Improvements relating to the Manufacture of Filters.
Year: 1893

page_text: Date of Application, 21st Oct., 1893
Complete Specification Left, 12th June, 1894-Accepted, 14th July, 1894
PROVISIONAL SPECIFICATION.
[Communicated from abroad by BITTEL & Co., of Worms-on-the-Rhine, in the
Empire of Germany.]
Improvements relating to the Manufacture of Filters.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, do hereby declare
the nature of this invention to be as follows:-
This invention relates to the manufacture of filters.
Many attempts have heretofore been made to produce artificial filters by
cementing together pulverized clay, pumice stone, sand, carbon or the like. The
products obtained in this manner possess however without exception the dis-
advantage that they are suitable only for filtering liquids which do not contain any
agents acting as solvents, such as alkalies or acids. The employment of such
filters is therefore limited to quite definite objects, such as for instance to the
filtration of drinking water.
The present invention relates to a process of manufacturing filters which, apart
from hydrofluoric acid, are quite insoluble in any of the liquids produced in
chemistry, more particularly in alkalies and acids, and which posses moreover the
advantage that, if a diminution in their effectiveness is perceptible after they have
been in use for some time owing to the pores being partially clogged up, they can
be revivified by annealing without causing a deleterious change in the filtering
material by the said annealing process. This object is achieved by cementing pure
quartz while observing certain precautions in such a manner with alkaline silicate
that the latter is changed by the cementing process itself in its chemical and
physical conditions and is transformed by ample enrichment with silicic acid into a
product which approximates quartz in its properties.
It is known that if common glass be employed for cementing quartz and the
process be conducted so that the chemical nature of the glass is preserved no
resistant filter can be produced, for glass as such, more especially if it is in that
finely divided state in which it exists in the filters, is attacked by dissolving agents,
thereby loosening the adhesion of the entire filtering material. If however the
alkaline silicate as it usually occurs in commerce receives a very high percentage
of silicic acid the resistance of the same to chemical agents is considerably increased
and a material is obtained which is very difficult of fusion and insensible to
variations of temperature. Use has been made of this fact as hereinafter set forth
in carrying the present process into effect.
Pure quartzose sand, preferably of splintery sharp-edged form, is intimately
mixed, according to the size of the grains and its other condition, with finely
pulverized glass from about one-quarter to about one-twentieth part of its volume
and subjected in moulds to a high temperature. The glass melts and is drawn by
capillary action to the points of contact of the grains of quartz with each other.
The high temperature is kept up for a comparatively long time, and then the
peculiar phenomenon is observed that the glass adhering in the liquid state to the
grains of quartz gradually becomes saturated more and more with silicic acid, is
rendered difficult of fusion and therefore assumes a more compact form.
Accordingly the grains of quartz which are easily movable at the beginning of the
annealing will, in the continuation of the annealing process, firmly adhere to each

page_text: other even at a high temperature. When this solidifying process has taken place
either completely or partially the operation is terminated and the filters may then
be slowly cooled and if necessary have their surfaces treated, or they may be set in
a frame, or the like.
The filters obtained in this manner offer, as above stated, a great resistance to
solvents and can be heated without becoming soft to a temperature which is far
above the melting point of ordinary glass, because the glass used for cementing the
grains of sand together has received a higher melting point by the cementing
process.
In order that, in carrying the above described process into practice, the filter
plates may possess an absolutely uniform thickness it is expedient to anneal them
not in the vertical but in the horizontal position. If the moulds were in the
vertical position the liquefied glass would pass downwards, and the lower part of
the plate would become comparatively dense whilst the upper part, by reason of the
small amount of the vitreous cement contained therein, would become too porous
and obtain too small a strength. The annealing of filter plates consisting of the
aforesaid mixture of sand and glass in horizontal moulds constitutes another
part of the present invention.
This invention relates in the third place to a special mode of constructing the
filter, for which the material obtained by the above described process is used.
The essential feature of this mode of construction consists in that two parallel
filter plates are held at a certain distance from each other at their outer edges by
an intermediate strip of any suitable material which is impervious to water but
forms a perfectly tight joint, and are firmly united by bolts or in any other desired
manner. It is expedient to put several such plates parallel to each other in a
common casing into which the water to be purified is caused to flow. The latter
penetrates the filtering material, passes into the interior cavity of the filter and can
thence be removed by suitable means.
In the case of filtering plates of very large dimensions it is advisable to use not
two but four plates to compose a single filter and this may be effected by separating
two pairs of filtering plates only on three of their sides by a strip placed between
them, while the fourth side is left open, and then putting the two halves of the
filter together so that the open sides will coincide. Their union may be effected
by any known means, for instance by a narrow sheet metal casing which covers
the joint between the two halves of the filter, or by one or more short pipes
inserted into the cavity of the filter at the points of contact between the two halves
of the same, the joint being made tight by cement, in order to prevent impure
water from penetrating into the interior cavity of the filter.
Should interruptions occur in the operation the interior cavity of the filter may
be inspected by removing the bolts, or in the case of a divided filter by lifting the
upper half from the lower half, and if any defects are found or certain parts of the
filter have been clogged up by impurities the plates may be exchanged for cleansing
purposes or they may be entirely replaced by new ones. A repair can therefore
always be effected in a very short time and without any material diminution in the
effectiveness of the filtering apparatus.
Dated this 21st day of October 1893

page_text: Improvements relating to the Manufacture of Filters.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 the manufacture of filters.
Many attempts have heretofore been made to produce artificial filters by
cementing together pulverized clay, pumice stone, sand, carbon or the like. The
products obtained in this manner possess however without exception the disadvantage
that they are suitable only for filtering liquids which do not contain any agents
acting as solvents, such as alkalies or acids. The employment of such filters is
therefore limited to definite objects such as for instance to the filtration of
drinking-water.
The present invention relates to a process of manufacturing filters which, apart
from hydrofluoric acid, are quite insoluble in any of the liquids produced in
chemistry, more particularly in alkalies and acids, and which possess moreover the
advantage that, if a diminution in their effectiveness is perceptible after they have
been in use for some time owing to the pores being partially clogged up, they can
be revivified by annealing without causing a deleterious change in the filtering
material by the said annealing process. This object is achieved by cementing
pure quartz while observing certain precautions in such a manner with alkaline
silicate that the latter is changed by the cementing process itself in its chemical
and physical conditions and is transformed by ample enrichment with silicic acid
into a product which approximates quartz in its properties.
It is known that if common glass be employed for cementing quartz and the
process be conducted so that the chemical nature of the glass is preserved no
resistant filter can be produced, for glass as such, more especially if it is in that
finely divided state in which it exists in the filters, is attacked by dissolving agents,
thereby loosening the adhesion of the entire filtering material. If however the
alkaline silicate as it usually occurs in commerce receives a very high percentage
of silicic acid the resistance of the same to chemical agents is considerably
increased and a material is obtained which is very difficult of fusion and insensible
to variations of temperature. Use has been made of this fact as hereinafter set
forth in carrying the present process into effect.
Pure quartzose sand, preferably of splintery sharp-edged form, is intimately
mixed, according to the size of the grains and its other condition, with finely
pulverized glass from about one-quarter to about one-twentieth part of its volume
and subjected in moulds to a high temperature. The glass melts and is drawn by
capillary action to the points of contact of the grains of quartz with each other.
The high temperature is kept up for a comparatively long time, and then the
peculiar phenomenon is observed that the glass adhering in the liquid state to the
grains of quartz gradually becomes saturated more and more with silicic acid, is
rendered difficult of fusion and therefore assumes & more compact form.
Accordingly the grains of quartz which are easily movable at the beginning of the
annealing will, in the continuation of the annealing process firmly adhere to each
other even at a high temperature. When this solidifying process has taken place
either completely or partially the operation is terminated and the filters may then
be slowly cooled and if necessary have their surfaces treated or they may be set in
a frame, or the like.
The filters obtained in this manner offer, as above stated, a great resistance to
solvents and can be heated without becoming soft to a temperature which is far

page_text: •
above the melting point of ordinary glass, because the glass used for cementing the
grains of sand together has received a higher melting point by the cementing
process.
In order that, in carrying the above-described process into practice, the filter
plates may possess an absolutely uniform thickness it is expedient to anneal them
not in the vertical but in the horizontal position. If the moulds were in the vertical
position the liquefied glass would pass downwards, and the lower part of the plate
would become comparatively dense whilst the upper part, by reason of the small
amount of the vitreous cement contained therein would become too porous and
obtain too small a strength. The annealing of filter plates consisting of the
aforesaid mixture of sand and glass in horizontal moulds constitutes another part of
the present invention.
This invention relates in the third place to a special mode of constructing the
filter, for which the material obtained by the above described process is used.
The essential feature of this mode of construction consists in that two parallel
filter plates are held at a certain distance from each other at their outer edges by
an intermediate strip of any suitable material which is impervious to water but
forms a perfectly tight joint, and are firmly united by bolts or in any other desired
manner. It is expedient to put several such plates parallel to each other in a
common casing into which the water to be purified is caused to flow. The latter
penetrates the filtering material, passes into the interior cavity of the filter and
can thence be removed by suitable means.
In the case of filtering plates of very large dimensions it is advisable to use not
two but four plates to compose a single filter and this may be effected by separating
two pairs of filtering plates only on three of their sides by a strip placed between
them, while the fourth side is left open, and then putting the two halves of the
filter together so that the open sides will coincide. Their union may be effected
by any known means, for instance by a narrow sheet metal casing which covers the
joint between the two halves of the filter, or by one or more short pipes inserted
into the cavity of the filter at the points of contact between the two halves of the
same.
In the accompanying drawing I have shown a filtering device constructed
according to my invention.
Figure 1 is a front elevation, and
Figures 2 and 3 a vertical and a horizontal section of the same.
Two filtering plates A A' are connected by bolts a and held at a certain distance
from each other by interposed strips 6 of lead or other suitable materials.
In the constructional example represented in the drawing it is assumed that a
filter of large dimensions is concerned, and the plates A and A' are therefore made
of two parts as above set forth so that the whole upper half of the filter may be
separated at will from the lower half. The union of the two halves of the filter is
effected by one or more short pipes c inserted at the joint into the interior cavity;
the joint being made tight by cement, in order to prevent impure water from
penetrating into the interior cavity of the filter.
Should interruptions occur in the operation the interior cavity of the filter may
be inspected by removing the bolts or in the case of a divided filter of the kind
shown in the-drawing by lifting the upper half from the lower half, and if any
defects are found or certain parts of the filter have been clogged up by impurities
the plates may be exchanged for cleansing purposes or they may be entirely replaced
by new ones. A repair can therefore always be effected in a very short time and
without any material diminution in the effectiveness 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, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
(1.) The process of manufacturing filters which are proof against alkalies and
acids; such process consisting in mixing quartz and powdered glass, and heating

page_text: the mixture, in the shape of the boxes or moulds to be constructed, to a temperature
sufficient to liquefy the glass, and maintaining such temperature until, owing to the
glass becoming richer in silicic acid (or the formation of hard glass) the filtering
material solidifies.
•
(2.) The burning of the filtering plates made of sand and glass in horizontal
moulds for the purpose of obtaining plates of uniform density.
(3.) A filtering structure erected by means of the filtering material obtained by
the process above referred to, and consisting of two plates, such as A A', directly
connected together by means of bolts or other fastening devices, capable of being
readily removed or disconnected, and without the employment of any external
metal frames, such plates being kept apart at the required distance from each other-
by strips of packing material inserted between them at their peripheries.
Dated this 12th day of June 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.