DESC:FIELD OF THE INVENTION
[001] The present invention relates to a fan. More particularly, the present invention relates to a blade for a fan.

BACKGROUND OF THE INVENTION
[002] Generally, a fan, for example a ceiling fan is electrically powered with the help of electric motors and mounted on the ceiling of a room. The ceiling fan has one or more fan blades to circulate air. The fan blades are usually of two types i.e., metal blades and fibre/polycarbonate blades. The metal blades can only be in a sheet-based structure, whereas the fibre/polycarbonate blades can have a hollow or a spine-based structure.
[003] The metal blades are made of a metal alloy having steel/aluminium and are usually thinner in profile. The metal blades are highly malleable and can be thinned out to a very high extent. However, the metal blades are difficult to change in profile and structure, hence limiting the aerodynamic abilities to a very large extent.
[004] Similarly, the fibre/polycarbonate blades are made from a fibre composite material. The fibre blades are constructed using moulding techniques, which make it easier to build the fibre blades in multiple parts and then join them together. As is generally known, the fibre blades are built that are hollow in structure or built with a structural support member inside the blades. The fibre blades can be constructed in multiple shapes and therefore, have better performing aerodynamic structure. Hence, the fibre blades provide a near seamless construction and cohesiveness in connection to a motor housing of the ceiling fan.
[005] Further, the fibre blades have the ability to be shaped in accordance with the performing design requirements and the blades can also be shaped in accordance with variable lengths, widths, aerofoil profile and can also be twisted. Hence, for high volume low speed, high speed fans, and the like, the fibre and polycarbonate blades are preferred over the metal blades.
[006] However, the currently known metal blades and the fibre/polycarbonate blades have the inability to be made in a manner so as to provide a better aerodynamic form. Thus, there is a need to provide a blade that has a seamless connection between the motor housing and the blade. Also, it is difficult to position and provide the existing fan blades with twist angles. Therefore, the conventionally available ceiling fans have less efficiency due to the existing fan blade design.
[007] Thus, there is a need in the art for a blade for a fan which solves at least the aforementioned problems.

SUMMARY OF THE INVENTION
[008] In one aspect, the present invention is directed towards a blade for a fan. The blade has an inner end and an outer end. The inner end is attached to a central hub of the fan and the blade extends from the inner end to the outer end. The blade has a predetermined lift angle with respect to a horizontal X-axis, whereby the outer end is at a higher elevation with respect to the inner end. Further, the blade has a plurality of sections as the blade extends from the inner end to the outer end. Each section of the plurality of sections is defined by an aerofoil profile and each section of the plurality of sections has a different twist angle.
[009] In a further embodiment of the invention, the predetermined lift angle is provided between the horizontal X-axis and an axis extending between a bottom point of the inner end of the blade and a tip point of the outer end of the blade.
[010] In a further embodiment of the invention, the plurality of sections is configured to be provided distally to each other.
[011] In a further embodiment of the invention, the width of the blade is constant across each of the plurality of sections.
[012] In a further embodiment of the invention, a section OO of the blade is provided at the inner end of the blade, and a thickness of the blade at the section OO is greater than the thickness of the blade at each of the sections AA, BB, CC, DD, EE.
[013] In a further embodiment of the invention, a distance from section OO to section AA, section AA to section BB, section BB to section CC, and section CC to section DD is equal to the width of the blade, and the distance from section DD to section EE is half of the width of the blade.
[014] In a further embodiment of the invention, the twist angle is an angle between a chord line of the aerofoil profile at each of the plurality of sections and a horizontal Y-axis extending in a width direction of the blade.
[015] In a further embodiment of the invention, the twist angle of the blade gradually increases from the section AA to the section BB of the blade, and the twist angle of the blade gradually decreases from the section BB to the section EE of the blade.
[016] In a further embodiment of the invention, the blade is made one of a plastic Acrylonitrile Butadiene Styrene (ABS) material, a Polyphenylene Ether (PPE) material or a Polyphenylene Oxide (PPO) material.

BRIEF DESCRIPTION OF THE DRAWINGS
[017] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1A and 1B shows a perspective view and a side view of a blade for a fan, in accordance with an embodiment of the invention.
Figure 2 shows a top view of the blade, in accordance with an embodiment of the invention.
Figure 3 shows a perspective view of the blade, in accordance with an embodiment of the invention.
Figure 4A shows a sectional view A-A of the ceiling fan blade with an aerofoil structure, in accordance with an embodiment of the invention.
Figure 4B shows a sectional view B-B of the ceiling fan blade with an aerofoil structure, in accordance with an embodiment of the invention.
Figure 4C shows a sectional view C-C of the ceiling fan blade with an aerofoil structure, in accordance with an embodiment of the invention.
Figure 4D shows a sectional view D-D of the ceiling fan blade with an aerofoil structure, in accordance with an embodiment of the invention.
Figure 4E shows a sectional view E-E of the ceiling fan blade with an aerofoil structure, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[018] The present invention relates to fan. More particularly, the present invention relates to a blade for a fan. The blade of the present invention is configured to provide higher airflow, higher air spread, higher aerodynamic efficiency and lower aerodynamic drag.
[019] Figure 1A and Figure 1B illustrate a perspective and a side view of a blade 100 for a fan, in accordance with an embodiment of the invention. Figure 2 illustrates a top view of the blade 100, in accordance with an embodiment of the invention. In an embodiment, one or more blades 100 are supported on a central hub housing a motor, and the blades 100 extends radially outward from the central hub. The blades 100 are directly mounted on to the central hub through a plurality of fasteners. In an embodiment, the fan is a ceiling fan, preferably a fan with a BLDC motor. As illustrated, the blade 100 extends from an inner end 100A to an outer end 100B. In an embodiment, the inner end 100A of the blade 100 is attached to the central hub of the fan, thereby supporting the blade 100 on the central hub.
[020] As illustrated in Figure 1B, the blade 100 has a predetermined lift angle (?) with respect to a horizontal X-axis. The predetermined lift angle (?) is provided such that the outer end 100B of the blade 100 is raised or at a higher elevation with respect to the inner end 100A of the blade 100. As illustrated in Figure 1B, the blade 100 has the predetermined lift angle (?) with respect to the horizontal X-axis, wherein the horizontal X-axis extends in a longitudinal direction of the blade 100. The predetermined lift angle (?) is defined as an angle between the horizontal X-axis and an axis extending between a bottom point of the inner end 100A of the blade 100 and a tip point of the outer end 100B of the blade 100.
[021] The provision of the predetermined lift angle (?), whereby the outer end 100B is raised with respect to the inner end 100B provides for an increased spread value of the airflow of the fan. Spread value of the airflow of the ceiling fan is generally defined as the radius of the airflow with a minimum velocity of air on a certain level below the fan. Thus, by virtue of the predetermined lift angle (?), a higher radius of airflow at certain level below the ceiling fan is achieved as compared to fans with blades with zero lift angle. For example, conventionally, without a lift angle, only the users directly below the ceiling fan would receive the airflow, however, in the present invention, due to the predetermined lift angle (?) of the blade 100, users that are not directly below the ceiling fan or away from the axis of the ceiling fan, will also receive sufficient airflow. In an embodiment, the predetermined lift angle (?) of the blade 100 is 8 degrees.
[022] Further, as illustrated in Figure 3, the blade 100 comprises a plurality of sections as the blade 100 extends from the inner end 100A to the outer end 100B. The plurality of sections are provided distally to each other. In an embodiment, the plurality of sections comprises of six sections OO, AA, BB, CC, DD, EE. As illustrated in Figure 3, width of the blade 100 remains constant across the length of the blade 100. In an embodiment, the width of the blade 100 remains constant from a section OO to a section EE. In an embodiment, a distance between each section of the plurality of sections is equal to the width of the blade 100, except distance between a section DD to the section EE, wherein the distance between the section DD to the section EE is half of the width of the blade 100. In other words, the distance from section OO to section AA, section AA to section BB, section BB to section CC, and section CC to section DD is equal to the width of the blade 100, and the distance from section DD to section EE is half of the width of the blade 100.
[023] As illustrated, the section OO of the blade 100 is at the inner end 100A of the blade 100. In an embodiment, a thickness of the blade 100 at the section OO is greater than the thickness of the blade at each of the sections AA, BB, CC, DD, EE. Since the blade 100 is connected to the central hub at the inner end 100A and at the section OO, thickness of the blade 100 at the section OO is high to provide sufficient structural support to the blade 100. As the blade 100 extends from the section OO to the section AA, the thickness of the blade 100 is gradually decreased.
[024] Herein, each section is defined by an aerofoil profile and has a different twist angle. As referenced in Figures 4A to 4E, the twist angle of the blade 100 gradually increases from section AA to section BB, and thereafter gradually decreases from section BB to section EE. The twist angle is defined as an angle between a chord line of the aerofoil and a horizontal axis. In an embodiment, the chord line (L-L’) of the aerofoil is defined as an imaginary straight line drawn between a leading edge and a trailing edge of an aerofoil, in the direction of the normal airflow. Thus, as illustrated, the twist angle at each section is defined as the angle between the chord line (L-L’) of aerofoil at that particular section and a horizontal Y-axis which extends in a width direction of the blade 100.
[025] In an embodiment, as illustrated in Figure 4A, at section AA, the twist angle of the blade 100 is 9.5 degrees. From section AA to section BB, the twist angle of the blade 100 gradually increases till section BB, wherein, as illustrated in the embodiment depicted in Figure 4B, the twist angle at section BB is 15.8 degrees. Thereafter, as explained hereinbefore, the twist angle of the blade 100 gradually decreases from section BB to section EE. In the embodiment depicted in Figure 4C, the twist angle at section CC is 14.4 degrees. Thereafter, in the embodiment depicted in Figure 4D, the twist angle at section DD is 13.5 degrees. Further, in the embodiment depicted in Figure 4E, the twist angle at section EE is 13.2 degrees.
[026] Thus, as a result, the aerofoil profile of each section and the twist angle of each section is defined such that the twist angle gradually increases and thereafter gradually decreases as explained hereinbefore. Such a configuration allows for achieving a higher lift coefficient i.e. that the lift force experience by the blade 100 is higher, which leads to a larger volume of air being pushed by the blade 100. The higher volume of air as well as increased spread value is achieved without increasing the sweep size of the fan (overall diameter of the fan).
[027] Such a configuration also allows for reduced drag of the blade 100, which results in lower power consumption while ensuring higher volume of air delivery. The configuration of the present invention allows for the lift value to be 20-60 times higher than the drag value, thus ensuring higher air delivery with lower power consumption.
[028] Further, in an embodiment, the blade 100 is made of one of a plastic Acrylonitrile butadiene styrene (ABS) material, a Polyphenylene Ether (PPE) material or a Polyphenylene Oxide (PPO) material, or any other mouldable or extrudable polymer compound. The blade 100 is formed by a moulding technique whereby a body of the blade 100 is integrally formed in a single piece. This ensures that the blade 100 is not only cost effective, but also lightweight which lowers the power consumption for sufficient air delivery. Further, the width of the blade 100 being constant also ensures that sufficient air delivery can be provided while reducing the weight, and also improving aesthetics.
[029] Advantageously, the present invention provides a blade for a fan which provides for higher spread value of airflow, as well as higher volume of airflow, without increasing the sweep size of the fan. Further, the present invention also provides for blade with higher aerodynamic efficiency, meaning that the value of lift is high while the value of drag is lower, meaning that high air delivery can be ensured while drawing less current.
[030] Further, the weight of the ceiling fan blade as provided in the present invention is less owing to the material used and the width of the blade being uniform. Further, the blade is cost-effective as the present invention uses plastic ABS material, or PPE material or PPO material.
[031] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.
,CLAIMS:1. A blade (100) for a fan, the blade (100) comprising:
an inner end (100A) and an outer end (100B), the inner end (100A) being attached to a central hub of the fan, the blade (100) extending from the inner end (100A) to the outer end (100B), the blade (100) having a predetermined lift angle (?) with respect to a horizontal X-axis, whereby the outer end (100B) of the blade (100) is at a higher elevation with respect to the inner end (100A) of the blade (100), and the blade (100) having a plurality of sections as the blade (100) extends from the inner end (100A) to the outer end (100B), each section of the plurality of sections is defined by an aerofoil profile and each section of the plurality of sections having a different twist angle.

2. The blade (100) as claimed in claim 1, wherein the predetermined lift angle (?) being provided between the horizontal X-axis and an axis extending between a bottom point of the inner end (100A) of the blade (100) and a tip point of the outer end (100B) of the blade (100).

3. The blade (100) as claimed in claim 1, wherein the plurality of sections being configured to be provided distally to each other.

4. The blade (100) as claimed in claim 1, wherein the width of the blade (100) being constant across each of the plurality of sections.

5. The blade (100) as claimed in claim 1, wherein a section (OO) of the blade (100) is provided at the inner end (100A) of the blade (100), and a thickness of the blade (100) at the section (OO) is greater than the thickness of the blade (100) at each of the sections (AA, BB, CC, DD, EE).

6. The blade (100) as claimed in claim 1, wherein a distance from section (OO) to section (AA), section (AA) to section (BB), section (BB) to section (CC), and section (CC) to section (DD) is equal to the width of the blade (100), and the distance from section (DD) to section (EE) is half of the width of the blade (100).

7. The blade (100) as claimed in claim 1, wherein the twist angle being an angle between a chord line of the aerofoil profile at each of the plurality of sections and a horizontal Y-axis extending in a width direction of the blade (100).

8. The blade (100) as claimed in claim 7, wherein the twist angle of the blade (100) gradually increases from the section (AA) to the section (BB) of the blade (100), and the twist angle of the blade (100) gradually decreases from the section (BB) to the section (EE) of the blade (100).

9. The blade (100) as claimed in claim 1, wherein the blade (100) is made of one of plastic Acrylonitrile Butadiene Styrene (ABS) material, a Polyphenylene Ether (PPE) material or a Polyphenylene Oxide (PPO) material.