Improvements in Tanning Skins and Hides.
Year: 1894

page_text: Date of Application, 7th July, 1894-Accepted, 17th Nov., 1894
Improvements in Tanning Skins and Hides.
We, THOMAS HENRY LEE BAKE of 7 Coburg Place Bayswater, Gentleman,
and HENRY ALFRED LEVERETT of 16 Tokenhouse Yard in the City of London
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 :-
This invention relates to the application of currents of hydrogen gas or any
suitable gaseous compound of same in which arsenic is present which are caused at
intervals to pass through the tanning liquor in the pit or vessel containing the hides
or skins to be tanned. By this action we greatly expedite the process of tanning
and at the same time produce at a cheap rate superior qualities of leather. The
invention is specially applicable to open tanning pits but the pits may if desired be
provided with covers for temporary closing if it is intended to save some of the
hydrogen gas and lead it back to the gasholder for further use instead of letting it
escape in the air from the open pit. The intermittent admissions of the gas may
be advantageously effected by adjustable automatic appliances. The hydrogen gas
may advantageously be produced by the aid of sulphuric acid of commerce acting
on ordinary zinc or iron or by passing steam through a retort containing pieces of
iron or other suitable material in these cases it will be found that arsenic will be
present with the hydrogen gas in quantities that will be sufficient: hydrogen gas
made by electrolysis would on the score of expense be objectionable.
The accompanying drawing illustrates one suitable mode out of many for carrying
the invention into effect being a vertical section through a pit and appurtenances
thereto. The pipe A from the hydrogen generator conveys the gas to the store or
gasholder B and the gas is by a pipe C led to a smaller gasbolder D and thence by
a pipe E to the lower part of tanning pits F containing the hides or skins which
may suitably be suspended from rods or crossbars G. Taps or valves A¹C' and E'
are provided to regulate the admission of the gas.
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The gas from the generator is admitted to the gasholder B the bell of which is
suitably weighted or loaded to the required pressure. Gas is admitted from it to
the smaller gasholder D which may be adapted in size for a number of tanpits and
has its bell suitably weighted for the pressure required to drive the gas through
the liquor in the pit or pits without causing the liquor to flow over or splash over.
By the use of the smaller gasholder D we ensure an even pressure of the gas
admitted to the tanpits and are enabled to regulate that pressure. In our invention
we consider it advantageous to use one large or a few large tanpits rather than a
number of small pits as now usual and indeed necessary because of the periodical
handling" of the skins. This handling we are enabled to dispense with. The
tap E' (or taps if a number of pits are used) having been opened the gas flows
into the lower part of the pit distributing itself into a nest of pipes H in the
lower part of the pit and issuing from fine holes in the said pipes passes up through
the spaces between the skins thereby agitating the liquor and passing off into the
the air at the open pit (or if desired when the cover K is put on and the weight
of the bell of the gasholder B has been suitably relieved, the gas is made to return to
the gasholder B). The hydrogen is admitted for the space of a minute or a few.
minutes only at a time, that is to say, at intervals of say one to four hours, all
according to the nature of the hides and the class of leather to be produced. An
unduly lengthened or continuous action of the gas is detrimental and produces
harsh or hard leather.

page_text: In some cases it is advisable to suspend for a day or more the periodical
admission of the gas in order to prevent the grain of the hide from being unduly
hardened.
The length of time of admission is or may be effected by the apparatus itself if
the cubic contents of the gasholders and the tanpits are properly proportioned.
When the valve or tap C between the two gasholders is closed and the tap or
taps El to the tanpit or pits are open the gas in the gasholder D will flow into
the pit or pits until its power to pass up through the liquor is equalled by the
resistance of the liquor and will thus cease of its own accord. The action will not
commence again until the gasholder D is recharged with sufficient gas pressure
from the gasholder B. The periodical opening and closing of the tap C between
the two gasholders B and D may be effected either by hand or automatically, by
means of suitable machinery. This machinery may be clockwork or any other
motor driving a shaft so as to make it rotate very slowly, to open and shut by
suitable tappets or other devices the said valve C¹ at the required intervals and for
the space of time required.
Or the valve C¹ may be made to control so small an opening that it takes from
say one to four hours to recharge the gasholder D, the time being determined by
giving one or more turns to the valve spindle which is formed with a very fine
screw thread accordingly, say, for instance, one turn in opening the valve
representing four hours to recharge, two turns, three hours and so on.
Any other suitable selfacting means may be applied for carrying out the purpose
in view. Instead of the valve C or in addition thereto we may provide a self-
acting automatic pressure reducing valve between the two gasholders so as to
prevent the pressure in the gasholder D from rising above a fixed maximum. The
admission from the gasholder D to the tanpits may then be effected by means of
taps or valves to the tanpits such valves being actuated by automatic machinery as
above described; and either to open and close simultaneously for all the pits, or
for one after the other.
The action of the hydrogen has the effect of shortening the period of tanning
skins and hides to such an extent that even those of thick substance may be
tanned in a comparatively short time, while (and this is a very important feature
or result of our invention) the fibre strength, the quality, the colour and the
appearance of the leather are equal to those of the leather produced by the
ordinary tanning process of many months duration. We also by this process avoid
the so-called " handling "of the skins which involves much time and labour and we
also effect a great saving in tanning material.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the saine is to be performed, we declare that what
we claim is:
1. The improvement in the process of tanning hides and skins consisting in
passing hydrogen, arsenic being present in small quantity, at intervals through the
tanning liquor in the pit or vessel containing the hides and skins to be tanned,
'substantially as set forth.
2. The improvement in the process of tanning bides and skins consisting in
passing hydrogen, arsenic being present in small quantity, at automatically
regulated intervals through the tanning liquor in the pit or vessel containing the
hides and skins to be tanned substantially as set forth.
3. The use in our improved process of tanning hides and skins of apparatus
constructed substantially as herein described.
Dated this 7th day of July 1894.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.