High volume low speed air-circulation fan

Abstract

A high volume, low speed (HVLS) fan for air circulation comprises a motor assembly including a stator and a rotor. A hub including a plurality of hub arms extending therefrom is operably connected to the rotor. A plurality of blades is provided, each blade connected to a hub arm. Each blade includes a relatively larger chord portion including a maximum chord of the blade disposed proximate to a root end of the blade, a swept-back portion disposed proximate to a tip end of the blade, and a relatively smaller chord portion including a minimum chord of the blade disposed therebetween. The rearmost extent of the swept-back portion is behind the rearmost extent of the relatively smaller chord portion. The blades can be made of molded plastic polymer material including non-polymer reinforcing materials encapsulated in a polymer matrix.

1 . A high volume, low speed (HVLS) fan for air circulation having an overall diameter within a range from 7 feet to 30 feet, the HVLS fan comprising:
 a motor assembly including a stator and a rotor, the rotor being configured to rotate when power is supplied;   a hub operably connected to the rotor to rotate around a central axis in a direction of rotation when the rotor rotates, the hub including a central hub body and a plurality of hub arms extending therefrom; and   a plurality of blades, each blade of the plurality of blades being operatively connected to a respective hub arm of the plurality of hub arms to rotate around the central axis in the direction of rotation;   wherein each blade includes a root end disposed adjacent the hub; a leading edge facing the direction of rotation, a tip end disposed distal from the hub, and a trailing edge facing away from the direction of rotation;   wherein each blade includes:
 a relatively larger chord portion including a maximum chord of the blade disposed proximate to the root end; 
 a swept-back portion disposed proximate to the tip end, and 
 a relatively smaller chord portion including a minimum chord of the blade disposed therebetween; and 
   wherein the rearmost extent of the swept-back portion is behind the rearmost extent of the relatively smaller chord portion.   
     
     
         2 . A HVLS fan in accordance with  claim 1 , wherein each blade is configured such that a rearmost tip of the swept-back portion trails behind a narrowest portion of the relatively smaller chord portion by a trailing distance expressed as a percentage of the length of the minimum chord of the blade, the trailing distance having a value within the range from 50 percent to 150 percent of the length of the minimum chord of the blade. 
     
     
         3 . A HVLS fan in accordance with  claim 1 , wherein each blade is configured such that a first length of the minimum blade chord of the blade in the relatively smaller chord portion has a length expressed as a percentage of a second length of the maximum blade chord in the relatively larger chord portion, the first length having s a value within the range from 45 percent to 75 percent of the second length. 
     
     
         4 . A HVLS fan in accordance with  claim 1 , wherein the hub is mounted to a first side of the rotor and the hub arms extending therefrom define a first blade plane, and the HVLS fan further comprises:
 a second hub mounted to a second side of the rotor, the second hub including a second central hub body and a plurality of second hub arms extending therefrom defining a second blade plane; and   a second plurality of blades, each blade of the second plurality of blades being operatively connected to a respective second hub arm of the plurality of second hub arms to rotate around the central axis with the rotor in the same direction of rotation with the hub and the first plurality of blades.   
     
     
         5 . A HVLS fan in accordance with  claim 1 , further comprising:
 wherein respective upper and lower surfaces of the hub arms and respective upper and lower surfaces of the central hub lie in respective common planes that are parallel to one another;   wherein each blade further comprises an angle block having a mounting surface configured parallel to a desired direction of rotation for the blade; and   wherein each blade is positioned at a predetermined angle of attack with respect to the direction of rotation when the mounting surface of the angle block is positioned parallel to the common planes of the hub and hub arms.   
     
     
         6 . A HVLS fan in accordance with  claim 5 , further comprising:
 a plurality of stiffening bars;   wherein a first end of a respective stiffening bar is connected to each respective hub arm of the central hub using first discrete fasteners; and   wherein a second end of the respective stiffening bar is connected to the mounting surface of the angle block of each respective blade using discrete fasteners.   
     
     
         7 . A HVLS fan in accordance with  claim 5 , wherein the blades have a cross sectional profile of an undercambered airfoil. 
     
     
         8 . A HVLS fan in accordance with  claim 1 , wherein each blade further comprises:
 a serrated pattern formed on a portion of the trailing edge;   the serrated pattern including a plurality of chevrons; and   wherein each chevron of the plurality of chevrons has a respective chevron length measured in the direction of airflow and a respective chevron width wherein measured perpendicular to the direction of airflow.   
     
     
         9 . A HVLS fan in accordance with  claim 8 , wherein the respective chevron lengths of respective chevrons in the serrated pattern decreases as the respective chevrons get farther from the root end of the blade. 
     
     
         10 . A HVLS fan in accordance with  claim 8 , wherein the respective chevron widths of respective chevrons in the serrated pattern decreases as the respective chevrons get farther from the root end of the blade. 
     
     
         11 . A HVLS fan in accordance with  claim 1 , further comprising:
 a plurality of vortex generators disposed on the upper surface of each blade; and   wherein the vortex generators are positioned proximate to the leading edge of the blade.   
     
     
         12 . A HVLS fan in accordance with  claim 11 , further comprising:
 a plurality of dimples formed in the upper surface of each blade; and   wherein the dimples are positioned in a region of the blade encompassing the vortex generators.   
     
     
         13 . A high volume, low speed (HVLS) fan for air circulation having an overall diameter within a range from 7 feet to 30 feet, the HVLS fan comprising:
 a motor assembly including a stator and a rotor, the rotor being configured to rotate when power is supplied;   a hub operably connected to the rotor to rotate around a central axis in a direction of rotation when the rotor rotates, the hub including a central hub body and a plurality of hub arms extending therefrom; and   a plurality of blades, each blade of the plurality of blades being operatively connected to a respective hub arm of the plurality of hub arms to rotate around the central axis in the direction of rotation;   wherein each blade includes a root end disposed adjacent the hub; a leading edge facing the direction of rotation, a tip end disposed distal from the hub, and a trailing edge facing away from the direction of rotation; and   wherein each blade is formed of a molded plastic polymer material including non-polymer reinforcing materials encapsulated in a polymer matrix.   
     
     
         14 . A HVLS fan in accordance with  claim 13 , wherein each blade has a non-uniform cross section viewed at different points along a span line extending through the blade perpendicular to the direction of rotation. 
     
     
         15 . A HVLS fan in accordance with  claim 13 , wherein the polymer matrix of the molded plastic polymer material is a polyamide and the non-polymer reinforcing material is glass fibers. 
     
     
         16 . A HVLS fan in accordance with  claim 13 , further comprising:
 a plurality of stiffening bars;   wherein a first end of a respective stiffening bar is connected to each respective hub arm of the central hub using first discrete fasteners;   wherein a second end of the respective stiffening bar is connected to the mounting surface of each respective blade using discrete fasteners; and   wherein the attached stiffening bar extends along the blade for distance in the range of 20 percent to 40 percent of the total length of the blade.   
     
     
         17 . A HVLS fan in accordance with  claim 16 , wherein each blade further comprises:
 an angle block formed on the upper surface of the respective blade and having an upper portion defining the mounting surface for the stiffening bar;   wherein the angle block is configured such that when the mounting surface is positioned against the stiffening bar, the blade has a predetermined angle of attack with respect to the direction of rotation for the blade.   
     
     
         18 . A HVLS fan in accordance with  claim 13 , wherein each molded plastic blade further comprises:
 a first portion including at least the root end of the blade and a first connector;   a second portion including at least the tip end of the blade and a second connector; and   wherein the first connector of the first portion is selectively attachable to the second connector of the second portion to form a complete blade.   
     
     
         19 . A blade for a high volume, low speed (HVLS) fan for air circulation, the HVLS fan including a rotatable hub operably connected to a motor assembly for rotating the hub around a central axis in a direction of rotation, the blade comprising:
 a blade body adapted for connection to a hub of a HVLS fan to rotate with the hub around a central axis in a direction of rotation;   wherein the blade body includes a root end disposed adjacent the hub; a leading edge facing the direction of rotation, a tip end disposed distal from the hub, and a trailing edge facing away from the direction of rotation;   wherein the blade body is configured to include:
 a relatively larger chord portion including a maximum chord of the blade disposed proximate to the root end; 
 a swept-back portion disposed proximate to the tip end, and 
 a relatively smaller chord portion including a minimum chord of the blade disposed therebetween; and 
 wherein the rearmost extent of the swept-back portion is behind the rearmost extent of the relatively smaller chord portion 
   
     
     
         20 . A blade for a HVLS fan in accordance with  claim 19 , wherein the blade body further comprises:
 a serrated pattern formed on a portion of the trailing edge;   the serrated pattern including a plurality of chevrons; and   wherein each chevron of the plurality of chevrons has a respective chevron length measured in the direction of airflow and a respective chevron width wherein measured perpendicular to the direction of airflow.   
     
     
         21 . A blade for a HVLS fan in accordance with  claim 19 , wherein the blade body further comprises:
 a plurality of vortex generators disposed on the upper surface of each blade; and   wherein the vortex generators are positioned proximate to the leading edge of the blade.   
     
     
         22 . A coaxial contra-rotating hub assembly (CCRHA) for a suspended fan, the CCRHA adapted for connection to a motor assembly including a rotor and a stator suspended by a downrod, the CCRHA comprising:
 a lower hub configured for operable attachment to a rotor of a motor assembly to rotate with the rotor relative to a stator and a downrod;   an upper hub configured to rotate freely about the downrod; and   a torque-divider assembly disposed between the upper hub and the lower hub such that an upper portion of the torque-divider assembly engages the upper hub, a lower portion of the torque-divider assembly engages the lower hub and a central portion of the torque-divider assembly engages at least one of the stator and the downrod to prevent relative motion between the central portion and the at least one of the stator and the downrod; and
 wherein rotation of the rotor in a first rotation direction causes the attached lower hub to rotate in the first rotation direction; 
 wherein rotation of the lower hub in the first rotation direction causes the engaged lower portion of the torque-divider assembly to move in a first motion direction; 
 wherein movement of the of the lower portion of the torque-divider assembly in the first motion direction causes the upper portion of the torque-divider assembly to move in a second motion direction opposite to the first motion direction; 
 wherein movement of the upper portion of the torque-divider assembly in the second motion direction causes the engaged upper hub to rotate in a second rotation direction opposite to the first rotation direction. 
   
     
     
         23 . A CCRHA for a suspended fan in accordance with  claim 22 , wherein the torque-divider assembly further comprises:
 a roller support operably attached to the stator of the motor assembly to prevent rotation relative to the stator; and   a plurality of rollers rotatably mounted on the roller support;   wherein each roller of the plurality of rollers is mounted on a respective portion of the roller support such that a respective axis of rotation for the respective roller extends perpendicularly from an axis of rotation for the upper hub and the lower hub;   wherein a respective lower portion of each respective roller frictionally engages the upper surface of the lower hub; and   wherein a respective upper portion of each respective roller frictionally engages the lower surface of the upper hub.