Patent Publication Number: US-2011062064-A1

Title: Filtration device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation Application of PCT Application No. PCT/JP2009/062744, filed Jul. 14, 2009, which was published under PCT Article 21(2) in Japanese. 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2008-198077, filed Jul. 31, 2008, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a filtration device for filtering a fluid containing matter to be removed, such as fine particles. 
     2. Description of the Related Art 
     A machine tool for precision machining, for example, uses a fluid such as a coolant for lubricating or cooling a part being machined. As the workpiece is machined, fine particles such as swarf, carbon, etc., as well as chips, become mixed in the fluid of this type, so that the fluid is gradually tainted and inevitably becomes contaminated. A filtration device is used to filter such a contaminated fluid. In a filtration device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-77479 (Patent Document 1), for example, chips produced by a machine tool are used as a filter medium. 
     The filtration device of Patent Document 1 described above captures magnetic impurities in the fluid by magnetizing the filter medium formed of chips by means of a solenoid. Since chips are used as the filter medium, however, the filtration precision varies considerably. Since the surfaces of the chips used as the filter medium are very rough, moreover, it is difficult to wash the filter medium in order to recover the filtration capability when the filtration capability is reduced. Thus, there is a problem that the chips as the filter medium need to be replaced frequently. 
     The inventor hereof has developed a filtration device that uses a large number of easily washable, spherical magnetic metal balls, such as steel balls, as a filter medium. In this filtration device, these magnetic metal balls are caused to attract and immobilize one another by means of a magnet. This filtration device is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2007-105706 (Patent Document 2). This filtration device has high filtration precision and its filter medium can be washed with ease. 
     A filter medium unit of the filtration device using the magnetic metal balls comprises a filter medium accommodation case and a large number of magnetic metal balls contained in the filter medium accommodation case. If the filter medium unit is contaminated to a certain degree, the magnetic metal balls of the filter medium unit need to be cleaned. In the filtration device described in Patent Document 2, a fluid (clean fluid) collected above the magnetic metal balls is poured toward a processing tank between the magnetic metal balls in a cleaning process. The magnetic metal balls are cleaned by this clean fluid. Sludge and the like contained in the fluid poured into the processing tank are removed by a processor such as a separator. In some cases, however, the magnetic metal balls may not be able to be fully cleaned by only pouring the fluid collected above the magnetic metal balls, so that there is room for further improvement in cleaning effect. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, the object of the present invention is to provide a filtration device in which magnetic metal balls can be fully cleaned in a cleaning process. 
     A filtration device of the present invention comprises a filter tank into which a fluid to be filtered is introduced, a filter medium unit contained in the filter tank, and a magnet unit which applies a magnetic field to the filter medium unit, the filter medium unit comprising a filter medium accommodation case and a large number of magnetic filter medium granules of a magnetic material contained in the filter medium accommodation case, the magnet unit comprising a magnet movable with respect to the filter medium unit between a first position and a second position and configured to apply the magnetic field to the magnetic filter medium granules, thereby causing the magnetic filter medium granules to magnetically attract and immobilize one another, when in the first position and to cancel the magnetic attraction between the magnetic filter medium granules when in the second position, the filtration device further comprising fluid supply means configured to pass the unfiltered fluid located below the magnetic filter medium granules to above the magnetic filter medium granules through the magnetic filter medium granules as the fluid in the filter tank is filtered, fluid discharge means configured to pour the filtered clean fluid located above the magnetic filter medium granules to below the magnetic filter medium granules through the magnetic filter medium granules as the magnetic filter medium granules are cleaned, and a submerged air discharging mechanism located above the magnetic filter medium granules and configured to downwardly eject air into the clean fluid above the magnetic filter medium granules, thereby urging the clean fluid toward the magnetic filter medium granules and introducing air bubbles into the clean fluid, as the magnetic filter medium granules are cleaned. 
     In the cleaning process for the magnetic filter medium granules, according to this structure, air is ejected into the filtered clean fluid located above the magnetic filter medium granules and toward the magnetic filter medium granules. As the clean fluid urged by the ejected air flows down between the magnetic filter medium granules, the magnetic filter medium granules can be effectively and thoroughly cleaned. Since the filtration capability is recovered in this way, high filtration accuracy can be obtained in a filtration process. 
     A preferred embodiment of the present invention further comprises auxiliary air supply means configured to apply an air pressure higher than the atmospheric pressure to the surface of the fluid above the magnetic filter medium granules when the magnetic filter medium granules are cleaned, thereby driving the fluid toward the magnetic filter medium granules. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a longitudinal sectional view of a filtration device according to one embodiment of the present invention; 
         FIG. 2  is a longitudinal sectional view of the filtration device taken along line F 2 -F 2  in  FIG. 1 ; 
         FIG. 3  is a sectional view enlargedly showing a part of a filter medium unit of the filtration device shown in  FIG. 1 ; 
         FIG. 4  is a side view showing a filtration operation of magnetic filter medium granules of the filtration device shown in  FIG. 1 ; 
         FIG. 5  is a longitudinal sectional view of the filtration device shown in  FIG. 1  with its magnets raised; 
         FIG. 6  is a sectional view typically showing a state in which filtration equipment with the filtration device shown in  FIG. 1  is operated for filtration; and 
         FIG. 7  is a sectional view typically showing a state in which the filtration equipment with the filtration device shown in  FIG. 1  is operated for cleaning. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One embodiment of the present invention will now be described with reference to  FIGS. 1 to 7 . 
     A filtration device  10  shown in  FIG. 1  comprises a filter tank  11 , filter medium units  12 , and magnet units  13 . A fluid to be filtered is introduced into the filter tank  11 . The filter medium units  12  are contained in the filter tank  11 . The magnet units  13  apply a magnetic field to the filter medium units  12 . The material of the filter tank  11  is a magnetic material, such as a ferrous metal. A cover housing  14  is disposed on top of the filter tank  11 . A dirty chamber  15  and clean chamber  16  are defined in the filter tank  11 . An unfiltered fluid Q 1  is contained in the dirty chamber  15 . A filtered clean fluid Q 2  is contained in the clean chamber  16 . 
     The dirty chamber  15  is located below the filter medium units  12 . The clean chamber  16  is located above the filter medium units  12 . The top of the clean chamber  16  is airtightly closed by a partition wall  17 . Magnet chambers  18  are defined below the partition wall  17 . The magnet chambers  18  extend vertically. Magnets  19  are contained in the magnet chambers  18 , individually. 
     A contaminated fluid inlet  20  that opens into the dirty chamber  15  is formed in a lower part of the filter tank  11 . A contaminated fluid that contains fine particles to be filtered is introduced into the dirty chamber  15  through the contaminated fluid inlet  20 . A clean fluid outlet  21  that opens into the clean chamber  16  is formed in an upper part of the filter tank  11 . 
     As shown in  FIG. 2 , a clean fluid pipe  22  is connected to the clean fluid outlet  21 . The clean fluid pipe  22  is connected with an air supply pipe  24 . The air supply pipe  24  is provided with an air valve  23  for use as atmospheric pressure releasing means. The clean chamber  16  can be opened to the atmosphere by opening the air valve  23 . A drain port  26  is provided at the bottom of the filter tank  11 , that is, at the bottom of the dirty chamber  15 . The drain port  26  comprises a drain valve  25 . 
     Preferably, a compressed air supply source  27  is connected to the air supply pipe  24 . The air supply source  27  can feed compressed air into the clean chamber  16  in the upper part of the filter tank  11 . The air valve  23 , air supply pipe  24 , and compressed air supply source  27  function as auxiliary air supply means  28 . 
     As shown in  FIG. 3 , the filter medium unit  12  comprises a filter medium accommodation case  30  and a large number of spherical, magnetic filter medium granules  31 . These magnetic filter medium granules  31  are contained in the filter medium accommodation case  30 . For example, the magnetic filter medium granules  31  are metal balls of a magnetic material, such as iron. These magnetic filter medium granules  31  attract one another in the manner shown in  FIG. 4  when subjected to a magnetic field. In a free state without application of any magnetic field, magnetic attraction is canceled, so that the magnetic filter medium granules  31  can move relative to one another to some extent. The surfaces of the magnetic filter medium granules  31 , like those of ball bearings, are shaped so as to be smooth and easily washable. 
     The respective diameters of all the magnetic filter medium granules  31  that are contained in the filter medium accommodation case  30  are equal to one another. Alternatively, a plurality of types of magnetic filter medium granules  31  with different diameters may be mixed with one another. Further, magnetic filter medium granules of a shape other than the spherical shape may be used. In short, the magnetic filter medium granules  31  should only be formed of a magnetic material, so that they may be of any shape. The magnetic filter medium granules  31  of the magnetic material attract one another to prevent their moving when subjected to a magnetic field by the magnet units  13 . When the magnetic field is removed, the magnetic filter medium granules  31  are released from mutual attraction. 
     The filter medium accommodation case  30  comprises a pair of nonmagnetic mesh members  35  and  36 , upper and lower, frame members  37 , and magnetism intensification plates  40 . The nonmagnetic mesh members  35  and  36  are formed of a nonmagnetic material, such as stainless steel (SUS304). The chemical composition of SUS304 comprises 0.08 or less carbon, 1.00 or less silicon, 2.00 or less manganese, 8.00 to 10.50 nickel, 18.00 to 20.00 chromium, and iron for the remainder. The frame members  37  are arranged around the nonmagnetic mesh members  35  and  36 . The magnetism intensification plates  40  are provided at respective end portions of the nonmagnetic mesh members  35  and  36 . The frame members  37 , like the nonmagnetic mesh members  35  and  36 , are formed of a nonmagnetic material, such as stainless steel (SUS304). The magnetic filter medium granules  31  are contained in a plurality of rows between the nonmagnetic mesh members  35  and  36 . 
     A large number of circulation holes  35   a  and  36   a  (shown in  FIG. 3 ) are formed in the nonmagnetic mesh members  35  and  36 , respectively. The circulation holes  35   a  and  36   a  are horizontally elongated slits. The width (smaller width) of these circulation holes  35   a  and  36   a  is less than the diameter of the magnetic filter medium granules  31 . Therefore, the magnetic filter medium granules  31  cannot pass through the circulation holes  35   a  and  36   a . In short, the nonmagnetic mesh members  35  and  36  are only expected to be able to support the contained magnetic filter medium granules  31  and allow a fluid to pass vertically through them. 
     The magnetism intensification plates  40  are provided on the filter medium units  12 . The magnetism intensification plates  40  are arranged individually on the respective horizontal end portions of the filter medium units  12 , that is, on those end portions thereof which are farther from the magnets  19 . The magnetism intensification plates  40 , which are formed of a magnetic material, such as iron, are located throughout overall length W (shown in  FIG. 2 ) transversely relative to the filter medium units  12 . When the magnets  19  are in a first position shown in  FIG. 1 , the magnetic filter medium granules  31  are located between the magnets  19  and magnetism intensification plates  40 . 
     The magnets  19  are contained in the magnet chambers  18 , individually, and can move vertically. An example of each magnet  19  is a strong permanent magnet. This magnet  19  moves relative to the filter medium unit  12  between the first position shown in  FIG. 1  and a second position shown in  FIG. 5 . When the magnet  19  is in the first position, a magnetic field is applied to the magnetic filter medium granules  31 , whereupon the magnetic filter medium granules  31  are caused to magnetically attract one another to be immobilized. When the magnet  19  ascends to the second position, the magnetic attraction between the magnetic filter medium granules  31  is canceled, so that the magnetic filter medium granules  31  are allowed to move to some extent. 
     The filtration device  10  comprises retaining means for moving the magnets  19  between the first position ( FIG. 1 ) and second position ( FIG. 5 ). An example of the restraining means comprises lift rods  45 , connecting member  46 , and operating member  47 . The connecting member  46  connects the respective upper end portions of the lift rods  45 . The operating member  47  is secured to the connecting member  46 . The lift rods  45  are inserted individually into magnet chambers  18  and can move vertically together with the magnets  19 . The operating member  47  is configured to be vertically driven manually or by means of an actuator (not shown). The magnets  19  can be moved between the first position and second position by the operating member  47 . 
     Submerged air discharging mechanisms  50  are arranged above the magnetic filter medium granules  31 . An example of each submerged air discharging mechanism  50  comprises a pipe  51  extending horizontally. A plurality of air jets  52  are formed in the lower surface of the pipe  51  at a predetermined pitch along the axis of the pipe  51 . As shown in  FIG. 2 , a compressed air supply source  55  is connected to each submerged air discharging mechanism  50  through an air supply pipe  53  and open/close valve  54 . Although the open/close valve  54  may be of a manually-operated type, it should preferably be a solenoid valve that is electrically opened and closed by a controller  56 . 
     As shown in  FIG. 3 , distance H from the lower surface of the pipe  51  of each submerged air discharging mechanism  50  to the upper surface of the filter medium accommodation case  30  ranges from, for example, 10 to 20 mm. An example of the diameter of each air jet  52  is 1.8 mm, and an example of an interval between the air jets  52  is 60 to 70 mm, although these values are not restrictive. 
     In cleaning the magnetic filter medium granules  31 , as shown in  FIG. 5 , compressed air  57  is supplied from the compressed air supply source  55  to each submerged air discharging mechanism  50 . The compressed air  57  is ejected toward the magnetic filter medium granules  31  of the filter medium units  12  through the air jets  52 . 
       FIGS. 6 and 7  show an outline of filtration equipment  60  comprising the filtration device  10 . This filtration equipment  60  comprises a dirty tank  61 , a clean tank  62 , the filtration device  10 , a sludge processor  63 , etc. The dirty tank  61  contains the fluid Q 1  to be filtered. The clean tank  62  contains the filtered clean fluid Q 2 . The contaminated fluid Q 1 , which contains fine particles and the like to be removed, is delivered to the contaminated fluid inlet  20  of the filtration device  10  through a pump  65 , pipe  66 , and valve  67 . The filtered clean fluid Q 2  in the clean chamber  16  is recovered into the clean tank  62  through a valve  70  and pipe  71 . 
     The pump  65  and pipe  66  function as fluid supply means  80 . The fluid supply means  80  drives the fluid Q 1  in the filter tank  11  from below to above the magnetic filter medium granules  31  as the fluid Q 1  is filtered. The drain valve  25  and drain port  26  function as fluid discharge means  81 . The fluid discharge means  81  has a function to pour the filtered clean fluid Q 2  located above the magnetic filter medium granules  31  as the magnetic filter medium granules  31  are cleaned. 
     The following is a description of a filtration process and cleaning process. 
     In the filtration process for filtering the contaminated fluid Q 1 , as shown in  FIG. 6 , the valves  67  and  70  are opened, and the drain valve  25  is closed. Then, the contaminated fluid Q 1  in the dirty tank  61  is fed into the dirty chamber  15  of the filtration device  10  by means of the pump  65 . Further, a magnetic field is applied to the magnetic filter medium granules  31  by moving the magnets  19  of the magnet units  13  to the first position ( FIG. 1 ). 
     As shown in  FIG. 4 , the magnetic filter medium granules  31  are immobilized in contact with one another by this magnetic field. If the magnetic filter medium granules  31  are secured to one another, a narrow “wedge-shaped” gap G is formed so as to be tapered toward each point C of contact between the magnetic filter medium granules  31 . As the contaminated fluid Q 1  flows near the contact point C between the magnetic filter medium granules  31 , fine particles S get deep into the gap G and are captured. If the fine particles S are formed of a magnetic material, the magnetized magnetic filter medium granules  31  attract the fine particles S. Thus, the contaminated fluid Q 1  fed into the dirty chamber  15  is filtered as it upwardly passes through the filter medium units  12 , and the fluid Q 1  flows into the clean chamber  16 . 
     If the amount of the fine particles S captured by the magnetic filter medium granules  31  increases, the filtration performance is reduced. The cleaning process is executed to recover the filtration performance. In the cleaning process, the pump  65  is stopped, and the valves  67  and  70  are closed, as shown in  FIG. 7 . The interior of the clean chamber  16  is opened to the atmosphere by opening the air valve  23  (shown in  FIG. 2 ). Further, the drain valve  25  is opened. By moving the magnets  19  to the second position ( FIG. 5 ), the magnetic field having been applied to the magnetic filter medium granules  31  is canceled so that the magnetic filter medium granules  31  are released from attraction. 
     The clean fluid Q 2  in the clean chamber  16  passes through the filter medium units  12  as it flows toward the dirty chamber  15  by its own weight. When this is done, an air pressure higher than the atmospheric pressure may be applied to the surface of the clean fluid Q 2  by introducing compressed air into the clean chamber  16  through the air supply pipe  24  (shown in  FIG. 2 ). By this air pressure, the clean fluid Q 2  can be quickly driven toward the dirty chamber  15 . 
     In the cleaning process, a large amount of air  57  is downwardly ejected toward the magnetic filter medium granules  31  through the air jets  52 , in the filtered clean fluid Q 2  located above the magnetic filter medium granules  31 . A large number of air bubbles are introduced into the clean fluid Q 2  by the air  57  ejected into the clean fluid Q 2 . The clean fluid Q 2  passes between the magnetic filter medium granules  31  by its own weight and flows toward the dirty chamber  15 . In addition, the clean fluid Q 2  is urged toward the magnetic filter medium granules  31  by the air  57  ejected through the air jets  52 . Accordingly, the clean fluid Q 2  with the air bubbles therein rushes down through the magnetic filter medium granules  31 . 
     The surfaces of the magnetic filter medium granules  31  are smooth spherical surfaces similar to those of ball bearings. Even if distance H from each air jet  52  to the filter medium accommodation case  30  is as short as 12 mm, therefore, the clean fluid Q 2  that strikes the magnetic filter medium granules  31  permeates between the magnetic filter medium granules  31 . As the clean fluid Q 2  flows along the peripheral surfaces of the magnetic filter medium granules  31 , it can thoroughly clean the entire magnetic filter medium granules  31 . 
     The auxiliary air supply means  28  shown in  FIG. 2  introduces air onto the fluid (clean fluid Q 2 ) collected above the magnetic filter medium granules  31  when the magnetic filter medium granules  31  are cleaned. By this air introduction, a pressure higher than the atmospheric pressure is applied to the surface of the clean fluid Q 2  above the magnetic filter medium granules  31 . Thus, the clean fluid Q 2  is assisted in rushing down between the magnetic filter medium granules  31 . 
     In the cleaning process, as described above, the clean fluid Q 2  located above the magnetic filter medium granules  31 , along with the air bubbles, rushes down between the magnetic filter medium granules  31  toward the drain port  26  from the clean chamber  16 . In this way, the surfaces of the magnetic filter medium granules  31  are cleaned by the clean fluid Q 2 . This is, as it were, jet cleaning. The sludge contained in the contaminated fluid discharged into the sludge processor  63  is separated from the fluid and recovered by the sludge processor  63 , e.g., a separator. 
     As described above, the filtration device  10  of the present embodiment can easily and quickly clean the magnetic filter medium granules  31  by means of the clean fluid Q 2  in the filter tank  11  as required if the magnetic filter medium granules  31  are contaminated to a certain degree or more. Thus, this filtration device  10  can recover its filtration capability in a short time. Since the cleaning process can be performed by directly using the filtration device  10  itself, moreover, the running cost is low. The filtration device  10  may be operated based on automatic switching between the filtration and cleaning processes by means of a timer. 
     The filtration device  10  of the present embodiment comprises the submerged air discharging mechanisms  50 . In the cleaning process for the magnetic filter medium granules  31 , the air  57  is ejected into the clean fluid Q 2  and toward the magnetic filter medium granules  31  through the air jets  52  that open in the lower surface of the pipe  51 . As the air  57  is ejected in this way, the clean fluid Q 2 , along with fine air bubbles in the clean fluid Q 2 , is directed to the magnetic filter medium granules  31 . This clean fluid Q 2  contacts the outer peripheral surfaces (spherical surfaces) of the magnetic filter medium granules  31  as it rushes downward. 
     As the clean fluid Q 2  flows in this way, matter to be removed, having so far been adhering to the outer peripheral surfaces of the magnetic filter medium granules  31 , is removed and discharged together with the clean fluid Q 2  toward the drain port  26 . Thus, the magnetic filter medium granules  31  can be almost completely cleaned, so that excellent filtration performance can be fulfilled in the filtration process to be resumed thereafter. 
     It is to be understood, in carrying out this invention, that the constituent elements of the filtration device, including the filter tank, magnetic filter medium granules, magnets, submerged air discharging mechanisms, may be embodied in suitably modified forms without departing from the spirit of the invention. Further, this invention is also applicable to filtration devices for filtering fluids other than a coolant. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.