CA2133821C - Building element and method of manufacturing such element - Google Patents

Abstract

An integral structural element having improved sound and/or vibration dampening capacity and being composed of two support plates (1, 2) having therebetween spaced layers (3) of a viscoelastic material formed by a liquid synthetic elastomeric ma-terial having good adhesive properties and having a temperature resistance high enough to stand the temperature rise occuring due to the internal friction of the material while subjected to vibrations. The viscoelastic material between said two support plates (1, 2) is formed as strings of elastomeric material which are spaced from each other by a distance of 50-500 mm leaving an air space between the two support plates (1, 2) in the areas between adjacent strings of viscoelastic material (3). Each string (3) of dampening material has a material thickness of 1-5 mm, and a width of 10-50 mm. The structural element may, at the surface thereof to be mounted on a structural base, carry a mat of a natural or synthetic felt fibre material, having a product weight of 300-1200 g/m2 and having a thickness of 3-10 mm.

Description

BUILDING ELEMENT AND METHOD OF MANUFACTURING SUCH ELEMENT
The present invention generally relates to a building element, and the invention is more particularly co,~ ,ed with a structural or a non-structural building element having improved sound damping and vibration dampino properties and being of the known type formed as an integral building unit and composed by two superimposed plate like structural parts having therebetween spaced thin strings or strips of~v:~o~ i. material.
By damping p,u~c.li~s is meant, in the following, both sound damping p~uy~llieS and vibration damping prup~,lids, and the invention is intended to damp both low frequency, medium frequency and high frequency sound and vibration. In house building by means of modern building material like concrete, gypsum boards, light weight concrete blocks, different types of plastic materials, but also by means of timber, building board, chip board and other types of wooden material there are often problems in that sounds, vibrations etc. transmit from one ap~""~e"l to another, both vertically and l~uli~ulll_'!y, not only by vibrations etc. in the material itself but also by air borne sounds and vibrations. Therefore the invention is conc~rl,~d with a structural or non-structural building element for use as a sound and vibration damping building element in house buiiding, like in floors, walls, ceilings etc.
Sound and vihration ll c,,, "~o, Idlion also causes the same type of problems in many types of apparatus like in telephone boxes, in loud speakers, in motor cars, in air planes, in ships, in motor hoods, in ~:rlig~lcllul~ etc.
Thus, by building material is meant any type of material which can be used as floor structures, wall structures, ceiling structures etc. in ordinary house building, and also for the manufacture of any other types of objects where there is a wish to take advantage of the sound damping or the vibration damping ~,u~ ., of the building element according to the invention or of both the sound damping and the vibration damping properties thereof.
A ~a~,,ut:" lg structural element of the above ",t:"lioned type is known for instance from the E~ritish patent No 1,514,516 which element C~lllpliadS two su~udlilllposed support elements like two metal plates, concrete slabs, plaster sheets or wooden fibre sheets having between said elements discontinuously extending strips or grids of a v-~ro~ material plt:a~lllillg air spaces between said strips or ~rids.
_ _ _ _ _ . . .

W093/21402 13-~821 2 PCr/SE92/00229~
In the manufacture of said known type of structural element there is used a sheet of viscoelaaLic material which is on both sides covered with glue or an adhesive material, for instance a double sticking tape. For obtaining the illL~lllledidLt~ strips of v;S~u~la~LiC materiâl of the product said composite viscoelastic sheet is cut into strips which are thereafter placed spaced from each other on a first support element, whereafter the second support element is laid down over said first support element having mounted thereon said spaced strips of viscoelastic material.
The cutting of the v:-coel,-~lic composite sheet material is complicated, both in that the cutting knife or roller knife easily sticl~s to the glue material: generally it is necessarV to freeze the viccopl~ctic material in order to make it pla~.liC~A.'y possible to cut it into strips; the known viscoelastic materials often are too hard to give a particularlv good damping effect; the method is labour consuming and time consumin6; there is often a risk that the co"")o~ structural element held together by the three-layer viscoPl~ctic material, including both the damping strip itself and also the two glue or tape layers, is dela,,,;,,dL~dl which is in particular a problem in using the structural element in walls and ceilings.
The object of the invention therefore has been to suggest a structural composite element of the above ~ iulled type - having improved sound damping and vibration damping properties as compared with previously known damping elements of the art;
- which element can be manufactured quickly and without involving much labour;
- which is more safely combined to a unitary product than the known elements;
- which can be safely applied even to porous support elements to form a safe joint between such elements;
- which is not apt to dela~ aLion;
- which has basically only one laver of material for providing both the connection between the two supporting element parts and for providing the particularlv good damping effect;
- which can be manufactured in continuous lengths, and can be cut into desired plate sizes;
- which can be formed with cooperating groove and tenon means for interactively covering large surface areas, etc.
The inventioned is based on the observation 93/21402 ~ ~ 3 3 8 21 Pcr/sE92/00229 - that surprisingly good damping effects can be obtained by using certain synthetic elaa~or"eric compounds - that the best damping effects are obtained if the v;:,. oeld~lic material is provided in the form of strings dots etc. which are spaced from each other, and if - the v;;~ oeldaliu material parts hâve a pr~dt~ d thickness and predetermined width, - that certain viscoelastic materials have a long lasting damping capability and are very resistant to aging - that such elastomeric (viscoel~ctic) materials can successfully be used in an originally liquid form in the continuous process of manufacture of the structural building element - whereby a liquid v;;,~o~ldalic glue or synthetic rubber material is applied inliquid form to one of the support elements in the form of spaced strings having a p,~d~ ,l"i"ed width and thickness and onto which is thereafter the second support element press applied.
The liquid Y:- o~ lic glue can be applied by portioning nozzles by rollers or by any other known method whereby the first support element is preferably moved past the glue application means.
As examples of useful v;~coeldalic liquid material may be mentioned styrene rubber nitrilic rubber and still more preferably silicon rubber ~;lllolupl~llic rubber and acrylic rubber all having good adhesive plUpdllit:s and all u,~rdbly having a temperature It:a;:~dllCe or maximum service temperature of 1 00C or more to be able to stand the temperature rise occurln~q due to the internal friction of the V;a~.OeldbLiC material while subjected to sound and vibration.
In a preferred embodiment of the inventive method a first layer of the viccQel~ctic material, that is a glue or rubber material is applied in liquid form to a first support element in the form of strings or dots etc. of a p~:dc,l~"~;.,ed width and thickness to provlde the intended v:~.oql 1!.
layer; the glue Is allowed to set or polymerize throughout which will generally take about ~8 hours at normal room temperatures; in a second step a thin layer of the same glue material Is applied on top of the polymerlzed ~Ida~ullldlic layer as a co,l,~e~Lion means for the superimposed second support element; Immediately thereafter said second support element Is press applied on top of the thin col~,)el Lioll layer; after the second glue layer has set or polymeriz~d the structural element can be cut 2 1 ~ ~ 8 ~ 1 PCI /SE92/0022 trimmed, be formed with groove and tenon means etc.
Alternatively the liquid synthetic damping material is mould into strips having the desired thickness and width and are thereafter covered with a thin layer of an adequate glue on one side, preferaby the same type of material as that of the polymeric strip; before the glue has set the strip is applied to a first- support element; is supplied with a thin layer of glue on the upper surface thereof; and the second support element is press applied to the first support element and the VisGQ~ iC material.
It has proved that a thickness of between 1 and 5 mm, or preferably 1.5 to 2.5 mm of the damping viscoelastic layer gives a surprisingly good effect. A less good damping effect is obtained with damping strips, dots etc. having less thickness than 1.0-1.5 mm. It has been found that a fully covering damping layer gives a less good damping effect than several spaced strings of damping material. Depending on the type of load from which vibrations are to be da"")ened there may be used damping strings of said thickness havin~ a width of about ten times the thickness, i.e. a width of about 10-50 mm.
The ddlll,J~ 19 strings preferably are spaced from each other by a distance which is about 5-10 times the width of the strin~, i.e. that the damping strings are spaced 50-500 mm. For a light weight load a spacing within the higher range of spacing is preferred, for a heavy load a spacing within the lower range of spacing is preferred.
In a still more preferred e",Lodi",~llL of the invention the structural element, con~ li"g of the two support elements of board, timber, metal, concrete, plastic material etc. and having the V;,~Qel~.`liC strings therebetween, the element has a felt material 31ued to the bottom surface, that is the surface facing the mounting surface like the floor, the wall, the ceiling etc. Said felt material may be a natural or synthetic felt fibre material having a thickness which is 3-10 mm or preferably 5-10 mm and also preferably having a product weight of 300-1200 g/m2. Very good damping effects have been ack"o~ dged for ordinary house floor structural elements by using, at the bottom surface of the lower support element a 100% polyester felt of needle/thermally bonded fibres, having a product weight of 300 - 1200 g/m2 and having a thickness of 3-10 mm, or preferably 5-9 mm. Other useful types of synthetic felt mats are made of viscose, polypropylene, polyurethane and polyamid (Nylonl. Bonded glass fibre material may be incorporated as a reinforcing element in the felt mat.

~O 93/21402 2 i ~ 3 8 ~1 PCI-/SE92/00229 Also natural fibre mats of wool or cotton are useful but it should in some appiications be foreseen that such mats are not subjected to moisture.
The invention is now to be described in connection to the accoi",ual~ lg drawing in which figure 1 is a rld~ dry vertical cross section view of a first embodiment of a structural element according to the invention. Figure 2 shows an alternative structural element according the invention. Figure 3 shows, partially in a broken up view two structural elements ~,on~le~,Lt:d to each other. Figure 4 is a perspective view illustrating a method of applving the visco~l~ctic material to a first support plate in the structural element of the invention. Figures 5-9 are five successive cross sectional views illustrating a preferred method of the manufacture of a structural element of the type shown in figure 2. Figure 10 is a didL~Ialllllla~ dl cross section through an available floor/ceiling of a building in which the invention has been tested, referred to as Test 1, and figures 11, 12 and 13 are alternative embodiments of a damping element according to the invention moùnted in the same building and referred to as Test 2, 3 and 4 respectively. Figure 14 is a diagram showing the damping of airborne sound passing the floor of figures 11-13, and figure 15, finally, is a similar diagram showing the impact lldllalll;i~aiun through the same floor.
The structural element of figure 1 comprises two support plates 1 and 2 which are spaced from each other by means of spaced strings 3 of a via~.ueldalic material of the above mentioned type which may be a synthetic rubber material having a thickness of 1-5 mm, a width of 10-50 mm, and which strings may be spaced from each other by 50-500 mm. The support plates 1 and 2 can be of any known material like timber, fibre board, building board, chip board, plywood, metal plate, concrete, plastic plate or any col"L,;,~dLion of said materials. The thickness of the support plates 1 and 2 can be varied âS desired and for the actual use. For an ordinary house floor structure the plates 1 and 2 may each have a width of 3-22 mm, or for many purposes preferably 8-15 mm. The lower plate 1, which is adapted to face the floor of the house can be made thinner than the upper plate 2, for instance so that the lower plate 1 has a thickness of 3-8 mm and the upper plate has a thickness of 8-22 mm - or vice versa.
Figure 2 shows an alternative ~Illbodi~ lL of the structural element, which differs from that of figure 1 in that it is has a bottom felt mat 4 as defined above, for instance a polyester mat having a thickness of about 3-10 mm, which is glue co""~-,L~d to the bottom surface of the bottom ... . . . .. _ _ . _ . .. .

WO 93/ZI402 6 pcr/sE92/oo22 support plate 1.
Figure 3 shows two structural elements 5 and adapted to be laid r~n a concrete base, on a light weight concrete base or on a timber base. The elements 5 and 6 are formed with groove and tenon means 7 and 8 at two edges or along all edges thereof for making it possible to join several elements to form for instance an integral floor wall or ceiling of a housing~
In the method of the invention there is used a liquid viscoelastic material of the above mentioned type. As illustrated in figure 4 said fluid glue/da""J~";"g material is preferably applied by means of several parallel nozzles 9 each leaving a string 10 of dampening material on a bottom structural plate 11 moYing at a controlled speed past the nozzles 9. Each nozzle 9 leaves a string of material which is of a p,~dt:~,ll,;.,ed width and thickness. The nozzles 9 are spaced with the same distance as the desired spacing of the strings 10. The spacing of the nozzles 9 like the speed of the bottom plate 11 and the thickness and width of the dampening strings 10 can be varied as desired coi1s;delill9 the field of use for the ddllllJ~II l8structural element. It is to be understood that the ~ n of the da"",dl, 19 strings 10 can be made by hand or by means of rollers etc.
Figure 5-9 did~ldlllllldLi~ . ly illustrate a method of manufacturing a structural element according to the invention:
- Figure 5 illustrates how the bottom plate 11 is moved in the direction of the arrow past the nozzle 9 which deposits a strino 10 of dampening material on top of the plate 11;
- Figure 6 illustrates that the da",,,)e" l9 material 10 is allowed to completely set or polymerize which will take 4-6 hours at normal room temperature; the material may be kept in this condition for several days or weeks until the process is to be proceeded;
- Figure 7 illustrates that a thin layer 12 of a glue, preferably of the same material as in the dampening string 10 is laid out or sprayed onto said string 10 from a nozzle 13;
- Figure 8 shows that i"""ed;dl~ly thereafter the second support element 14, the upper element is laid down on the strings 10 12 of dampening material and is pressed thereon by a p,~d~lllli"ed pressure 15 thereby completing the process for the manufacture of the structural element of figure 1;
- In case of making the structural element of figure 2 a felt 16 is sprayed with glue 17 and the element co " t~d in figure 8 is laid down on O 93/21402 7 213 3 ~ 2 i PCT/SE92/00229 said felt 16 and is pressed thereto by a pressure 18, and the glue 17 is allowed to set or polymerize.
Alternatively to the method illustrated in figures 5-9 it is also possible to mould the strings 10 separately bv using the nozzles 9, whereby the strings can be moulded in or on an adhesive repellent material. After said moulded strings have polymerized completely they can be stored or can be used directly in the process, whereby a thin layer of glue is applied to one surface of the strings, or to the upper surface of the bottom plate 11, the strings are press connected to the plate 11, glue is aplied to the upper surface of the strings 10 and the process proceeds like in figures 7-9.
Figure 10 shows the sound transmission through an ordinary timber floor of an dp~ L house. As shown in the diagram the structural element of the invention is best suited for dalll~Jel1il1g of high frequency sound or vibrations but is also to some extent useful for low frequency sound or vibrations. The un-dampened sound ~Id~ iOn in the actual building is shown with the full line, the sound dampened by the structure of figure 1 is shown with the dotted line 1- - -), and the sound dampened by the structure of figure 2 is shown with the broken line (~ . It is obvious that there is obtained a substantial reduction of sound L~d,1s,~,is~ivn by usingthe structural elements of the invention. A similar good effect is obtained for dampening of vibration and both sound and vibration in combination, whether the structural element is used in house building like in floors, walls or ceilings, or in machine boxes, in loud speakers, in motor cars, in boats, in airplanes etc.
It is to be understood that the structural element of the invention may be made both stiff and flexible. A flexible element, in which the plates are of metal plate or of plastics, and the complete element can be mounted on convex or concave surfaces, is well suited for use on curved surfaces lilce in motor cars, air planes, in boats and ships, in railway wagons, refrigerators, freezing boxes, many types of machine structures etc. The element is also well suited as a support base for machines, machine tools etc. thereby reducing the vibrations which otherwise necessarily are L~dns",iLLt:d through the floor, in particular floors of concrete, metal etc.
Tests have been made to determine the airborne sound insulation and the impact sound tldl1slllission of the products of the invention as illustrated in figures 10-13, and the results thereof are shown in the diagrams of figures 14 and 15. The tests were made in a test house WO 93/Z1402 213 3 8 ~ I B pr~T/SEs2tO022~
ro"".,i:,i"g a two storey detached house of brick/block construction. All tests 1 2 3 and 4 were made in the same pair of rooms with the floor of the upper room modified to produce the various test configurations. The calculated area of the separating floor was 14 m2. As shown in figure 10 the floor system comprised 29 x 44 mm timber joists set att 600 mm centres. The floor covering was 18 mm floring grade chipboard and the ceilins in the bottom room was 19 mm Gyproc planl< and 12 5 mm Gyproc wallboard fixed to the underside of the joists.
First the airborne sound insulation and the impact sound transmission were tested in Test 1 and the results thereof are plotted under point 1 of figures 14 and 15 in which diagrams the horizontal axis shows the freuency in Hz and the vertical axis shows the sound level difference in decibel (dB~ whereby the figure 14 illustrates the sound damping and figure 14 shows the impact sound L~d~ls"~ission through the floor/ceiling. In Test 2 the floor was covered with a floor element of the type described in connection to figure 2 and consisting from top to bottom of 6 mm fibreboard bonded to 18 mm chipboard by beads of v;;" oel~:,Lic dampening material as described above spaced by 100 mm.
It is obvious that the floor of Test 2 shown in figure 11 had a surprisingly good airborne sound damping effect and a similarly surprisingly good reduction of impact sound L,di,s,11ission as compared with the original floor shown in figure 10.
In Test 3 the chipboard layer of figure 11 was substituted by 18 mm cement particle board as illustrated in figure 12. In this case a sound slab of 100 mineral wool was laid between the joists. It is obvious that the sound damping and impact reduction was much better than for the original floor, and even better than that of Test 2.
To investigate the influence of the thickness of the support plates of the sound and vibration damping element Test 4 was carried out whereby the floor element consisted of 6 mm fibreboard bonded to 3 2 mm fibreboard by strings of the claimed visGoela~tic material. In this case the polyester felt had a thickness of only 6 mm.
As shown the sound and vibration damping effect was very similar to those of Test 2, and it therefore could be concluded that there is no need for having such thick floor element as in figure 11 - except possibly for strength technical reasons - and that it is often quite sufficient to have only 6 + 3 2 mm thick support elements.

~0 93/21402 PCI/SE92/00229 The diagrams of figures 14 and 15 very clearly show the good effect of the element according to the invention.
Re~ nce numerals support plate 2 support plate -3 string of v;.,~,or l~aLiC material 4 felt 5 structural element 6 structural element 7 groove and tenon means 8 groove and tenon means 9 nozzle 10 string of v -..oP~ material 11 bottom plate 12 string of glue 13 glue nozzle 14 upper plate 15 pressure ,,' Lion 1 6 felt 1 7 glue 18 pressure apl 'i :

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An integral structural element having an outer surface for bonding to a support base, said element having improved sound and vibration dampening capacity comprising an upper support plate and a bottom support plate having therebetween spaced layers of a viscoelastic material, formed as strings or dots of elastomeric material which are spaced from each other leaving an air space between said support plates in the areas between adjacent strings or dots of elastomeric material and a felt mat of a natural or synthetic felt fibre material on said outer surface to be bonded to a support base.

2. A structural element according to Claim 1, wherein the felt mat has a product weight of 300-1200 g/m and a thickness of 3-10 mm.

3. A structural element according to Claim 1, wherein the felt mat is selected from the group consisting of a polyester felt mat and a mat of viscose, polypropylene, polyurethane or polyamid, eventually bonded by a glass fibre material as a reinforcing element thereof.

4. A structural element according to Claim 1, wherein the bottom support plate is of less thickness than the upper support plate, whereby the bottom support plate has a thickness of 3-8 mm and the upper support plate has a thickness of 8-22 mm.

5. A structural element according to claim 1 wherein the viscoelastic material is a synthetic elastomeric material applied in liquid form and chosen among the materials including styrene rubber, nitrilic rubber, silicon rubber, chloroprenic rubber and acrylic rubber, all having good adhesive properties, and all having a temperature resistance or maximum service temperature of 100°C or more.

6. A structural element according to Claim 5, wherein each spaced layer of viscoelastic material has a material thickness of between 1 and 5 mm, and a width of 10-50 mm, and the layers are spaced from each other by a distance of 50-500 mm.

7. A structural element according to Claim 6, wherein the layers are spaced 50-200 mm.

8. A method of manufacturing a structural element having improved sound and/or vibration dampening capacity and being composed of a first support plate and a second support plate having therebetween spaced layers of a viscoelastic material comprising applying several spaced strings of a viscoelastic synthetic damping material in liquid form, having a good adhesive activity in a thickness of 1-5 mm, a width of 50-500 mm and spaced from each other by a distance of 50-500 mm on the upper surface of a first support plate, allowing said liquid viscoelastic material to polymerize, applying a second thin layer of a viscoelastic synthetic glue in liquid form on top of the strings of polymerized viscoelastic material, pressing a second support plate onto the second layer of viscoelastic material, allowing the second glue layer to polymerize thereby forming an integral three-part structural element, and finally applying a mat of natural or synthetic felt material of a predetermined product weight, and a predetermined thickness, over the surface of the structural element so as to face the surface onto which the element is to be fastened;
trimming and cutting the structural element.

9. Method according to Claim 9, wherein the strings of elastomeric material are applied by moving the first support plate at a predetermined speed past several nozzles laying out the strings of the polymeric material.

10. Method according to Claim 9, wherein the strings of polymeric material are moulded separately allowed to polymerize completely, and the surface of each string is covered with a thin layer of glue.