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CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/779,733, filed Mar. 13, 2013, entitled “Hydraulic Oscillating Power Generator,” the entire contents of which are incorporated herein by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to generating electricity and more particularly, although not necessarily exclusively, to automatic hydraulic cleaners for swimming pools and spas in which electricity is generated via oscillation of a magnet within a coil. 
       BACKGROUND OF THE INVENTION 
       [0003]    Conventionally, an automatic pool cleaner (“APC”) may be considered either “hydraulic” or “electric” depending on the source of energy employed to effect its movement within a pool, spa, or other water-containing vessel. “Electric” cleaners, sometimes also called “robots,” typically use electricity to power motors used to drive wheels or treads to allow the cleaners to move throughout the vessel. Although on-board batteries are sometimes considered to supply electricity to the robots, more likely electricity from mains outside the vessels is conveyed via electrical cords to the robots within the vessels. 
         [0004]    “Hydraulic” cleaners, by contrast, connect to external pumps and utilize water flow caused by operation of the pumps to effect their movement within a pool or spa. Some hydraulic cleaners connect to pump outlets; these devices are called “pressure-side” APCs, as pressurized water from pump outlets typically drives the cleaners. Alternatively, hydraulic cleaners may connect to inlets of pumps. These “suction-side” cleaners often include valves and supporting structure designed periodically to interrupt water flow through their bodies to the pumps. Periodic flow interruption creates a “water-hammer” effect, with the resulting energy used to move the APCs within pools. 
         [0005]    U.S. Pat. No. 4,742,593 to Kallenbach discloses exemplary valves useful in water-interruption, suction-side hydraulic APCs. A flexible-walled, “diaphragm” valve of the Kallenbach patent may be placed within a chamber of a body of an APC, with the chamber filling with water upon immersion of the APC within a pool. As noted therein:
       Expansion of the valve and release for it to reassume its relaxed condition is by the creation of a pressure differential across the valve member walls, i.e., a pressure difference between the chamber and the interior of the valve member. This is created by the suction [of the external pump]. The valve is autonomously opened and closed. Applied suction initially causes the valve to open; but with water flow established, the pressure within [the] valve drops below that of [the] chamber. The valve thus closes. The cycle autonomously repeats.
 
See Kallenbach at col. 2, 1. 64 to col. 3, 1. 6 (numerals omitted).
       
 
         [0007]    Similar water-interruption valves and associated structures are illustrated in U.S. Pat. No. 4,642,833 to Stoltz, et al. Like the valves of the Kallenbach patent, those of the Stoltz patent are positioned within chambers. In at least some embodiments of the Stoltz patent, water may flow into and out of the chambers via ports communicating with flow passages though the valves. See, e.g., Stoltz at col. 3, 11.8-21. 
         [0008]    Historically, hydraulic cleaners—and especially suction-side, water-interruption APCs—have been entirely mechanical devices, operating without any need for electricity. As electronic processors (and other electric devices) decrease in cost, weight, and size, however, hydraulic cleaners could benefit from on-board inclusion of these processors and devices. Inclusion requires a supply of electricity, however, just as is required currently for electric cleaners. Such supply could, of course, likewise be provided by electric mains via a cord or perhaps by an on-board battery or turbine. Each of these approaches is disadvantageous in at least some respects, however. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention permits electricity generation on-board hydraulic APCs while avoiding disadvantages associated with existing means for supplying electricity to (principally electric) cleaners. No abnormal disruption of the primary water flow though water-interruption cleaners need occur in order to generate electricity, for example, thus both avoiding any increased risk of clogging the associated valves with debris and maintaining the operational effectiveness of the valves. The invention also avoids problems associated with weight and recharging of on-board batteries and does not mandate any reduction in integrity of any electronics enclosure that might otherwise be caused by mechanical arms, rotating axles, or levers of impellers or turbines. 
         [0010]    Equally significant is that the present invention exploits the fact that, in certain water-interruption APCs, the valves and external pumps normally cause movement (of water) within the chambers associated with the valves. Rather than move only water within the chambers, the present invention moves one or more magnets as well. By placing wire coils outside the chambers, movement (oscillation) of the magnets may generate electricity through otherwise normal operation of the cleaners. The generated electricity preferably is used to power electrical devices (e.g. processors) on-board the cleaners, so as to increase their “intelligence,” although other devices either on-board or remote from the cleaners may also or alternatively be powered. 
         [0011]    It thus is an optional, non-exclusive object of the present invention to provide improved cleaners of swimming pools, spas, and other water-containing vessels (hereinafter sometimes separately or collectively referred to as “pools” or “swimming pools”). 
         [0012]    It is another optional, non-exclusive object of the present invention to provide mechanisms for generating electricity on-board hydraulic pool cleaners. 
         [0013]    It is also an optional, non-exclusive object of the present invention to provide electricity-generating mechanisms involving one or more magnets moving within one or more coils forming parts of APCs. 
         [0014]    It is a further optional, non-exclusive object of the present invention to provide movement of magnets as part of the normal operating principles of at least certain water-interruption cleaners. 
         [0015]    Other objects, features, and advantages of the present invention will be apparent to those skilled in appropriate fields with reference to the remaining text and drawings of this application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of portions of an exemplary pool cleaner of the present invention. 
           [0017]      FIGS. 2-3  are cross-sectional views of the portions of the exemplary pool cleaner of  FIG. 1 . 
           [0018]      FIG. 4  is a perspective view of the portions of the exemplary pool cleaner of  FIG. 1  also showing a wire or other electricity-conveying member. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Illustrated in  FIGS. 1-4  is body  10  consistent with the present invention. Body  10  may form part or all of a body of a pool cleaner such as a hydraulic, suction-side APC. If desired, for example, body  10  may substitute for corresponding structure of the disc cleaners disclosed in the Kallenbach and Stoltz patents. Body  10  may include inlet  14  and outlet  18 ; in use as a suction-side APC, body  10  receives debris-laden water via inlet  14  and passes the water out outlet  18  for transfer to a hose, and thence to a debris filter, connected to the inlet side of a pump of a water-recirculation system associated with a pool or spa. 
         [0020]    Body  10  preferably (but not necessarily) is formed of molded plastic material and comprises nominally lower and upper sections  22  and  26 , respectively. Advantageously, upper section  26  is a rigid cylindrical tube, while lower section  22  houses valve  30  in whole or in part. Those skilled in the art will, of course, recognize that upper section  26  need not necessarily be cylindrical or tubular in shape, and valve  30  may be housed other than in lower section  22 . As shown particularly in  FIG. 1 , upper section  26  beneficially may terminate, at outlet  18 , with a nut  34  or other structure intended to facilitate connection of body  10  to a hose or other structure. 
         [0021]    A preferred valve  30  is a flexible-walled diaphragm valve similar or identical to any of those depicted in the Kallenbach and Stoltz patents. Alternatively, valve  30  may be a diaphragm valve of the type detailed in either of U.S. Pat. No. 7,618,019 or 8,100,146 to van der Meijden, et al. or otherwise. As shown in  FIGS. 2-3 , valve  30  may have valve inlet  38  and valve outlet  42  and define an internal water flow path  46  therethrough. Valve  30  is depicted as being connected, via flanges and grooves (or otherwise as desired), to both lower section  22  (at inlet  14  and valve inlet  38 ) and upper section  26  (at valve outlet  42 ). 
         [0022]    In use, body  10  and valve  30  form a primary flow path P for debris-laden water. Under influence of the external pump, such water enters inlet  14 , travels through the interior of valve  30  along internal water flow path  46 , and exits upper section  26  at outlet  18 . When valve  30  mainly or completely closes, primary flow path P is interrupted, producing the water-hammer effect that causes movement of body  10  within the pool or spa. 
         [0023]    Additionally defined by body  10  is secondary flow path S. Secondary flow path S exists through connector  50  and lower section  22  externally of valve  30 . However, because of the sealing connection of valve  30  and lower section  22 , secondary flow path S is isolated from inlet  14  and valve inlet  38 . Connector  50  and lower section  22  externally of valve  30  thus collectively form a “chamber” similar to the chambers described in the Kallenbach and Stoltz patents, with connector  50  including a port  54  allowing fluid communication between it and upper section  26 . 
         [0024]    Conventionally, (only) water is present within the chamber formed by connector  50  and lower section  22  externally of valve  30 , entering through a leakage path or otherwise upon submersion of body  10 . When body  10  of the APC is immersed in water and the external pump is activated, less than ambient pressure is present at outlet  18 . This partial evacuation of body  10  causes debris-laden water to flow along primary flow path P until diaphragm valve  30  collapses. As valve  30  collapses it forms greater resistance to water flow along primary path P; influence of the pump causes water in the chamber to flow along secondary path S toward port  54 , hence forcing valve  30  to open. As valve  30  reopens, water again flows along primary flow path P, creating the cyclical results identified in the Kallenbach patent. 
         [0025]    Opening of valve  30  additionally causes water to flow away from port  54  (toward lower section  22 ) in the secondary flow path S. Thus, clear is that secondary path S is bi-directional, with water oscillating toward and away from port  54  within the chamber formed by connector  50  and lower section  22  externally of valve  30 . Shown especially in  FIGS. 2-3  is that at least one magnet  58  may be positioned within the chamber (displacing some water). By so positioning magnet  58 , it too is subject to oscillation as valve  30  opens and closes. In one version of the invention magnet  58  oscillates at 5.8 Hz, although other frequencies are acceptable. 
         [0026]    As depicted, magnet  58  is a solid mass with width slightly smaller than the diameter of connector  50 , allowing it to move generally longitudinally therein without substantial friction yet preventing much lateral movement. In this case magnet  58  advantageously may (but need not necessarily) be coated with a hard-wearing material to protect it from wear and corrosion. Alternatively, magnet  58  may be solid or particulate material within a container whose width is slightly smaller than the diameter of connector  50 . Bends, stops, or other structural features of connector  50  or lower section  22  (or both) may define a maximum travel distance of magnet  58  within the chamber. In the depicted version of body  10 , magnet  58  remains within connector  50  so as not to impact valve  30 . Magnet  58  need not necessarily always remain within connector  50 , although it preferably should not intersect or disrupt the primary flow path P of water and debris. 
         [0027]    One or more coils  62  may be wound or positioned about exterior  66  of connector  50 , hence effectively surrounding magnet  58 . As magnet  58  travels generally longitudinally within connector  50 , it cooperates with coils  62  in conventional manner to produce electricity.  FIG. 4  illustrates cable  70  which may house output wires conveying the generated electricity either elsewhere within body  10  or elsewhere. The generated electricity may be rectified if desired and, for example, collected in batteries or capacitors. Presently-preferred embodiments of the invention contemplate using the generated electricity to power processors, lights, steering mechanisms, or other equipment on-board body  10  of an APC. The electrically-powered equipment may perform numerous functions, non-limiting examples of which include enabling better cleaning coverage of pool floors and walls and recognizing and steering to seek particular debris within a pool. 
         [0028]    Magnet  58  and coil  62  thus form an exemplary electricity generator  74  that is outside primary flow path P and thus does not negatively impact debris collection by body  10 . Generator  74  requires no dedicated secondary flow to operate, instead exploiting existing back-and-forth water movement in secondary flow path S. Generator  74  functions regardless of orientation of valve  30 , and transfers mechanical action to electrical energy through connector  50  of body  10  without need for openings and seals that are prone to wear and leakage. 
         [0029]    Additionally, because magnet  58  likely is substantially heavier than the water it displaces, the outer water column corresponding to secondary flow path S may be shortened. In some embodiments of the invention, magnet  58  is approximately seven times heavier than the displaced water, allowing the outer water column to be shortened by a length approximately seven times the length of magnet  58  yet maintain the same pulsation frequency in valve  30 . This advantage of the invention exists regardless of whether magnet  58  produces electricity; indeed, it may be achieved by placement in connector  50  of some other non-magnetic mass heavier than water. 
         [0030]    The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention. As an example of such modifications, persons skilled in the art will recognize that generator  74  need not necessarily comprise magnets and coils, as in some situations other mechanisms of generating electricity using movements within body  10  may be employed instead. Likewise, valve  30  or another device may be placed so as to open and close in a water flow path of a pressure-side APC. The entire contents of the Kallenbach, Stoltz, and both van der Meijden patents are incorporated herein by this reference.

Summary:
Generation of electricity on-board, principally, certain hydraulic pool cleaners is described. Magnets may be caused to move within coils by (normal) cooperative actions of diaphragm-type valves and external pumps, thus generating electricity without changing the operational principles of the cleaners. The generated electricity may be used to power electrical devices either on-board the cleaners or elsewhere.