Drip tray lock mechanism for filter press

A filter press having an activating mechanism for holding the drip trays in a closed position before the stack of filter plates. The activating mechanism includes a fluid pressure cylinder which moves the drip trays between open and closed positions. The activating mechanism includes a linkage which moves into a locking position when the pressurized cylinder moves the trays into the closed position to automatically maintain the drip trays in the closed position even though pressure to the activating cylinder is relieved.

FIELD OF THE INVENTION 
This invention relates to a plate-type filter press having openable drip 
trays swingably positioned under the closed plate stack for collecting 
liquid leakage from the stack and, in particular, to an improved 
fluid-pressure activating mechanism to securely hold and effectively lock 
the drip trays in the closed position to prevent accidental opening 
thereof due to pressure loss in the activating pressure cylinder. 
BACKGROUND OF THE INVENTION 
During the filtration cycle of a plate-type filter press, wherein the 
individual plates are horizontally pressed together into a stack and are 
supplied with a slurry so as to effect separation of solids from the 
liquid, leakage of liquid from between the stack of plates is typically 
encountered. To control and gather the liquid which leaks from the stack, 
the filter press is normally provided with one and more typically two drip 
trays which are positionable in a generally horizontally closed 
orientation below the stack to collect the liquid thereon and feed it to 
an appropriate collection point. The drip trays are conventionally a pair 
of generally horizontally enlarged plate-like tray members which are 
individually supported adjacent opposite sides of the filter press and are 
positionable in a downwardly vertically suspended open position when 
opening of the stack and dumping of the solids is desired. These 
individual drip trays are then vertically swingable inwardly and upwardly 
in opposed relation to a closed position wherein they extend approximately 
horizontally and typically having edge portions which generally overlap to 
collect the liquid leakage thereon and supply the leakage to a collection 
trough which is generally formed along an edge of one drip tray. To effect 
the desired opening and closing of the drip trays, a mechanism employing a 
hydraulic pressure cylinder is typically supplied, and such mechanism 
generally requires that the hydraulic fluid be continuously supplied to 
the pressure cylinder to maintain it in a pressurized state when the drip 
trays are in the closed position. It has been observed, however, inasmuch 
as the filter press may remain in a closed position for a long period of 
time, that hydraulic pressure tends to leak down and hence the pressure in 
the cylinder holding the drip trays closed can likewise leak down. When 
this occurs, the weight of the trays acting through the connecting linkage 
back onto the cylinder causes retraction of the cylinder, and hence allows 
at least partial and undesired opening of the drip trays, whereby they 
hence are no longer disposed so as to provide the desired 
liquid-collecting function. 
It is thus an object of this invention to provide an improved activating 
mechanism for the drip trays of a plate-type filter press, which 
activating mechanism effectively causes a self-locking of the drip trays 
in the closed position, and thereby overcomes the disadvantage associated 
with prior presses as briefly described above. 
More specifically, in the filter press of the present invention 
incorporating therein an improved activating mechanism for the drip trays, 
the activating mechanism again includes a fluid pressure cylinder which 
moves the drip trays between open and closed positions. The activating 
mechanism, however, includes a linkage which effectively moves into a 
locking position when the pressurized cylinder moves the trays into the 
closed position, whereby this locking of the mechanism effectively 
automatically maintains the drip trays in the closed position even though 
the pressure to the activating cylinder is relieved. In the preferred 
embodiment, the activating mechanism involves an over-center mechanism and 
specifically a lever mechanism which moves past an over-center position 
just prior to the drip trays being pivotally moved into their closed 
position. Thereafter the pressure to the activating cylinder can be 
relieved, and the weight of the drip trays acting through the mechanism 
back on the over-center lever mechanism is such as to always urge the 
latter against a suitable stop, whereby the weight of the trays themselves 
hence automatically maintain the activating mechanism and the trays in the 
closed position, with the trays being movable back to the open position 
only when the activating cylinder is repressurized in a reverse direction. 
In addition to the advantages associated with the filter press and the 
improved activating mechanism described above, this improved activating 
mechanism is mechanically simple and reliable in operation, and 
inexpensive to construct, install and maintain. 
Other objects and purposes of the invention will be apparent to persons 
familiar with systems of this general type upon reading the following 
specification and inspecting the accompanying drawings.

Certain terminology will be used in the following description for 
convenience in reference only, and will not be limiting. For example, the 
words "upwardly", "downwardly", "rightwardly", and "leftwardly" will refer 
to directions in the drawings to which reference is made. The words 
"inwardly" and "outwardly" will refer to directions toward and away from, 
respectively, the geometric center of the press and designated parts 
thereof. Said terminology will include the words specifically mentioned, 
derivatives thereof, and words of similar import. 
DETAIL DESCRIPTION 
FIGS. 1 and 2 illustrate therein a somewhat conventional filter press 10 
having a pair of end supports 11 and 12 rigidly joined together by a pair 
of generally parallel and horizontally elongate rails 13, which rails and 
end supports hence define a generally rigid frame. The rails 13 are 
sidewardly spaced apart, and a plurality of conventional 
vertically-enlarged filter plates 14 are suspendingly supported 
therebetween. Each filter plate 14, in a generally conventional manner, 
has a pair of support arms 15 which project outwardly from opposite sides 
of the filter plate so as to slidably support the respective filter plate 
for horizontal longitudinal movement along the rails 13. 
The filter press 10 also has a movable follower or headplate arrangement 16 
which is disposed adjacent one end of the press frame and is supported for 
movement along the side rails 13. This follower or head 16 is displaceable 
horizontally along the rails by a conventional driving device 17, such as 
a conventional fluid pressure cylinder. The follower or head 16 and the 
opposed end support 11, which in effect defines a stationary pressure 
head, cooperate to confine the plurality of filter plates 14 therebetween, 
which plates are disposed in a generally horizontally stacked 
relationship. 
As is conventional, under normal operation, the driving device 17 is 
activated to move the head 16 rightwardly in FIG. 1 so that the stack of 
filter plates 14 are snugly and tightly held between the opposed heads 11 
and 16. These opposed heads have suitable conduits (not shown) connected 
therethrough for communication with the interior of the stack of filter 
plates. A slurry is supplied through one of the heads into the stack of 
filter plates, and the cleaned liquid flows outwardly through the head at 
the other end, whereupon the solids collect on the filters which extend 
across the frames defining the filter plates 14. 
To permit removal or dumping of the solids which collect on the filter 
plates, the movable head 16 is moved into the open position substantially 
as illustrated by FIG. 1, and the plates 14 are then individually moved 
leftwardly away from the stack toward the head 16 to permit solids to dump 
downwardly for deposit into a suitable collecting bin. To effect this 
sequential and individual opening movement of the filter plates 14, the 
filter press has a plate shifting mechanism 19 which typically moves 
longitudinally along opposite sides of the press, such as along the side 
rails 13, so as to engage and effect sequential shifting of individual 
plates 14 leftwardly along the rails into an open position. 
The filter press 10 also mounts a conventional drip tray arrangement 21 
thereon for disposition below the closed stack to collect liquid which 
leaks between the plates 14 of the stack. This drip tray arrangement 
includes a pair of enlarged drip trays 22 and 23 which are respectively 
disposed adjacent and extend longitudinally along opposite sides of the 
filter press. The drip trays 22 and 23 are supported on the frame of the 
press by suitable tray support means. In particular, the drip trays 22 and 
23 have suitable brackets on the underside thereof which are fixed 
respectively to horizontally elongate and generally parallel hinge or 
support shafts 24 and 25 so as to support the drip trays 22 and 23. These 
hinge shafts 24 and 25 extend horizontally and longitudinally along 
opposite sides of the filter press and are suitable rotatably supported, 
as by means of bearings 26 which mounts on the frame of the press. The 
drip trays 22 and 23 each define a generally horizontally enlarged 
plate-like liquid collecting member when in the closed position, with the 
one drip tray 22 projecting sidewardly inwardly beneath the stack by a 
distance which is roughly about or slightly greater than one-half the 
horizontal width of the stack so as to terminate in an inner free edge 27. 
The other drip tray 23 similarly projects horizontally sidewardly under 
the stack by a distance which is also about or slightly greater than 
one-half of the sideward width of the stack so as to terminate in a free 
edge 28. The drip trays have a suitable width such that the inner free 
edge portions partially horizontally overlap so as to not leave any 
horizontal gap therebetween. 
When in the closed position, the drip trays both extend dominally 
horizontally but have a slight sideward slope, with the drip tray 22 
having a slight downward slope as it projects inwardly toward the free 
edge 27, and the other drip tray 23 has a similar slight downward slope as 
it projects outwardly away from its free edge 28. In this manner, any 
liquid which falls onto the tray 22 then flows inwardly and off the edge 
27 onto the tray 23, and the liquids on the tray 23 then flow outward 
therealong and collect in a channel-like trough 29 which is formed 
adjacent the outer free edge of the drip tray 23. This trough 29 is 
disposed outwardly from the respective hinge shaft 25, and typically 
longitudinally slopes so as to permit the collected liquid to flow 
longitudinally therealong for disposal from one end as desired, such as to 
a suitable drain conduit (not shown). 
The press 10 includes an activating mechanism 31 which effects the desired 
movement of the drip trays 22-23 between the closed position illustrated 
by solid lines in FIGS. 1 and 2, and the open position indicated by dotted 
lines in FIGS. 1 and 2. In the open position the trays are individually 
suspended generally vertically downwardly and are angularly displaced 
approximately 90.degree. from the closed position. While FIGS. 1 and 2 
illustrate in solid lines the drip trays in the closed position, this is 
solely for convenience and illustration since it will be recognized that 
the trays will typically be open when the stack is being opened so as to 
dump the solids, as depicted by FIG. 1. 
The activating mechanism 31 includes a connecting or synchronizing linkage 
or mechanism which interconnects the hinge shafts 24 and 25 so as to 
always insure that the drip trays 22-23 are substantially simultaneously 
and synchronously moved in opposite rotational directions. This connecting 
linkage includes cranks or arms 32 and 33 which are non-rotatably fixed to 
and project radially from the respective hinge shafts 24 and 25, and these 
cranks 32 and 33 are in turn hingedly connected through an elongate 
connecting link 34 which extends transversely across the press. The cranks 
32 and 33 generally project radially from the respective hinge shaft on 
substantially diametrically opposite sides thereof. Hence, when one of the 
cranks 32-33 rotates in one direction, the connecting link 34 acting on 
the other crank 32-33 causes a corresponding and generally synchronous 
rotation of the other crank in an opposite rotational direction. 
The activating mechanism 31 for the drip tray arrangement also includes a 
pressure cylinder 35, typically a hydraulic cylinder, which has one end of 
the cylinder housing joined, typically hinged, to a stationary bracket 36 
fixed relative to the press frame. The pressure cylinder 35 has a 
conventional extendable and retractable rod 37 which projects outwardly 
from one end of the cylinder housing, and the rod 37 adjacent the free end 
thereof is hingedly interconnected to a crank or arm 38 which is secured 
to and projects radially from one of the hinge shafts, such as the hinge 
shaft 24 in an arrangement illustrated by FIGS. 1 and 2. 
With the prior art arrangement shown by FIGS. 1 and 2, the pressure 
cylinder 35 is pressurized to cause extension of the rod 37 and hence 
rotation of the crank 38 into the position shown in FIG. 2, and the 
connecting mechanism defined by the cranks 32-33 and connecting link 34 
thus cause the drip trays 22 and 23 to be swingedly moved in opposite 
rotational directions upwardly into the closed position illustrated by 
FIG. 2. In this closed position of the drip trays, however, the pressure 
cylinder 35 must be continuously pressurized to hold the drip trays in the 
closed position. If the extending pressure is removed from the cylinder 
35, such as due to leakage, then the weight of the drip trays tends to 
cause corresponding rotation of the respective hinge shafts 24 and 25 and 
this in turn causes a corresponding clockwise rotation of crank 38 which 
tends to contract the pressure cylinder 35, this being permissible due to 
the loss of extending pressure in the cylinder. This hence enables the 
individual drip trays 22 and 23 to swing downwardly away from their closed 
position and hence can result in loss of liquid collecting thereon since 
such liquid can then flow over the free edges 27 and 28 and be deposited 
directly onto the floor below the press. 
The overall filter press 10 and the structure and operation thereof as 
briefly summarized above is conventional. 
Referring now to FIGS. 3-6, there is illustrated an improved activating 
mechanism 31' so as to result in the drip trays 22-23 being effectively 
locked or stationarily held in their closed positions so as to prevent 
accidental release thereof due to pressure loss or release in the 
activating cylinder 35. Corresponding parts of the activating mechanism 
31' are identified by the same reference numerals utilized above for 
convenience in the following description. 
The activating mechanism 31' again includes the same connecting or 
synchronizing linkage or mechanism defined by the cranks 32-33 and the 
intermediate connecting link 34 so as to insure substantially simultaneous 
and synchronous rotation of the drip trays 22-23 in opposite rotational 
directions as these trays are moved between open and closed positions. To 
effect the opening and closing of the drip trays, the activating mechanism 
31 also includes the fluid pressure cylinder 35 (typically a hydraulic 
cylinder) whose cylinder housing is typically connected, as by a hinge, to 
a bracket 36. The pressure cylinder 35 also has the conventional 
extendable rod 37 associated with the other end of the cylinder, which rod 
37 in the present invention interconnects to a locking linkage 41 which in 
turn interconnects to one of the hinge shafts, this being the hinge shaft 
25 in the illustrated embodiment. 
The locking linkage or mechanism 41 is an over-center linkage that includes 
an intermediate lever or rocker 42 which is of a generally L or V shaped 
construction similar to a bell crank. The intermediate rocker 42 is 
provided with a pivot 43 at the apex thereof, which pivot 43 is supported 
on a suitable stationary bracket 44 and defines linkage support means for 
the locking mechanism 41. The pivot 43 defines a generally horizontal 
hinge axis which extends in the longitudinal direction of the press. The 
intermediate rocker 42 has a first arm 45 projecting outwardly from the 
pivot 43, which arm 45 adjacent its outer end has a horizontal pivot 46 
which connects to the free end of the pressure cylinder rod 37. The 
intermediate rocker 42 has a second arm 47 which projects radially 
outwardly from the pivot 43, and this arm 47 at its outer end has a 
horizontal pivot 48 which connects to one end of an elongate connecting 
link 49. This elongate connecting link 49 extends transversely of the 
press and at its other end is connected by a pivot 51 to an outer end of a 
drive member, and in particular, a crank or arm 52 which is fixed to and 
projects radially outwardly of the hinge shaft 25. The hinges or pivots 
43, 46, 48 and 51 are all substantially parallel to one another. 
As most clearly illustrated in FIGS. 5 and 6 which respectively illustrate 
the drip trays in the closed and open positions, the pressure cylinder 35 
is effectively contracted in the open position of FIG. 6 and the drip 
trays 22 and 23 are generally vertically downwardly suspended about the 
respective hinge shafts, and the weight of the drip trays and the force 
movements created thereby about the hinge shafts are transmitted to and 
through the crank 52 and the connecting link 49 so that the cylinder 35 is 
effectively contracted and the drip trays are thus maintained in the 
suspended position, this being a general neutral position wherein the 
movements throughout the linkage or mechanism are substantially balanced. 
However, when the drip trays are to be moved into the closed position 
illustrated by FIG. 5, the pressure cylinder 35 is energized to effect 
extension of the rod 37 which in turn causes a counterclockwise rotation 
of the rocker 42 about the hinge 43. This in turn causes the connecting 
link 49 to cause a clockwise driving rotation of the crank 52 from the 
FIG. 6 position to the FIG. 5 position, and this in turn causes a 
clockwise rotation of shaft 25 and of the drip tray 23 into the closed 
position. The intermediate connecting link 34 also is driven by crank 33 
and acts against crank 32 to cause a counterclockwise rotation of shaft 24 
so that the other drip tray 22 is simultaneously swung up into its closed 
position. As the activating mechanism 31 and the drip trays 22-23 swing 
upwardly and approach the closed position shown by FIG. 5, however, the 
counterclockwise rotation of the rocker 42 causes the pivot 48 to be 
vertically moved upwardly through and ultimately above a straight line 53 
which passes through the axes of the pivots 43 and 51 with the rocker arm 
47 ultimately abutting a fixed stop 54 which defines the closed position 
for the drip trays, in which position the pivot 48 is now disposed above 
the line 53. 
If the extending pressure to the cylinder 35 is relieved when the trays are 
in the closed position, then the force movement of the drip tray 22 tends 
to cause a clockwise movement about the hinge shaft 24 which is 
transmitted through connecting link 34 to tend to impose a 
counterclockwise movement on the hinge shaft 25. The weight of the drip 
tray 23 also tends to impose a counterclockwise movement on the hinge 
shaft 25. These counterclockwise movements imposed on hinge shaft 25 are 
transmitted through crank 52 to the connecting link 49 which, acting on 
pivot 48, in turn tends to cause a counterclockwise movement of the arm 47 
about the hinge 43 inasmuch as the pivot 48 is disposed above the line 53. 
Since arm 47, however, is abutted against the stop 54, the weight-induced 
movements of the drip trays 22 and 23 as transmitted through the hinge 
shafts and the connecting link 49 to the pivot 48 are effectively resisted 
by the stop 54, and thus the entire activating and tray arrangement is 
thus positively stationarily held (i.e. effectively locked) in the closed 
position, even though the extending pressure supplied to the cylinder 35 
is relieved. The drip tray arrangement is thus effectively locked in the 
closed position and will safely remain in this position for long periods 
of time. In fact, the drip tray arrangement can be positively swung away 
from the closed position back into the open position only by reversely 
energizing pressure cylinder 35 to cause initial contraction thereof 
sufficient to cause the pivot 48 to move downwardly onto the other side 
(i.e., below) the straight line 53, at which time the force movements 
created by the weight of the drip trays themselves will now assist in 
swingably moving the drip trays toward the open positions. 
With the improved activating mechanism as described above, the intermediate 
rocker 42 and specifically the pivot 48 which connects the rocker arm 47 
to the connecting link 49 effectively moves through an over-center 
position just prior to the drip trays 22-23 reaching their closed 
positions, whereby the drip trays hence are unable to move away from the 
closed position without requiring deliberate pressurization of the 
activating cylinder 35 so as to effect contraction of the cylinder and 
hence movement of the pivot 48 back through the over-center position. 
While the arrangement as described above illustrates the cylinder 35 as 
being extended during the closing movement and contracted during the 
opening movement, it will be appreciated that these could be reversed 
merely by repositioning the pressure cylinder relative to the intermediate 
rocker 42 so that the pressure cylinder would require contraction during 
the closing movement of the drip trays and extension during the opening 
movement thereof. 
In addition, while the fixed stop 54 is shown as cooperating directly with 
the rocker 42, it will be appreciated that the stop could be positioned 
for cooperation with some other part of the linkage. For example, the stop 
pin 54 could be positioned for cooperation with the other rocker arms 45, 
such as indicated by dotted lines at 54'. Alternately, the stop could be 
incorporated directly into the pressure cylinder to provide a defined 
maximum extension and/or contraction point. 
Although a particular preferred embodiment of the invention has been 
disclosed in detail for illustrative purposes, it will be recognized that 
variations or modifications of the disclosed apparatus, including the 
rearrangement of parts, lie within the scope of the present invention.