MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS

Abstract

 The present document concerns a machine for continuous dyeing of leather items, wherein said leather items are passed through two opposite rollers (1, 2) rotating about mutually parallel rotation axes perpendicular with respect to the direction of forward motion of the leather item (P), in "synchronous" mode, i.e. with the same direction as that of forward motion of the leather item. Such a machine being characterised in that the two rollers (1,2) consist of two cylinders the outer surface of which is engraved/knurled, with the formation of pits or other cavities suitable for transferring a predetermined amount of a film (9, 10) of liquid dye product at the same time on the two surfaces of the leather aforementioned product (P1).

Description

[0001] The present finding concerns a machine for continuous dyeing of leather items, according to the general part of claim 1.

[0002] It is known that leather items after tanning cannot yet be marketed, even if they are already imputrescible and equipped with hydrothermal stability; in practice, the characteristics of their appearance, such as the colour, the brilliance, the grain fineness, etc., must be modified by subjecting them to other chemical treatments, mainly to dyeing.

[0003] In the current state of the art, a first method for dyeing leather items is carried out by using drums containing a mixture of water and dye.

[0004] By the leather items remaining for a few hours in the rotary drum, the dye transfers from the water to the leather item, thus carrying out homogeneous dyeing of the leather items themselves.

[0005] In order to carry out the dyeing operation in a drum, substantial amounts of water are necessary, usually around 250% by weight with respect to the initial weight of the leather items being processed and an average processing time of 4/5 hours is required for each load, such a value being irrespective of the amount of leather items to be dyed for each load.

[0006] Consequently, therefore, to dye even one or very many leather items, discounting the time necessary to load and unload the leather items in the drum and the time taken to supply and discharge the water in the different processing steps, the dyeing time always remains the same.

[0007] Therefore, it is very clear that it is very expensive to dye medium/small batches of leather items due to the substantial execution time and the enormous consumption of water; for example, as seen earlier, to dye 1000 kg of leather items roughly 2.500 litres of water are needed, which must be disposed of in the purifier.

[0008] Again in the state of the art, as an alternative to dyeing in a drum, a so-called "immersion" dyeing process is used, based on the concept of impregnation and subsequent squeezing of the leather items that, transported sandwiched between two sliding belts, are firstly immersed in a dye solution, contained in the horizontal tank and then are squeezed by passing between two cylinders arranged at the outlet on said tank.

[0009] This second process is valid since it allows continuous transportation of leather items during the entire dyeing operation, with low water consumption with respect to dyeing in drums, but, at the same time, it also has some limitations and drawbacks.

[0010] Indeed, with immersion dyeing the dye is essentially applied onto the leather items, but it is not possible to control the amount of dye deposited on the leather item; all of this becomes even more relevant when the dye must be expressly of the so-called "surface dye" type, in that it only engages the outer surfaces thereof and not the entire section of the leather item.

[0011] Moreover, neither dyeing in a drum, nor immersion dyeing manages to dye the two surfaces of the leather items with mutually different dyes.

[0012] Document US 3762190 describes a machine for dyeing leather items, in which they are passed through two opposite rollers rotating about mutually parallel rotation axes that are perpendicular with respect to the direction of forward motion of the leather item.

[0013] In such a machine it is provided for it to be possible for the two rollers to have elevations of the spiral-shaped type or, alternatively, bands, brushes, pegs or pins on them. Such elements have the purpose of stretching out the leather items subjected to dyeing, reducing the possibility of creases or rough areas forming on the leather items themselves. In such a device, however, it is not possible to precisely control the amount of dye deposited on the two opposite surfaces of the leather items.

[0014] The aim of the present finding is to make a machine for dyeing leather items that is free of the drawbacks of similar known machines.

[0015] Specifically, the aim of the finding is to make a machine for continuous dyeing of leather items that makes it possible to control, for every processing operation, the amount of dye deposited at the same time on the two surfaces of the leather item.

[0016] A further aim of the finding is to make a machine for dyeing leather items that, while substantially reducing water consumption, still transfers all of the dye onto the leather item.

[0017] A further aim of the finding is to make a machine for dyeing leather items that is simple to build, easy to use and has low bulk.

[0018] Such aims are obtained by making a machine for dyeing leather items that is characterised in that the leather item is passed between two opposite engraved rollers, rotating in the same direction as that of forward motion of the leather items, which take care of depositing dye on the two surfaces of the aforementioned leather item.

[0019] Specifically, the two rollers, rotating about mutually parallel rotation axes that are perpendicular with respect to the direction of forward motion of the leather item, are provided on their surface with an incision, which allows a predetermined amount of dyeing liquid to be held that, in pressing contact with the leather item, is transferred and is absorbed by the aforementioned leather item, to carry out the dyeing operation.

[0020] The finding will be defined better through the description of a possible embodiment thereof, given as a non-limiting example, with the help of the attached tables of drawings, where:

• fig. 1 (table I) represents a schematic view of operation of the machine according to the finding;
• fig. 2 represents a detailed view of the dyeing area;
• fig. 3 (table II) represents an overall view of the machine according to the finding, with a circuit of the dyeing liquid;
• fig. 4 (table III) represents the overall view of the machine according to the finding, with two circuits of the cooling liquid.

[0021] As can be seen in fig. 1, the dyeing machine, indicated with reference numeral 100, consists of two engraved rollers, arranged opposite and parallel to one another 1 and 2, between which the leather item "P" slides, pulled forwards by the rotation in "synchronous" mode (V1, V2), i.e. in the same direction as the direction of forward motion of the leather item "P".

[0022] Each of the two rollers has the engraved outer surface, 3 and 4 respectively, licked with a dyeing product 5 and 6, contained in a tank 7 and 8, so that, when said surfaces 3 and 4 come into contact with the leather item "P" in the intermediate processing step, the transfer of a liquid film 9 and 10 of dyeing product 5 and 6 onto two corresponding surfaces of the leather item 11 and 12 takes place, so that, through the effect of the compression to which the leather item must be subjected to ensure it is pulled, the dyeing product is deposited on the surface or penetrates inside the fibres, respectively carrying out the "surface dyeing" or the "deep dyeing" of the aforementioned leather item (indicated with "P1" after the dyeing step), as a function of the type of engraving that determines the amount thereof.

[0023] In a preferred embodiment, the rollers 1 and 2 have the outer surface 3 or 4 suitably engraved/knurled, with the formation of pits or other cavities suitable for transferring the liquid film of dyeing product onto the surfaces of the leather items; in practice, the type and depth of the engraving/knurls on the surface of the rollers determine the amount of dyeing liquid film on the surface of the leather items, substantially as a function of their size in the diametral direction. Moreover, at least one of the two rollers consists of a metal drum coated with a layer of highly deformable material, which makes it possible to make regular contact between roller and leather item, also in the presence of non-uniform thicknesses and on surfaces 11 and 12 that have protruding areas and recesses. The other opposite roller can be entirely made from metal, with the surface suitably engraved, to transfer the liquid product onto the surface of the leather item in contact with the roller itself.

[0024] Constructively, the tank 7 of the upper roller 1 is obtained through a doctor blade 13, which has the function of scraping the excess amount from the engraved surface of dyeing liquid film 9, whereas the tank 8 consists of a tray 14, where the lower roller 2 partially immerses, associated with a doctor blade 15, which scrapes the excess liquid product from the surface 10.

[0025] Advantageously, the two rollers 1 and 2 rotate at variable speed and are mounted on mobile supports (not represented) that adjust the crushing pressure on the leather item "P", so as to be able to ensure uniform contact and obtain optimal dyeing of every type of leather item treated.

[0026] More in general, as can be seen in fig. 3, the machine 100 for dyeing leather items "P" mounts a carousel 20, adapted for supporting a plurality of interchangeable upper rollers 1 with different engravings as a function of the amount of dye to be transferred onto the surfaces of the leather items and comprises a closed recirculation circuit of the dyeing product, indicated with reference numeral 30, which foresees a collection tray 31, coupled with the upper roller 1 and an overflow device 32, coupled with the lower roller 2, for recovering the excess dyeing product, which is collected in a tank 33 from where, through a pump 34, it is sent back to the tanks 7 and 8.

[0027] Another embodiment of the machine, as can be seen in fig. 4, not for restrictive purposes, foresees two closed recirculation circuits of the dye that are independent from one another 30.1 and 30.2, one for the upper roller 1 and the other for the lower roller 2 consisting of the tray 31 of the roller 1 and the tray 14 of the roller 2 for recovering the excess dyeing products that are collected in the tanks 33.1 and 33.2 from which, through two pumps 34.1 and 34.2, they are sent independently back to the tanks 7, 8.

[0028] The machine is completed upstream with an external apparatus 40, to facilitate the introduction of the leather item "P" that, as a non-limiting example, consists of two opposite belts, which stretch out and transport the leather item up to the narrow area of the two rollers 1 and 2.

[0029] Downstream of the two rollers 1 and 2, in the case of sticky dyes, it may be necessary to use two small rollers 50, to detach the leather items that may have become stuck to one of the aforementioned two rollers 1 and 2.

[0030] Finally, a conveyor belt 60 takes away the processed leather items "P1".

[0031] The finding thus conceived can undergo modifications and variants and all of the details thereof can be replaced with technically equivalent elements, provided that it is all encompassed by the inventive concept defined by the following claims.

Claims

1. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, wherein said leather items are passed through two opposite rollers (1, 2) rotating about mutually parallel rotation axes perpendicular with respect to the direction of forward motion of the leather item (P), in "synchronous" mode, i.e. with the same direction as that of forward motion of the leather item, said machine being characterised in that the two rollers (1, 2) consist of two cylinders where the outer surface is engraved/knurled, with the formation of pits or other cavities suitable for transferring a predetermined amount of a film (9, 10) of liquid dye product simultaneously on two surfaces (11, 12) of a leather goods (P1).

2. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to claim 1, characterised in that the two rollers (1, 2) are mutually superimposed, consisting of an upper roller (1) and a lower roller (2).

3. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to claims 1 or 2, characterised in that at least one of the two rollers (1, 2) has the outer part coated with a highly deformable material, that allows a regular contact to be made between roller and leather item even with leather items of uneven thickness and with surfaces (11, 12) that have ridges and valleys.

4. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to one or more of the previous claims, characterised in that the engravings/knurls, with the formation of pits or other cavities on the outer surface of the rollers (1, 2), present a size in the diametral direction that depends on the "surface" or "deep" dyeing level to be produced on the surfaces (11, 12) of the leather (P).

5. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to one or more of the previous claims, characterised in that the two rollers (1, 2) are able to rotate a variable speed and are mounted on mobile supports, to adjust the squeezing pressure on the leather item (P).

6. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to claim 2, characterised in that it foresees a first tank (7) containing the dyeing product (5), licked by the upper roller (1), consisting on a doctor blade (13), which regulates the amount of liquid film (9) on the surface of the engraved cylinder.

7. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to claim 2, characterised in that it foresees a second tank (8) containing the dyeing product (6), licked by the lower roller (2), consisting on a tray (14), where the lower roller (2) is partially dipped, associated with a doctor blade (15), which regulates the amount of liquid film (10) deposited on the surface of the engraved cylinder.

8. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to claim 2, characterised in that it mounts a carousel (20), which supports a plurality of interchangeable upper rollers (1).

9. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to claim 2, characterised in that it foresees a closed recirculation circuit (30) of the dyeing product, consisting of a collection tray (31), coupled with the upper roller (1) and with an overflow device (32), coupled with the lower roller (2), for recovering the excess dyeing product, which is collected in a tank (33) from where, through a pump (34), it is sent back to the two tanks (7, 8).

10. MACHINE FOR CONTINUOUS DYEING OF LEATHER ITEMS, according to claim 2, characterised in that it foresees two closed recirculation circuits (30.1 and 30.2) of the dyeing products that are independent for each cylinder, consisting of two mutually independent collection trays (31 and 14), respectively coupled with the upper roller (1) and with the lower roller (2) for recovering the excess dyeing products, which are collected in the tanks (33.1, 33.2) from where, through two pumps (34.1, 34.2), they are sent back independently to the tanks (7, 8).

Drawing