US3897721A

US3897721A - Fumehood with compensating air supply

Info

Publication number: US3897721A
Application number: US485514A
Authority: US
Inventors: Warren Fuhst
Original assignee: ROCHELLE CORP
Current assignee: ROCHELLE CORP
Priority date: 1973-04-09
Filing date: 1974-07-03
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05

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.

Description

United States Patent Fuhst Aug. 5, 1975 1 1 FUMEHOOD WITH COMPENSATING AIR Primur Emminer-William E. Wayner SUPPLY Aiziismnr E.\'uminer--Henry C. Yuen [75] Inventor warren Fuhst Katonah N Y Arturney. Agent. or Firm-Ralph R. Roberts [73] Assignee: :hJe Rochelle Corporation. Fairfield. BS C [22] Filed July 3 1974 The fumehood of this invention is so constructed that i 70 or 80 percent of the hood exhaust is supplied to the 1 1 PP 435,514 interior of the hood from an outside air source and the Related U.S. Application Data [63] Continuation-impart of Ser. No. 349.034. April 9.

1973, abandoned.

i 1 U.S. C1. 98/115 R; 98/115 LH; 55/418; 55/D1G. 29 [51] Int. Cl. F211 l1/00;BO1D 51/00 158] Field ofSeareh ..98/1l5 LH. 115 R, 36. 98/115 VM. 115 K. 121 A; 55/418. DIG. 29

[56] References Cited UNITED STATES PATENTS 2.549.042 4/1951 Angermueller 98/115 LH 2.704.505 3/1955 Morn'son 98/115 LH 2.901.226 8/1959 Modine 55/418 3.111.077 11/1963 Cortright 98/1 15 LH 3.318.227 5/1967 Nelson et a1. l. 98/115 LH 3.340.788 9/1967 Landingharn et all 98/115 L H 3.408.914 11/1968 Bayern 98/1 15 LH 3.587.442 6/1971 Jakeway. 98/1 15 LH 3.604.333 9/1971 Nelson 98/115 LH 3.691.687 9/1972 Economoa 1. 98/115 [.H

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 he 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.

13 Claims. 22 Drawing Figures PATENTED AUG 51975 SHEET Fig.2

Fig. 2A

PATENTEU AUG 51975 SHEET PATENTED RUB 5 I975 SHEET WWW WWW 'm Hh ll m n 1 FUMEHOOD WITH COMPENSATING AIR SUPPLY CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my US. 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.

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 offitakes" (subclass I) 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 US. Pat. No. 3,340,788 to LANDINGHAM et al. as issued on Sept. 12th, 1967. Other hoods are depicted in US. Pat. No. 3,111,077 to CORTRIGHT as issued on Nov. 19th, 1963 and in US. 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 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 to 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 pres surized 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. I, this view taken on the line 22 of FIG. I 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. I, this view taken on the line 3-3 of FIG. I and looking in the direction of the arrows;

FIG. 4 represents a fragmentary sectional side view of the hood of FIG. I and diagrammatically showing a louvered control of the inlet flow of the room air, which flow is automatically actuated in response to the upand-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. ll 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 open- FIG. 12 represents a front view of the apparatus of FIG. 11, this view taken on the line l2l2 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 ll connected to an inlet duct generally indicated as 12. This duct is connected to inlets l4 and 16 which receive and deliver make-up air to the plenum portion above the chamber 10. Inlets l4 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 II, 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 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 1% 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 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. I is absent grill 38. This alternate fumehood, primarily for use where the fumes are heavy and/or dangerous, includes a duct 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. I, the front door 28 is made with an adjustable blade 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 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 I33 by passing this duct beneath the lab bench top.

Fumehood of FIGS. 9 and I0 Referring now to FIGS. 9 and I0, there is shown another fumehood wherein as in FIG. 8 there is provided an under floor duct I00 which as depicted is above a cabinet section 102. The floor I03 terminates at an upturned deflector I04. This leaves a narrow opening from the under floor duct I00 into the rear wall duct which is the channel between the rear wall I06 and front panel I07. 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 I09 occupies more than two-thirds of the upper area of the hood. The front portion of the plenum carries a baffle I10 which extends from the top of the hood to access opening III.

This baffle is a short distance such as about one inch behind door or sash II2. 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 III.

Fumehood of FIGS. II and 12 Referring next to FIGS. 11 and I2, 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 while ends 123 and 124 and the base plate I24 form the other three sides. Four doors, I26, 127, I28 and I29 are slidable sideways in tracks. The plenum carrying the compensating air occupies more than 75 percent of the upper area of the hood. As in FIG. 9, the rear wall duct 13] leading to the discharge outlet includes the back wall 132 and a front panel I34. The lower portion of panel I34 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. I3 through 16, a door is carried by a piano hinge I52 whose fixed leaf is secured to floor 153 of the hood. A U-shaped track I54 is carried by the side wall I55 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 I60 whose other end is pivotally connected to the lower end of door 150. At the pivoted connection of lever I59 and link 160 there is provided an axle I61 on which is rotatably carried a roller 162.

The lower end of sash 164 carries a plunger rod 165 5 which, as seen in FIG. I6, is disposed to engage the top of bushing 158 and as sash 112 is brought downward to the closed condition the bushing I58, 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 H2 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. I6 is carried on the left side of door 150 and is actuated by sash I12 in concert with the mechanism specifically shown in FIG. 16.

Automatic Louver Closure As In FIGS. I7, 18 and I9 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 I70, similar to those discussed above, has a floor 171 in which is provided an access hole I72. Through this hole passes an actuator pin 173 as a sash I12, such as in FIG. 13, is brought toward and to the floor 171. This actuator pin as it passes through access hole I72 strikes and moves pin 174 whose lower end is pivotally connected to a lever member I75 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 I76 has its other end pivotally connected to a lever I79 which is secured to the back side of lower louver plate I80. 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 I7I to urge the louver plates I78 and 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 I86, I87, I88 and I89 are pivotally mounted to rotate around their longitudinal axis. An actuating lever I90 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 I9I. This link is pivotally connected to arms I92, 193 and 194. Arm I92 is fixed to louver plate 188. Arm 193 is fixed to louver plate 187 and arm 194 is fixed to louver plate I86. A tension spring I95 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. I9 and 20 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 I82 is stretched to provide a sufficient bias to return the louver mechanism to a closed condition when the sash is raised.

In FIG. and with the sash 112 in its raised, accessopening, 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, I93 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 to 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 II 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 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 perfonned 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.

What is claimed is:

l. 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 crosssectional 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 I 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 crosssectional 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 onehalf 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.

i k i t i

Claims

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.

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.