US 3237548 A
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March 1, 1966 J. BAYERN FUMEHOOD WITH AUXILIARY AIR SUPPLY v R m m n r N A w m NH N 2 W w E A B W H w w 5 O J FIG.5
United States Patent "ice 3,237,548 FUMEI-IOOD WITH AUXILIARY AIR SUPPLY Joseph Bayern, Hicksville, N.Y., assignor to Joseph Bayern and Jean A. Bayern, Hicksville, N.Y., joint tenants Filed Jan. 23, 1964, Ser. No. 339,633 7 Claims. (Cl. 98--115) This invention relates to fumehoods having auxiliary air supply to supplement the room air so that a minimum of room air will be drawn into the hood in its operation. In particular, this invention relates to a fumehood having a face opening with a sash closure and having an auxiliary air supply which is supplied from outside of the circumference or perimeter of the top and sides of the face or sash opening of the device.
Prior to my invention, various types of fumehoods were well known and used for the purpose of drawing off undesirable gases, fumes or other substances which might poison or pollute the air, for the purpose of providing breatheable air around the working area or Working chamber associated with the fumehood.
Originally, fumehoods comprised a working chamber having an open front and means usually at the top of the chamber to exhaust air and undesirable gases or other substances from the chamber. This would permit a person or technician to conduct experiments and other processes within the chamber, and be free from the danger of inhaling the undesirable gases because the force of the exhaust would remove air from the room in which the fumehood was located through the working chamber, thence through the exhaust duct, carrying the undesirable gases and not permitting them to enter the room. It was then desirable to provide a transparent protective shield through which the technician could observe the reactions taking place within the fumehood. Such a transparent shield is in the form of a strong glass such as a safety glass or wired glass, and is placed within a sash so that the shield may be moved up or down to provide access to the working chamber.
In conventional fumehoods, closing the shield would reduce the intake area at the face of the working chamber until the intake area would be completely closed and block further flow of air. Thus, provision was made, by means of a grille or other opening, to provide for flow of air and continued operation of the device through a by-pass other than the face opening, even though the glass sash was completely closed. In order to overcome the correlated problem of changing the rate of flow of air by enlarging and reducing the size of the front opening of the chamber by raising and lowering the sash, an open grille of substantially the same size as the front opening of the chamber was placed above the front opening and communicating with the working chamber through the by-pass. The sash, which would be just large enough to cover the front opening, or the grille (or by-pass), could then be moved up and down to completely cover the grille (or by-pass) or completely cover the face opening, or in any intermediate position partially to cover the grille (or by-pass) and the front opening simultaneously. In this way, that portion of the front opening which would be reduced by the sash would be compensated for by a corresponding portion of the grille which would be uncovered as the sash was lowered.
Thus, air would be removed from the room at a constant rate of flow, whether the sash was up or down. This prevents high air velocities at the lower level of the working chamber which are undesirable. Thus, the constant volume fumehood, as these hoods are called, which may be operated without creating undesirable velocities, even with the sash substantially closed, solves this problem.
3,237,548 Patented Mar. 1, 1966 However, with the advent of air conditioning, need for a type of hood was dictated which could be operated without drawing large quantities of air from the room in which it was installed, the ideal hood, of course, being one which could supply its own air and would draw no air out of the room in which it was installed. Hoods have been developed which minimize the withdrawal of room air and are called air conditioning fumehoods. An example of such a hood is the one shown in United States Letters Patent No. 3,000,292 issued September 19, 1961, on application of C. A. Wojan.
In principle, these hoods supply air through an intake duct or port. The air is then removed through the exhaust port. In such hoods, there is no grille, and the glass sash may be substantially closed without affecting the velocity of the exhaust system. Such hoods work well with the sash closed. However, when the sash is opened, there is sometimes undesirable leakage of noxious fumes from the working chamber into the room, especially from the lower part of the working chamber.
In a hood without a by-pass, the face velocity increases to an undesirable speed as the sash is lowered, especially when the original face velocity is high. Such high face velocity is undesirable for many reasons; for example, hot plates are cooled off too rapidly, Bunsen burners are upset, and Bunsen burner flames are put out. In addition, delicate balances within the hood enclosure are disturbed, and delicate setups are in danger of being upset. This problem was partially solved in a laboratory fumehood disclosed in United States Letters Patent No. 2,819,- 666 issued January 14, 1958, on application of George L. McNeil et al., by providing for the auxiliary air to be supplied from chambers having a nozzle opening directing the auxiliary air outside of the open face opening of the device when the sash was up, or directly into the working chamber of the device by means of a by-pass port when the sash was down. While the construction of McNeil et al. overcomes the problem of face velocity increasing as the sash is closed, the problem still remained as to how to furnish the auxiliary air in an air conditioned fumehood without permitting it to be blown directly on the operator who stands in front of the face opening, and also to provide it particularly at the lower part of the face opening where there was greater danger of noxious fumes escaping during the operation of the hood.
It is therefore an object of this invention to provide a fumehood having auxiliary air supply in which the auxiliary air is supplied to the device from outside of the top and sides of the circumference or perimeter around the sash opening of the device, without interfering with the operator of the device, and to provide a fairly even distribution of auxiliary air from directly outside the sash or face opening of the device, when the sash is open, to minimize as much as possible the use of room air through the sash opening, and to prevent as much as possible the escape of noxious fumes out of the said sash opening.
It is another object of this invention to provide such an auxiliary air supply having means to adjust or control the distribution and flow of the auxiliary air to conform to the conditions of the size, and air currents, of the room or place in which the said hood is installed.
It is another object of this invention to provide a fumehood having an auxiliary air supply in which a portion of the auxiliary air is introduced into the device at the forward portion of the floor or table thereof to carry the heavier-than-air gases directly into the exhaust chamber and out of the fumehood.
It is a further object of this invention to provide such a device in which the desired face velocity does not increase to an undesirable speed by providing an air by-pass for the auxiliary air.
Further objects and advantages will appear in the specification hereinbelow. These objects and advantages are achieved in the forms of the invention illustrated in the accompanying drawings in which:
FIG. 1 is a face view of the apparatus with parts cut away to show baflies and air flow currents with sash up;
FIG. 2 is a view similar to FIG. 1 with sash down to show the reverse trend of air flow;
FIG. 3 is a section along the lines 3-3 in FIG. 1;
FIG. 4 is a section along the lines 44 in FIG. 2;
FIG. 5 is a section along the lines 55 in FIG. 3;
FIG. 6 is a section of the device along the lines 6-6 in FIG. 1, with portions cut away;
FIG. 7 is an elevational detail of an alternate form of grille of a side conduit;
FIG. 8 is an elevational detail of a further alternate form of grille of a side conduit; and
FIG. 9 is a detail of a flap of the invention in elevation.
Similar numerals refer to similar parts throughout the several views.
It is an important object in all fumehoods to move a large velocity air through the sash opening from the outside away from the operator into the hood. The rate of the movement of such air through the sash opening may be termed face velocity. It is very important to have the auxiliary air come from outside the sash because otherwise if the air comes from inside the sash opening, the most critical portion of the fumehood, that portion nearest the operator, is not cleared properly. For example, if it is desired to have a fumehood with a face velocity of 100 feet per minute at the sash opening, if air is supplied from inside the hood, it will move the high point of the velocity inside the hood, and there will be a minimum face velocity through the sash opening. By pro viding the auxiliary air at the outside top and sides of the sash opening, it is supplied outside of the plane (sash opening) where the highest velocity is desired, and creates this desired face velocity.
It is to be understood, of course, that the speed of the face velocity is controlled by the combined action of the suction or exhaust blower of the hood at the suction end of the hood and the auxiliary air blower pushing air through the openings outside the sash opening.
The fumehood may be constructed of any material strong enough for the purpose. It is also desirable for the construction material to be fireproof and for the floor or counter of the device to be acid resistant.
A main frame 10 is therefore provided, made of enameled steel coated with acid resistant paint. The floor or counter 11 should be of material such as stone, and suffi ciently thick to withstand acids, heat and damage reactions. The floor 11 may be a separate counter top over which the main frame 10 of the hood is placed, or it may be an integral part of the hood construction; or in another form of the device, such as a larger floor model, it could rest directly on the floor of a room rather than on a table, in which case the floor of the room could act as the counter or floor of the device.
The main housing 10 has a rear wall 12, a pair of side walls 14 and 15, a front wall 16 and a top 17. A working chamber 18 is formed between the floor 11, inner side walls 20 and 22 and an internal baffle 24. An exhaust chamber 26 is formed between the internal baffle 24, the side walls 20 and 22 and the rear wall 12. The working chamber 18 and the exhaust chamber 26 are connected by upper and lower exhaust apertures 28 and 30 respectively. The front of working chamber 18 is formed partially by the rear wall 32 of an auxiliary air chamber 34 and partially by the sash 36. The auxiliary air cham ber 34 is formed between rear wall 32, side walls 14 and 15 and front wall 16, and communicates with the working chamber 18 through a by-pass 38. The sash 36 is provided with a pane of safety glass or wired glass 40, and is adapted to slide up and down within sash guides 42 and 44. There is an inner face opening for the working chamber 18 in the plane substantially corresponding to sash guides 42 and 44. The inner face opening 50 is at the lower part of the device, and is beneath and to the rear of front wall 16. The height of the sash 36 should be sufficient to cover the inner face opening 50 when the sash 36 is completely lowered. The sash 36 may be maintained at various positions by balancing means such as a counterweight or sash balance (not shown) installed in any manner known to the art of hanging windows. The auxiliary air chamber 34 has a bottom wall 52 having a number of openings 54 and a flanged back portion 56. The back portion 56, together with rear wall 32, with bypass 38 between them, forms a common dividing structure between the auxiliary air chamber 34 and the working chamber 18, forming at the same time the rear of the auxiliary air chamber and the upper portion of the front of the working chamber 18. The device has a bottom conduit 58 formed by a floor extension 60, a foil 62 and the lower portion of the side walls 14 and 15. The bottom conduit 58 communicates with the auxiliary air chamber 34 by means of side conduits 64 and 66.
Side conduit 64 is comprised of side wall 14, internal partition 68, a lower leg of front wall 16, and an inner face wall 72. Side conduit 66 is comprised of wall 15, internal partition 76, lower leg 78 of wall 16, and inner face wall 80.
An exhaust collar 82 is provided in the top 17. Exhaust collar 82 communicates with exhaust chamber 26 and may be attached to any suitable type of duct or other means which should be connected to an exhaust blower (not shown), or other means of moving the air out of the exhaust chamber 26. I do not show the ducts or the exhaust pumps since these are wellknown to the art, and may be any type suitable for the purpose.
An intake collar 84 is provided above the auxiliary air supply chamber 34. A suitable duct (not shown) is attached to intake collar 84 and connected to an input blower (not shown) to provide an auxiliary air input for the device. Here again, the ducts and the input blowers need not be shown since these are well known in the art, and may be of any type suitable for the purpose.
The side conduits have vanes 86 which are located in openings or grilles 88 of the inner face walls 72 and respectively. The vanes 86 may be pivotted on pins 90 in sockets located at reference points 93 to provide for swinging movement of the flaps from an open position as shown in the left hand portion of FIG. 6 of the drawings to a closed position as shown in the right hand portion of FIG. 6 of the drawings. In the drawings, a single opening 88 is shown on each side of the side conduit containing three vanes 86 in each opening. This is submitted by way of illustration only as there may be any number of openings containing any suitable number of vane means.
The grille openings 88 have the vanes 86 to cover or, close selected portions of the grille openings. These vanes 86 may be individually adjusted, or they may be connected together to a single control in any manner known to the art. The grille openings 88 and vanes 86 may be either horizontal or verticle, or in any formation suited to the construction of the device.
It is preferred to put in verticle vanes 86 hinged by means of the pins 90 which may be closed by turning them inwardly toward the sash opening 50, since vanes 86 which close by turning inwardly toward inner face opening 50, would act as deflectors to deflect the supply of auxiliary air toward the sash opening 50 when they were partially closed.
It may be preferable to leave all of the vanes 86 to be individually adjusted since adjustment for each of the vanes 86 depends upon the position of the device 10 in' a room, the size of the room, the air currents in the room, proximity of air conditioning vents, proximity of hot air blowers, and other factors. Once the device 10 is installed in a room, and the vanes 86 are set, in accordance with the desires of the engineer or operator adjusting same, they will probably remain set until there is a change in one of the factors of the room and the air currents to require further adjustment.
The grilles or openings 88 at the inner sides of the side conduits 64 and 66 may be made in alternate form without vanes 86, or in further alternate form, with panels 91 containing perforated steel mesh 92, or panels 94 containing holes 96, such panels having various proportions of open area. In these forms of invention, the openings (mesh 92) or (holes 96) in the side openings 88 would be precalculated as to size and number at the factory since there would be no adjustment means. For example, if it were desired to have a hood installation where a greater volume of auxiliary air had to be moved into the bottom conduit 58 through the grille or aperture 100 at the rear of the bottom conduct 58 across the floor 11, then the side openings would be relatively few and/ or small. On the other hand, if it were desired to have a greater volume of air coming through the side conduits 64 and 66 at the sides of the outside of inner face opening 50, then the side openings would be relatively greater in number and/or larger. This will be more readily understood when the action of the air currents with the sash up and down are explained hereinbelow.
The grille or aperture 100 at the rear of bottom conduit 58 does not have a closure adjustment since it is desirable to have a constant flow of auxiliary air from grille 100 across the bottom of the devices to exhaust aperture 30 to clear off heavier-than-air gases that may fall to the floor 11 of the device.
A series of baffles 102 have been provided underneath the input cap- 84 to deflect the auxiliary air coming into the device, which would normally go straight down and through the openings 54 at the bottom of auxiliary air chamber 34, to the side conduits 64 and 66. These baflies 102' are placed directly in the'way of the stream of auxiliary air (see FIG. 1 of the drawings'and FIG. 5 of the drawings) and Will'cause some of the air to move to each side of the device and then down through the side conduits 64 and 66 to the bottom conduit 58.
I refer now to FIGS. 1, 3 and 5 of the drawings where the sash 36 is in up position. The pane 40 of the sash 36 covers by-pass opening 38. The inner face opening 50 is completely open. Let us assume that an input blower is blowing auxiliary air into input collar 84 of the device, and an exhaust blower is pulling exhaust air from exhaust collar 82 of the device. This creates air currents as shown by means of the arrows in FIGS. 1, 3 and 5 of the drawings. Air will come down through collar 84 into auxiliary chamber 34. Most of the air will go down through the openings 54 at the bottom of the auxiliary chamber, and then through face opening 50 to be exhausted through either the top or bottom exhaust apertures 28 and 30, through exhaust chamber 26 and out of collar 82. Some of the air will be baffied off by baffles 102 into side conduits 64 and 66 and come out through side openings 88 as shown by the arrow in the mentioned figures, and into the face opening 50, thence to working chamber 18 to be exhausted through exhaust apertures 28 and 30, exhaust chamber 26 and out of collar 82. Some of the air will go completely down into the bottom conduit 58, through grille 100, across the bottom of the device at fioor 11, through exhaust aperture 30 to exhaust chamber 26, and out of the device at exhaust collar 82.
As was stated above, the amount of air which will go through either of the mentioned paths may be determined by adjusting the vanes 86 of the device. When the flaps are in a more open position, more of the air will go through the side conduits, and when the flaps are in a more closed position, more of the air will go through bottom grille 100. It will be appreciated at this point that the inner face opening 50 is at the inner side of an imaginary oblong formed between the plane of the inner face opening 50 and the plane of an outer face opening 104, and that the entire imaginary oblong including outer face opening 104 and inner face opening 50 comprises a form of face opening means for the device. The ends of the oblong would be formed by the foil 62 on the bottom, the bottom wall 52 of the auxiliary air chamber 34, and the inner sides 72 and 80. Thus, all of the auxiliary air of the device which is supplied from outside of the inner face opening is contained within the imaginary oblong between planes 104 and 50. The entire inner face opening 50 will have face velocity currents throughout its entire area from air supplied from within this imaginary oblong inside of the outer face opening 104 and directly outside of inner face opening 50. None of this auxiliary air will be directed toward the operator or person standing in front of outer face opening 104. At the same time, there will be an internal stream of auxiliary air from grille toward exhaust aperture 30 to cover the bottom of the device and prevent escape of heavier-than-air gases. The net result is that a face velocity covering the entire inner face opening may be maintained so that, while the sash is up, there will be no stray currents moving against the desired flow permitting noxious gases to escape from the hood.
When the sash is down as shown in FIGS. 2 and 4 of the drawings, the auxiliary air will come down through the collar 84 into the auxiliary chamber 34, then through the by-pass opening 38 which is now uncovered when the sash 36 and pane 40 are in down position. The principal air flow will then be through by-pass opening 38 into working chamber 18 and out through exhaust apertures 28 and 30 to exhaust chamber 26 and up through exhaust collar 82. There will also be a slight reverse flow at the bottom openings 54 of auxiliary chamber 34 into the working chamber 18 through by-pass 38, and there will be some reverse flow from outside of the device into the grille openings 88 .and into side conduits 64 and 66, most of which will go up into auxiliary chamber 34 and through the by-pass 38 into the working chamber 18, and some of which will go through bottom conduit, out of grille 100, across floor 11 to exhaust aperture 30.
When sash 36 is down against the foil 62 closing the inner face opening 50, the described reverse flow from outside the device will result by design because the exhaust blower is set to pull slightly more cubic feet per minute of air than the .auxiliary blower is set to push into the device. This differential causes the reverse flow as shown and described when the sash 36 is down. This reverse flow is desirable to prevent escape of noxious fumes from the device when the sash is down and is adjusted to remove the least amount of room air necessary for this purpose.
The space between double walls 14 and 20 and double walls 15 and 22 may be utilized for auxiliary equipment such as electric wiring or other apparatus. It is not functional insofar as the device as shown and described is concerned.
The fumehood described herein has the advantage of using a minimum of room air, it does not blow air on the operator outside of the device, and effectively prevents the escape of noxious fumes when the sash is up.
While I have described my device in its preferred forms, there are other forms which it may take without departing from the spirit and scope of the invention, and I therefore desire to be protected for all forms coming within the scope of the claims hereinbelow. For example, the bottom wall 52 of the auxiliary air chamber 34 may be horizontal as shown or be inclined at an angle in either direction to furnish additional grille. area through the openings 54 should this be desired.
Wherefore I claim:
1. A fumehood having a main housing comprising a working chamber defined by at least one wall including face opening 'means at the front thereof; an auxiliary chamber located in front of said working chamber and above said face opening means having a rear portion common with the upper part of the front of said working chamber having at least one interchamber opening between the said working chamber and the said auxiliary chamber above the said face opening means; closure means comprising slideable panel means being at least as large in area as said face opening means and adapted to be moved on guide means in the main housing to selected positions relative to said face opening means and said interchamber opening, so that when said closure means is moved from said face opening means to said interchamber opening, said face opening means will be progressively uncovered and said interchamber opening will be progressively covered; said working chamber having exhaust means including at least one exhaust aperture for exhausting gases, and said auxiliary chamber having input blower means to provide auxiliary air to the auxiliary chamber; said auxiliary chamber having a bottom Wall portion comprising at least one opening below said interchamber opening outside of and above the said face opening means, and said working chamber having transverse aperture means at a front wall portion thereof beneath said face opening means in a position facing toward the rear of said working chamber and relatively near the lowest portion of the wall of said working chamber, said transverse aperture means being connected through conduit means to said input blower means of said auxiliary chamber.
2. The fumehood as described in claim 1, in which the exhaust means for the said working chamber comprises at least one exhaust aperture means positioned at the lower rear of the working chamber and at least one exhaust aperture means positioned at an upper portion of the working chamber, said exhaust aperture means being connected to exhaust blower means through conduit means.
3. A fumehood having a main housing comprising a working chamber defined by at least one wall including face opening means at the front thereof, an auxiliary air chamber comprising front, rear and bottom wall portions and positioned at the upper part of the front of the working chamber having a pair of conduits depending therefrom positioned at the sides of the front of the main housing, said conduits having inwardly disposed side wall portions substantially as wide as the bottom wall portion of the said auxiliary chamber, and being joined at the bottoms of the face opening means by a bottom conduit; interchamber opening means comprising at least one opening between the rear of said auxiliary air chamber and the said working chamber, said face opening means having a top portion defined by the bottom wall portion of the said auxiliary chamber, the sides of said face opening means being defined by the inwardly facing side wall portions of the said conduits and the bottom of said face opening means defined by the top of said bottom conduit thereby forming face opening means having an outer face opening and an inner face opening, closure means for the said face opening means comprising slideable panel means being at least as large in area as said inner face opening and adapted to be moved on guide means in the main housing behind the said inner face opening to selected positions relative to said inner face opening and said interchamber opening means so that when said closure means is moved from said inner face opening to said interchamber opening, said inner face opening will be progressively uncovered and said interchamber opening will be progressively covered, said bottom wall portion of the said auxiliary chamber as well as said inwardly facing side wall portions of said conduits having aperture means spaced between said outer face opening and said inner face opening, with said bottom conduit having aperture means communicating with the inside of said working chamber at a position substantially near the lowest portion of the wall of the said working chamber, and exhaust means comprising at least one exhaust aperture in the working chamber.
4. The fumehood as described in claim 3, in which. the exhaust means for the said working chamber comprises at least one exhaust aperture positioned at the lower rear of the working chamber and at least one exhaust aperture positioned at an upper portion of the Working chamber, said exhaust apertures being connected to exhaust blower means through conduit means.
5. The fumehood as described in claim 3, in which the aperture means, of the said side conduits spaced between the said outer and inner face openings of the said face opening means, are provided with vane means,
6. The fumehood as described in claim 3, in which the aperture means, of the said side conduits spaced between the said outer and inner face openings of the said face opening means, are provided with panel means having a plurality of openings therein.
7. The fumehood as described in claim 3, in which the aperture means, of the said side conduits spaced between the said outer and inner face openings of the said face opening means, are provided with panel means comprising a mesh material having openings therein.
References Cited by the Examiner UNITED STATES PATENTS 2,549,042 4/ 1951 Augermueller 981l5 3,021,776 2/1962 Kennedy 98-115 3,111,077 11/1963 Cortright 98-115 WILLIAM F. ODEA, Primary Examiner.
JOHN F. OCONNOR, Examiner.