Liquid purification or separation – Flow – fluid pressure or material level – responsive – Filter cleaning
Reexamination Certificate
2002-03-21
2004-06-22
Drodge, Joseph (Department: 1723)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Filter cleaning
C210S108000, C210S350000, C210S411000, C210S414000, C210S456000
Reexamination Certificate
active
06752920
ABSTRACT:
BACKGROUND
1. Field of Invention
This invention relates to a method and apparatus with the focus of providing a more efficient, reliable and cost effective means for the back flushing of filtering mechanisms. Specifically the invention is directed to providing an improved method and apparatus to facilitate high energy, efficient, reliable and most cost effective back flush cleaning of stacked disk filtration mechanisms.
2. Description of Prior Art
Modern industry and agriculture both require filtration technologies of varying capacities. Initially, innovative and higher efficiency filtration technologies evolved primarily out of the industrial market needs with agricultural filtration needs being satisfied by relatively simple and somewhat crude technologies. Concurrent with worldwide agricultural growth, and specifically as a consequence of the development of highly efficient drip tube irrigation technologies, the demand and resultant development of much more efficient, yet cost effective and reliable agricultural filtration processes burgeoned. Indeed, the previous trend of agricultural filtration technologies being primarily low cost derivatives of industrial designs has been superseded by the current industrial interest in employing modern agricultural derived technologies to industry. In many cases adaptation of agricultural based filtration technologies into industrial applications have been positive and straight forward. Other industrial applications however, have encountered problems. These problems are primarily linked to three issues. The first issue being chemical incompatibility between the materials of manufacture of the filtration equipment and the subject fluid and/or entrained components thereof. The second issue being process applications criteria, wherein the usual problems are associated with incompatible pressures and/or flow rates. The third issue relates to mechanical incompatibility of the fluid to be filtered solids concentration or characteristics, wherein the incompatibility relates to excessively high solids concentration and/or the adhesive nature of the solids. The consequence of these challenges being the necessity for a high cleaning cycle frequency. High cleaning cycle frequencies stresse and wears valves and other moving components, thereby invoking high maintenance, operating costs and impaired reliability.
In those applications in which chemical compatibility is an issue, fabrication employing compatible materials may be a technically feasible solution. However, in many such situations there is a high cost associated with either the chemically compatible raw material or the machining, molding, tooling or other fabrication processes necessitated by the compatible material specifications. In these cases, the economic burden associated with these costs must be evaluated on a case by case basis. The resolution of the second and third issues, particularly as they apply to disk filtration technologies, are the primary focus of this invention.
Disk filtration technology has been developed over many decades. There are generally two categories referenced in the art as disk filtration. One such category incorporates the parallel mounting of one or more disks comprised of a screening material encapsulating a substantially hollow platelike structure which is generally mounted on a filtrate conduit. In such art, the filtration process occurs across the disk encapsulating screens wherein the screens may or may not include the provision of a filter aid such as diatomaceus earth. This subcategory of filtration technology has been commonly employed in industry for decades.
The second category of disk filtration has been developed primarily, though not exclusively, through agricultural needs. This category is the primary focus of this invention. This category of the art, embodies the employment of multiple ring-type disks, generally, though not always, made of a plastic material, stacked together to compose a primarily hollow cylindrical assemblage. Unfiltered water is forced under pressure to pass between these disks in a substantially radial direction, typically from the external to the internal side of the stack. Various types of protrusions or surface topology of the disks provide for the catchment of particulate matter suspended in the fluid. The trammeling of particles thereby occurring upon the external surface of the cylindrical assemblage and/or upon the contacting surfaces of the disks. Wherein for clarity, the catchment surface external to the stack is substantially perpendicular to the direction of flow while that of the contacting surfaces is substantially coplanar with the direction of flow. The filtrate exits the disk stack and is ported to process for use.
The geometrical configuration and associated filtration mechanism of the disks as defined in the prior art are diverse. Reference is made to an early disk filter process wherein tapered disks with radially internal filtrate porting was proposed for removal of disperse sizing of particles as demonstrated in U.S. Pat. No. 1,643,299.
Other configurations practiced in the art are delineated in U.S. Pat. Nos. 2,847,126, 3,648,843, 3,827,568, 4,430,232, 4,707,259 and 4,726,900. In these practices perturbations and/or other spacing mechanisms are embodied on the disk surfaces so as to facilitate geometrical spacing between adjacent disks consistent with the required filtration size or grade. In such art the unfiltered water is constrained to pass radially between the disks of the cylindrical assemblage. Particles larger than the disk spacings therefore being trammeled upstream of the constrained fluid path. Various manifestations of this art have been further proposed in which the upstream configuration of the disks is so modified as to provide for a increased upstream surface lineage, thereby providing for an enhanced particle trammeling area. Reference is made to U.S. Pat. No. 4,410,430.
Further lessons of the art demonstrate the employment of surface grooves on one or both sides of the disks for the provision of flow channels between abutted disks. The size and geometry of said channels being the constraint on the passage of particles. Particles of sufficient size and/or geometry are trammeled at the entrance to the groove channels. Reference to these developments of the art are provided in U.S. Pat. Nos. 1,642,864 and 3,195,730.
As is compulsory with filtration processes in general, disk filtration processes require some means of filtration surface cleaning to remove the collected solids separated from the treated fluid. Some examples of the prior art show little discussion of this issue. It can only be assumed that in these cases either disposal or disassembly and manual cleaning must be the procedure of choice. The drawback of the disposal option being the expense of replacement. The disadvantage of the disassembly and cleaning option being the expense of labor and associated downtime.
Prior art has evinced many examples in which the disks are cleaned through mechanical means and/or hydraulic means. Such means being accomplished in automated, semi-automated or manually impelled processes.
An example cited in the prior art of a mechanical means for cleaning, demonstrates a cleaning mechanism wherein the disks are rotated relative to one another providing a scrapping mechanism and thereby facilitating removal of the collected debris. Reference U.S. Pat. No. 1,926,557 as an example of such art. The detriments inherent in this art are the mechanical complexities involved in maintaining the proper relative disk orientations and the rotary mechanisms necessary to facilitate the relative disk rotations. This art also suffers from the detrimental tendency to smear or extrude rather than remove those collected solids which are soft and pliable.
Prior art has demonstrated other mechanical cleaning methods wherein brushes are employed to clean accumulated debris from the outer cylinder assemblage surface. Reference is made to U.S. Pat. No. 2,422,735 relating to such an invention. This example of the art
Harris James Jeffrey
Harris James William
Cecil Terry K.
Crabtree Edwin H.
Drodge Joseph
Margolis Donald W.
Pizarro Ramon L.
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