Abstract:
A fume hood used in either a laboratory or industrial setting, the fume hood includes a cabinet formed with a chamber having a generally flat work surface, an open face and a sash door assembly for reciprocally opening and closing the open face. The fume hood further includes an airfoil directing airflow through the open face and into the chamber. A baffle is disposed in the fume hood. The baffle has a plurality of rows of regularly laterally spaced apertures wherein the rows are regularly spaced apart along the length of the baffle. The fume hood further includes an exhaust outlet from the chamber.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    I. Field of the Invention 
         [0002]    The present invention relates to a fume hood apparatus, and more particularly to a fume hood apparatus with a baffle member that efficiently evacuates contaminated air from the fume hood. 
         [0003]    II. Discussion of the Prior Art 
         [0004]    Fume hoods are used in both laboratories and industrial settings where hazardous or noxious chemicals are generated and released. In fact, fume hoods limit exposure to hazardous solids, liquids and gases. Generally a fume hood is a ventilated enclosed workspace which captures, contains and then exhausts hazardous or noxious fumes, vapors or particulate matter generated inside the hood. Fume hoods are used so that dangerous fumes and particles generated inside the hood are drawn away from the user to prevent or at least minimize inhalation of the contaminants. 
         [0005]    The American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (“ASHRAE”) has developed industry recognized standards for evaluating laboratory fume hoods known as the ANSI/ASHRAE Standard 110. The ASHRAE Standard 110 test is not a “pass/fail” test. The acceptance level is usually determined by the design team for new constructions. 
         [0006]    Conventional fume hood assemblies comprise a work chamber bounded by walls and an open front face which provides access to the work area. The opening may be reciprocally covered by a movable sash. The opening may be either partially or completely covered by the sash. The sash may be positioned by a counterbalance system using cables, weights and pulleys. The opening of the fume hood is often referred to as a “face”. The face area of the hood may either be fixed or, with use of a movable sash, may be altered based on the positioning of the sash. 
         [0007]    Conventional fume hoods also have an airfoil at the bottom front of the work chamber. The airfoil directs air across the fume hood&#39;s work surface to assist in evacuating fumes from the work surface. Airfoils were first used in connection with fume hoods because where there is no structure or device for directing the inward flow of air into the chamber, vortexes would form in the fume hood&#39;s chamber, such that if air pressure was varied even slightly the vortex would be disrupted and hazardous fumes would escape through the face of the fume hood. 
         [0008]    Conventional fume hoods include a baffle at the rear of the chamber. An abundant amount of air is supplied into the chamber from the surrounding laboratory space through the open face and the airfoil. Once inside the work chamber the air is drawn to slots in the baffle at the rear of the chamber by a fan or the chimney effect. The arrangement of slots in prior art baffles has typically followed only one of three patterns. The first pattern is to provide long slots. However, long slots in the baffle create pressure drop zones just below the opening, creating a roll of air that does not join the air stream efficiently. 
         [0009]    The second pattern is to use a plurality of small, staggered slots such as used in U.S. Pat. No. D604,827 to Lin (“Lin &#39;827 patent”). The arrangement used in the Lin &#39;827 patent makes for poor circulation of air in the center of the chamber while also creating pressure drop zones below each slot. When the slots are staggered and located close together in each assembly row, the air being drawn from the fume hood does not have sufficient space to form proper airflow channels. Furthermore, the close proximity of each slot to one another makes it difficult to make an adjustable flow system. 
         [0010]    The third slot pattern is to provide a perforated baffle, such as in U.S. Pat. No. 6,461,233 to Gilkison et al. (“Gilkison &#39;233 patent”). In the Gilkison &#39;233 patent, the baffle is of a generally planar construction and includes a plurality of apertures. The apertures are arranged in plenum zones. The Gilkison &#39;233 patent, like the Lin &#39;827 patent, teaches staggering the apertures such that no two apertures are directly lined up with one another. The principal difference between the baffle in the Gilkison &#39;233 patent and the baffle in the Lin &#39;827 patent is that the baffle in the Gilkison &#39;233 patent has comparatively more apertures. However, the baffle in the Gilkison &#39;233 patent produces an unreliable and inconsistent flow of air behind it. Because there is little separation between the apertures, and therefore little resistance in the air, the top rows of perforations pull an excessive amount of air while the lower layers are deprived of proper negative pressure to safely and correctly pull the necessary amount of air. Furthermore, variable exhaust is nearly impossible to attain due to the numerous apertures in the perforated baffle. 
         [0011]    Returning to the discussion of the flow of air in the prior art fume hoods, air is generally drawn into the fume hood from the laboratory through the open face and the airfoil. The air is then drawn through the slots in the baffle, up behind the baffle and is then exhausted through the exhaust system. Prior art fume hoods constantly evacuate air from the chamber and replace it with pre-conditioned air (i.e., heated or cooled) from the building in which the fume hood is located. Constantly circulating such air often consumes a great deal of energy. Furthermore, prior art fume hoods do not efficiently evacuate contaminated air and they allow the contaminated air to escape from the front of the cabinet through the face. 
         [0012]    Therefore, improved fume hood designs which reduce the amount of air required to be pumped into the chamber, reduce energy consumption and provide better containment of contaminants would be desirable. 
       SUMMARY OF THE INVENTION 
       [0013]    These objects and others are accomplished, in accordance with the illustrated embodiments of the present invention, by providing a fume hood that comprises a cabinet formed to define a chamber having a generally flat, horizontal work surface and an open flat face. A sash door is mounted at the front face for reciprocal movement on a vertical plane to provide an access opening to said chamber. The fume hood has an airfoil disposed above the work surface for directing airflow entering through the access opening and into the chamber. Because the airfoil is above the work surface, when the sash door is closed airflow is directed to sweep the work surface of contaminated air. A rear baffle is disposed within the chamber and is spaced forwardly from a rear wall of the cabinet. The baffle cooperates with the rear wall of the cabinet to define a vertical fume passage therebetween. The baffle includes a plurality of rows of regularly, laterally-spaced apertures with said rows being regularly spaced apart along the length of the baffle. The apertures function as ports which allow the contaminated air to be drawn into the vertical fume passage due to the Venturi effect resulting from the increase in velocity of the airflow up and behind the baffle. The fume hood also includes an air exhaust outlet from the chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The foregoing features, aspects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of an embodiment, especially when considered in conjunction with the accompanying drawings in which like numerals in the several views refer to corresponding parts: 
           [0015]      FIG. 1  is a perspective view of a fume hood structure in accordance with one embodiment of the present invention; 
           [0016]      FIG. 2  is a cross-sectional left side view of the fume hood structure in accordance with one embodiment of the present invention; 
           [0017]      FIG. 3  is a top view of the fume hood structure in accordance with one embodiment of the present invention; 
           [0018]      FIG. 4  is a cross-sectional right side view of the fume hood structure in accordance with one embodiment of the present invention; 
           [0019]      FIG. 5  is a partial perspective view of the fume hood structure in accordance with one embodiment of the present invention; 
           [0020]      FIG. 6  is a front view of the fume hood structure in accordance with one embodiment of the present invention; 
           [0021]      FIG. 7  is a cross-sectional left side view identical to  FIG. 2 , but also showing by arrows the flow of air through the fume hood; and 
           [0022]      FIG. 8  is a partial cross-sectional left view of the airfoil in a rounded shape; and 
           [0023]      FIG. 9  is a partial cross-sectional left view of the airfoil in an angular shape. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    This description of the preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top” and “bottom” as well as derivatives thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “connected”, “connecting”, “attached”, “attaching”, “join” and “joining” are used interchangeably and refer to one structure or surface being secured to another structure or surface or integrally fabricated in one piece, unless expressively described otherwise. 
         [0025]    The fume hood  100  of the present invention has a first outer side panel  110 , a second outer side panel  120 , a top panel  130  ( FIG. 3 ), a rear panel  140 , a front partial enclosure panel  150  with an open face  160 , and a bottom work surface  180  forming a cabinet. A work chamber is formed inside the cabinet by an inner panel  190  which is disposed proximate and in parallel relation to the first outer side panel  110 , the rear panel  140 , the second panel  120 , the top panel  130  and the bottom work surface  180 . The cabinet further includes a sash door  200  mounted below the front panel  150  to selectively cover open face  160 . 
         [0026]    As shown in  FIG. 3 , the top panel  130  includes a hinged access door  210  providing access to a lamp for lighting the interior chamber of the cabinet. An exhaust conduit  220  provides parts for connecting to an HVAC system. An automated sash assembly is placed on the top panel  130  to reciprocally move the sash door  200  on the vertical plane to cover the otherwise open face  160 . 
         [0027]    The automated sash assembly includes the sash door  200  and a first cable  230  attached to a first side  200 A of the sash door  200  and a second cable  240  attached at one end thereof to a second side  200 B of the sash door  200 . A first pulley  250  is provided on the top panel  130  for receiving the first cable  230  and directing the first cable  230  horizontally to a second pulley  260  on the top panel  130 . The second pulley  240  is disposed on an opposite end of the top panel  130  from the first pulley  250 . The second pulley  260  directs the first cable  230  downward through a slot  280  cut into the top panel  130 . A third pulley  300  on the top panel  130  receives the second cable  240  and directs the second cable  240  horizontally to a fourth pulley  310  on the top panel  130 . Pulley  310  directs the second cable  240  laterally to a fifth pulley  320  positioned proximate the slot  280 . Pulley  320  directs the second cable  240  down and through the slot  280 . 
         [0028]    As best seen in  FIG. 4 , a compartment is formed between the first outer side panel  110  and the inner panel  190 . A guide member  340  extends vertically from the work surface  180  between the first outer panel  110  and the inner panel  190 . A counterweight  360  is attached to an opposed end of both the first and second cable  230 ,  240 . The counterweight  360  is disposed between the rear panel  140  and the guide member  340 , to ensure that the counterweight  360  does not swing freely in the compartment. A motor (not shown) may be attached to one of the pulleys to rotate the pulley causing the sash door to be lifted and lowered automatically. 
         [0029]    The inner panel  190  further includes a removable section  195  which provides additional access to the space between outer panel  110  and the inner panel  190  of the fume hood  100 . 
         [0030]      FIG. 5  shows the novel baffle  370  of the fume hood  100 . The baffle  370  has a bottom end  380  in contact with the work surface  180 , and a top end  390  in contact with the top panel  130 . Furthermore, the top portion  450  of the baffle  370  has an upward and forward slope with respect to the vertical portion  460  of the baffle  370 . Because the top portion  450  of the baffle  370  is angled it allows for directed flow of air from the top section of the chamber. The baffle  370  is positioned so as to be spaced forwardly from the rear panel  140  of the cabinet forming a vertical fume passage  391  between the baffle  370  and the rear panel  140 . 
         [0031]    The apertures  440  function as ports for air to flow through. The apertures  440  in the preferred embodiment are substantially rectangular in shape. It is understood that the ports can be shaped in a different configuration. However, the shape and size of the apertures  440  in the preferred embodiment aid in facilitating suction of air from the fume hood  100  which will be discussed presently. The space between rows  400  and  410  is approximately 12″. Likewise, the spaces between rows  410  and  420 , and  420  and  430  are approximately 12″ as well. Each aperture  440  is preferably 1.5″ by 2.5″ in the disclosed embodiment, but limitation to this size is not to be inferred. 
         [0032]    Additionally, the baffle  370  has a plurality of screw holes  470  bored through the thickness dimension of the baffle  370 . Mounting screws  480  are screwed into the screw holes  470  to fasten the baffle  370  to the rear panel  140 . Each mounting screw  480  includes a fastening point  490 , which an apparatus rod (not shown), also known as a lattice rod, can be inserted. Apparatus rods are used to hold instruments or other items in the hood for experiments. Bracket members  500  extend from the rear wall  140  into the chamber and have bore holes (not shown) which align with the screw holes  470  of the baffle  370 . The mounting screws  480  are inserted through the screw holes  470  and into the bracket members  500  to hold the baffle to the rear of the fume hood  100 . 
         [0033]    Dampers (not shown) can be used in the passage defined between baffle  370  and rear wall  140  to direct the flow of air to specific areas of the baffle  370 . 
         [0034]    The fume hood  100  additionally includes an airfoil  510  ( FIG. 7 ), also known as an air directing member. The airfoil  510  acts as a bypass for air to flow into the work chamber when the sash door  200  is in a closed position. Because air can still flow into the work chamber through the airfoil  510  with the sash door  200  closed, the fume hood  100  maintains a safe environment and lowers the concentration of airborne contaminants within the fume hood  100 . The airfoil  510  is disposed in either a flush position (as shown in  FIG. 1 ) wherein the airfoil  510  is flush or coplanar with the work surface  180 , or in a low profile position (as shown in  FIG. 7 ) wherein the airfoil  510  is disposed above the work surface  180 . Typically, when in the low profile position, the airfoil  510  is disposed approximately ⅜″ above the work surface  180 . 
         [0035]    The airfoil  510  in the preferred embodiment extends the length of the open face  160 . Airfoil  510  can have a rounded shape  510   a  as shown in  FIG. 8  or an angular shape  510   b  as shown in  FIG. 9 . The shape of the airfoil  510  makes the fume hood  100  more ergonomic because the airfoil  510  can function as a wrist rest for the operator of the fume hood  100 . The ergonomic benefits of the airfoil  510  depend on placement of the fume hood  100  along a vertical axis, depending on whether the operator wishes to stand or sit. 
         [0036]    The airfoil  510  allows smooth, sweeping, laminar airflow to the work surface  180  in the chamber. The low profile configuration directs air not just into, but across the work surface  180 , therefore increasing the safety of the unit and efficiency of the airflow. When the sash door  200  is open, the airfoil  510  funnels air from outside the fume hood  100  into the work chamber without turbulence of flow separation. By directing the airflow from the bottom of the airfoil  510  across the work surface  180 , a low pressure zone is created and causes the incoming air from the open face  160  to join the stream of air entering the fume hood  100  from the airfoil  510 . When the sash door  200  is in a closed position, the flow of air from the airfoil  510  sweeps contaminated air from the work surface  180 . 
         [0037]    The arrows in  FIG. 7  show the direction of airflow into, through, and out of the fume hood  100 . Air from the room being drawn by an exhaust fan (not shown) enters the work chamber directly through the open face  160  at an angle about perpendicular to the open face  160 . The airflow is shown by arrows  520 . Air also flows into the fume hood  100  through the airfoil  510 . Inside the work chamber air is drawn toward the apertures  440 . From there the air is drawn into the vertical fume passage  390  through the apertures  440 , and rises up through the vertical fume passage  390  by virtue of the Venturi effect resulting from the increase in velocity of the airflow  520  as it rises up through the vertical fume passage  390 . The velocity of the airflow  520  is greater, and therefore more efficiently causes the air to reach the exhaust conduit  220 , and thereby more efficiently be exhausted from the chamber. 
         [0038]    This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.