US20120322353A1

US20120322353A1 - Fume hood

Info

Publication number: US20120322353A1
Application number: US13/161,000
Authority: US
Inventors: Clifford Christopherson
Original assignee: Activar Inc
Current assignee: Activar Inc
Priority date: 2011-06-15
Filing date: 2011-06-15
Publication date: 2012-12-20

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

I. Field of the Invention
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.
II. Discussion of the Prior Art
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.
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.
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.
Conventional fume hoods also have an airfoil at the bottom front of the work chamber. The airfoil directs air across the fume hood'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'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.
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.
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 '827 patent”). The arrangement used in the Lin '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.
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 '233 patent”). In the Gilkison '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 '233 patent, like the Lin '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 '233 patent and the baffle in the Lin '827 patent is that the baffle in the Gilkison '233 patent has comparatively more apertures. However, the baffle in the Gilkison '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.
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.
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

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

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:

FIG. 1 is a perspective view of a fume hood structure in accordance with one embodiment of the present invention;

FIG. 2 is a cross-sectional left side view of the fume hood structure in accordance with one embodiment of the present invention;

FIG. 3 is a top view of the fume hood structure in accordance with one embodiment of the present invention;

FIG. 4 is a cross-sectional right side view of the fume hood structure in accordance with one embodiment of the present invention;

FIG. 5 is a partial perspective view of the fume hood structure in accordance with one embodiment of the present invention;

FIG. 6 is a front view of the fume hood structure in accordance with one embodiment of the present invention;

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

FIG. 8 is a partial cross-sectional left view of the airfoil in a rounded shape; and

FIG. 9 is a partial cross-sectional left view of the airfoil in an angular shape.

DETAILED DESCRIPTION OF THE INVENTION

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.
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.
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.
The automated sash assembly includes the sash door 200 and a first cable 230 attached to a first side 200A of the sash door 200 and a second cable 240 attached at one end thereof to a second side 200B 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.

Claims

1. A fume hood, comprising:

(a) a cabinet formed to define a chamber having a generally flat bottom work surface, opposed side walls, a top wall, a rear wall and an open front and a sash door mounted at the open front of said chamber for reciprocal movement on a vertical plane to selectively provide an access opening to said chamber;

(b) an airfoil disposed proximate the open front and the work surface of the cabinet for directing air through the access opening and into the chamber;

(c) at least one baffle including a plurality of rows of regularly laterally spaced apertures wherein said rows are regularly spaced apart along the height of the baffle; and

(d) at least one air exhaust outlet from the chamber formed in the top wall.

2. The fume hood of claim 1 wherein the apertures of the baffle are substantially rectangular in shape.

3. The fume hood of claim 1 wherein there are at least four rows of laterally spaced apertures.

4. The fume hood of claim 1 wherein the rows of apertures are spaced apart in approximately 12-inch intervals.

5. The fume hood of claim 1 wherein the apertures are substantially uniformly sized.

6. The fume hood of claim 1 wherein the baffle extends upward for a predetermined distance and includes an upper portion that slopes upward and forward.

7. The fume hood of claim 1 wherein the baffle further includes a plurality of rows of mounting screws adapted to fasten the baffle to a rear segment of the cabinet.

8. The fume hood of claim 7 wherein the mounting screws provide fastening points adapted for insertion of apparatus rods.

9. The fume hood of claim 7 wherein there are two rows of mounting screws.

10. The fume hood of claim 1 and further including:

(a) a first cable connected to a first side of the sash door and a second cable attached to a second side of the sash door;

(b) a first pulley arranged on a top side of the cabinet for receiving the first cable and directing the first cable horizontally;

(c) a second pulley arranged on the top side of the cabinet for receiving the first cable after it is received by the first pulley and directing the first cable downward into a slot in the top wall of the cabinet;

(d) a third pulley arranged on a top side of the cabinet for receiving the second cable and directing the second cable horizontally;

(e) a fourth pulley arranged on the top side of the cabinet for receiving the second cable and directing the second cable laterally;

(f) a fifth pulley arranged on the top side of the cabinet for receiving the second cable and directing the second cable downward into the slot; and

(g) a counterweight attached to the first and second cable.

11. The fume hood of claim 10 wherein a motor pulls the first and second cables to raise the sash upward on a vertical plane.

12. The fume hood of claim 1 wherein the airfoil is adapted to be movable to a first position and a second position.

13. The fume hood of claim 12 wherein when the airfoil is in the first position the airfoil is flush with the work surface, and when the airfoil is in the second position it is raised relative to the work surface.

14. The fume hood of claim 13 wherein the airfoil has a rounded shape.

15. The fume hood of claim 13 wherein the airfoil has an angular shape.

16. The fume hood of claim 1 wherein the airfoil is disposed flush with the work surface.

17. The fume hood of claim 1 wherein the airfoil is disposed in a low profile position wherein the airfoil is disposed above the work surface.

18. The fume hood of claim 17 wherein the airfoil is disposed approximately ⅜″ above the work surface.

19. The fume hood of claim 1 wherein the airfoil extends the length of the open face.

20. A fume hood, comprising:

(a) a cabinet formed with a chamber and having an open front face;

(b) an automated sash assembly adapted to cover the open face;

(c) an airfoil directing airflow through the open front face into the cabinet;

(d) a baffle including a plurality of ports allowing the airflow to be drawn behind the baffle by way of the Venturi effect, resulting from an increase in velocity of the airflow up and behind the baffle; and

(e) at least one air exhaust outlet from the cabinet.

21. The fume hood of claim 20 wherein the automated sash assembly includes:

(a) a sash door mounted for vertical reciprocal movement in the open front face;

(b) a first cable connected to a first side of the sash door and a second cable attached to a second side of the sash door;

(c) a first pulley arranged on a top side of the cabinet for receiving the first cable and directing the first cable horizontally;

(d) a second pulley arranged on the top side of the cabinet for receiving the first cable after it is received by the first pulley and directing the first cable downward into a slot in the cabinet;

(e) a third pulley arranged on a top side of the cabinet for receiving the second cable and directing the second cable horizontally;

(f) a fourth pulley arranged on the top side of the cabinet for receiving the second cable and directing the second cable laterally;

(g) a fifth pulley arranged on the top side of the cabinet for receiving the second cable and directing the second cable downward into the slot; and

(h) a counterweight attached to the first and second cable.

22. The fume hood of claim 20 wherein the airfoil is adapted to be movable to a first and a second position.

23. The fume hood of claim 22 wherein when the airfoil is movable between a first position flush with a work surface and a second position raised relative to the work surface to thereby facilitate airflow over and through the front of the chamber.

24. The fume hood of claim 20 wherein the airfoil is flush with a work surface of the cabinet.

25. The fume hood of claim 20 wherein the airfoil is raised relative to a work surface of the cabinet facilitating airflow over and through the open front face.

26. The fume hood of claim 25 wherein the airfoil is ⅜″ above the work surface.

27. The fume hood of claim 20 wherein the airfoil extends the length of the open face.

28. The fume hood of claim 20 wherein the airfoil has a rounded shape.

29. The fume hood of claim 20 wherein the airfoil has an angular shape.

30. The fume hood of claim 20 wherein the ports are arranged in a plurality of rows and are regularly laterally spaced within said rows.

31. The fume hood of claim 30 wherein the ports are substantially rectangular in shape.

32. The fume hood of claim 30 wherein there are at least four rows of vertically spaced ports.

33. The fume hood of claim 30 wherein the rows of ports are spaced apart in 12-inch intervals.

34. The fume hood of claim 30 wherein the ports are substantially uniformly sized.

35. The fume hood of claim 20 wherein the baffle extends upward for a predetermined distance and includes an upper portion that slopes upward and forward.

36. The fume hood of claim 20 wherein the baffle further includes at least one row of mounting screws adapted to fasten the baffle to a rear segment of the cabinet.

37. The fume hood of claim 36 wherein the mounting screws provide fastening points adapted for insertion of apparatus rods.