Electromagnetic non-acoustic alarm

Abstract

The present invention relates to a non-acoustic alarm (100) for portable objects, comprising an electromagnetic motor device (200) which can be electrically controlled so as to generate a vibration effect, characterized in that the electromagnetic motor device comprises a movable magnetic circuit (210) and a fixed magnetic circuit (220); said movable magnetic circuit comprises a coil (211) and a ferromagnetic core portion (212) coupled to a magnetic cage (213) forming an extension of the ferromagnetic core portion; the magnetic assembly of said movable magnetic circuit constitutes a movable magnetic mass of said non-acoustic alarm (100) capable of generating said vibration effect; and it comprises a resilient connection element (60) which elastically connects the movable magnetic circuit (210) to the fixed magnetic circuit (220), shaped so as to guide and ensure that the movable magnetic circuit (210) undergoes a linear or quasi-linear oscillating movement during the electrical control of the electromagnetic motor device (200).

Description

Technical Field

[0001] This invention relates to a non-audible alarm for portable objects.

[0002] More specifically, the present invention relates to a small, non-audible alarm based on vibration and resonance, suitable for integration into a thin, portable object (e.g., a clock).

[0003] The present invention also relates to a portable object including such a non-audible alarm, such as a clock, and in particular a wristwatch. Background Technology

[0004] Traditional alarm clocks, mounted on portable objects, especially clocks, can provide sound information, such as that associated with events and / or time, by emitting sounds selected from a specific range or tone.

[0005] The main drawback of these alarms is that they are audible and can be perceived by the user's environment.

[0006] Furthermore, this type of sound alarm clock does not allow for the differentiation of the user's (wearer's) portable object from other portable objects belonging to people in the same environment.

[0007] Therefore, it should be understood that these sound alarms have several drawbacks: they are too conspicuous and can be perceived by people other than the user, which may be problematic in some environments; they do not allow the wearer to distinguish his / her portable object from other portable objects in the same environment, such as in a group of people.

[0008] To overcome this problem, silent, so-called noiseless vibration alarms have been proposed. These alarms include a motor that drives a mass body, configured to provide a vibrational effect that can be transmitted to the user. The advantage of this vibration is that it is only perceived by the user, allowing it to be less noticeable and less disruptive to people in the user's environment when triggered, such as upon waking, when a phone call comes in, or for information about a time change.

[0009] Such a non-audible alarm is disclosed, for example, in European Patent Document No. 0349230. The alarm includes a piezoelectric motor that rotates an eccentric counterweight movably mounted on a shaft.

[0010] However, due to the coaxial configuration of the alarm, it occupies a relatively large space, requiring a specific arrangement or even a complete overhaul of the clock to install it, which is problematic.

[0011] In addition, this type of non-audible alarm requires the use of a piezoelectric motor, and the manufacture of piezoelectric motors involves relatively complex technology.

[0012] To address this issue, European Patent Document No. 0625738A1 discloses a non-audible alarm developed with a simpler design, smaller overall size, and lower manufacturing cost.

[0013] The non-audible alarm device described in European Patent Document No. 0625738A1 includes an electromagnetic motor fixedly mounted on a support, which moves a mass to provide a vibration effect, the mass undergoing a quasi-linear oscillating motion.

[0014] This non-audible alarm consumes approximately 10mW.

[0015] However, in the field of portable objects, there is always a need to improve the design, overall size and / or power consumption of various components of portable objects (such as alarms, in particular), especially to improve the lifespan of portable objects by minimizing the power consumption of the various components that make up the portable object. Summary of the Invention

[0016] In this context, the present invention aims to provide a solution to at least one of the above-mentioned problems.

[0017] Specifically, the present invention aims to provide a simplified design of a non-audible alarm that can be easily integrated into portable objects, particularly clocks, without requiring significant structural modifications, and can be manufactured at low cost, for example, through high-speed, automated operation, with reduced power consumption.

[0018] In this context, the present invention relates to a non-audible alarm for portable objects, comprising an electromagnetic motor capable of being electrically controlled to produce a vibration effect, the non-audible alarm being characterized in that:

[0019] - The electromagnetic motor device includes a movable magnetic circuit and a fixed magnetic circuit; the movable magnetic circuit includes a coil and a ferromagnetic core, the ferromagnetic core being magnetically coupled to a magnetic cage forming an extension of the ferromagnetic core; the magnetic components of the movable magnetic circuit constitute a movable magnetic mass body of the non-audible alarm capable of producing the vibration effect;

[0020] - The non-audible alarm includes an elastic connecting element that elastically connects a movable magnetic circuit to a fixed magnetic circuit. This elastic connecting element is shaped to guide and ensure that the movable magnetic circuit undergoes linear or quasi-linear oscillating motion during the electronic control of the electromagnetic motor device.

[0021] In addition to the features mentioned above, the electromagnetic non-audible alarm according to the present invention may have one or more of the following supplementary features, which may be considered individually or in any technically feasible combination:

[0022] - A fixed magnetic circuit consists of two elements made of magnetic material;

[0023] - The two components, made of magnetic material, are permanent magnets;

[0024] - The fixed magnetic circuit includes a shunt to close the magnetic flux induced at the fixed magnetic circuit by the coil of the movable magnetic circuit;

[0025] - Flexible connecting elements are support components that accommodate both fixed and movable magnetic circuits;

[0026] - The support includes a fixed part that receives a fixed magnetic circuit and a movable part that receives a movable magnetic circuit. An elastic connecting element mechanically connects the movable part of the support to its fixed part, while guiding the movable magnetic circuit and ensuring that it undergoes linear or quasi-linear oscillating motion during the electronic control of the electromagnetic motor device.

[0027] - The fixing part of the support includes a fastening device that enables the fixing part of the support to be integrated with the portable object.

[0028] - The support member is formed by a lower half-shell and an upper half-shell, which are shaped to encapsulate the movable magnetic circuit and the fixed magnetic circuit of the electromagnetic motor device.

[0029] - Each half-shell of the support includes two lateral elastic tabs forming an elastic connecting element, the two lateral elastic tabs being configured laterally located on both sides of the electromagnetic motor device;

[0030] - The magnetic cage includes two branches that form pole shoes, and these two branches are configured to guide the magnetic field induced by the coil in the vicinity of the fixed magnetic circuit;

[0031] - The ferromagnetic core and the two branches forming the pole shoes, together with the fixed magnetic circuit, define the air gap. e The air gap e The extension of linear or quasi-linear oscillating motion perpendicular to the movable magnetic circuit;

[0032] - The non-audible alarm includes an electronic control unit configured to power a coil so that a movable magnetic circuit oscillates at its resonant frequency;

[0033] - The resonant frequency of the movable magnetic circuit is determined by the geometry of the elastic connecting element and the mass of the movable magnetic circuit;

[0034] - The geometry of the flexible connecting element and the movable magnetic circuit are configured such that the resonant frequency of the movable magnetic circuit is between 120Hz and 250Hz. This frequency range corresponds to the frequency that the user's wrist can best feel;

[0035] - The non-audible alarm includes an electronic control unit configured to power a coil so that a movable magnetic circuit oscillates at a selected frequency between 120 Hz and 250 Hz.

[0036] The present invention also relates to a portable object comprising a non-audible alarm according to the present invention.

[0037] Preferably, the portable object is a clock, such as a wristwatch. Attached Figure Description

[0038] The objects, advantages, and features of the invention will be better understood after reading the following detailed description given with reference to the accompanying drawings:

[0039] - Figure 1 This is a schematic overall perspective view illustrating an example embodiment of a non-audible alarm according to the present invention;

[0040] - Figure 2 It shows Figure 1 The exploded view of the non-audible alarm shown allows observation of the various components of the non-audible alarm according to the present invention;

[0041] - Figure 3 It shows Figure 1 A cross-sectional view of the non-audible alarm 100 shown along the intermediate cutting plane M1;

[0042] - Figure 4 yes Figure 3 Detailed views, particularly showing the different polarities of the magnetic circuit of the electromagnetic motor when the coil receives a positive power supply;

[0043] - Figure 5 yes Figure 3 Detailed views, particularly showing the different polarities of the magnetic circuit of the electromagnetic motor when the coil receives a negative power supply;

[0044] - Figure 6 It is a graph showing an example of powering an electromagnetic motor device of a non-audible alarm according to the invention to produce a vibration effect that is perceptible to the user.

[0045] - Figure 7 It is integrated Figure 1 The diagram shows a clock of a non-sound alarm according to the present invention.

[0046] In all the accompanying drawings, unless otherwise stated, the same elements have the same reference numerals. Detailed Implementation

[0047] Figure 1This is a perspective view schematically showing an example embodiment of a non-audible alarm 100 according to the present invention.

[0048] Figure 2 It shows Figure 1 The exploded view of the non-audible alarm 100 shown allows observation of the various components of the non-audible alarm.

[0049] Figure 3 It shows Figure 1 The non-audible alarm 100 shown Figure 1 The cross-sectional view shown is taken from the intermediate cutting plane M1.

[0050] The non-audible alarm 100 according to the present invention is an electromagnetic type non-audible alarm, which includes an electromagnetic motor device 200, which can be electrically controlled to move a movable part so as to generate a vibration effect through the oscillation of the movable part.

[0051] The non-audible alarm 100 according to the invention is particularly suitable for installation on small portable objects such as clocks 1.

[0052] By way of example, this clock 1 is Figure 7 It is shown schematically in the middle.

[0053] The watch 1 includes a case 2, which consists of a central part 3 and a back cover 4 conventionally fastened to the central part 3. The case 2 defines an interior space 5 configured to receive the watch movement (not shown) and a non-audible alarm 100 according to the invention.

[0054] The clock 1 also includes a power source, such as a battery (not shown), configured to power at least the non-audible alarm 100 according to the invention.

[0055] Preferably, a power supply is electrically connected to an electronic control unit 50, which is configured to drive an electromagnetic motor 200 of a non-audible alarm 100 according to the invention.

[0056] Now refer to Figures 1 to 3 The non-audible alarm 100 according to the invention, which is installed on clock 1, is described in more detail.

[0057] The non-audible alarm 100 includes:

[0058] - Support member 10, which may include a dedicated fastening device 70 that allows the non-audible alarm 100 to be fastened to the watch 1;

[0059] - Electronic control unit 50, which can be electrically connected to a power source provided with the portable object;

[0060] - An electromagnetic motor device 200 capable of generating a vibration effect, which is electrically connected to an electronic control unit 50.

[0061] The electromagnetic motor device 200 is electrically controlled by the electronic control unit 50 to move the movable part so as to obtain a vibration effect that can be perceived by the user wearing the watch 1 or a portable object, for example, through the back cover 4 which is in contact with the user.

[0062] The electronic control unit 50 is configured to excite the electromagnetic motor device 200 to the resonant frequency or a frequency close to the resonant frequency of the non-audible alarm 100.

[0063] Preferably, the electronic control unit 50 is configured to excite the electromagnetic motor device 200 and generate vibrations with a frequency between 120Hz and 250Hz.

[0064] The electromagnetic motor device 200 includes a magnetic circuit consisting of a movable magnetic circuit 210 and a fixed magnetic circuit 220. The movable magnetic circuit 210 and the fixed magnetic circuit 220 are supported by a support member 10.

[0065] The support member 10 is a multifunctional component, which includes fixed portions 11a and 11b that support the fixed magnetic circuit 220. The fixed portions 11a and 11b of the support member 10 also support the electronic control unit 50.

[0066] The fixed magnetic circuit 220 is integrally formed with the fixed portions 11a, 11b of the support member 10, for example, by means of a fastening device (e.g., by electric welding called spot welding).

[0067] The support member 10 also includes movable portions 12a and 12b formed to support the movable magnetic circuit 210.

[0068] The movable magnetic circuit 210 is integrally formed with the movable parts 12a and 12b of the support member 10 by a fastening device (e.g., by electric welding called spot welding).

[0069] The fixing portions 11a and 11b of the support member 10 are intended to be integrated with the watch, for example, at the back cover 4 of the watch 1, by means of threaded connection or adhesive.

[0070] like Figure 2 As shown, the fixing portions 11a and 11b of the support member 10 cooperate with the screw-type fastening device 70 so that the fixing portions 11a and 11b of the support member 10 become one with the clock 1.

[0071] The electronic control unit 50 is integrated with the fixed portions 11a and 11b of the support member 10, for example, by bonding or by a fastening device 70 that allows the support member 10 to be integrated with the clock 1.

[0072] The support member 10 also includes an elastic connecting element 60 that mechanically connects the movable portions 12a, 12b and the fixed portions 11a, 11b of the support member 10. The elastic connecting element 60 is formed of thin elastic flexible strips 60a, 60b, which extend in a plane perpendicular to the plane formed by the fixed portions 11a, 11b and the movable portions 12a, 12b of the support member 10 and parallel to the intermediate plane M1.

[0073] The elastic connecting element 60 is configured to provide support to the movable portions 12a, 12b of the support member 10, thereby providing support to the movable magnetic circuit 210, particularly in the z and y directions, while allowing the movable magnetic circuit 210 to be laterally displaced in the x direction by translational movement.

[0074] The elastic connecting element 60 is shaped to be flexible in a given direction (in this case, the x-direction) so as to allow the movable magnetic circuit 210 to... Figure 1 The oscillations, indicated by arrow D, in the transverse direction relative to the fixed magnetic circuit 220 are linear or quasi-linear.

[0075] In other words, the shape and arrangement of the elastic connecting element 60 relative to the movable magnetic circuit 210 and the fixed magnetic circuit 220, as well as the support member 10, allow the movable magnetic circuit 210 to make a lateral displacement relative to the fixed magnetic circuit 220, which is essentially a translation in the x-direction, under the control of the electronic control unit 50.

[0076] The elastic connecting element 60 is a flexible strip that is fixedly connected to the support member 10 or formed integrally with the support member 10.

[0077] The elastic connecting element 60 is located on both sides of the movable magnetic circuit 210.

[0078] The resilient connecting element 60 also has a resilient reset function, which is biased to allow the movable magnetic circuit 210 to return to a resting equilibrium position without applying any electrical load to the electromagnetic motor device 200.

[0079] For example, each resilient connecting element 60 consists of a lower tab 60a and an upper tab 60b, which are arranged symmetrically about the intermediate plane M1 at each edge of the electromagnetic motor device 200, thereby dividing the non-audible alarm 100 into two parts along the height.

[0080] The support member 10 is advantageously made of two separate components forming a lower half-shell 10a and an upper half-shell 10b, which are configured to encapsulate and hold the electromagnetic motor assembly 200, more specifically, the movable magnetic circuit 210 and the fixed magnetic circuit 220. Each half-shell 10a, 10b includes two lateral elastic tabs 60a, 60b forming the aforementioned elastic connecting element 60. Thus, the symmetrically arranged elastic tabs 60a, 60b are located laterally on both sides of the upper and lower portions of the electromagnetic motor assembly 200. Therefore, this configuration avoids displacement along the z-axis due to the elastic deformation of the elastic tabs 60a, 60b.

[0081] The half-shells 10a and 10b of the support member 10 are made of, for example, flat (e.g., metal) thin plates, and the elastic tabs 60a and 60b are integral with the fixed portions 11a and 11b and the movable portions 12a and 12b of the support member 10.

[0082] The movable magnetic circuit 210 includes a ferromagnetic core 212 and a coil 211 wound on the ferromagnetic core 212 in a conventional manner.

[0083] The ferromagnetic core 212 is coupled to the magnetic cage 213 at one of its magnetic poles, such that the magnetic cage 213 forms an extension of the ferromagnetic core 212. The ferromagnetic core 212 is integrally formed with the magnetic cage 213 by a dedicated fastening device (e.g., by a screw element 216).

[0084] The magnetic components of the movable magnetic circuit 210 are heavy enough to form a movable mass body capable of producing a vibration effect that can be perceived by the user.

[0085] exist Figures 1 to 3 In the example embodiments shown, and especially in Figure 2 As can be seen, the ferromagnetic core 212 and the magnetic cage 213 are separate; however, the ferromagnetic core 212 and the magnetic cage 213 can be integrated. Separate production makes it easier to wind the coil 211 onto the ferromagnetic core 212.

[0086] According to the present invention, the vibrating movable mass of the non-audible alarm 100 is formed by the movable magnetic circuit 210 of the magnetic circuit of the electromagnetic motor device 200. Therefore, the vibrating mass belongs to the magnetic circuit of the non-audible alarm 100.

[0087] In other words, the movable magnetic circuit 210 also acts as a movable mass of the vibration system, which makes it unnecessary in the non-audible alarm 100 according to the invention to have a specific additional mass, for example, made of a non-magnetic metal, which is mechanically connected to a part of the magnetic circuit and thus only acts as a vibrating mass and does not contribute to the magnetic circuit of the electromagnetic motor device.

[0088] Therefore, unlike the solutions of the prior art, the movable mass of the non-audible alarm 100 according to the present invention is a magnetic or ferromagnetic mass, which also constitutes the movable magnetic circuit 210 of the electromagnetic motor device 200.

[0089] The fixed magnetic circuit 220 includes two elements 221 and 222 made of magnetic material.

[0090] Preferably, the two elements made of magnetic material are permanent magnets.

[0091] Each permanent magnet 221, 222 has a permanent north-south magnetization axis (denoted as NS) perpendicular to the translational orientation of the movable magnetic circuit 210. The two permanent magnets 221, 222 have magnetization axes that are opposite to each other.

[0092] The fixed magnetic circuit 220 also includes a shunt 223 to close the magnetic flux at the fixed magnetic circuit 220 and keep magnetic leakage to a minimum. This optimizes the performance of the non-audible alarm.

[0093] The magnetic cage 213 includes two parallel branches 214 and 215, which are located laterally on both sides of the coil 211 and extend toward the fixed magnetic circuit 220.

[0094] Two branches 214 and 215 form the pole shoes of the ferromagnetic core 212 of the coil 211. These pole shoes are configured to guide the magnetic flux of the movable magnetic circuit 210 induced by the coil 211 near the fixed magnetic circuit 220 and more specifically near the permanent magnets 221 and 222.

[0095] Two branches 214 and 215 extend relative to permanent magnets 221 and 222.

[0096] The two branches 214 and 215 and the ferromagnetic core 212 together with the permanent magnets 221 and 222 define the air gap. e The air gap e Lateral displacement extension perpendicular to the movable magnetic circuit 210.

[0097] Operation of the non-audible alarm according to the present invention

[0098] Under the control of the electronic control unit 50, the coil 211 can be powered and generate magnetic flux, which can flow in the ferromagnetic core 212 and propagate to the magnetic cage 213 at the pole shoes 214 and 215, and can also be transmitted through the air gap. e It is closed by passing through permanent magnets 221, 222 and shunt 223.

[0099] When coil 211 receives a positive power supply, for example, in the form of a pulse, such as Figure 6 As shown, the ferromagnetic core 212 and the two branches of the magnetic cage 213 are polarized, as... Figure 4As shown. Different polarities interact with the polarities of permanent magnets 221 and 222, causing magnetic poles of the same sign to repel each other, while magnetic poles of opposite signs to attract each other, thereby generating a magnetic force that causes the movable magnetic circuit 210 to translate laterally to the left in the x-direction under the action of the permanent magnet polarities.

[0100] When coil 211 receives, for example Figure 6 When a negative power supply in the form of a pulse is applied, the polarity is reversed and the movable magnetic circuit 210 is transversely translated to the right in the x-direction under the influence of the permanent magnet's polarity, as shown. Figure 5 As shown.

[0101] Therefore, under the influence of alternating current, the movable magnetic circuit 210, guided by the elastic connecting element 60, will alternately shift laterally left and right in a translational motion in the x-direction. This shift will apply stress to the elastic connecting element 60, which will then return the movable magnetic circuit 210 to its initial position through elastic reset effects, thereby oscillating around the initial equilibrium or resting position through back-and-forth lateral translational motion. Thus, by selecting an appropriate power supply in terms of frequency and amplitude, a vibration effect perceptible to the wearer can be generated within the watch case 2 of the watch 1.

[0102] Advantageously, the electronic control unit 50 is configured to generate pulses in the form of alternating pulses, such as... Figure 6 The power supply provided to coil 211, as illustrated by example, maintains the oscillating motion of movable magnetic circuit 210, and the pulse compensates for the attenuation of the oscillating motion of movable magnetic circuit 210.

[0103] The non-audible alarm 100 according to the present invention and as described above has a small overall size, which makes it ideal for watch applications because its shape is essentially flat and thin, allowing it to be easily integrated into the watch case without any major modifications to other components. For reference only, such a non-audible alarm according to the present invention can be manufactured with an overall height of approximately 3 mm.

[0104] In particular, by eliminating the dedicated movable mass made of non-magnetic metal, the overall size and weight are reduced.

[0105] The non-audible alarm according to the invention features an optimized magnetic design with pole shoes and a shunt, which prevents magnetic leakage and optimizes magnetic efficiency. Therefore, the power consumption of this alarm is optimized and reduced. For reference only, the measured power consumption of this non-audible alarm is less than 10mW.

[0106] The inverted structure of the movable coil type of the non-audible alarm according to the present invention allows for the reduction of power consumption of such a non-audible alarm by moving the magnetic circuit portion including the coil, without the need to move a dedicated non-magnetic heavy mass.

[0107] Finally, compared to existing solutions, the proposed inverted structure avoids the need for a specific mass body, such as one made of tungsten. This also reduces the manufacturing cost of this non-audible alarm.

Claims

1. A non-audible alarm (100) for a portable object (1), the non-audible alarm (100) comprising an electromagnetic motor device (200) electrically controllable to produce a vibration effect, the non-audible alarm (100) being characterized in that: The electromagnetic motor device (200) includes a movable magnetic circuit (210) and a fixed magnetic circuit (220); the movable magnetic circuit (210) includes a coil (211) and a ferromagnetic core (212), the ferromagnetic core (212) being coupled to a magnetic cage (213) forming an extension of the ferromagnetic core (212); the magnetic components of the movable magnetic circuit (210) constitute a movable magnetic mass body of the non-audible alarm (100) capable of producing the vibration effect; The non-audible alarm (100) includes an elastic connecting element (60) that elastically connects the movable magnetic circuit (210) to the fixed magnetic circuit (220), the elastic connecting element (60) being shaped to guide and ensure that the movable magnetic circuit (210) undergoes linear or quasi-linear oscillating motion during the electrical control of the electromagnetic motor device (200). The elastic connecting element (60) is a support member (10) that receives the fixed magnetic circuit (220) and the movable magnetic circuit (210). The support member (10) includes a fixed portion (11a, 11b) receiving the fixed magnetic circuit (220) and a movable portion (12a, 12b) receiving the movable magnetic circuit (210). The elastic connecting element (60) mechanically connects the movable portion (12a, 12b) of the support member (10) to the fixed portion (11a, 11b) of the support member (10), while guiding the movable magnetic circuit (210) and ensuring that the movable magnetic circuit (210) undergoes linear or quasi-linear oscillating motion during the electrical control of the electromagnetic motor device (200). The fixing portion (11a, 11b) of the support member (10) includes a fastening device (70) that enables the fixing portion (11a, 11b) of the support member (10) to be integrated with the portable object (1).

2. The non-audible alarm (100) for a portable object (1) according to claim 1, characterized in that, The fixed magnetic circuit (220) includes two elements (221, 222) made of magnetic material.

3. The non-audible alarm (100) for a portable object (1) according to claim 2, characterized in that, The two elements (221, 222) made of magnetic material are permanent magnets.

4. The non-audible alarm (100) for a portable object (1) according to claim 3, characterized in that, The fixed magnetic circuit (220) includes a shunt (223) to close the magnetic flux at the fixed magnetic circuit (220).

5. The non-audible alarm (100) for a portable object (1) according to any one of claims 1-4, characterized in that, The support member (10) is formed by a lower half shell (10a) and an upper half shell (10b), which are shaped to encapsulate the movable magnetic circuit (210) and the fixed magnetic circuit (220) of the electromagnetic motor device (200).

6. The non-audible alarm (100) for a portable object (1) according to claim 5, characterized in that, The upper and lower half of the support member (10) each include two lateral elastic tabs forming the elastic connecting element (60), the two lateral elastic tabs being configured to be located on both sides of the electromagnetic motor device (200) in the lateral direction.

7. The non-audible alarm (100) for a portable object (1) according to any one of claims 1-4, characterized in that, The magnetic cage (213) includes two branches (214, 215) forming pole shoes, which are configured to guide the magnetic flux induced by the coil (211) in the vicinity of the fixed magnetic circuit (220).

8. The non-audible alarm (100) for a portable object (1) according to claim 7, characterized in that, The ferromagnetic core (212) and the two branches (214, 215) forming the pole shoe together with the fixed magnetic circuit (220) define an air gap (e), which extends perpendicular to the linear or quasi-linear oscillating motion of the movable magnetic circuit (210).

9. The non-audible alarm (100) for a portable object (1) according to any one of claims 1-4, characterized in that, The non-audible alarm (100) includes an electronic control unit (50) configured to power the coil (211) so that the movable magnetic circuit (210) oscillates at its resonant frequency.

10. A non-audible alarm (100) for a portable object (1) according to any one of claims 1-4, characterized in that, The non-audible alarm (100) includes an electronic control unit (50) configured to power the coil (211) so that the movable magnetic circuit (210) oscillates at a selected frequency between 120 Hz and 250 Hz.

11. A portable object (1) comprising a non-audible alarm (100) according to any one of claims 1-10.

12. The portable object (1) according to claim 11, characterized in that, The portable object is a clock.

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