A system and method for reducing the collection of debris in a fluid pumping system. The system and method may be used in pools, spas, or other applications in which fluids are circulated through a fluid-containing vessel. The system includes a first pump that circulates fluid. A screen is coupled to the input of the first pump and acts to prevent debris from reaching the first pump. A second pump may be used to remove debris from the screen.

TECHNICAL FIELD  
         [0001]    This invention relates to a system and method for pumping fluids, such as water. More particularly, the present invention relates to a self-cleaning screening system and method that reduces the collection of debris in water pumps and other devices in a fluid pumping system.  
         BACKGROUND  
         [0002]    In order to pump fluids, from one location to another, pipes are used as fluid conduits, and pumps are used to force fluid through the pipes. For example, in a pool or spa (or hot tub), a pumping system may be used to draw water into an inlet located in the pool or spa and to force the water out of an outlet back into the pool or spa. (Those skilled in the art will understand that the terms “spa” and “hot tub” are generally used interchangeably. For simplicity, the remainder of this description will use only the term “spa,” which will be understood to encompass spas and hot tubs.) Generally, such pumping systems will include one or more skimmers and/or filters located downstream from the inlet and upstream from a pump to prevent debris from reaching the pump, as build-up of debris at a pump's input may render the pump inoperable.  
           [0003]    Some debris, however, may not be trapped by the skimmer and filter, thereby allowing such untrapped debris to reach the pump. As a result, some pumping systems have incorporated a screen (or screen-trap) upstream of the pump's input in order to capture untrapped debris. While these screens do reduce and even prevent debris from reaching the pump, they must be manually cleaned and maintained, making them cumbersome and costly.  
           [0004]    Accordingly a need exists for a pumping system that includes an effective pump screen that can be cleaned and maintained automatically. The present invention provides such a pumping system.  
         SUMMARY  
         [0005]    The present invention is a pumping system and method that reduces the amount of debris that may clog and even render inoperable a pump or other apparatus in a fluid pumping system.  
           [0006]    The invention may be used in spa, hot tub, swimming pool, pond, aquarium, chemical treatment plant, or water treatment plant with a pumping system that includes, for example, a circulation pump and a high-speed pump. Circulation pumps are generally small, efficient pumps that are used for constant fluid circulation, while high-speed pumps are powerful pumps that are turned on periodically to operate, for example, water jets in a pool or spa. According to an embodiment of the invention, a high-speed pump may be turned on periodically to remove debris trapped in the screen, thereby automatically cleaning the screen.  
           [0007]    For convenience, the remainder of this description will refer to a “water” pumping system in a spa. But it will be understood that the present invention is not limited to spa pumping systems, but rather may be used in any suitable fluid pumping system, including swimming pools, ponds, aquariums, chemical plants, or water treatment plants, in which fluid is circulated by a fluid pumping system. In addition, the description refers to a “screen” or “screening” apparatus and method. It will be appreciated by those skilled in the art that the terms “screen” and “screening” are not intended to limit the invention in any way, but rather are broad terms intended to encompass any apparatus or device that can be used to separate, sift, block, or trap any debris or particulate matter carried by the water passing through the pumping system, including without limitation screens, sieves, filters, strainers, and sifters. Moreover, as embodied in this invention, the “screen” may operate passively or actively, or using a combination of both. An example of a passive “screen” would be a sifting grid located within a pipe. An example of an active “screen” would be a motorized filtration system.  
           [0008]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
       
    
    
     DESCRIPTION OF DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective view of a spa with a cutaway section showing parts of a pumping system in accordance with an embodiment of the present invention.  
         [0010]    [0010]FIG. 2 is a plan view of a pumping system in accordance with an embodiment of the present invention for use in a spa.  
         [0011]    [0011]FIG. 3A shows an embodiment of the screen in accordance with an embodiment of the present invention.  
         [0012]    [0012]FIG. 3B is a cross-sectional view along line  3 B- 3 B of FIG. 3A.  
         [0013]    [0013]FIG. 4A shows an alternative embodiment of the screen in accordance with an embodiment of the present invention.  
         [0014]    [0014]FIG. 4B is a cross-sectional view along line  4 B- 4 B of FIG. 4A. 
     
    
       [0015]    Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0016]    In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the present invention.  
         [0017]    [0017]FIG. 1 shows a spa  100 , including a cut-away section that reveals part of a water pumping system  101  used in the spa  100 . The spa includes a vessel  101 , in this case, a tub, for holding water. Those skilled in the art will appreciate that the tub is only an example of a vessel in accordance with the present invention. The various applications in which this invention may be used (e.g., swimming pools, aquariums, ponds) may have a different vessel, at least in shape and dimensions.  
         [0018]    In accordance with an embodiment of the present invention, the pumping system  101  of the spa  100  includes a circulation pump  102 , a jet pump  106 , and a screen  116 . Examples of suitable circulation pumps  102  include 98-Watt Circulation Pump manufactured by Laing Thermotech, Inc., as well as circulation pumps made by Grundfos, 3131 N. Business Park Ave., Freeno, Calif. 93727, or by Cal Pump, 13278 Ralston Ave., Sylmar, Calif. 91342. Examples of suitable jet pumps are the 3.0 or 4.0 HP 2-speed Sta-Rite pump, or single-speed pumps commonly used to filter pools or pump wells. The circulation pump  102  may be connected by a pipe  110  to circulation outlets  114  within the spa  100 , and the jet pump  106  may be connected by a pipe  112  to jets  104  within the spa  100 . A filtration inlet pipe  108  may be used to feed water from within the spa  100  to the input of the screen  116 , and a pipe  118  may be used to connect the input of the jet pump  106  to the screen  116  and the inlet pipe  108  at or near the input to the screen  116 . The output of the screen  116  may also be connected to the input of the circulation pump  102  by another pipe  120 . The arrows in FIG. 1 indicate the direction of flow of water through the pumping system  101 .  
         [0019]    As explained above, the circulation pump  102  is a relatively small, efficient pump for continuously circulating the spa water using the circulation outlets  114 . A separate jet pump  106 , which is relatively large and high-powered in comparison to the circulation pump  102 , is periodically used to pump water to the jets  104 . Such a two-pump system may be more efficient than using a single pump for both circulating water and providing water at high pressure to the jets  104 . This potential increase in efficiency results because the efficient low-power circulation pump  102  may be kept running at all times to keep the spa clean, while the high-power jet pump  106 , which generally requires substantially more power than the circulation pump  102 , need only be turned on periodically when operation of the jets  104  is desired.  
         [0020]    The screen  116  in the embodiment of FIG. 1 may be used to trap or filter debris being carried in the water passing through the inlet pipe  108 . Those skilled in the art will appreciate that spas generally include a skimmer and/or filter (not shown in FIG. 1) located between the inlet pipe  108  and the water in the spa  100 . Such a skimmer/filter is used to trap debris in the water of the spa  100  so that debris will not reach the spa's pumps. However, in conventional pumping systems, some debris is able to bypass the initial skimmer/filter. Debris that bypasses the skimmer/filter may build-up on the impeller of the circulation pump  102 , clogging the circulation pump  102  and even rendering it inoperable. Build-up of debris on the circulation pump  102  means that the pump  102  must be cleaned, which was done manually in conventional systems. Thus, in accordance with an embodiment of the present invention, the screen  116  is placed in the pumping system before the input to the circulation pump  102  to reduce the amount of water-borne debris that would otherwise reach the circulation pump  102 . The jet pump  106  may then be operated periodically or as necessary to pull debris out of the screen  116  and divert the debris to the primary filters (not shown) of the spa  100 . In addition, the powerful jet pump  106  may pump the debris back into the spa  100 , where it may be trapped by the skimmer/filter.  
         [0021]    [0021]FIG. 2 shows an exemplary spa pumping system  200  in accordance with an embodiment of the present invention. Those skilled in the art will appreciate, however, that the invention is not limited to spas; rather, the spa embodiment of the invention is merely shown as an example, and the invention can be applied to any filtered body of fluid, e.g., water. FIG. 2 shows a portion of a spa  204  having a surface  205  for holding water, with the water line being indicated by reference numeral  202 . The spa  204  is shown separately in the upper left and lower right portions of FIG. 2, but those skilled in the art will recognize that both portions are part of the same spa  204 . While not required, the pumping system  200  may include a skimmer  206  and a preliminary filter  208 . As indicated by the arrows in the skimmer  206  and preliminary filter  208 , water from the spa  204  passes through the skimmer  206  and the preliminary filter  208 , both of which are designed trap at least some of the debris present in the water so that the debris will not reach the downstream parts of the pumping system  200 . The downstream parts may include a screen,  222 , a circulation pump  226  connected by pipe  228  to a heater  230 , and an ozone generator  232  connected by a pipe  234  to an ozone injector  238 , which is also connected to the heater  230  by a pipe  236 . The optional ozone generator  232  and heater  230  may be coupled to the ozone injector  238 , which outputs heated, ozonated water into the spa  204  via an output pipe  240  (see also reference numeral  242 ).  
         [0022]    Some debris may escape the optional skimmer  206  and preliminary filter  208  and be carried in the water through pipes  210 ,  220 , and  224  to a circulation pump  226 . Accordingly, screen  222  is provided in the pumping system  200  to trap at least some of the debris that escapes the skimmer  206  and filter  208  before the debris can reach the input to the circulation pump  226  or any downstream features in the pumping system  200 , such as the heater  230  or ozone injector  238 . A jet pump  216 , which may be connected by pipe  214  to pipes  210  and  220  using a T-junction  212  or other suitable plumbing device, may be run periodically or as needed to pull trapped debris from the screen  222  and divert the debris to the primary filters of the spa  204 ; for example, the jet pump  216  may pump the debris back into the spa water  202 , where it may be trapped by the skimmer  206  and filter  208 . As such, the screen  222  may be automatically cleaned, obviating the need for cumbersome, time consuming, expensive manual cleaning of the screen  222 .  
         [0023]    In the embodiment of FIG. 2, the jet pump  216  is coupled to the screen  222  via pipes  220  and  214  and junction  212 . It will be appreciated, however, that the jet pump  216  and its coupling to the screen  222  could be configured differently. For example, pipe  214  could be eliminated. Alternatively, pipes  220  and  214  as well as junction  212  could be eliminated, with the jet pump  216  thus directly connected to the screen  222 .  
         [0024]    As those skilled in the art will appreciate, the screen  222  may be formed in a variety of ways. For example, as shown in FIGS. 3A and 3B, if the pipes  210  and  220  are cylindrical, a perforated, circular disk  302  may be inserted or integrally formed in pipe  220 , so that the planar surface of the disk  302  is orthogonal to the flow of water. The perforated disk  302  has sufficient perforations to allow water to pass through the pipe  220  and to trap debris carried in the water. The number and dimension of the performations may be altered as necessary to permit sufficient water flow. Of course, if pipe  220  has a different cross-sectional shape, for example, a square shape, the disk  302  would have a corresponding shape. FIGS. 4A and 4B show an alternative embodiment of the screen  222 , in which the screen  222  is formed from a flexible mesh  402  disposed over an opening  404  of pipe  220 . In this alternative embodiment, pipe  220  is separate from, and inserted into, T-junction  212 , allowing the flexible mesh  402  to be secured across the opening  404 . FIG. 4B is a cross-sectional view along line  4 B- 4 B in FIG. 4A, showing the flexible mesh  402  disposed over opening  404  in a manner that allows water to pass through the mesh  402  while at the same time trapping debris in the mesh  402 .  
         [0025]    A variety of methods may be used to effect operation of the jet pump  216  and thus automatic cleaning of the screen  222 . One method is to provide a conventional timer  244 , coupled to the jet pump  216 . The timer  244  may be set up to turn the jet pump  216  on and off periodically, for example, once a day for five minutes, using, for example, a conventional switch or relay  245  on the jet pump  216 . Such periodic running of the jet pump  216  allows the screen  222  to be cleaned automatically, as desired. The switch  245  could also be equipped with a manual feature, in addition to the timer  244 , allowing the jet pump to be manually turned on and off to clean the screen  222 , as needed, but without the need to manually remove the screen for cleaning. Alternatively, a conventional flow-sensing device  248  could be located before (or after) the circulation pump  226 . The flow sensing device  248  could be coupled, for example, to a conventional controller  246  that, based on the flow rate of water in pipe  224  (or pipe  228 ), operates to turn the jet pump  216  on and off. As yet another alternative, a pressure sensing device, current or voltage sensing device, or other monitoring device could be provided in the pumping system  200  to monitor operation of the circulation pump  226 , in known fashion. The pressure sensing device, current or voltage sensing device, or other monitoring device would then be coupled to the controller  246 . As performance of the circulation pump  226  is impeded by the build-up of debris in the screen  222 , the controller  246 , monitoring such impeded performance, could operate to turn the jet pump  216  on and off, using, for example, the switch or relay  245 . The controller  246  and sensor could be configured such that the controller turns on the jet pump  216  when the pressure, current, voltage, or other sensed parameter reaches, exceeds, or dips below a predetermined threshold level, in known fashion. Once the controller  246  determines that the sensed parameter has dropped back below or has gone back above the threshold level (for example, by a given amount), the controller could then operate to turn off the jet pump  216 , in known fashion. Operating the jet pump  216  would then act to remove the trapped debris from the screen  222 , allowing the circulation pump  226  to resume normal operation. It will be recognized from the above description that any time the powerful jet pump  216  is turned on and the circulation pump  226  is off, the jet pump  216  will pull water back through the jet pump  216  and thus clear the screen  222  of debris.  
         [0026]    Those skilled in the art will recognize that other methods of automatically operating the jet pump  216  exist. For example, an optical sensor could be used to monitor the amount of debris trapped in the screen  222 . All such alternatives fall within the scope and spirit of the present invention.  
         [0027]    Accordingly, using the present invention, any debris that is trapped in the screen  222  may be automatically cleaned using the jet pump  216 . This obviates the need for a human to manually clean the screen  222 . It will be appreciated, however, that the invention is not limited to a single jet pump. Some pumping systems, for example, in a spa, may use multiple jet pumps. Any one or a combination of such jet pumps could be used to effect cleaning of the screen  222 . Further, the invention is not limited to the use of a jet pump  216  to clean the screen  222 . Any suitable pump may be used to clean the screen  222 ; for example, a high-powered pump used for draining the pool or spa could be operated periodically in order to automatically clean the screen  222 . Moreover, the jet pump  216  may be replaced by any device capable of sucking or blowing debris from the screen  222 .  
         [0028]    In an alternative embodiment of the present invention, a dedicated high-power cleaning pump could be placed in line  210 . A check valve is then installed in line  214 . The dedicated pump in line  210  is then started when debris is to be removed from the screen  222 . As another alternative, instead of using the jet pump  216 , the circulation pump  226  may be run in reverse to clean the screen  222 . In this alternative, the filter  208  could be removed, and the debris would flow back into the spa  204 . The debris could then be removed from the spa water  202  manually or by replacing the filter  208 .  
         [0029]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the T-junction  212  shown in FIG. 2 need not be used; instead, pipes  210 ,  220 , and  214  may be an integral T-pipe. Moreover, several alternative embodiments have been described for controlling operation of the jet pump  216  to remove debris from the screen  222 . Any one, or a combination, of those embodiments may be used to control the jet pump  216 . Accordingly, other embodiments are within the scope of the following claims.