FILTER APPARATUS

Abstract: A filter apparatus (10) and method is provided wherein a filter tank (12) is adapted to receive unfiltered liquid (32). An outlet chamber (26) is located adjacent the bottom wall (18) of the filter tank and is separated therefrom by a perforated plate (24). A filter media (36) is movable across the rear (14), bottom and front (16) walls of the filter tank and accordingly, unfiltered liquid must pass through the filter media as well before entering the outlet chamber. A chain flight assembly (40) is provided which is movable across the filter media along the rear, bottom and front walls of the filter tank. As the chain flight assembly is continuous, a return path is across the top of the tank above the unfiltered liquid. A baffle (61) is provided near the rear wall within the filter tank. This baffle (61) extends sideways to near each side wall (20, 22) of the filter tank, upwardly above the level of the unfiltered liquid within the filter tank and downwardly to a point just above the flights (44) of the chain flight assembly above the filter media at the bottom of the filter tank. A spray header (76) is provided to spray filtered liquid between the rear wall of the filter tank and the baffle to prevent unfiltered liquid from bypassing the bottom of the baffle and entering the outlet chamber without passing through the filter media. Another spray header (72) is provided to wash the chain flight assembly while it passes above the filter tank.

Description: The present invention relates to a filtering apparatus. One type of industrial filtration apparatus or system includes a tank having a bottom, a rear and a sloped front wall joined by side walls to form the tank. An inlet device to supply unfiltered liquid to the filter tank is provided. An outlet chamber or vacuum box is usually located below the filter tank adjacent the bottom wall thereof. The outlet chamber is separated from the bottom wall of the filter tank by a perforated plate. A movable filter media, usually of the replaceable fabric or paper type, is fed into the filter tank, downwardly along the rear wall thereof, along the bottom wall such that any unfiltered liquid must pass through the filter media to enter the outlet chamber, and upwardly along the sloped front wall of the filter tank and outwardly therefrom for disposal of the used filter media. A chain flight assembly is typically provided in such filter devices. The chain flight assembly comprises two endless chain assemblies located adjacent each side wall of the filter tank; the chain assemblies are joined by flights. The chain flight assembly is movable by a drive mechanism inwardly from the adjacent the filter media along the rear, bottom, and sloped front wall of the filter tank. As the chain flight assembly is endless, a return path for the assembly is provided above the unfiltered liquid in the filter tank. It is possible for such filter apparatuses to operate by gravity wherein the unfiltered liquid passes through the filter media into the outlet chamber without further assistance. However, most typically such filter apparatuses include a pump attached to a discharge from the outlet chamber. Accordingly, a pressure differential can be established across the filter media thereby increasing capacity and flow rate of the filter device. Such a filter apparatus is shown in U.S. Patents Nos. 3,087,620 and 4,192,747. One problem with such filtration apparatuses is the tendency for unfiltered liquid to bypass the filter media and enter the outlet chamber without being filtered. This especially occurs at the rear of the filter wherein the filter media and chain flight assembly are travelling vertically downwardly along the rear wall of the filter tank. Such bypassing is believed to occur by the unfiltered liquid going arond the edges of the filter media wherein the unfiltered liquid then flows under the media and enters the outlet chamber without flowing through the filter media. An apparatus for filtering a liquid is known from FR-A 24 14 357 and has a separate chamber filled with clean liquid. This chamber extends all around the filtering region and is provided in order to assist the mechanical seals in their work, such seals being disposed around the filtering region and serving to prevent unfiltered liquids from entering. For such purpose, highly complex mechanical seals are required, which are in the form of a labyrinth seal. Moreover, very large chambers for the clean liquid are required in order to achieve this sealing action over the entire length of the filter belt. It is an object of the invention to prevent unfiltered liquid from entering beneath the filtering means by using simple component parts. Based on the preamble of the main claim, this object is achieved by the characterising features of said main claim. Preferably, in the filtering apparatus, said baffle has a generally rectangular, planar upper section in generally parallel and vertical alignment with the wall at said one end of said filter tank, a generally rectangular, planar middle section extending from said upper section at an acute angle to the plane of the upper section and a generally rectangular, planar lower section extending from said middle section at an acute angle to the plane of said middle section so as to be in a generally parallel planar alignment with said upper section. Depending on the sprocket assembly configuration for movement of the filter media and chain flight assembly, the baffle plate can take several configurations so long as it is relatively near the rear wall of the filter tank and extends near the bottom and to the side walls of the filter tank. Further preferably, in the last mentioned apparatus, said spray header comprises a supply pipe with a plurality of spray nozzles extending therefrom so as to provide a substantially uniform supply of clean liquid across the width of said baffle. The present invention and the objects and advantages thereof may be better understood by reference to the accompanying drawings showing an examplary embodiment of the invention in which: Figure 1 is a side view, in partial cross section, of a filter apparatus including a baffle plate and spray header in accordance with the present invention; Figure 2 is a detailed side view in partial cross section of the baffle plate and a slightly modified form of spray header of the filter apparatus of the present invention; Figure 3 is a plan view of the spray header of the Figure 2; and Figure 4 is a frontal view of the spray header of Fig. 3 and the baffle plate. Referring now to the drawings, a filter apparatus embodying the present invention is shown generally at 10. Filter apparatus 10 comprises filter tank 12 having rear wall 14, sloped front wall 16 and bottom wall 18 with side walls 20 and 22. Side wall 20 includes inlet 38 for liquid to be filtered. Bottom wall 18 includes a perforated plate 24 wherein there is capability for liquid to flow from filter tank 12 into outlet chamber 26. Outlet chamber 26 comprises a box like structure located below bottom wall 18 of filter tank 12 and is sealed thereto such that outlet line 28 connected to outlet chamber 26, when operatively connected to pump 30, can draw a partial vacuum in outlet chamber 26 thereby creating an effective pressure differential across perforated plate 24. Filter media roll 34 is mounted at the top of filter tank rear wall 14 whereby a porous filter media 36 is fed downwardly along rear wall 14 within filter tank 12, across bottom wall 18 and perforated plate 24 and upwardly along sloped front wall 16 of filter tank 12 whereupon filter media 36 exits filter tank 12 at the top of front wall 16 from which it can be properly disposed of. A chain flight assembly 40 is provided comprising endless chains 41 and 42 joined by flights 44. Chain flight assembly 40 is driven by drive mechanism 46 in a counterclockwise direction in viewing Figure 1, downwardly onto chain flight guide 52 onto roller guide 48, downwardly along rear wall 14 of filter tank 12, around roller guide 50 and along bottom wall 18 of filter tank 12, in contact with roller guide 54 and upwardly along front wall 16 of filter tank 12 back to drive roller 46. As chain flight assembly 40 passes along rear wall 14, bottom wall 18 and front wall 16 of filter tank 12, it contacts and acts to maintain filter media 36 against the referenced walls of filter tank 12. This is especially desirable in passing across preferated plate 24 as the chain flight assembly assists in keeping the filter media pressed against the outside edges of bottom wall 18 to ensure the majority of unfiltered liquid 32 must pass through filter media 36 before entering outlet chamber 26. Filter media 36 is typically a fabric or paper type media having reinforced edges operatively connected with chains 41 and 42. Upon the passage of a certain amount of unfiltered liquid through filter media 36, a buildup of particulate matter which was suspended in the unfiltered liquid 32 begins on filter media 36. Such buildup actually aids filtration in that liquid must pass through such buildup and the filter media before entering outlet chamber 26. However, upon the buildup of a substantial amount of filtered materials on filter media 36, the resistance to flow becomes too great and it becomes necessary to move or index filter media 36. This is accomplished by movement of chain flight assembly 40 in order to expose fresh filter media 36 across perforated plate 24 to thereby allow unfiltered liquid to flow through filter media 36 unimpeded by the buildup of filtered material on media 36. Most typically, prior to such indexing of filter media 36 and chain flight assembly 40, pump 30 is shut off in order that the pressure differential across filter media 36 can be decreased. Such pressure decrease facilitates the indexing of filter media 36 across perforated plate 24. Baffle 61 is located within filter tank 12 near rear wall 14. Baffle 61 comprises an upper generally rectangular, planar section 60, a middle generally rectangular, planar section 62 extending from upper section 60 at an acute angle about 45 degrees and a lower generally rectangular, planar section 64 extending from middle section 62 downwardly in a manner such that planar sections 60 and 64 are generally parallel. All sections of baffle 61 have side edges in close proximity to or preferably in contact with side walls 20 and 22 of filter tank 12. Baffle 61 is so selected and installed such that top edge of upper section 60 is always above the level of unfiltered liquid in filter tank 12 and the bottom edge of lower section 64 is just above chain flights 44 as they pass beneath lower chain guide 68 along bottom edge 18 of filter tank 12. The contact of the side edges of baffle 61 with side walls 20 and 22 of filter tank 12 is preferably watertight. Pump 30 removes filtered liquid from outlet chamber 26 sending the filtered liquid through discharge pipe 70 onward through pipe 71 to be reused in the industrial process. However, a portion of the filtered liquid is returned via pipe 73 to spray header 72 and through pipe 74 to spray header 76. Spray header 72 provides a spray of filtered liquid onto chain flight assembly 40 as it passes beneath spray heads 82 in spray header 72. This spray of filtered liquid acts to remove filtered solids and accumulated build up from chain flight assembly 40 washing such build up downwardly into unfiltered liquid 32 in filter tank 12. The spray of filtered liquid from spray header 76 exits through spray heads 78 and 80 downwardly behind baffle 61 to create a flow of filtered liquid outwardly from the bottom of lower baffle plate 64 and from the sides of baffle 61 if any nonwatertight gaps appear at such sides. The main flow beneath lower baffle 64 ensures that unfiltered liquid cannot enter behind filter media 36 as it passes downwardly along the inside of rear wall 14 of filter tank 12. Such spray of filtered liquid from spray heads 78 and 80, along with baffle 61 act to virtually eliminate the bypassing of filter media 36 by unfiltered liquid thereby assuring that any unfiltered liquid must pass through perforated plate 24 and filter media 36 prior to entering outlet chamber 26.

Claims: A filtering apparatus (10) comprising a filter tank (12) with an inlet (38) for unfiltered liquid and an outlet chamber (26) at the bottom of said filter tank, a filter media (36) between said filter tank and said outlet chamber and a continuous chain flight assembly (40) which passes over and through said filter tank and lays on said filter media, characterized by a baffle (61) within said filter tank to define a chamber (100) between the rear wall (14) of said filter tank and said baffle through which said filter media is introduced into said filter tank, said baffle extending from above the level of the unfiltered liquid in said filter tank to near the chain flight assembly along the bottom of said filter tank and in contact with or closely adjacent each side wall of said filter tank, means (30, 70, 76) for continuously introducing clean liquid into said chamber (100) and a spray means (72) supplied with clean liquid to wash said chain flight assembly as it passes over said unfiltered liquid in said filter tank so as to wash any particles of materials filtered from said unfiltered liquid off said chain flight assembly. A filter apparatus as claimed in claim 1 adapted to supply filtered liquid taken from said outlet chamber as said clean liquid. A filter apparatus as claimed in claim 1 or 2, wherein a perforated plate (24) is disposed between said outlet chamber and said filter tank. A filter apparatus as claimed in claim 1,2 or 3 wherein said baffle has a generally rectangular, planar upper section (60) in generally parallel and vertical alignment with the wall at said one end of said filter tank, a generally rectangular, planar middle section (62) extending from said upper section at an acute angle to the plane of the upper section and a generally rectangular, planar lower section (64) extending from said middle section at an acute angle to the plane of said middle section so as to be in a generally parallel planar alignment with said upper section. A filter apparatus as claimed in any of the claims wherein said spray header comprises a supply pipe with a plurality of spray nozzles (78, 80) extending therefrom. A filter apparatus as claimed in any of the claims wherein a chain flight assembly (40) having two continuous chain groups (41, 42) joined by a plurality of flight bars (44).

Inventors: WILLSON, DAVID H.
Applicants: FILTERWERK MANN & HUMMEL GMBH
Application year: 1987
Main classification: B01D29
IPC codes: B01D29, B01D33, B01D24