Improvements in Filter Presses.
Year: 1897

page_text: Date of Application, 15th Apr., 1897-Accepted, 17th July, 1897
COMPLETE SPECIFICATION.
Improvements in Filter Presses.
I, SAMUEL HENRY JOHNSON, of The Engineering Works, Stratford, London, E.
Engineer 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 has for its objects (a) The more perfect and effectual means of
applying hydraulic pressure to the movable head of Filter Presses for the purpose
of submitting the cakes formed in Filter Presses to a final squeeze under hydraulic
pressure, or for (b) closing the joints at the margins of the plates or frames forming
the filter cells, to make them liquid tight under pressure. (c) The maintenance
of such joints liquid tight under any variation of pressure which may obtain
within the cells when at work; and (d) the saving of labour involved in working
Filter Presses.
These improvements are effected in the class of Filter Presses in which the
movable head or follower is actuated by means of hydraulic or other fluid pressure
such as that described in the Scientific American Supplement February 11th 1882,
Bertin-Godot System, or in the British Specification of Patent No. 14415, A.D.
1886, or in the British Specification of Patent No. 7045 A.D. 1886, in which
fluid pressure is employed for pushing the plates or frames into juxtaposition ready
for being screwed up to make the joints tight by hand in some cases, and in others
for effecting this final closing of the joints also, either in conjunction with or
without an accumulator.
It has been found in practice that serious inconveniences or losses of time and
material arise:
(1) When Filter Presses are worked by any of the arrangements above referred
to, in consequence of variations of pressure between that exerted within the cells
under the working feed pressure of the liquid undergoing filtration and that which
is externally applied to the movable head for the purpose of making the joints.
liquid tight and of resisting in addition the internal working pressure, resulting
in the bursting out of the semi-fluid contents between the cell joints whenever the
external pressure becomes insufficient.
(2) When screw closed machines are worked by hand as auxiliary to fluid
pressure in the initial stage, in consequence of the labour necessary to screw up
the joints.
Now these inconveniences or losses I take care to avoid by the arrangements
hereinafter described whereby the external closing pressure exerted on the loose
head shall always he dependent upon and in excess of the internal pressure in
the filter cells.
This interdependence of the internal and external pressures I accomplish by
connecting the feed apparatus of the Filter Press directly or indirectly with an
Hydraulic Differential Intensifier before the feed main arrives at the inlet to
the Filter Press.
By means of this Intensifier the feed pressure is transmitted and intensified in
the Hydraulic Cylinder provided for actuating the movable head of the Filter

page_text: Press, the Hydraulic Ram of which I provide of such an area that the total pressure
exerted in closing the Filter Press shall always be considerably in excess of the
internal pressure tending to open the cell joints. It will be readily understood
that by so adjusting the proportions of the areas in the Intensifier and closing
ram, any desired excess of external over internal pressure may be secured, and
these pressures being interdependent it matters not what the feed pressure may
be. It may also be observed that in consequence of the arrangement of the
Intensifier being actuated by the feed pressure prior to its arrival within the
Filter Press, any alteration of pressure in the feed is anticipated by an increased
pressure in the closing mechanism.
In the case of Filter Presses having the filter cells telescoping into each other
so as to admit of the cakes, formed in the first instance as in an ordinary Filter-
Press, being finally finished by hydraulic pressure applied to the follower, I
employ an Intensifier worked by the pressure of the feed main combined with an
Hydraulic Ram actuating the follower as before described, but in this case I
provide stop valves on the feed inlet to the Filter Press, and between the Intensifier
and the Follower lam when filling the apparatus as a Filter Press in the first
stage, or formation of the cakes, the stop valve between the Intensifier and the
Follower Ram I keep closed, and then, as soon as the cakes are formed in the filter
cells in this stage, I close the feed inlet valve to the filter cells and open the valve
between the Intensifier and Follower Ram, which gives the final squeeze at high
pressure without the addition of any more liquid as in the first stage, and thus
secure more perfectly pressed and harder cakes although only the one source of
pressure is used, viz: that from the feed main which works the Filter-Press.
In order that this my Invention may be more fully ascertained I will now
describe several arrangements by means of which I carry out same, reference being
made to the Drawings accompanying this Specification.
Figs. 14, 12 and 1° show respectively Side Elevation partly in section, End
Elevation, and Plan, in which the corresponding parts are similarly lettered, of a
Filter Press F with Intensifier I, and Hydraulic Cylinder H with Ram R actuating
the movable Head or Follower E so as to close the chambers c¹ cl clll etc.
S M is
the Sludge Main which supplies the material into the Filter Press, which it may
be noticed is passed into and through the Intensifier under pressure on its way
to the charging inlet of the Filter Press. 6 is a baffle plate formed in the base
casting of the Intensifier with the view of altering the direction of the current of
sludge when passing through the Intensifier, and is intended to remove the effect
of ram action in a long feed pipe, which otherwise would unduly raise the pressure
inside the sludge press when the sludge would be passing at a high velocity. In
the arrangement shown, the effect of such ram action is translated so as to be
exerted on the major area of the differential ram piston of the Intensifier and so
on through the minor area of same to the movable closing ram R, thus exerting
the pressure due to such ram action externally so as to close the joints of the filter
cells more tightly together instead of forcing them apart as would be the tendency
if the pressure due to the ram action of the liquid in the Feed Main SM were
allowed to pass unobstructed and so be exerted internally.
WM is a branch from a water main or service pipe under pressure such as
would ordinarily occur in a normal town water supply and is admitted to the
actuating cylinder H by the valve v. A relief valve is also provided, which is
used when it is desired to draw back the movable head E by means of the counter-
weights W WI attached thereto by means of wire ropes passing over the
pulleys p p.
The service of water under low pressure is used to actuate the Ram R
during the major part of its stroke and its function is to push the filter-plates
along the tension bars into juxtaposition after the contents of the chambers have
been discharged and when it is desired to get ready for the next charge. It also
lifts the counter-weights W W₁, thereby storing the force to be employed when
opening the filter press again.
When the joint surfaces of the filter plates have been forced into juxtaposition

page_text: by the low service water pressure the valve is closed and the sludge valve SV
is turned on to the Intensifier, from which the high pressure water is delivered to
the cylinder H to give the final pressure necessary to make the cell joints 1 j jill
etc. liquid-tight. I sometimes provide a valve at the feed inlet of the Filter
Press fi which should be used to close this inlet when the high pressure from
the Intensifier is first admitted for the purpose of closing the joints of the filter
cells liquid-tight. It may then be gradually opened. This valve should be
employed when the available pressure in the low pressure water service is
insufficient.
When it is desired to open the Filter Press the Sludge Valve SV is shut off,
the relief valve r opened, which permits the sludge from the Intensifier to run
hack into the sludge storage receiver which is not shown in the drawing.
In some cases where the sludge to be filter-pressed is very gritty, or otherwise
of a character to injuriously affect the interior surface of the Intensifier, or the
hydraulic cup leathers in same, instead of introducing sludge from the Feed
fain SM into the Intensifier I admit this direct to the Filter-Press and employ
closed forcing receivers actuated by compressed air from a storage receiver in the
manner well known and commonly practised. I then employ a small auxiliary
forcing receiver charged with water but actuated by the compressed air from the
same storage receiver as is used for forcing the sludge, taking care that the water
has a more direct and shorter path from the water receiver to the Intensifier than
the sludge has from the sludge receiver to the Filter Press, so that the effect of
any sudden increase of pressure will be anticipated in the external pressure applied
to close the follower E. To avoid ram action in the sludge main SM I increase
the diameter of this pipe and contract it considerably at the feed inlet fi and thus
reduce the velocity in the pipe on which this ram action in part depends, but it
should be remembered that the quantity of water required in the Intensifier is
comparatively small, and its mobility is greater than the semi-fluids usually
requiring to be filter-pressed, and these conditions are in favour of the internal
being anticipated by the external pressure.
The auxiliary water forcing reciver working with a compressed air forcing
system may also be advantageous' employed to furnish the low pressure water
for actuating the Hydraulic Closing Ram H where a water service under pressure
is not available, or the pressure is insufficient.
Figs. 2, 2 and 2°, and 3^, 3º and 3° show modified forms of this my Invention,
i. which the corresponding reference letters with the number of the Fig. added
are used. Thus I is a Differential Ram. Intensifier of known construction, which
may be used instead of I Fig. 1; or, Fig. 23 is an arrangement showing the
actuating ram Rª B stationary on the fixed end standard of the Filter Press and
the Hydraulic Cylinder H B movable constituting the back boss of the movable
head or follower, the parts being merely transposed in a manner that would be
obvious to a person of experience and skill in such mechanism.
Figs. 3, 3 and 3° show an arrangement where the low pressure water service
is omitted and the high pressure from the Intensifier alone is used, the follower
being drawn back by hand by means of a winch handle wh and racks and
pinions rp, a movable thrust block TB being used, which is pushed to one side
to allow the hollow follower boss fb to telescope over the ram ends when the filter
press is being opened.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed; and having illustrated
it and the means by which it is to be carried into effect by adducing several
examples of modes in which it may be practically applied, I wish it to be distinctly
understood that I do not limit myself to variations such as are shown in the
examples cited, but what I claim as novel and as forming the substance of my
Invention is :-
1 The construction of Filter Presses working in combination with an Intensifier

page_text: re-acting on an Hydraulic Ram in which the working pressure of the feed liquor
before entering the filter chambers exerts pressure externally on the movable head
or follower in excess of the internal pressure, the condition being that the internal
pressure within the cells tending to force open the joints shall be exceeded by the
external pressure tending to press them together, so as to maintain the cell joints
fluid-tight, no matter what the working pressure may be, the internal and external
pressures being derived from the same source, the feed pressure & interdependent,
substantially as described.
2. In a system of Pneumatically fed Filter Press or Presses the combination
therewith of an auxiliary water forcing receiver actuated simultaneously by air
pressure common to both the sludge and water forcing receivers operating the
Intensifier with clean water instead of the feed liquor in the combination as
described in Claim No. 1. All substantially as and for the purposes described.
3. The employment of the auxiliary water forcing receiver as claimed in
Claim No. 2 in combination with the Hydraulic Closing Ram and counter-weights
for opening and closing Filter Presses in the first or low pressure stage.
Substantially as and for the purpose described.
4. in Filter Presses constructed with chambers telescoping into one another
for the purpose of submitting the cakes formed to a final high pressure without
the addition of fresh liquid, the combination of the feed main with the Intensifier
and Follower Ram arranged with the valves so that the feed pressure may be
exerted on the interior of the filtering cells to form the cakes, or on the exterior
through the Intensifier and ram to finish the cakes under high pressure,
substantially as and for the purpose described.
Dated this 14th day of April. 1897.