Claims:WE CLAIM:

1. A fan system (100) comprising:
• a fan (10) comprising an array of fan blades (12) extending outwardly from a centrally disposed hub (12a) and limited by a fan ring (12b), the fan (10) adapted to rotate about an axis of rotation “A” to cause air to move parallel to the axis of rotation “A”;
• a shroud (20) to support the fan (10); and
• at least one acoustic ring (30) secured to the shroud (20) and disposed in an annular space defined between the fan ring (12b) and the shroud (20), the at least one acoustic ring (30) adapted to reduce the noise generated as the fan (10) with the fan ring (12b) rotates within the shroud (20),

characterized in that the at least one acoustic ring (30) forms at least one vortex cavity (32) to reduce backflow of air through the annular space between the shroud (20) and the acoustic ring (30).

2. The fan system (100) as claimed in the previous claim, wherein the shroud (20) comprising an opening (20b) to permit airflow through the shroud (20) and across a heat exchanger (200), the fan (10) and the at least one acoustic ring (30) is disposed in the opening (20b).

3. The fan system (100) as claimed in any of the preceding claims, wherein the fan (10), the shroud (20) and the at least one acoustic ring (30) are concentrically disposed with respect to the axis of rotation “A”.

4. The fan system (100) as claimed in any of the preceding claims, wherein at least one acoustic ring (30) in conjunction with the shroud (20) defines the at least one vortex cavity (32).

5. The fan system (100) as claimed in the preceding claims comprises a first acoustic ring (30a) and a second acoustic ring (30b), wherein the fan (10), the shroud (20), the first acoustic ring (30a) and the second acoustic ring (30b) are concentrically disposed with respect to the axis of rotation “A”.

6. The fan system (100) as claimed in the claim 5, wherein the first acoustic ring (30a) and the second acoustic ring (30b) are connected to each other to define the at least one vortex cavity (32).

7. The fan system (100) as claimed in any of the preceding claims, wherein portion of at least one of the acoustic ring (30a, 30b) and the shroud (20) respectively defining at least one side wall (33a, 23a) of the vortex cavity (32) is forming at least one of acute angle, obtuse angle and right angle with a peripheral wall (35a, 35b) of the acoustic ring (30a, 30b).

8. The fan system (100) as claimed in claim 5, wherein the first acoustic ring (30a) and the second acoustic ring (30b) are over-molded with respect to each other.

9. The fan system (100) as claimed in the previous claim, wherein at least one of the first acoustic ring (30a) and the second acoustic ring (30b) is over-molded with respect to the shroud (20).

10. The fan system (100) as claimed in claim 5, wherein the first acoustic ring (30a) comprises first latching elements (34a) adapted to engage with corresponding second latching elements (20e) and (34b) formed on at least one of the shroud (20) and the second acoustic ring (30b) respectively to configure assembly between the first acoustic ring (30a) and at least one of the shroud (20) and the second acoustic ring (30b).

11. The fan system (100) as claimed in any of the preceding claims, wherein the fan ring (12b) is of L- section.

12. The fan system (100) as claimed in any of the preceding claims, wherein the fan ring (12b) is of I-section.

13. The fan system (100) as claimed in any one of the preceding claims, wherein the at least one vortex cavity (32) is facing the fan ring (12b).

14. The fan system (100) as claimed in any one of the preceding claims, wherein the at least one vortex cavity (32) is defined along at least a portion of a periphery of the acoustic ring (30).

15. The fan system (100) as claimed in any one of the preceding claims, wherein the at least one vortex cavity (32) is defined along entire periphery of the acoustic ring (30).

16. The fan system (100) as claimed in claim 5, wherein the first acoustic ring (30a) and the second acoustic ring (30b) defines two vortex cavities, first vortex cavity (32) defined by the shroud (20) and the first acoustic ring (30a) and second vortex cavity (32) defined by the first acoustic ring (30a) and the second acoustic ring (30b).
, Description:TITLE
A FAN SYSTEM

TECHNICAL FIELD
The present invention relates to a fan system, more particularly, the present invention relates to a fan system for a heat exchanger that is part of a cooling system of a motor vehicle.

BACKGROUND
Generally, a motor vehicle includes a fan system for directing ram air “ar” to a heat exchanger, such as for example, a radiator or a battery cooling system to undergo heat exchange with and to extract heat from a coolant flowing through heat exchange tubes of the radiator or the battery cooler. Referring to FIG. 1 of the accompanying drawings, the fan system 1 includes a fan 2 and a shroud 3. The fan 2 includes an array of fan blades 2a extending outwardly from a centrally disposed hub 2b of the fan 2 and limited by a fan ring 2c. More specifically, the fan ring 2c is secured to an outer tip 2d of the fan 2 and rotates therewith. The fan 2 rotates about an axis of rotation “a” to cause air to move parallel to the axis of rotation “a”. The fan 2 is driven by a motor 4 and directs the ram air “ar” towards the radiator. The shroud 3 is securely mounted on the radiator or battery cooler or a vehicle frame. The fan 2 rotates within an opening configured on the shroud 3 such that an annular space is defined between the shroud 3 and the fan ring 2c to prevent any contact between the rotating fan ring 2c and the shroud 3 when the fan 2 is rotating within the opening of the shroud 3.

However, due to the annular gap between the fan ring 2c of the fan 2 and the shroud 3, there are chances of back-flow “ab” that is undesirable as the back flow “ab” may lead to noise that is generally a problem needed to be addressed in vehicular environment. In conventional engine driven vehicles, the noise caused by back flow of air in the fan system is curbed by the noise of the internal combustion engine. However, the problem of noise created by back flow of “ab in case of electric vehicle is more crucial due to silent operation of electric drive in case of electric vehicle compared to the internal combustion engine. The back flow “ab” of the air further causes inefficient performance of the heat exchanger due to insufficient air reaching the heat exchanger. The conventional fan-assembly 1 fails to address this problem. The conventional sealing such as labyrinth sealing for sealing gap between fan ring 2c and shroud 3 of the conventional fan system 1 is ineffective in sealing the annular gap between the fan ring 2c and shroud 2. Accordingly, the conventional fan system 1 configured with the conventional sealing systems fails to reduce or prevent back flow, i.e. back flow and the drawbacks associated with the back flow.

Accordingly, there is a need for a fan system that eliminates the drawbacks associated with the backflow of air in a direction reverse to direction of ram air by directing back flow along the main flow and towards the heat exchanger for reducing the noise due to back flow of air and improving efficiency and performance of the heat exchanger.

OBJECTS
An object of the present invention is to provide a fan system that obviates the drawbacks associated with back flow of air through gap between a fan ring and a fixed shroud faced in conventional fan systems.

Another object of the present invention is to provide a fan system that configures a vortex cavity in the inherently formed gap between fan ring and fixed shroud to cause hindrance to backflow of air there-through.

A main object of the present invention is to provide a fan system that addresses problem of noise arising due to back flow of the air through inherently formed gap between fan ring and fixed shroud of the fan system.

Yet another object of the present invention is to provide a fan system that enhances efficiency and performance of a heat exchanger, for example, radiator by improving air supply to the radiator.

Still another object of the present invention is to provide a fan system that is simple in construction and easy to manufacture.

Yet another object of the present invention is to provide a fan system that do not require complex tooling to configure a vortex cavity in the inherently formed gap between the fan ring and fixed shroud of the fan system.

In the present description, some elements or parameters may be indexed, such as a first element and a second element. In this case, unless stated otherwise, this indexation is only meant to differentiate and name elements which are similar but not identical. No idea of priority should be inferred from such indexation, as these terms may be switched without betraying the invention. Additionally, this indexation does not imply any order in mounting or use of the elements of the invention.
SUMMARY
A fan system is disclosed in accordance with an embodiment of the present invention. The fan system includes a fan, a shroud and at least one acoustic ring. The fan includes an array of fan blades extending outwardly from a centrally disposed hub and limited by a fan ring. The fan rotates about an axis of rotation “A” to cause air to move parallel to the axis of rotation “A”. The shroud supports the fan. The at least one acoustic ring secured to the shroud and disposed in an annular space defined between the fan ring and the shroud reduces the noise generated as the fan with the fan ring rotates within the shroud. The at least one acoustic ring forms at least one vortex cavity to reduce backflow of air through the annular space between the shroud and the acoustic ring.

Specifically, the shroud includes an opening to permit airflow through the shroud and across a heat exchanger. The fan and the at least one acoustic ring is disposed in the opening.

Generally, the fan, the shroud and the at least one acoustic ring are concentrically disposed with respect to the axis of rotation “A”.

Specifically, at least one acoustic ring in conjunction with the shroud defines the at least one vortex cavity.

In a preferred embodiment of the present invention, the fan system includes a first acoustic ring and a second acoustic ring, wherein the fan, the shroud, the first acoustic ring and the second acoustic ring are concentrically disposed with respect to the axis of rotation “A”.
More specifically, the first acoustic ring and the second acoustic ring are connected to each other to define the vortex cavity.

More specifically, portion of at least one of the acoustic ring and the shroud respectively defining at least one side wall of the vortex cavity is forming at least one of acute angle, obtuse angle and right angle with peripheral wall of the acoustic ring.

Typically, the first acoustic ring and the second acoustic ring are over-molded with respect to each other.

Generally, at least one of the first acoustic ring and the second acoustic ring is over-molded with respect to the shroud.

Specifically, the first acoustic ring includes first latching elements that engages with corresponding second latching elements formed on at least one of the shroud and the second acoustic ring respectively to configure assembly between the first acoustic ring and at least one of the shroud and the second acoustic ring.

Generally, the fan ring is of L- section.

Alternatively, the fan ring is of I- section.

Specifically, the at least one vortex cavity is facing the fan ring.
Generally, the at least one vortex cavity is defined along at least a portion of a periphery of the acoustic ring.

Alternatively, the at least one vortex cavity is defined along entire periphery of the acoustic ring.

In accordance with an embodiment of the present invention, the first acoustic ring and the second acoustic ring defines two vortex cavities, the first vortex cavity defined by the shroud and the first acoustic ring and second vortex cavity defined by the first acoustic ring and the second acoustic ring.

Generally, the vortex cavity is defined by the peripheral wall and sidewalls, wherein the peripheral wall is disposed on a side opposite to the side of the first acoustic ring abutting against the shroud and extends parallel to the axis of rotation “A” of the fan, whereas the sidewalls extend toward the axis of rotation of the fan.

BRIEF DESCRIPTION
Other characteristics, details and advantages of the invention can be inferred from the description of the invention hereunder. A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying figures, wherein:

FIG. 1 illustrates a schematic representation of a conventional fan system without any arrangement for preventing back flow of air through annular gap between a fan ring and a shroud, also is illustrated an enlarged view of the annular gap;

FIG. 2 illustrates an isometric view of a fan system in accordance with an embodiment of the present invention;
FIG. 3 illustrates an exploded view of the fan system of FIG. 2;

FIG. 4 illustrates a schematic representation of the fan system of FIG. 2, also is depicted an enlarged view of an acoustic ring configured with a vortex cavity disposed in an annular gap between a fan ring and a shroud;
FIG. 5 illustrates an enlarged view of the vortex cavity of FIG. 4;

FIG. 6 illustrates an enlarged view of a vortex cavity in accordance with another embodiment configured by assembling a first acoustic ring and a second acoustic ring; and

FIG. 7a – FIG. 7d illustrate different shapes and configurations of the vortex cavities in accordance with different embodiments of the present invention.

It must be noted that the figures disclose the invention in a detailed enough way to be implemented, said figures helping to better define the invention if needs be. The invention should however not be limited to the embodiment disclosed in the description.
DETAILED DESCRIPTION
The present invention envisages a fan system for use in vehicle for cooling a coolant flowing through tubes of a vehicle heat exchanger, e.g. a radiator in case of an engine driven vehicle or a battery cooler in case of an electric vehicle, wherein, the fan system includes a fan, a shroud and at least one acoustic ring. The fan includes fan blades radially extending outwards from a hub and limited by a fan ring. The fan rotates about an axis of rotation “A” to cause air to move parallel to the axis of rotation “A”. The shroud is securely mounted over either one of a vehicle frame and a vehicle mounted heat exchanger and supports the fan and a motor driving the fan. The at least one acoustic ring is secured to the shroud and is disposed in an annular space defined between the fan ring and the shroud. The at least one acoustic ring reduces the noise generated as the fan with the fan ring rotates within the shroud. The acoustic ring defines a vortex cavity to reduce or prevent backflow of air through the annular space between the shroud and the acoustic ring. Preferably, there are two acoustic rings, wherein a first acoustic ring assembled to and in conjunction with at least one of the shroud and a second acoustic ring defines at least one vortex cavity between the shroud and the fan ring. More specifically, either there are two acoustic rings assembled together to configure a vortex cavity or a single acoustic ring is assembled to and in conjunction with the shroud configures the vortex cavity in the inherently formed annular gap between the shroud and the fan ring. The modular configuration of the acoustic ring enables forming of complex shaped vortex cavity without requiring complex tooling, wherein the complex shaped vortex cavity effectively prevents the back flow of the air through the annular gap. More specifically, the vortex cavity generates a vortex that causes hindrance to the back-flow “AB”, thereby substantially reducing the back flow “AB” and the drawbacks such as noise caused by and associated with the back flow “AB” of the air through the annular space. Further, the vortex redirects backflow to the main flow, thereby enhancing air supply to the heat exchanger to improve efficiency and performance of the heat exchanger.

Although, the fan system of the present invention is explained with example of fan system for a radiator of an engine cooling system of a vehicle. However, the fan system of the present invention is also applicable in any vehicular and non-vehicular applications, wherein back flow “AB” and drawbacks associated with the backflow “AB” through inherently formed annular gap between a shroud and a fan ring of the fan system is required to be prevented.

FIG. 2 - FIG. 5 illustrates a fan system 100 in accordance with an embodiment of the present invention. More specifically, FIG. 2 illustrates an isometric view of the fan system 100. FIG. 3 illustrates an exploded view of the fan system 100. The fan system 100 includes a fan 10, a shroud 20 and at least one acoustic ring 30.

The fan 10 includes a plurality of fan blades 12 radially extending outwards from a centrally disposed hub 12a and limited by a fan ring 12b. Referring to the FIG. 3, the fan blades 12 radially extending outwards from the hub 12a thereof. Each of the blades 12 includes radially inner portion secured to the hub 12a and a radial outer tip 12c to which the fan ring 12b is secured to. Particularly, the fan ring 12b is secured to the radial outer tip 12c of the fan blades 12 and rotates with the fan 10. The fan 10 is functionally coupled to a motor 40 and is driven thereby. More specifically, the hub 12a of the fan 10 includes a hole to receive and engage with a motor shaft emanating from the motor 40 and the fan rotates when the motor 40 is supplied with electric power. The fan blades 12 are disposed at an angular spacing with respect to each other. However, the present invention is not limited to any particular configuration of the fan with a particular number of blades and angular spacing between the blades as long as the fan is capable of being driven by the motor to create pressure difference across the fan and direct the air towards the heat exchanger.

The shroud 20 supports the fan 10 and the motor 40 that drives the fan 10. The shroud 20 includes mounting brackets 20a, an opening 20b, a motor housing 20c and an array of arms 20d. The mounting brackets 20a are for mounting of the shroud 20 over either one of a vehicle frame and a vehicle mounted heat exchanger. Specifically nut and bolts mount the shroud 20 over either one of a vehicle heat exchanger, vehicle frame and any other body. More specifically, bolts pass through aligned holes formed on the shroud 20 and either one of the vehicle heat exchanger, vehicle frame and any other body to engage with the corresponding nuts to mount the shroud 20 over either one of the heat exchanger, vehicle frame and any other body. However, the present invention is not limited to any particular arrangement for mounting the shroud 20 over either one of the vehicle frame, the vehicle-mounted heat exchanger and any other body. The opening 20b permits airflow through the shroud 20 and across the heat exchanger. The motor housing 20c is centrally disposed with respect to the opening 20b of the shroud 20 and securely receives and holds the motor 40 that powers the fan 10. The arms 20d connect the motor housing 20c to periphery of the opening 20b to securely hold the motor housing 20c in place.

Generally, the fan ring 12b is of L- section and is spaced from the fan ring 12b of the fan 10 to form annular gap between the fan ring 12b and the shroud 20. In accordance with another embodiment, the fan ring 12b is of I - section and is spaced from the fan ring 12b of the fan 10 to form annular gap between the fan ring 12b and the shroud 20. FIG. 4 illustrates a schematic representation of the fan system 100 with one acoustic ring 30a, particularly, a first acoustic ring 30a disposed between the shroud 20 and the fan ring 12b. The first acoustic ring 30a is assembled to and in conjunction with at least one of the shroud 20 and a second acoustic ring 30b defines at least one vortex cavity 32 to generate a vortex “V” therein. Preferably, the at least one vortex cavity 32 is defined along entire periphery of the acoustic ring 30. In accordance with an embodiment of the present invention, the at least one vortex cavity 32 is defined along at least a portion of a periphery of the acoustic ring 30.

The fan system 100 includes at least one acoustic ring 30 disposed in the annular gap between the shroud 20 and the fan ring 12b. The L- section of the fan ring 12b cause hindrance to the back flow, thereby preventing back flow of air through the annular gap between the fan ring 12b and the shroud 20. The fan 10, the shroud 20 and the at least one acoustic ring 30 are concentrically disposed with respect to the axis of rotation “A” of the fan 10. The at least one acoustic ring 30 in conjunction with the shroud 20 defines the vortex cavity 32.

In one embodiment as illustrated in FIG. 4, FIG. 5, FIG. 7a – FIG. 7c, there is one acoustic ring 30a that is assembled to the shroud 20 and in conjunction with the shroud 20 defines the vortex cavity 32. Referring to FIG. 4 and FIG. 5, a simple to configure L-shaped cutout formed on the acoustic ring 30a abuts against an inside wall of the shroud 20 to configure the vortex cavity 32. The first acoustic ring 30a is assembled to the shroud 20 by using snap fit arrangement or any other engagement means for securely mounting the first acoustic ring 30a to the shroud 20. The present invention is not limited to any particular method for securely mounting the first acoustic ring 30a to the shroud 20 as far as the first acoustic ring 30a is securely connected to the shroud 20.

In another embodiment, as illustrated in FIG. 6 and FIG. 7d, there are two acoustic rings, the first acoustic ring 30a and the second acoustic ring 30b are assembled to each other to define the vortex cavity 32. Specifically, the vortex cavity 32 is formed on at least one of the first acoustic ring 30a and the second acoustic ring 30b. The fan 10, the shroud 20, the first acoustic ring 30a and the second acoustic ring 30b are concentrically disposed with respect to the axis of rotation “A” of the fan 10. More specifically, referring to the FIG. 6, a simple to configure first L-shaped cutout formed on the first acoustic ring 30a is aligned with respect to simple to configure second L-shaped cutout formed on the second acoustic ring 30b and the first acoustic ring 30a is assembled to the second acoustic ring 30b to configure the vortex cavity 32 that is generally u-shaped. Referring to the FIG. 7d, the first acoustic ring 30a includes simple to configure l-shaped cutout formed thereon that in conjunction with another simple to configure cutout formed on the second acoustic ring 30b configures the vortex cavity 32. In accordance with another embodiment of the present invention, the first acoustic ring 30a and the second acoustic ring 30b defines two vortex cavities, first vortex cavity 32 defined by the shroud 20 and the first acoustic ring 30a and second vortex cavity 32 defined by the first acoustic ring 30a and the second acoustic ring 30b.

Generally, the first acoustic ring 30a includes first latching elements 34a that engages with corresponding second latching elements 34b formed the second acoustic ring 30b to configure assembly between the first acoustic ring 30a and the second acoustic ring 30b. In accordance with an embodiment of the present invention, the first acoustic ring 30a is assembled to the second acoustic ring 30b by using snap fit arrangement or any other engagement means for securely mounting the first acoustic ring 30a to the second acoustic ring 30b. In accordance with a preferred embodiment of the present invention, the first latching elements 34a formed on the first acoustic ring 30a is in form of protruding pins 34a. The protruding pins 34a engages with the second latching elements 34b in the form of the corresponding holes 34b configured on the second acoustic ring 30b to configure connection between the first acoustic ring 30a and the second acoustic ring 30b as illustrated in FIG. 6. Alternatively, the first acoustic ring 30a is configured with a hole that receives a protruding pin configured on the second acoustic ring to configure connection between the first acoustic ring 30a and the second acoustic ring 30b. In accordance with another embodiment, the first acoustic ring 30a and the second acoustic ring 30b are over-molded with respect to each other. However, the present invention is not limited to any particular arrangement of securely mounting the first acoustic ring 30a to the second acoustic ring 30b as far as the first acoustic ring 30a is securely connected to the second acoustic ring 30b to configure the vortex cavity 32 such that the vortex cavity 32 is facing the fan ring 12b.

Further, the assembly of the first and the second acoustic rings 30a and 30b is assembled to the shroud 20. Generally, the first acoustic ring 30a includes the first latching elements 34a that engages with corresponding second latching elements 20e formed the shroud 20 to configure assembly between the first acoustic ring 30a and the shroud 20. In accordance with an embodiment, the assembly of the first acoustic ring 30a and the second acoustic ring 30b is assembled to the shroud 20 by using snap fit arrangement or any other engagement means. In another embodiment, at least one of the first acoustic ring 30a and the second acoustic ring 30b is over-molded with respect to the shroud 20. However, the present invention is not limited to any particular arrangement for mounting the assembly of the first and the second acoustic ring 30a and 30b to the shroud 20 as far as the assembly of the first and the second acoustic rings 30a and 30b is securely mounted on the shroud 20 to configure the vortex cavity 32 such that the vortex cavity 32 is facing the fan ring 12b. The vortex cavity 32 is formed on the side of the acoustic ring 30 facing the fan ring 12b. With such configuration the back flow “AB” of the air through the gap between the shroud 20 and the fan ring 12b is obstructed by the vortex “V” created in the vortex cavity 32 and the back flow “AB” is prevented and the air is directed towards the heat exchanger.

Accordingly, the supply of air to the heat exchanger, particularly, the radiator is enhanced and the efficiency and performance of the radiator is improved. The first acoustic ring 30a and the second acoustic ring 30b are separate from each other and assembled to each other. Preferably, the first acoustic ring 30a and the second acoustic ring 30b are over molded with respect to each other. With such configuration, vortex cavity of complex configurations can be conveniently formed without requiring complex tooling.

In accordance with yet another embodiment of the present invention, the first acoustic ring 30a, the second acoustic ring 30b and a third acoustic ring 30c are connected to each other to define the vortex cavity 32. However, the present invention is not limited to any particular number and configuration of the acoustic rings assembled to form the vortex cavity as long as the acoustic rings cut outs formed thereon are assembled to each other to configure a complex shaped vortex cavity.

The vortex cavity 32 generates the vortex “V” therein and the vortex “V” cause hindrance to the back flow “AB” of the air through the inherently formed annular gap between the fan ring 12b and the shroud 20 of the fan system 100. The hindrance to the back flow “AB” of the air through the inherently formed annular gap between the fan ring 12b and the fan shroud generally increases with complexity of the configuration of the vortex cavity 32. However, configuring complex shaped vortex cavity “V” in the acoustic ring 30 is difficult and involves complex tooling. However, the modular configuration of the acoustic ring 30 of the present invention configures the complex shaped vortex cavity 32 without requiring complex tooling.

With the modular configuration of the acoustic ring formed by assembling the first and the second acoustic ring 30a and 30b, the complex shaped vortex cavity 32 can be formed without requiring complex tooling, wherein the complex shaped vortex cavity 32 effectively creates and retains the vortex therein to prevent the back flow of the air through the annular gap. More specifically, the vortex “V” created in the vortex cavity causes hindrance to and prevents back flow “AB” of air through an inherently formed annular gap between the shroud 20 and the fan ring 12b of the fan system 100. Such configuration, prevents backflow “AB” and addresses problems such as noise arising due to back flow “AB” of the air through inherently formed gap between the shroud 20 and the fan ring 12b of the fan system 100.

FIG. 7a – FIG. 7c illustrate different shapes and configurations of the vortex cavities “V” in accordance with different embodiments of the present invention. Specifically, the vortex cavity 32 depicted in the FIG. 7a – FIG. 7c is configured by aligning the cutout formed on the acoustic ring 30a to the corresponding cutout formed on the shroud 20 when the acoustic ring 30a is assembled with the shroud 20. More specifically, a portion of at least one of the acoustic ring 30a, 30b and the shroud 20 respectively defining at least one sidewall 33a, 23a of the vortex cavity 32 is forming at least one of acute angle, obtuse angle and right angle with a peripheral wall 35a, 35b of the acoustic ring 30a, 30b. The peripheral wall 35a, 35b and the sidewalls 33a, 23a define the cavity 32. The peripheral wall 35a, 35b is disposed on a side opposite to the side of the first acoustic ring 30a, 30b abutting against the shroud 20 and extends parallel to the axis of rotation “A” of the fan 10. Further, the sidewalls 33a, 23a of the vortex cavity 32 extends toward the axis of rotation “A” of the fan. More specifically, the side of the cavity 32 distal from the axis of rotation “A” is closed by the peripheral wall 35a, 35b and side of the cavity 32 proximal to the axis of rotation “A” remains open. In accordance with one embodiment of the present invention as illustrated in FIG. 7a, the portion of the shroud 20 defining the sidewall 23a of the vortex cavity 32 is forming an acute angle with the peripheral wall 35a of the first acoustic ring 30a. With such configuration, the vortex generated in the vortex cavity 32 is retained inside the vortex cavity 32. With such configuration, the air is trapped in the vortex cavity 32 and creates the vortex. The vortex cause hindrance to the back flow of the air through the annular gap between the fan ring 12b and the shroud 20, thereby preventing the backflow of air through the annular gap and reducing the noise caused by the back flow of the air.

In accordance with another embodiment of the present invention as illustrated in FIG. 7b, the portion of the shroud 20 defining the sidewall 23a of the vortex cavity 32 is forming an obtuse angle with the peripheral wall 35a of the first acoustic ring 30a.

In accordance with yet another embodiment of the present invention as illustrated in FIG. 7c, the portion of the shroud 20 defining the sidewall 23a of the vortex cavity 32 is forming an obtuse angle with the peripheral wall 35a of the first acoustic ring 30a. Further, the portion of the first acoustic ring 30a defining the sidewall 33a of the vortex cavity 32 is forming an acute angle with the peripheral wall 35a of the first acoustic ring 30a.

Such configuration of the shroud 20, the acoustic ring 30a and the vortex cavity 32 formed by the assembly of the acoustic ring 30a to the shroud 20 provides complex configuration to the vortex cavity 32 without requiring complex tooling, thereby forming and retaining of vortex in the vortex cavity 32 for preventing the back flow of air through the annular gap.

The vortex cavity 32 is of either one of rectangular, trapezoidal, triangular and polygonal cross section with one side open. Particularly, a sectional plane passing through the axis of rotation “A” of the fan 10, through the shroud 20 and the acoustic ring 30a at any point along the periphery thereof defines the cross section of the vortex cavity 32, wherein the cross section of the vortex cavity 32 can be either one of rectangular, trapezoidal, triangular and polygonal. More specifically, the peripheral wall 35a and the portions of the shroud 20 and the at least one acoustic ring 30a define at least three sides of polygonal cross section of the vortex cavity 32 with one side thereof open. However, the present invention is not limited to any particular shape of the vortex cavity 32 or number of acoustic rings assembled to configure the vortex cavity as long as the vortex cavity is capable of generating vortex “V” and retaining the vortex in the vortex cavity.

Similarly, FIG. 7d illustrates the vortex cavity 32 configured by assembling two different acoustic rings 30a and 30b. Specifically, the vortex cavity 32 depicted in the FIG. 7d is configured by aligning the cutout formed on the first acoustic ring 30a to the corresponding cutout formed on the second acoustic ring 30b, when the assembly of the first acoustic ring 30a and the second acoustic ring 30b is assembled with the shroud 20. More specifically, a portion of the first acoustic ring 30a defines the first sidewall 33a of the vortex cavity 32 and a portion of the second acoustic ring 30b defines the second sidewall 33b of the vortex cavity 32. The first sidewall 33a is orthogonal to the peripheral wall 35a of the first acoustic ring 30a. The second sidewall 33b is forming acute angle with the peripheral wall 35a of the acoustic ring 30a.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described herein.

In any case, the invention cannot and should not be limited to the embodiments specifically described in this document, as other embodiments might exist. The invention shall spread to any equivalent means and any technically operating combination of means.