Improvements in Filter Beds.
Year: 1895

page_text: Date of Application, 21st June, 1895
Complete Specification Left, 23rd Mar., 1896-Accepted, 25th Apr., 1896
Improvements in Filter Beds.
I, FRANCIS FAULKNER BROWN, of Curzon Park, Chester, in the County of
Cheshire, Mine Manager, do hereby declare the nature of this invention to be as
follows:-
My invention relates to the formation of filter beds for the mechanical filtration
of liquids, and has for its object to attain greater capacity of filter for a given
space, to more completely arrest the passage of organisins and other matters of all
kinds in suspension, to obviate discolouration of outflow, and generally to increase
rapidity of filtration and the efficiency of the filter.
If in a filter pebbles and sand of all sizes are mixed together, finer particles of
sand will fall between coarser particles and fill up and choke the interstices, and
thereby produce a practically impenetrable or but slowly permeable mass.
According to my invention I arrange the filtering material in a series of
superposed layers, each made up of carefully washed and graded co-equal particles
of sand, or of one or more layers of such carefully graded sands combined with
one or more layers of ungraded sand which has previously been washed free from
all fine sand which would otherwise block the interstices.
I arrange or prefer to arrange the particles making up the several layers in a
descendingly increasing order of magnitude, that is to say, from the finest graded
sand (to pass say a 120 x 120 mesh sieve) for the top layer, which may be covered
with a layer of ordinary sand, to coarse sand (to pass say a 20 x 20 mesh sieve)
for the lowest layer, the whole being supported on boulders or hollow bricks or the
like at the base.
In forming the filter bed care must be taken that the particles of each layer are
too large to pass into the interstices of the layer below it, and thus the very finest
sand may be used for the uppermost layer without danger of choking the bed or of
being washed therethrough.
Sand arranged in graded layers as above specified becomes in a short time more
or less consolidated, but its filtering efficiency not affected thereby as it would
be were it not carefully graded.
The thickness of layers may be varied according to circumstances, but for the
graded sand I find about 9 inches to be a suitable thickness, and for ungraded it
may be as much as 24 inches.
A filter bed formed in this way will not only have a much greater capacity than
that of an ordinary filter bed, but the layers of finer graded sand present
interstices so small as to arrest practically all organisms, while their number is so
great as not to affect the permeability.
Dated this 21st day of June 1895.
J. C. CHAPMAN,
Agent.

page_text: Improvements in Filter Beds.
I, FRANCIS FAULKNER BROWN, of Curzon Park, in the City of Chester,
Mine Manager, 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 the formation of filter beds for the mechanical filtration
of liquids, and has for its object to attain greater capacity of filter for a given
space, to more completely arrest the passage of organisms and other matters of all
kinds in suspension, to obviate discolouration of outflow, and generally to increase
rapidity of filtration and the efficiency of the filter.
If in a filter pebbles and sand of all sizes are mixed together, finer particles of
sand will fall between coarser particles and fill and choke the interstices, and
thereby produce a practically impenetrable or but slowly permeable mass.
According to my invention I arrange the filtering material in a series of
superposed layers, each made up of carefully washed and graded co-equal or as
far as may be equal-sized particles of sand, or of one or more layers of such
carefully graded sands combined with one or more layers of ungraded sand which
has previously been washed free from all fine sand which would otherwise block
the interstices.
I arrange or prefer to arrange the particles making up the several layers in a
descendingly increasing order of magnitude, that is to say, from the finest graded
sand (to pass say a 120 x 120 mesh sieve) for the top layer, which may be covered
with a layer of ordinary sand, to coarse sand (to pass say a 20 x 20 mesh sieve)
for the lowest layer, the whole being supported on boulders or hollow bricks or the
like at the base.
In forming the filter bed care must be taken that the particles of each layer are
too large to pass into the interstices of the layer below it, and thus the very finest
sand may be used for the uppermost layer without danger of choking the bed or of
being washed therethrough.
Referring to the accompanying diagrams illustrative of my invention, Fig. 1
shows in side elevation (on an exaggerated scale) three rows of graded sand, and
Fig. 2 shows the same arrangement of particles in plan, some of the top layer being
removed for better illustration.
It will be seen in both figures that the size of the particles 2 2 2 forming the
middle layer are too large to pass into the interstices between the larger
particles 111 forming the lowest layer, and in the same way the particles 333 of
the upper layer are too large to pass into the interstices of the middle layer, and
the arrangement may be continued for any number of superposed layers. This is
particularly shown in the case of the particles specially marked 2 and 3* (in
Fig. 2) which happen to come immediately over the interstices of the layer of larger
particles below same. If however the layer 3 were placed immediately above the
layer 1 (omitting layer 2) it is obvious that the particles 3 3 3 thereof would pull
through those of layer 1 and so choke the interstices; the intermediate layer 2
however prevents this.
Sand arranged in graded layers as above specified becomes in a short time more
or less consolidated, but its filtering efficiency is not affected thereby as it would
be were it not carefully graded.
The thickness of layers may be varied according to circumstances, but for the
graded sand I find about 9 inches to be a suitable thickness, and for ungraded it
may be as much as 24 inches.
Fig. 3 diagrammatically illustrates in section a filter built up of layers of graded
and ungraded particles. The lowermost stratum A resting upon the floor of the
b

page_text: tank T is composed of hollow porous bricks; the next layer B is composed of"
pebbles and coarse sand about 9 inches in depth; upon this is placed a layer C of
carefully graded sands the particles of which decrease in magnitude from the
bottom upwardly as above explained; next comes 24 inches or more of ungraded
sand D, above which another layer E about 6 inches thick of carefully graded.
sands as described in successive layers finer and finer from the bottom upwards; on
the top is some 6 inches of ordinary sand F as ordinarily used.
A filter bed formed in this way will not only have a much greater capacity than
that of an ordinary filter bed, but the layers of finer graded sand present interstices
so small as to arrest practically all organisms, while their number is so great as not
to affect the permeability.
Having now particularly described and ascertained the nature of this inven--
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. In a filter bed arranging the filtering material in a series of superposed layers
each layer made up of carefully washed and graded and as far as may be co-equal
particles of sand, the particles making up the several layers being in descending
order of magnitude, that is to say, from a layer of the finest graded material for
the top layer to the coarser graded material for the lowest layer, so that the
particles of no layer can pass into the interstices of its underlying layer as and for
the purposes set forth.
2. In a filter bed arranging the filtering material in a series of superposed layers,.
one or more being made up of carefully washed and graded sands arranged in
descending order of magnitude as explained, in combination with one or more
intervening layers of ungraded sand previously washed free from all fine sand
which would otherwise block the interstices of the graded layers, the whole being
supported in a tank upon hollow bricks or equivalent base substantially in the
manner and for the purposes set forth.
Dated this 92nd das of March 1806