Aircraft seat designed to absorb a vertical shock

Abstract

The invention relates to an aircraft seat, comprising a seat (7) including a cushion supported by a frame (10) and legs (12, 13, 15, 17) supporting this frame (10). This frame (10) comprises at least two beams (31, 32) running along two opposite edges of the cushion. The cushion is supported by several straps (19) extending from one beam to the other. At least one strap (19) has a cushioning portion (23) comprising a folded section (24) in which two faces of the same piece of this strap (19) run parallel to each other and are joined together by seams, such that these seams break when the strap (19) is subjected to tensile forces exceeding a threshold value. Figure 8

Description

Title of the invention: Aircraft seat designed to absorb a vertical shock 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. PREVIOUS STATE OF THE ART

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

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

[0004] In practice, the test is performed by installing a mannequin equipped with force sensors in the seat, and applying a vertical shock of predetermined intensity and duration to the assembly while measuring the forces exerted on the mannequin in the lumbar vertebral region during this shock. The test is considered successful if the lumbar forces measured during the shock remain below a predetermined threshold, which corresponds to a maximum value at which the forces exerted do not cause significant damage to the lumbar region.

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

[0006] In the case of helicopters, the vertical shock applied during the test corresponds to 30 g, so it is essential that the seat be 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 vertical displacement of the seat is permitted, enabling it to dampen the intensity of the applied shock, so that the shock experienced by its occupant is less intense. This distance is generally between 5 and 10 centimeters.

[0008] In [Fig. 1], a helicopter seat 1 is shown comprising a fixed frame 2 formed of two parallel, vertically oriented straight uprights, which supports a trolley 3 to which are rigidly fixed a seat 4 and a backrest 5, this trolley 3 being able to slide along the frame 2.

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

[0010] The movement of the carriage 3 along the frame 2 is damped by a mechanical system (not shown) that absorbs the impact energy. This damping system may be a fusible mechanical part that 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 that allows movement while absorbing the mechanical energy induced therein, generally by means of an irreversible deformation of a mechanical element.

[0011] Thus, and as can be seen in [Fig.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] The object of the invention is to remedy this drawback by providing a simple seat design capable of absorbing such a vertical shock. Description of the invention

[0013] To this end, the invention relates to an aircraft seat, comprising a seat including a cushion carried by a frame and feet carrying this frame, this frame comprising at least two beams along two opposite edges of the cushion, the cushion being carried by several straps extending from one beam to the other, characterized in that at least one strap has 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 and are joined together by seams, so that these seams break when the strap is subjected to high tensile forces.

[0014] With this arrangement, a downward vertical impact results in a significant increase in the tension of each strap, causing the progressive rupture of the fusible seams in the shock-absorbing portion of each strap while releasing some of the strap length. The impact energy is thus absorbed, reducing its intensity at the lumbar vertebrae of the seat occupant.

[0015] The invention also relates to a seat thus defined, comprising at least one strap forming a loop surrounding two beams.

[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 along the edges of the cushion, and comprising on 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 rest of this strap.

[0019] The invention also relates to a seat thus defined, comprising a strap provided with several cushioning portions. Brief description of the drawings

[0020] Fig. 1 is an overview of a helicopter seat according to the prior art;

[0021] Fig. 2 is an overview of the seat according to the invention shown in perspective;

[0022] Fig. 3 is a detail view showing in perspective a portion of the webbing of the seat according to the invention comprising a portion of damping in the normal state;

[0023] 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;

[0024] Fig. 5 is a side view of a damping portion of a seat strap of the seat according to the invention at the beginning of shock damping;

[0025] Fig. 6 is a side view of a damping portion of a seat strap of the seat according to the invention during shock damping;

[0026] Fig. 7 is a side view of a portion of the damping of a seat strap according to the invention after damping of a shock;

[0027] Fig. 8 is a partial view showing the seat frame according to the invention equipped with a strap in the normal state;

[0028] Fig. 9 is a partial view showing the seat frame according to the invention equipped with a strap at the beginning of shock absorption;

[0029] Fig. 10 is a partial view showing the seat frame according to the invention equipped with a strap during shock absorption;

[0030] Fig. 11 is a partial view showing the seat frame according to the invention equipped with a strap after shock absorption;

[0031] Fig. 12 is a partial view showing the frame of the seat according to the invention equipped with several straps in the normal state;

[0032] Fig. 13 is a partial view showing the frame of the seat according to the invention equipped with several straps at the beginning of shock absorption;

[0033] Fig. 14 is a partial view showing the seat frame according to the invention equipped with several straps during shock absorption;

[0034] Fig. 15 is a partial view showing the seat frame according to the invention equipped with several straps after shock absorption;

[0035] Fig. 16 is a side view of the seat according to the invention in which an occupant is installed in the normal state;

[0036] Fig. 17 is a side view of the seat according to the invention in which an occupant is installed during shock absorption;

[0037] Fig. 18 is a side view of the seat according to the invention in which an occupant is installed after shock absorption.

[0038] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0039] In [Fig. 1], an aircraft seat 6 comprises a seat 7 fixed to a floor 8 and supporting a backrest 9. The seat 7 has a lower frame 10 formed of beams assembled to constitute a frame to which pieces of foam and fabric are attached, forming a cushion 11 of this seat. This seat 6 also has legs by which its seat 7 is rigidly attached to the floor 8, these legs comprising here two rear legs 12, 13, two front legs 14, 15, and two intermediate legs 16, 17.

[0040] The backrest 9 comprises an upper frame 18 carrying pieces of fabric, and which is supported by the lower frame 10 of the seat by means of fasteners.

[0041] According to the invention, the seat 7 is equipped with straps which have cushioning portions in which these straps are folded and sewn onto themselves, so that during an impact, the tensile forces resulting from this impact in the straps cause the progressive tearing of the seams of their cushioning portions to absorb the energy of this impact.

[0042] In figures 3 and 4, a part of a strap 19 formed from a single piece of fabric comprises a first and a second running portion 21, 22 connected by a cushioning portion 23. Here, a single piece of fabric means that this part of the strap is formed from a single strip of fabric instead of being made up of several strips of fabric connected or butted together.

[0043] This cushioning portion 23 includes a folded part 24 in which two consecutive regions of the same face of the strap run alongside each other and are joined together by seams 26. This folded part 24 is here folded down along the first running portion 21 to present a limited bulk.

[0044] In terms of proportions, the folded part 24 has a total length corresponding here to approximately twice the width of the strap 19, the width of the strap being constant in itself.

[0045] When the strap 19 is subjected to tensile 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 are first subjected to these forces.

[0046] Since these stitching points 27 have a lower tensile strength than 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 [Fig.5], the first portion 21 and the second portion 22 move apart from each other, while the rupture of the stitching points 27 absorbs part of the energy of the impact of this shock.

[0047] As the shock continues to be exerted, i.e. during the shock, the remaining 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 up, absorbing part of the energy of the shock, and the first and second running portions 21, 22 continue to move apart from each other to release the length of the strap, which corresponds to the situation in [Fig.6].

[0048] At the end of the shock, as illustrated in [Fig.7], the folded part 24 is completely open, so that the strap 19 extends in a substantially curved downwards, having lost all its tension.

[0049] As can be seen in figures 8 to 15, the frame 10 of the seat 7 of the seat 6 according to the invention comprises two longitudinally extending lateral beams 29 and 30, which are connected to a front transverse beam 31 and a rear transverse beam 32. These beams are here round section beams, i.e. tubes, which can be made of metallic, plastic, composite or other material.

[0050] These four beams 29-32 are thus arranged in a rectangular configuration, to which the feet 12-17 are connected, ensuring that the assembly is held on the floor 8. The fixing of the beams 29-32 to each other and to the feet 12-17 is ensured by connecting elements of the type elbows or similar, each receiving one end of the beam.

[0051] In figures 8 to 11, the strap 19 is passed around the front beams 31 and rear beams 32 with its ends connected to each other, so as to form a loop enclosing these beams 31 and 32 by extending longitudinally, that is to say parallel to the side beams 29 and 30.

[0052] The ends of the strap 19 are connected to each other by a fastener 33, allowing the loop to be closed while the strap is under tension. This fastener, which is located here at mid-length of the lower part of the loop formed by the strap, is, for example, a snap fastener allowing easy assembly of the strap. an assembly operator.

[0053] The damping portion 23 of the strap 19 is located at mid-length of the upper part of the loop formed by this strap 19. In practice, and as can be seen in [Fig. 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.

[0054] An additional transverse strap 19 encircles the lateral beams 29 and 30 in a similar manner, that is to say by also forming a loop, and by extending perpendicularly to the loops formed by the four longitudinally oriented straps 19.

[0055] In practice, the lower frame 10 with the straps 19 that encircle it is covered with foam elements and upholstery fabric forming the lower cushion 11 which supports the buttocks of the seat occupant. This cushion 11 thus rests on the set of straps 19 which encircle the seat frame 10 7.

[0056] In the event of a downward vertical impact, the occupant in seat 6 exerts significant forces, due to their mass, on the seat cushion on which they are resting, and consequently on all the straps 19 supporting this cushion. These downward vertical forces result in high tensile stresses in the straps 19, which cause the progressive rupture of the seams connecting their shock-absorbing sections, so that these straps elongate while absorbing part of the impact energy.

[0057] More particularly, during the impact, i.e. at the beginning of the shock, the rapid and significant increase in tension forces in the straps 19 causes the first stitching points of the cushioning portions 23 to break, which corresponds to the situation illustrated in figures 4, 9 and 13. During this phase, the straps begin to lengthen as their stitching points give way one after another, absorbing energy.

[0058] As the shock continues, i.e. during the shock, the other stitching points give way, so that the straps continue to absorb energy by elongating as their damping portions 23 continue to open, which corresponds to figures 5, 10 and 14.

[0059] At the end of the shock, as illustrated in figures 6, 11 and 15, the cushioning portions are completely open because all the stitching points have given way, and the straps 19 have their maximum lengths.

[0060] As can be seen in Figures 16 to 18, when an occupant 34 is seated in the seat according to the invention, and is subjected to a downward vertical impact, the rupture of the cushioning portions 23 of the various 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.

[0061] Thus, in the normal state as in [Fig. 16], the cushion 11 is located essentially above the frame 10, and as the shock unfolds, it sinks into the frame 10 while the seams of the cushioning portions 23 gradually tear, as can be seen in [Fig. 17].

[0062] At the end of the impact, the central part of the cushion can be located substantially below the level of the beams constituting the reinforcement 10, as illustrated in [Fig. 18].

[0063] In the example of figures 12 to 15, the seat is equipped with four longitudinal straps and one transverse strap, but in general, the number of straps chosen and their arrangement depend on the design of the seat and the conditions of the test to be carried out.

[0064] As will be understood, the choice of the number of straps allows for optimization of performance in the test in question, as does 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 for these cuts.

[0065] In the example in the figures, each strap has a cushioning portion, but it is possible to provide that these straps have several cushioning portions, which may, if necessary, be sewn with threads having different breaking strengths.

[0066] In this case, the portion of the damping sewn with the thread of the lowest tension tears first during an impact, after which the other portion or portions of the damping sewn with thread of greater resistance give way, which optimizes the dynamics of shock absorption.

Claims

Demands

1. Aircraft seat (6), comprising a seat (7) including a cushion (11) supported by a frame (10) and legs (12-17) supporting this frame (10), this frame (10) comprising at least two beams (29-32) running along two opposite edges of the cushion (11), the cushion (11) being supported by several straps (19) extending from one beam (29-32) to the other, characterized in that at least one strap (19) has a damping portion (23), this damping portion (23) comprising a folded portion (24) in which two consecutive regions of the same face of this strap (19) run alongside each other and are joined together by seams (26), such that these seams break when the strap (19) is subjected to high tensile forces (T1, T2) and in which at least one strap (19) forms a loop surrounding two beams (29-32).

2. Seat (6) according to any one of the preceding claims, comprising at least one strap (19) equipped with a snap fastener (33) connecting its two ends to form a loop.

3. Seat (6) according to any one of the preceding claims, wherein the frame (10) comprises two side beams (29, 30) and two cross beams (31, 32) arranged in a rectangular shape along the edges of the cushion, and comprising on one side straps (19) extending from one cross beam (31, 32) to the other, and on the other side straps (19) extending from one side beam (29, 30) to the other.

4. Seat (6) according to any one of the preceding claims, comprising at least one strap (19) having a cushioning portion (23) the folded part of which (24) is folded down along the rest of this strap (19).

5. Seat (6) according to any one of the preceding claims, comprising a strap (19) provided with several cushioning portions (23).

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