Stepped leading edge fan blade

Abstract

A fan blade apparatus for use in a high-volume, low-speed fan wherein the fan blade includes a body portion, a leading edge portion and a trailing portion. The fan blade coupled to an electric motor configured to rotate in an intended direction wherein the leading portion of the fan blade is at the forefront of the rotation of the blade. The leading edge portion of the fan blade includes a series of steps extending along the length of the leading edge. The stepped configuration creates turbulent air flow when the electric motor rotates in the intended direction.

Claims

1. A fan blade comprising: a body portion having a hub side, an exterior side, a top surface, and a leading edge portion measurable along a longitudinal edge of the fan blade; a tail portion measurable along a trailing edge portion of the fan blade; the body portion having a width measurable between the leading edge portion and the trailing edge portion; a leading edge forming a plurality of steps including at least a first step, a second step, and a last step along a length of the leading edge wherein each of the plurality of steps decreases in a width edge of the fan blade between the leading edge and the trailing edge portion; the plurality of steps including a first air contact surface, a second air contact surface, and a last air contact surface, wherein the first air contact surface corresponds to the first step, the second air contact surface corresponds to the second step, and the last air contact surface corresponds to the last step and are aligned in a plane formed by a chord direction of the fan blade and a non-axial transverse direction of the fan blade; and the plurality of steps are each configured to create a vortex.

2. The fan blade of claim 1 wherein each of the plurality of steps include a straight portion, wherein at least a first step straight portion, a second step straight portion, and a last step straight portion are parallel to each other.

3. The fan blade of claim 2, wherein the leading edge is made of a material from the group consisting of fiberglass, graphite, composite plastic material, extruded polymer material, carbon fiber, or high-impact polystyrene.

4. The fan blade of claim 3, wherein a ratio of a width of the plurality of steps are proportional along the leading edge.

5. The fan blade of claim 2, wherein the first step of the plurality of steps is positioned along the leading edge closest to a centerline and the last step is positioned along the leading edge furthest to the centerline.

6. The fan blade of claim 2, wherein each of the first step, the second step, and last step are configured to be an equal length along the leading edge portion of the fan blade portion such that each of the first step, the second step, and the last step is proportional to a total length of the leading edge of the fan blade.

7. The fan blade of claim 2, wherein the plurality of steps comprising an edge that is configured at a 90° angle to the leading edge.

8. The fan blade of claim 1, wherein the body portion is aluminum.

9. The fan blade of claim 1, wherein the leading edge is made of a material from the group consisting of fiberglass, graphite, composite plastic material, extruded polymer material, carbon fiber, or high-impact polystyrene.

10. The fan blade of claim 9, wherein a ratio of a width of the plurality of steps are proportional along the leading edge.

11. The fan blade of claim 1, wherein the first step of the plurality of steps is positioned along the leading edge closest to a centerline and the last step is positioned along the leading edge furthest to the centerline.

12. The fan blade of claim 11, wherein each of the first step, the second step, and last step are configured to be an equal length along the leading edge portion of the fan blade portion such that each of the first step, the second step, and the last step is proportional to a total length of the leading edge of the fan blade.

13. The fan blade of claim 1, wherein each of the first step, the second step, and the last step are configured to be an equal length along a leading edge portion such that each of the first step, the second step and the last step is proportional to an overall length of the leading edge of the fan blade.

14. A method for movement of air along a leading edge of a fan blade of the method comprising the steps of: displacing air along the leading edge of the fan blade through a first step including a first air contact surface, a second step including a second air contact surface, and a third step including a third air contact surface, wherein the first air contact surface of the first step, the second air contact surface of the second step, and the third air contact surface of the third step are aligned in a plane formed by a chord direction of the fan blade and a non-axial transverse direction of the fan blade; generating a vortex along the first step, the second step, and a third step along the leading edge of the fan blade; rotating the fan blade around a centerline; measuring the velocity of the vortex at a first distance from the centerline of the fan blade; measuring a velocity of the vortex at a second distance in a direction perpendicular to the length of the fan blade; and generating the velocity of the vortex measuring four miles per hour as measured at a point located at a distance of 9 feet from the centerline and a distance of 15 feet in a direction perpendicular to a length of the fan blade.

15. The fan blade of claim 14, further comprising the step of generating the velocity of the vortex measuring four miles per hour at a location measuring 15 feet from the centerline and measuring 16 feet perpendicular to the length of the fan blade.

16. The fan blade of claim 15, further comprising the step of generating the vortex measuring two miles per hour at location measuring 42 feet from the centerline and measuring 16 feet perpendicular to the length of the fan blade.

17. The fan blade of claim 14, further comprising the step of generating the vortex measuring two miles per hour at location measuring 42 feet from the centerline and measuring 16 feet perpendicular to the length of the fan blade.

18. The fan blade of claim 17, further comprising the step of generating the velocity of the vortex measuring two miles per hour at a location measuring 26 feet from the centerline and measuring 16 feet perpendicular to the length of the fan blade.

19. The fan blade of claim 14, further comprising the step of generating the velocity of the vortex measuring two miles per hour at a location measuring 26 feet from the centerline and measuring 16 feet perpendicular to the length of the fan blade.

Description

DESCRIPTION OF THE FIGURES

(1) Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the following drawings:

(2) FIG. 1 is a perspective view of the fan of the present invention;

(3) FIG. 2A is a top plan view of the fan;

(4) FIG. 2B is a side elevation view of a fan of the present invention showing the step design;

(5) FIG. 3A is a top plan view of a fan blade of the present invention showing the stepped design;

(6) FIG. 3B is a top plan view of an alternative design of the fan blade of the current invention that includes five steps;

(7) FIG. 4 is a side view of the fan blade of the present invention;

(8) FIG. 5A is a perspective view of a fan blade of the current invention showing three steps;

(9) FIG. 5B is a perspective view of an alternate embodiment of the fan blade of the present invention; and

(10) FIG. 6 is graph of air speed versus distance from the center of the fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

(11) A typical high volume low speed fan has between four to eight fan blades. The fan blades are typically between 4-feet to 12-feet in length and have a width of 6 inches. Thus, the total diameter of a typical fan is between 8-feet (96 inches) to 24-feet (288 inches).

(12) In the preferred embodiment of the present invention, as shown in FIGS. 1, 2A and 2B, the fan 10 is mounted to a ceiling (not shown). The fan 10 is mounted to the ceiling using a standard mount such as a universal I-Beam clamp with a swivel 12. The fan 10 may include an optional drop extension 14 that is 1 foot, 2 foot, 4 foot or more in length, depending upon the distance from the ceiling to the floor. At the end of the drop extension 14 is a gear motor 16. The motor 16 is typically an electromagnetic motor. The horsepower of the motor varies depending upon the diameter of the entire fan 18. For example, an 8-foot and 12-foot fan typically has a 1 horsepower motor 16. The 16-foot fan typically includes a 1.5 horsepower motor 16, and a 20-foot and 24-foot fan typically has a 2.0 horsepower motor 16. Attached to the motor 16 is a fan blade mount 13 that has a centerline 15 at the center of the fan 10 and motor 16. The fan blade mount 13 connects a fan blade 30 to the motor 16. The fan blade 30 is typically affixed to the fan blade mount 13 by means of a plurality of fasteners such as a bolt, screw, pin, rivet or the like.

(13) The preferred embodiment shown in FIGS. 1, 2A and 2B includes five fan blades 30, however, there may be a greater number of fan blades, or there may be less than five fan blades. Each fan blade 30 has a leading edge 32, and a trailing edge 34 and an end cap 36. The fan blade 30 includes a blade body 38. The blade body 38 is typically made of an extruded aluminum alloy, but could be made of a composite metal, carbon fiber material, a graphite material, fiberglass, wood or other similar material. The leading edge 32 of the fan blade has steps 40, 42, 44 (as shown in FIGS. 2A and 3A) from the portion of the leading edge 32 fan blade 30 positioned closest to the centerline 15 of the fan blade mount 13.

(14) The stepped configuration of the leading edge 32 of the fan blade is shown in more detail in FIGS. 2A, 2B, 3A, 3B, 4 and 5A. The leading edge 32 of the fan blade 30 has a first step 40, a second step 42 and a third step 44. The steps extend from the blade body 38. The leading edge 32 of the fan blade 30, including the first step 40, the second step 42 and the third step 44, are preferably made of an extruded polymer material, such as high-impact polystyrene, but may be constructed of a composite plastic material, graphite, fiberglass, carbon fiber, aluminum or any material having similar features and properties to the identified materials.

(15) The steps 40, 42 and 44 preferably have generally equal lengths proportional to the length of the blade body 38. Thus, the first step 40 would be approximately ⅓ the total length 39 of the blade body 38. The second step would also be approximately ⅓ the total length 39 of the blade body 38. Likewise, the third step would be approximately ⅓ the total length 39 of the blade body 38. The steps 40, 42 and 44 have a width in a ratio of 3:2:1. Thus, the distance that the first step 40 extends 50 beyond the front edge of the blade body 38 is 3-inches; the distance the second step 42 extends 52 is 2-inches and the third step 44 extends 54 is 1-inch. Thus, the ratio of the distance the various steps 40, 42 and 44 extend beyond the front edge of the blade body 38 is 3:2:1. While the preferred embodiment has steps of proportional length and proportional width, it is not a requirement. The important aspect of the step configuration is that the leading edge has multiple steps, from the area of the fan blade 30 closest to the hub. The steps decrease the thickness of the blade in each step that proceeds from the hub.

(16) While the preferred number of steps is three with a ratio of 3:2:1, the number of steps may be more than three, so long as the ratio of length of the steps corresponds to the number of steps and the distances the various steps extend beyond the front edge of the blade body is a ratio equal to the number of steps. FIG. 3B shows a blade that has five steps. By way of example, a 20-foot diameter fan would have a fan blade 130 of approximately 10-foot in length 139. The ratio of the steps along the leading edge 136 in the preferred embodiment would be 5:4:3:2:1. Each step 140, 142, 144, 146, and 148 would be approximately 2 feet in length 156. The overall fan width 155 should not exceed 9-inches in the preferred embodiment. A fan blade 130 that exceeds a width of 9-inches may cause an undesirable load to be placed on the motor. It is, of course, possible for the distance to be greater than 9-inches if one chooses to construct a fan using a non-conventional fan motor. In the above example of the 5-step fan blade, the distance from the front edge of the fan body 138 to the leading edge of the step 140 should not necessarily exceed 3 inches. In the embodiment of a 5-step fan blade (FIG. 3B), the distance of the first step 50 would be approximately 3-inches. Each step would then decrease by 6/10 of an inch. The fan blade 130 has a trailing edge 134 as the fan blade 130 rotates.

(17) FIG. 4 is a side view of one of the preferred embodiments of the fan blade of the present invention which has 3 steps. The blade 30 includes a leading edge 32, a body 36 and a trailing edge 34. The leading edge 32 includes a series of steps 40, 42 and 44. The distance between the first step 40 and the second step 42 of the leading edge 32 is shown as 56. Likewise, the distance between the second step 42 and the third step 44 is shown as 58. The blade 30 has an upper portion 35 and a lower portion 37. The blade 30 also has a rearward portion 34. The steps 40, 42 and 44 along the leading edge 32 of the blade 30 provides vortex along the edge of the steps 60 and 62 as shown in FIG. 5A. The vortex created at the edges of the steps 60 and 62 create a greater turbulent airflow below the fan. The vortex created at the edges of the steps 60 and 62 also provide for greater airflow velocity in the area near the centerline 15 of the fan.

(18) The pitch P of the blade 30 along the top and bottom portion of the blade is approximately 22°. The design of the steps 40, 42 and 44 along the leading edge 32 of the blade 30 permits for the blade to accommodate up to a 22° pitch. Conventional HVLS fans typically have a pitch for the blade between 10°-15°. The stepped design of the leading edge of the fan blade allows for a pitch between 18° to 22° to be implemented without increasing the strain of the motor. The increased pitch promotes more downward airflow.

(19) The steps 40, 42 and 44 along the leading edge 32 of the fan blade 30 have edges 60 and 62 respectively. The edges 60 and 62 of the preferred embodiment have a recessed or Z-shaped configuration. This configuration is for aesthetic purposes. As shown in FIG. 5B, the steps 240, 242 and 244 have edges 260 and 262 that are at approximately a 90° angle to the leading edge 232 of the fan blade 230. The configuration of the edges 260 and 262 does not affect the function of the fan blade 230.

(20) An actual embodiment of the preferred invention was tested at a warehouse facility in Beaver Dam, Wis. The height of the facility was twenty-five feet from the floor to the ceiling. The high-velocity, low speed fan was a 24-foot diameter fan that was mounted twenty feet from the floor—in other words, the fan had approximately a five foot drop from the ceiling. The fan had five blades including three steps on each blade as depicted in FIGS. 3A, 3B and 4. The average velocity of the air was measured using a wind velometer gauge. The air velocity was measured at a height of 48-inches above the level of the floor. Measurements were taken at various distances, at approximately three-foot intervals, from the centerline 15 of the fan. Measurements were taken at each location using the wind velometer gauge over a time period of approximately thirty seconds. Because the airflow is not constant, the maximum and minimum airflow measurements were recorded over the thirty second period. The maximum and minimum velocity readings over the thirty second period were averaged and are set forth in the chart below:

(21) TABLE-US-00001 Distance from Velocity Center of Fan (Feet) (Miles Per Hour) 3 2.3 6 3.0 9 4.0 12 2.8 15 4.0 20 3.0 23 3.1 26 2.3 30 1.9 33 2.9 36 3.0 42 2.0 46 2.7 50 2.0 53 1.9 58 1.1 62 1.1
FIG. 6 is a graph of the average velocity in MPH of airflow created by the circulation of the fan 10 utilizing the blades 30 of the preferred embodiment at various distances from the centerline 15 of the fan. As shown in FIG. 6, for example, at approximately 8-feet and 16-feet from the centerline 15 of the fan, the average velocity of airflow 48-inches above the ground was 4 miles per hour. The human body typically feels 6 to 10° F. cooler (Relative Temperature) than the ambient temperature of the air when the air is circulating at 4 miles per hour. At airflow at a velocity of 2 miles per hour, the human body fees 3 to 5° cooler than the ambient temperature of the air. The benefit of the fan design is a greater velocity of air circulation is achieved within close proximity to the centerline 15 of the fan. In addition, the measureable air circulation extends to a distance of 62-feet from the centerline 15 of the fan 10.

(22) This chart shows that the stepped design has significant airflow coverage and overall air dispersion. The fan of the current invention has minimal airflow dead spots, especially within close proximity to the centerline of the fan.

(23) The fundamental operating principals and indeed many of the engineering criteria of fan blades for high-volume low-speed ceiling fans is similar to fan blades used in basically all forms of compressors, fans and turbine generators. In other words, the rotor blades can be used in a huge range of products such as for example, for helicopter blades, car fans, air conditioning units, water turbines, thermal and nuclear steam turbines, rotary fans, rotary and turbine pumps, and other similar applications.

(24) Although embodiments of the present invention have been described, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.