Side wind fume hood

Abstract

A side-through ventilation hood comprises a test support platform, a cabinet cavity arranged above the support platform and a cavity wall body constructed as the cabinet cavity, the cavity wall body comprising a left cavity side wall, a right cavity side wall and a cavity back wall arranged between the left cavity side wall and the right cavity side wall; it is characterized in that it also comprises a first guide back plate arranged above the support platform and close to the support platform, the first guide back plate is located in front of the cavity back wall and there is a spacing between them to form a first exhaust duct, the left and right side edges of the first guide back plate extend close to the left cavity side wall and the right cavity side wall in the left and right directions respectively, wherein the two side edges of the first guide back plate located in the lower area of ​​the cabinet cavity and the left cavity side wall and the right cavity side wall respectively have gradually expanding air openings between them to form a side-through ventilation structure, and the gradually expanding air openings are in a geometric shape that gradually increases from the top to the bottom.

Description

Technical Field

[0001] The invention relates to ventilation equipment for a laboratory, in particular to a side-winding fume hood. Background Art

[0002] Various harmful gases will be generated during chemical experiments. In order to be able to immediately discharge the harmful gases nearby, fume hoods are often used. Fume hoods are common local exhaust systems in chemical laboratories. They can exhaust harmful gases with a small amount of air, control the diffusion of harmful gases generated in the experiment to the laboratory, and ensure the health and safety of the experimenters. Common fume hoods mainly include a support table for experimental operations, a cabinet cavity arranged above the support table, and an exhaust fan connected to the cabinet cavity. An operating window is also provided on the fume hood to form an inlet and outlet channel for experiments on the support table for experimenters to perform experimental operations. Harmful gases are extracted from the cabinet cavity by the exhaust fan. All specifications require that the operating window position of the fume hood has a stable surface wind speed, and the amount of harmful gas leakage to the outside must be controlled to a very low level.

[0003] After long-term experiments and research, it was found that the provision of a guide back plate in the cabinet cavity is beneficial to reducing the generation of eddies and can also help to form a stable surface wind speed at the operating window. The guide back plate is generally arranged in the cabinet cavity and is arranged vertically like a screen (half of the vertical angle is between 75° and 90°) in front of the cavity back wall constituting the cabinet cavity, and an air duct is formed between the guide back plate and the cavity back wall to discharge the toxic gas in the cabinet cavity to the exhaust fan. However, the shapes and structures of the guide back plates of existing fume hoods vary. For example, the Chinese invention patent application with patent number 201710939219.1 and patent name fume hood discloses the following guide back plate mechanism: a plurality of through holes are provided on the guide back plate, and the through holes located at the lower part of the guide back plate are evenly distributed along the horizontal width direction; the through holes located at the upper part of the guide back plate gradually decrease from bottom to top in terms of the hole area relative to the unit area. In other embodiments, the through holes provided on the upper part of the guide back plate are gradually spaced apart from each other from bottom to top, the arrangement is gradually sparse, or the area of ​​a single hole is gradually reduced. In another embodiment, the through holes provided on the upper part of the guide back plate are arranged radially from top to bottom in the width direction, that is, when viewed from the front side, the arrangement of the through holes is narrow at the top and wide at the bottom along the center. Alternatively, the Chinese utility model patent with patent number CN201320231068.1 and patent name fume hood guide back plate discloses the following guide back plate: a fume hood guide back plate, comprising a plate body, exhaust holes are provided on the upper, lower, left, right sides and middle of the plate body, and the distances from the exhaust holes on the upper, lower, left and right sides of the plate body to the corresponding side edges of the plate body are equal. Experiments have found that the ventilation effect of the fume hood using the above two guide back plates is not ideal, and there is a phenomenon of some harmful gases leaking out. Summary of the invention

[0004] The guide structure of the guide back plate will affect the exhaust effect in the fume hood, and also affect the airflow movement characteristics of the space in front of the guide back plate. Its structure directly affects the fume hood's ability to capture harmful gases. The above two guide back plates disclosed in the existing patents 201710939219.1 and 201320231068.1 actually have common defects, including the following: First, although there is a gap with a uniform width from top to bottom between the guide back plate and the left and right side walls in the cabinet cavity, which can discharge a small amount of gas into the air duct behind the guide back plate, the vortex in the corner spaces on both sides of the lower cavity of the cabinet is very bad, and the gap with a uniform width from top to bottom close to them is not enough to solve this problem. The bad vortex in the corner spaces on both sides of the lower part causes the harmful gases accumulated in the corner spaces on both sides to be unable to be discharged in time for a long time, and even due to the suction effect of the vortex, it is easy to escape from the operating window to the outside of the fume hood, endangering the operation. The health of the workers; secondly, a large number of guide holes are arranged on the guide back plate, which will greatly destroy the original structural strength of the guide back plate and make the guide back plate easy to be broken. In order to overcome this defect, the thickness of the guide back plate has to be increased, which increases the cost of the guide back plate and is not easy to process; thirdly, all the guide holes on the guide back plate are processed by milling tools, and the milling tools are standard parts, and their sizes have been standardized. When processing the guide holes, only suitable milling tools can be selected from the standard specifications, which undoubtedly makes the ventilation area per unit length of the guide holes standardized, resulting in that after the length of the guide holes is specified, the ventilation area of ​​the guide holes cannot be flexibly and simply configured according to the specific structure, scope of use and other factors of the fume hood.

[0005] In order to solve the first technical problem mentioned above, the inventor tried to open a hollow air guide structure that allows air to flow on the left and right sides of the lower part of the guide back plate, such as a plurality of transversely arranged guide grooves, a plurality of evenly arranged guide holes, etc. However, after testing, it was found that although some vortices were improved, they were only slightly weakened, and there were still a large amount of harmful gases swirling in the left and right corner spaces of the front space. Therefore, it is not feasible to simply configure the guide structure, and how to configure a suitable guide structure still requires further in-depth research. In the subsequent multiple airflow tests, the inventor noticed a factor that cannot be ignored, that is, the changing trend of the air pressure distribution under the action of the exhaust fan during the operation of the fume hood, that is, the farther away from the exhaust fan, the smaller the air pressure, and on the contrary, the closer to the exhaust fan, the greater the air pressure, which has a great influence on the airflow distribution, and it is necessary to reasonably configure the position, ventilation area, shape and other parameters of the guide mechanism in accordance with this feature. Therefore, the inventor tried to open multiple rows of horizontally extending long strip air guide grooves arranged at intervals on the left and right sides of the lower part of the guide back plate, and the area of ​​the long strip air guide grooves gradually decreases from bottom to top, but the effect is still not ideal. This proves that simply making the ventilation area of ​​the air guide grooves have a regular change is still not able to solve the above technical problems.

[0006] One of the technical problems to be solved by the present invention is how to change the structure of the guide back plate so that the relatively heavy harmful gases accumulated in the space in front of the guide back plate, especially in the left and right corner spaces, can enter the air duct behind the guide back plate as much as possible. Based on this, the present invention first proposes a side-through ventilation hood, comprising a test support platform, a cabinet cavity arranged above the support platform and a cavity wall body constructed as the cabinet cavity, the cavity wall body comprising a left cavity side wall, a right cavity side wall and a cavity back wall arranged between the left cavity side wall and the right cavity side wall; it is characterized in that it also includes a first guide back plate arranged above the support platform and close to the support platform, the first guide back plate is located in front of the cavity back wall and there is a spacing between them to form a first exhaust duct, the left and right side edges of the first guide back plate extend in the left and right directions respectively close to the left cavity side wall and the right cavity side wall, wherein the two side edges of the first guide back plate located in the lower area of ​​the cabinet cavity and the left cavity side wall and the right cavity side wall respectively have gradually expanding air openings between them to form a side-through ventilation structure, and the gradually expanding air openings are in a geometric shape that gradually increases from the top to the bottom.

[0007] The inner cavity of the cabinet is an operating space for conducting various experimental activities. With the help of the inner cavity of the cabinet, harmful gases generated during the experiment can be temporarily collected therein to prevent them from spreading around.

[0008] The first air guide back plate is located in the cabinet cavity, in front of the cavity back wall, and the first air guide back plate and the cavity back wall can be arranged roughly parallel to each other, or the first air guide back plate is arranged obliquely relative to the cavity back wall, forming an air duct for exhaust between them.

[0009] Among them, the first guide back plate is arranged close to the support platform, and the lower area of ​​the first guide back plate is actually located in the lower area of ​​the cabinet cavity. It includes the bottom end surface of the first guide back plate, which can stand on the support platform, and can also have a certain appropriate spacing with the support platform in the up and down directions. The general spacing is set to 30mm~150mm, for example, 30mm, 68mm, 88mm or 150mm. The specific spacing size is determined according to other specific air inlet structures of the fume hood, the exhaust power of the exhaust fan, the applicable scope of the fume hood and other factors.

[0010] Among them, the left and right side edges of the first guide back plate extend close to the left cavity side wall and the right cavity side wall in the left and right directions respectively. This feature defines that the left and right side edges of the first guide back plate (excluding the part used to form the gradually expanding air opening) can be close to the left cavity side wall and the right cavity side wall respectively, and can also be respectively left with a certain appropriate spacing in the left and right directions between the left cavity side wall and the right cavity side wall. The width of the spacing is generally 1mm to 20mm, and the specific spacing size is determined according to other specific air inlet structures of the fume hood, the exhaust power of the exhaust fan, the applicable scope of the fume hood and other factors.

[0011] Among them, the two side edges of the first air guide back plate located in the lower area of ​​the cabinet cavity and the left cavity side wall and the right cavity side wall respectively have gradually expanding air openings to form a side air-through structure. The above characteristics first define that the first air guide back plate can be a plate body arranged in the lower area of ​​the cabinet cavity, in which case the two side edges of the first air guide back plate are also arranged in the lower area of ​​the cabinet cavity as a whole; or only the lower area of ​​the first air guide back plate is located in the lower area of ​​the cabinet cavity, in which case the two side edges of the lower part of the first air guide back plate are arranged in the lower area of ​​the cabinet cavity. The above characteristics also define the layout position of the gradually expanding air openings, which are located on the left and right sides of the lower area of ​​the cabinet cavity.

[0012] Among them, the gradually expanding air opening has a geometric shape that gradually increases from the top to the bottom. The above characteristics define the shape of the gradually expanding air opening, and the left and right widths of the gradually expanding air opening gradually increase from the top to the bottom.

[0013] According to the above technical scheme, compared with the prior art, the beneficial technical effects of the present invention are: first, since the two side edges of the first guide back plate located in the lower area of ​​the cabinet cavity and the left cavity side wall and the right cavity side wall respectively have gradually expanding air openings, that is, relatively large air guide gaps arranged continuously from top to bottom are formed on the left and right sides of the first guide back plate, respectively, thereby providing a flow channel for the relatively heavy macromolecular gases deposited in the left and right corners of the lower area of ​​the cabinet cavity to be discharged into the first exhaust duct in time, and also helping to reduce the resistance of airflow and the formation of vortices, thereby increasing the airflow speed. Secondly, when the fume hood is configured with an inhaled airflow as the control airflow and a pressure gradient that gradually increases from bottom to top is formed in the inner cavity of the hood, there will be a certain inhaled air velocity gradient between the highest point and the lowest point of the gradually expanding air opening. The shape change of the gradually expanding air opening, that is, the geometric shape that gradually increases from the top to the bottom, is conducive to forming a basically uniform inhaled air volume (air volume) on the gradually expanding air opening, thereby optimizing the distribution state of the airflow field at the left and right corners of the lower area of ​​the inner cavity of the hood, and further reducing the generation of eddies. In addition, compared with the gaps with uniform widths from top to bottom in the prior art, the lower part of the gradually expanding air opening has a relatively larger air flow area, so that the lower part of the gradually expanding air opening has a relatively larger air volume, thereby being able to capture more relatively heavy macromolecular gases that are deposited in the left and right corners of the lower area of ​​the inner cavity of the hood.

[0014] A further technical solution may be that there is a bottom spacing between the first guide back plate and the support platform that allows air to pass through; upper side gaps with uniform gap width are formed between the two sides of the upper area of ​​the first guide back plate and the left cavity side wall and the right cavity side wall, and the upper side gap is located above the gradually expanding air opening, and the gap width of the upper side gap is smaller than the gap height of the bottom spacing. According to the above technical solution, the bottom air guide passage is formed by the bottom spacing, which is conducive to capturing the heavier macromolecular gas that sinks into the lower area of ​​the cabinet cavity.

[0015] A further technical solution may be that the gradually enlarged air opening extends downward through the bottom end surface of the first air guide back plate and is combined with the bottom spacing. In this way, the gradually enlarged air opening and the bottom spacing together form a U-shaped bottom total air space, which can better capture the relatively heavy harmful gases deposited in the lower area of ​​the cabinet cavity. In addition, the processing of the gradually enlarged air opening is also facilitated.

[0016] A further technical solution may be that the maximum width of the gradually expanding air opening in the left-right direction is 35 mm to 45 mm, for example, 35 mm, 40 mm or 45 mm.

[0017] A further technical solution may be that the gradually expanding air opening is in the form of a right triangle, and its top angle is 3° to 13°, for example, 3°, 6°, or 13°.

[0018] In addition, in order to solve the second technical problem mentioned above, a further technical solution may be that a lower air guide passage extending left and right is provided on the first air guide back plate only on the plate body located in the lower area of ​​the cabinet inner cavity. The above feature defines that only one air guide passage, namely the lower air guide passage, is provided on the first air guide back plate, and no other air guide holes and grooves are provided, and the lower air guide passage is located in the lower area of ​​the cabinet inner cavity. According to the above technical solution, the lower air guide passage is also located in the lower area of ​​the cabinet inner cavity, so that the heavier harmful gases deposited in the lower area of ​​the cabinet inner cavity can be discharged in time. In addition, compared with the situation in which multiple rows of air guide slots are arranged on the plate body of the first air guide backplate located in the lower area of ​​the cabinet inner cavity, the air flow rate of the lower air guide passage is relatively stronger, which can not only better capture the harmful gases drifting to its surrounding area, but also provide conditions for configuring the appropriate air flow rate for the gradually expanding air opening, and can greatly simplify the guide structure of the first air guide backplate, reduce the damage to the original structural strength of the first air guide backplate, and facilitate the processing of the first air guide backplate.

[0019] A further technical solution may be that the wind passing area of ​​the lower wind guiding passage is not greater than the wind passing area of ​​the bottom spacing. According to the above technical solution, the wind passing area of ​​the lower wind guiding passage may be equal to or less than the wind passing area of ​​the bottom spacing.

[0020] A further technical solution may be that the lower air guide passage includes at least three first sub-passages, the at least three first sub-passages are arranged left and right, and each of the first sub-passages is in the shape of a long strip extending in the left and right direction. According to the above technical solution, when the lower air guide passage is formed, the first deflector can still maintain a suitable structural strength.

[0021] In order to form the gradually expanding air opening, the following technical solutions can be further selected, wherein the first technical solution is: the two sides of the first air guide back plate located in the lower area of ​​the cabinet cavity are inclined and narrowed towards each other, and the left cavity side wall and the right cavity side wall are upright. The second technical solution is: the lower area of ​​the left and right cavity side walls is gradually concave outward from top to bottom, and the two sides of the first air guide back plate located in the lower area of ​​the cabinet cavity are upright.

[0022] Secondly, in order to solve the third problem mentioned above, the present invention also proposes a new method for forming guide slots. A further technical solution is that it also includes a second guide back plate, the first guide back plate and the second guide back plate are separately arranged, the second guide back plate is located above the first guide back plate and arranged close to the first guide back plate, the second guide back plate is located in front of the back wall of the cavity and there is a spacing between them to form a second exhaust duct; it also includes a middle air guide aisle extending left and right, the middle air guide aisle is composed of the inter-plate spacing between the first guide back plate and the second guide back plate, the middle air guide aisle is located in the central area of ​​the cabinet cavity in the up and down directions, the wind passing area of ​​the lower air guide aisle is not greater than the wind passing area of ​​the bottom spacing, and the wind passing area of ​​the middle air guide aisle is smaller than the wind passing area of ​​the lower air guide aisle. In this way, it is very convenient to control the size of the spacing between the plates so that the middle air guide passage has a suitable wind passing area, and in particular, a narrow wind guide gap can be formed in a very simple way. The ventilation area of ​​the middle air guide passage is not limited by the size specifications of the milling tool and can be flexibly configured. In addition, the relatively light harmful gases that escape from the lower air guide passage and continue to drift upward can be captured by the airflow flowing through the middle air guide passage and brought into the air duct behind the second guide back plate. It can be found that by setting the bottom spacing, the lower air guide passage, and the middle air guide passage in sequence from bottom to top, and by configuring them with suitable ventilation areas, quantities, and layout positions, it is not only possible to effectively capture harmful gases of different weights, but also possible to provide conditions for configuring the suitable wind passing volume for the gradually expanding wind opening, and greatly simplify the guide structure of the guide back plate, reduce the damage to the original structural strength of the guide back plate, and facilitate the processing of the guide back plate.

[0023] A further technical solution may be that the cavity wall body also includes a cavity top wall arranged between the left cavity side wall and the right cavity side wall, and a total exhaust port is also provided on the cavity top wall; and also includes a third guide back plate located above the second guide back plate, the third guide back plate is located in front of the cavity back wall and there is a spacing between them to form a third exhaust duct, the lower end of the third guide back plate is connected to the upper part of the second guide back plate, the third guide back plate is arranged below the total exhaust port in an inclined upward structure, a splicing seam is provided between the second guide back plate and the third guide back plate, the wind passing area of ​​the splicing seam is not greater than the wind passing area of ​​the inter-plate spacing, and no wind hole grooves are provided on the second guide back plate and the third guide back plate, and the first exhaust duct, the second exhaust duct and the third exhaust duct are connected front and back to form an exhaust channel leading to the total exhaust port. According to the above technical solution, compared with the solution of setting the air hole groove on both the second guide back plate and the third guide back plate, the solution of not setting the air hole groove on the second guide back plate and the third guide back plate is conducive to increasing the air volume of the bottom spacing, the lower air guide aisle, the middle air guide aisle and the gradually expanding air opening, so that the ability to capture harmful gases deposited in the lower area and the central area of ​​the cabinet cavity can be maintained while simplifying the guide structure on the guide plate. Among them, the air flow area of ​​the splicing seam is not greater than the air flow area of ​​the middle air guide aisle, that is, the air flow area of ​​the splicing seam is less than or equal to the air flow area of ​​the middle air guide aisle, and the air flow area of ​​the splicing seam can even be zero, for example, when sealed with the help of a seal. In addition, the third guide back plate and the cavity back wall can be arranged roughly parallel to each other, or the third guide back plate can be arranged obliquely relative to the cavity back wall.

[0024] A further technical solution may be that a fixing seat is arranged between the first guide back plate and the cavity back wall, the fixing seat is U-shaped, including a top support wall and left and right support walls arranged on the left and right sides of the top support wall, an interlayer cavity is formed between the top support wall and the left and right support walls, a connecting column is arranged on the top support wall, and the tail of the connecting column extends into the interlayer cavity; the first guide back plate is pressed against the top support wall, and a fastener passes through the first guide back plate and is connected to the connecting column to fix the first guide back plate to the fixing seat. This facilitates the installation, removal and replacement of the first guide back plate.

[0025] A further technical solution may also include an operating window constructed opposite to the back wall of the cavity, the operating window extending left and right along the support platform, the operating window being used to form an entry and exit channel for conducting experiments on the support platform; a lower air supply device is provided at the door sill position of the operating window, the lower air supply device includes an air passageway capable of circulating supply air, the air passageway is used to supply air from the outside of the cabinet cavity to the nearby area on the support platform surface, the air outlet of the air passageway extends along the edge direction x of the support platform and the head and tail ends are respectively close to the left cavity side wall and the right cavity side wall of the cabinet cavity, the air outlet includes a head end air outlet expansion port, a tail end air outlet expansion port and a middle air outlet narrowing port located therebetween, the heights of the head end air outlet expansion port and the tail end air outlet expansion port relative to the support platform are respectively greater than the height of the middle air outlet narrowing port relative to the support platform. In this way, within the unit length range in the direction x, the amount of air blown out from the front end air outlet expansion port and the rear end air outlet expansion port is greater than the amount of air blown out from the middle air outlet narrowing port, so that the strong airflow at the front and rear ends regulates the airflow in the middle area, making the airflow blown out from the air outlet more stable and concentrated as a whole, effectively improving the airflow's ability to capture and clean harmful gases in the vicinity of the support platform surface. In addition, the front end air outlet expansion port and the rear end air outlet expansion port can provide a suitable air volume for the gradually expanding air opening, which is conducive to maintaining a balanced surface wind speed. The head and tail ends of the air outlet of the air passage are respectively close to the left and right side walls of the cabinet cavity, which can be interpreted as the head and tail ends of the air outlet and the left and right side walls of the cabinet cavity are close together or have a certain gap reserved, for example, it can be 1mm to 10mm. Of course, the smaller the gap between the left and right ends of the air outlet and the left and right side walls of the cabinet cavity, the larger the blowing range of the air outlet in the left and right directions. The door sill position of the operating window refers to the bottom position of the operating window. In the absence of special instructions, the same meaning is used below.

[0026] Since the present invention has the above characteristics and advantages, it can be applied to side-through ventilation hoods. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a three-dimensional structural schematic diagram of a fume hood to which the technical solution of the present invention is applied;

[0028] Figure 2 This is a structural schematic diagram of a fume hood in the main viewing direction to which the technical solution of the present invention is applied;

[0029] Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure in the AA direction;

[0030] Figure 4 yes Figure 3 The enlarged view of the C part in FIG.

[0031] Figure 5 : is a schematic structural diagram of the guide back plate in the main viewing direction, wherein the left and right dotted line parts respectively represent the left cavity side wall 31 and the right cavity side wall 32, and the dotted line part below represents the support platform 2;

[0032] Figure 6 yes Figure 3 A magnified view of part B in FIG.

[0033] Figure 7 is a schematic diagram of the three-dimensional structure of the fixing seat 8;

[0034] Figure 8 is a structural schematic diagram of the lower air supply device in the main viewing direction;

[0035] Fig. 9 It is a schematic diagram of the three-dimensional structure after the lower air replenisher is turned over to the back. DETAILED DESCRIPTION

[0036] The structure of the fume hood using the technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0037] like Figure 1 to Figure 3 and Figure 5 As shown, the present invention relates to a fume hood, comprising a test support platform 2, a cabinet cavity 3 arranged above the support platform 2, and a cavity wall body configured as the cabinet cavity 3, wherein the cavity wall body comprises a left cavity side wall 31, a right cavity side wall 32, and a cavity back wall 34 and a cavity top wall 33 arranged between the left cavity side wall 31 and the right cavity side wall 32. It also comprises an operation window 30 constructed opposite to the cavity back wall 34, the operation window 30 extends left and right along the front side edge 22 of the support platform 2, and the operation window 30 is used to form an inlet and outlet channel for conducting experiments on the support platform 2, and the hands of the experimenter can pass through the operation window 30 to extend into the cabinet cavity 3 to conduct various experimental operations, and the harmful gases generated during the experiment will be temporarily collected in the cabinet cavity 3 to avoid running around. A total exhaust port 330 is also provided on the cavity top wall 33, and the total exhaust port 330 is used to exhaust the air in the cabinet cavity 3; in other embodiments, the total exhaust port 330 can also be provided at a suitable place on the left cavity side wall 31, the right cavity side wall 32 or the cavity back wall 34, and the specific setting position can be reasonably determined according to the flow field design of the entire airflow of the fume hood.

[0038] An exhaust passage 6 connected to the main exhaust port 330 is provided in the cabinet inner cavity 3. An exhaust fan (not shown in the figure) connected to the main exhaust port 330 is also installed above the fume hood, and the exhaust fan is used to form a negative pressure in the cabinet inner cavity 3. When the exhaust fan is running, the harmful gas accumulated in the cabinet inner cavity 3 is sucked into the exhaust passage 6 and then discharged through the main exhaust port 330.

[0039] The basic goal of safe use of fume hoods is that, under the suction force of the exhaust fan, the design of the airflow field in the entire cabinet should ensure that the surface wind speed at the position of the operating window 30 is stable and uniform, the gas in the cabinet cavity 3 will not flow back from the position of the operating window 30, and the large molecular harmful gases deposited at the bottom of the cabinet cavity 3 can be removed in time and cannot flow back. Of course, there are many specific schemes to achieve the above basic goals, and the scheme proposed in the present invention is not the only one; secondly, to achieve the above basic goals, it is necessary to improve various local structures so that they can play their role in a fume hood product. For this reason, the present invention also mainly improves the local structure of the fume hood in order to achieve the corresponding technical effect. The corresponding local improvement schemes will be explained one by one in the following statements.

[0040] In order to achieve the above basic objectives, the present invention first improves the wind passing structure at the bottom of the guide back plate 5. Figure 3 As shown, the guide back plate 5 is provided in the cabinet inner cavity 3, and the guide back plate 5 and the cavity wall body of the cabinet inner cavity 3 are a split structure. The guide back plate 5 is located in front of the cavity back wall 34 and there is a distance between them to form the exhaust duct 6. For this reason, the guide back plate 5 actually also faces the operation window 30.

[0041] like Figure 5As shown, the guide back plate 5 includes a first guide back plate 51 disposed above the support platform 2 and close to the support platform 2. The first guide back plate 51 and the cavity back wall 34 are arranged substantially parallel to each other. Of course, in other embodiments, the first guide back plate 51 may be arranged obliquely relative to the cavity back wall 34. The first guide back plate 51 is located in front of the cavity back wall 34 and there is a distance between them to form a first exhaust duct 61 extending up and down, and the first exhaust duct 61 forms a partial channel of the exhaust duct 6. The left and right side edges of the first air guide back plate 51 extend close to the left cavity side wall 31 and the right cavity side wall 32 in the left and right directions, respectively. However, the two side edges of the first air guide back plate 51 located in the lower area of ​​the cabinet inner cavity 3 and the left cavity side wall 31 and the right cavity side wall 32 respectively have a gradually expanding air opening 71 and a gradually expanding air opening 71a, that is, the gradually expanding air opening 71 and the gradually expanding air opening 71a are located on the left and right sides of the lower area of ​​the cabinet inner cavity 3, and the gradually expanding air opening 71 and the gradually expanding air opening 71a are expanding air openings. The gradually expanding air opening 71 and the gradually expanding air opening 71a are in a geometric shape that gradually increases from the top to the bottom. In one preferred embodiment, the maximum width W of the gradually expanding air opening 71 and the gradually expanding air opening 71a in the left-right direction is 35 mm to 45 mm, for example, 35 mm, 40 mm or 45 mm. In addition, the two sides of the upper area of ​​the first air guide back plate 51 are spaced from the left cavity side wall 31 and the right cavity side wall 32 by a suitable spacing that does not need to be too large, specifically including an upper side gap 76 and an upper side gap 76a with uniform gap width, the upper side gap 76 is located above the gradually expanding air opening 71, and the upper side gap 76a is located above the gradually expanding air opening 71a. The gap width W4 of the upper side gap 76 and the upper side gap 76a is smaller than the width of the gradually expanding air opening 71 and the gradually expanding air opening 71a. The gap width W4 of the upper side gap 76 and the upper side gap 76a is also smaller than the gap height H of the bottom spacing 7 to be discussed below. The gap width W4 is generally 1mm to 20mm, for example, 1mm, 10mm, 20mm. The specific gap size is determined according to other specific air inlet structures of the fume hood, the exhaust power of the exhaust fan, the applicable scope of the fume hood, etc. The gaps with uniform width in the left and right directions between the two sides of the second guide back plate 52 and the third guide back plate 53 to be discussed below and the left cavity side wall 31 and the right cavity side wall 32 are also of the same width W4.

[0042] According to the above technical scheme, compared with the prior art, the beneficial technical effects are: first, since the two side edges of the first guide back plate 51 located in the lower area of ​​the cabinet cavity 3 and the left cavity side wall 31 and the right cavity side wall 32 respectively have gradually expanding air openings 71 and gradually expanding air openings 71a, that is, relatively large air guide gaps arranged continuously from top to bottom are formed on the left and right sides of the first guide back plate 51, respectively, so that a flow channel can be provided for the relatively heavy macromolecular gases deposited in the left and right corners of the lower area of ​​the cabinet cavity 3 to be discharged into the first exhaust duct 61 in time, and it is also beneficial to reduce the resistance of airflow and the formation of vortices, thereby increasing the airflow speed. Secondly, when the fume hood is configured with an inhaled airflow as the control airflow and a pressure gradient that gradually increases from bottom to top is formed in the cabinet cavity 3, there will be a certain inhaled air velocity gradient between the highest point and the lowest point of the gradually expanding air opening 71. The shape change of the gradually expanding air opening 71, that is, the geometric shape that gradually increases from the top to the bottom, is conducive to forming a basically uniform inhaled air volume (air volume) on the gradually expanding air opening 71, so that the distribution state of the airflow field at the left and right corners of the lower area of ​​the cabinet cavity 3 can be optimized, and the generation of eddy currents can be further reduced. In addition, compared with the gaps with uniform widths from top to bottom in the prior art, the lower part of the gradually expanding air opening 71 has a relatively larger air flow area, so that the lower part of the gradually expanding air opening 71 has a relatively larger air flow volume, so that more relatively heavy macromolecular gases deposited in the left corner of the lower area of ​​the cabinet cavity 3 can be captured. The gradually expanding air opening 71a can achieve the same technical effect as the gradually expanding air opening 71, and will not be discussed again here.

[0043] like Figure 5As shown, the first guide back plate 51 is close to the support platform 2 and is provided with a spacing, so that there is a bottom spacing 7 between the first guide back plate 51 and the support platform 2 for passing wind, and the gap width W4 of the upper side gap 76 and the upper side gap 76a are respectively smaller than the gap height H of the bottom spacing 7. In one preferred embodiment, the gap height H is generally 30 mm to 150 mm, such as 30 mm, 68 mm, 88 mm or 150 mm, and the specific gap height is determined according to other specific air inlet structures of the fume hood, the exhaust power of the exhaust fan, the applicable scope of the fume hood and other factors. According to the above technical solution, the bottom air guide passage is formed by the bottom spacing 7, which is conducive to capturing the heavier macromolecular gas that sinks into the lower area of ​​the cabinet cavity 3. In other embodiments, the bottom spacing 7 can be set to be close to zero, that is, the bottom end surface of the first guide back plate 51 stands on the support platform 2. Furthermore, the gradually enlarged air opening 71 and the gradually enlarged air opening 71a respectively extend downward through the bottom end surface of the first guide back plate 51 and are combined with the bottom spacing 7. In this way, the gradually enlarged air opening 71 and the gradually enlarged air opening 71a and the bottom spacing 7 form a U-shaped bottom total air space, which can better capture the relatively heavy macromolecular gas deposited in the lower area of ​​the cabinet inner cavity 3. In addition, it is also convenient to process the gradually enlarged air opening 71 and the gradually enlarged air opening 71a on the first guide back plate 51.

[0044] In order to form the gradually expanding air opening 71 and the gradually expanding air opening 71a, the following technical solutions may be further selected. The first technical solution is: Figure 5 As shown, the two side edges of the first air guide back plate 51 located in the lower area of ​​the cabinet cavity 3 are inclined and narrowed towards each other, and the left cavity side wall 31 and the right cavity side wall 32 are upright. In this embodiment, the first technical solution is adopted, and the gradually expanding air opening 71 and the gradually expanding air opening 71a are right-angled triangles, and their vertex angles Q are 3°~13°, for example, 3°, 6°, and 13°. The second technical solution (not shown in the figure): the lower areas of the left cavity side wall 31 and the right cavity side wall 32 are respectively in a shape that is gradually concave outward from top to bottom, and the two side edges of the first air guide back plate 51 located in the lower area of ​​the cabinet cavity 3 are upright.

[0045] In order to achieve the above basic objectives, the present invention proposes another improved solution for the structure of the guide back plate 5, which can be used alone or in combination with the gradually expanding air opening 71 and the gradually expanding air opening 71a in the fume hood product. Specifically, Figure 5As shown, a guide structure capable of guiding the airflow in the front space 35 into the exhaust channel 6 is provided on the guide back plate 5, that is, a lower air guide passage 72 extending left and right is provided only on the plate body located in the lower area of ​​the cabinet inner cavity 3 on the first guide back plate 51, and the air flow area of ​​the lower air guide passage 72 is not greater than the air flow area of ​​the bottom spacing 7, that is, the air flow area of ​​the lower air guide passage 72 can be equal to or less than the air flow area of ​​the bottom spacing 7. In this way, the lower air guide passage 72 is also located in the lower area of ​​the cabinet inner cavity 3, so that the relatively heavy macromolecular gas deposited in the lower area of ​​the cabinet inner cavity 3 can be discharged in time. In addition, compared with the case where multiple rows of air guide slots are provided on the lower area of ​​the first air guide back plate 51, the air flow rate of the lower air guide passage 72 is relatively stronger, which can not only better capture the harmful gases that drift to the vicinity thereof, but also provide conditions for configuring the appropriate air flow rate of the gradually expanding air flow opening, and can greatly simplify the air guide structure of the first air guide back plate 51, reduce the damage to the original structural strength of the first air guide back plate 51, and facilitate the processing of the first air guide back plate 51. Further, the lower air guide passage 72 includes at least three first sub-aisles, that is, there can be 3, 4 or other multiple first sub-aisles. In this embodiment, three first sub-aisles are provided, namely, the first sub-aisle 72a, the first sub-aisle 72b, and the first sub-aisle 72c, the three first sub-aisles are arranged left and right, and each of the first sub-aisles is in the shape of a long strip extending in the left-right direction. According to the above technical solution, the first guide plate 51 can still maintain a suitable structural strength when the lower air guide passage 72 is formed.

[0046] In order to achieve the above basic objectives, the present invention proposes another improved solution for the structure of the guide back plate 5, which can be used alone or in combination with the gradually expanding air opening 71 and the gradually expanding air opening 71a in the fume hood product. Specifically, Figure 3 and Figure 5As shown, the guide back plate 5 also includes a second guide back plate 52 which is separately arranged from the first guide back plate 51, the second guide back plate 52 is located above the first guide back plate 51 and arranged close to the first guide back plate 51, the second guide back plate 52 is located in front of the cavity back wall 34 and is arranged roughly parallel to each other and there is a spacing between them to form a second exhaust duct 62 extending up and down, and the second exhaust duct 62 also forms a part of the exhaust duct 6 (in other embodiments, the second guide back plate 52 can also be arranged obliquely relative to the cavity back wall 34). It also includes a middle air guide passage 73 extending left and right, the middle air guide passage 73 is composed of the inter-plate spacing 73 between the first guide back plate 51 and the second guide back plate 52, and the middle air guide passage 73 is roughly located in the central area of ​​the cabinet inner cavity 3 viewed in the up and down direction in the up and down direction, and the wind passing area of ​​the middle air guide passage 73 is smaller than the wind passing area of ​​the lower air guide passage 72. Compared with the prior art, the beneficial technical effects of the above technical solution are: first, since there is a bottom spacing 7 between the first guide back plate 51 and the support platform 2 for air to pass through, the bottom spacing 7 can be used to timely discharge the heavier macromolecular gases deposited in the lower area of ​​the cabinet cavity; secondly, since the lower air guide passage 72 is located in the lower area of ​​the cabinet cavity 3 and above the bottom spacing 7, the heavier macromolecular gases that escape from the bottom spacing 7 and continue to drift upward can be captured by the airflow flowing through the lower air guide passage 72 and brought into the air duct behind the guide back plate 5; furthermore, since only one lower air guide passage 72 is provided on the first guide back plate 51, and the lower air guide passage 72 The wind passing area of ​​72 is not greater than the wind passing area of ​​the bottom spacing 7. Thus, compared with the case where multiple rows of air guides are arranged on the first guide back plate 51, the wind passing volume of the lower air guide passage 72 is relatively stronger, and can better capture the harmful gases that drift to its vicinity, and can make the bottom spacing 7 have a suitable wind passing volume; again, the middle air guide passage 73 is composed of the inter-plate spacing between the first guide back plate 51 and the second guide back plate 5. Thus, it is very convenient to control the size of the inter-plate spacing to make the middle air guide passage 73 have a suitable wind passing area, especially to form a narrow air guide gap in a very simple way. The ventilation area of ​​the middle air guide passage 73 is not limited by the size specifications of the milling tool and can be flexibly configured. The relatively light harmful gases that escape from the lower air guide passage 72 and continue to drift upward can be captured by the airflow flowing through the middle air guide passage 73 and brought into the air duct behind the guide back plate 5.Based on this, it can be found that by setting the bottom spacing 7, the lower air guide aisle 72, and the middle air guide aisle 73 in sequence from bottom to top, and configuring them with appropriate ventilation areas, quantities and layout positions, not only can the harmful gases of different weights be effectively captured, but the guide structure of the guide back plate 5 can also be greatly simplified, reducing the damage to the original structural strength of the guide back plate 5, and facilitating the processing of the guide back plate 5.

[0047] like Figure 5 As shown, the guide back plate 5 also includes a third guide back plate 53 located above the second guide back plate 52, and the third guide back plate 53 is located in front of the cavity back wall 34 and can be arranged substantially parallel to each other between the cavity back wall 34. In other embodiments, the third guide back plate 53 can also be arranged obliquely relative to the cavity back wall 34. There is a spacing between the third guide back plate 53 and the cavity back wall 34 to form a third exhaust duct 63 extending up and down, and the first exhaust duct 61, the second exhaust duct 62 and the third exhaust duct 63 are connected front and back to form an exhaust channel 6 leading to the total exhaust port 330. The lower end of the third guide back plate 53 is connected to the upper part of the second guide back plate 52, and the third guide back plate 53 is arranged below the total exhaust port 330 in an inclined upward structure so that the third exhaust duct 63 is connected to the total exhaust port 330. A joint seam 74 is provided between the second guide back plate 52 and the third guide back plate 53, and the wind passing area of ​​the joint seam 74 is not greater than the wind passing area of ​​the inter-plate spacing 73, and no wind hole groove is provided on the second guide back plate 52 and the third guide back plate 53. According to the above technical scheme, compared with the scheme of providing wind hole grooves on both the second guide back plate 52 and the third guide back plate 53, it is beneficial to increase the wind passing volume of the bottom spacing 7, the lower guide channel 72, the middle guide channel 73 and the gradually expanding wind opening, so that the ability to capture harmful gases deposited in the lower area and the central area of ​​the cabinet cavity 3 can be maintained while simplifying the guide structure on the guide back plate 5. Among them, the wind passing area of ​​the splicing seam 74 is not greater than the wind passing area of ​​the middle air guide passage 73, that is, the wind passing area of ​​the splicing seam 74 is less than or equal to the wind passing area of ​​the middle air guide passage 73, and the wind passing area of ​​the splicing seam 74 can even be zero, for example, when sealed with the aid of a seal. In addition, a top spacing 75 is formed between the upper end of the third air guide back plate 53 and the cavity top wall 33 of the cabinet cavity 3. According to the above technical solution, the top spacing 75 is actually located in the upper area of ​​the cabinet cavity 3, so that the harmful gases that escape from the bottom spacing 7, the lower air guide passage 75, and the middle air guide passage 73 in sequence and continue to drift upward can be captured by the airflow flowing through the top spacing 75 and brought into the third exhaust duct 63 and then discharged from the cabinet cavity 3.

[0048] like Figure 3 , Figure 6 and Figure 7 As shown, in order to fix the guide back plate 5, a fixing seat 8, a fixing seat 8a and a fixing seat 8b are arranged between the guide back plate 5 and the cavity back wall 34. The structures of the fixing seats 8, 8a and 8b are the same, and the fixing seat 8 is taken as an example for description below. The fixing seat 8 is U-shaped, including a top support wall 83 and a left support wall 81 and a right support wall 82 arranged on the left and right sides of the top support wall 83. An interlayer cavity 80 is formed between the top support wall 83 and the left support wall 81 and the right support wall 82. A connecting column 85 is arranged on the top support wall 83, and the tail of the connecting column 85 extends into the interlayer cavity 80. The fixing seat 8 is locked on the cavity back wall 34 by screws. The fixing seat 8 is located between the second guide back plate 52 and the cavity back wall 34, the second guide back plate 52 is pressed against the top support wall 83, and the fastener 86 passes through the second guide back plate 52 and is connected to the connecting column 85 to fix the second guide back plate 52 to the fixing seat 8; an oblique slot 84 is provided on the top support wall 83, and the lower end of the third guide back plate 53 is inserted into the oblique slot 84 to connect to the upper part of the second guide back plate 52. The fixing seat 8a is provided between the first guide back plate 51 and the cavity back wall 34, the first guide back plate 51 is pressed against the top support wall of the fixing seat 8a, and the fastener passes through the first guide back plate 51 and is connected to the connecting column of the fixing seat 8a to fix the first guide back plate 51 to the fixing seat 8a. In this way, the installation, disassembly and replacement of the first guide back plate 51, the second guide back plate 52 and the third guide back plate 53 are simplified.

[0049] like Figure 2 , Figure 3 and Figure 4 As shown, the cabinet is also provided with a lower air supply device, the lower air supply device includes an air passage 10 capable of circulating air supply, and the air outlet 15 of the air passage 10 is arranged along the edge 22 of the support platform 2 in the direction x (wherein the direction x is Figure 2In the direction of the middle X-axis), the air passage 10 is used to supply air from the outside of the cabinet cavity 3 to the nearby area on the surface of the support platform 2, and the lower air supply device also includes an upper shell 1 that forms a partial channel wall of the air passage 10 and is located above the air passage 10. On the flow path of the supply air, the upper shell 1 includes a first shell portion 11, an intermediate transition shell portion 13 and a second shell portion 12 that are arranged in sequence, so that the air passage 10 is also correspondingly divided into a first section 101, an intermediate section 103 and a second section 102 that correspond to the first shell portion 11, the intermediate transition shell portion 13 and the second shell portion 12 and are connected, wherein the external air enters from the first section 101 and flows through the intermediate section 103 and then flows out from the second section 102; viewed from the cross-sectional direction perpendicular to the direction x (i.e. Figure 4 As shown in the figure), the inner side wall 11a of the first shell portion 11 is a plane wall extending upwardly along the airflow direction, and the inner side wall 13a of the intermediate transition shell portion 13 is an arc wall. The inner side wall 11a of the first shell portion 11 and the inner side wall 12a of the second shell portion 12 are smoothly transitioned and connected through the inner side wall 13a of the intermediate transition shell portion 13.

[0050] Among them, the air outlet 15 of the air passage 10 is arranged to extend along the direction x of the edge 22 of the support platform 2. The above characteristics define that the extension direction of the air outlet 15 of the air passage 10 is substantially consistent with the extension direction of the edge 22 of the support platform 2. Secondly, the air passage 10 is used to guide the air outside the cabinet cavity 3 to the nearby area on the surface of the support platform 2 to replenish air, that is, the air passage 10 is an air replenishment channel connecting the cabinet cavity 3 with the external space, and the air passage 10 is used to introduce the external air of the cabinet cavity 3 into the cabinet cavity 3, so as to replenish the gas for the cabinet cavity 3. In addition, the inner side wall 11a of the first shell part 11 is a plane wall extending in an inclined upward direction along the air flow direction, that is, the inner side wall 11a of the first shell part 11 is not a curved wall, and the inner side wall 11a of the first shell part 11 not only extends straightly from bottom to top, but also extends from outside to inside (from the outside direction of the cabinet cavity 3 to the inside direction of the cabinet cavity 3). The plane wall can not only guide the flow but also easily form a stable flow. The inner side wall 11a of the first shell 11 and the inner side wall 12a of the second shell 12 are smoothly transitioned and connected through the inner side wall 13a of the intermediate transition shell 13, so that the intermediate transition shell 13 can minimize the damage to the flat and stable flow formed by the plane wall.

[0051] Compared with the prior art, the beneficial technical effects of the above technical solution adopted by the lower air replenisher are: first, since the air passage 10 is used to replenish air from the outside of the cabinet cavity 3 to the nearby area on the surface of the support platform 2, it is beneficial to blow the harmful gases deposited in the nearby area on the surface of the support platform 2 toward the inside of the cabinet cavity 3, thereby reducing the amount of harmful gases leaking outward. Second, since the inner wall 11a of the first shell 11 is a plane wall extending upwardly along the direction of the airflow, at least part of the airflow entering the first section 101 can flow not only from bottom to top but also from outside to inside under the guidance of the inner wall 11a of the first shell 11, that is, at least part of the airflow under the guidance of the inner wall 11a of the first shell 11 has not only the kinetic energy of the movement trend flowing from bottom to top but also the kinetic energy of the movement trend flowing from outside to inside; secondly, the inner wall 11a of the first shell 11 is a plane wall, which is easy to form a steady flow; In addition, since the inner side wall 13a of the intermediate transition shell 13 is an arc wall, the inner side wall 11a of the first shell 11 and the inner side wall 12a of the second shell 12 are smoothly transitioned and connected through the inner side wall 13a of the intermediate transition shell 13, so that on the flow path from the first section 101 to the middle section 103, at least part of the gas can smoothly enter the second section 102 from the first section 101 under the guidance of the inner side wall 13a of the intermediate transition shell 13, effectively improving the undesirable phenomenon of a large number of vortices formed in the middle section 103. Because the inner side wall of the upper shell 1 has the above-mentioned structural improvement, the external airflow can enter the air passage 10 relatively more, so that more airflow can be added to the cabinet cavity 3, reducing the formation of a large number of vortices near the air outlet 15.

[0052] The structure of the inner side wall 12a of the second shell portion 12 can be various, and can be selected from the following three technical solutions according to actual needs: The first technical solution of the second shell portion 12: Figure 4As shown, the height position of the edge 22 of the support platform 2 is lower than the height position of the second shell part 12, and the inner side wall 12a of the second shell part 12 extends downward along the airflow direction, so as to force at least part of the airflow entering the second section 102 to flow from top to bottom and then pass through the air outlet 15 and dive onto the support platform 2. In this way, the amount of airflow blown out from the air outlet 15 and diving from top to bottom and the impact force of the airflow can be relatively increased. The diving airflow can relatively strongly flush and clean the harmful gas deposited on the surface of the support platform 2, and use the board surface guide effect of the support platform 2 to push the harmful gas toward the inner direction of the cabinet cavity 3 and away from the lower air replenisher. Furthermore, the rebound effect of the surface of the support platform 2 on the airflow can also be used to expand the flow range of the airflow, and the harmful gas that is scattered within a certain height range from the surface of the support platform 2 is pushed toward the inner direction of the cabinet cavity 3. It can be seen that the structure of the inner side wall 12a of the second shell 12 extending downward along the airflow direction effectively and with a very simple structure optimizes the fume hood's ability to capture harmful gases and reduces the amount of harmful gases leaking outward. Furthermore, a water-blocking boss 21 extending along the direction x is provided on the support platform 2, and a reference line A extending along the inclined direction of the inner side wall 12a of the second shell 12 enters the inner space of the water-blocking boss 21. In this way, under the guidance of the inner side wall 12a of the second shell 12, at least part of the airflow in the air passage 10 can pass over the water-blocking boss 21 in a downward dive manner to enter the inner space of the water-blocking boss 21 to flush and push the harmful gases deposited on the surface of the support platform 2. In addition, the water-blocking boss 21 can prevent the liquid spilled on the support platform 2 from dripping onto the ground. In order to simplify the processing of the second shell 12 and optimize the smoothness of the airflow in the air passage 10, the inner side wall 12a of the second shell 12 is a plane wall. This is more conducive to strengthening the impact of the dive airflow and further improving the fume hood's ability to capture harmful gases.

[0053] The other two technical solutions of the second shell 12 are: the inner side wall 12a of the second shell 12 extends upward along the direction of the airflow so that the airflow blown out from the air outlet 15 can be blown from bottom to top. In this way, even if the water blocking boss 21 is higher than the inner side wall 12a of the second shell 12, the airflow blown out from the air passage 10 can still enter the vicinity of the surface of the support platform 2 under the guidance of the inner side wall 12a of the second shell 12. Alternatively, the inner side wall 12a of the second shell 12 extends horizontally, so that the airflow blown out from the air outlet 15 can be blown horizontally.

[0054] like Figure 4As shown, the outer side wall 12b of the second shell 12 is a plane wall extending in an oblique downward direction along the airflow direction. In this way, part of the external air dives from top to bottom onto the support platform 2 under the guidance of the outer side wall 12b of the second shell 12 to form a second airflow, which can then merge with the airflow blown out from the air outlet 15 and swooping down onto the support platform 2 to coordinately push the harmful gas deposited on the surface of the support platform 2, thereby enhancing the cleaning ability of the harmful gas deposited on the surface of the support platform 2. Moreover, the outer side wall 12b of the second shell 12 is a plane wall, which is more conducive to strengthening the impact force of the second airflow and further improving the fume hood's ability to capture harmful gases. In addition, the outer side wall 11b of the first shell 11 is a plane wall extending in an oblique upward direction along the airflow direction, and the outer side wall 13b of the intermediate transition shell 13 is an arc wall, and the outer side wall 11b of the first shell 11 and the outer side wall 12b of the second shell 12 are smoothly transitioned and connected through the outer side wall 13b of the intermediate transition shell 13. In this way, part of the external air is blown from bottom to top under the guidance of the outer wall 11b of the first shell 11, so that the harmful gas floating at a certain height from the surface of the support platform 2 can be pushed forward away from the lower air replenishment device. Accordingly, under the guidance of the outer wall of the upper shell 1, the external air flow can be divided into tributaries flowing upward and downward, increasing the cleaning range of the air flow for harmful gases. In this embodiment, in order to simplify the structure and manufacturing process of the upper shell 1, the upper shell 1 can be made of a thin plate.

[0055] like Figure 4 As shown, the upper shell 1 covers at least a portion of the edge 22 of the support platform 2, and the support platform 2 becomes at least a portion of the lower wall of the air passage 10. This simplifies the lower air supply structure of the fume hood. The upper shell 1 also includes a tail plate 16 connected to the lower end of the first shell 11, and the tail plate 16 extends vertically in the up and down directions. An air inlet 14 of the air passage 10 is formed between the tail plate 16 and the edge 22 of the support platform 2, and the air inlet 14 is connected to the external space of the cabinet cavity 3. According to the above technical solution, the air inlet 14 is arranged downward, and when the experimenter stands beside the lower air supply device for experiment, the air inlet 14 will not be easily blocked by the experimenter's body to destroy the air supply effect.

[0056] In order to reduce the formation of eddy currents in the wind passage 10, Fig. 9As shown, the lower air supply device further includes an air guide vane 17 extending along the flow path of the supply air, and the air guide vane 17 is arranged in the air passage 10. In this way, the air flow in the air passage 10 is guided by the air guide vane 17 to reduce the generation of vortex. It also includes a wing connector 171, one end of which is connected to the air guide vane 17, and the other end is connected to the upper shell 1. The wing connector 171 and the air guide vane 17 can be a split structure or an integrated structure.

[0057] like Figure 1 , Figure 8 and Fig. 9 As shown, the lower air supply device is arranged at the door threshold position of the operating window 30 (the door threshold position of the operating window 30 refers to the bottom position of the operating window 30), and the front and rear ends of the air outlet 15 of the lower air supply device are respectively close to the left cavity side wall 31 and the right cavity side wall 32 of the cabinet inner cavity 3. The air outlet 15 includes a front end air outlet expansion port 151, a rear end air outlet expansion port 152 and a middle air outlet narrowing port 153 located therebetween, and the height H2 of the front end air outlet expansion port 151 relative to the support platform 2 and the height H3 of the rear end air outlet expansion port 152 relative to the support platform 2 are respectively greater than the height H4 of the middle air outlet narrowing port 153 relative to the support platform 2. In the direction x, the width W1 of the front end air outlet expansion port 151 and the width W2 of the rear end air outlet expansion port 152 are smaller than the width W3 of the middle air outlet narrowing port 153. In this way, within the unit length range in the direction x, the amount of air blown out from the front end air outlet expansion port 151 and the rear end air outlet expansion port 152 is greater than the amount of air blown out from the middle air outlet narrowing port 153, so that the strong airflow on both sides is used to regulate the airflow in the middle area, so that the airflow blown out from the air outlet 15 flows smoothly and concentratedly as a whole, effectively improving the airflow's ability to capture and clean harmful gases in the vicinity of the surface of the support platform 2. In addition, the airflow blown out from the front end air outlet expansion port 151 and the rear end air outlet expansion port 152 has a larger flow range in the up and down directions and a relatively larger flow rate than the middle air outlet narrowing port 153, so that the heavy molecular gases corresponding to the front and rear ends of the air outlet 15 that are located at the corners on both sides of the cabinet cavity 3 can be blown away more quickly. The head end wind outlet expansion port 151 and the tail end wind outlet expansion port 152 can provide appropriate air volume for the gradually expanding wind opening 71 and the gradually expanding wind opening 71a respectively, so as to help maintain a uniform surface wind speed.

[0058] Secondly, in the process of supplying air through the operation window 30 of the fume hood, the relevant technical standards generally require that the operation window 30 has a uniform and stable surface wind speed (about 0.5 m / s). Since the middle air outlet narrowing port 153 roughly corresponds to the central area of ​​the operation window 30, and the central area of ​​the operation window 30 itself has the largest air supply volume, and the head end air outlet expansion port 151 and the tail end air outlet expansion port 152 roughly correspond to the left and right sides of the operation window 30, the air supply volume of the left and right sides relative to the central area of ​​the operation window 30 is relatively small. In the above-mentioned layout structure, it is possible to further utilize the characteristics that the height of the head end air outlet expansion port 151 and the tail end air outlet expansion port 152 relative to the support platform 2 is respectively greater than the height of the middle air outlet narrowing port 153 relative to the support platform 2, to make up for the problem that the left and right sides of the operation window 30 are relatively insufficient in air supply and the central area of ​​the operation window 30 is excessive in air supply, which greatly improves the uniformity and stability of the surface wind speed of the operation window 30.

[0059] The front and rear ends of the upper shell 1 are respectively close to the left cavity side wall 31 and the right cavity side wall 32 of the cabinet inner cavity 3. The lower air supply device also includes a plug 18 arranged at the front end of the upper shell 1 and a plug 18a arranged at the rear end of the upper shell 1. The plug 18a has a similar structure to the plug 18. The plug 18 is used as an example for introduction below. The plug 18 includes a plug body 181 for blocking the end of the air passage 10 and a plug connection part 182 for fixing the plug body 181 to the upper shell 1. The screw passes through the plug body 181 of the plug 18 to fix the plug 18 to the left cavity side wall 31, and the screw passes through the plug body of the plug 18a to fix the plug 18a to the right cavity side wall 32. In this way, the plug 18 and the plug 18a can not only block the end of the air passage 10, but also be used to fix the lower air supply device. In addition, a movable cabinet door 4 is provided on the operating window 30, and the upper shell 1 can limit the lowest limit position of the cabinet door 4, that is, the cabinet door 4 can be pressed against the upper shell 1 when it falls. In this way, when the cabinet door 4 completely closes the operating window 30, the air outside the cabinet cavity 3 can still be guided to the nearby area on the surface of the support platform 2 through the air passage 10. In another embodiment, the air passage 10 of the present invention can also be applied to a structure in which a blower is installed at its inlet or a pipe connected to its inlet, and the lower air supply device can also be directly connected to the support platform 2.

Claims

1. A side-through ventilation hood, comprising a test support platform, a hood cavity arranged above the support platform, and a cavity wall body configured to form the hood cavity, wherein the cavity wall body comprises a left cavity side wall, a right cavity side wall, and a cavity back wall arranged between the left cavity side wall and the right cavity side wall; characterized in that: It also includes a first guide back plate arranged above the support platform and close to the support platform, the first guide back plate is located in front of the cavity back wall and there is a distance between them to form a first exhaust duct, the left and right side edges of the first guide back plate extend in the left and right directions respectively close to the left cavity side wall and the right cavity side wall, wherein the two side edges of the first guide back plate located in the lower area of ​​the cabinet cavity and the left cavity side wall and the right cavity side wall respectively have gradually expanding air openings to form a side air-passing structure, and the gradually expanding air openings are in a geometric shape that gradually increases from the upper part to the lower part; There is a bottom spacing between the first guide back plate and the support platform for air to pass through; upper side gaps with uniform gap width are formed between the two sides of the upper area of ​​the first guide back plate and the left cavity side wall and the right cavity side wall, and the upper side gaps are located above the gradually expanding air passing opening, and the gap width of the upper side gaps is smaller than the gap height of the bottom spacing; The gradually enlarged air passage opening extends downward through the bottom end surface of the first air guide back plate to be combined with the bottom spacing; It also includes a second guide back plate, the first guide back plate and the second guide back plate are separately arranged, the second guide back plate is located above the first guide back plate and arranged close to the first guide back plate, the second guide back plate is located in front of the cavity back wall and there is a distance between them to form a second exhaust duct; The cavity wall body also includes a cavity top wall arranged between the left cavity side wall and the right cavity side wall, and a total air outlet is also arranged on the cavity top wall; and also includes a third air guide back plate located above the second air guide back plate, the third air guide back plate is located in front of the cavity back wall and there is a spacing between them to form a third air outlet, the lower end of the third air guide back plate is connected to the upper part of the second air guide back plate, and the third air guide back plate is arranged below the total air outlet in an inclined upward structure, and the first air outlet, the second air outlet and the third air outlet are connected front and back to form an exhaust passage leading to the total air outlet; When the fume hood is configured with an intake airflow as the control airflow and a gradually increasing air pressure gradient from bottom to top is formed in the inner cavity of the hood, there will be a certain intake speed gradient between the highest and lowest points of the gradually expanding air opening. The shape change of the gradually expanding air opening, that is, a geometric shape that gradually increases from the top to the bottom, is beneficial to forming a basically uniform intake volume on the gradually expanding air opening, thereby optimizing the distribution state of the airflow field in the left and right corners of the lower area of ​​the inner cavity of the hood, and further reducing the generation of vortices.

2. The side-through ventilation hood according to claim 1, characterized in that: On the first air guide back plate, only a lower air guide passage extending left and right is arranged on the plate body located in the lower area of ​​the cabinet inner cavity.

3. The side-through ventilation hood according to claim 2, characterized in that: The wind passing area of ​​the lower wind guiding passage is not greater than the wind passing area of ​​the bottom spacing.

4. The side-through ventilation hood according to claim 2, characterized in that: The lower air guide passage includes at least three first sub-passages, the at least three first sub-passages are arranged left and right, and each of the first sub-passages is in the shape of a long strip extending in the left-right direction.

5. The side-through ventilation hood according to any one of claims 1 to 4, characterized in that: The two side edges of the first guide back plate located in the lower area of ​​the cabinet cavity are inclined and narrowed towards each other, and the left cavity side wall and the right cavity side wall are upright; or, the lower area of ​​the left and right cavity side walls is gradually concave outward from top to bottom, and the two side edges of the first guide back plate located in the lower area of ​​the cabinet cavity are upright.

6. The side-through ventilation hood according to claim 2 or 4, characterized in that: It also includes a middle air guide aisle extending left and right, and the middle air guide aisle is composed of the inter-plate spacing between the first guide back plate and the second guide back plate. In the up and down directions, the middle air guide aisle is located in the central area of ​​the cabinet cavity, the wind flow area of ​​the lower air guide aisle is not larger than the wind flow area of ​​the bottom spacing, and the wind flow area of ​​the middle air guide aisle is smaller than the wind flow area of ​​the lower air guide aisle.

7. The side-through ventilation hood according to claim 6, characterized in that: A joint seam is provided between the second guide back plate and the third guide back plate, and a wind passing area of ​​the joint seam is not larger than a wind passing area of ​​the inter-plate spacing. No wind hole slots are provided on the second guide back plate or the third guide back plate.

8. The side-through fume hood according to any one of claims 1 to 4, characterized in that: A fixing seat is arranged between the first guide back plate and the cavity back wall, the fixing seat is U-shaped, and includes a top support wall and left and right support walls arranged on the left and right sides of the top support wall, an interlayer cavity is formed between the top support wall and the left and right support walls, a connecting column is arranged on the top support wall, and the tail of the connecting column extends into the interlayer cavity; the first guide back plate is pressed against the top support wall, and a fastener passes through the first guide back plate and is connected to the connecting column to fix the first guide back plate to the fixing seat.

9. The side-through ventilation hood according to any one of claims 1 to 4, characterized in that: It also includes an operation window constructed opposite to the back wall of the cavity, the operation window extending left and right along the support platform, the operation window is used to form an entry and exit channel for conducting experiments on the support platform; a lower air supply device is arranged at the door sill position of the operation window, the lower air supply device includes an air passage that can circulate supply air, the air passage is used to supply air from the outside of the cabinet cavity to the nearby area on the support platform surface, the air outlet of the air passage extends along the edge direction x of the support platform and the head and tail ends are respectively close to the left cavity side wall and the right cavity side wall of the cabinet cavity, the air outlet includes a head end air outlet expansion port, a tail end air outlet expansion port and a middle air outlet narrowing port located therebetween, the heights of the head end air outlet expansion port and the tail end air outlet expansion port relative to the support platform are respectively greater than the height of the middle air outlet narrowing port relative to the support platform.

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