Casing for a heat-dissipating fan

Abstract

A casing for a heat-dissipating fan defines a space having an air inlet and an air outlet. A bottom plate is provided in the air outlet. The bottom plate rotatably supports a fan wheel having a hub and a plurality of blades extending outward from the hub. An annular wall is formed on the bottom plate and has an outer wall face that tapers gradually toward the bottom plate to form a conic shape.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a casing for a heat-dissipating fan. In particular, the present invention relates to a casing for a heat-dissipating fan with improved air output and without turbulence.

[0003] 2. Description of the Related Art

[0004] FIG. 1 of the drawings illustrates a conventional heat-dissipating fan comprising a casing 90 having a bottom plate 91. An axle tube 93 is engaged with an axle seat 92 formed on the bottom plate 91. A stator bobbin 94 is mounted around the axle tube 93. A bearing 95 is mounted in the axle tube 95 for rotatably holding a shaft 100 of a fan wheel 96. When the fan wheel 96 turns, an air stream is driven to flow from an air inlet 98 toward an air outlet 99. The air stream driven by the blades on the fan wheel 96 exits the air outlet 99, as illustrated by the longer arrows in FIG. 2. However, a portion of the air stream enters a gap between the bottom wall 91 and the stator bobbin 94, as indicated by the shorter arrows in FIG. 2. As a result, turbulence is generated and the amount of air output is decreased in addition to noise generated as a result of tangential wind.

[0005] FIG. 3 illustrates another conventional heat-dissipating fan, in which an annular wall 910 extends upward from the bottom plate 91 to prevent entrance of the air stream into the gap between the bottom plate 91 and the stator bobbin 94. However, since the annular wall 910 is perpendicular to the bottom plate 91, a portion of the air stream driven by the blades as a result of rotation of the fan wheel 96 impedes and is thus reflected by the annular wall 910. As a result, the problems of turbulence and noise remain unsolved.

SUMMARY OF THE INVENTION

[0006] It is the primary object of the present invention to provide a casing for a heat-dissipating fan, wherein the air stream driven by the blades as a result of rotation of the fan wheel may smoothly exit the air outlet. Thus, the turbulence generated as a result of impingement of the air stream on the bottom plate or annular wall is reduced, thereby increasing the amount of air output.

[0007] A casing for a heat-dissipating fan in accordance with the present invention defines a space having an air inlet and an air outlet. A bottom plate is provided in the air outlet. The bottom plate rotatably supports a fan wheel having a hub and a plurality of blades extending outward from the hub. An annular wall is formed on the bottom plate and has an outer wall face that tapers gradually toward the bottom plate to form a conic shape.

[0008] Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a sectional view of a conventional heat-dissipating fan.

[0010] FIG. 2 is an enlarged view of a circled portion of FIG. 1.

[0011] FIG. 3 is a view similar to FIG. 2, illustrating another conventional heat-dissipating fan.

[0012] FIG. 4 is a sectional view of a first embodiment of a casing of a heat-dissipating fan in accordance with the present invention.

[0013] FIG. 5 is an enlarged view of a circled portion in FIG. 4.

[0014] FIG. 6 is a view similar to FIG. 5, illustrating a second embodiment of the casing in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Preferred embodiments in accordance with the present invention will now be described with reference to the accompanying drawings.

[0016] Referring to FIGS. 4 and 5, a first embodiment of a casing for a heat-dissipating fan in accordance with the present invention generally includes a casing 1 defining a space 11 having an air inlet 12 and an air outlet 13. A bottom plate 14 is provided in a central portion of the air outlet 13. An axle seat or axle hole (not labeled) is provided on the bottom plate 14 for rotatably receiving a shaft (not shown) of a fan wheel 2. The fan wheel 2 includes a plurality of blades 22 extending radially outward from a hub 21 thereof.

[0017] An annular wall 15 extends upward and outward from the bottom plate 14, forming a conic shape. Namely, the annular wall 15 formed on the bottom plate 14 has an outer wall face that tapers gradually toward the bottom plate 14. Preferably, the annular wall 15 includes a top that is adjacent to but not in contact with a bottom of the hub 21, leaving a minimized gap between the hub 21 and the annular wall 15. The annular wall 15 includes an outer wall face 16 that is at an acute angle &thgr; with a plane on which the bottom plate 14 lies. Preferably, the outer wall face 16 is inclined and the angle &thgr; is 60°-80°. FIG. 6 illustrates a second embodiment of the invention, wherein the outer wall face 16 of the annular wall 15 includes an arcuate portion adjacent to the bottom plate 14. Thus, the air stream driven by the blades 22 as a result of rotation of the fan wheel 2 is smoothly outputted via the air outlet 13 in a maximum amount while avoiding generation of turbulence and noise.

[0018] Preferably, the annular wall 15 has a maximum outer diameter not greater than a diameter of the hub 21.

[0019] Although the invention has been explained in relation to its preferred embodiments as mentioned above, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention. It is, therefore, contemplated that the appended claims will cover such modifications and variations that fall within the true scope of the invention.

Claims

1. A casing for a heat-dissipating fan, the casing defining a space having an air inlet and an air outlet, a bottom plate being provided in the air outlet, the bottom plate being adapted to rotatably support a fan wheel having a hub and a plurality of blades extending outward from the hub, an annular wall being formed on the bottom plate and having an outer wall face that tapers gradually toward the bottom plate.

2. The casing for a heat-dissipating fan as claimed in claim 1, wherein the annular wall is conic.

3. The casing for a heat-dissipating fan as claimed in claim 1, wherein the annular wall includes a top that is adjacent to but not in contact with a bottom of the hub, leaving a minimized gap between the hub and the annular wall.

4. The casing for a heat-dissipating fan as claimed in claim 1, wherein the outer wall face of the annular wall is at an acute angle of 60°-80° with a plane on which the bottom plate lies.

5. The casing for a heat-dissipating fan as claimed in claim 1, wherein the outer wall face of the annular wall is inclined.

6. The casing for a heat-dissipating fan as claimed in claim 1, wherein the outer wall face of the annular wall has an arcuate portion adjacent to the bottom plate.

7. The casing for a heat-dissipating fan as claimed in claim 1, wherein the annular wall has a maximum outer diameter not greater than a diameter of the hub.