INERTIA-BASED UNLOCKING DEVICE FOR A SEAT BACKREST
The inertia-based unlocking device addresses the incompatibility of mechanical fuses in heavy seat backs by using a low-energy weight system to trigger a higher-energy mechanism, overcoming friction and meeting safety criteria for aircraft seats.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2024-04-25
- Publication Date
- 2026-03-13
AI Technical Summary
Current mechanical fuse devices in aircraft seats are incompatible with heavy seat backs due to their high rigidity, leading to poor Head Injury Criterion (HIC) scores and failing to meet Neck Injury Criterion (Nij) requirements, as they require significant thickness to withstand static stress during evacuation, and existing inertia-based unlocking systems fail to overcome frictional forces during high decelerations.
An inertia-based unlocking device with a low-energy weight system that triggers a higher-energy mechanism by using a housing, support, pin, weight, and elastic elements to overcome friction, allowing the seat back to rotate before head impact, meeting HIC and Nij criteria.
The device effectively reduces injuries by allowing the seat back to rotate before impact, meeting safety criteria and integrating easily into aircraft seats.
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Abstract
Description
Title of the invention: Inertial unlocking device for a seat back
[0001] The present invention relates to an inertia-based unlocking device for a seat back. The invention finds a particularly advantageous application in the field of aeronautics with aircraft seats.
[0002] To ensure a high level of safety, aircraft seats are subjected to tests representative of an air accident. During these tests, important criteria are the trajectory and the level of impact force experienced by the passenger. In particular, the Head Injury Criterion (HIC) corresponds to a score that must not exceed a threshold value. This HIC score depends on the maximum deceleration values experienced by the passenger's head during an impact, as well as on the time limits of a deceleration curve calculated during the test.There is also the "Nij" impact criterion, an acronym for "Neck Injury Criterion" according to Anglo-Saxon terminology, which represents the stresses on a passenger's cervical spine, combining tensile and compressive forces as well as flexion and extension moments experienced by the neck of a passenger and normalized against critical values.
[0003] In order to meet these impact criteria, it is important that the seat back does not offer excessive resistance to the passenger's head, which is thrown against it during the test. Furthermore, the seat back must be able to withstand significant stresses during its service life and during an evacuation, as it must be held stably in the raised position to avoid obstructing access to an emergency exit.
[0004] Current mechanical fuse devices integrated into seat backs are dependent on the weight of the seat back. In accordance with the requirements of the European Aviation Safety Agency (EASA), no rupture of this type of mechanical fuse should occur before head contact. This requirement makes the current design of mechanical fuses incompatible with a heavy seat back, since the thickness of the corresponding fuses must be significant to withstand a static stress of up to 150 daN for excessive loads during evacuation. This results in a poor HIC score due to the high rigidity of the seat back upon head impact. Furthermore, since head contact must trigger the rupture of the fuses, the Nij criterion is not met.
[0005] To avoid the constraints described above, inertia-based unlocking systems known as ILDs (Inertia Locking Devices) are known, as described in document EP3781433. This type of device is capable of triggering a rotation of the seat back before the head impacts, regardless of the weight of the seat back, in accordance with the regulations set out in document EASA A380 CRI D-39. However, existing devices based on the displacement of a low-mass, and therefore low-energy, element cannot overcome the frictional forces appearing in the seat back rotation mechanism when subjected to significant decelerations on the order of 16g.
[0006] The invention aims to effectively remedy the aforementioned drawbacks by proposing an inertia-based unlocking device comprising: - a housing, - a support disposed inside the housing carrying a pin extending in projection relative to the housing when said device is in a locked state, said pin being able to slide relative to the housing, - a weight able to move in translation under the effect of inertia, - a first shaft rotatably mounted inside an opening in the support, said first shaft having at least one end having a flat, - a second shaft having a first end provided with a flat intended to bear against the flat of the first shaft and a second end having a weight stop bearing against the weight, - a first elastic element disposed between the weight and the housing, - a second elastic element disposed between the second shaft and the housing,and - a third elastic element mounted in compression between the housing and the support, such that when the weight is subjected to strong deceleration, said weight is able to move in translation by compressing the first elastic element so as to move away from the weight stop, to release a rotation of the first shaft and the second shaft accelerated by the second elastic element causing a break in contact between the first shaft and the second shaft allowing a decompression of the third elastic element generating a translational movement of the pin towards the inside of the housing to bring the device into an unlocked state.
[0007] The invention thus makes it possible to use a low-energy weight system to trigger a higher-energy system that overcomes the high friction in the backrest rotation mechanism due to the high preload at a deceleration of approximately 16g. The invention also has the advantage of being easily integrated into an aircraft seat.
[0008] According to one embodiment of the invention, the first shaft is mounted to rotate relative to the support by means of at least one bearing interposed radially between the first shaft and the support.
[0009] According to one embodiment of the invention, the second shaft is mounted to rotate relative to the housing by means of at least one bearing interposed radially between the second shaft and the housing.
[0010] According to one embodiment of the invention, the bearing is made of a material with a low coefficient of friction.
[0011] According to one embodiment of the invention, a stiffness of the first elastic element is chosen so as to define an activation threshold of the inertia unlocking device.
[0012] According to one embodiment of the invention, the second elastic element is a torsion spring.
[0013] According to one embodiment of the invention, the second elastic element has one end bearing against the housing and one end bearing against a spring stop of the second shaft.
[0014] According to one embodiment of the invention, the third elastic element has a stiffness much greater than that of the first elastic element.
[0015] According to one embodiment of the invention, an axis of the weight extends in a direction perpendicular to an axis of the support.
[0016] The invention also relates to an aircraft seat comprising an inertia-based unlocking device as previously defined.
[0017] According to one embodiment of the invention, the housing is mounted on a seat structure and the pin is intended to cooperate with a correspondingly shaped housing made in a backrest when the inertia unlocking device is in the locked state.
[0018] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:
[0019] [Fig-1] Fig. 1 is a perspective view of a multi-seat seat equipped with a inertia unlocking device according to the present invention;
[0020] [Fig. 2a] [Fig. 2b] Figures 2a and 2b are perspective views of a device unlocking by inertia according to the invention respectively in a locked state and in an unlocked state;
[0021] [Fig. 3a] [Fig. 3b] Figures 3a and 3b are perspective and sectional views of a housing showing an inertia unlocking device according to the invention respectively in a locked state and in an unlocked state;
[0022] [Fig. 4a] [Fig. 4b] Figures 4a and 4b are side views illustrating a displacement of a weight when the inertia unlocking device according to the invention passes respectively from a locked state to an unlocked state following the application of a deceleration;
[0023] [Fig. 5a] [Fig. 5b] Figures 5a and 5b are perspective views illustrating a rotation of the shafts of the inertia unlocking device according to the invention allowing to release a decompression of an elastic element to move the device from a locked state to an unlocked state.
[0024] It should be noted that the structural and / or functional elements common to the different embodiments may have the same reference numerals. Thus, unless otherwise specified, such elements have identical structural, dimensional and material properties.
[0025] Figure 1 shows a seat 10 intended for installation in an aircraft cabin. The seat 10 comprises at least one seat 11 and at least one backrest 12 defining a seat. In this case, the seat 10 comprises three seats 11 and three backrests 12 to form three seats. This number of seats can, of course, be adapted according to the need and the space available inside the cabin. In particular, the seat 10 can have two seats, four seats, or more.
[0026] The seats 11 and backrests 12 are mounted on a seat structure 14. This seat structure 14 includes support legs 16 equipped with locks 17 to secure the seat 10 by clamping it onto rails (not shown) arranged on the floor of the aircraft cabin. The support legs 16 have openings for transverse reinforcement beams 15 of the seats 11.
[0027] Crossbars 19 carrying armrests 20 are mechanically connected to the beams 15. The crossbars 19 are arranged between two adjacent seats 11 as well as at the ends of the seat 10. The armrests 20 can be mounted to rotate freely or fixed relative to the crossbars 19.
[0028] An inertia unlocking device 21 for a backrest 12 is interposed between a backrest 12 and the seat structure 14.
[0029] As can be seen in Figures 2a and 2b, the device 21 comprises a housing 22 and a support 23 disposed inside the housing 22, carrying a pin 25 capable of sliding relative to the housing 22. The support 23 has a cylindrical shape and an axially through opening 24. Alternatively, the support 23 may have another shape, such as a parallelepiped shape. The pin 25 is disposed at one end of an arm 39 mechanically connected to the support 23. In particular, the arm 39 can be made of a material or rigidly assembled by fitting, gluing, or any other fastening technique suitable for the application. The arm 39 has a diameter greater than the pin 25. The difference in diameter between these two elements defines a shoulder.
[0030] The housing 22 is mounted on the seat structure 14 and the pin 25 is intended to cooperate with a correspondingly shaped housing made in the backrest 12 when the device 21 is in the locked state.
[0031] When the device 21 is in a locked state, the pin 25 protrudes from the housing 22, as shown in [Fig. 2a]. When the device 21 is in an unlocked state, the pin 25 is retracted inside the housing 22, as shown in [Fig. 2b]. The transition from the locked position to the unlocked position occurs under the effect of a strong deceleration.
[0032] To this end, a weight 26 is capable of translational movement under the effect of inertia. The weight 26 is cylindrical in shape but may alternatively be parallelepiped-shaped or any other shape suitable for the application. An axis XI of the weight 26 extends in a direction perpendicular to an axis X2 of the support 23. The housing 22 comprises a first portion 22.1 containing the weight 26 and a second portion 22.2 containing the support 23.
[0033] Furthermore, as can be seen in [Fig.3a], a first shaft 27 is rotatably mounted inside the opening 24 made in the support 23. For this purpose, at least one bearing 42, in this case two bearings 42, are interposed radially between the first shaft 27 and an inner face of the opening 24 of the support 23.
[0034] The bearings 42 are preferably ball bearings. Advantageously, the bearings 42 are made of a material with a low coefficient of friction, such as ceramic. Alternatively, the bearings 42 are made of metal or any other material suitable for the application.
[0035] One end of the first shaft 27 has a flat 28 intended to cooperate with a flat 31 of a second shaft 30, as can be seen in Figures 5a and 5b.
[0036] The second shaft 30 has a first end provided with a flat 31 intended to bear against the flat 28 of the first shaft 27 and a second end having a counterweight 32 bearing against the counterweight 26, as shown in [Fig. 3a]. The counterweight 32 extends radially beyond the shaft 27. The shaft 30 passes through a wall of the housing 22 separating the first portion 22.1 and the second portion 22.2.
[0037] The second shaft 30 is mounted to rotate relative to the housing 22 by means of at least one bearing 43 interposed radially between the second shaft 30 and the housing 22.
[0038] Another shaft 30' visible in figures 3a, 3b and 5b may have an end provided with a flat bearing against a second flat 28 of the first shaft 27. The shaft 30' is also mounted to rotate relative to the housing 22 by means of at least one bearing 43 interposed radially between the shaft 30' and the housing 22.
[0039] In the example shown, the bearings 43 are positioned on either side of the support 23. The bearings 43 are arranged inside housings in the casing 22 provided for this purpose.
[0040] The bearings 43 are preferably ball bearings. Advantageously, the bearings 43 are made of a material with a low coefficient of friction, such as ceramic. Alternatively, the bearings 43 are made of metal or any other material suitable for the application.
[0041] As shown in [Fig. 3a], a first elastic element 35 is disposed between the weight 26 and the housing 22. The stiffness of the first elastic element 35 is chosen to define an activation threshold for the inertial unlocking device. In the example shown, the first elastic element 35 is a helical spring. Alternatively, the first elastic element 35 may be in the form of a spring washer or any other elastic element suitable for the application.
[0042] A second elastic element 36 is disposed between the second shaft 30 and the housing 22. The second elastic element 36 is a torsion spring. The second elastic element 36 has one end bearing against the housing 22 and one end bearing against a spring stop 33 of the second shaft 30. The end of the torsion spring 36 can be disposed inside a retaining hole made in the spring stop 33.
[0043] A third elastic element 37 is mounted in compression between the housing 22 and the support 23. The third elastic element 37 is arranged around an arm 39 of the support carrying the pin 25. The third elastic element 37 has a stiffness much greater than that of the first elastic element 35, in particular in a ratio between 10 and 100. The third elastic element 37 preferably takes the form of a helical spring.
[0044] The operation of the unlocking device 21 according to the invention is described below. When the device 21 is in the locked state, the bearing surfaces of the flats 28, 31 extend along a plane perpendicular to a direction of application of the force of the third elastic element 37 on the support 23 along the arrow Fl (see [Fig. 3a]). The axis XI of the weight 26 is intended to be oriented along an axis of the seat 10.
[0045] As illustrated in figures 4a and 4b, when the seat 10 and therefore the weight 26 are subjected to a strong deceleration along the arrow F2, the weight 26 moves in translation, compressing the first elastic member 35 so as to move away from the weight stop 32.
[0046] This has the effect of releasing a rotation, along arrow F3, of the first shaft 27 and the second shaft 30 accelerated by the second elastic member 36.
[0047] As illustrated in figures 5a and 5b, the flats 28, 31 then rotate by 90 degrees so that their support plane extends vertically and parallel to the direction of application of the force of the third elastic member 37 along the arrow Fl.
[0048] This results in a break in contact between the first shaft 27 and the second shaft 30 allowing a decompression of the third elastic element 37 following the arrow Fl.
[0049] The decompression of the third elastic element 37 causes a translational displacement of the pin 25 towards the inside of the housing 22 to bring the device 21 into an unlocked state, as illustrated in figures 2b and 3b.
[0050] Unlocking the device 21 then allows the seat back 12 to rotate before head impact. This configuration makes it possible to meet the Head Injury Criterion (HIC) and the Nij impact criterion, which represents the stresses on the cervical spine. Thus, the invention helps to limit injuries to the neck and brain of a passenger.
[0051] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.
[0052] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variants that a person skilled in the art may consider within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination.
Claims
Demands
1. An inertia-operated unlocking device (21) characterized in that it comprises: - a housing (22), - a support (23) disposed inside the housing (22) carrying a pin (25) projecting from the housing (22) when said device (21) is in a locked state, said pin (25) being able to slide relative to the housing (22), - a weight (26) able to move translationally under the effect of inertia, - a first shaft (27) rotatably mounted inside an opening (24) in the support (23), said first shaft (27) having at least one end comprising a flat (28), - a second shaft (30) having a first end provided with a flat (31) intended to bear against the flat (28) of the first shaft (27) and a second end comprising a weight stop (32) bearing against the weight (26), - a first elastic element (35) disposed between the weight (26) and the housing (22),- a second elastic element (36) disposed between the second shaft (30) and the housing (22), and - a third elastic element (37) mounted in compression between the housing (22) and the support (23), such that when the weight (26) is subjected to strong deceleration, said weight (26) is able to move in translation, compressing the first elastic element (35) so as to move away from the weight stop (32), to release a rotation of the first shaft (27) and the second shaft (30) accelerated by the second elastic element (36), causing a break in contact between the first shaft (27) and the second shaft (30), allowing a decompression of the third elastic element (37), generating a translational movement of the pin (25) towards the inside of the housing (22) to bring the device (21) into an unlocked state.
2. Device according to claim 1, characterized in that the first shaft (27) is mounted to rotate relative to the support (23) by means of at least one bearing (42) interposed radially between the first shaft (27) and the support (23).
3. Device according to claim 1 or 2, characterized in that the second shaft (30) is mounted rotatably relative to the housing (22) by means of at least one bearing (43) interposed radially between the second shaft (30) and the housing (22).
4. Device according to any one of claims 1 to 3, characterized in that a stiffness of the first elastic member (35) is chosen so as to define an activation threshold of the inertial unlocking device.
5. Device according to any one of claims 1 to 4, characterized in that the second elastic element (36) is a torsion spring.
6. Device according to any one of claims 1 to 5, characterized in that the second elastic member (36) has one end bearing against the housing (22) and one end bearing against a spring stop (33) of the second shaft (30).
7. Device according to any one of claims 1 to 6, characterized in that the third elastic element (37) has a stiffness much greater than that of the first elastic element (35).
8. Device according to any one of claims 1 to 7, characterized in that an axis (XI) of the weight (26) extends in a direction perpendicular to an axis (X2) of the support (23).
9. Aircraft seat (10) comprising an inertia-based unlocking device (21) defined according to any one of the preceding claims.
10. Aircraft seat (10) according to claim 9, characterized in that the housing (22) is mounted on a seat structure (14) and the pin (25) is intended to cooperate with a correspondingly shaped housing made in a backrest when the inertial unlocking device is in the locked state.