GB2265813A - "Crash attenuating seat belt anchorage" - Google Patents

Abstract

A seat belt anchorage. especially for an aircraft passenger seat mounted on front and rear transverse round-section spars 12, 11, comprises a member 38 having an arm 40 extending under the rear transverse spar 11 and upwardly and rearwardly to a pivotal connection with one end of a link 32. The seat belt 25 is connected, via an attachment member 28 to the other end of link 32 and to a second link 34 which is secured to the seat frame via pivot pin 35 and shear pin 44. Furthermore, the link 34 is connected to the base of sheet metal seat pan 24 via support 46. In a crash, (Fig. 2) the shear pin 44 is broken and the arm 40 is wrapped progressively around the spar 11 and the length of the effective lever afforded by the free length of the arm 40 is thereby progressively reduced, whereby the resistance to bending of the arm increases progressively. Moreover, the consequent forward pivoting of link 34 deforms the seat pan 24 which minimises subsequent rearward movement of the passenger when the first deceleration peak has passed. <IMAGE>

Description

DESCRIPTION OF INVENTION Title: "Crash attenuating seat belt anchorage" THIS INVENTION relates to a crash-attenuating seat belt anchorage suitable, inter alia, for a passenger seat belt in a passenger aircraft.

Considerable effort has been directed, in recent years, to improving the prospects for passengers in passenger aircraft surviving serious injury in the event of crash and regulations have been adapted specifying minimum requirements as to the provisions which must be made for ensuring adequate survivability of crashes by passengers.

In particular, it is desirable to minimise the risk that a passenger seat will break free from the mountings which secure the seat to the passenger cabin floor, in the event of a crash. As technology in this area improves, such regulations are being up-dated to make the aforementioned requirements more stringent. Accordingly, and in the interests of improving passenger safety generally, it is an object of the present invention to provide an improved crash-attenuating seat belt anchorage for a seated passenger in a vehicle, for example in a passenger aircraft.

According to the present invention there is provided a crash-attenuating seat belt anchorage comprising a deformable member secured or adapted to be secured to a seat frame, and means for connecting said member to a seat belt, said deformable member being arranged to undergo energy-absorbing bending deformation in the event that the tensile force applied to the seat belt, and, through the seat belt and said deformable member, to the seat frame, exceeds a predetermined value.

An embodiment of the invention is described below by way of example with reference to the accompanying drawings in which: FIGURE 1 is a side view, partly in section, of part of a passenger aircraft seat embodying the invention, in its normal condition, and FIGURE 2 is a view, corresponding to Figure 1, but showing the seat after a crash.

Conventionally, passenger seats in a passenger aircraft are provided in blocks of two, three, four or more arranged side by side in a transversely extending row, each block having a horizontal transverse front spar, and a parallel horizontal transverse rear spar, to both of which frame members of all the seats in the block are secured, the block of seats being supported from the cabin floor by a supporting structure also secured to these transverse spars. The transverse spars are generally of round-section metal tubing.In the description which follows with reference to the drawings, a crash-energy absorbing seat belt mounting is described as applied to an aircraft passenger seat of the above-noted type in which each seat in the block has, on either side of the seat, a respective metal frame member 20 extending in the fore and aft direction, the frame members 20 on either side of the seat supporting a sheet metal seat pan 24 of the seat, the frame members 20 having front and back clamp formations 16, 17 which receive and are clamped to the front and rear transverse spars 12 and 11 respectively.

The seat back, seat cushion and upholstery are not shown in the drawings. It will be appreciated that the rear transverse spar 11 lies just below the junction of the base and the back of the seat. It will also be appreciated that the seats are arranged facing forwards in the aircraft, i.e. facing towards the nose of the aircraft.

Each passenger seat has a respective lap-type seatbelt, part of which is shown at 25, comprising two parts connected by a releasable buckle (not shown) and secured at its ends remote from the releasable buckle to respective anchorages provided on either side of the seat at the back of the seat base. Referring to Figure 1, each of the free ends of the seat belt remote from the buckle carries a respective metal attachment member 28 which is pivotable around a pin 30 on which is also pivotally mounted the forward end of a metal link 32, the pin 30 being rotatably journalled in the rearward end of a metal link 34. The link 34 is pivotally mounted, at its end remote from the pin 30, on a pin 35 passing through a complementary bore (not shown) in the adjoining portion of the adjoining frame member 20. A metal member 38 is also pivotally mounted on the pin 35.It will be appreciated that, as viewed in the drawings, the member 38 and links 34 and 32 mask from view significant parts of the near portion of the frame member 20, including the part of the frame member 20 which extends below the rear transverse spar 11 and the part of the frame member 20 which carries the pin 35.

The portion of the member 38 adjacent the pin 35 is of arcuate form, providing a concave part-cylindrical inner surface which snugly engages the outer surface of the rear spar 11, as shown. Thus, from the pin 35, the member 38 extends first rearwardly with a slight downward component and then rearwardly with an upward component, under the spar 11, then continues rearwardly and upwardly away from the spar 11, substantially tangentially with respect to the spar 11, to form an arm 40 terminating at an end 42 which is pivotally connected with the rear end of the link 32.

Each link 34 is normally fixed with respect to the adjacent frame 20 by a respective shear pin 44. Each link 34 is also secured to a seat pan support 46 secured in turn to the seat pan 24. The seat pan support 46 may, for example, take the form of a bar extending across the seat pan 24 from the link 34 on one side to the link 34 on the other. It will be appreciated that, for each seat, a respective belt anchorage arrangement including links 32, 34 and member 38 is mounted on each of the two frames 20 which are at the sides of the respective seat, these anchorage arrangements being mounted on the inner sides of the two frames 20 of the seat concerned and the respective seat pan 24 being disposed between these two anchorage arrangements.

The seat pan 24 has, along its rear edge, an upwardly turned flange 23 which normally extends upwardly behind the rear end of the seat cushion.

In a crash situation, in which the forwardly moving aircraft impacts with the ground, thereby rapidly decelerating the aircraft structure and the passenger seats, a passenger occupying the seat is flung forwards by his own momentum but is restrained by the seat belt 25.

Accordingly a substantial stress is applied via each end of the belt 25 and the respective attachment member 28 to the respective anchorage arrangement. When this stress exceeds a predetermined value the shear pin 44 of each anchorage arrangement is broken and the respective link 34 begins to pivot forwards whilst the respective arm 40 begins to be bent around the rear transverse spar 11, the respective link 32 pivoting in consequence relative to the member 38 and the link 34, about the pin 35 forming its pivotal connections with these components.

At the same time the seat pan support 46 and the part of the seat pan 24 secured thereto is forced forwards and downwards by the pivoting of links 34 about their pins 35 and is simultaneously twisted about a transverse axis in accordance with the angular movement of the links 34 about the pins 35. Consequently, the seat pan is deformed towards the position shown in Figure 2, in which the middle of the seat pan is belt downwardly into the form of a trough, whilst the portions of the seat pan behind the support 46 is swung forwards and upwards (including the upwardly bent flange 23 at the rear of the seat pan).As a result of this deformation of the seat pan, the rearward part of the seat pan, and the seat cushion (not shown) located thereon and on which the passenger is seated follow the forward movement of the passenger relative to the seat during the crash and thus during the bending of the arms 40 and prevent or minimise subsequent rearward movement of the passenger when the first deceleration peak has passed, so that the passenger is still firmly restrained by the seat belt in readiness for a subsequent deceleration peak. That is to say, the forward movement of the passenger relative to the seat during the first crash peak, with the deformation of the arm 40 and forward movement of the attachment members 28 would mean, in the absence of an appropriate counter-measure, that the passenger's seat belt would be relatively slack for any subsequent crash peak, which is undesirable. The described deformation of the seat pan, by ensuring that the passenger is supported, from behind, by an element which follows the forward movement of the seat belt mountings during the first crash peak, prevents such slackness of the seat belt from occurring.

In a variant, the material of seat pan 24 is extended upwardly, at the rear of the seat pan, for a substantial distance up the seat back and is connected at its upper end to the seat back, so that in a crash, the forward and downward deformation of the part of the seat pan lying forward of the link 34 is accompanied by a forward swinging movement, about its upper attachment point of the extension of the seat pan over the lower part of the seat back, again ensuring that no slack develops in the seat belt.

The deformation of the arms 40 absorbs part of the kinetic energy of the passenger during the crash. (To a lesser extent, the deformation of the seat pan D also absorbs some of the kinetic energy of the passenger). Such absorption of kinetic energy is relatively gradual so that there is less likelihood of injury to the passenger from the restraining forces applied by the seat belt The moment arm of each arm 40, i.e. the effective free length of the arm 40, is progressively reduced as the arm is bent around the spar 11, and this, assisted by the changing geometry of the anchorage arrangement due to the relative pivotal movements of the link, results in a gradual increase in the restraining force applied by the anchorage to the seat belt during the impact deceleration of the aircraft, thus minimising the likelihood of a sharp jerk being applied via the seat belt to the passenger as might otherwise occur upon a crash energy absorbing device reaching the end of its range of movement.

It will be appreciated that in addition to the seat belt mounting arrangement described, the seat may, be provided with other crash energy absorbing provisions, for example an arrangement permitting controlled energy absorbing deformation of the sub-structure (not shown) which supports the spars 11, 12 from the aircraft cabin floor.

However, crash-energy absorbing arrangements which depend upon forward movement of passenger seats relative to the cabin floor in the event of a crash are not currently favoured because, in order to maintain, in the event of a crash, a safe spacing between, for example, an occupied passenger seat and an unoccupied (and therefore relatively immobile) seat immediately in front, it is necessary to allow greater clearance between rows of seats in arrangements relying upon forward movements of seats for crash-energy absorption, so that the passenger carrying capacity of the aircraft is reduced. It is an object of the preferred embodiment of the invention to provide an effective means of absorbing the kinetic energy of a passenger relatively gradually, thereby minimizing the peak stress applied to the seat mountings securing the seat occupied by the passenger to the cabin floor, without the necessity of allowing forward movement of the seat itself, and thus without reduction of the passenger-carrying capacity of an aircraft.

It will also be appreciated that, whilst the preferred embodiment has been described as applied to an aircraft passenger seat, such an arrangement might, for example, be used with motor vehicle safety belts or in other analogous situations.

Claims (7)

1. A crash-attenuating seat belt anchorage comprising a deformable member secured or adapted to be secured to a seat frame, and means for connecting said member to a seat belt, said deformable member being arranged to undergo energy-absorbing bending deformation in the event that the tensile force applied to the seat belt, and, through the seat belt and said deformable member to the seat frame, exceeds a predetermined value.

2. A crash-attenuating seat belt anchorage according to claim 1, in combination with a seat frame affording a transverse round-section spar towards the rear of the seat, the deformable member comprising an arm extending under said spar and having a first part in contact or close proximity with the underside of said spar, the arm extending upwardly and rearwardly away from said spar, from said first part to a free end of said arm, and connecting means at the free end of said arm connecting said arm with the seat belt, so that when, in a crash situation, the force applied through the belt to the arm exceeds said predetermined value, the arm will be bent forwardly around said transverse spar so that the arm is wrapped progressively around said transverse spar and the length of the effective lever afforded by the free length of said arm is progressively reduced, whereby the resistance to bending of the arm increases progressively during such deformation.

3. The combination of claim 1 wherein said anchorage comprises, in addition to said arm, a first link pivotally connected at one end to the free end of said arm, a second link pivotally connected at one end with said deformable member at a position remote from said free end of said arm, said first and second links being pivotally connected, at their ends, with one another and with a belt attachment member, whereby said rear transverse spar extends through an aperture bounded by said deformable member and said first and second links.

4. The combination of claim 3 wherein said seat frame includes a further transverse spar at the front of the seat, a deformable seat pan secured to said front spar and extending over the rear spar, said seat pan being secured to said second link, whereby when, in a crash situation, said arm is bent by a forward pull on the belt, such bending is accompanied by pivotal movement of said first and second links relative to said deformable member1 each other and the frame, resulting in a forward movement of the part of the seat pan secured to said second link.

5. A crash attenuating seat belt anchorage, substantially as hereinbefore described with reference to and as shown in the drawings.

6. The combination of a seat with a seat belt anchorage, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

7. Any novel feature or combination of features described herein.