FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“BLADE FOR A CEILING FAN”
We, Bajaj Electricals Limited, an Indian National, of 45/47, Veer Nariman Road, Fort, Mumbai- 400001, Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD OF INVENTION
The present invention relates to a ceiling fan. Particularly, the present invention relates to a blade for a ceiling fan.
BACKGROUND
Ceiling fans are most domestically used comfort provider in sub-tropical/tropical regions worldwide. A conventional ceiling fan comprises a rod mounted on the ceiling, a motor unit connected with the rod, and a plurality of metal blades connected with the motor unit. In ceiling fans, the electric energy is transformed into mechanical energy by the rotation of the motor shaft. This energy is then converted into kinetic energy of the airflow by interaction with the blades. The conventional metal blades are usually flat and oriented at an inclination for cutting the air thereby provides circulation of air downwardly.
It is known in the art that the blade weight, blade configuration and profile of the blade plays significant role in performance of the ceiling fan. Accordingly, by enhancing the profile of the blade, it is possible to increase the coefficient of performance (COP) of a ceiling fan which describes the fan efficiency. However, alteration of the profile of the metal blades is difficult due to manufacturing limitations.
Also, it has seen that during operation of the fan, the air passes through an upper surface of the blade, may cause turbulence on the upper side of the blade. Such turbulence causes vibrations in the blade and said vibrations may results in failure of the blade and significantly affects the efficiency of the fan.
Efforts have been made to solve the said problems by inclusion of plastic blades. The prior art discloses providing a ceiling fan plastic blade with curved

shape which may enhance the air delivery and reduce the noise generated due to air cutting thereby provide a better solution with optimum electricity consumption. However, there is a limitation with respect to said blades as further improvement of air delivery and reduction of noise would not be possible without increase the length of the blades. Also, to cater the vibration, the thickness and width of blade is to be increased. Such increase in length and width of the blades may result in more weight and higher electricity consumption.
Therefore, there is need for a blade for a ceiling fan which can overcome one or more limitations stated above or any other limitations associated with the prior art.
SUMMARY OF THE INVENTION:
In order to overcome the above-mentioned problems, the present invention in a preferred embodiment provides a blade for a ceiling fan. The blade comprising a body having a thickness, longitudinally extends between a motor end and a tip end of the blade; an airfoil of the body comprising a leading edge, a trailing edge and a middle section defined along a profile of the airfoil; and the thickness of the airfoil varies along the profile, wherein a maximum thickness of the airfoil is defined at the middle section and a minimum thickness of the airfoil is defined at the leading edge.
As per an embodiment of the present invention, the body has the thickness, comprising a trailing edge thickness of the trailing edge, a leading edge thickness of the leading edge, and a middle section thickness of the middle section, wherein the trailing edge thickness measures between the leading edge thickness and the middle section thickness.

As per another embodiment of the present invention, the airfoil reduces turbulence to air cutting, thereby ensuring high efficiency, less noise during the air cutting and high air delivery.
As per yet another embodiment of the present invention, the blade has a depth between 3 mm and 6 mm increasing towards the tip end from the motor end.
As per yet another embodiment of the present invention, the blade has a twist angle between 12° and 9° decreasing from the motor end towards the tip end.
As per yet another embodiment of the present invention, the leading edge thickness is between 1 mm and 3 mm. The trailing edge thickness is between 1.5 mm and 3.5 mm. The middle section thickness is between 3.5 mm and 5.5 mm.
As per yet another embodiment of the present invention, the blade has a lift angle between 5° and 8°.
As per yet another embodiment of the present invention, the blade has a length between 545 mm and 555 mm.
As per yet another embodiment of the present invention, the blade comprising a joining portion for fixing the blade to a motor assembly, whereby the joining portion is having a thickness between 7 mm and 9 mm.
As per yet another embodiment of the present invention, the blade has a varying width between 95mm and 200 mm. The blade has a width at the joining portion between 190 mm and 200 mm. The blade has a width at the tip end

between 95mm and 105 mm. The blade has a width at the motor end, between 110 mm and 120 mm. The blade has a width at the middle section, between 125 mm and 135 mm.
As per yet another embodiment of the present invention, air delivery of the blade is between 250 and 270 CMM at 320 to 350 RPM, whereby sweep size of the fan is 1200 mm.
As per yet another embodiment of the present invention, the blade is made of a material selected from a group comprising aluminium, steel, galvanized sheet, compounded polymer, composites and combinations thereof.
As per yet another embodiment of the present invention, the blade is manufactured by a manufacturing process selected from a group comprising casting, molding, fabrication, powder metallurgy, extrusion and metal additive methodology.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF DRAWINGS
The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some

implementations of the system(s), in accordance with the present subject matter, are described by way of examples, and with reference to the accompanying figures, in which:
Fig. 1 illustrates a perspective view of a ceiling fan assembly, as per an embodiment of the present invention.
Fig. 2 illustrates a plan view of the blade of the ceiling fan, as per an embodiment of the present invention.
Fig. 3 illustrates a sectional view of the blade of the ceiling fan indicating lift angle, as per an embodiment of the present invention.
Fig. 4 illustrates cut sectional views of the blade of the ceiling fan indicating varying depth and twist angle, as per an embodiment of the present invention.
Fig. 5 illustrates cut sectional views of the blade of the ceiling fan indicating varying width, as per an embodiment of the present invention.
DETAILED DESCRIPTION
While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiment illustrated.
Before describing in detail, the various embodiments of the present

disclosure it may be observed that the novelty and inventive step are in accordance with a blade for a ceiling fan. It is to be noted that a person skilled in the art can be motivated from the present disclosure and can perform various modifications. However, such modifications should be construed within the scope of the invention.
Accordingly, the drawings are showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that an assembly, setup, system, device that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system or device or setup. In other words, one or more elements in the system or apparatus or device proceeded by "comprises a" does not, without more constraints, preclude the existence of other elements or additional elements in the assembly or system or apparatus or device.
The present invention in a preferred embodiment provides a blade for a ceiling fan having an improved profile with varying thickness for higher air delivery of the blade. The blade comprising a body having a thickness, longitudinally extends between a motor end and a tip end of the blade; an airfoil of the body comprising a leading edge, a trailing edge and a middle section defined along a profile of the airfoil; and the thickness of the airfoil varies along the profile, wherein a maximum thickness of the airfoil is defined at the middle section and a minimum thickness of the airfoil is defined at the leading edge. The thickness of the body comprising a trailing edge thickness of the trailing edge between 1.5 mm and 3.5 mm, a leading edge thickness of the leading edge

between 1 mm and 3 mm, and a middle section thickness of the middle section between 3.5 mm and 5.5 mm, wherein the trailing edge thickness measures between the leading edge thickness and the middle section thickness. The blade further comprising a joining portion for fixing the blade to a motor assembly, whereby the joining portion is having a thickness between 7 mm and 9 mm.
The blade has a depth between 3 mm and 6 mm increasing towards the tip end from the motor end and a twist angle between 12° and 9° decreasing from the motor end towards the tip end. The blade has a lift angle between 5° and 8°. The blade has a varying width between 95mm and 200 mm. The airfoil of the blade reduces turbulence to air cutting, thereby ensuring high efficiency, less noise during the air cutting and high air delivery. The blade has a length between 545 mm and 555 mm.
The subject matter is now described regarding the drawings, wherein like reference numerals are used to refer to like features/elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It may be evident; however, that such matter can be practiced without these specific details. In other instances, well–known structures are shown in diagram form to facilitate describing the invention.
Referring to figure 1, an exemplary blade (100) mounted on a ceiling fan (200) according to exemplary embodiment of the present invention is depicted. The ceiling fan (200) comprising a plurality of blades (100), a canopy (210) covering a down rod (not shown) and a motor assembly (220). The down rod comprising a pair of mountings provided at both ends to mount the ceiling fan (200) at the ceiling and to hold the motor assembly (220). The down rod is covered with the canopy (210) to provide aesthetic appeal to the ceiling fan (200). In an embodiment of the present invention, the plurality of blades (100)

are three in number. In another embodiment of the present invention, the plurality of blades (100) can be more than three based on the requirement. The plurality of blades (100) are adapted to be mounted on a hub of the motor assembly (220) with fastening means.
Referring to figures 1 to 5, the blade (100) comprising a body having a thickness. The blade (100) longitudinally extends between a motor end (110) and a tip end (120) of the blade and an airfoil (130) of the body comprising a leading edge (132), a trailing edge (134) and a middle section (136) defined along a profile of the airfoil (130). The leading edge (132) is the edge where the blade (100) starts compressing the air till the trailing edge (134). The thickness of the airfoil (130) varies along the profile, wherein a maximum thickness of the airfoil (130) is defined at the middle section (136) and a minimum thickness of the airfoil is defined at the leading edge (132). In an embodiment of the present invention, the blade (100) comprising a joining portion (140) for fixing the blade (100) to the motor assembly (220). In another embodiment of the present invention, the joining portion (140) is having a thickness between 7 mm and 9 mm.
The thickness of the blade (100) comprising a trailing edge thickness of the trailing edge (134), a leading edge thickness of the leading edge (132), and a middle section thickness of the middle section (134). In an embodiment of the present invention, the trailing edge thickness measures between the leading edge thickness and the middle section thickness.
Referring to figures 2 to 5, the blade (100) has been divided into four sections DD, EE, FF, and GG at predefined distances from the centre of the motor assembly (220), respectively. In an embodiment of the present invention, the sections DD, EE, FF, and GG are defined at 206 mm, 306 mm, 406 mm and 506 mm from the edge of the tip end (110) of the blade, respectively.

In an embodiment of the present invention, as shown in figure 2, the blade (100) has a varying width between 95mm and 200 mm. In another embodiment of the present invention, the blade has a width (117) at the joining portion (140) between 190 mm and 200 mm. In another embodiment of the present invention, the blade has a width (115) at the tip end (120) between 95mm and 105 mm. In yet another embodiment of the present invention, the blade has a width (111) at the motor end (110), between 110 mm and 120 mm. In yet another embodiment of the present invention, the blade has a width (113) at the middle portion (150), between 125 mm and 135 mm.
In a preferred embodiment of the present invention, as shown in figure 3, the blade (100) comprising a lift angle (101) from the motor end (110) towards the tip end (120) with respect to the horizontal plane defined as axis X. In another embodiment of the present invention, the lift angle (101) is between 5° and 8° at different sections i.e., DD, EE, FF, and GG as shown in figure 3. The lift angle (101) helps in improving the spread of the air velocity from the centre of the ceiling fan (200) thus ensure high air delivery.
In an embodiment of the present invention, as shown in figure 4, the blade (100) comprising a twist angle (103) along length of the blade from the motor end (110) to the tip end (120) with respect to the vertical plane defined as axis Y. The twist angle (103) decreases from the motor end (110) towards the tip end (120) of the blade. In another embodiment of the present invention, the twist angle (103) is between 12° and 9° decreasing from the motor end (110) towards the tip end (120) at different sections i.e., DD, EE, FF, and GG as shown in figure 4.
In an embodiment of the present invention, as shown in figure 4, the blade (100) has a depth (105) between 3 mm and 6 mm increasing towards the

tip end (120) from the motor end (110) at different sections i.e., DD, EE, FF, and GG. The depth (105) of the blade (100) helps in increasing the air pressure in the ceiling fan (200).
Referring to figure 5, the varying thickness of the blade (100) as defined along the profile of the airfoil (130) of the blade at different sections i.e., DD, EE, FF, and GG, ensure reducing turbulence at an upper surface (160) of the blade (100) thereby reducing vibrations. As the leading edge thickness is minimum, the resistance to air cutting is minimal. Further, when the air cut through the profile of the airfoil (130) of the blade, the air moves from the leading edge (132) towards trailing edge (134) of the blade through a lower surface (170) and the upper surface (160) of the blade. The air which passed through the lower surface (170) of the blade presses the air downwards. Further, as the profile of the airfoil (130) of the blade is such that leading edge thickness is minimum and the middle section thickness is maximum, the flow of air through the upper surface (160) become laminar. As the laminar flow of air is achieved at the upper surface (160) of the blade, the requirement of increasing thickness never arises. In an embodiment of the present invention, the ratio of thickness among leading edge thickness, middle section thickness and trailing edge thickness is 0.5: 1: 0.62, respectively. In another embodiment of the present invention, the leading edge thickness is between 1 mm and 3 mm. In yet another embodiment of the present invention, the trailing edge thickness is between 1.5 mm and 3.5 mm. In yet another embodiment of the present invention, the middle section thickness is between 3.5 mm and 5.5 mm.
In an embodiment of the present invention, the blade (100) has a length between 545 mm and 555 mm. The blade (100) is made of a material selected from a group comprising aluminum, steel, galvanized sheet, compounded polymer, composites and combinations thereof. Further, the blade (100) may be manufactured by a manufacturing process selected from a group comprising

casting, molding, fabrication, powder metallurgy, extrusion and metal additive methodology.
Accordingly, the blade of the ceiling fan as disclosed in the present disclosure provides an effective aerodynamic profile of the airfoil with variable width which ensures air delivery between 250 and 270 CMM at 320 to 350 RPM, whereby sweep size of the fan is 1200 mm. The airfoil of the blade reduces turbulence to air cutting, thereby ensuring high efficiency, less noise during the air cutting and high air delivery. Therefore, the blade ensures significant increase in air delivery and noise reduction without increasing the length and width of the blade. Accordingly, the ceiling fan provides more air delivery with less electricity consumption.
Although examples for the present disclosure have been described in language specific to structural features and/or methods, it should be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained as examples of the present disclosure.
While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the invention herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:
1. A blade (100) for a ceiling fan (200), the blade (100) comprising:
a body having a thickness, longitudinally extends between a motor end
(110) and a tip end (120) of the blade;
an airfoil (130) of the body comprising a leading edge (132), a trailing
edge (134) and a middle section (136) defined along a profile of the airfoil
(130); and
the thickness of the airfoil (130) varies along the profile, wherein a
maximum thickness of the airfoil (130) is defined at the middle section
(136) and a minimum thickness of the airfoil (130) is defined at the
leading edge (132).
2. The blade (100) as claimed in claim 1, wherein the body has the thickness, comprising a trailing edge thickness of the trailing edge (132), a leading edge thickness of the leading edge (134), and a middle section thickness of the middle section (136), wherein the trailing edge thickness measures between the leading edge thickness and the middle section thickness.
3. The blade (100) as claimed in claim 1 or claim 2, wherein the airfoil (130) reduces turbulence to air cutting, thereby ensuring high efficiency, less noise during the air cutting and high air delivery.
4. The blade (100) as claimed in any one of preceding claims 1 to 3, wherein the blade has a depth (105) between 3 mm and 6 mm increasing towards the tip end (120) from the motor end (110).
5. The blade (100) as claimed in any one of the preceding claims 1 to 4, wherein the blade has a twist angle (103) between 12° and 9° decreasing from the motor end (110) towards the tip end (120).

6. The blade (100) as claimed in any one of the preceding claims 1 to 5,
wherein the leading edge thickness is between 1 mm and 3 mm.
7. The blade (100) as claimed in any one of the preceding claims 1 to 5,
wherein the trailing edge thickness is between 1.5 mm and 3.5 mm.
8. The blade (100) as claimed in any one of the preceding claims 1 to 5, wherein the middle section thickness is between 3.5 mm and 5.5 mm.
9. The blade (100) as claimed in any one of the preceding claims 1 to 8, wherein the blade has a lift angle (101) between 5° and 8°.
10. The blade (100) as claimed in any one of preceding claims 1 to 9, wherein the blade (100) has a length between 545 mm and 555 mm.
11. The blade (100) as claimed in any one of preceding claims 1 to 10, wherein the blade comprising a joining portion (140) for fixing the blade to a motor assembly (220), whereby the joining portion (140) is having a thickness between 7 mm and 9 mm.
12. The blade (100) as claimed in any one of preceding claims 1 to 11, wherein the blade has a varying width (111,113,115,117) between 95mm and 200 mm.
13. The blade (100) as claimed in any one of preceding claims 1 to 12, wherein the blade has a width (117) at the joining portion between 190 mm and 200 mm.
14. The blade (100) as claimed in any one of preceding claims 1 to 12, wherein the blade has a width (115) at the tip end between 95mm and

105 mm.
15. The blade (100) as claimed in any one of preceding claims 1 to 12, wherein the blade has a width (111) at the motor end, between 110 mm and 120 mm.
16. The blade (100) as claimed in any one of preceding claims 1 to 12, wherein the blade has a width at the middle section (113), between 125 mm and 135 mm.
17. The blade (100) as claimed in any one of preceding claims 1 to 16, wherein air delivery of the plurality of blades (100) of the ceiling fan (200) is between 250 and 270 CMM at 320 to 350 RPM, whereby sweep size of the ceiling fan (200) is 1200 mm.
18. The blade (100) as claimed in any one of preceding claims 1 to 17, wherein the blade (100) is made of a material selected from a group comprising aluminum, steel, galvanized sheet, compounded polymer, composites and combinations thereof.
19. The blade (100) as claimed in any one of preceding claims 1 to 18, wherein the blade (100) is manufactured by a manufacturing process selected from a group comprising casting, molding, fabrication, powder metallurgy, extrusion and metal additive methodology.