Year: 1888

page_text: I, GEORGE WEBBER RHODES of Friern Park, North Finchley, Middlesex, Gentleman,
do hereby declare the nature of this invention to be as follows:-
Three factors which hasten the action of the tanning process on hides, skins &c.
are:
(1) The spongy condition of their grain, resulting from keeping them motionless in
the tanning liquor.
(2) The frequent renewal of the liquor touching their surfaces.
(3) The passage of an electric stream.
The spongy condition of the hides results from keeping them from rubbing against
or bruising each other while soaking, thus allowing the pores to swell out to the
utmost and so afford to the tanning liquor the most easy access to the innermost parts.—
The frequent renewal of the liquor around them operates by continually bringing new
particles of tanning matter into contact with the fibers; and finally the electric stream
favors the action of the tanning matter by a species of electrolysis. An apparatus
combining these three features offers the best means of thoroughly yet speedily tanning
the hides &c.-Sundry inventors have made use of one or the other of these principles,
but none so far have recognised and combined all three, which is the object of the
present patent.
1 put the hides to be tanned into a pit or stationary trough preferring to hang them
upright so as to allow of withdrawing any one at pleasure for examination.-The hides
thus rest motionless, so as to avoid rubbing against or bruising each other, and
thus secure the utmost development of the spongy state.-A stream of tanning liquoi
is then made to circulate between them in a continuous current, kept in motion by
rotating paddles or other equivalent propelling device, set at one end of the partition
separating the pit or trough into the two compartments of go and return.-The electric
stream is passed through the contents of the trough from end to end, and is furnished
by any generator such as galvanic batteries, a dynamo &c., according to the size of
the plant.

page_text: The quantity and strength of the tanning solution depends on the speed of tanning
wished. A good average for heavy hides is one pound of tannic extract of a specific
weight of 1.15 dissolved in a gallon of water to two pounds of hide.-The liquor
should circulate several times per minute through the trough.-The electricity in
passing polarizes the solution sending the basic principles towards the negative pole
(cathode), the acid elements towards the positive pole (anode).-This latter, if of the
ordinary oxydizable metals is attacked but no harm results therefrom to the tanning,
as most metallic salts rather help thus than hinder. Certain tanners are however
prejudiced against any process wherein metallic salts result, and such can avoid them
by making the anode, if of oxydizable metal, very small,—
-a mere wire-or by using
a nickel, platinum or carbon anode.
Dated this Seventh day of February 1888

page_text: 1, GEORGE WEBBER RHODES of Friern Park, North Finchley, Middlesex, Gentleman
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:
Important helps to hasten the tanning of hides and skins, are ;-
(1) The swollen state of their fiber, favored by keeping them motionless and banging
free in the tanning liquor.
The continual change or renewal of the liquor touching their surfaces.
The forced tannic oozing brought about by passing an electric stream directly
through them.
(4) The warming of the tanning bath.
The swollen condition of the fiber is favored to the utmost by hanging the skins free
of each other, so that they do not press, bruise nor rub together.-The pores becoming
thus opened to the full, a strong and forced oozing of the tanning liquor through
them is brought about by passing an electric stream directly through the skin, the
solution in contact with the surface of which is kept steadily in motion and changing,
in order to supply this oozing continually with fresh particles of tanning matter.-The
combination of these conditions alone brings about a speedy and thorough tanning
and constitutes my process, to which, however, 1 still add, when desired, the warming
of the bath up to the temperature of the bloodheat of the animal (96° Fahrenheit) by
means of the heat from the exhaust steam of the engine.
My plant consists of a pit or tank T, separated lengthwise by a wall or partition, W,
into compartments or channels communicating at their ends in such way that a
continuous stream of the tanning solution, moving along slowly and steadily, can be
kept up therein, by a motor located anywhere in this liquid circuit.-This motor may
be a pump or a paddle wheel; better however, and more compact is an upright
feathering paddle P, set at one end of the tank or pit, or series thereof.
The hides are hung up in rows in this tank or pit, and the electrodes A and Care
placed in between them, in such way that the anodes A and the cathodes O follow
each other alternately.-The cathodes are copper sheets nearly as large as the hides,
and distribute the electricity over the whole surface of the hides.-The anodes are of
coke, platinum or other conducting substance unattackable by oxygen.-Coke plates
of large size being hard to get, I use coke rods set at short stretches asunder in a
wooden frame, like a grate, this form of anode costing less than any other in
comparison with the amount of surface it gives. It is however bulky and brittle ;
where space and lightness are the ruling considerations, a preferable form consists of
a network of platinum wire, woven to form a coarse metallic cloth, like a sieve.
As the oxygen set free on the anodes is hurtful to the tannic solution, oxydizing it
into gallic acid, I hinder the two from coming together by putting the anodes within

page_text: a porous sack or diaphragm, made of any fit porous material, preferably of sailcloth
stretched over a wooden frame. The electricity passes freely through the porous sack,
within which the anode stands in simple water; and tho tannic solution is hindered
from entering or sweating through into the sack by the direction of the electric stream,
which chases it back steadily towards the cathodes. The oxygen forming on the
anodes rises to the surface in bubbles and escapes into the open air.
The hides should be hung far enough apart, say two to three inches, to allow a free
passage of the tanning liquor in between them. The clectricity finds its shortest way
from anode to cathode by passing directly through the skins, which offer in the fresh
state only a very trifling resistance, whereas the tanning liquor, being relatively a bad
conductor, offers so much that very little electricity tends to take the longer way
around the skins. As the hides become tanned their pores draw and shut and the
electric resistance becomes greater; but the relative resistance is readily re-established
by adding a little oil, essence of turpentine or other fatty matter to the tanning
solution, thus increasing its resistance even more than the increased resistance of the
hides. The feathering paddles beat this oil or turpentine essence into fine particles,
forcing it to mix mechanically with the water without being saponified. Its prosonce
adds to the quality of the leather, making it moro waterproof, an outcome which
cannot be had of ordinary tanning pits, wherein a fatty matter, if added, will rise to
the top and tan only the uppermost skins.
The electricity need not pass continuously through each skin.-The object being
to set up a forced osmosis of the tanning liquor through the skin and to allow the
tannin then the time to settle upon the fiber and permeate through the cells, the
electric stream is therefore thrown alternately from one row of skins to another,
allowing it to work a short time on each, and then passing it on to anothor row, and
so forth. In this way, by the time the tannin pumped into the inner parts of a skin
bas settled and its solution thus become thinned, the electricity arrives again and
pumps in a fresh lot of new liquid by the forced osmosis.-To pump in steadily would
simply be to waste electric force, as the overplus of unabsorbed tannin would only be
pumped out the opposite side of the skin. The shifting of the current of electricity
from row to row of skins can be done automatically by a clockwork-like goar connected
with the revolving paddle; or by any of the usual appliances for shunting electrical
currents and ten or twelve rows of skins can thus be served alternately by the same
electric stream, whose consumption is thus brought down to about 5 to 10 watts per
skin according to thickness; that is to say, from 75 to 150 hides can be tanned per
horsepower of force running the dynamo.
Any tanning matter in liquid form can be used in my process.-The solution at
first should be weak and gradually increase in strength as the tanning progresses; the
use of a strong solution at the beginning tans the outer layers of the hide too quickly
and by contracting the outer fibers partly shuts off the free passage of the tannin to
the inner layers. If the liquor used be a solution of extract of oak it is best to begin
with a strength marking 1004 specific weight on an areometer, and gradually increase
the strength till it reaches 1050 or 1060, as the hides approach completion.
From one to two wocks are needed to thoroughly tan an ox hide of good average
thickness; a cowhide tans in somewhat less time, according to weight; calf, horse
and sheep skins in a few days.-The tanning is much helped in every way by warming
the bath to about 96° Fahrenheit, a temperature somewhat above that generally found
in deep, well-built tanning pits, and equal to the bloodheat of the animal, at which
the fibers of the hide are in their true and natural state, that is neither contracted by
relative cold, nor relaxed by relative heat, and the resulting leather is therefore of the
best quality and grain.-This warming of the bath is done by utilizing the heat of the
engine's exhaust steam, the exhaust pipe being run through the tanning bath and
provided with a tap at its lowest point to allow the condensed steam, collecting as
water, to run off.-Copper, not iron, piping should be used, iron being attacked by
the tannic solution.-So also for all the metallic fittings in the bath. The movement
of the liquid, kept up by the paddle, distributes the heat evenly throughout the whole
bath.

page_text: The hides, before undergoing my process of tanning, can be prepared in any of the
usual ways; that is to say, the unhairing either by milk of lime or by sweating, and
the swelling either with or without sulphuric acid, abide exactly the same as in
ordinary tanning.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
1 claim is:
(1) The process of tanning by setting out froe-hanging motionless skins to the
combined action of electricity and of a moving tanning liquor.
The combination of heat with the above.
The porous diaphragm or partition, to isolate the anodes from the tanning
liquor.