IMPROVEMENTS, IN FILTER PRESSES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Henry Rawlings at the Office of the
Commissioners of Patents on the 21st March 1878.
HENRY RAWLINGS, of 108, St. Martin's Lane, Westminster, Filter Manu-
facturer. "IMPROVEMENTS, IN FILTER PRESSES."
In the construction of filter presses which force or compress the substance or
semi-fluid dealt with by pumping or other pressure into chambers, compartments,
or divisions provided with porous substances, materials, or fabrics, in, around, or
between them, and through which the fluid portion escapes or is forced, a necessity
generally exists for disconnecting, detaching, or otherwise taking asunder such a
machine or press before the substance so compressed can be removed, thereby
causing loss of time and great wear and tear. To obviate these objections I make
the filtering chamber and process distinct from, although intimately connected with,
the chamber, division, or compartment, in which the substance is compressed, and
communicating therewith through pipes or other connections by any substance,
material, or fabric suitable for the purpose, and which conducts the liquid portion
of the substance under treatment to that chamber; or the substance may enter the
filtering chamber without any such intervention.
The filtering apparatus consists of a hollow and perforated tube or pipe, on
which are arranged discs or plates of metal or other convenient material with holes
through them sufficiently large for their moving easily upon the pipe or tube, and
between each and every one of them some suitable fabric or material is placed
with a hole in it to correspond with that in the plates or discs, but slightly larger
in outside measurement than the plates or discs enclosing it. These being arranged
alternately on the perforated pipe or tube are inserted in the filtering chamber
with one or both ends of the pipe or tube projecting through it water-tight, and
by the application of a screw or lever any desired degree of compactness or com-
pression of the plates or discs upon the filtering material or fabric between them
may be obtained, and which will regulate the speed of flow of the liquid through it.
The substance or semi-fluid treated is forced by pumping or other pressure into
the compressing chamber or compartment, and the more liquid portion finds its
Prine d

page_text: way to the filtering chamber through the intervening materials or fabrics, which
keep back the grosser matters.
The direction of flow of the liquid through the filtering material or fabric is
opposite to that usually adopted, as instead of directing the flow from the inside
to the outside I direct the flow from the outside of the filtering process to the
centre, thereby concentrating the discharge of the liquid to the outlets of the pipe
or tube at either or both ends instead of its being distributed over the whole
outside surface of the apparatus. This also allows of the application of a reverse
action, by which the solid matters which have entered the pores or interstices of
the filtering material or fabric may be conveniently flushed off without removing
or disturbing it, and so saving considerable wear and tear of the fabric and
apparatus.
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The material or substance under treatment by compression may be removed
from the chamber or compartment by man-holes, by screw pressure, or by a
reciprocating action.
When the liquid or fluid resulting from the process is of the most value or
consequence, and the more solid residue comparatively valueless, only one chamber
may be required, and into which the arrangement of plates or discs on the pipes or
tubes may be placed direct with one or both ends of the pipe projecting through it,
and the residue may be flushed off or otherwise removed as convenience dictates.
Taking into consideration the natural downward tendency of mechanically sus-
pended substances in water to settle of themselves I prefer to place the filtering
chamber above the compressing chamber, but I do not restrict myself to this
arrangement; and if necessity arises I shall use any number of filtering chambers,
and in any relative position to the compressing chamber.
In the necessity of pumping gritty substances for compression, and which have
the tendency of causing great wear and tear of the pump plunger and machinery,
I interpose an elastic or semi-elastic diaphragm between the plunger (which works
in a water-tight chamber) and the substance or semi-fluid so pumped, and the
plunger as it rises or falls is followed by this diaphragm, which creates the same
relative action as if the plunger was immersed in the substance or semi-fluid so
pumped.
For valves I prefer to use some elastic or semi-elastic substance impinging upon
a seating with a knife edge near the margin, the centre portion of which being
honeycombed, so that sufficient support may be afforded to the elastic or semi-
elastic valve, without giving any rest or lodgment to any solid matters.