Improvements in or relating to Apparatus for Filtering Liquids.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improvements in or relating to Apparatus for Filtering Liquids.
A communication by DAVID WILLIAMSON, of New York, in the County and
State of New York, United States of America, Engineer.
I, WILLIAM PHILLIPS THOMPSON F.C.S. M.I.M.E. of the Agency for
Foreign Patent Solicitors 6, Lord Street, Liverpool and 6, Bank Street,
Manchester, both in the County of Lancaster & 323 High Holborn in the
County of Middlesex, Civil Engineer 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:-
This invention relates to an improvement in filters, and especially to that class of
filters in which the filtration is effected through or by means of a porous surface
or body, and more particularly to that class of filter in which the liquid to be
filtered is forced through the porous surface or body, by centrifugal force, applied
by any convenient means to the liquid to be trented.
In the various forms of filter heretofore in use in which the filtration is effected
by or through a porous surface or body, great difficulty is experienced, after a
certain time, in maintaining the operation of the filter, owing to the fact that the
porous surface or body becomes coated with the impurities and the efficiency of the
filter proportionately diminished. Now my correspondent has discovered that
when the porous surface or body is made in the form of an open or closed receptacle
which is arranged to be rapidly rotated upon a vertical axis, and the liquid to be
filtered is admitted directly to its interior, the centrifugal force of the current
created by the rotation of the vessel, will operate to force the liquid through the
porous sides of the vessel and effect filtration, while at the same time the precipitate
will be prevented, by the rotary motion of the vessel, from accumulating on its
sides; and if the former be made open at the top and the sides slightly inclined,
the impurities separated out will flow automatically over the walls of the vessel as
they accumulate, and may be thus automatically removed.
The application of this principle of a rotating body of liquid, to filtration
through a porous medium, which is the gist of the invention, will be best under-
stood by reference to the accompanying drawing forming a part of this Specifica-
tion, which shows the general application of the principle in its simplest forin, and
in which
Figure 1 is a vertical section of an apparatus of the simplest form; and
Figure 2 is a horizontal section on the line x of Figure 1.
Similar letters refer to similar parts throughout the several views.
In the drawings, C represents a tank of any convenient shape but preferably a
cylindrical drum as shown, constructed of sheet iron and open on top. The upper
edge ce may be turned inward as shown by the dotted line in Figure 1, to prevent
the ejection of the filtrate over the edge. The tank C is supported in any con-
venient manuer, as by means of the floor I, resting upon the beams II. Surrounding
the tank is a frame of timber, T, of convenient size and construction, arranged to
support a vertically rotating shaft, S, surmounted by a driving pulley S', which
may be driven by a belt from a steam engine or other convenient source of power,
which will give the necessary speed.
V is a porous vessel or cup, in the form of the frustum of a cone or cylinder,
open at the top, which is arranged within the tank C, as shown, and rests upon a
circular bottom plate D¹, of sheet metal or other convenient material, which
surrounds and is firmly attached to the shaft S at the point d', by means of a hub d
which is attached to the shaft S by the screw d', or in any other convenient
manner. The shaft S terminates in and rotates at its base in a step hearing F,.

page_text: placed on the bottom of the tank C, as shown, of convenient construction. The
cup or vessel V, is supported at the top by means of a ring J fastened to its inner
surface at the top and provided with radial spokes or arms, 9'9', terminating in a
central collar or hub g, which surrounds the shaft S. For attaching the vessel V
to the bottom plate D', a cylindrical flange d² may be provided upon the periphery
of the plate as shown in Figure 1. E is a loose collar which is arranged to slide
vertically a certain distance on the shaft S, above the hub g, and is provided with
radial arms which support an annular disc or ring R, which is of such diameter
at its outer circumference as to cover the periphery of the vessel V, at its upper
edge. By sliding the collar E vertically on the shaft S, the ring R may be raised
from the upper edge of the cup or vessel V to permit the discharge of the pre-
cipitate collected in the vessel from time to time.
For the purpose of catching and removing the precipitate overflowing from the
upper edge of the vessel or cup V, a curved and inclined shelf, L, or ledge is pro-
vided on the inner surface of the drum D, as shown in Figure 1. The highest
point of the shelf L, is nearly on a level with the upper edge of the vessel Vand
from this point the shelf inclines gradually downward around the inner surface
of the drum on either side of the highest point, until the two surfaces of the shelf
meet again at a point directly opposite to the highest point, at which point, which
is consequently the lowest point in the inclination of the shelf, an opening O is
provided in the cylindrical wall of the drum, through which the impurities can
escape by means of a suitable spout or discharge pipe P.
It will be obvious from the construction of the shelf that all impurities or pre-
cipitate U flowing over the periphery of the cup V, no matter at what point, must
flow downward on the shelf L, and pass out through the opening O. To prevent
the filtrate from flowing over the edge of the shelf, a cylindrical guard or shield L'
is provided at the edge of the shelf L, which guard is in such close proximity to
the walls of the vessel V that any precipitate escaping over the upper edge of the
vessel will flow downward over the edge of the guard L' and be caught upon the
shelf L. At the same time the guard serves to separate the filtered water as
it passes through the porous vessel V, from flowing over on to the shelf L and
becoming fouled.
The object of the disc or ring R is to form a partial cover for the vessel V,
which may be raised from time to time while the vessel is rotating to permit of the
discharge of the precipitate, and for the purpose of raising and lowering it on the
shaft S, a lever may be employed, provided with forked ends h³, encircling
the upper end of the collar E, and engaging therewith through two shoulders e e
formed thereon. The lever is pivoted to the frame T, and the point h' and a
toothed rack is provided at the side of the frame to hold the loose end of the
lever by raising and lowering the loose end of the lever, and engaging it with the
toothed rack, the ring R may be raised, lowered, or held at any given point at
pleasure.
The liquid to be filtered enters through the pipe A, controlled by a valve and
is discharged through the pipe B, controlled by the valve b.
The operation of the apparatus is substantially as follows:-
The pulley S¹ having been first connected to the source of power, the motion of
the motor will be transferred to the shaft S, and the shaft and the vessel V will
be rotated. The liquid to be filtered is permitted to enter through the pipe A
into the interior of the vessel V and will at once begin to rotate rapidly. The
effect of the rotation of the liquid will be to force the liquid through the porous
walls of the rotating vessel V, leaving all the impurities contained in the liquid; in
the vessel V, which impurities will gradually ascend along the surface of the cup,
owing to the inclination of the side walls, and when the cover is raised overflow
the upper edge of the same and collect as a precipitate U upon the shelf L, while
the purified liquid, after passing through the porous walls of the cup V, will collect
in the tank C, from which it may be drawn off from time to time through the
bipe B. as it accumulates.

page_text: In the ordinary form of filters in which filtration is effected through per-
manent and porous side walls, the operation of filtration is ordinarily extremely
slow and tedious, and in order to facilitate the same it is necessary to filter under
pressure, and thus greatly complicate the apparatus and increase the expense.
By arranging the apparatus in the forin indicated, not only is it possible to
produce the same effect as is produced by filtering under pressure, so far as rapidity
and efficiency of filtration are concerned, but also to effect more perfect regulation
of the speed of the filtration with great simplicity of construction and consequent
diminution of expense, for the reason that the speed of the apparatus and the con-
sequent amount of centrifugal.force exerted upon the filtering medium is much
more casily varied from time to time than the conditions of pressure can be varied
in a filtering apparatus which operates under pressure.
It will be obvious that the mere details of the apparatus form no part of the
real invention, and that the same may be modified from time to time as may be
found convenient, the gist of the invention consisting in the application of centri-
fugal force to filtering all classes of liquids through porous material.
Though it is old to use centrifugal force for the purpose of keeping a movable
body of filtering material in a vessel in such position that the body will always be
of the same thickness and a constant supply of liquid will be permitted to pass.
through the same, it is new to apply centrifugal force for the purpose of forcing a
liquid to pass through a permanent porous medium and thereby produce the same
effect as is produced by filtration therethrough, under pressure; thus at the
same time diminishing the cost of construction and facilitating the regulation of
the apparatus.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is :-
1. The hereinbefore described method of filtering all kinds of liquids, con-
sisting in placing the same in a vessel having permanent and porous side walls
rotating at a suitable speed, whereby the filtration through the porous vessel is.
effected by the centrifugal force imparted to the liquid.
2. The hereinbefore described method of filtering all kinds of liquids, consisting
in placing the same in an open-topped vessel having permanent and porous inclined
side walls, arranged to be closed by a movable cover, in forcing the liquid through
the sides of the vessel by the centrifugal force resultant from its rotation, in per-
mitting the impurities to escape from time to time out of the top of the vessel, by
raising the cover while the same is rotating, and in collecting the filtrate in an
exterior vessel.
3. In a filtering apparatus, the combination substantially as herein before set
forth, of a vessel having permanent and porous side walls, rotating at a suitable
speed, in which the liquid to be filtered is placed, and an exterior vessel for
collecting the filtered liquid emerging therefroin.
4. In a filtering apparatus, the combination substantially as hereinbefore set
forth, of a vessel having permanent and porous inclined side walls, rotating at a
suitable speed, in which the liquid to be filtered is placed, an exterior vessel for
collecting the filtered liquid emerging therefrom, and a shelf or trough in the
interior of the exterior vessel, for collecting and carrying off the precipitate thrown
over the edges of the filtering vessel.
5. In a filtering apparatus, the combination substantially as hereinbefore set
forth, of a tank for holding the filtered liquid, a vessel having permanent and
porous inclined side walls rotating in said tank, in which the liquid to be filtered
is placed, a shelf or trough on the inner surface of the tank for collecting and
carrying off the overflow from the rotating vessel, and an annular and movable
cover to the rotating vessel, substantially as described.
6. In a filtering apparatus, the combination with the tank C and the rotating
vessel having inclined side walls, of an inclined shelf or trough surrounding

page_text: the inner surface of the tank, an opening in the wall of the tank at the point
of lowest inclination of the shelf, for the automatic discharge of the precipitate,
and a protecting edge to the shelf for preventing contact with the filtered liquid
within the tank.
7. In a filtering apparatus, the combination with the rotating vessel having
inclined side walls, of an annular cover at its periphery, arranged to be raised and
lowered at pleasure, and to thereby control the discharge of the material passing
over the rim of the vessel.
Dated this 16th day of February 1800