US2549042A

US2549042A - Fume hood

Info

Publication number: US2549042A
Application number: US772173A
Authority: US
Inventors: Herman P Angermueller
Original assignee: Allied Chemical and Dye Corp
Current assignee: Allied Corp
Priority date: 1947-09-04
Filing date: 1947-09-04
Publication date: 1951-04-17
Anticipated expiration: 1968-04-17

Description

April 17, 1951 H. P. ANGERMUELLER 2,549,042

FUME HOOD 3 Sheets-Sheet 1 Filed Sept. 4, 1947 J7 INVENTOR lib/'mam ,PAlyefmI/I /wewv ATTORNEY Amig 17, 1951 l H. P. ANGERMUELLER 2,549,042

FUME Hoon Filed Sept. 4, 1947 3 Sheets-Sheet 2 INVENTOR Herman, Azggef/vzea @QMBY fsf ATTORNEY Patented Apr. 17, 1951 FUME Hoon Herman P. Angermueller, Cranford, N. J., as-

signor to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York Application September 4, 1947, Serial No. 772,173

3 Claims.

This invention relates to a fume hood for lab- Ioratory or other uses in which hazardous chemical reactions may be carried out, and heat, dust, toxic and odoriferous vapors and gases removed, thereby providing sanitary, safe and healthy working conditions for personnel, and to novel processes of Ventilating'such hoods.

Fume hoods heretofore available usually consist of a cabinet having a fixed or sliding window or door controlled service opening, which cabinet communicates with an exhaust fan for removal of the objectionable dust, vapors and gases generated within the hood. Of these two types of fume hoods the type involving the adjustable or sliding service door controlled service opening has been found to be superior. However, such fume hoods have certain vital objections. Thus, for example, in such fume hoods, the removal of dust and toxic or odoriferous gases is effected by an exhaust fan drawing in a sur'- plus amount of air from the room in which the fume hood is disposed through the service opening, which air circulates across the base of the hood to effect ventilation of this portion of the hood and remove relatively heavy gases and vapors and also through the upper portion of the hood to effect removal of the lighter gases and vapors. In the operation of these fume hoods it has been found invariably to be the practice that the adjustable door controlling the extent of the service opening is usually lowered only when excessive amounts of gases or odoriferous substance are generated and then the door is almost completely closed. When the door is thus positioned,

the hood does not properly perform its ventilating function because f the lack of entering air, and this, it will be noted, takes place under conditions when a large excess of air is `essential to effect the removal of the excessive amount of gases or odoriferous substances produced within the hood.

Another serious objection to such fume hoods is that the air required for ventilation is taken from the room in which the fume hood is disposed. Thus, dependent upon size and number of hoods in operation, considerable heat losses are necessarily entailed when the room is heated. When windows or doors in the room containing thehood are open, unfiltered out side air is drawn into the room thereby depositing considerable dust in the laboratory or other room in which the fume hood is disposed and also on the equipment in this room. This objectionable dust deposit also takes` place even though the windows and doors of the room are closed due to the fact that unfiltered outside air is drawn in through existing cracks or other leaky spaces in the room.

The above noted objection is particularly acute in those cases where the fume hoods are used in air conditioned rooms. Air conditioning is becoming more and more prevalent in laboratories and research institutions not only to improve the comfort of personnel but to provide dust-free and uniform operating conditions which are essential for the proper handling of many materials and instruments employed in modern research. When existing fume hoods are employed in air conditioned rooms not only do such hoods, depending upon then' size and number in operation, rob the room of large amounts of costly conditioned air, but the widely varying quantities withdrawn from the room, apart from' the cost factor, render it extremely diflicult to maintain satisfactory,T operating conditions in the air conditioning system.

Among the objects of this invention is to provide a fume hood which can with equal performance be used in an air conditioned or non-air conditioned room, which When used in an air conditioned room will not materially affect the air conditioning system by taking air from the room, Which may be ventilated uniformly and thoroughly and this independently of the position of the door controlling the service opening, in which the Ventilating air supply can be easily adjusted to insure removal of heavy gases and which can be easily converted from a fume hood having a support for equipment at table level to a hood of a height corresponding to that of the room enabling the installation within the hood of tall or heavy equipment at a level substantially the same as the level of the floor of the room in which the hood is disposed.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

In accordance with this invention, a fume hood having a service openingis ventilated by flowing a stream of air across this opening so as to produce a flowing curtain of air, minimizing the entry of air from the room in which the hood is `disposed into the hood, the air passing through theV hood to thorouhgly ventilate it. The preferred construction involves a housing defining a fume chamber having a service opening in its face, an air supply channel above said chamber leading into a duct which extends across said opening and through which air ilows to produce the flowing curtain of air extending across substantially the full area of the service opening,

thereby minimizing the entry of air from the` room in which the hood is disposed into the fume chamber, a fan for supplying air to the air supply channel, an exhaust channel also disposed above the fume chamber and communicably connected with the top of the fume chamber, an exhaust duct leading from the exhaust channel to the base of the fume chamber, an exhaust fan connected with the exhaust channel and a damper in the connection between the exhaust channel and the top of the fume chamber to regulate the relative proportions of air passing from the vair supply channel across the base of the fume chamber into the exhaust duct and passing through the upper portion of thefume chamber into the exhaust channel.

Desirably the fume chamber is provided with openings in side wall ducts connected with the air supply channel so that air sweeps into this fume chamber not only in a downward direction forming a curtain extending substantially completely across the face of the service opening but also from the side walls of the fume chamber to produce flowing side streams of air merging with the front stream, the resultant air stream flowing towards -the rear of the fume chamber across the base and upwardly through the top portion of the fume chamber. These side streams cooperate with the front or downwardly flowing stream to minimize the entry of atmospheric air from the room in which the fume hood is disposed into the fume chamber. ,Y

In the preferred embodiment a removable floor is disposed in the fume chamber to provide a support` for equipment at the usual table level. Upon removal of this floor a fume chamber is provided of a height which, if desired, is substantially equal to that of the room in which the fume hood is disposed. Tall or heavy equipment may be readily positioned in this chamber, the iloorof which desirably is the same as that of the room in which the fume hood is positioned.

In the accompanying drawings forming a part of this specication and showing for purposes of exemplication preferred forms of this invention without limiting the claimed invention to such illustrative instances:

Figure 1 is a front elevational View of a fume hood embodying this invention;

Figure 2 is a vertical'section taken in a plan c passing through line 2 2 on Figure 1; Y Figure 3 is a horizontal section partly in elevation, Vtaken in planes indicated by lines 3 3 onv Figure 2;

Figure 4 is a vertical section, on an enlarged scale, as compared with the scale of Figures l to 3, inclusive, taken in a plane passing through line 4 4 of Figure 2;

Figure 5 is 'a fragmentary plan view, on a still larger scale, showing one form of damperv mechanism for regulating the opening connecting the upper part of the fume chamber with the exhaust duct, viewing this mechanism from the direction indicated by the arrows 5 5 on Figure 2;

Figure 6 is a vertical section taken in a plane passing through line 6 6 of Figure 5;

Figure 7 is a front elevational view of a fume hood embodying a modied form of this invention; and

Figure 8 is a vertical section taken in a plane passing through line 8 8 of Figure '7.

4 side walls I4 and I5 extend from the level of the floor of the room in which the fume hood may be disposed to the top of the hood, these walls being imperforate, thus completely enclosing the hood on three sides. Side wall I 4 and I5 are suitably secured to the corner posts: one or more tie rods I6 pass between structural members such as angle irons secured to these side walls as shown in Figures 2, 3 and 4. A cover plate I'I closes the top of the hood. A front plate I8 extends from the cover plate I'I to a point. I9 spaced from a removable floor 20, Yforming a service opening 2l, desirably of rectangular shape. A door 22 having a window 23 which may be of glass or other transparent material, is slidably mounted so that it can completely or partially close the service opening 2|.

' Any desired mounting for door 22 may be employed. For example, the door may be suspended by a pair of ywires or ropes 23', each having a counterweight 24 at one end, passing over a pulley 25 and both having the other end fastened to the top of the door as at 25 and 21.

The door is thus mounted for sliding movement l just in front of plate I8; when in its upper position shown in Figures l and 2, its lower edge is iiush with point I9, leaving the service opening completely funobstructed. It may be moved to any desired position, regulating the extent of 32 spaced respectively from the side walls I4, I5

to produce side wall air ducts.,3 3, V34, respectively.

Each of the side walls 3I, 327h'as a series of elon-V gated openings 35 through which the

air ducts

33, 34 communicate with the fume chamber. Openings 35 are of suitable size and shape to uniformly distribute the air along the length of the yside walls. They may be of the shape Ishown in Figure 2 and are positioned in the side walls near the front of the fume chamber. Stud bolts 36, provided with wing nuts 37, are positioned just above and below each of these openings for receiving cover plates for blanking off the openings 35 when it is desired so to do. The base of this fume chamber .is defined by removable floor 20 which rests on the cross pieces 38 extending alongfthebase of the inner side walls 3l, 32 and isvsuitably fastened thereto.

VThe top of the fume chamber is defined by a plate 39 spaced from the top plate I'I and inclined downwardly from wall 28 toward the service opening 2|. A partition 4U extends parallel in the upper portion of the fume hood just above the fume chamber an exhaust channel I4I and an Referring to the drawings, II) is a Yfume hood,

desirably in the form of a rectangular cabinetv having corner posts II, suitably braced by cross pieces and angle irons I2. A rear wall I3 and An exchangeable bar 4a', desirably of wood, and

of a length equal to that of the air supply duct 43' is disposed vwithin duct 43Y contiguous to wall 44. Thus by inserting a bar 43 of proper thickness'in duct43, the effective outlet `width of this Communicating with the velocity therethrough. Disposed just above `the top of bar `43 in wall 44 is a series of spaced openings 44 which may be equi-spaced and extend along the full length of duct 43. Air flows through these openings directly to the corner dened by plate 39 and wall 44 to ventilato this corner and avoid the formation of a vacuum therein by -the relatively high velocity streams flowing through side wall openings 35 and duct 43. r The air supply channel 42 has at its opposite ends openings 45, 46 (Figure 4) communicating with the

air supply ducts

33, 34. Flow through openings 45, V4B into the

air supply ducts

33, 34 may be controlled or regulated by dampers 45 and 46 (Figure 4), respectively. An air supply conduit 4l extends into the top portion of air channel 42, desirably midway between the ends thereof. Conduit 41 communicates witha motordriven fan or blower 48 of any conventional type which is provided with an air supply conduit 49 leading to an air supply duct or to the atmosphere exterior of the building in which the fume hood may be positioned so that,.if desired, air is supplied under pressure to the Iair channel 42 from a source other than that of the room in which the fume hood is disposed.

The exhaust duct 29 leads into Vthe exhaust channel4 4l at 50. A conduit 5i leads from one side wall of exhaust channel 4l to a suitable exhaust fan of any lconventional type indicated diagrammatically at 52. Thisfandraws the exhaust products from the fume chamber and discharges them into a chimney flue or directly to the atmosphere or other suitable disposal point.

Plate 39 defining the base of the exhaust channel 4l, as shown in Figures 2, 3 and 5 is provided with a series of spaced rectangular openings 53 extending in substantially equi-spaced relation the full length of this exhaust channel. Cooperating with these openings is a sliding damper plate 54 (Figures 5 and 6) having spaced openings 55 therein separated by intervening `imperforate plate portions 5B. Hence, depending upon the position of the sliding plate 54, the openings 53 may be completely closed or left open to any desired extent. Plate 54 islmounted for sliding movement in `a pair of guides 5l, 58 suitably bolted or otherwise suitably secured to plate 39.

Movement of plate 54 may be effected by any suitable mechanism. For example, this plate may have xed thereto one end of a rod 58 as bywelding. The other end of this rod is threaded and passes through a threaded nut B keyed or integrally formed within a beveled gear I mounted for rotation in a bearing support `52 secured to the side wall l5. A beveled gear meshes with gear 6|; gear 63 is keyed to a shaft 64 rotatably mounted in bearings 65 on the side wall I5. A hand wheel 5S is xed to shaft 64 for effecting its rotation. l

Mounted on the back wall 28 of the fume charnber is a series of lines 61 which extend through side walls I4 and 3l and terminate within the fume chamber. These lines providesources of suitable media which may be required inthe operation of the equipment placed within the fume chamber; thus, for example, there may be a steam line, power line, compressed air line, warm and cold water lines, vacuum line, fuel gas line, etc. The rear of the fume chamber is provided `with a lead lined drainage trough 58 communicating with a drain line 59 leading to any suitable disposal point. f

Removable oor 20 desirably isposition'd about 3 feet above the floor of the room in which the fume hood is disposed so that it provides a support for equipment at a height which permits convenient placing of equipment thereon, i. e., at usual table level. When it is desired to place tall or heavy equipment within the fume chamber, removable floor 2U may be slid from its supports 33 thereby providing a fume chamber of room height having the rear and both sides cornpletely enclosed and having an opening in the face extending from point I9 to the floor of the room in which the chamber is positioned.

The modification of Figures 7 and 8 differs from that hereinabove described chiefly in `that the exhaust fan is mounted on the top of the fume hood and not on a side wall as shown in Figures l, 2, and 4. Parts in Figures 7 and 8 corresponding to those of Figures 1, 3 and 4 have been given like reference characters. In Figures 7 and 8, 'H

. indicates an exhaust fan mounted on the top of thefume hood and communicating with exhaust channel 4l. The exhaust fan 'H discharges into a conduit 'l2 leading into a stack 13. The exhaust fan 'il of Figures 7 and 8 and I52 of Figures 1 and e should be of suicient capacity to exhaust the volume of air supplied by the air supply fan 48 plus the gases liberated in the fume hood taking into account increased volumes due to heating of the air which may take place in its flow through hood. The placement of the exhaust fan contiguous to the air supply fan, as shown in Figures 7 and 8, is preferred in the interests of simplicity and compactness; the exhaust fan, however, may be placed on either side of the hood, or even on the back of the hood, if desired. Also the air supply fan may be positioned at any convenient point for supplying air to the air supply channel 42,

In operation, all the air required for ventilating the hood is delivered by the fan 48 equipped with a discharge damper (not shown) for con trolling flow of the air stream into air supply channel 42. rEhe air thus supplied ows through side wall openings 45, into the air supply ducts 34 through the openings 35, as indicated by the arrows on Figure 4. Air also ows through the duct 43 extending across the full face of the fume chamber producing a curtain of air which flows downwardly covering substantially the entire area of the service opening 2l and minimizing the entry of air from the room in which the fume hood is disposed into the fume chamber.

Adjustable damper plate 54 regulates the amount of the air thus supplied flowing through the upper portion of the fume chamber through openings 53 into the exhaust channel 4| relative to that flowing across the base of the fume chamber through openings 3U into the exhaust duct 29 and thence into the exhaust channel 4 I.. When the damper plate 54 is positioned so that openings 53 are completely unobstructed, approximately of the total air introduced into the fume chamber by fan 48 flows through the openings 53 into exhaust channel 4| and the remainder of the air across the base of the fume chamber into and through the base openings 30 leading into the exhaust duct 29. If equipment generating large amounts of heavy gases, i. e., heavier than air, is disposed within the fume chamber, hand Wheel is actuated to move plate 54 to partially or completely close openings 53 so that more or all of the air respectively will flow over and across table top 26 leaving through slots 30 and vthereby eiifeetivelspeentiiatingzthebase ofthe hinreben Y Y Y When employing: theihood as. av relatively high g cham-bei, i-Q- el., when the hoodl is used withA the- When-designinga hood. for use exclusively'with heavy' or' high'. equipment intended to bey mounted.

at the room o'o'r level, the exhaust openings 30 shown` in the drawings, for example, they may be placed just above the floor level leading into a` rear ductY communicating with the exhaustv channel ll.

In the Yfume chamber of this invention, it should be noted the ccunterbalanced door does not function to control. the air introduced into the fume chamber but chiey to protect the operator against splashing or leaks of gas or vapor from the equipment installed under vthe hood. The ventilation of the vhood is independent of the position of the sliding door Aand is optimum when the door is fully closed.

-It should be'iurther noted the hood of this invention, with equal performance, can be used in air-conditioned as well as non air-conditioned laboratories or other rooms without detrimental effect upon the atmospheric conditions of the room in which it is placed. Since little or no air is taken .from this room, heat losses during the winter time are negligible. If installed in an airconditioned room,l loss of more costly conditioned room air is likewise negligible. Unfiltered outside air containing the usual amounts of dust and bacteria are not caused to enter into the room in which the fume hood is disposed, thereby elimihating precipitation of dust and dirt in the room and upon the equipment and personnel therewithin.

Air yfiltered or uniiltered and tempered as may 2()-v `are desirably placed in a lower position than that i be desired is supplied by means of the fan 48 to the fume chamber at uninterrupted controlled velocity. When installing a plurality of fume hoods embodying this invention in a building, all of thel hoods may obtain their air supply from a common main air duct, which may contain filtered, preheated or otherwise tempered air serving as supply medium for one or more hood fans communicating with such main air duct. Similarly, one or more exhaust fans may be connected to a common main exhaust duct ccmmunicably connected withr the exhaust channels il o1" all 01' several fume hoods.

By rregulating the extent of damper openings 53, lthe direction of air ow through the fume chamber is adjusted to effect most eiiicient removal of heavy and light gases. By removing floor 20, the hood may'readily be converted Afrom a hood havingV 'a floor at usual table level to a Vhood room 'in which heavy or tall equipment may be `installed at room hoor level.

If, for any reason, it is desired to use the hood for removal of air from the room in -which the hood yis disposed, say in lieuHof-other Ventilating facilities; it .is-.only necessary.:A to shi-1t; on einsame ply.. fanon blower 48.,. inwhich'cas theexhaust: Y famiz will serve to draw in air. into the fiume chamberfrom theroom inwhich; the hoodtis disposed...

The. fume hood may be made of any" suitable: materials. of construction. Dry seasoned Wood is;

preferred for structural members, such as corner posts, spacers,` crosspieces, etc., all of which come.`

in contact. with the. exhaust fumes. Metal may be. used for the supply air? portion of the hood.

Traznsite, asbestosite treated plywood` or similar" materials-may be used for wallspartition sl channels'and ducts of theY hood. As is well known transite and asbestosite are Portland cement asbestos compositions. usually in board or sheet form.

metal orV any other selected materials may be employed to protect against corrosion,4 contamina-` tion and deformation of such parts which areV n subjected to severe service conditions.

above description or shown in the accompanying drawings shall beV interpreted as illustrative and not ina limitinggsense.4 Y

Thus, for example, while the service opening .hasl been shown in front of the :fume chamber, it may be disposed in either side wall or even in the top of the fume chamber and a blanket` or curtain of air passed thereacross into an exhaust duct to effect removal of fumes and ventilation of the chamber.

VWhat is claimed is:

l. A fume hood comprising, in combination,v a housing defining a fume chamber having a service opening in the front wall thereof, an air supply channel above said chamber, aian for supplying air to said channel, an exhaust channel also disposed above said chamber and connected with said chamberJ an exhaust fan connected with said exhaust channel, an air duct extending across said service opening and communicably connected with'said air supply channel for flow of airV through said air duct to produce a owing curtain of air extending substantially completely across said service opening, air ducts in the side walls of said .housing communicably Vconnected with said air supply channel V,for flow of air through said side wall air ducts into said fume chamber, a damper in the connection betweenV said exhaust channel and said fume chamberJ and an ,exhaust duct extending along the rearof said fume chamber and connecting said exhaust channel .with the base portion of said fumecham table level, `.the removal of said fioor permitting the installation of equipment in said chamber at substantially the floor level of said room, :means V for producing a owing curtain of air extending across said service opening,an exhaust channel fin 'the upper portion of said housing in communication with the upper portion of said fume chamber, and an exhaust duct leading downwardly from said exhaust channel and communicating with said fume chamber at a point in the neighborhood of said table level.

3. A fume hood comprising, in combination, a housing defining a fume chamber and consisting of rear, side and front walls, the front wall having an opening therein extending from the base thereof to a point short of the top of said housing and the rear and side walls being subsubstantially imperforate, the said housing being adapted to rest on the floor of a room, a removable floor for said hood disposed approximately midway between the top and bottom of said opening to provide a support within'said chamber for equipment at table level, removal of said floor permitting the installation of tall or heavy equipment within said chamber on the floor of said room, an air supply channel above said fume chamber, a fan for supplying air to said channel, an exhaust channel also disposed above said fume chamber and connected with said chamber, an exhaust fan connected with said exhaust channel, an air duct extending across said opening in the front wall and communicably connected with said air supply channel for flow of air through said air duct to produce a flowing curtain of air extending across said opening, air ducts in the side walls of said housing communicabl'y connected with said air supply channel for flow of air through said side wall air ducts into said fume chamber, a damper in the connection between said exhaust channel and said fume chamber, and an exhaust duct extending along the rear of said fume chamber and connecting said exhaust channel with said fume chamber at a level just above the level of said removable floor.

HERMAN P. ANGERMUELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,218,718 Throop Mar. 13, 1917 1,347,195 Weller July 20, 1920 1,520,267 Waltz Dec. 23, 1924 1,539,973 Truxal June 2, 1925 1,578,950 Bartling Mar. 30, 1926 1,606,442 Nichols V- Nov. 9, 1926 1,741,954 Reymiller Dec. 31, 1929 1,934,808 Liptay Nov. 14, 1933 2,438,606 Hulton Mar. 30, 1948 FOREIGN PATENTS Number Country Date Great Britain Aug. 25, 1938