Abstract:
A biological safety cabinet (BSC) has an air curtain to isolate air inside and outside the BSC. A most preferable slight concave curtain of air can be obtained. With the curtain, neither contamination in the BSC leaks out nor outside contamination enters the BSC. Furthermore, no circulation is formed in the BSC by blowing the air curtain. Thus, the operator using the BSC and the product in the BSC are both well protected.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a biosafety cabinet (BSC); more particularly, relates to forming an air-isolator at an opening of a door to isolate air flows inside and outside the BSC, to prevent circulations in the BSC, and to prevent contamination leakage from the BSC. 
       DESCRIPTION OF THE RELATED ARTS 
       [0002]    In many microbiological experiments or procedures, biological dangers may do harm to operators. BSC is used to protect germs in the cabinet and to prevent contamination inside from leaking out. 
         [0003]    Although BSC is used to protect germs in the cabinet and to protect the operator, events keep on happening that operators died because of contamination. It shows that BSC still has some problem. In an actual operation, there are two types of problems: (1) not obtaining the most proper design: They include insufficient suction amount, improper suction slot position, improper air supplier position, uneven flow rate at front opening, bad opening shape design, etc.; and (2) not operating in a best state: They include that the contamination is too much, the opening is too wide opened, that the suction amount is not well adjusted following an actual situation, etc. 
         [0004]    According to NSF/ANSI 49, 2002, which is a newly revised standard for a level II BSC, the BSCs can be divided into four categories: A1, A2, B1 and B2. 
         [0005]    Clark and Mullan, Rake, Kennedy, Kruse, etc. test BSCs for capabilities in exhausting contamination and found that the level II BSC can not resist a sudden change in indoor air pressure. Hence, the capability in exhausting contamination for a level II BSC has to be improved. 
         [0006]    In the B2 BSC, waste gases are totally exhausted without recycling; all gases are flowed through HEPA filter; and the gases are exhausted to the exhausting system of a building. The BSC has a HEPA filter on top to supply air by an air blower. Thus, outer air is not allowed to enter the cabinet directly; and environments inside and outside the cabinet are separated. Then the air is exhausted by an air-suction device at a rate of 0.57 cubic meters per second for obtaining a negative pressure in the cabinet. And, if air supply is not enough, a sash may be opened to supply air into the BSC from outside. Yet, in such a situation, the contamination in the BSC may leak out at the opening by the interference of the outside flow and/or the action of the BSC door. Therefore, traditional BSC is weak in defending interferences of side flow and door operation. Hence, the prior art does not fulfill all users&#39; requests on actual use. 
       SUMMARY OF THE INVENTION 
       [0007]    The main purpose of the present invention is to prevent contamination leakage from the BSC and to prevent circulations in the BSC. 
         [0008]    To achieve the above purpose, the present invention is an air curtain-isolated BSC, comprising a main body, a door, an air blower, a suction box, a gas sucker, a plurality of cross flow fans and a high efficiency particulate air (HEPA) filter, where the main body has a space to contain a harmful gas to be exhausted and has an open space at a side; the door is movably assembled to the main body at the side to control an opening and has an air-pushing veil; the air blower is connected to an air inlet on top of the main body to supply fresh air; the suction box is set beneath the main body and has a suction slot at an edge of the main body corresponding to the air-pushing veil of the door; the gas sucker is set at an exit of the suction box for exhausting the harmful gas; the HEPA filter is set on top of the main body to supply air by the air blower; and air flows inside and outside the BSC is isolated to prevent operators from damages owing to leakage of the contamination in the BSC, and to prevent contamination outside of the BSC from entering into the BSC to pollute a product in the BSC. Accordingly, a novel air curtain-isolated BSC is obtained. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0009]    The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
           [0010]      FIG. 1  is the perspective view showing the preferred embodiment according to the present invention; 
           [0011]      FIG. 2  is the side view showing the preferred embodiment; 
           [0012]      FIG. 3  is the view showing the preferred embodiment with the coordinated devices; 
           [0013]      FIG. 4  is the view showing the straight curtain; 
           [0014]      FIG. 5  is the view showing the slightly concave curtain; 
           [0015]      FIG. 6  is the view showing the severely concave curtain; and 
           [0016]      FIG. 7A  to  FIG. 7C  are the views showing the changes of the oscillating curtain at different times. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    The following description(s) of the preferred embodiment(s) is/are provided to understand the features and the structures of the present invention. 
         [0018]    Please refer to  FIG. 1  to  FIG. 3 , which are a perspective and a side views showing a preferred embodiment according to the present invention; and a view showing the preferred embodiment with coordinated devices. As shown in the figures, the present invention is an air curtain-isolated biosafety cabinet (BSC), comprising a main body  11 , a door  12 , an air blower  13 , a suction box  14 , a gas sucker  15 , a plurality of cross flow fans  20  and a high efficiency particulate air (HEPA) filter  16 , where air flows inside and outside the BSC are isolated with no air circulation and dissipation and thus contamination in the cabinet is well prevented from leakage. 
         [0019]    The main body  11  has a space to contain a harmful gas to be exhausted; and has an open space at a side. 
         [0020]    The door  12  is movably assembled to the main body  11  at a side. The door  12  has a handle  121  to move the door for controlling an opening  125 . A plurality of cross flow fans  20  is set on the door  12  and the door  12  is a telescopic sliding door to change opening size of the door  12 . The door blows air by setting a plurality of cross flow fans controlled by a cross-flow fan controller  2 . Air is blown from upper side of the door  12  to a section of honeycombs  123 . And then the air is continuously blown through a stabilizing passage  124  to dissipate turbulence energy to reach an opening  125  of the door  12 . 
         [0021]    Concerning supplying a down flow of air, the air blower  13  is controlled by an inverter  17   a  and is connected with the air inlet  111  on the top of the HEPA filter  16  to supply fresh air. 
         [0022]    The suction box  14  is set beneath the main body  11 ; and has a suction slot  141  located at an edge of the main body  11  corresponding to the air-pushing veil  122  of the door  12 . 
         [0023]    The gas sucker  15  is set at an exit of the suction box  14  to suck the harmful gas. Another inverter  17   b  is used to change a rotation rate of the gas sucker  15  to control an average blowing rate of the air blower  13  and an average sectional sucking rate of the suction slot  141 . A Venturi flow meter  18  is set between an exit of the gas sucker  15  and an exit of the suction box  14  to measure an air-blowing rate; and obtains a pressure difference between them with a coordination of a pressure transducer  19 . 
         [0024]    The HEPA filter  16  is deposed on top of the main body  11  to supply air in an average rate through the air blower  13 . Thus, with the above structure, a novel air curtain-isolated BSC is obtained. 
         [0025]    The present invention has the following characteristics: The door  12  is movably assembled at a side of the main body  11  and has an air-pushing veil  122 . The inverter  17   a  is used to control the air blower  13  and the air blower  13  is connected to the air inlet  111  on the HEPA filter  16  through a flexible pipe. A plurality of cross flow fans  20  is set on the door  12 ; and the door is a telescopic sliding door to change a position of mouth for blowing air. The cross flow fans  20  is controlled by a cross-flow fan controller  2  to provide a steady air flow to flow from the upper side of the door  12  and to flow through a section of honeycombs  123 . Then, the air is flowed through a stabilizing passage  124  to dissipate turbulence energy to reach the opening of the door  12 . The suction box  14  is set beneath the main body  11  and the suction slot  141  is located at an edge of the main body  11  corresponding to the air-pushing veil  122  of the door  12 , where a push-pull air-isolator is thus obtained. The flow fields of the BSC are examined through a flow visualization and are effectively controlled to prevent contamination in the cabinet from leakage; and the position of the suction slot  141  can be changed to suck the contamination more effectively. Through the HEPA filter  16  on the main body  11 , fresh air flow is supplied to meet a physical mechanism between air suction and air supply. Accordingly, the air curtain-isolated BSC obtains the physical mechanism between air suction and air supply; the air-isolator formed by the local air suction near the contamination source prevents the contamination from leakage; and, thus, energy is saved and contamination is prevented from leakage with practicality, convenience and safety. 
         [0026]    Please further refer to  FIG. 4  to  FIG. 7C , which are views showing a straight curtain, a slightly concave curtain and a severely concave curtain; and views showing the changes of the oscillating curtain at different times. As shown in the figures, push-pull air-isolators are divided into four type, comprising a straight curtain  71 , a slightly concave curtain  72 , a severely concave curtain and an oscillating curtain  74 . 
         [0027]    On using the present invention, flow fields in the main body  11  are described as follows: 
         [0028]    (a) Slightly concave curtain  72 : When an air-blowing velocity, an air-supplying velocity and an air-sucking velocity are adjusted to obtain a proper ratio, an air-isolator formed by the air from the door  12  is slightly concave inward the BSC. When the flow is close to the suction slot  141 , the air flow is pulled down to be prevented from flowing outside or inside the BSC. 
         [0029]    (b) Straight curtain  71 : When the air-sucking velocity is smaller than the above one and thus is weak, the air isolator formed by the air from the door  12  is straight and not concave with no circulation formed in the cabinet. 
         [0030]    (c) Severely concave curtain  73 : When the air-sucking velocity is big, the air-isolator is moved inwardly and is severely concave; and, thus, obvious circulations are formed in the BSC. 
         [0031]    (d) Oscillating curtain  74 : Obvious circulations are generated inside and outside the BSC with the air-isolator swinging in and out of the BSC at different times. 
         [0032]    With the above descriptions concerning the four types of flow fields, it is suggested to adjust push-pull velocities of air to obtain a slightly concave curtain  72  for operations in the BSC. 
         [0033]    To sum up, the present invention is an air curtain-isolated BSC, where an air-isolator is formed at an opening of a door for isolating air flows inside and outside the BSC to prevent operators from damages owing to contamination leakage from the BSC, and to prevent contamination outside of the BSC from entering into the BSC to pollute a product in the BSC. 
         [0034]    The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.