GB2096682A

GB2096682A - Double glazing

Info

Publication number: GB2096682A
Application number: GB8111637A
Authority: GB
Original assignee: BFG Glassgroup GIE
Current assignee: BFG Glassgroup GIE
Priority date: 1980-04-14
Filing date: 1981-04-13
Publication date: 1982-10-20
Also published as: NL177334C; DE3014246C2; CH646407A5; DE3014246A1; IT1137355B; IT8121141A0; BE888358A; AT374885B; ATA164881A; NL177334B; FR2480347B1; NL8101798A; GB2096682B; FR2480347A1

Abstract

An insulating double glazing unit has two panes (1), (2) and a spacer (3) with gas filling the interspace (4); the pane (2) is attached to the spacer, (3) on at least one edge (5) by means of a resilient bridging member (6), which comprises, a strip-like membrane having a small stiffness in bending compared with the stiffness in bending of the same width of window glass. Consequently, the membrane strip can respond to edgewise transverse vibrations of the attached pane edge by corresponding vibratory deformations, thus improving the sound-proofing properties. <IMAGE>

Description

SPECIFICATION Insulating window units This invention relupes to insulating window units of the type having an inner pane, an outer pane, a peripheral spacing frame, and gas filling the interspace, in which at least one of the panes is attached to the spacing frame on at least one edge by means of a resilient bridging profile section secured to the edge concerned. The interspace is preferably a sealed interspace. Both the inner pane and the outer pane, or either one of them, can be constructed as what is known as a composite glass pane. Alternatively, each can be formed as insulating window panes, each constituting an insulating window unit.

In a known embodiment of this type (see DE OS 20 31 576, Figure 2), the bridging profile section is a spring strip having concertina-fashion folds. The assembly is arranged so that the coupled panes can move like pistons to accommodate volume changes in the gas filling the interspace associated with temperature changes, the spring strip deforming correspondingly. Even if the coupled panes acquire an outwardly directed convexity under the pressure of the enclosed gas, the bridging profile section responds by deforming. In fact, the arrangement just described is intended to control dangerous bulging of the panes in a soundproofing double glazing unit. It does not however improve the soundproofing effect.The so-called soundproofing index remains relatively low in the known embodment, and lies in the 20-30 dB range, assuming that the breadth of the interspace between the inner and outer panes is approximately 10 mm.

Even if the breadth of the interspace is increased to 100 mm, which is beyond the practical limits for insulating window units of the heaviest attainable construction, the average and nominal soundproofing indices are only increased to about 38 dB and about 40 dB respectively.

Even when the thickest monolithic window glass available is used, air-filled double glazing units barely attain a nominal soundproofing index exceeding about 42 dB, assuming that the maximum insulating glass thickness is 70-80 mm.

In this context, the object of the inventivn is to provide an insulating window unit of the type in question with simple means whereby the soundproofing effect can be significantly improved.

According to the present invention, there is provided an insulating window unit having an inner pane, an outer pane, a peripheral spacing frame and gas filling the interspace, with at least one of the panes attached to the spacing frame on at least one edge by means of a resilient bridging profile section secured to the edge concerned, the bridging profile section being in the form of a strip-like membrane having a small stiffness in bending compared with the stiffness in bending of the same width of window glass, and the membrane strip can respond to edgewise transverse vibrations of the attached pane edge by corresponding vibratory deformations.

The term edgewise transverse vibrations denotes more or less sinusoidal vibrations of significant amplitude beyond the plane of the glass, running along its edge. Preferably, the stiffness in bending of the membrane strip, which can consist of metal, rubber or a plastics material, is 10-2 to 10-6 (preferably about 10-4 to 1 of6) times smaller than that of the same width of window glass. This ensures that the form of the above-mentioned edgewise transverse vibrations is not significantly distorted by the holding tension or other disturbing factors. The membrane strip is preferably formed as a flat uniform strip whose free breadth approximately equals or exceeds the thickness of the attached window pane.It is normally sufficient in an insulating window unit in accordance with the invention to secure one of the panes by means of a membrane strip on one edge to the spacing frame. However, it is within the scope of the invention to provide similar membrane strips on two opposite edges or on every edge of the pane. It is also within the scope of the invention to integrate the insulating window unit of the invention with additional panes, so as to assemble units having more than two panes.

The term membrane is employed in the static sense in this context. In fact, the membrane strip in an insulating window unit in accordance with the invention is primarily a static member, since it 5serves to hold or secure the associated pane.

Under stress and/or strain, the stresses set up in a membrane strip are in principle confined to the midplane and parallel thereto; in the thickness direction of the membrane they are distributed substantially uniformly. Consequently, its distortion does not bring about any significant restoring bending moments (in contrast to a spring member of the type used as bridging strips in the known embodiment described initially). The stiffness in bending of a membrane strip is low.

The prevailing theory and practice of insulating window units has never envisaged the use of such members. The prevailing theory and practice (cf.

Furrer 8 Lauber, Raum- und Bauakustik, Larmabwehr, 1972, pp. 197-230, notably Figure 159 on page 208 and Figure 164 on page 212) take into account the incident air-borne sound waves, the reflected sound waves which have no bearing on the soundproofing problems and the transmitted sound waves which determine the soundproofing index. If incident airborne sound waves coincide with bending waves in the insulating window unit, a serious resonance peak will form on the curve of sound attenuation against frequency. It is known to combat this resonance peak by constructing the spacing frame as a whole as a damping member.

However, spacing frames of this type do not possess the properties or exhibit the behaviour of the membrane strip on which the invention is based. It makes no significant contribution to the attenuation of edgewise transverse vibrations in the pane. Its damping action merely reduces the magnitude of the resonance peak in the sound attenuation curve. For this purpose, the spacing frame is constructed entirely from a material which acts by internal friction, for example, or from a suitably laminated arrangement of metallic components. The prevailing theory does not consider the problem of wave-energy reflection as an independent factor in the sound-proofing problem. Scientists have more recently investigated the reflection properties of plates (cf.

Akustika, 1975, pp. 244-245), and reflection from loudspeakers has also been extensively studied, but these investigations have contributed nothing to improving the soundproofing index of insulating window units of the type in question. According to the prevailing teaching, edgewise transverse vibrations in insulating window units of the type in question are suppressed in the region of the spacing frame.The invention on the other hand recognises that when the membrane strip is capable of responding to edgewise transverse vibrations in the attached pane edge by vibrating or deforming similarly, without offering any resistance that can disturb these vibrations or deformations, a major increase in the soundproofing index is achieved: with no other change in the design or form of the insulating window unit, 50% or more of the sound energy normally transmitted is now absorbed. The effect is particularly pronounced in the medium frequency range. Moreover, it is particularly pronounced when the panes have a combined glass thickness of 15 mm or more, the interspace breadth is in the range 10-70 mm, preferably 2550 mm, and the enclosed gas is other than air alone.In general, the combined glass thickness in insulating window units of the invention is in the 1035 mm range. The breadth of the interspace is preferably increased as the combined glass thickness is reduced. Typical breadths are 50 mm at a combined glass thickness of 10 mm, > 25 mm at 15 mm and > 10 mm at 20 mm.

Outstandingingly high soundproofing can be obtained if the gas occupying the interspace consists of a gas in which the velocity of sound is at least 10% lower than in air. However, particularly high soundproofing levels can also be attained when, in combination with the previously described construction and arrangement of the membrane strip, the occupying gas is one in which the velocity of sound is at least 20%, and preferably 30% higher than in air. In the case of very large insulating window units, it may be necessary to provide underpinning members under the edge of the pane, attached to the membrane strip. In this case, the spacings between underpinning members should exceed the wavelength of the edgewise transverse vibrations at the path-matching frequency. The term "path-matching frequency" relates to the wave coincidence phenomenon previously discussed.If, as the excitation frequency is increased, the wavelength in air becomes smaller than the bending-wave length in the glass pane at a certain frequency, the so-cailed coincidence effects are set up. They arise from a type of threedimensional resonance between the acoustic excitation of the glass pane and its free bending vibrations. This effect is known as the pathmatching effect and the frequency at which it occurs as the path-matching frequency. It is finally within the scope of the invention to attach an additional damping device to the membrane strip and/or the associated pane edge.

Furthermore, a covering lip can be placed with one edge on the pane associated with the membrane strip, on the face remote from the spacing frame, its other edge being attached to the spacing frame or an adjacent frame section.

Two embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, which are not to scale, and in which Figure 1 is a vertical section through part of an insulating window unit in accordance with the invention; Figure 2 is a fragmentary view looking in the direction of the arrow A of Figure 1; and Figure 3 corresponds to Figure 1 and shows another embodiment in accordance with the invention.

The insulating window units shown in the Figures each consists basically of an inner pane 1, an outer pane 2, a peripheral spacing frame 3 and a gas 4 filling the interspace. In both embodiments shown, the pane 2 is attached to the spacing frame 3 along its edge 5 by means of a resilient bridging profile section 6 secured to its edge and in the form of a strip-like membrane, which is shown thicker than in actual fact, in order to make the drawings clear.In fact, the membrane strip 6 has a small stiffness in bending compared with the associated glass pane 2, in relation to comparable widths. (The bending stiffness ratio V is calculated from the formula:

where Em is the elasticity modulus of the membrane, EG is the elasticity modulus of the glass pane, DM is the thickness of the membrane, and DG is the thickness of the glass pane).

Consequently, the membrane strip 6 is intended to respond to edgewise transverse vibrations 7 of the attached pane edge 5 by corresponding vibratory deformations 7, without resisting and thus disturbing these vibrations 7 or deformations.

The edgewise transverse vibrations 7 in question are depicted on an exaggerated scale in Figure 2. The membrane strip 6 can consist of metal, rubber or a plastics material. Its stiffness in bending should be 10-2 to 10-6 times smaller than that of the adjacent glass pane 2, over the same width. In practice, the ratio is usually in the approximate range 10-4 to 10-5. Moreover, the membrane strip 6 is formed as a flat uniform strip.

Its free breadth B shown in the Figures should approximately equal the thickness of the attached pane 2, but it may be larger or smaller.

The breadth DZ of the interspace in an insulating window unit in accordance with the invention is basically optional, but in both of the embodiments shown, the interspace breadth is preferably about 50 mm, while the two panes 1 and 2 have a combined thickness of about 14 mm or more. The gas filling 4 is other than air, or a mixture of a gas and air. It can consist of 40% SF6+60% air, or of helium. In the first case, the velocity of sound is at least 10% lower than air alone. In the second case the gas filling 4 consists of a gas in which the velocity of sound is at least 20% higher than in air.Comparing this insulating window unit with one of the prior art, in which the membrane strip 6 is replaced by a resilient bridging profile strip of substantial bending stiffness, or the pane concerned is attached directly to the spacing frame 3, given the same gas fillings, the unit of the invention has a nominal soundproofing index of about 50 dB, whereas that of the known forms with the same gas fillings is only 45 dB. (An increase of 5 dB in the soundproofing index denotes a reduction in sound energy by a factor of 3.2).

The soundproofing indices of a unit in accordance with the invention can be improved further by increasing the combined glass thickness, whereas no improvement is possible with the known units.

A broken line in Figure 1 indicates that an additional damping device 8 can be attached to the membrane strip 6. Figure 3 shows the device 8 in full line and, addtionally, a covering lip 9, with cne edge placed on the pane 2 on the face remote from the spacing frame 3, its other edge being attached to a section 10 in the frame 1 1.

Some specific examples will now be quoted in Further explanation.

The quoted nominal soundproofing indices were measured, unless otherwise stated, by the two-compartment method of DIN 52 210 on panes measuring 1.25 mmx 1.50 mm. Unless otherwise stated, the bridging profile section was a steel membrane strip 0.15 mm thick by 30 mm wide; it was bonded to the glass pane and the spacing frame over widths of 7 and 10 mm respectively, leaving a free breadth of 13 mm.

Comparison was made with insulating window units without a bridging profile section, both panes being bonded in the usual manner directly to the spacing profile section; for brevity, this onstruction will be referred to as "rigid", in contrast to the "flexible" type using a membrane.

Example 1 Outer pane thickness Dt=5 mm, Interspace breadth DZ=50 mm, filled with a gas comprising 70% SF, and 30% air, Inner pane thickness D2=4 mm, Rw rigid 43 dB, Rw flexibi dB, The 4 mm thick pane was mounted flexibly.

Example 2 D,=10 mm, DZ=30 mm, filled with a gas comprising 70% SF6 and 30% air, D2=4 mm, Rw rigid=42 dB, Rw flexible=46 dB, The 4 mm thick pane was mounted flexibly.

Example 3 D1=15 mm, DZ=50 mm, filled with air, D2=8 mm, Rw rigid=42 dB, Rw flexible=47 dB, The 8 mm thick pane was mounted flexibly.

Example 4 Do=19 mm, DZ=12 mm, filled with a gas comprising 70% SF, and 30% air, D2=8 mm, Rw rigid=41 dB, Rw flexible=47 dB, The 8 mm thick pane was mounted flexibly.

Example 5 D1=15 mm, DZ=12 mm filled with helium, D2=8 mm, Rw= Rw rigid=42 dB, Rw flexible=48 dB, The 8 mm thick pane was mounted flexibly.

The measurements were made on 6m2 insulating window units.

Example 6 Do=10 mm, DZ=50 mm, filled with a gas comprising 40% SF6 and 60% air, D2=4 mm, Rw rigid=45 dB, Rw flexible=50 dB, The 4 mm thick pane was mounted flexibly.

Example 7 Construction and gas filling as in Example 6, except that the free breadth of the steel membrane was halved to 6.5 mm, Rw flexible=50 dB.

Example 8 Construction and gas filling as in Example 7, except that a rubber lip 5 mm thick, of Shore hardness 40, was added as in Figure 3, Rw flexible=S1 dB.

Example 9 Construction and gas filling as in Example 6, except that the 0.1 5 mm thick steel membrane was replaced by an aluminium strip 0.1 mm thick, Rw flexible=50 dB.

Example 10 Geometry and gas filling as in Example 6, except that the flexible steel membrane was replaced by a rubber membrane 5 mm thick, of Shore hardness 40, Rw flexible=50 dB.

Example 11 D1=19 mm, DZ=50 mm, filled with a gas comprising 70% SF, and 30% air, D2=8 mm, Rw rigid=44 dB, Rw flexible=54 dB, The 8 mm thick pane was mounted flexibly.

The sound velocities for the gas fillings, relative to that for air, and the bending stiffness relationships, are given in the following two tables.

Table 1 Gas C {m/secJ CG/CHI, 100% air 329 40% SF6+60% air 197 0.60 70% SF6+30% air 156 0.47 100% He 966 2.94 Table 2 Membrane Glass V 0.15 mm steel 4 mm 1.6x104 8 mm 2.0x10-5 0.1 mm aluminium 4mm 1.6x10-5 5 mm rubber 4 mm ~1 x 10-5

Claims

1. An insulating window unit having an inner pane, an outer pane, a peripheral spacing frame and gas filling the interspace, with at least one of the panes attached to the spacing frame on at least one edge by means of a resilient bridging profile section secured to the edge concerned, the bridging profile section being in the form of a strip like membrane having a small stiffness in bending compared with the stiffness in bending of the same width of window glass, and the membrane strip can respond to edgewise transverse vibrations of the attached pane edge by corresponding vibratory deformations.

2. An insulating window unit as in Claim 1, wherein the membrane strip consists of metal, rubber or a plastics material and has a stiffness in bending smaller than that of the attached glass pane by a factor of 10-2 to 1 O-ff, preferably about 10-4to 10-5.

3. An insulating window unit as in either of Claims 1 and 2, wherein the membrane strip is formed as a flat uniform strip.

4. An insulating window unit as in any one of Claims 1 to 3, wherein the free breadth of the membrane strip approximately equals the thickness of the attached pane.

5. An insulating window unit as in any one of Claims 1 to 4, wherein a covering lip is placed with one edge on the pane associated -with the membrane strip, on the face remote from the spacing frame, its other edge being attached to the spacing frame or an adjacent frame section.

6. An insulating window unit as in any one of Claims 1 to 5, wherein the panes have a combined glass thickness exceeding 10 mm, and the interspace has a breadth of 10 to 70 mm, preferably in the range 25 to 50 mm, and the gas filling is different from air alone.

7. An insulating window unit as in Claim 6, wherein the gas filling consists of a gas in which the velocity of sound is at least 10% lower than in air.

8. An insulating window unit as in Claim 6, wherein the gas filling consists of a gas in which the velocity of sound is at least 20% and preferably 30% higher than in air,

9. An insulating window unit as in any one of Claims 1 to 8, having underpinning members under the edge of the pane attached to the membrane strip, and the spacings between the underpinning members exceeds the wavelength of the edgewise transverse vibrations at the socalled path-matching frequency.

10. An insulating window unit as in any one of Claims 1 to 9, wherein an additional damping device is attached to the membrane strip and/or the edge of the associated pane.

11. An insulating window unit substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

12. An insulating window unit substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.