Abstract:
A power generator for use in a unidirectional flowing fluid has a fixed part and a movable part, the movable part is mounted on the fixed part for reciprocal movement with respect to the fixed part between first and second positions. A valve element on the movable part is adapted to move between open and closed positions for relatively unimpeded and impeded flow. A valve actuation mechanism is connected to the valve element to move the valve element to the closed position when the movable element reaches the first position and to move the valve element to the open position when the movable element reaches the second position. An electrical generator is coupled to the fixed part and the moveable part and is adapted to generate electrical energy when the movable part moves between the first and second positions.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Patent Application No. 60/745,307, filed Apr. 21, 2006, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to power generation. In one of its aspects, the invention relates to a power generator that uses a unidirectional flowing fluid for generation of electrical energy. In another of its aspects, the invention relates to a system for generating electrical energy using a unidirectional flowing fluid. In another of its aspects, the invention relates to a method for generating electrical energy using a unidirectional flowing fluid. 
         [0004]    2. Description of the Related Art 
         [0005]    Power generators utilizing natural or renewable source of energy, such as water or air, have been heretofore proposed. Many of these generators use turbines that are turned as water or air impinges on the blades of the turbine. The rotational movement of the turbine is used to turn an electric generator or other similar device. The most common hydroelectricity generators require large dams and reservoirs to be built to produce electricity. These constructions can also adversely affect the environment by disrupting the natural flow of water and the surrounding ecosystem. Other power generators utilize tidal or wave action and wind as a source of renewable energy. However, these power generators are unreliable as both wave action and wind energy are not constant or predictable and thus produce a varying amount of electricity within a given time frame. 
         [0006]    These and other related types of power generators are disclosed in one or more of the following references: 
         [0007]    United States Patent Application Publication No. 2005/0073154 to Dudley, published Apr. 7, 2005 
         [0008]    U.S. Pat. No. 4,583,368 to Neuenschwander, issued Apr. 22, 1986 
         [0009]    U.S. Pat. No. 4,500,827 to Merritt et al., issued Feb. 19, 1985 
         [0010]    European Patent Application No. 0977343, published Jun. 23, 1988 
         [0011]    Japanese Patent Application Publication No. 63150472, published Feb. 2, 2000 
         [0012]    Japanese Patent Application Publication No. 11044288, published Feb. 16, 1999 
         [0013]    Japanese Patent Application Publication No. 9256941, published Sep. 30, 1997 
         [0014]    United Kingdom Patent Application No. GB 2210107, published Jun. 1, 1989 
         [0015]    U.S. Pat. No. 4,782,663 to Bellamy, issued Nov. 8, 1988 
         [0016]    U.S. Pat. No. 6,020,653 to Woodbridge et al., issued Feb. 1, 2000, and 
         [0017]    United Kingdom Patent Application No. GB 2143284, published Feb. 6, 1985. 
       SUMMARY OF THE INVENTION 
       [0018]    According to the invention, a power generator for use in a unidirectional flowing fluid comprises a fixed part and a movable part, wherein the fixed part is adapted to be fixed with respect to a flowing fluid, and the movable part is mounted to the fixed part for reciprocal movement with respect to the fixed part between first and second positions. A valve element is carried on the movable part and is adapted to move between an open position at which fluid flow with respect to the movable part is relatively unimpeded and a closed position in which the fluid flow with respect to the movable part is impeded to thereby move the movable part to the second position. A valve actuation mechanism is connected to the valve element to move the valve element to the closed position when the movable element reaches the first position and to move the valve element to the open position when the movable element reaches the second position. An electrical generator is coupled to the fixed part and the moveable part and is adapted to generate electrical energy when the movable part moves between the first and second positions. 
         [0019]    The movable part and the fixed part can take a number of different configurations that include, for example, a pair of telescoping tubes or the movable part can be a shaft and the fixed part can be a guide for the shaft. 
         [0020]    The electrical generator can also take a variety of forms that include the generation of electrical energy with the relative linear movement of the movable part with respect to the fixed part. For example, at least one coil winding can be mounted on one of the movable and fixed parts and at least one magnet on the other of the movable and fixed parts so that electrical current is generated as the magnet passes the coil winding. Alternatively, the movable part can be connected to an arm which is coupled to an eccentric coupling on a pulley/wheel/disk that can turn a rotating generator. Still further, the movable part can be connected to an arm which acts in a ratcheted movement to turn a rotating generator as the arm moves with the movable part when the valve is in the closed position. 
         [0021]    In one embodiment of the invention, a biasing member is mounted between the fixed part and the movable part for biasing the movable part toward the first position. The biasing means can comprise, for example, a tension spring or a compression spring. 
         [0022]    In another embodiment of the invention, the return of the movable member to the first position is accomplished by coupling two power generators together in parallel with the movable members coupled together, for example, with a cable and pulley, but with the movable members 180 degrees out of phase. 
         [0023]    The valve element can take a number of forms so long as it performs the function of opening and closing a passage for flow of the flowing fluid. For example, the valve element can be a butterfly valve, a ball valve, a clamshell valve, a slide valve, or a vane. 
         [0024]    The valve actuation mechanism can likewise take a number of forms so long as it performs the function of opening and closing the valve at the appropriate position of the movable element in the first and second positions. For example, the valve actuation member can be a simple mechanical devise such as a lever on the valve element and mechanical stop blocks on the fixed part. Alternatively, the valve actuation member can be electromechanical such as a motor that is connected to the valve element, sensing elements that detect the movable part in the first and second positions and a controller connected to the sensing elements and to the motor. Still further, the valve actuation member can be wholly electronic, such as the use of a solenoid operated valve element in lieu of the motor in the electromechanical valve actuator. 
         [0025]    In a preferred embodiment of the invention, a detent releasably retains the valve member in at least one of the open and closed positions, preferably in both the open and closed position. 
         [0026]    Further according to the invention, a system for generating power in a unidirectional moving fluid comprises any of the power generators described above positioned within the unidirectional moving fluid wherein the fixed and movable parts are arranged so that the direction of reciprocal movement of the movable part is aligned with the direction of movement of the moving fluid and the first position of the movable part is at an upstream portion of the moving fluid and the second position of the movable part is at a downstream portion of the moving fluid. 
         [0027]    The unidirectional moving fluid can be a number of sources that include a water stream, pressurized steam, for example, from a steam generator, or wind. 
         [0028]    The electrical generator of the power generating system can be connected to an individual user or can be connected to a power grid. 
         [0029]    The power generating system according to the invention can further include a second power generator as described above positioned within the unidirectional moving fluid wherein the movable parts of the respective power generators are coupled together for movement with each other but 180 degrees out of phase so that the movable part of the first power generator moves to the first position as the movable part of the second power generator moves to the second position. 
         [0030]    Still further according to the invention, a method for generating power comprises positioning any of the power generators described above into a unidirectional moving fluid wherein the fixed and movable parts are arranged so that the direction of reciprocal movement of the movable part is aligned with the direction of movement of the moving fluid and the first position of the movable part is at an upstream portion of the moving fluid and the second position of the movable part is at a downstream portion of the moving fluid and taping electrical energy from the electrical generator. 
         [0031]    The power generator according to the invention can produce a reliable amount of electricity and utilizes a renewable source of energy without disrupting the environment in which the power generator is located. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0032]    In the drawings: 
           [0033]      FIG. 1  is a side sectional view of a first embodiment of a power generator comprising an inner and outer tube according to a first embodiment of the invention. 
           [0034]      FIG. 2  is a top sectional view of the power generator from  FIG. 1 . 
           [0035]      FIG. 3  is a top view of the power generator from  FIG. 1 , illustrating a valve switching mechanism for the power generator. 
           [0036]      FIG. 4  is a side view of a valve position retaining device for the power generator. 
           [0037]      FIG. 5A-5C  are sectional views taken along line  5 A- 5 A of  FIG. 4 . 
           [0038]      FIG. 6  is a schematic illustration of the power generator from  FIG. 1  positioned in a unidirectionally flowing river. 
           [0039]      FIG. 7  is a side sectional view of the power generator from  FIG. 1 , with a valve in the inner tube in a closed position and the inner tube in an upstream position. 
           [0040]      FIG. 8A  is a view similar to  FIG. 7 , with the valve in the inner tube in a position between open and closed and the inner tube in a downstream position. 
           [0041]      FIG. 8B  is a top view of the power generator of  FIG. 8A . 
           [0042]      FIG. 9A  is a view similar to  FIG. 7 , with the valve in the inner tube in an open position and the inner tube in a further downstream position. 
           [0043]      FIG. 9B  is a top view of the power generator of  FIG. 9A . 
           [0044]      FIG. 10A  is a view similar to  FIG. 7 , with the valve in the inner tube in an open position and the inner tube in an upstream position. 
           [0045]      FIG. 10B  is a top view of the power generator from  FIG. 10A . 
           [0046]      FIG. 11  is a top view of the power generator, with the valve in the inner tube in a position between open and closed. 
           [0047]      FIG. 12  is a top view of the power generator, with the valve in the inner tube in a closed position and the inner tube in an upstream position. 
           [0048]      FIG. 13  is a side sectional view of a second embodiment of a power generator according to the invention. 
           [0049]      FIG. 14  is a top sectional view of the power generator from  FIG. 11 , with a valve in a closed position. 
           [0050]      FIG. 15  is a top sectional view of the power generator from  FIG. 11 , with a valve in an open position. 
           [0051]      FIG. 16  is a schematic illustration of a third embodiment of a power generator according to the invention. 
           [0052]      FIG. 17  is a schematic illustration of a fourth embodiment of a power generator according to the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0053]    A power generator according to the invention utilizes a flowing fluid to generate electricity. The fluid may be water, steam, or air. Referring to  FIGS. 1-2 , a power generator  10  according to one embodiment of the present invention is illustrated, and comprises a pair of concentric tubes  12 ,  14 . The inner tube  12  is substantially hollow, with an outer surface  16 , an inner surface  18 , a centrally extending cavity  20 , a first open end  22  and a second open end  24 . The outer tube  14  is substantially hollow, with an outer surface  26 , an inner surface  28 , a centrally extending cavity  30 , a first open end  32 , and a second open end  34 . The inner tube  12  is received concentrically within the outer tube  14 , preferably with a generally annular gap  36  between the outer surface  16  of the inner tube  12  and the inner surface  28  of the outer tube  14  to allow the tubes  12 ,  14  to move linearly relative to one another without friction. 
         [0054]    As illustrated, the tubes  12 ,  14  are have a cylindrical cross-section. However, the tubes  12 ,  14  may have any polygonal cross-section shape, such as, but not limited to, triangular, square, rectangular, hexagonal, elliptical, and ovoid. The tubes  12 ,  14  can be constructed from any suitable material that does not corrode when exposed to water or other elements of the environment in which the power generator  10  is utilized. Examples of suitable materials are stainless steel, non-ferrous metals, most plastics, glass, and/or concrete. 
         [0055]    The tubes  12 ,  14  are attached to one another at or near their respective first ends  22 ,  32 . The first end  32  of the outer tube is fixedly mounted to plate  38  having at least one aperture  40  for fluid to flow therethrough. At least one tension spring  42  is attached between the plate  38  and the inner tube  12 . More preferably, two tension springs  42  are attached between the mounting plate and the first end  22 , generally spaced 180° from each other on the circumference of the inner tube  12 . 
         [0056]    The inner tube  12  is further provided with a valve  44  for selectively occluding the cavity  20 . More specifically, the valve  44  is moveable between a first or open position wherein fluid may enter first end  22 , pass through cavity  20 , and exit through second end  24 , and a second or closed position wherein fluid is substantially prevented from exiting through second end  24 , although it is within the scope of the invention for small amount of fluid to pass through the second end  24  when the valve  44  is in the closed position. In the embodiment shown in  FIG. 1 , the valve  44  is a butterfly valve comprising a valve body  46  that is received within cavity  20 . The valve body  46  is sized to substantially occlude the cavity  20  in the closed position (shown in  FIG. 7 ). A valve stem  48  is attached to the valve body  46  and defines the axis about which the butterfly valve  44  pivots. A portion  50  of the valve stem  48  extends exteriorly of both tubes  12 ,  14  and a generally orthogonal position arm  52  extends from the portion  50 . 
         [0057]    Other suitable devices for selectively opening and closing the second end include other internal devices such as a ball check valve, and external devices such as a “clam-shell” valve or vanes having two or more parts that open outwardly or that slide in a direction perpendicular to the flow direction of the fluid or a device that inflates and deflates. 
         [0058]    The outer tube  14  is further provided with a device for limiting the movement of the inner tube  12 . Referring to  FIG. 3 , the outer tube  14  has an elongated slot  54  having first and second ends  56 ,  58 , respectively, that slidingly receive the valve stem  48 . The movement of the inner tube  12  relative to the outer tube  14  is limited to a distance defined by the length of the slot  54 . Thus, the first end  56  defines a maximum upstream position of the inner tube  12  and the second end  58  defines a maximum downstream position of the inner tube  12 . The slot  54  preferably has a width that is equal to or slightly greater than the width or diameter of the valve stem  48 . This relationship helps to prevent the inner tube  12  from drifting out of alignment with the outer tube  14 . 
         [0059]    The power generator  10  further has a valve switch that opens and closes the butterfly valve  44 . The valve switch can be any suitable mechanical or electrical mechanism. Mechanical mechanisms include, but are not limited to levers, springs, and gears. Referring to  FIG. 3 , a mechanical valve switching mechanism comprising a pair of stop blocks  60 ,  62  mounted on the outer surface  26  of the outer tube  14 . The first stop block  60  is positioned near or at the first end  56  of slot  54  and has an concavely curved surface  64  that is positioned to receive the position arm  52  as the valve stem  48  approaches the first end  56 . The curved surface  64  forces the valve body  46  from the open position to the closed position, as will be described in more detail below. The second stop block  62  is positioned at or near the second end  58  of slot  54  and has an angled surface  66  that receives the position arm  52  as the valve stem  48  approaches the second end  58 . The angled surface  66  forces the valve body  46  from the closed position to the open position, as will be described in more detail below. 
         [0060]    Referring to FIGS.  4  and  5 A- 5 C, the butterfly valve  44  has a valve position retainer  68  or detent that helps releasably retain the butterfly valve  44  in the open or closed position. The retainer  68  comprises a retaining block  70  fixedly attached to the inner tube  12 . Preferably, the retainer  68  is mounted to the outer surface  16  of the tube, but can also be attached to the inner surface  18 . The retaining block  70  has an inner disc-shaped cavity  72  that retains a rotatable valve stop ring  74  having a pair of dimples  76 ,  78  formed in the outer periphery of the stop ring  74 . The dimples  76 ,  78  are spaced 90° on the circumference of the stop ring  74  and are sized to alternately receive a ball bearing  80 . The ball bearing  80  is biased by a spring  82  received in a spring cavity  84  formed in the retaining block  70  and in communication with the disc-shaped cavity  72 . The stop ring  74  is fixedly attached to the valve stem  48 , such the stop ring  74  moves with the valve stem. When the butterfly valve  44  is in the closed position, illustrated in  FIG. 5A  in which the valve arm  52  is horizontal with respect to the orientation of the page, the ball bearing  80  is received in dimple  76 . When the butterfly valve  44  is in the open position, illustrated in  FIG. 5C  in which the valve arm  52  is vertical with respect to the orientation of the page, the ball bearing  80  is received in dimple  78 . As the butterfly valve  44  moves from the closed position to the open position, or vice versa, the ball bearing  80  is forced at least partially into the spring cavity  84  by the outer periphery of the stop ring  74  and compresses the spring  82 . When the ball bearing  80  reaches either dimple  76 ,  78 , the spring  82  forces the ball bearing into the dimple  76 ,  78  to retain the butterfly valve in the respective closed or open position. Thus, the dimples  76 ,  78  and the spring biased ball bearings  80  form a detent mechanism for releasably retaining the butterfly valve  44  in the open or closed position. 
         [0061]    The inner and outer tubes  12 ,  14  further have a means for generating electrical current. In the illustrated embodiment, one or more magnets  86  are mounted on the outer surface  16  of the inner tube  12 . The magnets  86  are preferably annular and extend around the outer circumference of the inner tube  12 . The outer tube  14  has one or more coil windings  88  on its inner surface  28 . As is commonly known, by passing the magnets  86  through the magnetic field of the coil windings  88 , electrical current can be induced in the coil windings. In another embodiment (not shown), the power generator can have a conventional electric generator attached, whereby the linear motion of the power generator is converted to rotational motion to rotate the electric generator. 
         [0062]    The power generator  10  is preferably positioned in a body of water having unidirectional flow, such as a river, stream, waterfall, or dam. The term “unidirectional” is used to convey that most fluid is flowing along a path defined along a single direction. Referring to  FIG. 6 , the power generator  10  is positioned in a river R so that the longitudinal axes of the tubes  12 ,  14  are substantially parallel to the direction of water flow, indicated by arrow F, and the first ends  22 ,  32  are positioned upstream relative to the second ends  24 ,  34 . It is also contemplated that the power generator  10  can also be mounted within a river with the longitudinal axes of the tubes  12 ,  14  canted with respect to the direction of fluid flow F. In either case, the flow rate of the river is fairly constant and thus will produce a fairly constant amount of electricity. 
         [0063]    The power generator  10  can further have a means for anchoring the power generator  10  within the body of water, such as a support  90  extending to the river bed B or tether extending to a fixed structure (not shown). The power generator  10  can also be attached to a mobile object, such as a boat, that would create the effect of flowing water even in a substantially still body of water. 
         [0064]    The power generator  10  can also utilize air as a source of energy. The power generator  10  can be mounted in an air stream. The air stream can be a naturally occurring air stream such as wind. The power generator  10  can also be attached to a mobile vehicle, such as automobile or airplane, that would create the effect of flowing air without needing a naturally occurring air stream. 
         [0065]    The power generator  10  can also utilize steam as a source of energy. For example, the steam that exits the turbines of a power plant could be ducted so that it used as the motive force for the power generator  10  instead of being directly exhausted to a condenser. 
         [0066]    A power grid  92  or other suitable power receptor can be operably coupled to the power generator  10  to receive and/or distribute the electric power produced by the power generator. A number of power generators  10  can be mounted in juxtaposed position in a moving fluid body and attached to a single power grid  92 . 
         [0067]    Referring to  FIGS. 7-10 , in operation, the power generator  10  is fixedly positioned in a unidirectional flowing fluid, where the direction of fluid flow is indication by arrow F. More specifically, the outer tube  14  or plate  38  is fixedly attached to a surface that is fixed with respect to the flowing fluid so that the inner tube  12  can move relative to the outer tube  14 . Referring to  FIG. 7 , with the butterfly valve  44  in the closed position, hydraulic or pneumatic pressure created by the flowing fluid against the valve body  46  is greater than the tension force of the springs  42 , and the inner tube  12  will begin to move downstream with respect to the outer tube  14 . As the inner tube  12  approaches a maximum downstream position, illustrated in  FIG. 8A , the butterfly valve  44  is opened by the stop block  62  engaging the position arm  52  to move the valve body  46  to the open position. Specifically, when the valve arm  52  reaches the stop block  62 , the valve arm  52  is engaged by the angled surface  66  and is pivoted counterclockwise with respect to the orientation of the page, as shown in  FIG. 8B , even as the inner tube  12  continues to move downstream. When the inner tube  12  reaches the maximum downstream position, as illustrated in  FIGS. 9A-9B , the valve arm  52  is generally horizontal with respect to the orientation of the page, as shown in  FIG. 9B  and the valve body  46  is completely open. The hydraulic or pneumatic pressure on the inner tube  12  is greatly reduced with the butterfly valve  44  in the open position, such that the tension force of the springs  42  is now greater. Accordingly, the inner tube  12  will begin to move upstream. The inner tube  12  will continue to move upstream until the stop block  60  engages the position arm  52 , as illustrated in  FIGS. 10A-10B . When the valve arm  52  reaches the stop block  60 , the valve arm  52  is engaged by the curved surface  64  and is pivoted clockwise with respect to the orientation of the page, as shown in  FIG. 11 , even as the inner tube  12  continues to move upstream. When the inner tube  12  reaches the maximum upstream position, as illustrated in  FIG. 12 , the valve arm  52  is generally vertical with respect to the orientation of the page, and the valve body  46  is completely closed, thus completing one cycle of power generation. The cycles will continue as long as there is sufficient force from a fluid to move the inner tube  12 . 
         [0068]    As the magnets  86  pass through the magnetic field of the coil windings  88 , electrical current is generated in the coil windings  88 . As discussed above, a power grid  92  can be operably coupled to the power generator  10  to receive and/or distribute the electric current produced by the power generator. 
         [0069]    A second embodiment of the power generator  110  is illustrated in  FIGS. 13-15 , in which like elements bear the same reference numeral increased by  100 . The outer tube  114  is provided with an annular groove  94  near or at its second end  134 . The groove  94  retains an O-ring  96 . A compression spring  98  is received between the O-ring and the second end  124  of the inner tube  112 . 
         [0070]    The operation of the power generator  110  is substantially the same as for the power generator  10 , with the following exceptions. As the inner tube  112  moves downstream with the butterfly valve  144  in the closed position, the spring  98  is compressed. When the butterfly valve  144  is opened, the compression spring  98  will uncoil and force the inner tube  112  upstream. 
         [0071]    A third embodiment of the power generator is illustrated in  FIG. 16 , where like elements bear the same reference numeral increased by  200 . The power generator  210  comprises a first pair of tubes  212 A,  214 A, and second pair of tubes  212 B,  214 B that operate on opposite cycles. While not specifically shown, each pair of tubes comprises the components discussed previously for tubes  12 ,  14 . The outer tubes  214 A,  214 B are mounted in a fixed position with respect to the flowing fluid and the inner tubes  212 A,  212 B are mechanically coupled together such that the movement of the first inner tube  212 A in a downstream direction is synchronized with movement of the second inner tube  212 B in an upstream direction, and vice versa in a cyclic pattern. One suitable mechanical coupling is illustrated in  FIG. 16 , where a fixed pulley  100  is and a cable  102  are attached between the inner tubes  212 A,  212 B. The inner tubes  212 A,  212 B can also be coupled using a gear transmission assembly. As an alternative to the third embodiment illustrated, the inner tubes  212 A,  212 B can be fixedly mounted, and the outer tubes  214 A,  214 B can be mechanically coupled and move relative to the inner tubes  212 A,  212 B. 
         [0072]    Referring now to  FIG. 17 , there is shown a fourth embodiment of the invention. Supports  220  are fixed to a stream bottom and mounted at an upper portion pillow blocks  222 A and  222 B in which an elongated shaft  224  is slidably received. Rings  226  and  228  are fixedly mounted in spaced relationship on the shaft  224  between the pillow blocks  222 A and  222 B. Limit switches  254  and  256  are mounted on the pillow blocks and positioned to contact the rings  226  and  228 . A yoke  230  is mounted to one end of the shaft  224  and pivotally supports a valve body  246  on a valve stem  248  in journals  250 . A gear motor  250  is mounted on one leg of the yoke  230  and has a splined output shaft which is adapted to mesh with a gear  249  non-rotatably mounted to the valve stem  248 . The gear motor is connected to a controller  264  through an electrical line  266  to control the movement of the motor  252  and thus position the valve body in an open position illustrated in  FIG. 17  and a closed position perpendicular to the position illustrated in  FIG. 17 . The controller  264  is connected to the limit switches  254  and  256  through electrical lines  258  and  260 , respectively, to control the gear motor  252 . The gear motor  252  is a reversible motor which can drive the gear  49  to rotate the valve stem  248  and thus the valve body  246  through an angle of about 90° degrees about the rotational axis of the valve stem  248 . A tension spring  242  is coiled around the shaft  224  between the pillow block  222  and the yoke  230  and is fixedly secured at one end to the pillow block  222  and at the other end to the yoke  230 . 
         [0073]    The distal end of the shaft  224  is slidably received in a linear generator which has coils that are in close proximity to the shaft  224 . Permanent magnets (not shown) are mounted on the distal end of shaft  224  in close proximity to the coils (not shown) that are within the linear generator  262 . Electrical energy is generated by the relative movement of the magnets with respect to the coil in the manner discussed above with respect to the first three embodiments of the invention. The linear generator has output wires (not shown) that are connected to a power grid in the manner disclosed above. 
         [0074]    In operation, the power generator of  FIG. 17  is positioned within a stream or other moving fluid body that has a direction of flow indicated by the arrow F. The supports  220  are anchored to the bottom of the stream so that the shaft  224  is parallel to the flow of the stream. When the valve body  246  is in the position illustrated in  FIG. 17 , the tension spring draws the yoke  230  and the shaft  224  upstream (to the left as viewed in  FIG. 17 ) until the ring  226  contacts the limit switch  256 . During this movement, magnets on the distal end of the shaft  224  will pass in close proximity to coils in the linear generator  252  to generate electrical current. When the ring  226  reaches its left most position in  FIG. 17 , the limit switch will close (or open) and the controller  264  will generate a control signal to the gear motor  252  to rotate the valve stem  248  and the valve body  246  90° degrees so that the plane of the valve body  246  is perpendicular to the flow of fluid (perpendicular to the plane of the drawing). At that time, the stream will force the shaft  224  downstream (to the right as illustrated in the drawing) against the tension in the spring  242  until the ring  228  reaches the limit switch  254  at the downstream pillow block  222 . During the movement of the shaft  224 , the linear generator  262  will generate further electricity due to the movement between the magnets on the distal end of shaft  224  past the coils in the linear generator  262 . The limit switch  254  will close (or open) and, as a result, the controller  264  will then generate a control signal to the gear motor  252  to rotate the valve stem  248  and thus the valve body  246  in a reverse direction so that the valve body  246  is parallel to the flow of the stream as illustrated in  FIG. 17 . At that time, the tension in the tension spring  242  will draw the shaft  224  upstream until the ring  226  meets the upstream pillow block  222 A and the limit switche  256 . The cycle then begins again. 
         [0075]    While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the foregoing description and drawings without departing from the spirit of the invention which is defined by the appended claims.