Abstract:
An efficient, high-volume fan producing a focused air flow comprises an electric motor having a central, segmented stator and a rotor with a set of permanent magnets and a back iron. The magnets are preferably rare-earth magnets such as neodymium magnets. The fan further features a plurality of lightweight blades, each blade comprising an airfoil cross section comprising a foam core that may be covered with a high tensile-strength skin or plastic coating. In the preferred embodiments, the high tensile-strength skin is an aluminum skin, and edges of the blades have edges are joined with a folded hem. The blades may have a windward tilt, and may be constructed so as to intentionally detach upon impact. The segmented stator, blade shape, and other aspects may be varied for different applications.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 61/549,965, filed Oct. 21, 2011, the entire content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to electric fans and, in particular, to efficient fan configurations capable of generating a highly focused air flow. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hundreds of electric fans have been designed and built over the last century, many of which have been patented or applied-for. As one example, published U.S. Application No. 2010/0119389 describes a modular brushless motor that may be reconfigured for different applications and power levels. A brushless ring motor comprises a circular ferromagnetic ring having an inner surface and an outer surface rotatable about a central axis, with a plurality of spaced-apart permanent magnets being bonded to one of the inner surface and outer surfaces of the ring. A stator assembly enables one or more coils to be mounted relative to the permanent magnets enabling a commercially available electronic speed controller to the drive the coils in cooperation with the magnets so as to turn the ring. The stator assembly enables different groups of coils to be mounted relative to the permanent magnets, and the ring is configured to accept different numbers of fan blades. However, the disclosed fan blades are substantially conventional. 
         [0004]    Published U.S. Application No. 2010/0148515 discloses a direct current brushless electric machine that operates as a generator when the power is flowing from a prime mover, such as the turbine blade extracting energy from the wind or water. The machine operates as a motor when the current is applied to the coils in a sequence to move the rotor when the turbine blades move the wind or water. Also described is an aerodynamic system comprising inner and outer annulus disposed driving fans, with a pressure differential flow enhancing aerodynamic housing, able to concentrate and make laminar rough and turbulent intake air molecule flows, creating a smooth rotationally organized downstream vortex field, with maximum power extraction from building structure directed velocity flow enhancements. 
         [0005]    A low profile permanent magnet synchronous motor with segment structure is described in Published U.S. Application No. 2011/0133589. The stator assembly has windings of conductive material, a first stator core, and a second stator core. The windings are located between the first and second stator cores. The first stator core has teeth extending through a layer defined the windings. The second stator core also has teeth extending through the layer defined by the windings. In some embodiments, the windings are a conductive coil. In other embodiments, the windings are comprised of multiple printed circuit boards. 
         [0006]    U.S. Pat. No. 7,066,721 discloses an “inside-out” ceiling fan motor wherein the stator is mounted to a downrod with an annular array of stator coils positioned about a rotor axis of rotation. A rotor is rotatably mounted about the stator. The rotor has a plurality of vanes spaced along the rotor periphery and canted at an angle of attack to a plane of rotor vanes rotation oriented normally to the rotor axis of rotation to scoop ambient air into the rotor during fan operation through the stator coils to cool them. 
         [0007]    U.S. Pat. No. 8,113,793 provides a fan with an “inrunner” motor. The fan includes a fan frame, a rotor and a stator. The fan frame includes a base. The rotor includes a hub, a bushing and a magnetic member, wherein the magnetic member sleeves on the bushing. The stator is disposed on the base and coupled with the rotor, and the stator includes a shaft through the bushing, wherein an end of the shaft is fixed on the base. The inventors claim that the configuration widens the airflow passage, increases heat dissipation efficiency, decreases rotating inertia, lowers noise, and extends the life span of the product. However, no specific blade designs are disclosed in detail. 
       SUMMARY OF THE INVENTION 
       [0008]    This invention relates to an efficient, high-volume fan exhibiting a focused air flow. Various components of that design have been optimized to achieve the desired performance level. These enhancements encompass motor construction and blade construction. The fan may further include one of a plurality of mounting systems and/or a motion sensor may be provided to enhance safety. 
         [0009]    A high-efficiency electric fan constructed in accordance with the invention comprises an electric motor having a central, segmented stator and a rotor with a set of permanent magnets and a back iron. In the preferred embodiments, both the magnets and back iron are encapsulated in plastic. The magnets are preferably rare-earth magnets such as neodymium magnets. 
         [0010]    The fan further features a plurality of lightweight blades, each blade comprising an airfoil cross section. Each blade may comprise a high tensile-strength skin with a foam core. In the preferred embodiments, the high tensile-strength skin is an aluminum skin, and edges of the blades have edges are joined with a folded hem. Detachable safety blades may also be used that are airfoil-shaped but may be all foam or foam with a thin plastic skin. The blades may have a windward tilt, and may be constructed so as to intentionally detach upon impact. The segmented stator, blade shape, and other aspects may be varied for different applications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows motor stators made of multiple layers of laminated electrical steel. These layers are mounted to a central mounting plate that is attached to the non-rotating shaft; 
           [0012]      FIG. 2  shows the stacks of stator plates coated with electrical resin, which seals them from moisture and helps insulate them from the copper windings; 
           [0013]      FIG. 3  illustrates a circular plastic ring that surrounds the magnets and the flux-conducting back iron; 
           [0014]      FIG. 4  depicts cover plates with mounted bearings, facilitating rotation about a fixed axle; 
           [0015]      FIG. 5  shows a fan blade constructed in accordance with the invention; 
           [0016]      FIG. 6  shows how the plastic encapsulates the components and helps seal them from dirt, magnetic particles, and water; 
           [0017]      FIG. 7  shows a maximum power configuration using stator lamination segments arranged to make a full circle; 
           [0018]      FIG. 8A  is a drawing that shows how conventional blades create small swirling currents of wind that result in noise and inefficiencies of air movement; 
           [0019]      FIG. 8B  is a drawing that illustrates the inventive use of a true aerodynamic airfoil shape that allows the air to smoothly slide along the surface of the blade to create a laminar flow; 
           [0020]      FIG. 9  is a CAD drawing of a linear (i.e., non-twisted) blade design; 
           [0021]      FIG. 10  is a CAD drawing of an entirely linear end design; 
           [0022]      FIG. 11  is a CAD draw showing an entirely linear isometric view; 
           [0023]      FIG. 12  is a CAD drawing depicted a linear twisted end; 
           [0024]      FIG. 13A  is a front view showing a 3-point mounting system; 
           [0025]      FIG. 13B  is a rear view of the 3-point mounting system; and 
           [0026]      FIG. 13C  is a side view of a 2-point mounting system, also best depicting how the blades may include a forward tilt to improve the direct flow of air. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    This invention relates to an efficient, high-volume fan exhibiting a focused air flow. Various components of that design have been optimized to achieve the desired performance level, including motor construction, blade construction, mounting arrangements and safety features. Each of these aspects is discussed in detail below. 
       Motor Construction 
       [0028]    Motor construction is an important step in making a fan more efficient. Typical fans are made using an induction motor that contains no magnets. In order in order for this type of motor to do any work, a magnetic field must first be induced. This induced magnetic field is responsible for losses and inefficiency. 
         [0029]    In the instant design, rare earth (i.e., neodymium) magnets are preferably used to increase efficiency and manufacturability. Although non-rare-earth permanent magnets may be used, stronger neodymium magnets increase magnetic flux and increase the required air gap between motor stator laminations and the magnets. This large air gap allows the face of the magnet to be covered with a layer of plastic. As shown in  FIG. 3 , this plastic is a circular ring  302  that surrounds the magnets  310  and the flux-conducting back iron  312 . As seen in  FIG. 6 , the plastic ring  302  encapsulates the components and helps seal them from dirt, magnetic particles, and water. 
         [0030]    Inward, toward the center of the magnetic ring, are the motor stator laminations with copper wire windings.  FIG. 1  shows motor stators made of multiple layers of laminated electrical steel  102 . These layers are mounted to a central mounting plate  104  that is attached to a non-rotating shaft. The shape of the stator laminations is similar to a letter “E,” with multiple fingers pointing radially outward toward the magnets.  FIG. 2  shows the stacks of stator plates coated with 3M 260 ScotchCast electrical resin which seals them from moisture and helps insulate them from the copper coils. The motor stator laminations may also be insulated from the copper coils through the use of plastic (nylon) bobbins. 
         [0031]    As seen in  FIG. 2 , the stator laminations are segmented so they are not a complete circle. Instead, multiple segments are assembled to determine the motors output power. As shown in  FIG. 7 , the maximum power configuration uses stator laminations segments to make a full circle. As seen in  FIGS. 3 ,  6  and  7 , each finger of the stator laminations has copper coils wrapped around it. The number of turns is different for each configuration of motor as well as the number of stator lamination segments used. The coils are connected to one another to further determine the motor configuration. A 3-phase control system is typically used. The Model ACS 355 general machinery drive from ABB (headquartered in Zurich, Switzerland) represents one of many suitable controllers. 
         [0032]    Outside of the magnet and back-iron plastic ring are two circular cover plates made of aluminum or other material. With reference to  FIG. 4 , these cover plates  402 ,  404  have bearings  412 ,  414  attached to them, facilitating rotation about a fixed axle. The cover plates and ring are then attached to each other in a sandwich configuration. 
         [0033]    In summary, the rotating components of the motor include the plastic ring with magnets and back-iron, and the cover plates with bearings. The non-rotating components include the stator lamination plates with coils, stator mounting plate, axle attachment block, and axle. The motor connecting wires go from the coils thru the axle attachment block, and come out of the motor thru a hole in the center of the axle. The axle can have a mounting plate on either end and is held still during operation. 
       Ring Covers 
       [0034]    In addition to the two cover plates that seal the motor, the preferred design further uses ring covers with a spoke assembly. This allows a larger diameter motor which provides more torque. In this large ring motor configuration, two pieces of plastic sandwich together the magnets and back-iron. Aluminum or other material covers this plastic. A bearing block spins on the fixed axel and has spokes that attach to the ring. The motor stator laminations are once again mounted to the stationary axle and located with the open fingers of the “E” shape at the magnets. The length and number of stator laminations determines the power capability of the motor. 
         [0035]    Overall, the ring construction may include any type of construction that incorporates a plastic or non-ridged material that is surrounded or sandwiched by a higher strength material. The plastic material is used as a spacer and as a barrier for the magnets and back iron against moisture and debris. The construction may further include a single-sided ridge ring or ring section that a non-ridged material is mounted. The magnets may be held or anchored by either the ridged or non-ridged material. 
       Fan Blades 
       [0036]    Traditionally fans blades comprise a flat piece of material extending radially from the central motor at a slight angle. As shown in  FIG. 8A , conventional blades create small swirling currents of wind that result in noise and inefficiencies of air movement. The fan blades used with this invention provide a true aerodynamic airfoil. This cross-sectional shape allows the air to smoothly slide along the surface of the blade to create a highly focused laminar flow, as shown in  FIG. 8B . This laminar flow helps contribute to low audible noise and wind that carries much farther than a standard flat blade. 
         [0037]      FIG. 5  shows a fan blade constructed in accordance with the invention. Such blades are constructed of a high tensile strength aluminum skin  502  with a polyurethane foam core  504 . This construction maximizes the characteristics of each material to create a very ridge structure. The high strength aluminum is located at the outside of the structure where it has the greatest moment. By themselves, the foam and the thin aluminum sheet are too weak to construct an airfoil. As such, it is important that the foam is adhered to the aluminum. This design holds the aluminum in place and results in a stable, efficient structure. The edges of this thin aluminum sheet are sealed by a hem. This hem is a multiple fold that seals the blade along its edge  510 , lengthwise. Detachable safety blades may also be used that are airfoil-shaped but may be all foam or foam with a thin plastic skin as opposed to aluminum. 
         [0038]    Each blade has a metal formed blade bracket  514  which adapts the blades to the motor ring. The bracket is attached to the blade with screws  512 . The bracket is also attached to the motor with 3 screws. The motor mounting screws go through the blade bracket, through the motor plates, into the plastic magnet ring, out of the opposite motor plate, through the opposite blade bracket and is held with a lock nut. The air foil blades are attached to the motor with 3 screws  512 . 
         [0039]    As mentioned, the blade design may be altered to suit particular applications.  FIGS. 9-12  are CAD drawings that show possible variations in blade twist and shape. In particular,  FIG. 9  depicts a linear airfoil (i.e., non-twisted) blade design, and  FIG. 10  shows an entirely linear end design.  FIG. 11  shows an entirely linear isometric view, and  FIG. 12  depicts a linear, twisted end design. 
         [0040]    The linear twisted blade is described as 2 similar blade cross section (airfoil shaped) at the ends of blade. One cross section is located at the tip (outside) of the fan and one located at the root (inside edge near motor). From each of these cross sections, a line can be drawn connecting the leading edges to each other and another line connecting the trailing edges to each other. These 2 cross sections can be at different angles in comparison to the axial flow of wind. This shape defines the geometry of a linear twisted blade. This blade geometry is favorable to produces uniform wind velocities across the downstream column of air. The effect of this helps produce better uniform air velocities compared to a completely linear blade which produces higher velocity toward the tip of the blade. 
         [0041]    A completely linear blade, in comparison, would be described as two cross sections of the same size and same angle, with relation to the axial air flow. This completely linear blade construction is most often manufactured using and extrusion processes. 
       Windward Tilt 
       [0042]    The blades are attached to the motor ring with a similar angle to traditional fans, but with a windward tilted angle, as perhaps best seen in  FIG. 13C . For a ceiling fan, however, the blades angle toward the ground. This windward angle does two things. First, it allows the fan to feed more air to the blades which allows more air to pass through the blades. Secondly, the windward angle creates a merging wind from each opposing blade. As the blades opposite each other focus wind toward one another, the wind combines and creates a single tunnel of wind ( FIG. 8B ). This wind carries much farther than standard flat and parallel blades. 
       Frame and Mounting 
       [0043]    The frame for the fan may be provided in a plurality of configurations.  FIGS. 13A and 13B  illustrate a 3-point mounting system typically used for creating horizontal wind. This is done by attaching 3 bars  1302 ,  1304 ,  1306  from the fixed axle  1310 . Two bars,  1302 ,  1304  are attached to the back of the motor axle, and one bar,  1306  is attached to the front of the axle  1310 . 
         [0044]    A second mounting type is for a more traditional ceiling fan, which uses tubing that attaches to the fan axel and extends up to the ceiling. A third mounting variation is a 2-point horizontal hanging frame. This includes 2 bars attached to the 2 ends of the fixed axle. As shown in  FIG. 13C , the end of the bars may be connected to adjustable chains or other material. This material allows for adjusting the elevation of the air flow. By varying the length of this connecting material, the fan&#39;s direction can also be aimed. 
       Safety Features 
       [0045]    To operate properly, it is important that fans have plenty of free flowing air to enter the blades. Mounting a fan close to obstructions like walls and ceiling can affect its performance. To overcome this issue some people mount fans in areas where they are not safe. In accordance with the invention, the light weight blade(s) will detach if they strike an object. Being made of a light weight material similar to Styrofoam, the detached blade may be reusable or in may need to be replaced. Such blades may be covered or coated with a plastic skin as opposed to a metal such as aluminum. 
         [0046]    Safety-blade fan system is described as a fan having low density light weight blade that does minimal damage to an object if it is hit by the fan. This includes blades or partial blade (blade tips) that detach or dislodge from the motor or rotating device during impact. The blades may deform and or break as a safety tactic. The blades may be reusable and capable to re-attach if they are not damaged. To further increase safety, when the blades detach they will be tumble to reduce their velocity and damage capability. 
         [0047]    Motion sensors are an additional method of improving fan safety. The disclosed fan systems can operate with motion sensors to stop fans when moving objects are in the vicinity. This application is helpful in industrial areas where fork trucks frequently raise their cargo high enough for fans to strike.