US2950776A - Ventilating air discharge muffler - Google Patents

Description

Aug. 30, 1960 J F. STEPHENS VENTILATING AIR DISCHARGE MUFFLER Filed July 19, 1956 2 Sheets-Sheet 1 J I 4 /Z 4,.

. 4 4 l/ 150 w l j 44 5 50 g X L la 56 \Tos EPl-l F STEPHENS INVENTOR A ORNEY Aug. 30, 1960 J. F. STEPHENS VENTILATING AIR DISCHARGE MUFFLER 2 Sheets-Sheet 2 Filed July 19, 1956 United States Patent VENTHJATING AIR DISCHARGE MUFFLER Joseph F. Stephens, Kansas City, Mo., assignor to Gustin- Bacon Manufacturin Company, Kansas City, Mo., a corporation of Missouri Filed July 19, 1956, Ser. No. 598,784 Claims. (Cl. 18142) My invention relates to a ventilating air discharge mufller and more particularly to an improved ventilating air discharge mufiler which reduces the noise generated in high velocity ventilating systems and which permits ready regulation of the flow of conditioned air through the mufller.

In modern air-conditioning, ventilating, and heating installations, high velocity systems are preferred since they permit use of distributing ducts having a small crosssectional area. These high velocity systems not only result in considerable savings in duct material owing to their small cross-sectional areas, but also require only a comparatively small space within the walls, floors, ceilings, and the like in which they are installed. One disadvantage inherent in a high velocity system is the generation of noise incident to the passage of the high velocity air through the system. This noise is particularly evident at the outlet grilles through which the conditioned air is discharged to the space to which air is supplied. In the prior art, in order to reduce this noise it has been the practice to interpose a plenum chamber between the small distribution ducts and relatively larger air outlets. In some cases the interiors of the chambers are lined with sound absorbing material.

In one type of unit employed in the prior art, a perforated metal cylindrical sleeve is secured to the inlet duct. A piston within the sleeve is moved to regulate the amount of air entering the plenum chamber by uncovering the correct number of holes in the perforated sleeve.

In another unit employed in the prior art, a conical metallic outlet from the distribution duct is disposed within the plenum chamber. In this unit a conical metallic damper is shiftable axially of the conical distribution duct outlet to regulate the supply of air. In both these units of the prior art the high velocity air entering the plenum chamber from the inlet duct first is met by metallic members which readily conduct sound into the area to which the air is to be supplied.

I have invented a ventilating air discharge muflier in which the high velocity air entering the plenum chamber from a distribution duct is met with members entirely composed of sound absorbing material rather than first by metallic elements as in the systems of the prior art. My mufiier affords ready regulation of the amount of air passing from the distribution pipe to the area to be supplied.

One object of my invention is to provide a ventilating air discharge muffler which substantially reduces the noise generated in high velocity air supply systems.

A further object of my invention is to provide a ventilating air discharge muffier in which high velocity air entering a plenum chamber from a distribution duct is met by members composed entirely of sound absorbing material.

Yet another object of my invention is to provide a ventilating air discharge mufiler in which the volume of air flowing from a distribution duct to an area to be supplied may readily be regulated.

Patented Aug. 30, 1960,

Other and further objects of my invention will appear from the following description.

In general my invention contemplates the provision of a ventilating air discharge mufiler including a plenum chamber having an inlet connected to an air distribution duct and an outlet opening into the area to be supplied With air. I mount a plurality of first baffies having irregular configurations in the chamber between the inlet and the outlet. I mount a plurality of second baffles having configurations complementary to the configurations of the first bafiles adjacent the first baifies to provide a plurality of tortuous air passages between the inlet and the outlet. My mufiler includes means for shifting the first and second bafiies with respect to each other to regulate the flow of air through the passages. My plenum chamber and bafiles are formed of material having good sound absorbing properties and having sutficient structural strength to retain the shape into which it is molded. In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

Figure 1 is an elevation of one form of my improved ventilating air discharge muifier.

Figure 2 is a sectional view in perspective of my improved ventilating air discharge mufller taken along the line 2-2 of Figure 1.

Figure 3 is a sectional view of my improved ventilating air discharge muffier taken along the line 33 of Figure 2.

v Figure 4 is an elevation of a second form of my improved ventilating air discharge mufiler.

' Figure 5 is a sectional view of my ventilating air discharge mufiler taken along the line 55 of Figure 4.

More particularly referring now to Figures 1 to 3 of the drawings, my mufiler, indicated generally by the reference character 10, includes a base 12, a top 14 and sides 16 and 18. I provide my mufiler 10 with an end 20 formed with an inlet 22 which may be connected to an air distribution duct (not shown). In the open end of my mufiler 10 remote from end 20 I mount by any convenient means a grating or grille, indicated generally by the reference character 24, through which air passes into the area to be supplied. Bottom 12, top 14, sides 16 and 18, and end 20 and inlet 22 are formed of sound absorbing material. Preferably I mold these members integrally from the material disclosed in the copending application of Joseph F. Stephens and Glenn W. Kerr, Serial No. 318,856, filed November 5, 1952, now Patent No. 2,778,759, for a Thermal Pipe Insulation. The material comprises glass fibers having an average diameter of no more than ten microns, impregnated with a synthetic resin in an amount from fifiteen percent to thirtyfive percent by weight of the finished material and cured under such pressure as to give the material a density of between two pounds per cubic foot and five pounds per cubic foot. This material has excellent sound absorbing properties and has sufficient structural strength to retain the shape into which it is molded without the use of auxiliary structural members. Any other appropriate sound absorbing material having sufficient strength to be molded may be employed.

Base 12, top 14, sides 16 and 18, and end 20 enclose a space forming a plenum chamber, indicated generally by the reference character 26 in which the high velocity air expands as it emerges from a distribution duct connected to inlet 22. The expansion of the high velocity air reduces the air stream velocity and thus contributes to the reduction of noise which otherwise would be incident to the passage of the high velocity air through: the grille 24.

Within the chamber 26 between the inlet 22 and the outlet grille 24 I mount a plurality of first baifies 28. In the form of my muffler shown in Figures 1 to 3, I employ only two baffles 28 secured to the respective sides 16 and 18 by members 30. It is to be understood that the members 36 may be formed integrally with baffles 28 with a serpentine, sinusoidal, or antractuous configuration. My mufller includes a plurality of second baflies 32 having similar configurations complementary to the configuration of baffles 28. Conveniently, I form a pair of adjacent baflies 32 integrally and disposej the assembly in nested relationship between a pair of baffles 28. This arrangement provides tortuous or sinuous paths, indicated generally by the reference character 34, for the passage of air from inlet 22 to grating 24.

1 form baffles 28 together with members 30 from sound absorbing material. Preferably I make these baflies from the material disclosed in the said copending application. Similarly, bafies 32 are formed of sound absorbing material. While in Figures 1 to 3 I have shown a number of baffles 28 and 32 which afford only two sinuous passages 34 between inlet 22 and grating 24, it is to be understood that I may employ a. large number of baffles making up a multiplicity of passages 34. If a plurality of passages are to be provided, I form a number of first assemblies each including a pair of bai'lies 28 joined by members 36 and a number of second assemblies, each including a pair of baffles 32. In order to form the passages 34, I dispose the assemblies including bafiies 32 in nested relationship between the assemblies including pairs of baffles 28. It will be appreciated that in this manner I may make as many tortuous or sinuous passages 34 as desired.

I provide means for moving the assembly including baffies 32 axially of the chamber 26 to regulate the flow of air through passages 34. A bracket 36 fixed between sides 16 and 18 by any convenient means such as screws or the like 38 rotatably carries a nut 40 mounted on the bracket by means of a peripheral groove 42. A threaded stud 44 fixed to the assembly including bafiies 32 by a plate or head 46 formed on the stud passes through and threadably engages nut 40. It will be appreciat'ed that when nut 40 is turned, the assembly including bafiles 32 will be shifted with respect to the baffles 28. A suitable opening (not shown) in grille 24 gives access to nut 46. If nut 46 is. turned a sufficient amount, baffles 32 contact baflies 28 and the passages 34 will be closed. These passages are fully open when baffles 32 are symmetrically disposed with respect to baffles 28. At its end remote from stud 44 the assembly including baffles 32 carries a guide pin 48 secured to the assembly by means of a plate 50 riveted or otherwise secured to the assembly. Guide pin 48 rides in a hole 52 formed in a bracket 54 extending across inlet 22 and secured to end 26 by any convenient means such as screws or rivets 56. The nut 46 may be turned empirically to adjust the baflies 32 to a point of minimum noise, that is, to' tune the arrangement to a position of greatest sound absorption.

It will be seen that this form of my invention first provides a plenum chamber 26 into which high velocity air entering inlet 22 expands. This expansion reduces the air stream velocity to contribute to the reduction of noise which otherwise would be incident to the passage of the high velocity air through grille 24. This form of my invention provides a plurality of sinuous or tortuous passages 34 which break the air stream into a number of smaller streams. This action of breaking up the air stream further reduces noise. It is thought that this result flows from the conversion of lower frequency sound, which latter is more efiectively absorbed by sound absorbing material. The sinuous or tortuous nature of the paths 34 presents a very large area of sound absorbing material. to air traveling along the paths.

As has been explained hereinabove, my mufiler is formed of a material which has sufficient structural strength to retain the shape to which it is molded. If desired I may provide my baffle with a sheath or skin 58 formed of a suitable material such as aluminum foil or the like. This sheath seals the baffle against the escape of air through the baffle wall. It also serves as a vapor barrier to prevent seepage of moisture through the bafiie walls.

Referring now to Figures 4 and 5, this form of my muffler, indicated generally by the reference character 60, includes a housing having a base 62, a top 64, respective sides 66 and 68 and an end 76 formed with an inlet 72. The housing, including base 62, top 64,

7 sides 66 and 68, and end 70, forms a plenum chamber,

indicated generally by the reference character 73, into which high velocity air passes from a distribution duct (not shown). The air expands and loses velocity in the chamber 73. In the open end of the battle remote from end 70, I mount a grille or grate, indicated generally by the reference character 74. it will be seen that the housing of the form of my muffier shown in Figures 4 and 5 is similar in all respects to the form shown in Figures 1 to 3 with the possible exception of its dimensions.

Within the housing including base 62, top 64, sides 66 and 68, and end 76, between the inlet 72 and the grille 74 I mount a plurality of first baffles 76 having a zigzag configuration. The baiiles 76 adjacent the respective sides 66 and 68 may be secured to the sides by extensions 76 formed integrally with the battles 76. In this form of my invention it will be seen that a pair of bafiies 76 are disposed substantially centrally of the base 62. These baflles are joined by ends 30 to form central bafiies 76 as a unitary piece. it will be understood that the baffles 76 adjacent the sides 66 and 68 are molded as integral pieces with extensions 73 from the material disclosed in the said copending application. Similarly, the two central baffles 76 may be made integral with ends 80 of the same material.

I dispose a pair of second baffles 62 joined by ends 84 between the bafile 76 adjacent side 66 and one of the central baflies 76. I dispose a second pair of second baffies 82 joined by ends 84 between the baffle 76 adjacent side 68 and the other central baffle 7 It will be seen that all the bafiles 82 have a zigzag configuration complementary to that of the baffles 76. This arrange ment provides a plurality of tortuous zigzag paths, indicated generally by the reference characters 66, between the inlet 72 and the outlet grille or grate 74. I construct this form of my mufiler with means for shifting the assemblies including bat-fies 62 with respect to the baffies 76 to regulate the flow of air through the passages 86 and to tune the assembly to a position of greatest sound absorption. A bracket 68 fixed between sides 66 and 68 by any convenient means such as screws or rivets 90 rotatably supports a nut 92. Nut )2 threadably engages a stud 94 fixed by any convenient means such as welding or the like to a U-shaped bracket 96, the respective legs of which are fixed to the assemblies including baflles 82. As nut 92 is turned, the baffles 32 shift relative to the baffles 76 to regulate the flow of air through passages 86. An opening (not shown) in grille 74 provides access to nut 92. If nut 92' is turned a sufficient number of times, the bafli'es 32 contact the baffles 76 and the passages 86 are closed. With the bafiies -82 symmetrically disposed with respect to the baffies 76, the maximum amount of air is permitted to pass through the passages 86. Guide pins 98 secured to the ends of the assemblies including bafii'es 82 remote from the bracket 26 ride in openings in a bracket 100 fixed between sides 66 and 68 by screws or rivets 162. Pins 98 and bracket 1% guide the assemblies including baflies 82 in their movement with respect to baffles 76.

It is to be understood that the housing including base 62, top 64, sides 66 and 68, and end 70 formed with inlet 72 are made of sound absorbing material. Preferably I employ the material disclosed in the said copending application. Similarly, I construct bafiies 76 and extensions 78 as well as bafiles 82 and ends 84 from the same material. If desired I may provide this form of my muffler with a sheath or skin 104 of aluminum foil or the like. While I have shown only two pairs of zigzag bafiles 82 and corresponding baflies 76 to provide four sinuous paths 86, it is to be understood that I may employ as many sets of bafiies as desired to provide a large number of sinuous paths.

In operation of my ventilating air discharge mufiler, high velocity conditioned air from a distribution duct (not shown) enters the inlet 22 or 72 and expands into the plenum chamber 26 or 73. As the air expands, its velocity drops. It is to be noted that in both forms of my invention air entering the plenum chamber is met substantially entirely by sound absorbing material. More particularly, it is to be noted that no metallic element with which the air comes into contact in passing through the mufi'ier extends from the inlet to the outlet of the housing. After expanding in plenum chamber 26 or 73, the air is divided into a plurality of independent streams and is guided along tortuous paths toward the duct outlet. In the form of my invention shown in Figures 1 to 3, passages 34 provide sinuous paths for the air. In the form of my invention shown in Figures 4 and 5, passages 86 provide zigzag paths for the air. The flow of air through passages 34 in the form of my invention shown in Figures 1 to 3 may readily be regulated by turning the nut 40. Similarly the flow of air through passages 86 in the form of my invention shown in Figures 4 and 5 may be regulated by turning nut 92. Upon emergingfrom the passages 34 or 86, the air flows through the grille 24 or 74 to the area to be supplied.

The construction of my mufiler substantially reduces the noise which otherwise would be incident to the passage of high velocity air through an outlet grille. First, expansion of the air into the plenum chamber 26 or 73 reduces the air stream velocity to contribute to the reduction of noise. Second, the breaking up of the air stream into a plurality of smaller streams reduces noise. Further, the sinuous or tortuous nature of the air passages provided eliminates any direct path for sound from the duct to the grille. These passages also expose a large surface area of sound absorbing material to the air in the course of its passage between the duct and the grille. Besides this, I may tune the arrangement to a position of minimum noise.

It will be seen that I have accomplished the objects of my invention. I have provided a ventilating air discharge mufiler which substantially reduces the noise which otherwise would be incident to the passage of a high velocity air stream through a grille. My mufiler not only accomplishes this result but also permits regulation of the flow of air through the muffler.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is therefore to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. Apparatus for feeding air from a supply duct to 811 area to be supplied with said air including in combination means forming a plenum chamber having an inlet for admitting air from said duct to said chamber to permit admitted air to expand and having an outlet to said area, means forming a pair of first bafile walls having sinuous surface configurations, means mounting said first battle wall forming means in said chamber between said inlet and said outlet, means forming a pair of second baffle walls having surface configurations complementary to the configurations of said first bafile wall surf-aces, means mounting said second bafile wall forming means within said chamber with said second bafile walls adjacent said first baffle walls to define a plurality of tortuous paths between said inlet and said outlet to divide the expanded air into a plurality of streams, means for moving said first bafile walls relative to said second bafiie walls simultaneously to vary the cross-sectional area of said paths defined by said first and second battle walls and means for connecting said moving means to said bafile wall forming means.

2. Apparatus as in claim 5 in which said chamber forming means and said bafile forming means are formed from a sound absorbing material.

3. Apparatus as in claim 1 in which said chamber forming means and said baffle forming means are formed of material made up of glass fibers and impregnated with resin.

4. Apparatus for feeding air from a duct to an area to be supplied with said air including in combination means forming a plenum chamber having an inlet for admitting air from said duct to said chamber to permit admitted air to expand and having an outlet to said area, a plurality of first bafi'les having walls with sinuous surface configurations, means mounting pairs of said first baflles in spaced relationship in said chamber between said inlet and said outlet, a plurality of means forming pairs of second bafiies having walls with surface configurations complementary to the surface configurations of said first baffles, means mounting the respective second baffle forming means between the baifles of said first battle pairs with said second baifie walls adjacent said first bafiie walls to define a plurality of tortuous paths between said inlet and said outlet for dividing the expanded air into a plurality of streams, means for moving said first and second bafiles relative to each other to vary the cross-sectional areas of the paths defined by the Walls of said baffles and means for connecting said moving means to said bafiles.

5. Apparatus as in claim 4 in which the respective means forming said second baffles comprise integral members having said second bafile walls and means for connecting said second bafile forming means for movement as a unit.

References Cited in the file of this patent UNITED STATES PATENTS 1,l73,583 Johnston Feb. 29, 1916 1,929,595 MacLeod Oct. 10, 1933 1,938,798 Bourne Dec. 12, 1933 2,075,316 Tyden Mar. 30, 1937 2,091,918 Finck Aug. 31, 1937 2,214,467 Lambert et al. Sept. 10, 1940 2,270,825 Parkinson et al Ian. 20, 1942 2,502,020 Olson Mar. 28,- 1950 2,759,556 Baruch Aug. 21, 1956 FOREIGN PATENTS 472,605 France Aug. 11, 1914 813,127 France Feb. 15, 1937 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 'Patent Nor 2,950,776 August 30 1960 Joseph F. Stephens It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 20, for the claim reference numeral "5" read 1 Signed and sealed this 4th day of April 1961:.

(SEAL) Att ERNEST W, SWIDER XQQ XXXXQQXK ARTHUR w. CROCKER Attesting Oflicer Acting Commissioner of Patents Patent Noa 2,950,776

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 7 August so 1960 Joseph F. Stephens It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 20 for the claim reference numeral "5"- read 1 Signed and sealed this 4th day of April 1961.

(SEAL) A t ERNEST W. SW IDER WXXXQQMM ARTHUR w. CROCKER Attesting Oflicer Acting Commissioner of Patents

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