Abstract:
A fume hood includes a top, bottom sidewalls, front panel and a back panel that define an enclosed workspace. The fume hood also includes a movable sash for opening and closing an access opening and an airfoil disposed proximate an edge portion of the opening to direct airflow through the opening and into the workspace. The airfoil is automatically raised from a down position to an up position when the sash is raised to a predetermined height. In addition, the airfoil may be automatically raised when the velocity of the airflow into the access opening decreases below a predetermined value. Once raised, the airfoil may be automatically or manually lowered to the down position. In one embodiment, the airfoil includes one or more fins having an angled portion that extends downwardly below the work surface of the fume hood when the airfoil is in the down position, thereby reducing the possibility of a potential spill when the technician removes an item from the workspace.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a fume apparatus, and in particular to a fume hood apparatus with a rotatable airfoil member that improves the containment performance of the fume hood apparatus and reduces the probability of the occurrence of spills, thereby improving safety during operation of the fume hood apparatus.  
           [0003]    2. Description of the Related Art  
           [0004]    Fume hoods are protective enclosures that provide ventilated and illuminated workspaces for laboratory or other applications. A fume hood in its most basic form is a box with an inlet and an outlet. The inlet generally has a movable sash capable of moving vertically or a combination of vertically and horizontally, which provides an opening that allows access to the workspace. The procedures performed inside the fume hood are exhausted at the back through the top of the fume hood to a heating, venting and air conditioning (HVAC) system.  
           [0005]    In some fume hood designs, an airfoil is mounted in a pivotal manner at the front of the work surface. Typically, the airfoil is flush or coplanar with the fume hood&#39;s work surface to provide a substantially unobstructed path for moving items in and out of the fume hood. When the airfoil is rotated to an up position, the direction of the airflow pattern is changed to improve the containment of airborne contaminants. However, there is a problem with a raised airfoil in that the technician may accidentally catch an item, for example, a beaker on the edge of the airfoil when the technician is removing the beaker, thereby increasing the probability of a spill.  
           [0006]    The inventors of the present invention have recognized that it is beneficial to automatically rotate the airfoil up and down when the sash is lower than a predetermined height and so as to minimize the potential for a spill when the technician is removing items from the workspace of the fume hood.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention comprises a fume hood apparatus including an enclosure, a movable sash and an airfoil member for directing airflow through the opening and along the fume hood&#39;s work surface. The airfoil member is automatically raised to a first position when the movable sash is positioned above a predetermined height above the bottom of the fume hood apparatus to effectively evacuate the work surface and the workspace of fumes and other waste materials. When the movable sash is positioned at or below the predetermined height, the airfoil member is automatically lowered to a second position that is flush or co-planar with the work surface, thereby minimizing the possibility of an accident when the technician removes an item from the workspace. Also, the airfoil member can be automatically raised or lowered when a velocity of the airflow through the access opening decreases below a predetermined value.  
           [0008]    In another aspect of the invention, the airfoil member includes one or more fins for directing the airflow through the opening and along the work surface. The fins may include one or more angled portions such that a portion of the airfoil member is positioned below the work surface when the airfoil members are in the second position.  
           [0009]    Various aspects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of the fume hood apparatus of the present invention;  
         [0011]    [0011]FIG. 2 is a cross-sectional view taken along line  2 - 2  of FIG. 1; and  
         [0012]    [0012]FIG. 3 is a cutaway perspective view of an alternate embodiment of the airfoil of the invention when in the down position; and  
         [0013]    [0013]FIG. 4 is an end view of the airfoil of FIG. 3 when in the up position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    Referring now to FIGS.  1 - 4 , a fume hood apparatus is shown generally at  10  according to the present invention. The fume hood apparatus  10  generally includes an enclosure comprising a cover or top  12 , a bottom  14  opposite the top  12 , sidewalls including a first end panel  16 , a second end panel  18  opposite the first end panel  16 , a front panel  20 , and a back panel  22  opposite the front panel  20 . The enclosure may be made of metal or any other material of high strength and rigidity.  
         [0015]    The enclosure defines a workspace  24  and an access opening  26  through which a technician may reach into the workspace  24 . A moveable sash  28  is slidably mounted to the enclosure in a frame member  29  to allow closing the opening  26  and precluding access to the workspace  24 . The sash  28  is preferably made of glass or any other similar material. The technician may raise the sash  28  to allow access through the opening  26  and air to flow into the workspace  24 , as indicated by the arrow  27  in FIG. 1, or the technician may lower the sash  28  to close the opening  26 .  
         [0016]    The fume hood apparatus  10  may include a baffle system (not shown) that cooperates with a fan (not shown) to evacuate the fumes generated in the workspace  24 . Typically, the baffle system lies at the back of the workspace  24  and directs the fumes to a discharge conduit (not shown). As the fan draws the air and fumes out of the workspace  24 , ambient air flows into the workspace  24 , primarily through the opening  26 . The bottom  14  defines a work surface that is used for positioning the fume hood apparatus  10  at a desired elevation for the technician. It will be understood that the invention is not limited by the type of baffle system, base member or airfoil, and that the invention can be practiced with any type of baffle system and base member well known in the art. Examples of a baffle system and base member are described in U.S. Pat. No. 5,556,331 to Bastian, the entire contents of which are herein incorporated by reference.  
         [0017]    Referring now to FIGS.  2 - 4 , an airfoil member  30  according to a first embodiment of the invention is shown. The airfoil member  30  is preferably located in the bottom of the access opening  26  and extends the length of the access opening  26 . In general, the airfoil member  30  includes a tube portion  30   a  and a flat portion  30   b  that provide that airfoil member  30  with an aerodynamic shape that facilitates the movement of air into the workspace  24 . The tube portion  30   a  may receive enclosure protuberances (not shown) that function as an axle at the ends of the airfoil member  30 . Alternatively, the tube portion  30   a  may be slightly longer than the other portions of the airfoil member  30  so that its end portions may extend into pockets (not shown) in the enclosure.  
         [0018]    The airfoil member  30  is pivotally mounted at one end to the enclosure to allow the airfoil member  30  to be rotated by the technician from an up position (shown as solid lines in FIG. 2) to a down position (shown in phantom in FIG. 2). In the up position, the airfoil member  30  directs air into the workspace  24  by allowing air to flow over and under the airfoil member  30  and into the workspace  24 . In the down position, the airfoil member  30  is substantially flush or co-planar with the fume hood&#39;s work surface  32  to allow better access to the workspace  24 . This arrangement allows incoming air to move fumes and other waste off of the work surface  32  and to the back of the work space  24  where the fan can discharge them from the fume hood apparatus  10 .  
         [0019]    One feature of the invention is that the airfoil member  30  is automatically raised to the up position when the movable sash  28  is positioned, for example, at or above a minimum height, “h”, in a range of about 10 to 24 inches above the bottom  14  of the fume hood apparatus  10 . Automatically raising the movable sash  28  can be accomplished by any means, such as a limit switch (not shown) on a corner post of the fume hood  10 , or the like. It will be appreciated that the invention is not limited by the minimum height, “h”, at which the airfoil member  30  will be raised because the surface area of the access opening  26  varies according to the width of the movable sash  28 .  
         [0020]    It will also be appreciated that this feature of the invention decreases the probability of accidents by a technician when removing an object from the workspace  24  as compared to conventional fume hood designs because the airfoil member  30  is raised only when the movable sash  28  is positioned at or above the minimum height, “h”. Also, the airfoil member  30  can be automatically raised to the up position when the velocity of the airflow through the access opening  26  decreases below a predetermined value, for example, in a range between about 50 to about 100 feet/minute. Raising or lowering the airfoil member  30  can be accomplished by any means, such as by use of an airflow sensor (not shown), or the like.  
         [0021]    Another feature of the invention is that the airfoil member  30  is automatically raised to an angle, “β”, with respect to the bottom  14  of the fume hood apparatus  10  that optimizes an amount of airflow into the workspace  24 . Preferably, the angle, “β”, is in a range between about 10 degrees and about 30 degrees, and more preferably about 20 degrees. However, it will be appreciated that the angle, “β”, will vary according to the dimensions of the workspace  24 . This feature of the invention ensures that the airfoil member  30  will be raised to maintain fume containment even though the movable sash  28  is positioned at or above the minimum distance, “h”, from the bottom  14 .  
         [0022]    A shelf  34  supports the airfoil member  30  in the down position and acts as a stop to prevent further clock-wise rotation of the airfoil member  30 . The shelf  34  rests on pins  36  (only one pin  36  is shown in FIG. 2) that lie on a top segment  38  of a base member  40  at predetermined intervals along the length of the shelf  34 . It should be noted that the shelf  34  is co-extensive with the airfoil member  30 .  
         [0023]    The top segment  38  of the base member  40  is a plate-like structure that defines the work surface  32 . The top segment  38  also defines a trough  42  generally disposed below the shelf  34  and another trough  44  disposed inwardly of the trough  42 . The troughs  42 ,  44  collect liquid run-off from the work surface  32 .  
         [0024]    [0024]FIGS. 3 and 4 show an airfoil member  50  according to an alternate embodiment of the present invention. Similar to the first embodiment, the airfoil member  50  includes a rounded portion  51 . However, unlike the first embodiment, the airfoil member  50  includes a first fin  52  having a first angled portion  52   a , a second angled portion  52   b  and a third angled portion  52   c . In addition, the airfoil member  50  includes a second fin  54  including a first angled portion  54   a  and a second angled portion  54   b . The airfoil member  50  also includes a means  54   c  for connecting the rounded portion  51  and the first and second fins  52 ,  54  together such that rotating the rounded portion  51  causes the first and second fins  52 ,  54  to rotate in unison with the rounded portion  51 . In the illustrated embodiment, the connecting means comprises a substantially perpendicular plate  57  (shown in phantom) that is bonded to the rounded portion  51  and the first and second fins  52 ,  54  using any well known means, such as welding, or the like. It will be appreciated that the number of fins does not limit the invention, and that the invention can be practiced with any desirable number of fins to provide an optimum amount of airflow into the workspace.  
         [0025]    As shown in FIG. 3, the first and third angled portions  52   a ,  52   c  are positioned below the work surface  32  and the second angled portion  52   b  is flush or co-planar with the work surface  32  when the airfoil member  50  is in the down position. Because of the position of the first and third angled portions  52   a ,  52   c  are positioned below the work surface  32 , the probability of accidents by a technician when removing an object from the workspace  24  is decreased as compared to conventional fume hood designs. When the airfoil member  50  is in the down position, the air flows under the rounded portion  51  and over the first fin  52  of the airfoil member  50 , as indicated by arrow  56 , to increase airflow into the workspace  24 . In addition, the air flows under the first fin  52  and over the second fin  54 , as indicated by the arrow  59 , to also increase airflow into the workspace  24 . In particular, the airflow is increased along the bottom  14  of the workspace  24 , thereby preventing fumes from escaping from the workspace  24 .  
         [0026]    [0026]FIG. 4 illustrates when the airfoil member  50  is in the up position. When in the up position, the air flows under the rounded portion  51  and over the first fin  52  as when the airfoil member  50  is in the down position (shown in FIG. 3). In addition, the air flows under and over the second fin  54  to increase the amount of airflow into the workspace  24 , and in particular, into the bottom  14  of the workspace  24 . Similar to the first embodiment of the airfoil member  30 , the airfoil member  50  is raised to the up position from the down position automatically when the movable sash  28  is raised to the minimum height, “h”, above the bottom  14  of the fume hood apparatus  10 . In addition, the airfoil member  50  is lowered to the down position from the up position when the movable sash  28  is lowered to the minimum height, “h”, about the bottom  14  of the fume hood apparatus  10 .  
         [0027]    While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.