DRUM-FILTER ARRANGEMENT

Abstract: An arrangement for scraping the filtered solids build up from the surface of a drum filter (l6) is disclosed, in which a scraper (96) is mounted with an edge against the surface so that rotation of the drum (l6) will accomplish scraping of the surface. Clutching engagement with a rotary drive member (72) is produced by a predetermined extent of axial shifting of the drum (l6) against the resistance of a spring bias force. The drum (l6) is also arranged to be subjected to an axial pressure force developed by flow through the filter so that clutching engagement is automatically produced upon build-up of solids to a predetermined extent to cause a level of pressure force to be developed to produce a consequent axial shifting sufficient to produce clutching engagement and rotation of the drum (l6). A drag out conveyor (92) moving through the tank (l2) engages a rotary sprocket (72) which comprises the rotary drive member, and the scraper edge (96) and drum (l6) are positioned to directly deposit the scraped solids on the conveyor (92) to be removed from the tank (l2).

Description: The present invention concerns a drum filter arrangement according to the preamble of claim 1. Drum filters are known of the type in which a filtering liquid flow passes through a filter media layer disposed about the axis of a cylindrical drum member. As filtration proceeds, filtered solids accumulate on the surface of the filter media layer. This filter cake acts as a fine filter media, and if the underlying filter media is itself coarse, a certain level of cake build-up is needed for optimum filtering performance. On the other hand, a greater pressure drop across the media layer will occur as this accumulation process continues, and may proceed to a point where the circulation pump will cavitate and it therefore is usually necessary to periodically clean the filter media. It is desirable to not remove the filter cake any more often than is necessary for proper flow circulation, since as noted, the cake acts as a fine filter media. While "precoating" of the cleaned filter can be done i.e., adding solids to the surface of the filter, this adds to the cost of operation and complexity of the filter apparatus. Various automatically operated scraping and backwashing arrangements are sometimes used to remove the filter cake, as an alternative to manual cleaning of the filter media to avoid shutdown and the labor involved in cleaning the filter, particularly for fully submerged tank filters. U.S.-A-4,407,720 granted to the present inventor discloses a fully submerged drum filter incorporating a rotary drive for a filter drum, and an arrangement for scraping and backwashing of successive areas of the filter media surface layer. In order to provide automatic control over the frequency of scraping, sensor devices have heretofore been utilized, to sense the development of excessive pressure drop across the filter media, and to allow activation of the scraping only when excessive build-up has occurred. In U.S.-A-4,407,720 cited above a description of such a system is given. However, the use of an electrical pressure sensor to control an electric drive motor is introduced at a considerable cost penalty, due to the inclusion of various necessary control components thereby entailed such as panels, relays, starters, etc. The inclusion of such components also increases the service requirements of the equipment. Such submerged drum and other filter units are contained in settling tanks, in which the heavier solids or sludge to be removed from a filtered liquid collect, and drag conveyors are often employed to carry out these heavy solids. For equipment using backwashing and scraping, these conveyors are relied on to remove the scraped solids from the tank, after these have settled to the tank bottom as sludge. This requires a significant time interval to allow the sludge to settle out, and a portion of the solids will typically remigrate to the filter surface if the filter is operated during this settling out time interval. Accordingly, it is an object of the present invention to provide a simple arrangement for a filter scraper which automatically initiates scraping of a drum filter when excessive solids build-up has occurred on the surface of the filter which does not require an electrically operated pressure sensor control device. This object is achieved by the above-mentioned drum filter arrangement comprising the features of the characterizing clause of claim 1. Further embodiments of the invention are disclosed in the subclaims. Summary of the Invention This object of the present invention is accomplished by providing a clutch arrangement operating to initiate rotation of the drum by a connection to a rotating drive member, the clutch brought into operation by a predetermined level of vacuum developed by the circulation pump drawing liquid through a predetermined solids build up on the filter. The rotation of the drum causes a scraping action to occur by the action of a scraper blade positioned against the periphery of the drum surface, the scraping action continuing until the pressure drop declines to a level below the predetermined level. In the preferred embodiment, as the drum is lowered into the settling tank, one end is received within a cradling sleeve segment and is thereafter moved axially into an aligned sealing sleeve by operation of a camming device, to be sealingly fit therein. The sealing sleeve surrounds a pump outlet opening in a sidewall of the tank and filtering flow passes out of the end of the drum to be passed through the pump outlet opening. A rotary drive sprocket is arranged to be engaged with a drag conveyor drive chain to be constantly rotated by movement of the conveyor through the tank. The drum is moved axially upon development of a predetermined level of vacuum against the force of a compression spring, to bring a clutch disc into driving engagement with the drive sprocket to be rotated thereby and so to initiate scraping. The scraper blade, drum filter, and conveyor are relatively positioned adjacent the tank walls so as to cause the scraped solids to be deposited directly within the flights of the drag conveyor to be carried out of the tank, thereby minimizing dispersal of the scraped solids within the liquid contained in the tank. Description of the Drawings FIGURE 1 is a transverse sectional view of a drum filter arrangement having a scraping arrangement according to the present invention with the filter drum shown in the installed partially shifted position in a settling tank, the partially shifted position allowing a normal operation of the filter. FIGURE 2 is a fragmentary sectional view of the drum filter arrangement shown in FIGURE 1 with the filter drum in the unshifted position prior to being shifted by operation of a cam lock mechanism, which unshifted position allows installation and removal of the filter drum. FIGURE 3 is a fragmentary sectional view of the drum filter arrangement shown in FIGURE 1 with the filter drum shown in the fully shifted position engaging the clutching arrangement to establish rotary driving of the drum. FIGURE 4 is a fragmentary view of a section through the periphery of the filter drum. FIGURE 5 is a fragmentary view in the direction of the arrows 5-5 in FIGURE 1, showing in phantom the cam lock mechanism operated to shift the filter drum. FIGURE 6 is a fragmentary endwise view of the drum filter arrangement installed in a settling tank, depicting the positional relationship of the scraper blade and the drag conveyor. Detailed Description In the following detailed description certain specific terminology will be employed for the sake of clarity and a particular embodiment described for the sake of clarity, but it is to be understood that the invention is not intended to be so limited, inasmuch as the invention is capable of taking many forms, and many variations are possible within the scope of the appended claims. Figure 1 illustrates a drum filter arrangement 10 lowered into a settling tank 12 adapted to receive and contain a liquid to be filtered to remove solid contaminants dispersed therein. Liquid introduced to the tank 12 is adapted to be drawn through a layer of a filter media 14 disposed about the surface of a generally cylindrical filter drum 16 to accomplish the filtering action, with liquid flow passing through axially extending compartments 18 to an end chamber 20 collecting the flow from all of the compartments 18. As seen in Figure 4, the filter drum 16 may be constructed of a circumferential array of U-shaped channels 19 welded together, with the open side thereof facing outwardly. The filter media 14 may advantageously be constituted by spaced windings 15 of tapered wire (known in the art as "wedgewire") wound over the channels 19 and welded thereto in the manner well known in the art. Liquid flows through spaces between windings 15 and into compartments 18 to accomplish the filtering action. The suction side of a pump is adapted to be connected to chamber 20 via fitting 24, to draw liquid from chamber 20. The filter drum 16 carries a bearing ring 26 at one end, formed of suitable bearing material, which ring 26 in turn mounts an O-ring seal 28 disposed in a recess 30 formed in the bearing ring 26. The bearing ring 26 in turn is slidably and sealingly fit into a sealing sleeve 32 welded to a side wall 34 of the tank 12 surrounding an outlet 36 aligned with fitting 24. With liquid being pumped from chamber 20, the entire end area of the filter drum 16 thus experiences a lowered pressure in compartment 20, which in turn develops an endwise axially directed pressure force tending to shift the filter drum 16 within the sleeve 32 towards the outlet 36. This pressure force increases as a greater and greater pressure drop develops across the filter media layer 14 with increasing solids accumulation on the surface thereof. This pressure force is relied on to cause an automatic clutching of the filter drum 16 to a rotary drive member at a predetermined level of solids accumulation, to initiate rotation of the filter drum 16 and scraping of the surface of the filter media 14 by a scraper to be described hereinafter. A clutching arrangement for accomplishing this automatic action is located at the opposite end of the filter drum 16, the left end as viewed in Figure 1. The left end of the filter drum 16 is supported on a bracket 38 including a vertically disposed holder plate 40 having a formed horizontal top portion 42 overlying a support 44 welded to tank side wall 46 to be held thereon upon lowering of the drum filter arrangement 10 into the tank 12. Stiffening end plates 48 may be secured along either edge of the holder plate 40 and top portion 42 to form an open-ended open bottom box, with the open end facing tank side wall 46. An elongated lifting handle 50 is welded to the top of portion 42, extending towards the center of drum filter arrangement 10 to enable lifting at a single point, with gusset 52 supporting the cantilevered length thereof. The holder plate 40 mounts a hub 54 passing therethrough and welded in position to be fixed to the holder plate 40. The hub 54 has a bore 56 which slidably receives an axle or hub shaft 58 aligned with the axis of filter drum 16 and itself passing through and welded to an end wall 60 welded to the end of the filter drum 16. The filter drum 16 is thus supported for rotation about its axis by hub shaft 58 and sealing sleeve 32. A clutch member comprised of a disc 62 is held with a threaded fastener 64 to the end of hub shaft 58, with one or more drive pins 66 rotatably fixing disc 62 to hub shaft 58 to insure rotation together of these elements. A leftward bias force is constantly exerted on the filter drum 16 in opposition to the pressure force described above. This is created by a compression spring 68 disposed in a counter bore 70 machined into hub 54, compressed between the adjacent face of the clutch disc 62 and the end of counterbore 70, so that the filter drum 16 is urged to the left as viewed in Figure 1, while the pressure force urges the filter drum 16 to the right. A rotary drive member comprised of a sprocket wheel 72 is rotatably mounted on the hub 54 located facing the clutch disc 62, axially located thereon with a snap ring 74 and thrust bearing 76. The filter drum 16 is shown in Figure 1 in an axially shifted position seated within sleeve 32, which is accomplished by a cam locking means operated by a handle 78 at the end of a handle shaft 80 extending upwardly in tank 12 to be operated from above after lowering of the drum filter arrangement 10 into the tank 12. A cam lock element 82 is affixed at the lower end of handle shaft 80 and located between holder plate 40 and drum end wall 60. Cam lock element 82 is formed with opposite curved camming surfaces 84 (Figure 5) which act to force the filter drum 16 to the right against the resistance of the spring 68 upon clockwise rotation of handle 78 as viewed in Figure 5, and lock the same in the fully shifted position, with the handle 78 against stop pin 86. Thus, the drum filter arrangement 10 may be lowered into the tank 12 until the filter drum 16 rests on a sleeve segment 88 aligned and extending from lower portion of sealing sleeve 32, as viewed in Figure 1, and handle 78 thereafter rotated until the filter drum 16 is shifted into sealing sleeve 32 sufficiently to be sealed therein. Additional axial shifting of the filter drum 16 may be accommodated by sleeve 32, so that upon development of a predetermined pressure force by sufficient accumulation of filter cake, the resisting force of spring 68 is overcome to bring clutch disc 62 into engagement with sprocket wheel 72 and establish a rotary driving engagement therebetween, as shown in Figure 3. Sprocket wheel 72 is rotated by engagement with one of the chains 90 of a drag out chain conveyor 92 mounted for movement through the tank 12, comprised of chains 90 and connected flights 94 welded at intervals between aligned links of chains 90. Thus, movement of the conveyor 92 through the tank 12 produces rotation of the sprocket wheel 72, rotating clutch disc 62 with the filter drum 16 fully shifted by development of a predetermined pressure force, which in turn rotates the filter drum 16. Referring to FIGURE 6, the drum filter arrangement 10 in the tank 12 is shown, in which a spring steel scraper blade 96 is mounted extending parallel to the axis of the filter drum 16, with the leading edge thereof in scraping contact with the surface of the filter media 14 or a fixed distance away to leave a predetermined depth of accumulated solids on the filter surface. A scraper baffle plate 98 is affixed to opposite tank side walls 34 and 46, and provide mounting for a scraper blade clamping bar 100. The drum filter arrangement 10 is mounted concentric to a curved tank bottom and side section 102, with sprocket wheel 72 acting to guide one of the conveyor chains 90 therearound. The position of the scraper blade 96 is such that scraped solids are directly deposited onto the flights 94 of the drag conveyor 92 rather than being dispersed into the tank liquid, and are thus directly carried out of the tank 12. The position of the drum filter arrangement 10 and baffle plate 98 act to confine the dispersal of sludge, and therefor also contribute to this purpose. Upon reaching the lip 104, the sludge passes out of the tank 12 and is collected by a suitable collection and disposal apparatus (not shown). The drag conveyor 92 is driven as by drive sprocket 106, and recirculated into the tank 12 by suitable further sprockets, not shown. Thus the sludge is prevented from again being dispersed in the tank to minimize redeposit on the filter media 14. Accordingly, it can be appreciated that a simple mechanical automatic control of the scraping cleaning of the filter drum has been provided by the pressure operated clutching engagement described. The elimination of an electrical sensor and electrical controls for starting and stopping a drive motor greatly lessens the cost of manufacturing this equipment.

Claims: A drum filter arrangement of the type having a filter media surface extending around the axis thereof and liquid drawn through said filter media (14) and collected in by means of a pump and an outlet passage (24), said arrangement comprising: a filter drum (16) mounted for rotation about its axis; a rotating drive member (72) for rotating said filter drum (16); a scraper blade (96) mounted against the periphery of the drum surface to scrape away solids deposited on said surface of said filter drum (16) as said drum rotates; means for automatically initiating drum rotation when a predetermined pressure drop across said filter drum (16) is reached, characterized in that said means for automatically initiating drum rotation comprise: (a) a clutching arrangement (62, 72) including a clutch member (62) connected to a hub shaft (58) at the end of said filter drum (16) as to rotate therewith, said clutch member (62) being shiftable from an idle position to a position engaging said rotating drive member (72) to establish a rotary driving connection between said rotating drive member (72) and said filter drum (16); (b) means causing said clutch member (62) to be acted on by the pressure drop across said filter drum (16) to tend to shift said filter drum (16) to said engaging position and including a tank (12) within which said filter drum (16) is mounted, and a sleeve (32) affixed to the inside of said tank (12) at the opposite end of the drum to the clutching arrangement (62, 72), this being the same end as said outlet passage (24) connected to said pump, wherein said filter drum (16) is adapted to have said end slidably received in said sleeve (32) and sealingly rotatable therein; said pump drawing liquid from within said sleeve (32) to generate a vacuum tending to axially move said filter drum (16) within said sleeve (32); said clutch member (62) being axially movable with said filter drum (16) to produce said shifting causing said engagement with said rotating drive member (72). (c) a spring (68) between said clutch and drive members (62, 72) resiliently urging said clutch member (62) to said idle position distant from said drive member (72) when the actual pressure drop is less than the predetermined pressure drop, and enabling said clutch member (62) to be shifted to said engagement position by the action of the actual pressure drop being at least the predetermined pressure drop. The arrangement according to claim 1, further including an end wall (60) closing off the opposite end of said filter drum (16) and said hub shaft (58) being affixed to said end wall (60) extending from said opposite end aligned with the axis of said filter drum (16), said clutch member (62) comprising a clutch disc affixed to said hub shaft (58), a hub sleeve (54) supported within said tank (12) and rotatably receiving said hub shaft (58), and wherein said spring (68) comprises a compression spring seated on said hub sleeve (54) at one end and against clutch disc (62) at the other end. The arrangement according to either one of claims 1 or 2, further including a sleeve segment (88) extending from one end of the lower portion of said sleeve (32), adapted to receive said one end of said filter drum (16) and position said drum for axial movement into said sleeve (32). The arrangement according to claim 3, further including a support bracket (42) having said hub sleeve (54) affixed thereto and adapted to be supported within said tank (12) upon lowering of said filter drum (16) into said tank (12) with said one end received within said sleeve segment (88). The arrangement according to any one of claims 1 to 4, further including a cam lock means (78, 80, 82) having a handle (78) mounted on a support bracket (42) to extend upwardly in said tank (12) and having a cam lock element (82) affixed to the lower end of said cam lock handle (78) to be movable therewith, said cam lock element (82) located to force said filter drum (16) towards said sleeve (32) against the action of said spring (68) upon predetermined movement of said cam lock handle (78), whereby said filter drum (16) may be seated within said sleeve (32) upon movement of said cam lock handle (78). The arrangement according to any one of the foregoing claims, further including a drag out chain conveyor (92) driven within said tank (12) for movement past said filter drum (16), and wherein said rotating drive member (72) is engaged with said conveyor (92) to be rotated therewith.

Inventors: BRATTEN, JACK R.
Applicants: BRATTEN, JACK R.
Application year: 1987
Main classification: B01D29
IPC codes: B01D24, B01D29, B01D33