FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“PLASTIC CEILING FAN WITH CARBON FIBRE REINFORCEMENT”
I/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.

FIELD OF INVENTION
The present invention generally relates to the design of a fan. In particular, the present invention relates to a blade of a fan with improved stiffness without significant increase in thickness of the blade.
BACKGROUND OF THE INVENTION
This section is intended to provide information relating to the field of disclosure and thus, any approach or functionality described herein should not be assumed to qualify as prior art merely by its inclusion in this section.
Fans have a plurality of blades disposed circumferentially about a central rotating hub. Each of the blades generally has an airfoil profile, such that, as the blades rotate about the central hub, air is pushed along a direction along the axis of the central hub. Particularly, in high volume flow fans, the blades are required to rotate at higher speeds to push a larger volume of air. Higher speed of rotation causes a higher flexural stress to be incident on the blades. In order to withstand this stress, the blades are preferred to have high stiffness.
Generally, the blades are made of a plastic, and in order to increase stiffness of the blades, glass fibre is embedded within the blade body. However, while incorporating glass fibre may cause strength of the blade to increase, it also causes the thickness of the blades to increase. Such a design adds to weight of the blade, resulting in potential loss in efficiency of fan due to the higher energy required to rotate heavier blades. Furthermore, such a design limits a choice of material for body of the blade to high strength plastics, which are expensive.
There is, therefore, a requirement in the art, for a blade of a fan to have increased stiffness without significantly increasing the thickness of the blade.
SUMMARY OF THE INVENTION
This section is intended to introduce one or more aspects and/or embodiments of the present disclosure in a simplified form and is not intended to identify any key advantages or features of the present disclosure.

In an aspect, the present disclosure provides a blade of a fan, characterized in that the blade comprises at least a slot extending along the length of the blade, wherein at least a stiffness element is disposed within the slot.
In an aspect, the stiffness element is insert moulded with the slot.
In an aspect, the blade comprises a plurality of slots, wherein the plurality of slots are separated by a predefined distance.
In an aspect, the predefined distance between adjacent slots is in the range of 15 to 30 millimeters.
In an aspect, the predefined distance between adjacent slots is 25 mm.
In an aspect, the stiffness element is carbon fiber rod.
In an aspect, the carbon fiber cross section is 1 to 3 mm.
In an aspect, the carbon fiber cross section is 2 mm.
In an aspect, the blade is made of a material selected from the group consisting of polypropylene (PP), high-impact polystyrene (HIPS), and acrylonitrile butadiene styrene (ABS).
In an aspect, the stiffness element is affixed in the slot via a binding agent.
In an aspect, the binding agent comprises at least an epoxy resin.
In an aspect, the present invention provides a fan comprising one or more blades, characterized in that at least one of the one or more blades comprises at least a slot extending along the length of the blade, wherein at least a stiffness element is disposed within the slot.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The present disclosure, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the description, taken in connection with the accompanying drawings. These and other details of the present invention will be described in connection with the accompanying drawings, which are furnished only by way of illustration and not in limitation of the scope of the present disclosure.

FIG. 1 illustrates a schematic sectional view of a blade of a fan, according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of one or more embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. Several features described hereafter may each be used independently of one another or in any combination with other features. An individual feature may not address any of the problems discussed above or may address only some of the problems discussed above. Some of the problems discussed above may not be fully addressed by any of the features described herein. Example embodiments of the present disclosure are described below, as illustrated in various drawings, in which same reference numerals refer to the same parts throughout the different drawings.
The present disclosure provides a fan, and a blade of a fan. In an embodiment, the fan comprises a plurality of blades. In an embodiment, the fan comprises at least 3 blades, at least 4 blades, or at least 5 blades. The plurality of blades is arranged circumferentially about a central rotating hub. In an embodiment, the plurality of blades is angularly separated at equal distances between one another. As the hub rotates, the blades coupled to the hub also rotate. The blades comprise an air foil profile, such that as the blades rotate about the hub, they direct a flow of air along a direction axial to the central hub. The blade is made of a lightweight material. The material is such as to be easily manufacturable. In an embodiment, the material is selected from a group consisting of a metal, an alloy, a plastic, a composite, a ceramic, glass, and combinations thereof. In a preferred embodiment, the material is selected from a group consisting of polypropylene (PP), high-impact polystyrene (HIPS), and acrylonitrile butadiene styrene (ABS).
The blade comprises at least one slot extending along the length of the blade. In an embodiment, the slot extends at least partially along the length of the blade.

In an embodiment, the slot extends at least 50% the length of the blade. In an embodiment, the slot is disposed proximal to the central hub. In another embodiment, the slot is disposed proximal to the free end of the blade. In an embodiment, the slot is arranged parallel to the longitudinal axis of the blade. In another embodiment, the slot is arranged at an angle relative to the longitudinal axis of the blade. In an embodiment, the slot comprises a depth extending into the thickness of the profile of the blade. In an embodiment, the depth is less than 50% of the average thickness of the profile of the blade. In an embodiment, the slot is machined into the blade by processes such as milling. In an embodiment, the slot is prefabricated during moulding of the blade.
In an embodiment, the blade comprises a plurality of slots extending along the length of the blade. In an embodiment, the blade comprises at least 2 slots. In a preferred embodiment, the blade comprises three slots. In an embodiment, the plurality of slots is arranged parallel to one another. In another embodiment, the plurality of slots is arranged at angles relative to one another, such that no two slots intersect with each other. In an embodiment, the slots are separated by a predefined distance. The predefined distance is defined along the lateral axis of the blade. In an embodiment, the predefined distance is in the range of 15 millimeters (mm) to 30 mm. In a preferred embodiment, the predefined distance is about 25 mm.
In an alternate embodiment, the plurality of slots is arranged at angles relative to one another, such at least two slots intersect with each other.
The blade comprises at least a stiffness element disposed within the slot. In an embodiment, each slot is adapted to accommodate a single stiffness element. In another embodiment, each slot is adapted to accommodate a plurality of stiffness elements. In such embodiments, each slot accommodates a plurality of stiffness elements, where the plurality of stiffness elements is arranged in series with each other, are stacked over one another, or a combination thereof. In an embodiment, the stiffness element is insert moulded with the slot. In an embodiment, the stiffness element comprises a material selected from a group consisting of plastic, metal, composite, carbon fiber, ceramic, and combinations thereof. In a preferred embodiment, the stiffness element comprises carbon fiber. In an embodiment, the

stiffness element is in the form of fibres, a rod, yarn, and combinations thereof. In a preferred embodiment, the stiffness element comprises carbon fiber rods. In an embodiment, the stiffness element rods have a cross section in the range of 1 mm to 3mm. In a preferred embodiment, the stiffness element rods have a cross section of about 2 mm. In an embodiment, the stiffness element rods have a uniform cross section throughout their length. In another embodiment, the stiffness element rods have a varying cross section throughout their length.
In an embodiment, the stiffness element is affixed to the slot via a binding agent. In an embodiment, the binding agent comprises at least an epoxy resin. In a preferred embodiment, the epoxy resin comprises acrylonitrile-based binding agents.
In an exemplary implementation of the invention, the fan comprises three blades disposed the fan comprises at least 3 blades arranged circumferentially about the central rotating hub. The three blades are angularly separated from each other equally. The blades are made of any one or a combination of PP, HIPS, and ABS. Each blade comprises three slots extending along the length of the blade. Each of the three slots is arranged parallel to one another, and is separated from an adjacent slot by the predefined distance of about 25 mm. Each slot accommodates a stiffness element therein. In other words, each blade comprises three stiffness elements disposed within the corresponding three slots. Each stiffness element comprises a carbon fibre rod having a cross section of about 2 mm. Each stiffness element is affixed to the corresponding slot via at least an epoxy resin.
FIG. 1 illustrates a schematic sectional view of a blade 100 of a fan, according to an embodiment of the present invention. The blade 100 comprises three slots 102-1, 102-2, 102-3 extending along the length of the blade 100. The slots 102-1, 102-2, 102-3 may individually be referred to as “the slot 102”, and collectively be referred to as “the slots 102”. The slots 102 are arranged substantially parallel to one another and are separated from each other by a predefined distance in the range of 15 mm to 30 mm. Stiffness elements 104-1, 104-2, 104-3 are disposed within respective slots 102-1, 102-2, 102-3. The stiffness elements 104-1, 104-2, 104-3 may individually be referred to as “the stiffness

element 104”, and collectively be referred to as “the stiffness elements 104”. The stiffness elements 104 are carbon fibre rods having a cross section in the range of 1 mm to 3 mm.
The stiffness elements 104 are insert moulded with the respective slots 102. The stiffness elements are affixed in the respective slots 102 via a binding agent. The binding agent comprises at least an epoxy resin, such as acrylonitrile-based binding agents.
In an example, the yield strength of the blade 100 comprising the stiffness elements 104 is about 110 megapascals (MPa). The yield strength of the blade 100 is almost double that of conventional glass fiber reinforced blades.
The blade 100 provides adequate stiffness due to presence of the stiffness elements 104 embedded in the body of the blade 100. The stiffness elements 104 are made of carbon fibre, which are lightweight, and therefore, do not cause a significant increase in weight of the blade due to incorporation of the stiffness elements in the body of the blade 100. Further, the stiffness elements 104 are embedded within slots 102 provided in the body of the blade 100. As a result, a thickness of the blade 100 is not significantly impacted, due to which aerodynamic efficiency of the blade 100 is further not adversely impacted. The use of such a blade 100 with improved stiffness allows the fan to rotate at greater speeds.
While the preferred embodiments of the present disclosure have been described hereinabove, it may be appreciated that various changes, adaptations, and modifications may be made therein without departing from the spirit of the disclosure and the scope of the appended claims. It will be obvious to a person skilled in the art that the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments may to be considered in all respects only as illustrative and not restrictive.
LIST OF REFERENCE NUMERALS
100 Blade

102 Slot
102-1 Slot
102-2 Slot
102-3 Slot
104 Stiffness Element
104-1 Stiffness Element
104-2 Stiffness Element
104-2 Stiffness Element

I/We Claim:
1. A blade (100) of a fan, characterized in that the blade (100) comprises:
at least a slot (102) extending along the length of the blade (100), wherein at least a stiffness element (104) is disposed within the slot (102).
2. The blade (100) as claimed in claim 1, wherein the stiffness element (104) is insert moulded with the slot (102).
3. The blade (100) as claimed in claim 1, comprising a plurality of slots (102), wherein the plurality of slots (102) are separated by a predefined distance along the length of the blade (100).
4. The blade (100) as claimed in claim 3, wherein the predefined distance between adjacent slots (102) is in the range of 15 to 30 millimeters (mm).
5. The blade (100) as claimed in claim 4, wherein the predefined distance between adjacent slots (102) is 25 mm.
6. The blade (100) as claimed in claim 1, wherein the stiffness element (104) is carbon fiber rod.
7. The blade (100) as claimed in claim 6, wherein the carbon fibre cross section is 1 to 3 mm.
8. The blade (100) as claimed in claim 7, wherein the carbon fibre cross section is 2 mm.

9. The blade (100) as claimed in claim 1, wherein the blade (100) is made of a material selected from the group consisting of polypropylene (PP), high-impact polystyrene (HIPS), and acrylonitrile butadiene styrene (ABS).
10. The blade (100) as claimed in claim 1, wherein the stiffness element (104) is affixed in the slot (102) via a binding agent.
11. The blade (100) as claimed in claim 10, wherein the binding agent comprises at least an epoxy resin.
12. A fan comprising one or more blades (100) as claimed in claim 1.