Micromechanical temperature sensing device

Abstract

The invention relates to a micromechanical temperature detection device (2), comprising:- a frame (4) comprising a first frame part and a second frame part,- an indicator (5),- at least one frangible junction portion connecting the indicator (5) to the first frame part so as to maintain the indicator (5) in a first initial position,- an elastic return structure (61) capable of exerting a return force on the indicator (5), wherein the movement of the second frame part relative to the first frame part beyond a predefined triggering distance causes a breakage of the frangible junction portion, releasing the indicator (5) which moves from a first initial position to a second final position under the effect of the return force exerted by the elastic return structure (6). Figure for abstract: Figure 1

Description

Title of the invention: Micromechanical temperature detection device FIELD OF THE INVENTION

[0001] The invention relates to a micromechanical temperature sensing device and a temperature sensing assembly incorporating such a device. STATE OF THE ART

[0002] In certain fields of activity, it is sometimes necessary to be able to monitor the health status of certain objects. In particular, it may be necessary to determine whether a piece of equipment has undergone temperature variations that could damage the equipment.

[0003] This may be the case, for example, of metrology instruments, transport containers, pyrotechnic materials, body protection equipment or, more generally, of any sensitive material or structure.

[0004] Indeed, when these devices are subjected to temperature variations having an amplitude greater than a certain value, certain essential components can be damaged, which can degrade their efficiency.

[0005] For example, body protection equipment, such as helmets or protective plates, may include multi-layer structures comprising an assembly of two or more layers formed from different materials. When these structures are exposed to high temperatures, for example because they are stored in buildings located in geographical areas subject to hot climates or because they are transported in vehicles exposed to the sun for a long period, the materials of the layers may expand with different expansion amplitudes which causes delamination of the structure, i.e. a separation of the layers from each other.These body protection equipment must be replaced or reconditioned when the equipment has undergone a rise in temperature likely to damage the multi-layer structure, so as not to compromise the safety of the operator whose protection is ensured by the equipment.

[0006] However, it can be difficult to determine whether a given piece of equipment has been subjected to a temperature likely to damage its structure. Indeed, damage caused by an increase in temperature is not always visually detectable.

[0007] A possible solution would be to equip certain equipment with sensors, making it possible to detect a temperature (or a temperature variation) above a certain threshold. Such sensors would make it possible to record a temperature likely to damage the equipment, which would provide information on the need to replace or recondition the equipment.

[0008] However, such sensors generally require an electrical power supply to operate, to store and / or to collect the detection information generated by the sensor.

[0009] The electrical power supply of such sensors can for example be provided by a battery. However, the addition of a battery complicates the installation of these sensors, by increasing their size, and requires being able to regularly check the state of charge of the battery. Summary of the invention

[0010] An aim of the invention is to propose a solution to facilitate the detection of the crossing of a temperature threshold experienced by components, which does not require an electrical power supply.

[0011] This aim is achieved within the framework of the present invention thanks to a micromechanical temperature detection device, comprising: - a frame comprising a first frame part and a second frame part, the first frame part and the second frame part being suitable for being fixed to a test body such that an expansion of the test body causes a displacement of the second frame part relative to the first frame part, in a first direction of displacement, - an indicator, - at least one frangible junction portion connecting the indicator to the first frame part so as to maintain the indicator in a first initial position, - an elastic return structure capable of exerting a return force on the indicator, wherein the first frame portion and the second frame portion are configured such that movement of the second frame portion relative to the first frame portion, in the first direction of movement, beyond a predefined trigger distance, causes a rupture of the frangible junction portion, and wherein the elastic return structure is configured such that once the frangible junction portion is ruptured, the indicator is moved relative to the first frame portion from the first initial position to a second final position under the effect of the restoring force exerted by the elastic return structure.

[0012] When the micromechanical temperature detection device is subjected to a temperature variation, the expansion (or retraction) of the test body causes a displacement of the second frame part relative to the first frame part. The amplitude of displacement of the second frame part relative to the first frame part depends on the temperature variation.

[0013] If the body temperature remains below a certain predefined threshold, then the amplitude of the displacement of the second frame part relative to the first frame part is insufficient to trigger a rupture of the frangible junction portion, and the indicator is maintained in the first initial position.

[0014] On the other hand, if the temperature of the body becomes greater than or equal to the predefined threshold, the displacement of the second frame part relative to the first frame part has a sufficient amplitude to trigger a rupture of the frangible junction portion, which causes the indicator to move from the first initial position to the second final position under the effect of the restoring force exerted by the elastic restoring structure.

[0015] By simply observing the position of the indicator, an observer is able to determine whether or not the test body has been subjected to a temperature above a limit temperature to be detected.

[0016] The proposed micromechanical temperature detection device thus makes it possible to record the occurrence of a temperature rise which could compromise the integrity of the component.

[0017] Such a micromechanical temperature detection device does not require an electrical power supply for its operation.

[0018] The micromechanical temperature detection device may further have the following characteristics:

[0019] - the second frame part comprises a striker arranged to exert a force thrust on the indicator when the displacement of the second frame part relative to the first frame part, in the first direction of displacement, exceeds the predefined triggering distance, the thrust force having the effect of breaking the joining portion connecting the indicator to the first frame portion;

[0020] - the frame comprises an attachment portion connecting the second frame part and the first frame part therebetween to hold the second frame part stationary in a fixed position relative to the first frame part when attaching the first frame part and the second frame part to the test body, the attachment portion being adapted to be broken once the first frame part and the second frame part are attached to the test body;

[0021] - the indicator comprises a first indicator part connected to the first part of frame by the joining portion and a second indicator part connected to the first frame part by the elastic return structure, the second indicator part being able to be moved from a first unlocked position to a second locked position in which the second indicator part is ver- rusty on the first part of the indicator;

[0022] - the second indicator part is moved from the first unlocked position rusted to the second locked position in a second direction of movement, against the elastic return force exerted by the elastic return structure;

[0023] - the indicator comprises a locking structure configured to lock the second part of indicator on the first part of indicator;

[0024] - the locking structure comprises at least one first tooth fixedly mounted on the first indicator portion and a second tooth fixedly mounted on the second indicator portion, the second tooth being adapted to be engaged with the first tooth when the second indicator portion is in the second locked position;

[0025] - the first tooth comprises a first sliding face and a first locking, and the second tooth comprises a second sliding face and a second locking face, arranged such that during movement of the second indicator part from the first unlocked position to the second locked position, the second sliding face of the second tooth slides over the first sliding face of the first tooth, allowing the first tooth to cross the second tooth, after which the second locking face of the second tooth abuts against the first locking face of the first tooth, preventing the second indicator part from returning to the first unlocked position;

[0026] - the second indicator part comprises a stop suitable for coming into contact with the frame so as to limit movement of the second indicator portion beyond the second locked position;

[0027] - the second indicator part has a notch allowing the insertion of a tool adapted to exert a thrust on the second indicator part to move the second indicator part towards the first indicator part from the first unlocked position to the second locked position;

[0028] - the elastic return structure has a first initial configuration deactivated, in which the elastic return structure does not exert a restoring force on the indicator, and a second primed configuration, in which the elastic return structure exerts the restoring force on the indicator;

[0029] - the locking structure and the elastic return structure are configured of such that until the second indicator portion is locked onto the first indicator portion, the elastic return structure is in the first initial unarmed configuration, and moving the second indicator portion from the first unlocked position to the first locked position causes the elastic return structure to move from the first initial unarmed configuration to the first locked position. initial configuration deactivated to the second configuration primed;

[0030] - the frame, the indicator, the joining portion and the elastic return structure are formed by etching in a single layer of a first material.

[0031] The invention further relates to a temperature sensing assembly, comprising a micromechanical temperature sensing device as defined above, and a test body, the test body being formed from a second material having a coefficient of expansion greater than the coefficient of expansion of the first material.

[0032] The invention also relates to a temperature detection assembly, comprising a micromechanical temperature detection device as defined above, and a support comprising a housing suitable for receiving the micromechanical temperature detection device, the housing having a bottom wall delimiting the housing, the bottom wall forming the test body on which the first frame part and the second frame part are fixed, the bottom wall having a visual marker positioned such that when the indicator is in one of the first initial position and the second final position, the indicator masks the visual marker for an external observer, and when the indicator is in the other of the first initial position and the second final position, the indicator uncovers the visual marker for the external observer.

[0033] In one embodiment, the temperature sensing assembly includes a cover adapted to be assembled to the support to close the housing, the cover being visually transparent to allow an outside observer to see the visual cue through the cover. PRESENTATION OF THE DRAWINGS

[0034] Other characteristics and advantages will emerge from the following description, which is purely illustrative and non-limiting and must be read in conjunction with the appended figures, among which:

[0035] - [Fig.l] schematically represents a temperature detection assembly temperature in accordance with a possible embodiment of the invention,

[0036] - [Fig.2] represents, schematically, in top view, the assembly of temperature detection, when the indicator is in the first initial position,

[0037] - [Fig.3] is a detail view showing the indicator in the first position initial,

[0038] - [Fig.4] represents, schematically, in top view, the assembly of temperature detection, during a movement of the second frame part relative to the first frame part,

[0039] - [Fig.5] is a detailed view of the indicator, during a movement of the second frame part relative to the first frame part,

[0040] - [Fig.6] schematically represents, in top view, the assembly of temperature detection, when the indicator is in the second final position,

[0041] - [Fig.7] is a detail view showing the indicator in the second position final,

[0042] - [Fig.8] is a photograph taken with a scanning electron microscope of a part of a micromechanical temperature sensing device, when the second indicator part is in the first unlocked position,

[0043] - [Fig.9] is a photograph taken with a scanning electron microscope of a part of a micromechanical temperature sensing device, when the second indicator part is in the second locked position,

[0044] - [Fig. 10] is a photograph taken with a scanning electron microscope of a part of a micromechanical temperature sensing device, showing a first for measuring a displacement between the second frame part and the first frame part. DETAILED DESCRIPTION OF AN EMBODIMENT

[0045] In [Fig.l], the temperature detection assembly 1 shown comprises a micromechanical temperature detection device 2 and a housing 3 suitable for containing the micromechanical temperature detection device 2.

[0046] The housing 3 comprises a support 31 and a cover 32.

[0047] The support 31 comprises a housing 33 suitable for accommodating the micromechanical temperature detection device 2, so as to immobilize the micromechanical temperature detection device 2 relative to the support 31.

[0048] The support 31 has a thickness of approximately 1.5 millimeters. The support 31 may be formed from a polymer material, for example polyoxymethylene (POM). The material forming the support 31 preferably has a coefficient of linear thermal expansion of between 120 and 130.106 K1.

[0049] As illustrated in [Fig.l], the support 31 may comprise several nested housings, suitable for accommodating micromechanical temperature detection devices of different sizes depending on requirements.

[0050] The cover 32 is suitable for being assembled to the support 31 to close the housing 33. The cover 32 can be fixed to the support 31 by gluing, for example with a silicone seal. The silicone seal can be arranged in a groove provided in the support 31.

[0051] In the example illustrated in [Fig.l], the cover 32 is formed from a material transparent to light radiation in a visible wavelength range (i.e., in a range between 380 and 780 nanometers for a wavelength in vacuum) so as to allow an observer to observe the device micromechanical temperature detection 2 through the cover 32.

[0052] The cover 32 may for example comprise a window having a thickness of approximately 0.3 millimeters.

[0053] The housing 33 comprises a bottom wall 34 having a visual marker 35. The visual marker 35 may be a raised area or a hollow area and / or a colored area, with a color different from that of the bottom wall 34, having dimensions sufficient to be easily visible by an observer, for example dimensions of the order of approximately 1 millimeter.

[0054] The various components of the micromechanical temperature detection device 2 have all been formed by an etching process in a single wafer comprising one or more layers of material. In the example illustrated in [Fig.l], the wafer used to manufacture the micromechanical shock detection device 2 comprises a single layer of material 21. The layer of material 21 has, for example, a thickness of approximately 200 micrometers. The material of the layer is, for example, silicon 21.

[0055] The material of the layer 21 preferably has a coefficient of linear thermal expansion less than 5.106 K1. The material forming the layer 21 has a coefficient of expansion lower than the coefficient of thermal expansion of the polymer material forming the support 31. More precisely, the coefficient of thermal expansion of the polymer material forming the support 31 is at least 10 times greater than the coefficient of thermal expansion of the material forming the layer 21, preferably at least 30 times greater than the coefficient of thermal expansion of the material forming the layer 21. In the case where the layer 21 is made of silicon, the coefficient of linear thermal expansion of the material of the layer 21 is equal to 3.10 6 K *.

[0056] The micromechanical temperature detection device 2 comprises a frame 4, an indicator 5, an elastic return structure 6.

[0057] In the example illustrated in Figures 1 to 3, the elastic return structure 6 comprises a first arm 61 and a second arm 62.

[0058] The frame 4 surrounds the indicator 5 and the elastic return structure 6.

[0059] The frame 4 has a generally rectangular shape. The frame 4 has a first axis XI (or longitudinal axis) and a second axis X2 (or transverse axis), extending perpendicular to the first axis XL

[0060] The frame 4 comprises a first upright 41, a second upright 42, a first cross member 43 and a second cross member 44. The first upright 41 extends along a first transverse edge of the frame 4, parallel to the second axis X2. The second upright 42 extends along a second transverse edge of the frame 4, opposite the first transverse edge, parallel to the second axis. The first cross member 43 extends along a first longitudinal edge of the frame 4, parallel to the first axis XI. The second crosspiece 44 extends along a second longitudinal edge of the frame 4, opposite the first longitudinal edge, parallel to the first axis XL

[0061] The frame 4 is formed in two parts 45 and 46. More specifically, the frame 4 comprises a first frame part 45, a second frame part 46, and attachment portions 49 connecting the second frame part 46 to the first frame part 45.

[0062] In the example illustrated in Figures 1 to 3, the first frame part 45 comprises the first upright 41, the first crosspiece 43 and a first portion 441 of the second crosspiece 44. The second frame part 46 comprises the second upright 42 and a second portion 442 of the second crosspiece.

[0063] In the example illustrated in Figures 1 to 3, the bottom wall of the support 31 constitutes a test body for the temperature detection device 2. Thus, in this example, the first frame part 45 and the second frame part 46 are each fixed to the bottom wall 34. The first frame part 45 is fixed to the bottom wall 34 in a first zone of the bottom wall 34 and the second frame part 46 is fixed to the bottom wall 34 in a second zone of the bottom wall 34, located at a distance L from the first zone along the first axis XL. The distance L may for example be equal to approximately 1.4 centimeters.

[0064] The first frame part 45 and the second frame part 46 may be fixed to the bottom wall 34 by gluing or by another fixing means.

[0065] In the example illustrated in Figures 1 to 3, the first upright 41 has first orifices 47. Similarly, the second upright 42 has second orifices 48. The first orifices 47 and the second orifices 48 pass completely through the layer of material 21. The second orifices 48 are separated by a distance L from the first orifices 47, along the first axis XL.

[0066] Thus, during gluing, the frame 4 is placed in contact with the bottom wall of the support 31, and glue is injected into the first orifices 47 and the second orifices 48. Once solidified, the glue filling the first orifices 47 fixes the first upright 41 to the bottom wall 34 of the support 31. Similarly, the glue filling the second orifices 48 fixes the second upright 42 to the bottom wall 34 of the support 31.

[0067] Alternatively, the first frame portion 45 and the second frame portion 46 could be attached to a different test body, which would not be a bottom wall 34 of a support 31. For example, the first frame portion 45 and the second frame portion 46 could be attached directly to a structure or object to be monitored.

[0068] During gluing, the attachment portions 39 hold the first frame part 45 and the second frame part 46 stationary, in a fixed position relative to each other. The attachment portions 49 thus ensure a predefined relative positioning of the first frame part 45 and the second frame part 46, during attachment to the test body 34.

[0069] Once the first frame part 45 and the second frame part 46 have been fixed to the test body 34, by gluing or by another means, the attachment portions 49 can be broken (as is for example visible in FIGS. 4 and 6), so as to allow a displacement of the second frame part 46 relative to the first frame part 45 parallel to the first axis XI, during an expansion of the test body 34.

[0070] As illustrated in Figures 1 and 2, the elastic return structure 6 connects the indicator 5 to the first frame part 45. More precisely, the first arm 61 connects the indicator 5 to the first frame part 45. The second arm 62 also connects the indicator to the first frame part 45. The elastic return structure is capable of exerting an elastic return force F1 on the indicator 5, parallel to the second axis X2.

[0071] In the example illustrated in Figures 1 to 3, each of the first arm 61 and the second arm 62 comprises a plurality of successive flexible beams connected to each other forming a zigzag structure, similar to a spring.

[0072] More specifically, in the example illustrated in Figures 1 to 3, the first arm 61 comprises a first series of flexible beams, including a first flexible beam 611, a second flexible beam 612 and a third flexible beam 613.

[0073] The second arm 62 comprises a second series of flexible beams, arranged symmetrically to the first series of flexible beams, relative to the second axis X2, the second series of flexible beams including a fourth flexible beam 621, a fifth flexible beam 622 and a sixth flexible beam 623.

[0074] The first flexible beam 611 has one end connected to the first cross member 43 and an opposite end, connected to one end of the second flexible beam 612. The second flexible beam 612 has one end connected to one end of the first flexible beam 611 and an opposite end, connected to one end of the third flexible beam 613. The third flexible beam 613 has one end connected to one end of the second flexible beam 612 and an opposite end connected to the indicator 5.

[0075] The fourth flexible beam 621 has one end connected to the first cross member 43 and an opposite end, connected to one end of the fifth flexible beam 622. The fifth flexible beam 622 has one end connected to one end of the fourth flexible beam 621 and an opposite end, connected to one end of the sixth flexible beam 623. The sixth flexible beam 623 has one end connected to one end of the fifth flexible beam 622 and an opposite end connected to the indicator 5.

[0076] As visible in [Fig.3], the temperature detection device 2 comprises in in addition to frangible joining portions 7 connecting the indicator 5 to the first frame part 45, so as to maintain the indicator 5 in a first initial position (position illustrated in figures 2 and 3). More specifically, the frangible joining portions 7 connect the indicator to the first portion 441 of the second cross member 44.

[0077] Furthermore, in the example illustrated in [Fig. 3], the indicator 5 comprises a first indicator part 51, a second indicator part 52 and a locking structure 53 configured to lock the second indicator part 52 onto the first indicator part 51. The first indicator part 51 is connected to the first frame part 45 (more specifically to the first portion 441 of the second cross member 44) by the frangible joining portions 7. The second indicator part 52 is connected to the first frame part 45 (more specifically to the first cross member 43) by the elastic return structure 6..

[0078] In the example illustrated in [Fig. 3], the locking structure 53 comprises first teeth 531 fixedly mounted on the first indicator part 51 and second teeth 532 fixedly mounted on the second indicator part 52. In [Fig. 3], the second teeth 532 are engaged with the first teeth 531 to secure the second indicator part 52 to the first indicator part 51.

[0079] When manufacturing the temperature sensing device 2, immediately after the step of etching the material layer 21, the second indicator portion 52 is initially in an unlocked position (position shown in [Fig.8]). In this position, the second teeth 532 are not engaged with the first teeth 531, and the second indicator portion 52 is positioned at a distance from the first indicator portion 51. The elastic return structure 6 is not deformed, so that it does not exert an elastic return force on the second indicator portion 52.

[0080] Before putting the temperature detection device 2 into operation, the second indicator part 52 is moved from the unlocked position (position shown in [Fig. 8]), to a locked position (position shown in [Fig. 9]). For this purpose, the second indicator part 52 is pushed towards the first indicator part 51 parallel to the first axis XI, so as to engage the second teeth 532 with the first teeth 531 of the locking structure 53.

[0081] The movement of the second indicator part 52 from the unlocked position (position illustrated in [Fig.8]) to the locked position (position illustrated in [Fig.9]) has the effect of generating an elastic deformation of the elastic return structure 6. More precisely, the beams 611 to 613 of the first arm 61 and the beams 621 to 623 of the second arm 62 are deformed (more precisely, bent). The elastic return structure 6 exerts on the second indicator part 52 an elastic return force F1 parallel to the second axis X2, in a first direction, tending to oppose the movement of the second indicator portion 52 towards the first indicator portion 51.

[0082] Once the second indicator part 52 is locked with the first indicator part 51, the elastic return structure 6 exerts on the indicator 5 an elastic return force F1, of constant intensity, parallel to the second axis X2, in the first direction. The elastic return force F1 tends to pull the indicator 5 towards the first crosspiece 43 and away from the second crosspiece 44.

[0083] As seen in [Fig. 3], the second indicator portion 52 may include a notch 521 for allowing insertion of a tool. The tool may be used by an operator or machine to exert a thrust on the second indicator portion 52 to move the second indicator portion 52 toward the first indicator portion 51 from the unlocked position (illustrated in [Fig. 8]) to the locked position (illustrated in [Fig. 9]).

[0084] Once the temperature sensing device 2 has been secured to the test body 34, the second indicator portion 52 has been locked to the first indicator portion 51, and the attachment portions 49 have been broken, the temperature sensing assembly is ready for use.

[0085] As is more particularly visible in [Fig.3], the second teeth 532 are adapted to be engaged with the first tooth 531 when the second indicator part 52 is in the second locked position.

[0086] For this purpose, each first tooth 531 comprises a first sliding face 533 and a first locking face 534. Similarly, each second tooth 532 comprises a second sliding face 535 and a second locking face 536, arranged such that during the movement of the second indicator part 52 from the first unlocked position to the second locked position, the second sliding face 535 of the second tooth 532 slides on the first sliding face 533 of the first tooth 531, allowing the first tooth 531 to cross the second tooth 532, after which the second locking face 536 of the second tooth 532 abuts against the first locking face 534 of the first tooth 531, preventing the second indicator part 52 from returning to the first unlocked position.

[0087] Furthermore, as can be seen in [Fig. 3], the second indicator part 52 may comprise stops 522 suitable for coming into contact with the second crosspiece 44 of the frame 4, so as to limit the movement of the second indicator part 52 beyond the second locked position, and to keep the locking faces 534 and 535 of the first teeth 531 and the second teeth 532 in abutment against each other.

[0088] As can also be seen in [Fig.3], the second frame part 46 comprises a striker 461 arranged opposite a contact face 511 of the indicator 5.

[0089] In the example illustrated in [Fig.3], the striker 461 is arranged to project from the second portion 442 of the second crosspiece 44 and the contact face 511 is formed by a shoulder in the first indicator part 51.

[0090] In operation, the temperature detection assembly 1 is initially in the initial configuration illustrated in Figures 2 and 3. In this initial configuration, the indicator 5 is in the first initial position.

[0091] In the first initial position, the indicator 5 masks the underlying visual marker 35. In other words, the underlying visual marker 35 is not visible to an observer who observes the micromechanical temperature detection device 2 through the cover 32 of the housing 3.

[0092] Furthermore, in the initial configuration illustrated in Figures 2 and 3, the striker 461 is located at a distance from the contact face 511 of the indicator 5.

[0093] As the temperature of the test body 34 varies, the material of the test body 34 expands and / or contracts.

[0094] The expansion and retraction of the material of the test body 34 has the effect of causing a correlative displacement of the second frame part 42 relative to the first frame part 41, parallel to the first axis XL

[0095] More specifically, the expansion of the material of the test body 34 has the effect of moving the second upright 46 away from the first upright 45.

[0096] The fixing points of the first frame part 41 on the test body 34 and the fixing points of the second frame part 42 on the test body 34 are spaced apart by a distance L + AL, AL being the amplitude of the displacement AL of the second frame part 42 relative to the first frame part 4L

[0097] The amplitude of the displacement AL of the second frame part 42 relative to the first frame part 41 is dependent on the variation in the temperature of the test body 34.

[0098] As long as the temperature of the test body 34 does not increase beyond a predefined threshold value, the second frame part 42 moves relative to the first frame part 41, without triggering the temperature detection device 2.

[0099] The temperature sensing assembly 1 is dimensioned so as to adjust the temperature threshold value to the intended application. The temperature sensing assembly 1 may for example be dimensioned so that the threshold value is approximately 70 degrees Celsius.

[0100] As illustrated in Figures 4 and 5, when the temperature of the test body 34 reaches the predefined threshold value, the second frame portion 42 is moved relative to the first frame portion 41 by a triggering distance predefined AL threshold.

[0101] When the displacement of the second frame part 42 relative to the first frame part 41, parallel to the first axis XI, exceeds the predefined triggering distance AL threshold, the striker 461 comes into contact with the contact face 511 of the indicator and exerts a thrust force F2 on the indicator parallel to the first axis XL

[0102] The thrust force F2 exerted by the striker 461 on the indicator 5 has the effect of breaking the frangible joining portions 7 connecting the indicator 5 to the first frame part 45.

[0103] For example, the temperature sensing assembly 1 may be sized such that when the temperature of the test body 34 changes from 20 degrees Celsius to 70 degrees Celsius, the second frame portion 42 is displaced relative to the first frame portion 41 by a threshold distance AL of 80 micrometers.

[0104] Once the frangible joining portions 7 are broken, the indicator 5 is no longer retained by the frangible joining portions 7 to the first frame part 45.

[0105] Consequently, the elastic return force F1 exerted on the indicator 5 by the elastic return structure 6 has the effect of moving the indicator 5 from the first initial position (position illustrated in FIGS. 4 and 5) to a second final position (position illustrated in FIGS. 6 and 7), parallel to the second axis X2.

[0106] As illustrated in Figures 6 and 7, once in the second final position, the indicator 5 no longer masks the underlying visual marker 35. In other words, the underlying visual marker 35 is visible to an observer who observes the micromechanical temperature detection device 2 through the cover 32 of the housing 3.

[0107] The temperature detection assembly 2 is then in the final configuration, as illustrated in Figures 6 and 7.

[0108] By simply observing the micromechanical temperature sensing device 2, an observer is able to determine whether the temperature sensing assembly 1 is in the initial configuration (in this case, the visual cue 35 is not visible) or whether the temperature sensing assembly 2 is in the final configuration (in this case, the visual cue is visible 35).

[0109] If the temperature detection assembly 1 is in the initial configuration, this means that the temperature detection assembly 1 has not undergone a temperature variation such that the temperature has exceeded the predefined temperature threshold.

[0110] If the temperature detection assembly 1 is in the final configuration, this means that the temperature detection assembly 1 has undergone a temperature variation such that the temperature has exceeded the predefined temperature threshold.

[0111] The proposed temperature detection assembly 1 can be used to detect the exceeding of a temperature threshold, for example:

[0112] - to detect the exceeding of a temperature threshold in an environment where the temperature is controlled (for example a container or a refrigerated building),

[0113] - to detect the exceeding of a temperature threshold representative of the occurrence of a fire,

[0114] - to detect the exceeding of a temperature threshold for the protection of people (for example to trigger a heatwave alert),

[0115] - more generally, to detect the exceeding of a temperature threshold on any sensitive material, equipment or structure.

[0116] As illustrated in Figures 3 and 10, the temperature detection device 2 may comprise a vernier in order to control the correct operation of the temperature detection assembly 1. The vernier 8 comprises a first graduation 81 formed on the first frame part 45 and a second graduation 82 formed on the second frame part 46, extending parallel to the first graduation, opposite the first graduation 81. The first graduation 81 and the second graduation 82 are arranged so that a movement of the second frame part 46 relative to the first frame part 45 parallel to the first axis XI, causes an offset of the second graduation 82 relative to the first graduation 81. By measuring the offset between the graduations 81 and 82, it is possible to determine a value of the thermal expansion AL in micrometers.

[0117] Each graduation 81, 82 comprises a series of marks or reliefs spaced from each other with a constant spacing pitch between two successive marks or reliefs. The spacing pitch can be chosen according to the desired reading accuracy. For example, the reading accuracy can be ± 1 μm. In this case, the vernier 8 can be read using a microscope.

Claims

Claims

1. Micromechanical temperature detection device (2), comprising: - a frame (4) comprising a first frame part (45) and a second frame part (46), the first frame part (45) and the second frame part (46) being suitable for being fixed to a test body (34) such that an expansion of the test body (34) causes a displacement of the second frame part (46) relative to the first frame part (45), in a first direction of displacement (XI), - an indicator (5), - at least one frangible junction portion (7) connecting the indicator (5) to the first frame part (45) so as to maintain the indicator (5) in a first initial position, - an elastic return structure (6) suitable for exerting a return force (Fl) on the indicator (5),wherein the first frame part (45) and the second frame part (46) are configured such that the displacement of the second frame part (46) relative to the first frame part (45), in the first direction of displacement (XI), beyond a predefined triggering distance (AL), causes a rupture of the frangible junction portion (7), and wherein the elastic return structure (6) is configured such that once the frangible junction portion (7) is ruptured, the indicator (5) is displaced relative to the first frame part (45) from the first initial position to a second final position under the effect of the restoring force (Fl) exerted by the elastic return structure (6).,

2. Micromechanical temperature detection device (2) according to claim 1, wherein the second frame portion (46) comprises a striker (461) arranged to exert a thrust force (F2) on the indicator (5) when the displacement of the second frame portion (46) relative to the first frame portion (45), in the first direction of displacement (XI), exceeds the predefined triggering distance (AL), the thrust force (F2) having the effect of breaking the joining portion (7) connecting the indicator (5) to the first frame portion (45).

3. Micromechanical temperature detection device (2) according to one of of claims 1 and 2, wherein the frame (4) comprises an attachment portion (49) connecting the second frame part (46) and the first frame part (45) together to hold the second frame part (46) stationary in a fixed position relative to the first frame part (45) during the attachment of the first frame part (45) and the second frame part (46) to the test body (34), the attachment portion (49) being adapted to be broken once the first frame part (45) and the second frame part (46) are attached to the test body (34).

4. Micromechanical temperature detection device (2) according to one of claims 1 to 3, wherein the indicator (5) comprises a first indicator part (51) connected to the first frame part (45) by the joining portion (7) and a second indicator part (52) connected to the first frame part (45) by the elastic return structure (6), the second indicator part (52) being adapted to be moved from a first unlocked position to a second locked position in which the second indicator part (52) is locked on the first indicator part (51).

5. A micromechanical temperature sensing device according to claim 4, wherein the second indicator portion (52) is moved from the first unlocked position to the second locked position in a second direction of movement (X2), against the elastic return force (F2) exerted by the elastic return structure (6).

6. A micromechanical temperature sensing device according to one of claims 4 and 5, wherein the indicator (5) comprises a locking structure (53) configured to lock the second indicator part (52) to the first indicator part (51).

7. A micromechanical temperature sensing device (2) according to claim 6, wherein the locking structure (53) comprises at least a first tooth (531) fixedly mounted on the first indicator portion (51) and a second tooth (532) fixedly mounted on the second indicator portion (52), the second tooth (531) being adapted to be engaged with the first tooth (531) when the second indicator portion (52) is in the second locked position.

8. A device according to claim 7, wherein the first tooth (531) comprises a first sliding face (533) and a first locking face (534), and the second tooth (532) comprises a second face sliding face (534) and a second locking face (535), arranged such that during movement of the second indicator part (52) from the first unlocked position to the second locked position, the second sliding face (534) of the second tooth (532) slides on the first sliding face (533) of the first tooth (531), allowing the second tooth (531) to cross the second tooth (532), after which the second locking face (536) of the second tooth (532) abuts against the first locking face (534) of the first tooth (531), preventing the second indicator part (52) from returning to the first unlocked position.

9. A device according to claim 8, wherein the second indicator portion (52) comprises a stop (522) adapted to come into contact with the frame (4) so ​​as to limit the movement of the second indicator portion (52) beyond the second locked position.

10. A micromechanical temperature detection device (2) according to one of claims 5 to 9, wherein the second indicator portion (52) comprises a notch (521) allowing the insertion of a tool capable of exerting a thrust on the second indicator portion (52) to move the second indicator portion (52) towards the first indicator portion (51) from the first unlocked position to the second locked position.

11. Micromechanical temperature detection device according to one of claims 1 to 10, wherein the elastic return structure (6) has a first initial deactivated configuration, in which the elastic return structure (6) does not exert a return force on the indicator (5), and a second activated configuration, in which the elastic return structure (6) exerts the return force (Fl) on the indicator (5).

12. A micromechanical temperature sensing device (2) according to one of claims 5 to 10 in combination with claim 11, wherein the locking structure (53) and the elastic return structure (6) are configured such that as long as the second indicator part (52) is not locked to the first indicator part (51), the elastic return structure (6) is in the first initial disarmed configuration, and that moving the second indicator part (52) from the first unlocked position to the first locked position has the effect of moving the structure elastic return (6) from the first initial deactivated configuration to the second activated configuration.

13. Micromechanical temperature detection device (2) according to one of claims 1 to 12, in which the frame (4), the indicator (5), the junction portion (7) and the elastic return structure (6) are formed by etching in a single layer (21) of a first material.

14. A temperature sensing assembly (1), comprising a micromechanical temperature sensing device (2) according to claim 13, and a test body (34), the test body (34) being formed from a second material having a coefficient of expansion greater than the coefficient of expansion of the first material.

15. A temperature detection assembly (1), comprising a micromechanical temperature detection device (2) according to one of claims 1 to 13, and a support (31) comprising a housing (33) suitable for receiving the micromechanical temperature detection device (2), the housing (33) having a bottom wall (34) delimiting the housing (33), the bottom wall (34) forming the test body on which the first frame part (45) and the second frame part (46) are fixed, the bottom wall (34) having a visual marker (35) positioned such that when the indicator (5) is in one of the first initial position and the second final position, the indicator (5) masks the visual marker (35) for an external observer, and when the indicator (5) is in the other of the first initial position and the second final position, the indicator (5) uncovers the visual marker (35) for the observer exterior.

16. A temperature sensing assembly (1) according to claim 15, comprising a cover (32) adapted to be assembled to the support (31) to close the housing (33), the cover (32) being visually transparent to allow an external observer to see the visual marker (35) through the cover (32).

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