GB2243540A - Improvements in or relating to seats for mounting on a vehicle floor - Google Patents

Abstract

With reference to (Fig. 1), an aircraft passenger seat (1) is mounted on a floor (2) of an aircraft and comprises a body support frame (3), and a pair of rear legs (4), and feet (6, 7) for attaching the frame (3) to the floor (2) so as to be pivotable about a substantially horizontal axis (8) towards and away from the floor (2). The seat (1) also comprises restraint means in the form of a telescopic device (9) for preventing the pivotable movement unless overridden by impact loadings applied to the seat of a predetermined magnitude. The device (9), which serves as a normally solid strut, is disposed between the support frame (3) and front blocks (27), and is secured thereto by pivotal connections (28, 29). Should an aircraft incorporating the seat (1) make a forced landing whereby the impact load applied to the seat in the direction (95) is up to, say, 9.0 g, the seat, with its occupant, will wish to rotate about axis (8) relative to the floor (2) and in the direction of arrow (96). However, frictional forces in the device (9), imposed by clamping rings (56, 57), resist such pivoting. Should an impact load applied to the seat (1) be, say, 12.0 g in magnitude, the device (9) is overridden by the excess load, thus causing the seat to pivot. This rotational or pivoting movement, indicated by arrow (96), causes the tubular member (40) (Fig. 2) of the device (9) to be forced downwardly, into the tubular member (41), so as to contract the device. As the member (40) is forced into the member (41), the rings (56, 57) apply a substantially uniform frictional gripping force on it which absorbs the excess energy, i.e. the 3.0 g difference between 9.0 g and 12.0 g imposed on the seat (1), as the centre of gravity of the seat and occupant is displaced forwardly. The device (9) is provided with means operable to apply a seat-restoring movement. The device (9) may be replaced by a rotary form of restraint means.

Description

IMPROVEMENTS IN OR RELATING TO SEATS FOR MOUNTING ON A VEHICLE FLOOR This invention relates to seats for mounting on a vehicle floor and is particularly concerned with passenger seats for mounting on a floor of an aircraft.

Such seats, and their mountings, have hitherto been designed and constructed so as to withstand impact loadings up to about 9.0g.

However there is now a need, in order to meet the requirements of improved safety regulations, to cater for substantially increased loadings. For example, up to 16.09.

Although future generations of aircraft can be designed with floors capable of withstanding the increased loadings, a problem exists in enabling present aircraft to meet the improved safety regulations.

According to one aspect of the present invention, a restraint means is provided for use with a seat intended for mounting on a vehicle floor and comprising a body support frame and means for attaching the support frame to the vehicle floor so as to be moveable relative to the floor, the restraint means being operable to prevent the relative movement unless overridden by impact loadings, of a predetermined magnitude, being applied to the seat.

The restraint means allows the body support frame to move relative to the floor on which it is mounted, in the direction of linear momentum of the vehicle, so as to limit loading of the floor, and thereafter to move away from the floor, towards its original position, so as to allow a person occupying the seat to evacuate the seat.

Two different forms of restrains means are envisaged.

In one form, the restraint means is operable with a controlled contraction movement so as to allow the body support frame to move towards the floor, and an independent, controlled extension movement so as to allow the frame to move away from the floor.

Means may be provided whereby movement away from the floor is assisted.

The restraint means preferably comprise friction means operable to provide a static friction force to resist loadings up to a threshold value of, for example, 9.09, but which is exceeded for greater loadings to permit controlled relative movement against a friction force.

We have appreciated that friction means operable between two relatively movable members will provide a relatively constant resistance to movement of the members thereby permitting a progressive response to an excessive loading, such that the energy is absorbed uniformly with time and consequently in an efficient manner.

Such a restraint means can provide a strut which acts as a solid strut up to a predetermined force and which is then deformable in a progressive manner.

The restraint means preferably comprises first, second and third relatively telescopable members, the first and second members having friction means arranged to act therebetween so as to prevent telescopic contraction of the first and second members until the friction force is overcome, whereupon contraction takes place against frictional resistance, the first telescopable member being adapted to be connected at its free end to a seat or vehicle floor, the third telescopable member being adapted to be connected at its free end to a vehicle floor or seat respectively, the third telescopable member being urged axially relative to the second member by a preloaded spring in the sense to telescopically expand the second and third members, a first pair of complementary abutments carried by the first and third members and being arranged normally to abut each other to hold the first and third members against relative telescopic expansion, and thereby to hold the spring pre-loaded, but permitting relative telescopic contraction of the first and third members when the first and second members are contracted, the free play between the abutment members produced by the contractive movement then being taken up, to re-expand the restraint means, by relative telescopic expansion of the second and third members under the force of the spring.

Preferably a second pair of complementary abutments is carried by the second and third members and normally in engagement with each other.

Thus, in the normal, relatively unstressed condition of the restraint means, the maximum length of the restraint means is set by the co-operation between the first pair of complementary abutments.

When the static friction force exerted by the friction means is overcome on an excessive contractive force being applied to the restraint means, the first member telescopes into the second and third members, which remain axially together but then, upon release of the excess load, the spring force re-expands the restraint means by urging the second member axially relative to the third member, the second member being held by the friction means against movement relative to the first member during the expansion process.

In another form, the restraint means comprise an inner member, an outer member, and an intermediate member disposed between the inner and outer members, all three members being rotatable relative to each other about a common axis, the restraint means being operable so that, on movement of the body support means towards the floor, the inner and intermediate members rotate together, relative to the outer member, and on movement of the body support frame away from the floor, the inner member rotates relative to the outer member.

Means may be provided whereby movement of the body support frame away from the floor may be assisted.

The restraint means may incorporate friction means operable to provide a substantially constant resistance to rotation between the outer and intermediate members up to a threshold value of, for example, 9.0 g.

The friction means preferably comprise a friction band brake.

The invention also comprises a seat for mounting on a vehicle floor and provided with restraint means of either form.

Two embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a side view of one type of floor-mounted aircraft seat, which incorporates one form of restraint means according to the invention, Figure 2 is a side view, in medial section, of the restraint means 9 of Figure 1, Figure 3 is a side view of one of the tubular components of Figure 2, Figure 4 is a fragmentary side view, to an enlarged scale, of another of the tubular components of Figure 2, Figures 5, 6 and 7 are side views of the components forming the contraction control means 100 of Figure 2, Figure 8 is a side view of yet another tubular component of Figure 2, Figures 9 and 10 are fragmentary side views, to an enlarged scale, of the parts enclosed by the areas IX and X of Figure 8, Figure 11 is a side view of another type of floor-mounted aircraft seat, Figure 12 is a front view, in medial section, of another fbrm of restraint means, applicable to the seat of Figure 11, and Figure 13 is a side view, also in medial section, of the restraint means of Figure 12.

With reference to Figure 1, an aircraft passenger seat 1 is mounted on a floor 2 of an aircraft.

The seat 1 comprises a body support frame 3, means including a pair of rear legs 4, blocks 5 and feet 6, 7 for attaching the support frame 3 to the floor 2 so as to be moveable, in a pivotable manner, about a substantially horizontal axis 8 towards and away from the floor 2.

The seat 1 also comprises restraint means in the form of a telescopic device 9 for preventing the pivotable movement unless overridden by impact loadings applied to the seat of a predetermined magnitude.

The seat 1 is one of a pair of identical seats, 1, disposed side by side, so as to form a seating unit.

The body support frame 3, which is common to both seats 1 of the unit, comprises a pair of transverse, substantially paralleldisposed beams 15, 16 of tubular form, joined by four laterally-spaced longitudinal members 17, forming a rigid structure.

Bottom seat cushions 18 are supported by the beams 15, 16. The four longitudinal members 17 (two per seat) extend rearwardly and upwardly to provide pivotal mountings 19 for the back-rests 20 of the seats.

The body support frame 3 is carried by the rear legs 4, which are laterally-spaced and which are braced by diagonal struts 25 to provide a rigid structure. This structure is pivotally secured to blocks 5 so as to be movable about the axis 8.

The feet 6, 7 are secured to the floor 2 by rails 26 fixed to the floor. The feet 6 are secured to the blocks 5. The feet 7 are secured to blocks 27.

The telescopic device 9 is disposed between the support frame 3 and the blocks 27 and is secured thereto by pivotal connections 28, 29.

The device 9 serves as a normally rigid strut.

Longitudinal struts 30 extend between the front and rear blocks 27, 5 to prevent sliding movement with respect to each other. The struts 30 also serve to provide additional bracing.

With reference now to Figure 2, the telescopic device 9 comprises an energy-absorbing or contractable portion 35 and a seat-restoring or extensible portion 36.

The energy-absorbing portion 35 comprises in turn an inner tubular member 40, the first tubular member, and the seat-restoring portion 36 an intermediate tubular member 41, the third tubular member.

Member 40 is slidably located by member 41, which is in turn slidably located by an outer tubular member 42, the second tubular member. Tubular members 40, 41, 42 are all of circular cross-section, viewed laterally.

As best shown in Figure 3, the member 42 is of stepped longitudinal cross-section, defining an upper chamber 43 and a lower chamber 44 of reduced diameter. The opening of chamber 43 is formed with a female screw thread 45. The lower end of chamber 44 is formed with an internal groove 46 of annular form.

With reference to Figure 4, the lower end of the outer surface of the tubular member 40 is formed with an annular groove 50. The groove 50 is of tapered cross-section, having a linear, radiallyextending bottom portion 50a and an inwardly and upwardly extending side portion 50b, included at about 12" to the central axis of the member 40.

The upper end of the tubular member 40 is provided with a hole 51 which forms part of the pivotal connection 28 (Figure 1).

Referring now to Figures 5, 6 and 7, components 55, 56 and 57 illustrated thereby together comprise friction means 100 (Figure 2) for controlling contraction of the device 9 or, more accurately, the tubular member 40 thereof. Figure 5 shows a securing ring 55, the exterior of which is formed with a male screw thread 60 which co-operates with female screw thread 45 of Figure 3. The upper surface of the ring 55 is formed with sockets 61 whereby the ring 55 may be rotated relative to the tubular member 42.

Figure 6 shows an outer clamping member 56 of hollow, frusto-conical form, with a tapered inner surface 62, inclined at about 7" to the central axis of the member 56.

Figure 7 shows an inner clamping member 57 also of hollow, frusto-conical form but with a tapered outer surface 63 co-operable with tapered surface 62 of Figure 7. In addition, the inner surface 64 of the member 57 is formed with longitudinally-extending slots so as to define juxtaposed resilient fingers 64a, 64b.

As shown in Figure 2, the inner member 57, the outer member 56 and the securing ring 55 are assembled so that the fingers 64a, 64b of the inner member 57 distort slightly so as to apply a clamping force to the outer surface of the member 40. The degree of clamping force applied is adjustable and depends on how firmly the securing ring 55 is tightened.

With reference to Figure 8, the lower end of the tubular member 41 is provided with a hole 70 which forms part of the pivotal connection 29 of Figure 1. An annular groove 71 is formed in the upper interior of the member 41 and houses a snap ring 72 (Figure 9), having a downwardly and inwardly tapering outer periphery i2a.

Surface 50a and ring 72 constitute a first pair of complementary abutments, which in the normal, undeflected condition of the device 9 engage each other.

As best seen in Figure 10, the outer surface of the tubular member 41 is formed with a series of peripheral grooves 75 of tapered form, each having a bottom, radially-extending surface 75a and an outwardly and upwardly extending side surface 75b, inclined at about 12" to the central axis of the member 41. There is also a single, larger groove 76, with a snap ring 77 resting on the bottom surface 76a thereof. The inner periphery of the ring 77 is inclined, so as to match the tapered surfaces 75b and 76b. Below the large groove 76 there is a peripheral groove 78 of rectangular cross-section which locates a snap ring 79. The snap ring 77 is located by the groove 46 (Figure 3).

With reference once again to Figure 2, a compression spring 85 is fitted over the exterior of the outer tubular member 42 and is held between a pair of annular plates 86, 87. The upper surface of the upper plate 86 abuts against a step 88 (Figure 3) formed in the upper region of the member 42 and the lower surface of the lower plate 87 abuts against the snap ring 79.

In the normal, undeflected condition of the device 9, a ledge 89 in the member 42 abuts with the adjacent end 90 of the member 41 to constitute a second pair of complementary abutments.

In the present example, should the aircraft incorporating the seat 1 make a forced landing whereby the impact load applied to the seat in the direction 95 (Figure 1) of linear momentum of the aircraft is up to 9.0g, the seat, with its occupant, will not tend to rotate about axis 8 relative to the floor 2 and in the direction of arrow 96.

This is because the frictional forces in the device 9 resist such pivoting.

However, should an impact load applied to the seat 1 be, say, 12.09 in magnitude, the device 9 is overridden by the excess load, thus causing the seat to pivot.

With reference now to Figure 2, this rotational or pivoting movement, indicated by arrow 96, causes the tubular member 40 of the device 9 to be forced downwardly, into the tubular member 41, so as to contract the device. As the member 40 is forced into the member 41, the friction means 100 (see also Figures 5, 6 and 7) apply a substantially uniform frictional gripping force on the tubular member. The frictional force exerted on the tubular member 40 absorbs the excess energy, ie the 3.09 difference between 9.0g and 12.09 imposed on the seat 1 as the centre of gravity of the seat and occupant is displaced forwardly.

During collapse of the device 9 the members 41 and 42 are held together against relative axial movement by the engagement between ledge 89 and end 90.

Collapse of the device 9 allows the excess energy to be absorbed.

However, it is now necessary for the seat 1 to be restored to substantially its original position, in order to allow the seat occupant to leave the seat.

There should be sufficient energy arising from elastic deformation of the seat structure which will cause the seat 1 to pivot backwards in the direction of arrow 97 (Figure 1). However, the spring 85 is provided to assist this elastic energy force, should it be needed.

The device 9 makes sure that the seat restoring movement takes place in a controlled manner.

With reference once again to Figure 2, in operation, free of the restraint hitherto provided by the ring 72, the spring 85, which is arranged in a pre-loaded condition, can now extend, causing relative movement between the tubular members 41 and 42, so as to tend to re-extend the device 9.

During assembly of the device 9, as the tubular member 42 is fitted over the tubular member 41, the tapered bottom end 90 (Figure 3) of the member 42 causes the snap ring 77 to contract radially until the groove 46 is disposed opposite the ring, allowing the ring 77 to expand into the groove 46, where it remains.

On extension of the device 9, as the member 42 moves upwardly and away from the anchored member 41, the ring 77 (Figure 10) is carried successively from groove 75 to groove 75, in a rachet-like manner.

Tubular member 42 cannot now return, as any attempt to do so is arrested by contact between the ring 77 and the first surface 75a it abuts.

Operation of the telescopic device 9 is a two-stage action.

Firstly, a controlled contraction movement whereby the tubular member 40 is driven downwardly into the stationary tubular member 41. Secondly, a controlled extension as the members 40, 42 are displaced upwardly away from the stationary member 41. The two displacements take place entirely separate from each other, since it will be appreciated that the members 40 and 41 are stationary relative to each other during the extension of the device 9.

The ring 72 ensures that accidental separation of the tubular member 40 from the tubular member 41 does not take place. It also prevents, until contraction of the device 9, extension of the spring 85. On assembly of the device 9 downward movement of the tubular member 40 within tubular member 41 causes the snap ring 72 to expand into its associated groove 71. Extension of the tubular member 40, away from tubular member 41, can continue until the ring 72 can contract into the groove 50 whereby it abuts the bottom portion 50a thereof.

The seat 1 is capable of satisfying both horizontal and vertical impact tests. Making the seat pivotable about the axis 8 allows the centre of gravity of the seat and its occupant to be displaced with both horizontal and vertical components of direction. The relative values of the components depend on the actual position of the axis 8, which will vary according to requirements.

In addition to absorbing excess "g" forces, the invention allows one type of standard aircraft seat to be converted, merely by replacing the conventional front support legs with the telescopic device 9.

The invention thus avoids the need for a major redesign of seat.

The compression spring 85 can be replaced by a compression/extension spring.

The seat 1 may be replaced by other forms of pivotable seats, as will be appreciated hereafter, with reference to Figures 11 to 13.

Figures 12 and 13 illustrate an alternative form of restraint means, namely restraint means 150, 170 which has particular application to the aircraft passenger seat 151 of Figure 11.

The seat 151, which is mounted on the floor 152 of an aircraft, comprises a body support frame 153 and means including pairs of rear legs 154, front legs 155 and leg support frames 156 for attaching the body support frame 153 to the floor 152 so as to be moveable, in a pivotable manner about substantially pairs of horizontal (and parallel) axes 157, 158 and 162, 163 towards and away from the floor 152. The front legs 155 are longer than the rear legs 154.

The seat 151 is one of a pair of identical seats, disposed side by side, so as to form a seating unit.

The body support frame 153, which is common to both seats 151 of the unit, comprises a pair of transverse, substantially paralleldisposed beams 159, 160 of tubular form. The leg support frames 156 are secured to the floor 152 by rails 161 fixed to the floor.

The ends of the front legs 155 are pivotably connected to the body support frame 153 and leg support frame 156 so as to be pivotable about axis 158 and axis 162.

The ends of the rear legs 154 are similarly connected so as to pivotable about axis 157 and axis 163.

Arrows 164, 165 indicate how the articulatory-mounted body support frame 153 can pivot about axes 157, 158 and 162, 163, which axes are disposed in common, substantially horizontal, planes 166, 167.

Normally the seat 151 is provided with a conventional telescopic strut extending between axes 157 and 162, or, alternatively, between axes 158 and 163 and operable to restrain pivotal movement of the seat.

In this embodiment, however, and with reference to Figures 12 and 13, the seat 151 is provided with restraint means 170 mounted on one leg 154 and comprising an inner member 171, and outer member 172 and an intermediate member 173 disposed between the inner and out members 171, 172. All three members 171, 172, 173 are rotatable relative to each other about a common axis, namely axis 163. As explained hereinafter, the restraint means 170 is operable so that, on pivotal movement of the body support frame 153 towards the aircraft floor 152 (Figure 11), the inner and intermediate members 171, 173 rotate together, relative to the outer member 172 and, on pivotal movement of the frame 153 away from the floor, the outer member 172 and leg 154, plus the Intermediate member 173, rotate together relative to the inner member 171.

The inner, intermediate and outer members 171, 173, 172 comprise a close-nested assembly. Members 171 and 173 are of tubular form and member 172 is of part tubular form, comprising a friction band secured to the leg 154 by bolts 174, 175. Bolt 175 is an adjusting bolt whereby a frictional load applied by the band formed by member 172, on the outer surface of member 173, can be adjusted.

Releasable locking means (not shown) secure the bolt 175 in place.

The member 172 is formed with a part-circumferential slot 180.

The inner member 171 comprises an extension of the transverse beam 159 (see Figure 13). The outer surface of the member 171 is formed with radially-extending wall-like projections 181, 182, disposed opposite to each other.

Projection 181 extends through the slot 180. Projection 182 is of shorter length and projects into a slot 186, referred to below.

Flats 183, 184 are formed on the outer surface of the inner member 171, and serve as ramps for rollers referred to below.

The intermediate member 173 is formed with a pair of partcircumferential slots 185, 186, disposed opposite to each other.

Slot 185, which is of stepped cross-section (see Figure 13) extends through the wall of the member 173 and locates part of the projection 181 as well as a roller 187. A step or shoulder surface 201 forms part of the slot 185. The slot 186 is bottom-ended, ie it has a closed outer surface 202, and locates the projection 182, as well as a roller 188. The rollers 187, 188 co-operate with the ramp-like flats 183, 184 in a manner described hereinafter.

The leg 154 is formed with a part-circular recess 195 which forms a bearing surface for the intermediate member 173. A ring 196 (Figure 13) of resilient material such as rubber is mounted on an annular recess 197 formed in the inner member 171 and is bonded to both the beam 159 (of which inner member 171 is an extension) and the intermediate member 173.

As explained hereinafter, the ring 196, which is pre-loaded in a sense so as to urge the intermediate member 173 to rotate relative to the inner member 171, provides means for assisting pivotal movement of the body support frame 153 (Figure 11) away from the aircraft floor 152.

Should the aircraft incorporating the seat 151 make a forced landing whereby the impact load applied to the seat in the direction of arrow 200 (Figure 11) of linear momentum of the aircraft is up to, say, 9.0 g, the seat, with its occupant, will not tend to rotate about axes 157, 158, 163, 164 as indicated by arrows 164, 165. This is because the frictional forces in the restraint means 170, due to tension in the brake band-like outer member 172, resist such movement.

However, should the impact load reach, say, 12.0 g in magnitude, the restraint means 170 is overridden by the excess load, thus allowing the seat 151 to move forward and pivot, ie tilt upwardly about axes 157, 158, 163, 164.

What happens is that the frictional force applied by the member 172 on the member 173, plus friction between the member 173 and the leg 154, is overridden.

As the body support frame 153 tilts upwardly, the leg 154 moves clockwise, as viewed in Figure 12, and about axis 157 (Figure 11).

Relatively speaking, the inner and intermediate members 171, 173 rotate together relative to the outer member 172 (and leg 154). For as the leg 154 and outer member 172 rotate clockwise, friction forces applied by these components tend to try and cause the intermediate member 173 to rotate clockwise as well. However because the inner member 171 remains stationary, the intermediate member 173 cannot rotate, due to contact between the projection 182 and the adjacent end face 198 of the slot 186. Thus, relatively speaking, the members 171 and 173 rotate within the outer member 172. This movement causes a gap to occur between the projection -181 and the adjacent end face 199 of the slot 180.

Relative rotation between the member 172 (and leg 154) on the one hand, and members 173, 171 on the other, results in the excess impact energy being absorbed by friction. Subsequently, however, it is desirable for the seat 151 to be restored to substantially its original position, so as to allow the occupant to leave the seat.

There should be sufficient energy arising from elastic deformation of the seat structure which will cause the seat 151 to pivot backwards. However, resilience in the pre-loaded rubber ring 196 will at least assist the elastic energy force.

As the seat moves backwards, it does so free of the restraining forces applied during its forward movement, for as the leg 154 now rotates anticlockwise, friction between the outer member 172 and leg 154 on the one hand, and the intermediate member 173 on the other, results in all of these components rotating together, relative to the inner member 171, in an unrestrained manner. The movement is influenced by the elastic energy referred to above, and/or the rubber ring 196.

The backwards movement also results in closing the gap between the projection 181 and slot end face 199, as well as opening the gap between the projection 182 and slot end face 198.

The rollers 187, 188 are provided to prevent oscillation, and operate in a manner corresponding to the ratchet-like function of the grooves 75 and member 42 referred to above with reference to Figure 10.

Should the seat 152 tend to move forwardly once again, the leg 154 and outer member 172 will again rotate In a clockwise direction.

Because of friction between the leg/outer member 154/172 combination on the one hand and the intermediate member 173 on the other, the latter will tend to rotate together with the former, relative to the inner member 171, closing the gap existing between the projection 182 and slot end face 198. The clockwise rotation of the intermediate member 173 causes, by friction, the rollers 187 and 188 to rotate and move up their ramp-like flats 183, 184 whereupon they jam against surfaces 201, 202 and lock the inner and intermediate members 172, 173 together. The forward movement of the seat 151 is therefore arrested.

Any return movement of the seat 151 will free the rollers 187, 188 whereby they are ready to come into operation again should this prove necessary.

Claims (14)

1. A restraint means provided for use with a seat intended for mounting on a vehicle floor and comprising a body support frame and means for attaching the support frame to the vehicle floor so as to be moveable relative to the floor, the restraint means being operable to prevent the relative movement unless overridden by impact loadings, of a predetermined magnitude, being applied to the seat.

2. Restraint means as claimed in claim 1, operable with a controlled contraction movement so as to allow the body support frame to move towards the floor, and an independent, controlled extension movement so as to allow the frame to move away from the floor.

3. Restraint means as claimed in claim 2, provided with means whereby movement away from the floor is assisted.

4. Restraint means as claimed in claim 1, 2 or 3, comprising friction means operable to provide a static friction force to resist loadings up to a threshold value, but which if exceeded, permits controlled relative movement against a friction force.

5. Restraint means as claimed in claim 4, comprising two relatively movable members, wherein the friction means provides a relatively constant resistance to movement between the members thereby permitting a progressive response to an excessive loading, such that energy is absorbed uniformly with time.

6. Restraint means as claimed in any one of claims 1 to 5, comprising a strut which acts as a solid strut up to a predetermined force and which is then deformable in a progressive manner.

7. Restraint means as claimed in any one of claims 1 to 6, comprising first, second and third relatively telescopable members, the first and second members having friction means arranged to act therebetween so as to prevent telescopic contraction of the first and second members until the friction force is overcome, whereupon contraction takes place against frictional resistance, the first telescopable member being adapted to be connected at its free end to a seat or vehicle floor, the third telescopable member being adapted to be connected at its free end to a vehicle floor or seat respectively, the third telescopable member being urged axially relative to the second member by a preloaded spring in the sense to telescopically expand the second and third members, a first pair of complementary abutments carried by the first and third members and being arranged normally to abut each other to hold the first and third members against relative telescopic expansion, and thereby to hold the spring pre-loaded, but permitting relative telescopic contraction of the first and third members when the first and second members are contracted, the free play between the abutment members produced by the contractive movement then being taken up, to re-expand the restraint means, by relative telescopic expansion of the second and third members under the force of the spring.

8. Restraint means as claimed in claim 7, wherein a second pair of complementary abutments is carried by the second and third members and normally in engagement with each other.

9. Restraint means substantially as hereinbefore described with reference to Figures 1 to 10 of the accompanying drawings.

10. Restraint means as claimed in claim 1, comprising an inner member, an outer member, and an intermediate member disposed between the inner and outer members, all three members being rotatable relative to each other about a common axis, the restraint means being operable so that, on movement of the body support means towards the floor, the inner and intermediate members rotate together, relative to the outer member, and on movement of the body support frame away from the floor, the inner member rotates relative to the outer member. Means may be provided whereby movement of the body support frame away from the floor may be assisted.

11. Restraint means as claimed in claim 10, incorporating friction means operable to provide a substantially constant resistance to rotation between the outer and intermediate members up to a predetermined threshold value.

12. Restraint means as claimed in claim 11, wherein the friction means comprises a friction band brake.

13. Restraint means substantially as hereinbefore described with reference to Figures 11, 12 and 13 of the accompanying drawings.

14. A seat for mounting on a vehicle floor and provided with restraint means as claimed in any one of claims 1 to 13.