Abstract:
One or more fan blades extend radially from a hub that is freely rotatable relative to a main drive shaft. The hub is coupled to the drive shaft so that, when the drive shaft is moved through an orbital path in a cyclical motion, the hub moves in a twirling action. As the hub twirls, a weighted distal end of the blade travels through an arcuate path to generate angular momentum sufficient to carry the blade through an uninterrupted rotational motion. The fan blade is structured and disposed to push a large volume of air as it rotates, thereby creating a steady current of airflow with minimal energy consumption.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to energy efficient fans and, more particularly, to an energy efficient fan having one or more fan blades fixed to a hub which is freely rotatable relative to a central drive shaft, and wherein twirling of the hub creates angular momentum of the fan blade which carries the blade through a continuous 360° rotational motion, thereby pushing a current of airflow. 
     2. Discussion of the Related Art 
     Motorized fans of various types are well known in the art. Typically, a hub is fixed to the end of a shaft which is rotatably driven by a motor. Several fan blades are fixed to the hub and pitched at an angle to move air as the hub and blades rotate. The amount of power required to drive the shaft and rotate the hub and blades at a specific RPM is primarily dependent on the size of the blades (i.e. surface area and length) as well as the pitch of the blades. More specifically, a significant amount of electrical energy is required to overcome the torque which is generated by the resistance of the fan blades when rotating, particularly at higher speeds. For this reason, the operation of electrically powered motorized fans, particularly those having a relatively large fan blade length or radius, can be costly when operating at higher RPMs. Accordingly, there remains a need in the fan art for an energy efficient fan which rotates one or more fan blades at a high RPM while consuming less energy than conventional motorized fans. 
     SUMMARY OF THE INVENTION 
     According to the present invention, one or more fan blades are fixed to a hub which is freely rotatable relative to a main drive shaft. In one embodiment, the inner circumference of the hub is greater than the outer circumference of the drive shaft so that when the shaft is moved in a cyclical motion, and the central longitudinal axis of the shaft travels through a continuous orbital path, the hub moves in a twirling action about the shaft. As the hub twirls, a weighted distal end of the blade travels through an arcuate path to generate angular momentum which is sufficient to carry the blade through an uninterrupted rotational motion, thereby resulting in rotation of the one or more fan blades. The fan blade is structured and disposed to push a large volume of air as it rotates, thereby creating a steady current of airflow with minimal energy consumption. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a diagram illustrating an orbital path of the longitudinal axis of a drive shaft in accordance with one preferred mode of operation of the energy efficient fan of the present invention; 
     FIG. 1A is a diagram illustrating an alternative orbital path of the longitudinal axis of the drive shaft; 
     FIG. 2 is a diagram showing a hub and fan blade fitted about the shaft traveling through the orbital path of FIG. 1; 
     FIG. 3 is a top plan view, in partial phantom, illustrating motion of the fan blades through a circular rotational path upon movement of the shaft about the orbital path of FIG. 1; 
     FIG. 4 is a front elevational view of an embodiment of the energy efficient fan of the present invention; 
     FIG. 5 is a top plan view, in partial phantom, of the fan apparatus of FIG. 4, illustrating motion of a fan blade panel through a circular path; 
     FIG. 6 is an isolated front elevational view of the base of the fan apparatus of FIG. 4; 
     FIG. 7 is a top plan view of yet another embodiment of the fan apparatus of the present invention; 
     FIG. 8 is a side elevational view of the fan apparatus of FIG. 7; and 
     FIG. 9 is a top front perspective view of the fan apparatus of FIG. 7 with one hub and blade assembly removed for purposes of clarity. 
    
    
     Like reference numerals refer to like parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the several views of the drawings which illustrate the principal of operation of the energy efficient fan  10  of the present invention and several embodiments thereof, there is provided a main drive shaft  12  and a hub  14  freely rotatable relative to the shaft. At least one primary fan blade or panel  16  is fixed to the hub  14  and rotatable therewith so that, as the hub  14  spins about the shaft  12 , the fan blade  16  is caused to travel through a circular path of rotation. The fan blade or panel  16  is specifically structured and configured to push a volume of air to create a current of airflow through a space upon rotation through the circular path. The hub  14  is loosely coupled to the shaft  12 , and in one embodiment has an inner circumference which is larger than the outer circumference of the shaft. Movement of the shaft  12  through an orbital path causes the hub to twirl about the shaft  12  while spinning or rotating relative to the shaft. 
     Referring initially to FIG. 1, an orbital path of the drive shaft  12  is shown wherein the central longitudinal axis  18  of the shaft is shown to move through a generally circular and continuous path. FIG. 1A illustrates an alternative motion of the shaft, wherein the central longitudinal axis  18  moves through a generally elliptical path. It should be noted that the path through which the central axis  18  of the shaft  12  travels, as seen in FIGS. 1 and 1A, may occur at only one or both ends of the shaft. More particularly, one end of the shaft may be held relatively stationary, serving as a pivot, while the opposite end of the shaft is moved through the orbital path, such as that shown in FIGS. 1 and 1A. Alternatively, both ends of the shaft may be moved in unison through the same motion, so that the orbital path of the central longitudinal axis  18  is uniform along the entire length of the shaft  12 . 
     Referring to FIG. 2, the hub  14  and fan blade  16  are shown coupled to the shaft  12  which is moving through a continuous orbital path. A weighted element  20  on the outer distal end  22  of the fan blade  16  provides angular momentum to carry the fan blade about the circular path of rotation as the hub  14  is twirled about the shaft  12 . As seen in FIG. 3, the angular momentum generated by the weighted element  20  on the primary fan blade carries the entire fan blade assembly, including three secondary blades  16   a ,  16   b ,  16   c  fixed to the hub  14 , through a circular path of rotation as the central axis  18  of the drive shaft moves through the orbital path and the hub freely rotates about the shaft. 
     Referring to FIGS. 4-6, one particular embodiment of a fan apparatus  10 ′ is shown wherein a fan panel  16 ′ is supported between upper and lower hub members  14   a  and  14   b . The fan panel  16 ′ is preferably formed of a flexible material such as fabric or a thin plastic film. The hub members  14   a ,  14   b  are fitted on vertical drive shaft  12 ′ and are freely rotatable relative thereto. A rod  30  is fitted to the fan panel  16 ′ and connects to the upper and lower hub members  14   a ,  14   b . The rod  30  may be rotatable relative to the upper and lower hub members to promote free rotation of the fan panel  16 ′ relative to the hub members and shaft. In operation, an upper end  34  of the shaft  12 ′ is moved in a reciprocating back and forth motion, as indicated by the arrows in FIG. 4, while the bottom end of the shaft  36  pivots on a base  38 . In this particular embodiment, the base is in the form of a rocker which is caused to rock back and forth in the direction of the arrow  40  shown in FIGS. 4 and 6. Upon movement of the central axis of the upper end of the shaft  12 ′ in the reciprocating continuous motion, as indicated by the arrow  42  in FIG. 5, a weighted element  20 ′ on the outer edge of the fan panel is thrown in a direction to create angular momentum. The angular momentum created by movement of the weighted element  20 ′ carries the fan panel  16 ′ about a circular path of rotation as shown by the arrows  44  in FIG. 5, while the hub members  14   a ,  14   b  freely rotate about the shaft  12 ′. Continuous back and forth reciprocating motion of the shaft results in continuous rotation of the fan panel  16 ′ in successive 360° circular paths about the shaft. As the fan panel  16 ′ moves through the circular path of rotation, a volume of air is pushed to create an air current through the air space surrounding the fan apparatus  10 ′. 
     Referring to FIGS. 7-9, another embodiment of the invention is shown, wherein a fan apparatus  10 ″ includes two or more fan blade assemblies  11   a  and  11   b  supported on a main drive shaft  12 . Each fan blade assembly  11   a ,  11   b  includes a hub  14  loosely fitted to the shaft  12  and rotatable thereabout in the twirling action described above. A plurality of fan blades  16  are fixed to each of the hubs  14  and extend radially outwardly therefrom, as best seen in FIG.  8 . At least one of the fan blade assemblies  11   a  is provided with a weighted element  20  at the end of either one of the fan blades  16  or a radial spoke  50 . 
     In accordance with the embodiment of FIGS. 7-9, the fan blade assemblies  11   a ,  11   b  are driven by a gear arrangement resembling a differential gear assembly. Specifically, first and second gear members  60   a  and  60   b  are rotatably fitted to a coupling  62 . The coupling  62  is fitted to the shaft  12  so that the coupling and gear members  60   a ,  60   b  are maintained between the fan blade assemblies  11   a ,  11   b . Pegs  64  extend radially from each of the gear members  60   a ,  60   b  to define gear teeth which are structured and disposed for intermeshing, driving engagement between the fan blades  16  on each of the hubs  14 . In operation, the main drive shaft  12  is moved so that the central longitudinal axis of the drive shaft travels through the cyclical orbiting motion. As the drive shaft is moved in this motion, the weighted element is set in motion to generate angular momentum which drives fan blade assembly  11   a . As the hub  14  and fan blades  16  of fan blade assembly  11   a  rotate, the intermeshing pegs  64  are engaged to drivingly rotate the gear members  60   a ,  60   b . This in turn drivingly engages fan blade assembly  11   b  to rotate the hub  14  and fan blades  16  of fan blade assembly  11   b  in a rotational direction which is opposite to the rotational direction of fan blade assembly  11   a . The fan blades  16  of each fan blade assembly  11   a ,  11   b  are specifically pitched to push air outwardly, in the opposite directions, as indicated by arrows  70  in FIG.  7 . It is further noted that the gear members  60   a ,  60   b  may be structured and disposed to draw a current of air between the fan blade assemblies  11   a ,  11   b , as indicated by arrow  72  in FIG.  7 . 
     While the present invention has been shown and described in accordance with preferred and practical embodiments thereof, it is recognized that departures from the instant disclosure are contemplated within the spirit and scope of the present invention as defined in the following claims under the doctrine of equivalents.