IMPROVEMENTS IN CISTERN FILTERS
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by George Edward Haycraft and Edward
Johnson at the Office of the Commissioners of Patents on the 21st September
1878.
GEORGE EDWARD HAYCRAFT, of the Broadway, Deptford, in the County of Kent,
Ironmonger, and EDWARD JOHNSON, of Greenwich, also in the County of Kent,
Sanitary Engineer. "IMPROVEMENTS IN CISTERN FILTERS."
The object of this Invention is the production of a cistern filter the action of
which shall have the effect of aërating the water as it leaves the filtering medium
with a chemically purified air, by these means giving freshness to the filtered
water.
And further to provide a filter all the parts of which are simple, easily adjustable,
inexpensive, and so arranged that the filtering medium can be readily cleansed or
renewed without removing the filter from the cistern.
The internal parts of the filter are so arranged that the rate of filtration can be
adjusted to the character of the water to be filtered and the standard of purity
required.
For this purpose we construct a circular container made of perforated metal or
earthenware or other material of any convenient size having a solid bottom with an
aperture in the centre of about two inches diameter, more or less, according to the
diameter of the container.
Over this centre aperture we place a finely perforated tube made of metal or
earthenware, or it may be a cylinder of highly porous earthenware, block charcoal,
or other material, of a length corresponding with the depth of the container, resting
on a flange fixed round the aperture, the tube being sufficiently loose to be easily
removed and replaced.
We then take another similar tube still more finely perforated, of about the same
length, and of such diameter as will allow it to slide freely inside the forementioned
tube, open at the bottom like the stationary tube. To the upper end of this inner
tube we attach a hollow rod or shaft, of any convenient length, to serve the double
purpose of a handle wherewith to move the sliding tube up and down, and to allow

page_text: access of air each time that water is drawn from the filter. The perforations in
these tubes are so regulated that they filter the water at a slower rate than the flow
from the discharge cock of the exit pipe, which is so proportioned to the rate of
filtration that a partial vacuum is created in the bottom of the filter, so creating a
down current of air through the centre tube.
To the top of this hollow shaft or handle we attach a perforated box of metal or
other material to contain charcoal in a granular form through which the air passing
down the tube becomes purified.
We then fill the space between the stationary centre tube or cylinder and the
outer wall of the container with suitable filtering material, by preference the
substance known as "Carferal charcoal."
The lid or cover is made of solid metal or earthenware or other material of a size
to enable it to slip inside the rim of the container and screwed or wedged closely
down upon the filtering material, so as to make the material as solid and compact as
possible, care being taken to close up the space between the circumference of the
lid and the sides of the container by suitable packing held down by screws or
wedges.
In the centre of this lid or cover is an aperture to correspond with the top of
the central tube and of sufficient diameter to enable the sliding tube to be drawn
up and down.
Fitted to this centre aperture we attach a tube of the same diameter as the
aperture and carry up the same to a height corresponding with the top of the water
cistern, the object being to prevent the unfiltered water reaching the interior of
the filter. The bottom of this tube is firmly attached to the lid or cover, and forms
a part of the same.
When it is required to flush or cleanse the filtering material the sliding tube is
withdrawn and a hose from the supply cock of the cistern is carried and fixed on to the
top of the stationary tube or shaft when the water is forced from the centre of the
filter to the circumference by the reverse action, the cistern having been previously
emptied and the discharge cock left open. By raising or lowering the slide tube
the rate of filtration may be adjusted to the state and character of the water to be
filtered.
In cases where water containing large quantities of suspended matter has to be
dealt with the fixed centre tube may be surrounded with one or two folds of finely
woven fabric such as hair cloth or specially made filter cloth, and a similar material
may be used to protect the outer surface of the container.
The bottom of the container is made double so as to provide storage room for the
filtered water, of a capacity to suit special requirements.
For the purpose of still further aërating the filtered water we fix an air tube in
the discharge cock of the filter in front of the plug, the lower end of which projects
into the mouth of the cock and is bevilled so as to catch the full force of the
current which causes a suction power to be exercised, drawing in air with every
discharge. The upper part of this air tube is fitted with a perforated charcoal box
to purify the air admitted into the cock.
The same appliance is advantageously fixed to the supply cock of the cistern, or
these air tubes may be applied on any part of the discharge pipe if the same is
provided with a stop-cock above the junctions.
The filter cloths we prefer to use we make from cocoa or rheea fibre, as these
are vegetable fibres which do not deteriorate readily when immersed in water.