Abstrict
A filter press includes a plurality of filter elements (filter
plates and filter frames) supported in the press stand for displacement
along the length of the press. A guide roller is supported on each
filter element alternatingly at opposite sides thereof. A continuous
filter cloth is trained about each guide roller for guiding the
filter cloth in a zigzag course between all adjoining filter elements.
At least some of the guide rollers are directly driven by a driving
mechanism. The driving mechanism has a sprocket drivingly connected
with each driven guide roller and having a rotary axis in alignment
with the rotary axis of the associated driven guide roller and a
guide wheel mounted on each filter element which supports a driven
guide roller. Each guide wheel has a rotary axis spaced parallel
from the rotary axis of the respective sprocket. The driving mechanism
further has an endless flexible drive member meshing in succession
with each sprocket and being deflected by the respective guide wheels
between every adjoining sprocket, whereby the flexible drive member
has a zigzag course.
Claims
I claim:
1. In a filter press including a press stand having a length dimension;
a plurality of plate-like filter elements and frame-like filter
elements oriented perpendicularly to said length dimension and arranged
alternatingly and supported in said stand for displacement parallel
to said length dimension and relative to one another; a closing
device operatively connected to the filter elements for pressing
the filter elements to one another into a filter element stack;
a guide roller supported on each filter element alternatingly at
opposite sides thereof as viewed in said length dimension; each
said guide roller having a horizontal axis of rotation oriented
perpendicularly to said length dimension; a continuous filter cloth
trained about each said guide roller for guiding said filter cloth
in a zigzag course between all adjoining filter elements; at least
some of said guide roller being driven guide rollers rotated by
driving means for pulling said filter cloth through said filter
elements in said zigzag course; the improvement in said driving
means comprising
(a) a sprocket drivingly connected with each said driven guide
roller and having a rotary axis in alignment with the rotary axis
of the respective driven guide roller;
(b) a guide wheel mounted on each filter element which supports
a driven guide roller; each guide wheel having a rotary axis extending
parallel with the rotary axis of the respective sprocket and spaced
therefrom in a direction which forms an angle other than zero with
the direction of said length dimension;
(c) an endless flexible drive member meshing in succession with
each said sprocket and being deflected by respective said guide
wheels between every adjoining sprocket, whereby said flexible drive
member has a zigzag course and is trained about each said sprocket
in the same direction; and
(d) motor means for driving said flexible drive member to unidirectionally
rotate said guide rollers.
2. A filter press as defined in claim 1, wherein said filter elements
are flanked by a head plate supporting said closing device and an
end plate; further wherein said motor means is mounted on one of
said plates; further comprising an additional guide wheel about
which said flexible drive member is trained; means for displaceably
mounting said additional guide wheel on said head plate; and tensioning
means for biasing said additional guide wheel for taking up any
slack of said flexible drive member.
3. A filter press as defined in claim 1, further comprising a first
series of end-to-end interconnected, alternating long-stroke and
short-stroke spacer elements; said first series extending parallel
to said length dimension along said filter elements at an upper
zone thereof; each spacer element of said first series having a
first end articulated to a plate-like filter element and a second
end articulated to an adjoining frame-like filter element; further
comprising a second series of end-to-end interconnected, alternating
long-stroke and short-stroke spacer elements; said second series
extending parallel to said length dimension along said filter elements
at a bottom zone thereof; each spacer element of said second series
having a first end articulated to a plate-like filter element and
a second end articulated to an adjoining frame-like filter element;
each said long-stroke spacer element having means permitting a relatively
large shift between the plate-like filter element and the adjoining
frame-like filter element interconnected by the respective long-stroke
spacer element; each said short-stroke spacer element having means
permitting a relatively small shift between the plate-like filter
element and the adjoining frame-like filter element interconnected
by the respective short-stroke spacer element; each said filter
element being connected to an adjoining, same filter element by
a long-stroke spacer element of one of said series and a short-stroke
spacer element of the other of said series, whereby in an open,
spaced-apart position of said filter elements each said frame-like
filter element assumes an inclined position to the vertical for
facilitating removal of a filter cake therefrom.
4. A filter press as defined in claim 1, further comprising a projection
and a complemental depression provided in an edge zone of at least
some of adjoining said filter elements; in a closed state of the
filter press each said projection on one filter element nesting
in said depression of an adjoining filter element for preventing
bending of the respective said plate-like filter elements during
filtering operation.
5. A filter press as defined in claim 1, wherein each frame-shaped
filter element has sloping wall faces along top, bottom and lateral
marginal zones; the improvement further comprising a tilting strip
attached at the wall face extending along the bottom marginal zone
of each frame-shaped filter element and holding means connecting
said tilting strip to a top part of the respective frame-shaped
filter element, whereby in a closed state of the filter press the
tilting strips lie flat on the wall face at the bottom marginal
zone of the respective frame-shaped filter elements and in an open
state of the filter press the tilting strips assume an inclined
position relative to the wall face at the bottom marginal zone of
the respective frame-shaped filter elements.
6. A filter press as defined in claim 5, further comprising a closing
latch arranged at ends of each said tilting strip; the closing latches
cooperating with an adjoining said plate-shaped filter element to
tilt said tilting strip onto the respective said wall face upon
closing the filter press.
7. A filter press as defined in claim 1, wherein said filter elements
are divided into at least two filter element blocks; each filter
element block being flanked by two delimiting plates; each said
filter element block being provided with a separate said driving
means for pulling said filter cloth.
8. A filter press as defined in claim 7, wherein each said drive
motor is mounted on a delimiting plate situated at that side of
the respective filter element block which is oriented towards said
closing device.
9. A filter press as defined in claim 8, wherein each said separate
driving means includes an additional guide wheel about which said
flexible drive member is trained; means for displaceably mounting
the additional guide wheel on a delimiting plate situated at that
side of the respective filter element block which is oriented towards
said closing device; and tensioning means for biasing the respective
said additional guide wheel for taking up any slack of the respective
flexible drive member.
10. A filter press as defined in claim 7, further comprising additional
separate drive means associated with each said filter element block;
each said additional drive means including a drive motor for propelling
a delimiting plate situated at that side of the respective filter
element block which is oriented away from said closing device.
11. A filter press as defined in claim 7, further comprising spacer
means interconnecting adjoining delimiting plates belonging to different
filter element blocks; said spacer means maintaining said adjoining
delimiting plates parallel to one another.
12. A filter press as defined in claim 7, further comprising a
compensating device disposed between adjoining filter element blocks;
said filter cloth being guided over each said compensating device
over a length equalling at least twice the vertically measured height
of said filter elements.
13. A filter press as defined in claim 7, further comprising a
filter cloth washing device mounted on adjacent delimiting plates
between each two said filter element blocks.
Description BACKGROUND OF THE INVENTION
The present invention relates to a filter press having a purality
of filter elements which are vertically oriented and mounted to
be horizontally displaceable in a press stand, a plate-shaped filter
element alternating with a frame-shaped filter element. By means
of a closing device, the filter elements can be pushed and pressed
together into a plate stack between a head plate and an end plate.
Guide rollers around which is guided an endless filter cloth moving
between the filter elements in a zigzag pattern are provided at
the upper and lower edges of the filter elements. A drive is provided
to pull through the filter cloth when the plate stack is open and
spacer elements are provided between the individual filter plates.
A filter press of the above-mentioned type is known from U.S. Pat.
No. 643,022. This prior art structure, aside from some structural
flaws, cannot be adapted to large filter presses with high throughput
and cannot be used for automatic operation.
SUMMARY OF THE INVENTION
It is an object of the invention, based on the prior art structure,
to provide a filter press which even in large filter presses, permits
the filter cloth to be pulled through without malfunction and provides
for a rapid and automatic ejection of the filter cake.
This object and others to become apparent as the specification
progresses, are accomplished by the invention, according to which,
briefly stated, the guide rollers are arranged at successive filter
elements, alternating at their upper and lower edges, and at least
part of the upper guide rollers are driven rollers. With this measure
it is possible, even in larger filter presses comprising 20 or more
filter elements, to pull the filter cloth through between the filter
plates without stresses or damage when the press is open, since
the drives need overcome only the friction forces acting on the
filter cloth between two driven guide rollers. It is particularly
advantageous to provide that all upper guide rollers are driven.
While it is possible in principle to provide each of the driven
guide rollers with its own drive motor, a preferred embodiment provides
that at least one end of the driven guide rollers is provided with
an entrainment member (hereafter gripper) which engages in a drive
means that connects the grippers of a plurality of guide rollers
and is in communication with a drive motor. Although in this arrangement
the drive motor must be much more powerful than one for individual
drives, the advantage of this arrangement is that the required synchronism
of the driven guide roller can be effected by means of the common
drive means. A further advantage is that in the treatment of corrosive
media, the vapors escaping from the filter press, when it is opened,
cannot destroy the drive since the sensitive drive motor can be
arranged in an area which lies outside the zone endangered by the
corrosive vapors while the grippers and the drive means connected
thereto can be made of corrosion resistant materials.
According to an advantageous further embodiment of the invention,
the grippers are toothed wheels and the drive means is a toothed
belt. The toothed wheels as well as the toothed belt are commercially
available components and are made of highly wear and corrosion resistant
materials.
Regarding the structural design of the drive formed by the drive
motor, the drive means and the grippers, it is of significance that
when the filter plate stack is opened (whereby beginning with the
end plate, the individual filter plates, which are connected together
by means of spacer elements, are separated one after the other in
an accordion-like manner), no positive forces act on the driven
guide rollers, i.e. no external torque must be applied to the guide
rollers. For this reason, either the drive means connecting the
individual grippers must be able to be uncoupled from the guide
rollers or idling couplings must be provided between the individual
grippers and their guide rollers. This solution, however, is relatively
expensive. Therefore, according to a preferred embodiment of the
invention, with each gripper there is associated a belt deflecting
mounted on the same filter element in axially parallel orientation
with the respective gripper. This arrangement has the advantage
that the guide wheel causes the toothed belt to move through the
individual grippers in a zigzag pattern. Since the space available
between each two guide rollers is determined by the thickness of
the filter elements and thus the diameters of the guide rollers
as well as the grippers are limited, the guide wheels for the toothed
belt must each be disposed somewhat below and offset to the side
of the associated guide roller. Consequently, the guide wheel has
to be pushed somewhat below the toothed gripper wheel of the adjacent
guide roller when the filter plate stack is pushed together. Thus,
in the closed state, the angle of enclosure for the toothed belt
on the guide wheel is more than 180.degree.. Since the guide wheel
pushes itself underneath the toothed gripper wheel by a certain
degree, when the filter press is in the pushed-together state, the
loop angle on the toothed gripper wheel is also more than 180.degree..
If now during opening, the filter plates are spread apart with
the aid of the closing device to the distance given by the spacer
elements, the loop angles of the toothed belt on the guide wheel
and on the toothed gripper wheel decrease, i.e. the toothed belt
is "unwound" from both wheels. In practice, this "unwound"
length of the toothed wheel corresponds to the required width between
two guide rollers given by the spacer elements so that during the
opening process no torque is applied to the guide rollers. This
assures, in a simple manner, an equalization of length for the opening
and closing process without requiring complicated coupling devices
or the like for this purpose.
According to another advantageous embodiment of the invention,
the drive motor for the toothed belt is mounted on the end plate
and a guide wheel for the toothed belt is displaceably mounted at
the head plate and is provided with a tensioning means. This design
provides an equalization of length for that side of the toothed
belt which is not in engagement with the grippers of the guide rollers.
When the plate stack is closed, the tensioning means moves the guide
wheel downwardly on the head plate, while during opening of the
plate stack the guide wheel is pulled upwardly against the force
of the tensioning means.
According to another advantageous embodiment of the invention,
the spacer elements which are fastened at the side of the filter
elements connect the individual filter elements together in a chain-like
manner. The spacer elements are arranged in a row to both sides
of the plate stack in the area of the upper edge as well as of the
lower edge. When seen in the longitudinal direction of a row of
spacer elements, a spacer element with a long stroke follows a spacer
element with a short stroke and the sequence of the different spacer
elements in the upper row is offset by one filter element with respect
to the spacer elements of the lower row. While in the closed plate
stack the individual filter elements are oriented parallel to one
another, by virtue of this design during opening only the plate-shaped
filter elements remain vertically aligned while the respective frame-shaped
filter elements disposed therebetween are tilted in the longitudinal
direction of the press. At the same time, the short stroke provides
the required free space between every two filter elements as required
for passage of the filter cloth after emptying. The tilting results
in a significant improvement for the ejection of the filter cake.
This is particularly applicable to filter presses in which the filter
chamber required for the filtration process is formed by a plurality
of elements as this is the case, for example, in frame filter presses
in which a frame with slurry inlet is disposed between two plates
provided with channeling and discharge channels or also in chamber
filter presses in which the filter plates have, at least on one
side, a dish-shaped recess so that contacting filter plates form
a filter chamber.
In a further, particularly advantageous embodiment of the invention,
the edge regions on facing areas of some of the filter elements
are provided with protrusions on one side and corresponding recesses
on the other side. These protrusions may, for example, be pins or
projecting strips and, particularly in the above-described frame
filter press, they serve the purpose of providing a form-locking
connection in the closed state between the frame and the filter
plates delimiting the frame so that the frame cannot be bent out
to the side under the pressure of the incoming slurry. Due to the
high closing forces, a relatively slight height is sufficient for
the projections to absorb the generated transverse forces while
the piece of filter cloth enclosed between a projection and the
associated recess will not be excessively stressed or damaged.
In a filter press in which the filter elements are formed by a
plate with discharge channeling on both sides and a frame with inner
walls which are inclined toward the plane of the frame, according
to an advantageous embodiment of the invention a tilting strip is
provided which is placed in each frame along the inner wall parallel
to the lower edge. The tilting strip is fastened by means of holding
means, preferably a cloth, to the inner wall parallel to the upper
edge. In the closed state, the tilting strip rests directly on the
inclined inner wall and is held in its position by the adjacent
filter plate. The cloth which is used as the preferred holding means
has a coarse weave with as little adhesion as possible for the filter
cake, for example a PTFE fabric. In the closed state the holding
cloth rests directly on the filter cloth of the contacting filter
plate on the other side. When the press is opened, and simultaneously,
the upper edge of the frame is tilted in the direction toward the
larger frame opening, the influence of the weight of the cake pulls
taut the holding cloth in the direction toward the larger frame
opening while at the same time the tilting strip is pushed over
the lower edge of the larger frame opening. This avoids the baking
of cake residues on the lower sealing face of the frame. If baking
does occur, it will occur only on the tilting strip so that with
the subsequent pushing together of the plate stack the lower sealing
face of the frame will also be free.
In a preferred embodiment of the invention, both ends of the tilting
strip are provided with a closing latch with which the tilting strip
can be brought in a simple manner into position at the inner wall
of the frame during the pushing together of the plate stack.
For filter presses with an especially high number of plates, a
further embodiment of the invention provides that the plate stack
is subdivided into at least two blocks of. The end of each block
of stacks is provided with a delimiting plate and each delimiting
plate on the side of a plate block facing away from the closing
direction is provided with its own drive and supports the length
equalization for the filter cloth drive means. The delimiting plate
on the side of a plate block facing the closing device supports
the drive motor for the filter cloth drive means and the delimiting
plates immediately adjacent one another between two stack blocks
are held in parallel alignment with one another by spacer means
even in the open state. Due to the accordion effect produced by
the spacer means, one closing device can open, for practical purposes,
only a limited number of filter elements since otherwise the stroke
to be handled by the closing device would be too large. A filter
press according to the embodiment as detailed above has the advantage
that very large filter presses can be assembled without requiring
a large stroke for the closing device. This can be accomplished
in that the delimiting plate of the plate block disposed on the
side facing away from the closing device takes over, with respect
to movement, the function of the head plate so that the adjacent
plate block can be opened with the aid of the drive of such a delimiting
plate while the preceding plate block is pushed together by the
drive. Simultaneously, however, the length equalization arrangement
for the stack block extending in the direction toward the closing
device is disposed on the delimiting plate.
While it is possible, in principle, to associate each plate block
with its own endless filter cloth, a particularly advantageous embodiment
of the invention provides that the endless filter cloth is brought
through the entire plate stack in a zigzag pattern and that a compensating
device is disposed between the adjacent delimiting plates of two
stack blocks. The filter cloth is guided over the compensating device
in a length which is at least twice the height of a filter plate.
This makes it possible to use only one filter cloth length even
for large plate stacks which are divided into a plurality of stack
blocks. With the aid of the compensating device it is then possible,
when the stack block is open, to pull a length of filter cloth corresponding
to the height of a filter plate through the stack block.
According to a further advantageous embodiment, the adjacent delimiting
plates between two blocks comprise filter cloth washing devices.
This makes it possible, even if a plurality of stack blocks are
provided, to introduce a clean piece of filter cloth into the respective
stack block during each opening process.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a side elevational view of a filter press according to
a preferred embodiment of the invention.
FIG. 2 is a sectional side elevational view of the structure of
FIG. 1.
FIGS. 3 and 4 are side elevational views of a detail of the preferred
embodiment in an open and in a closed position, respectively.
FIG. 5 is a top plan view of the structure of FIG. 4.
FIGS. 6 and 7 are sectional side elevational views of a preferred
embodiment of a detail of the invention in an open and in a closed
position, respectively.
FIG. 8 is a top plan view of a detail of FIG. 6.
FIGS. 9 and 10 are side elevational views of a preferred embodiment
of a detail of the invention in an open and in a closed position,
respectively.
FIGS. 11 and 12 are schematic sectional elevational views of another
preferred embodiment of a detail of the invention in an open and
in a closed position, reseptively.
FIG. 13 is a schematic side elevational view of a filter press
according to a further preferred embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows, in a side view, an embodiment of a filter press,
partially in the open state. In this embodiment, two spaced parallel
guide carriers 3 are mounted on uprights 1, 2. Between the two guide
carriers 3, there are disposed filter elements 4, 5, which are supported
on the guide carriers 3 by lateral pins or rollers 6. The configuration
of the individual filter elements will be described in further detail
below. The upright 1 is connected with a closing device 7 formed,
for example, of a hydraulic piston/cylinder arrangement whose piston
rod is connected with an end plate 8 displaceably supported by guide
rollers 9 on the two longitudinal carriers. A head plate 10 serving
as an abutment for the last filter element is connected with the
upright 2.
The filter elements 4, 5 together form a plate stack which in the
illustrated embodiment is subdivided into three stack blocks I,
II, III. The individual filter elements are connected together in
a chain-like manner by means of spacer elements 11, 12 whose design
and function will be explained in further detail below with the
aid of two embodiments. When the filter press is opened, the individual
filter elements can be pulled apart or pushed together like an accordion.
The individual stock blocks are separated by delimiting plate 13,
14. The delimiting plate 13 disposed on the side of the stack block
facing away from the closing device 7 is provided with its own drive
formed, for example, of toothed gears 15 arranged at both sides
of the delimiting plate 13. The toothed gears are in communication
with a drive motor and roll off on a toothed rod 16 disposed at
the longitudinal carriers 3. The delimiting plates 13, 14 are connected
together by means of coupling members 17 whose design approximately
corresponds to the spacer elements 12. The coupling members 17 are
designed in such a manner that, when the plate stack is opened,
the delimiting plates 13, 14 remain oriented parallel to one another.
The sectional view of FIG. 2 shows that in this embodiment the
plate stack is formed of two different filter frame-like filter
elements 4 and plate-like filter elements which are provided on
both faces with vertically downwardly oriented channeling. Each
frame-shaped filter element 4 has inner walls 18 which are inclined
with respect to the plane in which the element extends. An endless
filter cloth 19 is guided in a zigzag pattern between all plates
of the plate stack, its "idle portion" 19' extends above
the plate stack. When the plate stack is closed, one frame-shaped
filter element 4 with two flanking plate-like filter elements 5
form a filter chamber 20 which is covered with filter cloth at both
sides with respect to the channeling in the plate-shaped filter
element 5. The slurry inputs are arranged, in a known manner, at
a frame-shaped filter element 4 while the filtrate discharge devices
are provided, likewise in a known manner, at the plate-shaped filter
elements 5.
Before the essential structural details are explained in further
detail, the mode of operation of this filter press will be briefly
explained in more detail with the aid of FIGS. 1 and 2:
After all filter elements of the plate stack are pushed together
with the aid of the drives 15 and the delimiting plate 13 and with
the aid of the closing device 7 with the intermediary of the end
plate 8, to form a closed plate stack and are compressed with a
given closing pressure with the aid of the closing device 7, the
slurry to be filtered is introduced simultaneously into all filter
chambers 20. The solids are retained by the filter cloth 10 while
the filtrate flows out through the channeling in the plate-like
filter elements 5 and is extracted by means of known extraction
systems. A filter cake thus builds up in each filter chamber 20
from the retained solids so as to finally completely fill the filter
chamber. After the supply of slurry has been stopped, the head plate
8 is retracted with the aid of the closing device 7. The individual
filter elements are thus pulled apart like an accordion. Due to
the fact that the spacer elements 11 are designed for a "short
stroke", i.e. they leave only a small space between each two
adjacent filter elements, while the spacer elements 12 permit a
"large stroke", i.e. a broad distance between each two
filter elements and, moreover, the sequence of the spacer elements
in the upper row is arranged to be offset by one filter element
with respect to those in the lower row, there result the positions
of the individual filter elements as shown in FIGS. 1 and 2. The
plate-shaped filter elements 5 thus remain vertically oriented while
the frame-like filter elements 4 are tilted. In spite of a short
opening groove there then results a relatively wide gap at the lower
end through which the filter cake 21, indicated in FIG. 2, can drop
out at the bottom.
The drive 15 for the delimiting plate 13 has held the remaining
plate blocks II, III in the closed position. Since stack block I
has now been emptied, the drive for the delimiting plate 13 opens
the stack block II in the same manner, while stack block III is
still held in the closed state by delimiting plate 13'. After emptying
of the stack block II, finally, the stack block III is opened by
the drive 15 of the delimiting plate 13' and is emptied in the same
way.
As can be seen in FIG. 2, the individual filter elements are provided
with guide rollers 22 (at the frame-shaped filter elements 4) and
guide rollers 23 (at the plate-shaped filter elements 5) alternatingly
at the top and bottom. The filter cloth 19 is guided through the
entire plate stack in a zigzag pattern. The number of plates including
the delimiting plates is selected in such a manner that the filter
cloth is brought in two layers between each two delimiting plates
13, 14, and can be held by a compensating roller 25 disposed freely
in the cloth loop 24 formed in this way. The distance between the
delimiting plates 13, 14 in the open state is so dimensioned (by
an appropriate design of the coupling elements 17) that the compensating
roller can be moved freely through the space therebetween.
When the stack block is open, the arrangement described schematically
above makes it possible, with the aid of a drive means to be described
in detail below, to pull the filter cloth through the entire stack
block by a length which corresponds to the height of one filter
element. In the space between the delimiting plates 13, 14, the
comensating roller 25 then moves into the position shown in dashed
lines in the upper region of the delimiting plates. After the stack
block I has been pushed together via the drive 15 of the delimiting
plate 13 and the stack block II has been opened for emptying, the
filter cloth can be pulled through the open stack block II in the
same manner so that the compensating roller 25' of the cloth loop
24' moves upwardly while the cloth loop 24 and the compensating
roller 25 moves downwardly between the stack blocks I and II. Finally,
after emptying the stack block II, the filter cloth can be pulled
through by a corresponding length. The cloth loops 24 now disposed
between the delimiting plates can then each be subjected to a washing
process. The washing device is disposed either outside the press
or is formed by the two adjacent delimiting plates, in which case
the delimiting plates are designed in the usual manner as washing
devices. The thus resulting intermediate cleansing of the filter
cloth results in an improvement of the filtering output. The length
equalization of the filter cloth required for the opening and closing
process is effected by means of a preferably weighted tensioning
device 26 in the region of the end plate 10.
The drive for pulling through the filter cloth will be described
in detail with the aid of FIGS. 1, 3, 4 and 5. As can be seen from
the plan view of FIG. 5, each end of the guide rollers 22 has an
associated gripper 27, such as a toothed wheel. As can be seen from
the side view of FIG. 4, each gripper 27 is associated in axially
parallel relationship with a guide wheel 28. The axis of each guide
wheel is diposed somewhat below the axis of the gripper and projects
on one side beyond the plane of the associated frame-shaped filter
element 4. The mutual positions of the axes of gripper 27 and guide
wheel 28 are so designed that, in the closed state of the plate
stack (FIG. 3) each guide wheel 28 can slide by a certain degree
under the gripper 27 of the adjacent plate. A drive means 29 is
guided in a zigzag pattern as shown in FIG. 4 around the gripper
gears 27 and the guide wheels 28. The drive means may be formed
of a roller chain or the like; preferably, however, a toothed belt
will be used. The toothed belt is an endless belt and is, with its
working flight, trained about all grippers 27 of one stack block
and returns, with its idle flight 30, underneath the grippers. As
can be seen in FIG. 1, in the region of the end plate 8 the toothed
belt is guided over a drive wheel 31 which is connected with a drive
motor. At the delimiting plate 13 the toothed belt is guided over
a guide wheel 32 which is mounted to be vertically displaceable
on the delimiting pate 13 in the direction of the double arrow 33
so that here too the required length equalization is provided for
the opening and closing process. The guide wheel 32 is connected
with a tensioning means (not shown in detail) such as a weight,
a spring or the like so that during closing of the stack block the
slackened length of the idling reach of the toothed belt can be
taken up.
The stack blocks II and III are designed in the same manner as
the stack block I. Thus the drive motor for the drive gear 31' or
31", respectively, is mounted on each of the delimiting plates
14. While thus the filter cloth is brought through all blocks of
the plate stack, each stack block has its own drive.
As soon as a stack block is opened, as shown in FIG. 4, the toothed
belt 29 is pulled through in the direction of the arrow 34 by the
drive wheel 31 so that the filter cloth supported on the guide rollers
22 is pulled through the open stack block in the direction of the
arrow 35. The idling flight 30 of the belt 29 moves in the direction
of arrow 36.
If now, after completion of the cloth transport, the filter plate
element of the respective stack block are pushed together, the guide
rollers 22 must no longer be rotated since, due to the accordion-type
closing motion, part of the filter cloth has already been clamped
between the plates so that rotation of the guide rollers during
the pushing-together may cause undue tension in and possible damage
to the filter cloth. Such an occurrence, however, is avoided in
the embodiment of the drive described in connection with FIGS. 3,
4 and 5. If the filter elements are mved from the open position
shown in FIG. 4 to the closed position shown in FIG. 3, the angle
by which the portion of the toothed belt 29 disposed between the
guide roller 22 encloses the guide wheel 28 and the gripper 27 of
the adjacent filter element increases. With this "winding"
and "unwinding", respectively, during opening it is avoided
that during the closing or opening movement, respectively, the guide
roller 22 are caused to rotate. During the closing movement, the
idling flight 30 of the belt 29 is merely tensioned by the tensioning
means 32 in the direction of the arrow 36.
Because of the fact that the frame-shaped filter elements 4 can
tilt downwardly, the stroke required to open the plate stack can
be limited to a minimum amount so that short-stroke closing units
can be used even in large presses since the plate stack or the stack
blocks, respectively, need be opened, in the area of the lower edges,
only by an amount which is somewhat larger than the thickness of
the frame-shaped filter elements. However, in case of filter cakes
which tend to stick, when the filter cake slides out, solid residues
may adhere to the sealing face of the frame-shaped filter element
4 so that during the subsequent closing process the respective filter
chamber is not sealed tightly or the filter cloth engaging the sealing
face is damaged. In order to assure proper cake discharge even with
sticky products, without relinquishing the advantages of the short
opening stroke, a special embodiment of the frame-shaped filter
element 4 is illustrated in FIGS. 6, 7 and 8 and described in connection
therewith.
FIG. 6 shows a plurality of consecutive filter elements 4 and 5
on an enlarged scale. FIG. 6 clearly illustrates the channeling
37 on both sides of the plate-shaped filter elements 5. It can also
be seen that the frame-shaped filter elements 4 have inner walls
18 which are inclined with respect to the plane of the filter element.
At frame 4, on the inner wall associated with the upper edge, there
is provided a holding means comprising an open-weave cloth 38 which
covers the smaller opening of the frame. At the lower end of the
cloth 38 there is fastened a tilting strip 39 which extends over
the entire width of the lower inner wall 18. The tilting strip is
connected with the frame-shaped filter element only by means of
the cloth 38 and is connected with the cloth 38 only at its side
facing the smaller opening of the frame 4. If after completion of
the filtering process, the plate stack is pulled apart, the weight
of the adhering filter cake 21 tensions the cloth 38 so that the
tilting strip 39 can slide out downwardly through the broad gap
between the filter elements 4 and 5. The tilting strip 39 thus covers
particularly that region of the sealing surface 40 of the frame-shaped
filter element 4 where the risks of baking-on are especially high.
The tilting strip 39 is bent up at both its ends so that a closing
latch 41 is formed. The tip 42 of the closing latch 41 must be arranged
so that it lies higher than the edge 43 of the inner wall 28 of
the frame-shaped filter element so that when the filter elements
are brought together the plate 5 disposed in front of the tilting
strip will cause the tilting strip 39 to be pushed into the frame
opening as this is shown in the sectional view of FIG. 7.
FIG. 8 shows a top view of a lower corner of a frame-shaped filter
element 4 in which the tilting strip 39 and its closing latch 41
can be seen in the inserted state, that is, in the position according
to FIG. 7.
FIGS. 9 and 10 illustrate, in a separated and in a pushed-together
state, respectively, a further embodiment of the invention, comprising
with spacer elements which connect the filter elements together
in a chain-like manner. The spacer elements comprise links 11 with
short stroke and links 12 with long stroke connected alternatingly
end-to-end to form series at the top and at the bottom of the filter
element stack, at both sides thereof. On each filter element bolts
are mounted to which the links are articulated. Each link 11 is
provided with a circular opening through which the bolt 44 of the
filter element 5 passes and an elongated opening 45 through which
the bolt 44' of the adjacent filter element 4 passes. The link 12
has an approximately triangular shape and is likewise provided at
one end with a circular bore through which the bolt 44' of filter
element 4 passes and an elongated opening 46 whose length approximately
corresponds to the desired opening width between the filter element
4 and the next following filter element 5'. Through the opeing 46
passes on bolt 44" of the filter element 5'.
At the lower edge of the plate stack there is also provided a corresponding
row of spacer elements which, however, have a sequence which is
offset with respect to the upper row. Filter element 5, which has
a spacer element with short stroke at its upper end, that is a link
11, has a spacer element with long stroke, that is, a link 12, at
its lower end, while the connection between filter element 4 and
the next following filter element 5' at the lower end is effected
by a short-stroke link 11. This results in the desired oblique orientation
of the frame-shaped filter element 4 when in the open state, as
shown in FIG. 9.
FIGS. 9 and 10 also show an exemplary arrangement of the inlet
pipes for the slurry which are connected with the frame-shaped filter
elements 4 and which open, with the intermediary of a corresponding
channel, into the filter chamber 20 defined by the frame-shaped
filter element 4. The other ends of the inlet pipes are connected
to a slurry supply conduit. In other embodiments, the slurry is
introduced from the side, preferably in the upper region, through
lateral projections mounted on the plates 5 and frames 4. The projections
have bores which in the closed state of the plate stack form a closed
inlet channel.
FIGS. 9 and 10 show a filter element embodiment which in the closed
states prevents the frames from bending outwardly under the influence
of the pressure building up in the liquid in the filter chamber
20. For this purpose, the edge regions of the plate-shaped filter
elements 5 are provided with projections 47 which have associated
with them corresponding recesses 48 in the frame-shaped filter elements
4. The recesses 48 are so dimensioned that in the pushed-together
state, as shown in FIG. 10, the filter cloth 19 extending over the
recess can also be accommodated. As shown, the projections 47 may
be conical lugs distributed in a spaced arrangement along the periphery
of the respective filter 5, and the recesses 48 provided in the
filter elements 4 are accordingly cone-shaped. As an alternative,
the projections may be continuous or interrupted strip-shaped elements.
If the plate stack is pushed together, as shown in FIG. 10, the
frame-shaped filter element 4 is held in a form-locking manner against
forces parallel to the plane of the plate by the adjacent plate-shaped
filter element 5, thus avoiding bulging.
Since there is practically no change in the deflection of the filter
cloth 19 in the area of the lower guide rollers 23 in the open and
in the closed state, strippers or scrapers 49 may be disposed at
the lower frontal faces of the plate-shaped filter elements 4. The
strippes 49 are oriented in an oblique direction during opening
for removing residues of filter cake adhering to the filter cloth
as the latter is being pulled through.
FIGS. 11 and 12 show another embodiment of the spacer elements,
in the closed and open state, respectively. The spacer elements
are here formed of a continuous Fleyer (roller) chain which is connected
by pins 44 with the individual consecutive filter elements. In order
to realize the desired alternation of short stroke and long stroke,
the division of the chain is selected such that alternatingly three
or six chain links, respectively, are situated between successive
bolts 44. Here too, the sequence of short-stroke spacer elements
and long-stroke spacer elements is offset between the upper and
lower row of one side, as explained in connection with the embodiment
of FIGS. 9, 10.
The run-through of the filter cloth is effected in the same manner
as in the embodiment described in connection with FIGS. 9 and 10.
It is to be understood that, the invention is not limited to the
described embodiment of a frame filter press. Thus, the proposed
solution for the filter cloth drive and the blockwise opening and
closing of the plate stack can be used in the same manner for filter
presses in which the filter elements are so-called chamber filter
plates, that is, the filter plates are planar on one side but are
provided with cup or dish-like depressions on the other side which
then, in the closed state, together with the planar face of the
preceding filter plate, form the filter chamber. For this type of
press it is also advisable to arrange the spacer elements in such
a way that during opening, the plates are brought into an oblique
position. The difference is only in that all successive spacer elements
of one plate stack or one stack block, respectively, have the same
stroke, that merely the coupling of the first plate to the head
plate and of the last plate to the final delimiting plate or the
end plate, respectively, is effected in such a manner tha the oblique
orientation results when the filter elements are pulled apart. The
chamber plates may be conventional diaphragm chamber plates wherein
the dish-like depression on the one side of the filter plate forming
the filter chamber is lined by an elastic diaphragm. When the reverse
side of the diaphragm is pressurized the filter cake formed in the
filter chamber is compressed.
The smooth side of the filter plate may of course also be provided
with a diaphragm, which will be used with preference, if the starting
chamber depth (frame thickness) cannot be enlarged for technical
reasons.
The invention is furthermore not limited to the described, particularly
advantageous short-stroke opening system which is effected by the
block-wise opening and closing of a long filter plate stack. Instead
of the block-wise opening and closing, the closing device may be
mounted on a transverse yoke which is displaceable on longitudinal
carriers 3 together with the head plate 8 by means of its own drive
so that even longer presses can be operated with a short-stroke
closing device. In such an embodiment, after discontinuing the application
of the closing pressure, the entire plate stack is opened in an
accordion fashion by moving the transverse yoke and, after emptying,
performing the washing process and pulling through the filter cloth,
the plate stack is closed in the same manner by moving the transverse
yoke. After closing, the transverse yoke is immobilized on the longitudinal
carriers 3 by means of a separate locking device and then the closing
device is charged with the necessary closing pressure which is transmitted
to the longitudinal carriers by the locking device of the transverse
yoke. The structural length of such a filter press, however, is
greater than in the described embodiment with blockwise opening
and closing of the plate stack. The advantage of the last described
embodiment, however, is that here too, closing devices, particularly
hydraulic cylinders, with short stroke can be used.
In the embodiment of a filter press shown only schematically in
FIG. 13, the association of the individual filter elements 4, 5
with the movable end piece 8 is different than in the case of the
embodiment according to FIGS. 1, 2. Such an arrangement is advisable,
in particular, when the products to be filtered out tend to stick
together or to adhere to the frame-shaped filter element 4. Accordingly,
the plate stack is so designed that the plate-shaped filter element
5 which is connected directly with the end piece 8 by a short spacer
element 11 is followed by a frame-shaped filter element 4 whose
larger frame opening is oriented toward the head piece 10. It follows
that the sequence of the successive spacer elements with short and
long strokes is different than in the embodiment according to FIG.
1. Accordingly, in the upper row, the frame-shaped filter element
4 is connected, by long-stroke spacer element 12, with the plate-shaped
filter element 5 which is connected directly with the end piece
8. In the lower row, the same frame-shaped filter element 4 is connected
by a short-stroke spacer element 11. All subsequent filter elements
are then connected together alternatingly by long-stroke and short-stroke
spacer elements, as indicated schematically in FIG. 13. In this
embodiment, for example, the Fleyer (roller) chains shown in FIGS.
11 and 12 may serve as the spacer elements.
In the embodiment shown in FIG. 13, the guide rollers 22' which
are connected with the frame-shaped filter element 4 have a diameter
which is preferably substantially greater than the frame thickness.
The mounting of the guide rollers 22' is so situated with respect
to the center plane of the frame-shaped filter element 4 that the
excess of the roller diameter is essentially disposed on that side
of the frame-shaped filter element which has the smaller filter
surface.
The FIG. 13 embodiment of the filter press according to the invention
has the advantage that during the opening process the frame-shaped
filter elements 4 are lifted in succession off the filter cake and
thus its release from the frame occurs in parts and successively,
rather than simultaneously over the entire peripheral surface. The
guide roller 22' each time tensions in the opening direction the
filter cloth moving through the opening gap between each two filter
elements so that the filter cloth together with the filter cake
is lifted away from the contact surface. As indicated in FIG. 13,
in case of sticky products it can be assumed that the filter cake
will adhere substantially to that part of the filter cloth which
contacts the plate-shaped filter element so that during the subsequent
pulling through of the filter cloth while the plate stack or stack
block is open, the filter cake is stripped from the filter cloth
passing through in the direction of arrow 51 by means of scrapers
(not shown in detail) which are associated with the lower guide
rollers 23.
Since in the arrangement of FIG. 13 the weight of the adhering
filter cake stresses the piece of cloth which is pulled through
downwardly, that is, the weight of the filter cake is effective
in the transporting direction, care must be taken that inadvertent
movement of the filter cloth, due, for example, to insufficient
initial tension, is avoided. For this purpose the filter cloth is
guided at both sides of the plate stack or one stack block, as the
case may be, over respective brake rollers 52 or 53, respectively,
which are provided with a releasable braking means. The braking
means is coupled to the drive motor 31 in such a manner that the
brake is released when the drive motor is switched on. If a hydraulic
motor is used, the release can be effected hydraulically, that is,
at the moment at which the hydraulic motor is pressurized, the operating
pressure for the brake is released by a corresponding branch line.
Depending on the type of motor employed, a brake can be controlled
mechanically or electrically.
It will be understood that the above description of the present
invention is susceptible to various modifications, changes and adaptations,
and the same are intended to be comprehended within the meaning
and range of equivalents of the appended claims.
|