Abstract:
A ceiling fan including a motor having a rotatable rotor, a plurality of ceiling fans blades having a thickness, the blades connected to the rotor to rotate therewith and each of the ceiling fan blades comprising a thin edge along its leading edge that is thinner than the thickness of the ceiling fan blade to present less resistance and produce less turbulence and achieve high efficiencies.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to ceiling fans. More particularly, this invention relates to ceiling fan blades having a high-efficiency design.  
         [0003]     2. Description of the Background Art  
         [0004]     Presently, there exist numerous types of ceiling fans designed to be suspended from a ceiling for circulating air flow within the room. Typically, ceiling fans comprise a plurality of ceiling fan blades which are operatively connected to an electric motor for rotating the fan blades to produce the desired air flow. The components of the ceiling fan, particularly the ceiling fan blades, are designed to optimize the amount of air flow being circulated per watt of energy consumed to thereby achieve high efficiencies.  
         [0005]     The fan blades constitute one component of a ceiling fan which is an important factor in achieving high efficiencies. Ceiling fan blades commonly include an elongated planar or curvilinear structure having a proximal or root end which is coupled to a fan blade bracket which is, in turn, coupled to the rotor of the electric motor. The elongated planar fan blade is positioned by the fan blade bracket at an optimal angle (e.g., 11 to 17 degrees) to circulate air flow at high efficiencies.  
         [0006]     Elongated planar ceiling fan blades are commonly manufactured of a medium-density fiber (“MDF”), laminated plywood, carved wood or plastic. More particularly, MDF fan blades are manufactured from large sheets of MDF wood that are pressed together to the desired thickness, typically 5.5 millimeters. The surface of the MDF sheets are protected by vinyl sheets which are overlaid onto the MDF sheets and glued to the surface thereof (upper and lower) to form a watertight seal therewith. The MDF sheets are then positioned within a cutting machine which cuts out the individual ceiling fan blades from the MDF sheet in the desired pattern. The leading and trailing edges of the fresh-cut ceiling fan blade are then routed and sanded to produce a round edge with the vinyl extending thereto. The rounded edge of the ceiling fan blade is then painted with a waterproof paint to seal the rounded edge so that moisture cannot penetrate into the rounded edge and seep underneath the vinyl sheet. Warpage of the fan blade, which would otherwise deteriorate the fan blade causing it to wobble, is therefore minimized.  
         [0007]     Similar to MDF blades, plywood blades have been used for many years. Unlike MDF blades, plywood blades are typically lighter in weight, stronger and less likely to warp due to their cross grain construction and multiple plies. More particularly, conventional plywood commonly includes three plies of cross grain planar sheets of wood. During the manufacture of plywood fan blades, two sheets of the three ply plywood are glued to form a plywood sheet having six plies. The sheet of plywood is often covered with a vinyl material (upper and lower) that may include a solid color or a wood grain appearance. Alternatively, one or both sides of the plywood may be covered by a light colored paper. As in the case of manufacturing the MDF fan blades, the plywood sheets are then cut to the desired blade shape and their edges are routed and sanded to have a rounded edge. The rounded edges are then painted with a waterproof sealant to preclude any ingress of moisture that might otherwise cause delamination of the plywood.  
         [0008]     Plastic fan blades are most commonly used for outdoor fans and decorative fans, and may include a simulated wicker or rattan appearance. Plastic fan blades offer the advantage of being formed into curvilinear configurations, such as those shown in U.S. Pat. Nos. 6,659,721 and 6,309,541, the disclosures of which are hereby incorporated by reference herein. Unfortunately, however, since plastic is typically heavier than plywood or MDF, plastic fan blades result in higher resistance to the electric motor thereby necessitating increased torque. Moreover, due to gravity acting on the blades, the plastic blades must be thick enough to preclude them from warping or drooping over time. Consequently, plastic blades are often significantly thicker than their plywood or MDF counterparts. To reduce the likelihood of drooping, plastic blades may include a slightly raised center rib to add longitudinal strength.  
         [0009]     The rounded edges of MDF blades, plywood blades and plastic blades present a thick edge. Consumers view the thick edge with appreciation because the thick rounded edge gives the ceiling fan an appearance of better quality. Unfortunately, however, the thick rounded edge of conventional fan blades produce a significant air resistance and turbulence as the ceiling fan blades are rotated through the air to cause the desired air flow. The increased resistance and turbulence along the leading edge of the thick rounded leading edge of the fan blade appreciably reduces the efficiency of the ceiling fan. In the case of the thicker plastic blades, even greater inefficiencies are often experienced.  
         [0010]     Efforts to produce thinner blades that would correspondingly have thinner rounded edges, have met with little success since thinner blades do not have the necessary strength to function properly during continued use without droopage. Moreover, prior art techniques for “beveling” the leading edge of a ceiling fan blade, such as taught by Taiwan Patent Application 79200819, filed Jan. 22, 1990, the disclosure of which is hereby incorporated by reference herein, have not met with any commercial success. More particularly, beveling the leading edge of a ceiling fan blade such as taught by the Taiwanese patent application produces a relatively sharp knife edge that creates a hazardous condition in the event a person&#39;s hand or other object is moved into the path of the spinning fan blades. Indeed, industry safety regulations applicable to ceiling fans mandate that the leading edge of the fan blade must be greater than 3.30 millimeters thick so as to reduce the likelihood of injury should a person&#39;s hand or other object move into the path of the rotating fan blades.  
         [0011]     As noted above, recent improvements to ceiling fan blade designs have been achieved by manufacturing the ceiling fan blades in a longitudinal curvilinear configuration as opposed to a longitudinal planar configuration. The curvilinear blade commonly includes a substantial angle (e.g. 30 degrees) at its root or proximal end connected to the ceiling fan blade bracket which gradually tapers to the more traditional angle of 11 to 17 degrees toward the distal end or tip of the fan blade. The airfoil configuration imitates the airfoil wing of an airplane for increased “lift” correspondingly to increase air flow when the airfoil configuration is employed as a ceiling fan blade. This curvilinear configuration increases air flow at the center portion of the fan than what can be achieved by using planar fan blades. Unfortunately, like planar fan blades, curvilinear fan blades still produce appreciable resistance and turbulence along their leading edges.  
         [0012]     There presently exists a need in the ceiling fan industry for improved ceiling fan blades that operate safely to achieve high efficiencies. Therefore, it is an object of this invention to provide an improvement which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the ceiling fan blade art.  
         [0013]     Another object of this invention is to provide a ceiling fan having a high efficiency fan blade that meets industry-wide safety standards.  
         [0014]     The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.  
       SUMMARY OF THE INVENTION  
       [0015]     For the purpose of summarizing this invention, this invention comprises a ceiling fan having high efficiency fan blades. More particularly, several embodiments of the high efficiency fan blades of the invention each comprise a thin-edge configuration that effectively reduces thickness of the leading edge of prior art ceiling fan blades such that the thinner leading edge of the invention presents less resistance and produces less turbulence than thicker prior art fan blade edges. The thin-edge fan blades of the invention therefore result in high efficiencies.  
         [0016]     More particularly, one embodiment of the high efficiency ceiling fan blades of the invention comprises a generally planar or curvilinear elongated configuration (MDF, plywood, carved wood or plastic) with a reduced-thickness or thin leading edge. In one variation, the “thin” leading edge achieves a leading edge thickness equal to or appreciably greater than the industry standard minimum thickness. The thin leading edge then gradually tapers or steps into the thickness of a conventional MDF, plywood or plastic blade. The thin leading edge is preferably centered relative to the usual thickness of the blade. Alternatively, however, the reduced-thickness edge may be positioned at one surface of the fan blade, preferably the lower surface.  
         [0017]     Importantly, the thin leading edge of the invention is easily adapted to all types of ceiling fan blades that are currently being manufactured. For example, in the case of plastic fan blades, the thin edge design of the invention may be easily injection molded. In the case of plywood fan blades and MDF fan blades, the edge of the fan blade may be easily routed to the desired thin edge design and then sealed with a waterproof sealer painted onto the exposed edges.  
         [0018]     In another embodiment of the high efficiency ceiling fan blades of the invention, the upper surface of the ceiling fan blades may comprise a generally apex configuration defined by two planar surfaces formed at an angle leading from the opposing thin leading edges across the width of the fan blade to form an apex along a center line of the fan blade. Importantly, the thickness of the fan blade at the thin leading edges comprises a reduced thickness which is equal to or appreciably greater than the minimum thickness mandated by applicable ceiling fan safety regulations. It is noted that the thin leading edge of this embodiment of the invention is contemplated to be principally formed by plastic injection molding or through carved fan blades due to the angles involved that could not typically be achieved through the use of laminated plywood or MDF. Indeed, this second embodiment is particularly desirable for implementation with decorative plywood or carved wood fan blades that would normally require significant sanding or carving to achieve the desired decorative designs. Moreover, the apex configuration provides strength along the longitudinal length of the fan blade thereby reducing the likelihood of drooping due to gravity over extended periods of non-use.  
         [0019]     The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:  
         [0021]      FIG. 1  is a side elevational view of the ceiling fan of the invention with its thin edge ceiling fan blades;  
         [0022]      FIG. 2  is a transverse cross-sectional view of a conventional MDF ceiling fan blade showing the planar construction thereof, the laminated vinyl material to the opposing surfaces thereof and the waterproof sealant painted onto the leading and trailing edges thereof;  
         [0023]      FIG. 3  is a transverse cross-sectional view of  FIG. 1  of the thin edge ceiling fan blade of the first embodiment of the invention along lines  30 - 30  thereof as viewed toward the root of the fan blade;  
         [0024]      FIG. 4  is a is a transverse cross-sectional view of the second embodiment of the invention;  
         [0025]      FIG. 5  is a transverse cross-sectional view of the third embodiment of the invention;  
         [0026]      FIG. 6  is a transverse cross-sectional view of the fourth embodiment of the invention;  
         [0027]      FIG. 7  is a transverse cross-sectional view of the fifth embodiment of the invention; and  
         [0028]      FIG. 8  is a transverse cross-sectional view of the sixth embodiment of the invention as viewed toward the tip of the fan blade. 
     
    
       [0029]     Similar reference characters refer to similar parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]      FIG. 1  is a side elevational view of a conventional ceiling fan  10  comprising an electric motor assembly  12  and a plurality of ceiling fan blades  14  connected to the rotor of the motor assembly  12  by means of ceiling blade brackets  16 . The ceiling fan  10  is intended to be connected by means of a hanger and down rod assembly  18  to the ceiling  20  of a room. During operation in one direction, the rotating ceiling fan blades  14  circulate air downwardly from the ceiling  20  (typically during summer months). During operation in the reverse direction, the rotating ceiling fan blades  14  circulate air upwardly toward the ceiling  20  (typically during winter months). In either direction, the objective is to create a circulatory flow of air throughout the room to thereby reduce energy costs.  
         [0031]      FIG. 2  is a cross sectional view of a conventional ceiling fan blade  16  manufactured from an MDF material. More particularly, an MDF fan blade  16  comprises a generally planar elongated configuration having a width “W” and a thickness “T 1 ” composed of an MDF laminate  18 . Commonly, a sheet of a vinyl material  20  is glued to the upper and lower surfaces of the MDF material  18 . The vinyl material  20  may comprise many different colors and/or decorative appearances such as wood grains. The longitudinal edges  22  are routed to a bull nose configuration and sanded smooth. The bull nose rounded longitudinal edges  22  are then sealed by painting them with a waterproof sealant  24 . It is noted that when employing plywood instead of MDF, a similar procedure is used to route the bull nose rounded edges  22  that are then sealed with the sealant  24  painted thereon. In the case of plastic fan blades that are injection molded, the vinyl material  20  may alternatively comprise a paper material which too may comprise a variety of colors or decorative designs such as a wood grain.  
         [0032]     The many embodiments of the invention are now described in relation to  FIGS. 3-8 . More particularly, each embodiment of the invention comprises a ceiling fan blade  30  manufactured by any available manufacturing technique such as methods for producing MDF blades, plywood blades, plastic blades or carved blades, to create a generally planar or curvilinear fan blade  30  having a thickness T 1 . At least the thin leading edge  32  and alternatively also the trailing edge  34  comprise a reduced thickness T 2  which is appreciably thinner than the thickness T 1  of the fan blade  30 . The thin leading edge  32  of thickness T 2  more preferably equals or exceeds the applicable safety standard that defines the minimum thickness for ceiling fan blades.  
         [0033]     As shown in  FIGS. 3 and 4 , the thin leading edge  32  of the fan blade  30  of the invention is positioned in the middle of the thickness T 1  of the blade  30 . As shown in  FIG. 3 , the transition between the thin leading edge  32  and the opposing surfaces  30 U and  30 L of the fan blade  30  comprises a concave step  36  whereas in  FIG. 4 , the transition comprises a generally planar transition  38 . In both embodiments of  FIGS. 3 and 4 , the thin leading edge  32  may be sanded or chamfered to eliminate any sharp corners between the transitions  36  and  38  and the thin leading edges  32 .  
         [0034]     As shown in  FIGS. 5 and 6 , the thin leading edge  32  is positioned closer to the bottom surface  30 L of the fan blade  30  rather than being positioned midway as shown in the previous embodiments of  FIGS. 3 and 4 . More particularly, as shown in  FIG. 5 , the transition between the thin leading edge  32  and the upper surface comprises a stepped configuration  40  whereas the transition in  FIG. 6  comprises a generally planar transition  42 . As in the case of embodiments of  FIGS. 3 and 4 , the thin leading edges  32  may be sanded or chamfered to break any sharp edges that might otherwise occur with the respective transitions  4  and  42 .  
         [0035]     As noted above, the trailing edge  34  of the ceiling fan blade  30  of the invention may likewise comprise a thin edge  32  of one of the embodiments described above. The double thin edge embodiments are particularly useful in the event the ceiling fan  10  is operated in a reverse direction whereupon the blades rotate in reverse thus the former trailing edge becomes a leading edge, and vice versa. Furthermore, without departing from the spirit and scope of the invention, it should be appreciated that one embodiment of the thin leading edge  32  may be used with any of the other embodiments. Finally, it is noted that the embodiments of  FIGS. 3 and 4  are the same whether or not the blades are installed upside down in reverse whereas the embodiments of  FIGS. 5, 6  and  7  are not reversible.  
         [0036]     As shown in  FIG. 7 , still another embodiment of the thin edge ceiling fan blade  30  of the invention comprises a generally apex configuration wherein the upper surface  30 U of the fan blade comprises two angled surfaces  30 AU extending from opposing thin leading edges  32  and  34  to a longitudinal apex  30 A, preferably positioned at or proximate to the longitudinal center of the fan blade  30 .  
         [0037]     The longitudinal apex  30 A of the fan blade  30  according to this embodiment produces increased structural integrity along the longitudinal length of the fan blade  30  to further reduce wobbling or drooping over time.  
         [0038]     The foregoing embodiments of  FIGS. 1-6  were shown as generally planar ceiling fan blades  14  with its opposing surfaces being generally parallel to each other. However, as shown in  FIG. 8 , any of the thin edge embodiments of  FIGS. 1-6  may be incorporated into the leading edge  32  of curvilinear ceiling fan blades  14  such as those of U.S. Pat. Nos. 6,039,541 and 6,659,721, previously incorporated by reference herein.  
         [0039]     More particularly, as shown in  FIG. 8 , a curvilinear ceiling fan blade  14  comprises an airfoil  50  composed of an upper surface  50 U and a lower surface  50 L that produces a lifting force when rotated. Furthermore, a curvilinear fan blade  14  often comprises an increasing “twist” formed along its elongated configuration from its tip to its root, such that, preferably, the same volume of airflow is achieved along its entire length even though the tip of the blade  14  is moving faster than its root. The incorporation of the thin leading edge  32  of the invention into curvilinear fan blades  14  increases the efficiency by reducing resistance and turbulence.  
         [0040]     Without departing form the spirit and scope of this invention, as noted previously, the ceiling fan blades  30  may be manufactured from any available technique, with or without vinyl or paper materials on one or both of the surfaces  30 U and  30 L thereof and with or without sealing of the exposed longitudinal edges  32  and  36 - 42  thereof.  
         [0041]     The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.  
         [0042]     Now that the invention has been described,