U.S. patent application number 11/259119 was filed with the patent office on 2006-03-02 for fans and fan frames.
This patent application is currently assigned to DELTA ELECTRONICS, INC.. Invention is credited to Wen-Shi Huang, Lobato Lu, Ke-Nan Wang.
Application Number | 20060045774 11/259119 |
Document ID | / |
Family ID | 35943413 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060045774 |
Kind Code |
A1 |
Lu; Lobato ; et al. |
March 2, 2006 |
Fans and fan frames
Abstract
A fan with a fan frame and an impeller. The fan frame includes a
housing and a motor base. The housing includes a passage. The
passage forms an air outlet and an air inlet on both ends of the
housing. The motor base is disposed in the housing. The impeller is
disposed on the motor base. When the motor base is at the air
outlet or the air inlet, the bottom of the motor base locates on a
plane different from that of the air outlet or the air inlet. The
motor base is raised into the housing, increasing the area of air
flow intake or discharge. Additionally, during the operation of the
fan, noise, caused by vibrations generated by rotation of the
impeller and transferred to an exterior system via the motor base,
can be reduced.
Inventors: |
Lu; Lobato; (Taoyuan Hsien,
TW) ; Wang; Ke-Nan; (Taoyuan Hsien, TW) ;
Huang; Wen-Shi; (Taoyuan Hsien, TW) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
DELTA ELECTRONICS, INC.
|
Family ID: |
35943413 |
Appl. No.: |
11/259119 |
Filed: |
October 27, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10799420 |
Mar 12, 2004 |
|
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|
11259119 |
Oct 27, 2005 |
|
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Current U.S.
Class: |
417/423.7 ;
417/423.14 |
Current CPC
Class: |
F04D 29/545
20130101 |
Class at
Publication: |
417/423.7 ;
417/423.14 |
International
Class: |
F04B 35/04 20060101
F04B035/04; F04B 17/00 20060101 F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2004 |
TW |
093133821 |
Claims
1. A fan frame, comprising: a housing having a passage which forms
an air outlet and an air inlet on both ends of the housing; and a
motor base disposed in the housing, wherein when the motor base is
at the air outlet or the air inlet, a bottom of the motor base
locates on a plane different from that of the air outlet or the air
inlet.
2. The fan frame as claimed in claim 1, further comprising a
plurality of ribs disposed between the housing and the motor base
to support the motor base, wherein a cross section of each rib is
varied along a direction from the motor base to the housing.
3. The fan frame as claimed in claim 2, wherein a width of each rib
is varied along the direction from the motor base to the housing,
or the width of each rib gradually increases or decreases along the
direction of from the motor base to the housing.
4. The fan frame as claimed in claim 3, wherein the width of each
rib connecting to the motor base and housing is relatively greater
or less than that of a central part of the rib.
5. The fan frame as claimed in claim 2, wherein a thickness of each
rib is varied from along the direction of the motor base to the
housing, or the thickness of each rib gradually increases or
decreases along the direction of from the motor base to the
housing.
6. The fan frame as claimed in claim 5, wherein the thickness of
each rib connecting to the motor base and housing is relatively
greater or less than that of a central part of the rib.
7. The fan frame as claimed in claim 2, wherein the housing further
comprises an outward expansion portion at the air outlet or the air
inlet to increase an area of air flow intake or discharge.
8. The fan frame as claimed in claim 7, wherein the ribs are
connected to the outward expansion portion, and the outward
expansion portion is formed with a lead angle, a sloped angle, a
lead and sloped angle, or a curved angle.
9. The fan frame as claimed in claim 2, wherein the motor base
comprises a slope inclined radially to adjust an area of air flow
intake or discharge, and the slope is linear or curved.
10. A fan, comprising: a fan frame comprising: a housing having a
passage which forms an air outlet and an air inlet on both ends of
the housing; and a motor base disposed in the housing; and an
impeller disposed on the motor base, wherein when the motor base is
at the air outlet or the air inlet, a bottom of the motor base
locates on a plane different from that of the air outlet or the air
inlet.
11. The fan as claimed in claim 10, wherein the fan is applied to a
light source, a periphery of the passage comprises an inner
surface, and when light emitted by the light source enters the
passage, the light is blocked from penetrating the passage by the
inner surface.
12. The fan as claimed in claim 11, wherein the inner surface is a
concave surface depressed toward a central axis of the passage so
as to block the light emitted by the light source.
13. The fan as claimed in claim 11, wherein the inner surface is a
convex surface protruded toward a central axis of the passage, an
outer edge of the impeller is formed with a concave surface
opposing the curved surface so as to block the light emitted by the
light source.
14. The fan as claimed in claim 11, wherein the outer edge of the
impeller is parallel to the curved surface of the periphery of the
passage.
15. The fan as claimed in claim 11, wherein the inner surface
comprises a gradually shrinking surface and a gradually expanding
surface.
16. The fan as claimed in claim 11, wherein the inner surface
comprises a radially- and gradually shrinking curved surface and a
radially and gradually expanding curved surface, both of which have
different curvatures.
17. The fan as claimed in claim 11, wherein a maximum outer
diameter of the outer edge of the impeller exceeds a minimum inner
diameter of the periphery of the passage.
18. The fan as claimed in claim 11, wherein the impeller comprises
blades with flat, conical, curved or stepped edges.
19. The fan as claimed in claim 10, wherein each blade of the
impeller overlaps an adjacent blade in an axial direction of the
passage.
20. The fan as claimed in claim 10, wherein the motor base is a
part of a system having a fan assembly or the motor base forms a
casing sidewall of a system.
Description
[0001] The present invention is a continuation-in-part application
of the parent application bearing Ser. No. 10/799,420 and filed on
Mar. 12, 2004. Also, this Non-provisional application claims
priority under U.S.C. .sctn. 119 (a) on Patent Application No(s).
093133821 filed in Taiwan, Republic of China on Nov. 5, 2004, the
entire contents of which are hereby incorporated by reference.
BACKGROUND
[0002] The invention relates to fans and fan frames, and in
particular to fans and fan frames capable of reducing noise.
[0003] AS performance of electronic devices is promoted, heat
dissipation apparatus or systems are indispensable and are thus
provided in the electronic devices. If heat generated by an
electronic device cannot be efficiently dissipated, performance of
the electronic device may deteriorate or the electronic device may
be damaged. A heat dissipation apparatus thus plays an important
role in removing heat generated by electronic devices such as
integrated circuits (ICs). With promotion of package techniques,
the area of integrated circuits decreases. Heat accumulated in the
integrated circuit per unit area increases accordingly. Therefore,
a heat dissipation apparatus with high heat-dissipating efficiency
is required on the integrated circuit.
[0004] Fans are widely used in various heat-generating systems.
FIG. 1A is a schematic cross section of a conventional fan, and
FIG. 1B is a schematic view showing the fan of FIG. 1A applied to
an exterior system 1. A conventional fan 10 includes a frame 11, an
impeller 14, and a motor (not shown). The impeller 14 further
includes a hub 15 and multiple blades 16 radially connected to the
hub 15. The motor is disposed inside of the hub 15.
[0005] The impeller 14 and motor are in the frame 11, and the
impeller 14 is driven by the motor to rotate. The motor base 12 is
connected to the frame 11 by a plurality of ribs 13 and the ribs
support the motor base 12.
[0006] As shown in FIG. 1B, when the fan 10 is applied to a
heat-generating exterior system 1, the motor base 12 locates on the
same plane as the frame 11 such that space required by outtake
airflow is limited, the amount of airflow cannot be increased and
noise generated by the fan 10 cannot be reduced. Moreover, the fan
10 is fixed on and combined to a heat-generating device 2 in the
exterior system 1 by screws penetrating the frame 11. During the
operation of the fan 10, vibrations generated by the motor and
rotation of the impeller 14 are transferred to the heat-generating
device 2 and the exterior system 1 via the motor base 12 and ribs
13, thereby generating noise. Also, vibrations generated by the
motor may damage the heat-generating device-2 or other components
in the exterior system 1.
SUMMARY
[0007] Accordingly, the invention provides an improved fan and fan
frame to overcome the aforementioned problems. A motor base of the
fan is raised into the housing of the fan, whereby increasing the
area of air flow intake or discharge and providing a stable
airflow. Additionally, noise and vibrations, generated by rotation
of an impeller and transferred to an exterior system via the motor
base during the operation of the fan, can be reduced.
[0008] An exemplary embodiment of the invention provides a fan
frame including a housing and a motor base. The housing has a
passage, and the passage forms an air outlet and an air inlet on
both ends of the housing. The motor base is disposed in the
housing. When the motor base is at the air outlet or the air inlet,
the bottom of the motor base locates on a plane different from that
of the air outlet or the air inlet. The fan frame further includes
a plurality of ribs connected between the housing and the motor
base to support the motor base. The cross section, width or
thickness of each rib is varied along the direction from the motor
base to the housing. The housing further includes an outward
expansion portion at the air outlet or the air inlet to increase
the area of air flow intake or discharge. The motor base has a
slope inclined radially to adjust the area of air flow intake or
discharge, and the slope is linear or curved. Moreover, the motor
base is a part of a system having a fan assembly. The system is
preferably a power supply, a server, or a computer. The motor base
forms a casing sidewall of a system, such as a fan guard.
[0009] Another exemplary embodiment of the invention provides a
fan, such as an axial flow fan, including a fan frame and an
impeller. The fan frame has a housing and a motor base. The housing
has a passage, and the passage forms an air outlet and an air inlet
on both ends of the housing. The motor base is disposed in the
housing, and the impeller is disposed on the motor base. When the
motor base is at the air outlet or the air inlet, the bottom of the
motor base locates on a plane different from that of the air outlet
or the air inlet. The fan frame further includes a plurality of
ribs disposed between the housing and the motor base to support the
motor base. The cross section, width or thickness of each rib is
varied along the direction from the motor base to the housing. The
housing further includes an outward expansion portion at the air
outlet or the air inlet to increase the area through which the air
flows into and out of the housing. The outward expansion portion is
formed with a lead angle, a sloped angle, a lead and sloped angle,
or a curved angle. The motor base has a slope inclined radially to
adjust the area of air flow intake or discharge, and the slope is
linear or curved.
[0010] Moreover, the fan frame is applied to a light source. The
periphery of the passage is an inner surface, and the light is
blocked from penetrating the passage by the inner surface when
light emitted by the light source enters the passage. The outer
edge of the impeller is parallel to the curved surface of the
periphery of the passage. The inner surface includes one or
multiple gradually shrinking surfaces and gradually expanding
surfaces so as to block the light emitted by the light source.
Alternatively, the inner surface includes a radially and gradually
shrinking curved surface and a radially and gradually expanding
curved surface, both of which have different curvatures. In
addition, each blade of the impeller overlaps an adjacent blade in
an axial direction of the passage. The housing is substantially
rectangular, circular, elliptical, or rhombic. The motor base may
be a part of a system having a fan assembly. The system is
preferably a power supply, a server, or a computer. Additionally,
the motor base forms a casing sidewall of a system, such as a fan
guard.
[0011] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
[0012] The invention can be more fully understood by reading the
subsequent detailed description and examples with references made
to the accompanying drawings, wherein:
[0013] FIG. 1A is a schematic cross section of a conventional
fan;
[0014] FIG. 1B is a schematic view showing the fan of FIG. 1A
applied to an exterior system;
[0015] FIGS. 2A-2C are schematic views of fans of the first
embodiment of the invention;
[0016] FIG. 3A is a schematic view of a fan of the second
embodiment of the invention;
[0017] FIG. 3B is a schematic view showing the fan of FIG. 3A
applied to an exterior system;
[0018] FIGS. 4A-4D are schematic views of fans of the third
embodiment of the invention;
[0019] FIGS. 5A-5D are schematic views of fans of the fourth
embodiment of the invention;
[0020] FIGS. 6A and 6B are schematic views of fans of the fifth
embodiment of the invention; and
[0021] FIG. 6C is a schematic top view of an impeller of an
embodiment of the invention.
DETAILED DESCRIPTION
[0022] FIGS. 2A-2C are schematic views of fans 20 of the first
embodiment of the invention. As shown in FIG. 2A, the fan 20, a
preferred axial flow fan, includes a fan frame 21 and an impeller
24. The fan frame 21 is a housing 21 having a passage 27, and the
shape of the fan frame 21 is substantially rectangular, circular,
elliptical, or rhombic. The housing 21 includes a motor base 22 and
a plurality of ribs 23. The impeller 24 includes a hub 25 and
multiple blades 26 connected to the hub 25, and there is a motor
(not shown) disposed inside of the hub 25 for driving the impeller
24 to rotate. The impeller 24, motor base 22, and motor are
disposed in the housing 21. The impeller 24 is disposed on the
motor base 22 and is rotated by the motor. The ribs 23 are disposed
between the periphery 271 of the passage 27 and the motor base 22,
for supporting the motor base 22. The passage 27 forms an air
outlet 211 and an air inlet 212 on both ends of the housing 21, and
the air outlet 211 and air inlet 212 are on a first hypothetical
plane 221 and a second hypothetical plane 222, respectively.
[0023] To overcome the drawbacks in which the bottom of the
conventional motor base 12 is coplanar with the fan frame, the
motor base 22 is raised into the housing 21 to form a displacement
depth so as to provide a stable airflow. As shown in FIG. 2A, the
motor base 22 is preferably disposed at the air outlet 211, and the
bottom of the motor base 22 locates on a plane different from that
of the air outlet 211 (first hypothetical plane 221).
Alternatively, the motor base 22 can be disposed at the air inlet
212, and the bottom of the motor base 22 locates on a plane
different from that of the air inlet 212 (second hypothetical plane
222).
[0024] When the motor base 22 is raised into the housing 21, the
top of the hub 25 disposed on the motor base 22 protrudes the
second hypothetical plane 222, as shown in FIG. 2B. However,
operation and performance of the fan 20 is not adversely affected.
Further, considering of the situation that the fan 20 must be
disposed coordinately with other components in an exterior system
when the fan 20 is applied to the exterior system, the size of the
hub 25 is correspondingly adjusted. Thus, the top of the hub 25 can
just align the second hypothetical plane 222 (as shown in FIG. 2A)
or be slightly lower than the second hypothetical plane 222 (as
shown in FIG. 2C) so that the hub 25 does not adversely affect
operation of other components in the exterior system.
[0025] FIG. 3A is a schematic view of a fan 30 of the second
embodiment of the invention. Not only the motor base 32 is raised
into the housing 31 to form a displacement depth, but also there is
preferably an outward expansion portion 39 formed at the air outlet
311 or the air inlet 312 to increase an area of air flow intake or
discharge, thereby enhancing air pressure and airflow of the fan
30. Additionally, when the outward expansion portion 39 is disposed
at the air outlet 311, deceleration and rectification of the
airflow can be obtained. The outward expansion portion 39 can be
formed with a lead angle, a sloped angle, a lead and sloped angle,
or a curved angle. The ribs 33 can be directly connected to the
outward expansion portion 39 and motor base 32, for supporting the
motor base 32. Alternatively, the ribs 33 can be connected to other
portions, except the outward expansion portion 39, of the housing
31.
[0026] FIG. 3B is a schematic view showing the fan 30 of FIG. 3A
applied to an exterior system 3. The fan 30 is applied to the
exterior system 3 having a heat-generating device 4 such as
integrated circuits (ICs). Since a displacement depth exists
between the bottoms of the motor base 32 and the outlet of the
housing 31, a space for outtake airflow is enlarged, thereby
enhancing the amount of airflow of the fan 30. Additionally, the
outward expansion portion 39 achieves deceleration and
rectification of the airflow, thereby reducing the noise caused by
turbulent flow field. Furthermore, since the bottom of the motor
base 32 is higher than the outlet of the housing 31, vibrations
generated by the motor and rotation of the impeller 34 won't not be
transferred to the heat-generating device 4 or the exterior system
3 via the motor base 32 and ribs 33. Thus, the noise problem is
solved and damage to components caused by the aforementioned
vibrations can be prevented.
[0027] The motor base 32 can be considered as a part of a system
having a fan assembly, or the motor base 32 forms a casing sidewall
of a system, such as a fan guard. The system 3 is a power supply, a
server, or a computer.
[0028] The invention is not limited to the aforementioned
structure. For example, in addition to the structural design of the
motor base 32 and outward expansion portion 39, the thickness,
width, or cross section of the ribs can be designed to various
requirements. Referring to FIGS. 4A-4D, which are schematic views
of fans 40 of the third embodiment of the invention. As shown in
FIG. 4A, the housing 41 of fan 40 has an outward expansion portion
49, and the multiple ribs 43, connected to the outward expansion
portion 49 and motor base 42, can be arranged in radial manner. The
shape of ribs 43 can be, for example, columnar, curved, or
streamlined.
[0029] Specifically, if the ribs 43 are connected to the motor base
42 and fan frame 41 in nonlinear manner, the cross section of the
ribs 43 will not be continuous. For ease of description, the cross
sections of the ribs of all embodiments of the invention are
completely shown and the blades are shown in a clearer manner.
[0030] The thickness of each rib 43 is varied along the direction
from the motor base 42 to the housing 41. As shown in FIG. 4A, the
thickness of each rib 43 at the motor base 42 is smaller than that
at the housing 41. Further, the thickness of each rib 43 gradually
increases from the motor base 42 to the housing 41. The change in
the thickness of each rib 43 can be linear slope gradual reduction
or curve slope gradual reduction.
[0031] Alternatively, the thickness of each rib 43 at the motor
base 42 is greater than that at the housing 41. Further, the
thickness of each rib 43 gradually decreases from the motor base 42
to the housing 41, as shown in FIG. 4B. The change in the thickness
of each rib 43 can be linear slope gradual reduction (as shown in
FIG. 4B) or curve slope gradual reduction (as shown in FIG. 4C)
Further, the thickness of each rib 43 connecting to the motor base
42 and housing 41 is relatively greater than that of a central part
of the rib 43 and the thickness of each rib 43 is relatively less
than that of the central part of the rib 43, as shown in FIG. 4D.
Furthermore, the thickness of each rib 43 connecting to the motor
base 42 and housing 41 is least.
[0032] When the impeller 44 rotates, airflow speed increases
outwardly from the blades 46. Namely, the flow speed near the
housing 41 is faster than the speed near the motor base 42.
Additionally, varied thickness design is applied to each rib 43 so
that the distances between each rib 43 and the lower edges of the
blades 46 are different. In view of the direction of the airflow,
the distances between the blades 46 and each rib 43 are different.
Accordingly, when the impeller 44 rotates, adverse interaction
between the blades 46 and the ribs 43 can be reduced. The
resistance of airflow and noise can thus be reduced.
[0033] The width of each rib 43 is designed according to the
rotational direction of the blades 46. The width of each rib 43 is
varied along the direction from the motor base 42 to the housing
41. For example, each rib 43 at the motor base 42 is thinner than
at the housing 41. Further, the width of each rib 43 gradually
increases from the motor base 42 to the housing 41. The change in
the width of each rib 43 can be linear slope gradual reduction or
curve slope gradual reduction. In addition, the width of each rib
43 at the motor base 42 exceeds that at the housing 41. Further,
the width of each rib 43 gradually decreases from the motor base 42
to the housing 41. Similarly, the change in the width of each rib
43 can be linear slope gradual reduction or curve slope gradual
reduction. Alternatively, the width of each rib 43 connecting to
the motor base 42 and housing 41 is relatively greater than that of
a central part of the rib 43 while the central part of the rib 43
is thinnest through the rib 43. Furthermore, the width of each rib
43 connecting to the motor base 42 and housing 41 is relatively
less than that of the central part of the rib 43.
[0034] When the impeller 44 rotates, airflow speed increases
outwardly from the blades 46. Namely, the flow speed near the
housing 41 is faster than the speed near the motor base 42.
Additionally, the width of each rib 43 is varied along the
direction from the motor base 42 to the housing 41. In view of the
rotating direction of the blades 46, the width of each rib 43 is
varied. Accordingly, the influence caused by faster airflow at the
ribs 43 and housing 41 can be reduced by the aforementioned
structural design. The resistance of airflow and noise can thus be
reduced.
[0035] The width and thickness of each rib 43 can be changed and
better designed. For example, In view of the rotating direction of
the blades 46 and for each rib 43, the portion with a smaller width
can have a larger thickness. Thus, the strength of the housing 41
is not adversely affected due to thin ribs 43. For example, each
rib 43 at the motor base 42 is thinner than at the housing 41, and
each rib 43 at the motor base 42 is thicker than at the housing 41.
Alternatively, the width of each rib 43 at the motor base 42
exceeds that at the housing 41, and the thickness of each rib 43 at
the motor base 42 is less than that at the housing 41. The change
in the width and thickness of each rib 43 can simultaneously be
linear or curved. Accordingly, the cross section of each rib 43 is
varied along the direction from the motor base 42 to the housing
41, whereby preventing noise caused by the resistance of airflow
between the lower edges of the blades and the ribs.
[0036] FIGS. 5A-5D are schematic views of fans of the fourth
embodiment of the invention. The fan includes a raised motor base
52 and an outward expansion portion 59. Also, the motor base 52
includes a slope inclined radially to adjust the area of air flow
intake or discharge, whereby optimizing the flow field distributed
in the fan. Therefore, the noise of the fan can be further reduced
and performance of the fan is enhanced. The motor base 52 expands
outwardly from the bottom thereof, and the slope is linear (as
shown in FIG. 5A) or curved (as shown in FIG. 5B). Alternatively,
the motor base 52 inward shrinks from the bottom thereof, and the
slope is linear (as shown in FIG. 5C) or curved (as shown in FIG.
5D).
[0037] Moreover, the fan can be applied to an external system with
a light source L, such as a projector. Referring to FIGS. 6A and
6B, which are schematic views of fans of the fifth embodiment of
the invention. Similarly, the fan includes a raised motor base 62
and an outward expansion portion 69. Additionally, in the housing
61, the periphery 671 of the passage 67 includes an inner surface.
When light emitted by the light source L enters the passage 67, the
light is blocked from penetrating the passage 67 by the inner
surface. The inner surface can be a concave surface depressed
toward a central axis of the passage 67 so as to block the light
emitted by the light source L. Or, the inner surface can be a
convex surface protruded toward a central axis of the passage 67,
an outer edge of the impeller 64 is formed with a concave surface
opposing the curved surface so as to block the light emitted by the
light source L.
[0038] In addition, the inner surface may include one or multiple
gradually shrinking surfaces and gradually expanding surfaces, as
shown in FIG. 6A. Alternatively, the inner surface may include a
radially and gradually shrinking curved surface and a radially and
gradually expanding curved surface, both of which have different
curvatures, as shown in FIG. 6B. As long as the inner periphery of
the fan frame can match the curved blades, light emitted from the
light source L can be blocked from penetrating the passage by the
inner surface. Namely, the outer edge of the impeller 64 is
parallel to the inner surface of the periphery 671 of the passage
67. The gap between the blades 66 and the housing 61 can be
effectively sheltered. Thus, the fan can obstruct light from the
light source L. Additionally, the curved outer edges of the blades
66 can increase the area of the blades 66, enhancing unity of the
fan. Moreover, the displacement depth between the motor base 62 and
the bottom of the housing 61 can be adjusted by changing the inner
surface of the periphery 671 of the passage 67. Thus, the flow
field of the airflow between the impeller 64 and the housing 61 can
be adjusted and the noise caused by a turbulent flow field
effectively reduced.
[0039] FIG. 6C is a schematic top view of an impeller of an
embodiment of the invention. To effectively shelter the gap between
the blades and the housing, each blade 66a of the impeller 64
overlaps an adjacent blade 66b in an axial direction of the
passage. Also, each of the blades 66a and 66b has a flat, conical,
curved or stepped edge.
[0040] In conclusion, the invention can overcome the drawbacks of
the conventional fan in which the bottom of the motor base is
coplanar with that of the fan frame. In the present fan, the motor
base is raised into the housing of the fan frame to form a
displacement depth, whereby providing a stable airflow.
Additionally, the outward expansion portion can increase the area
of air flow intake or discharge. Thus, deceleration and
rectification of the airflow can be obtained, and air pressure and
air flow of the fan can be increased. Furthermore, ribs with a
design of varied thickness, width or cross section not only enhance
the strength of the fan. The distances between the lower edges of
the blades, but also reduce noise caused by adverse interaction
between the ribs and the rotating blades. Moreover, the motor base
can include a slope inclined radially, and the slope is linear or
curved. Thus, the noise of the fan can be reduced and performance
of the fan enhanced. Additionally, the housing with gradually
shrinking surfaces can match the curved outer edges of the blades
to shelter the gap between the housing and the blades. When the fan
is applied to a light-emitting device to dissipate heat generated
thereby, light leakage as in the conventional fan can be
prevented.
[0041] While the invention has been described by way of example and
in terms of preferred embodiment, it is to be understood that the
invention is not limited thereto. To the contrary, it is intended
to cover various modifications and similar arrangements (as would
be apparent to those skilled in the art). Therefore, the scope of
the appended claims should be accorded the broadest interpretation
so as to encompass all such modifications and similar
arrangements.
* * * * *