Claims:We Claim:

1. A casing (20) for a blower (10), the casing (20) comprising:
an outlet portion (205) of the casing (20) for air to be discharged from the blower (10);
characterized in that:
a plurality of projections (210) disposed along an internal surface (215) of the outlet portion (205), the plurality of projections (210) disposed along a circular band (220), an axis of the circular band (220) coaxial with an axis of the outlet portion (205).

2. The casing (20) as claimed in claim 1, wherein each projection in the plurality of projections (210) is an aerofoil, the aerofoil collinear to the axis of the outlet portion (205).

3. The casing (20) as claimed in claim 2, wherein a leading edge (225) of the each projection of the plurality of projections (210) face an internal portion (230) of the blower (10).

4. The casing (20) as claimed in claim 1, wherein each projection in the plurality of projections (210) has a corresponding projection from an opposite side of the outlet portion (205) of the casing (20), wherein the each projection and the corresponding projection extend towards each other.

5. The casing (20) as claimed in claim 1, wherein the outlet portion (205) of the casing (20) comprises two hemispherical halves (205a, 205b).

6. A blower (10), comprising:
a casing (20) for a blower (10), the casing (20) comprising an outlet portion (205) for the air to be discharged from the blower (10);
characterized in that:
a plurality of projections (210) disposed along an internal surface (215) of the outlet portion (205), the plurality of projections (210) disposed along a circular band (220), an axis of the circular band (220) coaxial with an axis of the outlet portion (205).

7. The blower (10) as claimed in claim 6, wherein each projection in the plurality of projections (210) is an aerofoil, the aerofoil collinear to the axis of the outlet portion (205).

8. The blower (10) as claimed in claim 7, wherein a leading edge (225) of the each projection of the plurality of projections (210) face an internal portion (230) of the blower (10).

9. The blower (10) as claimed in claim 6, wherein each projection in the plurality of projections (210) has a corresponding projection from an opposite side of the outlet portion (205) of the casing (20), wherein the each projection and the corresponding projection extend towards each other.

10. The blower (10) as claimed in claim 6, wherein the outlet portion (205) of the casing (20) comprises two hemispherical halves (205a, 205b).
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a casing for a blower and a blower.

Background of the invention
[0002] An air blower is also a type of power tool which is popularly used in industrial facilities. Air blowers are used to blow air at a required speed and volume in industries. The outlet of a blower is always open and during periods of non-use, there are chances of dust and small foreign particles entering the blower and damaging the internal components and fan. This can prove to be costly, as the internal parts need to be changed or the blower to be replaced if the damage is heavy. Breakage of fan blades may also lead to injury of the user as the fan blades can fly out of the outlet of the blower, when switched on.

[0003] A mesh covering the outlet of the blower was used to prevent entry of particles inside the outlet of the blower. Maintenance of the fitted component and decrease in volumetric efficiency of the blower were the problems associated with this. Moreover, caps for covering the outlet of the blower brought in the disadvantage of the caps being missed and lost as well. There is thus a need to mitigate the problems encountered above.

Brief description of the accompanying drawing
[0004] Figure 1 illustrates an isometric view of a blower;

[0005] Figure 2 illustrates an exploded front view of an outlet portion of the blower;

[0006] Figure 3 illustrates a front view of the assembled outlet portion of the blower; and
[0007] Figure 4 illustrates a cut side view of the outlet portion of the blower.

Detailed description of the embodiments
[0008] Figure 1 illustrates an isometric view of a blower. Figure 2 illustrates an exploded front view of an outlet portion of the blower. Figure 3 illustrates a front view of the assembled outlet portion of the blower and Figure 4 illustrates a cut side view of the outlet portion of the blower.

[0009] An air blower 10 as illustrated in Figure 1 comprises a casing 20 enclosing all the internal components of the blower 10 such as a fan and other electrical and fastening components. The blower 10 also comprises a handle (not shown in the drawings), which enables the blower 10 to be held or lifted.

[0010] As illustrated in Figure 1, the casing 20 of the blower 10 comprises an outlet portion 205 which allows the air to be discharged out of the blower 10. As illustrated in Figure 2, the outlet portion 205 further comprises a plurality of projections 210 disposed along an internal surface 215 of the outlet portion 205. The plurality of projections 210 are disposed along a circular band 220, an axis of the circular band 220 coaxial with an axis of the outlet portion 205. The circular band 215 and the axis of the outlet portion 205 will be described hereinafter.

[0011] Figure 3 illustrates a front view of the assembled outlet portion 205 of the blower 10. The space between the plurality of projections 210 allow the discharge of air from the blower 10. Figure 4 illustrates a cut side view of the outlet portion 205 of the blower 10. This shows only one half. There is another similar half with the plurality of projections 210. The circular band 220 is a band along which the plurality of projections are arranged or disposed along the internal surface 215 of the outlet portion 205. The band 220 is indicated for purposes of explanation. The axis of the outlet portion 205 is indicated by A-A. Each projection within the plurality of projections 210 is an aerofoil, the aerofoil disposed in such a way that they are collinear to the axis A-A of the outlet portion 205. In other words, the aerofoil shaped projections tend to be orientated along the axis A-A of the outlet portion 205. Moreover, the aerofoil shaped projections are orientated in such a way that a leading edge 225 of each projection of the plurality of projections 210 face an internal portion 230 of the blower 10. In other words, the leading edge 225 of each projection of the plurality of projections 210 face the flow of air from the internal portion 230 of the blower 10.

[0012] Each projection within the plurality of projections 210 has a corresponding projection in the plurality of projections 210 from an opposite side of the outlet portion 205 of the casing 20, wherein the each projection and the corresponding projection extend towards each other. The outlet portion 205 of the casing 20 comprises two hemispherical halves. There is described herewith with respect to Figure 2. Figure 2 shows two halves 205a and 205b of the outlet portion 205 of the casing 20. The two halves 205a and 205b are hemispherical which comprises projections. Each projection in any half 205a and 205b of the outlet portion 205 has a corresponding projection on the other half in 205a and 205b, which is from the opposite side of the outlet portion 205. As an example, 206a and 206b are corresponding projections from both halves 205a and 205b of the outlet portion 205. Similarly, 207a and 207b are corresponding projections from both halves 205a and 205b of the outlet portion 205.

[0013] For the purposes of description, the first half is 205a and the second half is 205b. Between all pairs of corresponding projections from the first half and the second half, one projection is longer than the corresponding projection. In other words, the corresponding projections on the first half and the second half are not equal in length. Moreover, between the successive corresponding projections, the longer projection alternates between the first half and the second half. For example, consider the projections 206a, 206b, 207a and 207b. Projection 206a on the first half 205a is shorter than the corresponding projection 206b on the second half 205b. And, projection 207a on the first half 205a is longer than the corresponding projection 207b on the second half 205b. This provides a continuing interval 208 between the corresponding projections on both halves that is inclined or curved or bending or wave shaped. This can be visualized from Figure 2 and Figure 3. The advantage of this is that long particles cannot enter inside the outlet portion 205.

[0014] The chord length of the aerofoil is 12 mm. The chord length for an aerofoil is the distance between the trailing edge and the point on the leading edge where the chord intersects the leading edge. The thickness of the aerofoil is 2 mm. The thickness to length ratio is 1:6. In one exemplary arrangement, the number of projections or ribs can be 7 with a rib to rib gap less than 4 mm. Other arrangements can be with a different number of ribs or projections, but maintaining a rib to rib gap of 4 mm or less.

[0015] Some of the advantages of integrating the above described aerofoil projections as a mesh with the two halves of the casing 205 are: reduction in separate components for acting as a mesh or filter for trapping foreign particles, easy tooling with plastic molding which reduces the overall component cost and cost of assembly. By using the aerofoil shaped projections acting as a mesh or filter for trapping or filtering foreign particles, the reduction in cost can be around 8 to 10%, when compared with using a separate mesh or filter attached to the outlet portion 205.

[0016] In another arrangement of the projections or the ribs, the length or the chord length of the ribs is reduced by 3mm in alternate ribs to achieve a rib to rib gap of 4mm or less than 4mm.
[0017] Other shapes of the ribs or projections that can be applied in the outlet portion 205 apart from aerofoil are planar, prismatic, bullet shaped and spherical. Provided below are the calculations for selecting the shape which provides for optimum volumetric efficiency. The length (L) is considered to be 12mm for all above shapes, for purposes of calculations. The air flow velocity (u) in the outlet portion 205 of the blower 10 is considered to be 66.1375 m/s based on the air quantity delivered by the blower 10 and the cross sectional area of the outlet portion 205. This is from empirical observations.

[0018] The drag coefficients (Cd) for the different shapes are as follows:
Flat plate (planar), Cd = 1.28
Prism, Cd = 1.14
Bullet, Cd = 0.295
Sphere, Cd = 0.07 to 0.5
Aerofoil, Cd = 0.045

[0019] The formula for determining D (drag force/unit area) = (Cd?u2)/2, where
Cd = Drag coefficient
? = density of the fluid (1.225 kg/m3 for air)
u = air flow velocity in the outlet portion 205 of the blower 10 (assumed to be 66.1375 m/s)

[0020] For the calculations, ? and u being constants, Cd is the least for an aerofoil when compared to other profiles and therefore, D which is the drag force/unit area will be the least for an aerofoil profile when compared to other profiles, which is based on the above formula.

[0021] Drag force is commonly understood by a person skilled in the art. It is known that drag force and volumetric efficiency are inversely proportional to each other and therefore, the lesser the drag force, the higher the volumetric efficiency.

[0022] The advantage of having an aerofoil profile to the projections or ribs is to maintain the volumetric efficiency at desirable limits. Another advantage is that the projections can be formed integral with the casing, which brings down the cost of manufacture and ease of manufacture of the casing.

[0023] The blower 10 comprises the casing 20 described above.

[0024] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.