Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS AND APPARATUS FOR TREATING LEATHER AND THE LIKE
TECHNICAL FIELD
The present invention concerns tannage of leather and the like.
BACKGROUND ART
It is known that animal skin is tanned, so as not to putrefy, with solutions that
remain irreversibly fixed thereon, turning it into hide.
This treatment includes different steps, which are often complex and requiring
o relatively much time.
When delivered to tannery, generally dried with salts, rawhide is initially
subjected to preparation for real tanning.
This preparation includes first a soaking step, i.e. removing impurities that
cover both inner flesh side and outer or grain side, as well as preserving
solutions, so as to bring the leather back to its natural softness.
The leather to be treated is soaked in drums containing suitable liquid
solutions.
These drums are provided inside with immovable paddles or stakes, which act
on the leather during drum rotation.
Therefore, the treatment consists of combined chemical action of the liquid
solution and the mechanical action performed on the leather and lasts six to
twenty four hours.
Afterwards, a fleshing step follows, with which the fat is removed from the
soaked leather, and subsequently liming treatment follows for removing hair
and reveal the derma.
Liming is performed in suitable drums with alkaline substances, such as
sulphides or lime, which make the leather tissue swell and dissolve the hair
roots.
More precisely, the leather swells up, the fats turn into calcium salts and
proteins forming the leather are modified due to breaking of principal and
secondary links of the proteic chains and, sl~hsequently, the hair detaches
- from the leather.
The substances used for liming, and at the same time for "opening" the
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leather pores in order to execute real tanning and dyeing, are highly polluting,which results in all known problems of waste disposal and/or purification.
Liming step requires usually twenty four hours.
Then, thus prepared leather is decalcined and bated, again in suitable drums.
s Due to decalcination step, usually with decalcinating salts, the retained lime is
removed.
Bating is a biological action which softens leather grain by enzymes which
partly dissolve elastic fibres, causing the leather relaxation.
Subsequently, the leather is subjected to pickling, i.e. treatment, which
o guarantees more rapid and complete penetration of the tanning salts.
In fact, bated leather, having basic reaction, cannot be tanned with e.g.
tanning salts of chromium, because it would result in a chemical reaction,
which would close the leather pores.
Therefore, the leather is acidified with small quantities of acid, with the
presence of salts (usually sodium chloride) so as to prevent swelling. This
step is performed in a drum and lasts an average of ten - twelve hours.
The real tanning treatment is carried out inside the aforementioned drums, by
means of vegetable solutions, such as natural or synthetic tanning solutions,
or by mineral salts, mainly chromium or the like salts.
The liming, bating, pickling and tanning steps altogether require an average of
not less than forty eight hours (it can vary according to the type of the leather
to be treated).
The tanned leather, suitably pressed to remove a part of absorbed water,
selected and skived, is subjected to dyeing treatment, otherwise called re-
tanning.
This dyeing step requires an average of eight hours.
Thus, the above mentioned tanning treatments require, as has been alreadysaid, much time, which can take an average of one week.
This results in the necessity for using a relatively big number of huge drums in3n order to achieve an adeqll~te productivity. The pieces of leather to be treated
are thrown into the drums in bulk and are subjected directly to a mechanical
action, which sometimes can damage them.
- A not minor disadvantage of traditional tanning processes derives from the
fact that the working environment is very harmful, due mainly to miasma
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produced by the aforementioned drums.
Moreover, there is a serious problem of disposal of liquids discharged at the
end of the above mentioned treatments, in particular of the substances used
for liming.
s
SUMMARY OF THE INVENTION
The object of the present invention is to propose a process, that allows
tanning treatments of leather and the like to be carried out in less time with
respect to the known systems, and that, at the same time, guarantees the
10 high quality of tanned leather as well as high throughput, the whole being
obtained with reduced quantity of required energy, with respect to known
techniques.
Another principal object of the present invention is to propose a process that
can be carried out by an apparatus, which allows to operate in a non-harmful
15 working environment, and which considerably reduces the problems
connected with waste disposal.
Yet a further object of the present invention is to propose a process, which
allows to reduce markedly a quantity of used substances with the same
quality of tanned leather.
20 Still another object of the invention is to propose a process, whose carrying out does not pollute the air.
Moreover, the invention has another object of proposing an apparatus, which
carries out the aforementioned method.
The above mentioned objects are obtained by a process of treatment of
2s leather and the like, which includes:
disposing spread pieces of leather to be treated, spaced apart, into a
container;
introducing liquid solutions into said container, in sequence and with
predetermined intervals, for pe, rvn"i"g various steps of leather tanning
30 treatment, said liquid solutions being discharged from the container, after
each step has been completed;
maintaining deprt:ssion inside said container, at least for the duration of eachsingle step;
generating, during each step, a relative movement between the liquid solution
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and said pieces of leather, so as to intensify the action of said liquid solution
on said pieces of leather.
The process is carried out by means of an apparatus which includes:
a container to be closed tight;
5 a plurality of supports, which can be introduced and withdrawn from said
container, and on which the corresponding spread pieces of leather are
fastened, these supports being situated in said container in such a way as to
keep said pieces of leather spaced out;
a hrst series of tanks containing predetermined liquid solutions for
lo corresponding leather treatment steps;
on/off and control means which connect each of said tanks to the container so
as to introduce therein the relative liquid solution for corresponding leather
treatment step;
suction means for maintaining depression inside said container at least while
15 performing the leather treatment steps;
means for generating relative movement between a liquid solution and said
pieces of leather so as to intensify the action of said liquid solution thereon.According to a different embodiment, the process includes:
disposing spread pieces of leather to be treated, spaced apart, into a first
20 container;
introducing liquid solution into said container for performing a step of leathertanning treatment;
maintaining depression inside said conta;ner during performing of said step;
generating, during said step, relative movement between the liquid solution
25 and said pieces of leather, so as to strengthen the action of said liquid solution
on said pieces of leather;
discharging said liquid solution from said hrst collldi"er;
withdrawing said pieces of leather from the first container;
repeating the above mentioned operations in further containers so as to
30 perform remaining steps of the leather tanning treatment.
According to a different embodiment, the apparaLus includes:
a plurality of containers to be closed tight, inside which predetermined leathertreatment steps are carried out;
, ,
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a plurality of supports, which can be introduced and withdrawn from said
~ containers, and on which the corresponding spread pieces of leather are
fastened, these supports being situated in said containers in such a way as to
- keep spaced out said pieces of leather;
s a first series of tanks containing predetermined liquid solutions for
corresponding leather treatment steps;
on/off and control means, which connect each of said tanks to the re~ative
container so as to introduce therein the relative liquid solution for a
corresponding leather treatment step;
lo suction means for maintaining depression inside each of said containers at
least during performing therein of the relative leather treatment steps;
means for generating, inside each of said containers, relative movement
between a corresponding liquid solution and said pieces of leather so as to
intensify the action of said li~uid solution thereon.
15 Further characleristics and features are pointed out in the sub-claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The characteristic features of the invention will become pointed out in the
following description, with particular reference to the enclosed drawings, in
20 which:
- fig. 1 shows a plan view of supporting means for a piece of leather to be
treated;
- figs. 2a, 2b and 2c show schematic views of containers into which the above
mentioned support means are ~lisposed, with different a"~nge"lents,
2s respectively;
- fig. 3 shows a schematic vertical section view of said container, during one
step of the leather treatment;
- figs. 4a and 4b, show ~iayra"~s of apparatuses for carrying out
corresponding tanning treatments accor li.,g to the method, being the subject
30 of the present invention;
- figs. 5a, 5b show diagrams of two different embodiments of the above
mentioned apparatus, which carry the method in a different way;
- fig. 6 shows a possible diagram of an apparatus, which carries the method in
a further way;
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- Fig. 7 shows a further embodiment of the apparatus;
- Fig. 8, shows a constructive variation of the apparatus container;
- Figures 9a and 9b show two schematic diagrams of a facility for vapour
recovey in both operation conditions.
s
BEST MODES OF CARRYING OUT THE INVENTION
With reference to the above mentioned figures, numeral 1 indicates a piece of
leather to be subjected to tanning treatment according to the subject process.
According to this process, the piece of leather to be treated 1 is spread on a
l0 respective open support, e.g. frame 2 shown in fig. 1.
The piece of leather 1 is fastened to the frame 2 by a series of expanders 3 of
known type.
The frames 2 supporting the spread pieces of leather 1 are introduced into a
container 4, kept fixed according to preferred embodiment, which is to be
s closed tight, for the treatment with a sl~it~h'E liquid solution introduced therein.
The frames 2 supporting the spread pieces of leather 1 are introduced into the
container 4 preferably in vertical arrangement, regularly spaced apart, as seen
in figure 2a.
Nevertheless, it is possible to arrange the frames 2 inside the container 4
horizontally (fig. 2b) or inclined (fig. 2c).
In case the pieces of leather are to be arranged vertically, it is sufficient tohang them on a suitable creel, not shown, so as to maintain them mutually
spaced apart.
As shown as an example in fig. 3, the upper part of the container 4, which
contains the treating liquid solution 5, is closed tight by a cover 6.
In its lower part, the container 4 has holder means 7 for the frames 2
supporting the pieces of leather 1.
Inside the container 4, there is also situated a heat exchanger 8, that heats
the liquid solution 5 to the desired temperature. The liquid solution 5 inside the
30 container 4, is swirled during the treatment of the leather pieces 1 spread on
the frames 2.
For this purpose, the container 4 features a deliver element 9, situated below
the holder means 7 for the frames 2 and formed by a grate provided with a
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series of ejectors 10, which eject air in form of bubbles.
Inside the container 4, over the liquid solution 5, depression is maintained by
suitable suction means 11 connected with the container by a pipe 110,
passing through one of two neutralisation tanks 111a, 111b, which will be
s described later. The advantage of keeping the container 4 in depression will
be pointed out in the following.
Moreover, due to this depression, a flow of air is sucked from outside via the
deliver element 9. Further, the depression reduces the quantity of energy
consumed for reaching the desired working temperature. Otherwise, the
0 aforementioned flow of air can be obtained by suitable compression means,
connected to the deliver element 9.
In the following, the same reference numbers will indicate means carrying out
the same functions.
The apparatus for tanning treatments, shown in fig. 4a, includes a series of
5 tanks 12, preferably tight, containing liquid solutions to be supplied to the
container 4 for the aforementioned treatments.
In particular, there are four tanks 12a,12b,12c,12d supplying liquid solutions
used correspondingly for the soaking, liming, pickling and tanning steps.
When needed, during the tanning treatment the leather pieces are also dyed.
The tanks are provided with respective heat exchangers 13a, 13b, 13c, 13d
which maintain the liquid solutions at desired temperatures. The heat
exchangers 13a, 13b, 13c, 13d are controlled by a control unit 14 by
connections indicated with S1, S2, S3 and S4.
The supply tanks are connected with respective jet pipes 15a, 15b, 15c and
2s 15d, equipped with related pumps 16a, 16b, 16c and 16d, controlled, in theirturn, by the control unit 14 through connections indicated with P1, P2, P3 and
P4.
The jet pipes 15a, 15b, 15c and 15d are connected to an inlet pipe 17 of the
container 4 by a valve means 18 which is controlled by the control unit 14.
The bottom of the container 4 features an outlet pipe 19, provided with a
pump 20, controlled by the control unit 14.
The outlet pipe 19 is connected alternatively, by a valve means 21, with
discharge pipes 22a, 22b, 22c and 22d, communicating with respective waste
tanks 23a, 23b,23c and 23d of the liquid solutions used in the container 4.
The waste tanks 23 communicate with corresponding supply tanks 12 by
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means of respective return pipes 24a, 24b, 24c, 24d, equipped with respective
pumps 25a, 25b, 25c, 25d, controlled by the control unit 14.
As an alternative constructive form, the discharge pipes 22a, 22b, 22c and
22d lead all to a unique manifold (which has not been shown) which is
5 connected to a suitable cleaner.
In practice, in order to perform each of the aforementioned tanning treatment
steps, the container 4 is fed with the liquid solution taken from the relative
supply tank 12.
According to a preferred embodiment, the apparatus includes also at least
lO other two tanks 30a, 30b, containing washing liquid solutions, which will be
described later, and provided with relative jet pipes 31, 31b, featuring relative
pumps 32a, 32b controlled by the control unit 14.
These pipes are connected to an inlet duct 33 of the container 4 by a valve
means 34 co"l,ollcd by the control unit 14.
S The aforementioned outlet pipe 19, connected to the bottom of the container
4, can be also connected, by the valve means 21, to one or the other of
discharge pipes 35a, 35b, flowing into the tanks 30a, 30b, respectively.
Inside the container 4, the liquid solution is swirled by the air flow produced,as has been previously described, in the liquid solution.
20 It is to be pointed out that before each single step is carried out, more
precisely, before the container is fed with liquid solution, depression is created
therein so as to swell the leather making it spongy and thus facilitating the
action of liquid solution thereon.
The above mentioned swirling causes a kind of massage on the leather
2s pieces, that replaces the mechanical action of known systems without
damaging the leather.
When each of said treatment steps is completed, the used liquid solution is
withdrawn from the container 4 and sent to the relative waste tank 23. After
having been regenerated, by means of techniques which are well known by
30 those skilled in the art, this liquid solution can be let again into the
corresponding supply tank 12, for a new tanning cycle.
The soaking treatment is carried out with the liquid solution contained in the
tank 12a; water, possibly added with chemical promoters.
Due to depression, created before the liquid solution has been introduced, the
3s leather absorbs water more easily, since it tends to swell naturally, thus
.. .. .
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becoming, as it has already been said, more spongy.
These factors, i.e. combined action of depression and swirling, reduce the
time required for the soaking step.
When the soaking has been finished, the leather pieces are washed with
5 water contained in the tank 30a.
The liming treatment is performed with the liquid solution contained in the tank12b, according to oxidising method, e.g. by sodium chlorite or enzyme agents.
It is to be pointed out that sodium chlorite cannot be used in the liming step
carried out in wooden drums, because it frees chlorine, which corrodes the
l o wood .
Since pulled by the suction means 11 and freed through the pipe 110, chlorine
enters one of the tanks 111a, 111b, which contains a solution of sodium
hyposulphite, that, as it is known, neutralises chlorine. In this way, the suction
means 11 are protected and the problem of disposal of substances used for
15 liming treatment, is resolved.
In the present case, the combined effect of depression, which swells the
leather, of sodium chlorite and of massage performed on the leather by the
swirled air, allows to carry out the liming treatment.
This is considerably advantageous for the following reasons:
20 - use of a substance, whose disposal (more precisely, neutralisation) is not
very troublesome;
- due to depression in working environment, the consume of energy is
reduced;
- the pieces of leather are not mechanically stressed.
2s It is also to be pointed out that the leather swelling makes also the pores
open, which is advantageous for subsequent tanning and dyeing treatments.
The liming step requires about five hours. After having been limed, the leather
is washed with the contents of the tank 30b.
The iiming step is followed by pickling step, which is carried out using the
30 con~ents of the tank 12c; the effect of this operation is intensified by the
massage of the leather performed by the swirling.
The liquid solution contained in the tank 12d is used for the real tanning step
and, when needed, for the dyeing step, the latter being performed by
colouring agents (e.g. vegetable colouring agents) dispersed in the liquid
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solution.
This liquid solution can also contain agents facilitating leather greasing. The
time required for accomplishment of these steps is reduced because the
pores remain open due to the depression effect. Also the quantity of tanning
and dyeing substances is lower with respect to traditional methods.
In fact, in the described conditions, (i.e. Ieather swollen, thus more spongy),
the concentration in the liquid solution of the tanning and dyeing agents, whichare transferred from the liquid solution to the leather (where they remain
irreversibly fixed), is reduced with respect to known systems, therefore the
o quantity of these agents is smaller, but the quality of the obtained result
remains the same. The pickling, tanning and dyeing operations require about
24 - 36 hours.
It is known that the real tanning l,~l",ent can be preceded by the so-called
pre-tanning and that dyeing (known also as re-tanning), carried out
simultaneously with the agents for leather greasing, can be performed
separately from and after the real tanning treatment.
The apparatus that carries out the above mentioned variants, is schematically
shown in fig. 4b, where the numeral 12e indicates the tank containing the
liquid pre-tanning products, 23e indicates the tank containing the waste liquid
after the pre-tanning has been completed, 30d indicates the tank containing
the solution for washing the leather after the pre-tanning has been completed,
12f indicates the tank with liquid solution for leather re-tanning and greasing
and 23f indicates the tank, which receives waste from the container 4 after the
last step has been completed.
Generally, it has been proved that the process, being the subject of the
present invention, allows to carry out leather tanning in considerably reduced
amount of time, with respect to the traditional techniques, guaranteeing at the
same time a high quality of the tanned leather.
This result is helped also by spreading of leather on the frames 2, swirling
30 movement due to the air flow produced in the liquid solution 5, with which the
- treatment is being carried out, and the depr~ssion effect.
In particular, it is to be pointed out that the leather pieces are not subject to
violent mechanical stresses, but only to a kind of massage produced by said
swirling movement, which results in obvious quality advantage.
- 35 An important feature of the subject process derives from the fact that it is
carried out in closed tight containers. Thus, the diffusion of miasma into the
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environment is avoided, improving the working conditions in the field of the
leather tanning treatment.
Moreover, the proposed process considerably reduces the problem of the
waste disposal and/or neutralisation and allows to save both energy and
substances used particularly for tanning and dyeing.
It must be stressed that the process herein described can be carried out also
without leather washing.
Fig. 5a shows another embodiment of the subject apparatus, in which more
treatment containers are used for carrying out a process with the same steps
o as described for the apparatus of the fig. 4a. There are provided four
containers 4a, 4b, 4c, 4d, arranged in a row and used respectively for the
steps of soaking, liming, pickling and tanning with simultaneous dyeing and
possibly greasing.
The tanks with solutions for carrying out these steps and subsequent
IS washings, are indicated with the same numerals as in fig. 4a and are provided
with valve means and pumps, not shown, since of the same type as described
previously.
In this case, the frames 2, supporting the spread pieces of leather, are
mounted, e.g. on a carrier 28, integral with conveying means 29, which
introduce and withdraw said carrier 28 into and from the containers 4a, 4b, 4c,
4d.
These conveying means 29 include e.g. a carriage 30, that is moved, by not
shown motor means, along a guide element 31 integral with a fixed frame 32
of the apparatus.
Consequently, in each container there is carried out a predetermined step of
the leather treatment and a possible washing of said leather.
Advantageously, the leather is washed in corresponding auxiliary containers
114a, 114b (see fig. 6).
More precisely, after being soaked in the container 4a, the leather is
withdrawn therefrom and introduced into the auxiliary container 114a, in which
it is washed with a liquid solution taken from the tank 30a.
The liming step is carried out in the container 4b and the subsequent washing
in the relative auxiliary container 114b.
This way of proceeding, i.e. washing the leather in auxiliary containers, avoids3s cleaning the containers 4a, 4b after the washing operations following soaking
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and liming, respectively.
The apparatus shown in fig. 5b carries out the treatment steps already
described with reference to fig. 4b.
In the containers 4a, 4b, 4c, 4d, the leather is soaked, limed, pickled, pre-
s tanned, tanned, and lastly, dyed with simultaneous greasing.
The containers, in which these steps are performed, are indicated with the
same numerals as in fig. 4b.
Also in this case, washing following the soaking, liming and pre-tanning steps
can be carried out in relative auxiliary containers like in the case illustrated in
l0 fig. 6.
It is obvious that if the leather treatment requires a number of operations
different from the two illustrated exai"ples (figs. 4a, 5a and 4b, Sb), the
apparatus will be correspondingly modified, while all the advantages of the
invention will be maintained.
S Also in the embodiments shown in Figures 5a,5b,6 the liquid solutions exiting
from their respective containers may be sent to a common discharge
manifold.
The preferred embodiment of the process features the following technical-
functional aspects:
- container 4 (or containers) kept fixed;
- pieces of leather spread and spaced apart;
- treatments carried out in a container, which is closed tight and kept in
depression already before the liquid solution has been introduced therein;
- swirling of the liquid solution, that causes a kind of massage of the leather.
According to a variation of the process, the container 4 (or containers 4a, 4b,
4c, 4d) can rotate about their transversal and/or longitudinal axis, so as to
create a relative movement between the pieces of leather and the liquid
solution used in a treatment step or subsequent washing.
Advantageously, the liquid solution contained in the tanks 111a, 111b reduces
30 dramatically and /or neutralises all the volatile compounds, which are
generated inside the container 4 (or containers 4a, 4b, 4c 4d, 4e, 4fl during
the leather treatment.
On this purpose, more containers 111 can be provided, arranged parallel one
to another, and each of them containing a liquid solution for reducing
~ , . . , . , . .. , . ....... . , . . ~ , .. . ... , ~ .. .
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dramatically andlor neutralising at ieast one predetermined volatile compound.
It is possible for the control unit 14 to act on suitable means (e.g. electric
valves) connected with these tanks, so as to introduce one or more of them,
arranged in a row, into the pipe 110, in relation to the treatment step being
s carried out in the container 4 and therefore, to the kind of the volatile
compound generated during this step.
In case of more containers, the pipe 110, connecting each of them to suction
means 11, is linked with a series of tanks 111 performing the above described
functions.
o Each supply tank can be provided with means for mixing the liquid solution
contained therein, means which are not shown since they are in the
knowledge of those skilled in the art.
Figure 7 shows another embodiment of the apparatus, in which numerals 201,
202, 203, 204 indicate supply tanks conlc.;.,i,,g the liquid solutions for soaking,
s liming, pickling and tanning. Numerals 212a, 212b, 212c, 212d indicate
corresponding heat exchanger (co"l,~l'ed by the control unit 14 via links S1,
SZ, S3, S4). Numerals 216a, 216b, 216c, 216d indicate the corresponding
supply pumps also operated by the control unit 14, via connections P1, P2, P3
and P4.
20 In this case, the ejector means, or grating 9 can be set in communication with
outside (normal operation condition of the container 4) via a related electric
valve 2~0 operated by the control unit.
As an alternative, the ejector means 9 can be connected to one or another of
a series of auxiliary supply tanks 300a, 300b, 300c, 300d (for i"stal~ce, four
2s tanks have been provided, however, their number can be bigger or smaller
than four), via related electric valves 301a, 301b, 301c, 301d also operated by
the control unit.
Each auxiliary supply tank contains a suitable substance, either pure or
properly diluted, which is to be used together with the liquid solutions of the
30 supply tanks 212a, 212b, 212c, 212d during a corresponding step of the
subjected process.
This configuration determines favourable conditions, in that it allows to mix
this substance with the liquid solution each time concerned, in the pre-
established percentage and/or weight, so as to affect in the desired way the
3s process steps.
In order to put this possible action into practice, the control unit 14 cuts off the
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connection between the container 4 and the outside environment (by means
of the electric valve 250) and sets the container 4 in connection with the
predetermined auxiliary supply tank, maintaining this connection for a short
time.
s Depression condition inside the container 4 allow in-flowing of the substance
coming from the auxiliary supply tank, into the container. The substance flow
can be determined by a pump 270, which has not been shown, and can be
measured by means of a proper meter, also not shown.
By using a grating 9 for injecting the substances into the container, it is
o possible to mix quickly the substances emitted with the liquid solution 5
already present inside the container.
As an alternative, these substances can be supplied to the container either at
the same time when the liquid solution 5 is introduced therein, or before liquidsolution introduction.
Moreover, the substances can be supplied to the container also without the
help of the grating 9, in accordance with other ways, which will be obvious to
those skilled in the art.
When at least one substance (or a dilution of this substance) has been
completely let in the container 4, connection between the container and the
auxiliary supply tank is cut off and connection between the container and
outside environment is restored. In the example shown in Figure 7, the
auxiliary supply tanks are associated to the container 4 where process steps
are carried out.
Advantageously, the auxiliary supply tanks can be connected to the
containers 4a,4b,4c,4d provided by the different configurations of Figures 5a
and 6, as well as to containers 4a,4b,4c,4d,4e,4f shown in Figure 5b, and the
substances which they contain are used in a way similar to the one just
described.
Figure 8 concerns a functional-structural feature of the container 4. In detail,there is shown a duct 600 which sets in communication the bottom region of
the container 4 with an intermediate region 601 thereof. More precisely, this
intermediate region is situated just under the free surface 602 of the liquid
solution 5 inside the container.
A pump is mounted along the duct and operated by the control unit 14, for
- 35 withdrawing liquid solution from the container 4, at the region 601, and re-
introducing the liquid solution at the bottom. This provokes continuous re-
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-15-
mixing of the liquid substance, thus avoiding, amongst others, settling of solidsubstances.
All what have just been said, brings to the result that the liquid substance is
utmost homogeneous in all parts.
s This functional-structural feature can be applied to each container 4a,4b,4c,4d
concerned in the embodiments of Figures 5a and 6, as well as to each
container 4a,4b,4c,4d,4e,4f included in the embodiments shown in Figure 5b.
With reference to Figures 9a,9b, numeral 500 indicates a vapour recovery
unit.
o Advantageously, more recovery units are provided, for instance in number at
least equal to the number of steps which form the process carried out inside
the container 4.
Figures 9a,9b show only one recovery unit, since the other ones operate
exactly in the same way.
15 This recovery unit includes an electric valve 404 mounted along a duct 450
which connects the suction means 11 and container inside. Two pipes
460,479, namely first pipe and second pipe, derive from the duct 450 and
have, mounted along them, a three-way electric valve 401 and a two-way
electric valve 402, respectively.
20 These pipes cross the tight cover of a condensation vessel 400, under which,
at its upper part, there is a baffle 480 arranged inclined. The first pipe 460
open end is positioned below the inclined baffle, while the second pipe 470
open end is positioned above the baffle.
The bottom of the vessel is connected to the bottom of the container 4, via a
25 piping 490 which has an electric valve 403.
All the just mentioned electric valves 401,402,403,404 are operated by the
control unit 14.
In the operation condition shown in ~igure 9a, the flow H sucked from the
colltainer 4 by the suction means 11 passes through the vessel 400. This flow
30 is sub~tarllially formed by a mix of air (introduced into the container via the
ejecting means 9) and vapour formed by the liquid solution 5. This mix
expands in the vessel, getting colder, and great part of the vapour condenses.
The liquid thus obtained is collected at the bottom of the vessel and its level
gradually increases.
A sensor 405 detects when a certain level has been reached and sends a
CA 022~3486 1998-10-30
WO 97/42350 PCT/IB97/00432
- 16 -
signal to the control unit 14, that determines the operation condition of Figure9b by operating the above mentioned electric valves.
In this condition, the vessel 400 is by-passed, because the valve 404 is on,
while the valve 401 sets the vessel inside in communication with the outside
environment and the second pipe 470 is cut off by setting the valve 402 off.
Since the container 4 is under depression, a flow K of liquid passes from the
vessel to the container. A proper sensor, that is not shown, detects the level in
the vessel being at the minimum and the control unit changes the operating
condition of the unit 500 restoring the condition of Figure 9a.
o What have just been said is an extremely advantageous feature, because in
this way great part of the evaporated liquid can be recovered and is not
brought to the suction means 11.
The baffle 480 forms a partition between the air-vapour mix inlet region (first
pipe 460) and the air suction region (second pipe 470), so that the minimum
s amount of vapour which is anyway sent to the suction means is negligible.
With a different liquid solution 5 (for process step different from the previousone~, a related recovery unit 500 is further provided with a manifold 410 which
sets in communication all the recovery units at one side with the top of the
container and at the other side with the bottom of the container, via a related
piping 490a. For each container 4a,4b,4c,4d (shown in Figures 5a and 6) and
4a,4b,4c,4d,4e,4f (shown in Figure 5b) one recovery unit 500 like the one just
described can be provided.
According to an interesting variation of the proposed process, advantageous
results obtained on the leather by combined action of depression and swirling
movement can be further increased and improved by subjecting the liquid
solution to ultrasounds.
This can be carried out by a suitable sonotrode of known type (not shown)
connected to the container and controlled by the control unit 14.
It is understood that what above, has been stated as a pure, non limitative
example, therefore possible functional variations of the proposed process
steps remain within the protective scope of the invention as claimed
hereinafter.
Similar observation are to be considered with reference to means and devices
which form the proposed apparatus, in which measure instruments can be
used to measure the inlet and outlet flow rate for each container or supply
tank which is each time concerned.
.. . . ..
