US20240263640A1

US20240263640A1 - High volume low speed air-circulation fan

Info

Publication number: US20240263640A1
Application number: US18/361,638
Authority: US
Inventors: Phillip S. Eggers
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-02-02
Filing date: 2023-07-28
Publication date: 2024-08-08
Also published as: WO2024162987A1

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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Design Application No. 29/883,744, filed Feb. 2, 2023, entitled BLADE FOR AN INDUSTRIAL AIR-CIRCULATION FAN (Atty. Docket No. EGRS60-35647), the contents of which are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The following disclosure relates to ceiling fans for air circulation, and specifically to high volume, low speed (HVLS) ceiling fans. In particular, configurations suitable for fans having an overall diameter of seven feet or greater are disclosed.

BACKGROUND

The HVLS (High Volume Low Speed) industrial fan market serves a need required by operators of large buildings where heat is a concern for product and employee needs. In 1998, the University of California—Riverside, hired a company to design a large fan for dairy cattle cooling. The resulting design is still commonly used by dozens of HVLS fan companies worldwide.
The conventional HVLS design includes a powerful motor which normally runs on high voltage like 220V/440V service, a heavy gearbox to slow the blade RPM, a complex hub to connect the blades to the gearbox, and a number of blades made from extruded aluminum. The typical weight of this design is around 400 lbs., which requires engineering studies on the ceiling structure's ability to support the weight. In some cases, guy wires are required to minimize wobble when running. Further, the 440V service can be an issue as many buildings do not offer this high voltage electrical service.
HVLS blade design has really not changed over the years, mostly due to the constraints of an extruded aluminum manufacturing process. An extruded blade has a constant profile that cannot take advantage of different speeds presented along the length of the blade. While the RPM is constant along the blade, the airspeed varies from slow at the inside to fast at the outer tip. Efficient blades have a longer chord and more aggressive pitch at the inside, and shorter chords and flatter pitch at the outer tip. The use of an extruded aluminum blade on most HVLS fans does not allow a variable pitch or chord length, making these blades very inefficient and undesirable. To counter this inherent restriction, many HVLS fan companies resort to custom winglets for marketing purposes, or simply increasing the length of the blades, now up to 30 feet in diameter. The outdated design is ripe for improvement.

SUMMARY

The current disclosure describes a new HVLS fan design, which uses injection molding rather than extruded aluminum for the blade construction. Injection molding allows the new design to incorporate modern airflow technology to improve the effectiveness of the fan, the efficiency of the fan, and the cost of the fan.
The new HVLS fan designs disclosed herein can include the features described below:
Ceiling Mount: In some embodiments, a HVLS ceiling fan system includes a simple ceiling mount that attaches to the ceiling in a robust manner, and then attaches to the down rod with a single bolt which allows the fan to level itself with gravity, if hanging from a sloped ceiling.
Motor: In some embodiments, the HVLS ceiling fan system includes a motor that is a state of the art DC motor which utilizes a Variable Frequency Drive (VFD) controller to control the speed and direction of the fan.
Hub: In some embodiments, the HVLS ceiling fan system includes a hub that attaches the blades to the motor and is a custom design for this new fan. In one embodiment, the hub is circular with 3 arms to attach to the blades. The hub has holes in the outer perimeter which allow through-bolts to attach it securely to the motor. Each of the 3 arms have a series of holes to attach each blade securely to the hub. There are no moving parts or complex angles on the hub.
Blades: In some embodiments, the HVLS ceiling fan system includes blades made using a plastic injection molding process, which allows for many cutting-edge airflow shapes and features.
In some embodiments, the blade includes a blade attach area that allows for a long arm to connect directly to the hub. This long arm will also provide some strength to the blade as it runs along the blade length.
In some embodiments, the blade includes a blade attach pad configured to be angled to provide the desired pitch of the blade, rather than twisting the hub arm which is expensive and time consuming.
In some embodiments, the leading edge of the blade is swept along the entire radius for efficiency, noise reduction, and improved air separation.
In some embodiments, the wingtip of the blade is a “raked wingtip” which rises from the balance of the blade and is aggressively swept to the rear, with an outward pitch. This feature throws air slightly outward and downward to further expand the effective air column and the coverage area. This expands the air column horizontally so air does not simply blow beneath the fan, but also outward slightly.
In some embodiments, the inner edge of the blade is gated on the underside with a raised border which prevents air from flowing off the inner edge of the blade onto the hub area.
In some embodiments, the top of the leading edge has a series of Vortex Generators (VG's) which help to improve airflow over the top of the blade by means of reducing airflow separation. Each set of VG's work to disrupt the airflow flowing over the top of the blade, which actually makes the air move in a more connected streamlined manner over the blade and then downward to provide more airflow under the blade.
The trailing edge of the blade has a series of graduated serrations to reduce noise from the airflow. The serrations start at the inner part of the blade with a larger tooth, then are reduced to a smaller size about mid blade, then to an even smaller size moving outward. Serrations have been proven to reduce the decibels on blades, including large wind turbine blades, by diffusing the air reattachment point, which is the area of highest airflow noise generation. This graduated-size configuration of serration is novel for use in high volume low speed fans. This blade design is expected to minimize the airflow reduction resulting from a reduced chord due to the serrations, and to address the higher speed of the outer portion of the blade with smaller serrations. An example from nature is instructive: Compare a pigeon's loud wing noise to that of an owl. The pigeon wing flaps loudly in flight, while an owl wing is perfectly quiet, because it is a predator which needs to sneak up on its prey. The owl's wing edges include a secondary, smaller set of feathers which act as a serration for the wing.
The overall cupping of the blade is a complex concave design with a reduced chord as it extends outward to the raked wingtip and is then angled slightly upward as discussed previously.
The improved efficiency of the blade allows for a shorter blade with comparable airflow to a much longer conventional extruded aluminum blade. In one embodiment, a three-blade setup has been proven to be an efficient number of blades for the HVLS fan. This reduces weight which makes installation easier, eliminates the guy wires, reduces cost with less material, reduces noise, minimizes electrical use, and reduces shipping cost. In some other embodiments, five-bladed and six-bladed setups are provided.
The balancing tabs are molded into the blade near the outer edge, which allow for precise balancing of each blade for smoother operation. The tabs can be sanded to remove material and weight for each blade.
In some embodiments, the blades for the HVLS fan are formed from a plastic material. In some embodiments, the plastic material used on the blade will include up to 20% of fiberglass to strengthen the blade.
In one embodiment, the HSLV fan has a blade diameter of 10 feet (120 inches), which requires blades of 48 inches each. Other sizes, smaller and larger, can also be used in other embodiments.
In one aspect thereof, a high volume, low speed (HVLS) fan for air circulation having an overall diameter within a range from 7 feet to 30 feet comprises a motor assembly including a stator and a rotor, the rotor being configured to rotate when power is supplied. A hub is 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. A plurality of blades is provided, 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. 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. Each blade further 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. The rearmost extent of the swept-back portion is behind the rearmost extent of the relatively smaller chord portion.
In one embodiment, 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.
In another embodiment, 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.
In yet another embodiment, the hub is mounted to a first side of the rotor and the hub arms extending therefrom define a first blade plane. A second hub is 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. A second plurality of blades, each blade of the second plurality of blades is operatively connected to a respective second hub arm of the plurality of second hub arms to rotate around the central axis in the same direction of rotation with the hub and the first plurality of blades.
In still another embodiment, 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. Each blade further comprises an angle block having a mounting surface configured parallel to a desired direction of rotation for the blade. 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.
In a further embodiment, a plurality of stiffening bars are provided. A first end of a respective stiffening bar is connected to each respective hub arm of the central hub using first discrete fasteners. 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.
In a still further embodiment, the blades have a cross sectional profile of an undercambered airfoil.
In another embodiment, each blade further comprises a serrated pattern formed on a portion of the trailing edge. The serrated pattern includes a plurality of chevrons. 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.
In yet another embodiment, 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.
In still another embodiment, 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.
In a further embodiment, a plurality of vortex generators are disposed on the upper surface of each blade. The vortex generators are positioned proximate to the leading edge of the blade.
In a still further embodiment, a plurality of dimples are formed in the upper surface of each blade. The dimples are positioned in a region of the blade encompassing the vortex generators.
In still another aspect, a high volume, low speed (HVLS) fan for air circulation having an overall diameter within a range from 7 feet to 30 feet comprise a motor assembly including a stator and a rotor, the rotor being configured to rotate when power is supplied. A hub is 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. A plurality of blades is provided, 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. 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. Each blade is formed of a molded plastic polymer material including non-polymer reinforcing materials encapsulated in a polymer matrix.
In one embodiment, 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.
In another embodiment, the polymer matrix of the molded plastic polymer material is a polyamide and the non-polymer reinforcing material is glass fibers.
In yet another embodiment, plurality of stiffening bars are provided. A first end of a respective stiffening bar is connected to each respective hub arm of the central hub using first discrete fasteners. A second end of the respective stiffening bar is connected to the mounting surface of each respective blade using discrete fasteners. The attached respective stiffening bar extends along the blade for distance in the range of 20 percent to 40 percent of the total length of the blade.
In still another embodiment, an angle block is formed on the upper surface of the respective blade and having an upper portion defining the mounting surface for the stiffening bar. 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.
In a further embodiment, each molded plastic blade further comprises a first portion including at least the root end of the blade and a first connector and a second portion including at least the tip end of the blade and a second connector. The first connector of the first portion is selectively attachable to the second connector of the second portion to form a complete blade.
In still another aspect a blade is provided 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 comprises 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. 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. 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. The rearmost extent of the swept-back portion is behind the rearmost extent of the relatively smaller chord portion.
In one embodiment, the blade body 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.
In another embodiment, the blade body 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.
In yet another embodiment, the blade body is configured to define an angle block having a mounting surface configured to be parallel to a desired direction of rotation for the blade.
In still another embodiment the mounting surface of the angle block is adapted for connection to a stiffening bar attached to the hub to control the angle of attack of the blade relative to the direction of rotation.
In one embodiment, the blade body further comprises a serrated pattern formed on a portion of the trailing edge, the serrated pattern including a plurality of chevrons. 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.
In another embodiment, the respective chevron lengths of respective chevrons in the serrated pattern decreases as the respective chevrons get farther from the root end.
In still another embodiment, the respective chevron widths of respective chevrons in the serrated pattern decreases as the respective chevrons get farther from the root end.
In yet another embodiment, the blade body further comprises a plurality of vortex generators disposed on an upper surface. The vortex generators are positioned proximate to the leading edge.
In a further embodiment, the blade body further comprises a plurality of dimples formed in the upper surface. The dimples are positioned in a region of the blade encompassing the vortex generators.
In a further aspect, a coaxial contra-rotating hub assembly (CCRHA) is provided for a suspended fan, the CCRHA being adapted for connection to a motor assembly including a rotor and a stator suspended by a downrod. The CCRHA comprises 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 is configured to rotate freely about the downrod. A torque-divider assembly is 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. Rotation of the rotor in a first rotation direction causes the attached lower hub to rotate in the first rotation direction. 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. 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. 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.
In one embodiment, 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. A plurality of rollers is rotatably mounted on the roller support. 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. A respective lower portion of each respective roller frictionally engages the upper surface of the lower hub and a respective upper portion of each respective roller frictionally engages the lower surface of the upper hub.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to the following description taken in conjunction with the accompanying Drawings in which:

FIG. 1 is a bottom view of an industrial air circulation fan in accordance with one embodiment having three blades configured in a single blade plane;

FIG. 2 is a bottom perspective view of an industrial air circulation fan in accordance with another embodiment having five blades configured in a single blade plane;

FIG. 3 is a bottom perspective view of an industrial air circulation fan in accordance with another embodiment having six blades configured in two blade planes;

FIG. 4A is a perspective view of a fan motor assembly with three-bladed hub in accordance with another aspect;

FIGS. 4B-4D are simplified schematic side views of industrial air circulation fans illustrating various configurations for hubs and blade planes, namely FIG. 4B shows a fan having a top mounted hub providing a blade configuration defining a single blade plane, FIG. 4C shows another fan having a bottom mounted hub providing a blade configuration defining a single blade plane, and FIG. 4D shows still another fan having dual top and bottom mounted hubs providing a blade configuration defining dual blade planes;

FIG. 5 is a top perspective view of a blade for an industrial air-circulation fan in accordance with another aspect;

FIG. 6 is a bottom perspective view thereof;

FIG. 7 is a tip end view thereof;

FIG. 8 is a root end view thereof;

FIG. 9 is a leading edge view thereof;

FIG. 10 is a trailing edge view thereof;

FIG. 11 is a top view thereof;

FIG. 12 is a bottom view thereof;

FIGS. 13A-13D show airfoil profiles of the blade for an industrial air-circulation fan of FIG. 11 accordance with another aspect, namely, FIG. 13A shows the root end profile, FIG. 13B shows the cross-sectional profile viewed along line 13B-13B of FIG. 11 , FIG. 13C shows the cross-sectional profile viewed along line 13C-13C of FIG. 11 and FIG. 13D shows the cross-sectional profile viewed along line 13D-13D of FIG. 11 ;

FIG. 14 is an enlarged bottom perspective view (with some outer portions omitted for purposes of illustration) of the five bladed embodiment of the industrial air circulation fan illustrating details of the lower structure;

FIG. 15 is an enlarged top perspective view (with some outer portions omitted for purposes of illustration) of the five bladed embodiment illustrating details of the upper structure;

FIG. 16 is a top view of a blade for an industrial air-circulation fan in accordance with an alternative embodiment; and

FIG. 17 shows another blade for an industrial air-circulation fan in accordance with yet another alternative embodiment; and

FIGS. 18A and 18B are, respectively, perspective and cross-sectional views of a coaxial contra-rotating hub assembly for an industrial air-circulation fan in accordance with yet another aspect.

DETAILED DESCRIPTION

Referring now to the drawings, wherein like reference numbers are used herein to designate like elements throughout, the various views and embodiments of a high volume low speed air-circulation fan are illustrated and described, and other possible embodiments are described. The figures are not necessarily drawn to scale, and in some instances the drawings have been exaggerated and/or simplified in places for illustrative purposes only. One of ordinary skill in the art will appreciate the many possible applications and variations based on the following examples of possible embodiments.
Referring first to FIG. 1 , there is illustrated a HVLS air-circulation fan 100 in accordance with one embodiment. The fan 100 can be configured in various sizes, but is particularly suited for HVLS fans having an overall diameter in the range of 7 feet to 30 feet, and especially those having an overall diameter in the range of 10 feet to 30 feet. The fan 100 includes a central hub 102 mounted on a motor assembly 104, which can be suspended from the ceiling of a structure using a downrod 106 (e.g., FIG. 2 ). Three fan blades 108 are connected to the hub 102 and configured to rotate (as denoted by arrow 109) in a single blade plane (i.e., plane of rotation). Each blade 108 has a blade body with a root end 110, which is disposed adjacent the hub 102, a leading edge 112, which faces the direction of rotation, a tip end 114 disposed distal from the hub, and a trailing edge 116, which faces away from the direction of rotation. As further described herein, each blade 108 can include a relatively larger chord portion 118 disposed proximate to the root end 110, a swept-back (i.e., “raked”) portion 120 disposed proximate to the tip end 116, and relatively smaller chord section 122 disposed therebetween. The trailing edge 116 of the blade 108 can further feature a serrated pattern 124 formed of notches, waves or chevron-shaped projections 126 (i.e., “teeth” or “chevrons”). In most embodiments, the blades 108 include both the swept-back portion 120 and the serrated pattern 124 on the trailing edge 116. However, in other embodiments, the blades 108 include the swept-back portion 120 but do not include the serrated pattern 124 on the trailing edge 116. In still other embodiments, the blades 108 include the serrated pattern 124 on the trailing edge 116 but do not include the swept-back portion 120.
In some embodiments, the blades 108 of the HVLS fan 100 can be made of molded plastic, which is unconventional for HVLS fans having blades with lengths ranging from 4 to 14 feet to provide having an overall diameter in the range of 7 feet to 30 feet due, e.g., to the comparatively high cost for molds and tooling needed for such large blade components. In the context of this disclosure, the term “made of molded plastic” means that the body of the blade 108 is primarily plastic, is not substantially covered by an external metal or metal alloy shell and does not contain an internal metal or metal alloy frame running completely therethrough. The molded plastic material for the bladed 108 can include, but is not limited to, polyamide (e.g., nylon), polycarbonate (PC), polyethylene (PE), polypropylene (PP), or acrylonitrile-butadiene-styrene (ABS). In some further embodiments, the molded plastic of the blades can further include non-plastic reinforcing fibers distributed in the plastic including, but not limited to, glass, fiberglass or carbon fiber. In some further embodiments, the molded plastic of the blades can further include hollow glass microspheres (“microballoons”) distributed in the plastic to reduce the weight and density of the blades. The processes that can be used for molding the molded plastic blades 108 include, but are not limited to, injection molding, roto-molding, vacuum forming and thermo-forming. In still other embodiments, the blades 108 are made from “laid up” composite material such as fiberglass/epoxy composite material or carbon-fiber/epoxy composite material where the matrix material is one of a polyester, a vinyl ester or epoxy. The use of such aforesaid composite materials is unconventional for HVLS fans having an overall diameter in the range of 7 feet to 30 feet, and especially those having an overall diameter in the range of 10 feet to 30 feet due, e.g., to the relatively high cost for tooling such large blade components and large facilities needed for vacuum and/or heat curing large elements of the blades. The processes that can be used for molding the laid-up composite blades 108 include, but are not limited to, hand lay up, vacuum bag molding and sandwich construction, i.e., wherein relatively thin, high-strength plastic skins are adhered to or formed around a lightweight plastic core material such as honeycomb, foamed plastic, etc. Whether using molded plastic or laid-up composite plastic, in some embodiments the blades 108 are formed in a single molding from root 110 to tip 114, whereas in other embodiments each blade can be formed as multiple sections that are joined together.
As further described herein, the relatively larger (i.e., wider) chord portion 118 of the blade 108 operates in an area of the blade's sweep close to the center of rotation where the linear speed of the fan blade (i.e., equal to the angular speed multiplied by the distance from the center of rotation) is relatively low. Because of the relatively wide blade chord, the portion 118 can produce sufficient air movement in the area below the center part of the fan 100 even with a relatively low linear speed. On the other hand, the relatively smaller (i.e., narrower) chord portion 122 of the blade 108 operates in an area of the blade's sweep further away from the center of rotation where the linear speed of the fan blade is relatively higher. Because of this relatively higher linear speed, the portion 122 can produce sufficient air movement directly below it even with a narrower chord. Additionally, the reduced chord portion 122 of the blade has a lower weight per unit width compared to the larger chord portion 118, which is important to reduce overall weight of the blade 108 while still providing sufficient air movement. The swept-back portion 120 of the blade 108 has a raked leading edge 128 and a rear-sweeping trailing edge 130 that, taken together, result in a progressively smaller chord as the portion extends towards the tip 114. Additionally, the swept back portion 120 can have an outward pitch that pushes the air slightly outward as well as downward to further expand the effective air column below the fan 100 (i.e., the moving air column below the fan expands to a diameter greater than that of the fan itself).
As further described herein, the serrated pattern 124 on the trailing edge 116 of the blade 108 reduces the noise generated by airflow over the trailing edge. The airflow direction across the rotating blade is generally opposite to the direction of rotation. It is known that straight-edged conventional blades can produce a low-frequency “whoop-whoop-whoop” sound as the entire airflow reattaches (i.e., from the top surface and the bottom surface) in a single line along the blade's trailing edge. In contrast, the serrated pattern 124 on the trailing edge 116 of the blade 108 causes the airflow to reattach at different parts of each chevron 126 at different times, thus mixing the air over an extended interval and thereby reducing the blade's sound signature. Additionally, in some embodiments, the chevrons 126 of the serrated pattern 124 are graduated in size along the trailing edge 116, e.g., with the largest/deepest chevrons being disposed proximate to the root 110 and the smallest/shallowest chevrons being disposed proximate to the tip 114.
In the illustrated embodiment of FIG. 1 , the motor assembly 104 is a direct-drive motor wherein the axis of rotation of the motor's rotor is coaxial with the axis of rotation of the fan hub 102 such that the hub can be attached directly to the rotor. In other embodiments (not shown), the motor assembly and fan hub can be physically separated but operatively connected using an indirect drive including, but not limited to, a gearbox, transmission, belt drive or pulley drive, that causes the hub to rotate when the rotor rotates. The remaining aspects of the HVLS fan 100 remain substantially identical regardless of whether direct drive or indirect drive is used between the motor and the hub.
Referring now to FIG. 2 , there is illustrated a HVLS air-circulation fan 200 in accordance with another embodiment. The fan 200 can be configured in various sizes, but is particularly suited for HVLS fans having an overall diameter in the range of 7 feet to 30 feet, and especially those having an overall diameter in the range of 10 feet to 30 feet. The fan 200 includes a central hub 202 mounted on a motor assembly 104, which can be suspended from the ceiling of a structure using a downrod 106. Five fan blades 108 are connected to the hub 202 and configured to rotate as denoted by arrow 109 in a single blade plane. The fan blades 108 of the five-bladed fan 200 can be substantially similar to the fan blades of the three-bladed version 100.
In the illustrated embodiment of FIG. 2 , the motor assembly 104 is a direct-drive motor wherein the hub 202 can be attached directly to the rotor. In other embodiments (not shown), the motor assembly and fan hub can be physically separated but operatively connected using an indirect drive that causes the hub to rotate when the rotor rotates. The remaining aspects of the HVLS fan 200 remain substantially identical regardless of whether direct drive or indirect drive is used between the motor and the hub.
Referring now to FIG. 3 , there is illustrated a HVLS air-circulation fan 300 in accordance with another embodiment. The fan 300 can be configured in various sizes, but is particularly suited for HVLS fans having an overall diameter in the range of 7 feet to 30 feet, and especially those having an overall diameter in the range of 10 feet to 30 feet. The fan 300 includes an upper hub 302 mounted on the top of a motor assembly 104 and a lower hub 303 mounted on the bottom of the motor assembly. Three fan blades 108″ are connected to the lower hub 302 and configured to rotate as denoted by arrow 109 in a first blade plane. Three fan blades 108′ are connected to the upper hub 303 and configured to rotate as denoted by arrow 109 in a second blade plane. In other words, all six fan blades 108′ and 108″ rotate in the same direction, however, the blades 108″ rotate in a blade plane that is spaced below the blade plane of blades 108′. The configuration of blades 108′ and 108″ in dual blade planes can improve the airflow provided by the fan 300 by initiating the downward air movement with the blades 108′ of the upper hub 303 and then further accelerating the air using the blades 108″ of the lower hub 302. Additionally, using dual hubs 302 and 303 can simplify providing HVLS fans of different volume ratings. It will be appreciated that the three-bladed hubs 302 and 303 of fan 300 are each similar to the three-bladed hub 102 of the fan 100. Thus, a low volume version of the fan (e.g., fan 100) can be configured with only one hub and a high volume version of the fan (e.g., fan 300) can be configured with dual hubs, wherein the individual hubs 102, 302 and blades 108 of the two configurations are the same.
In the illustrated embodiment of FIG. 3 , the motor assembly 104 is a direct-drive motor wherein the hub 302 can be attached directly to the rotor. In other embodiments (not shown), the motor assembly and fan hub can be physically separated but operatively connected using an indirect drive that causes the hub to rotate when the rotor rotates. The remaining aspects of the HVLS fan 300 remain substantially identical regardless of whether direct drive or indirect drive is used between the motor and the hub
While three-, five- and six-bladed fans are illustrated herein, it will be appreciated that HVLS fans as described herein can be made in configurations with different number of fan blades, including two, four, eight. Additionally, it will be appreciated that HVLS fans as described herein can be configured with top-mounted blade planes, bottom-mounted blade planes and dual (i.e., top and bottom) blade planes.
Referring now to FIGS. 4A-4D, additional details of the HVLS fans are provided. These HVLS fans can be configured in various sizes; however, the features and constructions aspects described herein are particularly suited for HVLS fans having an overall diameter in the range of 7 feet to 30 feet. It will be appreciated that FIGS. 4A-4D are illustrated in schematic form such that blades 108 are shown with very simplified contours rather than in their actual shape. Referring specifically to FIG. 4A, an exploded diagram illustrates the interconnection of elements in the central portion of a HVLS fan 400. Motor assembly 104 can include a stationary central portion known as a stator 404 mounted to the downrod 106. The downrod 106 is configured for mounting to the ceiling of a structure and is typically hollow to provide a central passage for running wires to the stator 404 for electrical power. The motor assembly 104 further includes a movable portion known as a rotor 406 that is rotatably mounted relative to the stator 404, and configured to rotate around a central axis when electrical power is supplied to the fan. In some embodiments the electrical power for rotation is supplied to the stator 404, in other embodiments the electrical power is supplied to the rotor 406, and in still other embodiments the electrical power is supplied to both stator and rotor. The rotor 406 is typically annular in configuration such that the stator 404 can be positioned within the center of the rotor. In some embodiments, the motor assembly 104 comprises a direct current (DC) motor powered by a variable frequency drive (VFD). In some embodiments, the motor assembly is a DC brushless-type motor that does not require commutators or other direct electrical connections between the stator 404 and the rotor 406. In other embodiments, the motor assembly 104 can be an alternating current (AC) motor. Regardless of whether it comprises a DC or AC motor, the motor assembly 104 can be direct drive or include a gearbox. In still other embodiments (not shown), the motor assembly and fan hub can be physically separated but operatively connected using an indirect drive that causes the hub to rotate when the rotor rotates. In such embodiments, the remaining aspects of the HVLS fan 400 remain substantially identical regardless of whether direct drive or indirect drive is used between the motor and the hub
Referring still to FIG. 4A, a hub 102 can be mounted directly to the rotor 406 using fasteners 408 or other attachments. The hub 102 includes a hub body 410 and a plurality of hub arms 412 extending therefrom, typically one hub arm for each blade 108. In some embodiments, the hub body 410 and hub arms 412 are formed as a single unitary article punched from a flat plate of material. In some embodiments, the top and bottom surfaces of the hub body 410 define a pair of planes and the hub arms 412 lie entirely between such planes. Since the hub 102 must support the weight of the attached blades 108, the hub is often formed of steel, steel alloys or other high strength materials. Significant manufacturing expense is thus avoided by making the hub body 410 and hub arms 412 of the hub 102 as a single flat punching as compared to conventional fans that use separately formed hub arms that must be fastened to the hub body or hub arms that must be twisted to an angle after punching.
Referring still to FIG. 4A, the blades 108 can be connected to the hub arms 412 using stiffening arms 414 connected to between the hub arms 412 and the blade. For purposes of simplicity, FIG. 4A shows the attachment of only a single blade 108 to the hub 102, but it will be appreciated that the remaining blades are attached in similar fashion. The stiffening arms 414 can be connected to the hub arms 412 using fasteners 416 such as bolts or screws. The blades 108 can be connected to the stiffening arm 414 using fasteners 418 such as bolts or screws. Since the individual blades 108 of a 10-foot diameter HVLS fan can be 4 feet in length (or more), and the individual blades of a 30-foot diameter HVLS fan can be about 14 feet in length, providing the stiffening arms 414 as separately attachable components allows the large HVLS fans to be shipped in smaller packaging and assembled on site. Further, since the stiffening arms 414 are separate elements from the hub arms 412, the length of the stiffening arms can be varied to accommodate different sized fan blades 108 while using the same hub 102. In addition, the material of the stiffening arms 414 can be a different material from the material of the hub 102 and hub arms 412. For example, in one embodiment, the hub 102 is made of steel and the stiffening arms 414 are made of steel. In another embodiment, the hub 102 is made of steel and the stiffening arms 414 are made of aluminum. In another embodiment, the hub 102 is made of steel and the stiffening arms 414 are made of carbon fiber composite material. It will be appreciated that the stiffening arms 414 do not simply connect the blade 108 to the hub 102, but also serve to provide structural strength to the blades to allow the blades to be as light as possible. For this reason, the stiffening arms 414 can extend along a significant span of the blades 108. The stiffening provided by stiffening arms 414 is particularly important when the blades 108 are made of lightweight molded plastic, laid-up composites or other lightweight material, and especially when the HVLS fans are configured with an overall diameter in the range from 7 feet to 30 feet.
Referring still to FIG. 4A, in some embodiments, the blades 108 are configured to define an angle block 420 at the mounting surface for the stiffening arms 414. In some embodiments, the angle block 420 is an integral molded-in portion of the molded plastic blade 108 to simplify construction. In some embodiments, the angle block 420 is a separate element from the blade 108 that can be made of plastic, metal or other material and captured between the stiffening arm 414 and the blade 408 by the fasteners 418. The angle block 420 allows the blade 108 to have an angle of attack (denoted “a”) between the direction of rotation 422 and the chord line 424 while still using a flat hub 102, flat blade arms 412 and flat stiffening arms 414. In this way, manufacturing and assembly of the HVLS fan 400 is greatly simplified, because the hub 102, hub arms 412 and stiffening arms 414 can all be formed of flat plate, and the angle blocks 420 allow the blades 108 to attach against the flat surface of the stiffening arm 414 while still providing a predetermined angle of attack a.
Referring now to FIG. 4B, there is shown a simplified schematic side view of industrial air circulation fan 430 similar to the fan 400 shown in FIG. 4A. It will be appreciated that some details of the schematic illustration in FIG. 4A (e.g., the number of fasteners) have been further simplified in FIGS. 4B-4D. The fan 430 has a top-mounted hub 102, i.e., the hub body 410 is mounted to the rotor 406 on the top side of the motor assembly 104, e.g., using fasteners 408. The stiffening arms 414 can be attached to the hub arms 412, e.g., using the fasteners 416, and the blades 108 can be attached to the stiffening plates 414, e.g., using fasteners 418, all as previously described. When rotating, the blades 108 define a blade plane (denoted “BP1” in FIG. 4B) above the motor assembly 104.
Referring now to FIG. 4C, there is shown a simplified schematic side view of another industrial air circulation fan 450 similar to the fan 400 shown in FIG. 4A. The fan 450 has a bottom-mounted hub 102, i.e., the hub body 410 is mounted to the rotor 406 on the bottom side of the motor assembly 104, e.g., using fasteners 408. The stiffening arms 414 can be attached to the hub arms 412, e.g., using the fasteners 416, and the blades 108 can be attached to the stiffening plates 414, e.g., using fasteners 418, all as previously described. When rotating, the blades 108 define a blade plane (denoted “BP1” in FIG. 4C) below the motor assembly 104. The selection of using a top-mounted hub as in fan 430 or a bottom-mounted hub as in fan 450 provides additional flexibility for configuring the fans 430, 450 to allow for be considerations such as supporting the weight of the blade assembly versus clearance from the ceiling.
Referring now to FIG. 4D, there is shown a simplified schematic side view of yet another industrial air circulation fan 470 similar to the fan 400 shown in FIG. 4A. The fan 470 has a first hub 102′ that is top-mounted, i.e., the hub body 410′ is mounted to the rotor 406 on the top side of the motor assembly 104, e.g., using fasteners 408′, and a second hub 102″ that is bottom-mounted, i.e., the hub body 410″ is mounted to the bottom side of the same rotor 406, e.g., using fasteners 408″. Respective upper and lower stiffening arms 414′ and 414″ can be attached to the respective upper and lower hub arms 412′ and 412″, e.g., using the fasteners 416 as previously described. Respective upper and lower blades 108′ and 108″ can be attached to the respective upper and lower stiffening arms 414′ and 414″, e.g., using fasteners 418, as previously described. When rotating, the upper blades 108′ define a first blade plane (denoted “BP1” in FIG. 4D) above the motor assembly 104 and the lower blades 108″ define a second blade plane (denoted “BP2” in FIG. 4D) below the motor assembly 104. The selection of using a top-mounted hub as in fan 430 or a bottom-mounted hub as in fan 450 provides additional flexibility for configuring the fans 430, 450 to allow for be considerations such as supporting the weight of the blade assembly versus clearance from the ceiling. It will be appreciated that the blades 108′ in the upper blade plane BP1 and the blades 108″ in the lower blade plan BP2 of the HVLS fan 470 rotate in the same direction.
As previously described, the configuration of a HVLS fan 470 with blades 108′ and 108″ in dual blade planes can improve the airflow provided by the fan by initiating the downward air movement with the blades 108′ of the upper hub 102′ and then further accelerating the air using the blades 108″ of the lower hub 102″. Using dual hubs 102′ and 102″ can simplify providing HVLS fans of different volume ratings. It will be appreciated that in some embodiments the hubs 102′ and 102″ can be identical, and further the blades 108′ and 108″ can be identical. Thus, a low volume version of the fan (e.g., fans 100, 200, 400, 430 and 450) can be configured with only one hub (either top-mounted or bottom-mounted) and a high volume version of the fan (e.g., fans 300 and 470) can be configured with dual hubs, wherein the individual hubs 102′ and 102″ and the individual blades 108′ and 108″ can be identical. In addition, a HVLS fan with dual blade planes allows the fan to have more blades overall while keeping the same spacing between successive in-plane blades to reduce interaction from the in-plane blades. Further, by using more blades spread across dual blade planes, the HVLS fan can have blades of shorter length (i.e., compared to fans with a single blade plane) for a given motor power and airflow volume, and the shorter blades have a lower tip speed, and thus lower tip noise, for the same rotational speed.
Referring now to FIGS. 5-12 and 13A-13D, additional details of the fan blades 108 are described. The blades 108 can be configured in various sizes, but are particularly suited for blades having an individual length of 3 feet to 14 feet, which can be used in HVLS fans having an overall diameter in the range of 7 feet to 30 feet, and especially those having an overall diameter in the range of 10 feet to 30 feet. Each blade 108 has a blade body with a root end 110, which is disposed adjacent the hub 102, a leading edge 112, which faces the direction of rotation 109, a tip end 114 disposed distal from the hub, and a trailing edge 116, which faces away from the direction of rotation. Each blade 108 can include a relatively larger (i.e., longer) chord portion 118 disposed proximate to the root end 110, a swept-back (i.e., “raked”) portion 120 disposed proximate to the tip end 114, and relatively smaller (i.e., shorter) chord section 122 disposed therebetween. It will be appreciated that the “chord” of the blade at any point is an imaginary, superimposed straight line that runs between the leading edge 112 and the trailing edge 116 parallel to the direction of rotation, and the “chord length” at that point is the length of the chord line. As seen in FIG. 5 , the chord 502 of the relatively larger chord portion 118 is longer than the chord 504 of the relatively smaller chord portion 122. The trailing edge 116 of the blade 108 can further feature a serrated pattern 124 formed of chevron-shaped projection 126 (i.e., “teeth” or “chevrons”).
In some embodiments (not shown), the blades 108 may include only the relatively larger chord portion 118 and the swept-back portion 120. In other words, the relatively larger chord portion 118 may extend the entire width of the blade 108 prior to the swept-back portion 120 with the blade chord continually increasing or remaining constant until reaching the swept back portion. Such increasing-chord or constant chord embodiments can include a serrated pattern 126 on the trailing edge 116 and all the other features described herein for the blades 108 except the relatively smaller chord section 122.
As best seen in FIG. 12 (a bottom elevation view of the blade 108), the swept-back portion 120 of the blade 108 has a raked leading edge 128 and a rear-sweeping trailing edge 130. The raked leading edge 128 defines a front sweep angle 506 formed between a span line 508 extending perpendicular to the direction of motion 109 and a front sweep line 514 extending between the leading front sweep point 516 and trailing front sweep point 518. In some embodiments, the front sweep angle 506 of the raked leading edge 128 is at least 45 degrees. In other embodiments, the front sweep angle 506 of the raked leading edge 128 is at least 55 degrees. In still other embodiments, the front sweep angle 506 of the raked leading edge 128 is at least 65 degrees. The rear sweeping trailing edge 130 defines a rear sweep angle 520 formed between the span line 508 and a rear sweep line 522 extending between the leading rear sweep point 524 and trailing rear sweep point 526. In some embodiments, the front sweep angle 506 of the raked leading edge 128 is greater than the rear sweep angle 520 of the trailing edge 130 such that the swept-back portion 120 has a progressively smaller chord moving outward along the span direction 506 toward the tip 114. In other embodiments, the front sweep angle 506 of the raked leading edge 128 is equal to the rear sweep angle 520 of the trailing edge 130 such that the swept-back portion 120 has a constant chord moving outward along the span direction 506 toward the tip 114. Additionally, the swept back portion 120 can have an outward pitch that pushes the air slightly outward as well as downward to further expand the effective air column below the fan 100 so that the moving air column below the fan expands to a diameter greater than the diameter of the fan itself.
In some embodiments, the length of the minimum blade chord 542 in the relatively smaller chord portion 122 can be expressed as a percentage (“Min/Max Chord Percent”) of the maximum blade chord 536 in the relatively larger chord portion 118. In the illustrated embodiment of FIG. 12 , the Min/Max Chord Percent is 59 percent. In other embodiments, the Min/Max Chord Percent of the relatively smaller chord portion 122 is within the range from 50 percent to 70 percent. In still other embodiments, the Min/Max Chord Percent of the relatively smaller chord portion 122 is within the range from 45 percent to 75 percent. Blades 108 configured with the Min/Max Chord Percent in the stated ranges provide improved performance in airflow, noise and/or energy use compared to blades having constant chord.
Referring still particularly to FIG. 12 , in some embodiments, the tip 114 of the swept-back portion 120 can extend behind (i.e., measured in the direction of motion 109) the trailing edge 116 of blade 108. For example, as shown in FIG. 12 , the rearmost (i.e., measured in the direction of motion 109) extent of the larger chord portion 118 is shown by line 530 and the rearmost extent of the swept-back portion 120 is shown by line 532, thus the swept-back portion extends behind the larger chord portion by a distance (denoted 534) (the “maximum chord trailing distance”). In the illustrated example, the maximum chord trailing distance 534 of the swept-back portion 120 is at least 29 percent of the of the blade's maximum chord length (denoted 536). In other embodiments, the maximum chord trailing distance of the swept-back portion 120 can be within the range from 0.5 percent to 40 percent of the blade's maximum chord length.
In some embodiments, the tip 114 of the swept-back portion 120 can extend behind the trailing edge 116 of the blade 108 wherein the frontmost extent of the smallest chord portion is shown by line 538 and the rearmost extent of the swept-back portion 120 is shown by line 532. such that the swept-back portion extends behind narrowest portion of the smaller chord portion by a distance (denoted 540) (the “minimum chord trailing distance”). In the illustrated example, the minimum chord trailing distance 540 of the swept-back portion 120 is at least 117 percent of the of the blade's minimum chord length (denoted 542). In other embodiments, the minimum chord trailing distance of the swept-back portion 120 can be within the range from 75 percent to 135 percent of the blade's minimum chord length.
The swept-back portion 120 of the blade 108 can constitute530 a significant portion of the overall blade. In some embodiments, the length of the raked leading edge 128 is at least 20 percent of the length of the entire leading edge 112 (including the raked leading edge). It will be appreciated that in this case, the length of the raked leading edge 128 and entire leading edge 112 are measured along the actual edges, and not just in the span direction 506. In other embodiments, the length of the raked leading edge 128 is at least 30 percent of the length of the entire leading edge 112 (including the raked leading edge). In still other embodiments, the length of the raked leading edge 128 is at least 35 percent of the length of the entire leading edge 112 (including the raked leading edge). Put another way, in some embodiments, the ratio Rs between the length of the raked leading edge 128 to the length of the remaining leading edge 112 (not including the raked leading edge) has a value of at least Rs=0.30. In other embodiments, the ratio has a value of at least Rs=0.40. In still other embodiments, the ratio has a value of at least Rs=0.50.
The swept-back portion 120 of the blade 108 can further include a weight tab 510 disposed on the surface of the blade for use in balancing the blades. In some embodiments, the weight tab 510 is a block of plastic extending above the surrounding surface of the blade 108, wherein the tab can be sanded or carved to remove material as needed to balance the blade. In some embodiments, the weight tab 510 is molded as an integral part of the blade 108. In other embodiments, an alternative balancing feature 510′ (not shown) is provided on the surface of the swept-back portion 120 of the blade 108, namely a concave feature, e.g., a slot, hole or dish, configured to receive and hold one or more discrete balancing weights (not shown), wherein the blade can be balanced by inserting or affixing weights of desired value to the balancing feature 510′.
The serrated pattern 124 on the trailing edge 116 of the blade 108 includes a series of notches, waves or chevrons 126 that prevent the trailing edge from being a straight line or simple curve. In some embodiments (e.g., FIGS. 5-12 ) the notches 126 can be configured as a series of triangular shapes, chevrons or “sawtooth” pattern. In other embodiments (e.g., FIGS. 1-3 ) the notches 126 can be configured in a semi-circular, curved, sinusoidal or other “wave” pattern. In still other embodiments the notches 126 can be rectangular, semi-hexagonal, or of mixed shape pattern, provided the notches, waves or chevrons give the trailing edge 116 a complex shape that is not a straight line or simple curve. Additionally, in some embodiments, the notches, waves or chevrons 126 of the serrated pattern 124 are graduated in size along the trailing edge 116, e.g., with the largest/deepest notches, waves or chevrons being disposed proximate to the root 110 and the smallest/shallowest notches, waves or chevrons being disposed proximate to the tip 114. The relatively larger size notches, waves or chevrons 126 are needed for sufficient air mixing at the trailing edge portion closer to the root 110 where the airflow speed is relatively low. As the trailing edge portions get farther from the root 110, the airflow speed increases and the notches, waves or chevrons can be smaller but still provide sufficient air mixing because of the relatively higher airflow speed. In some embodiments, the pitch (i.e., spacing) of the notches, waves or chevrons 126 of the serrated pattern 124 along the trailing edge 116 is relatively constant. In some other embodiments, the pitch of the notches, waves or chevrons 126 of the serrated pattern 124 is graduated along the trailing edge 116, e.g., with a relatively lower chevron pitch (i.e., lower number of chevrons per unit length of edge) being disposed proximate to the root 110 and a relatively higher chevron pitch (i.e., higher number of chevrons per unit length of edge) being disposed proximate to the tip 114. For example, as seen in FIGS. 11 and 12 , the chevrons 126 of the serrated pattern 124 on blade 108 are graduated from relatively larger size (i.e., length in flow direction measured from crest to trough) and relatively coarse (i.e., larger) pitch near the root 110 to relatively smaller size and relatively fine (i.e., smaller) pitch near the swept-back portion 120.
The serrated pattern 124 on the trailing edge of the blade mixes the air traveling over the blade with the air traveling under the blade in ways that reduce “trailing edge noise,” which is a significant source of sound whenever a blade or airfoil cuts through air. It is believed that the serrated shapes 126 on the trailing edge 116 break the airflow coming off the blade into small, quieter eddies instead of the usual large turbulence eddies found on a continuous edge.
Referring now particularly to FIGS. 5, 11 and 13A-D, the blade 108 can include an angle block 420 providing a mounting surface for connecting the blade to the hub 102 (e.g., via the hub arms 412 and/or the stiffening arms 414) and setting the angle of attack a of the blade relative to the direction of motion 109. In the illustrated embodiments, the angle block 420 is an integral molded-in portion of the molded plastic blade 108 to simplify construction. In the illustrated embodiment, the angle block 420 is molded to define strengthening ribs 544 to support the stiffening arms 414 (e.g., FIG. 4A). In the illustrated embodiment, the angle block 420 is molded to define through holes 546 to receive fasteners 418 for connecting the stiffening arms 414. As best seen in FIGS. 13A-B, the mounting surface of the angle block 420 can define a top plane 548 for supporting the hub arms 412 or stiffening bars 414. In some embodiments, the top plane 548 can be parallel to the direction of motion 109 of the blade 108, thereby allowing the use of hubs 102 with hub arms 412 and/or stiffening bars 414 having flat mounting surfaces (i.e., mounting surfaces parallel to the plane of rotation of the hub) such that bending or forming of the hub arms and/or stiffening bars 414 is not required to provide the blades 108 with a preselected angle of attack. In the FIGS. 13B-D, the angle of attack a is illustrated relative to line 109′, which is parallel to both the direction of motion and the mounting plane 548 provided by the angle block 420. As previously described, manufacturing and assembly of the HVLS fan can be simplified using this structure because the hub 102, hub arms 412 and stiffening arms 414 can all be formed of flat plate, and the angle blocks 420 allow the blades 108 to attach against the flat surface of the stiffening arm 414 while still providing a predetermined angle of attack a.
As illustrated, e.g., in FIG. 5 , the blades 108 can further include vortex generators 512 disposed on the upper surface behind the leading edge 112. Vortex generators are known for use to energize “sluggish” boundary layers in order to delay the onset of flow separation. In the context of air circulation fan blades, the increase in boundary layer energy produced by the vortex generators 512 serves to increase the downward airflow produced by the blades 108 and thus, increase the air circulation provided by the fan. In some embodiments, the vortex generators 512 can be configured as rectangular or triangular vanes extending from the upper surface of the blade 108 proximate to the leading edge 112. In other embodiments, the vortex generators 512 are configured in pairs of rectangular vanes extending from the upper surface of the blade 108 proximate to the leading edge 112 with the individual vanes in each pair being spaced away from one another such that the spaced-apart distance gets larger in the direction from leading edge 112 towards trailing edge 116. In the embodiment shown in FIG. 5 , seven pairs of vortex generators 512 are provided.
Referring now particularly to FIGS. 13A-13D, in some embodiments, the blades 108 can be configured to have an airfoil profile (i.e., when viewed in cross-section). In some further embodiments, the blades 108 can be configured to have an undercambered airfoil profile wherein the blade has a concave lower surface (i.e., viewed from below). In some embodiments, the blades 108 can have an airfoil profile and be configured to travel in a direction of motion 109 and produce downward airflow due to the airflow around the airfoil profile. In some embodiments, the blades 108 can be mounted to provide a positive angle of attack a between the direction of motion 109 and the blade's airfoil chord line 550 (i.e., the line running between the leading edge 112 and the trailing edge 116) to produce increased downward airflow.
Referring now to FIGS. 14 and 15 , additional details of a five-bladed HVLS fan 200 in accordance with one embodiment are illustrated. The fan 200 includes a motor assembly 104 configured to be suspended from the ceiling (not shown) with the downrod 106. The hub 102 is mounted on the motor assembly 104 using fasteners 408. In the illustrated embodiment, the hub 102 is mounted to the lower surface of the motor assembly 104, but in alternative embodiments the hub can be mounted to the upper surface of the motor assembly. The hub 102 includes outwardly extending hub arms 412, which in this embodiment are flat, meaning their upper and lower surfaces lie in the same respective planes as the upper and lower surfaces of the central hub 410. Stiffening arms 414 are attached to the hub arms 412 using fasteners 416. In this embodiment, the stiffening arms 414 are flat, meaning their upper and lower surfaces are parallel to one another. The blades 108 are connected to the stiffening arms 414 using fasteners 418. In this embodiment, the stiffening bars 414 serve to connect the blades 108 to the hub 102 and also to reinforce the blades. In the illustrated embodiments, the stiffening arms 414 extend along the blades 108 a distance equal to 33 percent of the total length of the blades (measured from the root 110). In some embodiments, the stiffening arms 414 extend a distance along the blades 108 equal to a distance in the range of 20 percent to 40 percent of the total length of the blades. In some embodiments, the stiffening arms 414 extend a distance along the blades 108 equal to a distance in the range of 15 percent to 50 percent of the total length of the blades. The blades 108 in the illustrated embodiment have an angle block 420 (FIG. 15 ) for attachment of the blades to the stiffening bars 414 at a predetermined angle of attack relative to the direction of motion of the blades.
Referring now to FIG. 16 , there is illustrated a blade for a HVLS fan in accordance with an alternative embodiment. The alternative blade 600 includes a root end 110, a leading edge 112, a tip end 114, and a trailing edge 116 similar to previous HVLS fans 100, 200, 300 and 400. The alternative blade 600 also includes a relatively longer chord portion 618 disposed proximate to the root end 110, a swept-back portion 620 disposed proximate to the tip end 116, and relatively shorter chord section 622 disposed therebetween, all of which are similar to the corresponding structures of HVLS fans 100, 200, 300 and 400 but can have different relative proportions between the respective portions. In particular, in the illustrated embodiment, the tip 114 of the swept-back portion 620 extends back to a position (denoted by line 632) between the rearmost extent of the relatively longer chord portion 618 (denoted by line 630) and the frontmost extent of the relatively shorter chord portion 622 (denoted by line 638). In other words, the tip 114 of the swept-back portion 624 is in front of the rearmost extent of the of the relatively longer chord portion 618 by a distance (denoted 634) that can be expressed as a percentage of the maximum chord length (denoted 636) (the “tip lead maximum chord percentage”). In the illustrated example, the tip lead maximum chord percentage of distance 634 compared to the blade's maximum chord length 636 is at least 9 percent. In other embodiments, the tip lead maximum chord percentage of the swept-back portion 620 can be within the range from 0.5 percent to 50 percent the blade's maximum chord length.
In the illustrated embodiment of FIG. 16 , the Min/Max Chord Percent of the minimum chord length 642 of the relatively smaller chord portion 622 expressed as a percentage of the maximum chord length 636 of the relatively larger chord portion 618 is 64 percent. In other embodiments, the Min/Max Chord Percent of the relatively smaller chord portion 622 is within the range from 50 percent to 70 percent. In still other embodiments, the Min/Max Chord Percent of the relatively smaller chord portion 622 is within the range from 45 percent to 75 percent. Blades 600 configured with the Min/Max Chord Percent in the stated ranges provide improved performance in airflow, noise and/or energy use compared to blades having constant chord.
In some embodiments, the tip 114 of the swept-back portion 620 can extend behind the trailing edge 116 of the blade 600 wherein the frontmost extent of the smallest chord portion is denoted by line 638 and the rearmost extent of the swept-back portion 620 is denoted by line 632, such that the swept-back portion extends behind narrowest portion of the smaller chord portion by a distance (denoted 640) (the “minimum chord trailing distance”). In the illustrated example, the minimum chord trailing distance 640 of the swept-back portion 620 is at least 64 percent of the of the blade's minimum chord length (denoted 642). In other embodiments, the minimum chord trailing distance of the swept-back portion 620 can be within the range from 76 percent to 0.5 percent of the blade's minimum chord length.
The trailing edge 116 of the blade 600 can further feature a serrated pattern 624 formed of notches, waves or chevron-shaped projection 626; however, the configuration of the serrated pattern 624 can be different from the pattern of HVLS fans 100, 200, 300 and 400. For example, the size of the chevrons 626 of the serrated pattern 624 relative to the maximum chord 636 on the blade 600 of FIG. 16 is smaller (i.e., shallower) than the size of the chevrons 126 relative to the maximum chord 536 of the blade 108 of FIGS. 5-12 . Further, the serrated pattern 624 on the blade 600 has less graduation in the size of the chevrons 626 between the root 110 and the swept-back portion 620. Further, the serrated pattern 624 on the blade 600 has less graduation in the pitch of the chevrons 626 between the root 110 and the swept-back portion 620.
Referring now to FIG. 17 , there is illustrated another blade for a HVLS fan in accordance with yet another alternative embodiment. The alternative blade 700 is substantially similar to the blade 600 previously described, except the upper surface of the blade is textured with a plurality of impressions 702 (“dimples”) similar to the dimples found on the surface of a golf ball. In the illustrated embodiment, the dimples 702 are disposed in a region (denoted 704) just downstream from the blade's leading edge 112 and in the same general area of the vortex generators 512 in FIGS. 15-12 . The dimples 702 energize the boundary layer of air flowing over the blade 700 to enhance the downward air circulation provide by the fan. In the illustrated embodiment, the dimples 702 are provided in addition to the discrete vortex generators 512. In other embodiments, the dimples 702 can be used without the discrete vortex generators 512.
Referring now to FIGS. 18A and 18B, there is illustrated a coaxial contra-rotating hub assembly (“CCRHA”) in accordance with another aspect. It will be appreciated that conventional HVLS fans can produce significant torque reactions on the supporting ceiling structure (e.g., via the downrod), which can necessitate reinforcement of the ceiling. However, a CCRHA can rotate a coaxial pair of HVLS fan hubs in opposite directions using a single motor assembly, which greatly reduces the torque reactions of the fan for a given power output (i.e., air circulation volume). In addition, contra-rotating blades allows the blades to be of shorter length for a given motor power and airflow volume, and the shorter blades have a lower tip speed, and thus lower tip noise, for the same rotational speed. The CCRHA 800 for a HVLS fan is adapted for use with a motor assembly 802 having a central stator 804 and annular rotor 806 similar to that previously described herein. The stator 804 is adapted for connection to a downrod 808, which in turn is connected to a stationary ceiling structure 810. When connected to the downrod 806, the stator 804 remains stationary, whereas the rotor 806 can rotate around the stator when the motor assembly 802 is energized.
The CCRHA 800 includes a lower hub 812, an upper hub 814 and a torque-divider assembly 816. The upper hub 812 and lower hub 814 can be substantially similar to the hubs previously described herein, e.g., hubs 202, 302, 303. Each hub 812, 814 includes a plurality of hub arms 818 for the attachment of blades 108 and/or stiffening bars 414 as previously described herein. In the illustrated embodiment, the lower hub 812 is affixed to the rotor 806 of the motor assembly using fasteners 820 so that the lower hub rotates with the rotor. The torque-divider assembly 816 is disposed above the lower hub 812, and the lower portion of the torque-divider assembly operably engages the upper surface of the lower hub. The upper hub 814 is disposed above the torque-divider 816 and configured to freely rotate relative to the downrod 808 and stator 806. The upper portion of the torque-divider assembly 816 operably engages the lower surface of the upper hub 8114. The torque-divider assembly 816 of the illustrated embodiment includes one or more rollers 822, with each roller rotatably mounted to a roller support 824 such that the axis of rotation for the roller (denoted 826) extends perpendicularly from the axis of rotation for the hubs (denoted 828). The roller supports 824 are operably connected to the stator 804 (including, e.g., via downrod 808) to remain stationary when the rotor 806 rotates. In the illustrated embodiment, the roller supports 824 are axles affixed to the downrod 808; however, in other embodiments the roller supports can be operably connected to the stator 804. The lower surface of each roller 822 rests on the upper surface of the lower hub 812, thereby providing operational engagement between the respective surfaces.
Referring still to FIGS. 18A-B, when the rotor 806 with attached lower hub 812 begins to rotate in a first rotation direction (denoted with arrow 832), the rollers 822 roll along the upper surface of the lower hub, but the center of each roller remains in place because they are held by the stationary roller supports 824. The upper hub 814 is positioned above the torque-divider 816 and configured to freely rotate relative to the stator 804 and downrod 808. In the illustrated embodiment, a bearing 830 is provided to keep the upper hub 814 positioned about the downrod 808 without transmitting torque therebetween. The upper hub 814 rests with its lower surface contacting the upper surface of the rollers 822, thereby providing frictional engagement between the respective surfaces and “trapping” the rollers 822 with simultaneous engagement of the upper hub 814 and the lower hub 812. As previously described, rotation of the rotor 806 with lower hub 812 in the first rotation direction 832 causes the rollers 822 to rotate with the lower surface moving in the same motion direction (denoted with arrow 834), however, the upper surface of the roller travels in the opposite motion direction (denoted with arrow 836). Since the upper surface of the roller 822 contacts the lower surface of the upper hub 814, the motion of the wheel's upper surface in opposite motion direction 836 causes the upper hub to rotate at the same speed as the lower hub, but in a second (i.e., opposite) rotational direction (denoted with arrow 838). Thus, the lower hub 812 and upper hub 814 are both powered to rotate by the single motor assembly 802, but with the direction of rotation of the respective hubs being opposite to one another.
The torque-dividing assembly 816 is preferably inexpensive to build and quiet during operation. In some embodiments, the rollers 822 can be urethane wheels using friction to operationally engage the upper and lower hubs 812 and 814 and the roller support 824 can comprise axles fixed through the downrod 808 or stator 804 to prevent rotation. In some embodiments, the urethane wheels of the rollers 822 can include ball-bearings at the roller support axles 824 for rolling between the hubs 812, 814 the with low noise and low vibration. In other embodiments, the rollers 822 can be made of different plastic, elastomer or metallic materials. In some embodiments, the rollers 822 can have a smooth outer surface to interface via friction with smooth surfaces on the respective hubs 812, 814. In other embodiments, the rollers can have a toothed outer surface to interface via toothed engagement with the respective hubs 812, 814 if toothed surfaces are provided thereupon.
In other embodiments (not shown), the CCRHA 800 can be positioned below the motor assembly 802 rather than above it, which requires only simple inversion of elements to produce the identical function. In still other embodiments (not shown), the CCRHA 800 can be used with an indirect drive motor, wherein the lower hub 812 is not attached directly to the rotor 806 of the motor assembly and the torque-dividing assembly 816 is not operatively attached to the stator 804. In such indirect-drive embodiments of the CCRHA 800, the motor assembly can indirectly drive one of the upper hub 814 or the lower hub 812 while the remaining hub remains free to rotate independently, and the central portion of the torque-divider apparatus 816 can be connected to a non-rotating portion of the hub supporting structure. In other respects, the indirect-drive embodiments of the CCRHA 800 will operate identically to the direct-drive counterparts.
Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

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:

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 swept-back portion disposed proximate to the tip end, 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

21. A blade for a HVLS fan in accordance with claim 19, wherein the blade body further comprises:

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.