Abstract:
An improved coolant cleaning method, system, and apparatus, are provided through the use of a filter disk assembly that defines and is rotatable about an axis of rotation of the disk, for removing particulate matter from a fluid flowing through the filter disk assembly in a direction substantially parallel to the axis of rotation of the filter disk assembly. A coolant cleaning system includes such a filter disk assembly, connected in fluid communication with an apparatus for circulating a flow of fluid through the filter disk assembly in a direction substantially parallel to the axis of rotation of the filter disk assembly. An apparatus for circulating a flow of fluid may include a dirty fluid reservoir, a conveyor for removing chips and particulate matter from the dirty fluid reservoir, a clean fluid reservoir, with the filter disk assembly providing the sole fluid communication path between the dirty and clean fluid reservoirs, and a fluid supply system having a pump for circulating fluid from the clean fluid reservoir through the disk filter assembly. Several filter disk assemblies may feed into a single clean fluid reservoir to achieve high volume flow rates of clean fluid. Alternatively several filter disk assemblies, having filter elements of increasingly finer mesh, feeding into several separate clean fluid reservoirs may be utilized to provide fractionally filtered coolant fluid having varying degrees of cleanliness as required for various machining operations. Embodiments of coolant fluid cleaning systems for machine tools are disclosed. Embodiments depicting retrofit of a filter disk assembly and/or an improved dynamic seal arrangement for a rotating filter according to the invention into prior fluid cleaning apparatus are disclosed. An apparatus is provided for removal of particulate matter from fluid above, below, and between an upper and lower portion of a horizontally traveling hinge belt conveyor.

Description:
FIELD OF THE INVENTION 
     This invention relates to systems for removing particulate matter suspended in a fluid, and more particularly to systems for removing fine particles from fluid utilized in conjunction with the machining of metal or non-metals. 
     BACKGROUND 
     There are many applications in which it is necessary for environmental reasons, or for the reclamation and recycling of resources, to separate particulate matter suspended in a liquid from the liquid itself. One example of such an application is the need to remove particulate matter from water used by an industrial floor cleaning machine, or a street sweeping machine, prior to disposing of the water in an environmentally safe manner. Another example of such an application is the removal of waste material from coolant used with cut-off saws or grinding machines. Yet another example of such an application is the necessity to separate chips and fine particles of waste material from coolants used with machine tools to facilitate the machining of metal or non-metallic materials. 
     The process of machining a workpiece into a finished part on a machine tool requires that a cutter of some sort be forced into the workpiece to carve away waste material portions of the workpiece and achieve the desired shape of the finished part. The action of the cutter against the workpiece generates both a large volume of chips or fine particles of waste material, and a substantial amount of heat in the cutter and workpiece. These chips or particles of waste material, and the heat generated, must be transported away from the cutter and workpiece during the machining process, in order to achieve dimensional accuracy of the finished part, and in order to allow the cutter to operate at the high speeds necessary to effectively and efficiently shape the finished part without overheating. 
     In order to remove the chips or particles, and the heat generated in the machining process, machine tools generally incorporate some sort of cooling and flushing system for directing a flow of a liquid coolant or oil at the workpiece and cutter during the machining process, to absorb the heat generated at the interface of the cutter and the workpiece, and to transport both the heat and chips or particles away from the cutter and workpiece. After flowing over the cutter and workpiece, the coolant fluid, with the chips or particles entrained, is collected and drained from the machine tool. 
     Modern machining processes are carried out at very high speeds, requiring a large flow of coolant fluid for effective removal of the chips and heat. Depending upon the machining process involved, a continuous flow of coolant is required during the machining process at flow rates in the range of 10 to 400 gallons a minute. This flow of coolant is typically supplied to the machine tool by a coolant fluid circulating and cleaning system which includes mechanisms for separating the chips and particles from the flow of coolant so that the coolant may be continuously re-circulated. 
     For larger sized chips or particles of waste material, the primary mechanism for separating the waste material from the cooling fluid involves utilizing the force of gravity. In some coolant cleaning systems utilizing scraper type conveyors, the coolant fluid drained from the machine tool is directed into a dirty fluid reservoir of the coolant cleaning system where the chips and particles are allowed to settle in the bottom of the reservoir. A conveyor mechanism then scrapes across the bottom of the reservoir to pick up the settled chips and particles and transports them to a chip collection bin or container. The coolant above the bottom of the tank is then drawn off by a pump and re-circulated to the machine tool. In other coolant cleaning systems, the coolant with entrained chips and particles is directed onto a screen, or a hinge belt conveyor system, as the fluid enters the dirty fluid reservoir, so that the fluid can run through the screen or hinge belt into the bottom of the reservoir, with the larger sized chips and particles being screened out and separated from the coolant fluid by the screen or hinge belt. The cleaned coolant below the screen or belt is then re-circulated to the machine tool. U.S. Pat. No. 5,858,218 to Setlock et al; U.S. Pat. No. 5,849,183 to Ota et al; U.S. Pat. No. 5,603,846 to Uchiyama et al; U.S. Pat. No. 5,167,839 to Widmer II et al; and U.S. Pat. No. 4,992,167 to Uchiyama; are illustrative of these approaches utilizing the force of gravity to separate the chips and particulate matter from the fluid. U.S. Pat. No. 4,895,647 is also illustrative of these approaches, and includes a permanent magnet disposed on the bottom wall of the reservoir to supplement the force of gravity with magnetic attraction of ferrous chips and particles. 
     Although these coolant cleaning systems utilizing the force of gravity work reasonably well for larger sized chips and particles, there are several inherent problems involved in the practical application of such systems which have led the designers of such systems to also include additional filtration devices in their systems. 
     For coolant systems relying on the force of gravity to cause the chips and particles of waste material to settle out on the bottom of the dirty fluid reservoir, one inherent problem is that the flow rates of coolant demanded by modern machining processes do not allow the fluid to remain stagnant in the dirty fluid reservoir long enough for smaller chips and fine particles of waste material to settle out in the bottom of the tank. While it would seem at first glance that theoretically all particles of waste material would eventually settle to the bottom of the tank, given enough time, practical considerations such as limitations on floor space prevent system designers from providing dirty fluid reservoirs large enough for this to happen. For example, a coolant system required to provide 400 gallons per minute of coolant to a machine tool would need to have a dirty fluid reservoir capable of holding 2000 gallons of coolant in order to allow the coolant to remain in the reservoir for a period of five minutes before being re-circulated to the machine tool. In practice, a reservoir this large simply takes up too much floor space for most applications, and as a compromise, the dirty fluid reservoir capacity of many coolant cleaning systems is designed to hold only enough coolant for the coolant to remain in the reservoir a minute, or a minute and one half at the most, before being re-circulated. This means that the coolant in the reservoir is never really stagnant, but is actually flowing through the reservoir at a rate high enough to keep some finer particles suspended in the fluid. Swirling and churning of the fluid in the tank, caused by draw down of the circulation pump and the action of conveyors, hinge belts, and the like moving through the reservoir, increase the percentage of finer particles that remain suspended in the coolant. 
     Even if the coolant in the dirty fluid reservoir could remain relatively stagnant, other factors such as viscosity and surface tension of the coolant would cause a certain percentage of fine particles to remain suspended in the fluid rather than settling out. This is particularly true for finer particle of light metals such as aluminum or magnesium. For the tight tolerances required in some machining operations, even this small percentage of suspended fine particles must be removed by some sort of filtration beyond that provided by the force of gravity. 
     Coolant cleaning systems that utilize a hinge belt or inlet screen to catch and convey away the chips and particles of waste material as the fluid enters the reservoir, rather than allowing them to settle to the bottom for removal by a conveyor, also must deal with the problem of removing the finer particles suspended in the fluid. All of the factors described above in relation to coolant cleaning systems relying on settlement of waste material in the bottom of the dirty fluid reservoir that cause finer particles to remain suspended in the fluid, such as swirling or churning of the fluid, surface tension effects, etc., are also present in cleaning systems that utilize inlet screens or hinge belts to capture the larger chips and particles as they enter the reservoir and allow the fluid to drain through into the reservoir by the force of gravity. For these systems, as a practical matter, the mesh size of the inlet screen or the spaces that allow passage of the fluid through the belt must be large enough to allow the majority of the waste material to be removed at very high rates, given the large volume of waste material that must be dealt with as a result of the high speeds of modern machining operations. Stated another way, floor space considerations place practical limitations on the size and operating capacities of particulate matter removal and conveying devices, resulting in their being designed to allow the passage of finer suspended particles in order to handle the volume of larger chips and particles in the space available for the inlet screen or conveyor. 
     In one approach to providing additional filtration of the coolant fluid, U.S. Pat. No. 5,738,782, to Schafer et al, utilizes an edge mounted stationary filter in a partition between a preliminary cleaning area and a clean chamber of a sedimentation chamber, and a scraper type cleaning device mounted on the edge mounted filter for removal of impurities adhering to the filter. It is not likely, however, that the approach taught by Schafer would allow the high coolant volume flow rates required for many modern machining operations. 
     In the most commonly utilized approach to providing additional filtration of the coolant fluid, a drum filter rotatable about an axis of rotation of the drum is provided. The drum includes a generally cylindrical shaped screen on the outer periphery of the drum. The drum filter is positioned within the dirty fluid reservoir in such a manner that fluid with entrained or suspended particles flows into the drum through the cylindrical screen in a direction of flow oriented generally perpendicular to the axis of rotation of the drum. An opening is provided in an end wall of the drum, and a corresponding opening is provided in a wall of the dirty fluid reservoir, so that once the fluid has flowed into the drum through the cylindrical filter in a direction perpendicular the axis of rotation, the cleaned fluid inside the drum can change direction inside the drum and exit through the opening in the end wall of the drum and the corresponding opening in the wall of the dirty fluid reservoir in a direction generally parallel to the axis of rotation of the drum. A dynamic seal is generally provided in the dirty fluid reservoir between the end wall of the drum and the wall of the dirty fluid reservoir to prevent the dirty fluid from bypassing the drum filter, and to prevent the cleaned fluid exiting the end wall of the drum from re-entering the dirty fluid reservoir. Backwash nozzles for directing a spray of fluid or air either at or outward through the cylindrical screen are also generally provided to remove particulate matter adhering to the outside of the cylindrical screen. Typically the backwash nozzles are located inside the drum. The drum is generally rotated either by a drum sprocket attached to the outer periphery of the drum in such a manner that a portion of a chip conveyor chain or belt moving under or over the outer periphery of the drum engages the sprocket and turns the drum, or by a separate drive apparatus for the drum. 
     Coolant cleaning systems utilizing drum filters are disclosed in U.S. Pat. No. 5,849,183 to Ota et al; U.S. Pat. No. 5,603,846 to Uchiyama et al; U.S. Pat. No. 5,167,839 to Widmer II et al; U.S. Pat. No. 4,992,167 to Uchiyama; and U.S. Pat. No. 4,895,647 to Uchiyama. Ota et al &#39;183, and Uchiyama &#39;167 disclose a filtration apparatus using multiple drum filters in a single filtration apparatus to provide fractional filtration of the dirty coolant so that filtered coolant with varying degrees of cleanliness can be supplied to match the cleanliness requirements of various machining operations. 
     Although such drum filters have been used for many years in coolant cleaning systems for machine tools, their use is subject to a number of problems, and further improvement is needed. Specifically, drum filters and their associated back washing and support systems are difficult to manufacture and maintain, and inherently subject to damage from the interaction of particulate matter being moved by the conveyor and the circumferential screen on the drum. 
     Where a drum filter is driven from a drag chain passing below the drum, or runs in close proximity to such a drag chain, as taught by Uchiyama &#39;647 and &#39;167, and by Widmer &#39;839, the waste material being conveyed out of the dirty fluid reservoir by the conveyor must pass under drum in the small space formed by the close proximity between the drum&#39;s cylindrical screen and the bottom of the reservoir. A buildup of chips in this area frequently results in damaging the screen and jamming the conveyor. Clearing such a jam, and replacing a damaged cylindrical screen is not an easy task, due to the shape and location of the parts involved. Clearing a jammed conveyor or filter drum is especially difficult in scraper conveyors in many instances, because the scraper blades are angled with respect to the direction of chain movement in such a manner that makes it difficult to reverse the direction of the chain. 
     In most drum filter systems, the back washing nozzles are located inside the drum and spray coolant or air radially outward through the cylindrical screen to dislodge any particulate matter adhering to the outside of the screen. Getting fluid plumbing or air supply lines routed into the interior of the drum for connection to the back wash nozzles significantly complicates the design and manufacture of the drum. And if one of the back wash nozzles should become plugged, getting to the affected nozzle to unplug it may require a significant amount of disassembly, reassembly, and associated down time for the coolant system, to complete what should be a relatively simple repair operation. 
     Prior drum filter systems also typically have had to rely on a dynamic seal located in the dirty fluid reservoir, where the seal is exposed to the abrasive action of chips and particles of waste material floating in or passing through the dirty fluid. Seal life is thus reduced. Furthermore, should they become damaged, replacement of these dynamic seals typically involves a significant amount of disassembly, reassembly, possible removal of the drum, and associated down time for the coolant system, to replace the seal. 
     In systems where a drag chain or hinge belt passes over the outer periphery of the drum, such as those disclosed in Ota &#39;183, Uchiyama &#39;846 and Uchiyama &#39;647, it may also be necessary to disconnect the chain or hinge belt so that the drum can be removed to replace the screen, unplug the nozzles, or replace the seal, thereby complicating repair procedures even further. 
     Because a drag chain conveyor or hinge belt conveyor cannot pass through the cylindrical space occupied by the drum, the fluid depth in the dirty fluid reservoir must be greater than it otherwise would have to be if the drum were not there. As a result of this extra depth, such drum filter systems often require a greater depth of coolant, and a taller dirty fluid reservoir profile than would otherwise be required. This extra depth slows the rate at which chips and particles settle to the bottom of the reservoir, because they have a longer vertical path through the viscous and swirling coolant, thereby increasing the length of time for such chips, etc., to cause damage to the seal or the screen while they are suspended in the fluid. Although the extra volume of fluid resulting from this extra depth might seem to provide an advantage in that the settling time between re-circulation is lengthened, the longer settling times required for the fluid to reach the bottom of the reservoir more than negate any advantage that the extra coolant volume might otherwise provide. 
     In some drum filter applications, such as those taught by Ota &#39;183, Uchiyama &#39;846, and Uchiyama &#39;647, a drag chain wraps around a significant portion of the periphery of the drum and is used to drive the drum about its axis of rotation. In such applications, the side loads imposed by the chain on bearings supporting the drum during even normal operation are large, requiring the bearings and support structures to be more robust than they would otherwise have to be. And to allow for the possibility that the side loads will increase several fold, if the chain or the drum should become jammed, the bearings and support structure must be designed to be much larger than they otherwise would need to be. 
     It is an object of our invention, therefore, to provide an improved fluid cleaning method and system. Further objects of our invention include providing: 
     1) an improved filter apparatus and method for removing fine particles from coolant fluid used in machine tool operations; 
     2) an improved apparatus and method as in 1) above that can be readily retro-fifted into existing coolant fluid cleaning systems; 
     3) an improved filter apparatus that can be more readily manufactured and/or maintained and repaired than prior filters; 
     4) an improved filter apparatus that can be utilized to provide fractional cleaning of fluids; 
     5) an improved coolant fluid cleaning system for providing fractional cleaning of fluids; 
     6) an improved dynamic seal for rotatable filter assemblies 
     7) an improved coolant system having a lower profile than prior coolant fluid cleaning systems, thereby allowing the use of a system having a fine filter in machine tools, such as lathes, which have heretofore not been able to utilize prior coolant filtration apparatus; 
     8) an improved coolant fluid cleaning system requiring less floor space than prior systems; and 
     9) an improved coolant fluid cleaning system capable of simultaneously removing particulate matter located above, below and in between the upper and lower portions of a chip conveyor belt. 
     SUMMARY 
     Our invention provides such an improved coolant cleaning method, system, and apparatus, through the use of a filter disk assembly that defines and is rotatable about an axis of rotation of the disk, for removing particulate matter from a fluid flowing through the filter disk assembly in a direction substantially parallel to the axis of rotation of the filter disk assembly. 
     According to one aspect of our invention, an improved coolant cleaning system includes such a filter disk assembly, connected in fluid communication with an apparatus for circulating a flow of fluid through the filter disk assembly in a direction substantially parallel to the axis of rotation of the filter disk assembly. According to various embodiments of our invention, the filter disk assembly may include a generally planar filter screen having openings for passage of the fluid through the filter screen in a direction substantially parallel to the axis of rotation of the disk assembly. In various embodiments of our invention the apparatus for circulating a flow of fluid may include a dirty fluid reservoir, a conveyor for removing chips and particulate matter from the dirty fluid reservoir, a clean fluid reservoir, with the filter disk assembly providing the sole fluid communication path between the dirty and clean fluid reservoirs, and a fluid supply system having a pump for circulating fluid from the clean fluid reservoir through the disk filter assembly. 
     According to a second aspect of our invention, a coolant fluid cleaning system according to our invention may include several filter disk assemblies feeding into a single clean fluid reservoir to achieve high volume flow rates of clean fluid. Alternatively, a coolant fluid cleaning assembly according to another aspect of our invention may include several filter disk assemblies, having filter elements of increasingly finer mesh, feeding into several separate clean fluid reservoirs to provide fractionally filtered coolant fluid having varying degrees of cleanliness as required for various machining operations. 
     According to a third aspect of our invention, an array of back wash nozzles is provided to blast particulate matter clinging to the filter disk assembly back directly onto a hinge belt conveyor in the dirty fluid reservoir so that the conveyor may readily carry the particulate matter blasted loose from the filter disk to a waste material collection bin. Unlike prior coolant fluid cleaning systems wherein such nozzles were inconveniently located inside of a filter drum, however, the back wash nozzles of our invention are completely accessible and serviceable without disturbing either the filter disk or the hinge belt conveyor, so that the nozzles can be conveniently serviced if necessary. 
     According to another aspect of our invention, an improved two stage dynamic seal is provided for the filter disk assembly, having an elastomeric portion located in the clean fluid reservoir, rather than in the dirty fluid reservoir as in prior drum filter arrangements. 
     The generally discoidal shape of a filter disk according to our invention allows conveying devices, such as drag chains or hinge belts, to be routed through areas that would have been occupied by the cylindrical screen of the drum filters used in prior coolant fluid cleaning assemblies. This provides a number of advantages. The filter elements in our filter disk assemblies are far better protected inherently from wear, damage, and clogging or jamming than the cylindrical screens used in prior coolant fluid cleaning systems using drum type filters. The filter disk assemblies, dynamic seals, and backwash nozzles according to various aspects and embodiments of our invention can all be readily serviced and even replaced in a matter of a very few minutes without disturbing any conveying devices. Fluid depths in the dirty fluid reservoir can be lower than in prior cleaning systems using drum type filters. 
     In some embodiments of our invention, the height of the conveying device can also be significantly reduced in a manner allowing a coolant fluid cleaning system, including a filter disk assembly according to our invention for filtering out fine particulate matter, to be utilized with machine tools such as turning centers which have so little room available that it was previously not possible to conveniently provide a system having both a conveyor for particulate matter and a filter for fine particulate matter. 
     Either a filter disk assembly and/or a dynamic seal according to our invention is readily adaptable to existing coolant fluid cleaning systems that formerly had no fine filtering capability, or were originally equipped with drum type filters. According to one aspect of our invention, an adapter kit is provided to retrofit either the filter disk and/or the dynamic seal of our invention into existing coolant fluid cleaning systems. 
    
    
     These and other aspects, advantages, and novel features of our invention will be readily apparent upon consideration of the following drawings and detailed description of preferred embodiments. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a side view of a coolant fluid cleaning apparatus, according to our invention, for use with a machine tool; 
     FIG. 2 is a top view of the coolant fluid cleaning apparatus for a machine tool depicted in FIG. 1; 
     FIG. 3 is a sectional view of the coolant fluid cleaning apparatus depicted in FIG. 1, taken along line  3 — 3 , as shown in FIG. 1; 
     FIGS. 4 and 5 are partial sectional views of the coolant fluid cleaning apparatus depicted in FIG. 1, taken respectively along line  4 — 4 , and  5 — 5 , as shown in FIG. 3; 
     FIGS. 6 a ,  6   b , and  6   c , are depictions of alternate embodiments of coolant fluid cleaning systems according to our invention; 
     FIG. 7 is a sectional view of an alternate embodiment of a coolant fluid cleaning apparatus, according to our invention, having a dedicated drive system for a filter disk assembly of the coolant fluid cleaning apparatus; and 
     FIG. 8 is a partial sectional view of an embodiment of our invention wherein an improved dynamic seal, according to our invention, is utilized with a drum type filter. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1 and 2 illustrate an exemplary embodiment of our invention in the form of a coolant fluid cleaning system  10  for a machine tool, which is not shown . The coolant fluid cleaning system  10  includes a filter disk assembly  12  defining and journalled , as described in greater detail below, for rotation about an axis of rotation  14  of the filter disk assembly  12 . The coolant cleaning system  10  further includes fluid circulating means  16 , operably connected in fluid communication with the filter disk assembly  12 , for circulating a flow of fluid through the filter disk assembly  12  in a direction  18  substantially parallel to the axis of rotation  14  of the filter disk  12 . 
     The fluid circulating means  16  includes a first fluid reservoir, in the form of a conveyor housing  20  of a hinge belt conveyor  22 . The conveyor  22  includes an inlet hopper  24  for receiving and retaining a flow of coolant fluid containing entrained chips and particles of waste material, hereinafter referred to as “dirty fluid,” from a machine tool. The dirty fluid entering the hopper  24  falls onto a particulate matter conveying means, in the form of a hinge belt  26 . The larger chips and particulate matter in the dirty fluid are caught by the belt  26 , and the fluid with entrained finer particles passes through openings in the belt  26  into the conveyor housing  20 . The larger chips and particles are then conveyed by the hinge belt  26  and drive means, in the form of a motor  28  and drive train  30  to a point of discharge  32 , where the chips and particulate matter carried on the hinge belt  26  are discharged from the conveyor  22  into a chip collection bin  34 . 
     The fluid circulating means  16  further includes an “L-shaped” second fluid reservoir  36  for receiving and retaining coolant fluid, hereinafter referenced as the clean fluid, after it has passed through the disk filter assembly  12 . As best seen in FIGS. 1 and 2, the conveyor housing  20  rests partially within the L-shaped clean fluid reservoir  36 . The conveyor housing  20  is a welded, fluid-tight, assembly. A seal plate  40  attached to a sidewall of the conveyor housing  20  defines an outlet opening  38  from the conveyor housing  20  and a sealing surface  42 , which mates with the filter disk assembly  12  in a manner described in greater detail below, such that the only passage for fluid from the conveyor housing  20  into the clean fluid reservoir  36  is through the filter disk assembly  12 . 
     As shown in FIG. 3, the filter disk assembly  12  includes a frame  44 , fixedly attached by a set screw, not shown, and a locking collar  45  to a shaft  46  journalled in bearings  48 ,  50  attached to the conveyor housing  20  for rotation about the axis of rotation  14  of the filter disk assembly  12 . A filter element in the form of a screen  52  is clamped to the frame  44  of the filter disk assembly  12  using a clamping plate  54  and screws  56 , as shown in FIGS. 3 and 4. In the exemplary embodiment, the screen  52  is flat, and fabricated from a stainless steel material having a mesh size of 20 to 400, with a mesh of 50 to 80 being preferred for most machine tool applications. 
     The ability to utilize a flat screen in our invention provides several advantages in comparison to the cylindrical shaped filters of prior fluid cleaning systems. A flat filter is much easier to fabricate than a cylindrical filter. It is also possible to fabricate a flat filter of materials, such as brittle ceramics, that could not be formed into a cylinder. Those having skill in the art will recognize, however, that filter elements of other materials or having configurations other than absolutely flat—convoluted, or crowned, for example—may also be utilized with efficacy in practicing our invention, and are considered by the inventors to be within the scope of the claims of this invention. Those having skill in the art will also recognize that the mesh size will be dependent upon the flow rate and degree of removal of fine particles required for a given application. It should also be noted that the term “screen” as used herein is intended to also encompass non-woven filter elements of other types formed by drilling, or other processes, 
     The frame  44  includes an outer axially extending flange  58  which is configured to extend through and fit with only a small running clearance into the outlet opening  38  in the seal plate  40 , as shown in FIGS. 3 and 5. The close fit between this flange  58  and the opening  38  provides the first stage of sealing the interface between the outlet opening  38  and the filter disk  12 . The filter disk frame  44  also includes a radially extending annular sealing flange  60  attached to the outer periphery of the axially extending flange  58  for attachment of a compliant V-shaped dynamic seal  64  fabricated from an elastomeric material. When the filter disk assembly is clamped in place on the shaft  46 , the V-shaped seal  64  is clamped between the sealing flange  60  and the sealing surface  42  of the conveyor housing  20 , to thereby provide the second stage of a dynamic seal preventing dirty fluid from flowing past the filter disk assembly  12  into the clean fluid reservoir  36 . 
     Those having skill in the art will readily recognize the superiority of a dynamic seal according to our invention as compared to the seals used in prior coolant fluid systems. Our seal is located in the clean fluid reservoir, rather than in the dirty fluid reservoir as in prior drum type filter arrangements, and is thus inherently protected against abrasion and damage from chips and particles entrained in the dirty fluid. Furthermore, the tight fit between the annular flange  58  of the filter disk assembly  12  and the outlet  38  provides a first stage of sealing against chips and particles that is not present in the dynamic seals of prior drum type filtration systems. Those having skill in the art will also grasp the advantages in manufacturability and maintainability provided by having the filter disk assembly  12  located in the clean fluid reservoir  36  and attached to the shaft in a manner that allows the filter disk  12  to be easily and quickly removed for replacement of the V-shaped seal  64 . 
     As shown in FIG. 3, the seal plate  42  includes an upper flange  39  and a lower flange  40  extending outwardly therefrom in a direction away from the conveyor  22 . These flanges  39 , 40  serve to protect the V-shaped seal  64  and the filter disc  12  from being bumped or damaged when the conveyor  22  is being moved inside or outside of the clean fluid reservoir  36 . 
     As shown in FIG. 5, the frame  44  of the filter disk  12  is configured to provide large openings for the flow of fluid  18  in a substantially axial direction between spoke-like legs  66  joining the axially extending flange  58  to a central hub portion  68  of the frame  44 . Particle lifting fins  62  are attached to some of the legs  66  in such a manner that when the filter disk assembly  12  is attached to the shaft  44 , the lifting fins  62  extend into the dirty fluid reservoir to scoop up particulate matter that may have collected adjacent the screen  52  in the dirty fluid reservoir, and carry the scooped up particulate matter to the top of the outlet opening  38 . 
     As shown in FIGS. 3 and 2, the fluid cleaning system  10  further includes back washing means in the form of an array of nozzles  70 , a backwash supply pump  72 , and a backwash fluid supply circuit  74 . The nozzles  70  are mounted outboard of the filter disc assembly  12  and oriented to direct a spray of clean fluid back through the screen  52 , in order to blast any particulate matter adhering to the dirty fluid reservoir side of the screen  52 , and any particulate matter scooped up by the lifting fins  62  back onto the upper surface of the hinge belt  26  so that the particulate matter blasted from the screen  52  by the back wash nozzles  70  can be conveyed out of the dirty fluid reservoir  20  and deposited in the chip collection bin  34 . 
     As shown in FIGS. 1-3, a cover  76  is provided to help direct the fluid spray from the backwash nozzles  70 . The cover  76  is attached to the upper flange with screws  75 . The cover  76  also functions as the mounting bracket for the back wash nozzles  70 . A portion of the backwash fluid supply circuit  74  adjacent the nozzles is preferably fabricated of a flexible hose so that the cover  76  with the nozzles  70  connected can be quickly lifted off once the screws  75  are removed. 
     As shown in FIGS. 2 and 3, the exemplary embodiment of our invention depicted in FIGS. 1-5 includes a second filter disk assembly  78 , and a second array of backwash nozzles  70 , mounted on the left side of the conveyor housing  20 , to allow a higher flow rate of clean fluid to flow through the filter disk assemblies  12 , 78  from the common dirty fluid reservoir  20 . The construction details of the second filter disk assembly  78  and the second array of nozzles  70  are essentially identical to the corresponding parts of the first filter disk assembly  12  and the first array of nozzles  70 , except that in some instances the parts and orientation are mirror images of the corresponding parts and orientations described above. 
     As shown in FIG. 3, the coolant fluid cleaning system  10  includes drive means in the form of a drive sprocket  80 , and a guide roller  82  operably connecting the first and second filter disk assemblies  12 , 78  to the hinge belt  26  in such a manner that the conveyor drive train  30  and motor  28  rotatably drive the filter disk assemblies  12 , 78 . The drive sprocket  80  is fixedly attached by a set screw bearing on a key in the shaft  44  in such a manner that as the hinge belt  26  is pulled through the conveyor  22  by the drive motor  28 , the shaft  44  and both filter disk assemblies  12 , 78  are rotated about their common axis of rotation  14 . 
     Because the hinge belt  26  of our invention can be routed between the filter disk assemblies  12 , 78 , as shown in FIG. 3, rather than over and/or under the outer periphery of the drum filters used in prior filter systems, a coolant fluid cleaning system according to our invention provides several significant advantages over prior fluid cleaning systems. The filter disk assemblies  12 , 78  of our invention can be located lower in the dirty fluid reservoir  20  than would have been possible with a drum type filter. This allows the fluid level in the reservoir to be lower than it would have to be with a drum filter, resulting in a more compact design taking up less valuable floor space and being adaptable to use with more types of machine tools than prior systems using drum filters. Settling action in the dirty fluid reservoir is improved because, with the lower fluid level, it takes less time for particulate matter to reach the bottom of the reservoir. Placing the filter disk assemblies  12 , 78  lower in the dirty fluid reservoir  20  also increases the area of the outlet opening  38  below the fluid level, thereby improving the filtering efficiency of the filter disks. And, because the filter disk assemblies  12 , 78  can be located lower in the dirty fluid reservoir  20  with respect to the lower portion of the hinge belt  26  than would be the case with a drum type filter, head pressure available to drive the fluid through the screens  52  of the filter disk assemblies  12 , 78  is greater for a given fluid depth than could be achieved if the hinge belt  26  had to run under the outer periphery of the filter disk assemblies  12 , 78 , as it would have had to do with a drum type filter. 
     Furthermore, as shown in FIGS. 1 and 3, because the hinge belt  26  does not have to travel over or under the outer periphery of the disks  12 , 78 , it is possible to design the drive mechanism for the filter disks in such a manner that only a minimal amount of deviation in the path of the hinge belt  26  is required to engage and drive the drive sprocket  80 , and the guide roller  82 . Because there is little deviation in the path of the hinge belt  26  as it passes over the sprocket  80  and guide roller  82 , side loads imposed on the bearings  48 , 50 , the shaft  44 , and their associated support structure are minimal, allowing the use of smaller bearings, etc., than would have been required if the hinge belt  26  could not pass between the filter disk assemblies  12 , 78 . 
     In a preferred embodiment of our invention, a series of stiff cleats  83  are intermittently attached to and extend outward from approximately every eighth hinge flap of the hinge belt  26 , to facilitate conveying the chips and particulate material to the chip bin  34 . In addition, one or more of the cleats  83  is omitted and replaced with a thin flexible scraper blade  84 , attached to the hinge belt and configured to sweep along the bottom surface of the conveyor housing  20 . As the hinge belt  26  traverses the bottom of the conveyor housing  20 , these cleats  83  and the scraper  84  sweep any particulate matter that has settled in the bottom of the dirty fluid reservoir  20  along the bottom, up the end of the conveyor housing  20  and onto the top surface of the hinge belt  26  so that this particulate matter can be conveyed to the chip bin  34 . 
     These cleats  83  and scrapers  84  on the hinge belt  26 , in combination with the other aspects and features of our invention described above, provide a coolant fluid cleaning system  10  having the capability of simultaneously removing particulate matter located above, below, and between the upper and lower portions of the hinge belt  26 . To the best of the inventor&#39;s knowledge and belief, no prior coolant fluid cleaning system has the capability to do this. Chips and particles of waste material entering the hopper  24  entrained in dirty coolant fluid drained from the machine tool initially encounter the upper surface of the upper portion of the hinge belt  26 . All material that is too large to pass through the gaps between the hinge flaps of the hinge belt  26  is immediately conveyed to the chip bin  34 . The finer particulate matter that passes through the hinge belt  26  is filtered out by the filter disk assemblies  12 , 78  and lifted back above the belt by the lifting fins  62 , or by adhering to the dirty side of the screen  52 , and then blasted off of the screen  52  and/or lifting fin  62 , back onto the upper surface of the hinge belt  26 , by the back wash nozzles  70 , to be conveyed to the chip bin  34  by the hinge belt  26 . Any particulate matter that makes it all the way to the bottom of the dirty fluid reservoir  20  by settling, or somehow bypassing or being carried around on the hinge belt  26 , is swept back up to the top side of the hinge belt  26  and conveyed to the chip bin  34 . 
     From the foregoing description, those having skill in the art will readily recognize that a coolant fluid cleaning method, system, and apparatus according to our invention provide significant advances over prior coolant fluid cleaning method, system, and apparatus. Those skilled in the art will further recognize that although we have described the invention herein with respect to certain specific embodiments and applications thereof, many other embodiments and applications are possible within the scope of our invention as described in the appended claims. 
     For example, although the exemplary embodiment illustrated in FIG. 1 utilized two filter disk assemblies  12 , 78  having identical configurations arranged to provide parallel flow paths between a single dirty fluid reservoir and a single clean fluid reservoir, other combinations are possible and contemplated by the inventors within the scope of the foregoing description and the appended claims. As shown in FIG.  6   a , additional filter disk assemblies  86  could be utilized to increase the number of parallel flow paths available, and in combination with adjustments in the screen mesh, allow the rate of flow of clean coolant and the degree of cleanliness to be adjusted to suit a particular application of our invention. Alternatively, by utilizing screens  52  of different mesh in several filter disk assemblies feeding separate clean fluid reservoirs, fractional filtration can be provided from a single dirty fluid reservoir. 
     As shown in FIG. 6 b , the filter disk assemblies of our invention can be located at positions along the side walls of the conveyor other than the position illustrated in FIGS. 1 through 5. A filter disk assembly  12  according to our invention can also be located in an end wall of a conveyor, and other types of conveying devices, such as an auger, a scraper chain, or a continuous belt, can be used in place of the hinge belt conveyor. 
     As shown in FIG. 6 c , the filter disk assemblies of our invention can be utilized in conjunction with a low profile conveyor, by locating the filter disc assemblies in a sump  88  formed in the bottom wall of the conveyor housing  20 , to provide a coolant fluid cleaning device having both chip conveying and fluid filtering capability in a system suitable for use on machine tools, such as lathes, that have not previously been able to utilize a fluid filter because there was simply not enough space available to accommodate the larger conveyor and filter apparatus of prior systems utilizing drum filters. 
     We also contemplate embodiments of our invention in the form of a kit for retrofitting filter disk assemblies and/or the improved dynamic seals of our invention into existing fluid cleaning devices that were originally designed without a fine filter, or including a drum type filter. 
     For example, as shown in FIG. 3, if the conveyor  22  had been originally built without a fine filter, such a kit for retrofitting filter disk assemblies  12 , 78  according to our invention into the conveyor  22  would include: a pair of seal plates  42 ; the filter disk assemblies  12 , 78 ; the back wash means; and adapter drive means for operatively connecting the filter disks  12 , 78  to the conveyor housing  20  and the existing hinge belt conveyor  26 . The adaptor drive means would include a shaft  46 , a drive sprocket  80 , the guide roller  82 , a pair of bearing support brackets  90  such as those shown in FIG. 5, the bearings  48 , 50 , and the various locking collars set screws, spacers, and the like used to secure and operatively connect the various elements of the adaptor drive means to the filter disk assemblies  12 , 78 . To retrofit the filter disk assemblies  12 , 78  into the conveyor  22 , the bearing plates  42  and the bearing support brackets  90  would be attached to the conveyor housing  20 , by welding for instance, and holes would be cut in the conveyor housing  20  corresponding to the outlet openings  38  in the seal plates  42 . The remainder of the parts in the retrofit kit as defined above would then be installed as shown in FIG. 3 to complete the retrofit. If the conveyor  22  had originally been built with a drum filter, the retrofit process would be essentially the same, but the drum would be removed in the retrofit process. As shown in FIG. 7, the retrofit process could be simplified by providing in the retrofit kit a separate drive motor  96  for the filter disk assembly  12  mounted on a motor mount plate  98  attached to the conveyor housing  20 , so that the need to operatively connect the filter disk assembly  12  to the existing drive means in the conveyor is eliminated. 
     As shown in FIG. 8, we also contemplate that the improved dynamic seal of our invention could be adapted for use with a drum type filter  99 . A seal plate  42  having an outlet opening  38  is attached to the conveyor housing  20  in the same manner as described herein with regard to mounting a filter disk assembly according to our invention. A seal adapter housing  57  having an axially extending annular portion  58  closely matching the diameter of the outlet opening  38  is attached to the filter drum  99 . The seal adapter housing  57  further includes a radially extending annular sealing flange  60 , and a stub shaft  59  for mounting the drum  99  in bearing  50 , which is in turn mounted in a bearing support bracket  93  attached to the conveyor housing  20 . A V-seal  64  is attached to the radially extending flange  60  and in such a manner that when the drum  99  with the seal adapter housing  57  attached is mounted for rotation about the axis  14 , the V-seal is compressed to provide a fluid seal between the seal plate  42  and the radially extending annular flange  60  of the seal adapter housing  57 . This arrangement provides the same advantages in a drum filter of two stage sealing and locating the V-seal in the clean fluid reservoir that are provided by the practice of the improved seal of our invention with filter disk assemblies according to our invention. 
     We wish to expressly state that, although many of the exemplary embodiments described herein are directed to the practice of our invention in a coolant fluid cleaning apparatus or system for a machine tool, we contemplate many other applications of our invention in other types of fluid filtering systems. Specifically, we contemplate that these other applications might include but not be limited to water filtration equipment, filtering of water used with automatic floor cleaning or street sweeping materials, and filtering of fluids used in conjunction with cut-off saws, grinding machines, and fluid jet cutters. 
     It is understood, therefore, that the spirit and scope of the appended claims should not be limited to the specific embodiments described and depicted herein.