Abstract:
A parts washing method which utilizes a centrifugal filter to substantially reduce the need to replace its solvent. Solvent in a washing basin flows down a drain in the parts washing basin, through a screen to a centrifugal filter assembly, with a disposable filter in the filter receptacle of the centrifugal filter assembly. Thus the contaminated solvent flows from the drain, into a disposable filter element located in a spinning filter receptacle, where centrifugal force draws the solvent back into the solvent container while the materials washed from the part remain in the disposable filter element. The clean solvent is collected in a reservoir and recirculated back to the wash basin.

Description:
This application is a Divisional of U.S. patent application Ser. No. 08/783,692 filed on Jan. 15, 1997, which will issue as U.S. Pat. No. 5,954,071 Sep. 21, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of parts washing apparatus and particularly to a parts washing apparatus having a centrifugal filter to separate foreign waste elements from a cleaning solvent. 
     2. Background Art 
     Parts washers are widely used in industrial applications, and in particular, automotive service shops. The most familiar part washer can be found in almost any service station in the country. It is comprised of a sink with a spigot and a drain that sits upon a standard 45 gallon drum. The drum is partially filled with a parts washing solvent. The solvent is pumped from the drum, through the spigot, where it flows over the dirty part, into the sink&#39;s drain, from which it falls back into the drum. In this manner, the solvent continuously flows over the dirty part while the operator washes the part in the sink. 
     The problem with these conventional parts washers is that the foreign material washed from the dirty part flows into the drum along with the solvent. In many applications, the foreign material will be comprised of metal shavings, dirt, sand, grit, and oil particulates. Since much of this debris will remain suspended in the solvent while the pump is running, the pump is continuously subjected to substances that will damage its internal seals. Much of the background art in this area has addressed this particular problem by placing a filter upstream of the pump to strain the foreign debris from the solvent before it reaches the pump. For instance, in U.S. Pat. No. 4,056,114 Boutillete), the pump is surrounded by a filter element. U.S. Pat. No. 3,890,988 (Lee) teaches a pump mounted at the top of a truncated cone that rests at the bottom of a solvent tank. The cone is made from a screen that is intended to filter the solvent before it reaches the inlet of the pump. 
     In U.S. Pat. No. 3,378,019 (Riolo et al.) the patent teaches a paper filter located below the drain. The solvent flows through the filter with only the assistance of gravity. U.S. Pat. No. 5,522,814 (Olson) also teaches a gravity filter comprising a compartment filled with waste cotton located below the drain. U.S. Pat. No. 2,675,012 (Scales) notes that these types of gravity filters are quickly obstructed by the gunk and will not filter the solvent. Accordingly, Scales teaches a complex set of superposed sludge settling trays of successively decreasing diameters. U.S. Pat. No. 2,085,075 (Delano) teaches a portable crankcase flusher and cleaner that introduces, extracts, and filters cleaning fluid from the crankcase of an automobile using a complicated reversible one-way valve. 
     Trapping the gunk and the solvent together until the solvent drains from the filter, however, insures that the gunk will retain a substantial amount of the solvent. This wet waste material will eventually condense into a thick, gummy, oily substance, commonly referred to in the art as “gunk.” 
     The second major effect of the foreign matter flowing freely into the drum along with the solvent is that, as the foreign material settles to the bottom of the drum it will accumulate and condense into gunk. This gunk layer will eventually foul, and probably damage, the pump. In any case, the solvent in the drum will eventually be so full of gunk and suspended matter that it will have to be replaced and the old solvent disposed of. In the age before hazardous waste laws, this problem was addressed in the art by using plastic drum liners that would capture the solvent, the foreign materials, and the gunk so that they could all be disposed of together - - - , probably ending up in a landfill (assuming the liner made it that far without being punctured). This disposable liner concept is taught in U.S. Pat. No. 3,890,988 (Lee). U.S. Pat. No. 3,552,814 (Olson); U.S. Pat. No. 4,056,114 (Boutilette). 
     Contrary to a suggestion in the Lee patent, it is no longer possible to remove the gunk and solvent together in a plastic liner to be disposed of in a landfill or, for the matter, in the dirt behind the service station. The solvents used in parts washers are now classified as hazardous waste materials and are heavily regulated by both state and federal law. There are severe civil and criminal penalties for the improper disposal of the waste materials associated with these parts washers. Similarly, it is no longer practical to clean the gunk from the parts washers because the gunk still has to be disposed of as hazardous waste. 
     Because of the hazardous waste laws, a huge industry has developed to service parts washers. The 1995 annual report from the largest of these service providers reports reclaiming more than 210 million gallons of contaminated fluids and discloses revenues in this area are in excess of $240 million dollars per year. Servicing the parts washers usually means removing the sink from the drum, capping the used drum off, and transporting the used solvent and gunk contained in the drum to a reprocessing plant. Evidencing the major concern that the industry has over hazardous waste liability, this service provider also advertises that it indemnifies the customer against liability hazardous waste spills that may occur while the solvent is being transported. 
     SUMMARY OF THE INVENTION 
     The various patents described above all address the same problem—dealing with the separation and removal of the gunk and preventing it from damaging the pump. They also all share a common problem—there is no way to stop the formation of the paste-like gunk that clogs filters, destroys pumps, and lessens the useful life of the solvent. The parts washing apparatus of the present invention significantly reduces these problems, and the hazardous waste problems associated with parts washers, by materially reducing the formation of the gunk by reducing the foreign waste material that reaches the solvent tank. This is done by employing a centrifugal filter assembly between the drain of the parts washing basin and the solvent storage tank. In this position, the centrifugal filter removes most of the foreign particulate matter from the solvent before the solvent is returned to its storage container. More importantly, however, is that the centrifugal filter removes the foreign waste material from the solvent before it can condense into the paste-like gunk at the bottom of the solvent storage tank. Instead, the centrifugal action of the filter squeezes the solvent from the foreign waste materials while the foreign waste material is still a small part of the solvent stream. A purified solvent is returned to the container, while the mostly-dried foreign matter is retained in the filter. 
     In the preferred form, a secondary “screen” filter is used at the drain of the basin to capture larger foreign objects, including components that may fall off the part being washed. A tertiary filter is also preferably placed in communication with the solvent transfer means between the pump output and the solvent inlet to “polish” the solvent by removing any fine particles or oils that may remain suspended in the solvent before it reaches the parts washing basin. These three filtering means enable the solvent to be recirculated almost indefinitely while remaining mostly free of gunk formation. 
     It is important to note that most of the foreign material is captured by the primary centrifugal filter, the secondary screen filter, and tertiary polishing filter, leaving a relatively clean solvent for reuse. In particular, these filters solve the problems associated with gunk accumulating at the bottom of a tank. The centrifugal action of the primary centrifugal filter spins most of the solvent out of the foreign material, leaving behind a body of foreign materials captured in the filter that is almost dry. Instead of capping off the whole solvent drum and sending it for reprocessing, the only material that need be sent to a hazardous waste facility are the disposable filters and their contents, which can easily be placed in a canister the size of a coffee can. This means that shipping and waste disposal fees will be significantly less, the danger of a hazardous waste spill will be considerably reduced, and the cost of replacing the solvent will almost be eliminated for most applications. 
     The parts washer assembly of the present invention can either be constructed as a complete unit or, a retrofit embodiment of the present invention can be installed in existing parts washers to incorporate the design benefits taught herein. In its preferred embodiment, as a complete parts washer, the apparatus is comprised of a parts washing basin that rests upon a drum acting as a solvent reservoir. The washing basin has a safety hood that is designed to drop and smother a fire if the fusible link holding it up is melted by a fire. The washing basin also has a solvent transfer means, (which usually comprises a spigot, but can also be a movable hose,) an access hatch and a drain. The drain is located in the center of the access hatch and the access hatch provides access to a centrifugal filter. The centrifugal filter assembly is mounted below the drain of the parts washing basin with a mounting bracket. The centrifugal filter assembly comprises a filter receptacle is rotatably mounted on the mounting bracket using a sealed bearing. Operatively connected to the filter receptacle is a motor that also is mounted on the mounting bracket. A pump hangs from the mounting bracket by a pump support and is submerged in solvent that partially fills the drum. To remove and replace the filter element located in the filter receptacle, the access hatch is removed from the parts washing basin, exposing the filter receptacle for easy access to the filter element. The filter element is removed from the filter receptacle and stored as hazardous waste for recycling. A replacement filter element is then draped inside the filter receptacle, with its upper edge folded over the upper edge of the filter receptacle, where it is secured to the filter receptacle with a securing means. 
     In a retrofit embodiment, the mounting bracket, together with the motor and the filter receptacle are removably mounted to the underside of the sink portion of an existing parts washer. The open portion of the filter receptacle should be positioned directly below the existing drain in the sink. The existing pump, or a new one, can be suspended from the mounting bracket using the pump support described below. However, if the original mounting of the existing pump does not get in the way of the retrofit assembly, it may be left in place. In either case, it is preferable that the pump and the centrifugal filter motor be wired in parallel to a single switch  170 , so that both operate when the parts washer is turned on. Given the difficulty in retrofitting an access hatch in a existing steel parts washing basin, the hatch assembly will usually be omitted in a retrofit application. Therefore, it is important to mount the centrifugal filter assembly of the retrofit kit to the existing parts washing basin in a removable manner so that the centrifugal filter assembly may be lowered and the filter element in the filter receptacle replaced. Alternatively, most drains found in existing parts washing basins will be about four inches wide, which is usually enough room to reach in through the drain to remove and replace the filter element. A secondary and tertiary filter, as described herein, are also preferably included in the retrofit of an existing parts washer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side cross-section view of the preferred embodiment of the parts washing apparatus of the present invention. 
     FIG. 2 is an enlarged portion of FIG. 1 showing the centrifugal filter assembly and mounting bracket. 
     FIG. 3 is a plan view looking downwardly into the parts washing basin and showing the access hatch and the drain. 
     FIG. 4 is a plan view taken along line  4 — 4  in FIG. 1 looking downwardly through an access hatch in the parts washing basin and showing the mounting of the centrifugal filter assembly. Portions of the centrifugal filter assembly are omitted in order to show the mounting bracket in more detail. 
     FIG. 5 is a cross-section view taken along line  5 — 5  in FIG. 4 that omits most the details of the centrifugal filter assembly in order to more clearly show the preferred manner in which the mounting bracket is attached to the underside collar of the parts washing basin. 
     FIG. 6 is an isometric view of the filter element used in the filter receptacle of the centrifugal filter assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In overview, the parts washing apparatus  10  of the present invention, illustrated in FIG. 1, is comprised of a parts washing basin  12 , a solvent reservoir  14  upon which the parts washing basin  12  rests, a centrifugal filter assembly  16  mounted to the parts washing basin  12  below its drain  18  and inside the solvent reservoir  14 , and a solvent transfer means  20  to transport the solvent  26  from the solvent reservoir  14  to the parts washing basin  12 . Attached to a mounting bracket  27  of the centrifugal filter assembly  16 , and descending from it, is a pump  22  that has its inlet  24  submerged in solvent  26 , and its outlet  28  connected to the solvent transfer means. The solvent  26  is contained in the solvent reservoir  14 . 
     While the parts washing apparatus  10  is in use, the pump  22  pumps solvent  26  from the solvent reservoir  14 , through the solvent transfer means  20 , where it enters the parts washing basin  12  at a solvent inlet  30 . From the solvent inlet  30 , the solvent  26  flows over a part placed in the parts washing bin  12  or held under the inlet  30 . The solvent  26  is contaminated with foreign matter from the dirty part while the part is being washed. This contaminated solvent  26  flows from the parts washing basin  12 , through the drain  18 , into a spinning centrifugal filter receptacle  32 . The spinning action of the centrifugal filter receptacle  32  employs centrifugal force to drive the solvent through a disposable filter element  34 , after which the solvent  26  falls back into the solvent reservoir way, the recirculation of the solvent  26  in the parts washing apparatus  10  provides a continuous flow of filtered solvent to the parts washing basin  12  for the washing of dirty parts, while both drying and containing most the waste from the dirty part in the disposable filter element  34 . 
     The preferred embodiment of the present invention will now be described. The parts washing basin  12  has a sink portion  36  with an attached flexible spout  38  acting as an inlet  30  for the solvent  26  and a drain  18  acting as a solvent outlet  39 . In some situations, it may be more convenient for the flexible spout  38  to have a connection for a flexible hose, or merely to have a flexible hose substituted for it. The sink portion  36  has a sink bottom wall  40  and a circumferential sink side wall  42 . For convenience of description and referring to FIG. 3, the sink wall  42  has a front portion  44  generally nearest the user, a rear portion  46  generally away from the user, a right side portion  48 , a left side portion  50 , and a top edge portion  52 . The top edge portion  52  is blunted or rolled over  53  so as not to present any sharp edges to the user. The sink side wall portion  42  and the top edge portion  52  are usually formed integrally with the sink bottom  40 , but separate pieces may be attached to form the sink if easier or more cost effective. 
     Although the flash point of solvents used in parts washers is fairly high, it is still possible for the solvent to catch on fire. Primarily for this reason, the rear edge  54  of a hood  56  is attached by hinges  58  to the rear portion  46  of the sink side wall  42  (FIG.  1 ). A support pin  60  is attached to an upper interior edge portion  62  of the hood  56 . A fusible link  64  is rotatably attached to the support pin  60  on the hood  56  and then to a support piston  66 , which is then rotatably attached to a pin  67  mounted on the left sink side wall  50 . The fusible link  64  is designed to melt during a solvent fire, which disengages the support piston  66  or bracket and allows the hood  56  to fall and cover the parts washing basin  12 . This contains the fire and deprives it of the oxygen need for combustion. It is preferred to use a piston for the support because the hood  56  is not only used for fire prevention. During normal use, the support piston  66  assists in smoothly lifting the hood  56 , and also preventing the hood  56  from suddenly slamming shut. Of course, a hinged bracket of conventional design could be substituted for the piston. A work light  68  can be affixed to the hood  56  for the convenience of the user. 
     The sink bottom wall  40  has an underside portion  70  located opposite the side that is contained in the sink portion  36 . Attached to this sink underside portion  70 , surrounding the drain  18 , is a downwardly extending collar  72 . The collar  72  serves to position the parts washing basin  12  on the solvent reservoir  14 , to act as a splash guard for the solvent  26  while it is being centrifuged, and as mounting point for attachment of the centrifugal filter assembly  16  and pump  22 . The collar  72  has several laterally extending flanges  74  attached a couple of inches below the sink underside portion  70 . To assemble the parts washing apparatus  10 , the parts washing basin  12  is lowered from above the solvent reservoir  14  into it, inserting the collar  72  until the flanges  74  rest on the solvent reservoir  14 . The spacing between the underside  70  of the parts washing basin  12  and the flanges  74  forms an access portion  75  through which the transfer pipe  76  and any necessary electrical wiring (not shown) to drive the pump  22  and centrifugal filter assembly  16  are placed. 
     In the preferred embodiment, the solvent reservoir  14  is an industry standard forty-five gallon steel drum. However, any convenient container could be used as long as it is capable of storing solvent in a safe manner and will support the parts washing basin at a comfortable height for the user. 
     The centrifugal filter assembly  16  is best seen in FIG.  2 . The centrifugal filter assembly  16  is mounted to the collar  72  with a mounting bracket  27 , so that a filter receptacle  32  is positioned directly below the drain  18 . The centrifugal filter assembly  16  is comprised of a filter receptacle  32  with an open top end  80 , a perforated circumferential side wall  82 , and a base  84 . The filter receptacle  32  is preferably made from stainless steel, although other solvent resistant metals and plastics may also be used. The filter receptacle base  84  has an interior upward facing imperforate portion  86  that is surrounded by the filter side wall  82  and an exterior downward facing portion  88 . Attached to the downward facing portion is a circular mounting disk  89  that has a filter shaft  90  attached. If more convenient or economical in mass production, the circular mounting disk  89  can be omitted and the filter shaft  90  attached directly to the downward facing portion  88 . 
     The centrifugal filter assembly  16  is attached to the collar  72  on the underside  70  of the parts washing basin  12  using the mounting bracket  27  illustrated in FIGS. 4 and 5. The mounting bracket  27  is comprised of a longitudinal member  92  and a transverse member  94  that are attached to form a cross. A sealed motor  96  is mounted to one side the transverse member  94  with its shaft  98  extending through a hole  99  in the transverse member  94  (FIG.  2 ). The weight of the sealed motor  96  and the filter receptacle  32  are approximately equal so that their respective weights balance the transverse member  94  at its connection with the longitudinal member  92 . While it is desirable to have this balance to ease the attachment and removal of the mounting bracket  27  to the parts washing basin  12 , the balance of these parts is not necessary for the proper operation of the invention because the resiliency of the mounting bracket will properly position and support the centrifugal filter assembly  16  even though they may differ significantly in weight. A motor shaft pulley  100  is then attached near the end of the motor shaft  98 . On the opposite side of the transverse member  94 , a sealed bearing  104  is attached coaxial with another opening  105 . The filter shaft  90  is placed within the sealed bearing  104  located in the opening  105  in the transverse member  94 . A filter pulley  107  is attached to the end of the filter shaft  90 . The motor shaft pulley  100  and the filter shaft pulley  107  are interconnected with a belt  102  so that, when energized, the motor  96  will spin the filter receptacle  32  about an axis with a generally vertical orientation drawn outwardly from the interior cavity  109  of the filter receptacle  32 . Of course, the size of the pulleys  100 ,  107  and the rated speed of the motor  96  will control the rate of rotation of the filter receptacle  32 . The faster this rate of spin, the greater the centrifugal force that will be exerted on the solvent entering the filter receptacle. Preferably, the filter receptacle will spin at approximately 450 to 500 revolutions per minute. At this rate of spin, the solvent is separated from the foreign waste materials without propelling the solvent upwardly toward drain  18  or unnecessarily atomizing it. Since the filter receptacle  32  is positioned with the interior cavity  77  of the collar  72 , when the solvent  26  is forced through the filter element  34  and the perforated filter side wall  82  during operation of the parts washing apparatus  10 , the solvent will either drop directly into the solvent reservoir  14  or be deflected into the solvent reservoir  14  by the interior surface  73  of the collar  72 . 
     Returning to FIG. 1, the pump  22  is removably attached by a pump extension  108  to the longitudinal member  92  through a hole which can be positioned anywhere on the longitudinal member  92 , as long as the pump mounting extension  108  does not interfere with either the belt  102  or the pulleys  100 ,  105 . 
     In FIG. 5, the attachment of the mounting bracket  27  to the collar  72  is illustrated. A support member  110  is attached to either side of the longitudinal member  92  so that each of the support members  110  extends upwardly to a point where its upper end  111  is removably connected to a bracket  112  that has been attached to the collar  72 . It should be noted that slight modifications of the mounting bracket can be made by those skilled in the art to attach the centrifugal filter assembly  16  to many of the parts washers currently in use or on the market. These “adapted” mounting brackets are included with the remainder of the centrifugal filter assembly  16 , described above, as the primary components in a retrofit kit to transform existing parts washers into the present invention. Secondary filter means  136  and tertiary filter means  148  are also preferably included with the retrofit kit, but can be deleted if already included on the existing parts washer. 
     In the preferred embodiment, two design features enable the filter receptacle to more efficiently use centrifugal force to separate the solvent from the waste. The first modification helps retain the solvent inside the filter receptacle until centrifugal force draws it through the filter media and the perforated side walls. Referring to FIG. 2, this is done by slightly slanting the perforated side wall  82  in a frusto-conical configuration upwardly and inwardly from the base  84  to the open top end  80 . This upward and inward slant is preferably 12 to 14 degrees inwardly toward the vertical axis  106 . The second design feature employs a deflecting member  118  that has a top rounded center portion  119  and a downwardly extending skirt  121  that slants outwardly from the vertical axis  106 . The deflecting member  118  is attached to, or formed integrally from, the center  119  of the interior upward facing portion  86  of the base member  84 . The purpose of the deflecting member  118  is to direct the solvent outwardly toward the side wall  82  and away from the center  119  of the filter receptacle  32  where the centripetal acceleration approaches zero and the solvent is less likely to be affected by the corresponding centrifugal force. 
     During normal use, a disposable filter element  34  is draped inside the filter receptacle  32 . Referring to FIG. 6, the upper open portion  126  of the disposable filter element  34  contains a securing means  127  that is folded over the open top portion  126  of the filter receptacle  32 . The securing means  127 , for instance, can be a string or elastic fiber that is sown into a channel  129  on the upper portion  126  of the disposable filter element  34 . The lower closed portion  128  of the filter element drapes over the deflecting member  118 . Preferably, the disposable filter element  34  is approximately the same size as the interior  109  of the filter receptacle  32 , so that, when the filter receptacle  32  is spinning, the walls  130  of the disposable filter element  34  will cling to the filter side wall  82 . The disposable filter element  34  is preferably made from a fine mesh linen cloth, although other filter media would work, for instance, a heavy, permeable paper filter. The preferred embodiment of the invention presently uses a 100 micron mesh linen for its filter media. 
     Returning to FIG. 3, the removable filter element  34  is accessed for service through a hatch  132  positioned above the filter receptacle  32  in the bottom portion of the sink  36 . As shown in FIG. 3, the hatch  132  is circular and concentrically surrounds and includes the drain  18 . The hatch lies in a round opening in the sink bottom wall  40  that has a circumferential lip that is formed lower than the upper surface of the sink bottom wall  40  in order to contain the circular hatch  132  (FIG.  1 ). The hatch  132  can be secured to the sink  36  with one or more screws  138  or can just rest in the indentation  134 . A screen  142  usually covers the drain  18  and is particularly useful for keeping needed components of the part being washed from being flushed into the centrifugal filter assembly  16 . In FIG. 3, the screen  142  is in the form of a disk that rests inside a circumferential indentation  143  (FIG. 1) that surrounds the drain  18 . FIG. 2 shows another screen  144  that is formed into the shape of a cup and also rests in the circumferential indentation  143  that surrounding the drain  18 . The cup screen  144  has an upper lip portion  141  that is held in indentation  143 . It also has a bottom portion  145  with a contiguous circumferential side wall  147  that are both formed from a screen material that will retain relatively large pieces of foreign material that are washed from parts while passing the solvent and smaller foreign materials. Depending on the preference of the user, the disk configuration screen  142 , the cup configuration screen  144 , both, or neither, can be placed in the drain  18 . Together, the screens  142 ,  144 , comprise the secondary filter assembly  136 . 
     A tertiary filter assembly  148  used to polish the solvent before being introduced to the parts washing basin  12  can optionally be included. The tertiary filter assembly  148  is one of common design and comprises a filter housing  150 , a filter media  154  inside the filter housing, a filter cap  152  to seal the filter housing, an inlet  156  connected to the pump side  158  of the solvent transfer means  20 , and an outlet  160  connected to the spigot side  162  of the solvent transfer means  20 . The filter media usually takes the form of a filter cartridge comprised of a fan-folded permeable paper material, although many other filter media could be used. 
     As mentioned above, existing parts washers can be adapted to the present invention by using a retrofit fit kit comprising a centrifugal filter assembly  16  with a mounting bracket  27  specially adapted to mount the centrifugal filter assembly  16  to the existing parts washer. The retrofit kit also preferably includes the secondary filter assembly  136  and the tertiary filter assembly  148 . 
     An existing parts washer will typically have a parts washing basin  12 , a drain  18 , and a collar  72  that are similar to those illustrated in FIG.  1 . As in the present invention, the centrifugal filter assembly  16  is mounted below the drain  18  of the existing parts washer by connecting bracket  112  either to the collar  72  or to the underside portion  70  of the parts washing basin  12 . Generally, bracket  112  has two ends joined at an angle to each other with a first end  113  attached to the upper end  111  of the support member  110  and the second end having a hole to receive a mounting bolt extending from the existing parts washer. 
     To mount the centrifugal filter assembly  10  to collar  72 , for instance, the second end of bracket  112  could be specifically configured to align with a hole drilled in collar  72  by the retrofit installer. Bracket  112  is then bolted to collar  72  through these aligned holes. Similarly, bracket  112  could be rotated ninety degrees so that the second end of the bracket is substantially parallel to the sink bottom  40  and aligned with a hole drilled by the installer in the sink bottom  40 . Bracket  112  is then bolted to sink bottom  40 . A washer is placed around the mounting bolt passing through the sink bottom  40  and the bracket  112  to prevent solvent leakage through the hole. Bracket  112 , therefore, can be thought of as an adapter for mounting the centrifugal filter assembly  10  to the existing parts washer. By altering its shape to conform to the existing parts washer and its length to properly position the centrifugal filter assembly  10  below drain  18 , almost any existing parts washer could retrofitted to the present invention. Of course, bracket  112  could be omitted and the mounting bracket  27  could be specifically adapted for support member  110  to be attached to each type of existing parts washer. By altering the length of bracket  112 , support  110 , the transverse member  94  and the longitudinal member  92 , the centrifugal filter assembly can be properly positioned in almost all existing parts washers. In any case, the means of attachment preferably allows the centrifugal filter  10  assembly to be removed while replacing filter element  34 . 
     The pump  22  on the existing parts washer can be left in place if it does not obstruct the installation of the centrifugal filter assembly  10 . Otherwise, the pump  22  is removed and then suspended by pump mounting extension  108  from mounting bracket  27 , as is described above. The pump  22  and the motor  96  are electrically connected in parallel with the electrical wires passing through access  72 . To complete the retrofit, the secondary filter means  136  is placed in drain  18  and the tertiary filter is connected in series with the solvent transfer means  20 , in the same manner as is described above. 
     The ease of maintenance of the parts washing apparatus  10  is one of the primary design benefits resulting from the teaching of this application. To clean the apparatus  10 , the user first removes the disk screen  142  and/or the cup screen  144  from the drain  18 . The user then removes the hatch  132  from the bottom portion of the sink portion  36 , exposing the filter receptacle  32  and the disposable filter media  34 . At this point, the user can dump the contents of the screens  142 ,  144  into the disposable filter element  34 , or the user can do the same after the disposable filter element  34  is removed. If necessary, the securing means of the disposable filter element  34  is loosened and the disposable filter element  34  is lifted from the filter receptacle  32 . Because of the centrifugal force placed on the disposable filter  34  element during its use, the disposable filter element  34  and its contents should be mostly free of solvent. The used disposable filter element  34  is then placed in a container to be processed by a solvent service provider. The disposable filter media in the tertiary filter  148  can also be removed at this time and placed in the reprocessing container. The user then replaces the disposable filter element from the tertiary filter  148  in the filter receptacle, re-installs the hatch  132  and replaces screens  142 ,  144 . If the tertiary filter  148  has been serviced, a new disposable filter element is placed in the tertiary filter  148  and the cap  152  replaced. 
     The entire service procedure on the parts washing apparatus  10  can be accomplished in a few minutes. The hazardous waste products removed from the system are all contained in the disposable filter element  34  and the disposable filter element of the tertiary filter assembly  148 . This relatively small volume of hazardous waste material is sealed in a small and light container that is mostly free of solvent and that can easily and safely be transported to a hazardous waste processing plant. The solvent  26  remains relatively free of contaminants and may be re-used for a much greater length of time than is now possible under the state of the art. 
     While this invention has been described in terms of a preferred embodiment, it is contemplated that persons reading the preceding description and studying the drawing will realize various alterations, permutations and modifications thereof. It is therefore intended that the following appended claims be interpreted as including all such alterations and modifications as fall within the true spirit and scope of the present invention.