U.S. patent application number 13/161000 was filed with the patent office on 2012-12-20 for fume hood.
This patent application is currently assigned to ACTIVAR, INC.. Invention is credited to Clifford Christopherson.
Application Number | 20120322353 13/161000 |
Document ID | / |
Family ID | 47354036 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120322353 |
Kind Code |
A1 |
Christopherson; Clifford |
December 20, 2012 |
FUME HOOD
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.
Inventors: |
Christopherson; Clifford;
(Lakeville, MN) |
Assignee: |
ACTIVAR, INC.
Minneapolis
MN
|
Family ID: |
47354036 |
Appl. No.: |
13/161000 |
Filed: |
June 15, 2011 |
Current U.S.
Class: |
454/56 |
Current CPC
Class: |
F24F 3/1607 20130101;
F24F 7/00 20130101 |
Class at
Publication: |
454/56 |
International
Class: |
F24F 7/00 20060101
F24F007/00 |
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 3/8'' 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 3/8'' 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.
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'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.
[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 '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.
[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
'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.
[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 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.
[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 3/8'' 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
510a as shown in FIG. 8 or an angular shape 510b 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.
* * * * *