Patent Abstract:
A back-flushing method is practiced with a back-flushing filter construction wherein a perforate filter screen providing filter openings also forms an internal chamber for receiving the effluent from a liquid stream. A filter piston is disposed in the internal chamber and operates to divide the chamber into first and second zones on opposite sides of the piston. By selectively reciprocating the piston, the effluent in the chamber is compressed and moved on both sides of the piston. Thus, the effluent back-flushes the filter openings and creates a rolling action in the liquid surrounding the filter screen on the upstream side to dislodge particulate debris accumulated on the filter screen.

Full Description:
FIELD OF THE INVENTION 
     This invention relates generally to methods of back flushing filters and more particularly to an improved back flushing filter construction which finds particular utility when used in the meat treating industry to filter liquid formulas that are injected into poultry, beef or pork by an injection machine by means of a pump that pumps the formulas into the meat through needles with small inlet and outlets. 
     THE PRIOR ART 
     The prior art is exemplified by prior issued patents such as U.S. Pat. No. 2,918,172 issued Dec.22, 1959, U.S. Pat. No. 3,074,560 issued Jan. 22, 1963 and U.S. Pat. No. 3,635,348 issued Jan. 18, 1972. With the constructions disclosed and claimed in those prior art patents, filter baskets capable of either continuous or intermittent rotation are cleaned with a doctor blade and may be additionally cleaned by a back-flushing shoe disposed inside of the basket and arranged to eject a narrow jet of liquid through a localized section of the filter basket to back-flush the filter openings as they move by the shoe. 
     Other prior art in the filtering art of conceivable interest includes such patents as U.S. Pat. No. 4,631,126; 4,762,615; 4,818,402; 4,931,180; 5,128,029; and 5,171,433. For example, a cleaning nozzle may be used to apply flushing liquid to a stack of discs that loosen when rotated in an opposite direction. Other forms of back wash arms are also disclosed. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention contemplates the utilization of a large stainless steel cylindrical filter basket, or cylinder, which can be disposed in the tub or tank of a liquid stream system having a plurality of filtering stages. The cylinder walls are perforated to form an array of filter openings, which may be so small that they get stopped up with tiny pieces of meat and ingredients in the liquid formulas flowing in the liquid stream. 
     Within the cylinder a disc plunger, or piston, is moved in a cylinder/piston relationship to compress and move effluent collected in the cylinder to back-flush the filter openings and creating a rolling action of the liquid all around the filter basket. 
     The operation of the filter and its back-flushing feature is automated by placing the disk plunger or piston under the control of a motor means controlled by an automatic cycling machine, thereby to cycle the disk plunger or piston through a series of reciprocations within the cylinder alternated with a period of rest. The result is a greatly enhanced and lengthened effective life cycle for the filtering system before shut-down and clean up is necessary. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view with parts broken away and with parts shown in cross section of a filter construction provided in accordance with the present invention and showing schematically how the filter construction is incorporated into a filtering system in order to practice the inventive methods contemplated by this invention. 
     FIG. 2 is a view somewhat similar to that of FIG. 1, but showing the filter construction standing alone before installation into a tub, or tank of a filtering system. 
     FIG. 3 is a top plan view of the filter construction of FIG.  2 . 
     FIG. 4 is a side elevational view of the filter base of the filter construction shown in FIG.  2 . 
     FIG. 5 is a plan elevational view of the filter base of FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 of the drawings, there is shown an exemplary form of a filter construction capable of practicing the methods of the present invention and connected schematically into a filtering system typical of systems used in the meat treating industry. It should be understood that the configuration of the exemplary filter illustrated for purposes of this disclosure could be changed to utilize other geometric shapes and forms without departing from the inventive features and advantages afforded by utilization of the novel concepts set forth. 
     Thus, in FIG. 1 there is disclosed a filter basket  10  which provides a cylinder  20  in which moves a disc plunger  30  actuated by a pair of piston rods  40  interconnected by a piston cross bar  50  so that the disc plunger, or filter piston  30  may be operated by a motor means such as an air cylinder  60 . 
     Such a filter basket  10  is utilized with particular utility in a filtering system wherein the filter basket  10  is placed in a tank or tub  70  confining and containing part of a liquid stream in which flows liquid to be filtered, for example, liquid formula of the kind used in treating meat products, and which liquid stream has an input and an output. When incorporated in such a filtering system, the air cylinder  60  is operatively connected by conduits  61  and  62  to a source of pressurized air  63 . 
     The filter basket  10  has an outlet  11  connected by a conduit  12  to a pump shown diagrammatically at  13  and which pump  13  pumps effluent from the filter basket  10  and directs it towards the output as shown by the arrow legend. An automatic cycling machine  80  having pre-settable control means is connected as at  81  to the source of pressurized air  63  and to the pump  13  as at  82  so that the operation of the disc plunger  30  may be selectively cycled in a selected operational pattern consisting of selectively different modes of performance, for example, the disc plunger  30  may be reciprocated within the cylinder  20  through a cycle of  4  or  5  operations and may then remain dormant, or at rest, for a pre-selected idle period of say 10-15 seconds. When so operated, the disc plunger  30  compresses and moves the effluent collected within the cylinder  20  to back-flush the liquid openings and to create a rolling action of the liquid surrounding the filter basket  10  in the tub or tank  70 . 
     Turning now to FIGS. 2-5 of the drawings, the detailed construction of the filter  10  may be better understood. First of all, there is provided a cylinder  20  which is in effect a circumferentially continuous filter screen  21  having  4  axially spaced strengthening ribs  22  embossed to extend outwardly. The walls of the filter screen  21  are perforate, i.e., the walls are provided with an array of openings  23  through which effluent passes from outside the filter basket  10  into a chamber provided by the interior of the cylinder  20 . 
     Referring to FIGS. 4 and 5, a filter base  24  receives the filter screen  21  at its lower edge on a raised circumferential seat  25 . In this form of the invention, the base  24  is circular and has a centrally disposed outlet opening  26 . A rim  27  extends radially outwardly from the seat  25  and terminates in an upwardly extending flange  28 . The rim  27  is apertured at four equally spaced apart locations  27   a  to accommodate four tie rods each designated by a common number at  29 . 
     In one exemplification of the invention, the filter screen  30  constitutes a  26  gauge stainless steel perforated member having filter openings 23 of 0.003 inches diameter on 0.055 center distance straight diameters, thereby providing approximately a 34% open area available for the filtering function. 
     The top edge of the filter screen  20  is engaged by a filter cap  31  having a rim  32  with four spaced openings  32 a which likewise accommodate the tie rods  29 . Thus, with the use of fastening means such as the nuts  33 , the tie rods  29  clamp the filter screen  20  between the filter base  24  and the filter cap  31 . 
     Disposed within the interior of the filter screen  20  is the disc plunger  30  sized and shaped to establish a piston/cylinder relationship with the filter screen  30 . The disc plunger  30  is movable on a vertical centerline axis established by the circularly configured filter disc  20 . 
     As previously noted, the circular configuration of the filter screen could assume a different geometric shape and the shape of the disc plunger could be correspondingly matched so that sizes and shapes other than the circular shape herein disclosed could be used without departing from the spirit of this invention. 
     As shown in FIG. 2, the disc plunger or filter piston  30  is connected to a pair of piston rods  40 , 40  and secured thereto by fastening means such as the nuts  34 . The piston rods  40 , 40  extend upwardly through the filter cap  31  and the free ends are interconnected with each other by means of a piston cross rod  50  and fastening means such as the nuts  35 . 
     The motor means selected for providing power assistance in operating the filter piston  30  in the present exemplary disclosure is an air cylinder  60  mounted on the filter cap  31  and includes a cylinder in which moves a piston (not shown) connected to a piston rod  61  coupled to the piston cross bar  50  by means of a coupling joint  62 . By supplying compressed air from the usual type of compressed air source  63 , the air cylinder  60  will actuate the disc plunger  30  between the full line position and the dotted line position as shown in FIG.  1 . As the disc plunger filter piston  30  is moved up and down, the liquid in the cylinder is compressed and moved to back-flush the filter openings  23  removing any materials and particles plugging the filter openings  23  and creating a rolling action of the liquid surrounding the filter basket  10 . 
     In one exemplification of the invention, the air cylinder  60  was a two position, four way spring returned pilot operated pneumatic valve electronically controlled in a selective working pattern by an automatic cycling machine  80  taking the form of a GT 3 D multi-function timer in line with a pattern selector timer logic controller. 
     In use the filter construction is particularly effective when placed in a liquid stream flowing in a tub or tank. By pre-setting the automatic control machine  80  to regulate the air cylinder  60  via the air pressure supply  63 , and in coordination with control of the pump  13 , the disc plunger  30  will be reciprocated up and down in the cylinder  30 , thereby to compress and move the effluent collected in the cylinder to back-flush the filter openings  23  and create a swirling, rolling action in the liquid outside of the filter basket  10 . Dislodging the materials and the particles plugging the filter openings will permit the filter basket  10  to operate efficiently for a much longer time without necessitating full shut-down of the filter stream for extensive system cleaning. 
     While a vertical stainless steel cylinder has been illustrated, the principles of the present invention could also be practiced if the filter and its plunger were disposed on a horizontal axis, or if the filter basket and its plunger were square or rectangular. 
     Although minor modifications might be suggested by those artisans skilled in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

Technology Classification (CPC): 1