Abstract:
An apparatus for removing solids from a liquid/solid mixture disposed in a tank and rising to a mixture level, the apparatus including a suction assembly defining a suction opening, the suction assembly linked to a vacuum that causes suction at the opening, a support assembly formed about the suction surface including first and second essentially circular housing walls having wall edges and a filter belt loop sealed to the edges and sized such that the belt is slack and subject to deformation between the edges, a belt section disposed to cover the suction opening and a processor controlling a motivator to periodically alter belt position with respect to the suction opening.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. Pat. Appln. No. 09/692,710 which was filed on Oct. 19, 2000 and which is entitled MEDIA VACUUM FILTER. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention relates to filters for use in removing solids from a solid/liquid mixture or metal working fluids and more specifically relates to a highly efficient filter assembly for use in swarf removal systems that can operate in large or small areas.  
           [0004]    Many industries employ machining and grinding devices such as drills, mills, cutting devices, grinding wheels, etc., to remove metal pieces, chips, “strings” and other fines from work items thereby forming the work items into final products. Hereinafter removed metal material will be referred to as swarf. To remove swarf often a liquid stream is employed that is directed at the machining point and that “washes” the swarf from the machining area.  
           [0005]    To collect the liquid for reuse a tank and conveyor are provided below the machining point. Swarf is washed into the tank and settles to the conveyor that is arranged near the bottom of the tank. Relatively heavy swarf settles quickly to the conveyor is transferred to a swarf collection bin. Smaller fines stay in suspension and eventually form a liquid/swarf mixture that is extremely “dirty”. Dirty liquid cannot be used for machining or grinding purposes primarily because such liquid can clog spraying hardware, load wheels, scratch parts and cause metal working fluid degradation.  
           [0006]    To render dirty liquid reusable most swarf handling systems include some type of filter to separate swarf from the liquid. Filtering effectiveness is extremely important as clean liquid reduces maintenance downtime, extends coolant life, improves machining precision and often extends tool life.  
           [0007]    Many different filter configurations have been implemented. One filter configuration includes a metallic drum having small holes in the drum side wall. The drum is disposed on its side and the underside of the drum is disposed below a liquid-solid mixture level so that there is a pressure differential between the inside and outside of the drum. Liquid pours through the drum holes into the drum interior while swarf fines are stopped by the drum wall. Eventually accumulated fines form a swarf cake on the undersurface of the drum (i.e., on the submersed wall section). Liquid inside the drum is removed to maintain the differential pressure within the drum. When the holes in the underside of the drum become clogged, the drum is rotated such that an adjacent drum side faces downward and filtering continues. Pressure sensors for determining when to rotate a drum filter due to clogging are known in the art. One configuration of the above described type is described in U.S. Pat. No. 3,000,507 (“the &#39;507 patent) entitled “Rotary Filter” that issued on Sep. 19, 1961.  
           [0008]    Drum filters of the above described type have several shortcomings. First, after clogging, the holes must be cleared prior to reuse. Second, often the drum holes cannot be made small enough to remove very small fines. Third, such filters often require extended periods to filter the amount of liquid required. Fourth, such filters often must be substantially submersed (see the &#39;507 patent) in order to cause a required pressure differential between the inside and outside of the drum. In addition to increasing the differential pressure, many drum filter references teach that a large portion of the drum should be submersed to increase filtering area.  
           [0009]    The industry has developed several systems for unclogging holes or removing accumulated solids from drum filters. The &#39;507 patent teaches a blower that blows air through drum holes from the inside of the drum thereby dislodging accumulated cake chunks and clearing the holes. A discharge chute is positioned under the discharge area so that dislodged chunks do not fall back into the tank. Unfortunately air blowers work best where drum holes are relatively large and therefore systems of this type often produce liquid that remains relatively dirty after filtering.  
           [0010]    Another filter cleaning solution has been to provide a mechanical “cake knife” along a filter path and adjacent a filter surface that effectively scrapes cake extremely important as clean liquid reduces maintenance downtime, extends coolant life, improves machining precision and often extends tool life.  
           [0011]    Many different filter configurations have been implemented. One filter configuration includes a metallic drum having small holes in the drum side wall. The drum is disposed on its side and the underside of the drum is disposed below a liquid-solid mixture level so that there is a pressure differential between the inside and outside of the drum. Liquid pours through the drum holes into the drum interior while swarf fines are stopped by the drum wall. Eventually accumulated fines form a swarf cake on the undersurface of the drum (i.e., on the submersed wall section). Liquid inside the drum is removed to maintain the differential pressure within the drum. When the holes in the underside of the drum become clogged, the drum is rotated such that an adjacent drum side faces downward and filtering continues. Pressure sensors for determining when to rotate a drum filter due to clogging are known in the art. One configuration of the above described type is described in U.S. Pat. No. 3,000,507 (“the &#39;507 patent) entitled “Rotary Filter” that issued on Sep. 19, 1961.  
           [0012]    Drum filters of the above described type have several shortcomings. First, after clogging, the holes must be cleared prior to reuse. Second, often the drum holes cannot be made small enough to remove very small fines. Third, such filters often require extended periods to filter the amount of liquid required. Fourth, such filters often must be substantially submersed (see the &#39;507 patent) in order to cause a required pressure differential between the inside and outside of the drum. In addition to increasing the differential pressure, many drum filter references teach that a large portion of the drum should be submersed to increase filtering area.  
           [0013]    The industry has developed several systems for unclogging holes or removing accumulated solids from drum filters. The &#39;507 patent teaches a blower that blows air through drum holes from the inside of the drum thereby dislodging accumulated cake chunks and clearing the holes. A discharge chute is positioned under the discharge area so that dislodged chunks do not fall back into the tank. Unfortunately air blowers work best where drum holes are relatively large and therefore systems of this type often produce liquid that remains relatively dirty after filtering.  
           [0014]    Another filter cleaning solution has been to provide a mechanical “cake knife” along a filter path and adjacent a filter surface that effectively scrapes cake chunks from the surface of the filter. While removing accumulated cakes from the surface of a filter drum, unfortunately this solution does little to clear swarf from filter holes or apertures.  
           [0015]    One other filter cleaning or clearing solution that has been adopted by many in the industry is to provide a liquid sprayer that sprays the back surface of a filter with a clean liquid to knock accumulated cake chunks off the filter. Where liquid clearance systems are used, the tank typically is extended under the clearance area so that clearance liquid and cake chunks are redeposited in the tank after a clearing process. The cake chunks, being relatively heavy, settle to the bottom of the liquid tank. To remove the cake chunks from the tank, a conveyor or drag chain is placed along the bottom of the tank that drags the chunks therefrom to a point above a swarf bin where the chunks are deposited.  
           [0016]    One other technique for loosening accumulated swarf cakes is to cause distortions in the shape of the filter media. To this end, after a cake has been formed, the cake naturally tends to maintain its compacted shape, even when the underlying filter shape is altered. Thus, when filter shape is altered, the cake often breaks into chunks and the chunks fall from the filter. U.S. Pat. No. 3,667,614 titled “Filtering Apparatus” which issued Jun. 6, 1972, teaches one configuration that relies in part on filter deformation for cake removal.  
           [0017]    To increase filter effectiveness some configurations provide a mesh or material filter media around the drum wherein the media includes much smaller holes and tortuous paths therethrough so that even extremely small swarf bits are removed from the liquid during filtering. In these cases the filter media is typically sealed to the drum via bands adjacent the top and bottom drum ends so that swarf cannot pass into the drum without passing through the filter media. Such sealing is extremely important to ensure that only clean liquid passes through the filter.  
           [0018]    To increase filtering speed some drum type filters increase the pressure differential between the inside and outside of the drum by removing air from within the drum to provide a vacuum therein. One patent that describes a system of this type is U.S. Pat. No. 5,954,960 (“the &#39;960 patent”) titled “Rotary Drum Type Dehydrator” which issued Sep. 21, 1999. While creation of a vacuum speeds up the filtering process, often, because air is pulled through the drum wall section that is not submersed while liquid passes through the submersed wall section, the vacuum is relatively ineffective unless a massive and, in some cases, prohibitively expensive pump is employed. The &#39;960 patent relies in part on the presence of a built up cake on the un-submersed section of the drum to increase the vacuum effect. Nevertheless, in order to facilitate efficient filtering typically the filter media should be rotated prior to complete clogging of the media (i.e., filtering efficiency is substantially reduced prior to complete clogging). Thus, the cake that accumulates prior to drum rotation typically is insufficient to block air from entering the inside of the drum.  
           [0019]    In addition to drum type filters other filter configurations have been developed that use a vacuum inside a filter chamber to increase filtering speed. U.S. Pat. No. 4,242,205 (“the &#39;205 patent”) teaches a filter box submersed inside a liquid-solid mixture tank wherein an upper wall of the box forms an opening and a flexible filter belt is arranged so that a portion of the belt covers the opening. The belt is periodically slid across the opening so that different filter sections cover the opening at different times and a liquid sprayer is used to clean the soiled filter sections. A vacuum is formed inside the box. In this case, because the filter box has only a single open wall a relatively small pump can be used to generate a vacuum in the box thereby increasing filtering speed.  
           [0020]    Unfortunately, the &#39;205 patent configuration also has several shortcomings. First, the &#39;205 patent configuration requires a complex sealing configuration to seal the filter belt to the edges of the box about the opening. To this end the &#39;205 patent configuration requires, among other things, two hold down chains linked to drive belt chains.  
           [0021]    Second, the &#39;205 patent configuration teaches a relatively complex belt path that increases hardware requirements and the space required to accommodate the configuration. Additional hardware for sealing and path configuration increase system costs appreciably.  
           [0022]    Third, while the &#39;205 patent configuration seal may operate properly while a vacuum is formed in the filter box, the &#39;205 patent configuration requires that the vacuum be broken prior to movement of the filter belt. After breaking the vacuum the filter belt is slid across the filter box edges which means that the sealing pressure holding the belt to the box has to be extremely small. If the sealing pressure were large the belt would likely wear and eventually tear as the belt is slid across the box opening. However, it is believed a smaller sealing pressure that would allow the &#39;205 patent configuration belt to slide against the opening would be insufficient to block “dirty” liquid from entering the filter box during belt movement.  
           [0023]    Fourth, as indicated above, the &#39;205 patent configuration also requires that at least one opening face upward. For this reason the &#39;205 patent configuration requires that the filter be completely submersed. This limitation requires that the liquid level in the tank be at least as high as the filter box depth and some clearance thereunder for a drag chain to drag cake chunks out of the box.  
           [0024]    Thus, there is a need for a swarf filtering configuration that removes extremely small swarf fines from liquid-solid mixtures relatively quickly, automatically replaces clogged filter media with clean media, automatically cleans clogged media and achieves all of the above goals relatively inexpensively and using hardware that is relatively small and that enables operation with a low tank liquid level.  
         BRIEF SUMMARY OF THE INVENTION  
         [0025]    It has been recognized that many of the disadvantages associated with the prior art can be overcome by providing a filter loop that is sealed at opposite ends to first and second housing walls wherein the loop is oversized so that the loop is loose or slack between the walls and about a girth around a central portion of the loop and providing a suction assembly including a header within the loop wherein the suction header defines both a reduced size suction chamber and an opening that opens into the chamber where a section of the loop covers the opening and the opening is positioned within a mixture tank below the mixture level.  
           [0026]    With a system as described above, the suction assembly increases the speed with which liquid can be filtered through the loop section adjacent the opening. It has been found that such a system can increase the liquid filtering rate to rates much higher than the rates achievable where much greater sections of a filter drum are submersed.  
           [0027]    In addition, with the system above., where the opening faces downward, the mixture level in the tank can be relatively low and still accommodate the filter configuration. A low mixture level means the tank size can be reduced in certain applications and that less liquid is required to facilitate the machine process.  
           [0028]    Moreover, the excess pressure caused by the reduced size suction chamber causes accumulation of tightly packed solid cakes on the filter loop that are heavier than cakes formed via other filter systems. When forced off the loop, the heavier cakes sink more readily within the tank liquid and do not disintegrate as readily in the tank prior to removal via a drag chain or conveyor.  
           [0029]    Furthermore, by providing sealing the loop to the housing edges essentially no unfiltered liquid can enter into the filter chamber.  
           [0030]    With the present invention the loop is sealed to housing wall edges during both filtering periods and loop movement periods to ensure that no dirty liquid passes into the suction chamber (or filtering chamber for that matter).  
           [0031]    Moreover, by providing an oversized filter loop, when the vacuum is turned off so that the suction stops, the loop becomes slack adjacent the header and the filter loop can be moved with respect to the header without damaging the filter loop. Then, when the suction is again caused, the filter section adjacent the opening is sucked against the header for support. One embodiment of the header includes a support screen across the opening to support the filter loop.  
           [0032]    The invention also includes a method wherein, with the configuration described above, with the opening below the mixture level suction is caused at the opening to begin the filtering process and after a condition related to filtering efficiency is sensed, the support housing and sealed filter are rotated until another filter loop section is adjacent the opening. Here the suction header remains stationary while the housing and loop are rotated.  
           [0033]    With the present filter assembly filtering speed can be increased in two different ways. First vacuum suction can be increased. Second, support housing and sealed loop rotation frequency can be increased. By combining both suction and rotation frequency increases overall filtering speed is increased appreciably.  
           [0034]    In one embodiment the invention includes a filter apparatus for separating liquid from solids in a tank, a liquid/solid mixture disposed in the tank in an amount such that the mixture rises to a mixture level within the tank and the apparatus comprises a housing formed about a chamber including first and second oppositely facing walls characterized by first and second wall edges the walls separated by at least one cross-member. The distance between the first and second walls defines a first dimension. A suction assembly includes a header forming an opening having an opening width and an opening length, the assembly supported in the chamber and juxtaposed with the tank such that the opening is below the mixture level. A filter loop has oppositely facing loop edges, the loop having first and second peripheral portions adjacent the loop edges and having a loop width between the first and second peripheral portions that is greater than the first dimension. The first and second peripheral portions are sealed against the first and second wall edges, respectively, such that the filter surrounds the chamber, a filter section is adjacent the opening, the filter width is between the walls and the filter is slack along the width dimension. A vacuum is linked to the assembly for causing suction at the opening. A motivator is provided for moving the loop with respect to the opening. A controller controls the vacuum and the motivator to periodically reduce suction at the opening and to move the loop adjacent the opening so that different loop sections cover the opening at different times.  
           [0035]    In one aspect a belt girth length around the central portion is greater than the loop edge length. The walls may be essentially circular and the fat least one crossmember includes at least first, second and third crossbars that traverse the distance between the first and second walls and may be linked to the walls adjacent the wall edges and such that the crossmembers are essentially equispaced about the periphery of each of the walls.  
           [0036]    In one embodiment the apparatus further includes first and second bands that seal the peripheral portions to the wall edges.  
           [0037]    The header may be characterized by a semi-cylindrical shape having a radius of curvature essentially equal to the radius of curvature of each of the walls and having a length essentially equal to the distance along a wall edge between adjacent crossmembers. The controller may control the position of the housing such that adjacent crossbars are on opposite sides of the opening whenever the suction level is increased to the second suction level.  
           [0038]    In one embodiment the combined distances between the first and second crossmembers, the second and third crossmembers and the third and first crossmembers comprise a support dimension and the support dimension is less than the wall edge length.  
           [0039]    In another embodiment the suction assembly includes first and second facing end plates and a media support screen that traverses the distance between the end plates, the support screen covering the opening. The suction assembly may further include guide bearings adjacent the support screen for guiding the loop therealong during movement.  
           [0040]    In another aspect the assembly may further include a clearing assembly for removing solids deposited on the loop, the clearing assembly linked to the processor and disposed adjacent the loop along the path of loop movement from the suction assembly, the controller controlling the clearing assembly to periodically disturb the solids deposited on a loop section adjacent the clearing assembly. One advantageous clearing assembly is a spray assembly comprising a liquid source linked to a spray nozzle, the nozzle disposed adjacent the loop and inside the chamber, the controller controlling the spray assembly to periodically spray liquid toward an adjacent loop section to disturb solids deposited thereon.  
           [0041]    In another embodiment a sensor is linked to the processor for determining and indicating when at least one condition related to filtering efficiency has occurred, and when the at least one condition has occurred, the processor causes the motivator to move the loop with respect to the opening. The sensor may sense vacuum pressure.  
           [0042]    In yet one more embodiment the configuration includes a disposable filter assembly including a support assembly, a filter ribbon, and a second motivator, the support assembly supporting a ribbon section adjacent the header on a side of the loop section adjacent the header opposite the header, the second motivator linked to the ribbon for moving the ribbon with respect to the header so that different ribbon sections are adjacent the header at different times, the controller linked to the second motivator for periodically moving the ribbon, a used end of the ribbon fed into a disposal bin.  
           [0043]    In addition to a complete filtering system the invention also includes a filter apparatus for use with a filter assembly, the assembly including a filter housing having first and second oppositely facing walls and at least one crossbar therebetween, the first and second walls having first and second edges, each edge characterized by a peripheral housing length, the distance between the housing edges defining a housing width, the filter apparatus comprising a flexible filter loop characterized by a loop width between oppositely facing first and second loop edges, each of the first and second loop edges characterized by a peripheral loop length, the peripheral loop lengths each essentially the same length as the peripheral housing lengths, the belt having a girth length about a central portion of the belt between the first and second loop edges that is greater than the peripheral loop length and having a width between the first and second loop edges that is greater than the housing width such that when the first and second loop edges are sealed to the first and second housing member edges the loop is slack between the first and second housing member edges and around the central belt portion.  
           [0044]    The filter apparatus is also for use with a suction assembly and a vacuum, the suction assembly disposed inside the filter housing, the suction assembly including a header that defines a suction opening, the vacuum linked to the header for creating suction at the opening, the loop length and width such that a loop section adjacent the opening is slack when the vacuum is off and is sucked up against the header when the vacuum is on.  
           [0045]    The invention further includes an apparatus for supporting a flexible filter belt loop, the loop characterized by a loop width between oppositely facing first and second loop edges. In this regard the support apparatus includes first and second oppositely facing housing walls characterized by first and second peripheral edges, respectively, each edge characterized by a peripheral housing length and formed so that one of the loop edges is sealable thereto and at least one crossmember linked to and between the first and second walls such that the distance between the housing edges defines a housing width, the crossmember having a cross sectional area substantially less than the surface area of each of the first and second walls. In one such embodiment each of the walls is essentially circular and the at least one crossmember includes first, second and third crossmembers that traverse the distance between the walls, the crossmembers linked to the walls adjacent the wall edges and equispaced about the edge peripheries.  
           [0046]    The invention further includes a filter apparatus for separating liquid from solids in a tank, a liquid/solid mixture disposed in the tank in an amount such that the mixture rises to a mixture level within the tank, the apparatus comprising: a housing formed about a filter chamber including first and second oppositely facing walls having by first and second wall edges, respectively, the walls separated by at least one crossmember, the filter chamber having a first volume; a suction assembly including a header forming a suction chamber having a second volume that is substantially less than the first volume, the header forming an opening that opens into the suction chamber, the assembly supported in the chamber and juxtaposed with the tank such that the opening is below the mixture level; a filter loop having oppositely facing loop edges, the loop having first and second peripheral portions adjacent the loop edges, the first and second peripheral portions sealed against the first and second wall edges, respectively; a vacuum linked to the assembly for causing suction at the opening; a motivator for moving the loop with respect to the opening and a controller for controlling the vacuum and the motivator to periodically reduce the suction at the opening from the second to the first suction level and move the loop adjacent the opening so that different loop sections cover the opening at different times.  
           [0047]    Thus, it has also been recognized that while a small suction chamber limits the amount of filter loop used at any given time for filtering purposes, a small suction chamber results in greater suction through the used filter section such that the overall amount of liquid filtered in a given period can be increased appreciably. Because filtering speed is increased the amount of cooling liquid required, reduces tank size, can in fact increase filtering speed, etc.  
           [0048]    These and other objects, advantages and aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0049]    [0049]FIG. 1 is a partial cross-sectional view of a filter assembly according to the present invention;  
         [0050]    [0050]FIG. 2 is a partial cross-sectional view of the filter assembly of FIG. 1 juxtaposed with respect to a material conveyor;  
         [0051]    [0051]FIG. 3 is a partial cross-sectional view of the housing support in FIG. 1;  
         [0052]    [0052]FIG. 4 is a side perspective view of the suction header of FIG. 2;  
         [0053]    [0053]FIG. 5 is a side elevational view of the suction header of FIG. 4;  
         [0054]    [0054]FIG. 6 is a flow chart illustrating a method according to the present invention; and  
         [0055]    [0055]FIG. 7 is a schematic of a system including a disposable belt assembly.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0056]    Nothing in this application is considered critical or essential to the present invention unless explicitly indicated as being “critical” or “essential”.  
         [0057]    A. Hardware Configuration  
         [0058]    Referring now to FIGS. 1 and 2, the present invention will be described in the context of the exemplary liquid/solid mixture cleaning system  10 . Although not illustrated, it is contemplated that system  10  is useable in a conventional liquid cleaning system including a swarf conveyor (not illustrated) the swarf and liquid fall under the force of gravity into a tank  12 . In FIGS. 1 and 2 the mixture rises to a mixture level  14 . The mixture is maintained essentially at level  14  by regulating a filtering rate as described in more detail below. As best seen in FIG. 2, tank  12  includes, among other walls, a bottom wall  40  and a sloped side wall  44  that extends up to a tank egress  46 .  
         [0059]    In addition to tank  12 , system  10  includes a motor  16 , a filter assembly  18 , a controller  20 , a vacuum pump and switch  22 , a drag conveyor system  9 , a waste or collection bin  38  and a plurality of control buses and other linkage devices described in more detail below. Filter assembly  18  is a “pseudo-drum” type filter assembly supported and mounted for rotation about a rotation axis  24 . The phrase pseudo-drum is used to describe assembly  18  as parts of assembly  18  are similar to parts that may be employed in a conventional drum filter while other important parts of assembly  18  are unique to assembly  18 .  
         [0060]    During operation of system  10 , periodically a drum portion of assembly  18  is rotated about axis  24  to improve the filtering characteristics of the system  10 . To rotate the drum portion of assembly  18 , assembly  18  is linked via a drive shaft  26  to motor  16 . Controller  20  is linked to motor  16  via a bus  28  to provide control signals thereto.  
         [0061]    Vacuum pump  22  is linked to a suction assembly that resides inside filter assembly  18  and that will be described in more detail below. Vacuum pump  22  is linked to controller  20  via a bus  30  so that controller  20  also controls vacuum pump  22 . Pump  22  includes a vacuum switch (not separately illustrated) that trips upon the occurrence of a programmed event related to the condition of filter assembly  18 . For example, the vacuum switch inside pump  22  may trip when the filter assembly becomes clogged such that filtering efficiency is reduced to a level below a threshold level associated with relatively efficient filtering. When the vacuum switch trips, pump  22  sends a signal to controller  20  via bus  30  indicating the inefficient filtering condition.  
         [0062]    In addition to being linked to motor  16  and pump  22 , controller  20  is also linked to a spray assembly valve  32  via bus  30  to open and close valve  32 . While controller  20  may be constructed via electronic hardware, preferably, controller  20  includes a microprocessor that can be programmed and reprogrammed to modify a filtering method such that the method caused is specifically suited to the conditions of the filtering environment. For example, drum rotation frequency may be altered, spray frequency may be altered, rotation speed may be altered and so on.  
         [0063]    Drag conveyor system  9  includes a belt  34  having spaced drag extensions  42 . Belt  34  is positioned adjacent bottom wall  40  and sloped wall  44  such that extensions  42  pass very close to walls  40  and  44  to move swarf chunks therealong. As swarf drops into tank  12 , solid swarf particles and cakes sink to the bottom of tank  12  and gather adjacent lower wall  40 . Conveyor belt  34  is guided along lower wall  40  and extensions  42  “drag” swarf along wall  40  and up inclined wall  44  to egress  46  high above mixture level  14 . As the swarf is conveyed up wall  44 , liquid on the swarf drips off until, at egress  46 , essentially all liquid has dripped off the swarf. At egress  46 , as conveyor belt  34  passes, the solid swarf falls via the force of gravity along the direction indicated by arrow  48  into bin  38  therebelow. When bin  38  is completely filled, bin  38  is removed and replaced by an empty bin. Conveyor belt  34  may be moved either continuously or in a sequence calculated to facilitate more efficient mixture cleaning.  
         [0064]    Referring still to FIGS. 1 and 2, support assembly  52  includes first and second oppositely facing circular housing walls  58  and  60 , respectively, and, in the embodiment illustrated, first, second and third cross-members or cross-bars  62 ,  64  and  66 . Wall  58  is rigid and is characterized by a circular peripheral edge  94 . An annular recess  58  is formed in edge  94  around the entire wall periphery that cooperates with a sealing band  110  to seal loop filter  50  thereto when assembly  10  is configured for operation. Similarly, wall  60  is rigid and is characterized by a circular peripheral edge  96  that forms an annular recess  100  that cooperates with a second sealing band  112  to seal loop filter  58  thereto. Each of edges  94  and  96  has an identical length referred to herein as a wall edge length.  
         [0065]    A central portion of wall  58  is integrally secured to shaft  26  which is in turn supported by a bearing  31  for rotation about axis  24 . Wall  58  is centrally linked to shaft  26  and turns therewith. Referring also to FIG. 3, an annular extending member  68  extends from a central portion of wall  60  in the direction opposite wall  58  and forms an annular channel  70  therethrough that is aligned with a central opening  71  in wall  60 . An external surface  72  of extending member  68  forms a ball-bearing receiving recess  74  which supports a ball-bearing  76 .  
         [0066]    A drum support  78  extending from a support surface (e.g., a floor, not illustrated) forms a hub  80  for receiving extending member  68 . An internal surface  82  of hub  80  forms an annular recess  84  facing recess  74  that also receives ball-bearing  76  thereby supporting member  68  and housing end  60  for rotation about axis  24 . Support  78  forms an opening  86  through which vacuum and spray pipes  88 ,  90 , respectively, extend, pipes  88  and  90  continuing through channel  70  and opening  71  into a filter chamber  29  between walls  58  and  60 . Pipes  88  and  90  are both linked to a reservoir pipe  99  that is pressurized so that when valve  32  is opened liquid is provided to pipe  88 . An elastomeric seal  92  hermetically seals the space between the surface defining opening  86  and the external surfaces of pipes  88  and  90  in any manner well known in the industry.  
         [0067]    Each of cross-bars  62 ,  64  and  66  is rigidly secured to walls  58  and  60  at opposite bar ends. Thus, walls  58  and  60  rotate in unison and walls  58  and  60  together with bars  62 ,  64  and  66  form a pseudo-drum support assembly  52 . Support assembly  52  is a pseudo-drum in that the space between walls  58  and  60  is drum-shaped (i.e., cylindrical) but there are no side walls per se. As best illustrated in FIG. 2, cross-bars  62 ,  64  and  66  are equispaced about the circumferential edges  94  and  96  of walls  58  and  60 . Thus, because there are three cross-bars  62 ,  64  and  66 , the cross-bars are separated by essentially  1200  with respect to axis  24 . The space between walls  58  and  60  is referred to as a filter chamber hereinafter.  
         [0068]    Referring still to FIGS. 1 and 2, filter loop  50  is formed of a flexible woven or perforated media such as a fibrous material that can be wrapped around the support assembly  52 . Exemplary filter loop materials include polyester, polypropylene, nylon and stainless steel mesh. Loop  50  has oppositely facing loop edges  102  and  104  and has peripheral portions  106  and  108  adjacent the loop edges  102 , 104 , respectively. Each loop edge  102 , 104  is essentially the same length as each of the wall edge lengths (e.g.,  94 ,  96 ) described above.  
         [0069]    When filter assembly  18  is assembled the peripheral portions  106  and  108  of loop  50  are sealed against wall edges  94  and  96 . To this end, peripheral portions  106  and  108  are positioned such that internal surfaces of portions  106  and  108  are adjacent edges  94  and  96 , respectively, and first and second sealing bands  110  and  112  are secured around the peripheral portions  106  and  108 . Bands  110  and  112  preferably force the peripheral portions  106  and  108  into recesses  98  and  100  thereby creating a robust seal. Bands  110  and  112  may be mechanically tightened or may rely on band elasticity (e.g., the bands may be elastomeric).  
         [0070]    Referring still to FIGS. 1 and 2, importantly, filter loop  50  is sized such that the loop dimension between sealed peripheral portions  106  and  108  is greater than the dimension D1 defined by walls  58  and  60 . Thus, as seen in each of FIGS. 1 and 2, filter loop  50  is “slack” or “loose” between walls  58  and  60 . In FIG. 1, loop  50  is shown as being slack above cross-bar  62  and in FIG. 2 loop  50  is illustrated as being slack between bars  62  and  60  and also between bars  62  and  64 . The slack nature of filter loop  50  facilitates filter support by a suction assembly  54  as will be explained in more detail below. At this point it should suffice to say that suction assembly  54  is juxtaposed within filter chamber  29  and between adjacent cross-bars (e.g.,  64  and  66 ) such that a mesh support wall (see  128  in FIG. 5) is recessed back from a surface defined by adjacent edge portions of walls  58  and  60  and the loop  50  dimension between walls  58  and  60  is large enough that the loop section adjacent wall  128  is capable of caving into filter chamber  29  until the adjacent loop section is supported by wall  128 .  
         [0071]    Referring still to FIGS. 1 and 2 and also to FIGS. 4 and 5, suction assembly  54  includes a suction header  114  that is linked to vacuum pump  22  via suction pipe  90 . In the embodiment illustrated, header  114  includes a base plate  116  and first and second ends plates  118  and  120 . Base plate  114  is rectangular having oppositely facing edges  111  and  110  and oppositely facing edges  115  and  117  and having a length L1 between edges  115  and  177  that is essentially the same length as dimension D1 between first and second housing walls  58  and  60  (see FIG. 1). Base plate  116  forms a centrally located opening  122 . An annular extension  126  is formed about opening  122  and extends to a side of base plate  116  opposite end plates  118  and  120 . Although not illustrated, extension  126  forms an annular passageway that may be threaded so as to receive an adjacent end of suction pipe  90 . In any event, pipe  90  is integrally secured to annular extension  126 .  
         [0072]    End plate  120 , as best illustrated in FIG. 4, has a straight edge  119  and a curved edge  121  that connects the opposite ends of the straight edge  119 . Similarly end plate  118  has a straight edge (not separately numbered) and a curved edge  125 . In the embodiment illustrated, the degree of curvature of curved edges  121  and  125  is similar to the degree of curvature of the wall edges  94  and  96 . The similarity in the degree of curvature between edges  121  and  125  and wall edges  94  and  96  is best illustrated in FIG. 2. The radius of curvature of edges  121  and  125  is slightly smaller than the radius of curvature of wall edges  94  and  96 . Referring still to FIGS. 4 and 5, the flat edges (e.g.,  119 ) of end plates  118  and  120  are secured to opposite edges of base plate  116  at opposite ends of length L1.  
         [0073]    Referring still to FIGS. 4 and 5, rigid mesh wall  128  traverses the distance between curved edges  121  and  125  having essentially the same radius of curvature as each of curved edges  121  and  125  and also traverses the distance between base plate edges  111  and  113 . Mesh wall  128 , base plate  116  and end plates  118  and  120  together define a semi-cylindrical suction chamber  124 . As illustrated in FIG. 5 central opening  122  through base plate  116  opens into suction chamber  124 . Thus, it should be appreciated that header  114  forms a suction opening covered by mesh wall  128  which has a length essentially equal to length L1 and has an opening width dimension that is essentially the same length as curved edges  125  and  121 .  
         [0074]    Referring still to FIGS. 4 and 5, four guide bearings collectively referred to by numeral  130  extend from external surfaces of end plates  118  and  120 . Bearings  130  help to reduce friction between filter loop  50  and an external surface of mesh wall  128  when loop  50  is rotated with respect thereto.  
         [0075]    Referring now to FIGS. 1, 2,  4  and  5 , suction assembly  54  is mounted within filter chamber  29  so that mesh wall  128  faces downward and so that mesh wall  128  is recessed slightly back from each of wails edges  94  and  96  (i.e., wail  128  is recessed from an imaginary surface corresponding to edges  94  and  96 ). In the embodiment illustrated, suction assembly  54  is rigidly mounted such that the suction assembly  54  does not move when motor  16  causes the support assembly  52  and filter loop  50  to rotate about axis  24 .  
         [0076]    With suction assembly  54  mounted inside filter chamber  29  and a “slack” filter loop  50  as described above, when vacuum pump  22  is turned on the loop  50  section adjacent mesh wall  128  (i.e., adjacent the opening formed by suction header  114 ) is sucked up against the external surface of mesh wall  128  such that the adjacent loop section is supported by the mesh wall for filtering purposes. Similarly when vacuum pump  22  is turned off, because loop  50  is “slack,” the loop section adjacent mesh wall  128  separates from the external surface of wall  128  and hangs in a slack manner. Because there is minimal friction between the loop  50  and mesh wall  128  after pump  22  or flow is turned off, support assembly  52  and filter loop  50  can be rotated about axis  24  without damaging the filter loop  50 .  
         [0077]    Referring now to FIGS. 1 and 2, spray assembly  56  includes spray control valve  32  positioned within spray pipe  88  and a spray header  134  linked to spray pipe  88  within filter chamber  29 . Spray header  134  is positioned within chamber  29  and forms a spray nozzle  136  that directs clean liquid at a back surface of loop  50  between two of the three support assembly cross-bars. For example, in FIG. 2, nozzle  136  is positioned within chamber  29  such that the spray generated by assembly  56  is directed at a section of filter loop  50  between cross-bars  62  and  64 . In FIG. 2 it is contemplated that loop  50  rotates in a counter-clockwise direction so that, after a partial rotation of loop  50 , the loop section initially adjacent suction assembly  54  is adjacent spray nozzle  136 . Referring still to FIGS. 1 and 2, when valve  32  is opened, clean liquid is provided to header  134  and is directed at loop  50  to knock swarf cakes therefrom.  
         [0078]    B. Operation  
         [0079]    Referring now to FIG. 6 a method according to the present invention is illustrated. Referring also to FIGS. 1 and 2, beginning at block  200  a filter assembly is provided that includes X crossbars  62 ,  64 ,  66 , between housing end walls  58  and  60 , a suction assembly  54  positioned within the filter chamber  29  and a “slack” filter loop  50  sealed to the housing wall edges  94  and  96  where the loop portions between adjacent crossbars are loop sections.  
         [0080]    At block  202  the suction opening (e.g., wall  128  in FIG. 5) is positioned within tank  12  below mixture level  14 . At this point, with vacuum  22  off, the filter loop section adjacent wall  128  is slack so that there is little pressure between the surface of loop  50  facing wall  128  and wall  128 . Where loop  50  is formed of a buoyant material (e.g., a fabric), there may be some pressure between loop  50  and wall  128  as the loop tends to rise within the mixture tank  12 . Nevertheless, the pressure from a buoyant material is so minimal that loop damage is unlikely. Thus, with vacuum  22  off, support assembly  52  and sealed loop  50  can be rotated about axis  42  without risking damage to loop  50 .  
         [0081]    Continuing, at block  204  vacuum pump  22  is turned on to cause suction through mesh wall  128 . The suction at wall  128  causes the loop section adjacent wall  128  to be sucked up against wall  128 .  
         [0082]    Referring still to FIGS. 1, 2 and  6 , at block  206  the switch associated with pump  22  monitors vacuum pressure (i.e., monitors some condition related to filtering efficiency). When the vacuum pressure remains below a pre-set pressure level corresponding to an acceptable efficiency rating the vacuum switch remains set and control loops back to block  204 . However, when vacuum pressure exceeds the pre-set threshold level the vacuum switch is tripped and controller  20  receives a signal therefrom. When controller  20  receives the “tripped” signal, control passes to block  208  where vacuum pump  22  pressure is reduced. In one embodiment pump  22  is turned off. At block  210 , after a vacuum reduction period, controller  20  causes motor  26  to rotate support assembly  52  and sealed loop  50  in a counter-clockwise direction until the next loop section (i.e., in FIG. 2, the section between bars  62  and  60 ) is adjacent wall  128  and the section originally adjacent wall  128  (i.e., the section) between bars  66  and  64 ) is adjacent spray header  134 .  
         [0083]    Next, control passes again to block  204  where controller  20  causes pump  22  to increase suction at wall  128  thereby sucking the loop section adjacent wall  128  against wall  128 . This process of providing suction at wall  128 , sensing an inefficient filter condition, reducing suction, rotating the support assembly  52  and sealed filter loop  50  and then again providing suction continues. Spray assembly  56  may be controlled to either continuously spray the back surface of loop  50  or to be sequenced with loop rotation. These and other spraying sequences are contemplated.  
         [0084]    It should be appreciated that suction chamber  24  (see FIG. 5) has a much smaller volume than drum filter chamber  29  (see FIG. 1) and therefore that a relatively small pump  22  can be used to cause a relatively large suction through the loop section adjacent wall  128 . In fact, despite the relatively small portion of loop  50  used to filter at any one time, it has been found that the increased suction can nevertheless increase filtering speed appreciably.  
         [0085]    It should also be appreciated that the suction caused by pump  22  increases swarf cake density/compactness thereby forming heavier and more robust cake chunks that, upon being dislodged from the loop, sink more readily to wall  40  where they are dragged out of tank  12  via belt  34 .  
         [0086]    Moreover, referring to FIG. 2, it should be appreciated that as loop  50  rotates and becomes deformed adjacent spray header  134 , swarf chunks break apart due to the deformation and drop back into tank  12 . This deformation, in conjunction with the spray from header  134  virtually ensures that loop sections returning to positions adjacent wall  128  are clean and ready to facilitate efficient filtering.  
         [0087]    One other advantage of the present invention is that filter loop replacement is relatively easy. The slack nature of the filter loop makes removal of old loops and replacement with new loops relatively easy.  
         [0088]    It should be understood that the methods and apparatuses described above are only exemplary and do not limit the scope of the invention, and that various modifications could be made by those skilled in the art that would fall under the scope of the invention. For example, while the invention is described above as including a filter loop that is essentially the same girth around every part of the loop, other loop configurations are contemplated that provide even more loop slack. For example, in one embodiment where peripheral loop edge lengths are equal and a central loop portion is between the loop edges, a girth length around the central portion may be greater than the edge lengths.  
         [0089]    In addition, while the invention is described as including alternating periods during which a vacuum is turned on and off, instead, the vacuum pressure may simply be changed between a high filtering pressure and a relatively low pressure selected to avoid loop damage during rotation.  
         [0090]    Moreover, more or less than three crossbars may be employed, the suction wall may be larger or smaller than the dimension between adjacent crossbars, the mesh wall may be other than semi-cylindrical (e.g. may be flat), the controller may identify some characteristics other than vacuum suction level (e.g., time) prior to reducing suction and causing rotation and some assembly (e.g., a mechanical cleaning knife, air knife, etc.) may be used to clean swarf cakes from loop  50 .  
         [0091]    Furthermore, the present invention can also be used in conjunction with a disposable filter belt to either routinely or periodically clean the mixture in a tank. For instance, in FIG. 7, a role of filter media  300  is linked to a second motivator or motor  302  to provide a secondary filter belt  304  in conjunction with simplified assembly  10 . In this embodiment support assembly  52 , loop  50 , bin  38  and suction header  54  are essentially identical to similarly marked components above and hence will not be explained again here in detail. The distinction in FIG. 7 is that secondary belt  304  is juxtaposed adjacent header  54  on a side of loop  50  opposite header  54 . Thus, when suction is provided at header  54 , liquid is drawn through belt  304  and loop  50  thereby filtering the liquid twice. Belt  304  is held in place via a support assembly generally identified by numeral  320 . After the swarf cake on belt  304  reduces filtering efficiency support  52  and sealed loop  50  are rotated such that the belt section adjacent header  54  moves toward bin  38  where the used/dirty belt is deposited.  
         [0092]    To apprise the public of the scope of this invention, the following claims are made: