Improvements in the Method of and Apparatus for Straining Paper-pulp.
Year: 1889

page_text: Date of Application, 14th Sept., 1889-Accepted, 19th Oct., 1889
COMPLETE SPECIFICATION.
Improvements in the Method of and Apparatus for Straining
Paper-pulp.
I, THEODOR VOLSTORF of the City of Berlin in the Kingdom of Prussia and
German Empire, Paste-board Manufacturer, 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:—
These Improvements relate to the method of and apparatus for straining paper-
pulp and removing lumps and knots therefrom, in an effectual manner and with a
minimum waste of water.
The straining apparatus is arranged in an inclined position and it is operated in
such a manner that the stock is gradually thinned as it approaches the exit from
the strainer.
These Improvements are illustrated by the accompanying drawings in which Fig. 1
is a longitudinal section; Fig. 2 is an external partial view of the perforated or slit
cylinder; Fig. 3 represents the internal cylinder with the worm thereon; Fig. 4 is
an end view of the external cylinder; and Fig. 5 is an upper end view of the
apparatus.
The cylinder a is open at its upper end and covered at its lower end and over its
circumference with perforated or slit plates or metallic gauze. It is mounted so as to
rotate in the tank n on an inclined spindle with its lower end c submerged below
the stock as indicated in Fig. 1 whilst the upper open end of the cylinder is wholly
above the level of the stuff in the tank.
Within the perforated cylinder a there is mounted on the same spindle a smaller
cylinder d having a funnel shaped opening at its upper end. The lower part of
this funnel shaped opening terminates in the pipe or passage which is concentric
with the cylinder and surrounds the spindle. The inclination of the sides of the
funnel e is arranged in such a manner that the material which is introduced through
the canal or trough g flows naturally into the tube f.
The cylinder d is closed at its lower submerged end by an annular plate / so as
to form a compartment i, which being hermetically sealed and filled with air acts
as a float and relieves the weight of the rotating pulp strainer.
A spiral or worm k of metal plate is attached to the inner circumference of the
cylinder a and the inner drum d. As illustrated the worm or spiral is arranged
with a pitch gradually decreasing towards its upper end and is intended by its
rotation to slowly raise the pulp and the contained knots. The stuff or pulp leaves
the strainer through the openings or perforations in the cylinder a and the knots
are discharged into the knot collecting box l. To ensure a tight joint between the
spiralk and the cylinder d the latter is made slightly conical and is forced into
position.
The cylinder d is furnished on its upper open end with an inner flange or rim p
to prevent any overflow from the canal g. "The perforated .cylinder a is provided
with an outer flange g by means of which the extracted knots are prevented from
flowing back into the vessel n.
The sand catcher is fitted with the loose plug :
s and t are the passages
through which the pulp which has been cleared of knots is carried away through
the passages s and t. Jet or sprinkling pipes u, v, and w are arranged in connection
with the apparatus, one of them u being arranged above the sieve cylinder in steps
so that it can be easily cleaned by removing the plugs u. The pipe v discharges
its water into the space between the upper ends of the two cylinders a and d where
the knots are led into the collector 1, while the pipe w plays upon the upper end
of vlinder a

page_text: The drum a has as usual a vibratory motion imparted to it to facilitate the escape
of the pulp through the perforations, while the knots are carried upwards by the
spiral k owing to the slow rotation of the cylinder a until they arrive at the open end.
The operation of the apparatus is as follows:-The pulp enters at g flows through
the funnel e and the annular passage finto the lower parts of the cylinder a whence
it and the contained knots are raised to the upper part by the rotation of the spiral
or screw. The higher the pulp is carried upwards the more it is thinned by the
action of the water from the sprinklers u, v, and w, so that the knots which are
already almost separated are cleared of the last particles of adhering pulp. The
thinned pulp then flows through the perforations into the tank n at a different level
to the pulp which has already been cleared.
The gradient or pitch of the spiral k increases at the upper end as shewn at m so as
to form a right angle with the edge o of the cylinder and retain some of the jet
water to float the knots out of the knot catcher and over the flange q.
The pulp which has been thinned by the jet water mixes with the thicker pulp
in the vessel n and is carried away by the outlet passage t.
By the employment of this knot catcher or pulp strainer the water which has
been used in the manufacture can be again utilised both for the manufacture and
for feeding the jet pipes, and is distributed in certain proportions. The water to
be used for the jets is passed through fine sieves so as to avoid as far as possible
the risk of clogging up the jet pipes. If however the pipes should become choked,
which cannot always be avoided even with pure water, more water flows directly
into the pulp strainer. The apparatus keeps itself constantly clean owing to the
regular removal of the knots.
For the purpose of effecting a perfect cleansing of the apparatus the pulp strainer
is raised into a horizontal position by lifting the lower end. The end plates which
are secured by screws or bolts are then removed and the inner cylinder d is with-
drawn from the spiral at the other end.
As an alternative method the cleansing may be effected by removing the plates
constituting the cylinder and with them their attached portions of the spiral.
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
I claim is
(1) The method of straining or separating knots and similar matters from paper
pulp by means of a rotary strainer in which the pulp is gradually attenuated by
water spray from the point at which the knots are separated, substantially as herein-
before described.
(2) In a rotary paper-pulp strainer; the combination arrangement and construction
of a perforated inclined cylinder, with an internal concentric cylinder, a central
passage through the internal cylinder, and a spiral or worm between the internal
and external cylinders; substantially as herein before described and as illustrated by
the accompanying drawings.
(3) In a rotary paper-pulp strainer; an air-filled hermetically closed cylinder
such as d, tending to act as a float and to relieve the weight of the apparatus ;
substantially as hereinbefore described and as illustrated by the accompanying
drawings.
(4) In a rotary paper pulp strainer; the construction and arrangement of the
termination of the spiral or worm with a decreasing pitch m and a flange o; sub-
stantially as and for the purpose herein before described and as illustrated by the
accompanying drawings.
Dated this 13th day of September AD 1889
WILLIAM E. HEYS,
Agent for the Applicant.