EP0138263B1 - Hides treating process and unit for removing wool therefrom and constituent means - Google Patents

Description

The invention relates to a method of treating the skins of sheep (or other similar species) with a view to separating the wool therefrom; it extends to a processing unit intended for the implementation of this process, as well as to new means constituting this unit.

The fellmongering industries aim to treat the skin to produce the one hand, bare skin (sometimes referred to as "pelts ^p) for the manufacture of leather tannery in the other, called the wool to undergo different treatments until spinning.

Two essential types of process are currently implemented in these stripping industries; these processes consist, in a first phase, of preparing the skins by quenching and sabering operations, then, in a second phase of ensuring an attack on the root of the hairs of the wool in order to weaken their resistance, finally, in a last phase, to execute the actual operation of stripping the skins (also known as "peeling") consisting in plucking the hair from the skin.

The preparation operations common to the two processes comprise a first quenching, carried out by stacking the skins one above the other and by immersing these stacks in quenching tanks, then a saberage operation, intended to remove the impurities contained in wool, finally, a second quenching, analogous to the first. These operations last approximately 48 hours.

In one of the older methods, the second phase is carried out by a bacteriological fermentation process, the average duration of which is around 4 days. Under these conditions, taking into account the preparation operations, the duration of a stripping cycle, in this type of process, is of the order of a week and this duration is one of the essential drawbacks of this process.

In the other process, the second phase consists of impregnating the flesh side of the skins with a solution based on sodium sulfide and stacking the skins on pallets, leaving them to remain for about 8 to 12 hours in order to allow diffusion of the sulfide to the flower side. This sulfide process thus has the advantage of significantly shortening the duration of the stripping cycle.

However, the sulfide process, as currently implemented, has several serious drawbacks. In the first place, the complete cycle which lasts about 60 hours remains long and it would be highly desirable to shorten it in order to make the materials more profitable and to reduce the necessary storage areas: in addition the quality of the skins and wools obtained is generally poor and very irregular from one skin to another. Indeed, during the stay of the skins in the form of stacking on the pallets, the wool is inevitably soiled by the sulphide which causes a more or less accentuated degradation of the latter; moreover, the skins situated above each stack are subjected to a sulphide action of shorter duration than the skins situated below: the skins above are in fact the last placed on the stack and the first withdrawn. Consequently, these skins (known as white skins) are difficult to strip off due to a too superficial action of the sulphide, while the skins below (known as black skins) have undergone too great an attack, leading to risks of degradation of the wool and a blackening of some of their areas, which then reduces the quality of the leathers made from them.

The present invention proposes to indicate a treatment process using sulphide as the known process but free from the abovementioned defects of this process.

Its main purpose is to indicate a process whose implementation time is considerably shortened and which makes it possible to produce skins and wools of good quality, uniform for all skins.

Another object of the invention is to reduce the personnel necessary for a given production, while making the work much less arduous for men.

Another objective is to provide a processing unit allowing an implementation of said process under the best conditions of profitability.

• a) tremper les peaux dans un bain aqueux plusieurs fois renouvelé, en disposant lesdites peaux en empilage vertical ou incliné, de façon que chaque peau présente une position verticale ou inclinée par rapport à l'horizontale,
• b) effectuer sur le côté fleur des peaux un sabrage connu en soi, adapté pour débarrasser celles-ci des impuretés contenues dans la laine,
• c) effectuer sur le côté chair des peaux un écharnage connu en soi, adapté pour débarrasser celles-ci des fragments de chairs et graisses,
• d) imprégner le côté chair des peaux au moyen d'une solution aqueuse de sulfure, de concentration sensiblement comprise entre 100 g/I et 300 g/1,
• e) disposer les peaux séparément les unes aux autres dans une atmosphère saturée en humidité à une température sensiblement comprise entre 20° et 35°C, pendant un laps de temps sensiblement compris entre 2 heures et 5 heures,
• f) effectuer sur les peaux une opération de délainage connue en soi, adaptée pour en séparer la laine.
• g) et rincer immédiatement la laine ainsi séparée de façon à en éliminer les traces de sulfure.

To this end, the treatment method according to the invention consists in combining the following successive operations:

• a) soaking the skins in an aqueous bath several times renewed, placing said skins in a vertical or inclined stack, so that each skin has a vertical or inclined position relative to the horizontal,
• b) carrying out a sabering known in itself on the flower side of the skins, adapted to rid them of the impurities contained in the wool,
• c) carry out a fleshing known in itself on the skin side, suitable for ridding the skin of fragments of flesh and fat,
• d) impregnating the flesh side of the skins by means of an aqueous solution of sulphide, of concentration substantially between 100 g / l and 300 g / l
• e) placing the skins separately from one another in an atmosphere saturated with humidity at a temperature substantially between 20 ° and 35 ° C, for a period of time substantially between 2 hours and 5 hours,
• f) carrying out a skinning operation known per se, adapted to separate the wool from it.
• g) and immediately rinse the wool thus separated so as to remove traces of sulphide therefrom.

• par le mode de mise en oeuvre de l'opération de trempe (a)
• par l'exécution d'une opération (c) d'écharnage (connue en soi en mégisserie) avant le traitement au sulfure,
• par la nature de l'opération (e) pendant laquelle s'effectue la diffusion du sulfure depuis le côté chair jusqu'au côté fleur en vue d'assurer une attaque de la racine des poils de la laine ;
• par l'exécution d'un rinçage immédiat de la laine après l'opération de délainage.

The process of the invention is therefore essentially different from the prior process mentioned above:

• by the mode of implementation of the quenching operation (a)
• by performing a flaking operation (c) (known per se in tanning) before the sulphide treatment,
• by the nature of the operation (e) during which the diffusion of the sulphide takes place from the flesh side to the flower side in order to ensure an attack on the root of the hairs of the wool;
• by performing an immediate rinse of the wool after the stripping operation.

As will be better understood below, the combination of these original characteristics leads, at the same time, to a noticeable reduction in the duration of the stripping cycles (duration less than 36 hours), and to a very improved and constant quality, as well skins than wools produced.

The quenching operation (a) can advantageously be carried out by stacking the skins flat in perforated cages, by causing each of said cages to pivot on itself in order to give the stack a vertical or inclined position, by placing said cages in at least one soaking basin, by supplying the latter with rinsing water, and by renewing this water several times.

Such quenching has proven to be extremely effective, despite a period which can be limited to 24 hours and without having to use wetting products (which are generally used in known processes); the skins arranged in vertical (or inclined) positions delimit between them vertical or inclined spaces which are traversed by streams of water during evacuations and the intense circulation thus generated between skins causes a much faster saturation of these and a very efficient training of deposits. This produces a quality re-greening, in a single quenching step, the duration of which can be of the order of half that required for quenching in known processes.

In particular, the quenching operation (a) can comprise between 2 and 4 water renewal and last approximately 24 hours. Preferably, fresh salted skins will be used (and not dried skins).

The saber operation (b) is an operation well known per se in the stripping industries and it is carried out continuously, in a traditional manner.

The addition of a skinning operation (c) is new in the stripping processes. Indeed, this operation which consists in ridding the flesh side of the fragments of fat and flesh is practiced only in tanning on the tripe skins, once these are stripped: in itself, the implementation of this operation is carried out as in tavern. We were able to realize that it did not cause any deterioration of the wool, on the flower side, and that its presence was essential for obtaining the final result at the end of the cycle; in fact, it provides a skin of uniform thickness with a homogeneous surface finish on the flesh side: these qualities then contribute to accelerating the diffusion of the sulphide towards the flower side and ensuring homogeneous treatment of all areas of the skin. .

The impregnation operation (d) can be carried out in a manner known per se, by arranging each skin with its flesh side situated upwards and by spraying the sulphide solution in the form of fine drops above the skin.

The operation (e) is one of the essential originalities of the process of the invention and makes a large contribution to obtaining skins and wool of good quality; it also makes it possible to shorten the production cycle, its average duration being of the order of 3 hours (instead of approximately 10 hours for the homologous operation of the conventional process). This operation (e) is essentially characterized in that, on the one hand, the skins are treated individually by separating them from each other and in that, on the other hand, they are arranged in a specific atmosphere suitable for promoting diffusion rapid and uniform sulphide, and this, for the same time for each skin, corresponding to the time necessary for the diffusion and attack of the hair root without blackening on the flower side or degradation of the wool.

According to a preferred method of covering, this operation (e) is carried out by introducing the skins into a tunnel containing a saturated atmosphere heated to a temperature of the order of 25 ° to 30 ° C, by causing each of said skins to circulate inside said tunnel between an inlet and an outlet thereof and by evacuating each skin at the end of its passage through said tunnel.

The temperature and hygrometry conditions can be ensured by injecting water vapor along the tunnel, in several zones, under conditions suitable for heating the skins in the vicinity of the entrance to the appropriate temperature and to then maintain the skins at said temperature up to the vicinity of the outlet.

The stripping operation (f) is carried out as soon as the skins leave the aforementioned tunnel; its covering is in itself classic.

Finally, the wool rinsing operation (g) which immediately follows the stripping operation prevents the wool from remaining in contact with traces of sulphide, the degradation action caused by this body being very rapid.

This rinsing operation can in particular be carried out in at least two rinsing tanks, at least one of which contains an aqueous bath added with hydrogen peroxide. This results in a radical elimination of all traces of sulphide, which then makes it possible to keep the wool in good condition.

• des moyens de sabrage.
• des moyens d'écharnage,
• des moyens de projection d'une solution de sulfure,
• un tunnel de forme allongée, équipé de moyens de conditionnement de son atmosphère interne et de moyens de circulation des peaux entre une entrée située au voisinage d'une extrémité du tunnel et une sortie située au voisinage de son autre extrémité ;
• des moyens de délainage,
• et des moyens de rinçage de la laine, adaptés pour l'élimination des traces de sulfure.

The invention extends to a processing unit allowing the implementation of the method defined above; this unit comprises, on the one hand, soaking means adapted to allow soaking the skins in vertical or inclined positions relative to the vertical, on the other hand, a treatment chain after soaking; this chain includes the following means, arranged in successive positions:

• saber means.
• flaking means,
• means for spraying a sulfide solution,
• an elongated tunnel, equipped with means for conditioning its internal atmosphere and means for circulating the skins between an inlet located near one end of the tunnel and an outlet located near its other end;
• means of stripping,
• and wool rinsing means, suitable for removing traces of sulphide.

• deux chaînes latérales en regard, guidée pour former deux tronçons horizontaux superposés, un tronçon ascendant et un tronçon descendant,
• une pluralité de barres transversales, articulées en balancelle entre les deux chaînes de façon à garder une même orientation sur tous les tronçons,
• des moyens d'entraînement séquentiel desdites chaînes.

According to a preferred embodiment, the circulation means which equip the aforementioned tunnel, essentially comprise:

• two opposite side chains, guided to form two superposed horizontal sections, an ascending section and a descending section,
• a plurality of transverse bars, articulated in a swing between the two chains so as to keep the same orientation on all the sections,
• means for sequentially driving said chains.

The invention extends, as such, to a tunnel as claimed.

• la figure 1 est un schéma symbolisant l'unité de traitement, essentiellement composée de moyens de trempage M et d'une chaîne T de traitement après trempage qui a été découpée en plusieurs sections A, B, C, D (les flèches indiquant le sens de circulation des produits),
• la figure 2 est une figure schématique montrant les moyens de trempage M,
• la figure 3A est une figure schématique de la section A de la chaîne de traitement T,
• la figure 3B est une figure schématique B de la chaîne T,
• la figure 3C est une figure schématique de la section C de la chaîne T,
• la figure 3D est une figure schématique de la section D de ladite chaîne T,
• la figure 4 est une coupe schématique d'un des ensembles de la chaîne de traitement (tunnel),
• les figures 5, 6 et 7 sont des vues de détail d'organes de cet ensemble,
• les figures 8a. 8b et 8c sont des vues schématiques illustrant la mise en place d'une peau dans le tunnel d'étuvage.

Other characteristics, aims and advantages of the method and of the processing unit in accordance with the invention will emerge from the description which follows with reference to the appended drawings, which are given by way of nonlimiting example; on these drawings which form an integral part of the present description;

• FIG. 1 is a diagram symbolizing the processing unit, essentially composed of soaking means M and of a chain T of treatment after soaking which has been cut into several sections A, B, C, D (the arrows indicating the direction circulation of products),
• FIG. 2 is a schematic figure showing the dipping means M,
• FIG. 3A is a schematic figure of section A of the processing chain T,
• FIG. 3B is a schematic figure B of the chain T,
• FIG. 3C is a schematic figure of section C of the chain T,
• FIG. 3D is a schematic figure of section D of said chain T,
• FIG. 4 is a schematic section of one of the assemblies of the processing chain (tunnel),
• FIGS. 5, 6 and 7 are detailed views of members of this assembly,
• Figures 8a. 8b and 8c are schematic views illustrating the placement of a skin in the steaming tunnel.

The unit shown by way of example in the figures enables the skinning of skins by a treatment cycle of duration of less than 1.5 days. Preferably, the treatment is carried out on fresh skin. The unit is constituted, upstream, by means for soaking the skins M and, after soaking, by a continuous processing chain T.

The soaking means comprise quenching basins such as basin 1 shown diagrammatically in FIG. 2. This basin is provided at the front with a watertight door 2, with water supply means of conventional type (water conduits of suitable flow) and conventional discharge means (drain provided on the lower horizontal face). Such basins known per se in the stripping industry allow filling and evacuation in about twenty minutes.

The skins to be soaked are arranged in several openwork cages such as 3 or 4; each cage of rectangular parallelepiped shape has an open face 3a of dimension adapted to introduce a flat skin as shown in Figure 2. Each cage can contain a stack of about 130 skins.

For loading, the cages are placed in abutment on the ground by their face opposite their open face and the skins are positioned flat in horizontal planes.

Each cage has a member for closing its open face, in the example of the chains 5, and at the end of loading, these are hung so as to block the stacking and immobilize the skins.

On a face 3b adjacent to the open face 3a, each cage comprises gripping means allowing it to be lifted and rotated using a conventional rotary lifting device. In the example, four hollowed-out studs such as 6 are secured externally to the cage to allow the passage of a fork of a machine (the ends of which can be seen in broken lines in FIG. 2).

The cage can thus be lifted and brought to pivot through 90 ° so as to come to rest in the basin 1 on the studs 6 of the face 3b, which act as support wedges. The skins are thus arranged vertically as illustrated for the cage 4 in FIG. 2.

The basin 1 can contain several levels of cages, thanks to guide tips 7 which allow these to be superimposed. For example, the dimensions of a basin can be adapted to contain 10 cages on two levels.

Once the cages have been introduced into the basin, the door 2 thereof is closed and the basin is filled with water. The skins are left for approximately 24 hours in this one, three water replenishments being carried out.

At the end of this operation, it can be seen that the skins are perfectly impregnated until saturation, the surface deposits having been removed.

The skins are then extracted from the basin and transported to the treatment chain T. Of course, as far as possible, the soaking means M will be located in the vicinity of the upstream part of the chain T (with the areas of handling necessary) in order to shorten transfers.

The treatment chain T is composed of several assemblies arranged one after the other, to allow continuous treatment of the skins.

At its upstream part (FIG. 3a) this chain does not include a saber 8 of a type known per se. which rids the wool of the impurities which it can contain.

On leaving the saber, the skins are taken up by a conveyor belt 9 whose width is less than that of the skins; these are thus arranged in a position suitable for facilitating the cutting of the tabs at the level of this mat.

This carpet then brings the skins to a flail 10 of a type known per se in taverns. This machine which works on the flesh side rids the skins of the fragments of flesh and fat which adhere to it and provides a skin of uniform thickness, having a homogeneous surface finish on the flesh side.

At the outlet of the flailer 10 (FIG. 3b), the skins are placed on a sulphide impregnation machine 11 (generally designated by "enchausseneuse"). This machine known in itself comprises a projection ramp which makes it possible to project a solution based on sulphide on the flesh side of each skin; for this purpose, the skin is arranged on a carpet constituted by parallel threads, with its flesh side facing upwards, and passes below the projection ramp.

The solution used is an aqueous solution containing a concentration of sodium sulfide approximately equal to 200 g / l; a percentage of lime can be added to this solution to improve the fixation of the sulfide on the skin.

The skins thus impregnated one by one are individually taken up by an operator to be introduced into a tunnel 12 for the diffusion of the sulfide.

This tunnel is constituted by a closed cell, of rectangular elongated rectangular shape whose length is in particular of the order of 40 m to 45 m. It is open, on the one hand, at its upstream end to form an inlet for the introduction and placement of the skins, on the other hand, at its downstream end, to form an opposite outlet for the removal of said skins after passage in the tunnel.

The tunnel 12 comprises in the vicinity of its lateral flanks two endless chains with rollers such as 13, which are each guided by two toothed wheels such as 14, located in the vicinity of the inlet and outlet and. between these, by side members such as 15, on which roll the rollers 13a of the chains (FIG. 5).

The two chains 13 located opposite thus form a conveyor having two superposed horizontal sections, a section descending at the level of the input wheels 14 and a section ascending at the level of the output wheels.

Between said chains is articulated a plurality of transverse bars such as 16. These rectangular section bars with rounded edges are articulated in a swing, as illustrated in detail figure 5, so as to always keep the same orientation in space whatever the section along which they are.

In the example shown in FIG. 5, each bar is carried on each side by the chains 13 by means of suspension lugs 17 and pins 18 housed in the hollow links of the chains 13.

The chains 13 are driven in a sequential movement by drive means 19 which are shown diagrammatically in FIG. 6. These means are in the example located on the side of the exit from the tunnel and include two synchronized hydraulic systems, mounted on both sides and on the other side of the tunnel outside of it, in the vicinity of its sides. These systems are suitable for sequentially rotating the transverse shaft 20 which carries the two wheels 14 for guiding the chains on the outlet side. (The drive of the output shaft is preferable, but, of course, it is also possible to provide the hydraulic drive systems on the input side).

Each hydraulic system comprises a hydraulic jack 21 whose body is articulated on a fixed support, and the movable rod on flanges 22 articulated around an axis 23. These flanges 22 carry a pawl 24 which is arranged to cooperate with a wheel with ratchet 25 mounted in rotation with the shaft 20.

The hydraulic jacks 21 located on each side of the tunnel are driven by a hydraulic unit and equipped with synchronization conditioning their synchronous operation; control means of conventional type make it possible to adjust the operation of the jacks so as to be able to adjust the average speed of the chains and the duration of the downtimes.

Such hydraulic means are perfectly suited to driving the chains 13 and their bars 16 because of the very high torque that they can develop, while benefiting from great structural simplicity (simple and inexpensive mechanical means, hydraulic power station of current type).

Furthermore, the tunnel 12 contains at least one washing tank 26, which is disposed at the horizontal return section of the conveyor (in the example located above the outward section). This tank 26 is provided with water inlet and outlet pipes allowing water to circulate therein. It is arranged so that the transverse bars 16 plunge into it during their journey along said return section.

It is to highlight that. when they reach the edges of the tank, the bars 16 mounted in a swing swivel upwards in contact with them, then come either to plunge into the tank or to extract from it; the edges of the tank have a suitable shape to favor the passage of the bars without jamming.

In addition, the tunnel 12 is equipped with several steam injection ramps such as 27 which each extend transversely in the lower part of said tunnel and allow the internal atmosphere of the latter to be saturated with moisture and to adjust the temperature precisely. These ramps are distributed in several zones along the tunnel; a ramp 27 is located in the vicinity of the entrance to the tunnel, its section being greater than that of the other ramps so as to be able to inject a flow of steam, capable of causing the skins to heat up to a temperature of 25 to 30 ° C. The other ramps are distributed with appropriate flow rates depending on their position so as to maintain the skins at this temperature.

Flow distribution means (symbolized by valves such as 28) make it possible to supply the ramps with steam with the appropriate flow rates.

In addition, the tunnel 12 is provided with suction means 29 and 30 which open in the vicinity of the entrance and exit of the tunnel in order to suck in steam at this level in order to reduce losses to the outside via said entry and exit. These means consist of hoods located above the inlet and outlet and by suction ducts allowing recycling of the sucked steam.

At the entrance to the tunnel 12, each skin is arranged individually on a transverse bar 16, after folding in half on itself. Figures 8a, 8b, 8c illustrate this operation: at the outlet of the casing machine 11, each skin is folded by an operator, along a fold line located along the spine of the skin, so that the flesh side either located inside and the flower side outside (Figures 8a and 8b); each skin is then suspended astride a bar 16. The length of these bars can be of the order of 4.2 m, so as to allow the placement of 8 skins close to each other.

• nombre total de barres transversales : de l'ordre de 250 à 300,
• écartement entre barres : environ 300 mm,
• avance du mouvement séquentiel par pas égaux à l'écartement entre barres,
• durée des arrêts : entre 30" et 60",
• temps mis à parcourir un pas : entre 30" et 60".

As an indication, the values of the essential parameters of the tunnel described above are as follows:

• total number of crossbars: around 250 to 300,
• spacing between bars: about 300 mm,
• advance of the sequential movement in steps equal to the distance between bars,
• duration of stops: between 30 "and 60",
• time taken to cover one step: between 30 "and 60".

These values allow operators to load and unload skins without difficulty at the level of the descending and ascending sections of the conveyor; the skins travel through the tunnel 12 for a time of the order of 3 hours, which can be adjusted as necessary by adjusting the characteristics of the sequential movement.

At the end of the tunnel 12 (FIG. 3C), the skins are subjected to a stripping operation on a stripping machine 31 of the traditional type, which separates the wool from it. It has been found experimentally that this work is of easy execution without risk of damage to the skins, taking into account the operations of prior preparation.

The tripe skins, ready to enter the tavern are removed in carriages 32, while the wool is conveyed to the rinsing on a conveyor belt 33.

The wool is introduced into a first rinsing tank 34 of a type known in itself, where it is rinsed with large amounts of water (FIG. 3D).

After wringing by means of a wringer 35, it is introduced by a conveyor belt 36 into a second rinsing tank 37 containing an aqueous bath supplemented with hydrogen peroxide, with a concentration which may be between 4 and 20 g of hydrogen peroxide per liter of water.

After wringing in a press 38, the wool, which is in good condition without any trace of sulphide, can be conveyed to the subsequent traditional treatment operations.

It should be noted that the assemblies likely to be in contact with the sulphide solution are made of anti-corrosion material, such as stainless steel (tunnel and internal organs, rinsing tanks).

Of course, the invention is not limited to the terms of the foregoing description but includes all of its variants.

Claims (24)

1. A method of treatment of skins with a view to separating the wool from them, consisting in combining the following operations in succession :

a) Steeping the skins in a bath of water which is renewed several times, the skins being arranged in a vertical or sloping stack so that each skin displays a position which is vertical or inclined with respect to the horizontal ;

b) Carrying out upon the hair side of the- skins a picking known in itself, suitable for disencumbering them of the impurities contained in the wool ;

c) Carrying out upon the flesh side of the skins a fleshing known in itself, suitable for disencumbering them of fragments of flesh and fat ;

d) Impregnating the flesh side of the skins by means of an aqueous solution of sulphide in a concentration lying substantially between 100 g/l and 300 g/I ;

e) Arranging the skins separately from one another in an atmosphere saturated with moisture at a temperature lying substantially between 20° and 35 °C for a period of time lying substantially between 2 hours and 5 hours ;

f) Carrying out upon the skins a wool-stripping operation known in itself, suitable for separating the wool from them ; and

g) Immediately rinsing the wool so separated so as to eliminate from it the traces of sulphide.

2. A method of treatment as in Claim 1, characterized in that the steeping operation (a) consists in stacking the skins flat in perforated cages (3, 4), causing each of the said cages to pivot about itself with a view to giving the stack a vertical or sloping position, arranging the said cages in at least one steeping-tank (1), feeding the latter with rinsing water and renewing this water several times.

3. A method of treatment as in Claim 2, characterized in that cages (3, 4) are employed which are of generally rectangular parallelepipedal shape and in that they are caused to pivot through 90° so as to arrange the skins in a vertical position, the cages resting upon one of their rectangular faces (3b) in this new position.

4. A method of treatment as in one of the Claims 2 or 3, characterized in that the steeping operation (a) comprises between 2 and 4 renewals of the water and lasts approximately 24 hours.

5. A method of treatment as in one of the Claims 1, 2, 3 or 4, characterized in that the impregnation operation (d) is effected by employing an aqueous solution of sodium sulphide in a concentration approximately equal to 200 g/I.

6. A method of treatment as in one of the Claims 1, 2, 3, 4 or 5, in which the impregnation operation (d) consists in arranging each skin with its flesh side situated uppermost and in scattering the sulphide solution in the form of fine drops over the said skin.

7. A method of treatment as in one of the Claims 1, 2, 3, 4, 5 or 6, characterized in that the operation (e) is effected by introducing the skins separately into a tunnel (12) containing a saturated atmosphere heated to a temperature of the order of 25° to 30 °C, causing each of the said skins to travel inside the said tunnel between an entrance to and an exit from it and discharging each skin at the end of its travel through the said tunnel.

8. A method of treatment as in Claim 7, characterized in that the operation (e) consists in :

Driving crossbars (16) along the tunnel (12) in a sequential motion composed of a succession of stops and translations ;

At the entrance to the tunnel (12) : Hanging the skins close together on the next bar (16), each skin being folded in two on itself with its flesh side inside ; and

At the exit from the tunnel : Removing the skins from the bar lying opposite the said exit.

9. A method of treatment as in Claim 8, characterized in that :

The bars (16) are driven along an endless path comprising a horizontal forwards section, a horizontal return section offset in height, and rising and descending sections connecting the aforesaid sections ;

The skins are hung at the level of one of the descending or rising sections ;

The skins are withdrawn at the level of the other rising or descending section after travelling along the forwards section ; and Washing of the bars is provided on the return section.

10. A method of treatment as in one of the Claims 7, 8 or 9, characterized in that along the tunnel (12) in several zones of it steam is injected under conditions suitable for heating the skins in the vicinity of the entrance up to the appropriate temperature and for keeping the skins at the said temperature until in the vicinity of the exit.

11. A method of treatment as in one of the Claims 1. 2. 3, 4. 5, 6, 7, 8, 9 or 10. characterized in that the wool-rinsing operation (g) is effected in at least two rinsing-tanks (34, 37) at least one of which contains a waterbath to which oxygenated water has been added.

12. A method of treatment as in Claim 11. characterized in that for the rinsing operation (g) one or more waterbaths are employed, containing between 4 and 20 g/i of oxygenated water.

13. A method as in one of the preceding Claims, in which the treatment is carried out on new skins.

14. A unit for treatment of skins with a view to implementing the method in accordance with one of the Claims 1 to 13, characterized in that it comprises steeping means (M) suitable for enabling the skins to be steeped in positions which are vertical or inclined with respect to the vertical. as well as a sequence (T) of treatment after steeping, combining the following means arranged at successive stations :

Picking means (8) ;

Fleshing means (10) ;

Means of scattering a sulphide solution (11) ;

A tunnel (12) of elongated shape, equipped with means (27, 28, 29, 30) of conditioning the atmosphere inside it and means (13, 16, 14, 19) of travel of the skins between an entrance situated in the vicinity of one end of the tunnel and an exit situated in the vicinity of its other end ;

Means (31) of stripping the wool ; and

Means (34, 37) of rinsing the wool, suitable for the elimination of the traces of sulphide.

15. A treatment unit as in Claim 14, characterized in that the steeping means (M) comprise on the one hand at least one steeping tank (1) endowed with a watertight door (2), with means of water supply and with discharge means, and on the other hand a plurality of cages (3. 4) each of rectangular parallelepipedal shape, each cage having one open face (3a), a member (5) for shutting off this face after the skins have been put in place and external means of seizure (6) suitable for enabling the said cage to be raised and made t6 pivot with the aid of a suitable machine.

16. A treatment unit as in Claim 15, in which the means of seizure of each cage consist of four blocks (6) hollowed out with a view to enabling the fork of a machine to be passed through, the said blocks being arranged on a face (3b) adjacent to the open face (3a) with a view to being able to serve as supporting blocks after rotation of the cage.

17. A treatment unit as in one of the Claims 14, 15 or 16, characterized in that the tunnel (12) is equipped with means of travel for the skins, comprising :

Two sidechains (13) opposite one another. guided in order to form two superimposed horizontal sections, one rising section and one descending section ;

A plurality of crossbars (16) articulated like swings between the two chains (13) so as to keep one and the same orientation along all the sections ;

Means (19) of sequential driving of the said chains.

18. A treatment unit as in Claim 17, characterized in that the tunnel (12) comprises on one of the horizontal sections at least one washing-tank (26) equipped with means of water circulation, the said washingtank being arranged so that the crossbars (16) plunge into it during the course of their travel along the said horizontal section.

19. A treatment unit as in one of the Claims 14, 15.16.17 or 18, characterized in that the means of conditioning the tunnel comprise a number of rows of steam injectors (27) arranged in a number of zones along the tunnel, means of distribution of delivery (28) enabling the said rows to be fed with a delivery which is a function of their position, and suction means (29, 30) having mouths in the vicinity of the entrance and exit in order at this level to suck away the vapour with a view to reducing the losses through the said entrance and exit.

20. A treatment unit as in Claim 17, characterized in that the means of sequential driving of the chains comprise two synchronized hydraulic systems (19) mounted on opposite sides of the tunnel (12) in the vicinity of its exit (or of its entrance), each system comprising one hydraulic jack (21), a pawl (24) arranged for being driven by the said jack and a ratchet wheel (25) arranged for being driven in sequential rotation by the said pawl, the ratchet wheels of the two systems being mounted at the two ends of a cross-shaft (20) carrying sprockets (14) for guidance of the chains at the level of the exit (or of the entrance) of the tunnel.

21. A treatment unit as in one of the Claims 14, 15, 16, 17, 18, 19 or 20, characterized in that the tunnel (12) exhibits a length lying between 40 and 45 m, and is equipped with a total number of bars (16) lying between 250 and 300, the sequential driving means (19) being suitable for creating times at standstill, each of a duration lying between 30" and 60", and translations of a length of step equal to the spacing between bars and of duration lying between 30" and 60".

22. A treatment unit as in one of the Claims 14, 15, 16, 17, 18, 19, 20 or 21, characterized in that the means of rinsing the wool comprise at least two rinsing-tanks (34, 37), at least one of which contains a waterbath to which oxygenated water has been added.

23. A treatment unit as in one of the Claims 14, 15, 16, 17, 18, 19, 20, 21 or 22, characterized in that a conveyor belt (9) of width less than that of the skins extends between the picking means (8) and the fleshing means (10).

24. A sweating-tunnel intended to favour the diffusion of a liquid product in the heart of skins, comprising the characteristics of the characterizing part of the claims 17 and 18 combined or not with the characteristics of the characterising part of one of the claims 19, 20 or 21.

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