JPH0220041Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of the Invention) 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).

(Description of Prior Art) From the standpoint 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 noxious and noxious gases generated inside the processing chamber are properly exhausted outside without escaping 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 speed of 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.

In consideration of this point, a draft chamber has been proposed in which the rotation 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 velocity. Since it is necessary to control the rotation speed of the fan for each draft chamber, it cannot be used in a centralized exhaust control system using multiple draft chambers, and has the drawback of requiring complicated motor control. In addition, in the case of a draft chamber that supplies air by shielding the front opening with an air curtain, changing the rotation speed of the exhaust fan may 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 changing 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.

The draft chamber related to Utility Model Publication No. 47-36855 is
In order to form a complete air curtain even when the opening of the front door is small, a portion of the supplied air is introduced directly into the processing chamber.
In order to maintain the inflow air velocity at the desired value using this method under the condition that the supply and exhaust volumes are constant, as the opening degree of the front door becomes smaller, more supply air is introduced directly into the processing chamber. As a result, the amount of air supplied as the air curtain decreases, resulting in the same problem of turbulence in the air flow of the air curtain as described above. moreover,
By directly introducing a large amount of supply air into the processing chamber, the flow of air within the processing chamber becomes intense, and there is no point in controlling the inflowing wind speed from the front opening.

(Purpose of the invention) Therefore, the main purpose of this invention is to provide a draft chamber that can obtain a desired inflow air velocity without changing the supply/exhaust volume and does not disturb the airflow in the processing chamber. That's true. 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 this invention includes first and second branch paths for branching the air supply from the air supply means and guiding it to the processing chamber and the exhaust means, respectively. are provided, and the air volume branched into these branch paths is controlled by the branch air volume control means, thereby making it possible to always obtain a desired inflow wind speed.

(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 within the main body 1, a front door 3 provided at the front opening of this processing chamber 2 so as to be openable and closable, and an outside of this front door 3. The air supply fan 4, which is two elements constituting the air supply means, generates an air current so as to form an air curtain along the upper side of the front opening of the processing chamber 2. a first ventilation path 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; 8, a bypass damper 9 as a bypass ventilation amount control means for controlling the amount of air flowing in the bypass ventilation path 8, and a bypass damper 9 as a bypass ventilation amount control means for controlling the amount of air flowing in the bypass ventilation path 8; first and second branch passages 10 and 11 for guiding the two ventilation passages 7, respectively; an opening degree sensor 12 for detecting the opening degree of the front door 3;
and first and second dampers 13 and 14 as branch air volume control means for controlling the air volume branched to the first and second branch paths 10 and 11, respectively, according to the detection output of the opening degree sensor 12. It is configured.

Air is supplied to the air supply fan 4 through the air supply duct 4a, and air is exhausted from the exhaust fan 6 through the exhaust duct 6.
Each is carried out through a. These air supply duct 4a and exhaust duct 6a communicate with the outside of the laboratory in which this draft chamber main body 1 is provided.

FIG. 2 is an explanatory diagram showing an example of the configuration of the opening degree sensor 12. As shown in FIG. As shown in FIG. 2, the opening sensor 12 is mounted on a rack 1 extending along the direction of movement of the front door 3 so as to move as the front door 3 opens and closes.
5. A pinion 16 disposed to rotate in mesh with the rack 15; a potentiometer 1 for converting the rotation of the pinion 16 into an electrical signal;
7, and a reduction gear (not shown) for reducing the rotation of the pinion 16 and transmitting the reduced rotation to the potentiometer 17.

Next, the operation will be explained. First, the worker
Before starting the experiment, the air supply fan 4 and the exhaust fan 6 are rotated by a switch (not shown). The ratio of the displacement amount of the exhaust fan 6 to the air supply amount of the air supply fan 4 is maintained at a constant ratio of 10:8 to 10:7 from the viewpoint of energy saving, as described above.

Next, the operator opens the front door 3 and enters the processing chamber 2.
Set the experimental equipment inside and start the experiment. During the experiment, the degree of opening of the front door 3 is constantly monitored by the opening degree sensor 12. That is, front door 3
is opened or closed and the rack 15 moves up and down, the pinion 16 rotates, and this rotation is transmitted to the rotary potentiometer 17 via a reduction gear (not shown), and from this potentiometer 17 the opening degree of the front door 3 is adjusted. A corresponding electrical signal is derived. This electric signal is used as a detection signal of the opening degree sensor 12 to control the rotation angles of the first and second dampers 13 and 14. Regarding the control of this rotation angle,
This will be explained below.

Now, the displacement of exhaust fan 6 is Q _OUT (= constant),
Let the air supply amount Q _IN1 (=constant) of the air supply fan 4 be assumed, and for simplicity, consider an ideal state in which all of Q _IN1 is exhausted through the processing chamber 2 and the bypass ventilation path 8. In this case, if the amount of air supplied from the laboratory room where this draft chamber main body 1 is installed (that is, the amount of air sucked from the laboratory room into the processing chamber 2 and the bypass ventilation path 8) is Q _IN2 , then Q _OUT = Q _IN1 +Q _IN2 …(1) holds true. As mentioned above, Q _OUT :Q _IN1 is 10:
Since it is set to 8 to 10:7, Q _IN2 is a constant value corresponding to a ratio of 2 to 3 (ie, 20 to 30% of Q _OUT ).

A part Q _A of the air supply amount Q _IN1 of the air supply fan 4 is supplied as an air curtain through the first ventilation passage 5, and the other part Q _B is supplied through the first branch passage 10 to the processing chamber 2. The remaining part Q _C is directly introduced into the second
The air is guided to the second ventilation path 7 through the branch path 11 and is directly exhausted. Therefore, the following formula holds.

Q _IN1 = Q _A + Q _B + Q _C …(2) Also, Q _S is the amount of air exhausted from the processing chamber 2 through the second ventilation path 7, and Q S is the amount of air exhausted from the bypass ventilation path 8 through the second ventilation path 7. Letting Q _L be Q _OUT =Q _C +Q _S +Q _L ...(3).

By the way, the processing chamber 2 can be accessed from the front opening of the processing chamber 2.
_{The amount of air drawn into the interior Q ​} −Q _L )/S (5). However, S is the area of the front opening.

Here, consider the case where the front door 3 is fully open, as shown in FIG. 1B. In this case, the opening degree sensor 1
In response to the detection output of 2, the first and second dampers 13 and 14 are actuated by a drive means such as a motor (not shown).
These dampers 13 and 14 are positioned in the illustrated position, that is, in a position where both the first and second branch paths are fully closed. Therefore, Q _B
=O, Q _C =0, so from equation (2), Q _IN1 =Q _A ...(6). In other words, the same amount of air supply Q _IN1 from the outside is blown out as air curtain Q _A. At this time, the inflow wind speed V _S at the front opening is
From equations (5) and (6), _VS = (Q _IN1 + Q _IN2 − Q _L )/S …(7), and further using equation (1), VS = (Q _OUT − Q _L )/S …(8) becomes. As mentioned above, the displacement of the exhaust fan 6
Q _OUT is constant, for example about 33~ at commercial power supply 60Hz.
Assume 35m ³ /min. Further, if the width of the opening of the front door 3 when fully opened is 1.5 m and the height is 0.7 m, the opening area S = 1.05 m ² . Now, if the bypass damper 9 is fully closed and Q _L =0, an inflow wind speed V _S of V _S =33/1.05÷60 = 0.523 m/s can be obtained from equation (8). This inflow wind speed satisfies the standard of 0.4 to 0.5 m/s required by law (for example, Article 16 of the Ordinance on Prevention of Organic Solvent Poisoning, Article 7 of the Ordinance on Prevention of Hazards from Specified Chemical Substances, etc.). In addition, the rotation angle of the bypass damper 9 can be adjusted manually or by a drive device such as a motor (not shown) to increase the amount of bypass ventilation.
As is clear from equation (8), if Q _L is changed,
A desired inflow wind speed V _S can be obtained.

Next, as shown in FIG. 3, consider a case where the opening degree of the front door 3 is medium. In this case, as shown in the figure, the first damper 13 is positioned in an open state at an intermediate position, and the second damper 14 is positioned in a fully closed state. That is, as the front door 3 is closed from the fully open state (the state shown in FIG. 1B), only the first damper 13 is activated by the motor or the like (not shown) in response to the detection output of the opening degree sensor 12. The drive device gradually moves the second damper (second damper 1).
4 remains fully closed), in proportion to the opening degree of the front door 3.
It changes Q _A and Q _B. If this is expressed as a formula, it becomes as follows.

Q _A = KQ _IN1 (0<k≦1) …(9) Q _B = (1-k) Q _IN1 …(10) Q _C =0 …(11) Here, K is the opening degree of the front door 3. It is a proportional coefficient, and is changed by rotating the first damper 13.

When the opening degree of the front door 3 is gradually reduced in this state, the value of k gradually decreases in proportion to the opening degree, and the value of Q _A decreases. Along with that,
The airflow of the air curtain becomes turbulent, and the airflow begins to flow into the room without being sucked into the processing chamber 2 and the bypass ventilation path 8, which adversely affects the indoor air conditioning.

Generally, in the case of air curtains, the wind speed is
It is known that clean rectification is achieved if the flow rate is 0.5 m/s or more. Therefore, as shown in FIG. 4, when the opening degree of the front door 3 falls below a certain value and the air velocity of the air curtain becomes insufficient, the first Damper 1
3 is positioned at a position where the first ventilation passage 5 is fully closed (in other words, the first branch passage 10 is fully opened), thereby blocking the air curtain. In this case, if the value of Q _B becomes too large, the first
The wind speed blown out from the branch path 10 into the processing chamber 2 becomes too high and disturbs the airflow within the processing chamber 2.
Since there is no point in controlling the inflow wind speed V _S from the front opening, a part of Q _IN1 is directly routed to the exhaust side through the second branch path 11 while ensuring that the ventilation capacity in the processing chamber 2 does not fall below a certain level. I'll let you escape. For this purpose, the first damper 13 completely closes the first ventilation passage 5, and at the same time, the second damper 14 is positioned at a position rotated by a predetermined angle as shown in FIG.

The state shown in FIG. 4 can be expressed as follows.

Q _A = 0 ... (13) Q _B = mQ _IN1 (0 < m < 1) ... (14) Q _C = (1 - m) Q _IN1 ... (15) Here, m is the rotation angle of the second damper 14 It is an arbitrary coefficient depending on , and is appropriately determined in the range of 0<m<1.

At this time, from equations (15) and (16), the inflow velocity V _S at the front opening is as follows: V _S =(Q _IN2 −Q _L )/S (16). Since Q _IN2 is constant, V _S can be maintained at a desired value by changing Q _L by adjusting the bypass damper 9 according to the degree of opening of the front door 3. Also, as Q _B =mQ _IN1 , the first branch road 10
Since the wind speed from the inside of the processing chamber 2 is weakened,
The airflow within the processing chamber 2 is not disturbed.

Note that the manner of controlling the first and second dampers 13, 14 and the bypass damper 9 is not limited to the above example, and may be changed as appropriate to obtain desired performance. For example, in the state shown in Figure 3, the first
Not only the damper 13 but also the second damper 14 may be rotated by a predetermined angle or according to the detection output of the opening degree sensor 12, and in this case as well, a desired inflow wind speed can be obtained. Also, the first
The damper 13 does not necessarily need to be rotated in proportion to the degree of opening of the front door 3, but may be rotated appropriately to obtain any desired inflow wind speed. moreover,
In the embodiment described above, the first and second dampers 13,
Although the angle adjustment at 14 is performed according to the degree of opening of the front door 3, it may be performed by other methods, for example, by actually measuring the inflow wind speed value, and the adjustment may also be performed manually. It's okay.

(Effects of the invention) As described above, according to this invention, the first and second branch paths are provided for branching the air supply from the air supply fan and guiding it to the processing chamber and the exhaust fan, respectively. The incoming wind speed is controlled by controlling the amount of air branched into the road.
A desired inflow air velocity can be obtained while keeping the supply/exhaust volume constant, and the airflow within the processing chamber is not disturbed. In this case, since the supply and exhaust volumes are constant, complex motor control is not required, and the ratio of supply and exhaust volumes can be set to minimize the effect on indoor air conditioning, resulting in energy-saving effects. A high draft chamber can be achieved. Moreover, since the air curtain is cut off when the wind velocity of the air curtain is insufficient, it is possible to form an effective air curtain that does not disturb indoor air conditioning. Furthermore, by providing a bypass ventilation path, even more effective control of the inflow wind speed becomes possible.

[Brief explanation of the drawing]

1A and 1B are a front view and a side sectional explanatory view showing a draft chamber which is an embodiment of this invention, respectively; FIG. 2 is an explanatory view showing an example of the configuration of an opening degree sensor; FIGS. Figure 4 is the first
FIG. 3 is an explanatory diagram of the operation of the draft chamber shown in the figure. 2... Processing room, 3... Front door, 4... Air supply fan, 6... Exhaust fan, 10... First branch path, 1
1... Second branch road, 12... Opening degree sensor, 13
...First damper, 14...Second damper.

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, and a supply for generating airflow so as to form an air curtain along the outside of the front door. a first branching path for branching the air supplied by the air supply means and guiding it into the processing chamber; an exhaust means for exhausting the gas in the processing chamber; a second branching path for branching and leading to the exhaust means; and a branching for controlling the speed of inflowing air from the opening by controlling the amount of air branched to the first and second branching paths, respectively. A draft chamber comprising an air volume control means. (2) The draft channel according to claim 1, wherein the branch air volume control means controls the air volume branched into the first and second branch paths depending on the degree of opening of the front door. Ba. (3) The branch air volume control means includes a detection means for detecting that the degree of opening of the front door has become below a predetermined value, and a detection means for controlling the air supply of the air supply means in response to a detection output of the detection means. 3. The draft chamber according to claim 2, further comprising means for branching all of the channels into the first and second branching paths. (4) further comprising: a bypass ventilation path having an inlet communicating with the outside of the processing chamber and an outlet communicating with the exhaust means; and bypass ventilation amount control means for controlling the amount of air flowing into the bypass ventilation path. A draft chamber according to claim 1 of the utility model registration claim.