Abstract:
A fan assembly generally comprising at least one fan blade unit of at least two curved fan blades centrally attached to a hollow rotational shaft through which air flows into the fan blade and exits on the leeward edge of the fan blade tip;

Description:
DOMESTIC PRIORITY 
       [0001]    This application claims the benefit of the filing date for Provisional Application No. 61/268,165, filed Jun. 9, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a solar powered fan assembly. 
         [0004]    2. Description of the Prior Art 
         [0005]    Most home owners especially those in the Southwestern United States, have somewhere located on the roof of their house an exhaust fan designed to move hot air from the attic space to the outside. These exhaust fans are commonly referred to as turbine fans because of the arrangement of the blades and work on the simple principle that hot air rises. As the air inside an attic heats up, it rises creating a current which causes the fan blades to rotate. 
         [0006]    It is commonly known in the art that a temperature differential across the external structure of a fan can be used to turn the blades of such fan. For instance, U.S. Pat. No. 5,381,048, issued to William Baird for Solar Venturi Turbine; U.S. Pat. No., 3,757,146, issued to Wesley Love, for Thermoelectric Generator; and, US Patent Publication No. 2008/0087315, to Glenn Deming for Thermoelectric Fan for Radiation Based Heaters, and Methods Related Thereto; all disclose a fan that produces electrical energy based upon a temperature gradient. Additionally, U.S. Pat. No. 6,707,669, to Jen Lee, for Heat Dissipation Apparatus; U.S. Pat. No. 5,544,488 to Randall Reid for Sel Powered Heat Transfer Fan; and US Patent Publication 2008/0134690 to Randall Reid for Self Powered Heat Transfer Fan, disclose fans which do not produce electrical energy but which are powered completely by temperature differentials. 
         [0007]    What is not shown in the prior art is a fan assembly in which the rotational force by which the fan turns is created by virtue of hot air rising through the internal structure of such fan. 
       SUMMARY OF THE INVENTION 
       [0008]    It is, therefore, an object of the present invention to provide a fan assembly which allows air flow through the internal structure of such fan to create the rotational force necessary to cause the fan to turn. Other objects and advantages of the present invention will become apparent from the following detailed description when viewed in conjunction with the accompanying drawings, which set forth certain embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a side view of the fan assembly of the present invention. 
           [0010]      FIG. 2  is a top view of the fan assembly of the present invention. 
           [0011]      FIG. 3  is a close up side view of a single fan blade. 
           [0012]      FIG. 4  is a close up top view of a single fan blade. 
           [0013]      FIG. 5  is an illustration of the fan assembly of the present invention in operation. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    The detailed embodiments of the present invention are disclosed herein. It should be understood, however, that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. 
         [0015]    As depicted in  FIG. 1 , the fan assembly of the present invention comprises a series of fan blade units [ 2 ] centrally attached to a hollow rotational shaft [ 1 ] having a closed bottom [ 8 ] and top [ 9 ]. The bottom [ 8 ] and top [ 9 ] of the rotational shaft [ 1 ] can be attached to the respective surfaces of a typical attic fan or skylight using any conventional means so long as the rotational shaft [ 1 ] can freely turn. At the bottom [ 8 ] of the rotational shaft [ 1 ] are air entry ports [ 3 ] which allow air to enter the shaft [ 1 ]. Although any number of air entry ports [ 3 ] may be used so long as each port has a corresponding opposite port, the current invention utilizes two of such ports. While three fan blade units [ 2 ] are shown in  FIG. 1 , only one fan blade unit [ 2 ], that being the fan blade unit located at the top of the hollow rotational shaft [ 1 ], the moving unit [ 15 ], is necessary for the operation of the present invention. 
         [0016]      FIGS. 2 ,  3  and  4  illustrate the moving unit [ 15 ] of the present invention. Although four fan blades [ 10 ] of particular geometry are shown in  FIG. 2 , any number or shape of vanes may be use so long as the blades [ 10 ] remain balanced upon the rotational shaft [ 1 ]. As shown in  FIG. 3 , the upper [ 4 ] and bottom [ 5 ] surfaces of the fan blades [ 10 ] of the moving unit [ 15 ] are curved in such a manner as to allow a space [ 6 ] between the two. To allow sunlight to shine through the upper [ 4 ] curved surface of the fan blades [ 10 ] of the moving unit [ 15 ], such surface is made from clear plastic, although any surface which is transparent will suffice. The bottom [ 5 ] curved surface of the fan blade [ 10 ] of the moving unit [ 15 ] is made from any opaque material of sufficient strength and rigidity as to support the fan blade [ 10 ]. To further increase air flow by increasing the temperature differential,  FIG. 3  shows that within the space [ 6 ] between the two curved surfaces [ 4  and  5 ], a strip [ 7 ] of lightweight heat absorbing material may be placed. There are many types of material that will absorb heat currently available which include chemical compounds, chemical liquids, most types of metal, sand and rock. In the present invention, a strip of copper has been found to absorb heat adequately without detrimentally effecting the weight of the fan blade [ 2 ]. While not necessary for the operation of the fan assembly of the present invention, instead of a heat absorption strip [ 7 ] or in addition to,  FIGS. 3 and 4  depict the placement of water filled tubes [ 12 ] which function, in addition to increasing heat differential, to deflect the flow or air towards the fan blade exit ports [ 13 ]. 
         [0017]    As shown in  FIG. 1 , air enters the bottom of the rotational shaft [ 1 ] through the air entry ports [ 3 ]. As the hot air rises it will reach the moving unit [ 15 ].  FIG. 4  illustrates that each of the four (4) fan blades [ 10 ] of the moving unit [ 15 ] are connected to the rotational shaft [ 1 ] in such a way as to allow air from the shaft to enter the fan blade [ 10 ]. While the size and geometry of the fan blade air entry port [ 11 ] is not critical, in the present invention, the fan blade air entry port is simply a hole. As depicted in  FIGS. 3 ,  4  and  5 , sunlight penetrating the upper curved surface [ 4 ] of the fan blade [ 10 ] will cause the air, the water filled tube [ 12 ], and the heat absorbing strip [ 7 ] to heat increasing the temperature and pressure differential across such blade. As shown in  FIG. 3 , the fan blade exit ports [ 13 ] are located at the leeward edge of the fan blade [ 10 ] tip. The hot air exiting through the fan blade air exit ports [ 13 ] will creating a rotational force which will cause the fan assembly to turn. The other fan blade units [ 2 ] depicted in  FIG. 1  are not open to the hollow rotational shaft [ 1 ] and act only to assist in the rotation of the hollow rotational shaft [ 1 ]. 
         [0018]    The fan assembly of the present invention can be used in many different applications such as to replace existing attic fans. Furthermore, the fan of the current invention could be placed within a skylight. 
         [0019]    While the preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.