Improvements in the Process and Apparatus for Tanning Hides and Skins with Electrolytic Action.
Year: 1892

page_text: Date of Application, 24th June, 1892 /
Complete Specification Left, 10th Mar., 1893-Accepted, 22nd Apr., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Process and Apparatus for Tanning Hides and
Skins with Electrolytic Action.
I, ETIENNE JEAN FINOT of No. 16 Rue Drouot, Paris, France, Engineer do
hereby declare the nature of this invention to be as follows :-
:—
My invention relates to the method of tanning wherein the hides or skins while
submitted to the action of the tanning liquor are at the same time subjected to
electrolytic action whereby the process of tanning is greatly accelerated.
It has been found that in this process the combined electrolytic and tanning
action is greatly facilitated by maintaining a relative motion between the hides and
the tanning liquor and in order to effect this, either the hides and liquor have been
placed in a revolving drum as in the "Worms and Bale
process, or the hides
have been moved to and fro or round in a circular path as in the "Groth"
process.
Both these processes have the disadvantage that the hides, in being moved more
or less rapidly frequently become entangled and knotted together, thereby
preventing the regular and uniform action of the liquor and electric current
thereon.
Furthermore, the electric current is made to pass through the entire volume of
liquid contained in the bath, which necessitates the use of currents of comparatively
high tension, and consequently greatly increases the cost of the process.
My present invention has for its object to reinedy these defects, by producing the
necessary flow of the tanning liquor while the hides are maintained stationary.
It consists in suspending the hides in the tanning bath in such a manner that they
are entirely immersed and are in communication with the negative pole of a suitable
electric circuit while the positive pole is connected to such a part of the bath as
will enable the current while traversing that part of the liquor which is in
immediate contact with the hides to pass to the negative pole by the shortest
possible route. The bath is maintained at a suitable constant temperature by any
known means, such as by the introduction of a jet of steam, and the various
chemicals, such as alkalis, acids, and tannin are introduced gradually and in the
required order as the process of tannin proceeds, whereby the hides are made to
pass without manipulation through the several usual stages of treatment, the
strength of the current being. also graduated according to the requirements of each
stage. At the same time a current of carbonic acid gas is introduced into the bath
in order to maintain open the pores of the hides by enabling them to resist the
contraction due to the action of the tannin.
While the above described process is going on, the body of liquor is made to
circulate continuously in contact with the hides, and portions thereof are dis-
charged from time to time, so as to bring freshly dosed portions of the liquor in
contact with the hides; such circulation of the liquor also serves to prevent
polarisation of the electrodes and to actuate the transformation and precipitation of
the putresible nitrogen compounds contained in the pores of the hides, so as to
enable the combination of the tannin with the hides to take place more rapidly.
This process, which can be applied in the ordinary tanning pits of tanneries, will
enable an ox hide to be converted into leather in about 250 hours at most, a cow
hide in about 200 hours a calf skin in 120 hours and a sheep or goat skin in
80 hours.
:
The arrangement of apparatus which I prefer to employ for carrying out my
said process is as follows.

page_text: •
A tank is charged with the tanning, liquor which is made to circulate either by
a centrifugal pump withdrawing the liquor at one point, and introducing it again at
another point, or by the rotation of a screw blade or blades placed at the bottom
of the tank. The hides or skins are suspended in the tank closely side by side and
are connected in any suitable manner to metal or carbon plates constituting the
negative electrodes which are fixed to the sides or ends of the tank, preferably at
each end, while a plate or plates constituting the positive electrode is or are fixed
either on the bottom of the tank or on parts of the sides opposite those where the
negative electrodes are fixed. Carbonic gas is forced in by a pump (which may be
'the same one that effects the circulation of the liquor) through a perforated rose
situated at the bottom of the tank.
• When one charge of liquor in the bath has become exhausted or requires to be
replaced by a charge of a different composition it is partially or wholly-drawn off
through a discharge pipe at bottom provided with a cock, and the fresh charge is
introduced at top.
Dated this 24th day of June 1892.
:
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Process and Apparatus for Tanning Hides and
Skins with Electrolytic Action.
1, ETIENNE JEAN FINOT, of No. 16 Rue Drouot Paris, France, Engineer, do
hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement: —
My invention relates to the method of tanning wherein the hides or skins, while
submitted to the action of the tanning liquor, are at the same time subjected to
electrolytic action whereby the process of tanning is greatly accelerated.
It has been found that in this process the combined electrolytic and. tanning
action is greatly facilitated by maintaining a relative motion between the hides and
the tanning liquor and in order to effect this, either the hides and liquor have been
placed in a revolving drum as in the "Worms and Bale"
process, or the hides
have been moved to and fro or round in a circular path as in the "Groth"
.process.
Both these processes have the disadvantage that the hides, in being moved more
or less rapidly, frequently become entangled and knotted together, thereby
preventing the regular and uniform action of the liquor and electric current
thercon.
Furthermore, the electric current is made to pass through the entire volume of
liquid contained in the bath, which necessitates the use of currents of comparatively
high tension, and consequently greatly increases the cost of the process.
My present invention has for its object to remedy these defects, by producing
the necessary flow of the tanning, liquor while the hides are maintained stationary.
It consists in suspending the hides in the tanning bath in such a manner that they
are entirely immersed and are in communication with the negative pole of a suitable
.electric circuit while the positive pole is connected to such a part of the bath as
will enable the current while traversing that part of the liquor which is in
immediate contact with the hides, to pass to the negative pole by the shortest.
possible route.
[ .
The bath is maintained at a suitable .constant temperature by any known means,
such as by the introduction of a jet of steam, and the various chemicals, such as
alkalies, acids, and tannin are, introduced gradually and in the required order as
the process of tannin proceeds, whereby the hides are made to pass without
.

page_text: manipulation through the several usual stages of treatment, the strength of the
current being also graduated according to the requirements of each stage. At the
same time a current of carbonic acid gas is introduced into the bath in order to
maintain open the pores of the hides by enabling them to resist the contraction due
to the action of the tannin.
While the above described process is going on, the body of liquor is made to
circulate continuously in contact with the hides, and portions thereof are discharged
from time to time, so as to bring freshly dosed portions of the liquor in contact.
with the hides; such circulation of the liquor also serves to prevent polarisation
of the electrodes and to activate the transformation and precipitation of the
putrescible nitrogen compounds contained in the pores of the hides, so as to enable
the combination of the tannin with the hides to take place more rapidly. This
process, which can be applied in the ordinary tanning pits of tanneries, will enable
an ox hide to be converted into leather in about 250 hours at most, a cow hide in
200 hours, a calf skin in 120 hours, and a sheep or goat skin in 80 hours.
In order that ny said invention may be readily understood I will describe by
way of example the arrangement of apparatus for carrying it into effect as shewn
on the accompanying drawing.
Fig. 1 shews diagrammatically a vertical section of a tanning pit A in which the
circulation of the liquid is effected by a rotary pump B, which can, at will, also be
used for introducing a gas such as carbonic acid."
Fig. 2 shews a cross section of a tanning pit A in which the circulation of the
liquid is effected by means of a screw propeller C.
The hides are suspended entirely submerged in the tanning pit; in the case of
large skins, they are stretched across from one end to the other, side by side, as
shewn at Fig. 1; in the case of smaller skins, it suffices to suspend them as shewn
at Fig. 2; in both cases they are connected to the negative electrode formed of
one or more plates N of lead, copper, or carbon fixed on the sides of the pit and
connected with each other, while the positive electrode is formed by one or more
plates P of lead or carbon arranged either upon the bottom of the pit or at the
sides. The gas is introduced by means of the pump B which draws it in by the
pipe and propels it into the pit through the pipe & arranged at the bottom and
terminating in a perforated rose.
The circulation of the liquid is effected by means of the same pump, the suction
being effected either through the pipe and the discharge through pipe ¿", or
conversely.
In Fig. 2 the circulation is obtained by means of the screw propeller C driven
by any suitable transmission, such as that shewn.
The electric current is supplied by a dynamo D or any other current generator,
the strength of the current from which is regulated at H by any known means,
the current being led thence to the electrodes P and N by suitable conductors.
The hides, free from the foreign matters which have been used in their pre-
paratory treatment are placed in the pit and are not removed until they are com-
pletely tanned. During the entire operation the liquid is made to circulate
continuously while at the same time an electric current is made to pass through the
bath. The hides having become swelled to the required degree, the tannin is
introduced, a portion of the charge being removed from time to time through the
pipe G on opening the cock R, or by other means, in order to enable the spent
liquor to be replaced by degrees by freshly dosed liquor introduced through the
upper pipe L. The strength of the electric current is so calculated that the whole
of the tannin introduced is at once fixed in the hides in combining with the gelatine
for transforming it into leather. When the requisite quantity of tannin has thus
been taken up, its introduction is stopped, as is also the removal of the spent
liquor, but the electric current is continued as also the circulation of the liquor,
until the whole of the tannin present has been absorbed by the hides, which will
then be completely tanned.

page_text: Laving now particularly described and ascertained the nature of this inven
and in what manner the same is to be performed, I declare that what I
m is :-
:-
An improved method of tanning hides and skins rapidly by the aid of electricity
prising the following features:
a. The complete immersion of the hides in the tanning liquid in a stretched or
suspended condition and in communication with the negative pole of the
circuit of an electric generator.
b. The maintenance of the tanning bath at a constant temperature by suitable
means such as by the introduction of steam."
c. The graduated increase of the percentage of alkalies, acids and tannin of
the bath, whereby the strength of the bath can be proportioned according
to the progress of the tanning process.
d. The introduction into the bath of a current of carbonic acid for the purpose
of keeping open the pores of the hides by causing them to resist the con-
traction due to the action of the tannin.
e. Continual circulation of the liquids over the hides which remain stationary,
and renewal of the dosed liquids on the surfaces, for preventing the
polarisation of the electrodes and for activating the transformation and
precipitation of the putrescible nitrogenised matters enclosed in the pores
of the hides, thus rendering more rapid the combination of the tannin with
the leather, all substantially as herein described.
Apparatus for carrying out the process of tanning by electricity as set forth
he preceding claim, combined and operating as herein described with reference
he drawings.
Dated this 10th day of March 1893.
.
ABEL & IMRAY,
Agents for the Applicant.