DESC:FIELD OF INVENTION
The present invention relates generally to improved fan blades and, more particularly, to fan blades with modified lift angle in order to optimize the air delivery cone below.
BACKGROUND OF THE INVENTION
Ceiling fans have been around for many years as a useful air circulator. The popular blade style over the years is a flat planar rectangular blade that can have a slight tilt. The performance of a fan in terms of pressure, volume flow, fluid velocity, power, and efficiency depends on a number of factors, the most critical of which are:
(a) the design and type of fan;
(b) the size of the fan;
(c) the speed of rotation of the fan impeller;
(d) the condition of the fluid passing through the fan; and
(e) the geometry of the fan blades comprising the impeller.
Consequently, it is a goal of fan design to develop fan blade geometries that optimize operating characteristics and performance.
Given below is a table that gives details about how others have solved the problem and what are the disadvantages or limitations in the solution,
Patent number How they solved Disadvantages of approach
CN2392015 Contains a fan blade whose center line is curved upwards at the tip and claims to increase area of air flow as the air flows perpendicular to the center line of the blade • Does not mention the resultant air cone angle
• Does not mention how the blade will withstand centrifugal forces acting on it
• As the blade is held at one end it will tend to flatten thereby losing the elliptical form given to the blade
CN2414237 1. By bending 1/3rd of the blade toward ceiling to a certain angle
2. By bending half of the blade length toward ceiling in a curvature shape
3. By mounting the whole blade lifting the tip of the blade toward ceiling • The length which is bent at an angle is 1/3rd of the blade it has very less surface area to push enough amount of air resulting in insufficient air flow
• In the 3rd method although the whole blade is mounted at an angle it does not consider structural stability of the blade while running at higher speeds so, it will lose its designed angle due to centrifugal forces acting on it
• The above point applies to all three methods that are mentioned in the prior art and will result in inefficient intended output
CN2505629 By mounting 3 set of blades (2 blades in each set) at an incremental interval of lift angles of around 12-15 degrees from each group one above the other it attempts to increase air delivery cone angle • At higher speeds the fan blades leave a trail of turbulent air behind them when they cut air and as per this prior art when 3 blades one above the other from symmetric position perform this air cutting action the fan will generate huge amount of noise due to so many blades creating turbulence in the air of closed room.
• As the fan blades are pushing air they face resistance from the air at different levels depending on the characteristics of air, in this prior art when 6 blades are mounted on a single fan they put tremendous amount of load on the motor which will have to be designed for heavy duty purpose. So, this prior art becomes electrically very inefficient as it draws power in multi-folds as compared to commonly available fan in the market
• The prior art does not provide any solution for the structural stability of the blade as in this case blade remaining at designed angle is of greater importance because more than one blade is mounted one above the other. So, the product become unstable when running at higher speeds

CN2508030 The fan contains in addition to motor and blades, a vibration damper, hanger rod and a lifter and the blades can be adjusted at different lift angles from horizontal to get wider range of air supply • The prior art talks about adjusting blade angle with the help of a flexible mechanism that are connected to the blade but does not mention any detail about how the blade is rigidly fixed at an angle when the whole assembly of connecting rods, lifter mechanism of the fan is rotating at high speeds. At higher speeds the whole mechanism puts heavy loads on the installation and is a potential risky situation if not installed rigidly.
• The connecting rod from lifter is fixed closer to the motor hub and remaining length of the blade is left hanging in the air. So, when the blades are lifted to the highest angle they are bound to give-in to centrifugal force and sag flat thereby failing to push air to larger area in the room.
• Looking at the schematic diagram it shows lot of sub systems constructed above the level of fan motor and blades, this construction makes the structure taller and when installed in the house the effective distance of the rotating fan becomes longer to such an extent that the rotating fan may hit the people on the floor hence the whole product becomes dangerous for use.
CN203067308 By inclining the fan blade fastening bracket towards roof the fan blows wind towards periphery below that fan thereby giving air to the larger area under the fan • Fastening of the blade to the motor hub is done at one edge and does not even overlap the blade leaf to improve its structural strength and the whole blade is left hanging in air. This arrangement makes the blade loosely hanging in air and when the fan is running it will result in increased flapping of the blade which in turn creates dynamic imbalance in the product when running.
• Due to fastening at one edge of the blade when the fan is running the blades are adversely influenced by centrifugal force and lose its tilted orientation and fails to generate large fan area under it.
• The prior art says the fan is a smaller one and when blade are fastened at a tilted orientation it required more powerful motor to push more air to reach the people below it as against the normal sized fans are able to perform and the prior art does not mention the capacity of the motor to compensate lack of optimum length of the blade, hence, the product may not deliver sufficient amount of air for a satisfactory output.
US9528529B1 By bending a portion of the fan blade in an angularly directed position • As shown in the drawing of this prior art only a portion of the blade is angularly directed towards ceiling hence there is less surface area to push air. In this case with smaller surface area the blade will not be able to blow enough air to reach the people on the floor to feel heightened comfort and cooling.
• At the same time the portion that is in horizontal position also loses some portion of the blade and hence will not provide sufficient air flow just under the fan
• The drawing does not show any strengthening element on the blade where it is bent and when the fan is rotating at high speeds the upwardly tilted portion is going to come under the influence of centrifugal force and get pushed away from the axis of the fan. In that situation there is great amount of stress coming on the bend line and as per the drawing in this prior art the blade is not provided with any structural element to overcome these stresses. So, in the long run the blade may develop cracks at the bend line and break eventually which is a safety risk.

Accordingly, it would be desirable to provide a fan blade configuration that increases fan efficiency (increased cone angle and volume flow at lower speeds and lower power requirements), decreases noise and vibration, and creates a more focused and collimated volume flow.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide ceiling fan blades that are aerodynamically optimized to move up the air delivery cone to approximately 50% or more air than traditional flat planar ceiling fan blades.
Another object of the subject invention is to provide ceiling fan blades that are quieter and provide greater comfort than traditional flat planar ceiling fan blades.
Another objective of the subject invention is to provide ceiling fan blades that are less prone to wobble than traditional flat planar ceiling fan blades.
Another object of the present invention is to provide ceiling fan blades designed for superior airflow with reduced low operational speeds approximately 40 revolutions per minute and up to approximately 350 revolutions per minute(rpm).
Another object of the present invention is to provide ceiling fan blades being more aesthetically appealing than traditional flat planar ceiling fan blades. Also a fan blade support T-shaped clip is used for connecting / mounting the fan blade to fan motor hub.
Yet another object of the present invention is to provide ceiling fan blades having a coverage area of up to 9140 square inches, which would be up to approximately 45% increase in coverage over conventional 48 inch diameter fans.
Yet another object of the present invention is to provide ceiling fan blades which delivers air farther away from just below it so that people sitting on the furniture close to walls as is the common practice in household lay outing. So that people need not go to where the fan only can deliver air, but air is delivered to them where they are sitting. The cone angle of 42o at high range and 24o to 28o at mid-range angles is achieved.
Other features and advantages will be apparent from the following description, including the drawings, and from the claims set forth.
BRIEF DESCRIPTION OF THE ACCOMPANTING DRAWINGS
The various described embodiments will hereinafter be described in conjunction with the appended drawings provided to illustrate and not limit the described embodiments, wherein like designations denote like elements, and in which:
Figure 1 illustrates the concept of air delivery cone in accordance with the present invention;
Figure 2 illustrates the concept of lift angle in accordance with the present invention;
Figure 3 illustrates the optimized lift angle in accordance with the present invention;
Figure 4(a) illustrates the increase in cone angle when the blades are mounted at higher lift angle in accordance with the present invention;
Figure 4(b) illustrates the reduced fan sweep diameter with respect to increase in lift angle in accordance with the present invention;
DETAILED DESCRIPTION
Before various embodiments are explained in detail, it is to be understood that the described embodiments are not limited in application to the construction and arrangement of the structures, components, steps, and/or examples set forth in the following description or illustrated in the drawings. The described embodiments are capable of other forms and may be carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for purpose of description and should not be regarded as limiting.
A ceiling mounted fan with 3 OR 4 sheet metal blades whose resultant cone of air delivery reaches a larger area in a standard household room in India. Unlike the fans available in the market that deliver air just below the fan, this fan extends its air delivery cone farther so that people sitting on chairs and sofas are also able to receive breeze to feel soothing comfort. The invention achieves this by means of aerodynamically designed and structurally stable blades and a suitable powerful induction motor.
Air delivery cone is a cone created by flowing air that is pushed by the ceiling fan when it rotates at a designed speed (Revolutions Per Minute). This cone is determined by measuring the diameter of the fan when it is in rotation and the extent to which it blows air on the floor. And only within this area a person can feel air blowing on the skin and feel comfort and cooling effect. The common fans available in the market create a cone that is closer to cylindrical shape in which case very little air blown by the fan reaches the people who are sitting away from the fan and close the room walls. This invention attempts to extend the area covered by fan, so that blowing air reaches the people sitting close to wall to give more comfort to them without people needing to move below the fan.
Velocity of flowing air determines cooling effect on the skin and air cone determines reach of air flow. This velocity and air delivery cone of flowing air is determined by various aerodynamic factors of fan construction like, number of blades, width and length of the blades, attack angle of blade, lift angle of blade, power of motor, twist angle of blade. This invention explores the effects of these factors and has optimized few parameters like motor power, lift angle and width and length of blade to achieve extension in the air delivery cone. By conducting various experiments on different combinations of these parameters this invention has arrived at an optimum design which is able to extend the air delivery cone of the fan by 33%. The uniqueness of this invention is that it achieves extension in air delivery cone without requiring drastic changes from the current construction and architecture of the ceiling fans and with minimal increase in the product cost. When the fan requires little changes in the product architecture it appears visually similar to the current fans thereby increasing its acceptance among the consumers without intimidation.
Ceiling fans are products made to push air by means of rotating blades to flow at a higher velocity than the ambient air in enclosed spaces and when this air flowing at higher velocity blows on peoples’ skin they feel cooling effect thereby making them feel more comfortable and relaxed. Ceiling mounted fans are essentially axial type of fans which means they throw air parallel to the axis of their rotation. Due to this reason there is a limit to area under the fan to which the fan can throw air at a higher velocity. The blades on the fan are mounted in a way that the tip of the blade is lifted to a certain height and due to this the resultant flow of air below the fan creates what is known as air delivery cone angle also known as spread (Figure 2). Which means the area on the floor to which flowing air reaches is larger than the diameter of the fan in rotation. A typical ceiling fan available in the market can create a cone angle of around 16 to 18 degrees.
Considering a scenario of a fan being used at a household room in India the size of a living room in a typical urban house is around 10x12 feet and a height of 9 and a half to 10 feet and the furniture are arranged closer to the room walls. As explained earlier the due to smaller air delivery cone the flowing air reaches just to the feet of people sitting on chairs and sofas. So, there is very less of air blowing on peoples’ skin and hence dis-satisfactory comfort level and relaxation. This scenario is more pronounced in humid climates where there is higher level of perspiration due to humidity in the air and even when the fan is running at a higher speed people do not receive sufficient flow of air to feel cooling effect when it is needed the most. So, in this scenario due to smaller cone angles although the fan throws air at higher velocity it reaches just on the feet of the person and at the same time there is same level of sweating on the face when the fan is not running thereby defeating the very purpose of using a ceiling fan itself. If one wants to make use of air flowing at higher velocity one has to move towards the center of the room where the fan is mounted, in this case it becomes difficult for all the people in the room to sit under the fan in a cramped space due to smaller air delivery cone angle. So, the current ceiling fans cannot push air to where people are sitting but rather people need to come to where fan can blow the air which leave people feeling dissatisfied by the performance of current ceiling fans.
As the ceiling fans are axial flow fans they throw air parallel to the axis of their rotation. The elements in a fan that actually move air are the blades and in ceiling fans the blades are generally made of sheet metals and mounted horizontally with slight tilt towards ceiling which is built in a part called shank which holds the blade and fixed to the motor hub. With this construction current ceiling fans produce air cone angle of around 16 to 18 degrees overall as shown in Fig 1.
As discussed above the axial nature of air flow is able to create a narrow cone of angle and is insufficient in giving better comfort to people. So, to increase the cone angle air flow has to happen in mixed type of flow pattern and this can be achieved by altering one of the aerodynamic aspects of fan which directly impact cone angle which is lift angle. Based on several experiments the lift angle as depicted in Fig 3, has been increased to 45o degrees to achieve larger cone angle of around 42o. With this lift angle the blades are oriented in such a way that it creates mixed flow pattern air flow. So, instead of throwing the air right below it, the fan throws air at an angle which reaches larger area in the room and results in increase in air delivery cone angle.
AS shown in Fig 4, from close to horizontal position when the lift angle is increased to different angles the cone angle also increases with it, but cone angle cannot be said to be directly proportional to the lift angle. This invention also proposes that a mid-range of air delivery cone angle can be achieved by designing smaller lift angles between 10o to 25o. At this range of lift angles, cone angle of around 24o to 28o can be achieved which can be used as a mid-range of air delivery cone angles.
The Fig 4 (a), shows increase in cone angle when the blades are mounted at higher lift angle of 45o. The point to be noted here is the difference in the fan sweep diameter which has come down to 1000mm. This is because the fan sweep diameter is measured from center axis to the tip of the blade in horizontal plane. So, when the lift angle of the blade is increased the fan sweep diameter decreases with the length and other angles of the blade remaining same. The Fig 4(b) shows the difference in the fan sweep diameter in respect of lift angle.

AIR FLOW RESISTANCE
Below table mentions the quality of air in which the fan rotates. The below data is used for conduction fluid dynamic simulations

AIR FLOW COVERAGE VIS A VIS SPEED
Speed – 280 RPM
Blade lift angle – 45 degrees
Power consumption – 124 watts
Covering the area – 13,418 square inches
Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made in complete specification, none of which depart from the spirit or scope of the present when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

,CLAIMS:
1. A fan capable of optimizing the air delivery cone below comprising of:-.
a plurality of fan blades that have a proximal attachment end configured for connecting the fan blade to fan motor hub, characterized in that:
the said blades are mounted at higher lift angle of 45o.
2. The fan capable of optimizing the air delivery cone below, as claimed in claim 1, wherein the said air delivery cone angle is of around 42o at high speed.
3. The fan capable of optimizing the air delivery cone below, as claimed in claim 1, wherein at high range and the said air delivery cone angle is of around 24o to 28o at mid-speed range.
4. The said air delivery cone angle is of around 10o to 14o at low-speed range
5. The fan capable of optimizing the air delivery cone below, as claimed in claim 1, wherein fan sweep diameter is reduced.
6. The fan capable of optimizing the air delivery cone below, as claimed in claim 1, wherein the said blades are mounted with fan blade support T-shaped clip is configured for connecting the fan blade to fan motor hub.