Patent Description:
Traditionally, acoustic insulation is made with panels formed by a single layer or multiple layers. When a sound is transmitted from a first environment, upstream of the panel, to a second environment, downstream of the panel, the efficacy of the acoustic insulation of the panel is expressed by means of the sound-insulating power (transmission loss), i.e. a ratio in decibels of the sound pressure that is transferred to the downstream environment to the sound pressure incident on the panel in the upstream environment.

The sound-insulating power varies based on the frequency of the sound and the physical properties of the panel, in particular its density and its stiffness or elasticity. In the multilayer panels, stiffer layers and more elastic layers are usually alternated. Such a panel can be physically modelled as a system with a series of masses and springs, which reduce the propagation of the sound between the two sides of the panel.

The choice of materials for the layers of the panel is therefore essential for the performance of the traditional panels. The materials that make up the most effective panels are relatively expensive.

It is then worth noting that in the most traditional applications, the increase in performance of a panel follows an increase in thickness and weight.

Acoustic shielding panels based on the metamaterial technology are also known in the art. Unlike traditional panels, where the stiffness and mass properties are determined by the elasticity and density of the microscopic structure of the chosen materials, as well as by their thickness, in metamaterials multiple macroscopic components are connected to each other in such a way as to confer the desired properties of mass and stiffness.

This has the potential to significantly reduce the costs of the acoustic shielding devices. In fact, in them it is no longer necessary that the material inherently has the desired properties of density and elasticity, but the required properties can be obtained by conferring to the material an appropriate three-dimensional shape. Therefore, significantly cheaper and eco-sustainable materials can be potentially chosen, as long as they are suitably shaped.

In addition, metamaterials allow to achieve high performance with lower weights and thicknesses than the traditional panels.

Examples of metamaterial-based noise and vibration shielding devices are described in documents <CIT> and <CIT>. In them, the panel is formed by substantially cubic modules connected to each other. Each module has planar mass elements arranged along the faces of the cube, without the faces of the cube being joined together along the edges. Instead, the faces of the cube are connected by stiffening elements placed inside the cube, with various possible substantially linear conformations, in particular straight or curvilinear, like for example circular or arched.

Patent document <CIT> discloses a connection module connecting two panels forming a noise and vibration absorbing board. The connection module comprises a lower body, an upper body, and elastic springs connecting the lower body and the upper body.

Similar shielding devices were made initially by 3D printing, and then by other serial, and therefore cheaper, industrial processes. However, there is the need to implement other serial production processes, and optimise the structure of metamaterial shielding devices for this purpose.

Aim of the present invention is to allow the realization of acoustic shielding devices based on metamaterials, which are realizable with simpler and economically competitive industrial processes.

This and other aims are achieved thanks to the application of a connection module for the realization of a noise shielding device, and by an acoustic shielding device, according to any one of the appended claims.

Two panels of the device can be connected to each other by means of multiple connection modules. Each connection module comprises a base element and a suspended mass element, spaced apart from each other in a thickness direction and connected to each other by means of connection elements. A first face of the base element is provided for connection to a first panel of the device, and a second face of the suspended mass element is provided for connection to the second panel.

A perimeter edge of the suspended mass element, and an inner edge of an opening of the base element, are shaped so that, in a projection in the thickness direction, the shape of the suspended mass element is internal to the shape of the opening of the base element.

Thanks to this shape, the module can be made simply by injection moulding. The cost of injection moulding itself, and of the materials suitable for injection moulding, for example regenerated PVC, are drastically lower than 3D moulding, and more competitive than the traditional panels. The regenerated PVC also makes the product eco-sustainable.

At the same time, by optimising the shape of the suspended mass element and of the connection elements, the desired mass and stiffness properties can be obtained in order to achieve an optimal sound-insulating power, with limited thicknesses and weights.

Further features and advantages of the invention will be recognisable by a person skilled in the art from the following detailed description of exemplary embodiments of the invention.

For a better understanding of the following detailed description, some embodiments of the invention are illustrated in the accompanying drawings, wherein:.

A noise shielding device is indicated in the figures by the numeral <NUM>. The shielding device <NUM> comprises two stiff panels <NUM>, arranged parallel to each other, spaced apart from each other in a thickness direction X-X, and facing each other in the thickness direction X-X. The two panels <NUM> therefore delimit a gap <NUM> between them, shown in <FIG>.

The two panels <NUM> may be made in a known manner in one or more layers, without, however, the panels <NUM> necessarily having significant noise shielding properties per se.

The shielding device <NUM> further comprises a plurality of connection modules <NUM>, preferably identical to each other. Therefore, the modules <NUM> can be realized in series and used in the most appropriate number and position for the specific desired application.

The modules <NUM> are arranged between the two panels <NUM>, inside the gap <NUM>, and connect the two panels <NUM> to each other. It is worth noting that the modules <NUM> can be provided separately from the panels <NUM>, and subsequently assembled with panels <NUM> of simple realization and easily available, to make a shielding device <NUM>. In the following, a single connection module <NUM> will be described with reference to the characteristics of all modules <NUM>.

The connection module <NUM> is realizable by injection moulding, and is preferably formed in a single piece. The preferred material for the connection module <NUM> is polyvinylchloride (PVC), specifically regenerated PVC.

With reference to <FIG>, the module <NUM> comprises a base element <NUM> and a suspended mass element <NUM>, connected to each other. The base element <NUM> and the suspended mass element <NUM> each comprise a first face <NUM>, <NUM> facing toward a first of the two panels <NUM>, and a second face <NUM>, <NUM>, opposite the respective first face <NUM>, <NUM> and facing toward a second of the two panels <NUM>.

The first face <NUM> of the base element <NUM> is configured for connection to the first panel <NUM> and is in contact with the first panel <NUM>, while the first face <NUM> of the suspended mass element <NUM> is spaced apart from the first panel <NUM>. The second face <NUM> of the base element <NUM> is spaced apart from the second panel <NUM>, while the second face <NUM> of the suspended mass element <NUM> is configured for connection to the second panel <NUM> and is in contact with the second panel <NUM>. Therefore, the base element <NUM> and the suspended mass element <NUM> are spaced apart or staggered from each other in the thickness direction X-X.

For the purpose of connection with the panels <NUM>, the first face <NUM> of the base element <NUM> and the second face <NUM> of the suspended mass element <NUM> are preferably substantially planar.

It is worth noting that multiple modules <NUM> of the device <NUM>, arranged between the same panels <NUM>, can all have the base element <NUM> connected to the same first panel <NUM> and the suspended mass element <NUM> connected to the same second panel <NUM>, or each panel can be connected to the base element <NUM> of at least one module <NUM> and to the suspended mass element <NUM> of at least another module <NUM>. It is to be understood that, for each module <NUM>, the first face <NUM> of the base element <NUM> and the second face <NUM> of the suspended mass element <NUM> are fixed to two distinct panels <NUM>.

The suspended mass element <NUM> has a perimeter edge <NUM>, around the second face <NUM>, with a first predetermined shape, also referred to below as the shape of the suspended mass element <NUM>. The preferred shape for the suspended mass element <NUM> is illustrated in <FIG>. <FIG> show other simplified examples, with suspended mass elements of rhomboidal and circular shape.

For the purpose of the realization by injection moulding, the base element <NUM> has a through opening <NUM> having an inner edge <NUM> with a second predetermined shape, also referred to below as the shape of the opening <NUM>. The first predetermined shape, when projected along the X-X thickness direction, is internal to the second predetermined shape. A projection view along the thickness direction X-X is shown in <FIG>. In other words, the shape of the suspended mass element <NUM> is such that the suspended mass element, if translated along the thickness direction X-X would be suitable to be contained in the opening <NUM> of the base element <NUM>. However, this translation is prevented in the preferred embodiments for the connection modes between the suspended mass element <NUM> and the base element <NUM>, detailed below.

With regard to the shapes of the suspended mass element <NUM> and of the opening <NUM> of the base <NUM>, it is worth noting that, as is known, injection moulding entails pouring liquid material between two half-moulds, causing the liquid material to solidify, and separating the half-moulds from each other. The described conformation of the suspended mass element <NUM> and of the opening <NUM> of the base element <NUM> allows the separation of the half-moulds also following the solidification of the material.

In the preferred embodiment, to optimise noise damping, the shape of the suspended mass element <NUM> defines in the second face <NUM> a central portion <NUM> of the suspended mass element <NUM> and a plurality of lobes <NUM> of the suspended mass element <NUM>. The lobes <NUM> are distributed circumferentially around the central portion <NUM>, and protrude radially from the central portion <NUM>. Preferably, each lobe <NUM> has one or more tabs <NUM> extending predominantly in the radial direction.

The conformation of the lobes <NUM> and of the tabs <NUM> can be chosen by the persons skilled in the art in such a way as to:.

In this description, by radial direction is meant a direction, in a plane perpendicular to the thickness direction X-X, extending away from a centre, placed in the central portion <NUM> of the suspended mass element <NUM>. Instead, by circumferential direction is meant a direction, in a plane perpendicular to the thickness direction X-X, which wraps around the aforementioned centre. The radial, circumferential and thickness directions therefore identify a system of cylindrical coordinates.

The perimeter edge <NUM> of the suspended mass element <NUM> and the inner edge <NUM> of the opening <NUM> of the base element <NUM> delimit a gap <NUM> between them. In particular, the perimeter edge <NUM> and the inner edge <NUM> are spaced apart from each other in the thickness direction X-X and/or in the radial direction.

In preferred embodiments, the inner edge <NUM> of the base element <NUM> develops at least in part along the perimeter edge <NUM> of the suspended mass element <NUM>, although spaced apart therefrom. Therefore, some portions of the inner edge <NUM> and of the perimeter edge <NUM> (even if they were curvilinear) can be substantially parallel, i.e. be positioned at a substantially constant distance from each other, along their length extension.

In the illustrated embodiment, the shape of the opening <NUM> has a plurality of peninsula portions <NUM> which, in a projection in the thickness direction X-X, are positioned between consecutive lobes <NUM> of the suspended mass element <NUM>. The peninsula portions <NUM>, in a projection in the thickness direction X-X, extend radially towards the central portion <NUM> of the suspended mass element <NUM>.

In addition, the shape of the opening <NUM> has a plurality of gulf portions <NUM> joining consecutive peninsula portions <NUM>.

The connection module <NUM> has a plurality of connection elements <NUM> connecting the base element <NUM> and the suspended mass element <NUM>. The connection elements <NUM> are preferably shaped as connection legs, i.e. elements with predominantly linear development, without necessarily being straight, for example straight, curvilinear, broken lines, or a combination thereof.

The connection elements <NUM> are also made in one piece with the base element <NUM> and the suspended mass element <NUM>, in the same injection moulding process. Therefore, all these elements are made of the same material, substantially stiff.

The leg conformation of the connection elements <NUM> confers stiffness but also elasticity to the module <NUM>. In fact, depending on the frequency of a vibration, for example acoustic, which is transmitted in sequence from the first panel <NUM>, to the base portion <NUM>, to the connection elements <NUM>, to the suspended ground portion <NUM>, to the second panel <NUM>, or vice versa, the stiffness or elasticity properties of the connection elements <NUM> are prevalent.

Therefore, at the frequencies that are intended to be damped the most, the connection elements <NUM> can be designed so that the connection module <NUM> is similar to a mass and spring system, with the masses represented by the base and suspended mass elements <NUM>, <NUM>, and the springs represented by the connection elements <NUM>.

Each connection element <NUM> has a first end portion <NUM> connected to the base element <NUM>, a second end portion <NUM> connected to the suspended mass element <NUM>, and a joining portion <NUM> connecting the first and second end portion <NUM>, <NUM>. The connection element <NUM> can advantageously develop substantially linearly between the first and second end portion <NUM>, <NUM>. Preferably, the two end portions <NUM>, <NUM> are spaced apart from each other at least in a radial direction. The spacing in the radial direction allows to increase the length of the connection elements <NUM>, increasing the elasticity properties thereof.

For this purpose, preferably the connection elements <NUM> connect the base element <NUM> to the central portion <NUM> of the suspended mass element <NUM>. More in detail, the connection elements <NUM> connect gulf portions <NUM> of the opening <NUM> of the base element <NUM> with the central portion <NUM> of the suspended mass element <NUM>.

While the central portion <NUM> is connected to the connection elements <NUM>, the lobes <NUM> increase the mass of the suspended mass element <NUM> and the surface of its second face <NUM> useful for connection to the second panel <NUM>.

For the purpose of the realization by injection moulding, the joining portions <NUM> of the connection elements <NUM>, in a projection along the thickness direction X-X, join the shape of the suspended mass element <NUM> to the shape of the opening <NUM>, and are preferably external to the shape of the suspended mass element <NUM> and internal to the shape of the opening <NUM>. Therefore, in a projection in the thickness direction X-X, the shape of the opening <NUM> encloses the assembly of the shape of the suspended mass element <NUM> and of the joining portions <NUM> of the connection elements <NUM>.

It is worth pointing out that some of the gulf portions <NUM>, in a projection in the thickness direction X-X, are arranged around lobes <NUM> of the suspended mass element <NUM>, while other gulf portions <NUM>, always in a projection, can be arranged around connection elements <NUM>. At these latter gulf portions <NUM>, the inner edge <NUM> of the opening <NUM> may also deviate significantly from the outer edge <NUM> of the suspended mass element <NUM>.

The base element <NUM>, in addition to the opening <NUM> with the inner edge <NUM>, has an outer contour <NUM>. In the illustrated embodiments, the outer contour <NUM> has four sides, and is substantially shaped as a square. However, other shapes are possible, preferably such as to allow multiple modules <NUM> to be placed side by side along the sides of their outer contours <NUM>, such as for example triangular or hexagonal shapes, or even other shapes, such as circular shapes.

In the preferred embodiment, the outer contour <NUM> of the base element <NUM> has a plurality of interlocking portions <NUM>, <NUM>, shaped for fixing multiple connection modules <NUM>, preferably identical, side by side to one another. For example, the interlocking portions <NUM>, <NUM> may comprise male interlocking portions <NUM>, with an interlocking element protruding from the outer contour <NUM>, and female interlocking portions <NUM>, recessed towards the inside of the outer contour <NUM> and shaped to receive respective male interlocking portions <NUM>.

Each side of the outer contour <NUM> may have a single interlocking portion <NUM>, <NUM> or multiple interlocking portions <NUM>, <NUM>, which may all be male interlocking portions <NUM>, all female interlocking portions <NUM>, or a combination thereof.

It is worth noting that, in the shielding device <NUM>, the connection modules <NUM> can be arranged spaced apart or in contact with each other, preferably interlocked with each other through the interlocking portions <NUM>, <NUM>. This is shown schematically in <FIG> and <FIG>, where for simplicity's sake the modules <NUM> have been represented substantially square, with a low level of detail, and dashed as they are covered by one of the panels <NUM>.

So far, a shielding device <NUM> has been described, two panels <NUM> of which have been mentioned, with a single gap <NUM> between them, and connection modules <NUM> in this gap <NUM>. Embodiments with three or more panels <NUM>, which delimit two or more gaps <NUM>, and multiple connection modules <NUM> in each gap <NUM> for connecting pairs of consecutive panels <NUM> are also possible.

Claim 1:
Connection module (<NUM>) for a noise shielding device (<NUM>), the connection module (<NUM>) being obtainable by injection moulding and comprising:
- a base element (<NUM>) having a first face (<NUM>) configured for connection to a first panel (<NUM>) of the shielding device (<NUM>),
- a suspended mass element (<NUM>) spaced apart from the base element (<NUM>) in a thickness direction (X-X), the suspended mass element (<NUM>) having a second face (<NUM>) configured for connection to a second panel (<NUM>) of the shielding device (<NUM>),
- a plurality of connection elements (<NUM>) connecting the base element (<NUM>) and the suspended mass element (<NUM>),
wherein:
- the suspended mass element (<NUM>) has a perimeter edge (<NUM>) with a first predetermined shape,
- the base element (<NUM>) has an opening (<NUM>) having an inner edge (<NUM>) with a second predetermined shape,
characterised in that
- the first predetermined shape, when projected along the thickness direction (X-X), is internal to the second predetermined shape.