Piezoelectric actuation device with improved robustness

Abstract

The present disclosure relates to a piezoelectric actuation device comprising: a housing comprising a wall defining a cavity and having an upper edge, and a support mounted in the cavity, the support comprising: - o a upper wall which is deformable in bending, and - o a rigid side wall extending around and from the upper wall and forming, together with the upper wall, an internal recess; - a rigid push-button configured to move between: o a free position, in which the push-button is tangent to the upper edge, and o a stressed position in which the push-button bears against the side wall and deforms the upper wall of the internal recess; - a piezoelectric element positioned in the internal recess; and - a printed circuit accommodated in the internal recess and electrically connected to the piezoelectric element.

Description

[0001] Piezoelectric actuator device with improved robustness

[0002] TECHNICAL FIELD

[0003] The present invention relates to a waterproof and robust piezoelectric actuation device. More specifically, the invention relates to an actuation device operating in an environment subject to meteorological and physical disturbances which may disrupt normal operation.

[0004] STATE OF THE ART

[0005] Piezoelectric actuation devices are used in many applications, for example human-machine interfaces.

[0006] These actuation devices are based on the application of dynamic pressure to a piezoelectric element, the deformation of which results in the generation of an electrical voltage.

[0007] However, these actuating devices may be used on devices subject to significant shocks, acts of deliberate damage or bad weather such as rain, frost or high temperatures. Such events may cause malfunctions of these actuating devices, disturbances in the generation of electrical voltage or a fracture of an element constituting the actuating device.

[0008] Document FR 2 893 353 A1, in the name of the applicant, proposes a piezoelectric actuation device comprising a housing, an actuation wall and a piezoelectric element arranged in the housing.

[0009] But such a device cannot withstand significant impacts without breaking or deteriorating, the actuating wall being deformable, as is the part of the housing in contact with the piezoelectric element.

[0010] In addition, there is a significant need for sealing piezoelectric actuator devices to prevent water infiltration which could have consequences on the electrical operation of the switch but also on its deformation in the event of frost.

[0011] GENERAL STATEMENT

[0012] An aim of the disclosure is to solve at least one of the problems previously cited. To this end, according to one aspect of the present disclosure, there is provided a piezoelectric actuation device comprising: a housing comprising a wall defining a cavity and having an upper edge, a support mounted in the cavity and separating the cavity into an upper cavity, between the support and the upper edge, and a lower cavity, the support comprising: o an upper wall deformable in flexion, and o a rigid side wall extending around and from the upper wall and forming with the upper wall an internal housing; a rigid push button positioned in the upper cavity and configured to move between: o a free position, in which the push button is tangent to the upper edge, and o a constrained position in which the push button bears against the side wall and deforms the upper wall the internal housing;a piezoelectric element positioned in the internal housing and secured to the top wall; and a printed circuit housed in the internal housing and electrically connected to the piezoelectric element.;

[0013] This piezoelectric actuator protects the flexible upper wall of the housing from excessive pressure. Indeed, from a certain applied pressure, the rigidity of the actuator and the shoulder provided in the housing prevent further bending of the flexible part of the housing.

[0014] In addition, the actuation device exhibits significant robustness while allowing deformation of the piezoelectric element in order to generate a signal.

[0015] Advantageously, but optionally, the disclosed method comprises at least one of the following characteristics, taken alone or in any combination:

[0016] - the push button is irremovably connected to the upper wall of the support;

[0017] - the upper wall comprises an upper face and the push button comprises a contact face opposite the upper face, the upper face and the contact face are spaced from each other, when the push button is in the free position, by at least a first pin extending from the upper face or from the contact face; - the upper face of the upper wall comprises the first pin, said first pin being tubular, and the push button comprises a groove complementary to the first pin, such that the groove of the push button engages in the first pin of the upper wall;

[0018] - the device comprises a light source arranged in the lower cavity;

[0019] - the support is translucent and includes a lateral extension extending into the upper cavity around and from the upper wall to the upper edge, so that the support guides the light emitted by the light source towards the upper edge of the housing;

[0020] - the device includes a seal positioned between the push button and the upper wall;

[0021] - the piezoelectric element is fixed against the upper wall by a double-sided adhesive pad;

[0022] - the device comprises a compression spring, cylindrical in revolution and arranged in the internal housing between the printed circuit and the piezoelectric element (5), the electrical connection between the printed circuit and the piezoelectric element (5) being ensured by the spring;

[0023] - the housing is hermetically isolated from the lower cavity by a layer of resin;

[0024] - the support is in one piece.

[0025] DESCRIPTION OF FIGURES

[0026] Other characteristics, aims and advantages will emerge from the following description, which is purely illustrative and not limiting, and which must be read in conjunction with the attached drawings in which:

[0027] Figure 1 illustrates an exploded view of a piezoelectric actuator device according to one embodiment of the present disclosure;

[0028] Figure 2 illustrates an axial section of a piezoelectric actuator device according to an embodiment of the present disclosure;

[0029] Figure 3 illustrates an axial section of a piezoelectric actuator device according to a particular embodiment of the present disclosure; Figure 4 illustrates an exploded view of a luminous piezoelectric actuator device according to an embodiment of the present disclosure;

[0030] Figure 5 illustrates an axial section of a light piezoelectric actuator device according to one embodiment of the present disclosure.

[0031] Throughout the figures, identical elements have identical references.

[0032] DETAILED DESCRIPTION OF EMBODIMENTS

[0033] In the following description and unless otherwise specified, an axial direction corresponds to the direction of the longitudinal axis X, which is the direction of actuation of the device, and a radial direction is a direction perpendicular to the longitudinal axis X and intersecting the longitudinal axis X. Furthermore, an axial plane is a plane containing the longitudinal axis X and a radial plane is a plane perpendicular to the longitudinal axis X. A circumference is understood to be a circle belonging to a radial plane and whose center belongs to the longitudinal axis X. A tangential or circumferential direction is a direction tangent to a circumference: it is perpendicular to the longitudinal axis X but does not pass through the longitudinal axis X.We will call upper what is longitudinally on the side of a user with respect to the device and lower what is on the side opposite the user with respect to the device, in other words the side of the system to be controlled in which a device 1 is used. In the figures, the device is shown with its upper part at the top and its lower part at the bottom.

[0034] Furthermore, we will call deformable that which is capable of deforming elastically when pressure is exerted along the longitudinal axis X. More precisely, we will call deformable that which is capable of deforming in bending. And we will call rigid that which does not deform (or deforms by an amplitude less than a certain value less than that of the deformable element) under the application of the same force as that applied to the deformable element.

[0035] The piezoelectric actuating device 1 is, for example, a push button actuating a piezoelectric element. This device 1 is a modular device that can be used as such in a system to be controlled or combined with other switches to form a switching device incorporated in a human-machine interface in a system to be controlled.

[0036] Figure 1 illustrates the device 1 in exploded view along the longitudinal axis X. The device 1 comprises a housing 2 defining a cavity 23, a push button 3, a push button support 4 (hereinafter simply called support), a piezoelectric element 5 and a printed circuit 6. The push button 3, the support 4, the piezoelectric element 5 and the printed circuit 6 form a modular assembly independent of the housing 2 and which can be positioned, once assembled, in the cavity 23 of the housing 2.

[0037] The case

[0038] As illustrated in Figure 2, the housing 2 houses the other components of the device 1. The housing 2 allows the other components of the device 1 to be fixed to the system to be controlled on which the device 1 is implemented, such as, for example, a bicycle, a scooter, etc.

[0039] The housing 2 comprises a wall 21 delimiting the cavity 23. The wall 21 is preferably cylindrical and of circular section. It extends along the longitudinal axis X from a lower circular edge 213, forming a lower part of the device 1, to an upper edge 214, configured to be in contact with the exterior of the device 1. The upper edge 214 extends in a plane orthogonal to the longitudinal axis X.

[0040] The wall 21 comprises a concentric inner surface 211 and an outer surface 212. The wall 21 is rigid and non-deformable.

[0041] The wall 21 of the housing 2 may comprise a rigid shoulder 24. The shoulder 24 extends radially towards the inside of the cavity 23 from the internal surface 211. Advantageously, the shoulder 24 may allow positioning and locking of the support 4 in the cavity 23.

[0042] The housing 2 is preferably made of a metallic material.

[0043] Support

[0044] The support 4 can be positioned in the housing 2, as illustrated in Figure 2, in other words in the cavity 23. The support 4 then separates the cavity 23 into an upper cavity 231 and a lower cavity 232. The upper cavity 231 is between the support 4 and the upper rim 214.

[0045] The support 4 is made of a single piece. The support 4 comprises a flexurally deformable top wall 42 and a rigid side wall 41 extending around and from the top wall 42. The side wall 41 and the top wall 42 form an internal housing 411, in the housing 2.

[0046] The internal housing 411 is configured to house the piezoelectric element 5 and the printed circuit 6. The upper wall 42 therefore isolates the piezoelectric element 5 and the printed circuit 6 from the upper cavity 231 and thus makes it possible to protect the piezoelectric element

[0047] 5 and the printed circuit 6 from the outside and therefore from bad weather, shocks etc.

[0048] The support 4 can advantageously rest against the shoulder 24 of the housing 2, in other words on an upper part of the shoulder 24. Advantageously, the housing 2 can comprise a rim 43 at the intersection between the upper wall 42 and the side wall 41. The rim 43 can extend radially towards the outside of the support 4 and rest on the shoulder 24 of the housing 2 so as to position and block the support 4 in the cavity 23. The rim 43 can therefore have a contact surface with the shoulder 24 of the housing 2.

[0049] According to a particular embodiment, illustrated for example by figure 3, the contact surface between the rim 43 and the shoulder 24 of the housing 2 can form a truncated conical surface, around the longitudinal axis X. Such a surface makes it easier to position and robustness the device 1. Advantageously, the support 4 can comprise hooks 45. The hooks are configured to retain the support 4 in the housing 2 and thus prevent the support 4 from coming out of the housing 2 when it is subjected to extreme weather conditions.

[0050] The upper wall 42 comprises an external face 421 and an internal face 422 opening into the internal housing 411.

[0051] According to one embodiment, the external face 421 of the upper wall 42 comprises a pin 423 centered on the longitudinal axis X extending from the external face 421 advantageously into the housing 231. The pin 423 may be of hollow cylindrical shape and is advantageously centered on the longitudinal axis X. The pin allows the push button 3 to be fixed to the support 4.

[0052] The support 4 may advantageously be made of an opaque thermoplastic material, such as ABS, polyamide or polybutylene terephthalate (PBT).

[0053] Button

[0054] The push button 3 is housed in the cavity 23 of the housing 2. Preferably, the push button 3 is housed in the upper cavity 231. The push button 3 is preferably in the form of a rigid circular plate. The push button 3 comprises an external face 30 and an internal face 31. The external face 30 is configured to receive the contact of a user's finger. The external face 30 of the push button 3 forms an interface for access to the device 1 by the user and may be subject to regular degradation. The internal face 31 of the push button 3 is arranged facing the external face 421 of the upper wall 42.

[0055] The push button 3 is movable by sliding in the upper cavity 231 along the longitudinal axis X. By pressure exerted by an operator on the external face 30, the push button 3 can translate between a rest position, called the free position, in which the actuating device is inactive and a constrained position for actuating the device 1.

[0056] In the rest position of the push button 3, the external face 30 extends in a plane tangent to the upper edge 214 of the housing 2. In the constrained position, the push button 3 comes to bear against the rigid side wall 41 of the support 4 and deforms the upper wall 42 towards the internal housing 411. The longitudinal translation of the push button 3 is thus limited by the rim 43.

[0057] According to one embodiment, the contact face 31 of the push button 3 comprises a pin 33 centered on the longitudinal axis X and extending from the contact face 31 into the upper cavity 231.

[0058] According to another embodiment, the external face 421 of the upper wall 42 comprises a pin 423 centered on the longitudinal axis X extending from the external face 421, into the upper cavity 231.

[0059] According to another embodiment, the contact face 31 of the push button 3 comprises a pin 33 centered on the longitudinal axis X and extending from the contact face 31 into the upper cavity 231 and the external face 421 of the upper wall 42 comprises a groove complementary to the pin 33.

[0060] According to another embodiment, the external face 421 of the upper wall 42 comprises a pin 423 centered on the longitudinal axis X and extending from the external face 221 into the upper cavity 231 and the contact face 31 of the push button 3 comprises a groove 32 complementary to the pin 423.

[0061] According to a preferred embodiment, illustrated by Figure 2, the contact face 31 of the push button 3 comprises a groove 32 centered on the longitudinal axis X and the external face 421 of the upper wall 42 comprises a pin 423 extending into the upper cavity 231 towards the contact face 31. Preferably, the contact face of the push button 3 comprises, in addition to the groove 32 centered on the longitudinal axis X, a central pin 33 surrounded by the groove 32. The pin 423 of the upper wall 42 is advantageously a hollow cylinder configured to engage in the groove 32 and to receive the pin 33 of the contact face. Advantageously, the distance between the bottom of the groove 32 and the end of the pin 33 of the contact face is smaller than the height of the pin 423 of the upper wall 42.

[0062] Thus, in the free position, a space is provided between the contact face and the external face 421 of the upper wall 42 and, in the stressed position, the contact face can come to bear against the side wall 41 and the pin 423 of the upper wall 42 can bear against the contact face 31 and thereby cause the upper wall 42 of the support 4 to bend. According to a possible embodiment, the distance between the bottom of the groove 32 and the end of the pin 33 of the contact face is greater than the height of the pin 423 of the upper wall 42 and it is the pin 33 of the contact face 31 which causes the deformation of the upper wall 42, in the stressed position.

[0063] Preferably, the pin 423 is a hollow cylindrical pin extending along the longitudinal axis X and the groove 32 is complementary to the pin 423, so that the pin fits into the groove. The pin 423 and the groove 32, and possibly the pin 33 of the button, make it possible to connect the push button 3 to the upper wall 42 of the support 4.

[0064] Advantageously, the pin 423 and the pin 33 respectively comprise additional irremovable fixing means such as lugs or a non-return clip.

[0065] Thus, the push button 3 is integral with the housing 2 once mounted thereon. The push button 3 cannot be detached from the housing 2 without damaging the push button 3 and / or the housing 2.

[0066] Advantageously, the housing 2 further comprises a seal 7. The seal is positioned in the upper cavity 231, advantageously against the inner surface 211 of the side wall 21 and between the push button and the upper wall 42. The seal 7 is configured to protect the space between the contact face 31 of the push button 3 and the outer face 421 of the upper wall 42 from the intrusion of a foreign body such as water or dust. In addition, the seal 7 can prevent the movement of the push button 3 from the free position to the constrained position from being blocked, which would be due to the presence of a blocking element or in the event of frost which would transform infiltrated water into ice.

[0067] Piezoelectric element

[0068] As seen in Figure 2, the piezoelectric element 4 is positioned on the inner face 422 of the upper wall 42 of the support. The piezoelectric element 5 can therefore take the shape and undergo the deformations, in other words the bending, of the upper wall 42. Thus, the deformation of the upper wall 42 of the support caused by the pressure of the push button 3 in the constrained position, causes a deformation of the piezoelectric element

[0069] 5.

[0070] The piezoelectric element 5 is therefore fixed directly to the support 2. The piezoelectric element 5 is housed in an internal housing 411 and thus protected from the outside.

[0071] Preferably, the piezoelectric element 5 has the shape of a disc centered on the longitudinal axis X but it could have any other shape without departing from the scope of the invention.

[0072] The piezoelectric element 5 can be fixed to the internal face 422 of the upper wall 42 of the support 4 by means of a double-sided adhesive pad 51.

[0073] The piezoelectric element 5 is adapted to generate an electrical voltage under the effect of a dynamic pressure exerted via the upper wall 42.

[0074] The piezoelectric element 5 may thus comprise electrodes made of brass, silver and / or another electrically conductive material, covered with a layer of piezoelectric ceramic. For purely indicative purposes, a piezoelectric element marketed by the company Murata under the reference 7BB-12-9 may be used. Such a piezoelectric element 5 may comprise a brass plate with an external diameter of 12 mm and a thickness of 0.1 mm, forming the first electrode, covered with a layer of piezoelectric ceramic 9 mm in diameter. A second silver electrode 8 mm in diameter is arranged on the surface of the ceramic layer. The total thickness of this element is 0.22 mm.

[0075] The piezoelectric element 5 is configured to operate for a lifetime greater than about fifty million cycles, a cycle comprising the passage of the push button 3 from a free position to a constrained position and its return to the free position.

[0076] Thus, the device 1 makes it possible to convert mechanical energy given by a user who presses the push button 3 into electrical energy.

[0077] Printed circuit board

[0078] The printed circuit 6 is positioned in the cavity 23 of the housing 2. The printed circuit 6 is housed in the internal housing 411 of the support 2 and is thus also protected from the outside. Thus, the support 2, the piezoelectric element 5 and the printed circuit 6, as well as the push button 3 fixed to the support 2 form a modular assembly which can be positioned directly mounted in the housing 2. The printed circuit 6 is electrically connected to the piezoelectric element 5, as visible in Figure 2. The printed circuit 6 is equipped with components adapted to convert the voltage generated by the piezoelectric element and consequently establish a closed contact between two connection elements 61 (for example two electrical wires) between the piezoelectric element 5 and the system to be controlled. The switching time depends on the force and speed of pressing the push button 3.

[0079] The electrical connection between the piezoelectric element 5 and the printed circuit 6 is provided by one or two compression springs 9a, 9b which are made of electrically conductive material. The springs 9a, 9b are in contact, on the one hand, respectively with a first and a second electrode (not illustrated) present on the face of the piezoelectric element opposite the upper wall 42 of the housing and, on the other hand, with tracks of the printed circuit connecting the two connection elements 61.

[0080] According to a preferred embodiment, the springs 9a, 9b are coaxial. The first spring 9a, called the external spring, has a diameter greater than that of the second spring 9b, called the internal spring. Particularly advantageously, the external spring 9a has a diameter slightly smaller than that of the cylinder of the support, so that the cylinder also guides the external spring 9a.

[0081] Furthermore, the device 1 preferably comprises a retaining element 10 for the internal spring and a guiding element 11 for the external spring. For example, the retaining element may consist of an axial pin with a diameter slightly smaller than that of the internal spring 9b, around which the internal spring 9b is arranged. The guiding element for the external spring 9a may comprise a hollow cylinder in which the external spring 9a can slide. The guiding element and the retaining element ensure that the springs 9a, 9b are well positioned in contact with the electrodes of the piezoelectric element 5 during the assembly of the device 1 and more specifically of the support 4 of the piezoelectric element 5 and of the printed circuit 6 and that they remain so when the push button 3 is actuated. The assembly is particularly simple since it does not require any welding and can be automated.

[0082] Advantageously, the guide element 11 of the external spring 9a can allow the printed circuit 6 to be fixed in the internal housing 411.

[0083] Preferably, the printed circuit 6 is electrically connected to a system in which the housing 2 is housed, for example in the system to be controlled. The printed circuit 6 can be connected thereto by two conductors 61 sized according to the electrical needs of the device 1. Advantageously, the printed circuit 6 is configured to filter the voltage generated by the piezoelectric element so as not to generate a control signal by mistake, for example when the generated voltage is the result of an untimely shock on the system to be controlled on which the device 1 is implemented.

[0084] Backlighting

[0085] Advantageously, the device 1 may comprise a backlighting system, as seen in FIG. 4. The backlighting system comprises a light source 8.

[0086] The light source may comprise one or more light-emitting diodes (LEDs), for example LEDs of different colors.

[0087] The light source 8 is arranged in the cavity 23 of the housing 2, as visible in FIG. 5. More precisely, the light source 8 is housed in the internal cavity 232 of the housing 2.

[0088] The light source 8 comprises conductive wires 81 sized according to the electrical requirements of the device 1 and suitable for connecting the device 1 to the system to be controlled.

[0089] According to a preferred embodiment, the support 4 is translucent so as to be able to allow light to pass through it. In this case, the support 4 therefore also fulfills a light guide function from the light source to the upper face of the push button. A user can thus see the light emitted by the controlled light source turn on according to certain conditions.

[0090] Preferably, the support 4 comprises a lateral extension 44 in the upper cavity 231 around and from the upper wall 42. The lateral extension 44 forms a cylinder extending longitudinally from a plane tangent to the upper wall 42 and to a plane tangent to the upper edge 214 of the housing.

[0091] Thus, the support 4 extends longitudinally in the cavity 23 from the internal cavity 231 in which the light source 8 is housed and to the outside of the housing 2, i.e. to the upper edge 214 of the wall 21 of the housing. In other words, the support 4 forms an internal portion of the side wall of the housing from the internal cavity to the upper edge 214. The support 4 is thus capable of: allowing the light emitted by the light source in the cavity 23 to be visible from the outside at the push button 3, and more precisely, all around the push button, between the upper edge 214 of the wall 21 of the housing 2 and the push button 3; protecting the piezoelectric element 5 and the printed circuit 6 from the outside and from extreme conditions; and facilitate the mounting of the piezoelectric element 5, the printed circuit 6 and the push button 3 in the housing 2.

[0092] In this embodiment, the support is advantageously molded from a translucent thermoplastic material, such as polycarbonate.

[0093] Device 1 is suitable for operation in an environment subject to temperatures ranging from -40°C to +75°C and for withstanding intentional impacts. Device 1 has a robustness greater than IK06 according to the impact protection index (IK) according to standard EN 62-262.

[0094] The device 1 advantageously comprises a degree of sealing greater than IP69K according to the sealing protection index (IP).

[0095] The force required to move the push button 3 to the constrained position is between 1 and 10 N and preferably between 2 and 8 N. The movement of the push button 3 from the free position to the constrained position is between 0.10 mm and 0.50 mm and preferably 0.15 mm.

[0096] Assembly process

[0097] The assembly method comprises the placement, in the cavity 23 of the housing 2, of the support 4. The piezoelectric element 5 and the printed circuit 6 equipped with the connection elements and the electrical connection means such as, for example, the compression springs 9a, 9b could have been positioned beforehand in the support 4.

[0098] Then, in the embodiment according to which the device comprises a backlighting system, the light source 8 is installed in the lower cavity 232. Advantageously, resin 12, for example epoxy resin, can be injected into the lower cavity 232 in order to seal the device 1, except in the internal housing 411 which remains free of it. In the case of a device 1 with a backlighting function, transparent resin 12, for example transparent silicone resin, can be injected into the internal cavity 232 between the support 4 and the light source 8, in order to seal the device 1 and protect the support 4 while allowing the passage of light. Resin 12, for example epoxy resin, can be injected into the other part of the internal cavity 232.

[0099] Furthermore, the seal 7 and the push button 3 are placed in the lower cavity 231, by clipping onto the upper wall 42 of the support 4. The push button 3 can be fixed onto the upper wall 42 of the support 4 before positioning the support 4 in the housing 2. When the device is assembled, the springs 9a, 9b are in the free or slightly stressed state.

[0100] Thus, when the push button 3 is at rest, the springs do not apply significant stress but are only stressed so as to ensure contact with the piezoelectric element 5, which prevents it from being damaged.

[0101] When dynamic pressure is exerted on the push button 3, the latter presses on the upper wall 42, the springs can compress while ensuring the electrical connection between the electrodes of the piezoelectric element 5 and the printed circuit 6, and this without degradation of the piezoelectric element. The presence of the shoulder 43 makes it possible, among other things, in the case where abnormally high dynamic pressure is exerted on the push button 3 (for example in the event of an act of vandalism), to avoid damage to the piezoelectric element, by blocking the deformation of the upper wall 42 by the push button 3 pressing on the shoulder 43.

[0102] Thus, the device according to the invention is particularly suitable for use in environments which require increased protection against intentional damage.

Claims

CLAIMS 1. Piezoelectric actuation device (1) comprising: a housing (2) comprising a wall (21) defining a cavity (23) and having an upper edge (214), a support (4) mounted in the cavity (23) and separating the cavity into an upper cavity (231), between the support (4) and the upper edge (214), and a lower cavity (232), the support (4) comprising: o an upper wall (42) deformable in flexion, and o a rigid side wall (41) extending around and from the upper wall (42) and forming with the upper wall (42) an internal housing (411); a rigid push button (3) positioned in the upper cavity (231) and configured to move between: o a free position, in which the push button (3) is tangent to the upper edge (214), and o a constrained position in which the push button (3) bears against the side wall (41) and deforms the upper wall (42) the internal housing (411);a piezoelectric element (5) positioned in the internal housing (411) and fixed to the upper wall (42); and a printed circuit (6) housed in the internal housing (411) and electrically connected to the piezoelectric element (5).; 2. Device (1) according to claim 1, wherein the push button (3) is irremovably connected to the upper wall (42) of the support (4).

3. Device (1) according to any one of claims 1 to 2, in which the upper wall (42) comprises an upper face (421) and the push button (3) comprises a contact face (31) opposite the upper face (421), the upper face (421) and the contact face (31) are spaced from each other, when the push button (3) is in the free position, by at least one first pin (423, 33) extending from the upper face (421) or from the contact face (31).

4. Device (1) according to claim 3, in which the upper face (421) of the upper wall (42) comprises the first pin (423), said first pin being tubular, and the push button (3) comprises a groove (32) complementary to the first pin (423), such that the groove (32) of the push button (3) engages in the first pin (423) of the upper wall (42).

5. Device (1) according to any one of claims 1 to 4, comprising a light source (8) arranged in the lower cavity (232).

6. Device (1) according to claim 5, wherein the support (4) is translucent and comprises a lateral extension (44) extending into the upper cavity (231) around and from the upper wall (42) to the upper edge (214), so that the support (4) guides the light emitted by the light source (8) towards the upper edge (214) of the housing (2).

7. Device (1) according to any one of claims 1 to 6, comprising a seal (7) positioned between the push button (3) and the upper wall (42).

8. Device (1) according to any one of claims 1 to 7, in which the piezoelectric element (5) is fixed against the upper wall (42) by a double-sided adhesive pad (51).

9. Device (1) according to any one of claims 1 to 8, comprising a compression spring (9a, 9b), cylindrical in revolution and arranged in the internal housing (411) between the printed circuit (6) and the piezoelectric element (5), the electrical connection between the printed circuit (6) and the piezoelectric element (5) being ensured by the spring (9a, 9b).

10. Device (1) according to any one of claims 1 to 9, in which the housing (232) is hermetically isolated from the lower cavity (232) by a layer of resin (12).

11. Device (1) according to any one of claims 1 to 10, in which the support (4) is in one piece.

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