JPH0220040Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a draft chamber that can freely adjust the amount of air sucked into a processing chamber to obtain an optimum inflow air velocity (controlled air velocity).

(Prior Art and its Problems) From the viewpoint of safety, draft chambers are required by law to meet certain safety standards regarding the speed of inflowing air through the front opening. In other words, in order to ensure that harmful and toxic gases generated inside the processing chamber are properly exhausted outside without leaking into the laboratory, the front opening of the processing chamber is Regardless, it is necessary that air always flows into the processing chamber at a constant wind speed or higher. For this reason, conventional draft chambers use exhaust fans with a large exhaust capacity so as to satisfy this standard even when the front door is fully open. Therefore, when using the front door with a small opening, the wind speed of the air flowing into the processing chamber from the door opening becomes extremely high, disturbing the airflow in the processing chamber, and especially causing flames in burners etc. This may have an undesirable effect on the experiment in which it is used.

Taking this into consideration, a draft chamber has also been proposed in which the rotational speed of the exhaust fan is controlled according to the amount of opening and closing of the front door to obtain a constant inflow air speed. Since it is necessary to control the rotation speed of the exhaust fan for each draft chamber, it cannot be used in a centralized exhaust control system using multiple draft chambers, and it also has the drawback of requiring complicated motor control. In addition, in the case of a draft chamber in which air is supplied by shielding the front opening with an air curtain, changing the rotation speed of the exhaust fan will disrupt the balance between the exhaust volume and the supply air volume, causing the inside of the laboratory to has a negative effect on air conditioning (heating and cooling, etc.). In other words, when the ratio of exhaust volume to supply air volume is maintained at a constant ratio of 10:8 to 10:7, the influence of the draft chamber on indoor air conditioning is minimized, and it is most desirable from an energy saving perspective. If the rotation speed of the exhaust fan is changed, this balance will be lost. The above balance can be maintained by changing the rotation speed of the air supply fan at the same time as the rotation speed of the exhaust fan, but as the rotation speed of the air supply fan decreases, the airflow in the air curtain becomes weaker. As a result, much of the supplied air flows into the room, disrupting the air conditioning in the room.

(Purpose of the invention) Therefore, the main purpose of the invention is to provide a draft chamber that can obtain a desired inflow air velocity without changing the rotational speed of the exhaust fan. Another object of this invention is to provide a draft chamber that can always achieve an optimum inlet air velocity without adversely affecting indoor air conditioning.

(Structure of the invention) In order to achieve the above object, the draft chamber according to the invention is provided with a bypass ventilation passage having an inlet communicating with the outside of the processing chamber and an outlet communicating with the exhaust means, and a By controlling the air volume with the bypass ventilation volume control means, even when the exhaust volume of the exhaust means is fixed,
Regardless of the opening degree of the front door, the desired inflow air velocity can always be obtained.

(Description of Embodiments) FIG. 1A is a front view showing a draft chamber which is an embodiment of this invention, and FIG. 1B is a side sectional explanatory view thereof. As shown in FIG. 1B, this draft chamber includes a processing chamber 2 provided in the main body 1, a front door 3 provided in the front opening of the processing chamber 2 so as to be openable and closable, and an outside of the front door 3. An air supply fan 4, which is two elements constituting an air supply means for generating an air current to form an air curtain along the a first ventilation passage 5 for guiding the gas to a predetermined position; an exhaust fan 6 which is two elements constituting an exhaust means for exhausting gas in the processing chamber 2; and a first ventilation passage 5 for connecting the exhaust fan 6 and the processing chamber 2. 2 ventilation passages 7, a bypass ventilation having an inlet 8a that opens opposite to the outlet of the first ventilation passage 5 so as to receive the airflow of the air curtain outside the processing chamber 2, and an outlet 8b that communicates with the second ventilation passage 7; passage 8, an opening degree sensor 11 as a detection means for detecting the opening degree of the front door 3, and this opening degree sensor 11
It is composed of a damper 9 and a damper control device 10 as bypass ventilation volume control means for controlling the volume of air flowing in the bypass ventilation passage 8 according to the detection output of the main body 1. A front door 12 is provided for shielding from the outside.

Further, as shown in FIG. 1A, a wind speed setting switch 13 is arranged on the front panel portion of the main body 1 for setting a desired inflow wind speed value. Air is supplied to the air supply fan 4 through an air supply duct 4a, and air is exhausted from the exhaust fan 6 through an exhaust duct 6a. These air supply ducts 4
a and the exhaust duct 6a communicate with the outside of the laboratory in which this draft chamber main body 1 is provided.

FIG. 2 is a block diagram showing an example of the damper control device 10, and FIG. 3 is a block diagram of the aperture sensor 1.
FIG. 1 is an explanatory diagram showing an example of the configuration of FIG. As shown in FIG. 2, the damper control device 10 includes a comparison calculation circuit 14 for comparing and calculating the detection output from the opening degree sensor 11 and the set value of the wind speed setting switch 13.
and a damper drive unit 15 for adjusting the rotation angle of the damper 9 based on the output signal of the comparison calculation circuit 14. As the damper drive unit 15, for example, a motor or the like is used. As shown in FIG. 3, the opening degree sensor 11 includes a rack 16 extending along the direction of movement of the front door 3 so as to move with the opening and closing of the front door 3, and a rack 16 arranged so as to mesh with the rack 16 and rotate. 17, a potentiometer 18 for converting the rotation of the pinion 17 into an electric signal, and a reduction gear (not shown) for decelerating the rotation of the pinion 17 and transmitting it to the potentiometer 18. .

Next, the operation will be explained. First, the worker
Before starting the experiment, turn the wind speed setting switch 13
The optimum inflow wind speed value V _S according to the experimental content is determined by
is set, and the air supply fan 4 and exhaust fan 6 are rotated by a switch (not shown). The wind speed setting switch 13 may be, for example, a three-stage selection switch. The ratio of the displacement amount of the exhaust fan 6 and the air supply amount of the air supply fan 4 is:
As mentioned above, from the viewpoint of energy conservation, the ratio is kept constant at 10:8 to 10:7.

Next, the worker opens the front door 12 and the front door 3.
Open the chamber, set the experimental equipment in the processing chamber 2, and start the experiment. During the experiment, the opening condition of the front door 3 was
It is constantly monitored by the aperture sensor 11.
That is, when the front door 3 is opened and closed and the rack 16 moves up and down, the pinion 17 rotates, and this rotation is transmitted to the rotary potentiometer 18 via a reduction gear (not shown).
An electrical signal corresponding to the degree of opening of the front door 3 is derived from this. This electrical signal is transmitted to the opening degree sensor 1
1 is applied to one input of the comparison arithmetic circuit 14 as a detection signal of 1.

On the other hand, the other input of the comparison calculation circuit 14 is given the desired inflow wind speed value V _S set by the wind speed setting switch 13, and the comparison calculation circuit 14
Based on both input signals, a rotation command signal for rotating the damper 9 by a predetermined angle is output. The damper drive unit 15 controls the amount of ventilation in the bypass ventilation passage 8 by rotating the damper 9 by the predetermined angle in response to this rotation command signal, thereby controlling the amount of air in the front door 3.
The wind speed of the air flowing into the processing chamber 2 from the lower opening is maintained at a desired value V _S set by the wind speed setting switch 13 .

Here, the reason why the inflow wind speed value V _S can be maintained constant by rotating the damper 9 will be explained. Now, Q _OUT the displacement of the exhaust fan.
(= constant), the ventilation amount of the third ventilation passage 8 (i.e. the third
Q _A is the amount of exhaust gas exhausted from the ventilation path 8 through the second ventilation path 7, and S is the area of the opening on the lower side of the front door 3.
Then, the amount of exhaust gas exhausted from the processing chamber 2 through the second ventilation path 7 (i.e., the amount of air sucked into the processing chamber 2) Q _B is Q _B = Q _OUT − Q _A ...(1) Therefore, the inflow wind speed value V _S from the opening is expressed by the following equation.

V _S = Q _B /S = (Q _OUT - Q _A )/S ...(2) Now, since Q _OUT = constant, by detecting the opening degree of the front door 3 with the opening degree sensor 11, S
By knowing the change in (proportional to the degree of opening) and adjusting the rotation angle of the damper 9 based on the detected output to change Q _A , it is possible to always maintain the inflow wind speed value V _S constant.

As is clear from the above equation (2), V _S and Q _A have a linear relationship, so as a relatively simple configuration of the comparison calculation circuit 14, for each wind speed setting condition (three stages in the above example), The rotation angle of the damper 9 is predetermined on a one-to-one basis with respect to the opening height of the front door 3, and a signal instructing the predetermined rotation angle is output in accordance with the detection output of the opening degree sensor 11. You can also do this. Note that the same function as described above can also be easily achieved by a mechanical configuration in which the rotation of the pinion 17 is directly associated with the rotation of the damper 9.

Excess air supplied from the air supply fan 4 through the ventilation path 5 as an air curtain is sucked through the inlet 8a of the bypass ventilation path 8 and exhausted. At this time, since the ratio of exhaust volume and air supply volume is 10:8 to 10:7, the air in the laboratory corresponding to the ratio 2 to 3 is in the 1st B.
As shown by the dotted line in the figure, the gas is sucked into the processing chamber 2 and the bypass ventilation path 8 and exhausted.

When continuing the experiment unattended, close the front door 12.
By fully closing the chamber, a more complete air curtain can be formed and further energy savings can be achieved in terms of air conditioning within the laboratory. In this case, for example, as shown in FIG.
9 may be provided, and the air supply fan 4 may be configured to operate only when the frontmost door is fully closed.

In the above embodiment, a draft chamber in which an air curtain is formed by an air supply fan has been described, but this invention can be applied to a draft chamber that does not have an air supply fan (air curtain). can be applied,
In this case as well, the same effects as in the above-mentioned embodiments can be achieved. Furthermore, although the angle of the damper 9 is adjusted according to the degree of opening of the front door 3, it may also be adjusted by actually measuring the inflow wind speed, or the adjustment may also be done manually. good.

(Effects of the invention) As described above, according to this invention, a bypass ventilation path is provided between the outside of the processing chamber and the exhaust fan, and the inflow wind speed is controlled by controlling the amount of ventilation in this bypass ventilation path. Since it is maintained constant, there is no need to change the rotation speed of the exhaust fan to maintain the inflow air speed constant as in the conventional method.
It can also be easily applied to centralized exhaust control when multiple draft chambers are used. In addition, the optimum inflow wind speed can always be obtained according to the experimental content without complicated motor control. Furthermore, if this idea is applied to an air curtain type draft chamber, the inflow air speed can be maintained constant regardless of the opening degree of the front door, while the exhaust volume and air supply volume can always be fixed at the optimal values. Therefore, it is possible to form the most effective air curtain, thus ideally reducing the impact on the air conditioning in the laboratory, and achieving the most desirable draft chamber from the point of view of energy saving. Can be done.

[Brief explanation of the drawing]

Figures 1A and 1B are a front view and a side sectional explanatory view showing a draft chamber as an embodiment of this invention, Figure 2 is a block diagram showing an example of a damper control device, and Figure 3 is an opening degree. FIG. 2 is an explanatory diagram showing an example of the configuration of a sensor. 2...Processing chamber, 3...Front door, 4...Air supply fan, 6...Exhaust fan, 8...Bypass ventilation path,
9...Damper, 10...Damper control device, 11...
...Aperture sensor.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A front door that can be opened and closed at the front opening of the processing chamber, an exhaust means for exhausting the gas in the processing chamber, and a door that communicates with the outside of the pre-treatment chamber. a bypass ventilation passage having an inlet and an outlet communicating with the fore-air exhaust means; and a bypass ventilation volume control means for controlling the volume of air flowing into the bypass ventilation passage to control the speed of inflowing air from the opening. Draft Chiyamba. (2) further comprising air supply means for generating airflow to form an air curtain along the outside of the front door; A draft chamber according to claim 1 of the utility model registration claim, which is open so as to receive the draft chamber. (3) The bypass ventilation amount control means includes a damper provided in the bypass ventilation passage, a detection means for detecting the degree of opening of the front door, and a detection means for controlling the damper in response to a detection output of the detection means. and a damper control means for rotating the draft chamber by a predetermined angle.