Improvements in Filter Presses.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Filter Presses.
SAMUEL HENRY JOHNSON and CHRISTOPHER CLARKE HUTCHINSON of The
Engineering Works, Carpenter's Road, Stratford, Mechanical Engineers, 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:-
Our invention has for its object improvements in the construction of filter
presses. Firstly, so as to facilitate the escape of the filtered liquid after it has
passed through the filtering cloths and the distribution of wash water, solvents, air or
steam, at the back of the filtering cloths. Secondly, so as to preserve the filter
cloths used on such machines by preventing the undue wear of same at the surfaces
where they are nipped together round the margins of the filter chambers, and
Thirdly, so as to facilitate the changing of the filter cloths and to secure tight joints
in the inlet, outlet and washing passages. All as hereinafter fully described and
ascertained, reference being made to the accompanying drawings.
Hitherto the surface structure of the partition plates in filter presses has been
either grooved, circularly or vertically and with an occasional cross groove to forui
leaders for the filtrate towards the outlet, or else the egress of the liquid was
provided for by the employment of a perforated plate carried on projections which
gave facilities for the ready flow of the liquid at the back thereof. The grooved
structure is objectionable on account of the smallness of the area of the leader
grooves proving to be an obstruction to the ready egress of the liquid. The
perforated plate covering possesses the disadvantage that by far the greater portion of
the area of the filtering cloth is backed and rendered more or less impermeable
thereby, the only area which works efficiently being that occupied by the perforations,
so that in machines as usually constructed, only about a tenth of the cloth works to
its maximum degree of efficiency, the remainder being backed by the perforated
plate.
Now by our system of construction we avoid these objections, and secure our first
object by making the surface structure of the plates to consist of series of bosses or
projections standing out from the surface of the filter plates with deep intersecting
channels between them, care being taken that the most prominent surface of the
projections shall be of such form and area as to give sufficient support to the filter
cloths without injury, by this means we are enabled to secure that as much as nine-
tenths of the whole area of the filtering cloth shall be made available in its most
effective condition for filtration, that is to say, not backed on the other side by an
obstructing surface, so that only one-tenth of the cloth will be in a condition in
which the filtration is impeded. These studs or bosses may be of any suitable form
complying with the conditions in the above description, for example, they may be
bemispherical, conical with flat tops or hexagonal truncated pyramids, but we prefer
that they should be of square truncated pyramidal form which facilitates the
construction of such surfaces, and the sides forming the grooves should be in section
inclined at an angle of about 60 or 70 degrees to each other so that the cloth shall
be kept well away out of the grooves when under pressure and thus leaving an ample
and full space for the free passage of liquids, steam or gases as may be desired.
In determining the space between the surfaces of support for the cloth from boss
to boss, due regard should be had to the strength of the cloth, but for all ordinary
purposes a space not exceeding three-sixteenths of an inch where thin cloths are used
will be found sufficient to withstand a pressure of 150 lbs. per square inch it is
obvious that where paper is desired to be used instead of cloth as the filtering
T
:

page_text: medium, the pyramids should be smaller and closer together, and if the spaces to be
bridged by the paper, nowhere exceed three-sixteenths of an inch in width strong
filter paper can be used and will withstand efficiently a pressure of 100 lbs. per inch
or more. This arrangement of pyramidal studs or projecting bosses provides
larger capacity for the passage of the fluids underneath the cloth, and admits of the
flow in any required direction with a minimum of obstruction, whether from washing
passages to be distributed over the surface of the plate or for the filtrate to the
outlet, or for the introduction of steam or air as is sometimes done, the numerous
intersections of the net-work of channels greatly facilitates the flow in the desired
direction, and where thick liquids have to be dealt with, this is more important and on
account of the decreased friction in the passages the machine is more efficient.
Another advantage it possesses over perforated plates which may have provisions
for the free flow of the liquid underneath them is, the accessibility of such surfaces
for cleaning with facility in every part, a matter of great importance where
fermentable or putrescible substances have to be dealt with, such as beer, wine, sugar,
meat juice, &c.
To accomplish our second object, we form the rim of the filter plates or frames,
which constitute the filter chainbers, on one side where they meet together with
grooves in them and in these grooves we insert elastic packings, such packings
being moulded on the internal side where the pressure is exerted with a projecting
lip which closes more tightly on the surface adjoining according as the pressure is
increased. Or we construct the grooves into which the packings are inserted so that
the internal sides of such grooves where the pressure is exerted shall leave the elastic
packing only partially supported in such a way that on tightening up the machine, the
spreading of the elastic material of the packings, takes place only on the unsupported
inner side, so forming a projecting lip on which the internal pressure is exerted, thus
effecting an hydraulic joint.
We
e are aware that india rubber packings have been proposed for use in the joints
of filter presses, vide English Patent No. 587, 1867, but these require more pressure
to make them liquid tight and consequently injure the cloths more than the hydraulic
lipped packings, herein described.
Our third object more particularly applies to the form or construction of filter
press wherein these passages are carried in projections from the chambers clear of
the filtering cloths. Filter presses with these external passages have hitherto been
made in either of two ways:-
Firstly, the joint surfaces of the projecting lugs carrying the openings which form
the passages have been surfaced in the same plane as the joints round the rims of the
filtering chambers which joint on the filtering cloths, and in order to make up the
space occupied by the filtering cloths and joint the projecting lugs to one another
when the machine is screwed up for work, it has hitherto been necessary to provide
short sleeves made of the same kind of cloth as the filter cloths in use, such sleeves
covering the joint surfaces and having openings corresponding to the passages
therein.
The second plan is to form recesses in the joint surfaces round the openings in the
lugs and fitting into these recesses elastic rings so as to form the joints between the
respective lugs when the machine is screwed up. It will be obvious from the above
description that the joints in all these passages require to be made by the direct
pressure of the screw which forces the chambers together.
Now these systems are subject to inconveniences in consequence of the same
pressure being required to make the joints on the cloths as is necessary for securing
tight joints round the margins of the chambers, so that when..alterations-in-thickness
of the cloths, used for filtering occur, which inevitably takes place either from the
effect of the material being worked in the machine, consolidating in the pores of the
cloths or from other causes the unequal thicknesses occasioned thereby at the different
joint surfaces on the chambers occasion constant leakage either from the chambers or
between the lugs forming the passages. Now these inconveniences we take care to

page_text: avoid by using the main screw of the machine for the purpose of making the
joints round the respective chambers only, the tightness of the joints on the various
inlet and outlet passages in the projecting lugs not depending on the pressure of the
main screw, but on the internal pressure of the liquid in the passages when the
machine is at work, and this we accomplish by fixing in the hole of every alternate
lug an elastic packing ring having two projecting lips thereon which under the
hydraulic pressure at which the filter is working is pressed against the planed
surfaces of the adjoining lugs, by this means we avoid undue pressure at any of the
joints of the external passages, the function of the screw being only to bring the
yielding lips of the joint rings into gentle pressure with the surfaces of the lugs,
depending for tightness altogether on the hydraulic pressure, by this means perfectly
tight joints can be obtained even with varying thicknesses of cloth, and a considerable
economy of time is effected in working filter presses of this type.
In order that this our invention may be more clearly understood we will now
proceed to describe the accompanying drawings
Fig. 1. is a front elevation of a partition plate with part of its surface constructed
in accordance with our invention.
Fig. 2. is a vertical section of a filter plate constructed in accordance with our
invention and showing a couple of filtering cloths thereon as they are placed
preparatory to putting them together in the filter press.
a
Fig. 3 is a sectional view of the joint surfaces of two adjoining filter press plates,
r is an india rubber packing with a moulded hydraulic lip inserted into the groove g
on one side of the filter plate, this packing joints against the surfaces of the
adjoining filter plate, the filtering cloth being secured between them without injury
and perfectly water tight.
Figs. 4 & 5, show two sectional views illustrating the square rubber packing. In
Fig. 4. before the joint is pressed together and Fig. 5, showing the altered form of
the india rubber packing when the joint is closed with the projecting lip / formed by
the distortion of the rubber under the closing pressure on the inside where the
supporting side of the groove, Fig. 4. at y' has been partially removed leaving the
space for the rubber lip to expand.
Fig. 6. shows a section of a series of lugs forming the feed passage in a plate and
frame filter press it will be seen that the lips of the hydraulic jointings are made to
project outwards beyond the joint surface so as to insure contact with their joint
surfaces notwithstanding the employinent of thick filter cloths.
(A) is the hydraulic joint ring fixed in the lug (B) which projects and forms the
feed passage from the plates or filtering diaphragmns, (C) is the lug corresponding to
same attached to the distance frame which forms the depth of the filtering chamber,
and in this lug is cored the passage through which the filtering chamber is fed. If
it were desired to introduce liquid into the filtering diaphragins at the other side of
the cloth (when it is desired to wash for instance, or to draw off the filtrate in a
closed passage) then the hydraulic packing would be put in the distance frame lug
and the cored port into the filtering diaphragm as is quite obvious.
Short lengths of elastic tube having the two ends projecting into the openings in
the adjoining lugs would also accomplish a similar result, but we do not find this
arrangement so convenient or practicable as that already described.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed we declare that what we
claim is
1. In a filter press the construction of the partition diaphragms having their
surfaces formed of projecting studs with a reticulation of interspaces between them
to facilitate the flow of fluids beneath the cloths substantially as described.
2. In a filter press the employment of hydraulic lipped packings in the rims of the
filter plates whether moulded with the lips, or the lips formed by the operation of
closing the joints in the manner and for the purposes described.

page_text: 3. In the feed and delivery passages of filter presses the elastic packing ring with
lips projecting so as to come into gentle contact with the joint surfaces of the
adjoining lugs so contrived that the pressure due to the working of the machine,
becomes the effective agent in securing the tightness of the joints, substantially as
described and shown.
SAML. H. JOHNSON.
C. C. HUTCHINSON.