Abstract:
A system and method for separating free oil from industrial coolant comprises directing said fee oil and coolant through a coalescing cartridge having a plurality of polymeric elements therein into a tank having a plurality of settling chambers. Free oil is removed from the coolant through oleophilic attraction between the free oil and the surface of the polymeric elements. Free oil remaining in the coolant is further separated from therefrom through Gravitational separation. A plurality of weirs and baffles interposed between the settling chambers provide continuous return of purified coolant to the system and periodic decanting of separated free oil.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. application Ser. No. 09/076,953 filed on May 13, 1998, now U.S. Pat. No. 5,989,415, which is a continuation-in-part of U.S. application Ser. No. 08/784,084, now U.S. Pat. No. 5,795,478, filed on Jan. 15, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to liquid purification systems and more particularly to a system and method for removing free oil from coolant utilized in industrial machining applications. 
     Industrial machining operations generally require the use of coolants to prevent damage to tools and minimize wear caused by excessive heat. Typically, a coolant comprises an oil-in-water emulsion wherein water is the continuous phase, oil is the disperse phase, and soap is the emulsifying agent. 
     The oil-in-water emulsion is stabilized by electro-mechanical forces which are weakened or destroyed by contaminants in the form of metallic ions, free oil and bacterial action. The primary culprit in coolant deterioration is free or “tramp” oil which must be removed to maintain the stability and equilibrium of the emulsion. 
     SUMMARY OF THE INVENTION 
     The aforesaid problem is solved, in accordance with a preferred constructed embodiment of the pre sent invention, by an improved free oil separation system and method that removes free oil from an oil-in-water emulsion. The oil separation system is disposed downstream of the machining process to accept contaminated coolant produced during the machining operation. 
     The oil separation system and method of the present invention comprises a plurality of spaced polymeric elements, for example polypropylene tubes, that are positioned above a primary settling chamber. Contaminated coolant flows through the elements without restriction. Oleophilic surface attraction between the polymeric elements and free oil in the coolant attracts and binds the free oil to the walls of the vertically oriented elements where further coalescing of the free oil occurs. The coolant and coalesced oil globules then flow out of the polymeric elements and into a primary settling chamber where gravitational separation of the free oil from the coolant occurs. 
     Coalesced free oil globules rise upwardly, passing over a primary oil weir and into a secondary settling chamber. Partially cleansed processing fluid is directed beneath a primary coolant baffle thence over a primary coolant weir where free oil again rises and flows into the secondary settling chamber. A primary decant chamber, separated from the secondary settling chamber by a decant chamber wall, is provided with an outlet conduit to allow purified coolant to flow back to the system. Once in the secondary settling chamber, partially cleansed coolant flows over a secondary fluid weir where a second outlet conduit which is opened and closed by a normally open outlet valve is provided to return the remaining purified coolant to the system. 
     Free oil decanting is accomplished by closing the normally open outlet valve until the coolant and free oil level in the secondary settling chamber rises to the level required to allow free oil on the surface thereof to flow over a waste oil weir into a waste oil chamber. The waste oil chamber is provided with a waste oil conduit that allows for decanting of free oil. The waste oil chamber is further provided with a bottom that prevents separated free oil that flows over the waste oil weir from draining back into the secondary settling chamber. 
     The aforesaid operation is controlled by a timer that provides for a predetermined waste oil removal period during which the normally open outlet valve is energized closed thereby raising the free oil and coolant level in the secondary settling chamber to allow free oil to flow over the waste oil weir for decanting. By adjusting a fluid inlet valve that controls coolant and free oil flow into the inlet plenum, flow through the separator may be limited such that the total flow through the secondary settling chamber is five to ten percent of the total flow through the entire system. 
     This flow limitation allows for maximum efficiency in free oil separation and decanting. Furthermore, the use of flow limited multistage gravitational separation eliminates the necessity of employing a surface skimmer to remove free oil from the surface of the oil-in-water emulsion. Known in the art surface skimmers often suffer from the disadvantage that they remove large quantities of coolant mixture from the system, in addition to surface resident free oil, thereby providing for inefficient separation of free oil from coolant. 
     Therefore, one object of the instant invention is to provide an oil separation system and method that collects and decants a greater concentration of waste oil than known oil separators. 
     A further object of the present invention is to provide an oil separation system and method that decants waste oil without employing inefficient surface skimmers. 
     Further objects, features and advantages of the instant invention will be readily apparent from the following detailed description thereof with reference to the accompanying drawing Figures and claims appended hereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional elevational view of a preferred constructed embodiment of the present invention. 
     FIG. 2 is a view of the present invention taken along the line  2 — 2  of FIG.  1 . 
     FIG. 3 is a view of the instant invention taken in the direction of the arrow  3  of FIG.  1 . 
     FIG. 4 is a sectional elevational view of the present invention showing only the flow of separated oil through the system. 
     FIG. 5 is a view of the present invention taken along the line  5 — 5  of FIG.  4 . 
     FIG. 6 is a sectional elevational view of an alternative embodiment of the invention showing a coalescing cartridge disposed within an inlet plenum. 
     FIG. 7 is a view of an alternative embodiment of the present invention taken along the line  7 — 7  of FIG.  6 . 
     FIG. 8 is a view of an alternative embodiment of the present invention taken in the direction of the arrow  8  of FIG.  6 . 
     FIG. 9 is a sectional elevational view of an alternative embodiment of the present invention showing only the flow of separated oil through the system. 
     FIG. 10 is a view of an alternative embodiment of the present invention taken along the line  10 — 10  of FIG.  9 . 
     FIG. 11 is an electrical schematic of a control circuit for the solenoid valves utilized in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIGS. 1,  2 , and  3 , a system and method for separating free oil from industrial coolant comprises an oil coalescing cartridge  10  for acceptance of free oil and coolant through an inlet conduit  12 . The inlet conduit  12  is provided with an inlet valve  14  which may be utilized to adjust the total oil and coolant flow into the separator. The oil coalescing cartridge  10  is comprised of spaced polymeric elements  16  positioned proximate a primary settling chamber  20  such that the entering oil and coolant mixture pass through the cartridge  10  and into the settling chamber  20 . In a preferred constructed embodiment of the present invention the oil coalescing cartridge  10  is comprised of a plurality of polymeric elements  16 , for example high-density polyethylene tubes 4 to 5 feet in length, arranged vertically above the primary settling chamber  20 . 
     In an alternative embodiment of the instant invention shown in FIGS. 6,  8  and  9 , the primary settling chamber  20  is further provided with an intake plenum  18  that is separated from the primary settling chamber  20  by an inlet weir  22  extending upwardly from the bottom of the intake plenum  10  and an inlet baffle  24  extending downwardly from the top of the settling chamber  20 . The coalescing cartridge  10  is then positioned within the intake plenum  18  such that the entering oil and coolant pass downwardly through the cartridge  10  and into the inlet plenum  18 . The inlet weir  22  then directs the oil and coolant upwardly from the bottom of the intake plenum  10  towards the inlet baffle  24 . The inlet baffle  24  then directs the fluid flow downwardly into the primary settling chamber  20 . 
     As seen in FIGS. 1 and 3, a secondary settling chamber  30  is separated from the primary settling chamber  20  by a primary coolant baffle  32  extending downwardly from the top of the primary settling chamber  20 , a primary coolant weir  34  extending upwardly from the bottom of the secondary settling chamber  30  and a decant chamber wall  36 , also extending upwardly from the bottom of the secondary settling chamber  30 . Primary coolant weir  34  and decant chamber wall  36  depend from a first wall of the secondary settling chamber  30  to define a primary decant chamber  38 . The primary coolant baffle  32  directs coolant upwardly from the primary settling chamber  20 , over the top of primary coolant weir  34  and into primary decant chamber  38 . The primary decant chamber  38  is provided with a conduit  40  for withdrawing purified coolant continuously therefrom. 
     In accordance with the preferred constructed embodiment of the instant invention and as shown in FIGS. 1 and 3, a secondary coolant weir  50  abuts the decant chamber wall  36  on a first side and a secondary coolant chamber wall  56  on a second side. The secondary coolant chamber wall  56  depends from the first wall of the secondary settling chamber  30  and abuts the secondary coolant weir  50  on one side. A secondary decant chamber  58  is bounded by secondary coolant chamber wall  56 , secondary coolant weir  50 , decant chamber wall  36 , and the first wall of the secondary settling chamber  30 . Furthermore, the secondary decant chamber  58  is provided with an outlet conduit  52  that is opened and closed by a normally open solenoid valve  54  for releasing purified coolant back to the system. The normally open valve  54  is solenoid actuated in an alternative embodiment of the instant invention. 
     As best seen in FIGS. 2 and 3, secondary coolant baffle  60  is positioned between decant chamber wall  36  and secondary coolant chamber wall  56 , parallel to secondary coolant weir  50 . The secondary coolant baffle  60  is spaced from the bottom of the secondary settling chamber  30  such that purified coolant flows from secondary settling chamber  30  under the secondary coolant baffle  60  thence over secondary coolant weir  50  into secondary decant chamber  58  prior to returning to the system through conduit  52 . The secondary decant chamber  58  is further provided with a bottom  62  that prevents purified coolant from flowing back into the secondary settling chamber  30 . 
     In a preferred constructed embodiment of the instant invention and in accordance with FIGS. 3 and 4, a primary oil weir  70  is interposed between the primary settling chamber  20  and the secondary settling chamber  30  adjacent to the primary fluid baffle  32 . The primary oil weir  70  separates the primary settling chamber  20  from the secondary settling chamber  30  such that coalesced free oil on the surface of the coolant in the primary settling chamber  20  passes over the primary oil weir  70  and into the secondary settling chamber  30 . 
     As shown in FIGS. 3,  4  and  5 , a waste oil weir  80  is disposed within secondary settling chamber  30  adjacent to the secondary coolant weir  50  such that free oil floating on the surface of the coolant in secondary settling chamber  30  flows up and over waste oil weir  80  when the level in the secondary settling chamber  30  is sufficiently high. For reasons explained hereinbelow, the top of the waste oil weir  80  must be higher than the top of secondary coolant weir  50  such that coolant will flow over secondary fluid weir  50  prior to reaching the top of waste oil weir  80 . The waste oil weir  80  depends from a waste oil bottom  88  that prevents free oil flowing over the waste oil weir  80  from flowing back into the secondary settling chamber  30 . A waste oil chamber  82  is bounded by the waste oil weir  80 , the secondary coolant chamber wall  56 , the waste oil bottom  88 , and first and second walls of the secondary settling chamber  30 . The waste oil chamber  82  is further provided with a waste oil conduit  84  that allows free oil to be decanted at timed intervals as explained hereinbelow. 
     In an alternative embodiment of the instant invention as shown in FIGS. 9 and 10, the waste oil conduit  84  is opened and closed by a normally closed solenoid actuated valve  86  for oil decanting at timed intervals. 
     As shown in FIG. 11 both the normally open valve  54  and the normally closed valve  86  utilized in the alternative embodiment of the present invention are actuated by a timer  90  that energizes the solenoid valves for predetermined time intervals. The timer duration may be selected to maximize separator efficiency while providing for regular decanting of free oil collected in the waste oil chamber  82  depending on the concentration of free oil in the coolant and the flow rate through the system. In one embodiment of the present invention the timer may be activated or deactivated by a conventional pushbutton  92 , or alternatively, by any switching means, when free oil decanting is desired. 
     Operation of the oil separation system begins when oil-contaminated coolant supplied through the intake conduit  12  passes through the oil coalescing cartridge  10  into the primary settling chamber  20 . Alternatively, and in accordance with the alternative embodiment of the present invention as shown in FIG. 6, the oil and coolant supplied through the intake conduit pass downwardly through the oil coalescing cartridge  10  and into the intake plenum  18 . The oil and coolant are directed upwardly by the inlet weir  22  and then downwardly into the primary settling chamber  20  by the inlet baffle  24 . The inlet baffle  24  minimizes flow turbulence caused by flow through the coalescing cartridge  10  and distributes oil and coolant flow evenly through the primary settling chamber  20 . 
     In the primary settling chamber  20  the lighter coalesced oil rises to the top of the oil and coolant mixture and the denser coolant settles to the bottom thereof. The primary coolant baffle  32  then directs the partially cleansed coolant into the primary decant chamber  38  defined by primary coolant weir  34  and decant chamber wall  36  where it flows back to the coolant system through the conduit  40 . Referring to the flow of separated, free oil through the system depicted in FIG. 9, the coalesced oil on the surface of the primary settling chamber  20  passes over the primary oil weir  70  and into the secondary settling chamber  30 . In order to assure complete separation of the free oil from the coolant, inlet flow may be limited by adjustment of the inlet valve  14  such that the oil-contaminated coolant resides in the primary settling chamber  20  for ten to twenty minutes before flowing back into the system. 
     The remaining coolant in the secondary settling chamber  30  is allowed to settle to the bottom of the chamber  30  and is then directed downwardly by the secondary coolant baffle  60  over the secondary coolant weir  50 , and into secondary coolant chamber  58 . The outlet conduit  42  and the normally open valve  44  allow the purified coolant to flow back into the system. In one embodiment of the instant invention the amount of flow out of the secondary coolant chamber  58  is in the range of 5 to 10 percent of the total flow through the separation system. Therefore, the flow out of the primary decant chamber  38  is 90 to 95 percent of the total flow through the system. 
     Free oil collects on the surface of the coolant in the secondary settling chamber  30  until the timer  90  times out, thereby initiating free oil decanting. Timer  90  is initiated at preset time intervals to actuate the normally open valve  54 . When the normally open valve  54  is actuated it closes, thereby terminating the flow of coolant out of the secondary coolant chamber  58  and causing the level of coolant, and oil on the surface thereof, in the secondary settling chamber  30  to rise. When this oil and coolant level in the secondary settling chamber  30  reaches the top of the waste oil weir  80 , the free oil collected on the surface of the coolant passes over the waste oil weir  80  thence into the waste oil chamber  82  and out of the system through the waste oil conduit  84 . 
     In accordance with the alternative embodiment of the instant invention as shown in FIGS. 9 and 10, upon initiation of the timer  90  at its preset time interval the normally closed valve  86  is energized to the open position and thus free oil is decanted from the chamber  82  through the waste oil conduit  84 . The timer  90  duration is adjustable depending on the amount of free oil to be decanted. The normally closed valve  86  prevents inadvertent decanting from the waste oil chamber  82  until decanting is desired. Additionally, pushbutton  92  may remove electrical power from timer  90 , thereby terminating the timed operation of the solenoid actuated valves for purposes of maintenance or manual decanting of free oil. 
     Although the preferred embodiments of the instant invention have been disclosed in detail, it will be appreciated by one of ordinary skill in the art that the various structural and operational features herein disclosed are susceptible to modification without departing from the scope of the following claims.