[0001] This invention relates to a thermally insulating and sound absorbent panel.
[0002] Panels are known consisting of a layer of mineral wool (glass wool or rock wool)
covered on one or both sides with a thin containing sheet of paper, cardboard, plastics,
metal etc.
[0003] When used in particular for forming ventilation ducts, these panels are generally
covered externally with an aluminium sheet and lined internally with glass cloth or
an aluminium sheet.
[0004] If the internal lining is of glass cloth, the duct formed with such panels has a
considerable tendency to form dust clouds consisting of glass fibres which have been
separated by the air flow and entrained by it along the duct.
[0005] If however the lining is of aluminium sheet the dust cannot form, but the duct emits
considerable noise on air passage because of the poor sound absorption power of aluminium.
[0006] In an attempt to solve these problems it has also been proposed to internally line
panels used for constructing ventilation ducts with sheets of embossed aluminium which
because of their surface "roughness" attenuate the phenomenon of acoustic reverberation.
[0007] However the sound absorption problem is only partly solved by this means, and on
the other hand embossing can only be effected on aluminium sheets of a certain thickness
(at least 60µ), leading to a considerable weight and high cost of the panel and the
duct formed from it.
[0008] To increase the sound absorption of such panels it has also been proposed to interrupt
the surface continuity of the embossed aluminium with a series of holes distributed
over its entire surface.
[0009] However not even this solution, which again requires aluminium sheets of a thickness
suitable for embossing, has proved satisfactory because if the holes are too small
only poor sound absorption is achieved, whereas if the holes are larger there is indeed
reasonable sound absorption however undesirable dust formation occurs.
[0010] These drawbacks are overcome according to the invention by a thermally insulating
and sound absorbent panel as described in claim 1.
[0011] The present invention is further clarified with reference to the enclosed sheet of
drawing showing in partially perspective view a panel according to the invention.
[0012] As can be seen from the drawing, the panel according to the invention, used in particular
for forming a ventilation duct, comprises an inner layer 2 of glass wool or rock wool,
covered on both sides with two aluminium sheets 4, 6 applied by conventional methods.
Specifically, the aluminium sheet 4, which lies on the inside of the formed ventilation
duct, has been previously subjected to an embossing process but has a thickness of
about 40µ, ie a thickness less than the minimum thickness necessary for embossing.
In this manner it is subjected by the embossing rollers to a series of stretchings
and microlacerations extending over its entire surface.
[0013] The dimensions of these microlacerations are such that they are sufficient to interrupt
the surface continuity of the sheet and hence give the resultant panel sufficient
sound absorption characteristics, but at the same time are insufficient to allow the
fibres of the mineral wool layer to pass and hence lead to undesirable dust formation.
[0014] The dimensions of these microlacerations can in fact be so small that they can be
seen in the aluminium sheet only by transparency, and hence are invisible in the formed
panel, so eliminating the uncertainty which can sometimes make such a product poorly
desirable.
[0015] Finally, because of the very small thickness of the aluminium sheet, the weight and
cost of the panel are considerably less than those of panels of sometimes poorer performance.
[0016] In the description reference has been made to a panel for lining ventilation ducts,
however the panel can also be advantageously used interposed between two plasterboards
to insulate false ceilings, and in other acoustic and/or thermal applications.
1. A thermally insulating sound absorbent panel consisting of a layer (2) of mineral
wool covered with two aluminium sheets (4,5), particularly for ventilation ducts,
characterised in that at least that covering layer located on the inside of the formed
duct consists of an aluminium sheet (4) of thickness less than the minimum thickness
required for subjecting to embossing, so that following embossing its surface comprises
microlacerations of dimensions sufficient to interrupt the surface continuity of the
sheet, but insufficient to allow passage of mineral wool fibres.
2. A panel as claimed in claim 1, characterised in that the aluminium covering sheet
(4) has a thickness of about 40µ.
