Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
1999-03-01
2001-02-27
Thorpe, Timothy S. (Department: 3746)
Pumps
Motor driven
Electric or magnetic motor
C417S360000, C417S423140, C415S213100
Reexamination Certificate
active
06193478
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an improved construction of a fan, having an increased air flow rate and reduced vibration.
DESCRIPTION OF RELATED ARTS
FIG. 1A
is a front view of a prior art fan in an assembled state.
FIG. 1B
is a sectional side view of the same fan. The arrows shown in
FIG. 1B
represent the flow field produced by the fan. As shown in FIG.
1
A and
FIG. 1B
, the fan comprises an impeller
2
, which rotates and cuts the surrounding fluid enabling the surrounding fluid to form an axial flow; a motor
1
having a stator (not shown) and a rotor (not shown) for driving the impeller
2
to rotate; a casing
9
for mounting motor
1
and covering the outer circumference of impeller
2
, including a motor mounting seat
4
for fixing motor
1
and a frame
3
for covering the outer circumference of the impeller
2
. The whole casing
9
is directly fixed to a system housing
6
when in use.
Basically, a fan is utilized to promote air circulation resulting in heat dissipation. The better the air circulation, the more effective the heat dissipation is. However, when the fan is installed in a system, due to the obstruction of the system housing
6
, members within the system (including those members from which heat is to be dissipated) and the casing
9
etc., the air inlet is narrowed, resulting in increased flow resistance and reduced quantity of the air flow, thus deteriorating its performance of heat dissipation. Moreover, such a prior art fan inevitably creates, during rotation, a vortex flow in the vicinity of the narrow gap between the impeller tip T and the casing
9
(see FIG.
1
B), resulting in an unpleasant noise.
FIG. 2
shows the flow field of a prior art suction fan installed outside the system. In this figure, the fan sucks the air current on the right side to the left side of the system so as to facilitate heat dissipation of the inner members
10
, also acting as obstructions in the flow field, within the system. The disadvantage of this prior art suction fan resides in that, due to the existence of frame
3
, the source of air sucked into and through the fan is restricted to only the axial air current flowing from the right to the left.
Similarly,
FIG. 3
shows the flow field of a prior art suction fan installed within the system. The way of installing this prior art suction fan resembles the aforementioned prior art suction fan installed outside the system as shown in FIG.
2
. Its disadvantage resides in that, due to the existence of frame
3
, the flow field exit of the air current blown out from the fan is restricted to only the portion free from being hindered by the members
10
within the system, acting as obstructions in the flow field.
Similarly,
FIG. 4
shows the flow field of a blowing fan installed within the system, and
FIG. 5
shows the flow field of a blowing fan installed outside the system. On analyzing the flow field of
FIG. 4
, it is noticed that the disadvantage of the fan within the system is that the source of air sucked into and through the fan is restricted to only the axial air current flowing from the right to the left. Moreover, on analyzing the flow field shown in
FIG. 5
, it is seen that the disadvantage of the fan within the system is that the air current blown out from the fan is limited to only the axial air current flowing from the right to the left.
Summing up the above analysis with respect to the flow fields of
FIGS. 2
to
5
, it is noticed that the disadvantage of each of the prior art fans is that the air flow rate through each fan is reduced due to reduced area of its air entrance or air exit subject to the influence of frame
3
.
An object of this invention is to enlarge the air entrance and the air exit of a fan so as to increase the air flow rate of the fan, thereby facilitating the heat dissipation efficiency of the fan.
Besides, as shown in
FIG. 1B
, since the motor mounting seat
4
is connected to motor
1
on the one hand and also directly fixed to the system housing
6
on the other hand, it cannot efficiently absorb or reduce the vibration produced during operation of the motor. Thus, vibration produced by the motor
1
is directly transmitted to the system housing
6
through the motor casing
4
, resulting in an annoying noise level. This is also a problem that this invention wishes to solve.
SUMMARY OF THE INVENTION
In order to solve the aforementioned problem, this invention provides an improved construction of a fan which enlarges the air entrance or the air exit, increases the air flow rate, and reduces the noise produced.
According to this invention, an improved construction of a fan fixed to a system housing when in use, includes: an impeller which rotates and cuts the surrounding fluid enabling the surrounding fluid to form an axial flow, and which extends over a length in the axial direction of the fan; a driving device having a stator and a rotor adapted to drive the impeller to rotate; and a casing including a mounting seat fastened to the system housing for mounting the stator onto the system housing, and a frame adapted to cover outside the outer circumference of the impeller; characterized in that the frame of the casing covers only part of the length in the axial direction outside the outer circumference of the impeller.
In the above improved construction of a fan, the frame and the mounting seat may be independent members which are fastened together.
In the above improved construction of a fan, the mounting seat is preferably formed by vibration absorptive material at least at one of the portion where the mounting seat is fastened to the system housing and the portion where the mounting seat is fastened to the frame.
In the above improved construction of a fan, preferably at least one washer is sandwiched between the system housing and the mounting seat so as to isolate the system housing from the mounting seat, thereby preventing the vibration produced by the fan from being transmitted to the system housing.
In the improved construction of a fan according to this invention, the mounting seat and the frame may also be integrally formed.
In the above improved construction of a fan, the mounting seat is preferably formed by vibration absorptive material at the portion where the mounting seat is fastened to the system housing.
In the above improved construction of a fan, preferably at least one washer is sandwiched between the system housing and the mounting seat so as to isolate the system housing from the mounting seat, thereby preventing the vibration produced by the fan from being transmitted to the system housing.
By adopting the above improved construction of a fan according to this invention, the air entrance or the air exit of the fan is enlarged, thus increasing the air flow rate produced in the system. Also, the air resistance is reduced, thus restraining the impeller tip from creating vortex flow and noise. Besides, provision of a mounting seat partially formed by vibration absorptive material at least near the location where the mounting seat is fastened to the system housing or to the frame of the fan (hereunder referred to as “the absorptive fastening portion”) and also washer(s) sandwiched between the system housing and the mounting seat greatly reduces vibration of the fan.
REFERENCES:
patent: 4120615 (1978-10-01), Keem et al.
patent: 4152094 (1979-05-01), Honda et al.
patent: 4189281 (1980-02-01), Katagiri et al.
patent: 4352635 (1982-10-01), Saunders
patent: 4568243 (1986-02-01), Schubert et al.
patent: 4711135 (1987-12-01), Horiuchi et al.
patent: 4807718 (1989-02-01), Lotz
patent: 3236353 (1984-04-01), None
Lin Kuo-Cheng
Liu Yung-Hua
Delta Electronics , Inc.
Gray Michael K.
Thorpe Timothy S.
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