IMPROVEMENTS IN THE APPARATUS AND PROCESSES FOR TANNING
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by James Marius Macrum at the
Office of the Commissioners of Patents, with his Petition, on the 13th
April 1866. A communication from abroad by James Johnston, of
Alleghany City, in the State of Pennsylvania, United States of America.
I, JAMES MARIUS MACRUM, of 36, Hill Street, Knightsbridge, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE APPARATUS AND PROCESSES FOR TANNING," to be as
follows:-
This Invention relates to certain apparatus and processes for the purpose of
more speedily, effectually, and safely causing the tannin to penetrate and
incorporate itself with hides or skins which have been prepared in the usual
manner for tanning. The hides or skins to be tanned are in the first place
subjected to a succession of immersions in tan liquid, alternating with brief
intervals of exposure in a vacuum or partial vacuum. This first part of the
process is carried out by having the skins laid on a rack or racks, or
stretched on franes secured in a proper position in an air-tight revolving vat
or vessel of cylindrical shape, mounted so as to have its axis in a horizontal line
and to revolve freely between strong supports placed at the two ends thereof,
into this vessel a quantity of tan liquid is to be admitted from a fixed vat or
vats, adjacent and so arranged that the tan liquid may flow through a pipe from
the one into the other. All the apertures must now be closed and the air

page_text: exhausted by means of an air pump, so as to make as perfect a vacuum as
possible above the tan liquid in the revolving vat, which is now to be set in
motion and kept revolving till it appears that the skins have absorbed as much
as they will do in this stage of the process. It must be stopped, however, at
intervals to apply the air pump to it in order to make the vacuum more
perfect and to change the tan liquid which should also be of increased strength
at each change. The duration and relative proportions of the immersions and
of the intervals of exposure in the vacuum are regulated either by the greater
or less quantity of tan liquid admitted into the revolving vessel, or by providing
by suitable gearing for a slower motion from the point of immersion to the
point of emersion, and for a more rapid motion while the skins are passing
through the vacuum, for it is generally desirable to have the skins immersed
in the tan liquid for longer intervals than they are kept in the vacuum.
The revolving vat is to be provided with apertures for putting in the skins
and the tan liquid and removing the same for applying the air pump, and (if
the same vessel be used not only for the above part of the process, but for
that hereafter to be described, which it is not absolutely necessary that it
should be), also for applying the apparatus for hydrostatic pressure, all of
which apertures being so arranged and fitted as to be capable of being
made air-tight when required. If considered more convenient the revolving
vessel may be supplied with tau liquid through apertures in the axle arms
thereof, connected by means of air-tight coupling boxes with pipes communica-
ting with the fixed vats.
The second part of the process consists in subjecting the skins which have
been thus treated to a strong bydrostatic pressure either in the revolving
vat or in another suitable vessel provided with apparatus for applying such
pressure, to this end the vessel employed must be completely filled with strong
tan liquid, and the hydrostatic pressure should be gradually increased from
time to time till the process of tanning is completed, which, generally
speaking, will require about six or eight days, and then the skins are to be
taken out, carried, dressed, and manipulated in the ordinary manner.