CN216044620U - Combined fan - Google Patents

Abstract

The utility model discloses a combined fan. The combined fan comprises a first fan and a second fan, wherein a plurality of mounting flanges are uniformly distributed on the first fan, assembling lugs in one-to-one correspondence with the mounting flanges are arranged on the second fan, and aligning grooves and mounting grooves are formed in the assembling lugs. The alignment groove is used for visual alignment with the mounting flange during initial assembly of the first fan and the second fan; the mounting groove is used for being clamped with the mounting flange in a one-to-one correspondence mode when the first fan and the second fan are assembled in a rotating mode. The combined fan provided by the utility model can be assembled only by simple operation of firstly carrying out axial visual alignment and then carrying out radial slight rotation, does not need to be additionally provided with connecting pieces or use extra assembling tools, is time-saving and labor-saving, improves the assembling efficiency, reduces the assembling cost, ensures that the whole assembling process is simple, convenient and quick, and has stable and reliable assembling state and neat and attractive assembling effect.

Description

Combined fan

Technical Field

The present invention relates to a combined fan, and more particularly, to a serial combined fan.

Background

With the rapid development of electronic technology, many electronic devices are developed to have high performance and high speed, and accordingly, the heat generated by the electronic devices is more and more, and if the heat is not dissipated in time, the reliability and the service life of the electronic devices will be seriously affected, and even the electronic devices will be damaged. Therefore, heat dissipation has become one of the important issues in many electronic products. Therefore, in the industry, a fan is usually added to an electronic product to dissipate heat of an electronic component, and when a single fan cannot meet the heat dissipation requirement, a combined fan is often used to dissipate heat.

The combined fan is formed by connecting two or more fans in series, and two adjacent fans are connected together in a screw connection mode or a riveting assembly mode. However, these assembling methods are complicated, inconvenient, time-consuming and labor-consuming, and therefore how to assemble the combined fan in the simplest and most convenient and fast connecting manner is a key problem to be solved by the present invention.

SUMMERY OF THE UTILITY MODEL

In view of the above, the present invention particularly provides a combined fan, which includes:

the first fan comprises a first fan frame, the lower end of the first fan frame is provided with a first axial positioning surface, the outer wall of the first fan frame is uniformly provided with a plurality of first normal positioning surfaces, and each first normal positioning surface is provided with an installation flange;

the second fan comprises a second fan frame, a second axial positioning surface matched with the first axial positioning surface is arranged at the upper end of the second fan frame, and assembling lugs in one-to-one correspondence with the mounting flanges are convexly arranged on the outer wall of the second fan frame; wherein the content of the first and second substances,

the inner wall of the assembling lug is provided with a second normal positioning surface matched with the first normal positioning surface;

the inner wall of the assembling lug is also provided with a positioning groove which penetrates through the top surface of the assembling lug; when the first fan and the second fan are initially assembled, the mounting flange is visually inserted into the alignment groove in the axial direction of the second fan;

the inner part of the assembling lug is provided with an installation groove matched with the installation flange, and the installation groove is communicated with the alignment groove; and when the first fan and the second fan are assembled in a rotating mode, the mounting flanges and the mounting grooves are clamped in a one-to-one corresponding mode.

In the above-mentioned combined fan, one end of the alignment groove, which is away from the second normal positioning surface, is provided with a limiting portion to limit a rotation direction when the first fan and the second fan are assembled.

In the above combined fan, a semicircular anti-drop rib is convexly arranged at the top of the mounting groove, and the axial direction of the anti-drop rib is located in the radial direction of the second fan; the top surface of the mounting flange is concavely provided with an anti-falling clamping groove matched with the anti-falling ribs.

In the above combined fan, a guide portion is disposed at a front end of the mounting flange in the assembly rotation direction, and the guide portion is disposed in an inclined plane to guide the anti-separation rib to be screwed into the anti-separation groove.

In the above combined fan, one end of the top surface of the mounting flange, which is far away from the guiding portion, is provided with a first axial limiting surface, and the top of the mounting groove is provided with a second axial limiting surface which is matched with the first axial limiting surface.

In the above combined fan, a second tangential positioning surface is arranged on the side wall of the mounting groove far away from the alignment groove, and a first tangential positioning surface adapted to the second tangential positioning surface is arranged on the mounting flange.

In the above-mentioned combined fan, a bottom surface of the mounting flange is coplanar with the first axial positioning surface, and a bottom surface of the mounting groove is coplanar with the second axial positioning surface.

In the above combined fan, a through hole is formed in the outer wall of the assembling lug in the radial direction of the second fan, the through hole corresponds to and is communicated with the mounting groove, and the outer dimension of the through hole is not less than that of the mounting groove.

In the combined fan, the upper end of the first fan frame is provided with the first flange, the lower end of the second fan frame is provided with the second flange, and the first flange and the second flange are both provided with the plurality of mounting holes.

In the above combined fan, the outer wall of the first fan frame is further provided with a plurality of first straight walls, the first straight walls are located between two adjacent first normal positioning surfaces, and the first straight walls are flush with one side wall of the first flange.

In the combined fan, the outer wall of the second fan frame is provided with the arc-shaped walls in one-to-one correspondence with the first normal positioning surfaces, the outer wall of the second fan frame is further provided with a plurality of second straight walls, the second straight walls are located between every two adjacent arc-shaped walls, and the second straight walls are flush with one side wall of the second flange.

In the above combined fan, the first fan further includes a first central hub located at the center of the first fan frame, and a plurality of first reinforcing ribs radially arranged are connected between the first central hub and the first fan frame; the lower end surface of the first central hub is coplanar with the first axial locating surface.

In the above combined fan, the second fan further includes a second central hub, the second central hub is located at the center of the second fan frame, a plurality of second reinforcing ribs radially arranged are connected between the second central hub and the second fan frame, and the upper end surface of the second central hub is coplanar with the second axial positioning surface; the second reinforcing ribs correspond to the first reinforcing ribs one to one and are sequentially connected in shape.

Compared with the prior art, the utility model has the following effects:

1) based on the combined fan, through the structural design of the alignment groove, the visual alignment and the quick positioning during the initial assembly of the first fan and the second fan are realized; the anti-misoperation design of the quick assembly of the first fan and the second fan is realized by definitely limiting the rotation direction of the first fan and the second fan during the assembly through the arrangement of the limiting part;

2) based on the combined fan, the simple and convenient assembly and anti-drop design between the first fan and the second fan are realized through the matching design of the mounting flange and the mounting groove, and the stable and reliable assembly state of the first fan and the second fan is ensured;

3) the combined fan provided by the utility model can be assembled only by simple operation of firstly carrying out axial visual alignment and then carrying out radial slight rotation, does not need to be additionally provided with connecting pieces or use extra assembling tools, is time-saving and labor-saving, improves the assembling efficiency, reduces the assembling cost, ensures that the whole assembling process is simple, convenient and quick, and has stable and reliable assembling state and neat and attractive assembling effect.

The foregoing summary of the utility model and the following detailed description of the embodiments are provided to illustrate and explain the principles of the utility model and to provide further explanation of the utility model as claimed.

Drawings

FIG. 1 is a perspective assembly view of the modular fan of the present invention;

FIG. 2 is an exploded perspective view of the modular fan of the present invention;

FIG. 2a is an enlarged view of a portion of FIG. 2A;

FIG. 2B is a partial enlarged view of FIG. 2 at B;

FIG. 3 is an exploded perspective view of another embodiment of the modular fan of the present invention;

FIG. 4 is a cross-sectional view of the mounting flange and mounting ears of the modular fan of the present invention;

fig. 5 is a sectional view showing the structure of a mounting groove and a mounting flange of the combined fan of the present invention.

Wherein, the reference numbers:

10 … first fan

11 … first fan frame

111 … first axial locating surface

112 … first normal locating surface

113 … mounting flange

1131 … anti-drop card slot

1132 … guide part

1133 … first tangential orientation surface

1134 … first axial limiting surface

114 … first straight wall

12 … first flange

13 … first hub

14 … first reinforcing rib

20 … second fan

21 … second fan frame

211 … second axial positioning surface

212 … mounting lug

213 … second Normal locating surface

214 … alignment groove

215 … mounting groove

2151 … anti-slip rib

2152 … second tangential orientation surface

2153 … second axial limiting surface

216 … limitation part

217 … through hole

218 … curved wall

219 … second straight wall

22 … second flange

23 … second hub

24 … second reinforcing rib

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The exemplary embodiments of the present invention and the description thereof are provided to explain the present invention and not to limit the present invention. Additionally, the same or similar numbered elements/components used in the drawings and the embodiments are used to represent the same or similar parts.

With respect to directional terminology used herein, for example: up, down, left, right, front or rear, etc., are simply directions with reference to the drawings. Accordingly, the directional terminology used is intended to be illustrative and is not intended to be limiting of the present teachings.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

As used herein, "and/or" includes any and all combinations of the described items.

References to "plurality" herein include "two" and "more than two"; reference to "multiple sets" herein includes "two sets" and "more than two sets".

Certain words used to describe the present application are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the present application.

Referring to fig. 1, the combined fan of the present invention includes a first fan 10 and a second fan 20, wherein the first fan 10 is provided with a plurality of mounting flanges 113, and the second fan 20 is provided with mounting lugs 212 corresponding to the mounting flanges 113 one to one; the mounting flanges 113 are correspondingly mounted in the mounting lugs 212, so that the first fan 10 and the second fan 20 are assembled, and the assembly effect is neat and attractive.

Referring to fig. 2-4, the first fan 10 includes a first fan frame 11, and a first axial positioning surface 111 is disposed at a lower end of the first fan frame 11; the second fan 20 comprises a second fan frame 21, and a second axial positioning surface 211 adapted to the first axial positioning surface 111 is arranged at the upper end of the second fan frame 21. The axial assembly of the first fan 10 with the second fan 20 is limited by the cooperation of the first axial locating surface 111 and the second axial locating surface 211.

Furthermore, a plurality of first normal positioning surfaces 112 are uniformly distributed on the outer wall of the first fan frame 11, and each first normal positioning surface 112 is provided with a mounting flange 113; the outer wall of the second frame 21 is provided with a protruding assembling ear 212 corresponding to the mounting flange 113, and the inner wall of the assembling ear 212 is provided with a second normal positioning surface 213 adapted to the first normal positioning surface 112. The normal assembly of the first fan 10 with the second fan 20 is limited by the cooperation of the first normal positioning surface 112 and the second normal positioning surface 213.

Furthermore, the inner wall of the mounting lug 212 is also provided with an alignment groove 214 penetrating through the top surface of the mounting lug 212; when the first fan 10 and the second fan 20 are initially assembled, the mounting flange 113 is visually inserted into the alignment groove 214 in the axial direction of the second fan 20. Through the arrangement of the alignment groove 214, visual alignment and quick positioning when the first fan 10 and the second fan 20 are initially assembled are realized.

Further, the fitting ears 212 are provided inside with fitting grooves 215 fitted to the fitting flanges 113, and the fitting grooves 215 communicate with the aligning grooves 214. When the first fan 10 and the second fan 20 are assembled in a rotating manner, the first axial positioning surface 111 and the second axial positioning surface 211 are attached to each other, and the mounting flanges 113 are clamped in the mounting grooves 215 in a one-to-one correspondence manner, so that the first fan 10 and the second fan 20 are assembled. It can be understood that the installation groove 215 is in communication with the alignment groove 214, so that after the installation flange 113 is inserted into the alignment groove 214, the installation flange 113 can be clamped into the installation groove 215 by rotating a small angle, and the first fan 10 and the second fan 20 can be assembled.

Referring to fig. 2, 2b and 5, a limiting portion 216 is disposed at an end of the alignment groove 214 away from the second normal positioning surface 213 to limit a rotation direction of the first fan 10 and the second fan 20 when they are assembled.

Further, the first normal positioning surface 112 is a circular arc surface, and thus the second normal positioning surface 213 is also a circular arc surface adapted to the first normal positioning surface 112. It will be appreciated that the outer wall of the mounting flange 113 is also radiused. The radial dimension of the defining portion 216 is greater than the radial dimension of the first normally positioned surface 112 but less than the radial dimension of the mounting flange 113 to define a rotational direction of the first fan 10 when assembled with the second fan 20. Through the arrangement of the limiting part 216, the rotating direction of the first fan 10 and the second fan 20 during assembly is definitely limited, and the anti-error design of the quick assembly of the first fan 10 and the second fan 20 is realized, so that the assembly of the combined fan can be completed only by slightly rotating without specially considering the rotating direction during assembly.

Further, the above arrangement enables the rotation tracks of the first normal positioning surface 112, the second normal positioning surface 213 and the outer wall of the mounting flange 113 to be in a constant circular arc shape when the first fan 10 is rotatably assembled with the second fan 20, which facilitates the matching design of the assembly structure of the first fan 10 and the second fan 20. In the process of assembling the first fan 10 and the second fan 20, the first normal positioning surface 112 and the second normal positioning surface 213 are attached to each other, so as to firstly accurately guide the axial insertion of the mounting flange 113 and the alignment slot 214, thereby ensuring that the clamping length of each mounting flange 113 is consistent with that of the corresponding mounting slot 215. Therefore, the matching design of the first normal positioning surface 112 and the second normal positioning surface 213 avoids the normal play between the first fan 10 and the second fan 20, and ensures the stable assembly state of the first fan 10 and the second fan 20.

Referring to fig. 2 to 4, a semi-cylindrical anti-slip rib 2151 is protruded from a top of the mounting groove 215, and an axial direction of the anti-slip rib 2151 is located in a radial direction of the second fan 20; the top surface of the mounting flange 113 is concavely provided with an anti-falling clamping groove 1131 matched with the anti-falling rib 2151.

Further, the top of the mounting flange 113 is provided with a guide portion 1132 at the front end of the mounting rotation direction thereof, and the guide portion 1132 is provided in a slant surface to guide the anti-drop rib 2151 to be screwed into the anti-drop groove 1131. It is understood that the guide portion 1132 is disposed at a slope-like slope in a direction opposite to the assembling rotation direction of the first fan 10 where the mounting flange 113 is located. To explain, in the process of rotationally assembling the first fan 10 and the second fan 20, the semi-cylindrical anti-slip rib 2151 goes beyond the high position of the joint of the guide portion 1132 and the anti-slip groove 1131 under the dual actions of the inclined surface of the guide portion 1132 and the external rotational force, and is screwed into and snapped into the anti-slip groove 1131.

It can be understood that, since the whole anti-drop rib 2151 is semi-cylindrical and the axial direction thereof is located in the radial direction of the second fan 20, when the fan is rotationally assembled, the whole anti-drop rib 2151 protrudes higher than the other anti-drop rib 2151 and is clamped into the anti-drop slot 1131; the clamping mode is simple and convenient, and the clamping is in place in one step; in addition, because the anti-slip rib 2151 is matched with the semi-cylindrical structure of the anti-slip groove 1131, after the anti-slip rib 2151 is clamped into the anti-slip groove 1131, the high position of the joint of the guide portion 1132 and the anti-slip groove 1131 is difficult to overcome by the same rotating external force, so that the anti-slip rib 2151 is separated from the anti-slip groove 1131, and the clamping and positioning effects are really achieved. Therefore, the above arrangement realizes simple assembly and anti-drop design between the first fan 10 and the second fan 20, ensures stable and reliable assembly state of the two fans, and does not expose the two fans after assembly, thereby not affecting the appearance of the combined fan.

Referring to fig. 2a, 3 and 4, a first axial limiting surface 1134 is disposed at an end of the top surface of the mounting flange 113 away from the guiding portion 1132, and a second axial limiting surface 2153 adapted to the first axial limiting surface 1134 is disposed at a top of the mounting groove 215. After the first fan 10 and the second fan 20 are assembled, the first axial positioning surface 111 is attached to the second axial positioning surface 211, and the first axial limiting surface 1134 is also attached to the second axial limiting surface 2153, so that the axial movement between the assembled first fan 10 and the assembled second fan 20 is avoided, and the stable assembly state of the first fan 10 and the assembled second fan 20 is ensured.

Referring to fig. 2-5, a second tangential positioning surface 2152 is disposed on a sidewall of the mounting groove 215 away from the alignment groove 214, and a first tangential positioning surface 1133 adapted to the second tangential positioning surface 2152 is disposed on the mounting flange 113. After the first fan 10 and the second fan 20 are assembled in place in a rotating manner, the first tangential positioning surface 1133 is attached to the second tangential positioning surface 2152 to limit the continuous rotation between the first tangential positioning surface and the second tangential positioning surface, so that the clamping state of the anti-falling rib 2151 and the anti-falling clamping groove 1131 is stable, namely the clamping state of the mounting flange 113 and the mounting groove 215 is stable, the tangential play which possibly occurs between the assembled first fan 10 and the assembled second fan 20 is avoided, and the stable assembly state of the first fan 10 and the assembled second fan 20 is ensured.

Referring to fig. 2-3, the bottom surface of the mounting flange 113 is coplanar with the first axial positioning surface 111, and the bottom surface of the mounting groove 215 is coplanar with the second axial positioning surface 211. The arrangement makes the structural design of the mounting flange 113 and the mounting groove 215 simple and neat, and the structural manufacturability is better.

Referring to fig. 2b and 5, the outer wall of the mounting lug 212 is provided with a through hole 217 in the radial direction of the second fan 20, the through hole 217 corresponds to and communicates with the mounting groove 215, and the outer dimension of the through hole 217 is not smaller than the outer dimension of the mounting groove 215. This through hole 217 is provided to facilitate the molding of the mounting groove 215.

Referring to fig. 2 and 3, a first flange 12 is disposed at an upper end of the first frame 11, a second flange 22 is disposed at a lower end of the second frame 21, and a plurality of mounting holes are disposed on the first flange 12 and the second flange 22. The above arrangement enables connection between the modular fan and other external components.

Further, the outer wall of the first fan frame 11 is further provided with a plurality of first straight wall surfaces 114, the first straight wall surfaces 114 are located between two adjacent first normal positioning surfaces 112, and the first straight wall surfaces 114 are flush with a side wall of the first flange 12. The outer wall of the second frame 21 is provided with arc-shaped walls 218 corresponding to the first normal positioning surfaces 112 one by one, the outer wall of the second frame 21 is further provided with a plurality of second straight walls 219, the second straight walls 219 are located between two adjacent arc-shaped walls 218, and the second straight walls 219 are flush with one side wall of the second flange 22. The combined fan is more neat and attractive in appearance.

Further, the first fan 10 further includes a first central hub 13, the first central hub 13 is located at the inner center of the first fan frame 11, and a plurality of first reinforcing ribs 14 radially arranged are connected between the first central hub 13 and the first fan frame 11; the lower end face of the first central hub 13 is coplanar with the first axial locating face 111. The second fan 20 further includes a second central hub 23, the second central hub 23 is located at the inner center of the second fan frame 21, a plurality of second reinforcing ribs 24 radially arranged are connected between the second central hub 23 and the second fan frame 21, and the upper end surface of the second central hub 23 is coplanar with the second axial positioning surface 211; the second reinforcing ribs 24 correspond to the first reinforcing ribs 14 one by one and are connected in the shape. The arrangement enhances the structural strength of the first fan 10 and the second fan 20, and the arrangement of the reinforcing ribs is beautiful and smooth, thereby not generating adverse effect on the flow field of the combined fan.

Referring to fig. 1 to 5, a fan assembly method of a combined fan according to the present invention is briefly described, including the following steps:

1) initial assembly in the axial direction:

first, the first fan 10 and the second fan 20 are placed in a manner that the first axial positioning surface 111 and the second axial positioning surface 211 are opposite to each other;

then the mounting flanges 113 are inserted into the alignment grooves 214 in a one-to-one correspondence in the direction of S1 shown in fig. 2;

2) and (3) radial rotating assembly:

the first axial positioning surface 111 and the second axial positioning surface 211 are pressed against each other to be tightly attached;

the first fan 10 is rotated in the direction of S2 shown in fig. 2, or the second fan 20 is rotated in the direction of S2 shown in fig. 2, so that the mounting flanges 113 are fastened to the mounting grooves 215 in a one-to-one correspondence, thereby completing the assembly of the combined fan.

It should be noted that, since the setting of the upper limit portion 216 of the alignment groove 214 clearly defines the assembly rotation direction in this step, and realizes the design of preventing the first fan 10 and the second fan 20 from being assembled quickly, the assembly of the combination fan can be completed only by slightly rotating without specially considering the rotation direction during the assembly.

In summary, the combined fan provided by the utility model solves the problems of complexity, inconvenience, time and labor consumption of the assembly process of the existing combined fan, realizes that the combined fan can be assembled only by simple operation of firstly axially visually aligning and then radially slightly rotating, does not need to additionally arrange a connecting piece or use an additional assembly tool, is time-saving and labor-saving, improves the assembly efficiency, reduces the assembly cost, and ensures that the whole assembly process is simple, convenient and quick, the assembly state is stable and reliable, and the assembly effect is neat and attractive.

Although the present invention has been described with reference to the foregoing embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the utility model.

Claims (13)

1. A modular fan, comprising:

the first fan comprises a first fan frame, the lower end of the first fan frame is provided with a first axial positioning surface, the outer wall of the first fan frame is uniformly provided with a plurality of first normal positioning surfaces, and each first normal positioning surface is provided with an installation flange;

the second fan comprises a second fan frame, a second axial positioning surface matched with the first axial positioning surface is arranged at the upper end of the second fan frame, and assembling lugs in one-to-one correspondence with the mounting flanges are convexly arranged on the outer wall of the second fan frame; wherein the content of the first and second substances,

the inner wall of the assembling lug is provided with a second normal positioning surface matched with the first normal positioning surface;

the inner wall of the assembling lug is also provided with a positioning groove which penetrates through the top surface of the assembling lug; when the first fan and the second fan are initially assembled, the mounting flange is visually inserted into the alignment groove in the axial direction of the second fan;

the inner part of the assembling lug is provided with an installation groove matched with the installation flange, and the installation groove is communicated with the alignment groove; and when the first fan and the second fan are assembled in a rotating mode, the mounting flanges and the mounting grooves are clamped in a one-to-one corresponding mode.

2. The modular fan of claim 1 wherein an end of the alignment slot distal from the second normal alignment surface defines a limiting portion to limit the direction of rotation of the first fan when assembled with the second fan.

3. The modular fan of claim 1 wherein the groove top of said mounting groove is provided with a semi-cylindrical anti-slip rib in a protruding manner, and the axial direction of said anti-slip rib is located in the radial direction of said second fan; the top surface of the mounting flange is concavely provided with an anti-falling clamping groove matched with the anti-falling ribs.

4. The combination fan as claimed in claim 3, wherein the top of the mounting flange is provided at a front end in an assembling rotation direction thereof with a guide portion having a slope to guide the anti-slip rib to be screwed into the anti-slip groove.

5. The modular fan of claim 4 wherein the top surface of the mounting flange is provided with a first axial limiting surface at an end thereof remote from the guide portion, and the top of the mounting groove is provided with a second axial limiting surface adapted to the first axial limiting surface.

6. The modular fan of claim 1 wherein a second tangential orientation surface is provided on a side wall of said mounting slot remote from said alignment slot, and a first tangential orientation surface is provided on said mounting flange for mating with said second tangential orientation surface.

7. The modular fan of claim 1 wherein the bottom surface of said mounting flange is coplanar with said first axially facing surface and the bottom surface of said mounting slot is coplanar with said second axially facing surface.

8. The combination fan as claimed in claim 1, wherein the outer wall of the mounting lug has a through hole formed in a radial direction of the second fan, the through hole corresponds to and communicates with the mounting groove, and an outer dimension of the through hole is not smaller than an outer dimension of the mounting groove.

9. The combined fan as claimed in claim 1, wherein a first flange is provided at an upper end of the first fan frame, a second flange is provided at a lower end of the second fan frame, and a plurality of mounting holes are formed at the first flange and the second flange.

10. The modular fan of claim 9 wherein the outer wall of the first frame further comprises a plurality of first straight walls, the first straight walls are located between two adjacent first normal positioning surfaces, and the first straight walls are flush with a side wall of the first flange.

11. The modular fan of claim 10 wherein the outer wall of the second frame has arcuate walls that correspond one-to-one to the first normal alignment surfaces, and the outer wall of the second frame has a plurality of second straight walls that are disposed between two adjacent arcuate walls and are aligned with a sidewall of the second flange.

12. The modular fan of claim 1 wherein said first fan further comprises a first central hub located at the center of the interior of said first frame, said first central hub and said first frame having a plurality of radially disposed first ribs connected therebetween; the lower end surface of the first central hub is coplanar with the first axial locating surface.

13. The modular fan of claim 12 wherein said second fan further comprises a second central hub, said second central hub being located at the center of the interior of said second frame, a plurality of second reinforcing ribs radially disposed being connected between said second central hub and said second frame, the upper end surface of said second central hub being coplanar with said second axially located surface; the second reinforcing ribs correspond to the first reinforcing ribs one to one and are sequentially connected in shape.

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