Filtering system for swimming pools
This is a continuation of application Ser. No. 438,695 filed Nov. 2, 1982, now abandoned. 
    
    
     SUMMARY AND OBJECTS OF THE INVENTION 
     This invention relates generally to liquid filter apparatus and more specifically to a novel filter assembly especially useful in filtering water from swimming pools or the like. 
     Swimming pool water must be cleaned of dirt and other particulate contaminants and various proposals have been offered, such as those shown in U.S. Pat. Nos. 2,792,943; 2,851,164; 3,622,001; and 4,219,423. A known filter system which has performed reasonably well employs diatomaceous earth in powder form on a porous filter surface as the primary filter media. 
     Of primary concern with filter systems of this type is the duration of their effective performance life and the ease with which they may be cleaned. In prior systems employing diatomaceous earth quite often the filter surface became prematurely blocked by dirt trapped therein and it was necessary to flush the system completely in order to restore its filtering capabilities. This had to be done quite frequently, thereby consuming a considerable amount of time and wasting a substantial amount of filter media. 
     Accordingly, the primary object of this invention resides in the provision of a novel filter system for a swimming pool employing diatomaceous earth as a filter media, and including apparatus by which the diatomaceous earth may be automatically regenerated periodically to enhance the performance of the filter system and prolong its effective life. 
     Another object of this invention resides in the provision of a novel filter system comprising a filter tank, a support unit mounted centrally within the tank and including a perforated center tube and a plurality of substantially star shaped bag support elements spaced along the tube, and a flexible, expandable, cylindrical, porous filter bag supported loosely on the star shaped elements. During normal operation of the filter, water flows into the tank through the outside surface of the bag into the central tube and back to the swimming pool. The bag assumes the star shape of the elements to provide maximum filtering surface area. 
     Still another object of this invention resides in the provision of a novel filter system in accordance with the above wherein a powdered filter media such as diatomaceous earth is contained within the tank and during normal operation forms a filter cake on the outside surface of the bag to improve its filtering capabilities. When the bag becomes clogged due to the accumulation of dirt on the filter cake, the direction of water flow into the tank is reversed for a short period of time, e.g. a few seconds, so that water entering the inside of the bag from the central tube abruptly expands the bag to its cylindrical shape and releases the dirt from the outside surface of the bag, thereby regenerating the diatomaceous earth and prolonging the effective life of the filter. 
     A further object of the invention resides in provision of the novel filter system described above, wherein a multi-position valve is mounted directly on the tank for quick convenient actuation between the normal filtering cycle and the regenerating cycle. 
     Still other objects and advantages of the invention will become apparent upon reading the following detailed description of the invention with reference to the accompanying drawings wherein like numerals denote like elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a general perspective view of the novel filter system according to the invention employing a single filter bag; 
     FIG. 2 is a fragmentary sectional elevational view taken generally along line 2--2 of FIG. 1 and illustrating the novel filter tank assembly of the invention; 
     FIG. 3 is a fragmentary sectional plan view taken along line 3--3 of FIG. 2 and illustrating the star shaped bag support elements; 
     FIG. 4 is a plan view taken along line 4--4 of FIG. 2 and schematically illustrating the cycle positions of the rotary control valve; 
     FIG. 5 is a fragmentary sectional elevational view of a modified form of the invention employing a plurality of filter bags within a single filter tank assembly; and 
     FIG. 6 is a fragmentary plan view taken generally along line 6--6 of FIG. 5. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, the filter system 10 of the invention comprises a conventional pump assembly 12 having an inlet line 14 and strainer 16 adapted to receive contaminated water from a pool. Water is carried via conduit 18 from pump 12 to inlet 20 of a conventional multi-port rotary valve 22 mounted on top of an upright, generally cylindric filter tank assembly 24. A pressure gauge 19 indicates water pressure in the line side 18 of pump 12. 
     As shown in FIGS. 2 and 3, tank assembly 24 includes an outer cylindrical plastic casing 26 mounted on a bottom base 28 and having a removable top cover 30 fastened to casing 26 by retaining band 32. An inlet conduit 34 connects tangentially to the bottom of casing 26 and an outlet conduit 36 extends centrally upward from cover 30. A normally capped clean out drain fitting 38 is provided at the bottom of casing 26. 
     A flexible cylindrical porous filter bag 40 is located concentrically within casing 26 and loosely slips over a rigid support unit 42 formed by a perforated central can tube 44 having a plurality of holes 45 therein and a plurality of generally star shaped plastic support discs 46 fixed in spaced relationship on tube 44 by way of retaining rings 47. The lower end of tube 44 pinches the closed end of bag 40 within a female socket 48 on the bottom of tank 26 and the upper end of the tube fits within outlet 36. The open upper end of bag 40 is retained on tube 44 by ring clamp 50. 
     Cylindrical filter bag 40 is preferably of a fine-woven polypropylene cloth and is sufficiently large in expanded diameter to provide enough surface area of fabric so that the bag in its collapsed condition may conform to the undulating, corrugated star shape of discs 46 as shown in full line in FIG. 2. On the other hand, the diameter of bag 40 in its expanded cylindrical condition is smaller than the inside diameter of casing 26. For example in an actual construction, the largest diameter on discs 46 is about 5 inches, the outside diameter of bag 40 in its expanded condition is about 6 inches, and the inside diameter of casing 26 is about 71/2 inches. This is evident from FIG. 3 where bag 40 is shown in phantom line in its expanded cylindrical condition. The significance of this relationship will become more apparent from the operational description below. 
     To assist in the filtering operation, a predetermined amount of powdered diatamaceous earth is added to tank 26 outside of bag 40 so as to form a filter cake 51 completely around the outside surface of bag 40 as shown in FIGS. 2 and 3. 
     As mentioned above, rotary valve 22 is a multi-position valve which selectively provides a number of operating cycles through and around filter assembly 24. As shown in FIGS. 1 and 2, valve 22 has a bottom fitting 52 which connects to fittings 36 and thereby mounts the valve directly on the top of assembly 24. 
     In a normal &#34;filter&#34; mode of operation, valve 22 receives dirty water from pump 12 and fitting 20 and directs that water by way of a bottom fitting 54 and flexible hose 56 into tangential tank inlet 34. The pressurized swirling water around bag 40 forces the bag to collapse and conform to the shape of elements 46 shown in FIGS. 2 and 3. The diatomaceous earth in tank 26 adheres to the outside surface of the bag to form filter cake 51. as the water passes through cake 51 and bag 40 into perforated tube 44, dirt particles are trapped against the outer face of cake 51. The clean filtered water then passes by way of tube 44, fitting 52, and connecting ports within valve 22 to a return fitting 58 which leads back to the pool. 
     During the filtering operation, maximum filtering surface area is provided by the generally undulating or pleated configuration of bag 40. The spaced disc elements 46 furnish sufficient support for bag 40, but at the same time, because they are fairly thin, they do not significantly affect water flow through the bag. 
     After a period of filtering operation, the length of which will of course be dependent upon the original condition of the dirty pool water, water flow through cake 51 and bag 40 will become obstructed as dirt particles accumulate on the outside face of the cake. This will be indicated by a pressure rise sensed by gauge 19. When this occurs, valve 22 is rotated to a &#34;backwash&#34; or regenerate position for a short period of time, e.g. 5 seconds, in which water will flow from pump 12 and fitting 20 directly to fitting 52 and into tube 44. Internal porting within valve 22 connects fitting 54 to a drain line 60. 
     The sudden burst of water entering the inside of bag 40 via tube 44 instantaneously expands the bag to its cylindrical phantom line condition shown in FIG. 3 and causes the dirt particles to be released from cake 51. Because the expanded diameter of bag 40 is less than the inside diameter of casing 26, no contact is made between the bag or cake and casing 26, consequently the dirt particles are freely released from cake 51, fall to the bottom of tank 26 and are passed to drain 60 by way of fitting 34 and hose 56. 
     Because the direction of water flow is reversed for only such a short period of time and because of its adhering affinity for bag 40, most of the diatomaceous earth forming cake 51 remains in close proximity to the outside surface of the bag and little is lost during its regenerating cycle. When valve 22 is returned to its &#34;filter&#34; position, bag 40 returns to its collapsed form and filter cake 51 immediately reforms in a clean, regenerated condition on the outside of the bag. 
     The filter assembly 24 may be regenerated several times before it becomes necessary to totally clean the unit and replace diatomaceous earth within the tank. Consequently, the effective performance life of the assembly is extended. 
     A modified form of the invention shown in FIGS. 5 and 6 may be used when increased filter capacity is desired. This modification includes a plurality of filter bags 62 mounted on support units 64 arranged in parallel upright relationship, the upper outlet ends of which are connected to a common outlet fitting 66 extending through the top of casing 68. The construction and function of multiple bags 62 and support units 64 are identical to bag 40 and unit 42 of the assembly of FIG. 2. During filtering operation each of the bags 62 conforms to the star shape of units 64 as water flows inwardly through bags 62 to fitting 66. During the backwash or regenerating cycle bags 62 are rapidly expanded to free the dirt. Bags 62 are sized so that upon expansion they do not contact the inner wall of casing 68; thereby permitting the dirt to be quickly released from the diatomaceous earth. 
     The use of the term &#34;star-shaped&#34; as applied to support elements 46 is intended to encompass broadly any wavy or corrugated configuration which may be used to increase substantially the effective filter surface area of bag 40. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.