Abstract:
Conventional large area fans generally create a cylinder of air having a diameter that is essentially equal to the diameter of the fan. Larger diameter fans require heavier-duty motors and gearboxes to drive the longer fan blades and are heavier, and thus are more difficult to mount, require heavier-duty mounting fixtures, and are more likely to fall. One large area fan according to this invention forms a cone of air. Some fan blades according to this invention have a relatively straight leading edge portion attached to the fan and a generally curved trailing portion extending downwardly from the relatively straight leading edge portion that interacts with the air to create a conical or cone-shaped flow of air from the fan. Other fan blades have a curved segment and are attached to the fan at theirs leading edges. In some such fan blades, one end is offset from the other end.

Description:
This application claims benefit under 35 U.S.C. §119 of U.S. Provisional Patent Application 60/569,349, filed May 7, 2004, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a fan usable to create a flow of air in a large space, such as a barn. 
     2. Related Art 
     Fans for large spaces, such as warehouses, barns used to house dairy cows and the like, generally have very long blades. One such conventional fan has a 24-foot diameter (approximately 7.3 meters). That is, the fan has blades that extend 12 feet (approximately 3.7 meters) from the axis of rotation of the fan. However, the moving air created by such known fans for large spaces generally is in the form of a cylinder having a diameter that is essentially equal to the diameter of the fan. Thus, to create a larger area in which the air moves, it is necessary to provide larger blades to such conventional fans, thus creating a fan having a larger diameter. This in turn creates a larger cylinder of moving air. 
     SUMMARY OF DISCLOSED EMBODIMENTS 
     However, merely increasing the size of the fan blades is problematic. In particular, larger diameter fans require heavier-duty motors and gearboxes to drive the longer fan blades. Larger diameter fans are also heavier, and thus are more difficult to mount, require heavier-duty mounting fixtures, and are more likely to fall. For example, the gearboxes in conventional large diameter fans are prone to failure, such as by the gearbox shafts breaking. Additionally, while conventional large diameter fans for large spaces have safety catch devices, the size of such large diameter fans can overwhelm the safety catch device, causing them to fail. 
     This invention provides a fan for a large space that has an intermediate length blade. 
     This invention separately provides a fan for a large space that is able to create moving air in an area that is larger in diameter than the diameter of the fan blades. 
     This invention separately provides a fan for a large space that creates a generally cone-shaped region of moving air. 
     This invention separately provides a fan for a large space that has fan blades that are attached to a base structure at locations adjacent to leading edges of the fan blades. 
     This invention separately provides a fan having relatively shorter blades that can create moving air over an area that is at least as large as an area over which a relatively larger conventional large area fan creates the moving air. 
     This invention separately provides a fan, having a relatively smaller motor and gearbox compared to a conventional fan for large spaces, that has a similar coverage area. 
     This invention separately provides a fan, having a relatively similarly-sized motor and gearbox compared to a conventional fan for large spaces, that has a larger coverage area. 
     This invention separately provides a fan having a safety catch that is sufficient to support the weight of the fan blades and mounting structure. 
     In various exemplary embodiments of a large area fan according to this invention, the fan includes a plurality of relatively shorter blades connected to a rotating plate. The rotating plate is connected to a shaft of a gearbox. The gearbox is connected both to a motor and to a suspension structure. 
     In various exemplary embodiments, the fan blades have a relatively straight leading edge portion and a generally curved trailing portion. The blades are attached to the rotation plate by their relatively straight leading edges. In various exemplary embodiments, the relatively straight leading edges lay flat against the rotating plate. The relatively curved trailing portions of the blades extend downwardly from the relatively straight leading edge portion and the rotating plate, and interact with the air to create a conical or cone-shaped flow of air from the fan. 
     In various other exemplary embodiments, at least a portion of the fan blades are in the shape of a segment of a curve, such as a circle, and are attached to the rotating plate at their leading edges. In various exemplary embodiments, such fan blades are twisted such that one end is offset from the other end of the blades. The blades are attached to the rotation plate with the concave side facing down. 
     In various exemplary embodiments, the suspension structures include a pole, a channel iron or other device usable to support the fan, fan blades, gear box and motor, a swivel device that allows the fan and fan blades to rotate relative to the pole, channel iron or other device, in case of a failure, a safety catch device, and/or one or more adaptor plates usable to connect the gear box and/or safety catch device to the pole, channel iron or other support device. The support structure is connected to and extends from a wall or ceiling that at least partially encloses the large space for which the fan is employed. 
     In various exemplary embodiments, as the fan blades according to this invention rotate with the rotating plate, they deflect or displace air. In various exemplary embodiments, some of the displaced air moves downwardly from the fan blades, while some of the displaced air moves radially along the fan blade, in addition to or in place of the downward flow. In various exemplary embodiments, the overall air flow has both radial and axial components, such that the air flow forms a cone-like shape as it leaves some exemplary fans according to this invention. 
     These and other features and advantages of various exemplary embodiments of the compositions, structures and methods according to this invention are described in, or are apparent from, the following detailed descriptions of various exemplary embodiments of the compositions, structures and methods according to this invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Various exemplary embodiments of the compositions, structures and methods according to this invention will be described in detail, with reference to the following figures, wherein: 
         FIG. 1  is a bottom plane view of one exemplary embodiment of a fan including a fan blade hub according to this invention, and a first exemplary embodiment of a fan blade according to this invention; 
         FIG. 2  is a bottom plan view of the fan of  FIG. 1 , showing the first exemplary embodiment of the fan blades and stiffening elements in greater detail; 
         FIG. 3  is a side perspective view along the first exemplary embodiment of the fan blade according to this invention; 
         FIG. 4  is a bottom plane view of one exemplary embodiment of the fan shown in  FIG. 1  that incorporates a second exemplary embodiment of the fan blade according to this invention; 
         FIG. 5  is a bottom plan view of the fan of  FIG. 4 , showing the second exemplary embodiment of the fan blades and stiffening elements in greater detail; 
         FIG. 6  is a side perspective view along the second exemplary embodiment of the fan blade according to this invention; 
         FIG. 7  illustrates the flow of air that occurs when the first exemplary embodiment of the fan blades according to this invention rotate; 
         FIG. 8  illustrates the flow of air that occurs when the second exemplary embodiment of the fan blades according to this invention rotate; 
         FIG. 9  is a side perspective view of one exemplary embodiment of a support structure according to this invention; 
         FIG. 10  is a top perspective view of one exemplary embodiment of a fan hub assembly and the support structure shown in  FIG. 9 ; of a fan according to this invention; 
         FIG. 11  is an exploded view of the mounting plate, safety plate and catches, gear box and support structure of  FIG. 10 . 
         FIG. 12  is a side view of the fan hub assembly and the support structure according to this invention 
         FIG. 13  is a side view of a first exemplary embodiment of a fan according to this invention when installed in a large space; and 
         FIG. 14  is a side view of a second exemplary embodiment of a fan according to this invention when installed in a large space; and 
         FIG. 15  is a top perspective view of one exemplary embodiment of the support structure and the fan hub assembly according to this invention as installed. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  is a bottom plan view of one exemplary embodiment of a fan  100 , including a plurality of a first exemplary embodiment of the fan blades  110  and one exemplary embodiment of a fan blade hub plate  210  according to this invention. As shown in  FIG. 1 , in various exemplary embodiments, the fan  100  includes 12 first exemplary fan blades  110  that extend radially from a fan blade hub assembly  200 . The first exemplary fan blades  110  can be any desired length that is useful in a given application. For many typical applications, each fan blade  110  can be about 4 feet to about 8-12 feet long (approximately 1.2 meters to about approximately 2.4-3.7 meters), or longer, as discussed below. In various exemplary embodiments, the first exemplary fan blades  110  are about 96 inches long and are approximately 3-4 inches wide, but can be any desired width that allows for a generally cone-shaped region of moving air to be created. 
     As shown in  FIGS. 1 and 2 , in various exemplary embodiments, the first exemplary fan blades  110  are attached to the underside of the fan blade hub assembly  200 . In the exemplary embodiment shown in  FIGS. 1 and 2 , the first exemplary fan blades  110  are bolted on to a fan blade hub plate  210  of the fan blade hub assembly  200  at two places using bolts  122  and  124 . Alternatively, the first exemplary fan blades  110  can be welded or otherwise suitably attached to the fan blade hub plate  210  using any known or later developed technique. In various exemplary embodiments, a support member or stiffening element  120  is also attached to one side of each first exemplary fan blade  110 . In particular, in the exemplary embodiment shown in  FIGS. 1 and 2 , the stiffening element  120  is attached to the underside of each first exemplary fan blade  110  using the bolts  122  and  124 , as well as a third bolt  126 . In this exemplary embodiment, the fan blades  110  are held between the fan blade hub plate  210  and the support members or stiffening elements  120 . 
     It should be appreciated that, in the exemplary embodiment shown in  FIGS. 1 and 2 , the bolts  124  are located about one inch away from the hub end of the first exemplary fan blades  110  and about one inch behind the leading edge of the first exemplary fan blades  110 . The bolts  124  are also located approximately 6-8 inches from the center of the fan blade hub plate  210 . Similarly, the bolts  122  are located about one inch away from the outer edge of the fan blade hub plate  210  and about one inch behind the leading edge of the first exemplary fan blades  110 . It should also be appreciated that, in the exemplary embodiments shown in  FIGS. 1 and 2 , the fan blade hub plate  220  is 30 inches in diameter and has a 10-inch-diameter reinforcing plate at its center that is used to attach the fan blade hub plate  210  to the spindle of a gearbox. Thus, it should be appreciated that the preceding discussion is exemplary, and different locations for the bolts  122  and  124  relative to the first exemplary fan blades  110  and the fan blade hub plate  210  can be used for the first exemplary fan blades  110  and/or fan blade hub plates  210  having different dimensions. 
     In the exemplary embodiment shown in  FIGS. 1 and 2 , the support members or stiffening elements  120  are generally rectangular prism shaped and extend approximately ⅓ of the length of the fan blades  110  along the first exemplary fan blades  110 . It should be appreciated that the support members or stiffening elements  120  can be omitted if the first exemplary fan blades  110  are sufficiently stiff enough to create the cone of moving air and to reliably rotate with the fan blade hub plate  210  at the rotational speeds that the large area fan  100  is designed to operate at. In general, this will depend, at least in part, on one or more of: the designed operational rotational speeds of the large area fan  100 , the size of the fan blade hub plate  210 , how the first exemplary fan blades  110  are attached to the fan blade hub plate  210 , the material used for the first exemplary fan blades  110 , the width of the first exemplary fan blades  110 , the design of the curvature of the first exemplary fan blades  110  and/or the length of the first exemplary fan blades  110 . 
     If the support members or stiffening elements  120  are used, it should be appreciated that such support members or stiffening elements  120  are not limited to the shape and/or dimensions outlined with respect to the exemplary embodiment shown in  FIGS. 1 and 2 . That is, the length, width, thickness, and/or location of the first exemplary fan blades  110  and/or their connection to the support members or stiffening elements  120  can be anything that appropriately or sufficiently stiffens the first exemplary fan blades  110  to a desired value. Thus, if less stiffening is desired, the stiffening elements  120  can be shorter, narrower, thinner, made of a less stiff material and/or attached differently to the first exemplary fan blades  110  and/or the fan blade hub plate  210 . 
       FIG. 3  shows the free end of one exemplary embodiment of the first exemplary fan blade  110  according to this invention. In particular,  FIG. 3  shows a first exemplary fan blade  110  that was formed by extruding the fan blade material through a die. In the exemplary embodiment of the first exemplary fan blade  110  shown in  FIG. 3 , the leading edge  111  of the first exemplary fan blade  110  can be rounded, flat or blunt, and has a thickness of about 0.15 inches. It should be appreciated that other thicknesses for the first exemplary fan blade  110  can be used as desired, so long as the first exemplary fan blade  110  retains sufficient strength and rigidity to withstand use as a fan blade of the fan  100 . 
     It should be appreciated that, as shown in  FIGS. 1 and 2 , because the first exemplary fan blades  110  are curved, the trailing edge of one first exemplary fan blade  110  can extend over the leading edge of the trailing first exemplary fan blade  110  for the portions of the first exemplary fan blades  110  that are adjacent to the fan hub plate  210 . 
     In the exemplary embodiments outlined above, the first exemplary fan blades  110  can be obtained by extrusion or by bending a strip of sheet metal around ajig or template to obtain the curved portions  116  of the first exemplary fan blades  110 . It should be appreciated that, using this last process, it is possible to apply different degrees of curvature to the strip of sheet metal as it is bent. Thus, for example, at the hub end  112  that is to be attached to the fan blade hub plate  210 , the curved portion  116  of the first exemplary fan blade  110  could have a relatively smaller amount of curvature (i.e., larger radius of curvature), while at the free end  114 , the curved portion  116  of the first exemplary fan blade  110  could have a relatively greater degree of curvature (i.e., smaller radius of curvature). It should further be appreciated that, when using a first exemplary fan blade  110  formed by bending a sheet of material, the curvature of intermediate portions of the curved portion  116  of the first exemplary fan blade  110  could change continuously and constantly, could change continuously but at different rates at different places along the length of the first exemplary fan blade  110 , could change in discrete but constant steps or could change in discrete but differing step sizes for at least some of the steps, or even combinations of these. 
     In various exemplary embodiments, the curved portions  116  of the first exemplary fan blades  110  are formed as arc segments of a simple curve, such as a circle, an ellipse, a parabola or the like. In various exemplary embodiments, the curved portions  116  of the first exemplary fan blades  110  are formed as segments of a circle. In various exemplary embodiments, the first exemplary fan blades  110  are extruded using 6005 or 6061 aluminum as a starting material. The extruded first exemplary fan blades  110  can then be heat treated or aged. One exemplary set of heat treating parameters include treating the extruded first exemplary fan blades  110  for 5-9 hours at a temperature of 300°-500° F. 
     In various exemplary embodiments, the first exemplary fan blades are  110  extruded by first heating up a billet or log of material, such as aluminum or other material, that has sufficient strength and rigidity to be usable as a first exemplary fan blade  110  according to this invention. Such other materials can include other metals, such as iron, steel, copper, alloys of one or more of these or other metals and/or other materials, plastics, such as PVC, suitable thermosetting plastics, ceramics, composites and the like. In general, any material that can be formed into an appropriate first exemplary fan blade  110  according to this invention and that has sufficient mechanical properties that permit that material to survive as a first exemplary fan blade  110  in a fan  100  according to this invention for a suitable length of time can be used to form the first exemplary fan blades  110 . 
     In exemplary embodiments using aluminum as a starting material, before extruding, the aluminum log or billet is heated at temperatures of about 400°-to about 500° C. (about 750° to about 1000° F.). However, it should be appreciated that this range can be extended in either direction depending on the type of aluminum. Once extruded, the aluminum first exemplary fan blades  110  are relatively soft and malleable. After the first exemplary fan blades  110  are extruded, they are aged or heat treated to reduce their malleability, and to increase their hardness and/or stiffness. In various exemplary embodiments, such as for aluminum first exemplary fan blades  110 , the aging process produces a fine dispersion of alloying materials, such as magnesium and silicon, increases the strength of the extruded aluminum material. 
     It should be appreciated that the extruded first exemplary fan blades  110  can be of any desired width, with any desired radius of curvature for the curved portions  116 , and have any desired arc length and shape for the curved portions  116 . The shape, size, thickness and radius of curvature depend on the shape of the orifice on the steel die used to form the extruded first exemplary fan blade  110 . 
     In various exemplary embodiments, the fan blades  110  are formed with the trailing edge having a slight thinning or taper and/or with the leading and trailing edges slightly rounded. Typically, the first exemplary fan blades  110  will be approximately 0.14 inch-0.16 inch thick. However, any desired thickness can be used. 
     In various other exemplary embodiments, the first exemplary fan blades  110  are cut and formed from a sheet of aluminum. This sheet can have any appropriate thickness and can be cut into any desired shape. The sheet can be cut so that the edges meet at right angles, i.e., square, or can be cut at an angle to create an offset between the ends of the first exemplary fan blades  110 . The cut sheets are then bent around a form or jig at the desired radius for the curved portions  116 . The first exemplary fan blades  110  can then be heat treated or aged as desired to improve or control their mechanical properties. 
     In various exemplary embodiments, such as that shown in  FIG. 3 , the thickness of the first exemplary fan blade  110  gradually decreases from some point at or between a leading edge  111  and a trailing edge  113 . The thickness at the trailing edge  113  is, for example, 0.072 inch and, in various exemplary embodiments, is 35% to 70% of the thickness of the leading edge  111 . In various exemplary embodiments, as shown in  FIG. 3  the trailing edge  113  is also rounded. 
       FIG. 4  is a bottom plan view of one exemplary embodiment of a fan  100 , including a second exemplary embodiment of a plurality of fan blades  150  and one exemplary embodiment of the fan blade hub plate  210  according to this invention. As shown in  FIG. 4 , the fan  100  includes 12 second exemplary fan blades  150  that extend radially from the fan blade hub assembly  200 . The second exemplary fan blades  150  can be any desired length that is useful in a given application. For many typical applications, each second exemplary fan blade  150  can be about 4 feet to about 8-12 feet long (approximately 1.2 meters to about approximately 2.4-3.7 meters), or longer, as discussed below. In various exemplary embodiments, the second exemplary fan blades  150  are about 96 inches (approximately 2.4 meters) long and are approximately 4-6 inches (approximately 101.6-152.4 millimeters) wide, but can be any desired width that allows for a generally cone-shaped region of moving air to be created. 
     As shown in  FIGS. 4 and 5 , in various exemplary embodiments, the second exemplary fan blades  150  are attached to the underside of the fan blade hub assembly  200 . In the exemplary embodiment shown in  FIGS. 4 and 5 , the second exemplary fan blades  150  are bolted on to the fan blade hub plate  210  at two places using bolts  162  and  164 . Alternatively, the second exemplary fan blades  150  can be welded or otherwise suitably attached to the fan blade hub plate  210  using any known or later developed technique. In various exemplary embodiments, a second exemplary support member or stiffening element  160  is also attached to one side of each second exemplary fan blade  150 . In particular, in the exemplary embodiment shown in  FIGS. 4 and 5 , the stiffening element  160  is attached to the underside of each fan blade  150  using the bolts  162  and  164 , as well as a third bolt  166 . In this exemplary embodiment, the second exemplary fan blades  150  are held between the fan blade hub plate  210  and the support members or stiffening elements  160 . 
     It should be appreciated that, in the exemplary embodiment shown in  FIGS. 4 and 5 , the bolts  164  are located about one inch (approximately 25.4 millimeters) away from the hub end of the second exemplary fan blades  150  and about one inch (approximately 25.4 millimeters) behind the leading edge of the second exemplary fan blades  150 . The bolts  164  are also located approximately 6-8 inches (approximately 152.4-203.2 millimeters) from the center of the fan blade hub plate  210 . Similarly, the bolts  162  are located about one inch (approximately 25.4 millimeters) away from the outer edge of the fan blade hub plate  210  and about one inch (approximately 25.4 millimeters) behind the leading edge of the second exemplary fan blades  150 . It should also be appreciated that, in the exemplary embodiments shown in  FIGS. 4 and 5 , the fan blade hub plate  220  is 30 inches (approximately 762 millimeters) in diameter and has a 10-inch-diameter (approximately 254 millimeters) reinforcing plate at its center that is used to attach the fan blade hub plate  210  to the spindle of a gearbox. Thus, it should be appreciated that the preceding discussion is exemplary, and different locations for the bolts  162  and  164  relative to the second exemplary fan blades  150  and the fan blade hub plate  210  can be used for second exemplary fan blades  150  and/or fan blade hub plates  210  having different dimensions. 
     In the exemplary embodiment shown in  FIGS. 4 and 5 , the support members or the stiffening elements  160  extend approximately ⅓ of the length along the second exemplary fan blades  150  and taper toward the leading edge of the second exemplary fan blades  150 . It should be appreciated that the support members or stiffening elements  160  can be omitted if the second exemplary fan blades  150  are sufficiently stiff enough to create the cone of moving air and to reliably rotate with the fan blade hub plate  210  at the rotational speeds that the large area fan  100  is designed to operate at. In general, this will depend, at least in part, on one or more of: the designed operational rotational speeds of the large area fan  100 , the size of the fan blade hub plate  210 , how the second exemplary fan blades  150  are attached to the fan blade hub plate  210 , the material used for the second exemplary fan blades  150 , the width of the second exemplary fan blades  150 , the design of the curvature of the second exemplary fan blades  150  and/or the length of the second exemplary fan blades  150 . 
     If the support members or stiffening elements  160  are used, it should be appreciated that such support members or stiffening elements  160  are not limited to the shape and/or dimensions outlined with respect to the exemplary embodiment shown in  FIGS. 4 and 5 . That is, the length, width, thickness, and/or location of the second exemplary fan blades  150  and/or their connection to the support members or stiffening elements  160  can be anything that appropriately or sufficiently stiffens the second exemplary fan blades  150  to a desired value. Thus, if less stiffening is desired, the stiffening elements  160  can be shorter, narrower, thinner, made of a less stiff material and/or attached differently to the second exemplary fan blades  150  and/or the fan blade hub plate  210 . 
       FIG. 6  shows the free end of one exemplary embodiment of a second exemplary fan blade  150  according to this invention. In particular,  FIG. 6  shows a second exemplary fan blade  150  formed by extruding the fan blade material through a die. In the exemplary embodiment of the second exemplary fan blade  150  shown in  FIG. 6 , the leading edge  151  of the second exemplary fan blade  150  can be rounded, flat or blunt, and has a thickness of about 0.15 inches (approximately 3.81 millimeters). It should be appreciated that other thicknesses for the second exemplary fan blade  150  can be used as desired, so long as the second exemplary fan blade  150  retains sufficient strength and rigidity to withstand use as a second exemplary fan blade  150  of the fan  100 . 
     It should be appreciated that, as shown in  FIGS. 4 and 5 , because the second exemplary fan blades  150  are curved, the trailing edge of one second exemplary fan blade  150  can extend over the leading edge of the trailing second exemplary fan blade  150  for the portions of the second exemplary fan blades  150  that are adjacent to the fan hub plate  210 . 
     In the exemplary embodiments outlined above with respect to  FIGS. 4-6 , the second exemplary fan blades  150  can be obtained by extrusion or by cutting a pipe of constant curvature into sections. As also outlined above, a third exemplary method for obtaining the second exemplary fan blades  150  is to bend a strip of sheet metal around a jig or template to obtain a curved second exemplary fan blade  150 . It should be appreciated that, using this last process, it is possible to apply different degrees of curvature to the strip of sheet metal as it is bent. Thus, for example, the hub end  152  of the second exemplary fan blade  150  that is to be attached to the fan blade hub plate  210  could have a relatively smaller amount of curvature (i.e., larger radius of curvature), while the free end  154  of the second exemplary fan blade  150  could have a relatively greater degree of curvature (i.e., smaller radius of curvature). It should further be appreciated that, when using a second exemplary fan blade  150  formed by bending a sheet of material, the curvature of intermediate portions of the second exemplary fan blade  150  could change continuously and constantly, could change continuously but at different rates at different places along the length of the second exemplary fan blade  150 , could change in discrete but constant steps or could change in discrete but differing step sizes for at least some of the steps, or even combinations of these. 
     For second exemplary fan blades  150  that are obtained by cutting an 8-inch (approximately 203.2 millimeters) (nominal) inside diameter pipe into six equal portions, due to the saw blade kerf, the second exemplary fan blades  150  have an arc length of, for example, 58.5 degrees. As indicated above, the ends of the second exemplary fan blades  150  are offset circumferentially. In various exemplary embodiments, for second exemplary fan blades  150  that are approximately 96 inches (approximately 2.4 meters) long, an offset of approximately 1 inch (approximately 25.4 millimeters) is appropriate. This results in the second exemplary fan blades  150  being not quite at right angles between the long and short edges. In various exemplary embodiments, for 96-inch (approximately 2.4 meters) second exemplary fan blades  150  with a one-inch (approximately 25.4 millimeters) offset, the edges meet at 89.4 or 90.6 degree angles. 
     The support members or stiffening elements  160  can be formed using the same technique as for the second exemplary fan blades  150 . For example, when extruding a 96-inch (approximately 2.4 meters) fan blade, a 96-inch (approximately 2.4 meters) support member extrusion will also be formed. After twisting, and heat treating or aging, the support member extrusion is then cut into three approximately 3, 30 to 32-inch (approximately 762 to approximately 812.8 millimeters) segments. These segments are then cut lengthwise to create at least three support members or stiffening elements  160 . 
     In various exemplary embodiments, the support members or stiffening elements  160  can be formed by cutting each of the support member extrusion segments roughly in half, roughly along a diagonal of the segment. However, it should be appreciated that the support members or stiffening elements  160  are not necessarily, nor even usually, formed by simply cutting along the diagonal. For example, the support members or stiffening elements  160  can be formed by starting the cut into the segment at one end of the segment and about 20%-25% in from the trailing or leading edge and cutting to the other end through a point that is an approximately equal amount in from the leading or trailing edge respectively. 
     Assuming that the fan blade extrusion section does not have a tapering thickness towards the trailing edge or smaller feature, the section is thus cut into two equal portions, such that 6 support members or stiffening elements  160  can be obtained from one such extrusion. However, if the extruded second exemplary fan blades  150  have a tapering thickness and/or a rounded or feathered trailing edge, the portions of the segments containing the trailing edge of the extrusion may not be usable as stiffening elements or support members  160 . If not usable, those portions of the segments will typically be discarded s scrap. 
     Additionally, it should be appreciated that, in the exemplary embodiments shown in  FIGS. 4-6 , due to the offset between the ends of the fan blades  150 , the portions of the second exemplary fan blades  150  held against the fan hub plate  210  are held against the fan blade hub plate  210  in a slightly more horizontal position than the position of the portions of the second exemplary fan blades  150  that are distant from the fan blade hub plate  210 . Thus, the second exemplary fan blades  150  tend to present a larger profile to the air at the portions of the second exemplary fan blades  150  that are distant from the fan hub plate  210 . This tends to cause air to spill out of the far end of the fan blades  110  as the second exemplary fan blades  150  rotate with the fan  100 . 
     In various exemplary embodiments, the second exemplary fan blades  150  are formed as arc segments of a simple curve, such as a circle, an ellipse, a parabola or the like. In various exemplary embodiments, the second exemplary fan blades  150  are formed as segments of a circle. While this circle can have any desired radius, one particularly useful second exemplary fan blade  150  is formed as an approximately 60° arc length segment of an 8-inch (approximately 203.2 millimeters) circle. It should be appreciated that this circle radius is typically measured from the inside surface of the second exemplary fan blade  150 , but could be measured from the outside surface. It should also be appreciated that the second exemplary fan blades  150  can have any arc length that allows for a generally cone-shaped region of moving air to be created. 
     In various exemplary embodiments, the second exemplary fan blades  150  are extruded using 6005 or 6061 aluminum as a starting material. In various exemplary embodiments, after being extruded, the second exemplary fan blades  150  are twisted along their axis such that the free end of the second exemplary fan blades  150  are offset from the hub ends of the second exemplary fan blades  150  in the opposite direction from the direction of rotation. Any desired amount of offset can be used. However, in general, the larger the amount of offset, the greater the radial air flow will be. The extruded second exemplary fan blades  150  can then be heat treated or aged. One exemplary set of heat treating parameters include treating the extruded second exemplary fan blades  110  for 5-9 hours at a temperature of 300°-500° F. 
     In exemplary embodiments using aluminum as a starting material, before extruding, the aluminum log or billet is heated at temperatures of about 400°-to about 500° C. (about 750° to about 1000° F.). However, it should be appreciated that this range can be extended in either direction depending on the type of aluminum. Once extruded, the aluminum second exemplary fan blades  150  are relatively soft and malleable. Consequently, the second exemplary fan blades  150  are easily twisted to create the desired offset between the hub and free ends of the second exemplary fan blades  150 . In various exemplary embodiments, the second exemplary fan blades  150  are twisted using a fan blade twisting machine specifically designed for that purpose. However, it should be appreciated that any device usable to twist the second exemplary fan blades  150  according to this invention can be used. 
     After the second exemplary fan blades  150  are twisted, they are aged or heat treated to reduce their malleability, and to increase their hardness and/or stiffness. In various exemplary embodiments, such as for aluminum second exemplary fan blades  150 , the aging process produces a fine dispersion of alloying materials, such as magnesium and silicon, increases the strength of the extruded aluminum material. 
     It should be appreciated that the extruded second exemplary fan blades  150  can be of any desired width, with any desired radius of curvature, and have any desired arc length and shape. The shape, size, thickness and radius of curvature depend on the shape of the orifice on the steel die used to form the extruded fan blade. 
     In various exemplary embodiments, the second exemplary fan blades  150  are formed with the trailing edge having a slight thinning or taper and/or with the leading and trailing edges slightly rounded. Typically, the second exemplary fan blades  150  will be approximately 0.14 inch-0.16 inch (approximately 3.6 to approximately 4.1 millimeters) thick. However, any desired thickness can be used. 
     In various other exemplary embodiments, the second exemplary fan blades  150  are cut from a sheet of aluminum. This sheet can have any appropriate thickness, and can be cut into any desired shape. The sheet can be cut so that the edges meet at right angles, i.e., square, or can be cut at an angle to create an offset between the ends of the second exemplary fan blades  150 . The cut sheets are then bent around a form or jig at the desired radius. The second exemplary fan blades  150  can then be heat treated or aged as desired to improve or control their mechanical properties. It should be appreciated that, if the sheets are cut square, after bending the square-cut sheet, the resulting second exemplary fan blades  150  can be twisted to offset one end relative to the other using the fan blade twisting machine described above. 
     In various other exemplary embodiments, the second exemplary fan blades  50  are formed by cutting an 8-inch (approximately 203.2 millimeters) (nominal) inside diameter schedule-10 (6063) aluminum pipe. The outer diameter of the pipe is approximately 8.3 inches (approximately 210.8 millimeters), and the thickness of the pipe is approximately 0.148 inches (approximately 3.76 millimeters). The pipe is cut axially, i.e., along, rather than across, the axis into 6 second exemplary fan blades  150 , with each second exemplary fan blade  150  extending in an arc that is approximately 56-60 degrees wide, depending on the kerf thickness. It should be appreciated that, in various exemplary embodiments, the second exemplary fan blades  150  are not cut straight down the pipe, but cut with a slight spiral, so that the free end of the resulting second exemplary fan blade  150  is off set relative to the hub end. That is, one end of the second exemplary fan blade  150  is offset circumferentially relative to the other end by a small amount. In various exemplary embodiments, this offset is approximately one inch (approximately 25.4 millimeters) along the circumference for a 96-inch (approximately 2.4 meters) long fan blade  150 , although any desired offset amount can be used. 
     As indicated above, it should be appreciated that the second exemplary fan blades  150  can be formed by appropriately bending a metal sheet of suitable thickness, width and length. For example, an exemplary aluminum sheet that is between 0.1″ and 0.2″ thick can be cut into strips that are between 4 and 5 inches (approximately 101.6 and approximately 127 millimeters) wide and of a desired length. These sheet metal strips can then be bent against a form or jig that imparts one or more suitable curves to the sheet metal strip. In some exemplary embodiments of such a fan blade  150 , this exemplary fan blade  150 , when having the above-outlined dimensions, can have approximately the same shape as the second exemplary fan blades  150  outlined above that are cut from the 8-inch (approximately 203.2 millimeters) (nominal) inside diameter schedule-10 aluminum pipe. 
     It should further be appreciated that the metal pipe or metal sheet need not be made of aluminum, or even metal. Rather, any other suitable metal, such as iron, steel, stainless steel, copper or the like could be used. Furthermore, any suitable non-metal material, such as plastic, such as PVC pipe, or the like can be used in place of the aluminum pipe or sheet. It should be appreciated that, in general, any material that can reliably withstand the stresses of being used as a first or second exemplary fan blade  110  or  150  in a large area fan  100  according to this invention over a sufficiently long period of time is suitably usable for the fan blades  110  or  150 . 
     In various exemplary embodiments, such as that shown in  FIG. 6 , the thickness of the second exemplary fan blade  150  gradually decreases from some point at or between the leading edge  151  to a trailing edge  153 . The thickness at the trailing edge  153  is, for example, 0.072 inch (approximately 1.83 millimeters) and, in various exemplary embodiments, is 35% to 70% of the thickness of the leading edge  151 . In various exemplary embodiments, the trailing edge  153  is also rounded, as shown in  FIG. 6 . 
     In the exemplary embodiment shown in  FIG. 6 , the second exemplary fan blade  150  has a nominal arc length of 60° and a nominal radius of curvature of 4 inches (approximately 101.6 millimeters). Thus, the second exemplary fan blade  150  has a nominal width of 4.19 inches (approximately 106.4 millimeters) (2·4·π/6) at its inner face  156  and a nominal width of 4.34 inches (approximately 110.2 millimeters) (2·4.148·/6) at its outer surface  158 . It should be appreciated that the second exemplary fan blades  150 , if designed for a nominal arc length of 60°, can have actual arc lengths between, for, example, at least about 55° and up to about 65° or more. This occurs at least in part due to the method of manufacturing and the method for offsetting the free end relative to the hub end. For example, when extruding the second exemplary fan blade  150 , the second exemplary fan blade  150  does not need to be exactly 60°. Rather, the second exemplary fan blade  150  can have any arc length that allows a sufficiently conical air flow from the fan  100 . Similarly, when cutting the second exemplary fan blade  150  from an 8-inch (approximately 203.2 millimeters) (nominal) inside diameter pipe, a kerf equal to the thickness of the cutting blade will be lost, which could be up to 1°-2° of the arc width of the second exemplary fan blade  150 . It should also be appreciated that any desired arc length could be used, especially when extruding the second exemplary fan blades  150 . 
     In the exemplary embodiments shown in  FIGS. 1 ,  2 ,  4  and  5 , the fan  100  includes 12 fan blades  110  or  150 . In general, the fan  100  can use any desired number of fan blades  110  or  150 . However, the fan  100  will typically have at least two fan blades  110  or  150  for balancing purposes. The maximum number of fan blades  110  or  150  will generally depend on the length of the fan blades  110  or  150 , the thickness of the fan blades  110  or  150 , the radial distance, that the ends of the fan blades  110  or  150  lie at on the fan hub plate  210 , and the amount of overlap between adjacent fan blades  110  or  150 , if any. It should be appreciated that, for any given fan blade hub assembly  200 , there will be a maximum fan blade weight that the fan blade hub assembly  200  will be designed to safely support, a maximum amount of torque that a motor and a gear box (discussed below) can safely apply to the fan blades  110  or  150 , and a maximum amount of angular stress that the fan blade hub assembly  200  is safely designed to withstand. 
     That is, the fan blade hub assembly  200  is typically designed to support a maximum dead weight of the fan blades  110  or  150 . Similarly the fan blade hub assembly  200  is typically designed to output a maximum amount of torque to the fan blade hub plate  210  and thus to the fan blades  110  or  150 . Additionally, as the fan blades  110  or  150  rotate, significant forces are applied to the fan blades  110  or  150  by the air as it is moved by the fan blades  110  or  150 . Due to lever arm action, this force can increase significantly as the length of the fan blades  110  or  150  increases. This force is directly translated to the fan blade hub plate  210  and thus to the gearbox and the motor of the fan blade hub assembly  200 . 
     In general, due to those factors, a particular fan  100  will have a given blade length that generally should not be exceeded for a given full number of blades that that fan  100  is designed to use. To go beyond this given blade length, a number of the fan blades may be removed and/or the rotational speed of the fan may be decreased. For example, for a 12-blade fan  100  designed to use up to 8-ft fan blades  110  or  150 , to use 12-foot (approximately 3.7 meters) fan blades  110  or  150 , the number of fan blades  110  or  150  may be reduced to 9, 8, 6 or even 4 blades, and/or the rotational speed of the fan  100  may be reduced. In general, the number of fan blades  110  or  150  that are removed should be selected to keep the fan blades  110  or  150  in balance around the fan blade hub assembly  200 . 
     Similarly, to go beyond this given blade length or to add additional fan blades, the sizes of one or both of the gearbox and/or the motor may be increased and/or the rotational speed of the fan  100  may be decreased. In general, for a given combination of motor and gearbox, the number of fan blades  110  and/or  150  and the rotational speed of the fan  100  can be adjusted to keep the fan  100  operating within the limits of the motor and gearbox. Alternatively, if a particular number of fan blades  110  and/or  150  and a particular fan blade length is desired, a different gearbox and/or motor having larger size(s), which are sufficient for the desired number of fan blades  110  and/or  150  and/or fan blade length, can be used with the fan  100 . 
     For example, for a 16-blade fan  100  having 8-foot (approximately 2.4 meters) fan blades  110  and/or  150 , i.e., a “17-foot” fan  100 , the fan  100  can use a 2 hp motor and a larger, 70-rpm gearbox. Such a fan  100  having this number and length of fan blades  110  and/or  150  will generally move approximately twice as much air as a fan  100  having 12 8-foot (approximately 2.4 meters) long fan blades  110  and/or  150 . In general, it is possible for a fan  100  according to this invention having 12-foot (approximately 3.7 meters) long fan blades  110  or  150 , i.e., a “25-foot” fan  100 , to have between 6 and 16 blades given the appropriate sizes for the fan blade hub  200 , the motor  250  and the gearbox  230 . 
     It should also be appreciated that the dimensions of the fan blades  110  or  150  and the fan blade hub plate  210  and the number of fan blades  110  or  150  are not limited to those used in the exemplary embodiments outlines above. In general, there is an inverse relationship between the width of the fan blades  110  or  150  and the maximum number of fan blades  110  or  150 . That is, generally, but not necessarily, as the fan blades  110  get larger or smaller, fewer or more fan blades  110  or  150 , respectively, can be used in a large area fan  100  according to this invention. In general, this relationship will depend in part on the amount of overlap between adjacent fan blades  110  or  150 , which in turn depends on the degree of curvature and/or shape of the fan blades  110  or  150  at the fan blade hub plate  210 , as this generally controls how much overlap there can be between adjacent fan blades  110  or  150  at the fan blade hub plate  210 . 
     It should also be appreciated that the dimensions of the fan blade hub plate  210  and the locations of the bolts  122  or  162  and  124  or  164  relative to the fan blades  110  or  150 , respectively, and the fan blade hub plate  210  are not limited to those set forth in the above-outlined exemplary embodiments. That is, for example, the fan blade hub plate  210  could be larger or smaller than that outlined above. The fan blade hub plate  210  will generally be sized to securely and reliably hold the fan blades  110  so that the fan blades  110  can be rotated at appropriate rotational speeds to move an appropriate column of air in the large space in which the large area fan  100  is installed. 
     Unlike traditional fan blades that are shaped like propellers or airfoils, the fan blades  110  and  150  do not push, force or displace all of the air that contacts the fan blades  110  and  150  in a downward direction. Instead, as shown in  FIGS. 7 and 8 , due to the concave shape of the fan blades  110  and  150 , respectively, while a not insubstantial portion  130  of the air scooped up by the fan blades  110  is redirected downwardly, another portion  132  of the air begins to travel radially outwardly from the fan blade hub plate  210  along the fan blade  110 . It should also be appreciated that, as the distance of a given portion of a fan blade  110  from the fan blade hub plate  210  increases, the linear (not rotational) speed of that portion of the fan blade  110  in the plane of rotation increases relative to air that is stationary along the plane of rotation. Additionally, with respect to the second exemplary fan blades  150 , because the profile of the second exemplary fan blades  150  becomes increasingly perpendicular to the plane of rotation of the fan blades  110  when moving from the hub end  152  to the free end  154  of the fan blades  150 , the increasingly distant portions of the fan blades  150  scoop out increasing amounts of air, while also acting to better contain the radially-flowing air arriving from the closer portions of the fan blades  110 . 
     As a result of one or more of these factors, while not in a significant portion  130  of the air contacted by the fan blades  110  and  150  is directed downwardly, a portion  132  of the air moved by the fan blades  110  and  150  is directed radially along the fan blades  110  and  150 . That is, there is a vector flow  142  of air downward from the fan blades  110  and  150  and a vector flow  144  of air radially along the fan blades  110  and  150 . The net effect, due to the sum of these two vector air flows, is a vector flow  140  of air that extends downwardly at an outward angle from the fan blades  110  and  150 , as shown in  FIGS. 7 and 8 , respectively. Because the fan blades  110  and  150  sweep out a circle in the plane of rotation, as the downward and outward vector flows  142  and  144  of air from the fan blades  110  and  150  are similarly swept out, the overall flow  140  of air from the fan blades  110  and  150  is in the shape of a truncated cone extending from the plane of rotation of the fan blades  110  or  150 . 
     That is, the air moved by the fan blades  110  and  150  has both a downward vector  142  and an outward  144  vector, causing the air to move from the fan  100  in the shape of a cone. Accordingly, the fan  100  is able to move air through an area that is larger in diameter than the diameter of a circle swept out by the fan blades  110  or  150 . As a result, relative to conventional fans used to move air in large spaces, the fan  100  can use smaller fan blades  110  or  150  to move air through the same area as a larger fan blade or similar sized fan blades  110  or  150  can be used to move air over a larger area. 
     It should also be appreciated that, relative to conventional fan blades that are shaped like air foils or like propellers, the fan blades  110  and  150  scoop out and redirect a larger volume of air. Thus, the fan blades  110  and  150  tend not only to move air over a larger area, but also move a larger amount of air. 
     Thus, it should be appreciated that, depending on one or more of the area to be covered by one or more large area fans  100  according to this invention, the number of such large area fans  100  to be used, and the desired amount of moving air per unit area, the number of such large area fans  100  and/or the amount of offset provided to the fan blades  110  or  150  can be adjusted to increase or decrease the area coverage of each large area fan  100 , the number of large area fans  100  needed to cover a given area and/or the air flow per unit area of coverage to desired values. 
     In the exemplary embodiments shown in  FIGS. 4-6  and  8 , the profile of the fan blade  150  changes to present the width of the fan blade  150  that is at least at an increasing angle to the plane of rotation. In the exemplary embodiments outlined above with respect to  FIGS. 4-6  and  8 , this increasing profile is due to the offset or twist applied along the axis of the fan blades  150 . It should be appreciated that, as the amount of offset increases, the rate of change of the profile increases and the maximum amount of change increases. It is believed that this tends to increase the size of the radial vector flow  144 , which in turn increases the angle at which the conical flow  140  leaves the fan blades  150 , relative to the axis of the fan  100 . This tends to increase the area coverage of the large area fans  100  according to this invention. 
     Referring to  FIG. 8  in particular, it should be appreciated that, in the exemplary embodiment described above, the varying profile presented by the fan blades  150  results from the twist in the fan blades  150 . As shown in  FIG. 8 , due to this varying profile, portions of the fan blades  150  that are distant from the fan blade hub plate  210  tend to scoop up or collect more air than do the portions of the fan blades  150  that are closer to the fan hub plate  210 . 
       FIG. 9  shows one exemplary embodiment of a support structure  300  usable with the large area fan  100  according to this invention. The support structure  300  is typically attached at one end to a rafter, a ceiling joist or other structure of the building or other space in which the large area fan  100  is to be located that is capable of supporting the weight and forces of the large area fan  100 . 
     As shown in  FIG. 9 , the support structure  300  includes a channel iron, rod or other long support member  310  that is capable of supporting the weight of the large area fan  100  and that is capable of withstanding the rotational forces generated by the large area fan  100  as it rotates. In the exemplary embodiment shown in  FIG. 9 , the support member  310  is a u-shaped channel iron. As shown in  FIG. 9 , a sleeve assembly  320  is located near one end of the support member  310  just above a mounting plate  330  that is located at the end of the support member  310 . This mounting plate  330  is typically permanently and securely attached to the support member  310 , such as by welding, bolting and/or the like. The support plate  330  generally will have a number of holes drilled onto it through which the fan hub assembly  200  can be attached using bolts and/or the like. 
     The sleeve assembly  320  includes an inner sleeve member  324  about which are placed a fixed upper outer sleeve member  322  and a free large rotatable lower outer sleeve member  326 . The inner sleeve member  324  will be securely attached to the support member  310 , such as by welding or the like. It should be appreciated that any known or later developed method for securely attaching the upper outer sleeve member  322  to the inner sleeve  324  can be used. Typically, the outer fixed sleeve member  322  will be securely attached to the inner sleeve member  324 . In various exemplary embodiments, the fixed upper outer sleeve member  322  is welded to the inner sleeve member  324 . In various exemplary other embodiments, the fixed upper outer sleeve member  322  is glued or otherwise adhered to the inner sleeve member  324 . It should be appreciated that any known or later developed method for securely attaching the upper outer sleeve member  322  to the inner sleeve  324  can be used. 
     The lower outer sleeve member  326  typically contains two or more eye bolts or the like that allow guy wires to be attached to the lower outer sleeve member  326  and to support points on the building enclosing the large space in which the large area fan  100  is mounted. The sleeve assembly  320  and the guy wires act to stabilize the position of the bottom of the support structure  300  and the attached fan blade hub assembly  200 . The lower outer sleeve  326  and the guy wires attached to it allow the support structure  300  to rotate around its axis without stretching or otherwise straining or stressing the guy wires. This will be described in greater detail below. 
       FIG. 10  shows one exemplary embodiment of a fan hub assembly  200  according to this invention, as attached to the exemplary embodiment of the support structure  300  showing  FIG. 9 . As shown in  FIG. 10 , the fan hub assembly  200  includes the fan plate  210 , a safety and mounting plate assembly  220 , a gear box  230  and a plurality of safety catches  240 .  FIG. 11  shows these elements of the fan hub assembly  200  in an exploded view that allows the details of these elements to be seen in greater detail. 
     As shown in  FIGS. 10 and 11 , the fan blade hub plate  210  includes a center mounting plate  212  and a mounting collar  214 . The mounting collar  214  includes a mounting screw set screw or the like  216  that extends through the thickness of mounting collar  214 . In various exemplary embodiments, the mounting collar  214  is welded or otherwise securely attached to the mounting plate  212 , which is in turn, welded or otherwise securely attached to the fan blade hub plate  210 . In various exemplary embodiments, the mounting collar  214  can have a constant thickness or can have a trapezoidal cross section such that the thickness of the mounting collar  214  are thicker near the mounting plate  212  and are thinner away from the mounting plate  212 . In various other exemplary embodiments, the mounting collar  214  and the mounting plate  212  can be machined from a single piece of metal or the like. It should be appreciated that, when the mounting collar  214  is welded or otherwise attached to the mounting plate  212 , stabilizing bars extending at an angle from the outer surface of the mounting collar  214  to the mounting plate  212  can be used to provide additional stability between the mounting collar  214  and the mounting plate  212 . 
     As further shown in  FIGS. 10 and 11 , a series of mounting holes  218  are located around the edge of the fan blade hub plate  210 , while a second series of mounting holes  219  are located around the mounting plate  212 . It should be appreciated that the bolts  222  and  224  respectively will pass through the bolt holes  219  and  218 , respectively. As shown in  FIGS. 10 and 11 , in various exemplary embodiments, a pair of inner and outer bolt holes  218  and  219  for a particular fan blade  110  or  150  need not be arranged along a radius of the fan blade hub plate  210 . Rather, as shown in  FIGS. 10 and 11 , a single set  217  of the bolt holes  218  and  219  are located such that a particular fan blade  110  or  150  does not lie along a radius of the fan blade hub plate  210 . Rather, a given fan blade  110  or  150  is attached to the fan blade hub plate  210  using the bolt holes  218  and  219  such that the free end  114  or  154  of the fan blade  110  or  150  respectively, is slightly ahead of the hub end  112  or  152 , respectively, along the circumferential direction of the large area fan  100 . 
     As shown in  FIGS. 10 and 11 , the mounting and safety plate assembly  220  includes a mounting plate  222  and a safety plate  224 . As most easily seen in  FIG. 11 , the mounting plate  222  includes a first set of bolt holes that align with bolt holes on the mounting plate  330  of the support assembly  300 . A second set of bolt holes on the mounting plate  220  align with bosses provided on the gear box  230 . As shown in  FIG. 11 , a fairly large hole is formed in the center portion of the safety plate  224 . As shown in  FIG. 10 , when the fan blade hub assembly  200  is assembled, the mounting collar  214  extends through the hole in the safety plate  224 . 
     As shown in  FIGS. 10 and 11 , the gear box  230  includes an output drive shaft or spindle  232  and an input mounting plate  234 . When the fan blade hub assembly  200  is assembled, the output drive shaft or spindle  232  extends through the center opening in the safety plate  224  when the mounting plate  220  is bolted to the gear box  230 . The drive shaft or spindle  232 , along with the mounting and safety plate assembly  220 , is connected to the fan blade hub plate  210  by extending the drive shaft or spindle  232  into the center portion of the mounting collar  214  and tightening the mounting screw  216 . In various exemplary embodiments, the drive shaft or spindle  232  will have a matching hole into which the mounting screw  216  will extend. It should be appreciated that, in various exemplary embodiments, this hole on the spindle  232  can be either threaded or unthreaded. 
     As shown in  FIGS. 10 and 11 , a series of safety catch plates  240  are mounted to the fan blade hub plate  210  and extended up and over the top surface of the safety plate  224  of the mounting and safety plate assembly  220 . As shown in  FIG. 10 , pairs of mounting holes  242  on the safety catch plates  240  align with two of the mounting holes  219  on the fan blade hub plate  210 . In general, the bolts  222  are sufficiently long enough to extend through the fan blades  110  or  150 , the fan blade mounting plate  210  and the bolt holes  242  of the safety catch plate  240  to allow the safety catch plates  240  to be securely attached to the fan blade hub plate  210 . In normal operation, the safety catch plates  240  rotate with the fan blade hub plate  210 , with their inter-projecting portions  244  extending over but not contacting the safety plate  224 . However, should the drive shaft or spindle  232  fail, the mounting collar  214  and/or the mounting plate  212  become detached from the fan blade hub plate  210  and/or the spindle  232  slip out of the mounting collar  214 , rather than the fan blade hub plate  210  and all of the attached fans  110  crashing to the ground, the projecting portions  244  of the safety catch plates  240  will catch or hang on the safety plate  224 . Thus, the safety catches  240 , in combination with the safety catch plate  224 , prevent mounting failures between the gear box  230  and the fan blade hub plate  210  from resulting in catastrophic failure of the large area fan  100 . 
     Accordingly, it should be appreciated that the safety catches  240  be sufficiently strong enough to support the weight of the fan blade hub plate  210  and the attached fan blades  110  or  150  and that the bolts  122  and  162  be sufficiently strong enough to support the weight of the fan blade hub plate  210 , the hub assembly  200  and the fan blades  110  or  150 , respectively. Likewise, the safety plate  224  needs to be sufficiently strong and rigid enough to support the weight of the fan blade hub plate  210  and the fan blades  110  or  150 . Similarly, the connection between the mounting plate  222  and the safety plate  224  and the bolts connecting the mounting plate  222  to the mounting plate  330  need to be sufficiently strong enough to support the weight of the fan blade hub plate  210  and the attached fan blades  110  or  150 . 
       FIG. 12  is a side view in part cross sectional view of the assembled support structure  300  and fan blade assembly  200  showing the spatial relationships between the fan blade hub plate  210 , the safety catches  240 , the safety plate  224  and mounting plate  222 , the drive shaft or spindle  230  and the mounting collar  214 , along with the bolts  122  or  152  and the various bolts connecting the mounting plate  222  to the gear box  230  and to the mounting plate  330 . 
       FIG. 13  shows a first exemplary embodiment for mounting one exemplary embodiment of a large area fan  100  and fan blades  110  according to this invention inside a building having a large area to be covered by the large area fan  100 . As shown in  FIG. 9 , the building  400  has a ceiling rafter or joist  410  to which the support structure  300  is mounted. The building  400  also has electric service  420  apprising a first conduit  422  leading to a junction box  426  and a flexible wiring element  424  extending from the junction box  426  and extending down the support member  300  to a motor  250  of the fan blade hub assembly  200 . As shown in  FIG. 13 , a number of guy wires are attached to the lower outer sleeve  326  of the sleeve assembly  300 . In the exemplary embodiment shown in  FIG. 13 , the large area fan is mounted such that the fan blades  110  are more or less parallel to the floor of the building  400 . 
       FIG. 14  shows a second exemplary embodiment for mounting one exemplary embodiment of a large area fan  100  and fan blades  150  according to this invention inside a building having a large area to be covered by the large area fan  100 . As shown in  FIG. 14 , it should be appreciated that the support structure  310  can be attached to the rafter  410  or the like in a way that tilts the fan blades  150  (or  110 ) relative to the floor of the building  400 . In various exemplary embodiments, the tilt is typically on the order of about 5° to about 10°. By tilting the larger fan  100 , the large area fan  100  can be located further to one side of the building  400 , that is, away from the center line of the building  400 . When the large area fan  100  is tilted, and placed off to one side of the building  400 , in operation, the large area fan  100  is still able to generate sufficient air movement to cover the entire width of the building  400 . 
       FIG. 15  illustrates one exemplary embodiment of the guy wires  350  and the sleeve assembly  320  of the support structure  300 . As shown in  FIG. 15 , a number of attachment points or eyelets  328  are mounted on the outer surface of the lower outer sleeve member  326 . A plurality of guy wires, each comprising a wire  352 , a turnbuckle  354  and a hook  356  are attached to the attachment points or eyebolts  328 . 
     As suggested above, as the fan blades  110  or  150  of the large area fan  100  rotate, a significant torque or rotational force is transmitted from the fan blades  110  or  150  through the fan hub assembly  200  to the support structure  300 . When the fan blades  110  or  150  are rotating in a forward direction, this force is a backwards torque due to the mass of the air being moved by the fan blades  110  or  150  and the distribution of that mass along the fan blades  110  or  150 , as well as the drag generated as the fan blades  110  or  150  move through the air in the large space in which the large area fan  100  in placed. In general, this force will generally gradually build up when the large area fan  100  is first turned on and will generally gradually dissipate once the large area fan  100  is turned off. 
     However, in various situations, the large area fan  100  may experience an immediate or abrupt loss of power. This can occur due to a loss of power due to a storm or other power outage, a circuit breaker tripping due to a short circuit condition, a power surge or the like, a gearbox failure, a motor failure, or the like. In any case, the large area fan  100  may experience a situation where the fan blades  110  or  150  come to a stop in a very short amount of time. While the fan blades  110  or  150  may immediately stop moving relative to the fan blade assembly  200 , due to the large amount of rotational energy stored in the fan blades  110  or  150 , the fan blades  110  or  150  will typically continue to rotate relative to ground, slightly causing the support member  310  to twist on its axis. 
     The sleeve assembly  320  allows the support member  310  to twist without putting any additional stress or strain on eyebolts  328 , the guy wires  352 , the turnbuckles  354  and/or the hooks  356 . Without the sleeve assembly  320 , it is possible that this twisting of the support member  310  could stretch one or more of the guy wires  352  and/or break one or more of the eyebolts  328 , the guy wires  352 , the turnbuckles  354  and/or the hooks  356 . 
     In various exemplary embodiments, the gear box  230  is a 90 degree angle worm gear box, which may or may not include an integral motor. It should be appreciated that, while the fan blades  110  or  150  may put less strain on the gearbox  230  and/or motor  250  than a conventional large area fan, the gearbox  230  and the motor  250  nonetheless must be of sufficiently high duty. The applicant has determined that light duty gear motors, such as the Emerson 45-rpm 3N176 gear motor will experience 50% or more failures within one year of operation. The applicant has determined that heavier duty gear boxes and separate motors, such as a 1 hp Leeson motor and a Boston 44-rpm IL364 gearbox will withstand over one year of normal use without failure. 
     While this invention has been described in conjunction with the exemplary embodiments outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that are or may be presently unforeseen, may become apparent to those having at least ordinary skill in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention. Therefore, the invention is intended to embrace all known or later-developed alternatives, modifications variations, improvements, and/or substantial equivalents. It should also be appreciated that, in the above description, dimensions have been given in English units with approximate metric equivalents. Where present, the metric units are approximations and are not intended to be further limiting than the previously stated English units.