Abstract:
A filter comprises a cage that captures a foraminous center tube. The cage comprises end plates secured to multiple posts. A screen is wrapped with at least one full inner wrap around the center tube and with at least one full outer wrap around the posts. The screen is held in place with elastic bands or the like that surround and press the outer wrap against the posts. The center tube may be free to move within the cage. Alternately, the center tube, end plates, and posts may be integral with each other. When inserted into a chamber, liquid flows through the screen outer and inner wraps in two stages. The liquid then flows through holes in the center tube, through the interior of the center tube, and out the chamber. The filter is cleaned by unwrapping the screen, cleaning it, and rewrapping it over the center tube and posts.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to fluid filters, and more particularly to liquid filters having cleanable screens. 
     2. Description of the Related Art 
     Many different kinds of fluid filters have been developed over the years. They are available in a wide variety of sizes and shapes. The filtering media are also widely variable to suit the particular fluid to be filtered. 
     A particularly important type of filter is used with swimming pools. The filters are necessary to keep the water clean from such contaminants as grass, leaves, plastic, and paper. 
     In recent years, relatively small portable swimming pools have become increasing popular. Such pools are sometimes referred to as soft side pools, and they are marketed under trademarks such as Sand And Sun and Easy Set. Soft side pools are larger than traditional children&#39;s wading pools, but they are smaller than full size above-ground or in-ground pools. In some cases, soft side pools are quite large; one commercially available model is 18 feet long and four feet wide. Some soft side pools are inflatable using air pressure. Other models use the pool water to stabilize the pool in place. 
     The soft side pool invariably includes a pump system that continuously circulates water in the pool. Water is drawn out of the pool and then looped back into the pool through the pump system. 
     Like the larger above-ground and in-ground pools, soft side pools must be kept clean in order to assure maximum enjoyment by their users. Consequently, it is a common practice to include a water filter in the pump system. The filter traps solid debris from the water and permits only filtered water to circulate back to the pool. Eventually the filter becomes clogged. 
     In the past, the filters of soft side pool pump systems were disposable. That is, when the filters became clogged, they were discarded and replaced with a new filter. Depending on the amount of pool usage, a filter lasted between approximately one and two weeks. Consequently, it was a costly matter to keep the pools clean. Further, the discarded filters eventually ended up in landfills, which was undesirable from an environmental standpoint. 
     Thus, a need exists for improvements in filters for soft side pools. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a filter is provided that is considerably less and expensive and more environmentally satisfactory than prior filters. This is accomplished by apparatus that includes a cleanable flexible screen. 
     In addition to the screen, the filter of the invention is comprised of a cartridge that holds the screen. The cartridge is designed with a center tube, opposed end plates, and multiple posts. At least one end plate has a central opening. The end plates are secured to opposite ends of the posts so as to form a cage. The center tube is captured in the cage. Preferably, the center tube is free to move inside the cage. The center tube has a rather thin wall through which are several holes. 
     The screen of the invention may be of any suitable material and mesh. For example, the screen may be made of fiberglass and have openings approximately 0.06 inches square. The screen has a width between two longitudinal edges that is substantially equal to the distance between the cartridge end plates. The length of the screen between two ends is sufficient to enable the screen to wrap at least one time around the center tube and at least one time around the posts. A longer length screen is also within the scope of the present invention. 
     To assemble the filter, the screen is placed between the cartridge end plates with the screen longitudinal edges adjacent associated end plates. One end of the screen is laid against the center tube with the screen running end outside the posts. The center tube is rotated inside the cage at least one complete turn such that the center tube has at least one full inner wrap of the screen around it. Then the screen running end is wrapped at least one full outer wrap around the posts. There is a connecting section of the screen between the inner and outer wraps. If desired, there may be more than one wrap of screen around either or both the center tube and the posts. When the wraps are completed, the screen second end is a free end outside of the outer wrap. The screen is held in place on the cartridge by one or more ties, clamps, or bands that surround and hold the screen outer wrap against the posts. 
     In use, the filter is interchangeable with prior filters in a liquid pump housing. For example, the pump housing may have a chamber with a closed end and an open end, and a sealing ring that seals against the chamber open end. An inlet to the pump housing directs liquid to the chamber, from which the liquid flows through the wraps of screen and through the holes in the center tube into the center tube. The result is that the filter acts as a two stage filter, with the first stage being the screen outer wrap around the cartridge posts and the second stage being the screen inner wrap around the center tube. From the interior of the center tube, the liquid flows out an end plate and the sealing ring. 
     When the filter is dirty, the pump sealing ring is removed, and the filter is pulled from the pump chamber. The ties or bands are removed, and the screen is unwound from the cartridge. The screen is washed with plain water as needed, and then it is replaced on the cartridge. In that manner, clear liquid is discharged from the pump housing without having to replace either the filter or any of its components. The filter is cleanable as often as necessary without additional cost, detriment to the environment, or chemicals. 
     In a modified embodiment, the cartridge end plates, center tube, and posts are integral with each other. The screen is wrapped around the center tube without rotating the center tube independently of the end plates and posts. In all other respects, the modified filter is substantially identical to the filter with the loose center tube. 
     The method and apparatus of the invention, using a flexible cleanable screen, thus, filters liquids in an economical way. The necessity of discarding an entire dirty filter is eliminated, thus enhancing the environmental aspects of the invention. 
     Other advantages, benefits, and features of the invention will become apparent to those skilled in the art upon reading the detailed description of the invention and studying the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of the pool pump filter of the invention. 
         FIG. 2  is a top view of  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken along line  3 — 3  of  FIG. 2 . 
         FIG. 4  is a cross-sectional view taken along line  4 — 4  of  FIG. 1 . 
         FIG. 5  is a view similar to  FIG. 4 , but on an enlarged scale. 
         FIG. 6  is a view generally similar to  FIG. 3 , but showing a modified embodiment of the invention. 
         FIG. 7  is an exploded perspective view of the pool pump filter of the invention in combination with a pump. 
         FIG. 8  is a cross-sectional view showing the pool pump filter of the invention assembled in a pool pump. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     Looking at  FIGS. 1–4 , an inexpensive pool pump filter  1  is illustrated that includes the present invention. The pool pump filter  1  is particularly useful for cleaning the water in soft side portable swimming pools. However, it will understood that the invention is not limited to recreational applications. 
     The pool pump filter  1  is comprised of a cartridge  3  and a screen  5 . The screen  5  is removeably wrapable around the cartridge  3  and is held in place with one or more flexible bands  7 . 
     The cartridge  3  includes a pair of generally identical end plates  9  and  11 . The end plates  9  and  11  are illustrated as being rectangular in shape, but circular or other shapes are also acceptable. Each end plate has a outer periphery  13 , a central opening  15 , and opposed end surfaces  17  and  19 . Extending between and secured to the end plates are a number of posts  20 . In the illustrated construction, there are four posts  20 , but more or fewer may be used, if desired. The ends of each post are received in associated holes  18  in the end plates and secured in place by any suitable means, such as an adhesive or clamps. In the particular construction illustrated, the posts are secured to the end plates by set screws  22 . The end plates and posts together form a cage  21 . 
     Captured in the cage  21  is a center tube  23 . Preferably, the center tube  23  has a length that is slightly less than the distance between the end surfaces  19  of the end plates  9  and  11 . The center tube has an interior  24  bounded by an inner diameter  25  that is approximately the same size as the central openings  15  in the end plates. The center tube has an outer diameter  27  that loosely fits between the posts  20 . Thus, the center tube is free to move within the cage both axially between the end plates and radially between the posts, although the axial movement is quite small compared with the radial movement. The center tube wall  29  between the inner and outer diameters  25  and  27 , respectively, defines a number of rather large holes  31 . Together, the cage and center tube constitute the cartridge  3 . 
     The screen  5  may be made from any material that is impervious to water or other liquid with which pool pump filter  1  will be used. Aluminum and fiberglass are two representative suitable materials. Similarly, the screen openings may be sized to suit the particular application. For portable soft side pools, I have found that a fiberglass screen with openings approximately 0.06 inches square works very well, although smaller openings are also acceptable. 
     The screen  5  is fabricated with opposed longitudinal edges  33  that are spaced apart slightly less that the distance between the end plate surfaces  19 . The screen also has two ends  35  and  37 ,  FIG. 5 . 
     To assemble the screen  5  to the cartridge  3 , the screen end  37  is fed in the direction of arrow  41  from outside the cartridge between two posts, such as posts  20 A and  20 B in  FIG. 5 , and is laid against the center tube  23 . That action pulls the screen running end between the posts  20 A and  20 B in the direction of arrow  41 . For clarity, the screen end  37  is shown spaced from the center tube in  FIG. 5 . The screen is wrapped around the center tube at least one full turn to make an inner wrap as shown at reference numeral  39 . More than one turn may be used to make the inner wrap  39 , if desired. Wrapping the screen around the center tube is easily accomplished by rotating the center tube while holding the cage  21  stationary. That action further pulls the screen running end between the posts  20 A and  20 B in the direction of arrow  41 . After the screen has been wrapped around the center tube, the screen running end is wrapped around all the posts  20 . At least one full turn is required around the posts to make an outer wrap as shown at reference numeral  44 . There is a connecting section  42  of the screen running end between the inner and outer wraps  39  and  44 , respectively. The second screen end  35  constitutes a free end and is alongside an underlayer of the outer wrap. Finally, one or more ties or bands  7  are placed over the screen to surround the screen outer wrap and hold it against the posts to complete the pool pump filter  1 . Common commercially available elastic bands are satisfactory for the bands. For clarity, the band and screen are shown spaced from each other and from the posts in  FIG. 5 . 
     In  FIGS. 7 and 8 , the pool pump filter  1  is shown in use with a pump  43 . The particular pump  43  is used to circulate water in a portable soft side pool. The pump has a housing  45  with an annular wall  57  that defines part of a chamber  47 . As illustrated, the chamber  47  has a closed bottom end  52  and an open top end  59 . The pump may include a locator piece  48  at the closed end  52 . The locator piece has a pilot  50 . The locator piece pilot  50  fits inside the opening  15  of the filter end plate  11 . At the top of the chamber is a sealing ring  53 . The sealing ring  53  is retained in place by a cap  55  that threads onto the pump housing wall  57 . The sealing ring seals against the end surface  59  of the pump housing wall  57 . The sealing ring is fabricated with a pilot  61  that fits inside the opening of the filter end plate  9 . 
     Water from the pool flows through a tube, not shown, into an inlet  49  of the pump  43 . From the inlet  49 , the water flows through a motor driven pump, not illustrated in the drawings, and through a passage  51  to the chamber  47 , arrow  60 . The water flows through the screen outer wrap  44 , through the screen inner wrap  39 , and through the center tube holes  31  to the center tube interior  24 , arrow  62 . It is thus seen that the pool pump filter  1  is a two stage filter, one stage being the screen outer wrap and the other stage being the inner wrap  39 . From the center tube interior, the water flows out an outlet  63  of the sealing ring  53 , arrow  65 . A tubing, not shown, connects the sealing ring outlet  63  to the pool. 
     When the pool pump filter  1  is dirty, it is cleaned in a very simple and speedy manner. The cap  55  is unthreaded from the pump housing  45 , and the sealing ring  53  is removed. The filter is taken out of the pump chamber  47 , and the bands  7  are removed. The screen  5  is unwrapped from the cartridge posts  20  and center tube  23 . The screen is then cleaned in any suitable way, such as by spraying it with a garden hose. When the screen is clean, it is re-wrapped in the cartridge  3  as previously described. In that way, the filter of the invention is reusable, which greatly reduces the cost of maintaining the pool as well as saves on space in landfills. 
     Further in accordance with the invention, the cartridge for the pool pump filter may be made as a single piece. Turning to  FIG. 6 , a pool pump filter  67  is illustrated having a cartridge  69  that is molded as single piece from a suitable plastic material. The cartridge  69  has a pair of end plates  71  that are integral with and are spaced apart by a center tube  73 . The center tube  73  has a rather thin wall that defines a number of holes  75 . Also integral with the end plates  71  are at least two and preferably more posts  77 . A screen substantially similar to the screen  5  of the pool pump filter  1  described above is used with the filter  67 . Further, the screen is wrapped with inner and outer wraps in a manner identical to the wraps  39  and  44 , respectively, of the filter  1 . The result is the pool pump filter  67  that functions identically to the filter  1 . 
     In summary, the results and advantages of portable soft side pools can now be more fully realized. The pool pump filter of the invention provides reusable cleaning advantages as well as environmental advantages. This desireable result comes from using the combined functions of the flexible screen  5 . The screen is wrapped in inner and outer wraps  39 , and  44 , respectively, around the cartridge center tube and posts. As a result, the filter acts as a two stage filter. The rotatable nature of the center tube  23  in the cage  21  of the filter  1  makes the screen particularly easy to install and remove. For both cartridge designs  3  and  69 , a dirty screen is easily removed, washed, and replaced on the cartridge. The filter of the invention is entirely interchangeable with prior filters used in soft side pools. The versatility of the invention is further demonstrated by the fact that the center tube may be separate from or integral with the end plates. 
     It will also be recognized that in addition to the superior performance of the pool pump filter of the invention, its construction is such as to cost less than traditional filters. Also, its reusable nature eliminates the need for landfill space as is necessary for prior throw-away filters. 
     Thus, it is apparent that there has been provided, in accordance with the invention, a pool pump filter that fully satisfies the objects, aims, and advantages as set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.