Improvements in and relating to Apparatus for Filtering Liquids.
Year: 1895

page_text: Date of Application, 20th Mar., 1895
Complete Specification Left, 14th Dec., 1895-Accepted, 1st Feb., 1896
PROVISIONAL SPECIFICATION.
Improvements in and relating to Apparatus for Filtering Liquids.
I, JOHANNES BERTHOLD CHRISTIAN KRÖHNKE, of 3 Eppendorfer Chaussee,
Hamburg, in the Empire of Germany, Gentleman, do hereby declare the nature of
this invention to be as follows:-
My invention relates to apparatus for filtering liquids, and the object of the
same is to afford facilities for the proper cleaning and regaining the original
capacity of the filtering material without requiring the renewal of the same when a
certain time in use.
An apparatus constructed according to my said invention consists substantially
of a drum or casing adapted to turn upon two horizontal hollow axes and closed at
its two ends; in its simplest constructional form this drum or casing has its interior
divided by two transverse partitions into three chambers, that is to say, a large
chamber in the middle, and two narrower lateral chambers.
The middle chamber constitutes the filtering chamber proper, while the two
lateral chambers serve respectively for the introduction of the unfiltered water or
liquid admitted through the hollow axis of the drum, and for the reception of the
filtered water or liquid which has passed through the middle chamber and which
flows through the second hollow axis.
I fill the middle chamber for the most part, but not completely, with sand or
other filtering material; the partitions between the chambers consist of wire gauzes
which are fine enough for retaining the filtering material and are preferably
strengthened exteriorly by a coarse grating against the pressure of the water and
sand or other filtering material. The partition between the middle chamber and
the outlet chamber is previous only below to about one to two-thirds of its height
(stretched over with wire gauze), its other upper part being impervious in order to
prevent unfiltered water passing over an upper empty space directly into the outlet
chamber. The outlet opening in the corresponding hollow axis prolonged to the
outside is adapted to be partially or wholly closed for regulating the speed of
filtration. At their lower peripheral surface the two lateral chambers moreover
may be provided with adjustable outlet openings for cleaning purposes. The sand
or other filtering material is filled into the middle chamber through an opening in
the upper peripheral surface of the drum adapted to be closed, and the air in the
upper space of this chamber can escape at the commencement of the filtration
through a suitable stop cock.
The object of the aforesaid upper free space in the middle chamber is particularly
designed to admit an effectual cleaning of the filter, as will be understood from the
following:-
When for instance after prolonged use the filter has become clogged the drum is
As either prior to the turning
caused by suitable gear to turn upon its axis.
movement the drum has been filled with water and the outlet opening closed, or a
slight flow of water is maintained through the drum during the turning movement,
the grains of sand or other filtering material are kept in continual motion relatively
to each other by the water during the rotation of the drum; rooin being left them
for this purpose by reason of the said upper free space in the middle filter chamber.
accordingly they rub against each other, thereby not only rinsing but also
triturating and dividing the deposited and adhering slime.and dirt which the water

page_text: carries away through the outlet in the hollow axis. The current of the water
during this cleaning process may continue in the same direction as during the
filtration, but it is obvious that the contrary direction is more convenient and
moreover the thorough cleaning of the filtering material and rinsing the slime is
obtained in less than half the time and consequently the waste of water corre-
spondingly reduced. In a few minutes the sand or other granular filtering
material becomes in this manner quite clean again and regains its original filtering
capacity without requiring to be renewed. The rubbing of the filtering material
may be augmented by inclined rods which may serve at the same time for stiffening
the walls of the filter, but still more by iron balls or rounded stones within the
filtering material which being raised to a certain height by projections
provided on the interior periphery of the drum fall down through the filtering
material.
In order that the wire gauze shall not become worn in consequence of the
friction caused by the filtering material it may also be protected by coarse wire-
work on the side of the filtering material. Of course the several parts of the
drum are connected with each other as far as needful so as to enable them to be
: easily removed.
After the cleaning has taken place the first water having passed the filtering
material is allowed to flow off through the lower cock of the lateral outlet chamber
or else through the hollow axis of the latter until the filter is again in working
order, which requires from about 5 to 10 minutes.
If it is desired to sterilize the filter, boiling water or steam niay be passed
through the same while the drum rotates, or the closed drum filled almost wholly
with water is caused to rotate after a little caustic soda or lime milk has been
added, washing out with water after the completed sterilization by again opening
the inlet and outlet. As dry filtering sand absorbs about 20 per cent. of water
and becomes sufficiently liquid with 25 per cent., the consumption of disinfecting
agents (which may partly be used again) is very small. For instance caustic soda
forming one-four thousandth part of the weight of sand constitutes with the water
in the sand and the water which fills the narrow lateral chambers a liquor
containing about 10 per cent. of caustic soda, which is more than strong enough
not only for killing in an hour all micro organisms but for almost entirely dissolving
the same.
In view of the facility with which the filter can be cleaned and sterilized it is
expedient to use sand which is as fine-granular as possible and is freed by water
only from clayey slime. A filter with sand the grains of which are of such a size
that it does not pass through the meshes of the wire gauze will get into working
order much more rapidly than a filter charged with coarse sand, filters with the
same rapidity as the latter if this is sufficiently stopped up to give a faultless
filtrate. When the finest sand is used a layer having a thickness of 10 centimetres
is ample; for coarser sand the layer will require to be proportionately thicker.
As the parts of dirt are chiefly deposited only on the surface of a layer of sand
over which the impure water is led into the layer and form there a filtering layer,
the before-described filter has two filtering surfaces, that is to say a surface at
a right angle to the rotary axis along the partition between the middle or filtering
chamber and the lateral inlet chamber and a horizontal filtering surface upon
the layer of sand in the middle chamber. Accordingly the filtering drum may
have small dimensions and yet possess a great capacity.
In order that the liquid to be filtered may be passed through the drum in such a
manner that the filtering surfaces will be utilized to the greatest extent and the
liquid does not leave the filtering chamber insufficiently purified. I may arrange
both in the inlet chamber and in the outlet chamber a channel which may extend
in the direction of a radius from the inlet or outlet opening of the rotary axis close
to the peripheral surface of the drum. Moreover I may arrange in the filtering
chamber at the height of the layer of sand and against the partition between the
filtering and the inlet chamber an angular plate projecting into the same, and

page_text: designed to prevent any disturbance of the upper exposed edge of the surface of
the filtering material. The liquid rises in the said radial channel of the inlet
chamber, a portion is then distributed in the filtering chamber and passes through
the vertical perforated partition towards the before-mentioned filtering surface,
whilst the other portion passes through the perforated partition above on to the
borizontal filtering surface of the sand. By reason of the upper unperforated part
of the partition between the outlet chamber and the filtering chamber and the said
radial outlet channel the liquid passes everywhere through the sand: The said
angular plate prevents the passage of the liquid in one corner of the surface of the
sand, whereby the deposited layer of slime would be stirred up and disturbed in its
filtering action.
The three chambers the inlet, filtering and outlet chamber of the before-described
apparatus for filtering liquids may also be arranged a number of times side by side
in a single casing so that the liquid to be purified will be distributed to all the
groups of chambers and filtered in larger quantities.
Such a combination of several groups of chainbers may have a common inlet
channel from which the liquid passes into the several inlet chambers. The purified
liquid is then collected from all the outlet chambers in a common outlet tube and
may thence be conducted to the place where it is used. The collecting tube
passing through the several groups of chambers may be provided with flanges
which bear against the partitions between the filtering and outlet chambers and
prevent the passage of still impure liquid along the outside of the collecting tube
from the inlet chambers into the outlet chambers respectively, in consequence of
settling of the filtering material.
In some cases and particularly in application with a multiple filtering apparatus
I dispense with the aforesaid radial channels both in the inlet chambers and in the
outlet chambers and I arrange the filtering chambers within the common casing or
drum in such a manner that for each pair of filtering chambers only one outlet
chamber is required and the filtered liquid conducted through a common channel
at the upper surface of the drum to the hollow outlet axis. Thus the collecting
tube of the purified liquid need not pass through the several groups of chambers
and the possibility of still impure liquid escaping into the outlet chambers of the
filtering apparatus is entirely obviated.
Dated this 20th day of March 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.
Improvements in and relating to Apparatus for filtering a
I, JOHANNES BERTHOLD CHRISTIAN KRÖHNKE, of No. 3 Eppendorfer
Chaussee, Hamburg, in the Empire of Germany, Gentleman, 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 :-
My invention relates to apparatus for filtering liquids, and the object of the
same is to afford facilities for the proper cleaning and regaining the original of the
filtering material without requiring the renewal of the same when a certain time
in use.
An apparatus constructed according to my said invention consists substantially
of a drum or casing adapted to turn upon two horizontal hollow axes and closed at
its two ends; in its simplest constructional form this dram or casing has its
interior divided by two transverse partitions into three chambers, that is to say, a
large chamber in the middle, and two narrower lateral chambers.
The middle chamber constitutes the filtering chamber proper, while the two

page_text: lateral chambers serve respectively for the introduction of the unfiltered water or
liquid admitted through the hollow axis of the drum, and for the reception of the
filtered water or liquid which has passed through the middle chamber and which
flows thence through the second hollow axis, as will now be fully described.
In the accompanying drawing
Figure 1 is a sectional side elevation of my improved filtering apparatus in its
simplest constructional form;
Figure 2 is a vertical section of the apparatus on the line I-II, Figure 1 ;
Figure 3 is a sectional side elevation of a multiple filtering apparatus made
according to my said invention, and
Figure 4 illustrates a modification of the same.
Similar letters of reference are employed to indicate like parts wherever such
may occur in the figures of the drawing.
a is the filtering chamber, b the inlet chamber and c the outlet chamber of the
liquid to be filtered. The liquid is admitted through the hollow axis b, passes
through the chambers a and c and flows thence through the hollow axis c'.
с
The
For operating the filtering apparatus I fill the middle chamber a for the most
part, but not completely, with sand or other filtering material; the partitions
between the chambers consist of wire gauze which is fine enough for retaining the
filtering material and preferably strengthened exteriorly by a coarse grating
against the pressure of the water and sand or other filtering material. The
partition between the middle chamber and the outlet chamber is pervious only
below to about one third to two thirds of its height (stretched over with wire
gauze, its other upper part being impervious in order to prevent unfiltered water or
liquid passing over an upper empty space directly into the outlet chamber.
outlet opening in the corresponding hollow axis c¹ prolonged to the outside is
adapted to be partially or wholly closed for regulating the speed of filtration.
their lower peripheral surface the two lateral chambers b and c moreover may be
provided with adjustable outlet openings or stop-cocks and c² for cleaning
purposes. The sand or other filtering material is filled into the middle chamber a
through an opening a' in the upper peripheral surface of the drum adapted to be
closed by a cover a, and the air in the upper space of this chamber can escape at
the commencement of the filtration through a suitable stop-cock a which may be
arranged on the cover a¹ or other suitable place.
At
The object of the aforesaid upper free space in the middle chamber is particularly
designed to admit an effectual cleaning of the filter, as will be understood from the
following.
When for instance after prolonged use the filter has become clogged the drum
is caused by suitable gear in connection with any suitable driving mechanism to
turn upon its axis. As either prior to the turning movement the drum has been
filled with water and the outlet opening closed, or a slight flow of water is maintained
through the drum during the turning movement, the grains of sand or other
filtering material are kept in continual motion relatively to each other by the water
during the rotation of the drum, room being left them for this purpose by reason
of the said upper free space in the middle filter chamber a accordingly they rub
against each other, thereby not only rinsing but also triturating and dividing the
deposited and adhering slime and dirt which the water carries away through the
outlet in the hollow axis c'. The current of the water during this cleaning process
may continue in the same direction as during the filtration, but it is obvious that
the contrary direction is more convenient and moreover the thorough cleaning of
the filtering material and rinsing the slime is obtained in less than half the time
and consequently the waste of water correspondingly reduced. In a few minutes
the sand or other granular filtering material becomes in this manner quite clean
again and regains its original filtering capacity without requiring to be renewed.
The rubbing of the filtering material may be augmented by inclined rods (not
represented), which may serve at the same time for stiffening the walls of the
.hiier, but still more by iron balls a² or rounded stones within the filtering material

page_text: which being raised to a certain height by projections a³ provided on the interior
periphery of the drum fall down through the filtering material.
In order that the wire gauze shall not become worn in consequence of the
friction caused by the filtering material it may also be protected by coarse-
wirework on the side of the filtering material. Of course the several parts of the
drum are connected with each other as far as needful so as to enable them to be
easily removed.
After the cleaning has taken place the first water having passed the filtering
material is allowed to flow off through the lower cock c2 of the lateral outlet
chamber c or else through the hollow axis c¹ of the latter until the filter is again.
in working order, which requires from about 5 to 10 minutes.
If it is desired to sterilize the filter, boiling water or steam may be passed through
the same while the drum rotates, or the closed drum filled almost wholly with
water is caused to rotate after a little caustic soda or lime milk has been added,
washing out with water after the completed sterilization by again opening the
inlet and outlet. As dry filtering sand absorbs about 20 per cent. of water and
becomes sufficiently liquid with 25 per cent., the consumption of disinfecting
For instance caustic soda
agents (which may partly be used again) is very small.
forming one-four thousandth part of the weight of sand constitutes with the water
in the sand and the water which fills the narrow lateral chambers a liquor
containing about 6th per cent. of caustic soda, which is more than strong enough
not only for killing in an hour all micro organisms but for almost entirely dissolving
the same.
In view of the facility with which the filter can be cleaned and sterilized it is.
expedient to use sand which is of as fine a grain as possible and is freed by water
only from clayey slime. A filter with sand the grains of which are of such a size
that it does not pass through the meshes of the wire gauze will get into working
order much more rapidly than a filter charged with coarse sand, filters with the
same rapidity as the latter if this is sufficiently stopped up to give a faultless.
filtrate. When the finest sand is used a layer having a thickness of 10 centimetres.
is ample for coarser sand the layer will require to be proportionately thicker.
As the parts of dirt are chiefly deposited only on the surface of a layer of sand!
over which the impure water is led into the layer and form there a filtering-
layer, the before. described filter has two filtering surfaces, that is to say a
surface at a right angle to the rotary axis along the partition between the
middle or filtering chamber a and the lateral inlet chamber b, and a horizontal
filtering surface upon the layer of sand in the middle chamber a. Accordingly
the filtering drum may have small dimensions and yet possess a great capacity.
In order that the liquid to be filtered may be passed through the drum in such
a manner that the filtering surfaces will be utilized to the greatest extent and
the liquid does not leave the filtering chamber insufficiently purified I may arrange
both in the inlet chamber b and in the outlet chamber c a channel m and n which
may extend in the direction of radius from the inlet or outlet opening of the
Moreover I may arrange
rotary axis close to the peripheral surface of the drum.
in the filtering chamber a at the height of the layer of sand and against the
partition between the filtering and the inlet chamber a and b an angular plate
projecting into the sand and designed to prevent any disturbance of the upper
exposed edge of the surface of the filtering material. The liquid rises in the said
radial channel m of the inlet chamber, a portion is then distributed in the lateral
chamber and passes through the vertical perforated partition towards the before-
mentioned filtering surface, whilst the other portion passes through the perforated
partition above on to the horizontal filtering surface of the sand. By reason of the
upper unperforated part of the partition between the outlet chamber and the
filtering chamber, and the said radial outlet channel n the liquid passes everywhere
through the said. The said angular plate o prevents the passage of the liquid in
one corner of the surface of the sand, whereby the deposited layer of slime would
be stirred up and disturbed in its filtering action.

page_text: The three chambers a b c (the inlet, filtering and outlet chambers) of the before-
described apparatus for filtering liquids may also be arranged a number of times
side by side in a single casing so that the liquid to be purified will be distributed to
all the groups of chambers and filtered in larger quantities.
Such a combination of several groups of chambers (Figure 3) may have a common
iulet channel bd from which the liquid passes through upward extending channels m
into the several inlet chambers b. The purified liquid is then collected from all the
outlet chambers c in a common outlet tube through the radial pipes n and may
thence be conducted to the place where it is used. The collecting tube c passing
through the several groups of chambers may be provided with flanges c which bear
against the partitions between the filtering and outlet chambers a and c and
prevent the passage of still impure liquid along the outside of the collecting
tube from the inlet chambers into the outlet chambers c, respectively, in
consequence of settling of the filtering material.
In some cases and particularly in application with a multiple filtering apparatus
I dispense with the aforesaid radial channels m and n both in the inlet chainbers b
and in the outlet chambers c within the common casing or drum, Figure 4, in such
a manner that for each pair of filtering chambers a only one outlet chamber c is
required and the filtered liquid conducted through a common channel at the
upper surface of the drum to the hollow outlet axis c'. Thus the collecting tube c³,
Figure 3, of the purified liquid need not pass through the several groups of chambers
and the possibility of still impure liquid escaping into the outlet chambers c of the
filtering apparatus is entirely obviated.
The filtering chambers which can be made accessible through detachable
covers a may also be supplied with a number of balls or the like for supporting
the whirling and rubbing of the filtering material for the purpose of cleaning
the latter on rotating the drum as herein before set forth with regard to the filtering
apparatus shown in Figures 1 and 2. Furthermore mud and air cocks are to be
provided at suitable places of the drum wherever they may be deemed expedient or
required for satisfactory working of the filtering apparatus.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. A filter comprising .a casing divided into inlet and outlet chambers and an
intermediate filtering chamber by a foraminous and a partly foraminous and partly
solid partition respectively, tubular journals for said casing, one of said journals
having its outlet proximate to the inner periphery of the casing above the filter
bed within the inlet chamber, and the other journal having its inlet within the
outlet chamber, likewise above the filter bed proximate to the inner periphery
of the casing and the non foraminous portion of the partition between said outlet
and filter chambers, for the purpose set forth.
2. A filter comprising a casing divided into inlet and outlet chambers and an
intermediate filtering chamber by a foraminous and a partly foraminous and partly
solid partition respectively, tubular journals for said casing, one of said journals
having its outlet proximate to the inner periphery of the casing above the filter
bed within the inlet chamber, and the other journal having its inlet within the
outlet chamber likewise above the filter bed proximate to the inner periphery of
the casing and the non foraminous portion of the partition between said outlet and
filter chambers, in combination with the plate o extending obliquely from one of
the partitions into the filter chamber for the purpose set forth.
3. A filter comprising a revoluble casing divided into inlet and outlet chambers and
an intermediate filtering chamber provided with tubular journals, said journals
communicating with said inlet and outlet chambers respectively, said filter chamber
partly filled with a granular material, in combination with solid bodies a² loosely
contained in the filtering chamber, for the purpose set forth.
4. A filter comprising a revoluble casing divided into inlet and outlets chambers

page_text: and an intermediate filtering chamber and provided with tubular journals, said
journals communicating with said inlet and outlet chambers respectively, said filter
chamber partly filled with a granular filtering material, and valved purge pipes
for the inlet and outlet chambers, in combination with solid bodies a loosely
contained in the filtering chambers, for the purpose set forth.
5. A filter comprising a revoluble cylindrical casing divided into inlet and outlet
chambers and an intermediate filtering chamber partly filled with a granular
filtering material, radial ledges a³ projecting from the periphery of the casing into
the filter chamber, and tubular journals for said casing communicating respectively
with the inlet and outlet chambers, in combination with solid bodies a² contained in
the filtering chamber, for the purpose set forth.
6. A filter comprising a casing divided into a plurality of chambers by solid
partitions each of said chambers divided by a foraminous partition and a partly
foraminous and partly non foraminous partition into inlet and outlet chambers and
an intermediate filtering chamber, respectively, tubular journals for said casing,
one of said journals in communication with all the inlet chambers above the filter
bed in the filter chambers, and the other journal in communication with all the
outlet chambers likewise above the filter bed, in the filter chambers between a solid
partition and the impermeable portion of a contiguous partition, for the purpose
set forth.
7. A filter comprising a revoluble cylindrical casing divided interiorly by non-
foraminous partitions into a plurality of cylindrical spaces, said spaces divided. by
a foraminous and a partly foraminous and partly solid partition into three
chambers a b C, tubular journals for said casing, one of said journals communicating
with all the chambers through ducts having their inlet proximate to the inner
periphery of such chambers between a non-foraminous partition and the non-
foraminous portion of one of the foraminous partitions, the other journal
communicating with all the chambers through ducts having their outlet likewise
proximate to the inner periphery of such chambers between a non-foraminous
and a foraminous partition and a filtering material contained in the chambers a,
substantially as and for the purpose set forth.
Dated this 14th day of December 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.