IMPROVE- MENTS IN TANNING LEATHER, AND IN THE APPARATUS TO BE EMPLOYED FOR THAT PURPOSE
Year: 1864

page_text: LETTERS PATENT to William Smith, of Salisbury Street, Strand, in the
County of Middlesex, Civil Engineer, for the Invention of "IMPROVE-
MENTS IN TANNING LEATHER, AND IN THE APPARATUS TO BE EMPLOYED FOR THAT
PURPOSE." A communication from abroad by Monsieur Aimard Jullien,
residing at Mantes, in the Empire of France.
Sealed the 28th April 1865, and dated the 2nd November 1864.
PROVISIONAL SPECIFICATION left by the said William Smith at the
Office of the Commissioners of Patents, with his Petition, on the
⚫ 2nd November 1864.
. I, WILLIAM SMITH, of Salisbury Street, Strand, in the County of Middlesex,.
Civil. Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN TANNING LEATHER, AND IN THE. APPARATUS TO BE EMPLOYED
POR THAT PURPOSE" (communicated to me from abroad by Monsieur Aimard
Jullien, residing at Mantes, in the Empire of France) to be as follows:-
Instead of subjecting the articles to be tanned to the process of tanning
in open pits, or in vessels wholly or partially closed, or by the more or less
rapid circulation of the tanning liquor under atmospheric pressure produced
by the employment of a vacuum pump in combination with a closed or par-
tially closed vessel; instead, also, of the employment of the pressure of dead
weights alternately applied and removed, or the employment of rollers and
other mechanical means in combination with repeated immersions or steep-
ings; and instead also of subjecting the articles to be tanned to a pressure of

page_text: one or two atmospheres in combination with the tanning liquid alone, I
employ the following means:-Within a strong vessel which is capable of
being afterwards closed hermetically and resisting considerable internal
pressure I place, first a layer of tan to the thickness of about three inches,
then a hide, say, an ox hide, then a thickness of tan, then another hide, and
so on alternately until the vessel is filled; the cover is then securely fitted,
and tanning liquor which has been prepared from oak bark and concentrated
and graduated by evaporation (according to the stage of the process) is run
into the vessel, which is filled quite full from a reservoir and the connection
therewith shut off. I then apply pressure by means of a pump, which is
used to force in the additional quantity of tanning liquor to make up any
diminution in bulk from leakage or other cause. The pressure is continued
with a low strength of juice or tanning liquor upon thick ox hides, for about
ten days, after which the liquor is drained off and a liquor of greater strength
is then charged into the vessel as before, and an increased pressure is then
applied by means of a force pump and continued for a longer period' than
before, say, for fifteen days, when this liquor is drawn off and a liquor of still
greater strength is substituted, and a still greater pressure than before is
applied by means of the pump, and continued for a still longer period, say,
twenty days.
Thus, to recapitulate, I separate the hides by means of layers of tan within
a hermetically-closed vessel of great strength, and I apply from time to time
the tanning liquor of increasing strength for increasing periods, in each case
under an increase of pressure, and by this means I am enabled to tan the
thickest hides in a period of about forty-five days, which in the ordinary way
requires eight to ten months time, and I tan them as thoroughly and as per-
fectly throughout as can be done by the much longer and much more expensive
process of open-pit tanning, and without deterioration of the strength and
market value of the leather.
The temperature at which I find it most useful to perform the process
according to this Invention is at from 18° to 20° on the Reaumur scale, and
the pressure which I find it most useful to apply for the purpose of completing
the process of tanning according to my plan is 40 atmospheres or 600 pounds
per square inch for the thickest hides. For skins of lesser thickness and of
softer nature or more open structure, such as calf skins, I decrease the
strength of the tanning liquor, and of the pressure under which it is applied,
as also the time during which it is continued, inasmuch as calf skins require
only an ultimate pressure of ten atmosphères or so continued for about ten
days. In every case it is intended that the pressure, whatever it may be,

page_text: shall be maintained constant by means of an air vessel placed in any
convenient position above the large vessel.
. The apparatus which I employ consists of a suitably large and strong
cylindrical or other form of metal vessel, having a cover or covers capable of
being readily removed and replaced air-tight, the vessel and its covers and
fittings being capable of resisting an internal pressure exceeding forty atmo-
spheres with safety, with a cock and pipe for discharging the liquor after it
has been used. A reservoir for containing the tanning liquor or solution of
oak bark or other liquid preparation should be connected with the tanning
vessel by means of a pipe and a cock to shut off the supply. The superior
part of the tanning vessel should be fitted with an air vessel having a mano-
meter mounted thereon, and there must be a connection also with the force
pump, by means of which the pressure within the tanning vessel is accumulated
and maintained. The force pump may be fitted in any convenient position,
and the connecting pipes should be fitted with valves, and also with cocks for
shutting off the connection of one part of the apparatus from the other.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Smith in the Great Seal Patent Office on the
2nd May 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
SMITH, of Salisbury Street, Strand, in the County of Middlesex, Civil
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Second day of November, in the year of our Lord
One thousand eight hundred and sixty-four, in the twenty-eighth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
I, the said William Smith; Her special license that I, the said William
Smith, my executors, administrators, and assigns, or such others as I,
the said William Smith, my executors, administrators, or assigns, should-
at any time agree with, and no others, from time to time and all
times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN TANNING LEATHER, AND IN THE APPARATUS TO BE EMPLOYED
FOR THAT PURPOSE," a communication to me from Monsieur Aimard Jullien, a
Foreigner, residing Mantes, in the Empire of. France, upon the condition

page_text: (amongst others) that I, the said William Smith, my executors' or adminis-
trators, by an instrument in writing under my hand and seal, or under the
hand and seal of one of them, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be per-
formed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said William Smith, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement and accompanying Sheet of Drawings :-
'
Instead of subjecting the articles to be tanned to the process of tanning in
open pits, or in vessels wholly or partially closed, or by the more or less rapid
circulation of the tanning liquor under atmospheric pressure produced by
the employment of a vacuum pump in combination with a closed or partially
closed vessel; instead also of the employment of the pressure of dead weights
alternately applied and removed, or the employment of rollers and other
mechanical means in combination with repeated immersions or steepings;
and instead also, of subjecting the articles to be tanned to a pressure of one
or two atmospheres in combination with the tanning liquid alone, I employ
the following means:-Within a strong vessel which is capable of being
afterwards closed hermetically and resisting considerable internal pressure,
I place first a layer of tan to the thickness of about three inches, then a
hide, say, an ox hide, then a thickness of tan, then another hide, and so on
alternately until the vessel is filled; the cover is then securely fitted, and
tanning liquor which has been prepared from oak bark and concentrated and
graduated by evaporation (according to the stage of the process) is run into
the vessel, which is filled quite full from a reservoir and the connection
therewith shut off. I then apply pressure by means of a pump, which is
used to force in the additional quantity of tanning liquor to make up any
diminution in bulk from leakage or other cause. The pressure is continued
with a low strength of juice or tanning liquor upon thick ox hides for about
ten days, after which the liquor is drained off and a liquor of greater strength
is then charged into the vessel as before; and an increased pressure is then
applied by means of a force pump and continued for a longer period than
before, say, for fifteen days, when this liquor is drawn off and a liquor of still
greater strength is substituted and a still greater pressure than before is
applied by means of the pump and continued for a stilll onger period, say,
twenty days.

page_text: Thus, to recapitulate, I separate the hides by means of layers of tan within
a hermetically-closed vessel of great strength, and I apply from time to time
the tanning liquor of increasing strength for increasing periods, in each case
under an increase of pressure, and by this means I am enabled to tan the
thickest hides in a period of about forty-five days, which in the ordinary way
requires eight to ten months time, and I tan them as thoroughly and as
perfectly throughout as can be done by the much longer and much more
expensive process of open-pit tanning, and without deterioration of the strength
and market value of the leather.
:
The temperature at which I find it most useful to perform the process
according to this Invention is at from 18° to 20° on the Reaumur scale, and the
pressure which I find it most useful to apply for the purpose of completing the
process of tanning according to my plan is forty atmospheres or six hundred
pounds per square inch for the thickest hides. For skins of lesser thickness and of
softer nature or more open structure, such as calf skins, I decrease the strength
of the tanning liquor and of the pressure under which it is applied, as also the
time during which it is continued, inasmuch as calf skins require only an
ultimate pressure of ten or fifteen, atmospheres or so continued for, about ten
days. In every case it is intended that the pressure, whatever it may be;
shall. be maintained constant by means of an air vessel placed in any
convenient position above the large vessel.
}
The apparatus which I employ consists of a suitably large and strong
cylindrical or other form of metal vessel, having a cover or covers, capable.of
being readily removed and replaced air-tight, the vessel and its cover and
fittings being capable of resisting an internal pressure exceeding forty atmo-
spheres with safety, with a cock and pipe for discharging the liquor after it
has been used. A reservoir for containing the tanning liquor or solution of
oak bark or other liquid preparation should be connected with the tanning
vessel by means of a pipe and a cock to shut off the supply. The superior
part of the tanning vessel should be fitted with an air vessel having a mano-
meter mounted thereon, and there must be a connection also with the force
pump, by means of which the pressure within the tanning vessel is accumulated
and maintained. The force pump may be fitted in any convenient position,
and the connecting pipes should be fitted with valves and also with cocks for
shutting off the connection of one part of the apparatus from the other.
In the accompanying Sheet of Drawings, Figure 1 is a vertical section of a
cylindrical-shaped vessel or apparatus constructed according to this Invention;
and is designed for the lower or lesser pressures and to be employed for
tanning the thinner and softer skins, whilst Figure. 2 represents a similar
"

page_text: apparatus, intended to be employed for the higher pressures and for the thicker
skins or hides.
The following letters represent corresponding parts in both arrangements.
A, the body of the apparatus, which is shewn as cylindrical; B, pipe for the
introduction of the tanning liquid, connected with C, a hydraulic pressure
pump, not shown in Figure 1; D is the moveable cover, fitted with the regu-
lating valve E, the air receiver F, and the manometer or pressure gunge G;
whereas in the apparatus shewn in Figure 1 this cover is a man-hole cover
fastened on the body of the apparatus by means of bolts (a, a,) sufficient to
resist the minor pressures, for which this' apparatus is designed. The higher
pressures to be employed in the apparatus, shewn in Figure 2, involve the
necessity for a more perfect means of securing the cover, which is shewn as
being effected by means of a frame consisting of the double T-irons H, H',
and the tie-bolts I, I', the double T-irons H, H¹, being secured to the top and
bottom by means of wedges K, K³, by which the bottom and top are securely
held together. H (Figure 1) and L (Figure 2) is the packing, ring for the
joint; I (Figure 1) and M (Figure 2) the discharge cock for drawing off the
tanning liquid. In both Figures (1 and 2) the thicknesses of some skins and
layers of tan are shewn, J and K, Figure 1, and N and O, Figure 2 repre-
senting respectively the skins and layers of material, as before described. In
the arrangement shewn in Figure 1 the filling and emptying of the vessel is
effected by unfastening the bolts a, a, and removing the cover D; whereas in
the arrangement, Figure 2, the tie-bolts I, I', as well as the bolts a have to be
unfastened for the same purposes.
Having described my Invention of "Improvements in Tanning Leather, and in
the Apparatus to be employed for that Purpose," a communication to me from
Monsieur Aimard Jullien, a foreigner residing at Mantes, in the Empire of
France), and having illustrated in the accompanying Sheet of Drawings the
apparatus employed, I wish it to be understood that what I claim is,-
First, the interposition of layers of bark tan between the hides or skins to
be operated upon in combination with tanning liquor or solution of bark,
within a close vessel and under considerable pressure, as herein described.
or
Second, the employment of solutions or liquid extracts of oak bark (alone
in combination with other liquids, extracts, or materials) of varying degrees
of strength, within a close vessel, in combination with the stratified arrange-
ment of skins or hides and tan or equivalent material, as herein-before described,
under pressure, produced by a forcing pump or other equivalent means, in the
manner and for the purpose herein described.
Third, the use or employment of a strong and close pressure-resisting vessel
:

page_text: in combination with the stratified arrangement of materials, as described, and
the use of fluid extract or decoction of oak bark, constantly applied under
pressure, in the manner and for the purpose herein-before set forth.
In witness whereof, I, the said William Smith, have hereunto set my
hand and seal, this First day of May, One thousand eight hundred
and sixty-five.
Witness,
JAMES STEVENSON,
19, Salisbury Street,
Strand, W.C.
WILLIAM SMITH, C.E. (L.B.).