CN110939254A - Wind cap - Google Patents

Abstract

The invention provides a hood, which comprises an outer air duct, a flow guide body and an inner air duct; the outer air guide cylinder is covered on the outer side above the hood connecting pipe, an upward exhaust channel is formed in the outer air guide cylinder, and the flow guide body is supported on the outer air guide cylinder and is positioned in the exhaust channel; the guide body is arranged on one side above the smoke outlet at the top of the hood connecting pipe, the inner air duct extends upwards along the upper end face of the guide body to form a side wall which can receive rebound wind or rainwater generated after falling to the inner wall of the outer air duct, and a drainage section which is communicated with the upper part and the lower part and exhausts the air is formed between the side wall and the inner wall of the outer air duct; the smoke exhausted from the smoke outlet at the top of the hood connecting pipe is bent after passing through the flow guide body, passes through the flow guide section and is exhausted from the outlet at the top of the outer air guide cylinder. The invention can not only prevent wind or rain from falling and flowing backwards, but also prevent wind or rain from rebounding and flowing backwards, thus thoroughly solving the problem of flowing backwards of the wind cap.

Description

Wind cap

Technical Field

The invention relates to the technical field of building exhaust passages, in particular to a backflow-preventing hood, and particularly relates to a hood capable of preventing rebound wind or rainwater from falling into an exhaust passage after impact caused by large kinetic energy of wind or rainwater in a strong wind condition.

Background

At present, the blast caps installed at the air outlets of the roofs of residential exhaust duct systems can be divided into three categories: the first type of hood is a flat or umbrella-shaped top cover plate arranged right above the air outlet, and the flue gas is discharged from the lower part of the top cover plate to the periphery. The disadvantages of this type of hood are: the structure is too simple, and when encountering the cross rain of oblique wind, the wind and rain can flow backward into the exhaust passage easily, thereby not only preventing the smoke in the exhaust passage from being discharged normally, but also enabling the rainwater to flow into the indoor space along the exhaust passage. The second type of hood is an improvement on the first type of hood, and is characterized in that a rainproof shutter is arranged at an exhaust port below a top cover plate, so that the rainproof performance of the hood is improved to a certain extent, but the effective ventilation area of the exhaust port is obviously reduced, the air velocity at the exhaust port is reduced, the exhaust wind resistance of the hood is obviously increased, and unsmooth exhaust is caused. To solve this problem, it is necessary to significantly increase the size of the louver, resulting in a waste of building space and an unattractive appearance. The third type of hood is also an improvement on the first type of hood, a circle of wind shielding side plate is arranged on the outer side of the exhaust port below the flat plate cover plate or the umbrella-shaped cover plate, and smoke is discharged outwards from a gap between the cover plate and the side plate. If the clearance between the wind shielding side plate of the hood and the cover plate is too small, the exhaust wind resistance is large, and the difficulty in smoke exhaust is caused; if the clearance between the wind shielding side plate of the hood and the cover plate is too large, the wind and rain can flow backward into the exhaust passage inevitably in the weather of oblique wind and transverse rain.

In order to overcome the defects in the prior art, the applicant provides an improvement (application number is 201821919248.8) through multiple tests, and a top cover and a wind-proof and rain-proof outer cover which are matched with each other are arranged, so that wind and rain are prevented from flowing backwards into the exhaust passage, the wind and rain-proof outer cover has nearly complete wind and rain-proof backflow capacity under most conditions, however, in practice, the phenomenon that wind or rain flows backwards into the exhaust passage still exists when the wind and rain flows into the exhaust passage in areas with frequent storm and rainstorm is found, the applicant observes and tests on site for multiple times, finds that the wind or rain flowing backwards into the exhaust passage is rebounding wind or rain, and rebounds a small part of wind or rain after being impacted under the condition that the wind or rain has larger kinetic energy, and changes the original motion track and rebounds and splashes into the exhaust passage.

At present, no scheme capable of solving the problem of wind or rainwater rebounding exists in the field of exhaust ducts, and even the phenomenon that wind or rainwater can rebound to cause backflow is not found.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the hood which can prevent wind or rainwater from falling and flowing backwards and can prevent wind or rainwater from rebounding and flowing backwards, so that the problem of flowing backwards of the hood is thoroughly solved.

The first purpose of the invention is to provide a hood, which comprises an outer air duct, a flow guide body and an inner air duct;

the outer air guide cylinder is covered on the outer side above the hood connecting pipe, an upward exhaust channel is formed in the outer air guide cylinder, and the flow guide body is supported on the outer air guide cylinder and is positioned in the exhaust channel;

the guide body is arranged on one side above the smoke outlet at the top of the hood connecting pipe, the inner air duct extends upwards along the upper end face of the guide body to form a side wall which can receive rebound wind or rainwater generated after falling to the inner wall of the outer air duct, and a drainage section which is communicated with the upper part and the lower part and exhausts the air is formed between the side wall and the inner wall of the outer air duct;

the smoke exhausted from the smoke outlet at the top of the hood connecting pipe is bent after passing through the flow guide body, passes through the flow guide section and is exhausted from the outlet at the top of the outer air guide cylinder.

In the technical scheme of the invention, the structure that the outer air guide cylinder is matched with the flow guide body forms a main air guide part, and the flue gas exhausted from the top smoke outlet of the hood connecting pipe is bent upwards after passing through the flow guide body and is exhausted from the top outlet of the outer air guide cylinder; the main purpose of the inner air duct is to prevent wind and rain from flowing backward, especially in the case of strong wind and strong rain (with large kinetic energy), at this time, the wind or rain poured into the inner air duct from the top outlet of the outer air duct can generate rebound wind or rain after hitting the inner wall of the outer air duct, at this time, the flow guide body of the conventional structure cannot receive the rebound wind or rain (for example, application 201821919248.8 in the past of the applicant), the rebound wind or rain in this case can be poured into the hood connecting pipe backward, a backward flowing phenomenon is generated, and adverse effects are generated on smoke exhaust and exhaust in the exhaust passage, and the backward flowing phenomenon is a main problem to be solved by the hood in the prior art.

Further, in order to receive the rebound wind or the rainwater which generates the backflow phenomenon, the applicant sets an inner air duct above the flow guide body through a large number of experiments, so that on one hand, the smoke discharged from the top smoke outlet of the hood connecting pipe can be guided, and on the other hand, the inner air duct is used for receiving the rebound wind or the rainwater which is generated after falling to the inner wall of the outer air duct, so that the rebound wind or the rainwater can dissipate energy and is far away from the top smoke outlet of the hood connecting pipe, and particularly the wind or the rainwater which dissipates the energy flows downwards along the side wall.

Wherein, in order to reduce the shared space of hood, the height of lateral wall so sets up: the rebound wind or rain water can be received at least once, namely, the wind or rain water falling from the top outlet of the outer air duct can impact on the side wall after one rebound and cannot directly rebound to the top smoke outlet of the hood connecting pipe.

Wherein, the height of the side wall can be adjusted adaptively according to the specification of the product.

In order to avoid unnecessary wind resistance of the inner air guide cylinder to the smoke exhaust process, preferably, the side wall of the inner air guide cylinder is arranged in a vertical shape or an inward inclined shape, so that the effective flow area of the flow guide section cannot be reduced or even gradually increased along the smoke exhaust direction, and the smoke is rapidly exhausted.

Specifically, the flue gas is discharged from the top outlet of the outer air duct, the outer wall of the outer air duct is more regular, the production and manufacturing processes are facilitated, unnecessary assembly processes are avoided, and the production is facilitated.

According to another embodiment of the present invention, the surface of the sidewall is provided with a buffering structure capable of absorbing the bouncing wind or the rainwater, for example, a layer of absorbent cotton is adhered, and then, for example, the surface of the sidewall is provided with a porous (blind hole) structure or a micro-protrusion structure, etc., so as to improve the energy dissipation rate of the sidewall to the bouncing wind or the rainwater, so that the bouncing wind or the rainwater can be better dissipated to be quickly discharged.

According to another embodiment of the invention, the external air duct is supported by a bracket on the hood connecting pipe or on the hood base of the roof floor.

According to another embodiment of the invention, the flow guide body is a square cone, a round cone or a wedge-shaped cone with a small lower end and a large upper end so as to better form an induced air effect, and the flow guide body guides the flue gas in the blast cap connecting pipe to change the direction so as to eliminate the vortex phenomenon, thereby reducing the wind resistance and realizing the process of smoothly discharging the flue gas.

According to another embodiment of the present invention, the baffle is formed with a chamfered portion at a junction with the inner air guide duct, and the bottom of the sidewall is provided with a drip line which is disposed to protrude downward from a lower end of the sidewall without exceeding the chamfered portion, wherein rainwater collected downward along the sidewall directly drops from the drip line without slipping onto the baffle.

Correspondingly, the arrangement mode that the water dripping line does not exceed the chamfered part downwards can avoid the water dripping line to obstruct the air guide effect of the flow guide body.

According to another embodiment of the invention, the effective flow area of the flow guiding section is not less than the effective flow area of the top smoke outlet of the hood connecting pipe.

According to another specific embodiment of the invention, the cross section of the outer air duct is circular, square or regular polygon, and the cross section of the inner air duct is circular, square or regular polygon matched with the outer air duct.

According to another embodiment of the invention, the top of the inner air duct is closed to form a top cover, and a slope-shaped rain dispersing structure with a convex center is arranged on the outer side above the top cover so as to quickly guide and discharge rain falling on the top cover.

According to another specific embodiment of the invention, the upper end of the outer air duct is inwardly closed to form a conical rain-proof platform, the conical rain-proof platform is obliquely arranged from bottom to top in a folded mode, so that the situation that rainwater obliquely and directly falls to a gap space between the air deflector and the hood connecting pipe and enters the exhaust passage is prevented, and in addition, the height of the whole outer air duct can be reduced, so that the occupied space is saved.

The invention also provides a wind cap, which comprises a wind cap connecting pipe, an outer air duct covering the smoke outlet at the top of the wind cap connecting pipe, and a flow guide body arranged in the outer air duct, wherein a vertical inner air duct is arranged above the flow guide body, and the side wall of the inner air duct can receive rebound wind or rainwater generated after falling to the inner wall of the outer air duct, so that the rebound wind or the rainwater can dissipate energy and is far away from the smoke outlet at the top of the wind cap connecting pipe.

The invention has the following beneficial effects:

the hood adopts the mode that the outer air guide cylinder, the inner air guide cylinder and the flow guide body are sleeved inside and outside, so that the turning of smoke is less when the smoke flows in the hood, the wind resistance is small, and the smoke discharge is smoother; the smoke is discharged to the upper high altitude, so that the smoke-discharging device is not only suitable for floors without people, but also more suitable for floors without people, and the using function of the floors is not influenced.

In addition, the inner air duct provided by the invention is provided with the side wall which can receive rebound wind or rainwater generated after falling to the inner wall of the outer air duct, so that the rebound wind or rainwater is discharged downwards along the side wall after energy dissipation, and is far away from the top smoke outlet of the hood connecting pipe, the phenomenon that the rebound wind or rainwater is poured into the exhaust passage is avoided, and the problem of wind and rain rebound pouring is solved.

In addition, the side wall is provided with the water dripping line, and the water dripping line extends downwards from the lower end of the side wall and does not exceed the chamfer part between the flow guide body and the inner air guide cylinder, so that rainwater gathered downwards along the side wall directly drops from the water dripping line and cannot slide onto the flow guide body.

In addition, the upper end of the outer air duct is inwardly closed to form a conical rainproof platform, so that the height of the whole outer air duct is reduced, and the occupied space is saved.

In addition, the material of the hood of the present invention may be metal, such as stainless steel, galvanized steel sheet, aluminum alloy, corrosion-resistant carbon steel, etc.; but also non-metals such as glass reinforced plastic, concrete, plastic, etc.

In addition, the hood of the invention has wide applicability, is not only suitable for the wind and rain prevention of the terminal exhaust port of the residential exhaust passage, but also suitable for the wind and rain prevention of the exhaust port of the large catering industry, and is also suitable for the wind and rain prevention design of the terminal of the smoke exhaust system in the building ventilation field and the industrial fields of chemical industry, metallurgy and the like.

In addition, the blast cap of the invention has regular structure, the smoke outlet is positioned at the upper end, the lower end can be closed (only a rainwater outlet is reserved) or not, the periphery of the outer part can be advertised, the appearance is attractive, and the smoke outlet can not be seen beside or below the blast cap.

When natural wind which is obliquely downward blows on the inner side of the outer air duct, the natural wind rebounds to the inner air duct and then flows downwards along the inner air duct, and cannot flow backwards into the exhaust passage, so that the defect that the natural wind rebounds and flows backwards due to the fact that the inner air duct is not arranged in the existing backflow-preventing wind cap is overcome; when rainwater drops on the top cover, the rainwater can be scattered in four directions, and in the rain splashing weather, the rainwater can directly impact the inner wall of the outer air duct, part of the impacted rainwater splashes and rebounds to the side wall of the inner air duct, then a dripping line flows along the side wall of the inner air duct, passes through a gap between the outer air duct of the hood and the connecting pipe of the hood and drips on the floor outside the hood, and the existing anti-backflow hood is not provided with the inner air duct, so that a small amount of rainwater can be rebounded and splashed to the inside of the exhaust passage after the rainwater impacts the inner wall of the outer air duct, and the backflow phenomenon is caused.

The present invention will be described in further detail with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic view of the structure of the hood of the present invention;

FIG. 2 is an enlarged schematic view of the drip line of FIG. 1;

FIG. 3 is a schematic view of the installation of the hood of the present invention;

FIG. 4 is a schematic view of the working principle of the wind cap of the present invention for preventing flat wind from flowing backward;

FIG. 5 is a schematic view of the working principle of the wind cap of the present invention for preventing the wind from flowing backward;

FIG. 6 is a schematic view of the working principle of the hood of the present invention for preventing the reverse flow of rain water;

FIG. 7 is a schematic top view of a square configuration of the hood of the present invention;

FIG. 8 is a schematic top view of the circular configuration of the hood of the present invention;

FIG. 9 is a schematic structural view of an alternative external air duct of the hood of the present invention;

FIG. 10 is a schematic view showing the structure of another blast cap connecting pipe according to the present invention;

FIG. 11 is a schematic view of the present invention in a configuration for bilateral wall-by-wall installation;

FIG. 12 is a schematic view of a single side wall mount of the present invention.

Detailed Description

A wind cap comprises an outer wind guide cylinder 10, a current carrier 20 and an inner wind guide cylinder 30.

Referring to fig. 1, the outer air guide duct 10 is covered on the upper outer side of the hood connecting pipe 40, an upward exhaust channel 10a is formed inside the outer air guide duct 10, and the air guide body 20 is supported on the outer air guide duct 10 and located in the exhaust channel 10a, wherein the outer air guide duct 10 is supported on the hood connecting pipe 40 or on the hood base of the roof floor through a bracket 11, as shown in fig. 3, the outer air guide duct 10 is supported on the hood connecting pipe 40 through the bracket 11;

referring to fig. 1 again, the bracket 11 has a certain distance from the top smoke outlet of the hood connecting pipe 40, and when the dripping rainwater drops on the bracket 11, the dripping rainwater cannot splash into the hood connecting pipe 40, preferably, the bracket 11 can also be a cylindrical support rod, so that the outer air duct 10 is stably supported, and meanwhile, the rainwater is prevented from splashing; still preferably, the bracket 11 may be further disposed to be inclined so that the dripping rainwater is splashed away from the top smoke outlet of the hood connecting pipe 40.

The guide body 20 is arranged on one side above the top smoke outlet of the hood connecting pipe 40, the inner air guide cylinder 30 extends upwards along the upper end surface of the guide body 20 to form a side wall 30a which can receive rebound air or rainwater generated after falling to the inner wall of the outer air guide cylinder 10, and a drainage section 12 which is communicated with the upper part and the lower part and exhausts air is formed between the side wall 30a and the inner wall of the outer air guide cylinder 10, wherein the effective flow area of the drainage section 12 is not less than that of the top smoke outlet of the hood connecting pipe 40; the flue gas discharged from the top smoke outlet of the hood connecting pipe 40 is bent after passing through the flow guide body 20, passes through the flow guide section 12, and is discharged from the top outlet of the outer air duct 10.

Wherein, baffle 20 is that the lower extreme is little, the big square cone of upper end, circular cone or wedge awl to better formation induced air effect, the guide flue gas flows to the top in an inclined direction, reduces the windage of discharging fume, and baffle 20 guides the flue gas redirecting in hood connecting pipe 40, in order to eliminate the vortex phenomenon, thereby reduces the windage, realizes the smooth and easy exhaust process of flue gas.

In other examples of the present invention, the surface of the side wall 30a of the inner air duct 30 is provided with a buffer structure capable of absorbing the bouncing wind or the rain water, for example, a layer of absorbent cotton is adhered, or the surface of the side wall 30a is provided with a porous (blind hole) structure or a micro-protrusion structure, so that the bouncing wind or the rain water can be better dissipated to be discharged quickly.

Further, referring to fig. 2, the baffle 20 of the present invention is formed with a chamfered portion 21 at a connection with the inner air duct 30, a bottom of the sidewall 30a is provided with a drip line 31, the drip line 31 is disposed to protrude downward from a lower end of the sidewall 30a and not to exceed the chamfered portion 21, wherein rainwater gathered downward along the sidewall 30a directly drops from the drip line 31 without sliding onto the baffle 20.

Accordingly, the arrangement manner of the dropping line 31 not exceeding the chamfered portion 21 downward, see the dashed line in fig. 2, can avoid the blocking of the wind guiding effect of the current carrier 20 by the dropping line 31.

Still further, in order to reduce wind resistance, the baffle 20 and the inner air duct 30 are arranged in such a manner: a plurality of connecting rods 13, for example, four connecting rods, are uniformly distributed on the periphery of the inner air guide cylinder 30, one end of each connecting rod 13 is connected to the inner air guide cylinder 30, and the other end of each connecting rod 13 is connected to the outer air guide cylinder 10, so that the inner air guide cylinder 30 and the guide body 20 are fixed; wherein the connecting rod 13 can be a horizontal rod or an inclined rod.

In the present invention, the cross section of the outer air guiding duct 10 is circular, square or regular polygon, and the cross section of the inner air guiding duct 30 is circular, square or regular polygon adapted to the outer air guiding duct 10, such as the square shown in fig. 7, and further such as the circular shown in fig. 8.

In another preferred example of the present invention, the outer air guide duct 10 may have a frustum shape in the vertical direction, and for example, as shown in fig. 9, the outer air guide duct includes an upper section 10b and a lower section 10c, the upper section 10b and the lower section 10c are symmetrical, the upper section 10b is a tapered pipe having a large upper end and a large lower end, and the lower section 10c is a tapered pipe having a large upper end and a small lower end, and in this case, the inner air guide duct 30 is preferably of a circular structure.

Correspondingly, the outer air duct 10 may also be a taper pipe with a small upper end and a large lower end, or a taper structure with a small part may be provided, for example, the upper end of the outer air duct 10 is inwardly closed to form a taper rain-proof platform 14, the taper rain-proof platform 14 is obliquely arranged from bottom to top in a closed manner, so as to prevent rainwater from directly falling into a gap space between the air deflector 20 and the hood connecting pipe 40 to enter the exhaust passage in an inclined manner, and in addition, the height of the whole outer air duct 10 may be reduced, so as to save the occupied space.

For example, the bottom of the external air duct 10 is inwardly closed to form a conical shape, so that rainwater can be conveniently discharged after being collected, and rainwater falling on the mounting base of the roof hood from the outside can be prevented from splashing.

In the invention, the outer periphery of the regular outer air duct 10 can be used for advertising, the appearance is beautiful, and the smoke exhaust outlet of the hood can not be seen beside or below.

Specifically, the top of the inner air duct 30 is sealed to form a top cover 32, and a slope-shaped rain dispersing structure with a convex center is arranged on the outer side above the top cover 32 so as to quickly drain and discharge rainwater falling on the top cover 32, wherein the slope-shaped rain dispersing structure can be in a triangular cone shape, a frustum shape, a step shape and the like, and can guide rainwater to be discharged.

The hood connecting pipe 40 of the present invention may be a straight pipe as shown in fig. 1, in which the size of the air inlet is greater than or equal to that of the exhaust passage, and the raised portion of the mounting flange 50 is positioned inside the connecting pipe to prevent rainwater from entering the exhaust passage, so that the hood portion is mounted and fixed on the hood mounting base of the roof of the building through the hood connecting pipe 40 and the mounting flange 50, as shown in fig. 3.

In other examples of the present invention, the blast cap connecting pipe 40 may also be a taper pipe with a large upper end and a small lower end, as shown in fig. 10, and the size of the air inlet at the lower end is greater than or equal to the specification size of the exhaust passage; the mounting flange 50 is located inside the connecting pipe to prevent rain water from entering the interior of the exhaust duct.

Referring to fig. 4-6, the process of the present invention for preventing wind and rain is shown.

Fig. 4 shows the working principle of wind-proof horizontal natural wind flowing backward, and the natural wind in the horizontal direction blows behind the outer air duct 10 of the hood and spreads all around, and does not flow backward and blow into the hood, and does not obstruct the emission of smoke.

The working principle of preventing the wind from flowing backwards in an inclined manner is shown in fig. 5, the natural wind which is inclined downwards blows behind the top cover 32 of the hood, is scattered towards the periphery, flows downwards along the drainage section 12 between the inner air duct 30 and the outer air duct 10 of the hood, and finally flows out of the hood from the position between the hood connecting pipe 40 and the outer air duct 10, and cannot flow backwards into the exhaust passage, at the moment, the drainage section 12 guides the wind entering the hood to be discharged vertically downwards, and cannot blow into the hood connecting pipe 40.

Fig. 6 shows the working principle of preventing rainwater (anti-rebound wind) from flowing backward, if rainwater drops between the inner air duct 30 and the outer air duct 10 of the wind cap, the rainwater directly passes through the exhaust passage 10a and falls on the floor; if rain drops on the top cover 32 of the wind cap, the rain drops and is scattered around the top cover 32, wherein the rain mainly flows downwards along the inner air duct 30 and drops from the water dropping line 31, and the rest rain directly impacts and flows onto the inner wall of the outer air duct 10 and then flows downwards along the inner wall of the outer air duct; and a part of rainwater can rebound and splash on the side wall 30a of the inner air guide cylinder 30 after impacting the inner wall of the outer air guide cylinder 10, flow to the position of the water dripping line 31 along the side wall 30a of the inner air guide cylinder 30, and drip on the floor outside the hood from the water dripping line 31, and in the whole process, the rainwater can not float in the exhaust passage regardless of the position of the anti-backflow hood.

In other examples of the present invention, in order to adapt to the installation of the wind cowl, the single-side wall-by-wall installation or the double-side wall-by-wall installation is performed, and only adaptive adjustment needs to be performed on each part of the wind cowl, taking the double-side wall-by-wall installation as an example, referring to fig. 11, at this time, the wind cowl connecting pipe 40 is close to the wall, the outer wind guiding cylinder 10 may be directly fixed on the wall, or the inner wind guiding cylinder 30 and the flow guiding body 20 may be prefabricated on one side wall 10d of the outer wind guiding cylinder 10 in a fixing manner of the bracket in fig. 1 to perform fixed installation.

At this time, the smoke discharged from the top smoke outlet of the hood connecting pipe 40 is discharged upwards from the right drainage section, and the principle of preventing reverse air or rainwater from flowing backwards is the same as that of the structure in fig. 1, and is not repeated herein; the structure of the single-side wall is shown in fig. 12, which is only an adaptive change of the above structure, and the description is not repeated here.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the scope of the invention. It will be appreciated by those skilled in the art that variations may be made without departing from the scope of the invention, and equivalents may be resorted to without departing from the scope of the invention.

Claims (10)

1. A hood, comprising:

an outer air duct;

a flow conductor; and

an inner air duct;

the outer air guide cylinder is covered on the outer side above the hood connecting pipe, an upward exhaust channel is formed in the outer air guide cylinder, and the flow guide body is supported on the outer air guide cylinder and is positioned in the exhaust channel;

the guide body is arranged on one side above the top smoke outlet of the hood connecting pipe, the inner air duct extends upwards along the upper end face of the guide body to form a side wall which can receive rebound air or rainwater generated after falling to the inner wall of the outer air duct, and a drainage section which is communicated with the upper part and the lower part and exhausts the air is formed between the side wall and the inner wall of the outer air duct;

and the smoke discharged from the smoke outlet at the top of the hood connecting pipe passes through the flow guide body and then is bent, passes through the flow guide section and then is discharged from the outlet at the top of the outer air duct.

2. The hood according to claim 1 wherein the surface of the sidewall is provided with a buffer structure capable of absorbing the bouncing wind or rain water.

3. The hood according to claim 1 wherein said outer duct is supported by a bracket on said hood connecting duct or on a hood base of a roof floor.

4. The hood of claim 1 wherein the flow conductor is a small lower end, large upper end square cone, circular cone or wedge cone.

5. The hood as set forth in claim 4 wherein said baffle is formed with a chamfered portion at a junction with said inner air guide duct, and a bottom of said side wall is provided with a drip line which is disposed to protrude downward from a lower end of said side wall without exceeding said chamfered portion.

6. The hood according to claim 1 wherein the effective flow area of the flow-inducing segment is not less than the effective flow area of the hood connection tube top exhaust.

7. The hood according to claim 1 wherein the cross-section of the outer duct is circular, square or regular polygon, and the cross-section of the inner duct is circular, square or regular polygon that fits the outer duct.

8. The hood according to claim 1 wherein the top of the inner duct is closed to form a top cover, and a central convex slope rain dispersing structure is provided on the upper outer side of the top cover.

9. The hood according to claim 1 wherein the upper end of said outer duct converges inwardly to form a tapered rain platform.

10. A hood is characterized by comprising a hood connecting pipe, an outer air duct covering a smoke outlet at the top of the hood connecting pipe, and a flow guide body arranged in the outer air duct, wherein a vertical inner air duct is arranged above the flow guide body, and the side wall of the inner air duct can receive rebound air or rainwater generated after the rebound air or rainwater drifts to the inner wall of the outer air duct, so that the rebound air or the rainwater can dissipate energy and is far away from the smoke outlet at the top of the hood connecting pipe.

Images