Impeller for a cooling fan

1. Field of the Invention

The present invention relates to an impeller, and more particularly to an impeller for a cooling fan, wherein blades of the impeller have different configurations.

2. Description of Related Art

With continuing development of the electronic technology, electronic components such as CPUs generate more and more heat that is required to be dissipated immediately.

Conventionally, a fan is used to produce an airflow that can remove heat from the electronic component. The fan comprises a stator and a rotor being rotatable with respective to the stator. The rotor further comprises a hub and a plurality of blades extending radially from the hub. In use, the blades of the rotor rotate around the stator to engender the airflow towards the electronic component, thus cooling the electronic component continuously.

Increasing a revolving speed of the fan blades relatively increases the amount of airflow; therefore, a heat dissipation efficiency is relatively improved. However, increasing the revolving speed may cause a noise level of the fan to raise correspondingly, thus making an operator near the fan feel uncomfortable.

What is needed, therefore, is an impeller for a fan which can overcome the above-mentioned disadvantage.

An impeller for a cooling fan includes a hub having a circular wall and an annular wall extending downwardly from a rim of the circular wall, and a plurality of blades extending radially from the annular wall of the hub. Each of the blades includes a first portion near the hub and a second portion away from the hub, wherein each of the first portions is identical to an adjacent one of the first portions, and each of the second portions is different from an adjacent one of the second portions with a different height, thereby reducing a noise level of the impeller when it rotates.

Other advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

Many aspects of the present apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an isometric view of an impeller for an electric fan in accordance with a preferred embodiment of the present invention;

FIG. 2 is a front view of FIG. 1 ;

FIG. 3 is a side view of FIG. 1 ;

FIG. 4 is a view similar to FIG. 1 , with different parts of the impeller being marked;

FIG. 5 is an enlarged view of a circled part V of FIG. 4 ;

FIG. 6 is an enlarged view of a circled part VI of FIG. 4 ; and

FIG. 7 is an enlarged view of a circled part VII of FIG. 4 .

Referring to FIG. 1 , an impeller 10 for a cooling fan (not shown) of a preferred embodiment of the present invention comprises a hub 20 and a plurality of blades 30 extending radially from a periphery of the hub 20 . The impeller 10 in the shown preferred embodiment is for a centrifugal fan (blower).

The hub 20 comprises a circular wall 22 and an annular sidewall 24 extending upwardly and perpendicularly from a rim of the circular wall 22 in a manner that a cylindrical space (not labeled) is defined between the circular wall 22 and the sidewall 24 . The circular wall 22 is flat. A protrusion 26 projects upwardly from a central area of a top face of the circular wall 22 , wherein a cross-sectional area of the protrusion 26 gradually decreases along an upward direction. Thus, the protrusion 26 forms a tapered configuration. A hole (not labeled) is defined at a top face of the protrusion 26 to engage with a shaft (not shown), thus allowing the hub 20 to perform a rotation in respective to a bearing (not shown) in which the shaft extends.

The blades 30 extend radially and outwardly from the sidewall 24 of the hub 20 . The blades 30 are arranged on the hub 20 in balance for preventing the impeller 10 from rotating unstably. Each of the blades 30 comprises a first portion 32 located close to the hub 20 , and a second portion 34 located far away from the hub 20 , in comparison with the first portion 32 . Every two neighboring first portions 32 of the blades 30 are identical to each other, and every two neighboring second portions 34 of the blades 30 are different from each other. Each of the first portions 32 of the blades 30 has a top face 322 coupling with a top surface (not labeled) of the sidewall 24 of the hub 20 , a bottom face 324 (shown in FIG. 3 ) attached to an outer surface of the sidewall 24 of the hub 20 , and a pair of opposite lateral faces 320 connecting the outer surface (not labeled) of the sidewall 24 of the hub 20 and between the top face 322 and the bottom face 324 . The pair of opposite lateral faces 320 are approximately planar surfaces and parallel to each other, and the bottom face 324 and the top face are concave surfaces and recessed toward each other. A distance between two adjacent first portions 32 increases outwardly to define an acute angle therebetween.

The second portion 34 is curved from an end of the first portion 32 along a counterclockwise direction as viewed from FIG. 1 . The second portion 34 has a top face 342 extending from the top face 322 of the first portion 32 , a bottom face 344 coupling with the bottom face 324 of the first portion 32 , and a pair of opposite lateral faces 340 extending from the pair of opposite lateral faces 320 of the first portion 32 , respectively. The top face 342 and the bottom face 344 are parallel to the circular wall 22 of the hub 20 , and the pair of opposite lateral faces 340 coupled with each other via a curved end face (not labeled), which is located at a free end of the second portion 34 .

Referring to FIG. 2 , one of the pair of lateral faces 340 is a concave surface, which connects with a corresponding one of the opposite lateral faces 320 of the first portion 32 to cooperatively act as a windward side; another one of the pair of lateral faces 340 is a convex surface, which cooperates with another one of the opposite lateral faces 320 of the first portion 32 to function as a leeward side. The pair of opposite lateral faces 340 are concentric with each other and tangent to the pair of opposite faces 320 of the first portion 32 , respectively.

As shown in FIG. 3 , the bottom faces 344 of the second portions 34 of the blades 30 are coplanar with each other. A distance (H 1 ) from the top face 342 to the bottom face 344 of each of the second portions 34 is different from a distance (H 2 ) from the top face 342 to the bottom face 344 of an adjacent one of the second portions 34 , whereby two adjacent second portions 34 have different heights. Referring to FIGS. 4-7 , according to the different heights, the second potions 34 can be approximately divided as three types: first type of second portions 34 a with top faces 342 a , second type of second portions 34 b with top faces 342 b and third type of second portions 34 c with top faces 342 c . For the first type of second portions 34 a , the top faces 342 a thereof are spaced from corresponding top faces 322 of the first portions top 32 , to form steps 3420 a therebetween. For the second type of second portions 34 b , junctions 3420 b each having a shape like a rigid are formed between the top faces 342 b and corresponding top faces 322 of the first portions 32 . For the third type of second portions 34 c , top faces 342 c thereof are directly extended from corresponding top faces 322 of the first portions 32 .

In a performance analysis of the cooling fan with the impeller 10 of the present invention, under the same condition of air pressure and air flow rate, a noise level of the fan with the impeller 10 is apparently lower than that of a conventional fan (not shown), due to the second portions 34 of the blades 30 of the impeller 10 having different heights. The first type of the second portions 34 a is higher than the second type of the second portions 34 b , which in turn is higher than the third type of the second portions 34 c . As a result, the noise level in the present invention can be greatly reduced by the different heights of the blades 30 . The geometric arrangement that the second portions 34 of the blades 30 of the impeller 10 have different heights is able to lower the amplitude of the harmonic wave of the sound generated by the rotation of the impeller 10 , thereby reducing the noise level.

It is believed that the present invention and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.