Patent Publication Number: US-2023144453-A1

Title: Ceiling fan blade

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 17/400,222, filed on Aug. 12, 2021, which is a continuation of U.S. patent application Ser. No. 16/458,333, filed on Jul. 1, 2019, now U.S. Pat. No. 11,111,930, issued Sep. 7, 2021, which claims priority to and the benefit of U.S. Provisional Patent Application No. 62/695,863, filed on Jul. 10, 2018, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Ceiling fans are machines typically suspended from a structure for moving a volume of air about an area. The ceiling fan includes a motor, with a rotor and stator, suspended from and electrically coupled to the structure. A set of blades mount to the rotor such that the blades are rotatably driven by the rotor, and can be provided at an angled orientation to move volume of air about the area. As the cost of energy becomes increasingly important, there is a need to improve the efficiency at which the ceiling fans operate. 
     BRIEF DESCRIPTION 
     In one aspect, the disclosure relates to a blade for a ceiling fan having a fan motor rotating at least one blade iron. The blade includes an airfoil body having an outer surface extending between a leading edge and a trailing edge to define a chord-wise direction, and separating the outer surface into an upper surface and a lower surface, and the outer surface extending between a root and a tip to define a span-wise direction. A blade iron mount is provided at the root. The airfoil body comprises at least three distinct cross sections along the span-wise direction: a first cross section comprising a flat lower surface and a lifting cross section; a second cross section comprising a flat lower surface and a flat upper surface; and a third cross section located between and transitioning from the first to the second cross sections. 
     In another aspect, the disclosure relates to a ceiling fan assembly including a motor including a rotatable rotor and a stationary stator, with the stator configured to drive the rotor. At least one blade coupled to the rotor and having an airfoil body including an outer surface extending between a leading edge and a trailing edge to define a chord-wise direction, and separating the outer surface into an upper surface and a lower surface, and the outer surface extending between a root and a tip to define a span-wise direction. A blade iron mount is provided at the root. The airfoil body comprises at least three distinct cross sections in the span-wise direction: a first cross section comprising an airfoil cross section; a second cross section comprising a flat lower surface and a flat upper surface; and a third cross section located between and transitioning from the first to the second cross sections. 
     In yet another aspect, the disclosure relates to a blade for a ceiling fan including an airfoil body having an outer surface extending between a leading edge and a trailing edge to define a chord-wise direction, and separating the outer surface into an upper surface and a lower surface, and the outer surface extending between a root and a tip to define a span-wise direction. The airfoil body comprises at least three distinct cross sections along the span-wise direction: a first cross section comprising an airfoil cross section; a second cross section comprising a flat upper surface and a flat lower surface; and a third cross section located between and transitioning between the first cross section and the second cross section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG.  1    is a schematic view of a structure with a ceiling fan including a set of blades suspended from the structure. 
         FIG.  2    is a top view of one blade from the set of blades or  FIG.  1    having different sections as a first section, a second section, and a third section as illustrated by separating lines. 
         FIG.  3    is a sectional view of the first section of the blade of  FIG.  2    taken along section III-III. 
         FIG.  4    is a sectional view of the second section of the blade of  FIG.  2    taken along section IV-IV. 
         FIG.  5    is a sectional view of the third section of the blade of  FIG.  2    taken along section V-V. 
         FIG.  6    is a side view of the blade better showing the first section of  FIG.  3   , the second section of  FIG.  4   , and the third section of  FIG.  5   . 
         FIG.  7    is a perspective side view of the blade depicting the contours of the first section of  FIG.  3   , the second section of  FIG.  4   , and the third section of  FIG.  5   . 
         FIG.  8    is a top view of a fan blade having five exemplary sections as illustrated by separating lines. 
         FIG.  9    is a section view of a fan blade having a flat bottom airfoil shape. 
         FIG.  10    is a section view of a fan blade having a symmetric airfoil shape. 
         FIG.  11    is a section view of a fan blade having a semi-symmetric airfoil shape. 
         FIG.  12    is a section view of a fan blade having an early airfoil shape with a deep camber. 
         FIG.  13    is a section view of a fan blade having a late airfoil shape. 
         FIG.  14    is a section view of a fan blade having an under-camber airfoil shape with a uniform thickness. 
         FIG.  15    is a section view of a fan blade having a flat upper surface, a flat lower surface, a flat leading edge, and a flat trailing edge. 
         FIG.  16    is a section view of a fan blade having a varying angle of attack to form a twist. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is related to a ceiling fan and ceiling fan blade, which can be used, for example, in in residential and commercial applications. Such applications can be indoors, outdoors, or both. While this description is primarily directed toward a residential ceiling fan, it is also applicable to any environment utilizing fans or for cooling areas utilizing air movement. 
     As used herein, the term “set” or a “set” of elements can be any number of elements, including only one. All directional references (e.g., radial, axial, proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, upstream, downstream, forward, aft, etc.) are only used for identification purposes to aid the reader&#39;s understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of aspects of the disclosure described herein. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and can include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to one another. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto can vary. 
     Referring now to  FIG.  1   , a ceiling fan  10  is suspended from a structure  12 . In non-limiting examples, the ceiling fan  10  can include one or more ceiling fan components including a hanger bracket  14 , canopy  16 , a downrod  18 , a motor adapter  20 , a motor housing  22  at least partially encasing a motor  24  having a rotor  26  and a stator  28 , a light kit  30 , and a set of blade irons  32 . In additional non-limiting examples, the ceiling fan  10  can include one or more of a controller, a wireless receiver, a ball mount, a hanger ball, a light glass, a light cage, a spindle, a finial, a switch housing, blade forks, blade tips or blade caps, or other ceiling fan components. A set of blades  34  can extend radially from the ceiling fan  10 , and can be rotatable to drive a volume of fluid such as air. The blades  34  can be operably coupled to the motor  24  at the rotor  26 . The blades  34  can include a set of blades  34 , having any number of blades, including only one blade. 
     The structure  12  can include an exemplary ceiling  40  from which the ceiling fan  10  is suspended, and a set of walls  42 . It should be understood that the structure  12  is schematically shown and is by way of example only, and can include any suitable building, structure, home, business, or other environment wherein moving air with a ceiling fan is suitable or desirable. An electrical supply  44  can be provided in the structure  12 , and can electrically couple to the ceiling fan  10  to provide electrical power to the ceiling fan  10  and the motor  24  therein. It is also contemplated that the electrical supply be sourced from somewhere other than the structure  12 , such as a battery or generator in non-limiting examples. 
     A wired controller  46  can be electrically coupled to the electrical supply  44  to control operation of the ceiling fan  10  via the electrical supply  44 . Similarly, the wired controller  46  can be communicatively coupled to the ceiling fan  10 , configured to control operation of the ceiling fan  10 . Non-limiting examples of controls for the ceiling fan  10  can include fan speed, fan direction, or light operation. Furthermore, a wireless controller  48 , alone or in addition to the wired controller  46 , can be communicatively coupled to a controller or a wireless receiver in the ceiling fan  10  to control operation of the ceiling fan  10 . It is further contemplated in one alternative example that the ceiling fan be operated by the wireless controller alone  48 , and is not operably coupled with the wired controller  46 . 
     Referring now to  FIG.  2   , a single fan blade  34  includes a body  60  with a first upper surface  62  and a second lower surface  64 , a root  66  and a tip  68 , and extends between a first side edge  70  and a second side edge  72 , which can be a leading edge and a trailing edge, for example, depending on the direction of rotation of the blade. In one example, the upper surface  62  can face the ceiling  40 , while the lower surface  64  can face a floor of a structure  12 . The tip  68  can includes a front surface between the first upper surface  62  and the second lower surface  64 , having a convex shape, for example. The root  66  can be proximate the motor  24  when mounted to the ceiling fan  10 , while the tip  68  can be distal. The root  66  can have a rear surface between the first upper surface  62  and the second lower surface  64  that is flat, for example. The tip  68  has a greater or longer chord than the root  66 , such that the chord length increases between the first and second side edge  70 ,  72 , and can be increasing continuously from the root  66  to the tip  68 . In one example, the rate of increase of the chord length can be constant. A span-wise axis  74  can be defined extending between the root  66  and the tip  68  defining a span-wise direction. In one non-limiting example, the span-wise axis  74  can be defined equidistant between the first side edge  70  and the second side edge  72  extending between the root  66  and the tip  68 . A chord-wise axis  82  can define a chord-wise direction extending between the first side edge  70  and the second side edge  72 , and can be arranged orthogonal to the span-wise axis  74 , for example. In one example, the body  60  can increase in length measured along the chord-wise axis  74 , such that the blade widens extending from the root  66  to the tip  68 . In other examples, the chord length can vary along the span-wise axis  74 , such that it is variable, continuously increasing, or continuously decreasing. 
     A blade iron mount  76  can mount to and extend from the first upper surface  62 , and can include a flat mount surface  78 . In non-limiting examples, the blade iron mount  76  can be a gasket and can be made of a substantially rigid material suitable for mounting the blade  34  to the motor  24 , while simultaneously dampening vibrations between the blade  34  and the motor  24 , such as foams, neoprenes, rubbers, polymers, polyurethane, elastics, composites, or plastics in non-limiting examples. A set of mount apertures  80 , shown as three mount apertures  80 , can be provided in the mount surface  78 . The set of mount apertures  80  can be threaded, in one example, configured to threadably receive a fastener such as a screw to fasten the blade  34  to the motor  24 . 
     The blade  34  can be separated into a first section  90  having a first cross section or profile, a second section  92  having a second cross section or profile, and a third section  94  having a third cross section or profile. In one example, the first section  90  can be symmetrical, such as about the span-wise or chord-wise axes  74 ,  82 . The first section  90  can be positioned at and extend from the root  66 , extending toward the tip  68  along the span-wise axis  74 . 
     The second section  92  can be arranged at the tip  68 , extending toward the root  66 . In one non-limiting example, the second section  92 , having the second profile with the flat lower surface  64  and the flat upper surface  62  can be located only at the tip  68 , with only the tip  68  including the flat upper and lower surfaces  62 ,  64 . Alternatively, it is contemplated that the second section  92  occupies a larger span-wise portion of the blade  34 . 
     Referring now to  FIG.  3   , taken across section III-III of  FIG.  2   , a cross section of the first section  90  includes the airfoil profile shown as a flat bottom airfoil, including the flat second lower surface  64 , and an asymmetric, convex, first upper surface  62 . The first section  90  can include a first maximum thickness  104  for the airfoil profile of the first section  90 , defined between the first upper surface  62  and the second lower surface  64  along the first section  90 , which can be measured orthogonal to the first upper surface  62 , the second lower surface  64 , or both, for example, or can be measured relative to a chord-line defined by the airfoil cross section. It should be appreciated that a thickness between the first upper surface  62  and the second lower surface  64  can vary between the first side edge  70  and the second side edge  72 , due to the airfoil cross-sectional shape, or that the first maximum thickness  104  an be positioned differently than that shown based upon the particular shape of the airfoil cross section. 
     The first section  90  can include a cross section that can be a lifting cross section or an airfoil cross section. The lifting cross section or airfoil cross section can be any cross section or profile that is shaped to generate lift in at least one direction of rotation, for example, and can include any airfoil cross-sectional shape such as a flat bottom airfoil, a symmetrical airfoil, a semi-symmetrical airfoil, an under-camber airfoil, in non-limiting examples, or any other airfoil shape, such as those having an early camber, a late camber, no camber, a varying or constant thickness, a large or small thickness, or any other suitable aerodynamic airfoil feature forming the lifting cross section. Such aerodynamic airfoil features can be any such feature that is adapted to increase operational efficiency of the ceiling fan  10  due to the profile reducing aerodynamic drag or turbulence, utilizing Bernoulli&#39;s Principle, or increasing boundary layer attachment along at least a portion of the first upper surface  62  or the second lower surface  64  in non-limiting examples. 
     It should be appreciated while the flat bottom airfoil shape of the first section  90  includes a generally low camber, any camber is contemplated, such as a deep camber or any camber therebetween. Furthermore, while not shown it is contemplated that the camber can include a small or large thickness, or can optionally include a reflex trailing edge. 
     The blade  34  can be oriented at an angle of attack  100 , with the blade  34  arranged at an angle relative to the horizontal  102 , such that the second lower surface  64  is offset from the horizontal where the lower surface  64  confronts the air during rotation of the blade  34 . Arranging the blade  34  at the angle of attack  100  can move a volume of air during rotational movement of the fan blade  34 . 
     Referring now to  FIG.  4   , taken across section IV-IV of  FIG.  2   , the second section  92  includes a cross section or profile with a flat first upper surface  62  and a flat second lower surface  64 . A second maximum thickness  106  can be defined between the first upper surface  62  and the second lower surface  64  at the second section  92 . The second maximum thickness  106  can be measured orthogonal to the first upper surface  62 , the second lower surface  64 , or both, for example. The thickness can be constant along most of the second section  92 , as the first upper surface  62  and the second lower surface  64  can be flat and parallel to one another, with the exception that the first and second side edges  70 ,  72  are radiused, providing a curved transition between the upper surface  62  and the lower surface  64 . The second maximum thickness  106  can be less than that of the first maximum thickness  104 , as is appreciable, such that the aerodynamic airfoil shape of the first section  90  provides for an increased thickness as opposed to that of the second section  92  including the flat upper and lower surfaces  62 ,  64 . It should be appreciated that the first section  90 , having the greater first maximum thickness  104 , is visible behind the second section  92  in  FIG.  4   . 
     Additionally, the blade  34  at the second section  92  can be arranged at the angle of attack  100 , while it is contemplated that the second section  92  may not be arranged at the angle of attack  100  or a different angle of attack  100  than that of the first section  90 . In another non-limiting example, the angle of attack  100  can vary along the span-wise axis  74 , best shown in  FIG.  14   . 
     Referring now to  FIG.  5   , taken across section V-V of  FIG.  2   , the third section  94  includes a transition section that transitions from the first section  90  to the second section  92 . The third section  94  can include a third maximum thickness  108 , that is less than the first maximum thickness  104  of  FIG.  3   , but greater than the second thickness  106  of  FIG.  4   , resultant of the transition between the first section  90  and the second section  92 . The third maximum thickness  108  can be measured orthogonal to the first upper surface  62 , the second lower surface  64 , or both, for example. The first section  90  is visible behind the third section  94 , as is appreciable in  FIG.  5   . The thickness along the airfoil cross section of the third section  94  can vary, resultant of the shape of the airfoil cross section. It should be appreciated that the third section  94  includes an airfoil shape with a lesser camber than that of the first section  90 , as it transitions to the second section  92  with no camber. 
     At the tip  68 , the blade  34  includes both the flat upper surface  62  and the flat lower surface  64 , with the flat lower surface  64  extending fully along the span of the blade  34 . Thus, when the user views the blade  34  from the bottom or the tip  68  looking along the blade  34 , the airfoil shape is not seen nor readily recognized. Furthermore the second section  92  in combination with the flat second lower surface  64  of the first section  90 , provides for a traditional aesthetic with an unadorned bottom surface  64  for the fan blade  34  as it transitions to the airfoil section  90 , which is preferable to the consumer, where an entire fan blade having the airfoil cross section does not. The third section  94  provides for a smooth transition between the first and second sections  90 ,  92 , which reduces aerodynamic losses while providing an aesthetically pleasing look to the consumer between the first and second sections  90 ,  92 . 
     Referring now to  FIG.  6   , the first section  90  can extend from the root  66  to the tip  68  for at least 80% of the span, for example, or can be about 90% or 95% of the span, in other non-limiting examples, or any value between 80% span and 95% span. It should be appreciated that the first section  90  can occupy lesser portions of the span than those portions as described, such as less than 80% span or greater than 95% span. 
     The second section  92  can be about 3-10% or 5-10% of the span, extending along the span-wise axis  74 , in non-limiting examples. It should be appreciated that other ranges or sizes for the second section are contemplated, such as those less than 3% span or greater than 10% span, for example. In one example, the second section  92  can be symmetrical along the chord-wise axis  82 . The third section  94  can be positioned between the first and second sections  90 ,  92  and can transition from the first section  90  to the second section  92 . The third section  94  can include a remaining portion of the blade  34  unoccupied by the first and second sections  90 ,  92 , such as between 5-15% span in one non-limiting example. It should be appreciated that other ranges or sizes for the thirds section  94  are contemplated, such as less than 5% span or greater than 15% span, for example. 
     Referring now to  FIG.  7   , the blade  34  can include different contours for the different sections  90 ,  92 ,  94 . For example, the airfoil profile for the first section  90  can include a convex, rounded surface for the upper surface  62 . The third section  94 , transitioning between the first section  90  and the second section  92 , can include a slight taper for the upper surface  62 , relative to the plane parallel to the flat lower surface  64 . Furthermore, the upper surface  62  at the third section  94  can include a convex curve to transition between the first and second section  90 ,  92 . Alternatively, it is contemplated that the upper surface  62  of the third section  94  can be concave, flat, linear, discrete, step-wise, or any variation thereof suitable for transitioning between the first and second sections  90 ,  92 . 
     In operation, the lifting or airfoil cross section of the first section  90  generates an increased downward force imparted to the air passing along the blade  34 , which can be the result of the lift generated by the blade shape. The increased downward force increases the overall volume of air moved by the fan blade, as opposed to a blade without the lifting or airfoil cross section of the first section  90 . Utilizing the angle of attack  100  in combination with the lifting or airfoil cross section can further increase the overall volume of air moved by the fan blade  34 , while requiring a lesser overall energy cost relative to the flow volume generated by the blades  34 , as opposed to a traditional fan blade that is flat along the entire length of the blade. Thus, the blade  34  as described provides for aerodynamic and efficiency improvements along the first section  90  of the blade  34 . In one example, such an airfoil shape can provide for an increase in overall performance measured in total flow volume by 30% or more. In one example, the blade  34  can provide a 7%-40% increase in maximum air velocity, as opposed to a blade having an upper and lower surface that are both flat along the extent of the blade. Additionally, increases in maximum air velocity greater than 40% are possible. Similarly, the blade  34  can provide an increase in flow volume of 5% to 35%, as opposed to a blade having a wholly flat upper and lower surface. Additional increases in flow volume greater than 35% are possible. 
     Referring now to  FIG.  8   , an alternate blade  134  having five different sections  190 ,  192 ,  194 ,  196 ,  198 , having two transition sections  194 ,  196 , as opposed to the three sections  90 ,  92 ,  94  and the single transition section  94  of  FIG.  2   . The blade  134 , similar to that of  FIG.  2   , can include a body  160  including a first upper surface  162  and a second lower surface  164  extending between a root  166  and a tip  168  to define a span-wise axis  174 . A first side edge  170  and a second side edge  172 , such as a leading edge and a trailing edge, can extend from the root  166  to the tip  168  between the first upper surface  162  and the second lower surface  164 . A span-wise axis  174  can be defined extending between the root  166  and the tip  168 , and can be arranged equidistant from the first and second side edges  170 ,  172 , for example. 
     A chord-wise  182  direction can be defined extending between the first and second side edges  170 ,  172 , orthogonal to the span-wise axis  174  and anywhere along the blade  134 . As shown, the root  166  is longer than the tip  168  in the chord-wise direction, such that the body  160  includes a decreasing width extending toward the tip  168 , measured in the chord-wise direction. Alternatively, the blade  134  can have a constant chord along the length of the blade  134 , or a changing chord, such as having a constant rate of change for the chord extending between the root and the tip. Furthermore, any variation of the chord is contemplated as defining the geometry of the blade, such as a constant, varying, step-wise, unique, or non-constant variation of the width of the blade measure in the chord-wise direction. Alternatively, it is contemplated that the body  160  can include any blade shape, such as geometric, squared, rectangular, triangular, rounded, unique, variable, converging, diverging, widening, thinning, or thickening in non-limiting examples. While the root  166  and the tip  168  are shown as flat linear portions, the root  166  or tip  168 , or both, can be flat, linear, rounded, curved, arcuate, concave, convex, sinusoidal, stepped, jagged, unique, variable, or any combination thereof in non-limiting examples, such that a myriad of shapes for the root  166  and the tip  168  are contemplated. Similarly, a myriad of geometries or shapes for the first and second side edge  170 ,  172  are contemplated, such as linear, flat, rounded, curved, arcuate, concave, convex, sinusoidal, stepped, jagged, unique, or variable, or any combination thereof, in non-limiting examples. Where the shapes for the first or second side edges  170 ,  172  are non-linear, or non-uniform among the edges  170 ,  172 , the span-wise axis  174  can be non-linear. Therefore, it should be appreciated that a wide variety of different blade shapes are contemplated. A blade iron mount  176 , which can be a gasket, can mount to the body  160  on the first upper surface  162 , and can be substantially similar to the blade iron mount  76  as described in  FIG.  2   , including a set of mount apertures  180 . 
     The body  160  can be separated into five sections, including the first three sections as a first section  190 , a second section  192 , and a third section  194 , which can be substantially similar to the first section  90 , the second section  92 , and the third section  94  of  FIG.  2   , for example. 
     The third section  194  can begin or end halfway between the root  166  and the tip  168 , or at 50% span-wise distance  150  relative to the span-wise axis  174 . In such an example, either the first section  190  or the second section  192  can cover 50% of the blade in the span-wise direction. The third section  194  can cover 5-15% of the blade  134 , or lesser mounts such as 5%, 2%, or 1% in non-limiting examples, while it is contemplated that the third section  194  can cover larger portions of the blade  134 , such as 33%, 50%, or more. The second section  192  then covers the remaining area of the blade  134 , extending to the tip  168  for example. 
     Alternatively, the transition section  194  can begin or end at thirds of the blade  134 , at either of the 33% span-wise distance  152  along the span-wise axis  174 , or 66% s span-wise distance  154  along the span-wise axis  174 . In such an example, either the first section  190  or the second section  192  can cover either 33% or 66% of the blade, while the other of the first section  190  or the second section  192  covers the remaining section unoccupied by the third section  194 . 
     The blade  134  can optionally include a fourth section  196  and a fifth section  198 . The fifth section  198  can be arranged at the root  166  and the fourth section  196  can be arranged between the first section  190  and the fifth section  198 . The fourth section  196  can include a transitional cross section or profile similar to that of the third sections  94 ,  194  as described herein, and the fifth section  198  can include a cross section including the flat upper and lower surfaces  162 ,  164  similar to the second sections  92 ,  192  as described herein. The fourth section  196  can provide for transitioning between the lifting or airfoil profile of the first section  190  to the flat profile of the fifth section  198 . In one non-limiting example, the fourth section  196  can be arranged complementary to the blade iron mount  176 , beginning and ending relative to the span-wise extent of the blade iron mount  176 . The fifth section  198  can terminate at the root  166 . 
     It should be appreciated that the blade  134  can be separated into three sections, or five sections, while it is further contemplated that the blade  134  can include any number sections which can be arranged in a myriad of different ways. It is preferable that the area occupied by sections having an aerodynamic lifting or airfoil profile is maximized, to maximize aerodynamic benefits, while balancing with sections having the flat upper and lower surfaces to provide a desirable consumer aesthetic and unadorned bottom surface  164 . Increasing the length of the transitional sections can provide for some aerodynamic benefit, while maintaining the traditional aesthetic for the fan. Therefore, a balance can be struck between the sizing of the different sections, and the aerodynamic or aesthetic needs of the particular fan or implementation thereof. 
     Referring now to  FIGS.  7 - 12   , six different exemplary aerodynamic lifting or airfoil cross sections or profiles are shown, while it should be understood that the possibilities for airfoil profiles are not limited to just those shown in the figures, but may be a combination thereof or utilizing other features providing an aerodynamic or efficiency benefit. Utilizing the different aerodynamic lifting or airfoil cross sections in combination with a tip having a flat upper surface and a flat lower surface can provide for improved blade efficiency while providing the consumer with a traditional blade aesthetic appearance having an unadorned bottom surface. 
     Referring now to  FIG.  9   , an airfoil cross section having a flat bottom airfoil profile  208 . The flat bottom airfoil  208  can include an upper surface  212  and a flat lower surface  214  extending between a leading edge  216  and a trailing edge  218 . The flat bottom airfoil  208  can be asymmetric about the vertical axis  210  equidistant from the leading and trailing edges  216 ,  218 . The upper surface  212  can have an arcuate, convex shape, for example. The flat lower surface  214  is flat, similar to that of  FIGS.  3 - 5   . In one example, a blade having the flat bottom airfoil profile  208  can be arranged at an angle of attack. The enlarged upper surface  212  can provide for generating increased downward force from the blade to increase blade efficiency by increasing total volume flow generated by the flat bottom airfoil  208 . 
     Referring now to  FIG.  10   , a cross-sectional profile for a fan blade can be a symmetric airfoil  230 , including an upper surface  232  and a lower surface  234 , extending between a leading edge  236  and a trailing edge  238  to define a linear chordline  240  extending between the leading edge  236  and the trailing edge  238 . The symmetric airfoil  230  can be arranged at an angle of attack  242 , for example, orienting the chordline  240  offset from an axis of rotation or a horizontal axis, to increase aerodynamic performance of the symmetric airfoil  230 . The symmetric airfoil  230  positioned at the angle of attack  242  can increase the overall downward flow volume generated by the blade, as well as other aerodynamic benefits. 
     Referring now to  FIG.  11   , a cross-sectional profile for a fan blade can include a semi-symmetric airfoil  250 . The semi-symmetric airfoil  250  can include an upper surface  252  and a lower surface  254 , extending in a chord-wise direction between a leading edge  256  and a trailing edge  258  that has a non-linear chordline between the leading edge  256  and the trailing edge  258 . The upper surface  252  and the lower surface  254  can be rounded unevenly, such that one is surface  252 ,  254  is longer than the other. The semi-symmetric airfoil  250  can be a balance between the flat bottom airfoil of  FIG.  9    and the symmetric airfoil of  FIG.  10   , for example, and can be arranged at an angle of attack to increase flow volume. The semi-symmetric airfoil  250  can increase the overall downward flow volume generated by the blade, as well as other aerodynamic benefits. 
     Referring now to  FIG.  12   , a profile for a fan blade can be an under-camber airfoil profile  270  including an upper surface  272  and a lower surface  274 , and extending between a leading edge  276  and a trailing edge  278 . The upper surface  272  can be convex, while the lower surface  274  can be generally concave. The under-camber airfoil  270  can be an early airfoil, having the concavity for the lower surface  274  begin near the leading edge  278 . The leading edge  256  and the trailing edge  258  can be rounded or radiused in non-limiting examples, while flat or other geometries are contemplated. The under-camber airfoil  270  can be arranged at an angle or attack, and can provide for increased downward force generated by the blade to improve total flow volume, increasing blade efficiency. 
     Referring now to  FIG.  13   , a profile for another fan blade can be an under-camber airfoil  290  including an upper surface  292  and a lower surface  294 , and extending between a leading edge  296  and a trailing edge  298 . As compared to  FIG.  12   , the under-camber airfoil  290  of  FIG.  13    is a late airfoil, providing for a concave lower surface  294  that begins further from the leading edge  296 , and includes an inflection point  300  nearer to the center of the airfoil  290  between the leading and trailing edges  296 ,  298 . The under-camber airfoil  290  can be arranged at an angle or attack, and can provide for increased downward force generated by the blade to improve total flow volume, increasing blade efficiency. 
     Referring now to  FIG.  14   , an aerodynamic profile for a fan blade can be another under-camber airfoil  310 , including a convex upper surface  312  and a concave lower surface  314 , with a leading edge  316  and a trailing edge  318 , having a uniform thickness between the upper surface  312  and the lower surface  314 . The under-camber airfoil  310  can be arranged at an angle or attack, and can provide for increased downward force generated by the blade to improve total flow volume, increasing blade efficiency. 
     A lifting or airfoil cross section, portion, or an aerodynamic profile as described herein, such as that of  FIG.  2 ,  3   , or  6  showing the first section  90 ,  190  can include any of the profiles shown in  FIGS.  7 - 12   , or any combination of elements thereof, or any other geometry suitable to increase operational efficiency of a ceiling fan due to the aerodynamic section or profile reducing aerodynamic drag, turbulence, or increasing boundary layer attachment along at least a portion of one or more surfaces, as opposed to a traditional profile or blade shape. The tip  68 ,  168  having the second section  92 ,  192 , of  FIG.  2 ,  4   , or  6  provides the consumer with a pleasing, traditional fan blade aesthetic appearance and unadorned bottom surface, while realizing the benefits of the first section  90 ,  190 . Similarly, utilizing a fifth section  198 , as shown in  FIG.  8    provides for both a tip  168  and a root  166  having the flat upper and lower surfaces  162 ,  164 , which provides for a traditional consumer aesthetic with an unadorned bottom surface when viewing the blade  134  along either the root  166  or the tip  168 , while realizing the aerodynamic benefit of the first section  190 . 
     Referring now to  FIG.  15   , a blade cross section  330  can include an upper surface  332  and a lower surface  334 , each surface  332 ,  334  being flat and parallel to one another. A leading edge  336  and a trailing edge  338  can be flat and arranged orthogonal to the upper and lower surfaces  332 ,  334 . Alternatively, it is contemplated that the leading and trailing edges  336 ,  338  can be rounded or beveled. The blade cross section  330  provides for an aesthetic for a ceiling fan that is appreciable to consumers that consumers are used to seeing in traditional ceiling fans. The blade cross section  330  can be utilized in the second sections  92 ,  192  as described herein, for example. 
     Referring now to  FIG.  16    another exemplary blade  350  can include a blade cross section  352 , having an upper surface  354  and a lower surface  356  that are parallel to one another. The blade cross section  352  can be arranged at a tip of the blade  350 , for example. Additionally, the blade  350  can include an airfoil cross section  360 , shown as an exemplary symmetric airfoil (partially in broken line). The airfoil cross section  360  also includes the upper surface  354  and the lower surface  356 . The lower surface  356  at the airfoil cross section  360  is arranged at an angle of attack  362 , relative to a horizontal axis  364 , as well as relative to the lower surface  334  of the blade cross section  352 . Thus, the airfoil cross section  360  can be arranged at the angle of attack  362 , while the blade cross section  352  is not, to define a twist  366  for the blade  350 . In one example, the twist  366  can be positioned at a transition section, such as the third section  94  of  FIG.  2   . Thus, the airfoil cross section  360  can provide for improved aerodynamic performance at the angle of attack  362 , while the blade cross section  352  remains in a visibly flat position aesthetically pleasing to the consumer. 
     The blades and sections thereof as described herein provide for both increased total flow volume for a ceiling fan, resulting in increased efficiency, while maintaining the aesthetic appearance having an unadorned bottom surface of a ceiling fan that consumers desire. More specifically, the airfoil cross section provides for increased downward force on air which increases the total volume of airflow, while the flat upper and lower surfaces of the blade match traditional fan blade styles. Additionally, the third section provides for a smooth transition between the airfoil section and the blade section, which minimizes losses, while provides for an aesthetically appealing transition between the sections. 
     To the extent not already described, the different features and structures of the various features can be used in combination as desired. That one feature is not illustrated in all of the aspects of the disclosure is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different aspects described herein can be mixed and matched as desired to form new features or aspects thereof, whether or not the new aspects or features are expressly described. All combinations or permutations of features described herein are covered by this disclosure. 
     This written description uses examples to detail the aspects described herein, including the best mode, and to enable any person skilled in the art to practice the aspects described herein, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the aspects described herein are defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.