IMPROVEMENTS IN THE MODE OR MEANS OF TREATING TAN OR SPENT BARK TO RENDER THE SAME SUITABLE FOR USE IN THE MANUFACTURE OF PAPER."
Year: 1881

page_text: LETTERS PATENT to William Guest, of Deptford, in the County of Kent,
not in business, and Charles Court, of Rotherhithe, in the County of Surrey,
Engineer, for an Invention of "IMPROVEMENTS IN THE MODE OR MEANS OF
TREATING TAN OR SPENT BARK TO RENDER THE SAME SUITABLE FOR USE
IN THE MANUFACTURE OF PAPER."
PROVISIONAL SPECIFICATION left by the said William Guest and Charles
Court at the Office of the Commissioners of Patents on the 18th June
1881.
WILLIAM GUEST, of Deptford, in the County of Kent, not in business, and
CHARLES COURT, of Rotherhithe, in the County of Surrey, Engineer. " IMPROVE-
MENTS IN THE MODE OR MEANS OF TREATING TAN OR SPENT BARK TO
RENDER THE SAME SUITABLE FOR USE IN THE MANUFACTURE OF PAPER."
We take the tan or spent bark and put the quantity thereof required to be
operated on into a hopper or other receptacle and cause the same to be delivered
therefrom by mechanical arrangements and to pass between and be crushed by
two or more suitably formed revolving rollers. By the action of the rollers tho
fibrous tan and the knots therein are opened up. We prefer to feed the tan to the
rollers in a semi-dry state. The fibrous tan and its knots having been thus opened
up, or the fibres to an extent separated, the mass is introduced in convenient
quantities into a rotary boiler or agitator containing an admixture of water and
caustic soda in solution in proportion of about one twentieth part of the soda to
the quantity of water used, and when the boiler or agitator is closed the
steam is admitted therein and the whole mass is agitated by means of arms or
cutters therein and the separating or opening process is thereby further
continued.
The mass may be washed in water in the boiler or in a separate vessel.
When it is desired to bleach the mass it is subjected to the action of bleaching
materiala

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Quest and Charles Court in the Great Seal Patent Office
on the 17th December 1881.
WILLIAM GUEST, of Deptford, in the County of Kent, not in business, and
CHARLES COURT, of Rotherhithe, in the County of Surrey, Engineer. " IMPROVE-
MENTS IN THE MODE OR MEANS OF TREATING TAN OR SPENT BARK TO
RENDER THE SAME SUITABLE FOR USE IN THE MANUFACTURE OF PAPER."
The object of this Invention is to utilize what is known as tan or spent bark by
preparing a fibre therefrom suitable for conversion into paper. It has been proposed
from time to time to reduce all kinds of vegetable fibres to pulp or "half stuff" for
paper makers' use,
but many of the fibrous materials mentioned as suitable for this
purpose, and among them spent bark, have offered insuperablo obstacles to the
paper maker through the cost of their conversion into "half stuff" and the inferior
character of paper that could be produced therefrom. The spent bark of the
tanner contains knots or hard portions, which, notwithstanding the rough grinding
operation to which the bark is subjected before use by the tanner and the
subsequent steeping received in the tan pits, retain all their hardness and consistency
and yield up little or none of their tanning property.
By the process of treatment which we will now proceed to describe we first
reduce the knots to their constituent fibres and then extract therefrom the tannin
or tannic acid, which becomes a valuable marketable product.
In Sheet I. of the accompanying Drawings Fig. 1 is a sectional elevation of the
crushing mill which we employ in preparing the spent bark for the after treatment,
and Fig. 2 is a back elevation of the same; A, A, are side frames braced together
by stay rods and carrying bearings for three rollers B, C, D, the rollers B and C
being by preference fluted; E is a hopper carried by the framing and serving to
deliver tho spent bark to be operated upon between the rollers B and C. Tho
roller B acts as a feed roller and the roller C is a crushing roller, it being held in
contact with the roller D by means of levers F, F, pivotted to the main framing
and resting on the brasses of the axle of the roller C, which brasses aro free to slide
in vertical slots made in the side frames; F', FL, are tension springs, which connect
the levers F with a fixed point on the framing and thus cause the levers to bear
down the crushing roller C upon the roller D. The pressure put on these levers we
propose to regulate by means of adjusting nuts, shewn in the Drawing; G is a
driving shaft having its bearings in the side frames and receiving rotary motion
through a band from any prime mover; G¹, G¹, are the fast and loose band pulleys
on this shaft, and g is a spur pinion on the opposite end of the shaft. This pinion g
gears into a spur wheel b on the axle of the roller B and serves to impart a slow
rotary motion to that roller. On the end of the shaft G near the band pulleys is
keyed a spur wheel g¹, which gears with a wheel d on the axle of the roller D.
Keyed to the opposite end of the axle of the roller D is a spur wheel d' of a similar
pitch, and gearing into this wheel is a wheel c of similar pitch keyed on the axle
of the roller C. Supposing the hopper E to be charged with the spent tan,
-preferably in a dry state, on rotary motion being imparted to the mill the roller B
will force the tan forward into the bite of the rollers C, D, the tan being guided
thereto by an adjustable scraper H situate between the rollers B and D and shewn
detached at Figures 3. As the material is subjected to the crushing action of the
rollers the hard knots will be reduced to a fibrous state and the crushed bark or
tan will be delivered out of the machine on to an inclined board I, whence it is
collected into a suitable receptacle. The scraper H when properly adjusted will
serve to clear the rollers B and D from any adhering fibres and thereby maintain

page_text: the efficiency of the mill. The edge of the scraper next the roller B is by preferenco
serrated, as shewn in the detached views, but this is not essential. The spent bark,
when reduced by the crushing process just described, is submitted to a steeping
process with agitation for the purpose of extracting therefrom the tannin still
remaining in the bark. For this purpose we use the arrangement of apparatus
shewn in Sheet II. of the Drawings, which consists of a rotary steam tight boiler,
in which is enclosed a series of revolving blades. Fig. 4 is a longitudinal section
of this apparatus; Fig. 5 is a transverse section taken in the line 1, 2, of Fig. 4;
and Fig. 6 is a plan view of the same; K is a horizontal cylindrical boiler dome
shaped at its ends and fitted with hollow trunnions which work in roller bearings
carried by the end frames L. Through the trunnions of this boiler passes
a hollow axle M, on which is mounted a series of blades or stirrers N
arranged helically around the hollow axle. One end of this axle is closed,
and the open end fits into the stuffing box M communicating with a
steam supply pipe M². The hollow axle is pierced to allow of steam issuing
from it into the boiler K, and it is fitted with band pulleys m, m, for
imparting an axial motion thereto. Keyed to one of the trunnions of the boiler
is a spur wheel k, into which gears a pinion o keyed on a driving shaft O,
having its bearings on the end frames. The driving gear we so arrange as to
rotate the hollow axle and the boiler in opposite directions, the boiler making, say,
twenty five revolutions per minute, and the axle with its beaters running at some
four times that speed. The boiler it will be scen is provided with four manholes
for admitting the material to be treated, and for discharging the same. These
manholes, which are preferably oval, are arranged longitudinally of the boiler, and
are closed by loose covers, which are secured by clamping screws that work through
bars overlying the holes, and held in place by lugs projecting from the cover seat.
The upper side of the boiler is provided with steam discharge cocks, and the under
side of the boiler with cocks for discharging the liquor. These cocks we fit with
strainers to prevent the fibres entering and clogging up the passages.
This
apparatus is intended to operate upon some half a ton of the crushed spent tan at
one time. It is discharged into the boiler through the manholes, and about forty
gallons of water is added thereto. In order to quicken the operation of extracting
the tannin, we add to the contents of the boiler a saturated solution of caustic soda
in the proportion of five pounds of soda or thereabouts to cach hundredweight of
the spent tan to be operated upon. We then admit steam at about thirty pounds
pressure to the boiler through the porforations in the hollow axle, and set the
boiler and the beaters in motion. This we continue for about two hours, by which
time the bark fibres will be separated and deprived of the tannic acid contained
therein. Preparatory to discharging the now prepared fibres we shut off the steam
to the hollow axle M upon the steam discharge cocks, and open also the discharge
cocks for the liquor, which falling into suitable receivers is then ready for the use
of the tanner. When the liquor has been run off we open the manholes, turn the
boiler to bring the manholes to the underside, and then by means of rakes discharge
the prepared fibre into barrows.
A modification of this apparatus is shewn in the partial longitudinal section,
Fig. 7, the object being to provide a central support for the cylindrical boiler shell
when the apparatus is made on a large scale. This support consists of a circular
skeleton frame P, which is made fast by bolts to the shell of the boiler, and is
formed with a hub to fit the hollow axle and rotate smoothly thereon. This
central stay or support will prevent the sagging of the boiler, the central axlo
being of suitable strength to sustain the weight of the boiler and its loud.
The next step in the process is to subject the fibre to a rinsing operation, which
is carried on in an apparatus similar to that just described, or in a washing drum
having radial dashboards similar to those used in tan yards and bleach works.
This rinsing operation consists in agitating the fibre for about half an hour in clear
water. When removed from this agitator the fibre is passed through a second
crushing mill, similar to that described above, but having rollers with flutes of a

page_text: finer gauge. The passage of the fibre between these squoczing rollers will not
only discharge the water contained therein, but will complete the separation of
such fibres as may have been partially separated by the first crushing operation.
The fibre thus prepared according to our Invention is now fit for conversion into
paper. If it is desired to convert it into white paper the fibro must be bleached in
any well known and approved manner, but for inferior or coarse papers no
bleaching of the material will be required.
From the foregoing description it will be understood that the advantages of our
improved mode of preparing fibres for paper making are, first, that the fibres of the
ground spent bark retain their normal length, and are otherwise uninjured by the
process; and, secondly, a valuable product consisting of tannic acid is for the first
time obtained from the spent bark.
Having now set forth the nature of our Invention of "Improvements in the
Mode or Means of Treating Tan or Spent Bark to Render the same Suitable for
Use in the Manufacture of Paper," and explained the manner of carrying the same
into effect, we wish it to be understood that under the above in part recited Letters
Patent we claim,―
The mode of treating tan or spent bark as above described, whereby the natural
fibres of the bark are separated and converted into "half stuff" in an economical
manner, and the tannic acid contained in the spent bark is extracted in a
concentrated form.
In witness whereof, I, the said Charles Court, have hereunto set my hand and
seal, the Fifteenth day of December, in the year of our Lord One thousand
eight hundred and eighty one.
CHARLES COURT. (Ls.)