US3085647A - Acoustic curb - Google Patents

Description

A ril 16, 1963 L. J. JENN ETAL ACOUSTIC CURB 3 Sheets-Sheet 1 Filed Nov. 7, 1960 INVENTORS. LOUIS J. JENN and y WILLIAM E. MORRISON )(WMWMWJJMdWW AH-ornm .s

A ril 16, 1963 L. J. JENN ETAL ACOUSTIC CURB 3 Sheets-Sheet 2 Filed Nov. 7, 1960 mmvrox LOUIS J.JENN and y WILLIAM E. MORRISON XJMMWJMfi/M A Horn 5V5 A ril 16, 1963 L. J. JENN ETAL 3, 7

ACOUSTIC CURB Filed Nov. 7, 1960 3 Sheets-Sheet 3 39 k 38 M wam INVENTOR.

\ LOUISJ.JENN and H y WILLIAM E.MORmsou Xmmmz J/aZ/d/M A1 forn gys United States Patent Q 3,085,647 ACOUSTIC CURB Louis J. Jenn and William E. Morrison, Indianapolis, Ind.,

assignors to Jenn-Air Products Company, Inc., Indianapolis, Ind., a corporation of Indiana Filed Nov. 7, 1960, Ser. No. 67,837 6 Claims. (Cl. 181-56) This invention relates generally to a sound attenuator designed for use primarily with power operated air exhausters. More particularly, the invention relates to a prefabricated acoustic curb designed to support a centrifugal roof exhauster, the curb being constructed so as to provide maximum sound attenuation with a minimum of pressure loss or restriction to the flow of air through the curb.

In recent years the problem of reducing the sound level of power exhausters has received considerable attention from industry at large. With the increasing application of power exhausters to structures such as libraries, schoolrooms, hospitals, conference rooms, churches, auditoriums and the like, the problem of baffling the sound from the exhausters so that the interior of the room or other structure remains relatively quiet, has become increasingly important. Structures have been utilized by the inventors herein having a primary, central baffle which is disposed axially transverse to the direction of air flow through the curb, the baffle extending beyond the boundaries of the air inlet and air outlet openings. Air flowing through the curb is thus forced to take a tortuous path around the baffle and through the air outlet opening. This structure has proven quite satisfactory for most applications, however, in the larger size curb structures, adapted for use with high capacity systems, the primary baflle extending completely across the air flow path obstructs the flow of air through the curb to a degree such that pressure losses through the curb are objectionably large. The structure of the present invention overcomes this difficulty for large size curb structures by providing a bypass opening through the primary baffle, the bypass opening being preferably centrally located and shielded or masked by an auxiliary baffle spaced downstream of the bypass opening and extending transversely across the opening.

The primary object of the present invention is to provide an acoustic curb adapted for large size, high capacity systems where increased air flow path cross section is necessary, the baffle arrangement being such as to effectively intercept sound from the exhauster without in creasing the pressure drop across the curb to objectionable values.

A further object of the present invention is to provide an acoustic curb structure utilizing corner members which function to support the primary bafiie and distribute the weight of the exhauster fan to the four corners of the curb structure.

The full nature of the invention will be understood from the accompanying drawings and the following description and the claims.

FIG. 1 is a perspective view of the structure of the present invention omitting the exhauster fan and its accompanying hood.

FIG. 2 is a perspective view similar to FIG. 1 but with the curb cap removed.

FIG. 3 is a perspective, exploded view of the structure shown in FIG. 2, the bafile assembly being viewed from its underside.

FIG. 4 is a further perspective view of the bafiie assembly showing its underside.

FIG. 5 is a perspective view of the base of the curb structure.

FIG. 6 is a schematic, cross-sectional view, on an en- 3,085,647 Patented Apr. 16, 1963 larged scale of the curb structure shown in FIG. 1 taken generally along the line 66 of FIG. 1 with a portion of a low contour type centrifugal exhaust fan being shown in place on the structure.

Referring initially to FIGS. 1 and 5, the curb structure 10 is shown as including a sheet metal tube or box 11 having a preferably square cross-sectional configuration. The base of the box 11 is provided with an outwardly inclined flange portion 12 which merges with a horizontally disposed base plate 13. The base plate may be fabricated of sections to provide mitered corners, the sections forming a central inlet aperture 14.

The assembly is adapted to overlie an opening in the roof of a structure on which the curb is installed, with the inlet aperture 14 in the base plate 13 registering with thereof opening. The marginal portions of the base plate 13 extending beyond the inclined portion 12 may be suitably sealed to the adjacent building roof (not shown).

As may best be seen in FIG. 1, the box portion of the curb structure carries a cap 15 whose outer margin is formed to provide a downwardly turned flange 17 closely overlying the adjacent box 11 and secured thereto by any suitable means such as sheet metal screws 18. The central portion of the cap is provided with a preferably square outlet opening bounded by an upturned flange 19. This flange 19 defines an outlet opening 20 adapted to mount an exhaust fan assembly as will subsequently be pointed outwith reference to FIG. 6.

As may best be seen in FIG. 2, the cap structure 15 rests upon strips 21 of a resilient sound absorbing ma terial such as sponge rubber overlying the inturned marginal upper edge of the box 11. The cap structure and the exhaust fan carried thereby are further supported by four corner assemblies indicated generally at 22 in FIG. 2. As may best be seen in FIG. 3, these corner assemblies comprise diagonally inwardly extending strips 23. The inner ends of the strips 23 are cut and bent outwardly so as to form tongues 24 which are rigidly secured to the sidewalls 26 of a tray-shaped auxiliary baffle support 27. The upper marginal edges of the strips 23 mount a preferably square primary baffle support plate 28 provided with a preferably square central aperture 2 9 therethrough. As will be evident from FIGS. 3 and 4 the auxiliary baflle support member 27 extends outwardly beyond the margins of the aperture 2 9 in the plate 28.

The outer ends of the strips 23 are provided with flanges 31 which extend at acute angles from the plane of the strips and parallel the sides of the box 11. Rigidly secured to the inner faces of each of the flanges 31 or integrally formed from the ends of the flanges 31 are brackets 32 which are for-med to hook over the resilient material 21 carried by the upper margin of :the box 11. The assembly is thus suspended, by means of the hooking brackets 32 from the upper margin of the box '11.

The outer ends of the strips 23 are further provided with diagonally inwardly extending members 33 having a gusset portion 34 and a horizontal flanged upper margin which is provided with an overlying strip of resilient material 36. As will be evident from comparing FIG. 2 with FIG. 1 these inwardly extending members 33 underlie the diagonal corner portions of the cap 15 and transfer the weight resting on the cap to the corner portions of the box 11.

The structure so far described accommodates sound absorbing and attenuating material which may be of any suitable composition but herein preferably takes the form of slabs or sheets of fibreglass cut and shaped to the proper dimensions. The inner surfaces of the box 11 are lined with strips of acoustic material as indicated at 37 in FIG. 2. The sheet 28 supports a primary baffle 38 of acoustic material, the primary baffle being cut out as indicated at 39 in FIG. 2 so as to provide an aperture registering with the aperture 29 in the plate 28. It will be understood that apertures and 29 are preferably coaxial with the inlet and outlet openings 14 and 29 respectively in the complete assembly, however, they might be offset sidewardly therefrom an might also be discontinuous, that is, their total area might be made up of two or more component apertures. The tray-shaped member 27 receives a slab of acoustic material which provides an auxiliary bafile for the opening 29, this auxiliary baffle being indicated at 41 in FIG. 6. The portion of the base plate 13 which lies inboard of the vertical walls of the box 11 is also provided with acoustic material to form a baffle 42.

Referring to FIG. 6, the operation of the structure just described will now be set out. FIG. 6 is a schematic illustration of the structure of FIGS. 1-5 and includes a portion of an exhaust fan assembly 43 mounted on the cap 15. The exhaust fan assembly includes a base portion 44 having a depending flange 46 which closely overlies the flange 19 on the cap 15. Attached to the portion 44 is a section 47 which encircles the lower portion of a conventional centrifugal blower wheel indicated generally at 43. It will be understood that the section 47 supports the blower wheel, a drive motor therefor and a cover member (not shown). With the exhaust fan in operation, air will be drawn through the inlet opening 14 and will generally follow the paths indicated by arrows in FIG. 6 to be discharged through the curb structure. Air will flow around the auxiliary baffie 41 and through the central aperture 39 in the baffie 38. Air will also flow around the outer margins of the baflle 38. The presence of the central aperture 39 in the bafiie 38 and the auxiliary bafile 43 which shields the aperture 39 reduces the pressure loss in the curb structure from the loss which would occur if the bafiie 38 were not provided with central air passage. The auxiliary bafile 41 acts as an acoustic block for the aperture 39.

It should be noted that the corner assemblies which are suspended from the upper margin of the box 11 serve not only to support the bafiles 38 and 41 in proper, spaced relation, but by means of the gusset sections 33 serve to transfer the weight of the exhaust fan assembly to the corner areas of the curb structure.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

What is claimed is:

1. A curb structure for supporting an exhaust fan assembly comprising a base plate having a central inlet aperture therein, a tubular body portion extending vertically from said base plate and encircling said inlet aperture, said body portion being square in cross-section, a baffie support assembly, elements carried by said baffle support assembly and engaging the upper margin of said body portion whereby said assembly is suspended within said body portion, said baffle support assembly including upper and lower elements each extending diagonally inwardly from the corners of said body portion, a primary sound-attenuating bafile supported on said lower elements in a position overlying said inlet aperture with its margins spaced from said body portion, said primary baflie having a central aperture therein coaxial with said inlet aperture, an auxiliary sound-attenuating baffle supported by said lower elements between said primary 'baffie and said inlet aperture, said Iauxiliary baffle being disposed generally parallel to said primary bafiie and extending outwardly beyond the margins of said central aperture in the primary baffle, and a cap member adapted to have mounted thereon an exhaust fan assembly, said cap member overlying the upper end of said body portion and supported by said upper elements of the bafiie support assembly, said upper elements serving to transfer the weight carried by said cap member to the corner areas of said body portion and said auxiliary baflle serving to acoustically shield the central aperture in said primary baffle.

2. A curb structure for supporting an exhaust fan assembly comprising a base plate having a central inlet aperture therein, a tubular body portion extending vertically from said base plate and encircling said inlet aperture, said body portion being square in cross-section, a bafiie support assembly disposed within said body portion, said baffle support assembly including upper and lower elements each extending diagonally inwardly from the corners of said body portion, a primary sound-attenuating bafile supported on said lower elements in a position overlying said inlet aperture with its margins spaced from said body portion, said primary b-afiie having a central aperture therein coaxial with said inlet aperture, an auxiliary sound-attenuating baffle supported by said lower elements between said primary baflle and said inlet aperture, said auxiliary baffle being disposed generally parallel to said primary baflle and extending outwardly beyond the margins of said central aperture in the primary bafiie, and a cap member adapted to have mounted thereon an exhaust fan assembly, said cap member overlying the upper end of said body portion and supported by said upper elements of the b allie support assembly, said upper elements serving to transfer the weight carried by said cap member to the corner areas of said body portion and said auxiliary baflle serving to acoustically shield the central aperture in said primary baffie.

3. A curb structure for supporting an exhaust fan assembly comprising a base plate having a central inlet aperture therein, a tubular body portion extending vertically from said base plate and encircling said inlet aperture, said body portion being square in cross-section, a b afiie support assembly disposed within said body portion, said 'bafile support assembly including element extending diagonally inwardly from the corners of said body portion, a primary sound-attenuating baflle supported on said elements in a position overlying said inlet aperture with its margins spaced from said body portion, said primary battle having at least one aperture therein, an auxiliary soundattenuating bafile supported by said elements between said primary baffle and said inlet aperture, said auxiliary baifie being disposed generallly parallel to said primary 'bafile and extending outwardly beyond the margins of said aperture in the primary baffle, and a cap member adapted to have mounted thereon an exhaust fan assembly, said auxiliary baffie serving to acoustically shield the aperture in said primary bafiie.

4. A curb structure for supporting an exhaust fan assembly comprising a tubular body portion one end of which defines an inlet aperture, said body portion being square in cross-section, a bafiie support assembly disposed within said body portion, said baffle support assembly including elements extending diagonally inwardly from the corners of said body portion, a primary sound-attenuating bafiie supported on said elements in a position overlying said inlet aperture with its margins spaced from said body portion, said primary baffle having at least one aperture therein, an auxiliary sound-attenuating baflie supported by said elements between said primary baffle and said inlet aperture, said auxiliary baffle being disposed generally parallel to said primary baffle and extending outwardly beyond the margins of said aperture in the primary baffle, said auxiliary baflle serving to acoustically shield the aperture in said primary baffle.

5. A curb structure for supporting an exhaust fan assembly comprising a tubular body portion one end of which defines an inlet aperture, a bafile support assembly disposed within said body portion, said baffle support assembly including elements extending generally radially inwardly from the inner surface of said body portion, a primary sound-attenuating baflle supported on said elements in a position overlying said inlet aperture with its margins spaced from said body portion, said primary baffle having at least one aperture therein, an auxiliary sound-attenuating bafl'le supported by said elements between said primary baflie and said inlet aperture, said auxiliary bafile being disposed generally parallel to said primary bafile and extending outwardly beyond the margins of said aperture in the primary bafile, said auxiliary baffle serving to acoustically shield the aperture in said primary bafiie.

6. A sound-attenuating structure for supporting a power driven air moving device, said structure including a body portion providing axially aligned inlet and outlet apertures, a primary sound-attenuating baffle mounted within said body portion to overlie said inlet aperture and having its margins spaced from said body portion, at least one aperture in said primary baffle, and an auxiliary bafile disposed within said body portion between said primary bafiie and said inlet aperture and extending outwardly beyond the margins of said aperture in the primary bafi'le to acoustically shield said primary baffle aperture.

References Cited in the file of this patent UNITED STATES PATENTS 1,289,856 Maxim Dec. 31, 1918 2,576,860 Shapiro Nov. 27, 1951 2,644,389 Dauphinee July 7, 1953 2,750,865 Tutt June 19, 1956 2,875,678 Shepherd Mar. 3, 1959 FOREIGN PATENTS 780,718 Great Britain Aug. 7, 1957

Claims (1)

1. 6. A SOUND-ATTENUATING STRUCTURE FOR SUPPORTING A POWER DRIVEN AIR MOVING DEVICE, SAID STRUCTURE INCLUDING A BODY PORTION PROVIDING AXIALLY ALIGNED INLET AND OUTLET APERTURES, A PRIMARY SOUND-ATTENUATING BAFFLE MOUNTED WITHIN SAID BODY PORTION TO OVERLIE SAID INLET APERTURE AND HAVING ITS MARGINS SPACED FROM SAID BODY PORTION, AT LEAST ONE APERTURE IN SAID PRIMARY BAFFLE AND AN AUXILIARY BAFFLE DISPOSED WITHIN SAID BODY PORTION BETWEEN SAID PRIMARY BAFFLE AND SAID INLET APERTURE AND EXTENDING OUTWARDLY

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