Patent Publication Number: US-2010123319-A1

Title: Mechanically-driven electric generator

Description:
BACKGROUND 
     1. Technical Field 
     This invention relates generally to production of electric power, and more particularly to conversion of potential energy into electric power. 
     2. Description of Related Art 
     Generation of electrical energy is a well known and established field. Much research has focused on applications where a rotating shaft drives a generator system in order to produce electrical energy. Various types of energy may be used to rotate the shaft, such as tidal energy, wind energy, kinetic energy, solar energy, and potential energy. 
     In general, systems for producing electric power have three sections. First, the system taps a source of energy. Second, a power transmission system (PTS) extracts this energy so it can be sent to a generator. There are many varieties of PTS units, such as sprocket/chain, pulley/belt, and gear train systems. Third, an electric generator receives the kinetic energy from the PTS unit and converts it into electrical energy. 
     Some recently-developed generators harvest wave energy from the ocean. Other generators convert kinetic energy into electrical energy. Another known solution for generating electrical energy involves conversion of potential energy, which may be gravitational. 
     Gravitational potential energy decreases as an object falls from a higher position to a lower position relative to a gravitational field. As the force of gravity performs work on the falling object, potential energy is released. The amount of released energy is proportional to the falling object&#39;s mass, the distance it fell, and the gravitational acceleration. 
     Near the surface of the Earth, for example, the acceleration of gravity is a constant g=9.8 m/s 2 . Thus, the change in gravitational potential energy for an object falling near the Earth&#39;s surface is equal to g times the object&#39;s mass and the total change in height. Various devices can convert this energy into another form so that it can be used to perform useful work elsewhere. Historically, watermills have been used to extract gravitational potential energy from falling water. In order to grind grain, as an example, the force of the water&#39;s movement would drive the blades of a wheel that, in turn, would rotate an axle driving the grist mill&#39;s other machinery. This technique for producing kinetic energy from gravitational potential energy was later used in hydroelectric plants, where falling water would turn a turbine, converting the kinetic energy of the turbine&#39;s motion into electrical energy. Most hydroelectric plants are quite large, requiring massive expenditure of money to build dams across wide rivers. However, some rural communities use micro-hydro systems as stand-alone power systems. Such systems may involve a pipe that taps a stream at the top of a hill and drops the water down a slope to power an electric generator. 
     However, micro-hydro systems have several known problems. Maintenance costs for the generator mechanism may become prohibitive if it is repeatedly damaged by water. The stream may flood, further damaging the system or depositing debris that blocks the intake. Alternatively, during a drought, there may not be enough water flowing in the stream to run the generator. These problems are inherent to any system that extracts gravitational potential energy from flowing water. 
     In remote areas, particularly in dry regions where flowing water is unavailable, there is a need for a portable generator that can provide cheap energy. Such a generator could be used, for example, in a mountainous region with steep cliffs but no surface streams. While the topography of the area would represent a large amount of potential energy, that energy could not be tapped by a micro-hydro system if no water is available. 
     Thus, there is a need for a way to generate electrical energy from gravitational potential energy without relying upon water. There is also a need to provide a generator that is inexpensive and can be easily transported. Such a generator could act as a stand-alone power system in a rural area without the known problems of a hydroelectric system. 
     SUMMARY OF THE INVENTION 
     Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the various exemplary embodiments, but not to limit the scope of the invention. Detailed descriptions of a preferred exemplary embodiment adequate to allow those of ordinary skill in the art to make and use the inventive concepts are provided by the entire disclosure. 
     It is an object of the invention to provide a mechanically-driven electric generator that may comprise a tandem system that transforms potential energy into kinetic energy; a pulley belt system, coupled to the tandem system, that increases a rotational speed of the kinetic energy; and a gearbox system, coupled to the pulley belt system, that converts the kinetic energy having the increased rotational speed into alternating current (AC) voltage. 
     In various exemplary embodiments, the tandem system may comprise a primary weight; a connector, coupled to the primary weight; and an equalizing weight, coupled to the connector. The tandem system may further comprise a first pulley system coupled to the primary weight; and a second pulley system coupled to the equalizing weight. 
     In various exemplary embodiments, the first and second pulley systems each may comprise a fixed sub-assembly; and a movable sub-assembly. The fixed and movable sub-assemblies may each comprise a large pulley having a first diameter; a small pulley having a second diameter, wherein said second diameter is smaller than said first diameter; and a support unit that couples said large pulley to said small pulley. Alternatively, the fixed and movable sub-assemblies may each comprise a large pulley having a first diameter; a medium pulley having a second diameter, wherein said second diameter is smaller than said first diameter; a small pulley having a third diameter, wherein said third diameter is smaller than said second diameter; and a support unit that couples said large, medium, and small pulleys. 
     In various exemplary embodiments, the connector may link the movable sub-assembly of the first pulley system to the movable sub-assembly of the second pulley system. Alternatively, the connector may link the movable sub-assembly of the first pulley system to the movable sub-assembly of the second pulley system. 
     In various exemplary embodiments, the primary weight and the equalizing weight may comprise movable weight units. These movable weight units may be adjusted to make the equalizing weight heavier than the primary weight, thereby making a former equalizing weight into a new primary weight and reversing a rotary direction of the generator. 
     In various exemplary embodiments, the pulley belt system may comprise a drum that receives rotational energy from the tandem system; first and second driving belts that transmit the rotational energy; and a plurality of pulley units that increase rotational speed by having cascaded gear ratios. Each pulley unit may further comprise a driving pulley and a driven pulley. Rotational speed may increases in proportion to gear ratios defined by relative diameters of the driving pulley and the driven pulley. The pulley belt system may further comprise at least four of the pulley units. 
     In various exemplary embodiments, the pulley belt system may further comprise an idler unit that maintains tension on the second driving belt. This idler unit may further comprise a steel core encased within a Teflon™ strip; a Teflon™ disk holder; and a threaded rod. 
     In various exemplary embodiments, the gearbox system may comprise a gearbox unit that receives rotational energy from the pulley belt system; a generator system that converts the rotational energy into electrical energy; and a coupler that links the gearbox unit and the generator system. The gearbox system may further comprise a converter that transforms alternating current (AC) from the generator system into direct current (DC). 
     In various exemplary embodiments, a mechanically-driven electric generator may comprise a primary weight having a plurality of movable weight units that is lowered to release gravitational potential energy; a counterweight having a plurality of movable weight units that controls the rate of speed at which the primary weight is lowered; a plurality of tandem system pulleys that turn at a first rotational speed when the primary weight is lowered; a pulley belt system having driving and driven pulleys, coupled to the tandem system pulleys, that increase the first rotational speed to a second rotational speed in proportion to diameter ratios of the driving and driven pulleys; and a gearbox system, coupled to the pulley belt system, that converts the kinetic energy at the second rotational speed of the pulley belt system into electrical energy. 
     In various exemplary embodiments, a method of generating electrical energy may comprise the following steps: storing potential energy in a primary weight by raising the primary weight to a predetermined elevation; coupling the primary weight to a counterweight and a plurality of tandem pulleys; lowering the controlled weight at a speed controlled by the counterweight and turning the plurality of tandem pulleys to transform the potential energy into kinetic energy; transferring the kinetic energy from the plurality of tandem pulleys to a pulley belt system having a plurality of driving and driven pulleys; converting the kinetic energy from a lower rotational speed to a higher rotational speed in proportion to diameter ratios of the driving and driven pulleys; applying the kinetic energy at the higher rotational speed to a gearbox system; and converting the kinetic energy at the higher rotational speed into electrical energy in the gearbox system. 
     Advantageously, the invention provides a solution for cheap generation of electrical energy. The device requires little maintenance and may operate for long periods of time. If designed for individual needs, the device may be small enough to be stored at home and transported to other locations easily. 
     The foregoing objects and advantages of the invention are illustrative of those that can be achieved by the various exemplary embodiments and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, these and other objects and advantages of the various exemplary embodiments will be apparent from the description herein or can be learned from practicing the various exemplary embodiments, both as embodied herein or as modified in view of any variation that may be apparent to those skilled in the art. Accordingly, the present invention resides in the novel methods, arrangements, combinations, and improvements herein shown and described in various exemplary embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is next described with reference to the following drawings, where like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1   a  depicts an elevation view of an exemplary mechanically-driven generator; 
         FIG. 1   b  depicts an end view of an exemplary mechanically-driven generator; 
         FIG. 2  shows an exemplary tandem system for the generator of  FIG. 1   a;    
         FIG. 3  shows an exemplary pulley belt system for the generator of  FIG. 1   a;    
         FIG. 4   a  shows an elevation view of an exemplary gearbox system for the generator of  FIG. 1   a;    
         FIG. 4   b  shows an end view of an exemplary gearbox system for the generator of  FIG. 1   a;    
         FIG. 5  depicts another exemplary tandem system; 
         FIG. 6  depicts a further example of a tandem system; and 
         FIG. 7  shows an alternative arrangement for the idler pulley unit within the pulley belt system of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, in which like numerals refer to like components or steps, there are disclosed broad aspects of various exemplary embodiments. 
     In various exemplary embodiments, a generator of electrical energy enables people to produce power at an affordable price with minimal maintenance for long periods of time. The device may be manufactured in different scales, ranging from small to large, depending upon individual needs. Unlike hydroelectric systems, the device does not require a constant supply of water, so it may be installed in almost any location. 
     The device has a number of advantages over existing generators. It does not require the use of a battery for storage of power. It can be assembled and disassembled quickly. One needs minimal training to be able to use this device. The component parts of the device, upon disassembly, can be stored in a small space, such as the trunk of a car, a closet, or a tool room. Consequently, the device can also be transported easily. 
       FIG. 1   a  depicts an elevation view of an exemplary mechanically-driven generator  100 . This generator comprises three main sections, a tandem system  200 , a pulley belt system  300 , and a gearbox system  400 , each of which will be described in detail below. Tandem system  200  converts vertical motion of weights into rotational energy. Pulley belt system  300  receives the rotational energy from tandem system  200  and increases its speed. Gearbox system  400  converts that high-speed rotational energy from pulley belt system  300  into electrical energy. 
       FIG. 1   b  depicts an end view of exemplary mechanically-driven generator  100 . Tandem system  200  is not visible at this angle. As illustrated by  FIG. 1   b , pulley belt system  300  drives gearbox system  400 . By means of cascaded gear ratios, low-speed rotation at the top of pulley belt system  300  produces high-speed rotation at the bottom of pulley belt system  300 , rotation that is fast enough to generate electrical energy in gearbox system  400 . 
       FIG. 2  shows an exemplary tandem system section  200  of electric generator  100 . Tandem system  200  converts potential energy into rotational energy by using a cable  210  to couple a primary weight  220  to an equalizing weight  230 . Cable  210  may be a rope or another suitable means for permitting gradual movement of primary weight  220  relative to equalizing weight  230 . Tapping potential energy, cable  210  receives as input the vertical motion of primary weight  220  downward relative to equalizing weight  230 . In response, cable  210  rotates a first pulley system  240 , coupled to primary weight  220 , and a second pulley system  250 , coupled to equalizing weight  230 . In this way, the potential energy released by the relative movement of primary weight  220  with respect to equalizing weight  230  is transformed into rotational energy. 
     First pulley system  240  comprises a first sub-assembly  241  and a second sub-assembly  242 . In a similar manner, second pulley system  250  comprises a third sub-assembly  251  and a fourth sub-assembly  252 . First sub-assembly  241  and the third sub-assembly  251  may be fixed to the top of tandem system  200 , while second sub-assembly  242  and fourth sub-assembly  252  move up and down in accordance with the relative motions of primary weight  220  and equalizing weight  230 . The difference in weight between primary weight  220  and equalizing weight  230  should be selected to determine the rate of descent of primary weight  220 , ensuring that primary weight  220  drops at a controlled rate of speed. The speed should be slow enough to reduce the risk of injury to a person who is operating generator  100 . 
     Each sub-assembly  241 ,  242 ,  251 , and  252  in tandem system  200  may comprise three units: a large pulley  270 , a small pulley  271 , and a support unit  272 . Fixed sub-assemblies  241  and  251  have large pulleys  270  on top while movable sub-assemblies  242  and  252  have small pulleys  271  on top. Large pulleys  270  and small pulley  271  may be rotating drums or wheels with curved convex rims that may be mounted on a hook or base for stability. A rope, belt, chain, or other suitable means may move along the drum&#39;s rim to change the direction of motion of large pulley  270  or small pulley  271 . The drum may be grooved to ensure that the rope cannot slip off. 
     For tandem system  200 , applicable weight values for primary weight  220  and equalizing weight  230  may be selected to produce a desired amount of rotational energy in pulley systems  240  and  250 . For example, primary weight  220  may be 500 kg while equalizing weight  230  may be 400 kg. The total length of cable  210 , coupling primary weight  220  to equalizing weight  230 , may be about 15 meters. As will be apparent to those of skill in the art, other weights and lengths may be used, depending upon the amount of energy that is needed and the physical location where generator  100  is installed. 
     Movable weight units  280  may be added to either primary weight  220  or equalizing weight  230 . In this way, the motion of the device may be reversed. Once enough movable weight units  280  are added to equalizing weight  230  so that it outweighs primary weight  220 , equalizing weight  230  may function as a new primary weight  220 . After the weight-loading process is finished, tandem system  200  may operate again, causing pulley systems  240  and  250  to rotate backwards relative to the previous cycle. 
       FIG. 3  depicts an exemplary pulley belt system section  300  of the electric generator  100 . 
     Pulley belt system  300  may act as a PTS unit, transmitting rotational energy generated by tandem system  200 . Drum  310  may receive torque and speed from cable  210  and send this rotational energy into a first pulley  320 . Cable  210  may be wrapped, for example, one turn around drum  310 . 
     The addition of movable weight units  280  to primary weight  220  so that primary weight  220  is significantly heavier than equalizing weight  230  may cause primary weight  220  to drop a vertical distance that may be about two meters or another appropriate distance. This vertical motion may produce rotation in drum  310  at a speed that is proportional to the number of pulleys within tandem system  200 . 
     A first belt  330  transfers rotational energy sent from drum  310  to first pulley  320  into second pulley  325 . In one embodiment, pulley belt system  300  may have a cascaded sequence of eight pulleys  320 ,  325 ,  340 ,  345 ,  350 ,  355 ,  360 , and  365  arranged so that the following pairs of pulleys constitute pulley units ( 320 ,  325 ); ( 340 ,  345 ); ( 350 ,  355 ); ( 360 ,  365 ). For each pulley unit, the first pulley in the sequence has a larger diameter and drives the second sequence. Thus, pulleys  320 ,  340 ,  350 , and  360  are driving pulleys while pulleys  325 ,  345 ,  355 , and  365  are driven pulleys. 
     This arrangement may allow the rotational speed to steadily increase in proportion to the relative sizes of the driving and driven pulleys, a parameter that may be called a gear ratio. The gear ratio may be defined as the diameter ratio between driving pulleys  320 ,  340 ,  350 , and  360  and driven pulleys  325 ,  345 ,  355 , and  365 . Because the driving pulleys  320 ,  340 ,  350 , and  360  have larger diameters than driven pulleys  325 ,  345 ,  355 , and  365 , the rotational speed of driven pulleys  325 ,  345 ,  355 , and  365  may be proportionally faster than the rotational speed of driving pulley  320 ,  340 ,  350 , and  360 . These ratios may be inversely proportional to the ratios of the respective speeds of the driving pulleys  320 ,  340 ,  350 , and  360  and driven pulleys  325 ,  345 ,  355 , and  365 . This speed may be somewhat slower than the actual ratio due to friction. 
     The final pulley unit  365  may rotate at a sufficient speed for generation of electrical energy. For this purpose, a second belt  370  may be coupled to pulley unit  365  to extract its rotational energy. An idler unit  380  may be coupled to second belt  370  to provide additional tension. 
     The use of eight pulleys  320 ,  325 ,  340 ,  345 ,  350 ,  355 ,  360 , and  365  is merely exemplary, as the actual design of pulley belt system  300  will depend upon the desired rotational speed of pulley unit  365  and the gear ratios of the pulleys  320 ,  325 ,  340 ,  345 ,  350 ,  355 ,  360 , and  365 . 
     First belt  330  may be approximately three meters in length. Second belt  370  may be approximately four meters in length. The length of both first belt  330  and second belt  370  may be varied depending upon the size of pulley units  320 ,  325 ,  340 ,  345 ,  350 ,  355 ,  360 , and  365 . 
     The eighth pulley  365  may be moving at a speed fast enough that electric power can be efficiently generated. To produce such a high speed, the gear ratios between the first pair of pulleys  320 ,  325 , the second pair of pulleys  340 ,  345 ; the third pair of pulleys  350 ,  355 ; and the fourth pair of pulleys  360 ,  365  may be approximately 10:1. Alternatively, smaller gear ratios may be used, producing a significantly slower rotational speed to prevent the large wheels from rotating at dangerous speeds. 
       FIG. 4   a  shows an elevation view of an exemplary gearbox system  400  for generator  100 . 
     As shown in  FIG. 4   a , gearbox system  400  may comprise a gearbox pulley  410  coupled to the second driving belt  370  of pulley belt system  300  that receives rotational energy from the last pulley unit  365  in pulley belt system  300 . Idler unit  380  may provide tension to maintain second belt  370  in contact with gearbox pulley  410  and ensure that second belt  370  remains mounted. 
       FIG. 4   b  shows an end view of an exemplary gearbox system  400  for generator  100 . 
     As shown in  FIG. 4   b , the rapid motion of gearbox pulley  410  drives gearbox  420 , thereby sending energy into T1 grid coupling  430 . Coupling  430  powers generator system  440 , the final stage of gearbox system  400 . An AC/DC converter may transform alternating current (AC) from generator system  440  into direct current (DC). 
     Gearbox  420  may itself include internal parts (not shown) that further increase the rotational speed transmitted through coupling  430  to generator system  440 . By reducing the torque needed to drive gearbox system  400 , the use of gear ratios to increase rotational speed within gearbox  420  may permit generator  100  to get a longer run out of each weight-drop. If a prefabricated gearbox is used, gearbox  420  may have a rotational speed of 5000 rotations per minute (rpm) at ¼ horsepower. As will be apparent to one of ordinary skill in the art, other rotational speed and power values may also be used. 
       FIG. 5  depicts another exemplary tandem system  500  for generator  100 . 
     Tandem system  500  differs from tandem system  200 , previously described with reference to  FIG. 2 , by having four units for each sub-assembly  241 ,  242 ,  251 , and  252 . While each sub-assembly  241 ,  242 ,  251 , and  252  in tandem system  200  comprised three units: a large pulley  270 , a small pulley  271 , and a support unit  272 , each sub-assembly  241 ,  242 ,  251 , and  252  in tandem system  500  has a large pulley  510 , a medium pulley  520 , a small pulley  530 , and a support unit  540 . Fixed sub-assemblies  241  and  251  have large pulleys  510  on top while movable sub-assemblies  242  and  252  have small pulleys  530  on top. 
       FIG. 6  depicts a further example of a tandem system  600  for a generator  100 . 
     Like  FIG. 5 , each sub-assembly  241 ,  242 ,  251 , and  252  in tandem system  600  has a large pulley  610 , a medium pulley  620 , a small pulley  630 , and a support unit  640 . However, fixed sub-assembly  241  is not coupled by cable  242  to fixed sub-assembly  251 . Instead, tandem system  600  uses a second cable  650  to couple four pulley units  660 ,  670 ,  680 , and  690  between movable sub-assembly  242  and movable sub-assembly  252 . 
       FIG. 7  shows an alternative arrangement  700  for idler unit  380  within pulley belt system  300  of  FIG. 3 . 
     In order to increase the efficiency of the overall system, arrangement  700  may achieve an optimal traction force between the last pulley unit  365  and second belt  370 . This arrangement comprises a steel core  710  encased within al Teflon™ strip  720 , a threaded rod  730 , and a Teflon™ disk holder  740 . It may be important to control frictional forces, as the efficiency of the system may be reduced if sliding friction slows the movement of the pulley belt system  300 . 
     From the above description, it will be apparent that the invention disclosed herein provides a novel and advantageous system and method for generation of electrical energy. The foregoing discussion discloses and describes merely exemplary methods and embodiments of the present invention. One skilled in the art will readily recognize from such discussion that various changes, modifications and variations may be made therein without departing from the spirit and scope of the invention. Accordingly, disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.