CN215521379U - Volute for centrifugal fan and centrifugal fan applying volute - Google Patents

Abstract

The utility model relates to a volute for a centrifugal fan and the centrifugal fan using the same, comprising: the volute comprises a volute main body and a volute body, wherein the volute main body comprises a front cover plate, a rear cover plate and a ring wall, and the ring wall is arranged between the front cover plate and the rear cover plate and is provided with a first end part and a second end part; the volute tongue piece is rotatably connected to the first end part of the annular wall and defines an air outlet with an adjustable expansion angle together with the front cover plate, the rear cover plate and the second end part of the annular wall; the first end part of the annular wall is provided with a first arc-shaped wall, the cross section of the first arc-shaped wall is C-shaped, the notch of the first arc-shaped wall faces the air outlet, a placing cavity is defined on the inner side of the first arc-shaped wall, the volute tongue piece is provided with a rotating connecting part, at least part of the rotating connecting part is contained in the placing cavity of the first arc-shaped wall, and the rotating connecting part is provided with an arc-shaped wall surface which can be always attached to the inner surface of the first arc-shaped wall in the rotating process. The clearance between the edge of first arc wall and the rotation connecting portion of snail tongue spare can be to the incoming flow of air current back to, has avoided receiving the direct impact of air current, has reduced the abnormal sound.

Description

Volute for centrifugal fan and centrifugal fan applying volute

Technical Field

The utility model relates to the technical field of centrifugal fans, in particular to a volute for a centrifugal fan and a centrifugal fan applying the volute.

Background

Centrifugal fans, especially multi-blade centrifugal fans, are widely used in air conditioners, range hoods, air fresheners, ventilators and other household appliances because of their advantages of compact structure, high pressure coefficient, large flow coefficient, low noise and the like. Once the multi-wing centrifugal fan is designed, manufactured and processed, all structural dimension parameters of the multi-wing centrifugal fan are uniquely determined. However, in the actual use process of the fan, the working air volume of the fan can be adjusted according to specific requirements, and in this case, the outlet type uniquely determined by the original fan may become a negative factor. Moreover, due to the diffusion effect of the multi-wing centrifugal fan, the airflow at the outlet of the fan is in an expansion trend after being thrown out by the impeller, so that when the outlet of the fan is designed, the outlet at one side of the volute tongue is expanded outwards by a certain angle, and the obstruction is avoided. However, when the working air volume of the fan is reduced and the airflow thrown out by the impeller is not enough to fill the whole outlet, the outlet area on the volute tongue side can generate large vortex due to the existence of strong speed difference to bring vortex noise, and simultaneously, the outflow of the air in the fan can be further blocked, so that the overall noise of the fan is increased.

Therefore, a centrifugal fan structure with an adjustable expansion angle of the volute tongue side outlet appears, and as disclosed in the utility model patent in china with application number cn201820384681.x (publication number CN208154761U), an air conditioner is disclosed, which comprises: the volute component comprises a volute body, a volute tongue and a diffusion section, the volute tongue is connected with the lower surface of the outlet end of the volute body and can rotate relative to the volute body, the diffusion section is connected with the front end of the volute tongue so as to be driven by the volute tongue to synchronously rotate, and the diffusion section is provided with an air guide section extending downwards. The wind wheel is arranged in the wind guide air duct, and at least one part of the indoor heat exchanger is arranged in the shell and is positioned between the air inlet and the inlet end of the volute main body.

However, the volute for the centrifugal fan in the above patent still has certain disadvantages, and in order to realize the flexible rotation of the volute tongue, a gap is inevitably formed between the volute tongue and the volute annular wall, wherein the area near the volute tongue is most impacted by the airflow thrown out by the impeller, and the gap between the volute tongue and the volute annular wall in the above patent just faces the incoming flow direction of the airflow, and the existence of the gap can generate great noise, so that the noise is greatly increased.

SUMMERY OF THE UTILITY MODEL

The first technical problem to be solved by the utility model is to provide a volute for a centrifugal fan, which can effectively reduce the generation of large abnormal sound caused by the direct impact of airflow at the rotating connection position of a volute tongue and the annular wall of the volute, aiming at the current situation of the prior art.

The second technical problem to be solved by the present invention is to provide a centrifugal fan using the above volute, aiming at the current situation of the prior art.

The technical scheme adopted by the utility model for solving the first technical problem is as follows:

a volute for a centrifugal fan, comprising:

the volute comprises a volute body and a volute body, wherein the volute body comprises a front cover plate, a rear cover plate and a ring wall, the front cover plate and the rear cover plate are arranged oppositely, and the ring wall is arranged between the front cover plate and the rear cover plate and is provided with a first end part and a second end part which are opposite in the length direction;

the volute tongue piece is rotatably connected to the first end part of the annular wall and defines an air outlet with an adjustable expansion angle together with the front cover plate, the rear cover plate and the second end part of the annular wall;

the first end part of the annular wall is provided with a first arc-shaped wall, the cross section of the first arc-shaped wall is C-shaped, the notch of the first arc-shaped wall faces the air outlet, a placing cavity is defined at the inner side of the first arc-shaped wall, the volute tongue piece is provided with a rotating connecting part, at least part of the rotating connecting part is contained in the placing cavity of the first arc-shaped wall, and the rotating connecting part is provided with an arc-shaped wall surface which can be always attached to the inner surface of the first arc-shaped wall in the rotating process.

In order to realize the rotating fit between the rotating connecting part of the volute tongue piece and the first arc-shaped wall, the rotating connecting part comprises a second arc-shaped wall with a C-shaped cross section, and the outer wall surface of the second arc-shaped wall is attached to the inner wall surface of the first arc-shaped wall so as to form the arc-shaped wall surface of the rotating connecting part.

In order to drive the volute tongue piece to rotate, the volute tongue piece is automatically and flexibly adapted to different air volume states, the volute further comprises a driving motor arranged on the volute main body, the driving motor is located on the inner side of the second arc-shaped wall, and an output shaft of the driving motor is connected with the second arc-shaped wall and is coaxially arranged with the second arc-shaped wall, so that the volute tongue piece is driven to rotate by taking the output shaft of the driving motor as a rotation center.

In order to realize the driving connection of the driving motor and the volute tongue piece, the inner side of the second arc-shaped wall is provided with a connecting column, the end part of the connecting column is provided with a limiting hole, and an output shaft of the driving motor is inserted in the limiting hole.

In order to ensure that the worm piece can rotate stably, the first arc-shaped wall is provided with a first port and a second port which are opposite in the length direction, the rear cover plate is provided with a first extending part which covers the first port, the front cover plate is provided with a second extending part which covers the second port, the driving motor is connected to the inner wall of the first extending part, the inner wall of the second extending part is provided with a positioning column, the connecting column is provided with a positioning hole corresponding to the positioning column, and the positioning column is in rotating fit with the positioning hole.

Preferably, the connecting column is integral with the second arcuate wall. It is contemplated that the connecting stud and the second arcuate wall may be separate pieces joined together by welding or by a connecting piece

In order to avoid interference with rotation of the volute tongue piece due to an overlarge central angle corresponding to the arc length of the cross section of the first arc-shaped wall, limit the rotation angle of the volute tongue piece and avoid that a gap opening between the first arc-shaped wall and a rotation connecting part of the volute tongue piece cannot face away from incoming flow better due to an undersize central angle corresponding to the arc length of the cross section of the first arc-shaped wall, and a tangent line of the cross section of the first arc-shaped wall at one end adjacent to the air outlet is parallel to a plane where the second end of the annular wall is located. Above-mentioned structural design for the clearance opening orientation between the rotation connecting portion of first arc wall and snail tongue spare deviates from the air current incoming flow direction in the spiral case just, has effectively avoided receiving the direct impact of air current, has further reduced the production of abnormal sound.

The technical scheme adopted by the utility model for solving the second technical problem is as follows: a centrifugal fan applying the volute for the centrifugal fan is disclosed.

Compared with the prior art, the utility model has the advantages that: the first end part of the volute annular wall is provided with a first arc-shaped wall, the cross section of the first arc-shaped wall is C-shaped, the notch faces the air outlet, at least part of the rotation connecting part of the volute tongue piece is accommodated in the accommodating cavity limited by the inner side of the first arc-shaped wall, therefore, the gap between the edge of the first arc-shaped wall and the rotation connecting part of the volute tongue piece can be opposite to the incoming flow of the air flow, the direct impact of the air flow is avoided, the generation of abnormal sounds is reduced, meanwhile, the outer wall surface of the first arc-shaped wall can also guide the air flow from the front side to the air outlet, the air flow resistance is reduced, and the smoothness of the air flow at the air outlet is ensured.

Drawings

Fig. 1 is a schematic perspective view of a centrifugal fan according to an embodiment of the present invention;

FIG. 2 is a schematic perspective view of a centrifugal fan according to an embodiment of the present invention (the volute tongue is rotated to another angular position);

FIG. 3 is a cross-sectional view of a centrifugal fan of an embodiment of the present invention taken perpendicular to the axis of the volute;

FIG. 4 is a schematic structural diagram of a volute tongue of a centrifugal fan according to an embodiment of the present invention in different rotation angles;

FIG. 5 is a schematic perspective view of the tongue member of FIG. 1 without the tongue member (the driving motor is not shown);

FIG. 6 is a schematic perspective view of FIG. 5 flipped to another angular position;

FIG. 7 is a perspective view of a tongue of the present invention;

FIG. 8 is a perspective view of another angle of the tongue of the present invention;

FIG. 9 is a perspective view of another angular position of the tongue member according to the embodiment of the present invention;

FIG. 10 is a schematic view of the structure of FIG. 3 with the tongue omitted;

FIG. 11 is a perspective view of a tongue of another embodiment of the present invention;

FIG. 12 is an exploded view of FIG. 11;

FIG. 13 is a perspective view of a tongue of a worm according to yet another embodiment of the present invention;

fig. 14 is an exploded view of fig. 13.

Detailed Description

The utility model is described in further detail below with reference to the accompanying examples.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present invention and to simplify the description, but are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and that the directional terms are used for purposes of illustration and are not to be construed as limiting, for example, because the disclosed embodiments of the present invention may be oriented in different directions, "lower" is not necessarily limited to a direction opposite to or coincident with the direction of gravity. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

Referring to fig. 1-10, a centrifugal fan includes a volute and an impeller 30 disposed in the volute. The volute comprises a volute tongue body and a volute tongue piece 20, wherein the volute body comprises a rear cover plate 11, a front cover plate 12 and a ring wall 13, the front cover plate 12 is arranged opposite to the rear cover plate 11, the ring wall 13 is arranged between the front cover plate 12 and the rear cover plate 11, and specifically, the ring wall 13 is provided with a first end 131 and a second end 132 which are opposite in the length direction. The volute tongue 20 is rotatably connected to the first end 131 of the annular wall 13 and defines, together with the rear cover 11, the front cover 12 and the second end 132 of the annular wall 13, the outlet mouth 15 whose divergence angle is adjustable. In addition, the front cover plate 12 of the volute body is provided with an air inlet which is opposite to the impeller 30, when the centrifugal fan operates, external air flow enters from the air inlet along the axis of the impeller 30, is radially thrown out through the centrifugal action of the impeller 30 and is discharged from the air outlet 15. The above-mentioned spiral casing structure with the rotatable adjustment of the spiral tongue piece 20 is the prior art and will not be described herein.

When the working air quantity of the centrifugal fan is larger, the volute tongue piece 20 can be correspondingly adjusted in a rotating mode, so that the outlet on the volute tongue side is expanded to be in a larger angle state. When the working air volume of the centrifugal fan is small, the expansion angle of the volute tongue side outlet is correspondingly adjusted to be in a small state. In order to ensure that the plane of the air outlet 15 remains unchanged before and after the rotation adjustment of the volute tongue 20, the volute tongue 20 of the present embodiment is integrally plate-shaped and has a first connection end 21 and a second connection end 22 in the length direction, specifically, the first connection end 21 of the volute tongue 20 is rotatably connected to the first end 131 of the annular wall 13, and correspondingly, the second connection end 22 of the volute tongue 20 is slidably constrained on at least one of the front cover plate 12 and the rear cover plate 11 along the plane of the air outlet 15 in a manner of being telescopically adjustable with respect to the first connection end 21 of the volute tongue 20, as shown in fig. 4.

The volute tongue 20 of the present embodiment comprises a first plate 23, a second plate 24 and a driving motor 28, wherein the first plate 23 is rotatably connected with the first end 131 of the annular wall 13, the second plate 24 is connected with at least one of the front cover plate 12 and the rear cover plate 11, and the first plate 23 and the second plate 24 are constrained together in a relatively sliding manner. Specifically, in order to simplify the overall structure of the tongue piece 20, the first plate 23 and the second plate 24 are connected in a magnetic attraction manner, wherein the first plate 23 and the second plate 24 both have magnetic attraction surfaces, the magnetic attraction surfaces of the first plate 23 and the second plate 24 can be attached together, in the rotation adjustment process of the first plate 23, the first plate 23 and the second plate 24 can slide relative to each other along the magnetic attraction surfaces, and the magnetic attraction force can keep the connection between the first plate 23 and the second plate from loosening, which is shown in detail in fig. 7-9.

Referring to fig. 3 and 10, the first end 131 of the annular wall 13 of the present embodiment has a first arc-shaped wall 14 with a C-shaped cross section and a notch facing the air outlet 15, that is, the first arc-shaped wall 14 extends in a curved manner toward the position of the air outlet 15, a mounting cavity 143 is defined inside the first arc-shaped wall 14, and the outer wall surface of the first arc-shaped wall 14 forms a flow guide surface for guiding the air flow toward the air outlet 15. Correspondingly, the end of the first plate 23 of the volute tongue 20 is provided with a rotating connecting part 210, and at least part of the rotating connecting part 210 is accommodated in the accommodating cavity 143 of the first arc-shaped wall 14 and is provided with an arc-shaped wall surface which can be always attached to the inner surface of the first arc-shaped wall 14 in the rotating process. The "cross-section" of the first arcuate wall 14 described above refers to a cross-section of the first arcuate wall 14 in a plane perpendicular to the axis O of the volute.

With continued reference to fig. 7-9, the rotating connection portion 210 of the first plate 23 of the volute tongue 20 comprises a second arc-shaped wall 211 and a connecting column 212, wherein the second arc-shaped wall 211 has a C-shaped cross section, and the second arc-shaped wall 211 has a shape substantially identical to the shape of the first arc-shaped wall 14, and is a circular arc-shaped wall, and the two arc-shaped walls are coaxially arranged. After the rotation connecting portion 210 is assembled in place, the outer wall surface of the second arc-shaped wall 211 and the inner wall surface of the first arc-shaped wall 14 are attached to each other, so that the arc-shaped wall surface of the rotation connecting portion 210 is formed. The connecting column 212 is located inside the second arc-shaped wall 211 and close to the side of the front cover plate 12, and specifically, the connecting column 212 and the second arc-shaped wall 211 are a single piece. One end of the connecting column 212 has a limiting hole 213, and the other end has a positioning hole 214. The "cross section" of the second arc-shaped wall 211 described above refers to a section of the first arc-shaped wall 211 on a plane perpendicular to the axis O of the volute.

Referring to fig. 5 and 6, the driving motor 28 is also located inside the second arc-shaped wall 211, and is specifically arranged side by side with the connecting column 212 in the axial direction of the second arc-shaped wall 211. The output shaft of the driving motor 28 is coaxial with the second arc-shaped wall 211 and is inserted into the limiting hole 213 of the connecting column 212 so as to drive the volute tongue piece 20 to rotate by taking the output shaft of the driving motor 28 as a rotation center. Wherein the volute has an axis O, and the axis of the output shaft of the drive motor 28 is parallel to the axis O of the volute. In addition, the cross section of the output shaft of the driving motor 28 may be a non-circular structure, and the positioning hole 214 is a structure matched with the non-circular structure, so that the positioning hole and the positioning hole are limited in the circumferential direction.

The first arc-shaped wall 14 has a first port 141 and a second port 142 opposite in the length direction. The rear cover 11 has a first extension 110 covering the first port 141, and the front cover 12 has a second extension 120 covering the second port 142, wherein the driving motor 28 is fixedly connected to an inner wall of the first extension 110. The inner wall of the second extending portion 120 has a positioning post 111, and the positioning post 111 can be inserted into the positioning hole 214 of the connecting post 212 for rotation fit. The "lengthwise direction" of the first arcuate wall 14 of the present embodiment refers to a direction parallel to the axis O of the volute.

Referring to fig. 5 and 7, the two opposite side surfaces of the front cover plate 12 and the rear cover plate 11 of the present embodiment adjacent to the air outlet 15 are respectively provided with a second strip-shaped chute 16, and the second strip-shaped chute 16 extends along the edge of the front cover plate 12 or the rear cover plate 11 to ensure that the second strip-shaped chute is parallel to the plane where the air outlet 15 is located. The second connection end 22 of the tongue 20 has bosses 241 at both lateral sides, that is, the bosses 241 are provided at both lateral sides of the end of the second plate 24 far from the first plate 23. The two protruding columns 241 are slidably constrained in the corresponding second strip-shaped sliding grooves 16 respectively. The outer diameter of the convex column 241 is matched with the width of the second strip-shaped sliding groove 16, so that stable sliding of the convex column and the second strip-shaped sliding groove is ensured.

In order to avoid interference with the rotation of the volute tongue member 20 due to an excessively large central angle corresponding to the arc length of the cross section of the first arc-shaped wall 14, limit the rotation angle of the volute tongue member 20, and avoid that the gap opening between the first arc-shaped wall 14 and the rotation connection portion 210 of the volute tongue member 20 cannot face away from the incoming flow better due to an excessively small central angle corresponding to the arc length of the cross section of the first arc-shaped wall 14, a tangent line a of the cross section of the first arc-shaped wall 14 at one end adjacent to the air outlet 15 is parallel to a plane where the second end portion 132 of the ring wall 13 is located, so that the gap opening between the first arc-shaped wall 14 and the rotation connection portion 210 of the volute tongue member 20 faces away from the incoming flow direction of the air flow in the volute casing, thereby effectively avoiding direct impact of the air flow and further reducing the generation of abnormal sound. That is, during rotation of the volute tongue 20 relative to the volute body, there is a first limit condition close to the first end 131 of the annular wall 13 and a second limit condition away from the first end 131 of the annular wall 13, and in the first limit condition of the volute, the plane of the volute tongue 20 is substantially parallel to the plane of the second end 132 of the annular wall 13, specifically, the rotation track of the volute tongue 20 is shown by the dotted line in the figure. The position of the first limit state and the second limit state may be defined by the length of the second strip-shaped chute 16 or the shape of the first arc-shaped wall 14.

The length of the volute tongue piece 20 of the volute can be adjusted in a telescopic mode in the rotating process, wherein in the rotating process of the volute tongue piece 20, the end portion of the volute tongue piece 20 cannot be exposed out of the plane where the air outlet 15 of the volute is located, and therefore the problem of interference between the volute tongue piece 20 and a pipe connected to the air outlet 15 cannot occur. On the other hand, when the volute tongue piece 20 rotates to different angles, the length of the volute tongue piece 20 can be adjusted in a telescopic mode, so that the plane where the air outlet 15 of the volute casing is located cannot change, namely in the rotation process of the volute tongue piece 20, the problems that extra airflow separation is caused due to the fact that the wall plate on the volute tongue side is shortened, resistance is formed due to the fact that the wall plate on the volute tongue side is lengthened to extrude the airflow at the outlet, and the like cannot occur, and the airflow at the air outlet of the volute casing can still reach the optimal flowing state after the angle of the volute tongue piece 20 is adjusted. In this embodiment, the rotation connection portion 210 of the volute tongue member 20 is located inside the first arc-shaped wall 14, and the first arc-shaped wall 14 determines the position of the throat portion of the air outlet 15 of the volute, so that the air outlet area of the throat portion of the centrifugal fan is not affected before and after the adjustment of the outlet angle at the volute tongue side and in the adjustment process, and therefore, the performance of the fan is not changed suddenly, and the normal and stable operation of the fan is ensured.

On the basis of the above embodiments, other embodiments can be obtained by replacing and improving the related technical features. For example, in addition to the above-mentioned magnetic attraction manner, the telescopic sliding fit between the first plate 23 and the second plate 24 may also be a sliding constraint fit between a sliding block and a sliding groove, and referring to fig. 11 and 12 in particular, one of the first plate 23 and the second plate 24 has a first strip-shaped sliding groove 25 arranged along the extending direction thereof, and the other has a sliding block 26 correspondingly slidably constrained in the first strip-shaped sliding groove 25. Preferably, the first strip-shaped sliding grooves 25 are formed in the second plate 24, specifically, the first strip-shaped sliding grooves 25 are respectively formed on both lateral sides of the upper surface of the second plate 24, the notches of the two strip-shaped sliding grooves are oppositely arranged, and correspondingly, sliding blocks 26 capable of being clamped into the first strip-shaped sliding grooves 25 are formed on both lateral sides of the lower surface of the first plate 23. For another example, referring to fig. 13 and 14, the first plate 23 and the second plate 24 may be slidably connected by a slide rail 27. In order to ensure the smoothness of the relative movement between the first plate 23 and the second plate 24, the slide rail 27 of the present embodiment is preferably a ball slide rail 27, and the ball slide rail 27 is disposed between two opposite planes of the first plate 23 and the second plate 24, and connects the first plate 23 and the second plate 24.

Claims (8)

1. A volute for a centrifugal fan, comprising:

the volute comprises a volute body and a volute body, wherein the volute body comprises a front cover plate (12), a rear cover plate (11) and a ring wall (13), the front cover plate (12) and the rear cover plate (11) are arranged oppositely, the ring wall (13) is arranged between the front cover plate (12) and the rear cover plate (11) and is provided with a first end portion (131) and a second end portion (132) which are opposite in the length direction;

the volute tongue piece (20) is rotatably connected to the first end part (131) of the annular wall (13) and defines an air outlet (15) with an adjustable divergence angle together with the front cover plate (12), the rear cover plate (11) and the second end part (132) of the annular wall (13);

the method is characterized in that: the first end (131) of the annular wall (13) is provided with a first arc-shaped wall (14) which is C-shaped in cross section and the notch of which faces the air outlet (15), a placing cavity (143) is defined on the inner side of the first arc-shaped wall (14), the volute tongue piece (20) is provided with a rotating connecting part (210), at least part of the rotating connecting part (210) is accommodated in the placing cavity (143) of the first arc-shaped wall (14), and the rotating connecting part is provided with an arc-shaped wall surface which can be always attached to the inner surface of the first arc-shaped wall (14) in the rotating process.

2. The volute for a centrifugal fan according to claim 1, wherein: the rotating connecting part (210) comprises a second arc-shaped wall (211) with a C-shaped cross section, and the outer wall surface of the second arc-shaped wall (211) is attached to the inner wall surface of the first arc-shaped wall (14) to form the arc-shaped wall surface of the rotating connecting part (210).

3. The volute for a centrifugal fan according to claim 2, wherein: the volute comprises a volute body and is characterized by further comprising a driving motor (28) arranged on the volute body, the driving motor (28) is located on the inner side of the second arc-shaped wall (211), an output shaft of the driving motor (28) is connected with the second arc-shaped wall (211) and is coaxially arranged with the second arc-shaped wall (211), and therefore the volute tongue piece (20) is driven to rotate by taking the output shaft of the driving motor (28) as a rotation center.

4. The volute for a centrifugal fan according to claim 3, wherein: the inner side of the second arc-shaped wall (211) is provided with a connecting column (212), the end part of the connecting column (212) is provided with a limiting hole (213), and the output shaft of the driving motor (28) is inserted into the limiting hole (213).

5. The volute for a centrifugal fan according to claim 4, wherein: the first arc-shaped wall (14) is provided with a first port (141) and a second port (142) which are opposite in the length direction, the rear cover plate (11) is provided with a first extending part (110) for covering the first port (141), the front cover plate (12) is provided with a second extending part (120) for covering the second port (142), the driving motor (28) is connected to the inner wall of the first extending part (110), the inner wall of the second extending part (120) is provided with a positioning column (111), the connecting column (212) is provided with a positioning hole (214) corresponding to the positioning column (111), and the positioning column (111) is in rotating fit with the positioning hole (214).

6. The volute for a centrifugal fan according to claim 4, wherein: the connecting column (212) is integral with the second arcuate wall (211).

7. The volute for a centrifugal fan according to any of claims 1-6, wherein: the tangent of the cross section of the first arc-shaped wall (14) at one end adjacent to the air outlet (15) is parallel to the plane of the second end (132) of the annular wall (13).

8. A centrifugal fan to which a scroll casing for a centrifugal fan according to any one of claims 1 to 7 is applied.

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