US 3340788 A
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. M om m@ Hwy Ila R. LANDINGHAM ETAL FUME HOOD INCLUDING AIR DEFLECTING BAFFLE l Filed Feb. 28,. 1966 sept. 12,1967
United States Patent Office 3,340,788 Patented Sept. 12, 1967 3,340,788 FUME HOOD INCLUDING AIR DEFLECTING BAFFLE Richard E. Landingham, Lake Tapawingo, Mo., and Robert J. South, Prairie Village, Kans., assignors to Laboratory Construction Company, Kansas City, Mo., a corporation of Missouri Filed Feb. 28, 1966, Ser. No. 530,424 4 Claims. (Cl. 98-115) This invention relates to turbulence control for fume hoods and, more particularly, to structure for enhancing streamline flow of air into a fume hood of the type having a vertically shiftable panel within the access opening thereof.
It is the primary object of our invention to provide turbulence control structure for fume hoods of the aforementioned type wherein the structure operates in combination with the shiftable panel for directing air into the hood in an unbroken, low resistance manner to thereby provide optimum streamline flow, irrespective of the vertical position of the panel.
Air flowing through fume hood sweeps the working area thereof and this desired sweeping action is retarded if air moves by turbulent flow through the hood rather than by streamline or laminar ilow. Thus, conventional hoods without structure for minimizing turbulent flow must operate at relatively high flow velocities to maintain the necessary sweeping action.
Accordingly, it is an important object of the present invention to provide turbulence control structure operating with the panel as above described wherein smooth airfoil surfaces are presented by the structure to cause uninterrupted ilow of air into the hood. Turbulent ilow characteristics, i.e. erratic varying of the magnitude and direction of flow velocity, are thus minimized and the desired sweeping action is thereby efficiently maintained.
In the drawing:
FIGURE 1 is a perspective view of a fume hood utilizing turbulence control structure made pursuant to the teachings of our invention;
FIG. 2 is a schematic, vertical, cross-sectional view of a first type of fume hood showing the air ilow pattern therewithin when the panel is lowered;
FIG. 3 is a view similar to FIG. 2 showing the air flow pattern when the panel is raised;
FIG. 4 is a schematic, vertical, cross-sectional view of a second type of fume hood showing the air flow pattern therewithin when the panel is lowered;
FIG. 5 is a view similar to FIG. 4 showing the air ilow pattern when the panel is raised;
FIG. 6 is an enlarged, schematic, cross-sectional view taken along line 6-6 of FIG. l; and
FIG. 7 is an enlarged, fragmentary, detailed, crosssectional View taken along line 7--7 of FIG. 1.
The fume hood of the present invention, broadly designated by the reference numeral 10, includes a bottom working surface 12, a top wall 14, opposed side walls 16, a rear wall 18, and a front wall 20 commencing at top wall 14 and terminating at the front access opening 22. A pair of vertical wall sections 24 integral with corresponding side walls 16 and front wall 20 slope inwardly into hood to present corresponding inclined, outwardly and laterally facing airfoil surfaces 26. An inner partition 27 is mounted on rear wall 18 in closely spaced relationship thereto.
A pair of opposed, vertical channel track elements 28 are secured to front wall and sections 24 and extend from working surface 12 to top wall 14 in side-by-side relationship to sections 24. A rectangular panel 30 is received by track elements 28 for vertically shiftable travel therein, there being counterbalance means (not shown) for maintaining panel 30 in a desired vertical position. Shifting of panel 30 permits entrance of varying amounts of air into front opening 22, the passage of air through opening 22 being limited by the relative position of the lower horizontal edge 32 spanning opening 22.
An elongated baille 34, having its longitudinal axis horizontally disposed, spans the distance across opening 22 and is attached to lower'edge 32 of panel,30 by a monolithic member 36. Referring to FIG. 7, member 36 includes a pair of elongated channels 38 and 40 connected to each other along the bights thereof by a web 42 to dispose the channels in angular relationship. Channel 38 embraces lower edge 32 of panel 30 and channel 40 embraces the uppermost edge of baille 34, whereby the transverse axis of the latter slopes downwardly from panel 30 and inwardly into the hood. A handle 44 extends laterally outwardly from channel 38 and spans the distance across opening 22.
The sloping angle of baille 34 presents a lower, inclined, outwardly and downwardly facing airfoil surface 46 and an upper, inclined, inwardly and upwardly facing airfoil surface 48. The sloping or inner obtuse angle formed between panel 30 and baille 34 is preferably within the range of about 135 to 150 for optimum results.
In the drawing, two types of internal structures for hood 10 are shown in FIGS. 2-5. It will be appreciated that the general form of the hood and panel assembly as shown in FIGS. l, 6 and 7 are common to the types of hood shown in FIGS. 2-6 and, therefore, like reference numerals designate similar parts. With reference to FIGS. 2 and 3, hood 10a includes a vertical divider 50 depending from top wall 14 to divide the top portion of hood 10a into a front compartment 52 and a rear compartment 54. An air intake fan 56 is mounted within compartment 52 and an exhaust blower 58 is mounted within rear compartment 54. Intake fan 56 is positioned to draw air through the inlet 60 formed in top wall 14 and then direct the air through compartment 52 through an air diffuser 62, whereupon the air enters the working compartment 64 of hood 10.
Air within compartment 64 is drawn upwardly along both faces of partition 27 by the operation of exhaust blower 58 which directs the air through an outlet 68 formed in top wall 14. When panel 30 is in the lower position shown in FIG. 2, baille 34 will be disposed adjacent working surface 12, but will be spaced a small distance thereabove to per-mit air to flow beneath baille 34 into compartment 64. Baille 34 will be within the path of air flowing into compartment 64 through opening 22 and will deflect the air along the sloping airfoil surface 46 in an uninterrupted manner to effect a streamline flow of air into compartment 64.
Air flowing through opening 22 and diffuser 62 will v be circulated through compartment 64 in a balanced pattern essentially free of any turbulent flow, whereby the sweeping action of the circulating air on working surface 12 and the upper areas of compartment 64 will be efiiciently achieved. Thus, blower 58 may be operated at a relatively low Velocity to maintain the necessary sweeping action.
When panel 30 is in the raised position shown in FIG. 3, the lower airfoil surface 46 will again be within the path of a portion of air flowing through opening 22 and will thus provide a uniform deflection of the air to enhance the smoothness of air flow within compartment 64. Lower airfoil surface 46 cooperates with the laterally facing surfaces 26 of wall sections 24 to cumulatively effect optimum streamline flow through opening 22.
It will also be noted in FIG. 3 that air flowing through diffuser 62 will be directed against upper airfoil surface 48 of baille 34, whereby the latter deilects the ilow of air in a smooth manner at a constant velocity and direction along airfoil surface 48 to cause streamline ow of the air. Thus, when panel 30 is in its raised position, the upper and lower airfoil surfaces of bafe 34 will both act to retard turbulence within compartment 64 and thereby enhance the smooth and eiiicient circulation of air therewithin.
In FIGS. 4 and 5, a fume hood 10b is illustrated and is provided with a divider 150 forming a front compartment 152 and a rear compartment 154 within the upper portion of the hood. An exhaust blower 158 is mounted within compartment 154 and is adapted to draw air out of working compartment 164 along the opposed faces of partition 27 for directing air through outlet 168. An air inlet in the form of a bypass 160 is formed in front wall 20, and air passing therethrough enters compartment 152 for subsequent flow into compartment 164 through opening 162.
Lower airfoil surface 46 Will provide streamline ow of air through opening 22 into compartment 164 of hood b in the same manner as described above with respect to hood 10a. When panel 30 of hood 10b is in its lower position as shown in FIG. 4, air enters through bypass 160 and subsequently flows into compartment 164. However, when panel 30 is in the raised position shown in FIG. 5, the passage of air through bypass 160 will be blocked and air will enter only through opening 22. Thus, the primary turbulence control in this type of hood is provided by lower airfoil surface 46 and its cooperating airfoil surfaces 26 of wall sections 24.
It will be appreciated that the various airfoil surfaces of the turbulence control structure of the present inven tion will cumulatively provide uninterrupted flow of air into the working area of the fume hood and will aid efficient circulation through the hood as indicated by the ow pattern arrows in FIGS. 2-6. Since the direction of air will remain unchanged at every point on the airfoil surfaces, variances of velocity magnitude and direction will be minimized and thus, turbulent ow will be substantially reduced. It is particularly noteworthy that air flowing directly beneath edge 32 of panel 30 will have a streamline character irrespective of the vertical position of panel 30 since bafde 34 is designed to shift therewith. Therefore, an efficient fume hood is provided which can effectively maintain the necessary sweeping action at a relatively low blower velocity.
Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:
1. In combination with a fume hood having an air outlet, a front access opening, a vertically shiftable panel within the opening, permitting entrance of varying amounts of air into the front opening as the panel is shifted, and an air inlet above the opening, said panel having a horizontal lower edge spanning the opening, structure for controlling air turbulence within the hood comprising:
an elongated baffle spanning the distance across the opening,
said baffle having its longitudinal axis horizontally disposed,
means attaching the baffle to the panel at said lower edge thereof within the path of air owing into the hood through the air inlet and through the opening for vertical movement therewith, rendering the baffle effective in all vertical positions of the panel, said air inlet being located above the baffle when said baille is in its uppermost position,
the transverse aXis of the baie sloping at an angle downwardly from the panel and inwardly into the hood, presenting a lower, inclined, outwardly and downwardly facing airfoil surface for streamline ow of air into the hood through the opening, and an upper, inclined, inwardly and upwardly facing airfoil surface for 'streamline ow of air into the hood through said inlet.
2. The invention of claim 1, said means comprising a monolithic member having a pair of elongated channels connected to each other along the bights thereof to dispose the channels at said sloping angle, one of the channels embracing said lower edge of the panel and the other channel embracing said bale, there being a handle extending laterally outwardly from said one channel.
3. The invention of claim 1, said sloping angle being within the range of about to 150.
4. The invention of claim 1, and a pair of vertical wall sections on the hood adjacent said opening, said sections sloping inwardly into the hood presenting corresponding inclined, outwardly and laterally facing airfoil surfaces for cooperating with said lower surface of the baffle for streamline iow of air into the hood through the opening.
References Cited UNITED STATES PATENTS 2,819,666 1/1958 McNeil 98-115 3,000,292 9/1961 Wojan 98--115' 3,111,077 11/1963 Cortright 98-115 3,218,953 11/1965 Grow et al. 98-115 MEYER PERLIN, Primary Examiner.
M. A. ANTONAKAS, Assistant Examiner.