U.S. patent number 3,897,721 [Application Number 05/485,514] was granted by the patent office on 1975-08-05 for fumehood with compensating air supply.
This patent grant is currently assigned to The Rochelle Corporation. Invention is credited to Warren Fuhst.
United States Patent |
3,897,721 |
Fuhst |
August 5, 1975 |
Fumehood with compensating air supply
Abstract
The fumehood of this invention is so constructed that 70 or 80
percent of the hood exhaust is supplied to the interior of the hood
from an outside air source and the other 20 to 30 percent of the
hood exhaust is supplied from the room in which the hood is used. A
constant volume of outside, low pressure air is supplied to the top
of the hood while compensating louvers through the front of the
hood are positioned to provide a deflected air stream down the face
or front of the door. The flow of high volume, low velocity,
outside air toward and into the hood chamber is adjusted by louvers
to equalize all flow and permit very light or fragile materials to
be treated within the hood without blowing from their supported
condition particularly when the door is opened. The exhaust flow is
high velocity to insure a positive inward flow to prevent
accidental or unwanted blow back onto persons working at or near
the hood. The door which is moved to open and close the access
opening into the hood carries a deflector which is hinged at its
upper end and its lower end is guided and carried by a track so
that the make up air is deflected inwardly from the lower edge of
the door in an automatically increased or decreased condition as
the door is opened and closed.
Inventors: |
Fuhst; Warren (Katonah,
NY) |
Assignee: |
The Rochelle Corporation
(Fairfield, NJ)
|
Family
ID: |
26996013 |
Appl.
No.: |
05/485,514 |
Filed: |
July 3, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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349034 |
Apr 9, 1973 |
|
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Current U.S.
Class: |
454/59;
55/DIG.29; 55/418 |
Current CPC
Class: |
B08B
15/023 (20130101); Y10S 55/29 (20130101); B08B
2215/003 (20130101) |
Current International
Class: |
B08B
15/00 (20060101); B08B 15/02 (20060101); F23J
011/00 (); B01D 051/00 () |
Field of
Search: |
;98/115LH,115R,36,115VM,115K,121A ;55/418,DIG.29 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wayner; William E.
Assistant Examiner: Yuen; Henry C.
Attorney, Agent or Firm: Roberts; Ralph R.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of my U.S. patent
application, Ser. No. 349,034 and filed Apr. 9th, 1973, now
abandoned, and entitled, "Fumehood with Compensating Air Supply".
With the acceptance of the present application and the assigning of
a Ser. No. thereto the application, Ser. No. 349,034 is expressly
abandoned.
Claims
What is claimed is:
1. A fumehood which receives and diffuses into the interior chamber
a compensating make-up air supply of low velocity air and supplying
with said low velocity air a greater part of the hood exhaust
volume, said fumehood including: (a) a fumehood enclosure of metal
and having side walls, a top and bottom; (b) an access opening
formed in and through a front wall of said fumehood; (c) a
substantially vertically disposed, selectively movable door carried
by said front wall and by which the access opening into the hood
interior and work space is covered and uncovered; (d) means for
receiving and distributing through a plenum positioned in the top
of the hood an outside source of high volume, low pressure air; (e)
louvers mounted in said plenum and adjusted so as to feed like
amounts of air at like velocities through a multiplicity of
downwardly directed outlets so that the downward flow of air with
the door closed is distributed evenly over the work space in the
hood, said plenum and the adjustably mounted louvers having their
discharge position above the work space of the hood and occupying
at least two-thirds of the cross-sectional area of the hood and
with the source of high volume, low pressure air fed through said
plenum and louvers providing at least seventy percent of the
exhaust volume from said hood; (f) an air inlet means formed in the
front wall of the fumehood and a short distance above the access
opening and providing an inlet from the room into the interior of
the hood, said air inlet positioned so that when the movable door
is at its upper limit said inlet is substantially closed by said
door and when the door is moved to its down position the inlet is
open to the room, this inlet when the door is in a closed position
providing a supply of air from the room of not more than thirty
percent of the exhaust volume of the hood; (g) a front duct
extending from the room to a position where at its lower end it is
at about the upper edge of the access opening in the front wall,
said duct having its rear wall substantially parallel to the front
wall and a short distance therefrom this duct is closed to the
supply of high volume, low pressure air, the door movable in said
duct and as the door is in closed condition an air current is
guided to direct a flow of air from said access opening down the
inner surface of the door when and while the door is in a closed or
nearly closed condition, said duct providing a downwardly guided
air flow from the access opening into the midportion of the work
area of the hood without room supplied air flow disrupting the
controlled air flow in the hood; (h) a discharge inlet positioned
at the upper rear portion of the hood, this upper discharge inlet
connected to an exhaust system for removing the inlet air flowing
into the hood, this upper discharge inlet disposed to accommodate
about one-half of the exhaust volume; (i) a discharge inlet
positioned at the rear lower portion of the hood and disposed to
accommodate the remaining one-half of the exhaust volume, this
lower inlet connected by an appropriate duct work to the exhaust
system which is connected to the upper discharge inlet, and (j) a
deflector carried on the inner portion of the door and movable
therewith, said deflector disposed downwardly and inwardly so as to
deflect and direct inwardly the downwardly flowing air adjacent the
closed door and directing said flow of air toward the discharge
inlet positioned at the rear lower portion of the hood, said
deflector when the door is in its closed condition sealing the
bottom of the door and the front of the hood to assure that the
hood is closed except for the low pressure, high volume air through
the plenum and the air from the room which is fed in through the
air inlet above the door and through the front duct forming a
portion of the front face of the hood.
2. A fumehood as in claim 1 in which the deflector carried on the
door is automatically adjusted by and with the movement of the
door, this adjustment provided by apparatus so arranged that the
deflector exerts the greatest inward deflection when and as the
door is at and near its closed condition.
3. A fumehood as in claim 2 in which the automatic adjustment
apparatus includes a hinge by which the upper edge of the deflector
is attached to the door and the lower portion of the deflector is
guided and retained by a track disposed at a selected angle
divergent to the path of the door and with the deflector movable
and moved in a limited arc around the pivot pin of the hinge.
4. A fumehood as in claim 3 in which the track is pivotally
attached at its upper end to the fumehood side walls and the lower
end is adjustably secured to a fixed portion of the fumehood, the
lower portion of the deflector having a roller adapted to fit and
roll within the track.
5. A fumehood as in claim 4 in which there are two like tracks, one
being carried on one side wall portion and the other on an opposite
side wall portion with two rollers carried on the deflector, one on
each end of the deflector and also carried within a track.
6. A fumehood as in claim 3 in which the track is a bar which is
pivotally attached at its upper end to the fumehood side walls and
the lower end is adjustably secured to a fixed portion of the
fumehood, the lower end of the deflector having a pair of spaced
rollers adapted to engage opposite portions of the bar and follow
the track bar.
7. A fumehood as in claim 1 in which the air duct means from the
room into the hood includes an under floor duct which is open to
the front and immediately below the lowest portion of the access
opening of the fumehood, said under floor duct extending from this
inlet to an outlet which is connected to a back wall duct open to
both this bottom under floor duct and the discharge inlet at the
lower rear of the fumehood.
8. A fumehood as in claim 7 in which the opening from the fumehood
into the lower end of the back wall duct is adjusted by a regulator
blade adjustably secured to the fumehood to throttle this portion
of the exhaust flow and provide the desired division and velocity
of air and fumes from the bottom portion of the fumehood and from
the bottom duct.
9. A fumehood as in claim 7 in which the under floor duct has its
front opening provided with adjustable shutter means by which this
front opening is opened and closed and at least one actuating
member is disposed to be engaged as the door is moved toward and to
its access opening closing condition and with this actuating member
opening the adjustable shutter when and as the door is closed, and
also permitting the adjustable shutter to move to a closed
condition as the door is opened.
10. A fumehood as in claim 1 in which the source of high volume,
low pressure air is fed through an inlet duct having a flow
diverting means which is actuated in response to a failure of the
exhaust system, said flow diverting means shutting off all flow of
low pressure, high volume air to the hood and directing this flow
to other areas such as the atmosphere.
11. A fumehood which receives and diffuses into the interior
chamber a compensating make-up air supply of low velocity air and
supplying with said low velocity air a greater part of the hood
exhaust volume, said fumehood including: (a) a fumehood enclosure
of metal and having side walls, a top and bottom; (b) an access
opening formed in and through a front wall of said fumehood; (c) a
substantially vertically disposed, selectively movable door carried
by said front wall and by which the access opening into the hood
interior and work space is covered and uncovered; (d) means for
receiving and distributing through a plenum positioned in the top
of the hood an outside source of high volume, low pressure air; (e)
louvers mounted in said plenum and adjusted so as to feed like
amounts of air at like velocities through a multiplicity of
downwardly directed outlets so that the downward flow of air with
the door closed is distributed evenly over the work space in the
hood, said plenum and the adjustably mounted louvers having their
discharge position above the work space of the hood and occupying
at least two-thirds of the cross-sectional area of the hood and
with the source of high volume, low pressure air fed through said
plenum and louvers providing at least seventy percent of the
exhaust volume from said hood; (f) an air inlet means formed in the
front wall of the fumehood and a short distance above the access
opening and providing an inlet from the room into the interior of
the hood, said air inlet positioned so that when the movable door
is at its upper limit said inlet is substantially closed by said
door and when the door is moved to its down position the inlet is
open to the room, this inlet when the door is in a closed position
providing a supply of air from the room of not more than thirty
percent of the exhaust volume of the hood; (g) a front duct
extending from the room to a position where at its lower end it is
at about the upper edge of the access opening in the front wall,
said duct having its rear wall substantially parallel to the front
wall and a short distance therefrom this duct is closed to the
supply of high volume, low pressure air, the door movable in said
duct and as the door is in closed condition an air current is
guided to direct a flow of air from said access opening down the
inner surface of the door when and while the door is in a closed or
nearly closed condition, said duct providing a downwardly guided
air flow from the access opening into the midportion of the work
area of the hood without room supplied air flow disrupting the
controlled air flow in the hood; (h) a discharge inlet positioned
at the upper rear portion of the hood, this upper discharge inlet
connected to an exhaust system for removing the inlet air flowing
into the hood, this upper discharge inlet disposed to accommodate
about one-half of the exhaust volume; (i) a discharge inlet
positioned at the rear lower portion of the hood and disposed to
accommodate the remaining one-half of the exhaust volume, this
lower inlet connected by an appropriate duct work to the exhaust
system which is connected to the upper discharge inlet; (j) a
deflector carried on the inner portion of the door and movable
therewith, said deflector disposed downwardly and inwardly so as to
deflect and direct inwardly the downwardly flowing air adjacent the
closed door and directing said flow of air toward the discharge
inlet positioned at the rear lower portion of the hood, said
deflector when the door is in its closed condition sealing the
bottom of the door and the front of the hood to assure that the
hood is closed except for the low pressure, high volume air through
the plenum and the air from the room which is fed in through the
air inlet above the door and through the front duct forming a
portion of the front face of the hood, and (k) additional air inlet
means from the room which is an entry way into an under floor duct
which is open to the front and immediately below the lowermost
access opening of the fumehood this under floor duct passing
beneath the floor of the fumehood and connecting to a back wall
duct which is open to both this under floor duct and the bottom
discharge inlet at the bottom rear of the fumehood and at least one
adjustable shutter is provided in the under floor duct for opening
and closing the front opening of said under floor duct, this
shutter being a single door which is hingedly supported and is
actuated by a plunger moved by the door as it approaches, reaches
and leaves its bottom position.
12. A fumehood as in claim 11 in which the adjustable shutter means
is a plurality of louver members pivotally mounted and connected by
linkage means so as to be simultaneously moved in response to the
position of the door.
13. A fumehood as in claim 12 in which there is provided a tension
means adapted to urge the louver members into a closed condition.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
With respect to the classification of art as established in the
United States Patent Office the present invention pertains to the
general Class entitled, "Ventilation" (Class 98) and more
particularly to the subclass entitled, "hoods and off-takes"
(subclass 115) and also to the subclass entitled, "protecting air
current" (subclass 36).
2. Description of the Prior Art
Compensation fumehoods, of course, are well known in the art with
one such hood being represented in U.S. Pat. No. 3,340,788 to
LANDINGHAM et al. as issued on Sept. 12th, 1967. Other hoods are
depicted in U.S. Pat. No. 3,111,077 to CORTRIGHT as issued on Nov.
19th, 1963 and in U.S. Pat. No. 3,604,333 as issued to NELSON on
Nov. 5th, 1969. In these and in other patents the hoods are
provided with an auxiliary air supply. However, in operation these
hoods prove less than satisfactory in that the velocity of air
being fed from the auxiliary supply to the interior of the hood is
excessive for small and fragile articles subject to blowing. At
this same time the velocity and direction of make-up air is such as
to often cause air and fumes in the hood to be forced therefrom
into the room. In some systems the make-up air is fed to the outer
or exterior of the hood and then caused to be fed into the hood
through the open door in the manner of an air curtain. In many
known systems the inwardly directed flow of make-up air into the
hood is not equally distributed resulting in unsatisfactory
internal conditions.
In the present invention 70 to 80 percent of the exhaust air from
the hood is furnished as make-up or compensating air of high
volume, low velocity air. This compensating air, by a system of
louvers, is fed in a controlled and balanced flow into the top of
plenum portion of the hood. Air from the room may be fed into the
hood through a louvered portion at the front of the hood and within
the hood is diverted down the front of the hood and door. The door
has a hinged deflector which is carried on a track means so as to
provide an automatically adjusted variable deflection of the room
and make-up air at the front of the hood so as to urge the air
stream toward the rear and bottom of the hood. As this hood is also
designed to draw 20 to 30 percent of its discharge volume from the
room itself, there is a positive flow of this room air to and into
the hood as in most fumehoods. However, the volume of air drawn
from the room is very low in comparison to known prior art devices.
As reduced to practice and as seen in the accompanying drawings,
there are shown several preferred embodiments. One embodiment
provides an automatically adjustable feeding of room air into and
down the inside front of the hood and the other or alternate
embodiment shows a louver feed for creating a negative pressure at
the lower rear of the hood in order to insure that heavy gases and
the like which are developed in using of the hood are drawn from
the lower back of the hood and expelled through a back duct in the
usual manner. In all embodiments the door is disposed to close the
access opening tightly to seal the hood against discharge of fumes
from the access opening in case of a small explosion. In the
embodiments to be shown and described the air drawn from the room
should never vary regardless of the door position. Operation of the
hood in any other manner will result in either blowback of
contaminators or in a radical imbalance of heating and cooling
systems.
SUMMARY OF THE INVENTION
This invention may be summarized at least in part by reference to
its objects.
It is an object of this invention to provide, and it does provide,
a fumehood in which at least 70 to 80 percent of the air discharged
from the hood is supplied as compensating air of high volume, low
velocity and delivered to the top or plenum portion of the hood and
the remaining 20 to 30 percent of the discharge air is room air fed
to the interior of the hood through a louvered opening above the
door or as a feed duct beneath the floor of the hood.
It is a further object of this invention to provide, and it does
provide, a fumehood in which the top or plenum of the hood is
supplied with high volume, low pressure air and by means of a
vertically reciprocated door and a hinged deflector which is
carried on the lower inside of the door and by an adjustably
positioned guide means a deflecting flow is provided for both the
pressurized air and the air drawn from the room.
The hood of this invention may be of any selected configuration.
Usually, however, it is rectangular in shape with one of the broad
wall members being the surface in which an access opening is
provided and a vertically movable door or sash is mounted to close
said opening. In the present invention this door has a deflector
mounted on its lower inner portion, this deflector has its lower
portion carried on an adjustable track so that as the door or sash
is moved up and down the lower end of the deflector is caused to
move inwardly and outwardly to insure that the air supply delivered
within the hood and from the room is directed toward the back of
the hood and from there is expelled by the exhaust fan rather than
allowing any internal pressure in the hood to be developed causing
back flow of the hood content gases and the like into the room. In
its closed condition the door or sash completely covers the access
opening to insure that no explosion or accidental disruption of
exhaust will cause danger to the occupants of the room. The hood,
to be hereinafter more fully described, receives from an exterior
source a high volume of low pressure air and by louvers and
deflectors this air is fed at a relatively equal velocity and
volume into the top or plenum of the hood. Generally more than
eighty percent of the hood area receives and guides the inflow so
as to provide a high volume, low velocity supply of air to all the
hood. In one embodiment, a portion of the air directed downwardly
and inwardly from the movable door is also compensated for by
louvers at the upper end of the movable door. In other embodiments
a lower exterior duct draws air from the room and bottom front of
the hood and its feeding to a rear discharge duct results in a
negative pressure to be developed at the lower back of the hood.
Automatic louver control for this lower duct is also disclosed.
In addition to the above summary the following disclosure is
detailed to insure adequacy and aid in understanding of the
invention. This disclosure, however, is not intended to prejudice
that purpose of a patent which is to cover the inventive concept no
matter how it may later be disguised by variations in form or
additions of further improvements. For this reason there has been
chosen specific embodiments of the fumehood for use in a laboratory
and the like and showing a preferred means for supplying
compensating high volume, low pressure, outside air to provide 70
to 80 percent of the exhaust air from the hood. A specific
embodiment and alternate embodiments thereof have been chosen for
the purposes of illustration and description as shown in the
accompanying drawings wherein :
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents a front or face view of a preferred embodiment of
the fumehood and showing in particular the proposed arrangement of
the adjustable members used with the fumehood to control the air
flow in the hood;
FIG. 2 represents a sectional side view, partly diagrammatic and
further showing the arrangement of the components of the hood of
FIG. 1, this view taken on the line 2--2 of FIG. 1 and looking in
the direction of the arrows;
FIG. 2A represents in an enlarged scale a partly fragmentary
sectional side view of FIG. 2 and in a partly diagrammatic manner
particularly showing a front duct by which air from a front access
opening is guided down the inside face of the movable door;
FIG. 3 represents a plan or top view of the fumehood and looking
downwardly at the hood of FIG. 1, this view taken on the line 3--3
of FIG. 1 and looking in the direction of the arrows;
FIG. 4 represents a fragmentary sectional side view of the hood of
FIG. 1 and diagrammatically showing a louvered control of the inlet
flow of the room air, which flow is automatically actuated in
response to the up-and-down movement of the door used with the
fumehood, this view taken on the line 4--4 of FIG. 5;
FIG. 5 represents a fragmentary front view of the louvered portion
of FIG. 4, this view being partly diagrammatic and showing one
arrangement by which the louvered mechanism may be actuated;
FIG. 6 represents a side view of an alternate means of
automatically guiding and moving a curved deflector hingedly
secured to the hood door, this deflector being guided by a curved
track principle so as to provide the desired direction of downward
flow of the air fed in from the top of the fumehood;
FIG. 7 represents a fragmentary front view showing an alternate
arrangement of the hood of FIG. 1, in this embodiment an under
bottom air channel rather than a top grill opening into the hood is
provided so as to feed room air to the rear of the chamber;
FIG. 8 represents a side view of the apparatus of FIG. 7, this
fragmentary side view taken on the line 8--8 of FIG. 7 and looking
in the direction of the arrows;
FIG. 9 represents a diagrammatic side view of an alternate
arrangement of a bench-type fumehood having an under bottom air
channel with a louvered opening;
FIG. 10 represents a front view of the apparatus of FIG. 9, this
view taken on the line 10--10 of FIG. 9 and looking in the
direction of the arrows;
FIG. 11 represents a diagrammatic side view of a fumehood similar
to the hood of FIG. 9 but depicting a large, floor-type hood with
walk-in capability and with an under bottom air channel with a
louvered opening;
FIG. 12 represents a front view of the apparatus of FIG. 11, this
view taken on the line 12--12 of FIG. 11 and looking in the
direction of the arrows;
FIG. 13 represents a fragmentary front view of the bench-type hood
of FIG. 9 and showing the lower portion and an automatic door
opening means for the under bottom air channel;
FIG. 14 represents a fragmentary side view of the bench-type hood
under bottom door closing device of FIG. 13;
FIG. 15 represents in an enlarged scale a side view similar to FIG.
14 and showing in detail the components of the door closing
apparatus;
FIG. 16 represents a front view, partly fragmentary of the
apparatus shown in FIG. 17;
FIG. 17 represents a front view, partly fragmentary of yet another
under floor door closing apparatus;
FIG. 18 represents a fragmentary side view, partly diagrammatic of
the mechanism of the door closing apparatus of FIG. 17;
FIG. 19 represents in an enlarged scale a diagrammatic showing of
the arrangement of the door closing apparatus of FIG. 18;
FIG. 20 represents in a scale similar to FIG. 19 an alternate
biasing means for the apparatus of FIG. 19, and
FIG. 21 represents an exploded isometric view of a typical fumehood
and of the several components and their relationship to each
other.
In the following description and in the claims various details will
be identified by specific names for convenience; however, these
names are intended to be generic in their application.
Corresponding reference characters refer to like members throughout
the several figures of the drawings.
The drawings accompanying, and forming part of, this specification
disclose certain details of construction for the purpose of
explanation of the broader aspects of the invention, but it should
be understood that structural details may be modified in various
respects without departure from the concept and principles of the
depicted fumehoods and that the invention may be incorporated in
other structural forms than shown.
Description of the Embodiment of FIGS. 1, 2 and 3
In FIGS. 1, 2, 2A and 3 the fumehood of this invention is depicted
as being a rectangular chamber generally indicated as 10.
Conventionally, this like most fumeheads is made of sheet metal
with a treated surface such as painting, plating or the like
provided to accommodate the particular operation conditions. Other
materials, of course, may be used where desired or required to
comply with specifications. This chamber has its upper bonnet or
plenum portion 11 connected to an inlet duct generally indicated as
12. This duct is connected to inlets 14 and 16 which receive and
deliver make-up air to the plenum portion above the chamber 10.
Inlets 14 and 16 are each provided with blade deflectors 20 which
are adjustably mounted so as to be selectively positioned by the
installation supervisor or supplier to direct the flow of high
volume, low pressure air to the plenum 11 to achieve a balanced and
evenly distributed flow. In the plenum 11, deflector blades 22 are
provided to further divide, guide and distribute the flow of
compensating air toward and into the chamber portion of the
hood.
At the lower end of the plenum portion there is provided a louvered
portion 24 which has a plurality of deflector blades which are
adjusted so as to guide and distribute the make-up air and provide
an even downward flow of the air. This downward stream of air
usually occupies about two-thirds of the horizontal cross area of
the chamber. As seen in FIGS. 2 and 2A, there is provided a light
means 26 which is illuminated when door 28 is raised from a closed
condition. This light may be manually actuated for observation.
Door 28 in the fully lowered condition tightly closes access
opening 29.
At the upper rear of the chamber 10 there is provided outlet ducts
30 and 32. Duct 30 is open to a very small portion of the upper
rear of the chamber 10 while duct 32 is connected to back wall
conductor 33 whose lower end is open to the bottom back of the
chamber. Flow of air to and through conductor 33 is regulated by
means of an adjustable regulator blade 34 which is raised or
lowered to provide an opening to establish the desired amount of
current flow to the exhaust through duct 32. The exhaust system
provided for this system desirably has an excess capacity which is
throttled to provide the desired rate of evacuation of the
chamber.
The door or sash 28 of this hood is carried in vertical tracks 35
and for ease of operation is conventionally counterbalanced as by
weights 36. With the door in the down or closed condition a grill
opening 38 in the upper front wall and positioned slightly below
the louvered portion 24 is uncovered so that room air is drawn into
the confines of the hood. Louvers are placed in or behind this
grill opening to control the volume and direction of the flow of
air from the room and to the interior of the hood. As seen in FIG.
2A the flow of room air is through a front duct which has its upper
closed end placed above the grill opening and has its lower opening
at or slightly above the top of the access opening 29. This duct
conventionally includes a back plate 39 placed a short distance
back of the path of the door or sash 28 which moves within the
duct. The width of this duct may be 1 to 11/2 inches in the case of
smaller vent hoods, or in the case of very large vent hoods may be
as deep as three inches. When the door is in the closed or nearly
closed condition, the air flowing through this access opening and
down the front duct wipes the inside of the door. This downwardly
directed air is so directed as to avoid moving material in the
midportion of the work area and thus avoids disturbing the work
area by room supplied air which may be as much as 30 percent of the
total volume. The size of the grill opening 38 and the louvers
arranged therein are sized so as to accommodate the inward flow of
air from the room which makes up the lesser portion of the total
exhaust air. On the bottom of the door 28 there is adjustably
carried a plate 40 which is adjusted to provide a desired precise
engagement of the lower edge of this plate 40 to the floor 41 of
the hood. Carried on each of the sides of the chamber and adjacent
the door opening are guide tracks 42 whose lower ends are pivotally
supported by brackets 44 adjustably secured to the frame of floor
41 of the hood.
Attached as by a piano-type hinge 46 secured to the back side of
the door 28 is a deflector 48. This deflector may have its lower
end weighted as by a rod on whose ends are rotatably mounted
rollers 50. These rollers are retained and guided in the tracks 42
so that as the door 28 is moved up and down the deflector 48 is
automatically moved toward or away from the door to provide a
selected deflection path which changes in accordance with the
height position of the door from the floor. In several reduced to
practice fumehoods it has been found that deflector 48 is most
effective if made with an arcuate configuration and mounted as
shown.
Automatically Adjusted Louver of FIGS. 4-5
Depicted in FIGS. 4 and 5 is a louvered apparatus which may be used
instead of the louvered distributor portion 24 of FIGS. 1-3. In
this alternate apparatus there is provided a series of louver
blades 60 pivotally mounted and which may or may not be of like
size. These blades are carried on pivot rods 62 carried by support
means in the side wall 64. These louver blades, by means of pivoted
connector members 66 and 68, may be swung around pins 62 to
selected attitudes with all the blades taking the same attitude. On
the back face of door 28 are mounted cam pads 70 and 72 which are
vertically positioned at selected heights so as to engage extending
portions of connectors 66 and 68. Pad 72, for example, engages
connector member 66 and positions louver blades 60 when the door 28
is in the closed condition. Pad 70 which is offset inwardly from
pad 72 engages connector 68 as the door is raised and causes the
louver blades 60 to be set to the desired angle while and as the
door is raised and remains in this raised condition.
Alternate Deflector as Seen in FIG. 6
Referring next to the alternate deflector guide as seen in FIG. 6,
there is depicted apparatus in which a guide bar 80 is used instead
of the track 42 of FIG. 2. Hinge 46 and deflector 48 are
substantially identical to the ones shown in FIG. 2 except that
instead of roller 50 a trolley member which includes rollers 82 and
84 are mounted on and are retained in a fixed spaced relationship
by a bar 86. As thus arranged the rollers 82 and 84 engage opposite
sides of bar 80 to guide the deflector 48 toward or away from door
28 in accordance with the position of the door and the bar 80.
Fumehood of FIGS. 7 and 8
Referring next to FIGS. 7 and 8, there is shown another hood
arrangement wherein the hood of FIG. 1 is absent grill 38. This
alternate fumehood, primarily for use where the fumes are heavy
and/or dangerous, includes a duct 90 which is disposed below hood
floor 41. The front of this duct extends across the width of the
hood and usually has a louvered section 92 at or in its inlet end.
These louvers guide the incoming air through the inlet so as to
develop the desired suction at or near the front base portion of
the hood. The rear of this duct 90 is open to back wall duct 133
which is similar, if not identical, to duct 33 in FIG. 2. Bottom 41
terminates short or back wall 94 and is turned upwardly to provide
a guide for the flow through duct 90.
The forward wall of duct 133 is identified as 96 and has an
adjustable blade 34 by which the opening between floor 41 and
forward wall 96 is regulated. As in the hood of FIG. 1, the front
door 28 is made with an adjustable blade 40 carried near its lower
edge. The lower portion of this same front door also has a
deflector 48 hingedly attached to the inner side of the door and
automatically adjusted by means of track 42 or, if desired, by the
bar 80 of FIG. 6. Duct 90, where the fumehood is supported by a lab
bench and the like, is usually formed and attached to back wall
duct 133 by passing this duct 90 beneath the lab bench top.
Fumehood of FIGS. 9 and 10
Referring now to FIGS. 9 and 10, there is shown another fumehood
wherein as in FIG. 8 there is provided an under floor duct 100
which as depicted is above a cabinet section 102. The floor 103
terminates at an upturned deflector 104. This leaves a narrow
opening from the under floor duct 100 into the rear wall duct 105
which is the channel between the rear wall 106 and front panel 107.
This front panel 107 at its lower end is bent forwardly and
downwardly at 108 to provide an access opening from the chamber to
the rear wall duct 105 at its floor line. As in the prior described
hoods the inlet plenum 109 occupies more than two-thirds of the
upper area of the hood. The front portion of the plenum carries a
baffle 110 which extends from the top of the hood to access opening
111.
This baffle is a short distance such as about one inch behind door
or sash 112. A pivoted deflector 114 is carried on the lower edge
of the door and when this door is fully lowered the deflector
engages the floor to provide a positive closing of the access
opening 111.
Fumehood of FIGS. 11 and 12
Referring next to FIGS. 11 and 12, there is depicted a floor-type
hood which is adapted for large retorts that stand more than 2 feet
from the floor. This hood has an under floor duct 120, as in FIG.
10, with the front of this duct having a munipulative louver 121.
The floor 122 provides the upper portion of duct 120 while ends 123
and 124 and the base plate 124 form the other three sides. Four
doors, 126, 127, 128 and 129 are slidable sideways in tracks. The
plenum 130 carrying the compensating air occupies more than 75
percent of the upper area of the hood. As in FIG. 9, the rear wall
duct 131 leading to the discharge outlet includes the back wall 132
and a front panel 134. The lower portion of panel 134 is bent
forwardly and thence downwardly to provide an access opening from
the hood chamber to the rear wall duct 131 at the floor level. At
the upper portion of the hood, a duct 136 is provided to remove
about one-half of the exhausted air from the hood. As reduced to
practice, the output from the combined exhaust ducts are at not
less than 2,000 cubic feet per minute.
Automatic Louver Mechanism of FIGS. 13 thru 20
Referring next to FIGS. 13 through 20, there is depicted
automatically-actuated louver mechanisms for an under floor duct
such as shown in FIGS. 8, 9 and 11. As shown in the mechanism of
FIGS. 13 through 16, a door 150 is carried by a piano hinge 152
whose fixed leaf is secured to floor 153 of the hood. A U-shaped
track 154 is carried by the side wall 155 of the under floor duct.
On a slide guide 156 is slidably mounted a bushing 158 which
pivotally carries the upper end of a lever 159. The lower end of
this lever is pivotally connected to a link 160 whose other end is
pivotally connected to the lower end of door 150. At the pivoted
connection of lever 159 and link 160 there is provided an axle 161
on which is rotatably carried a roller 162. The lower end of sash
164 carries a plunger rod 165 which, as seen in FIG. 16, is
disposed to engage the top of bushing 158 and as sash 112 is
brought downward to the closed condition the bushing 158, lever 159
and link 160 are moved to the condition shown in phantom outline in
FIG. 15. The inward movement of this linkage causes door 150 to be
swung inwardly to open the under floor duct to the influence of
exhaust air. A spring or weight, not shown, automatically urges the
door 150 to a closed condition as sash 112 is raised and a plunger
rod 165 is raised therewith. A lever mechanism but as a mirror
image of that as is shown in FIG. 16 is carried on the left side of
door 150 and is actuated by sash 112 in concert with the mechanism
specifically shown in FIG. 16.
Automatic Louver Closure As In FIGS. 17, 18 and 19
Referring next to the drawing in which is shown an automatic louver
closure wherein a plurality of segments are pivotally mounted and
are opened and closed to open the front of an under floor duct. As
shown, a hood 170, similar to those discussed above, has a floor
171 in which is provided an access hole 172. Through this hole
passes an actuator pin 173 as a sash 112, such as in FIG. 13, is
brought toward and to the floor 171. This actuator pin as it passes
through access hole 172 strikes and moves pin 174 whose lower end
is pivotally connected to a lever member 175 and link 176. Member
175 is fixed to the center portion of louver plate 178 which is
pivotally mounted for rotation around its longitudinal axis. Link
176 has its other end pivotally connected to a lever 179 which is
secured to the back side of lower louver plate 180. This louver
plate is also pivotally mounted for rotation around its
longitudinal axis. Tension spring 182 is secured to lever member
175 and the floor 171 to urge the louver plates 178 and 180 to a
closed condition.
Automatic Louver Closure Mechanism as in FIG. 20
Alternately shown in FIG. 20 is a multiplate louvered mechanism for
closing of an entrance of under floor duct. This arrangement is
also figuratively shown in FIG. 18. As shown, louver plates 186,
187, 188 and 189 are pivotally mounted to rotate around their
longitudinal axis. An actuating lever 190 is fixedly connected to
louver plate 189 so as to rotate this plate as it, the lever 190,
is moved. The other end of lever 190 is pivotally connected to drag
link 191. This link is pivotally connected to arms 192, 193 and
194. Arm 192 is fixed to louver plate 188. Arm 193 is fixed to
louver plate 187 and arm 194 is fixed to louver plate 186. A
tension spring 195 has its lower end secured to a structure portion
and its upper end to the lower end of link 191.
Operation of Automatic Louvers of FIGS. 19 and 20
With the sash 112 in its up or open position, the automatic louver
assemblies of FIGS. 19 and 20 are closed. The sash 112 is moved
downwardly for closing the access opening of the hood and at a
determined distance from the closing position of this opening the
actuator pin 173 is brought into effective engagement with the
louver opening mechanism. In FIG. 19 this mechanism begins to open
when pin 173 engages and moves pin 174 downwardly. Lever members
175, 176 and 179 are simultaneously moved until they achieve the
"louver open" condition as depicted in phantom outline. In the
"sash closed", "louver open" condition, the upper louver plate 178
is rotated about forty-five degrees counterclockwise around its
longitudinal axis and lower louver plate 180 is rotated a like
amount but clockwise around its longitudinal axis. Spring 182 is
stretched to provide a sufficient bias to return the louver
mechanism to a closed condition when the sash is raised.
In FIG. 20 and with the sash 112 in its raised, access-opening,
opened condition, the louver mechanism is closed as in FIGS. 18 and
20. As sash 112 is moved downwardly the actuator pin 173 engages
actuator lever 190 to rotate it counterclockwise around its pivoted
support means. As it rotates so does the connected louver plate
189. Simultaneously link 191 and connected arms 192, 193 and 194
are moved to eventually achieve the condition of the phantom
outline. Louver plates 186, 187 and 188 are rotated
counterclockwise and spring 195 is stretched to provide the
required bias to again close the louvered mechanism when and as the
sash 112 is raised.
Exploded View of a Typical Fumehood as in FIG. 21
Referring finally to FIG. 21, there is shown an exploded view of a
typical fumehood and the related arrangement of the several
components which comprise the hood. As depicted, this hood has a
pair of like sash members 200 and 201. Each sash has a pivoted
lower curved deflector 202 which in the sash closed condition
engages the floor, not shown. Upper facing members 204 and 205 are
formed with guideways into which the associated sash slides up and
down. A small slot opening 206 and 207 is provided in the
respective upper facing member and permits a small amount of room
air to enter the hood when the associated sash is in its closed
condition. Header spacer 209 provides the front wall of the plenum.
Baffle 210 extends downwardly from spacer 209 to provide the front
guide path for room air drawn into the hood through slots 204 and
205 when and as sash 200 and 201 are lowered to close the hood.
End members 212 and 213 are carried by base sections 214 and 215
which mount to the bench or floor. End plates 217 and 218 are
secured to end members 212 and 213 to provide hollow walls for
insulation, etc. Forward wall 220 is secured to rear wall 222 for
the forming of the rear wall duct. Deflectors 224 are arranged to
direct the up flow toward four outlets. Collector 226 not only
directs the rear wall duct to four connectors 228 but also the
exhaust from the upper rear portion of the hood is fed through
these connectors to an exhaust system.
The compensating air is fed to the hood through two like ducts
which preferably have a safety deflector system employing pivoted
members 229 and 230 carried in duct 232. This safety system is
actuated when exhaust air fails or falls below a defined volume
limit. Directionally adjusted vanes 234 spread the high volume, low
velocity compensating air as it passes from duct 232 and through
elbows and to diffusing transition sections 238. This stream of air
passes through adjusted louver section 240 and into the hood.
Lights 242 illuminate the interior of the hood when actuated or the
sash is raised.
Filters 244 may be used in conjunction with the incoming low
pressure compensating air. Plate 246 and header member 248 close
the front of the outlet duct and the rear of the plenum above the
louvers 240. In all essentials except for guide tracks for
deflector 202 the hood of FIG. 21 is like the hood of FIGS. 1 and 2
except that this hood has a pair of sashes for a double capacity
hood.
Use and Operation of the Fumehood
Although the embodiments, above-described, are generally identified
as fumehoods this term is applied only as a general identification
of the apparatus since fumes do not necessarily have to be
developed. This apparatus is intended to evacuate the hood by
negative pressure and to supply 70 to 80 percent of the air
exhausted through the rear wall ducts from high volume, low
pressure air fed into the plenum through one or more inlets.
Deflectors distribute this flow to the plenum and by means of a
louver system the high volume, low pressure flow is directed as an
even blanket flow toward the lower area of the hood. The outlet
duct from the upper hood and rear wall outlet duct are connected to
an exhaust fan, not shown, so as to draw the make-up or
compensating air supplied as well as the ten to thirty percent of
room air through slots in the front wall, the open sash and/or
under floor ducts.
To insure that the make-up air and/or fumes in the hood of FIG. 1
are expelled through the ducts 30 and 32 and no fumes are lost when
the door 28 is opened, the automatically adjusted deflector 48 on
door 28 as it is initially raised is at its maximum inward extent
and deflection angle. This deflection angle decreases as the door
is raised to provide a larger opening into the hood. This upward
movement of the door also cuts off the room air flow through grill
38 to the interior of the hood. Where the hood is equipped with the
automatic louver of FIGS. 4 and 5, the flow path of low pressure
air downwardly from the plenum 11 and into the hood operating area
is automatically changed by the upward and downward movement of the
door 28 as the cam pads 70 and 72 are selectively and alternately
brought in way of the ends of connector members 66 and 68. Baffle
39 insures that the flow through the grill 38 flows down the front
of the hood and toward the flow to disturb as little as possible
the balanced flow through the plenum.
The embodiment of FIGS. 7 and 8 eliminates the grill inlet 38 next
to the plenum while there is provided the under floor duct 90 to
draw any leak or initial out flow of hood air from the lower end of
the hood. This opening from the hood to the inlet to duct 133 is
adjusted by positioning regulator blade 34 to suit the desired air
current flow through duct 90 and the bottom of the hood. The under
floor duct removes heavy gases and insures that any seepage is
positively discharged.
In all hoods the plenum delivering the high volume, low pressure
air occupies at least two-thirds of the upper area of the hood. The
exhaust duct system except for two or three inches used for the
tubular light occupies nearly all the remainder of the hood area.
The balancing of the evacuation from the upper portion of the hood
and from the lower rear of the chamber insures that the maximum
portion of exhaust air is supplied by the high volume, low pressure
compensating air supply.
In reduced to practice tests, fumehoods in various sizes and in
accordance with the above construction and air flow arrangement
have performed superbly. The furnishing of seventy to eighty
percent of the exhaust air as low pressure, high volume, make-up
air through the controlled louvered discharge from the plenum
maintains the heating efficiency of the room and reduces to a very
low level the air current flow over the specimen being treated. The
automatic actuation of a deflector on the raising and lowering of
the door or sash eliminates the escape of air into the room to the
extent that if it does occur it is unmeasurable. In tests made by a
certified testing laboratory smoke and flow currents indicate that
these results are achieved because all the input air is at a low
pressure and is at a sufficient volume to prevent unwanted pressure
differential areas except at the negative pressure inlets to the
ducts connected to the exhaust system. These negative pressure
inlets have adjustable control means so that every installation is
tailored to the particular operating conditions such as natural air
currents in the room, heat or cooling requirements in the hood,
average size of speciment and treating means, etc. The hood, in the
various embodiments above shown and described, is, of course, made
in many sizes and materials to suit the required conditions. The
providing of high volume, low pressure air whose velocity does not
exceed 125 feet per minute and is diffused through a louvered area
which is at least two-thirds the hood area has provided a highly
satisfactory hood which, as far as is known, provides superior
protection and efficiency to those of other designs presently in
the field.
Terms such as "left", "right", "up", "down", "bottom", "top",
"front", "back", "in", "out", "clockwise" and the like are
applicable to those embodiments shown and described in conjunction
with the drawings. These terms are merely for the purpose of
description and do not necessarily apply to the position in which
the fumehood may be constructed or used.
While these particular embodiments of the fumehood have been shown
and above-described it is to be understood the invention is not
limited thereto since modifications may be made within the scope of
the accompanying claims and protection is sought to the broadest
extent the prior art allows.
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