IMPROVEMENTS IN FILTER-PRESSES
Year: 1882

page_text: LETTERS PATENT to Samuel Henry Johnson, F.C.S., of Engineering Works,
Stratford, in the County of Essex, for an Invention of "IMPROVEMENTS IN
FILTER-PRESSES.”
PROVISIONAL SPECIFICATION left by the said Samuel Henry Johnson at
the Office of the Commissioners of Patents on the 4th March 1882.
SAMUEL HENRY JOHNSON F.C.S. of Engineering Works Stratford in the County
of Essex " IMPROVEMENTS IN FILTER PRESSES.'
"
This invention has for its object improvements in the method of constructing
filter presses with the view of making them more efficient and capable of standing
higher pressures than with certain materials has been heretofore found practicable.
It has been found that when the material with which a filter press is employed for
the purpose of separating the solids from the liquid consists in part of fibrous or
other matter which have a tendency to bind or collect as the process of filtration
proceeds so as to produce a resisting obstruction in the filtering cells then by con-
tinuing the operation the accumulation of such matter becomes so compact as to
cut off the flow of liquid in some of the filtering cells thereby removing the normal
pressure of working from such cell or cells for the time being. The consequence of
this is that there no longer exists equal and opposite pressures on both sides of the
filtering diaphragms of such machines and the equilibrium of pressure is destroyed
and unless the diaphragms are made exceedingly strong fracture of the diaphragms
of such obstructed chambers occurs.
Where the surfaces of the diaphragms are large or where the pressure employed
is high or where the material of which the filtering diaphragms are made is soft
brittle or otherwise incapable of resisting the strain (lead tin or alloys of same for
instance) then the improvements hereinafter described become applicable.
These improvements consist-
Firstly In forming the diaphragms with projections on the filtering or drainage
faces corresponding with similar projections on the adjoining diaphragms throughout
the series of cells the last diaphragm at each end of the series being similarly
supported on the head and follower of the filter press when in operation. These

page_text: projections are surfaced either by planing turning or other known means so that
their surfaces shall lie in the same plane as the joint surfaces of the rims of the
filtering diaphragms or so that when the series of cells is screwed together with the
cloths covering the surfaces of the diaphragms these projections shall bear against
each other with the cloth between them so as to form a continuous resisting stay
preventing the collapse of the plates.
Secondly Where it is considered desirable to form the filtering faces of the
diaphragms in lead or tin or their alloys (for example for filtering acids) then
either in conjunction with the aforementioned method of staying the diaphragms or
or alone I form the diaphragms with solid more resisting cores of iron or steel
perforated or otherwise previously tinned and I cast the metal or alloy on such
cores which will thus be adherent thereto and if perforated joined at the opposite
sides of the diaphragm through the perforations in the iron or steel core and by
this means any necessary degree of rigidity may be imparted to the less resisting
material.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Samuel Henry Johnson in the Great Seal Patent Office on the
4th September 1882.
SAMUEL HENRY JOHNSON F.C.S. of Engineering Works Stratford in the County
of Essex "IMPROVEMENTS IN FILTER PRESSES."
This Invention has for its object improvements in the method of constructing
filter presses with the view of making them more efficient and capable of standing
higher pressures than with certain materials has been heretofore found practicable.
It has been found that when the material with which a filter
press is employed
for the purpose of separating the solids from the liquid consists in part of fibrous
or other matter which have a tendency to bind or collect as the process of filtration
proceeds so as to produce a resisting obstruction in the filtering cells then by con-
tinuing the operation the accumulation of such matter becomes so compact as to
cut off the flow of liquid in some of the filtering cells thereby removing the normal
pressure of working from such cell or cells for the time being. The consequence of
this is that there no longer exists equal and opposite pressures on both sides of the
filtering diaphragms of such machines and the equilibrium of pressure is destroyed
and unless the diaphragms are made exceedingly strong fracture of the diaphragms
of such obstructed chambers occurs.
Where the surfaces of the diaphragms are large or where the pressure employed is
high or where the material of which the filtering diaphragms are made is soft,
brittle or otherwise incapable of resisting the strain (lead tin or alloys of same for
instance) then the improvements herein after described become applicable. These
improvements consist.
Firstly. In forming the diaphragms with projections on the filtering or drainage
faces corresponding with similar projections on the adjoining diaphragms through-
out the series of cells the last diaphragm at each end of the series being similarly
supported on the head and follower of the filter press when in operation. These pro-
jections are surfaced either by planing turning or other known means so that their
surfaces shall lie in the same plane as the joint surfaces of the rims of the filtering
diaphragms or so that when the series of cells is screwed together with the cloths
covering the surfaces of the diaphragms, these projections shall bear against each
other with the cloth between them so as to form a continuous resisting stay
preventing the collapse of the plates.
Secondly. Where it is considered desirable to form the filtering faces of the
diaphragms in lead or tin or their alloys (for example filtering acids) then either
in conjunction with the aforementioned method of staying the diaphragms or alone.
I form the diaphragms with solid more resisting cores of iron or steel perforated or
otherwise previously tinned and cast the metal or alloy on such cores which will
thus be adherent thereto and if perforated joined at the opposite sides of the
diaphragm through the perforations in the iron or steel core and by this means any
necessary degree of rigidity may be imparted to the less resisting material.
In order that my said invention may be most fully understood and readily
carried into effect I will proceed to describe the Drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.

page_text: through the plate by which one chamber of the press communicates with another.
d. d. are the drainage grooves leading down to the liquor outlet e.
The cloths used are double and have holes in the centre. The two cloths forming
a pair are sewn together around the central hole one of the cloths of the pair is
passed through the hole in the plate and the cloths are then distended upon cloth
holders fixed upon the plate at f. f. When the series of plates of which the press
is composed are locked up together by the screw at the end of the press the cloths
become firmly nipped between the turned surfaces at b. b.
In respect to these arrangements no novelty is claimed but the novel feature
consists in the provision upon the faces of the plate, or isolated projections g. 9.
between which also the cloths are nipped. Through these projections one plate
supports another from end to end of the press. The tops of the projections g. 9.
should be in the same planes with the turned faces b. b.
The most suitable material for the plate is cast iron, excepting in those cases
where iron is liable to be acted upon by the matter to be treated.
Figure 3 is a front elevation and Figure 4 is a transverse section of a plate
suitable for use when filtering acids; it has a wrought iron interior h, covered with
soft metal of which the acid has no injurious action-say with lead hardened by a
small addition of antimony. I use iron moulds in casting these plates and heat the
interior body h. before introducing it into the mould. The soft metal is cast
sufficiently thick to avoid difficulty in obtaining a sound casting and it is then
turned over the entire surface.
To prevent the body plate h floating in the mould it is made with spurs pro-
jecting from it radially and these are received into recesses in the mould. The
spurs are afterwards cut off and the soft metal covering is made good.
Figure 5 is a front elevation and Figure 6 a transverse section of a distance ring
which is sometimes interposed between plate and plate when thick press cakes are
required. There is an interior wrought iron ring with supporting lugs and soft
metal is cast around it.
Having thus described the nature of my said Invention and the manner of
performing the same I would have it understood that I claim :—
First. The method by which press plates are caused the one to support the
other, consisting in providing suitable projections upon their drainage faces
substantially as described.
Second. The construction of press plates with an interior body of iron or steel
and a covering of soft metal, substantially as described.
In witness whereof I the said Samuel Henry Johnson have hereunto set my
hand and seal this Fourth day of September in the year of our Lord One
thousand eight hundred and eighty two.