US 3218953 A
Description (OCR text may contain errors)
Nov. 23, 1965 H. N. GRow ETAL FUME HOOD CONSTRUCTION 4 Sheets-Sheet 1 Filed Feb. 21, 1963 102 Harig HIIIIIIIIIIIIIIJHIIIWM PFI INVENTORS, G T0 LU,
l I l Il l Il Nov. 23, 1965 H.v N. GROW ETAL 3,218,953
FUME HOOD CONSTRUCTION Filed Feb. v2l, 1965 4 Sheets-Sheet 2 Nov. 23, 1965 H. N. GROW ETAL FUME lHOOD CONSTRUCTION 4 Sheets-Sheet 5 Filed Feb. 21. 1963 00 nuu0n0u0n0w000 00 0 0000 0 0 000000 0 0000 l0000000000000 0 0000 0000 00000000000 willi/lllIlI/ll/llll. Ill/llll//l INVENTORS. Af. Grof,
Harig BY Leo @Pula v @aad H. N. GROW I-:TAL
FUMEv HOOD CONSTRUCTION Nov'. 23, 1965 4 Sheets-Sheet 4 Filed Feb. 2l, 1963 m .L n @m I I Im. I| A NI Il @Im 1 w InIWIJ. Ivl o o o o o o o AII I. III" N I I IL MMI .I Q 0 \O O O O "Il ll. D0 1 .JI II 000 o o wNI o o o "I+ Il. "II 00M I1 O 0 O 0 O I I IIN I OOQmOOOQN/ mn IT. \@N @I Im m I1 I I--- II IIPILIII n ...IIIIIIIIIIH I I I I I I I l l I I I I I I I l l l l l l fI. INSI IIIIIIIIIIIII m u b/Nnf. m u rf I RSI m m .PJQIIInw/I. .HIWWIIIH IIIIhrIIlHn .H un .U m n I im@ u mll "III" .n IIIIIhI" IIUIIIIIU" n .|||.||hm\"||||.|||||||||l|."llll||" n T l I I I I l I I I l I l I I I 4 l I I I I I I I I I I I I I I I l I I I L.
m 1 53 INVENTORS. HQTAZGTOZU, BY Leo PQS, 4%, y
United States Patent() Filed Feb. 21, 1963, Ser. No. 260,128 3 Claims. (Cl. 98-115) This invention relates to fume hoods, and, more particularly, to a fume hood for use in a chemistry laboratory and the like.
It is a primary object of this invention to provide a fume hood including novel means for introducing into the fume hood air taken from the room in which the hood is located as well -as air from an external source.
It is another object to provide a fume hood of the foregoing character, wherein air from an external source is introduced at the sides of an access opening of the hood.
Another object is to provide a hood of the foregoing character, having means for evenly distributing air flow at the sides of the access opening.
Still another object is to provide a fume hood having a novel baille for regulating the flow of air to an exhaust opening of the hood.
A still further object is to provide a fume hood of the foregoing character, wherein the surfaces of the hood exposed to corrosive fumes are made of a non-corrodable material.
t Other objectsand advantages of the invention will become apparent from the following description taken in conjunction with the -accompanying figures of the drawings, in which:
FIG. 1 is -a front elevational view of a fume hood embodying the invention;
FIG. 2 is an enlarged sectional view taken along the line 2 2 of FIG. 1;
FIG. 3 is an enlarged fragmentary sectional view taken on the line 3 3 of FIG. 1;
FIG. 4 is an enlarged fragmentary sectional View taken on the line 4 4 of FIG. l;
FIG. 5 is an enlarged fragmentary sectional view taken on the line 5 5 of FIG. 2;
FIG. 6 is -a fragmentary sectional view similar to a portion of FIG. 2, showing an alternative form of the fume hood;
FIG. 7 is an enlarged fragmentary sectional view taken on the line 7 7 of FIG. 6;
FIG. 8 is a front elevational view showing another alternative form of the fume hood; and
FIG. 9 is a sectional View taken on the line 9 9 of FIG. 8.
In general, a fume hood embodying the invention is a generally box-like unit adapted to be positioned on a base, and comprises back, top and two side walls. An exhaust opening is formed in the top wall'. A front wall, which forms an -air supply unit, has an access opening and a secondary air inlet. Room air enters the access opening, and secondary air from an external source enters the air inlet and ilows through air passageways to an air outlet at the sides comprising the vertical and top sides of the access opening. Air from these two sources ioWs through the hood and out through the exhaust opening. Filter and screen assemblies are positioned in the air outlets, 4and baffles lare positioned in the air pasageways to evenly distribute air flow through the air outlets.
vMounted within the structure between the access and exhaust openings is an -adjustable baie for regulating the llow of air through the hood. The ilow regulator baflle comprises upper and lower baflle sections, each section being mounted adjacent the back wall for pivotal Patented Nov. 23, 1965 nce movement about a horizontal axis. The pivotal axis of the upper section is intermediate its top and bottom edges and the axis of the lower section is at its bottom edge. The top edge of the lower section is exibly attached to the bottom edge of the upper section, and an air passageway is provided between the two sections. Ai-r passageways are also provided over and under the two balile sections, the relative sizes of the latter passageways being adjustable by pivoting the baille sections.
A sash assembly for closing the access opening and a light assembly may also be provided, and the interior inner surfaces of the hood exposed to corrosive fumes may be made of non-corrodable material.
The fume hood shown in FIGS. 1 to 5 is indicated generally by the numeral 10 and is adapted to be positioned on a base indicated generally by the numeral 11. The hood 10 comprises a top wall 12, two side walls 13 and 14, a back wall .16, and -a front wall 17. The upper surface of the base 11 forms a bottom wall for the hood 10.
Each side wall 13 and 14 comprises a substantially rectangular frame member 18 (FIG. 3) which may be formed yfrom a tubular material such as aluminum or steel, and a side panel 19 preferably made of a noncorrodable material. The side panels 19 are secured to the frame members 18 preferably by bonding. If desired, an opening 21 may be formed in either or both side panels 19, which is normally closed by a removable section 22 also preferably formed from a non-corrodable material. The section 22 is held in place in the opening 21 by two vertical cleats 23 and 24, and upper cleat 26 and a bottom cleat 27. The vertical cleats 23 and `24 and the upper cleat =26 are secured to the outside surface of the side panel 19 with a portion overlying section 22. The bottom cleat 27 is secured -to the outside surface of the section 22 with a portion overlying the panel 19. The upper edge of the section 22 is secured to the top cleat 26 by screws 28, preferably made of nylon. The section 22 may be taken out of the opening 21 by removing the screws .28 and then tilting the section 22 inwardly and lifting it upwardly.
The back wall =16 comprises a back panel 31 (FIGS. 2 and 3) which is positioned against the rearward edges of the side panels 19 and overlies the rearward outer surfaces of the frame members 18. The back panel 31 is secured to the frame members 18 by either bonding or by screws. In the event screws are used, they preferably do not extend into the interior of the hood so that they cannot be reached by corrosive fumes. The back wall also preferably includes an angular member 32 having one arm secured to the outside lower edge of the back panel 31 `as by bonding, and its other arm seated on the upper surface of the base 11'.
The top wall 1|2 comprises a top panel 33 which overlies the upper surface of the frame members 18 of the side Walls 13 and 14 and the upper edge of the back panel 31 of the back Wall 16, and is secured to the frame members 18. The top panel 33 is also secured to one arm of an angle 35 which has its other arm secured to the back panel 3'1. The top panel 33 has an exhaust opening formed therein adjacent the back wall 16, and a cylindrical flange 34 may be provided around this opening for attachment to a duct of a blower system.
The front wall 17 forms an air supply unit, and has an access opening and a secondary air inlet formed in it. The front wall 17 comprises left and right cornerposts 40 and 41 (FIGS. l and 3) secured to the side walls 13 and 14, respectively, and a center assembly 42 which eX- tends between and is secured to the two vcornerposts 40 and 41. Each cornerpost comprises an Iangle 43 (FIG. 3) which is seated against the forward and outer side surfaces of the adjacent frame member 18 and secured thereto by a plurality of vertically spaced nut and bolt combinations 44. A column 46 is secured as by welding to the forward side of each angle 43, the outer edge portion of each column 46 being turned rearwardly as shown in FIG. 3. Each cornerpost also includes a cover 47 which has a portion spaced forwardly of the column 46, and an outer portion which is also turned rearwardly and is secured as by welding to the rearwardly turned edge portion of the column 46. The top and bottom edges of the column 46 and the cover 47 may be folded inwardly as shown at 50 in FIG. 3, and the upper and lower ends of each cornerpost may be enclosed by suitable plates 45.
As shown in FIG. l, the inner edges of the columns 46 and the covers 47 of the two cornerposts 40 and 41 slant inwardly and upwardly from the base 11 to the center assembly 42, these slanted edges of the cornerposts forming two sides of the `access opening. The surface of the base 11 forms the bottom side of the access opening and the lower edge of the center assembly 42 forms the top side of the access opening.
The space between the inner slated edges of the columns 46 and the covers 47 form air outlets. With reference to FIGS. 2 and 5, a filter 48 and a screen 49 are enclosed by a suitable frame 51 and positioned across each outlet. The inner edges of the columns 46 and covers 47 may be turned toward each other, and the frame 51 secured as by screws to these inturned edges. The filter 48 may be made of a plurality of matter layers of expanded metal. The screen 49 is also preferably made of expanded metal but having greater thickness and mesh than the filter material and it is positioned such that its strands slant toward the interior of the hood, as shown in FIG. 5. By this construction, when secondary air passes through the outlets, it is directed into the interior of the hood by the slanted strands. In FIG. 3, the filter and screen assembly has been removed for convenience of illustration.
The center assembly 42 of the front wall 17 is above the access opening, and comprises an inner panel 53 (FIG. 2) secured at its vertical side edges to the two columns 46, and an outer panel 54 spaced forwardly of the inner panel 53 and having its vertical side edges secured to the two covers 47 of the cornerposts. The inner panel 53 is preferably made of a non-corrodable material. Further, the inner surfaces of the columns 46 are also preferably lined with sheets S6 (FIG. 3) of noncorrodable material, and a non-corrodable corner brace 57 may be secured as by bonding to each side panel 19 and the adjacent corner brace 57.
The upper edge of the inner panel 53 is spaced below the upper edge of the outer panel 54, and a metal bracket 58 (FIG. 2) is secured to the inner panel 53 and extends up to the level of the upper edge of the outer panel 54. A top cover 59 is secured to the upper edges of the outer panel 54 and the bracket 58, the cover 59 enclosing the top of the front wall 17 and having a secondary air inlet formed therein. A flange 60 may be formed around this inlet opening.
At the Ibottom of the center portion 42, a filter 61 and a screen 62 are provided which may be similar to the filter 48 and the screen 49 shown in FIG. 5. The filter 61 and the screen 62 may be mounted in a suitable frame and secured to the bottom edges of the back and front panels 53 -and 54, and the strands of the screen 62 are formed to direct air into the interior of the structure.
With reference to FIGS. 1 and 2, a horizontal distribnting ballie 63 is fastened to the inner and outer panels 53 and 54 for the purpose of improving the ow characteristics of secondary air flowing from the air inlet to the outlets at the sides of the access opening. The baffle 63 has downturned forward and rearward edges which extend behind clips 64 (FIG. 2) secured to the inner and outer panels 53 and 54. Thus the baffle 63 may be removed simply by lifting it upwardly. Further, this baffle 63 may be perforated if desired.
When in use, the ange 60 is connected to an external source of secondary air which may be air from outside the building, from a corridor, etc. This secondary air 1s supplied under pressure and ows through the passageway formed between the inner and outer panels 53 and 54 of the front wall 17, around the bafe 63 and out of the front wall 17 through the outlets at the sides of the access opening. The filters 48 and 61 cause a slight back pressure to be built up within the air passageway of the front wall 17 by restricting the ow of air through them, and this back pressure causes the liow of air through the three lters 48 and 61 to be substantially evenly distributed. The screens 49 and 62 protect the filters 48 and 61 and also direct the secondary air into the interior of the hood. Due to the slanted inner edges of the columns 46 and the covers 47, the cross sectional area of the air passageways at the vertical-sides of the access opening is greater :at the top than at the bottom of the access opening. Accordingly, the flow of air through the outlets in the vertical sides will be substantially evenly distributed throughout the height thereof.y
The fume hood further includes a light assembly, indicated generally by the numeral 70, for lighting the interior of the hood 10. The light assembly 70 comprises a sheet 71, preferably made of a non-corrodable material, which has its end edges in abutment with and secured to the side panels 19 of the side walls 13 and 14, and its rearward edge in abutment with the panel 33 of the top wall 12. From the top panel 33, the sheet 71 slants downwardly and toward the front wall 17. An opening 72 is formed in the sheet 71, and a pane 73 of translucent material such as glass is positioned over the opening 72 on the upper side of the sheet 71 and is held in place by a bracket 74. Two generally V-shaped braces 76 and 77 are secured to the outer surface of the sheet 71 at its forward and rearward edges, the rearward brace 77 also being secured to the undersurface of the top panel 33. The light assembly 7 0 further includes a three bulb fiuorescent light fixture 78 having the outside of its refiector secured to a bracket 79. The light fixture 78 iS supported by a cover 81 which is secured to the bracket 79 and has a portion overlying the top panel 33 of the top wall 12. The cover 81 is further secured by screws to the V-shaped bracket 76. The light fixture 78 may be easily removed for maintenance simply by lifting the cover 81 and the light assembly 78 out of the hood.
The flow of air through the fume hood is regulated by a baffle 8S mounted between the access opening of the front wall 17 and the exhaust opening of the top wall 33. The baffle 85 comprises an upper section 86 adjacent the back wall 16 for pivotal movement about a horizontal axis which is intermediate its top and bottom edges, and a lower section 87 mounted adjacent the back wall 16 for pivotal movement about a horizontal axis which is adjacent its bottom edge.
The lower section 87 comprises a lower panel 88 and two lower pivot blocks 89 and 90 (FIGS. l and 2), the two pivot blocks 89 and 90 being secured to the lower corners of the lower panel 88. Preferably a slot is formed in the upper surface of each of the pivot blocks 89 and 90 which receives the bottom edge of the panel 88, and the pivot blocks 89 and 90 are preferably bonded to the lower panel 88. The lower bafile section 87 iis supported on two lower support blocks 92 and 93 which may be bonded to the side panels 19 of the side walls 13 and 14 at the lower rear corners of the hood. Arcuate grooves are formed in the upper surfaces of the support blocks 92 and 93, and the lower surfaces of the pivot blocks 89 and 90 are also arcuate and are seated in the grooves of the blocks 92 and 93.
The upper baffle section 86 comprises an upper pivot strip 96 which is secured to the bottom and top edges of an upper panel 97 and an intermediate panel 98. The
which the lower and upper edges of the panels 97 and 98 extend, these slots preferably being formed at an obtuse angle of, for example, 135 The upper section 85 is positioned so that the lower panel 98 extends generally downward toward the base 11 and the upper panel 97 slants upwardly toward the top wall 12 and forwardly.
The upper pivot strip 96 extends across the entire width of the panels 97 and 98, and is supported at its ends by two upper support blocks 99 and 100 which are preferably secured to the side panels 19 of the side walls 13 and 14 by bonding. An arcuate groove is formed in the upper surface of each block 99 and 100 which receives the lower arcuate surface of the upper pivot strip 96. The upper corners of the intermediate panel 98 are recessed, as the points indicated generally by the numeral 101 (FIG. 1), to provide space for the upper support blocks 99 and 100.
The bottom edge of the intermediate panel 98 is attached to the top edge of the lower panel 88 by a plurality of spaced apart llexible connectors 102 (FIGS. 1 and 2). The connectors 102 maintain the adjacent edges of the panels 88 and 98 in iixed spaced apart relation.
The horizontal widths of the three panels 88, 97 and 98 and the upper pivot block 96 are made somewhat less than the distance between the s-ide panels 19 of the side walls 13 and 14 so that air gaps exist between the vertical edges of the panels 88, 97 and 98 and the inner surfaces of the side panels 19.
The upper and lower baille sections 86 and 87 are pivotal from an intermediate position, indicated in full lines in FIG. 2, to a bottom panel closed position indicated by dashed lines in FIG. 2, and a bottom panel open position indicated by dash dot lines in FIG. 2. In the bottom panel closed position, the top edge of the lower panel 88 rests against the back panel 31 and the top edge of the upper panel 97 is spaced a considerable distance from the top wall 12. Air ilows to the exhaust opening over the top edge of the upper panel 97, through the space between the bottom and top edges of the intermediate and lower panels 98 and 88, and around the vertical edges of the upper and intermediate panels 97 and 98. This position of the baille is preferable when lighter than air fumes are to be exhausted since they tend to rise to the top of the hood. When heavier than air fumes are to be exhausted, the baille sections may be pivoted to the bottom panel open position where the top edge of the lower panel 88 is spaced a considerable distance from the back wall 16 and the top edge of the upper panel 97 engages the top Wall 12. Fumes and air then flow through the space between the bottom edge of the lower panel 88 and the upper surface of the base 11 and the back panel 31, through the space between the bottom and top edges of the intermediate and lower panels 98 and 88, and along the vertical edges of the three panels 88, 97 and 98. The fumes do not flow over the top edge of the upper panel 97 since it engages the top wall 12. In the intermediate position, the top edges of the upper and lower panels are spaced from the panels of the top and bottom walls and air ilows around the top and bottom edges of the baille and through the space between the battle sections. The heights of the baille panels are preferably chosen such that the adjacent edges of the intermediate and lower panels are at substantially the height of a beaker when mounted above a standard Bunsen burner, and since the space between these two panels is always open, fumes from the beaker will be quickly withdrawn.
From FIG. 2 it will be noted that the center of gravity of the upper baille section 86 is to the left of its horizontal axis of rotation, which produces a tendency of an upper baille section 86 to pivot in the counterclockwise direction, and consequently the lower baille section to pivot in the clockwise direction. To maintain the baille sections at a selected position, a baille latch (FIGS. 1 and 2) is provided. This latch 105 comprises a ratchet block 106 secured to the back panel 31 of the back wall 16 the block extending through a vertical slot 107 (FIGS. 1 and 4) formed at the upper center of the lower panel 88. The ratchet block 106 has a plurality of notches 108 formed in its upper surface which receive a downwardly extending lip formed on the lower end of a stop block 109. The stop block 109 is slidably mounted for movement in a vertical direction within the slot 107 of the lower panel 88 by means of two vertically extending grooves 111 formed in opposite sides of the stop block 109, the vertical margins of the slot 107 extending into the grooves 111. A handle 112 may be secured as by bonding to the forward side of the stop block 109. To adjust the position of upper and lower sections of the baille 85, the handle 112 and the stop block 109 are lifted to an upward position where the lip of the stop block 109 is out of engagement with the ratchet block 106. The stop block 109 may then be moved in either the forward or rearward direction until the sections of the bailles are in the desired position, and the stop block 109 is then lowered to bring its lip into one of the grooves 108 of the ratchet block 106. Since the ratchet block 106, in this instance, has iive grooves 108, the baille 85 may be locked in any one of iive positions including the three positions previously described.
The fume hood may also include a sash assembly mounted on the front wall 17 for varying the amount of room air drawn into the hood and for closing the access opening of the front wall when desired. With reference to FIGS. 1 to 3, the sash assembly comprises a 'sash 120 having a panel of glass 121 lsecured within a rectangular frame 122. The sash is preferably constructed such that its inner surface, which may be exposed to corrosive fumes, is constructed entirely of a non-corrodable material. A column 123 is secured to the cover 47 of each cornerpost 40 and 41, and the sash 120 is slidably mounted for movement in a vertical direction within a slot formed between each column 123 and the adjacent cover 47 of the cornerpost. Guides 124 (FIGS. 2 and 3) are secured to the vertical edges of the sash 120 as by screws, the guides 124 being positioned within the slots of the columns 123 and guiding the movement of the sash 120. Means is preferably provided for counterbalancing the weight of the sash 120, this means comprising a cord 126 (FIG. 2) attached at one end to each vertical side of the sash 120 and passed over the top of the pulley 127. The cords 126 are attached at their other ends to weights 128 (FIG. 3). The pulleys 127 (FIG. 2) are rotatably mounted on the columns 123 adjacent their upper ends. A stop 129 (FIG. 2) may be secured to each vertical edge of the Sash 120 and positioned to engage a suitable strap (n-ot shown) secured to each column 123 adjacent its upper end and thereby limit the upward movement of the sash 120. Above the access opening of the lfront wall 17, the space between the two columns 123 is preferably enclosed by a front cover 130 (FIGS. 1`to 3) which extends ybetween and is secured to the two columns 123.
When the sash 120 is in the lowered position, substantially all of the air passing through the hood enters through the secondary outlets at the sides of the access opening. As the sash 120 is raised, the proportion of room air to secondary air entering the hood progressively increases.
FIGS. 6 and 7 show a portion of the front wall of a fume hood which may be identical with the fume hood shown in FIGS. 1 to 5 with the exception that the sash assembly and the columns 123 are eliminated. In the construction shown in FIGS. 6 and 7, room air always enters the hood in addition to the secondary air entering the fume hood .through the air outlets at the sides of the access opening.
FIGS. 8 and 9 show another alternative construction of the fume hood. This fume hood comprises a front wall 140, a back wall 141, a top wall 142, two side walls 143 and 144, and a bottom wall formed by a base 145. The walls 141 may be identical with the corresponding walls of the hood shown in FIGS. l to 6. An exhaust opening is formed in the top wall 142 and is provided with a flange 146 which may be connected to an exhaust duct. A flow regulator baille 147 is mounted within the hood for regulating the llow of air to the exhaust opening. The baille 147 may be the same as the baille 85 shown in FIG. 2 with the exception that a plurality of openings 14S may be formed in the lowermost panel to prevent fumes from accumulating at the forward surface of this panel. These openings 148 may be eliminated if desired. Further, a light assembly 149 which may be identical with the light assembly 70 shown in FIG. 2, is preferably mounted at the juncture of the front and top walls 140 and 142 for lighting the interior of the hood.
The front wall 140 is preferably secured to the two side walls 143 and 144, and has an access opening, indicated generally by the numeral 151, and a secondary air intake 152 formed therein. The intake 152 may be connected to a secondary air duct 153 extending from an external source of air under pressure. The front wall 140 has spaced apart front and back panels 154 and 155 which form an air passageway therebetween leading from the secondary air intake 152 to the upper horizontal and two vertical sides of the access opening 151. A horizontal distributing baille 157, which is preferably provided with perforations 158, is mounted within the air passageway below the secondary air intake 152. This baille 157 again may be removably mounted on clips (not shown) as shown in FIG. 2.
The access opening 151 on its upper horizontal and two vertical sides is separated from the air passageway of the front wall 140 by screen and filter assemblies. The numeral 159 indicates the screen and filter assembly for the upper horizontal side of the access opening 151 and the numeral 161 indicates the screen and iilter assemblies for the two vertical sides of the access opening. The assemblies 159 and 161 are the same as those shown in FIGS. 2 and 5. A double thickness of filter material may be provided in the upper assembly 159 to increase the restriction of air flow at the upper side of the access opening 151 and thereby improve the air ilow characteristics at the vertical sides of the access opening 151. Further, a plurality of pressure control bales 162 and 163 are preferably mounted in the portion ofthe air passageway adjacent each vertical side of the access opening 151. The bafiles 162 and 163 are preferably perforated, and the ballles 162 slope upwardly from the front panel 154 in the direction of the back panel 155 while the baffles 165 slope downwardly from the front panel 154 toward the back panel 155, the baflles 162 and 163 thus having a zig-zag arrangement. The edges of the adjacent batlles 162 and 163 preferably engage each other, and are provided to ensure a satisfactory -secondary air llow pattern at the vertical sides of the access opening 151.
Where the use of a non-corrodable material is referred herein, a composition comprising Portland cement and asbestos fibers mixed with acid resisting bond and filter is preferred.
1. A fume hood comprising front, back, top and two side walls secured together in a box-like conguration, said top wall having an exhaust opening formed therein and said front wall having an access opening formed therein, and a baille mounted between said access and exhaust openings, said baille comprising upper and lower sections each in the form of a generally rectangular panel, horizontal pivot means mounted on adjacent walls adjacent said back wall for mounting said upper and lower sections, said pivotal means for said upper section being intermediate its top and bottom edges and the pivotal axis of said lower section being adjacent its bottom edge, and a plurality of flexible connector means spaced along the adjacent edges of said upper and lower sections and holding said sections in spaced relation to form a gap, the bottom edge of said lower section being spaced from said back wall and the top edge of said lower section being movable into and out of engagement with said back wall on pivoting said lower section to the control flow of air from the lower part of the hood, and the top edge of said upper section being movable into and out of engagement with said top wall on pivoting said upper section to control the ilow of air from the upper part of said hood.
2. A fume hood as in claim 1, wherein the bottom edge of said upper section is spaced forwardly of the top edge of said lower section to permit flow of air therebetween for all pivoted positions of said sections, the llow of air from the upper and lower parts of the hood being inversely variable by pivoting said upper and lower sections.
3. A fume hood as in claim 1, and further including an adjustable latch means comprising a part secured to one of said walls of said fume hood and a part mounted on one of said sections for holding said baille in an adjusted position.
References Cited by the Examiner UNITED STATES PATENTS 2,549,042 4/ 1951 Angermueller 98-115 2,627,220 2/195 3 Morrow 98--115 2,704,505 3/ 1955 Morrison 98-115 3,021,776 2/1962 Kennedy 98-115 3,111,077 11/1963 Cortright 98-115 ROBERT A. OLEARY, Primary Examiner.