Filter method and apparatus

A method and apparatus are disclosed for mechanically locking a movable filter shell of a pressure filter in filtration position adjacent a second fixed filter shell, in order to accommodate and resist higher internal filtering pressures. In the method, a gasket between the two filter shells is compressed to an extent greater than necessary to achieve a liquid tight seal, in response to movement of the movable shell toward the fixed shell. Next, a locking member is freely inserted between the movable shell and an abutment with clearance being provided in order to facilitate the insertion of the locking member due to the movable shell excessively compressing the gasket. Upon initiation of the filtration cycle, the movable shell is slightly displaced away from the fixed shell in response to internal filtration pressures, with the locking member preventing further displacement in order to maintain the gasket in water-tight sealing compression. Upon termination of the filtration cycle, the movable shell is slightly displaced toward the fixed shell, to provide clearance for free withdrawal of the locking member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This disclosure relates generally to an automated liquid filter apparatus 
and method, and more particularly to a filter method and apparatus 
including a clamping and locking mechanism to maintain the shells of the 
filter in a liquid-tight closed position during a filtration cycle. 
2. The Prior Art 
Pressure filters of the plate and frame type have been used for many years 
in many different applications. Generally speaking, this type of filter 
may be described as a frame on which there are a number of indented loose 
plates with filtering surfaces, the plates being clamped together to form 
a series of hollow chambers and being capable of withstanding high 
internal pressures. The filtering surfaces are usually ribbed or grooved 
and covered with cloths of filtering material. 
The regular plate and frame filter press consists of a filter press frame 
made of two end supports rigidly held together by horizontal steel bars. 
Upon these horizontal bars are placed a varying number of flush plates and 
frames clamped together, thereby forming a hollow chamber. There could be 
many of these plates stacked against each other and mating at the edges 
which are machined to form a joint surface. 
This type of a filter is usually closed by a screw or hydraulic ram for 
pressing the plates and filter press frames together. Most of these types 
of plate and frame filters are normally opened and closed by hand but, in 
some larger size units, automatic devices are often used. The filter 
itself, however, in its entirety cannot be considered an automated piece 
of equipment because constant manual attention is required to perform 
various functions. 
The filter press has found wider application than any other type of filter. 
It is structurally simple without complicated auxiliaries making for low 
initial cost and low installation cost. Additionally, it can be operated 
by unskilled labor and considerable pressures can be applied to large 
filter areas in a compact space. The greatest disadvantage of the filter 
press is its intermittent operation and the labor involved therein. Since 
the size of the plate and frames are generally within some reasonable 
size, such as 10 to 20 square feet per unit, and the thickness of the cake 
formation is generally up to about 2 inches, it is quite evident that if a 
heavy slurry were pumped to this type of a filter frequent cycling would 
occur. Since there are many chambers that the cake is in and since these 
chambers all have to be separated, the time consumed to do this is 
laborious and expensive. Therefore, this type of a filter is restricted on 
the total solids that it can handle in a given period of time. Many times 
it is required that the solids be discharged from the filter as a dry 
cake. With this type of a filter, then, it is necessary to drain the 
frames completely before they can be opened. If this is not done, the cake 
will discharge as a wet slurry. There are also many conditions where the 
cake is somewhat compressible or where weak structured solids are present, 
such that filling the frame becomes very difficult. Therefore, it becomes 
apparent that even though this type of filter has universal application, 
it also has some severe restrictions. 
In order to overcome these difficulties inherent in the basic plate and 
frame filter, a simplified single plate type of filter was shown in U.S. 
Pat. Nos. 2,867,324, 2,867,325 and 2,867,326. These patents, all by the 
applicant, describe a simplified single plate filter that is completely 
automated. These filters proved to be of great value in the filtration art 
in that they could be placed in areas where no manual attention was 
required and the filters could go through the process of filtration and 
dry sludge removal without any manual attention. 
These filters were primarily used on applications where a large volume of 
liquid was being pumped to the filter at a relatively moderate suspended 
solids concentration. Usually the total solids of the influent to the 
filter were less than 0.1%. However, with the large flow rates, in the 
neighborhood of 30 to 50 GPM/ft..sup.2, it is apparent that these filters 
could filter and discharge a considerable amount of solids. 
One inherent characteristic of this type of filter was its limitation on 
operating pressures. The filter, being substantially a box that is divided 
in half, had to have a greater external force to keep the box closed than 
the internal forces that were generated by the hydraulic pressures. For 
instance, with 10 psi internal pressure, each square foot of the filter 
had to have an external counter force of at least 1,440 pounds to maintain 
the forces in equilibrium. Therefore, a filter with 10 square feet of 
filter area had to have external cylinders or external forces greater than 
15,000 pounds to overcome an internal force of 10 psi. Since most of these 
filters were used on fairly porous suspended solids that were generated 
from machining operations, the pressure range in which this equipment 
operated was quite satisfactory. 
It was found that this type of filter was extremely good for dewatering 
various types of sludges. Most of the dewatering jobs had higher 
concentrations and finer suspended solids than were ever applied to this 
kind of filter. A typical slurry could very well be in a 5 to 10% 
concentration with most of the suspended solids being finer than 300 mesh. 
The flow rate through these filters was reduced to a considerable extent 
because of the nature of the suspended solids that were being filtered. 
Many types of slurries actually could not be filtered effectively with 
this type of filter because, in order to get acceptable flow rates, higher 
pressures were required than could be applied to this particular type of 
filter. Generally, the limitation on this simplified plate and frame 
filter was about 10 to 12 pounds internal hydraulic pressure. Since, on 
certain applications greater pressure was required, the applicant 
developed the invention embodied in U.S. Pat. No. 3,333,693 directed to a 
modified, single plate, pressure filter that had the main body of the 
filter fixed and a seal that was the only closure and movable part of the 
filter. In this type of apparatus, larger filter areas could be utilized 
and operating pressures could be increased to approximately 20 psi. This 
movable seal filter, although a substantial improvement over the movable 
shell filter, still was not capable of high enough filtration pressures to 
tackle most of the different dewatering jobs. 
A typical dewatering job could be defined as the filtration of coal 
tailings in a coal mining and processing operation where the suspended 
solids could be from 1 to 40% with the solids being finer than 300 mesh. 
These types of operations usually have some extreme fines present that 
also tend to lock up and close the porosity of the filter cake and reduce 
the flow rate considerably. On these types of sludges and many other 
similar ones, higher pressures in the neighborhood of 50 to 100 psi can 
improve flow rate and filter through-put considerably. Since the 
quantities of sludge also are many tons per hour, it becomes imperative 
that this type of a filter be capable of filtering and discharging these 
large quantities automatically and with the maximum through-put both in 
liquid and in solids. 
Thus, the prior art has not provided a practical filtration method or 
structure to accommodate relatively high hydraulic pressures during a 
filtration cycle. 
SUMMARY OF THE INVENTION 
These prior art problems and disadvantages are overcome by the present 
invention, which embodies the concept of mechanically locking together two 
filter shells so that internal pressures of up to at least the range of 
about 100 psi to 250 psi can be easily accommodated and so that the filter 
can discharge the sludge that it has accreted on the filter belt 
automatically in a fast, efficient manner. 
This is accomplished in one aspect of the invention by a pressure filter 
which includes a filter medium interposed between aligned shell members 
defining an inlet chamber for receiving contaminated liquid under pressure 
and a discharge chamber receiving clarified liquid flowing through the 
filter medium. The shells include opposed peripheral sealing surfaces, 
with at least one of the sealing surfaces being defined by a compressible 
gasket. One of the shells is movable and is displaced by an appropriate 
power means, such as a pneumatic cylinder and piston arrangement. 
Mechanical means are included for locking the displaceable shell in a 
filtration position adjacent the other shell after the displacement means 
has displaced the movable shell toward the other shell and caused the 
gasket to be compressed to establish an essentially water-tight seal 
around the periphery of the two shells. The mechanical locking means 
includes a pair of spaced abutment surfaces, wherein one of the surfaces 
is placed in engagement with the movable shell during the filtration cycle 
and the other of the surfaces is simultaneously placed in engagement with 
a spaced, fixed locking surface, thereby resisting the internal filtration 
pressure which exerts an opening force on the movable shell. 
In one of the preferred embodiments, the mechanical locking means includes 
a pivotally mounted, elongated locking strut which is mounted on the 
movable shell. A fluid pressure piston and cylinder arrangement is also 
mounted on the movable shell for pivoting the locking strut into position 
between the movable shell and the spaced locking surface, which in this 
embodiment is positioned in a direction away from the other shell. 
In a second preferred embodiment, the mechanical locking means includes a 
blocking beam carried by the movable shell. A fluid pressure piston and 
cylinder arrangement displaces the beam in a direction essentially 
perpendicular to the direction of movement of the movable shell for 
selective alignment with the spaced locking surface, which in this 
embodiment is likewise positioned in a direction away from the other 
shell. 
In the method, a first movable shell is moved from a first position spaced 
from a second, fixed shell to a second position adjacent the other shell 
for filtration. During the final phases of this displacement, a gasket 
which is interposed between opposed, aligned peripheral sealing surfaces 
on each of the shells is compressed to establish an essentially 
water-tight seal between the filter shells. Next, a force bearing member 
is positioned in alignment with the movable shell and an abutment surface 
to lock the movable shell in the filtration position. The filtration 
process itself is initiated by introducing contaminated liquid under 
pressure into an influent chamber defined by one of the shells, then 
flowing the liquid through the filter medium to accumulate contaminants, 
and then receiving clarified liquid from the filter medium in an effluent 
chamber defined by the other of the shells. During the initial phases of 
flowing liquid into the filter assembly, the movable shell is slightly 
displaced away from the other shell in response to the internal pressure 
of the contaminated liquid. The displacement of the movable shell during 
this phase of the operation is limited by the force bearing member to 
maintain the movable shell in a filtration position adjacent the other 
shell and to maintain the gasket in compression for an essentially 
water-tight seal between the separable shells. 
After the filter medium has accumulated a significant quantity of 
contaminants, liquid flow through the filter shells is terminated, thereby 
relieving the internal pressures in the filter shell assembly. Upon the 
pressure relief, the movable shell is slightly displaced toward the other 
shell against the resistive force of the compressible gasket, to provide 
clearance to accommodate displacement of the force bearing member to a 
second position to unlock the movable shell. Finally, the movable shell is 
displaced away from the other shell to accommodate the discharge of the 
accumulated contaminants. 
In the most preferred method, the movable shell is displaced by a pneumatic 
piston and cylinder arrangement and pressure is applied to the movable 
shell by this cylinder throughout the filtration cycle. 
In one preferred method aspect, the force bearing member is comprised of a 
pivotally mounted locking strut carried by the movable shell, and the step 
of positioning the force bearing member in the locking position is 
characterized by pivoting the strut into a position essentially parallel 
to the direction of movement of the movable shell. 
In another preferred method embodiment, the force bearing member is 
comprised of a slidable beam carried by the movable shell, and the step of 
positioning the force bearing member in the locking position is 
characterized by moving the beam in a direction essentially perpendicular 
to the direction of movement of the movable shell. 
Accordingly, the present invention provides several advantages not provided 
by the prior art. For example, the present invention accommodates higher 
filtration pressures, thereby enabling the utilization of flat-bed type 
filtration equipment in many more specialized applications. Additionally, 
the present invention provides the ability to make filters much larger 
than was heretofore permissible, thereby enabling the accommodation of 
drastically increased influent quantities. Further, large expensive, 
maintenance-requiring clamping equipment, such as large hydraulic presses, 
are eliminated. Another advantage is related to the excessive compression 
of the gasket, which provides clearance for free insertion of the locking 
devices into position for maintaining the movable filter shell in position 
during the filtration cycle. 
These and other advantages and meritorous features of the invention will be 
more fully appreciated from the following detailed description and the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention relates primarily to an improved mechanism for 
locking the separable shells of a filter assembly together in order to 
accommodate higher filtration pressures. A first embodiment of this 
invention is illustrated particularly in FIGS. 1-3; and a second 
embodiment of the invention is primarily illustrated in FIGS. 7 and 8. 
FIGS. 4-6 relate to both embodiments and illustrate the manner of 
compressing a gasket between the shells in order to provide clearance 
between locking abutment surfaces. 
The Embodiment of FIGS. 1-3 
Referring more particularly to the drawings, FIGS. 1-3 illustrate a fixed 
filter shell 10 as supported by a base member 12. A movable filter shell 
20 is vertically aligned with the lower shell 10 and is vertically 
displaced by a piston and cylinder arrangement, including a piston 42 
interconnected with the filter shell and a cylinder 41, which is mounted 
to a support structure. The general configuration and arrangement of the 
upper and lower shells is essentially the same as that shown in 
applicant's U.S. Pat. No. 3,497,063, incorporated by reference. 
A load carrying structure 50 generally surrounds the upper and lower shells 
10 and 20, with the various beam components of the structure being rigidly 
mounted together, for example by welding. More particularly, the structure 
includes four corner legs 52 and two primary horizontal cross beams 54 
extending between respective pairs of corner legs 52. A plurality of 
secondary horizontal beams 56 are mounted to the underneath side of each 
of the primary horizontal beams 54 and provide fixed abutment surfaces for 
the locking structure, as will be more fully described below. 
Additionally, the structure 50 includes secondary vertical legs 58 which 
extend from the support 12 to the secondary horizontal beams 56 for 
rigidifying purposes. 
A filter shell locking structure is represented generally by reference 
numeral 60 and includes elongated locking struts 62 which are pivotally 
mounted on shafts 64. Mounting brackets 66 are appropriately secured to 
the top of the movable shell 20 and rotationally support the shafts 64 so 
that the locking struts 62 may be pivoted about the axis of the shafts. 
Hydraulic piston and cylinder actuating means 68 are interconnected with 
the locking struts 62 to effect the pivoting movement, with the cylinders 
68 being mounted to the top of the movable filter shell 20 by mounting 
brackets 69. 
As shown in FIG. 1, a roll of disposable filter medium is supported on a 
shaft 72 which is mounted on a pair of the corner legs 52 by a pair of 
brackets 74. This arrangement permits the filter medium 70 to be 
periodically indexed into the filter assembly between the filter shells 10 
and 20 in a conventional manner to replace medium which has accumulated 
contaminants. Alternatively, a reusable filter medium may be used, in 
which case the medium is mounted on a chain conveyor system mounted 
externally of the two filter shells. In either of these two embodiments, 
the medium will be supported by a grate 76 (shown in FIGS. 4-6) which is 
mounted on a flange 12 on the fixed shell 10. 
A sealing gasket assembly 80 is provided around the aligned peripheries of 
the filter shells, as shown in FIGS. 4-6. This assembly is essentially 
conventional, and includes a fixed upper retainer plate 81 mounted on 
flange 21 of the upper shell 20. A removable upper retainer plate 82 is 
secured to plate 81 by a bolt 83, thereby securing an upper gasket 84 to 
the periphery of the upper shell 20. 
On the lower shell 10, the sealing gasket assembly includes a fixed 
L-shaped retainer bracket 85 secured to the shell 10, a vertical retainer 
plate 86 secured to a flange 11 on the shell 10, and an L-shaped bracket 
member 87 removably secured to plate 86 by a bolt 88. As shown, a lower 
gasket 89 is retained in position between bracket members 85 and 87 around 
the entire periphery of the lower fixed shell 10. 
Both gaskets 84 and 89 may be comprised of a suitable resilient, 
compressible gasket material for the purposes of this invention, namely to 
establish a water-tight seal around the periphery of the shells and to 
accommodate displacement of the upper shell 20 relative to the lower shell 
10 to provide a clearance for the locking struts 62, as will be more fully 
explained below. 
In operation, the upper shell 20 will be raised to the position shown in 
FIGS. 1,2, and 4 in order to accommodate the discharge of contaminants 
which have been accumulated upon filter medium 70. After properly 
positioning the filter medium for a filtration cycle, cylinder arrangement 
40 is actuated by pumping fluid under pressure into cylinder 41 to extend 
piston rod 42. The downward extension of piston rod 42 displaces movable 
filter shell 20 downwardly toward the fixed filter shell 10 so that the 
gaskets 84 and 89 are compressed to establish a water-tight seal around 
the periphery of the filter assembly. In accordance with the present 
invention, the gaskets 84 and 89 are compressed to a condition as shown in 
FIG. 5, this compression being greater than that necessary to establish a 
water-tight seal. This excessive compression establishes a clearance so 
that the locking struts 62 may be freely pivoted into the position shown 
in FIG. 3 to serve as a force bearing member in abutment with both the 
upper shell 20 and the horizontal cross beams 56. For example, the gaskets 
84 and 89 may be collectively compressed by approximately 3/8 of an inch 
in FIG. 5, during which time the locking struts are pivoted into the 
position shown in FIG. 3. Thus, locking struts 62 should be dimensioned to 
have a length slightly less than the distance between the top of movable 
shell 20 and the bottom of cross beams 56 when the gaskets are compressed 
to the extent of FIG. 5. 
Next, the movable upper shell 20 is slightly displaced upwardly to place 
the locking struts 62 in abutment with both the cross beams 56 and the 
upper shell 20. This displacement may be on the order of about 3/16 of an 
inch and may be accomplished primarily in one of two ways. First, pressure 
may be continuously applied by piston rod 42 to the shell 20 during a 
filtration cycle. In this event, upper shell 20 will remain in the 
position shown in FIG. 5 until contaminated liquid flows under pressure 
into a receiver or influent chamber defined by the shell 20. In response 
to the internal hydraulic pressure created by the contaminated liquid, the 
shell 20 is forced upwardly slightly to the position shown in FIG. 6, with 
the gaskets 84 and 89 still being sufficiently compressed to maintain an 
essentially water-tight seal around the periphery of the filter assembly. 
Alternatively, pressure from cylinder 41 may be relieved after locking 
strut 62 is pivoted into position, resulting in a slight displacement of 
the movable shell 20 away from the fixed shell 10 in response to the 
resilient forces from the compressed gaskets 84 and 89. In this second 
alternative mode of operation, the upper shell 20 will also be slightly 
displaced upwardly upon the initiation of the filtration cycle by flowing 
contaminated liquid under pressure into shell 20, thereby placing the 
locking struts in compression to lock the movable shell in filtration 
position. Again, even though the compression of the seals is slightly 
relaxed, a water-tight seal is maintained. 
Accordingly, it will be appreciated that the relative dimensions may be 
expressed as follows: The distance between the upper surface of shell 20 
and the lower abutment surface of beams 56 may be represented as a 
dimension "d" when shell 20 is in the position of FIG. 5. The elongated 
length of strut 62 may be represented as a dimension "d-x", where x is 
approximately equal to about 3/16 of an inch. Likewise, the distance 
between the top surface of upper shell 20 and the lower abutment surface 
of beams 56 in the position of FIG. 6 may also be represented by the 
dimension "d-x". 
As will be appreciated, the contaminated liquid under pressure flows from 
the receiver chamber of the movable shell 20, through the filter medium 
70, through the grate 76 and into an effluent or discharge chamber defined 
by the lower, fixed shell 10. After a period of time, the filter medium 70 
becomes clogged by an accretion of contaminants, requiring a discharge of 
the contaminants for further filtration. At this point of the process, the 
flow of contaminated liquid into the influent chamber is discontinued, 
resulting in a return of the internal pressure of shell 20 to atmospheric. 
If pressure has been applied continuously by clinder 40, the upper, 
movable shell 20 will be displaced downwardly to the position shown in 
FIG. 5 in response to the termination of contaminated liquid flow, thereby 
providing the desired clearance for pivoting the locking struts from the 
position of FIG. 3 to that of FIG. 2. In the alternative event that 
pressure has not been continuously applied by piston 42 during the 
filtration cycle, the movable shell 20 will remain essentially in the 
position shown in FIG. 6 after the termination of contaminated liquid 
flow. 
Thereafter, piston rod 42 may be extended slightly in response to the 
introduction of fluid under pressure into cylinder 41 thereby slightly 
displacing movable shell 20 downwardly to compress the gaskets to the 
condition as shown in FIG. 5 in order to provide clearance for freely 
pivoting the locking struts 62 to the position of FIG. 2. After the struts 
26 are pivoted, piston rod 42 is retracted to raise shell 20 so that 
accumulated contaminants may be discharged. 
The Embodiment of FIGS. 7 and 8 
Referring now more particularly to FIGS. 7 and 8, a second embodiment of 
the invention is disclosed wherein components which are identical to the 
components shown in FIGS. 1-3 are represented by reference numerals 
greater by a factor of 100 than those shown in FIGS. 1-3. For example, 
this embodiment includes a fixed, bottom filter shell 110 supported upon a 
base 112. An upper shell 120 is vertically aligned with the bottom shell 
110 and movable by a hydraulic cylinder 141 and piston 142. As will become 
apparent, the sealing gasket assembly and its mode of compression may be 
identical to that shown in FIGS. 4-6. Additionally, a pair of horizontal 
beam 156 are secured to beams 154 of the support structure, in order to 
provide abutment surfaces for the locking structure. 
The only difference between this embodiment and that of FIGS. 1-3 resides 
in the particular locking structure, which is represented generally by 
reference numeral 200. More particularly, the locking structure includes a 
pair of horizontally displacable beam 210 carried on the top surface of 
the movable shell 120. These beams 210 are displacable by locking 
cylinders 212 and associated piston rods 214, the locking cylinders being 
secured to the top of the movable shell 120. 
In operation, the upper filter shell 120 is raised by piston rod 142 to the 
position shown in FIG. 7 to accommodate the discharge of contaminants 
which have been accumulated on a filter medium between the filter shells. 
After the discharge of contaminants, piston 142 is displaced downwardly in 
response to fluid being pumped into cylinder 141, causing the upper shell 
120 to be displaced downwardly to the position shown in FIGS. 8 and 5. In 
this position, the gasket members are excessively compressed to provide a 
clearance so that the locking beams 210 may be freely displaced from a 
position relative to the upper shell 120 which is shown in FIG. 7, to a 
position in alignment with the abutment beams 156. As in the prior 
embodiment, the vertical elongated dimension of the locking beams 210 
should be slightly less than the distance between the bottom surfaces of 
beams 156 and the top surface of shell 120 when the shell 120 is displaced 
to the position of FIG. 5, thus providing clearance for the free insertion 
of the beams 210 into their locking positions. 
After the beams 210 have been positioned as shown in FIG. 8, pressure may 
be either relieved or continuously applied by piston rod 142, as more 
fully explained previously in connection with the discussion relating to 
FIGS. 4-6. In short, the upper shell 120 is slightly displaced upwardly 
during the filtration cycle to the position as shown in FIG. 6, placing 
the beams 210 in compression to lock the shell 120 in a filtration 
position to maintain a liquid-tight seal around the filter shells. After 
the termination of filtration flow, shell 120 is displaced slightly toward 
the fixed shell 110 to the position of FIG. 5, in order to provide a 
clearance between the lower abutment suraces of beams 156 and the upper 
surface of filter shell 120 in order to facilitate the removal of the 
beams 210 from their position shown in FIG. 8 to their position shown in 
FIG. 7. Thereafter, piston rod 142 is retracted to raise filter shell 120 
to the position of FIG. 7 to accommodate the removal of accumulated 
contaminants. 
As in the embodiment of FIGS. 1-3, the vertical dimension of beams 210 may 
be represented by the dimension "d-x", where "d" is the dimension between 
the upper surface of shell 120 and the lower abutment surface of beams 156 
in the position of FIG. 5. 
It will be understood that the foregoing description is merely exemplary of 
the overall invention, which is limited only by the appended claims.