embodiment, the leather separating roller 5 may comprise a plurality of rollers arranged axially, having their axes according to the transverse direction TR of the rubber conveyor belt 4. Figure 6 and Figure 7 This possible construction can be seen well in Figure 7 middle, Figure 7 The output section of the machine according to the invention is shown. In particular Figure 7 In the case where the rubber conveyor belt 4 is made transparent, the leather separating roller 5 is made visible, which as a whole comprises a plurality of rollers arranged axially with an axis according to the transverse direction TR of the rubber conveyor belt 4 so as to cover the entire width of the rubber conveyor belt 4.

[0060] According to the invention, the pulling drum 2 has an outer diameter DT in the range between 200 mm and 250 mm, whereas the paving drum has a diameter DI in the range between 140 mm and 190 mm.

[0061] However, the diameters of the two rollers are preferably selected so that their ratio DT / DI is less than 1.5. This involves a series of constructive advantages.

[0062] According to a preferred embodiment, the rubber layer 6 has a thickness ranging between 10 mm and 30 mm. Its hardness can be comprised between 15 Shore and 35 Shore.

[0063] Advantageously, even rubber conveyor belts have a hardness that can be measured in about 20-25 Shore.

[0064] The rubber conveyor belt 4 has a thickness ST of less than 10 mm, preferably less than 8 mm.

[0065] The reduced thickness ST of the conveyor belt, together with the reduced diameter DS of the hide separating roller, contributes to obtaining an effective hide separating function without defects.

[0066] Reference Figure 2 , which shows an enlarged view of the contact area between the paving roller and the underlying contrast and / or transport system in a first operating state.

[0067] In this first operating state, the machine is arranged so that the point of tangency P between the paving drum 3 and the conveying surface 7 of the rubber conveyor belt 4 lies exactly on the line L connecting the centres of the traction drum 2 and the engraved paving drum 3 .

[0068] In this first operating state, the point of tangency P is then located precisely at the traction drum 2 , thus ensuring a firm and effective comparison with the pressure exerted by the paving drum 3 .

[0069] Advantageously, as shown in the figures, the two rollers may be offset relative to the vertical line V, so that the line L connecting the respective centers does not correspond exactly to the vertical line V. In the case of a vertical line it is meant a line orthogonal to the ideal horizontal plane of the machine.

[0070] It is clear that this offset facilitates the adjustment of the machine in order to bring it from one operating state to another.

[0071] As from Figure 3 and Figure 4 As is evident in the drawing, the different operating states are defined in dependence on the distance D between the drive roller 2 and the rubber conveyor belt 4, which is measured along the direction connecting the point of tangency and the engraved paving drum 3 with the center of the rubber conveyor belt 4 and the engraved paving drum 3.

[0072] Two different configurations cover the distance D in the range of 0 and 5 mm.

[0073] In order to vary this distance D, an adjustment mechanism is provided in order to allow a corresponding translation of the point of tangency P according to the transport direction T, in the longitudinal direction of the rubber conveyor belt 4 .

[0074] like Figure 1 and Figure 3 As shown, according to a possible embodiment, the adjustment mechanism comprises an intermediate idler wheel 8 which is arranged between the drive roller 2 and the leather separating roller 5 .

[0075] The axis of rotation of the intermediate idler roller 8 is capable of translation along a vertical line V between two predefined positions.

[0076] The translation along the vertical line V of the intermediate idler roller 8 changes the inclination of the conveyor belt 4 along the transport direction T in the downstream section of the contrasting region with the engraved paving drum 3 .

[0077] The adjustment mechanism may further provide a system for translating the axis of rotation of the engraved paving drum 3 , still along the vertical line V.

[0078] Translating the axis of rotation of the engraved paving drum 3 along the vertical line V has the effect of increasing (or decreasing) the distance between the two drums 2 , 3 .

[0079] In a particularly preferred embodiment of the invention, the adjustment mechanism provides the possibility of translating both the intermediate idler roller 8 and the engraved paving drum 3 according to the vertical direction V simultaneously.

[0080] Figure 4 Representing a second operating state of the machine 1 , the conveyor belt 4 is caused to rise even more at the contact area between the rollers and thus leaves a gap D between the conveyor belt and the drive roller.

[0081] like Figure 4The translation of the axis of rotation of the engraved paving drum 3 along the vertical line V in the context of the vertical line V results in the tangent point P being moved upwards by translating itself in the longitudinal direction of the rubber conveyor belt 4 according to the transport direction T, as indicated by the arrow F in FIG. Figure 2 The operating status moves.

[0082] In this second operating state, the tangent point P falls in a point where there is air below the rubber conveyor belt 4 (thickness D is in the range of 0 to 5 mm). Obviously, in this point, the paving drum 3 will be subjected to a gentler and more flexible contrast only by the rubber conveyor belt 3.

[0083] The use of such an apparatus involves advantages from at least two perspectives:

[0084] "Functional" advantages: the machine includes the advantages of both types of roller pavers currently on the market (with rubber conveyor belts and rubber rollers) by allowing to broaden the range of implementable items;

[0085] • "Management" advantage: by using a machine that allows combining two different types of machines, it allows managing production in a more flexible and optimized way.

[0086] The invention has been described so far with reference to preferred embodiments. This means that each of the technical solutions implemented in the preferred embodiments described herein by way of example can be advantageously combined with other technical solutions in different ways relative to what is described in order to create additional embodiments belonging to the same inventive core but all falling within the scope of protection of the claims reported below.

Claims

1. A reverse roller leather finishing machine (1) comprising a traction roller (2) and an engraved spreading roller (3), the traction roller (2) serving as a drive roller for a rubber conveyor belt (4) wound between the drive roller and at least one idler roller (5, 8) and having a conveying surface (7), wherein the conveying surface (7) of the rubber conveyor belt (4) is tangent to the engraved paving drum (3) at a tangent point (P), It is characterized by The traction roller (2) comprises a rubber layer (6), and in that the at least one idler roller (5, 8) comprises a leather separating roller (5) having a diameter in the range of 10 mm and 80 mm, and the rubber conveyor belt (4) has a thickness of less than 10 mm, and The traction drum (2) and the paving drum (3) are offset relative to a vertical line (V), so that a line (L) connecting the center of the traction drum (2) and the center of the paving drum (3) does not correspond to the vertical line (V).

2. The machine according to claim 1, wherein the rubber layer (6) has a hardness ranging from 15 Shore to 35 Shore.

3. Machine according to claim 1 or 2, wherein the rubber layer (6) has a thickness ranging between 10 mm and 30 mm.

4. The machine according to claim 1 or 2, wherein the rubber conveyor belt (4) has a hardness in the range of 20 Shore and 25 Shore.

5. Machine according to claim 1 or 2, wherein the rubber conveyor belt (4) has a thickness of less than 8 mm.

6. The machine according to claim 1 or 2, comprises a mechanism for adjusting the distance (D) between the driving roller (2) and the rubber conveyor belt (4), the distance being measured along a direction connecting a point of tangency (P) of the engraved spreading roller (3) with the center of the rubber conveyor belt (4) and the engraved spreading roller (3), the mechanism being configured to translate the point of tangency (P) accordingly along the longitudinal direction of the rubber conveyor belt (4), the mechanism comprising an intermediate idler roller (8) arranged between the driving roller and the leather separating roller (5), the axis of rotation of the intermediate idler roller (8) tending to translate between two predefined positions along a direction (V) substantially orthogonal to the conveying surface of the rubber conveyor belt.

7. Machine according to claim 6, wherein said distance (D) is comprised between 0 mm and 5 mm.

8. Machine according to claim 6, wherein the means for adjusting the distance (D) between the drive roller (2) and the rubber conveyor belt (4) include a system for translating the axis of rotation of the engraved paving drum (3) along the direction (V).

9. Machine according to claim 1 or 2, wherein the leather separating rollers (5) comprise a plurality of rollers arranged in an axial direction, having their axes according to the transverse direction (T) of the rubber conveyor belt (4).

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