EP1420624A2

EP1420624A2 - A shielding device

Info

Publication number: EP1420624A2
Application number: EP03024843A
Authority: EP
Inventors: Francesco Butera; Gianluca c/o C.R.F. Capretti; Antonino Veca
Original assignee: Centro Ricerche Fiat SCpA
Current assignee: Centro Ricerche Fiat SCpA
Priority date: 2002-11-14
Filing date: 2003-10-31
Publication date: 2004-05-19
Anticipated expiration: 2023-10-31
Also published as: DE60309814T2; EP1420624A3; ITTO20020988A1; ATE346181T1; DE60309814D1; EP1420624B1; ES2275056T3

Abstract

A shielding device comprises a fabric (3) defining a plurality of meshes which are designed to assume a restricted configuration and a stretched-out configuration, and actuation means (4) made of active material, which are operatively connected to the fabric (3) and can be activated to bring about passage of said meshes from the restricted configuration to the stretched-out configuration, and vice versa. The actuation means are preferably in the form of a thread (4), interwoven or in any case anchored to the fabric, made of a shape-memory alloy or polymer, or of an electro-active polymer. The device finds, for example, application in the construction of shields for light beams, windows or panels for aeration/ventilation, and filters for adjustable cross section. <IMAGE>

Description

The present invention relates to a shielding device, comprising switchable shielding, supporting means for supporting the shielding means and actuation means, operative to cause passage of the shielding means from a resting position to a working position, and vice versa.

Devices of the type indicated are used, for example, to prevent or attenuate passage of flows of air or light beams and usually comprise a fixed frame and a movable panel, which is carried by the fixed frame and can be displaced between a closing position and an opening position.

The purpose of the present invention is to provide a shielding device of the type referred to above, which can be applied in an extremely wide range of fields, and which presents simplicity of fabrication and low costs.

With a view to achieving the above purpose, the subject of the invention is a shielding device of the type referred to above, characterized in that the shielding means comprise a fabric defining a plurality of meshes that are able to assume a restricted configuration and a stretched-out configuration, and in that the actuation means are operatively connected to the fabric and can be activated to cause passage of said meshes from the restricted configuration to the stretched-out configuration, and vice versa.

In this way, when the meshes of the fabric are in the restricted configuration, the fabric intercepts or attenuates passage of air or light through the device. Instead, when the meshes are in the stretched-out configuration, passage of air or light is enabled or facilitated.

According to a preferred embodiment, the fabric is of an elastic type, and the actuation means comprise at least one actuator element made of an active material, for example, a shape-memory alloy (SMA).

SMA actuators are in themselves known and have already found a wide range of applications in different technical fields. In general, they make use of at least one element formed by a SMA metal alloy, which is able to change its configuration once a pre-set transition temperature has been exceeded.

In other possible embodiments, the active material used for obtaining the actuator means of the device may be a shape-memory polymer (SMP) or an electro-active polymer (EAP).

According to the invention, the actuator element preferably has the form of a thread, directly sewn or interwoven into the fabric and constrained to a supporting structure which keeps the fabric in position.

The actuator element can be connected to electric-supply means, which heat it via the Joule effect above a transition temperature of its own, it being possible for said electric-supply means to be driven by control means according to the signal issued by a temperature sensor.

Alternatively, the actuator element made of active material directly detects the temperature of the air and is directly activated thereby to a transition value that can be adjusted in the course of preparation of the material itself.

Thanks to the characteristics specified above, the shielding device according to the invention can be made with extremely simple and low-cost means.

Further characteristics and advantages of the invention will emerge from the ensuing description with reference to the annexed drawings, which are provided purely by way of non-limiting example, and in which:

Figure 1 is a schematic front view of a shielding device according to the invention, in a first operative condition;
Figure 2 is a view of a detail of Figure 1, at an enlarged scale;
Figure 3 is a schematic front view of the shielding device according to the invention, in a second operative condition; and
Figure 4 is a view of a detail of Figure 2, at an enlarged scale.

In Figures 1 and 2, the number 1 designates as a whole the structure of a shielding device made according to the present invention, which is here assumed as being designed to intercept or attenuate the passage of a light beam.

In the case provided by way of example, the device 1 comprises a fixed framework, consisting of a quadrilateral frame, designated by 2. The frame 2 may be made of metal sectional elements joined to one another, or else of a single piece of plastic material.

Designated, as a whole, by the reference number 3 is a quadrilateral shield; in the case provided by way of example, the shield 3 is fixed, along the sides which delimit the respective perimeter, to the internal edges of the frame 2 by fixing means in themselves known, illustrated only schematically and designated by 2A.

According to the invention, the shield 3 set in the frame 2 is made of a fabric the meshes of which are designed to stretch out, when the fabric is subjected to tension.

For this purpose, in the preferred embodiment of the invention, the shield 3 is made of an elastic or elongatable fabric. The fabrics of the type indicated are in themselves known and do not call for any detailed description herein. Thus, in this perspective, it is emphasized that the fabric forming the shield 3 may be made of any elastic material suitable for the purpose.

Visible in Figure 2 is an enlarged detail of the fabric that makes up the shield 3, made by interweaving or superimposing a series of weft threads, designated by 3A, with a series of warp threads, designated by 3B, to obtain the meshes 3C. In the operative condition illustrated in Figure 1, the meshes 3C are in a restricted condition so as to intercept or in any case attenuate the passage of the light beam.

According to a further important aspect of the invention, the stress capable of bringing about tensioning of the shield 3, and hence stretching-out of the meshes 3C of the fabric of which it is made up, is produced via actuation means made of active material.

In a preferred embodiment of the invention, the active material used is a metal shape-memory alloy. As mentioned above, these metal materials have the capability of reassuming their initial configuration if they are deformed and then subjected to an appropriate thermal treatment. In particular, the shape-memory alloys undergo a transformation of crystalline phase when they are made to pass from their more rigid configuration at a high temperature (austenite) to the configuration characterized by lower energy and temperature (martensite). When an SMA element is brought to a low temperature, it assumes a configuration of a martensitic type, with low yielding limit, and is easily deformable. Following upon heating, the alloy arranges itself in another crystalline structure, of the austenitic type, and hence reassumes its initial configuration and shape.

The temperature at which the alloy "recalls" its primitive shape can be modified by varying the composition or by appropriate types of heat treatment.

The alloys of major interest that present the "shape-memory" property are the ones which recover the deformation to a considerable extent or which generate a considerable force during the phase transition, such as for example the alloys Ni-Ti, Ni-Ti-Cu, Cu-Al-Zn, and Cu-Al-Ni.

In the case illustrated in the figures, the shape-memory actuation means of the device 1 are configured in the form of a continuous thread, designated as a whole by 4.

The thread 4 is constrained to the frame 2, in first points designated by 5, and to the fabric that makes up the shield 3 in second points, designated by 6; for this purpose, as may be noted in the figures, the thread 4 has a "zigzag" development between the frame 2 and the shield 3. The means for anchoring the SMA thread 4 to the frame 2 may be of any known type. On the other side, the thread 4 can be sewn or interwoven in the points 6 of the fabric 4.

Designated by the reference number 7 are two electrical conductors, provided for causing an electric current to flow through the thread 4, and thus heat it up via the Joule effect. The conductors 7 are connected to electric-supply means 8, of a type in themselves known.

Following upon heating caused by the passage of the electric current, the shape-memory thread 4 exceeds its own transition temperature and is brought to a configuration of reduced length, as illustrated in Figure 3.

Hence, in this condition the thread 4 subjects the shield 3 to a tensile force at the anchorage points 6 so as to bring the latter closer to the anchorage points 5.

Consequently, in the area delimited by the constraining points 6, the fabric of the shield 3 undergoes elongation, with the weft threads 3A and the warp threads 3B that move away from one another, thanks to the elasticity of the material which forms them. In this way there is brought about an increase in the size of the meshes 3C, as may be immediately noted from a comparison between Figures 2 and 4. In this stretched-out configuration of the meshes 3C, the passage of light through the device is evidently enabled or facilitated as compared to the operative condition of Figure 1.

The electric-supply means 8 are of the switchable type, in such a way that the thread 4 can be heated up when desired, so as to bring the device 1 into the working condition illustrated in Figure 3. Return to the resting condition represented in Figure 1 may be subsequently brought about by interrupting electric supply to the means 8. In this way, the temperature of the thread itself will decrease until it drops below the transition temperature of .the shape-memory alloy, with the consequent return of the thread 4 to its elongated configuration so that the meshes 3C of the elastic fabric will close again as may be seen in Figure 2.

The shape-memory material used for making the actuator means provided according to the invention could be of a non-metallic type, and in particular be made up of a shape memory polymer or SMP. As is known, such polymers are able to modify their stiffness and shape according to the temperature to which they are exposed and pass rapidly, if heated, from a vitreous state to a highly deformable rubbery state, and then return equally rapidly, when they are cooled down, to their original shape and hardness. Furthermore, in a way similar to the metal alloys, thanks to their "memory", SMPs can reassume their original shape an infinite number of times, if they are again brought back beyond their critical temperature. In the application according to the invention, the elastic fabric will be mounted under tension on the frame 2, and the thread 4 made of SMP will be set so as to overcome, in the "stiff" condition, the elasticity of the fabric, in order to maintain the meshes 3C in the position represented in Figure 2. When the transition temperature is reached, this will bring about transition of the thread 4 made of SMP to the respective "deformable" condition, with the consequent possibility of the fabric being stretched so as to bring the meshes 3C into the condition represented in Figure 4. Activation of the thread 4, when this is made of SMP, will be obtained directly as a result of the environmental temperature to which the thread itself is exposed.

In a further possible embodiment, the material used for making the actuator means of the shield 3 could be an electro-active polymer or EAP, i.e., a polymer material capable of undergoing deformation if an electric field is applied thereto, the said polymer material being selected, in particular, from among:

electrostrictive polymers, i.e., polymers which, when they are subjected to electric fields, react with a reduction in the dimension parallel to the field, and an enlargement in a direction normal thereto;
ion-polymer-metal composites (IPMCs), i.e., polymers with terminations capable of ionizing in polar liquids (one of the most widely used IPMCs is NAFION® produced by DuPont, which is used as "artificial muscle") ;
conductive polymers, i.e., polymers which change, as their ionization varies, their mechanical properties and dimensions and may consequently be used, to great advantage, both as sensitive elements and as mechanical actuators.

In the application according to the invention, activation of the thread 4, when this is made of an electro-active polymer, is hence obtained by applying a suitable electric field thereto.

Of course, the possibilities of application of the shielding device according to the invention are numerous.

As has been said, the device 1 can be used for intercepting/attenuating or enabling passage of light, for example for making curtains or the like for building structures or motor-vehicles.

Likewise, the device 1 may be used for controlling aeration or ventilation of certain environments. It is in fact evident that in the case of the condition represented in Figure 3, a flow of air or other aeriform through the device 1 is facilitated as compared to the condition represented in Figure 1. In this perspective, for example, the electric-supply means 8 may be driven according to the signal issued by a temperature sensor.

The invention can moreover be advantageously used for making filters with variable cross section.

In one possible embodiment, the thread 4 can be provided for detecting directly the temperature of the air so as to be activated by said temperature at a transition value, which can be adjusted in the stage of preparation of the SMA or of the active polymer used. In this perspective, for example, the thread 4 could be activated by the air inside a closed environment when very high internal temperatures are reached (as in the case of a motor vehicle parked in the sun) so as to reduce the "greenhouse" effect.

Provision of a fabric having a large number of through openings capable of increasing in size, in a way similar to what occurs in natural skin with opening of the pores, likewise enables panels for fine diffusion of air in motor vehicles to be obtained, so as to increase the comfort of the user and to reduce the possibility of damage to the health caused by traditional systems for direct conveyance of air currents within the passenger compartment. In this perspective, the device according to the invention can be used as an element with controllable and modulatable transpirability, which is particularly suitable for air diffusion in the passenger compartment of a motor vehicle through the dashboard, seats, roof and door panels.

Of course, without prejudice the principle of the invention, the details of construction and the embodiments may vary widely with respect to what is described and illustrated herein purely by way of example, without thereby departing from the scope of the present invention.

The fabric that forms the shield 3 may obviously be made up of superimposed or interwoven threads.

The functions of the frame 2 could be performed by any structure in a fixed position with respect to the shield 3, for example one made up of the walls that delimit a passage or window of which it is intended to control passage of light or air. In this case, the fabric that forms the shield 3 will preferably be provided with a anchoring edge of its own.

The actuation means of the device according to the invention could consist of a number of elements made of active material which are distinct from one another and not necessarily in the form of thread. In this case, therefore, the actuation means may be actuated selectively, for controlling the operative condition of different areas of the shield 3.

Finally, it is to be pointed out that the thread 4 or the actuator means made of active material of another form, which replace the thread, do not necessarily need to be constrained between the shield 3 and the structure that supports them, it being in fact possible for the actuator means to be integrated only in the fabric and in its possible anchoring edge.

The fabric used for the purposes of implementation of the invention may possibly be represented entirely by fibres of active material (SMA, SMP or EAP) interspersed with one another so as to form a fabric capable of varying its own "porosity" following upon application of an external stimulus, which, as explained previously, may be of an electrical or thermal type in the case of SMA elements, only thermal in the case of SMP elements or only electrical in the case of EAP active fibres.

Claims

A shielding device comprising shielding means (3) which can be switched between a first operative position and a second operative position, supporting means (2, 2A) for supporting the shielding means (3) and actuation means (4), operative for causing switching of the shielding means (3) between the first operative position and the second operative position, said device being characterized in that said shielding means comprise a fabric (3) defining a plurality of loops or meshes (3C) which are designed to assume a restricted configuration and a stretched-out configuration, and in that said actuation means (4) are operatively connected to said fabric (3) and can be activated to cause passage of said meshes (3C) from the restricted configuration to the stretched-out configuration, and vice versa.
The device according to Claim 1, characterized in that said fabric (3) is elastic or elongatable.
The device according to Claim 1, characterized in that said actuation means comprise at least one actuator element made of an active material (4) selected in the group consisting of shape-memory alloys, shape-memory polymers, and electro-active polymers.
The device according to Claim 3, characterized in that said actuator element (4) is at least in part integrated in said fabric.
The device according to Claim 4, characterized in that said actuator element (4) is in the form of a thread, sewn, interwoven or constrained in any way in more than one point to said fabric (3).
The device according to Claim 4, characterized in that said shielding means (3) are at least in part made of fibres of active material, which make up both at least in part said fabric and said actuator element (4).
The device according to Claim 3, characterized in that said actuator element (4) is constrained between said fabric (3) and said supporting means (2).
The device according to Claim 7, characterized in that said supporting means comprise a quadrilateral frame (2).
The device according to Claim 3, characterized in that said actuator element (4) is connected to electric-supply means (7, 8), which heat it via the Joule effect above its transition temperature.
The device according to Claim 9, characterized in that said electric-supply means (7, 8) are controlled according to signals issued by a temperature sensor.
The device according to Claim 3, characterized in that said actuator element (4) is arranged for being activated according to a temperature to which the element itself is exposed.
The device according to Claim 11, characterized in that said actuator element (4) detects directly said temperature and is activated by the latter at a pre-set transition value.
Use of a device according to one or more of the preceding claims, for the purposes of fabrication of a window for aeration or ventilation, for selectively preventing/attenuating or enabling/facilitating passage of a flow of air.
Use of a device according to one or more of Claims 1 to 12, for the purposes of fabrication of a shield for selectively preventing/attenuating or enabling/facilitating passage of a light beam.
Use of a device according to one or more of Claims 1 to 12, for the purposes of fabrication of a filter with variable cross section.
Use of a device according to one or more of Claims 1 to 12, for the purposes of fabrication of an element for diffusion of air within the passenger compartment of a motor vehicle, in particular integrated in a dashboard, a seat, a roof or a door panel.
A building structure, characterized in that it comprises one or more devices according to any one of Claims 1 to 12.
A motor-vehicle, characterized in that it comprises one or more devices according to any one of Claims 1 to 12.