Abstract:
A wind-driven power source comprises a propeller-driven rotor structure and a stator structure carrying clusters of copper-wire wound ferromagnetic cores as voltage generators. The cores are arranged in pairs spaced apart by hard rubber rollers which engage the inside surface of a load ring forming part of the rotor structure. The overall rotor structure comprises the large diameter load ring, a smaller diameter root ring and a plurality of aerodynamic blades extending radially outwardly from the root ring and secured either by saddle blocks or integral bonding to the load ring. The load ring may be aluminum or plastic. Permanent magnets are arranged around the load ring to interact with the voltage generator structures to produce three-phase electricity.

Description:
FIELD OF THE INVENTION 
     This patent relates to wind wheels and to wind-driven electricity generators using wind wheels. More particularly, the disclosure herein describes a wind-driven generator of minimal complexity, lightweight and optimized efficiency which can be constructed of low cost components. 
     BACKGROUND 
     It is known to use wind wheels to perform mechanical functions and to generate electricity. An early wind wheel electrical generator is disclosed in U.S. Pat. No. 1,233,232, issued Jul. 10, 1917, to A. H. Heyroth. The Heyroth wind wheel comprises a large diameter rotor ring carrying permanent magnets and a center axle which supports the rotor ring by means of radial spokes. Rotation of the rotor ring causes the permanent magnets mounted thereon to move past stationary magnetic cores and the changes of flux value through the cores result in the generation of electrical voltages in windings carried by the cores. 
     A similar but more recent device is shown in U.S. Pat. No. 6,064,123, issued May 16, 2000, to Nils Gislason. 
     Still another device is shown in U.S. Pat. No. 6,664,655 issued Dec. 16, 2003, to Charles S. Vann. The Vann wheel comprises a large number of short radial blades fixed between two large-diameter, concentric metal rings. The outer ring is supported for rotation on three outside rollers and the ring can be magnetized so as to form part of a voltage generator or a motor. 
     SUMMARY 
     This disclosure describes a wind wheel particularly, but not exclusively, suited for use in an electricity generator. To the extent so used, the generator involves optimal application of the following principles: 
     1. Higher rotor speeds generally result in higher generator output power. 
     2. Higher rotor speeds are more easily achieved with a lighter, lower-mass rotor structure; and 
     3. It is advantageous to minimize torque and moments drag forces on the rotor structure. 
     The wind wheel of the present invention affords optimal use of these principles in a rotor structure comprising shell diameter root ring, a larger diameter outer ring, and a plurality of lightweight blades structurally connected at their inner ends to the root ring and at a midpoint to the outer ring. The outer ring is used in a rotary support system typically using rollers to allow the rotor to rotate about an axis which is common to the root and outer rings. 
     When used in an electricity generator, the lightweight rotor can carry a plurality of spaced permanent magnets to co-act with one or more stationary core arrangements to produce electricity as the rotor rotates. 
     The present arrangement requires no center axle and has the potential to produce high rotor speed for any given wind force or speed without the need for a gear box. The use of a midpoint structural ring providing support at the midpoints of the blade allows for the use of lightweight materials such as foam core composition for blade construction. 
     These and other advantages of the invention will be best understood from a reading of the following specification which describes the preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  is a perspective view of a portion of a “wind farm” employing three generators constructed in accordance with the present invention and mounted on poles; 
         FIG. 2  is a detail of one of the generators of  FIG. 1 ; 
         FIG. 3  is a cross-section of one of the propeller blades of the structure of  FIG. 2 ; 
         FIG. 4  is a detail of the structure of  FIG. 2  showing the arrangement of voltage generator core structures straddling an inside roller as part of the stator structure for the device of  FIG. 2 ; 
         FIG. 5  is a detail of the structure of  FIG. 2  showing the core structures, permanent magnets and propeller blade mounting structure in three-dimensional detail; 
         FIG. 6  is a side view of the structure of  FIG. 5  showing part of the rotor in cross-section; 
         FIG. 7  is a cross-section of a blade showing additional rotor structure; 
         FIG. 8  is a representative circuit diagram generating three-phased power from the structure of  FIGS. 1–7 ; 
         FIG. 9  is a plan view of an alternative embodiment of a rotor structure; and 
         FIG. 10  is a partial cross-section of the structure of  FIG. 9  in greater detail showing the support rollers for the rotor of  FIG. 9  and the relationship between the permanent magnets and the voltage-generating structures mounted on the stator. 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIG. 1 , there is as shown a portion of a “wind farm,” including identical wind-driven power sources  10 ,  11  and  12  mounted on poles  14 ,  15  and  16  to collect wind and produce electricity from the energy contained therein. Since all of the sources  10 ,  11  and  12  are identical, only source  10  will be described in detail. 
     Referring now to  FIGS. 2–7 , source  10  comprises a stator structure  18  made up of three triangularly arranged aluminum struts  19  mounted on the pole  14 . The stator structure  18  includes three generating units  20  and  21  mounted on plates  50  and  22  described in greater detail with reference to  FIGS. 4 and 5 . Again, the units  20 ,  21  and  22 , although in different locations on the power source  10 , are identical and unit  20  is described as representative. 
     Unit  20  comprises two ferromagnetic iron cores  26  and  28  closely arranged around opposite sides of and straddling a roller  30  which is one of three stator-mounted rollers symmetrically arranged on the plate  50  of the stator structure  18 . The rollers  30  support a rotor structure  32 , the largest component of which is an aluminum ring  34 . This is variously referred to herein as the “outer ring” or the “load ring” and, in this embodiment, includes a number of components, including a ferrous metal backer ring  48  and an array of permanent magnets  36  bonded to the radially inner surface of the broken ring, to generate electricity. The aluminum ring  34  makes the structure light and easy to accelerate while the iron backer ring  48  provides a flux path for the magnetic system. The rotor structure  32  further includes lightweight composite aerodynamic blades  38 ,  40  and  42  which, as best shown in  FIGS. 2 and 3 , are preferably made by overlaying a rigid foam plastic core  44  with a synthetic resin exterior covering  46 . 
     The rotor structure  32  further comprises a non-ferrous root ring  45  to which the blades  38 ,  40  and  42  are attached at their inner ends. The root ring  45  may be of a composite, plastic construction or of other relative lightweight material. By way of example, the blades  38 ,  40  and  42  may be approximately five feet in length. The root ring  45  may be approximately two feet in diameter and the aluminum load ring  34  may be approximately six feet in diameter. As such, the load ring  34  is attached near the radial midpoint of the rotor structure  32  to add strength and rigidity to the blades to resist torque deflection. The blades are cambered with the pitch of approximately forty-two degrees at the inner or root end thereof and approximately one-half of one degree at the outside tips. The pitch changes gradually from end to end. 
     Referring to  FIGS. 2 through 5 , the stator and rotor structures will be described in greater detail. The stator structure  18  comprises aluminum plates  50  at the apices of the triangular support struts shown in  FIG. 6 . Each plate  50  holds a pair of spaced apart, laminated, iron cores  26  and  28  wound with copper coils  29  and  31 . Between each set of two core structures  26  and  28  is rotatably mounted a hard rubber roller  30  which engages the outer surfaces of a polycarbonate track  52  running over the outside surfaces of the permanent magnets  36  which are bonded to a steel backer ring  48  mounted on the aluminum load ring  34  to provide a continuous magnetic flux path. Non-magnetic spacers  33  are disposed between the permanent magnets  36 . The polycarbonate track  52  is a thin film bonded over the flat surface defined by the combination of the magnets  36  and the spacers  33 , as best shown in  FIGS. 5 and 6 . 
     The rollers  30  make contact with and ride on the flat surface provided by the polycarbonate track  52  for smooth vibration-free rotation of the load ring  34  of the rotor structure  32 . The ferromagnetic cores  26  and  28  are located in close proximity to but spaced from the polycarbonate ring by approximately 0.180 inch. In a practical embodiment of the size described above, it has been found that the magnetic force of attraction between the permanent magnets and the ferromagnetic core structures  26  and  28  is approximately 40 pounds per voltage generation unit for a total of 80 pounds of attraction at each of the three stator structures  18  as the magnetic rotor rotates past. In order that the aluminum load ring  34  be able to withstand these attractive forces without deflection, the rotor rollers  30  are preferably mounted symmetrically between the closely matched pairs of cores  26  and  28  for maximum resistance to deflection so that they contact the inside surface of the load ring directly between the core structures. Additional rollers  37  are rotatably mounted behind the stator structure as shown in  FIG. 6  to provide thrust support; i.e., support in the direction parallel to the axis of rotation. 
     The blade support structure is best shown in  FIGS. 5 ,  6  and  7  to comprise saddle blocks  54  which receive and conform to the inside surfaces of each of the blades  38 ,  40  and  42 . Clamp blocks  56  and  58  attach by way of cap screws to the saddle blocks to trap the blades  38 ,  40  and  42  and hold them firmly to the load ring  34  for overall rigidity. 
     Stops  58  are preferably attached by cap screws to plates  60  on the stators  18  to prevent the rotor  32  from moving forwardly of the stator structure. The spacing between the stops  59  and the outer surface of the load ring  34  may be on the order of ¼ inch; minimal reverse thrust loading is experienced and thus no outside rollers are required. 
     By way of summary, each of the generator units comprises a stator structure  18  consisting of a triangular frame made of struts  19  and three symmetrically arranged pairs of generating units  20 ,  21  and  22 . Each generating unit includes a pair of ferromagnetic cores  26  and  28  and wound coils straddling a roller  30  adapted to ride on the radially inner track  52  of the load ring  34 . The load ring  34  is integrally attached to each of the lightweight propeller blades  38 ,  40  and  42  at approximately the midpoints thereof to add structural stiffness. The inside surface of the load ring  34  is provided with an array of permanent magnets  36  which move in radially spaced relationship to the stator cores  26  and  28  to generate voltages in the cells as the propeller blades  38 ,  40  and  42  drive the rotor ring in a circular path. 
     Referring now to  FIG. 8 , a representative electrical system based on the use of 160 permanent magnets on the inside of the six foot load ring  34  is shown. The system comprises clusters  64 ,  66  and  68  of six coils each spaced to create a three-phase electrical system. The two matching-phase coils in each cluster are wired in series. There are six identical clusters. Each cluster has its respective matching phased coil pairs wired in parallel to form an output circuit. Each of these output circuits has a capacitor bank  70 ,  72  and  74  connected between the leads to correct the power factor. Each circuit is then fed to one of the full-wave rectifiers  76 ,  78  and  80 , respectively, to provide unregulated DC voltage to an output circuit comprising resistors  84 ,  86  and  88 . The circuit of  FIG. 8  shows voltage meters in strategic locations to monitor output. Each coil is in a representative example consisting of 100 turns and the air gap between the cores of the generator structures and the magnets are approximately five millimeters. 
     In a successfully operated embodiment, the weight of the blades are approximately 36 pounds total and safely rotated at a speed of up to 250 revolutions per minute. The total weight of the magnets is approximately 15 pounds and the rollers  30  are 4 inches in diameter and made of hard rubber. 
     Referring now to  FIGS. 9 and 10 , an alternative rotor structure  100  will be described. The rotor structure comprises a load ring  102  made of molded lightweight plastic and having an aerodynamic or wedge-shaped cross-section as shown in  FIG. 10 . The plastic load ring  102  is physically integrated with the blades  104 ,  106  and  108  at approximate midpoints thereof as shown in  FIG. 9 . The inner ends of the blades are bonded by standard fiberglassing techniques to the smaller diameter root ring  110 . The term “fiberglassing” is intended to encompass composite structures of various kinds including those using fibers of graphite, glass and other materials. 
     Whereas the permanent magnets  36  of the embodiment of  FIG. 4  are mounted on the radially inside surface of the load ring  34 , the permanent magnets  114  of the embodiment of  FIGS. 9 and 10  are arrayed annularly around the leeward or downwind surface  130  of the load ring  102  and are bonded to an annular ferromagnetic backer ring  112  which is cast into the load ring  102  as shown in  FIG. 10 . A plastic surface can be placed atop the magnets for weather proofing. Rollers  124  bear against the inside surface  126  of the load ring  102  and are arranged in the symmetrical and equally-spaced arrangement shown in  FIG. 9 . Those rollers are carried by the stator structure  116  which, like the first embodiment, is made up of a triangular arrangement of beams. Ferromagnetic core structures  118  with wound coils  120  are also placed on the stator structure  116  closely adjacent to the track of the permanent magnets  114  as the rotor rotates. Thrust support is provided by means of rollers  128  which bear against the surface  130  radially inboard of the track of the permanent magnets  114 . 
     In this embodiment, the generating units are essentially out of the airstream, i.e., in the shadow of the load ring  102  to reduce losses due to windage. Only the radial rollers  124  and smaller portions of the stator structure lie in the windstream. This structure may be made extremely light in weight and extremely rigid because of the possibility for integrating with epoxy-bonding, fiberglassing techniques and the like. The electrical arrangement of  FIG. 8  may also be used in combination with the structures of  FIGS. 9 and 10 . 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.