Anti-fracture fan structure

Details Anti-fracture fan structure Anti-fracture fan structure

2000-07-28

2002-01-22

Look, Edward K. (Department: 3745)

Fluid reaction surfaces (i.e., impellers)

Support mounting, carrier or fairing structure

Reexamination Certificate

active

06340292

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an anti-fracture fan structure, particularly to an anti-fracture fan structure that has a plurality of ribs in predetermined shapes to prevent the fan from fracturing due to heat expansion.
BACKGROUND OF THE INVENTION
A fan is widely used to dissipate heat generated by electrical devices such as desktop computers or notebook computers.
FIG. 1
is a schematic illustration that shows a conventional fan structure. Referring to
FIG. 1
, the fan includes a hub
11
and a shielding-can
12
. The hub
11
has an inner surface
111
. A plurality of blades
112
are arranged around the hub
11
. A plurality of ribs
113
are provided around the inner surface
111
.
The hub
11
is usually made of a material such as plastic or resin. The shielding-can
12
is usually made of a metallic material that has a high strength property, and is mounted inside the hub
11
by press fitting in order to prevent a ring-shaped magnet (not shown), that is situated around the inner surface of the hub
11
, from being deformed. Thus, the magnetic leakage phenomenon can be avoided.
The ribs
113
are useful for mounting the shielding-can
12
into the hub
11
and preventing the hub
11
from being fractured.
In general, the fan starts operating at a lower temperature. The temperature of the fan gradually rises owing to the heat energy generated from the fan or the heat energy transferred from a heat sink (not shown). For example, it is possible that the temperature of the fan rises from −10° C. to 50° C.
However, the hub
11
and the shielding-can
12
have different heat expansion coefficients because the hub
11
and the shielding-can
12
are made of different materials. For example, the heat expansion coefficient of a PC (poly carbonate) material constituting the hub
11
is about 2.5×10
−7
in/in °F., while the heat expansion coefficient of a metal material constituting the shielding-can
12
is about 6.5×10
−6
in/in °F., which is 26 times as large as that of the PC material. As a result, if the fan is subjected to heat energy, the shielding-can
12
expands faster than the hub
11
, causing the hub
11
to fracture from the pressure of the expanding shielding-can
12
.
SUMMARY OF THE INVENTION
To overcome the above drawback, it is therefore an object of the invention to provide an anti-fracture fan structure in which the hub is not easily fractured by the pressing force of the shielding-can when the fan expands.
To achieve the above objective, there is provided an anti-fracture fan structure including a hub, a plurality of blades, and a plurality of ribs. The hub has an inner surface formed inside and encircling it. The plurality of blades are arranged outside and around the hub. The plurality of ribs projects from the inner surface of the hub into the inside of the hub. Each of the plurality of ribs is not perpendicular to the inner surface of the hub.
Furthermore, the anti-fracture fan further includes a shielding-can situated inside the hub and in contact with the plurality of ribs.
Moreover, the hub can be formed of a plastic material and the shielding-can can be formed of a metal material.
The ribs can be easily warped when the shielding-can expands. Therefore, the hub is not easily fractured by the expansion of the shielding-can when the fan expands with heat.


REFERENCES:
patent: 4123197 (1978-10-01), Keem et al.
patent: 5975853 (1999-11-01), Lackey
patent: 6200095 (2001-03-01), Bucher et al.

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