Abstract:
A filter incorporates a magnetic separator comprised of a series of side by side but spaced apart permanently magnetized bars interconnected to form a train, movably mounted through a tank into which is introduced liquid contaminated with ferromagnetic particles to be removed. The bar train includes a section overlying a vacuum box in the tank which also is overlain with a filter media to remove particles not removed by the separator. The bar train may be mounted to a flight conveyor included in the filter, or alternatively have its own support and drive. A scraper station is located at a discharge end of the tank for removal of accumulated particles from the bars. Scraper blocks are slidably mounted on the bars and remain there throughout the machine cycle, each of the blocks successly engaged with a plate on a band cylinder as the bars are moved into the scraping station. The cylinder is stroked to wipe the bars at the scraper station.

Description:
BACKGROUND OF THE INVENTION 
     This invention concerns industrial filters of a type designed to filter cutting fluids. These fluids are used in the machining of metal parts, such as engine blocks, manifolds, cylinder heads, etc. to cool and lubricate, and to carry off chips, etc. The cutting fluids are directed at the parts during machining, and in mass production installations are collected for filtration and reuse. 
     Large quantities of metal particles along with grit from grinding and other material, are typically generated which must be removed by the filter apparatus. In some operations such as honing, very fine metal particles are generated which tend to quickly clog the filter media, requiring increased filter capacity and/or reduced filter flow rates. The larger metal turnings sometimes cause tearing of the media. A type of filter apparatus widely used for this application comprises a tank into which the contaminated liquid is introduced and within which a media sheet material is advanced over a vacuum box. Liquid is drawn through the media sheet section overlying the vacuum box to be filtered. 
     The media and conveyor are indexed periodically to bring a fresh media section over the vacuum box. 
     A flight conveyor extending over the media is driven to assist in moving large quantities of filtered solids out of the tank. 
     Applicant has previously patented a method using such apparatus featuring a combination of a permanent and disposable sheet material filter media. See U.S. Pat. No. 5,624,579, issued on Apr. 29, 1997, which describes this filter. 
     If the metal particles could be removed from the liquid, the filter load could be greatly reduced, such that flow to the filter could be increased and, a smaller filter therefor used, and/or the indexing rate reduced. 
     This is particularly true where fine metal particles are present, such as with honing machines. These very fine particles are accompanied with oils which tend to be drawn to the metal particles, the oils tend to clog the filter media. 
     Magnetic separators have previously been devised which use permanently magnetized elements which attract ferromagnetic particles to remove the same from suspension in the liquid in a tank. Such separators have heretofore been separate from the primary filter, increasing the floor space required. 
     Magnetic separator elements have typically comprise an array of elongated permanently magnetized bars arranged side by side in a tank with intervening spaces through which the liquid is circulated. The metal particles are attracted to the magnetized bars, which are periodically scraped off, the scrapings collected by a conveyor removing the same from the tank. 
     Uniform circulation of liquid over the bars have been difficult to achieve, as the liquid tends to flow directly to a tank outlet, creating localized regions of higher and lower flow rates. Higher flow velocities tend to allow metal particles to escape the magnetic attraction of the bars and pass out of the separator. 
     Furthermore, scraping mechanisms heretofore employed have been bulky, using long power cylinders projecting to one side of the tank, and have not provided a particularly effective scraping action. 
     It is an object of the present invention to provide a filter method and apparatus of the type described which incorporates a magnetic separator to simplify and reduce the size of the combined apparatus. 
     It is a further object to provide a magnetic separator of improved performance. 
     It is yet another object to provide an improved scraper mechanism for a magnetic separator. 
     SUMMARY OF THE INVENTION 
     These and other objects which will become apparent upon a reading of the following specification and claims are achieved by a combined vacuum filter and magnetic separator provided by interconnecting a series of magnetized bars to form a train of bars able to be advanced over the vacuum box so that the distributed liquid flow to the vacuum box uniformly flows over the array of magnetized bars at a relatively low flow rate. The uniform dispersed flow of liquid to the vacuum box insures distributed low velocity flow across the magnetized bars extending over the vacuum box, such that there is very effective pickup of metal particles by the bars. 
     The liquid then passes through a permanent media belt and, optionally, also through a disposable media sheet both driven through the tank by a flight conveyor. 
     The magnetized bar array is recirculated through the tank to the discharge end of the tank where a scraper mechanism successively engages the magnetized bars to scrape off the accumulated metal particles from each bar in the series. 
     According to another feature of the invention, the magnetic bars are either mounted to a flight conveyor to be recirculated back around the tank by the conveyor drive, or by a separate guide and drive arrangement. 
     The invention also features an improved scraper mechanism, comprising a series of polymeric scraper blocks, each mounted on respective magnetized bars in the series. A slot in each block receives a pusher arm of the scraper mechanism as the bars are successively indexed into a scraper station, the pusher arm comprised of a flat bar fit into the rectangular slot, to hold the scraper block square to the bar axis for true traversing movement when driven back and forth by an index cylinder. The cylinder is preferably an internal band cylinder which may be mounted coextensively with the bars so as to be able to be confined entirely within the tank. 
     The scraper mechanism is located at the discharge end of the filter tank so that when the scraper blocks scrape the accumulated particles onto an unmagnetized region at a far end of each bar, the scrapings fall through the discharge chute and are collected together with the material discharged by the flight conveyor and media. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified diagrammatic view of a filter apparatus according to the present invention. 
     FIG. 2 is a fragmentary perspective view of a section of the magnetized bar train, flight conveyor and media belts used in the filter apparatus of FIG.  1 . 
     FIG. 3 is an enlarged fragmentary end view of a section of the magnetized bar array, flight conveyor, and media sheets shown in FIG.  2 . 
     FIG. 4 is a top view of a typical scraper block mounted on each pair of adjacent magnetized bars. 
     FIG. 5 is a side view of the scraper block shown in FIG.  4 . 
     FIG. 6 is an end view of the scraper block shown in FIG.  4 . 
     FIG. 7 is a plan view of a set of magnetized bars showing two scraper blocks in the home position. 
     FIG. 8 is a front elevational view of the magnetized bars in the scraping station showing the associated indexing band cylinder. 
     FIG. 9 is a diagrammatic sectional view of a filter apparatus according to the invention, with an alternative arrangement for recirculating the series of interconnected magnetized bars separately from the flight conveyor. 
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
     Referring to the drawings, and particularly, FIG. 1, a filter apparatus  10  of the same general type described in U.S. Pat. No. 5,624,579 is shown, which includes an open tank  12  adapted to receive liquid to be filtered from a utilizing system (not shown), normally operating with a controlled liquid level by means of suitable valving and controls well known to those skilled in the art. 
     The particular configuration of tank shown includes a vertical rear wall  16  connected via a rounded corner to an upwardly sloping bottom  18 . A vacuum or clean liquid box  20  is mounted beneath, the tank bottom  18  with a perforate bottom section  22  allowing an outflow of liquid from the tank interior  24  into a collection chamber defined by the vacuum box  20  induced by a pressure differential created by operation of a pump P having an inlet connected to the vacuum box  20 . 
     The inclined tank bottom  18  terminates at the height of the horizontal top edge  26  of the pair of sidewalls  28 , together defining the confined volume of the interior  24  of the tank  12 . 
     Each sidewall  28  extends beyond the upper end of the tank bottom  18  to create a mounting and receiving structure for a flight conveyor indexing drive assembly  30  for a flight conveyor  50  circulated through the tank conveyor. Such drive assembly can include a motor  32  and belt or chain rotating a main sprocket  34 , in turn driving drive sprockets  36  with a chain  38  to periodically enable an incremental advance of the flight conveyor loops  40 A,  40 B to bring a fresh segment of a filter media sheet  48  over the perforate section  22 . Suitable indexing drive (and flow valving controls) are well known to those skilled in the art, and are therefore not here described. 
     A pair of endless conveyor chain loops  40 A,  40 B (FIG. 2) are guided for circulation around the interior  24  of the tank  12 , extending down the rear wall  16 , around the sprockets  42 ,  44 , both driven by main drive sprocket  36  and returning across the upper region of the tank interior  24  to second guide sprockets  46 . 
     An endless or continuous permanent filter sheet media loop  48  is also provided, having one segment  50  which enters the tank interior  24  by descending the rear end wall  16 , beneath the chain conveyor loops  40 A,  40 B. 
     The permanent sheet media  48  must be porous to enable filtration, and may be constructed or woven synthetic of natural fibers forming a fabric of suitable weave tightness for the particular filtering application, as well known to those skilled in the art. 
     While a pronounced separation is indicated in FIG. 1, it should be understood that this is for clarity of illustration only, and that the rear segment  50  of the permanent media  48  would be against the end wall  16  and that chain loops  40 A,  40 B would be immediately above, with the intermediate disposable filter media  52  optionally sandwiched between, as described further below. 
     The permanent sheet media  48  extends around the guide sprocket  42  and up the tank bottom  18 , over the perforate section  22 , to the end of the tank bottom  18 . At this point, the permanent media  48  takes a divergent path from that of the conveyor chain loops  40 A,  40 B, passing down over a guide roller  54  located beneath the bottom  18 . Accumulated solids are dumped as the surface is inverted and scraped off the permanent sheet media  48  by the scraper edge  56 , collected as by a collector receptacle (or conveyor)  60  positioned below. 
     A jet spray manifold pipe (not shown) may be mounted extending across the width of the permanent sheet media  48  to provide washing of the media by jets directed at the backside as is well known in the art. The wash liquid is collected and may be returned to the tank  24  for filtration. 
     The permanent sheet media  48  then passes beneath the tank  12  and vacuum box  20 , passing around guide rollers  68 , up the outside of rear wall  16  to a guide roller  70  at the top of the rear wall  16  for reentry into the tank  12 . 
     If a disposable media is not employed, indexing advance of the permanent sheet media is produced by direct frictional engagement of the chain conveyor loops  40 A,  40 B lying atop the permanent media  48  as they ascend the tank bottom  18 . Flights  62  connect the loops  40 A,  40 B extending across the width of the permanent media  40  which serves to carry the weight of the solid material accumulating atop the permanent media  48  so that frictional advance of the filter media is easily enabled. 
     The divergent routing of the chain conveyor loops  40 A,  40 B and the permanent media belt loops  48  after leaving the tank  12  allows a disposable sheet media  52  to be inserted into the convergent space between the permanent media  48  and conveyor loops  40 A,  40 B at the point of entry at the rear wall  16  and advanced along with the permanent media  48  so as to lie along belt loop  48  as indexing advance atop the tank bottom  18  proceeds. In this instance, the conveyor loops  40 A,  40 B exert a frictional force on the disposable media  52  and the disposable media  52  exerts a frictional force on the permanent media  48 , so as to be simultaneously advanced together when indexing occurs by frictional driving. 
     The disposable media  52  passes out of the tank  12  at the end of the bottom  18 , where it may be collected for disposal. 
     FIG. 2 shows that the chain loops  40 A,  40 B are guided back around the upper region of the tank  12 . 
     The filter media  52  are shown separated and in line form for clarity of illustration, as it should be understood that the lower segments of the chain conveyor loops  40 A,  40 B, the disposable media  52 , and the permanent media  48  lie directly atop each other. 
     The edges of the permanent media  48  are preferably coated, as by a hot press impregnation with a urethane plastic. This will improve sealing and wear resistance. 
     According to the concept of the present invention, a magnetic separator is integrated into the filter apparatus  10 , by providing a side by side spaced apart series of permanently magnetized bars  72  extending across the spacing between the chain convey loops  40 A,  40 B and interconnected together so as to form a train of bars  72  able to be advanced through the interior of the tank  12  in the same manner as the conveyor  50 . The magnetized bars  72  in the embodiment shown in FIG. 1 are interconnected as by being directly mounted to the chain loops  40 A,  40 B in pair sets by means of brackets  74  welded to inboard chain links  76  intermediate the flights  62  of the flight conveyor  50  (best seen in FIGS.  2  and  3 ). 
     Thus, the train of magnetized bars  72  form a double layer extending between the inlet  80  and the perforate wall  22  and overlying filter sheet media  48 ,  52 . 
     A distributed flow pattern will exist, by the generally diffuse flow out through the media  48 ,  52  and the perforate wall  22  of the vacuum box  20 . Thus, a low velocity equalized distribution of dirty liquid will flow past over all of the magnetized bars  72  in that region of the tank interior  24  so that metal particles in the liquid will be collected more or less equally by all of the bars  72  in this region. This is much improved over prior magnetic separators in which the liquid flow tends to be concentrated in localized areas in being directed towards a small area outlet typical of prior art separators. 
     The sets of pairs of magnetized bars  72  are indexed together with the chain loops  40 A,  40 B until reaching a scraping station  82  located at the discharge end of the tank  12  and disposed over the collector  60 . 
     Each pair of magnetized bars  72  carries a scraper block  84  constructed of a suitable high strength polymeric material such as Nylon so as to be freely slidable thereon by being received in holes  86  (FIG. 5) fit to the outside diameter of the magnetized bars  72 . 
     The fit of the bars  72  in the holes  86  is loose enough to allow sliding but tight enough to be effective to scrape the entire surface of the bars  72  when slid down the lengths thereof. An intermediate clearance space  85  is formed between each end face of the blocks  84  so that half ring pairs  87  are formed. This allows any material entering the clearance space to escape rather than to be packed and jam the block  84  as could occur if the holes  86  extended the entire width of the block  84 . 
     The top of each scraper block  84  is formed with a slot  88 , which may have a tapered lead in section  90  at each end (FIGS. 4,  6 ). 
     The slots  86  are received on a guide bar  89  extending along the path fo the series of interconnected bars  72  so as to be aligned with a flat pusher plate  92  of an indexing band cylinder  94  located at the scraping station, so that as each adjacent pair of bars  72  are indexed into the scraping station the respective scraper block  84  is engaged with the pusher plate  92  (FIGS. 7,  8 ). It is noted that the indexing distance of the flight conveyor  50  must be matched to the distance between pairs of blocks  84 . 
     The band cylinder  94  is of a commercially available type in which the output element extends through a lengthwise slot in the cylinder wall, along which it moves in either direction when being stroked. This eliminates the long actuator rod protruding from power cylinders of more conventional designs, saving space and allowing the cylinder  94  to be contained entirely within the space between the conveyor loops  40 A,  40 B. 
     It will be understood that suitable controls including timers, switches, valves, etc., will be utilized to produce periodic advance of the conveyor  50  and train of bars  72 , which are well known to those skilled in the art. 
     The magnetized bars  72  are permanently magnetized only in the central section “A” so as to have unmagnetized sections “B” at either end. The scraper blocks  84  move into sections “B” when the cylinder  94  is operated to facilitate the removal of metal particles therefrom by the respective scraper blocks  84  traversing down each adjacent pair of magnetized bars  72 . 
     The scraper blocks  84  are each returned to their home position by the cylinder  94  prior to the next index. 
     The flat pusher plate  92  fit to a flat sided slots  88  insures that the blocks  84  will be held in alignment with the longitudinal axis of the associated bars  72  to insure smooth sliding. 
     The use of a scraper block permanently associated with each bar reduces the wear as compared with typical prior designs in which a scraper or a pair of scrapers were located at a scraping station which were used to scrap all of the bars. 
     FIG. 9 shows a second embodiment of filter apparatus  10 A, in which the interconnected series of magnetic bars  72  are mounted on chain loops  102  separate from the flight conveyor  50  may be recirculated separately from the chain light conveyor  40 , along a path within the chain light conveyor  40  with its own separate drive  98  and guide rollers  100 . In this case, separate guide tracks (not shown) would also be necessary.