Airplane seat designed to absorb vertical impacts

Description

TECHNICAL FIELD

[0001] The invention relates to an aircraft seat capable of absorbing a vertical shock in order to reduce damage to its occupant in such a case, this seat being intended to equip in particular a helicopter. STATE OF THE PRIOR ART

[0002] Generally speaking, aircraft seats must successfully pass tests to certify that a certain level of safety for the people transported is ensured in the event of an accident, crash or emergency landing.

[0003] In the case of helicopter seats, one of these tests is to determine whether the seat is capable of absorbing a vertical shock of predetermined intensity, to limit the damage suffered by its occupant in such a situation. More specifically, this test is designed to correspond to a case of forced, i.e. violent, vertical landing of the helicopter.

[0004] In practice, the test is carried out by installing a dummy equipped with force sensors in the seat, and applying a vertical shock of a predetermined intensity and duration to the assembly while measuring the forces experienced by the dummy in the region of the lumbar vertebrae during this shock. The test is passed if the lumbar forces measured during the shock remain below a predetermined threshold, which corresponds to a maximum value for which the forces experienced do not cause significant lesions in the lumbar region.

[0005] In the case of aircraft, the criteria defining vertical impact correspond to a vertical acceleration of 14 g, i.e. 14 times the acceleration of gravity at the Earth's surface. In practice, aircraft seats do not require any special adaptations to pass this test.

[0006] In the case of helicopters, the vertical shock applied during the test corresponds to 30 g, so it is on the contrary essential that the seat is specifically designed to support and cushion such a vertical shock by absorbing its energy.

[0007] To allow for the absorption of such a shock, a certain distance of vertical movement of the seat is allowed, which allows it to absorb the intensity of the shock applied, so that the shock suffered by its occupant is of lesser intensity. This distance is generally between 5 and 10 centimeters.

[0008] On the figure 1 , a helicopter seat 1 is shown comprising a fixed frame 2 formed of two parallel rectilinear uprights oriented vertically, which carries a carriage 3 to which a seat 4 and a backrest 5 are rigidly fixed, this carriage 3 being able to slide along the frame 2.

[0009] In normal operation, the carriage is locked on the frame which supports it, whereas in the event of a high intensity downward vertical impact, the carriage 3 with the seat and backrest move downwards along the frame, so as to absorb the intensity of the impact.

[0010] The movement of the carriage 3 along the frame 2 is damped by a mechanical system (not shown) absorbing the energy of the impact. This damping system may be a fusible mechanical part which deforms plastically to allow sliding while absorbing its energy. It may also be a metal cable deforming on a set of rollers, or any other arrangement allowing movement while absorbing the mechanical energy induced by it, generally by means of an irreversible deformation of a mechanical element.

[0011] Thus, and as visible on the figure 1, the need to absorb a high intensity vertical shock leads to a general seat structure that is much more complex and expensive than that of a conventional seat.

[0012] Generally speaking, the seats known from documents JP2013163452A and US20110043008A1 disclose, among other things, an arrangement for absorbing a vertical shock, comprising several straps each comprising a damping portion, this damping portion comprising a folded part in which two consecutive regions of the same face of this strap run alongside each other while being secured to each other by seams. Document US2021138398A1 discloses several straps each comprising a damping portion consisting of strap portions equipped with frangible absorption seams, and mentions the use in aircraft.

[0013] The aim of the invention is to remedy this need by providing a simple seat design capable of absorbing such a vertical shock. STATEMENT OF THE INVENTION

[0014] To this end, the invention relates to an aircraft seat, comprising a seat including a cushion carried by a frame as well as feet carrying this frame, this frame comprising at least two beams running along two opposite edges of the cushion, the cushion being carried by several straps extending from one beam to the other, in which at least one strap comprises a damping portion, this damping portion comprising a folded part in which two consecutive regions of the same face of this strap run along each other while being secured to each other by seams, so that these seams break when the strap is subjected to high tensile forces, and in which at least one strap forms a loop surrounding two beams.

[0015] With this arrangement, a downward vertical impact results in a significant increase in the tension of each strap, causing the fusible seams of the cushioning portion of each strap to gradually break while releasing strap length. The impact energy is thus absorbed to reduce its intensity at the lumbar vertebrae of the seat occupant.

[0016] The invention also relates to a seat thus defined, comprising at least one strap equipped with a fastener connecting its two ends to form a loop.

[0017] The invention also relates to a seat thus defined, in which the frame comprises two lateral beams and two transverse beams arranged in a rectangular shape running along the edges of the cushion, and comprising on the one hand straps extending from one transverse beam to the other, and on the other hand straps extending from one lateral beam to the other.

[0018] The invention also relates to a seat thus defined, comprising at least one strap having a cushioning portion, the folded part of which is folded down along the remainder of this strap.

[0019] The invention also relates to a seat thus defined, comprising a strap provided with several damping portions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] There [ Fig. 1 ] is an overview of a helicopter seat according to the state of the art; The [ Fig. 2 ] is an overall view of the seat according to the invention shown in perspective; The [ Fig. 3 ] is a detail view showing in perspective a part of the strap of the seat base according to the invention comprising a damping portion in the normal state; The [ Fig. 4 ] is a side view of a damping portion of a seat strap of the seat according to the invention in the normal state; The [ Fig. 5] is a side view of a cushioning portion of a seat strap of the seat according to the invention at the start of shock absorption; The [ Fig. 6 ] is a side view of a damping portion of a seat strap of the seat according to the invention during shock absorption; The [ Fig. 7 ] is a side view of a damping portion of a seat strap of the seat according to the invention after damping an impact; The [ Fig. 8 ] is a partial view showing the frame of the seat of the seat according to the invention equipped with a strap in the normal state; The [ Fig. 9 ] is a partial view showing the frame of the seat base according to the invention equipped with a strap at the start of shock absorption; The [ Fig. 10 ] is a partial view showing the frame of the seat of the seat according to the invention equipped with a strap during shock absorption; The [ Fig. 11] is a partial view showing the frame of the seat base according to the invention equipped with a strap after absorbing a shock; The [ Fig. 12 ] is a partial view showing the frame of the seat of the seat according to the invention equipped with several straps in the normal state; The [ Fig. 13 ] is a partial view showing the frame of the seat base according to the invention equipped with several straps at the start of shock absorption; The [ Fig. 14 ] is a partial view showing the frame of the seat of the seat according to the invention equipped with several straps during shock absorption; The [ Fig. 15 ] is a partial view showing the frame of the seat of the seat according to the invention equipped with several straps after absorbing a shock; The [ Fig. 16 ] is a side view of the seat according to the invention in which an occupant is installed in the normal state; The [ Fig. 17] is a side view of the seat according to the invention in which an occupant is installed during shock absorption; The [ Fig. 18 ] is a side view of the seat according to the invention in which an occupant is installed after absorbing an impact. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0021] On the figure 1 , an aircraft seat 6 comprises a seat 7 fixed to a floor 8 and carrying a backrest 9. The seat 7 comprises a lower frame 10 formed of beams assembled to constitute a frame to which pieces of foam and fabric forming a cushion 11 of this seat are fixed. This seat 6 also comprises feet by which its seat 7 is rigidly secured to the floor 8, these feet here comprising two rear feet 12, 13, two front feet 14, 15, and two intermediate feet 16, 17.

[0022] The backrest 9 comprises an upper frame 18 carrying pieces of fabric, and which is carried by the lower frame 10 of the seat by means of fasteners.

[0023] According to the invention, the seat 7 is equipped with straps which comprise damping portions in which these straps are folded and sewn onto themselves, such that during an impact, the tension forces resulting from this impact in the straps cause the progressive tearing of the seams of their damping portions to absorb the energy of this impact.

[0024] On the Figures 3 and 4, a part of a strap 19 formed from the same piece of fabric comprises a first and a second current portion 21, 22 connected by a damping portion 23. Here, the term "the same piece of fabric" means that this part of the strap is formed from the same strip of fabric instead of being made up of several strips of fabric connected or joined to each other.

[0025] This damping portion 23 comprises a folded part 24 in which two consecutive regions of the same face of the strap run alongside each other, being secured to each other by seams 26. This folded part 24 is here folded down along the first running portion 21 to have limited bulk.

[0026] In terms of proportions, the folded part 24 has a total length corresponding here substantially to twice the width of the strap 19, the width of the strap being constant in itself.

[0027] When the strap 19 is subjected to tension forces T1 and T2 applied to its running portions in directions opposite to the damping portion 23, the stitching points 27 located at the junction of the folded part 24 and the first and second running portions 21, 22 undergo these forces first.

[0028] As these stitching points 27 have a lower tensile strength than that of the strap, when these tensile forces T1 and T2 become greater than a threshold, upon impact of a shock, these stitching points 27 give way, which has the effect of starting to open the folded part 24. Under these conditions, and as illustrated in the Figure 5, the first portion 21 and the second portion 22 move away from each other, while the breaking of the stitching points 27 absorbs part of the energy of the impact of this shock. As the shock continues to be exerted, that is to say during the shock, the rest of the seams 26 gradually give way, from the stitching points 27 towards those of the free end 28 of the folded part 24. The folded part 24 then continues to open while absorbing part of the energy of the shock, and the first and second current portions 21, 22 continue to move away from each other to release the length of strap, which corresponds to the situation of the figure 6 .

[0029] At the end of the shock, as illustrated in the figure 7 , the folded portion 24 is completely open, so that the strap 19 extends substantially curved downwards having lost all its tension.

[0030] As visible on the figures 8 to 15, the frame 10 of the seat 7 of the seat 6 according to the invention comprises two lateral beams 29 and 30 extending longitudinally, which are connected to a front transverse beam 31 and to a rear transverse beam 32. These beams are here beams with a round section, that is to say tubes, which can be provided in metallic, plastic, composite or other material.

[0031] These four beams 29-32 are thus arranged in a rectangular arrangement, to which the feet 12-17 are connected, ensuring that the assembly is held on the floor 8. The beams 29-32 are fixed to each other and to the feet 12-17 by connecting elements of the elbow or similar type, each receiving one end of the beam.

[0032] On the figures 8 to 11, the strap 19 is passed around the front 31 and rear 32 beams with its ends connected to each other, so as to constitute a loop surrounding these beams 31 and 32 while extending longitudinally, that is to say parallel to the side beams 29 and 30.

[0033] The ends of the strap 19 are connected to each other by a fastener 33 allowing the loop to be closed while putting this strap under tension. This fastener, which is here located mid-length of the lower part of the loop formed by the strap, is for example a snap-on fastener allowing easy assembly of the strap for an assembly operator.

[0034] The damping portion 23 of the strap 19 is located halfway along the upper part of the loop formed by this strap 19. In practice, and as visible on the figure 12, four straps 19 are mounted in the same way around the front and rear beams, extending longitudinally, parallel to each other, and being regularly spaced from each other in the transverse direction.

[0035] An additional transverse strap 19 encloses the side beams 29 and 30 in a similar manner, that is to say by also forming a loop, and by extending perpendicular to the loops formed by the four straps 19 oriented longitudinally.

[0036] In practice, the lower frame 10 with the straps 19 which enclose it is covered with foam elements and a covering fabric forming the lower cushion 11 receiving the posterior of the occupant of the seat. This cushion 11 thus rests on the set of straps 19 which surround the frame 10 of the seat 7.

[0037] In the event of a vertical downward impact, the occupant installed in the seat 6 exerts, due to his mass, significant forces on the cushion of the seat on which he is resting, and thereby on all the straps 19 carrying this cushion. These vertical forces directed downwards result in high tension forces in the straps 19, which cause the progressive rupture of the seams connecting their shock-absorbing portions, so that these straps lengthen, absorbing part of the energy of the impact.

[0038] More particularly, upon impact, that is to say at the start of the shock, the rapid and significant increase in the tension forces in the straps 19 causes the first stitching points of the damping portions 23 to break, which corresponds to the situation illustrated in the figures 4 , 9 And 13During this phase, the straps begin to stretch as their stitching breaks one after the other, absorbing energy.

[0039] As the impact continues, i.e. during the impact, the other stitching points give way, so that the straps continue to absorb energy by stretching as their cushioning portions 23 continue to open, which corresponds to the figures 5 , 10 And 14 .

[0040] At the end of the shock, as illustrated on the figures 6 , 11 And 15 , the cushioning portions are completely open due to all the stitching having given way, and the straps 19 are at their maximum lengths.

[0041] As visible on the figures 16 to 18, when an occupant 34 is installed in the seat according to the invention, and is subjected to a vertical downward impact, the rupture of the damping portions 23 of the different straps 19 increases the lengths of these straps, so that the cushion 11 carried by these straps 19 sinks into the frame 10 with the occupant.

[0042] Thus, in the normal state as on the figure 16 , the cushion 11 is located essentially above the frame 10, and as the shock takes place, it sinks into the frame 10 while the seams of the damping portions 23 gradually tear, as seen in the figure 17 .

[0043] At the end of the impact, the central part of the cushion can be located substantially below the level of the beams constituting the frame 10, as illustrated in the figure 18 .

[0044] In the example of the figures 12 to 15, the seat is equipped with four longitudinal straps and one transverse strap, but generally speaking, the number of straps chosen and their arrangement depend on the design of the seat and the conditions of the test to be passed.

[0045] As will be understood, the choice of the number of straps makes it possible to optimize the performance in the test in question, as well as the width of these straps, the length of the folded parts forming the cushioning portions, the density of the seams, and the breaking strength of the thread used in these cuts.

[0046] In the example of the figures, each strap has a damping portion, but it is possible to provide that these straps have several damping portions, which can where appropriate be sewn with threads having different breaking strengths.

[0047] In this case, the cushioning portion sewn with the lowest tension thread tears first during an impact, after which the other cushioning portion(s) sewn with higher strength thread break, which optimizes the shock absorption dynamics.

Claims

1. An aircraft seat (6), comprising a seating (7) including a cushion (11) carried by a frame (10) as well as feet (12-17) carrying this frame (10), this frame (10) comprising at least two beams (29-32) housing two opposite edges of the cushion (11), the cushion (11) being carried by several straps (19) extending from one beam (29-32) to the other, wherein at least one strap (19) includes a damping portion (23), this damping portion (23) comprising a folded part (24) in which two consecutive regions of the same face of this strap (19) being housed while being secured to each other via seams (26), so that these seams break when the strap (19) undergoes high tensile stresses (T1, T2) and wherein at least one strap (19) forms a loop surrounding two beams (29-32).

2. The seat (6) according to one of the preceding claims, comprising at least one strap (19) equipped with a snap-on fastener (33) connecting the two ends thereof to form a loop.

3. The seat (6) according to one of the preceding claims, wherein the frame (10) includes two lateral beams (29, 30) and two transverse beams (31, 32) arranged in a rectangular shape housing the edges of the cushion, and comprising, on the one hand, straps (19) extending from one transverse beam (31, 32) to the other and, on the other hand, straps (19) extending from one lateral beam (29, 30) to the other.

4. The seat (6) according to one of the preceding claims, comprising at least one strap (19) having a damping portion (23) whose folded part (24) is folded down along the remainder of this strap (19).

5. The seat (6) according to one of the preceding claims, comprising a strap (19) provided with several damping portions (23).