CN215172507U - Check valve and lampblack absorber - Google Patents

Abstract

The application provides a check valve and a range hood, wherein the check valve is internally provided with an inlet, an outlet and a channel for communicating the inlet and the outlet; the inner wall of the channel is convexly provided with a step surface, the minimum distance from the side edge of the step surface to the central axis of the channel is D1, the distance between the inner walls at the outlet along the set direction is D2, and D1 is not less than 30% of D2; wherein the set direction passes through the center of the outlet and is perpendicular to the central axis. The utility model provides a be equipped with the step face in the passageway of check valve, avoided the passageway directly from the import to the export, but pass through this step face and carry out the transition, slowed down the passageway and gone wrong to the export from the import, reduced the cross sectional dimension's between import and the export difference to when having fluid to pass through this passageway, not so that because cross sectional dimension increases suddenly and leads to fluid to disperse gradually, density diminishes, and make the inside flow field of check valve become chaotic, even produce serious flow separation phenomenon.

Description

Check valve and lampblack absorber

Technical Field

The application relates to the technical field of fluid non-return, in particular to a non-return valve and a range hood.

Background

Nowadays, in more and more mechanical devices, the problem of fluid backflow is usually involved, so as to block the backflow of the corresponding fluid medium, such as water, smoke, steam, etc., for example, by the action of the weight of the check valve itself, which uses a circular flap as the opening and closing member, and the pressure of the fluid medium.

In the case of the cigarette machines, most of the cigarette machines discharge oil smoke vapor to the smoke pipe through the centrifugal fan and discharge the oil smoke vapor through the smoke pipe. In order to prevent the backflow of the smoke vapor, a check valve is generally arranged between the centrifugal fan and the smoke tube to prevent the backflow of the smoke vapor of the range hood under the standby working condition.

Specifically, the centrifugal fan comprises a volute and an impeller positioned in the volute. The check valve is respectively connected with the outlet of the volute and the inlet of the smoke pipe. At present, the cross section of the outlet of the volute is usually rectangular, and the smoke tube is circular.

In the prior art, the inlet rectangle and the outlet circle of the check valve are surrounded by a plane formed by a plurality of points and sectional lines of the inlet and the outlet to form the geometric shape of the check valve. Thus, the passageway of the check valve directly connects the inlet to the outlet, that is, the passageway includes a smooth inner wall that directly connects the inlet to the outlet. For a check valve with a large geometric difference between the inlet and outlet cross sections and a smaller cross section size of the inlet than the outlet, the change of the cross section shape of the passage along the height direction of the check valve is severe (the difference of the cross sections is large, and the overlapping part is small). When fluid passes through the channel of the check valve and enters the channel section with larger cross-sectional dimension from the channel section with smaller cross-sectional dimension, the fluid is gradually dispersed and has smaller density, the flow direction of corresponding molecules is also disordered, and then the flow field in the check valve is disordered, even serious flow separation phenomenon is generated, so that the fluid can not be smoothly discharged from the outlet of the check valve, and the disordered impact on the inner wall of the channel of the check valve, thereby affecting the performance of corresponding mechanical equipment, particularly the noise performance.

SUMMERY OF THE UTILITY MODEL

The application provides a check valve and lampblack absorber to solve current check valve and violently change along its direction of height's cross sectional shape, and lead to the confusion in the inside flow field of check valve, appear serious separation phenomenon that flows even, and then influence the especially problem of noise performance of the performance of complete machine.

In order to solve the technical problem, the application provides a check valve, wherein an inlet, an outlet and a channel for communicating the inlet and the outlet are arranged in the check valve; the inner wall of the channel is convexly provided with a step surface, the minimum distance from the side edge of the step surface to the central axis of the outlet is D1, the distance between the inner walls of the outlet along the set direction is D2, and D1 is not less than 30% of D2; wherein the set direction passes through the center of the outlet and is perpendicular to the central axis.

Wherein, the step face is perpendicular to the central axis.

Wherein, the step face and the central shaft are arranged at a preset angle, and the side edge inclines to the direction close to the inlet.

Wherein, the side of the step surface is a straight line, a plurality of sections of broken lines or an arc line.

Wherein, the side of the step surface is a straight line which is vertical to the set direction.

Wherein, along the direction perpendicular to the central axis, the dimension between the inner walls of the passage at the inlet is smaller than the dimension between the inner walls of the passage at the outlet.

The inlet is rectangular, the outlet is circular, and the diameter of an inscribed circle of the inlet is smaller than that of the outlet; the direction is set to the diameter direction of the outlet intersecting the step surface, and D2 is the inner diameter of the outlet.

Wherein the step surface extends obliquely to an edge connecting the inlet and the outlet.

The step surface comprises a plurality of sub-step surfaces, the sub-step surfaces are arranged along a straight line set on the inner wall of the channel, and the set straight line is an intersection line of a cross section perpendicular to a plane where the inlet is located and the inner wall of the channel.

And in every two adjacent sub-step surfaces, the minimum distance between the side edge of the sub-step surface close to the outlet and the central axis is greater than the minimum distance between the side edge of the sub-step surface far away from the outlet and the central axis.

The channel comprises a first channel section and a second channel section, and partial edges of the joint of the first channel section and the second channel section are connected by a step surface; the inlet is connected with the first channel section, and the outlet is connected with the second channel section; the minimum dimension between the inner walls of the second channel section is not less than the maximum dimension between the inner walls of the first channel section; the first channel section and the second channel section are both cylindrical or conical; alternatively, either one of the first channel section and the second channel section is cylindrical and the other is conical.

In order to solve the above technical problem, the present application adopts another technical solution: there is provided a range hood, wherein the range hood comprises a check valve as defined in any one of the above.

The beneficial effect of this application is: different from the prior art, the check valve provided by the application is internally provided with an inlet, an outlet and a channel for communicating the inlet and the outlet; the inner wall of the channel is convexly provided with a step surface, the minimum distance from the side edge of the step surface to the central axis of the outlet is D1, the distance between the inner walls of the outlet in the direction vertical to the central axis is D2, and D1 is not less than 30% of D2. Wherein, because of being equipped with this step face in the passageway, avoided the direct export from the import of passageway among the prior art, but pass through this step face and carry out the transition, slowed down the passageway and gone wrong to the export from the import, reduce the cross sectional dimension's between the import of check valve and the export difference, so that when there is fluid through this passageway, not so that lead to the fluid to disperse gradually because cross sectional dimension increases suddenly, density diminishes, and make the inside flow field of check valve become chaotic, even produce serious flow separation phenomenon, and then also make this fluid can be more smooth and easy discharge from the export, and not so that chaotic striking on the passageway inner wall of check valve, with the noise performance of the cigarette machine of effectively promoting integration this check valve.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic perspective view of a first embodiment of a check valve of the present application;

FIG. 2 is a cross-sectional view in the direction of A-A of the check valve of FIG. 1;

FIG. 3 is a schematic perspective view of a second embodiment of the check valve of the present application;

FIG. 4 is a cross-sectional view in the direction B-B of the check valve of FIG. 3;

FIG. 5 is a schematic perspective view of a third embodiment of a check valve of the present application;

fig. 6 is a schematic structural diagram of an embodiment of a range hood of the present application.

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples. It is to be noted that the following examples are only illustrative of the present application, and do not limit the scope of the present application. Likewise, the following examples are only some examples and not all examples of the present application, and all other examples obtained by a person of ordinary skill in the art without any inventive step are within the scope of the present application.

The terms "first", "second" and "third" in this application are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any indication of the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of the feature. In the description of the present application, "a plurality" means at least two, e.g., two, three, etc., unless explicitly specifically limited otherwise. All directional indicators (such as upper, lower, left, right, front and rear … …) in the embodiments of the present application are only used to explain the relative positional relationship between the components, the movement, etc. in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is changed accordingly. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Referring to fig. 1-2, fig. 1 is a schematic perspective view of a check valve according to a first embodiment of the present invention, and fig. 2 is a sectional view of the check valve in fig. 1 in a direction of a-a. In the present embodiment, the check valve 10 is provided with an inlet 11, an outlet 12, and a passage 13 communicating the inlet 11 and the outlet 12.

The inlet 11 and the outlet 12 of the check valve 10 are particularly used for connecting other mechanical components to effectively prevent the backflow of a fluid medium, such as water, oil smoke or water vapor, when the fluid medium enters from the inlet 11 and is discharged to the outlet 12 through the channel 13.

Wherein, the channel 13 includes an inner wall 131, and the inner wall 131 is convexly provided with a step surface 132. That is, the projection of the side of the step surface 132 onto the plane of the outlet 12 is inside the outlet 12.

Wherein, when the minimum distance between the side edge of the step surface 132 and the central axis 14 of the outlet 12 is D1 and the distance between the inner walls at the outlet 12 in the set direction is D2, then D1 is not less than 30% of D2. The set direction passes through the center of the outlet 12 (the geometric center of the outlet 12) and is perpendicular to the central axis of the outlet 12. The central axis 14 is a line that is the geometric center of the outlet 12 and perpendicular to the plane of the outlet 12; and the side edge of the step surface 132 is a free end edge of the step surface 132 facing the central axis 14. It should be noted that D1 is the line distance between the line segment where the side edge of step surface 132 is located and central axis 14; the distance between the two inner walls of the outlet 12, which perpendicularly intersect the central axis 14 and pass through the center of the outlet 12, is D2, as described above.

For example, when the side of the step surface 132 is a line segment, the D1 specifically refers to the length of a perpendicular line segment from the central axis 14 to the line segment; when the outlet 12 is circular, the central axis 14 is the central axis of the outlet 12 passing through the center of the circle; then D2 is the diameter of the circle and the length of the perpendicular segment is no less than 30% of the diameter.

It will be appreciated that since the step surface 132 is disposed to project from the inner wall of the passage 13, that is, in the direction from the inlet 11 to the outlet 12, the step surface 132 is formed by the inner wall 131 extending in a direction away from the central axis 13. In other words, in the cross section of the passage 13 parallel to the central axis 14, due to the step surface 132, the distance between the inner walls 131 on both sides of the step surface 132 is different, the tendency of the size of the passage 13 to continuously vary from the inlet 11 to the outlet 12 is thus effectively limited, i.e. the difference in cross-sectional size between the inlet 11 and the outlet 12 of the non-return valve 10 is reduced, so that the cross-sectional dimension of the passage 13 from the inlet 11 to the outlet 12 is limited by the step surface 132, which slows down the change in cross-section of the passage 13 from the inlet 11 to the outlet 12, so as not to gradually disperse and become less dense when fluid passes through the passage 13, so that the corresponding flow field becomes disordered and even generates serious flow separation, and further the fluid can be discharged from the outlet 12 more smoothly, without disorganized impact on the inner walls of the passageway 13 of the check valve 10 to effectively improve the noise performance of a range hood incorporating the check valve 10.

Alternatively, in some embodiments, the dimension between the inner walls of the channel 13 at the inlet 11 is smaller than the dimension between the inner walls of the channel 13 at the outlet 12 along the direction perpendicular to the central axis 14, that is, the cross-sectional dimension of the channel 13 increases gradually from the inlet 11 to the outlet 12.

Alternatively, in a specific embodiment, the inlet 11 is rectangular and the outlet 12 is circular, and the diameter of the inscribed circle of the inlet 11 is smaller than the diameter of the outlet 12. At this time, the setting direction is the diameter direction of the outlet 11 intersecting the step surface 132, and D2 is the inner diameter of the outlet 12.

Alternatively, in some embodiments, the step surface 132 is perpendicular to the central axis 14 of the outlet 12, i.e., the step surface 132 is disposed parallel to the plane of the outlet 12. And when the minimum distance from the side edge of the inlet 11 to the central axis 14 of the outlet 12 is not less than 30% of D2, the projection of the side edge portion of the step surface 132 close to the central axis 14 on the plane of the inlet 11 may also coincide with the side edge portion of the inlet 11. Further, a portion of the side edge of the step surface 132 may be directly connected to a portion of the side edge of the outlet 12.

Alternatively, in some embodiments, the step surface 132 is disposed at a predetermined angle with respect to the central axis 14, and the side edge of the step surface 132 is inclined toward the inlet 11. And when the minimum distance from the side edge of the inlet 11 to the central axis 14 of the outlet 12 is not less than 30% of D2, the projection of the side edge portion of the step surface 132 close to the central axis 14 on the plane of the inlet 11 may also coincide with the side edge portion of the inlet 11. Further, a portion of the side edge of the step surface 132 may be directly connected to a portion of the side edge of the outlet 12.

The preset angle may be one of any reasonable angles such as 30 °, 45 °, and 90 °, which is not limited in this application.

Alternatively, in a particular embodiment, the step surface 132 extends obliquely to the edge of the connecting outlet 12.

Alternatively, in a specific embodiment, the channel 13 comprises a first channel segment (not shown) and a second channel segment (not shown), and a portion of the edges at the intersection of the first channel segment and the second channel segment are connected by a step surface 132. The inlet 11 is connected to the first channel section and the outlet 12 is connected to the second channel section. That is, the first channel segment and the second channel segment are respectively located at the upper and lower sides of the step surface 132, wherein the minimum dimension between the inner walls of the second channel segment is not smaller than the maximum dimension between the inner walls of the first channel segment. That is, the size of the channel 13 increases from the inlet 11 to the outlet 12; i.e. the dimension between the inner walls of the channel 13 at the inlet 11 is smaller than the dimension between the inner walls of the channel 13 at the outlet 12. More specifically, the first channel section and the second channel section are both cylindrical or conical. Alternatively, in other embodiments, either the first channel segment or the second channel segment is cylindrical and the other is conical. It is understood that the cylindrical shape may be a cylindrical shape, a prismatic shape; the taper may be a cone, a pyramid, and it is also understood that the taper in this application is only a part of the taper in a geometric sense, that is, the cross-section of the taper in this application is trapezoidal.

For example: as shown in fig. 2, in this embodiment, the first channel section is tapered and the second channel section is cylindrical. More specifically, the cross-sectional shape of the first channel section is a right trapezoid, and the cross-sectional shape of the second channel section is a rectangle. Also, in this particular embodiment, the first and second channel segments further comprise a partially common side wall, that is, there is a step surface 132 where portions of the first and second channel segments meet. It will be appreciated that in other embodiments, the intersection of the first channel section and the second channel section is a step surface 132.

Optionally, the side of the step surface 132 is a straight line, a plurality of broken lines or an arc line.

Alternatively, in one embodiment, the sides of the step surface 132 are straight and perpendicular to the set direction, wherein the set direction passes through the center of the outlet 12 and is perpendicular to the central axis 14. For example, when the inlet 11 of the check valve 10 is intended to be connected to a volute of a range hood and the outlet 12 thereof is connected to a smoke pipe of the range hood, the set direction may specifically correspond to a direction from the central axis 14 to a volute tongue of the volute.

Referring to fig. 3-4, fig. 3 is a schematic perspective view of a check valve according to a second embodiment of the present application, and fig. 4 is a sectional view of the check valve of fig. 3 in the direction of B-B. The check valve of the second embodiment of the present application differs from the first embodiment of the present application only in that: in the second embodiment, the channel 23 of the check valve 20 includes an inner wall 231, the inner wall 231 is convexly provided with a step surface 232, and the step surface 232 further includes a plurality of sub-step surfaces, and the plurality of sub-step surfaces are arranged along a straight line set on the inner wall of the channel 23.

Wherein the given straight line is in particular the intersection of a cross-section perpendicular to the plane in which the inlet 21 is located and the inner wall of the channel 23.

Optionally, the number of the sub-step surfaces is one of any reasonable number, such as 2, 3, and 5, which is not limited in this application.

Optionally, in some specific embodiments, in every two adjacent sub-step surfaces, the minimum distance between the side of the sub-step surface close to the outlet 22 and the central axis 24 is greater than the minimum distance between the side of the sub-step surface far from the outlet 22 and the central axis 24.

The specific description is given by taking the example that the number of the sub-step surfaces is 2, and the step surface 232 specifically includes the first sub-step surface 2321 and the second sub-step surface 2322. In other embodiments, the step surface 232 may further include a setting corresponding to any reasonable number of sub-step surfaces, such as 3 or 4, which is not described herein again.

Optionally, in some specific embodiments, the first sub-step surface 2321 and the second sub-step surface 2322 are both perpendicular to the central axis 24, that is, the first sub-step surface 2321 and the second sub-step surface 2322 are both disposed parallel to the plane of the outlet 22. And when the minimum distance from the side edge of the inlet 21 to the central axis 24 of the outlet 22 is not less than 30% of D2, the projection of the second sub-step surface 2322, i.e., the side edge portion of the sub-step surface closest to the inlet 21 and close to the central axis 24, on the plane of the inlet 21 may also coincide with the side edge portion of the inlet 21. And further, the first sub-step surface 2321, that is, a portion of the side of the sub-step surface closest to the outlet 22 may also be directly connected to a portion of the side of the outlet 22.

Optionally, in some specific embodiments, the first sub-step surface 2321 and the second sub-step surface 2322 are disposed at a first preset angle and a second preset angle with respect to the central axis 24 of the outlet 22, respectively, and the side edges of the first sub-step surface 2321 and the second sub-step surface 232 are inclined toward the inlet 21. And when the minimum distance from the side edge of the inlet 21 to the central axis 24 of the outlet 22 is not less than 30% of D2, the projection of the second sub-step surface 2322, i.e., the side edge portion of the sub-step surface 232 closest to the inlet 21, which is close to the central axis 24, on the plane where the inlet 21 is located may also coincide with the side edge portion of the inlet 21. Further, the first sub-step surface 2321, that is, a portion of the side of the sub-step surface 232 closest to the outlet 22 may also be directly connected to a portion of the side of the outlet 22.

The first preset angle and the second preset angle may be the same or different, and may be any one of reasonable angles such as 30 °, 45 ° and 90 °, which is not limited in the present application.

Optionally, in some embodiments, the first sub-step surface 2321 is disposed at a first predetermined angle with respect to the central axis 24 of the outlet 22, and the side of the first sub-step surface 2321 is inclined to approach the inlet 21, and the second sub-step surface 2322 is perpendicular to the central axis 24 of the outlet 22. In other embodiments, the second sub-step surface 2322 may be disposed at a first predetermined angle with respect to the central axis 24 of the outlet 22, a side of the second sub-step surface 2322 is inclined toward the inlet 21, and the first sub-step surface 2321 is perpendicular to the central axis 24 of the outlet 22, which is not limited in this application.

In some specific embodiments, when the minimum distance from the side edge of the inlet 21 to the central axis 24 of the outlet 22 is not less than 30% of D2, the projection of the second sub-step surface 2322, that is, the side edge portion of the sub-step surface 232 closest to the inlet 21, close to the central axis 24, on the plane of the inlet 21 may also coincide with the side edge portion of the inlet 21. And further, the first sub-step surface 2321, that is, a portion of the side of the sub-step surface 232 closest to the outlet 22 may also be directly connected to a portion of the side of the outlet 22.

Optionally, the side edges of the first sub-step surface 2321 and the second sub-step surface 2322 are both line segments, and the side edges of the first sub-step surface 2321 and the second sub-step surface 2322 are both perpendicular to a set connection line segment between the set position point on the outlet 22 and the central axis 24.

Referring to fig. 5, fig. 5 is a schematic perspective view of a check valve according to a third embodiment of the present application. The check valve in the third embodiment of the present application is different from the check valve in the first embodiment of the present application or the check valve in the second embodiment of the present application only in that: in the third embodiment, the side edge of the step surface 332 of the check valve 30 is curved.

In another aspect of the present application, a range hood is further provided, please refer to fig. 6, and fig. 6 is a schematic structural diagram of an embodiment of the range hood according to the present application. Wherein, lampblack absorber 6 in this embodiment includes: check valve 60, check valve 60 includes an inlet 61, an outlet 62, and a passage 63 connecting inlet 61 and outlet 62. The check valve 60 is any one of the check valves 10, 20 and 30 according to the above embodiments of the present application, and will not be described herein again.

Wherein the range hood 6 further comprises a volute 600 and a smoke tube (not shown), as can be seen from the above description, the inlet 61 of the check valve 60 is connected to the volute 600, and the outlet 62 of the check valve 60 is connected to the smoke tube, so as to output the corresponding generated smoke to the smoke tube via the passage 63 of the check valve 60 and discharge the smoke. Since the range hood 6 of the present application uses the check valve 60 in the above-mentioned embodiment of the present application, and as can be seen from the above description of the above-mentioned embodiment of the present application, the check valve 60 limits the trend that the size of the passage 63 continuously changes from the inlet 61 to the outlet 62 by providing a step surface (not shown) in the passage 63, and reduces the difference in cross-sectional size between the inlet 61 and the outlet 62 of the check valve 60, so that when smoke or vapor passes through the passage 63, the smoke or vapor is not gradually dispersed and has a reduced density, so that the flow field inside the check valve 60 becomes chaotic, and even a severe flow separation phenomenon occurs, and the smoke or vapor can be discharged from the outlet 62 more smoothly, and does not collide with the inner wall of the passage 63 of the check valve 60 in a chaotic manner, so as to effectively improve the noise performance of the range hood 6 integrated with the check valve 60.

It will be appreciated that in other applications where a check valve is required, particularly where two components of different dimensions, even cross-sectional shapes, are to be joined, the check valve of the present application is equally applicable and will not be described further herein.

The above description is only a part of the embodiments of the present application, and not intended to limit the scope of the present application, and all equivalent devices or equivalent processes performed by the content of the present application and the attached drawings, or directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims (12)

1. A check valve is characterized in that an inlet, an outlet and a channel for communicating the inlet and the outlet are arranged in the check valve;

the inner wall of the channel is convexly provided with a step surface, the minimum distance from the side edge of the step surface to the central axis of the outlet is D1, the distance between the inner walls of the outlet along the set direction is D2, and the D1 is not less than 30% of the D2;

wherein the set direction passes through the center of the outlet and is perpendicular to the central axis.

2. The check valve of claim 1,

the step surface is perpendicular to the central shaft.

3. The check valve of claim 1,

the step surface and the central shaft are arranged at a preset angle, and the side edge inclines towards the direction close to the inlet.

4. The check valve of claim 1,

the side edge of the step surface is a straight line, a plurality of sections of broken lines or arc lines.

5. The check valve of claim 4,

the side edge of the step surface is a straight line, and the straight line is perpendicular to the set direction.

6. The check valve of any one of claims 1-5,

the dimension between the inner walls of the passage at the inlet is smaller than the dimension between the inner walls of the passage at the outlet in a direction perpendicular to the central axis.

7. The check valve of claim 6,

the inlet is rectangular, the outlet is circular, and the diameter of an inscribed circle of the inlet is smaller than that of the outlet; the set direction is a diameter direction of the outlet that intersects the step surface, and D2 is an inner diameter of the outlet.

8. The check valve of claim 6,

the step surface extends obliquely to an edge connecting the outlet.

9. The check valve of claim 6,

the step surface comprises a plurality of sub-step surfaces, the sub-step surfaces are arranged along a straight line set on the inner wall of the channel, and the set straight line is an intersection line of a cross section perpendicular to a plane where the inlet is located and the inner wall of the channel.

10. The check valve of claim 9,

in every two adjacent sub-step surfaces, the minimum distance between the side edge of the sub-step surface close to the outlet and the central axis is larger than the minimum distance between the side edge of the sub-step surface far away from the outlet and the central axis.

11. The check valve of any one of claims 1-5,

the channel comprises a first channel section and a second channel section, and partial edges of the joint of the first channel section and the second channel section are connected by the step surface; the inlet is connected with the first channel section, and the outlet is connected with the second channel section; the minimum dimension between the inner walls of the second channel section is not less than the maximum dimension between the inner walls of the first channel section;

the first channel section and the second channel section are both cylindrical or conical;

alternatively, either one of the first channel section and the second channel section is cylindrical and the other is conical.

12. A range hood, characterized in that it comprises a check valve according to any one of claims 1 to 11.

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