IMPROVEMENTS IN FILTERING OR STRAINING LIQUIDS AND APPARATUS THEREFOR.
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Gustav Valentin Alsing at the Office
of the Commissioners of Patents on the 4th October 1879.
GUSTAV VALENTIN ALSING, of Bradford, in the County of York, Civil Engineer.
"IMPROVEMENTS IN FILTERING OR STRAINING LIQUIDS AND APPARATUS THEREFOR.'
The object of this Invention consists in a method of filtering or straining
liquids so that the residue does not choke up the filter medium, which hitherto has
been a great difficulty to overcome with all filters and strainers.
In carrying out this Invention, the liquid to be filtered or strained is conducted
into a receptacle, the form of which I prefer to be that of a square box or tank with
an open top wider than the bottom. I do not however confine myself to this form,
which may be altered to suit circumstances. In this receptacle I fix through two
of its sides, and parallel to the bottom, a hollow round shaft in such a way that a
drum or pulley, which will be described hereinafter, can rotate on it.
This drum or pulley I prefer to construct of iron, or a combination of wood and
iron, but which may also be made of any other suitable material.
The rim of this drum or pulley consists of a hollow ring, which may be round, or
form an octagon or any other sided polygon, the inner circumference of which
presonts a waterproof surface, and can be made of iron plate, wood, or any other
suitable material, whereas the outer circumference is perforated and made of any
suitable material, but which I prefer to be of wirework. The ends of the ring are
closed, so that only the outer periphery is perforated, and the space between the
outer and inner circumference is divided into as many compartments as there are
arms to each nave of the drum.
In the centre of the drum are one or more naves, which I prefer to be three, and
which are connected to the rim by hollow arms, such as metal pipes, or made of
other material. These hollow arnis are screwed or fastened into and between the
naves and rim, thus giving the drum the appearace of a belt pulley. The naves I
construct with a flange, to which I fasten other arms, consisting of bars or other
suitable supports for the rim, but which merely serve to strengthen the structure.
At the places where the naves rotate on the shaft, and in the centre line of the
hollow arms, a piece or slit is cut out of the shaft, the width of which I prefer to
be equal to the inner diameter or surface of the hollow arms, and the length to one
half of the circumference of the shaft, or part of the same.
These slits serve to conduct the liquid into the shaft by the hollow arms from
the rim, and the shaft is fixed so that the slits are turned towards the bottom of
the receptacle. When the drum rotates round its hollow shaft, and when the arms

page_text: are in front of the slits, the liquid in the receptacle has got free access to the inside
of the shaft, whereas in other positions the liquid is prevented from entering.
At one end of the drum a tooth or ratchet wheel is fixed to it, and can thus by
means of this and suitable gearing be made to move round continuously or at
intervals. I also fix two other common rollers or pulleys of the same width as the
drum in a line with and to one side of it, the one nearer than the other.
Round the drum and these pulleys I stretch a filtering belt consisting of canvass
or other suitable filtering or straining material, and which covers the entire width
of the drum, so that no liquid can pass into it except through the filter belt.
From the top of the drum the filter belt is carried over the farther pulley and
then back over the nearer one, which is placed so close to the drum that the liquid
cannot get access between the belt and the periphery of the drum.
The hollow shaft on which the drum rotates is closed at the one end; the other
end is connected to an air exhauster. By means of this air exhauster a vacuum is
produced in the hollow shaft, arms, and rim, so that the liquid by the outer
atmosphere is forced through the filter belt and ejected through outlet pipes.
When the drum now is set in motion in a direction towards the other pulleys the
filter belt moves with it in the same direction, and carries the residue on its outer
surface. After having passed over the first pulley, that which is farthest away
from the drum, and moving backwards to the second, it first meets a scraper, which
is so constructed that it continuously presses against the whole width of the belt, and
scrapes off the residue with which the filter belt is coated.
It then passes over a washing apparatus consisting of water and steam sprays
which reclean and wash the belt, which hereby is prepared for further filtering, and
which thus can be carried on continuously without having to stop for the cleaning
of the apparatus or filter medium and preventing this from getting choked.
I have especially invented the herein before described apparatus and method for
filtering sewage and sewage sludge, but may be used for all other liquids containing
solids in suspension.