Abstract:
An electric generation system includes a plurality of connected water filled chambers, each having a pivoting door that sequentially covers and exposes an access port through which buoyant objects travel to an ascending water filled tube leading to a bucket conveyor that drives a generator. The pivoting doors are synchronized so that one is opened while the other is closed. The doors are opened and closed by hemispherical cams driven by a motor. The pivoting doors propel buoyant objects towards the tube.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to electric generation, and, more particularly, to a system with a plurality of connected tanks each having a pivoting door that covers and exposes an access port through which buoyant objects travel to an ascending water filled tube leading to a bucket conveyor. 
       BACKGROUND 
       [0002]    Various generators powered by rotary objects driven by the weight of massive buoyant objects raised to a determined height in a buoyant tube are known. For example, several prior patents disclose systems that use buoyancy to lift a heavy buoyant object to an elevated height, where the object rolls onto an arm or into a cup extending from a wheel or conveyor. The weight of the ball then causes the wheel or conveyor to rotate, which drives an electric generator. Examples of prior patents and applications disclosing such electric generation systems include US 20060042244, JP-A-2002-138944, JP-A-H10-141204, and WO2007034502A1. 
         [0003]    Means for repeatedly loading balls into the bottom of a water filled tube, without sacrificing the water, vary widely from system to system. For example, U.S. Pat. No. 5,944,480, US 20060042244 and JP-A-H10-141204 rely upon a vacuum effect, such as the effect achieved when a finger is placed over the top of a straw, to retain liquid in the tube while a port is opened at the bottom of the tube through which a buoyant object is introduced. JP-A-2002-138944 uses a contoured piston with a water-tight seal to slide balls into the tube. 
         [0004]    US 20030151258 describes a system that uses a pair of spaced apart sliding doors to define an intermediate chamber. The doors operate similar to a breach door and muzzle door of a submarine torpedo tube. A first door slides open while the other door remains closed to provide access to the intermediate chamber without sacrificing liquid in the tube. The second door opens after the first door closes and the buoyant object is in the intermediate chamber. When the second door is opened, the buoyant objects floats from the intermediate chamber into the tube. This process repeats for each buoyant object. The patent describes programming to control actuators to automatically slide open and slide closed each door, according to a determined cycle. No mechanism is provided to propel 
         [0005]    While these prior art systems may be useful for their intended purpose, they require complex equipment to maintain a vacuum, or complex equipment to independently operate doors and valves, and equipment that consumes considerable energy. Such systems are prone to failure and inefficiently consume a substantial portion of the generated energy. What is needed is a simpler, reliable, and more energy efficient system. 
         [0006]    The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above. 
       SUMMARY OF THE INVENTION 
       [0007]    To solve one or more of the problems set forth above, in an exemplary implementation of the invention, an electric generation system according to principles of the invention, includes a plurality of connected water filled tanks, each having a pivoting door that covers and exposes an access port through which buoyant objects travel to an ascending water filled tube leading to a bucket conveyor. The plurality of tanks include an entry tank and a transitional tank. The transitional tank is fluidly coupled to the water filled tube. The pivoting doors are synchronized so that one is opened while the other is closed. When the door to the entry tank is opened, a buoyant object may enter the entry tank. As the door to the entry tank pivots closed, it urges the buoyant object towards the door to the transitional tank. When the door to the entry tank closes, the door to the transitional tank opens. The access port for the transitional tank is in the path of the buoyant object. After the buoyant object passes through the access port for the transitional tank, the door pivots closed. The pivoting door propels the buoyant object towards the tube. This process of each door, in turn, opening and then closing to propel the buoyant object without spilling any water from the tanks or tube is repeated for each buoyant object. After a buoyant object enters the tube it floats towards the surface. A subsequent buoyant object that floats toward the surface will help urge the uppermost buoyant object from the tube onto a chute that leads to the top receiving position of a bucket conveyor. The buoyant object rolls or slides from chute into a bucket of the bucket conveyor. The weight of the buoyant object drives the bucket conveyor. A gearbox and generator are mechanically coupled to the bucket conveyor. The bucket conveyor drives the generator, which produces electric power. At the bottom of the bucket conveyor, each bucket is emptied into a hopper or chute. The hopper or chute leads to the entry door of the entry tank. 
         [0008]    The doors are sequentially opened and closed using a single motor and cams. A cam with a semicircular profile acts directly or indirectly upon each door. During half of the cycle the cam urges the door closed. During the other half of the cycle, the cam allows the door to open. The weight of the door cause the door to open when the cam is not urging it closed. One or more counterweights and/or springs may facilitate opening by urging the door into an open position. A single motor drives both cams. 
         [0009]    Thus, the invention provides a closed loop system that continuously feeds buoyant objects to the top receiving position of a bucket conveyor that drives an electric generator. Only a single electric motor consumes power, which is a small fraction of the power generated by the system. 
         [0010]    In a particular exemplary embodiment, an electric generation system according to principles of the invention includes a conveyor, a liquid-filled tank, a liquid filled buoyancy column, an inclined chute extending from the buoyancy column to about the conveyor, a plurality of buoyant objects and a generator assembly. Each of the buoyancy objects has an outer diameter and is buoyant in the liquid-filled tank and in the liquid filled buoyancy column, and having a mass sufficient to cause the conveyor to rotate. The conveyor includes an upper sprocket, a lower sprocket, a continuous chain engaging and entrained about the upper sprocket and the lower sprocket, and a plurality of carriers coupled to the continuous chain. The conveyor includes a descending side at which the carriers move in a downward direction from the upper sprocket to the lower sprocket. The conveyor also includes an ascending side at which the carriers move in an upward direction from the lower sprocket to the upper sprocket. Each of the plurality of carriers provides a surface for supporting one of the buoyant objects when the carrier is on the descending side. The liquid filled tank includes an entry chamber, an entry port, an entry door, a transitional chamber, a transitional port and a transitional door. The entry chamber is positioned below the lower sprocket. The entry port provides an opening through which a buoyant object enters the entry chamber. The entry door is hingedly mounted to the liquid filled tank. The entry door is pivotally movable from a closed position to an open position. In the closed position the entry door provides a watertight seal over the entry port. In the open position the entry door allows access for a buoyant object to pass through the entry port. The entry port is positioned to receive buoyant objects deposited from the conveyor. Pivoting motion of the entry door propels the buoyant object in the entry chamber towards the transitional chamber. The transitional chamber is in fluid communication with the entry chamber and positioned in a path of flow from the entry chamber to the transitional chamber. The transitional port provides an opening through which a buoyant object enters the transitional chamber from the entry chamber. The transitional door is hingedly mounted to the liquid filled tank. The transitional door is pivotally movable from a closed position to an open position. In the closed position the transitional door provides a watertight seal over the transitional port. In the open position the transitional door allowing access for a buoyant object to pass from the entry chamber into the transitional chamber through the transitional port. The transitional port is positioned to receive buoyant objects floating from the transitional chamber. Pivoting motion of the transitional door propels the buoyant object in the transitional chamber towards the buoyancy column. The buoyancy column is an elongated tubular container fluidly coupled to the transitional chamber and extending upwardly to a height above the chute. The buoyancy column has an outlet at a height about level with the chute. The buoyancy column is filled with a liquid (e.g., water) to about the outlet. The buoyancy column has an inner diameter that is greater than the outer diameter of each of the buoyancy objects. The chute extends from a position adjacent to the outlet of the buoyancy column to the descending side of the conveyor. A motor is operably coupled to the entry door via an entry door coupling and to the transitional door via a transitional door coupling. The motor causes the entry door to pivot open only when the transitional door is closed. The motor causes the transitional door to pivot open only when the entry door is closed. The motor causes the entry door to remain open for a first time duration sufficient to allow a buoyant object to enter the entry chamber. The motor causes the transitional door to remain open for a second time duration sufficient to allow a buoyant object to enter the transitional chamber from the entry chamber. The first duration is about equal to the second duration. The second duration repeatedly commences after the first duration. The first duration repeatedly commences after the second duration. The generator assembly includes an electric generator and a generator coupling rotatably connecting the electric generator to the conveyor. 
         [0011]    Each of the buoyant objects may be a hollow sphere, including a sealable fill port providing access to an interior compartment of the hollow sphere and being used to partially fill the interior compartment with water. Each of the buoyant objects weighs between 200 to 500 pounds. 
         [0012]    In a particular preferred embodiment, the entry door coupling includes a first cam with a hemispherical cross section shape and the transitional door coupling includes a second cam with a hemispherical cross section shape. The first cam is oriented to cause the entry door to pivot open only when the transitional door is closed. The second cam is oriented to cause the transitional door to pivot open only when the entry door is closed. The first cam and the second cam are rotatably driven by the motor. The first cam and second cam may act directly against the entry door and transitional door, respectively. Alternatively, the entry door coupling may include a first crank that is coupled to the entry door and against which the first cam acts. The transitional door coupling may include a second crank that is coupled to the transitional door and against which the second cam acts. 
         [0013]    The buoyancy column may be substantially vertical or inclined. 
         [0014]    The generator assembly may include a gearbox coupled to the electric generator between the generator coupling and electric generator. The gearbox converts a first rotational speed of the generator coupling to a second rotational speed input of the electric generator. The generator coupling may include a drive shaft, a continuous drive chain and a generator sprocket and/or a continuous drive belt and a generator pulley. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The foregoing and other aspects, objects, features and advantages of the invention will become better understood with reference to the following description, appended claims, and accompanying drawings, where: 
           [0016]      FIG. 1  is a high level schematic of an electric generator system powered by bucket conveyor driven by massive buoyant objects according to principles of the invention; and 
           [0017]      FIG. 2  is a perspective view of an exemplary generator for a system according to principles of the invention; and 
           [0018]      FIG. 3  is a schematic of an exemplary bucket conveyor for a system according to principles of the invention; and 
           [0019]      FIG. 4  is a perspective view of an exemplary bucket conveyor for a system according to principles of the invention; and 
           [0020]      FIG. 5  is a perspective view of a buoyant object for a system according to principles of the invention; and 
           [0021]      FIG. 6  is a perspective view of half of a buoyant object for a system according to principles of the invention; and 
           [0022]      FIG. 7  is a perspective view of bucket for a system according to principles of the invention; and 
           [0023]      FIG. 8  is a perspective view of bucket holding a buoyant object for a system according to principles of the invention; and 
           [0024]      FIG. 9  is a perspective view of tube and chute for a system according to principles of the invention; and 
           [0025]      FIG. 10  is a first schematic of tanks and doors for a system according to principles of the invention; and 
           [0026]      FIG. 11  is a second schematic of tanks and doors for a system according to principles of the invention; and 
           [0027]      FIG. 12  is a third schematic of tanks and doors for a system according to principles of the invention; and 
           [0028]      FIG. 13  is a side view of a motor and cams in a first position for a system according to principles of the invention; and 
           [0029]      FIG. 14  is a perspective view of a motor and cams in a first position for a system according to principles of the invention; and 
           [0030]      FIG. 15  is another perspective view of a motor and cams in a first position for a system according to principles of the invention; and 
           [0031]      FIG. 16  is a perspective view of a section of tanks with doors in a first position for a system according to principles of the invention; and 
           [0032]      FIG. 17  is another perspective view of a section of tanks with doors in a first position for a system according to principles of the invention; and 
           [0033]      FIG. 18  is a side view of a motor and cams in a second position for a system according to principles of the invention; and 
           [0034]      FIG. 19  is a perspective view of a motor and cams in a second position for a system according to principles of the invention; and 
           [0035]      FIG. 20  is another perspective view of a motor and cams in a second position for a system according to principles of the invention; and 
           [0036]      FIG. 21  is a perspective view of a section of tanks with doors in a second position for a system according to principles of the invention; and 
           [0037]      FIG. 22  is another perspective view of a section of tanks with doors in a second position for a system according to principles of the invention. 
       
    
    
       [0038]    Those skilled in the art will appreciate that the figures are not intended to be drawn to any particular scale; nor are the figures intended to illustrate every embodiment of the invention. The invention is not limited to the exemplary embodiments depicted in the figures or the specific components, configurations, shapes, relative sizes, ornamental aspects or proportions as shown in the figures. 
       DETAILED DESCRIPTION 
       [0039]      FIG. 1  is a high level schematic of an electric generator system powered by bucket conveyor driven by massive buoyant objects according to principles of the invention. Apparatus  100  is a bucket conveyor with a plurality of parallel chains driving upper and lower sprockets  165 ,  170 . A plurality of buckets  160  are attached to the chains  195 . On the receiving side of the conveyor  100 , which is the side facing chute  145 , the buckets receive heavy buoyant objects. 110 ,  112 ,  114 , after they roll or slide down the chute  145  into an available bucket  160 . The weight of the heavy buoyant object causes the bucket to travel downwardly. When the bucket  160  reaches the bottom position  140 , the bucket  160  pivots, thereby dumping the object into a chute or hopper  135  that leads to an entry tank  115  via an entry door  125 . 
         [0040]    In an exemplary embodiment, the buoyant objects are hollow balls, e.g., hollow steel balls. In a particular preferred embodiment, the balls are fillable steel balls, weighing between 200 to 500 pounds. An access port in the balls allows the balls to be partially filled with a liquid, such as water, to control the weight and buoyancy of the ball. The balls must be capable of floating up the water-filled buoyancy column  105 . However, the invention is not limited to steel balls, or hollow steel balls, or balls. Any buoyant objects suitable for driving a bucket conveyor and progressing through a series of tanks as described below may be utilized. For convenience of reference, the buoyant objects are referred to herein as balls. 
         [0041]    The entry door  125  and transitional door  130  provide water-tight seals when closed. They open and close by pivoting about a hinge. Gasket material may be provided along the edge of the door to provide a water-tight seal. The doors may be comprised of 1-inch steel plate, about 3 feet by 3 feet. One or more torsion springs or counterweights  133  may be provided to urge the doors open. The counterweights  133  may be coupled directly or indirectly to the door by a pulley  131  and lanyard  132 . A cam, as described below urges each door  125 ,  130  closed temporarily. When a cam is not urging a door closed, the door opens under the influence of its own weight, and/or the counterweight and/or the torsion spring. 
         [0042]    The entry door  125  opens enough to allow one buoyant object  110  to enter the entry tank  115  through the door  125 . The entry tank  115  is filled with water. The weight of balls on top of the entering ball, force the entering ball below the water line. As the access door  125  closes, it urges the ball towards transitional tank  120 . Additionally, if another ball enters the entry tank  115  while a ball is already in the entry tank  115 , the second ball would urge the first ball towards the transitional tank  120 . 
         [0043]    The transitional tank  120  is a water-filled tank that extends between the entry tank and the buoyancy column. A pivoting door  130  over an access port allows access to the transitional tank  120  from the entry tank  115 . The transitional tank door  130  opens only when the entry tank door  125  is closed. In that manner the water contained in buoyancy column  105  is not spilled. After the ball enters the transitional tank  120  the transitional door  130  closes. Only after the transitional door  130  closes, does the entry door  125  open to allow entry of another ball. A ball in the transitional tank floats towards the buoyancy column  105 . The tank  120  may feature a sloping top to facilitate progression of the ball towards the column. Concomitantly, a second ball entering the transitional tank will urge the first ball to the buoyancy column  105 . 
         [0044]    The buoyancy column  105  is water filled column sized to receive the balls and allow them to float to a height above the receiving height of the bucket conveyor  100 . Upon entering the buoyancy column  105 , a ball floats to the top of the buoyancy column  105 . An opening  150  at the top of the buoyancy column  105  is level with a portion of a chute  145 . The ball  112  at top is urged above the water level onto the chute  145  by one or more balls  110  below it in the buoyancy column. The number of submerged balls required to urge a top ball onto a chute will vary depending upon buoyancies and weights. In some embodiments, two or more submerged balls may be required. 
         [0045]    The chute  145  is an inclined channel, such as a trough or tube, for conveying balls from the top of the buoyancy column  105  to a lower level, i.e., the receiving height of the ball conveyor  100 . The receiving height is a height at which a bucket  160  is positioned to receive a ball on the downward moving side of the bucket conveyor  100 . Preferably, it is the maximum height for receiving a ball. 
         [0046]    An electric generator  190  is mechanically coupled to and driven by the bucket conveyor. The coupling may be in the form of gears, belts and pulleys, chains and sprockets, drive shafts, and the like. By way of example and not limitation, chain  180  may be driven by a bottom sprocket  171  which may drive the generator. In this embodiment, the bottom sprocket  171  for driving the generator is separate from but connected to and rotates with the sprocket  170  for driving the conveyor chains  195 . 
         [0047]    Referring now to  FIG. 2 , a perspective view of an exemplary generator assembly  190  for a system according to principles of the invention is provided. The generator  190  includes a gear box  192  configured to ensure adequate rotational speed for producing electricity. The gear ratio of the drive gear  194  and sprocket  171  may be varied to achieve a desired torque and rotational speed. By way of example and not limitation, many generators are designed to operate at 1800 or 3600 generator rotor rpm. Shaft  172  is coupled to the bottom sprocket  170  of the bucket conveyor. Other configurations within the scope of the invention may use a gear train, drive shaft or belts and pulleys to drive the gear box  192 . Driving the bucket conveyor causes the shaft  172  to rotate, which causes the generator  190  to rotate. 
         [0048]    The generator  190  may be any electric generator that converts mechanical energy to electrical energy, such as a conventional generator that produces direct current with the use of a commutator. The electrical energy may be stored, such as in batteries. The electrical energy may be metered. The electrical energy may be supplied to one or more loads, to circuits, and/or to a grid. Various electrical energy transmission and conversion devices may be interposed between the generator and the load. Such devices may include, without limitation, an inverter to convert DC to AC, battery charge regulation circuitry, and voltage regulators to maintain a determined voltage level. These and other electrical devices may be used to harness and efficiently transmit the generated electrical energy. 
         [0049]    Referring now to  FIGS. 3 and 4 , schematics of an exemplary bucket conveyor for a system according to principles of the invention are shown. The generator drive gear  171  is omitted from these views. The bucket conveyor with a plurality of parallel chains drives upper and lower sprockets  165 ,  170 . A plurality of buckets  160  are attached to the chains  195 . On the receiving side of the conveyor  100 , the concave compartment of the buckets faces upwardly. When the bucket  160  reaches the bottom position, the bucket  160  pivots, thereby dumping the object into a chute or hopper that leads to an entry tank via an entry door. 
         [0050]      FIG. 5  provides a perspective view of a buoyant object for a system according to principles of the invention. The buoyant object is a hollow ball  110 , as illustrated by the perspective view of half  111  of the ball in  FIG. 6 . A threaded removable plug  112  seals an access port that allows the ball  110  to be partially filled with a liquid. When screwed in place, the outer surface of the plug  112  is substantially flush with the outer surface of the ball  110 . In this manner, the plug  112  does not interfere with smooth rolling or sliding motion of the ball. In an exemplary embodiment, the balls  110  are fillable steel balls, weighing between 200 to 500 pounds. The balls are capable of floating up the water-filled buoyancy column  105 . However, the invention is not limited to steel balls, or hollow steel balls, or balls. Instead, any buoyant objects suitable for driving a bucket conveyor and progressing through a series of tanks as described below may be utilized. 
         [0051]      FIG. 7  provides a perspective view of an empty exemplary bucket  160  for a system according to principles of the invention.  FIG. 8  shows the bucket  160  containing a ball  110 . As is shown, the exemplary bucket provides a concave compartment into which the ball may rest. However, the invention is not limited to such geometries. Any structure capable of holding a ball along the downward path of the conveyor may be utilized. By way of example and not limitation, inclined planar shelves that hold the balls adjacent to the chain may be utilized in lieu of bucket-like containers, without departing from the scope of the invention. 
         [0052]      FIG. 9  is a perspective view of buoyancy column  105  and a chute  145  for a system according to principles of the invention. An opening  150  at the top of the buoyancy column  105  is level with a portion of the chute  145 . A ball that has floated to the top of the buoyancy column is urged above the water level onto the chute  145  by one or more balls below it in the buoyancy column. The number of submerged balls required to urge a top ball onto a chute will vary depending upon buoyancies and weights. In some embodiments, two or more submerged balls may be required. The chute  145  is an inclined channel, such as a trough or tube, for conveying balls from the top of the buoyancy column  105  to a lower level, i.e., the receiving height of the ball conveyor  100 . The receiving height is a height at which a bucket  160  is positioned to receive a ball on the downward moving side of the bucket conveyor  100 . Preferably, it is the maximum height for receiving a ball. On the receiving side of the conveyor  100 , which is the side facing chute  145 , the buckets receive heavy buoyant objects  110 ,  112 ,  114 , after they roll or slide down the chute  145  into an available bucket  160 . The weight of the heavy buoyant object then causes the bucket to travel downwardly. 
         [0053]      FIGS. 10 through 12  provide schematics of tanks and doors for a system according to principles of the invention. The different figures illustrate different door arrangements. For example, in  FIG. 10 , the entry door  125  and transitional door  130  are on side panels of the tanks  115 ,  120 , hinged along their top edges. A chute  117  leads balls into an access port in the side panel of the entry tank  115  when the entry door is opened. In  FIG. 11 , the entry door  125  and transitional door  130  are on side panels of the tanks  115 ,  120 , but hinged along their bottom edges. A chute  117  leads balls into an access port in the side panel of the entry tank  115  when the entry door is opened. In an alternative arrangement, as in  FIG. 12 , the entry door  125  is on top of the entry tank  110  and the transitional door  130  is on a side panel. Again, a chute  117  delivers balls to the entry door access when the entry door  125  is opened. These and other arrangements of an entry door  125  and transitional door  130  are possible, and come within the scope of the invention. 
         [0054]      FIGS. 13 through 15  provide various views of a motor and cams in a first position for a system according to principles of the invention. In  FIGS. 13-15 , the entry door  125  is shown urged closed while the transitional door  130  is opened. The motor  215  is an electric motor that drives the cams  200 ,  205 . By way of example and not limitation, the motor  215  may be a 6V, 12V or 24V DC motor. The chain  220  is entrained on sprockets  210 ,  225 ,  230 . The motor  215  thereby causes the cams  200  to rotate. In this exemplary embodiment, a chain drive  220  couples the motor  215  to cam drive sprockets  225 ,  230 . Other rotary linkages such as drive shafts, gear trains, belts and pulleys and combinations thereof to drive both cams  200 ,  205  at the same rotational rate with a single motor  215 , without departing from the scope of the invention. 
         [0055]    Each cam  200 ,  205  comprises a semicircular lobe (i.e., a lobe having a semicircular cross section shape) that urges a door  125 ,  130  closed. In one embodiment, the cams  200 ,  205  act upon crank arms  235 ,  242  that are coupled to the pivot pins of the door hinges. Pivoting rotation of the crank arms  235 ,  242 , about their respective crank shafts  240 ,  243 , causes the doors  125 ,  130  to correspondingly pivot, such as from an open position to a closed position. To facilitate rotation and prevent leakage, bearings and seals may be provided in or against the walls of the tanks, at openings through which the crank shafts  240 ,  243  extend. 
         [0056]    In a preferred embodiment, the cams are used to urge the doors  125 ,  130  closed. A door may open under the influence of gravity when a cam is not urging the door closed. In the exemplary embodiment, a cam urges a door closed by acting on a crank arm coupled to the door. In another embodiment, the cams may be in the tank and act directly on the doors. Additionally, one or more torsion springs or counterweights  133  ( FIG. 1 ) may be provided to help urge the doors open. The counterweights  133  may be coupled directly or indirectly to the door by a pulley  131  and lanyard  132 . When a cam  200 ,  205  is not urging a door closed, the door opens under the influence of its own weight, and/or the counterweight and/or the torsion spring. 
         [0057]    The cam timing is set to allow a door to open only for half of a cycle and only when the other door is closed. The semicircular cams  200 ,  205  are oriented to act on each door for half of a cycle. A cycle is a complete rotation of each cam. The cams  200 ,  205  are configured to rotate at the same rate. One cam  200  acts on one door  125 , causing the door  125  to remain closed, while the other cam  205  allows the other door  130  to open. The other cam  205  acts on the other door  130 , causing the other door to remain closed, while the first cam  20   o  allows the entry door  125  to open. Each door  125 ,  135  remains open for half of a cycle and closed for half of a cycle. Based upon the preferred configuration, the entry door  125  is closed, the entire time the transitional door  130  is open. Also, based upon the preferred configuration, the entry door  125  is open, the entire time the transitional door  130  is closed. In this manner, the two doors  125 ,  130  are never open at the same time. Consequently, the water contained in the buoyancy column  105  does not spill out of the tanks  115 ,  120  through the open doors. 
         [0058]    Referring now to  FIGS. 16 ,  17 , perspective views of a section of tanks with doors in a first position for a system according to principles of the invention is shown. The entry door  125  is urged closed (as shown in  FIGS. 13-15 ) while the transitional door  130  is opened. Thus, the closed entry door  125  prevents water from spilling out of the system. The opened transitional door  130  allows a ball to float from the entry tank  115  into the transitional tank, towards the buoyancy column  105 . 
         [0059]    The pivoting doors act as paddles, propelling the balls. Opening and closing motion of the doors provides a paddling effect that propels floating balls from the entry tank  115  to the transitional tank  120  and then to the buoyancy column  105 . 
         [0060]      FIGS. 18 through 20  provide various views of a motor and cams in a second position for a system according to principles of the invention. In  FIGS. 18-20 , the entry door  125  is shown opened while the transitional door  130  is closed (as shown in  FIGS. 21 and 22 ). 
         [0061]    The cams are used to urge the transitional door  130  closed while the entry door is not urged closed and allowed to open. A door may open under the influence of gravity when a cam is not urging the door closed. In the exemplary embodiment, a cam urges a door closed by acting on a crank arm coupled to the door. In another embodiment, the cams may be in the tank and act directly on the doors. Additionally, one or more torsion springs or counterweights  133  ( FIG. 1 ) may be provided to help urge the doors open. The counterweights  133  may be coupled directly or indirectly to the door by a pulley  131  and lanyard  132 . When a cam  200 ,  205  is not urging a door closed, the door opens under the influence of its own weight, and/or the counterweight and/or the torsion spring. Based upon the preferred configuration, the entry door  125  is open, the entire time the transitional door  130  is closed. In this manner, the two doors  125 ,  130  are never open at the same time. Consequently, the water contained in the buoyancy column  105  does not spill out of the tanks  115 ,  120  through the open doors. 
         [0062]    Referring now to  FIGS. 21 ,  22 , perspective views of a section of tanks with doors in a second position for a system according to principles of the invention is shown. The entry door  125  is opened (as shown in  FIGS. 18-20 ) while the transitional door  130  is urged closed. Thus, the closed transitional door  130  prevents water from spilling out of the system. The opened entry door  125  allows a ball to enter the entry tank  115  from where it can subsequently drift into the transitional tank  120  when the transitional door  130  opens and the entry door  125  closes. 
         [0063]    The pivoting doors act as paddles, propelling the balls. Opening and closing motion of the doors provides a paddling effect that propels floating balls from the entry tank  115  to the transitional tank  120  and then to the buoyancy column  105 . 
         [0064]    A system according to principles of the invention may operate continuously so long as the mechanical components continue to operate. A system according to principles of the invention is scalable. The heights of the buoyancy column and conveyor, the number and mass of balls, and the size of the generator, may be sized to achieve a desired output. Additionally, the cycle time of the cams may be increased or decreased by adjusting the rotational speed of the driving motor. Furthermore, the size of the cams may be adjusted to vary cycle times. 
         [0065]    While an exemplary embodiment of the invention has been described, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum relationships for the components and steps of the invention, including variations in order, form, content, function and manner of operation, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. The above description and drawings are illustrative of modifications that can be made without departing from the present invention, the scope of which is to be limited only by the following claims. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents are intended to fall within the scope of the invention as claimed.