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Publication numberUS2089492 A
Publication typeGrant
Publication dateAug 10, 1937
Filing dateJul 6, 1935
Priority dateJul 6, 1935
Publication numberUS 2089492 A, US 2089492A, US-A-2089492, US2089492 A, US2089492A
InventorsRobert D Lambert
Original AssigneeAmerican Radiator Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
US 2089492 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

Aug. lo

R, D. LAMBERT DUCT v Filed July 6 1935 3 Sheets-Sheet l INVENTOR,


Aug. 1o, 1937. R. D; LAMBRT 2,089,492


Filed July 6, 1935 3 SheetS-S'neet 2 Aug- 10, 1937 R. D. LAMBERT 2,089,492


Filed July 6. 1935 3 Sheets-Sheet 3 Jyjz INVENTOR.

4ax/9. (A

Patented Aug. 10,' 1937 UNITED s'rixl'riss BATENT lOFFICE:

l DUCT Application July 6, 1935, Serial No. 30,206

2 Claims.

t square or rectangular ducts formed of sheet` metal, but such ducts are inadequate to meet the present day needs in that they are relatively diilicult and expensive to install and because they transmit both the sounds of moving air and the i mechanical sounds of the apparatus to the rooms of the building to winch the ducts areconnected. An object of the present invention is to provide a relatively inexpensive duct which is strong vand durable, which will eectively absorb sound waves, which may be readily cut into any desired length with ordinary carpenters tools and which may be easily installed with a minimum of labor expense. The invention consists in the novel construction and combination of parts, tov be' more fully described hereinafter, and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawinga'to be taken as a part' of this specification, I have fully and clearly illustrated a preferred embodiment of my inven-A tion, in which drawings Figure 1 is a vertical, sectional view taken through a building and showing my invention as used for conveying conditioned air to the rooms and for conveying return air from the rooms to an air conditioner; l

Fig. 2 is an enlarged, elevational view of a portion of a laminated duct constructedin accordance with the present invention and showing the .10 ends of the layers unwrapped to illustrate more clearly the details of construction of the duct; Fig. 3 is a transverse section through the duct, the view being taken on the line 3--3 of Fig. 2.

Fig. 4 is a fragmentary, transverse, sectional view of the duct taken on a further enlarged scale and illustrating more clearly the structural details of the duct;

Fig. 5 is a view similar in character to Fig. 2

and illustrating a modified form of construction;

.50 Fig. 6 is anenlarged, fragmentary, transverse,

sectional View taken on the line 6-6 of Fig. 5;'

f-Flg.. '7 is a view similar in character to Fig. 2 .3 'and illustrating a. further modified form of duct construction;

55 Fig. 8 is an enlargefragmentary, transverse,

(ci. 13s-frs) sectional view taken on the line 8-8 of Fig. 7,;

Fig. 9 is a view similar in character to Fig. 2 and illustrating a third modified form of duct;

Fig. 10 is an enlarged, fragmentary, transverse, sectional view taken on the line Iii-i0 of Fig. 9; 5 Fig. 11 is a view similar in character to Fig. 2

and illustrating a fourth modified form;

Fig. 12 is an enlarged, fragmentary, transverse, sectional view taken on the line i2--i2 of Fig. 11; 10

Fig. 13 is a view similar in character to Fig. `2 and illustrates as fifth modified form of my lmproved duct;

Fig. 14 is an enlarged, fragmentary, sectional view on the line i4-i4 of Fig. 13; v15

Fig. 15 is a perspective view illustrating a square or rectangular duct constructed in accordance with the present invention;

Fig. 16 is an enlarged, fragmentary, sectional view taken on the line i6-i6 of Fig. 14 20 Fig. 17 is an enlarged, fragmentary, sectional view of a duct illustrating a further modified form of construction:

Fig. 18 is an enlarged, fre gmentary, section'al view of a duct illustrating a still further modified 25 form of construction, and y Fig. 19 is an enlarged, fragmentary, sectional view illustrating another modification of my improved duct construction.

In accordance with one preferred embodiment 30 of my invention I provide a duct which is composed of a plurality of layers of fibrous material and secure the layers together by a suitable adhesive. The interior portions of the duct or those portions which contact the moving air, are formed 35 of materials suitable for absorbing or deadening sound waves which is an important feature in installations where the air is propelled by blowers, fans, or the like, or is subjected to humidifying sprays. In the absence of sound deadening, 40 such mechanical noises as these and the noise of the air moving through the fan and restricted passages of the apparatus would be transmitted to the rooms by the duct and result in discomfort to the occupants. 'I'he intermediate portions of 45 the duct may be formed of one or more layers of material which function as a strengthening or stiffening means for the duct. The outside portions of the duct may be made fire-proof or, if desired, all of the layers may .be made of flreproof material, or material treated `with a fireproofing agent. The outside layer may also function as a stiffening means.

As Iwill presently appear, the three functions of Sound". deadening, strength and fire-proof are l40 and absorbing qualities. l The corrugations in the 45 stiifening and strengthening the duct, and the preferably present in each modification shown in the drawings. However, these functions need' not necessarily be performed by any one layer or group of layers of material, as a separate layer or layers may be provided for performing each function, or more than one function may be performed by the same layer or layers of material. In addition, one or all of the layers of material may be made of materials having the characteristic of repelling moisture.

Referring now in detail to the construction illustrated, the reference character III indicates a room of a dwelling house comprising walls I I and a floor I2. Air at the proper humidity and temperature may be delivered to the room Ii from an air conditioner I 3 by a duct Il, the air entering the room through a grille 'covered opening Il in the floor I2. Return air is conducted from the room I0 to the conditioner Il by a duct I6 which is similar in construction to the duct I l, the duct IB being connected to the room by a second grille covered opening I1 in the floor I2. Thus far, I have described one application of my improved form of duct. Other applications will be apparent as the description proceeds.

As stated previously, the ducts I I and I1 may be formed in a variety o'f ways. In the modi-n cation shown in Figs. 2, 3, and 4, I have shown the duct -II as comprising an lnteiior'or inner layer 2l of perforated asphaltum paper, a second layer 2i of corrugated paper board, two lay ers 22 and 23 of ordinary cardboard, and an exterior layer 24 of sheet asbestos, for example. ixi-l paper or woven form. Asphaltum paper is prox i,

vided because it 1s ammsture repeuing material;

and the perforations are providedl in the mate- 1 rial so that sound waves will permeate the walls of the duct. -If desired, the asphaltum paper may., also be wrinkled to aid in its sound deadening paperlayer 2| provide open spaces `2l for deadening and absorbingsound waves passing through the perforations of the interior layer 2l. 'I'he cardboard layers 22 and 2l are for the purpose of" 'exterior layer 2l oi' asbestos or its equivalent is for the purpose of rendering the ductnr'e-proof. A'Ihe ducts Il and|1 may be made in a4 variety of ways without departing froml certain of the broader aspects of my invention. In Figs. 2, 3, and 4, I have illustrated a cylindrical duct formed of spirally wound layers of materials The interior layer 20 may be spirally wound on a mandrei, ,with the edges of adjacent oonvolutions 5 5 -abutting one another. The n ext layer 2l may be spirally wound on the interior layer and in such a manner that thesfmeeting edges-of each oonvolution also adioin one another and are spaced. longitudinally of the duct from the meeting edges oi' the convolutions of the interior layer 2li. Each remaining layer may be spirally wound on the previously wound layer in a similar manner. v Each layer maybe secured to the previously wound layer by a suitable adhesive, whichv `is 05 preferably fire-proof; for example. by a solu` tion of sodium silicate or water glass, thus renderlng the duct more fire-proof, and"'incldentally contributing toits strength and rigidity. 'I'he sodium silicate is indicated at 2l in Fig. 4. If def sired, al1 of the materials may be treated as by coating or impregnation with a fire-proofing agent, such, for example, as the sodium silicate solution. In such a case, the exterior layer of asbestos may be omitted, if desired. In rigs. 5 and s I have shown s duct Hs formed in asimilar manner and with materials performing similar functions as the duct and materials shown in Figs. 2,' 3, and 4; In Figs'. 5 and 6 the interior layer 2li|` is formed of a perforated, closely woven fabric similar to oil cloth, known commercially as kribble cloth, the perforations performing the same sound absorbing func' tion as the layer 2 0, previously described. The layer 2|* may be formed of spirally wound cord or rope of fibrous material such as hemp or cotton and theconvolutions thereof are spaced apart for the purpose of more effectively absorbing or deadening the sound waves passing through the layer20. The rope or cord may be several separate and parallel strands arranged in groups and the groups spirally wound as a unit on the layer 20", as shown, or the rope may be a single strand continuously wound to .provide the spaced convolutions. The layers 22", 23', and 24, are formed .of cardboard and asbestos, as in the case of Figs. Lil, 3L and 4. 'I'he several layers may be secured togeth'er by a fire-proof adhesive and may be impregnated or coated with a fire-proofing agent as explained in connection with the previously described embodiment.

- In Figs. 7 and 8 I have illustrated a still different selection of materials for the several layers forming' the duct. The duct Ilb is provided with an interior layer 20 of loosely woven cloth so that the sound waves will permeate the same. 'I'he layer 2| b is formed of corrugated paper, the layers 22h and 2lb of,cardboard and the layer 2lb of asbestos.

, cardboard and the layer 24 of asbestos.

In rigs. 11 and 12 the interior layer m is formed of perforated oil-cloth or kribble cloth,

the layer 2|'i is formed of heavy, coarsely woven,

fibrous cloth, such as Jute nber, burlap, or the like, such a cloth providing the open for absorbing the sound. The layers 22I and!!d are formed of cardboard and the layer '244 of as- In Figs. 13 and 14, the layers 2l', 22 and 2l' are formed of the'same materials as the corresponding layers in Figs. 5, 7, 9, and ll, but the open spaces for the absorption of sound behind the layer 20 are provided by bands 21 of paper or other suitable material spaced longitudinally of the duct as shown, to form spaces 2l between the bands and the layers 2l and 22'.

In Figs. 15 and 18 I haveillustrated a duct Il' `whichV is rectangular in cross-section and is formed of the same layers of material as Figs. 2. 3 and 4. Ihe rectangular duct may be formed in any suitable manner; for example, the layers may be spirally wound on a rectangular mandrel.

'In Fig. 17 I have illustrated a portion of a laminated duct, wherein instead of having two interior layers to deaden the sound, as is the' of cardboard and the layerfll 4is formed of asbestos or other suitable fire-resisting material. In Fig. 181 have illustrated a duct having only two layers 40 and 4I. The layer 40 is on Ithe inside of the duct and is formed or fiber board perforated as indicated at 4Z forreceivin'g and absorbing the sound waves. The yilber board 5 performs the dual function of strength and sound absorbing. The layer 4| is formed o! asbestos.

In Fig. 19 I have illustrated three layers of illier board 40, 4l!b and 40, which are perforated 'as vindicated at 425.42b and 42 respectively. As shown, the perforations 42* are relatively small and are arranged'relatively close together.. The perforations 42" are larger than pe'rioratio'ns 142* and spaced farther apart, and the perforations 42 are still larger and spaced still farther apart. 'I'his construction provides extremely eective sound deadening, as theperi'orations o! the several layers overlap and communicate with one another and thereby provide spacesfwhich increase in size toward the outside of the duct, for receiving and absorbing .the sound waves. The layer 4l'l is formed -of suitable nre-prooi' material. From the above it will be readily seen that I have provided aduct which is unusually strong and durable. is .nre-prooi'. and one which will effectively absorb sound, thus providing a duet which meets therequirements of air conditioning and ventilating apparatus. The duct is formed of material which can be readily c ut and joined by the conventional carpenters or their equivalents.

what I claim and desire tqsecure sy' Letters Patent of the United States is:

1. An elongated laminated tubular duct for conducting air and like iluids and formed oi a plurality of superimposed layers oi fibrous material; said 'duct comprising an inner or vilrst l layer' oi ilbrous material having a multitude of -small openings therethrough for the passage of sound waves from the inside of the duct; a second layer covering and directly secured to the exterior surface of the inner layer and formed of a ilbrous material having relatively large air of receiving and deadening the sound waves 'transmitted through the relatively small opener of perforated'paper, a second layer of corrugated paper covering and directly secured to the inner layer and so arranged that sound waves passing from the interior space of the duct through the perforations of the inner layer will enter the relatively large spaces between corrugations in the second layer and be deadened thereby, and a third layer of relatively stiff ilbrous material engaging and covering' the second layer.


A 10 spaces communicating with the relativelyl small' 4 openings through the inner layer for the purpose

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2485392 *Dec 13, 1944Oct 18, 1949Burgess Manning CompanySilencer with cloth gas-conducting conduit
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US2674336 *Oct 6, 1950Apr 6, 1954C W Lemmerman IncAcoustical panel
US2720276 *Dec 19, 1951Oct 11, 1955Droeger Carl CSound deadening means for jet engine test stands
US2727214 *Nov 2, 1949Dec 13, 1955Bell Telephone Labor IncAcoustic delay line using solid rods
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U.S. Classification138/149, 138/144, 138/DIG.400, 181/224, 138/150
International ClassificationG10K11/16, F16L9/21, F16L55/02
Cooperative ClassificationF16L55/02, Y10S138/04, F16L9/21
European ClassificationF16L55/02, F16L9/21