EP1606780A2

EP1606780A2 - Flexible membrane device for measuring at least one physiological information with, corresponding sensor module and method

Info

Publication number: EP1606780A2
Application number: EP04742365A
Authority: EP
Inventors: Philippe Cosquer; Clément GUEZOU; Bruno Donval; Stéphane BRUNO
Original assignee: Aphycare Technologies
Current assignee: Aphycare Technologies
Priority date: 2003-03-25
Filing date: 2004-03-25
Publication date: 2005-12-21
Also published as: FR2853119B1; CA2520041A1; WO2004086325A2; WO2004086325A3; US20060189850A1; FR2853119A1

Abstract

The invention concerns a device for measuring at least one physiological information in an individual, comprising a flexible membrane, designed to be urged into contact with said individual's skin and contributing to the delimitation of a deformable space for a soft substance, said substance transmitting to at least one sensor a physical constraint exerted upon said membrane.

Description

Device for measuring at least one physiological piece of information with flexible membrane, corresponding sensor module and manufacturing method.

The field of the invention is that of determining and using one or more physiological information representative of the state of a human or animal subject.

More specifically, the invention relates to autonomous devices, at least as regards the reading of stress measurements, and capable of providing physiological information and corresponding decisions, for example to report an abnormal situation or indicate a sleep phase. A particular field of the invention is thus that of the detection of certain abnormal situations, in particular pathological situations, and in particular falls, in a human subject. The purpose of such detection is in particular to transmit an alarm to a third person (natural person or services, etc.) performing a remote monitoring function. The invention can find applications in many situations, and can in particular equip the elderly and / or people with reduced mobility, isolated workers, children, animals, etc.

Known remote alarm systems generally consist of an assembly carried by the subject and connected to a fixed base, for example by an HF link. In the event of an abnormal situation, the fixed base transmits a coded message, conveyed for example by the telephone network, to a specialized center. In some institutions, the message can be conveyed by an internal network.

In all cases, these systems provide for an a posteriori and voluntary triggering of the process, following a fall or discomfort. This therefore supposes that the subject has the capacity and the will to do so.

Various remote alarm systems are already known. In particular, there are devices worn in the form of a medallion around the neck, which require a tightening or pulling action to issue an alarm. Besides the fact that they are passive systems (requiring a voluntary action of the wearer), these devices often produce false alarms, for example at night, when they are worn and clinging accidentally in bedding. In addition, we do not know when they are not worn.

There are also known motion sensors, which provide information on abnormal night activity, or position sensor systems fitted to beds in certain medical services.

In this case, the device of the invention is worn by a user, and can inform, possibly remotely, a third party, in the case of an abnormal situation.

Such a device is described in particular in patent document FR-2 808 609. This device can be in the form of a watch strap.

As illustrated in FIG. 1, the watch-watch device 11 is held on the wrist using an elastic strap 12, similar to that of a conventional watch. Heart pulse 13 crosses vessels 14, muscle, tissue

15 and the skin and then propagates through the bracelet 12, which creates a stress on a sensor 16.

Thus, the physiological parameters accessible at the wrist are the image of the cardiac impulse, from which we can deduce the pulse and respiratory rate, and if necessary the blood pressure.

By placing a temperature probe very close to the skin, we also obtain the local temperature.

Another particular field of the invention is that of sleep analysis, and in particular the recognition and quantification of the different phases of sleep in a subject. In this case, the invention relates to an autonomous and portable device for recognizing sleep phases, which implements the same means, or similar means, the analysis of the measurements being adapted accordingly.

The applications of recognition and quantification of sleep phases are numerous. They range from the medical field (aid in the diagnosis of sleep apnea in pulmonology, sleep disorders, etc.) to the “general public” field (evaluation of the quality and quantity of sleep awakening in a preselected phase).

A disadvantage of this device is that it is relatively complex mechanically, due to the presence of the piston, and that its mounting may be difficult. It assumes a relatively high number of parts, grouped in a reduced space.

In addition, the presence of a contact plate against the wearer's skin may prove to be uncomfortable, because of its rigidity and its material or texture.

Another disadvantage is that the piston can, in certain situations, function insufficiently, in particular because it moves in only one direction.

Finally, due to the structure of the shell + piston system, the shell can in certain cases come into abutment against a bone thus altering, or even preventing, the measurement. The object of the invention is in particular to overcome these various drawbacks of the state of the art. More specifically, an objective of the invention is to provide a device for measuring at least physiological information, the manufacture of which is simple, and requires a reduced number of parts.

Another object of the invention is to provide such a device, which is more comfortable for the user to wear. Yet another object of the invention is to provide such a device, which is more effective than known systems.

These objectives, as well as others which will appear more clearly hereinafter, are achieved according to the invention using a device for measuring at least physiological information in an individual, comprising a flexible membrane, provided for coming into contact with the skin of said individual and participating in the definition of a deformable space for a flexible substance, said substance transmitting to at least one sensor at least one physical stress suffered by said membrane. Said deformable space is defined by a support (for example a printed circuit) on which are mounted said sensor (s) and said membrane, so that said substance is in direct contact with said one or more sensors.

It is thus possible to remove the piston, and the rigid element in contact with the skin of the wearer. The membrane and the substance it contains are deformable, or flexible, the space occupied (or cavity) by the substance can therefore itself deform, so as to allow a new distribution of the volume under the effect of a stress, which can be detected by sensors.

We therefore obtain a simple and efficient system. In particular, the collecting surface covers a large area, avoiding any risk in relation to contact with a bone (the membrane marrying the surface of the skin). Preferably, said membrane comprises means for securing to said support. In particular, said membrane can define at least one housing provided for receiving said support, allowing rapid and efficient joining. It may for example be at least one groove, a notch, and / or a groove. Likewise, said membrane advantageously comprises means for securing to a shell element of said device.

Thus, said membrane preferably defines at least one housing provided for receiving said shell element. It may for example be at least one groove, a notch, and / or a groove. Preferably, these securing means act by clipping, so as to allow easy and efficient mounting.

According to another advantageous aspect of the invention, said membrane has at least two zones of different rigidities.

In particular, said membrane may advantageously have a main contact zone, intended to come into contact with the skin of said individual, and a peripheral zone, extending over the contour of said main contact zone.

Preferably, each of said zones performs a distinct function, belonging to the group comprising the measurement of stresses, the transmission of stresses, the rigidity of the shape of said membrane. According to a first advantageous embodiment of the invention, the thickness of said peripheral zone is less than the thickness of said main contact zone.

According to a second advantageous embodiment, said membrane is obtained by overmolding of at least two materials of different rigidities.

Preferably, said membrane is made of at least one anallergenic material.

According to another advantageous characteristic of the invention, said membrane and / or said substance has an elastic character. This allows the unit to be brought back into a position of equilibrium.

For example, the membrane may have a flexibility of the order of 60 ShoreA.

It is also advantageous, so that the volume of the cavity remains substantially constant, that said substance is an incompressible or weakly compressible material.

This substance has an elasticity advantageously chosen so as to optimize a compromise between the speed of return to the initial position of said membrane and the amplitude of the resulting oscillation.

According to a first advantageous embodiment, said substance is a dielectric material.

In a particular embodiment, said substance is a silicone gel.

According to yet another aspect of the invention, the device comprises at least one transducer for measuring at least one dynamic stress, representative of a wave of arterial pressure and / or of a relative movement.

It can also advantageously include, alternatively or in addition, at least one transducer for measuring at least one static stress.

Advantageously, it further comprises a temperature sensor of said substance, representative of the skin temperature of said user. According to a preferred embodiment, the said sensor or sensors comprise at least one piezo-capacitive sensor and / or at least one piezo-resistive sensor and / or at least one switching contact at a predetermined pressure.

Preferably, said support is a printed circuit carrying electronic components for carrying out the amplification, the conditioning, the processing of electrical signals and / or a decision relating to a state of said carrier, means for supplying electrical energy and / or a communication interface.

Advantageously, said device comprises a shell formed of two complementary shell elements, a lower shell element carrying said membrane and an upper shell element.

Preferably, said shell elements are secured by screwing and / or clipping and / or bonding, also ensuring sealing for said fluid. Two types of sealing are thus ensured: the fluid must be maintained in its cavity and the device must be sealed (bath and shower). Preferably, the properties of the membrane and of the assembly are used to achieve this. Screws are there to compress the flexible areas and guarantee the tightness of the assembly. Mounting by clips or gluing is also possible. Advantageously, the device comprises a retaining strap, secured to said upper shell element.

According to a particular embodiment, said retaining strap and / or said upper shell element has a capacity of extensibility and elastic recovery, so as to facilitate the application of prestress to said device. Said retaining strap and at least a portion of said shell can advantageously form a single piece made of a flexible material.

The device of the invention may in particular comprise processing means analyzing at least one physical constraint transmitted by said fluid to determine at least one of the information belonging to the group comprising: - at least one blood pressure information;

- at least one piece of information representative of the pulse;

- at least one piece of information representative of blood pressure;

- at least one piece of information representative of breathing; - at least one piece of information representative of the activity of said individual;

- at least one piece of information representative of a fall;

- at least one piece of information representative of the shape of the wave;

- at least one piece of information representative of the skin temperature in the wearing area;

- at least one worn / unworn device information;

- at least one piece of information representative of the development and / or the variance of one of said previous pieces of information.

This allows for a very large number of applications. The invention also relates to a sensor module in itself, intended to equip or cooperate with a device as described above.

Such a module comprises a flexible membrane, intended to come into contact with the skin of said individual and participating in the definition of a deformable space for a flexible substance, said substance transmitting to at least one sensor at least one physical constraint undergone by said membrane . It can for example then be added in a case of the wristwatch type.

The invention also relates to the method of manufacturing such a device for measuring at least one physiological item of information. This process advantageously comprises the following steps: - mounting the necessary electronic components on a support;

- joining of said membrane and of said support, defining a deformable space;

- injection of said substance into said space.

According to an advantageous embodiment, said substance is injected into said space in a liquid form. Preferably, said support is inserted into at least one housing defined in said membrane, and said membrane is assembled to a lower shell element, using at least one housing provided for this purpose on said membrane (self-maintenance). . The method advantageously comprises a step of assembling a shell formed from a lower shell element and an upper shell element. Said shell elements can in particular be secured by screwing and / or clipping and / or gluing.

Other characteristics and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment of the invention, given by way of simple illustrative and nonlimiting example, and of the appended drawings among which:

- Figure 1 shows a device according to the prior art, already commented on in the preamble; - Figures 2A and 2B are two overall views of a device according to the invention (excluding bracelet);

- Figures 3A and 3B are two exploded views of the device of Figures 2A and 2B;

- Figure 4 is a view of an embodiment of a membrane of the device of Figures 2A and 2B;

- Figure 5 is a sectional view of the membrane of Figure 4, secured to a printed circuit;

- Figures 6 and 7 are enlargements of two elements of the section of Figure 5; - Figure 8 illustrates in a simplified manner a method of manufacturing a device of Figures 2A and 2B.

The invention is therefore based on the use of flexible materials, making it possible to analyze one or more physiological information. These can then be analyzed, within the framework of several applications, such as for example the detection of falls or abnormal situations, or the monitoring of sleep phase. The embodiment described below relates to an intelligent multi-sensor assembly (“smart device”) making it possible to measure, process and analyze physiological phenomena such as the blood pressure wave, which is the source of several vital information, and including pulse, respiratory rate, blood pressure, and associated variances and waveform. This device also makes it possible to detect movements representative of the activity of the user, or wearer, as well as the skin temperature ...

As can be seen in FIGS. 2A and 2B, the device of the invention can be produced in the form of a case similar to that of a conventional watch, at least as regards its shape and its dimensions. As will be seen later, this device comprises a housing 21, a membrane 22, and a transparent upper surface 23, allowing the display of information, for example in the form of a liquid crystal screen. This information can in particular group together conventional information that is found on a watch, as well as physiological information, or corresponding alerts.

The implementation of the device of the invention therefore revolves around four main blocks, which appear more clearly in the exploded views of FIGS. 3A and 3B:

- a flexible membrane 22; - A substance, or a fluid, for the transmission of physical quantities to transducers, this fluid being confined in a space defined in particular by the membrane 22; transducers, mounted on an electronic card 24 (or support or printed circuit) carrying the various electronic amplification and filtering components necessary for signal conditioning, the processing unit, the communication interfaces, and the means delivering electrical energy (battery housed in the housing 25);

- a mechanical sub-assembly and a retaining strap (not shown). The first three blocks form the intelligent sensor assembly, which is encapsulated in the last block.

FIGS. 3A and 3B show the arrangement of these different blocks, according to an advantageous embodiment of the invention. The flexible membrane 22 forms with the electronic support 24, after assembly, a deformable cavity or space. The lower shell element 26 is secured to the membrane, as will be seen later, so as in particular to temporarily maintain the assembly.

The substance, or the fluid, is then injected at the initial liquid stage into this cavity, through an orifice provided for this purpose. This fluid will transmit the physical constraints outside the transducers, mounted on the electronic card 24, on the side of the cavity or drawing information from this cavity. This fluid becomes, at the final stage, in accordance with the characteristics set out below, and also makes it possible to reinforce to some extent the maintenance of the assembly.

This sub-assembly, formed of the membrane, the electronic unit, the fluid at the final stage, and possibly the lower shell, forms the essential part of the invention, or sensor module, which can then be put in place in a housing. . In the embodiment illustrated in FIGS. 3A and 3B, this sub-assembly is inserted into an upper shell 27. It is centered using the membrane 22, which also provides a seal for the assembly, a once assembled.

The anchoring strap (not shown) is preferably anchored on the upper shell 27. These two elements form the fixing block. Screws hold the sensor module to this fixing block. They also guarantee a slight compression of the upper part of the membrane, thus ensuring the tightness of the assembly.

Other types of joining, for example by clipping or by gluing, can of course be envisaged, in addition or as an alternative. According to the invention, the volume of the cavity defined by the membrane 22 and the support 24 remains constant or practically constant, and can deform, under the effect of an external mechanical stress. The assembly formed by the membrane and the substance must therefore have a deformable property. In this case, there is a transfer of energy between the external constraints and the assembly formed by the membrane and the substance giving rise to the appearance of phenomena perceptible by the transducers.

The substance is therefore preferably incompressible, or weakly compressible, so as not to absorb part of this energy. In order to allow a new distribution of the volume under the effect of a stress, the substance and the membrane must be deformable. In addition, at least one of these two elements must be elastic, in order to return to the equilibrium position. It can be either one and / or the other. In the case described below, both are. The embodiment of the membrane is illustrated in FIG. 4, and in the corresponding section view of FIG. 5. FIGS. 6 and 7 are enlargements of two parts of the section of FIG. 5.

This membrane, made of flexible material, and the substance therefore have an essential role in the implementation of the measuring principle. They indeed make it possible to capture the various external mechanical stresses (including their variations) generated in particular by the wave of arterial (or blood) pressure and by the relative movements of the device with respect to the body.

These stresses propagate through these two flexible elements towards the transducers carried by the support 24. It is the properties of the materials which allow the transmission of these external mechanical stresses to the transducers.

It is therefore noted that, compared to the prior techniques, there is no probe or piston. It is the "flexible belly" of the device which makes it possible to collect the information sought. The membrane is made up of several different stiffness zones. In the embodiment illustrated by FIGS. 4 to 7, there are 3 zones, each fulfilling a specific function:

a first zone 51 (FIG. 7) which is the most flexible zone, having the function of allowing external mechanical stresses to propagate towards the transducers. This area is located on the periphery of the membrane. In the illustrated embodiment, it is a variation in thickness which provides variations in flexibility. This first zone is in this case the finest; - A second zone 52 of rigidity greater than the first zone 51, making it possible to present a maximum of surface and thus to overcome the positioning problem of the device. This zone of higher rigidity makes it possible to avoid excessive deformation of the cavity, which could cause poor distribution of the substance. It can however be noted that the elasticity property of the fluid makes it possible to limit this problem; a third zone 53 (FIG. 6) which allows the membrane to be fixed with the other elements of the sensor. It makes integral, by its shape the electronic support and the membrane, using the groove 561. This groove makes it possible to seal the space receiving the substance, when the electronic support 24 is inserted in the groove 561 Furthermore, this third zone 56 makes it possible to seal the whole of the sensor / shell block, thanks to the slight stress exerted by the screws, after the lower shell element has been secured to the membrane at throat aid 562.

The membrane can advantageously be made of 60 ShoreA. Such a membrane gives good results, associated with the fluid mentioned below.

It will be noted that the variation in thickness of the membrane is only a particular embodiment, and that a similar result can be obtained, for example using several materials of different rigidity, for example by overmolding.

The membrane being in direct contact with the skin, it is preferably made of an allergenic material. The substance used is advantageously a gel. Its role is to allow the transmission of mechanical stresses, as well as to maintain the membrane in the correct operating position, and preferably to propagate temperature variations.

This substance must preferably be incompressible, elastic, chemically stable over time and have dielectric properties.

Advantageously, this fluid has a liquid character during manufacture, in order to be more easily injected. It then acquires its final state within the cavity. This change of characteristic is made without any clearance.

The dielectric nature makes it possible not to disturb the electrical operation of the electronic unit, and to protect it from contact with the membrane. This effectively protects electronic components from short circuits.

The elastic nature of the fluid must respect a compromise between the speed of return to the initial position, which must be high, and the amplitude of the resulting oscillation, so as to obtain a critical regime. An advantageous fluid is a silicone gel. It may especially be the silicone gel distributed by Dow Corning (registered trademark), reference Sylgard 527 (registered trademark).

In the embodiment described, the following information is particularly sought: - measurement of dynamic stresses (the blood pressure wave and the movements); measurement of static mechanical stresses (tightening); temperature measurement. For the measurement of static mechanical stress, when it is a question of guaranteeing a minimum static stress, the use of a tilting contact at a miniature pressure switch may be suitable. When a more precise measurement is necessary, a piezoresistive type sensor can be used, such as the MPX2300D sensor from Motorola (registered trademark). The measurement of the dynamic stress is preferably carried out using piezo-capacitive type transducers. This type of transducers associated with an appropriate electronic assembly makes it possible to efficiently convert the dynamic mechanical stresses picked up by the sensor block into information usable by the processing unit. The temperature measurement can advantageously be carried out using a PTC probe and an associated electronic assembly or using a commercial integrated sensor such as LM62 (registered trademark) or an equivalent. This type of sensor wired to the electronic support will allow skin temperature to be measured, except for inertia. FIG. 8 illustrates, in the form of a simplified flowchart, an embodiment of a method of manufacturing a device according to the invention.

According to this method, the electronic card (81) is first assembled, by conventionally mounting all the necessary electronic components thereon.

Then, this electronic card is secured (82) to the membrane, using the groove 561 (FIG. 6). There is then a space, or cavity, sealed, defined by this membrane 22 and the electronic card 24. The assembly formed by the membrane and the card are inserted in the lower shell element 26 which forms a base and the this assembly is held in place by groove 562.

The substance can then be injected (84), preferably in liquid form, through an opening provided for this purpose, into the housing defined by the membrane and the electronic card.

It then only remains to put in place (85) the upper shell element 27, or cover. It is easily attached to the membrane, thanks to the groove 562. provided for this purpose. Finally, stress screws are reported, which allow the two shell elements 26 and 27 to be joined to one another, and to strengthen the seal, by confining the edges of the membrane 22.

It will be noted that the operating range of the device is increased when the encapsulation assembly formed by the upper shell element and the bracelet has a capacity for extensibility and elastic recovery. This makes it easy to guarantee the application of a prestress, which may prove to be essential for proper operation. Failing to possess this property, the adjustment and therefore the obtaining of an adequate prestressing, can prove to be particularly difficult to carry out, even if it remains practicable. According to an advantageous embodiment, two parts are provided, the upper shell element 27, and the bracelet (not shown). According to this embodiment, it is the bracelet which has the property of extensibility. This can of course be limited to a portion of the bracelet. According to another approach, provision can be made for the upper shell element and the bracelet to form a whole, of which all or at least part, in contact with the skin, would be flexible.

Claims

1. Device for measuring at least physiological information in an individual, characterized in that it comprises a flexible membrane, intended to come into contact with the skin of said individual and participating in the definition of a deformable space for a substance flexible, said substance transmitting to at least one sensor at least one physical stress undergone by said membrane, said deformable space being defined by a support on which are mounted said sensor (s) and said membrane, so that said substance is in direct contact with said sensor (s).

2. Device according to claim 1, characterized in that said membrane comprises means for securing to said support.

3. Device according to claim 2, characterized in that said membrane defines at least one housing provided for receiving said support.

4. Device according to any one of claims 1 to 3, characterized in that said membrane comprises means for securing to a shell element of said device.

5. Device according to claim 4, characterized in that said membrane defines at least one housing provided for receiving said shell element.

6. Device according to any one of claims 3 to 6, characterized in that said securing means act by clipping.

7. Device according to any one of claims 1 to 6, characterized in that said membrane has at least two zones of different rigidities.

8. Device according to claim 7, characterized in that said membrane has a main contact zone, intended to come into contact with the skin of said individual, and a peripheral zone, extending over the contour of said main contact zone.

9. Device according to any one of claims 7 and 8, characterized in that each of said zones performs a distinct function, belonging to the group comprising the measurement of stresses, the transmission of stresses, the rigidity of the shape of said membrane.

10. Device according to any one of claims 7 to 9, characterized in that the thickness of said peripheral zone is less than the thickness of said main contact zone.

11. Device according to any one of claims 7 to 10, characterized in that said membrane is obtained by overmolding of at least two materials of different rigidities.

12. Device according to any one of claims 1 to 11, characterized in that said membrane is made of at least one anallergenic material.

13. Device according to any one of claims 1 to 12, characterized in that said membrane and / or said substance has an elastic character.

14. Device according to any one of claims 1 to 13, characterized in that said substance is an incompressible or weakly compressible material.

15. Device according to any one of claims 1 to 14, characterized in that said substance is a dielectric material.

16. Device according to any one of claims 1 to 15, characterized in that said substance is a silicone gel.

17. Device according to any one of claims 1 to 16, characterized in that it comprises at least one transducer for measuring at least one dynamic stress, representative of a blood pressure wave and / or of a movement relative.

18. Device according to any one of claims 1 to 17, characterized in that it comprises at least one transducer for measuring at least one static stress.

19. Device according to any one of claims 1 to 18, characterized in that it comprises a temperature sensor of said substance, representative of the skin temperature of said user.

20. Device according to any one of claims 1 to 19, characterized in that said sensor (s) comprise at least one piezo-capacitive sensor and / or at least one piezo-resistive sensor and / or at least one tilting contact at a predetermined pressure.

21. Device according to any one of claims 1 to 20, characterized in that said support is a printed circuit carrying electronic components for carrying out the amplification, conditioning, processing of electrical signals and / or a decision relating to a state of said carrier, means for supplying electrical energy and / or a communication interface.

22. Device according to any one of claims 1 to 21, characterized in that it comprises a shell formed of two complementary shell elements, a lower shell element carrying said membrane and an upper shell element.

23. Device according to claim 22, characterized in that said shell elements are secured by screwing and / or clipping and / or bonding, also ensuring sealing for said fluid.

24. Device according to any one of claims 22 and 23, characterized in that it comprises a retaining strap, secured to said upper shell element.

25. Device according to claim 24, characterized in that said retaining strap and / or said upper shell element has a capacity of extensibility and elastic recovery, so as to facilitate the application of prestressing to said device.

26. Device according to claim 25, characterized in that said retaining strap and at least a portion of said shell form a single piece made of a flexible material.

27. Device according to any one of claims 1 to 26, characterized in that it comprises processing means analyzing at least one physical stress transmitted by said fluid to determine at least one of the information belonging to the group comprising: - at least blood pressure information; - at least one piece of information representative of the pulse;

- at least one piece of information representative of blood pressure;

- at least one piece of information representative of breathing;

- at least one piece of information representative of the activity of said individual;

- at least one piece of information representative of a fall;

- at least one piece of information representative of the shape of the wave;

- at least one piece of information representative of the skin temperature in the wearing area. - at least one worn / unworn information;

28. Sensor module for device according to any one of claims 1 to 27, characterized in that it comprises a flexible membrane, intended to come into contact with the skin of said individual and participating in the definition of a deformable space for a flexible substance, said substance transmitting to at least one sensor at least one physical stress suffered by said membrane.

29. A method of manufacturing a device for measuring at least one physiological information according to any one of claims 1 to 27, characterized in that it comprises the following steps:

- mounting the necessary electronic components on a support;

- joining of said membrane and of said support, defining a deformable space;

- injection of said substance into said space.

30. The method of claim 29, characterized in that said substance is injected into said space in a liquid form.

31. Method according to any one of claims 29 and 30, characterized in that said support is inserted in at least one housing defined in said membrane.

32. Method according to any one of claims 29 to 31, characterized in that said membrane is assembled to a lower shell element, using at least one housing provided for this purpose on said membrane.

33. Method according to any one of claims 29 to 32, characterized in that it comprises a step of assembling a shell formed from a lower shell element and an upper shell element.

34. Method according to claim 33, characterized in that said shell elements are secured by screwing and / or clipping and / or gluing.