US2704505A - morrison - Google Patents

Description

March 22, 1955 R. B. MORRISON 2,704,505

FUME Hoon WITH ADJUSTABLE BAFFLE Filed May 19, 1951 5 sheets-sheet l March 22, 1955 R. B. MORRISON 2,704,505

FUME Hoon WITH ADJUSTABLE BAFFLE Filed May 19, 1951 s sheets-sheet 2 March 22, 1955 R. B. MORRISON 2,704,505

FUME Hoon WITH ADJUSTABLE BAFFLE:

Filed May 19, 1951 v s sheets-sheet 3 United States Patent O "ice 1 2,704,505 FUME HOGD WITH ADJUSTABLE BAFFLE Robert B. Morrison, Muskegon, Mich., assignor to E. H.

Sheldon & Co., Muskegon, Mich., a corporation of Michigan Application May 19, 1951, Serial No. 227,143 8 Claims. (Cl. 98-115) My invention relates generally to fume hoods, and more particularly to fume hoods provided with means for varying the relative amounts of air and fumes drawn from the top and bottom portions of the hood.

In fume hoods used in chemical and other laboratories, it is, of course, desirable that all of the fumes generated within the hood cabinet be withdrawn. It has therefore become the practice to provide some kind of baille structure near the rear wall of the fume hood cabinet, with openings along the upper and lower edges of the baille, the width of these openings having usually been made adjustable by providing adjustable extensions of the baille. These baille extensions were usually about ilve inches wide and from three to six feet in length, and the upper baille was located about eight feet above iloor level. These extensions of the baille therefore were diiicult to adjust, since it required loosening a number of thumbscrews, sliding the baflle extension upwardly or downwardly, depending upon the desired size of the opening, and again tightening the thumbscrews. lf laboratory apparatus had been set up on the work surface of the hood, this apparatus would frequently have to be removed in order to enable the operator to get at and reach the thumbscrews so as to make the necessary adjustment of the baille extensions. Even after removal or such laboratory apparatus, the attendant would practically have to climb into the hood in order to get at the upper baille extension and adjust its position. Adjustments could therefore not readily be made while the chemical reaction or heating of chemicals was taking place within the fume hood.

It will be understood that, depending upon the fumes to be exhausted from the hood, that is, whether they were lighter or heavier than air, it would be necessary to adjust the bailles, that is, if the fumes were lighter than air the aperture at the top of the baille would have to be widened while the extension at the lower end of the baille would be narrowed, so that the rising fumes would be withdrawn through the exhaust duct. On the other hand, if the fumes produced were heavier than air, it was desirable to adjust the baille extensions so that the opening at the bottom was wide and that at the top narrow.

In an endeavor to avoid the difficulty of direct manual adjustment of the baille extensions, some manufacturers have provided external levers or operating handles by which the positions of the baille extensions could be adjusted, but due to the fact that the fume hoods are usually about three to six feet wide, a single lever at the center of the hood would usually result in tilting and binding of the baille extension. Furthermore, any metallic parts within the hood were subject to severe corrosion by the fumes generated within the hood, and for these and other reasons, such means for extending the baffles which were operated from the outside of the hood have proved unsatisfactory.

Furthermore, the removal of such baille plates for cleaning presented numerous diillculties since, generally speaking, the bailles were longer than the front access opening to the hood.

In the fume hood of my invention, these diillculties are avoided by providing a single baille structure without adjustable extensions, the baille, however, being mounted for tilting movement along a horizontal axis passing through its center of gravity, the baille being formed of two sheets which are individually removable so as to be easily manipulated when the baille structure is to be disassembled for cleaning. The balle is so arranged that it swings freely but will maintain any position to which it is adjusted, and as it swings in one direction it will increase the size of the upper opening and decrease the size of the lower, and vice versa.

It is thus a primary object of my invention to pro- Patented Mar. 22, 1955 vide an improved fume hood which may be readily adjusted for eillcient operation under various conditions, and which has a baille which is easily disassembled and removed from the hood.

Other objects will become apparent from the following description, references being had to the accompanying drawings, in which:

Ll Fg. l is a perspective view of the improved fume 1 OO Q Fig. 2 is a horizontal vertical sectional View taken on the plane of the line 2 2 of Fig. 1;

Fig. 3 is a vertical sectional view taken on the plane of the line 3 3 of Fig. l; and

Fig. 4 is a vertical sectional view taken on the plane of the line 4 4 of Fig. 3.

The fume hood comprises a cabinet having an upper front wall 10, side walls 11, a slidable sash 12, preferably made of plate glass mounted in suitable guideways 13 and counterbalanced in the usual manner by sashweights 14. A top 15, having a iluorescent lamp housing 16 thereon, a rear wall 18, and a slab 20, providing a working surface, complete the hood cabinet. This fume hood is usually mounted on a cabinet or chest of drawers 21, so that the working surface of the slab 20 will be at table height.

An exhaust duct 22 leads from the top of the hood to the customary exhaust fan 24, which exhausts to the atmosphere the mixed air and fumes from one or a number of fume hoods.

The baille for controlling the ilow of the fumes and air from the interior of the hood to the duct 22, cornprises a pair of sheets or panels 26, 27 of sheet asbestos composition, corrosion resistant metals, or any other substance which is resistant to corrosion by chemical fumes. These sheets are secured to a pair of support bars 28, 29, each by means of a pair of thumbscrews 30, the thumbscrews extending through the sheets 26 and 27 and being threaded into plates 32 which are of substantial area so as to distribute clamping force. The plates 32 may be secured to the sheets 26 and 27 in any convenient manner. It will be noted that the support bars 28 and 29 are formed so that the sheets 26 and 27 are positioned at an obtuse angle, although this is not essential. The sheets may be in alignment, but in the particular hood shown the angular arrangement allows for more usable space above the slab 20.

A member 36, secured to the top 15, extends across the width of the fume hood and forms a limit stop for the upper edge of the upper baille sheet 26. The support bars 28 and 29 have pintles 40 of a suitable noncorrodable material, such as fiber, a suitable plastic, or corrosion resistant metal, secured therein. These pintles extend from the sides of the bars and rest in U-shaped sockets 42 secured to the side walls 11. A button 44 is secured to the lower panel 27 along the vertical center line thereof in a position where it may be conveniently grasped by the laboratory technician.

The effective area of the opening at the top of the hood is determined by the distance between the upper edge of the sheet 26 and the lower edge of the stop member 36, while the effective area of the opening at the bottom of the hood is determined by the distance between the lower edge of panel 27 and the rear wall 18 of the hood.

When the baille is swung clockwise to the maximum extent, in the position in which it is illustrated in full lines in Fig. 3, the ilow from the bottom of the hood will be at the maximum, and, except for leakage around the edges of the baille structure, will be in the directions generally indicated by the full line arrows. The baille is adjusted to this position when the fumes produced by the particular chemical reaction are substantially heavier than air.

When the fumes being produced are substantially lighter than air, the baille is adjusted to the position shown in dotted lines in Fig. 3, in which there is substantially no opening at the bottom of the hood and maximum opening along the top of the hood. Under these conditions, most of the air will be drawn from the upper portion of the hood, generally as indicated by the dotted line arrows.

The baille may be adjusted to any position intermediate the two extreme full line and dotted line positions shown in Fig. 3, to produce the desired ilow of air through lthe hood. Such adjustment may readily be made at any time during use of the hood without disturbing any ap paratus set up on the slab 20, and thus the laboratory technician may easily and quickly obtain the type of air ilow required for the particular reaction which is taking place within the hood.

As previously indicated, the baille is pivoted upon an axis passing through its center of gravity, and the pintles 40 are made relatively large so that the baille will be retained in any position of adjustment by the friction of the pintles 40 in their sockets 42.

When it becomes desirable or necessary to clean the baille structure, the lower panel 27 thereof may be loosened by unscrewing the thumbscrews 30. Thereafter the upper panel 26 may be unfastened by unscrewing its thumbscrews 30, After this has been done, the support bars 28 and 29 may be removed merely by withdrawing their pintles 40 from the sockets 42 and removing them from the hood enclosure. Thereafter the panels 26 and 27 may readily be removed from the closure, although their length is greater than the width of the working opening, since they may be tilted suiciently to permit their easy removal. After being washed, and repainted with a suitable chemical resistant paint, if necessary, they may be replaced by performing the removing operations in reverse order.

The baille structure of this fume hood is extremely simple in construction and in operation and forms a very eilective means readily to adjust for fumes of different specific gravity which may be generated within the hood. The aggregate areas of the openings at the top and the bottom of the baille are substantialy the same, irrespective of the position to which the baille structure may be adjusted, and the load on the exhaust fan or blower is thus substantialy constant. Also, the velocity of air tlow through the access opening of the hood will be constant whenever the window is in fully open position, although it will be understood that this rate of ilow through the access opening in the hood may be increased by partly closing the window sash 12.

While I have shown and described a preferred embodiment of my invention, it will be apparent that numerous variations and modifications thereof may be made without departing from the underlying principles of the invention. I therefore desire, by the following claims. to include within the scope of the invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

l. In a fume hood having front, rear, and side walls.

a bottom provided with a working surface, and a top 5 forming a hollow chamber, means forming an access opening into said chamber near said bottom, and means forming an exhaust opening adjacent said top; a pivotally tiltable baille structure between the access and exhaust openings, comprising a pair of supports pivoted to the respective side walls, a pair of panels disposed one over the other and extending horizontally between said supports, and means for detachably securing the panels to the supports; the top and bottom edges of the baille respectively being disposed close to the top of the hood and to the bottom of the rear wall and defining there between top and bottom variable openings for passage of air and fumes toward the exhaust opening; the sizes of said variable openings being determined by the extent of tilt of said baille, and bearing a generally inverse relationship, one to the other.

2. The combination set forth in claim l in which the supports hold one of the panels at an obtuse angle relative to the other.

3. The combination set forth in claim l in which the bottom edge of the baille cooperates with the rear wall of the hood to determine the size of the bottom opening.

4. The combination set forth in claim 1 in which the baille structure pivots on an axis which lies close to the center of gravity of the pivoted baille structure.

5. ln a fume hood having front, rear, and side walls, a bottom provided with a working surface, and a top forming a hollow chamber, means forming an access opening into said chamber near said bottom; a baille Lli) structure spaced from the rear wall and extending between the side walls of the hood; means for mounting the baffle structure for pivotal movement along a horizontal axis substantially at its center of gravity; means forming an exhaust opening from the chamber, the access opening and the exhaust opening being located on opposite sides of the baille, the upper edge of the baille forming, in cooperation with means at the top of the hood, a iirst variable opening connecting the access opening with the exhaust opening; the lower edge of the baille forming, with adjacent portions of the rear wall and of the bottom, a second variable opening connecting the access opening with the exhaust opening; the respective sizes of the two Variable openings, at different angular positions of the baille, bearing a generally inverse relationship one to the other; and manually engageable means on the baille structure for adjusting the angular position of the baille and for determining the consequent relative sizes of the two variable openings.

6. ln a fume hood having front, rear, and side walls, a bottom provided with a working surface, and a top forming a hollow chamber, means forming an access opening into said chamber near said bottom; a baille in the rear portion of the chamber extending between the side walls and having its upper and lower edges respectively near the top and bottom of the chamber; means for supporting the baille for pivotal movement on a substantially central horizontal axis; means forming an exhaust opening from the chamber at the side of the baille generally opposite from the access opening, means cooperating with the upper edge of the baille to dene a variable opening at the top of the chamber; means including the rear wall, cooperating with the lower edge of the baille to deilne a variable opening at the bottom of the chamber; the respective sizes of the top and bottom variable openings being determined by the extent of tilt of the baille and bearing a generally inverse relationship one to the other; and said variable openings forming passageways through which substantially all of the air entering the access opening must flow to reach the exhaust opening.

7. ln a fume hood having front, rear, and side walls, a bottom provided with a working surface, and a top forming a chamber, means forming an access opening into said chamber near said bottom; a baille structure spaced from the rear wall and extending between the side walls of the hood with its upper and lower edges spaced a short distance from the top and bottom of the hood, respectively; means for mounting the baille structure for pivotal movement on a horizontal axis substantially at its center; means forming an exhaust opening from the chamber at the side of the baille generally opposite from the access opening, the upper edge of the baille forming, with means at the top of the hood, a variable opening connecting the access opening with the exhaust opening; the lower edge of the baille forming, with means at thc bottom of the hood, including the rear wall, a second variable opening; the sizes of the two variable openings bearing a generally inverse relationship, one to the other; and manually engageable means on the baille structure for adjusting the angular position of the baille, and for thereby determining the relative sizes of said variable openings.

8. A fume hood comprising in combination; a hood structure defining a chamber having upper and lower ends; means dening an access opening into the lower end of said chamber; a generally upright baille; means sup porting said baille for adjustable tilting movement about an axis medially located in relation to the baille; means deilning an exhaust opening from said chamber; said access opening and said exhaust opening being located on opposite sides of said baille; and said hood structure including means positioned to eoaet with the upper edge of said baille to form a iirst opening between said access opening and said exhaust opening, and means coacting with the lower edge of said baille to define a second opening from said access opening to said exhaust opening; said first and second openings being varied inversely in size upon tilting movement of said baille.

References Cited in the ille of this patent UNITED STATES PATENTS 1,578,950 Bartling Mar. 30, 1926 1,774,072 Whitmore Aug. 26, 1930 1,972,917 Buckel Sept. 11, 1934

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