US2541159A - Sound deadener for vibratory bodies - Google Patents

Description

Feb. 13, 1951 P, H, GElGER 2,541,159

SOUND DEADENER FOR VIBRATORY BODIES Filed Jan. 22, 1946 3 Sheets-Sheet l 79M www Feb. 13, 1951 P. H. GEIGER 2,541,159

SOUND DEADENER FOR VIBRATORY BODIES Filed Jan. 22, 1946k 3 Sheets-Sheet 2 1 IN V EN TOR.

Feb. 13, 1951 P. H.'GE|GER SOUND DEADENER FOR VIBRATORY BODIES 5 Sheets-Sheet 5 n Filed Jan. 22, 1946 Tijl? Sav Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE SOUND DEADENER `FOR. VIBRATORY BODIES Paul H. Geiger, Ann Arbor, Mich.

Application J armar-y' 22, 194.6, Serial No. :642,599

12 Claims. l

This invention relates to sound deadeners andv relates particularly to sound deadeners adapted to damp the vibrations of audible frequency of surfaces of bodies so as to minimize the intensity and duration of the soundl produced by such vibrations.

Whenever a body is freeto vibrateat an audible frequency without substantial damping of the vibrations, it is noisy in that whenever it isl struck or otherwise excited it sets up vibrationswhich result-in persistent sound, the intensityr of which dependsr upon the intensity or amplitude of vibration of the surface of the body. The noisiness oi such bodies can. be counteracted by damping the vibrations so that the amountand duration of the sound radiated into the air are reduced.

One of the elds in which sound deadeners-areV used extensively at the present time and which" is illustrative of the practical. commercial utility of sound deadeners, is the automobile eld, the

sound deadener being used for the' purpose of dampingthe vibrationsof the metal panels of the doors,y top, luggage compartment, etc., ofA auto-v mobile bodies so thatthe automobile will not have an objectionable rumble or tinny sound.

Sound deadeners have heretofore been madein several forms. Some sound-deadener materials are made up in a semidiqu-id form and are applied to the vibratory surface to be damped as by use of a spray gun and after application are baked or air dried. O ther sound deadeners are made in the form of felts or blanketsior appli-v cation by means of an adhesive. Usually, such feite-r blankets are indented prior to application so that they may more readily be con-formed to the contoursof irregularly-shaped parts o-automobile bodies. rEhe use of such sound deadeners has, however, proved. to be disappointing. Inthe rst place, the damping of the sound-producingy vibration has not proven to-be particularly effective. For example, the natural frequencies of vibrationY of an auto-mobile door panel. vary from about l50 cycles per second'to 60() or more, there being certain frequencies within thevrange which are particularly pronounced, depending upon the siaeyand shape of the door panel. The vibrations of higherv frequency are more readily damped than the lower frequemiies.r However, it is the lower frequencies that are particularly objection` able in producing the rumble or tinny noise oi' automobiles and the sound deadener materials heretofore used have had only a slight damping effect on vsuch vibrations.

Another disadvantage of scundeadener ma.:

terials heretofore` used is that it is difficult tol obtain uniformity of. effectiveness. For example,

materials which appear to be identical as tar as..

specifications are concerned with respect to Weight and kindof material, amount of saturation, etc., may diier Widely insound deadening effect.

It is a purpose of this invention to providev sound deadener means for damping the vibra be made so as to` have a predetermined vibration damping eiectand` so as to-afford uniformity in effectiveness. It is a further purpose of this` inventionV to provide sound deadeners which have the above-mentioned advantages and which at the same time are simple and. inexpensive Vto manufacture. It is important for many cornmercial applications that a sound deadener `be light in Weigh-t, and it is a further purpose of this invention-to providea sound deadener which can be made very light in Weight and which at the same time is highly efective.

According to this invention, a sound deadener is allorded which has greatly increased effective ness because of. the employment. of a Special structure which is operative onY a new principle.

a base portion. for attachment to a surfacev ofav vibrating body and` a Weight-carrying portion.

Between the Weight-carrying portionv and the base. portion is a flexible portion having substantial mechanical hysteresis uponflexure, namely, the capacity when ilexed of converting all or a largeproportion of the force required to cause they ilexure into heat. The weight is affixed to the Weight-carrying portion of the Weight support and. is carried thereby for free vibrator'yniotion relative to the surface to which the baseportionofV the weight support is attached. Whenk the base portion off the weight support is affixed,

to a surface of the vibratingv body, the iiex'ible portion of the weight support is disposed s'othat' the inertia suppliedby the Weight causes flexure o'f the flexible portion. ofthe Weight support. The

result of such Alexiire of the ilexible portionY 'f the weight support is to accomplish a very rapid conversionofythermechanical energy of the vi .braune .body *into- .rfeat with resultant effectivev damping of the vibration of the body and deadening of the sound.

By use of a localized weight or mass disposed for free vibratory motion with ilexure of a inate-- rial having substantial mechanical hysteresis, it is possible to dissipate the energy of a vibrating body by conversion into heat many times as effectively as is possible with conventionalsounddeadening materials. While the sound deadener of this invention involves the useV of localized weight, the structure as a whole is so highly effective that a sound deadener embodying this invention can be made which weighs much less than conventional sound-deadener materials and which at the same time is much more eiective.

The new principle which is utilized in sound deadeners according to this invention, lends itself to many different structural embodiments. Certain of these structural embodiments are shown, merely by way of exempliiication in the accompanying drawings, wherein:

Fig. 1 is a plan view of a sound deadener embodying this invention;

Fig. 2 is a sectional elevation on a larger scale of the sound deadener of this invention as applied to the surface of a vibrating body;

Fig. 3 is similar to Fig. 2 showing an alternative embodiment of this invention;

Fig. 4 is a plan view of an alternative sound deadened embodying this invention;

Fig. 5 is a sectional elevation on a larger scale of the sound deadener shown in Fig. 4 as applied to the surface of a vibrating body;

IFig. 6 is a plan View of a further alternative embodiment of this invention;

'Fig. 7 is a sectional elevation on an enlarged scale of the sound deadener shown in Fig. 6 as applied to the surface of a vibrating body;

Fig. 8 is a plan view of a single sound-deadener element as applied to the surface of a test plate;

Fig. 9 is a sectional elevation of the sounddeadener element and test plate shown in Fig. 8;

Fig. 10 is a plan view of the test plate and sound-deadener element shown in Fig. 8 with four additional similar sound deadener elements also applied to the plate;

Fig. 11 is a plan view of a further embodiment of a sound-deadener device according to this invention which is applied to the exterior of a tubular body;

Fig. 12 is a sectional elevation taken on the line |2-|2 of Fig. 11;

Fig. 13 is a sectional elevation of a still further modification of this invention wherein mechanical hysteresis is obtained by surface friction, and 5f' Fig. 14 is a plan view of the sound-deadener device shown in Fig. 13.

The embodiments of this invention shown in Figs. 1 to 7 are well adapted for application to the inside of the metal panels of automobiles such as the doors, the top, the luggage compartment, etc. to deaden the noise of the car. The naterial that is employed for the weight support advantageously is composed of felt that has been impregnated with a bituminous waterproofing binder material. Such a material has relatively high mechanlcal hysteresis, in that the material requires substantial force to flex it but has very little resilience. Because of this combination of properties, felt impregnated with bitumen is well-adapted for use according to this invention due to the fact that the force expended in flexing the material is largely converted into heat. A material such as felt impregnated with.l bitumen is to be contrasted with a vmaterial such as spring steel which has the property of storing mechanical energy imparted as a result of deformation instead of dissipating the mechanical energy by conversion into heat. Spring steel or other` springy and highly-resilient materials are not suitable for use as the nexible portion of sound-deadener devices embodying this invention. On the contrary, the portion of the sounddeadener devices which is subjected to iiexure should be such that the internal friction of the material converts into heat the energy required to produce ilexure. While a resilient material such as springy steel is unsuitable, a fiexible member made of such material can be utilize., however, if the parts are arranged so as to accomplish rubbing friction between surfaces upon flexure, the rubbing friction converting a substantial portion of the energy required to produce fleXure into heat.

Referring to the embodiment of this invention shown in Figs. 1 and 2, the weight support of the sound deadener is composed of sheet material 20 having a plurality of cup-shaped deformations therein which are indicated generally by the reference character 2|. The sheet material 20, may, for example, be conventional organic ber felt which has been impregnated with a bituminous saturant. The impregnated sheet may, for example, weigh about 0.25 pound per square foot. Secured to the bottom of the cup-shaped deformations 2l are the weights 22, one weight being employed for each deformation. The weights 22 may be composed of any suitable material. When, as in the embodiment shown, the sheet material of the weight support is composed of felt impregnated with bitumen7 the weights 22 may desirably be composed of some finely-divided mineral material such as sand, barytes or the like, the particles of which are bonded together by a bituminous binder. The weights may be caused to adhere to the sheet material by a blending of the bitumen in the sheet ma and the bitumen in the weights so as to provide a permanent adhesive bond. Each of the weights may, for example, weigh about .6 oz. The cupshaped deformations may be about 2% to 3 inches in diameter with the centers spaced apart about 4 to 5 inches.

In Fig. 2, the sound deadener is shown afxed to plate 23 for the purpose of damping the vibrations of this plate. The deformed sheet material constitutes the weight support of the sounddeadener elements, and the portions of the sheet material 20 which are between the rims of the individual cup-shaped deformations constitute the base portions 24 of the weight support, which base portions are adapted to be secured to the plate 23. The base portions 24 can be secured to the plate 23 by use of a suitable adhesive such as a suitable asphalt cement (not shown).

Referring to each of the cup-shaped deformations which constitute the operative elements of the sound-deadener material, it is apparent that between the base portion 24 thereof and the weight-carrying portion 26 thereof to which the weight 22 is attached, there is a flexible portion 25 whereby the weight 22 and the weiffit-carrying portion 26 of the weight support are disposed for free vibratory motion toward and away from the plate 23. From a somewhat different l'ointI of view, it is apparent that the base portion 24 of each of the sound-deadening elements provides spaced base means for attachment to a body for dampingthe virbations thereof and that the weight sattached to a bridging member between the spaced base means at an intermediate point of the bridgingA member.

When the plate 23 is struck or otherwise excited so as to vibrate. normal to the surface thereof,.theibase portions 24 of the sound-deadening elements will vibrate with the surface ofthe plate 23. Due, however, to the inertia Vof the weights 22, theweights 22 will not follow lthe vibratory motion of the plate 23 and there will-be nexure ofthe `flexible portions V25 of sound-deadening elements. Since the sheet material of which the weight support is composed, including the flexible portions thereof, hassubstantial mechanical hysteresis, the energy which produces the flexing of the ilexible portions 25 of the sounddeadening elements is converted 'into heat. Moreover,the inertia provided by the weights 22 produces such'a pronounced iiexure of the rmaterial having mechanical hysteresis that the energy originally contained in the vibrating plate is' very rapidly dissipated byl conversion into heat with the-'result that the vibration is damped very quickly and thesound radiated from the vibrating plate soon becomes inaudible.

`While `it is believed `that for most vibration frequencies the weights 22 remain relatively stationary as compared with the vibratory'motion of the surface'of'the body to which the sound deadener is attached, itfmay be the case thatv for certain frequencies of vibration, the weights 22 will be causedto vibrate at an amplitude greater than the amplitude of vibration of the surface ofthe body to which the sound deadener i'sattached. However, in either event, there will be a pronounced ilexing of ethematerial having substantial mechanical hysteresis due to the action `of the weight-)sand the vibrations of the surface of the body will be eiie'ctively damped due tothe rapid dissipation of the energy ofthe vibrating body in the form of heat.

ReferringA to Fig. 3, the structureV of the sounddeadening elements of thesound deadener is the same as that shown in Figs. 1 and 2, and the structural elements thereof have been indicated bythe same reference characters that are used in connection with the foregoing description of' the embodiment of this invention shown in Figs. I and 2. In Fig. 3, however, the sound deadener comprises a second layer 21 of sheet material which may, 'for example, be bituminized felt of the same type that is used in the sheet 2l) which contains the cup-shaped deformations 2l therein. 'The embodiment of this invention which is shown in Fig. 3 may be made up at the factory containing the sheets 20 and 21 in .permanently bonded Arelation as by use of an adhesive (not shown. The sound-deadener material thus formed is theny adapted for attachment to a vihnatedisuriface byadhering the sheet 2l thereof face-to-face with a vibrating surface, such as" the surface of plate 23, as' by means of a suitable adhesive (not shown). In such case, the sheet 21 constitutes part oi the base portion oi the sound-deadening elements which is adapted to be securedto a vibrating surface. By having the sheet 21 disposed so as to underlie the cupshaped deformations', it is possible Yto provide a greater area for' direct adhesion betweenthel sound deadener and the vibrating surface. In the embodimentof this invention shown in Fig/3, it is apparentthat the weights 22 andthe weightcarrying' portion of the weight supports. of the sound-deadening elements'are maintained by the weight supports for tree. vibrat'ory motion towere and. away from. the vibrating; surface 'to' which thesound-deadener material is secured. By free vibratory movement, it is to be understood that the weight 22and the weight-carrying portion 26 of each of the weight supports d not contact the vibrating vsurface or anyother' body such as the sheet material 21 of' Fig. 3 that Vibrates with the vibrating surface of the plate 23 when the sound deadener is subjected to the ordinary conditions of use.

In Figs. 4 and 5, an alternative embodiment of this invention is `shown wherein the's'ounddeadening elements are shaped so that a maximum number of the sound-deadening elements can be provided for a given area of surface. The

sheet material 28 has cup-shaped deiormatic'uis'A 29 therein which are of generally'sq'uare sha-pe.- The weights 30 are attached to the bottom of the cup-shaped deformations 29. The portions 3| of the sheet material 28 are adhesively united to the sheet material 32, which in turn is adapted to be secured to the surface of the body 33 in' face-to-'face relation therewith. In the embodiment of this invention shown in Fig'. 4, it isv desirable to use the layer of the sheetmaterial 32 for providing the Aadhesion tothe surfacef the body 33 due to the limited area of the `por tions 3i between the rims of the cup-shaped deformations. However, the sheet material' 32 may be omitted, if desired. The sheet material 28 is composed of some material such as bituminized felt which has substantial mechanical hysteresis, and the principle of operation ofthe embodiment of this invention lshown in Figs. 4 and 5 is vessentially the same as that of the embodiment of this invention shown Yin Figs'. l, 2 and 3, However, by increasing the numberl of individual sound-deadening elements which can be applied to a given area of vibrating surface, the amount of energy required to flex the' material having substantial mechanical hysteresis is increased and the effectiveness of the sound deadener is also'increased.

It is not essential that the sound-dead'enin'g elements be made by producing cup-shapedA deformations in sheet material. In'Figs. '6 and 7, a sound deadener embodying this invention is shown in which ordinary ilat sheet material is used. Two layers of sheet material are em'- ployed. One layer 34 is in the form of a continuous sheetl which may, for example, be biturninized felt. At spaced intervals 'about the sheet, the weights 35 are secured thereto. A second sheety 36 may likewise beL composed of bituminiaed felt, and has apertures 31 'therein' which are shown as circular but may be of vany other desired shape, The apertures in the sheet 36- are disposed at intervals corresponding to the spacing of the weights on the sheet 34 "and the sheet 36 is adhered'to the sheet 34' 'as' 'by use'A oi an adhesive (not shov'vn)` so that the weights 35 wll'be disposed respectively substantially'rat the mid-point of the apertures 31.- The sound deadener, made as above described, can be secured to the surface of a body .38 .as by the use 'of a suitable adhesive (not shown) for adhering the sheet 35 to thev surfaceof the,body In the embodiment of this. inventionshown in Figs. 6 and 7, itA is apparent that a weight support is provided inA which me sheet 3'6 as the' base' portionv and in which the sheet 3l provides a flexible portion 39 between the basel portion and the weights 35'. Moreover, theweights 35 `are"disposed for free vibratorynicey Vtion toward' and awasrroituefsurface body 38 to which the sound-deadening material is secured.

Any of the embodiments of this invention shown in Figs. l to 7 is extremely eifective in damping the vibrations of a vibrating surface and is extremely eilect-ive in deadening the sound caused by the vibrations of such surface. The effectiveness of the sound deadener of this invention may be illustrated in connection with the following description of the results obtained by the use of isolated sound-deadening elements for damping the vibrations or" a vibrating plate.

The effectiveness of a sound deadener may be effectively determined by application of the sound deadener to a steel plate measuring by 2O by 1/4 inches which has been prepared so that it will have a natural frequency ci vibration of i60 cycles per second, the accepted frequency comparative test. Vibrations of low frequency in the audible range have been found to be the most difficult to damp by means of a sound deadener and any sound deadener which is effective for damping vibrations of low frequency will be eiectiye for all ordinary commercial applications. By providing a steel plate of standard size and frequency of vibration, an accurate standard of comparison is afforded. Such a plate can be mounted so that it will be free to vibrate as by suspending it from a flexible cord or by supporting the plate at its nodes on resilient supports. if the plate is struck or otherwise excited, the plate will continue to vibrate for a considerable time. For testing the rate of decay of vibration, the sound produced by the vibration of the plate can be picked. up by a microphone which is connected to an oscilloscope which records oscillations in direct correspondence to the amplitude of the vibration of the vibrating plate. By photographing the amplitude oi oscillations as shown by the oscilloscope upon a photographic nlm moved at a constant speed, the time for producing a given amount of of the amplitude of vibration can be accurately measured. From the data so recorded, the rate of decay of the sound pro-duced by the 'vibrating plate can be calculated in terms of decibels per second. rThe rate of decay of the sound produced by the vibrating plate without any sound-deadening material applied thereto is substantially 0.5 decibel The eilectiveness o a sound deadf A. to the plate will be evidenced by an increase in the rate of decay expressed in decibels per second that results from the use of a sound deadener. The greater the rate of sound decay, the more effective is the action of the sound deadener in damping the vibrations of the plate.

For purposes of comparison, bituminized felt weighing about .26 pound per square foot was applied to one surface of the test plate above described, using the bituminous asphalt cement. The felt was impregnated to the extent of about 109% by Weight of the weight of dry fibers with the saturating asphalt having a softening point of about 100 F. The felt had been indented so as to provide a multiplicity of small indentations throughout the lateral extent thereof. Such indented felt is typical of the bituminous organic fiber felt material that is extensively used for sound deadening in automobiles. When the plate was tested for determining the effectiveness of this sound-deadenng material, it was found that the sound decay was at the rate of about 3 declbels per, second. This does not constitute any very substantial increase in the rate of sound decay as compared with the bare plate.

As shown in Figs. 8 and 9, a single sounddeadening element embodying this invention was applied to the test plate 40. The weight support of the sound-deadening element consisted of a single cup-shaped body 4| substantially three inches in diameter and composed of the same felt material that was used for overall application to the test plate in the conventional manner in the test previously described. In the center of the cup-shaped material, a weight 42 weighing about .3 ounce was secured. As shown, the sound-deadening element was placed in the center of the test plate. When the plate with the sound-deadener element embodying this invention was tested for determining the effectiveness of the sound-deadening element, it was found that the rate of sound decay was about 14 decibels per second. When it is considered that the single sound-deadening element averaged only about 0.01 pound per square foot of the surface area of the test plate, as against .26 pound per square foot for the overall application of felt in the convention manner, it is apparent that the sound-deadener element of this invention, on a weight-for-weight basis, had over times the sound-deadening effectiveness of the felt per se. In order to demonstrate the essentiality of the Weight 42, the weight 42 was removed from the sound-deadening element and the plate was again tested With the weight support 4l only ailixed thereto. It was found that without the weight, the rate of sound decay was only 1.0 decibel per second and that the weight support 4| by itself and Without the weight affixed thereto had virtually no effectiveness in damping the vibrations of the plate.

In Fig. 10, the plate 40 is shown with a sounddeadening element 43 affixed to the center thereof which sound-deadening element is identical with the sound-deadening element shown in Figs. 8 and 9 and described above. In addition to the sound-deadening element 43, four additional sound-deadening elements 44, 45, 46 and 41 were affixed to the plate in the position shown, each of these sound-deadening elements being identical with the sound-deadening element 43. The plate, when tested with the sound-deadening elements 43, 44, 45, 45 and 41 applied thereto as shown in Fig. 10, exhibited a rate of sound decay of about 19 decibels per second. It may be noted that the sound-deadening eifect as produced by the ve sound-deadening elements as compared with the sound-deadeuing effect -produced by a single element is not in direct proportion to the number of elements applied. This is due, however, to the fact that the sounddeadening element 43 in Fig. 10 is located at the position in the test plate at which maximum amplitude of vibration occurs. The amplitude of vibration of the test plate in the regions covered by the elements 44, 45, 46 and 41 is considerably less than the amplitude of vibration of the test plate in the center thereof. In other Words, the amount of energy of vibration which is dissipated in the form of heat is greatest when a sound-deadening element is positioned at the location Where maximum amplitude of vibration occurs.

With further reference to the test plate shown in Fig. 10, the Weights were removed from the sound-deadening elements 43, 44, 45, 46 and 41 leaving only the weight supports composed of. feltafllxed to the test plate. When the plate deadening unit or a limited number thereof at tions.

was subjected to test in this condition, it was found that the rate of sound decay was only 1.25 decibels per second showing that the presuse of this invention for damping the vibration of metal panels in automobile bodies, since for such purpose the sound-deadening material is usually made up in sheet form comprising a plurality of the sound-deadening-elements as has been illustrated in the embodiments of this invention shown in Figs. 1 to 7. However, the `use of individual sound-deadening elements as shown in Figs. 8, 9 and 10 indicates the special advantages that can vbe obtained by the use of the sound-deadening elements of this invention at selected locations on the surface of a vibratlng body. Such use of the sound-deadening `elements of this invention is of a special utility when reduction in weight is of importance since avery high degree of sound-deadening effect can be obtained for the weight of material applied to the vibrating surface. For example, the vibration of large panels in airplanes can be very effectively damped by placing a single soundone or more selected zones of limited area at which the amplitude ofY vibrationof the vibrating surface is greatest.

In order to further demonstrate the effectiveness of the sound deadener Vof this invention, a f sheet of felt of the same kind thatH resulted in a sound decay of about 3 decibels .per second when applied in fiat condition to the surface. of

the plate, was deformed so as to afford cupkvshaped deformations of the kind shown inl Figs.

1 and 2, the deformations being Asubstantially 3 inches in diameter and spaced five inches apart center Vto center. Weights weighing about .3 ounce were attached to each of the deforma- Upon applying thesound-deadener material as thus produced to .the test plateas `shown in Figs. l and 2, it was found that the rate of sound decay was 46 decibels per second. In .other Words, the vibration of the plate was damped extremely rapidly. Upon removing the weights from the cup-shaped deformations, it wasfound that the rate of 4sound decay was only 2.25 decibels per second, thereby showing the essentiality of the weights in aording the extremely rapid damping action which is obtainable accord- `ing to this invention.

The sounddeadener of this invention is applicable not only. to fiat surfaces but isialso appli- ,cable to any surface of a body which is subject `to vibration. Moreover, .the sound deadener of this .invention may'be'made in shapes-other than -a cup shape. In Figs. 11 and -12,-a sound deadener `embodying this invention is shown asapplied to the tube li'for the purpose ofr damping the :vibrations thereof. The weight support of the sound- .deadener element may be composedof any suit- .able material having mechanical hysteresis-and may, for example, be composed of a metal such as lead or tin. In this embodiment of the invention, the weight `support is in the form of a strip which is indicated generally by the reference character 49 andwhich includes the base portion 50, the'weight-carrying portion 5| and the portion 52 which is subjected to iiexure. The `base v.portion 50 provides spaced lbase means with a f Ibridging member therebetween to which the weight 53' isattached for free vibratory motion toward and away/from'the tube 48; In this embodirnent of the invention, the weight is secured to the under side of-the weight-carrying portion of the weight sup-port. The base portion 5|) of the lweight' support is shown as attached to the tube l'lcy 'meansof bands 54, although any rother lsecuring means may be -used so-as to cause the base vportion of the weight support to vibrate integrally with any vibration of the surfaoe'of the tube 48. It is apparent that the operation ofthe embodiment of this invention thatis shown in Figs. ll and i2 is the-same as the operation of the embodiments of this invention which have been hereinabove described.

es stated hereinabove, it is-not essentialv that the flexible portion lof the base portien'be composed of material which per se has the property of mechanical hysteresis upon flexure dueto internal friction, for' the Vmechanical hysteresis vcan-be obtained 4as -a result: of: friction between surfaces. An embodiment of this invention wherein the mechanical hysteresis is obtained'by friction resulting from-relative movement of contacting surfaces isfshown in Figs. 13 and 14. The weigh-t support of the sound-deadening element com-prises the base portions 5 5 which maybe metal vspacing mem-bers. Between the base portions 515 -isthe resilient metal strip 'Swhich is fiexible and whichinand ofitself mayhave little or no mechanical hysteresis upon exure. `In conjunction with the metal strip-5 6 there are employed the metal-strips' A51 and 57 which are composed of resilient meta-1 and which have' a conformation prior to assembly such ythat the 4str-ips 5i and 51 will be maintained in v.pressure contact with the lstri-p 51e-during vibration of the strip 56 in normal `use of the sound-deadening element. 'IheestripsSQ/E and 5"'1 and the spacing members 55 are affixed tothe plate'58 by the bolts 59. A 'weight-60 is'aiiixed tothe center of the strip 56by the lbolt Si and, lfor purposes` of illustration, the weight is shown as having two parts, one part'bei-ng 4on each side of the strip 55. When'the'plate -58is excited-so as to vibrate 4normallytc the surface thereof, the inertiav of ythe rweight G'll' will cause' flexure of Vthe strip 56. vWhen the strip 55 is flexed,- the vsurfaces at the interface *betweenthe strip 56-and the strips `5l and 5-'1 lare rubbed-relatively to each other with resultant friction `which dissipates in the form ,of heat the mechanical energy for producing the flexure.

While embodiments Vofthis invention have 'been shown-for purposes ofl illustration wherein vthe weight support of the sound-deadening element comprises spaced base means with a bridging member therebetween, this isnot essential. For

`example, the -sonnd-deadening elements,k shown 'in anyof Figs. 1l, 12, 13 Iandlfl-may be modified understood that the sound deadener maybe one wherein the' member carrying the Weightismade fast tothe base portion bybein'g'v secured'th'ereto by an adhesive -or other securing means asv` in any of the embodiments shown in Figs. 6, 7, 13

and 14, or may be one wherein all or a part of the base portion is made in one piece with the flexible or bridging member as in the embodiments shown in Figs. 1-5, 1l and 12. Similarly, in the embodiment shown in Fig. 3, the portions 24 of the sheet 20 are to be regarded as "integral with the sheet 21, and the same is true with reference to the portions 3| of sheet 28 which are united with the sheet 32 in the embodiment shown in Figs. 4 and 5.

It is apparent that the sound deadener of this invention may be varied considerably as compared with the embodiments thereof that have been described hereinabove and shown in the accompanying drawings. Thus, the weight support can be varied in its form and dimensions depending upon the material used and the nature and size of the body to which the weight support is to be secured. In general, it may be stated, however, that the dimensions of the weight support should be consistent with aixing a suitable number of elements, which are flexed by the weight, to a surface of a vibrating body so that the vibrations may be effectually damped. When the sound-deadening elements consist of opposed base means with a bridging member having a flexible portion therebetween, the distance between the spaced means will generally not be greater than about 7 inches. On the other hand, the distance between the spaced base means, is generally at least about 0.5 inch. For use in damping the vibrations of the metal panels in the bodies of automobiles, the distance between the spaced base means will generally be of the order of 1.5 to 3.5 inches. The Weight support can be of any shape that is adapted to carry the weight for free vibratory motion when the base portion of the weight support is aflixed to a body for integral movement with a vibrating surface of the body.

The bituminized felt above referred to may have as a base not only organic fibers but also asbestos fibers. In addition impregnating materials other than bitumen may be employed such as flexible synthetic resins. Other materials having substantial mechanical hysteresis may be employed such as leather or such as fabrics which, by virtue of the weaving thereof, or by virtue of a binder impregnant have suiiicient stiffness to carry the weight and at the same time have flexibility. Flexible synthetic resin sheet material may also be used. The use of metals such as lead and tin has been previously mentioned. Such materials per se have substantial mechanical hysteresis upon flexure.

The weight that is aflixed to the weight support should have substantial mass so that the inertia of the weight will subject the weight support to substantial flexure when the base portion of the sound deadener is caused to vibrate in unison with a vibrating surface to which it is attached. The mass of the weight is not critical but the mass selected will, of course, depend upon a number of variables including the `dimensions and form of the weight support and the stiffness and strength of the material of which the flexible portion of the weight support is composed. In the case of sound-deadener elements which are cup-shaped or are otherwise provided with base means spaced 0.5 to '7 inches apart and in which the weight support is composed of bituminized felt, the individual weights will ordinarily weigh from about 0.1

`ounce to about 1.0 ounce.` When it is considered that the entire weight support of an individual weight support composed of such material weighs only about 0.5 to 1 ounce, it is apparent that the weight constitutes a mass weighing several times the weight of the weight-carrying portion of the weight support to which the weight is attached, and` that a localized mass is provided which, by its inertia, causes vigorous fiexure of the weight support when the weight support is axed to a vibrating surface. While the Weight should provide a localized mass weighing several times the weight support should be consistent with a'iilxing which it is attached, it should not be so heavy as to cause excessive sagging of the weight support which would permit the weight or the weight-carrying portion to contact the vibrating surface or any other member integral therewith during normal use of the sound deadener. In other words, the weight and weight-support are made so that the weight support carries the weight for free vibratory movement relative to the base portion of the weight support when the base portion is attached to a surface of a vibrating body, such vibratory movement being induced by the inertia of the weight when the base portion of the weight support is subjected to the vibration of a surface to which it is attached.

The weights may, of course, be comosed of any suitable material such as a finely-divided material (preferably of high density) bonded together by a binder. Alternatively, a metal, e. g. lead may be used. The weight can be affixed to the weight support in any suitable way as by means of an adhesive or by some mechanical securing means.

The sound deadener of this invention may be used wherever it is desired to effectively dampen the vibrations of a body. The application of the sound deadener of this invention to panels of automobile bodies, to panels of airplanes, to parts of railroad coaches, to housings for machinery, to walls and partitions, to piping, etc. is merely illustrative.

While this invention has been described in connection with certain specific embodiments thereof, it is to be understood that this has been done merely for purpose of exemplication and that the scope of this invention is to be governed by the language of the following claims.

I claim:

l. A sound deadener for damping the vibration of a vibrating body comprising a weight and a weight support, said weight support comprising a base portion adapted to be afilxed to a surface of said vibrating body for integral vibratory movement of said base portion with said surface, a weight carrying portion spaced substantially from said base portion, and between said base portion and said weight carrying portion flexible sheet material having substantial mechanical hysteresis upon flexure, said weight being an essentially unitary localized mass whose inertia is several times greater than that of said weightcarrying portion of said support and being aflixed to said weight carrying portion of said support and carried thereby for free vibratory motion relative to said surface when said base portion of said weight support is aixed to said surface, and said flexible sheet material of said weight support being disposed for flexure due to the inertia of said weight when'the base portion of said weight support is subjected to vibration of said surface.

2. A sound deadener for application to a body :annate presenting a vibratory surface 'for damping vibrations normal to said surfacelwhich comprises a said weight being affixed to and carried by said weightv carrying portion of said weight support, said weight support being adapted to maintain said weight carrying portion thereof and said weight carried thereby spaced from and overhanging said surface when said base portion of said weight support is affixed to said body so as to permit free vibratory movement of said weight toward and away from said surface upon flexure of said flexible portion of said weight support,

and the inertia of said weight being several times greater than the inertia of the weight carrying portion of said weight support and being adapted to subject said flexible portion of said weight support to substantial exure upon vibration of said base portion of said weight support at an audible frequency normal to said surface when said base portion of said Weight support is afiixed to said body.

3. A sound deadener for application to a body presenting a vibratory surface for damping vibrations of said surface normal to said surface, said sound deadener comprising a weight and a weight support, said weight support comprising flexible sheet material which has substantial mechanical hysteresis upon flexure and which provides a bridging member between and integral with oppositely disposed base means of a base portion of said weight support adapted to be aiiixed to said body for integral movement with said surface, the density of said weight being substantially greater than that of said flexible sheet material providing said bridging member, said weight being affixed to said bridging member at en intermediate position between said base means, said weight providing a localized mass the inertia of which is several times greater than that of the portion of said bridging member to which it is affixed leaving the balance of the span of said bridging member essentially free of any such mass, and said weight being maintained by said bridging member for free vibratory movement toward and away from said surface when said base portion of said weight support is affixed to said body.

4. A sound deadener according to claim 3 wherein the portion of said bridging member to which said weight is affixed is substantially parallel t0 said surface when said base portion of said weight support is affixed to said body.

5. A sound deadener according to claim 3 wherein said flexible sheet material comprises felted fiber impregnated with bituminous binder.

6. A sound deadener according to claim 3 wherein the oppositely disposed base means are spaced apart by a distance of the order of 0.5 to 7 inches.

7. A sound deadener for application to a body presenting a vibratory surface for damping vibrations of said surface normal to said surface, said sound deadener comprising flexible sheet ma- Cil terial 'whichlhas substantial mechanical hysterea sis upon Viiexure and which is'provided with a plurality of shallow essentially fiat bottom cup 'shaped "deformations, a weight being securedto the bottom of each of a plurality of said cup shaped deformations for free vibratory motion, :the inertia of said weight being adapted to cause vflex-ure 'of said sheet material when the rim portion of the cup shaped deformation carrying same is vibrated at an audible frequency. normal Ato the bottom portion thereof.

8. A sound deadener according to claim '7 wherein va second sheet of sheet-,material is integrally united with the rim portion of said cup shaped deformations and is adapted for face-toface seourement to a vibratory surface.

9. A sound deadener according to claim 7 wherein said flexible sheet material is composed of bituminized felt, wherein said cup shaped deformations are of the order of 1.5 to 3.5 inches across, and wherein said weights weigh from about .1 to 1.0 ounce.

10. A sound deadener element comprising a weight and a weight support, said weight support comprising bituminized felt in the form of spaced support means with a bridging member therebetween and secured thereto, said spaced support means being spaced from about 0.5 to about 7 inches apart and being adapted to be affixed to a vibratory surface, said weight weighing about .1 to about 1.0 ounce and being affixed to said bridging member adjacent the center thereof between said support means, and said bridging member carrying said weight for free vibratory motion toward and away from said surface when said base means of said weight support is aixed to said vibratory surface.

1l. A sound deadener for application to a body presenting a vibrating surface for damping vibrations normal to said surface comprising in integral sheet form a plurality of weights afxed respectively to a plurality of support means therefor provided by a succession of spaced base p01'- tions adapted to be afxed to said body for integral movement with said vibratory surface and by bridging members extending between said base portions, said weights being secured to said bridging members for free vibratory movement toward and away from said surface and being localized in approximately mid-position between said spaced base portions, and said bridging members comprising flexible sheet material having substantial mechanical hysteresis disposed between said weights and said base portions and adapted to be flexed by the inertia of said weights when said base portions are afxed to said surface and are caused to vibrate at an audible frequency.

12. A sound deadener for application to a body presenting a vibratory surface for damping Vibrations of said body, said sound deadener comprising a Weight and a weight support, said Weight support comprising a base portion including oppositely disposed base means and a bridging member integral with said base means, said oppositely disposed base means being spaced apart by a distance of the order of 0.5 to 7 inches, said base means being adapted to be aixed to said body for integral movement with a surface thereof, said weight being affixed to said bridging member and localized at approximately mid-position between said base means, said base means when aiiixed to said body being adapted to carry said weight for free vibratory movement relative to said surface, said bridging member comprising a 15 weight carrying `portion which carries said weight, the inertia of said weight being several times greater than the inertia of said weight carrying portion of said bridging member and the density of said weight being substantially greater than that of said bridging member, and said bridging member comprising fiexible sheet material which is between said weight carrying portion and said base means, which has substantial mechanical hysteresis upon fiexure and which is adapted to 10 be fiexed by the inertia of said Weight when said base means is afixed to said surface of said body and isl caused to vibrate therewith at an audible frequency.

PAUL H. GEIGER.

l 6 REFERENCES CITED The following references are of record i the iile of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,541,159 February 13, 1951 PAUL H. GEIGER It is hereby certified that error appears in the printed speoica-tion of the above numbered patent requiring correction as follows:

Column 2, line 24, for eieetive read efectiva; column 3, line 30, for the Word deadened read deadener; Column l1, line 29, before means insert base; column l2, line 12, before support insert of tite portion of the weight; same line, after support strike out should be consistent with afixing; line 13, before which insert to; line 29, for comosed read composed;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Olce.

Signed and sealed this 8th day of May, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant 'ommz'ssioner of Patents.

Certificate of Correction Patent No. 2,541,159 February 13, 1951 PAUL H. GEIGER- It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 24, for eective7 read efectiva; column 3, line 30, for the Word deadened read deadener; column 11, line 29, before means insert base; column 12, line 12, before support insert of the portion of the weight; same line, after support strike out should be consistent with afxing line 13, before which insert to; line 29, for comosed read composed;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 8th day of May, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents.

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