fume hood

Abstract

To improve the containment performance of the fume hood. [Solution] The fume hood comprises a generally box-shaped fume hood body in which a working chamber is defined, and a baffle plate provided at the front of the rear of the fume hood body. The fume hood body has left and right support columns connected to the front ends of its left and right sides. In a horizontal cross-section, each support column protrudes from a vertical plane including the corresponding side of the body toward the opposite support column, and each support column has a front inclined surface that is inclined such that the distance from the vertical plane gradually increases toward the rear, and a rear inclined surface that is inclined such that the distance from the vertical plane gradually decreases toward the rear.

Description

Technical Field

[0001] The present invention mainly relates to a draft chamber for installation and use in laboratories and research rooms such as those in research institutions and educational institutions.

Background Art

[0002] When performing operations such as chemical experiments, a local exhaust device is used to prevent harmful atmospheres such as toxic gases and odors generated incidentally to the operation from diffusing into the surrounding environment. One type of local exhaust device is called a "draft chamber".

[0003] The working chamber of the draft chamber is sucked by an exhaust fan and maintained at a negative pressure. There is a movable sash in the front of the draft chamber. When the sash is opened, the air in the laboratory flows into the working chamber from the sash opening surface due to the pressure difference, and then is sucked from the working chamber into the exhaust duct and finally discharged into the outdoor atmosphere. Since such an air flow is formed, the harmful atmosphere in the working chamber does not flow out into the room such as the laboratory where the draft chamber is installed, and the safety of the operator is ensured.

[0004] An example of a draft chamber is disclosed in Patent Document 1. In the draft chamber of Patent Document 1, the surfaces of the columns defining both left and right ends of the opening surface are inclined. Due to this inclination, the distance between the surfaces of the columns becomes smaller as it approaches the working space. This enables the air in the laboratory to smoothly flow into the working space and helps to ensure good containment performance. However, there is room for further improvement in the type of columns of Patent Document 1.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] This invention provides a technology that can further enhance the containment performance of a fume hood. [Means for solving the problem]

[0007] According to one embodiment of the present invention, a generally box-shaped fume hood is provided, having a left side, a right side, and a rear, with an opening at the front and a working chamber defined inside; and a baffle plate provided in front of the rear, wherein an exhaust passage for discharging the atmosphere inside the working chamber to the outside is formed between the baffle plate and the rear. The fume hood has a left support and a right support connected to the front ends of the left side and the right side, respectively, and defining the left and right ends of the opening, respectively. In a horizontal cross-section, each support protrudes from a vertical plane including the corresponding side toward the opposite support, and in a horizontal cross-section, each support has a front inclined surface that is inclined such that the distance from the vertical plane gradually increases toward the rear, and a rear inclined surface that is inclined such that the distance from the vertical plane gradually decreases toward the rear. [Effects of the Invention]

[0008] According to the above embodiment of the present invention, the cross-sectional shape of the support column and its connection and positional relationship with the side surface make it possible to prevent the formation of a harmful boundary layer that adversely affects containment performance in the area near the support column and the area near the side surface of the support column.

[0009] Further features and advantages of the present invention are described in the dependent claims and "Modes for Carrying Out the Invention". [Brief explanation of the drawing]

[0010] [Figure 1]This is a perspective view showing the external appearance of a fume hood according to one embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view of the fume hood shown in Figure 1, taken by cutting it along a vertical plane (YZ plane) extending in the front-to-back direction at its center in the left-to-right direction (X direction), and viewed in the positive X direction. [Figure 3] Figure 1 is a perspective view showing the appearance of the baffle plate installed in the fume hood. [Figure 4] Figure 1 shows a cross-sectional view of the right-side support column of the fume hood and its surrounding components (sash, side panel) as seen in the negative Z direction, after cutting through a horizontal plane (XY plane) extending in the front-to-back direction. [Figure 5] Figure 1 is a schematic longitudinal cross-sectional view comparing the airflow near the work surface around the opening of the fume hood with and without the auxiliary air discharge section. [Figure 6] Figure 1 is a schematic cross-sectional view showing the airflow near the support column near the opening of the fume hood, in comparison with a comparative example. [Modes for carrying out the invention]

[0011] A draft chamber 1 according to one embodiment of the present invention will be described below with reference to the attached drawings. To facilitate understanding the directional relationships between the drawings, an XYZ Cartesian coordinate system has been established, and coordinate axes are indicated in each drawing. The X direction is the left-right direction, the Y direction is the front-back direction, and the Z direction is the up-down direction.

[0012] As shown in Figures 1 and 2, the fume hood 1 has a base 7 and a generally box-shaped fume hood body 10 (hereinafter simply referred to as "body 10" for simplicity) mounted on the base 7. The body 10 has a bottom surface (bottom panel) 12 which serves as a work surface, left and right sides (side panels) 14 (14L, 14R), a back (back panel) 16, a top surface (ceiling panel) 18 (not visible in Figure 1), and a front surface 20. The bottom surface 12, left and right sides 14 (14L, 14R), back surface 16, top surface 18, and front surface 20 define a generally box-shaped (rectangular) internal space. The front surface 20 consists of a fixed transparent panel 22 and a sash 24 that can move in the vertical direction.

[0013] A baffle plate 26 is provided inside the main unit 10. The baffle plate 26 has a lower part 26L that extends vertically slightly in front of the rear surface 16, and an upper part 26U that extends diagonally forward and upward from the lower part 26L. An exhaust passage 28 is formed between the lower part 26L of the baffle plate 26 and the rear surface 16, and between the upper part 26U and the ceiling surface 18.

[0014] The space enclosed by the bottom surface 12, the pair of left and right side surfaces 14, the front of the ceiling surface 18, and the baffle plate 26 can be used as a workspace 4.

[0015] The exhaust passage 28 is drawn in by an exhaust fan 32 via an exhaust duct 30 installed on the ceiling surface 18. The exhaust fan 32 may be part of the fume hood 1, or it may be installed in the building in which the fume hood 1 is installed.

[0016] As shown in Figure 3, numerous slits 34 are formed in the lower part 26L of the baffle plate 26. As shown in Figure 2, a gap 36 extending continuously in the left-right direction is formed between the lower end of the lower part 26L of the baffle plate 26 and the bottom surface 12. A gap 38 extending continuously in the left-right direction is formed between the upper front end of the upper part 26U of the baffle plate 26 and the ceiling surface 18.

[0017] At the front end of each side surface 14, columns 40 (40L, 40R) extending in the vertical direction are connected. Each column 40 is provided with a guide structure 42 for guiding the vertical movement of the sash 24. The guide structure 42 consists of a groove 42G extending in the vertical direction provided in the column 40. In the grooves 42G of the left and right columns 40, the left and right ends of the sash 24 or the protrusions protruding from the left and right ends are slidably inserted respectively.

[0018] The left and right columns 40, the lower edge of the fixed transparent panel 22, and the front edge of the bottom surface 12 define the opening 6 in the front surface of the work chamber 4. The opening width of the opening 6 is determined according to the vertical position of the sash 24. When the sash 24 is lowered to the lower limit position, the height direction width of the opening 6 is, for example, about 50 mm.

[0019] When the exhaust fan 32 is operated with the opening 6 appropriately opened, the inside of the exhaust passage 28 is exhausted to become negative pressure. Along with this, the air in the work chamber 4 flows into the exhaust passage 28 through the slit 34 (FIG. 3) of the baffle plate 26 and the gaps 36, 38 (FIG. 2) at the ends, and is exhausted from there through the exhaust duct 30 and the exhaust fan 32. The air in the laboratory (the room where the draft chamber 1 is installed) flows into the work chamber 4, which has become negative pressure due to this exhaust, through the opening 6. In FIG. 2, the air flow at this time is indicated by arrows.

[0020] As shown in FIG. 3, the plurality of slits 34 formed in the vertical portion, i.e., the lower portion 26L, of the baffle plate 26 are arranged according to a predetermined pattern. These plurality of slits 34 are provided over the entire area in the lateral direction of the baffle plate 26 in the lower side portion 26A of the lower portion 26L, which is the area between the lower end 26B of the lower portion 26L and a predetermined height position 26H. The above-mentioned "predetermined height position 26H" is a height position higher than the height position of the lower edge of the sash 24 at the height position during the experimental operation of the sash 24 (for example, a height position such that the height direction width of the opening 6 is within the range of 300 to 500 mm, and more specifically, a height position such that it is 400 mm). By doing so, it becomes possible to realize a clean and uniform airflow velocity distribution within the opening 6. In the illustrated embodiment, it has become possible to realize a clean and uniform flow such as within ±20% of the average wind speed on the capture surface.

[0021] FIG. 4 depicts a cross-section of the right support column 40R(40) and its peripheral components (the right side surface 14R(14) and the sash 24) at the substantially central portion of the opening 6 in the height direction, cut by a horizontal plane. The support column 40R protrudes into the opening 6 from the vertical plane (a plane parallel to the YZ plane) including the right side surface 14R towards the opposite support column 40L, that is, towards the left.

[0022] The right support column 40R has a front inclined surface 44, a rear inclined surface 46, and a central surface 48. The central surface 48 is a vertical surface substantially parallel to the YZ plane. As seen in the horizontal cross-section of FIG. 4, the central surface 48 extends in the front-rear direction (Y direction). The groove 四十二G described above for guiding the vertical movement of the sash 24 is provided on the central surface 48.

[0023] As seen in the horizontal cross-section of FIG. 4, the front inclined surface 44 is inclined such that the distance from the plane including the side surface 14R(14) gradually increases as it goes rearward. The angle α formed by the front inclined surface 44 with respect to the central surface 48 can be 30 to 60 degrees. The angle α is preferably 40 to 50 degrees.

[0024] In the horizontal cross-section of Figure 4, the rear inclined surface 46 is inclined such that the distance from the plane containing the side surface 14R(14) gradually decreases as it moves towards the rear. The angle β that the rear inclined surface 46 makes with respect to the central surface 48 can be 30 to 60 degrees. The angle β is preferably 40 to 50 degrees.

[0025] The cross-sectional shape of the left support column 40L can be substantially mirror-symmetrical to the cross-sectional shape of the right support column 40R, although the cross-sectional shapes may differ slightly.

[0026] As indicated by the arrows in Figures 2 and 5, when air flows from the space inside the laboratory into the workroom 4, a boundary layer BL with reduced air velocity is formed near the bottom surface 12 and side surface 14 due to the resistance the air receives from these surfaces 12 and 14 (see Figure 5(A)). This can lead to air stagnation, and in some cases backflow, near these surfaces 12 and 14, potentially resulting in a decrease in containment performance.

[0027] To solve the above-mentioned problems near the bottom surface 12, an auxiliary air discharge section (gas discharge section) 50 is provided at the front end of the bottom surface 12, as shown in Figures 2 and 5(B), which discharges auxiliary air (gas) at a relatively small flow rate towards the rear along the bottom surface 12. Here, the most common gas discharged is air, so the name "auxiliary air" is used, but any gas other than air, such as nitrogen, may be discharged from the auxiliary air discharge section 50. The flow of the auxiliary air (gas) is shown by arrow 50F in Figures 2 and 5(B). The auxiliary air discharge section 50 can be composed of an elongated auxiliary air discharge nozzle that extends over the entire left-right direction of the front end of the bottom surface 12 and has a plurality of auxiliary air discharge ports spaced apart in the left-right direction (X direction). Although not shown in detail, air is supplied to the auxiliary air discharge section 50 from an air supply fan located below the bottom surface 12 via an air supply pipe, thereby discharging auxiliary air along the bottom surface 12 with a generally uniform air velocity distribution in the left-right direction. This prevents air from stagnating or backflowing near the bottom surface 12. This configuration is publicly known and is widely used in the applicant's products under the trademark "Support Air". Figure 5 schematically shows the air velocity distribution with and without auxiliary air, with (A) showing the case without auxiliary air and (B) showing the case with auxiliary air.

[0028] The above-mentioned problem near the side surface 14 is solved by using a support column 40 having the cross-sectional shape shown in Figure 4. This will be explained using Figure 6. Figure 6(A) is one embodiment of the present invention in which the support column 40 has a rear inclined surface 46. Figure 6(B) is a comparative example in which the support column does not have a portion corresponding to the rear inclined surface, and the portion corresponding to the central surface 48 in the embodiment and the side surface corresponding to the side surface 14R are generally flush.

[0029] In the comparative example shown in Figure 6(B), friction between the air flowing into the work chamber and the side wall creates a boundary layer BL with reduced air velocity near the side wall. Because the side wall is long (roughly corresponding to the depth of the work chamber), the boundary layer may develop and peel off as it goes further into the side wall. This may cause air stagnation or backflow near the wall, which in turn may reduce containment performance.

[0030] In the embodiment shown in Figure 6(A), the air flowing into the working chamber 4 experiences frictional force from the central surface 48 of the support column 40 as it flows near the central surface 48. However, because the length of the central surface 48 is short, the boundary layer does not develop excessively, and sufficient containment performance can be ensured. Furthermore, since a rear inclined surface 46 is provided following the central surface 48, it is possible to suppress the formation of vortices near the rear end of the central surface 48 as the airflow leaves the central surface 48. This also contributes to improving containment performance.

[0031] In the comparative example described above, the decrease in containment performance due to the formation of an air boundary layer BL near the side wall can also be addressed by providing an auxiliary air discharge unit (its configuration may be the same as the auxiliary air discharge unit 50 shown in Figure 4) along the support column 40 to discharge air along the wall. However, providing auxiliary air discharge units on both the left and right support columns is relatively costly. Therefore, it is more advantageous to address the issue by changing the shape of the support column 40, as in the embodiment.

[0032] As can be seen by comparing Figures 6(A) and (B), a secondary effect of providing the rear inclined surface 46 is that the width of the work chamber 4 in the left-right direction can be increased behind the support column 40 compared to the conventional example. Appropriate equipment can be installed in this expanded additional space. Examples of appropriate equipment include a supply unit (such as a faucet) for supplying an appropriate liquid (e.g., water) and a collection unit (such as a pan) for collecting the liquid that drips from it. The additional space may also be used simply to expand the work chamber 4.

[0033] A user interface for operating the fume hood 1 can be provided on the front inclined surface 44 of the support column 40. As the user interface, an operating switch 61 or an operating handle 62 can be provided, as schematically shown in Figure 1. The operating switch 61 can be used, for example, to turn the working room lighting on and off, or to adjust the rotation speed of the exhaust fan 32. A nozzle 63 for discharging fluid used in experiments conducted in the working room 4 can be provided on the rear inclined surface 46 of the support column 40. The operating handle 62 may be configured to control the discharge of fluid from the nozzle 63.

[0034] As can be understood from the flow control mechanism described above, it is undesirable to form irregularities on the central surface 48 that would disrupt the flow. In the illustrated embodiment, only the groove 42G for guiding the sash 24 is formed on the central surface 48, and the area of ​​the central surface 48 other than the groove 42G is substantially smooth (flat).

[0035] According to the above embodiment, the containment performance of the fume hood 1 can be improved.

[0036] The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the scope and spirit of the claims. [Explanation of symbols]

[0037] 1. Fume hood 4. Workshop 6 openings 10. Fume hood body 14L,14R side 16 Back 24 Sash 26 Baffle Plate 40 pillars 42 Guide Structure 44 Front slope 46 Rear slope 48 Central plane

Claims

1. A generally box-shaped fume hood body having a left side, a right side, and a back, with an opening at the front and a defined working chamber inside, A baffle plate provided in front of the rear surface, wherein an exhaust passage for discharging the atmosphere inside the work chamber to the outside is formed between the baffle plate and the rear surface, Equipped with, The fume hood body has a left support column and a right support column that are connected to the front ends of the left and right sides, respectively, and define the left and right ends of the opening, respectively. Viewed in a horizontal cross-section, each of the support columns protrudes from the vertical plane including the corresponding side surface toward the opposite support column. A fume hood, wherein, in a horizontal cross-section, each support column has a front inclined surface that is inclined such that the distance from the vertical plane gradually increases as it moves backward, and a rear inclined surface that is inclined such that the distance from the vertical plane gradually decreases as it moves backward.

2. The system further includes a movable sash that moves vertically to open and close the opening, Viewed in a horizontal cross-section, each of the support columns further has a central surface provided between the front inclined surface and the rear inclined surface, The draft chamber according to claim 1, wherein a guide structure for guiding the sash in the vertical direction is provided on the central surface of each of the support columns.

3. The fume hood according to claim 2, wherein the central surface of each of the support columns is parallel to a vertical plane including the corresponding side surface.

4. The fume hood according to claim 1, wherein a user interface for operating the fume hood is provided on the front inclined surface of the support column.

5. The fume hood according to claim 4, wherein the user interface includes an operating switch or an operating handle.

6. The draft chamber according to claim 5, wherein the user interface includes the operating handle, a nozzle for discharging fluid is provided on the rear inclined surface of the support column, and the discharge of fluid from the nozzle is controlled by the operating handle.

7. The draft chamber according to claim 1, wherein the baffle plate has a vertical portion extending in the vertical direction, and a plurality of slits are formed in the vertical portion according to a predetermined pattern, and air in the working chamber flows into the exhaust passage through the plurality of slits, and the plurality of slits are provided over the entire area of ​​the baffle plate in the left-right direction in the lower portion from the lower end of the vertical portion to at least a predetermined height position, and the predetermined height position is a height position higher than the height position of the lower edge of the sash at the height position during experimental work of the sash.

8. The fume hood according to claim 7, which does not have a gas discharge section that discharges gas from the vicinity of the support column of the opening in a direction along the side surface.

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