IMPROVEMENTS IN FILTERING APPARATUS
Year: 1882

page_text: LETTERS PATENT to John Frederick Cooke Farquhar and Walter Oldham
both of 24 Long Acre in the County of Middlesex for an Invention of
"IMPROVEMENTS IN FILTERING APPARATUS."
PROVISIONAL SPECIFICATION left by the said John Frederick Cooke
Farquhar and Walter Oldham at the Office of the Commissioners of Patents
on the 25th August 1882.
JOHN FREDERICK COOKE FARQUHAR and WALTER OLDHAM both of 24 Long
Acre in the County of Middlesex. IMPROVEMENTS IN FILTERING APPARATUS
"
This Invention has for its object improvements in filtering apparatus.
"
In the Specification of a former Patent granted to us N° 1051 in the year 1879
we described scraping the top of the filter bed during the process of filtering so
as to remove the slime or dirt deposited and thus preserve a free passage for the
fluid to be filtered.
Our present improvements relate to this method of filtering.
We avoid the necessity of having a box on the rotating shaft to contain the
refuse scraped off the filter bed by making the shaft hollow and introducing
through it the fluid to be filtered. The shaft has on its end a hollow head which
carries the cutter or scraper. The lower side of this head is a flat plate which is
perforated with numerous holes. The fluid to be filtered passes down the inside
of the shaft into the hollow head and out through the perforations and so directly
onto the filter bed without coming into contact with the refuse scraped off which
passes up the inclined cutter and so to the top of the hollow head.
In order that the descent of the scraper may be very slow compared with its
speed of rotation we drive it in the following manner. The main or engine shaft
has upon it a bevelled pinion which gears with a bevelled pinion or crown wheel
carried by a nut on a screw at the end of the hollow shaft carrying the cutter. .
The inner circumference of the crown wheel has upon it a ring of teeth which gear
with a pinion on the top of a short vertical shaft having a similar pinion at its
lower end which gears with a pinion fixed to the hollow shaft. This latter pinion

page_text: has one less tooth than the crown wheel and thus a differential motion is obtained
for example if the pinion has 100 teeth to 101 of the crown wheel and the pitch
of the screw is 1 centimetre the cutter plate will only descend one tenth of a
millimetre at each revolution. The pinion on the short vertical shaft above
mentioned can be thrown into and out of gear by means of a clutch, the nut on
the hollow shaft is then alone driven and the cutter plate is rapidly raised.
The fluid to be filtered is admitted to the hollow shaft through a circular
connection which rises and falls with the shaft but is prevented by a guide from
turning with it. The fluid passes from the supply pump or reservoir to this
connection through a flexible pipe.
We now make the filtering cylinder of a single casting on the bottom of which
is placed the grid. In our former Specification a flat grid was described extending
over the whole surface of the bottom of the cylinder. This has the inconvenience
that unless great care is taken in packing the bed part of the liquid passes
unfiltered between the bed and sides of the cylinder mixing with and spoiling the
filtered liquid that has passed through the centre of the bed. We now make the
grid somewhat smaller in diameter than the cylinder and of an arched form so that
if the liquid passes down the sides of the cylinder it cannot escape at the outer
circumference at the bottom but is compelled to penetrate a certain thickness of
filtering material before it can find its way out through the domed and elevated
grid.
We sometimes replace the grid by a tube leading to the outlet and formed of an
open spiral of wire or otherwise and covered with cloth or flannel.
We simplify and diminish the cost of hand filters by omitting the differential
driving gear. The entrance of the liquid and construction of the cutter head is
similar to that in the power filter before described but the surface of the bed is
scraped only from time to time during the process of filtration when the person in
charge finds the speed of filtration diminishing owing to the surface of the filter
bed getting choked In this case the screw on the end of the hollow shaft passes
through a fixed nut, the cutter plate being turned and raised and lowered by means
of a hand wheel on the shaft.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Frederick Cooke Farquhar and Walter Oldham in the Great
Seal Patent Office on the 24th February 1883.
JOHN FREDERICK COOKE FARQUHAR and WALTER OLDHAM both of 24 Long
Acre in the County of Middlesex "IMPROVEMENTS IN FILTERING APPARATUS
This Invention has for its object improvements in filtering apparatus.
"
In the year 1879 we obtained a Patent (N° 1051) for what was then a novel
system of filtering and which consists in continuously scraping the top of the filter
bed during the process of filtering so as to remove the slime or dirt deposited and
thus preserve a free passage for the fluid to be filtered.
Our present improvements relate to this method of filtering.
Heretofore in such filtering apparatus it has been the practice to have a box on
the rotating shaft carrying the scraper to receive the refuse scraped off the filter
bed. We now avoid this necessity by making the shaft hollow and introducing
through it the fluid to be filtered so that the fluid enters beneath the material
removed by the scraper from the upper part of the filter bed. The shaft bas on
its end a hollow head which carries the cutter or scraper. The lower side of the
head is a flat plate which is perforated with numerous holes. The fluid to be filtered
passes down the inside of the shaft, into the hollow head and out through the.
perforations and so directly on to the filter bed without coming into contact with
the refuse scraped off, which passes up the inclined cutter and so to the top of the
hollow head.
Another improvement relates to the mechanism for actuating the scraper.
In order that the descent of the scraper may be very slow compared with its
speed of rotation we drive it in the following manner. The main or engine shaft
has upon it a bevelled pinion which gears with a crown wheel carried upon a long
sleeve nut which is held in a bearing upon the frame. A screwed axis descends
through the nut and the hollow shaft of the cutter head is attached to it at its
lower end.
The inner circumference of the crown wheel has upon it a ring of teeth which
gear with a pinion loose on the top of a short vertical spindle carried in bearings
by the frame. The same spindle has a similar pinion fixed upon it at its lower
end which gears with a toothed wheel on the screwed axis already mentioned.
The axis is grooved longitudinally and receives a feather in the boss of the wheel.
so that the axis can move longitudinally but cannot rotate independently of the
wheel. This toothed wheel has one less tooth than the ring on the crown wheel
and thus a differential motion is obtained for example if the wheel has 100 teeth
to 101 of the ring on the crown wheel and the pitch of the screw is 1 centimetre
the cutter plate will only descend one tenth of a millimetre at each revolution.
The vertical spindle above mentioned can be thrown out of gear and locked by
means of a clutch, the sleeve nut is then driven whilst the screw is held from
rotating and the cutting plate is rapidly raised or lowered.
The Huid to be filtered is admitted to the hollow shaft through a connection or.
sleeve provided with stuffing boxes which rises and falls with the shaft but is
prevented by a guide from turning with it. The fluid passes from the supply
pump or reservoir to this connection through a flexible pipe.
Another part of our invention relates to the construction of the filtering cylinder
or vessel.
Heretofore a flat grid extending over the whole surface of the bottom of the
cylinder has been employed to support the filtering bed. This has the inconvenience
that unless great care is taken in packing the bed part of the liquid passes unfiltered
between the bed and sides of the cylinder mixing with and spoiling the filtered.

page_text: liquid that has passed through the centre of the bed. We now make the grid
somewhat smaller in diameter than the cylinder and of an arched form so that if
the liquid passes down the sides of the cylinder it cannot escape at the outer
circumference at the bottom but is compelled to penetrate a certain thickness of
filtering material before it can find its way out through the domed and elevated
grid.
We sometimes replace the grid by a tube leading to the outlet and formed of
an open spiral of wire or otherwise and covered with cloth or flannel.
We simplify and diminish the cost of hand filters by omitting the differential
driving gear. The arrangements for the entrance of the liquid and construction of
the cutter head are similar to that in the power filter before described.
The screw on the end of the hollow shaft passes however through a fixed nut
and the cutter plate is turned and raised and lowered by means of a hand wheel
on the shaft. The surface of the bed is in this case scraped only from time to time
during the process of filtration when the person in charge finds the speed of filtration
diminishing owing to the surface of the filter bed getting choked.
Figure 1 is a vertical section of a filtering apparatus constructed according to
our invention and adapted to be driven by a motive power engine. Figure 2 a
top plan view. Figure 3 a bottom plan view of the same. Figure 4 shews a
bottom plan view and a vertical section of the cutter head. Figure 5 is a vertical
section of a like apparatus of smaller proportions and adapted for use with hand
labor.
Figure 6 is a vertical section of a filter adapted for domestic use. Figures 7 and 8
are details relating to the domestic filter.
Referring to Figure 1.
A is the vessel in which the filtering material is contained.
B is a domed grating supporting the filtering bed.
C is a hollow head carrying the blade for cleaning the filtering bed by removing
the deposit which the liquid under treatment leaves upon it.
The head is perforated on the under side for the liquid to descend to the filter
bed. There is also an inclined passage through the head and in this the blade or
cutter is fixed, so as to project just below the under surface of the head (like the
iron of a plane) and the material removed from the filter bed by the blade passes
up the inclined trunk to the upper side of the head.
D is the tube serving as an axis it carries head C and by it the liquid to be
filtered is brought into the vessel A..
E a moveable tube through which the liquid is supplied.
F a sleeve with stuffing boxes surrounding the tube D and communicating
with it.
G the exit for the filtered liquid.
H the cover for the vessel A, when the apparatus is at work it is secured in its
place by suitable clamps.
I the screw by which the head C with the cleaning blade which it carries is
slowly lowered when the apparatus is at work.
JK driving pulleys.
La bevilled wheel and M is a ring of spur teeth formed of a piece with the
wheel L. The wheel L is mounted upon a bronze nut through which the screw I
works.
Na wheel on the screw I revolving with it but allowing the screw to descend.
OP pinions on a vertical shaft and gearing respectively with M and N, which
differ in size by a tooth and consequently give rise to the differential speed in the
rotation of the screw and nut which causes the descent of the screw.
Qa sliding clutch. By means of this clutch the upper pinion O can be made
fast with its axis at the time when the disc C is required to revolve and slowly to
ascend; when the disc is required rapidly to rise the clutch being drawn down-
wards by the means which the Drawing indicates and engaging with the frame
the rotation of the pinion P and of the wheel N is arrested.

page_text: R is a cock for drawing off liquid or semi-liquid mentioned from the upper part
of the vessel A and for establishing an equilibrium of pressure before removing the
cover. By making a manhole on top of cover H and adjusting to it a wide
trumpet shaped pipe fitted with a large cock or valve the material separated by
the filtration may be drawn off without stopping or interfering with the filtration.
This applies more particularly to liquids containing a large amount of matter in
suspension,
This apparatus is especially suited for the filtration of liquids such as wine which
should not be exposed to the air for the process is entirely carried on in closed
vessels, and even if need be these vessels may be charged with special atmospheres
suited to the liquids. Also the cylinders can be jacketted so as to be able to
maintain the interior of the cylinders at a temperature best suited to assure the
fluidity or treatment of the liquid.
The hand machine Figure 5 is similar to that already described except that the
screw passes through a fixed nut and the head with the cutter is only removed
from time to time.
The delivery for the filtered liquid is also differently arranged, it is by a
permeable tube entering the side of the vessel A. The tube may consist of a strong
helical coil of turned iron wire covered with a bag of thick flannel. This
arrangement is also applicable to the larger machines.
In Figure 6 the supply to the filter is from a vessel X mounted on the upper end
of the tube or axis D which carries the rotating head C and cutter. The tube or
axis passes through a stuffing box on the cover of the vessel A; it has a screw
thread cut upon it and this works through a nut upon a standard fixed to the cover.
This nut may be either fixed or loose in socket of standard. If loose the nut turns
round with the screw and allows the cutter to revolve on surface of filter bed
without descending; when it is desired to make the cutters to descend and cut off
the surface of the bed, the nut is arrested by the hand or otherwise while the screw
is turned. The tube or axis has handles upon it by which from time to time it may
be turned, Figure 7 represents the underside of the head C.
In some cases we provide a receptacle on the upper part of the rotating head to
receive the filtering medium when disturbed by the cutter.
In place of employing the vessel X the filter may be supplied by a flexible tube
from any tap from which the water or liquor may be drawn. The arrangement in
such a case is represented at Figure 8.
In this figure the flexible tube has to be disconnected when it is desired to make
the cutter head rotate. To avoid this disconnecting of tube a stuffing box
permitting of rotary movement may be adjusted to upper end of axis D.
Many filtering materials may be employed with these filters, sawdust or dyers or
other refuse wood fibre pulverised especially such as has been carbonised in a retort
is very good for many purposes, also animal or vegetable wool or hair and other
materials of a similar nature either used separately or mixed with sawdust &c in
the manner best suitable to the liquid to be filtered. In cases, such as the filtration
of sewage, the presence of animal wool in the mixture of deposit and filter bed
obtained at the end of the process of filtration will increase the fertilising value of
the mixture. For filtering beer brewers grains may be employed for other
purposes granulated charcoal either animal or vegetable either used separately or
mixed with other filtering material will be suitable and in each c. se the filtering
material should be selected in reference to the liquid to be treated.
Having thus described the nature of our said Invention we would have it
understood that we claim :—
First. The method of admitting the liquid to be filtered at the under side of the
head carrying the cutter or scraper and at once in contact with the cleaned face of
the filter bed.
Second. The gear by which the cutter head is rotated and caused slowly to
descend and is rapidly raised or lowered.
Third. The method of supporting the filtering bed upon a domed grid and the

page_text: arrangement by which imperfectly filtered liquid descending against the sides of
the filtering vessel is prevented from passing unfiltered out of the filter.
Fourth. The method of drawing off the filtered liquid shewn in Figure 5 of the
Drawings.
.
Fifth. The construction of filtering apparatus substantially as described and
represented in the annexed Drawings.
In witness whereof I the said Walter Oldham have hereunto set my hand
and seal this thirteenth day of February in the year of our Lord One
thousand eight hundred and eighty three.
WALTER OLDHAM (L.S.)