GB2305947A - Sound insulation of floors - Google Patents

Abstract

A floor component includes a foam material 4 made up of a mixture of open cell and closed cell foam particles. The foam material is attached to a rigid strip 5 and a flexible web 6 whereby the component may be attached to a flooring joist by means of the web so that floor boards 10 may be laid on the component. The foam has acoustic and vibration insulating properties and can be used in the refurbishment of existing floors.

Description

SOUND INSULATING FLOOR The present invention relates to the field of floors for buildings, and particularly to floor components and floor constructions having vibration insulating properties.

It is known to refurbish an existing floor having a plurality of floor joists with a view to improving the acoustic insulation properties of the floor, by overlaying a new floor deck on top of the joists, there being a plurality of foam strips between the new floor deck and the existing joists.

A known foam strip comprises a first layer of open celled foam which is arranged to rest on top of a joist, a layer of closed cell foam which lays on top of the layer of open celled foam, a thin plywood strip, of thickness around Smm, and a flexible web which extends laterally either side of the strip and is arranged to secure the foam strip to the joist.

The closed cell foam is directed at attenuating impact sounds for example as caused by shock loads on the floor. The open cell foam layer is directed at attenuating airborne sounds. Acoustic energy in the cavities is dissipated in the interstices of the open cell foam layer.

Typically the closed cell foam layer is of thickness lOmm, and the open cell foam layer is of thickness 12mm in unloaded state. When installed, under normal flooring loadings, the open cell foam compresses vertically, to a residual layer thickness of 8 to 9mm, whilst the closed cell foam layer remains substantially of the same thickness. Thus, the floor loading may affect the airborne sound attenuating properties of open cell of the foam layer.

According to one aspect of the present invention there is provided a floor component comprising: a plurality of floor components each comprising an elongate foam strip; and a plurality of floor boards laid on said foam strips, characterised in that said foam comprises a plurality of open cell foam particles and a plurality of closed cell foam particles.

Preferably said open cell foam particles and said closed cell foam particles are mixed together in substantially random orientation.

Said mixture comprises a composition of 10% to 50% by volume of said open cell foam particles and 10% to 50% by volume of said closed cell foam particles.

Preferably said open cell foam particles and said closed cell foam particles are bonded together.

Preferably said foam has a density in the range 50 to 120 kgm-3, and suitably in the range 75-3 to 95 kgm-3.

Preferably said foam layer is of thickness in an un-compressed state in the range lOmm to 30mm, and suitably of around 20mm.

Preferably said flooring component comprises an elongate rigid strip bonded to said foam layer.

Preferably said flooring component comprises a sheet material bonded between a said rigid strip and said foam layer, said sheet material extending laterally to both sides of said foam strip.

Preferably said rigid strip is of a thickness less than the thickness of a said floor board.

Preferably a said rigid strip comprises a timber or plywood strip.

According to the second aspect of the present invention there is provided a floor construction comprising: a plurality of floor components each comprising an elongate foam strip; and a plurality of floor boards laid on said flooring components, characterised in that said foam comprises a plurality of open cell foam particles and a plurality of closed cell foam particles.

Preferably, said floor components are each glued or nailed or screwed to a said joist.

Preferably, said floor boards are glued to said floor components.

The invention includes a floor construction comprising: a plurality of flooring joists; a plurality of floor boards; a plurality of flooring components each comprising a foam strip positioned between a said joist and one or more said floor boards, each said foam strip attached to the respective joist by a flexible web.

Preferably, said web extends either side of said joist.

Preferably, said flexible web extends laterally outwardly from a base of said foam, for attachment to a respective said joist.

Preferably, said web extends between said foam strip and said respective joist.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 shows a first flooring component according to a first specific embodiment of the present invention; Figure 2 shows a floor construction comprising the component of figure 1; Figure 3 shows a transfer characteristic of acceleration transmissibility against frequency for a sample of reconstituted foam; Figure 4 shows a characteristic of input-output phase difference against frequency for the reconstituted foam sample; and Figure 5 shows a theoretical characteristic of transmissibility against frequency ratio.

Referring to Figure 1 of the accompanying drawings, there is shown a floor component 10 used in the floor construction of Figure 2.

The floor component 7 comprises a foam layer 4 of reconstituted foam, a rigid strip 5 of thickness less than the thickness of a floor board, and typically around 6mm and bonded between the foam layer and the rigid strip 5, the plastics material web 6 extending either side of the elongate foam strip.

The rigid strip 5 is preferably plywood or timber.

Referring to Figure 2 of the accompanying drawings, a floor construction comprises a flooring deck 1 made up of a plurality of floor boards 10, e.g. a conventional elongate wooden floor boards or chipboard tongue and groove floor boards, the floor boards supported on a plurality of joists 2, the joists supporting a suspended ceiling 3, and between the floor boards and the joists a plurality of elongate flooring components 4, each flooring component comprising a layer of reconstituted foam made up of a mixture of open cell foam particles and closed cell foam particles, the layer of foam bonded to a rigid plywood strip 5 of thickness 3 to 7mm, and suitably around 6mm, and a flexible sheet web 6, suitably of a plastics material, the web bonded between the plywood strip 5 and the foam layer 4.

The foam layer 4 placed between the floor boards 1 and the joists 2, and is attachable to either side of the joist by, for example gluing or nailing the web 6 to either side of the joist to secure the flooring component in position, and to prevent the second flooring components moving during fitting of the deck 1. The floor boards 1 may be glued directly to the foam layer 4.

Suitably, the foam layer has a thickness of around 18 to 20mm, and a width of 30 to 60mm and suitably 45mm.

In use, the flooring deck comprising the floor boards 1 rests upon the reconstituted foam layers 4 and on the joists 2. Vibrations and shocks on the flooring deck 1 and acoustic noise produced by those vibrations and shocks are dampened by the foam layers 4.

Each foam layer 4 comprises a substantially randomly oriented mixture of open cell foam particles and closed cell foam particles, bonded together.

The closed cell foam particles may form support for the open cell foam particles. The open cell foam particles may absorb airborne acoustic vibration, and thus provide an acoustically insulating medium between the flooring deck 1 and the joists 2. The closed cell foam particles may absorb shock loadings on the floor, e.g. dropping heavy objects on the flooring deck, and reduce the transmission of shock loading vibrations to the joist 2.

The foam particles may vary in size, but are suitably chopped up particles of reclaimed foam, which may have dimensions in the range 0.5mm to 20mm. The particles of open cell foam and closed cell foam are bonded together to form a unitary foam layer, under conditions of elevated temperature and pressure above room temperature and pressure. A conventional bonding agent may be mixed in with the particles prior to subjecting to the elevated temperature and pressure.

The acoustic absorption and acoustic insulation properties of the foam can be varied by varying the proportion of closed cell foam particles to open cell foam particles. The density of the foam may be selected by varying the proportions of open cell to closed cell particles.

Suitably the density of the reconstituted foam is of the order of 85kgm 3, and may be in the range 5e120kgm.

Referring to figure 3 of the accompanying drawings, on a small scale laboratory test of a 20mm thick reconstituted foam layer, as compared with an 18mm thick reconstituted foam layer, a transfer function of acceleration transmissibility versus frequency was measured. The transfer functions for 20mm foam and 18mm foam are shown in figure 3 herewith. A low transfer function, i.e. low value of acceleration transmissibility is desirable for isolation of vibration.

The transfer function of figure 3 demonstrates an average acceleration transmissibility for 20mm thick foam layer to be lower than that for an 18mm thick foam layer, over a range 300Hz to 2kHz.

Referring to figure 4 of the accompanying drawings, the same foam layers were then tested for input/output phase difference. The phase difference between input/output signals for 18mm and 20mm foam thickness foam samples was relatively low, in the range 20 to 50Hz. For applied frequencies in the range 60 to 100Hz the phase differences became significantly higher. The thicker the foam layer, the lower the frequency at which a high input-output phase difference was achieved.

A natural frequency for the layers is arbitrarily taken to be the frequency at which a phase difference between an input and output vibration is equal to 90 .

For a 20mm thick reconstituted foam layer, the natural frequency is around 6 to 8Hz lower than for an 18mm thick foam layer.

A relatively low natural frequency is beneficial for the reasons explained in Appendix 1 herewith.

For an elongate foam layer have width 45mm and height 20mm in uncompressed form, it was found experimentally that for an evenly distributed weight of 120kgm-2, compression of the foam layer by 0.3 to 0.5mm was experienced. For a weight of 240kgm the foam layer compressed by 2mm plus a minus 0.3mm for a weight of 360kgm the foam layer was found compressed by 4mm plus a minus 0.5mm.

For a weight of 480kgm-2 the foam has found to compress by about Smm and for a weight of 600kgm the foam was found to compress by about 6mm, giving a compressed foam layer thickness of about 14mm.

For higher pressures, the foam layer compressed significantly. For a weight of 8750kgm-2 the foam layer of 20mm thickness and compressed state was found to compress to a thickness of around 2mm.

Under compression, primarily the closed cell foam particles bear the weight of the floor deck, and the open cell foam particles occupy the spaces between particles of closed cell foam. Because the open cell foam particles and closed cell particles are randomly interspersed and orientated, provided sufficient proportion of closed cell particles, and each of sufficient size are included, the open cell particles can be prevented foam compressing to a greater extent and the interstices in the open cell foam can remain open to a greater extent under vertical loading of the floor, as compared with a prior art laminate layer of open cell foam and closed cell foam.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Appendix 1 Transmissibility for a single degree of freedom system is given by equation 1.

T = 1 1-(ff) fn where ff = forcing frequency.

= natural frequency.

A graph of transmissibility against the ratio (ff:fn) transmissibility is illustrated in figure 8 herewith.

It can be seen from equation 1 and figure 8 that when the forcing frequency (off) is equal to the natural frequency (fn) transmissibility goes to infinity although in real situations this does not occur because of damping present. When transmissibility falls below 1 then there is an element of isolation in the floor component. A perfect isolator would show transmissibility equal to zero. Figure 8 shows that as the ratio (ff:fD increases above a value of 1 then transmissibility falls and thus isolation increases. For good vibration isolation therefore one usually looks for a flooring construction or flooring component with a natural frequency as low as possible.

Claims (19)

1. A floor component comprising: an elongate strip of foam material; characterised in that said foam material comprises a plurality of open cell foam particles and a plurality of closed cell foam particles.

2. A flooring component according to claim 1 in which said open cell foam particles and said closed cell foam particles are mixed together in substantially random orientation.

3. A floor component according to claim 1 or 2, in which said mixture comprises a composition of 10% to 50% by volume of said open cell foam particles and 10% to 50% by volume of said closed cell foam particles.

4. A floor component according to any one of the preceding claims, in which said open cell foam particles and said closed cell foam particles are bonded together.

5. A floor component according to any one of the preceding claims, in which said foam has a density in the range 50 to 120 kgm3, and suitably in the range 75 to 95 kgm~3.

6. A floor component according to any one of the preceding claims, in which said foam layer is of thickness in an un-compressed state in the range iOmm to 30mm, and suitably of around 20mm.

7. A floor component according to any one of the preceding claims, comprising an elongate rigid strip bonded to said foam layer.

8. A floor component according to claim 7, comprising a sheet material web bonded between a said rigid strip and said foam layer, said sheet material web extending laterally to both sides of said foam strip.

9. A floor component according to any one of claims 7 to 8, wherein said rigid strip is of a thickness less than a thickness of a said floor board.

10. A floor component according to any one of claims 7 to 9 in which said rigid strip comprises a timber or plywood strip.

11. A floor construction comprising: a plurality of floor components each comprising an elongate foam strip; and a plurality of floor boards laid on said flooring components, characterised in that said foam comprises a plurality of open cell foam particles and a plurality of closed cell foam particles.

12. A floor component according to claim 11 in which said floor components are each glued or nailed or screwed to a said joist.

13. A floor construction are to claim 12 or 13 wherein said floor boards are glued to said floor components.

14. A floor construction according to any one of the preceding claims comprising: a plurality of flooring joists; a plurality of floor boards; a plurality of flooring components each comprising a foam strip positioned between a said joist and one or more said floor boards, each said foam strip attached to the respective joist by a flexible web.

15. A floor construction according to claim 14, in which said web extends either side of said joist.

16. A floor construction according to claim 14 or 15 wherein said flexible web extends laterally outwardly from a base of said foam, for attachment to a respective said joist.

17. A floor construction all to claim 16 in which said web extends between said foam strip and said respective joist.

18. A floor construction substantially as herein described with reference to the accompanying drawings.

19. A flooring component substantially as herein described with reference to the accompanying drawings.