Abstract:
A filter apparatus includes a endless filter belt loop disposed in an interior space within a tank which receives liquid to be filtered. The filter belt has a series of closely spaced parallel guide-flight bars attached which are successively engaged by an extendible element on a pivot plate which is periodically oscillated to under the filter belt. The bars are received in guide spaces to hold the filter belt in position over a filter support having openings allowing filtering flow therethrough. Collapsible sealed hoses partially filled with liquid are used as edge seals extending along the guide spaces over side edges of the filter belt and are expanded by engagement of an upper end of each of the hoses with a squeeze member on the pivot plate. The squeeze members are moved off the hoses when the pivot plate is oscillated to advance the filter belt during indexing to release the sealing pressure and allow filter belt indexing movement. The pivot plate oscillation also operates a beater bar to guide the belt to dislodge solids from the belt. In a vacuum version, the filter belt support is provided by molded plastic support pieces assembled over a solid curving support plate in the tank.

Description:
BACKGROUND OF THE INVENTION 
     This invention concerns filters and more particularly liquid filters of a type including a filter media disposed in a tank into which liquid to be filtered is collected. The filter media often takes the form of a strip of paper or woven fabric material. 
     The filter media is disposed over a support having perforations or other openings allowing liquid to flow through the support after passing through the filter media to be filtered. The filtered liquid is collected in a space below the support. 
     A typical use is in filtering machining coolant/lubricant to remove chips and fine particles. 
     The chips or other solid debris accumulate atop the filter media and must be periodically removed from the tank. 
     In conventional filter apparatus of this type, a filter media belt is arranged to be periodically advanced incrementally to bring a section of the filter media to a location at one end of the tank where the chips and accumulated solids are discharged. 
     The filter media has taken two different forms, i.e. a woven fabric belt formed into an endless loop providing a “permanent” media and a disposable media comprised of a paper strip which fed in at one end of the tank and discharged for disposal at the other end. 
     The permanent media passes around a roller at each end of the tank so as to be recirculated through the tank with repeated indexing. 
     Periodic indexing of the filter belt allows the solids such as chips filtered out of the liquid to be progressively carried out of the tank by a series of incremental movements, and successive sections of the belt moved back into position for continued filtering. 
     The filter media also typically becomes clogged with fine solids after continued operation requiring cleaning of each section, as by being washed with clean liquid. 
     Disposable media is simply collected and discarded with the chips and other solids. This type of filter using a disposable media is described in U.S. Pat. No. 4,481,108 granted to the present inventor. 
     Disposable media filters may be more expensive to operate and entail a greater maintenance burden due to the need to stock and replace rolls of media and to collect and dispose of the used media. 
     For this reason, a filter apparatus using only permanent media belt filter may be lower in cost to operate and therefore may be preferable to some users, at least for some applications. 
     Filter apparatus using this type of filter media is shown in U.S. Pat. Nos. 6,066,255 and 4,390,428. 
     In some filter apparatus, both disposable and permanent media are used. 
     Both types of filter apparatus are sometimes provided with sealing to prevent dirty liquid from passing around the side edges of the filter belt or strip to allow dirty liquid to bypass the filtering action. 
     One type of seal comprises lengths of inflatable tubing extending along and over the side edge of the media which is inflated to press the media edges against a guide surface to seal the same, as described in the &#39;108 patent referenced above. An inflatable filter belt seal is also shown in U.S. Pat. Nos. 4,390,428 and 5,601,729. 
     This type of edge sealing is effective but the tubing needs to be deflated during indexing to allow movement of the filter belt when a fresh belt segment is moved over the perforate support. This necessitates the use of control valves and a source of air pressure adding to the complexity and cost of the apparatus. 
     Depending on the size of the filter and the type of solids being filtered out, a conveyor may be required in addition to the filter media as in order to move a large volume of chips out of the tank. Typically, the conveyor comprises a series of vertical flight plates connected together with chain loops at either of the ends of the flight bars. The flight plates are arranged on edge and extending across the filter media and in engagement therewith to hold down and drive the bars media. The flights are primarily intended to act as a conveyor to carry large volumes of chips out of the tank. 
     The flights being made of metal are heavy, and their weight is used to hold the permanent media belt against the perforated support plate, as there may be a tendency for the belt to float up and allow dirty liquid to flow around the edges of the belt. 
     The flight conveyor chains and plates add substantially to the cost of the apparatus, as they must also be mounted, driven and controlled in similar fashion to the permanent media belt. 
     In other filter apparatus, such as shown in U.S. Pat. No. 6,066,255, drive chains are attached to the filter media belt to directly drive the same. This arrangement also is complicated and costly and sometimes causes bunching and wadding of the media belt, etc. as the belt may stretch or shrink relative the chain loops. 
     It is the object of the present invention to provide a low cost and simple filter apparatus of the permanent media belt type described. 
     It is another object to provide a filter media belt which simplifies the indexing drive and eliminates the need for a separate chip conveyor. 
     SUMMARY OF THE INVENTION 
     The above objects and other objects which will become apparent upon a reading of the following specification and claims is achieved by providing a permanent filter media belt loop mounted for incremental indexing movement through a tank. 
     The filter belt is driven to produce periodic indexing movement by a simplified indexing drive successively engaging each of a series of light weight drive-flight bars mounted to the belt as by being held in pockets spaced along the filter belt, which also act as conveyor flights to produce a combination permanent media belt and conveyor capable of carrying solids such as machining chips out of the tank. The relatively closely spaced drive-flight bars have opposite ends protruding out of the associated pocket which are confined by guide surfaces fixed on each side of the filter belt to insure that belt remains positioned against the filter belt support through the curved portions of the support surface even when being indexed. 
     The indexing drive mechanism includes an engagement element such as a stepped shape engagement block on each side of the media belt which are extendible with an associated actuator to engage a respective end of each drive-flight bar. The blocks have a stepped shape to mate with each bar end when the associated actuators extend a plunger on which each block is mounted. 
     The assembly of each block and associated actuator are each mounted on a respective pivot plate pivotable about an axis centered on a filter media return idler drum, attached to a concentric shaft passing through the center of the idler drum. 
     A reversible rotary actuator is connected to the shaft so that when both engagement blocks are engaged, pivoting of the pivot plates causes indexing the filter belt. Upon retraction and disengagement of the blocks and reverse rotation of the rotary actuator back to a start position, the blocks are in position to begin the next indexing cycle over the succeeding drive flight bar. 
     The drive-flight bars are sufficiently high, approximately three quarters of an inch to an inch or more in height and preferably approximately square in section, to also act as conveyor flights to capture solid debris as the belt ascends a tank incline out of the liquid in the tank, so that the filter belt acts as a conveyor as the belt is repeatedly and incrementally advance by the periodic indexing to progressively carry chips and other solids out of the liquid to an elevated end of the tank, where they are discharged. 
     A simplified filter belt edge sealing arrangement is also provided, comprised of a pair of sealed flat tenable tubes or hoses mounted in a confined space extending along and over each filter belt edge. A smaller diameter tube is disposed within each flattenable hose to partially distend each flat hose to minimize the extent of compression is necessary to inflate the hose. A squeeze plate is attached to each pivot plate to be rotated against a respective hose when moved to the start position, compressing the same to expand the hoses and generate sealing pressure on the filter belt edges. 
     This eliminates the control valve formerly needed to pressurize and depressurize the seal by independent means. 
     The pivot plates may also be used to retract a spring mounted beater bar which then springs back and strikes the filter belt to dislodge solids therefrom. This occurs several times in each indexing cycle, and likewise does not require any additional controls. 
     According to another aspect of the present invention, the vacuum box support for the filter belt within the tank can advantageously be provided by interfit elastomeric mats or pieces, each having flow openings therein which are installed on a continuously curving tank partition wall so as to form a filter belt support surface extending through the tank to eliminate a tighter single bend needed to ascend out of the tank and to shorten the overall length of the tank. 
     The drive-flight bars have ends contained within guide surfaces which together with the relatively close spacing of the bars act to hold the filter belt in position against the support surface so that light weight plastic bars can be used to eliminate the chains and metal flights formerly used. Mechanically connected chains driving the filter belt are also not required. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial view of a filter apparatus according to the present invention. 
         FIG. 2  is a front elevational view of the filter apparatus shown in  FIG. 1  with the front tank wall removed to show the interior components. 
         FIG. 3  is a plan view of the apparatus shown in  FIGS. 1 and 2 . 
         FIG. 4  is a view of the transverse section  4 - 4  taken in  FIG. 2 . 
         FIG. 5  is an enlarged view of the detail shown in circle  5  in  FIG. 4 . 
         FIG. 6  is an enlarged view of the detail shown in circle  6  in  FIG. 4 . 
         FIG. 7  is an enlarged view of the detail shown in circle  7  in  FIG. 2 . 
         FIG. 8  is an enlarged view of the detail shown in the circle  8  in  FIG. 2 . 
         FIG. 9  is a further enlarged portion of a transverse section through the filter apparatus showing the flow paths of the filtered liquid. 
         FIG. 10  is a fragmentary enlarged view of a part of the tank and vacuum box components of the filter apparatus shown in  FIG. 1 . 
         FIG. 11  is an enlarged end view of the belt washer components. 
         FIG. 12  is an elevational of one of the pivot plate assemblies included in the filter apparatus shown in  FIG. 1 . 
         FIG. 13  is a pictorial view of the pivot plate assembly shown in  FIG. 12 . 
         FIG. 14  is a plan view of a fragmentary segment of a filter belt assembly included in the filter apparatus shown in  FIG. 1 . 
         FIG. 15  is an edge view of the filter belt assembly segment shown in  FIG. 14 . 
         FIG. 16  is an end view of an alternate form of a belt beater assembly included in the filter apparatus shown in  FIG. 1 . 
         FIG. 17  is an elevational view of the beater assembly shown in  FIG. 16 . 
         FIG. 18  is a pictorial view of a gravity type filter apparatus according to another embodiment of the invention with one side wall of the tank removed to show the components inside the tank. 
         FIG. 19  is an elevational view with the front wall removed of the apparatus shown in  FIG. 18 . 
         FIG. 20  is a view of the section  20 - 20  in  FIG. 18 . 
         FIG. 21  is an enlarged view of the components enclosed in the circle  21  in  FIG. 20 . 
         FIG. 22  is an enlarged view of the components in the circle  22  in  FIG. 19 . 
         FIG. 23  is an enlarged view of the components in the circle  23  in  FIG. 19 . 
         FIG. 24  is a further enlarged view of the components shown in  FIG. 24 . 
         FIGS. 24A-24I  are diagrammatic views of the operation of the belt indexing components shown in  FIG. 24  and included in the filter apparatus shown in  FIG. 18 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
     Referring to the drawings and particularly  FIG. 1 , a vacuum filter apparatus  10  is depicted incorporating features of the present invention. 
     A generally rectangular tank  12  open to atmospheric pressure is adapted to receive contaminated liquid to be filtered, typically directed therein through a pipe (not shown). 
     The tank  12  includes opposite side walls  14 , and a bottom wall  16  typically fabricated from steel plates. 
     A curving solid partition plate  18  extends lengthwise along the tank  12 , held between the two sidewalls  14 . A stepped recess  20  is formed along the lowest segment  18 A of the partition plate  18  to accommodate a series of interfit planar rectangular support pieces  22  which are just thick enough so that the upper surface thereof is flush with the adjacent portions of the partition plate  18 . 
     This provides a substantially continuous support surface for a segment of woven fabric filter belt loop  24  which has an upper run  24 A overlying the support pieces  22 . 
     A pair of respective side channels  26  are formed by inverted angles  28  welded to the outer edge of the lower partition plate segment  18 A in the region of the recess  20  to create adjacent slightly raised surfaces  30  over which the edges of the advancing segment  24 D of the filter belt  24  are supported as best seen in  FIG. 9 . 
     The support pieces  22  are preferably commercially available molded plastic “cushion tiles” conventionally used to create floor matting by being arranged in an array and hooked together to form a larger area substantially continuous filter media support surface. 
     Openings  32  are formed by a grid pattern in the pieces  22  with short feet  34  at each corner of the grids creating flow spaces in both through directions and lengthwise directions underneath the surfaces of the support pieces  22 . 
     Liquid is drawn through the filter belt  24  in the region overlying the support pieces  22  and passes into these clearance spaces. Some of the flow is to the side and is collected in the channel space  26  on either side of the support pieces  22  through holes  27  in the side of the angles  28 . Additional flow occurs in a lengthwise direction under the support pieces  22  which is collected in a cross channel  36  formed by an inverted channel piece  38  welded or otherwise connected to the tank two side walls  14  and on one side is connected to the suction inlet  40  of a pump  42 . 
     The side channels  26  open into the cross channel  36  to direct all flow to the pump inlet  40 . Since flow occurs in both sideways and lengthwise directions beneath the pieces  22 , an adequate flow area is provided despite the shallow depth of the recess  20 . 
     The pieces  22  are designed to be hooked together and may be trimmed as needed to form an uninterrupted support for the advancing segment of the filter best  24 . 
     The pieces  22  are molded from an elastomeric material to be flexible, and to be able to conform to the continuously curved lower segment support plate  18 A to provide a durable filter belt support at low cost. 
     The curved bottom of the plate  18 A is advantageous since this eliminates the tight corners normally required to create the redirection necessary to produce ascent of the filter belt  24  out of the liquid. Such corners are disadvantageous since the fabric filter belt  24  tends to be pulled away from a tightly curved support when the filter belt  24  is indexed, as will be described in detail below. 
     A seal is provided for each side edge of the advancing segment of the filter belt  24 A against each of the guide surfaces  30 . This seal comprises a pair of sealed compliant tubes or hoses  44 , each containing a volume of liquid sufficient to mostly but not completely fill and inflate the hoses  44 , and also having an inner stiffer round tube  46  which is smaller in diameter and which maintains its round shape to partially distend the compliant hoses  44  and reduce the extent of compression needed to fully inflate the hoses  44 . 
     The hoses  44  are pressurized except during indexing, as will be described in order to press the edges of the filter belt  24  against the guide surfaces  30  to create sealing pressure thereon. An upper surface guide  48  is created over each hose  44  by a series of angles  50  welded to each side wall  14  to confine the hoses  44 . A pair of guide bars  52  and  54  confine the hoses  44  laterally, with guide bars  54  also guiding the exposed end of a spaced apart series of drive-flight bars  56  mounted extending parallel to each other and across the width of the filter belts, distributed along the entire length of the filter belt  24 . 
     The ends of the filter belt  24  are connected together by clips in the well known fashion to form an endless loop which is incrementally recirculated by periodic indexing, with a return run  24 B extending beneath the partition plate  18  as seen in  FIGS. 1 and 10 . 
     The drive-flight bars  56  may be mounted to the filter belt  24  by being tightly received in pockets  58  formed by fabric flaps  60  each formed into a loop defining a pocket  58 , the ends sewn to the upper surface of the filter belt  24  as seen in  FIG. 15 . The exposed ends of the fabric forming the pockets preferably have a layer of polyurethane coating  62  to prevent fraying. 
     The drive-flight bars  56  are relatively closely spaced to each other along the filter belt  24  at regular intervals related to the length of indexing travel, i.e. such as an 8 inch pitch ( FIG. 14 ). 
     The pockets  58  are shorter than the full width of the filter belt  24  so that the ends of the drive-flight bars  56  are exposed and extend partially over the side edges of the filter belt  24 , but terminate well short of the outermost edges as seen in  FIGS. 5 and 6 , to provide space for the hoses  44  and exposed filter belt side bands to enable sealing thereof. 
     The drive-flight bars  56  may be constructed of a durable plastic such as polypropylene or polyethylene which are suitably lightweight and present a low friction surface. 
     The drive-flight bars  56  are of a substantial height, i.e. approximately ¾″ to 1¼″ in height so as to be able to act as conveyor flights and to reliably positively engaged to carry out indexing. That is, chips can be captured by the drive-flight bars  56  as the filter belt advancing segment  24  ascends the exit side of the partition plate  18  (to the right as viewed in  FIG. 1 ). The chips (or other solids) would otherwise slide back down the filter belt  24  if the bars  56  were not included. 
     The drive-flight bars  56  also serve the purpose of holding the filter belt  24  down in position over the support sections  22 , preventing float as the ends thereof are confined by the undersurface  48  of the angles  50 . 
     The flight bars  56  are relatively closely spaced, i.e. typically, 8 inches apart, so that the filter belt  24  does not lift off the curved surfaces even when the filter belt is being pulled during an index cycle. The guiding by the drive-flight bars  56  also acts to counter any tendency of the filter belt  24  to float, as is sometimes caused by the formation of air bubbles beneath filter belts. 
     Thus, the need for a separate flight conveyor is avoided by the integrated filter belt and conveyor achieved by the addition of the drive-flight bars  56 . 
     The flight bars  56  also provide a reliable positive drive feature for accomplishing indexing movement of the filter belt  24  in order to convey chips out and to allow cleaning of successive sections of the filter belt  24  as will be described below. 
     Each end of the compliant hoses  44  is plugged with a fitting  64  having a threaded stem passed through a support plate  66  welded to a respective side plate  14  on the left end. The right end is plugged with a fitting  64 , but held by the plate  66  welded to a side wall  14  and hook  68  ( FIG. 7 ). A liquid is contained within each hose  44  to partially inflate the same. 
     In their partially inflated state, the hoses  44  do not exert a significant pressure on the side edges of the filter belt  24 . 
     However, the right upper end of each hose  44  is normally squeezed between an associated pair of opposed curved plates  70 ,  72 . The curved anvil plate  70  is hinged at  74  to be adjustably located towards and away from the squeeze plate  72  ( FIG. 7 ) by an adjustment bolt  76  threaded into a fixed plate  78  and having a protruding end engaging the inside of the plate  70 . 
     Each squeeze plate  72  is mounted to an associated rotary pivot plate  80  which is normally positioned as shown in  FIG. 7  in which the upper end of the associated hose  44  is squeezed as shown. This expands the remaining length of the hoses  44  to exert a sealing pressure on a respective side band of the filter belt  24  to establish a seal preventing bypass flow of liquid around the filter belt edges. 
     Each pivot plate  80  also mounts a short stroke linear actuator  82  having a downwardly directed plunger attached to an engagement element here comprised of a stepped block  84  positioned above an idler drum  86  around which the filter belt  24  is routed to be recirculated back into the tank as successive index cycles occur. 
     A second smaller diameter idler drum  88  is located at the opposite end of the tank  12  to complete the recirculation path of the filter belt  24 . 
     The stepped block  84  on each side of the filter belt  24  is located above a respective exposed end of a drive-flight bar  56  with the riser part of the block stepped shape located behind the rear face of the driver-flight bar  56 . 
     As will be described hereinafter, at the beginning of each index cycle initiated by a timer included in the system controls (not shown), linear actuator  82  is activated causing the stepped block  84  to descend and rest against the top of the respective end of the flight bar  56 . The pivot plate  80  is then advanced clockwise to engage the drive-flight bar  140  and thereafter begins pulling the filter belt  24  to the right, by means of an associated rotary actuator  86  and a cross shaft  88  which is connected to each pivot plate  80  by a set of collars  90  on each plate  80 . When this occurs, the curved squeeze plates  72  are both moved away from their respective hoses  44  to relieve the sealing pressure, and allow the filter belt  24  to be free to be advanced. 
     The filter belt  24  is passed around over a curved return guide plate  92  with successive indexing incremental movements. 
     The pivot plate  80  also has an arced opposite edge having three contact rods  94 - 1 ,  94 - 2 ,  94 - 3  affixed thereto which successively engage a belt beater angle  95  as the actuator plate  80  is pivoted through an arc. 
     Each rod  94 - 1 ,  94 - 2 ,  94 - 3  causes an angle  95  to be pushed up bending up a spring steel sheet holding the angle  95 , and thereafter releases the same to cause impact of the angle  95  against the inside of the belt  24 , knocking loose any solids on the belt  24 . This happens three times during each pivoting of the pivot plate  80 . 
     The movement of the filter belt  24  at full advance of the pivot plate  80  is slightly greater than the 8 inch pitch of the drive-flight bars  56 , so that upon retraction of the stepped blocks  84  and return to the start position, the stepped blocks  84  are again properly aligned with the rise surface spaced slightly behind the rear face of the next flight bar  56  to insure engagement therewith when the next indexing cycle is initiated. 
     As per conventional practice, a clean tank  96  is located over the tank  12  into which is diverted a small volume of clean filtered liquid. The liquid is drained out of the vacuum box by a pump  98  driven by a motor  100 . The suction side of the pump  98  is connected to an inlet pipe  102  connected to channel  38 . A small proportion of the flow is diverted to the clean tank  96  which fills to the level of a weir  97  and then overflows into a pipe  99  to direct the overflow back into the tank  12 . This arrangement eliminates the need for a control valve to stop diversion of clean liquid after the clean tank  96  is refilled. 
     The pump outlet  106  is connected to piping (not shown) for directing clean liquid to the using equipment and to the clean tank  96 , and to a belt cleaning arrangement described below. 
     A stand pipe  104  allows clean liquid from the clean tank  96  to be drawn out to supply the using equipment and to be reintroduced into the tank  12  when preparing for indexing to neutralize the vacuum created across the belt  24  and allow movement of the belt  24 . A check valve allows a small flow back into the channel  38  to neutralize the vacuum in the well known fashion. 
     Some of the filtered liquid is introduced into a channel  108  ( FIG. 11 ) affixed to the partition plate  18  via an opening  110  in a sidewall  14  and piping (not shown) connected to fittings  112  ( FIG. 3 ). Channel  108  is welded or otherwise attached to the underside of partition plate  18 . 
     A machined slot  114  in the plate  18  creates a jetting outflow into the underside of the filter belt  24  to create a cleaning action for each segment of the belt  24  flushing out the solid contaminants as it again descends into the tank  12 . 
     The system controls are not here described in detail, as typical controls are well known and described in the above identified U.S. patents. 
     To provide an even lower cost filter apparatus, a lower capacity gravity filter  116  can be provided incorporating some of the features of the invention described above in the vacuum filter apparatus, as shown in  FIGS. 18-24 . Some variations in the components of the filter apparatus are incorporated in this embodiment. 
     The gravity filter apparatus  116  is designed to have a lower profile so as to be able to be placed under individual machine tools. Covers  119  are provided to prevent splash or the entrance of dirt or trash. A cover opening would normally be made aligned with the location of liquid discharge of a particular machine tool (not shown), and a liquid collector inlet fitted therein 
     A low height rectangular tank  118  is provided, having a bottom plate  120 , two sidewalls  122 , and two end walls  124 ,  126  to create a confined space  128  for receiving contaminated liquid and collecting liquid which has been filtered. 
     The tank interior space  128  is subdivided by a filter media support comprised of a curved perforate plate  130  extending down from either end and affixed to each sidewall  122 . 
     A combined conveyor-filter belt  132  is provided as in the above described filter apparatus, which comprises a strip of woven fabric having its ends joined to form a closed loop and having a series of flight bars  134  attached as with open ended loop pockets  136  sewn or otherwise attached extending across the width of the fabric belt as in the above-described embodiment. The pockets  136  are relatively closely spaced parallel to each other. 
     A pair of horizontal plates  138  project in from a respective side plate  122  and extends along and over the perforate plate  130  and partially overhanging the side bands of the filter belt  132 , and also extend over a respective end  140 A,  140 B of drive-flight bars  140  received and held in a respective pocket  136  on the filter belt  132 . 
     A pair of short vertical plates  142  extending beneath the plates  138  confine the ends  140 A,  140 B of the drive-flight bars  140 . 
     A pair of hose seal assemblies  144  overlying the outer edges of the filter belt  132  are also confined by the vertical guide plates  142 . 
     The hose seal assemblies  144  each include an outer sealed compliant hose  146  and an inner tube  148  which hold its round shape. A liquid partially fills the outer hose  146  which extends to a height above the maximum liquid level L MAX  in the tank  118 . 
     The hoses  146  are each bent back into a U-shape at either end as best shown in  FIGS. 22 and 23 , with plug assemblies  150 ,  152  sealing the hoses  146 . 
     A holder fitting  154  holds each bight formed by the upper folded over hose ends. 
     A pump  156  driven by a motor  158  removes filtered liquid from the collection space  160  in the tank  118  and maintains a minimum level differential. 
     A liquid level sensor  162  has an end positioned at the lower liquid level L MIN  to control the pump operation to keep a sufficient head differential to ensure adequate gravity induced flow through the filter belt  132 . 
     A pair of indexing drive mechanisms  164  is provided on each side of a return idler drum  166  around which the filter belt  132  passes into to be directed back into the tank space  160  beneath the perforate plate  130 . 
     The return idler drum  166  is mounted within an upwardly angled elevated portion  160 B at the left side of the tank  118 . 
     The idler drum  166  is free to rotate on a cross shaft  168  which is oscillated by a rotary actuator  170 . 
     Mounted to a respective end of the shaft  168  are a pair of pivot plates  172  each located at a respective end of the drum  155  and fixed to the shaft  168  to be oscillated therewith, included in each of a pair of indexing drive mechanisms  164 . The drive mechanisms  164  also each include a plunger assembly, including a plunger  174  mounted to a respective pivot plate  172 . 
     The plunger assemblies each also include an engagement element comprising a stepped block  176  and a linear actuator  178 , the plunger assemblies each mounted to an upper portion  180  of a respective pivot plate  172 . 
     Each stepped block  176  is shaped to engage a respective end  140 A,  140 B of a drive-flight bar  140  when the actuator  178  acts to extend the plunger assembly  174  downwardly as in the above described embodiment. 
     The rotary actuator  170  is actuated after the drive flight bar  140  aligned beneath the plunger assemblies is engaged by both stepped blocks  176  to rotate both pivot plates  172 . 
     A series of contact rods  182  are affixed to an arcuate bottom portion  172 A of each pivot plate  172  which successively engage a beater assembly  184 , as in the above described embodiment to cause repeated bending and release of a spring steel sheet  185  clamped at one end to a fixed angle  183  to cause a projecting angle side  186  to strike the return segment  132 B of the filter belt  132  to tend to dislodge any entrapped solids in the belt fabric. 
     A hinged anvil plate  190  which has a flat segment  192  is adjustably located against a threaded step bolt  194  to be positioned against the folded back segment  146 A of the sealed hose  146 . A squeeze plate  196  also having a flat segment  198  is mounted to each pivot plate  172  and located so as to compress the associated hose  146  and create sealing pressure in the main length thereof exerted on the outer side bands of the filter belt segment  132 A. 
     In  FIG. 24 , a pair of curved end guides  200  are shown each fixed to a tank side wall  122  which are located to engage and guide a respective filter belt outer band, while the drive-flight bars  140  engage a main guide plate  202 . 
     The return segment  132 B passes around a second idler drum  188  at the left end of the tank  118 . 
     As in the above first described apparatus, a belt washer is located just after the second idler drum  188  to direct a spray of clean liquid at the inside of the filter belt advancing segment  132 A. 
     Suitable controls cause a periodic operation of the indexing mechanism to to incrementally advance the upper segment of the filter belt  132 A to the right. 
       FIGS. 24A to 24I  show the steps of each indexing cycle. 
     In  FIG. 24A , the plunger assembly is inactivated and a drive flight bar  140  is located just ahead of the stepped feature. This relationship is insured by setting the rotary stroke to be slightly greater than the pitch between the drive-flight bars  140 . 
     In this initial position, the squeeze plates  196  are compressing both of the hoses  146  to expand the remaining lengths thereof, generating a sealing pressure on the filter belt outer edges. 
     In  FIG. 24B  the linear actuator  178  has been activated to bring the stepped block engagement element  176  down against the top of the guide-flight bar  140 . As noted, the trailing side of the drive-flight bar  140  is located slightly ahead at the end of the previous indexing cycle to insure proper engagement with the stepped block  176 . 
     The hoses  146  remain compressed by the squeeze plates  196 . 
     In  FIG. 24C  the rotary actuator  170  has rotated the shaft  160  and pivot plates  172  clockwise to engage and slightly advance the drive-flight bar  140 , pulling the filter belt  132  around the idler drum  172 . The squeeze plates  196  have at the same time been advanced to move away from the hoses  146 , so that the filter belt  132 A has been released to be freely movable. 
     In  FIG. 24D , the first rod contacts  182 - 1  have pushed the beater bar  184  back by continued advance of the pivot plates  172  and the filter belt  132  has further advanced. 
     In  FIG. 24E , the beater bar  184  has been released to impact the filter belt segment  132 B to knock out retained solids (collected in a receptacle not shown) while the filter belt  132  is further advanced. 
     In  FIG. 24F , the second rod contacts  182 - 2  have engaged the beater bar  184  and deflected the same back, while the filter belt  132  is further advanced. 
     In  FIG. 24G , the filter belt  132  is further advanced, and the third rod contacts  182 - 3  engage the beater bar  184 . 
     In  FIG. 24H , the pivot plate  172  has been rotated almost to its fullest extent and the beater bar  184  has been deflected back. 
     In  FIG. 24I , the beater bar  184  has been released to again impact the filter belt segment  132 B as the pivot plate  172  reaches its fullest extent of advance and the linear actuator  178  has against retracted the stepped block  176  to disconnect the pivot plate  172  from the drive-flight bars  140  and filter belt  132  and allow it to be returned to the start position ready for the next cycle. 
     The filter belts are preferably monofilament fabrics. Monofilament fabrics are made by weaving single extruded filaments in both the warp and weft directions to create unique fabrics. The fabrics have precise and measurable opening sizes and can therefore be rated in microns. These fabrics have high flow rates and low-pressure drops compared to multifilament fabrics. Monofilament fabrics capture particles on their surface, have excellent particle release and are easy to clean. Monofilament fabrics have high stiffness so they have less tendency to wrinkle. Monofilament fabrics also have high tensile strength and less tendency to stretch. 
     Fabrics can be made of many different materials, based upon the application; polyester, nylon, polypropylene, PTFE or others. 
     The most common fabric weaves are satin or twill because they give a smooth surface on the product capture side of the belt. Another weave which is very useful in the embodiments of the invention is the “double layer weave” which is produced by simultaneously weaving a fine filter mesh together with a coarse support mesh. The two layers are woven together in the loom to form a two layer composite fabric that allows for high throughput and fine particle capture efficiency as well as reduces wrinkling and stress failures. The double layer weave allows a heavy fabric to have a fine weave, which is a major advantage, since it is durable and strong to wear well, yet can remove fine solids. 
     SEFAR AMERICA weaves and supplies fabrics which may be used in the filter apparatus as described above. 
     Examples of these fabrics are: 
     07-1005-W1118: Single layer, polyester, monofilament, satin weave, fabric with 118 micron openings, 740 microns thick, 12.7 oz./yd weight; 
     07-84323W060: Double layer, polyester, monofilament fabric, 60 microns opening, 780 micron thickness, 10.2 oz./yd2 weight; and 
     07-9001-K020: Double layer, polyester, monofilament fabric, 20 microns opening, 825 micron thickness, 19.5 oz./yd2 weight. 
     It is also desirable to treat the filter belt edges by impregnating, the same with liquid polyurethane to seal the interstices and improve sealing. A two-part liquid polyurethane can be applied to the edges and compressed in a press to fill the internal spaces. This makes these edges impervious to liquids and also providing a smooth surface to reduce frictional drag when indexing. 
       FIGS. 16 and 17  show an alternate form of beater bar  208  which doesn&#39;t employ the spring steel blade to generate a spring force. Such blades can corrode in a watery environment Rather a pair of coil springs  210  connect a mounting angle  212  fixed extending between the two sides  122  of the tank and a beater angle  214 . Beater angle  212  has a longer projecting side  216  which strikes the filter belt after the springs  210  are stretched when the angle  212  is engaged and released by contacts on the pivot plate  172  in the manner described.